Browse Prior Art Database

Method for the Suppression of Flicker on Interlaced Color Images

IP.com Disclosure Number: IPCOM000040003D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Aggarwal, JK: AUTHOR [+3]

Abstract

A simple method that reduces flicker on color images by applying a vertical filter to the image is described. The resulting image, when displayed on an interlaced device, will demonstrate considerably less flicker. In addition, since information is effectively transferred from the odd lines of the image to the even lines, every other line of the image can be discarded and the image displayed on a non-interlaced device, without losing the original content of the image. The phosphors on commercially manufactured televisions and many raster displays must be refreshed 60 times per second in order for the human eye to see a steady flicker-free image. The technology prevalent in most displays of this type, however, can only refresh the screen completely in 1/30 of a second.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Method for the Suppression of Flicker on Interlaced Color Images

A simple method that reduces flicker on color images by applying a vertical filter to the image is described. The resulting image, when displayed on an interlaced device, will demonstrate considerably less flicker. In addition, since information is effectively transferred from the odd lines of the image to the even lines, every other line of the image can be discarded and the image displayed on a non-interlaced device, without losing the original content of the image. The phosphors on commercially manufactured televisions and many raster displays must be refreshed 60 times per second in order for the human eye to see a steady flicker-free image.

The technology prevalent in most displays of this type, however, can only refresh the screen completely in 1/30 of a second. In order to avoid unacceptable flicker, all odd-numbered lines, the first field, are displayed in the first 1/60 of a second, and then all even-numbered lines, the second field, are displayed in the next 1/60 of a second, for an overall refresh rate of 1/30 of a second. The use of this technique, known as interlacing, produces an image that appears stable to viewers at a normal viewing distance in many situations. However, single horizontal lines of a given color or sharp vertical transitions in color and intensity from one scan line to the next still exhibit irritating and distracting flicker.

Previous work to reduce flicker in interlaced devices has concentrated on changing the refresh rates of interlaced devices and developing new phosphors with longer persistence. Work in these areas does not address the vast amount of television hardware already available commercially. Other work has concentrated on designing fonts and images that eliminate the characteristics of images that cause flicker by avoiding single pel (picture element) lines and sharp transitions in color and intensity. The description of an improved method will begin with a definition of terminology and notation. A pixel Pi is defined as a vector of color values in RGB color space <Ri, Gi, Bi>. The perceived distance between two pixels, denoted by Pi - Pj , is defined to be the sum of the square of the differences between the color components of the pixel victors,
i.e., (Ri - Rj)2 + (Gi - Gj)2 + (Bi - Bj)2 . The method for flicker suppression, disclosed herein, compares vertically adjacent pixels. The perceived distance between vertically adjacent pixels is computed. If this distance exceeds a certain threshold, the color di...