Distance measurement by means of optical interferometry

[ikatz]

Hi,

I have been assigned to a new task in my job where I have to investigate on measuring the distance to an object by means of optical interferometry (Michelson interferometry). I have been looking for info on the subject but have not been really lucky.

I have been able to obtain the confocal signal (mostly Gaussian curve) in the photodiode and with that I might be able to get the distance to the object, but what my bosses really want is to use the interferometric signal to get that distance instead of the confocal. The problem is that I don't understand where does that signal come from, since it has a higher frequency and is mostly noise, so I don't know how am I going to process it to obtain any interesting data from it.

Could somebody explain how should I process this signal or at least provide a link to useful info since I am running out of ideas

Thanks in advance!

 

[berkeman]

Hi,

I have been assigned to a new task in my job where I have to investigate on measuring the distance to an object by means of optical interferometry (Michelson interferometry). I have been looking for info on the subject but have not been really lucky.

I have been able to obtain the confocal signal (mostly Gaussian curve) in the photodiode and with that I might be able to get the distance to the object, but what my bosses really want is to use the interferometric signal to get that distance instead of the confocal. The problem is that I don't understand where does that signal come from, since it has a higher frequency and is mostly noise, so I don't know how am I going to process it to obtain any interesting data from it.

Could somebody explain how should I process this signal or at least provide a link to useful info since I am running out of ideas

Thanks in advance!

AFAIK, you can only use laser interferometry for relative distance measurements (like changes in distance). HP used to make some of the instrumentation for that:

http://www.vaisala.com/files/HP_Laser_Interferometers.pdf

.

 

[ikatz]

Thanks for answering so soon. In my scenario the HW architecture is already built, it is similar to the Michelson Interferometer but instead of having a movable mirror we will eventually have an object.

So, depending on the distance to that object I will get a signal composed by the confocal signal and the interferometric signal, but I do not understand what is the source of the latter one, since I thought that it should have the same frequency the confocal signal has.

A workmate has told me that he thinks I should process the interferometric signal in order to obtain a senoidal signal, but my results show a signal that is hardly senoidal...