Noob question re. Laser Diodes and Required Optics

Thread Starter

gavbro

Joined May 17, 2024
8
Hello All,

I'm an IT Nerd that dabbles in electronics as a hobby, so please pardon the potentially 'stoopid' question!
I'm working on a project that requires the use of a low-power ~650nM laser in the 5-10mW range, and I've hit a surprising wall in the quest to source a discrete component that I can drop onto a PCB that will work with minimal fuss. In fact, for the purposes of this post, assume I’m simply trying to build a low-cost laser pointer using discrete components from a quality/reliable source. Also, I’m not trying to do anything hyper critical (like measure distances, read/write data, cut material, etc.) – I merely want a bright red spot to be projected against a surface up to 25 yards away (unnecessarily expensive LD’s & optics will be an overkill for my application).

I use Mouser and Digikey for my component needs (I'm in the US) and there don't seem to be very many options for what I'm looking for (my first surprise). From what I can gather, this is what is available from Mouser, tho Digikey is pretty much the same: https://www.mouser.com/c/optoelectronics/lasers/laser-diodes/?output power=7 mW~~10 mW&rp=optoelectronics/lasers/laser-diodes|~Output Power

I purchased a small batch of the cheapest options available (https://www.mouser.com/ProductDetail/755-RLD65NZN5-00A) to test, and was disappointed to see that the light output is very much dispersed into a dim approximately 2-3" circle from about the same distance away from the emitter. From what I have been able to glean online, it would appear I need to additionally figure out and acquire collimation and/or focusing lenses plus some kind of mechanical assembly to hold everything together.

Is my understanding above correct? Is a turnkey pre-focused PCB mountable laser diode component simply not a 'thing'? (I really just want to drop a component onto a PCB that can project a bright red spot when driven)

Assuming the above is correct, where can I get more information on the specifics of what I would need and where to acquire such hardware (in bulk)? It looks like the ROHM brand LD’s are the most popular/available on Mouser and Digikey, and I have scoured the ROHM website for some kind of guides/application notes on this subject, but couldn’t find anything of substance (they have great info on high-end applications like LIDAR & driver circuits, but nothing for my simple use case)? This makes me think I’m missing a fundamental piece of this puzzle – I would assume if a component needed supporting peripherals to be useful, the manufacturer would provide some kind of guidance in their datasheets or supplemental documentation? Also, wouldn’t the likes of Mouser also sell the peripherals needed?

The final point making me think I’m missing a fundamental piece of this puzzle is the fact that there appears (to me) to be a huge chasm between the cheap Amazon/Ali LD's and the 'high-end' Mouser/Digikey components - no middle ground? I can buy 20 (pre-focused) Laser Diode’s from Amazon for around $8.00 (https://www.amazon.com/gp/product/B088PQQ9XV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1). These work great for what I need, but I would never consider this as a serious production option (obvious concerns with quality and long-term supply). Were I to try creating one of these devices using parts I can reliably source I’m looking at costs of up to $30 ea. even using 'cheap' lenses and mechanical assemblies (the ROHM website does offer lenses, but these are approaching $100 ea.) I understand the Amazon components would easily classify as ‘cheap garbage’, but the price difference between $0.40c and $30.00+ ea. seems excessive?

Any pointers you could give this noob would be greatly appreciated.

Thanks!
 

Tonyr1084

Joined Sep 24, 2015
7,991
If you have already read my answer then it would appear I answered too quickly. You've already found laser modules on Amazon. I haven't used mine extensively but I've been happy so far. Keep them cool, don't over-power them or they can burn out, as I have found out.

As to why there's no middle ground between higher end and cheap Amazon products - - - I'm unsure. Is there a question we can answer besides "why is there no middle ground price range?"
 

Irving

Joined Jan 30, 2016
4,047
Not sure of your application, but when I had a similar requirement a few years back - wanting to know where a robot's cameras were pointing - I bought a cheap (<$15) spirit level and repurposed the diode from that. I'd hazard a guess that if you bought a few of these you'd find one with a manufacturers name on it.. given the cost of the level, the diode can't be more than a couple of $$$ in large quantities, an therein maybe lies the reason you're struggling - they aren't shipped in small quantities but in their 1000's maybe for that price. At the 10-50 level they may well be $20 - $25 each.

Maybe this site can help you: https://laserpointerforums.com/
 

Thread Starter

gavbro

Joined May 17, 2024
8
If you have already read my answer then it would appear I answered too quickly. You've already found laser modules on Amazon. I haven't used mine extensively but I've been happy so far. Keep them cool, don't over-power them or they can burn out, as I have found out.

As to why there's no middle ground between higher end and cheap Amazon products - - - I'm unsure. Is there a question we can answer besides "why is there no middle ground price range?"
Thank you for responding, much appreciated!

I think I buried the nature of my question in too many layers (sorry!). The reason I mentioned 'no middle ground' is because I feel as though I'm overlooking something obvious.

I guess the gist of what I'm trying to understand/confirm is:
What exactly do I need (discrete component wise) to project a bright red spot onto a surface up to 25 yards away at a price point in the ball park of low-cost laser pointers (let's say less than $10 ea. all-in), and where can I purchase the components in bulk to do so? Key requirements:
1. The solution must be PCB mountable (just the laser light emitting part, not any mechanical / optical parts)
2. All components must be available from a quality/reliable source (if the prototype pans out I'm looking at possible productions runs in the 1,000's). This necessarily excludes ultra cheap Amazon/Ali type mystery grab bags.
3. I don't mind paying a $$ premium for low volumes while prototyping, but whichever source/brand I land on must have volume discounts that can get me down to my < $10 ea. price point.

I'd like to keep things as simple as possible. Simplistically speaking, I'd love to buy a SMD Laser Diode that has all necessary optics capable of projecting a bright spot when driven by a CC source. Seeing as though this does not seem to be a 'thing', what other options do I have to achieve the same outcome simply and cost effectively?
 

Thread Starter

gavbro

Joined May 17, 2024
8
Not sure of your application, but when I had a similar requirement a few years back - wanting to know where a robot's cameras were pointing - I bought a cheap (<$15) spirit level and repurposed the diode from that. I'd hazard a guess that if you bought a few of these you'd find one with a manufacturers name on it.. given the cost of the level, the diode can't be more than a couple of $$$ in large quantities, an therein maybe lies the reason you're struggling - they aren't shipped in small quantities but in their 1000's maybe for that price. At the 10-50 level they may well be $20 - $25 each.

Maybe this site can help you: https://laserpointerforums.com/
Thank you Irving, I appreciate the response!

I did something similar to your suggestion but with cheap Amazon laser pointers and the stand-alone laser diodes. I wasn't very successful in that endeavor as the no-name brand products had (unsurprisingly) no meaningful diode manufacturer markings. The price range you mention are close to what I'm seeing on Mouser.com for ROHM brand laser diodes. I suspect this is going to be the only meaningful option(s) I have.

Seems like the only piece left to figure out is where to get the optics I will need (and some guidance on how to get the correct specs).
 

Tonyr1084

Joined Sep 24, 2015
7,991
Find a manufacturer and talk to them. Ask them about bulk discounts and possibly a sample for a prototype. You might get lucky and get something you can use along with the information required to know what the final cost of your project would be if built in bulk.

Feeling a little pressed to understand why you want something most people can get for a few bucks; I'm talking the whole laser pointer. But then again I don't know your final purpose. I may be missing the mark rather drastically.
 

Thread Starter

gavbro

Joined May 17, 2024
8
Find a manufacturer and talk to them. Ask them about bulk discounts and possibly a sample for a prototype. You might get lucky and get something you can use along with the information required to know what the final cost of your project would be if built in bulk.

Feeling a little pressed to understand why you want something most people can get for a few bucks; I'm talking the whole laser pointer. But then again I don't know your final purpose. I may be missing the mark rather drastically.
Thanks Tony!

I've been phoning around and have gotten some good feedback from suppliers. Basically it would appear my experience so far is accurate, the only options I have (as a general hobbyist) are the cheap Amazon/Ali products or 'high-end' (expensive) components. It looks like I can achieve what I'm after for around $40 ea. at low prototyping volumes, and then get that down to just over $20 ea. at 1000+ volumes.

I would assume the folks that make the 'cheap stuff' are big enough to design/manufacture their own components at just the right spec/quality/price point to meet their needs exactly, and no more.

The concept I'm playing around with is a device that will attach to the end of a CO2 powered BB gun to have the laser momentarily activated by the CO2 gas every time the BB is fired (minus the pellets of course). This is part of a larger gaming system I'm writing software for. The reason I want control over the component specifics is to keep size to an absolute minimum - I'm hoping to get the resultant muzzle device down to the 10-15mm size range (much bigger and it becomes an awkward stick out appendage).
 

Thread Starter

gavbro

Joined May 17, 2024
8
You could just reverse engineer the optics part.
It is only a tube and lens and a spacer to keep them focused.
Yeah, that's pretty much where I'm at now. I was 'low-key' hoping someone would tell me I sucked at online research and would point me to a $0.74 drop in turnkey component, nothing else needed (one can always dream I guess) ;)

I've resigned myself to following this rabbit hole to the very end, starting with these:
- https://www.edmundoptics.com/p/60mm-dia-x-120mm-fl-uncoated-plano-convex-lens/2356/
- https://www.amazon.com/gp/product/B0CL1G1NL5/ref=ox_sc_act_title_2?smid=A17O8U969TLM8D&psc=1
 

MisterBill2

Joined Jan 23, 2018
19,398
Hello All,

I'm an IT Nerd that dabbles in electronics as a hobby, so please pardon the potentially 'stoopid' question!
I'm working on a project that requires the use of a low-power ~650nM laser in the 5-10mW range, and I've hit a surprising wall in the quest to source a discrete component that I can drop onto a PCB that will work with minimal fuss. In fact, for the purposes of this post, assume I’m simply trying to build a low-cost laser pointer using discrete components from a quality/reliable source. Also, I’m not trying to do anything hyper critical (like measure distances, read/write data, cut material, etc.) – I merely want a bright red spot to be projected against a surface up to 25 yards away (unnecessarily expensive LD’s & optics will be an overkill for my application).

I use Mouser and Digikey for my component needs (I'm in the US) and there don't seem to be very many options for what I'm looking for (my first surprise). From what I can gather, this is what is available from Mouser, tho Digikey is pretty much the same: https://www.mouser.com/c/optoelectronics/lasers/laser-diodes/?output power=7 mW~~10 mW&rp=optoelectronics/lasers/laser-diodes|~Output Power

I purchased a small batch of the cheapest options available (https://www.mouser.com/ProductDetail/755-RLD65NZN5-00A) to test, and was disappointed to see that the light output is very much dispersed into a dim approximately 2-3" circle from about the same distance away from the emitter. From what I have been able to glean online, it would appear I need to additionally figure out and acquire collimation and/or focusing lenses plus some kind of mechanical assembly to hold everything together.

Is my understanding above correct? Is a turnkey pre-focused PCB mountable laser diode component simply not a 'thing'? (I really just want to drop a component onto a PCB that can project a bright red spot when driven)

Assuming the above is correct, where can I get more information on the specifics of what I would need and where to acquire such hardware (in bulk)? It looks like the ROHM brand LD’s are the most popular/available on Mouser and Digikey, and I have scoured the ROHM website for some kind of guides/application notes on this subject, but couldn’t find anything of substance (they have great info on high-end applications like LIDAR & driver circuits, but nothing for my simple use case)? This makes me think I’m missing a fundamental piece of this puzzle – I would assume if a component needed supporting peripherals to be useful, the manufacturer would provide some kind of guidance in their datasheets or supplemental documentation? Also, wouldn’t the likes of Mouser also sell the peripherals needed?

The final point making me think I’m missing a fundamental piece of this puzzle is the fact that there appears (to me) to be a huge chasm between the cheap Amazon/Ali LD's and the 'high-end' Mouser/Digikey components - no middle ground? I can buy 20 (pre-focused) Laser Diode’s from Amazon for around $8.00 (https://www.amazon.com/gp/product/B088PQQ9XV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1). These work great for what I need, but I would never consider this as a serious production option (obvious concerns with quality and long-term supply). Were I to try creating one of these devices using parts I can reliably source I’m looking at costs of up to $30 ea. even using 'cheap' lenses and mechanical assemblies (the ROHM website does offer lenses, but these are approaching $100 ea.) I understand the Amazon components would easily classify as ‘cheap garbage’, but the price difference between $0.40c and $30.00+ ea. seems excessive?

Any pointers you could give this noob would be greatly appreciated.

Thanks!
My experiencwe with laser diodes and optics from DIGIKEY, several years ago, was TOTALLY MISERABLE and a serious failure. the assembly process had a poor production yield, and the projected spot was never close to round.
So I purchased laser assemblies from a supplier, "Creative Technologies" and the assemblies worked very well, and the price was less.
UNfortunately CT is unwilling to answer emails, and demands phone calls. A request for a quote of price and delivery for a quantity of 50 assemblies was never answered.
 

Ya’akov

Joined Jan 27, 2019
9,264
Welcome to AAC.

I was going to say, “I hate to be that guy…” but I guess I am that guy…

Please be extremely cognizant of the dangers of even “low powered“ lasers. 5-10mW is not eye safe. It would be more of a concern for a frequency doubled green laser which is using an IR diode as the pump, but even with a red laser real, permanent eye damage is possible.

This said, I was unable to follow the actual progress of the thread so my (possibly… probably?) redundant contribution is to buy laser modules of the desired wavelength and power, then cannibalize them. The optics have physical limits on their size so you won’t be able to reduce that below a threshold that might be bigger than you‘d prefer. If your muzzle device is machined, adding a “lobe” to accommodate the extra bulk may be too costly, but if you are using 3DM for it, it’s not a big deal.

As a datapoint, for what it’s worth, the laser in the Olight Arkfeld flashlight below is an explicitly eye safe green laser which appears to be no larger than ~5mm and may be as small as 3mm. You might consider green instead of red since you will need much less power if you use green due to the response curve of the eye. I don’t think you will be happy with real eye safe levels in any case, so please make sure you’ve got the safety angle covered.

IMG_3002.jpeg
 

Thread Starter

gavbro

Joined May 17, 2024
8
Welcome to AAC.

I was going to say, “I hate to be that guy…” but I guess I am that guy…

Please be extremely cognizant of the dangers of even “low powered“ lasers. 5-10mW is not eye safe. It would be more of a concern for a frequency doubled green laser which is using an IR diode as the pump, but even with a red laser real, permanent eye damage is possible.

This said, I was unable to follow the actual progress of the thread so my (possibly… probably?) redundant contribution is to buy laser modules of the desired wavelength and power, then cannibalize them. The optics have physical limits on their size so you won’t be able to reduce that below a threshold that might be bigger than you‘d prefer. If your muzzle device is machined, adding a “lobe” to accommodate the extra bulk may be too costly, but if you are using 3DM for it, it’s not a big deal.

As a datapoint, for what it’s worth, the laser in the Olight Arkfeld flashlight below is an explicitly eye safe green laser which appears to be no larger than ~5mm and may be as small as 3mm. You might consider green instead of red since you will need much less power if you use green due to the response curve of the eye. I don’t think you will be happy with real eye safe levels in any case, so please make sure you’ve got the safety angle covered.

Thanks Ya’akov, I appreciate you taking the time to respond!

The reason I chose 5-10mW is because that is the power range of laser pointers and existing bore type dry fire practice devices, and I would assume that the risk of injury is low enough that posted warnings and proper use guidelines will ensure safe eyeballs. (pretty much 'Don't shine this into your eyeball, and don't point it at anyone')
Also, my device is not intended to be directed at humans, but rather to 'play' against modules with built in laser detectors and paper targets monitored by a smart phone / tablet.

I think I have things figured out enough to keep going, I received some cheap lenses from Amazon yesterday (https://www.amazon.com/dp/B07MCZZVS1?psc=1&ref=ppx_yo2ov_dt_b_product_details) and gave it a quick test against some ROHM Laser Diode's I bought (https://www.mouser.com/ProductDetail/755-RLD65NZN5-00A). It seemed like this would work, I got a decent focused spot just fiddling with orientation and distance by hand. I'll 3D print a jig to hold/align everything accurately to confirm, but quite happy (and confident) with results so far. Assuming this works well, I'll just have to incorporate accommodations for this into the enclosure - not too worried about that (it will be a machined part).

I wanted to try source all my components from a reliable and quality vendor & manufacturer in the off-chance I get this concept to work and decide to produce at quantity - looking to incorporate an existing module into my device has always been an option, but one I prefer to keep in my back pocket only if I've exhausted every other option.

Cheers and thanks again!
 

MisterBill2

Joined Jan 23, 2018
19,398
The laser modules I purchased were about $21 each for the first order of 20. They were 7.5 mm diameter and about 1.6Cm long. half of the first batch did not have the beam axis close enough to the case axis, so the next batch of 50 were bore-sighted, which brought the price up to $25 each. The bare lasers fro Digikey were $26 each, plus the lenses were an extra$26 above that. AND these modules came with color coded leads attached. So ready made modules are the way to go.. Not only better quality, but already assembled and verified, and less expensive as well.
As for eye safety concerns, the things exiting the front of a gun are a lot more hazardous than the laser beam used for aiming it.
 

Ya’akov

Joined Jan 27, 2019
9,264
As for eye safety concerns, the things exiting the front of a gun are a lot more hazardous than the laser beam used for aiming it.
I’m sorry Bill, but hard as I look, I am not finding the logic in this. What is it supposed to mean?

”Something is hazardous.”
”Well, something else in proximity to that is a lot more hazardous.”
”…”
 

BobTPH

Joined Jun 5, 2013
9,264
I’m sorry Bill, but hard as I look, I am not finding the logic in this. What is it supposed to mean?

”Something is hazardous.”
”Well, something else in proximity to that is a lot more hazardous.”
”…”
m
Did you miss this?
The concept I'm playing around with is a device that will attach to the end of a CO2 powered BB gun
 
Last edited:

Thread Starter

gavbro

Joined May 17, 2024
8
I’m sorry Bill, but hard as I look, I am not finding the logic in this. What is it supposed to mean?

”Something is hazardous.”
”Well, something else in proximity to that is a lot more hazardous.”
”…”
I think that was just a tongue-in-cheek reference (in the context laser bore sighting devices for a real firearms) that a 5mW laser exiting the barrel of a gun is a lot less hazardous than the objects usually exiting the barrel of a gun (bullets).
 

Thread Starter

gavbro

Joined May 17, 2024
8
The laser modules I purchased were about $21 each for the first order of 20. They were 7.5 mm diameter and about 1.6Cm long. half of the first batch did not have the beam axis close enough to the case axis, so the next batch of 50 were bore-sighted, which brought the price up to $25 each. The bare lasers fro Digikey were $26 each, plus the lenses were an extra$26 above that. AND these modules came with color coded leads attached. So ready made modules are the way to go.. Not only better quality, but already assembled and verified, and less expensive as well.
As for eye safety concerns, the things exiting the front of a gun are a lot more hazardous than the laser beam used for aiming it.
Interesting, seems that you have gone down a similar path to what I'm exploring now. The prices you mentioned are very much in line with what I am seeing as well. I do consider pre-built LD's to be an option for what I want, but I'd like to exhaust all options for me being able to design/assemble a complete solution first (including my own constant current source, enclosure with mounts, etc.). Right now I have some $3 ROHM Laser Diodes (from Mouser) and cheap lenses from Amazon to experiment with for around $0.50c ea. (but I can have quality lenses made in the US at 100+ bulk quantities for around $4-$5 ea.) - initial tests look promising, but I'll 3D print a fixture to accurately hold/adjust the components this week to verify. If that all works out I'll get away with LD + Lens for under $10 - I can live with that.
 

MisterBill2

Joined Jan 23, 2018
19,398
We discovered that not only were the assembled laser modules less expensive, they eliminated the alignment process in our product, which, since it includes four lasers aimed precisely at four detectors, an hour of alignmment time was saved for each product assembled. THAT ALONE paid for the change from assembling the laser packages.
 

Ya’akov

Joined Jan 27, 2019
9,264
I think that was just a tongue-in-cheek reference (in the context laser bore sighting devices for a real firearms) that a 5mW laser exiting the barrel of a gun is a lot less hazardous than the objects usually exiting the barrel of a gun (bullets).
The trouble is, lasers and eye safety are a much more serious issue than people have considered them. Dismissing the danger, even in jest, is just not OK. Particularly from someone who generally knows what he’s talking about and can be taken as an authority.

I didn’t take it as levity—and I know Bill very well.

I should note that all you did was restate what he said, my question still stands—what’s the logic? It seems you’d have to be ignoring the projectiles while focusing on the laser, or that somehow the greater danger of the projectiles negates the lesser danger of the laser. Neither of which makes sense.

Not to belabor this (too late, of course—but I did say I was “that guy”) this is one of several areas in electronics-related content where safety is often neglected. This is not to say you are neglecting it, but there are many more people reading these posts that writing them and this will be here for a long time.

For anyone reading this who doesn’t know, the dangers of small lasers are often ignored, underestimated, or mocked but the results can be very bad. Again, not in your case, since you are sourcing your diodes from known vendors but actual measurements of lasers from China marked <5mW show they can be 150mW or more!

The listings and labels can’t be trusted and a 150mW laser in your eye is a good recipe for a bad day—followed by many bad days.
 
Top