Wedge prism

The term "optical wedge" refers to any shallow angle between two plane surfaces of a window.

Many applications exist for wedge prisms, including laser-beam steering, rangefinding and variable focusing.

When the wedges are rotated to angle in opposite directions, they cancel each other out, and the beam is allowed to pass straight through.

This method is common in aerial or space launch-vehicle photography, when the distance to the object is changing very rapidly.

[2] The wedge prism is primarily used in a similar manner as an angle gauge in variable-radius plot sampling.

Wedge prisms can be difficult to use in wet conditions due to the effect water droplets have on the optical properties of the glass.

The amber provides the same function as the clear wedge prism, only it reduces glare and is easier to use on overcast or cloudy days.

Other tools often used to accompany the wedge prism in taking forest inventory are clinometers, Biltmore sticks, relascopes, and diameter tapes.

Figure 1. View through 10 factor wedge prism of an "IN" tree.
Figure 2. View through 10 factor wedge prism of a "Borderline" tree.
Figure 3. View through 10 factor wedge prism of an "OUT" tree.