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Optical Services — Optical Testing
For aspheric, plano and spherical optics up to 2.5m in diameter.
ITT has the experience and facilities to test the quality of aspheric, plano and spherical optical components up to 100in. (2.5m) in diameter during fabrication, and verify their systems performance.
We design complex optical test schemes and analyze the results in support of a wide variety of applications, including: optics for ground-based telescopes, remote sensing cameras, space-based observatories, high-energy laser systems, microlithography systems and intersatellite laser communications links.
Optics for many of these applications require ion figuring to achieve the highest optical surface figure quality. At ITT, this capability alone has driven development of ever-higher optical metrology accuracy to test surface accuracy and performance.
Testing Hardware
Given the wide variety of optics manufactured at ITT over many years, we have made a significant capital investment in test set hardware.
Set up in one of our optical testing facilities, test sets range from our sophisticated test benches with phase-sensing interferometry equipment to large-scale configurations inside five-story-tall vibration-isolated towers.
Having a range of facilities in place gives us the latitude to develop the test set configuration that is best suited for your project.
Test Analysis
Capturing optical figure and performance data is a first step in the test sequence. A crucial second step requires analysis of the measurements recorded by the test system. To validate the results of data captured by our test systems, we routinely develop our own analysis software. Analysis functions provide detailed surface topography information for all types of optical components.
In large test systems, such as the test set constructed for the Chandra Observatory's high-resolution mirror assembly, we developed software to control system alignment drives, position test mirrors, operate monitoring instrumentation, and calculate the positioning error and correction of the mirrors under test.
Testing Services
State-of-the-Art Testing Services
Large Mirror Testing
Mirrors exceeding 2m in diameter are tested in one of two types of vibration-isolated test towers at ITT - one for plano surfaces and the other for curved surfaces. The 15m high towers are mounted on "air springs" that have vertical, lateral and rocking motion resonances below 2.0 Hz. Both towers can accept specially designed mounts that simulate zero-G effects on mirror surfaces.
Most of our large testing facilities are equipped with circulating air systems and a thermocouple temperature-sensing system to achieve rapid thermal stabilization of test optics and optical air-path test media.
Plano Transmission and Surface Testing
We can test precision flats and windows with an accuracy better than 0.025 waves rms at 0.6328 microns, using 0.06 to 0.9m aperture Fizeau interferometers. Plano surfaces larger than 2m in diameter can be tested in a zero-G simulated environment with our Ritchey-Common test.
Concave Surface Testing
Optics up to or exceeding 2.5m in diameter can be measured to an accuracy of 0.015 waves rms at 0.6328 microns over a radius of curvature of 0.5 to 2.30m. These optics are tested in one of our vibration-isolated, thermally-controlled towers.
Long Radius of Curvature Measurement
Long radius of curvature mirrors and long focal length lenses, from 0.1m to 0.8m in diameter, are measured on our 10m-lens bench. The bench can measure a radius of curvature range of 0.5 to 9.5m with an accuracy to ±0.02mm. It is used to test mirrors for microlithography stepper machines.
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