Methods of autodyne interferometry of the distance by injected current modulation of a semiconductor laser

Background and Objectives: Two methods of distance interferometry for two types of wave modulation of laser radiation have been presented. The methods of triangular and harmonic wave modulation of a signal have been described. The advantages of the triangular wave modulation method in combination with the use of the frequency of the self-mixing signal spectrum, as well as the advantages of the harmonic wave modulation method in combination with the use of the amplitudes of the self-mixing signal spectrum have been shown. Equipment: The equipment includes a frequency-modulated semiconductor self-mixing laser diode RLD-650 on quantum-size structures with a diffraction-limited single spatial mode with the wavelength of 654 nm. Results: A comparative analysis of these methods of measuring the distance to the object has shown the advantages of the harmonic wave modulation of the laser diode at the distance of less than 35 cm, as well as the advantages of the triangular wave modulation method at distances of more than 40 cm. Conclusion: The results of computer simulation have shown that the accuracy of determining the distance at the harmonic wave modulation decreases with increasing the distance to the measured object. However, at small distances, its value is much smaller than at the triangular wave modulation of laser radiation.