ADONIS Optical Layout

A tip-tilt and a deformable mirror (M4 and M3) correct the image motion and the image blur, respectively.
After this correction a dichroic splits the light into two channels: the wavefront sensor channel working in the visible and the imaging channel working in the infrared (lambda > 1 µm).
The Shack Hartmann wavefront sensor channel (F/8.09) is equipped with two intensified cameras, for low flux and high flux Natural Guide Star sources. An optical system images the pupil of the telescope on the lenslet array located in front of each wavefront sensor.

The high flux Shack Hartmann wave front sensor is an intensified Reticon working with WFS reference star brighter than 8.[ m_V<8]
The low flux Shack Hartmann dedicated to reference stars between 8 and 13 is an Electron Bombarded CCD (EBCCD).

An off-axis elliptical relay mirror (M6) is located at the exit pupil, and can be remotely tilted on RA and declination. M6 is computer controlled and its motion is pre-programmable by the user, in the observing sequence.
It allows the user to map, nod or chop at will. That is also to record the sky infrared background between exposures without offsetting the telescope. The field available to mosaic is 30 arcsec in radius, and it is currently limited by the size of the dichroic.
The F/45 infrared focus may be equipped both with COMIC or SHARPII+ infrared camera, as well as with user instruments.

References

[1]: Hubin N. et al., New adaptive optics prototype system for the ESO 3.6m telescope: Come-On-Plus, SPIE 1780-87 (ESO pre-print no 48)
[2]: Rousset G. et al., First diffraction limited astronomical images with adaptive optics, Astron. and Astrophys., 230, L29-L32, (1990)
[3]: Rigaut F. et al., Adaptive optics on the 3.6m telescope: results and performance, Astron. and Astrophys., 250, 280- 290, (1991)