Liquid Crystal Variable Attenuator/High Contrast Optical Shutter

• Company: Meadowlark Optics Inc.
• Type: Other
• Diameter / Dimension: 5mm - 76.2mm
• Applications: Astronomy, Biomedical/Medical, Communications, Industrial, Military, Scientific Research, Other
• Contrast Ratio: 500:1 at single wavelength
• Wavefront Distortion: ≤ λ/4 (at 632.8 nm)
• Surface Quality: 40 - 20 scratch‐dig
• Beam Deviation: ≤ 2 arc min
• Reflectance: ≤ 0.5% at normal incidence

Meadowlark Optics’ Liquid Crystal Variable Attenuator (LCVA) offers real‐time, continuous control of light intensity. Our attenuator consists of an LC Variable Retarder (with attached compensator) operating between crossed linear polarizers. With crossed polarizers, light transmission is maximized by applying the correct voltage to achieve half‐wave retardance from the LC cell. Half‐wave operation rotates the incoming polarization direction by 90°, so that light is passed by the second polarizer. Minimum transmission is obtained with the retarder operating at zero (or a whole number of) waves.

Transmission decreases as the applied AC voltage amplitude increases (half‐ to zero‐waves retardance). The relationship between transmittance T and retardance (in degrees) for crossed polarizer configuration is given by: T(Θ) = 1/2 [1 ‐ cos(Θ)] Tmax where Tmax is the maximum transmittance when retardance is exactly one‐half wave (or 180°).