HK1169934B - Optical spectroscopy device for non-invasive blood glucose detection and associated method of use - Google Patents

Description

Spectroscopic analysis apparatus for non-invasive blood glucose detection and related methods of use

Background

Diabetes is a chronic disease that, when left uncontrolled, causes severe damage to many body systems over time, including nerves, blood vessels, eyes, kidneys and the heart. The national institute of diabetes, digestive and renal disease (NIDDK) estimates that 2360 million people or 7.8% of the population in the united states suffer from diabetes in 2007. Worldwide, the World Health Organization (WHO) estimates that more than 1.8 million people suffer from diabetes, and they estimate that this figure will increase to 3.66 million by 2030 and 3030 million in the united states. According to WHO, it is estimated that 110 million people die from diabetes in 2005. They estimate that the number of diabetic deaths will increase by more than 50% overall between 2006 and 2015 and by more than 80% in high income countries.

The economic burden from diabetes is considerable for both the individual and the society as a whole. According to the American diabetes Association, the annual total economic cost of diabetes in the United states in 2007 is estimated to be 1740 billion dollars. This figure increased by 420 billion dollars since 2002. This 32% increase means a dollar amount of over 80 billion per year.

A key point in diabetes management is that diabetic patients self-monitor blood glucose (SMBG) concentrations in a home environment. By frequently testing blood glucose levels, diabetics can better manage medications, diet, and exercise to maintain control and prevent long-term adverse health outcomes. Indeed, the Diabetes Control and Complications Trial (DCCT) following 1,441 diabetic patients for several years indicates that those diabetic patients who receive a heightened control plan of multiple blood glucose tests per day are only one-fourth, half, and one-third more advanced diabetic eye disease, renal disease, and have had early forms of these three types of complications, than the standard treatment group.

However, due to the inconvenience and pain of drawing blood percutaneously prior to analysis, patients can be frustrated by regularly using current monitoring techniques, which results in many diabetics not adhering to good glycemic control that should have been performed. Therefore, non-invasive measurement of blood glucose concentration is a desirable and beneficial development for the management of diabetes. A non-invasive monitor will perform painless tests multiple times a day and is more suitable for children with diabetes. According to papers published in 2005 (j.wagner, c.malchoff and g.abbott, Diabetes Technology & Therapeutics, 7(4)2005, 612-.

There are many non-invasive methods for blood glucose determination. One technique for non-invasive blood chemistry testing involves the collection and analysis of spectral data.

Extracting information about blood characteristics (e.g., blood glucose concentration) from spectra or other data obtained by spectroscopic analysis is a complex problem due to the presence of other components (e.g., skin, fat, muscle, bone, interstitial fluid) in the region being sensed in addition to blood. These other components will affect these signals in such a way as to cause the readings to change. More specifically, the resulting signal may be much larger in magnitude than the portion of the signal corresponding to blood, and thus limits the ability to accurately extract blood characteristic information.

Drawings

In the drawings, which are not necessarily to scale, like reference numerals designate substantially similar components throughout the several views. Like reference numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, and not by way of limitation, various embodiments discussed in the present document.

Fig. 1 illustrates a graph of a pulse wave corresponding to light absorption by arterial blood, in accordance with some embodiments;

FIG. 2 is a simplified block diagram illustrating components of an optical measurement system according to the present invention;

FIG. 3 illustrates an existing optical configuration for performing optical measurements of a biological sample, in accordance with some embodiments;

FIG. 4A illustrates a first alternative embodiment for performing optical measurements of a biological sample;

FIG. 4B illustrates a preferred embodiment for performing optical measurements of a biological sample;

FIG. 4C illustrates a second alternative embodiment for performing optical measurements of a biological sample;

FIG. 5 is a cross-sectional view of an exemplary light funnel and half angle (α); and

fig. 6 is a cross-sectional view of an exemplary light funnel and light source.

Detailed Description

The following detailed description includes references to the accompanying drawings, which form a part hereof. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, which are also referred to herein as "examples," are described in sufficient detail to enable those skilled in the art to practice the invention. The embodiments may be combined, other embodiments may be utilized, or structural and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

In this document, unless otherwise indicated, the terms "a" or "an" are used to include one or more than one, and the term "or" is used to refer to a non-exclusive "or". Also, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Furthermore, all publications, patents, and patent documents mentioned in this document are incorporated by reference in their entirety as if individually incorporated by reference. In the event of inconsistent usages between this document and those documents incorporated by reference, the usage in the incorporated references should be considered supplementary to this document; for contradictory inconsistencies, the use in this document prevails.

Embodiments of the present invention relate to optical components, such as light funnels for illumination and measurement of optical properties of samples. Although spectral sampling of a human or animal body area is exemplified, embodiments relate to all types of optical instruments, including optical detectors, microscopes, spectrometers, and the like.

Spectroscopic analysis can be used to determine the amount of light absorbed by a biological sample, such as a human finger. By measuring the amount of light absorbed by the finger, the blood glucose, cholesterol and hemoglobin levels of a person can be determined non-invasively. Fingertip measurements are generally preferred because of the large number of capillaries concentrated within the fingertip and because of the conversion of arterial to venous blood that can occur within the fingertip. However, the technique of the present invention is not limited to the use of human fingers. For example, the use of other samples such as a human ear lobe may be desirable.

When light is transmitted through a biological sample, such as a human finger, the light is absorbed and scattered by various components of the finger, including skin, muscle, bone, fat, interstitial fluid, and blood. However, it has been observed that the light absorption by the human finger exhibits a small periodic pattern corresponding to the heartbeat. FIG. 1 depicts a periodic detector photocurrent I corresponding to light absorption of arterial blood in capillaries caused by a user's heartbeat_DGraph 102 of (t). Although the amplitude of the periodic pattern is small compared to the total photocurrent generated by the detector, considerable information can be extracted from the periodic pattern of graph 102. For example, assuming a person's heart rate is sixty beats per minute, the time between the beginning of any pulse beat and the end of that pulse beat is one second. During this one second period, the photocurrent will have a maximum or peak 104 reading and a minimum or valley 106 reading. The peak 104 reading of the graph corresponds to the time when there is a minimum amount of blood in the capillary, while the valley 106 reading corresponds to the time when there is a maximum amount of blood in the capillary. By using the information provided by the peaks and valleys of the periodic plot, light absorption and scattering by major finger components not in the capillaries (e.g. skin, fat, bone, muscle and interstitial fluid) can be excluded. The reason why these major components not in the capillaries are excluded is that they are unlikely to change over the time interval of one heartbeat. In other words, the light absorbed by the blood can be detected based on the peaks and valleys of the graph 102.

Assuming that the peak value of the periodic photocurrent generated by the photo-sensing device is I_PAdjacent valleys of the periodic photocurrent are I_VAnd the photocurrent generated by the light sensing device in the absence of the sample is I₀The transmittance corresponding to the peak and valley photocurrents can then be defined as:

and

the corresponding peak and valley absorptances are:

A_V＝-log(T_V) (3)；

and

A_P＝-log(T_P) (4)；

A_Vand A_PThe difference between reflects the light absorption and scattering by the blood in the finger only:

the algorithm shown in equation (5) only needs to monitor the photocurrent corresponding to the light intensity transmitted through the finger. Thus, there is no need to determine the photocurrent generated by the light sensing device without a human finger.

Fig. 2 is a simplified block diagram illustrating components of a current optical measurement system, generally indicated by reference numeral 200, that uses the "pulsatile" principle to determine the amount of light absorbed and scattered solely by blood in a sample (e.g., a human finger). A power source 201, such as a battery, provides power to a light source 202 that generates a plurality of light beams 204, 206, 208, 210 directed toward the top of the user's finger. In accordance with one aspect of the optical measurement system 200, each of the beams 204, 206, 208, 210 has the same wavelength range, typically from about 700nm to about 1600 nm. Although the optical measurement system 200 is described herein as generating four (4) beams, it is contemplated that the light source 202 may be altered to generate fewer beams or additional beams in other embodiments.

The first aperture 212 ensures that the beams 204, 206, 208, 210 illuminate a target area of a sample (e.g. a human finger). The second aperture 214 ensures that the portion of the beam transmitted through the sample illuminates the lens 216. The beams 204, 206, 208, 210 are attenuated by the sample and components of the optical measurement system 200, and the attenuated beams 218, 220, 222, 224 then exit the sample. The attenuated beams 218, 220, 222, 224 illuminate the lens 216, and the lens 216 collects the attenuated beams 218, 220, 222, 224 so that they more effectively impinge on the detector block 226.

The detector block 226 is positioned directly below the lens 216 and includes a plurality of Light Sensing Devices (LSDs) 228, 230, 232, 234, such as photodiode arrays. In accordance with one aspect of the optical measurement system 200, each of the light sensing devices 228, 230, 232, 234 is tuned to detect a particular spectrum (or spectra) of light. For example, each light sensing device may be associated with a corresponding Interference Filter (IF), such as filters 236, 238, 240, 242. The interference filter transmits one or more spectral bands or spectral lines of light and substantially blocks other spectral bands or spectral lines.

Each of the light sensing devices 228, 230, 232, 234 generates a corresponding photocurrent signal 244, 246, 248, 250 that is proportional to the intensity of light received by the particular light sensing device. The photocurrent signal generated by the photodiode can be converted to another form of signal, such as an analog voltage signal or a digital signal.

The processor 243 is coupled to the detector block 226 and is configured to calculate changes in the photocurrent signals 244, 246, 248, 250. In an exemplary embodiment, the processor 243 executes an algorithm, such as that shown in the equation indicated above by the number (5), to calculate the change in light absorption (Δ a) caused only by blood in the finger. This quantitative calculation of the light absorption of the blood can then be used to determine the properties of the blood. For example, the blood glucose level of the user may be determined by comparing the calculated light absorption value to predetermined values corresponding to different blood glucose levels stored in a memory (not shown).

A difficulty associated with finger-based pulse detection methods is the low signal-to-noise ("S/N") ratio, since the amplitude of the periodic pattern (i.e., the difference between the peak and valley values) is typically 1% -2% of the total photocurrent generated by the light intensity transmitted through the sample (e.g., a human finger). To obtain a 100: 1S/N ratio in the determination of Δ A, the baseline noise of the device used to measure the light absorption by the sample should be no greater than 3.0 × 10 within a bandwidth of 10Hz^-5Absorbance (peak to peak).

However, 3.0 × 10 within a 10Hz bandwidth^-5Is difficult to obtain with the low light intensity levels used by some battery-powered handheld non-invasive blood chemistry measurement devices.

A known solutionThe scheme involves data averaging. To increase the S/N ratio, the average of Δ a defined by the following equation is used for further calculations to extract the blood glucose concentration:in this equation, M is the number of heart beats within the time interval of the pulsation measurement. However, this method requires a long data acquisition time due to the fact that the heart rate is of the order of once per second. For example, 25 seconds would be required to increase the S/N ratio by a factor of 5, and 100 seconds would be required to increase the S/N ratio by a factor of 10. In contrast, current commercial blood drawing glucose meters can determine blood glucose levels within 5 seconds. Furthermore, long detection times will significantly increase measurement errors due to finger motion, light intensity drift, temperature variations, etc.

Another solution involves increasing the intensity of the light irradiation. However, due to size limitations of some devices, it may not be possible or effective to increase the illumination intensity to achieve a desired baseline noise level (e.g., battery depletion). Therefore, there is a need for a system and method to increase the amount of light intensity that can be detected by such devices without significantly increasing device size, light illumination intensity, and battery power consumption.

Fig. 3 depicts a configuration of a conventional prior art device for measuring the amount of light absorbed by a sample, such as a human finger. The lamp 302 generates near infrared ("NIR") radiation or a light beam from 700nm to 1600 nm. The generated NIR beam enters the entrance aperture 304 and passes through the sample. The NIR light beam transmitted through the sample passes through exit aperture 306 to impinge on lens 308. Lens 308 collimates the light beams and projects them onto filter array 310 and then onto detector array 312. The device also includes a wall housing 314 to prevent stray light from reaching the light detector.

The optical system shown in fig. 3 has a very low light intensity efficiency. Light enters the sample via the entrance aperture 304. Typically, to accommodate the small finger size of a child, entrance aperture 304 has a diameter of about 0.25(1/4) inches or less. Light transmitted through the sample is collected through the exit aperture 306. The exit aperture 306 typically has a diameter of about 0.25(1/4) inches or less. Most of the light intensity emitted from the lamp 302 cannot reach the target due to the small solid angle of illumination. The optical configuration shown in fig. 3 also has a small solid angle for light collection. Light is emitted from the exit aperture 306 into the entire 2 pi solid angle below the sample. The total light intensity collected using the optical system shown in fig. 3 is typically about 10% of the light intensity emitted through aperture 306. In addition, the entire light intensity distribution from 700nm to 1600nm is transmitted to each detector in the detector array 312, and each detector typically detects only a relatively narrow wavelength bandwidth of 10 nm. Thus, up to 98% (or more) of the light intensity is wasted.

Fig. 4A depicts an optical measurement system 400 for performing optical detection of a biological sample according to an exemplary first alternative embodiment. The system includes a light illumination funnel 412 that may be constructed according to the techniques described below with reference to fig. 5. A small light source 402, such as a lamp, is arranged in an inner portion of a light illumination funnel 412 and generates a plurality of light beams 404, 406, 408, 410. Each of the beams 404, 406, 408, 410 has the same wavelength range, for example, from about 700nm to about 1600 nm. Although the optical measurement system 400 is described herein as generating four (4) beams, it is contemplated that in other embodiments the light source may be altered to generate fewer beams or additional beams.

Light beams 404, 406, 408, 410 from the light source 402 exit the light illumination funnel 412 through exit openings 416, some of which are reflected by the sidewalls of the funnel. The exit opening 416 of the light illumination funnel 412 has a diameter greater than or equal to the funnel diameter 414 near the front end. The electrodes 413 and 415 of the light source 402 are connected to the lamp control board 401. For example, according to one embodiment, the funnel diameter 414 is about 0.125(1/8) inches and the diameter of the exit opening 416 is about 0.25(1/4) inches. Thus, in contrast to the configuration shown in fig. 3, the light illumination funnel 412 focuses the light beams 404, 406, 408, 410 in substantially the same direction towards the top of the sample. The light illumination funnel may significantly increase the total light intensity received by the target area, and thus the S/N ratio, compared to the configuration of fig. 3.

Fig. 5 depicts a cross-sectional view of an exemplary light funnel 512. Light funnel 512 may be used as a light illumination funnel, such as 412 in fig. 4A, 4B, or 4C, or a light collection funnel, such as 434 in fig. 4C. The exemplary light funnel 512 includes a generally cylindrical outer wall 502 having a diameter D1, and an interior portion defined by an inner wall 506 having a generally frustoconical shape. The inner portion of the funnel has a diameter D2 at the front end 504. The funnel has an exit opening 508 at the rear end. The opening 508 (light outlet) has a diameter D3 that is greater than D2. The separation distance between the two ends is L and the half angle of the frusto-conical shape of the inner surface is a. The half angle may be less than, for example, about 45 degrees. In an exemplary embodiment, the half angle α has a value of about 5 degrees to about 25 degrees. Light funnel 512 may be formed from a plastic, metal, or other suitable material or compound/material layer, having any desired index(s) of refraction. According to one aspect, the light funnel 512 is formed of metal and the surface of the inner wall 506 is made highly reflective. Using the light illumination funnel, the total light illumination intensity received by the target area may be increased by a factor of 3 to 4 over the light illumination configuration shown in fig. 3.

Fig. 6 depicts an exemplary optical device, generally indicated by reference numeral 600, that includes a light source 606, such as a lamp, and a light illumination funnel 612. A printed circuit board ("PCB") 602 for lamp power control may be located near or in contact with the front end of the light illumination funnel. A light source 606, such as a lamp, is connected to the plate 602 via a wire passing through the front end of the funnel. A light source 606, such as a lamp, may be mounted to the PCB 602. The PCB 602 receives power through a power cord 604 connected to a power source, such as the power source 201 shown in fig. 2, e.g., a battery. When power is supplied through the power line 604, a light source 606, such as a lamp, generates a plurality of light beams, such as the light beams 404, 406, 408, and 410 shown in fig. 4A, 4B, and 4C. The position of the light source 606, such as a lamp, inside the funnel can be adjusted to maximize the illumination intensity received by the large opening 608 (light exit).

In an exemplary embodiment, the light illumination funnel 612 is mounted to the PCB 602 via screws, posts, or other connectors. The frustoconical shape of the inner surface of the light illumination funnel 612 serves to converge and focus the light beams 404, 406, 408, 410 shown in fig. 4A, 4B, and 4C from the lamp into a generally conical light beam toward the finger.

Referring again to FIG. 4A, the beams 404, 406, 408, 410 are attenuated by the sample and the components of the optical measurement system 400. The attenuated light beam then passes through an exit aperture 418 and is collected by a condenser lens 420, such as an aspheric lens. The light beam 421 exiting the condenser lens 420, such as an aspheric lens, may then pass through a filter 426 to a detector 428.

An advantage of using a condenser lens 420, such as an aspheric lens, for light collection is its large solid angle for light collection. When properly configured, the total light intensity received by each detector can be increased by a factor of 3 to 4, compared to the light collection configuration shown in fig. 3, where a condenser lens 420, such as an aspheric lens, is used to collect light emitted from the target area. The combination of illuminating the funnel 412 with light and the condenser lens 420 (e.g., an aspheric lens) as a light collector can increase the total light intensity received by each detector by a factor of about 9 to about 16 compared to the optical configuration shown in fig. 3.

The detector block 428 is located below the condenser lens 420, such as an aspheric lens, and may include a plurality of light sensing devices, such as photodiode arrays. Each light sensing device detects a particular spectrum of light. In an exemplary embodiment, an interference filter 426 is placed on top of each photo-sensing device.

A processor, such as processor 243 shown in fig. 2, may be coupled to detector block 428 and configured to calculate a change in the current signal generated by the light sensing device. For example, as described above with reference to fig. 2, the processor 243 executes an algorithm such as that shown in equation (5) to calculate the change in light absorption (Δ a) caused only by blood in the finger. This quantitative calculation of the light absorption of the blood can then be used to determine the properties of the blood.

Fig. 4B illustrates a preferred embodiment of an optical arrangement for performing optical detection of a biological sample and generally indicated by reference numeral 460. The light source 402 generates a plurality of light beams 404, 406, 408, 410. The light source 402 may be, for example, an incandescent light source or an infrared light emitting diode. According to one aspect of the optical measurement system 460, each of the beams 404, 406, 408, 410 has the same wavelength range, for example, from 700nm to 1600 nm. Although the optical measurement system 460 is described herein as generating four (4) beams, it is contemplated that in other embodiments the light source can be altered to generate fewer beams or additional beams. Light beams 404, 406, 408, 410 from the light source 402 exit the light illumination funnel 412 through an exit opening 416. The diameter of the exit opening 416 of the light irradiation funnel 412 is larger than or equal to the diameter of the opening 414 on the top, and the two electrodes 413 and 415 of the light source 402 are connected to the lamp control board 401 through the opening 414. For example, according to one embodiment, the diameter of the entrance opening 414 is about 0.125(1/8) inches and the diameter of the exit opening 416 is about 0.25(1/4) inches. Thus, in contrast to the configuration depicted in fig. 3, light illumination funnel 412 focuses light beams 404, 406, 408, 410 to substantially the same direction toward the top of the user's finger. The light illumination funnel may significantly increase the total light intensity received by the target area, and thus the S/N ratio, compared to the configuration of fig. 3.

In the exemplary preferred embodiment depicted in FIG. 4B, indicated by reference numeral 460, the light beams 404, 406, 408, 410 are attenuated by the sample and the components of the optical measurement system. The attenuated NIR light beam then passes through an exit aperture 418, is collected by a condenser lens 420, such as an aspheric lens, and is projected onto a transmission grating device 422. The transmission diffraction grating 422 angularly decomposes the various wavelength components of the mixed NIR light beam into a spectrum of wavelengths that monotonically increase in the direction depicted by arrow 430. In other words, since the diffraction angle depends on the wavelength, different wavelength components of the light beam are sent to different directions by the diffraction grating 422. The spectrum 424 exiting the transmission diffraction grating 422 may then be narrowed by an optional interference filter array 426. The light is detected by a photodetector array 428, such as a photodiode. The detectors in the array 428 may be positioned such that a detector tuned to a particular spectrum of light receives light within that spectrum from the transmission diffraction grating 422. For example, the center wavelength of each interference filter in the filter array 426 may be arranged to monotonically increase to coincide with a respective wavelength component of the spectrum from the transmission diffraction grating 422. It will be apparent that the use of filters such as filter array 426 is optional and not necessary.

In contrast to the collection optics of fig. 3, where the entire light intensity distribution from 700nm to 1600nm is sent to each detector, the approach of using a transmission diffraction grating will limit the spectrum sent to each detector to wavelength components close to the center wavelength of the detector (and/or corresponding filter). As a result, the amount of wasted light is greatly reduced and the intensity of light received by the photodiode can be increased by a factor of 10 to 20, as compared to the light collection configuration described with reference to fig. 4A. Accordingly, the combination of the light irradiation funnel 412, the condensing lens 420 (e.g., an aspheric lens) as a light collector, and the transmission grating 422 as a wavelength separation device may increase the intensity of light received by the photodiode by about 100 to about 200 times, as compared to the optical configuration shown in fig. 3.

Fig. 4C illustrates an exemplary second alternative embodiment, generally indicated by reference numeral 462. Although the optical measurement system 462 is described herein as generating four (4) beams, it is contemplated that in other embodiments the light source can be altered to generate fewer beams or additional beams. Light beams 404, 406, 408, 410 from the light source 402 exit the light illumination funnel 412 through an exit opening 416. The diameter of the exit opening 416 of the light irradiation funnel 412 is larger than or equal to the diameter of the opening 414 on the top, and the two electrodes 413 and 415 of the light source 402 are connected to the lamp control board 401 through the opening 414. For example, according to one embodiment, the diameter of the entrance opening 414 is about 0.125(1/8) inches and the diameter of the exit opening 416 is about 0.25(1/4) inches. The light illumination funnel 412 illuminates a sample (e.g., a finger). The beams 404, 406, 408, 410 are attenuated by the sample and components of the optical measurement system. The attenuated beams 436, 438, 444, 446 emerge from the sample. The attenuated light beams 436, 438, 444, 446 enter the light collecting funnel 434 through an entrance opening 442 (first opening) and exit the light collecting funnel 434 through an exit opening 440 (second opening). The diameter of the entrance opening 442 of the light collection funnel 434 is less than or equal to the diameter of the exit opening 440. For example, according to one embodiment, the diameter of exit opening 440 is about 0.625(5/8) inches and the diameter of entrance opening 442 is about 0.25(1/4) inches. The light collection funnel 434 may project the collected light onto the filter array 426.

The light collection funnel 434 may be constructed according to the techniques described below with reference to fig. 5. For example, the exemplary light collection funnel 434 has a generally cylindrical outer wall 502 and a central opening defined by a frustoconical inner wall 506. The light collection funnel 434 may also be formed of a plastic, metal, or other suitable material or compound/material layer, having any desired index of refraction(s). The light collecting funnel 434 may be formed of metal and the surface of the frustoconical inner wall may be made highly reflective. The total collection efficiency of the light collection funnel 434 has been observed to exceed 80%, which is eight times that obtained using the conventional optical collection structure shown in fig. 3. The combination of illuminating the funnel 412 and the light collection funnel 434 with light may increase the intensity of light received by the detector by a factor of about 20 to about 30 compared to the optical configuration in fig. 3.

The filter array 426 and the detector array 428 are located below the exit opening 440 of the light collection funnel 434 and include a plurality of light sensing devices, such as the light sensing devices 228, 230, 232, 234 shown in fig. 2, such as photodiode arrays. In an exemplary embodiment, the light sensing devices each detect one particular wavelength of light.

Embodiments of the invention may also include methods of using the apparatus or light collection system described above. The light source may contact the target area through the illumination funnel sufficient to generate transmitted, reflected, or reflected light. The transmitted, reflected, or reflected light may enter the light collection system and be directed to, for example, one or more detectors.

Thus, several embodiments of the novel invention have been shown and described. It will be apparent from the foregoing that certain aspects of the present invention are not limited by the specific details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. As used in the foregoing specification, the terms "having" and "including" and similar terms are used in the sense of "optionally" or "may include" rather than "necessarily". Many changes, modifications, variations and other uses and applications of the subject construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow. It is to be understood that the embodiments disclosed herein include any and all combinations of features described in any of the dependent claims.

Claims (22)

1. An apparatus for concentrating light, the apparatus comprising:

a first outer wall having a front end, a rear end, an inner surface and an outer surface, the inner surface defining an interior portion having a front end and a rear end;

a light source disposed within the interior portion;

wherein the first outer wall has an opening in the rear end, the opening having an opening diameter;

wherein the inner portion has a frustoconical shape;

wherein the inner portion has a first cross-sectional diameter at the opening equal to the opening diameter and a second cross-sectional diameter near the leading end less than the opening diameter; and

wherein the inner surface is light reflective.

2. The apparatus for concentrating light of claim 1, wherein the first outer wall comprises metal and the inner surface is polished.

3. The apparatus for concentrating light of claim 1, wherein a half angle of the frustoconical shape is less than 45 degrees, wherein the half angle of the frustoconical shape is taken relative to a perpendicular bisecting the shape of the frustoconical shape extending from the second cross-sectional diameter to the first cross-sectional diameter.

4. The apparatus for concentrating light of claim 3, wherein the half angle of the frustoconical shape is greater than 5 degrees and less than 25 degrees.

5. The apparatus for concentrating light of claim 1, further comprising a condenser lens positioned below the opening for receiving light through the sample.

6. The apparatus for concentrating light of claim 5, wherein the condenser lens is an aspheric lens.

7. The apparatus for concentrating light of claim 5, further comprising an aperture between the sample and the condenser lens.

8. The apparatus for concentrating light of claim 5, further comprising:

a plurality of filters;

wherein each filter of the plurality of filters is positioned to receive light from the condenser lens and emit filtered light onto a corresponding photodetector of a plurality of photodetectors; and

wherein each of the plurality of light detectors is tuned to detect light in a spectrum emitted by a corresponding filter of the plurality of filters.

9. The apparatus for concentrating light of claim 8, further comprising an aperture between the sample and the condenser lens.

10. The apparatus for concentrating light of claim 5, further comprising a diffraction grating positioned below the concentrating lens.

11. The apparatus for concentrating light of claim 10, further comprising an aperture between the sample and the condenser lens.

12. The apparatus for concentrating light of claim 10, further comprising:

a plurality of filters;

wherein each filter of the plurality of filters is positioned to receive light from the condenser lens and emit filtered light onto a corresponding photodetector of a plurality of photodetectors; and

wherein each of the plurality of light detectors is tuned to detect light in a spectrum emitted by a corresponding filter of the plurality of filters.

13. The apparatus for concentrating light of claim 1, further comprising:

a second outer wall having a front end, a rear end, an inner surface and an outer surface, the inner surface defining an interior portion having a front end and a rear end;

wherein the interior portion of the second outer wall has a first opening in the rear end and the interior portion of the second outer wall has a second opening in the front end, the first opening having a first cross-sectional diameter, the second opening having a second cross-sectional diameter, and the first cross-sectional diameter being greater than the second cross-sectional diameter;

wherein the inner portion has a frustoconical shape and is light reflective; and

wherein a sample can be placed between the opening in the first outer wall and the second opening in the front end of the second outer wall.

14. The apparatus for concentrating light of claim 13, further comprising:

a plurality of filters;

wherein each of the plurality of optical filters is positioned to receive light from the first opening in the back end of the second outer wall and emit filtered light onto a corresponding one of a plurality of optical detectors; and

wherein each of the plurality of light detectors is tuned to detect light in a spectrum emitted by a corresponding filter of the plurality of filters.

15. The apparatus for concentrating light of claim 12, further comprising an aperture between the sample and the condenser lens.

16. A method for concentrating light, the method comprising:

utilizing a light source located within an interior portion of a first outer wall, wherein the first outer wall has a front end, a back end, a light reflective interior surface and an exterior surface, the interior surface defining an interior portion, the interior portion having a frustoconical shape with a front end and a back end, and the first outer wall having an opening within the back end, the opening having an opening diameter and the interior portion having a cross-sectional diameter at the opening equal to the opening diameter and a second cross-sectional diameter near the front end that is less than the opening diameter.

17. The method for concentrating light of claim 16, further comprising:

a condenser lens positioned below the opening for receiving light passing through the sample is utilized.

18. The method for concentrating light of claim 17, wherein the condenser lens is an aspheric lens.

19. The method for concentrating light of claim 17, further comprising:

an aperture is used between the sample and the condenser lens.

20. The method for concentrating light of claim 17, further comprising:

utilizing a plurality of filters, wherein each of the plurality of filters is positioned to receive light from the condenser lens and emit filtered light onto a corresponding one of a plurality of photodetectors, and each of the plurality of photodetectors is tuned to detect light in the spectrum emitted by the corresponding one of the plurality of filters.

21. The method for concentrating light of claim 16, further comprising:

utilizing a second outer wall having a front end, a rear end, an inner surface and an outer surface, the inner surface defining an inner portion that is frustoconical, light reflective, and has a front end and a rear end, and the inner portion of the second outer wall having a first opening within the rear end and the inner portion of the second outer wall having a second opening within the front end, the first opening having a first cross-sectional diameter, the second opening having a second cross-sectional diameter, and the first cross-sectional diameter being greater than the second cross-sectional diameter; and

placing a sample between the opening in the first outer wall and the second opening in the leading end of the second outer wall.

22. The method for concentrating light of claim 21, further comprising:

utilizing a plurality of optical filters, wherein each of the plurality of optical filters is positioned to receive light from the first opening within the back end of the second outer wall and emit filtered light onto a corresponding plurality of optical detectors, and each of the plurality of optical detectors is tuned to detect light in the spectrum emitted by a corresponding optical filter of the plurality of optical filters.