PROCEEDINGS ARTICLE | June 28, 2006
Proc. SPIE. 6269, Ground-based and Airborne Instrumentation for Astronomy
KEYWORDS: Infrared cameras, Near infrared, Optical filters, Cameras, Sensors, Adaptive optics, Optical testing, Integrated optics, Optics manufacturing, Cryogenics
This paper presents the integration and first results for the CAMCAO NIR camera. The camera was built
for the ESO Multi-conjugate Adaptive optics Demonstrator, where it is presently operating, to evaluate the
feasibility of this Adaptive Optics technique. On a second phase it will work directly at the Nasmyth focus of the
VLT. CAMCAO is a high resolution, wide field of view NIR camera, that is using the 2k×2k HgCdTe HAWAII-
2 infrared detector from Rockwell Scientific, controlled by the ESO IRACE system. The camera operates in
the near infrared region between 1.0 μm and 2.5 μm wavelength using an eight position filter wheel with J, H,
K', K-continuum and Brγ filters. Both the integration experience and the results obtained in the mechanical,
vacuum, cryogenics and optical tests are presented, including all relevant parameters in the ESO specifications.
The requirement of mechanical stiffness together with light weight was achieved yielding a total weight of less
than 90 Kg. The camera fulfills both cryogenic and vacuum stability requirements. The temperature within
the detector is maintained at 80K by an accurate control loop, ensuring mK stability, after cooling down the
detector at a rate kept below 0.5 K/min. The optical performance tests were made using a Fizeau interferometer
both for the individual optical components and complete setup. The infrared optical validation measurements
were performed by re-imaging a point source in the camera focal plane and measuring the PSF with the detector.
The computed Strehl ratio reached 95% in the central region of the FoV, with values larger than 90% in a area
covering 88% of the focal plane.
