Diffractive optical elements (DOE) use a microstructure surface relief profile for their optical function. A DOE transmits light that can be reshaped to nearly any desired distribution. The DOE encodes the shape of the desired intensity pattern and maintains other parameters of the light source.
DOEs have design flexibility, which lets them have optical functions that can otherwise not be achieved at all. In addition, compared to refractive optical elements, DOES are often thinner and lighter, making them ideal replacements in some applications. This article explores the various kinds of diffractive optics solutions and their functions:
Diffractive Beam Splitter
This type of diffractive optical element works by splitting the incident laser beam into a 1-dimensional or 2-dimensional array of beams. Often, it is used in combination with a focusing lens. In this application, the output beam array becomes an array of focused spots at a particular distance behind the lens. Applications of diffractive beam splitters include multi-focal microscopy, multi-channel splitting for 1D or 2D sensors, camera calibration, and others.
Diffractive Pattern Generators
Diffractive optics allows the creation of complex patterns that have a very high depth of field. The pattern is composed of a lot of spots that may overlap. The high accuracy of the microstructures makes the diffraction angles to be quite precise, particularly when using a frequency stabilized laser source. A diffractive pattern generator is used for structured light and pattern projection for 3D sensing applications. Also, it can be used for graphics, range, and chart projection for alignment and measurements.
Diffractive Beam Shapers
These DOEs are particularly useful in laser machining, automated wafer inspection, and laser eye surgery. They convert an input beam with a known intensity profile to a beam with a different defined output intensity distribution. Diffractive beam shapers normally change a typical Gaussian beam from a laser into a circular or square flat-top beam. They are often used in laser material processing, biomedical devices, and lithography.
Diffractive diffusers can be found in different applications like LIAR and face recognition. Usually, they are a vital element in displays, time-of-flight, and diffuse- and structured-light systems. These DOEs have surface relief structures configured to diffract light. They are designed using sophisticated simulation algorithms to generate certain patterns and intensity profiles. They can be customized to generate any speckle-free pattern with nearly any intensity profile and field-of-view. Developers can make different light distributions for the application wavelength.