Colour and brightness tracking in a cathode ray tube display system

Claim 2

Colour and brightness tracking control apparatus for a colour cathode ray tube display instrument system subjected to viewing under a wide range of ambient light conditions comprising a cathode ray tube having a display screen for emitting images in a plurality of different colours dependent upon the independent and variable energisation of cathode means for producing at least two independent primary colours the relative brightnesses of which determine the plurality of colours, video command means for commanding at least one image to be displayed in at least one predetermined colour comprised of components of said two primary colours at the required relative brightness levels:, ambient light sensor means for providing a signal corresponding to the range between the extremes of ambient light conditions existing in the vicinity of the display instrument, computer means including memory means containing data representing the independent cathode energisations required to produce each of said primary colour component relative brightnesses over said range of ambient light conditions, and processor means responsive at least in part to the light sensor means for continuously computing a reference display brightness and for deriving from the memory means cathode energisation data required to produce said two primary colour component relative brightnesses at the existing ambient light conditions, and means responsive to the video command means and the derived cathode energisation data for energising the cathode means, thereby to produce the predetermined colour image at the existing ambient light conditions.

Claim 3

Apparatus according to Claim 1, wherein computer means comprises digital computer means.

Claim 4

Apparatus according to Claim 1 or 2 and further including manual brightness control means for supplying a signal corresponding to a desired display brightness, and means for supplying the desired brightness signal to the processor means for computing the reference brightness as a function of both the ambient light sensor signal and the manually controlled brightness signal.

Claim 5

Apparatus according to Claim 3, wherein the computed reference display brightness is based primarily on the light sensor signal for relatively high ambient light conditions, and is based primarily on the manual control brightness signal for relatively low ambient light conditions.

Claim 6

Apparatus according to any of the preceding claims, wherein the display system is for installation in an aircrait cockpit, and wherein the system further comprises remote light sensor means responsive, in use, to the lighting conditions exteriorly of the aircraft cockpit for supplying a signal in accordance therewith, and means for supplying-the last mentioned signal to the processor means for computing a reference brightness boost factor as a function of the ambient light sensor signal and the remote light sensor signal.

Claim 7

Apparatus according to any of the preceding claims, wherein the video command means commands a predetermined colour for each of at least two images, one stroke written and one raster written, wherein the memory means further includes data representing the cathode energisation required to produce each of said primary colour component brightnesses for each image over the range of ambient light conditions, wherein the processor means further includes means responsive at least in part to the light sensor means for continuously and independently computing a reference display brightness for each of said images and for deriving from the memory means cathode energisation data required to produce the primary colour component brightnesses for each of the images at the existing ambient light conditions, and wherein the video command responsive means further includes means for deriving the cathode energisation data for energising the cathode means, thereby to produce the predetermined colours for each of the images at the existing ambient light conditions.

Claim 8

Apparatus according to any of the preceding claims, wherein the cathode energisation means comprises further memory means responsive to the processor means for receiving from the processor means the derived cathode energisation data required to produce said primary colour component brightnesses at the reference ambient brightness, and wherein the video command means addresses the further memory means for extracting the relative cathode energisations.

Claim 9

Apparatus according to claim 7, wherein the memory means comprises a programmable read only memory, and wherein the further memory means comprises random access memory means.

Claim 10

Apparatus according to any of the preceding claims, wherein the memory means contains intensity factors for each of said plurality of colours, the intensity factors for a given colour being associated respectively with the independent primary colours and proportioned with respect to each other in accordance with the relative brightnesses of said primary colours to produce said colour, and brightness versus cathode energisation data for each primary colour in accordance with the gamma characteristics of the cathode ray tube, and wherein the processor means is responsive to the intensity factors and to the reference display brightness for deriving therefrom reference brightness addresses and for addressing the gamma characteristic data therewith for providing the cathode energisation data..

Claim 11

Apparatus according to claim 2 and any claim appended thereto, wherein the digital computer means includes means for converting the signal from the light sensor means into an equivalent logarithmic signal, wherein the data contained in the memory means is stored in logarithmic format, and wherein the processor means includes means for computing the reference display brightness and for deriving the cathode energisation data by linear combinations of logarithmic values.

Claim 12

ll. Colour and brightness tracking control apparatus for a colour cathode ray tube display instrument system subjected to viewing under a wide range of ambient light conditions comprising a cathode ray tube having a display screen for emitting images in a plurality of different colours dependent upon the individual and variable energisation of cathode means for producing at least three individual primary colours the relative brightnesses of which determine the plurality of colours, video command means for commanding a predetermined plurality of colours in which a plurality of images are to be displayed, each of the colours comprising a plurality of predetermined components of the primary colours at predetermined relative brightness levels, ambient light sensor means for providing a signal which varies in accordance with the extremes of ambient light intensities existing in the vicinity of the display instrument, digital computer means including memory means containing data representing the individual cathode energisations required to produce each of said primary colour component relative brightness levels required to produce each of the predetermined plurality of colours over the range of ambient light intensity conditions, and processor means responsive at least in part to the light sensor means for continuously computing a reference display brightness dependent upon the existing ambient light intensity conditions and for deriving from the memory means the cathode energisation data required to produce each of the predetermined plurality of colours at the existing ambient light intensity conditions, and means responsive to the video command means and the derived cathode energisation data for energising the cathode means thereby to produce the predetermined plurality of colour images at the existing ambient light intensity conditions.

Claim 13

ll. Colour and brightness tracking control apparatus for a colour cathode ray tube display instrument system subjected to viewing under a wide range of ambient light conditions comprising a cathode ray tube having a display screen for emitting images in a plurality of different colours dependent upon the individual and variable energisation of cathode means for producing at least three individual primary colours the relative brightnesses of which determine the plurality of colours, video command means for commanding a predetermined plurality of colours in which a plurality of images are to be displayed, each of the colours comprising a plurality of predetermined components of the primary colours at predetermined relative brightness levels, ambient light sensor means for providing a signal which varies in accordance with the extremes of ambient light intensities existing in the vicinity of the display instrument, digital computer means including memory means containing data representing the individual cathode energisations required to produce each of said primary colour component relative brightness levels required to produce each of the predetermined plurality of colours over the range of ambient light intensity conditions, and processor means responsive at least in part to the light sensor means for continuously computing a reference display brightness dependent upon the existing ambient light intensity conditions and for deriving from the memory means the cathode energisation data required to produce each of the predetermined plurality of colours at the existing ambient light intensity conditions, and means responsive to the video command means and the derived cathode energisation data for energising the cathode means thereby to produce the predetermined plurality of colour images at the existing ambient light intensity conditions.