JPH09211515A - Collapsible type lens barrel and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent inadvertent photographing in a collapsible condition by providing a camera with a collapse detecting means detecting whether it is the collapsible condition or not and making the aperture of a diaphragm device a minimum value or a value proximate to the minimum value when the collapsible condition is detected by the collapse detecting means. SOLUTION: When a photographer half-presses a release button, a switch S1 is turned on, and a controller 21 judges whether the collapse detecting means S4 is on (collapsible condition) or not. When the means S4 is on, whether the means S4 was on or not in the preceding run is judged, and a signal expressing the collapsible condition is transmitted to a body in the case the means S4 is on. The controller 20 of the body performs release/lock and the stop-down of the diaphragm device 14 based on the signal. When the means S4 is off, whether the means 4 was off or not in the preceding run is judged, and transmits a signal expressing non-collapse to the body in the case the means 4 is not off. The controller 20 of the body opens the diaphragm device based on this signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a collapsible lens barrel capable of taking a retracted state in which the total length in the optical axis direction is further shortened compared to the state in which the total length in the optical axis direction is shortest at the time of photographing. More specifically, the present invention relates to a retractable lens barrel and a camera capable of preventing erroneous shooting when retracting.

[0002]

2. Description of the Related Art Interchangeable lens barrels for single-lens reflex cameras, especially zoom lens barrels, have the problem that they are bulky when they are carried or stored, and a collapsible lens barrel has been developed to solve this problem. ,It is used. In this retractable lens barrel, by moving at least a part of the shooting lens toward the camera body side in the optical axis direction when not shooting, the overall length in the optical axis direction during shooting was further shortened compared to the state where the total length in the optical axis direction was the shortest. It is configured to be in a collapsed state.

[0003]

By the way, in the conventional retractable lens barrel, when the user looks into the viewfinder while the lens barrel is in the retracted state, the subject image looks vague although it is out of focus. There was a problem that it would end up.

The present invention has been made to solve the above problems, and is a retractable lens barrel and a collapsible lens barrel which can prevent erroneous photographing in the retracted state. An object of the present invention is to provide a camera provided with an adjustable lens barrel.

[0005]

In order to achieve the above object, the invention according to claim 1 can take a retracted state in which the total length in the optical axis direction is further shortened compared to the shortest state in the optical axis direction at the time of photographing. In the collapsible lens barrel, collapsing detection means for detecting whether or not the collapsible state is present is provided, and when the collapsing state is detected by the collapsible state detecting means, the diaphragm aperture of the diaphragm device is set to a minimum value or a value close thereto. It is characterized in that

According to a second aspect of the present invention, there is provided a camera including a retractable lens barrel capable of taking a retracted state in which the total length in the optical axis direction is further shortened compared to the state in which the total length in the optical axis direction at the time of photographing is the shortest. A collapse detecting means for detecting whether or not the lens barrel is in a collapsed state is provided, and when the collapse detecting means detects that the lens barrel is in a collapsed state, the diaphragm aperture of the diaphragm device is set to a minimum value or a value close thereto. It is characterized by having done.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. 1 and 2 are sectional views of a retractable lens barrel of a camera according to an embodiment of the present invention in an optical axis direction. FIG. 1 shows a state in which a taking lens is in a wide position, and FIG. The position is shown.

In FIG. 1, the lens barrel 1 is a zoom lens barrel, which is a cylindrical fixed barrel 2 and is provided inside the fixed barrel 2 to hold a front lens group L1 which is a taking lens. Front lens group moving frame 3 and a cylindrical rear group lens moving frame 4, which is provided inside the fixed barrel 2 and holds a rear lens group L2 that is a photographing lens, and a zoom operation ring provided on the outer periphery of the fixed barrel 2. 5, a cam ring 6 and a linear guide cylinder 7 provided between the fixed barrel 2, the front lens group moving frame 3 and the rear lens group moving frame 4. A protective glass 3a is attached to the front part of the front lens group moving frame 3.

The zoom operation ring 5 is attached to the fixed barrel 2 so as to be rotatable about the optical axis L but not to move in the optical axis L direction. On the inner surface of the zoom operation ring 5, an engaging groove that extends in the optical axis direction and is slidably engaged with a pin 8 planted on the outer surface of the end of the cam ring 6 on the camera body side (right side in FIG. 1). 5a is engraved. Incidentally, 9 is a rubber ring for slip prevention mounted on the outer periphery of the zoom operation ring 5.

A male helicoid screw 6a is engraved on the outer surface of the cam ring 6 on the camera body side. The male helicoid screw 6a is screwed onto a female helicoid screw 2a engraved on the inner surface of the peripheral wall of the fixed barrel 2. ing. A pin 8 implanted on the outer surface of the end of the cam ring 6 on the camera body side (right side in FIG. 1) penetrates an escape hole 2b provided in the peripheral wall of the fixed barrel 2 and engages with the engagement groove 5a of the zoom operation ring 5. Is engaged with. When the zoom operation ring 5 is rotated, the cam ring 6 rotates via the pin 8, and the cam ring 6 moves in the optical axis direction by the action of the helicoid screws 6a and 2a.

On the inner surface of the cam ring 6, a front group lens moving frame 3 is provided.
Front group pin 1 planted on the outer surface of the camera body side end of
0 is slidably engaged with a cam groove 12, and a rear group pin 11 is slidably engaged with an outer surface of an end of the rear group lens moving frame 4 on the object side (left side in FIG. 1). A cam groove 13 is formed. The shapes of the cam grooves 12 and 13 will be described later.

A guide hole 7a through which the front group pin 10 penetrates and is slidably engaged with the straight guide cylinder 7,
The rear group pin 11 penetrates and a guide hole 7b with which the rear group pin 11 is slidably engaged is formed so as to extend in the optical axis direction (only 7a is shown in FIG. 1). An engaging portion 7c protruding outward is formed on the outer surface of the end of the linear guide cylinder 7 on the camera body side. The engaging portion 7c is an optical axis formed on the inner surface of the peripheral wall of the fixed cylinder 2. It is slidably engaged with an engagement groove 2c extending in the direction. A convex portion 7d extending in the circumferential direction is formed on the outer surface of the linear guide cylinder 7 near the end on the camera body side. The convex portion 7d is a circumferentially extending engagement formed on the inner surface of the cam ring 6. It is slidably engaged with the groove 6b.

FIG. 3 shows the cam grooves 12 and 13 by unfolding the peripheral wall of the fixed barrel 2 and also the guide holes 7a of the linear guide barrel 7.
7B is a diagram showing a front group pin 10 and a rear group pin 11. FIG. A portion between the wide position and the tele position of the cam groove 12 is formed in an arc shape that bulges toward the camera body side, and a portion between the wide position and the storage position is slanted from the wide position toward the camera body side. Has been formed. On the other hand, the portion between the wide position and the tele position of the cam groove 13 is formed in a skewed shape that is slanted from the wide position toward the subject side, and between the wide position and the stored position is formed in a straight line extending in the rotational direction. ing.

When the pins 10 and 11 are in the wide position, the lens barrel 1 is in the state shown in FIG. 1 and its appearance is as shown in FIG. 8 (b). When the cam ring 6 rotates in the direction of arrow B, the front group pin 10 and the rear group pin 11 move in the cam grooves 12 and 13 toward the storage position, and when the storage ring reaches the storage position, the lens barrel 1 is shown in FIG. Then, the appearance becomes that shown in FIG. 8 (c). Further, when the cam ring 6 rotates in the direction of arrow A, the front group pin 10 and the rear group pin 11 move in the cam grooves 12 and 13 toward the tele position, and when the tele ring position is reached, the appearance of the lens barrel 1 becomes The state shown in FIG. The operation will be described below in detail.

When the zoom operation ring 5 is rotated in the direction of arrow A with the pins 10 and 11 in the wide position, the cam ring 6 moves in the optical axis direction toward the subject while rotating in the same direction, and the linear guide cylinder 7 rotates. However, it moves to the subject side in the optical axis direction together with the cam ring 6. When the cam ring 6 rotates, the front group pin 10 and the rear group pin 11 move in the cam grooves 12 and 13 toward the tele position. Since the front group pin 10 is restricted from moving in the optical axis direction only by the guide hole 7a with respect to the linear guide tube 7, it reciprocates in the optical axis direction with respect to the linear guide tube 7. Therefore, the front lens group moving frame 3 also reciprocates in the optical axis direction with respect to the linear guide cylinder 7.

On the other hand, since the rear group pin 11 is restricted from moving in the optical axis direction only by the guide hole 7b with respect to the linear guide tube 7, it moves to the object side in the optical axis direction with respect to the linear guide tube 7. . Therefore, the rear lens group moving frame 4 also moves toward the subject side in the optical axis direction with respect to the linear guide tube 7. Since the linear guide tube 7 is moved toward the object side in the optical axis direction with respect to the fixed tube 2, the rear lens group moving frame 4 is moved toward the object side in the optical axis direction with respect to the fixed tube 2. By moving the front lens group moving frame 3 and the rear lens group moving frame 4 as described above, as the pins 10 and 11 approach the tele position, the overall length of the lens barrel 1 in the optical axis direction becomes longer and reaches the tele position. When it is done, it becomes the longest (see FIG. 8 (a)). Further, by moving the front lens group moving frame 3 and the rear lens group moving frame 4 as described above, the distance between the front lens group L1 and the rear lens group L2 in the optical axis direction is continuously changed to perform the zooming operation. Be seen.

When the zoom operation ring 5 is rotated in the direction of arrow B with the pins 10 and 11 in the wide position, the cam ring 6 moves in the optical axis direction to the camera body side while rotating in the same direction, and the linear guide cylinder 7 becomes Although it does not rotate, it moves to the camera body side in the optical axis direction together with the cam ring 6. As the cam ring 6 rotates, the front group pin 10 and the rear group pin 11 move into the cam grooves 12, 1
Move inside 3 toward the storage position. Since the front group pin 10 is restricted from moving in the optical axis direction only by the guide hole 7a with respect to the linear guide tube 7, it moves to the camera body side in the optical axis direction with respect to the linear guide tube 7. Therefore, the front lens group moving frame 3 also moves to the camera body side in the optical axis direction with respect to the linear guide tube 7. Since the linear guide tube 7 is moved toward the camera body side in the optical axis direction with respect to the fixed tube 2, the front lens group moving frame 3 is moved toward the camera body side in the optical axis direction with respect to the fixed tube 2.

On the other hand, the rear group pin 11 does not move with respect to the linear guide cylinder 7 because the guide hole 7b restricts the movement of the rear group pin 11 only in the optical axis direction. Therefore, the rear lens group moving frame 4 also does not move with respect to the linear guide tube 7. Therefore, the front lens group moving frame 3 and the rear lens group moving frame 4 approach each other.

Front lens group moving frame 3 and rear lens group moving frame 4
By moving as described above, the total length in the optical axis direction of the lens barrel 1 is shortened, so that the lens barrel 1 is further shortened than the state of FIG. 1 (FIG. 8B) which is the shortest state at the time of shooting. When the front group pin 10 and the rear group pin 11 reach the storage position, the total length in the optical axis direction becomes the shortest as shown in FIG. 2 (FIG. 8C). It should be noted that the collapsed state in this specification means not only a state in which the total length in the optical axis direction is the shortest but also a state in which the total length in the optical axis direction is shorter than the state in which the total length in the optical axis direction at the time of shooting is the shortest (the state of FIG. 1 in this embodiment) It includes a state that is as short as possible.

Next, the diaphragm device 14 of the lens barrel 1 will be described. The diaphragm blade 15 made of a thin plate includes a diaphragm cam plate 16 in which a cam groove (not shown) engaged with a cam pin 15a fixed to the front surface is engraved, and the diaphragm blade 15
It is provided in a state of being sandwiched by a diaphragm support plate 17 that rotatably supports a rotary pin 15b fixed to the rear surface side. The diaphragm cam plate 16 is fixed to an annular support portion 4a formed on the rear lens group moving frame 4 so as to project therefrom.
7 is rotatably supported around the optical axis L by this support portion 4a.

A gear is formed on the outer periphery of the diaphragm support plate 17, and the gear is engaged with a gear 18a fixed to the rotary shaft of the diaphragm motor 18. When the diaphragm motor 18 is driven, the diaphragm support plate 17 rotates around the optical axis L, the diaphragm blades 15 rotate around the center line of the rotary pin 15b, and the cam pin 15a is guided by the cam groove of the diaphragm cam plate 16. The diameter of the diaphragm is reduced to a predetermined diameter. When the diaphragm blade 15 is narrowed down to the minimum diameter, it is detected by a diaphragm detection switch (not shown).

In this embodiment, the diaphragm blade 15 is driven by the motor provided in the lens barrel 1, but it may be driven by the driving force transmitted from the camera body side by the lever or the coupler. . The mechanism is publicly known and its detailed description is omitted.

The lens barrel of the present invention is provided with a collapse detecting means for detecting whether or not the lens barrel is in the collapsed state. In this embodiment, the collapsing detection means is, as shown in FIG. 4, an extension portion 19a provided on the wide side of the conductor pattern 19 of the zoom encoder provided on the outer periphery of the fixed barrel 2.
And a switch formed by a brush (not shown) attached to the zoom operation ring 5 and slidably contacting the zoom encoder 19, and when the lens barrel is in the retracted state, the brush indicates the arrow of the extension portion 19a. It comes in contact with the range indicated by.

FIG. 5 is a diagram schematically showing the control system of the camera of this embodiment. In FIG. 5, 20 is a control device for the camera body, 21 is a control device for the lens barrel 1, and S1 is turned on by half-pressing a release button (not shown) on the camera body.
The switch S2 is a switch for starting photometry and AF, the switch S2 is a switch that is turned on when the release button is fully pressed to start the release operation, the aperture detection switch S3, and the collapse detection means S4. The control device 20 of the camera body and the control device 21 of the lens barrel 1 are connected so that signals can be exchanged.

FIG. 6 is a flow chart showing a procedure when the control device 21 for the lens barrel sends a signal for retracting or non-collapsing to the control device 20 for the camera body. When the photographer presses the release button halfway, switch S1 turns on,
The controller 21 turns on the collapsing detection means S4 in step # 5.
It is determined whether or not (collapsed state). If S4 is ON, the process proceeds to step # 10, and it is determined whether or not the collapse detection means S4 was ON last time.
In step 15, a signal indicating the collapsed state is transmitted to the body.
Based on this signal, the body control device 20 prohibits the release operation (release lock) and narrows down the diaphragm device 14. On the other hand, in step # 10, the previous collapse detection means S4
Is not ON, the process proceeds to step # 20, and the signal transmission to the body as described above is not performed.

If the collapsing detection means S4 is OFF in step # 5 (in use), the process proceeds to step # 25.
It is determined whether or not the collapsing detection means S4 was OFF (used) at the previous time. If not, the process proceeds to step # 30, and a signal indicating the used state (non-collapsed) is transmitted to the body. Based on this signal, the body control device 20 releases the release lock and opens the diaphragm device 14. If the collapsing detection means S4 is OFF in step # 25, the process proceeds to step # 20 and the signal transmission to the body as described above is not performed.

FIG. 7 is a flow chart showing the control sequence of the diaphragm device 14 by the diaphragm control means incorporated in the camera body controller 20. When the release button is half-pressed, the switch S1 is turned on, and the control device 21 of the lens barrel 1 causes the aperture detection switch S3 and the collapse detection means S.
Based on the signal from No. 4, data regarding whether the aperture is in the retracted state or not, is sent to the control device 20 of the camera body. The aperture control means receives this data in step # 105, and determines in step # 110 whether or not the lens barrel 1 is in the retracted state. If it is in the collapsed state, proceed to step # 115,
Release lock is performed, and in step # 120, the diaphragm device 14 is moved to the control device 21 of the lens barrel 1 to the minimum diameter (FIG. 9C).
Send the signal to narrow down to the state shown in.

Since the viewfinder screen becomes dark as shown in FIG. 10 (c) when the diaphragm blade 15 is narrowed down to the minimum diameter, the photographer knows that the lens barrel 1 is in the retracted state, and stops the photographing. To do. Next, step # 12
At 5, it is determined whether the switch S1 is OFF. If the photographer cancels the photographing (that is, removes his / her finger from the release button), the switch S1 is turned off.
Proceed to 130 to end the operation.

When it is determined in step # 110 that the lens barrel 1 is not in the retracted state, the process proceeds to step # 135,
It is determined whether or not the diaphragm device 14 is narrowed down by the diaphragm detection switch S3. If the diaphragm device 14 is narrowed down, a signal for opening the diaphragm device 14 is sent to the control device 20 of the lens barrel 1 in step # 140. As a result, the aperture is opened (see FIGS. 9A and 9B) and the viewfinder screen becomes brighter (see FIGS. 10A and 10B). Therefore, the photographer does not make the lens barrel 1 retracted. To confirm.

Then, photometry and AF are performed in step # 145, the release lock is released in step # 150, and the process proceeds to step # 125. When the photographer releases his / her finger from the release button (when the photographing is finished or when the photographing is stopped), the switch S1 is turned off.
And ends the operation. If S1 is not OFF, the process returns to step # 105. If the diaphragm device 14 has not been narrowed down in step # 135, the process skips step # 140 and proceeds to step # 145.

The present invention is not limited to the above embodiment, and various modifications can be considered. For example, in the above-described embodiment, the control device for the lens barrel sends data on the retracted state and the aperture state to the control device for the camera body, and the aperture control means incorporated in the control device for the body determines whether or not the retracted state. The control signal for narrowing down the diaphragm device is sent from the diaphragm control means to the control device for the lens barrel, but instead of this, the control device for the lens barrel determines whether or not the lens barrel is in the collapsed state. The devices may be narrowed down. With the lens barrel configured as described above, even when the lens barrel is attached to a camera body that does not include an aperture control unit, the same effect as that of the above-described embodiment (the viewfinder screen becomes dark in the collapsed state, preventing accidental shooting) Can be obtained).

Further, although the diaphragm device is narrowed down to the minimum diameter in the above embodiment, the value may be close to the minimum diameter as long as the finder screen can be darkened. Further, instead of narrowing down the diaphragm device, a display device such as a liquid crystal is provided in the finder optical system, and the finder screen is made dark based on the signal from the collapse detection switch S4, or an indication indicating that the camera is in the collapsed state (for example, NG) may be performed.

Further, in the above embodiment, the cam groove of the cam ring is extended to the wide side to provide the storage position, but it may be extended to the tele side to provide the storage position.

Further, the main switch of the camera body may be turned on when the lens barrel is retracted, and the main switch may be turned off when the lens barrel is in use. In this way, not only can you prevent the shutter from being released when retracting,
There is no need to operate the main switch, improving operability.

In this case, if the main switch can be turned on / off by manual operation, it is necessary to put the lens barrel in use when it is necessary to turn on the camera other than photographing operation such as film exchange. It is preferable because it does not exist.

In the above embodiment, the diaphragm device is narrowed down when the lens barrel is retracted, and is opened when the lens barrel is used.
Alternatively, as shown in FIG. 11, the lens barrier 22 may be closed when the lens barrel is in the retracted state, and may be opened when the lens barrel is in the used state.

With this arrangement, as in the above embodiment, when the lens barrel is in the retracted state, the state shown in FIG.
As shown in Fig. 12, the viewfinder screen becomes dark, and when the lens barrel is in use, the viewfinder screen becomes bright as shown in Fig. 12 (a). Therefore, the photographer asks whether the lens barrel is in the retracted state. I can know. In addition, it is possible to prevent forgetting to open and close the lens barrier, and it is not necessary to open and close the lens barrier, which improves operability.

In this case, when the zoom operation ring is operated, the lens barrier may be mechanically interlocked to open and close. If the main switch is turned off when the lens is retracted and turned on when used, the shutter can be prevented from being released when the lens barrier is closed, and power consumption can be saved. it can.

In each of the above embodiments, a lock mechanism for locking the zoom operation ring may be provided. With this arrangement, since the zoom operation ring does not rotate when the lens is replaced, the lens can be easily replaced. FIG. 13 is an external view showing one embodiment thereof, and the lens barrel 1 is provided with a lock button 23 for operating a lock mechanism.

Further, a click mechanism for holding the zoom operating ring at the wide position or the tele position may be provided so that the zoom operating ring does not rotate to the retracted position unless a rotational force of a certain amount or more is applied to the zoom operating ring. This way,
It is possible to prevent the lens barrel from being inadvertently collapsed during shooting.

Further, in the above embodiment, the cam groove of the cam ring for performing the zooming operation is formed so as to guide the taking lens to the storage position, and the lens barrel is retracted by operating the zoom operation ring. However, instead of this, the cam groove or helicoid screw of the cam ring or helicoid ring for focus adjustment is formed so as to guide the taking lens to the storage position, and the lens barrel is operated by operating the focus operation ring. You may make it a collapsed state. FIG.
FIG. 4 is an external view showing an embodiment thereof, and by operating the focus operation ring 24, the lens barrel can be in a use state shown in (a) and a collapsed state shown in (b). .

[0042]

As described above, according to the present invention,
When the lens barrel is in the retracted state, the viewfinder screen becomes dark and the photographer can be notified that the lens barrel is in the retracted state, so it is possible to prevent accidental shooting when the lens barrel is retracted. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the optical axis direction of a retractable lens barrel 1 of a camera according to an embodiment of the present invention, showing a taking lens L1
It is a figure which shows the state in which L2 is in a wide position.

FIG. 2 is a cross-sectional view of the retractable lens barrel 1 of FIG. 1 in the optical axis direction, showing a state in which the taking lenses L1 and L2 are in a storage position.

FIG. 3 is a plan view of the peripheral wall of the fixed barrel 2 showing the cam grooves 12, 13
FIG. 6 is a view showing the guide holes 7a and 7b of the linear guide cylinder 7, the front group pin 10 and the rear group pin 11 together.

FIG. 4 is a diagram showing an extension portion 19a provided on a conductor pattern 19 of the zoom encoder.

FIG. 5 is a diagram schematically showing a control system of the camera of this embodiment.

FIG. 6 is a flowchart showing a procedure when the control device 21 for the lens barrel sends a signal for retracting or non-collapsing to the control device 20 for the camera body.

FIG. 7 is a flowchart showing a control sequence of the diaphragm device 14 by the diaphragm control means incorporated in the control device 20 of the camera body.

FIG. 8 is a diagram showing an outer appearance of the lens barrel 1 at the time of tele, wide, and retracted.

FIG. 9 is a diagram showing a diaphragm at the time of tele, wide, and retracted.

FIG. 10 is a diagram showing a state of a finder screen at the time of tele, wide, and retracted.

FIG. 11 is a diagram showing an example in which the retracting operation of the lens barrel and the lens barrier are linked.

FIG. 12 is a diagram showing a state of a finder screen in use and in collapsed state of FIG. 11.

FIG. 13 is a diagram showing an example in which a lock mechanism for holding the lens barrel in a retracted state is provided.

FIG. 14 is a diagram showing an example in which a lens barrel is retracted by a focus operation ring 24.

[Explanation of symbols]

 1 collapsible lens barrel 2 fixed barrel 3 front group lens moving frame 4 rear group lens moving frame 5 zoom operating ring 6 cam ring 7 straight guide cylinders 7a, 7b guide hole 8 pin 9 rubber ring 10 front group pin 11 rear group pin 12 cam groove 13 cam groove 14 diaphragm device 15 diaphragm blade 16 diaphragm cam plate 17 diaphragm support plate 18 diaphragm motor 18a gear 19 zoom encoder conductor pattern 19a extension (a part of collapsing detection means) 20 camera body controller 21 lens Lens barrel control device 22 Lens barrier 23 Lock button 24 Focus operation ring L1 Front group lens (shooting lens) L2 Rear group lens (shooting lens) S1 Photometry / AF switch S2 Release switch S3 Aperture detection switch S4 Collapse detection means

Claims (2)

[Claims] 1. A retractable lens barrel that can be in a retracted state in which the total length in the optical axis direction is further shortened compared to the state in which the total length in the optical axis direction at the time of photographing is shortest. Is provided
A collapsible lens barrel, wherein the diaphragm aperture of the diaphragm device is set to a minimum or a value close to it when the collapsing detecting means detects that the collapsing state is present. 2. A camera provided with a retractable lens barrel capable of taking a retracted state in which the overall length in the optical axis direction is further shortened compared to the shortest state in the optical axis direction at the time of photographing, wherein the lens barrel is in the retracted state. A camera which is provided with a collapsing detection means for detecting whether or not the collapsing detection means detects the collapsing state so that the diaphragm aperture of the diaphragm device is set to a minimum value or a value close thereto. .