Beam Homogenizers with Microlens Array Homogenizer Explained

Laser optics are often required to generate a uniform intensity profile for optimal processing. A microlens array homogenizer is one of the top practical tools for achieving this function. A detailed analysis of beam homogenisers starts with evaluating microlens array homogenisers, including operational principles and beneficial features with typical implementation examples. The discussion includes examining supplementary aspects that involve diffractive optical element design and beam characteristics and their application within optical systems.

What is a Microlens Array Homogenizer?

A microlens array homogeniser contains multiple small lenses arranged in a grid. These lenses use their focusing powers to produce uniform brightness across the output area. Because many application have high homogeneity needs, the homogeniser device is critical in such applications, including laser machining, lithography, and medical systems.

Microlens arrays differ from single lenses in splitting the incoming light beam before the recombined beams produce uniform light output. How light is redistributed controls the intensity profile, resulting in a beam that works well for precise applications.

Working Principle

The working mechanism of the microlens array homogeniser uses beam splitting combined with beam recombination. Each microlens within the array divides the transmitted laser beam into smaller units so that all the beam sub-sections exist inside the array. All sub-beams reach the focal plane, creating an identical image determined by the sub-aperture. The beam uniformity improves because multiple identical images overlap, producing light output with stable intensity.

Key Features:

●      Uniform Output: The light distribution mechanism in a homogeniser produces an output beam with uniform brightness.

●      Flexibility: Compatible with various wavelengths and beam profiles.

●      Compact Design: Suitable for integration into small optical systems.

Applications of Microlens Array Homogenizers

1. Laser  surface treatment

High quality in laser surface treatment requires strict adherence to precision and consistent operations. A microlens array homogeniser spreads the intensity of the laser beam across the whole beam to prevent defects, enhancing surface treatment performance.

2. Medical Aesthetic Applications

Medical systems that remove tattoos and blemishes need uniform beam distribution to ensure safe and effective treatments.

3. Lithography

Modern semiconductor manufacturing through lithography requires uniform profiles to achieve high-quality processing results. A microlens array homogeniser is an essential component in some of these lithography techniques.

Integration With Optical Components

Microlens array homogenisers are frequently used with various optical elements to achieve better performance. Key components include:

1. Diffractive Optical Element Design

When absolute precision is needed, diffractive optical elements (DOEs) are used as the lenses in a microlens array. Valid for moderate NA micro lenses, diffractive MLAs have no tolerances on angles or ROC, making them perfect for precise UV laser homogenization.

2. Beam Expander

While a micro lens array homogenizer generates a homogeneous light source of fixed angular size, the homogenization quality depends on the number of micro lenses covered by the beam.   An adjustable beam expander that changes the laser beam diameter is often required.

3. Lens Systems

A combination of focusing lenses and collimators functions as a lens system to redirect and refocus the beam during both microlens array homogeniser operation stages. These lenses manage focal length aperture and diffraction effects.

Conclusion

The microlens array homogeniser is a crucial optical tool for smoothing laser beams for industrial and medical applications. Combining DOEs with beam expanders and advanced lens systems makes these homogenisers more compelling when considering laser system performance. Modern optical systems depend on these precision-managing devices for their light management capabilities.

FAQs

What is the difference between a microlens array homogenizer and a traditional lens?

A traditional lens’s primary function is to focus light, while a microlens array homogeniser achieves uniform light distribution through light redistribution. This technology is superior to standard lenses when homogeneity requirements exist in applications.

Can a microlens array homogenizer be used with any laser?

Excimer lasers’ precise requirements and those of other lasers make them ideal candidates for working with diffractive microlens array homogenisers. Users must make specific changes according to the beam profile and wavelength specifications.

How does focal length affect the performance of a microlens array homogenizer?

The angle of divergence generate by the MLA is determined by the micro lenses focal length and aperture size. Selecting the correct focal length remains essential to realizing the intended beam homogenisation results.