Head mounted display device

The application claims priority from Japanese Patent Application No. 2009-080759, filed on Mar. 30, 2009, the entire subject matter of which is incorporated herein by reference.

1. Field of the Disclosure

The disclosed feature relates to a head mounted display device, in which an image display unit is attached to a frame having a front part to be positioned before eyes of an user and a temple part mountable on the user's ear, connected with a side edge portion of the front part. In particular, the disclosed feature relates to the head mounted display device, in which the image display unit is detachably attached to a front edge portion of the temple part.

2. Description of the Related Art

Various head mounted display devices (hereafter HMD) have been commercialized as portable displays for TV games and personal digital assistances. For example, in Japanese Unexamined Patent Application Publication No. 2007-148131 (hereafter JP 2007-148131), an eyeglass type HMD is disclosed as an example of HMD. In the eyeglass type HMD, an image display unit is disposed in front of a frame of the eyeglass type HMD such that the image display unit is adjustable in a right-and-left direction. Particularly, an adopter member, in which a permanent magnet is embedded, is detachably disposed in the upper edges of both a left rim and a right rim that support lens of the eyeglass type HMD. A rail is fixed to the adopter member by the permanent magnet, and a retaining shaft is movably disposed in the rail. The image display unit is fixed to the frame via a holding ring. The holding ring surrounds the image display unit and is fixed to the retaining shaft by a screw nut.

In U.S. Pat. No. 6,204,974 (hereafter U.S. Pat. No. 6,204,974), another eyeglass type HMD is disclosed. In the eyeglass type HMD, a housing assembly for housing an image display unit is retained in a temple of a frame of the eyeglass type HMD by a clamp assembly that includes a mounting fixture and a clamp. In detail, a pair of pins extend from the mounting fixture that is retained in the housing assembly. The pair of pins penetrate the temple from the outside of the temple, and the housing assembly is retained in the temple at a rearward position apart from a connection part connecting the temple and a front supporting eyeglass lenses.

In U.S. Pat. No. 4,869,575 (hereafter U.S. Pat. No. 4,869,575), there is disclosed an eyeglass type HMD similar to the eyeglass type HMD disclosed in U.S. Pat. No. 6,204,974. In the eyeglass type HMD, an eyeglass frame has a front supporting eyeglass lenses, a pair of connection parts fixed in both sides of the front, and a pair of temples rotatably mounted on both connection parts. A clip type mounting means has an arm and is detachably attached to one of the temples. A display unit having a screen is mounted on a front edge portion of the arm.

In the eyeglass type HMD disclosed in JP 2007-148131, the image display unit is retained in the frame by retaining means such as the retaining shaft that extends downward from the upper edges of the left rim and the right rim. The retaining means such as the retaining shaft would interrupt a user's front view when the user's view moves from images, displayed on the image display unit, to a large display or document in front of the user. In the eyeglass type HMD disclosed in U.S. Pat. No. 6,204,974, the housing assembly is retained in the temple at a rearward position apart from the connection part. Likewise, in the eyeglass type HMD disclosed in U.S. Pat. No. 4,869,575, the clip type mounting means is attached in the temple at a rearward position apart from a rotation position where the temple is rotatably mounted on the connection part. Generally, when the frame is mounted on the user, the temple would deform according to the shape of the user's head. The deformation of the temple may shift the position of images displayed on the image display unit. In the eyeglass type HMDs disclosed in U.S. Pat. Nos. 6,204,974 and 4,869,575, required is adjustment of the position of displayed images according to the deformation of the temple.

A need has arisen for the eyeglass type HMD that allows for clearing the user's front view and for suppressing an effect on a position of the image display unit by the deformation of the temple.

According to an aspect of the present invention, a head mounted display device comprises a frame, an image display unit, an extension member, and a retaining mechanism. The frame includes a front part, a connection part, and a temple part. The front part is mountable on a user's nose and extends in a right-and-left direction in front of the user's eye. The connection part is fixed to at least one edge portion of right and left side edges of the front part and extends in a rearward direction from the one edge portion. The temple part is mountable on the user's ear and rotatably connected with the connection part around a rotation axis extending along an up-and-down direction. The image display unit includes an optical system and is configured to generate an image to be displayed for the user. The extension member extends in a forward direction from the one edge portion. The retaining mechanism is configured to retain the image display unit detachably in the extension member.

According to another aspect of the present invention, a mounting device is utilized for an image display unit having an optical system to generate an image to be displayed for a user. The mounting device comprises a frame, an extension member, and a retaining mechanism. The frame includes a front part, a connection part, and a temple part. The front part is mountable on the user's nose and extends in a right-and-left direction in front of the user's eye. The connection part is fixed to at least one edge portion of right and left side edges of the front part and extends in a rearward direction from the one edge portion. The temple part is mountable on the user's ear and rotatably connected with the connection part around a rotation axis extending along an up-and-down direction. The extension member extends in a forward direction from the one edge portion. The retaining mechanism is configured to retain the image display unit detachably in the extension member.

Other objects, features, and advantages will be apparent to those skilled in the art from the following detailed description and accompanying drawings.

An embodiment of an eyeglass type HMD are described with reference to the accompanying drawings, which are given by way of example only, and are not intended to limit the present invention.

FIG. 1 is a schematic perspective view of a frame 10 mounted on a user according to the embodiment.

FIG. 2 is a perspective view of entire structure of a HMD 1 according to the embodiment.

FIG. 3 is a perspective view that shows a state in which an image display unit 100 is detached from the frame 10 .

FIG. 4 is a plan view of entire structure of the frame 10 with the image display unit 100 attached.

FIG. 5 is a front view of the frame 10 shown in FIG. 4 .

FIG. 6 is a left side view of the frame 10 with the image display unit 100 detached.

FIG. 7 is a partially cross-sectional view that shows a connection part 30 A, a temple body 42 A, and an extension member 51 A enlarged in a disassembled state.

FIG. 8A is a cross-sectional view of a front part 20 taken along the line A-A in FIG. 4 . FIG. 8B is a cross-sectional view of the connection part 30 B taken along the line B-B in FIG. 4 . FIG. 8C is a cross-sectional view of a temple body 42 B taken along the line C-C in FIG. 4 .

FIG. 9 is an enlarged perspective view of the image display unit 100 with an attachment instrument 60 attached.

FIG. 10 is an enlarged perspective view of parts of the attachment instrument 60 in a disassembled state.

FIG. 11A is a left side view of an instrument body 61 of the attachment instrument 60 .

FIG. 11B is a rear view of the instrument body 61 . FIG. 11C is a cross-sectional view of the instrument body 61 taken along the line D-D in FIG. 11A . FIG. 11D is a cross-sectional view of the instrument body 61 taken along the line E-E in FIG. 11B .

FIG. 12 is an enlarged cross-sectional view that shows a state in which a frame attachment part 67 of the instrument body 61 fits to a notch aperture 52 A of the extension member 51 A.

FIG. 13A is a left side view of a slide member 62 of the attachment instrument 60 . FIG. 13B is a rear view of the slide member 62 . FIG. 13C is a right side view of the slide member 62 . FIG. 13D is a cross-sectional view of the slide member 62 taken along the line G-G in FIG. 13A

FIG. 14A is a left side view of a slide frame 63 of the attachment instrument 60 . FIG. 14B is a plan view of the slide frame 63 . FIG. 14C is a rear view of the slide frame 63 . FIG. 14D is a cross-sectional view of the slide frame 63 taken along the line H-H in FIG. 14A .

FIG. 15A is a left side view of a disk member 64 of the attachment instrument 60 . FIG. 15B is a plan view of the disk member 64 . FIG. 15C is a right side view of the disk member 64 .

FIG. 16 is a partially cross-sectional view that shows a state in which a holding arm 94 of a cable holding clip 90 fits to a holding aperture 48 A of a closure portion 47 A.

FIG. 17 is a cross-sectional view of the cable holding clip 90 taken along the line I-I in FIG. 16 .

FIG. 18 is an explanatory perspective view that shows a state in which the attachment instrument 60 is detached from the extension member 51 A positioned apart from the connection part 30 A with the temple part 40 A rotated in a counterclockwise direction, right before the image display unit 100 is attached to the extension member 51 A.

FIG. 19 is an explanatory perspective view that shows a state in which the attachment instrument 60 has been attached to the extension member 51 A.

FIG. 20 is an explanatory perspective view that shows a state in which the attachment instrument 60 is attached to the extension member 51 A positioned close to the connection part 30 A with the temple part 40 A rotated in a clockwise direction.

FIG. 21 is an explanatory perspective view that shows a state in which the cable holding clip 90 is held in the temple body 42 A.

FIG. 22 is a partially cross-sectional view that shows a positional relation between the instrument body 61 and the connection part 30 A with the attachment instrument 60 and the extension member 51 A positioned close to the connection part 30 A.

Embodiment

An embodiment, and its features and advantages, may be understood by referring to FIGS. 1-22 , like numerals being used for corresponding parts in the various drawings. In the embodiment, a retinal scanning display (hereafter RSD) is used as an image display unit. RSD usually includes a light source and a light scanner. The light source, e.g., RGB lasers, emit image light according to image signals. The light scanner, e.g., a galvano mirror, two-dimensionally scans the image light to project an image on a user's retina. Since the structure and operation of RSD are well known (see e.g., U.S. Pat. No. 7,234,813), we omit detailed explanation of the internal structure of RSD.

<<External Entire Structure>>

Referring to FIGS. 1-2 , we explain the entire structure of HMD 1 . HMD 1 includes an eyeglass type frame 10 (hereafter frame 10 ), a retaining mechanism 50 , an image display unit 100 retained on the frame 10 by the retaining mechanism 50 , and a control apparatus 200 as an example of an external apparatus for supplying signals to the image display unit 100 . The control apparatus 200 is connected to the image display unit 100 via a cable 110 . In this embodiment and the drawings above, an up-and-down direction, a front-and-rear direction, and a right-and-left direction are based on the user in FIG. 1 . These directions are also shown in FIG. 1 with arrows.

<Structure of Frame>

Referring to FIGS. 3-6 , we explain the structure of the frame 10 . In FIG. 3 , the frame 10 includes a front part 20 , a pair of left and right connection parts 30 A and 30 B, and a pair of left and right temple parts 40 A and 40 B.

(Structure of Front Part)

The front part 20 , mounted on the user as shown in FIG. 1 , extends in the right-and-left direction. A pair of nose mounting parts 21 A and 21 B are fixed to a central portion of the front part 20 as shown in FIG. 4 . The nose mounting parts 21 A and 21 B are mounted on the use's nose when the frame 10 is mounted on the user. A protective cover 22 is fixed to a lower portion of the front part 20 , and is disposed to cover the user's eyes when the frame 10 is mounted on the user as shown in FIG. 1 . The protective cover 22 is formed from a transparent film of a synthetic resin to prevent a part of the image display unit 100 from touching the user's eye.

(Structure of Connection Part)

As shown in FIG. 4 , the connection parts 30 A and 30 B are fixed to left and right side edges of the front part 20 , respectively. The connection parts 30 A and 30 B extend in a rearward direction at an angle such that they open to the right-and-left direction. The connection parts 30 A and 30 B are integrally formed with the front part 20 . The temple parts 40 A and 40 B are rotatably connected with the connection parts 30 A and 30 B with mounting screws 41 A and 41 B, which extend in the up-and-down direction, respectively. Namely, the temple parts 40 A and 40 B are rotatable around rotation axes that extend in the up-and-down direction of the mounting screws 41 A and 41 B, respectively. Forward portions 31 A and 31 B of the connection parts 30 A and 30 B are formed to protrude outside of the connection parts 30 A and 30 B.

(Structure of Temple Part)

The temple parts 40 A and 40 B include temple bodies 42 A and 42 B, ear mounting parts 43 A and 43 B, and auxiliary guide members 44 A and 44 B, respectively. The temple bodies 42 A and 42 B include connection portions 45 A and 45 B for rotatably connecting the temple bodies with rear end portions of the connection parts 30 A and 30 B. The auxiliary guide member 44 A and 44 B connect the temple bodies 42 A and 42 B with the ear mounting parts 43 A and 43 B. Since both the connection parts 30 A and 30 B, and both the temple parts 40 A and 40 B are symmetric in their structure, we explain the left side connection part 30 A and the left side temple part 40 A, referring to FIG. 4 , FIG. 6 and FIG. 7 .

The temple body 42 A is rotatably connected with the rear end portion of the connection part 30 A with the mounting screw 41 A. The temple body 42 A straightly extends in the front-and-rear direction. As shown in FIG. 6 , the auxiliary guide member 44 A is connected with a rear end portion of the temple body 42 A, and extends forward along the temple body 42 A under the temple body. The auxiliary guide member 44 A is disposed at a given distance from the temple body 42 A. As shown in FIG. 4 , a forward portion of the auxiliary guide member 44 A is curved toward the inside of the frame 20 . A front end of the forward portion of the auxiliary guide member 44 A is bent toward the outside of the frame 20 . A slide aperture 46 A is formed from a space between the temple body 42 A and the auxiliary guide member 44 A. The slide aperture 46 A is opened at its front end. A closure portion 47 A is formed at a position where the temple body 42 A and the auxiliary guide member 44 A are connected. The closure portion 47 A closes a rear end of the slide aperture 46 A. As shown in FIG. 3 , a holding groove 48 A is formed at a rear end of the closure portion 47 A. The slide aperture 46 A slopes down in a front direction. A space of the opened end of the slide aperture 46 A in a up-and-down direction is set to be larger than a space of the closed end of the slide aperture 46 A near to the closure portion 47 A. A cable holding clip 90 described hereinafter can slide along the slide aperture 46 A, and is formed to fit to the holding groove 48 A.

In FIG. 4 , the ear mounting part 43 A is fixed to the front bent end of the auxiliary guide member 44 A, and extends rearward with curving toward the inside of the frame 10 . In FIG. 6 , the ear mounting part 43 A is disposed under the temple body 42 A. When the user mounts the frame 10 with usually wearing eyeglasses for adjusting sight, the front part 20 and the temple body 42 A of the frame 10 is placed above a front part and a temple part of a frame of the eyeglasses worn by the user, because of such disposition of the ear mounting part 43 A under the temple body 42 A. Therefore, the user can easily mount the frame 10 without interfering with the front part and the temple part of the eyeglass frame.

Referring to FIG. 7 , we explain a structure for connecting the connection part 30 A and the temple part 40 A. The connection portion 45 A is formed to protrude from a right side surface of the temple body 42 A, and has a hole into which the mounting screw 41 A is inserted. The connection portion 45 A has a planar surface 45 A- 1 vertical to the right side surface of the temple body 42 A, an inclined planar surface 45 A- 2 sloped rearward from the vertical planar surface 45 A- 1 , and a curved surface 45 A- 3 formed continuously to the inclined planar surface 45 A- 2 . The connection part 30 A includes a pair of rear end portions which hold the connection portion 45 A therebetween in a up-and-down direction. In FIG. 7 , one rear end portion 32 A is shown with the other rear end portion severed. The rear end portion 32 A has a hole into which the mounting screw 41 A is inserted. The rear end portion 32 A further has an inclined planar surface 32 A- 1 engageable with the inclined planar surface 42 A- 2 . When the temple part 40 A is rotated in a counterclockwise direction around an axis of the mounting screw 41 A, the inclined planar surface 32 A- 1 allows the temple part 40 A to be rotated without the curved surface 45 A- 3 interfering with the inclined planar surface 32 A- 1 . When the temple part 40 A is rotated in a clockwise direction around an axis of the mounting screw 41 A, the inclined planar surface 32 A- 1 is engaged with the inclined planar surface 45 A- 2 . By engagement of both inclined planar surfaces, an angular position of the temple part 40 A can be determined such that the image display unit 100 is positioned in front of the user's eye, as shown in FIG. 4 .

Since the ear mounting parts 43 A and 43 B include portions which are directly in touch with ears of the user, these portions are covered with a synthetic resin material having adequate elasticity such that the user feels soft when mounting the frame 10 .

(Cross-Sectional Shape of Frame)

In a cross-sectional shape of the front part 20 in a direction perpendicular to a longitudinal direction of the front part 20 , a length in the front-and-rear direction, i.e., a width, is larger than a length in the up-and-down direction, i.e., a height. As shown in FIG. 8A , the width DW 1 is larger than the height DL 1 . In cross-sectional shapes of the connection parts 30 A and 30 B in a direction perpendicular to a longitudinal direction of the connection parts 30 A and 30 B, a length in the right-and-left direction, i.e., a width is smaller than a length in the up-and-down direction, i.e., a height, whereas the width DW 2 is sufficiently larger than the height DL 1 of the front part 20 , as shown in FIG. 8B . In cross-sectional shapes of the temple bodies 42 A and 42 B in a direction perpendicular to a longitudinal direction of the temple bodies 42 A and 42 B, a length in the right-and-left direction, i.e., a width is smaller than a length in the up-and-down direction, i.e., a height. As shown in FIG. 8C , the width DW 3 is smaller than the height DL 3 , and is substantially equal to the height DL 1 of the front part 20 . Bending moments around the rotation axes of the mounting screws 41 A and 41 B are put on the front part 20 and the connection parts 30 A and 30 B when the frame 10 is mounted on the user. Since cross-sectional shapes of both the front part 20 and the connection parts 30 A and 30 B are larger in ratio of width to height than those of the temple bodies 42 A and 42 B, the deformation of the front part 20 and the connection parts 30 A and 30 B, caused by the bending moments, is smaller than the deformation of the temple bodies 42 A and 42 B.

In addition to the difference in the cross-sectional shape described above, constituent materials are also different among the front part 20 , the connection parts 30 A and 30 B, and the temple bodies 42 A and 42 B. The front part 20 and the connection parts 30 A and 30 B are made from pure titanium, and the temple bodies 42 A and 42 B are made from beta titanium. Since the Young's modulus, namely longitudinal elastic modulus, of pure titanium is larger than that of beta titanium, the front part 20 and the connection parts 30 A and 30 B are more rigid against pull and compression forces than the temple bodies 42 A and 42 B, namely harder to deform. The auxiliary guide members 44 A and 44 B are formed integrally with the temple bodies 42 A and 42 B, and are made from beta titanium. Therefore, the temple bodies 42 A and 42 B, and the auxiliary guide member 44 A and 44 B are less rigid against pull and compression forces than the front part 20 and the connection parts 30 A and 30 B, namely easier to deform.

<Structures of Retaining Mechanism and Extension member>

A retaining mechanism 50 retains the image display unit 100 in the extension member 51 A or 51 B, allowing the user to choose a preferred retaining state of the image display unit 100 either in the extension member 51 A or 51 B. The retaining mechanism 50 includes an attachment instrument 60 as a main component.

(Structure of Extension Member)

A pair of left and right extension members 51 A and 51 B are formed in the temple parts 40 A and 40 B. Since both the extension members 51 A and 51 B are symmetric in their structure, we explain the left extension member 51 A. In FIG. 7 , the extension member 51 A extends forward the connection portion 45 A of the temple body 42 A, and is formed integrally with the temple body 42 A. The extension member 51 A is made from beta titanium. A notch groove 52 A is formed in a right side surface of the extension member 51 A.

(Structure of Attachment Instrument)

Referring to FIGS. 9-15 , we explain a structure of an attachment instrument 60 . In FIG. 10 , the attachment instrument 60 includes an instrument body 61 , a slide member 62 , a slide frame 63 , and a rotation disk 64 as main components. These main components are made from a synthetic resin material.

The instrument body 61 has an attachment hole 65 penetrating in the front-and-rear direction at its upper portion, and has an attachment groove 66 at its lower portion. The attachment hole 65 is formed such that a front end of each of the extension members 51 A and 51 B is inserted into the attachment hole 65 . The attachment groove 66 is formed such that the slide member 62 fits to the attachment groove 66 .

In FIG. 11C , a frame attachment part 67 is formed at an upper portion of the instrument body 61 . A lower end of the frame attachment part 67 extends inside of the attachment hole 65 . An unit attachment part 68 is formed at a lower portion of the instrument body 61 . A lower end of the unit attachment part 68 extends inside of the attachment groove 66 . In FIG. 12 , the lower end of the frame attachment part 67 fits to the notch groove 52 A of the extension member 51 A. An elastic force of the attachment part 67 itself maintains fitting of the lower end to the notch groove 52 A. When the lower end of the frame attachment part 67 fits to the notch groove 52 A, a rear end surface of the instrument body 61 shown in FIG. 12 abuts onto the vertical planar surface 45 A- 1 of the connection portion 45 A. Such abutment of the rear end surface and the vertical planar surface 45 A- 1 restricts rearward movement of the instrument body 61 relative to the extension member 51 A. In addition, since the forward portion 31 A of the connection part 30 A shown in FIG. 7 protrudes just in front of a front end surface of the instrument body 61 , the instrument body 61 is prevented from moving forward and then falling out of the extension member 51 A, when the lower end of the frame attachment part 67 fits to the notch groove 52 A.

In FIGS. 13A-13D , the slide member 62 includes a rectangular platelike slide portion 69 and a circular protrusion 70 . The circular protrusion 70 is formed to protrude from one side surface of the platelike slide portion. A pair of holding grooves 71 and 71 are formed inside of the circular protrusion 70 . As shown in FIG. 13C , two rows of multiple engagement grooves 72 are formed in the up-and-down direction in the other side surface of the platelike slide portion 69 . In a state where the slide member 62 is mounted by fitting to the attachment groove 66 , the unit attachment part 68 of the instrument body 61 is engaged with the engagement groove 72 of the slide member 62 by elasticity of the unit attachment part 68 itself, thereby retaining the engagement position of the slide member 62 with the engagement groove 72 , namely a position of the slide member 62 in the up-and-down direction. A projection 73 is formed to protrude toward the inside of the attachment groove 66 in a lower edge portion of the instrument body 61 . The projection 73 prevents the slide member 62 fitting to the attachment groove 66 from falling out of the attachment groove 66 . The user releases the slide member 62 from engagement with the projection 73 by elastically deforming a lower edge portion of the instrument body 61 in which the projection 73 is formed, when removing the slide member 62 from the attachment groove 66 .

In FIGS. 14A-14D , the slide frame 63 includes a platelike support portion 73 , and an upper arm portion 74 and a lower arm portion 75 , which extend horizontally from upper and lower ends of the support portion 73 . The support portion 73 has a circular fitting recess 76 , and a circular fitting hole 77 . The fitting hole 77 is disposed inside of the fitting recess 76 and is formed to fit to an exterior peripheral surface of the circular protrusion 70 . An angular position of the slide frame 63 relative to the slide member 62 can be changed around a center of the circular protrusion 70 , namely an axis extending in the left-and-right direction, by fitting the circular protrusion 70 to the fitting hole 77 . One row of multiple upper engagement grooves 78 are formed in an upper surface of the upper arm portion 74 to extend in the left-and-right direction. In addition, one row of multiple lower engagement grooves 79 are formed in an lower surface of the lower arm portion 75 to extend in the left-and-right direction. In FIG. 9 , the upper arm portion 74 and the lower arm portion 75 are formed to fit to an upper attachment hole 101 and a lower attachment hole 102 disposed in a right side surface of the image display unit 100 . When both arm portions 74 and 75 fit to both attachment hole 101 and 102 , both engagement grooves 78 and 79 are elastically engaged with a pair of upper and lower resilient parts, not shown, disposed inside of the image display unit 100 . The upper and lower resilient parts are similar in structure to a resilient part such as the frame attachment part 67 and the unit attachment part 68 . Both engagement grooves 78 and 79 retain an attachment position of the image display unit 100 relative to the slide frame 63 , namely a position in the left-and-right direction, by engagement with the upper and lower resilient parts. A pair of upper projection portions 80 and 80 are disposed at front and rear corners of a left side end of the upper arm portion 74 . A pair of lower projection portions 81 and 81 are disposed at front and rear corners of a left side end of the lower arm portion 75 . Both projection portions 80 and 81 are engageable with engagement members disposed in the vicinity of both attachment holes 101 and 102 , in order to prevent both arm portions 74 and 75 from falling out of both attachment holes 101 and 102 . The user releases both projection portions 80 and 81 from engagement with the engagement members, by elastically deforming the projection portions 80 and 81 .

In FIGS. 15A-15C , a rotation disk 64 includes a disk portion 82 and a pair of holding projections 83 and 83 protruding from one side surface of the disk portion 82 . The disk portion 82 is formed to fit to an interior peripheral surface of the circular fitting recess 76 of the slide frame 63 . Both holding projections 83 and 83 are inserted under pressure into both holding grooves 71 and 71 of the slide member 62 through the fitting hole 77 . By such insertion under pressure, one side surface of the disk portion 82 , in which both holding projections 83 and 83 are formed, is pressed to come into frictional contact with a bottom surface of the fitting recess 76 of the slide frame 63 , namely a right side surface of the fitting recess 76 shown in FIG. 14D . An angular position of the slide frame 63 relative to the slide member 62 can be changed, and the angular position can be maintained by frictional resistance of such contact between both surfaces.

The attachment instrument 60 of the present embodiment includes the instrument body 61 , the slide member 62 , the slide frame 63 , and the rotation disk 64 . Owing to such structure of the attachment instrument 60 , a position of the image display unit 100 relative to the left side extension member 51 A can be adjusted both in the up-and-down direction and in the left-and-right direction. In addition, an angular position of the image display unit 100 can be changed around the circular protrusion 70 . That is to say, an angular position of the image display unit 100 can be changed around an axis in the left-and-right direction in which a center line of the circular protrusion 70 extends. The axis in the left-and-right direction is perpendicular to the front-and-rear direction which the extension member 51 A extends, and is perpendicular to the up-and-down direction which the mounting screw 41 A extends. The attachment instrument 60 can be attached to the right side extension member 51 A with the angular position of the image display unit 100 changed 180 degrees. Likewise, the angular position of the image display unit 100 relative to the right side extension member 51 A can be adjusted.

<Structure of Cable Holding Clip>

Referring to FIGS. 16-17 , we explain a structure of the cable holding clip for holding a cable 110 in the temple bodies 42 A and 42 B. In FIG. 2 , the cable holding clip 90 is fixed to the cable 110 in a position away from the image display unit 100 by an adequate length such that the cable 100 extending from the image display unit 100 does not touch the face of the user when the image display unit 100 is mounted on the frame 10 . In FIG. 16 , the cable holding clip 90 has a holding hole 91 penetrating through the clip 90 in the front-and-rear direction. The cable holding clip 90 is fixed to the cable 110 with glue, after the cable 110 has been inserted into the holding hole 91 .

The cable holding clip 90 is made from a synthetic resin material and includes a contact surface 92 , a fitting portion 93 protruding from the contact surface 92 in the right direction, and a holding arm 94 extending rearward with protruding from the fitting portion 93 . The contact surface 92 is engageable with both a left side surface of the temple body 42 A and a left side surface of the auxiliary guide member 44 A. The fitting portion 93 is formed so as to slide by fitting to the slide aperture 46 A. The holding arm 94 is formed so as to fit to the holding groove 48 A formed in a right side surface of the closure portion 47 A. In FIG. 17 , the holding arm 94 has a width substantially equal to a width of the slide aperture 46 A in the up-and-down direction.

<Structures of Image Display Unit and Control Apparatus>

The image display unit 100 contains minimal optical systems because the weight of the image display unit 100 should be reduced as possible. In order to reduce the weight, other optical systems are contained in the control apparatus 200 . In the present embodiment, the control apparatus 200 contains a red-green-blue (RGB) image signal supply circuit, RGB laser sources, a laser source driver, and a laser coupling optical system for the RGB laser beams. The cable 110 includes an optical fiber that transmits a coupled RGB laser beam. The image display unit 100 contains internal optical systems such as a collimate lens, a horizontal scan part, a vertical scan part, and an eye lens. In FIG. 9 , the image display unit 100 has a light emitting aperture 103 . A translucent half mirror 104 is attached to a proximal portion of the light emitting aperture 103 . An angle between the half mirror 104 and the light emitting aperture 103 is adjustable by tweaking the half mirror 104 .

The image display unit 100 emits the coupled RGB laser beam from the cable 110 to the half mirror 104 via the internal optical systems. The coupled RGB laser beam is reflected by the half mirror 104 and enters the user's eye. When the RGB laser beam stops entering the user's eye, the user can look at a landscape before the eyes through the half mirror 104 .

<<Operation>>

Referring to FIGS. 18-22 , we explain an operation of the embodiment. For each user, it is different whether a left side or a right side is eye-friendly for mounting the image display unit 100 . Thus, the user first chooses one of the connection parts 30 A and 30 B for mounting the image display unit 100 . The user changes by 180 degrees an angular position of the attachment instrument 60 relative to the image display unit 100 , according to whether the image display unit 100 is mounted on the connection part 30 A or 30 B. In FIG. 18 , a positional relation between the attachment instrument 60 and the image display unit 100 is for attaching the image display unit 100 to the left side connection part 30 A.

In case of mounting the image display unit 100 in the right side connection part 30 B, the user changes by 180 degrees an angular position of the attachment instrument 60 relative to the image display unit 100 shown in FIG. 18 . When the user changes the angular position of the attachment instrument 60 by 180 degrees, the image display unit 100 is used in a state where the unit 100 is rotated by 180 degrees from a state shown in FIG. 18 . In this case, an image to be displayed by the laser beam transmitted via the cable 110 is required to be rotated by 180 degrees.

In the present embodiment, we explain how the image display unit 100 is mounted on the left side connection part 30 A.

<Positional Adjustment of Image Display Unit Relative to Attachment Instrument>

First, the user needs to determine a position of the image display unit 100 relative to the frame 10 in the up-and-down direction. If the user tends to frequently look at a large display or document in front of the user with seldom looking at images from the image display unit 100 , the image display unit 100 is mounted in a relatively lower position so as to clear the user's front view. On the other hand, if the user tends to frequently look at images from the image display unit 100 with rarely moving the user's view, the image display unit 100 is mounted in a position close to the frame 10 because clearing the user's front view is not required. According to the usage of the image display unit 100 , the user can adjust a position of the image display unit 100 relative to the attachment instrument 60 both in the up-and-down direction and in the left-and-right direction, and also an angular position of the unit 100 relative to the attachment instrument 60 . Concretely, the user can adjust a position of the image display unit 100 in the up-and-down direction with moving the attachment instrument 60 relative to the unit 100 in the up-and-down direction so that the engagement grooves 72 of the slide member 62 may shift a position for engagement with the unit attachment part 68 of the instrument body 61 . The user can adjust a position of the image display unit 100 in the left-and-right direction with moving the attachment instrument 60 relative to the unit 100 in the left-and-right direction so that both engagement grooves 78 and 79 of the slide frame 63 may shift positions for engagement with the upper and lower resilient parts disposed inside of the image display unit 100 . In addition, the user can adjust an angular position of the image display unit 100 with rotating the attachment instrument 60 relative to the unit 100 so that the circular fitting recess 76 and the circular fitting hole 77 of the slide frame 63 may be rotated along both circumferential surfaces of the circular protrusion 70 of the slide member 62 and the disk portion 82 of the rotation disk 60 .

<Retaining Operation of Image Display Unit>

Under a state that the frame 10 is not mounted on the user, the user separates the extension member 51 A from the connection part 30 A by rotating the left side temple part 40 A in a counterclockwise direction as shown in FIG. 18 . The user fits the attachment hole 65 of the instrument body 61 to the front end portion of the extension member 51 A. With this fitting operation, the frame attachment part 67 of the instrument body 61 fits to the notch groove 52 A of the extension member 51 A. By fitting of the frame attachment part 67 to the notch groove 52 A, a position of the attachment instrument 61 relative to the extension member 51 A is determined in the front-and-rear direction, so that the attachment instrument 60 is retained in the frame 10 . In addition, a rear end surface of the instrument body 61 abuts onto the planar surface 45 A- 1 of the connection portion 45 A of the temple body 42 A. By this abutment, the instrument body 61 is prevented from moving reward on the extension member 51 A. In FIG. 19 , it is shown that the image display unit 100 is mounted on the frame 10 .

In order to certainly keep the state of mounting the image display unit 100 , the user rotates the temple part 40 A in a clockwise direction around an axis of the mounting screw 41 A, from a state of the temple part 40 A shown in FIG. 19 , so that the extension member 51 A and the instrument body 61 come close to the connection part 30 A. In FIG. 20 , it is shown that the extension member 51 A and the instrument body 61 are placed close to the connection part 51 A. In the state of the instrument body 61 shown in FIG. 20 , the front portion 31 A of the connection part 30 A is disposed to protrude in front of the front end surface of the instrument body 61 . By the protruding configuration of the front portion 31 A, the instrument body 61 is prevented from moving forward and falling out of the extension member 51 A. The image display unit 100 is certainly retained in the extension member 51 A by an easy operation, namely rotating the temple part 40 A. There is no need for a special operation such as screwing a retaining screw.

<Holding Operation of Cable>

In FIG. 20 , the cable holding clip 90 fixed to the cable 110 is separated from the temple part 40 A. In the state of the cable holding clip 90 shown in FIG. 20 , the user fits the fitting portion 93 and the holding arm 94 of the clip 90 to the slide aperture 46 A, and then moves rearwards the clip 90 along the slide aperture 46 A. The holding arm 94 fits to the holding groove 48 A of the closure portion 47 A as shown in FIG. 16 , so that the cable holding clip 90 is held in the temple body 42 A. Usually, the user fits the frame attachment part 67 of the instrument body 61 to the notch groove 52 A of the extension member 51 A, thereby retaining the attachment instrument 60 in the frame 10 . After retaining the attachment instrument 60 , the user performs an operation for attaching the cable holding clip 90 to the temple 40 A. In FIG. 21 , it is shown that the cable holding clip 90 is retained in the temple part 40 A.

<Mounting Operation of Frame>

The user mounts the frame 10 on the user's head with the cable holding clip 90 retained in the temple part 40 A as shown in FIG. 21 . As shown in FIG. 1 , the user mounts the nose mounting parts 21 A and 21 B on the user's nose, and mounts the ear mounting parts 43 A and 43 B on the user's ear. The distance between the temple parts 40 A and 40 B, especially the distance between the ear mounting parts 43 A and 43 B changes according to the size of the user's head. The distance usually becomes larger than the distance under the natural state shown in FIG. 4 . This widened distance between the temple parts 40 A and 40 B causes bending moments around the rotation axes of the mounting screws 41 A and 41 B. A clockwise bending moment around the rotation axis of the retaining screw 41 A is put on the temple body 42 A.

When the distance between the temple parts 40 A and 40 B is widened, the inclined planar surface 45 A- 2 of the connection portion 45 A of the temple body 42 A is engaged with the inclined planar surface 32 A- 1 of the rear end portion 32 A of the connection part 30 A, so that the temple part 40 A is prevented from rotating in the clockwise direction in FIG. 22 . The extension member 51 A and the instrument body 61 are positioned relative to the connection part 30 A. In order to prevent the instrument body 61 from moving rearwards, the rear end surface of the instrument body 61 is engaged with the planar surface 45 A- 1 of the connection portion 45 A, while other portions including the front end surface of the instrument body 61 are positioned relative to the connection part 30 A without engagement with the connection part 30 A. That is to say, the instrument body 61 does not come into contact with the connection part 30 A, until the temple part 40 A is prevented from rotating in the clockwise direction in FIG. 22 by engagement of the inclined planar surface 45 A- 2 with the inclined planar surface 32 A- 1 . Since the instrument body 61 does not come into contact with the connection part 30 A, the extension member 51 A does not deform by the bending moment around the axis of the mounting screw 41 A which is caused by rotation of the temple part 40 A in the clockwise direction. Although the temple body 42 A disposed rearwards from the connection portion 45 A deforms by the bending moment when the distance between the temple parts 40 A and 40 B is further widened after the temple part 40 A is prevented from rotation in the clockwise direction, the extension member 51 A disposed forward from the connection portion 45 A hardly deforms. As a result, the extension member 51 A and the instrument body 61 are not influenced by the bending moment, thereby maintaining a constant positional relation with the connection part 30 A. The position of the image display unit 100 relative to the user's eye is prevented from changing when the user mounts the frame 10 .

In addition, the front part 20 and the connection part 30 A are more rigid than the temple body 42 A, namely harder to deform against the bending moment caused by the user's operation of rotating the temple part 40 A, so that the position of the image display unit 100 is prevented from changing with deformation of the front part 20 and the connection part 30 A.

The cable holding clip 90 is retained in the closure portion 47 A which is formed integrally with the temple body 42 A, and the attachment instrument 60 is retained in the extension member 51 A fixed to the temple body 42 A. By such structure of the cable holding clip 90 and the attachment instrument 60 , the distance between the image display unit 100 and the closure portion 47 A in which the cable holding clip 90 is retained is not changed even if the user rotates the temple part 40 A in the state that the image display unit 100 is attached to the frame 10 as shown in FIG. 21 . As a result, excessive tension is not put on the cable 110 when the user rotates the temple part 40 A. The cable holding clip 90 is certainly prevented from detaching from the closure portion 47 A and drooping in front of the user's face. In considering a different structure from the present embodiment, namely a structure that the attachment instrument 60 is retained in the front part 20 or the connection part 30 A, the distance between a position of the retained attachment instrument 60 and a position of the cable holding clip 90 retained in the temple part 40 A is changed when the user rotates the temple part 40 A. In such different structure, there is a possibility that excessive tension is put on the cable 110 by change of the distance between the above positions when the user rotates the temple part 40 A. In addition, there is a possibility that the cable holding clip 90 is detached from the temple part 40 A when the user rotates the temple part 40 A. Therefore, there are problems in mounting the frame 10 in such different structure. In the present embodiment, it is easy for the user to mount or remove the frame 10 and the image display unit 100 , because there is not any trouble such as drooping of the cable 110 and detaching of the cable holding clip 90 .

The user may change the direction, in which the coupled RGB laser beam emits, so as to clearly look at images from the image display unit 100 by tweaking the half mirror 104 with the frame 10 mounted on the user. Further, the user may adjust a position of the image display unit 100 relative to the attachment instrument 60 in the up-and-down direction and in the left-and-right direction, and also angular position of the image display unit 100 relative to the attachment instrument 60 around a rotation axis of the mounting screw 41 A with the frame 10 mounted on the user.

<Removing Operation of Image Display Unit>

In order to remove the image display unit 100 from the frame 10 , the user rotates the temple part 40 A in the counter-clockwise direction from the state of retaining the image display unit 100 in FIG. 21 , after the user detaches the frame 10 from the user's head. By rotating the temple part 40 A, the attachment instrument 60 and the extension member 51 A is separated from the connection part 30 A. The front end surface of the instrument body 61 is released from a state where it is prevented from forward movement in the extension member 51 A, so that it is possible for the user to move forward the attachment instrument 60 in the extension member 51 A. Even though the temple part 40 a is rotated, the cable holding clip 90 is maintained in a state where the clip 90 is retained in the closure portion 47 A. The user may release the cable holding clip 90 from engagement with the holding groove 48 A of the closure portion 47 A, by gently sliding the clip 90 in the forward direction. When the user detaches the attachment instrument 60 from the extension member 51 A by forwardly moving the attachment instrument 60 in the above state of releasing the cable holding clip 90 , the clip 90 is moved in a direction of sloping down toward the opened end of the slide aperture 46 A. The cable holding clip 90 is naturally removed from the opened end of the slide aperture 46 A. In some cases, the cable holding clip 90 is naturally removed from an intermediate part of the slide aperture 46 A before the clip 90 reaches the opened end of the slide aperture 46 A, because the fitting portion 93 and the holding arm 94 of the clip 90 are substantially equal to the slide aperture 46 A in width. Further, the cable 110 and the cable holding clip 90 removed from the slide aperture 46 A are not caught on the temple body 42 A, because the image display unit 100 is disposed under the extension member 51 A and the slide aperture 46 A is formed below the temple body 42 A. As a result, it is easy for the user to remove the image display unit 100 from the frame 10 .

Considered is a case that a resilient force of the holding arm 94 of the cable holding clip 90 is strong enough to maintain fitting of the holding arm 94 to the holding groove 48 A, but is not so strong that excessive tension is put on the cable 110 . In this case, when the user detaches the attachment instrument 60 from the extension member 51 A by moving forward the attachment instrument 60 in the state of retaining the cable holding clip 90 in the closure portion 47 A, the clip 90 is moved toward the opened end of the slide aperture 46 A, so that the clip 90 is naturally removed from the opened end or from an intermediate part of the slide aperture 46 A before the clip 90 reaches the opened end.

<<Advantages of Embodiment >>

In the present embodiment described above, there are following advantages.

The retaining mechanism 50 is configured to retain the image display unit 100 in the extension member 51 A. The retaining mechanism 50 is prevented from interrupting the user's front view. The retaining mechanism 50 makes it possible to dispose the image display unit 100 in an area at which the user easily look, without a large movement of the direction of eyes. Furthermore, when the user mounts the frame 10 on the user's head, the temple part 40 A deforms according to the size of the user's head, but the extension member 51 A is hardly influenced by deformation of the temple part 40 A because the extension member 51 A is disposed in front of the connection portion 45 A of the temple part 40 A connected to the connection part 30 A. The position of the image display unit 100 retained in the extension member 51 A is prevented from changing by deformation of the temple part 40 A. As a result, the extension member 51 A prevents a position of an image to be displayed in the user's eye by the image display unit 100 from changing by deformation of the temple part 40 A.

The user retains the image display unit 100 in the extension member 51 A by attaching the unit attachment part 68 of the attachment instrument 60 to the image display unit 100 and also by fitting the frame attachment part 67 of the attachment instrument 60 to the extension member 51 A. As a result, it is easy for the user to retain the image display unit 100 in the frame 10 by fitting the frame attachment part 67 to the extension member 51 A.

The image display unit 100 is retained in the extension member 51 A with the front end portion of the extension member 51 A fitting to the attachment hole 65 of the frame attachment part 67 . As a result, it is easy for the user to retain the image display unit 100 in the extension member 51 A by fitting the attachment hole 65 to the front end portion of the extension member 51 A in a state where the temple part 40 A is rotated such that the extension member 51 A is placed apart from the connection part 30 A.

The forward portion 31 A of the connection part 30 A prevents the frame attachment part 67 from moving forward when the user mounts the temple part 40 A on the user's ear in a state where the front end portion of the extension member 51 A fits to the attachment hole 65 . As a result, the image display unit 100 is certainly prevented from removing from the extension member 51 A when the user mounts the temple part 40 A on the user's ear.

The image display unit 100 is retained in the extension member 51 A with the resilient lower end of the frame attachment part 67 engaged with the notch groove 52 A of the extension member 51 A. As a result, it is easy for the user to retain the image display unit 100 in the extension member 51 A by fitting the frame attachment part 67 to the extension member 51 A, and also the elastic force of the resilient lower end certainly maintains the state of retaining the image display unit 100 .

The unit attachment part 68 of the attachment instrument 60 is detachably attached to the image display unit 100 . As a result, it is easy for the user to attach the image display unit 100 to or detach the unit 100 from the unit attachment part 68 , so that the user can exchange the unit 100 readily.

A part of the image display unit 100 or a member attached to the unit 100 fits to the attachment groove 66 of the instrument body 61 . The resilient lower portion of the unit attachment part 68 maintains the state of fitting of the part of the unit 100 or the attached member to the attachment groove 66 . As a result, it is easy for the user to attach the image display unit 100 to the instrument body 61 by fitting the part of the unit 100 or the attached member to the attachment groove 66 , and also the elastic force of the resilient lower portion certainly maintains the state of retaining the image display unit 100 .

An angular position of the image display unit 100 is adjustable around an adjustment axis in the left-and-right direction in which a center line of the circular protrusion 70 extends. As a result, the user can adjust the angular position of the unit 100 to the easiest position to look at a displayed image with mounting the temple parts 40 A and 40 B on the user's ears.

The instrument body 61 has the attachment hole 65 penetrating in the front-and-rear direction. The angular position of the image display unit 100 is adjustable around the adjustment axis by at least 180 degrees. As a result, it is possible for the user to attach the attachment hole 65 to either of the left and right extension members 51 A and 51 B, so that the user may retain the image display unit 100 in either of the left and right sides of the frame 10 with changing the angular position of the unit 100 by 180 degrees.

Both the front part 20 and the connection parts 30 A and 30 B are more rigid than the temple parts 40 A and 40 B. When the user mounts the temple parts 40 A and 40 B on the user's ears, the deformation of the temple parts 40 A and 40 B little affects the front part 20 and the connection parts 30 A and 30 B. Since the image display unit 100 is retained in the extension member 51 A extending in front of the connection portion 45 A in which the rigid connection part 30 A is connected with the temple part 40 A, the image display unit 100 is kept in a fixed position relative to the user's eye.

The slide aperture 46 A extends in the front-and-rear direction along the temple part 40 A, and is opened at its front end portion. The cable holding clip 90 is attached from the opened front end portion and is slidable along the slide aperture 46 A. As a result, it is easy for the user to attach the cable holding clip 90 to the slide aperture 46 A from the opened front end portion. In addition, when the user detaches the image display unit 100 from the extension member 51 A, the cable holding clip 90 connected with the image display unit 100 via the cable 110 slides forward along the slide aperture 46 A, and then is certainly detached from the opened front end portion. Thus, it is easy for the user to detach the image display unit 100 and the cable holding clip 90 from the frame 10 .

The resilient holding arm 94 of the cable holding clip 90 is engageable with the closure portion 47 A which closes the rear end of the slide aperture 46 A. As a result, the cable holding clip 90 is kept at a fixed position in the temple part 40 A, so that the cable 110 is maintained adequately loosening between the image display unit 100 and the cable holding clip 90 .

When the fitting portion 93 of the cable holding clip 90 fits to the slide aperture 46 A, the resilient holding arm 94 is placed in the other side of the temple part 40 A with protruding from the fitting portion 93 , and extends rearward in a direction parallel to the slide aperture 46 A. As a result, when the user slides the cable holding clip 90 along the slide aperture 46 A to engage the resilient holding arm 94 with the holding groove 48 A of the closure portion 47 A, the frictional resistance between the resilient holding arm 94 and the closure portion 47 A is applied in parallel to a extending direction of the holding arm 94 . Thus, the user can smoothly engage the holding arm 94 with the holding groove 48 A, without deformation of the holding arm 94 in a direction intersecting with the extending direction of the holding arm 94 .

The image display unit 100 is retained under the extension member 51 A. The temple part 40 A includes the temple body 42 A and the auxiliary guide member 44 A, which is disposed under the temple part 40 A and extends forward in parallel to the temple part 40 A. The slide aperture 46 A is formed between the temple part 40 A and the auxiliary guide member 44 A. As a result, when the user detaches the image display unit 100 from the extension member 51 A, the cable holding clip 90 slides forward along the slide aperture 46 A and then is detached downward from the slide aperture 46 A. Thus, it is easy and smooth for the user to detach the image display unit 100 and the cable holding clip 90 without the cable 110 caught on the temple body 42 A.

Modifications of Embodiment

Although the embodiment has been described above in detail, the scope of this invention is not limited thereto. It will be appreciated by those of ordinary skill in the relevant art that various modifications may be made without departing from the scope of the invention. We explain several examples of the modifications here. Accordingly, the embodiment disclosed herein is exemplary, and are not limiting the scope of the invention. It is to be understood that the scope of the invention is to be determined by the claims which follow.

In the embodiment, only one connection part may be configured to be fixed to one side of the front part 20 . In this configuration, one temple part is connected with the one side of the front part 20 via the connection part, while the other temple part is connected directly with the other side of front part 20 .

In the embodiment, any type of a device capable of displaying an image to the user may be utilized as the image display unit 10 . For example, there may be utilized a display device having a liquid crystal screen in place of the retinal scanning display. In addition, the optical system for emitting an image light beam includes a lens and a mirror for emitting the image light beam from the image display unit 100 . As the optical system, there may be utilized either of a system equipped with light sources such as laser sources and a system to which light beams are transmitted from light sources via an optical fiber.

Any configuration may be utilized as the retaining mechanism 50 , if it is possible to attach the image display unit 100 to or detach the unit 100 from the extension member 51 A and also to retain the unit 100 at a fixed position in the extension member 51 A, without the unit 100 and the extension member 51 A disassembled or damaged.

In the embodiment, the instrument body 61 is not limited to a configuration that the attachment hole 65 fits to the extension member 51 A from the front direction. For example, the instrument body may be configured to be attached to the extension member from the up-and-down direction or from the left-and-right direction.

In the embodiment, the instrument body 61 is not limited to a configuration having the attachment hole 65 penetrating in the front-and-rear direction. For example, in place of the attachment hole 65 , the instrument body may have a fitting recess which is opened only at its rear end so that the forward portion of the extension member can fit to the fitting groove.

In the embodiment, the forward portion 31 A of the connection part 30 A is limited to a configuration that the forward portion 31 A is always in contact with a part of the instrument body 61 when the user mounts the temple parts 40 A and 40 B on the user's ears with the front end of the extension member 51 A fitting to the attachment hole 65 . For example, the forward portion of the connection part may come into contact with the instrument body so as to prevent the instrument body from moving forward, when the instrument body is moved forward beyond an acceptable limit.

In the embodiment, the extension member 51 A is not limited to a configuration having the notch groove 52 A engageable with the resilient frame attachment part 67 . For example, the extension member may have a projection in its side surface, in place of the notch groove 52 A.

In the embodiment, any configuration may be utilized as the instrument body 61 and the image display unit 100 , if it is possible to attach the image display unit 100 to or detach the unit 100 from the instrument body 61 , without the instrument body 61 and the unit 100 disassembled or damaged.

In the embodiment, any type of a cable may be utilized as the cable 110 , if it is possible to transmit a signal necessary for displaying an image. For example, the cable may be of an optical fiber which transmits light beams such as RGB laser beams in case the control apparatus 200 includes built-in light sources. Alternatively, the cable may be of a signal line which transmits RGB image signals in case the image display unit 100 includes built-in light sources. Further, any configuration may be utilized as the control apparatus 200 . For example, the control apparatus may be configured as an external apparatus to control the display operation of the image display unit 100 . Alternatively, the control apparatus may be configured as an external processing apparatus which can receive a signal such as image data via the Internet or a wireless communication system and then transmit the signal to the image display unit 100 via a connection line, in case the image display unit 100 includes a built-in control device for controlling the display operation.

In the embodiment, the resilient holding arm 94 is not limited to a configuration that the holding arm extends in parallel to the slide aperture 46 A. For example, the holding arm may be configured to extend in a direction intersecting with the slide aperture 46 A and to fit to the closure portion 47 A.

In the embodiment, the image display unit 100 is retained in either of the left and right sides of the frame 10 . The two image display units 100 may be retained in the frame 10 . Namely, one image display unit 100 may be retained in the left side of the frame 10 , and the other image display unit 100 may be retained in the right side of the frame 10 .

In the embodiment, the attachment instrument 60 is attached to the extension member 51 A from the forward portion. The attachment instrument may be attached to the extension member 51 A in the left-and-right direction or in the up-and-down direction. In this modification, it is required to form a groove and a projection to be engaged each other in a direction perpendicular to the attachment direction in which the attachment instrument is attached, in order to prevent the attachment instrument from falling out of the extension member. Further, in the embodiment, the extension member 51 A extends forward from the connection portion 45 A of the temple part 40 A. Alternatively, any forward portion extending in front of the connection portion 45 A may be utilized as the extension member 51 A. For example, the extension member includes the forward portion, and a rearward portion which is connected to the forward portion and extends rearward from the connection portion 45 A. In this modification, the image display unit 100 may be retained in the rearward portion. Furthermore, if the forward portion of the extension member is bent by 180 degrees so as to extend rearward, the attachment instrument may be attached from the rear end of the bent forward portion.

In the embodiment, the attachment instrument 60 is configured to be not in contact with the connection part 30 A, when the attachment instrument 60 comes close to the connection part 30 A by rotation of the temple part 40 A with the attachment instrument 60 retained in the extension member 51 A. Alternatively, a part of the attachment instrument may be pressed by engagement with the connection part. In this modification, when the temple part 40 A is rotated, the bending moment might cause the extension member retaining the attachment instrument to deform. Since the connection part is more rigid than the temple part and the extension member, the extension member deforms within a limited amount according to the shape of the connection part. Thus, the connection part is maintained at a fixed position relative to the connection part, so that the position of the image display unit is hardly changed by the bending moment.

In the embodiment, the attachment instrument 60 includes the instrument body 61 , the slide member 62 , the slide frame 63 and the rotation disk 64 in order to adjust the position of the image display unit 100 in the up-and down direction and in the left-and-right direction as well as the angular position of the unit 100 . If it is not necessary to adjust the position of the unit 100 in the left-and-right direction, the slide member 62 may be connected directly with the unit 100 to be rotatable relative to the unit 100 .

In the embodiment, the front part 20 and the connection parts 30 A and 30 B are different from the temple bodies 42 A and 42 B in constituent materials and cross-sectional shapes. Owing to theses differences, the former are more rigid than the latter. However, either constituent materials or cross-sectional shapes may be different between the former and the latter.

In the embodiment, the attachment instrument 60 of the same shape is attached to either of the left and right extension members 51 A and 51 B. Alternatively, two special attachment instruments may be utilized corresponding to the left and right extension members 51 A and 51 B.