Power spectral density (PSD) from LDV data

Hello everyone

Could you please tell me how to calculate PSD from LDV data?

Can you help me to develop a code for this?

Just for details: This paper analyzed PSD from LDV, http://journals.cambridge.org/download.php?file=%2FFLM%2FFLM555%2FS002211200600927Xa.pdf&code=a4ed3ef95163a522329e7a33e0a9df0e

Thanks