Achieving a smaller beam diameter with 803T optics

[Krutz]

could you make a pic of your lensholder?
with diffuse wings, it could be a bit off the focusing distance. or its the good old violet-blurry-vision ;-)

how thin was your beam? if its a few mm beam, like others reported, it would be good for burning without needing to focus at all!

manuel

 

[dr-ebert]

Here we go. Pictures of dots were taken with a distance of 8m (26ft). In the pictures are also a ruler (difficult to see) and my index finger for giving a size reference:

1) Lensholder with 803T lens, next to standard Aixiz acrylic lensholder

2) dot with 803T lens

3) dot with standard Aixiz acrylic lens (back opened)

4) dot of LPC-815 for comparison (Virtualvillage AR coated acrylic)

The pictures don't do the differences you see justice. The exposure automatics have made the difference look much smaller than it is in reality (it's a cell-phone camera, no manual settings). The dots with the Aixiz and VV lens are round; the distortions you see at 12 o'clock in #3 and 1 o'clock in #4 are ghosts from reflections in the camera lens. After taking these pictures, I think I'll stay with the Aixiz lens.

 

[Krutz]

thanks for the pics, dr-ebert!

will post some in a minute too..

manuel

 

[Krutz]

lets see if i can embed the thumbs as nicely as dr-ebert? ;-)

i begin with what you all ask for, dot-pics!

all violet ones are a 803 diode. 130mW with an aixiz acrylic, 140mW with the 803 lens. at aperture, the aixiz produces a round dot with 5mm diameter, just like with a red diode. the 803 lens produces an oval dot, 1x2mm!

(so, how do i embed those thumbs here, now?)

405-803-1.jpg:
803 lens, close to best possible collimation, 2.5m distance.

405-803-2.jpg
405-803-3.jpg:
thats what it looks like when you didnt bring the lens close enough to the diode. remember, its a 0.8mm distance in between only! screw one turn further in (after pic 3) and its a dot. and yes, one turn more, and it widens as fast again.

405-803-5.jpg:
violet-blocking glasses, non-fluorescent surface, 50cm distance

405-803-6.jpg:
comparison to the red one. yes, i cant see anything neither there.. ;-)

(how do i embed thumb?)

 

[Krutz]

next, dot at a greater distance, i would guess 12m.

405-803-8.jpg:
the dot. a pita to collimate! could perhaps be a tad tighter, but the rings will stay.

405-803-9.jpg:
violet-blocking glasses

405-803-10.jpg:
the beam and distance. with that much scatter (rings), it would overload my cam, therefore the blocking of the laser itself

 

[Krutz]

P1460069.jpg:
the lenses, aixiz and 803. not sure if the 803 is centered well enough, perhaps that would help against rings. or simply blacken the outer (ringy structured?) part?

405-aixiz-6.jpg:
how far the aixiz turns in

405-aixiz-7.jpg:
..and the 803 lens. its all the way down, and the lens is at the very end of the nut!

thats the problem with most of the distorted pics i saw: the lens isnt close enough to the diode.

 

[Krutz]

comparisons to aixiz and 650nm:

the violet ones all are with an aizix lens. back is stock, not opened, for a cleaner dot. it makes almost no difference in output-power, a few mw or %, less than 5% as far as i remember my tests some time ago.

the red ones are with all three lenses, aizix, 803 and virtualvillages one. the tendency is the same (803 ringy and smaller, VV's one being same better than aixiz' one in every aspect).

 

[Krutz]

now for the powerreadings:

405nm 803 diode:
130mw with aixiz (back "closed", stock), dot round and 5mm wide
140mw with 803 lens, oval dot, 1x2mm

650nm LOC diode:
304mw with aixiz (back "closed", stock), dot round and 5mm wide
380mw with virtualvillage (back open, stock), dot round and 5mm wide
390mw with 803 lens, round(!) dot, 2mm

all measured with a thermal head, where the dotsize influences the reading a bit..


so here you go.
overall feeling? the dot gets uglier with a 803 lens. which doesnt matter much, since after a few meters the dot blurs anyway because of eye-focus-problems. the dot doesnt look worse after several meters. for closeup, the dot is smaller (=brighter) but with a little more visible noise (one or two blurry wings). its not the perfectly round dot we are used of, but not too bad. it looks nicer than the pics suggest. the beam is *much* tighter. with a 2mm beam, which is a quarter of the original area, you wont need to focus to burn or burst balloons. which is good, since you cant easily focus anyway. its hard to focus, rotating the lens a few degree changes the dot already extremely! and you cant (easily) have the metal ring to focus. you have to rotate the lens with your finger on/in the barrel, which does sting when the laser is on. that means: laser off, rotate a few degree, laser on, again and again.

for me:
i dont burn with my lasers, so i prefer the slightly more beautiful dot, for my violet.
with reds, i dont expect anything to beat VV's lens for a reasonable price.

manuel

 

[dr-ebert]

Quite a lot, that will take some time to digest!

One thing: 130mW for BR and 380mW for red are easily 30-40% more of what most people get with the standard currents of 120 resp. 420mA. What currents do you use?

I embed the pictures by first attaching them as a thumbnail, then editing the post. In a second window showing my post I click on a thumbnail to get the full-size pic, right-click into that, select "copy grafics address" (FF), press the "imbed image" button in the edit window and paste the address. A bit convoluted, but works.

Edit: I find the BR rather easy to focus. It doesn't turn into a tiny dot when focussing (because that wavelength is diffracted too much by the eye, so essentially you're highly shortsighted at that wavelength), but the fuzzy image turns into a disk with sharply defined circles and other structure in it when it's in focus. A bit difficult to describe, try it out!

Edit 2: I'll have to try the 803T lens with my red as well.

Edit 3: tried it... massive scatter, rings 30cm or more out from the central dot (at 5m distance), and I couldn't properly focus the dot (unlike with BR), it looks like a small astigmatism - nothing that's visible from 5m, but close up, yes.

Possibly there is indeed something wrong with my lens. I have only one 803T sled, possibly I'll try getting at the other lens at the point where the LD was.

 

[Krutz]

ah, i just found out that attached pics are automatically renamed?!? if some mentioned pic isnt "found", let me know!

oh, i feared something like this, dr-ebert.. not sure if i will go through all this here ;-)
thanks for the pointer!

i focus my violets by pointing as far away as possible, when i see the brightest dot and brightest specle its what i think its focussed. the dot doesnt look much larger or smaller when fine-tuning..
"disk"? perhaps were referring the same ;-)

currents: 130mA for the 803t. the first diode died already, but what the heck.. ;-)
for the LOC, cant find my note on this. i believe i set it to 500mA. it goes down in power after a while, although its well heatsinked. the 5.6mm can seems to be the weakest link here, by now..
both with a rcr123a and flexdrive (3 or 4).

manuel

 

[rog8811]

I embed the pictures by first attaching them as a thumbnail, then editing the post. In a second window showing my post I click on a thumbnail to get the full-size pic, right-click into that, select "copy grafics address" (FF), press the "imbed image" button in the edit window and paste the address. A bit convoluted, but works.

Thankyou
Regards rog8811

 

[dr-ebert]

You're welcome!

 

[Jimmymcjimthejim]

Wow Krutz, thanks for the analysis!
I was questioning this mod in terms of power, but I knew it had to have some form of increase since the lens is AR coated.

 

[dr-ebert]

Btw, shouldn't this thread rather be in Experiments & Modifications?

 

[BuildAbluraylaser]

Does this mod use the regular acrylic lense?

Because I can't see any lense nut...

 

[Bionic-Badger]

It's the regular acrylic lens. You'll need to cut open the back and pop out the old lens. I ended up destroying the original lens in mine.