Video signal processing

Abstract

In a video signal processing device, a black-white expansion circuit performs black-white expansion of a luminance signal (Y signal) included in a video signal to generate an expanded luminance signal (Y′ signal). A luminance ratio ‘n’ is computed as the rate of the expanded luminance signal (Y′ signal) to the luminance signal (Y signal). A first color difference signal (U signal) and a second color difference signal (V signal) included in the video signal are respectively multiplied by the luminance ratio ‘n’ (=Y′/Y) to give an expanded first color difference signal (U′ signal) and an expanded second color difference signal (V′ signal). This arrangement of the invention effectively enables black-white expansion with no color change, while attaining reduction of the overall circuit scale.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the general configuration of a liquid crystal projector as one application of video signal processing device in a first embodiment of the invention;

FIG. 2 is a block diagram showing the structure of a video signal processing circuit included in the liquid crystal projector of the first embodiment shown in FIG. 1;

FIG. 3 is a graph showing a plot of luminance conversion characteristic specified by a luminance conversion characteristic specification circuit included in the video signal processing circuit of FIG. 2;

FIG. 4 is a block diagram showing the general configuration of another liquid crystal projector as another application of video signal processing device in a second embodiment of the invention; and

FIG. 5 is a flowchart showing a video signal processing routine according to a computer program Pr.

Claims

1. A video signal processing device for processing a video signal, the video signal processing device comprising:a three signal acquisition module that obtains a luminance signal, a first color difference signal, and a second color difference signal from the video signal;a black-white expansion module that performs black-white expansion of the luminance signal to generate an expanded luminance signal;a luminance ratio computation module that computes a rate of the expanded luminance signal to the luminance signal as a luminance ratio;a first color difference signal expansion module that expands the first color difference signal according to the computed luminance ratio to give an expanded first color difference signal; anda second color difference signal expansion module that expands the second color difference signal according to the computed luminance ratio to give an expanded second color difference signal.

2. The video signal processing device in accordance with claim 1, wherein the first color difference signal expansion module multiplies the first color difference signal by the computed luminance ratio to give the expanded first color difference signal, and the second color difference signal expansion module multiplies the second color difference signal by the computed luminance ratio to give the expanded second color difference signal.

3. The video signal processing device in accordance with claim 1, the video signal processing device further comprising:a delay operation module that respectively delays the expanded luminance signal as well as the first color difference signal and the second color difference signal obtained by the three signal acquisition module to enable external output of the expanded luminance signal, the expanded first color difference signal, and the expanded second color difference signal at an identical timing.

4. An image display apparatus including the video signal processing device in accordance with claim 1.

5. A computer program product that causes a computer to process a video signal, the computer program product comprising:a first program code of obtaining a luminance signal, a first color difference signal, and a second color difference signal from the video signal;a second program code of performing black-white expansion of the luminance signal to generate an expanded luminance signal;a third program code of computing a rate of the expanded luminance signal to the luminance signal as a luminance ratio;a fourth program code of expanding the first color difference signal according to the computed luminance ratio to give an expanded first color difference signal;a fifth program code of expanding the second color difference signal according to the computed luminance ratio to give an expanded second color difference signal; anda computer readable medium that stores the first through the fifth program codes.

6. The computer program product in accordance with claim 5, wherein the fourth program code includes: a program code of expanding the first color difference signal multiplies the first color difference signal by the computed luminance ratio to give the expanded first color difference signal, andthe fifth program code includes:a program code of expanding the second color difference signal multiplies the second color difference signal by the computed luminance ratio to give the expanded second color difference signal.

7. The computer program product in accordance with claim 5, the computer program further comprising:a sixth program code of enabling external output of the expanded luminance signal, the expanded first color difference signal, and the expanded second color difference signal at an identical timing.

8. A video signal processing method of processing a video signal, the video signal processing method comprising:obtaining a luminance signal, a first color difference signal, and a second color difference signal from the video signal;performing black-white expansion of the luminance signal to generate an expanded luminance signal;computing a rate of the expanded luminance signal to the luminance signal as a luminance ratio;expanding the first color difference signal according to the computed luminance ratio to give an expanded first color difference signal; andexpanding the second color difference signal according to the computed luminance ratio to give an expanded second color difference signal.