The laser focusing lens is the last optical device in the laser path. And the focusing lens is usually a plano-convex lens or a curved lunar surface lens.

What is the purpose of the focusing lens?

Laser cutting and engraving machines use a laser beam that is approximately one quarter of an inch (240 parts per thousand) in diameter. For high quality engraving and precision cutting, the laser beam uses a system of reflectors and focusing lenses to redirect the laser.

The laser system uses a plano-convex lens to focus the laser. The laser enters the convex lens and begins to converge to a focal point, through which the light emanates.

This focal point converts the laser beam into a very small and precise spot with very accurate results for a variety of applications. As the laser beam leaves the focusing lens and is positioned within the desired focal distance, it begins to cut or engrave.

The focusing tolerance (depth of focus) is the area where the beam diameter is smallest. The larger the lens, the longer the focal length. This is especially important if you want to cut through thick material, in which case you need a larger lens. The shorter the focal length of the lens, the faster the convergence/divergence, the smaller the focal spot and the shorter the depth of focus.

As the focal spot becomes smaller, sharper details can be seen in the processed laser image, resulting in a brighter, more detailed image.

Which focusing lens is best for which type of project?

The most common laser lenses are 1.5-inch, 2-inch, 2.5-inch and 4-inch. All lenses are suitable for cutting and engraving work.

Which lens is best for your application?

1.5-inch lenses.

High resolution engraving.

Best for thin (less than 1/16 inch) materials.

Small type or very fine detail engraving.

Approximately 40% smaller than 2.0-inch focus lenses.

Thickness of about 38.5 mm, suitable for very thin materials.

2.5-inch lens.

Most commonly used in laser systems.

Versatile, engraving and cutting applications.

Graphics with medium detail and resolution.

Most pieces are approximately 63.5 mm thick.

4-inch lens.

Used for longer vertical distances.

For cutting thicker materials.

Approximately 101.6 mm thick for very thick materials.

As an important conclusion, you can see that the more delicate and detailed the graphic is, the smaller the lens should be. For cutting thick materials, it is recommended to use the largest size lens.

Important Notes

The lens you need is directly related to your application. The following are some important considerations that will define the lens you must use.

The output of the laser device (laser beam power)

Material and application (cutting or engraving).

The level of detail of the graphic.

The thickness of the material.

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