Data blending multiple dispersive range monochromator
Aspects of blending data detected by a monochromator over multiple wavelength ranges is described herein. In one embodiment, the monochromator includes a diffraction grating, a grating drive motor that rotates the diffraction grating to provide, by diffraction of broadband light, first dispersed wavelengths of light and second dispersed wavelengths of light, a detector that detects a first reflection from the first dispersed wavelengths of light and a second reflection from the second dispersed wavelengths of light, and processing circuitry that blends data values from the first reflection and data values from the second reflection together to provide a spectrum of combined data values. By blending data detected over multiple ranges, measurements of relatively high precision and quality can be provided over a wider spectral range.
1. A monochromator, comprising:
a diffraction grating;
a grating drive motor to rotate the diffraction grating to provide, by diffraction of light, dispersed wavelengths of light;
a detector configured to detect a range of first data values from a first reflection of the dispersed wavelengths of light and a range of second data values from a second reflection of the dispersed wavelengths of light, wherein at least a portion of the range of first data values overlaps in an overlapping range of wavelength with at least a portion of the range of second data values; and
processing circuitry configured to:
control the grating drive motor to regulate an angular velocity of the diffraction grating over a first range of motion for the first reflection of the dispersed wavelengths of light and over a second range of motion for the second reflection of the dispersed wavelengths of light;
define a blending range in the overlapping range of wavelength;
subtract at least one data value among the range of first data values in the blending range from at least one data value among the range of second data values in the blending range to determine at least one difference value;
add the difference value to individual data values in the range of first data values; and
weight and sum individual data values among the range of first data values with corresponding data values among the range of second data values based on respective positions in wavelength of the individual data values among the range of first data values over the blending range.
2. The monochromator of claim 1 , wherein the processing circuitry is further configured to subtract each data value among the range of first data values from a respective data value among the range of second data values over the blending range to determine difference values over the blending range.
3. The monochromator of claim 2 , wherein the processing circuitry is further configured to:
average the difference values to generate an average difference over the blending range;
add the average difference to each data value in the range of first data values.
4. The monochromator of claim 1 , wherein the processing circuitry is further configured to, starting from one end of the blending range to another, weight and sum each data value among the range of first data values with a correspondingdata value among the range of second data values based on respective positions in wavelength of each first data value over the blending range.
5. The monochromator of claim 1 , wherein:
the detector comprises a first detector and a second detector;
the first detector is configured to detect the first range of data values; and
the second detector is configured to detect the second range of data values.
6. The monochromator of claim 5 , wherein the processing circuitry is further configured to:
control a sample tray drive motor to position a sample tray to cast the first reflection of the dispersed wavelengths of light onto the first detector to detect the first range of data values; and
control the sample tray drive motor to reposition the sample tray to cast the second reflection of the dispersed wavelengths of light onto the second detector to detect the second range of data values.
7. The monochromator of claim 1 , wherein:
the detector is further configured to detect a range of third data values from a third reflection of the dispersed wavelengths of light, wherein at least a portion of the range of second data values overlap in a second overlapping range of wavelength with at least a portion of the range of third data values;
define a second blending range in the second overlapping range of wavelength; and
the processing circuitry is further configured to weight and sum individual data values among the range of third data values with corresponding data values among the range of second data values over the second blending range.
8. The monochromator of claim 1 , wherein the diffraction grating comprises a first periodic surface region and a second periodic surface region.
9. The monochromator of claim 1 , wherein the diffraction grating comprises a tandem diffraction grating, the tandem diffraction grating comprising a first diffraction grating, a second diffraction grating, and a mounting assembly having a rotatable shaft to rotate the tandem diffraction grating.
10. The monochromator of claim 9 , wherein:
the first diffraction grating comprises a first periodic surface for a first range of ultra-violet (UV) to visible (VIS) wavelengths; and
the second diffraction grating comprises a second periodic surface for a second range of near-infrared (NIR) to infrared (IR) wavelengths.
11. A method, comprising:
controlling, with a processing circuit in an instrument, a grating drive motor to regulate an angular velocity of a diffraction grating over a first range of motion for a first reflection of dispersed wavelengths of light and over a second range of motion for a second reflection of the dispersed wavelengths of light;
detecting, with a detector in the instrument, a range of first data values from the first reflection of the dispersed wavelengths of light and a range of second data values from the second reflection of the dispersed wavelengths of light, wherein at least a portion of the range of first data values overlaps in an overlapping range of wavelength with at least a portion of the range of second data values;
subtracting, with a processing circuit, at least one data value among the range of first data values from at least one data value among the range of second data values to determine at least one difference value;
adding, with the processing circuit, the difference value to individual data values in the range of first data values; and
weighting and summing, with the processing circuit, individual data values among the range of first data values with corresponding data values among the range of second data values based on respective positions in wavelength of the individual data values among the range of first data values.
12. The method of claim 11 , wherein the detector comprises a first detector and a second detector, and the method further comprises:
detecting the first range of data values with the first detector; and
detecting the second range of data values with the second detector.
13. The method of claim 12 , further comprising
controlling a sample tray drive motor to position a sample tray to cast the first reflection of the dispersed wavelengths of light onto the first detector to detect the first range of data values; and
controlling the sample tray drive motor to reposition the sample tray to cast the second reflection of the dispersed wavelengths of light onto the second detector to detect the second range of data values.
14. The method of claim 11 , wherein:
the dispersed wavelengths of light are dispersed from a tandem diffraction grating including a first diffraction grating and a second diffraction grating;
the first reflection of the dispersed wavelengths of light are dispersed from the first diffraction grating; and
the second reflection of the dispersed wavelengths of light are dispersed from the second diffraction grating.
15. The method of claim 14 , wherein:
the first diffraction grating comprises a first periodic surface for a first range of ultra-violet (UV) to visible (VIS) wavelengths; and
the second diffraction grating comprises a second periodic surface for a second range of near-infrared (NIR) to infrared (IR) wavelengths.
16. A device, comprising:
monochromator instrumentation comprising a diffraction grating, a grating drive motor to rotate the diffraction grating to provide dispersed light, and a detector configured to detect data values from the dispersed light; and
processing circuitry configured to:
control the grating drive motor to regulate an angular velocity of the diffraction grating over a first range of motion for a first reflection of dispersed light and over additional ranges of motion for a plurality of additional reflections of the dispersed light;
direct the monochromator instrumentation to detect a range of data values from the first reflection of the dispersed light;
direct the monochromator instrumentation to detect a plurality of subset ranges of data values from the plurality of additional reflections of the dispersed light, wherein at least a portion of the range of data values overlaps in an overlapping range of wavelength with the plurality of subset ranges of data values;
generate an average subset range of data values based on the plurality of subset ranges of data values;
weight and sum each data value among the range of data values with a corresponding data value among the average subset range of data values based on respective positions in wavelength of each data value over a blending range.
17. The device of claim 16 , wherein the processing circuitry is further configured to define the blending range as a portion of the overlapping range of wavelength.
18. The device of claim 17 , wherein the processing circuitry is further configured to, for each data value among the range of data values over the blending range, subtract a corresponding data value among the average subset range of data values to determine difference values over the blending range.
19. The device of claim 18 , wherein the processing circuitry is further configured to:
average the difference values to generate an average difference over the blending range; and
add the average difference to each data value in the average subset range of data values to generate a shifted average subset range of data values.
20. The device of claim 19 , wherein the processing circuitry is further configured to weight and sum each data value among the range of data values with a corresponding data value among the shifted average subset range of data values based on respective positions in wavelength of each data value over the blending range.