hi,
If you want to build a low power pulsed laser to measure from say 0.5mtr thru 10mtr you can do it this way.
At the instant the laser diode is pulsed, set a 74F series monostable, start a fast run down linear voltage ramp.
On receiving the laser echo, reset the TX M/S and start a slow [*100] ramp up to zero volts of the TX ramp down voltage.
From the instant the RX echo pulse is detected start a 15MHz counter and stop the counter when the ramp up reaches 0V.
In the counter chain you have a count proportional to double the distance measured.
By chosing the 15MHz xtal [ speed of light is 300,000,000/sec] the counter chain gives a transit time count of 100* the actual transit time.
If you require more details please ask.