PHASE INTERFEROMETERS

VERTICAL? OR HORIZONTAL?


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Model 4VPS Phase Interferometer
for Plano or Spherical work.

The 4-inch aperture vertical Interferometer at the left is our Model 4VPS which has been configured for either Plano or Spherical work on surfaces of moderate radii of curvature.

For Plano work the vertical format is usually preferred since there is no need to mount the test piece in a separate fixture. 

The operator merely places the test piece on the integral tip/tilt table and makes the appropriate adjustment.

If a transmission sphere is attached to measure a spherical surface, the length of the rails seriously limits how far away the test piece can be placed. 

Thus, the vertical format can be used to measure spherical surfaces of only moderate radii of curvature.

Low Cost Phase Interferometer for Plano Work

Model 4HPR Phase Interferometer 
for Plano work only.

In general, a vertical interferometer can be used in almost any quiet environment, with appropriate vibration isolation if required, while a horizontal interferometer really requires an optical table as well as some accessories -- most notably a 5-axis tip/tilt fixture, especially if spherical measurements are to be made.

At the immediate right is our low cost 2-inch aperture PHASE MITETM Model 2VP interferometer, for those working with smaller optics.

Model 2VP PHASE MITETM
2-inch Plano work only

The 4-inch aperture horizontal Interferometer shown above is our Model 4HP which is the preferred model if both Plano and long radii spherical measurements are to be made. 

While the horizontal format requires that the test piece be mounted in a separate tip tilt fixture, if the instrument is installed on an optical table, neither Plano nor long radii spherical surface measurements present a problem.

As far as performance is concerned, the Models 4VPS and 4HP both offer the same features as well as the same accuracy.  The choice between vertical and horizontal formats is entirely driven by the application.
 
 

 


 
 
MEASUREMENT
VERTICAL FORMAT
HORIZONTAL FORMAT
Plano Surfaces Easy setup using integral Tip/Tilt Table Requires external Tip/Tilt fixture, preferably set up on an optical table.
Spherical Surfaces short radii of curvature Requires appropriate Transmission Sphere and five axis fixture to center and position test piece. Requires appropriate Transmission Sphere and five axis fixture to center and position test piece.
Spherical Surfaces long radii of curvature Requires appropriate Transmission Sphere and five axis fixture to center and position test piece.

Radius of curvature that can be measured is limited by length of vertical rails.

Requires appropriate Transmission Sphere and five axis fixture to center and position test piece.

No limitation on radius of curvature that can be measured.

Transmitted Wave front Requires reference flat or reference sphere, but not an easy setup for vertical format interferometers. Requires reference flat or reference sphere, and with appropriate fixtures, is readily setup on an optical table.
Radius of Curvature measurement Not readily measured on vertical interferometer. With appropriate scale and transmission spheres, radius of curvature is readily measured with a horizontal interferometer.
Homogeneity of substrate Not an easy setup on a vertical interferometer, but can be done if appropriate fixture is provided. With appropriate fixtures and reference mirror, homogeneity readily measured with a horizontal interferometer.

Graham Optical Systems,   9530 Topanga Canyon Blvd., Chatsworth, California 91311
For Further Information today, call Gordon Graham today at (818) 700-1263    E-mail: techinfo@grahamoptical.com 
Copyright © 2014 Graham Optical Systems  All Rights Reserved    Durango is a trademark of Diffraction International
This page last updated, February 20, 2014