Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode? Cheers -lev
On January 26, 2022 6:32:09 AM UTC, "David Lanzendörfer" <leviathan@libresilicon.com> wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
dc32 used 2 and got a phase differential which increased accuracy. actually, it was infrared but you get the idea. source is somewhere, uses an ATTINY. mirror not needed, works with any reflective surface. i saw well over a year ago some maker actually used a DVD sensor (taken from a DVD player) which did 2D phase differential, when it produces a circle instead of an oval the 4 readings in 4 quadrants are equal and you have focus. the nice thing is, if the oval is squashed one way you are too close, squashed the other way is too far. l.
You want to use a Position Sensitive Device. Normally this has been used to track an object that has been illiminated by a modulated laser. So Lens-Array -PSD.x PSD.y , Demodulation-Amps for selectable channel (15KHz to ?80KHz) - Analog Flight regulator (Takes also Gyro and Gravity) , Flap Servos to Flaps which control the thrust vector of a laser guided missile. So here you can use the same approach to have laser guided position feedback for a handling controller. PID is enough. Cheers LuJa On January 26, 2022 11:24:18 AM GMT+01:00, lkcl <luke.leighton@gmail.com> wrote:
On January 26, 2022 6:32:09 AM UTC, "David Lanzendörfer" <leviathan@libresilicon.com> wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
dc32 used 2 and got a phase differential which increased accuracy. actually, it was infrared but you get the idea. source is somewhere, uses an ATTINY. mirror not needed, works with any reflective surface.
i saw well over a year ago some maker actually used a DVD sensor (taken from a DVD player) which did 2D phase differential, when it produces a circle instead of an oval the 4 readings in 4 quadrants are equal and you have focus.
the nice thing is, if the oval is squashed one way you are too close, squashed the other way is too far.
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Hi all https://osioptoelectronics.com/technology-corner/frequently-asked-questions/... Hamamatsu produces PSDs. Many photo detectors at CERN are made by Hanamatsu as well as Lead Glass and other photonic stuff. https://www.hamamatsu.com/us/en/index.html There should be something usable. Also a laser can be modulated with different high frequencies and by comparing the phase between these modulated frequencies one can get the time of flight, hence the position. It should be possible to modulate a fiber transmitter for 100km monomode 1310nm fiber with a pulsecode signal and to decode the signal using the receiver of the fiber trx. So fiber trx used are quite cheap. Fiber patch cord also. So it is just a matter of how to control the fiber trx at low level and how to feet a "datastream" to it that will reveal time delays if one xors txdata and rxdata using fast ecl logic and some serdes approach. Cheers Luja On January 26, 2022 7:32:09 AM GMT+01:00, "David Lanzendörfer" <leviathan@libresilicon.com> wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
Cheers -lev
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Hi That's literally what I've been talking about. The idea was to build a primitive PSD from a photo diode... Hmm... But yeah. It's probably better to use a dedicated sensor. I don't have endless budget tho, and the endproduct is supposed to be somewhat affordable, so I'll check and compare prices. Cheers -lev On Wednesday, January 26, 2022 10:45:28 AM WET Ludwig Jaffe wrote:
Hi all
https://osioptoelectronics.com/technology-corner/frequently-asked-questions/ position-sensing-devices.aspx
Hamamatsu produces PSDs. Many photo detectors at CERN are made by Hanamatsu as well as Lead Glass and other photonic stuff.
https://www.hamamatsu.com/us/en/index.html
There should be something usable.
Also a laser can be modulated with different high frequencies and by comparing the phase between these modulated frequencies one can get the time of flight, hence the position. It should be possible to modulate a fiber transmitter for 100km monomode 1310nm fiber with a pulsecode signal and to decode the signal using the receiver of the fiber trx. So fiber trx used are quite cheap. Fiber patch cord also. So it is just a matter of how to control the fiber trx at low level and how to feet a "datastream" to it that will reveal time delays if one xors txdata and rxdata using fast ecl logic and some serdes approach.
Cheers
Luja
On January 26, 2022 7:32:09 AM GMT+01:00, "David Lanzendörfer" <leviathan@libresilicon.com> wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
Cheers -lev
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Hi So... Hamamatsu in general seems to be damn expensive, except for the S12443: https://www.hamamatsu.com/resources/pdf/ssd/s12443_kmpd1137e.pdf For this one I found a component with integrated controller online: https://www.aliexpress.com/item/4000859822629.html I'll ask the vendor for a datasheet, because 30 Euros are the most affordable I've seen so far. Cheers -lev On Wednesday, January 26, 2022 10:56:32 AM WET David Lanzendörfer wrote:
Hi That's literally what I've been talking about. The idea was to build a primitive PSD from a photo diode... Hmm... But yeah. It's probably better to use a dedicated sensor. I don't have endless budget tho, and the endproduct is supposed to be somewhat affordable, so I'll check and compare prices.
Cheers -lev
On Wednesday, January 26, 2022 10:45:28 AM WET Ludwig Jaffe wrote:
Hi all
https://osioptoelectronics.com/technology-corner/frequently-asked-question s/ position-sensing-devices.aspx
Hamamatsu produces PSDs. Many photo detectors at CERN are made by Hanamatsu as well as Lead Glass and other photonic stuff.
https://www.hamamatsu.com/us/en/index.html
There should be something usable.
Also a laser can be modulated with different high frequencies and by comparing the phase between these modulated frequencies one can get the time of flight, hence the position. It should be possible to modulate a fiber transmitter for 100km monomode 1310nm fiber with a pulsecode signal and to decode the signal using the receiver of the fiber trx. So fiber trx used are quite cheap. Fiber patch cord also. So it is just a matter of how to control the fiber trx at low level and how to feet a "datastream" to it that will reveal time delays if one xors txdata and rxdata using fast ecl logic and some serdes approach.
Cheers
Luja
On January 26, 2022 7:32:09 AM GMT+01:00, "David Lanzendörfer"
<leviathan@libresilicon.com> wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
Cheers -lev
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Hello, It is required that the PD gets a beam from the LD and the target simultaneously. Also, there are 2 mechanisms [1] : one depends only on phase interference (this is doable with separate PD and LD). It produces a sinewave-like output that tells the displacement but not the direction of movement. The other relies on that the back-reflected beam from the target passes trough the laser medium before reaching the PD, where it undergoes nonlinear mixing (inside the LD). Its output produces a sawtooth-like waveform, showing both displacement and direction, so it can be fed into a counter, that's we need. Therefore, we'll need an arrrangement where the LD is tapped at both ends, one facing to the target and the other towards the PD (that's what we have with LDs w integrated PD). Regards, Ferenc [1] https://www.spiedigitallibrary.org/journals/optical-engineering/volume-57/is... On 1/26/22 07:32, David Lanzendörfer wrote:
Hi What about just buying a new cheap Chinese laser diode and a photo diode and then putting a mirror onto the lense carrier, which reflects the laser diode beam back to the photo diode next to the laser diode?
Cheers -lev
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participants (4)
-
David Lanzendörfer -
Ferenc Éger -
lkcl -
Ludwig Jaffe