JPH0456934A - Camera shutter device using light shielding fluid - Google Patents

Abstract

PURPOSE:To miniaturize a compact camera by adsorbing and discharging light shielding fluid for a sealed gap enclosed with a pair of lenses and that of lens- barrels. CONSTITUTION:A sealed room 5 is formed with the confronting planes of a pair of convex lenses 3, 4 and the side wall parts of a pair of lens-barrels 1, 2, and a light shielding fluid adsorbing/discharging tube 6 formed along the side wall of the rear lens-barrel 2 is communicated with the sealed room 5. The sealed gap 5 is packed completely with the light shielding fluid in a state where a shutter is closed, and incident light passing a lens aperture is absorbed by the light shielding fluid, and is cut off perfectly. Thence, when the exposure operation of a camera is performed, the light shielding fluid is adsorbed from the sealed gap 5 by operating an adsorbing/discharging means. Thereby, since a shutter device can be formed in space enclosed with the pair of lenses 3, 4 and that of lens-barrels 1, 2, it follows that the major diameter of the shutter coincides with that of the lens-barrel, which enables the camera to be remarkably miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shutter device for performing an exposure operation of a camera. In particular, the present invention relates to a so-called between-shutter device disposed between lens groups suitable for compact cameras.

[Conventional technology]

The structure of a conventional between-shutter device will be briefly explained with reference to the drawings. FIG. 5A is a cross-sectional view of a conventional shutter device taken along the optical axis, and FIG. 5B is a cross-sectional view taken along line BB in FIG. 5A.

As shown in the figure, the conventional shutter device has a pair of light shielding blades 2.
1 and 22. A pair of light shielding blades 21
and 22 are arranged between the front group lens 23 and the rear group lens 24, and open and close the lens aperture.

The front group lens 23 is supported by the front lens barrel 25,
The rear group lens 24 is supported by a rear lens barrel 26.

Flanges are formed on opposing end surfaces of the front lens barrel 25 and the rear lens barrel 26, and when they are combined, the shutter chamber 2
7. In this shutter chamber 27, a pair of light shielding blades 2
1 and 22 are housed, forming a so-called between shutter. The light shielding blades 21 and 22 are rotatably supported by a bin 28 at their peripheral portions.

FIG. 5B shows a case where the shutter device is in a fully closed state. As shown in the figure, the pair of light shielding blades 21 and 22 are arranged so as to overlap each other in the central portion, completely shielding the lens aperture 29. In order to perform the exposure operation in this state, the pair of light shielding blades 21 and 22 are rotated in opposite directions about the pin 28. That is, the front lens barrel 25
The lens travels along the flange portion of the lens, opens the lens opening 29, and is retracted to the flange portion. The 20 rotation operation is performed by driving the pair of light shielding blades 21 and 22 using an actuator (not shown).

[Problem to be solved by the invention]

In the above-mentioned conventional between-shutter device, since the pair of light-shielding blades 21 and 22 are retracted from the lens opening 29 in opposite directions to perform the exposure operation, a storage space is required for the retracted state of the light-shielding blades, and the shutter There is a problem in that the outer diameter of the device is significantly larger than the lens aperture diameter, that is, the fully open effective diameter. That is, the outer diameter of the shutter has to be increased by the outer diameter of the flange portion forming the shutter chamber 27. This poses a major obstacle in reducing the size of compact cameras.

In order to achieve miniaturization, for example, a structure in which each light shielding blade is divided has been proposed. However, if the light shielding blades are divided, a problem arises in that the driving mechanism thereof becomes complicated. At the same time, it is also necessary to downsize the actuator for driving the light shielding blades. However, when the actuator is made smaller, its output torque inevitably decreases, which hinders the high-speed running of the light-shielding blades, and there are problems such as variations in exposure amount due to differences in posture.

[Means for solving problems]

In view of the problems of the conventional mechanical between-shutter device described above, an object of the present invention is to provide a between-shutter device using a light-shielding fluid and having a structure suitable for a compact camera.

A camera shutter device according to the present invention is arranged in a combination structure of a lens group and a lens barrel that supports the lens group. A particular pair of adjacent lenses selected from the lens group and the side wall of the lens barrel form a sealed chamber. That is, a sealed gap is formed between the opposing lens pair. The size of this gap is set to increase from the center of the lens toward the periphery. Further, a suction/discharge means is connected to the sealed chamber, and is adapted to suction and discharge the light-shielding fluid into the gap.

Preferably, the suction/exhaust means includes a suction/exhaust pipe disposed along the side wall of the lens barrel and communicating with the periphery of the sealed cavity, and a suction/exhaust pump connected to the suction/exhaust pipe. Further, the selected specific lens pair has opposing lens surface shapes selected from a combination of convex and flat, concave and convex, and convex and convex.

[For production]

In the above-described structure, the sealed gap is completely filled with the light-blocking fluid when the shirt shirt is closed. Therefore, incident light passing through the lens aperture is absorbed by the light shielding fluid and completely blocked. Next, when performing an exposure operation of the camera, the suction/discharge means is activated to suck the light-shielding fluid from the sealed gap. At this time, since the gap size is set to increase from the center of the lens toward the periphery, the light-shielding fluid moves from the center of the lens opening toward the periphery. That is, the lens aperture begins to open from the center toward the periphery.

After the desired amount of exposure is obtained, the suction/discharge means is operated in the opposite direction to discharge the suctioned light-shielding fluid into the sealed gap. As a result, the sealed gap is again completely filled with the light-shielding fluid and the exposure operation is completed.

〔Example〕

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1A shows a schematic cross-sectional view along the optical axis of a camera shutter device that uses a light-shielding fluid, and FIG.
FIG. 3 is a cross-sectional view taken along the line BB shown in FIG. A. FIG. As shown in the figure, the camera shutter device includes a camera lens group consisting of a plurality of lenses. This lens group is divided into a front group located on the subject side and a rear group located on the film side. The front group is supported by the front lens barrel 1, and the rear group is supported by the rear lens barrel 2. At the rearmost end of the front lens barrel 1, a specific front group convex lens 3 is arranged. Further, a specific rear group convex lens 4 is arranged at the frontmost end of the rear lens barrel 2. That is, the front group convex lens 3 and the rear group convex lens 4 are arranged opposite to each other with a predetermined gap interposed therebetween. In addition, the rear end surface of the front lens barrel 1 and the front end surface of the rear lens barrel 2 are coupled to each other. Therefore, the opposing surfaces of the pair of convex lenses 3 and 4 and the pair of lens barrel 1
A sealed chamber 5 is formed by the side wall portions 2 and 2. A light-shielding fluid intake/exhaust pipe 6 formed along the side wall of the rear lens barrel 2 communicates with the sealed chamber 5 .

As shown in FIG. 1B, the aforementioned sealed chamber 5 is formed in a portion surrounded by the annular side wall of the lens barrel 1.

A lower lens opening is located in the center of this sealed chamber 5. In this embodiment, four light-shielding fluid intake/exhaust pipes 6 are formed, and the communication holes of each intake/exhaust pipe are formed at equal angular intervals around the periphery of the sealed chamber 5. However, the structure of the light-shielding fluid intake and exhaust pipe is not limited to the illustrated example, and it is sufficient that at least one communication hole 8 connected to the sealed chamber 5 is formed. Furthermore, when a plurality of communication holes are formed, the light-shielding fluid may be sucked and discharged from a common suction and discharge pipe via branch pipes.

As described above, since the shutter device according to the present invention is formed in a space surrounded by a pair of lenses and a lens barrel, the outer diameter of the shutter coincides with the outer diameter of the lens barrel, allowing for significant miniaturization.

Next, the surface shape of the pair of lenses defining the air gap will be described with reference to FIGS. 2A to 2C. In the example shown in FIG. 2A, a combination of a convex lens 3 and a flat lens 4 is used. That is, the opposing surfaces of the lens pair have a convex shape and a flat shape, and the dimensions of the gap 5 are set so as to increase from the center of the lens toward the periphery.

In the example shown in FIG. 2B, convex lens 3 and convex lens 4
A combination of is used. That is, each of the pair of opposing surfaces has a convex shape, and the size of the gap 5 similarly increases from the center of the lens toward the periphery.

Furthermore, in the example shown in FIG. 2C, a combination of a convex lens 3 and a concave lens 4 is used.

That is, one of the pair of opposing surfaces has a convex shape and the other has a concave shape. In this case, since the radius of curvature of the convex plane is set smaller than the radius of curvature of the concave plane, the size of the gap 5 similarly increases from the center of the lens toward the periphery.

With this structure, the light-shielding fluid filled in the sealed gap 5 can move from the center toward the periphery in accordance with the suction operation, and the lens aperture can be continuously enlarged. Conversely, as the light-shielding fluid is discharged into the sealed gap, the fluid moves from the periphery toward the center, thereby shielding the lens aperture. The shutter mechanism using such a light-shielding fluid utilizes the surface tension of the fluid itself, and in particular, it has a structure in which the size of the sealed gap increases from the center toward the periphery, so that the lens aperture can be continuously shielded. I can do it. For this reason, mercury, for example, is used as the light shielding fluid. Mercury has a large surface tension and can completely block incident light m-t.

As another example, a mixture of a light shielding substance and a viscous fluid may be used.

Finally, the operation of the shutter device according to the present invention will be explained in detail with reference to FIGS. 3A to 4B.

FIG. 3A shows the closed cavity completely filled with light shielding fluid 9. FIG. As shown in the figure, a suction/drainage pump 10 is connected to the suction/drainage pipe 6, and the pump 10 is operated to discharge the light shielding fluid 9 into the sealed space via the suction/drainage pipe or the communication pipe 6.
We will introduce the following. When mercury is used as the light shielding fluid 9, a mercury pump is used as the suction/discharge pump IO.

FIG. 3B shows the exposure operation of the shutter device. When the suction/discharge pump IO is operated to perform a suction operation, the light-shielding fluid 9 is suctioned from the sealed gap 5 through the communication pipe 6 . At this time, the light shielding fluid 9 moves from the center of the lens aperture toward the periphery. An opening is formed in the center according to the amount of movement, and the incident light passes through.

By controlling the suction amount of the suction pump 10, the effective opening diameter can be specified, and by controlling the suction holding time of the suction pump 10, the exposure time can be specified. Therefore, a programmed shutter can be easily obtained by controlling the operation of the suction pump [1] according to the brightness of the subject. Incidentally, when the exposure operation is completed, the suction/drainage pump IO performs the evacuation operation again to fill the sealed gap 5 with the light shielding fluid 9 to completely shield the lens aperture.

FIG. 4A is a schematic diagram showing changes in the shape of the shutter opening during the exposure operation. As shown in the figure, the opening shape changes in concentric circles in the radial direction from the center to the periphery. This change is exactly the same as in the conventional shutter device using light-shielding blades.

FIG. 4B is a graph showing the relationship between the elapsed time and the aperture diameter during the exposure operation of the shutter device according to the present invention.

As shown in the figure, the shutter aperture diameter begins to expand rapidly at the start of exposure, and the expansion speed decreases as time passes. That is, since the sealed gap size is set to increase from the center of the lens toward the periphery, the light-shielding fluid moves at high speed in the center and at a low speed in the periphery. Therefore, ideal exposure operations can be performed.

〔Effect of the invention〕

As explained above, according to the present invention, the structure is such that the shutter operation is performed by suctioning and discharging the light-shielding fluid into the sealed gap surrounded by the pair of lenses and the lens barrel, so the conventional light-shielding blades are not used. Compared to the conventional mechanical shutter structure, the outer diameter of the shutter can be significantly reduced, which is highly effective in contributing to the miniaturization of compact cameras. Further, since a pump or the like for suctioning and discharging the light-shielding fluid can be connected via a communication pipe, there is a great degree of freedom in its arrangement. Therefore, unlike the conventional mechanical shutter structure, there is no restriction that the actuator must be placed near the light-shielding blade, and the outer diameter of the shutter can be omitted and miniaturized to the extent that it matches the outer diameter of the lens mirror. be. In addition, since the dimensions of the sealed gap are set to expand from the center toward the periphery, the shutter opening expands concentrically and rises quickly, allowing ideal exposure operation to match the brightness of the subject. It has the effect of being able to do things.

[Brief explanation of the drawing]

FIG. 1A is a sectional view taken along the optical axis of the shutter device according to the present invention, FIG. 1B is a sectional view taken along line BB shown in FIG. 1A, and FIGS. 2A to 2C are sealed Figures 3A and 3B are schematic diagrams showing examples of cross-sectional shapes of air gaps, and Figure 4A is a schematic diagram for explaining the operation of the shutter device according to the present invention.
is a schematic diagram showing changes in the aperture shape of the shutter device according to the present invention, FIG. 4B is a graph showing changes over time in the aperture diameter of the shutter device according to the present invention, and FIG. 5A is a diagram showing the conventional shutter device along the optical axis. and FIG. 5B is a cross-sectional view taken along line BB of the conventional shutter device shown in FIG. 5A. 1... Front lens barrel 3... Front group convex lens 5... Sealed chamber 7... Lens opening 9... Light shielding fluid

Claims (1)

[Claims] 1. A lens group, a lens barrel that supports the lens group, and a sealed space surrounded by a pair of adjacent lenses included in the lens group and a side wall of the lens barrel. A camera shutter device comprising a sealed chamber whose gap size increases from the center of the lens toward the periphery, and suction/discharge means for sucking and discharging a light-shielding fluid into the sealed chamber. 2. The camera shutter device according to claim 1, wherein the suction/drainage means comprises a suction/drainage pipe arranged along the side wall of the lens barrel and communicated with the periphery of the sealed gap, and a suction/drainage pump connected to the suction/drainage pipe. 3. The camera shutter device according to claim 1, wherein the lens pair has opposing lens surface shapes selected from a combination of convex and flat, convex and convex, and concave and convex.