Optical speckle eliminator, optical system and device comprising same, and method for eliminating speckles of optical signals

Abstract

An optical fiber subassembly for reducing optical speckle generated in an optical system includes an optical fiber, a vibratory element, such as a piezoelectric element, and a controller. The optical fiber has a first end adapted to receive light from a light source associated with the optical system and a second end for transmitting light from the light source to a surface on which a speckle pattern may be generated. The optical fiber extends through the vibratory element such that the vibratory element at least partially surrounds a portion of the optical fiber intermediate the first end and the second end. The controller is operably coupled to the vibrating element for vibrating the vibrating element at a frequency faster than a threshold frequency sufficient to reduce speckle generated on the surface.

Description

[0001] Related applications

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 440,109, filed on January 20, 2023, which is incorporated herein by reference in its entirety. Background Art

[0003] The present disclosure relates to the reduction of optical speckle, and more particularly to optical systems and optical devices in which optical signals propagating along optical fibers are affected by optical speckle.

[0004] Speckle can be caused by the self-interference of light on a surface, such as a screen or target, causing intensity variations that can be observed by an observer or instrument. This self-interference can be an undesirable side effect of using narrow-bandwidth sources, such as lasers. Speckle can also appear when light is transmitted through a material, as the material's surface structure can randomly alter the light's phase and polarization. The resulting speckle pattern can produce noticeable, undesirable intensity variations on the surface, often manifesting as shimmering or grainy structures.

[0005] For example, but not limited to, laser-based projection displays often exhibit speckle, which can reduce image clarity and distract viewers. Several methods for reducing speckle contrast have been proposed based on the spatiotemporal decorrelation of speckle patterns. For example, U.S. Patent Application No. 2018 / 0252863 describes a system having a light source configured to output illumination light and a display system that receives the illumination light. The display system may be a projector for displaying a film or image. An optical fiber is configured to direct the illumination light from the light source to the display system, and a vibration device is attached to the optical fiber. The vibration device communicates with a controller that senses speckle and, in response, activates the vibration device. The vibration device is operable to vibrate at a frequency greater than a threshold frequency to reduce speckle. The refractive index profile of the optical fiber can be designed to eliminate speckle in the output illumination light without losing too much light.

[0006] Similarly, Japanese Patent Publication No. 63-082336 (Fiber Actuator) describes a system that places pressing members on both sides of an optical fiber to apply pressure to the optical fiber using a piezoelectric element driven by a voltage from a control unit. The control unit supplies a periodic wave to the piezoelectric element, which cancels polarization effects in single-mode optical fibers and speckle effects in multimode optical fibers, thereby achieving stable and accurate photometry. Summary of the Invention

[0007] In one aspect, a fiber optic subassembly for reducing optical speckle generated in an optical system is disclosed. The fiber optic subassembly includes an optical fiber, a vibrating element, and a controller. The optical fiber has a first end and a second end, the first end being adapted to receive light from a light source associated with the optical system, and the second end being adapted to transmit the light from the light source to a surface on which a speckle pattern can be generated. The optical fiber extends through the vibrating element such that the vibrating element at least partially surrounds a portion of the optical fiber intermediate the first and second ends. The controller is operably coupled to the vibrating element to vibrate the vibrating element at a frequency faster than a threshold frequency sufficient to reduce speckle generated on the surface.

[0008] In one embodiment, the vibration element is a piezoelectric element.

[0009] In another embodiment, the vibrating element circumferentially surrounds the optical fiber.

[0010] In another embodiment, the vibrating element is cylindrical in shape, and the optical fiber traverses a central axis of the vibrating element.

[0011] In another embodiment, the optical fiber subassembly further includes at least one material disposed between the vibrating element and the portion of the optical fiber at least partially surrounded by the vibrating element.

[0012] In another embodiment, the material comprises an adhesive for securing the vibrating element to the optical fiber.

[0013] In another embodiment, the fiber optic subassembly further comprises a fiber optic connector, the first end portion of the optical fiber is located in the fiber optic connector, and the vibration element is located within the fiber optic connector.

[0014] In another embodiment, the fiber optic connector is of a type selected from the group consisting of LC, SC, FC, ST, SMA, and MTP / MPO connectors.

[0015] In another embodiment, the fiber optic subassembly further includes a wire electrically coupleable to the vibrating element and the controller for supplying electrical energy to the vibrating element.

[0016] In another embodiment, the wire extends through an end of the fiber optic connector.

[0017] In another embodiment, the wire is releasably connected to the vibrating element through a side wall of the fiber optic connector.

[0018] In another aspect, a speckle reducer is integrated into a fiber optic connector. The fiber optic connector includes a fiber optic connector housing, an optical fiber having a ferrule therein, and a vibrating element. The optical fiber has a first end extending into the fiber optic connector housing and through the ferrule. The vibrating element is disposed within the housing and attached to the first end of the optical fiber, and is operable to vibrate at a frequency that reduces optical speckle.

[0019] This summary is provided to introduce a series of concepts in a simplified form, which will be further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram showing an example of a light source that provides light via an optical fiber to an optical system that may generate speckle.

[0021] Figure 2 Shown Figure 1 An example of an optical fiber and a vibrating element is shown, where the vibrating element circumferentially surrounds a portion of the optical fiber.

[0022] Figure 3 is a cross-sectional view of an example of a fiber optic connector.

[0023] Figure 4 yes Figure 3 An isometric view of the assembled fiber optic connector is shown.

[0024] Figure 5 is a simplified schematic diagram of one non-limiting example of an optical arrangement in which the optical speckle reducer described herein may be employed. DETAILED DESCRIPTION

[0025] The present disclosure recognizes the speckle problem in existing optical systems and discloses an optical speckle reducer that is easy to set up, small in size, and highly power efficient.

[0026] Figure 1is a schematic diagram illustrating one example of a light source 110 providing light via an optical fiber 120 to an optical system 112 (such as a projector, a display device, or more generally, any other arrangement that may generate speckle). Optical system 112 may be a system used in any of a variety of applications, including, for example, any of laser-based displays (head-up displays, cinema displays, microdisplays, etc.), laser beam homogenizers, laser-based metrology, microscopy, spectroscopy, interferometry, lithography, and various types of laser-based communication systems, probes, sensors, monitors, illuminators, and the like. While light source 110 may typically be a laser light source, in general, the light source may be any narrowband light source capable of generating speckle.

[0027] The optical fiber 120 can be a coated, uncoated, jacketed or unjacketed single-mode or multimode optical fiber, a glass optical fiber, a plastic optical fiber, a step-index optical fiber, a graded-index optical fiber, or any other type of optical fiber. The diameter of such an optical fiber can range from, for example, a few microns to about 1 mm or more.

[0028] The vibration element 140 circumferentially surrounds a portion of the optical fiber 120. In some embodiments, the vibration element 140 may only partially surround a portion of the optical fiber 120. The vibration element 140 may be any suitable element capable of applying vibration energy to the optical fiber 120 at a frequency and amplitude that can reduce or eliminate speckle generated by the optical system 112. In some embodiments, a plurality of vibration elements 140 may be disposed along the optical fiber 120. In one embodiment, the vibration element is a piezoelectric element. Examples of suitable piezoelectric materials include, but are not limited to, crystals, ceramics and lead-free piezoelectric ceramics, III-V and II-VI semiconductors, and polymers. In other embodiments, suitable vibration elements may be, but are not limited to, devices such as speakers, actuators, vibrators, motors, transducers, vibration motors, shakers, buzzers, and the like. Figure 1 Also shown is a controller 125 which supplies power to the vibration element 140 via a wired connection.

[0029] Figure 2A specific example of an optical fiber 120 and a vibrating element 140 is shown, which vibrating element 140 circumferentially surrounds a portion of the optical fiber 120. In this example, the vibrating element 140 is provided in the form of a cylindrical piezoelectric element that is positioned along a portion of the optical fiber 120, wherein the optical fiber extends through the central axis of the cylindrical piezoelectric element. The piezoelectric element is designed to contract circumferentially when subjected to an electric potential. A layer 150 of filler, adhesive, epoxy, or other suitable material may be provided between the optical fiber 120 and the piezoelectric element 140 to help transfer mechanical energy from the piezoelectric element to the optical fiber in a uniform manner. The filler 150 also provides electrical isolation between the piezoelectric element 140 and the optical fiber 120. The piezoelectric element 140 may be positioned anywhere along the length of the optical fiber, including at the end of the optical fiber.

[0030] Although Figure 2 Vibrating element 140 is shown as cylindrical, but more generally, the piezoelectric element can have any desired shape and configuration, including configurations where the piezoelectric element circumferentially surrounds the optical fiber in a circumferentially asymmetric manner as well as in a symmetrical manner. Vibrating element 140 can remain exposed or can be covered by a protective cover placed only over vibrating element 140 or along the entire optical fiber 120.

[0031] As described above, the vibrating element can be positioned anywhere along the length of the optical fiber. In some embodiments of the subject matter described herein, the vibrating element can be positioned around a portion of the optical fiber that is located within a fiber optic connector. Fiber optic connectors are components used to terminate the ends of optical fiber cables and are generally capable of connecting and disconnecting faster than fiber fusion splices. Fiber optic connectors can be used in a variety of different applications, including, for example, splicing fiber segments into longer lengths, connecting optical fibers to active devices such as transceivers, detectors, and repeaters, or connecting optical fibers to passive devices such as switches or attenuators. The core function of a fiber optic connector is to hold or position the ends of two optical fibers so that the core of one fiber is axially aligned with the core of the other fiber. Another function of a fiber optic connector is to align light emitted from a light source with the optical fibers. Thus, light from one optical fiber can be coupled to another optical fiber or transmitted between optical fibers as efficiently as possible. Yet another function of a fiber optic connector is to provide mechanical stability and protection for the optical joint in its operating environment. Typically, stability and joint protection are key features of connector design (e.g., minimizing the effects of differential thermal expansion and mechanical movement).

[0032] Fiber optic connectors can be categorized into different types based on a variety of different classification methods. For example, these connectors can be classified based on the connector's pin end face (PC, UPC, and APC) or based on the type of transmission medium (single-mode and multimode fiber optic connectors). Common standard types of fiber optic connectors include LC, SC, FC, ST, SMA, and MTP / MPO connectors.

[0033] Generally speaking, most fiber optic connectors include several common components, including, for example, a ferrule, a connector body, and a connector coupling mechanism. The ferrule is a thin, usually cylindrical structure used to hold the optical fiber in place. The ferrule is typically made of ceramic, metal, or plastic. The optical fiber is precisely aligned and secured within the ferrule to ensure optimal light transmission. The connector body is the outer housing that surrounds the ferrule and provides mechanical support and protection. The connector coupling mechanism is the mechanism that makes the connector easy to attach and detach. Common coupling mechanisms include threaded connectors, push-pull connectors, and bayonet connectors.

[0034] In accordance with the subject matter described herein, a vibrating element (such as a piezoelectric element) can surround a portion of an optical fiber located within any type of fiber optic connector, including connectors that conform to one or more established standards (such as those described above), or connectors that are proprietary in nature. In this way, the fiber optic connector effectively functions as an optical speckle eliminator. In non-limiting specific examples, a vibrating element according to the present disclosure can be integrated into the following assemblies: 1) a high-power assembly that uses high-power SMA and high-power industrial FD-80 connectors to provide a fiber optic link between a laser source and a target; 2) a high-temperature assembly that is used for optical sensing in a sealed, high-temperature environment; 3) a single-fiber assembly that is used for a wide range of applications including spectroscopy, industrial sensing, and low-power laser delivery; and 4) a bundled assembly that is used to perform various photonic systems for optical sensing and laser power delivery for industrial, medical, military, and research applications.

[0035] Figure 3 is a cross-sectional view of an example of an optical fiber connector 200, and Figure 4 2 is an isometric view of the same assembled fiber optic connector 200. The connector 200 includes a connector body 210, a connector coupling mechanism 220, and a ferrule 230. Figure 3Also shown is an optical fiber 240 extending into the connector body 210. A piezoelectric element 250 (or other vibrating element) is located within the connector body 210 and circumferentially surrounds the optical fiber 240. The piezoelectric element 250 can be positioned in any suitable location within the connector body 210 that allows it to circumferentially surround the optical fiber 240. Generally, the piezoelectric element 250 will be longitudinally aligned with the optical fiber 240 and the connector body 210 and positioned so that the optical fiber 240 can pass completely through the piezoelectric element. As previously described, a layer of filler, adhesive, epoxy, and / or other suitable material can be positioned between the optical fiber 240 and the piezoelectric element 250 to secure the piezoelectric element 250 in place and help transfer mechanical energy from the piezoelectric element 250 to the optical fiber in a uniform manner. The dimensions of the piezoelectric element 250 can be selected so that it can impart sufficient vibrational energy to the optical fiber 240 while being small enough to fit within the connector body 210. For example, in some embodiments, the piezoelectric element 250 can have an overall length of 4 mm to 50 mm, an inner diameter of 0.2 mm to 40 mm, and an outer diameter of 0.5 mm to 50 mm.

[0036] In a non-limiting embodiment, a controller (e.g., Figure 1 The controller 125 shown in the figure or other suitable device is used to apply a voltage to the piezoelectric element. The voltage is used to control the aforementioned contraction of the piezoelectric element and the application of pressure on the optical fiber. The pressure on the optical fiber can be applied periodically or in a random, pseudo-random or other complex manner to change the polarization state of the optical signal propagating along the optical fiber. For example, a 50 / 60 Hz cycle form of a commercial power supply in the form of a sine wave can be used. For a composite / complex cycle form, an electrical signal can be generated by superimposing different waveforms and frequencies using a signal generator or the like. In other embodiments, the voltage applied to the piezoelectric element can be in the range of 300 Hz to 70 kHz.

[0037] The voltage can be supplied to the piezoelectric element 250 within the connector body 210 in any of a variety of ways. For example, a wire can extend from the interior of the connector body 210 and protrude from a distal end of the connector body 210 away from the connector coupling mechanism 220. In other embodiments, the wire can protrude from a proximal end of the connector coupling mechanism 220. In still other embodiments, the wire can protrude from the side of the connector body 210 using, for example, a detachable plug, thereby providing a releasable connection.

[0038] In some embodiments, a controller or equivalent device is operable to sense speckle in the optical fiber and, in response, apply an appropriate control signal to the piezoelectric element to reduce the speckle. Figure 1In the exemplary system shown, controller 125 can be used to sense speckle generated in optical system 112. Vibrating element 140 can be in communication with controller 125, which senses the speckle generated in optical system 112 and, in response, activates vibrating element 140. In another embodiment, vibrating element 140 can be in a normally on state.

[0039] Figure 5 FIG2 is a simplified schematic diagram of a non-limiting example of an optical arrangement that can employ the optical speckle eliminator described herein. The optical system in this example is a fluorescence microscope for performing fluorescence microscopy. As shown, the arrangement includes a laser source 310, in which the optical speckle eliminator described herein is employed. The optical speckle eliminator can employ a fiber assembly 350 having a vibrating element that circumferentially surrounds all or a portion of an optical fiber 320, from which light is emitted by the laser source 310. The vibrating element can be positioned along any suitable portion of the optical fiber 320, including within a fiber connector connected to the laser source 310. Light from the optical fiber 320 is directed to a beam splitter 325, which directs the light to a fluorescence microscope 330 for excitation of fluorescent molecules. The resulting fluorescence is directed back to the beam splitter 325 and, after any necessary filtering by a filter 345, to a detector 340. The detector 340 can be associated with a display or a camera. By using the optical speckle eliminator described herein, optical speckle in the resulting image is reduced.

[0040] It should be noted that the applications of the optical speckle remover disclosed herein are not limited to the above applications. It is obvious to those skilled in the art that various modifications and variations can be made to the embodiments disclosed herein without departing from the spirit or scope of the present disclosure.

Claims

1. A fiber optic subassembly for reducing optical speckle generated in an optical system, comprising: an optical fiber having a first end portion adapted to receive light from a light source associated with the optical system and a second end portion for transmitting light from the light source to a surface capable of generating a speckle pattern thereon; a vibrating element through which the optical fiber extends such that the vibrating element at least partially surrounds a portion of the optical fiber intermediate the first end and the second end; and A controller is operably coupled to the vibrating element for vibrating the vibrating element at a frequency faster than a threshold frequency sufficient to reduce speckle generated on the surface.

2. The optical fiber subassembly of claim 1, wherein the vibrating element is a piezoelectric element.

3. The fiber optic subassembly of claim 1, wherein the vibrating element circumferentially surrounds the optical fiber.

4. The fiber optic subassembly of claim 1, wherein the vibrating element is cylindrical and the optical fiber traverses a central axis of the vibrating element.

5. The fiber optic subassembly of claim 1, further comprising at least one material disposed between the vibrating element and the portion of the optical fiber at least partially surrounded by the vibrating element.

6. The fiber optic subassembly of claim 5, wherein the at least one material comprises an adhesive for securing the vibrating element to the optical fiber.

7. The fiber optic subassembly of claim 1, further comprising a fiber optic connector, wherein the first end of the optical fiber is located in the fiber optic connector, and the vibrating element is located within the fiber optic connector.

8. The fiber optic subassembly of claim 1, wherein the fiber optic connector is of a type selected from the group consisting of LC, SC, FC, ST, SMA, and MTP / MPO connectors.

9. The fiber optic subassembly of claim 1, further comprising a wire electrically coupleable to the vibrating element and the controller for supplying electrical energy to the vibrating element.

10. The fiber optic subassembly of claim 9, wherein the wire extends through an end of the fiber optic connector.

11. The fiber optic subassembly of claim 9, wherein the wire is releasably connected to the vibrating element through a side wall of the fiber optic connector.

12. An optical fiber connector integrated with a speckle canceller, comprising: a fiber optic connector housing having a ferrule therein; an optical fiber having a first end extending into the fiber optic connector housing and through the ferrule; and A vibrating element is disposed within the housing and attached to the first end of the optical fiber, the vibrating element being operable to vibrate at a frequency that reduces optical speckle.

13. The optical fiber connector of claim 12, wherein the vibrating element at least partially surrounds the first end portion of the optical fiber.

14. The optical fiber connector of claim 13, wherein the vibrating element comprises a piezoelectric element.

15. The fiber optic connector of claim 12, wherein the vibrating element is located within the fiber optic connector housing but outside the ferrule.

16. The fiber optic connector of claim 12, wherein the vibrating element is located within the ferrule.

17. The optical fiber connector according to claim 12, wherein the vibration element is cylindrical, and the optical fiber crosses the central axis of the vibration element.

18. The fiber optic connector of claim 17, further comprising at least one material disposed between the vibrating element and the portion of the optical fiber at least partially surrounded by the vibrating element.

19. The fiber optic connector of claim 18, wherein the at least one material comprises an adhesive for securing the vibrating element to the optical fiber.

20. The fiber optic connector of claim 12, wherein the type of the fiber optic connector is selected from the group consisting of LC, SC, FC, ST, SMA, and MTP / MPO connectors, wherein the vibrating element circumferentially surrounds the first end portion of the optical fiber.

21. The fiber optic connector of claim 12, wherein the vibrating element circumferentially surrounds the first end portion of the optical fiber.

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