Spectrometric using broadband filters with overlapping spectral ranges
First Claim
1. A spectrometer which includes a filter arrangement, in addition to any optional filters for limiting an operational wavelength range of the spectrometer, the filter arrangement comprising a plurality of broadband optical filters or broadband optical filter areas each of known transmission and being located or selectively locatable in a path of collected incident spectral radiation;
- at least one detector arranged to measure the spectral radiation passing through at least one of the broadband filters located in the path of collected incident spectral radiation; and
signal-processing means for recovering the spectrum of the collected spectral radiation from measurements by the detector.
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Abstract
The invention provides a spectrometer (10) which includes a filter arrangement (16,18), in addition to any option filters (20) for limiting an operational wavelength range of the spectrometer, the filter arrangement (16,18) comprising a plurality of broadband optical filters or broadband optical filter areas each of known transmission and being located or selectively locatable in a path of collected incident spectral radiation (44). The spectrometer further includes at least one detector (24) arranged to measure the spectral radiation passing through at least one of the broadband filters located in the path of collected incident spectral radiation, and signal-processing means (34) for recovering the spectrum of the collected spectral radiation from measurements by the detector (24).
39 Citations
18 Claims
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1. A spectrometer which includes
a filter arrangement, in addition to any optional filters for limiting an operational wavelength range of the spectrometer, the filter arrangement comprising a plurality of broadband optical filters or broadband optical filter areas each of known transmission and being located or selectively locatable in a path of collected incident spectral radiation; -
at least one detector arranged to measure the spectral radiation passing through at least one of the broadband filters located in the path of collected incident spectral radiation; and
signal-processing means for recovering the spectrum of the collected spectral radiation from measurements by the detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 16)
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13. A method of obtaining a measurement of an incident spectrum s over N wavelength bands or zones, the method including
filtering the incident spectrum s through J optical broadband filters or filter combinations to provide J individual filtered spectrums; -
converting the J filtered spectrums to J measured analogue electrical signals;
converting the J measured analogue electrical signals to a vector d of J measured digital signals, where the vector d=Bs+v and B is a matrix whose row vectors represent the effects of any hardware components, used to obtain the measured digital signals, on the measured digital signals, and v is a noise vector; and
multiplying a signal recovery matrix G with the vector d of the measured digital signals, to provide the measured incident spectrum Ŝ
, i.e. Ŝ
=G d whereG=VΛ
rU′
or the pseudo inverse of B;
Λ
r=diag{1/γ
1, . . . , 1/γ
r,0, . . . , 0}, the subscript rindicating that only the r largest singular values are used; and
B=UΣ
V′
, the singular value decomposition of B, where U and V are J×
N and N×
N orthogonal matrices, the matrix Σ
is a N×
N diagonal matrix containing the singular values of B in descending order, i.e. Σ
=diag{γ
1, . . . , γ
N}, γ
1≧
γ
2. . . ≧
γ
N≧
0, and r is an integer in the range 1<
r≦
N selected to minimize the measurement error. - View Dependent Claims (14, 17)
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15. A spectrometer which includes a filter arrangement, in addition to any optional filters for limiting an operational wavelength range of the spectrometer, the filter arrangement comprising a plurality of broadband optical filters or broadband optical filter areas each of known transmission and being located or selectively locatable in a path of collected incident spectral radiation.
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18. A new spectrometer or a new method of obtaining a measurement of an incident spectrum, substantially as herein described.
Specification