JPH0433481A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain automatic exposure adjustment under a wide image pickup condition from pickup at night to pickup at daytime by arranging a liquid crystal panel into an optical path. CONSTITUTION:A light from an object 1 is made incident in a lens system 2 and collected and the image is formed on a solid-state image pickup element (CCD) 4 via a liquid crystal panel 3 and photoelectric converted and converted into a pickup video signal by a signal processing circuit 5. Moreover, a control circuit 7 drives the liquid crystal panel 3 in response to a luminance level detected by a level detection circuit 6 and a detection output by a photodetector 8 to give a control signal to a drive circuit 10. Then the liquid crystal panel 3 is arranged in an optical path between the CCD 4 and the lens system 2, and an infrared ray out filter and an infrared ray transmission filter are arranged alternately in the horizontal direction. Thus, the pickup condition causing a change in the intensity of the infrared ray together with normal exposure adjustment is coped with the liquid crystal panel 3 in front of the image pickup element.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an imaging device such as a video camera with an incident light amount adjustment mechanism.

(b) Conventional technology In ordinary video cameras, even if the illuminance of the subject varies depending on the imaging environment, such as under the sun or indoors, the amount of light incident on the image sensor is always kept constant, and the brightness level of the captured video signal is kept constant. In order to avoid the situation where 0 is extremely high and 0 is low, a mechanical aperture mechanism is installed.
Since it is composed of several blades and a mechanism for opening and closing these blades, the diaphragm mechanism itself is not suitable for miniaturization, has a large number of components, and consumes a lot of power. had.

Therefore, Japanese Patent Application Laid-open No. 169587/1987 (H04N5
/238) is an example of adjusting the amount of incident light by placing a liquid crystal panel in front of the image sensor and electrically controlling the light transmittance of this liquid crystal panel, without using a mechanical aperture mechanism. Proposed.

(c) Problems to be Solved by the Invention The above-mentioned prior art does not take into account sensitivity in the infrared region at all. In other words, in normal video cameras, in order to avoid saturation of the image sensor itself when the infrared light is strong, an infrared cut filter made of glass or plastic is inserted into the image sensor itself. However, when shooting at night, the image sensor has low sensitivity in the infrared region and is prone to underexposure.

(d) Means for Solving the Problems The present invention makes it possible to control not only the light transmittance but also the spectral characteristics of a plurality of filter pixels of a liquid crystal panel arranged between a lens system and an image sensor, and furthermore, it is possible to control the spectral characteristics of a plurality of filter pixels of a liquid crystal panel arranged between a lens system and an image sensor. It is characterized by controlling these light transmittance and spectral characteristics according to the intensity of light.

(e) Function Since the present invention is constructed as described above, it is possible to cope with photographing conditions in which the intensity of infrared light is changed in addition to normal exposure adjustment by using the liquid crystal panel in the front stage of the image sensor.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall circuit block diagram. Light from an object (1) is incident on a lens system (2), is focused, passes through a liquid crystal panel (3), forms an image on a solid-state image sensor (CCD) (4), is photoelectrically converted, and is converted into a signal. The processing circuit (5) converts it into a captured video signal.

The brightness signal in this captured video signal is detected by a brightness level detector (
Level detection is performed in step 6), and the detection result is supplied to the control circuit (7). Light detection! (8) is a side light means that detects the brightness of the subject, and the detection result is transmitted to the control circuit (7).
) and an infrared emitting lamp (9).

The infrared light emitting lamp (9) determines that it is night photography and emits light when the output of the photodetector (8) is smaller than a predetermined level.

The control circuit (7) sends a control signal to the drive circuit (10) that drives the liquid crystal panel (3) according to the brightness level detected by the level detection circuit (6) and the detection output from the photodetector (8). emanate.

The liquid crystal panel (3) is placed in the optical path between the CCD (4) and the lens system (2), but it is placed closer to the lens system (2) than the CCD (4). This is because the amount of light is not affected by the pixel arrangement of the color filter of the liquid crystal panel. Here, an example of the color filter arrangement of the liquid crystal panel (3) is shown in FIG. (BG) in Figure 2 is the fourth
A BG filter, that is, an infrared cut filter, has the characteristics shown in Figure 4 (a), and (R) represents an R filter, that is, an infrared transmission filter, that has the characteristics shown in Figure 4 (b), and both filters are arranged horizontally. arranged alternately.

Next, the light amount adjustment operation by the liquid crystal panel (3) will be specifically explained. The photodetector (8) detects the brightness at the time of photographing, and if it is determined that the photograph was taken in daylight where sufficient brightness can be obtained, the control circuit (7) activates the R filter (
The light transmittance of the pixel corresponding to the R) portion is made extremely small to substantially turn off the R filter, and in this state, the BG is set so that the brightness level obtained from the level detector (6) becomes the target level. By controlling the light transmittance of the pixel corresponding to the filter (BG) part, the optimum light amount can be adjusted to the CCD (4
) to achieve optimal exposure conditions. The spectral sensitivity characteristics of the CCD (4) at this time are shown by the curve (B) in Figure 5.
).

On the other hand, if the detection level at the photodetector (8) is so dark that it does not reach the predetermined value, it is determined that night photography is being performed, and R
The OFF state of the filter (R) is released, that is, the BG
Light transmittance of pixels in filter (BG) part is approximately 100%
At the same time, the light transmittance of the pixels in the R filter (R) part is set to approximately 100%, and as much light as possible is transmitted to the CCD (4
), and at the same time, the infrared lamp (9) attached to the imaging device is made to emit light so that sufficient output can be obtained from the CCD (4). Incidentally, the spectral sensitivity characteristics of the CCD (4) at this time are as shown by the curve (A) in FIG.

The arrangement example of the color filters of the liquid crystal panel (3) is not limited to that shown in Fig. 2, but the filters of the liquid crystal panel may be divided into a lattice shape as shown in Fig. 3, and the R filter and the BG filter may be arranged. It is also possible to arrange them so that they are adjacent on all four sides.

In addition, the level detector (6) doubles as the photodetector (8) that determines whether the photo is taken in daylight or at night, so that when the brightness level is below a predetermined level, the photo is taken at night, and when the brightness level is above a predetermined level, the photodetector (8) is used. It is also possible to determine that the photograph was taken in daylight.

(g) Effects of the Invention As described above, according to the present invention, the extremely simple configuration of disposing a liquid crystal panel in the optical path facilitates automatic exposure adjustment under a wide range of shooting conditions, from night photography to daylight photography. becomes possible.

[Brief explanation of the drawing]

The drawings all relate to embodiments of the present invention, and FIG. 1 is an overall circuit block diagram, FIGS. 2 and 3 are diagrams showing the filter arrangement of the liquid crystal panel, FIG. 4 is a characteristic diagram of each filter, and FIG. 5 is a diagram showing the filter arrangement of the liquid crystal panel.
The figure is a spectral sensitivity characteristic diagram of a CCD.

Claims (1)

[Claims] (1) A lens system that collects light and forms an image on an image sensor, an imaging device that captures the formed image and outputs a captured video signal, a detection device that detects brightness, and the lens system. and the imaging device, and includes a liquid crystal panel having a plurality of filter pixels whose light transmittance and spectral characteristics can be controlled by the output of the detection device.