There are many applications for range
finders (
Wiki)
such as: photography (to adjust the lens focus), golf (to determine
what club to use), military (adjust weapon for range and target
designation), rifle scope graticule (known height) etc.
Radar, Sonar & Optical Pulse
These are "time of flight" systems
where the round trip propagation time is measured and divided by twice
the propagation velocity.
Optical
The oldest optical system is based on
the concept of
stadia. The idea is
that you can determine distance by measuring the included angle of an
object of known height.
Examples:
K&E 76 0000 Alidade,
Leitz 115A transit
Another system is based on the "split image" that's made to align by
rotating a mirror. The difference in angle between the two
mirrors can be solved based on their separation into the range.
This is the method used by "rangefinder" cameras and the military
rangefinders that look like a drain pipe as well is civilian
rangefinders like the hand held
Edscorp Field Range Finder.
Image property range finders are used in modern digital cameras.
One way these work is to look at the image contrast as the lens is set
a various focal lengths. The highest contrast image is deemed to
be the best focused.
Time of flight is used in modern digital optical range finders like the
Busshnell golf binoculars and the Laser Technology Criterion
units. These typically have one lens for the outgoing pulse of IR
light and a separate lens to focus the light on a fast photo sensor.
Bushnell Golf Yardage Pro 400 Binoculars
One objective lens is for the IR
transmitter and the other is for the IR receiver. There is a
small visual telescope in the center that's for the operator to observe
where the spot is pointing. The two large lens are black in
color,
not clear like optical
binoculars. The
range is displayed in units of either meters or yards, a little to
coarse for
surveying.
Laser Technology Criterion
This is the model 400 that includes tree measuring functions. The
range is displayed in 1/100 of a meter, i.e. a cm which is less than
1/2" so are excellent for surveying. In fact part of the set is a
fork mount that fits a standard surveying tripod.
Operation
After power on you will see one of the top menus. Use the up or
down arrows to scroll to the desired menu. In my case they are:
TREE
CONDUCTOR CLEARANCE
SURVEY
SYSTEM
TREE
Once you have selected the appropriate top menu press the ENTER button.
For Example:
POWER (on)
<down>
<down> i.e. SURVEY
ENTER i.e. BASIC MEASUREMENTS
ENTER display is:
HD:-------.-- M
AZ:------.- DEG
<press trigger>
display blanks change into data and pressing up or down scroll arrow
shows more data like inclination, slope distance, etc.
When in Survey measurement mode and the trigger is pressed you hear a
buzzing sound as the laser range finder and other sensors are
working. When aimed at a wall about 4 feet away the spot size as
viewed using the
PAS-6 IR scope is about an
inch high and half an inch wide.