I'm interested in building my own laser doppler vibrometer using laser diodes. The reason I mention laser diodes is because (1) I want it to be cheap and (2) I want to incorporate it into robotics projects. However, I'm unsure if it's possible to build something that satisfies my requirements for reasonably cheap (say, the components of such an LDV would cost < 500 USD). Specifically, I am trying to measure vibrations that have a frequency of 1 MHz – I am not trying to build a general-purpose measurement device, as most commercial LDV devices are. I was thinking of using self-mixing laser interferometry with a laser diode, but the research I've read seems to indicate that such self-mixing laser diode systems don't get anywhere close to 1 MHz. Is it possible to build such a reasonably cheap device? And, if so, how? I would greatly appreciate any references to research papers.
EDIT: I also read this Reddit thread from 8 years ago, where the OP seems to be trying to build their own LDV.
EDIT2: The distance the LDV would have to operate is very short (say, 1 meter or less).