US 6,504,943 B1 · Information-efficient spectral imaging sensor

Abstract

A programmable optical filter for use in multispectral and hyperspectral imaging. The filter splits the light collected by an optical telescope into two channels for each of the pixels in a row in a scanned image, one channel to handle the positive elements of a spectral basis filter and one for the negative elements of the spectral basis filter. Each channel for each pixel disperses its light into n spectral bins, with the light in each bin being attenuated in accordance with the value of the associated positive or negative element of the spectral basis vector. The spectral basis vector is constructed so that its positive elements emphasize the presence of a target and its negative elements emphasize the presence of the constituents of the background of the imaged scene. The attenuated light in the channels is re-imaged onto separate detectors for each pixel and then the signals from the detectors are combined to give an indication of the presence or not of the target in each pixel of the scanned scene. This system provides for a very efficient optical determination of the presence of the target, as opposed to the very data intensive data manipulations that are required in conventional hyperspectral imaging systems.

Claims18

Dependent claims

A method emphasizing a first aspect of a set of spectral data from an imaged scene with a line-scanning multispectral sensor having m-pixels per row, with n spectral bins sensed per pixel in a row, the method comprising:

utilizing a previously-created first spectral basis vector having n elements to identify the first aspect, some of which elements have negative values and the rest having positive values, said vector being derived from a training set of a multiplicity of n element spectra that includes at least one spectrum of the first aspect and at least one spectrum of the constituents of the background materials in the scene;
to collecting light from the imaged scene and presenting it to the sensor;
attenuating the light in the affected spectral bins of each pixel of a row in a first channel of the sensor based on the value of the respective positive value elements of the first spectral basis vector;
attenuating the light in the affected spectral bins of each pixel of that row in a second channel of the sensor based on the value of the respective negative value elements of the first spectral basis vector;
imaging the modulated light in the first and second channels onto respective first and second linear arrays of detectors, each detector in each array corresponding to a pixel in that row, to provide first and second detector signals;
and
combining the first and second detector signals to provide an indication of the presence or not of the first aspect in the scanned pixels.

4 more elements

A line scanning, multispectral sensor having at least two optical channels to emphasize at least one aspect of a scanned scene comprising:

a slit to form a linear image of m pixels in a row;
means to direct the light from the slit for each pixel into first and second channels of light with the light in each channel being dispersed into n spectral bins and to present this light to individual optical attenuators for each spectral bin in each channel, wherein the levels of attenuation, if any, in each attenuator in the first channel correspond to the positive elements in a first spectral basis vector that emphasizes a first aspect of the scanned scene and the levels of attenuation, if any, in each attenuator in the second channel correspond to the negative elements in a spectral basis vector;
detector arrays for each channel with a detector for each spectral bin therein to provide an electrical signal corresponding to the strength of the light leaving the attenuators in each spectral bin in each channel;
and
means to combine the signals from the two detector arrays to emphasize the first aspect of the scanned scene;
wherein the first spectral basis vector is derived from a training set of a multiplicity of n element spectra that includes at least one spectrum of the first aspect and at least one spectrum of the constituents of the background materials in the scene to emphasize the first aspect of the scanned scene.

3 more elements

A line scanning, multispectral sensor having at least two optical channels to emphasize at least one aspect of a scanned scene comprising:

optical elements suitable to image a scene onto a slit;
a slit to form a linear image that is separable into m pixels in a row;
a second optical element suitable to recollimate the light from the slit onto a dispersing element;
a dispersing element to split the light from the slit into n spectral bins that are disposed normal to the axis of the slit;
a third optical element suitable to converge the light from the dispersing element and image the n spectral images of the slit onto n rows of a micromirror array;
a micromirror array comprising a linear array of n individual micromirror assemblies with each assembly corresponding to a single spectral bin such that each assembly is controlled to reflect the light from for its spectral bin into at least two different positions, with a first and second position corresponding to first and second channels, wherein the light in a spectral bin is reflected into the first channel if the corresponding element in a first n element spectral basis vector is positive and the light in that spectral bin is reflected into the second channel if the corresponding element in the first spectral basis vector is negative;
p1 a fourth optical element suitable to reimage the light in the first channel from the micromirror array onto a first m-element detector array;
a fifth optical element suitable to reimage the light in the second channel from the micromirror array onto a second m-element detector array;
and
means to combine the signals from the first and second detector arrays to emphasize the first aspect in each of the pixels of the scanned scene, wherein the first spectral basis vector is derived from a training set of a multiplicity of n element spectra that includes at least one spectrum of the first aspect and at least one spectrum of the constituents of the background materials in the scene to emphasize the first aspect of the scanned scene.

7 more elements

A line scanning, multispectral sensor having at least two optical channels to emphasize at least one aspect of a scanned scene comprising:

optical elements suitable to image a scene onto a slit;
a slit to form a linear image that is separable into m pixels in a row;
a second optical element suitable to recollimate the light from the slit onto a first polarizer;
a dispersing element to separate the light into n spectral bins;
a third optical element suitable to recollimate and refocus the light from the dispersing element onto an array of liquid crystal spatial light modulators (SLMs);
an array of SLMs with one SLM for each spectral bin, with each SLM being responsive to signals from a controller with respect to the amount of rotation imparted to the polarization vector of the light passing through that SLM corresponding to the positive and negative elements of a first spectral basis vector;
a fourth optical element suitable to recollimate the light from the array of SLMs onto an analyzing polarizer;
an analyzing polarizer that directs unrotated light from the array of SLMs into a first optical channel and directs rotated light from the array of SLMS into a second optical channel;
a first optical channel that includes a fifth optical element suitable to focus light onto a first detector array;
a second optical channel that includes a sixth optical element suitable to focus light onto a second detector array;
and
means to combine the signals from the first and second detector arrays in order to emphasize a first aspect in the pixels of the scanned scene, wherein the first spectral basis vector is derived from a training set of a multiplicity of n element spectra that includes at least one spectrum of the first aspect and at least one spectrum of the constituents of the background materials in the scene to emphasize the first aspect of the scanned scene.

9 more elements

Dependencies are inferred from the claim text.

Information-efficient spectral imaging sensor

Life of this patent

Information-efficient spectral imaging sensor

Life of this patent

Abstract

Claims18