JPS6275427A - Diaphragm control mechanism for single-lens reflex camera - Google Patents

Abstract

PURPOSE:To improve the reliability of diaphragm control of a single-lens reflex camera by abutting a setting member upon a diaphragm locking lever at the attraction of an electromagnet to an armature and an auxiliary spring is laid in the direction for abutting the diaphragm locking lever upon the setting member. CONSTITUTION:During the lifting of a mirror after diaphragm stopping control, abutting of a projection 6a upon the tip part 62b of a driving arm 62 is released by the rotation of a gear 6 in the arrow direction. During the descending of the mirror, a diaphragm locking lever 15 is rotated around a supporting shaft 15c in the clockwise direction and a locking claw 15b is disengaged from a rachet wheel 13c. Then, the armature 19 is attracted again to the electromagnet 20 and the driving arm 62 is separated from one arm 60b against the electricity of the spring 63 on the basis of the rotation of the gear 6, and the abutting of the projection 6a upon the tip part 62b is released. Consequently, the reliability of diaphragm control is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aperture control mechanism in a single-lens reflex camera in which a movable reflecting mirror is driven up and down and an aperture is driven by a motor built into the camera.

[Prior Art] In single-lens reflex cameras, which use exposure control modes such as a program control method or a shutter time priority method, and use a built-in motor to drive the movable reflection mirror up and down and drive the aperture, the camera uses a photometered value of subject brightness, etc. A method has been proposed in which the aperture aperture of the lens is detected within the camera body based on the exposure condition determining factors, and an electromagnet is used to control the stop of the aperture member. In this method, the electromagnet's I
After the release, the IJ moving piece (hereinafter referred to as armature) is placed in a state where it locks the aperture member or a part linked to the aperture by the repulsive action of the electromagnet when the aperture aperture is properly controlled, and after the shooting operation is completed, Specifically, after the shutter has finished running, the locking state is immediately released, the electromagnet is returned to the attracting state, the set state is set, and the diaphragm is returned to the open state.

[Problems to be Solved by the Invention] However, in such conventional cameras with built-in motors or cameras in which an external motor such as a motor drive device is attached to the camera body, the spring that performs the setting operation is charged when the film is wound. This increases the hoisting load and complicates the mechanism. In addition, in an electric winding camera with a built-in motor, the setting operation is performed in conjunction with the film winding operation after the shutter trailing curtain runs, which makes the winding mechanism complicated, and the aperture control including the winding mechanism and the electromagnet. Since positioning accuracy with respect to the mechanism is required, there is also the drawback that the cost of the camera increases due to improved component accuracy and complexity during assembly.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks caused by setting the armature and charging the spring for setting the armature in conjunction with the conventional winding mechanism, and to provide highly reliable aperture control for a single-lens reflex camera. There is a mechanism to provide.

[Means and effects for solving the problems] In the present invention, the diaphragm locking lever supported by the armature and the setting member having an elastic function are brought into contact with each other when the electromagnet and the armature are set by attraction, and the above-mentioned An auxiliary spring is stretched in a direction in which the aperture locking lever and the set member come into contact with each other, and the electromagnet is attracted to the electromagnet through the set member by the rotating member that rotates in the normal direction when the mirror is up and reversely when the mirror is down.

[Example] The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a perspective view of an aperture control mechanism of a single-lens reflex camera showing an embodiment of the present invention. In Figure 1,
The light that passes through the photographic lens (not shown) and passes through the diaphragm aperture enters the camera body, and is reflected upward by the movable reflection mirror 22 installed diagonally at an angle of 45@ on the photographic optical axis O, and is used for focusing. It is transmitted and diffused to the screen 40. The optical image of the focusing screen 40 can be observed as an erect image in a finder through a pentaprism 41 and an eyepiece 42. Further, near the eyepiece lens 42, a photometric light receiving element 43 is arranged facing the exit surface of the pentaprism 41. An aperture, a focal plane shutter, etc. (not shown) are provided behind the movable reflection mirror 22.

The light receiving element 43 for photometry measures the brightness of the subject by the release operation of the camera, and transmits the brightness information to a known CPU 5.
0 (see Figure 4). The CPU calculates the number of refinement stages ΔAv (apex calculation value) together with the determining factor information of the exposure conditions set at the front. Thereafter, the micromotor 1 is driven. A large-diameter spur gear 3a meshes with the output gear 2 of the motor, which rotates in the direction of the arrow.A bevel gear 3b is integrally provided with the gear 3a. 4a is engaged. A spur gear 4b is integrally attached to the bevel gear 4a, a large diameter gear of a step gear 5 meshes with the spur gear 4b, and a set member driving gear 6 meshes with the small diameter gear. Therefore, as the output gear 2 rotates in the direction of the arrow, the gears 3a, 3b, 4a, 4b and 5 rotate in the direction of the arrow, transmitting power, and rotate the gear 6 in the direction of the arrow. A protrusion 6a is provided on the front side of this drive gear 6.
is provided integrally with the gear 6, and engages with an interlocking pin 7a implanted on the rear surface of the gear 7, which is rotatably disposed coaxially with the gear 6. A transmission gear 8 is meshed with the gear 7, and a gear 9a is meshed with the gear 8. Gear 9b is fixed on the same axis as gear 9a,
The gear 9b meshes with a gear portion 10a of an aperture ring 10 that rotates about the optical axis 0. Therefore, the rotation of gear 7 is caused by the rotation of gear 8. It is transmitted to the aperture ring 10 via gears 9a and 9b. This aperture ring 10 has a spring 1
1 is stretched between a fixed member (not shown) inside the camera, and a rotating force in the direction of the arrow is applied to this spring 1.
1 is applied to the output gear 2 and the gear part 10a.
In the initial state, the protruding piece 10 is held in a magnetically stable position by the rotational force that is significantly reduced between the gear trains connecting the motor 1 and the cogging force.
d is held at a position where it abuts against a stop pin 25 for regulating the initial position. Further, in this rotational position, the aperture opening switch SWI is closed by the protruding piece 10c extending from the aperture ring 10. When the gear 6 rotates in the direction of the arrow in this state, the interlocking pin 7a follows the protrusion 6a due to the elasticity of the spring 11, and the gear 7.8.9a
.

9b and the aperture ring 10 each rotate in the direction of the arrow, and the aperture opening switch SWI becomes open.

Further, a small diameter gear of a stepped gear 12 is engaged with the gear 8 in the camera body, and a pinion 13a that constitutes the aperture control member 13 is engaged with the large diameter gear, and this pinion 13a and a ratchet wheel 13c are integrated. The diaphragm control member 13 is configured as follows. The ratchet ring 13c has a locking pawl 15b of the aperture locking lever 15.
is now disengaged.

The support shaft 13d to which the ratchet wheel 13c and pinion 13a are fixed is provided with an aperture detection means consisting of a pulse signal generation means. This signal generation means includes a slit forming member 13 integrally attached to the support shaft 13d.
b and a photo ink printer 14. The slit forming member 13b is a circular plate with a large number of equally spaced notches, and a photo ink converter 14 in which a light emitting diode and a light receiving element are formed facing each other is sandwiched between the slit portions of the slit forming member 13b. It is provided. As a result, the rotation of the aperture ring 10 is controlled by the gear 9b.
, 9a, 8 and the stepped gear 12 to the pinion 13a to rotate the slit forming member 13b.
Along with this rotation, the photointerrupter 14 generates a number of digital pulse signals corresponding to the aperture diameter.

The aperture locking lever 15 is formed of a vertically elongated lever, and its upper fulcrum is rotatably supported by a support shaft 15a, and the locking pawl 15b is opposed to the ratchet ring 13c in the middle. It is formed in a position where A charging arm 15c is formed at the upper edge of this locking lever 15 and is bent toward the rear.
A rigid arm portion 17a of a set lever 17 constituting a set member is in contact with c. This set lever 17 is rotatably supported at its central fulcrum by the support shaft 15a, and its arm 17b is horizontal so as to behave elastically, and its tip is placed on the rotation path of the projection 6a. The thin arm 17a extends below the charge arm 15c. The narrow arm 17a is brought into contact with the charging arm 15c due to the elasticity of the auxiliary spring 18, which has a weak elasticity, and is stretched between its tip and the immovable member.

Further, an armature 19 that is attracted by a release type electromagnet 20 is pivotally supported at the lower part of the aperture locking lever 15, and when the armature 19 is attracted to the electromagnet 20, the aperture locking lever 15 is locked. The retaining pawl 15b is held at a position spaced apart from the ratchet ring 13c. As is well known, the release type electromagnet 20 has a permanent magnet 20a between the yokes around which the coils are wound.
It is a so-called combination magnet, which is configured by disposing a magnetic bypass section (not shown), and in an initial state, the aperture locking lever 15 is stretched between a stationary member (not shown) inside the camera body and the locking lever 15. Ta,
Separation spring 1 having a stronger elasticity than the spring 18
6 and is attracted to the electromagnet 20.

On the other hand, the back side of the gear 6 is shown in FIGS. 3(a) to 3(a).
As shown in c), a partially arcuate end cam 6b is formed, and when the gear 6 rotates and the diaphragm in the interchangeable lens, which will be described later, is narrowed down to the minimum aperture diameter, the end cam 6b is mirror driven. Actuation pin 2 fixed to lever 21
It serves to rotate the lever 21 around the support shaft 21a in the mirror-up direction (clockwise in FIG. 3(a)) via the lever 1c. The movable reflection mirror 22 is rotatably held around a support shaft 22a fixed to the upper part of both sides, and is lowered by a mirror down spring 23 and comes into contact with a mirror positioning pin 24 so as to be on the optical axis 0. A mirror drive bin 22b is fixed to one side of the reflecting mirror 22, and when the mirror drive lever 21 is rotated clockwise, the upper side of the lever 21 is rotated. As a result, the bin 22b is pushed up to perform the mirror raising operation (see FIG. 3(c)).Then, at the mirror raising completion position, the bent portion 2 of the mirror drive lever 21 is pushed up.
1b operates the mirror up switch SW2 from the off state to the on state. This switch SW
2 closes, the motor 1 stops, and at that time the mirror drive lever 2 is held at the top dead center of the end cam 6b of the gear 6 at the mirror raised position.

The above is the aperture control mechanism disposed within the camera body.

Next, as shown in FIG. 1, the diaphragm mechanism installed in the interchangeable lens has several supporting bottles 33a planted at equal intervals around the optical axis O in the diaphragm case 33, which is a fixed member. The aperture blades 32 are pivotally supported in each support bin 33a through their support holes 32b. The aperture plate 30 that operates the aperture blades 32 is rotatably arranged around the optical axis 0, and the aperture plate 30 is provided with a plurality of aperture cam grooves 30b having a known shape. has been,
Driving pins 32a installed in each of the proofing blades 32 are fitted into each of the cam grooves 30b, respectively. A bent arm portion 30a for connection is formed on a part of the outer periphery of the aperture plate 30 and extends along the optical axis 0 to the camera body, and this arm portion 30a and the lens barrel A weakly elastic spring 31 is stretched between a stationary member (not shown) inside. Therefore, when the interchangeable lens is attached to the camera body, the arm portion 30a is always in contact with the upper surface of the inwardly protruding piece 10b of the aperture ring 10 due to the spring 31. Note that the shape of the aperture cam groove 30b is formed such that the rotation angle of the bent arm portion 30a and the aperture diameter formed by the drive bottle 32a are in a proportional relationship.

The aperture control mechanism of this embodiment is configured in this manner.

Next, to explain its operation, Fig. 2(a) to Fig. 2(
r) shows the operation of the aperture drive stop control mechanism extracted from FIG. 1, and FIG. 2(a) shows the initial state before photographing. In this embodiment, the narrowing operation is performed by rotating the gear 6 approximately 180' in the direction of the arrow from the initial state, and if the electromagnet 20 does not act during the narrowing operation, the narrowing operation can be performed from the open aperture state to the minimum aperture state. The mirror is then rotated by about 180 to 300' from the initial state to raise the mirror.

Now, when the release operation causes the motor 1 and the output gear 2 to rotate in the direction of the arrow, and the aperture ring 10 rotates in the direction of the arrow via the gear train, the aperture blades 32 start the aperture operation with this rotation, and the number of aperture stages increases. When the number of pulse signals corresponding to ΔAv is generated from the photoinkrater 14, the electromagnet 20 is activated by a signal from the CPU.
A degaussing current is applied to the coil in the direction of attenuating the force that attracts and displaces the armature 19, and the armature 19 is separated from the electromagnet 20 by the tightening elasticity of the separation spring 16, so that the throttle locking lever 15 is moved from the support shaft 15a. The locking pawl 15b is rotated counterclockwise around the ratchet ring 13c.
jumps between the claws and suddenly stops the rotation of the diaphragm control member 13.
The aperture diameter is determined. FIG. 2(b) shows a state in which the aperture aperture is determined to be approximately midway between the open and minimum apertures.

Further, since the motor 1 continues to rotate in the same direction thereafter, the following engagement between the protrusion 6a and the interlocking pin 7a is released, and the gear 6 further rotates in the direction of the arrow. In addition, when the subject is very bright', when the aperture is stopped down to the minimum aperture diameter with rJ, the protruding piece 10d comes into contact with the minimum aperture position regulating stopper 26 (see Figure 1), so the arrow-shaped protrusion 6a
The following engagement between the interlocking pin 7a and the interlocking pin 7a is released, and the gear 6 similarly rotates in the direction of the arrow. As described above, when the gear 6 rotates from the initial state to about 180° to 300°, the mirror-up operation of the movable reflecting mirror 22 shown in FIGS. This is done by the action of the cam 6b.

In the middle of this mirror raising operation, the protrusion 6a of the gear 6 comes into contact with the horizontal arm 17b of the set lever 17, but since the lever 17 rotates counterclockwise while stretching the spring 18, as the gear 6 rotates, the protrusion 6a comes into contact with the horizontal arm 17b of the set lever 17. The horizontal arm 17b is disengaged. FIG. 2(c) shows that the protrusion 6a and the horizontal arm 17b come into contact with each other while the mirror is rising, and as the spring 18 stretches, the charge arm 15c and the narrow arm 17a separate, and the protrusion 6a and the horizontal arm 1
7b is about to be released from contact.

Here, since the spring 18 is an extremely weak spring, the increase in the load on the motor due to the spring 18 at this time is extremely small.

When the movable reflective mirror 22 has been raised in this way and the mirror 2 is retracted from the photographing optical path, the mirror up switch SW2 is turned on, the motor 1 is stopped, and the gear 6 is turned on as shown in FIG. 3(C). In the state shown in FIG. 2(d), the protrusion 6a stops at a position separated from the horizontal arm 17b.

When the switch SW2 is turned on, the front curtain of the shutter starts, and the movement of the rear curtain of the shutter is controlled by the shutter speed control means. When the shutter trailing curtain finishes running, the motor 1 now starts reversing. As a result, the gear train from output gear 2 to gear 6 operates, and each gear rotates in the direction opposite to the arrow shown in FIG. As a result, the mirror drive lever 21
The movable reflecting mirror 22 rotates counterclockwise due to the elasticity of the spring 23, and the movable reflecting mirror 22 descends until it comes into contact with the positioning pin 24. Further, the switch SW2 changes from the on state to the off state. On the other hand, the protrusion 6a comes into contact with the horizontal arm 17b again, and the spring 1
Since the thin arm 17a and the charging arm 15c are in contact with each other due to the tightening elasticity of the 8, the aperture locking lever 15 is rotated clockwise around the support shaft 15a, and the locking pawl 15b is engaged with the ratchet ring 13c. The stopped state is released and the armature 19 is attracted to the electromagnet 20 again. Then horizontal arm 1
7b is elastically deformed, as shown in FIG. 2(e), and is released from contact with the protrusion 6a.

FIG. 2(f) shows the state immediately after the operating state shown in FIG. 2(e). At the moment when the contact between the protrusion 6a and the horizontal arm 17b is released, the set lever 17 momentarily rotates counterclockwise against the elasticity of the spring 18 due to the repulsive energy stored by the elastic deformation of the horizontal arm 17b. be.

This operation ensures that the rear armature 19 and the electromagnet 20 are attracted to each other. To explain this in a little more detail, if the aperture locking lever 15 and the set lever 17 were integrally formed, the repulsive energy stored by the elastic deformation of the horizontal arm 17b would cause the armature 19 and the electromagnet 20 to move when they are released. This may act as a strong impact on the attraction surface, causing the armature 19 to separate from the electromagnet 20. Therefore, in the present invention, the armature 19
In order to maintain the adsorption state of the electromagnet 20 with high reliability,
A means is adopted in which the aperture lock lever 15 and the set lever 17 are formed separately, and the two are connected by a spring 18 having weak elasticity.

With the armature 19 being attracted to the electromagnet 20 in this manner, the gear 6 continues to rotate in reverse, and the protrusion 6a and the interlocking pin 7a come into contact again, charging the spring 11 of the aperture ring 10 as shown in FIG. 2(a). Returns to the initial state shown in . Further, in conjunction with this, the aperture plate 30 is also reversed by the elasticity of the spring 31, and the aperture blades 32 are opened. Then, when the protruding piece 10d comes into contact with the stop pin 25, the protruding piece 10c
operates the aperture opening switch SWI from off to on, stops motor 1, and returns the finder to the observation state. Subsequently, the film is wound and the shutter is charged by known means (not shown), and the camera returns to the next photographing preparation state.

Next, FIGS. 4 and 5 show an electric circuit for performing programmed exposure control and automatic exposure control with shutter speed priority using the aperture control mechanism of the first embodiment shown in FIGS. 1 to 3. This shows a block diagram of.

In the case of program exposure control, as shown in FIG. The lens opening FNo information Avo is sequentially inputted from the FNo information input means 53.
Human power is applied to PU50. Then, the CPU 50 calculates the number of stops ΔAy and the shutter time Tv based on a preset program.

After the calculation, the CPU 50 outputs signals necessary for display to the display means 56. When a signal is output from the CPU 50 to the motor drive circuit 55 due to the release operation, the drive circuit 55 drives the motor 1 and starts driving the aperture and mirror. Along with this, the photo interrupter 14 sends pulse signals of a number corresponding to the change in the aperture diameter to the CPU 50.
Enter. When the CPU 50 receives the number of pulses corresponding to the number of aperture stages ΔAy, it outputs a signal to the magnet drive circuit 54, and the release type electromagnet 20 performs aperture stop control. Further, when the mirror up switch SW2 is turned from off to on due to mirror up completion, the CPU 50 outputs a stop signal to the motor drive circuit 55, and the motor 1 stops operating. Subsequently, a signal is output from the CPU 50 to the shutter speed control means 57 to control the shutter operation.

After the trailing curtain of the shutter finishes running, the CPU 50 outputs a motor reversal signal to the motor drive circuit 55, and the motor 1 rotates in the reverse direction. Then, when the mirror up switch SW2 changes from the on state to the off state, the CPU 50 outputs a stop signal to the motor drive circuit 55, and the motor 1 stops reverse rotation. Next, a signal is sent from the CPU 50 to the winding/shutter charge drive control means 58 to wind the film and charge the shutter, thereby completing the photographing.

In the case of automatic exposure control with shutter speed priority, as shown in FIG. 5, the luminance information detection circuit 51, film sensitivity information manual means 52, and lens opening FNo.
Each information from By, Sy.

In addition to the input of Avo, the shutter time information Tv set by the shutter time setting means 59 is input to the CPU 50, and the same operation as in the program exposure control shown in FIG. 4 is performed, except that the number of aperture steps ΔAv is determined. Let's do it.

Next, other examples of the aperture drive stop control mechanism are shown in FIGS. 6(a) to 6(a).
This will be explained with reference to FIG. 6(d). This aperture drive/stop control mechanism is constructed by replacing the set lever 17 and the auxiliary spring 18 in the embodiment shown in FIG. The structure is the same as that of the previous embodiment except that . FIG. 6(a) is a perspective view showing only the main parts thereof, and shows the initial state. A fulcrum of a set lever 60 and a base of a drive arm 62 are each rotatably supported on a support shaft 15a of the aperture locking lever 15, and extend below the charging arm 15c of the aperture locking lever 15. The thin arm 60a of the set lever 60 is connected to the thin arm 60a of the set lever 60 by a coil spring 61 which has a much weaker elasticity than the separation spring 16, and the set lever is bent horizontally and extended toward the rear.
A drive arm 62 is located below one arm 60b of 60 and has a tip 62b extending onto the rotation path of the protrusion 6a.
and are connected by a coil spring 63 having a stronger elasticity than the separation spring 16. Therefore, one arm is 60 in a lifetime.
b is in contact with the upper side 62a of the drive arm 62.

FIG. 6(b) shows the initial state before release, and FIG. 6(C) shows the mirror being raised after the aperture stop control. That is, the protrusion 6a and the tip 6 of the drive arm 62
2b, the charge arm 1 resists the elasticity of the spring 61.
This is the moment when the narrow arm 60a separates from 5C and the protrusion 6a and the tip end 62b of the drive arm 62 are about to come out of contact with each other due to the rotation of the gear 6 in the direction of the arrow. Figure 6(d)
shows the mirror being lowered, and the protrusion 6a and drive arm 6
Drive arm 62 due to contact with tip 62b of No. 2
rotates clockwise around the support shaft 15a, and as the charge arm 15c of the thin arm 60a is pushed up by the elasticity of the spring 63, the aperture locking lever 15 rotates clockwise around the support shaft 15c. The engagement between the locking pawl 15b and the ratchet ring 13c is released, the armature 19 is re-adsorbed to the electromagnet 20, and the drive arm 62 is separated from the arm 60b against the elasticity of the spring 63 due to the rotation of the gear 6. , the protrusion 6a and the tip 62b are about to come out of contact.

Other operations are similar to those of the first embodiment.

In addition, in this aperture drive stop control mechanism, the connection spring 6
Although a compressible coil spring is used in 1.63, it goes without saying that a torsion spring may also be used.

The advantage of the diaphragm drive/stop control mechanism shown in FIG. 6 is that in addition to having all the advantages of the mechanism of the first embodiment, it also has the advantage of ensuring a span for using the elastic deformation of the plate member. Since this can be avoided, the mechanism can be made smaller and the entire camera can be made smaller.

[Effects of the Invention] According to the present invention, since the aperture control electromagnet and armature are set by effectively utilizing the rotational movement of the motor built into the camera body, the number of parts can be reduced by simplifying the mechanism. It is possible to reduce the number of motors and improve the ease of assembly, thereby reducing the cost of the camera, and improving the performance of the camera by reducing the motor load and improving the reliability of the mechanism.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the aperture control mechanism of a single-lens reflex camera showing the first embodiment of the present invention, and FIGS. 2(a) to 2(f) show the aperture drive stop in FIG. 1 above. An enlarged front view showing the operating mode of the control mechanism, and FIGS. 3(a) to 3(c) are a side view, rear view, and operation of the mirror drive mechanism taken out from FIG. 1, respectively. FIGS. 4 and 5 are electrical circuit block diagrams showing the operation of a camera that employs the aperture control mechanism shown in FIG. 1, and FIGS.
FIG. 6(d) shows another example of the aperture drive stop control mechanism, FIG. 6(a) is a perspective view thereof, and FIG. 6(b) to FIG. 6(d) show the operation mode, respectively. FIG. 1...Motor 10...Diaper ring 13c...Ratchet ring (limb engagement member) 15.
......Aperture locking lever 15b...Latching claw 19...Armature 20...Electromagnet (release type) 22. ...
・・・・・・Movable reflective mirror 30・・・・・・・Filtering member 2 drawings (b) 4 drawings 5 drawings Procedure amendment (self-motivated) November 1985
June 72nd, Mr. Uga Michibu, Commissioner of the Patent Office, Country Ha1, Indication of the Case, 1985 Patent Patent No. 2.15
950 No. 2, Title of the invention - Aperture control mechanism 3 of an eye reflex camera, relationship to the case of the person making the correction Patent applicant address: 2-43-2 Hatagaya, Shibuya-ku, Tokyo Name (037) Olympus Optical Industry Co., Ltd. Company 4, Agent 5, Subject of amendment: “Detailed explanation column of the invention in the specification” and “Drawings” (1
) The statement "Mirror up switch SW2 goes from on to off" written in lines 3 to 4 on page 20 of the specification will be corrected to "the aperture opening switch SWI goes from off to on." (2) Among the drawings attached to the application, Figure 2 (f) will be corrected to the attached drawing.

Claims (1)

[Scope of Claims] A single-lens reflex camera in which a movable reflecting mirror is driven up and down and the aperture is driven by a motor built into the camera, and when the aperture reaches an appropriate aperture, an electromagnet is operated to stop the aperture member, The diaphragm locking lever, which engages and disengages from the locked member interlocked with the diaphragm member, and which has an armature in a part thereof, is always urged in the direction of its engagement position, and is interlocked with the mirror when the mirror is lowered. The aperture locking lever is moved by a member against the urging force to separate from the locked member, and the armature of the aperture locking lever is returned to a position where it is attracted to the electromagnet. Aperture control mechanism.