Spectrometry system with diffuser having output profile independent of angle of incidence and filters
A spectrometer comprises a plurality of isolated optical channels comprising a plurality of isolated optical paths. The isolated optical paths decrease cross-talk among the optical paths and allow the spectrometer to have a decreased length with increased resolution. In many embodiments, the isolated optical paths comprise isolated parallel optical paths that allow the length of the device to be decreased substantially. In many embodiments, each isolated optical path extends from a filter of a filter array, through a lens of a lens array, through a channel of a support array, to a region of a sensor array. Each region of the sensor array comprises a plurality of sensor elements in which a location of the sensor element corresponds to the wavelength of light received based on an angle of light received at the location, the focal length of the lens and the central wavelength of the filter.
1. A spectrometer to measure spectra of a sample comprising:
a diffuser configured to receive incident light from the sample and transmit diffuse light, wherein an angular profile of the transmitted diffuse light is substantially fixed and substantially independent of an angle of incidence of the light from the sample;
an optical filter to receive transmitted diffuse light from the diffuser, wherein an effective range of wavelengths passed with the optical filter is greater than a bandwidth of the optical filter; and
a detector to measure the spectra with the transmitted diffuse light from the optical filter.
2. The spectrometer of claim 1 wherein a transmission spectrum of the optical filter varies with an angle of incidence on the filter and receives the transmitted diffuse light with the angular profile of the transmitted diffuse light substantially fixed and substantially independent of the angle of incidence of the light from the sample.
3. The spectrometer of claim 1 , wherein the optical filter comprises an array of optical filters.
4. The spectrometer of claim 3 wherein transmission spectra of a plurality of filters of the array of optical filters vary with an angle of incidence on the filter and receive the transmitted diffuse light with the angular profile of the transmitted diffuse light substantially fixed and substantially independent of the angle of incidence of the light from the sample.
5. The spectrometer of claim 3 , further comprising a lens array.
6. The spectrometer of claim 1 wherein the optical filter comprises multiple sub-filters and one point on the detector receives light from the multiple sub-filters.
7. The spectrometer of claim 1 further comprising a pre-filter before the optical filter in a light path.
8. The spectrometer of claim 7 wherein the pre-filter is chosen from a group consisting of: (a) absorbing glass and (b) interference filter.
9. The spectrometer of claim 1 wherein the diffuser comprises a cosine diffuser.
10. The spectrometer of claim 1 wherein a second diffuser is located between the diffuser and the sample.
11. The spectrometer of claim 10 wherein a distance between the diffuser and the second diffuser is at least 0.5 mm.
12. The spectrometer of claim 3 wherein the transmission spectra of the filters in the array of optical filters vary with an angle of incidence on the array of optical filters.
13. The spectrometer of claim 2 wherein the filter comprises a plurality of interference filters.
14. The spectrometer of claim 13 wherein the plurality of interference filters is deposited only on a single side of a substrate.
15. The spectrometer of claim 14 wherein the single side of the substrate having the plurality of interference filters is facing towards a lens array.