JPS60151617A - Feeding circuit for camera - Google Patents

Abstract

PURPOSE:To prevent the malfunction of a photometry circuit due to the drop in source voltage by performing simultaneously or individually photometry and conduction for winding operation according to the output level of a power source battery. CONSTITUTION:When the voltage of the power source battery BAT1 is above a specific level, a winding motor M1 for film feeding is powered on with the output of a comparator CMP1, and a switch SW4 is turned off when the winding operation is completed to stop the power supplying. At this time, the photometry circuit lm is also powered on. When the voltage of the power source battery BAT1 drops below the specific level, the photometry circuit lm is inhibited from being powered on while the winding motor M1 is powered on.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photometric circuit for a camera, and more particularly to preventing malfunction of the photometric circuit when the power supply voltage drops.

For cameras with a built-in motor drive or to which a motor drive device can be attached, 1.
The aim is to be able to take a large number of photos per second, that is, to achieve high-speed continuous shooting. For this reason, in order to perform continuous shooting as quickly as possible, we use a large, high-performance winding motor, and if the quick return mirror returns during winding and becomes ready for photometry, there is no need to wait for the winding to complete. Some innovations have been devised to start metering immediately after the camera has finished winding the camera, and to finish the metering operation by the time the winding is complete, thereby shortening the interval between shots.

However, if you try to shorten the interval between shots by performing photometry during winding, the photometry circuit will perform photometry while the motor of the motor drive circuit is operating, which may cause the power supply voltage to drop due to motor energization. Due to the fluctuation, the operating voltage applied to the photometry circuit also fluctuates, which may cause a photometry error. This is especially true when the power supply for the photometry circuit and motor drive circuit is from the same power source, such as in a camera with a built-in motor drive, and when the voltage of the power supply battery drops, the motor is energized and photometry is performed at the same time. If the motor is energized, the photometry error becomes noticeable, and therefore, it is necessary to adopt a configuration in which photometry is not performed while the motor is energized, and photometry is performed after the energization is stopped.
I had no choice but to take longer intervals between shots.

The present invention has been made in view of the above-mentioned matters, and includes a built-in motor drive device for film feeding or a motor drive device to which the motor drive device can be installed, and a photometric circuit, so that power is supplied to the photometric circuit and the motor drive device from the same device. In a power supply circuit for a camera that shares a power source, a voltage detection circuit (R,
A first power supply circuit (corresponding to TRI in the embodiment) forming a power supply path for supplying power to the motor drive device during operation (corresponding to 8, R9, VO2, CMPI);
A second power supply circuit (corresponding to TR3 in the embodiment) forms a power supply path for supplying power from the power source to the photometric circuit.

), and a prohibition means (corresponding to the ORI in the embodiment) that operates in response to the output signal of the voltage detection circuit and prohibits the power supply circuit of the power supply tube 2 for supplying power to the motor drive device from supplying power to the photometry circuit. When the voltage drops, the power supply to the photometry circuit is started after the power supply to the motor drive device is stopped.
Also, when the power supply voltage is high, power is supplied to the photometry circuit even while power is being supplied to the motor drive device, enabling high-speed continuous shooting under normal conditions when the voltage is high. This solves the problem of high-speed snapshots and photometry errors by setting up a power supply state that prevents photometry errors.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit connection diagram showing an embodiment of a camera equipped with a power supply control circuit according to the present invention.

In the figure, vCI is a constant voltage source, and the operational amplifier (described later)
Bias voltage is applied to the non-inverting input terminals of OPl and OF2 (hereinafter referred to as OP amplifier). Tel is a constant current source, (')PL, OF2, OF2 is an OP amplifier,
Dl is a wetness detection diode, and H2 is a photodiode as a light receiving element, which outputs a photocurrent proportional to the subject brightness. H3 is a diode for logarithmic compression, 几1 is a posistor,
TL2 is a resistor, and a block em surrounded by a broken line forms a well-known photometric circuit.

Reference numeral 1 denotes a known exposure calculation circuit which receives the output of the OP amplifier OP3, calculates and outputs a TV value or AV value based on the output of the photometry circuit, and outputs the TV value of the exposure result to a known exposure control mechanism 2 to be described later.
Output value or AV value.

Reference numeral 2 denotes an exposure control mechanism which receives the TV value or AV value inputted from the exposure calculation circuit 1 and controls the shutter speed or aperture value of the camera during the O-space operation.

The switch 8W1 is a main power supply switch for supplying power to the circuit shown in FIG. 1, and is turned on, for example, in conjunction with the first stroke operation of the camera.

Power supply for BAT14, CMP1 hakonhalator, VO
2 is a constant voltage source. R8 and R9 are resistors.

The voltage of the power supply battery BA'll is divided by resistors R8 and 9, and applied to the non-inverting input terminal of the comparator CMP1.

The constant voltage source VC2 is applied to the inverting input terminal of the humpator CM'P1. A power supply voltage detection circuit is formed by resistors R, 8, 1't9, constant voltage source vC2, and comparator CMPI.

Ml is a winding motor for film feeding linked to a known film feeding/shutter charging structure (not shown);
TRI is a transistor R3, and 1'L4 is a resistor.

For example, SW4 is linked to the shutter rear curtain and the shirt is closed. It will be closed at the end of the trailing curtain run in the evening, and the winding operation will be completed. It is a switch that is opened at times.

ORI is an OR gate, O81 is a monostable multivibrator, and INI is an inverter. Further, SW2 is a release switch that is linked to a second stroke operation of a release button (not shown), and R5 is a resistor. ORGATE OR,
1 is applied with the output of the comparator CMPI and the switch SW4. Further, the output of the OR gate ORI is applied to the C input terminal of a monostable multivibrator 081 as a timer circuit.

AND 1 is the 3 person game and game) AN
The Q output of the monostable multivibrator 081 is applied to DI via the inverter INI.

Further, the output of SW4 and the output of SW2 are applied to other terminals of the ANDI.

When the monostable multivibrator 081 receives a rising pulse switching from a low level to a high level to its C input terminal, a single pulse that becomes high level for a short period of time (a certain period of time) is outputted from its Q output terminal.

TR3 is a transistor, ml, and 10 are resistors.

The output of the ORI is applied to the base of the transistor TR3 via a resistor R10'. Note that the transistor TR3 constitutes a switching power supply circuit for all circuits of the photometric circuit surrounded by broken lines.

O82 is a monostable multivibrator, TR2 is a transistor, R6 is a resistor, and Mg1 is a release operation start magnet. C of monostable multivibrator 082
The input terminal is connected to the output terminal of ANDI. When the release operation start magnet Mgl is energized, the release operation locking member that has been held until then is unlocked, and a series of release operations are thereafter performed. When the monostable multivibrator 082 receives a rising pulse that switches from a low level to a high level and a Berni level is applied to its C input terminal, a single pulse that becomes high level for a short time (a certain period of time) is outputted from its Q output terminal.

Next, the operation of this embodiment will be explained. When the first stroke of the release button is performed and the power supply switch SWI is closed, power is supplied to all circuits other than the photometry block surrounded by the broken line. Assuming that the camera is now in the state where winding has been completed, SW4 is open, and therefore a high level signal is applied to one end of the input terminal of ORI via resistor R4, and OR,1 is a high level signal. Output a signal. Since this high level signal is applied to the base of transistor TR3 via resistor RIO,
The transistors T11 and T3 are turned on, and power is supplied to the photometry circuit block surrounded by the broken line. Constant current source ICI, constant voltage source vC1, OP amplifier OP1. OR2, OR3, diode DI, l)2
, D3 and resistor I(, 1, R2 is a well-known photometric circuit, so l'+' 1l
Although detailed explanation will be omitted, first, a photocurrent corresponding to the brightness of the object flows through the photodiode D2, and the photocurrent is logarithmically compressed by the OP amplifier OP2 and the logarithmic compression diode I)3. Also, constant current circuit TCI, diode D
1. By applying the output of the humidity compensation circuit constituted by the OP amplifier OPI to the non-inverting input of the OP amplifier OP2, a diode D1. Cancels the reverse saturation current of D3.

Therefore, the output of the OP amplifier OP2 logarithmically compresses the subject brightness and becomes a voltage proportional to the absolute temperature.

The voltage is applied to the posister RJ1, the resistor R2, and the OP amplifier OP.
3, the output of the OP amplifier OP3 becomes a logarithmically compressed value that does not depend on the temperature of the object brightness. This voltage value is input to the exposure calculation circuit 1, and the exposure calculation circuit 1 calculates an appropriate value based on the voltage value.゛The TV value or AV value for normal exposure is calculated and output.

In this state, when the second stroke of the release button is operated and the switch SW2 is closed, all the input terminals of the ANDI become high level. That is,
As mentioned above, the switch SW4 is open when the winding is completed, and the output Q of the multivibrator 081 is set to a high level through the inverter INI.
) Since it is input to AND 1, all inputs of AND gate AND 1 become high level when switch SW2 is closed, and AND gate -) ANDI outputs a high level, and as a result, the C of monostable multivibrator -5O82
A rising signal that switches from low level to high level K is applied to the input terminal, and the monostable multivibrator 03
2 outputs a pulse that is at a high level for a short period of time. Since this pulse is applied to the base of the transistor TR,2 through the resistor 6, the transistor TR2 is in the ON state during this time, and the magnet (Mgl) is energized, the release operation locking member is released, and a series of release operations is performed. is performed, the arithmetic circuit output at that point is latched, and the A calculated by the exposure arithmetic circuit 1 latched by the exposure control mechanism 2 is obtained.
Aperture value or shutter speed control is started according to the V value or TV value.

When the exposure control by the exposure control mechanism is completed and the shutter is closed, the switch 4 is closed in conjunction with this, and a low level signal is applied via the base niha resistor R3 of the transistor 'l'R1.

Therefore, the transistor TR1 becomes operational upon completion of the exposure, and energization of the motor M1 is started to perform film feeding and shutter charging operations by film feeding and shutter charging mm. On the other hand, when the switch SW4 is closed, a low-level signal is applied to one end of the input terminal of the OR gate 0R10, but when the power supply voltage is high, a high-level signal is always applied from the humpator CMPI. 0ILI is maintained at a high level and photometry is performed even during film winding. On the other hand, similarly switch S
By closing W4, a low level signal is also applied to one end of the input terminal of the ANDI, and the AND
At this point, the output signal of I switches from high level to low level. Furthermore, when the winding is completed and the switch SW4 is opened in conjunction with this, a high level signal is again applied to the base of the transistor 'It via the resistors R4 and R3, so that the transistor TR1 is turned off again. Then, the winding motor M1 stops rotating. Furthermore, when the switch SW4 is opened, a high level signal is applied to the ANDI game (ANDI), but if the photographer has released the release button at this point, the switch SW2 is opened.
Since the gate is open, ANDI continues to output a low level, and no further release operation is performed and single shooting is performed. On the other hand, if the photographer continues to press the release button, the winding is completed because switch SW2 remains closed, and when switch SW4 is opened, the output signal of AND gate AND1 also switches from low level to high level. Since the rising signal is again applied to the C input terminal of the monostable multivibrator 082, the monostable multivibrator O82 outputs a pulse again, and the second release operation is started. Therefore, from now on, the photographer should release the release button and switch SW2.
Continuous shooting will continue until the area is opened. In this way, when the power supply voltage is high, the photometering circuit em constantly performs photometry even during winding, so it is possible to proceed to the next release operation as soon as winding is completed, thus minimizing the interval between shots. become.

Next, the operation when the power supply voltage is lower than the H constant level will be explained.

When the camera has completed winding, 8W4 is open. As mentioned above, when the switch SWI is turned on by the first stroke operation of the release button, a high level signal is sent through the resistor R4 to the OR gate. The OR gate OR1 outputs a high-level signal that is input to one end of the input terminal of OR1, turning on the transistor TR3, and the photometry circuit block em surrounded by the broken line enters the power supply state and applies a voltage corresponding to the subject brightness to the next stage of exposure. Output to the arithmetic circuit 1. After this, the second stroke of the release button is operated,
When the switch SW2 is opened, all the input terminals of the three-player ANDI become high level as described above, so the ANDI outputs a high level signal, and therefore the C input of the monostable multivibrator 082 Since a rising signal is applied to the terminal, the monostable multivibrator O82 outputs a pulse that becomes high level for a short time, and this pulse similarly turns on the transistor TR,2 via the resistor 6, so that the magnet Mgl is turned on. By energizing, the locking of the release operation locking member is released, a series of release operations is performed, and exposure control is performed by the exposure control mechanism 2 in the same manner as in the above case. When the exposure control by the exposure controller M is completed, the switch SW4 is closed as described above, the winding motor starts to be energized, and the film feeding and shutter charging operations are started. or,
At the same time, by closing switch SW4, ORI)
A strange signal that changes from high level to low level is applied to the input terminal of . Also, in this case, since the power supply voltage has decreased, the comparator 0 open P1 is outputting a low level, and as a result, when the exposure is completed, both ORI input terminals become low level,
The OR gate OR1 will output a low level signal. Therefore, the transistor T I via the resistor R10
A low level signal is applied to the base of t3, and transistor '13 is turned off. Therefore, the power supply to the block 1m of the photometry circuit surrounded by the broken line is cut off.
Circuit operation stops. Thereafter, when the film winding is completed, the switch 8W4 is opened in conjunction with this, and the winding motor MTI is de-energized and the film feeding and shutter charging operations are stopped. At this time, switch S
At the opening of W4, a high level signal appears again in the anime) A
NI)1 and the OR gate OR,1.

Therefore, the OR gate OR1 outputs a high level signal again, and as a result, power is supplied again to the photometry circuit block /m shown by the broken line, and the photometry operation starts. At the same time, a rising signal switching from low level to high level is applied to the C input terminal of monostable multivibrator O81, so monostable multivibrator O81 outputs one pulse that becomes high level for a short time. This pulse output is inverted to a signal that becomes low for a short time via an inverter INI, and then inputted to one end of the input terminal of ANDI. Therefore, when the voltage dU m pressure is decreasing, the photometering circuit starts operating as soon as the winding is completed, but for a certain period of time after the winding is completed, by closing the AND gate ANT) 1, the photometering circuit starts operating until the second release operation starts. A delay will be applied. Therefore, during this delay time, the power supply voltage, which has greatly decreased (fluctuation) during winding, is recovered, and the output of the photometry circuit after the above-mentioned time has elapsed shows a stable value.

After this delay time ends, the output of the inverter INI becomes high level, and if the photographer continues to press the release button, the output of the inverter INI will turn off after the delay time (ANDI).
The output is switched from low level to high level again, monostable multivibrator 082 generates a pulse again, and the second release operation starts. Therefore, even when the power supply voltage drops, continuous shooting continues until the photographer releases the release button and the switch SW2 is opened.

With the above structure, when the power supply voltage is high, the photometering operation is performed while the film is being fed by the motor drive, and even when the next shooting is started almost as soon as the film winding is completed, and high-speed continuous shooting is performed, the photometry remains unchanged. Since the output is stable, correct exposure is guaranteed, and when the voltage drops, metering is performed after film winding is completed, and then the next shooting starts, so although the frame speed will decrease, correct exposure is guaranteed. You will get it.

FIG. 2 is a circuit diagram showing another embodiment of the present invention, and the same components as in the embodiment of FIG. 1 are given the same symbols. In FIG. 2, CON is a counter in which the high level from ANDI is input to the inner pull terminal and the one-shot circuit 083 is input to the reset hat terminal, and this counter functions as a timer circuit. AND2.

AND3 is an AND gate OR, 2 is an OR gate, and these logic circuits are the outputs of the counter CON, Q, , Q
The select circuit for selecting 2 is made up of 6゛η.

The difference between FIG. 2 and FIG. 1 is that the select circuit and counter are provided.

Next, the operation of the embodiment shown in FIG. 2 will be explained.

When the first stroke of the release button is operated, the switch 8W1 is turned on, and similarly to the first #A embodiment, the transistor TIL3 is turned on and power supply to the photometry circuit block em is started. After this, when the second stroke operation is performed, the switch 8W2 becomes active, and the AND gate AN
High level is sent from D1 and one shot circuit 083
is triggered and the counter CON is reset. On the other hand, the 71 level from the above AND gate ANI)1 is input to the iner pull terminal en of the counter CON, so the counter CON becomes a count Y1 and counts the clock pulses from the clock pulse generator CP, After a constant count, the output pulse is stopped from output Q. Assuming that the pressure at the source is high enough, the comparator CMPI outputs a high level, so
AND2 sends out the normal pulse from the counter QI, and this pulse is transmitted to transistor TR2 via OR2, magnet Mgl is actuated to start the release operation, and exposure is performed in the same way as in the embodiment shown in FIG. Control is exercised.

When the switch SW4 is turned on after the exposure control is completed, the motor M1 is activated to feed the film and charge the shutter in the same manner as in the embodiment shown in FIG. At this time, as mentioned above, since the output in the comparator CM is at a high level, transistor I and 3 are kept in the on state.
The photometry operation is performed even during film winding, which is the same as in the embodiment shown in FIG.

When the film winding is completed as described above, the switch SW4 is turned off and power supply to the motor M1 is stopped.If the release button is kept pressed, the switch SW4 is turned off and the power supply to the motor M1 is stopped.
Since W2 remains on, the game is turned on) AND
A high level is sent out again from I, and this high level causes the counter CON to perform the counting operation again, and the release operation is executed again in the above operation, and thereafter, the above operation is continued until the release button is released.

Next, a case where the voltage is below a predetermined level will be described.

In this case as well, the photometry circuit block e is
Power is supplied to m, and for the second stroke operation, a high level is sent from ANT)1, and the counter CON starts counting.Meanwhile, in this case, the humbalator CMP1 is sending out a low level. So, instead of Antogame)AND2, Antogame)AND
3 is in the selected state and therefore the counter CO
The counting operation of N continues for a long time compared to when the power supply voltage is sufficient, and when a pulse is sent from the output Q2, the pulse is connected to the transistor T via ORG)01(,2).
A voltage is applied to the base of R2, and a release operation is performed in the same manner as described above to perform an exposure operation. When the exposure is completed, the switch SW4 is closed, the motor M1 is activated, and the film winding operation is started. Further, when the switch SW4 is opened, the transistor TR3 is turned off, and power supply to the photometry circuit block is prohibited during film winding.

After this, when the film winding is completed, switch SW4
Since the transistor 'I'R3 is turned on, power supply to the photometric circuit block en1 is started. or,
When the switch 8W4 is opened, a high level is sent from ANDI again, so the counter CON performs the counting operation again, and the output Q of the counter CON
When a pulse is sent from 2, the release operation is performed again, and the above-mentioned operation is repeated thereafter.

Therefore, even in the embodiment shown in FIG. 2, the circuit operates with exactly the same function as the embodiment shown in FIG. state.

As explained above, in the present invention, when the voltage of the power supply battery is sufficiently high and there is no photometry error even when the motor is energized and the photometry operation is performed at the same time, the photometry and the winding energization are performed at the same time to increase the frame speed as much as possible. On the other hand, if the battery voltage drops to such a level that it may cause a photometry error if the motor is energized and the photometering operation is performed at the same time, then the photometry operation should be started after the motor energization is stopped. Although the frame speed decreases when starting, the structure is designed to eliminate photometry errors as much as possible, so it is possible to solve the problem of achieving both frame speed and photometry errors.

Further, in the embodiment, a camera with a built-in motor drive device was illustrated, but it goes without saying that the present invention is also applicable to a camera in which the motor drive device is formed separately and is attached to the camera.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of a camera equipped with a power supply circuit according to the present invention, and FIG. 21 is a circuit diagram showing another embodiment of the present invention. em...ii+l optical circuit, CMPI...comparator 'I'lL1, T1t3...transistor, O81...multivibrator-CON...
Counter patent applicant Canon Co., Ltd.

Claims (1)

[Claims] In the power supply circuit for a camera, which has a built-in film feeding motor drive device or a motor drive device to which the motor drive device can be installed, and which also includes a photometry circuit and shares the same power supply for power supply to the photometry circuit and the motor drive device, as described above. a first power supply circuit forming a power supply path for detecting a power supply voltage and supplying power to the motor drive device during the raising operation when the voltage is below a predetermined level; and a first power supply circuit for supplying power from the power supply to the photometric circuit. A second power supply circuit forming a power supply path, and a prohibition means that operates in response to the output signal of the voltage detection circuit and prohibits the power supply circuit of the intermediate power supply 2 for supplying power to the motor drive device from supplying power to the photometric circuit. A power supply circuit for a camera characterized by: