Dimension measuring apparatus

Abstract

Abstract Apparatus for measuring a dimension associated with a remote object without contacting the object itself uses a beam of light which is directed at a surface of the object and a reflected portion of the beam is detected at a photodetector element. The particular dimension of the object is determined mathematically by measuring the distance by which the reflected light signal is offset from a predetermined point on the photodetector which is aligned with a reference plane at the object. By the use of two heads and respective light beams and photodetectors, the thickness of a remote object can be measured. In order to compensate for the angular relationship between the object's surface and that of the photodetector, a linearizing calibration circuit is included in which preset corrections are recorded in programmable memory units. The calibration settings are determined during manufacture and correct for each normally non-linear reading at incremental distances within a prescribed measurement range. To provide the correction signals there are provided means (60) for guiding a simulated reference surface (70) along a predetermined path. Means (70A, 66) are provided at the simulated reference surface (70) for establishing its position on the path and independent light sources (12A) direct light signals (12B) at the simulated reference surface (70) at each of a plurality of discrete positions along the path. Detectors (12E) receive reflective components of the light signals on reflection from the simulated reflection surface (70). Means are provided for measuring the linear accuracy of the reflected components and for generating a corresponding plurality of compensating signals (72) with respect to any non-linearity. The compensating signals are stored in accordance with the discrete positions along the path corresponding to the generation of a reflected component requiring the compensation signals.

Inventors

• 👤 Karl-Erik Morander

Bibliographic Details