Solid-state image sensor

• US 7,990,447 B2
• Filed: 06/14/2007
• Issued: 08/02/2011
• Est. Priority Date: 06/14/2006
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Iida, Yoshinori, Itoh, Goh, Honda, Hiroto, Egawa, Yoshitaka
• Primary Examiner(s): Tran; Sinh
• Assistant Examiner(s): Peterson; Christopher K
• Application Number:
  US11/815,903
• Publication Number:
  US 20100157091A1
• Time in Patent Office: 1,510 Days
• Field of Search: 348/294, 3482231-2251, 382/162, 382/167
• US Class Current: 348/294
• 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;
W′=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 processing 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 band 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 in a first visible light wavelength band within the visible light wavelength band, as compared to a transmissivity in a first remaining portion of the visible light wavelength band outside the first visible wavelength band;

a plurality of third pixels, each having a second color filter having a higher transmissivity in a second visible light wavelength band, different from the first visible light wavelength band, within the visible light wavelength band, as compared to a transmissivity in a second remaining portion of the visible light wavelength band outside the second visible wavelength band; and

a plurality of fourth pixels, each having a third color filter having a higher transmissivity in a third visible light wavelength band, different from the first and second visible light wavelength bands, within the visible light wavelength band, as compared to a third remaining portion of the visible light wavelength band outside the third visible 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.

2. The sensor according to claim 1,

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 C1w, C2w and C3w;

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

an interpolation processing section configured to correct the color data value of the target pixel by using the color data values C1w, C2w and C3w generated by the color separation processing section and the color data value of the target pixel around the white color pixel.

4. The sensor according to claim 3,

wherein the interpolation processing section corrects the color data value of the target pixel by using the color data values C1w, C2w, C3w 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.

5. The sensor according to claim 1,

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.

6. The sensor according to claim 1, wherein

the first visible light wavelength band corresponds to red light;

the second visible light wavelength band corresponds to green light; and

the third visible light wavelength band corresponds to blue light.

7. The sensor according to claim 1,

wherein the color ratios Km (m=1, 2 and 3) are expressed by the following expressions, where R_average, G_average, and B_average are averages of color data values R, G, and B, respectively, of a plurality of pixels around the target pixel W: