CFA compatible resolution reduction in a single sensor electronic camera

• US 5,418,565 A
• Filed: 02/15/1994
• Issued: 05/23/1995
• Est. Priority Date: 02/15/1994
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Smith, Craig M.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Cohen, Cheryl
• Application Number:
  US08/196,603
• Time in Patent Office: 462 Days
• Field of Search: 348/266, 348/272, 348/273, 348/233
• US Class Current: 348/273
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: H04N 1/00204 with a digital computer or a digital computer system, e.g. an internet server programmed control between transmitter and receiver or between image input and image output device H04N1/32561
• CPC Class Codes: H04N 1/2112 using still video cameras
• CPC Class Codes: H04N 1/2137 with temporary storage before final recording, e.g. in a frame buffer
• CPC Class Codes: H04N 2101/00 Still video cameras
• CPC Class Codes: H04N 2201/0034 Details of the connection, e.g. connector, interface
• CPC Class Codes: H04N 2201/0077 Types of the still picture apparatus
• CPC Class Codes: H04N 2201/212 Selecting different recording or reproducing modes, e.g. high or low resolution, field or frame
• CPC Class Codes: H04N 2209/046 Colour interpolation to calculate the missing colour values
• CPC Class Codes: H04N 23/631 Graphical user interfaces [GUI] specially adapted for controlling image capture or setting capture parameters
• CPC Class Codes: H04N 23/65 Control of camera operation in relation to power supply
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

An electronic camera is adapted for processing images of different resolution to provide a user selectable image record size. A buffer memory is provided for storing color image pixels from a sensor corresponding to at least one image. Processing responsive to a resolution mode switch controls the order in which color image pixels are selected for output storage in both vertical and horizontal directions. The order selected by the resolution switch includes a full resolution mode, and at least one reduced resolution mode in which the low resolution color image pixels are calculated to exactly replicate the pixel geometry of the original CFA image. This simplifies the image processing for the rest of the imaging chain because the same algorithms can be used regardless of the selected image resolution.

Claims

1. An electronic camera adapted for capturing and processing images of different resolution, said camera comprising:

an image sensor having a two-dimensional array of photosites covered by a pattern of luminance and chrominance color filters;

means for generating an image signal corresponding to a two-dimensional image captured by said image sensor;

means for selecting one of a plurality of resolution levels for the image signal, said resolution levels providing a full resolution image arranged according to said pattern of color filters and at least one reduced resolution image; and

a processor responsive to a selected reduced resolution level for operating on the image signal by averaging areas of said captured image to produce a reduced resolution image arranged according to a pattern that replicates the pattern of color filters seen in the full resolution image.

2. A camera as claimed in claim 1 wherein said image sensor is covered by a pattern of luminance and chrominance color filters having a predetermined geometrical arrangement, and wherein said processor produces a reduced resolution image arranged according to a pattern that proportionately replicates the predetermined geometrical arrangement of color filters seen in the full resolution image.

3. A camera as claimed in claim 2 wherein the pattern of the reduced resolution image corresponds to pixel locations in the full resolution image that are separated in each dimension by at least one color filter location.

4. An electronic camera adapted for capturing and processing images of different resolution, said camera comprising:

an image sensor having a two-dimensional array of pixels covered by a pattern of luminance and chrominance color filters having a predetermined geometrical spatial arrangement;

means for generating an image signal comprised of pixels corresponding to a two-dimensional image captured by said image sensor;

means for selecting one of a plurality of resolution levels for the image signal, said resolution levels providing a full resolution image and at least one reduced resolution image; and

a processor responsive to a selected reduced resolution level for operating on the pixels comprising the image signal by producing a reduced resolution image arranged according to a pattern that replicates the predetermined spatial arrangement of the color filters seen in the full resolution image.

5. A camera as claimed in claim 4 wherein the reduced resolution image comprises a reduced resolution array of processed pixels output by said processor.

6. A camera as claimed in claim 5 wherein said processor operates upon pixels comprising the image signal by averaging pixels surrounding said processed pixel location to produce a reduced resolution image that replicates the predetermined spatial arrangement of the color filters seen in the full resolution image.

7. An electronic camera adapted for capturing and processing images of different resolution, said camera comprising:

an image sensor having a two-dimensional array comprised of pixels covered by a color filter array composed of at least three differently-colored filters arranged in a predetermined geometry;

means for generating an image signal corresponding to a two-dimensional array of color image pixels captured by said image sensor;

means for selecting one of a plurality of resolution levels for the image signal, said resolution levels providing a full resolution image having pixels arranged according to said color filter array and at least one reduced resolution image; and

a processor responsive to a selected reduced resolution level for operating on the image signal by averaging image pixels covered by the same-colored filter to produce a reduced resolution image arranged according to a pattern that replicates the predetermined geometry of the color filter array seen in the full resolution image.

8. A camera as claimed in claim 7 wherein said processor produces a reduced resolution image having a pattern of color pixels spatially distributed in a regular way to replicate the predetermined geometry of the color filters seen in the full resolution image.

9. A camera as claimed in claim 7 wherein the color pixels comprising the reduced resolution pattern correspond to pixel locations in the full resolution image that are separated in each dimension by at least one pixel location.

10. A camera as claimed in claim 7 wherein the color filter array is a Bayer array composed of a luminance color filters arranged in a checkerboard separated by two different types of chrominance color filters.

11. A camera as claimed in claim 10 wherein the luminance color filter is a green filter and the chrominance color filters are red and blue filters.

12. An electronic camera adapted for processing images of different resolution, said camera comprising:

an image sensor for generating an image signal representative of color image pixels arranged in vertical and horizontal directions as obtained from a two-dimensional array of photosites covered by a color filter array of luminance and chrominance color filters;

a buffer memory having sufficient capacity for storing the color image pixels corresponding to at least one image;

an output memory, connected subsequent to the buffer memory, for storing processed image signals obtained from the buffer memory;

a resolution mode switch for selecting a pixel resolution of the image by specifying an order in which the color image pixels are selected for storage in both vertical and horizontal directions, said order including a full resolution mode in which all color image pixels are selected and at least one reduced resolution mode in which a fewer number of color image pixels are selected;

a controller responsive to the pixel resolution selected by the resolution mode switch for accordingly changing the number of horizontal and vertical pixels that represent the image, said controller effecting an averaging of the color image pixels for the reduced resolution mode to produce a reduced resolution image arranged according to a pattern that replicates the color filter array of color filters seen in the full resolution image; and

means for storing the selected color image pixels in said output memory, whereby said output memory is able to store more images in said reduced resolution mode than in said full resolution mode.

13. A camera as claimed in claim 12 wherein said buffer memory is operable to store all of the color image pixels from said image sensor and wherein said controller effectuates the averaging for the selected pixel resolution by accordingly selecting appropriate pixels from said buffer memory for processing and storage in said output memory.

14. A camera as claimed in claim 13 wherein the color filter array is a Bayer array.

15. A camera as claimed in claim 14 wherein the reduced resolution image is composed of processed color pixels, said controller effecting the averaging of same-colored pixels in the immediate neighborhood of the processed color pixel.

16. A camera as claimed in claim 12 further comprising means for compressing the selected color image pixels, whereby said storing means stores compressed color image pixels in said output memory.