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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...

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...

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...

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...

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.

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 ...

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.

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...

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...

Joe, Just listened to a webinar on "Materials and Methods for Creating 3D GRIN Diffractive Optics in Photopolymers." In the course of the webinar, the speaker brought up scattering and noise in a holographic volume recording and recommended this paper: https://opg.optica.org/ao/abstract.cf...