Pixel defect detector for solid-state imaging device

• US 7,106,371 B1
• Filed: 09/08/1999
• Issued: 09/12/2006
• Est. Priority Date: 09/08/1998
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Zhang, Xiaomang, Kubo, Noboru
• Primary Examiner(s): Ho, Tuan
• Assistant Examiner(s): WHIPKEY, JASON T
• Application Number:
  US09/391,473
• Time in Patent Office: 2,561 Days
• Field of Search: 348/246, 348/247, 348/187
• US Class Current: 348/246
• CPC Class Codes: H04N 25/68 applied to defects

Abstract

A pixel defect detector of the present invention is used for a solid-state imaging device comprising a plurality of photoelectric transducers. The pixel defect detector includes: a calculation section for obtaining output characteristics of a subject photoelectric transducer for varied amounts of light incident thereupon so as to determine the presence/absence of a defect in the subject photoelectric transducer based on the output characteristics thereof.

Claims

1. A pixel defect detector for a solid-state imaging device comprising a plurality of photoelectric transducers, the pixel defect detector comprising:

a calculation section for obtaining output characteristics of a subject photoelectric transducer for at least three amounts of light incident thereupon so as to determine the presence/absence of a defect in the subject photoelectric transducer based on the output characteristics thereof, wherein

an output corresponding to a non-defective photoelectric transducer is calculated based on outputs from a plurality of photoelectric transducers neighboring the subject photoelectric transducer for at least one of the amounts of incident light without requiring specific amounts of incident light, and

the calculated output corresponding to a non-defective transducer is used in determining the presence/absence of a defect in the subject photoelectric transducer.

2. A pixel defect detector for a solid-state imaging device according to claim 1, wherein:

the pixel defect detector further comprises a picture memory for storing an output signal from the photoelectric transducer; and

the calculation section determines the output characteristics of the subject photoelectric transducer using the output signal of the subject photoelectric transducer stored in the picture memory.

3. A pixel defect detector for a solid-state imaging device according to claim 1, wherein:

the output characteristics of the subject photoelectric transducer are represented by a plurality of output signals of the subject photoelectric transducer in response to different amounts of light incident thereupon, respectively.

4. A pixel defect detector for a solid-state imaging device according to claim 1, wherein:

the pixel defect detector further comprises an optical system for projecting a picture onto the solid-state imaging device; and

the output of the photoelectric transducer is determined while the optical system is defocused with respect to the solid-state imaging device.

5. A pixel defect detector for a solid-state imaging device comprising a plurality of photoelectric transducers, the pixel defect detector comprising:

a picture memory for storing outputs from a subject photoelectric transducer in response to different amounts of light incident thereupon, respectively; and

a calculation section for determining a photoelectric coefficient a of the subject photoelectric transducer and an offset output level b of the subject photoelectric transducer in the absence of incident light based on the amounts of incident light, the outputs from the subject photoelectric transducer therefor, and Expression (1) below, so as to compare the photoelectric coefficient a and the offset output level b with a predetermined reference photoelectric coefficient a₀ and predetermined reference offset output level b₀, respectively, thereby determining the presence/absence of a defect in the subject photoelectric transducer;

y(x)=ax+b 

 

(1)

where y(x) denotes the output of the subject photoelectric transducer, and x denotes the amount of incident light, wherein

an output corresponding to a non-defective photoelectric transducer is calculated based on outputs from a plurality of photoelectric transducers neighboring the subject photoelectric transducer for at least one of the amounts of incident light without requiring specific amounts of incident light, and

the calculated output corresponding to a non-defective transducer is used in determining the presence/absence of a defect in the subject photoelectric transducer.

6. A pixel defect detector for a solid-state imaging device according to claim 5, wherein:

the pixel defect detector further comprises an optical system for projecting a picture onto the solid-state imaging device; and

the output of the photoelectric transducer is determined while the optical system is defocused with respect to the solid-state imaging device.

7. A pixel defect detector for a solid-state imaging device according to claim 5, wherein:

the amount of incident light x is determined by applying, to Expression (2) below, the predetermined reference photoelectric coefficient a₀, the predetermined reference offset output level b₀, and a reference output signal y₀;

x=(y₀−

b₀)/a₀ 

 

(2).

8. A pixel defect detector for a solid-state imaging device according to claim 5, wherein N amounts of incident light x₀, x₁, x₂, . . . , x_n-1 of the subject pixel to be examined and the actual output levels y₀, y₁, y₂, . . . , y_n-1 of the subject pixel to be examined, obtained respectively for each of the N amounts of incident light are substituted into the following expression (7)

9. A pixel defect detector for a solid-state imaging device comprising a plurality of photoelectric transducers, the pixel defect detector comprising:

a picture memory for storing outputs from a subject photoelectric transducer in response to different amounts of light incident thereupon, respectively; and

a calculation section for determining a photoelectric coefficient a of the subject photoelectric transducer and an offset output level b of the subject photoelectric transducer in the absence of incident light based on the amounts of incident light, the outputs from the subject photoelectric transducer therefor, and Expression (1) below, so as to compare the photoelectric coefficient a and the offset output level b with a predetermined reference photoelectric coefficient a₀ and predetermined reference offset output level b₀, respectively, thereby determining the presence/absence of a defect in the subject photoelectric transducer;

y(x)=ax+b 

 

(1)

where y(x) denotes the output of the subject photoelectric transducer, and x denotes the amount of incident light, wherein

an output corresponding to a non-defective photoelectric transducer is calculated based on outputs from a plurality of photoelectric transducers neighboring the subject photoelectric transducer for at least one of the amounts of incident light,

the amount of incident light x is determined by applying, to Expression (2) below, the predetermined reference photoelectric coefficient a₀, the predetermined reference offset output level b₀, and a reference output signal y₀;

x=(y₀−

b₀)/a₀ 

 

(2), and

the output y₀ is set to a median among outputs from the plurality of photoelectric transducers neighboring the subject photoelectric transducer.

10. A pixel defect detector for a solid-state imaging device according to claim 9, wherein:

the neighboring photoelectric transducers comprise only those which display the same one of a plurality of colors to be displayed as that of the subject photoelectric transducer.

11. A pixel defect detector for a solid-state imaging device according to claim 9, wherein N amounts of incident light x₀, x₁, x₂, . . . , x_n-1 of the subject pixel to be examined and the actual output levels y₀, y₁, t₂, . . . , y_n-1 of the subject pixel to be examined, obtained respectively for each of the N amounts of incident light are substituted into the following expression (7)

12. A pixel defect detector for a solid-state imaging device comprising a plurality of photoelectric transducers, the pixel defect detector comprising:

a picture memory for storing outputs from a subject photoelectric transducer in response to different amounts of light incident thereupon, respectively; and

a calculation section for determining a photoelectric coefficient a of the subject photoelectric transducer and an offset output level b of the subject photoelectric transducer in the absence of incident light based on the amounts of incident light, the outputs from the subject photoelectric transducer therefor, and Expression (1) below, so as to compare the photoelectric coefficient a and the offset output level b with a predetermined reference photoelectric coefficient a₀ and predetermined reference offset output level b₀, respectively, thereby determining the presence/absence of a defect in the subject photoelectric transducer;

y(x)=ax+b 

 

(1)

where y(x) denotes the output of the subject photoelectric transducer, and x denotes the amount of incident light, wherein

an output corresponding to a non-defective photoelectric transducer is calculated based on outputs from a plurality of photoelectric transducers neighboring the subject photoelectric transducer for at least one of the amounts of incident light, and

the presence/absence of a defect in the subject photoelectric transducer is determined by applying the photoelectric coefficient a of the subject photoelectric transducer, the offset output level b of the subject photoelectric transducer, the reference photoelectric coefficient a₀, and the reference offset output level b₀, to Expression (3) below;

no defect, if |a₀−

a|<

Δ

a and |b₀−

b|<

Δ

b 

 

(3)

where Δ

a and Δ

b are predetermined threshold values.

13. A pixel defect detector for a solid-state imaging device according to claim 12, wherein:

the reference photoelectric coefficient a₀ and the reference offset output level b₀ are prescribed for each of the colors to be displayed.

14. A pixel defect detector for a solid-state imaging device according to claim 12, wherein:

the pixel defect detector further comprises a determination section for determining a color to be displayed by the subject photoelectric transducer based on address data of the subject photoelectric transducer; and

the reference photoelectric coefficient a₀ and the reference offset output level b₀ are proscribed based on the determination by the determination section.

15. A pixel defect detector for a solid-state imaging device comprising a plurality of photoelectric transducers, the pixel defect detector comprising:

a picture memory for storing outputs from a subject photoelectric transducer in response to different amounts of light incident thereupon, respectively; and

a calculation section for determining a photoelectric coefficient a of the subject photoelectric transducer and an offset output level b of the subject photoelectric transducer in the absence of incident light based on the amounts of incident light, the outputs from the subject photoelectric transducer therefor, and Expression (1) below, so as to compare the photoelectric coefficient a and the offset output level b with a predetermined reference photoelectric coefficient a₀ and predetermined reference offset output level b₀, respectively, thereby determining the presence/absence of a defect in the subject photoelectric transducer;

y(x)=ax+b 

 

(1)

where y(x) denotes the output of the subject photoelectric transducer, and x denotes the amount of incident light, wherein

an output corresponding to a non-defective photoelectric transducer is calculated based on outputs from a plurality of photoelectric transducers neighboring the subject photoelectric transducer for at least one of the amounts of incident light, and

the presence/absence and the type of defect in the subject photoelectric transducer are determined by applying the photoelectric coefficient a of the subject photoelectric transducer, the offset output level b of the subject photoelectric transducer, the reference photoelectric coefficient a₀, and the reference offset output level b₀, to Expression (4) below;

no defect, if |a₀−

a|<

Δ

a and |b₀−

b|<

Δ

b;

a black blemish, if |a₀−

a|≧

Δ

a; and

a white blemish, if |b₀−

b|≧

Δ

b 

 

(4)

where Δ

a and Δ

b are predetermined threshold values.

16. A pixel defect detector for a solid-state imaging device according to claim 15, wherein:

the reference photoelectric coefficient a₀ and the reference offset output level b₀ are prescribed for each of the colors to be displayed.

17. A pixel defect detector for a solid-state imaging device according to claim 15, wherein:

the pixel defect detector further comprises a determination section for determining a color to be displayed by the subject photoelectric transducer based on address data of the subject photoelectric transducer; and

the reference photoelectric coefficient a₀ and the reference offset output level b₀ are prescribed based on the determination by the determination section.