Method and apparatus for automatically adjusting the raster in projection television receivers

A method for adjusting a width of a raster in a rear projection television receiver, said method comprising the steps:

• mounting optical sensors on the inside of the rear projection television receiver outside of a display screen at both lateral sides of the display screen;
• displaying a test pattern consisting of a raster projection pattern;
• and
• adjusting the width of the raster based on the outputs of the optical sensors located on the lateral sides of the display screen.

A method for adjusting a linearity of a raster in a rear projection television receiver, said method comprising the steps:

• mounting optical sensors on the inside of the rear projection television receiver outside of a display screen at the top and bottom of the display screen;
• displaying a test pattern consisting of a raster projection pattern;
• and
• adjusting the linearity of the raster based on the outputs of the optical sensors located at the top and bottom of the display screen.

A method for adjusting a height of a raster in a rear projection television receiver, said method comprising the steps:

• mounting optical sensors on the inside of the rear projection television receiver outside of a display screen at the top and bottom of the display screen;
• displaying a test pattern consisting of a raster projection pattern;
• and
• adjusting the height of the raster based on the outputs of the optical sensors located at the top and bottom of the display screen.

A method for adjusting a raster geometry in a rear projection television receiver, said method comprising the steps:

• mounting optical sensors on the inside of the rear projection television receiver outside of a display screen at both lateral sides and above and below the display screen;
• setting the height and width controls for the raster to respective maximum values;
• displaying a first test pattern consisting of a raster projection pattern;
• measuring and storing the maximum output from said optical sensors;
• displaying a second test pattern consisting of a center adjust pattern;
• adjusting the centering of the raster based on the outputs of the optical sensors located on the lateral sides of the display screen;
• displaying the first test pattern;
• adjusting the width of the raster based on the outputs of the optical sensors located on the lateral sides of the display screen;
• adjusting the height of the raster based on the outputs of the optical sensors located above and below the display screen;
• adjusting the linearity of the raster based on the outputs of the optical sensors located above and below the display screen;
• and
• re-adjusting the height of the raster based on the outputs of the optical sensors located above and below the display screen.

An arrangement for adjusting a raster geometry in a rear projection television receiver, said rear projection television receiver having an input for receiving television signals, a video processing circuit for processing said received television signals and for forming color video signals and deflection control signals, color video signal projectors for projecting light signals corresponding to said color video signals in dependence on said deflection signals, and a display screen on which said light signals are projected, wherein said video signal processing circuit includes control input means for receiving control signals for controlling a centering, height, width and linearity of a raster formed by at least one of said color video signal projectors, characterized in that said arrangement comprises:

• a pattern generator coupled to the video signal processing circuit for applying selected test patterns to said video signal processing circuit, said test patterns including a center adjust pattern and a raster projection pattern;
• a plurality of optical sensors mounted inside of the rear projection television receiver outside of the display screen at both lateral sides and above and below the display screen;
• a sensor output selector for selecting an output signal from one of said plurality of optical sensors;
• an analog-to-digital converter for digitally converting the selected optical sensor output signal;
• a controller having an input coupled to receive the digitally converted sensor output signal, a first output coupled to said sensor output selector for selecting one of the sensor output signals, a second output coupled to the video signal processing circuit for causing the video signal processing circuit to process the test pattern from the pattern generator, a third output coupled to the pattern generator for selecting one of the test patterns, and fourth outputs coupled to the control input means of the video signal processing circuit for controlling the centering, height, width and linearity of the raster generated by said one color video signal projector, wherein said controller performs the following functions:
• sets the height and width controls for the raster to respective maximum values;
• displays a first test pattern consisting of a raster projection pattern;
• measures and stores the maximum output from said optical sensors;
• displays a second test pattern consisting of a center adjust pattern;
• adjusts the centering of the raster based on the outputs of the optical sensors located on the lateral sides of the display screen;
• displays the first test pattern;
• adjusts the width of the raster based on the outputs of the optical sensors located on the lateral sides of the display screen;
• adjusts the height of the raster based on the outputs of the optical sensors located above and below the display screen;
• adjusts the linearity of the raster based on the outputs of the optical sensors located above and below the display screen;
• and
• re-adjusts the height of the raster based on the outputs of the optical sensors located above and below the display screen.