Thank you for reply,
Dear, the sensor should sense distance of min. 1 milimeter and max 4 meter or max 4m meter not necessary 1 meter max is ok.
As .....pulse laser with some finite time and and detect the counts for known distance for finite period then you can use the same logic for change in distance.... Good Luck
... distance measurement where reflective target movement time is greater than the detection time where detector and reflective target must be in single direction and beam receive path must be maintained ...