Newbie on DCG holography

Dichromated Gelatin.
msxc
Posts: 30
Joined: Wed Jan 07, 2015 1:08 am

Newbie on DCG holography

Post by msxc »

Hi DIY Holographers,

Just recently completed my small and claustrophobic coating box(codename "IKEA"), so I may contribute here.

Regarding laminar flow.
Drinking straws are easily available and cheap, but I couldn't find easy way of gluing them together. It is ok to glue few, but for any real size of honeycomb that would take ages. Instead I found other material- corrugated plastic. Cutting small stripes and gluing them together is much faster. Inspiration came from this video (http://www.youtube.com/watch?v=a8qeq_mwKj0).

And the box itself, well let the picture tell the story:
holo_darkroom-12.jpg
Please don't call it as a Trash bin- It doesn't like it at all :twisted:
Fan is powerful (kitchen stove exhaust, with 3step regulation), layer of pre-filter, HEPA, and then "honeycomb". Small and claustrophobic, but no dust will come inside. I'm not sure if it is not too powerful because drying plates is really fast.

msxc
Joe Farina
Posts: 804
Joined: Wed Jan 07, 2015 2:10 pm

Newbie on DCG holography

Post by Joe Farina »

Wow, msxc, superb coating station. That's an excellent (and also cheap and easy) way to make a clean enclosure. By the way, my straws were not glued, they were simply wedged into position. I too was very proud of my first large laminar flow, and also nicknamed it -- "Thor" ;)
MilanKarakas

Newbie on DCG holography

Post by MilanKarakas »

Joe Farina wrote:Hello Milan,
Hello, Joe.
Thanks for the update. If you have confidence in your laser and power meter, you should be ok. Around 40mW of green light is quite good.
Yes, I have confidence. Only problem is with my body heat (blackbody, or continuum radiation) - when I am close to this instrument, it shows few mW more, If I am behind ('cold', or reference side), then it shows few mW less. This is because this instrument works on light -> thermal conversation. I forgot it's real name, but it is listed as 'thermal power (or energy) meter', something like this one:

http://www.ophiropt.com/laser-measureme ... -low-power

Mine is not black anodized aluminum, that is big mistake (reacting very slowly, to get real reading, up to 15 seconds or so). All power entering sensor (simple peltier elements, or TEC, painted black with high temp. resistant painting), goes over P/N silicon elements, and re-emits at it's back side (mine emits/receive at all sides).

It is temperature independent, even when hot, it can measure power. Only sudden change in temperature difference front/back may cause false reading.

Did not use it's calibrating heater wire inside because then I should subtract losses due to glass cover reflection, paint reflection, etc. Calibrated on known power of various lasers. Lucky coincidence is that it shows exactly 0.1 mV per 1 mW with cover glass.

Glass cover is because this sensor is very broadband - from microwave range (depend of 'window' opening - should be more than 1/2 lambda), up to VUV (not x-rays, or gamma-rays, although this may be done by using thick lead block). Glass is transparent from cca. 400 nm up to about 2 um, and blackbody radiation ranging from 2 um and up to tens of micrometers.

Proper shape of the sensor should be deep inverted cone (hollow), so that light entering doesn't reflect back. Mine is flat (it is difficult to make this cone, don't know how to make it), so there are some losses during reading.

Alternative to this design is thermal power meter with two holes, one active, and one reference - this is more forgiving because both holes read the same background power (stray light, body radiation, etc.). I will consider built it later.
The thing which reduces (and in fact should eliminate) turbulence in the laminar flow is the front grill or honeycomb. So if you have that, then you shouldn't need the layers is back, and this should greatly increase air flow. As a possible way to make a honeycomb, the following idea came to mind: cut many pieces (maybe a few hundred) of PVC pipe (say ~2 inches long), lay them flat, and glue together with PVC cement. Also brush the cement over surfaces (if they are dusty from being cut). The only question in my mind regarding this idea is that the thickness of PVC tubing (which is substantial) might conceivably cause a problem. But I doubt it.
Oh, well. I made it incorrectly. That is because I am googling for some design, and found only abstract drawing, not fine details. Didn't know that I should use something that directing air... my bad.
Or use any similar idea with available materials.
I will try to find something. If nothing else, I can use impregnated paper with something which can provide god mechanical stability after drying. Then I can make some honeycomb structure with paper stripes.

BTW, this honeycomb, how thick or deep it should be to ensure good work?


Thank you very much for your informations.

Best--
m--
MilanKarakas

Newbie on DCG holography

Post by MilanKarakas »

msxc wrote:Hi DIY Holographers,
Hi.
Just recently completed my small and claustrophobic coating box(codename "IKEA"), so I may contribute here.
Cute name. :)
Regarding laminar flow.
Drinking straws are easily available and cheap, but I couldn't find easy way of gluing them together. It is ok to glue few, but for any real size of honeycomb that would take ages. Instead I found other material- corrugated plastic. Cutting small stripes and gluing them together is much faster. Inspiration came from this video (http://www.youtube.com/watch?v=a8qeq_mwKj0).
WOW! You give me excellent idea, and saved my time!

I can roll cheap paper sheets over some rod (maybe 2 cm in diameter), then secure with scotch tape, and then remove. Such made tubes then I can stack in honeycomb structure by another tape (masking tape works the best), and whole thing incorporating inside laminar flow hood. Only problem I have here is limited space.

Anyway, I should to consider make another hood. I made this one close to kitchen elements and walls only because I have not any proper material. Maybe some cardboard box from old CRT TV set. Also, I wanted it to be close to kitchen heating elements because there mixing chemical and don't want it to cool down too much.

Now I think I have solution to that: Portable heating element (hot plate).
And the box itself, well let the picture tell the story:

Please don't call it as a Trash bin- It doesn't like it at all :twisted:
Fan is powerful (kitchen stove exhaust, with 3step regulation), layer of pre-filter, HEPA, and then "honeycomb". Small and claustrophobic, but no dust will come inside. I'm not sure if it is not too powerful because drying plates is really fast.
Pretty impressive! You give me good idea. Will see what I have here that can convert into something similar. Thank you again for the inspirations.
msxc
Best--
m--
Joe Farina
Posts: 804
Joined: Wed Jan 07, 2015 2:10 pm

Newbie on DCG holography

Post by Joe Farina »

Hello Milan,

That's a good question as to how deep the honeycomb should be. I can't really answer it, because I've only used straws. Up above, msxc mentioned the use of corrugated plastic in his design. I think this is a good choice (but I didn't get a chance to watch the video that was linked to). If that is the same kind of material I'm thinking about, it's like the corrugated fiberglass sheet they sell at home centers, as a roofing material. If it really is fiberglass, it might be rather tough to cut (probably the same as fiberglass-reinforced PCB material). But maybe they have solid plastics also at the home centers, which can easily be cut. These corrugated sheets are wavy, and from memory the "waves" are about 2 or 3 centimeters high. So these sheets could be cut in strips, and glued together ridge-to-ridge. This would make channels (like straws) perpendicular to the hepa filter.

I would think the longer the channels, the better, but of course space is limited. If you can make the channels any length, I would go for maybe 10 to 30 centimeters, depending on the size of the openings. If the openings are small (i.e., straws) probably 10cm would be good (I used short cocktail straws, not full size drinking straws). If you're using large openings like corrugated sheet (openings might be as much as 5cm), I would make the depth of the honeycomb as large as the table permits.

Hopefully msxc will chime in.
MilanKarakas

Newbie on DCG holography

Post by MilanKarakas »

Joe Farina wrote:Hello Milan,
Hello Joe
That's a good question as to how deep the honeycomb should be. I can't really answer it, because I've only used straws. Up above, msxc mentioned the use of corrugated plastic in his design. I think this is a good choice (but I didn't get a chance to watch the video that was linked to). If that is the same kind of material I'm thinking about, it's like the corrugated fiberglass sheet they sell at home centers, as a roofing material. If it really is fiberglass, it might be rather tough to cut (probably the same as fiberglass-reinforced PCB material). But maybe they have solid plastics also at the home centers, which can easily be cut. These corrugated sheets are wavy, and from memory the "waves" are about 2 or 3 centimeters high. So these sheets could be cut in strips, and glued together ridge-to-ridge. This would make channels (like straws) perpendicular to the hepa filter.
Oh, well. At least some reference. I may setup small box with CPU fan, HEPA filter, and something which will serve as a laminar flow 'director' (don't know proper name for this part). I got inspiration by looking at this page:

http://www.aircleansystems.com/process_vertical.htm

Judging by picture, it is not longer than 20 cm. Perhaps no more than 10 cm, but unknown material and diameter of the openings.
I would think the longer the channels, the better, but of course space is limited. If you can make the channels any length, I would go for maybe 10 to 30 centimeters, depending on the size of the openings. If the openings are small (i.e., straws) probably 10cm would be good (I used short cocktail straws, not full size drinking straws). If you're using large openings like corrugated sheet (openings might be as much as 5cm), I would make the depth of the honeycomb as large as the table permits.
That is good starting point, or good reference point to start experimenting with that. If I build small box, cca. 10x10 cm, and say 20 cm long, just as a model for big structure, then I can carefully inspect amount of remaining dust with expanded laser beam (or other strong light).

Now, something come in my mind: my space is limited by surface on the desk, but I have some room vertically. Instead making horizontal flow, perhaps I can make vertical one, like on picture on the link above.

I found that this thing is very important, not only for film preparation, but also may be used for dealing with delicate optics, where all dust particles may stick to it and ruin it's properties - especially lasers.
Hopefully msxc will chime in.
Yes, that is very good 'timing'.

---

Best--
--
msxc
Posts: 30
Joined: Wed Jan 07, 2015 1:08 am

Newbie on DCG holography

Post by msxc »

Hello again!

I don't have lots of space in my lab/darkroom, so that was a real limiting factor in planning things (room much smaller than what Graham Saxby recommends for a holo-lab, maybe enough for SBRs :D).
From looking online I couldn't get a good idea for the details of good laminar flow bench (I asked about it here- thanks for all inputs! http://holoforum.org/forum/viewtopic.php?f=6&t=442).

During the trip to IKEA I stumped upon the box foe dirty laundry in which I could fit my hands, coating rod and some space for drying plates at the same time(so much easier than building things from wood, and also that is material easy to clean from gelo, dust and any other spillage that will happen inside). Used box is nice since it has a doors, and safe-light can be provided by shining laser through it from outside- light is nicely dispersed and even inside ;)
Kitchen fans are also in the same shop;-). I got one with 360l/h flow and lots of pressure to push air through any filters.

Now, from online search and pictures I got the impression that commercial hoods do use almost "bare" HEPA as the stream supply(or it looks like that). HEPA filters are shaped quite honeycom-ish, but why not to use extra stream straightening though.

Corrugated plastic that I found (online shop) is quite same looking as in the linked video. It is soft (no dust when handling) and easy to cut with sharp knife (box cutter). I've used too soft knife that bends when cutting so the edges are not to straight, but it is not a beauty contest;). I couldn't fit to long honeycomb without sacrificing too much of a working space so I used only 2.5cm strips.
Now to the operation. Flame test is not perfect, maybe because of not long channels, but with some tweaking (like putting small layer of pre-filter on the center of honeycomb grid to equalize flow) I can eliminate most of dust. By running the fan for some time before any works, and attacking the working area with powerful vacuum cleaner just before inserting anything it seams that dust is pretty much eliminated.
I don't have yet well established coating routine of working with the box, and I thing that this is as important as box itself. But I think that design is a good base for improvements;). Time will tel:)

Greatings,
msxc
MilanKarakas

Newbie on DCG holography

Post by MilanKarakas »

msxc wrote:Hello again!
Hello.
I don't have lots of space in my lab/darkroom, so that was a real limiting factor in planning things (room much smaller than what Graham Saxby recommends for a holo-lab, maybe enough for SBRs :D).
From looking online I couldn't get a good idea for the details of good laminar flow bench (I asked about it here- thanks for all inputs! http://holoforum.org/forum/viewtopic.php?f=6&t=442).
I build my improvised laminar flow hood in rush, and already spend too much time finding available materials. I made everything wrong!

Space in lab is one issue. I will consider make portable laminar flow hood, because this is mostly used during emulsion preparation, not needed later during exposure and processing holograms.

Aside that hood, will try to make at least two filtering units for cleaning air in my lab; 'Cottrell precipitator', and HEPA (or crude version) filter 'air cleaner'. First one is capable to remove dry/wet particles/droplets, by using of high voltage PSU, corona wire/needle and flat plates where particles/droplets collects. It working slowly compared to forced air and HEPA filter, but resulted air is very clean and free of nasty chemicals that may be present in air (oils, other vapors and odors, and everything else that may condense/precipitate on it's surfaces - even water and alcohol vapor if surfaces are sufficiently cold)

HEPA filter, or just crude filter may remove most of the rest of the particles. Actually, this filter should be used first.
During the trip to IKEA I stumped upon the box foe dirty laundry in which I could fit my hands, coating rod and some space for drying plates at the same time(so much easier than building things from wood, and also that is material easy to clean from gelo, dust and any other spillage that will happen inside). Used box is nice since it has a doors, and safe-light can be provided by shining laser through it from outside- light is nicely dispersed and even inside ;)
Kitchen fans are also in the same shop;-). I got one with 360l/h flow and lots of pressure to push air through any filters.
Good idea to use such box. Not sure I can find one, or afford it. Next few days will spend calling my friends, asking whether someone has some idea or box they do not need any more.
Now, from online search and pictures I got the impression that commercial hoods do use almost "bare" HEPA as the stream supply(or it looks like that). HEPA filters are shaped quite honeycom-ish, but why not to use extra stream straightening though.
Yes, they use bare HEPA filter, but different construction than mine. Mine is even NOT HEPA filter as I hoped - surgical masks are just good enough for it's purpose - to remove droplets, and crude dust particles. Googled around, and found this video about difference between surgical and respirator masks ("Surgical masks are NOT respirators").:

http://www.youtube.com/watch?v=ovSLAuY8ib8

And, here is wikipedia about HEPA filters, and possible explanation why they not use anything else but this filter (corrugated aluminum filter separator!):

http://en.wikipedia.org/wiki/HEPA

Other page has some words more:

http://www.macsa.asia/index.php?tpid=0034

"HEPA type or HEPA like filters may be made in similar ways to true HEPA filters and may even resemble them. They do not have to meet the same standards as true or absolute HEPA filters. They often capture only 85 to 90 percent of particles and that percent can fall even lower for particles of 1 micron and below. HEPA type filters are less expensive than true or absolute HEPA filters.

Telling the Difference
Look for the serial number and test results printed on true or absolute HEPA filters. Make sure that the test results at .3 microns are 99.97 percent or above. The size of .3 microns is the testing standard, because most filters will perform better with both smaller and larger particles. Double-check the test results at .3 microns to make sure your filter is a true or absolute HEPA. "

Today found one company in my country (Croatia) which are supplier of various kind of filters:

http://translate.google.hr/translate?sl ... %26id%3D67

Called this company, and guy who talking with me laughing a lot when I mentioned my attempt to make filter with surgical masks. But, after nice conversation, he said that maybe they have some filters that does not pass strict quality tests, and maybe they will give me one for free.

The most interesting concept of laminar flow filter is shown here (only small picture):

Image

Not sure small metallic part serve as for air flow shaping, or not. The name of this product is "AstroCel TM Hood".

Another picture showing different approach:

Image

Name: "AstroCel TM RSC"

All in all, this made it clear to me that I had wrong approach to my construction.

My construction on the flickr picture should be recorded in history of 'hall of shame' :D

http://www.flickr.com/photos/milan_kara ... otostream/
Corrugated plastic that I found (online shop) is quite same looking as in the linked video. It is soft (no dust when handling) and easy to cut with sharp knife (box cutter). I've used too soft knife that bends when cutting so the edges are not to straight, but it is not a beauty contest;). I couldn't fit to long honeycomb without sacrificing too much of a working space so I used only 2.5cm strips.
Now to the operation. Flame test is not perfect, maybe because of not long channels, but with some tweaking (like putting small layer of pre-filter on the center of honeycomb grid to equalize flow) I can eliminate most of dust. By running the fan for some time before any works, and attacking the working area with powerful vacuum cleaner just before inserting anything it seams that dust is pretty much eliminated.
I don't have yet well established coating routine of working with the box, and I thing that this is as important as box itself. But I think that design is a good base for improvements;). Time will tel:)
Here I have two options; if firm mentioned above provide me something, then I need to built only box and attach fan. If not, then I will consider using different filter (cutting surgical mask, gluing it on wooden frame, and bad result afterward is not fun). Not sure what will appear. As msxc said: Time will tell.
Greatings,
msxc
Greetings,
m--
msxc
Posts: 30
Joined: Wed Jan 07, 2015 1:08 am

Newbie on DCG holography

Post by msxc »

Beauty of DIY- every problem can be solved in infinite number of ways:) :D
It would be nice to see more of DIY holographers made solutions in this forum

msxc
MilanKarakas

Newbie on DCG holography

Post by MilanKarakas »

msxc wrote:Beauty of DIY- every problem can be solved in infinite number of ways:) :D
Yes, and it take infinite time too. :(

Today tried to find some DIY polarizer (or anything I already have here), and found one diffraction grating in perfect condition. After some time, it fell to floor - twice, and two corners cracked. And that is not all... surface is now contaminated. Not fun. Someone gifted me that many years ago, and I saved it until now, and screwed up this part in few minutes. I am so unhappy.

Since it can't make 'exclusion' of unwanted part of the bad polarization, decided to see something else. One thing become strange: instead one spot - got two spots. My first thought is that this grating is bad one, but it is not. My laser has two frequencies, closely spaced (later discovered third one, pretty weak, but it is there). All that additional frequencies come to play when module temperature reaches 27C or more. Later tried freeze ceramic tile, and make small fridge around laser. Temperature was 15C, and no stray frequencies up to 26C or more.

Only bad thing is that at low temperature KTP crystal has low efficiency. Moved module from heatsink little bit, and got frequency stability and good doubling efficiency.

Then tried BGO crystal. I have few intended for scintillator for detecting gamma rays. Eight is enough to cover one PMT and I have 10, so two are spare crystals. Both surfaces are pretty good polished, and I need only one.

Found one very useful page with online calculator for various materials:

http://refractiveindex.info/?group=CRYS ... =Bi12GeO20

(not sure mine is this type or lighter one)

If I have heavier one, then refractive index is better than that of diamond (BGO: 2.61657 @ 532 nm). At Brewster angle, reflecting 'good' polarization up to 55.5%, while the rest is lost inside crystal (too long crystal, only two faces polished). Tried to put glass plate on diverged beam after this crystal serving as a polarizer, and unwanted reflected fringes are just barely observable, while illuminating power is estimated to be about 50% of ~40 mW from my DPSS module (I wish to have real polarizing beamsplitter cube, but.. eh...). Now, it look like real stuff, except end power may be very low (after addition of spatial filter/pinhole, stirring mirrors,...) maybe 15 mW or so will remain.

I wish I have money and buy decent 532 nm laser, ranging from 50 - 100 mW. Seems that making DIY laser diode laser is easier than messing with DPSS module.

But, at least I learned something about Nd:YVO4 and KTP crystals. It will be good to have separate mirrors, crystals and made setup with good polarizer intracavity - that way nothing will be lost, clean beam will be amplified and 'exported' out through OC mirror/IR filter.

My last finding about laserpointers without glued IR filters make me wonder whether it is possible to place some 1064 nm mirror in front of the laser and by placing polarizing element there, maybe will get some feedback and made it more stable + better polarization ratio.... Don't know (maybe will sacrifice one pointer). :D
It would be nice to see more of DIY holographers made solutions in this forum
I hope so. At least new people.
msxc
Best--
m--
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