JPH04366821A - Battery check circuit for camera - Google Patents

Abstract

PURPOSE:To excellently perform various driving including the light emission of an auxiliary light source by a battery even when the auxiliary light source is provided. CONSTITUTION:The battery check circuit of the camera wherein the auxiliary lamp 7 is incorporated so as to prevent a red-eye phenomenon checks the battery by switching the decision level to a level higher than a decision level in normal operation when a red-eye phenomenon prevention mode is selected. For example, the voltage division ratio of the battery voltage is set as the decision level and switched for comparing operation to check the level.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery check circuit for a camera, and more particularly to a battery check circuit for a camera provided with an auxiliary light source separate from a strobe light source to prevent red-eye.

0002

[Prior Art] A battery is used as a driving source for various types of cameras.
The capacity has been checked to ensure that basic operations such as strobe photography and film winding can be carried out smoothly.

[0003] Incidentally, in flash photography using a camera, the so-called red-eye phenomenon, in which the eyes of subjects such as people appear red, has traditionally been a problem, but recently measures have been taken to reduce and prevent this red-eye phenomenon. In other words, the red-eye phenomenon is a phenomenon in which when a strobe is used on a human or animal, the strobe light enters the eyeball through the pupil, and this light is reflected from the blood vessels within the eyeball, causing the eye to appear red. Therefore, conventionally, in order to prevent the above-mentioned red eye, a weak light is emitted in advance (pre-flash) to reduce the diameter of the subject's pupil before the actual shooting.
This is done to reduce the incidence of strobe light into the pupil.

[0004] When performing the above-mentioned pre-emission using a lamp built into the camera, a method has been proposed in which one strobe light source (lamp) such as a xenon tube is used to emit light using two types of capacitors; In order to facilitate discharge control, a method has been proposed in which an auxiliary light source is provided separately from the strobe light source. According to this, the auxiliary light source causes pre-emission of light in synchronization with the shooting button, and after the pupil diameter of the subject is reduced, the main light emission is performed using the strobe light source.

[0005]

[Problem to be Solved by the Invention] However, in cameras using the above-mentioned auxiliary light source, the power required to operate the auxiliary light source is greater than the power of other drive units, and conventional battery checks are insufficient. There is. In other words, a lamp with a relatively large luminous flux of irradiation light is used as the auxiliary light source, and it takes about 1 second for the pupil to react when preventing red eye.
A power greater than that of other drive units (e.g. 600mA)
degree) is required. For example, in the case of a strobe light source, the light emitting power is large, but the capacitor is charged once and this charged power is used to cause the xenon tube to emit light. Therefore, an auxiliary light source requires a large amount of power even when compared to a strobe light source.

On the other hand, the battery check level setting of a camera is usually set to the lowest possible level so that many pictures can be taken while the functions and performance of the camera are satisfied. Therefore, under these circumstances, when the above-mentioned auxiliary light source is built into the camera, there may be cases where the auxiliary light source is unable to obtain the amount of light emitted to prevent red-eye, and even though the auxiliary light source is able to emit light, , which may cause problems in subsequent driving. For example, even if the battery is determined to be good after a battery check, basic operations such as firing an auxiliary light source, firing a strobe during exposure, and winding the film after taking pictures may not be possible.

The present invention has been made in view of the above-mentioned problems, and its object is to provide a camera that can perform various drives including light emission of the auxiliary light source using a battery even when an auxiliary light source is provided. The purpose is to provide a battery check circuit.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a battery check circuit for a camera with a built-in auxiliary light source to prevent red-eye phenomenon, when a red-eye prevention mode is selected. is characterized in that the battery is checked by switching to a higher judgment level than the normal judgment level.

[0009]

[Operation] According to the above configuration, a battery check is performed by comparing, for example, a voltage obtained by dividing the battery voltage with a reference voltage. In the red-eye prevention mode, the voltage division ratio is switched to a voltage division ratio lower than the voltage division ratio set in the normal state, and this voltage division ratio is compared with the reference voltage. Therefore, in the red-eye prevention mode, checking is performed at a substantially higher level than in normal times.

0010

[Embodiment] Fig. 1 shows the configuration of a battery check circuit for a camera according to an embodiment, and Fig. 2 shows an external appearance of a camera according to an embodiment. A lens barrel 3 having a photographic lens 2 is disposed on the front surface of the camera 1 so as to be movable forward and backward. A finder 4, an autofocus (AF) light emitting section 5a, an AF light receiving section 5b, and a strobe light emitting section 6 with a built-in xenon tube are provided on the front surface of the camera body 1, and the lens barrel 3 and the strobe light emitting section are also provided. An auxiliary light source (lamp) 7 is disposed between the two.

A shutter button 8 and a strobe mode switching button 9 are provided on the top surface of the camera body 1, and the shutter button 8 performs a photographing operation as described later with a two-stage switch (S1, S2). Further, the strobe mode switching button 9 has, for example, a structure in which a knob slides in a groove, and is configured to switch between red-eye prevention red-eye prevention mode, low-brightness automatic flash mode,
It is possible to switch between forced flash modes such as daytime synchronization.

In FIG. 1, a CPU (central processing unit) 11 that controls the entire camera operation is provided with an auxiliary lamp 7 via a switching transistor 12, and a battery (battery) is connected to the other side of the auxiliary lamp 7. For example, 6V)
13 are connected. Further, the strobe mode switching button 9 is connected to the CPU 11 so as to input its selection signal, and although not shown, an autofocus (A
F) section, shutter control section, flash control section, automatic exposure (
The AE) section etc. are also under general control by the CPU 11.

A check start transistor 14 is provided for starting the battery check, and the positive terminal of the battery 13 is connected to the emitter terminal of this transistor 14, and the base terminal is connected to the A of the CPU 11 via a resistor. Connected to the terminal. Further, resistors R1, R2, and R3 are connected in series between the collector terminal of the transistor 14 and the ground, and a resistor for switching the determination level in the red-eye prevention mode is connected between the resistors R1 and R2. A switching transistor 15 is provided with its collector terminal connected, the emitter terminal of this transistor 15 is connected to the ground, and the base terminal is connected to the CPU 1.
Connected to the B terminal of 1. Furthermore, a comparator 16 for determining the battery level is provided, the positive input terminal of which is connected between the resistors R2 and R3, and the negative input terminal of which is provided with a reference voltage Vref for comparison, The output terminal of the comparator 16 is connected to the C terminal of the CPU 11.

According to such a check circuit, the CPU
When the A terminal of 11 is set to Low level, the check start transistor 14 is turned on, and the voltage of the battery 13 is applied to the series resistors R1 to R3. Under normal conditions, the voltage is divided by the resistors R1, R2 and resistor R3. The resulting voltage value is supplied to the positive input terminal of the comparator 16,
6, it is compared with the reference voltage Vref. If the partial voltage of the battery voltage is higher than the reference voltage Vref, it is determined that the capacity (power) is sufficient, and the comparator 1
6 inputs a high level output to the C terminal of the CPU 11, and if it is lower than the reference voltage Vref, it is determined that the capacity is insufficient and a low level output is supplied from the comparator 16.

Further, when the red-eye prevention mode is selected, the CPU 11 sets its B terminal to High level and turns on the switching transistor 15. Then, the resistor R1 and the resistor R2 will be connected to the ground, and the voltage of the battery 13 will be divided by the resistor R2 and the resistor R3. Assuming that the battery voltage is the same, the above normal A voltage lower than the voltage division at the time is supplied to the comparator 16. Therefore, unless the battery capacity is higher than normal, it is determined that the battery capacity is insufficient, and the determination level is set high.

The embodiment has the above configuration, and its operation will be explained below based on FIG. 3. In FIG. 3, first, in step 101, the first stage switch S of the shutter button 8 is
1 is turned on, it is determined in step 102 whether or not the red-eye prevention mode is set with the strobe mode switching button 9. If "N", the process moves to step 104, but if "Y", the next step is performed. The process moves to step 103 and the switching transistor (TR) 15 is turned on by the CPU 11. Then, in the next step 104, the check start transistor (TR) 14 is turned on by the CPU 11, and the process moves to the next step 105. Therefore, in the embodiment, the determination level of the battery check is switched depending on whether or not the switching transistor 15 is turned on at step 103, and if it is not the red-eye prevention mode, the battery 13 is switched on as described above. A high divided voltage is supplied from the battery 13 to the comparator 16 to check the battery for a low judgment level, while in the red-eye prevention mode, a low divided voltage is supplied from the battery 13 to the comparator 16 to check for a high judgment level. A battery level check will be performed.

In step 105, it is determined whether the output of the comparator 16 (C terminal input of the CPU 11) is High, and when it is "N", the battery capacity is insufficient. Therefore, the process proceeds to step 106, where the transistors 14 and 15 are turned off, and in step 107, processing (display processing, etc.) for battery exhaustion is performed. On the other hand, if "Y" is determined in step 105, this means that the battery capacity is sufficient, so after turning off the transistors 14 and 15 in step 108, step 109 is performed to turn off the transistors 14 and 15 for focus control and exposure control. Photometry and distance measurement processing are performed.

In the next step 110, it is determined whether or not the second stage switch S2 (release switch) of the shutter button 8 is turned on. If "Y", step 1 is executed.
The process moves to step 11, where it is further determined whether or not the red-eye prevention mode is in effect, and if "N", the process moves to step 113, where focus control and exposure control are performed. Furthermore, if "Y" is determined in step 111, the red-eye prevention mode is in effect, so the auxiliary lamp 7 is turned on for approximately 1 second and the process proceeds to step 113. After the shooting is completed, the film is wound. In this way,
When the red-eye prevention mode is set, by performing a battery check at a high level, not only the auxiliary lamp 7 can emit light, but also the subsequent operation can be maintained in good condition.

In the above embodiment, the reference voltage V of the comparator 16
ref is kept constant and the input battery voltage is varied, but of course the reference voltage Vref may be switched, and the battery voltage may be determined by using an A/D converter without using the comparator 16. The value may be converted into digital data and compared with a reference value within the CPU 11.

Further, in the embodiment, the auxiliary lamp 7 is used to prevent red-eye, but this auxiliary lamp 7 can also be used to emit auxiliary light in a low brightness state, for example, in passive autofocus control. It is.

[0021]

[Effects of the Invention] As explained above, according to the present invention,
When the red-eye prevention mode is selected, the battery is checked by switching to a higher judgment level than the normal judgment level, so the pre-flash to prevent red-eye is effective even when an auxiliary light source is installed. At the same time, it is possible to reliably execute subsequent camera drives such as strobe light emission and film winding.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of a camera battery check circuit according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the external configuration of the camera of the embodiment.

FIG. 3 is a flowchart showing the operation of the embodiment.

[Explanation of symbols]

7... Auxiliary light source (lamp), 9... Strobe mode switching button, 11...
CPU, 13...Battery, 14...Check start transistor, 15
... switching transistor, 16 ... comparator, R1, R2, R3 ... resistor.

Claims (1)

[Claims] [Claim 1] In a battery check circuit for a camera with a built-in auxiliary light source to prevent red-eye phenomenon,
A camera battery check circuit characterized in that when a red-eye prevention mode is selected, the battery is checked by switching to a higher determination level than the normal determination level.