Time-resolved and wavelength-resolved spectroscopy for characterizing biological materials
View Patent ↗One embodiment of the present invention provides a system that characterizes a biological sample by analyzing light emissions from the biological sample in response to an excitation. The system first radiates the biological sample with a laser impulse to cause the biological sample to produce a responsive light emission. Next, the system uses a wavelength splitting device to split the responsive light emission into a set of spectral bands of different central wavelengths. The system applies temporal delays to the set of spectral bands so that each spectral band arrives at an optical detector at a different time, thereby allowing the optical detector to temporally resolve the responsive light emission for each spectral band separately. Next, the system captures the delayed spectral bands within a single detection window of the optical detector. The system then processes the captured spectral bands.
1. A method for characterizing a biological sample by analyzing light emissions from the biological sample in response to an excitation, the method comprising:
radiating the biological sample with a laser impulse to cause the biological sample to produce a responsive light emission;
splitting the responsive light emission into a set of spectral bands of different central wavelengths;
applying temporal delays to the set of spectral bands so that each spectral band arrives at an optical detector at a different time, thereby allowing the optical detector to temporally resolve the responsive light emission for each spectral band separately;
capturing the set of delayed spectral bands within a timing-controlled single detection window of the optical detector; and
processing the captured spectral bands.
2. The method of claim 1 , wherein applying a temporal delay to a spectral band involves:
coupling the spectral band into a delay device;
allowing the spectral band to travel through the delay device; and
receiving the spectral band from the output of the delay device, wherein the delay device introduces a controlled temporal delay to the spectral band while traveling through the delay device.
3. The method of claim 2 , wherein the delay device is an optical fiber with a predetermined length.
4. The method of claim 3 , wherein the controlled temporal delay is determined by the properties of the optical fiber and the length of the optical fiber.
5. The method of claim 1 , wherein splitting the responsive light emission into the set of spectral bands involves:
dividing the responsive light emission into spectral bands using a first stage of a wavelength splitting device; and
if necessary, subdividing one or more spectral bands using a second stage of a wavelength splitting device.
6. The method of claim 5 , wherein prior to splitting the responsive light emission, the method further comprising:
collecting the responsive light emission in an optical fiber; and
directing the collected responsive light emission onto the first stage of the wavelength splitting device.
7. The method of claim 5 , wherein an output of the first stage of the wavelength splitting device can be coupled to an input of the second stage of the wavelength splitting device through:
a direct coupling; or
an optical fiber coupling.
8. The method of claim 1 , wherein splitting the responsive light emission into the set of spectral bands involves using multiple stages of a wavelength splitting device.
9. The method of claim 5 , wherein the wavelength splitting device can include:
a dichroic filter cube;
a dichroic prism;
a dichroic mirror;
a diffraction grating;
an acousto-optic modulator; or
any other wavelength splitter devices.
10. The method of claim 1 , wherein the responsive light emission is a fluorescence decay of the biological sample caused by the laser impulse excitation.
11. The method of claim 10 , wherein the temporal delay between adjacent spectral bands is sufficiently long to temporally separate the fluorescence decay profile of each of the spectral bands.
12. The method of claim 1 , wherein the optical detector is a photomultiplier tube (PMT).
13. The method of claim 12 , wherein the PMT is a gated PMT which provides a detection window sufficiently wide to capture the set of spectral bands.
14. The method of claim 1 , wherein a spectral band is further refined with an optical bandpass filter.
15. A system for characterizing a biological sample by analyzing light emissions from the biological sample in response to an excitation, comprising:
a pulsed laser configured to radiate the biological sample with a laser impulse to cause the biological sample to produce a responsive light emission;
a wavelength-splitting mechanism configured to split the responsive light emission into a set of spectral bands of different central wavelengths;
a temporal-delay mechanism configured to apply temporal delays to the set of spectral bands so that each spectral band arrives at an optical detector at a different time, thereby allowing the optical detector to temporally resolve the responsive light emission for each spectral band separately;
a detection mechanism configured to capture the set of delayed spectral bands within a timing-controlled single detection window of the optical detector; and
a processing mechanism configured to process the captured spectral bands.
16. The system of claim 15 , wherein the temporal-delay mechanism is configured to:
couple the spectral band into a delay device;
allow the spectral band to travel through the delay device; and to
receive the spectral band from the output of the delay device, wherein the delay device introduces a controlled temporal delay to the spectral band while traveling through the delay device.
17. The system of claim 16 , wherein the delay device is an optical fiber with a predetermined length.
18. The system of claim 17 , wherein the controlled temporal delay is determined by the properties of the optical fiber and the length of the optical fiber.
19. The system of claim 15 , wherein the wavelength-splitting mechanism is configured to:
divide the responsive light emission into spectral bands using a first stage of a wavelength splitting device; and if necessary, to
subdivide one or more spectral bands using a second stage of a wavelength splitting device.
20. The system of claim 19 , further comprises:
a collection mechanism configured to collect the responsive light emission using an optical fiber; and
a directing mechanism configured to direct the collected responsive light emission onto the first stage of the wavelength splitting device.
21. The system of claim 19 , wherein an output of the first stage of the wavelength splitting device can be coupled to an input of the second stage of the wavelength splitting device through:
a direct coupling; or
an optical fiber coupling.
22. The system of claim 15 , wherein the wavelength-splitting mechanism is configured to use multiple stages of a wavelength splitting device.
23. The system of claim 19 , wherein the wavelength splitting device can include:
a dichroic filter cube;
a dichroic prism;
a dichroic mirror;
a diffraction grating;
an acousto-optic modulator; or
any other wavelength splitter devices.
24. The system of claim 15 , wherein the responsive light emission is a fluorescence decay of the biological sample caused by the laser impulse excitation.
25. The system of claim 24 , wherein the temporal delay between adjacent spectral bands is sufficiently long to temporally separate the fluorescence decay profile of each of the spectral bands.
26. The system of claim 15 , wherein the optical detector is a photomultiplier tube (PMT).
27. The system of claim 26 , wherein the PMT is a gated PMT which provides a detection window sufficiently wide to capture the set of spectral bands.
28. The system of claim 15 , wherein a spectral band is further refined with an optical bandpass filter.