README: add 10780 info

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Sebastien Bourdeauducq 2019-11-18 14:08:47 +08:00
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* Reference laser: HP 5501B from eBay. Those are exceptionally well-built and documented, making diagnostics and repairs easier.
* Photodetectors: HP 10780 from eBay. With the operating parameters of the prototype, the frequency of the input laser fringes is high enough during the useful portion of the corner cube's trajectory that the 10780's cut-off frequency is not an issue. The advantages of those devices are the built-in polarizers, the alignment aids, and the well-designed relatively fast photodiode amplifiers and detectors.
* Photodetectors: HP 10780 from eBay. With the operating parameters of the prototype, the frequency of the input laser fringes is high enough during the useful portion of the corner cube's trajectory that the 10780's cut-off frequency is not an issue. The advantages of those devices are the built-in polarizers, the alignment aids, and the well-designed relatively fast photodiode amplifiers and detectors. In case a 10780A does need modifications, the schematics are here: http://repairfaq.cis.upenn.edu/Misc/Lasers/hp/hp10780.jpg. The mating connector for the round 4-pin connector on the HP 10780 is extremely rare and expensive; one way to deal with them is to replace them with Chinese "XS9-4" connectors.
* Logic analyzer: Glasgow https://github.com/GlasgowEmbedded/Glasgow (Sigrok + fx2lafw was initially attempted, but abandoned due to USB bugs at high sample rates).
* Interface to the logic analyzer: the "line receiver" part of http://www.repairfaq.org/sam/uMD1/uMD1.htm
* Optics and mounts: eBay or http://www.cdhoptics.com/. Do not order the cheapest mount from DHC as it is particularly bad (e.g. bends when the screw into the optical breadboard is tightened, with obvious results on the optical alignment). Instead, ask for the "high stability" one (GCM-5302M), which is barely more expensive but will save you a lot of frustration.