| abstract |
An optical filter for use with visual display devices such as cathode ray tubes (CRT's) used with video display terminals (VDT's), television sets and the like enhances the viewability of characters and graphics displayed by increasing the contrast ratio, i.e., relative brightness, between illuminated picture elements (pixels) and un-illuminated pixels. The filter comprises a thin, transparent flexible polyvinyl chloride (PVC) plastic film adherable to the faceplate of the CRT or other display device by surface adhesion alone. Dyes are incorporated into the plastic film which color the film subtractively complementarily to the emission color of the display, thereby causing reduced light transmittance for wavelengths close to wavelength of peak light emission of the display device. The filters are attached to the faceplate of the CRT or other display device, by first coating one surface of the film with water, pressing the film against the faceplate, and drawing a straight edge or similar rigid edged surface across the outer surface of the film, thereby squeegeeing water from between the film and faceplate, and adhering the film thereto. A magenta colored filter, subtractively complementarily colored to the peak emission color of CRT having a green phosphor, is used with that color CRT. A bluish colored filter is used with CRT's having an amber colored phosphor. A neutral density, or gray colored filter is used with multi-color and black and white displays. |