Patent Description:
Hyperspectral imaging involves the acquisition of a three dimensional datacube of a scene, collecting intensity through one spectral and two spatial domains. The datacube is in the format I(x,y,λ). Each slice of the data cube comprises an xy image corresponding with a particular wavelength of light. Conventional hyperspectral imagers rely on two main capture methods: capture of a datacube using a scanning 2D sensor, or spatially multiplexing spectral information to be retrieved after post processing. Scanning imagers are limited in orientation and must scan (hence the name), which is a process that takes considerable time and introduces motion artefacts. Multiplexing imagers largely avoid errors introduced by scanning, but require significant sacrifice of spatial information or complex sensors to achieve hyperspectral imaging. Multiplexing imagers are limited in resolution and or are difficult to manufacture.

In order to achieve a single-shot hyperspectral capture and to circumvent the resolution sacrifice of multiplexing spectrometers, algorithmic imaging approaches have been trialled. The most notable examples has been the Coded Aperture Snapshot Spectral Imager (CASSI) and its variants. CASSI relies on compressed sensing - a signal processing framework for reconstructing underdetermined linear systems. By manipulating an incoming signal into a format viable for a compressed sensing reconstruction, CASSI can reconstruct a hyperspectral datacube from a signal obtained from a single exposure of a conventional two-dimensional detector. However, whilst CASSI achieves single shot imaging without significant sacrifice of spatial resolution nor complex multiplexing, it can only capture datacubes at limited resolution with occasional artefacts.

<CIT> discloses an imaging system that uses a dynamically varying coded mask to time-encode multiple degrees of freedom of a light field in parallel and a detector and process to decode the encoded information.

<NPL> discloses a DMD based hyperspectral imaging system in which the DMD is configured to scan an effective entrance slit for a spectrometer in order to achieve hyperspectral imaging.

<CIT> discloses a single shot spectral imager or imaging system which acquires multiplexed spatial and spectral data in a single snapshot with high optical collection efficiency and with the speed limited only by the readout time of the detector circuitry. The imager uses dispersive optics together with spatial light modulators to encode a mathematical transform onto the acquired spatial-spectral data. A multitude of encoded images is recorded simultaneously on a focal plane array and subsequently decoded to produce a spectral/spatial hypercube
It is an object of the present disclosure to overcome or at least ameliorate the shortcomings associated with known hyperspectral imaging devices and hyperspectral imaging methods.

According to a first aspect of the present disclosure there is provided a hyperspectral imaging device, as defined by independent claim <NUM>.

The imaging device may be configured to obtain the datacube from a single shot (e.g. one frame of data from the first and second array detectors). In some embodiments the imaging device may be configured to obtain the datacube from more than one shot (for example, from two shots, three shots or more).

The provision of more than one encoding pattern in the detected light fields enables a tomographic reconstruction of the original hyperspectral datacube thereby enhacing fidelity over approaches in which a data is captured based on a single encoding pattern.

In some embodiments, more than two encoded light fields may be provided and detected, for example, there may be four different encoded light fields (and each may have a different encoding).

The encoder may be arranged to provide spatially separated first and second encoded light fields.

The first and second light fields may comprise complementary spatial patterns (whether the first and second encoded light fields are spatially or temporally separated). The complementary spatial patterns may be complementary random or pseudorandom spatial patterns.

The encoder may be configured to reflect the first and second encoded light fields in different directions.

Some embodiments may combine spatial and temporal separation of encoded light fields, detecting both temporally and spatially separated encoded light fields (e.g. by a reconfigurable encoder that provides spatially separated first and second light fields, and collecting more than one shot from the detectors, with different encoder patterns).

Advantageously, the generation of first and second copies of the light field which are encoded with complementary spatial patterns and separately sheared prior to detection provides for greater fidelity in the datacube reconstruction. This is analogous to tomography whereby the first and second copies effectively correspond to projections of the datacube along different directions, thereby providing additional information about the datacube than if only a single sheared and encoded copy were used. The combination of encoding and shearing with detection of two or more copies may be referred to as compressive tomography.

The at least one dispersive element comprises a first dispersive element configured to apply a first spectral shear to the first encoded light field, and a second dispersive element configured to apply a second spectral shear to the second encoded light field.

The at least one dispersive element may be or comprise a transmissive dispersive element. One or both of the first and second dispersive elements may be a transmissive dispersive element.

The first and second spectral shears may have different magnitudes.

The first and second spectral shears may have different spatial directions.

The encoder may comprise a digital micromirror device, a static mask, a liquid crystal device (e.g. liquid crystal on silicon).

The encoder may be or comprise a transmissive encoder. The encoder and the at least one dispersive element may both be transmissive. Using transmissive components may enable easier miniaturisation of the hyperspectral imaging device, and in particular when performing compressive tomography.

The encoder may comprise a first encoder portion configured to provide the first encoded light field and a second encoder portion configured to provide the second encoded light field. The first and second encoder portions may be disposed on or along respective first and second discrete imaging paths. The first and second discrete imaging paths may be parallel to one another. Discrete imaging paths may remove the need for reflective elements such as a beam splitter, which may further enable easier miniaturisation of the hyperspectral imaging device.

The first and second dispersive elements may be disposed on the respective first and second discrete imaging paths.

The hyperspectral imaging device may further comprise a spectral encoder configured to spectrally encode the first and second sheared light fields prior to detection by the at least one array detector. This allows the hyperspectral imaging device to encode in both the spatial and spectral domains. This provides an additional degree of freedom in encoding, which may allow for a higher degree of incoherence (randomness) in the sampling of the datacube and in turn may improve reconstruction of the datacube.

The spectral encoder may comprise a first spectral encoder portion configured to spectrally encode the first sheared light field, and a second spectral encoder portion configured to spectrally encode the second sheared light field. The first and second spectral encoder portions may be disposed on or along the respective first and second discrete imaging paths. The spectral encoder may be a transmissive encoder.

The at least one array detector may comprise a first and second array detector, respectively arranged to detect the first and second sheared light fields.

The hyperspectral imaging device further comprises a a third array detector. A beam beam splitter may be arranged between the input and the encoder to provide a portion of the light field to the third array detector and the remaining portion of the light field to the encoder.

The portion of the light field provided to the third array detector is unsheared (or spectrally undispersed).

The hyperspectral imaging device may further comprise a focussing or relay element located between the input and the encoder.

The focussing element may be arranged to image the scene onto the encoder.

At least one of the dispersive elements may comprise a concave grating.

The at least one dispersive element may comprise a combination of a focussing element (e.g. refractive or reflective) and a planar grating. The planar grating may comprises a transmissive grating, double Amici prism etc..

The at least one dispersive element may be arranged to image the first and second sheared light fields onto the at least one array detector respectively. For example, the first and second dispersive element may be configured to respectively image the first and second sheared light fields on the first and second array detectors.

The encoder and the at least one dispersive element may be integrated into a single component. The single component may be configured to provide first and second light fields which are both encoded and sheared. This may further enable easier miniaturisation of the hyperspectral imaging device.

The integrated encoder and at least one dispersive element may comprise an encoding pattern disposed on the at least one dispersive element. The at least one dispersive element may be a diffraction grating. The encoding pattern may be lithographically printed onto the at least one dispersive element.

The processor may be arranged to determine the datacube by solving a minimization problem.

The minimization problem may comprise a regularizer that promotes sparsity.

The processor is arranged to process an output from the third detector jointly with the outputs from the first and second detectors to determine the datacube. The processor may be arranged to solve a minimization problem of the form: <MAT> where S<NUM> is the signal detected by the first detector, S<NUM> is the signal detected by the second detector, S<NUM> is the signal detected by the third detector, k<NUM>, k<NUM> and k<NUM> are weighting factors, o<NUM>, o<NUM> and o<NUM> are measurement operators dependent on the encoder, the first and second dispersive elements and the beam splitter, φ(I) is a regularizer that promotes sparsity, α is a regularization paramter, ∥. ∥ denotes the l<NUM> norm and I = I(x,y,λ) is the datacube.

According to a second aspect of the present disclosure there is provided a method of hyperspectral image acquisition, as defined by claim <NUM>, comprising:.

The features (including optional features) of any aspect may be combined with those of any other aspect, as appropriate. The features described with reference to the imaging device of the first aspect may be used in the method of the second aspect (e.g. the method may obtain the datacube from a single shot etc).

Example embodiments will be described, by way of example only, with reference to the drawings, in which:.

It should be noted that the Figures are diagrammatic and not drawn to scale. The same reference signs are generally used to refer to corresponding or similar feature in modified and different embodiments.

<FIG> illustrates a hyperspectral imaging device <NUM>. The hyperspectral imaging device <NUM> is capable of single shot hyperspectral imaging. The hyperspectral imaging device <NUM> comprises an input <NUM> for receiving a light field <NUM> from a scene <NUM>, an encoder <NUM>, first <NUM> and second <NUM> dispersive elements, first <NUM> and second <NUM> array detectors and a processor <NUM>.

The input <NUM> may comprise an aperture (for example, or a slit), and is configured to direct light from the scene toward the encoder <NUM>.

The encoder <NUM> is arranged to receive at least a portion of the light field <NUM> from the input and transform it to provide spatially separated first <NUM> and second <NUM> encoded light fields having complementary binary spatial patterns. The encoder <NUM> may be a binary encoder comprising an array of reflective elements (e.g. mirrors) that direct light either in a first direction <NUM>, or in a second direction <NUM>, different to the first direction <NUM>. For example, the encoder <NUM> may consist of a plurality of a first type of reflective element and a plurality of a second type of reflective element. There may be similar (e.g. equal) numbers of the first and second type of reflective element, but this is not essential. The first type of element may be configured to reflect light incident on the encoder <NUM> in the first direction <NUM>. The second type of element may be configured to reflect light incident on the encoder <NUM> in the second direction <NUM>. The light reflected in the first direction <NUM> comprises a first encoded light field, and the light reflected in the second direction comprises a second encoded light field.

The reflective elements may be fixed (for example, the encoder <NUM> may comprise a fixed mirror array). Alternatively, the pattern of the first and second type of reflective element may be reconfigurable. For example, the encoder <NUM> may comprise an array of moveable micro-mirrors, such as a digital micro-mirror device (which are rapidly moveable between a first angular position and a second angular position). A reconfigurable encoder <NUM> may be advantageous, since additional information about a relatively slowly changing scene may be obtained by using different encoding patterns and combining the resulting data in order to obtain a hyperspectral image cube (i.e. using more than one shot).

In other embodiments, the encoder <NUM> may not be entirely reflective. For example, in some embodiments a beam splitter may be used to provide light to a first array of apertures and to a second array of apertures, complementary to the first array. The encoder in this sort of embodiment comprises the first and second array of apertures. In some embodiments, a partially reflective encoder may be employed, in which a proportion (e.g. <NUM>%) of the incident light is encoded and transmitted, and a proportion of the incident light is encoded and reflected.

Returning to <FIG>, the first and second dispersive elements <NUM>, <NUM> are arranged to apply first and second spectral shears to the first and second encoded light fields respectively to provide first <NUM> and second <NUM> sheared light fields. The dispersive elements <NUM>, <NUM> may comprise reflective dispersive elements such as diffraction gratings, but any dispersive element may be used (including transmissive dispersive elements). It may be advantageous for the first and second spectral shears to be different (for example, positive and negative), but this is not essential.

The first and second dispersive elements <NUM>, <NUM> may be curved diffraction gratings, configured to image the first and second sheared light fields onto the respective detectors. In other embodiments, the first and second dispersive elements <NUM>, <NUM> may each comprise a flat diffraction grating and a focussing element (e.g. a lens or mirror), with the focussing element configured to image the sheared light field onto the detector.

The first and second array detectors <NUM>, <NUM> are arranged to detect the first and second sheared light fields respectively. The processor <NUM> is arranged to process outputs from the first and second detectors <NUM>, <NUM> to determine a datacube <NUM> corresponding to a hyperspectral image of the scene.

The two sheared light fields <NUM>, <NUM> may be expressed as: <MAT> where the subscripts <NUM> and <NUM> denote the first and second sheared light field respectively, and coefficients a represent systematic aberrations and filtering, and coefficients c represent the dispersion from the respective dispersive element. Note that the coefficients c<NUM> and c<NUM> need not have opposite signs. I denotes the input datacube I(x, y, λ).

Reconstruction of the hyperspectral datacube <NUM> may be performed by the processor <NUM>. The data acquisition process may be expressed as: <MAT> where S is the signal detected at the respective detector, coefficients k are scaling factors to balance the intensity differences between the signals and the 'o's represent the measurement operators for the signals. Image reconstruction within the compressed sensing framework may be conducted by solving the minimisation problem: <MAT> where φ(I) is a regularizer that promotes sparsity, α is a regularization paramter, ||. || denotes the l<NUM> norm and I = I(x, y, λ) is the datacube. The minimisation problem posed in (<NUM>) may be solved using an existing methodology (e.g. TwIST, LASSO, wavelet deconvolution etc).

The use of a complementary encoding scheme with two detectors enables a single shot hyperspectral image to be obtained in which none of the incident light is wasted, and which enables efficient tomographic reconstruction of the hyperspectral datacube, because the encoding of the light detected at the first and second detector is complementary.

<FIG> shows an embodiment <NUM>, in which a beam splitter <NUM> is also provided. Furthermore, lenses <NUM>, <NUM> are included (not all of which are labelled). The description of elements with the same reference numerals in <FIG> are equally applicable to <FIG>.

The beam splitter <NUM> which splits the light field <NUM> into a first portion 104a and a second portion 104b. The second portion 104b is directed towards the encoder <NUM> whereas the first portion 104a is directed towards a third array detector <NUM>. The third array detector <NUM> is be configured to take a direct image (i.e. the sum of the intensities from an un-sheared image over the full spectral range at each x, y pixel position). The signal detected by the third detector may be expressed as: <MAT>.

The data acquisition process with the additional third detector may be expressed as: <MAT>.

The reconstruction of the image datacube may be conducted by solving the minimisation problem (which uses similar notation to (<NUM>)): <MAT>.

In the embodiment of <FIG>, the focussing lens <NUM> is shown, which focuses the light from the input <NUM> at the encoder <NUM> and the third detector <NUM>. Such a focussing lens may also be used in the embodiment of <FIG> to focus light at the encoder <NUM>. Although a refracting lens is shown, a focussing element comprising a reflector may alternatively be used.

The addition of the third detector, which obtains a direct image, provides further information for the reconstruction of the hyperspectral datacube. This direct image is also straightforward to compare visually with the output datacube to provide confidence that this is correct.

Also depicted in <FIG> are two focussing lenses <NUM> for each of the optical paths from the encoder <NUM> to the first and second array detectors <NUM>, <NUM>. A similar arrangement of lenses may also be used in the embodiment of <FIG>. A lens between the encoder <NUM> and the first dispersive element <NUM> collimates the light from the encoder <NUM> at the first dispersive element <NUM>. A further lens <NUM> between the first dispersive element <NUM> and the first array detector <NUM> focusses the light from the first diffractive element <NUM> at the first array detector <NUM>. A similar arrangement is used for the other detection path (leading to the second array detector <NUM>).

Preferably, the lenses are matched, with focal length f2, so that the distance from the dispersive element <NUM>, <NUM> to the encoder <NUM> and the array detector <NUM>, <NUM> is the same (with the lenses placed halfway between the encoder and dispersive element, and halfway between the dispersive element and the first array detector).

Although refractive lenses are depicted in the example embodiment of <FIG> (which may be readily available, compact and low cost), reflective elements may be used instead, which may be advantageous in that they will tend not introduce any unwanted dispersion.

<FIG> shows another embodiment of a hyperspectral imaging device <NUM>. The description of elements with the same or like reference numerals in <FIG> and <FIG> are equally applicable to <FIG>. The hyperspectral imaging device <NUM> comprises an input <NUM> for receiving a light field <NUM> from a scene <NUM>, an encoder <NUM>, first <NUM> and second <NUM> dispersive elements, first <NUM>, second <NUM> and third <NUM> array detectors and a processor <NUM>. The hyperspectral imaging device <NUM> operates using the same principles as for the hyperspectral imaging devices <NUM>, <NUM> described above, but utilises transmissive components rather than reflective components. Use of transmissive components may enable easier miniaturisation (and potentially reduced cost) of the hyperspectral imaging device <NUM>, by avoiding use of reflective components (such as digital micro-mirror devices, beam splitters and reflective diffraction gratings), and in particular when performing compressive tomography.

In the embodiment shown, the hyperspectral imaging device <NUM> comprises first 301a, second 301b and third 301c discrete, separate imaging paths from the scene <NUM> to the respective array detectors <NUM>, <NUM>, <NUM>. In the embodiment shown, the discrete imaging paths 301a, 301b, 301c are parallel to one another to avoid the need for a beam splitter, which may further ease miniaturisation of the hyperspectral imaging device <NUM>. The direction of the arrows from the input <NUM> along each imaging path 301a, 301b and 301c are schematic in nature and do not necessarily illustrate the physical path of light through the hyperspectral imaging device <NUM>.

The encoder <NUM> comprises a first encoder portion 308a and a second encoder portion 308b. The first encoder portion 308a operates as part of the first discrete imaging path 301a, in conjunction with the first dispersive element <NUM> and the first array detector <NUM>. In the embodiment shown, an imaging lens 340a is located between the input <NUM> and the first encoder portion 308a, and a relay lens 342a is located between the first encoder portion 308a and the first dispersive element <NUM>. In other embodiments, the imaging lens 340a and the relay lens 342a may be omitted. Similarly, the second encoder portion 308b operates as part of the second discrete imaging path 301b, in conjunction with the second dispersive element <NUM> and the second array detector <NUM>. In the embodiment shown, an imaging lens 340b is located between the input <NUM> and the second encoder portion 308b, and a relay lens 342b is located between the second encoder portion 308b and the second dispersive element <NUM>. In other embodiments, the imaging lens 340b and the relay lens 342b may be omitted.

The first 308a and second 308b encoder portions are each arranged to receive at least a portion of the light field <NUM> from the input <NUM> and transform it to provide respective first <NUM> and second <NUM> encoded light fields. The first <NUM> and second <NUM> encoded light fields have different spatial patterns. In the embodiment shown, the first 308a and second 308b encoder portions are transmissive encoders, for example first and second arrays of apertures or masks. In some embodiments, the first 308a and second 108b encoder portions are complementary to one another to produce first <NUM> and second <NUM> encoded light fields comprising complementary spatial patterns, but this is not essential.

The first <NUM> and second <NUM> dispersive elements are arranged to apply first and second spectral shears to the first <NUM> and second <NUM> encoded light fields respectively, to provide first <NUM> and second <NUM> sheared light fields. In the embodiment shown, the first <NUM> and second <NUM> dispersive elements are each transmissive dispersive elements, such as a transmissive diffraction grating. It may be advantageous for the first and second spectral shears to be different (for example, positive and negative), but this is not essential.

The first <NUM> and second <NUM> array detectors are arranged to detect the first <NUM> and second <NUM> sheared light fields respectively. The processor <NUM> is arranged to process outputs from the first <NUM> and second <NUM> detectors to determine a datacube <NUM> corresponding to a hyperspectral image of the scene. The processor <NUM> may reconstruct the hyperspectral datacube <NUM> according to equations (<NUM>) to (<NUM>) discussed above.

The third discrete imaging path 301c runs from the input to the third array detector <NUM> which provides a direct image of the scene <NUM>, providing further information for the reconstruction of the hyperspectral datacube <NUM>. The direct image is straightforward to compare visually with the output datacube <NUM> to provide confidence that the datacube <NUM> is correct. In the embodiment shown, an imaging lens 340c is located between the input <NUM> and the third array detector <NUM>. In some embodiments, the imaging lens 340c may be omitted.

<FIG> shows a further embodiment of a hyperspectral imaging device <NUM>. The hyperspectral imaging device <NUM> is substantially similar to the hyperspectral imaging device <NUM> described above, although the imaging and relay lenses are not depicted.

The hyperspectral imaging device <NUM> further comprises a spectral encoder <NUM>. The spectral encoder <NUM> is configured to spectrally encode the first <NUM> and second <NUM> sheared light fields prior to their detection by the first <NUM> and second <NUM> array detectors respectively. In the embodiment shown, the spectral encoder <NUM> is arranged after the respective dispersive elements <NUM>, <NUM> in the first 301a and second 301b imaging paths. In the embodiment shown, similar to the encoder <NUM>, the spectral encoder <NUM> comprises a first spectral encoder portion 440a configured to spectrally encode the first sheared light field <NUM>, and a second spectral encoder portion 440b configured to spectrally encode the second sheared light field <NUM>. The first spectral encoder portion 440a operates as part of the first imaging path 301a, while the second spectral encoder portion 440b operates as part of the second imaging path 301b. In some embodiments, the first 440a and second 440b spectral encoder portions are complementary to one another, but this is not essential.

In the embodiment shown, the spectral encoder <NUM> is a transmissive encoder, for example one or more arrays of apertures. As described above, use of transmissive components may enable easier miniaturisation of the hyperspectral imaging device <NUM>. In other embodiments, the spectral encoder may be a reflective encoder, for example a digital micro-mirror device.

The hyperspectral imaging device <NUM> described above only encodes in the spatial domain using the encoder <NUM>. The spectral encoder <NUM>, in conjunction with the encoder <NUM> enables the hyperspectral imaging device <NUM> to encode in both the spatial and spectral domains. An additional degree of freedom in encoding may allow for a higher degree of incoherence (randomness/orthogonality) in the sampling of the datacube <NUM>, which may improve reconstruction.

Alternatively, the spectral encoder <NUM> may be used independently of the encoder <NUM> (which may be omitted from the hyperspectral imaging device <NUM>) in order to provide only spectral encoding. It will also be appreciated that a spectral encoder (such as spectral encoder <NUM>) could be implemented in the hyperspectral imaging devices <NUM>, <NUM> described above. The spectral encoder may be implemented as a single spectral encoder, or as a plurality of spectral encoder portions. For example, if the first <NUM> and second <NUM> encoded light fields (and consequently the first <NUM> and second <NUM> sheared light fields) are temporally separated, a single spectral encoder <NUM> may be employed to spectrally encode the first <NUM> and second <NUM> sheared light fields.

In the above described embodiments, encoding and dispersion is performed by two discrete, separate components, namely the encoder <NUM>, <NUM> and the at least one dispersive element <NUM>, <NUM>, <NUM>, <NUM>. <FIG> shows an embodiment of a hyperspectral imaging device <NUM>. The hyperspectral imaging device <NUM> is similar to the embodiments shown in <FIG> and <FIG>.

However, in the embodiment shown in <FIG>, the encoder <NUM> and the at least one dispersive element <NUM>, <NUM> are integrated into a single component. The single component is an integrated encoding and dispersion element <NUM>. The integrated encoding and dispersion element <NUM> provides first <NUM> and second <NUM> light fields which are both encoded and sheared. Effectively, the integrated coding and dispersion element <NUM> provides both the first encoded light field <NUM> and the first sheared light field <NUM> as a single first encoded and sheared light field <NUM> (and correspondingly the second encoded light field <NUM> and the second sheared light field <NUM> as a single second encoded and sheared light field <NUM>).

In the embodiment shown, the first encoder portion 308a and the first dispersive element <NUM> on the first imaging path 301a have been replaced have been replaced by a first integrated encoding and dispersion element 550a (and correspondingly second encoder portion 308b and second dispersive element <NUM> on the second imaging path 301b by an integrated encoding and dispersion element 550b).

In the embodiment shown, the integrated encoder and dispersive element <NUM> is a transmissive component. In some embodiments, the integrated encoding and dispersion element <NUM> may comprise a dispersive element (for example, a diffraction grating such as a transmissive diffraction grating) on which an encoding pattern is disposed (for example, using a lithographic process).

The integrated encoding and dispersion element <NUM> shortens the beam paths in the discrete imaging paths 301a, 301b of the hyperspectral imaging device <NUM>, which may further enable easier miniaturisation of the hyperspectral imaging device <NUM>.

Optionally, a spectral encoder such as spectral encoder <NUM> described above may be used in conjunction with the integrated encoding and dispersion element <NUM> in order to encode in both the spatial and spectral domains.

Claim 1:
A hyperspectral imaging device (<NUM>, <NUM>, <NUM>, <NUM>) comprising an input (<NUM>) for receiving a light field (<NUM>) from a scene (<NUM>), an encoder (<NUM>), at least one dispersive element (<NUM>, <NUM>), at least one array detector (<NUM>, <NUM>) and a processor (<NUM>), wherein:
the encoder (<NUM>) is arranged to receive at least a portion of the light field (<NUM>) from the input (<NUM>) and transform it to provide a first and second encoded light field (<NUM>, <NUM>) having different binary spatial patterns;
at least one dispersive element (<NUM>, <NUM>) is arranged to apply spectral shear to the first and second encoded light fields (<NUM>, <NUM>) respectively to provide first and second sheared light fields (<NUM>, <NUM>);
at least one array detector (<NUM>, <NUM>) is arranged to detect the first and second sheared light fields (<NUM>, <NUM>); and
the processor (<NUM>) is arranged to process an output from the at least one array detector (<NUM>, <NUM>) to determine a datacube (<NUM>) corresponding to a hyperspectral image of the scene (<NUM>); and
the at least one dispersive element comprises a first dispersive element (<NUM>) configured to apply a first spectral shear to the first encoded light field (<NUM>), and a second dispersive element (<NUM>) configured to apply a second spectral shear to the second encoded light field (<NUM>),
the at least one array detector comprises a first (<NUM>) and second (<NUM>) array detector, respectively arranged to detect the first and second sheared light fields (<NUM>, <NUM>);
characterized in that
the hyperspectral imaging device further comprising a third array detector (<NUM>), arranged to receive an unsheared portion of the light field (<NUM>); and wherein
the processor (<NUM>) is further arranged to process an output from the third detector (<NUM>) jointly with the outputs from the first and second detectors (<NUM>, <NUM>) to determine the datacube (<NUM>).