KR20060076811A - Image sensor using a single pga - Google Patents

Abstract

The present invention relates to an image sensor using a single PGA. The image sensor according to the present invention divides a plurality of gains for a plurality of color pixels into a plurality of partial gains, extracts one partial gain for each gain for a color pixel, and encodes them into a plurality of single gains. A gain encoder that sequentially outputs single gains in synchronization with the analog data collected from the color pixels, a gain decoder that decodes the single gain received from the gain encoder into partial gains for each color pixel, and analog data and color pixels collected from the color pixels. A programmable gain amplifier (PGA) for outputting amplified analog data based on the partial gain decoded by a corresponding gain decoder and an analog to digital converter (ADC) for converting and outputting the amplified analog data into digital data.

PGA, ADC, Image Sensor, Gain, Partial Gain

Description

Image sensor using a single PGA}             

1 is a view showing the configuration of an image sensor according to the prior art.

2 is a view showing the configuration of another image sensor according to the prior art.

3 is a diagram illustrating a configuration of an image sensor according to an exemplary embodiment of the present invention.

4 is a diagram showing an internal configuration of a PGA according to an embodiment of the present invention.

FIG. 5 is a timing diagram illustrating a method in which gain for each color pixel is encoded in synchronization with analog data in a gain encoder according to an exemplary embodiment of the present invention. FIG.

<Explanation of symbols for the main parts of the drawings>

33: Programmable Gain Amplifier (PGA)

37: ADC (Analog to Digital Converter)

35: Gain Decoder

39: Gain Encoder

41: sub amplifier

The present invention relates to an image sensor using a single PGA.

The image sensor refers to a semiconductor device that converts an optical image into an electrical signal. An image sensor for realizing a color image includes an array of color filters on the light sensing portion that receives and receives light from the outside to generate and accumulate photocharges. The color filter array (CFA) consists of three colors: red, green, and blue, or three colors: yellow, magenta, and cyan. It is made of collar. In addition, the image sensor is composed of a light sensing portion for detecting light and a logic circuit portion for processing the detected light into an electrical signal to make data. The logic circuit portion of the conventional image sensor will be described with reference to FIGS. 1 and 2 as follows.

1 is a view showing the configuration of an image sensor according to the prior art.

Referring to FIG. 1, a conventional image sensor includes a programmable gain amplifier (PGA) for amplifying each pixel value by color pixel arrays of R, G, and B according to respective gain and offset correction values, and an analog amplified by PGA. An analog to digital converter (ADC) 13 for converting data into digital data and a multiplexer 15 for integrating digital data received from each ADC 13 and outputting image output data are included. 2 is a view showing the configuration of a conventional image sensor according to another embodiment. The image sensor shown in FIG. 2 is a case where R and B are bundled and processed into one PGA. In this case, the image sensor includes two PGAs 11 and an ADC 13. For example, although not described, a conventional image sensor may be configured with color pixels R, Gr, Gb, and B, which will require four PGAs and an ADC.

As described above, the conventional image sensor is composed of a plurality of PGAs and ADCs corresponding to each color pixel, and of course, addition of a multiplexer is required. Therefore, in the conventional image sensor, the gain value and the offset must be corrected for each PGA, and the linearity of each PGA is different, which causes problems in the operation of the AWB. In addition, due to the large number of PGAs, the area of the logic circuit portion is increased, power consumption is high, and multiplexer circuits integrating data output by each PGA and ADC are required.

An object of the present invention for solving the above problems is to provide an image sensor capable of processing all R pixels, G pixels, B pixels using a single PGA.

Another object of the present invention is to provide an image sensor using a single PGA that can simplify the circuit and reduce power consumption and internal footprint.

Another object of the present invention is to provide an image sensor using a single PGA that can eliminate non-uniform gain ratios and offsets.

In order to achieve the above objects, according to an aspect of the present invention, a plurality of gains for a plurality of color pixels are divided into a plurality of partial gains, and one partial gain is sequentially extracted for each gain for the color pixels. A gain encoder for sequentially outputting the single gains in synchronization with the analog data collected by the color pixels after encoding with a plurality of single gains, and a gain for decoding the single gain received from the gain encoder into the partial gain for each color pixel A programmable gain amplifier (PGA) for outputting amplified analog data based on a decoder, analog data collected from the color pixels, and a partial gain decoded by the gain decoder corresponding to the color pixels, and converting the amplified analog data into digital data To analog output (Analog to Digital C) It is possible to provide an image sensor using a single PGA including an onverter.

In a preferred embodiment, the single gain is characterized by including partial gains for the plurality of color pixels. In addition, the PGA includes as many sub-amps as the number of partial gains, and the sub-amps are coupled in series. The plurality of partial gains may be gains of the sub amplifiers, respectively. The color pixel may be any one of an R pixel, a G pixel, a B pixel, a Gr pixel, and a Gb pixel. In addition, the gain decoder is characterized in that included in the PGA.

Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram illustrating a configuration of an image sensor according to an exemplary embodiment of the present invention.

Referring to FIG. 3, an image sensor according to the present invention includes a single programmable gain amplifier (PGA) 33 and an analog to digital converter (ADC) 37, and further includes a gain encoder 39 and a gain decoder 35. Include. Here, the PGA 33 and the gain decoder 35 constitute an AGC (Auto Gain Control) 31, and the AGC 31 corresponds to an analog signal processor.

The PGA 33 amplifies the analog data 43 collected at each color pixel with a gain corresponding to each color pixel. The ADC 37 performs a function of outputting analog data amplified by the PGA 33 as digital data. The digital data output from the ADC 37 corresponds to the output of the video signal. The gain encoder 39 and the gain decoder 35 each encode and decode the gain 45 for each color pixel on the time axis.

An operation method of the image sensor having the above configuration will be described below. First, gains 45 for each color pixel are stored in the R, Gr, Gb, and B gain registers inside the image sensor. The gain 45 for each color pixel is a single gain 41 having a size of 8 bits in the gain encoder 39 in synchronization with the analog data 43 collected in each color pixel that is output in synchronization with a clock. Is encoded. The encoding process in the gain encoder 39 will be described in detail with reference to FIG.

Meanwhile, analog data 43 collected from each color pixel is input to the PGA 33. The single gain 41 encoded in synchronization with the analog data 43 is decoded by the gain decoder 35 and then input to the PGA 33. The PGA 33 amplifies the analog data according to the gain corresponding to each color pixel based on the received analog data 43 and the decoded gain and outputs the analog data to the ADC 37. Thereafter, the analog data amplified by the PGA 33 is converted into digital data by the ADC 37 and output as an image signal.

In this configuration, the gain decoder 35 may be designed to be located inside or outside the PGA 33. In the present invention, for convenience of description, the case in which the color pixel array of the image sensor includes R pixels, Gr pixels, Gb pixels, and B pixels has been described as an example, but the color pixel array includes R pixels, G pixels, B pixels, or G Pixels, B / R pixels, or Cy pixels, Mg pixels, Ye pixels may also be used.

4 is a diagram illustrating an internal configuration of a PGA according to an exemplary embodiment of the present invention.

4, the PGA 33 according to the present invention includes a plurality of sub amplifiers 34, and each sub amplifier 34 is coupled in series. Although the PGA 33 is described as being composed of three sub amplifiers 34 in the figure, the number of sub amplifiers 34 is not necessarily limited to three. Here, the PGA 33 includes sub amplifiers 34 as many as the number of partial gains in which the gain for each color pixel is divided by the gain encoder, and the partial gains correspond to the gains of the sub amplifier 34, respectively. A single gain including the partial gains for each color pixel encoded at the gain encoder is decoded into the partial gains for each color pixel at the gain decoder 35, which are gains of the sub amplifier 34 at the gain decoder 35. Are respectively applied. The PGA 33 having the above structure amplifies the received analog data one by one as many steps as the number of sub-amplifiers 34, instead of amplifying them at once. For example, if the gain for the R pixel has a partial gain of R1, R2, and R3, when the analog data collected at the R pixel is input to the PGA 33, the analog data is a sub having a gain of R1, R2, and R3, respectively. It is amplified in three stages by the amplifiers 34.

FIG. 5 is a timing diagram illustrating a method in which gain for each color pixel is encoded in synchronization with analog data in a gain encoder according to an exemplary embodiment of the present invention.

Referring to FIG. 5, ADIN 51 is analog data collected from color pixels and input to PGA, GAIN 55 is partial gain for each color pixel, and ADOUT 57 is amplified analog data output from PGA. .

The ADIN 511 is input to the PGA in accordance with the CLOCK 53 signal, and the GAIN 55 is encoded in the gain encoder in synchronization with the ADIN 51 and decoded in the gain decoder and then input as the gain value of the PGA. do. Here, if the gain for the R pixel is called gain R and the gain for the G pixel is called gain G, the gain R and the gain G are divided in the gain encoder by R1, R2, R3 and partial gains of G1, G2, and G3, respectively. . In this case, the gain R and the gain G have values corresponding to the product of R1, R2, R3 and partial gains of G1, G2, and G3, respectively. The divided gains divided in the gain encoder are encoded as a single gain in the gain encoder and are output in synchronization with the ADIN 51. That is, when analog data of the R pixel, which is the initial value of the ADIN 51, is input to the PGA, the partial gains R1, R2, and R3 of the gain R are encoded with a single gain, and are sequentially input to the gain decoder and the PGA. Wherein the single gain includes partial gain for a plurality of color pixels. In the example of this figure, it can be seen that R1, which is a partial gain of gain R, is encoded with a single gain along with G3, which is partial gain of gain G. In the example of this figure, only the color pixel R and the color pixel G have been described as an example, but may further include the color pixel B, and it is also applicable to the case having four color pixels. In addition, although the partial gain is described in the case of three in the example of this figure, the number of partial gains is not necessarily limited to this number and may be designed to have a plurality of numbers.

The single gain is decoded as a partial gain for each color pixel in the gain decoder and input to the PGA. When all partial gains are input to the PGA, the amplified analog data ADOUT 57 is output to the out end of the PGA.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

According to the present invention, the use of a single PGA in the image sensor has the effect of simplifying the circuit, reducing power consumption and internal area, and eliminating non-uniform gain ratios and offsets.

Claims (6)

A plurality of gains for a plurality of color pixels are divided into a plurality of partial gains, one partial gain for each of the gains for the color pixels is sequentially extracted, encoded into a plurality of single gains, and then collected in the color pixels. A gain encoder that sequentially outputs the single gains in synchronization with analog data; A gain decoder for decoding the single gain received from the gain encoder into the partial gain for each color pixel; A programmable gain amplifier (PGA) for outputting amplified analog data based on the analog data collected from the color pixels and the partial gain decoded by the gain decoder corresponding to the color pixels; And ADC (Analog to Digital Converter) for converting and outputting the amplified analog data into digital data Image sensor using a single PGA comprising a. The method of claim 1, The single gain comprises partial gains for the plurality of color pixels Image sensor using a single PGA characterized in that. The method of claim 1, The PGA includes as many sub-amps as the number of partial gains, the sub-amps being coupled in series Image sensor using a single PGA characterized in that. The method of claim 3, Wherein the plurality of partial gains are each gain of the sub-amplifier Image sensor using a single PGA characterized in that. The method of claim 1, The color pixel is any one of an R pixel, a G pixel, a B pixel, a Gr pixel, and a Gb pixel. Image sensor using a single PGA characterized in that. The method of claim 1, The gain decoder is included in the PGA Image sensor using a single PGA characterized in that.

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