Doppler imager
A system comprises an imaging device that includes a two dimensional array of pixels. Each pixel of the array includes a first optical filter having a first pass band arranged to filter excitation light reflected by a moving object and a first detector configured to detect light transmitted through the first optical filter and to generate a first electrical signal. Each pixel of the array also includes a second optical filter having a second pass band arranged to filter excitation light reflected by a moving object and a second detector configured to detect light transmitted through the second optical filter and to generate a second electrical signal. The imaging device further includes circuitry that generates output signals from each of the pixels based on the first electrical signal and the second electrical signal of the pixel. The output signal includes information about the speed and direction of the moving object.
1. A system comprising:
an imaging device comprising a two dimensional array of pixels, each pixel of the array comprising:
a first optical filter having a first pass band arranged to filter excitation light reflected by a moving object;
a first detector configured to detect light transmitted through the first optical filter and to generate a first electrical signal having an amplitude proportional to an overlap between a spectrum of the excitation light with the first pass band;
a second optical filter arranged to filter excitation light reflected by the moving object, the second optical filter having a second pass band different from the first pass band; and
a second detector configured to detect light transmitted through the second optical filter and to generate a second electrical signal having an amplitude proportional to an overlap between a spectrum of the excitation light with the second pass band; and
circuitry configured to generate output signals from the pixels, each output signal based on the first electrical signal and the second electrical signal of a pixel, the output signal including information about speed and direction of the moving object;
wherein the output signal comprises a difference between the first signal and the second electrical signal normalized by a sum of the first and second electrical signals.
2. The system of claim 1 , wherein a sign of the output signal indicates a direction of the moving object.
3. The system of claim 1 wherein a rate of change of the output signal indicates a speed of the moving object.
4. The system of claim 1 , wherein a full width half maximum (FWHM) of one or both of the first and second optical filters is less than a FWHM of the spectral range of the excitation light.
5. The system of claim 1 , further comprising a third detector configured to detect light reflected by the moving object and to generate a third electrical signal, wherein the circuitry is configured to correct for reflectivity errors in one or both of the first and second signals based on the third electrical signal.
6. An integrated imaging device comprising:
a wafer substrate;
pixels of the integrated imaging device disposed on the substrate, each pixel comprising:
a first optical filter having a first pass band arranged to filter excitation light reflected by a moving object;
a first photosensor configured to detect light transmitted through the first optical filter and to generate a first electrical signal having an amplitude proportional to an overlap between a spectrum of the excitation light with the first pass band;
a second optical filter arranged to filter excitation light reflected by the moving object, the second optical filter having a second pass band different from the first pass band;
a second photosensor configured to detect light transmitted through the second optical filter and to generate a second electrical signal having an amplitude proportional to an overlap between a spectrum of the excitation light with the second pass band; and
electrical circuitry disposed on the substrate, the electrical circuitry configured to generate an output signal based on the first and second electrical signals, the output signal including information about speed and direction of the moving object, the electrical circuitry further configured to generate a differential signal based on the first and second electrical signals and generate a normalized differential signal based on the differential signal divided by a sum of the first and second electrical signals.
7. The integrated imaging device of claim 6 , further comprising a third photosensor configured to detect light reflected by the moving object and to generate a third electrical signal.
8. The integrated imaging device of claim 7 , wherein the circuitry is configured to correct for reflectivity errors in one or both of the first and second signals based on the third electrical signal.
9. The integrated imaging device of claim 6 , wherein at least one of the first and second optical filters comprises a Fabry-Perot etalon filter.
10. The integrated imaging device of claim 6 , wherein a full width half maximum (FWHM) of one or both of the first and second optical filters is less than a FWHM of the spectral range of the excitation light.
11. A method comprising:
optically filtering excitation light reflected by a moving object using at least one first optical filter having a first pass band;
sensing light transmitted through the first optical filter and generating at least one first electrical signal having an amplitude proportional to an overlap between a spectrum of the excitation light with the first pass band;
optically filtering the excitation light reflected by a moving object using at least one second optical filter having a second pass band;
sensing the light transmitted through the second optical filter and generating at least one second electrical signal having an amplitude proportional to an overlap between a spectrum of the excitation light with the second pass band; and
generating at least one output signal based on a difference between the first electrical signal and the second electrical signal; and
determining speed and direction of the moving object based on the output signal;
wherein the output signal is a differential signal and the differential signal is normalized by a sum of the first and second electrical signals.
12. The method of claim 11 , further comprising:
sensing unfiltered light reflected by the moving object;
generating a third electrical signal having an amplitude corresponding to the unfiltered light; and
correcting for reflectivity errors in the output signal based on the third electrical signal.
13. The method of claim 11 , wherein a sign of the output signal indicates a direction of the moving object.
14. The method of claim 11 , wherein a rate of change of the output signal indicates a speed of the moving object.