JPH0462058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flash photography control device, and more particularly to a flash photography control device that performs appropriate light adjustment regardless of the subject.

Conventionally, when performing flash photography, it is necessary to adjust the amount of flash according to the distance to the subject, so the method used is to adjust the flash of a strobe or other device based on distance information from the distance setting ring of the A shooting lens. Method B: A strobe or the like is equipped with a light-receiving element that receives the reflected light from the subject, and the amount of flash is adjusted based on the output of the element.C: The light-receiving element that receives the reflected light from the subject is connected to a camera lens, This method involves adjusting the amount of flash by receiving light through an aperture.

However, using any of the above methods, it is difficult to obtain an appropriate flash amount for various subjects. The reason for this is that when photographing various subjects, for example, subjects with extremely high or low reflectance, subjects that are particularly close when photographing or copying, and when there are secondary subjects in front of the subject, etc. With any of the above methods, it is not possible to obtain a flash amount that provides appropriate exposure.

For example, when photographing a short-distance subject using method A above, since the flash device is installed at a location far from the optical axis of the photographic lens, the amount of flash cannot be controlled as a function of the subject distance. Furthermore, when photographing using method B or C, the amount of light received changes depending on the reflectance of the subject, so for example, if there is a part of the subject with extremely high reflectance, the reflected light from that part will As a result, the part of the subject you are aiming for will be underexposed and you will not be able to obtain the appropriate amount of flash.

Furthermore, in the method of inputting the distance information of the subject using the distance ring of the lens, as in method A above, due to the relationship with the amount of extension of the lens, the closer the moving amount of the distance ring is, the higher the resolution is, while the farther the distance ring is moved, the higher the resolution is. Because of the low value, there are problems such as a decrease in the accuracy of flash amount control at long distances. Particularly in the case of a wide-angle lens, since the amount of movement of the focusing plane is small when setting the subject distance, the resolution of the distance ring decreases as the lens becomes wider, which has the disadvantage that accurate light control cannot be expected. In some cases, such problems can be solved by measuring the distance using an automatic focus detection device, but in some cases, for example, there are some secondary objects in front of the main subject. Furthermore, since the automatic focus detection device cannot necessarily detect the main subject at which it is aimed, appropriate flash photography may not be performed in all cases. In addition, if the subject is a person standing in a field, that is, the background is far away and the main subject is also relatively far away, the reflected light from the subject itself will not return and the above B or B. Method C has the disadvantage that it is not possible to control the amount of flash at the same time.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a flash photography control device that controls the amount of flash light with uniform accuracy for any subject.

The present invention has a configuration to achieve the above object, and includes a light receiving means (PS ₁ , C ₁ , L ₁ in FIG. , corresponds to CP ₁ )
and object distance information circuit (DVL, OP ₄ in Figure 1)
corresponds to ) and an information circuit (OP ₅ in FIG. 1, (corresponds to OP ₆ ), and a monitor circuit for monitoring the amount of flash light emitted (corresponds to
Corresponds to PS ₂ , C ₂ , and L ₂ . ), and if the signal is generated from the light receiving means before the amount of flash light emission monitored by the monitor circuit reaches the first value, the flash is stopped when the amount of flash light emission reaches the first value. However, if the signal is not generated from the light receiving means before the monitored amount of flash light emission reaches the second value, the amount of flash light emission is equal to the second value.
The flash light is stopped when the flash light emission amount reaches the value , and when the signal is generated from the light receiving means when the monitored flash light emission amount is between the first and second values,
A flash light amount control circuit that stops the flash in response to the signal (CP ₂ , CP ₃ , A ₁ , A ₂ , I ₁ , OR ₁ ,
This corresponds to SCR102, SCR103, and C104 in FIG. ) is provided.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. In Figure 1, A, B, C,
indicates an external terminal provided on the camera body, terminal C is an X contact that closes in synchronization with the front shutter curtain, B terminal is a terminal to be connected to the dimmer circuit of a flash light emitting device, which will be described later, and A terminal is an Terminals connected to the light receiving element PS2 provided behind the light emitting section of the flashlight emitting device, for example, the xenon tube, are shown. Note that PS2 is installed so that it directly receives only the light from the xenon tube and does not receive the reflected light from the subject. PS1 is provided behind the photographing lens of the camera, for example, at a position where it receives light reflected from the film surface. C1 and C2 are light receiving elements PS1 and C2, respectively.
Capacitor connected to PS2, SW10, SW
11 is a capacitor shorting switch and an X contact
It is linked with SW12, SW11 and SW10
is closed when switch SW12 is open, that is, when the shutter is closed. On the other hand, when the shutter reaches the fully open state, SW10 and SW1
1 is opened and charging of capacitors C1 and C2 is started.

OP1 indicates an operational amplifier, and a constant voltage V _c from a constant voltage circuit (not shown) is input to its non-inverting input. On the other hand, a variable resistor SVL is connected to the inverting input, and the output from OP1 is connected to a variable resistor such that the higher the film sensitivity, the higher the output voltage. ing. OP2 is an operational amplifier circuit connected to the output of the amplifier OP1 via a resistor R2, and a resistor R3 is connected in the circuit.
OP4 is an operational amplifier whose non-inverting input is connected to a variable resistor DVL that is variable in conjunction with the distance setting ring of the photographing lens, and its output is connected to the input of the amplifier OP3 via a resistor R5. AVL indicates a variable resistor that is variable in conjunction with the aperture of the photographic lens used. The output of amplifier OP3 corresponds to the film sensitivity, set subject distance, and aperture value.The lower the film sensitivity, the farther the subject distance, or the smaller the aperture diameter, the higher the voltage output. The variable resistor DVL is set so that the closer the resistance value thereof is, the higher the voltage is at the output of the amplifier OP4.

The output of amplifier OP3 is operational amplifier OP5, OP6.
are connected to their non-inverting inputs, respectively.

R10 is a return resistor connected to the return circuit of OP5, and R12 and R13 are amplifiers OP5 and OP6.
is a resistor connected between the outputs of.

CP2 and CP3 are comparison circuits connected to the outputs of amplifiers OP5 and OP6, respectively, A1 and A2 are AND circuits,
OR1 indicates an OR circuit.

Operational amplifier circuits OP5 and OP6 adjust the distance to the subject, aperture, and film sensitivity, respectively, using resistors.
By setting DVL, AVL, and SVL, an output indicating the upper and lower limits of the appropriate flash amount for the shooting conditions determined by setting DVL, AVL, and SVL is obtained from the output terminal and the comparison circuit
Applied to CP2 and CP3. L1 and L2 indicate logarithmic compression circuits, the output of the circuit L1D is sent to the comparator circuit CP1, and the output of the circuit L2 is sent to the comparator circuits CP2,
Connected to the non-inverting input of CP3. In addition, I
1 indicates an inverter circuit.

FIG. 2 shows a circuit of a flash light emitting device used together with the circuit shown in FIG. Main capacitor, NE is resistor R102,
The neon tube connected in series to R103, TT's secondary coil is the trigger electrode of the xenon tube XE, and its primary coil is a trigger thyristor.
SCR101 is a trigger transformer to which a trigger capacitor is connected, SCR102 is a main thyristor connected in series to a xenon tube, C104 is a point commutation capacitor, SCR103 is a commutation thyristor S, and the anode of thyristor SCR103 and the cathode of SCR102 There is a resistance R between
108, a capacitor C105 is connected. Note that the above-mentioned commutation circuit using the main thyristor and the commutation thyristor is a known circuit, so a detailed explanation thereof will be omitted.
R111, R112, D104, and C106 each indicate a resistor, diode, and capacitor for the malfunction prevention circuit, and transistor TR1
01 is shown to prevent the commutation capacitor from becoming conductive before the xenon tube emits light via 01. In the above circuit, when the main capacitor C101 is fully charged, the neon tube lights up to indicate that it can emit light, and the capacitor C102 is charged. When a trigger signal is applied from terminal C, the charge in capacitor C102 is discharged through resistors R103, R104, and the gate and cathode of SCR101, and the thyristor is discharged.
Since SCR101 is conductive, capacitor C1
The charge of 03 is discharged through the primary coil of the transformer TT, and a voltage induced on the secondary side is applied across the xenon. During this time, the transistor TR101 is non-conductive only when flash light is being emitted, and only when a light emission signal is applied from the J terminal B, that signal is applied to the gate of the thyristor SCR103. In other words, when a flash is emitted,
Because the voltage of main capacitor C101 drops,
The charge stored in capacitor CA106 is transferred to xenon tube XE hand thyristor SCR102 resistor R1
12, the base of the transistor TR101,
Apply a reverse bias voltage between the emitters, TR101
is non-conducting. Therefore, in this state, when a light emission stop signal is applied to the gate of SCR103, SCR10
3 is in a conductive state. In addition, when no light is emitted, the base current is applied to the transistor TR101 via the resistors R111 and R112, so even if a light emission stop signal is applied, the thyristor
SCR103 never becomes conductive.

Based on the above configuration, its operation will be explained below.
When the shutter is fully opened, the switch SW12 is turned on and a trigger signal is passed through the terminal C to make the thyristor SCR101 conductive. As a result, a trigger voltage is applied to the xenon tube, and at the same time, thyristor SCR102 becomes conductive via capacitor C105 and resistor R108. Therefore, the xenon tube starts emitting light, and the light receiving element PS2
receives the flash directly from the xenon tube. The output of the light receiving element PS2 is integrated by a capacitor C2, and the compressed output is applied to comparison circuits CP2 and CP3 via a compression circuit L2.

As a subject, if its reflectance is very high,
Or, if there is a secondary subject in front of the main subject, the light receiving element
The output from PS1 provides a voltage corresponding to the amount of reflected light from the subject to the integrating capacitor C1. V
1 has a voltage waveform that rises rapidly because the subject has a high reflectance or is a secondary subject.
The output of the comparison circuit CP1 becomes high level after time t1. However, since the other inputs of the AND circuits A1 and A2 are not at high level, no light emission stop signal is generated.

Photodetector PS2 and integrating capacitor C1
As a result, a voltage shown by the V2 curve in FIG.
Since the voltage is higher than the output voltage of OP6, the comparison circuit CP3 forms a high level signal, and the AND circuit A2 applies a light emission stop signal to the thyristor SCR103 via the OR circuit OR1. Therefore, the light emission of the xenon tube XE is stopped for the purpose described above.

FIG. 4 shows the characteristic V1 described above when the reflectance of the subject is low or when the subject is relatively far away. In this case, since the amount of reflected light from the subject is relatively small, the V1 characteristic increases with a relatively gentle curve. Before the comparison circuit CP1 becomes high level, the comparison circuit CP3,
CP2 gradually increases to a high level, so time
When the comparison circuit CP2 becomes high level at t3, a light emission stop signal is generated from the OR circuit OR1.

As mentioned above, the reflectance of the subject or the subject is appropriate, that is, the PS obtained through the photographic lens.
When an appropriate amount of flash light is reached, not based on the signal from 1, but according to the photographing conditions set in advance, a light emission stop signal is obtained by the light receiving element PS2. When the subject is appropriate, that is, when its reflectance or appropriate scene is to be photographed, the output of the light receiving element PS1 is sent to the comparison circuit as shown in Figure 5.
The inversion time point t1 of CP1 is within the appropriate light emission amount range under the set photographing conditions, that is, between the time points t2 and t3.

In the above embodiment, an example was described in which the distance to the subject is manually set. Kosho 55-33005
The distance ring can be automatically set by using a device of the type shown in the No. 1, and using a focus detection element to detect the contrast of the main photographing area in the subject and driving the focusing motor. good. In this case, even if there is a secondary subject near the main subject and the photographing lens cannot be set accurately according to the distance to the main subject, the approximate subject distance information is set to the variable resistor DVL in the above embodiment. Therefore, depending on this set amount, the flash light emission is performed within a predetermined range of light amount. Therefore,
If the main subject is within the depth of field, a sharp image will be obtained, and appropriate photography will be performed with an approximately appropriate amount of flash light. However, when performing flash photography, since there are many dark subjects to be photographed, it goes without saying that it is desirable to use an active type autofocus device. As described above, the present invention solves the disadvantage of not being able to obtain an appropriate amount of flash with the dimming method that controls the amount of flash by receiving the reflected light from the subject, by providing an additional circuit. , regardless of the reflectance of the subject.
Another advantage is that it is possible to control the amount of flash light appropriately for most subjects. Also, even if the distance to the subject is set somewhat incorrectly, if there is a subject whose light control range is determined by the set distance, the appropriate exposure amount will be obtained, so in most cases This makes it possible to obtain an appropriate amount of exposure for the subject, and the effect is remarkable.

[Brief explanation of the drawing]

FIG. 1 shows a control circuit applied to a flash photography device according to the present invention, FIG. 2 shows a flash light emitting circuit used together with the control circuit shown in the first drawing, and FIGS. 3 to 5 illustrate the operation of the control circuit shown in the first drawing, respectively. Figure 3 is an explanatory diagram of the operation when the subject has a high reflectance, and Figure 4 is
The figure shows an explanatory diagram of the operation when the reflectance of the subject is low or the distance to the subject is relatively large, and FIG. 5 shows an explanatory diagram of the operation when photographing a proper subject. PS1...Subject reflected light receiving element, PS2...Xenon tube light emission amount receiving element, CP2, CP3...Comparison circuit, OP5, OP6...Dimming appropriate range signal forming circuit.

Claims (1)

[Claims] 1. A light receiving means that receives reflected light from a subject due to a flash and generates a signal when the amount of received light reaches a predetermined value, and a first value corresponding to the amount of flash that corresponds to distance information from a subject distance information circuit. an information circuit that sets a second value corresponding to a flash amount larger than the first value; a monitor circuit that monitors the flash light amount; and an information circuit that monitors the flash light amount that is monitored by the monitor circuit. If the signal is generated from the light receiving means before reaching the first value, the flash is stopped when the amount of flash light emission reaches the first value, and the monitored amount of flash light emission is equal to the second value. If the signal is not generated from the light receiving means before reaching the value, the flash is stopped when the amount of flash light emission reaches the second value, and the amount of flash light emission monitored is equal to the first and second values. A flash photography control device comprising a flash light amount control circuit that stops flashing in response to the signal when the signal is generated from the light receiving means at a certain time.