TWI545953B - Image sensor and method for driving thereof - Google Patents

Description

Image sensor and driving method thereof

The present invention claims priority to Korean Patent Application No. 10-2011-0139625, filed on Dec. 21, 2011, which is hereby incorporated by reference.

The present invention provides an additional circuit for detecting noise of a reference signal of each column and each row in a pixel array in an image sensor, and therefore, due to a change in the reference signal ( Fluted), the comparator reduces fixed pattern noise for accurate image processing.

The present disclosure relates to an image sensor and a method of driving the same, and more particularly to an image sensor including an additional adjustment circuit for causing a comparator to detect in a typical pixel array. Noise to compensate for noise occurring in analog-like front-end circuits with typical pixel and pixel array configurations, and the driving method of the image sensor.

The analog correlation double sampling (CDS) circuit was used in 1974 to reduce the noise of charge coupled device (CCD) image sensors and was later applied to a complementary metal oxide semiconductor (CMOS) image sensor. .

FIG. 1A is an example of an analog CDS circuit, and FIG. 1B is an operation timing. Referring to Figures 1A and 1B, the operation of a CDS circuit will be described in terms of the operation of a pixel. First, in operation (1), when a reset transistor RST is turned on in a cell pixel cell 10, the voltage of a floating diffusion region FD reaches a power supply voltage Vaapix. When a switch PCLP and a switch SH are enclosed in a column of cells 20 of a column of lines, wherein the column lines have a plurality of pixels arranged in a column, a voltage Vclp is applied to a node b, thus crossing a capacitor Csh The voltage becomes about 0V and is initialized. Next, in the operation (2), the power supply voltage Vaapix of the floating diffusion FD, for example, the voltage level, is output via a transistor M1, and a voltage Va_rst is generated at an output node a. Then, at job (3), the switch PCLP is turned off. It enables a singal sampling operation. In operation (4), when a transfer transistor TX is turned on, the voltage of the floating diffusion region FD becomes an image voltage Vimg due to the accumulation of photocharges in a photodiode PD and transmitted to the floating diffusion through the transmission transistor TX. District FD. In operation (5), an image voltage Vimg is applied to the output node a through the transistor M1, and therefore, the voltage of the output node a is changed from Va_rst to Va_img. Therefore, the voltage applied to the node b is changed from Vclp to Vclp - (Va_rst - Va_img) = Vclp - ΔV.

At this time, since a voltage difference is detected by the capacitance Csh, the noise influence from the transistor M1 can be removed. However, this analog CDS circuit is susceptible to noise damage occurring at one stage after the capacitor Csh, for example, the fixed pattern noise of the comparator itself. In particular, when there are a plurality of comparators arranged in each column, the offset voltage at each comparator changes, so it is necessary to perform noise processing for each column. In addition, since the distance between the comparators changes in each line, it is also necessary to consider the noise processing of the distance. The fixed pattern noise from these comparators can occur due to a change in a reference signal generator input to a comparator.

The present invention provides an additional circuit for detecting noise of a reference signal for each column and each row of a pixel array in an image sensor, so that the comparator reduces fixed pattern noise due to fluctuations in the reference signal. In addition, accurate image processing can be performed.

In one embodiment, an image sensor processes a signal output from the plurality of pixels: a counting circuit receives an image signal output from a pixel array, the pixel array includes the one pixel and the one row a plurality of pixels, and converting the received image signal into digital data, the counting circuit comprising a column corresponding to the pixel array of the comparator; an adjusting circuit comprising a plurality of switches, and a column line arranged with the plurality of switches And a line of lines, wherein a reference signal for comparing operations of the counting circuit is applied to one end of the switches, and the other end is connected to the comparators; and a controller generates a control signal for driving the arrangement The switches of the line of the adjustment circuit and the noise of the comparators corresponding to each column of the pixel array.

In another embodiment, an image sensor processing a signal output from the plurality of pixels includes: a counting circuit receiving an image signal output from a pixel array, the pixel array being included in one column and one row The plurality of pixels, and converting the received image signal into digital data, the counting circuit comprising a column corresponding to the pixel array of the comparator; and an adjusting circuit comprising a plurality of switches and a line of the array arranged with the switches ( Row line), wherein a reference signal for comparing the operations of the counting circuit is applied to one end of the switches, and the other end is connected to the comparators; and a controller generates a control signal for each time The one line of the pixel array is controlled to drive a plurality of switches in the line of the adjustment circuit and to detect noise of a plurality of comparators corresponding to each column of the pixel array.

In still another embodiment, a method for driving an image sensor to process a signal output from a plurality of pixels, wherein the image sensor includes: a counting circuit receiving an image output from a pixel array a pixel, the pixel array includes the pixels in a column and a row, and converts the received image signal into digital data, and the counting circuit includes a column corresponding to a pixel array of the comparator; An adjustment circuit includes a plurality of switches and a row line arranged with the switches, the method comprising: driving a plurality of switches arranged in the one line of the pixel array; and operating according to the comparators Timing, generating a reference signal; detecting noise of a plurality of comparators corresponding to each column of the pixel array; controlling, in each row of the pixel array, a plurality of pixels for a predetermined period; and The noise detected by the comparators corrects an image signal corresponding to some pixels.

One or more embodiments of the present invention will be described in conjunction with the drawings. Other features will become apparent from the description and drawings.

In the following, the disclosure and examples of the present invention will be described and illustrated in detail in accordance with the embodiments of the invention.

The invention will be described in detail with reference to the drawings. In the description of the present invention "pixel control for each line of a pixel array", a pixel control signal can be output for controlling the pixels in each line by each line. For example, a pixel control signal can be described as: in a pixel, a series of operations performed by a signal applied from a row of decoders to control on-off of a crystal that constitutes a pixel. A reset signal and an image signal are output from each pixel.

FIG. 2 illustrates a configuration of an image sensor according to an embodiment. Referring to FIG. 2, an image sensor according to an embodiment includes a counter circuit 400, an adjustment circuit 200, and a controller 500. The counting circuit 400 receives an image signal output from the pixel array 100. The pixel array 100 includes a plurality of pixels in a matrix, and converts the image signal into digital data. At the same time, the counting circuit 400 includes comparators 401, 402 corresponding to one of the columns of the pixel array 100. The adjustment circuit 200 includes a plurality of switches SW1, SW2, SW3, SW4, SW5; and a column line 210 and a row line 220. A reference signal Vref for comparison operation of the counting circuit 400 is applied to one end of the switches, and the other end thereof is connected to the comparators 401, 402. The controller 500 generates a control signal for driving the switches SW1, SW2, and SW3 arranged in the row 220 of the adjustment circuit 200 and controlling the noise of the comparators 401 and 402 of each column of the corresponding pixel array 100. . In addition, the image sensor may further include an additional comparator 410 for detecting a noise signal outputted from one of the alignment lines 210 of the adjustment circuit 200. Furthermore, the image sensor further includes a row of decoders 300 for outputting a pixel control signal to each row. The pixel control signal controls the pixels of each row according to the control of the controller 500.

The controller 500 can control the pixel array 100 by each row and can output an image signal from the pixel array 100. The controller 500 can apply a signal to each of the rows 104, 102 for a predetermined period of time, and apply a signal to drive the switches arranged on the row of lines 220 of the adjustment circuit 200. For example, the image signal is output from a frame of all pixels of the pixel array 100 and converted into a frame. Accordingly, controller 500 can drive additional comparator 410 and comparators 401, 402 in synchronization with the output of the signal from the row of lines 220. Furthermore, the image sensor according to an embodiment includes: the reference signal generator 450 generates the reference signal Vref to the switches SW1, SW2, SW3, SW4, SW5 arranged on the column line 210 and the row line 220 of the adjustment circuit 200. One end. The reference signal is, for example, a ramp signal. The reference signal is input to the switches, so it is used in the comparison operations of the comparators 410, 401, 402.

For example, if there is a noise from the additional comparator 410, the difference between the signals from the additional comparator 410 is as long as the power/power of the accessing rows 102, 104 and 220 is grounded. The noise is the same as 0. In addition, since the electrical characteristics of the comparators 401, 402 are different from those of the comparator 410, even if the same signal level is provided as an input, the output signals may have small level differences, and at the outputs. These small level differences are treated as fixed pattern noise. That is, the columns 101, 103 of the pixel array 100 have fixed pattern noises "a" and "b", respectively. Therefore, since the noises "a" and "b" are respectively subtracted from the difference between the output signals of the pixels 102 and 104 from the pixel array 100, an image signal output from the pixel array 100 can be read. And the fixed pattern noise is excluded. That is, during a frame, before a signal is output from the pixel array 100 and converted, the switches SW1, SW2, SW3 of the adjustment circuit 200 are driven to detect the additional comparator 410 and the comparators 401, 402. A noise signal. Thus, using the detected noise signal, an image signal from the pixel array 100 can be read without the fixed pattern noise.

The previous description assumes that the power/ground noise of the adjacent rows 102, 104 is the same as the power/ground noise of row 220. However, in practice, the noise can be changed in each row of the pixel array 100. The noise difference for each row of pixel array 100 can be a difference in power/ground noise due to different timings under different circuit operating conditions. The noise in each row of the pixel array can be extracted based on the noise detected from the column of lines 210 of the adjustment circuit 200. For example, as described above, even if the noise signal of the additional comparator 410 is 0, the noise signal is a signal that is detected when the line 220 of the adjustment circuit 200 is driven, and is applied every time. A signal is applied to each row 102, 104 of the pixel array 100, and a signal is applied to the column of lines 210 of the adjustment circuit 200 to drive the switches SW4, SW5. At this time, the noise has values other than 0, for example, "c" and "d", which can be detected from the additional comparator 410. Therefore, when the image signal of each pixel array 100 is correct, then (a+c, b+c, a+d, b+d) is treated as noise from the pixels 10, The image signals of 20, 30, and 40 are deducted, and then removed by an arithmetic operation, that is, subtraction.

Therefore, according to the present invention, the adjustment circuit 200 is additionally disposed in the existing pixel array 100. In addition, when the pixel array 100 is driven and the adjustment circuit 200 has only one operation switch, the noise for the comparators 401, 402 of each column and the noise for each row of the pixel array 100 can be in each frame. Was detected. Based on this, the noise of each image signal output from the pixel array 100 can be removed.

FIG. 3 illustrates a configuration of an image sensor according to another embodiment. Referring to FIG. 3, an image sensor according to another embodiment includes a counting circuit 400, an adjustment circuit 250, and a controller 500. The counting circuit 400 receives an image signal output from a pixel array 100 comprising a plurality of pixels for a matrix; and converting the image signal into digital data. At the same time, the counting circuit 400 includes a column of the pixel arrays 100 corresponding to the comparators 401, 402. The adjustment circuit 250 includes a row of lines 220 having a plurality of switches SW1, SW2, SW3. A reference signal Vref used for comparison by the counting circuit 400 is applied to one end of the switches SW1, SW2, SW3, and the other end is connected to the comparators 401, 402. When the row lines 102, 104 of each pixel array 100 are controlled, the controller 500 generates a control signal for driving the switches SW1, SW2, SW3 arranged in the row 220 of the adjustment circuit 250, and performing Controlling to detect noise of the comparators 401, 402 of each column of the corresponding pixel array 100. The image sensor of FIG. 3 is identical to the image sensor of FIG. 2 except that the adjustment circuit 250 includes only one row of lines 220 and no line of lines. Instead, an output signal of operator 230 is applied to drive an additional comparator 410. The operator 230 can be an OR operator and the row of drive signals row_sel of the pixel array 100 can be applied as an input signal. That is, each time a signal of each line is applied to the pixel array 100, the row drive signal row_sel is on, so the output of the operator 230 is on. Thus, the signal from the additional comparator 410 can be output. Each time the signal is output, the additional comparator 410 can detect the noise by detecting a reference signal Vref. The operator 230, which replaces the column of lines, is disposed outside the adjustment circuit 100 to drive the additional comparator 410. Each row of the pixel array 100 is controlled, such as the driving system of the image sensor shown in FIG. The image sensor is the same, so the repeated description will be omitted.

4 illustrates a method for driving an image sensor in accordance with an embodiment.

In operation S11, in an image sensor, an open relationship of a line of an adjustment circuit is driven.

In operation S12, a reference signal is generated based on the operational timing of the plurality of comparators. The generation of the reference signal may be continuous before the job S11 according to the timing at which the reference signal is generated.

In operation S13, a noise system corresponding to a plurality of comparators of each column of the pixel array is detected. That is, the noise of the comparators connected to a switch of an adjustment circuit and an additional comparator can be detected by driving a switch that adjusts one of the line lines of the circuit in the image sensor. For example, the detected noise is later used to remove noise on an image signal, so that it can be temporarily stored during the driving of the frame of the pixel array.

In operation S14, a plurality of pixels for each row of the pixel array are controlled for a predetermined period. For example, a signal from a row of decoders is sequentially applied to a driving frame of the pixel array, and thus the image signals from all the pixels of the pixel array are output.

In operation S15, the noise signals corresponding to the image signals of the pixels are removed according to the noise detected from the comparators.

Furthermore, the method for driving an image sensor shown in FIG. 4 can be applied to the method of driving the image sensors of FIGS. 2 and 3. That is, the same happens in FIG. 2 and FIG. 3: a switch for driving one of the row lines in an adjustment circuit, and detecting the first comparators before the pixel array drives a frame. Noise, and then a series of operations that output and calibrate an image signal from the pixel arrays. The reason is that the column of the switches in the adjustment circuit is not separately executed due to the driving timing of the switches SW4 and SW5 of FIG. 2 but is synchronized with the driving of the pixels of each row of the pixel array.

Heretofore, a method for driving an image sensor according to an embodiment has been described. The method for driving an image sensor can be applied to a user interface method for tracking a stored motion detection target area and inputting corresponding moving data, and can be stored as an electrical recording code. In a computer readable recording medium.

According to an embodiment, the fixed pattern noise occurring in the analog circuit constituting an image sensor can be removed by the configuration of an additional circuit.

Although the embodiments have been described with reference to the embodiments of the present invention, it is understood that many other modifications and embodiments may be made in the spirit and scope of the principles of the present disclosure. In particular, the various variations and modifications of the component parts and/or combinations of the subject matter, the drawings and additional claims, will still fall within the scope of the present disclosure. In addition, the alternation of component parts and/or permutations will obviously fall within the scope of the present technology.

10, 20, 30, 40. . . Pixel

100. . . Pixel array

101, 103. . . Column

102, 104. . . Row

200. . . Adjustment circuit

210. . . Column line

220. . . Line

230. . . Operator

250. . . Adjustment circuit

300. . . Row decoder

400. . . Counting circuit

401, 402, 410. . . Comparators

450. . . Reference signal generator

500. . . Controller

a, b. . . node

Csh. . . capacitance

FD. . . Floating diffusion zone

M1. . . Transistor

PCLP. . . switch

RST. . . Reset transistor

Row_sel. . . Line drive signal

SH. . . switch

SW1, SW2, SW3, SW4, SW5. . . switch

S11~S15. . . step

TX. . . Transfer transistor

Vaapix. . . voltage

Vclp. . . Voltage

Vref. . . Reference signal

FIG. 1A illustrates a correlated double sampling (CDS) circuit.

FIG. 1B illustrates a timing diagram of the CDS.

2 illustrates an image sensor in accordance with an embodiment.

FIG. 3 illustrates an image sensor according to another embodiment.

4 is a flow chart of driving an image sensor according to an embodiment.

10, 20, 30, 40. . . Pixel

100. . . Pixel array

101, 103. . . Column

102, 104. . . Row

200. . . Adjustment circuit

210. . . Column line

220. . . Line

300. . . Row decoder

400. . . Counting circuit

401, 402, 410. . . Comparators

450. . . Reference signal generator

500. . . Controller

SW1, SW2, SW3, SW4, SW5. . . switch

Vref. . . Reference signal

Claims (14)

An image sensor that processes a signal output from a plurality of pixels, comprising: a counting circuit that receives an image signal output from a pixel array, the pixel array including the pixels in a column and a row And converting the received image signal into digital data, the counting circuit includes a column corresponding to a pixel array of a comparator; an adjusting circuit comprising a plurality of switches, and a column line and a row arranged with the switches a line, wherein a reference signal for a comparison operation of the counting circuit is applied to one end of the switches, and the other ends of the switches are connected to the comparators; an additional comparator detects the Adjusting one of the line outputs of the circuit to output a noise signal; and a controller generating a control signal for driving the switches arranged on the line of the adjustment circuit and detecting each column of the corresponding pixel array The noise of the comparators. The image sensor of claim 1, wherein the open relationships in the column of lines of the adjustment circuit are driven according to control of each row of the pixel array of the controller; The controller controls the noise signal according to one of the additional comparators to detect noise for each row of the pixel array. The image sensor of claim 1, further comprising a reference signal generator applying the reference signal to one end of the switches in the column of the adjustment circuit and the row of lines. The image sensor of claim 1, wherein the controller sequentially controls a plurality of pixels in the plurality of row lines constituting the pixel array and generates a signal for a predetermined period of time. Each of the switches in the line of the adjustment circuit is driven every cycle. The image sensor of claim 1, wherein the controller sequentially controls the comparators of the counting circuit at each predetermined period and generates a signal for driving the additional comparison for each period. Device. The image sensor of claim 4 or 5, wherein the controller removes the pixel from the pixel according to the noise detected from the additional comparator and the comparators. Outputs noise of one of the image signals. An image sensor for processing a signal outputted from a plurality of pixels, comprising: a counting circuit for receiving an image signal outputted from a pixel array, the pixel array comprising the plurality of pixels in a row and a row And converting the received image signal into digital data, the counting circuit comprising a column corresponding to the pixel array of the comparator; an adjusting circuit comprising a plurality of switches, and a line arranging the switches, Wherein a reference signal is used for a comparison operation of the counting circuit Adding to one end of the switches, and the other ends of the switches are connected to the comparators; an additional comparator detecting a noise signal of a reference signal generator to generate the reference signal; and a controller Generating a control signal, the control signal is used to drive a plurality of switches in the line of the adjustment circuit each time the line of the pixel array is controlled, and the controller detects that the corresponding picture is drawn The noise of the comparators in each column of the prime array. The image sensor of claim 7, further comprising a reference signal generator for applying the reference signal to one end of the switches arranged in a line in the adjusting circuit. The image sensor of claim 7, wherein the controller sequentially controls the comparators of the counting circuit at each predetermined period and generates a signal for driving the additional comparison for each period. Device. The image sensor of claim 9, wherein the controller removes the output from the pixel array according to a noise signal detected by the additional comparator and the comparators. A noise of an image signal. A method for driving an image sensor to process a signal output from a plurality of pixels, wherein the image sensor comprises: a counting circuit receiving an image signal output from a pixel array, the pixel array being included in a column And the paintings in a row And converting the received image signal into digital data, and the counting circuit includes a column corresponding to the pixel array of the comparator; and an adjusting circuit comprising a plurality of switches and a column line arranged with the switches a line, the method comprising: generating a reference signal according to a working timing of the comparators; detecting noise of the comparators corresponding to each column of the pixel array; in each row of the pixel array, continuing Controlling a plurality of pixels by a predetermined period; and removing noise corresponding to one of the pixels of the pixels according to the noise detected by the comparators, wherein the adjusting circuit further includes an additional comparator To detect a noise signal of a reference signal generator, the reference signal generator generates the reference signal and detects noise of the comparators by using a signal from the additional comparator. The method of claim 11, wherein the adjusting circuit further comprises a column of lines arranged with a plurality of switches, and further comprising: driving each time when a plurality of pixels for each row of the pixel array are controlled The switches in the column of lines; and detecting a noise signal for each row of the pixel array. The method of claim 11, further comprising applying the reference signal To one end of the switches arranged on the line of the adjustment circuit. The method of claim 11, wherein the noise detection of the comparators corresponding to each column of the pixel array further comprises: generating a signal for driving the adjustment circuit for the predetermined period The switches in the line.