GB869713A - Improvements in or relating to cathode ray tube display systems - Google Patents

Abstract

869,713. Cathode-ray oscilloscopes; cathoderay tube circuits; pulse radar. DECCA RECORD CO. Ltd. March 11, 1960 [Dec. 11, 1958], No. 40073/58. Class 40(7) [Also in Groups XX and XL(b)] A cathode-ray tube (C.R.T.) display system comprises means for applying a sequence of deflection signals to beam deflector means to produce marker traces sequentially on the C.R.T. screen, means for individually controlling the positions of the various marker traces on the screen, a first polarizing filter in front of the screen and having different frequency transmission characteristics forlight polarized in different planes, a second filter selectively transmitting light of one plane of polarization, and means effecting relative rotation of the two filters in synchronism with the marker trace scanning sequence whereby selected traces in the sequence appear differently coloured when seen through the two filters. C.R.T. 10 is provided to give a P.P.I. display of filtered information from radar 11 and marker lines showing echo direction and speed, and characters from generator 14, in inter-radar-scan periods. Orthogonal deflection coils, 15, 16 are fed from waveform generators 17, 18 as described in Specification 818,477, scanning rate and shift inputs being applied in regular sequence by switch control unit 21. Filters 25, 26 are arranged to transmit red and blue light respectively, each filter transmitting the coloured light if the incident light is polarized in one plane and white light is polarized in a transverse plane, the filters having their respective planes of polarization in which these colours are transmitted at right angles; filter 27 transmits light polarized in one plane only and is rotated about the C.R.T. axis. Filters 25, 26 may be such that the planes of polarization in which red and bluelightare transmitted are at 120 degrees. Switches 20 are synchronized with filter 27 rotation by photo-cell 30 which senses markings on the filter's periphery. Radar or asdic echoes may be displayed in one colour and interscan markers in another colour, filter 27 and switches 20 being driven synchronously with pulse repetition rate when the latter is low. In a modification a three colour system is afforded by three filters so arranged that the planes of polarization in which the distinctive colours are transmitted lie mutually at 120 degrees and two rotating analyzing filters are employed, Fig. 2 (not shown). Colour may be used to indicate aircraft height. More than one interscan may be arranged between radar display scans.