Radiation delivery device for microscope systems

Abstract

It is known to use multimode optical fibers for light delivery in microscope systems. A problem with using multimode fibers is that the high coherence of the light source leads to speckle patterns. [Solution] A microscope laser beam delivery device (14) includes a twelfth optical diffuser (50) and a second optical diffuser (60), each configured to periodically move at a different frequency. Each optical diffuser may include a rotating disk. Laser light (18) is spatially randomized by the first rotating diffuser, and the spatial pattern is further randomized by the second diffuser. The second diffuser prevents any spatial pattern from repeating after one rotation of the first diffuser. This prevents beat patterns when light is imaged through a rotating confocal disk and otherwise improves uniformity.

Description

[Technical Field]

[0001] The present invention relates to radiation delivery devices, particularly, but not exclusively, for use in microscope systems, and more particularly to radiation delivery devices having multimode optical fibers. [Background technology]

[0002] In fluorescence microscopes, the use of laser light as a light source can provide much higher brightness than other light sources. Traditionally, single-mode optical fibers are used to deliver laser light to microscopes. However, the resulting Gaussian-like mode distribution requires delivering significantly less light at the edges of the image, or eliminating most of the light by using only the more uniform central portion of the Gaussian distribution. Summary of the Invention [Problem to be solved by the invention]

[0003] It is known to use multimode optical fibers for the light supply in microscope systems in order to provide a uniform light intensity across the image. The problem with using multimode fibers is that the modes supported by the fiber can generate coherent interference due to the high coherence of the light source. This creates a speckle pattern in the image, which causes small spatial variations in the image even if the overall illumination envelope is flat.

[0004] A known solution to this problem is to use an eccentric motor to vibrate the optical fiber, helping to homogenize the light from the fiber and provide a uniform image. This design requires the fiber to be wrapped around the eccentric motor multiple times to fill the space and impart vibration to the microscope system in order to provide sufficient vibration. As a result, this solution has two main drawbacks: it is relatively large and generates significant vibration. This is particularly problematic in integrated imaging systems, where compact size is required. It is also difficult to isolate vibration from imaging systems, where nanometer precision is typically required. Alternatively, multimode lasers can be used, which impart a degree of randomness to the light, thereby eliminating the need for an eccentric vibration motor. However, limiting microscope designs to multimode laser diodes is considered too restrictive in terms of wavelength, performance, and cost.

[0005] It is desirable to solve the problems described above. [Means for solving the problem]

[0006] A first aspect of the present invention is a radiation delivery device comprising: a radiation beam input;

[0033] The radiation beam power; beam delivery means configured to deliver a radiation beam along an optical path from said radiation beam input to said radiation beam output; and The beam delivery means comprises: a first optical homogenizing means; a second optical homogenizing means; and A radiation delivery device is provided, wherein the first optical homogenizing means and the second optical homogenizing means are configured to move periodically at different frequencies.

[0007] Preferably, the first optical homogenizing means comprises a first optical diffuser that intersects the optical path and is movable relative to the optical path. The first optical diffuser may be optically transmissive. Alternatively, the first optical diffuser may be optically reflective.

[0008] Preferably, the second optical homogenizing means comprises a second optical diffuser that intersects the optical path and is movable relative to the optical path. The second optical diffuser may be optically transmissive. Alternatively, the second optical diffuser may be optically reflective.

[0009] In a preferred embodiment, one or both of the first optical homogenizing means and the second optical homogenizing means are rotatable relative to the optical path, and preferably, if rotatable, the first optical homogenizing means and the second optical homogenizing means are rotatable at different speeds.

[0010] In a preferred embodiment, the first and second optical diffusers are rotatable and are rotated in use at different speeds relative to each other.

[0011] Typically, the first and second optical diffusers are positioned in the optical path such that the radiation beam is transmitted from the first optical diffuser to the second optical diffuser, in use.

[0012] Typically, the radiation beam output comprises an output optical fiber, preferably a multimode optical fiber. The beam delivery means is configured to direct the radiation beam into an entrance end of the output optical fiber. The beam delivery means may be configured to direct the radiation beam from a second optical diffuser, preferably through free space, to the output optical fiber. The output fiber may comprise an optical coupler at the entrance end of the output fiber, configured to receive the radiation beam, preferably from free space, and direct the radiation beam into the entrance end of the output fiber. The optical coupler may comprise at least one optical element for de-magnifying the radiation beam. The optical coupler may comprise at least one optical element for focusing the radiation beam into the entrance end of the output fiber.

[0013] In a preferred embodiment, the radiation beam input comprises an input optical fiber, preferably a multimode optical fiber. The beam delivery means is configured to direct the radiation beam from an exit end of the input optical fiber to the first optical homogenizing means. The beam delivery means may be configured to direct the radiation beam from the input optical fiber, preferably through free space, to a first optical diffuser.

[0014] An optical coupler may be provided at the exit end of the input fiber. The optical coupler is desirably configured to receive the radiation beam from the exit end of the input fiber and to emit the radiation beam into free space. The optical coupler may have at least one optical element for expanding the radiation beam. The optical coupler may have at least one optical element for focusing or imaging the radiation beam onto the first optical homogenizing means.

[0015] In one embodiment, the second optical homogenizing means comprises means for moving the output fiber periodically, preferably back and forth.

[0016] In a preferred embodiment, the periodic movement of each of the first and second optical homogenizing means is configured such that the cross-sectional spatial pattern of the radiation beam at the radiation beam output after one period of whichever of the first or second homogenizing means has the higher frequency is substantially uncorrelated with the cross-sectional spatial pattern of the radiation beam at the radiation beam output after the previous period of the one of the first or second homogenizing means has the higher frequency.

[0017] Preferably, the first optical homogenising means is movable so as to modify the cross-sectional spatial pattern of the radiation beam, and the second optical homogenising means is movable so as to further modify the cross-sectional spatial pattern of the radiation beam.

[0018] Another aspect of the present invention provides a microscope system comprising a radiation source module, a microscope module and a radiation delivery device of the first aspect, the radiation delivery device configured to provide a radiation beam from the radiation source module to the microscope module.

[0019] Another aspect of the present invention provides a method for homogenizing a radiation beam, the method comprising: directing the radiation beam towards a first optical homogenizing means; directing the radiation beam from a first optical homogenizing means to a second optical homogenizing means; and periodically moving the first optical homogenizing means and the second optical homogenizing means at different frequencies.

[0020] A preferred method includes modifying the cross-sectional spatial pattern of the radiation beam by moving the first optical homogenizing means, and further modifying the cross-sectional spatial pattern of the radiation beam by moving the second optical homogenizing means.

[0021] Another aspect of the present invention is an apparatus for homogenizing a radiation beam, the apparatus comprising: means for directing the radiation beam to a first optical homogenizing means; means for directing the radiation beam from the first optical homogenizing means to a second optical homogenizing means; means for periodically moving the first optical homogenizing means; and means for periodically moving the second optical homogenizing means, wherein the moving means are configured to move the first optical homogenizing means and the second optical homogenizing means at different frequencies.

[0022] In a preferred embodiment, laser light from a multimode fiber is spatially randomized by a first rotating diffuser or homogenizer and coupled into a second multimode fiber. A second diffusing means or homogenizer may be used to further randomize the spatial pattern, particularly the cross-sectional spatial pattern of the laser / radiation beam. The second diffusing means prevents any spatial pattern from repeating after one revolution or cycle of the first diffuser. This prevents beat patterns when the light is imaged through a rotating confocal disk and improves uniformity in other cases. In a preferred embodiment, the second diffusing means is a second rotating diffuser operating at a different speed than the first. In other embodiments, the second diffusing means is a device that physically moves the second fiber.

[0023] The preferred embodiment does not limit the coherence of the laser source, provides reduced vibrations, and very good uniformity in space.

[0024] Further advantages of the present invention will become apparent to those skilled in the art after reviewing the following description of specific embodiments and after reviewing the accompanying drawings.

[0025] An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which like parts are numbered like, and in which: [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a block diagram of a microscope system according to one aspect of the present invention, including a radiation delivery device according to another aspect of the present invention. [Figure 2] FIG. 2 is an example block diagram of a radiation source module that is part of the microscope system of FIG. 1. [Figure 3] FIG. 2 is a schematic diagram of a first exemplary optical coupler. [Figure 4] FIG. 10 is a schematic diagram of a second exemplary optical coupler. [Figure 5] FIG. 2 is a schematic diagram of a rotating diffuser plate. [Figure 6] FIG. 1 is a block diagram of an alternative microscope system according to one aspect of the present invention, including an alternative radiation delivery device according to another aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring to Figure 1 of the drawings, there is shown an optical microscope system according to one embodiment of the present invention, generally designated 10. Microscope system 10 comprises a radiation source module 12, a radiation delivery device 14, and a microscope module 16. Microscope system 10 is configured such that a radiation beam 18 emitted by radiation source module 12 is delivered to microscope 16 by radiation delivery device 14. Radiation delivery device 14 is configured to deliver radiation beam 18 along an optical path from a beam input to a beam output. In particular, radiation delivery device 14 comprises beam delivery means for delivering beam 18 between the input and output, the beam delivery means comprising first and second optical homogenizing means, as will be described in more detail later herein.

[0028] FIG. 2 shows an example of a typical radiation source module 12. The radiation source module 12 has one or more radiation sources 20 for generating and emitting radiation. In typical embodiments, the radiation is light, particularly in the ultraviolet (UV), visible, or NIR (near-infrared) wavelength range. In preferred embodiments, the radiation source module 12 may therefore be described as a light source module having one or more light sources 20. In preferred embodiments, the light is laser light, and each light source 20 comprises a laser device. However, each radiation source may comprise any light source capable of generating and emitting radiation. Radiation sources include, but are not limited to, light-emitting diodes (LEDs), laser diodes, solid-state devices, superluminescent diodes (SLDs), or arc lamps. Each radiation source 20 is configured to generate and emit radiation or light at one or more wavelengths. In the example of FIG. 2, two laser devices 20 are shown. However, it will be understood that in alternative embodiments, there may be one radiation source or more than two radiation sources. Each laser device 20 may be a single-mode laser device or a multi-mode laser device. In a preferred embodiment, the radiation source module 12 emits light, preferably laser light, at multiple wavelengths. That is, the radiation source module 12 may comprise a multi-wavelength radiation or laser source. As shown, this can be achieved by providing the module 12 with multiple radiation sources 20, each generating radiation at a different wavelength or in a different frequency range. Alternatively, the radiation source module 12 may emit radiation at a single wavelength. In a preferred embodiment in which the radiation source module 12 comprises one or more laser devices 20, the resulting beam 18 comprises coherent laser light.

[0029] Optionally, radiation source module 12 comprises a radiation control and conditioning unit 22 for changing the cross-sectional shape and / or size of beam 18 emitted from module 12. In embodiments having more than one radiation source 20, control and conditioning unit 22 may include control and conditioning sub-units (not shown) corresponding to each radiation source 20. Control and conditioning unit 22 (or each respective sub-unit) may comprise any optical element or combination of optical elements (not shown) for controlling and conditioning beam 18 in any desired conventional manner. For example, control and conditioning unit 22 (or each respective sub-unit) may comprise a Galilean telescopic beam expander, or an anamorphic prism, or cylindrical optics, and / or any other conventional beam shaping means, and / or an acousto-optic tunable filter (AOFT) or a mechanical shutter.

[0030] Embodiments in which the radiation source module 12 has more than one radiation source 20 may include a light combining unit 24 having one or more optical elements arranged in any conventional manner for combining the respective beams from each radiation source 20 to generate the output radiation beam 18. The light combining unit 24 may include, for example, one or more mirrors and / or beam splitters and / or dichroic beam combiners. In the illustrated embodiment, the light combining unit 24 is positioned after the light conditioning unit 22. Thus, the light from the laser sources 20 is conditioned before being combined. In an alternative embodiment (not shown), the light combining unit 24 is positioned before the light conditioning unit 22. Thus, the light from the laser sources 20 is combined before being conditioned.

[0031] The radiation source module 12 typically includes an optical coupler 26 through which the radiation beam 18 is emitted from the module 12. The optical coupler 26 includes one or more optical elements (not shown) for directing the beam 18 into an optical fiber. Typically, the optical coupler 26 has one or more lenses (e.g., a collimator lens, a condenser lens, and / or a microscope objective lens) for focusing the beam 18 onto the end of the optical fiber. The configuration may be such that the optical coupler 26 emits the beam 18 into free space.

[0032] Referring again to FIG. 1 , in a typical embodiment, radiation delivery device 14 includes an input optical fiber 30 having an entrance end 32 for receiving radiation beam 18 from radiation source module 12. Entrance end 32 may receive radiation beam 18 from free space. In a preferred embodiment, optical coupler 26 is configured to focus radiation beam 18 onto entrance end 32 of fiber 30. The cross-sectional shapes and dimensions of beam 18 and the optical core of fiber 30 are compatible to enable transmission of beam 18 along fiber 30. This compatibility may be achieved, at least in part, by control and adjustment unit 22. In an alternative embodiment (not shown), input optical fiber 30 may be omitted, as will be described in more detail later herein.

[0033] The radiation delivery device 14 also has an output means, which preferably comprises an output optical fiber 34 having an exit end 36 from which the radiation beam 18 is delivered to the microscope module 16. The exit end 36 may emit the radiation beam into free space.

[0034] The optical fibers 30, 34 may be conventional. The optical fibers 30, 34 typically have an optically transparent core (not shown) for transmitting the beam 18. The core is surrounded by a transparent cladding material (not shown), typically having a lower refractive index than the core. The core and cladding material may be formed of any suitable material, for example, glass (silica) or plastic. The fibers 30, 34 may be described as optical waveguides. The fibers 30, 34 may be in any known form, for example, a type known as a light pipe. A light pipe has an optically transparent core (e.g., formed of glass or plastic) but may not have a cladding material.

[0035] In a preferred embodiment, the output optical fiber 34 is a multimode optical fiber. While it is preferred that the input optical fiber 30 be a multimode optical fiber, it may alternatively be a single-mode optical fiber. A multimode optical fiber is an optical fiber that supports multiple propagation paths or modes of light. Multiple paths or modes may be supported in parallel over a wide range of wavelengths. In contrast, a single-mode optical fiber supports only one mode. Multimode fiber generally has a larger core diameter (typically 50-400 micrometers) than single-mode fiber. The core diameter of a multimode optical fiber is larger than the wavelength of light transmitted therein. The core of the multimode fiber 30, 34 may have a circular cross-section, a square cross-section, a rectangular cross-section, or any other suitable cross-section.

[0036] By way of example, input fiber 30 may have a core diameter of 50 μm and a numerical aperture (NA) of 0.12. Output fiber 34 may have a core diameter of 200 μm and a numerical aperture (NA) of 0.12. In a typical embodiment, the core diameter of input fiber 30 is smaller than the core diameter of the output fiber.

[0037] Optionally, an input connector (not shown) and an output connector (not shown) may be provided or connectable to the entrance end 32 of optical fiber 30 and the exit end 36 of optical fiber 34, respectively. The input and output connectors may be of any suitable conventional type.

[0038] Microscope module 16 may include any conventional type of microscope (not shown) that requires a radiation beam to illuminate or excite a sample. For example, the microscope may be a wide-field microscope, a confocal microscope, e.g., a spinning-disk confocal microscope, or other optical microscope. Microscope module 16 may be conventional and may include any other elements necessary for the operation of a microscope and apparent to those skilled in the art. Microscope module 16 typically includes an optical coupler (not shown) for receiving radiation beam 18 from exit end 36 of optical fiber 34. The optical coupler may have any conventional arrangement including one or more optical elements, as appropriate for the application. For example, the optical coupler may include any one or more single lenses, multiple lenses, mirrors, multiple mirrors, or any combination of suitable optical elements. In an alternative embodiment (not shown), radiation delivery device 14 may be coupled to any other end system requiring radiation beam 18, such as a projection display device.

[0039] The input fiber 30 has an exit end 33 from which the radiation beam 18 is emitted. The beam 18 may be emitted into free space from the end 33. In a preferred embodiment, an optical coupler 40 is provided at the exit end 33 of the input fiber 30. The optical coupler 40 is configured to receive the beam 18 from the exit end 33 of the input fiber 30 and to emit the beam 18 into free space.

[0040] Optical coupler 40 may comprise any conventional type of optical fiber-to-free-space coupler. Optical coupler 40 typically comprises one or more optical elements (not shown) positioned to receive beam 18 from fiber 30 and direct it toward an object in free space. Optionally, optical coupler 40 includes a collimator. Optical coupler 40 typically comprises one or more optical elements for expanding beam 18. Desirably, optical coupler 40 comprises one or more optical elements for focusing or imaging beam 18 onto an object. Optical coupler 40 typically includes one or more lenses that perform some or all of the above-identified tasks, as applicable. FIG. 3 illustrates an exemplary embodiment of optical coupler 40 having a collimator 41 and a lens 42 that expands and focuses beam 18 onto an object in free space.

[0041] The output fiber 34 has an entrance end 35 for receiving the radiation beam 18. The beam 18 may be received by the end 35 from free space. In a preferred embodiment, an optical coupler 44 is provided at the entrance end 35 of the output fiber 34. The optical coupler 44 is configured to receive the beam 18 from free space and direct the beam 18 into the entrance end 35 of the output fiber 34. The optical coupler 44 may comprise any conventional type of free-space-to-optical fiber coupler. The optical coupler 44 has one or more optical elements (not shown) arranged to receive the beam 18 from free space and direct it into the entrance end 35 of the output fiber 34. Typically, the optical coupler 44 has one or more optical elements for reducing the beam 18. Preferably, the optical coupler 44 has one or more optical elements for focusing the beam 18 into the entrance end 35 of the output fiber 34. The optical coupler 44 typically includes one or more lenses to perform the required tasks. 4 shows an exemplary embodiment of optical coupler 44. Optical coupler 44 includes a lens 46 for reducing and focusing beam 18 into the entrance end of output fiber 24.

[0042] In alternative embodiments, one or the other or both couplers 40, 44 may be omitted. If either coupler 40, 44 is removed, the corresponding end 33, 35 of each fiber 30, 34 may be positioned directly adjacent (i.e., no more than 2 mm apart) to the respective diffuser plate 50, 60. The divergence angle is consistent with that of each fiber 30, 34.

[0043] The radiation delivery device 14 includes a first optical homogenizing means in the preferred form of a first optical diffuser 50 disposed between the input fiber 30 and the output fiber 34. In a preferred embodiment, the first optical diffuser 50 is disposed between the optical couplers 40, 44. The arrangement is such that the beam 18 is transmitted from the input fiber 30 to the output fiber 34 through the first optical diffuser 50. In a preferred embodiment, the optical coupler 40 is configured to direct the beam 18 towards the optical diffuser 50 and preferably to focus the beam 18 onto the first optical diffuser 50. In an embodiment, the optical coupler 40 is configured to image the beam 18 onto the optical diffuser 50. Effectively, the optical coupler 40 expands the beam 18.

[0044] In an alternative embodiment (not shown), the input fiber 30 (and coupler 40) may be omitted. In that case, the beam 18 may be directed from the imaging or radiation source module 12 directly to the optical diffuser 50. The optical coupler 26 typically includes one or more optical elements (not shown) arranged to direct the beam 18 from the module 12 to an object in free space. Optionally, the optical coupler 26 includes a collimator. The optical coupler 26 typically includes one or more optical elements that expand the beam 18. Desirably, the optical coupler 26 includes one or more optical elements for focusing or imaging the beam 18 on the object. The optical coupler 26 typically includes one or more lenses for performing some or all of the tasks identified above, as applicable. In such an embodiment, the optical coupler 26 may be as shown in FIG. 3. The apparatus 14 may include any suitable input means for receiving the beam 18 from the radiation source module 12. For example, the input means may simply comprise an aperture (not shown) and / or may optionally comprise one or more optical elements such as lenses.

[0045] In a preferred embodiment, optical coupler 44 is configured to receive beam 18 and direct beam 18 into the entrance end 25 of output fiber 34. Typically, optical coupler 44 reduces beam 18 to match the numerical aperture (NA) of output fiber 34.

[0046] Conveniently, optical couplers 40, 44 are aligned with one another on a common axis, and beam 18 may travel from coupler 40 to coupler 44 along an optical path that is coincident with or parallel to the common axis. Alternatively or additionally, optical coupler 40 may include one or more beam guiding devices (not shown) for guiding beam 18 along the optical path to first diffuser 50. And / or optical coupler 44 may include one or more beam guiding devices (not shown) for receiving and aligning the optics of coupler 44 with beam 18. In this case, couplers 40, 44 do not necessarily have to be aligned with one another. More generally, delivery apparatus 14 may include one or more beam guiding devices (e.g., any suitable arrangement of one or more mirrors, one or more beam splitters, and / or one or more lenses) that guide beam 18 along an optical path from the input of apparatus 14 (e.g., from input fiber 30 in preferred embodiments) to the output of apparatus 14 (e.g., from output fiber 34 in preferred embodiments). With such a structure, the optical path between the input and output of apparatus 14 need not necessarily be linear. The one or more beam guiding devices, if present, form part of the beam delivery means of apparatus 14, which also includes the optical homogenization means.

[0047] The optical diffuser 50 may have any conventional form. In preferred embodiments, the diffuser 50 is optically transmissive, but may also be optically reflective. For example, the diffuser 50 may be formed from a translucent, but preferably non-transparent, material or an optically reflective material, and / or may have one or more of a surface structure, an internal structure, a surface marking, a surface coating, or lenses to provide an optical diffusion effect. For example, the diffuser 50 may be formed from frosted glass, Teflon, a holographic material, or an opal glass. In preferred embodiments, the diffuser 50 comprises an engineered diffuser in which a pseudo-random pattern is etched into an optically transmissive substrate, typically formed of glass or plastic. In alternative embodiments, the diffuser 50 may comprise a reflective diffuser. By way of example, the diffuser 50 may be configured to provide diffusion with a half angle between 1° and 3°.

[0048] In a preferred embodiment, the first optical diffuser 50 comprises a rotatable optical diffuser. FIG. 5 shows an example of a rotatable optical diffuser 50. The optical diffuser 50 conveniently comprises a disk engaged with a rotational drive means, conveniently comprising a motor 52, although a disk is not required. The motor 52 is operable to rotate the diffuser 50 about its center. The illustrated diffuser 50 may be referred to as a rotating disk diffuser. Rotational movement of the diffuser 50 is preferably about an axis parallel or substantially parallel to the path of the beam 18 or a common axis between the illustrative couplers 40 and 44. In a preferred embodiment, the axis of rotation is not perfectly parallel to the beam path or the common axis (e.g., it may be offset from parallel by 0.5° to 5°) to avoid reflections into the fiber end 33. In an alternative embodiment, the diffuser 50 may be a reciprocating diffuser 50. To this end, the diffuser plate 50 may be engaged with any suitable reciprocating actuator (not shown) for imparting a reciprocating motion to the diffuser plate 50. For example, the reciprocating actuator may comprise a vibration device, e.g., a piezoelectric driver. The reciprocating motion of the diffuser plate 50 is preferably orthogonal or tilted relative to the path of the beam 18 or the common axis between the couplers 40, 44. In either case, the preferred arrangement is one in which the diffuser plate 50 intersects with the path of the beam 18 and can move relative to the path of the beam in order to have a diffusing effect on the beam 18 being used.

[0049] In a preferred embodiment, diffuser 50 is optically transmissive such that beam 18 passes through diffuser 50 as it travels from coupler 40 to coupler 44. Conveniently, diffuser 50 intersects the common axis between couplers 40, 44. Diffuser 50 may be positioned in a plane that is orthogonal or tilted relative to the path of beam 18. It is preferred that the diffuser be positioned in a plane that is substantially, but not perfectly, perpendicular to the path of beam 18.

[0050] In a preferred embodiment, optical coupler 40 focuses or images beam 18 onto diffuser 50, preferably while expanding it. Thus, beam 18 forms a spot on diffuser 50 that is larger than the cross-sectional area of ​​beam 18 emitted from coupler 40. For example, the expansion factor may be between 2x and 20x. In a preferred embodiment, the expansion factor performed by coupler 40 is greater than the demagnification factor performed by coupler 44. For example, coupler 40 may expand beam 18 by 8x, while coupler 44 demagnifies beam 18 by 2.5x.

[0051] The diffuser 50 diffuses or scatters the beam 18. This has the effect of spatially randomizing or modifying the light, particularly in the transverse cross-section, i.e., perpendicular to the direction of propagation. The light may be spatially randomized / modified with respect to its intensity or amplitude and / or phase. The spatial randomization suppresses speckle, which can occur as a result of coherence in the light generated by the radiation source module 12. Speckle tends to occur in highly coherent light sources (single-mode spatially and temporally) and moderately coherent light sources (single-mode spatially and multimode temporally).

[0052] The radiation delivery device includes a second optical homogenizing means in the preferred form of a second optical diffuser 60. The second optical diffuser 60 is positioned between the input fiber 30 and the output fiber 34. In a preferred embodiment, the second optical diffuser 60 is positioned between the optical couplers 40, 44. In this arrangement, the beam 18 is transmitted from the input fiber 30 to the output fiber 34 through the first and second optical diffusers 50, 60. In the illustrated embodiment, the second diffuser 60 is positioned between the first diffuser 50 and the output fiber 34, although it may alternatively be positioned between the first diffuser 50 and the input fiber 34.

[0053] The second optical diffuser 60 may have any conventional form. In a preferred embodiment, the diffuser 60 is optically transmissive, but may alternatively be optically reflective. For example, the diffuser 60 may be formed from a translucent, but preferably non-transparent, material or an optically reflective material, and / or may have one or more of a surface structure, an internal structure, a surface marking, a surface coating, or lenses to provide an optical diffusion effect. For example, the diffuser 60 may be formed from frosted glass, Teflon, a holographic material, or an opal glass. In a preferred embodiment, the diffuser 50 comprises an engineered diffuser in which a pseudo-random pattern is etched into an optically transmissive substrate, typically formed of glass or plastic. In an alternative embodiment, the diffuser 60 may comprise a reflective diffuser. By way of example, the diffuser 60 may be configured to provide diffusion over a half angle of between 1°-3°.

[0054] In a preferred embodiment, the second optical diffuser 60 comprises a rotatable optical diffuser, for example, of the type shown in FIG. 5 . Thus, the second diffuser may be a rotating disk diffuser. The rotational movement of the diffuser 60 is preferably about an axis parallel or substantially parallel to the path of the beam 18, or, in this example, parallel or substantially parallel to the common axis between the couplers 40 and 44. In a preferred embodiment, the axis of rotation is not perfectly parallel to the beam path or the common axis (e.g., it may be offset from parallel by 0.5° to 5°). In an alternative embodiment, the diffuser 60 may be a reciprocating diffuser 60. To this end, the diffuser 60 may be engaged with any suitable reciprocating actuator (not shown) to impart a reciprocating motion to the diffuser 60. For example, the reciprocating actuator may comprise a vibration device, e.g., a piezoelectric driver. The reciprocating motion of the diffuser 60 is preferably orthogonal or tilted relative to the path of the beam 18 or the common axis between the couplers 40 and 44. In either case, the preferred arrangement is one in which the diffuser plate 60 intersects the path of the beam 18 and can be moved relative to the path of the beam in order to have a diffusing effect on the beam 18 being used.

[0055] In a preferred embodiment, diffuser 60 is optically transmissive such that beam 18 passes through diffuser 60 as it travels from coupler 40 to coupler 44. Conveniently, diffuser 60 intersects the common axis between couplers 40, 44. Diffuser 60 may be positioned in a plane that is orthogonal or tilted relative to the path of beam 18. It is preferred that the diffuser be positioned in a plane that is substantially, but not perfectly, perpendicular to the path of beam 18 (e.g., offset between 0.5° and 5° from normal).

[0056] The first and second diffusers 50, 60 may be spaced apart in the direction of travel of the beam 18 by any suitable distance, for example, between 1 mm and 10 mm. Optionally, one or more lenses, for example, one or more relay lenses (not shown), may be provided between the diffusers 50 and 60.

[0057] FIG. 6 illustrates an alternative embodiment of an optical microscope system 10′. Unless otherwise noted, system 10′ may be the same as system 10 of FIG. 1, and the same or similar descriptions may apply, as would be apparent to one skilled in the art. In system 10′, first and second optical diffusers 50′, 60′ comprise reflective diffusers. For example, diffusers 50′, 60′ may have optically reflective front-facing surfaces 51′, 61′, respectively. Front-facing surfaces 51′, 61′ may include structures, markings, and / or other optical diffusing means for diffusing beam 18. System 10′ is positioned such that beam 18 emanating from coupler 40 is reflected by each diffuser 50′, 60′ and directed toward coupler 44. In other embodiments (not shown), either the first or second diffuser may be optically transmissive and the other diffuser may be optically reflective, with the system arranged so that the beam is reflected by one diffuser, transmitted through the other diffuser, and directed to the output fiber.

[0058] The second diffuser plate 60, 60' may rotate in the same direction as the first diffuser plate 50, 50' or in the opposite direction. Effectively, the first and second diffuser plates 50, 50', 60, 60' are rotated at different speeds. Desirably, the second diffuser plate 60, 60' is rotated slower than the first diffuser plate 50, 50'. For example, the speed of the second diffuser plate 60, 60' may be between 5% and 95% of the speed of the first diffuser plate 50, 50'. By way of example, the first diffuser plate 50, 50' may be rotated at approximately 5000 rpm, while the second diffuser plate 60, 60' may be rotated at approximately 4800 rpm.

[0059] More generally, the first and second diffuser plates 50, 50', 60, 60' are effectively moved at different speeds relative to one another, whether the movement is rotational or reciprocating. In preferred embodiments, particularly but not exclusively where each diffuser plate 50, 50', 60, 60' is rotatable, any one of the diffuser plates 50, 50', 60, 60' is rotated or otherwise moved at a speed between 5% and 95% of the speed of the other diffuser plate 60, 60', 50, 50'. For rotating diffusers, the speed may be the speed of rotation or the frequency of rotation. For reciprocating diffusers or other reciprocating elements, the speed may be the linear speed or the frequency of the reciprocating motion.

[0060] The second diffuser 60, 60' also diffuses or scatters the beam 18, further randomizing or altering its spatial pattern, particularly in its transverse cross-section. Typically, the spatial pattern of the beam 18 is further randomized or altered with respect to its intensity (or amplitude) and / or phase. In this arrangement, the non-uniformity of the spatial pattern varies with time, so that over time (e.g., during a camera exposure), the non-uniformity averages out, resulting in a substantially uniform, or at least uniform, spatial pattern. If only one periodic homogenizer is used, an instantaneous cross-sectional snapshot of the beam after one homogenizer cycle will appear substantially identical to the previous cycle. That is, there will be a correlation between the respective spatial patterns at the end of each cycle, which may appear as a periodic pattern in the image formed by the microscope. Using a second homogenizer ensures that any such correlation is small; that is, a periodic pattern will not occur until both homogenizers return to the same initial state, which takes significantly longer than one cycle of the first homogenizer. The subsequent spatial pattern formed by the two homogenizers is predictable, but appears random in practice.

[0061] Advantageously, the second diffuser 60, 60' thus prevents the beam 18 from forming a visible periodic spatial pattern, particularly due to the periodic movement of the first diffuser 50, 50'. As a result, the beam 18 provided by the radiation delivery device 14 has a more uniform or homogenized intensity, which can provide more uniform illumination of the sample. If the microscope is a confocal microscope, the action of the second diffuser 60, 60' prevents the formation of beat patterns when imaging light through a rotating confocal disk.

[0062] In alternative embodiments, the second diffuser 60 may be disposed between the fiber 34 and the microscope 16, or may be integrated within the microscope to receive the beam 18 from the end 36 of the fiber 34. In other alternative embodiments (not shown), the second optical diffusing means may include means for moving the output fiber 34 relative to the path of the beam 18, preferably in a reciprocating or other periodic manner. For example, this may be achieved by engaging the output fiber 34 with a vibration device to vibrate the fiber 34. Any suitable conventional vibration motor or other vibration device, such as a piezoelectric driver, may be used for this purpose. Preferably, the vibration speed or frequency is different from that of the first diffuser 50, 50'. The movement of the output fiber 34 has a diffusing effect on the light transmitted to the fiber 34. However, more importantly, the movement of the output fiber 34 is asynchronous with the rotation of the diffuser 50, thereby disrupting any other periodic spatial patterns that may be produced by the periodic movement of the diffuser 50. Advantageously, the jamming effect of vibrating fiber 34 may be achieved without wrapping fiber 34 around a vibrating device, for example, by vibrating the end of fiber 34 or an unwound length of fiber 34.

[0063] More generally, the first and second optical homogenizing means are operated at different frequencies such that their movements are asynchronous. Specifically, the first and second optical homogenizing means are periodically moved at different frequencies. In a preferred embodiment, this is achieved by rotating the first and second diffusers 50, 50', 60, 60'. In a preferred arrangement, the first diffusers 50, 50' and the second diffusers do not move in synchronous or phase relationship. The desynchronization of the movements prevents repeating patterns from occurring in the output beam 18, i.e., the radiation beam emerging from the exit end 36 of the output fiber 34. Repeating patterns can adversely affect the quality of the image formed by a microscope or other end system. In a preferred embodiment, the periodic movement of each of the first and second optical homogenizing means is configured such that the cross-sectional spatial pattern (particularly the cross-sectional intensity pattern) of the radiation beam 18 output from the fiber 34 after one period of either the faster or higher frequency one of the first or second homogenizing means is uncorrelated or substantially uncorrelated with the cross-sectional spatial pattern (particularly the cross-sectional intensity pattern) of the radiation beam 18 output from the fiber 34 after the previous period of the faster or higher frequency one of the first or second homogenizing means. The respective patterns are uncorrelated or substantially uncorrelated in that the cross-sectional patterns, particularly the cross-sectional intensity patterns, do not repeat after each period of the higher frequency homogenizer.

[0064] In use of the preferred embodiment, light from the exit end 33 of the input fiber 30 is imaged or directed by the optical coupler 40 to the first diffuser 50 to form a spot, preferably an enlarged spot, on the first diffuser 50. The beam 18 propagates from the first diffuser 50 to the second diffuser 60, forming a corresponding spot on the second diffuser 60. Optionally, one or more relay lenses are provided between the diffusers 50, 60 to relay the spot from the first diffuser to the second diffuser 60. The beam 18 is directed from the second diffuser 60 to the optical coupler 40 (e.g., as a result of alignment of the couplers 40, 44 as shown and / or by any other conventional beam-guiding element or elements). The coupler 40 then directs the beam 18 into the entrance end 35 of the output fiber 34. The coupler 44 may be configured to image or focus the spot on the second diffuser 50 onto the fiber 34, preferably with demagnification.

[0065] The diameter of the beam 18 and the properties of the diffusers 50, 60 are advantageously designed to provide efficient coupling of light into the output fiber 34 and to provide sufficient uniformity from the fiber 34. For example, to couple light from the diffusers 50, 60 into the output fiber 34, the beam diameter incident on the diffuser 50 (Dd), the effective total diffusion angle of the diffusers 50, 60 (half the angle alpha), the core diameter of the fiber 34 (Df), and the numerical aperture (NA) of the fiber 34 may approximately satisfy the following relationship: Dd*sin(alpha) <Df*NA···[1]

[0066] The larger the value of Dd*alpha, the greater the loss, but the more the diffuser moves, the more the mode changes, and therefore a more uniform image. If the beam 18 striking the diffuser 50 is not collimated, it will have a small spread in angle (half the angle theta), so equation [1] can be replaced by: Dd*sin(alpha+theta) <Df*NA···[2]

[0067] The light entering fiber 34 must have an angle smaller than the acceptance angle (NA) of fiber 34 and a spatial extent less than the fiber diameter (Df). This may be achieved by imaging a spot on second diffuser 60 through optical coupler 44 into fiber 34 with a demagnification factor M. Desirably, the demagnification factor satisfies the following in order to meet the size requirement: Dd / M <Df···[3] The demagnification also satisfies the following angular requirements (the angle theta may be omitted for a collimated input beam): M*sin(alpha+theta) <NA···[4]

[0068] The present invention is not limited to one or more of the embodiments described herein, and may be amended or modified without departing from the scope of the present invention.

Claims

1. 1. A radiation delivery device comprising: a radiation beam input; radiation beam power; and beam delivery means configured to deliver a radiation beam along an optical path from said radiation beam input to said radiation beam output; and The beam delivery means comprises: a first optical homogenizing means; a second optical homogenizing means; and The radiation delivery device, wherein the first optical homogenizing means and the second optical homogenizing means are configured to move periodically at different frequencies.

2. 2. The radiation delivery system of claim 1, wherein said first optical homogenizing means comprises a first optical diffuser intersecting said optical path and movable relative to said optical path.

3. 3. The radiation delivery device of claim 2, wherein the first optical diffuser is optically transmissive or optically reflective.

4. 4. A radiation delivery device according to claim 1, wherein the second optical homogenizing means comprises a second optical diffuser intersecting the optical path and movable relative to the optical path.

5. 5. The radiation delivery device of claim 4, wherein the second optical diffuser is optically transmissive or optically reflective.

6. 6. The radiation delivery device of claim 1, wherein one or both of the first optical homogenizing means and the second optical homogenizing means are rotatable relative to the optical path.

7. 7. The radiation delivery system of claim 6, wherein the first optical homogenizing means and the second optical homogenizing means are rotatable at different speeds.

8. the first optical homogenizing means comprises a first optical diffuser, and the second optical homogenizing means comprises a second optical diffuser; 8. A radiation delivery device according to claim 1, wherein the first and second optical diffusers are rotatable and, in use, rotated at different speeds relative to each other.

9. the first optical homogenizing means comprises a first optical diffuser, and the second optical homogenizing means comprises a second optical diffuser; 9. The radiation delivery device of claim 1, wherein the first and second optical diffusers are positioned in the optical path such that, in use, the radiation beam is transmitted from the first optical diffuser to the second optical diffuser.

10. the radiation beam output comprises an output optical fiber, preferably a multimode optical fiber; 10. A radiation delivery device according to any preceding claim, wherein the beam delivery means is configured to direct the radiation beam into an entrance end of the output optical fibre.

11. 11. A radiation delivery device according to claim 10 when dependent on claim 9, wherein the beam delivery means is configured to direct the radiation beam from the second optical diffuser to the output optical fiber, preferably through free space.

12. the output fiber having an optical coupler at an input end of the output fiber; the optical coupler is configured to receive the radiation beam, preferably from free space, and direct the radiation beam into the entrance end of the output fiber; 12. The radiation delivery device of claim 11, wherein the optical coupler optionally includes at least one optical element for reducing the radiation beam.

13. 13. The radiation delivery device of claim 12, wherein the optical coupler comprises at least one optical element for focusing the radiation beam into the entrance end of the output fiber.

14. the radiation beam input comprises an input optical fiber, preferably a multimode optical fiber; 14. A radiation delivery device according to any preceding claim, wherein the beam delivery means is configured to direct the radiation beam from an exit end of the input optical fibre towards first optical homogenising means.

15. 15. A radiation delivery device according to claim 14 when dependent on claim 9, wherein the beam delivery means is configured to direct the radiation beam from the input optical fibre to a first optical diffuser, preferably through free space.

16. an optical coupler is provided at the exit end of the input fiber; 16. A radiation delivery device according to claim 14 or 15, wherein the optical coupler is preferably configured to receive the radiation beam from the exit end of the input fibre and to emit the radiation beam into free space.

17. 17. The radiation delivery device of claim 16, wherein the optical coupler comprises at least one optical element for expanding the radiation beam.

18. 18. A radiation delivery device according to claim 16 or 17, wherein the optical coupler comprises at least one optical element for focusing or imaging the radiation beam onto the first optical homogenizing means.

19. 11. A radiation delivery system according to claim 10, wherein said second optical homogenizing means comprises means for moving said output fiber periodically, preferably reciprocally.

20. 20. The radiation delivery device of claim 1, wherein the periodic movement of each of the first and second optical homogenizing means is configured such that the cross-sectional spatial pattern of the radiation beam at the radiation beam output after one period of whichever of the first and second homogenizing means has a higher frequency is substantially uncorrelated with the cross-sectional spatial pattern of the radiation beam at the radiation beam output after a previous period of which of the first and second homogenizing means has a higher frequency.

21. the first optical homogenizing means is movable to modify a cross-sectional spatial pattern of the radiation beam; 21. The radiation delivery device of claim 1, wherein the second optical homogenizing means is movable to further modify the cross-sectional spatial pattern of the radiation beam.

22. 24. A microscope system comprising a radiation source module, a microscope module and a radiation delivery device according to any one of claims 1 to 23, The radiation delivery device is configured to provide a beam of radiation from the radiation source module to the microscope module.

23. 1. A method for homogenizing a radiation beam, comprising: The method comprises: directing the radiation beam towards a first optical homogenizing means; directing the radiation beam from the first optical homogenizing means to a second optical homogenizing means; periodically moving the first optical homogenizing means and the second optical homogenizing means at different frequencies; A method comprising:

24. changing a cross-sectional spatial pattern of the radiation beam by moving the first optical homogenizing means; 24. The method of claim 23, further modifying the cross-sectional spatial pattern of the radiation beam by moving the second optical homogenizing means.

25. 1. An apparatus for homogenizing a radiation beam, comprising: The device comprises: means for directing the radiation beam towards a first optical homogenizing means; means for directing the radiation beam from the first optical homogenizing means to a second optical homogenizing means; means for periodically moving the first optical homogenizing means; means for periodically moving the second optical homogenizing means; and and wherein both of said moving means are configured to move said first optical homogenizing means and said second optical homogenizing means at different frequencies.

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