JPH0243526A - Camera with flash charging control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a camera that uses a strobe (flash device), and more specifically, the present invention relates to a camera that uses a strobe (flash), and more specifically, it has a built-in strobe or an external strobe, and is used for photometry of cameras such as shooting dark scenes and backlit scenes. Based on the output from the circuit, when it is determined that firing the strobe would provide a more appropriate exposure, the flash will fire automatically, and when it is determined that it is not necessary to fire the flash, such as when shooting an outdoor scene in the daytime. This relates to a camera that prohibits light emission.

[Prior Art] In recent years, various cameras have been proposed that have a built-in or external strobe that determines dark scenes, backlit scenes, etc. during the photometry stage, and automatically fires the strobe as necessary.

In recent cameras mentioned above, if the strobe starts charging after determining that the scene is dark or backlit, you will have to wait to press the release button until the strobe has finished charging. In order to improve this problem, this camera automatically charges the strobe at the end of the previous shooting operation, so that there is no waiting time for the next shooting operation. has been devised.

[Problems to be Solved by the Invention] In these conventional cameras, when the charging voltage of the strobe reaches the voltage necessary for light emission, charging is immediately stopped.

However, when a flash capacitor stops charging, leakage occurs little by little, and the charging voltage gradually decreases.

As a result, when I actually try to take the next photo,
Due to leakage, the voltage may drop below the voltage required for firing, and in this case, supplementary charging is required just before taking a picture, and you still have to wait for the release operation.

The present invention aims to solve the above problems.

[Means for solving the problem] Immediately after taking a photo using a strobe light, in preparation for the next photo shoot, the strobe is charged until the voltage charged in the strobe reaches the minimum voltage required for firing. After that, charging was continued for a certain period of time, and then charging of the strobe was stopped.

[Function] The camera according to the present invention does not stop charging even when the detection means detects that the voltage charged to the strobe exceeds a certain voltage at which charging is completed, and then activates a timer to charge the strobe for, for example, 2 seconds. After that, charging is stopped and the camera is ready for the next flash photography.

[Embodiment] FIG. 1 is a circuit connection diagram showing an embodiment of an electric circuit of a camera with a built-in strobe according to the present invention.

In Figure 1, 1 is the power supply battery VBA in the strobe circuit.
2 is a microcomputer for controlling operation, and 3 is an A/D conversion circuit. Reference numeral 4 denotes a photometric element made of a silicon photodiode or the like, which is composed of a plurality of photometric elements and is of a split type so that photometry can be performed by dividing the screen. The output of this photometric element 4 is A/D converted by an A/D conversion circuit 3 and then transmitted to the microcomputer 2 via a pass line BuS.

Further, SW is a switch that is turned on in conjunction with pressing down of the camera release button, and R1 is a pull-up resistor. MCI is an electromagnet that is energized when a mechanical member (not shown) that locks the shutter front curtain from running, and MC2 is a mechanical member (not shown) that locks the shutter rear curtain from running. ) is an electromagnet that is energized when the lock is released. TRI is a switching transistor for switching the energization of the electromagnet MGI, and TR2 is the electromagnet! This is a switching transistor for switching energization of 11G2. The bases of the transistors TRI and TR2 are connected to the output port P4. of the microcomputer 2 via base resistors R5 and R6, respectively. Connected to P5.

The output of the converter 1 is connected to a strobe light emitting circuit. Further, TC is a trigger capacitor for starting light emission, and one end of this 1 to trigger capacitor TC is grounded, and the other end is connected to the output of converter 1 via resistor R2, and is also connected to the output of converter 1 via coil C1. It is connected to the thyristor 31. The gate of this thyristor Sl is connected to the output port P1 of the microcomputer 2,
The microcomputer 2 controls whether the strobe lights up or not.

Also, MC is the main capacitor, and XE is the xenon tube. R3 and R4 are voltage dividing resistors for detecting the voltage charged in the main capacitor MC, and the divided and charged voltage is applied to the input port of the microcomputer 2.
2 and transmits whether or not the main capacitor MC is sufficiently charged. Here, resistance R3, resistance R
4 is a detection circuit that detects that the voltage charged in the flash device exceeds a certain voltage. TR3 is a switching transistor for supplying power to the strobe light emitting circuit including the converter 1, and its base is connected to the output port PO of the microcomputer 2 via a base resistor R7, and it is determined whether the microcomputer 2 supplies power or not. is controlled. Here, the switching transistor TR3 and the resistor R7 correspond to the first output means of the present invention, and the microcomputer 2 corresponds to the first control means of the present invention.

The operation of the electric circuit configured as shown in FIG. 1 will be explained based on an operation flowchart of the microcomputer 2.

FIG. 2 shows one operation flowchart 1 of the microcomputer 2.

Step 1 Determine whether the release switch SW is on.

If the release switch SW is on, the process goes to step 2; if it is off, the process returns to step 1, and the process continues in a loop. If the release button is pressed down, the process branches from step 1 to step 2.

Step 2: Output a high level signal from the output port PO, turn off the switching transistor TR3, and cut off the power supply to the strobe light emitting section.

Step 3 The output of the photometric element 4 is converted by the A/D conversion circuit 3 to obtain photometric data. Based on this photometric data, it is determined whether the scene is dark or backlit, and whether or not it is necessary to fire the strobe light is determined.

Step 4 Based on the determination result in step 3, if there is no need to emit light, the process branches to step 19, and if it is necessary to emit light, the process branches to step 5. If it is a backlit scene that requires light emission or a dark scene, the process branches to step 5.

Step 5: Output a low level signal from the output port PO, turn on the switching transistor TR3, and start supplying power to the ROBO light emitting section.

Step 6: Remember that the strobe has fired, and set register A, which determines whether or not to charge the strobe, to 1.

Step 7 To prevent the device from overheating, the maximum charging time for the strobe is 10
Start a second timer.

Step 8: Determine whether or not the strobe is fully charged by reading input capo-P2. The voltage dividing resistors R3 and R4 are set so that the charging voltage exceeds the input threshold of the microcomputer 2 when the charging voltage becomes sufficient, so when it is input as a high level signal, it is assumed that charging is complete.
Branching to step 11. If charging is not completed, the process branches to step 9.

Step 9 Determine whether the 10 second timer has timed up,
If the time-up occurs, it means that the strobe has not been charged within the predetermined time, and the process branches to step 10. If the time has not expired, the process returns to step 8 and loops through this period.

If the strobe completes charging during the process, proceed from step 8.
Branching to step 11.

Step 10: Since the charging has not been completed within the predetermined time, the switching transistor TR3 is turned off, and the charging is stopped while the strobe is not fully charged, and the sequence is ended. This means the battery needs to be replaced.

Step 11 After the strobe is fully charged, charge it for another 1 second. As a result, even if the charging voltage gradually decreases due to leakage during operations such as raising the mirror or driving the aperture, the voltage can be raised to a level that allows the light to be emitted without any problems. .

Step 12 Since a considerable amount of power is consumed to raise the mirror and drive the aperture, the switching transistor TR3 is turned off and charging of the strobe is stopped.

Step 13 Turn on the motor (not shown) and flip up the mirror 45 degrees.

Step 14 The aperture of the lens is narrowed down to a predetermined position according to the photometric value.

Step 15: By outputting a high level signal from the output capacitor P4, the switching transistor TRI is turned on, the electromagnet MGI is energized, the front shutter curtain (not shown) is driven, and exposure is started.

Step 16: By outputting a high level signal from the output port P1, the thyristor SN is turned on, and the charge accumulated in the trigger capacitor TC is discharged through the coil C1. The coil C1 applies a high-voltage induced electromotive force to the outer circumference of the xenon tube XE, thereby causing the xenon tube XE to emit light. Here, the thyristor SI corresponds to the second output means of the present invention, and the microcomputer 2 corresponds to the second control means of the present invention.

Step 17: Wait until the exposure time ends to obtain proper exposure according to the photometric value.

Step 1B: By outputting a high level signal from the output boat P5, the switching transistor TR2 is turned on, the electromagnet MG2 is energized, the shutter trailing curtain (not shown) is driven, and the exposure is completed.

Note that in step 4, when there is no need for strobe light emission, the process branches to step 19, but the flowchart from step 19 onwards will be explained.

Step 19: Remember that the strobe has emitted light, and set register A, which determines whether or not to charge the strobe, to 0. If it is 0, it means that no strobe light was emitted.

The following steps are the same as when strobe light is emitted, so I will briefly explain them: Step 20 is the same as Step 13, Step 21 is the same as Step 14, Step 22 is the same as Step 15, Step 23 is the same as Step 17, Step 24 performs the same operation as step 18.

A series of operations related to exposure are performed in steps 20 to 24, but since the thyristor 31 is not turned on, the strobe light is not emitted regardless of whether charging is completed or not.

Step 25: Electrify the film feeding and shutter spring charging motors (not shown) to carry out feeding and charging.

Step 26 After the release, it is determined whether the release button is still pressed. If the release button is pressed, it means that continuous shooting is being performed, so return to step 2. or,
If the release button is not pressed, the process moves to step 27, and a check flow is entered to determine whether or not to charge the strobe in preparation for the next photograph.

Step 27 Regardless of whether the strobe emits light or not, register A is checked here after the exposure operation is completed. If register A is O, the strobe is not charged and returns to step 1, which is the starting position, in preparation for the next release button activation. If it is not 0, the process branches to step 28.

Step 2B: When the register A is not 0, a low level signal is output from the output port PO, the switching transistor TR3 is turned on, and power supply to the strobe light emitting section is started in preparation for the next photographing.

Step 29: To prevent overheating of the charging equipment, start a 10-second timer, which is the upper limit of charging time for the strobe.

Step 30: Determine whether the strobe is fully charged by reading input port R2. The voltage dividing resistors R3 and R4 are set so that the charging voltage exceeds the input threshold of the microcomputer 2 when the charging voltage becomes sufficient, so when it is input as a high level signal, it is assumed that charging is complete.
The process branches to step 33. If charging is not completed, the process branches to step 31.

Step 31 Determine whether the 10 second timer has timed up,
If the time has elapsed, it means that the strobe has not been charged within the predetermined time, and the process branches to step 32.

If the time has not expired, the process returns to step 30 and loops through this period. If charging of the strobe is completed during the process, the process branches from step 30 to step 33.

Step 32: Since charging has not been completed within the predetermined time, switching transistor TR3 is turned off, charging of the strobe is stopped, and the sequence is ended.

Step 33 After the strobe is fully charged, charge it for another 2 seconds. As a result, there was a considerable amount of time left before the clothes were photographed.
Even if the charging voltage gradually decreases due to leakage during that time, the voltage can be increased to a level that allows flash photography without worrying about release time lag.

Step 34 Turn off the switching transistor TR3 and stop charging the strobe. Thereafter, the camera returns to the starting position, step 1, to prepare for the next release button activation.

As you can see from the explanation of the flow in Figure 2, when taking a photo with a strobe, in preparation for the next photo, charge the strobe to the minimum voltage required for firing, and then charge it for another 2 seconds. After this is done, the strobe will stop charging.

[Effects of the Invention] As explained above, according to the present invention, after flash photography, flash charging is performed and even if the charging completion voltage is reached, charging is continued for a certain period of time, so that a small amount of leakage of the flash capacitor is prevented. Even if there is a problem, there is no need to take time to charge the flash the next time you take a photo, and you can take a photo immediately without missing a photo opportunity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the electric circuit of the camera of the present invention, and FIG. 2 is an explanatory diagram showing one example of the operation of the circuit of FIG. 1. 1...Converter 2...Microcomputer 3...A/D conversion circuit 4...Photometric element VBAT
...Power supply battery R3...Switching transistor MC...Main capacitor XE...Xenon tube Sl...thyristor and 4 others

Claims (1)

[Scope of Claims] 1. In a camera using a flash device, a first output means outputs a permission signal for charging the flash device, and a detection device detects that the voltage charged in the flash device exceeds a certain voltage. means, a first control means for controlling switching between charging the flash device based on a signal from the first output means and stopping charging based on an output signal from the detection means; and a second control means for allowing the flash device to emit light during photographing. output means, and a second control means for switching and controlling flash light emission and light emission stop at the time of photography according to a signal from the second output means, and the second control means controls the switching between flash light emission and light emission stop at the time of photographing, and 1. A camera with a flash charging control circuit, further comprising a means for reactivating the first output means to further charge the flash for a certain period of time after the flash is charged by the first control means.