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'[OT]: "Lasers again" distance measurement + extre'
2001\02\07@122235 by jamesnewton

face picon face
Audio Tone Generator -> Modulates output of RF VCO -> Linear AMP ->
Directional Antenna pointed at offending car -> Car Radio -> Car Speakers ->
Air in the Car -> Car Windows -> Laser Inferiometer mounted with Antenna ->
Audio Amp -> PLL -> Logic Inverter -> Ramp Wave Integrator -> VCO Frequency
Input.

If the Jerk is listening to his radio, he hears a loud "WELP" then a very
loud tone. Then you flip a switch that holds the VCO Frequency Input and
switches from the Tone Generator to a MIC and you say... "THIS IS THE VOICE
OF GOD, DON'T EVER DO THAT AGAIN"

---
James Newton spam_OUTjamesnewtonTakeThisOuTspamgeocities.com 1-619-652-0593


{Original Message removed}

2001\02\07@141823 by David VanHorn

flavicon
face
>
>This is what Like Dave VanHorn said:
>
>         "You simply mix the received light with the transmitted light.
>         Dark means out of phase, bright means in-phase."
>
>I must agree with him but I agree with you too. You can easily modulate a
>laser light by controlling the current. This allows you to send pulses by
>connecting the laser to a square wave generator and then it's possible to
>compare the phase between the incoming and transmitted pulse.

You can do both I suppose, modulate the beam with one carrier, and phase
detect that to get distance, then use the interference rate to get speed,
during the interval that the beam is on.


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2001\02\08@040313 by Andy Faulkner

picon face
What is all this phase stuff you keep talking about.

Are you meaning that if you send a square wave
modulation down a lasers beam buy modulation, the
further you get away you get a change in the frequency
of the modulation.




--- David VanHorn <.....dvanhornKILLspamspam@spam@CEDAR.NET> wrote:
{Quote hidden}

=====

Andy Faulkner andyf97spamKILLspamyahoo.com
Pyrosync International http://www.pyrosync.co.uk

Tel +44 778 896  6087.....................UK Dial 0778 896 6087

Fax +44 870 132 3275.....................UK Dial 0870 132 3275
http://www.event-supplies.co.uk http://www.spectacular-fireworks.co.uk


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2001\02\08@054150 by Roman Black

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face
Andy Faulkner wrote:
>
> What is all this phase stuff you keep talking about.
>
> Are you meaning that if you send a square wave
> modulation down a lasers beam buy modulation, the
> further you get away you get a change in the frequency
> of the modulation.

Hi Andy, switch the laser on/off at 1MHz. Sense
the reflected signal with a high gain amp with no phase
shift (someone suggested FM radio chip).
The reflected signal travels twice the distance.
Speed of light delay (time of flight) causes a phase shift
between the transmitted squarewave and received squarewave.

You can simply AND or XOR (etc) the two squarewaves to give
a pwm signal that depends on distance.
Changing the modulated frequency affects the possible
max range of the system.

People have suggested problems with isolating the receiver
amp from the transimtter RF noise. Also sensing phase
using the "hump" of the received signal, not the zero
crossing point. I have a design mostly finished for this
technique for hobby robotics and have learned a bit
from the discussion here so far. Thanks everyone! :o)
-Roman

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