mosses from an old manse: 4/24/11

Friday, April 29, 2011

Holography typically requires manipulating the laser beam with lenses, mirrors, beamsplitters, pinholes, etc. All of these elements must be positioned in space and held steady to within about 1/100,000 inch for up to several minutes. To accomplish this task, most traditional optical laboratories use expensive micro-positioning mounts to hold the optics. To isolate the optics from room vibrations, they are mounted on a foot thick granite slab floated on compressed nitrogen pistons. These set-ups cost many thousands of dollars.

Jerry Pethick suggested a much simpler but equally effective system using sandboxes floating on automobile innertubes. A 4X6 foot or 4X8 foot slab of concrete was poured and a 2 foot deep box made of cinder blocks was built on top to hold the sand. The slab and box were then floated on innertubes for vibration isolation. Optics were mounted on the ends of 2 inch diameter PVC pipe sunk into the sand. With Pethick's method, adjusting the position of the beam was simply a matter of moving the pipes in the sand. Once released, the pipes held their position. After making all the adjustments, we tapped the pipes with a finger to give them a final "set", then let the table "settle" for 30 minutes before exposing a hologram. I saw several very high quality 8X10 holograms made with this system using small 1mW lasers with 5 minute or longer exposure times.

Animals Dream by Jerry Pethick

This preoccupation with space led to a desire to manipulate space itself, like other sculptural elements of material and form, metaphor and echo, the ideas that push and pull one into creative commitment. My interest that started in learning about material structure and visual aesthetics formed a curiosity about space itself - a perceptual space that becomes another element to play with and to weave into low technology constructs as well as the high technology of electronic images, diversified by the vast range of the computer...