SIGNAL CONVERSION APPARATUS AND METHOD, AND PROGRAM AND RECORDING MEDIUM

• US 20150312542A1
• Filed: 02/14/2014
• Published: 10/29/2015
• Est. Priority Date: 02/14/2013
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: SUGINOHARA, Hidetsugu, YOSHII, Hideki, YAMANAKA, Satoshi
• Granted Patent: US 9,578,296 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: H04N 9/64 Circuits for processing colour signals H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85
• CPC Class Codes: H04N 9/69 for modifying the colour signals by gamma correction controlling camera response for colour signals H04N23/83
• CPC Class Codes: H04N 9/77 Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase circuits for matrixing H04N9/67

Abstract

A maximum value Yimax and a minimum value Yimin of input pixel data Ri, Gi, Bi for each pixel are determined. A saturation adjustment value X is determined using a function g (Yimax, Yimin), white pixel data Wo is determined using a function f (Yimin), and these are used to determine output pixel data Ro, Go, Bo. Even the saturation represented by RGB three-color data is high, conversion to RGBW four-color data with improved brightness can be made, without changing the hue.

Claims

1. A signal conversion apparatus comprising:

a pixel value comparison unit for outputting a maximum value Yimax and a minimum value Yimin of input pixel data Ri, Gi, Bi of red, green and blue for each pixel;

a saturation adjustment value calculation unit for determining a saturation adjustment value X by using a first function g (Yimax, Yimin) which does not exceed an upper limit L which is given from the maximum value Yimax, and the minimum value Yimin, by;

2. The signal conversion apparatus as set forth in claim 1, wherein the saturation adjustment value calculation unit comprises:

an upper limit calculation unit for determining the upper limit L from the maximum value Yimax and the minimum value Yimin;

a provisional value calculation unit for determining a provisional value of the first function from the minimum value Yimin, by a third function gt (Yimin); and

a decision unit for determining a smaller one of the upper limit L and the provisional value gt (Yimin) as the first function g (Yimax, Yimin).

3. The signal conversion apparatus as set forth in claim 1, wherein the saturation adjustment value calculation unit comprises a LUT for receiving, as inputs, the maximum value Yimax and the minimum value Yimin, and outputting the saturation adjustment value X.

4. The signal conversion apparatus as set forth in claim 1, wherein

the second function f (Yimin) is a function which monotonically increases with respect to the minimum value Yimin, and

when the minimum value Yimin is zero, the second function f (Yimin) is also zero.

5. The signal conversion apparatus as set forth in claim 1, wherein

the first function g (Yimax, Yimin) and the second function f (Yimin) are changeable.

6. An image display apparatus comprising:

the signal conversion apparatus as set forth in claim 1, and

a display unit for displaying an image using the pixel data of four colors of red, green, blue and white.

7. The image display apparatus as set forth in claim 6, wherein

the display unit has a difference between the luminance of white displayed by the pixel data of red, green and blue of a certain gradation value, and the luminance of white displayed by the pixel data of white of the same gradation value, and

when the white pixel data Wo producing a display luminance which is identical to the display luminance obtained when the output pixel data Ro, Go, Bo of red, green and blue are all of a certain first gradation value Ta, is of a second gradation value Wa, the saturation adjustment value X is set with reference to a value obtained by multiplying the second function f (Yimin) by a ratio Wa/Ta of the second gradation value to the first gradation value.

8. A signal conversion method comprising:

a pixel value comparison step for outputting a maximum value Yimax and a minimum value Yimin of input pixel data Ri, Gi, Bi of red, green and blue for each pixel;

a saturation adjustment value calculation step for determining a saturation adjustment value X by using a first function g (Yimax, Yimin) which does not exceed an upper limit L which is given from the maximum value Yimax, and the minimum value Yimin, by;

9. A program for having a computer execute each step of the signal conversion method as set forth in claim 8.

10. A computer-readable recording medium storing the program as set forth in claim 9.