JPH0114005Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention uses a microprocessor (hereinafter referred to as
This CPU is equipped with control circuits such as
The present invention relates to a camera motor drive circuit suitable for driving a motor of a camera, etc., which uses signals from a camera to control a motor for driving a camera mechanism or a camera lens.

The applicant has already proposed an automatic focus adjustment device (Japanese Patent Application No. 101723/1983) in which a control circuit such as a CPU is mounted on a camera, and the motor that drives the camera lens is controlled by signals from the CPU. It has been done.

The automatic focus adjustment device will be briefly explained with reference to FIG.

The invention is an automatic focus adjustment device that performs automatic focus adjustment by moving the lens 101 forward and backward using a motor 110 based on focus adjustment information.

This device includes a motor drive circuit 116, a sensor 111 in which a number of light-receiving layers are arranged on a plane perpendicular to the optical axis of the objective lens 101, and an A-digital converter that converts the video output of the sensor 111 from analog to digital.
Predicted value calculation that calculates the outputs of the D conversion 113 and the A-D conversion 113 and calculates data indicating how far the current position of the objective lens is from the in-focus position as a predicted control value for the objective lens. 114, a movement amount detector 107 that detects the amount of movement of the lens driven by the drive circuit, and a control circuit 115.

The operation of the control circuit 115 will be explained with reference to the flowchart shown in FIG.

The control circuit 115 activates the sensor 111 with the AF activation signal (step 20), and activates the A-D converter 113 and predicted value calculator 114 (step 21) (step 22).

Then, the predicted value calculator 114 calculates the predicted value (N).

First, it is determined whether the predicted value (N) is within a predetermined tolerance range (within _N0 ) (step 30).

For example, if the predicted value (N) of the calculated movement amount is zero or a value close to zero (N≦N ₀ ), the lens 10
1 is considered to be at the end point position and the focus adjustment is completed (step 31).

If the above conditions are not satisfied, the motor drive circuit 116 is activated to drive the motor 110 (step 25).

The amount of movement of the lens 101 by the motor 110 is detected by the movement amount detector 107 comprised of photocouplers 27, 28, and 29 (step 26).

The detected value is sent to the control circuit 115 every moment, and the control circuit 115 compares the detected value (N') with the predicted value (N) (step 27).
When N≈N', a motor drive stop signal is generated to stop the motor 110 (step 28).

Then, the above (step 20), (step 21), and (step 22) are performed, and the new predicted value (N) obtained in (step 22) is zero or close to zero (N≦N ₀ ) in (step 30). If so, it is assumed that the lens 101 is at the end position and the focus adjustment is completed (step 31).

That is, the invention performs automatic focus adjustment of the lens by repeating a predicted value (N), driving the lens by only the predicted value (N), and evaluating the result of driving the lens.

In such automatic focusing of a lens, if the CPU is not properly connected to a power source, the CPU may operate unreliably and incorrect control information may be output.

Since it is not possible to install a power supply with sufficient capacity on the camera, a configuration is adopted in which the power supply is connected only when necessary.

Even when the power is connected, it takes some time until enough voltage is supplied to reliably operate the CPU.

If the motor is driven by information output from the CPU or the like in such a transient state, various problems will occur.

For example, if the objective lens is already at the infinity position and the motor is rotated further in the infinity direction due to an incorrect signal, extreme force will be applied to the gear train, damaging the drive system or interfering with the next operation. give something.

An object of the present invention is to provide a camera motor drive circuit that can operate the motor of the focus adjustment device and the motor that drives the camera mechanism without error.

In order to achieve the above object, a camera motor drive circuit according to the present invention will be explained in conjunction with an embodiment as follows.

The camera motor drive circuit according to the present invention includes a control circuit (CONT) having a microprocessor 55 mounted on the camera, and controls the camera mechanism and lens based on the results of arithmetic processing of data input to the control circuit (CONT). In a camera of a type in which power is supplied from a built-in power supply battery B to a circuit that supplies current to a motor 1 that drives a motor 1, a motor drive signal is generated from a voltage detection circuit 405, the control circuit (CONT), and the output of the control circuit. A voltage holding circuit, TR ₁ , 400, 40, processes the power battery output to provide a regulated voltage to the preamplifier 403.
1, a motor drive current generation circuit 404 that receives power directly from the power supply battery B and supplies a drive current to the motor based on the output signal of the preamplifier 403;
The voltage detection circuit 405 deactivates the preamplifier and cuts off the supply of current to the motor when the output of the voltage holding circuit, TR ₁ , 400, 401 becomes less than a predetermined voltage. is configured to do so.

Hereinafter, the present invention will be explained in more detail with reference to the drawings and the like.

Fig. 3 is a circuit diagram showing an embodiment of the camera motor drive circuit according to the present invention, and Fig. 4 is a circuit diagram showing detailed connections of the preamplifier, motor drive current generation circuit, and voltage detection circuit of the motor drive circuit. be.

In FIG. 3, B is a power battery built into the camera. The negative pole of this power supply battery B is connected to the bus bar 406 of the circuit via the main switch MS. The emitter of the transistor TR1 for cutting off power supply is connected to the positive electrode of the power supply battery B, and the base of this transistor TR1 is connected to the anode of the thyristor SCR via a resistor. The cathode of the thyristor SCR is the busbar 4 of the circuit.
Connected to 06. A series circuit of a diode _D3 and a switch _SW1 is connected in parallel with the thyristor SCR.

This switch _SW1 is a switch that is closed in the first region of depression of a release button, which will be described later, and generates a first release signal.

A capacitor _C1 is connected to the collector of the transistor TR1 for cutting off power supply. This capacitor _C1 and resistor R1, resistor R2 and resistor R
The line connecting the connection point of resistor R1 and resistor R2 to the gate of the thyristor SCR forms a turn-on control circuit for the thyristor SCR.

The anode of the thyristor SCR is connected to the collector of a power supply cutoff transistor TR1 via a capacitor _{C2 and} a resistor R3. The collector of the transistor TR ₂ is connected to the connection point between the capacitor C ₂ and the resistor R3, the emitter is connected to the bus 406, and the base is included in the control circuit described later.
It is connected to the port of CPU55. This transistor TR ₂ , the resistor R3, and the capacitor C ₂ are
The signal from the control circuit controls the thyristor SCR.
A turn-off control circuit is formed to turn off the power.

The DC-DC converter 400 is a circuit that boosts the voltage of a power supply battery B connected via a power supply cutoff transistor TR1. This DC−DC
The output voltage of the converter 400 is determined by the voltage stabilization circuit 4.
01 and stabilized, camera control circuit
Connected to CONT and part of motor drive circuit MD. The control circuit CONT has CPU55, this CPU5
5 and the number of pulses measured by the photocoupler 27 (FIG. 6) are compared, and if they match, the motor is stopped. Note that a photometry block 53, which will be described later,
The AE circuit 54, distance measuring circuit 56, focus display section 58, gate 59, etc. are also included in the control circuit and receive power from the power supply circuit, but are not shown in this figure. The motor drive circuit MD is
Preamplifier 4 that amplifies the output of AD converter 402
03, a motor drive current generation circuit 404, and a power supply voltage detection circuit 405. The motor drive current generation circuit 404 is directly connected to the power supply battery B,
A preamplifier 403 and a power supply voltage detection circuit 405 are connected to the voltage stabilization circuit 401.

The cathodes of diode D ₁ and diode D ₂ are connected to the remote control plug 80, and the anode of diode D ₁ is connected to the thyristor.
The anode of the SCR and the anode of the diode _D2 are connected to the CPU 55 of the control circuit CONT.
The diode D ₁ , the diode D ₂ , and the remote control plug 80 are circuit parts used when operating the camera in remote control mode. The detailed structure of this part will be described later with reference to FIG.

The basic operation of the power holding circuit 52 is to hold the power (power hold) by closing the switch _SW1 .
However, when the control circuit CONT completes execution of a predetermined sequence, the holding of the power supply (power hold) is released. Detailed operations related to camera operation will be described later as operations of the power hold section 52 of the camera shown in FIG.

FIG. 4 shows detailed connections of the motor drive circuit MD. In FIG. 4, the circuit in the range indicated by a broken line 403 is a motor drive current generation circuit, the part surrounded by a broken line 405 is the power supply voltage detection circuit, and the remaining part is a circuit part corresponding to the preamplifier 403. .

V11 and V12 are input terminals of the preamplifier 403, and the signal from the CPU 55 is input to the AD converter 40.
2, it is AD converted and connected.

When a high level signal is connected to the input terminal V11 of the preamplifier 403 and a low level signal is connected to the input terminal V12, the transistors TR11 and TR13 of the motor drive current generation circuit 404 are turned on, and the motor drive current generation circuit 404 is turned on. The output terminal VO1 and the positive VO2 become zero, and current is supplied to the motor 1 from the right direction in the figure.

When a low level signal is connected to the input terminal V11 of the preamplifier 403 and a high level signal is connected to the input terminal V12, the transistor TR14 and the transistor TR12 of the motor drive current generation circuit 404 are turned on, and the motor drive current generation circuit 404 is turned on. The output terminal VO1 is zero and the output terminal VO2 is positive, and the motor 1 is supplied with a current in the opposite direction.

When a high level signal is connected to the input terminals V11 and V12 of the preamplifier 403, the transistors TR11 and TR12 of the motor drive current generation circuit 404 are turned on, and when the motor 1 is rotating, the motor 1 Since the back electromotive force of motor 1 is short-circuited, the brake is applied to motor 1 and
will be stopped.

Next, the configuration and operation of the voltage detection circuit 405 that detects the voltage of the voltage holding circuit will be explained.

Transistor TR19 and transistor TR20
form a differential amplifier. transistor tr
The voltage of the voltage holding circuit is connected to the base of 19.
Voltage obtained by dividing VDD by resistor R12 and resistor R11
Vf1 is connected. Vf1 is given by the following formula.

Vf1=VDD·R11/(R11+R12) A voltage Vf2 obtained by subtracting the voltage drop between the emitter and collector of the transistor TR22 from the voltage VDD of the voltage holding circuit is connected to the base of the transistor TR20. Transistor TR22
The collector current of is made constant by transistor TR21, transistor TR22, diode _D4 , etc.

Changes in the voltage VDD of the voltage holding circuit and the above Vf1,
The relationship between Vf2 is shown in FIG.

In FIG. 5, VDDL indicates the minimum voltage at which the CPU 55 operates reliably. A voltage of Vf1≧Vf2 is applied to the input terminal of the differential amplifier of this voltage detection circuit when VDD≧VDDL. Also VDD
When <VDDL, a voltage of Vf1<Vf2 is applied. Therefore, the voltage detection circuit is connected to the CPU55.
The voltage VDD that allows the CPU55 to operate reliably (VDD≧
When VDDL) is applied, transistor TR19 is turned on and transistor TR18,
Turn on transistor TR17.

When a voltage VDD (VDD<VDDL) at which the CPU 55 cannot reliably operate is applied to the CPU 55, the voltage detection circuit turns off the transistor TR19, the transistor TR18, and the transistor TR17.

When the transistor TR17 is turned off, the transistor TR16 and the transistor TR15 connected in series with the transistor TR17 are turned off, so that the amplifier is connected to the input terminal V1.
1. Even if a signal is applied to V12, it will not be amplified.

Therefore, the motor drive current generation circuit 404 is
The motor 1 is driven only by a signal when a sufficient voltage is applied to the CPU 55, and the motor 1 is not operated by an unstable signal.

Next, an outline of a camera to which the motor drive circuit is applied will be explained.

FIG. 6 is a schematic diagram illustrating an embodiment of an automatic focusing camera to which the power supply holding circuit according to the present invention is applied.

The drive motor 1 is a motor used for both lens focusing drive and camera operation drive.

The rotation of a pinion 2, which is the output shaft of the motor 1, is transmitted to a gear 4 via a reduction gear train 3, which is connected to and drives a clutch gear 5.

The clutch gear 5 switches the power transmission by moving an electromagnetic clutch 6 up and down in the figure in response to a control signal.

In the figure, the clutch gear 5 is coupled to a gear 7, and the driving force from the motor 1 is transmitted to the camera drive mechanism 9 via the gears 7 and 8. The camera drive mechanism 9 has a known configuration as a part that performs the shutter, film winding, and mirror drive shutter release.
It should be understood that this is the part that executes motorized camera operations other than AF (automatic focus adjustment).

When a signal is connected to the electromagnetic clutch 6 in the state shown in this figure, the clutch gear 5 is moved downward, the clutch gear 5 separates from the gear 7, and meshes with the lens drive gear 12, and the driving force from the motor 1 is used to drive the lens. system can be switched.

The switch 10 is a switch that detects that the clutch gear 5 is in the upper state in the figure, and the switch 11
is a clutch position detection switch that detects that the clutch is in the lower position, and these switches form a clutch information sensor that detects and outputs the state of the clutch. The lens drive gear 12 rotates through gears 13 to 20.
The signal is then transmitted to the coupling 34 of the camera mount, and then to the coupling 24 on the lens side. The main lens 30 is coupled to a coupling ring 24 on the lens side via a helicoid 26, and is moved forward and backward by the rotation of the gear 25.

The light beam that has passed through the main lens 30 passes through a semi-transparent part at the center of a mirror 31 that also serves as a finder optical path, and is changed in optical path by an auxiliary mirror 32, and is then directed to a distance measuring sensor 33 (first
This corresponds to the sensor 111 described in connection with the figure. )
guided by.

As described above, the focus detection calculation result (predicted value) by the distance measuring sensor 33 is output as the number of pulses (N) until focusing.

Detection of the lens drive amount corresponding to the predicted value is as follows:
The amount of rotation of gear 20 in the lens drive system is expressed as gear 2.
1. The rotation of this disk 28 is detected by an LED 29 and a phototransistor 27, and is input to a control circuit (CPU) to be described later. When the predicted value is reached, the motor 1 is A signal is generated to stop the motor, the distance measurement sensor 33 performs another measurement, and when it is confirmed that the desired movement has been performed, an output confirming completion of focus adjustment is generated. If the above reconfirmation is not possible, drive the motor 1 again.

FIG. 7 is a system block diagram of the camera.

The release button 50 is a release button for operating a switch 51 consisting of switch contacts Ca, Cb, and Cc.

The switch contact Cb in the center is connected to the camera body, and the switch contacts Ca and Cb are connected to the camera body as described above.
SW ₁ switch contacts Cb and Cc form SW ₂ , and SW ₁
It is possible to close only SW ₁ and SW ₂ continuously. The switch contact Cc is connected through _D2 , and the switch contact Ca is connected through diodes _D3 and _D1 to a contact 70A of a remote control terminal 70 provided on the camera body.

Contact 7 of remote control terminal 70
0A is supported by the remote control terminal main body 70 via an insulator 70B.

During remote control, a remote control plug 80 is connected to this remote control terminal 70, and a contact 80B of the remote control plug 80, a contact 70A of the remote control terminal 70, a main body of the remote control plug 80, and a main body of the remote control terminal 70 are connected. is connected.

Contact 80B of remote control plug 80
is supported by the main body of the remote control plug 80 via an insulator 80B.

The main body of the remote control plug 80 and the contact 80B are configured to be short-circuited by a switch 80C that is closed by a remote control signal. If this switch 80C is shorted,
TR1 is turned on, the CPU starts working, and checks the voltage of the anode of _D2 in the initial state. Since switch 80C is on, the anode voltage of _D2 goes low, allowing the CPU to determine that it is in remote mode.

The photometry block 53 is a well-known photometry block for automatic exposure determination, and the AE circuit 54 is a circuit that determines the shutter speed and aperture value from the photometry output of the photometry block 53 and other conditions. The AE display section 60 is a display section that displays photometric data determined by the AE circuit 54.

The power hold section 52 is a power holding circuit for the camera according to the present invention described above, and is connected to the switch 51.
When SW ₁ is closed (hereinafter referred to as when the first release signal is generated), the AE circuit 54,
This circuit maintains power for the CPU 55 and distance measuring circuit 56. The distance measuring circuit 56 is a circuit corresponding to the predicted value calculation circuit 114 described in connection with FIG.

The output of the distance measurement sensor 33 is connected to the distance measurement circuit 56 . The focus display section 58 is a display section that displays the output of the distance measuring circuit 56 as whether distance measurement is possible or not, and if distance measurement is possible, the calculated value (N) is divided into pre-focus, front focus, and rear focus. Distance measurement failure may be caused by the subject itself not having enough contrast (for example, a white wall) or by insufficient lighting. It is designed to light up with a small duty to distinguish between the two.

The exposure control device 61 is a circuit that controls an electromagnet that controls the rear curtain based on the output of the AE circuit 54. The gate 59 is a gate that determines motor drive conditions for executing the original function of the camera mechanism, and is included in the control circuit CONT.

Next, the operation of the camera will be explained starting from normal operation, which is not a remote control operation.

The remote control plug 80 is not connected or the remote control plug 80 is not connected.
Even if the remote control plug 80 is connected, normal photographing is performed when the switch 80C of the remote control plug 80 is not closed.

When the main switch MS shown in FIG. 3 is closed, a preparation state is formed, but the transistor TR1 for cutting off the power supply is in an OFF state and almost no current is supplied to the control circuit CONT.

When the release button 50 (Fig. 7) is pressed and SW ₁ of the switch 51 is turned on and the first release signal is generated, the power hold section 52 is activated.
The power supply cutoff transistor TR1 is immediately turned on, and the voltage of the power supply battery B is connected to the DC-DC converter 400.

A boosted voltage appears and the voltage stabilization circuit 40
1, but the voltage stabilization circuit 401
The output does not become VDD instantaneously, but this voltage, which gradually rises, is supplied to the camera control circuit CONT.

On the other hand, the collector voltage of the transistor TR1 for cutting off the power supply is determined by the turn-on control circuit of the thyristor SCR formed by the capacitor _C1 , resistor R1, resistor R2, and a line connecting the connection point of the resistor R1 and resistor R2 to the gate of the thyristor SCR. is connected to the gate of the thyristor SCR through the thyristor SCR, and makes the thyristor SCR conductive to form a power hold state. That is, even if the switch _SW1 is opened for a short time and the first release signal disappears, the power hold state is maintained due to the conduction of the thyristor SCR.

Before the voltage of the voltage stabilizing circuit 401 reaches the predetermined voltage, VDDL mentioned above, the output of the CPU 55 is
Even if the voltage is applied to the preamplifier 403 via the AD converter 402, the voltage detection circuit 405 disables the preamplifier, so even if the CPU 55 generates a signal in an unstable state, the motor drive current is generated. circuit 4
No signal is transmitted to 04.

The voltage of the voltage stabilizing circuit 401 is a predetermined voltage.
When VDD is reached, the CPU 55 starts executing the program. As a result, the AE circuit 54 operates,
Exposure control data is calculated and the AE in the viewfinder
Data is displayed on the display device.

Further, the CPU 55 and the distance measuring device mainly involved in focus detection operate to calculate a predicted value (N) indicating how much the lens should be driven from the aforementioned current position of the lens. This step corresponds to (step 20), (step 21), and (step 22) in FIG.

When it is impossible to calculate the predicted value (N), for example when the subject is unpredictable, the focus display section 58 is blinked and the above-mentioned display is performed.

In this case, the clutch 57 described in connection with FIG. 6 is not operated to the lens drive side, and a standby state is formed in which the sequence does not proceed any further.

On the other hand, when distance measurement is possible and (N), where (N>N ₀ ) is obtained, a switching signal is sent to the clutch 6, and the clutch that is on the camera mechanism drive side (state C) is 6 to the lens drive side (L state), and move the gear 5 from top to bottom in FIG. 3 to switch to the lens drive system.

As a result, the rotation of the motor 1 (FIG. 6) is transmitted to the lens 30, and the encoders 27, 28, 29
motor 1 until the detection corresponding to (N) above is detected.
is driven.

This step is shown in Figure 2 (Step 25)
corresponds to

As a result, the lens 30 is moved toward the focal point, and when the encoders 27, 28, and 29 detect the end of the movement (N), the motor 1 is stopped. This step corresponds to (step 26), (step 27), and (step 28) in FIG. 2 above.

In this state, the CPU 55 and the distance measuring circuit 56 are operated to perform the steps described above (Step 20), (Step 21), and
22) to determine whether the newly obtained predicted value (N) is within a predetermined tolerance range (within N ₀ ) (step 30). As a result, if proper lens position adjustment has been performed, the circle at the center of the focus display section 58 is lit to indicate completion of focus adjustment, and a switching signal is sent to the clutch 6.
The clutch 6, which was on the lens drive side (state L), is moved to the camera mechanism drive side (state C), and the gear 5 is moved from bottom to top in FIG. 6 to switch to the camera drive system.

If the lens position is not adjusted properly,
The switching is not performed, but distance measurement and readjustment are performed.

When the release button 50 is pressed halfway as shown in FIG. 4, that is, only SW ₁ is turned on and only the first release signal is generated, the clutch 6, which is on the lens drive side (L state), is The predetermined sequence is ended by switching to the mechanism drive side (state C).

When the second release signal is not generated at the end of this sequence, a positive voltage of V ₀ is generated at the output port connected to the transistor TR2 of the CPU 55. This voltage causes transistor TR2 to conduct instantaneously, and its collector voltage immediately becomes the voltage of bus 406. Due to this sudden drop in the collector potential, the voltage at the connection point of the capacitor C ₂ and the thyristor SCR (the anode of the thyristor SCR becomes more negative than the voltage on the bus 406, and the thyristor SCR is turned off.
The transistor TR1 for cutting off the power supply is turned off. When the transistor TR1 for cutting off the power supply turns off, the input terminal voltage of the DC-DC converter 400 drops rapidly, the power supply voltage of the CPU 55 drops, the operation becomes unstable, and a voltage appears at the output port. Also, since the transistor TR1 for cutting off the power supply is already turned off, the thyristor
The SCR will never be turned on, and the power will not be connected to the CPU 55 again to cause it to run out of control. By cutting off the power, the focus state is memorized (fixed).

Therefore, after focusing with the release button 50 pressed halfway (with only SW ₁ closed), it is possible to change the composition by shifting the subject position.

Furthermore, if refocusing is required at this stage, if you release your finger from the release button 50, SW ₁ will be turned off, all distance measurement information will be cleared, and the state will be the same as the original state.

When the release button 50 is pressed again to turn SW ₁ on, the power is held in the same manner as described above, and the above operation is repeated to perform distance measurement and readjustment.

After completing a predetermined sequence by switching the clutch 6, which was on the lens drive side (L state), to the camera mechanism drive side (C state), the release button 50 is further pressed and SW _{1 is} pressed.
When the SW ₂ is turned on (the second release signal is generated), the sequence of operations of the camera mechanism is executed.

The input terminal of the gate 59 receives a focus signal indicating that focus adjustment has been completed, a clutch operation completion signal indicating that the clutch 6 has been switched to the camera side, and a second release signal, all of which are sent to the input terminal for the next camera. Motor rotation start (step) of mechanism operation sequence
200) is started.

When the motor starts rotating (step 200), the narrowing down operation starts (step 201), and almost at the same time, the mirror lifting operation (step 202) is performed.
When the aperture is completed in accordance with the rotation of the motor and the mirror has finished rising, the tension of the front curtain is released and the front curtain starts (step 203), and a trigger (not shown) is activated to use this start point as the reference for exposure.
SW is activated.

Since the AE circuit 54 is already in operation and the data for obtaining the appropriate exposure amount has been calculated, the exposure control circuit 61 determines the timing for running the rear curtain.

In other words, when proper exposure is obtained, the trailing curtain holding magnet is turned off and the trailing curtain starts (step 204).
Then, the shutter operation is completed (step 205).

This signal starts the motor 1 again (step 206), lowers the mirror (step 207), winds the film (step 208), and simultaneously charges the shutter (step 209). This results in
When the winding operation is completed (step 300), the motor 1 is stopped, and one photographing operation of the camera is completed.

Here, it is determined whether the first release signal is being output continuously (step 301), that is, it is determined whether the photographer intends to take continuous photographs or only one shot. If the photographer has already taken his finger off the release button 50, it is assumed that he intends to take a single picture, and the power is released (step 303) to end the photographing operation.

On the other hand, if the release button is held down for continuous shooting, the first release signal will still be output, so the distance measurement information will be cleared (step 302) and distance measurement will start again, as described above. The action will be repeated again.

Next, the remote control operation of the device will be explained. As a remote control system,
Any suitable system can be used, such as a wireless system that uses infrared rays or a wired system.

In the remote control system, when the switch 80C of the remote control plug 80 is closed, a first release signal is generated.

The generation of the first release signal causes the power hold circuit 52 to operate, forming a hold state of the circuit power supply.

The second release signal is connected to a gate 59 that forms part of the control circuit, but since no other signals, no focus signal, and no clutch operation completion signal are connected to the gate 59, no output appears and the camera mechanism is not connected. The operation does not start.

By holding the circuit power supply, the AE circuit 54
operates to calculate exposure control data and display the data on the AE display device in the viewfinder.

Further, the CPU 55 and the distance measuring device mainly involved in focus detection operate to calculate a predicted value (N) indicating how much the lens should be driven from the aforementioned current position of the lens. This step corresponds to (Step 20) (Step 21) (Step 21) in Figure 2.
22).

The operations performed when the predicted value (N) cannot be calculated are the same as those described above.

In cases where distance measurement is possible, the above (N) provided that (N
>N ₀ ), a switching signal is sent to the clutch 6, and the clutch 6, which was on the camera mechanism drive side (state C), is switched to the lens drive side (state L), from above in FIG. Move the gear 5 downward to switch to the lens drive system.

As a result, the rotation of the motor 1 (FIG. 6) is transmitted to the lens 30, and the encoders 27, 28, 29
motor 1 until the detection corresponding to (N) above is detected.
is driven.

This step is shown in Figure 2 (Step 25)
corresponds to

As a result, the lens 30 is moved toward the focal point, and when the encoders 27, 28, and 29 detect the end of the movement (N), the motor 1 is stopped. This step corresponds to (step 26), (step 27), and (step 28) in FIG. 2 above.

In this state, the CPU 55 and the distance measuring circuit 56 are operated to perform the steps described above (Step 20), (Step 21), and
22) to determine whether the newly obtained predicted value (N) is within a predetermined tolerance range (within N ₀ ) (step 30). As a result, if proper lens position adjustment has been performed, the circle at the center of the focus display section 58 is lit to indicate completion of focus adjustment, and a switching signal is sent to the clutch 6.
The clutch 6, which was on the lens drive side (state L), is moved to the camera mechanism drive side (state C), and the gear 5 is moved from bottom to top in FIG. 6 to switch to the camera drive system.

If the lens position is not adjusted properly,
It is the same as described above that the switching is not performed and the distance measurement and readjustment are repeated until the determination result becomes appropriate.

When the clutch 6, which has been on the lens drive side (L state), is switched to the camera mechanism drive side (C state), a clutch operation completion signal is output from the clutch 6 to the gate 59.

Since the second release signal is connected to the gate 59 from the beginning, a signal for driving the camera mechanism is output from the gate 59, and the sequence of operations of the camera mechanism is executed.

When the motor starts rotating (step 200), the aperture operation starts, a series of camera mechanism operations are performed, and when the winding operation is completed (step 200)
300), the motor 1 is stopped and one operation of photographing the camera is completed, which is the same as described above.

Here, it is determined whether the first relay release signal is being output continuously (step 301), that is, it is determined by the remote control whether the photographer intends to take continuous photographs or only one shot.

Remote control plug switch 80C
If it is already open, both the first and second release signals have disappeared, so it is assumed that the intention is to take one picture, and the power supply is released (step 303) to end the photographing operation.

On the other hand, switch 8 of the remote control plug
If 0C is closed, the first release signal has been output, so the distance measurement information is cleared (step 302), distance measurement is started again, and the operation from the beginning is repeated again.

Since the power supply holding circuit according to the present invention is configured and operates as described above, power is supplied to the circuit only when necessary, and when sufficient voltage is not applied to the CPU 55 to ensure stable operation, the motor is The drive circuit is inactive.

That is, in the camera motor drive circuit according to the present invention, when the supply voltage VDD of the voltage holding circuit TR ₁ , 400, 401 drops below a certain level, the preamplifier is disabled.

This disables the motor drive current generation circuit 404, so information from the control circuit (CONT) is not transmitted to the motor drive current generation circuit 404, and no motor drive current is supplied.

However, since the voltage is connected to the control circuit (CONT), the necessary information is stored, and if the supply voltage VDD of the voltage holding circuit, TR ₁ , 400, 401 recovers for some reason, , there is a possibility that operation will resume immediately.

Therefore, it is completely possible to prevent the motor from being driven incorrectly due to uncertain information.

Although the embodiment has been described in detail above, various modifications can be made to this embodiment within the scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the principle of an automatic focusing device controlled by a motor drive circuit according to the present invention, and FIG. 2 is a flowchart illustrating the operation of the device according to the block diagram. FIG. 3 is a circuit diagram showing an embodiment of a camera motor drive circuit according to the present invention. FIG. 4 is a circuit diagram showing detailed connections of the preamplifier, motor drive current generation circuit, and voltage detection circuit. FIG. 5 is a graph for explaining the operation of the voltage detection circuit. FIG. 6 is a schematic diagram of an autofocus camera to which a motor drive circuit according to the present invention is applied. FIG. 7 is a system block diagram of the camera. 1...Motor, 2...Pinion, 3...Reduction gear train,
4...Gear, 5...Clutch gear, 6...Clutch, 7
~8...Camera side gear, 9...Camera drive mechanism, 1
0, 11, 51... Switch, 12... Lens drive gear, 13-20... Lens drive side gear, 21, 22
...Encoder connection gear, 23, 24...Connection shaft, 2
5... Helicoid drive gear, 26... Helicoid, 2
7... Phototransistor, 28... Perforated disk, 29
...LED, 30...Main lens, 31...Main mirror, 3
2... Secondary mirror, 33... Distance measurement sensor, 34... Coupling, 50... Release button, 52... Power hold unit, 53... Photometry block, 54... AE circuit, 55... CPU, 56... Distance measurement circuit, 58... Focus Display section, 59...gate, 60...AE display section,
61...Exposure control circuit, 70...Remote control terminal, 80...Remote control plug, _D1 , _D2 ...Diode (for remote control), _D3 ...Diode (for starting), B...Power battery, MS...Main switch, CONT ...Control circuit, MD...Motor drive circuit, TR1...Transistor for cutting off power supply,
SCR...Thyristor, TR2...Transistor (for turn-off), 400...DC-DC converter, 40
1... Voltage stabilizer, 402... AD converter, 403...
Preamplifier, 404...Motor drive current generation circuit,
405... Voltage detection circuit, 406... Bus bar.

Claims (1)

[Scope of utility model registration request] The camera is equipped with a control circuit that includes a microprocessor, and based on the results of arithmetic processing of the data input to the control circuit, power is supplied from the built-in power supply battery to a circuit that supplies current to the motor that drives the camera mechanism and lens. In a camera of the type provided, a voltage detection circuit, said control circuit, and a voltage holding circuit that processes said power battery output to provide a stabilized voltage to a preamplifier that generates a motor drive signal from the output of said control circuit. circuit, and a motor drive current generation circuit that receives power directly from the power supply battery and supplies a drive current to the motor based on the output signal of the preamplifier, and the voltage detection circuit detects that the output of the voltage holding circuit is at a predetermined level. A motor drive circuit for a camera, characterized in that the preamplifier is deactivated to cut off the supply of current to the motor when the voltage drops below the voltage.