Hologram Equipment basics

Starting point for beginners questions.
Julian
Posts: 6
Joined: Thu Jan 15, 2015 5:31 pm

Hologram Equipment basics

Post by Julian » Fri Dec 27, 2019 8:23 am

Dear All, I am planning to build a new holography Lab/ Studio after a 35 year break. I am struggling to find suppliers for certain bits of equipment. This is because the books that I am reading are very out of date.I have have posted several posts in The Facebook Forum but only receive one or two answers to my questions,

I am trying to price out a new lab/studio and cannot find suppliers for certain equipment, such as 12” Collimating mirrors, photo meters, laser shutters etc.

Please can you recommend a suitable light meter for holography. I will probably use a Coherent 532 200 milliwatt laser and be making 10 x 8” plates or larger.

jrburns47
Posts: 88
Joined: Mon Sep 14, 2015 2:48 pm
Location: Oyster Bay, NY

Re: Hologram Equipment basics

Post by jrburns47 » Fri Dec 27, 2019 9:24 am

There are a lot of used meters on eBay for very good prices. Depends on your budget. I used a Newport 820 for decades with an argon up to about 500mw. Make sure you get an AC powered version and not the battery version - the batteries aren’t made anymore. You’ll need a detector head - the basic old Newport detector is/was an 818SL. You may want to get the OD1 filter for it for higher power. These aren’t intended for use with an undiverged beam. The model 840 is a nice smaller unit - they use a rechargeable battery but can also be used with the charger if the battery is defunct. There have been some nice deals on 2832-c and 2835-c units recently. I would stay away from the otherwise nice 1815-c because it uses four AA batteries unless you’re prepared to be diligent about battery removal when you’re going to not use it for a few weeks. Battery leakage will ruin them. Suggest getting your hands on an old Newport catalog for useful comparison charts of meters and detector heads. Be careful that detector connectors are correct for the particular meter that you’re using since some meters, like the 1835-c have different connector options when originally purchased and eBay resellers often don’t know the difference- unless you know what you’re looking at, it can be easy to get stuck with a “door stop”. There are of course many other good brands of meters & detectors and you can make your own dirt cheap from an appropriate photovoltaic sensor and multimeter.

holomaker
Posts: 738
Joined: Wed Jan 07, 2015 8:01 am

Re: Hologram Equipment basics

Post by holomaker » Fri Dec 27, 2019 9:58 am

Get one of these off eBay ($50)simple analog power meter , usually minus sensor, then get a Photovoltaic cell and a short focus lens onto the front , depending on your needs It can be calibrated by a local college or w any known laser output source, this meter can be now used w any visible laser source ! I have many of these photo cells if any one wants one pm me ...and I have the wavelength conversion chart .. and as Jody’s recommendation neutral density filter for higher powers than 100mW
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Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

Re: Hologram Equipment basics

Post by Joe Farina » Fri Dec 27, 2019 10:42 am

For measuring relative intensities only, there are some inexpensive choices. One old standby is to use a cheap cadmium sulfide photocell hooked up to an analog multimeter (the kind with a needle rather than a digital display). The sensitivity ranges on the meter can be changed depending on the intensity of light being measured. Another option is to use a wide-area silicon photo cell (the kind used for solar-powered devices), again hooked to an analog multimeter. With a silicon cell, I've measured the current directly on the meter, without fear of blowing the fuse, because the current generated was very small. Measuring a wide area can be helpful for spread-out beams of laser light. Both cadmium sulfide and silicon cells have a wide range of sensitivity in the visible spectrum, and both are cheap on eBay and elsewhere.

For measuring laser power, things get a bit more complicated when different wavelengths and power levels are involved. I've used a Coherent LaserCheck, which is convenient, but I haven't checked prices lately. One downside to the LaserCheck is that it has a non-replaceable battery, and my battery is low. I've been using it for about 20 years.

I've been looking at these power meters from China, has anyone tried one?:

https://www.ebay.com/itm/Pocket-mini-La ... SwuU9dKFA4

Steven
Posts: 37
Joined: Sat Jan 31, 2015 8:14 pm
Location: Cornwall, UK

Re: Hologram Equipment basics

Post by Steven » Thu Jan 02, 2020 12:28 am

As for a collimating mirror, why not use a parabolic mirror designed for a telescope?
I was told by an holographer many years ago that a spherical mirror was more suitable for holography, as they are often used off-axis.
Maybe an optical expert can interject here?

I only measured the power of my unexpanded laser beam once, just to confirm the laser's performance.
Now I only measure the power density of the expanded beam hitting the plate.
I used this info into make my own:
http://redlum.xohp.pagesperso-orange.fr ... meter.html

For a shutter, I use a modified moving coil meter and a remote electronic timer.
The electronic timer is an off the shelf unit designed for camera use.
Some use parts from a failed hard drive with a small mirror attached as a shutter and dump the beam to a heatsink.

YMMV, but unless you are considering advanced techniques like real image plain holograms, you shouldn't need a collimating mirror.
I'm just using single beam Denisyuk for display holograms.
I don't need the beam collimated, or an expensive optical table and heavy scaffolding to hold optical components.
I'm using a Coherent Compass and a short FL concave mirror as my beam expander.
The beam path from the concave mirror to the 5"x7" plate is about 3.8 metres, so it's not too divergent,
but expanded enough to give an even exposure across most of the plate.

My honest advice would be to leave the collimating mirror off your shopping list until you have a definite need for it.

Steven.
Success through failure - the amateur DCG holographer's path to enlightenment.

holomaker
Posts: 738
Joined: Wed Jan 07, 2015 8:01 am

Re: Hologram Equipment basics

Post by holomaker » Thu Jan 02, 2020 9:10 am

Yes good words above ! a 12x12” first surface Mirror and a good long throw to the beam,(folded) and Image plane configurations can be done!( with a bit of distortion of coarse!) 👁 👁 (

And” where does one get a large front surface mirror from” you may ask , keep an eye out for the rear projection TV set. You have seen them Being thrown out many times. The back may be lined with a front surface mirror.Throw some pliers and a screwdriver in your car next time you see one ....

BobH
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Joined: Tue Jan 06, 2015 10:26 pm
Location: Mesa, AZ

Re: Hologram Equipment basics

Post by BobH » Sat Jan 04, 2020 10:11 am

Spherical mirrors suffer just as much as parabolic mirrors when the input beam is tilted off axis. The parabolic mirror gives a collimated output, while the spherical mirror will never do that. Always use parabolic (telescope) mirrors. Be careful to not get one that has a center spot permanently etched in the middle of it!

When recording a "master" hologram for use to make another hologram, it's acceptable to use such a mirror off axis IF the same mirror is used to play it back and it's used at the same off-axis angle to give the hologram's conjugate (real) image. The astigmatism and coma will be "cancelled out" in that case, and the image will not be distorted.

For the reference beam of the transfer hologram, a spherical mirror may be used to give a converging beam, converging to the location of the intended illumination source. That mirror will need to be big however, to give proper clearances. Many holographers have just used diverging light for the transfer reference, and you can certainly see their imagery swing and distort as the viewer moves around in front of the hologram. Unmatched conjugate illumination is not the path to success for making images you want to look real. If you want them to swing and distort, no problem.

holomaker
Posts: 738
Joined: Wed Jan 07, 2015 8:01 am

Re: Hologram Equipment basics

Post by holomaker » Sat Jan 04, 2020 10:39 am

If u can make it as a one beam , using a long throw will reduce the swing greatly... possibly can get 6” used parabolic cheaply, otherwise invest in the laser and save for a good 12”+ parabolic....

Special images international, 1979? Mort Segal made all his rainbow transfers without using any collimating, he would push the projections , looked more magical then real backin the day ...

BobH
Posts: 377
Joined: Tue Jan 06, 2015 10:26 pm
Location: Mesa, AZ

Re: Hologram Equipment basics

Post by BobH » Sat Jan 04, 2020 10:59 am

You're right Dave. One CAN make the hologram with any divergence in the reference, and an image WILL play back with the unmatched conjugate, but whether the distortions and swing are acceptable depends on whether you want to sell it or not. If you're Rudy Berkhout, you work with those issues and can make something beautiful. If you want integrity, and a believable reproduction of the object recorded, the swing and distortions accepted historically don't cut it (and I'm guilty of it too). This is one of the reasons holography isn't to be seen anywhere (essentially).

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