Abstract: The optical instrument includes a body mounted for X-Y movement above a generally planar object and carries a wide-angle lens, and a plurality of collecting mirrors disposed at angular locations about and spaced from the axis of the lens. A reversing mirror is located above the lens and sensors are disposed in the instrument. The images from the surface under observation are reflected by the collecting mirrors through the wide-angle lens against the reversing mirror for imaging on the sensors. The light is transposed into electrical signals for analysis in a computer. The conveyor for conveying the generally planar object clamps the lateral margins of the object and includes sections movable generally in the direction of the axis of the lens and independently of one another to ensure that the surface of the object under observation lies in a plane generally parallel to a horizontal plane.