Method of aligning optical system using a hologram and apparatus therefor

A method of aligning an optical system having an optical element installed in a barrel, the method comprising:

• providing a hologram element;
• aligning the optical element with the hologram element in the barrel so that test beams returned from the barrel travel on a same optical path as an incident path of the test beams onto the barrel;
• measuring alignment errors of the optical element from interference patterns formed by reference beams and the returned test beams;
• and
• aligning the optical element to remove the alignment errors.

An optical system comprising:

• a barrel;
• and
• at least one optical element having a hologram element formed thereon, wherein:
• the at least one optical element is placed in a predetermined position of the barrel so that test beams diffracted by the hologram element travel along a same optical path as test beams incident on the optical system.

An optical system comprising:

• a barrel;
• and
• at least one optical element mounted in the barrel, wherein:
• the barrel further comprises a unit in which to place a hologram element in a predetermined position of the barrel.

A method of measuring an alignment error in an optical system, having at least one optical element, the method comprising:

• providing a computer generated hologram element on a same optical path as the at least one optical element;
• generating an interference pattern on an image surface between a reference beam and a test beam reflected or refracted by the hologram element;
• and
• determining a magnitude of the alignment error of the optical element according to a number of circles in the interference pattern.

An optical system having included features for measuring an alignment error of the optical system, the optical system comprising:

• a barrel;
• and
• at least one optical element mounted in the barrel, the at least one optical element having a computer generated hologram written on a peripheral area of the optical element, wherein:
• the computer generated hologram is usable with an external interferometer to generate an interference pattern on an image surface of the interferometer between a reference beam of the interferometer and a test beam of the interferometer which is reflected or refracted by the hologram element,
• a magnitude of the alignment error of the optical element is determinable according to a number of circles in the interference patern, and
• a direction of the alignment error is determinable according to a displacement of a center of the interference pattern from a center of the image surface.