JPS6247290B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a so-called physical property aperture or physical property shutter in which an electric or magneto-optical element whose light transmittance changes by the application of an electric or magnetic field is used in the aperture or shutter device of a single-lens reflex camera. The present invention provides a device that can also be used as various warning devices. Conventionally, mechanical apertures have been mainly used as aperture devices for cameras, but mechanical apertures require a mechanical mechanism to operate, and in the case of cameras that use interchangeable lenses, A complicated connection mechanism is required to connect the camera body and the aperture mechanism of the interchangeable lens, which increases the cost of the camera, increases its size, and limits the degree of freedom in design. In view of this point, various so-called physical apertures have been proposed in which an electric or magneto-optical element whose light transmittance changes upon application of an electric or magnetic field is used as a camera aperture. Examples of the electric or magneto-optical elements include Kersel transparent ferroelectric materials (PLZT) that utilize birefringence, liquid crystals, and Faraday elements, which are used in combination with polarizers and analyzers.
In addition, electrochromic devices and devices that utilize electrophoretic phenomena are also known. These physical apertures have many features not found in conventional mechanical apertures. First, it is small and lightweight because no mechanical coupling mechanism is required. This greatly increases the degree of freedom in camera design. Further, since there is no shock or sound generated during the aperture operation, the photographer does not feel uncomfortable, and the aperture confirmation operation can be easily performed with a single switch. In addition, since the physical aperture is operated by at least an electric circuit, it is highly compatible with the recent trend toward electronic cameras, and has great advantages such as being a major step towards achieving an all-electronic camera in the future. It is something. It goes without saying that a physical shutter device in which the physical element is replaced by a conventional mechanical shutter also has the same advantages as the aperture. The present invention is characterized in that the above-mentioned physical aperture is also used as a display element for various warnings, and its structure is such that the light passing through the photographic lens is transmitted through the viewfinder optical system into the viewfinder, and the object image is displayed in the viewfinder. In a camera that is made visible,
The diaphragm (corresponding to 4 in Fig. 3 of the embodiment) is composed of an electric or magneto-optical element whose light transmittance changes by electric or magnetic control, and a device for warning of under-over exposure, low battery, etc. Warning circuit (B, A, 46, 4 in Fig. 3 of the embodiment)
Corresponds to 7. ) A control circuit for continuously or intermittently applying a signal to the electric or magneto-optical element to reduce its light transmittance and put it in a light-blocking state in response to a warning signal from (Embodiment 3) of
Corresponds to PG ₁ , AN ₁ and AN ₂ . ), and at the time of warning, the entire surface of the viewfinder is continuously or intermittently darkened to perform a warning operation. Conventionally, warning operations such as camera exposure warnings or battery abnormality warnings have been performed by swinging out the pointer of an ammeter or blinking a light emitting diode (LED). Since it is located in the corner of the viewfinder or outside the viewfinder field of view, if the photographer is solely focused on composing the subject, he or she may easily overlook the above-mentioned warning operation. According to the present invention, the entire surface of the viewfinder is continuously or intermittently darkened to perform a warning operation, so there is no fear that the photographer will overlook it, and since the aperture device also serves as a warning device, the warning device There is no need to provide a separate unit, and there is a great advantage in terms of cost. In addition, the above-mentioned aperture or shutter/warning device,
In order to achieve this using a conventional mechanical diaphragm or shutter device, a complicated mechanism for driving the mechanical diaphragm or shutter device is required, and it is almost impossible to achieve an intermittent dark state. In the present invention, since the physical property aperture device is also used as a warning device, the viewfinder can be easily brought into a dark state continuously or intermittently by simply applying an electric signal. Hereinafter, the present invention will be described in detail based on Examples. FIG. 1 shows the structure of a physical property squeezing device used in the present invention. Here, a case is shown in which a liquid crystal is used as the electro-optical element. 1 shows an area control type aperture, and FIG. 2 shows a light transmittance control type physical property aperture. The area control type is a method that changes the aperture value by controlling the area through which light passes, like a conventional mechanical aperture, and the light transmittance control type is a method that changes the aperture value by changing the applied voltage. This method changes the aperture value by controlling the ratio. In the diagram of FIG. 1, 1 and 2 are transparent glass substrates,
3a to 3h and 3a' to 3e' are one transparent substrate 1
A circular or donut-shaped divided transparent electrode is formed thereon by vapor deposition or the like, and 4 is a common transparent electrode formed on the other transparent substrate 2 . Reference numeral 5 denotes a nematic liquid crystal sealed between the two transparent substrates, and the nematic liquid crystal is aligned in a twist mode. Separators 8 and 9 maintain the spacing between the transparent substrates 1 and 2 and prevent the nematic liquid crystal material from flowing out. Reference numerals 6 and 7 denote polarizing plates disposed outside the transparent substrate, and the polarization directions of the polarizing plates 6 and 7 are set at an angle of 90 degrees to each other. The nematic liquid crystal subjected to twist mode alignment has an optical rotation effect that rotates the polarization direction of incident polarized light by 90 degrees when no voltage is applied. The polarization direction of the light is rotated by 90 degrees, and the light can pass through the polarizing plate 7. Therefore, the physical aperture is in a light transmitting state when no voltage is applied. Next, when an alternating current voltage is applied between the selected divided transparent electrode and the common transparent electrode, the twisted mode alignment state of the nematic liquid crystal existing therebetween is disrupted, and the optical rotation effect disappears. Therefore, the polarized light incident on the nematic liquid crystal 5 passes through as it is without having its polarization direction rotated, and is blocked by the polarizing plate 7 in the next stage. Therefore, the physical aperture is in a light-blocking state when a voltage is applied. A predetermined aperture value can be obtained by appropriately selecting the divided transparent electrodes and applying an alternating current voltage according to the aperture value information on the camera side. In the light transmittance control method shown in FIG. 2, when the effective value of the AC voltage applied between the uniform continuous transparent electrodes 3' and 4' is changed, the characteristic curve of the applied effective voltage and the light transmittance of the liquid crystal cell changes. As shown in the diagram above, the light transmittance changes as the applied voltage changes, and the amount of exposure is adjusted. FIG. 2 shows a configuration in which the above physical aperture is incorporated into a single-lens reflex camera. In the figure, 20 and 21 are photographing lenses, 19 is the physical aperture installed on its principal point surface, 22 is a reflection mirror that makes a quick return movement, 23 is a focusing plate,
24 is a pentaprism, 25 is an eyepiece lens, 26 is a focal plane shutter, 27 is a film, and 28 is a drive circuit for the physical aperture. In the present invention, the physical property diaphragm 19 narrows down to a predetermined value during shutter operation or aperture confirmation operation, and continuously or intermittently shuts off light over the entire surface when various warning signals are generated. Therefore, the photographer visually recognizes that the entire inside of the viewfinder is in a dark state. The photographic lens is an interchangeable lens, and the drive circuit 28
is housed in the camera body side, install the electrical sections 28' and 28'' on the interchangeable lens side and the camera body side, respectively, to connect the physical aperture 19 and the drive circuit 28 electrically when attaching the interchangeable lens. Next, the driving circuit of the physical aperture according to the present invention is shown in Fig. 3. The specifications of this circuit are as follows: An area control type physical aperture is used. Assuming a shutter-priority automatic exposure camera. In the event of overexposure, underexposure, or battery abnormality, the physical diaphragm will intermittently shut off light and issue a warning. When the shutter is operating, the physical diaphragm will issue a warning signal. Even if there is a problem, the aperture operation is performed without warning. The aperture confirmation operation can be easily performed by closing the electric switch. In the figure, A is the photometry calculation circuit, B is the battery check circuit, and C is the shutter control circuit. In the photometry calculation circuit A, 30 is a photovoltaic element (SPC) for photometry, and 31 is an operational amplifier (hereinafter abbreviated as OP amplifier) that constitutes the SPC head amplifier. A logarithmic compression diode 32 is connected to the SPC 30 and its negative feedback path. 36 is an OP amplifier constituting a summing amplifier, the non-inverting input terminal of which is grounded, and the inverting input terminal being grounded. It is connected to the output of the OP amplifier 31 via a resistor 33, and to the negative power terminal via a variable resistor 34 for inputting preset shutter speed information and ASA sensitivity information of the film used. 35 is a negative feedback resistor. 37 is an analog switch whose input is the OP amplifier 36.
The output is the input. 38 is an A/D converter connected to its output;
Converts the input analog signal into a 3-bit binary code and outputs it. 39 is a latch circuit, and 61 is a switch that is closed by the shutter release. When the switch is closed, the latch circuit 39 latches and outputs the input signal. A decoder 62 converts the input latch signal into a decimal code and outputs it. OR1 to OR7 are two-input OR gates, the first of which is
Each output of the decoder 62 is connected to the input terminal, and the outputs of OR2 to OR7 are connected to the other input terminals of OR1 to OR6, respectively. EX1 to EX8 are 2 input exclusive OR
In the gate, 1 input terminal of EX1 to EX7 is the above OR
Connected to the outputs of gates OR1 to OR7. EX
The other input terminals of 1 to EX8 are connected to pulse generation circuits.
The output of PG2 is input. The frequency of the output pulse of the pulse generating circuit is set to about several tens to several hundred Hz. Exclusive OR gates EX1 to EX8 above
The output of the divided transparent electrodes 3a to 3 of the physical property aperture device is
Connected to h. Further, the common transparent electrode 4 is connected to the output of the pulse generating circuit PG2. In the battery check circuit B, 41 is a Zener diode, 40 is a current limiting resistor of the Zener diode 41, 42 and 43 are voltage dividing resistors,
44 is a normally open switch that operates in conjunction with a battery check button (not shown). 45 is an OP amplifier that constitutes a comparator circuit, and its non-inverting input is connected to resistor 4.
0 and a Zener diode 41, and the inverting input is connected to a connection point between voltage dividing resistors 42 and 43. During a battery check, when the electromotive voltage of the power supply battery becomes less than a predetermined value, an H level signal is generated from the output of the OP amplifier 45. 46 and 47 are OP amplifiers that constitute comparison circuits for overexposure and underexposure detection, respectively.The non-inverting input of the OP amplifier 46 is connected to the output of the OP amplifier 36, and the inverting input is connected to the reference circuit. A voltage V ₁ is applied. The inverting input of the OP amplifier 47 is connected to the output of the OP amplifier 36, and the reference voltage V ₂ is applied to the non-inverting input. The above reference voltage is set to be V ₁ >V ₂ . OR8 is a three-input OR gate, to which the outputs of the OP amplifiers 45, 46, and 47 are input.
A differential circuit 64 is connected to the output of OR8, and when the output of OR8 is inverted to H level, a positive differential pulse is generated. Reference numeral 65 denotes a differentiating circuit which is connected to the output of the OR gate OR8 via the buffer circuit 63, and generates a negative differential pulse when the output of OR8 is inverted to L level. 67 is an RS flip-flop circuit whose set input and reset input terminals are connected to the outputs of the differentiating circuits 64 and 65, respectively. 66 is a switching transistor, its emitter is the positive power supply and the collector is
The reset input and base of the RS flip-flop circuit 67 are connected to the output of the inversion circuit 68 via a resistor. AN1 is a two-input AND gate, and one input thereof receives the Q output of the RS flip-flop circuit 67. AN2 is a 2-input AND gate. One input receives the output of the AND gate AN1, and the other input receives the pulse generator PG.
1 output is input. Also, the output of AND gate AN2 is the above-mentioned OR
Gate OR7 and exclusive OR gate EX
8 and the inverting circuit 68 . In the shutter control circuit C, 48 is a switch that is closed by operating a shutter release button (not shown) and is interlocked with the switch 62 of the latch circuit. 49 is a differential circuit, and when the switch 48 is closed, a negative differential pulse is generated from the differential circuit 49. 50 is a one-shot multivibrator which generates one pulse when triggered by the negative differential pulse. Reference numeral 51 denotes a switching transistor whose base is connected to its output via a resistor, and whose collector is connected to an electromagnetic magnet 52 for canceling the first clamp. Reference numeral 53 denotes a switch that closes when the trailing shutter curtain (assuming a focal plane shutter) has completed running. Reference numeral 54 denotes a differential circuit, and when the switch 53 is closed, a negative differential pulse is generated. 55 is an RS flip-flop circuit whose set and reset inputs are connected to the outputs of the differentiating circuits 49 and 54, respectively. The output thereof is input to the other input of the AND gate AN1, as well as to the inverting circuit 60 and the delay circuit 56'. The output of the inverting circuit 60 is input to the control terminal of the analog switch 37. Reference numeral 55' denotes an NPN type switching transistor for starting the time setting, the base of which is connected to the output of the delay circuit 56' via a resistor. 56 is a variable resistor that changes according to preset shutter speed information, and 57 is a time-fixing capacitor, which is connected in parallel to the switching transistor 55'. 5
8 is an OP amplifier that constitutes a comparator, and its non-inverting input terminal is connected to the variable resistor 56 and capacitor 57.
The reference voltage V is applied to the inverting input terminal. 59 is OP amplifier 5
This is an electromagnetic magnet for shutter rear curtain control connected to the output of No. 8. The operation of this circuit configured as described above will be explained next. First, normal aperture operation will be explained. When the subject light that has passed through the photographic lens enters the photometric SPC 30, a voltage corresponding to the logarithm of the subject brightness and the open T-number of the photographic lens is generated at the output of the SPC head amplifier 31. This voltage is added to the preset shutter speed information and the film's ASA sensitivity information in an adder circuit 36 at the next stage, and a voltage corresponding to the number of aperture stages information (△AV) to be controlled is generated at its output. do. During shutter operation, the RS flip-flop circuit 55
Since the output of the inverting circuit 60 is at the L level, the output of the inverting circuit 60 is at the H level, and therefore the analog switch 37
is turned on, and the output voltage of the OP amplifier 36 is generated at the output of the analog switch 37. This voltage is converted into a 3-bit binary code by the A/D converter 38 in the next stage, and in conjunction with the shutter release operation, the switch 61 is closed and the binary code is latched by the latch circuit 39. It is output, further converted into a decimal code by the next stage decoder 62, and then sent to the OP amplifier 36.
Decoder 62
One of the outputs is selectively set to H level. If output 1 is currently selected and is at H level during the output of the decoder 62, the other outputs are at L level, so only one input of OR gate OR1 is at H level, and all inputs of OR2 to OR7 are at L level. Therefore, only the output of OR1 becomes L level, and OR
The outputs of 2 to OR7 are at L level. Therefore, the exclusive OR gate EX1 outputs the output pulse PL2 from the pulse generation circuit PG2.
A pulse with a phase opposite to that of the pulse PL2 is outputted, and a pulse with the same phase as the pulse PL2 is outputted from EX2 to EX8. In this state, an effective current voltage is applied only between the divided transparent electrode 3a and the common transparent electrode 4, so only that part is in a light-blocking state, and the aperture is 1
It becomes a state of narrowing down. Next, during the output of the decoder 39, when output 4 is selected and becomes H level, the 1 input of OR gate OR4 is at H level, so its output becomes H level. Therefore, since the 1st input level of OR3 is H level, its output becomes H level, and sequentially OR2, OR1
Similarly, the output becomes H level. In other words, OR
The outputs of the gates OR1 to OR4 go to H level, and the outputs of OR gates OR5 to OR7 go to L level. Therefore, the phases of the output pulses from exclusive OR gates EX1 to EX4 are opposite to pulse PL2, and the phases of output pulses from EX5 to EX8 are in phase with pulse PL2. In this state, since an effective alternating current voltage is applied between the divided transparent electrodes 3a to 3d and the common transparent electrode 4, that portion is in a light-blocking state and the diaphragm is closed in four steps. The subsequent narrowing down operation is performed only during the shutter operation (or during the narrowing down operation). Otherwise, the output of the RS flip-flop circuit 55 is at the H level and the output of the inverting circuit 60 is at the L level, so the analog switch 37 is turned off and the output of the OP amplifier 36 is not transmitted to the next stage. Therefore, no narrowing down operation is performed. Next, the operation of the shutter control circuit C will be explained. When the shutter release button (not shown) is pressed, a negative differential pulse is generated from the next-stage differentiating circuit 49, and this negative differential pulse triggers the next-stage one-shot multivibrator 50, and its output is One pulse is generated, and during the period of that pulse width, the next stage switching transistor 5
1 is turned on, the coil 52 is energized, the first clamping of the shutter is released, and the quick return mirror starts to move up, and after that is completed, the shutter leading curtain starts running and the exposure of the film starts. be done. Also, due to the negative differential pulse from the differentiating circuit 49,
The RS flip-flop circuit 55 is set and its output is inverted to L level, and at the same time the inverting circuit 6
The output of 0 is inverted to H level, the analog switch 37 is turned on, a voltage corresponding to the ΔAV value information is generated at its output, and the aperture operation is performed as described above. Further, when the output of the RS flip-flop circuit 55 becomes L level, the output of the delay circuit 56' becomes L level with a slight delay, the switching transistor 55' is turned off, and the time setting capacitor 57 becomes variable. When the charging voltage of the time-limiting capacitor 57 reaches a predetermined value through the resistor 56, the non-inverting input level of the comparator circuit 58 becomes higher than the inverting input level V, and its output becomes H.
level, the power supply to the coil of the electromagnetic magnet 59 for controlling the shutter trailing curtain is cut off, the shutter trailing curtain starts running, and the exposure operation ends. When the trailing curtain of the shutter finishes running, the switch 53 is closed and a negative differential pulse is generated from the output of the differential circuit 54, which resets the RS flip-flop circuit and returns it to its initial state. In this state, the output of the RS flip-flop circuit 55 is at H level, so the inverting circuit 60
The output becomes L level, and the analog switch 37
is turned off, and the narrowing down operation is canceled. Next, a warning operation in case of overexposure will be explained.
In this case, the output voltage value of the OP amplifier 36 becomes high, the non-inverting input level of the OP amplifier 46 forming the comparison circuit becomes higher than the inverting input level _V1 , and the output of the OP amplifier 46 becomes H level,
Therefore, the output of OR gate OR8 also becomes H level.
This inversion operation to the H level generates a positive differential pulse from the output of the differentiating circuit 64, which sets the next stage RS flip-flop circuit 67 and inverts its Q output to the H level. First, if the shutter is not working, as mentioned above,
Since the output of the RS flip-flop circuit 55 becomes H level, the output level of AND gate AN1 also becomes H level. Pulse generator circuit PG1 outputs pulses with a repetition frequency of about 2Hz, so when the output of AND gate AN1 goes to H level,
AND gate AN2 opens and the AND gate AN2
The pulse voltage from the pulse generating circuit PG1 is outputted from the pulse generating circuit PG1. When the pulse waveform is at H level,
Since 1 input of OR gate OR7 is at H level, its output becomes H level, 1 input of OR gate OR6 also goes to H level, and sequentially OR gates OR6 to OR1
All outputs become H level. Therefore, the phase of the output pulse waveform from each output of exclusive OR gates EX1 to EX8 is determined by the pulse generation circuit PG2.
The phase is opposite to that of the output pulse PL2, and each divided transparent electrode 3a to 3h of the physical property aperture and the common transparent electrode 4
An effective alternating current voltage is applied between the two, and the physical aperture becomes completely light-blocking. During the L level period of the output pulse of the AND gate AN2, the analog switch 37 is off, so each output of the OR gates OR1 to OR7 goes to the L level, and the exclusive OR gates EX1 to
The phase of the pulse voltage output from EX8 becomes the same phase as pulse voltage PL2, and the physical aperture is now completely in a light-blocking state. By the way, when the above-mentioned physical aperture enters the light blocking state, since this is a TTL photometry camera, the amount of light incident on the light receiving element 30 is extremely reduced, and as a result, the OP
The output voltage of the amplifier 36 decreases, and the overexposure warning signal disappears even though it is actually overexposed, and the output of the OR gate OR8 goes low.
Therefore, a negative differential pulse is generated from the differentiating circuit 65, which resets the RS flip-flop 67, and its Q output and
There is a fear that the output of the AND gate AN1 will go to L level and the physical property aperture warning operation will not be performed. In this circuit, a switching transistor 66 and an inverting circuit 68 are provided in consideration of this point. In other words, the output level of AND gate AN2 is H.
When the physical property diaphragm enters the light blocking state, the output of the inverting circuit 68 becomes L level and the switching transistor 66 is turned on. The above
The reset terminal of the RS flip-flop circuit 67 is always at H level, and the negative differential pulse generated from the differentiating circuit 65 is applied to the switch transistor 66.
Therefore, the RS flip-flop circuit 67 is not reset. Conversely, when the output of AND gate AN2 is at L level, the output of inverting circuit 68 is at H level, and switching transistor 66 is turned off. At this time, if the brightness of the subject decreases and falls within the appropriate exposure level range, the output of the OR gate OR8 is inverted to L level, and at this time, the negative differential pulse from the differentiating circuit 65 causes the RS flip-flop circuit 67 to is reset, its Q output becomes L level, the outputs of AND gates AN1 and AN2 are also held at L level, and the physical property aperture warning operation ends.
In other words, the switching transistor 66 invalidates the negative differential pulse generated from the differentiating circuit 65 when the physical aperture is in the dark state, and prevents the RS flip-flop circuit 67 from being reset when the physical aperture is in the dark state, thereby preventing the above-mentioned malfunction. This prevents the occurrence of As described above, when overexposure occurs, an overexposure warning signal is generated from the OP amplifier 46 forming the comparator circuit, the output of the OR gate OR8 goes to H level, and the entire surface of the physical property aperture device becomes the pulse generator PG1.
It turns on and off at a cycle of , and the photographer can see that the entire surface of the viewfinder alternates between dark and dark states, and can detect overexposure. Conversely, when underexposure occurs, the output level of the OP amplifier 36 decreases and the negative input level of the OP amplifier 47 becomes lower than the positive input level _V2 , so its output is inverted to H level, and thus the output of the OR gate OR8. It also becomes H level. Thereafter, as in the case of overexposure, the physical property aperture device is turned on and off completely to issue an underexposure warning. Next, the operation at the time of battery abnormality warning will be explained.
When the battery warning button is pressed and the switch 44 in circuit B is closed, if the electromotive force of the power supply battery has decreased due to exhaustion, the voltage dividing resistors 42 and 43
The potential at the dividing point becomes lower than the constant voltage level at the Zener diode 41, so the output of the OP amplifier 45 is inverted to H level, and the output of OR gate OR8 is also inverted to H level. Thereafter, in the same manner, the physical property restricting device is turned on and off completely to issue a battery abnormality warning. Furthermore, when a shutter release operation is performed when any of the above warning signals is generated and the output of the OR gate OR8 is at the H level, the output of the RS flip-flop circuit 55 is at the L level during the shutter operation period. , the output of AND gate AN1 is L
level, the AND gate AN2 does not open, no warning is displayed, and at this time, the narrowing down operation is performed as described above. Furthermore, when the aperture confirmation switch 69 is closed to confirm the depth of field, the output of the RS flip-flop circuit 55 is forced to the L level.
The outputs of AND gates AN1 and AN2 go to L level, and even if there is some kind of warning signal, the warning operation of the physical property aperture cannot be performed. Also, at this time, the inverting circuit 60
Since the output becomes H level, the analog switch 37 is turned on, and the output of the decoder 62 is selected according to the output analog voltage value, thereby performing a narrowing operation of the physical property aperture. In this embodiment of the circuit, the delay time of the delay circuit 56' in the shutter control circuit C is adjusted so that the timing at which the switching transistor 55' for starting the timer starts turning off coincides with the timing at which the leading shutter curtain starts running. I'll keep it. Next, the second drive circuit of the physical property aperture according to the present invention
An example of this is shown in FIG. The specifications of this circuit are as follows. A physical aperture with light transmittance control is used. Assuming a shutter-priority TTL metering auto-exposure camera. In the event of overexposure, underexposure, or battery abnormality, the physical property diaphragm intermittently enters a light blocking state and performs a warning operation. During shutter operation, the physical diaphragm performs a narrowing operation without issuing a warning operation even when there is a warning signal. The narrowing confirmation operation can be easily performed by closing the electric switch, and the narrowing confirmation operation has priority over the warning operation. In the figure, A is a photometric calculation circuit, B is a battery check circuit, and C is a shutter control circuit. Since the circuit is similar to that shown in FIG. 3, a description thereof will be omitted. 78 is a capacitor for storing the △AV information generated at the output of the OP amplifier 36, and 79 is a changeover switch, which is normally connected to the a side, and in conjunction with the shutter release operation or aperture confirmation operation, the b
Switch to the side. 46 and 47 are OP amplifiers that constitute comparison circuits for overexposure and underexposure detection, respectively.The non-inverting input of the OP amplifier 46 is connected to the output of the OP amplifier 36, and the inverting input is connected to the reference circuit. A voltage V ₁ is applied. The inverting input of the OP amplifier 47 is connected to the output of the OP amplifier 36, and the reference voltage V ₂ is applied to the non-inverting input. Here, V ₁ >V ₂ . OP8 is a 3-input OR gate, and the OP amplifiers 45 and 46
and 47 outputs are input. A differentiation circuit 64 is connected to the output W, and when the output of OR8 is inverted to H level, a positive differentiation pulse is generated. 65 is connected to the output of the OR gate OR8 via the buffer circuit 63, and when the output of OR8 is inverted to L level, a negative differential pulse is generated.
67 is an RS flip-flop circuit whose set input and reset input terminals are connected to the differentiator circuit 6, respectively.
Connected to outputs 4 and 65. 66 is a switching transistor, its emitter is a positive power supply, and its collector is an RS flip-flop circuit 67.
The reset input and base of the circuit are connected via resistors to the outputs B' of analog switches 76 and 77, which will be described later. 70 is a logic conversion circuit whose truth table between inputs Q ₁ and Q ₂ and outputs A, B, and C is as shown in Table 1.

[Table] 72 is an inversion circuit connected to the output C of the logic conversion circuit 70, PG4 is a pulse generation circuit that generates a pulse train with a repetition frequency of about 1 to 2 Hz, and 73 is an inversion circuit connected to the output thereof. . 74-7
7 is an analog switch, analog switch 74
The input of the analog switch 75 is connected to the output of the inversion circuit 73, the control input is connected to the output of the inversion circuit 72, the input of the analog switch 75 is connected to the output A of the logic conversion circuit 70, and the control input is connected to the output C. are doing. The input of the analog switch 76 is connected to the output B of the logic conversion circuit 70, the control input thereof is connected to the output C, and the input of the analog switch 77 is connected to the output B of the logic conversion circuit 70.
It is connected to the output of PG4, and its control input is connected to the output of the inverting circuit 72. 80 is an inverting circuit connected to the output of the inverting circuit 71; 81 and 82 are analog switches;
The input of No. 1 is connected to the b contact of the changeover switch 79, and the control input thereof is connected to the output of the inversion circuit 80. analog switch 8
A positive power supply +V _CC is applied to the input of No. 2, and its control input is connected to the output of the inverting circuit 71. PG3 is a pulse generating circuit whose repetition frequency is on the order of tens to hundreds of Hz, and 83 is an inverting circuit connected to its output. 84 and 85 are analog switches, both of whose inputs are connected to the output AL1 of the analog switches 81 and 82, and the control input of 84 is connected to the output of the inverting circuit 83;
The control input of 85 is the pulse generating circuit.
Connected to the output of PG3. 86 and 87 are also analog switches, and the input of 86 is the output PL1 of the analog switch 84,
The control input is the analog switch 76.
and the output B' of 77. The input of the analog switch 87 is connected to the output PL2 of the analog switch 85, and the control input is connected to the output A' of the analog switches 74 and 75. 65 is the light transmittance control type physical property diaphragm shown in 2 in FIG. 1, and 3' and 4' are its common transparent electrodes.
3' is the output PL1 of the analog switch 84,
4' is the output of the analog switches 86 and 87.
Connected to PL3. Reference numeral 69' in the shutter control circuit C is a normally open switch for checking the aperture, which is connected between the Q output Q1 of the RS flip-flop circuit ₅₅ and the positive power supply terminal. The operation of this circuit configured as described above will be explained next. (1) When there is no warning signal W (1-1) When the shutter is not operating In this case, the output W of the OR gate OR8 remains at the L level and the RS flip-flop circuit 67 is not set, so its Q output _Q2 is at the L level. level. Also, as described above, the Q output _Q1 of the RS flip-flop circuit 55 is at the L level except during the shutter operation. In this state, as shown in Table 1, output A is at L level, output B is at H level, output C is at H level, and the output of the inverting circuit 72 is at L level. Yotsute analog switch 75
and 76 are turned on, and analog switches 74 and 77 are turned off. Therefore, output A' becomes L level and output B' becomes H level. Further, since _Q1 is at L level, the output of inverting circuit 71 becomes H level, and the output of inverting circuit 80 becomes L level. Therefore, analog switch 81 is turned off, analog switch 82 is turned on, and its output AL1 becomes H level. Since pulse voltages of opposite phases are input to the control inputs of analog switches 84 and 85, the analog switches 84 and 85
4 and 85 are turned on and off alternately, and their output
Rust voltages having mutually opposite phases are generated in PL1 and PL2 as shown in FIG. 4. As mentioned above, the output
Since A' is at L level and B' is at H level, analog switch 86 is turned on and analog switch 87 is turned off. Therefore, the output PL3 generates a pulse with the same phase and period as the PL1, and the effective voltage applied between both common transparent electrodes 3' and 4' of the physical property aperture 65 becomes zero, and the physical property aperture 65 does not perform aperture operation. Further, when the narrowing down confirmation operation is performed and the switch 69' is closed, _Q1 becomes H level and _Q2
remains at the L level, so from Table 1, the output A
becomes H level, output B becomes L level, and output C
maintains the H level. Therefore, as before the confirmation operation, analog switches 75 and 76 are turned on, and analog switches 47 and 77 are turned off, but this time the output
A' is inverted to H level and output B' is inverted to L level. Further, a narrowing down confirmation operation is performed, and in synchronization with the closing of the switch 69', the changeover switch 79 is switched to the b side. Since _Q1 is at H level, the output of inverting circuit 71 is at L level,
The output of the inverting circuit 80 becomes H level, the analog switch 81 is turned on, and the analog switch 82 is turned off. Therefore, the storage capacitor 78 is connected to the output AL1.
The storage voltage (△AV information) is output. At this time, the output PL of analog switches 84 and 85
1 and PL2, as shown in FIG. 4, pulse voltages are generated whose peak values are equal to the ΔAV information voltage and whose phases are opposite to each other. As mentioned above, when output A' is at H level, the output
Since B' is at L level, the analog switch 86 is turned off and the analog switch 87 is turned on, so that the same pulse as PL2 is generated at its output PL3. Therefore, the common transparent electrode 3' of the physical property aperture
and 4' are applied with pulse voltages having opposite phases and whose peak values correspond to the ΔAV information. Therefore, the light transmittance of the physical aperture decreases in accordance with the voltage, and a predetermined aperture is achieved. (1-2) Shutter is operating In this case, the same as when checking the narrowing down
Since Q ₁ is H level and Q ₂ is L level, output A
is at H level, B is at L level, and C is at H level, and the physical property aperture performs a predetermined narrowing down in the same manner as described above. (2) When warning signal W is present (2-1) Other than during shutter operation First, we will discuss the case where the narrowing down confirmation operation is not performed. Now, assuming that an overexposure warning is issued, in this case, as mentioned in Figure 3,
The output of the OP amplifier 46 is inverted to H level, and the OR
The output W of the gate OR8 is inverted to H level.
This inversion operation generates a positive differential pulse from the differentiating circuit 64, which sets the RS flip-flop circuit 67 and outputs its Q output.
_Q2 is inverted to H level. Since Q ₁ is at L level, from Table 1, output A is at H level and output B is at L level.
Level C becomes L level. Since the output of inverting circuit 72 becomes H level, analog switches 74 and 77 are turned on and analog switches 75 and 76 are turned off. Since low-period pulse voltages having opposite phases are input to the inputs of the analog switches 74 and 77, the pulse voltages shown in FIG. 4 are generated at the outputs A' and B'. Since the _Q1 output is at L level except during shutter operation, the output of inverting circuit 71 is at H level, the output of inverting circuit 80 is at L level, analog switch 81 is turned on, and analog switch 82 is turned off. Therefore, the output AL1 becomes H level, and the outputs PL1 and PL2 of the analog switches 84 and 85 are as follows.
4. Pulse voltages having mutually opposite phases shown in FIG. 2 are generated. Since the control inputs of the analog switches 86 and 87 are inputted with pulse voltages having a relatively low frequency (1 to 2 Hz) and opposite phases to each other as shown in FIG.
and 87 are alternately turned on and off in synchronization with the pulse voltage. Therefore, as shown in FIG. 4, the output PL3 generates a pulse voltage whose phase is reversed in synchronization with the pulses of the outputs A' and B'.
Since the pulse voltages PL1 and PL3 are applied to the common transparent electrodes 3' and 4' of the physical aperture, the physical aperture is turned on and off alternately in synchronization with the pulses A' and B'.
The light is turned off, and the physical aperture is intermittently in a light-blocking state to perform a warning operation. Also, at this time, there is a concern that the warning signal may disappear due to a decrease in the amount of light incident on the light-receiving element 30, as in the embodiment shown in FIG. At this time, since the output B' is at the L level, the switching transistor 66 is on, and the negative differential pulse generated from the differentiating circuit 65 is absorbed by the inversion of the output of the OR gate OR8 to the L level. to prevent the RS flip-flop circuit 67 from being reset,
Warning action continues. Next, a case where the narrowing down confirmation operation is performed will be described. In this case, the switch 69' is closed, so the _Q1 output goes to H level, the output of inverting circuit 71 goes to L level, and the output of inverting circuit 80 goes to H level. Therefore, analog switch 81 is turned on and analog switch 82 is turned off. At this time, both Q ₁ and Q ₂ are at H level, so from Table 1, output A is at H level, output B is at L level,
C becomes H level, and therefore, as described above, the outputs A' of analog switches 74 to 77 become H level, and the outputs B' become L level. Therefore, the analog switch 86 is turned off and the analog switch 87 is turned on to perform a predetermined narrowing down operation. (2-2) During shutter operation In this case as well, _Q1 becomes H level, and a predetermined narrowing down operation is performed in the same manner as in the narrowing down confirmation operation. In other words, the narrowing down operation has priority over the warning operation. In the above embodiments, only a circular aperture is used, but there is no need to be limited to this. Next, FIG. 5 shows a specific aperture shape according to the present invention when a star-shaped aperture is used. Using such a star-shaped aperture has the effect of preventing a decrease in resolution when the aperture is small. FIG. 6 shows divided transparent electrodes 3a to 3a shown in FIG.
A concrete configuration method of 3h is shown below. In FIG. 1, 1 is a transparent glass substrate, 3a to 3h are round or donut-shaped divided transparent electrodes, and 3a-1 to 3h-1 are extraction electrodes from each of the divided transparent electrodes. This is for connection with the drive circuit. A method for drawing out this drawing electrode is shown in FIG.
This figure shows a cross-sectional view along line A-A' in Figure 1, where 3h-1 is the divided transparent electrode 3h.
The lead-out electrode 3h-1 is insulated and separated from the other divided transparent electrodes 3a to 3g by a transparent insulating layer 80. The other extraction electrodes are similarly constructed. With the structure described above, there is no fear that part of the divided transparent electrode will be missing due to the extraction electrode, or that the extraction electrode and other divided transparent electrodes will come into electrical contact, resulting in an ideal physical property aperture. We offer several electrode configurations. In FIGS. 1 and 6, only the transparent electrode disposed on one of the transparent substrates is divided according to the aperture aperture value, but next, an embodiment of the present invention in which the transparent electrodes on both transparent substrates are divided is shown in Figure 7. In the figure, 1 and 2 are transparent glass substrates, 3a to 3d are divided transparent electrodes formed on the transparent glass substrate 1,
4a to 4e are divided transparent electrodes formed on the transparent glass substrate 2, 3a-1 to 3d-1 and 4a-1 to
4e-1 is the above-mentioned divided transparent electrodes 3a to 3d, and 4
It is constructed in the same manner as shown in FIG. 5 with extraction electrodes a to 4e. 6 and 7 are polarizing plates, and 8 and 9 are spacers. If the aperture is to be narrowed down by one step, pulses of opposite phase may be applied between the divided transparent electrodes 3a and 4a, and pulses of the same phase may be applied between 3a and 4b and between the other upper and lower divided transparent electrodes. In addition, when narrowing down the aperture by two steps, pulses with opposite phases are applied between the transparent electrodes 3a and 4a and between 3a and 4b, and pulses with the same phase are applied between the transparent electrodes 3b and 4b and between the other transparent transparent electrodes. Just apply it. The same holds true when narrowing down further. As described above, by utilizing the fact that the portions of the upper and lower divided transparent electrodes to which pulses of mutually opposite phases are applied are in a light-blocking state, the phase of the pulse voltage applied to each divided transparent electrode is controlled by the drive circuit to a predetermined level. It is possible to obtain an aperture diameter of . In the above embodiments, a case has been described in which a liquid crystal is used as an electro-optical element, but the present invention is not limited thereto, and any electric or magneto-optical element can be used. In addition, the aperture shape of the physical aperture is not limited to circular or star-shaped, but may be changed in consideration of optical performance.
It can be of any shape, and it is not necessarily necessary to narrow down from the open side, but it is also possible to narrow down from the center, and it is not limited to this, and it is possible to narrow down any part as desired. The most appropriate method may be selected based on optical performance. In addition, in the embodiment, the narrowing down is performed one stage at a time, but in order to bring out the intermediate stage, 1/2 stage, 1/2 stage,
Alternatively, it is also easy to narrow down the range by 1/3 step. As described above in detail based on the embodiments, the present invention is characterized in that, in a single-lens reflex camera, the overexposure warning device is also used as a physical aperture device, so that the entire surface of the viewfinder is continuously or intermittently Since the warning operation is performed in a dark state, it provides an effective warning device that will not be overlooked, and there is no need to separately install a warning device, which has a great cost advantage. Since a prohibition means (transistor 66 in the embodiment) for prohibiting resetting of the overexposure warning signal holding means when the electric or magneto-optical element is in a light-blocking state is provided, problems that occur in a TTL photometry camera such as the present invention can be avoided. ,
That is, it is possible to solve the problem that the overexposure warning signal disappears due to the light blocking state during the overexposure warning operation, and the overexposure warning operation is no longer performed. All of the examples described above using the embodiment diagrams are examples in which a physical aperture device as an exposure control member is also used as a warning display, but it is not limited to an aperture, but a shutter or a shutter that is also installed as an aperture can also be used as a warning display. Needless to say, it is also possible. However, when configured as a shutter or a shutter that also serves as an aperture, as with single-lens reflex cameras incorporating a mechanical lens shutter, which has been known for a long time, an auxiliary shutter built into the mirror box of the camera and the opening/closing of the lens shutter are used. Sequential control is required so that the operations are carried out in a predetermined order, and this can be easily achieved by changing the conventional drive control of a mechanical lens shutter to control of the voltage applied to a physical shutter.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram showing an embodiment of a physical property aperture device according to the present invention, in which FIG. 1 shows an area control type physical property aperture, and FIG. 12 shows a light transmittance control type physical property aperture. FIG. 2 is a schematic diagram showing the structure when the physical aperture shown in FIG. 1 is incorporated into a single-lens reflex camera, and FIG. 3 is a circuit connection diagram showing an embodiment of the physical aperture driving circuit according to the present invention. 4. FIG. 4 1 is a circuit connection diagram showing a drive circuit for a physical aperture according to another embodiment of the present invention, FIGS. 4 2 to 5 are waveform diagrams of various parts for explaining the operation of the circuit in FIG. The figure shows an example of the aperture shape of the physical property aperture according to the present invention, FIG. 6 is a structural diagram showing the structure of the physical property aperture device shown in FIG. 1, and FIG. 7 shows the physical properties in another embodiment of the present invention. FIG. 2 is a structural diagram showing the configuration of a diaphragm device. 1, 2...Transparent glass substrate, 3a-3h, 3a'-
3e'...Divided transparent electrode, 4...Common transparent electrode, 5...Nematic liquid crystal, 6, 7...Polarizing plate, 8, 9...Separator.

Claims (1)

[Scope of Claims] 1. The light passing through the photographic lens and the exposure control member is measured by a photometer, and the light is transmitted through the viewfinder optical system into the viewfinder so that the image of the subject can be viewed through the viewfinder. In the camera, the exposure control member is constituted by an electric or magneto-optical element whose light transmittance is changed by electric or magnetic control, and a warning signal from a warning circuit for issuing an overexposure warning according to the output of the photometry means is provided. Providing a control circuit for continuously or intermittently applying a signal to the electric or magneto-optical element in response to reduce its light transmittance and put it into a light blocking state,
and means for holding the warning signal in response to the generation of the warning signal, and prohibiting means for inhibiting the reset of the holding means in response to the generation of the warning signal when the electric or magneto-optical element is in a light-blocking state. A camera having a physical aperture, characterized by comprising: