JPH0324836B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic still camera with little image distortion.

2. Description of the Related Art Conventionally, electronic still cameras have been known that use a solid-state imaging device such as a CCD and an ultra-small magnetic disk, and record an image of a subject on the magnetic disk as a video signal. Such electronic still cameras are usually provided with a power switch, and when the power switch is turned on, power is supplied to the solid-state image sensor, magnetic disk device, etc., and the electronic still camera starts operating. Solid-state image sensing devices are generally configured in accordance with television camera standards, and therefore repeat exposure, charge accumulation, and video signal generation at a 1/60 second cycle while the power switch is on.
Furthermore, the magnetic disk is constantly rotating while the power is on. When the release button is pressed and the release switch operates, the video signal writing circuit of the magnetic disk device operates for 1/60 seconds to record one frame worth of video signal generated from the solid-state image sensor.

By the way, in such an electronic still camera, if you press the release button soon after turning on the power switch, the video signal will be recorded before the rotation speed of the magnetic disk reaches a certain speed, and the video signal will not be recorded. There were inconveniences such as image distortion and poor resolution. Further, in order to solve this problem, if the power source is left on for a long time, the power source such as the battery will be consumed. Furthermore, as mentioned above, the exposure time of this electronic still camera is fixed at about 1/60 second, which is the same as that of a television camera, so when photographing fast-moving objects, image distortion occurs.

The first purpose of the present invention is to detect the rotational speed of the magnetic disk and record a video signal when the magnetic disk reaches a constant speed, thereby recording an image without distortion even when the release button is pressed immediately after power is turned on. It is to be. A second object of the present invention is to photograph a fast-moving subject without distortion. In order to achieve this second objective, the electronic still camera of the present invention is provided with a physical shutter or an electromagnetic shutter for adjusting the exposure time of the solid-state image sensor, and the projected image obtained through these shutters is A video signal is recorded after the magnetic disk reaches a certain speed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of one embodiment of the present invention. In other words, in the past, the release signal from the release switch was directly used as the trigger signal to start the recording operation of the magnetic disk device, but the first
In the apparatus shown in the figure, a trigger signal for starting a recording operation is sent to the magnetic disk device through a gate 1 that opens when the rotational speed of the magnetic disk exceeds a predetermined rotational speed. In the figure, 2 is a second-stage release switch, 3 converts the rotation speed into voltage, and compares it with a reference voltage to generate a rotation detection signal when the magnetic disk is rotating at a predetermined rotation speed or higher. This is a rotation speed detection circuit. In addition, this rotation speed detection is done by attaching a magnet to the part that interlocks with the magnetic disk.
The number of times the N and S poles of the magnet pass in front of the detection head may be detected, or a combination of a perforated disk and a photocoupler, or a combination of a gear and a detection head may be used. Alternatively, the rotational speed detection output of a servo motor for driving a magnetic disk may be used.

FIG. 2 is a block diagram showing another embodiment of the present invention. In the figure, 11 is a camera lens optical system such as a lens and aperture, 12 is an electromagnetic shutter,
13 is a solid-state image sensor such as a CCD; 14 is a video signal circuit including a video signal amplifier, an FM modulator, etc.;
15 is a gate circuit, 16 is a recording head, 17 is a magnetic disk, 18 is a magnetic disk rotation speed detection circuit, and 19 is a control circuit for sending operating signals to each part of this electronic still camera.

Next, the operation of this electronic still camera will be explained with reference to the time chart shown in FIG. The release button of this camera uses a two-stage operation mechanism similar to that of general TTL metering type silver halide film cameras, and according to the pressing stroke a, the first stage release switch is first pressed, then the second stage release button is pressed. The switch operates b, c. The first stage release switch is the power switch for the entire camera, and when this switch operates, power is supplied to the magnetic disk drive motor and each circuit, and when the magnetic disk 17 begins to rotate, well-known TTL photometry is performed along with d. An appropriate shutter speed or aperture is determined for the set aperture or shutter speed (for example, f). Next, when the second release switch operates and a release signal is generated, the output e of the magnetic disk rotation speed detection circuit 18 causes the magnetic disk 1 to be
After waiting until the number of rotations of the shutter 7 reaches a predetermined number of rotations or more, the electromagnetic shutter 12 is operated in synchronization with the transfer pulse of the solid-state image sensor 13g. Subsequently, the solid-state image sensor 13 records one frame worth of video signals generated in response to the image projected through the camera lens optical system 11 on the magnetic disk 17 using a well-known method.

In the above-described embodiment, the electromagnetic shutter is operated after waiting for the magnetic disk to reach a predetermined rotation speed, but for example, when the release signal c is generated, the accumulated charge in the solid-state image sensor 13 is cleared,
The electromagnetic shutter may be operated and then put on standby, and the next time the rotation detection signal c is generated, the stored charges may be read out (transferred) from the solid-state image sensor 13 and recorded on the magnetic disk.

As described above, according to the present invention, even if the rotation of the magnetic disk is started by pressing the first step of the release button, the speed of the magnetic disk is always kept at a constant speed during recording. It is possible to reduce the power consumption of electronic still cameras without causing image distortion or resolution insufficiency due to insufficient or fluctuations, and by controlling the exposure time of the solid-state image sensor using electromagnetic shutters, physical shutters, etc. Even in the case of a fast object, a still image of one frame can be faithfully reproduced on a magnetic disk, and an image without image distortion can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the main parts of one embodiment of the present invention, Fig. 2 is a block diagram showing another embodiment of the invention, and Fig. 3 explains the operation of the still camera shown in Fig. 2. This is a time chart for 1...Gate, 2...Second release switch,
3... Rotation speed detection circuit, 11... Camera lens optical system, 12... Electromagnetic shutter, 13... Solid-state image sensor, 14... Video signal circuit, 15... Gate circuit, 16... Recording head, 17... ...magnetic disk, 18... rotation speed detection circuit, 19... control circuit.

Claims (1)

[Claims] 1. An electronic still camera that is equipped with an image sensor that generates a video signal corresponding to an image of a subject and a magnetic disk device that records the image signal from the image sensor in response to a release signal from a release switch. The release switch consists of a first and second stage release switch that operate sequentially in accordance with the operation of the release button, and also includes a means for detecting the rotational speed of the magnetic disk, and a means that operates when the second stage release switch is operated. and an electromagnetic shutter or a physical property shutter that exposes the image sensor, and when the first stage release switch operates, it starts the magnetic disk and starts supplying power to each part of the device, and the second stage An electronic still camera characterized in that a video signal is recorded on the magnetic disk when a release switch is operated to operate the shutter and the magnetic disk reaches a certain speed.