Optical Dist sensors

[Andrew Dalgleish]

Generating the pattern is pretty easy with a PC and printer, although the   
resolution wouldn't be good enough. If you print it out at some huge   
resolution then reduce it photographically it'd be ok. Any photographer   
could do it for you. Or print it inverse then just use the film negative.

You need at least two sensors anyway (one for cylinder #1 TDC and one for   
angular resolution), so going to 3 or more isn't going to be much dearer.

Using two (or more) "tracks" with quadrature encoding could give you very   
fine angular resolution.
++++++++++++
 --__--__--__ Sensor 1
_--__--__--_ Sensor 2
 -_-_-_-_-_-_ Exclusive OR
++++++++++++
 ---___---___ Sensor 1
_---___---__ Sensor 2
__---___---_ Sensor 3
 -_-_-_-_-_-_ Exclusive OR
++++++++++++
(view this with a fixed-pitch font, eg Courier)

Makes me wonder why I piddled around using counter chips all these years.

Hmm... time to investigate multiple sensor arrays.
I recall seeing a 16-pin DIP with 8 photo-transistors in it years ago.
A British magazine had a kit to store programs, etc. on paper.
Can anyone help my memory?
Regards,
Andrew Dalgleish
Axon Research, Pty Ltd
6 Wallace Ave,
Toorak, VIC
3142
AUSTRALIA
Tel +61-3-9826-5538
Fax +61-3-9824-0083