PSF and MTF Measurement Methods for Thick CCD Sensor Characterization
Knowledge of the point spread function (PSF) of the sensors to be used in the Large Synoptic Survey Telescope (LSST) camera is essential for optimal extraction of subtle galaxy shape distortions caused by gravitational weak lensing. We have developed a number of techniques for measuring the PSF of candidate CCD sensors to be used in the LSST camera, each with its own strengths and weaknesses. The two main optical PSF measurement techniques that we use are the direct Virtual Knife Edge (VKE) scan as developed by Karcher, et al. and the indirect interference fringe method after Andersen and Sorensen that measures the modulation transfer function (MTF) directly. The PSF is derived from the MTF by Fourier transform. Other non-optical PSF measurement techniques that we employ include {sup 55}Fe x-ray cluster image size measurements and statistical distribution analysis, and cosmic ray muon track size measurements, but are not addressed here. The VKE technique utilizes a diffraction-limited spot produced by a Point-Projection Microscope (PPM) that is scanned across the sensor with sub-pixel resolution. This technique closely simulates the actual operating condition of the sensor in the telescope with the source spot size having an f/number close to the actual telescope design value. The interference fringe method uses a simple equal-optical-path Michelson-type interferometer with a single-mode fiber source that produces interference fringes with 100% contrast over a wide spatial frequency range sufficient to measure the MTF of the sensor directly. The merits of each measurement technique and results from the various measurement techniques on prototype LSST sensors are presented and compared.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1019473
- Report Number(s):
- BNL-94959-2011-JA; PSISDG; KA04; TRN: US1103631
- Journal Information:
- Proceedings of SPIE - The International Society for Optical Engineering, Vol. 7742; ISSN 0277-786X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data
Is flat fielding safe for precision CCD astronomy?