Spectral analysis of a sample requires illuminating the entire sample and obtaining spectral information therefrom. For samples having a mixture of substances, spectral unmixing includes obtaining independent spectra for various regions of interest of the sample. Thus, the sample must be divided into regions of interest and each region is independently analyzed.
Conventional spectral unmixing techniques fall into one of three general techniques. The first technique is point-scanning and operates by illuminating the sample at a first region (a point) to obtain the spectral image of the region before repeating the illumination/scanning at a second region. For efficiency, the regions are selected such that each region is adjacent to the previously-scanned region. The point-scanning technique is time-consuming and inefficient. Moreover, the point scanning technique is impractical where, for instance, the sample is in vivo and moving the illumination source, the sample or the gathering optics is not practical.
A second technique is the line-scan technique and operates by illuminating a line (e.g., a row or a column) on the sample at a time. Here, the illumination source excites all substances on the illuminated line and obtains the spectra for the illuminated region. The operation is repeated for the subsequent line until the entire sample is illuminated. This technique is time-consuming and inefficient.
The third technique is the wide-field illumination which allows illuminating the entire sample at once. The optical signal collected from the sample is communicated to an optical filter such as a liquid crystal tunable filter (“LCTF”) which receives the entire field of view of the sample but only processes one wavelength at a time. This techniques is time consuming as only one wavelength can be processed during any given time interval. In addition, it does not enable sampling a particular region of the entire field of view.
Other miscellaneous techniques provide mechanical devices which move the sample, the illumination source or both. These techniques have moving parts which are also inefficient and, at times, impractical.
In one embodiment, the disclosure relates to a method comprising: collecting photons from the sample having a plurality of regions to form a sample optical data set; selectively transmitting a first portion of the optical data set through a first of a plurality of apertures of an electro-optical shutter, each of the plurality of apertures optically communicating a portion of the optical data set; geometrically conforming the first portion of the optical data set for communication with a spectrometer opening; processing the conformed first portion of the optical data set at the spectrometer to obtain a spectrum for a first of the plurality of sample regions.
In another embodiment, the disclosure relates to a method comprising: collecting photons from a sample having a plurality of regions to form a sample optical data set; transmitting the optical data set through a plurality of apertures of an electro-optical shutter to a spectrometer to form a spectral image of the sample; selecting a first region of interest from said spectral image; selectively transmitting a first portion of the optical data set through a first group of apertures among the plurality of apertures, the first group of apertures communicating with the first region of interest; and processing the first portion of the optical data set at the spectrometer to obtain a spectrum for the first region of interest.
In another embodiment, the disclosure relates to a system comprising: a first optical train for collecting photons from a sample having a plurality of regions and forming a sample image; an electro-optical shutter having a plurality of apertures, each aperture optically communicating with one of the plurality of sample regions to provide an optical data set for each corresponding region; a second optical train for receiving and geometrically conforming the optical data set for each region and communicating said optical data set to a spectrometer opening; and a spectrometer for processing the conformed optical data set for each region to obtain a spectrum for the region.
In still another embodiment, the disclosure relates to a system comprising: a processor for receiving a sample spectrum and identifying presence of a first substance at each of a first and a second region from among a plurality of sample regions; an electro-optical shutter having a plurality of apertures, each aperture communicating an optical signal with one of the plurality of sample regions; a controller for receiving instructions from the processor to: (a) locate the first region and the second region from among the plurality of sample regions, (b) identify a first aperture corresponding to the first region and a second aperture corresponding to the second region, (c) communicate a first optical signal from the first region through the first aperture and communicate a second optical signal from the second region through the second aperture; a spectrometer for receiving the first optical signal and the second optical signal and forming a combined optical signal for the first substance.
These and other embodiments of the disclosure will be discussed in relation to the following non-limiting and exemplary drawings in which:
Objective lens 120 receives and collects photons 116. Objective lens 120 can also define an optical train configured to receive photons 116 and form a sample optical data set 122 therefrom. Lens 130 receives sample optical data set 122 and reduces the field of view of the optical data set 122 to a size 132 compatible with spectrometer opening or slit 142 of dispersive spectrometer 140. In spectrometer 140, reflective mirror 143 communicates the reduced field of view 132 of the optical data set 122 to reflection grating array 145. Grating 145 disperses optical signals 144 into multiple spectral orders 146, which are in turn directed through reflective mirror 147 to illuminate charge-coupled device 150.
While illumination source 110 may illuminate the entire sample at once, the spectrum can only be collected at a specific point or location of the sample. To obtain a spectrum of another region of the sample, the illumination source 110, sample 115 or both must be moved. This procedure is time-consuming and inefficient.
Alternatively, regions 210, 220 and 230 can comprise a first chemical substance with a corresponding chemical spectrum. The presence of the first chemical substance throughout the sample 200 may be such that its spectral signal overwhelms a weaker signal from a second substance at region 240. Therefore, it may be desirable to study the chemical spectrum of region 240 without receiving interference from regions 210, 220 and 230. As stated, conventional detection system, such as system 100 of
Objective lens 314 receives and collects sample photons 316. Objective lens 314 can also define an optical train configured to receive sample photons 313 and form a sample optical data set having field of view 311. Lens 316 receives and focuses field of view of optical data set 311 to a size compatible for communication with shutter 320. Shutter 320 can comprise a solid state electro-optical device having a two-dimensional array of controllable apertures 325. Thus, shutter 320 can communicate selective portions of the sample's field of view by selectively and independently opening one more of the appropriate apertures 325. Moreover, shutter 320 can be electronically controlled by a processor (not shown) to thereby operate without any mechanical or moving parts.
Selective portions of the optical data set 322 corresponding to one or more regions of interest can be optically transmitted through shutter 320 while blocking optical transmission from the remaining regions of the sample. In one embodiment, each aperture 325 of shutter 320 correspond with a particular region of sample 315. Thus, an optical data set communicated through a particular aperture 325 can define the optical image (or spectrum) from the corresponding region of sample 315.
The selected portions of optical data set 322 can be processed by lens 330 to geometrically conform the selected portions of data set 332 for optical communication with slit 342 of spectrometer 340. The step of geometrically conforming can comprise expanding or contracting the selected portions of optical data set 322 in one or more directions. The geometrically-conformed portions of the optical data set can be processed at spectrometer 340 and CCD 350 to obtain a spectrum for the selected sample region.
In one embodiment, all apertures 325 can be enabled simultaneously to communicate and to form an image of the sample at the CCD. Thus, the field-of-view (FOV) of CCD 350 can comprise the entire image of sample 315. In another embodiment, a single aperture can be enabled to optically communicate optical data set of a select region of the sample with spectrometer 340. According to this embodiment, the FOV at the CCD comprises only the image of the selected region.
Conventional spectrometers have a long and narrow spectrometer opening or slit. Such slits are typically narrow along the X-axis and wide on the Y-axis. Therefore, any optical communication between shutter 420 and spectrometer 440 may include one or more optical lenses for geometrically conforming the FOV of optical data set 419 transmitted through shutter 420. The geometric conformation may be non-uniform. That is, the geometric conformation of the optical data set may contract the data set in one direction while expanding the data set in another direction. Moreover, the geometric conformation can be configured to communicate the entire optical data set without losing any optical information.
To this end,
As stated, the optical data set may be geometrically conformed in at least two directions before it can be received at spectrometer slit 442.
The embodiments of the disclosure can be implemented with transmissive shutters, reflective shutters or a combination thereof. For example,
The shutter can be an electro-optical shutter having a plurality of apertures dispersed in different dimensions. In one embodiment of the disclosure, each aperture is configured to optically communicate with a corresponding region of the sample. Thus, a region of interest can be selectively identified by allowing optical communication through a corresponding aperture. The optical communication can be enabled for a plurality of regions of interest simultaneously or sequentially (step 940). In another embodiment, all apertures can be simultaneously enabled to provide optical data set for the entire sample at once. Thus, the entire sample can be studied to identify one or more regions of interests. Once such regions of interest have been identified, select apertures corresponding to the regions of interest can be enabled to obtain a plurality of images corresponding to the regions of interests. Advantageously, the entire operation can be implemented without changing the illumination source, moving the sample or the illumination source or mechanically manipulating the apertures of the shutter.
In step 950, a plurality of lenses (collectively, a second optical train) can be used to geometrically conform the select portion of the optical data set. The geometrically conforming step can be optionally implemented. The optical data set communicated through the shutter is then directed to a spectrometer slit (step 960). In one embodiment, the image is further conformed to fit the spectrometer slit in order to avoid optical signal loss. Finally, in step 970 one or more spectra is formed from the optical signal. The spectra can depict a region of interest, a plurality of regions of interest or the entire sample. Depending on the spectra, steps 910-970 may be repeated for subsequent regions of interests.
Spectrometer 1040 can communicate with processor 1060. For example, processor 1060 can receive spectra or optical images from spectrometer 1040. Based on information received from spectrometer 1040, processor 1060 can determine the subsequent action of system 1000. For example, processor 1060 can instruct illumination source 1010 to illuminate sample 1015 with photons of different wavelength for a subsequent measurement. The communication between processor 1060 and illumination source 1010 can be duplex. That is, illumination source 1010 can report its illumination wavelength to processor 1060.
Processor 1060 can control apertures of shutter 1020 either directly or through controller 1070. Controller 1070 can define a DC/DC converter or any other electronic circuitry for enhancing communication between processor 1060 and shutter 1020. In another embodiment (not shown), processor 1060 communicates directly with shutter 1020.
In an exemplary implementation, processor 1060 receives a spectra from spectrometer 1040 and determines a first and a second regions of interest in sample 1015. Processor 1060 can then determine the location of the first and the second regions of interest in sample 1015 and a corresponding first and second apertures. Next, controller 1060 can direct controller 1070 to enable the first and the second apertures of shutter 1020 while disabling (i.e., blocking) signal communication through the remaining apertures of shutter 1020. In one implementation, the first aperture is enabled independently of the second aperture to communicate an optical signal of the first region of interest. Subsequently, the second aperture is enabled independently of the first aperture to communicate an optical signal of the second region of interest. In another implementations, the first and the second apertures are enabled simultaneously to communicate optical signals of the first and the second apertures simultaneously.
Spectrometer 1040 can form spectra for the first and the second regions of interest and communicate the spectra to processor 1060. Processor 1060 can then identify a third region of interest of sample 1015 along with its corresponding aperture and direct system 1000 to obtain a spectrum for the third region of interest. The process can continue iteratively to compile the desired spectra from sample 1015.
In another implementation, processor 1060 can receive an initial spectrum of sample 1015 from spectrometer 1040. From the initial spectrum, the processor can identify a region of interest having a weaker optical signal overwhelmed by the optical signal from its surrounding regions. Processor 1060 can direct controller 1070 to disable optical communication from the surrounding regions so as to allow spectrometer 1040 to receive a stronger optical signal from the region of interest.
The above description is not intended and should not be construed to be limited to the examples given but should be granted the full breadth of protection afforded by the appended claims and equivalents thereto. Although the disclosure is described using illustrative embodiments provided herein, it should be understood that the principles of the disclosure are not limited thereto and may include modification thereto and permutations thereof.
The instant disclosure claims the filing-date benefit of Provisional Application No. 60/756,124, filed Jan. 4, 2006, entitled “Dense Spectral Unmixing and Image Reconstruction (DSUIR)”, the disclosure of which is incorporated herein by reference in its entirety. Cross-reference is made to patent applications filed simultaneously herewith and entitled “Method and Apparatus for Dense Spectrum Unmixing and Image Reconstruction of a Sample” (Attorney Docket No. CHE01 118) the specification of each of the cross-referenced applications being incorporated herein in its entirety.
Number | Date | Country | |
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60756124 | Jan 2006 | US |