Orientation detection and alignment method and apparatus

Abstract

A method and apparatus for detecting orientation with respect to predetermined frames of reference particularly for use in aligning vehicle headlamps relative to frames of reference such as the true horizontal and the longitudinal axis of the vehicle. Orientation relative to the true horizontal is detected by comparing the electrical responses of two photocells which have a peak spectral response at a predetermined wavelength and which bracket a gas bubble provided in an upwardly curved transparent housing containing both the bubble and a fluid. The photocells are illuminated through the housing by associated light emitting diodes which have peak emissivities at wavelengths matched to the peak spectral response of the corresponding photocells. Orientation relative to a predetermined axis such as the axis of the vehicle is detected by detecting the orientation of a planar surface defining two brightness zones relative to a light beam originating at a light source as a concentrated light spot and diverging along the length of the beam. When aiming headlamps, the two orientation detecting means are mounted on a pair of headlamp aiming tools which are retained on the headlamps in a predetermined orientation relative thereto. Signals related to the detected orientation are generated by the orientation detectors and are selectively applied to a headlamp position adjusting means to modify the position of the headlamps in response to the detected orientations. The appropriate orientation signal may be selected automatically in response to the position of the adjusting means.