U.S. patent application number 13/482123 was filed with the patent office on 2012-09-20 for lighting design of high quality biomedical devices.
This patent application is currently assigned to LUMENCOR, INC.. Invention is credited to Arlie R. Conner, Claudia B. Jaffe, Steven M. Jaffe.
Application Number | 20120235061 13/482123 |
Document ID | / |
Family ID | 42353413 |
Filed Date | 2012-09-20 |
United States Patent
Application |
20120235061 |
Kind Code |
A1 |
Jaffe; Claudia B. ; et
al. |
September 20, 2012 |
LIGHTING DESIGN OF HIGH QUALITY BIOMEDICAL DEVICES
Abstract
The invention relates to a plurality of light sources to power a
variety of applications including microarray readers, microplate
scanners, microfluidic analyzers, sensors, sequencers, Q-PCR and a
host of other bioanalytical tools that drive today's commercial,
academic and clinical biotech labs.
Inventors: |
Jaffe; Claudia B.;
(Portland, OR) ; Jaffe; Steven M.; (Portland,
OR) ; Conner; Arlie R.; (Portland, OR) |
Assignee: |
LUMENCOR, INC.
BEAVERTON
OR
|
Family ID: |
42353413 |
Appl. No.: |
13/482123 |
Filed: |
May 29, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13416125 |
Mar 9, 2012 |
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13482123 |
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12691601 |
Jan 21, 2010 |
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13416125 |
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61147040 |
Jan 23, 2009 |
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Current U.S.
Class: |
250/459.1 ;
250/208.2; 362/555 |
Current CPC
Class: |
G01J 1/58 20130101; G02B
6/0003 20130101; G01J 3/10 20130101; G01N 21/64 20130101 |
Class at
Publication: |
250/459.1 ;
362/555; 250/208.2 |
International
Class: |
F21V 9/16 20060101
F21V009/16; F21V 8/00 20060101 F21V008/00; G01N 21/64 20060101
G01N021/64 |
Claims
1. A method for analyzing a sample comprising: (a) pumping at least
one luminescent light pipe to generate at least a first excitation
light and driving at least one LED light source to generate at
least a second excitation light; (b) directing the at least first
excitation light and the at least second excitation light onto a
single optical axis using one or more dichroic mirrors to create an
excitation light beam; (c) directing the excitation light beam onto
the sample; (d) detecting light from the sample with one or more
detectors; and (e) switching at a frequency no less than 2 kHz to
modulate the excitation light beam.
2. The method of claim 1, wherein step (a) comprises pumping at
least one luminescent light pipe to generate at least a first
excitation light and driving at least four LED light sources to
generate at least a second excitation light including at least four
colors of light.
3. The method of claim 1, wherein step (a) includes pumping the
luminescent light pipe with an LED light source.
4. The method of claim 1, wherein step (e) comprises switching at a
switching frequency no less than 5 kHz to modulate the excitation
light beam.
5. A solid-state light engine adapted to analyze a sample having
one or more tags, wherein the solid state light engine comprises: a
light pipe coupled to a solid state light source, and a plurality
of LED light sources, wherein the light pipe and the plurality of
LED light sources are adapted to produce a plurality of beams of
excitation light having a plurality of colors; wherein the solid
state light source and the plurality of LED light sources are
switchable at a frequency of 2 kHz or more to modulate the
plurality of beams of excitation light; a plurality of dichroic
mirrors positioned to direct the plurality of beams of excitation
light onto a single optical axis; and wherein the plurality of
beams of excitation light are adapted to selectively detect the one
of more tags within the sample.
6. The solid-state light engine of claim 5, wherein the solid state
light source comprises an LED light source.
7. The solid-state light engine of claim 5, wherein the solid state
light source and the plurality of LED light sources are switchable
at a frequency of 5 kHz to modulate the plurality of beams of
excitation light.
8. The solid state light engine of claim 5, wherein the plurality
of colors includes blue, cyan, orange, red, green, and teal.
9. The solid-state light engine of claim 5, wherein the at least
one light pipe comprises a luminescent material.
10. The solid-state light engine of claim 5, further comprising a
plurality of collimators to collimate the plurality of beams of
excitation light.
11. The solid-state light engine of claim 5, further comprising a
filter slider adapted to selectively filter said first excitation
light.
12. The solid-state light engine of claim 5, wherein the at least
one light pipe comprises a luminescent material including one or
more of: rare earths, transition metals, and donor-acceptor
pairs.
13. The solid-state light engine of claim 5, further comprising
relay optics including one or more optical fibers adapted to couple
the plurality of beams of excitation light to the sample.
14. The solid-state light engine of claim 13, wherein the relay
optics are constructed in a loop so that light can pass through one
or more capillaries multiple times to enhance excitation
efficiency.
15. A solid-state light engine comprising: a plurality of LED light
sources, and a luminescent light pipe pumped by a solid state light
source, wherein the luminescent light pipe and the plurality of LED
light sources are adapted to produce a plurality of beams of
excitation light having a plurality of colors; wherein the solid
state light source and the plurality of LED light sources are
switchable at a frequency of 2 kHz or more to modulate the
plurality of beams of excitation light; a plurality of dichroic
elements positioned to direct the plurality of beams of excitation
light onto a single optical axis; and relay optics adapted to
direct the plurality of beams of excitation light from the single
optical axis to a sample.
16. The solid state light engine of claim 15, wherein the solid
state light source and the plurality of LED light sources are
switchable at a frequency of 5 kHz or more to modulate the
plurality of beams of excitation light.
17. The solid state light engine of claim 15, wherein the plurality
of colors includes blue, cyan, orange, red, green, and teal.
18. The solid state light engine of claim 15, wherein the solid
state light source is an LED light source.
19. The solid-state light engine of claim 15, wherein the at least
one light pipe comprises a luminescent material including one or
more of: rare earths, transition metals, and donor-acceptor
pairs.
20. The solid-state light engine of claim 15, wherein the solid
state light source and the plurality of LED light sources are
independently switchable at a frequency of 5 kHz or more to
modulate the plurality of beams of excitation light.
Description
CLAIM OF PRIORITY
[0001] This present application is a continuation application of
U.S. patent application Ser. No. 13/416,125, filed Mar. 9, 2012,
entitled "Lighting Design of High Quality Biomedical Devices" which
is a continuation application of and claims priority to U.S. patent
application Ser. No. 12/691,601, filed Jan. 21, 2010, entitled
"Lighting Design of High Quality Biomedical Devices" which claims
the benefit of priority under 35 U.S.C. .sctn.119(e) to U.S.
Provisional Patent Application No. 61/147,040, filed on Jan. 23,
2009, entitled "Lighting Design of High Quality Biomedical
Devices," all of which applications are incorporated herein by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to using Light Emitting Diodes
for illumination.
BACKGROUND OF THE INVENTION
[0003] Among the trends redefining 21st century biomedical
diagnostics and therapeutics is the design of low-cost portable
analyzers. Because light is a powerful tool in many of today's most
widely used life science instruments, high intensity, low cost
light engines are essential to the design and proliferation of the
newest bio-analytical instruments, medical devices and miniaturized
analyzers. The development of new light technology represents a
critical technical hurdle in the realization of point-of-care
analysis.
SUMMARY OF THE INVENTION
[0004] Embodiments of the present invention are directed to methods
and devices for converting the output of a specific color LED and
generating a broader band of wavelengths of emission including not
only the specific color but additional color output. Specific
embodiments, as will be described below, minimize backward directed
light while increasing the total range of wavelengths emitted.
[0005] Lighting for life sciences is a broad and general category.
Not only are the source specifications varied but so too are the
equally important optical delivery requirements. Spectral and
spatial lighting requirements for sensing on the head of an optical
probe or within a single cell in a flowing stream differ in output
power by orders of magnitude from the requirements of a
multi-analyte detection scheme on an analysis chip or within the
wells of a micro-titer plate. The number of colors, spectral
purity, spectral and power stability, durability and switching
requirements are each unique. Illuminating hundreds of thousands of
spots for quantitative fluorescence within a micro-array may be
best served by projection optics while microscopes set demanding
specifications for light delivery to overfill the back aperture of
the microscope objective within optical trains specific to each
scope body and objective design.
[0006] While lighting manufacturers cannot provide all things to
all applications, it is precisely this breadth of demand for which
a light engine can be designed. To that end, products are not
simple sources, but rather light engines: sources and all the
ancillary components required to provide pure, powerful, light to
the sample or as close to it as mechanically possible. Such designs
have resulted in products that embody a flexible, hybrid solution
to meet the needs of the broad array of applications for biotech. A
qualitative comparison of light engine performance as a function of
source technology is summarized in Table 1.
TABLE-US-00001 TABLE I A qualitative comparison of light engine
performance as function of the source technology employed Source
Useable Temporal Heat Technology Light Uniformity Response
Generation Durability Cost Arc Lamp med poor none high low high
Laser high poor none low low very high LED low poor fast low high
medium Tungsten low poor none medium low medium Light Pipe high
high fast low high low
[0007] Historically arc lamps are noted to be flexible sources in
that they provide white light. The output is managed, with numerous
optical elements, to select for the wavelengths of interest and for
typical fluorescence based instruments, to discriminate against the
emission bands. However their notorious instability and lack of
durability in addition to their significant heat management
requirements make them less than ideal for portable analyzers.
Moreover, large power demands to drive them present a barrier to
battery operation within a compact design.
[0008] Lasers require a trained user and significant safety
precautions. While solid state red outputs are cost effective, the
shorter wavelength outputs are typically costly, require
significant maintenance and ancillary components. Color balance and
drift for multi-line outputs is a serious complication to
quantitative analyses based on lasers. Moreover, the bulk of
fluorescence applications do not need coherent light, are
complicated by speckle patterns and do not require such narrow band
outputs. Overcoming each of these traits requires light management
and adds cost to the implementation of lasers for most
bio-analytical tools.
[0009] Finally LEDs, have matured significantly within the last
decades. LEDs are now available in a relatively wide range of
wavelengths. However their output is significantly broad so as to
require filtering. Additionally, output in the visible spectrum is
profoundly reduced in the green, 500-600 not. The LED also presents
trade-offs with respect to emission wavelength dependent intensity,
broad emission spectrum (spectral half width on the order of 30 nm
or more), poor spectral stability, and the wide angular range of
emission. In addition, the process used to manufacture LED's cannot
tightly control their spectral stability; anyone wishing to use
LED's in applications requiring a good spectral stability must work
directly with a supplier to essentially hand-pick the LED's for the
particular application. Finally, LED's generate light over a wide
angular range (50% of light intensity emitted at 70.degree.). While
optics can narrow the emission band and focus the light output, the
resulting loss in power and increase in thermal output further
limit the feasibility of LED light engines.
[0010] Most importantly, these light technologies cannot be readily
improved for bioanalytical applications. The associated light
engine market simply does not justify the large investment
necessary to overcome fundamental performance limitations. As a
result, analytical instrument performance and price is constrained
by the light source with no clear solution in sight. Moreover the
numerous manufacturers of lamps and lasers provide only a source,
not an integrated light engine. Companies such as ILC Technology,
Lumileds, Spectra-Physics, Sylvania and CooILED require some sort
of mechanics and or electro-optics such as acousto-optic tunable
filters (AOTFs), excitation filters (with a wheel or cube holder),
shutters and controllers.
[0011] While no one lighting solution can best satisfy all
instrument architectures, a light pipe engine combines the best of
solid state technologies to meet or outperform the traditional
technologies listed in Table I on the basis of all figures of merit
for all individual wavelengths. Key to this performance is the
light pipe architecture. Single outputs, such as red from a diode
laser, may be competitive. However, no family of outputs can by
assembled that bests the light pipe disclosed herein. In an
embodiment of the invention, a light pipe engine can emit
narrowband light exceeding 500 mW/color with intensifies up to 10
W/cm.sup.2 depending on the application. In an embodiment of the
invention, bandwidths as narrow as 10 nm are achievable. While such
output power and overall emission intensity is impressive, the most
significant figure of merit for quantifying the value of any
lighting subsystem for bio-analytics is the intensity of high
quality illumination provided to the sample. This is a factor
dictated by the instrument design and sample volume and clearly
very application specific.
[0012] In the case of medical devices and portable diagnostics the
present light pipe invention offers a smart alternative for light
generation. The light pipe engine is an optical subsystem; it
consists of lamp modules for each discrete output based on solid
state technologies tailored to best satisfy that output requirement
complete with collection and delivery optics. The capabilities of
the light pipe engine are highlighted in Table 2. The high
performance illumination provided by the light pipe engine is
embodied in a single compact unit designed to replace the entire
ensemble of lighting components. The sources, excitation filters,
multicolor switching capabilities and fast pulsing are contained
within one box such that no external optics or mechanics are
required.
TABLE-US-00002 TABLE II Light pipe engine metrics of an embodiment
of the invention, designed to meet the needs for portable
fluorescence assays and biomedical devices. Key Metrics: Spectral
Output Up to eight colors spanning UV-Vis-NIR >_ 100 mW/spectral
band 1-10 W/cm Peak Wavelength Optimal for different floors,
adjustable bandwidths Power Stability >99% over 24 hours
Spectral Width 10 to 50 nm Spectral Drift <1% in 24 hours Color
Dependence None Lifetime >5000 hrs Footprint amenable to
portability Maintenance None, no replacement components for the
light engines lifetime
[0013] An inexpensive lighting solution, uniquely well suited to
the production of safe, effective and commercially viable life
science tools and biomedical devices can be attained using a
solid-state light engine. In an embodiment of the invention, this
light engine can provide powerful, pure, stable, inexpensive light
across the Ultraviolet-visible-near infrared (UV-Vis-NIR). Light
engines are designed to directly replace the entire configuration
of light management components with a single, simple unit. Power,
spectral breadth and purity, stability and reliability data will
demonstrate the advantages of these light engines for today's
bioanalytical needs. Performance and cost analyses can be compared
to traditional optical subsystems based on lamps, lasers and LEDs
with respect to their suitability as sources for biomedical
applications, implementation for development/evaluation of novel
measurement tools and overall superior reliability. Using such
sources the demand for portable, hand-held analyzers and disposable
devices with highly integrated light sources can be fulfilled.
Lamp
[0014] In various embodiments of the present invention, a lamp
emits wavelengths of light, which excite fluorescence from
photosensitive targets in the sample of interest. In various
embodiments of the present invention, a lamp can be in the form of
a tube, rod, or fiber of varying or constant diameter. In various
embodiments of the present invention, a constituent light pipe can
be made of glass, plastic, single or multiple inorganic crystal(s),
or a confined liquid. In various embodiments of the present
invention, a pipe either contains or is coated with a layer or
layers containing, a narrow band luminescent material such as
organic or inorganic compounds involving rare earths, transition
metals or donor-acceptor pairs. In various embodiments of the
present invention, a lamp emits confined luminescence when excited
by IR, UV, or visible light from an LED, Laser, fluorescent tube,
arc lamp, incandescent lamp or other light source. In an embodiment
of the present invention, a lamp operates through the process of
spontaneous emission, which results in a much larger selection of
available wavelengths than is available for efficient stimulated
emission (laser action).
Relay Optics
[0015] In an embodiment of the present invention, relay optics
consist of light pipes, optical fibers, lenses and filters, which
optically transport the light from a lamp to one or more
capillaries and light pipes, optical fibers, lenses and filters
which collect and transport any generated fluorescence to an
appropriate detector or array of detectors, in conjunction with
adaptors for coupling the excitation light into the capillaries,
coupling the emission light out of the capillaries and for
enhancing physical discrimination of the excitation and emission.
In an embodiment of the present invention, relay optics, including
fibers, can be constructed in a loop or as a cavity so that light
from a lamp can pass through one or more capillaries multiple times
to enhance excitation efficiency.
[0016] In an embodiment of the present invention, a number of lamps
each emitting one or more color of light can have their constituent
light pipes coupled in parallel or in series acting to produce
multiple colors simultaneously or in sequence. In an embodiment of
the present invention, one or more lamps can illuminate single
channels, multiple parallel channels, multiple channels in multiple
dimensions, numerous spots along the analysis channel and/or
reservoirs connected to the flow streams.
[0017] In an embodiment of the present invention, lamps can be
illuminated continuously during the measurement process or can be
pulsed on and off rapidly to enable time-based detection methods.
In an embodiment of the present invention, a lamp can be switched
off between measurements, to eliminate the heat output. This can be
contrasted with alternatives such as arc lamps or lasers that are
unstable unless they are operated continuously.
Illumination and Collection System
[0018] In an embodiment of the present invention, a flexible
illumination and collection system for capillary/fluorescence
apparatus allows for a varying number of samples to be analyzed
simultaneously. `Simultaneously` is herein defined as occurring
close in time. Two light pipes can irradiate two capillaries at the
same time and the fluorescence from the molecules in one of the
capillaries can be delayed due to physical or chemical effects
relating to absorption, phosphorescence and/or fluorescence
resulting in a delay in the fluorescence from the molecules in one
of the capillaries. This excitation is still considered to result
in `simultaneous detection`. In an embodiment of the present
invention, an illumination and collection system can be adjusted
for uniform illumination of multiple capillaries. In an embodiment
of the present invention, illumination systems can irradiate an
array of channels in an array of capillaries. In an embodiment of
the present invention, an array of channels can be etched, molded,
embossed into the capillaries. In an embodiment of the present
invention, a set of wells intimately connected to fluidic conduits
can be stepped along the length of the fluidic conduit such that
they can be interrogated at numerous sites for the purposes of
creating a map or image of the reacting species.
[0019] In an embodiment of the present invention, an illumination
and collection system can emit multiple colors as desired. In an
embodiment of the present invention, an illumination and collection
system can be pulsed on and off as desired to reduce heat
generation. In an embodiment of the present invention, an
illumination and collection system can be pulsed on and off to
allow time-based fluorescence detection.
[0020] In an embodiment of the present invention, illumination
systems can irradiate homogeneous reactions within fluidic conduits
or reservoirs. In an embodiment of the present invention,
illumination systems can irradiate heterogeneous reactions on the
surface of fluidic conduits or reservoirs. In an embodiment of the
present invention, illumination systems can irradiate homogeneous
or heterogeneous reactions on the surface of or within the pores of
a porous reaction support.
[0021] Other objects and advantages of the present invention will
become apparent to those skilled in the art from the following
description of the various embodiments, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0022] Various embodiments of the present invention can be
described in detail based on the following figures, wherein:
[0023] FIG. 1 shows a schematic of a light engine subsystem
consisting of a lamp module and delivery optics;
[0024] FIG. 2 shows light engine output relative to a typical metal
halide lamp and 75 W xenon bulb;
[0025] FIG. 3 shows light pipe engine with <10 ns rise and fall
times for fast switching between bands;
[0026] FIG. 4 shows light engine stability over 24 hours of
use;
[0027] FIG. 5 shows a eight color light engine layout, including a
light pipe and five other solid state light sources, with dichroic
mirrors to create a single coaxial 8-color beam. Each individual
light source is collimated so as to be efficiently combined and
after color combination, the beam is refocused into a light guide
for transport to the device or system to be illuminated according
to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Shown in FIG. 1, is the light pipe engine 100 of an
embodiment of the invention. An individual lamp module driven by
light pipe technology consists of an excitation source 102,
typically one or more LEDs, and a light pipe 104. In an embodiment,
the excitation source 102 and light pipe 104 can be housed in a
cylindrical waveguide 106. The excitation source 102 drives
luminescence in the light pipe 104, which is composed of a glass or
polymer fiber. In an embodiment, light pipe 104 includes a mirror
108. Glass fibers are either doped with a rare earth metal or
activated with a transition metal. Polymer fibers are doped with a
dye. The fibers have fast response and decay times and can achieve
a high efficiency through the design of delivery optics. The design
and selection of the fiber determines the peak wavelength of the
output illumination; options exist to span the UV-Vis-NIR spectrum.
The bandwidth of the luminescence is narrow and can be further
defined with the use of band pass filters 110 integrated into the
delivery optics. In an embodiment, the delivery optics may include
a band pass filter 110 connected to a coupler 112, which can be
attached to an optical delivery pipe 114 which leads to an
instrument (e.g., a microtiter plate) 116. Output intensity is
determined through the design of the pipe's excitation source.
[0029] The light pipe geometry provides a unique opportunity to
shape and direct the angular and spatial range of outputs. Combined
with a high output power, the delivery optics can be readily
tailored to couple the light with various instruments and
analyzers. Sensors, optical probes, microscope objectives or
through liquid light guides, two-dimensional oligomer and micro
fluidic chips, and micro titer plates are all illumination fields
that light pipe engines can readily support. Moreover, high output
power enables illumination of large areas within a chip, micro
array or micro titer plate and, as a result, support high-speed
throughput in instruments where to date only scanning modes of
operation could be envisioned.
[0030] The preferred mode of light pipe excitation is the
application of one or more LED's. This approach takes advantages of
the benefits of LED illumination: low cost, durability, and, at an
appropriate excitation wavelength, high output power to drive the
light pipe. In so doing the LED's shortcomings are managed. The
lack of spectral stability and the high angular output
characteristic of LED's do not impact the luminescence of the light
pipe. Instead, the innovation of the light pipe enables
circumvention of the principle of etendue conservation. All light
sources must conform to this dictate, which requires the spread of
light from a source never exceed the product of the area and the
solid angle. Etendue cannot decrease in any given optical
system.
[0031] The ability to modulate solid-state source outputs provides
a unique opportunity for multiplexed fluorescent assays. Current
light engine designs employ solid state materials with fast
luminescence (approximately 10 ns.) The light pipe and LED have
similar modulation capabilities thus multiple light pipes tuned to
different output wavelengths can be employed to selectively detect
multiple fluorescent tags within a given analysis. In addition,
pulse modulation and phase modulation techniques enable
fluorescence lifetime detection and afford improved signal to noise
ratios. Each of the solid state units is truly off when it is off
so low background signals and high contrast ratios are
possible.
[0032] Table III shows an embodiment of the present light pipe
engine invention's product and performance features. As
improvements are made to LED's and the cost of semiconductor lasers
continue to decline, the tool chest of options available to light
lipe engines will continue to evolve. The desired light engine can
ultimately be powered by a combination of light pipe, LED's and
lasers. The knowledge and competency to integrate any of these
lighting technologies into the delivery optics supports the
requirements of each specific application and provides technical
and commercial value.
TABLE-US-00003 TABLE III The light pipe engine feature set.
Wavelengths UV - Vis - NIR Colors Up to eight Intensity 1-10
W/cm.sup.2 Bandwidths Adjustable Size Compact Ease of Use Yes
Modulation Up to 5 kHz Color control Independent System Control
Manual or computer Heat output Minimal Life time Long
Eight Light Engine Subsystem
[0033] FIG. 5 shows a schematic for a eight color light engine
layout. In an embodiment of the invention, a eight color light
engine 500 includes a luminescent rod 502 and five other solid
state light sources 504, with dichroic mirrors 506 to create a
single coaxial 8-color beam 508 (for example selected from UV 395,
Blue 440, Cyan 485, Teal 515, Green 550 or 575, Orange 630 and Red
650 nm) leading to an output 510. In this embodiment, a manual or
electromechanical filter slider 512 allows green yellow filtering
of YAG generating 550 or 575 nm light. Additional colors can be
used. For example, a color band centered at 550 nm can be replaced
with a color band centered at 560 nm. Each individual light source
is collimated so as to be efficiently combined and after color
combination, the beam is refocused into a light guide for transport
to the device or system to be illuminated according to an
embodiment of the invention.
[0034] The light engine subsystem is designed to interface to the
array of bioanalytical tools with the expectation that the end user
can take for granted the high quality of the illumination. Table IV
summarizes four bioanalytical applications for which light engines
including light pipes could replace more traditional illumination
subsystems and offer performance and cost advantages. For example,
Kohler illumination in transmitted light microscopy requires that
the light be focused and collimated down the entire optical path of
the microscope to provide optimal specimen illumination. Even light
intensity across a fairly large plane is a critical requirement.
For stereomicroscopy, lighting is achieved with ring-lights at the
objective and fiber optic lights pointed at the specimen from the
side. In both cases, the light engine must efficiently couple to a
fiber optic cable.
TABLE-US-00004 TABLE IV Performance and cost analysis of the light
pipe engine vs. traditional illumination subsystems in four key
bioanalytical applications Fluorescence specification Sanger
Sequencing Q-PCR Flow Cytometry Microscopy Light engine Light Ar
Ion Light Metal Light Lasers Light Metal Pipe Laser Pipe Halide
Pipe Pipe Halide Intensity 150-250 150-250 0.5-1 0.2-1, 150-250
150-250 <50 1-50, W/cm.sup.2 very .lamda. very .lamda. specific
specific Wavelength 505 nm multiline 4 colors >2 colors 4 colors
Bandwidth, 10-30 26 10-30 15 10-30 <5 10-30 15 nm Stability 0.1%
>1% 0.1% >1% 0.1% >1% 0.1% >1% Switching, <0.03
1-10, <0.03 40, ext. <0.03 1-10, <0.03 40, ext. ms ext.
shutter ext. shutter shutter shutter MTBF, hrs >10,000 <4,000
>10,000 <1,000 >10,000 <4,000 >10,000 <1,500
Price <$3K >$5K <$7.5K >$10K <$5K >$5K <$7.5K
>$10K
[0035] For portable diagnostic tools, the delivery optics must
provide even illumination over a small volume. These requirements
are similar to, but less restrictive than those presented by
capillary electrophoresis. Capillary electrophoresis requires an
intense (10 mW) light focused onto the side of a capillary tube
with characteristic dimensions on the order of a 350 pm outer
diameter and a 50 pro inner diameter. To achieve this goal, the
delivery optics were comprised of a ball lens to collect and
collimate light from the lamp module (already coupled into an
optical fiber), a bandpass filter to provide a narrow bandwidth of
illumination, and an aspheric lens to focus the light at the center
of the capillary bore. This approach yielded an 80 pin spot size
and the desired 10 mW of delivered power to the capillary tube.
[0036] The design of delivery optics for microfluidic immunoassays
requires both the even illumination required for optical microscopy
and the small volume illumination required for capillary
electrophoresis. Light engines capable of delivering even
illumination at the active sites in a microfluidic array for
detection of fluorescent tagged biomarkers have been designed for
immunochemical as well as genomic applications. The advantages of
the luminescent light pipe are providing commercial, readily
available light engine solutions for illumination-detection
platforms optimized for portable diagnostic tools.
Spectral Bands and Output Power
[0037] In various embodiments of the present invention, the light
pipe engine performs well compared with the output power across the
visible spectrum to other lamps (see FIG. 2). Such comparisons beg
for disclaimers as the outputs of the commonly employed lamps
change in time and degrade with usage. The light pipe engine is all
solid state so they it is significantly more stable and
reproducible. FIG. 2 was taken within the manufacturers' specified
lifetime for each lamp, by an independent user well trained in
biophotonics, these outputs represent typical performances of a
common metal halide bulb, 75 W xenon bulb and that of the light
pipe engine.
[0038] Such output comparisons are further complicated by
mismatches between the spikes of the metal halide bulb and light
pipe light engine output bands, However, noting such disparities it
is fair to claim the outputs of the light engine across the visible
spectrum compare well against the outputs of a metal halide bulb in
spectral windows that match the excitation energies of some of the
most commonly used fluors for biotech: around 390 nm where DAPI and
Hoescht can be excited; in the window most commonly associated with
a cyan line of an argon ion laser and often used to excite Alexa
dyes, green fluorescent proteins and fluoresceins; and in the red
where neither of the lamps provides appreciable power for the likes
of Cy5. The light engine also bests the Xenon lamp across the
palate of excitation wavelengths most common to biotech: the Xenon
lamp underperforms particularly in the violet, cyan, blue and red
regions of the visible spectrum. Of course, more powerful Xenon
lamps are often employed to provide enhanced performance at a
significant maintenance cost.
[0039] In another embodiment of the present invention, as seen in
FIG. 2, the output of the green and amber bands have essentially
doubled, such that on a photon per photon basis the area under the
curve for the arc lamp vs. light engine are the same. Certainly the
peak shapes, and figures of merit (height, FWHM, etc.) differ.
However, no compromise in output power, even for the 546 nm band of
the arc lamp, should be incurred as a consequence of using a light
pipe engine replacement.
[0040] Alternatively, a light pipe engine can be employed in a
short duty cycle mode for power starved applications. When
feasible, pulse widths of less than 100 ms at 10% duty cycles can
actually improve the power output per band by a factor of 1.5 to
2.0 over longer duty cycles or in continuous mode of operation.
Applications that employ multiple lasers and acousto-optic tunable
filters (AOTFs) but need safe, cost effective and easy to employ
lighting solutions might benefit from such light engine
performance. Fluorescence microscopy for multicolor detection could
take advantage of this option, for example. As could numerous other
bioanalytical platforms such as a light engine replacement for the
optical excitation from AOTF-based multicolor fluorescence
detection for short tandem repeat (STR) analysis in a
micro-eletrophoretic device, a glass microchip.
Fast Switching
[0041] Because of the solid state nature and independently operable
designs of the lamp modules, coupled to fast (approximately 10 ns)
decay times of typical materials employed, a light pipe based light
engine outperforms any broad spectrum source in terms of support
for fast analyses. Lamp based sources are coupled to filters and/or
shutters with mechanical supports that relegate them 1 to 50
millisecond regimes. Even LED based lamps require filtering for
most quantitative fluorescence based analyses. The light pipe based
light engine incorporates all that filtering into its highly
integrated design. Therefore switching times are limited today by
the electronics of the boards controlling the sources. Rise times
of less than 20 .mu.s and fall times of less than 2 us are typical
(see FIG. 3). Moreover each color can be switched independently and
is compatible with triggering by TTL, RS232 and USB and intensity
control by RS232, USB or manually. This supports experiments where
simultaneous excitation of multiple tags could previously only be
done with multipass excitation filters and broadband sources. Using
a light pipe engine, effectively instantaneous excitation of
individual reporters can be manipulated within microsecond time
frames to achieve rapid, serial exposure of a biologic event to the
various excitation bands with no external hardware beyond the light
engine itself.
Stability
[0042] Because a light pipe based light engine is based on solid
state technologies, they are extremely stable both in short
duration experiments and over long term use. FIG. 4 depicts this
stability. Light engines are powered by 24 V power supplies
operated in DC mode, therefore there is no 60 Hz noise. All colors
perform similarly. In 24 hours of continuous operation, the output
fluctuates on the order of 1%. Short term stability on the order of
1.0 ms is approximately 0.5%. Short term stability for 0.1 ms is
diminished by a factor of ten to 0.05%.
[0043] The foregoing description of the various embodiments of the
present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed. Many
modifications and variations will be apparent to the practitioner
skilled in the art. Embodiments were chosen and described in order
to best describe the principles of the invention and its practical
application, thereby enabling others skilled in the art to
understand the invention, the various embodiments and with various
modifications that are suited to the particular use contemplated.
It is intended that the scope of the invention be defined by the
following claims and their equivalents.
[0044] Other features, aspects and objects of the invention can be
obtained from a review of the figures and the claims. It is to be
understood that other embodiments of the invention can be developed
and fall within the spirit and scope of the invention and
claims
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