JPH0364049B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photometry circuit for flash photography. 2. Description of the Related Art It is known to take a photograph by irradiating a subject with a flash in daylight conditions such as backlight conditions, which is a so-called daytime synchronized photographing method. The basic control method for daytime synchronized photography is to detect the brightness of external light (natural light), determine the aperture according to the brightness, and operate the dimmable flash device under this determined aperture. A method is used to compensate for the underexposure of the main subject. In this case, if the appropriate light control level for normal flash photography is set as the light control level, the exposure amount due to external light will be added to the appropriate exposure amount due to the adjusted flash amount as the exposure amount for the main subject. Therefore, it is necessary to set the light control level during daytime synchronized photography to a level that is about 1 to 2 steps underexposed compared to the appropriate light control level during normal flash photography. However, during daytime synchronized photography, if the aperture is always determined according to the brightness of outside light and flash photography is performed by light control using the daytime synchronized photography method described above, the following disadvantages occur. For example, if the subject is located far away, the flash energy required to properly expose the subject will be large. On the other hand, if the aperture is controlled based on the brightness of outside light at this time, the aperture value may be set to a value on the narrower side compared to the limit aperture value required to obtain proper exposure, and at this aperture value the flash When taking pictures, the consumption of flash energy increases. The present invention has been developed in view of the above-mentioned problems.When the subject is close, the aperture value is set according to the brightness of external light, and when the subject is far, the aperture value is set according to the subject distance. This is an attempt to solve the above-mentioned problem by setting a value. Next, the present invention will be explained. FIG. 1 is a circuit diagram showing an embodiment of a flash device to which a photometric circuit according to the present invention is applied. In the figure, 1 is a light receiving element, and a filter 56 for setting film sensitivity is provided in front of the light receiving element. Reference numeral 2 denotes an operational amplifier (hereinafter referred to as an OP amplifier) which connects the light receiving element between input terminals. Capacitors 53, 52, 50, 48, and 49 are selectively connected between the input and output terminals of the operational amplifier as described later. The capacitors 53 and 52 are integral capacitors for pre-distance measurement that are connected to the OP amplifier to form a mirror integrator during pre-distance measurement by pre-flash, and 48 to 50 are OP amplifiers used to perform dimming by main light-emission. This is an integrating capacitor for dimming that is connected to the mirror integrator for dimming. The capacitance of the capacitor 53 and capacitor 52 is one pair.
31, and the capacitance when capacitor 50 and capacitors 48 and 49 are connected in parallel is also 1.
It is set to 31 vs. SW ₁ is an analog switch composed of a switching element such as an FET or a transistor for connecting the capacitor 53 to the OP amplifier 2. It is turned on when it is at a low level (hereinafter referred to as "0") and turned off when it is at a low level (hereinafter referred to as "0").
The control input C of the switch is connected to the output of a dimming timer 13 (described later) via an inverter 47, and when the dimming timer 13 is activated (timer 13
outputs “1” only when activated. ) is turned off. SW ₂ is an analog switch having the same configuration as the above-mentioned switch SW ₁ , which connects the capacitor 52 to the OP amplifier 2 via a mode changeover switch SWD ₂ , which will be described later. The control input C of the switch is AND gate 4
It is connected to the output of 3. One input of the AND gate 43 is connected to the output of the dimming timer 13 via an inverter 47, and the other input is connected to the output of the OR gate 42. Also, one input of the OR gate 42 is connected to the output of the pre-distance measuring timer 14 (outputs "1" only when the timer is activated) via an inverter 36, and the other input is connected to a flip-flop (hereinafter referred to as FF). .) Connected to the Q output of 8. With the above configuration, the AND gate 43 operates when both the dimming timer and the pre-distance measurement timer are inactive, and when the dimming timer is inactive.
And it outputs "1" only when the Q output of FF8 is "1". Therefore, the switch SW ₂ is turned on only under the above circumstances. SW ₃ is a switch having the same configuration as the switch SW ₁ that connects the capacitor 50 to the OP amplifier 2, and the control input C of this switch is connected to the inverter 36.
It is connected to the output of the pre-distance measuring timer 14 via. Therefore, the switch SW ₃ is turned off only when the pre-distance measurement timer is activated. SW ₄ is a switch that works with the above switch SWD ₂ .
Capacitor 4 connected in parallel via SWD ₄
This is a switch having the same configuration as the above switch SW ₁ for connecting 9 and 48 to the OP amplifier 2, and the control input C of this switch is connected to the output of the AND gate 45. One input of the AND gate 45 is connected to the output end of the pre-range-finding timer 14 via the inverter 36, and the other input end is connected to the output end of the OR gate 44. Also, one input of the OR gate 44 is connected to an inverter 47.
The other input is connected to the output of the OR gate 40. With the above configuration, the AND gate 45 outputs "1" only when both the dimming and pre-distance measurement timers are inactive, the pre-distance measurement timer is inactive, and the output of the OR gate 40 is "1". However, switch SW ₄ is turned on only under the above circumstances. SW _G is the capacitor 48 to 50, 52, 5
This switch has the same structure as the switch _SW1 which acts as a count switch for short-circuiting the switch SW1. The control input C of the switch SW _G is the NOR gate 4
The input of the NOR gate 46 is connected to the output terminals of the timers 13 and 14, and the switch _SWG is turned on only when both the timers 13 and 14 are inactive. Table 1 summarizes the operation of each of the above switches.

【table】

[Table] 3 is for A-D conversion of the output of OP amplifier 2.
The AD conversion circuit is a known parallel AD conversion circuit consisting of a plurality of comparators. The conversion circuit sets all outputs D ₁ to D ₅ to "0" when the output of the OP amplifier 2 is lower than the first level Level L1, and when the output of the OP amplifier 2 is between the first and second level Level L2. In this case, "1" is output from the output _D1 , and thereafter, as shown in FIG. Each level from LevelL1 to LevelL5 is set to a value that is doubled by a multiplier coefficient. The set input S of the FF8 is connected to the output _D5 of the AD conversion circuit, and is set to make the Q output "1" when the output of the OP amplifier 2 reaches the fifth level LevelL5 or higher. 4 is a rising signal that is input to the clock terminal CP via the inverter 36 when the pre-distance measurement timer 14 inverts the output of the AD conversion circuit 3 from "1" to "0" (after the pre-distance measurement time has elapsed). A latch circuit 5 latches in response to the output of the latch circuit 4 and the Q output of FF8 in FIG.
The decoder outputs "1" from one predetermined output terminal, and the flash aperture value (designated aperture value) is selected at each output of the decoder as shown in FIG. 3b. As is clear from Table 1 above, in the initial state, each switch SW ₁ to _{SW 4} and SW _G is in the on state.
Each of the capacitors 48 to 50, 52, and 53 is shot, and then, when pre-distance measurement, which will be described later, is performed and the pre-distance measurement timer is activated, SW ₂ to _{SW 4} ,
Since SW _G is off and SW ₁ is on, the integration operation of the reflected light from the subject by the OP amplifier 2 during preliminary distance measurement is performed by the capacitor 53, and the integrated output is sent to the AD conversion circuit 3 as described above. Figure 3a
It is converted to a digital value as shown below. Therefore, when the output of the OP amplifier 2 during pre-distance measurement is less than Level L5, "1" is output from a predetermined output of one of the decoders Q ₀ to Q ₄ as shown in Figure 3b, and the specified aperture is selected.
A predetermined aperture value from F1 to F4 is specified. or,
When the output of OP amplifier 2 becomes Level L5 or higher during pre-distance measurement, FF8 is set as described above, and therefore the output reaches Level L in the integral operation process during pre-distance measurement.
When the value becomes higher than 5, the switch SW ₂ is turned on to satisfy the condition (c) in Table 1, and 53 and 52 are connected in parallel as the integrating capacitor of the OP amplifier 2. As mentioned above, the capacitance ratio of capacitors 53 and 52 is set to 1:31, so OP amplifier 2
When the output reaches Level 5, as shown in Figure 2 c
The output of OP amplifier 2 decreases to below LevelL1,
Thereafter, the integration operation is performed with the capacitors 53 and 52 connected in parallel for a period of time regulated by the pre-distance measurement timer. Therefore, when Level L5 or higher occurs during pre-distance measurement operation, the capacity of the integrating capacitor of OP amplifier 2 is switched, the output of OP amplifier 2 shifts to Level L1 or lower again, and the integral operation is executed from that state. Then, as shown in Figure 3b, the output of the decoder 4 outputs "1" from the predetermined output terminals of _Q5 to _Q10 according to the AD conversion value based on the output of the OP amplifier 2 after the integrating capacitor is switched. Specify a predetermined aperture value from F5.6 to F32 as the aperture value. As mentioned above, Levels 1 to 5 are set by multiplier coefficients, so the relationship between the output value of OP amplifier 2 at the end of pre-distance measurement (received light amount level by pre-distance measurement) and each level is that the output value of OP amplifier 2 is LevelL1 when V ₁ (the received light level at that time is E ₁ )
If it reaches OP amp 2 as shown in Figure 3c,
When the output is 2V ₁ (2E ₁ ), LevelL2, 4V ₁ (4E ₁ )
Level L3 is reached when the voltage is 8V ₁ (8E ₁ ), and Level L4 is reached when the voltage is 8V 1 (8E 1 ). The aperture changes by one step each time the distance measurement output (amount of light received) doubles. Also, during pre-distance measurement, the output of OP amplifier 2 is 16V ₁
(16E ₁ ), that is, when Level L5 or higher is reached, the switch SW ₂ is turned on as described above, and the capacitance of the integrating capacitor changes 32 times. Therefore, when the amount of received light reaches _16E1 , which is twice the above _8E1 , the output of the OP amplifier 2 changes to 1/32 times. The amount of light received is 16E ₁
Since the output of the OP amplifier 2 when the voltage reaches 16V 1 is 16V ₁ , as described above, the 16V ₁ is multiplied by 1/32 and the output of the OP amplifier 2 shifts to 16V ₁ /32=1/2V ₁ . Therefore, when Level L5 is reached, the output of OP amplifier 2 is V ₁
Below, that is, Level L1 or lower, the AD conversion circuit output becomes D ₁ to D ₅ = “0”, and with this and the Q output of FF8 “1”, the decoder 5 outputs as shown in Figure 3b.
Output “1” from _Q5 and specify F5.6. In this way, the capacitance of the capacitor is switched at Level L5 or higher, and when the amount of received light is 16E ₁ , the output of OP amplifier 2 is halved.
Since the output of OP amplifier 2 is changed to V ₁ , the output of OP amplifier 2 changes in a multiple series every time the received light amount level changes by a factor of 1. As a result, the received light amount changes as shown in Figure 3c.
V ₁ (Level1) when 32E ₁ , 2V ₁ when 62E ₁
(Level L2) is shown. Therefore, even after the output of the OP amplifier 2 reaches Level 5 or higher during pre-distance measurement, the output of the AD conversion circuit changes as shown in Figure 3c, every multiple change in the level of received light, and the Tecoder 5 also changes its output at the level 3.
As shown in FIG. b, the output is changed every time the AD conversion output changes, that is, every time the received light level changes by a multiple. Therefore, based on the results of the pre-distance measurement operation, the aperture is always adjusted by 1 for each change in the multiple coefficient of the received light level due to the pre-distance measurement.
It can be specified by step change. 6 is a multiplexer as a data selector that selects and outputs the output of the decoder 5 or the output of the ring counter 10 described later, and this multiplexer allows output only when "1" is applied to the inhibit terminal b. At the same time, when "1" is applied to the control terminal a, the contents of the ring counter 10 are selected, and when "0" is applied, the output of the decoder 5 is selected and output. 7 is a D/D converter for converting the signal (digital) from the multiplexer 6 into a voltage (analog).
In the A conversion circuit, when a "1" signal is applied to the input Q ₁₀ , the voltage corresponding to F32 is applied, the "1" signal to Q ₉ is applied to the voltage corresponding to F22, and the same applies to Q ₈ to _{Q 0.}
When "1" is applied to , a voltage corresponding to the aperture value of each stage from F16 to F1 is output. A _V is a terminal for transmitting the D/A conversion output to an aperture control device of the camera (not shown) and setting the aperture of the camera to the specified aperture value. Reference numeral 11 denotes a display circuit for driving a digital display 12 such as a 7-segment or dot display based on the output of the multiplexer 6. 27 is the main capacitor for main light emission, 28,2
9 is a bleeder resistor that divides the charging voltage of the main capacitor, 16 is a comparator that has one input terminal as the output of the bleeder resistor and the other input that applies a reference level Vref, which determines the charging level of the main capacitor 27 for main light emission. When a predetermined level is reached, "1" is output as a charge completion signal. Reference numeral 17 denotes a light emitting diode for displaying charging completion in response to the charging completion signal. Reference numeral 22 denotes a transistor that enters a standby state in response to a charge completion signal, and the collector of the transistor 22 is connected to a terminal _TV via a resistor 21. The terminal _TV is connected to a terminal of a camera (not shown), and a constant voltage is applied to the terminal during the first stroke operation of the camera, and the transistor 22
When turned on, a constant current flows through the terminal _TV , switching the camera mode (shutter and aperture control) from daylight to flash. A comparator 15 compares the constant voltage applied to the terminal _TV with a reference level Vref, and outputs "1" when the constant voltage is applied to the terminal during the first stroke of the camera. 19 is the charge completion signal and the comparator 15
This is an AND gate that outputs "1" in response to "1" from the AND gate 19. With the above configuration, "1" pre-range measurement starts from the AND gate 19 when charging is completed and the first stroke operation of the camera is performed. "1" as a signal is sent. 14 is the pre-distance measurement timer, which outputs a "1" signal for a predetermined period of time in response to the pre-distance measurement start signal. 25 is an auxiliary discharge tube as a light source for pre-distance measurement;
It is triggered by the trigger circuit 24 in response to "1" of the timer 14, discharges the charge in the main capacitor 26 for pre-distance measurement, irradiates the object, and performs the pre-distance measurement operation described above. X is an X contact that connects to the synchro switch of the camera, and inputs the synchro switch on signal when the synchro switch is activated, and connects it to the inverter 23.
The signal is transmitted to the dimming timer 13 via the dimming timer 13, and the dimming timer 13 outputs a "1" signal for a predetermined period of time. 32
is a trigger circuit which operates in response to "1" from the dimming timer 13, which operates the main light emitting discharge tube 33 to discharge the charge in the main capacitor 27 and emit flash light. Reference numeral 34 denotes a light emission stop circuit that includes a known commutation capacitor and the like and stops the discharge of the discharge tube 33 in response to a light emission stop signal of "1" from the AND gate 35. In this embodiment, as described above, the OP amplifier 2 and the capacitors 50, 49, and 48 constitute a mirror integrator for dimming, and even during dimming operation.
The AD conversion circuit 3 detects the output of the OP amplifier 2, and when the output level of the OP amplifier 2 reaches a predetermined value, the AND gate 35 outputs "1" and the flash light emission is stopped as described above. There is. _A1 ～
A ₅ and O ₁ to O ₅ constitute a dimming condition setting circuit for setting the level of the amount of light received by the mirror integrator in the dimming operation to a value corresponding to the specified aperture selected above. These are an AND gate and an OR gate, and these circuits execute flash amount adjustment according to the photographing aperture. The input of the OR gate _O1 is connected to _Q0 to _Q1 , _Q6 of the decoder 5, and as is clear from Fig. 3b above, the photographing aperture is
Outputs "1" and selects AND gate A ₁ when using large apertures below F1.4 and F8. Also the and gate
The other input of A ₁ is connected to the output D ₁ of the AD conversion circuit 3, which allows the shooting aperture to be set to F1.4 or less and
When the output of the OP amplifier 2 (light reception level) reaches the above Level L1 at F8, "1" is output from the AND gate _A1 , and this "1" is transmitted to the AND gate 35 via the OR gate 41, and light is emitted. Outputs a stop signal to stop flash emission. Shooting aperture (designated aperture) during flash control operation below
The relationship between , the selected state of the OR gate and the AND gate, and the output of the OP amplifier (received light amount level) when the flash light emission is stopped is as shown in Fig. 3d. Since the OR gate 40 is connected to the decoder outputs Q ₆ to Q ₁₀ via the multiplexer 6, it outputs "1" when the aperture is smaller than F8 (see FIG. 3b). With the above configuration, when the aperture is F1.4 or less, the flash operation is stopped when the output of OP amplifier 2 reaches Level L1 as described above, and at F2, the AND gate A ₂
is selected and the output of the OP amplifier reaches Level L2, in response to the AD conversion output D ₂ = “1”, the gate A ₂
"1" is sent out from "1", and "1" is outputted from the AND gate 35 as described above due to the "1", and the flash light emission is stopped. Also, at F2.8, gate A ₃ is selected and OP amp 2
AD conversion output D ₃ when the output reaches Level 3 =
In response to "1", "1" is sent from gate _A3 and the flash is stopped. Similarly, when the output of the OP amplifier 2 reaches Level L4 at F4, and when the output of the OP amplifier 2 reaches Level L5 at F5.6, the flash operation is stopped. Now, if the output of the OP amplifier 2 when reaching Level L1 is V ₁ and the received light amount level at that time is E ₁ , as described above, each level Level L1 to Level 5 is
is set in a multiple series, so at an aperture of F1.4 or less as shown in Figure 3d, the output of OP amplifier 2 is V ₁ ,
In other words, the flash stops when the amount of light received reaches E ₁ , and F2
Then, when the output of the OP amplifier reaches 2V ₁ , that is, the amount of received light reaches 2E ₁ , it reaches Level L2 and stops flashing. Also, at F2.8, when the OP amplifier 2 output reaches 4V ₁ , that is, the amount of received light reaches 4E ₁ , the flash reaches Level 3 and stops flashing, and at F4 and F5.6, the amount of received light increases as shown in Figure 3 d. When reaches 8E ₁ , 16E ₁ , LevelL
4. The flash stops when it reaches Level 5. Therefore, when the aperture is opened more than F5.6, the amount of light received when the flash stops changes by a multiple of one stop change of the aperture.
The amount of flash light is also precisely adjusted according to the aperture setting, just like a normal auto strobe. Further, on the aperture side smaller than F8, as described above, "1" is output from a predetermined output of one of the decoders _Q6 to _Q10 , and "1" is sent from the OR gate 40. Therefore, since the condition (g) in Table 1 is satisfied, switch SW ₄ is turned on, and capacitors 49 and 48, which are connected in parallel to 50, are added as dimming capacitors. As mentioned above, the capacitance of capacitor 50 and capacitor 4
Since the capacitance of the parallel connection bodies of 8 and 49 is set at a ratio of 1:31, the capacitance of the integral capacitor for dimming is 32 times the integral capacitance of F1 to F5.6.
Therefore, when the aperture is F8, the received light level is E ₁
32 times 32E ₁ , the output of OP amplifier 2 becomes V ₁
It reaches Level L1. Also, at F8, use the AND gate as shown in Figure 3 d.
Since A ₁ is selected, the output of OP amplifier 2 is
When LevelL1 is reached, the AND gate is executed as described above.
“1” is output from A ₁ and the flash light emission is stopped, and in the end, when F8 is set, the amount of light received at F5.6 is 16E ₁
The flash will stop when the level of received light reaches twice that of _32E1 . Also, since gate A ₂ is selected at F11, the output of OP amplifier 2 is twice as high as Level L1.
The flash stops when it reaches 2V ₁ , ie, Level L2. As mentioned above, OP amplifier 2 has a level of received light.
Since V ₁ , that is, Level L1 is reached at 32E ₁ , the flash stops when the received light amount level reaches 64E ₁ , which is twice that of F8, at F11. In the same way, even when the aperture is smaller than F8, the level of received light when the flash stops changes in multiples for a one-step change in the aperture, as shown in Figure 3d, and the entire aperture range used. Over time, the amount of flash light is appropriately controlled with respect to the set aperture value, similar to the dimming operation of a normal auto strobe. SW _MD is a mode selection switch; when selectively connected to the a side, it becomes the first mode (fully automatic mode), and when connected to the b side, it becomes the second mode (manual magic mode). 38 _-1 is an inverter, 38 _-2 is an AND gate, and 38 _-4 and 39 are OR gates, and these gates constitute a control logic for operating the multiplexer 6 in the mode selected by the selection switch. 9 is a magnitude comparator that compares the output of the decoder 5 and the output of the counter 10, and outputs "1" from the output terminal Out when the output of the decoder > the output of the counter. . The ring counter 10 shifts the output by one step (Q ₀ '-Q ₁₀ '→Q ₀ ') every time the switch SW ₁₁ is turned on, and shifts the output to "1" from a predetermined output end.
Output a signal. It should be noted that the above-mentioned shift may be continuously executed when the switch SW ₁₁ is kept on for a predetermined period of time or more. Also, switch
SWD ₂ and SWD ₄ are interlocking switches, which are linked to a daytime synchro mode selection means (not shown), so that when the daytime synchro mode is selected, SWD ₄ is turned off, and SWD ₂ is turned off in place of the capacitor 52. Connected to resistor 54. Furthermore, switch SW ₁₂ is a switch that is linked to the above-mentioned switch SW _MD and turns on when the switch SW _MD is connected to the a side, and when this switch is turned on, the charging completion level is reduced in the above-mentioned first mode, and the quick shooting performance is improved. It is designed to improve the The camera used in the embodiment of FIG. 1 is, for example, the camera disclosed in Japanese Unexamined Patent Application Publication No. 52-50722, and the functions and configuration of the camera are well known and applicable to the present invention. Since it is not directly related, its explanation will be omitted. Next, the operation of the embodiment shown in FIG. 1 will be explained. First, the first mode (auto mode) will be explained. Assume that the flash device shown in FIG. 1 is attached to the camera, and switch SW _MD is connected to side a to select the first mode. In this state, AND gates 38 _-2 and 38 _-3 both output "0", and "0" is applied to control terminal a of multiplexer 6, allowing multiplexer 6 to send out the output of decoder 5. I am doing it. In this state, when the power of the flash device (not shown) is turned on, the main capacitor 27,
26 is charged, and the charging state of the main capacitor 27 for main light emission is detected by the comparator 6. In addition, in the first mode, switch SW ₁₂
is on, so the charging completion level is set to a lower value than in other modes. When the charging of the main capacitor is completed, a charging completion signal is sent from the comparator 16, and the light emitting diode 17 lights up, indicating that charging is completed. After this, when the photographer performs a first stroke operation of the camera (not shown), a constant voltage is applied to the terminal _TV from the camera side. Furthermore, since the charge completion signal is applied to the base of the transistor 22, the transistor 22 is turned on and draws a predetermined current from the terminal _TV . As a result, the camera switches its mode from daylight mode to flash mode, and the aperture control is adjusted in response to the aperture signal from terminal A _V. Also, since the comparator 15 outputs "1" due to the constant voltage from the terminal _TV , the AND gate 19 outputs "1" in response to the "1" of the comparator 15 and the charge completion signal, and performs the pre-measurement. The distance timer 14 is activated, and "1" is sent out from the timer 14 for a predetermined period of time. Since the trigger circuit 24 is activated by the output "1" of the timer 14, the sub-discharge tube 25 is connected to the main capacitor 26 for pre-distance measurement in synchronization with the starting point of the timer 14 for pre-distance measurement (t ₁ in FIG. 2). The charged charge is discharged and pre-emission starts as shown in FIG. 2a. On the other hand, as shown in Table 1, the switches SW ₁ to SW ₄ and SW _G are all in the on state in the initial state, and due to the output change (from "0" to "1") when the timer 14 is activated. The one-shot circuit 37 operates to reset the FF8, and the Q output of the FF8 is set to "0" at the time of pre-emission start, so when the timer 14 operates, (a), (d), (f), and (h) in Table 1 are activated. ), (i)
Each condition is satisfied. So, switch SW _G ,
SW ₂ to _{SW 4} are turned off and SW ₁ is turned on, and the condenser 53 starts integrating the amount of light reflected from the subject due to the pre-light emission. The capacitor 53
The light amount integration operation is executed until the switch SW _G is turned on, and the switch SW _G is turned on when the distance measurement timer 14 becomes inactive as shown in (i) of Table 1, so the pre-range measurement timer 14 The above integration operation is performed during a predetermined operating time of . The integral amount (light received) of the condenser is determined according to the amount of light reflected from the subject based on the pre-emission by the light receiving element 1 during the pre-distance measurement timer time, so the farther the subject is, the more the above-mentioned integral amount ( amount of light received) will be a low value. Therefore, as mentioned above, when the subject is farther than the predetermined distance, the above-mentioned integral output (output of OP amplifier 2) at the end of the pre-distance measurement operation becomes less than the above-mentioned Level L5, and based on the output of the OP amplifier 2, as described above. Do A
- The output of the D conversion circuit indicates the received light amount level by the pre-distance measurement operation, that is, a predetermined value within the range of I in FIG. It is latched by the latch circuit 4 in synchronization with the rising signal from the inverter 36 at the time of inversion (when the pre-range measurement timer operation ends). The output of the latch circuit 4 is transmitted to a decoder 5. During pre-distance measurement operation, when the output of OP amplifier 2 does not exceed Level L5 as described above, FF8
Since the Q output is set to "0" without being set, the decoder 5 outputs "1" from a predetermined output terminal among the outputs _Q0 to _Q4 as shown in FIG. 3B, based on the above AD conversion output. At this time, the multiplexer selects the output of the decoder 5 as described above, and "1" from the AND gate 19 is input to the inhibit input terminal b via the OR gate 39. , the output of the decoder 5 is sent out via the multiplexer 6, and
The signal is transmitted to the A conversion circuit 7. Decoder output Q ₀ ~ _{Q 4}
indicates the aperture value from F1 to F4, so D
-A conversion circuit 7 outputs a voltage corresponding to a predetermined aperture value from the aperture values F1 to F4 according to the level of light received during pre-distance measurement, that is, the subject distance, based on the decoder output _. and sends it to the camera's aperture control device. In addition, when the subject is close, the integrated output (amount of light received) of OP amplifier 2 increases as described above during distance measurement operation, and the amount of light received increases as described above.
In order to exceed Level L5, the AD conversion circuit 3 sends "1" from the output D5 as shown in Figure _3a during distance measuring operation, sets FF8 as shown in Figure 2d, and sets the Q output of FF8 to "1". Eggplant. Therefore, as mentioned above, when the output of the OP amplifier 2 exceeds Level L5 during the distance measuring operation and "1" is sent from the output _D5 of the AD conversion circuit 3 (t2 in Fig. ₂ ), the switch _SW2 is activated. When turned on, the capacitance of the integrating capacitor is increased and the subsequent integrating operation is executed during the pre-range measurement timer operation time. Therefore, in this case, as mentioned above, the AD conversion circuit output shows a predetermined value in the range c in Figure 3 according to the received light amount level by pre-distance measurement, that is, the subject distance.
The AD conversion output is latched in the latch circuit 4 as described above. At this time, as mentioned above, since the Q output of FF8 is "1", the decoder 5 is
Based on the AD conversion output, "1" is sent from a predetermined output terminal of _Q5 to _Q10 , and the multiplexer 6
The decoder output is sent to the D-A converter circuit 7 via
tell. Output Q ₅ ~ Q ₁₀ of decoder 5 is aperture value
In order to represent F5.6 to F32, the D-A conversion circuit 7 selects a predetermined amount of light received at the pre-distance measurement level among the aperture values of F5.6 to F32 based on the decoder output, that is, a predetermined value corresponding to the subject distance. A voltage corresponding to the aperture value of is sent from the terminal A _V to the aperture control device of the camera. Through the above operations, the aperture value is determined for each step from F1 to F32 in accordance with the subject distance as shown in FIG. 4 in the pre-distance measuring operation. After this, when the second stroke operation of the camera is performed, the aperture control device of the camera adjusts the aperture based on the voltage from the above terminal _A Adjusted to value. Further, the front shutter curtain of the camera starts running and exposure starts, and the synchro switch linked to the front shutter curtain turns on, and a synchro switch on signal is transmitted to the dimming timer 13 via the X contact X and the inverter 23. , the timer 13
operates and changes its output from "0" to "1". The trigger circuit 32 is activated by "1" from the timer 13, triggering the main light emitting discharge tube 33, which discharges the charge of the main condenser 27 and emits a flash light for photographing as shown in FIG. 2a. When the timer 13 starts operating (t ₄ in Figure 2)
It will start at Switches SW ₁ to SW ₄ and SW _G operate from the time when the pre-distance measurement timer becomes inactive at the end of the pre-distance measurement operation (t ₃ in Figure 2) to the time when the dimming timer starts operating (t ₄ in Figure 2). ) in Table 1 (a), (c),
Since conditions (e), (g), and (i) are satisfied, all are on, and each capacitor 48 to 50, 52, and 53
are all in a reset state. Therefore, when the dimming timer 13 is activated at time t4 in FIG. ₂ to perform the light amount integration operation for dimming, the dimming condenser starts the integrating operation from the initial state. Now, the aperture specified in the pre-distance measurement operation described above is
Assume that the aperture value is more open than F5.6. In this case, as shown in FIG. 3b, the decoder 5
Since any one of the outputs Q ₅ to _{Q 0} of outputs indicates “1” and the outputs Q ₆ to _{Q 10} output “0”,
The OR gate 40 also outputs "0". Therefore, when the dimming timer 13 starts operating, the values in Table 1 are
Conditions (b), (d), (e), (h), and (j) are satisfied and the switch is activated.
SW ₁ , SW ₂ , SW ₄ , SW _G are turned off and the switch is turned off.
Only SW ₃ is on. Therefore, the condenser 50 performs integration by the light receiving element 1 and the OP amplifier 2 with respect to the amount of light reflected from the subject due to the main light emission. Now, if the specified aperture is F1 or F1.4, "1" is output from the output Q ₀ or Q ₁ of the decoder 5, so the AND Gate A ₁ is selected, and in response to the D ₁ output (“1”) of the AD conversion circuit 3 when the output of the OP amplifier 2 reaches the above Level L1 in the above integration operation, the AND gate A ₁ outputs “1”. is sent out, and the “1” is sent to the AND gate 3 via the OR gate 41.
5, the AND gate 35 transmits a "1" signal as a flash stop signal to the light emission stop circuit 34, and stops the flash light emission. Also, when the specified aperture is F2, AND gate _A2 is selected as is clear from Figure 3d, and when the amount of light received by the above integral operation reaches twice the value of F1 and F1.4 as described above, the OP amplifier 2 When the output reaches Level L2, "1" is sent from the AND gate _A2 , and the flash light emission is stopped as described above. Hereinafter, as described above, in response to a one-step change in the specified aperture, the level of the amount of light received when the flash light emission is stopped changes in a multiple series (FIG. 3d), and the amount of flash light emission is determined in accordance with the aperture value. Also, when the specified aperture is between F8 and F32, the third
As shown in Figure b, any one of the outputs Q ₆ to _{Q 10} of the decoder 5 becomes "1", so the OR gate 40 outputs "1", and therefore, at the start of the dimming operation, (b ), (d), (e), (g), and (j) are satisfied, switches SW ₁ , SW ₂ , and SW _G are turned off, and switches SW ₃ and SW ₄ are turned on. For this reason, capacitors 48 to 50 are selected as the integrating capacitor in dimming operation, so the aperture is F1 to F5.6.
It is 32 times the capacity of the integrating capacitor when . Therefore, even if the aperture is smaller than F8, the level of received light due to the above-mentioned integral operation when the flash light emission stops changes in a multiple series precisely with respect to a one-stop change in the aperture, as shown in Figure 3d. This is as stated above. As described above, in the light adjustment operation, the amount of light received is accurately changed in a multiple series in response to a one-step change in the photographing aperture, that is, the amount of flash light emission is changed, an accurate light adjustment operation is executed, and the flash is stopped. Incidentally, since the camera mode is switched to flash mode as described above, the shutter speed of the camera is regulated to a flash synchronization speed of, for example, 1/60 second. In this way, in the first mode, the aperture is determined according to the subject distance by pre-flash, and the light control level is set based on the aperture value.
Since accurate exposure can always be guaranteed and the pre-flash amount is used as a factor in determining the aperture, the charging completion level can be kept low and the aperture can be determined based on the main capacitor charging potential GNO at that point. Therefore, there is no need to perform flash photography again until the main capacitor has been charged to a fairly high level, as is the case with ordinary auto strobes, and the ability to take quick photographs is also improved. As mentioned above, in the embodiment, Fig. 3c
The diaphragm is changed by one stop each time the multiple series of the received light amount level changes during pre-distance measurement, as shown in FIG. On the other hand, the amount of light received during pre-ranging is determined according to the subject distance as described above, and each time the subject distance becomes 1/2 times the distance, the amount of light received during the same pre-ranging time doubles. In the example, the aperture is the fourth
As shown in the figure (the vertical axis is a logarithmic scale of aperture value, and the horizontal axis is a logarithmic scale of distance), it is configured so that it changes by one step every time the subject distance changes by a factor of √2. However, as shown by the dotted line in Fig. 4, there are cases where it is desired to extend the distance range for the aperture value normally used during flash photography, such as F5.6, and in this case, the above-mentioned condenser 52
By setting the capacity of 53 to 31 times or more, it is possible to arbitrarily increase the distance range at the normally used aperture value. That is, for example, if the capacitance of the capacitor 52 is 53
If the setting is set to be 63 times larger than is above level
When Level L5 is exceeded and the integrating capacitor 52 is connected to the OP amplifier 2 as described above, the capacity of the integrating capacitor becomes 64 times, and the OP amplifier 2 at that time
The output of is multiplied by 1/64. As mentioned above (Figure 3 c) when reaching Level L5
The output of OP amplifier 2 is 16V ₁ . Therefore, as mentioned above, when the 16V ₁ is multiplied by 1/64 and the output of OP amplifier 2 reaches Level L5, OP amplifier 2
The output of will shift to 1/4V ₁ . Also, when the output of OP amplifier 2 shows Level L5, that is, 16V ₁ , the received light level is twice that of Level L4 as described above.
Since it is 16E ₁ , the aperture changes by one stage in response to a double change in the amount of light received at Level 5 as well as in the case described above, but the voltage ratio until the OP amplifier reaches V ₁ after that is 1/4V ₁ :V ₁ , indicating a voltage ratio of 4 times. Therefore, the output of the OP amplifier is Level L5,
That is, after reaching 16V ₁ (1/4V ₁ ), LevelL1 (V ₁ )
The level of the amount of light received until reaching _{Level L5} is also four times as high as 64E1, and the level of the amount of light received until the aperture changes by one step after reaching Level L5 is four times as large. Also, after that, each time the output of OP amplifier 2 changes twice, such as 2V ₁ and 4V ₁ , it reaches the levels of LevelL2 and LevelL3, so the aperture also changes by one stage for each multiple series of the output of OP amplifier 2. As a result, the diaphragm changes one step at a time in accordance with the multiple change in the level of the amount of received light. Therefore, when the capacitance of the capacitor 52 is 63 times that of the capacitor 53, the relationship between the amount of received light and the aperture is as shown in Table 2.

[Table] As is clear from Table 2, from F1 to F5.6, the aperture changes by one step for every multiple change in the amount of light received, so the aperture changes by one step for every √2 change in the subject distance. However, when moving from F5.6 to F8, the amount of light received changes four times, so the subject distance when changing from F5.6 to F8 doubles, and in the end the subject distance increases.
The aperture will not change by one step until it changes twice as much as it did at F5.6. Also, from F8 to F32, as with F1 to F5.6, the aperture changes by one step for a doubling of the amount of light received, so in this range, the aperture changes by one step for every √2 change in the subject distance. becomes. Therefore, the fourth
As shown by the dotted line in the figure, the distance range in which the F5.6 aperture is used can be increased relative to the distance range for other apertures. Next, the daytime synchronization mode will be explained.
Before explaining the operation in daytime sync mode, daytime sync photography will be explained. Normally, daytime synchronized photography is performed under bright shooting conditions where the brightness level of outside light is higher than a predetermined value, the aperture is determined based on the subject light (external light), and the amount of flash light for the main subject is adjusted normally. Flash intensity due to light operation (light intensity determined based on shooting aperture and subject distance)
This reduces the exposure to the background and the main subject, giving almost appropriate exposure to the background and main subject. In the present invention, in view of the aspect of daytime synchronization described above, daytime synchronization is executed only when the brightness is bright, and in the daytime synchronization mode, the above-mentioned determination of aperture and flash amount is satisfied. be. Next, its operation will be explained. In the daytime synchronization mode, switch SWD ₂ is connected to resistor 54 instead of decoder 52, and switch SWD ₄ is turned off. Also, at this time, connect the switch SW _MD to the a side. After setting the switch in this state and charging the main capacitor, the camera's first
When the stroke operation is performed, the preliminary ranging operation is executed as described in the first mode above. If the subject brightness is brighter than a predetermined value, the charging operation of the capacitor 53 will be faster, so the output of the OP amplifier 2 will exceed Level L5 during preliminary ranging regardless of the subject distance, as shown in Figure 5c.
Switch SW ₂ is turned on as described in the first mode above. For this reason, a resistor 54 as an impedance means is connected in the feedback path of the OP amplifier 2, and the output of the OP amplifier 2 thereafter is connected to the capacitor 5.
In place of the integrated value of the amount of light according to 3, a value corresponding to the brightness of the light incident on the light receiving element 1 is obtained. That is, since the capacitor 53 has a small capacity as mentioned above,
The output of the OP amplifier 2 will be determined by the resistor 54. During the pre-flash, the output of the OP amplifier 2 shows a value affected by the pre-flash as shown in Figure 5c, or after the pre-flash stops, it takes a value depending on the brightness of the outside light. . Also, since the pre-flash ends in a short time compared to the pre-range measurement timer time,
The output of the OP amplifier 2 at the end of the pre-distance measurement operation ( _t3 in Figure 5) represents the brightness of external light, and as a result, the latch is activated at the end of the pre-distance measurement operation as explained in the first mode above. The digital value latched in the circuit 4 is a value corresponding to the brightness of external light. In this embodiment, a resistor is connected to the OP amplifier 2 only when the brightness of outside light is high as described above.
Since the output of the OP amplifier 2 is made to correspond to the brightness, the contents of the latch circuit obtained as described above are made to represent an aperture smaller than F8. That is, the above operation is performed only when the brightness of external light is a brightness value corresponding to an aperture value smaller than F5.6 when converted to an aperture value. Therefore, the output of the OP amplifier 2 at the end of the distance measurement operation is distributed as shown in FIG.
“1” is sent from one output terminal of the decoder 5 output Q ₆ to Q ₁₀ representing ~F32, and based on the brightness
Aperture values from F8 to F32 are selected. Note that the output selection operation of the decoder 6 based on the output of the OP amplifier 2 is the same as in the first mode, so its explanation will be omitted. When the second stroke is performed after the aperture value is determined according to the brightness as described above, the aperture is adjusted to the aperture value according to the brightness as described in the first mode. At the same time, a dimming operation is executed. As mentioned above, the aperture value for daytime synchronization is
Since the aperture is smaller than F8, a predetermined one of the _Q6 to _Q10 outputs of the decoder 5 is sending out "1", so the OR gate 40 is outputting "1". Therefore, in the above dimming operation,
As described in the first mode, the switch SW ₄ is turned on, and the integrating capacitor in the dimming operation is composed of the capacitors 50, 48, and 49, and the AND gates A ₁ to _{A 5} are connected based on the aperture value.
Among them, a predetermined gate is selected and the amount of flash is correctly controlled based on the photographic aperture as described in the first mode _.
is in the off state, so the integrating capacitor at this time actually consists of 50 and 48.
Therefore, the capacitance of the integrating capacitor (consisting of 50, 48, and 49) formed during the dimming operation in the first mode is reduced by a predetermined amount. Therefore, the amount of flash light for the same subject is also reduced by a predetermined amount compared to the case of the first mode, so the amount of exposure from the flash and the amount of exposure from external light are added together as the amount of exposure for the main subject. Also, an appropriate amount of exposure can be guaranteed without overexposure. As mentioned above, when synchronizing during the day, when the subject is far away, the flash aperture value is set according to the subject distance, and when the subject is close, the flash aperture value is set according to the brightness of the outside light. This allows appropriate daytime synchronized shooting while reducing energy consumption.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a flash device to which a photometric circuit according to the present invention is applied; FIG. 2 is a waveform diagram illustrating the operation of the embodiment in FIG. 1 in a first mode;
3a to 3e are explanatory diagrams for explaining the operation of the embodiment in FIG. 1, FIG. 4 is an explanatory diagram showing the aperture value controlled by the embodiment in FIG. 1, and FIG. 5 is according to the embodiment in FIG. 1. FIG. 3 is a waveform diagram for explaining the operation of daytime synchronization mode. 1... Light receiving element, 2... Operational amplifier, 48-5
0, 52, 53... Capacitor, 3... AD conversion circuit, 4... Latch circuit, 5... Decoder,
8...Flip-flop, SW ₁ ~ SW ₄ , SW _G ...
Switch.

Claims (1)

[Claims] 1. A distance signal forming circuit that forms a signal according to the distance of a subject; detecting a signal from the distance signal forming circuit; and outputting a first signal when the signal indicates a distance shorter than a predetermined distance; a detection circuit that outputs a second signal when the distance is longer than a predetermined distance; and a detection circuit that outputs a second signal when the distance is longer than a predetermined distance; An aperture determining device for flash photography, comprising an aperture value determining circuit that forms an aperture value for flash according to a signal from the distance signal forming circuit.