Maximum useful focal length

[Nutball]

I was able to unscrew the lens in the lens holder in my pocket laser, now I can focus it to a pretty small dot at long range. Sometime I'll get a picture of their dots at about 60ft.

 

[Nutball]

Update: I was wrong in my assumption of how the lens holder works in the pocket laser, it isn't exactly adjustable, but has many signs of it that threw me off. There is the stainless steel cap with a centered lens holder that appears to be glued to the cap. I thought I saw and adjustable front lens retaining ring, but it might be just part of the lens holder shell. Then there's a front and back lens with a spacer ring, then the rear retaining ring that screws into the lens holder. I had only backed this out letting the lenses slide around freely sometimes focusing how I wanted. I might be able to add a spacer ring in front of the lenses if I can find something that fits. Cutting a white nylon washer comes to mind, but it could be hard with the precision required.

As for the up close focal point beam diameter based on burn marks and this picture of the beam in water I estimate it to be 0.2-0.4mm, probably closer to 0.2mm.

 

[paul1598419]

This is common with these cheap 660nm <5 mW lasers. They are set for the best focus and are usually not adjustable.

 

[Nutball]

You missed what I have said. I was able to focus the cheap red <5mW from its setting of 5ft to infinity and far beyond if I wanted to. I couldn't focus the Sanwu beyond 3ft, it's the one with the lenses that can't easily be adjusted within the focusing cap. I have messaged them, I hope they come out with some long range caps for the pocket lasers because I have seen great potential out of it when I loosened the lenses.

 

[diachi]

You missed what I have said. I was able to focus the cheap red <5mW from its setting of 5ft to infinity and far beyond if I wanted to. I couldn't focus the Sanwu beyond 3ft, it's the one with the lenses that can't easily be adjusted within the focusing cap. I have messaged them, I hope they come out with some long range caps for the pocket lasers because I have seen great potential out of it when I loosened the lenses.

Not sure what's up with yours, but as far as I can see the lens on my 650 pocket is removable/adjustable inside the lens cap (I've got the 3 element in mine). Even then, the divergence is pretty decent to begin with, I've had no need to adjust it. No need for a "long range cap".

 

[Nutball]

I thought mine LOOKED adjustable, but as far as I know it is not unless there is a front adjustable retaining ring. Such a ring appears to have its threads glued, the rear doesn't, but either way I'd need to remove the lens holder to adjust the front, but it appears glued to the cap, and I'm not confident I could re align and glue it in straight, or remove it without scratching things. What's your focal point distance with the lens cap fully screwed on the laser? Mine makes it's dot smallest at about 3ft from the laser, then it is like a narrow beam flashlight with a 5" dot at 50ft. I can only adjust it closer from there to about 3".

Pics are sideways because the editor said they are too tall. Small dot is the 5mW, big is the pocket laser at lowest power, both at 40ft. I just realized I'm pointing them towards an airplane :tsk::shhh:

 

[BowtieGuy]

I just went back to the Sanwu pocket laser order page and noticed that it states -

Focusing lens (optional)*

Standard lens
G-2 lens (add $10)
G-7 lens (add $10)

I don't know which option you purchased, but it sounds as if the one you have may have the standard lens and may not be adjustable, while some versions may be focusable.
Have you contacted Podo with your concerns.

 

[diachi]

I thought my LOOKED adjustable, but as far as I know it is not unless there is a front adjustable retaining ring. Such a ring appears to have its threads glued, the rear doesn't, but either way I'd need to remove the lens holder to adjust the front, but it appears glued to the cap, and I'm not confident I could re align and glue it in straight, or remove it without scratching things. What's your focal point distance with the lens cap fully screwed on the laser? Mine makes it's dot smallest at about 3ft from the laser, then it is like a narrow beam flashlight with a 5" dot at 50ft. I can only adjust it closer from there to about 3".

Dot pics coming soon

Mine is "focused to infinity". I'd need several bounce mirrors to answer your question with the length of my apartment. Safe to say the divergence is much lower than what you're seeing.

What lens did you get?

Can you post some pictures? EDIT: Missed your last sentence.

I just went back to the Sanwu pocket laser order page and noticed that it states -

Focusing lens (optional)*

Standard lens
G-2 lens (add $10)
G-7 lens (add $10)

I don't know which option you purchased, but it sounds as if the one you have may have the standard lens and may not be adjustable, while some versions may be focusable.
Have you contacted Podo with your concerns.

I have the standard (3 element) and it is threaded, as is normal with the 3 element. Can't tell if the cap it attaches to is or not though. Having it threaded makes sense from a construction point of view, much easier to properly adjust with a threaded fitting. Of course, once set you'd glue the lens holder in place.

 

[Nutball]

I got the G7

Yea, I'm talking to him. He at first thought my 5mW was green saying they have special lenses allowing for longer FL than red and blue and that a BE is needed for red and blue, but I was able to get infinite focus with loose lenses, so the lens holder just needs tweaking. I am not confident in my skills to do that.

If you guys think I got a fluke, I'll direct Podo here to my pictures and see what he thinks. It really takes such a small adjustment I guess they could have messed up hen making it, but It would have to be perfect to get both burning range focus and infinite with the thread space on the laser. Also I figure they would have caught any problems during testing which should include a focus QC

 

[Nutball]

I'm so happy! I unscrewed the brass diode mount from the steel battery case by a few degrees, added super glue to the threads with a super fine tip applicator to lock the threads, dabbed some glue accelerator residue on, and now at 60ft, it's hard to tell, but it looks like I can focus just past 60ft probably to infinity. I took it outside and pointed at stuff up to 300ft away and it looks just like a pointer should, nice little dot

Min focus distance is 2.25" before the cap loosens off of the supporting o-ring

In case someone else has to do it, I needed to use pliers to unscrew the brass module. I used a 1/32" thick square of shrunk heat shrink tubing folded over for more thickness, and used that to protect the threads from damage from the pliers. Then I used some rubber for gripping the case. A rubber band would probably work.