Noise reduction apparatus

• US 20060204126A1
• Filed: 09/13/2005
• Published: 09/14/2006
• Est. Priority Date: 09/17/2004
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Kanda, Yamato
• Granted Patent: US 7,486,838 B2
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

A noise reduction apparatus is disclosed. A noise amount estimating unit estimates a noise amount in a focused pixel. A smoothing unit smoothes the focused pixel. A control unit controls the smoothing unit on the basis of the noise amount and information on the focused pixel and neighboring pixels thereof.

Claims

1. A noise reduction apparatus comprising:

a noise amount estimating unit which estimates a noise amount in a focused pixel;

a smoothing unit which smoothes the focused pixel; and

a control unit which controls the smoothing unit on the basis of the noise amount and information on the focused pixel and neighboring pixels thereof.

2. The noise reduction apparatus according to claim 1, wherein the smoothing unit has a filtering section which adds/averages signal values of the focused pixel and the neighboring pixels, and the control unit has a coefficient setting section which sets a filter coefficient for use in the filtering section on the basis of the noise amount and a signal value difference between the focused pixel and the neighboring pixels.

3. The noise reduction apparatus according to claim 2, wherein the coefficient setting section has a coefficient calculator which calculates the filter coefficient for the neighboring pixels except for the focused pixel as an increasing function relative to the noise amount.

4. The noise reduction apparatus according to claim 2, wherein the coefficient setting section has a coefficient calculator which calculates the filter coefficient for the neighboring pixels except for the focused pixel as a decreasing function relative to the signal value difference between the focused pixel and the neighboring pixels.

5. The noise reduction apparatus according to claim 1, wherein the control unit has a judging section which judges whether an area in the vicinity of the focused pixel is a flat portion or an edge portion on the basis of the noise amount, and the smoothing unit has a flat portion processing section which performs processing when the area in the vicinity of the focused pixel is judged to be the flat portion by the judging section, and an edge portion processing section which performs processing when the area in the vicinity of the focused pixel is judged to be the edge portion by the judging section.

6. The noise reduction apparatus according to claim 5, wherein the edge portion processing section has an analogous pixel detector which detects the neighboring pixel whose signal value is analogous to that of the focused pixel on the basis of the noise amount, and an inter-analogous-pixel processor which performs processing by use of the signal values of the analogous pixel and the focused pixel.

7. The noise reduction apparatus according to claim 1, wherein the noise amount estimating unit has a signal value level calculating section which calculates a signal value level for noise estimation in the focused pixel by use of the signal values of the focused pixel and the neighboring pixels thereof.

8. The noise reduction apparatus according to claim 7, wherein the noise amount estimating unit has a temperature measuring section which measures a temperature of an image pickup device, and uses the temperature of the image pickup device to calculate the signal value level for noise estimation in the focused pixel.

9. The noise reduction apparatus according to claim 7, wherein the noise amount estimating unit has an OB dispersion calculating section which obtains dispersion of signals of an optical black (OB) area within the image pickup device, and a temperature estimating section which estimates the temperature of the image pickup device from the dispersion, and the noise amount estimating unit uses the estimated temperature of the image pickup device to calculate the signal value level for noise estimation in the focused pixel.

10. The noise reduction apparatus according to claim 7, wherein the noise amount estimating unit has a gain information obtaining section which obtain gain information relative to an imaging signal, and uses the gain information to calculate the signal value level for noise estimation in the focused pixel.

11. The noise reduction apparatus according to claim 1, further comprising a directionality judging unit which judges a level of directionality in the vicinity of the focused pixel, wherein the control unit further controls the smoothing unit on the basis of the level of directionality.

12. The noise reduction apparatus according to claim 1, further comprising a particular color judging unit which judges whether or not the area in the vicinity of the focused pixel has a particular color, and the control unit further controls the smoothing unit on the basis of information on the particular color.