Liquid crystal tunable filter

LCTFs enable high image quality and allowing relatively easy integration with regard to optical system design and software control.

However, they emit lower peak transmission values in comparison with conventional fixed-wavelength optical filters due to the use of multiple polarizing elements.

[3][4][5] Multiple LCTFs in separate imaging paths can be used in optical designs when the required wavelength range exceeds the capabilities of a single filter, such as in astronomy applications.

Environmental factors that can cause degradation of filters are extended exposure to high heat and humidity, thermal and/or mechanical shock (most, but not all, LCTFs utilize standard window glass as the principal base material), and long-term exposure to high photonic energy such as ultraviolet light which can photobleach some of the materials used to construct the filters.

However, since they rely on the acousto-optic effect of sound waves to diffract and shift the frequency of light, imaging quality is comparatively poor, and the optical design requirements are more stringent.

LCTFs circa 2014 with integrated circuitry for control and power (left), or an older model with a separate electronics controller box and thick, shielded cable (right).