Method of correcting gradation and image display system employing the same

• US 6,816,155 B1
• Filed: 03/29/2000
• Issued: 11/09/2004
• Est. Priority Date: 03/29/1999
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Ogawa, Eiji
• Primary Examiner(s): Tran, Henry N.
• Application Number:
  US09/537,679
• Time in Patent Office: 1,686 Days
• Field of Search: 345/207, 345/687, 345/690, 345/589-591, 345/596-597, 348/180, 348/189, 348/236, 348/254, 348/609, 382/274, 382/275, 382/300, 358/521, 358/525, 358/429, 358/455, 358/456, 358/457, 358/458
• US Class Current: 345/207
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: H04N 17/04 for receivers
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82

Abstract

The method of gradation correction of input image data to be displayed on an image display apparatus converts to logarithmic data first characteristic values which represent the display characteristics inherent in the image display apparatus and second characteristic values which represent the desired gradation to be eventually realized with the image display apparatus, respectively, and optionally interpolating both the logarithmic data, constructs a gradation correction table based on both the logarithmic data of the first characteristic values and the logarithmic data of the second characteristic values and performs gradation correction on the input image data to the image display apparatus using the gradation correction table. The image display system displays on the image display apparatus the thus corrected image data on which the gradation correction is performed by implementing the method. The method and system are capable of producing a smooth enough correction LUT (look-up table) to allow gradation correction to be performed in such a way that the image display apparatus will eventually provide the intended display characteristics. Therefore, the system can display a high quality image that has no defects such as artifacts.

Claims

1. A method of gradation correction of input image data to be displayed on an image display apparatus, comprising the steps of:

acquiring first characteristic values which represent the display characteristics inherent in the image display apparatus;

converting the first characteristic values to logarithmic data;

acquiring as the logarithmic data second characteristic values which represent the desired gradation to be eventually realized with the image display apparatus;

constructing a gradation correction table based on the logarithmic data of said first characteristic values and the logarithmic data of said second characteristic values that have been converted logarithmically; and

performing gradation correction on the input image data to the image display apparatus using said gradation correction table.

2. The method according to claim 1, wherein said logarithmic data of the second characteristic values are acquired by inputting directly the logarithmic data of the second characteristic data or by inputting the second characteristic data and then converting the second characteristic data to the logarithmic data.

3. A method of gradation correction according to claim 1, further comprising the step of:

interpolating said logarithmic data of said first characteristic values and said logarithmic data of said second characteristic values that have been converted logarithmically;

wherein said gradation correction table is constructed based on said logarithmic data of said first characteristic values and said logarithmic data of said second characteristics values.

4. The method according to claim 3, wherein said interpolation is selectable from between high-order interpolation and linear interpolation.

5. The method of claim 4, wherein the higher order interpolation comprises a quadratic interpolation.

6. The method according to claim 3, wherein said interpolation is adapted to be switched between high-order interpolation and linear interpolation depending upon a number of discrete points to be interpolated.

7. The method of claim 1, wherein the first characteristic value corresponds to luminance of the display.

8. The method of claim 7, further comprising interpolating said logarithmic data of said first characteristic value and said logarithmic data of said second characteristic values that have been converted logarithmically, wherein said gradation correction table is constructed based on said logarithmic data of said first characteristic values and said logarithmic data of said second characteristic values.

9. The method of claim 8, wherein the higher order interpolation comprises a quadratic interpolation.

10. The method according to claim 1, wherein said input image data is data for displaying a predetermined test pattern, said predetermined test pattern is displayed on a display screen of said image display apparatus, transmitted light from said display screen in accordance with said predetermined test pattern displayed on said display screen is measured, output luminance data corresponding to said input image data is obtained, and said first characteristic values are acquired from said obtained output luminance.

11. An image display system, comprising:

an image display apparatus on which displays input image data;

a first characteristic value acquiring device which acquires first characteristic values which represent display characteristics inherent in said image display apparatus;

a first logarithmic conversion device which converts the first characteristic values to logarithmic data;

a logarithmic data acquiring device which acquires logarithmic data of second characteristic values which represent the desired gradation to be eventually realized with said display apparatus;

a gradation correction table constructing device by which a gradation correction table is constructed based on said respective logarithmic data of said first characteristic values and said second characteristic values that have been converted logarithmically; and

a gradation correction device which performs gradation correction on said input image data using said gradation correction table;

wherein the corrected input image data on which said gradation correction is performed by said gradation correction device is displayed on said image display apparatus.

12. An image display system according to claim 11, further comprising:

an interpolation device for interpolating said respective logarithmic data of said first characteristic values and said second characteristic values, respectively;

wherein said gradation correction table constructing device constructs said gradation correction table based on said respectively logarithmic data of said first characteristic values and said second characteristic values that have been interpolated, respectively.

13. The system according to claim 12, wherein said interpolation device adapts to switch the interpolation between high-order interpolation and linear interpolation depending upon a number of discrete points to be interpolated.

14. The system according to claim 12, wherein said interpolation device can select the interpolation between high-order interpolation and linear interpolation.

15. The system of claim 14, wherein the higher order interpolation comprises a quadratic interpolation.

16. The system according to claim 11, wherein said logarithmic data acquiring device is a direct input device which inputs directly the logarithmic data of the second characteristic values.

17. The system according to claim 11, wherein said logarithmic data acquiring device comprises an input device which inputs the second characteristic values and a second logarithmic conversion device which converts the second characteristic values to the logarithmic data.

18. The system according to claim 17, wherein said first and second logarithmic conversion devices are one logarithmic conversion device.

19. The system according to claim 11, wherein said first characteristic value acquiring device is a luminance meter with which a transmitted light from said image display apparatus is measured and that provides luminance data for obtaining the first characteristic values.

20. The system of claim 19, further comprising:

an interpolation device for interpolating said respective logarithmic data of said first characteristic values and said second characteristic values,

wherein said gradation correction table constructing device constructs said gradation correction table based on said respective logarithmic data of said first characteristic values and said second characteristic values that have been interpolated.

21. The system of claim 20, wherein the interpolation device selectively sets interpolation between higher order interpolation and linear interpolation.

22. The system according to claim 19, wherein said input image data is data for displaying a predetermined test pattern and said predetermined test pattern is displayed on a display screen of said image display apparatus, and wherein said luminance meter measures transmitted light from said display screen in accordance with said predetermined test pattern displayed on said display screen, obtains output luminance data corresponding to said input image data and acquires said first characteristic values from said obtained output luminance data.

23. The system according to claim 11, wherein said input image data is data for displaying a predetermined test pattern and said predetermined test pattern is displayed on a display screen of said image display apparatus, and wherein said first characteristic value acquiring device measures transmitted light from said display screen in accordance with said predetermined test pattern displayed on said display screen, obtains output luminance data corresponding to said input image data and acquires said first characteristic values from said obtained output luminance data.