JPH0243525A - 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), 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 can be used to detect scenes in the dark, backlight, etc. from a photometry circuit. Based on the output,
This invention relates to a camera that automatically causes a strobe to emit light when a proper exposure can be obtained by emitting a strobe light, and prohibits the flash when it is not necessary to emit light.

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

These cameras determine whether it is a dark scene or a backlit scene, and if the strobe's charging voltage reaches a certain voltage required for firing, it will take a picture, and if the strobe's charging voltage is low, it will take a picture. In this case, supplementary charging of the strobe is performed until a constant voltage is reached, and a photographing operation is performed when the constant voltage is reached.

[Problem N to be Solved by the Invention] In the conventional camera described above, when the charging voltage of the strobe reaches the voltage necessary for emitting light, a photographing operation is immediately performed.

However, when a strobe light emitting capacitor stops charging, it usually leaks little by little and the charging voltage gradually decreases.

On the other hand, the camera's shooting operations include flipping up the 45-degree mirror and closing down the aperture of the shooting lens to a predetermined value.After this, the shutter is opened to begin the exposure operation, and then the strobe is fired. Therefore, it usually takes about 50 milliseconds from the time charging is stopped until the light is emitted.

As a result, even if there is sufficient charging voltage to fire the light immediately before starting the shooting operation, when the light actually fires, the
There is also a possibility that the voltage may be lower than the voltage required for light emission due to leakage, causing problems such as the inability to take pictures with proper exposure.

The present invention aims to solve the above problems.

[Means and Effects for Solving the Problems] According to the present invention, in a camera using a strobe, a first output means outputs a strobe charge permission signal, and a strobe is activated by a signal from the first output means. If a first control means is provided to control switching between charging and charging stop, and the strobe is to fire, it can also be used when it is determined that the charging voltage of the strobe exceeds the voltage required to ensure proper exposure. As a precaution, the camera was charged for a certain period of time before taking a picture.

That is, after starting the shooting operation, the 45-degree mirror flips up,
Even if there is leakage of the light emitting capacitor during the aperture operation of the photographic lens, or even if there is no leakage, supplementary charging is performed for a certain period of time to absorb the leakage before photographing.

[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 a power supply battery VBA for the strobe circuit.
A DC/DC converter boosts T, 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 the photometric element 4 is A/D converted by the A/D conversion circuit 3 and then transmitted to the microcomputer 2 via the 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. MGI is an electromagnet that is energized when a mechanical member (not shown) that locks the shutter front curtain from running, and MG2 is an electromagnet that is energized when 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 a switching transistor for switching the energization of the electromagnet MG2.

And the transistor TRI. The base of TR2 is connected to the output ports -R4 and R5 of the micro combinator 2 via base resistors R5 and R8, respectively.

The output of the converter 1 is connected to a strobe light emitting circuit. Further, TC is a trigger capacitor for starting light emission, one end of this trigger capacitor 9-TC is grounded, the other end is connected to the output of converter 1 via resistor R2, and is connected via coil C1. Connected to thyristor SI. The gate of this thyristor SI is connected to the output port Pl of the microcomputer 2,
The microcomputer 2 controls whether or not the strobe emits light.

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.
2 and transmits whether or not the main capacitor MC is sufficiently charged. Here, resistance R3, resistance R
4 is a detection means for detecting 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 determines whether or not power is supplied from the microcomputer 2°C. to control; Switching transistor TR3 and resistor R7
corresponds to the first output means of the present invention, and the micro convenience store 1-toyo 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 the operation flowchart 1 of the microcomputer 2.

FIG. 2 is a flowchart of one operation of the microcomputer 2. As shown in FIG.

Determine whether the stellar pulley 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, 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 unit.Step 3: Convert the output of the photometric element 4 with the A/D conversion circuit 3, and perform photometry. Get 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 If the judgment result in step 3 is satisfied and 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 A low level signal is output from the output capo--PO, the switching transistor TR3 is turned on, and power supply to the strobe light emitting section ~\ is started.

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: The zero-divider resistors R3 and R4, which determine whether the strobe has completed charging by reading the input port P2, are set so that they exceed the input threshold of the microcomputer 2 when the charging voltage becomes sufficient. Therefore, when it is input as a high level signal, it is assumed that charging is complete and the process branches to step 11. If charging is not completed, step 9
Branch into.

Step 9 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, so the process branches to step 10. If the time has not elapsed, the process returns to step 8, and the process loops. If charging of the strobe is completed on the way, the process branches from step 8 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 mirror-up and aperture driving, the voltage can be raised to a level high enough to allow light emission without 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 A motor (not shown) is energized and the mirror is flipped up 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 port 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 SI 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 electromotive force to the outer periphery of the xenon tube XE, thereby causing the cannon tube XE to emit light.

Here, the thyristor SI corresponds to the second output means in the present invention, and the microcomputer 2 corresponds to the second control means in the present invention.

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

Step 18: By outputting a high level signal from the output port P5, the switched transistor TR2 is turned on, the electromagnet IAG2 is energized, the shutter rear curtain (not shown) is run, 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: Memorize each time the strobe fires and set register A, which determines whether or not to charge the strobe, to O. If it is 0, it means that no strobe light was emitted.

The following steps will be briefly explained as they are the same as when strobe light is emitted, but step 20 is the same as step 13, step 21 is the same as step 14, step 22 is the same as step 15, and step 23 is the same as step 1. , 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 SI is not turned on, the strobe light is not emitted regardless of whether charging is completed or not.

Step 25: The motors (not shown) for feeding the film and charging the shutter spring are energized 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, continuous shooting is in progress, so go back to step 2. If the release button is not pressed, go to step 27 to charge the flash in preparation for the next shot. Enter the check flow to decide whether to proceed.

Step 27 Regardless of whether the strobe fires or not, after the exposure operation is finished, register A is checked here. If register A is 0, the strobe is not charged and returns to the starting position in step 1. , prepare for the next release button activation.

If it is not 0, the process branches to step 28.

Step 28: 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 The upper limit of strobe charging time is 10 to prevent overheating of the device.
Start a second timer.

Step 30 The voltage dividing resistors R3 and R4, which determine whether the strobe has completed charging by reading the input port P2, are set so that they exceed the input value of the microcomputer 2 when the charging voltage becomes sufficient. Therefore, when it is input as a high level signal, it is assumed that charging is complete and the process branches to step 33. If charging is not completed, step 3
Branch to 1.

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 on the way, 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 drops due to leakage during that time, it is possible to maintain a high voltage 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 pictures that require a strobe, even if it is determined that the strobe charging voltage is higher than the voltage required to guarantee proper exposure, the After charging for one second, the camera is designed to take a picture.

[Effects of the Invention] As explained above, according to the present invention, even if there is a leak in the light emitting condenser during the flip-up of the 45-degree mirror, the diaphragm operation of the photographic lens, etc. after starting the automatic shooting operation, In addition, during shooting, supplementary charging is performed for a certain period of time to accommodate the amount of leakage, thereby avoiding the problem of not being able to shoot with proper exposure due to insufficient voltage charged in the light emitting capacitor when the exposure operation is actually performed. Can be done.

[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. l... Converter 2... Microcomputer 3... A/D conversion circuit 4... Photometric element VBAT.
・・Power battery TR3・Switching transistor MC・Main capacitor XE・Xenon tube I・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 detects that the charged voltage of the flash device exceeds a certain voltage. a detection means; a first control means for controlling switching between charging the flash device based on the signal from the first output means and stopping charging based on the 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 the flash unit to emit light and to prohibit light emission during photographing based on the signal from the second output means, and further includes a second control means for switching and controlling the flash unit to emit light and to prohibit light emission according to the signal from the second output means; 1. A camera with a flash charge control circuit, characterized in that a means is added for outputting a flash charge signal from the output means and supplementary charging of the flash for a certain period of time immediately before photographing.