Cell imaging device, cell imaging method, and sample cell

This application is a Continuation of International Application No. PCT/JP2015/006469, filed on Dec. 25, 2015, which in turn claims the benefit of Japanese Patent Applications No. 2014-265931 and No. 2014-265984 filed on Dec. 26, 2014, the disclosures of which Applications are incorporated by reference herein.

1. Field of the Invention

The present invention relates to a cell imaging device, a cell imaging method, and a sample cell for taking an image of a cell contained in a liquid sample.

2. Description of the Related Art

International Publication WO2008/007725 discloses an analyzer which takes images of particles included in urine in a preparation placed on a stage, and which analyzes the particles by using the obtained images. International Publication WO2008/007725 also indicates that: in order to avoid occurrence of focal displacement due to manufacturing errors of each preparation, a focusing mark is provided on one face of a glass slide of a coverslip; and focusing adjustment is performed such that the focal point is at the focusing mark. In International Publication WO2008/007725, the analyzer moves the stage by a predetermined distance in the vertical direction relative to the objective lens from the focusing position obtained through focusing adjustment using the focusing mark, and sets an analysis start position at which observation of particles is to be started. Next, the stage is moved in the vertical direction by a very small distance from the analysis start position. Then, when a focused state is detected, it is determined that a particle is present at the focusing position, and an image of the particle is taken at the focusing position. Subsequently, in order to take an image of a new particle in a different visual field region, the stage is moved in the horizontal direction and then stopped, the stage is moved up and down by a predetermined distance in the vertical direction relative to the focusing position of the immediately-preceding visual field region. Then, when a focused state is detected, an image of the particle is taken at this focusing position.

In the analyzer disclosed in International Publication WO2008/007725, the relative distance between the stage and the objective lens is changed in the vertical direction in each visual field region to detect a focusing position, and taking an image of a particle is performed at the detected focusing position. Thus, it takes a long time to take an image. In addition, every time the stage is moved to a new visual field region, the stage is moved in the horizontal direction and then stopped, and thus, particles in the preparation vibrate due to the stop of the stage. Therefore, in order to obtain a clear image of a particle, it is necessary to wait until such particle vibration stops. Thus, it could take a long time to take an image.

A cell imaging device includes: sample cell including an internal space for holding a liquid sample containing cells; an imaging unit including an objective lens and configured to take images of cells contained in the liquid sample held in the internal space; a first drive unit configured to move at least one of the sample cell and the objective lens in a first direction; a second drive unit configured to move at least one of the sample cell and the objective lens in a second direction that is different from the first direction; and a controller configured to control the first drive unit, the second drive unit, and the imaging unit such that images of cells contained in the liquid sample held in the internal space are taken at a plurality of imaging positions, while at least one of the sample cell and the objective lens is moved in the second direction while at least one of the sample cell and the objective lens is moved in the first direction.

A cell imaging method includes: introducing a liquid sample containing cells into an internal space of a sample cell; and taking, at a plurality of imaging positions, images of cells contained in the liquid sample held in the internal space, while moving at least one of the sample cell and the objective lens in a second direction while moving at least one of the sample cell and the objective lens in a first direction, the second direction being different from the first direction.

A cell imaging device includes: a sample cell comprising an internal space for holding a liquid sample containing cells, and a first reference mark and a second reference mark which are distanced from each other; an imaging unit comprising an objective lens and configured to take images of cells contained in the liquid sample held in the internal space; a first drive unit configured to move at least one of the sample cell and the objective lens in a first direction; a second drive unit configured to move at least one of the sample cell and the objective lens in a second direction that is different from the first direction; and a controller configured to, on the basis of a first focusing position of the objective lens with respect to the first reference mark and a second focusing position of the objective lens with respect to the second reference mark, control the second drive unit so as to move in the second direction at least one of the sample cell and the objective lens, and control the first drive unit so as to move in the first direction at least one of the sample cell and the objective lens, the controller configured to control the imaging unit so as to take, at a plurality of imaging positions, images of cells contained in the liquid sample held in the internal space.

A cell imaging method includes: detecting a first focusing position of an objective lens with respect to a first reference mark of a sample cell and a second focusing position of the objective lens with respect to a second reference mark of the sample cell; introducing a liquid sample containing cells, into an internal space of the sample cell; and on the basis of the detected first focusing position and the detected second focusing position, moving at least one of the sample cell and the objective lens in a second direction, and moving at least one of the sample cell and the objective lens in a first direction that is different from the second direction, and taking, at a plurality of imaging position, images of cells contained in the liquid sample held in the internal space.

A sample cell having an internal space for holding a liquid sample containing cells includes: a flow-in part for introducing the liquid sample into the internal space; a flow-out part for discharging the liquid sample from the internal space; a first reference mark provided at a position to the flow-in part side in the internal space, and configured to be used in focal point adjustment for taking images of the cells; and a second reference mark provided at a position to the flow-out part side in the internal space, and configured to be used in focal point adjustment for taking images of the cells.

According to the present invention, the time period of taking images of cells in a liquid sample can be shortened compared to conventional techniques.

These and other objects, features, aspects, and effects of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram showing a configuration of a cell imaging device according to Embodiment 1;

FIG. 2 is a perspective view showing a configuration of a sample cell according to Embodiment 1;

FIG. 3 is a diagram showing a configuration of a reference mark;

FIG. 4 is a schematic diagram showing a fluid circuit of the cell imaging device;

FIG. 5 is a front view showing configurations of a light source unit and an imaging unit;

FIG. 6 is a flow chart showing the procedure of a moving speed determination operation according to Embodiment 1;

FIG. 7 is a diagram for explaining determination of a moving speed of an objective lens;

FIG. 8 is a flow chart showing the procedure of a urine sample imaging process according to Embodiment 1;

FIG. 9 is a diagram for explaining an offset amount of the objective lens;

FIG. 10 is a diagram for explaining focal point adjustment of the imaging unit performed in imaging operation;

FIG. 11 is a diagram showing a display example of images of cells;

FIG. 12 is a schematic diagram showing a configuration of a sample cell according to Embodiment 2;

FIG. 13 is a flow chart showing the procedure of a moving speed determination operation according to Embodiment 2;

FIG. 14 is a flow chart showing the procedure of a urine sample imaging process according to Embodiment 2;

FIG. 15 is a schematic diagram showing a configuration of a cell imaging device according to Embodiment 3;

FIG. 16 is a side view showing an imaging mechanism of the cell imaging device according to Embodiment 3;

FIG. 17 is a rear view showing a base block according to Embodiment 3;

FIG. 18 is a graph showing change in the focal point position of the objective lens when no heater was provided to a lens block and the base block according to Embodiment 3;

FIG. 19 is a flow chart showing an initialization operation performed at the time of activation of a cell analyzer according to Embodiment 3;

FIG. 20 is a flow chart of a temperature control process according to Embodiment 3; and

FIG. 21 is a graph showing change in the focal point position of the objective lens when temperature control was performed according to Embodiment 3.

Hereinafter, preferred embodiments are described with reference to the drawings.

(Embodiment 1)

<Configuration of Cell Imaging Device>

With reference to FIG. 1 , a configuration of a cell imaging device is described. A cell imaging device 100 includes a sample cell 10 , a placement unit 20 , a light source unit 40 , an imaging unit 50 , a drive unit 60 , a controller 70 , and a display unit 80 . The cell imaging device 100 is a device that takes images of cells contained in a liquid sample such as, for example, cells in a urine sample collected from a subject. The cell imaging device 100 is configured to fill a urine sample into the sample cell 10 and to take images of cells in the sample cell 10 by means of the imaging unit 50 while the sample cell 10 is moved in the horizontal direction. The liquid sample as the imaging target may be any biogenic sample that contains a plurality of kinds of cells having different sizes, and may be blood, celomic fluid, or uterine cervix tissue, for example.

FIG. 2 is referred to. The sample cell 10 includes: an internal space 11 for holding a urine sample; an inlet 12 connected to the internal space 11 ; and an outlet 13 connected to the internal space 11 . The sample cell 10 has a flat rectangular parallelepiped shape elongated in one direction, and is formed from a translucent material. The internal space 11 is a space having a flat rectangular parallelepiped shape elongated in one direction, and is provided inside the sample cell 10 . The longitudinal direction of the internal space 11 is the same as the longitudinal direction of the sample cell 10 . Each face of the internal space 11 is flat.

From one end of the internal space 11 , the inlet 12 extends in a direction perpendicular to the longitudinal direction. From the other end of the internal space 11 , the outlet 13 extends in the same direction as the inlet 12 . Each of the inlet 12 and the outlet 13 is open at one lateral face of the sample cell 10 .

The sample cell 10 includes: a first reference mark 16 a at a position to the outlet 13 side of the internal space 11 ; and a second reference mark 16 b at a position to the inlet 12 side of the internal space 11 . The first reference mark 16 a and the second reference mark 16 b are each provided on a bottom face 11 a of the internal space 11 .

The first reference mark 16 a and the second reference mark 16 b may be provided at a place other than the bottom face 11 a of the internal space 11 , such as the top face or the bottom face of the sample cell 10 , the top face of the internal space 11 , or the like.

With reference to FIG. 3 , the shape of the first reference mark 16 a is described. Since the shape of the second reference mark 16 b is the same as the shape of the first reference mark 16 a , description of the shape of the second reference mark 16 b is omitted. The first reference mark 16 a includes a plurality of minute grooves 161 each formed through laser beam machining. The line width of each minute groove 161 is several micrometers and the length thereof is several tens micrometers. Three minute grooves 161 that are parallel to one another are regarded as one set, and a plurality of sets of the minute grooves 161 are formed in a rectangular region, whereby the first reference mark 16 a is formed. The longitudinal direction of each minute groove 161 extends in the same direction as the longitudinal direction of the internal space 1 of the sample cell 10 .

FIG. 4 is referred to. The inlet 12 of the sample cell 10 is connected to an aspiration tube 151 via a tube and a solenoid valve. The outlet 13 of the sample cell 10 is connected to a pump 152 via a tube and a solenoid valve. The pump 152 is connected via a tube and a solenoid valve to a container 153 that contains a buffer solution. The buffer solution is filled in the tube for urine sample introduction. The container 153 is connected to a washing vessel 154 via a tube and a solenoid valve. Buffer solution is supplied to the washing vessel 154 and is also used as a washing liquid. A waste liquid container 155 is provided below the washing vessel 154 .

The aspiration tube 151 is inserted in a sample container 160 which is a urine collection tube. Through operation of the pump 152 , the urine sample in the sample container 160 is aspirated from the aspiration tube 151 . After a predetermined amount of the urine sample is aspirated, the aspiration tube 151 is pulled out of the sample container 160 . The pump 152 continues operating also after the aspiration tube 151 has been pulled out of the sample container 160 , whereby air is aspirated through the aspiration tube 151 , and the urine sample is introduced from the inlet 12 into the internal space 11 . By the pump 152 operating until the urine sample comes out of the outlet 13 , the urine sample is filled in the entire internal space 11 .

After images of cells contained in the urine sample are taken, washing of the aspiration tube 151 and the sample cell 10 is performed. For the washing, the aspiration tube 151 is moved to the washing vessel 154 . Through operation of the pump 152 , the buffer solution is supplied to the internal space 11 , whereby the internal space 11 is washed. The urine sample pushed out of the internal space 11 is discharged through the aspiration tube 151 into the washing vessel 154 . Through further operation of the pump 152 , the buffer solution is discharged through the aspiration tube 151 , whereby the inside of the aspiration tube 151 is washed. The washing vessel 154 is supplied with the buffer solution from the container 153 , and the outside of the aspiration tube 151 is washed. The waste liquid from the washing vessel 154 is stored in the waste liquid container 155 .

After the washing has been completed, the next urine sample is aspirated by the aspiration tube 151 , to be introduced into the internal space 11 of the sample cell 10 .

FIG. 2 is referred to, again. The sample cell 10 is fixed to the placement unit 20 such that the bottom face 11 a provided with the first reference mark 16 a and the second reference mark 16 b are on the lower side in the internal space 11 . The sample cell 10 is fixed to the placement unit 20 so as to be inclined by a predetermined angle in a predetermined direction relative to the horizontal direction. Even if the placement unit 20 is configured such that the sample cell 10 is not inclined relative to the horizontal direction, there are cases where the sample cell 10 becomes slightly inclined relative to the horizontal direction due to the difference among devices. The sample cell 10 becomes inclined upwardly relative to the horizontal direction in some cases, and downwardly relative to the horizontal direction in other cases. Therefore, in the present embodiment, the sample cell 10 is made inclined in advance in a predetermined direction relative to the horizontal direction, whereby, in the imaging operation described later, the direction in which an objective lens 52 is moved can be made constant for each urine sample, and the moving mechanism and the movement control for the objective lens 52 can be simplified.

The sample cell 10 is mounted to the placement unit 20 such that the sample cell 10 cannot be removed therefrom. The sample cell 10 may be made as a disposable sample cell. In this case, the placement unit 20 is configured such that the sample cell 10 is removable.

FIG. 1 is referred to, again. The drive unit 60 includes a first drive unit 61 and a second drive unit 62 , and moves the sample cell 10 and the objective lens 52 of the imaging unit 50 . The first drive unit 61 includes an electric motor. The placement unit 20 is moved by the first drive unit 61 in a first direction which is one direction in the horizontal direction. The first direction is a direction in which the internal space 11 is elongated.

FIG. 5 is referred to. The light source unit 40 is provided below the placement unit 20 . The light source unit 40 includes an LED light source 41 , a diffuser 42 , and a lens 43 . The light source 41 is a pulsed-light-emitting light source which emits pulsed light at equal intervals. Each lighting time period is 140 to 200 μsec. A second direction which is the optical axis direction of the light source unit 40 is a direction that crosses the horizontal direction. The second direction is the vertical direction, for example. In order to apply light to the sample cell 10 , the light source 41 applies light upwardly. Above the light source 41 , the diffuser 42 and the lens 43 are disposed. Light emitted from the light source 41 is diffused by the diffuser 42 , and is made into collimated light by the lens 43 . The collimated light is applied to the sample cell 10 .

The imaging unit 50 is provided above the placement unit 20 . The imaging unit 50 includes: an image pickup element 51 which is a CCD image sensor or a CMOS image sensor; and the objective lens 52 . The image pickup element 51 and the objective lens 52 are disposed such that, along the same optical axis as that of the light source unit 40 , the image pickup element 51 is at the upper side and the objective lens 52 is at the lower side. The image pickup element 51 and the objective lens 52 are held in one lens barrel. That is, the distance between the image pickup element 51 and the objective lens 52 is not changed. The magnification of the objective lens 52 is 15-fold, but is not limited to 15-fold as long as the magnification allows enlargement of, to an appropriate size, images of cells such as white blood cell, red blood cell, and epithelial cell, and other particles such as cast that are contained in urine.

FIG. 1 is referred to, again. The second drive unit 62 includes an electric motor. The imaging unit 50 is moved in the second direction by the second drive unit 62 . By the imaging unit 50 being moved in the second direction, the focal point of the objective lens 52 is adjusted.

The controller 70 includes a microcomputer and a memory, and controls each of the light source unit 40 , the imaging unit 50 , the first drive unit 61 , the second drive unit 62 , and the display unit 80 . The image obtained by the imaging unit 50 is provided to the controller 70 . The controller 70 performs a predetermined process on the obtained image. The controller 70 includes a focusing detection unit 71 which performs automatic focusing operation for the imaging unit 50 .

Image processing may be configured as a process that is performed by a personal computer. In this case, the controller 70 communicates with a personal computer, and transmits images of cells to the personal computer. The personal computer performs image processing such as cutting out a partial image for each cell.

The display unit 80 includes a liquid crystal display panel. The display unit 80 is connected to the controller 70 , is controlled by the controller 70 , and displays a screen. On the display unit 80 , a taken image, a partial image obtained through image processing, or the like is displayed. When the image processing is performed by a personal computer, a taken image, or a partial image obtained through the image processing may be displayed on a display unit of the personal computer.

<Operation of Cell Imaging Device>

The cell imaging device 100 take images of, by means of the imaging unit 50 , cells contained in a urine sample filled in the internal space 11 of the sample cell 10 . In the imaging operation, while the sample cell 10 is moved at a constant speed in the first direction, the objective lens 52 is moved in the second direction at a uniform speed which is a moving speed according to the inclination of the sample cell 10 , and images are taken in a plurality of visual fields of the imaging unit 50 . Accordingly, without detecting the focused state in each visual field, it is possible to set the focal point to a vicinity of the bottom face of the internal space 11 . The moving speed of the objective lens 52 in the second direction is determined during initialization operation of the cell imaging device 100 before taking images for the urine sample is performed. Such operation of the cell imaging device 100 is described below.

When a user activates the cell imaging device 100 , the cell imaging device 100 performs an initialization operation. The initialization operation includes a moving speed determination operation for determining the moving speed of the imaging unit 50 used when images of cells in urine are taken. With reference to FIG. 6 , the moving speed determination operation is described.

In step S 101 , the controller 70 controls the pump 152 to fill the flow path up to the aspiration tube 151 with the buffer solution from the container 153 . As a result, the buffer solution is held in the internal space 11 of the sample cell 10 .

In step S 102 , the controller 70 controls the first drive unit 61 to move the placement unit 20 such that the first reference mark 16 a to the outlet 13 side of the sample cell 10 is disposed on the optical axis of the imaging unit 50 . Hereinafter, the position of the placement unit 20 realized when the first reference mark 16 a is disposed on the optical axis of the imaging unit 50 is referred to as “initial position”. The position of the placement unit 20 realized when the second reference mark 16 b to the inlet 12 side of the sample cell 10 is disposed on the optical axis of the imaging unit 50 is referred to as “final position”.

In step S 103 , the controller 70 detects a first focusing position which is the focusing position of the objective lens 52 at the initial position. The controller 70 performs the automatic focusing operation three times in order to detect the first focusing position. In the automatic focusing operation, the second drive unit 62 moves the objective lens 52 in the second direction, and the focusing detection unit 71 detects a state where the focal point is at the first reference mark 16 a.

The automatic focusing operation is of a contrast detection type. The position of the objective lens 52 at which the contrast of the image obtained by the image pickup element 51 is maximized is detected as the focusing position of the objective lens 52 . The detected focusing position is stored in the memory of the controller 70 .

An automatic focusing operation other than that of the contrast detection type may be employed. For example, a known automatic focusing operation of a type such as phase contrast detection type, line sensor type, ultrasound type, infrared radiation type, or the like may be employed.

Among the obtained three focusing positions, the controller 70 excludes one that has the most deviated numerical value indicative of the focusing position, and obtains the mean value of the remaining two focusing positions. The controller 70 stores in the memory the obtained mean value as the first focusing position.

In step S 104 , the controller 70 controls the first drive unit 61 to move the placement unit 20 to the final position.

In step S 105 , the controller 70 detects a second focusing position which is the focusing position of the objective lens 52 at the final position. In order to detect the second focusing position, the controller 70 performs the automatic focusing operation three times.

Among the obtained three focusing positions, the controller 70 excludes one that has the most deviated numerical value indicative of the focusing position, and obtains the mean value of the remaining two focusing positions. The controller 70 stores in the memory the obtained mean value as the second focusing position.

The number of times of execution of the automatic focusing operation in the detection of the first and second focusing positions is not limited to three, and may be one or a plural number other than three. However, increase in the number of times of the automatic focusing operation results in an increased operation time period, and thus, the number of times of the automatic focusing operation is preferably as small as possible. From the viewpoint of detection accuracy, it is preferable to perform the automatic focusing operation a plurality of times.

In the detection of the first focusing position, the mean value of two focusing positions is calculated. However, the first focusing position is not limited thereto. The first focusing position may be the mean value of three focusing positions, or may be the middle one among the three focusing positions. The same applies to the second focusing position.

In step S 106 , the controller 70 determines the moving speed of the objective lens 52 by using the first focusing position and the second focusing position.

With reference to FIG. 7 , determination of the moving speed of the objective lens 52 is described. As described above, the sample cell 10 is placed on the placement unit 20 so as to be inclined relative to the horizontal direction. As shown in FIG. 7 , in a case where the sample cell 10 is inclined, when taking images is performed using a plurality of positions in the sample cell 10 as visual fields, the position of the objective lens 52 which allows the focal point to be on the bottom face 11 a of the internal space 11 is different in each visual field. Therefore, if the sample cell 10 is horizontally moved in the first direction while the objective lens 52 is rested, the distance between the objective lens 52 and the bottom face 11 a of the sample cell 10 changes. Thus, even if the focal point is on the bottom face 11 a in one visual field, the focal point will not be on the bottom face 11 a in another visual field. In order to cause the focal point to be on the bottom face 11 a in every visual field, it is necessary to keep constant the distance between the objective lens 52 and the bottom face 11 a while the sample cell 10 is moved in the first direction. That is, the position of the objective lens 52 which allows the focal point to be on the bottom face 11 a of the internal space 11 is on a straight line 52 a which is parallel to the bottom face 11 a . The straight line 52 a is a straight line that passes through the first focusing position and the second focusing position.

In the imaging operation with respect to one urine sample, taking images is performed in a plurality of visual fields of the sample cell 10 . As described later, in the imaging operation, while the first drive unit 61 is moving the placement unit 20 at a uniform speed in the first direction, the imaging unit 50 performs taking images a plurality of times. Since cells in a urine sample having been introduced into the internal space 11 are located above the bottom face 11 a , the cell imaging device 100 causes, in each visual field, the focal point of the objective lens 52 to be at a position that is above the bottom face 11 a by a constant distance.

During the imaging operation, in order to keep the focal point of the objective lens 52 at the position above the bottom face 11 a by the constant distance, the second drive unit 62 moves the imaging unit 50 at a uniform speed in the second direction. At this time, the moving speed in the first direction of the placement unit 20 and the moving speed in the second direction of the imaging unit 50 are combined together, whereby the objective lens 52 and the sample cell 10 relatively move at a uniform speed in an oblique direction. In step S 106 , while the placement unit 20 is moved at a uniform speed in the first direction, a moving speed at which the objective lens 52 is moved relative to the sample cell 10 along the straight line 52 a is determined.

The time period from the start to the end of the imaging operation, that is, the time period in which the second drive unit 62 moves the objective lens 52 (hereinafter, referred to as “set time period”) is set in advance. The set time period is also a time period in which the first drive unit 61 moves the placement unit 20 . The moving speed of the objective lens 52 is the speed at which the objective lens 52 moves from the first focusing position to the second focusing position in the set time period. Specifically, the distance between the first focusing position and the second focusing position in the second direction is calculated, and the calculated distance is divided by the set time period, whereby the moving speed of the objective lens 52 is determined.

In a case where three or more reference marks are provided to the sample cell 10 so as to be distanced from one another in the first direction, the focusing position may be detected at each of the reference marks, and the moving speed may be determined from the detected three or more focusing positions.

When the controller 70 has determined the moving speed of the objective lens 52 , the controller 70 stores the speed information indicating the moving speed in the memory. The speed information is information to be used in focal point adjustment in each visual field for the objective lens 52 . The speed information is also information that reflects the inclination of the bottom face 11 a of the internal space 11 .

FIG. 6 is referred to, again. After step S 106 , the controller 70 ends the moving speed determination operation.

Upon ending the initialization operation, the cell imaging device 100 enters a standby state. The standby state is a state which allows reception of a urine sample.

In the standby state, when the cell imaging device 100 has received from the user an instruction to start taking images for the urine sample, the cell imaging device 100 performs a urine sample imaging process. Hereinafter, with reference to FIG. 8 , the urine sample imaging process is described.

In step S 201 , the controller 70 controls the aspiration tube 151 and the pump 152 to aspirate a predetermined amount of the urine sample from the sample container 160 and introduce the urine sample into the internal space 11 of the sample cell 10 . The urine sample has no reagent such as a staining liquid or a diluent mixed therein, and has not been subjected to a centrifugation process.

In step S 202 , the controller 70 waits for a predetermined time period, such as 100 seconds, for example. Accordingly, the urine sample held in the sample cell 10 is left still for the predetermined time period, cells sediment in the urine sample, and many of the cells are located on the bottom face 11 a of the internal space 11 .

In step S 203 , the controller 70 controls the first drive unit 61 to move the placement unit 20 to the initial position.

In step S 204 , the controller 70 detects the first focusing position which is the focusing position of the objective lens 52 at the initial position. The controller 70 performs the automatic focusing operation three times in order to detect the first focusing position. Among the obtained three focusing positions, the controller 70 excludes one that has the most deviated numerical value indicative of the focusing position, and obtains the mean value of the remaining two focusing positions. The controller 70 stores in the memory the obtained mean value as the first focusing position.

The reason why the first focusing position is detected again in step S 204 although the first focusing position has been detected in the moving speed determination operation is to eliminate any displacement of the focusing position that could be caused by a lapse of time. In some cases, a lapse of time causes change in the temperature of the room where the cell imaging device 100 is placed, and such a temperature change could cause change in the distance between components of the cell imaging device 100 , for example, the distance between the objective lens 52 and the sample cell 10 . Therefore, if the objective lens 52 is located at the first focusing position that has been detected in the moving speed determination operation, the focal point of the objective lens 52 may fail to be on the bottom face 11 a due to the temperature change. Therefore, the first focusing position is detected again in step S 204 , to ensure the focal point of the objective lens 52 to be on the bottom face 11 a of the internal space 11 .

In step S 205 , the controller 70 obtains an imaging start position which is obtained by correcting the first focusing position to a position that is above the first focusing position by a predetermined offset amount.

With reference to FIG. 9 , the offset amount is described. When the objective lens 52 is at the first focusing position, the focal point of the objective lens 52 is on the bottom face 11 a . Since many of the cells are located on the bottom face 11 a , the focal point of the objective lens 52 is not on the cells. If an image of a cell is taken in this state, an unclear image of the cell is obtained. Therefore, in order to cause the focal point of the objective lens 52 to be at the cell, the objective lens 52 is moved upwardly by about a distance corresponding to the radius of the cell, thereby locating the focal point of the objective lens 52 near the center of the cell.

The offset amount is stored by the controller 70 in advance. If the offset amount is set to, for example, 5 to 6 μm, the focal point of the objective lens 52 can be at a red blood cell. However, the offset amount may not be 5 to 6 μm. The offset amount may be set as appropriate according to the size of the cell of interest.

In a case where the first reference mark 16 a and the second reference mark 16 b are provided to a place other than the bottom face 1 a of the internal space 11 of the sample cell 10 , the offset amount may be set as the distance in the second direction from the face where the first reference mark 16 a and the second reference mark 16 b are provided to the center position of the cell of interest.

FIG. 8 is referred to, again. In step S 206 , the controller 70 controls the second drive unit 62 to locate the objective lens 52 at the imaging start position. In step S 207 , the controller 70 reads out speed information from the memory.

In step S 208 , the controller 70 performs the imaging operation. In the imaging operation, the controller 70 controls the first drive unit 61 and the second drive unit 62 to simultaneously start moving the placement unit 20 in the first direction and moving the imaging unit 50 in the second direction. The first drive unit 61 moves, without stopping, the placement unit 20 in the first direction at a set speed for a set time period. The second drive unit 62 moves, without stopping, the imaging unit 50 in the second direction at a speed indicated by the speed information for a set time period.

FIG. 10 is referred to. In the imaging operation, the controller 70 controls the imaging unit 50 to perform taking images a plurality of times. Associated with movement of the placement unit 20 , the visual field of the objective lens 52 is moved from the first reference mark 16 a to the second reference mark 16 b . Thus, the imaging unit 50 performs taking images at a plurality of visual fields in a region between the first reference mark 16 a and the second reference mark 16 b.

While the placement unit 20 is continually moved in the first direction at the set speed, the imaging unit 50 is continually moved in the second direction at the speed indicated by the speed information. Thus, the objective lens 52 is moved relative to the sample cell 10 , in parallel with the bottom face 11 a of the internal space 11 . That is, the objective lens 52 is moved in the second direction in accordance with the inclination of the internal space 11 of the sample cell 10 . When the placement unit 20 is at the initial position, the focal point of the objective lens 52 is located above the bottom face 11 a by an offset amount therefrom. Thus, the focal point of the objective lens 52 is moved on a straight line that is above the bottom face 11 a by the offset amount. Therefore, while the objective lens 52 and the sample cell 10 are moving relative to each other, the focal point position of the objective lens 52 is located in the vicinity of the bottom face 11 a of the internal space 11 in each visual field. As a result, the state where the focal point of the objective lens 52 is at a cell is maintained, and a clear cell image can be stably obtained. In addition, while the placement unit 20 is continually moved in the first direction at a uniform speed, the light source 41 emits pulsed light at equal intervals. Thus, without the need to stop the placement unit 20 every time an image is to be taken, it is possible to obtain an unblurred image.

In the imaging operation, focal point adjustment is performed, without detecting the focused state in each visual field and by moving the objective lens 52 at a uniform speed which is a determined moving speed. Therefore, the time period of the imaging operation can be shortened. In addition, the focal point position is not affected by the density of cells or the sizes of cells in the urine sample, and the focal point position in each visual field can be made uniform. Since images are taken while the sample cell 10 is continually moved in the first direction without being stopped, the sample cell 10 need not be stopped in order to take an image in each visual field, and vibration of cells in the liquid sample due to the stop of the sample cell 10 can be suppressed. Therefore, there is no need to wait until vibration of cells stops, and clear cell images can be stably obtained.

When a set time period has elapsed from the start of movement of the imaging unit 50 and the placement unit 20 , the placement unit 20 reaches the final position. That is, the second reference mark 16 b is located on the optical axis of the imaging unit 50 . At this moment, the imaging unit 50 and the placement unit 20 stop and the imaging operation is completed.

In the urine sample imaging process, with respect to taking images for one urine sample, the automatic focusing operation is performed only for the detection of the first focusing position at the initial position. However, a configuration may be employed in which in the moving speed determination operation, as information for performing the focal point adjustment for each visual field, speed information indicating a determined moving speed and information indicating the detected first focusing position are stored, and in the urine sample imaging process, positioning of the objective lens 52 at the initial position is performed by using the stored information indicating the first focusing position. This configuration eliminates the need to detect the focused state at the initial position in the urine sample imaging process, and taking images for the urine sample can be performed in a still shorter time period. However, as described above, there are cases in which, due to temperature environment and the like in the facility, the first focusing position determined in the moving speed determination operation may fail to allow the focal point of the objective lens 52 to be on the bottom face 11 a of the internal space 11 . Therefore, from the viewpoint of obtaining a clear image in focus, it is preferable to detect the first focusing position for each urine sample.

In a case where taking images is consecutively performed for a plurality of urine sample, temperature change does not substantially occur between consecutive image-taking operations performed on urine samples because the time interval therebetween is short. Thus, a configuration may be employed in which, instead of detecting the first focusing position for each urine sample, the first focusing position is detected every plurality of urine samples, such as every 10 urine samples, for example. Accordingly, it is possible to suppress the number of times of detecting the first focusing position, while maintaining the state where the focal point is at a cell in each urine sample, thereby being able to save the time period.

In the urine sample imaging process, the automatic focusing operation may be performed at the initial position and the final position, whereby the first focusing position and the second focusing position may be detected. In this case, the controller 70 determines the moving speed of the imaging unit 50 for each urine sample. Thus, there is no need to perform the moving speed determination operation during the initialization operation. Accordingly, the inclination angle of the bottom face 11 a of the internal space 11 can be accurately specified for each urine sample.

FIG. 8 is referred to, again. The image outputted as a signal from the image pickup element 51 is inputted to the controller 70 and stored. In step S 209 , from each image obtained by the imaging unit 50 , the controller 70 performs image processing and cuts out a partial image for each cell or other particle.

In step S 210 , the controller 70 causes the display unit 80 to display the cut out partial image. FIG. 11 shows a display example of images in the cell imaging device. As shown in FIG. 11 , on the display unit 80 , a plurality of images of cells and other particles contained in one urine sample are displayed side by side. After step S 210 , the controller 70 ends the urine sample imaging process.

Instead of using the first reference mark 16 a and the second reference mark 16 b , the relative distances among a plurality of positions in the bottom face la of the internal space 11 may be detected by using an optical or ultrasound-type distance sensor. Then, coordinates of each of the plurality of positions may be obtained on the basis of the detected relative distances, and then information reflecting the inclination of the sample cell 10 on the basis of the obtained coordinates may be obtained.

(Embodiment 2)

As shown in FIG. 12 , a sample cell 210 of the cell imaging device is not provided with a reference mark on a bottom face 211 a of an internal space 211 . The other configurations of the cell imaging device are the same as the configurations of the cell imaging device 100 described above, and thus, description thereof is omitted.

The cell imaging device determines the moving speed by using a control sample that contains standard particles each having a set size. The standard particles contained in the control sample have a uniform size.

When the user activates the cell imaging device, the cell imaging device performs an initialization operation. The initialization operation includes a moving speed determination operation for determining the moving speed of the imaging unit 50 used when images of cells in urine are taken. With reference to FIG. 13 , the moving speed determination operation is described.

In step S 121 , the controller 70 controls the aspiration tube 151 and the pump 152 to aspirate a predetermined amount of a control sample from a sample container containing the control sample and introduce the control sample into the internal space 211 of the sample cell 210 .

In step S 122 , the controller 70 waits for a predetermined time period, such as 100 seconds, for example. Accordingly, the control sample held in the sample cell 210 is left still for the predetermined time period, standard particles sediment in the control sample, and many of the standard particles are located on the bottom face of the internal space 211 .

In step S 123 , the controller 70 controls the first drive unit 61 to move the placement unit 20 such that a first position in the internal space 211 of the sample cell 210 , such as a position to the outlet 13 side, for example, is on the optical axis of the imaging unit 50 .

In step S 124 , the controller 70 detects a first focusing position which is the focusing position of the objective lens 52 at the first position. The controller 70 performs an automatic focusing operation three times in order to detect the first focusing position. In the automatic focusing operation, the second drive unit 62 moves the objective lens 52 in the second direction, and the focusing detection unit 71 detects a state where the focal point is at a standard particle present at the first position.

Among the obtained three focusing positions, the controller 70 excludes one that has the most deviated numerical value indicative of the focusing position, and obtains the mean value of the remaining two focusing positions. The controller 70 stores in the memory the obtained mean value as the first focusing position.

In step S 125 , the controller 70 controls the first drive unit 61 to move the placement unit 20 such that a second position in the internal space 211 of the sample cell 210 , such as a position to the inlet 12 side, for example, is on the optical axis of the imaging unit 50 .

In step S 126 , the controller 70 detects a second focusing position which is the focusing position of the objective lens 52 at the second position. The controller 70 performs the automatic focusing operation three times in order to detect the second focusing position.

Among the obtained three focusing positions, the controller 70 excludes one that has the most deviated numerical value indicative of the focusing position, and obtains the mean value of the remaining two focusing positions. The controller 70 stores in the memory the obtained mean value as the second focusing position.

In step S 127 , the controller 70 determines the moving speed of the objective lens 52 by using the first focusing position and the second focusing position. The operation in step S 127 is the same as the operation in step S 106 , and thus, description thereof is omitted. After step S 127 , the controller 70 ends the moving speed determination operation.

Upon ending the initialization operation, the cell imaging device 200 enters a standby state. The standby state is a state which allows reception of a urine sample.

In the standby state, when the cell imaging device 200 has received from the user an instruction to start taking images for the urine sample, the cell imaging device 200 performs a urine sample imaging process. Hereinafter, with reference to FIG. 14 , the urine sample imaging process is described.

In step S 221 , the controller 70 controls the aspiration tube 151 and the pump 152 to aspirate a predetermined amount of the urine sample from the sample container 160 and introduce the urine sample into the internal space 11 of the sample cell 10 . The urine sample has no reagent such as a staining liquid or a diluent mixed therein, and has not been subjected to a centrifugation process.

In step S 222 , the controller 70 waits for a predetermined time period, such as 100 seconds, for example. Accordingly, the urine sample held in the sample cell 210 is left still for the predetermined time period, cells sediment in the urine sample, and many of the cells are located on the bottom face of the internal space 211 .

In step S 223 , the controller 70 controls the first drive unit 61 to move the placement unit 20 such that the first position in the internal space 211 of the sample cell 210 is on the optical axis of the imaging unit 50 .

In step S 224 , the controller 70 detects an imaging start position which is the focusing position of the objective lens 52 at the first position. The controller 70 performs the automatic focusing operation three times in order to detect the imaging start position. In each automatic focusing operation, the focusing detection unit 71 detects a state where the focal point is at a cell present at the first position. Among the obtained three focusing positions, the controller 70 excludes one that has most deviated numerical value, and obtains the mean value of the remaining two focusing positions. The controller 70 stores in the memory the obtained mean value as the imaging start position.

In step S 225 , the controller 70 controls the second drive unit 62 to locate the objective lens 52 at the imaging start position. In step S 226 , the controller 70 reads out speed information from the memory. Since the imaging start position is the position where the focal point is at a cell, there is no need to perform correction using an offset amount.

In step S 227 , the controller 70 performs an imaging operation. The operation in step S 227 is the same as the operation in step S 208 , and thus, description thereof is omitted.

In step S 228 , from each image obtained by the imaging unit 50 , the controller 70 performs image processing and cuts out a partial image for each cell or other particle.

In step S 229 , the controller 70 causes the display unit 80 to display the cut out partial image. After step S 229 , the controller 70 ends the urine sample imaging process.

(Embodiment 3)

With reference to FIG. 15 , another embodiment of the cell imaging device is described. A cell imaging device 100 A according to Embodiment 3 is configured to perform temperature control for suppressing focal point displacement of the objective lens due to temperature change. Description of the same configurations as those of Embodiment 1 is omitted.

The cell imaging device 100 A includes as the imaging unit: an objective lens 52 A; a lens block 53 which is a lens holder that holds the objective lens 52 A; and an image pickup element 51 A provided so as to be spaced away from the lens block 53 . The lens block 53 has a hollow cubic shape. The lower face of the lens block 53 is provided with a hole into which an upper end portion of the objective lens 52 A can be inserted, whereby the lens block 53 is configured to be able to hold the objective lens 52 A inserted through the hole. As shown in FIG. 16 , the lens block 53 is mounted to a linear slider 54 , and is configured to be movable along the linear slider 54 in the second direction which is the optical axis direction. The lens block 53 is configured to move in the optical axis direction along the linear slider 54 when a pulley 62 B and a belt 62 C are driven by an electric motor 62 A. The electric motor 62 A is a stepping motor. The image pickup element 51 A and the linear slider 54 are fixed to a base block 90 which is a base plate, and the lens block 53 is moved in the optical axis direction relative to the image pickup element 51 . Compared with a case where the lens barrel holding the image pickup element and the objective lens is moved in the optical axis direction as in the cell analyzer 100 of Embodiment 1, since the weight of the member that is moved in the optical axis direction is reduced, the electric motor 62 A, the pulley 62 B, and the belt 62 C which serve as a drive mechanism can be downsized.

As shown in FIG. 15 , the placement unit 20 is mounted to a linear slider 21 . The placement unit 20 is placed in the horizontal direction. The linear slider 21 is fixed to the base block 90 such that the linear slider 21 is inclined by a predetermined toward the vertical direction relative to the horizontal direction. The inclination angle of the linear slider 21 is very small, and thus, the linear slider 21 is fixed to the base block 90 in a substantially horizontal direction. When a belt 61 B is driven by an electric motor 61 A, the placement unit 20 is moved in a substantially horizontal direction along the linear slider 21 . Two sample cells 10 A, 10 B are fixed to the placement unit 20 . When the placement unit 20 is moved, the sample cells 10 A, 10 B are also moved integrally with the placement unit 20 . Since taking images for a plurality of urine samples can be performed in parallel by use of the two sample cells 10 A, 10 B, the imaging process can be efficiently performed.

A heater 91 for performing temperature control of the objective lens 52 A is mounted to the lens block 53 . The heater 91 is a rubber heater. The heater 91 is mounted to the entirety of one lateral face of the lens block 53 , and is configured to heat the lens block 53 . A thermistor 92 is mounted to the lens block 53 , and the temperature of the lens block 53 is detected by the thermistor 92 . Instead of the thermistor 92 , a thermocouple may be used as a temperature sensor. The lens block 53 is formed from aluminium having a high thermal conductivity. By the lens block 53 being heated by the heater 91 , air inside the lens block 53 is warmed, and the warmed air reaches the objective lens 52 A. The objective lens 52 A includes a lens part and a tubular part surrounding the lens part. The air warmed in the lens block 53 enters the tubular part of the objective lens 52 A, whereby the temperature of the lens part is controlled. It is sufficient that the lens block 53 is formed from a material having a high thermal conductivity, and may be formed from copper. The heater 91 is provided to the lens block 53 which has a wider surface area than the objective lens 52 A, and thus, even in a case where the surface area of the objective lens 52 A is too small to provide a heater thereto, temperature control of the objective lens 52 A can be effectively performed.

As shown in FIG. 16 , the image pickup element 51 A, the electric motor 61 A, the electric motor 62 A, the linear slider 54 , and the linear slider 21 are fixed to the base block 90 . With respect to the base block 90 , a heater 93 for performing temperature control of the base block 90 is mounted to the face thereof that is opposite to the face where the image pickup element 51 A and the like are mounted. The heater 93 is also a rubber heater, and is configured to heat the base block 90 . As shown in FIG. 17 , a thermistor 94 is mounted to the base block 90 , and the temperature of the base block 90 is detected by the thermistor 94 . Instead of the thermistor 94 , a thermocouple may be used as a temperature sensor. The base block 90 is formed from aluminium having a high thermal conductivity. It is sufficient that the base block 90 is formed from a material having a high thermal conductivity, and the base block 90 may be formed from copper, for example.

As shown in FIG. 15 , the base block 90 , the image pickup element 51 A, the lens block 53 , the objective lens 52 A, the placement unit 20 , the electric motors 61 A, 62 A, and the like are disposed in a housing 30 . In addition, a cell analyzer 100 A has mounted thereto a temperature sensor 95 for detecting the ambient temperature outside the device.

In a case where the objective lens 52 A is used in an environment in which temperature change occurs, there is a risk of occurrence of focal point displacement because the lens part of the objective lens 52 A expands or contracts associated with the temperature change. For example, while the cell imaging operation is performed after activation of the cell imaging device 100 A, the image pickup element 51 A generates heat and the temperature is increased. If heat generated by the image pickup element 51 A is conducted to the objective lens 52 A, the temperature of the objective lens 52 A itself increases due to the heat, thus leading to a risk of occurrence of focal point displacement. FIG. 18 is a graph showing change in the focal point position of the objective lens 52 A in a case where the heaters are not provided to the lens block 53 and the base block 90 . This graph shows the result of an experiment in which the ambient temperature of the cell analyzer 100 A was 32° C. As shown in this graph, while the imaging operation is performed after activation of the device, the temperature of the image pickup element 51 A increases and the temperature of the lens block 53 also increases, accordingly. The “number of pulses” at the vertical axis on the right side of the graph shown in FIG. 18 indicates the number of drive pulses provided to the motor 62 A in order to adjust the objective lens 52 A from the origin position thereof to a predefined focal point position. As shown in the graph, as the temperature of the lens block 53 increases, the focal point position of the objective lens 52 A is displaced, and the number of drive pulses for adjusting the objective lens 52 A to the predefined focal point position increases. In this experiment, change as great as about 25 pulses occurred from the activation of the device until the stabilization of the focal point position of the objective lens 52 A. In addition, it took 200 minutes or longer until the temperature of the lens block 53 was stabilized after the activation of the device, and thus, it took a long time for the focal point position of the objective lens 52 A to be stabilized. Therefore, until the focal point position of the objective lens 52 A is stabilized, it is necessary to perform focal point adjustment of the objective lens 52 A every time a new urine sample is introduced into a sample cell, and thus, the imaging operation takes time.

In Embodiment 3, the heater 91 is mounted to the lens block 53 holding the objective lens 52 A, and the temperature of the lens block 53 is controlled to be constant by the heater 91 . Specifically, the temperature of the lens block 53 is controlled at 41° C. Since the heat of the heater 91 is conducted via the lens block 53 to the objective lens 52 A, the temperature of the objective lens 52 A is also kept constant. Thus, temperature change of the objective lens 52 A is suppressed, whereby occurrence of focal point displacement can be suppressed.

The temperature of the objective lens 52 A is affected not only by the heat from the image pickup element 51 A but also by the ambient temperature of the cell imaging device 100 A in some cases. In Embodiment 3, the heater 93 is also mounted to the base block 90 , and the temperature of the base block 90 is controlled to be constant. The temperature of the base block 90 is controlled so as to be the same as the temperature of the lens block 53 , and is specifically controlled at 41° C. The base block 90 is disposed in the housing 30 , and air circulation into and out of the housing 30 is blocked. Thus, the temperature of the air in the housing 30 can be maintained at substantially the same temperature as the base block 90 , whereby temperature change can be suppressed. Accordingly, the temperature of the air around the objective lens 52 A disposed in the housing 30 can be maintained at substantially the same temperature as the base block 90 , and thus, influence of change in the ambient temperature of the cell imaging device 100 A can be suppressed, and the focal point displacement of the objective lens 52 A can be further suppressed.

Since the lens block 53 holding the objective lens 52 A is disposed so as to be spaced away from the image pickup element 51 A, thermal conduction therebetween can be suppressed from occurring. Thus, heat generated by the image pickup element 51 A is suppressed from being conducted to the objective lens 52 A, whereby occurrence of focal point displacement due to increase in the temperature of the objective lens 52 A can be further prevented.

With reference to FIG. 19 and FIG. 20 , an operation procedure of the cell analyzer 100 A is described. FIG. 19 is a flow indicating an initialization operation performed at the time of activation of the cell analyzer 100 A. Upon activation of the cell analyzer 100 A, in step S 321 , the controller 70 determines, on the basis of a detection result from the temperature sensor 95 , whether an outside-device temperature T, i.e., the temperature in the room where the cell analyzer 100 A is placed, is higher than or equal to T 1 . The temperature T 1 is 15° C., for example, but may be another temperature. When the outside-device temperature T is higher than or equal to T 1 , the controller 70 starts in step S 322 temperature control by means of the heaters 91 , 93 , and then, determines in step S 323 whether a time period M 1 has elapsed. The time period M 1 is 15 minutes, for example, but may be another time period. When the time period M 1 has elapsed, the controller 70 performs a moving speed determination operation in step S 327 . The moving speed determination operation is the same as the operation described with reference to FIG. 6 . After the moving speed determination operation, the controller 70 shifts to a standby state in step S 328 .

When the outside-device temperature T is lower than T 1 , the controller 70 determines in step S 324 whether the outside-device temperature T is higher than or equal to T 2 . The temperature T 2 is 10° C., for example, but may be another temperature that is lower than the temperature T 1 . When the outside-device temperature T is higher than or equal to T 2 , the controller 70 starts in step S 325 temperature control by means of the heaters 91 , 93 , and then determines in step S 326 whether a time period M 2 has elapsed. The time period M 2 is 25 minutes, for example, but may be another time period that is longer than the time period M 1 . When the time period M 2 has elapsed, the controller 70 performs the moving speed determination operation in step S 327 , and shifts to a standby state in step S 328 . In this manner, if the ambient temperature of the cell analyzer 100 A is high, the time period up to shifting to a standby state is shortened, and if the ambient temperature is low, the time period up to shifting to a standby state is made long. By changing the time period up to shifting to a standby state in accordance with the ambient temperature of the cell analyzer 100 A, it is possible to reliably set the temperature of the objective lens 52 A to a target temperature even when the ambient temperature is low.

When the outside-device temperature T is lower than T 2 , the controller 70 causes in step S 329 the display unit 80 to display “imaging not allowed”, and returns to step S 321 without shifting to a standby state. When the ambient temperature of the cell analyzer 100 A is too low relative to a normally expected temperature, even if temperature control by means of the heaters 91 , 93 is performed, focal point displacement of the objective lens 52 A could occur. Therefore, in such a case, taking images of poor accuracy can be prevented from being performed, by prohibiting the imaging operation.

Next, with reference to FIG. 20 , a temperature control process performed by the heaters 91 , 93 is described. The temperature control process is continued until a shut-down instruction is received after the temperature control process is started in step S 322 or step S 325 . Upon the start of the temperature control process, in step S 421 , the controller 70 determines, on the basis of a detection result from the thermistor 92 , whether the temperature of the lens block 53 , i.e., the temperature of the objective lens 52 A, is higher than or equal to a target temperature T G . The target temperature T G is 41° C., for example. When the temperature of the objective lens 52 A is lower than the target temperature T G , the controller 70 turns on the heater 91 in step S 423 . When the temperature of the objective lens 52 A is higher than or equal to the target temperature T G , the controller 70 turns off the heater 91 in step S 422 .

Subsequently, in step S 424 , the controller 70 determines, on the basis of a detection result from the thermistor 94 , whether the temperature of the base block 90 is higher than or equal to the target temperature T G . The target temperature T G is 41° C., for example. When the temperature of the base block 90 is lower than the target temperature T G , the controller 70 turns on the heater 93 in step S 426 . When the temperature of the base block 90 is higher than or equal to the target temperature T G , the controller 70 turns off the heater 93 in step S 425 .

In step S 427 , the controller 70 determines whether a shut-down instruction has been received. When the shut-down instruction has not been received, the controller 70 repeats the processes of step S 421 to S 426 . Thus, the operation is repeated in which: when the temperatures of the objective lens 52 A and the base block 90 reach the target temperature T G , their corresponding heaters are turned off; and when the temperatures of the objective lens 52 A and the base block 90 become lower than the target temperature T G , their corresponding heaters are turned on. Accordingly, the temperatures of the objective lens 52 A and the base block 90 can be maintained at temperatures close to the target temperature T G .

With reference to FIG. 21 , a result of an experiment is described in which temperature control by means of the heaters 91 , 93 was performed. This experiment was performed under a condition of: the ambient temperature of the cell analyzer 100 A being 32° C.; and the set temperature of the heaters 91 , 93 being 41° C. As shown in the graph in FIG. 21 , upon activation of the cell analyzer 100 A, the temperature of the image pickup element 51 A increases due to heat generation. However, since the base block 90 is heated by the heater 93 , the difference in temperature between the base block 90 and the image pickup element 51 A is reduced compared with a case shown in FIG. 18 . Accordingly, heat transfer from the image pickup element 51 A to the base block 90 is suppressed, the temperature of the image pickup element 51 A is stabilized soon, and the temperature of the base block 90 is stabilized soon at 41° C. In the experiment shown in FIG. 21 , the temperatures of the base block 90 and the lens block 53 are stabilized at 41° C. in about 10 minutes. As shown in the graph, while the temperature of the lens block 53 is stable, substantially no displacement of the focal point position of the objective lens 52 A occurred. When the focal point position of the objective lens 52 A at the lapse of about 15 minutes after the activation of the device is used as the reference, the displacement of the focal point position of the objective lens 52 A is within 5 pulses, and the width of the change in the focal point position has been greatly reduced compared with the case shown in FIG. 18 . Thus, when the temperature control by means of the heaters 91 , 93 is performed, the focal point position of the objective lens 52 A can be quickly stabilized. Thus, after the focal point position has been stabilized, the frequency of performing the focal point adjustment of the objective lens 52 A can be reduced, and the imaging process can be efficiently performed. For example, it is possible to also reduce the number of times of performing the focal point adjustment every time images of a new urine sample are to be taken, and thus, it is possible to quickly perform the imaging process.

The target temperature for the base block 90 and the lens block 53 may not be 41° C. However, the target temperature is preferably a temperature higher than the ambient temperature of the cell analyzer 100 A, and is preferably a temperature higher than, for example, 25° C. which is generally considered as room temperature in the technical field of the present invention. If the target temperature is made closer to the temperature of the image pickup element 51 A, the temperatures of the base block 90 and the lens block 53 can be quickly stabilized, accordingly. However, if the target temperature is too high, the cells in the urine sample in the sample cell 10 A, 10 B might be influenced. Thus, it is particularly preferable that the target temperature is higher than or equal to 38° C. and lower than 42° C.

It should be noted that the embodiment disclosed herein is merely illustrative in all aspects and should not be construed as being restrictive. The scope of the present invention is defined not by the description of the above embodiment but by the scope of the claims, and includes meaning equivalent to the scope of the claims and all modifications within the scope.