Optically Extended MEMS Scanning Transforms Imaging Ladar

Abstract

The scanning range of a MEMS mirror can be increased by adding optics that amplify the scanning angle. This “optical extension ” technique allows miniaturization of 3-D real-time imaging ladar systems to a size that opens up many new applications. Although laser radar (ladar) has been actively pursued by the military and civilian industries for decades, only recently have the techniques of optically extending the scanning range of microelectro-mechanical systems (MEMS) mirrors made miniaturization of 3-D real-time ladar possible. This next-generation 3-D ladar will be highly accurate, economical, eye-safe, and small enough to hold in one’s hand. Today’s scanning 3-D ladar can have greater angular, range, and ultimately better display resolution than alternative imaging techniques. It can be used to “see ” targets that are invisible to other imaging devices and has already found many practical applications. Unlike 1-D ladar, which is currently being used by law enforcement to catch speeders, 3-D imaging ladar is being used for target identification, terrain mapping, 3 D documentation of buildings/objects, robotic navigation, and more. The major barriers to expansion of 3-D real-time ladar are weight and cost-the smallest existing device weighs more than 15 kg and the average cost for 3-D ladar units is about $100,000. 1 real-time digitizer with peak and time-interval analysis algorithm clock (e.g., VCO) electrical pulse generator/driver λ/2 plate polarizing beam splitter λ/4 plate mirror driver MEMS laser Mirror collimating lens (2-axis) focusing lens amplifier photo-detector bandpass filter reflected signal target transmitted signal FIGURE 1. A possible design for a next generation scanning 3-D real-time LADAR device built around a scanning MEMS mirror.