Search found 401 matches

by Din
Sat Aug 12, 2023 11:40 am
Forum: General Holography
Topic: collimated reference beams
Replies: 5
Views: 4326

Re: collimated reference beams

Joe, I’m not sure if you mentioned what laser you were using as I read through. But I find the PL 530 laser has a hotspot more so than other lasers do. What that means if you need to throw more light away on the edges and use that central version like you had to with, other typical Diode Lasers , i...
by Din
Wed Aug 02, 2023 11:11 am
Forum: DCG
Topic: Bacteria?
Replies: 2
Views: 2367

Re: Bacteria?

It sounds unlikely to be bacteria. Bacteria attacks organic molecules such as gelatin, so it's possible your gelatin got contaminated if left open. But, on heating and stirring the gelatin the bacteria would probably get dispersed, and is unlikely to clump the way you show. It could have attacked th...
by Din
Sun Jul 30, 2023 9:19 am
Forum: General Holography
Topic: collimated reference beams
Replies: 5
Views: 4326

Re: collimated reference beams

You could be right about light loss due to reflections, it depends on the polarisation. Loss of Reflectivity at Brewster's angle only occurs for 'p' (TM) polarisation. Even if you have 'p' polarisation, it would depend on your reference plane. We used a side reference and one problem was to make sur...
by Din
Sat Jul 22, 2023 8:54 am
Forum: DCG
Topic: energy distribution across DCG plate
Replies: 2
Views: 2484

Re: energy distribution across DCG plate

It is important to have roughly even illumination of the reference beam, but technically it's not possible (unless you have a beam flattening device). However, within a rough estimate, we can assume an even beam if the edges of the beam are greater than 1/e of the centre ( e = Euler's number). So, a...
by Din
Tue Jun 27, 2023 12:24 pm
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6059

Re: question about PFG-04

A couple of points: It's true that dark reaction improves the image, up to a point. Beyond that point, performance decreases. Remember, what you're after is modulation, the difference between base hardness and the hardness of the planes - or, rather the ratio of hardness of plane to not-plane. Initi...
by Din
Mon Jun 26, 2023 12:41 pm
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6059

Re: question about PFG-04

Joe Farina wrote: Mon Jun 26, 2023 8:00 am By the way, Martin, since you are the best-read person in holography that I know of, do you recall any studies concerning the hardening/dark reaction of gelatin/dichromate at high (~9) pH? I'm drawing a blank. Thanks.
Joe,
It's in Kosar.
dark_reaction.jpg
dark_reaction.jpg (95.38 KiB) Viewed 3540 times
by Din
Sun Jun 25, 2023 1:42 pm
Forum: DCG
Topic: Diazo (Speedball) gelatin hologram
Replies: 33
Views: 194430

Re: Diazo (Speedball) gelatin hologram

Here's the contents page for DCG and other materials. I used the method of carbon printing (chap 2.1b) to show it was possible to use DCG as a resist material. We recorded a thin hologram on DCG with depth < 1u, and then transferred the image to a piece of plastic by casting. We poured Norland onto ...
by Din
Sun Jun 25, 2023 1:32 pm
Forum: DCG
Topic: Diazo (Speedball) gelatin hologram
Replies: 33
Views: 194430

Re: Diazo (Speedball) gelatin hologram

Martin wrote: Sat May 06, 2023 4:34 am
Din wrote: Thu May 04, 2023 10:40 am Joy tells me that I tried to throw it out when we left Triple Take behind, but she rescued it; she knows it's somewhere, but doesn't know where.
That sounds exciting. Would be nice to see it online some day.
Martin, Joy found the book I inherited from Don Broadbent.
non-silver.jpg
non-silver.jpg (35.85 KiB) Viewed 85329 times
by Din
Wed Jun 21, 2023 11:09 am
Forum: DCG
Topic: "bad" batch of dichromate chemical?
Replies: 6
Views: 3215

Re: "bad" batch of dichromate chemical?

The quality of the colors (i.e., saturated and bright, my idea of "narrowband') came out worst on the thickest layer, best on the #36 bar layer, and reasonably good with the #24 bar (thinnest) layer. So maybe in an ideal world, thicker may be better for narrowband, but in practice a medium-thi...
by Din
Tue Jun 20, 2023 1:19 pm
Forum: DCG
Topic: "bad" batch of dichromate chemical?
Replies: 6
Views: 3215

Re: "bad" batch of dichromate chemical?

There are several possibilities. One is that the cheap pot. dichromate had impurities in it that blocked the polymerisation process, leading to a lack of image-specific cross-linking. Another possibility is that the coating was too deep/shallow, ie the emulsion depth was too high/low, and/or there w...