Method and Apparatus for Resolution Improvement in Digital Capturing

• US 20080131022A1
• Filed: 12/03/2007
• Published: 06/05/2008
• Est. Priority Date: 12/01/2006
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Potikha, Elizaveta, Vitsnudel, Ilia, Sorek, Noam
• Granted Patent: US 8,126,284 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 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: G06T 3/403 Edge-driven scaling; Edge-based scaling
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

A method and apparatus for enhancing the resolution of digital images. For each image a white balanced image is generated, which takes into account the differences in the colors of the sensor cell upon which the values are generated. Edge detection filters are then activated on the white balanced image and a weight is determined, indicating the probability that a feature which was detected as an edge is indeed an edge. At the last step, each detected edge is multiplied by the probability and is added to the luminance component, thus enhancing the edges. Preferred embodiments of the white balance image generation. Generating the white balanced image, detecting the edges and determining the weights are disclosed for sensors operating in Line Addition On mode and for sensors operating in Line Addition Off mode.

Claims

1. A method for enhancing the resolution of a digital image captured by a capturing device comprising a sensor, the method comprising the steps of:

receiving the digital image from the sensor;

generating a white balanced image from the digital image;

detecting an at least one edge on the white balanced image; and

determining a weight for each of the at least one edge.

2. The method of claim 1 further comprising the step of adding to a luminance component generated from the digital image a sum of products, wherein each product is a multiplication of the at least one edge and the weight.

3. The method of claim 1 wherein the sensor operates in Line Addition On mode.

4. The method of claim 3 wherein the white balanced image is generated by multiplying all sensor values of a predetermine color in a constant number so as to obtain uniform values for mosaic cells of different types in areas capturing a grayscale image.

5. The method of claim 3 wherein the weight for each of the at least one edge is determined according to at least one parameter from the group consisting of:

a weight indicating if a significant color pattern is present;

the presence of additional edges in the vicinity of the at least one edge;

the difference between vertical neighboring cells in the white balanced image;

the absence or presence of horizontal edges; and

local illumination range intensity.

6. The method of claim 5 wherein the weight for each of the at least one edge is determined as the minimum of the at least one parameter.

7. The method of claim 1 wherein the sensor operates in Line Addition Off mode.

8. The method of claim 7 wherein the white balanced image is generated by multiplying all sensor values of a predetermine color in a constant number so as to obtain uniform values for mosaic cells of different types in areas capturing a uniform color.

9. The method of claim 7 wherein substantially all pixels in the white balanced image are generated by performing mathematical operations, wherein each operation is performed on cells belonging to a single row of the digital image.

10. The method of claim 9 wherein the value of green cells is multiplied by a predetermined factor, and the value of each cell is incremented in the average value of its horizontal neighboring cells.

11. The method of claim 9 wherein the at least one edge is a horizontal edge.

12. The method of claim 7 wherein substantially all pixels in the white balanced image are generated by performing mathematical operations wherein each operation is performed on pixels belonging to a single column of the digital image.

13. The method of claim 12 wherein the value of green cells is multiplied by a predetermined factor, and wherein the value of each cell is either incremented by the average value of its vertical non-immediate neighboring cells or is assigned the average value of its two vertical immediate neighboring cells.

14. The method of claim 12 wherein the at least one edge is a vertical edge.

15. The method of claim 1 wherein the weight is used for eliminating false edges.

16. The method of claim 7 wherein the weight is determined by analyzing vertical and horizontal edges strength on a luminance component of the digital image.

17. The method of claim 1 wherein the sensor is a CCD sensor or a CMOS sensor.