The main optics bench of UnISIS is very open, and system components can be repositioned easily for test purposes. This design is possible because the optics bench sits at the Coude focus where space is not an issue. The optics bench itself is 5x16 feet. The picture below displays the full width of the system but excludes both ends of its 16-foot length.
A heavy red line is superimposed over the image of the optics bench to show the path of starlight through the adaptive optics system. Parts of this path are obscured by various components, and a brief explanation is required. First, note that you are looking down on the main optics bench from above. The boxy aluminum frame in the foreground encloses the optics bench. Normally this frame holds a lid and side-panels that protect the system from air currents and dust. Only for the purpose of taking this picture was the optics bench cover removed. Second, sitting in the middle of the optics table on tall legs is a second smaller raised optics table with a black surface finish. It is loaded with test equipment and will not be explained further, except to say that the path of starlight through the adaptive optics system travels under this smaller optics table even though the red lines do not indicate so.
An angle was selected for this photograph to show most system components along the path of the natural star light, so the path followed by the return laser light is more obscured. The return path of the laser guide star light is identical to that of the natural star light from components 1 to 5, with 5 being the ADC = Atmospheric Dispersion Corrector. At point 5, the 351nm laser light hits the front surface of the ADC (the ADC has a dichroic coating on its front surface) and is reflected to the lower left in this picture to 10. Laser Guide Star Fold Mirror. The fold mirror sends the laser return to the upper right (under the raised auxiliary optics table) to 11. Pockels Cell Switch where the beam is reversed in direction, passes through the lenslet array and enters 12. Laser Guide Star Wave Front Camera.
