Laser casing parallel to laser itself?

[imagelab]

Need some advice:

Basically, we are trying build an apparatus with 2 lasers (set apart at a fixed distance of 2 cm, accurate to the 0.1 mm) which can then be attached to a variety of cameras by the 1/4 in. screw standard for tripod attachments.

We had a previous system built, but the problem is that the casing which houses the laser does not accurately parallel the laser itself.

I need to find small lasers (green preferably) that have a very small diameter (preferably no more than 1-2 mm in diameter) with small casing which is accurately parallel to the laser it houses. And these lasers need to be able to make contact with sensitive skin without any harmful effects.

Sorry if this is a very basic question, but I really don't know much about lasers and we are in some real need of advice.

I can post pictures of our previous system if necessary to give a better idea.

Any help would be great.

Thanks.

 

[ElektroFreak]

DPSS lasers (like all green lasers) are prone to having beams which exit off-center and at a slight angle. It is possible to find green lasers which emit perfectly straight beams, but you will pay a premium for it.

I recommend buying two adjustable optics mounts and mirrors for them (here's an example of the mount). Then you can bounce each beam off of a mirror and then adjust the mirror to get the beams parallel.

 

[imagelab]

Would this be the case for red lasers as well? As long as it fits the same general idea, we could do red. We simply prefer green.

 

[ElektroFreak]

Most of the time red diode lasers will emit very close to a parallel beam, but you'll still end up paying if you need real precision. Using adjustable mounts is the proper way to adjust beam position precisely. You can even get micropositioners that will allow you to make adjustments to sub-micron precision, but they are expensive.

You most likely will also need to make use of shims or some other leveling method for the laser module itself.

 

[rog8811]

Here is an off the wall idea for you. When I was a newbie I started using camera rangefinders as beam combiners, you could use it the other way with one green laser. By shining the laser into the eye piece you will get 2 beams, then all you need to do is adjust the ranging knob until you get parallel beams!
You can pick up cheap ones from ebay, they usually have a hot shoe mount so adaptors are available for tripods.
Vintage Watameter Rangefinder with Case VGC on eBay (end time 02-Jul-09 13:12:11 BST)

Regards rog8811

 

[laserist]

Need some advice:

Basically, we are trying build an apparatus with 2 lasers (set apart at a fixed distance of 2 cm, accurate to the 0.1 mm) which can then be attached to a variety of cameras by the 1/4 in. screw standard for tripod attachments.

We had a previous system built, but the problem is that the casing which houses the laser does not accurately parallel the laser itself.

I need to find small lasers (green preferably) that have a very small diameter (preferably no more than 1-2 mm in diameter) with small casing which is accurately parallel to the laser it houses. And these lasers need to be able to make contact with sensitive skin without any harmful effects.

Sorry if this is a very basic question, but I really don't know much about lasers and we are in some real need of advice.

I can post pictures of our previous system if necessary to give a better idea.

Any help would be great.

Thanks.

You might want to consider using a single laser and a optical assembly consisting of a 50% beam splitter and a mirror bonded to achieve the offset and alignment you require.

 

[HIMNL9]

If you need really only 2 cm (20 mm) between your beams, the solution suggested from laserist is, probably, the better one, cause all the common modules are 12 mm of diameter, so not too much space for work ..... but if you want to try with 2 modules, just take a piece of aluminium, long enough for host the modules (as example, 2 of the 5 / 10 mW green ones from o-like are ok), and drill 2 holes through them, 13 mm of diameter (yes, 13, not 12).

Then, drill and thread 6 holes (drill 2,4mm, then thread them M3 thread screw all longs), for each one of 13mm, and using M3 grains, you can use them for align your modules til the beams are exactly paralleles .....

Look at the draw, for some more clear explication, cause i'm not so good with English (draws are bad quality, i just sketched my idea handy on-the-fly, hope the idea is clear ..... it's the same principle of the "Y" shape aligners, just a bit more "homemade" )

Ofcourse, if you have machines, or can do it from someone that have machines, doing the holes for the alignment grains at "Y" shape and 120 degrees are also better, and in this case you can also shape the block with rounded corners, for more easy handling and working, but if you only have a column drill like me, this way is the more easy one.

I can draw it more precise, if you want, but i need a bit of time for that, sorry.

 

[imagelab]

If you need really only 2 cm (20 mm) between your beams, the solution suggested from laserist is, probably, the better one, cause all the common modules are 12 mm of diameter, so not too much space for work ..... but if you want to try with 2 modules, just take a piece of aluminium, long enough for host the modules (as example, 2 of the 5 / 10 mW green ones from o-like are ok), and drill 2 holes through them, 13 mm of diameter (yes, 13, not 12).

Then, drill and thread 6 holes (drill 2,4mm, then thread them M3 thread screw all longs), for each one of 13mm, and using M3 grains, you can use them for align your modules til the beams are exactly paralleles .....

Look at the draw, for some more clear explication, cause i'm not so good with English (draws are bad quality, i just sketched my idea handy on-the-fly, hope the idea is clear ..... it's the same principle of the "Y" shape aligners, just a bit more "homemade" )

Ofcourse, if you have machines, or can do it from someone that have machines, doing the holes for the alignment grains at "Y" shape and 120 degrees are also better, and in this case you can also shape the block with rounded corners, for more easy handling and working, but if you only have a column drill like me, this way is the more easy one.

I can draw it more precise, if you want, but i need a bit of time for that, sorry.

This was actually one of our ideas initially. However, the problem we thought we would run into was the constant calibration that would be necessary. Basically, this is the problem we are currently having with our laser systems now. We are constantly having to calibrate and re-calibrate them because the slightest movement would offset the lasers. They were much better at first, but after a year or so they deteriorated and loosened.

We need to be able to transport this system relatively easily and perform the tasks necessary within a short time frame. So, we feel like using a calibration module to ensure alignment on a regular basis might not necessarily be the best way to go.

I like the idea of using mirrors, but the question then is to create the device in a way that's both portable, compact, and obviously functional.

Thanks for the suggestions so far! This is very insightful.

 

[ElektroFreak]

This was actually one of our ideas initially. However, the problem we thought we would run into was the constant calibration that would be necessary. Basically, this is the problem we are currently having with our laser systems now. We are constantly having to calibrate and re-calibrate them because the slightest movement would offset the lasers. They were much better at first, but after a year or so they deteriorated and loosened.

We need to be able to transport this system relatively easily and perform the tasks necessary within a short time frame. So, we feel like using a calibration module to ensure alignment on a regular basis might not necessarily be the best way to go.

I like the idea of using mirrors, but the question then is to create the device in a way that's both portable, compact, and obviously functional.

Thanks for the suggestions so far! This is very insightful.

One thing you'll need to keep in mind is that lasers (particularly DPSS lasers) beams drift over time. When you purchase a laser from a commercial supplier, many times you will see a value for beam pointing stability. If you don't want to have to recalibrate often you'll want a laser with the lowest possible beam pointing stability value. (Here's a spec sheet for a green DPSS laser from CNI. You'll notice the beam pointing stability value. You want this number to be as low as possible.) If your needs are really demanding, avoid buying any laser that does not list this value, as the beam might drift too much.

 

[imagelab]

One thing you'll need to keep in mind is that lasers (particularly DPSS lasers) beams drift over time. When you purchase a laser from a commercial supplier, many times you will see a value for beam pointing stability. If you don't want to have to recalibrate often you'll want a laser with the lowest possible beam pointing stability value. (Here's a spec sheet for a green DPSS laser from CNI. You'll notice the beam pointing stability value. You want this number to be as low as possible.) If your needs are really demanding, avoid buying any laser that does not list this value, as the beam might drift too much.

Would I be able to use something like the laser you linked in an optic system to create to equidistant points that would fit on a 25 cm x 15 cm plate?

 

[rog8811]

You might want to consider using a single laser and a optical assembly consisting of a 50% beam splitter and a mirror bonded to achieve the offset and alignment you require.

Which is exactly what a rangefinder is, it no longer matters that the beam does not come out straight. As there is only a single source the beam direction has only to be set once. If the distance between the beams is too wide in the rangefinder housing you can strip these units for the mirrors, mounts and adjusters to use on a purpose built base.



The photoshopped picture shows a rangefinder from a russian camera that I used as a combiner, it is 40mm between beams if used as shown, the nice thing is that all optics are micro adjustable with lock screws for set and forget.

Regards rog8811

 

[ElektroFreak]

Would I be able to use something like the laser you linked in an optic system to create to equidistant points that would fit on a 25 cm x 15 cm plate?

Yes, with the right optics. A 50/50 beamsplitter (as suggested previously in this thread) will split a single beam into two equal beams at a 90 degree angle (you can see this in the figure Rog posted above). Each beam will be half the power of the original single beam. I feel that this approach will be best for your needs since it eliminates the need for two lasers. Therefore, the beam characteristics of both split beams will be identical at all times. Adding other optics such as mirrors would allow you to manipulate those beams in any way necessary. To keep such a device portable will require some creativity, but it is possible. After all, optical drive manufacturers can cram three laser sources and a host of optical components like beam splitters and lenses into a part of the drive that's less than 3"x3" square.

EDIT: I misread your question the first time I read it, and NO that module would not be good to use in a system that needs to fit on a 25x15cm plate, but there are systems that will work. I'll post later with examples..

 

[HIMNL9]

Uh, the one that ElectroFreak linked for you, is a 450mW unit ..... are you sure that for an application that require you to point it at peoples, it's the better choice ?

Isn't better a 5 / 10 mW unit, for this type of uses ?

 

[ElektroFreak]

^If you look closely, that line of lasers ranges from 1-450mW.

 

[HIMNL9]

^ LOL, sorry ..... was looking only at the link, and just seen 450mW ..... my guilty :can:

 

[Justin]

The above suggestions are very good, but I think I can do one better. Laserglow has a new version of our Brightline PRO green alignment lasers with guaranteed parallelism between the body and beam to within <0.1°. We offer these with dot or line-generating optics in 5 mW or 20 mW versions. The series model number would be LPS-532-XX-XX-XX. Please contact me directly via email or phone and I'd be happy to offer you an off-the-shelf solution which will suit your application. We actually have most of them in stock right now so we may be able to fill your order in a matter of days.

Justin Hosaki
jhosaki@laserglow.com
416.729.7976