Atomic force microscope

An interferometer, comprising a light source, for emitting a light beam;

• a light splitter, for splitting the light beam into a signal light beam and a reference light beam;
• optics for guiding the signal light beam and the reference light beam to impinge on a target object and a reference object respectively, and to guide light reflecting off the target object and the reference object;
• and
• a detector that operates to determine differences in optical path length between the signal light beam and reference light beam to determine information about movement of the target object relative to the reference object,
• where the detector includes a monolithic quadrature phase analyzer and at least two photodetectors.

An interferometer, comprising

• a light source, for emitting a light beam;
• a light splitter, for splitting the light beam into a signal light beam and a reference light beam;
• optics for guiding the signal light beam and the reference light beam to impinge on a target object and a reference object respectively, and to guide light reflecting off the target object and the reference object;
• and
• a detector that operates to determine differences in optical path length between the signal light beam and reference light beam to determine information about movement of the target object relative to the reference object,
• where at least one optical element in the interferometer is assembled from at least two glass isosceles triangular prisms each with a vertex angle less than 89° or more than 91°.