Optical apparatus

DETAILED DESCRIPTION The problem of the present invention is to provide a simply constructed, economically manufacturable but operationally reliable optical apparatus for determining the angle at which light from a scanning light spot is reflected by the being monitored.
At all times the apparatus must intercept at least a considerable part of the light emanating from the surface at different angles and within this light part must be able to determine angular differences at least in several angular stages.
According to the invention, this problem is solved in that in the area of the light beams emanating from the surface is provided a lamellar stepped mirror arrangement which extends in the scanning direction.
The stepped mirror is constructed of individual planar mirrors which are arranged parallel to one another and deflect the light which strikes them to an optical system namely a focusing lens.
An array of of photo detectors is positioned in the focal plane of the lens and the array is arranged perpendicular to the optical axis of the lens.
The arrangement is preferably such that in the case of a completely satisfactory surface light that is reflected by the monitored surface at a right angle thereto; is combined in the focus of the lens.
Light diverging from this normal direction at any angle is also concentrated in the focal plane but at a point which is laterally displaced to a greater or lesser extent from the focus.
In the simplest case, the reception screen can comprise a ground glass plate on which appears a light spot distribution characteristic for the surface which can be monitored by simply observing divergencies from a normal distribution.
Preferably, however, the reception screen comprises a plurality of photoelectric or photosensitive cells which are appropriately connected to an evaluating electronic system which transmits an error signal when signals exceeding a specific value appear on receivers located outside the centre.
By suitable refinement of the electronic system, it is possible to detect even minor differences in the relative state of the surface being monitored