Extending focal range

[Jeff Greer]

Is there any way to extend the length/depth that my laser burns so that my laser stays in good burning range? It seems like I only have a range of .1875 be for it putters out and wont burn. It would be nice if I didn't need to cheat the focus and re-burn a convex surface. I have a Epilog Legand EXT 75 watt.

Thanks, Jeff

[Michael Hunter]

4" lens - if you can afford it !!!!

[Mark Sipes]

are you sure the lens in installed with the dome side up??

just ckecking..... and the answer is no ....its a magnifing glass and the focal lenght is fixed

[Rich Harman]

There are dual focus lenses (http://www.sintecoptronics.com/FocusingLensDualFocus.asp). Haven't heard from anyone that has used one though.

What lens are you using now? Any increase in focal length will give you more depth of field.

You should be able to get a Chinese 4" (100mm) lens for a fraction of the cost of one from Epilog.

[Jeff Greer]

I guess I need to research a little more before I ask questions!!! Just educated my self on lenses - although there is a lot more to learn I am sure. Looks like a 4.0 is what I am wanting. So next is to source one and then make a mount.

Thank you for the input.

[Mark Sipes]

So what I am reading ....a 4" lens with allow the item being lased to go say 1/8" to 1/4 out of focus and still provide a clean clear image....... I have my doubts......how does a dual focus lens work? I'm no expert in optics but unless you are combining lenses to get a compound effect I still do not see how that addresses Jeff's initial concern. He is not looking for a lense to increase engraving distance but rather stay in focus over an uneven, warped , convex surface with greater tolerence than .1875"

"Is there any way to extend the length/depth that my laser burns so that my laser stays in good burning range? It seems like I only have a range of .1875 be for it putters out and wont burn" 75 watts

[Rodne Gold]

Those lenses are for big industrial lasers , wont work on ours at all. The concept however could be used in our lasers if someone did a custom grind .....

[Rich Harman]

I'm no expert in optics but unless you are combining lenses to get a compound effect I still do not see how that addresses Jeff's initial concern.

That's how they work, it is essentially two lenses in one. Don't how they would work for engraving, they are created with cutting in mind.

Any increase in focal length is going to provide an increase in DOF (what he needs), along with an increase in spot size and a decrease in energy density. If it were possible to remove the beam expander ("Radiance Optics") - then that would also increase his DOF - and spot size.

[Marc Nicoloudis]

I was having trouble a bit of trouble cutting through uneven materials in the past. Because my laser came supplied with a 1.5" FL lens, I decided to try a 2.5" lens, and have been pleasantly suprised with the cutting ability of the longer focal length. My cut speed has also increased. I ordered from Light object, and the gentleman even ordered the smaller lense that my machine required. I also ordered an additional lense holder for a quick change set up, should the need arise. Picked up 2 new lenses for just over $100-Marc

[Dan Hintz]

There are dual focus lenses (http://www.sintecoptronics.com/FocusingLensDualFocus.asp). Haven't heard from anyone that has used one though.

I did a "review" on these years back... tried to get them to donate one as a giveaway for the SMC laser group meeting that year, but it never materialized. It would be great for deep cutting, but you really want a strong machine (100W+) to begin with to get the most benefit.

[Jeff Greer]

So what I am reading ....a 4" lens with allow the item being lased to go say 1/8" to 1/4 out of focus and still provide a clean clear image....... I have my doubts......how does a dual focus lens work? I'm no expert in optics but unless you are combining lenses to get a compound effect I still do not see how that addresses Jeff's initial concern. He is not looking for a lense to increase engraving distance but rather stay in focus over an uneven, warped , convex surface with greater tolerence than .1875"

"Is there any way to extend the length/depth that my laser burns so that my laser stays in good burning range? It seems like I only have a range of .1875 be for it putters out and wont burn" 75 watts




I see how it works. Draw out a triangle that is 2.0 tall and one that is 4.0 tall. If you mirror/flip it, you can somewhat see how the focus stays in a tighter pattern - thus giving more effective depth range. At least that is how I am seeing it. I have seen people in videos engrave over a lot more convex surface then I can and I wonder how they did that - this must be it.

[Dan Hintz]

Just be aware, a longer DOF equates to a larger engraving dot... you lose a bit of clarity, but for many substrates (like wood) this isn't a major concern.

[Jeff Greer]

Well I ordered the 4.0 lens assembly from Epilog. It came with the extended automatic touch off probe, extended air nozzle, and manual focus gauge - nice complete unit for $350.00. After building dies and molds for a living - I wouldn't screw around and build my own lens holder and buy a unmounted lens to try and save a penny for the quality I bought.

"drum roll sounding"

AND it worked like I thought it might by extending the focal range enough that I didn't have to cheat the focus and re run the parts to get the areas that dropped below the 2.0 lens focus point. YAAA!!!