by Din » Tue Nov 01, 2016 1:11 pm
Hi Grayham, I've inserted the sensitivity curves for dcg. Curve 1 in the lower picture is the sensitivity of dcg before exposure, and the one to use to determine exposure. If you look at the 488 point and the 532 point, you'll see that sensitivity at 532 drops by about 20% odd from the 488 point, or, in other words, at 532 it's about 5 times slower. As a reference, when I shoot 4in x 5in ( 10cm x 12.5cm) in a split beam setup from an 8in x 10in (20cm x 25cm) H1 master, I generally need an exposure of about 1 - 5 minutes. This is based on an exposure of roughly about a 25 mJ/cm^2 exposure. But, this is terribly dependent on how good your H1 is (the weaker the H1, the weaker is the object beam and the longer the exposure), how hard the dcg is and other factors.
DCG doesn't really have an "exposure" as such because you're hardening the emulsion by exposure, or rather, you're increasing the modulation. So, for example, for a HOE, I sometimes go to hundred of mJ/cm^2, which is apparently the number you heard. However, this only applies to HOEs, for display you don't need to go that high.
- dcg_sensitiity008.jpg (38.32 KiB) Viewed 9535 times
Edit: This figure is from "Topics in Applied Physics, vol 20. Holographic Recording materials"
Hi Grayham, I've inserted the sensitivity curves for dcg. Curve 1 in the lower picture is the sensitivity of dcg before exposure, and the one to use to determine exposure. If you look at the 488 point and the 532 point, you'll see that sensitivity at 532 drops by about 20% odd from the 488 point, or, in other words, at 532 it's about 5 times slower. As a reference, when I shoot 4in x 5in ( 10cm x 12.5cm) in a split beam setup from an 8in x 10in (20cm x 25cm) H1 master, I generally need an exposure of about 1 - 5 minutes. This is based on an exposure of roughly about a 25 mJ/cm^2 exposure. But, this is terribly dependent on how good your H1 is (the weaker the H1, the weaker is the object beam and the longer the exposure), how hard the dcg is and other factors.
DCG doesn't really have an "exposure" as such because you're hardening the emulsion by exposure, or rather, you're increasing the modulation. So, for example, for a HOE, I sometimes go to hundred of mJ/cm^2, which is apparently the number you heard. However, this only applies to HOEs, for display you don't need to go that high.
[attachment=0]dcg_sensitiity008.jpg[/attachment]
Edit: This figure is from "Topics in Applied Physics, vol 20. Holographic Recording materials"