JPH0447699Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aperture detection device for a camera equipped with a program shutter using shutter blades that also serve as aperture blades.

[Conventional technology]

It is well known that when photographing a standard subject, a proper exposure can be obtained by ending the exposure operation when the integral value of the exposure amount reaches the value determined by the film sensitivity. In the case of a camera that can control the aperture aperture and shutter speed independently, when the aperture aperture is specified, the shutter speed is determined according to the field brightness, and when the shutter speed is specified, it corresponds to the field brightness. Proper exposure can be obtained by determining the aperture aperture.

However, in order to perform this kind of exposure control, there is a problem that the aperture blades, shutter blades (shutter curtains), and their drive devices must be provided independently, which makes them expensive, and it is difficult to create images with regard to the aperture effect and shutter effect. There is also the problem that unless you have specialized knowledge, you will not be able to make full use of this expensive mechanism.

For this reason, compact cameras are generally equipped with a program shutter that uses a shutter blade that also functions as an aperture blade.
As shown in the figure, while opening the approximation to a straight line,
The exposure operation ends when the integral value of the exposure amount reaches a value determined corresponding to the film sensitivity.

By the way, in the case of this type of program shutter,
The amount of exposure is proportional to the exposure time after the shutter blade reaches its open aperture, and in the so-called triangular region until the shutter blade reaches its open aperture, the amount of exposure per unit time increases as the exposure time passes. , when using a photodetector with a γ value of 1, in the so-called triangular region where the shutter blade reaches its open aperture, it is necessary to perform γ correction using some method according to the aperture characteristics of the shutter blade. Unable to control exposure.

Note that the γ value here is one of the numerical values representing the characteristics of the light receiving element, and in the case of a photovoltaic element, the photocurrent is
It refers to the value of γ when the reciprocal of the resistance value of the photoconductive element is proportional to the γ power of field brightness.

Typical means for gamma correction in this triangular region are: (1) Adjusting the aperture area of the light receiving element with a sub-diaphragm blade that opens and closes in conjunction with the shutter blade, so that the photocurrent increases as the aperture increases. (2) A predictive control method that predicts the shutter blade aperture characteristics and electrically corrects the charging current of an integrating circuit for exposure control based on the predicted aperture position. It is being

However, in the case of the sub-aperture blade method (1), the photocurrent fluctuates following the actual aperture characteristics of the shutter blades, so sufficient exposure accuracy can be obtained even if the aperture characteristics of the shutter blades change. On the other hand, it has been pointed out that the provision of the sub-diaphragm blades limits the arrangement location and shape of the shutter blade itself, and also limits the arrangement location of the light receiving element. In addition, in the case of the predictive control method (2), although it has the advantage that the location of the light receiving part is not mechanically restricted, the running characteristics of the shutter blade must be extremely stable in order for such a prediction to hold true. In order to stabilize the running characteristics of the shutter blades, it is necessary to provide a speed regulating mechanism such as a governor, which increases manufacturing costs, and also increases the inertial weight, which requires a large charging force. There is.

Then, if you track the change in aperture due to the movement of the shutter blade and electrically correct the charging current of the integration circuit for exposure control in accordance with the actual aperture value,
While supplementing the problems of both of the above methods, the advantage of the auxiliary aperture blade method is that exposure errors do not occur due to fluctuations in the running characteristics of the shutter blades, and the advantage of the predictive control method is that there is no restriction on the location of the light receiving section. There is a need for an aperture detection device that is capable of incorporating this technology and detecting changes in aperture due to the movement of the shutter blade with high accuracy.

Furthermore, it is well known that many compact cameras have a built-in small strobe with a fixed guide number. When using a strobe with a fixed guide number, it is necessary to control the F-number when synchronizing the strobe according to the film sensitivity and shooting distance. (1) An aperture restriction method that places a member that enters the travel path of the shutter blade and limits the aperture according to the film sensitivity and shooting distance; (2) A method that predicts the travel characteristics of the shutter blade and A predictive control method is known in which a strobe light emitting circuit is triggered at a timing when an F value determined in accordance with sensitivity and shooting distance is obtained.

However, in the case of the aperture restriction method (1), since the aperture position of the shutter blade is mechanically limited, it has the advantage of being able to obtain stable exposure accuracy regardless of fluctuations in the running characteristics of the shutter blade. It has been pointed out that the provision of a mechanical member that limits the shutter blade itself limits the location and shape of the shutter blade itself. In addition, in the case of the predictive control method (2), there is no need for an interlocking mechanism, so there are no restrictions on the shape or location of the shutter blades. If the running characteristics are not extremely stable, exposure errors will occur, and in order to stabilize the running characteristics of the shutter blades, it is necessary to provide a speed regulating mechanism such as a governor, which increases manufacturing costs.
There is a problem in that the inertial weight also increases and a large charging force is required.

Then, by tracking the change in aperture due to the movement of the shutter blade and firing the strobe at the timing when the F value determined according to the film sensitivity and shooting distance is actually obtained, the problems of both of the above methods can be solved. However, there is a need for an aperture detection device that can take advantage of the advantages of each, and in that sense can detect changes in aperture due to the movement of the shutter blade with high accuracy.

Various pulse encoders have been known as devices for detecting the current position of moving members, especially in the field of industrial equipment.
Considering its suitability for detecting aperture position,
It is no longer possible to guarantee sufficient detection accuracy because it must be stored in an extremely narrow space within the camera body, the camera position changes depending on the subject, and the power supply voltage also fluctuates.

[Means for solving problems]

The present invention was developed in view of the current situation.The camera body is housed in an extremely narrow space, and the camera position changes depending on the subject.
It is an object of the present invention to provide an aperture detection device that can guarantee sufficient detection accuracy under the condition that the power supply voltage also fluctuates.

In summary, the aperture detection device of the present invention includes a driving means for driving a shutter blade, and a slit at a position corresponding one-to-one to the opening position of the shutter blade, with appropriate intervals along the operating direction. a first plate-like body having a photographing aperture; a second plate-shaped body forming an operating space for the operating member between the light guide slits and having a light guide slit having a smaller area than the slit of the operating member; a light emitting element, which is located on the opposite side of the plate-shaped body from the working space of the working member and emits projection light into the working space through the light guide slit; and a detection means having a light-receiving element that receives reflected light from the plate-shaped body, and the actuating member has a reflectance of at least a surface on the detection means side that is lower than the detection level of the detection means. the first plate-like body has a reflective surface on the side of the working space that has a reflectance that provides reflected light higher than the detection level of the detection means,
The light guide slit has a reflectance of the surface on the side of the detection means at a level that allows only reflected light lower than the detection level of the detection means to be obtained, and the projection light and the reflected light of the detection means are arranged in the same light guide. The above object is achieved by making it so that it can pass through a slit.

[Effect]

According to the aperture detection device of the present invention, when the actuating member travels in the actuating space formed between the first plate-like body and the second plate-like body, the slit formed in the actuating member moves into the second plate-like body. The light guide slit formed in the plate-shaped body is traversed at appropriate time intervals. At this time, the level of light received by the light receiving element constituting the detection means fluctuates, and the aperture is detected by pulsing and counting this. In the present invention, the actuating member travels in a small operating space formed between the first plate-like body and the second plate-like body, and also moves between the first plate-like body and the second plate-like body. Since the thickness is also small, the detection operation can be performed with the minimum necessary thickness.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

The present invention is applied to a program shutter equipped with shutter blades that also serve as aperture blades.
First, FIG. 1 shows an example of the basic configuration of a program shutter having shutter blades that also serve as aperture blades.

In FIG. 1, 1 and 2 indicate shutter blades that also serve as aperture blades, and the shutter blades 1 and 2
are rotatably supported on shafts 1a and 2a, respectively. Further, 3 indicates a blade opening/closing ring which is rotatably held around the optical axis, and the blade opening/closing ring 3 is always urged counterclockwise by a spring 4 and is implanted in the blade opening/closing ring 3. pins 3a, 3
b denotes a long groove 1 formed in each of the shutter blades 1 and 2;
b, 2b. Further, 5 indicates a solenoid, which is an example of an actuator for rotating the blade opening/closing lever 3 clockwise.

To explain its operation, first, in the initial state, the solenoid 5 is demagnetized and the blade opening/closing ring 3 is biased counterclockwise by the spring 4. Therefore, the blade opening/closing ring 3 is stopped at the position where the claw 3c contacts the stopper 6, and the shutter blades 1 and 2 close the aperture 7.

When the solenoid 5 is energized in this state, the blade opening/closing ring 3 rotates clockwise against the tension of the spring 4 while the pins 3a and 3b lock the long grooves 1b and 2b. rotate clockwise around the shafts 1a and 2a to gradually open the aperture 7, and when the pawl 3d of the blade opening/closing ring 3 comes into contact with the stopper 6, the aperture 7 becomes an open diameter. . Then, when the solenoid 5 is demagnetized at the timing when proper exposure is obtained, the blade opening/closing ring 3 is rotated counterclockwise by the tension of the spring 4, and the shutter blades 1 and 2 close the aperture 7 and perform the exposure operation. end.

The specific configuration of the exposure control device will be described later, but this type of exposure control device performs a charging operation corresponding to the photocurrent flowing to the light receiving element in conjunction with the shutter release, and the charging level reaches a predetermined value. The exposure operation is terminated when this happens.

As already explained, in the case of this type of program shutter, the amount of exposure per unit time increases as the aperture increases in the triangular region up to the open aperture, so a light receiving element with a γ value of 1 is used. In this case, it is necessary to increase the charging current as the diameter increases. The aperture detection device of the present invention is designed to be able to detect the aperture value with high precision, so if the charging current is corrected based on the change in aperture detected by the aperture detection device over time, appropriate exposure can be achieved. can be given.

Furthermore, when photographing with a strobe, proper exposure can be provided by synchronizing the strobe at the timing when the output of the aperture detection device indicates an F value determined in accordance with the film sensitivity and photographing distance.

When detecting the aperture of the photographic lens using a photoelectric encoder, various methods can be considered, such as a method of detecting the amount of rotation of the shutter blade 1 (or 2), a method of detecting the amount of rotation of the blade opening/closing ring 3, etc. However, in the following, an example in which the amount of rotation of the shutter blade 1 is detected will be explained.

That is, a large number of slits 8a are formed on the circumference of the shutter blade 1 around the shaft 1a at locations that do not interfere with the operation of other mechanical members, and the slits 8a extend from the light emitting element 8b to the light receiving element 8c. By causing the light receiving element 8c to generate a pulse every time the optical path is opened or closed, and counting the pulses, the current aperture can be detected numerically.

FIG. 2 is an enlarged view of the main part of this encoder 8, and FIG. 3 is a sectional view taken from A in FIGS. 1 and 2.

A ground plate 8 is provided near the light emitting element 8b and the light receiving element 8c.
d and the base plate 8e are fixed to the camera body while maintaining a parallel state. In this embodiment, the reflectance of the base plate 8d is extremely high, and the reflectance of the shutter blade 1 is extremely low. The shutter blade 1 is supported so as to float between the base plate 8d and the base plate 8e, and the distance between the base plate 8d and the base plate 8e is set to the minimum necessary distance without interfering with the movement of the shutter blade 1. ing.

Furthermore, a light guide 8f with extremely low reflectance and transmittance is embedded in the opening formed in the base plate 8e, and a slit 8f with an area sufficiently larger than that of the slit 8a formed in the shutter blade 1 is located approximately in the center of the light guide 8f. A small light guide slit 8g is formed. The irradiation direction of the light emitting element 8b and the direction of incidence of the light receiving element 8c are both directed toward the light guide slit 8g, and the line segment connecting the light emitting element 8b and the light receiving element 8c is in the advancing direction of the slit 8a (that is, the direction of the shutter blade 1). direction of travel).

Therefore, the light beam emitted from the light emitting element 8b passes through the light guide slit 8g, is reflected by the base plate 8d or the shutter blade 1, passes through the light guide slit 8g again, and enters the light receiving element 8b. In this embodiment, the reflectance of the shutter blade 1 is extremely low, and the reflectance of the base plate 8d is extremely high, so that the slit 8a formed in the shutter blade 1 crosses the light guide slit 8g. The photocurrent flowing through the light-receiving element 8c varies greatly each time, and if this is pulsed and counted, the rotation angle of the shutter blade 1 (i.e., the aperture of the photographic lens) can be quantified and detected. .

FIG. 4 shows an example of a circuit for quantifying the rotational position of the shutter blade 1 (ie, the current F value) in response to changes in the photocurrent flowing through the light receiving element 8c.

First, in Fig. 4, 1, 8a, 8b, 8
c, 8d, 8e, 8f, and 8g are the already explained shutter blade 1, slit 8a, light emitting element 8b, light receiving element 8c, base plate 8d, 8e, light guide 8f,
Each light guide slit 8g is shown, and in the illustrated embodiment, a photodiode is used as an example of the light emitting element 8b, and a phototransistor is used as an example of the light receiving element 8c.

The collector side of the light receiving element 8c is connected to the positive pole of the power supply, and the emitter side is connected to the ground via the resistor _R1 , so that the light energy incident on the light receiving element 8c is converted into a voltage at the terminal level of the resistor _R1 . The terminal level of the resistor _R1 is connected to the operational amplifier 1 via the DC cut capacitor 11.
applied to the inverting input of 2. This operational amplifier 12
The output of comparator 13 is applied to the inverting input of comparator 13, a reference level is applied from bias power supply 14 to the non-inverting input of comparator 13, and the output of comparator 13 is connected to the clock terminal of counter 20.

Next, the operation of this embodiment will be explained with reference to the above matters.

First, as the solenoid 5 is energized, the shutter blade 1 travels between the base plate 8d and the base plate 8e, and the slit 8a formed in the shutter blade 1 successively crosses the position of the light guide slit 8g.

On the other hand, the light emitted from the light emitting element 8b passes through the light guide slit 8g, is reflected by the base plate 8d or the shutter blade 1, passes through the light guide slit 8g again, and reaches the light receiving element 8c. As mentioned above, in this embodiment, the reflectance of the base plate 8d is sufficiently high and the reflectance of the shutter blade 1 is sufficiently low, so that each time the slit 8a passes through the light guide slit 8g, the light is incident on the light receiving element 8c. The amount of light emitted fluctuates greatly, and the terminal level of resistor _R1 also fluctuates accordingly.

The terminal level of this resistor R ₁ is amplified by an operational amplifier 12 and applied to an inverting input of a comparator 13 after a portion equivalent to the dark current of the light receiving element 8 c is removed by a DC cut capacitor 11 . Then, the comparator 13 compares this with the reference level applied from the power supply 14 and converts it into a pulse. Therefore, a pulse is generated from the comparator 13 every time the slit 8a passes the light guide slit 8g, and this pulse is sent to the counter 20. added to the clock terminal,
Since the counter 20 is counted up (or counted down), the rotational position of the shutter blade 1 is quantified as the count value of the counter 20.

Incidentally, the shutter blade 1 may be tilted due to a change in camera posture or other reasons, but in this embodiment, the shutter blade 1 is configured to pass through a small space between the base plates 8d and 8e. The inclination of the shutter blade 1 is restricted to a minimum in the vicinity of the encoder 8.

In addition, when the shutter blade 1 runs unstable due to changes in the camera posture as described above, the shutter blade 1 normally moves in the direction of movement, that is, through the slit 8a.
However, in this embodiment, as described above, the line segment connecting the light emitting element 8b and the light receiving element 8c is the slit 8 formed in the shutter blade 1.
Since it is perpendicular to the traveling direction of the light emitting element 8d, the angle of incidence of the light emitted from the light emitting element 8d onto the shutter blade 1 is hardly affected by the inclination of the shutter blade 1.

Furthermore, in this embodiment, the change in the amount of light incident on the light receiving element 8c is converted to the terminal level of the resistor _R1 , and this terminal level is compared with a reference level to form a pulse. When the reflectance of the shutter blade 8d is increased and the reflectance of the shutter blade 1 is decreased, and the light emitted from the light emitting element 8b is reflected on the ground plate 8d and enters the light receiving element 8c, the terminal level of the resistor _R1 is turned on. When the light emitted from the light emitting element 8b is reflected by the shutter blade 1 and enters the light receiving element 8c, the terminal level of the resistor _R1 becomes the off level.
The inclination of the shutter blade 1 affects the terminal level of the resistor _R1 when the shutter blade 1 blocks the light guide slit 8g.
If the shutter blade 1 tilts when it blocks the light guide slit 8g, there will be resistance.
Since the terminal level of _R1 is further lowered than the original off level, it has no effect on the pulsing.

Furthermore, in the case of the aperture detection device of this embodiment, the light guide 8f is formed to have extremely low reflectance and transmittance, so that some of the light emitted from the light emitting element 8b is reflected by the light guide 8g and transmitted to the light receiving element. Very few components reach the light receiving element 8c.
The dark current flowing through c is extremely small and is sufficiently removed by the DC cut capacitor 11.

Furthermore, as mentioned above, the area of the light guide slit 8g is sufficiently smaller than the area of the slit 8a formed in the shutter blade 1, so the slit 8a formed in the shutter blade 1 instantly cuts through the light guide slit 8g. As a result, the photocurrent flowing through the light-receiving element 8c exhibits rapid rise and fall, making it possible to form accurate pulses.

Then, if the charging current of the integrating circuit for exposure control is controlled by the rotational position of the shutter blade 1 digitized as the count value of the counter 20 (i.e., the current F value), the shutter blade 1, Exposure control corresponding to the aperture characteristics of 2 becomes possible, and if the strobe is synchronized when the F value detected as described above reaches a level determined according to the film sensitivity and shooting distance. , accurate exposure control in flash photography becomes possible.

Therefore, next, we determined the method of controlling the charging current of the integrating circuit for exposure control and the strobe synchronization timing in flash-matic mode based on the actual F value detected by the aperture detection device according to the present invention. An example of a method for doing this will be explained with reference to FIG.

In FIG. 5, 30 is a known exposure control circuit;
Reference numeral 40 indicates a drive circuit for driving the shutter blades 1 and 2, and 50 indicates a sequence circuit for controlling various sequences.

First, the exposure control circuit 30 shown in FIG.
31 is used without bias, and in order to support a wide range of brightness, the log diode 32 is used as a feedback resistor for the operational amplifier 33.
3 is supplied with a bias voltage V ₁ from a bias power supply 34 .

Therefore, the light changes to SPD31 depending on the field brightness.
When the photocurrent is incident on the SPD 31, a photocurrent flows in the opposite direction, and a voltage drop V ₂ is generated across the log diode 32 due to this photocurrent. If the switching transistor 35 is cut off at this time, the log diode 3 is connected to the bias voltage V ₁ of the bias power supply 34 at the output terminal of the operational amplifier 33.
The output voltage of the operational amplifier ₃₃ is applied to the base of the logarithmic expansion transistor 36 to control its collector current, and the collector current of the transistor 36 causes the capacitor 37 to It will be charged.

The charge level of this capacitor 37 is applied to the inverting input of the comparator 37, and when this matches the reference level applied from the bias power supply 39 to the non-inverting input of the comparator operating member 8, the shutter close signal generated by the comparator 38 is generated. In response to this, the transistor 41 is cut off, the solenoid 5 is demagnetized, and the shutter blades 1 and 2 are closed. Note that the transistor 310 connected in parallel with the capacitor 37 activates the exposure control circuit 30, and when the transistor 310 is cut off in conjunction with the shutter release, the charging operation of the capacitor 37 is started.

In the seed structure exposure control circuit 30, when the transistor 35 is cut off, the transistor 36
The collector-emitter current becomes the charging current of the capacitor 37, and this charging current is determined by the voltage drop _V2 generated in the log diode 32 due to the photocurrent flowing through the light receiving element 31. is a necessary condition for charging the capacitor 37, so the greater the ratio of the cut-off time of the transistor 35 per unit time, the greater the amount of charge stored in the capacitor 37 per unit time.

Therefore, the ratio of the cut-off time of the transistor 35 (i.e., the duty ratio of the exposure control circuit 30) is determined in accordance with the actual aperture of the photographing lens that is numerically detected and detected by the aperture detection device of this embodiment. This makes it possible to perform γ correction in the so-called triangular region until the shutter blades 1 and 2 reach their open apertures.

More specifically, a pulse of a predetermined period generated by the duty conversion circuit 80 is applied to the base of the transistor 35, and the off-time ratio of this pulse can be determined in accordance with the count value of the counter 20. .

Various methods can be considered for varying the off-time ratio of pulses generated by the duty conversion circuit 80, but in the illustrated example, the duty conversion circuit 80 is designed to facilitate digitization and microcomputerization. The duty conversion circuit 80 itself includes an oscillator 81 for generating a reference clock, and a pulse width conversion circuit 82 with a built-in time table. Time data is read from the time table, and the off time of the pulse is determined in accordance with this time data.

As already explained, in the case of a program shutter with this type of structure, the amount of exposure per unit time increases as the shutter blades 1 and 2 open, so as the count value of the counter 20 increases, the pulse Needless to say, time data such that the ratio of the off time of the pulse applied from the width conversion circuit 82 to the transistor 35 increases is prepared in a time table built in the pulse width conversion circuit 82. Furthermore, it is well known that even if the field brightness is the same, if the film sensitivity differs, the required exposure amount will change. Therefore, for example, if we assume a camera compatible with DX film (a film in which the film sensitivity, number of sheets, etc. are written in a conductive pattern at a predetermined location on the cartridge), the output of the DX circuit 70 is used to convert the pulse width into the pulse width conversion circuit 82. The off-time ratio of the pulse applied to the transistor 35 may be determined by selecting a page of the built-in time table or by changing the multiplication rate for time data read from the time table. Furthermore, DX circuit 7
0 encodes the on/off pattern of a group of contacts that turn on and off in response to the conductive pattern written on the DX film cartridge, and can be easily constructed using a well-known encoder circuit.

If the camera does not support DX film, the dial value of the film sensitivity setting dial may be input as the terminal level of the sliding resistor, and this may be converted into a digital code.

In the above example, the off-time ratio of the pulse applied to the transistor 35 is determined by the time table built into the pulse width conversion circuit 82 in order to facilitate microcomputerization, but the duty conversion circuit 80 For example, a sawtooth wave is applied to one input of the comparator, and the reference level of this comparator is set to the counter 2.
It may be determined in accordance with the count value of 0 and the output of the DX circuit 70.

Next, a circuit for determining strobe tuning timing will be explained.

When using a strobe with a fixed guide knife, once the film sensitivity and photographing distance are determined, the F value that provides the appropriate exposure can be calculated through arithmetic processing.

First, the film sensitivity is obtained as the output of the DX circuit, and the photographing distance is obtained as the output of the distance measuring circuit 90. Specifically, the distance measuring circuit 90 may detect, for example, the amount of heycoid delivery as the terminal level of a sliding resistor, or may be a distance measuring circuit for autofocus.

Then, by applying the film sensitivity information and photographing distance information from the DX circuit 70 and the distance measuring circuit 90 to the arithmetic circuit 100, it is possible to calculate the F value that provides the appropriate exposure through arithmetic processing. The formula for determining the F value in accordance with the film sensitivity, photographing distance, and guide number is well known. The F value information obtained by the arithmetic circuit 100 is then given to the digital comparator 110.

On the other hand, as described above, the actual F value of the photographic lens has already been quantified as the count value of the counter 20.

Therefore, the count value of the counter 20 is given to the digital comparator 110, and the digital comparator 1
10 is the EFU circuit 1 at the timing when the count value of the counter 20 and the output of the arithmetic circuit 100 match.
By adding a trigger signal to 20, it is possible to cause the strobe to emit light at the timing when the actual aperture reaches the appropriate F value.

The EFU circuit 120 is a known circuit including a xenon discharge tube, a capacitor, a trigger coil, etc.

Although the above example shows an example in which the movement of the shutter blade 1 is tracked, the present invention can be applied to any flat plate-like member that is linked to the movement of the shutter blade.

〔effect〕

As explained above, according to the present invention, the actuating member in which the slit is formed travels in a small space between the pair of parallel base plates, so that even if the camera posture changes, the inclination of the actuating member will not change at the detection point. is regulated to a minimum and is normally tilted in a direction that does not easily affect the direction of incidence on the light receiving element, so it is possible to detect the aperture with high accuracy without being affected by attitude changes.

Furthermore, in the present invention, the reflectance of the actuating member is configured to be lower than that of the first plate, so even if the actuating member is tilted for some reason, the detection level at the light receiving element remains the standard. Since it acts in a direction away from the level, the tilting of the actuating member has no effect on the detection accuracy. In addition, there is no foreign material such as optical glass intervening in the optical path, and only reflective surfaces such as metal surfaces or vapor-deposited surfaces are formed, and the portions that actually act as reflective surfaces are Since the area is sufficiently narrower than that of the detection device, there is a risk that the thickness of the detection device increases and that, due to repeated movement of the actuating member, for example, parts may fall off, scratches or other optical damage may occur in the reflected optical path. There is also less sex.

Furthermore, when the power supply voltage decreases due to power consumption, the detection level and the reference level decrease at the same time, so a slight decrease in the power supply voltage does not affect detection accuracy.

[Brief explanation of the drawing]

Fig. 1 is a mechanical diagram of a program shutter according to an embodiment of the present invention, Fig. 2 is an enlarged view of the main parts of Fig. 1,
Fig. 3 is a sectional view taken from A in Figs. 1 and 2, Fig. 4 is a circuit diagram showing an example of a circuit for quantifying the aperture value, and Fig. 5 is a detection by the aperture detection device of the present invention. FIG. 6 is a circuit diagram showing an example of a control circuit including a circuit for γ correction and a circuit for determining strobe synchronization timing according to the selected aperture, and FIG. 6 is an aperture characteristic diagram of a general program shutter. 1...Shaft blade, 8a...Slit, 8b
...Light emitting element, 8c...Light receiving element, 8d...Main plate, 8e...Main plate, 8f...Light guide, 8g
...Light guide slit, R ₁ ...Resistance, 10
...Waveform shaping circuit, 20...Counter.

Claims (1)

[Claims for Utility Model Registration] Slits are formed in the drive means for driving the shutter blades and at appropriate intervals along the operating direction at positions that correspond one-to-one with the opening positions of the shutter blades. an actuating member; a first plate-like body having a photographing aperture; and a first plate-like body having a photographing aperture, the body being disposed opposite to the first plate-like body, and having a space between the first plate-like body and the first plate-like body. a second plate-like body forming an operating space of the actuating member and having a light guide slit having a smaller area than the area of the slit of the actuating member; and the second plate-like body. a light emitting element, which is located on a side surface of the actuating member opposite to the actuating space and emits projection light into the actuating space through the light guide slit; and an actuating member or a first plate-shaped body. a detection means having a light-receiving element that receives reflected light from the actuating member, and the actuating member is capable of obtaining only reflected light having a reflectance of at least a surface on the detection means side that is lower than a detection level of the detection means. the first plate-shaped body has a reflective surface having a reflectance that allows reflected light to be obtained higher than the detection level of the detection means, and the light guide slit has a reflective surface on the side of the working space, and the light guide slit has The reflectance of the surface on the side of the detection means is set to a level that allows only reflected light that is lower than the detection level of the detection means, and the projected light and the reflected light of the detection means pass through the same light guide slit. caliber detection device.