toc1955's video: Wavelength Measurement with a Homemade Motorized Michelson Interferometer

(Adolf Cortel, August 2020). The video shows how the wavelengths of several lasers can be measured with a homemade interferometer with a movable mirror. One of the mirrors is mounted on a stage with a micrometer which is displaced by a motor with a big reduction. If interested in this setup, I described it in another youtube video: https://www.youtube.com/watch?v=HThoFYb4jXY I bought the motor in amazon (DC, 12 V 6 RPM) and I added further reduction (1:35.4) with a gear “box” made of pulleys and belts of the type used in 3D printers. Several calibrations showed that the stage is displaced 0,0018003 mm/s, which means and increase/decrease of the optical path of 3.600 micrometers/second. Instead of counting the number of individual fringes corresponding to a total displacement of the mirror measured with the micrometer, the value of the wavelength is deduced in a very fast way by using a Vernier sensor of light placed in the screen to capture the movement of the fringes. With a simpler Labview vi the Fourier Transform of the captured light signal gives the fringes displaced per second, and from the calibrated speed of the stage (3.600 micrometers/s) the wavelength is deduced. Avoiding vibrations is essential and everything has to be “cushioned” using the proper absorber; soft and spongy fabric works fine. The values of the wavelengths are within a 2% of the nominal value. The music is the nice song “Al final tot anirà bé” by Dr. Prats, which has been very popular in Catalonia during the confinement months. I'm using it without having rights only for the educational purposes to which this video is aimed.