Sub-millimeter wave frequency heterodyne detector system
View Patent ↗The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.
1. A method of imaging a sample comprising the steps of:
generating a signal beam of optical radiation having a frequency between 300 and 3000 gigahertz;
generating a reference beam of optical radiation having a frequency between 300 and 3000 gigahertz and different from the signal beam;
splitting the signal beam into first and second portions and causing the first portion of the beam to be scanned with respect to the sample;
splitting the reference beam into first and second portions;
mixing the first portion of the signal beam that has interacted with the sample with the first potion of the reference beam to create a measurement intermediate frequency signal;
mixing the second portion of the signal beam and the second portion of the reference beam to create a reference intermediate frequency signal; and
processing the measurement and reference intermediate frequency signals in order to derive magnitude and phase information as a function of position of the first portion of the signal beam on the sample and either storing the information or displaying the information in the form of an image.
2. A method as recited in claim 1 , wherein said phase information is derived by determining the relative phase difference between the measurement and reference intermediate frequency signals.
3. A method as recited in claim 1 , wherein said processing step includes feeding the measurement and reference intermediate frequency signals into a lock-in amplifier.
4. A method as recited in claim 1 , wherein said first portion of the signal beam is laterally scanning with respect to the sample to permit generation of two-dimensional image information.
5. A method as recited in claim 4 , wherein the two dimensional image information is displayed.
6. A method as recited in claim 5 , wherein the displayed image information is relative power as a function of scan position.
7. A method as recited in claim 1 , wherein said signal and reference beams are generated by optically pumped far infrared lasers.
8. A method as recited in claim 1 , wherein said signal and reference beams are generated by quantum cascade lasers.
9. A method as recited in claim 1 , wherein the signal beam interacts with the sample through transmission.
10. A method as recited in claim 1 , wherein said signal beam interacts with the sample by reflection.
11. A method as recited in claim 1 , wherein the sample is a biological sample.
12. A system for imaging a sample comprising:
a first generator for generating a signal beam of optical radiation having a frequency between 300 and 3000 gigahertz;
a second generator for generating a reference beam of optical radiation, having a frequency between 300 and 3000 gigahertz that is different from the signal beam;
a first beam splitter for dividing the signal beam into first and second portions;
means for scanning the first portion of the signal beam with respect to the sample;
a second beam splitter for dividing the reference beam into first and second portions;
a first mixer for mixing the first portion of the signal beam after interaction with the sample with the first potion of the reference beam to create a measurement intermediate frequency signal;
a second mixer for mixing the second portion of the signal beam and the second portion of the reference beam to create a reference intermediate frequency signal; and
a processor for processing the measurement and reference intermediate frequency signals in order to derive magnitude and phase information as a function of position of the first portion of the signal beam on the sample, said magnitude and phase information capable of being converted into image information.
13. A system as recited in claim 12 , wherein the processor functions to determine the relative phase difference between the measurement and reference intermediate frequency signals.
14. A system as recited in claim 12 , wherein the processor includes a lock-in amplifier.
15. A system as recited in claim 12 , wherein said scanning means laterally scans the first portion of the signal beam with respect to the sample to generate two-dimensional image information.
16. A system as recited in claim 15 , further including a display for displaying the two dimensional image information.
17. A system as recited in claim 16 , wherein the displayed image information is relative power as a function of scan position.
18. A system as recited in claim 12 , wherein the generators are optically pumped far infrared lasers.
19. A system as recited in claim 12 , wherein the generators are quantum cascade lasers.
20. A system as recited in claim 12 , wherein the signal beam interacts with the sample through transmission.
21. A system as recited in claim 12 , wherein said signal beam interacts with the sample by reflection.
22. A method of imaging a sample comprising the steps of:
generating a submillimeter wave frequency optical radiation signal beam;
generating a submillimeter wave frequency optical radiation reference beam having a frequency different from the signal beam;
splitting the signal beam into first and second portions and causing the first portion of the beam to be scanned with respect to the sample;
splitting the reference beam into first and second portions;
mixing the first portion of the signal beam that has interacted with the sample with the first potion of the reference beam to create a measurement intermediate frequency signal;
mixing the second portion of the signal beam and the second portion of the reference beam to create a reference intermediate frequency signal; and
processing the measurement and reference intermediate frequency signals in order to derive magnitude and phase information as a function of position of the first portion of the signal beam on the sample and either storing the information or displaying the information in the form of an image.
23. A method as recited in claim 22 , wherein said phase information is derived by determining the relative phase difference between the measurement and reference intermediate frequency signals.
24. A method as recited in claim 22 , wherein said processing step includes feeding the measurement and reference intermediate frequency signals into a lock-in amplifier.
25. A method as recited in claim 22 , wherein said first portion of the signal beam is laterally scanning with respect to the sample to permit generation of two-dimensional image information.
26. A method as recited in claim 25 , wherein the two dimensional image information is displayed.
27. A method as recited in claim 26 , wherein the displayed image information is relative power as a function of scan position.
28. A method as recited in claim 22 , wherein the signal beam interacts with the sample through transmission.
29. A method as recited in claim 22 , wherein said signal beam interacts with the sample by reflection.
30. A system for imaging a sample comprising:
a first generator for generating a submillimeter wave frequency optical radiation signal beam;
a second generator for generating a submillimeter wave frequency optical radiation reference beam having a frequency that is different from the signal beam;
a first beam splitter for dividing the signal beam into first and second portions;
means for scanning the first portion of the signal beam with respect to the sample;
a second beam splitter for dividing the reference beam into first and second portions;
a first mixer for mixing the first portion of the signal beam after interaction with the sample with the first potion of the reference beam to create a measurement intermediate frequency signal;
a second mixer for mixing the second portion of the signal beam and the second portion of the reference beam to create a reference intermediate frequency signal; and
a processor for processing the measurement and reference intermediate frequency signals in order to derive magnitude and phase information as a function of position of the first portion of the signal beam on the sample, said magnitude and phase information capable of being converted into image information.
31. A system as recited in claim 30 , wherein the processor functions to determine the relative phase difference between the measurement and reference intermediate frequency signals.
32. A system as recited in claim 30 , wherein the processor includes a lock-in amplifier.
33. A system as recited in claim 30 , wherein said scanning means laterally scans the first portion of the signal beam with respect to the sample to generate two-dimensional image information.
34. A system as recited in claim 33 , further including a display for displaying the two dimensional image information.
35. A system as recited in claim 34 , wherein the displayed image information is relative power as a function of scan position.
36. A system as recited in claim 30 , wherein the signal beam interacts with the sample through transmission.
37. A system as recited in claim 30 , wherein said signal beam interacts with the sample by reflection.