View Full Version : Checking focal distance

Bruce Dorworth
01-19-2012, 3:13 PM
My laser came with a disk that is used to determine focus on my laser. Is there a test to determine what the best focus distance is? I serched the forum and you tube and did not find what I was looking for.

One method that I saw(but can not find again) was to a slanted stack of paper. When you cut a line up the stack you will be able to see the thinest line.

Your help will be greatly appreciated.


Dan Hintz
01-19-2012, 3:20 PM
Not paper, anodized aluminum.

Measurements are up to you, but for simplicity let's assume a 10" long strip with one end on the table and the other end on a 1" high block. Set the table height so you are supposedly focused right in the middle of the strip. Engrave a line from end to end of the strip. If the smallest line is right in the middle of the strip, your focus is set correctly. If it's not, measure the distance from the center of the strip to the actual location of the smallest engraving. Let's say it's 0.5" farther down the ramp... this says your true focal point is actually 0.5/10 = 0.05" lower than what you currently have it set for.

Rich Harman
01-19-2012, 4:13 PM
I use wood or MDF rather than anodized aluminum. Works just fine, it's easy to tell where the line is thinnest. Besides, I don't have much anodized aluminum.

Bruce Dorworth
01-19-2012, 4:43 PM
Thanks Dan and Rich! That is exactly what I was looking for. I will probably use wood first and if that doesn't work I will then try the Aluminum.

Thanks again,

Dan Hintz
01-19-2012, 8:34 PM
Find some roof flashing at your local Borg... they usually have brown/putty in stock, and if you're lucky you can find black/white (I ordered a 2'x50' roll). It lasers at almost as high a resolution as anodized and provides a very flat surface. I wouldn't recommend wood if someone asked me, but if that's what you have on hand...

Rich Harman
01-19-2012, 8:48 PM
What's wrong with using wood?

Rodne Gold
01-20-2012, 12:56 AM
The problem with wood is that there is a char on the edges of the engravings and that wont allow you to see the absolute "crispest" line , you also need a printers or 10x jewelers loupe to inspect the mark to be really accurate.

Dan Hintz
01-20-2012, 7:01 AM
We need a little graphic with an arrow pointing up and "what he said" next to it ;)

Bruce Dorworth
01-20-2012, 1:18 PM
Thanks Rodney!! That makes perfect sense. I am off to the big box store to get some painted metal.

I will post my results later.


Rich Harman
01-20-2012, 9:26 PM
Well you guys have me quite confused. My eyesight aint anything like it used to be and I have little problem finding the focus using a piece of wood.

Maybe it's the method?

I place the wood on the table, tilted so that I know that one end will be well below focus and the other end above.

I manually jog the laser and hit the fire button as it passes over the wood. I have the power set so that it makes a crisp, but not too dark line, line.

The resulting line on the wood starts out wide gets narrow then widens again. It is very easy to see where the midpoint of the narrow line is. That is where it is in focus.