Engineers have developed a method for checking mirrors of large telescopes using holograms

To control the quality of mirrors of large telescopes and other space optics, they have long been used.

special images created usinglaser on quartz plates. It is important that the holograms themselves are sufficiently accurate. To solve this problem, Russian photonics have developed a method for recording specialized marks in the field of a hologram. And this happens during the process of recording it on a record.

These marks are microlattices, the points in which are located in a checkerboard pattern. When light passes through them, a complex diffraction pattern is formed from many beams of light.

The recording process of microgrids is divided into severalstages. To begin with, the first part of the "marks" is recorded, and even before the hologram. Then, when the hologram recording begins, the second part of the microgrids is added at predetermined places. The process of creating holograms takes up to 12 hours.

When the hologram recording is complete, through eacha laser beam is passed through the mark, and then the diffraction pattern is analyzed. If the picture is disturbed, that is, the microlattices have shifted relative to each other during recording, then the hologram will also be inaccurate. If the picture is accurate, then the plate can be used to test space optics as a reference sample.

“Our proposed method can determineerrors in the image with a scale of up to 10 nm, which ensures the accuracy of holograms. This is very important when used to test the quality of telescope mirrors. For example, our institute has produced holograms that were used as standards for polishing the surface of the largest mirror in Russia - 6 m in diameter - of the Large Azimuth Telescope (BTA). Also, our laboratory has created holograms for a similar test of the mirrors of the James Webb Space Telescope. "

Ruslan Shimansky, researcher at the Institute of Automation and Electrometry SB RAS

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