Necessary for a laser store to have a LPM?

[Toke]

I would imagine the administrative problems would be bigger than the purely practical ones.

The metering would require a LPM, goggles, an stack of batteries, and an IR filter. (right?)

Having the tester put a sticker* on the box of each laser is just the first step, getting from there to having the tested lasers appearing on the website require a decision of whether they need a article number (SKU) each or can be grouped into ranges.

*the sticker should read "total output" and "IR filtered output"

 

[lasersbee]

I would imagine the administrative problems would be bigger than the purely practical ones.

The metering would require a LPM, goggles, an stack of batteries, and an IR filter. (right?)

Having the tester put a sticker* on the box of each laser is just the first step, getting from there to having the tested lasers appearing on the website require a decision of whether they need a article number (SKU) each or can be grouped into ranges.

*the sticker should read "total output" and "IR filtered output"

Yeah... your right... it is just too much trouble...:undecided:

Lets just believe what most of the sellers are telling us so we can
complain about the lousy underspec Lasers we receive on the Forum...

Yeah.... that makes more sense....

Jerry

 

[John7788]

(There seems to be something wrong with the reply system, I just replied, but now my words have disappeared. )

Thanks for all you suggestions and explanation, which are essential to me. After reading all your replys carefully again and again, I have known much more about IR and LPM.
Just receive a helpful PM from jerry, I will consider your idea. Jerry, We have been friends for long, so forget my joke in my PM!
But now still wondering what makes a good LPM? Some more knowledge about LPM will be appreciated. Will different lasers need different IR? For example, will a IR for 532nm do well in a 650nm laser's test ? And it will be perfect, if some information about the price is given

 

[Toke]

Yeah... your right... it is just too much trouble...:undecided:

Lets just believe what most of the sellers are telling us so we can
complain about the lousy underspec Lasers we receive on the Forum...

Yeah.... that makes more sense....

Jerry

I am trying to point out that the metering is the easy part. :scowl:

To me getting the lasers categorised, numbered and added to the webpage with correct inventory tracking would be a bigger headache.

Of course it could be done by simply binning them in 50mW+ 100mW+ and 150mW+ categories. The buyer would pay for and get one from the e. g. 50mW+ bin with a sticker on the box saying e.g. "111mW total" "76 mW 532".

I am not sure if the level of overspec from such simple categorising is a good deal for the seller.

 

[John7788]

I am trying to point out that the metering is the easy part. :scowl:

To me getting the lasers categorised, numbered and added to the webpage with correct inventory tracking would be a bigger headache.

Of course it could be done by simply binning them in 50mW+ 100mW+ and 150mW+ categories. The buyer would pay for and get one from the e. g. 50mW+ bin with a sticker on the box saying e.g. "111mW total" "76 mW 532".

I am not sure if the level of overspec from such simple categorising is a good deal for the seller.

Yes, you are right, there will be all kinds of problems. But in my view, there is a solution for each problem. I'm going to find the best solutions

 

[Toke]

Yes, you are right, there will be all kinds of problems. But in my view, there is a solution for each problem. I'm going to find the best solutions

Thank you,
I find that considering the problems in advance is a great help to avoid/solving them in advance.

 

[Tech_Junkie]

Here is why we always recommend O-Like when people ask where to buy a good laser.

http://laserpointerforums.com/f50/o-like-red-ir-test-results-56537.html

Susie tests all their lasers, and sends the underspec units back to the manufacturer.

 

[John7788]

I'd like to check their website, they seem to be really honest company.

By the way, I remember I started a poll to find out what is the most important factor for a laser. According to the results, ( What do you concerned most about lasers?) the output is not the factor which customers care most. The price and quality seem to gain the most votes

But after reading hundreds of threads, I find the most important thing seems to be output. There seems to be some conflict

I have spend much time on consumer psychology to know more about customers' needs and idea, but still have some problems sometime.

 

[HIMNL9]

But now still wondering what makes a good LPM? Some more knowledge about LPM will be appreciated.

Basically, the sensitivity, the repetitivity, and the precision and calibration, are the better things to look in any LPM, also with insensitivity in differences of measured wavelenght .....

I mean, if you need to test low-powered lasers, you need a LPM that is sensitive enough to measure also them with a decent accuracy ..... repetitivity, i mean it as "if you take 10 measures of the same laser in the same conditions, they must be identicals" (or, at least, reasonably identicals) ..... precision and calibration are obvious things, as for any measure instruments, you need an LPM that measure the correct amount of power from the beam (no need to get a 0,01% accuracy lab unit, for take on-the-fly measures in a shop, but if you want a decently accurate measure, you need at least a 5% or more precise unit) .....

About the insensitivity to different wavelenghts, this is a separate argument ..... there are basically 2 different types of LPMs (well, there are 5, in fact, but you don't need them, so basically the classes of LPMs that can be used in a shop are 2) ..... photodetectors and thermal detectors ..... photodetectors are the more sensitive type of measuring heads, for laser powers (they can measure microwatts), but they have also the inconvenient that they are extremely sensitive to differences in wavelenghts ..... the photodiodes used for them, none of them have a "flat response curve" to different wavelenghts, so, for use one of them, you need to know both the different wavelenghts of the laser that you are measuring, and the correction chart for the different wavelenghts, and after, you need to multiply the reading for the correction factor for that specific wavelenght, for get the real value ..... can not give too much problem, for a private, but in a shop, i guess it can be a real pain you-know-where .....

The second class of LPMs is the one that uses thermal sensors, or "thermopiles" ..... there are two different types, of sensors called thermopiles, one is made using Peltiers sensors in reverse use, and one is made using a lot of bimetallic junctions "printed" on the back of a very thin disk, painted on the reading side with substances that ensure the maximum possible light absorption ..... the first type (peltier cells) are a slightly less sensitive to very low powers (but there are some good ones, like as example the ones that Jerry sell), and can have a slight thermal derive for prolonged reading cycles, but are almost ininfluent to the point where you hit the sensor with the beam (i mean, the reading don't change too much if you point the beam on the center or on the borders), and are less delicate and cheaper than thermopiles ..... bimetal thermopiles are more sensitive to low powers, and intrinsecally less sensitive to thermal derive from prolonged reading cycles, but must be used pointing the beam the more centrally possible, for have a correc reading, cause are more sensitive also to the point where you point the beam (mean, pointing at the center, you have the correct reading, where pointing at the borders, you read more power than the real one), and are more delicate and have higher costs .....

Will different lasers need different IR? For example, will a IR for 532nm do well in a 650nm laser's test ? And it will be perfect, if some information about the price is given

Well, no, only green DPSS (or, more precisely, all the DPSS types of lasers, but mainly we speak about green, speaking about IR leaking), have IR leaking ..... this cause the green light is obtained "pumping" infrared light in the crystal that double the frequency, so part of the IR light (both 808nm and 1064nm) can leak out with the green ..... if the module is well built, with crystal sealed in the heatsink and AR / HR layers well done, the IR leaking is minimal, but usually "commercial" (read "cheap" ) pointers uses simply a glued crystal set, glued in a corner of the heatsink holder, without any seal, and with only an AR coating, so the IR leakage is higher (and, ofcourse, worse is the building, more is the IR leakage) .....

Laser diodes does not have IR leakage at all, they lase directly in the declared wavelenght, so there's no need at all to filter out IR from them, they just don't produce it.

Hope this was that what you want to know, if you need any other informations, just ask :beer:

 

[Tech_Junkie]

I'd like to check their website, they seem to be really honest company.

By the way, I remember I started a poll to find out what is the most important factor for a laser. According to the results, ( What do you concerned most about lasers?) the output is not the factor which customers care most. The price and quality seem to gain the most votes

But after reading hundreds of threads, I find the most important thing seems to be output. There seems to be some conflict

I have spend much time on consumer psychology to know more about customers' needs and idea, but still have some problems sometime.

John you miss read the poll. Quality is the specs, and the build quality. They would rather have a low power quality laser, than a high powered low quality one. The reason being that high powered, low quality lasers do not last long. Also not everyone cares about high power. Some people like low power too. Its less dangerous.

 

[John7788]

HIMNL9, thanks for your really helpful post!

John you miss read the poll. Quality is the specs, and the build quality. They would rather have a low power quality laser, than a high powered low quality one. The reason being that high powered, low quality lasers do not last long. Also not everyone cares about high power. Some people like low power too. Its less dangerous.

Then, how can I test the quality with a LPM? I thought specs was output.

By the way, can you give me some suggestions where to get a reliable LPM ? the more the better, then I can compare with each other before make my decision, I'd like to get a nice one.

 

[millirad]

Possibly a Laserbee II , purchased from Jerry?

 

[BKarim]

it is mandatory to check output power.
remember my story: i bought a 100mW pen at focaprice, hoping it would be at least 50mW.
but in fact it is no more than 20mW :yabbmad:


checking quality is easy: just point the laser to a small black disk on a white surface.
a good laser will throw one (and not two) small point on the black disk and very little parasite light on the white surface.

 

[HIMNL9]

There are some different possibilities, for get a decent LPM, with thermopile reading head ..... one is from Jerry, he sell laserbee units ..... one is from Kenom (you need to ask him, anyway, i don't remember really if he sold all his ones) ..... there was another user, nospin, that was selling similar units with thermopiles ..... on ebay you can also find some more "professional" units (but, ofcourse, the prices are higher, also for used units), just pay attention to avoid the ones that sell them "as is", and those to sell them without the reading head, or "no accessories" (some sellers tend to considerate the reading head an "accessory", where instead, without it, an LPM is just a high cost paperweight ), or that sell them with "100W" or higher reading heads (you need a 5 or 10W maximum reading head, if you want to read correctly also low powers) .....

Or also, maybe, you can find someone that sell one of these meters here, for "ceased activity", or cause they have one extra, or for any reason, but this very randomly .....

This for not have to spend a lot of money going to buy them in specialized shops, cause, imho, for the use that you need, there is no reasons to buy a lab professional unit spending thousands of $ (it's a personal opinion, ofcourse) ..... only, independently from what you decide to buy, i suggest you to avoid "photodiodes" ones, and to buy a thermopile one ..... can be less cheap, but much more easy and immediate to use .....

 

[Tech_Junkie]

Specs are output, but also beam quality. Two things with beam quality are divergence, and transverse mode.

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

A quality laser will have a small number for divergence, under 1 mRad is best. And a Transverse mode of 00.

How to Calculate Laser Beam Divergence | eHow.com

Then take the numbers and run it through this calculator.

pseudonomen137's JScript mRad Calculator

That will give you a lasers divergence.

Jerry sells a great hobbyist LPM.

 

[John7788]

still a long way to go for me to become professional.....:bumpit::bumpit:
Thanks all