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Most astronomy gratings are ruled on the MIT “B engine,” which was built by Professor George Harrison and moved to Rochester in 1968. This engine has the capacity to rule plane gratings with the greatest precision ever achieved; these gratings may be up to 400 mm wide, with grooves (between 20 and 1500 per millimeter) up to 300 mm long. It uses a double interferometer control system, based on a frequency-stabilized laser, to monitor not only table position, but to correct residual yaw errors as well. The "B engine," produces gratings with nearly theoretical resolving powers, virtally eliminating Rowland ghosts and minimizing stray light.
We have the ability to test and certify efficiency, surface figure (wavefront) and stray light characteristics on all of our gratings through the following capabilities. |
Efficiency: 190 nm through 2.5 µm using one or more of our 4 custom designed instruments- Surface Figure: Zygo interferometer, PMI (phase measuring interferometer) and our 5-meter Littrow mount (the “five meter bench”)
- Scattered Light: 10-meter Czerny-Turner monochromator (the “ten meter bench”), custom designed and built scatter testing apparatus
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In addition, our Richardson Gratings team developed the capability in the mid-1990's to replicate two large submaster gratings onto one monolithic substrate. Except for a "dead space" between the two replicated areas, the entire face of the larger product substrate contains the groove pattern. This mosaic grating must have its two grating areas aligned to very high accuracy if the mosaic is to perform as one high-quality grating. Typical specifications for two 308 x 408 mm ruled areas on a 320 x 840 mm substrate are one arc second alignment of the groove directions, one arc second tilt between the two faces, and one micron displacement between the two grating planes. These gratings can have resolving power better than R = 1,000,000.
Please contact us to discuss the development of a custom master if you do not find a grating that matches your requirements in our catalog. |