Microlens array is an array composed of lenses with micron-scale optical aperture and relief depth. Like the traditional lens, the smallest functional unit can also be a spherical mirror, an aspherical mirror, a cylindrical mirror, a prism, etc. It can also realize focusing, imaging, beam transformation and other functions in the micro-optical angle. Moreover, because of its small unit size and high integration, it can form many new optical systems and complete functions that traditional optical elements cannot complete.

The microlens array can be divided into refractive microlens array and diffractive microlens array. 1、

Refractive (ROE) microlens array;

Based on the refraction principle of geometric optics, light will bend to the high refractive index region at the junction of two transparent media (such as air and glass). The higher the refractive index of the material, the stronger the refraction ability of the incident light. Through this principle, a complete laser wavefront is divided into many tiny parts in space, and each part is focused on the focal plane by a corresponding small lens, and the light spots overlap, thus homogenizing the light in a specific area and shaping the laser beam accurately. Its applications mainly include spot shaping and beam conversion.

2. Diffractive microlens array;

Based on the diffraction principle of physical optics, light is modulated by the surface relief structure of lens array to change the wavefront phase, thus realizing the modulation and transformation of light waves. After the laser passes through each diffraction unit, it diffracts and interferes at a certain distance (usually infinity or lens focal plane), forming a specific light intensity distribution.

It is mainly used in optical communication, medical beauty and other fields to solve the problems of high-order aberration correction and spot shape modulation with arbitrary light distribution. According to different uses, DOE can usually be divided into beam shaping, beam splitting, structured light, multifocal and other special beam generation.

Use restrictions:

1) diffractive optical elements are sensitive to the angle of incident light, which requires good optical path adjustment accuracy and stability;

2) Most diffractive optical elements precisely control the wavefront phase of the incident laser, so other elements in the optical path, such as reflective/transmissive lenses and lenses, should use devices with high precision and low wave difference, otherwise the final effect will be affected.