KR20060020236A - Cmos image sensor - Google Patents

Abstract

The present invention is to provide a CMOS image sensor for improving the image quality by removing offset noise caused by the path difference of the same pixel data, the first and second for transmitting the pixel data in the present invention for this purpose Analog data bus; A swapping unit for swapping and outputting the same pixel data transmitted to the first and second analog data buses through the same path; First and second ASPs for amplifying pixel data applied to the first and second output lines of the swapping unit and outputting the amplified pixel data through the A and B paths; A demultiplexer for outputting pixel data of the A and B paths alternately through one line, and reconstructing and outputting the order of the pixel data twisted by the swapping unit in the original image response in response to a control signal; And an analog-digital unit for converting and outputting output data of the demultiplexer into a digital signal.

Swapping, offset, pixel data, path, analog signal processing (ASP)

Description

CMOS image sensor {CMOS IMAGE SENSOR}             

1 is a block diagram of a CMOS image sensor according to the prior art.

FIG. 2 is an internal circuit diagram of the ASP unit of FIG. 1. FIG.

3 is an internal circuit diagram of an ASP unit according to an embodiment of the present invention.

4A and 4B illustrate the operation of the first swapping part of FIG. 3.

5 is an operational waveform diagram of the demultiplexer of FIG.

* Explanation of symbols for the main parts of the drawings

112, 114: First and second analog data buses

120: swapping part

132, 134: ASP-A, ASP-B

140: Demultiplexer

150: ADC unit

The present invention relates to a complementary metal oxide semiconductor (CMOS) image sensor, and more particularly, to a CMOS image sensor for improving image quality by eliminating offset due to a path difference.

As is well known, an image sensor is a semiconductor device that converts an optical image into an electrical signal. Among these, a charge coupled device (CCD) includes individual MOS capacitors in close proximity to each other. A charge carrier is a device that is stored and transported in a capacitor, and a CMOS image sensor is a device that employs a switching method of forming a pixel array using a CMOS integrated circuit fabrication technology and sequentially detecting an output thereof. CMOS image sensors have the great advantage of low power consumption, which is very useful for personal portable systems such as mobile phones.

1 is a configuration diagram of a CMOS image sensor according to the related art, and illustrates a process of processing image data (analog signals) obtained from pixels.

Referring to FIG. 1, a CMOS image sensor according to the prior art includes N (R), G (Green), and B (Blue) pixels in a row direction and M in a column direction. (N, M are integers) arranged in a matrix to form the pixel array 10, and a CDS unit 20 composed of one CDS (Correlated Double Sampling) for each column is placed on the lower side of the pixel array unit 10. Is placed. In the right side of the pixel array unit 10, an ASP unit (Analog Signal Processor) 30 for processing an analog signal output from the CDS unit 20 is disposed.

In addition, the signal output from the CDS unit 20 is transmitted to the ASP unit 30 through the analog data bus, the analog data bus is composed of the first analog data bus 52 and the second analog data bus 54. do.

The output of each CDS of the CDS unit 20 is controlled by the selector 60 controlled by the selection signals CS0, CS1, CS2... Generated by the column driver 40. It is loaded on the data buses 52 and 54. The selector 60 is composed of a conventional switch connecting the CDS output terminal and the analog data bus.

For reference, the CDS samples the reset signal and the data signal at each pixel and loads them on the analog data bus, and the ASP unit 60 obtains a difference between the reset signal and the data signal. It amplifies. Thus, it is possible to obtain pure pixel data for the image of the actual subject.

FIG. 2 is an internal circuit diagram of the ASP unit 30 of FIG. 1.

Referring to FIG. 2, the ASP unit 30 includes ASP-A and ASP-B 32 and 34 for amplifying data applied to the first and second analog data buses 52 and 54, respectively, and ASP-. A demultiplexer 36 for alternately outputting pixel data of the A and ASP-Bs 32 and 34 into one line, and an ADC unit 38 for converting the output signal of the demultiplexer 36 into a digital signal and outputting the digital signal. It is provided.

1 and 2, the operation of the CMOS image sensor according to the prior art will be briefly described.

First, when the CMOS image sensor reads data of a pixel, pixels of any row of the pixel array unit 10 are transferred to each CDS of the CDS unit 20 at the same time (same clock). Subsequently, the output of the CDS unit 20 is controlled by the column driver 40 and applied to the first and second analog data buses 52 and 54 by the selector 60 and sequentially transferred to the ASP unit 30. do.

On the other hand, considering the order in which the data of the pixels located in the first and second rows are loaded on the first and second analog data buses 52 and 54, it is shown in Table 1 below.

First row Second row First analog data bus B ₁₁ B ₁₃ B ₁₅ … G ₂₁ G ₂₃ G ₂₅ … Second analog data bus G ₁₂ G ₁₄ G ₁₆ … R ₂₂ R ₂₄ R ₂₆ …

Subsequently, the data of the first and second analog data buses 52 and 54 are alternately selected and output by the demultiplexer 36, and are converted into digital signals OUT by the ADC unit 38. Is output.

Meanwhile, referring to Table 1, the pixel data of the odd-numbered column of the pixel data positioned in the same row sampled by the CDS unit 20 at one time is selected by the selector 60 by the first analog data bus 52. It can be seen that the pixel data of the even-numbered column is applied to the second analog data bus 54.

However, depending on the column in which the same G pixel data is located, the A path is passed through the first analog data bus 52 or the B path is passed through the second analog data bus 54. Will pass. R and B pixel data also passes through A or B paths (A-Path and B-Path), depending on the column in which they are located. In this way, although the same data is passed through different paths, the result is offset noise.

If an offset occurs due to such a path difference, offset noise may appear on the actual image, thereby degrading the quality of the image.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems of the prior art, and an object thereof is to provide a CMOS image sensor for improving image quality by removing offset noise caused by path differences of the same pixel data. .

According to an aspect of the present invention, a CMOS image sensor includes a first and a second analog data bus for transmitting pixel data; A swapping unit for swapping and outputting the same pixel data transmitted to the first and second analog data buses through the same path; First and second ASPs for amplifying pixel data applied to the first and second output lines of the swapping unit and outputting the amplified pixel data through the A and B paths; A demultiplexer for outputting pixel data of the A and B paths alternately through one line, and reconstructing and outputting the order of the pixel data twisted by the swapping unit in the original image response in response to a control signal; And an analog-digital unit for converting and outputting the output data of the demultiplexer into a digital signal.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

3 is a block diagram illustrating an ASP unit according to an embodiment of the present invention.

Referring to FIG. 3, an ASP unit according to an embodiment of the present invention may include first and second analog data buses 112 and 114 and first and second analog data buses 112 and 114 for transmitting pixel data. A and B paths (A) by amplifying the swapping unit 120 and the pixel data applied to the first and second output lines of the swapping unit 120 so as to swap the same pixel data transmitted through the same path. ASP-A and ASP-B (132, 134) for output as -Path, B-Path) and pixel data of A and B paths (A-Path, B-Path) are alternately output through one line However, in response to the control signal (swp_ctr), the demultiplexer 140 for restoring and outputting the order of the pixel data twisted by the swapping unit 120 to the original image and the output data of the demultiplexer 140 as the digital signal OUT. ADC unit 150 for converting and outputting is provided.

Next, an operation of a CMOS image sensor having an ASP unit according to an exemplary embodiment will be described.

First, FIG. 4A illustrates a case where the swapping unit 120 passes pixel data of a first row applied through the first and second analog data buses 112 and 114.

After the CDS section samples and stores the pixel data "B ₁₁ , G ₁₂ , B ₁₃ , G ₁₄ , B ₁₅ , G ₁₆ , ..." located in the first row, the selection section (not shown) causes an odd number of columns. Pixel data " B ₁₁ , B ₁₃ , B ₁₅ ,… " positioned in the first column is applied to the first analog data bus 112, and pixel data " G ₁₂ , G ₁₄ , G ₁₆ , Is applied to the second analog data bus 114. Subsequently, when the swapping unit 120 passes the pixel data of the first and second analog data buses 112 and 114, it is A and B through the corresponding ASP-A and ASP-B 132 and 134 of each bus. Passed by path (A-Path, B-Path). Accordingly, the B pixel data "B ₁₁ , B ₁₃ , B ₁₅ , ..." of the first row passes through the A path, and the G pixel data "G ₁₂ , G ₁₄ , G ₁₆ , ..." represents the B path ( B-Path). Arranged in this order is the column corresponding to the first row of Table 2.

First row Second row  Path A B ₁₁ B ₁₃ B ₁₅ … R ₂₂ R ₂₄ R ₂₆ …  Path B G ₁₂ G ₁₄ G ₁₆ … G ₂₁ G ₂₃ G ₂₅ …

4B is a diagram illustrating that the swapping unit 120 swaps and outputs pixel data of the first and second analog data buses 112 and 114.

As shown in the figure, the G pixel data "G ₂₁ , G ₂₃ , G ₂₅ , ..." applied to the first analog data bus 112 and the R pixel data "applied to the second analog data bus 114" are shown. R ₂₂ , R ₂₄ , R ₂₆ ,... "Are outputted while crossing each other by the swapping operation of the swapping part 120. Subsequently, each output signal of the swapping unit 120 passes through the A and B paths A-Path and B-Path through the corresponding ASP-A and ASP-B 132 and 134, respectively. This arrangement corresponds to the column of the second row of Table 2, wherein R pixel data "R ₂₂ , R ₂₄ , R ₂₆ , ..." denotes an A path and G pixel data "G ₂₁ , G" ₂₃ , G ₂₅ ,... Can be seen to go through the B-Path.

As described above, the ASP unit of the present invention includes a swapping unit to pass pixel data of odd-numbered rows and to swap pixel data of even-numbered rows, so that the R and G pixel data use the A path and the G pixel data. Passes through the A path.

Therefore, the above-described CMOS image sensor according to the present invention includes a swapping unit to transmit the same pixel data through the same path, thereby eliminating offset caused by the same pixel data passing through different paths as in the related art.

Subsequently, the demultiplexer 140 alternately outputs pixel data of the A and B paths (A-Path and B-Path) through one line in response to the control signal (swp_ctr), and outputs it according to the control signal (swp_ctr). The order of doing is different. This will be described with reference to the drawings.

FIG. 5 is an operation waveform diagram of the demultiplexer 140, and illustrates a selection path of the demultiplexer according to the control signal swp_ctr and an output of the demultiplexer. In addition, in case of 'α', pixel data of the first row is applied through A and B paths (A-Path and B-Path), and in case of 'β', pixel data of the second row is applied.                     

First, in the case of 'α', since the control signal swp_ctr has a logic level 'L', the demultiplexer 140 alternately outputs pixel data in the order of the A path and the B path. . Accordingly, B ₁₁ pixel data applied to the A path is first output, and then G ₁₂ pixel data applied to the B path is output.

In addition, in the case of 'β', since the control signal swp_ctr has a logic level 'H', the demultiplexer outputs pixel data of the B path and then outputs paxel data of the A path. Therefore, G ₂₁ pixel data applied to the B path is output, followed by R ₂₂ pixel data.

As described above, Table 3 summarizes pixel data output by the demultiplexer through the process.

'α' case (first row) 'β' case (second row) Demultiplexer B ₁₁ G ₁₂ B ₁₃ G ₁₄ B ₁₅ G ₁₆ … G ₂₁ R ₂₂ G ₂₃ R ₂₄ G ₂₅ R ₂₆ …

Referring to Table 3, it can be seen that the demultiplexer rearranges and outputs the order of pixel data that is distorted by the swapping unit.

Therefore, the CMOS image sensor according to the present invention described above includes a swapping unit to remove an offset caused by a difference in a path through the same pixel, so that the same pixel data is swapped to pass through the same path. In addition, because of such swapping, the pixel array is output in the same order as that of the pixel array because the pixel array is rearranged in a different order from the pixel array.

As such, the CMOS image sensor according to the present invention can remove offset noise caused by the path difference, thereby improving image quality.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

The present invention described above improves image quality by removing offset noise generated by swapping the same pixel data through different paths. In addition, since the order of pixel data is changed due to swapping, the original pixel image is restored through a process of demultiplexing it.

Claims (3)

First and second analog data buses for transmitting pixel data; A swapping unit for swapping and outputting the same pixel data transmitted to the first and second analog data buses through the same path; First and second ASPs for amplifying pixel data applied to the first and second output lines of the swapping unit and outputting the amplified pixel data through the A and B paths; A demultiplexer for outputting pixel data of the A and B paths alternately through one line, and reconstructing and outputting the order of the pixel data twisted by the swapping unit in the original image response in response to a control signal; And An analog-digital unit for converting output data of the demultiplexer into a digital signal and outputting the digital signal; CMOS image sensor having a. The method of claim 1, The swapping unit, While the odd pixel data is transmitted to the first and second analog data buses, the signal is passed to the first and second output lines, and the pixel data of the first analog data bus is transmitted while the even pixel data is transmitted. And swapping pixel data of the second analog data bus to the first output line to the second output line. The method according to claim 1 or 2, A pixel array unit in which R (Red), G (Green), and B (Blue) pixels are arranged in a matrix in N rows in a row direction and M in a column direction (N and M are integers); A CDS unit disposed at a lower side of the pixel array unit and configured by one correlated double sampling (CDS) for each column; A column driver for generating a selection signal; And A selection unit for applying the output signal of the CDS to the first or second analog data bus in response to the selection signal; CMOS image sensor further comprising.

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