Aperture unit controlled by magnetic field and a heater embeded in a cylindrical member and imaging system using same

1. Technical Field

The present disclosure relates to optical imaging and, particularly, to an aperture unit and an imaging system using the aperture unit.

2. Description of Related Art

In imaging technologies, an aperture admits light into a system for a distinct period of time, to expose photographic film or a light-sensitive electronic sensor to the amount of light required to capture an image. As the value of the aperture increases, the amount of light admitted increases accordingly. Imaging systems often employ apertures of fixed value. This is inconvenient when the imaging system is applied in different environments.

Therefore, what is needed is an aperture unit and an imaging system using the same, which can overcome the limitations described.

In the drawings, all the views are schematic.

FIG. 1 is a cross-section of a first embodiment of an imaging system, according to the disclosure.

FIG. 2 is a view of a cylindrical member of an aperture unit of the imaging system shown in FIG. 1 , showing the cylindrical member in a first state.

FIG. 3 is similar to FIG. 2 , but showing the cylindrical member in a second state.

FIG. 4 is a cross-section of a second embodiment of an imaging system, according to the disclosure.

FIG. 5 is a cross-section of a third embodiment of an imaging system, according to the disclosure.

Referring to FIG. 1 , a first embodiment of an imaging system 100 according to the disclosure includes a lens unit 20 , a holder 30 , an aperture unit 40 , an image sensor 50 , a control unit 10 , and a circuit board 60 . The aperture unit 40 and the image sensor 50 are arranged in the holder 30 . The control unit 10 is electrically mounted on the circuit board 60 .

The lens unit 20 includes a barrel 21 , a lens 22 , a spacer ring 23 , and a filter 24 . The lens 22 , the spacer ring 23 , and the filter 24 are arranged in the barrel 21 in that order from the object side to the image side of the lens unit 20 . The barrel 21 is threadedly engaged with the holder 30 .

The aperture unit 40 includes a cylindrical member 41 , magnetic fluid 45 , a heater 460 and a magnetic field generator 43 . The cylindrical member 41 includes an upper plate 410 , a lower plate 420 parallel to the upper plate 410 , and a hollow cylinder 430 . The hollow cylinder 430 connects the upper plate 410 to the lower plate 420 to cooperatively define a cylindrical chamber 440 . The magnetic fluid 45 is received in the chamber 440 . The heater 460 is embedded in the hollow cylinder 430 , and operable to heat the magnetic fluid 45 in the chamber 440 . The upper plate 410 and the lower plate 420 are transparent and the hollow cylinder 430 can be opaque. The cylindrical member 41 with the magnetic fluid 45 and the heater 460 is positioned between the lens unit 20 and the image sensor 50 . The circuit board 60 is positioned between the image sensor 50 and the magnetic field generator 43 .

Further referring to FIG. 2 and FIG. 3 , the magnetic fluid 45 includes a solvent 452 , a plurality of magnetic nano-particles 454 dispersed therein, and a surfactant (not shown). The solvent 452 is transparent. The solvent 452 is water, alcohol, methanol, hexamethylene, or octane. The nano-particles 454 are small enough to permit transparency of the solvent 452 when evenly dispersed therein. In the present embodiment, the nano-particles 454 are ferrosoferric oxide nano-particles or manganese zinc ferrite nano-particles. Diameters of the nano-particles 454 are in the range from about 10 nanometers (nm) to about 100 nm. A weight percentage of the nano-particles 454 in the magnetic fluid 45 is in the range from about 1% to about 4%. Each of the nano-particles 454 is enveloped by the surfactant to allow even dispersal thereof in the solvent 452 when no magnetic field is applied. In FIGS. 1 and 2 , the aperture unit 40 is shown in an initial (fully transmissive) state. The surfactant is polyvinyl alcohol, oleic acid, linoleic acid, or olive oil. Light passing through the lens unit 20 , the upper plate 410 , the magnetic fluid 45 , and the lower plate 420 arrives at the image sensor 50 in this exemplary embodiment.

The heater 460 is a resistance heater in this exemplary embodiment. When the heater 460 is activated, it enhances the diffusion speed of the nano-particles 454 in the solvent 452 . Accordingly, the transparent magnetic fluid 45 with the nano-particles 454 uniformly dispersed in the solvent 452 is quickly generated. The heater 460 is electrically connected to the circuit board 60 and the control unit 10 and activated by the control unit 10 .

The image sensor 50 can be a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device, and is mounted on and electrically connected to the circuit board 60 . In the present embodiment, the circuit board 60 is a printed circuit board.

The magnetic field generator 43 magnetizes the magnetic fluid 45 . The magnetic field generator 43 includes an annular electromagnet 431 and a coil 433 wound therearound. The coil 433 is electrically connected to the circuit board 60 and the control unit 10 and activated by the control unit 10 . A magnetic field is generated by the electromagnet 431 when the coil 433 is electrified, and the magnetic field is absent when the coil 433 is not electrified.

In operation of the imaging system 100 , in an initial state, the nano-particles 454 are dispersed evenly in the solvent 452 , as shown in FIGS. 1 and 2 . The magnetic fluid 45 is, at this time, substantially fully transparent, and light passes through the lens unit 20 , the upper plate 410 , the magnetic fluid 45 , and the lower plate 420 substantially unimpeded to arrive at the image sensor 50 . At this time, the aperture unit 40 has a large value.

Referring to FIG. 3 , in a second state, the coil 433 is electrified by the control unit 10 , and the electromagnet 431 of the magnetic field generator 43 generates a magnetic field. The nano-particles 454 are attracted by the magnetic field to form an annular nano-particle layer 490 on an inner surface of the lower plate 420 . As a result, light passing from the upper plate 410 is partially blocked by the nano-particle layer 490 , and arrives at the image sensor 50 . At this time, the aperture unit 40 has a small value.

Referring to FIG. 1 again, when the coil 433 is not electrified by the control unit 10 , the magnetic field is absent, and the nano-particles 454 of the nano-particle layer 490 are substantially uniformly diffused in the solvent 452 by random diffusion. Further, the heater 460 is activated by the control unit 10 to speed the diffusion of the nano-particles 454 in the solvent 452 . In summation, the imaging system 100 can controllably achieve two aperture values in the illustrated embodiment. Furthermore, the imaging system 100 can achieve a desired variety of discrete aperture values by the control unit 10 appropriately controlling the strength of the magnetic field generated by the magnetic field generator 43 .

Referring to FIG. 4 , a second embodiment of an imaging system 100 a is shown. The imaging system 100 a differs from the imaging system 100 basically only in the structure and arrangement of a magnetic field generator 43 a thereof.

The magnetic field generator 43 a includes a first annular electromagnet 431 a , a first coil 433 a wound around the first electromagnet 431 a , a second annular electromagnet 431 b , and a second coil 433 b wound around the second electromagnet 431 b . The first electromagnet 431 a , the first coil 433 a , the second electromagnet 431 b and the second coil 433 b are arranged coaxially.

When the first coil 433 a and the second coil 433 b are electrified by a control unit 10 a , the first electromagnet 431 a and the second electromagnet 431 b generate a magnetic field. Accordingly, nano-particles 454 a are attracted by the magnetic field, and a double annular nano-particle layer 491 is formed on an inner surface of a lower plate 420 a . The double annular nano-particle layer 491 includes a first annular nano-particle layer 490 a , and a second annular nano-particle layer 490 b coaxially within the first annular nano-particle layer 490 a.

Advantages of the imaging system 100 a of the second exemplary embodiment are similar to those of the imaging system 100 of the first exemplary embodiment. Furthermore, the imaging system 100 a can achieve a desired variety of discrete aperture values by the control unit 10 a appropriately controlling the strength of the magnetic field generated by the magnetic field generator 43 a . In particular, the strength of the magnetic field generated by the first electromagnet 431 a can be controlled independently of the strength of the magnetic field generated by the second electromagnet 431 b , or in unison with the strength of the magnetic field generated by the second electromagnet 431 b , and vice versa. Thereby, a wide variety of formations of the double annular nano-particle layer 491 can be obtained.

Referring to FIG. 5 , a third embodiment of an imaging system 100 c is shown. The imaging system 100 c differs from the imaging system 100 basically only in that a magnetic field generator 43 c further includes a second annular electromagnet 431 c and a second coil 433 c wound around the second electromagnet 431 c coaxially. The second electromagnet 431 c surrounds a hollow cylinder 430 c . The second coil 433 c is electrically connected to a control unit 10 c . The control unit 10 c is configured for electrifying the coil 433 and the second coil 433 c.

When only the second coil 433 c is electrified by the control unit 10 c , the second electromagnet 431 c of the magnetic field generator 43 c generates a magnetic field to which nano-particles 454 c are attracted. A second annular nano-particle layer 490 c is formed accordingly on an inner surface of the hollow cylinder 430 c . The inner diameter of the second annular nano-particle layer 490 c is different from that of the annular nano-particle layer 490 formed only by the electromagnet 431 . That is, the second annular nano-particle layer 490 c is formed differently from the annular nano-particle layer 490 , under control of the control unit 10 c.

Advantages of the imaging system 100 c of the third exemplary embodiment are similar to those of the imaging system 100 of the first exemplary embodiment. Furthermore, the imaging system 100 c can achieve a desired variety of discrete aperture values by the control unit 10 c appropriately controlling the strength of the magnetic field generated by the magnetic field generator 43 c . In particular, the strength of the magnetic field generated by the electromagnet 431 can be controlled independently of the strength of the magnetic field generated by the second electromagnet 431 c , or in unison with the strength of the magnetic field generated by the second electromagnet 431 c , and vice versa. Thereby, a wide variety of formations ranging between the nano-particle layer 490 and the second annular nano-particle layer 490 c can be obtained.

It is to be understood, however, that even though numerous characteristics and advantages have been described with reference to particular embodiments, the present invention is not limited to the particular embodiments described and exemplified, and the embodiments are capable of considerable variation and modification without departure from the scope and spirit of the appended claims.