MEMS Spatial Light Modulator Demonstrator

MEMS Spatial Light Modulators (SLMs) are used to modulate the entire cross section of an incident beam of light simultaneously with high spatial resolution. Usually, MEMS thin film technology is used to fabricate an array of micromirrors on top of a CMOS backplane. Each mirror can be addressed and moved individually to control either intensity or phase of one pixel. SLMs are used in a range of applications from video projectors to Adaptive Optics (astronomy, ophthalmology) and mask writers in the semiconductor industry. Contrary to the digitally addressed SLMs in projectors that use time multiplexing to generate grey levels, the SLMs developed by Fraunhofer IPMS are addressed with analogue voltages that enable the chip to directly generate analogue intensities. Micronic Laser Systems ABs mask writers exploit this feature to shift the generated patterns with accuracies far smaller than the system’s pixel resolution. The mirrors of the Fraunhofer IPMS device are specified for monochromatic light between 248 nm up to 520nm, enabling not only the use of the DUV excimer wavelengths, but also the less aggressive (and less costly) near UV light sources. One example where the mirrors could be used is pattern generation for printed circuit boards, but also other areas that require a combination of both, high resolution as well as throughput. The SLM is capable of addressing 1 million pixels at a framerate of 2 kHz (that is, 2 Gpixel/s). The demonstrator setup visualizes the function of the SLM. A green LED generates a light beam, lenses and mirrors guide the light onto the SLM, where it is modulated.