Implementation of LiDAR Autofocusing on Vintage Manual Camera Lenses

Abstract

The rapid transition to modern digital camera systems has rendered many high-quality, manual-focus vintage lenses functionally obsolete, contributing to unnecessary optical waste. This project demonstrates the viability of rehabilitating legacy optics by retrofitting a 1970s Micro-Nikkor 55mm f/3.5 lens with an autonomous, electromechanical autofocus (AF) system. The primary objective was to design a modular, standalone AF actuator costing under $120, utilizing off-the-shelf electronics and accessible FDM 3D printing. Mechanically, the system replaces the original aluminum focus ring with a custom 0.8 MOD geared ring, driven by a high-torque Feetech STS3032 serial bus servo mounted to a custom "hot-swappable" chassis. The control architecture is governed by a Seeed Studio XIAO nRF52840 microcontroller running a custom MicroPython stack. Distance mapping is achieved autonomously via a Benewake TF-Luna LiDAR sensor operating at 100Hz over an I2C bus. To resolve serial bus contention between the 3.3V microcontroller and the 5V servo, a custom half-duplex UART driver was developed utilizing a 74AHCT125N logic buffer gate. The final prototype successfully maps subject distance to multi-turn absolute servo coordinates, proving that high-precision focal translation can be achieved independently of proprietary DSLR communication protocols. While the prototype successfully met torque, precision, and integration constraints , the current iteration utilizes discrete absolute positioning. Future development will incorporate a full Proportional-Integral-Derivative (PID) control loop for fluid subject tracking and explore "Hybrid AF" via DSLR signal interception. This project ultimately establishes an open-source hardware proof-of-concept foundation for upcycling vintage glass into the modern photographic ecosystem.