Image processing method, image processing apparatus, and projector

• US 20040032982A1
• Filed: 06/11/2003
• Published: 02/19/2004
• Est. Priority Date: 06/27/2002
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Nishizawa, Masato
• Granted Patent: US 7,245,764 B2
• Time in Patent Office: Days
• US Class Current: 382/171
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 5/147 Scene change detection
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response

Abstract

To provide an image processing method, an image processing apparatus, and a projector which determine a scene-change so as to perform an optimal tone conversion, luminance correction, or the like, for each scene of a moving image. [Solving Means] An image processing apparatus 100 includes a normalized-luminance-histogram computing unit 101 for computing a normalized luminance histogram for each frame, histogram buffers 201a and 201b for storing normalized luminance histograms of respective comparing frames, a scene-change-detecting reference-value computing unit 102 for computing scene-change-detecting reference values α and β corresponding to correlations between two normalized luminance histograms of the first and second frames respectively stored in the histogram buffers 201a and 201b, and a scene-change determining unit 103 for determining whether a change in scenes between images of the first and second frames has occurred or not, in accordance with the scene-change-detecting reference values α and β.

Claims

1. An image processing method comprising the steps of:

computing a normalized luminance histogram of each frame;

computing scene-change-detecting reference values corresponding to correlations between two normalized luminance histograms of first and second frames computed in the step of computing a normalized luminance histogram of each frame; and

determining whether a change in scenes between images of the first and second frames has occurred or not, in accordance with the scene-change-detecting reference values.

2. The image processing method according to claim 1, wherein the scene-change-detecting reference values include at least first and second scene-change-detecting reference values.

3. The image processing method according to claim 2, wherein, in order to compute the first scene-change-detecting reference value, the step of computing scene-change-detecting reference values comprises the steps of:

computing the product of two distribution frequencies at each corresponding luminance level of the two normalized luminance histograms of the first and second frames;

computing the square value of the distribution frequency at the corresponding luminance level of the normalized luminance histogram of the first frame;

computing an absolute difference in the product and the square value; and

computing the sum total of the absolute differences in a range of the luminance levels from the minimum luminance to the maximum luminance.

4. The image processing method according to claim 2, wherein, in order to compute the second scene-change-detecting reference value, the step of computing scene-change-detecting reference values comprises the steps of:

computing the product of two distribution frequencies at each correspondingluminance level of the two normalized luminance histograms of the first and second frames;

computing the square value of the distribution frequency at the corresponding luminance level of the normalized luminance histogram of the second frame;

computing an absolute difference in the product and the square value; and

computing the sum total of the absolute differences in a range of the luminance levels from the minimum luminance to the maximum luminance.

5. The image processing method according to claim 2, wherein the scene-change determining step comprises the steps of comparing at least one of the first and second scene-change-detecting reference values with a predetermined threshold;

and determining that a change in the scenes has occurred when said at least one of the scene-change-detecting reference values is equal to or greater than the predetermined threshold.

6. The image processing method according to claim 5, wherein the comparing and determining steps determine that a change in the scenes has occurred when both the first and second scene-change-detecting reference values are equal to or greater than another threshold which is smaller than the predetermined threshold.

7. The image processing method according to claim 5, wherein the comparing and determining steps determine that a change in the scenes has occurred when the sum of the first and second scene-change-detecting reference values is equal to or greater than a predetermined value.

8. An image processing apparatus comprising:

a normalized-luminance-histogram computing unit for computing a normalized luminance histogram of each frame;

a normalized-luminance-histogram storage unit for storing the normalized luminance histogram of the frame;

a scene-change-detecting reference-value computing unit for computing scene-change-detecting reference values corresponding to correlations between two normalized luminance histograms of first and second frames stored in the normalized-luminance-histogram storage units; and

a scene-change determining unit for determining that a change in scenes between images of the first and second frames has occurred or not, in accordance with the scene-change-detecting reference values.

9. A projector comprising:

a light source for feeding illumination light;

a space modulation element for modulating the light from the light source in accordance with an image signal;

the image processing apparatus according to claim 8 for processing an image from the space modulation element; and

a projection lens system for projecting the image processed by the image processing apparatus.