KR20110092701A - Photo detecting device and unit pixel thereof - Google Patents

Abstract

PURPOSE: A unit pixel pattern of a photo sensitive device and the photosensitive device including the same are provided to improve photosensitivity by controlling the size of a pixel or each filter according to the eyes of a user. CONSTITUTION: A pixel array(31) includes a color filter array. An analog signal processor(32) performs correlated double sampling. The analog signal processor performs automatic gain control to dynamically change the amplification gain according to the intensity of the brightness at each frame. A digital signal processor(33) corrects the color of a signal outputted from the analog signal processor and processes an image signal including interpolation.

Description

Unit pixel pattern of the photosensitive device and a photosensitive device including the same {PHOTO DETECTING DEVICE AND UNIT PIXEL THEREOF}

Embodiments of the inventive concept relate to a light sensing device, and more particularly, to a signal-to-noise ratio, a light sensing device capable of improving light sensitivity, and a unit pixel pattern that can be used in the light sensing device. .

The optical sensing device captures an external image, converts it into an electrical signal, and outputs it. The photosensitive device is classified into a CMOS type and a Charge Coupled Device (CCD) type, and recently, it has advantages such as high integration, low power consumption, and production cost. CMOS type sensors, for example, have been spotlighted.

The present invention provides a light sensing method that can improve the signal-to-noise ratio, sensitivity, and the like by varying the pixel size of a corresponding color component according to the spectral distribution (e.g., the specific gravity involved in light brightness) and appropriate interpolation. The stage of the device and the light sensing device provide a pixel pattern.

The unit pixel pattern of the light sensing device according to the embodiment of the present invention may include a first pixel having the largest contribution to the light intensity, a second pixel having a smaller contribution to the contrast compared to the first pixel, and A third pixel having a smaller contribution to contrast than two pixels is included, and the size of the first to third pixels is determined according to the contribution to the contrast.

An optical sensing device according to an embodiment of the present invention includes a first pixel having the largest contribution to light and shade, a second pixel having a smaller contribution to contrast compared to the first pixel, and a comparison with the second pixel. A pixel array including a third pixel having a small contribution to contrast, wherein the first to third pixels each include a unit pixel of a photosensitive device whose size is determined according to the contribution to the contrast; and And a signal processor for processing an output signal of the pixel array, wherein the signal processor performs interpolation using specific coefficients given according to the degree of contribution to the contrast of the first to third pixels.

The light sensing device and the unit pixel pattern of the light sensing device according to the embodiment of the present invention can sufficiently compensate for the luminance component, thereby improving the signal-to-noise ratio and the light sensitivity.

The detailed description of each drawing is provided in order to provide a thorough understanding of the drawings cited in the detailed description of the invention.
1 shows a color filter array in a conventional form.
2 illustrates patterns of a color filter array according to an embodiment of the present invention.
FIG. 3 is a schematic block from an optical sensing element including a pattern of the color filter array shown in FIG. 2 to an interpolation part.
4 is a diagram schematically illustrating an operation of reading an output signal having a pattern as shown in FIG.
5 is a diagram showing digital RGB output data after analog-to-digital conversion.
FIG. 6 schematically shows a data storage state in a memory in which each pixel and data value as shown in FIG. 5 is stored in a digital form.
FIG. 7 is an example of an algorithm for performing interpolation on the pixel array data shown in FIG. 6.
8 illustrates various types of unit color filter arrays.
9 is a circuit diagram illustrating photodetecting devices according to an exemplary embodiment of the present invention.
10 is a block diagram of an optical sensing device according to an exemplary embodiment of the present invention.
FIG. 11 is a schematic block diagram of a semiconductor system including the light sensing device illustrated in FIG. 10.

Specific structural or functional descriptions of the embodiments according to the inventive concept disclosed herein are provided for the purpose of describing the embodiments according to the inventive concept only. It may be embodied in various forms and is not limited to the embodiments described herein.

Embodiments according to the inventive concept may be variously modified and have various forms, so embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments in accordance with the concept of the invention to the specific forms disclosed, it includes all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are intended to distinguish one element from another, for example, without departing from the scope of the invention in accordance with the concepts of the present invention, the first element may be termed the second element, The second component may also be referred to as a first component.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between. Other expressions describing the relationship between components, such as "between" and "immediately between," or "neighboring to," and "directly neighboring to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is described, and that one or more other features or numbers are present. It should be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and are not construed in ideal or excessively formal meanings unless expressly defined herein. Do not.

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

1 shows a color filter array in a conventional form.

1 (a) shows a general Bayer pattern. R denotes a red filter, G denotes a green filter, and B denotes a blue filter.

FIG. 1B illustrates various arrangements in which a white filter and RGB are arranged in a stripe or mosaic form.

The signal output from any one of the various types of color filter arrays shown in FIG. 1 is converted into an electrical signal, followed by analog signal processing, digital signal processing, and interpolation. The primary colors are red, blue, and green. However, as can be seen in the structure of FIG. 1, it can be seen that G and white, which play a greater role in the brightness (or contrast) of light, have the same filter size as other colors.

Therefore, the human eye is sensitive to the brightness of light, so that in the filter structure having the same size, not only the light sensitivity is reduced, but also the signal-to-noise ratio tends to be degraded.

2 illustrates patterns of a color filter array according to an embodiment of the present invention. In FIG. 2, an example including only RGB is illustrated, and the following will be described with reference to each pattern.

G for filtering the wavelengths of the green region is most widely (or most) distributed between R for filtering the wavelengths of the red region with the longest wavelength and B for filtering the wavelengths of the shortest region. However, the unitary coli filter array including the existing RGB uses RGB having the same size, and the other filter, for example, G having twice the number of R or B in the diagonal direction of the unit color filter array. Placed.

According to an exemplary embodiment of the present invention, the filter (or the pixel) does not have to be separated into two or more filters corresponding to the color which contributes more to the light intensity than other colors, and the size of the filter (or the pixel) is different from the other color. Adjust it to be larger than the size of the corresponding filter (or pixel).

In addition, in the case of other colors such as blue color and red color, the contribution of the red color to the contrast is large compared to the contribution of the blue color, thereby making the size of R larger than the size of B.

For example, the size of the color-specific filter (or pixel) may be determined at different ratios according to the ratio that contributes to the contrast. For example, if the ratio of green color, red color, and blue color contributes to the contrast is 6: 2.5: 1.5, the size ratio of the filter (or pixel) per color in the unit color filter array or unit pixel pattern is equal to the contrast contribution ratio. The same can be set to 6: 2.5: 1.5.

The present invention can improve the light sensitivity and signal-to-noise ratio by adjusting the size of each filter (or pixel) to fit the human eye, unlike the size of a conventional uniform filter (or pixel).

2A illustrates a color filter array in which four unit patterns are arranged, and each pattern includes RGB having different sizes according to contrast ratios.

As shown in FIG. 2B, B and B are disposed adjacent to each other and R and R are disposed adjacent to each other in each pattern constituting the color filter array.

The pattern shown in (c) of FIG. 2 is a modified example of the pattern shown in (b) of FIG. 2, and the pattern shown in (d) of FIG. 2 is a modified example of the pattern shown in (a) of FIG. to be.

The difference in each pattern shown in FIG. 2 causes a difference in calculation in each subsequent interpolation, and has a difference in each characteristic.

On the other hand, the color filter array (or pixel array positioned below the color filter array) structure is a mosaic in which 3 * 3, 4 * 4, etc. are applied in addition to the application form of 2 * 2, as in the example described with reference to FIG. It can also be implemented as an array or a stripe array.

FIG. 3 is a schematic block from an optical sensing element including a pattern of the color filter array shown in FIG. 2 to an interpolation part.

For example, the pixel array 31 including a color filter array having a structure as shown in FIG. 2D receives an optical signal projected on an external image and corresponds to the optical signal through photoelectric conversion. Outputs an electrical signal. The analog signal processor 32 includes correlated double sampling (CDS), automatic gain control (AGC) for dynamically converting amplification gains according to the intensity of luminance per frame, and analog to digital conversion (Analog). to Digital Conversion (ADC).

The digital signal processor 33 may perform color correction, gamma correction, saturation control, luminance control, and interpolation on the signal output from the analog signal processor 32. General image signal processing including interpolation).

Here, the CDS scheme may include all of analog, digital, analog / digital mixture, or dual CDS scheme.

4 is a diagram schematically illustrating an operation of reading an output signal having a pattern as shown in FIG.

Since the read operation is performed in the same way as the low unit read method, it reads from the N-2 line (N-2 line) to the (N + 3) line (N + 3 line) sequentially, and outputs the signal for each row. Is output in column units.

5 is a diagram showing digital RGB output data after analog-to-digital conversion.

The analog electrical signal output from the pixel array 31 is output as a difference between the reset signal and the detection signal through the CDS, so that most of the fixed pattern noise (FPN) is removed. The signal from which most of the FPN is removed is converted into a digital signal through the ADC and output. FIG. 5 is a diagram illustrating values output from the color filter array (or pixel array) structure illustrated in FIG. 4 in proportion to their sizes.

On the other hand, if each filter has the same size as in the prior art, as shown in Figure 5 is weighted by the size of each filter to the degree of sensitivity to the human eye will not be able to obtain data.

FIG. 6 schematically shows a data storage state in a memory in which each pixel and data value as shown in FIG. 5 is stored in a digital form.

In FIG. 6, the size of the filter (or pixel) and the difference in size are not shown, but only the size is stored in a memory having a similar structure for each pixel position. The memory is commonly referred to as line memory. Line memory includes volatile memory such as dynamic random access memory (DRAM) or static random access memory (SRAM), resistive random access memory (RRAM), phase-change random access memory (PRAM), and magnetic memory (MRAM). Non-volatile memory such as Random Access Memory, NAND flash memory, or NOR flash memory.

The digital value stored in the memory has a red color value, a green color value, or a blue color value for each pixel through an interpolation process.

FIG. 7 is an example of an algorithm for performing interpolation on the pixel array data shown in FIG. 6. Referring to FIG. 7, since pixel ₃₄ is composed of G ₃₄ pixels having a green color value, the red color value (R ₃₄ ) and the blue color value (B ₃₄ ) at the pixel ₃₄ are determined by the algorithm shown in FIG. 7. It can be calculated through

That is, using the red pixels R ₃₅ , R ₄₃ , R ₂₃ , and R ₃₂ around the G ₃₄ pixel, it is possible to calculate the red color value R ₃₄ using, for example, an averaging scheme. The weights may be weighted using the coefficients α, β, γ, δ, ε, ζ, and η, which are determined accordingly, and then averaged.

The blue color value B34 for pixel 34 is the coefficients (α, β, γ, δ, ε, ζ, and η) determined according to the surrounding blue pixels B ₄₄ , B ₃₃ , B ₂₄ , B ₃₆ and position. It can be calculated by weighting using and then averaging.

On the other hand, the interpolation algorithm is possible by a variety of methods in addition to this averaging method, and the difference from the conventional method is that the coefficients weighted during interpolation (α, β, γ, δ, ε, ζ, and η) because the size of each pixel is determined by an array. ) Is different.

8 illustrates various types of unit color filter arrays.

Various combinations of yellow (Y), magenta (Mg), cyan, and white (W), which are known to have excellent light sensitivity due to less interference than the three primary colors of light, are red, green, and blue. Color filter arrays or unit pixel pattern structures may be possible.

In this case, the size of the pixel may be determined according to the comparison of the spectrum distribution for each color. FIG. 8A illustrates a structure including a white filter W, a red filter R, and a blue filter B. The white filter W has the same or higher contrast than the green filter G. The contribution to is reflected, indicating that the filter (or pixel size) is significantly larger than the red filter (R) and the blue filter (B).

Referring to (b) of FIG. 8, the magenta filter (Mg) and the cyan filter (Cy) are replaced with the red filter (R) and the blue filter (B), and the cyan filter (Cy) on the light spectrum distribution is magenta. It can be seen that the magenta filter Mg has a larger contribution than the filter Mg, and the size of the magenta filter Mg is larger than that of the cyan filter Cy.

8C is composed of the green filter G, the magenta filter Mg, and the cyan filter Cy, and it can be seen that the size of each filter is determined according to the contribution of contrast.

FIG. 8 (d) shows a form composed only of complementary color filters such as yellow filter Ye, cyan filter Cy, and magenta filter Mg. In case of yellow filter Ye and cyan filter Cy, Since the contributions to light and shade in the light spectrum distribution are similar to each other, it can be seen that the sizes of the two filters (Ye and Cy) are similar to each other.

 The ranks that contribute to the contrast of each color filter are as follows.

 White filter (W) ≥ Yellow filter (Ye) ≥ Cyan filter (Cy) ≥ Magenta filter (Mg) ≥ Green filter (G) ≥ Red filter (R) ≥ Blue filter (B) and the ratio and order of the size difference Depends on the size of the external light, the reflection medium, or the characteristics of the sensor.

Table 1 is an example which shows the ratio of the degree which contributes to the contrast by each color filter when the white filter W is set to one.

White Yellow Cyan Magenta Green Red Blue One 0.413326 0.40484 0.370953 0.211048 0.189011 0.181942

9 is a circuit diagram illustrating photodetecting devices according to an exemplary embodiment of the present invention.

Referring to FIG. 9A, a photosensitive device according to an exemplary embodiment may include a photo sensitive device (PD), a transmission transistor (TX), a floating diffusion node (FD), It may include a reset transistor Rx, a drive transistor (or a source follow transistor, DX), and a selection transistor SX.

The photo detector PD receives light from the outside and generates a photocharge based on the received light. According to an embodiment, the light detector PD may be turned on / off in response to a control signal output from a controller (not shown). When the light detector PD is in the on state, the light detector PD may generate photocharges by sensing incident light. On the other hand, when the light detector PD is in the off state, the light detector PD does not detect incident light. The photo detector PD may include at least one of a photo diode, a photo transistor, a photogate, a pinned photo diode (PPD), and a combination thereof.

The operation of the photosensitive device will be described in detail. In response to the gating operation of the transfer transistor TX, the photocharge generated by the photodetector PD is transferred to the floating diffusion node FD. More specifically, when the transfer control signal TG is at the first level (eg, the high level), the transfer transistor TX is turned on, and the photocharge generated by the photo detector PD is transferred to the floating diffusion node FD. Delivered.

The drive transistor DX acts as a source follower buffer amplifier to buffer a signal corresponding to the charge charged in the floating diffusion node FD.

In addition, the selection transistor SX performs a switching operation and an address operation for selecting the photosensitive device in response to the selection control signal SEL.

The photocharge stored in the floating diffusion node FD and driven by the drive transistor DX is reset by the reset transistor RX. More specifically, the reset transistor RX resets the photo charges stored in the floating diffusion region FD at regular intervals for the CDS operation in response to the reset control signal RS.

In FIG. 9A, an optical sensing device including one photodetector PD and four MOS transistors TX, RX, DX, and SX is illustrated, but embodiments of the present disclosure are not limited thereto. The embodiment according to the present invention may be applied to all circuits including at least three transistors including the drive transistor DX and the selection transistor SX and the photodetector PD. Another embodiment of the photosensitive device is shown in FIGS. 9 (b) to 9 (d).

The photosensitive device shown in FIG. 9B is a photosensitive device including three transistors and includes a photodetector PD, a reset transistor RX, a drive transistor (or a source follow transistor, DX), and a select transistor. (SX) may be included.

The photosensitive device illustrated in FIG. 9C is a photosensitive device including five transistors, and includes a photodetector PD, a reset transistor Rx, a drive transistor (or a source follow transistor, DX), and a selection. In addition to the transistor SX, it further includes one transistor GX.

The photosensitive device illustrated in FIG. 9D is a photosensitive device including five transistors, and includes a photodetector PD, a reset transistor Rx, a drive transistor (or a source follow transistor, DX), and a select transistor. In addition to (SX), it further includes two transistors (GX, PX).

Meanwhile, as described above, the various types of photosensitive devices as illustrated in FIG. 9 may have independent structures, or may share at least one component with each other. For example, in the configuration of FIG. 9A, two or four pixels independently configure only the photodetector PD and the transfer transistor TX, and the rest of the pixels are independent of each other through timing control. can do.

10 is a block diagram of an optical sensing device according to an exemplary embodiment of the present invention. Referring to FIG. 10, the photodetector 112 includes a pixel array 11, a row address decoder 13, a row driver 12, a column address decoder 16, A column driver (15), a sample & hold block (Sample & Hold Block, 17), an ADC (18), and an ISP (Image Signal Processor, 19).

The pixel array 11 may have a structure including the unit color filter array shown in FIGS. 2 and 8. However, the pixel array 11 may have an array in which other color filters (Mg (magenta), Cy (cyan), Ye (yellow), B (Black), W (white), etc.) other than RGB may be mixed. Of course.

Each of the plurality of pixels constituting the pixel array 11 may include pixel signals (eg, a red color signal, a green color signal, a blue color signal, a mazeta color) in response to a plurality of control signals generated by the row driver 12. Signal, cyan color signal, yellow color signal, or white color signal) may be output in a column unit.

The controller 14 includes a pixel array 11, a row address decoder 13, a row driver 12, a column address decoder 16, a column driver 15, a sample and hold block 17, an ADC 18, And a plurality of control signals for controlling the operation of the ISP 19, and may generate address signals for outputting a signal sensed by the pixel array 11.

More specifically, the controller 14 may select a row address to select a row line to which any one pixel is connected for outputting a signal detected at any one of a plurality of pixels implemented in the pixel array 11. The decoder 13 and the row driver 12 may be controlled.

In addition, the controller 14 may control the column address decoder 16 and the column driver 15 to select a column line to which any one pixel is connected.

The row address decoder 13 decodes the row control signal output from the controller 14, outputs the decoded row control signal, and the row driver 12 outputs the decoded row control signal output from the row address decoder 13. In response, the row line of the pixel array 11 is selectively activated.

The column address decoder 16 decodes a column control signal (eg, an address signal) output from the controller 14 and outputs the decoded column control signal, and the column driver 15 is output from the column address decoder 16. The column line of the pixel array 11 is selectively activated in response to the decoded column control signal.

The sample and hold block 17 may sample and hold the pixel signal output from the pixel selected by the row driver 12 and the column driver 15.

The ADC 18 analog-to-digital converts signals output from the sample and hold block 17 to output analog-digital converted pixel data. In this case, the sample and hold block 17 and the ADC 18 may be implemented as one chip.

The ADC 18 may further include a CDS circuit (not shown) for correlating double sampling the signals output from the sample and hold block 17, and the ADC 18 may include a signal and a comparison signal, for example, output through the CDS. Ramp signals (not shown) can be compared and the comparison results can be output as analog-digital converted pixel data.

The ISP 19 performs digital image processing based on the pixel data output from the ADC 18. The ISP 19 performs interpolation as described above and outputs the interpolated signal. In addition, the ISP 19 may further perform an edge enhancement function for strengthening an edge, a function for suppressing pseudo color components, and the like.

FIG. 11 is a schematic block diagram of a semiconductor system including the light sensing device illustrated in FIG. 10.

For example, the semiconductor system 110 may be a computer system, a mobile communication terminal, a camera system, a scanner, a navigation system, a videophone, a director. Supervision System, Automatic Focus System, Tracing System, Operation Monitoring System, Image Stabilization System, etc. may be exemplified, but the present invention is not limited thereto. no.

Referring to FIG. 11, a computer system, which is a type of semiconductor system 110, includes a bus 111, a central information processing unit (CPU) 114, an optical sensing device 112, and a memory device 113.

In addition, the semiconductor system 110 may further include an interface (not shown) connected to the bus 111 to communicate with the outside. In this case, the interface may be, for example, a serial interface or a wired interface, and may be a wireless interface.

The CPU 114 may generate a control signal for controlling the operation of the light sensing device 112, and may provide a control signal to the light sensing device 112 through the bus 111.

The memory device 113 may receive an image signal output from the light sensing device 113 through the bus 111 and store the image signal.

Meanwhile, the light sensing device 112 may be integrated with the CPU 114 and the memory device 113, and in some cases, a digital signal processor (DSP) may be integrated together, or the light sensing device may be integrated. Only 112 may be integrated into a separate chip.

In the present specification, a color filter and a pixel capable of detecting an optical signal passing through the color filter may be used as the same meaning.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like.

The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

11: pixel array
12: low driver
13: row address decoder
14: control unit
15: column driver
16: column address decoder
31: pixel array
32: analog signal processing unit
33: digital signal processing unit

Claims (8)

A first pixel that contributes the most to the intensity of light, a second pixel that contributes less to the contrast than the first pixel, and a third pixel that contributes less to the contrast than the second pixel. Include,
The unit pixel pattern of the light sensing device of the first pixel to the third pixel is determined in size depending on the degree of contribution to the contrast. The method of claim 1,
The unit pixel pattern of the light sensing device according to the size of the first pixel to the third pixel is determined according to the ratio of the degree of contribution to the contrast. The method of claim 2,
The unit pixel pattern of the photosensitive device, wherein the size of the first pixel to the third pixel is determined in proportion to the ratio of the degree of contribution to the contrast. The method of claim 1,
The first pixel is a unit pixel pattern of the light sensing device including a green color or a white color. A first pixel having the greatest contribution to light and darkness, a second pixel having a smaller contribution to the contrast than the first pixel, and a third pixel having a contribution to the contrast less than the second pixel. A pixel array including unit pixels of the photosensitive device, the size of which is determined according to the degree of contribution to the contrast;
A signal processor configured to process an output signal of the pixel array;
And the signal processing unit interpolates using a specific coefficient given according to the degree of contribution to the contrast of the first to third pixels. The method of claim 5,
The size of the first pixel to the third pixel is determined according to the ratio of the degree of contribution to the contrast. The method of claim 6,
The size of the first pixel to the third pixel is determined in proportion to the ratio of the contribution to the contrast. The method of claim 5,
The first pixel includes a green color or a white color.

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