JPS5833368A - Electronic camera - Google Patents

Abstract

PURPOSE:To shorten the response time of an electronic shutter and to minimize the size of a TV camera, etc., by providing an electronic shutter to an optical system and deciding the exposure time of the electronic shutter by the level of a video signal. CONSTITUTION:An electronic shutter 4 is provided contiguously to the position of the diaphragm of an optical system of an electronic camera. The shutter 4 consists of the ferrodielectric ceramic 5 which is held between electrodes 5a and 5b provided between two deflecting plates 4a and 4b. When an electric field is applied to the ceramic 5, the ceramic 5 transmits the light. While the ceramic 5 cuts off the light when the application of the electric field is cut. An optical image given from the system 2 is applied to an image pickup element 6, and the video signal is delivered to the output side by the signal given from a control signal producing circuit 7. The level of the video signal is detected by a level detecting circuit 10, and this level is compared with the output fed from a lamp signal producing circuit 12 through a comparator 11. Then the shutter 4 is controlled by the result of comparison obtained through the circuit 11 and via a driving circuit 13. Thus, a TV camera device is small-sized and the response time is shortened for the shutter 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses, for example, a solid-state image sensor (such as a CCD), obtains an electrical video signal from an image obtained through an optical system, and converts this video signal into a rotating magnetic sheet recorder using, for example, a rotating magnetic sheet recorder. This invention relates to an electronic camera that records on a sheet, and in particular allows the exposure time of the optical system to always be set to the optimum value.

An embodiment of the electronic camera of the present invention will be described below with reference to the drawings.

Figure 1 shows the appearance of an electronic camera. In Figure 1, (1) is a video signal forming circuit that uses a solid-state image sensor to obtain an electrical video signal from an optical device, and a circuit that records this video signal. An electronic camera body equipped with a rotating magnetic sheet recorder, etc.; (2) an interchangeable lens device constituting the optical system;
(3) is a battery pack that constitutes a power source.

This example will be explained with reference to FIG. 2. In this example, an electronic shutter (4) is provided at a predetermined position of the optical system (2), for example, adjacent to the aperture. This electronic shutter (4) consists of two deflection plates (
A ferroelectric ceramic electric cap (5) sandwiched between electrodes (5 m) and (5b) is provided between (4 m) and (4 b),
When an electric field is applied to this ferroelectric ceramic IC (5), light passes through it, and when this electric field is turned off, no light passes through it.

The optical image obtained through this optical system (2) is supplied to a solid-state image sensor, for example, a COD (6). This solid-state image sensor (6) is connected to a synchronization signal and control signal generation circuit (7).
), and an electrical video signal corresponding to the optical image is obtained on the output side. The video signal obtained on the output side of this solid-state image sensor (6) is supplied to the signal processing circuit (8), and the synchronization signal from the synchronization signal and control signal generation circuit (7) is supplied to this signal processing circuit (8). This signal processing circuit (8
), a synchronization signal is added to the video signal to make a complete video signal. The output terminal (8) of this signal processing circuit (8)
The video signal obtained in step a) is supplied to a rotating magnetic sheet recorder to record it.

Further, in this example, the video signal obtained on the output side of the solid-state image sensor (6) is supplied to the clamp circuit (9). In this clamp circuit (9), the horizontal synchronizing signal position of the luminance signal is clamped to a predetermined level.

The luminance signal obtained at the output side of this clamp circuit (9) is supplied to the ronos filter 0α constituting the level detection circuit, and the average level signal (10a) of the luminance signal is supplied to the output side of this four-pass filter α. and this average level signal (
10m) is supplied to one input terminal of a comparison circuit OD constituting a pulse width modulation circuit. Further, the synchronization signal and control signal generation circuit (7) supplies a vertical synchronization signal as shown in FIG. 4 to the ramp signal generation circuit fi3, and in this ramp signal generation circuit (Iz), A ramp signal (12) which is synchronized with the vertical synchronization signal and gradually attenuates with the passage of time is obtained, and this ramp signal (12) is supplied to the other input terminal of the comparator circuit al.
In 1, the ramp signal (1
When the two levels are higher than the average level signal (ton) of the luminance signal supplied to one input terminal, it becomes a high level signal "1", and when this is lower, it becomes a low level signal 60.
”. Therefore, in this case, when the level of the average level signal (10a) of the luminance signal is high, the comparator circuit α1)
When the average level signal (10a) has a low level, the pulse width of the signal obtained at the output side of the comparison circuit αυ becomes large.

That is, a pulse width modulated signal having a pulse width inversely proportional to the average level signal (IQa) of the luminance signal is obtained on the output side of the comparator circuit αυ. The pulse width modulation signal obtained on the output side of the comparison circuit aυ is sent to the electronic shutter (4) via the drive circuit a3.
), and the exposure time of this electronic shutter (4) is controlled by this pulse width variation t1 signal.

Since this example is configured as described above, for example, when the average level signal of the luminance signal as shown in FIG. A pulse width modulation signal as shown in FIG. 4C is obtained, and the exposure time of the electronic shutter (4) is determined by this signal.

Therefore, in the present invention, the exposure time of the electronic shutter (4) is determined so that the level of the video signal output from the image sensor (6) is always constant, and the best exposure time can always be obtained. Also, conventional TV cameras use motors etc. to adjust exposure with the iris, and the response time is relatively slow, making them unsuitable for miniaturization.Also, it is difficult for conventional camera shutters to respond quickly, but this According to the invention, since the exposure time is determined electrically, the response time is extremely fast and the device is suitable for miniaturization.

Furthermore, by measuring the pulse width of the pulse width modulation signal on the output side of the comparison circuit aυ, the exposure time can be displayed on the finder. Furthermore, in the above example, by controlling the pulse width modulation signal supplied to the drive circuit (13) by the system controller, it is possible to open the electronic shutter during multiple exposure or when using a strobe.

It goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

[Brief explanation of the drawing]

1 and 4 are diagrams for explaining the present invention, FIG. 2 is a configuration diagram showing an embodiment of the electronic camera of the present invention, and FIG.
The figure is a configuration diagram showing an example of an electronic shutter. b (2) is an optical system, (4) is an electronic shutter, (6) is an image sensor, aω is a level detection circuit, 0υ is a comparison circuit, (Iz
is a ramp signal generation circuit. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In an electronic camera that converts an image obtained through an optical system into an electrical video signal, an electronic shutter is provided in the optical system, and the exposure time of the electronic shutter is determined depending on the level of the video signal. An electronic camera characterized by: