What is depth of focus or focus tolerance?

Depth of Focus (or Focus Tolerance)

The depth of focus refers to the range along the optical axis within which a laser beam remains acceptably sharp as the focus area doubles. This range extends from the focal plane where the laser beam is precisely focused. Understanding the depth of focus is crucial in laser technology, as it helps in selecting the appropriate lens for specific applications.

Terminology: Depth of Focus

The depth of focus, also known as the depth of sharpness, describes the range within which an image remains sufficiently sharp and in focus. This means that an imaging system, such as a laser beam, can be adjusted within this range without causing noticeable blurring. The depth of focus thus defines how tolerant a system is to variations in the position of the object being imaged. 

BMLaser Fiber Laser Focus Lens.

1. Standard High Efficiency Low Loss Anti-reflectance.
2.Double-sided AR coating process, High transmittance.
3. High Purity Fused Silica, High Temperature Resistance.
4. Long life time, More durable.
5.Total Absorption:<30PPM,Transmission:>99.8%
6. Applicable to laser cutting, laser welding, laser cladding systems etc.

Effects of Focus Tolerance on the Laser Beam

Focus and focus tolerance are critical factors to consider when cutting or engraving with a laser. Selecting the appropriate lens for your specific application is as important as achieving the correct focus.

For fine and highly detailed laser engravings, a lens with a shorter focal length is essential. A shorter focal length lens provides a smaller focus area, which results in higher resolution and finer detail—ideal for intricate designs. For instance, a 1.5-inch lens used with a CO2 laser is suited for detailed engravings, achieving resolutions exceeding 500 dpi.

Conversely, when cutting through thicker materials, a lens with a longer focal length is more suitable. A longer focal length lens offers a larger focus area, which helps to accommodate the increased material thickness and ensures efficient cutting performance.

Choosing the right lens and optimizing focus based on the material and desired outcome will significantly impact the quality and precision of your laser work.