REDUCED SPECKLE ILLUMINATION SYSTEM AND METHOD - Patent application

Abstract

A laser source is provided, the laser source comprising at least one diode and a length of optical fiber disposed between the laser source and a target location such that the optical fiber transmits light pulses from the laser source as a light source to the target location, the location being illuminated by the light source to reduce speckle in a captured image of the target. Also provided is a method of providing source light for generating an image, the method including generating illumination using one or more laser diodes and passing the illumination through an optical fiber having a plurality of bends such that the source light is emitted from the optical fiber to illuminate the target with the source light, the source light reducing speckle in an image of the target.

Description

[Technical field]

[0001] Related Applications This application claims priority to and the benefit of U.S. Patent Application No. 63 / 125,259, entitled "Reduced Speckle Illumination Systems and Methods," filed December 14, 2020, and U.S. Patent Application No. 63 / 287,335, entitled "Reduced Speckle Illumination Systems and Methods," filed December 8, 2021. The foregoing applications are incorporated herein in their entireties for all purposes.

[0002] The present disclosure relates to the field of laboratory lighting systems. [Background technology]

[0003] Historically, speckle in conventional imaging has been addressed by averaging many different speckle patterns during a camera exposure. However, such solutions are active in nature and also occur in the time domain, as they operate by generating a large number of speckle patterns and averaging the results over time. Some examples of these approaches include vibrating an optical fiber, passing light through a rotating disk of ground glass, and passing light through a rotating collection of optical fibers.

[0004] The rotating disk can be, for example, 2 inches in diameter, rotated at 50,000 rpm, and have a displacement velocity at the disk edge of 10 micrometers / 100 ns. However, this configuration requires a significant amount of hardware, which can increase the complexity and footprint of the low speckle instrument. The vibrations used to produce multimode illumination can be in the range of tens of Hz to tens of kHz, and a 10 ns pulse can require a vibration frequency of over 10 MHz, since the displacement is proportional to 1 / frequency. However, vibration-based approaches can result in undesirable hardware complexity.

[0005] While the above techniques can be effective in reducing speckle in some cases, they also occur on millisecond timescales, which makes the solutions less suitable for the short exposure times required for flow cytometry. Thus, there is a long-felt need in the art for speckle reduction systems and methods suitable for use in flow cytometry applications, and in particular, systems and methods that provide speckle reduction on timescales suitable for flow cytometry. Summary of the Invention

[0006] To meet the stated long-standing need, the present disclosure first provides a light source for capturing an image, the light source comprising: a laser source including at least one diode; and an optical fiber arranged to transmit light pulses having multiple modes between the laser source and a target location to reduce speckle in a captured image of a target at the target location, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a peripheral wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber.

[0007] Also provided is a method that includes operating a light source according to the present disclosure (eg, according to any one of aspects 1-21) to illuminate a target.

[0008] Further provided is a method, the method including placing an optical fiber in optical communication with an illumination source, such that the optical fiber is positioned to transmit light from the illumination source to a target disposed at a target location, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a peripheral wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber.

[0009] Also provided is a method of providing source light for generating an image, the method including generating illumination using one or more laser diodes and passing the illumination through an optical fiber present in one or more layers wrapped around a spindle, the spindle optionally including a circumferential wall with the optical fiber wound therebetween, the layer including at least one taut turn of the optical fiber, the passing being performed such that multimode source light is emitted from the optical fiber to illuminate a target with the illumination light, the illumination reducing speckle in an image of the target.

[0010] A cytometer is further disclosed that includes a flow cell configured to contain one or more particles therein, the flow cell defining a target area, and an illumination train including at least: (1) a laser source including at least one diode; and (2) an optical fiber in optical communication with the laser source, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a peripheral wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber.

[0011] Further disclosed is an imaging apparatus comprising: a sample zone configured to contain a sample therein; an illumination train including at least (1) a laser source including at least one diode; and (2) an optical fiber in optical communication with the laser source, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a circumferential wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber; and an image capture device configured to capture an image of the sample disposed within the sample zone area while illuminated by illumination from the at least one diode transmitted through the optical fiber, the imaging apparatus further optionally comprising a motion train configured to provide relative motion between the sample in the sample zone and the illumination from the at least one diode transmitted through the optical fiber.

[0012] Further provided is a light source comprising a laser source including at least one diode and an optical fiber arranged to transmit light between the laser source and an imaging plane to reduce the coherence of the light and reduce speckle at the imaging plane, the optical fiber having at least a portion bent around a support to create mechanical tension in the optical fiber.

[0013] Also provided is a method that includes operating a light source according to the present disclosure (eg, a light source according to any one of aspects 47-74). [Brief description of the drawings]

[0014] In the drawings, which are not necessarily drawn to scale, the same numerals may represent similar components in different views. Similar numerals with different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various aspects discussed in the present document. In the drawings: [Figure 1] Illustrative illustrations of single mode and multimode illumination transmitted through various optical fibers are provided. [Diagram 2] 1 provides an exemplary image of a 10 micrometer bead illuminated by a 10 ns illumination pulse transmitted through a 2 m optical fiber. [Diagram 3] 1 provides an example depiction of speckle contrast as a function of the length of the fiber through which illumination is transmitted. [Figure 4] 1 provides a diagram of an exemplary laser assembly according to the present disclosure showing multiple laser diodes in optical communication with an optical fiber; [Diagram 5] We provide an illustration of a bead illuminated by a 100 ns illumination pulse transmitted through 2 m of optical fiber (left) and an equivalent bead illuminated by a 100 ns illumination pulse transmitted through 50 m of optical fiber (right). [Figure 6] 1 provides an illustration of an exemplary system according to the present disclosure. [Figure 7] Illustrated are a tightly wound fiber spool (left panel) and a loosely wound fiber spool (right panel). [Figure 8] 1 provides an illustration of a fiber spool with fiber wound over another fiber loop resulting in a bulge in the fiber wound over the inner fiber loop. [Figure 9] Illustrated layers of neatly wound fibers (left panel) and randomly wound fibers (right panel) are provided, showing the resulting fiber intersections. [Figure 10] 1 provides an illustration of an exemplary fiber winding configuration. [Figure 11] 1 provides a cutaway view of layers of fiber on a spool of wound fiber. [Figure 12] An image of a loosely wound fiber spool (right panel) and an image collected with the loosely wound fiber spool (left panel) are provided. [Figure 13] An image of a tightly wound fiber spool (right panel) and an image collected with the tightly wound fiber spool (left panel) are provided. [Figure 14] 13 provides images produced by different fibers spun with the techniques described in this disclosure, illustrating the consistency and repeatability of the techniques. [Figure 15] 1 provides an illustration of a technique for manufacturing wound fiber according to the present disclosure showing winding of optical fiber on a custom spool, with the optical fiber being fed by a supply spool; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present disclosure may be understood more readily by reference to the following detailed description of the preferred embodiments and examples contained therein.

[0016] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. In case of conflict, the present document, including definitions, shall prevail. Preferred methods and materials are described below, but methods and materials similar or equivalent to those described herein can be used in practice or testing. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and are not intended to be limiting.

[0017] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0018] As used in the specification and claims, the term "comprising" includes the embodiments "consisting of" and "consisting essentially of." As used herein, the terms "comprising," "including," "having," "having," "can," "comprise," and variations thereof, are intended to be open-ended transitional phrases, terms, or words that require the presence of the specified components / steps and permit the presence of other components / steps. However, such descriptions should be construed to describe compositions or processes as "consisting of" and "consisting essentially of" the listed components / steps, which permits the presence of only the specified components / steps with any possible resulting contaminants, and excludes other components / steps.

[0019] As used herein, the terms "about" and "approximately" mean that the quantity or value in question may be approximately or nearly the same as another value specified. As used herein, it is generally understood to be a nominal value indicating a variation of ±10%, unless otherwise indicated or inferred. The term is intended to convey that similar values ​​promote the same results or effects as described in the claims. That is, it is understood that the amounts, sizes, formulations, parameters, and other quantities and characteristics need not be precise, but can be approximated and / or larger or smaller as necessary, reflecting tolerances, conversion factors, rounding, measurement errors, etc., and other factors known to those skilled in the art. In general, the amounts, sizes, formulations, parameters, or other quantities or characteristics are "about" or "approximate", whether or not they are expressly stated as such. When "about" is used before a quantitative value, it is understood that the parameter also includes the specific quantitative value itself, unless otherwise stated.

[0020] Additionally, unless indicated to the contrary, numerical values ​​should be understood to include numerical values ​​that are the same when reduced to the same number of significant digits, and numerical values ​​that differ from the stated value by less than the experimental error of conventional measuring techniques of the type described in this application to determine the value.

[0021] All ranges disclosed herein are inclusive of the recited endpoints, independent of the endpoints, 2 grams and 10 grams, and all intermediate values. The endpoints of the ranges and any values ​​disclosed herein are not limited to the exact ranges or values, but are sufficiently imprecise to include values ​​that are approximations of these ranges and / or values.

[0022] As used herein, approximation terms may be applied to modify any quantitative expression that may vary without resulting in a change in the basic function involved. Thus, values ​​modified by terms such as "about" and "substantially" may not be limited to the precise values ​​specified. In at least some instances, approximation terms may correspond to the precision of an instrument for measuring the value. The modifier "about" should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the expression "about 2 to about 4" also discloses the range "2 to 4". The term "about" can refer to plus or minus 10% of the indicated number. For example, "about 10%" can indicate a range of 9% to 11%, and "about 1" can mean 0.9 to 1.1. Other meanings of "about" may be apparent from the context, such as rounding, for example, "about 1" can also mean 0.5 to 1.4. Additionally, the term "comprising" should be understood to have the open-ended meaning of "including," but it also includes the closed-ended meaning of the term "consisting." For example, a composition that includes components A and B can be a composition that includes A, B, and other components, but can also be a composition that consists only of A and B. All documents cited herein are incorporated by reference in their entirety for all purposes.

[0023] As CMOS sensors offering higher speed and quantum efficiency are developed, cameras are becoming more suitable for flow cytometry applications. Coupled with the advancement of high-power laser diodes and the resulting reduction in price per watt of optical power, combining a high-speed camera with a laser source is a compelling approach for use in flow cytometry imaging. However, the effectiveness of such an approach may be somewhat compromised by the presence of undesirable laser speckle in the images collected by the camera.

[0024] To reduce this undesirable speckle, the present disclosure provides, among other things, the use of optical fibers to deliver multimode illumination to a target, which reduces speckle in imaging of that target.

[0025] Multimode illumination can be achieved in many ways, for example, using multimode fibers. Multimode fibers can contain thousands or even tens of thousands of propagation modes. Each mode has a different spatial path during propagation, as shown in FIG. 1 attached hereto. This can result in a temporal diffusion of the light at the fiber output. As a rough description of speckle reduction, the different modes can be considered as many different sources, which generate different speckle patterns.

[0026] In addition to geometric mode diffusion, additional perturbations to the fiber and / or pump can be introduced that can increase coupling to higher order modes. For example, increasing the cone angle of the pump light entering the fiber can increase mode coupling. This can couple light into higher order modes propagating at larger angles within the fiber. For this reason, fibers with relatively high numerical apertures and higher mode numbers can be used. As a non-limiting example, fibers with numerical aperture values ​​of, for example, about 0.2 to about 0.55 can be used. To further mix the modes and access higher orders, curving, wrapping, or otherwise bending the optical fiber can have the effect of bending the light from lower modes to higher modes over long distances.

[0027] The source bandwidth can further mix the modes. Different wavelengths have different mode patterns, thereby creating different mode structures across an array of wavelengths. Thus, a multi-mode light source (e.g., laser diode) can be used, e.g., a first diode emitting at a first wavelength and a second diode emitting at a second wavelength. Multi-mode diodes can also be used, e.g., diodes lasing at multiple wavelengths.

[0028] Existing approaches use relatively short optical fibers over which short lengths passive mode mixing is small and ineffective in reducing speckle in images. As described elsewhere herein, some techniques use vibration or movement to deform the fiber optic cable, thereby creating and then accessing more geometric modes for use in averaging multiple speckle patterns.

[0029] Most applications involve vibrating the fiber on the millisecond time scale, since most conventional microscopy techniques use exposure times of tens to hundreds of milliseconds. However, for the high-speed imaging required in flow cytometry, mode mixing must be achieved within a time window of around 100 nanoseconds, several orders of magnitude shorter than the time window suitable for conventional microscopy. This relatively short time window therefore precludes the use in flow cytometry of most current active speckle reduction techniques.

[0030] In this disclosure, the properties of multimode fiber are used for ultrafast speckle reduction techniques. This can be achieved by using the slow mode mixing / pulse spreading properties of multimode fiber combined with the listed additive perturbations to increase mode mixing. In this embodiment, different fiber lengths and laser wavelength bandwidths can be used than those found in standard imaging applications.

[0031] Fast speckle reduction can be achieved by using each of the techniques listed above to increase passive mode mixing. Independently, no mixing is adequate, but by moving parameters away from the current standard and combining techniques, adequate speckle reduction can be achieved on very short time scales.

[0032] In one embodiment, a relatively long (e.g., 50 m long) multimode high numerical aperture fiber is inserted between the light source and the imaging target. The fiber can be wound around a spindle with successive bends that can allow access to additional modes. Furthermore, the light source bandwidth can be increased by coupling light from multiple laser diodes of slightly different wavelengths into the fiber. Each of these effects is additive.

[0033] figure The accompanying figures are merely illustrative and do not necessarily limit the scope of the disclosure or the appended claims.

[0034] FIG. 1 provides an exemplary diagram of single mode and multimode illumination transmitted through various optical fibers—single mode / step index, multimode / graded index, and multimode / step index.

[0035] FIG. 2 provides an example image of a 10 micrometer bead illuminated by a 10 ns illumination pulse transmitted through a 2 m optical fiber.

[0036] 3 provides an example depiction of speckle contrast as a function of the length of the fiber through which illumination is transmitted. As shown, the NA of the fiber (0.2 corresponds to line 300, 0.3 corresponds to line 302, and 0.4 corresponds to line 304) can affect the speckle contrast developed as a function of fiber length. As an example, at a fiber length of 50 m, a fiber with an NA of 0.4 exhibits relatively low speckle contrast compared to a fiber with an NA of 0.2.

[0037] 4 provides a diagram of an exemplary laser assembly according to the present disclosure. As shown, the assembly can include multiple laser diodes in optical communication with an optical fiber.

[0038] FIG. 5 provides an illustration of (left) a 10 micron bead 504 moving at 4 m / s in a background 506 and illuminated by a 100 ns pulse of illumination delivered through a 2 m multimode optical fiber, and (right) an equivalent bead 500 (moving in a background 502) illuminated by a 100 ns pulse of illumination delivered through a 50 m multimode optical fiber wound on a spindle, both fibers having an NA of 0.5. Multiple laser diodes with a wavelength of around 405 nm were used to illuminate the 50 m long fiber with a high NA of 0.5. The target was strobed using light pulses synchronized between the multiple diodes of about 100 nanoseconds, with an exposure time of about 6 microseconds. Thus, use of the disclosed technique resulted in a noticeable difference (right panel) over the comparative technique (left panel).

[0039] FIG. 6 provides a diagram of an exemplary system according to the present disclosure. As shown, the system 600 can include a controller 602 that can communicate with one or more laser diodes 604, which can be single mode or multimode diodes. The laser diodes 604 can communicate with an optical fiber 606, which can be a multimode fiber. The fiber 606 can also be wrapped around a spindle (or multiple spindles) and can be otherwise curved or bent. Illumination delivered from the fiber 606 can be delivered to a location 610, such as a flow cell, a microscope stage, or other location where a sample is illuminated. An image capture train 608 then captures an image of the illuminated sample at the sample location 610, which image exhibits reduced speckle. Although the controller 602 can communicate with the image capture train 608, this is not a requirement and the image capture train can communicate with an alternative controller.

[0040] FIG. 7 provides an illustration of a tightly wound fiber spool (left panel) and a loosely wound fiber spool (right panel). As shown, the loosely wound fiber does not have a consistent radius around its circumference. Without being bound to a particular theory or embodiment, winding the fiber tightly creates a constant bend radius such that only certain orders of propagation modes are retained within the fiber core. In contrast, if the fiber is a loosely wound spool or there is slack in the fiber, the bend radius of the fiber is not well controlled and light may be coupled into different orders of modes other than the desired mode.

[0041] FIG. 8 provides an illustration of a fiber spool in which the fiber is "crossed" over another fiber loop, resulting in a bulge in the fiber wrapped over the inner fiber loop. Without being bound to a particular theory or embodiment, having such a crossover can result in a non-uniform radius of the fiber. Winding the fiber over another loop of fiber can introduce different bend radii that can result in generating different order modes. Thus, when the fiber is neatly wound around a spindle or spool, such a wrap reduces the number of crossovers and avoids having small bends of different radii that can potentially propagate higher order modes and / or reduce fiber transmission.

[0042] Figure 9 provides an illustration of a neatly wrapped layer of fiber (left panel) and a randomly wrapped layer of fiber (right panel) showing the resulting fiber crossovers. As shown in Figure 8, the presence of such crossovers (of which there are several in Figure 9) can lead to non-uniform or inconsistent fiber radii.

[0043] Figure 10 provides an illustration of an exemplary fiber winding configuration. Without being bound to a particular theory or embodiment, the fiber can be wrapped around a spindle in a roll-to-roll manner, where the fiber source and / or fiber-winding spindle rotates circumferentially and the source and / or take-up spindle moves axially to achieve fiber wrapping with no or substantially no crossovers, as shown in Figure 8. The fiber windings can be arranged in an alternating left-right winding pattern, for example, as shown in Figure 11.

[0044] 11 provides a cutaway view of layers of fiber on a spool of wound fiber. As shown, a given layer of fiber can have the same number of turns as the layer below or above the given layer, although this is not a requirement.

[0045] In FIG. 11, the number in the circle refers to the nth loop of the winding process. The two vertical lines refer to the walls on the spool. The winding process starts with the 1st loop on the bottom layer, then the 2nd loop, the 3rd loop, and so on. When the fiber reaches the other wall, it moves up to the next layer and continues to wind on the second layer. This process continues until the entire length of the fiber (e.g., 50 meters) is wound on the spool. Throughout the winding process, the fiber can be tightly wound to ensure a consistent bend radius.

[0046] FIG. 12 provides images of a loosely wound fiber spool (right panel) and an image collected with the loosely wound fiber spool (left panel). As shown, areas of contrast in the images are difficult to discern. Without being bound to any particular theory, the loosely wound fiber resulted in higher order modes near the center of the beam, poor contrast, and significant speckle.

[0047] Figure 13 provides an image of a tightly wound fiber spool (right panel) and an image collected with the tightly wound fiber spool (left panel). As shown (and by comparison with Figure 13), the images show improved contrast relative to Figure 12, which was made using a loosely wound fiber spool.

[0048] 14 provides images produced by different fibers wrapped according to the techniques described in this disclosure, showing the consistency and repeatability of the technique. Without being bound to a particular theory or embodiment, tighter wrapping results in better "mode filtering" that removes higher order modes of the illumination transmitted through the fiber. Again, without being bound to a particular theory or embodiment, inconsistent bend radii can in some cases allow higher order modes to propagate, increasing speckle.

[0049] FIG. 15 provides an illustration of a technique for producing wound fiber according to the present disclosure, showing winding of optical fiber on a custom spool, with the optical fiber being fed by a supply spool.

[0050] Aspects The following embodiments are illustrative only and are not intended to limit the scope of the application or the appended claims.

[0051] Aspect 1. A light source for capturing an image, comprising: a laser source including at least one diode; and an optical fiber arranged to transmit light pulses having multiple modes between the laser source and a target location to reduce speckle in a captured image of a target at the target location, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a peripheral wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber. By "tight" it is meant that there is no slack in the optical fiber, e.g., there is substantially no space underneath the optical fiber. An example is shown in Figure 11, where the turn of the optical fiber (e.g., turn N+3 shown in Figure 11) has no slack. The laser source can include one, two, three, or more diodes, e.g., a plurality of diodes. The diodes can be single-mode diodes, but can also be multimode diodes. The one or more laser sources can provide illumination at one or more wavelengths, e.g., 405, 450, 488, 532, 561, and 640 nm. The diodes can also provide illumination in a wavelength range, e.g., 400-410 nm. Aspect 2. The light source of aspect 1, wherein the layer of optical fiber includes at least two taut turns of optical fiber that are substantially parallel to one another. As described elsewhere herein, the optical fiber may be disposed around the spindle, but this is not a requirement as the optical fiber may be disposed in a tray or other feature that accommodates bends or undulations in the optical fiber. Without being bound to a particular theory or embodiment, the optical fiber may be disposed in or even on the housing of the instrument. In this manner, the unit may be configured to accommodate relatively long lengths of optical fiber while maintaining a relatively small footprint. The light source may include a spindle around which the optical fiber is placed to induce a bend in the optical fiber. The spindle may be circular in cross section, but may also be oval or polygonal in cross section. The spindle may have a constant diameter along its height, but may also vary in diameter, for example, be conical or frusto-conical. The spindle may taper upward, but may also be wider at its top and narrower at its bottom. Such a spindle may include, for example, a constant cross-sectional profile. The spindle may have a variable cross-section, for example, by being expandable. In such an embodiment, adjusting the cross-section of the spindle (e.g., by enlarging the cross-sectional dimensions of the spindle, by changing the cross-sectional profile of the spindle, by reducing the cross-sectional dimensions of the spindle) may provide an adjustment of the illumination delivered to the target. Aspect 3. The light source of aspect 1 or 2, wherein the turns of the optical fiber in the outer layer are substantially parallel to the turns of the optical fiber in the inner layer immediately below the outer layer. A light source according to the present disclosure may also include a processing or control train that may be configured to adjust the settings of the illumination provided to the target (e.g., by changing the characteristics of the illumination provided by one or more laser diodes, by modifying the characteristics of the optical fiber) to achieve a particular speckle contrast. Speckle contrast is defined as the standard deviation of spatial intensity divided by the average intensity measured over a region and is expressed as a unitless number. Without being bound to a particular theory, typically lower speckle contrast values ​​are desirable. As an example, if a first set of light source settings produces a desired speckle contrast for a first sample but not for a second sample, a processing or control train can be configured to adjust the illumination settings such that the desired speckle contrast is achieved for the second sample. The illumination settings can be adjusted in an automatic manner, although the illumination settings can also be adjusted in a manual manner. Aspect 4. The light source of any one of aspects 1-3, wherein the turns of the optical fiber in the outer layer do not intersect with the turns of the optical fiber in the inner layer immediately below the outer layer. Such a configuration is shown in FIG. Aspect 5. A fiber optic cable comprising an inner layer of optical fiber including a plurality of taut turns of optical fiber and an outer layer of optical fiber including a plurality of taut turns of optical fiber; (i) the plurality of taut turns of the optical fiber in the outer layer are parallel to one another; (ii) the plurality of taut turns of the optical fiber in the inner layer are parallel to one another; (iii) The light source of any one of aspects 1-4, wherein the plurality of taut turns of the optical fiber in the outer layer are parallel to the plurality of turns of the optical fiber in the inner layer. Such a configuration is shown in FIG. Embodiment 6. The light source of any one of embodiments 1-5, wherein the spindle has a constant cross-sectional dimension. Embodiment 7. The light source of any one of embodiments 1-5, wherein the spindle has a variable cross-sectional dimension. Embodiment 8. The light source of any one of embodiments 1 to 7, wherein the spindle has a cross-sectional dimension of about 1 cm to about 10 cm. Aspect 9. The light source according to any one of aspects 1 to 8, wherein the light pulses from the laser source are synchronized. As an example, if the laser source includes three diodes, the light pulses from the three diodes can be synchronized with each other. However, synchronization is not a requirement. Aspect 10. The light source of any one of aspects 1-9, wherein the light from the laser source is pulsed at about 100 nanoseconds to strobe the target. The light pulse can be from about 5 milliseconds to about 1 nanosecond, e.g., from about 1 millisecond to about 1 nanosecond, or from about 0.5 milliseconds to about 10 nanoseconds, or even from about 100 nanoseconds to about 10 nanoseconds. Aspect 11. The light source of any one of aspects 1-10, further comprising an image capture device configured to capture a capture image of the target, the capture image optionally having an exposure of about 6 microseconds. The image capture train can include a camera (CCD, sCMOS, CMOS), a PMT array, an avalanche photodiode, a photodiode array, or other module. The image capture train can include a processor configured to process the images collected by the image capture train. Embodiment 12. The light source according to any one of embodiments 1 to 11, wherein the optical fiber is a multimode optical fiber. Embodiment 13. The light source according to any one of embodiments 1 to 12, wherein the optical fiber is a high numerical aperture optical fiber. As an example, a fiber having a numerical aperture greater than about 0.22 is considered a high numerical aperture optical fiber. Aspect 14. The light source according to any one of Aspects 1 to 13, wherein the numerical aperture of the optical fiber is about 0.5. The numerical aperture can be, for example, about 0.1 to about 0.5, e.g., about 0.1 to about 0.5, about 0.15 to about 0.45, about 0.2 to about 0.4, about 0.25 to about 0.35, or even about 0.3. Aspect 15. The light source according to any one of Aspects 1 to 14, wherein the length of the optical fiber is from about 2 meters to about 75 meters. The fiber can be, for example, from about 2 to about 75 meters, from about 5 to about 70 meters, from about 10 to about 65 meters, from about 15 to about 60 meters, from about 20 to about 55 meters, from about 25 to about 50 meters, from about 30 to about 45 meters, or even from about 35 to about 40 meters. Aspect 16. The light source of aspect 15, wherein the optical fiber is about 50 meters long. Aspect 17. A light source according to any one of aspects 1 to 16, wherein the laser source includes a plurality of laser diodes, each of the plurality of laser diodes being spatially separated from the other laser diodes of the plurality of laser diodes. Aspect 18. The light source according to any one of aspects 1 to 17, wherein the location of the target is spatially separated from the plurality of laser diodes. Embodiment 19. The light source according to any one of embodiments 1 to 18, wherein the laser source includes a first laser diode that generates the source light at a predetermined wavelength. Embodiment 20. A light source according to any one of embodiments 1 to 19, wherein the laser source comprises at least one multimode laser diode. Aspect 21. A light source according to any one of aspects 1 to 20, wherein the laser source includes a plurality of laser diodes, at least one of the plurality of laser diodes generating light at a different wavelength than another of the plurality of laser diodes. Aspect 22. A method comprising operating a light source according to any one of aspects 1 to 21 to illuminate a target. The target can be located in a flow cell, e.g., in a flow cytometer. The target can be moving (e.g., cells in a flow cytometer), but can also be stationary. For example, the target can be located in a microscope system, e.g., at a position on a microscope stage. Embodiment 23. The method of embodiment 22, further comprising collecting an image of the target. Aspect 24. A method comprising: placing an optical fiber in optical communication with an illumination source, such that the optical fiber is positioned to transmit light from the illumination source to a target disposed at a target location, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a peripheral wall between which the optical fiber is wound, the layer including at least one taut winding of the optical fiber. Example 25. The method of example 24, wherein the layer of optical fiber includes at least two taut turns of optical fiber that are substantially parallel to one another. Example 26. The method of any one of Examples 24-25, wherein the turns of the optical fiber in the outer layer are substantially parallel to the turns of the optical fiber in the inner layer immediately below the outer layer. Example 27. The method of any one of Examples 24-26, wherein the turns of the optical fiber in the outer layer do not intersect with the turns of the optical fiber in the inner layer immediately below the outer layer. Aspect 28. The optical fiber is present as an inner layer of optical fiber including a plurality of taut turns of optical fiber and an outer layer of optical fiber including a plurality of taut turns of optical fiber; (i) the plurality of taut turns of the optical fiber in the outer layer are parallel to one another; (ii) the plurality of taut turns of the optical fiber in the inner layer are parallel to one another; (iii) The method of any one of aspects 24 to 27, wherein the multiple taut turns of the optical fiber in the outer layer are parallel to the multiple turns of the optical fiber in the inner layer. Aspect 29. A method of providing source light for generating an image, comprising: generating illumination using one or more laser diodes; and passing the illumination through an optical fiber present in one or more layers wrapped around a spindle, the spindle optionally including a peripheral wall with the optical fiber wound therebetween, the layer including at least one taut turn of the optical fiber, the passing being performed such that multimode source light is emitted from the optical fiber to illuminate a target with the illumination light, the illumination reducing speckle in an image of the target. Aspect 30. The method of aspect 29, wherein the illumination is generated by at least two laser diodes that generate light at different wavelengths from each other, such that the at least two laser diodes generate illumination having multiple modes. Embodiment 31. A method according to any one of embodiments 29 to 30, wherein generating the source light includes generating synchronous light pulses from at least one laser diode. Aspect 32. A method as described in any one of aspects 29 to 31, wherein generating the illumination includes pulsing at least one of the one or more laser diodes at a period of about 100 nanoseconds to strobe the target. Aspect 33. The method of any one of aspects 29 to 32, further comprising capturing an image of the target with an image capture device, the image capture device optionally having an exposure of about 6 microseconds. Example 34. The method of any one of Examples 29 to 32, wherein the optical fiber is a multimode optical fiber. Embodiment 35. The method of any one of embodiments 29 to 34, wherein the optical fiber is a high numerical aperture optical fiber. Embodiment 36. The method of embodiment 35, wherein the optical fiber has a numerical aperture of about 0.5. Embodiment 37. The method of any one of embodiments 29 to 36, wherein the length of the optical fiber is about 2 meters to about 50 meters. Aspect 38. The method of aspect 37, wherein the length of the optical fiber is about 50 meters. Aspect 39. A method according to any one of aspects 29 to 38, wherein the illumination is generated by a plurality of laser diodes, each of the plurality of laser diodes being spatially separated from the others of the plurality of laser diodes. Embodiment 40. The method according to any one of embodiments 29 to 39, wherein the target is located within a flow cell. Embodiment 41. The method of any one of embodiments 29 to 40, further comprising providing relative motion between the illumination and the target. Embodiment 42. The method of any one of embodiments 29 to 41, wherein the target is stationary during application of illumination. Embodiment 43. A method according to any one of embodiments 29 to 42, wherein the target is moving during application of the illumination. Aspect 44. A cytometer comprising: a flow cell configured to contain one or more particles therein and defining a target area; and an illumination train including at least: (1) a laser source including at least one diode; and (2) an optical fiber in optical communication with the laser source, at least a portion of the optical fiber being in one or more layers wound around a spindle, the spindle optionally including a peripheral wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber. The cytometer can include one or more of hydrodynamic or sheath fluid focusing and acoustic radiation pressure focusing. Hydrodynamic focusing is known to those of skill in the art, and an exemplary discussion of acoustic radiation pressure focusing can be found, for example, in U.S. Patent Application Publication No. 2020 / 0072795 by Kaduchak et al. Aspect 45. The cytometer of aspect 44, further comprising an image capture device configured to capture an image of a target positioned within the target area while illuminated by illumination from at least one diode transmitted through an optical fiber. Aspect 46. An imaging device comprising: a sample zone configured to contain a sample therein; an illumination train including at least (1) a laser source including at least one diode; and (2) an optical fiber in optical communication with the laser source, wherein at least a portion of the optical fiber is in one or more layers wound around a spindle, the spindle optionally including a circumferential wall between which the optical fiber is wound, the layer including at least one taut turn of the optical fiber; and an image capture device configured to capture an image of a sample positioned within the sample zone area while illuminated by illumination from the at least one diode transmitted through the optical fiber, the imaging device further optionally comprising a motion train configured to provide relative motion between the sample in the sample zone and the illumination from the at least one diode transmitted through the optical fiber. Aspect 47. A light source comprising: a laser source including at least one diode; and an optical fiber arranged to transmit light between the laser source and an imaging plane to reduce the coherence of the light and reduce speckle at the imaging plane, the optical fiber being bent at least in part around a support to create mechanical tension in the optical fiber. Aspect 48. The light source according to aspect 47, wherein the support is characterized as a spindle. Aspect 49. The light source according to aspect 47, wherein the support is characterized as a post. Embodiment 50. The light source of any one of embodiments 47-49, wherein the support defines a constant cross-sectional dimension. Embodiment 51. The light source of any one of embodiments 47 to 50, wherein the optical fiber includes at least one turn surrounding the support. Aspect 52. The light source of aspect 51, wherein the optical fiber includes a plurality of turns surrounding the support. Aspect 53. The light source of aspect 52, wherein the optical fiber includes multiple layers surrounding the support, each layer including multiple turns. Aspect 54. The light source according to any one of aspects 47 to 53, wherein the light source is configured to produce less than about 2% speckle at the imaging plane. Aspect 55. The light source of aspect 54, wherein the light source is configured to produce less than about 1% speckle at the imaging plane. Aspect 56. The light source of aspect 54, wherein the light source is configured to produce approximately 1% speckle at the imaging plane. Embodiment 57. The light source according to any one of embodiments 47 to 56, wherein the optical fiber has a long-term bend radius, and the optical fiber is bent at a radius smaller than the long-term bend radius. Embodiment 58. A light source according to any one of embodiments 47 to 57, wherein the transmittance of light through the optical fiber is about 60% to about 90%. Aspect 59. The light source according to aspect 58, having a transmittance of about 75% to about 90%. Embodiment 60. The light source according to any one of embodiments 47 to 59, wherein the imaging surface is disposed within a flow cell. Aspect 61. The light source according to aspect 60, wherein the flow cell is included in a flow cytometer. Embodiment 62. The light source according to any one of embodiments 47 to 61, wherein the mechanical tension maintains the optical fiber in tension. Embodiment 63. A light source according to any one of embodiments 47 to 62, wherein the laser source provides light as light pulses, and the light pulses are optionally synchronized. Aspect 64. The light source of aspect 63, wherein the light from the laser source is pulsed at about 100 nanoseconds to strobe the target. Aspect 65. The light source of any one of aspects 47 to 64, further comprising an image capture device configured to capture a capture image of the target, the capture image optionally having an exposure of about 6 microseconds. Embodiment 66. The light source according to any one of embodiments 47 to 65, wherein the optical fiber is a multimode optical fiber. Embodiment 67. The light source according to any one of embodiments 47 to 66, wherein the optical fiber is a high numerical aperture optical fiber. Embodiment 68. The light source according to any one of embodiments 47 to 67, wherein the numerical aperture of the optical fiber is about 0.5. Embodiment 69. A light source according to any one of embodiments 47 to 68, wherein the length of the optical fiber is from about 2 meters to about 75 meters. Aspect 70. The light source according to aspect 69, wherein the length of the optical fiber is about 50 meters. Embodiment 71. A light source according to any one of embodiments 47 to 70, wherein the laser source includes a plurality of laser diodes, each of the plurality of laser diodes being spatially separated from the other laser diodes of the plurality of laser diodes. Embodiment 72. A light source according to any one of embodiments 47 to 71, wherein the laser source includes a first laser diode that generates source light at a predetermined wavelength. Embodiment 73. A light source according to any one of embodiments 47 to 72, wherein the laser source includes at least one multimode laser diode. Aspect 74. A light source according to any one of aspects 47 to 73, wherein the laser source includes a plurality of laser diodes, at least one of the plurality of laser diodes generating light at a different wavelength than another of the plurality of laser diodes. Embodiment 75. A method comprising operating a light source according to any one of embodiments 47 to 74. Aspect 76. The method of aspect 75, comprising illuminating one or more particles or cells in an imaging plane. Aspect 77. The method of aspect 76, further comprising collecting an image of a target illuminated by a light source and positioned on an imaging plane.

Claims

1. A light source comprising: a laser source including at least one diode; an optical fiber arranged to transmit light pulses having multiple modes between the laser source and the target location to reduce speckle in a captured image of a target at the target location, at least a portion of the optical fiber is in one or more layers wound around a spindle; the spindle optionally includes a peripheral wall between which the optical fiber is wound; an optical fiber, the layer including at least two taut turns of the optical fiber.

2. 10. The light source of claim 1, wherein the turns of the optical fiber in an outer layer are substantially parallel to the turns of the optical fiber in an inner layer immediately below the outer layer.

3. 10. The light source of claim 1, wherein the turns of the optical fiber in an outer layer do not intersect with the turns of the optical fiber in an inner layer immediately below the outer layer.

4. an inner layer of optical fiber including a plurality of taut turns of the optical fiber; and an outer layer of optical fiber including a plurality of taut turns of the optical fiber; (i) the plurality of taut turns of the optical fiber in the outer layer are parallel to one another; (ii) the plurality of taut turns of the optical fiber in the inner layer are parallel to one another; 10. The light source of claim 1, wherein (iii) the plurality of taut turns of the optical fiber in the outer layer are parallel to a plurality of turns of the optical fiber in the inner layer.

5. The light source of claim 1 , wherein the spindle has a constant cross-sectional dimension.

6. The light source of claim 1 , wherein the spindle has a variable cross-sectional dimension.

7. The light source of claim 1 , wherein the spindle has a cross-sectional dimension of about 1 cm to about 10 cm.

8. The light source of claim 1 , wherein the light pulses from the laser sources are synchronized.

9. The light source of claim 1 , wherein light from the laser source is pulsed for about 100 nanoseconds to strobe the target.

10. The light source of claim 1 , further comprising an image capture device configured to capture the captured image of the target, the captured image optionally having an exposure of about 6 microseconds.

11. The light source of claim 1 , wherein the optical fiber is a multimode optical fiber.

12. The light source of claim 1 , wherein the optical fiber is a high numerical aperture optical fiber.

13. 10. The light source of claim 1, wherein the optical fiber has a numerical aperture of about 0.

5.

14. The light source of claim 1 , wherein the optical fiber has a length of about 2 meters to about 75 meters.

15. 15. The light source of claim 14, wherein the optical fiber has a length of about 50 meters.

16. The light source of claim 1 , wherein the laser source comprises a plurality of laser diodes, each of the plurality of laser diodes being spatially separated from other laser diodes of the plurality of laser diodes.

17. The light source of claim 1 , wherein the target location of the target is spatially separated from the plurality of laser diodes.

18. The light source of claim 1 , wherein the laser source comprises a first laser diode that generates the light source light at a predetermined wavelength.

19. The light source of claim 1 , wherein the laser source comprises at least one multimode laser diode.

20. 10. The light source of claim 1, wherein the laser source comprises a plurality of laser diodes, at least one of the plurality of laser diodes producing light at a different wavelength than another of the plurality of laser diodes.

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