E-Bay 301 405 Laser

[Wallyl]

BTW I bought this Green 301 Laser from this outfit....at a "buy it now" deal....it works very well. While it is not in the same class as "premium" models, it is a very decent LASER IMHO....for the cost, you cannot go wrong owning one.

G301 Green Laser Pointer Pen Adjustable Focus 532nm Super Lazer Visible Beam | eBay

 

[Alaskan]

I have removed the plastic lens assembly, but not the lens from the plastic, yet. At some point I will give it a try. I just finished testing the output with and without the lens assembly on the unit. Without the lens assembly in front I'm seeing about 35 percent more output power (IR and green combined). Of course, that output is not well collimated but I made sure all of the green light would fall on 75 percent of my laser power meters sensor. I am sure there is some inaccuracy, but I tried moving the laser in and out from the power sensor to make sure I was getting a good reading. I noticed if I moved the laser fairly close to the sensor I would get a higher power reading, I'm not sure why three inches away vs six inches away would make that much difference, but it did make a noticeable difference. Because of that I made the measurements with and without the lens from the same distance.

 

[Wallyl]

Any ideas as to where one could get a replacement glass lens assembly that will fit?

 

[Alaskan]

Yea, I might have some in hand, let me see what happens when I replace it with a glass one and let you know where to get them. Also, I tested another 20 of my G301 units and found several which would not put out more than 40-50 mw but for the price, still good. Just that they are not stable, after a few minutes many can drop to 20 or less mw if starting out that low. If I had a more massive heatsinking for the modules, I am sure they would not heat up so fast and would then be far more stable.

 

[Wallyl]

Thank you...I appreciate it. I am not concerned that they drop output after two minutes as I use mine intermittently anyway.

I have a 303 & a 301....the 301 is slightly (noticeably brighter)... I had a second 301 that was equal to the 303; I gave it away to a buddy.

 

[Alaskan]

Well, I tried a rather spendy lens compared to the cost of the laser itself, the S1, by popping the original lens out of the plastic holder using a small plastic rod and cotton to protect from scratching the back side of the lens, pushing through from the back side. I then replaced it with this 5.6mm diameter glass lens made for simple diode collimation and should have known it would not work because its focal point is so short, these use a longer focal point lens which has a concave back side. The diameter of the original lens which has a small flat lip molded around its edge is close to 6.5mm so a glass plano-convex replacement lens should be about that diameter but no bigger. If you can find a glass lens which is 6 to 6.5mm diameter with a focal length of 10 to 15 mm that might work and you can keep the original lens holder too. If you are going to buy one, measure the distance inside the tube from the top of the plastic lens down deep inside the unit to the top of the tube where the plastic lens sits to know a more accurate focal distance so you can know the proper focal length.

I looked around ebay to try to find a lens which looks just like the one I popped out of this laser module and found this: http://www.ebay.com/itm/20pcs-Plast...779?pt=LH_DefaultDomain_0&hash=item5d3fda8fbb

Edit, the above lens is too big to work, it is 8mm diameter!

(Not the metal parts, just the lens) and this is the same diameter with a 8 to 13mm focal length. Not sure these are the same lens, but they could be. I don't have something to measure the distance from the bottom expander lens to the top or end of the tube where the output collimating lens sits to be able to tell you the right focal length, from the looks of things, 10mm might be too short. Also, if that is an expander lens down there in the tube near the crystal, then finding the right focal length is more than just the physical distance. You might have to try a few different focal lengths to hit it right, I'd start out with a 10mm FL as a best guess, looking at those other lenses I linked you to which are probably the same thing, 8 to 13mm FL might be the right one, regardless of the distance from the bottom of the tube to the collimation lens in the original holder being deeper than 13mm, due to the expander lens in the bottom.

After saying all that, I am new to lasers as well as optics, a more senior member with far more knowledge should be consulted first, these are just WAG's from me. Sorry, WAG upon WAG is all I can do without knowing more about the original lens and optics inside.. I'm wondering if the reason a longer focal length lens is used in these lasers (compared to a simple diode laser) is to improve the divergence? Maybe for some other reason, anyone here know?

 

[Wallyl]

Thank you for the information.

 

[Alaskan]

Late Edit:

I took a closer look at the original lens in the G301 laser and it is a plano-convex, not curved on the back side as I first thought and its diameter is closer to 6.4-6.5mm but anything from 5.6 to 6mm should fit well enough too.

I removed the expander lens and crystal from one of my weak G301 532nm lasers to measure the pure IR coming out of its diode and it was over 200mw. With the lens holder tube back on (the plastic lens in place) the IR power was measured at about 50mw because the raw beam-width of the IR diode is too wide, most of the power is then spread out inside the side walls of the tube and not exiting it. Putting the lens cap back on and even with the reduced output I could focus the IR to a point and burn things with it, but only if a few inches from the object, the focus did not have enough range to make a fine burning spot if over a foot away, judging by the fuzzyness of the dim red dot I could see. Even so, it is collimated enough to be a danger 100 or more feet away, keep that in mind and that even if the output of a IR or any laser diode isn't collimated, it can still blind you, the lens in your eye becomes the collimator. More than one person has been harmed by thinking the raw output of a laser diode isn't a problem, it is, as the lens in your eye will focus the energy just like a regular lens.

Later update: I removed the plastic collimation lens from the end of the tube and threaded in a S1 (close to G2) lens into the opposite end of the same tube nearest the laser diode and was able to focus all of the power, minus losses, into one very small rectangle spot with very crisp edges, so it was focused well, just needs beam shaping to turn it into a dot, if that is what you want. The power output after collimation was measured at 225 mw using this method.

I tried to focus the 532nm this way prior to the removal of the plastic expander lens glued on to the crystal assembly but it wouldn't work, the focal length of the S1 was too short to be used with this lasers expander lens. I then removed the expander lens and tried to collimate the green without it but this didn't work. Apparently, the green output of the crystal is such a tiny dot it is too small of a percentage of the 5.6mm lens I had up against it, because of this there wasn't much lensing action and I couldn't do anything with it as far as focus without some expansion first, that taught me a lot.

532nm module from G301 laser:

Exploded view of module with original parts:

Original lens on the end of the tube, expander lens and crystal all removed, S1 lens threaded into bottom of tube to turn the unit into a 200mw output IR burning laser. There are no other optics in the tube now, except the one I added:

Reassemble without all of the other parts by just adding a S1 or G2 lens (Aixiz lens will work too) and focus the tube by screwing it back down into the module to the right depth. Now you have something more dangerous, be damn careful with it, better yet, don't do this unless you are an experienced laser tech. IR lasers are far more dangerous than visible light lasers because you have no chance of a blink response, this will blind you before you even know you are hit in the eye. Personally, a small burning laser like this is very boring to me and probably should be disassembled to prevent someone from accidentally harming themselves with it. I really only did this because I destroyed my G301 laser by removing parts from it to show you what is inside and to take a power measurement of the IR diode, otherwise I wouldn't do this to a perfectly good laser, weak or not. Something interesting to me is that the plastic lens which was glued to the crystal assembly (the active or curved part of it) is nearly the same diameter as the crystal. This taught me that an expander lens must be close to the diameter of the beam to work well. Taking this apart and experimenting was a great way to start understanding the device, well worth it for me.

This thread drifted away from blue-ray, my apologies, I should have started another thread for this. Still, you could do this same mod with a 401 445nm laser using one of these Aixiz type lenses to replace the plastic lens and it ought to work fine, if it has the same kind of tube to hold the lens, or modified to be able to use it. Only thing is, the cost of one of these lenses might exceed the cost of the laser.