JPH07109470B2 - Automatic exposure control device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an automatic exposure control device for a program shutter using a shutter blade that also serves as an aperture blade, and in particular,
The present invention relates to an automatic exposure control device that detects the time for which a shutter blade travels a predetermined distance from the start of travel to the pinhole to correct the closing timing of the shutter blade.

[Prior art and its problems]

The purpose of the automatic exposure control is to make the integrated amount of light received on the film surface a value that is determined according to the film sensitivity. Therefore, the automatic exposure control device uses the photocurrent flowing through the light receiving element to open the shutter blade. The exposure operation is completed at the timing when the integrated value reaches a predetermined reference voltage. By the way, in the program shutter using the shutter blade that also serves as the diaphragm blade, the shutter blade is gradually opened. Therefore, in the triangular opening area up to the opening diameter, the film surface illuminance changes with the passage of exposure time. Will rise. However, as long as the field brightness is constant, the photocurrent is constant regardless of the opening position of the shutter blades.
Proper exposure control cannot be achieved if the photocurrent is uniformly integrated in conjunction with the opening operation of the shutter blades. Therefore, in general, appropriate exposure compensation is performed so as to match the aperture characteristics of the shutter blades intended at the time of design. However, even if the automatic exposure control device is adjusted so that the proper exposure is obtained when the camera is shipped, there is no guarantee that the aperture characteristics of the shutter blades are always stable, and the shutter blades may change over time or due to changes in the affected attitude. If the aperture characteristics of fluctuate, exposure errors may occur. In order to prevent the exposure error caused by the variation of the aperture characteristic of the shutter blade, a method of detecting the actual aperture characteristic of the shutter blade by a photo interrupter and correcting the automatic exposure control device can be considered. In this case, it is required to provide two series of photo interrupters for detecting the opening positions of the shutter blades. This is because a camera having a program shutter of this kind generally has a flashmatic control device using a built-in strobe, and the flashmatic control device has a photointerrupter for detecting the strobe emission timing. This is because the strobe is a thyristor trigger and its operation delay does not need to be taken into consideration, while automatic exposure control causes a mechanical closing delay, and therefore it is not appropriate to use the same photo interrupter. Therefore, when the exposure is corrected by the photo interrupter, in addition to the photo interrupter for the flashmatic control, the photo interrupter for the exposure correction is provided in a separate series, which complicates the related mechanism of the shutter blades. Occurs.

[Means for solving problems]

The present invention has been made in view of such problems,
A new automatic exposure control that can perform exposure compensation that matches the actual aperture characteristics of the shutter blades without providing a separate blade position detection mechanism for flashmatic control The purpose is to provide a device. The automatic exposure control device of the present invention detects the actual opening characteristic of the shutter blade in advance by detecting the time required for the shutter blade to travel a predetermined amount in the period before the pinhole becomes a pinhole after the shutter blade is released. The exposure is corrected by grasping it, and the following means are provided to achieve the above object. (A). Mark points are continuously provided along the traveling operation line on the shutter blade or on a member interlocking with the shutter blade. (B). A sensor that generates a pulse in response to the passage of the mark point is provided at the passage point of the mark point. (C). Exposure compensation is performed by grasping the opening characteristic of the shutter blade based on the pulse interval generated by the sensor in response to at least two mark points before the pinhole in the mark point. (D). More preferably, the strobe tuning timing is controlled by the pulse generated by the sensor in response to the mark point after the pinhole in the mark point.

[Action]

The automatic exposure control device of the present invention controls the exposure correction and the strobe synchronization timing corresponding to the variation of the aperture characteristics of the shutter blades by a series of blade position detection devices. The exposure compensation corresponding to the variation of the aperture characteristic of the shutter blade is
At least 2 before the pinhole in the mark point
The opening rising speed of the shutter blade is grasped by measuring the time required for the above mark points to pass the position of the sensor, and when the shutter blade rises rapidly, the exposure is negatively corrected, and conversely If it rises slowly, it is performed by correcting the exposure plus. More specifically, this exposure correction is performed by adjusting the output current of the optical amplifier or adjusting the reference voltage that is compared with the integrated value of the photocurrent. The strobe synchronization timing is controlled by detecting the aperture position by the pulse generated by the sensor in response to the mark point after the pinhole in the mark point, and the aperture position of the shutter blade corresponds to the film sensitivity and the influence distance. Synchronize the flash at the timing you did. Since one series of blade position detecting devices is used for exposure correction before the pinhole and for flashmatic control after the pinhole, there is no need to consider the shutter blade closing delay time.

【Example】

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view of shutter blades that also serve as diaphragm blades used in a program shutter according to an embodiment of the present invention. The shutter blade 1 is swingably supported by a shaft 2 on the main plate, and the shaft 2 supports the shutter blade 1 and a shutter blade (not shown) whose opening and closing portions are symmetrical. A boss 3 of a blade opening / closing member (not shown) is engaged with the elongated hole 1a formed in the shutter blade 1. When the boss 3 is moved downward in the drawing, the shutter blade 1 is centered on the shaft 2. Then, the V-axis 1b formed on the shutter blade 1 opens the aperture 5 and the exposing operation is performed. The time when the relative position of the aperture 5 with respect to the shutter blade 1 becomes the state shown by the alternate long and short dash line in FIG. 1 is the open aperture. The shutter blade 1 is provided with, for example, 9 perforations along the circumference centered on the axis 2, and these perforations are sequentially marked points P _{0 to} P ₈ . When the shutter blade 1 rotates clockwise, the mark points P _{0 to} P ₈ sequentially pass through the photoelectric sensor 4. In this embodiment, since the mark points P _{0 to} P ₈ are perforation marks, the photoelectric sensor 4 is a transmission type in which a light emitter and a light receiver are arranged on both sides of the shutter blade 1. When the mark points P _{0 to} P ₈ are reflection marks, the photoelectric sensor 4 is of a reflection type. The mark points P _{0 to} P ₈ and the positions of the shutter blades have a correspondence relationship as shown in Table 1. Incidentally, generally marked point P ₂ is a compact camera for detecting a flash sync timing in so-called flashmatic control having a program shutter
.. P ₈ and the photoelectric sensor 4, and the characteristic point in this embodiment is that the mark point P ₀ .P ₁ is arranged in front of the mark point P ₂ for pinhole detection, and the mark point P
_The exposure is corrected according to the time from when ₀ is detected to when the mark point P _{1 is} detected, so that flashmatic control and automatic exposure control are performed by only one series of photointerrupters. Now, prior to the description of a specific embodiment, the basic principle of the present invention will be described with reference to FIGS. 2 and 3. First, FIG. 2 shows the relationship between the opening area (vertical axis) and the exposure time (horizontal axis) of the shutter blade that also serves as the diaphragm blade. After the shutter blade 1 is opened, the shutter blade 1 opens substantially linearly to reach the opening diameter. . It should be noted that, although the aperture characteristics differ in detail depending on the shape of the shutter blade 1 and the drive mechanism thereof, the above tendency is basically shown. In FIG. 2, if the curve a indicated by the thick line is the characteristic curve that is planned at the time of shipment, the amount of light received on the film surface becomes appropriate when the shutter blade opens with the characteristic similar to the curve a. The exposure control device is adjusted. However, the aperture characteristics of the shutter blades may change due to aging, camera posture changes, etc. For example, if the same exposure control is performed when the curve b shown by a thin line rises gently, underexposure may occur. or,
If the same exposure control is performed when the curve abruptly rises as shown by the dotted line c, overexposure results. Therefore, in the present embodiment, the mark points P _{0 to} P ₁ provided in the area from the start of travel of the shutter blade to the pinhole are formed.
The actual opening characteristic of the shutter blade 1 is predicted by detecting the passage time of the exposure time, and the exposure is corrected accordingly. FIG. 3 is a block diagram showing the principle of the exposure control device, 10 is an optical amplifier, 11 is an example of a photo detector
A photo diode (hereinafter simply referred to as SPD), 20 is a bias voltage circuit of the optical amplifier 10, 6 is a magnet for closing / releasing the shutter blade 1, 30 is a comparator, 31 is a condenser for integrating field light, 40 Denote reference voltage circuits of the comparator 30, respectively. To explain the basic operation, the optical amplifier 10 outputs a current corresponding to the field light incident on the SPD 11, and the output current of the optical amplifier 10 charges the integrating capacitor 31. When the charge level of the capacitor 31 reaches the output voltage of the reference voltage circuit 40, the output of the comparator 30 is inverted to H level and demagnetizes the magnet 6, so that the shutter blade 1 closes and the exposure is completed. Now, the first mode of exposure correction is to adjust the output voltage of the reference voltage circuit 40 according to the passage time of the mark points P _{0 to} P ₁ . In the circuit of FIG. 3, exposure is positively corrected if the output voltage of the reference voltage circuit 40 is increased under conditions of constant field brightness, and exposure is negatively corrected if the output voltage of the reference voltage circuit 40 is decreased. It Therefore, if the output voltage of the reference voltage circuit 40 is increased as the passage time of the mark points P _{0 to} P ₁ becomes longer, proper exposure correction is performed. Next, the second mode of exposure correction is to adjust the output voltage of the bias voltage circuit 20 according to the passage time of the mark points P _{0 to} P ₁ . In the circuit of FIG. 3, if the output voltage of the bias voltage circuit 20 is increased under the condition that the brightness of the field is constant, the output current of the optical amplifier 10 is increased. The exposure is positively corrected because the output current of the optical amplifier 10 is reduced by decreasing. Therefore, if the output voltage of the bias voltage circuit 20 is lowered as the passage time of the mark points P _{0 to} P ₁ becomes longer, proper exposure correction is performed. FIG. 4 shows an embodiment including a circuit for performing the exposure compensation of the first mode, and the elements shown in FIG. 3 are assigned the same reference numerals as those in FIG. Reference numeral 4 denotes the photoelectric sensor also shown in FIG. 1, and a pulse generated by the photoelectric sensor 4 is added to the window gate circuit 50, the latch circuit 60, and the counter 61 each time the mark points P _{0 to} P ₈ pass. First, the latch circuit 60 is for controlling the integration start timing of the field light, and is known per se. As shown in the characteristic curve of FIG. 2, the aperture 5 becomes a pinhole after a lapse of a predetermined time after the shutter blade 1 starts traveling. The latch circuit 60 performs a latch operation by using the first pulse generated by the photoelectric sensor 4 as a trigger,
The delay circuit 62 is activated. The delay time of the delay circuit 62 is set on the basis of the time from when the mark point P ₀ passes through the photoelectric sensor 4 until the aperture 5 actually becomes a pinhole and the closing delay time of the blade, and after the set time elapses. When the output of the delay circuit 62 falls, a transistor for switching
63 is cut off and charging of the capacitor 31 is started. Next, the counter 61 is for quantifying the aperture diameter in flashmatic control. That is,
Since the photoelectric sensor 4 generates a pulse each time the mark points P _{0 to} P ₈ pass, the aperture value can be digitized by counting the pulses generated by the photoelectric sensor 4. As is well known, the aperture value at the time of strobe tuning when a strobe with a fixed guide number is used is uniquely determined if the film sensitivity and the shooting distance are determined. Therefore,
The output of the counter 61 indicating the aperture value is added to the decoder 64 together with the ISO information and the influence distance information, and the decoder 64 outputs a known strobe when the combination of the count value of the counter 61, the ISO information and the shooting distance information becomes an appropriate combination. A light emission trigger signal is applied to the light emitting circuit 65. Next, the window gate circuit 50 is for raising the output from the first pulse to the second pulse generated by the photoelectric sensor 4, for example, SR type flip-flop 51. It is composed of a D-type flip-flop 52 and an AND gate 53. The operation will be described. The flip-flop 52 is reset in the initial state and its output is at the H level. Therefore, when the flip-flop 51 is set by the pulse generated by the photoelectric sensor 4 when the mark point P ₀ passes, the AND gate
The output of 53 rises. After that, the flip-flop 52 latches the Q output of the flip-flop 51 by the pulse generated by the photoelectric sensor 4 when the mark point P ₁ passes, so that the output of the flip-flop 52 falls,
The output of the AND gate 53 falls. Therefore, the output of the AND gate 53 indicates the mark point P _{0 at} the position of the photoelectric sensor 4.
Goes high until the mark point P ₁ passes. Therefore, if the output of the AND gate 53 is used as a window and the reference pulse generated during the rising time of this window is counted, the time from when the photoelectric sensor 4 detects the mark point P ₀ until it detects the mark point P ₁ is determined. I can know. In this embodiment, the output of the AND gate 53 is applied to the AND gate 66, and the reference pulse generated by the oscillator 67 is applied to the other input of the AND gate 66. Therefore,
The reference pulse generated by the oscillator 67 passes through the AND gate 66 while the output of the AND gate 53 is at the H level and the counter pulse is counted.
Since the counter 68 is incremented, the count value of the counter 68 indicates the passage time of the mark points P _{0 to} P ₁ , and the reference voltage circuit 40 is controlled by the count value of the counter 68. As described above, if the output voltage of the reference voltage circuit 40 is increased, the exposure is positively corrected, and if the output voltage of the reference voltage circuit 40 is decreased, the exposure is negatively corrected under the condition that the field brightness is constant. . The longer the passage time of the mark points P _{0 to} P ₁ (that is, the larger the count value of the counter 68) is, the more the exposure needs to be corrected. Therefore, the larger the count value of the counter 68 is, the more the reference voltage is increased. If the output voltage of the circuit 40 is increased, proper exposure correction is performed. A specific example of the reference voltage circuit 40 is shown in FIG. The circuit of FIG. 5 shows that when a current is applied to the resistor 41, the resistor 41
The voltage generated at the
The opening pattern of the shutter blade 1 is reflected in the reference voltage of the comparator 30 by determining the operation pattern of the current adding circuit corresponding to the count value of 68. In FIG. 5, I _{1 to} I ₄ are constant current sources for addition, S _{1 to} S ₅ are current switches, and the current switches S _{1 to} S _{5 form} a switching transistor sw and a current mirror circuit. It is composed of a diode d and a transistor t. Here, the operation of each of the current switches S _{1 to} S ₅ will be described. The current applied to the collector-base connection point of the diode d forming each of the current switches S _{1 to} S ₅ flows to the ground through the transistor sw when the switching transistor sw is conducting, but the transistor sw is cut off. Then, it flows into the diode d. Since the transistor t forms a current mirror circuit with the diode d, a current equal to the current flowing through the diode d will flow through the transistor t. Then, the current is supplied from the constant current source I ₁ ~I ₄ Each current Suichi S ₁ to S _4, since the output transistor t is connected to the diode 42, the constant current source I ₁ ~I ₄ The current value of the
If the operation pattern of the transistors sw for switching S _{1 to} S ₄ is controlled by the output of each stage of the counter 68 (low active in this embodiment), the current added corresponding to the count value of the counter 68 is fed to the diode 42. Will flow to. Since the diode 42 forms a current mirror circuit with the transistor 43, the transistor 43 has a diode
A current equal to the current flowing through 42 flows, and this current flows through resistor 41.
Is supplied to. Next, the current switch S ₅ is supplied with current from the constant current source 46, and the switching transistor sw is connected to the Q output of the flip-flop 45 set by the pulse generated by the one-shot circuit 44. The output transistor t of the current switch S ₅ is connected to the diode 47. Further, 49 is a constant current source for supplying a bias current to the resistor 41. Therefore, until the flip-flop 45 is set, the current flowing through the constant current source 46 flows through the diode via the current switch S ₅ , and the same current flows through the diode 47 and the transistor 48 forming the current mirror circuit. The current flowing through the transistor 43, the current flowing through the constant current source 49, and the current flowing through the transistor 48 are added to the resistor 41 and supplied, but after the flip-flop 45 is set, the resistor 41 is connected to the transistor 43. Current and constant current source
The current flowing through 49 is added and supplied. Next, the operation of this embodiment will be described with reference to the above matters. The current ratio of each of the constant current sources I _{1 to} I ₄ varies depending on the aperture characteristics of the shutter blade 1, but here it is assumed that the constant current sources I ₁ , I ₂ , I ₃
-It is assumed that the current ratio of I ₄ is 1: 2: 4: 8. First, in the set state of the shutter blade 1, all the circuit elements are in the initial state. The SPD 11 is always exposed to the field light, and the optical amplifier 10 outputs a current corresponding to the field brightness, but in the initial state, the output of the delay circuit 62 is at the H level and the transistor is a transistor.
Since 63 is conducting, the capacitor 31 is not charged. Further, since the flip-flop 45 in FIG. 5 has been initially reset, the switching transistor sw of the current switch S ₅ is cut off, and the current flowing in the constant current source 46 is supplied to the diode 47 via the current switch S _5. Current, and a current equal to this flows in the transistor 48. Therefore, a voltage sufficiently higher than the collector level of the transistor 63 is generated at the terminal of the resistor 41, the output of the comparator 30 becomes L level, the magnet 6 is excited, and the shutter blade 1 is held in the set state. . When a shutter button (not shown) is pressed, the shutter blade 1 rotates clockwise about the shaft 2 to open the aperture 5, and in the process of opening, the mark points P _{0 to} P ₈ are sequentially detected by the photoelectric sensor. 4 and the photoelectric sensor 4 generates a pulse each time the mark points P _{0 to} P ₈ pass. Then, the pulse generated by the photoelectric sensor 4 is applied to the window gate circuit 50, the latch circuit 60 and the counter 61. First, in the latch circuit 60, the mark point P ₀ is the photoelectric sensor 4
It is set by the pulse generated by the photoelectric sensor 4 when passing through, and the delay circuit 62 is activated by this output. The window gate circuit 50 sets its output to the H level from the time when the mark point P ₀ passes through the position of the photoelectric sensor 4 to the time when the mark point P ₁ passes, and the reference pulse generated by the oscillator 67 is the wind gate. While the output of the circuit 50 is high, the AND gate 66 is passed through and the counter 68 is incremented. The time when the output of the window gate circuit 50 is at the H level becomes shorter as the traveling speed of the shutter blade becomes faster. Now, it is assumed that the opening characteristic of the shutter blade 1 is adjusted so that eight reference pulses are applied to the counter 68 while the output of the window gate circuit 50 is at the H level. When the shutter blade opens according to the expected characteristics, eight reference pulses are added, so that the counter 68 has only its fourth-stage output active (L level),
Only the switching transistor sw in the current switch S ₄ is cut off. Therefore, the current of weight [8] flowing through the constant current source I ₄ flows through the diode 42 through the current switch S ₄ , and the same current flows through the transistor 43. Then, the flip-flop 45 is set by the pulse generated by the one-shot circuit 44 at the falling edge of the output of the AND gate 53, so that the current switch S ₅ is cut off. Therefore, a current obtained by superimposing the current of weight [8] flowing through the transistor 43 and the bias current flowing through the constant current source 49 flows through the resistor 41, and the voltage generated at the resistor 41 at this time is applied as a reference voltage to the comparator 30. It When the output of the delay circuit 62 becomes L level and the transistor 63 is cut off at a timing when a predetermined time has elapsed after being triggered by the latch circuit 60, the capacitor 31 is charged by the current supplied from the optical amplifier 10. At the timing when the charging voltage reaches the reference voltage of the comparator 30, the output of the comparator 30 becomes H level, the magnet 6 is demagnetized, and the shutter blade 1 is closed and released. Now, if the rising curve of the shutter blade 1 becomes gentle due to aging, camera posture, or other reasons, the time during which the output of the wind gate circuit 50 is at the H level becomes longer, and the counter 68 has eight or more pulses. Added. For example, if 12 pulses are applied to the counter 68 while the output of the window gate circuit 50 is at the H level, the counter 68 outputs the third stage output and the fourth stage output at the H level. Therefore, the current of weight [4] flowing through the constant current source I ₃ and the current of weight [8] flowing through the constant current source I ₄ flow to the diode 42 via the current switch S ₃ and the current switch S ₄ , so that the diode 42 A current of weight [12] flows through. Then, since the current flowing through the diode 42 flows through the transistor 48 through the above path, the reference voltage applied to the comparator 30 rises. Therefore, when the output current of the optical amplifier 10 is the same, the time required for the output of the comparator 30 to be inverted to the H level becomes long, and the exposure is positively corrected. On the contrary, if the shutter blade 1 suddenly rises as shown by the curve c in FIG. 2 for some reason, the time during which the output of the window gate circuit 5 is at the H level becomes short, and the pulse applied to the counter 68 is Less than 8 shots. For example, if four pulses are applied to the counter 68 while the output of the window gate circuit 50 is at the H level, only the third stage output of the counter 68 will be at the H level. Therefore, the current of weight [4] flowing through the constant current source I ₃ flows through the diode 42 through the current switch S ₃ , so that the diode 42
A current of weight [4] flows through 42. And the diode
Since the current flowing through 42 flows through the transistor 48 through the above path, the reference voltage applied to the comparator 30 decreases. Therefore, when the output current of the optical amplifier 10 is the same, the time required for the output of the comparator 30 to be inverted to the H level is shortened, and the exposure is negatively corrected. In the case of stroboscopic photography, the pulse generated by the photoelectric sensor 4 is counted by the counter 61 and the current aperture value is digitized,
The strobe light emission circuit 65 is triggered when the aperture value reaches a value determined according to the film sensitivity and the shooting distance. still,
The method of inputting the film sensitivity and the shooting distance is known. Next, FIG. 6 shows an embodiment in which the level of the bias voltage circuit 20 of the optical amplifier 10 is adjusted.
The configuration up to the preceding stage is the same as the example of FIGS. 4 and 5 already described. When adjusting the level of the bias voltage circuit 20, see Fig. 4.
Contrary to the embodiment shown in FIG. 5, the mark points P _{0 to} P ₁
If the output voltage of the bias voltage circuit 20 is lowered as the passage time of the signal becomes longer, the proper exposure correction is performed. Therefore, in the embodiment of FIG. 6, the current corresponding to the count value of the counter 68 is changed. The operation pattern of the subtraction circuit is determined. In the embodiment of FIG. 6, the voltage generated in the resistor 21 when a current is applied to the resistor 21 is applied to the optical amplifier 10 as a bias voltage. In the initial state, when a current is supplied from the constant current source 22 to the diode 23, a current equal to the current flowing through the diode 23 flows through the transistor 24 forming the current mirror circuit together with the diode 23, and this current is supplied through the diode 25. . Then, a current equal to the current flowing through the diode 25 flows through the diode 25 and the transistor 26 that constitutes the current mirror circuit, and this current becomes a resistance.
The voltage generated in the resistor 21 when flowing through the resistor 21 is supplied to the optical amplifier 10 as a bias voltage. The optical amplifier 10 has an operational amplifier 12, a logarithmic compression diode 13 and a logarithmic expansion transistor 14,
When the field light is incident on D11, a photocurrent corresponding to the field brightness flows in the reverse direction to SPD11 via the diode 13, and a voltage obtained by logarithmically compressing the photocurrent is generated across the diode 13. Since the bias voltage is applied to the positive-phase input of the operational amplifier 12, a voltage generated by superimposing the bias voltage on the voltage generated across the diode 13 is generated at the output of the operational amplifier 12, and this is logarithmically expanded in the transistor 14. Generated current flows, the capacitor 31 for integrating the field brightness is the transistor 1
It is designed to be charged by the current that flows through it. Now, while the output of the window gate circuit 50 is H level, 8
Under the condition that the opening characteristic of the shutter blade 1 is adjusted so that the reference pulse to be emitted is applied to the counter 28, when the shutter blade 1 opens according to the predetermined characteristic, the counter 68 will Only the output of the fourth stage becomes active (L level), and only the switching transistor sw in the current switch S ₄ is cut off. Therefore, a current equal to the current of the weight [8] flowing through the constant current source I ₄ flows to the ground via the transistor t of the current switch S ₄ . Since the current flowing in the transistor t of the current switch S ₄ is supplied from the constant current source 22, the current flowing in the diode 23 is reduced by the component corresponding to the weight [8]. Since the current flowing through the resistor 21 is equal to the current flowing through the diode 23, the current flowing through the resistor 21 becomes a value obtained by subtracting the current of weight [8] from the current of the constant current source 22, and the voltage generated at the resistor 21 at this time. Is applied as a bias voltage to the optical amplifier 10 and reflected in the output current of the optical amplifier 10. Now, when the aperture characteristic of the shutter blade 1 becomes gentle as shown by the curve b in FIG. 2, it is required to positively correct the exposure. When the opening characteristic of the shutter blade 1 becomes gentle as shown by the curve b in FIG. 2, the count value of the counter 68 increases, and for example, the counter 68 counts 12 while the output of the window gate circuit 50 is at the H level. Then, the third stage output and the fourth stage output of the counter 68 become active (L level). Therefore, in this case, since the switching transistor sw in the current switch S ₃ and the current switch S ₄ is cut off, the current of weight [4] flowing through the constant current source I ₃ and the constant current source I ₄ flow. The current of weight [8] is the current switch S ₃ and S ₄
Through to the ground. As a result, the current flowing through the diode 23 is reduced by a component corresponding to the weight [12], so that the bias voltage of the optical amplifier 10 is lower than that when the shutter blade is opened as in the initial characteristic, and the output current of the optical amplifier 10 is decreased. Also decreases, so the exposure is positively corrected. On the contrary, when the aperture characteristic of the shutter blade 1 becomes steep as shown by the curve c in FIG. 2, it is required to correct the exposure negatively. When the aperture characteristic of the shutter blade 1 becomes steep as shown by the curve c in FIG. 2, the count value of the counter 68 becomes small. For example, while the output of the window gate circuit 50 is H level, the counter 68 counts 4 times. Then, only the output of the third stage of the counter 68 becomes active (L level). Therefore, in this case, the switching transistor sw in the current switch S ₃ is cut off, so that the constant current source I ₃
The current of weight [4] flowing through the current flows through the current switch S ₃ to the ground. As a result, the current flowing through the diode 23 is reduced by the component corresponding to the weight [4], so that the bias voltage of the optical amplifier 10 is increased and the output current of the optical amplifier 10 is higher than that when the shutter blade is opened due to the initial characteristic. Also, the exposure will be negatively corrected. The actual aperture characteristic of the shutter blade 1 is
Various modes are conceivable depending on the shape of itself and the drive mechanism, but the basic tendency is as described above.
Appropriate exposure correction can be performed by appropriately adjusting the current values of the constant current sources I _{1 to} I ₄ . Further, in the above, the current switches S _{1 to} S ₄ are directly operated by the output of the counter 68.
If the current switch is operated by decoupling the output of, the number of stages of the current switch can be increased, and more precise exposure correction can be performed. Further, in the above, an example in which a photo interrupter is used as an example of the means for detecting the blade position has been shown. However, the present invention uses the blade position detection device for the flashmatic possessed by the compact camera, and in flashmatic control. Is a feature that the actual aperture characteristics of the shutter blades are grasped by using the area before the pinhole which is not used yet, and the exposure correction in automatic exposure photography is performed. All known elements can be used, and the location of the mark points is not limited to the shutter blade, and any member that interlocks with the opening operation of the shutter blade can be used. Furthermore, it goes without saying that the method itself for grasping the actual aperture characteristics of the shutter blades using the area before the pinhole can be applied to a camera that does not have a flashmatic control circuit.

【effect】

As described above, according to the present invention, since the aperture characteristic of the shutter blade at each photographing can be grasped and the proper exposure correction can be performed, even if the aperture characteristic of the shutter blade varies for each photographing. Proper exposure can be given. However, since one series of blade position detectors is used for automatic exposure control before the pinhole and for flashmatic control after the pinhole,
A single blade position detector is required.

[Brief description of drawings]

FIG. 1 is a plan view of the shutter blades, FIG. 2 is a characteristic diagram showing the aperture characteristics of the program shutter, FIG. 3 is a block diagram showing the principle of the present invention, and FIG. 4 is one embodiment of the present invention. FIG. 5 is a circuit diagram mainly showing the reference voltage circuit in the embodiment shown in FIG. 4, and FIG. 6 is a circuit diagram of a main part of another embodiment of the present invention. 1 ...... shutter blade, 4 ...... photoelectric sensor P ₀ to P ₈ mark points 10 ...... optical amplifier, 20 ...... bias voltage circuit 30 ...... comparator, 40 ...... reference voltage circuit 50 ...... window gate circuit 67 ...... Oscillator, 68 …… Counter I _{1 to} I ₄ …… Constant current source S _{1 to} S ₄ …… Current switch

Claims (4)

[Claims] 1. An output current of an optical amplifier corresponding to the illuminance of a light receiving element which is always exposed to the field light is integrated, and a shutter blade which also serves as a diaphragm blade is closed at the timing when the integrated value coincides with a reference voltage. In the automatic exposure control device, mark points are continuously provided along a traveling operation line on the shutter blade or on a member interlocked with the opening operation of the shutter blade, and the mark point is provided at a passage point of the mark point. A sensor for generating a pulse in response to passage is provided, and at least 2 before the pinhole in the mark point.
An automatic exposure control device characterized in that the aperture characteristic of the shutter blade is grasped by the pulse interval generated by the sensor in response to the mark point to perform exposure correction. 2. The automatic exposure control device according to claim 1, wherein at least two points before the pinhole in the mark point are included.
An automatic exposure control device, characterized in that exposure compensation adapted to the opening characteristic of the shutter blade is performed by controlling the reference voltage according to a pulse interval generated by the sensor in response to the mark point. 3. The automatic exposure control device according to claim 1, wherein at least two points before the pinhole in the mark point are provided.
The automatic exposure is characterized in that the output current of the optical amplifier is controlled in accordance with the pulse interval generated by the sensor in response to the above-mentioned mark points to perform exposure correction adapted to the opening characteristic of the shutter blade. Control device. 4. The automatic exposure control device according to claim 1, 2, or 3, wherein a pulse generated by the sensor in response to a mark point after the pinhole in the mark point is used. An automatic exposure control device characterized by controlling strobe synchronization timing.