[SOLVED] Laser range finder problem in measuring

[chippevijaya]

Dear friends,
i am developing a laser range finder. I am sending the pulse with 14W OSRAM pulsed laser and i am sending the 50ns pulse.
my doubt is. the phaser difference between transmitting pulse to receiving pulse would be 6.6ns, but it is not happening. The APD response is going to transimpedance amplifier and then to comparator, at these two stages it is taking more delay, and the delay is varying if distance of target varies.

How can i resolve this...

 

[jiripolivka]

I do not understand what "phaser difference" is, and the value of 6.6 ns relates to time delay. Naturally, as the target distance varies, due to the speed of light the delay varies, too.

Start with an oscilloscope and see what the pulse is at photodiode output, then at the following stages.

 

[chippevijaya]

Thank you for responding,
The time delay between the pulse sending to pulse received is having more delay than required, it is happening by the transimpedance amplifier and comparator, even change in 10ns in resulting wrong distance. how to avoid it?

 

[FvM]

It means your transimpedance amplifier, trigger circuit or photodiode are too slow or the circuit is unsuitable.

 

[keith1200rs]

You need to give a lot more information. There will be time delays in everything - the laser driver, photodiode, transimpedance amplifier etc. You need to define those delays.

Keith

 

[jiripolivka]

Thank you for responding,
The time delay between the pulse sending to pulse received is having more delay than required, it is happening by the transimpedance amplifier and comparator, even change in 10ns in resulting wrong distance. how to avoid it?

As you need to measure the "shorter" delay due to target return and in your receiver the elements cause longer delays, I would suggest to use the same electronics in the reference channel where the photodiode detects the transmitted pulse, the receiving photodiode the returned pulse.
Assuming both channels have the same delay, their output pulses will give the time difference corresponding to the light pulse traveling to the target and back which is the desired output.

Typical pulse electronics introduce longer pulse delays than light traveling through a clear space.