Imaging apparatus and image signal processing method producing wide dynamic range

• US 6,922,209 B1
• Filed: 03/23/1999
• Issued: 07/26/2005
• Est. Priority Date: 09/01/1998
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Na, Woon, Hwang, Jung-Hyun
• Primary Examiner(s): Moe, Aung
• Assistant Examiner(s): Tillery, Rashawn N
• Application Number:
  US09/273,643
• Time in Patent Office: 2,317 Days
• Field of Search: 348/230.1, 348/679, 348/222.1, 348/362, 348/229.1, 348/296, 348/254, 348/645, 348/646, 348/647, 348/672, 348/678, 348/674, 348/675, 348/677, 348/722.1, 348/302, 348/600, 358/550, 358/443, 382/168, 382/171, 382/172
• US Class Current: 348/229.1
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

An imaging apparatus and method provides a wide dynamic range and is capable of displaying an improved color in low-luminance regions, and an image signal processing method thereof. In the imaging apparatus, a first process divides the voltage level of an analog image signal into a plurality of sections and amplifies the analog image signal with a plurality of different gains according to each section, and a second process converts the analog image signal amplified with the different gains into a digital signal, and non-linearly gamma-corrects the digital signal according to each section. The plurality of different gains may be inversely proportional to the luminance level of the analog image signal. Thus, the level of an analog signal in a low-luminance region is amplified with a gain greater than in a high-luminance region before gamma correction, so that signal-to-noise (S/N) ratio in the low-luminance region of an image is increased, thereby improving sensitivity of the image following gamma correction. Accordingly, a wide dynamic range is provided. An optional chrominance controller of the imaging apparatus controls chrominance gain of the digital signal and outputs the result, thereby displaying an improved color in low-luminance regions of the image.

Claims

1. An imaging apparatus comprising:

first signal processing means including a first analog-to-digital converter for converting an analog image signal into a first digital signal for partitioning the level of the analog image signal into a plurality of sections, a gain selector for selecting a corresponding gain from a plurality of different gains according to each of the plurality of sections, and an amplifier for amplifying the analog image signal by the plurality of gains according to each of the plurality of sections, at least two of the sections having different corresponding gains; and

second signal processing means including a second analog-to-digital converter for converting the analog image signal amplified by the plurality of different gains into a second digital signal, and a gamma corrector for non-linearly gamma-correcting the second digital signal according to each section of the plurality of sections on which the amplification of the analog image signal by the first signal processing means is based.

2. The imaging apparatus of claim 1, wherein the plurality of different gains are provided by a microcomputer.

3. The imaging apparatus of claim 1, wherein the plurality of different gains are approximately inversely proportional to the luminance level of the analog image signal.

4. The imaging apparatus of claim 1, further comprising a chrominance controller for controlling chrominance gain of the non-linearly gamma corrected digital output of the second signal processing means.

5. The imaging apparatus of claim 4, wherein the chrominance controller comprises:

a low pass filter for passing a low-frequency component of the non-linearly gamma corrected digital output of the second means, to output a luminance signal;

a chrominance gain selector for partitioning the level of the luminance signal into a plurality of second sections, and for selectively outputting a corresponding second gain among a plurality of different second gains according to each section;

a high pass filter for passing a high frequency component of the non-linearly gamma corrected digital output of the second means, to output a chrominance signal;

a multiplier for multiplying the chrominance signal by the corresponding second gain from the chrominance gain selector;

an adder for adding the output of the multiplier to the luminance signal;

a divider for dividing the output of the adder by approximately 2; and

a clipper for outputting a digital 0 if the output of the divider is less than 0, and for outputting the maximum value of the output of the second signal processing means if the output of the divider is greater than the maximum value of the output of the second signal processing means.

6. The imaging apparatus of claim 5, wherein the plurality of different second gains are approximately inversely proportional to the level of the luminance signal.

7. An imaging apparatus comprising:

an amplifier for amplifying an analog image signal by a predetermined gain;

an analog-to-digital converter for converting the amplified analog image signal into a digital signal;

a chrominance controller for controlling chrominance gain of the converted output of the analog-to-digital converter; and

a digital signal processor for processing the output of the chrominance controller.

8. The imaging apparatus of claim 7, wherein the chrominance controller comprises:

a low pass filter for passing a low-frequency component of the converted output of the analog-to-digital converter, to output a luminance signal;

a chrominance gain selector for dividing the level of the luminance signal into a plurality of sections, and for selectively outputting a corresponding gain among the plurality of different gains according to each section;

a high pass filter for passing a high frequency component of the converted output of the analog-to-digital converter, to output a chrominance signal;

a multiplier for multiplying the chrominance signal by the corresponding gain output from the chrominance gain selector;

an adder for adding the output of the multiplier to the luminance signal;

a divider for dividing the output of the adder by a factor; and

a clipper for outputting a digital 0 if the output of the divider is less than 0, and for outputting the maximum value of the output of the analog-to-digital converter if the output of the divider is greater than the maximum value of the output of the analog-to-digital converter.

9. The imaging apparatus of claim 8, wherein the plurality of different gains are approximately inversely proportional to the level of the luminance signal.

10. The imaging apparatus of claim 8, wherein the factor is approximately 2.

11. An image signal processing method comprising:

converting an analog image signal into a first digital signal for partitioning the level of the analog image signal into a plurality of sections, selecting a corresponding gain among a plurality of different gains according to each of the plurality of sections and amplifying the image signal by the plurality of different gains according to each of the plurality of sections, at least two of the sections having different corresponding gains; and

converting the image signal amplified by the plurality of different gains into a second digital signal, and non-linearly gamma-correcting the second digital signal according to each section of the plurality of sections on which the amplification of the analog image signal is based.

12. The method of claim 11, wherein the plurality of different gains are provided by a microcomputer.

13. The method of claim 11, wherein the plurality of different gains are approximately inversely proportional to the luminance level of the analog image signal.

14. The method of claim 11, further comprising controlling chrominance gain of the non-linearly gamma-corrected second digital signal.

15. The method of claim 14, wherein controlling comprises:

passing a low-frequency component of the non-linearly gamma-corrected digital signal, to output a luminance signal;

partitioning the level of the luminance signal into a plurality of second sections, and selecting a corresponding second gain among a plurality of different second gains according to each second section;

passing a high-frequency component of the nonlinearly gamma-corrected digital signal, to output a chrominance signal;

multiplying the chrominance signal by the corresponding selected second gain;

adding the result of the multiply to the luminance signal;

dividing the result of the add by approximately 2; and

clipping to 0 if the result of the division is less than 0, and clipping to the maximum value of the gamma-corrected digital signal if the result of the division is greater than the maximum value of the gamma-corrected digital signal, and outputting the result.

16. The method of claim 15, wherein the plurality of second gains are approximately proportional to the luminance level of the analog image signal.