JPS5941566B2 - Shutter control device for flash photography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shutter control device that detects that the terminal voltage of a flash discharge lamp power supply capacitor is above a predetermined level and automatically obtains an exposure time suitable for flash photography. It is something.

Conventionally, such a shutter control device was disclosed in Japanese Patent Application Laid-open No. 50
Various methods have been proposed in Japanese Patent Laid-Open No. 51-10933 and Japanese Patent Application Laid-Open No. 51-10933.

However, in order to realize the shutter control device as described above, it is necessary to somehow switch the normal exposure time control according to the settings or calculation results to an exposure time suitable for flash photography. In order to utilize the terminal voltage of the flash discharge lamp power supply capacitor, which has the property of dropping below a predetermined level during light emission, various considerations were required. For example, in order to reliably change the exposure time,
It was necessary to add some means for remembering that the terminal voltage of the flash discharge lamp power supply capacitor was above a predetermined level even after light emission. In view of the above, an object of the present invention is to
It is an object of the present invention to provide a shutter control device that can reliably switch to a shutter speed suitable for flash photography by detecting that a flash discharge lamp power supply capacitor is at a predetermined level, without adding a storage means as described above. This is the purpose.

That is, as is clear from FIG. 1, the present invention continues to output the shirt shutter closing activation prevention level at least from the time when the shirt starter is opened until a time corresponding to the setting or calculation result has elapsed, and thereafter. Exposure time control circuit C, Trl, s4, c2, which inverts the output to the shirt shutter closing activation permission level.
s3, R6, B, and when the terminal voltage of the flash discharge lamp power supply capacitor in the flash discharge lamp device does not reach a predetermined value, the shutter close start permission level is reached, and when the above terminal voltage reaches the predetermined value, the shutter closes. A terminal (connection point of R3 and R4) that receives a charging voltage detection signal that reaches the activation prevention level and then returns to the shutter closing activation permission level when the light is emitted, an electromagnet M that activates the closing of the shutter, and the above exposure time. electromagnet control logic circuits Tr2 and Tr7 that cause the electromagnet to start closing the shutter only when the output of the control circuit and the charging voltage detection signal both reach the shutter closing activation permission level; and the charging voltage detection signal. is at the shutter closing activation prevention level, the exposure time control circuit activates the shutter closing within a predetermined short time after the shutter is opened and before the flash discharge lamp device emits light, regardless of the above settings or calculation results. Reversal forcing circuit Tr6, R5 for reversing from the blocking level to the shutter closing activation permission level
It is characterized by having the following.

As a result, when the charging voltage detection signal is at the shutter closing activation permission level during exposure, the electromagnet activates the shutter at the timing of reversal of the exposure time control circuit according to the setting or calculation result. When the charging voltage detection signal is at the shutter closing activation prevention level during exposure, the charging voltage detection signal changes from the shutter closing activation prevention level when the flash discharge lamp device emits light. The electromagnet starts closing the shutter at the timing of the change to the closing activation permission level. The present invention will be explained in detail below with reference to the illustrated embodiments.

In FIG. 1 showing an embodiment of the shutter control circuit of the present invention, E is a power source, S1 is a power switch, and A, indicated by a block, is a photoelectric element that receives object light transmitted through a photographic lens. an amplifier circuit for extracting a desired photoelectric output from the 1000 Hz, and a calculation that adjusts the photoelectric output according to the set film sensitivity and aperture value to produce an output corresponding to the appropriate shutter value obtained from photographic calculations of these exposure factors. This is a known photometric circuit including a circuit, etc., and its output, that is, photometric output is stored in a storage capacitor C1 via a storage switch S2. Trl is a transistor that outputs a current according to the voltage of the storage capacitor C1, and forms an automatic control timer circuit with a timer capacitor C2 charged by the output current.
R6 is a variable resistor for manually setting the shutter speed.
When the movable contact piece of the changeover switch S3 is connected to the terminal m side, a manual control timer circuit is formed with the timer capacitor C2. S
4 is a count start switch for the automatic control and manual control time limit circuits. Reference numeral B designates a transistor control circuit, which is configured to make the first switching transistor Tr2 conductive when the charging voltage of the time limit capacitor C2 is low, and to turn off the first switching transistor when the charging voltage exceeds a predetermined value. .

Reference numeral M designates an electromagnet that locks the shutter closing member in the charge position while being energized, and releases the lock upon demagnetization to start closing the shutter. Figure 2 shows a circuit for making the flash discharge lamp F emit light. In the figure, Ef is a flash power source, S5 is a power switch, and D is a blocking oscillator circuit, which is the main circuit for supplying power to the flash discharge lamp. Capacitor C.

This is a circuit that generates a high voltage to charge the battery. C3 is a trigger capacitor, which is provided on the camera side and is connected to the synchro contact X.
By closing the trigger switch S6, which is connected to the flash discharge lamp light emitting circuit through the
It is then discharged through the coil and the flash discharge lamp F is triggered. S7 is opened and closed in conjunction with power switch S5, and while power switch S5 is open, flash discharge lamp F is not triggered even if the main capacitor is sufficiently charged. Returning to Figure 1, t
is the camera's synchro terminal, that is, it is installed on the accessory grip of the camera or on the side of the camera body to connect the flashlight switch S6 inside the camera to the flash discharge lamp emitting circuit when the flash device is attached to the camera. The input terminal is connected to the main capacitor C from this human power terminal to the transistor Tr3 via the high resistance R1 and the bias resistance R2. A voltage corresponding to the charging voltage is applied. In the circuit shown in Fig. 2, the resistance value of the high resistance R1 is the same as that of the trigger capacitor C when the trigger switch S6 is open.
3 is set high enough to substantially prevent discharge. If a field effect transistor is used as the transistor Tr3, this high resistance becomes unnecessary. Transistor Tr3 is main capacitor C.

When the charging voltage of C exceeds a predetermined level, the main capacitor C becomes conductive, supplies base current to the transistor Tr4 whose collector is connected to its base, and makes the transistor Tr4 conductive. When the voltage of the transistor Tr4 falls below a predetermined level, it becomes non-conductive and is set to cut off the transistor Tr4. R
3. R4 is an output resistor, and when the transistor Tr4 is turned on, a transistor Tr5 has a collector connected to a display light emitting diode, a transistor Tr6 has a collector connected to a resistor R5 forming a CR time circuit with a time capacitor C2, and the first switching transistor Tr
The second switching transistor Tr7 connected to the electromagnet M in parallel with the second switching transistor Tr2 is set to conduct. According to such a circuit, if a flash device is not attached to the camera, or even if a flash device is attached but its power switch S5 is not closed, a flash device is attached to the camera and its power switch is turned off. Main capacitor C even if S5 is closed.

is not charged to a predetermined level, transistor Tr3 is in a cutoff state, so transistors Tr4 to T
r7 is also cut off, and when the shutter is released, the count start switch is opened and the time capacitor C2 is charged by a current proportional to the inverse logarithm of the photometric output stored in the storage capacitor C1 or a current flowing through the variable resistor R1. When the charging voltage of the time capacitor C2 reaches a predetermined level, the transistor Tr2 is cut off and the shutter is closed, thereby performing normal exposure time control. On the other hand, when the main capacitor of a flash device that is attached to the camera body and whose power switch is closed is charged to a predetermined level or higher, transistors Tr3 to Tr6 become conductive.
When the light emitting diode L lights up to indicate the completion of charging of the main capacitor and the shutter is released in this state, the electromagnet M is initially connected to the first and second switching transistors Tr2.
, Tr7, but the time capacitor C2
is the output current of the transistor Trl or the current flowing through the variable resistor R6, as well as the transistor Tr6 flowing through the resistor R5.
The charging voltage reaches a predetermined value in a very short time, ie, before the shutter is fully opened and the trigger switch is closed, thereby cutting off the first switching transistor.

At this time, the electromagnet M is connected to the second switching transistor Tr7.
is supplied via the trigger switch is closed,
When the flash discharge lamp F emits light, the main capacitor C. The terminal voltage suddenly drops, the transistors Tr3 to Tr7 are cut off, the light emitting diode L is turned off, and the electromagnet M is cut off from power supply to start shutter closing. That is, flash discharge lamp F
The shutter closes in response to the light emission. In the embodiment shown in FIG. 1 above, the power supply to the electromagnet M is cut off immediately after the flash discharge lamp F starts emitting light, but due to the inertia of the interlocking mechanism from the electromagnet M to the shutter curtain or blade, the flash discharge continues. The shutter is guaranteed to be open while the light F is on.

As mentioned above, the electromagnet M is controlled by the logic circuit consisting of the transistor Tr7 and the transistor Tr2, and the charging voltage detection signal to the base of the transistor Tr7 and the output from the exposure time control circuit to the base of the transistor Tr2 are both output when the shutter is closed. Shutter closing is activated only when the condition becomes low level, which permits activation of shutter closing.

Therefore, in the normal shooting state where the charging voltage detection signal is at a low level, the output from the exposure time control circuit is reversed from a high level to a low level to allow this, depending on the settings or calculation results. At this timing, the above conditions are satisfied, 2, and shutter closing is activated. on the other hand,
In the flash photography preparation state where the charging voltage detection signal goes to the level..., first, the resistor R5 is
The output of the exposure time control circuit is forcibly inverted from high level to low level by the action of transistor Tr6. However, at this time, the charging voltage detection signal is at a high level that prevents the shutter closing from being started, so the above condition is not satisfied and the shutter is not started to close. Then, the above condition is satisfied for the first time when the charging voltage detection signal changes from high level to low level during light emission, and shutter closing is activated. This ensures that an exposure time suitable for flash photography is achieved during flash photography. As is clear from the above, according to the present invention, the output of the exposure time control circuit used for normal shutter speed control is forcibly and quickly reversed, and the output of the exposure time control circuit and the charging voltage detection signal are Through logical processing, it is possible to reliably activate the shutter closure at the timing of light emission without adding any new means for storing that the voltage of the flash discharge lamp power supply capacitor is above a predetermined level. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example of a flash discharge lamp light emitting circuit coupled with the present invention. A: Photometric circuit, C2: Time constant capacitor, R5: Low resistance,
Tr6: transistor switch, Tr2: first switching transistor, Tr7: second switching transistor, M: electromagnet, F: flash discharge lamp, CO: flash discharge lamp power supply capacitor, S6: trigger switch.

Claims (1)

[Claims] 1. An exposure time control circuit that continues to output the shutter closing activation prevention level at least until a time corresponding to the setting or calculation result has elapsed from the shutter opening activation, and thereafter inverts the output to the shutter closing activation permission level. When the terminal voltage of the flash discharge lamp power supply capacitor in the flash discharge lamp device does not reach a predetermined value, the shutter closing activation permission level is reached, and when the terminal voltage reaches the predetermined value, the shutter closing activation prevention level is reached. At the same time, a terminal receives a charging voltage detection signal that becomes the shutter closing activation permission level again when light is emitted, an electromagnet that activates shutter closing, and an output of the exposure time control circuit and the charging voltage detection signal are connected to the shutter. The electromagnet control logic circuit causes the electromagnet to start closing the shutter only when the shutter closing activation level is reached, and the exposure time control circuit sets the exposure time control circuit when the charging voltage detection signal is at the shutter closing activation prevention level. or a reversal forcing circuit that inverts the shutter closing activation prevention level to the shutter closing activation permission level within a predetermined short time after the shutter opening activation and before the flash discharge lamp device emits light, regardless of the calculation result. During exposure, when the charging voltage detection signal is at a shutter closing activation permission level, the electromagnet activates shutter closing at the timing of reversal of the exposure time control circuit according to the setting or calculation result. At the same time, when the charging voltage detection signal is at the shutter closing activation prevention level during exposure, the charging voltage detection signal changes from the shutter closing activation prevention level to the shutter closing activation permission level when the flash discharge lamp device emits light. A shutter control device for flash photography, characterized in that the electromagnet starts closing the shutter at the timing of a change to .