Brandon Hellman

Multi-beam and single-chip LIDAR with discrete beam steering by digital micromirror device

A novel Digital Micromirror Device (DMD) based beam steering enables a single chip Light Detection and Ranging (LIDAR) system for discrete scanning points. We present increasing number of scanning point by using multiple laser diodes for Multi-beam and Single-chip DMD-based LIDAR.

Light recycling beam steering on a DMD lidar

Spatial light modulators (SLMs) that operate in a phase modulation mode enable beam steering with higher diffraction efficiency compared to amplitude modulation mode, thus potentially be used for an efficient beam steering with no moving part. Currently, Twisted Nematic phase SLMs are widely adopted for phase modulation. However, their refresh rate is typically in the range below kilohertz. Recently, a new method for binary and spatial phase modulation using Digital Micromirror Device (DMD) was proposed by a research group in Germany. In the method, complemental self-images of DMD, corresponding to on- and off-pixels, are formed by two auxiliary optics while adding a pi phase shift between two images. The optics function as recycling of light in a coherent manner. The method enables over kilohertz refresh rate and higher diffraction efficiency in binary phase modulation mode to conventional amplitude binary modulation. As alternatives to the binary phase modulation, we propose and experimentally evaluated high-speed beam steering by DMD based on light recycling. In our experiment, with binary phase modulation mode, system output efficiency reaches 8%. It can be doubled to 16% with light recycling method. Efficiency is still low compared to the reported value of 27% without light recycling. To further increase beam efficiency, system loss was analysed.

Single detector imaging lidar by digital micromirror device for large field-of-view and mid-range mapping applications

An imaging lidar system is presented which combines the high speed of a Digital Micromirror Device (DMD) and the higher range of a 1D collimated scanning output. The system employing 1D line object illumination along with DMD placed at focal plane enables flexible optimization of system metrics, such as field of view, angular resolution, maximum range distance and frame rate.

Beam steering by digital micro-mirror device for multi-beam and single-chip lidar

A novel method of beam steering, utilizing a mass-produced Digital Micromirror Device (DMD), enables a reliable single chip Light Detection and Ranging (LIDAR) with a large field of view while having minimum moving components. In the single-chip LIDAR, a short-pulsed laser is fired in a synchronous manner to the micromirrors rotation during the transitional state. Since the pulse duration of the laser pulse is substantially short compared to the transitional time of the mirror rotation, virtually the mirror array is frozen in transition at several discrete points, which forms a programmable and blazed grating. The programmable blazed grating efficiently redirects the pulsed light to a single diffraction order among several while employing time of flight measurement. Previously, with a single 905nm nanosecond laser diode and Si avalanche photo diode, a measurement accuracy and rate of <1 cm and 3.34k points/sec, respectively, was demonstrated over a 1m distance range with 48° full field of view and 10 angular resolution. We have also increased the angular resolution by employing multiple laser diodes and a single DMD chip while maintaining a high measurement rate of 3.34k points/s. In addition, we present a pathway to achieve 0.65° resolution with 60° field of view and 23k points/s measurement rate.

Wide field-of-view and mid-range distance imaging LIDAR by digital micro-mirror device

A Digital Micro-mirror Device enables a fast, wide field-of-view, mid-range distance mapping while minimizing requirements for mechanical scanning components. The optical architecture offers a compact, low-cost solution to an imaging LIDAR with a single detector.

3D visualization of optical ray aberration and its broadcasting to smartphones by ray aberration generator

The ray formalism is critical to understanding light propagation, yet current pedagogy relies on inadequate 2D representations. We present a system in which real light rays are visualized through an optical system by using a collimated laser bundle of light and a fog chamber. Implementation for remote and immersive access is enabled by leveraging a commercially available 3D viewer and gesture-based remote controlling of the tool via bi-directional communication over the Internet.

Images Transfer through Thin Image Guides by Pseudo Phase Conjugation

Image transfer through glass substrates by total internal reflections suffer from a Kaleidoscope-like artifacts which severely limits field of view. A retro-reflector array compensates for the artifact along with all the monochromatic and chromatic aberrations.