Two-axis angular deviation measurement system with target image rotating means

In a system for measuring angular deviation in a transparency, said system having a predetermined optical axis and including an opaque object having a transparent pattern formed therein by a pair of transversely-aligned segments, an incoherent light source for illuminating said object, and means for projecting an image of said transversely-aligned segments through a test region of space, the improvement which comprises:

• (a) means for receiving said projected image and for transmitting it, after having removed any effects of lateral displacement of the image, into a predetermined channel;
• (b) a linear detector array aligned with said optical axis and positioned in said predetermined channel for detecting a lateral shift in the position of the image of one of said transparent pattern segments due to angular deviation for a particular point on said transparency, the lateral shift occurring, if at all, when the transparency is inserted into the test area;
• and
• (c) said receiving means including means actuatable for rotating the image of said transparent pattern segments about said optical axis to dispose the image relative to said array such that any lateral shifts in the position of, first, the image of one and, then, the image of the other of said segments are detected successively by said array.