Electronic endoscope system for reducing random noise of a video signal

• US 6,900,829 B1
• Filed: 03/31/1997
• Issued: 05/31/2005
• Est. Priority Date: 04/03/1996
• Status: Expired due to Term

• Current Assignee: Hoya Corporation
• Original Assignee: Pentax Corporation (Hoya Corporation)
• Inventors: Iketani, Kouhei, Ozawa, Ryo
• Primary Examiner(s): LEE, Y YOUNG
• Application Number:
  US08/829,187
• Time in Patent Office: 2,983 Days
• Field of Search: H04/N00.7/18, 348/65, 348/68, 348/70, 348/72, 348/76, 348/71
• US Class Current: 348/71
• CPC Class Codes: A61B 1/045 Control thereof
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/10068 Endoscopic image
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

An electronic endoscope system which captures an image of an object and displays the same on a display device is provided with a noise reduction system. The noise reduction system reduces noise included in a frame of an image signal for each color component. The noise-reduced color components are stored in a buffer, and then output as a video signal to be transmitted to a display where a color image of the object is displayed.

Claims

1. An electronic endoscope system, comprising:

an image capturing system, which receives sequential frames of an optical image of an object and sequentially outputs a plurality of image signals respectively corresponding to a plurality of color components of said sequential frames of said optical image;

a frame memory for storing image signals;

a noise reduction system, which reduces random noise included in each of said plurality of image signals by combining a non-noise-reduced image signal previously stored in said frame memory and including first random noise, with a non-noise-reduced current image signal from said image capturing system and including second random noise, to form a noise-reduced image signal, and outputs a plurality of said noise-reduced image signals, respectively corresponding to said plurality of image signals;

a memory which receives said plurality of noise-reduced image signals for each of said sequential frames of said optical image; and

a video signal generating system, which generates a video signal for each of said sequential frames based on said noise-reduced image signals, corresponding to said plurality of color components.

2. The electronic endoscope system according to claim 1, wherein said video signal includes color components signals corresponding to said plurality of color components.

3. The electronic endoscope system according to claim 1, wherein said plurality of color components includes color components of three primary colors.

4. The electronic endoscope system according to claim 1, further comprising a display device which receives said video signal and displays an image of said object.

5. The electronic endoscope system according to claim 1, wherein said image capturing system uses a field sequential color imaging process.

6. The electronic endoscope system according to claim 1, said image capturing system comprising an image receiving element having a plurality of pixels, and wherein said noise reduction system reduces noise based on both a previous image signal and a current image signal from corresponding pixels of said image receiving element.

7. The electronic endoscope system according to claim 6, wherein said noise reduction system adds said previous image signal stored in said frame memory to said current, unstored image signal and then multiplies the sum by ½

to obtain said noise-reduced image signal.

8. The electronic endoscope system according to claim 1, wherein said image capturing system comprises a white light source, a plurality of color filters, a light transmitting member, and a CCD (Charge Coupled Device), wherein, in sequence and for a predetermined period of time, light emitted by said light source passes sequentially through one of said plurality of color filters and is transmitted through said light transmitting member to illuminate said object, and wherein said plurality of color components correspond to said plurality of filters.

9. The electronic endoscope system according to claim 1,

wherein said noise reduction system forms said noise-reduced image signal by feeding forward a non-averaged image signal previously stored in said frame memory and including said first random noise, and combining the previously stored non-averaged image signal with a non-averaged current image signal from said image capturing system and including said second random noise, to form said noise-reduced image signal.

10. The electronic endoscope system according to claim 1, wherein said noise reduction system combines said non-noise-reduced image signal previously stored in said frame memory and including first random noise, with said non-noise-reduced current image signal from said image capturing system and including said second random noise, to form said noise-reduced image signal, without first multiplying by coefficient either of said first non-noise-reduced image signal previously stored in said frame memory and including said first random noise or said non-noise-reduced current image signal from said image capturing system and including said second random noise, by:

adding said non-noise-reduced image signal previously stored in said frame memory and including said first random noise, with said non-noise-reduced current image signal from said image capturing system and including said second random noise, and then multiplying by ½

, to form said noise-reduced image signal.

11. The electronic endoscope system according to claim 1, wherein said noise reduction system combines said non-noise-reduced image signal previously stored in said frame memory and including first random noise, with said non-noise-reduced current image signal from said image capturing system and including said second random noise, to form said noise-reduced image signal such that said noise-reduced image signal is a sum of said non-noise-reduced image signal previously stored in said frame memory and including first random noise multiplied by a predetermined coefficient and said non-noise-reduced current image signal from said image capturing system and including said second random noise multiplied by said predetermined coefficient.