Autocollimator

An autocollimator for providing an output signal indicative of the angular displacement of a light reflector, the autocollimator comprising:

• illuminating means and optic means for producing first and second light beams and for projecting the two light beams onto said light reflector located at a predetermined distance from said light source;
• said reflector reflecting the two light beams a long different return light paths towards a position sensitive light detector means located adjacent to said optic means;
• said light reflector being subject to angular displacement;
• and
• said light reflector when in a first position reflecting both light beams onto said light detector;
• and the light reflector when displaced in one direction relative to said first position, causing the first and second light beams to move in a first direction across the light detector means, with the first beam preceding the second beam;
• and the reflector when displaced in another direction, opposite to the one direction, causing the first and second light beam to move in a second direction opposite the first direction across the light detector means, with the first beam following the second beam;
• and
• said light detector means being responsive to the incidence of each one of said first and second light beams and including means for producing a signal indicative of the angular displacement of the reflector in response to each light beam reflected from the reflector onto said light detector means for enabling the light detector means to produce a signal indicative of the angular displacement of the reflector even when only one of the first and second light beams is incident thereon, whereby the two beams increase the range of measurable angular displacement which the light reflector undergoes.

An autocollimator comprising:

• an illumination means and an optics system for producing first and second light beams and for directing the first and second light beams towards a light reflector located at a predetermined distance from the light source;
• where the light reflector is subject to angular displacement which is to be measured;
• said reflector reflecting the two light beams back along slightly non-parallel paths towards an optical aperture of a light receptor and onto different portions of a surface of a position-sensitive light detector means;
• said light detector means being responsive to the incidence of each one of said first and second light beams and including means for producing a signal indicative of the incidence of each one of said first and second light beams and the changes in the position, if any, of each beam;
• and
• wherein, for a non-displaced position of the reflector, both beams are reflected into the optical aperture of said light receptor and onto said light detector;
• and
• wherein, when the light reflector is subjected to angular displacement in one direction, the two light beams are caused to sweep across the optical aperture such that the first light beam precedes and moves ahead of the second light beam and, even when the first light beam is no longer incident on the optical aperture, so long as the second light beam is incident on the optical aperture, the second beam provides information as to the angular displacement of the reflector;
• and
• likewise, when the light reflector is subjected to angular displacement in an opposite direction to said one direction, the two light beams are caused to sweep across the optical aperture such that the first light beam moves behind the second light beam and, even when the second light beam is no longer incident on the optical aperture, so long as the first light beam is incident on the optical aperture, the first beam provides information as to the angular displacement of the reflector;
• wherein the two beams increase the range of measurable angular displacement which the light reflector undergoes.