Browse Prior Art Database

Smear Control for Scrolling Displays

IP.com Disclosure Number: IPCOM000051870D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Gatrell, M: AUTHOR [+3]

Abstract

Scrolling of images or blocks of text across a CRT display screen incorporating a medium-to-long persistence phosphor leaves a trail or smear of after-image which is annoying to the operator and hinders the reading of the displayed information. The problem is alleviated by providing the screen with a low intensity background illumination automatically invoked during the scrolling operation.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 69% of the total text.

Page 1 of 2

Smear Control for Scrolling Displays

Scrolling of images or blocks of text across a CRT display screen incorporating a medium-to-long persistence phosphor leaves a trail or smear of after-image which is annoying to the operator and hinders the reading of the displayed information. The problem is alleviated by providing the screen with a low intensity background illumination automatically invoked during the scrolling operation.

The relevant parts of a microprocessor-controlled display terminal to which the smear control feature has been added are shown in the figure. A CRT display device 1 is connected via display buffer 2 to common bus 3 of microprocessor controller 4. Input is conventionally by means of keyboard 5 which supplies data and control signals to the bus 3 via keyboard adapter 6. The microprocessor 4 functions in the normal manner to load output data into the display buffer from where video signals are supplied to the CRT. The phosphor coating incorporated in the CRT has a persistence in the region of 0.1 second. Typically, the X and Y deflection circuits 7 operate to scan the tube at a rate of 35 to 50 frames per second.

Under these operating conditions, image smear is unacceptably obtrusive.

The modification to this otherwise conventional arrangement involves the provision of a scrolling register 8 which functions in response to scroll commands from the keyboard or elsewhere to supply a logic-level digital signal to video switching circuit 9 for the...