ILiliasam·Mar 12, 2020
> "What is the limiting factor on the precision"
Precision in this project is limited by rise time of the received signal. Meanwhile, this time is limited by rise time of laser's current. It is too long now - 10 ns.
Theoretical TDC resolution is ~13mm per BIN.
You could see real results here: https://github.com/iliasam/OpenTOFLidar/wiki/Resolution-of-t...
> "How did you calculate the appropriate laser lens and standoff"
I can't say that there was too much calculations.
The is some information here: http://www.ti.com/lit/ug/tiduc73b/tiduc73b.pdf (part 2.3.5)
and here: http://www.ti.com/lit/ug/tiducm1b/tiducm1b.pdf (part 2.3.2)
Laser's lens should have maximum possible focal length, but it must not crop light beam from the diode.
Photodiode's lens should have maximum Entrance pupil
> "Is the CS mount lens's focal length important, or is the
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re no need for a sharp image at all distances?"
You need to have sharp image at big distances. At short distances it is not important - light signal is high enough.
> "Why use one CS-mount lens and one M12 lens, rather than two M12 lenses?"
I think that it is easier to find lens with big "Entrance pupil" with CS mount that with M12 mount. Bigger mount - bigger lens diameter, bigger "Entrance pupil".
> "Do you need any sort of dynamic gain"
I don't have any kind of electrical gain control. There is an ability to change APD gain, but I don't use it.
> "optical filtering on the received signal"
I don't have filter in my LIDAR, but it is necessary to have it if you are going to run LIDAR at sunlight.
I give links to a several interference filters in "LidarTotalBOM.xlsx".
> "Did you need much fancy $$$$ test equipment to get the design working".
All that I have is Tektronix TDS540D oscilloscope (bought at the Ebay for $300) and multimeter.