SOLID-STATE IMAGE SENSOR

• US 20100157091A1
• Filed: 06/14/2007
• Published: 06/24/2010
• Est. Priority Date: 06/14/2006
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Egawa, Yoshitaka, Iida, Yoshinori, Itoh, Goh, Honda, Hiroto
• Granted Patent: US 7,990,447 B2
• Time in Patent Office: Days
• US Class Current: 348/223.100
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H04N 2209/046 Colour interpolation to calculate the missing colour values
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 25/133 including elements passing panchromatic light, e.g. filters passing white light
• CPC Class Codes: H04N 25/135 based on four or more different wavelength filter elements

Abstract

A solid-state image sensor has a plurality of pixels, a read-out circuit and a signal processing section. The plurality of pixels includes a plurality of first pixels, a plurality of second pixels, a plurality of third pixels and a plurality of fourth pixels. The signal processing section includes a color acquisition section, a first judgment section configured to determine whether or not the white data value W in the target pixel block is smaller than a predetermined first set value, and a white color correction section configured to perform correction processing of the white color data value W in the target pixel block based on the following Expression (1) when the judgment result of the first judgment section is NO, and to output the white data value W by itself without performing the correction processing based on the Expression (1) when the judgment result of the first determination section is YES;

W¹=S₁C₁+S₂C₂+S₃C₃  (1)

• • where each of S₁, S₂, and S₃ is a coefficient that is determined based on a color balance.

Claims

1. A solid-state image sensor, comprising:

a plurality of pixels which are formed in matrix form on a semiconductor substrate, each pixel having a photoelectric converting element which outputs an electric signal obtained by photoelectric conversion;

a read-out circuit configured to read out the electric signals outputted from the plurality of pixels; and

a signal processing section configured to perform signal process with respect to the electric signals read out from the read-out circuit,

wherein the plurality, of pixels includes;

a plurality of first pixels which leads incident light of a visible light wavelength to a corresponding photoelectric conversion element via a transparent layer;

a plurality of second pixels, each having a first color filter having a higher transmissivity with respect to a first visible light wavelength band in a visible light wavelength band, as compared with the other visible light wavelength band;

a plurality of third pixels, each having a second color filter having a higher transmissivity with respect to a second visible light wavelength band different from the first visible light wavelength band in a visible light wavelength band, as compared with the other visible light wavelength band; and

a plurality of fourth pixels, each having a third color filter having a higher transmissivity with respect to a third visible light wavelength band different from the first and second visible light wavelength bands in a visible light wavelength band, as compared with the other visible light wavelength band,

wherein the signal processing section includes;

a color acquisition section configured to acquire a first color data value C₁, a second color data value C₂, a third color data value C₃ and a white color data value W in a target pixel block including a plurality of pixels to perform signal process;

a first judgment section configured to determine whether or not the white data value W in the target pixel block is smaller than a predetermined first set value; and

a white color correction section configured to perform correction processing of the white color data value W in the target pixel block based on the following Expression (1) when the judgment result of the first judgment section is NO, and to output the white data value W by itself without performing the correction processing based on the Expression (1) when the judgment result of the first determination section is YES;

W′

=S₁C₁+S₂C₂+S₃C₃ 

 

(1)

where each of S₁, S₂, and S₃ is a coefficient that is determined based on a color balance.

2. The sensor according to claim 1, further comprising:

a second judgment section configured to judge whether the white data value W in the target pixel block is larger than a second set value smaller than the first set value before the first judgment section performs the judgment process; and

a preceding block color adjustment section configured to determine the respective color data values in the target pixel block based on the respective color data values in a preceding pixel block when the judgment result of the second judgment section is NO,

wherein the first judgment section performs the judgment process when the judgment result of the second judgment section is YES.

10. The sensor according to claim 1,

wherein the color acquisition section performs interpolation process based on the white color data value and the color data values of the first to third colors except for white color around the target pixel, to detect the color data values C₁, C₂ and C₃ and the white color data value W of the target pixel.

16. The sensor according to claim 1,

wherein the signal processing section has a signal output section configured to output luminance data and color difference data corresponding to the three color data values C₁, C₂ and C₃ and the white color data value W.

17. The sensor according to claim 1,

wherein the pixel block includes the first to fourth pixels of two rows and two columns arranged adjacently;

and

the first and second pixels in the pixel block are arranged diagonally.

18. The sensor according to claim 1,

wherein the pixel block includes the first to fourth pixels of two rows and two columns arranged adjacently;

the second pixel has a first color filter having a higher transmissivity with respect to a visible light wavelength band of green color, as compared with the visible light wavelength band of the other color;

the third pixel has a second color filter having a higher transmissivity with respect to a visible light wavelength band of red color, as compared with the visible light wavelength band of the other color; and

the fourth pixel has a third color filter having a higher transmissivity with respect to a visible light wavelength band of blue color, as compared with the visible light wavelength band of the other color.

19. The sensor according to claim 1,

wherein the pixel block has 16 pixels of four rows and four columns arranged adjacently,

the pixel block including:

a first pixel line arranged by every one line in the pixel block, which has the first pixel;

a second pixel line arranged between the neighboring first pixel lines, which has a plurality of pixels each having a color filter having a higher transmissivity with respect to a plurality of colors of visible light wavelength bands different from each other, as compared with visible light wavelength bands of the other colors except for the plurality of colors.

20. The sensor according to claim 19,

wherein a ratio of pixels having the color filter having a higher transmissivity with respect to a visible light wavelength band of green color, as compared with the visible light wavelength bands of the other colors except for green color is the largest in the second pixel line.

21. The sensor according to claim 19,

wherein three types of pixels having transmissivity different from each other with respect to three type colors are alternatively arranged in the second pixel line.

23. The sensor according to claim 1,

wherein the read-out circuit reads out the signals at the same time for one horizontal line or in sequence for each one pixel with respect to the plurality of pixels.

24. The sensor according to claim 1,

wherein the signal processing section is formed on a semiconductor substrate different from a semiconductor substrate on which the plurality of pixels and the read-out circuit are formed, the output of the read-out circuit being inputted to the signal processing section.

25. The sensor according to claim 1,

wherein the second, third and fourth pixels have an infrared cut filter for cutting off an infrared ray;

and

the first pixel leads the incident light to the photoelectric converting element without the infrared cut filter.

3. A solid-state image sensor, comprising:

a plurality of pixels which are formed in matrix form on a semiconductor substrate, each pixel having a photoelectric converting element which outputs an electric signal obtained by photoelectric conversion;

a read-out circuit configured to read out the electric signals outputted from the plurality of pixels; and

a signal processing section configured to perform signal process with respect to the electric signals read out from the read-out circuit,

wherein the plurality of pixels includes;

a plurality of first pixels which leads incident light of a visible light wavelength to a corresponding photoelectric conversion element via a transparent layer;

a plurality of second pixels, each having a first color filter having a higher transmissivity with respect to a first visible light wavelength band in a visible light wavelength band, as compared with the other visible light wavelength band;

a plurality of third pixels, each having a second color filter having a higher transmissivity with respect to a second visible light wavelength band different from the first visible light wavelength band in a visible light wavelength band, as compared with the other visible light wavelength band; and

a plurality of fourth pixels, each having a third color filter having a higher transmissivity with respect to a third visible light wavelength band different from the first and second visible light wavelength bands in a visible light wavelength band, as compared with the other visible light wavelength band,

wherein the signal processing section includes;

a color acquisition section configured to acquire a first color data value C₁, a second color data value C₂, a third color data value C₃ and a white color data value W in a target pixel block including a plurality of pixels to perform signal process;

a color separation processing section configured to separate the white data value into a plurality of colors based on the following Expressions (2) to (4) to generate the first color data value C1_W of a first color, the second color data value C2_W of a second color and the third color data value C3_W of a third color;

C1_W←

W·

K₁ 

 

(2)

C2_W←

W·

K₂ 

 

(3)

C3_W←

W·

K₃ 

 

(4)

where K₁, K₂, and K₃ indicate color ratios, and are determined by the color data values C₁, C₂ and C₃.

4. The sensor according to claim 3

wherein the color ratios K_m (m=1, 2 and 3) are expressed by the following Expression (5) by using the color data values C₁, C₂ and C₃ in the pixel blocks.

5. The sensor according to claim 3,

wherein the signal processing section has a white color judgment section configured to judge whether the white color data value W is a predetermined set value or more;

and

the color separation processing section separates the white color data value into a plurality of colors based on the Expressions (2) to (4) when the judgment result of the white color judgment section is YES, and separates the white color data value into a plurality of colors based on the following Expression (6) when the judgment result of the white color judgment section is NO, to generate the color data values C1_W, C2_W and C3_W.

6. The sensor according to claim 3, further comprising:

an interpolation processing section configured to correct the color data value of the target pixel by using the color data values C1_W, C2_W and C3_W generated by the color separation processing section and the color data value of the target pixel around the white color pixel.

7. The sensor according to claim 6,

wherein the interpolation processing section corrects the color data value of the target pixel by using the color data values C1_W, C2_W, C3_W generated by the color separation processing section and the color data value of the target pixel around the white color pixel, in order to set pixel arrangement in the pixel block to a Bayer array.

8. The sensor according to claim 3,

wherein the signal processing section has an interpolation processing section configured to perform interpolation process based on the color data values C₁, C₂ and C₃ acquired by the color acquisition section and the white color data value W to calculate the interpolated color data value and the white color data value for each pixel;

and

the color separation processing section performs color separation process by the Expressions (2) to (4) by using the color data value interpolated by the interpolation processing section and the white color data value.

9. A solid-state image sensor, comprising:

a plurality of pixels which are formed in matrix form on a semiconductor substrate, each pixel having a photoelectric converting element which outputs an electric signal obtained by photoelectric conversion;

a read-out circuit configured to read out the electric signals outputted from the plurality of pixels; and

a signal processing section configured to perform signal process with respect to the electric signals read out from the read-out circuit,

wherein the plurality of pixels includes;

a plurality of first pixels which leads incident light of a visible light wavelength to a corresponding photoelectric conversion element via a transparent layer;

a plurality of second pixels, each having a first color filter having a higher transmissivity with respect to a first visible light wavelength band in a visible light wavelength band, as compared with the other visible light wavelength;

a plurality of third pixels, each having a second color filter having a higher transmissivity with respect to a second visible light wavelength band different from the first visible light wavelength band in a visible light wavelength band, as compared with the other visible light wavelength; and

a plurality of fourth pixels, each having a third color filter having a higher transmissivity with respect to a third visible light wavelength band different from the first and second visible light wavelength bands in a visible light wavelength band, as compared with the other visible light wavelength,

wherein the signal processing section includes;

a color acquisition section configured to acquire a first color data value C₁ of first color, a second color data value C₂ of second color, a third color data value C₃ of third color and a white color data value W in a target pixel block including a plurality of pixels to perform signal process;

a judgment section configured to judge whether the color data values C₁, C₂ and C₃ are smaller than a predetermined set value; and

a low-illuminance correction section configured to retrieve the color data value judged to be smaller than the set value based on the white color data value and the color data value larger than the set value when two larger values among the color data values C₁, C₂ and C₃ are judged to be smaller than the set value.

11. The sensor according to claim 9,

wherein the low-illuminance correction section has a first color correction section configured to determine a value obtained by subtracting a value obtained by multiplying two color data values among the color data values C₁, C₂ and C₃ by the coefficients S₁, S₂ and S₃ determined by color balance from the white color data value W as the remaining one color data value among the color data values C₁, C₂ and C₃ when only the remaining one color data value is smaller than the set value.

12. The sensor according to claim 9, further comprising a storage section configured to store a first color data value C₁^P of first color, a second color data value C₂^P of second color, a third color data value C₃^P of third color and a white data value W obtained by a preceding signal process of the signal processing section,

wherein the signal processing section corrects the color data values C_j, C₂ and C₃ and the white color data value W corrected by the low-illuminance correction section by using the data values C₁^P, C₂^P, C₃^P and W stored in the storage section.

13. The sensor according to claim 12,

wherein the low-illuminance correction section has a second color correction section configured to determine a value obtained by prorating a value obtained by subtracting one data value among the color data values C₁, C₂ and C₃ from the white color data value W with two color data values stored in the storage section as new two color data values when the two color data values are smaller than the set value.

14. The sensor according to claim 12,

wherein the low-illuminance correction section has a third color correction section configured to determine values obtained by prorating the white color data value W with three color data values C₁^P, C₂^P and C₃^P stored in the storage section as new data values C₁, C₂ and C₃ when all of the color data values C₁, C₂ and C₃ are smaller than the set value.

15. The sensor according to claim 9,

wherein the low-illuminance correction section has a fourth color correction section configured to determine the color data values C₁, C₂ and C₃ as C₁=W/S₁, C₂=W/S₂ and C₃=W/S₃ by using the white color data value W and the coefficients S₁, S₂ and S₃ determined by the color balance when at least one of the color data values C₁, C₂ and C₃ is smaller than the set value.

22. A solid-state image sensor, comprising:

a plurality of pixels which are formed in matrix form on a semiconductor substrate, each pixel having a photoelectric converting element which outputs an electric signal obtained by photoelectric conversion; and

a read-out circuit configured to read out the electric signals outputted from the plurality of pixels,

wherein the plurality of pixels are sorted out into a plurality of pixel blocks in units of two or more pixels; and

the plurality of pixels is in a square shape slanted by 45°

with respect to two axes of image pick-up surface, the neighboring pixels being arranged without placing any space, the first and fourth pixels being arranged along a row different from each other.