Laserbee or ?

[norty303]

James, based on a comparison with a calibrated coherent meter (I believe it was) the laserbee records high in the 0 to 20mW range, so actual power is less than what is displayed. It's in an old thread on here, it may have been Doc.

[edison]

I've got a 3.2W Laserbee deluxe and its been fine for me so far.
If it gets to the point where I can't measure a single module on it, I'll be in a different sort of business arena anyway, and so a new power meter will simply be one of those 'things' you gotta have.

I,m in that bussiness arena But your right for most purposes the laserbee is great. I just wish it could do 10 watt and a bigger display in a slightly modern case if i would buy another one,

[norty303]

Turns out my long term memory is awesome

See graph near bottom if thread

http://www.photonlexicon.com/forums/...ee+calibration

Interesting debate actually about what is/is not required to measure shows.

[Robin]

I got an Ophir OEM thermal head a few years back and have been really happy with its performance. They're extremely easy to get up and running and do a reasonable job measuring laser output power. As far as determining what the numbers on an Ophir OEM head mean, the Ophir OEM sensor catalogue states:

"Head is defined by head type - sensitivity - calibration wavelength
For example: 150W-A-1-C means type 150W-A, sensitivity 1V/W, calibration for CO2"

The head you're interested in is probably anything between a 20C to 150C (the "W" in the example above means the head is water cooled, while "C" means conduction cooled). While these heads are usually calibrated for specific wavelengths, they are capable of measuring wavelengths from .19 to 10.6μm (although you'll want to consult the head's documentation in the unlikely event you end up measuring really short wavelengths well below those we use in projectors for info on derating). I use a 150C-A-.1-AX which, according to the documentation, is capable of measuring up to 5W free standing or 60W if heat sinked. Their smaller OEM thermal head, the 20C-A, is capable of measuring 4W free standing or 20W if heat sinked. Another tip is to look for a head with an "A" after the first dash. This indicates it has a built in amplifier which allows you to hook it up to a DC PSU and a multimeter and start measuring beams.

Handy Ophir instructions are handy:

http://www.photonlexicon.com/wiki/in...r_Instructions

Also, this article on measuring laser energy is very informative (thanks James Stewart):

http://www.ophiropt.com/laser-measur.../tutorial/bc20

[edison]

Time to get mine heatsinked then

[steviobee]

So there is this one:
http://www.ebay.co.uk/itm/Ophir-OEM-...item337f093e02

But seems a lot of money. Perhaps more use for someone with higher power lasers to test?

Here is the list of some Ophir models: http://www.ophiropt.com/laser-measur...-power-sensors

I got an Ophir OEM thermal head a few years back and have been really happy with its performance. They're extremely easy to get up and running and do a reasonable job measuring laser output power. As far as determining what the numbers on an Ophir OEM head mean, the Ophir OEM sensor catalogue states:

"Head is defined by head type - sensitivity - calibration wavelength
For example: 150W-A-1-C means type 150W-A, sensitivity 1V/W, calibration for CO2"

The head you're interested in is probably anything between a 20C to 150C (the "W" in the example above means the head is water cooled, while "C" means conduction cooled). While these heads are usually calibrated for specific wavelengths, they are capable of measuring wavelengths from .19 to 10.6μm (although you'll want to consult the head's documentation in the uniquely event you end up measuring really short wavelengths well below those we use in projectors for info on derating). I use a 150C-A-.1-AX which, according to the documentation, is capable of measuring up to 5W free standing or 60W if heat sinked. Their smaller OEM thermal head, the 20C-A, is capable of measuring 4W free standing or 20W if heat sinked. Another tip is to look for a head with an "A" after the first dash. This indicates it has a built in amplifier which allows you to hook it up to a DC PSU and a multimeter and start measuring beams.

Handy Ophir instructions are handy:

http://www.photonlexicon.com/wiki/in...r_Instructions

Also, this article on measuring laser energy is very informative (thanks James Stewart):

http://www.ophiropt.com/laser-measur.../tutorial/bc20

[JStewart]

Adam, thanks for pointing out that old thread which has some useful bits of information in it, (keeping all the bitchin’ aside!).

One of these Laserbee devices might almost be ok to use for measuring irradiances in the ‘safe’ regions, especially for galvanometer audience scanning applications where you could be looking at 10mW/cm^2, which is the same as 6.4mW/ Laserbee detector size.

I think it will be a bit of a struggle with irradiances much lower though.

The Coherent Lasercheck can easily cope with measuring values that are in the tens of uW/cm^2, which makes that meter more suitable for measuring low irradiance levels such as from diffraction gratings and scanning beams. The downside though is that the meter has to measure each wavelength in the beam seperately.

I asked Laserbee’s maker what the response time was to changes in irradiance that are in the mW/cm^2 region, so I could try and get a reasonable idea about how effective it was at locating hot spots - i.e. are we looking at a 1s time to react?, or 5s+ to stabilise. I don’t think Jerry understood the question as he replied as follows:

Hi James,
unfortunately for your requirements our LaserBee LPM products use a Thermopile sensor that was designed for CW Laser testing and can't really be used for MPE measurements due to the Thermopile's slower response time than an optical sensor. An LPM with an optical sensor can read the very fast scanned outputs of a Laser Projector much quicker and would be a better choice.

regards,
Jerry Bauer Pres.
J.BAUER Electronics

Looks like the lowest cost option still is the Lasecheck, unless you want to make an amplifier for a photodiode and then perform a calibration.

James

[norty303]

Hi James

I've been using my Laserbee in exactly the fashion you described. I came to the conclusion that as long as the Laserbee was showing under 8mW, I was ok (this took into account the high reading and gives a little more 'range' to play with).
I found that I needed to fix the head to an adjustable pole placed on the floor in order to keep it in the beam position long enough (like those photographers telescopic poles), but it didn't take more than a couple of seconds to respond to the hot spot, and the peak hold function was very useful whilst I concentrated on looking for the bright spot on the sensor!

Incidentally, I should point out that for any 'normal' size gig (clubs, small/medium festival stages, etc) where scanning the audience is going to happen at 15 or 20 metres or so from the projector, unless you are using additional equipment like a divergent lens, you are NOT going to get down to MPE in a worthwhile manner. So unless you are also going to spend money of those extra bits, save your cash on the meter and simply don't crowd scan.

E.g. using the highest power (-6 diopter) SafetyScan lens, I managed to get 800mW of 532nm down to 7.1mW on the Laserbee at 15m, with a BAM set at 70% (although the modulation is not linear, the actual power taken off was probably only about 10%). Without the lens I couldn't see the beam hardly at the point it was reading safe.

Given how few people seem to be aware of, or even taking power measurements, I'd be happy if people were actually checking their irradiance, and getting somewhere near MPE. Splitting hairs over the fine detail of measurements is something to do once everyone is actually taking them (is my, probably contentious, opinion...)

Oh yeah, and don't forget the scanfail...

[JStewart]

I agree absolutely Adam!

[Robin]

So there is this one:
http://www.ebay.co.uk/itm/Ophir-OEM-...item337f093e02

You should check the documentation to be certain, but I'm fairly certain the "UA" indicates that head has a built in amplifier and uses a usb connector (most likely designed to mate with one of Ophir's USB meters).

On of the things I've noticed about my 150C-A-.1-AX when I measure higher output powers is that the read out takes a little over five seconds to hit peak, and then it settles down gradually before becoming stable. The stable reading is always lower than what I see at the meter's peak.

Incidentally, I should point out that for any 'normal' size gig (clubs, small/medium festival stages, etc) where scanning the audience is going to happen at 15 or 20 metres or so from the projector, unless you are using additional equipment like a divergent lens, you are NOT going to get down to MPE in a worthwhile manner. So unless you are also going to spend money of those extra bits, save your cash on the meter and simply don't crowd scan.

Wise words.