JPS63148243A - Device for preventing imprint of lens sticking matter - Google Patents

Abstract

PURPOSE:To prevent a foreign matter from being imprinted by advancing an ND filter to the center part of a lens under specific condition where the foreign matter is imprinted and using a program consisting of a stop aperture larger than that before the ND filter is interposed and corresponding shutter speed when the ND filter is interposed. CONSTITUTION:A control circuit 15 receives an input from a detector such as a focal length detector 16, an object distance detect 17, and a stop value detector 18 and supplies operation signals to a program circuit 19 and a swing actuator 13. Namely, a stop value, focal length range, or focal length has the probability of foreign matter imprinting, the control circuit 15 supplies the operation signal to the swing actuator 13 to put the ND filter 11 on the optical path. At the same time, an instruction for determining exposure according to a program chart which is shifted to an EV value side where the stop aperture is large is supplied to the program circuit 19. Consequently, the probability that foreign matter sticking on the rear part of a lens system is imprinted in a picture plane is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a device for preventing minute foreign matter such as dust attached to a camera lens system from being imprinted on a screen.

"Prior art and its problems" In a normal camera, even if foreign matter such as dust adheres to the lens system, if it is minute, it will not be reflected on the screen.This is because the light rays that control the screen On the other hand, the area occupied by dust is small, and the dust image becomes blurred due to the phenomenon of light diffraction.

However, in the zoom lens currently being developed by the applicant,
The position of the exit point is very close to the film surface at one focal length end. For this reason, it has been found that when the lens system approaches the film surface at a small aperture where the exit l diameter is below a certain value, dust attached to the center of the rearmost lens system is imprinted on the screen. .

FIGS. 4(A), (8), and (C) are schematic diagrams for explaining this problem. Figures (A) and CB) depict the state in which the lens system is closest to the film surface F, and the state in which it is not imprinted as a black dot and the state in which it is imprinted, respectively. When a foreign object Q of dφ is attached to the center, if the exit pupil P of the lens system is small and the distance from the rear end of the lens system to the film surface F is small, the center of the film surface " Foreign matter Q (this causes a phenomenon of a decrease in the amount of light. This decrease in the amount of light is the phenomenon of foreign matter imprinting. Foreign matter Q has a size of 0.3 mm diameter, which is likely to stick when handled in an overcrowded manner. Assuming that, the minimum injection distance P that cannot be recognized as a foreign object is, for example, F 13.5 (in the case of (A) in the same figure),
When the FI exceeds 3.5 (for example, F22), it is clearly recognized as a foreign substance ((B)).

On the other hand, if the lens system is moved forward as shown in FIG. 3C, even if the aperture diameter is the same as that of F22, the problem of light intensity reduction due to foreign matter Q will not occur.

It is thought that this movement of the lens system and the exit pupil toward the maximum position is expanding as the zoom magnification of the lens system increases and the lens system becomes more compact.The above phenomenon of foreign matter imprinting is There is a possibility of forming a film. Also, in a type of camera that obtains long and short bifocal focal lengths M by moving the focus switching lens forward and backward within the optical path,
Similar problems may arise.

``Object of the Invention'' The present invention is based on the discovery of such problems regarding the imprinting of foreign objects.
[The purpose is to obtain.]

"Summary of the Invention" The present invention provides that under specific conditions where foreign matter is imprinted,
It was completed based on the idea of opening the aperture of the program shutter by moving the ND filter to the center of the lens, which means that under any conditions, the aperture value would not reach a value that would cause foreign objects to be photographed. It is something.

That is, the present invention is a program shutter type camera equipped with a zoom lens system or a long/short bifocal switching lens system. In a camera that captures images on film in a specific focal length M range or in combination with a focal length, an ND filter is provided in the optical path of the lens system so that it can move forward and backward, and this ND filter is moved to In the aperture value and focal length or focal length M range, the actuator is used to advance the optical path of the lens system, and the program diagram of the program shutter is roughly determined according to the amount of light transmitted through this ND filter. It is characterized by different settings for when it is not inserted and when it is inserted.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a conceptual diagram of the mechanical configuration of the device of the present invention.

Inside the lens system, a swinging arm 12 having a No. filter 11 at its tip is provided near the part where the optical path is most narrowed down. The outer end of this swinging arm 12 is connected to the swinging shaft )4 of a swinging actuator 13, and when the swinging actuator]3 is driven, the No. filter 1
1 (swing arm 12) swings back and forth by an angle θ between an advanced position 11E toward the center of the lens system and a retracted position. The swing actuator 13 may be one that swings by turning on and off a magnet, for example.

The diameter of the No. filter 11 is set to be at least larger than the diameter corresponding to the diameter of the injection II violet P where the imprint of the foreign matter Q becomes a problem. The swing arm 12 is made of a transparent material, is placed in a position where it will not be imprinted on the screen, or has a diameter or width set to a size that will not be imprinted on the screen. Of course, the swing actuator 13 is also arranged in a position where it will not be imprinted, but for this purpose, the swing shaft 14 of the swing actuator 13 and the outer end of the swing arm 12 are aligned with the optical axis. It is possible to take measures such as connecting with an interlocking bar in a direction parallel to.

The No. 1 filter 11, the swing arm 12, and the swing actuator 13 are supported within a lens barrel that supports the lens system Lt, and move in the optical axis direction together with the lens system by the zooming operation.

Fig. 2 shows a program diagram of the program shutter according to the present invention, and Fig. 3 shows a program diagram when the problem of foreign object imprinting does not occur. TO° to T
If the problem of foreign matter imprinting does not occur, as shown in figure 3, when the shutter speed changes to the highest 1/250 second, as shown in figure 3, Interlocking EV value (-) Matsu EV You can control exposure from EV 9 (WIDE end, TOo) to EV18, 75 (E end, T7").

However, in the above example, at TO' at the WIDE end, if the aperture value is F1a, 5 or less, the problem of foreign matter imprinting occurs. Therefore, in the present invention, the region S in FIG. 3 that does not include F1a, 5 or less is regarded as the foreign object imprinting region, and when this region is reached, the program diagram of the program shutter is changed as shown in FIG. According to the amount of light transmitted through the ND filter 11, the exposure is controlled by shifting to a lower EV value side with a smaller aperture value (larger aperture).

The region S is determined based on approximately 1/190 seconds, which is the shutter speed on the diagram where TO becomes F1a, 5, and the maximum EV value that results in the same shutter speed. Therefore, the minimum aperture value increases with T1, T2, . . . T7.

Since the rearmost lens system generally moves forward when moving to the E side, there is little chance of foreign matter being captured even if the aperture value is around F42.
On the side, the shutter speed is approximately 1/190 seconds IF.
! : Used as a standard.

The control circuit 15 shown in FIG.
6. In response to inputs from composition devices such as the subject distance detection device 17 and the aperture value detection device 18, an operation signal is given to the program circuit 19 and the swing actuator 13. In other words, when the aperture value (and focal length M range or focal length M) is a value that does not have the possibility of foreign matter imprinting, the swing actuator 1
No operating signal is given to ND filter 3, and the ND filter 11 is not allowed to advance into the optical path. At this time, the program circuit 19 gives an instruction to control exposure based on a normal program diagram.

On the other hand, in a state where there is a possibility that a foreign object may be imprinted, the control circuit 15 gives an operation signal to the swing actuator 13, and the ND filter 11! Advance into the light path. At the same time, an instruction is given to the program circuit 19 to determine exposure based on the program diagram shifted to the EV value side with a smaller aperture value.

FIG. 2 is an example in which the light transmittance of the ND filter 11 is 25%. Taking the same case at the WIDE end as an example, when the aperture value exceeds F1a, 5 (EV 15), the ND filter ]1 advances into the optical path. From then on, exposure is controlled by the area in which the EV value is shifted by 1.75 degrees to the lower aperture value side. That is, when the EV becomes 15.25 as a result of shifting to the lower EV value side, the aperture value becomes approximately F8.5 and the aperture becomes larger, thereby avoiding the problem of foreign matter imprinting. The shutter speed at this time is approximately 1/13
Although it is slower at 5 seconds, there is no practical problem, and with TO, exposure control is possible up to EVI 7. If F1a again
, 5, it is possible to shift the program diagram to the low EVi side again by stacking the ND filters or replacing them with ND filters with lower transmittance. By turning this around, it is also possible to photograph a subject with a high EV value.

The above is an explanation about TO at the WIDE end, but ■1
The story is exactly the same for ~T7. The maximum EV value is
In this example, it is 18.75 for T7 at the E end.

The above is an example of a zoom lens system, but in a bifocal Eve camera, only when a switching lens is inserted where foreign matter imprinting becomes a problem, an ND filter is inserted and a low EV value of the program diagram is used. All you have to do is shift to the side.

"Nine Achievements of the Invention" As described above, according to the device of the present invention, in a specific combination of the position of the lens system and the aperture value, there is a possibility that foreign matter attached to the rear part of the lens system will be imprinted on the screen. You can reduce it. In particular, the present invention prevents the diaphragm aperture from dropping below a certain value by advancing the ND filter into the optical path, thereby preventing the imprinting of foreign matter without lowering the controllable EV value to a low level. can.

[Brief explanation of the drawing]

FIG. 1 is a front view of the main parts showing an example of the mechanical configuration of the device of the present invention, FIG. 2 is a program diagram showing an example of a program for the program shutter used in the device of the present invention, and FIG. A program diagram showing an example of a program when there is no problem; Figures 4 (A), (8), and (C) are optical paths showing how foreign objects are imprinted by a combination of a specific aperture value and a specific lens system position. and a light amount distribution diagram. 11... ND filter, 12... Swinging arm, 13
... Rocking actuator, ]5 ... Program circuit, ... Lens system, P ... Injection g violet, Q ... Foreign object, F ... Film surface. Patent Applicant Asahi Kogaku Kogyo Co., Ltd. Agent Kunio Miura Shigeto Matsui Yoshimi Sasayama'z*-+Q zc'-V Sha99゛fu, hey Fig. 3 Teitosaneichi-IJE? ! ;F (voluntary) 1986
September 1 (l,■ Patent Office Director General Kunio Kawa
! “Sa1, '1 Display of 1986 Patent Application No. 296175 2, Name of invention Name of device for preventing reflection of lens deposits (052) Asahi Optical Co., Ltd. Representative Toru Matsumoto 5, Target of correction Column for the title of the invention, the full text of the specification, and Drawing 6, contents of the amendment (1. Description amending the name of the invention to "Device for preventing reflection of deposits on a lens" (corrected full text) 1. Name of the invention Lens Apparatus 2 for preventing reflection of deposits, Claims (1) A programmable shutter type camera equipped with a zoom lens system or a long/short bifocal switching lens system, comprising: an ND filter that can move forward and backward into the optical path of the zoom lens system; , an actuator for advancing this ND filter into the optical path of the zoom lens system, and when inserting this ND filter, depending on the transmitted light 11, an aperture aperture larger than the millimeter in which this ND filter is inserted and a corresponding shutter speed are provided. 3. Detailed Description of the Invention "Technical Field J The present invention is directed to the prevention of dust, etc. adhering to the lens system of a camera. [Prior art and its problems] In a normal camera, even if foreign matter such as dust adheres to the lens system, if it is minute, it will be removed. The dust does not appear on the screen.This is because the dust occupies a small area relative to the light rays that control the screen, and the dust image becomes blurred due to light diffraction.However, in the zoom lens currently being developed by the applicant. teeth,
The position of the exit pupil approaches the film surface side greatly at one focal length tlQ. For this reason, it has been found that when the lens system approaches the film surface in the case of small patterns where the exit pupil diameter is greater than a certain value, dust adhering to the center portion of the rearmost lens system is reflected on the screen. FIGS. 4(A), 4(B), and 4(C) are schematic diagrams for explaining this problem. Same figure (A), (B)
is a state in which the lens system is closest to the film plane F (at the shortest focal length Il), and shows the state in which it does not appear as a sunspot and the state in which it appears in the image. When a foreign substance Q of dφ is attached to
If the exit pupil P of the lens system is small and the distance from the rear end of the lens system to the film plane F is small, the film plane F
A phenomenon in which the amount of light decreases due to the foreign substance Q occurs in the center of the image. This decrease in light intensity is the phenomenon of foreign matter being reflected. As a foreign substance Q,
Assuming an object with a diameter of 0.3 mm that is likely to adhere during normal handling, the minimum exit pupil P that cannot be recognized as a foreign object is F 13.5 (see the same figure).
(8)), and if the aperture is smaller than this (for example, F22), it is clearly recognized as a foreign object (in the case of (8)).
B)). On the other hand, as shown in the same figure (C), when the lens system is moved to the long focus side, foreign particles may be detected even if the aperture diameter is the same as F22 on the short focus side. The problem of light intensity reduction due to Q does not occur. In other words, if the distance between the lens system and the film surface is a certain value or more, the foreign object Q will not appear in the image. This movement of the lens system and the exit pupil to the rearmost position is thought to be in the direction of expansion as the zoom magnification of the lens system increases and the lens system becomes more compact. There is a possibility of generalization. Also, in a type of camera that obtains long and short bifocal focal lengths by moving the focus switching lens forward and backward within the optical path,
Similar problems may arise. ``Object of the Invention'' The present invention is based on the discovery of the problem of foreign matter reflection in a programmable lens shutter camera having a zoom lens, and an object of the present invention is to provide an apparatus in which foreign matter is not reflected in the camera. “Summary of the Invention” The present invention provides that under specific conditions in which foreign objects are reflected, ND
In addition to advancing the filter to the center of the lens, when inserting this ND filter, a program consisting of a combination of a larger aperture aperture and a corresponding shutter speed than before inserting the ND filter is used to increase the aperture value at which foreign objects are captured. It was completed based on the idea of preventing this from happening. That is, the present invention provides a programmable shutter type camera equipped with a zoom lens system or a long/short bifocal switching lens system, which includes an ND filter that can move forward and backward into the optical path of the zoom lens system, and an ND filter that is placed in the optical path of the zoom lens system. When the ND filter is inserted, the exposure is controlled by a program that combines an aperture aperture larger than the one at which the ND filter is inserted and a shutter speed corresponding to the aperture aperture, depending on the amount of transmitted light. This is a characteristic feature. "Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a conceptual diagram of the mechanical configuration of the device of the present invention. Inside the lens system, a swinging arm 12 having an ND filter 11 at its tip is provided near the part where the optical path is most narrowed down. The outer end of this swing arm 12 is connected to a swing shaft 14 of a swing actuator 13, and when the swing actuator 13 is driven, the ND filter 1
1 (swing arm 12) swings back and forth by an angle θ between an advanced position E toward the center of the lens system and a retracted position R. The swing actuator 13 may be one that swings by turning on and off a magnet, for example. The diameter of the ND filter 11 is set to be at least larger than the diameter corresponding to the diameter of the exit pupil P where reflection of the foreign matter Q becomes a problem. The swing arm 12 is made of a transparent material, is placed in a position where it will not be imprinted on the screen, or has a diameter or width set to a size that will not be imprinted on the screen. Swing actuator 1
3 is of course arranged at a position where it will not be reflected in the photograph, but for this reason, the swing shaft 14 of the swing actuator 13 is
It is possible to take measures such as connecting the oscillating arm 12 and the outer end of the swinging arm 12 with an interlocking bar in a direction parallel to the optical axis. The ND filter 11, the swing arm 12, and the swing actuator 13 are supported within a lens barrel that supports a lens system, and move in the optical axis direction together with the lens system during a zooming operation. FIG. 2 shows a program diagram of the program shutter according to the present invention, and FIG. 3 shows a program diagram in the case where the problem of foreign object reflection does not occur. The program diagram in Figure 3 shows that T
It is a figure when it changes in 8 steps of O degree - T7'. If the problem of foreign matter reflection as mentioned above does not occur, the third
As shown in the figure, from EV 9 (ll[DE end, TOo) to E
Exposure can be controlled up to V 19.75 (position E end, T7°). However, in the above example, when the aperture value is F13.5 or less at TOo at the IIIDE end, the problem of foreign objects appearing in the image occurs. Therefore, in the present invention, the region S in FIG. 3 where the aperture aperture is smaller than F 13.5 is regarded as the foreign object reflection region, and when this region is reached, the ND filter 11 is adjusted as shown in FIG. According to the amount of transmitted light, exposure is controlled by shifting to a program consisting of a combination of a larger aperture aperture and shutter speed. In the program diagram TO on the wide end side, the area S is
Based on the shutter speed of approximately 17190 seconds on the diagram that corresponds to F 13.5, program diagram T1 on the tele side.
~Maximum EV with the same shutter speed at T7
Determined by value. As is well known, in a zoom lens, when the mechanical aperture aperture is the same, the aperture value increases as the focal length increases, so the minimum aperture value in the region S is TI, T2...TI (the aperture aperture becomes smaller). On the E side, the rearmost lens system generally moves forward, so there is little chance of foreign objects being captured even if the aperture is around F45. Also, a shutter speed of approximately 17190 seconds is used as a reference. The control circuit 15 shown in FIG. 1 includes a focal length detection device 16.
In response to human power from detection devices such as the subject distance detection device 17 and the aperture value detection device 18, operating signals are given to the program circuit 19 and the swing actuator 13. That is, when the aperture value and the focal length range or the focal length are such that there is no possibility of foreign matter being reflected in the image, no operation signal is given to the swing actuator 13, and the ND filter 11 is not advanced into the optical path. At this time, the program circuit 19 gives an instruction to control exposure based on a normal program diagram. On the other hand, in a state where there is a possibility of foreign matter being reflected, the control circuit 15 gives an operation signal to the swing actuator 13 to move the ND filter 11 into the optical path. At the same time, for the program circuit engineer 9, a program shifted to the EV value side with a larger aperture aperture, I! Give instructions to determine exposure based on the i1 diagram. In other words, exposure is controlled using a larger aperture aperture than before inserting the ND filter and a corresponding shutter speed. FIG. 2 shows an example in which the light transmittance of the ND filter 11 is 25%. Program diagram T at the end of IIIDE now
For example, when the aperture value exceeds F13.5 (EV 15), the ND filter 11 moves into the optical path. From then on, exposure control is performed using a region in which the EV value is shifted by 1.75 to the lower aperture value side. That is, when the EV becomes 15°25, the aperture value becomes approximately F8.5, and the aperture becomes large, thereby avoiding the problem of foreign matter being reflected. The shutter speed at this time is approximately 17135 seconds, but this does not pose any practical problem. And with TO, exposure control is possible up to EV17. If F13.5 is reached again, it is possible to shift the program diagram to the low EV value side again by stacking the ND filter or replacing it with an ND filter with low transmittance. By repeating this process, the third scene of the subject with a high EV value will also become perfect. The above is an explanation of TO at the WIDE end, but T1
The story is exactly the same for ~T7. The maximum EV value is
In this example, T E 1. In the case of TI at the E end! 9.75
It is. The above is an example of a zoom lens system, but in a bifocal type camera, only when a switching lens is inserted that causes a problem of foreign matter in the image, an ND filter is inserted and a program line shifted to a lower EV value side. It is sufficient to perform exposure control based on the diagram. ``Effects of the Invention'' As described above, according to the device of the present invention, it is possible to reduce the possibility that foreign matter attached to the rear of the lens system will be reflected in the screen at a specific combination of the position of the lens system and the aperture value. In particular, the present invention prevents the aperture aperture from falling below a certain value by advancing the ND filter into the optical path, so it is possible to prevent foreign matter from appearing in the image without lowering the controllable EV value to a low level. 4. Brief description of the drawings Fig. 1 is a front view of the main parts showing an example of the mechanical configuration of the device of the present invention, and Fig. 2 is a program line showing an example of a program for the program shutter used in the device of the present invention. Figures 3 and 3 are program diagrams showing program examples when there is no problem with foreign object reflections, and Figures 4 (8), (11), and (C) show the program diagrams for specific aperture values and specific lens system positions. 11 is an optical path diagram and a light amount distribution diagram showing how foreign objects are reflected in the combination. 11...Nl) filter; 12... Swinging arm; 1
3... Swing actuator, 15... Program circuit, L-... Lens system, P... Exit pupil, Q... Foreign object,
F...Film surface. Patent Applicant Asahi Optical Co., Ltd. Agent Kuni Miura Daido Shigeto Matsui Yoshimi Sasayama Lamb's Notebook rB'-V Figure 3

Claims (1)

[Claims] (1) In a program shutter type camera equipped with a zoom lens system or a long/short bifocal switching lens system, minute foreign matter adhering to the rearmost lens surface of the lens system may
In a camera that is photographed on film at a combination of a specific aperture value and a specific focal length range or focal length of the lens system, an ND filter that can move forward and backward into the optical path of the lens system;
An actuator is provided to advance this ND filter into the optical path of the lens system at the above-mentioned specific aperture value and focal length or focal length range where minute foreign matter is imprinted, and when inserting this ND filter, the actuator is set according to the amount of transmitted light. , the program diagram of the program shutter is set to a low EV with a small aperture value.
A lens-imprint prevention device characterized by controlling exposure by shifting to the value side.