HeCd Omnichrome Laser with Controller

joryman · Post by **joryman** » Sun Mar 27, 2011 7:32 pm

I have a nearly new (32 hours on the meter) Melles Griot Omnichrome 56 Series, 442nm, HeCd laser and controller for sale. It was being used by a major projector manufacturer for laser projection research. That research was abandoned, hence the 32 hours on the head. This system sold new for something like $12K (USD). This is an excellent system being offered at a very attractive price. I want to give hobbyists first crack at this system. If it hasn't sold in a week or two I will list it on other sites. I can supply photos. Let me know what you'd like to see. Here are the specifics:

Laser Head:
Manufacturer: Melles Griot
Date of Manufacturer: May 2000
Model: Omnichrome 56 Series
Model Number: 4056-S-A01
Lasing Medium: HeCd
Serial Number: H3257
Output Power: 17.5mW (label), 15mW (specification), 10.5mW (warranty)
Mode: TEM00
Wavelength: 442nm
Beam Diameter: 0.32mm
Beam Divergence: 2.1mrad
M^2: 1.2
RMS Noise (DC-2MHz): 2%
Hours: 32
Weight: 24 lbs (10.9 kg)
Shipping Weight 30 lbs (including LV and HV cables) (13.6 kg)
Condition: Like new, in the original shipping box with foam surround. Not a scratch on it.

Controller:
Manufacturer: Melles Griot
Model: Ominichrome
Model Number: LC-500
Input Power: Switchable 90 - 130 VAC or 190 -250 VAC
Line Frequency: 47- 63 Hz
Operating Temperature: +5°C to +40°C
Regulatory Compliance: cTUVus, CE, CDRH, and IEC
Remote Interface: EIA-232 (aka "RS-232"), Cable and software not supplied
Date of Manufacturer: July 27, 1999
Serial Number: 1263
Weight: 22lb (10.2 kg)
Shipping Weight: 26lb (11.8 kg)
Condition: Excellent. One small (~10mm) scratch on the side. A few rub marks, mostly on the sides. Not in the original packaging

Accessories:
LV Interconnect Cable
HV Interconnect Cable
Standard IEC320 Power Cord (North American only)
No manual
No EIA-232 Cable
No remote control software

Price:
$2,990 (USD) plus shipping from Portland, Oregon USA, preferably by Fedex or UPS ground. Shipping and insurance (required) at buyers expense. Payment via PayPal preferred. Contact me for international shipping terms.

Contact:
joryman via PM from this forum
Phone: +1.503.869.5815

142laser · Post by **142laser** » Mon Mar 28, 2011 7:32 am

Hello everyone,
This is a fair deal and the laser is a high quality product. However these lasers have a very short (maybe 1 cm) coherence length and are not in general any good for holography. Best, Phil, 142laser

joryman · Post by **joryman** » Mon Mar 28, 2011 11:58 am

Hi Phil and Everybody,

According to the Melles Griot datasheet, the 56 series Omniichrome lasers have a typical coherence length of 10cm. The main target market for the Omnichrome HeCd lasers is holography. I can can mail the Melles Griot datasheet to anybody that is interested.

Do you have specific experience with the 56 series Omnichrome? I haven't measured the coherence length of this specific laser, but according to Melles Griot it should have a coherence length of 10cm or so, which should be good enough for 10cm x 10cm holograms. The output power of 17.5mW is more of a concern to me than the coherence length. However, the output power issue is mitigated by the fact that photo-resist is very sensitive at 442nm.

I can supply the datasheet from Melles Griot to anybody that is interested.

Joe Farina · Post by **Joe Farina** » Mon Mar 28, 2011 12:11 pm

Jeffrey Weil is a user of HeCd for holography, hopefully he will chime in.

I haven't used one, but my understanding is that a typical HeCd has a coherence length of around 10cm, and isotopic-enriched HeCd is about 30cm.

142laser · Post by **142laser** » Tue Mar 29, 2011 9:05 am

I stand corrected; I remembered wrong for sure. 10 cm is not much but with care one can get the path length's about equal abd the TEM 00 beam from a HeHd should make nice small holograms.

joryman · Post by **joryman** » Mon Apr 18, 2011 2:13 pm

I have finally been able to get a copy of the original Melles Griot user manual for this HdCd laser. It's in PDF format. Let me know if you're interested in seeing it.

I'm also open to offers.

142laser · Post by **142laser** » Tue Apr 19, 2011 10:29 am

It is a shame the laser is not higher power as the short wavelength is good. One can buy Coherent Sapphire 488-20 lasers used for $1K-$2K now and most of these are 22 mW and SLM. See my ads posted here for them.

Phil

Jeffrey Weil · Post by **Jeffrey Weil** » Wed Apr 20, 2011 4:01 pm

Joe Farina wrote:Jeffrey Weil is a user of HeCd for holography, hopefully he will chime in.

I haven't used one, but my understanding is that a typical HeCd has a coherence length of around 10cm, and isotopic-enriched HeCd is about 30cm.

Hello Joe,

The isotopic He/Cd has about 15 cm of usable coherence. The biggest holo your going to make is about 6 inches square. And that would be difficult even with 200mw. 200mw is the most you can get in that freq with good beam quality and enough coherence.

17mw is nothing. Resist might be more sensitive at 441.6 than other laser freq's we use but it is not "sensitive" at all. If you were to do a split beam transmission that was 1 inch square your exposures could be up to 15 minutes on the transfer using 17mw. Of course there are many many variables not listed here but that would be a pretty typical exposure time.

You also have to take into account were talking about resist for embossing. If your just making a master on resist, and your going to show it that way, you can get away with less exposure. Most holograms are close ended, you make the holo and that's that. If it's a bit dimmer in the corners it's not a big deal. For embossing the master is only the start. Lots of other processes to do. If you have that same dim corner, it won't emboss at all. Now you don't have a dim corner, you have nothing.

So, you have to really spread out the ref beam and other things that wastes lots of light. If your shooting only resist and not going further to emboss you might get your exposure times down to a few minutes. Still a long time for a one inch holo. And here's the real problem, 17mw might not be enough to even start the reaction if your shooting split beam work.

17mw would only be useful for small diffraction gratings. No h1's or diffuse objects. Just two expanded beams hitting the plate.

Jeff Weil

Jeffrey Weil · Post by **Jeffrey Weil** » Wed Apr 20, 2011 8:09 pm

I should have mentioned it's not too bad a choice for doing some full color silver. It's a good price and you should get about 5000 hours out of the tube. Hard to say as I don't know that particular laser but that's a common number for a He/Cd, maybe more as it's a small one. Nothing else at this price will be as deep a violet and have as nice a beam profile.

For 4x5's it might be pretty good. I bet silver is pretty fast at that frequency.

And, if your in a pinch and are willing to slow things down it would be a so-so emergency replacement for a larger He-Cd or other laser in a dot matrix machine.

Jeff

Martin · Post by **Martin** » Thu Apr 21, 2011 12:46 am

Jeffrey Weil wrote:So, you have to really spread out the ref beam and other things that wastes lots of light. If your shooting only resist and not going further to emboss you might get your exposure times down to a few minutes. Still a long time for a one inch holo. And here's the real problem, 17mw might not be enough to even start the reaction if your shooting split beam work. Jeff Weil

Couldn't you make a master on AgX and contact copy it into resist?