Home | Optical Fabrication | Test Equipment | Exhibit Schedule | Contact Us
PC Controlled Lens Benches | PC Auto-collimator | Modular Auto-collimator
Electronic Auto-collimator | Spherometers
Collimators and Telescopes
In optical metrology, collimators and telescopes are mostly used together to measure different optical and geometrical parameters.
A telescope mounted in the front of a collimator enables the simultaneous observation of both collimator and telescope reticle. When a collimator is perfectly aligned to a telescope the reticles are superimposed and no displacement occurs.
The presence of an angle between the the collimator and telescope axes is shown by a linear displacement d between the two reticles. The displacement d gives the size of the angular disalignment of the two instruments:
= d / f
To ease the angular alignment of equipment with flat surfaces, a special type of instruments can be used: the square body collimators and telescopes. The reticles of these instruments are accurately aligned to the outer square body surfaces.
Measurement of Optical Parameters
A typical application is the measurement of the effective focal length EFL. A highly corrected collimator set to infinity (emerging beam is parallel) has a reticle with a pair of spaced lines located in its focal plane. The image of the reticle is projected over the lens under test and focused in its focal plane. By means of a microscope (or a telescope with a supplementary achromat) the size of spaced lines is determined and the EFL calculated:
f = fcol S' / S
A collimator set to infinity contains a reticle with a dark or bright cross. The lens under test is placed in a precision rotary holder. The image of a reticle projected over the lens under test is observed by means of a telescope with additional achromat having a graduated reticle.
While rotating the holder with the lens, the circle described by the reticle image is measured.
© 1997 - 2011 Mildex, Inc.