Abstract:
An active sensor a method for optical illumination and detection provides low cost and high-speed optical scanning of bio-arrays, DNA samples/chips, semiconductors, micro-electromechanical systems and other samples requiring inspection or measurement. A plurality of illumination sources forming a parallel multi-pixel array is used to illuminate one or more samples via an imaging system or by placement in close proximity to the samples. The array may be a line array or a two-dimensional array. A plurality of detectors is integrated within the multi-pixel illumination array or provided in a separate array, each detector for detecting optical properties of the sample that results from illumination by one or more associated illumination sources. One detector may be associated with multiple illuminators or one illuminator may be associated with multiple detectors. Filters may be integrated within the illumination path and/or detection paths to provide wavelength and/or polarization discrimination capability and microlenses may also be incorporated within the illumination path and/or detection paths to provide focusing or imaging. The illumination sources may be provided by TFT-LCD devices, diode emitters, organic LEDs (OLEDs), vertical cavity emitting lasers (VCELs) or other light sources that may be integrated to form a high-density illumination matrix. The detectors may be PIN photo-diodes or other suitable detectors that are capable of integration within the illumination matrix.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to optical measurement systems, and more specifically, to an active sensor illumination and detection apparatus for performing sample measurements using associated detector/illuminator groups integrated on one or more substrates. 
   2. Background of the Invention 
   One-dimensional and two dimensional measurement and inspection of samples is commonly performed in many industries, including biotechnology, semiconductor, micro electro-mechanical systems (MEMS) and others. For example, in the biotechnology industry, fluorescence measurements are used to determine the response of biological matter to illumination, thus revealing information about the composition and structure of a sample. Typically, for biological fluorescence tests, a sample or a material that is introduced to a sample is “tagged” with a fluorescent compound, the sample is illuminated with a laser, and the resulting fluorescent emissions are mapped to determine the locations of the fluorescent compound after interaction with the sample. For example, a prospective cancer drug may be tagged with a fluorescent compound and introduced to a sample having cancerous tissue. Then the sample is washed to remove excess fluorescent compound. The sample is illuminated and resulting fluorescent emissions are mapped to determine whether or not the prospective drug has bound to the cancer active sensor cells. 
   The above-described process is typically performed on a bio array, which may be a sample of DNA, gene chips including multiple DNA strands, microtiter plates with wells filled with various biocompounds, or microfluidic lab-on-a-chip devices. In each case, the device or sample is illuminated, typically by a scanning laser or filtered light source. Then, the resulting fluorescence (or lack thereof) is mapped. The mapping is typically performed by either a scanning confocal microscope (SCM) or by imaging onto a charge-coupled-device (CCD) sensor. 
   The disadvantages of the above-described systems and methods are long scanning times and moving parts for the SCM-based approach and lack of sensitivity and poorer spatial resolution for the CCD-based approach. A third alternative has been implemented, using a scanning laser and a photomultiplier tube for detection, but the cost of the scanning laser and detectors is a disadvantage, as well as the requirement of a moving mechanism. 
   In another application, in the inspection of color quality in materials, for example dye color, the sample may be illuminated and the sample&#39;s optical behavior measured to determine the properties of the sample. Measurement may be made of reflectivity, absorption, transmission, secondary emission or other optical property in order to determine sample characteristics. In order to measure a sufficient field of view, precise control over the color and angular spectrum must be maintained for both illumination and detection systems. The above requirements necessarily add tremendous complexity to any measurement tool. 
   In the field of MEMS and semiconductor manufacture, repetitive patterns are inspected for defects or anomalies. The device under inspection is illuminated and scattered and/or reflected light is imaged to determine properties of the device under inspection. Such illumination and detection techniques can be quite complex in order to provide the necessary sensitivity and resolution. 
   Therefore, it is desirable to provide an alternative method and system for providing active illumination and detection for one-dimensional and two-dimensional inspection of samples having low cost, sufficient resolution, high sensitivity and high scanning speed for a broad range of applications. 
   SUMMARY OF THE INVENTION 
   The above objectives of providing a method and system for performing active one-dimensional and two-dimensional optical measurements having high speed, high sensitivity and low cost is accomplished in a method and apparatus. The apparatus comprises an active sensor including multiple illumination sources integrated to form a multi-pixel matrix. The matrix may have multiple rows and columns or may include just one row. 
   Multiple detectors are also integrated within illumination source matrix, each for detecting optical behavior of a sample resulting from the illumination of the sample by one or more of the illumination sources. One detector may be associated with multiple illuminators or one illuminator may be associated with multiple detectors. Filters may be integrated within the illumination and/or detection paths for providing wavelength and/or polarization discrimination capability and lenses may also be integrated within the illumination and/or detection paths providing variable working distances. A lens may be shared between one or more detectors and one or more illumination sources. 
   The foregoing and other objectives, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings, wherein like reference designators indicate like elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a pictorial diagram depicting an active sensor system including an apparatus in accordance with an embodiment of the present invention. 
       FIG. 2A  is a pictorial diagram depicting details of an active sensor in accordance with an embodiment of the present invention. 
       FIG. 2B  is a pictorial diagram depicting details of an active sensor in accordance with another embodiment of the present invention. 
       FIG. 2C  is a pictorial diagram depicting details of an active sensor in accordance with yet another embodiment of the present invention. 
       FIG. 2D  is a pictorial diagram depicting details of an active sensor in accordance with still another embodiment of the present invention. 
       FIG. 3  is a pictorial diagram depicting details of an active sensor in accordance another embodiment of the present invention. 
       FIG. 4  is a pictorial diagram depicting details of an active sensor system in accordance another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   While the below description is limited, by the way of example, to the measurement of a fluorescent sample, it is understood that the function will be similar for samples such as colored materials, MEMS or semiconductor devices, and/or repetitive patterns, and other applications. In order to avoid repetition, it is understood that the same description will be applicable to other applications that measure optical properties of samples. 
   Referring now to the figures and in particular to  FIG. 1 , a system including an active sensor  10  in accordance with an embodiment of the present invention is shown. Active sensor  10 , which includes a plurality of active sensor active sensor cells  11 , is placed in close proximity with a sample frame  12 , that may contain samples of biological matter tagged with a fluorescent material, or other samples under inspection such as a semiconductor device, for which a standard handling frame may be employed. Active sensor cells  11  each include one or more detectors and one or more illumination elements integrated on the substrate. While the depiction shows a two-dimensional active sensor  10 , active sensor  10  may also be a one-dimensional active sensor, comprising only one row of active sensor cells  11 . 
   The detection elements within active sensor cells  11  are coupled to a processing subsystem for detecting light scattered or emitted from associated portions of the samples. The association is by virtue of the proximity of the active sensor cells  11  to the sample frame  12  so that the fields of the detectors generally do not substantially overlap, or so that any overlap is generally limited to adjacent pixels. Similarly, the illumination element fields also do not substantially overlap in general and can be used to selectively illuminate portions of the samples. Sample frame  12  may comprise a plurality of wells, as in a microtiter plate or other multi-sample/multi-cell device, in which case, the spacing and location of active sensor cells  11  can be dictated by the spacing and location of wells in sample frame  12 . One cell  11  may correspond to a single well, giving active sensor  10  the ability to simultaneously process optical information at each cell without requiring a scanning mechanism. 
   Alternatively, sample frame  12  may comprise a single contiguous sample, such as a tissue sample or single sample having multiple discrete portions such as a DNA gel. Where discrete boundaries are not present, it may be desirable to sequentially illuminate the illumination elements individually, or program an illumination pattern such that adjacent illumination elements do not cause illumination of portions of a sample associated with other illumination elements. Illumination control subsystem  16  provides for control of illumination elements within active sensor cells  11  and is coupled to a processing subsystem  14  that receives the outputs of detectors within active sensor cells  11 . The interconnection of illumination control subsystem  16  with processing subsystem  14  permits synchronization of illumination and detection permitting accurate determination of response time and correlation of detected fluorescent emissions to the activation of an illumination element within a cell  11 . In addition, illumination elements can be pulsed or modulated and detection elements can be shuttered or time-gated to allow complex temporally resolved measurement schemes. 
   In other embodiments of the present invention, sample frame  12  may hold samples comprising a matrix of colored elements or samples may have a scattering pattern such as found on MEMS or semiconductor devices. The function of the system is identical to that described previously except that the detected light is no longer fluorescent emission, but scattered light. 
   The illumination elements included within active sensor cells  11  are substrate-integrated sources that may be provided by TFT-LCD devices, diode emitters, organic LEDs (OLEDs), vertical cavity emitting lasers (VCELs) or other light sources that may be integrated to form a high-density illumination matrix. The detectors included within active sensor cells  11  may be PIN photo-diodes, CCD sensors, CMOS sensors or other detectors that are suitable for integration within the illumination matrix. Lenses are optionally included for coupling a cell or field of active sensor cells  11  to samples or portions thereof and may be implemented using standard microlenses, graded-refractive-index (GRIN) lenses, fiber couplers or other suitable focusing/coupling or imaging mechanism. 
   Referring now to  FIG. 2A , details of an active sensor  10 A including active sensor cells  11 A, in accordance with an embodiment of the present invention are shown.  FIG. 2A  also shows an exemplary sample frame  12 A including sample elements  20  (depicted as wells in a microtiter plate) that are associated with particular active sensor cells  11 A via proximity of sample frame  12 A to active sensor  10 A. A substrate  28 A supports active sensor cells  11 A and a cover glass  22  is optionally included to protect active sensor cells  11 A and may be spaced above active sensor cells  11 A as shown, or placed in contact with active sensor cells  11 A. 
   The structure of active sensor cells  11 A is shown in balloon  23 A. A single illumination element  24 A is paired (associated) with a single detector  27 A for detecting fluorescence of biological matter deposited in an associated sample element  20 A due to illumination from illumination element  24 A (or other optical characteristics in non-fluorescence measurements). A microlens  25 A is optionally integrated over illumination element  24 A and detector  27 A for focusing or imaging a field of illumination element  24 A and detector  27 A on or within sample element  20 A. A filter  26 A is integrated between detector  27 A and microlens  25 A for providing a passband response around a specific optical wavelength and/or a polarization characteristic, providing wavelength and/or polarization selectivity in the output response of detector  27 A, whereby a specific fluorescence band is detected by detector  27 A. Illumination element  24 A is generally a narrowband emitter in the present configuration, but in some applications may be a broadband source, depending on whether or not the measurement being made is dependent on a specific excitation wavelength. The embodiment depicted in  FIG. 2A , is exemplary of a single-detector, single-illumination element pairing that is associated with a unique portion of a sample or unique samples of a sample frame by virtue of the sample proximity. Other configurations depicted in other embodiments below or otherwise understood to be encompassed by the present invention include other groupings of multiple or single detectors to multiple or single illumination elements or arrangements including a multi-pixel illumination element array interspersed with a multi-pixel detector array where no specific grouping of detectors and illumination elements is employed. Similarly, it is understood that various geometric arrangements of the illumination/detector pair can be used, including side-by-side, concentric arrangements, quad detectors and others and that an imaging system may be used so that the array or arrays do not have to be placed in close proximity to the samples. 
   Referring now to  FIG. 2B , details of an active sensor  10 B including active sensor cells  11 B, in accordance with another embodiment of the present invention are shown.  FIG. 2B  also shows an exemplary sample frame  12 A including sample elements  20  that are associated with particular active sensor cells  11 B via proximity of sample frame  12 A to active sensor  10 B. A substrate  28 B supports active sensor cells  11 B and cover glass  22  is optionally included to protect active sensor cells  11 B and may be spaced above active sensor cells  11 B as shown, or placed in contact with active sensor cells  11 B. 
   The structure of active sensor cells  11 B is shown in balloon  23 B. A single illumination element  24 B is paired (associated) with a single detector  27 B for detecting fluorescence of biological matter deposited in an associated cell forming sample element  20 A due to illumination from illumination element  24 B (or measuring other optical characteristics in non-fluorescence measurements). A microlens  25 B is optionally integrated over illumination over illumination element  24 B and detector  27 B for focusing or imaging a field of illumination element  24 B and detector  27 B on or within well  20 A. A filter  29 B is integrated between illumination element  24 B and microlens  25 B for providing a passband response around a specific optical wavelength and/or polarization characteristic, providing a narrowband and/or polarization-controlled illumination source. Illumination element  24 B is generally a broadband emitter in the present configuration. 
   Another filter  26 B is integrated between detector  27 B and microlens  25 B for providing a passband response around a specific optical wavelength and/or a polarization characteristic, providing wavelength and/or polarization selectivity in the output response of detector  27 B, whereby a specific fluorescence band is detected by detector  27 B. Filters  26 B and  29 B are not constrained to have the same passband wavelength, as the fluorescent response of a material may differ greatly from the specific excitation wavelength used to excite the biological sample. The embodiment of cell  11 B depicted in  FIG. 2B  is another example of a single-detector single-illumination element pairing. Other possible combinations include a filtered illumination source with an unfiltered detector, polarized illumination source with filtered detector and other combinations of passband and/or polarizer filters. 
   Referring now to  FIG. 2C , details of an active sensor  10 C including active sensor cells  11 C, in accordance with yet another embodiment of the present invention are shown.  FIG. 2C  also shows an exemplary sample frame  12 A including sample elements (wells)  20  that are associated with particular active sensor cells  11 C via proximity of sample frame  12 A to active sensor  10 C. A substrate  28 C supports active sensor cells  11 C and cover glass  22  is optionally included to protect active sensor cells  11 C and may be spaced above active sensor cells  11 C as shown, or placed in contact with active sensor cells  11 C. 
   The structure of active sensor cells  11 C is shown in balloon  23 C. Multiple illumination elements  24 C are paired (associated) with a single detector  27 C for detecting fluorescence of biological matter deposited in an associated sample element  20 A due to illumination from illumination elements  24 C (or other optical characteristics in non-fluorescence measurements). A microlens  25 C is optionally integrated over illumination over illumination elements  24 C and detector  27 C for focusing or imaging a field of illumination elements  24 C and detector  27 C on or within well  20 A. A filter  26 C is integrated between detector  27 C and microlens  25 C for providing passband response around a specific optical wavelength and/or a polarization characteristic, providing wavelength and/or polarization selectivity in the output response. Illumination elements  24 C are generally narrowband emitters having separate predetermined illumination wavelengths in the present configuration and are generally controlled by illumination control subsystem  16  so that fluorescent response of samples or portions thereof to multiple predetermined wavelength excitation can be determined by enabling first one set of illumination elements in active sensor cells  11 C corresponding to a first wavelength and then a second set of illumination elements in active sensor cells  11 C corresponding to a second wavelength and observing the response using detectors  27 C. The embodiment depicted in  FIG. 2C  is an example of multiple-illumination element, single-detector grouping. The number of associated illumination elements to a single detector also may be greater than two. 
   Referring now to  FIG. 2D , details of an active sensor  10 D including active sensor cells  11 D, in accordance with still another embodiment of the present invention are shown.  FIG. 2D  also shows an exemplary sample frame  12 A including sample elements (wells)  20  that are associated with particular active sensor cells  11 D via proximity of sample frame  12 A to active sensor  10 D. A substrate  28 D supports active sensor cells  11 D and cover glass  22  is optionally included to protect active sensor cells  11 D and may be spaced above active sensor cells  11 D as shown, or placed in contact with active sensor cells  11 D. 
   The structure of active sensor cells  11 D is shown in balloon  23 D. Multiple detectors  27 D are paired (associated) with a single illumination element  24 D for detecting fluorescence of biological matter deposited in an associated sample element  20 A due to illumination from illumination element  24 D (or other optical characteristics in non-fluorescence measurements). A microlens  25 D is optionally integrated over illumination element  24 D and detectors  27 D for focusing or imaging a field of illumination element  24 D and detectors  27 D on or within well  20 A. Multiple filters  29 D are integrated between detectors  27 D and microlens  25 D for providing a unique passband response around a specific optical wavelength for each detector  27 D in a cell  11 D, providing multiple narrowband detector responses. Alternatively or in combination, filters  29 D may provide multiple polarization responses, providing the ability to determine polarization ratios, and so forth. Illumination element  24 D is generally a narrowband emitter for exciting a sample or portions thereof and detectors  27 D in conjunction with filters  29 D provide separate responses to the illumination, whereby multiple fluorescence band emissions can be simultaneously detected in response to narrowband excitation. The embodiment depicted in  FIG. 2D  is an example of single-illumination element, multiple-detector grouping. The number of associated detectors to a single illumination element also may be greater than two. 
   Referring now to  FIG. 3 , details of an active sensor system in accordance with an embodiment of the present invention are shown. Two separate array devices are employed, device  10 E is a detection array that includes elements as depicted in balloon  23 E, including detectors  27 E filters  26 E and microlens  25 E. Device  10 F is an illumination array including illumination elements  24 F and microlenses  25 F as depicted in balloon  23 F. However, the elements may be variations on the depicted structure in accordance with the above-described element types and either or both arrays may include both illumination and detection elements. For example to provide a transmission and reflection/scattering measurement, device  10 F may also include detection elements for detecting back-scattered light associated with each illumination element and/or sample element  20 E. 
   The system of  FIG. 3  is particularly suited for transmission measurements as detector device  10 E is on the opposite side of samples  20 E from illumination device  10 F. Groups associating detectors  27 E and illumination elements  24 F in the system of  FIG. 3  are associated by the location the fields of light transmitted by particular illumination elements  24 F and received by particular detectors  27 E, rather than also being associated by proximity as in the other exemplary embodiments described above, and as such, comprise the active sensor “cells” in the present embodiment. Both device  10 E and device  10 F are fabricated on substrates ( 28 E and  28 F respectively) and may include cover glasses ( 22 E and  22 F respectively). It should be noted in all of the above examples, filtering may be provided by a “gel” or colored cover glass that is provided in addition to or in place of the illustrated cover glasses for providing a wavelength/or polarization filtered optical characteristic within the system. 
   Referring now to  FIG. 4 , an active sensor system in accordance with yet another embodiment of the present invention is depicted. Active sensor  10 G, which may be any of the active sensors described above or variations thereon, is coupled by an imaging lens  41  to sample elements  20 G. The imaging system may alternatively be or include optical fibers, waveguides of other type or any known method for “remoting” (or “relaying”) an image from sample elements  20 G to active sensor  10 G. As long as a grouping via the image is made between illumination elements and detection elements within active sensor  10 G, detection of individual sample element  20 G behavior is provided. Optical paths (such as optical paths  42  and  43 ) associate co-located detection and illumination elements within active sensor  10 G with a particular sample element (e.g., optical path  42  associates a particular detector/illuminator with sample element  20 G). Alternatively, separate detection and illumination devices may be provided and coupled via beam-splitters, couplers or physical arrangement (angular orientation, etc.), so that an association between one or more detection elements and one or more illumination elements is preserved. While the embodiment shown uses a single lens  41  to relay light between active sensor  10 G element groups and sample elements with an inverted position relationship, other lens/relaying-device configurations may be employed including position-rectified configurations. 
   While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form, and details may be made therein without departing from the spirit and scope of the invention.