PhaseView wavefront sensor aligns RGB lasers for picoprojectors

Palaiseau, France--Wavefront sensors are sometimes used in the laser-picoprojector industry to align the three small red-green-blue (RBG) lasers in X, Y, Z, and Ɵ so that they share the same optical axis and focus. Conventional wavefront sensors are based on a microlens array that divides the incoming light beam in smaller beams focused onto a CCD or CMOS camera. PhaseView says it has developed a better kind of wavefront sensor for this job; instead of using an array of microlenses, the technique relies on direct phase extraction from intensity images.

PhaseView says the conventional sensors have limitations in terms of resolution (number of microlenses) and tilt range acceptance (lenslet aperture); in addition, as the intensity image is sampled, these sensor types are restricted to sole use as wavefront sensors and cannot be used also as a laser beam profiler for intensity distribution analysis.

In contrast, PhaseView's wavefront sensor is a standard CCD or CMOS camera that allows real time acquisition of two image planes separated by a short distance along the propagation axis. An algorithm based on transport intensity equations extracts the phase information from the set of intensity images. As a result, says PhaseView, the spatial wavefront resolution is identical to camera resolution, providing a detailed (500 x 500) wavefront map that allows fine tuning of laser beams.

The sensor aperture has a large tilt measurement range (> 20°) because it is not limited by individual microlenses. It simultaneously delivers wavefront and intensity data, meaning that both high resolution wavefront analysis and laser-beam profiling can be done with a single sensor. A defocus measurement repeatability is 0.3 nm helps to accurately determine the optimum beam-waist position.

The company's BeamWave 500 AT sensor has software that displays XYZƟ adjustment parameters and beam-intensity properties in real time. Low- and high-order aberrations are found using Zernike analysis and intensity distribution analyses are done.

For more info, see www.phaseview.com