Absolute calibration of null correctors using dual computer-generated holograms

Proteep C. V. Mallik; Rene Zehnder; James H. Burge; Alexander Poleshchuk

doi:10.1117/12.782680

21 November 2007 Absolute calibration of null correctors using dual computer-generated holograms

Proteep C. V. Mallik, Rene Zehnder, James H. Burge, Alexander Poleshchuk

Proceedings Volume 6721, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes; 672104 (2007) https://doi.org/10.1117/12.782680
Event: 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 2007, Chengdu, China

Abstract

There is an increasing need for precision large aspheric optics with small focal ratios for astronomical and space applications. However, testing such optics presents a challenge. Interferometric testing of aspheric surfaces often requires the use of null lenses. Many of these null lenses are tested using a certification computer-generated hologram (CGH) for better error calibration. We present a method that will measure large aspheres to a greater level of accuracy than is presently possible. We use segmented and superposed CGH elements to certify and calibrate null lens errors absolutely to a high degree of accuracy. In such holograms two different phase functions are encoded on the CGH by means of aperture division. One subaperture generates a spherical wavefront that is used to determine the pattern errors of the hologram while the second subaperture reconstructs an aspherical wavefront used to calibrate the wavefront errors of the null lens. This careful calibration process involves the removal of both axisymmetric and non-axisymmetric errors in the null test. Once this is accomplished, the null lens may be used to test the asphere to a high degree of accuracy. Our initial results show that we can test 4-meter class aspheric mirrors to better than 1nm rms surface error. In current experiments we have set a goal of measuring such mirrors to better than 1nm rms surface error.

Citation Download Citation

Proteep C. V. Mallik, Rene Zehnder, James H. Burge, and Alexander Poleshchuk "Absolute calibration of null correctors using dual computer-generated holograms", Proc. SPIE 6721, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 672104 (21 November 2007); https://doi.org/10.1117/12.782680

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available