ADC Designs

Simple Counter-Rotating Prisms (Risley Prism)

• A pair of identical crossed prisms will produce a dispersion compensation of zero up to a maximum set by prism angle and distance from focal plane.
• Advantages: Simple.
• Disadvantages: Variable angle of input beam moves pupil around ; must be located far from focal plane to minimize this.

Crossed Pairs of Amici Prisms

• A more sophisticated design ( same fig ) replaces the simple prisms with Amici prisms.
• Advantages: Zero-deviation; compact.
• Disadvantages: Wavelength coverage is set by properties of contrasting glass types; typically very poor transmission in UV.

Linear ADC

• A pair of identical prisms with variable separation has the effect of translating input beams (and hence images) of different wavelength.
• Advantages: Fused Silica can be used (available, good optical/UV transmission)
• Disadvantages: Not very compact