Solid-state imaging device, driving method thereof, and camera

Abstract

A solid-state imaging device which optimizes gains for each color without a need for complicated control of changing the resistance values of variable resistances and switching switches depending on pixels from which signals are to be read, while preventing an S / N deterioration in AD conversion. The solid-state imaging device comprises: a plurality of pixels arranged in a matrix; column amplifiers, each amplifying signals generated by pixels of a corresponding one of columns of the matrix; and column AD converters, each performing AD conversion on a signal generated by a corresponding one of the column amplifiers, wherein each of the plurality of pixels corresponds to a color among colors, and each of the column amplifiers amplifies output signals generated by all pixels of a corresponding one of the colors, among pixels of the corresponding column of the matrix.

Description

technical field [0001] The present invention relates to a solid-state imaging device that converts light into electrical signals, and more particularly to a solid-state imaging device that includes an amplifier and an analog-to-digital converter for each column of a plurality of pixels arranged in a matrix. Background technique [0002] In a solid-state imaging device (color image sensor) capable of supporting colors, it is necessary to adjust the white balance in accordance with changes in the color temperature of an object or the like. For example, the color of the subject changes depending on the type of light (sunlight, fluorescent lamp, etc.), so it is necessary to process it in the solid-state imaging device so that the white color of the subject corresponds to the color temperature at this time. It is also white in the image signal. [0003] In the past, in order to adjust the white balance, either increase the number of bits (resolution) of the A / D converter and use...

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Problems solved by technology

[0007] However, a problem in the conventional method of increasing the number of bits of the AD converter for white balance is that, for example, as described in the above-mentioned Patent Document 2, a ramp waveform is used for the reference signal, and the reference signal changes until the corresponding When the comparator in the column shows that the pixel signal matches the reference signal, the counting clock increases, and the time it takes to count in the AD conversion method increases.

For example, to increase 1 bit, the AD conversion time will be doubled, which hinders the high-speed frame rate.

Also, for multi-bit, it is conceivable to use a plurality of the above-mentioned comparator circuits and perform parallel processing. In this case, the problem that occurs due to the increase of the circuit scale is that the chip area increases or the power consumption increases. Big and so on

In addition, in order to increase the number of bits of the AD converter, it is also considered that the frequency of the clock that can be used for conversion is increased, so there is a problem that the clock speed reaches the limit or the power consumption due to high-speed driving increases.

[0008] In addition, in the technique of the above-mentioned Patent Document 1, complex control such as appropriately changing the resistance values ​​of the variable resistors VR1 to VR4 or switching the switches SW1 to SW4 in accordance with the colors assigned to the readout pixels is required.

[0009] In addition, the problem in the technique of the above-mentioned Patent Document 2 is that the gain is adjusted for each color by changing the inclination of the ramp waveform. When a large gain is required, the inclination of the ramp waveform needs to be very small. In this way, the 1-bit comparison voltage used to compare the pixel signal and the reference signal will be reduced, that is to say, the weighted voltage will be reduced, resulting in an increase in the error during AD conversion and a decrease in the S / N ratio (signal / noise ratio). Difference

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