Development of Laser Driver for Gauge Block Interferometer

Gauge block plays an important role in dimensional metrology as a standard for calibration. There are several techniques to calibrate gauge block, one of which is an optical method, such as, Michelson interferometer. The interference pattern is recorded for gauge block comparison. The stability of light source is important for the calibration. In this work, we developed a reliable constant current control circuit of 7 mW laser diode for the gauge block interferometer with a closed-loop feedback temperature control, which utilized the advantage of an embedded system. A PID controller was used to maintain the temperature at 25.0 °C within ± 0.5 °C of uncertainty. We tested the system for 60 minutes by monitoring the stability of the laser wavelength. The results showed that the wavelength of the laser was unstable during the first 20 minutes before becoming constant at 655.525 nm.