Kinds of Laser Pointer pen

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Jeffrey Weil

Kinds of Laser Pointer pen

Post by Jeffrey Weil »

Hello Everyone,

Forget about using these for lighting up display holo's unless your willing to rebuild them a little bit. They have very short duty cycles. Not enough heat sinking and most of them don't use any kind of coolers. Burn one for 10 min solid and you'll probably burn it out. They really should be lit up for less than 30 sec at a time.

Jeff Weil
NorthBeach Holography Inc.
Colin Kaminski

Kinds of Laser Pointer pen

Post by Colin Kaminski »

Thank you Jeff. I had a green pointer that would drift out of calibration every 5 minutes. I think the heat would change diode and make it out of range for the doubling crystal.
Jeffrey Weil

Kinds of Laser Pointer pen

Post by Jeffrey Weil »

Colin Kaminski wrote:Thank you Jeff. I had a green pointer that would drift out of calibration every 5 minutes. I think the heat would change diode and make it out of range for the doubling crystal.
Hello Colin,

Here's something you might be interested in. I just bought a thermopile meter for 300 bucks. New surplus. More are available.

In case some of you don't know what a thermopile meter is I'll explain. Most of our meters have a silicon detector or something like that. Perfect for expanded and diffuse beams but if you put a laser of any real power into it the sensor would be burnt out. Also they are small sensors, It's usually impossible to get the entire raw beam into the active area. The disk on this thermopile is 1/2 inch large. More than enough to get any holography laser into the sensor area.

A thermopile is a bunch of thermocouples in series. A thermocouple is two different metals connected, when heat is applied to that junction a voltage is produced. Thermoelectric power. When you shine a laser on the sensor disk in the thermopile it makes a voltage relative to the heat the laser is producing. It compares the target disk to the outside housing. The temp difference between the two is heat produced by the laser.

A decent thermopile is a lot of cash, the standard is the Coherent model. The sensor is 950 bucks plus the meter. There's another company called Ophir that also makes them. New they are 650 bucks, for only the sensor.

The nice thing about a thermopile is it's a broadband device, no conversions to read different wavelengths and it can handle watts of power. Pretty much any non pulsed laser we use for holography can be read with this without error, math or wavelength selector knobs.

The ophir head puts out 1 millivolt for every milliwatt of laser energy put into it. So all you really need to use it is a volt meter and a power supply to run it. If you get just a thermopile from somewhere like ebay you'll need a split power supply to run it. This Ophir model uses +12 and -12 volts dc. The finished meter I got has a dc to dc converter inside so all you need is the wall wart they supply with it.

Some of the ophir heads were put on the surplus market, new units. They were all bought up by a few people producing meters and selling them on forums.

I got this one

http://laserpointerforums.com/f64/new-5 ... 50226.html

Here's a review of it

http://laserpointerforums.com/f52/lpm-o ... 50064.html

and here's my youtube video of mine with a 5mw red and a 150mw green.

http://www.youtube.com/watch?v=5euXRzzwmXs

The accuracy of this kind of meter is not in the display, it's the sensor itself. It contains a low noise op amp and the circuity to make this work. The display is just an off the shelf volt meter module in a box, so don't worry about the homemade style of this meter. It should be as accurate as any 1500 dollar meter you can buy.

Jeff Weil
NorthBeach Holography Inc.
Colin Kaminski

Kinds of Laser Pointer pen

Post by Colin Kaminski »

Thank you Jeff!

I hope you don't mind that I added it to the wiki:

http://www.holowiki.com/index.php/Light ... hermopiles
Jeffrey Weil

Kinds of Laser Pointer pen

Post by Jeffrey Weil »

Colin Kaminski wrote:Thank you Jeff!

I hope you don't mind that I added it to the wiki:

http://www.holowiki.com/index.php/Light ... hermopiles
Sure, no problem.

There's a few other meters that use these surplus thermopiles. Some even do data logging. I'll send you some links later. I just woke up from doing a laser show until 5am last night! Dress rehearsal is tonight and then the big show tomorrow.

It's a big latin music award show with Shakira and Julio Iglesias Jr. If you see it on television, that's me needing some sleep!

Jeff Weil
NorthBeach Holography Inc.
Jeffrey Weil

Kinds of Laser Pointer pen

Post by Jeffrey Weil »

Hello Everyone,

Here's the links to other meters being sold on forums.

http://laserpointerforums.com/f64/annou ... 47620.html

Thats the kenometer. It uses the nice Ophir thermopile sensor and has a pretty display and data logging. The build quality could be better.

http://laserpointerforums.com/f64/usb-l ... 43922.html

That is the Laserbee. Nice build quality with surface mount components but a home made thermopile like device. It's really a thermo cooler run in reverse mounted to a heat sink. It's still accurate though according to the reviews I've read.

Jeff Weil
NorthBeach Holography Inc.
Joe Farina

Kinds of Laser Pointer pen

Post by Joe Farina »

I did a test with that "10mW" pointer by attaching it to a 3.3 volt AC/DC wall-plug (switching) transformer. I ran it for about 200 minutes before stopping the test. The attached graph shows the results, using a lasercheck.
Attachments
10mWpointer.gif
10mWpointer.gif (5.37 KiB) Viewed 9411 times
Joe Farina

Kinds of Laser Pointer pen

Post by Joe Farina »

Ooops, I should have said the test was done for 100 minutes, not 200, even though I wrote 200 on the graph.
Joe Farina

Kinds of Laser Pointer pen

Post by Joe Farina »

rzeheb wrote:I wonder how much of that 188 mw was really IR?
Upon further testing, maybe a lot.

I kept wondering why I was getting odd readings, since they were too high for the amount of 532nm light I was seeing. Also, since I was mixing the output with a 5mW Hene, the "5mW" from the green pointer wouldn't even come close to the expected yellow color for the mixture of 532 and 633. It took more like "35mW" to get a decent yellow, and even that seemed too red.

So I posted the above infomation too soon, please disregard it. I would like to find a filter that blocks ~808 and ~1064, but lets the 532 through.

I would write more, but my eyes are sore, I think I got a stray reflection from the pointer :doh:
Jeffrey Weil

Kinds of Laser Pointer pen

Post by Jeffrey Weil »

Hello Joe,

This idea isn't as good as your filter for getting a reading but close. Do you have a narrowband mirror for that freq? It would reflect the green but not the ir. You would have some loss in the green too but only a few percentage points. It would at least let you know about how much ir you have.

Jeff Weil
NorthBeach Holography Inc.
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