Angle sensor with CCD

DETAILED DESCRIPTION The present invention provides a wheel alignment system for measuring the angular relationship between the four wheels of an automotive vehicle.
Angle measurements are taken using four head units which are attached to the wheels of the vehicle.
Each head unit includes a linear CCD which produces a CCD output signal representative of a field of view.
The head unit also includes a light radiation source which is directed to a CCD on another head unit.
A slit is formed in a mask which is interposed between the radiation source and the CCD.
Each mask is attached to a head unit in front of the CCD.
The mask allows only a narrow line of radiation to fall on the linear CCD.
The linear CCD and the slit are positioned so that an angle between the CCD and the line of radiation is generally 90 degrees.
If the radiation source and the linear CCD are moved relative to each other, the position of the line of radiation moves along the linear CCD.
The apparatus includes a controller for operating the linear CCD and the radiation sources and for analyzing the output of the head units from the linear CCDs to derive an angular relationship of the wheels in an automotive vehicle Noise is limited in the measurements using a noise substraction technique.
Calibration data is stored in an EEPROM on each of the head units.