An autocollimator based on the laser head of a compact disc player

The design and construction of a small compact autocollimator based on the laser head of a compact disc player is described. The instrument provides a cheap and simple means of measuring angles over a total angular range of 1200 mu rad ( approximately 200 arcsec) with a resolution of better than +or-0.006 mu rad. The 100 mu rad central region of the measurement range is linear to better than 2%. The autocollimator head is compact and can operate over long distances and with high ambient lighting. The unit described can, with a single measurement head, be used to simultaneously measure angles in two orthogonal directions.