Confocal microscopy for high-precision non-contact optical measurements

Micah A. Johnson; Charles C. Kankelborg; Rubin Meuchel; Roy Smart

doi:10.1117/12.2319597

19 September 2018 Confocal microscopy for high-precision non-contact optical measurements

Micah A. Johnson, Charles C. Kankelborg, Rubin Meuchel, Roy Smart

Proceedings Volume 10747, Optical System Alignment, Tolerancing, and Verification XII; 107470A (2018) https://doi.org/10.1117/12.2319597
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States

Abstract

The EUV Snapshot Imaging Spectrograph (ESIS) is a slitless, tomographic imaging spectrograph for observing the solar transition region in extreme ultraviolet (EUV) at 63nm wavelength. An array of concave diffraction gratings re-image from the telescope prime focus to our CCD detectors. The instrument is aligned and focused in visible light, using substitute diffraction gratings ruled for the red HeNe laser line. To transfer precise alignment and focus of the visible gratings to the EUV gratings, we have developed a minitaturized, three point, noncontact measurement system, TEA (Transfer ESIS Alignment). TEA locates the grating surface using confocal microscopy, with three independent channels scanned together on a single stage, to specify the position and orientation of the spherical surface. Challenges for this measurement include the small size of the ESIS gratings (~ 16X20μm), their curved surfaces, diffraction effects, the alignment of tiny optics within TEA, and the mechanics used to repeatability mount the gratings. Our testing shows that the intrinsic repeatability of our measurement apparatus is approximately 2μm. In practice, however, our error is dominated by the process of mounting the grating subsystem in TEA, which introduces 12μm differences between subsequent runs. This level of repeatability meets our requirements for ESIS.

Conference Presentation

Citation Download Citation

Micah A. Johnson, Charles C. Kankelborg, Rubin Meuchel, and Roy Smart "Confocal microscopy for high-precision non-contact optical measurements", Proc. SPIE 10747, Optical System Alignment, Tolerancing, and Verification XII, 107470A (19 September 2018); https://doi.org/10.1117/12.2319597

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