Digital photography device and method

• US 6,046,772 A
• Filed: 07/24/1997
• Issued: 04/04/2000
• Est. Priority Date: 07/24/1997
• Status: Expired due to Fees

• Current Assignee: Howell, Ltd.
• Original Assignee: Paul Howell
• Inventors: Howell, Paul
• Primary Examiner(s): Garber, Wendy
• Assistant Examiner(s): CHRISTENSEN, ANDREW BRUCE
• Application Number:
  US08/899,550
• Time in Patent Office: 985 Days
• Field of Search: 348/242, 348/266, 348/273, 348/219, 382/162, 382/167, 358/518
• US Class Current: 348/273
• CPC Class Codes: H04N 1/486 with separate detectors, each detector being used for one specific colour component
• CPC Class Codes: H04N 2209/046 Colour interpolation to calculate the missing colour values
• CPC Class Codes: H04N 2209/049 having three pick-up sensors
• CPC Class Codes: H04N 23/13 with multiple sensors
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/17 Colour separation based on photon absorption depth, e.g. full colour resolution obtained simultaneously at each pixel location
• CPC Class Codes: H04N 25/48 Increasing resolution by shifting the sensor relative to the scene

Abstract

A combination of digital camera design and digital photography technique that allows a single digital camera to be used for both single-shot and multiple-shot color operation. The invention includes a digital camera half of the light-sensing elements of which--the "majority pixels"--are sensitive to a first primary color and the other half of which--the "minority pixels"--are divided about equally between those sensitive to a second primary color and those sensitive to a third primary color. Further, these light-sensitive elements are arranged so that by a simple lateral shift of the array, typically by the width of a single pixel, every one of the majority pixels will be moved into a position previously held by one of the minority pixels. When used in conjunction with known pixel-interpolation methods this camera produces single-shot digital images equal or better in color quality to any existing single-shot digital camera. Shooting a scene twice, with the array shifted as indicated above between the two shots, and using known interpolation techniques to determine all three primary colors at each pixel location, a final photograph essentially as good as any provided by traditional three-shot digital photography can be achieved. For cameras having the requisite array of photosensitive elements, but not incorporating a mechanism for moving the array separately from the rest of the camera, the present invention can be practiced by rotating the described camera about an axis lying in the principal plane of and passing through the principal point of the camera'"'"'s lens.

Claims

1. Digital camera apparatus for both single-shot and multiple-shot use, the apparatus comprising

(a) a digital camera incorporating a lens with principal plane and principal point for focusing an image on an array of electronic light-sensing elements uniformly distributed across points of a focal plane, a color filter matrix for selecting from said array a first subarray sensitive to a first primary color, a second subarray sensitive to a second primary color, and a third subarray sensitive to a third primary color, where said first subarray includes approximately half of said light-sensing elements, said second subarray includes approximately one-quarter of said light-sensing elements, and said third subarray includes approximately one-quarter of said light-sensing elements,

(b) means for shifting said image within said focal plane so that each of said points of said focal plane that had been occupied by a member of said first subarray are thereafter occupied by a member of said second subarray or a member of said third subarray,

(c) means for capturing and electronically storing a first photograph of said image prior to said shifting and a second photograph subsequent to said shifting,

(d) software means for electronically combining only said first photograph and said second photograph so as to produce a composite color photograph.

2. The apparatus as described in claim 1 wherein said software means uses intensity information for said first primary color obtained collectively in said first photograph and in said second photograph as a normalizing factor in producing said composite color photograph.

3. The apparatus as described in claim 2 wherein said first primary color is green, said second primary color is blue, and said third primary color is red.

4. The apparatus as described in claim 3 wherein said means for shifting is an electronic-shift control for moving said array with respect to said camera.

5. The apparatus as described in claim 3 wherein said means for shifting is a camera-rotation device to rotate said camera about a rotation axis passing through said principal point.

6. The apparatus as described in claim 5 where said camera-rotation device comprises a flexure stage element having a secured end, a free end, and a means to drive said free end laterally with respect to said secured end so as to bend said flexure stage element about a bending axis and wherein said camera is couplable to said flexure stage element so that said bending axis lies in said principal plane and passes through said principal point.

7. The apparatus as described in claim 6 where said means to drive is a ram controlled by a piezoelectric cell.

8. A digital camera and compositing circuit comprising a spatially-uniform array of light-sensitive elements extending over a focal plane of said camera, half of said elements being sensitive to green light (green pixels), one-quarter of said elements being sensitive to red light (red pixels), and one-quarter of said elements being sensitive to blue light (blue pixels),

and where said elements are distributed so that a transverse move of said array within said focal plane by a distance equal to that between adjacent elements will move one of said green pixels into a location previously occupied by one of said red pixels or by one of said blue pixels, such that said camera can take a first photograph prior to said transverse move and a second photograph subsequent to said transverse move and said compositing circuit can produce through interpolation and normalization a composite color photograph made up of data captured in only said first photograph and said second photograph, wherein said normalization depends only on data collected by said green pixels.

9. Digital camera and compositing circuit as described in claim 8 wherein said array is mounted on a movable stage located at said focal plane and said transverse move is accomplishable by moving said stage with respect to said digital camera.

10. Digital camera and compositing circuit as described in claim 8 in combination with flexure stage apparatus capable of rotating said camera about an axis passing through a principal plane.

11. A method for performing both single-shot and multiple-shot digital photography with a single digital camera, said method comprising the steps of

(a) selecting a digital camera that has a matrix array of photosensors on a stage such that roughly half of said photosensors are sensitive only to green light (green pixels), roughly one quarter are sensitive only to red light (red pixels), and roughly one quarter are sensitive only to blue light (blue pixels) and further such that said array of green pixels, red pixels, and blue pixels are deployed so that a first shift of said array by either a column or a row will result in each of said green pixels moving into a position occupied by one of said red pixels or one of said blue pixels prior to said first shift and that a second shift equal in direction and amount of said first shift will cause each of said green pixels to occupy a position occupied by one of said green pixels before said first shift and each of said red pixels to occupy a position occupied by one of said red pixels before said first shift and each of said blue pixels to occupy a position occupied by one of said blue pixels before said first shift,

(b) firmly mounting said camera with respect to a scene to be photographed,

(c) capturing and storing a first photograph of said scene with said camera,

(d) moving said stage so that said array is shifted by one column or one row,

(e) capturing and storing a second photograph of said scene with said camera,

(f) electronically combining said first photograph with second photograph in order to produce a full color image a point corresponding to each said photosensor in said array, wherein said electronically combining includes an interpolation of red data for locations not occupied by a red pixel during either said first photograph or said second photograph and an interpolation of blue data for locations not occupied by a blue pixel during either said first photograph or said photograph, where said interpolation of red data and said interpolation of blue data are both carried out subject to normalization using data from said green pixels obtained sequentially in said first photograph and said second photograph.