Originally Posted by honggexjq

hi,the 1mm error is not a strict requirement and if i can make a sample device with a 10mm error,that'll be OK.
I decided to use a sinewave cuz i want to use the phase-shift method to measure the distance.Can you give me some advice if a loose error requirement is allowed?

hi,
Can you post your phase shift measurement circuit.?

Originally Posted by honggexjq

sorry, but now i'm only at the emitting and receiving stage,and haven't reached the following phase-detect stage yet.Anyway,the basic idea is to measure the phase shift between the emitted sine wave and the received sine wave.As you can see,my first mission is to produce a sine wave and then capture an acceptable sine wave

hi,
OK.
How do you plan to construct the TX module.?
Is the TX module going to be moving or stationary?

Also can you say what the target that reflects the laser beam will be.

Originally Posted by honggexjq

TX module is stationary and the target is some plant.

Hi,
Reason for asking is to determine if the target is 'cooperative'
example: a retro prism or reflector or is it non cooperative.?

I'm not sure what you mean by 'plant', in English that could mean a piece of equipment??

Originally Posted by ericgibbs

Hi,
Reason for asking is to determine if the target is 'cooperative'
example: a retro prism or reflector or is it non cooperative.?

I'm not sure what you mean by 'plant', in English that could mean a piece of equipment??

haha,sorry for my poor english.By saying plant i mean those with leaves,like grass.So it's non cooperative.
maybe someday i should practice my english with a native like you

Originally Posted by honggexjq

haha,sorry for my poor english.By saying plant i mean those with leaves,like grass.So it's non cooperative.
maybe someday i should practice my english with a native like you

hi,
Your English is just fine.

A point to note is that when working with non cooperative targets, the strength of the echo signal can effect the apparent range.

This is partly due to the rise times of the receiver circuits.

If you examine the response curves for your receiver amplifiers you will see that for low signal levels the 'time' response is not linear.

This means that strong echo's appear to have a shorter overall response time which makes the measured distance shorter.

Do you follow.?