Patent Grant
10788678
This invention relates to high brightness solid state illumination systems, particularly illumination systems for fluorescence imaging and analysis.
High radiance illumination sources are required for fluorescence imaging and analysis, including fluorescence microscopy. Some applications require broadband or white light illumination. Other applications require relatively narrow band illumination of a particular wavelength range in the ultraviolet (UV), visible or infrared (IR) spectral region.
For example, conventional microscopy illumination systems typically utilize short arc lamps such as high pressure mercury, metal halide, and xenon lamps. These lamps are capable of very high radiance and are suitable sources for direct coupled illumination systems, as well as light guide coupled illumination systems, e.g. using a liquid light guide or a fiber light guide. Nevertheless, it is recognized that there are a number of problems associated with conventional lamp technologies, such as short lifetime, temporal variation of the output power, high voltage operation (typically kilovolts are required to strike the lamp), and use of mercury. The latter is now seen as an environmental hazard and subject to regulations to limit use in numerous countries throughout the world.
Solid state light lighting technology has progressed significantly in recent years and some high brightness light sources using solid state Light Emitting Devices (LEDs), e.g. light emitting diodes, are now available that can potentially provide sufficiently high radiance, broadband illumination for replacement of conventional arc lamps. Solid state LED light sources can offer advantages over conventional arc lamps, such as, much improved lifetime, lower cost of ownership, lower voltage operation, lower power consumption (enabling some battery operated portable devices), and freedom from mercury. Additionally LED light sources can be readily controlled electronically, by modulating the current or voltage driving the device, which allows for fast switching and intensity control through the LED driver, which can be a significant advantage in many applications.
Nevertheless, despite technological advances in LED technology, high brightness LED light sources are not available to cover all wavelengths required for illumination systems for fluorescence imaging and analysis. In particular, the output of LED devices still do not match the radiance of traditional arc-lamps in some regions of the visible spectrum, especially in the 540 nm to 630 nm spectral band, i.e. in the green/yellow/amber range of the visible spectrum. The solid state lighting industry refers to this issue as the “green gap”. Emission in this region of the spectrum is fundamentally limited by the lack of availability of semiconductor materials having a suitable band gap to produce light of the required wavelength.
This is a particular problem for fluorescence imaging and analysis which may, for example, require illumination of a biological sample with a relatively narrow band of illumination of a particular wavelength that is absorbed by a selected fluorophore or marker in the substance under test.
For example, a traditional fluorescence illumination system, e.g. for fluorescence imaging or microscopy, comprises a short arc mercury lamp which provides light emission having spectral peaks near 365 nm, 405 nm, 440 nm, 545 nm and 575 nm. Standard fluorophores that are commonly used for fluorescence imaging and analysis are selected to have absorption spectra having peaks optimized to match these lamp emission peaks. To replace a standard mercury lamp illuminator with a LED based illuminator, it is desirable to be able to provide emission at the same wavelengths and with a comparable output power. There are suitably powerful LEDs that are commercially available for emission at 365 nm, 405 nm, 440 nm. However, in view of the “green gap” mentioned above, there are currently no single color, high brightness LEDs commercially available for emission at 545 nm and 575 nm.
It is well known in the art of LED lighting and illumination to use LEDs in combination with luminescent materials, i.e. fluorescent materials or phosphors, to generate light of wavelengths that are outside the range emitted directly by the LEDS, i.e. by wavelength conversion. In particular, a UV or blue light emitting LED may be combined with a remote or direct die-contact phosphor layer or coating to obtain broadband light emission of a desired color temperature. For example, a blue light emitting diode or diode array with an emission peak in the range between 445 nm and 475 nm is combined with a phosphor layer comprising particles of Ce:YAG (cerium doped yttrium aluminum garnet) suspended in an encapsulant material such as silicone, which is deposited directly on the LED. The blue light from the LED is absorbed by the phosphor and generates a broadband green/yellow/amber light which combines with the scattered blue light to produce a spectrum that provides the perception of white light. The overall brightness is limited by the blue light intensity from the LED and thermal quenching of the phosphor, and the spectrum provides limited emission in regions of the spectrum seen as green/yellow, approximately 560 nm and amber, approximately 590 nm.
Thus, relative to a mercury lamp, commercially available white light LEDs that use a blue light emitting LED combined with a Ce:YAG phosphor, produce significantly weaker emission in the 545 nm and 575 nm regions. For example, at the objective plane of a microscope, output power at 545 nm and 575 nm from such a white light LED was found to be about 10 times lower than the output power from a mercury lamp. This level of power is insufficient for most conventional fluorescence microscopy applications.
By increasing the drive current, some improvement of the light output can be achieved, but fundamentally, the power in this circumstance is limited by the maximum drive current density (i.e. current per unit area) and factors, such as, the LED optical to electrical conversion efficiency, the LED output intensity, the phosphor quantum efficiency, and thermal quenching of both the LED and phosphor, as well as the cooling capacity. Even in the best case, the output from an overdriven air cooled white LED is still 4 to 5 times less than a conventional lamp within the 545 nm and 575 nm spectral range and the lifetime may be significantly reduced by overdriving the device.
The following references provide some other examples of the use of LED sources combined with fluorescent materials or phosphors in other forms.
U.S. Pat. No. 7,898,665 to Brukilacchio et al., issued Mar. 1, 2011, entitled “Light Emitting Diode Illumination System,” for example, discloses a system comprising an arrangement of multiple LEDS that are coupled to a fluorescent rod which emits at a different wavelength to provide sufficiently high brightness illumination for applications such as microscopy or endoscopy. For example a single crystal of Ce:YAG may be pumped by multiple LEDs to generate yellow or amber emission. However, the efficiency of such a device would be limited by total internal reflection due to the high index of refraction of Ce:YAG and requires coupling of multiple LEDs to generate output of sufficient brightness, which increases the cost, size, thermal and electrical requirements.
To provide a more compact and efficient system, the above referenced related U.S. Patent application No. 61/651,130, discloses an illumination system that comprises a laser light source, e.g. providing blue light emission in the 440 nm to 490 nm range, for excitation of a wavelength conversion module comprising a wavelength conversion medium, such as Ce:YAG crystal, of a particular shape and size, set in a mounting for thermal dissipation, and an optical concentrator. The shape and size of the wavelength conversion crystal, provides a compact light source with a configuration suitable for applications that require high brightness and narrow bandwidth illumination at a selected wavelength, e.g. for fluorescence microscopy, or other applications requiring étendue-limited coupling or light guide coupling. While effective, due to the particular shape and size of the crystal and cooling requirements, this system is currently relatively costly to manufacture. A solution that is lower cost, compact and provides a broader spectrum is desirable for some applications.
Thus, there is a need for improved or alternative high radiance illumination sources, particularly those that can provide illumination at wavelengths of 545 nm and 575 nm, for example, for fluorescence imaging and analysis applications.
The present invention seeks to overcome or mitigate one or more disadvantages of known high brightness illumination systems for fluorescence imaging and analysis, or at least provide an alternative.
Thus, one aspect of the present invention provides a method of providing high brightness illumination for fluorescence imaging and analysis, comprising: providing a first light source comprising a light emitting device (LED) and a phosphor layer, the LED emitting a first wavelength λ1 within an absorption band of the phosphor layer and the phosphor layer emitting broadband light emission of longer wavelength comprising light in a wavelength band ΔλPHOSPHOR; providing a second light source comprising a laser emitting a second wavelength λ2, within the absorption band of the phosphor layer; and while operating the LED to generate emission at λ1 and ΔλPHOSPHOR, concurrently optically pumping the phosphor layer with laser emission λ2 to increase emission intensity in the phosphor emission wavelength band ΔλPHOSPHOR. In some implementations, the phosphor layer is optically pumped by the LED or the laser, but not concurrently by both.
The method may comprise optically coupling emission comprising λ1 and ΔλPHOSPHOR, along a common optical axis, to an optical output. The method may comprise providing another light source emitting another wavelength λ3, and optically coupling emission comprising λ1, ΔλPHOSPHOR and λ3, along a common optical axis, to an optical output.
By way of example, the LED light source may comprise a standard white light emitting LED light source, i.e. comprising a blue light emitting LED emitting at wavelength λ1 and a yellow Ce:YAG phosphor layer or coating providing broadband emission over a wavelength band ΔλPHOSPHOR. Typically, during normal operation of the blue light emitting LED, the phosphor layer is not saturated by light from the blue LED. Thus, concurrent optical pumping of the phosphor layer with the laser wavelength λ2, within the absorption band of the Ce:YAG phosphor layer, effectively increases the phosphor emission ΔλPHOSPHOR in the green, yellow and amber regions of the spectrum.
In particular, the supplementary laser optical pumping of the phosphor provides increased optical output over the emission band of the phosphor, so that sufficiently high radiance can be achieved at specific wavelengths, e.g. 545 nm and 575 nm, which are conventionally used for fluorescence imaging and analysis applications.
Another aspect of the present invention provides an illumination system for fluorescence imaging and analysis, comprising: a light source module comprising: a first light source comprising a first light emitting device (LED) and a phosphor layer, the first LED for providing emission at a first wavelength λ1 within an absorption band of the phosphor layer and the phosphor layer providing broadband light emission of longer wavelength comprising light in a wavelength band ΔλPHOSPHOR; a second light source for providing laser emission at a second wavelength λ2, within the absorption band of the phosphor layer; a controller for driving the first light source to generate emission at λ1 and ΔλPHOSPHOR and for concurrently driving the laser and optically pumping the phosphor layer with the laser wavelength λ2, to increase emission in the emission band of the phosphor ΔλPHOSPHOR; and optical coupling means for coupling light emission to an optical output of the illumination system.
Thus a laser pumped LED light source unit or module is provided, which has a high radiance output in the emission band of the phosphor ΔλPHOSPHOR. The pump laser wavelength λ2 may be the same as the LED wavelength λ1, or different from λ1, provided it is within the absorption band of the phosphor layer. The laser is preferably a solid state laser, e.g. a laser diode, and the control unit provides LED/laser controllers and LED/laser drivers. A suitable choice of phosphor allows for an optical output with high brightness at particular wavelengths, e.g. for applications such as fluorescence imaging and analysis. The phosphor layer may be selected to cover a band within the spectral range from 350 nm to 750 nm and more particularly from 530 nm to 630 nm, i.e. within in the green gap.
In particular, this system provides for high brightness (i.e. high radiance) illumination, e.g., in the 545 nm and 575 nm bands, which are commonly used for fluorescence imaging and analysis, such as, for fluorescence microscopy and for array slide scanners.
The optical coupling means comprises one or more optical elements such as lenses or optical concentrators for focusing the laser emission onto the phosphor layer, collecting emission at λ1 and ΔλPHOSPHOR, and coupling the emission at these wavelengths to the optical output of the light source module.
For example, the optical coupling means comprises an optical element for coupling the laser wavelength λ2 to the phosphor layer for optical pumping of the phosphor layer and for coupling emission from the first LED and the phosphor layer, comprising λ1 and ΔλPHOSPHOR, to the optical output. Preferably the optical element comprises a dichroic element that acts as a beam-splitter/combiner for coupling the laser wavelength λ2 onto the phosphor layer for optical pumping of the phosphor layer and for coupling emission from the first LED and the phosphor layer, comprising λ1 and ΔλPHOSPHOR, to the optical output.
If the pump laser wavelength λ2 is less than the wavelength emission λ1 of the LED, in a preferred embodiment, the dichroic element has a band edge λD greater than the laser wavelength λ2, so that it reflects the laser emission λ2 and transmits output light emission comprising λ1 and ΔλPHOSPHOR.
As an example, λ1 comprises emission in the range from 445 nm to 475 nm, i.e. from a blue LED, and ΔλPHOSPHOR covers the emission wavelength range from 500 nm to 750 nm. Preferably ΔλPHOSPHOR covers the emission wavelength range from at least 530 to 630 nm (i.e. the “green gap”), and the pump laser wavelength λ2 is 450 nm or less.
A dichroic beam-splitter/combiner, having a band edge wavelength λD, between λ1 and λ2, may be positioned for reflecting the laser emission λ2 and transmitting output light emission comprising λ1 and ΔλPHOSPHOR. For example, for wavelength ranges in the example above, if the pump laser wavelength λ2 is 440 nm, and the blue LED emits λ1 in the range from 445 nm to 475 nm, the dichroic element has a band edge λD of 443 nm.
The illumination system may further comprise one or more additional light sources, e.g. at least one of a LED light source providing an emission wavelength λ3 and an LED light source providing emission at wavelength λ4. For example, these additional LED light sources are individual LED light sources that provide outputs λ3 and λ4 in the near UV and UV spectral regions, respectively. Optical coupling elements are provided to couple outputs at these and other wavelengths, along a common optical axis, to the optical output of the system.
Optical coupling elements may include a second dichroic element, i.e. a dichroic beam-splitter/combiner, for combining outputs λ3 and λ4, and then the first dichroic element combines λ3 and λ4 with λ1 and ΔλPHOSPHOR. For example, the first LED has an emission band λ1 in the range between 440 nm and 490 nm and more preferably between 445 nm and 475 nm. The ΔλPHOSPHOR band emitted by the phosphor layer is in the range from 500 nm to 750 nm and more preferably in the range from 530 nm to 630 nm. If the phosphor layer is Ce:YAG as described above, the laser wavelength λ1 is preferably 450 nm or less, for optical pumping of the phosphor layer. The additional individual LED light sources provide λ3 comprising near UV emission in the range from 410 nm to 445 nm and λ4 comprising UV emission in the range from 370 nm to 410 nm or from 350 nm to 390 nm.
In this example, a second dichroic element having a band pass edge wavelength between λ3 and λ4, e.g. 409 nm, is used to combine these two wavelengths. Then, if the laser pump wavelength λ2, and LED emission at λ3 and λ4, are all on the short wavelength side of the 443 nm band edge wavelength λD of the first dichroic element, this element combines λ3 and λ4 with λ1 and ΔλPHOSPHOR, along the primary optical axis, to provide an optical output comprising each of these wavelengths.
Optionally the system may comprise one or more additional individual LED light sources and/or one or more additional light source modules for light emission in other spectral bands. For example, additional light sources may provide spectral bands that are in the ultraviolet and near ultraviolet region. These additional sources may comprise, e.g.: a UV LED emitting in the range from 350 nm to 390 nm, e.g. having a peak at 365 nm; or a UV LED emitting in the range from 370 to 410 nm, e.g. having a peak at 385 nm; or a phosphor coated UV LED emitting in the near UV range from 410 nm to 445 nm.
In one embodiment, the at least one additional light source or light source module comprises a LED providing emission at λ4 and a phosphor layer (Phosphor2) providing a broad emission band ΔλPHOSPHOR2. For example, if both λ4 and ΔλPHOSPHOR2 lie on the same side (i.e. the short wavelength side in the example above) of the band edge wavelength λD of the first dichroic element, the dichroic element combines λ4 and ΔλPHOSPHOR2 with λ1 and ΔλPHOSPHOR, to enable coupling of each of these wavelength bands, along the primary optical axis, to the optical output of the light source unit.
Typically, an optical filtering system within a fluorescence imaging system, such as a fluorescence microscope, provides for further filtering of a selected wavelength band from the output of the illumination system.
If desired, the illumination system may also comprise one or more additional LED light source modules, providing other wavelength bands. It may comprise an additional laser pumped LED light source module, i.e. a second pump laser emitting a wavelength λ5 within an absorption band of a second phosphor layer (Phosphor2), for optically pumping the second phosphor layer (Phosphor2). A second dichroic beam-splitter/combiner may be provided, having a wavelength edge that is selected to reflect the laser wavelength λ5 and transmit the emission bands at λ4 and ΔλPHOSPHOR2.
Another aspect of the present invention provides illumination system for fluorescence imaging and analysis, comprising: first and second light source modules and a controller;
the first light source module for providing emission in a first wavelength band, comprising: a first light source comprising a first LED and a first phosphor layer, the first LED providing emission at a first wavelength λ1 within an absorption band of the phosphor layer and the first phosphor layer providing broadband light emission ΔλPHOSPHOR1; a second light source comprising a laser emitting at a second wavelength λ2, within the absorption band of the first phosphor layer; wherein the controller concurrently drives the first light source to generate emission comprising λ1 and ΔλPHOSPHOR1 and drives the laser for optically pumping the first phosphor layer with the laser wavelength λ2 to increase emission in the emission band of the phosphor ΔλPHOSPHOR1;
the second module for providing emission in a second wavelength band different from the first wavelength band, comprising: a third light source comprising second LED and a second phosphor layer different from the first phosphor layer, the second LED emitting at a wavelength λ4 within an absorption band of the second phosphor layer and the second phosphor layer providing broadband light emission ΔλPHOSPHOR2; a fourth light source comprising a laser emitting at a wavelength λ5 within the absorption band of the second phosphor layer; wherein the controller concurrently drives the second light source to generate emission comprising λ4 and ΔλPHOSPHOR2 and the laser for optically pumping the second phosphor layer with the laser wavelength λ5 and the laser wavelength λ5, to increase emission in the emission band of the second phosphor ΔλPHOSPHOR2; and
optical coupling means comprising at least one dichroic beam-splitter/combiner for coupling one or more of λ1, ΔλPHOSPHOR1, λ4 and ΔλPHOSPHOR2, along a common optical axis, to an optical output of the illumination system.
The optical coupling means comprises optical coupling elements such as a coupling lens, an optical concentrator or other optics, and one or more dichroic elements having suitable passband, i.e. dichroic beam-splitters/combiners, to enable the LED light sources and laser light sources to be compactly arranged and for optically coupling the light emission from the LEDs and the phosphor layers to the primary optical axis, aligned to the optical output of the illumination system. The optical coupling elements may comprise dichroic elements for splitting and/or combining emission wavelengths from each light source, as required, and preferably first and second dichroic beam-splitters/combiners having band edges selected for reflecting laser wavelengths λ2 and λ5, respectively.
An illumination system, according to preferred embodiments of the invention, has the potential of meeting and exceeding the output of the best arc lamps systems available today at particular wavelengths used for fluorescence microscopy, while overcoming at least some of the limitations of existing high brightness LED light sources.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, of preferred embodiments of the invention, which description is by way of example only.
In the drawings, identical or corresponding elements in the different Figures have the same reference numeral, or corresponding elements have reference numerals incremented by 100 in successive Figures.
A schematic diagram showing elements of an illumination system 1000, according to a first embodiment of the invention, is shown in
As shown in
The first light source 110 may be a phosphor coated LED, mounted on a suitable heatsink for thermal management, e.g. a phosphor LED which provides high brightness white light illumination, i.e. comprising a blue light emitting LED 112 having a deposited phosphor coating 114 providing emission over a desired wavelength band ΔλPHOSPHOR in the longer wavelength visible range. Under normal operation of the first light source 110, even when the LED 112 is driven at higher current or voltage (i.e. the maximum driving current is limited by a maximum driving current density), the phosphor layer 114 is not saturated by the blue light emission from LED 112. Thus, supplementary optical pumping of the phosphor 114, using the pump laser 120, significantly increases the optical output of the phosphor emission band ΔλPHOSPHOR. The pump laser wavelength λ2 may be the same or different from the LED wavelength λ1, provided it is also within the absorption band of the phosphor layer 114.
Thus, under normal operation, without laser pumping, driving the LED 112 generates light from the LED itself at wavelength λ1 together with emission in the emission band of the phosphor ΔλPHOSPHOR. By concurrently optically pumping the phosphor with the laser wavelength λ2, the optical output in the emission band of the phosphor ΔλPHOSPHOR is increased significantly, as will be further explained below with reference to
A preferred arrangement for high brightness illumination systems for fluorescence imaging and analysis, comprises two or more light source modules, i.e. providing different output wavelengths, and optical elements for coupling outputs from the two or more light source modules along a primary optical axis to the optical output of the system.
Thus, a schematic diagram showing elements of an illumination system 1000-1, according to a second embodiment of the invention, is shown in
Preferably, other optical coupling elements such as lenses or optical concentrators are also provided for more efficiently coupling the laser emission λ2 to the phosphor, and for collecting the light emission λ1+ΔλPHOSPHOR, and coupling this light emission, to an optical output 160 of the light source unit 100. However, for simplicity these additional optical elements are not shown in
Thus, by way of example, the light source module 100-1 for illumination system 1000-1 comprises a first light source 110 comprising the LED1 112 emitting λ1 in the range 445 nm to 475 nm having a phosphor 114 emitting ΔλPHOSPHOR in the range 500 nm to 750 nm, which is pumped by the second light source 120 comprising the laser emitting λ2 at 440 nm. The band edge wavelength λD of the dichroic element is selected at 443 nm, i.e. between λ1 and λ2, and arranged to reflect the laser wavelength λ2, and transmit λ1 and ΔλPHOSPHOR. Thus, the optical output of the illumination module 100 comprises λ1+ΔλPHOSPHOR.
Referring again to
An illumination system 2000 according to a third embodiment is shown in
The drive system 180 is similar to that shown in
For example, the first light source 110 may comprise a blue light emitting LED 112 emitting a wavelength λ1 in the range from 445 nm to 475 nm, with a phosphor layer 114 emitting in ΔλPHOSPHOR in the 530 nm to 630 nm band. The second light source 120 comprises a laser emitting at λ2, i.e. at 440 nm in the absorption band of the phosphor layer 114, and the dichroic element 116 has a 443 nm edge, i.e. as described with respect to the light source unit 100-1 shown in
An illumination system 3000 according to a fourth embodiment is shown in
An illumination system 4000 according to a fifth embodiment is shown in
An illumination system 5000 according to a fifth embodiment, comprising a light source unit 500 is illustrated in
In each of the embodiments described above, the pump laser system 120 may comprise a solid state laser, e.g. a single laser diode or a laser diode array. Each LED light source may comprise a single LED or a LED array. The phosphor layer for LED1 is integrated with LED1, i.e. a direct die contact layer or coating deposited on LED1, or a phosphor suspended in an encapsulant such as silicon, also in direct contact with LED1. The Phosphor2 layer for LED4 is similarly integrated with LED4. In a variation of the module 100-2 shown in
To simplify optical coupling, it is preferable that each dichroic element is selected to reflect the pump laser wavelengths, i.e. λ2 or λ5, in the embodiments described above. Additionally, to provide for effective optical coupling of the pump laser to the phosphor layer and efficient collection of the light emission from each light source, optical coupling elements such as lenses or optical concentrators are used. For simplicity these elements are not shown in the preceding Figures.
In various implementations (including those described throughout this application), any one of these optical coupling elements (e.g., coupling lens 124A, compound parabolic concentrator 124B, or tapered concentrator 124C, etc.) can positioned relative to the phosphor as shown in
In some implementation, the optical coupling element may be a non-conical tapered concentrator, such as a tapered hexagonal or square rod. One example of a tapered hexagonal rod is shown in
In another variant of the optical coupling elements, shown in
In summary, a solid state high radiance illumination source as disclosed herein is capable of providing for high intensity illumination at each of a number of wavelengths commonly used for fluorescence analysis and imaging. The laser pumped LED and arrangement of optical components provide for a compact light source unit that may comprise one or more individual LED light sources or LED light source modules, providing different wavelength outputs. The system provides an alternative to conventional arc lamps, and addresses limitations of other available solid state LED light sources to provide high brightness at selected wavelengths, particularly in the 530 nm to 630 nm range.
The high radiance solid state illumination system also provides advantages over conventional lamp illumination sources, for example, allowing for electronic control of intensity and pulse generation as disclosed in PCT International patent application no. PCT/CA2012/00446 entitled “Light Source, Pulse Controller and Method for Programmable Pulse Generation and Synchronization of Light Emitting Devices”.
The light source unit 200 includes a first light source module 100-1 (with a first light source 112, a phosphor light source 114, a second light source 120, and a first dichroic optical element (D1) 116), a second light source module 100-2 (with a third light source 130), a third light source module 100-3 (with a fourth light source 140) and a second dichroic element (D2) 118. Each of the first, second, third, and fourth light sources 112, 120, 130 and 140 in the illustrated implementation is a light emitting diode (LED). Of course, in various implementations, any or all of these may be a different kind of light source. In some implementations, any or all of these may be a laser. In one exemplary alternative configuration, the second light source 120 is a laser, while the first light source 112, the third light source 130, and the fourth light source 140 are light emitting diodes.
The control unit 180 has a power supply 182, a controller 184 and drivers 186, which are coupled by electrical connections 188 to the light source unit 200. The control unit 180 is generally adapted to control the light source unit 200.
In various implementations, including the one shown in
The first light source 112 is configured to emit light at a first wavelength λ1 within an absorption band of the phosphor light source 114. The second light source is configured to emit light at a second wavelength λ2 also within the absorption band of the phosphor light source 114. The third light source 130 is configured to emit light at a third wavelength λ3. The fourth light source 140 is configured to emit light at a fourth wavelength λ4. The phosphor light source 114 is configured (e.g., when being pumped or excited) to emit light having a wavelength in a wavelength band ΔλPHOSPHOR. In a typical implementation, the wavelength of light emitted by the phosphor light source 114 is longer than the first wavelength λ1.
The controller 180 is configured to drive the first, second, third and/or fourth light sources, concurrently or otherwise. For example, in some implementations, the controller 180 is adapted to drive the first light source 112 and the second light source 120 to pump the phosphor light source 114 concurrently. In some implementations, the controller 180 is adapted to drive only one of the first light source 112 or the second light source 120 at a given time to pump the phosphor light source, without concurrently driving the other. For example, in one implementation, the controller 180 is adapted to drive the second light source 120 to optically pump the phosphor light source 114 without concurrently driving the first light source 112 to optically pump the phosphor light source 114. In a typical implementation, one or more (or both) of the third light source 130 and fourth light source 140 are configured to operate while the phosphor light source 114 is being pumped.
The first dichroic optical element (D1) 116 in the illustrated implementation is configured to: 1) direct light emitted by the second light source 120 at the second wavelength λ2 onto the phosphor light source 114, 2) direct light emitted by the phosphor light source 114 in the wavelength band ΔλPHOSPHOR (and, optionally, light emitted by the first light source 112 at the first wavelength λ1) to an optical output 160 of the illumination system, 3) direct light emitted by the third light source 130 at the third wavelength λ3 to the optical output 160 of the illumination system, and 4) direct light emitted by the fourth light source 140 at the fourth wavelength λ4 to the optical output 160 of the illumination system.
The second dichroic optical element (D2) 118 in the illustrated implementation is configured to: 1) direct the light emitted by the third light source 130 at the third wavelength λ3 to the first dichroic optical element (D1) 116, and 2) direct the light emitted by the fourth light source 140 at the fourth wavelength λ4 to the first dichroic optical element (D1) 116.
Light emitted from each respective one of the first, second, third and fourth light sources 112, 120, 130, 140 follows a particular path through the illustrated light source unit 200. In this regard, light from the first light source 112 (if energized) is directed onto the phosphor light source 114 and travels through the first dichroic optical element (D1) 116 to the optical output 160. Light from the second light source 120 is directed by the first dichroic light source (D1) 116 onto the phosphor light source 114. Light from the phosphor light source 114 travels through the first dichroic optical element (D1) 116 to the optical output 160. Light from the third light source 130 travels through the second dichroic optical element (D2) 118 and is then reflected by the first dichroic optical element (D1) 116 to the optical output 160. Light from the fourth light source 140 is reflected by the second dichroic optical element (D2) 118 toward the first dichroic optical element (D1) 116 and is then reflected by the first dichroic optical element (D1) 116 toward the optical output 160.
Thus, in the illustrated implementation, light from the third light source 130 and light from the fourth light source 140 travel between the first dichroic optical element (D1) 116 and the second dichroic optical element (D2) 118 along a first common optical path. Moreover, light emitted by the first light source 112 (if the first light source 112 is energized), light emitted by the phosphor light source 114, light emitted by the second light source 120, light emitted by the third light source 130, and light emitted by the fourth light source 140 travel from the first dichroic optical element (D1) 116 to the optical output 160 along a second common optical path.
In some implementations, the illustrated system is operable within and switchable between multiple operating modes. These operating modes can include, for example, any two or more of the following: a first operating mode (e.g., a low power mode) in which only the first light source 112 is optically pumping the phosphor light source 114, a second operating mode (e.g., a medium power mode) in which only the second light source 120 is optically pumping the phosphor light source 114, and a third operating mode (e.g., a high power mode) in which the first light source 112 and the second light source 120 are concurrently optically pumping the phosphor light source 114. In some implementations, the illumination system is switchable between any or all three of these (and possibly more) operating modes.
If the system is operable within and switchable between multiple operating modes, in general, the controller 180 typically implements any switching that happens. Moreover, in some implementations, the system has a user interface device 181 (e.g., a knob, toggle switch, touch screen, etc.) that enables a user to specify which of the available operating modes (e.g., low power/intensity, medium power/intensity or high power/intensity) the system should be operating in. In these implementations, the controller 180 can be configured to implement the switching in response to an instruction from the user interface device 181. In some implementations, the system can be adapted to switch between available operating modes automatically (i.e., without specific input from a human at the time of the switching). In these implementations, the switching may occur automatically in response to a software instruction, a timing signal, or the like.
Due to the extra optical elements and the different overall configuration in system 9000 as compared to the system 6000 in
For example, in system 9000, light from the first light source 112 is directed onto and pumps the phosphor 114, travels through the third dichroic optical element 119, may be (or may not be) partially filtered by the optical filter 121 travels through the first dichroic optical element 116 and through the optical output 160. Light from the second light source 120 is reflected by the third dichroic optical element 119 onto the phosphor 114 to pump the phosphor 114. Light from the third light source 130 travels through the second dichroic optical element 118, is reflected by the first dichroic optical element and travels through the optical output 160. Light from the fourth light source 140 is reflected by the second dichroic optical element 118 and reflected again by the first dichroic optical element 116 and then travels through the optical output 160.
In various implementations, one or more of the systems disclosed herein may be operable within and switchable between multiple operating modes. These operating modes can include, for example, any two or more of the following: a first operating mode (e.g., a low power mode) in which only a first light source 112 is optically pumping the phosphor light source 114, a second operating mode (e.g., a medium power mode) in which only a second light source 120 is optically pumping the phosphor light source 114, and a third operating mode (e.g., a high power mode) in which the first light source 112 and the second light source 120 are concurrently optically pumping the phosphor light source 114. An illumination system may be switchable between any or all three of these (and possibly more) operating modes.
If a system is operable within and switchable between multiple operating modes, in general, the controller 180 typically implements any switching that happens. Moreover, in some implementations, if the system has a user interface device (i.e., device 181 in
The chart in
As shown in the chart of
In some implementations, the techniques and systems disclosed herein facilitate generating a relatively large amount of Yellow/Green light without increasing the size of the light emitting area and mixing this with other discrete LED wavelengths to form a broad spectrum light source. In a typical implementation, Yellow light is generated in the phosphor layer (or component) after absorbing blue light, which may be injected from the front of the layer (or component), from the back of the layer (or component), or from both. Also, in some implementations, pump 1 is LED1 and produces a Blue light, the Phosphor Layer is (but need not be) part of LED1, and pump 2 is a laser that produces Blue light. It has been found that, in practice, in some implementations, concurrently pumping the phosphor layer (e.g., with LED1 & a pump laser) may create a high heat load (e.g., on LED1—where the phosphor layer is integrated with LED1) and for many applications the pump laser and phosphor layer provided enough optical power, even when LED1 is not operational.
The light source unit 200 in the illustrated implementation has a plurality of light emitting diodes (LEDs), including LED3, LED4, LED5, LED6, and LED7, a plurality of dichroic optical elements D1, D2, D3, D3, D4, D5, and D6, a phosphor light source 114, and a pump laser 120. In a typical implementation, the system 10000 also has a plurality of other optical elements (e.g., lenses, collimators, light guides, and the like), which are not shown in
During system 10000 operation, one or more (or, more typically, all) of the LEDs (LED3, LED4, LED5, LED6 and LED7) and the pump laser 120 produce light, the dichroic optical elements (D1, D2, D3, D3, D4, D5, and D6), as applicable, collectively direct the light produced by the LED(s) and/or pump laser 120 and into a single system output.
In a typical implementation, each respective one of the LEDs (LED3, LED4, LED5, LED6 and LED7) and the pump laser 120 is configured to produce light at a particular wavelength. More specifically, according to the illustrated implementation, LED3 is configured to produce light at one wavelength λ3, LED4 is configured to produce light at another wavelength λ4, LED5 is configured to produce light at yet another wavelength λ5, LED6 is configured to produce light at still another wavelength λ6, LED7 is configured to produce light yet another wavelength λ7, and the pump laser 120 is configured to produce light at wavelength λ2. In a typical implementation, each of these wavelengths (λ2, λ2, λ4, λ5, λ6, and λ7) is different than the others. However, in some implementations, some of those wavelengths may be the same or similar to others.
In a typical implementation, the phosphor light source 114 is configured to fluoresce at a wavelength λphosphor when optically stimulated (or pumped) by the pump laser. In a typical implementation, the light produced by the pump laser 120, at wavelength λ2, is within an absorption band of the phosphor light sources 114.
During system 10000 operation, light produced by the pump laser, at wavelength λ2, is reflected off of dichroic optical element D3 toward the phosphor light source 114. This light, at wavelength λ2, causes the phosphor light source 114 to fluoresce, at wavelength λphosphor. The light from the phosphor light source 114, at wavelength λphosphor, passes through dichroic optical element D3, is reflected off dichroic optical element D4, and passes through dichroic optical element D1 to the system output. Light from LED5, at wavelength λ5, is reflected off dichroic optical element D5, passes through dichroic optical elements D4 and D1 to the system output. Light from LED6, at wavelength λ6, passes through dichroic optical elements D5, D4, and D1 to the system output. Light from LED3, at wavelength λ3, passes through dichroic optical element D2, and is reflected off dichroic optical element D1 to the system output. Light from LED7, at wavelength λ7, is reflected off dichroic optical elements D6, D2, and D1 to the system output. Light from LED4, at wavelength λ4, passes through dichroic optical element D6, and is reflected off dichroic optical elements D2 and D1 to the system output.
The system 10000 is configured, therefore, such that when all of the LEDs, the pump laser 120, and the phosphor light source 114 are emitting light, the light exiting the system output is a combination of all the light produced by all of the LEDs and the phosphor light source 114. Moreover, when any sub-group of the LEDs, the pump laser 120, and the phosphor light source 114 are emitting light, the light exiting the system output is a combination of all the light being produced by the LED(s) and/or phosphor light source 114 that are emitting light.
The control unit 180 in the illustrated implementation has a power supply 182, an LED/laser controller 184, and LED/laser drivers 186. The power supply 182 is generally configured and operable to provide power to other components including, for example, the LED/laser controller 184 and/or the LED/laser drivers 186. The LED/laser drivers 186 are coupled by electrical connections 188 to the LEDs and to the pump laser 120 in the light source unit 200. The LED/laser drivers 186 are configured to drive (concurrently or otherwise) every one of the LEDs and the pump laser 120 in the light source unit 200. The LED/laser controller 184 is generally configured to control operation of the LED/laser drivers 186.
In some implementations, if the system 10000 is operable within and switchable between multiple operating modes (e.g., a low power/intensity mode, a medium power/intensity mode, or a high power/intensity mode), in general, the controller 180 may cause switching between those operating modes. In one exemplary implementation, a low power/intensity mode might call for only one or more (but less than all) of the light emitting components in the light source unit 200 to be operational and, therefore, emitting light. In one exemplary implementation, a high power/intensity mode might call for all of the light emitting components in the light source unit 200 to be operational and, therefore, emitting light. In one exemplary implementation, a medium power/intensity mode might call for operating more light emitting components than the low power/intensity mode calls for, but operating fewer light emitting components than the high power/intensity mode calls for.
In some implementations, the user interface 181, which may be a knob, toggle switch, touch screen, etc., enables a user to specify which of the available operating modes (e.g., low power/intensity, medium power/intensity or high power/intensity) the system 10000 should be operating in. In these implementations, the controller 180 can be configured to implement the switching in response to an instruction from the user interface device 181. In some implementations, the system can be adapted to switch between available operating modes automatically (i.e., without specific input from a human at the time of the switching). In these implementations, the switching may occur automatically in response to a software instruction, a timing signal, or the like, sometimes without any contemporaneous input from a human user whatsoever. In various implementations, the user interface 181 may provide a user with other ways to access, view and/or enter information into the system.
Thus, it can be seen that, in the implementation represented in
Moreover, in the implementation represented in
Additionally, in the implementation represented in
Moreover, in the implementation represented in
The various light emitting components in the illustrated light source unit 200 can be adapted to emit light at various wavelengths. In one specific exemplary implementation, λ2 (from pump laser 114) is 450 nanometers, λ3 (from LED3) is 475 nanometers, λ4 (from LED4) is 430 nanometers, λ5 (from LED5) is 635 nanometers, λ6 (from LED6) is 735 nanometers, λ7 (from LED7) is 385 nanometers, Δλphosphor (the range of wavelengths from phosphor light source 114) is 500-600 nanometers.
In this specific exemplary implementation, dichroic optical element D3 may be configured to transmit λphosphor (from phosphor light source 114), which is 500-600 nanometers, but reflect 445-460 nanometers (e.g., a range that would include the light emitted by pump laser 120, at λ2 (e.g., 450 nanometers)).
One detailed exemplary optical configuration of a light source unit, like the light source unit 200 in
The optical configuration of the light source unit 200 in
In various implementations, each optical element OE1, OE2, OE3, OE4, OE5, OE6, OE7, OE8, and OE9 may be configured to perform any one or more of a variety of different optical functions. These optical functions may include, for example, collimating, focusing, mixing, etc. As an example, in a typical implementation, including the implementation shown in
In some implementations, the pump laser 120 and collimating and focusing optics OE1, OE2, in the light source unit 200 of
Although embodiments have been described in detail above by way of example, it will be apparent that modifications to the embodiments may be made. For example, each LED light source referred to as a LED, and it is apparent that each may be a single LED or an LED array of multiple LED, and the phosphor layer may be directly coated on the emitter surface of the LED or LED array, or provided as an overlying phosphor containing layer. For simplicity single optical elements such as lenses are illustrated, but compound lens or other suitable coupling optics may be used. It will also be apparent that additional LED light sources may be added and similarly optically coupled to the optical output using optical coupling elements comprising dichroic beam-splitter/combiners. However, to reduce reflective and transmissive losses, and reduce size and cost, it may desirable to provide a simple design with fewer components.
Additionally, various features from different implementations described herein may be combined in ways not explicitly shown in the drawings or otherwise described explicitly.
The wavelengths and/or wavelength ranges indicated in this description should not be construed as limiting examples. The wavelengths and wavelength ranges indicated herein may vary.
Although embodiments of the invention have been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and not to be taken by way of limitation, the scope of the present invention being limited only by the appended claims.
This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 15/924,943, entitled High Brightness Solid State Illumination System for Fluorescence Imaging and Analysis, which was filed on Mar. 19, 2018, which was a continuation of then co-pending U.S. patent application Ser. No. 14/862,492, entitled High Brightness Solid State Illumination System for Fluorescence Imaging and Analysis, which was filed on Sep. 23, 2015, said application is a continuation-in-part (CIP) of U.S. patent application Ser. No. 13/897,237, entitled High Brightness Solid States Illumination System for Fluorescence Imaging and Analysis, which was filed on May 17, 2013, which was related to co-pending U.S. patent application Ser. No. 13/900,089, filed May 22, 2013, entitled “High Brightness Illumination System and Wavelength Conversion Module for Microscopy and Other Applications”, which claims priority from U.S. Provisional patent application Ser. No. 61/651,130, filed May 24, 2012. Each of these prior applications is incorporated herein by reference in its entirety.
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| Number | Date | Country | |
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| Child | 15924943 | US |
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| Child | 16217585 | US | |
| Parent | 13897237 | May 2013 | US |
| Child | 14862492 | US |
