JPH0470633A - Camera with accessory show - Google Patents

Abstract

PURPOSE:To prevent the rupture of an electronic device in a camera by providing a means for inhibiting the release action of the camera according to a signal from a means for detecting voltage impressed on the X contact of an accessory shoe. of CONSTITUTION:This camera is provided with the voltage detection means 23 for detecting the voltage impressed on the X contact of the accessory shoe and a release action inhibiting means 29 for inhibiting the release action of the camera according to the signal from the means 23. In the case of mounting an electronic flash device on the accessory shoe, whether or not it is a high voltage electronic flash device is discriminated on a camera side by the means 23. In the case of judging that the high voltage electronic flash device is mounted, the light emitting action of the electronic flash device is inhibited from being performed. Thus, the rupture of the electronic device in the camera is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a camera having an accessory shoe for mounting a flash device or the like.

<Prior Art> Conventionally, the X contact on the accessory shoe of a camera has been used for the purpose of instructing the start of light emission of an external electronic flash. - The camera is configured so that it is normally off and turns on when the camera's shutter is fully open, and the external electronic flash detects this on state and starts firing. is designed to get you started.

FIGS. 2 and 3 each show an example of the electric circuit of a conventional general electronic flash device.

In the conventional example shown in FIG. 2, a main capacitor 3 and a xenon tube 4 are connected in parallel with a DC/DC converter 2 connected to a battery 1 to boost the battery voltage to a high voltage, and the xenon tube 4 emits light. Trigger coil for starting 5. A series body of a trigger capacitor 6 and a charging resistor 7 is connected, and the connecting end of the charging resistor 7 with the trigger capacitor 6 and the negative electrode side of the converter 2 are connected to contacts 8 and 9, respectively, which are connected to the accessory terminal on the camera side. It is connected to the. The contact 8 is an X contact connected to the center of the accessory shoe, and the contact 9 is a ground contact connected to the outer periphery of the accessory shoe.

In the case of this electronic flash device, when the contacts 8 and 9 are short-circuited at the time of release, the electric charge accumulated in the trigger capacitor 6 is discharged through the trigger coil 5, and at this time, a single coil is attached to the outer periphery of the xenon tube 4. A high voltage boosted by the main capacitor 3 is applied, and as a result, the charges stored in the main capacitor 3 are discharged through the xenon tube 4, thereby performing a light emitting operation.

In addition, in the conventional example shown in FIG. 3, the input terminal of a one-shot multivibrator 12 is connected to the contact 8 as a circuit different from the conventional example shown in FIG. 6 and the charging resistor 7 and the ground side, the one-shot multivibrator 1
The input terminal 2 is connected to the positive electrode of the battery 1 via a pull-up resistor 13.

When a switching signal switching from a high level to a low level is input to the input terminal of the one-shot multivibrator 12, a signal that becomes high level for a short period of time is outputted from the output terminal, and the Cyrisk 10 is turned on.

In the case of this electronic flash, if contact 8 and contact 1 are short-circuited at the time of release, the one-shot multivibrator 1
Since a switching signal that switches from a high level to a low level is input to the input terminal 2, the one-shot multivibrator 12 outputs a signal that becomes high level for a short period of time, and the thyristor 10 is turned on. As a result, the charge accumulated in the trigger capacitor 6 is discharged through the trigger coil 5, and the trigger coil 5
A high voltage boosted by the main capacitor 3 is applied.
The electric charge accumulated in the xenon tube 4 is discharged through the xenon tube 4, thereby performing a light emitting operation.

<Problem to be solved by the invention> When comparing these two conventional examples, there is no difference in function itself;
When performing a light emitting operation, in the circuit example shown in Fig. 2, a high voltage for causing the xenon tube 4 to emit light is directly applied to the X contact of the accessory shoe, and the current flowing through the trigger coil 5 is applied directly to the X contact. On the other hand, in the circuit example shown in Figure 3, the one-shot multivibrator 12 is connected to the X contact.
The 71f current flowing to the trigger coil 5 does not flow to the X contact but flows through the thyristor 10.

In recent years, with the electronicization of cameras, LSIs and ICs such as microcomputers are commonly installed inside the camera, but such electronic devices have the form of the circuit example shown in Figure 2 above. (hereinafter referred to as high-voltage electronic flash)
If used, it will be relatively easily destroyed by induced noise or surge.

In addition, especially in recent cameras, there is a built-in electronic flash that is separate from the external electronic flash, and when the subject is dark or backlit, the built-in electronic flash automatically stops firing. Some cameras have this function, but in the case of such cameras, there are many cases in which the X contact is input directly to the control IC for controlling the light emission of the electronic flash device.

In such cases, if a high r1-electronic flash device is used,
A high voltage will be applied directly to the control IC, and the control IC will be easily destroyed.

In order to prevent the destruction of these electronic devices, when using a high-voltage electronic flash, a shielding member is used to prevent the high-voltage current from directly affecting the electronic devices, or a diode with high voltage resistance is used to prevent the high-voltage current from flowing to ICs, etc. Countermeasures such as providing another current path have been taken, but this has had the problem of being extremely expensive and not very effective against IC destruction.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a camera having an accessory shoe that prevents electronic devices inside the camera from being destroyed by a high-voltage electronic flash.

Means for Solving the Problems> In order to achieve the above-mentioned object, the camera of the present invention includes an accessory shoe and a detection means for detecting a voltage applied to the X contact of the accessory shoe. The camera has means for inhibiting the release operation of the camera based on a signal from the means.

Further, it is preferable to have a display means for displaying a warning based on a signal from the voltage detection means.

<Operation> In a camera having an accessory shoe configured as described above, when an electronic flash device is attached to the accessory shoe, the camera side uses a voltage detection means to determine whether or not it is a high voltage electronic flash device. When it is determined that a flash device is attached, the electronic flash device does not emit light, thereby preventing damage to the electronic device inside the camera.

Further, at this time, by displaying on the display means that the high-voltage electronic flash device is attached, it is possible to prompt the photographer with a warning.

<Example> Hereinafter, one embodiment of the present invention will be described based on FIG.

In the figure, 20 is an X contact that is connected to the center of the accessory shoe terminal of the camera, and 21 is a ground contact that is also connected to the outer periphery of the accessory shoe. Connected to the device side contact.

Reference numeral 22 is a switch that is turned on when the camera is released, and is connected to both ends of contacts 20 and 21. In a focal-brain shutter, etc., the switch turns off when the front curtain finishes running and the shutter is fully open. Turns on.

23 is a high input voltage type comparator, and the X contact 20 is connected to its non-inverting input terminal. 24 is a constant voltage output circuit that always outputs 10V, and its output is input to the inverting input terminal of the comparator 23. Then, the comparator 23 connects the voltage manually applied from the X contact 20 with the IO
When the voltage at the X contact 20 is larger, a high level signal is output, and when the voltage at the X contact 20 is smaller, a low level signal is output.

Reference numeral 25 denotes an LED for indicating that a high-voltage electronic flash device is attached, and its anode is connected to the output terminal of the comparator 23, and its cathode side is grounded via a resistor 26. A switch 27 is linked to a release button of a camera (not shown), and is turned on when the release button is pressed. 28 is a pull-up resistor for pulling up the switch 27. 29 is an OR gate, the output of the comparator 23 is applied to one end of its input terminal,
A signal from a switch 27 is applied to the other end.

The output of the OR gate 29 is input to the input terminal of the microcomputer 30. The microcomputer 30 functions as a sequence controller for the operation of the entire camera, and reads the on/off state of the release button and outputs a signal for operating the camera actuator from an output port (not shown). and performs a series of camera operations.

The operation of this embodiment having the above configuration will be explained.

First, when an electronic flash of a type other than a high-voltage electronic flash is installed, for example, when the conventional electronic flash shown in FIG. The voltage of the battery that is the power source is applied, but
This voltage is only 5 to 6 V at most, and therefore the comparator 3 outputs a low level signal. As a result, the LE indicating the high-voltage electronic flash
Since a low level is applied to the anode of D25, LE
D25 remains unlit.

Further, a low level signal is applied to one end of the input terminal of the OR gate 29. As a result, when the switch 27 is off, one end of the input terminal is at a high level, so the output of the two OR gates is a high level output, and conversely, when the switch 27 is on, both input terminals are at a low level, so The output is low level.

Therefore, the microcomputer 30 reads this signal from the input port P1 and determines that the release button is pressed when a low level signal is input.
After that, a series of exposure operations will begin.

Exposure control controlled by a microcomputer is well known, so the explanation will be omitted, but when the switch 22 is turned on during shutter operation, the X contact 20 is connected to the ground, and the Since a switching signal switching from a high level to a low level is input to the input terminal of the Schott-Fultivibrator 12, the light emission operation is performed by the above-described operation.

Next, when a high-voltage electronic flash is attached, for example, when the conventional electronic flash shown in FIG. 2 is attached, the X contact 20 of the accessory shoe terminal on the camera side is The voltage stored in the capacitor 3 is applied as is. Normally, a boosted voltage of about 300 V is required for flash light emission, and this voltage is directly applied to the X contact 20.

Therefore, the comparator 23 outputs a high level signal. As a result, it indicates that a high-voltage electronic flash device is installed, and a high level is applied to the 7th node of ED25.
The D25 lights up and tells the person with disabilities that he or she cannot release the camera because a high-voltage electronic flash has been installed.

Further, a high level signal is applied to one end of the input terminal of the two OR gates. For this reason, ORGATE 29
The output becomes high level depending on the state of the switch 27, and no signal indicating that the release button is pressed is ever input to the micro combinator 30, so that no exposure operation is started.

Naturally, the switch 22, which is turned on when the shutter is running, remains off, and the high-voltage electronic flash device does not emit light, which could lead to destruction of the electronic device.

In the above-mentioned example, the comparator 23 detects the voltage, and the two OR gates prevent the information from being transmitted to the microcomputer 30 even if the release button is pressed, but the voltage is detected by the A-D converter. ,A-
The result of the D conversion is directly input to the input port P1 of the microcomputer 30, and the release button is also configured to be input directly to the microcomputer 30 without going through a gate. Needless to say, this can be realized by programming so that the exposure operation is not performed even if the release button is pressed.

<Effects of the Invention> As explained above, the present invention determines whether or not a high-voltage electronic flash device is attached by reading the applied voltage applied to the X contact of the accessory shoe with a voltage detection means,
If it is determined based on the signal from the voltage detection means that a high-voltage electronic flash device is attached, its light emitting operation is prohibited, thereby silently preventing damage to the electronic device inside the camera.

In addition, by activating the warning display means with the signal from the voltage detection means, a warning is issued to the II photographer that the high-voltage electronic flash device is attached and that the photographing operation cannot be performed, making it possible to reliably eliminate operational errors. can.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram of a camera having an accessory shoe according to an embodiment of the present invention, Fig. 2 is an electrical circuit diagram of a conventional high-voltage electronic flash device, and Fig. 3 is a non-conventional high-voltage electronic flash device. It is an electric circuit diagram of a general electronic flash device. 20... pressure detection means), 25
...Display LED (display means), 27-...Switches linked with the release button, two...Or gate (
Release operation inhibiting means), 3o...microcomputer. Patent Applicant Canon Co., Ltd. Agent Patent Attorney 1) Mitsuru Mura Figure 3 Figure 2

Claims (1)

[Scope of Claims] 1. It has an accessory shoe and a detection means for detecting the voltage applied to the X contact of the accessory shoe, and has means for inhibiting the release operation of the camera based on a signal from the voltage detection means. A camera having an accessory shoe characterized by. 2. The camera with an accessory shoe according to claim 1, further comprising display means for displaying a warning based on a signal from the voltage detection means.