Gradation converting device, gradation converting method, and computer program

• US 20090196525A1
• Filed: 01/30/2009
• Published: 08/06/2009
• Est. Priority Date: 02/01/2008
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: TSUKAMOTO, Makoto, TAKAHASHI, Naomasa, NISHIO, Ayataka, HIRAI, Jun
• Granted Patent: US 8,295,636 B2
• Time in Patent Office: Days
• US Class Current: 382/263
• CPC Class Codes: G09G 3/2048 with addition of random noise to an image signal or to a gradation threshold
• CPC Class Codes: G09G 3/2059 using error diffusion
• CPC Class Codes: H04N 1/4052 by error diffusion, i.e. transferring the binarising error to neighbouring dot decisions

Abstract

A gradation converting device that converts gradation of an image includes: a dither unit that applies dither to the image by adding random noise to a pixel value forming the image; and a one-dimensional ΔΣ modulation unit that applies one-dimensional ΔΣ modulation to the image applied with the dither.

Claims

1. A gradation converting device that converts gradation of an image, the gradation converting device comprising:

dither means for applying dither to the image by adding random noise to a pixel value forming the image; and

one-dimensional Δ

Σ

modulation means for applying one-dimensional Δ

Σ

modulation to the image applied with the dither.

2. A gradation converting device according to claim 1, wherein the dither means has an HPF (High Pass Filter) for filtering a signal, filters the random noise with the HPF, and adds high-frequency components of the random noise obtained as a result of the filtering to the pixel value.

3. A gradation converting device according to claim 2, wherein a filter coefficient of the HPF is determined such that high-frequency characteristics of amplitude characteristics of the HPF are opposite characteristics of spatial frequency characteristics of a human vision.

4. A gradation converting device according to claim 3, wherein the filter coefficient of the HPF is determined on the basis of characteristics of spatial frequencies equal to or lower than a spatial frequency corresponding to resolution of displaying means for displaying the image applied with the Δ

Σ

modulation among the spatial frequency characteristics of the human vision such that the high-frequency characteristics of the amplitude characteristics of the HPF are the opposite characteristics of the spatial frequency characteristics of the human vision.

5. A gradation converting device according to claim 4, further comprising setting means for setting the filter coefficient of the HPF on the basis of the spatial frequency characteristics of the human vision and the resolution of the displaying means.

6. A gradation converting device according to claim 5, wherein the setting means further adjusts the filter coefficient of the HPF according to operation by a user.

7. A gradation converting device according to claim 1, wherein

the one-dimensional Δ

Σ

modulation means includes;

a one-dimensional filter for filtering a quantization error;

arithmetic means for adding up a pixel value of the image applied with the dither and an output of the one-dimensional filter; and

quantizing means for quantizing an output of the arithmetic means and outputting a quantized value including the quantization error as a result of the one-dimensional Δ

Σ

modulation, and

a filter coefficient of the one-dimensional filter is determined such that high-frequency characteristics of amplitude characteristics of noise shaping performed by the one-dimensional Δ

Σ

modulation means are opposite characteristics of spatial frequency characteristics of a human vision.

8. A gradation converting device according to claim 7, wherein the filter coefficient of the one-dimensional filter is determined on the basis of characteristics of spatial frequencies equal to or lower than a spatial frequency corresponding to resolution of displaying means for displaying the image applied with the Δ

Σ

modulation among the spatial frequency characteristics of the human vision such that the high-frequency characteristics of the amplitude characteristics of the noise shaping are the opposite characteristics of the spatial frequency characteristics of the human vision.

9. A gradation converting device according to claim 8, further comprising setting means for setting the filter coefficient of the one-dimensional filter on the basis of the spatial frequency characteristics of the human vision and the resolution of the displaying means.

10. A gradation converting device according to claim 9, wherein the setting means further adjusts the filter coefficient of the one-dimensional filter according to operation by a user.

11. A gradation converting device according to claim 7, wherein

the one-dimensional filter includes:

plural delaying means for storing an input to thereby delay the input; and

multiplying means for multiplying outputs of the plural delaying means and the filter coefficient together, and

the one-dimensional filter causes, in a horizontal blanking period of the image applied with the dither, the delaying means to keep stored values in the delaying means stored without initializing the stored values.

12. A gradation converting device according to claim 7, wherein

the one-dimensional filter includes:

plural delaying means for storing an input to thereby delay the input; and

multiplying means for multiplying outputs of the plural delaying means and the filter coefficient together, and

the one-dimensional filter initializes, with a random number, stored values in the delaying means in a horizontal blanking period of the image applied with the dither.

13. A gradation converting method for a gradation converting device that converts gradation of an image, the gradation converting method comprising the steps of:

the gradation converting device applying dither to the image by adding random noise to a pixel value forming the image; and

the gradation converting device applying one-dimensional Δ

Σ

modulation to the image applied with the dither.

14. A computer program for causing a computer to function as a gradation converting device that converts gradation of an image, the computer program causing the computer to function as:

dither means for applying dither to the image by adding random noise to a pixel value forming the image; and

one-dimensional Δ

Σ

modulation means for applying one-dimensional Δ

Σ

modulation to the image applied with the dither.

15. A gradation converting device that converts gradation of an image, the gradation converting device comprising:

a dither unit applying dither to the image by adding random noise to a pixel value forming the image; and

a one-dimensional Δ

Σ

modulation unit applying one-dimensional Δ

Σ

modulation to the image applied with the dither.