A filter device for acquiring a hyperspectral image comprises a filter device frame, an optical filter, and an actuator, configured to control, relative to the frame, a position of the optical filter along a first direction. The optical filter presents continuously variable transmission wavelength along the first direction.

An optical filter includes a first mirror that has a first uniform thickness, a second mirror that has a second uniform thickness, and a spacer that is positioned between the first mirror and the second mirror. The spacer has a variable thickness along a first axis of the optical filter. In some implementations, a thickness profile of the spacer, along the first axis, includes one or more portions that have a non-linear slope with an absolute value that is greater than zero.

Disclosed is a wavelength selection module for a metrology apparatus. The wavelength selection module comprises one or more filter elements being operable to receive an input radiation beam comprising multiple wavelengths to provide selective control of a wavelength characteristic of a corresponding output radiation beam. At least one of said one or more filter elements comprises at least two linear variable filters.

A two-layer hybrid solid wedged etalon was fabricated and combined with a traditional imager to make a compact computational spectrometer. The hybrid wedge was made of Nb.sub.2O.sub.5 and Infrasil 302 and was designed to operate from 0.4-2.4 μm. Initial demonstrations used a CMOS imager and operated from 0.4-0.9 μm with spectral resolutions<30 cm.sup.−1 from single snapshots. The computational spectrometer operates similarly to a spatial Fourier Transform infrared (FTIR) spectrometer with spectral reconstruction using a non-negative least squares fitting algorithm based on analytically computed wavelength response vectors determined from extracted physical thicknesses across the entire two-dimensional wedge. This computational technique resulted in performance and spectral resolutions exceeding those that could be achieved from Fourier techniques. With an additional imaging lenses and translational scanning, the system can be converted into a hyperspectral imager.

An infrared spectrometer for operation in the mid-infrared spectral range is presented, where the spectrometer includes a Bragg-mirror-based spectral filter that is operative for providing an interrogation signal whose spectral content is dispersed along a first direction at a filter aperture. The filter aperture is imaged through a sample by a thermal-imaging camera to create a focused image that is based on the interrogation signal and the absorption characteristics of the sample. As a result, embodiments in accordance with the present disclosure can be smaller, less complex, and less expensive than infrared spectrometers known in the prior art.

A method for producing a spectral gradient filter on a substrate including: providing the substrate with a first surface to be coated; providing a shadow mask that includes a bordered coating area with an edge, wherein the geometry of the shadow mask is adjusted to the desired gradient profile of the gradient filter; creating a masked substrate by fixing the shadow mask on the first substrate surface to be coated in such a way that parts of the substrate surface are covered, but the substrate surface is essentially exposed in the coating area; and carrying out PVD coating so that parts of the shadow mask lie directly on the surface of the substrate so that no vapour migration occurs in the area of these parts during the coating process and the shadow mask is detachably fixed to the substrate so that the shadow mask can be used for several coatings.

Provided is an optical filter including a first filter region including a first layer of a first refractive index and a plurality of first metal nanostructures in the first layer, and a second filter region including a second layer of a second refractive index and a plurality of second metal nanostructures in the second layer, wherein the first refractive index is different from the second refractive index.

Methods, devices and systems for confocal microscopy of human tissues or other samples are described that can be manufactured at a low cost, and are small and portable. One apertureless confocal microscope includes a dispersion element that produces output beams having different spectral components for illumination of a target, such as a tissue. The confocal microscope also includes one or more lenses that receive reflected beams from the target and focus the reflected beams onto a linear variable filter. The linear variable filter is positioned to receive the focused light to allow a particular range of spectral components of light to pass through the linear variable filter that is a function of a spatial location of the focused light incident on the linear variable filter. The described confocal microscopes, among other features and benefits, can greatly facilitate disease diagnosis in medical applications.

A spectrometer and a spectral detection and analysis method implemented by the spectrometer. The spectrometer includes an optical device and a detection device. The optical device includes at least one light filter, each of which including at least two light filtering units, so that the optical device can emit at least two kinds of monochromatic light. The detection device includes at least one detector, each of which comprising at least two detection units facing at least two light filtering units in the corresponding light filter in a one-to-one relationship. The monochromatic light emitted from the light filtering unit is emitted along the direction perpendicular to the direction of the light emitting surface.

A background subtracted spectrometer for airborne infrared radiometry. The background subtracted spectrometer may comprise: a filter array, a detector, and a dewar containing liquid nitrogen. The filter array may be configured to selectively pass different spectral bands of infrared radiation. The filter array may comprise: at least one linear variable filter and a plurality of bandpass filters. The detector may comprise a focal plane array configured to receive the different spectral bands of infrared radiation simultaneously transmitted through the filter array. The detector may generate one or more electrical signals indicative of infrared radiation intensity as a function of wavelength. The filter array may be coupled to the focal plane array of the detector, and the filter array and detector may be conductively cooled by the liquid nitrogen to improve signal-to-noise ratio and spectral measurements. The background subtracted spectrometer preferably lacks a circular variable filter and relay lens.