Image processing apparatus and method

• US 8,417,031 B2
• Filed: 03/04/2009
• Issued: 04/09/2013
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Kasahara, Ryosuke
• Primary Examiner(s): Park, Chan S
• Assistant Examiner(s): MOTSINGER, SEAN T
• Application Number:
  US12/379,889
• Publication Number:
  US 20090226086A1
• Time in Patent Office: 1,497 Days
• Field of Search: None
• US Class Current: 382/167
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"
• CPC Class Codes: H04N 25/611 Correction of chromatic aberration
• CPC Class Codes: H04N 25/6153 for colour signals
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

An image processing method of processing an image obtained by using an optical system having a wide field angle and a large magnification chromatic aberration includes the steps of applying magnification chromatic aberration correction processing to the image, applying separation processing to the image after the step of applying the magnification chromatic aberration correction for separating the image into a brightness signal and a color signal, and applying a high band emphasis processing only to the brightness signal after the step of applying the separation processing.

Claims

1. An image processing method of processing an image obtained using an optical system having a wide field angle and a large magnification chromatic aberration, said method comprising the steps of:

applying magnification chromatic aberration correction processing to the image by storing color components of the image in coordinate conversion memories and performing a coordinate conversion on the color components stored in the coordinate conversion memories, each of the coordinate conversion memories including a memory area having a size that corresponds to a maximum amount of deviation in the color components in comparison to a reference color component caused by the magnification chromatic aberration;

applying separation processing to the image after the step of applying the magnification chromatic aberration correction for separating the image into a brightness signal and a color signal; and

applying a high band emphasis processing only to the brightness signal after the step of applying the separation processing.

2. The image processing method as claimed in claim 1, further comprising the step of combining the brightness signal subjected to the high band emphasis processing and the color signal.

3. The image processing method as claimed in claim 2, further comprising the step of smoothing the color signal in parallel to the high band emphasis processing of the brightness signal.

4. The image processing method as claimed in claim 3, further comprising the step of changing an intensity of the smoothing in accordance with a luminance of a photographic subject.

5. The image processing method as claimed in claim 3, wherein said step of smoothing the color signal is executed only when the luminance decreases to a prescribed dark level.

6. The image processing method as claimed in claim 1, wherein said magnification chromatic aberration correction is executed by partially converting coordinates of multi color components in the step of executing the magnification chromatic aberration correction processing.

7. The image processing method as claimed in claim 6, and wherein a coordinate conversion amount of a first color component is calculated with reference to a coordinate of the reference color component, and wherein a coordinate conversion amount of a second color component is calculated in accordance with the coordinate conversion amount of the first color component.

8. The image processing method as claimed in claim 7, further comprising:

a step of applying distortion correction processing to the image separately from the step of applying magnification chromatic aberration correction processing.

9. The image processing method as claimed in claim 8, wherein said step of applying distortion correction processing is executed after the step of applying the high band emphasis processing.

10. An image processing apparatus for processing an image obtained by an optical system having a wide field angle and a large magnification chromatic aberration, comprising:

a magnification chromatic aberration correction device configured to correct magnification chromatic aberration per color component by storing color components of the image in coordinate conversion memories and performing a coordinate conversion on the color components stored in the coordinate conversion memories, each of the coordinate conversion memories including a memory area having a size that corresponds to a maximum amount of deviation in the color components in comparison to a reference color component caused by the magnification chromatic aberration, an amount of coordinate conversion performed for a first color component calculated with reference to a coordinate of the reference color component, and an amount of coordinate conversion performed for a second color component calculated in accordance with the amount of coordinate conversion performed for the first color component;

a separation device configured to separate the image subjected to the magnification chromatic aberration correction into brightness and color signals; and

a MTF correction device including a filter configured to emphasize a high band of the brightness signal.

11. The image processing apparatus as claimed in claim 10, further comprising a combining device configured to combine the brightness signal subjected to the high band emphasis and the color signal.

12. The image processing apparatus as claimed in claim 10, wherein said MTF correction device further comprising a filter configured to smooth the color signal.

13. The image processing apparatus as claimed in claim 12, wherein an intensity of smoothing by the filter is changed in accordance with the lightness of a photographic subject.

14. The image processing apparatus as claimed in claim 12, wherein said filter becomes effective when the lightness of a photographic subject decreases to a prescribed dark level.

15. The image processing apparatus as claimed in claim 14, wherein said magnification chromatic aberration correction device partially converts coordinates of multi color components.

16. The image processing apparatus as claimed in claim 15, wherein said magnification chromatic aberration correction device calculates a coordinate conversion amount of a first color component with reference to a coordinate of the reference color component, and calculates a coordinate conversion amount of a second color component in accordance with the coordinate conversion amount of the first color component.

17. The image processing apparatus as claimed in claim 16, further comprising a distortion correction device configured to correct distortion of the image.

18. The image processing apparatus as claimed in claim 17, wherein said distortion correction device is arranged in the later step of the MTF correction device.