Robots and drones are presently in the industry’s focus to serve a critical role in Industry 4.0 and the Transportation Revolution. Integration of robots and drones in these areas improves efficiency and safety, adds flexibility in operation, and reduces operating costs. However, they are still far from achieving the optimal performance needed to execute autonomous tasks at high levels. As these platforms are battery operated, all sub-systems that augment their capabilities must be low-power solutions. In the case of airborne drones, it is also critical that solutions are ultra-light weight and of small form factor. Additionally, robots will be employed in the modern working environment in tandem with humans, but adequate human-robot interaction and intention communication solutions do not currently exist. Consequently, MEMS mirrors-based sensing and interaction systems designed for robots and drones are essential as they offer solutions with the lowest power consumption, weight, and cost in high volume. However, existing MEMS Mirror based solutions have not achieved the necessary compactness and efficiency for robotics. In this paper we describe and demonstrate MEMS Mirror-based 3D perception sensing (SyMPL 3D Lidar) and animated visual messaging (Vector Graphics Laser Projection with Playzer) systems optimized for robots and drones. These sub systems each consume <1W in power, at least 10x lower than other solutions in the market, weigh <50g, and have small form factors. Furthermore, we will show that combining these two systems leads to new capabilities and functionalities that meet the demands of robot vision and human-robot interaction.
LiDAR systems in applications such as autonomous mobile robots, drones, vehicles, and other commercial applications that demand compact, low-cost, and dynamic scanning will inevitably turn to MEMS mirrors as the beam-steering component. Beam scanning-based LiDAR architectures have a significant advantage as the full power and attention of the sensor is given sequentially to each point (voxel) in the scan. Competitive LiDAR designs typically utilize scanning and are differentiated by their scanning architecture and the specific hardware utilized, with the general goal of moving away from bulky mechanical and motor-based systems and toward compact silicon-based MEMS technology.
Both single-axis and dual-axis MEMS mirrors are employed to enable two-dimensional (2D LiDAR) and three dimensional (3D LiDAR) point cloud sensing, respectively. The underlying time-of-flight sensor can be generic – a laser rangefinder or single-point LiDAR, with any typical wavelength or sensing method (pulsed ToF, AMCW, FMCW, etc.). The sensor is arranged with scanning elements which brings forth challenging trade-offs, discussed here. Architectures differ in whether transmitter and receiver are arranged coaxially or biaxially, each with its advantages and disadvantages. We present a hybrid architecture, Synchronized MEMS Pair LiDAR (SyMPL), which simplifies the coaxial design significantly and increases its efficiency by removing any beam splitting components or beam dumps. Multiple prototype LiDARs are compared and evaluated on the basis of SNR, scan speed, robustness to shock and vibration, eye safety, and resilience to mutual interference and echo signals. The work discusses the varying impacts on manufacturing and cost for applications demanding large volumes of LiDAR systems.
An updated Programmable Light System (PLS) is demonstrated using a MEMS Mirror Module (MMM), allowing users to program the brightness and shape of a projected white light in a variety of dynamic solid-state lighting applications, e.g. in automotive dynamic headlights. The MMM is a new module which consists of a fast beam steering MEMS mirror with high optical laser power handling and a smart MEMS Driver with real time monitoring of the MEMS mirror for better system safety and mirror control. The PLS consists of the MMM, a multi-Watt 445-450nm laser source with beam shaping optics, a phosphor target, and projection optics to project a white light within the field of view of up to 60°. Devices such as the 1.2mm diameter A3I12.2 and 2.0mm diameter A7M20.1 aluminum coated mirror have been tested at >8W of CW power before seeing any damage to the device. The A7M20.1 MEMS mirror has been extensively tested (>100 hours) with 4W of CW power at room temperature with no physical damage. Same 4W operation, has also been successfully tested at elevated environmental temperature of 100°C during extended tests.
PLS prototypes to date utilize only ~1W-2W laser diode sources, as limited by power of available laser diodes. The extended tests and thermal studies of the MMM however show that operation at up to 100°C with e.g. 4W CW power could be safely run for at least 10000 hours, even with MEMS mirrors with a simple aluminum coating (no protection or enhancement layers).
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