About using rp_lock_in_pid for FPGA phase resolution

[Todaycrrc]

hi guys recently I was using your software to go for an experiment and would like to enquire about how to achieve phase resolution of optoelectronic signals through your software. Can you give me some advice? Thank you. I appreciate it.

[marceluda]

It depends on how you used the App to measure the phase.

If you take the value from the web interface then you should know that this value is an indirect measurement. That means that it's not obvious which resolution it has.

The direct measurement of the App are the variables X and Y. they have at least 14 bit resolution... but can be higher, up tu 27 ( https://marceluda.github.io/rp_lock-in_pid/TheApp/instruments/instruments_04_lock-in/ ).

Then tha phase is phi = arctan(- y / x ) ... so, you can think from there what does it mean "resolution" to you after the math...

[Todaycrrc]

I'm sorry for not understanding you too well, as you said on the app we can only discover x and y, if I need to go and calculate phi I don't get it directly from the GUI straight away, so do I need to go and add a maths formula or by calculating it myself, as I've recently been doing interference experiments so I am a bit lost and can't get a good idea correctly. Thanks

[Todaycrrc]

Hello author, my experiment was to go for a digital phase meter for an interferometer, and then I found this software of yours, because I found some parts of your software that can be used directly, I would like to ask how I should improve it to make it happen.

[marceluda]

Sincerely, I don't understand what you are trying to build.

The App itself can be used as a phase meter. Right now it can report to you the phase making the calculation I told you from X and Y.

It probably can be enhanced for that dutty specifically ... but never study that problem in particular.

El jue, 29 feb 2024 a las 4:13, Todaycrrc @.***>) escribió:

Hello author, my experiment was to go for a digital phase meter for an interferometer, and then I found this software of yours, because I found some parts of your software that can be used directly, I would like to ask how I should improve it to make it happen.

— Reply to this email directly, view it on GitHub https://github.com/marceluda/rp_lock-in_pid_h/issues/9#issuecomment-1970540916, or unsubscribe https://github.com/notifications/unsubscribe-auth/ACALCQD3VKDWSDOQ2ZND4YLYV3KIZAVCNFSM6AAAAABD36URFWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSNZQGU2DAOJRGY . You are receiving this because you commented.Message ID: @.***>

[Todaycrrc]

Actually my aim is to go for an optical range difference instrument, but as a first step to get the optical range difference of the 2 sources I need to know their phase difference, so in a single frequency interferometer this can be achieved directly by the maths you mentioned, I mean is it possible to get the arctan function on web gui or do I need to add the code again? thank you.

[Todaycrrc]

Hi, the purpose of my experiment is about Lissajous' curves, the requirement is to use redpitaya which is an fpga development board for the experiment, so I've been thinking about how to get the phase difference and then get the optical distance difference through x, y, and finally calculate the Lissajous' curves, but I'm not very good at it with my poor FPGA skills so I'd like to ask for advice on how to change the code to achieve it.

[marceluda]

I'm still not sure about what you try to do. With the App you can measure any phase difference between the lock-in reference and the signal you measure in X / Y . The web interface lets you see the phase ... in the oscilloscope channel:

https://marceluda.github.io/rp_lock-in_pid/TheApp/instruments/instruments_02_scope/

[Todaycrrc]

My purpose is to complete a project about: Precision demodulation for homodyne interferometer modulated with a combined sinusoidal and triangular signal, so I am thinking about using this GUI to complete the phase difference measurement of two optical signals and the calculation of arctan.

[Todaycrrc]

Recently my project needs to undergo modification due to some issues, initially my idea was to complete the correction of Lissajous' curves in redpitaya 125-14 rather than in MATLAB or labview as I wanted to get a more novel way of completing the measurements of the optical range difference, but I found it very difficult on the 125-14, the Maybe I can only do the optical range difference measurements in redpitaya by phase locking amplification and be aware of the nonlinear relationships, this is giving me a headache, can you provide some help. Can you offer some help.

[Todaycrrc]

Hello.

I recently found this while researching how to implement ellipse fitting in real time, please advise how to go about implementing real time ellipse fitting using FPGAs, this problem has been bothering me for a long time and I have not found a similar code anywhere, I would like to get some help from your side, sorry if I am disturbing you.