Color image processing method and apparatus

• US 6,618,502 B1
• Filed: 09/30/1999
• Issued: 09/09/2003
• Est. Priority Date: 09/30/1998
• Status: Expired due to Fees

• Current Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Inventors: Nakagawa, Mitsuhisa, Okada, Fujio, Negishi, Keiichi
• Primary Examiner(s): Au, Amelia M.
• Assistant Examiner(s): LAROSE, COLIN M
• Application Number:
  US09/409,661
• Time in Patent Office: 1,440 Days
• Field of Search: 382/162, 382/167, 358/520, 358/516, 358/518, 358/515, 358/521, 348/645-649, 348/29, 348/34, 348/272, 348/273, 348/255, 348/256, 348/655, 348/223.1, 348/225.1, 348/228.1, 348/229.1, 348/603, 348/224.1
• US Class Current: 382/167
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

In a first signal suppressing process, in cases where a signal level of a certain color signal among color signals obtained from an image sensing operation is higher than a predetermined signal level, the certain color signal is suppressed. An image sensing operation with a comparatively large exposure quantity and an image sensing operation with a comparatively small exposure quantity are performed alternately. It is detected that suppression of a certain color signal is performed in the first signal suppressing process when the image sensing operation with a comparatively large exposure quantity is performed. A calculation is made to find composition ratios of the color signals, which are obtained from the image sensing operation with a comparatively small exposure quantity. A second signal suppressing process is performed for suppressing at least one color signal other than the certain color signal such that the composition ratios become identical with the calculated composition ratios.

Claims

1. A color image processing method, comprising the steps of:

i) performing an image sensing operation for detecting an image of an object,

ii) obtaining a plurality of color signals, which carry color image information of the object, in accordance with an output having been obtained from the image sensing operation, and

iii) performing a first signal suppressing process in which, in cases where a signal level of a certain color signal among the plurality of the color signals is higher than a predetermined signal level, the certain color signal is suppressed,

wherein the improvement comprises the steps of;

a) controlling the image sensing operation such that an image sensing operation with a comparatively large exposure quantity and an image sensing operation with a comparatively small exposure quantity are performed alternately,

b) detecting that suppression of a certain color signal among the plurality of the color signals is performed in the first signal suppressing process when said image sensing operation with a comparatively large exposure quantity is performed,

c) calculating composition ratios of the plurality of the color signals, which are obtained from said image sensing operation with a comparatively small exposure quantity, and

d) performing a second signal suppressing process for suppressing at least one color signal other than said certain color signal in accordance with an output, which has been obtained from said detection of suppression and which represents that said suppression of said certain color signal is performed, said second signal suppressing process being performed such that the composition ratios of a plurality of color signals, which are obtained from said second signal suppressing process, become identical with said calculated composition ratios.

2. A method as defined in claim 1 wherein said image sensing operation with a comparatively large exposure quantity is performed by performing exposure for a comparatively long time, and said image sensing operation with a comparatively small exposure quantity is performed by performing exposure for a comparatively short time.

3. A color image processing apparatus, comprising:

i) image sensing means for performing an image sensing operation for detecting an image of an object,

ii) color signals separating means for obtaining a plurality of color signals, which carry color image information of the object, in accordance with an output having been obtained from the image sensing means, and

iii) first signal suppressing means for performing a first signal suppressing process in which, in cases where a signal level of a certain color signal among the plurality of the color signals is higher than a predetermined signal level, the certain color signal is suppressed,

wherein the improvement comprises the provision of;

a) image sensing operation control means for causing said image sensing means to alternately perform an image sensing operation with a comparatively large exposure quantity and an image sensing operation with a comparatively small exposure quantity,

b) detection means for detecting that suppression of a certain color signal among the plurality of the color signals is performed by the first signal suppressing means when said image sensing operation with a comparatively large exposure quantity is performed,

c) composition ratio calculating means for calculating composition ratios of the plurality of the color signals, which are obtained from said image sensing operation with a comparatively small exposure quantity, and

d) second signal suppressing means for performing a second signal suppressing process for suppressing at least one color signal other than said certain color signal in accordance with an output, which has been obtained from said detection means and which represents that said suppression of said certain color signal is performed, said second signal suppressing process being performed such that the composition ratios of a plurality of color signals, which are obtained from said second signal suppressing means, become identical with said calculated composition ratios.

4. An apparatus as defined in claim 3 wherein said image sensing operation control means controls such that said image sensing operation with a comparatively large exposure quantity is performed by performing exposure for a comparatively long time, and said image sensing operation with a comparatively small exposure quantity is performed by performing exposure for a comparatively short time.