Methods and apparatus for shallow gradient artifact reduction in image display systems

Patent metadata

Field	Value
Publication number	US-10798346-B2
Application number	US-201815913556-A
Country	US
Kind code	B2
Filing date	Mar 6, 2018
Priority date	Nov 14, 2016
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

In described examples, a method includes: receiving an array of image data pixels for display by a spatial light modulator; dividing the array of image data pixels into a plurality of blocks. For the blocks of the plurality of blocks, the method includes: computing a mean value for pixels in the block; computing a variance for pixels in the block; and, in response to the mean value and the variance, retrieving an indicator of a likelihood of a visible artifact for the block; and in response to the retrieved indicator, outputting a signal to selectively increase or reduce a load time of the spatial light modulator for displaying the array of image data pixels.

First claim

What is claimed is:

1. A method, comprising:
with a controller circuit;
receiving first and second blocks of pixel data;
computing first mean values of a first color component in the pixel data;
computing second mean values of a second color component in the pixel data;
computing first variances of the first color component in the pixel data;
computing second variances of the second color component in the pixel data; and
using the first and second mean values and the first and second variances as address values to retrieve indicators of a likelihood of a visible artifact, and adjusting a time between successive loadings of the first and second blocks into memory cells of a spatial light modulator, responsive to the retrieved indicators, in which the likelihood of the visible artifact is reduced by reducing the time between the successive loadings, and the likelihood of a visible artifact is increased by increasing the time between the successive loadings.

2. The method of claim 1 , wherein the visible artifact is a visible pulse width modulation temporal contour artifact.

3. The method of claim 1 , wherein the first and second blocks are part of a two-dimensional array of pixel data.

4. The method of claim 1 , wherein adjusting the time includes:
responsive to the retrieved indicators, selectively clearing or setting binary flags;
summing the binary flags to form a summation value;
comparing the summation value to a threshold value; and
responsive to the comparing, adjusting the time.

5. The method of claim 1 , further comprising:
with the spatial light modulator, modulating light responsive to the successive loadings.

6. The method of claim 1 , wherein computing the first mean values includes:
adding an intensity value of the first color component to a running sum of pixel intensity values.

7. The method of claim 6 , wherein computing the first mean values includes:
dividing the running sum of pixel intensity values by at least a number of pixels in one of the first or second blocks.

8. The method of claim 1 , wherein computing the first variances includes:
computing a squared intensity value of the first color component, and adding the squared intensity value to a running sum of squared intensity values.

9. The method of claim 8 , wherein computing the first variances includes:
computing a standard deviation for at least one of the first or second blocks, responsive to the running sum of squared intensity values and a selected one of the first mean values.

10. The method of claim 9 , wherein computing the standard deviation includes:
computing the standard deviation as a square root of: the running sum of squared intensity values minus the selected first mean value squared.

11. The method of claim 1 , wherein computing the first variances includes:
computing a difference between a maximum pixel intensity value of the first color component in a selected one of the first or second blocks and a minimum pixel intensity value of the first color component in the selected block.

12. The method of claim 1 , further comprising:
computing third mean values of a third color component in the pixel data; and
computing third variances of the third color component in the pixel data; and
using the third mean values and the third variances as address values to retrieve the indicators.

13. The method of claim 1 , wherein the spatial light modulator is a digital micromirror device or a liquid-crystal-on-silicon device.

14. A system, comprising:
a spatial light modulator having control inputs and memory cells, the spatial light modulator configured to: load pixel data into the memory cells responsive to the control inputs; and modulate light responsive to the pixel data in the memory cells; and
a controller circuit having control outputs coupled to the control inputs, the controller circuit configured to adjust a time between successive loadings of first and second blocks of pixel data into the memory cells, in which a likelihood of a visible artifact is reduced by reducing the time between the successive loadings, and the likelihood of the visible artifact is increased by increasing the time between the successive loadings;
the controller circuit configured to adjust the time between the successive loadings by performing steps including:
computing first mean values of a first color component in the pixel data;
computing second mean values of a second color component in the pixel data;
computing first variances of the first color component in the pixel data;
computing second variances of the second color component in the pixel data;
using the first and second mean values and the first and second variances as address values to retrieve indicators of the likelihood of the visible artifact; and
controlling the control outputs to adjust the time between the successive loadings, responsive to the retrieved indicators.

15. The system of claim 14 , wherein the visible artifact is a visible pulse width modulation temporal contour artifact.

16. The system of claim 14 , wherein the steps include:
responsive to the retrieved indicators, selectively clearing or setting binary flags;
summing the binary flags to form a summation value;
comparing the summation value to a threshold value; and
responsive to the comparing, adjusting the time.

17. The system of claim 14 , wherein computing the first mean values includes:
adding an intensity value of the first color component to a running sum of pixel intensity values.

18. The system of claim 17 , wherein computing the first mean values includes:
dividing the running sum of pixel intensity values by at least a number of pixels in one of the first or second blocks.

19. The system of claim 14 , wherein computing the first variances includes:
computing a squared intensity value of the first color component, and adding the squared intensity value to a running sum of squared intensity values.

20. The system of claim 19 , wherein computing the first variances includes:
computing a standard deviation for at least one of the first or second blocks, responsive to the running sum of squared intensity values and a selected one of the first mean values.

21. The system of claim 20 , wherein computing the standard deviation includes:
computing the standard deviation as a square root of: the running sum of squared intensity values minus the selected first mean value squared.

22. The system of claim 14 , wherein computing the first variances includes:
computing a difference between a maximum pixel intensity value of the first color component in a selected one of the first or second blocks and a minimum pixel intensity value of the first color component in the selected block.

23. The system of claim 14 , wherein the spatial light modulator is a digital micromirror device or a liquid-crystal-on-silicon device.

Assignees

• Texas Instruments Inc

Inventors

• Morgan Dan
• Kempf Jeffrey Matthew

Classifications

• H04N9/3123 Primary

  using pulse width modulation · CPC title

• H04N9/3111

  for displaying the colours sequentially, e.g. by using sequentially activated light sources (sequential projection in colour photography G03B33/08) · CPC title

• H04N9/3155

  for controlling the light source (light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406) · CPC title

• H04N9/3179

  Video signal processing therefor · CPC title

• H04N9/3164

  using multiple light sources · CPC title