Abstract: To permit the testing of surfaces which have constricted access, such as grooves, bore holes and the like, a housing retains a laser light source, a collimator, a beam splitter and light detector. Light is reflected from the collimator, by a parallel offset dual parallelogram prism into an elongated hollow arm (8) which is pivotally mounted by a pivot axis (12) in the housing. The housing retains a positioning element (15) positioning the arm accurately with respect to the housing. A position transducer or sensing means senses repositioning of the housing to maintain the light spot from the laser, which is projected into the arm and outwardly thereof at right angles through an objective lens in focus. If the profile changes, the reflected light spot changes position on the light detector which controls the positioning system (15) to reposition the arm to maintain focus.