Among the lenses I salvaged from the computer projector was a larger double concave lens. I decided to use the same lens holder design for the concave lens that I built for the smaller lenses including the same shock absorber brick. It holds the concave lens just as well as the smaller lenses and the holder only had to be a bit larger to fit the larger concave lens.
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2605c01 Brick 1 x 2 x 2&1/3 Shock Absorber Complete, Modified with Spring Unit
1 Small Pulley
1 Technic axle 3
1 Lego plate 1 X 6
1 Lego brick 1 X 2 with cross axle hole (970631)
4 Lego plates 1 X 1
2 Lego plates 1 X 8
2 Slope bricks 1 x 2, 45 degrees
2 Lego bricks 1 X 8
12 Lego bricks 1 X 1
Here’s how I built my Lego optical lab lens holder for the double convex lens salvaged from the computer projector: