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Multi-conjugate liquid crystal tunable filter

A filter, filter stage technology, applied in the field of optical filters

Inactive Publication Date: 2008-03-05
CHEMIMAGE CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The term "spectral imaging" is understood to include, but not be limited to, exploiting spatially precise wavelengths to resolve two-dimensional images of objects in selected wavelength images

Method used

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  • Multi-conjugate liquid crystal tunable filter
  • Multi-conjugate liquid crystal tunable filter
  • Multi-conjugate liquid crystal tunable filter

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Embodiment Construction

[0041] In some spectral imaging applications it is advantageous for a filter to have very fine resolution and also be robustly tunable. At the same time, there is a need for a strong signal level in the final photoresponsive sensor element, enabling a good signal-to-noise ratio while acquiring relatively fast images. Simultaneously satisfying these objectives is difficult, thus resulting in design compromises. According to one aspect of the present invention, a preferred arrangement is provided for tight bandwidth separation, high transmission rates and tunability to at least one selectable set of wavelength bands. This is achieved by cascading multiple tunable Solc wavelength bandpass filter stages.

[0042] Any one Solc level can have a medium value of precision. Accuracy is the ratio of the free spectral region FSR (that is, the wavelength span between the bandpass peaks) to the full width at half maximum (FWHM, full width measured at half maximum) of the peak bandwidth. ...

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Abstract

A hyper-spectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers forming interference filters. The retarders can include tunable birefringent elements such as liquid crystals controlled in unison, fixed retarders and / or combined tunable and fixed birefringences. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging.

Description

technical field [0001] The present invention relates to optical filters with tunable wavelength passbands for use in hyperspectral imaging. An optimized design is employed to utilize multiple stages to obtain a high filter accuracy ratio while maintaining a high optical power transfer ratio. [0002] The inventive tunable conjugate filter has a plurality of consecutively arranged birefringent filter stages, each stage has several stacked wavelength delay elements. Preferably, each stage of the stacked wavelength delay element has a Solc-type filter structure for that stage. A Solc structure represents an equally birefringent wavelength retarder stacked between polarizers. The wavelength delay elements have a specific rotational relationship with each other. The retarder can be embodied as a liquid crystal tunable birefringent stack element, or by a stack element with a fixed retarder adjacent to the tunable birefringent liquid crystal. In other embodiments, individual reta...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02F1/01
CPCG02F1/13473G01J3/447G02F2203/055G01J3/0224G01J2003/1269G01J3/2823
Inventor 王兴华王晨晖
Owner CHEMIMAGE CORP
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