Focal Length testing - APC LensPro for Omtech Polar


Focal testing for the APC LensPro for Omtech Polar 2”, 2.5” and 4” focal length lens. Looking at the new lenses, wanted to find the best focal distance and then max and min tolerances for each lens.

This information can then be used to adjust height when trying to cut thicker materials; as you will adjust focal length to make sure entire cut is within the tolerance range.

Focal Length:

Understanding the Importance of Focal Length in Laser Engraving Systems

The focal length is a critical parameter in the operation of laser engraving systems. It is not merely a numerical value; rather, it serves as a cornerstone for achieving optimal performance and precision in your engraving projects.

In technical terms, the focal length is defined as the distance from the laser lens to the point where the laser beam converges into a highly focused spot. This distance plays a pivotal role in determining both the size of the work area and the level of detail achievable in the engraving process.

Short Focal Lengths

A shorter focal length offers a tighter focus, allowing for extremely detailed work. This is particularly beneficial for intricate designs or applications where precision is paramount. However, it is worth noting that a shorter focal length narrows the effective working area, limiting the size of the material that can be engraved.

Long Focal Lengths

Conversely, a longer focal length provides a larger working area, ideal for engraving bigger pieces or for projects that do not require fine detail. However, this comes at the cost of reduced precision, as the laser beam will be less focused compared to shorter focal lengths.

APC LensPro for Omtech Polar 2”

Using a 3mm basswood sheet for testing; at default home-z finding 63mm total spacing.

Measuring nozzle clearance; shows 22mm range max with a 3mm baswood sheet (or 25mm useable space before smashing the nozzle into bed).

note: The 63mm is measured from top of platform.

First test:

Wide sweep, based on the above measures.

We can see 48mm is showing the best results; which is not surprising as the manufacturer recommendation is 47.8mm for distance.

The 47.8mm L tool to measure from top of platform to material


Looking at results; we can start observing the tolerance of laser is 42mm and 53mm (at the very max). We can safely assume that 11mm is about the max cutting depth before we start seeing issues.

At 40mm; you are basically hitting the piece; I’d say normal limits should be 41mm-54.

Breaking that down into next test at 1mm increments.