Prism parameters
deg
The two prisms are assumed identical.
Example: BK7 ≈ 1.5168 at 587.6 nm.
m
Used to calculate the expected spot displacement.
0° — maximum deviation
180° — zero
360° — maximum
0.0°
relative prism rotation
Deviation of one prism
—
degrees
Resultant beam deviation
—
degrees
Resultant deviation
—
milliradians
Beam steering direction
—
degrees from the initial beam
Expected spot displacement on screen:
—
Engineering model
δ₀ = asin(n · sin A) − A
δR = √(δ₁² + δ₂² + 2δ₁δ₂ cos θ)
Model: standard 2D Risley vector geometry.
Each prism has the same apex angle and refractive index.
The single-prism deviation is calculated with the
normal-incidence prism relation; the two deviation vectors
are then combined according to their relative rotation θ.
This is an engineering/paraxial model rather than a full
sequential 3D ray trace through both prisms.
Beam geometry
Incident beam
Prism #1
Prism #2
Resultant beam