CRT display device with variable light transmission panel

Claim 1

In a CRT display device including an envelope having a faceplate of predetermined light transmissivity, a luminescent screen disposed on an inner surface of the faceplate and electron beam producing means disposed within the envelope for exciting the screen to effect production of a luminescent image, the improvement comprising means for controllably reducing ambient light reflections, said means including: (a) a variable light transmissivity panel disposed adjacent an outer surface of the faceplate for intercepting ambient light radiation reflected from the screen and for passing light radiation from the luminescent image, the light transmissivity of said panel varying with the magnitude of an applied control signal; (b) a light sensor disposed in proximity to the faceplate for sensing the intensity of ambient light received at the faceplate; and (c) control circuitry, electrically connected to the light sensor and to the variable light transmissivity panel, for producing the control signal; during operation of the display device said control signal varying in response to the intensity of ambient light received at the light sensor and effecting variation of the panel light transmissivity inversely to variation of said ambient light intensity; and during non-operation of the display device said control signal effecting a minimum transmissivity of the panel.