CATHODE RAY TUBE FOR SIMULTANEOUSLY DISPLAYING GRAPHIC AND ALPHANUMERIC INFORMATION

Abstract: A CRT for displaying graphic information, preferably radar images, as well as alphanumeric information, preferably tables, adapted such that the CRT screen is provided with fluorescent coatings having different persistence times on different parts of the screen surface.

Description: CATHODE RAY TUBE FOR SIMULTANEOUSLY DISPLAYING GRAPHIC AND ALPHANUMERIC INFORMATION TECHNICAL FIELD The invention refers to a cathode ray tube (CRT) for simultaneously displaying graphic and alphanumeric information. BACKGROUND ART Computer systems for processing position information from radar monitoring equipment are often used for controlling and guiding air and maritime traffic. Furthermore, other kinds of information, such as route, arrival time, collision risk etc., are collected and processed. All this information is displayed to traffic controlles who, with the aid of it, control traffic in progress. The radar images which are displayed are reproduced at a frequency corresponding to the rotational speed of the radar scanner, which is normally of the magnitude of one revolution per second. The requirement for obtaining an acceptable display of the radar scans is that the CRT display persistence time is long. This long persistence time is a disadvantage when displaying alphanumeric information. When such information is changed the display will be blurred, due to the persistence time. Furthermore, the fluorescent coating will be destroyed if stationary information is continuously displayed. To avoid these problems the radar information is generally displayed on one CRT having a long persistence time, while the alphanumeric information is displayed on another CRT having a short perisistence time. This solution, however, is both expensive and voluminous. DISCLOSURE OF INVENTION The invention relates to a CRT, which solves the aforementioned problems with simultaneously displaying the graphic and alphanumeric information. This is done by the screen of the CRT being provided with one zone having a short, and another zone having a long persistence time. The characterizing features of the invention are disclosed in claims 1 and 2. BRIEF DESCRIPTION OF DRAWINGS The invention, the characterizing features of which are apparent from the following patent claims, will now be described in detail with reference to the accompanying drawing, on which Figure 1 illustrates a display screen with the displayed information split up into zones, and Figure 2 illustrates a length section of the screen. BEST MODE FOR CARRYING OUT THE INVENTION Figure 1 illustrates a display screen in accordance with the invention displaying radar image and alphanumeric information. A radar image of an airplane in the air is desplayed in the upper zone A of the screen. Superposed on the radar image there is displayed a computer-generated image. The latter is a stylized map of the area in question, airplane identification symbols etc. This zone A is provided with a fluorescent coating 1 of a material with the commercial denotation P26, this coating having a persistence time of about 50 seconds. Persistence time is defined as the time it takes for luminescence to deteriorate to 5% of its initial value. A computer-generated alphanumeric image is displayed in the lower zone B of the screen. It may, for example, contain information as to the route, calculated arrival time etc for different airplanes. This zone B of the screen is provided with a fluorescent coating 2 with the commercial denotation P39. This coating has a persistence time of about two seconds. Figure 2 illustrates the screen in length section, where the front glass 3 of the screen is provided with a fluorescent coating 1 of the material P26 over one part of its surface, and with a coating of the material P39 over another part of its surface.

Claims: CLAIMS 1 Cathode ray tube for simultaneously displaying graphic and alphanumeric information, characterized in that the screen of the CRT is split into various zones each provided with a fluorescent coating having desired persistence time. 2 CRT as claimed in claim 1, characterized in that the screen of the CRT is split into zones, one zone (A) having a fluorescent coating (1) with a long persistence time for displaying the graphic image, and a zone (B) having a fluorescent coating (2) with a short persistence time for displaying the alphanumeric information. OMPI

Inventors: CLAESSON ANDERS, RAM STIG BERTIL, CLAESSON, ANDERS, RAM, STIG, BERTIL
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1984
Main classification: H01J29
IPC codes: G01S7, H01J29