JPH0759088B2 - Solid-state image sensor with optical white - Google Patents

Description

The present invention relates to a two-dimensional solid-state image sensor, and more particularly to a solid-state image sensor for a single-plate color camera.

"Prior Art" Conventionally, this type of solid-state imaging device has been constituted by three regions as shown in FIG. That is, the video signal is output while feeling the light, and because the scanning period (non-blanking period) is the effective pixel area 1 output as a video signal from the TV camera and the light is detected, the video signal is output. It consisted of an invalid pixel area 3 that is not output as a video signal from the TV camera because it is within a line period (also referred to as a blanking period or a BLK period), and an optical black region 2 that generates a black reference signal without light being sensed. . CCD (Charge Coupled Decode) is set in the effective pixel area 1 and the invalid pixel area 3.
A color filter 5 of a primary color or a complementary color is attached on the light receiving surface of the vice) 4, and a light shielding plate 6 is attached on the CCD substrate 4 in the optical black area 2.

4A and 4B are waveform diagrams of an output signal obtained from the conventional solid-state imaging device, and B is a waveform of a part of A in an enlarged time axis. The pulse-shaped waveform 13 having a constant amplitude above the time axis has a repetition frequency of, for example, 7 to 15 MHz.
Is called a reset pulse, and the lower waveform 14 is a video signal. In the figure, the periods t ₁ and t ₅ correspond to the invalid pixel region 3, and the periods t ₂ and t ₄ correspond to the optical black region 2. The period t ₃ is a period in which there is no corresponding CCD region, t ₆ is a horizontal BLK period, and t ₇ is a horizontal video period (horizontal non-BLK period) corresponding to the effective pixel region.

By the way, the human eye has some adaptability to light, and a white subject looks white both in indoor lighting and outdoors. However, since video cameras do not have the adaptability of the human eye, white subjects can be seen as reddish white or bluish white, for example, depending on the lighting conditions at the shooting site (mainly due to differences in light sources). A color signal having such a hue can be obtained via the image pickup tube. Therefore, it is necessary to correct the obtained color signal so that the color tone of a white subject in the reproduced image can be reproduced as white as faithfully as possible. Therefore, a white balance adjusting circuit is used in the video camera. (By doing so, it goes without saying that the color tone of a general subject can be faithfully reproduced to some extent regardless of the difference in lighting conditions.) In the conventional single-plate color camera using one solid-state image sensor, , A manual white balance method that manually adjusts the white balance as a white balance method, a one-push auto white balance method that captures a white object and white balances it, or a sensor that automatically adjusts the white balance at all times Sensor type full auto white balance system, TTL (Through The Lense) type full auto white that automatically balances white balance by comparing and averaging the red (RY) and blue (BY) components of the screen Balanced methods have been put to practical use.

However, each method has advantages and disadvantages, and it is not always possible to achieve perfect color balance. That is, the manual white balance method has a drawback that it is very troublesome because it is necessary to manually re-adjust the white balance each time the imaged scene changes. Even with the one-push auto white balance method, there is a drawback in that it is necessary to press the button to re-adjust the white balance if the shooting scene changes, and the color cannot be adjusted without a white subject. In addition, the sensor type full auto white balance method has a drawback in that the colors do not match when zooming up to shoot a distant subject at a telephoto position because the color temperature of the ambient light on the front surface of the camera is detected. The drawbacks of each of these methods can be solved by using the TTL full auto white balance method. However
The TTL full-auto white balance method has a drawback that the saturation of colors is reduced because it compares red and blue components with reference values and reduces strong color components to average them. Further, this method has a problem that if the sky enters the upper part of the screen during outdoor shooting, the color temperature of the sky is higher than that on the ground, and the color balance on the ground tends to be lost. Further, when the illuminance is low, it is difficult to achieve color balance because the signal levels of the red (RY) and blue (BY) components in the screen are low.

An object of the present invention is to solve these problems of the conventional TTL full-auto white balance method and to improve the color balance even when the screen has a sky at the top and low illumination without reducing the color saturation. The present invention aims to provide a new solid-state image sensor that contributes to the realization of the TTL full auto white balance method.

[Means for Solving the Problem] In the solid-state image pickup device with optical white of the present invention, a band-shaped light-shielding plate is attached to a pair of left and right peripheral portions of the light-receiving surface of the two-dimensional solid-state image pickup device to form an optical black region. A band-shaped white filter is attached to the upper, lower, left, and right peripheral portions of the light-receiving surface of the image sensor excluding the optical black area to form an optical white area, and the light-receiving surface surrounded by the optical white area is formed. The color filter is attached, and the effective pixel area is formed by the entire area of the image pickup element to which the color filter is attached or the area excluding the upper and lower and left and right peripheral portions, and the image pickup to which the color filter is attached. An invalid pixel area is formed by the area other than the effective pixel area and the optical white area in the element. There.

"Embodiment" An embodiment of the present invention is shown in Fig. 1 by assigning the same reference numerals to portions corresponding to Fig. 3, and duplicate description will be omitted. In the solid-state imaging device of the present invention, a white filter 11 is attached to the peripheral portion or all of the invalid pixel region 3 instead of the conventional color filter 5, and an optical white (also referred to as OW) generating a white reference signal is formed. A region 3a is provided. Ie
The OW region 3a is for sensing the light transmitted through the white filter 11 and generating a white reference signal.

FIG. 2 is an output waveform obtained from the solid-state image sensor of FIG. 1, and parts corresponding to those of FIG.
Overlapping description is omitted. Period t ₁ corresponding to invalid pixel region 3
And t ₅ are divided into periods (also referred to as OW signal periods) t _1a and t _5a corresponding to the OW region 3a and periods t _1b and t _5b other than the periods.
(However, there are cases where t _1b = 0 or t _5b = 0.)
The video signal at t _1a and t _5a is a white reference signal, and its peak value gives a reference for white luminance (brightness).

The solid-state image sensor according to the present invention can be used in a single-plate color camera to adopt the TTL full auto white balance method. In this case, the process circuit in the video camera automatically and automatically adjusts the white balance in accordance with the white reference signal. Adjustment control is possible. A comparator or a microcomputer may be used as the control means.

If the sky appears at the top of the screen when shooting outdoors, white balance is adjusted by the white reference signals (also called the OW signal) in the OW areas on the left and right of the screen and the OW signal is weighted on the top and bottom, and averaged. By performing processing such as conversion, it is possible to always achieve optimum white balance.

It is possible to adjust the white balance by using the OW signals at the top, bottom, left and right of the screen even at low illuminance, and there is no fear of reducing the saturation as in the past. Since the OW signal is a signal that exists only during the BLK period, it does not adversely affect the video signal output of the camera.

"Effects of the Invention" As described above, the solid-state imaging device of the present invention is provided with the optical white (OW) region in which the white filter is attached to the invalid pixel region around the effective pixel region.
By using the white reference signal obtained from the OW area, the white balance adjustment can always be automatically performed by the process circuit in the video camera, and the saturation of the reproduced image is not deteriorated by the white balance adjustment. In addition, the white balance can be adjusted by using the element of the present invention even when the screen has a sky in the upper part or when the illuminance is low, and the conventional problems can be solved.

[Brief description of drawings]

1A and 1B are a plan view and an AA sectional view of an embodiment of the present invention, FIG. 2 is a signal waveform diagram output from the embodiment of FIG. 1, and FIGS. FIG. 4A is a plan view and a sectional view taken along the line AA of the solid-state image sensor of FIG. 4, FIG. 4A is a signal waveform diagram output from the solid-state image sensor of FIG. 3, and FIG. 4B is a time axis of a part of FIG. 4A. It is an enlarged waveform diagram.

Claims (1)

[Claims] 1. A two-dimensional solid-state image sensor has a pair of left and right peripheral portions of a light-receiving surface on which a band-shaped light-shielding plate is attached to form an optical black region, and the upper and lower parts of the light-receiving face of the image sensor except for the optical black region. A band-shaped white filter is attached to the left and right peripheral portions to form an optical white region, and a color filter is attached to the light-receiving surface surrounded by the optical white region, and the color filter is attached. An effective pixel area is formed by the entire area of the image sensor or an area excluding the upper and lower and left and right peripheral parts, and by the area other than the effective pixel area in the image sensor to which the color filter is attached and the optical white area. A solid-state image sensor with optical white, characterized in that an invalid pixel region is formed.