can direction be detected ?

Hello

I have a disk that goes foward and backwards ....
I wonder if there is any way I can know the direction that disk is going.
The main problem may be is that I can not touch that disk in any way .....

I have seen some kind of laser speedometer that pointing something is turning can
detect it's speed ... may be something like that ?

Thanks to all

Does the disk move forward or backward (displacement) or does it rotate?
If moving, how rapidly (m/s)? How far from the measuring station is the disk, and what size is it?

If displacement is reasonably rapid, then the Doppler effect for reflected sound waves could possibly be used to determine both the disk velocity and direction of displacement.

You are right the disk does not move. The disk rotates foward and backwards.

Have you ever seen a mechanical watch ? Those watches have an small wheel that rotates foward and backwards.
That wheel is called 'balance wheel'. I need to know that wheel direction. The speed is between 100 to 200 milli seconds
each rotation....
size ... from 5 to 12 milimeters
the distance to the measuring device can be as close as 10 milimeters but not closer

Choose the right tool for the job! If you have access to a PC with a video camera, then a frame-by-frame analysis would tell you the rotational rate and direction.

One option is to add a quadrature encoder to the device.

This goes over the programing part of an encoder, it works this way regardless of the mechanics of the encoder .

For mechanics it really depends on the rest of the device to determine the best methods to go about it.

sivi1234:
You are right the disk does not move. The disk rotates foward and backwards.

Have you ever seen a mechanical watch ? Those watches have an small wheel that rotates foward and backwards.
That wheel is called 'balance wheel'. I need to know that wheel direction. The speed is between 100 to 200 milli seconds
each rotation....
size ... from 5 to 12 milimeters
the distance to the measuring device can be as close as 10 milimeters but not closer

How promptly do you need to know the direction? How much latency in detecting a
change in direction can you tolerate?