Dynamic focusing using a MEMS mirror in a coherent lidar.

Area of Science:

• Optical Engineering
• Sensing Technology
• Photonics

Background:

• Coherent lidar systems require precise focus for optimal performance.
• Fixed-focus systems struggle to detect targets at varying distances, especially those with low signal strength.
• Dynamic focus adjustment is crucial for enhancing lidar capabilities.

Purpose of the Study:

• To investigate the efficacy of dynamic focus control in coherent lidar systems.
• To compare theoretical predictions with experimental results of a dynamic focus lidar.
• To demonstrate the improvement in signal detection and target visibility.

Main Methods:

• Implementation of a Micro-Electro-Mechanical Systems (MEMS) variable-focus mirror with a fast response time (<200 µs).
• Integration of the MEMS mirror into a coherent lidar system with a 25 mm exit pupil.
• Experimental validation of dynamic focus adjustment from 2.2 m to infinity during intra-scan sweeps.

Main Results:

• Experimental signal strength improvement exceeding 20 dB for near-field targets, aligning with theoretical models.
• Demonstrated ability to dynamically adjust lidar focus on-the-fly within a single raster scan.
• Three-dimensional point clouds revealed previously undetectable targets when dynamic focus was employed.

Conclusions:

• Dynamic focus control using MEMS technology significantly enhances coherent lidar performance.
• The system effectively improves signal-to-noise ratio and target detectability across different ranges.
• This technique offers a viable solution for overcoming limitations of fixed-focus lidar systems.