Digital noise reduction through selective pixel comparison

• US 6,546,149 B1
• Filed: 10/15/1999
• Issued: 04/08/2003
• Est. Priority Date: 10/15/1999
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: InFocus Corporation (Lap-Shun Hui, MBA)
• Inventors: Ruggiero, Carl J., Lasneski, Alan
• Primary Examiner(s): Do, Anh Hong
• Application Number:
  US09/418,415
• Time in Patent Office: 1,271 Days
• Field of Search: 382/172, 382/270, 382/275, 348/241, 348/607, 386/114, 375/240
• US Class Current: 382/275
• CPC Class Codes: G06T 2200/28 involving image processing hardware
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• 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 method of reducing noise in a digitally sampled image is achieved in which an entire frame image is divided into regions which are used to determine the relative noise level of the static image over a period of several frames. The relative noise level is taken as a measurement and is then used by the firmware to make adjustments during the digital sampling process. By using less than the entire frame of the image information the method of reducing noise can be implemented without requiring the presence of a frame buffer.

Claims

1. A method of reducing noise in a conversion of an analog video signal to a digital video signal for display on a digital display object having pixels arranged in lines and columns, the analog video signal including an analog video data signal generated to produce frames of digital video data with each frame including a plurality of lines of pixel components, the method comprising the steps of:

dividing a first frame of digital video data into different regions each including at least one line of the pixel components;

generating a pixel clock signal having a pixel clock phase for sampling every line in each region to determine a line within each region having a highest number of pixel components;

storing the highest number lines of each region;

changing the pixel clock phase;

producing a second frame of digital video data and comparing corresponding lines of pixel components within the second frame with the highest number lines of the first frame to determine whether the highest number is different between the first and second frames and represents a miscount;

repeating the above steps a number of times for subsequent frames of digital video data; and

adjusting the pixel clock phase to correspond to the pixel clock phase of the frame of digital video data having the lowest miscount.

2. The method of claim 1, in which the first, second, and subsequent frames of digital video data are consecutive frames.

3. The method of claim 1, wherein the frame of analog video data is divided into four regions.

4. The method of claim 1, wherein the selected lines within each region are stored in a memory array.

5. The method of claim 1, wherein the selected lines are chosen based on the number of pixel components having a value greater than a predetermined pixel value threshold.

6. The method of claim 4, wherein the step of determining a total number of pixel components in the selected lines of each frame entails comparing the selected lines stored in the memory array with corresponding lines of a consecutive frame.

7. The method of claim 1, in which the digital video signal carries a static image over a period of several frames.