Optical element alignment and retention for optical instruments

An optical element holder includes receptacles for retaining optical elements, and is configured to move a selected optical element into an optical path whereby a light beam passes through the selected optical element. The optical element holder is configured to retain the optical elements in a manner that mitigates or avoids misalignment of the optical elements, thereby mitigating or avoiding unwanted deviations in the path of the light beam. The optical element holder may be part of a microscope or other optical instrument.

TECHNICAL FIELD

This present invention generally relates to devices and methods for aligning and retaining optical elements, such as filters, lenses, or the like, in an optical element holder such as an optical element wheel or slide, and to systems utilizing such devices and methods.

BACKGROUND

Optics-based instruments may utilize various types of optical elements for modifying light incident on the optical elements. Depending on the type, an optical element may modify light by, for example, filtering, collimating, focusing, inverting, beam steering, beam splitting, attenuating, etc. As one specific example, optical filters are utilized when it is desired to transmit light at a specific wavelength while preventing transmission of light at other wavelengths. An array of optical filters having different wavelength transmission characteristics may be provided to enable a user of the instrument to select a wavelength for transmission among different wavelengths made available by the array of optical filters. The array of optical filters may be mounted in a filter holding device such as a filter wheel that allows a selected optical filter to be rotated into an operating position at which the selected optical filter becomes part of an optical path and thus is effective for filtering light propagating along that optical path. Another type of filter holding device is a filter slide that allows a selected optical filter to be linearly translated into the operating position. Other types of optical elements, such as lenses, windows, mirrors, etc., may likewise be supported as an array in an optical element holding device.

Examples of instruments that often provide optical element holding devices such as filter wheels include various types of microscopes, one example being a confocal microscope that acquires images of a sample under analysis at different wavelengths (colors). Another example are devices (e.g., optical readers, plate readers, multi-mode readers, etc.) that measure a particular type of optical property or activity of a sample such as reflection/scattering, luminescence, fluorescence, absorbance, etc. A further example are devices that produce spectral data from a sample, such as spectroscopy devices, spectrophotometers, etc. Some of these optical instruments provide both an “excitation” light path from a light source to the sample under analysis and an “emission” light path from the sample to a light detector. That is, the excitation light path is utilized to irradiate the sample, and the emission light path is utilized to transmit the light reflected or emitted from the irradiated sample to the light detector for measurement or imaging. Such instruments may include both an optical element holding device (e.g., an “excitation” filter wheel) positioned in the excitation light path and another optical element holding device (e.g., an “emission” filter wheel) positioned in the emission light path.

An optical element holding device typically provides a number of individual mounting locations, referred to herein as optical element receptacles, at which respective optical elements are retained. Individual optical elements may be loaded into respective receptacles and thereafter removed as needed. In an ideal case, the optical element holding device retains each optical element in a fixed, repeatable position in the corresponding receptacle. In this way, when any of the optical elements currently mounted to the optical element holding device is moved into the optical path, that optical element is in the same position relative to the optical path as any other optical element previously or subsequently moved into the optical path. Also, when any of the optical elements currently mounted to the optical element holding device is replaced with a new optical element in the same receptacle, the new optical element will be in the same position in the receptacle as the optical element previously occupying that particular receptacle. Moreover, for many types of optical elements (e.g. filters and certain types of lenses), in the ideal case the optical element holding device retains each optical element in a perfect orientation (or perfectly aligned position) in the corresponding receptacle. When an optical element is retained in the perfectly aligned position and is moved by the optical element holding device into an optical path, the optical filter will be perfectly aligned with the optical path and thus with the light beam propagating along the optical path. Consequently, the light beam follows a straight path (e.g., is not turned or shifted) through the optical element holding device including while the light beam passes through the thickness of the optical element.

However, in practice some optical element holding devices provide slots through which the optical elements are loaded and thereafter removed. For example, a wheel-type holding device may provide radial slots such that the optical elements are loaded and removed along radial directions. Such holding devices provide a small but perceptible clearance in each optical element receptacle to facilitate loading and removal of the optical elements. That is, each receptacle is sized such that there is some open space between the optical element residing in the receptacle and the surrounding structure of the holding device. This clearance may allow the optical element to be inadvertently loaded into the receptacle with an angular tilt, which results in the light beam being shifted or tilted. Additionally, after loading an optical element into the receptacle (even if properly done such that the optical element is initially well aligned), the optical element may become misaligned over time. For example, operational vibration may cause the optical elements to shift or tilt over time. Misalignment may be problematic for various types of optical elements. For example, when several optical filters (i.e., different color filters) are utilized during a single image acquisition, these angular tilts in the optical filters may induce a phenomenon referred to as “pixel shift.” Pixel shift refers to the misalignment between the individual color images that occurs as a result of the optical element tilt. When these misalignments are large they are easily seen in the resultant image. Existing means for affixing optical filters and other types of optical elements require rigid mechanical fastening methods such as threaded collars or retaining features that offer each of replacement. One example is disclosed in U.S. Pat. No. 6,313,960.

Therefore, there is a need for improving retention and alignment of optical elements in filter wheels and other types of optical element holding devices. There is also a need for mitigating or eliminating problems caused by the clearance associated with the optical element receptacles of optical element holding devices, such as misalignment and attendant disadvantages.

SUMMARY

To address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides methods, processes, systems, apparatus, instruments, and/or devices, as described by way of example in implementations set forth below.

According to one embodiment, an optical element holder for an optical instrument includes: a body comprising an optical input side, an optical output side, a thickness along a longitudinal axis between the optical input side and the optical output side, and a plurality of receptacles configured to retain respective optical elements and generally arranged in a transverse plane orthogonal to the longitudinal axis, wherein each receptacle is open to the optical input side and to the optical output side to define an optical path through the body parallel to the longitudinal axis; and a plurality of pusher components extending from the body, each pusher component comprising a spring member and at least one contact surface positioned to be biased by the spring member toward at least one of the receptacles and into contact with an optical element retained in the receptacle, wherein each pusher component is configured to apply a biasing force against at least one optical element retained in a respective one of the receptacles to retain the at least one optical element in an aligned position at which the at least one optical element is parallel to the transverse plane.

According to another embodiment, an optical instrument includes: a light detector; optics configured for establishing an optical path to the light detector; and an optical element holder according to any of the embodiments disclosed herein, wherein the optical element holder is configured for selectively moving each of the receptacles into the optical path.

DETAILED DESCRIPTION

FIG. 1is a schematic view of an example of an optical instrument (or optical system)100according to some embodiments.FIG. 1may be considered as being generally representative of any optical instrument that provides one or more light paths and multiple optical elements, and enables selection of one or more the optical elements for positioning in a selected light path in a given application of the optical instrument. Specifically,FIG. 1illustrates an example of a microscope (or microscope system) according to some embodiments. The microscope may be a confocal microscope, a wide-field microscope, or other type of microscope. Non-limiting examples of other types of optical instruments are noted above, such as devices that measure/detect various types of light, devices that acquire spectral data, etc. Generally, the structure and operation of various types of microscopes and other optical instruments are understood by persons skilled in the art, and thus certain components and features of the optical instrument100are described only briefly to facilitate an understanding of the subject matter taught herein.

The optical instrument100may generally include a light source104configured for generating excitation (illumination) light106for exciting (or illuminating) a sample108under analysis, a sample holder or stage110for supporting the sample108, a light detector (or image sensor)112for collecting emission light114emitted from the sample108and thereby capturing an image of the sample108, various optics for defining (i.e., establishing or providing) an excitation (or illumination) light path from the light source104to the sample108, and various optics for defining an emission (or detection) light path from the sample108to the light detector112. In confocal embodiments, the optics include one or more confocal devices such as, for example, a pinhole or spinning disk (not shown) positionable in an intermediate image plane and simultaneously in the excitation light path and the emission light path (or separate confocal devices may be separately positioned in the excitation light path and the emission light path). In some embodiments, the optical instrument100may be configured for detecting light reflected (scattered) from the sample108at the same wavelength as the light utilized to illuminate the sample108. In other embodiments, the optical instrument100may be configured for exciting the sample108at a specific excitation wavelength and detecting fluorescent light emitted from the sample108at a longer wavelength in response to the excitation. In these latter embodiments, a fluorescent agent or fluorophore (e.g., fluoroscein) may be added to the sample108as appreciated by persons skilled in the art. For convenience, unless specified otherwise or the context dictates otherwise, the term “excitation” encompasses “illumination” of a sample108for the purpose of collecting light reflected or scattered from the sample108, as well as excitation of a sample108for the purpose of collecting fluorescent emission light emitted by the sample108. Also for convenience, unless specified otherwise or the context dictates otherwise, the term “emission light” encompasses either reflected (or scattered) light or fluorescent emission light.

The sample stage110positions the sample108at a sample plane. The sample stage110may generally be any platform for supporting the sample108, or the sample108and a substrate supporting the sample108(e.g., a glass slide or container), in a fixed position thereon. In some embodiments, the sample stage110may be movable by manual or motorized actuation. That is, the position of the sample stage110may be adjustable by the user along the x-axis, y-axis, and/or z-axis. In the present context, the z-axis is taken to be the optical axis that is orthogonal to the sample plane, and the x-axis and y-axis are taken to lie in the sample plane. The sample108may generally be any object for which imaging is desired and which is mountable to the sample stage110. For example, the sample108may be biological (e.g., spores, fungi, molds, bacteria, viruses, biological cells or intracellular components, biologically derived particles such as skin cells, detritus, etc.) or non-biological (e.g., chemical compound, particulate matter, etc.).

The light source104may be any light source suitable for the type of microscopy (or other optics-based analysis) being implemented in a given embodiment. For example, the light source104may be a solid-state light source such as a light emitting diode (LED) or a solid-state laser, or alternatively may be a semiconductor-based laser (laser diode or LD). In some embodiments, the optical output of the light source104may be the tip of an optical fiber that is imaged onto (conjugate to) an intermediate image plane provided by optics and the sample plane where the sample108is positioned. In some embodiments, the light source104may include a plurality of light sources (e.g., multiple LEDs) that generate light at different wavelengths. Such wavelength-specific light sources may be mounted to a wavelength selector, such as a motorized wheel (not shown) that enables automatic (computerized) selection of the wavelength-specific light source and thus the wavelength of the excitation light106to be utilized in a given application.

The light detector112may be any imaging device suitable for the type of microscopy (or other optics-based analysis) being implemented in a given embodiment. For example, the light detector112may be the type of imaging device that forms the basis of cameras. In typical embodiments, the light detector112is a multi-pixel (or pixelated) imaging device such as, for example, a charge-coupled device (CCD) or an active-pixel sensor (APS) based on complementary metal-oxide-semiconductor (CMOS) technology. In some embodiments, the optical instrument100may include an eyepiece (not separately shown) to enable the user to view the sample, in which case appropriate optical components (e.g., beam splitter) are provided to split the emission light path so that the emission light114is directed to both the light detector112and the eyepiece. Thus, the light detector112inFIG. 1may be considered as schematically representing an imaging device, or both an imaging device and an eyepiece. Alternatively, the light detector112may be a broadband light source that operates in conjunction with an excitation filter (not shown) that only allows the desired excitation wavelength of light to pass. In some embodiments, a plurality of different wavelength-specific excitation filters may be mounted to a wavelength selector (e.g., a motorized wheel) to enable selection of the excitation wavelength to be passed while blocking other wavelengths.

The intermediate optics (optical components) involved in defining the excitation light path and/or emission light path may vary widely from one embodiment to another. Depending on the particular optical component, defining a light path may include modifying the light beam in some fashion, such as focusing, inverting, splitting, or resizing the light beam, etc. As illustrated inFIG. 1, the optics may include a dichroic beam splitter or mirror116(also known as a dichroic filter). The beam splitter116is configured to transmit light at the wavelengths contemplated for the excitation light106, and to reflect light at an angle (e.g., ninety degrees) at the wavelengths contemplated for the emission light114. Alternatively, the beam splitter116may be and positioned to transmit the emission light114and to reflect the excitation light106. In some embodiments, the beam splitter116may include a plurality of beam splitters having different optical reflection/transmission characteristics. Such beam splitters may be mounted to a wavelength selector, such as a motorized wheel (not shown) that enables automatic (computerized) selection of the beam splitter with the desired reflection/transmission spectrum. The optics may also include a microscope lensing system118that includes components such as an objective lens. Generally, the lensing system118is configured for transmitting and focusing the excitation light106onto the sample108, and collecting the emission light114emitted from the sample108and focusing the emission light114onto the light detector112. The optics may also include an optical element holder (or holding device)120discussed further below. Other examples of optics (not shown) may include, but are not limited to, one or more collimating lenses, relay lenses, field lenses, tube lenses, windows, etc., as appreciated by persons skilled in the art.

Generally, the optical element holder120is configured for securely retaining a plurality of optical elements124, and is movable to enable selection of a desired optical element124for use in a given experiment. In typical embodiments, the optical elements124are disk-shaped but alternatively may be polygonal. In the illustrated example, the optical elements124are emission filters having different transmission characteristics (i.e., colors). The optical filters function to block unwanted wavelengths and thereby prevent them from reaching the light detector112. As such, the optical element holder120functions as a wavelength selector in the illustrated example. In typical embodiments the optical element holder120is rotatable about a central axis to enable wavelength selection, in which case the optical element holder120may be a wheel or carousel. In other embodiments the optical element holder120may effect a different type of movement, such as linear sliding as noted above. Movement of the optical element holder120may be motorized and automated (computerized) in a manner appreciated by persons skilled in the art. As shown inFIG. 1, during operation the optical element holder120positions a selected optical element124in an operative position at which the selected optical element124is optically aligned with the path of the emission light114, whereby the emission light114is incident on, and modified (e.g., filtered) by, the selected optical element124prior to reaching the light detector112.

The optical element holder120may be generally disk-shaped or have another type of planar geometry. Thus, the optical element holder120may have two opposing sides dictating the dominant planar dimensions (two-dimensional size) of the optical element124and a thickness between the two opposing sides. One of the two opposing sides is an optical input side128at which the emission light114is received from the sample108(and any intervening optics), and the other side is an optical output side130from which the modified (e.g., filtered) emission light114propagates toward the light detector112(and any intervening optics). The thickness of the optical element holder120may be defined generally along (parallel to) the optical axis of the emission light114that is transmitted through the optical element holder120from the optical input side128to the optical output side130.

The optical element holder120may generally include a body132on or in which the optical elements124are retained. The body132may be monolithic or an assembly of two or more components. The body132includes openings134aligned with the respective optical elements124to enable light to reach the optical elements124. Similar openings are provided on the opposite side (not shown) of the body132. One or more surfaces of the body132may define optical element receptacles (not shown), examples of which are described further below, in which respective optical elements124are loaded. The optical element receptacles may be configured to define fixed, repeatable operating positions of the respective optical elements124at which the optical elements124are securely retained. In the illustrated disk- or wheel-type embodiment, the optical element receptacles (and the optical elements124loaded therein) are positioned at a radial distance from the central axis of rotation of the optical element holder120, and are circumferentially spaced from each other about the central axis. In some embodiments, the optical element receptacles may be configured as radial slots that include radial openings or grooves136through which the optical elements124are loaded into and removed from the body132. In other embodiments, the body132may include other means for loading and removing the optical elements124.

In the illustrated example ofFIG. 1, the optical element holder120just described is positioned in the emission light path and thus serves as an emission filter holder. Alternatively, the optical element holder120may be an excitation filter holder that is positioned in the excitation light path. As a further alternative, an optical filter holder may be positioned in the emission light path to serve as an emission filter holder (as specifically illustrated inFIG. 1), and another optical filter holder (not specifically shown) may be positioned in the excitation light path to serve as an excitation filter holder. Moreover, in other embodiments the optical instrument100may provide a single light path such as an emission light path. As one non-limiting example, the optical instrument100may be a luminometer that measures luminescent light emitted from the sample108as a result of chemical or biological activity, i.e., without requiring stimulation by excitation light.

Moreover, in the context of the present disclosure, the term “optical element” or “optics element” refers to any type of component or device configured for modifying light incident on that component or device. The modification effected by the optical element may be, for example, filtering, blocking (i.e., 100% blocking as opposed to wavelength-dependent filtering), collimating, focusing, inverting, beam steering, beam splitting, attenuating, etc. Optical element holders as described herein may support any of these different types of optical elements, and in some embodiments a combination of two or more different types of optical elements. For example, the optical elements124mounted to the optical element holder120in a given application may simultaneously include filters and also one or more lenses, such as a phase alignment lens.

It will also be understood thatFIG. 1is a high-level schematic depiction of an example of the optical instrument100consistent with the present disclosure. Other optics, electronics, and mechanical components and structures not specifically shown inFIG. 1may be included as needed for practical implementations. As one example, the optical instrument100may also include a computing device (not shown) communicating with the light detector112. The computing device may receive images captured by the light detector112or measurement data outputted by the light detector112, and digitize, record and/or otherwise process the images or measurement data. The computing device may also process captured images or acquired measurement data as needed for displaying the images or measurement data on a display device such as a computer screen. The computing device may also be configured for processing the images so as to enhance or control the display of the images in a desired manner. The computing device may also communicate with the optical element holder120so as to control its movement, such as to index a selected optical element124into an optical path. Generally for these purposes, the computing device may include hardware (microprocessor, memory, etc.) and software components, as well as user interface (both input and output) devices, as appreciated by persons skilled in the art.

FIG. 2is a schematic cross-sectional view of a portion of a conventional optical element holder220at which one of the optical elements124is positioned. As described above, the optical element holder220may be an emission filter holder as illustrated inFIG. 1, or may be an excitation filter holder, or may hold optical elements124of another type. For reference purposes,FIG. 2shows a longitudinal (or central) axis242and a transverse (or radial) axis244orthogonal to the central axis242. In the illustrated disk- or wheel-type embodiment, the longitudinal axis242is the central axis (i.e., the axis of rotation) of the optical element holder220. The transverse axis244lies in a transverse plane orthogonal to the central axis242. The transverse plane may be defined by rotating the illustrated transverse axis244about the central axis242, or by considering the transverse axis244in conjunction with another transverse axis246(directed into and out of the drawing sheet) that is orthogonal to the transverse axis244and to the central axis242. In this example, the body of the optical element holder220includes a first body portion252and a second body portion254between which an optical element receptacle256is located. The optical element receptacle256includes, or is in open communication with, a radial opening236. Thus, in the present embodiment, the optical element124is loaded into the optical element receptacle256via the radial opening236generally along the radial direction. Respective openings258and260of the first body portion252and the second body portion254are optically aligned with each other and with the optical element124, thereby enabling a light path to be established through the optical element holder220including through the optical element124. Either side of the optical element holder220(the top side or the bottom side, from the perspective ofFIG. 2), may serve as the optical input side while the other opposing side serves as the optical output side. The body of the optical element holder220(including the first body portion252and second body portion254) has a thickness along (in a direction parallel to) the central axis242.

The body of the optical element holder220includes a plurality of distinct surfaces. Each optical element receptacle256(and associated radial opening236) may be defined by at least one of the surfaces of the optical element holder body. In some embodiments, these surfaces may include a (first) transverse receptacle surface262of the first body portion252, a (second) transverse receptacle surface264of the second body portion254generally facing the first transverse receptacle surface262, and a longitudinal receptacle surface266extending between the first transverse receptacle surface262and the second transverse receptacle surface264. One or more of these surfaces262,264, and266may be adjoined to one or more of the other surfaces262,264, and266. In the present context, the first transverse receptacle surface262and the second transverse receptacle surface264are “transverse” in that they generally extend along the transverse or radial axis244and thus are coplanar with the transverse plane orthogonal to the central axis242(the plane that is defined in one direction by the illustrated transverse or radial axis244). Similarly, the longitudinal receptacle surface266is “longitudinal” in that it generally extends along the central axis242, although the longitudinal receptacle surface266may include local structural features that are not be perfectly parallel with the central axis242.

As described above, in an ideal case the optical element holder220(in particular, the optical element receptacle256and surrounding body portions252and254) retains the optical element124in perfect alignment with the optical path, such that the light beam (e.g., an emission light beam, excitation light beam, etc., depending on how the optical element holder220is being utilized) follows a straight path (e.g., is not turned or shifted) through the optical element holder220including while the light beam passes through the thickness of the optical element124.FIG. 2shows an ideal (or desired) light beam270. In some embodiments, the ideal case may correspond to the optical element124being oriented (lying) in the transverse plane. However, in practice the optical element receptacle256has a clearance to facilitate inserting the optical element124into its proper operating position in optical element receptacle256. This clearance may correspond to the open space between the optical element124and the surface(s) of the optical element holder220defining the boundaries of the optical element receptacle256, such as the first transverse receptacle surface262, the second transverse receptacle surface264, and the longitudinal receptacle surface266in the illustrated example. This clearance may allow the optical element124to be inadvertently loaded with an angular tilt (e.g., relative to the transverse plane), which results in a shifted light beam272as shown inFIG. 2. Additionally, operational vibration may cause the optical elements124to shift or tilt over time. This misalignment may result in “pixel shift” as described above and/or cause other problems. Accordingly, to mitigate or eliminate this pixel shift the clearance in the optical element holder220should be mitigated or eliminated or otherwise addressed.

FIG. 3is a schematic cross-sectional view of an example of an optical element holder320according to some embodiments. Similar of the view ofFIG. 2,FIG. 3illustrates a portion of the optical element holder320where one of the optical elements124is positioned. As described above, the optical element holder320may be an emission filter holder as illustrated inFIG. 1, or may be an excitation filter holder, or may hold optical elements124of another type. As a frame of reference,FIG. 3also shows a longitudinal or central axis342of the optical element holder320and a transverse or radial axis344orthogonal to the central axis342. The body of the optical element holder320includes a first body portion352and a second body portion354between which a plurality of optical element receptacles356are located, one of which is shown inFIG. 3. In the present embodiment, the optical element124is loaded into the optical element receptacle356generally along the radial direction via a radial opening336. The first body portion352and the second body portion354include respective openings358and360aligned with each optical element receptacle356, which enable a light path to be established through the optical element124when the optical element124is moved (e.g., rotated in the present embodiment) to the operative position shown inFIG. 1. Each optical element receptacle356(and associated radial opening336) may be defined by one or more surfaces of the optical element holder body. In some embodiments, these surfaces may include a (first) transverse receptacle surface362(which is perpendicular to the central axis242) of the first body portion352, a (second) transverse receptacle surface364of the second body portion354generally facing the first transverse receptacle surface362, and a longitudinal receptacle surface366extending between the first transverse receptacle surface362and the second transverse receptacle surface364.

To address the problem of optical element misalignment, the optical element holder320includes a plurality of pusher components374positioned at the respective optical element receptacles356, one pusher component374and associated optical element receptacle356being shown inFIG. 3. Depending on the embodiment, one or more pusher components374may be positioned at each optical element receptacle356. That is, the optical element holder320may be configured for single-point or multi-point (e.g., dual-point) biasing at each optical element receptacle356. Generally, each pusher component374is configured for pushing or biasing (applying a pushing or biasing force376to) the corresponding optical element124in a manner effective to retain the optical element124in an aligned position in the optical element receptacle356at which the optical element124is generally parallel to the transverse plane, i.e., is not shifted or tilted. To achieve this retained alignment, in some embodiments each pusher component374may be configured for applying the biasing force376to the corresponding optical element124at an angle to both axes of the optical element holder320, i.e., at an angle to the central axis342and to the transverse or radial axis344, such that the optical element124is forced or biased into contact with (i.e., the optical element124bears against) at least one surface of the optical element holder320. The pushing or biasing force376thus has a force component in a direction along the central axis342and a force component in a direction along the transverse or radial axis344. The pusher component374is positioned so as to contact the optical element124, and thereby apply the force to the optical element124, at some point while the optical element124is inserted into the optical element receptacle356. The surface with which the optical element124is forced into contact is one or more surfaces defining the optical element receptacle356, and thus may be the first transverse receptacle surface362, the second transverse receptacle surface364, and/or the longitudinal receptacle surface366.

Generally, the pusher component374may be structured, oriented, and positioned in any manner effective for applying the angled pushing or biasing force376. In the illustrated embodiment, the pusher component374includes a contact surface378for contacting the optical element124and a spring member380(schematically depicted inFIG. 3) capable of storing potential energy and applying the angled pushing or biasing force376. The contact surface378may be curved, for example spherical or conical (e.g. parabolic, hyperbolic, etc.), or may be a flat surface that is angled (e.g., 45 degrees to the central axis342and to the transverse axis344) to provide a biasing force at a desired angle. The contact surface378may be attached or integrally adjoined to the spring member380, or may be a separate component with which the spring member380contacts. The spring member380may be a spring element distinct from a main structural portion of the pusher component374, or may be a deflectable structural portion of the pusher component374. In some embodiments, the spring member380may be a planar structure having an elongated (or dominant) dimension and is deflectable in a direction generally orthogonal to the elongated dimension. For example, the spring member380may be a flat spring, such as a strip of material having opposing planar surfaces defined by a length and a width, and a thickness between the opposing planar surfaces. The length may be greater than the width and the thickness and thus may be the elongated (or dominant) dimension. In this case, the strip of material is deflectable in a direction generally orthogonal to its length. For example, the strip of material may be mounted as a cantilever, or otherwise has at least one free (unconstrained) end at which the strip of material is deflectable. In some embodiments, the entire solid structure of the pusher component374is deflectable and thus functions as the spring member380. The pusher component374may be an integral part of the body of the optical element holder320, or may be attached, fastened, or otherwise mechanically referenced to the optical element holder body as needed for effectively applying the angled pushing or biasing force376. In some embodiments, two or more contact surfaces378may be positioned at each optical element receptacle356. In such embodiments, all of the contact surfaces378may be located on the same side of the optical element124(i.e., the upper side or lower side, from the perspective ofFIG. 3), or some contact surfaces378may be located on the opposite sides of the optical element124.

In operation, as each optical element124is loaded into a corresponding optical element receptacle356, the optical element124comes into contact with the contact surface378of the pusher component374. To facilitate loading, the optical element124may be gripped and handled by any suitable technique as appreciated by persons skilled in the art. The optical element124may slide along the contact surface378for a small distance (and against the biasing force imparted by the pusher component374) before being urged by the pusher component374into its final operative position (also referred to herein as the aligned position) in the optical element receptacle356. The pusher component374is configured, and positioned relative to the optical element receptacle356, such that the final operative position of the optical element124in the optical element receptacle356is a distinct, repeatable position that does not vary from one iteration of loading and removing the optical element124to another iteration. Moreover, at the operative position, the optical element124is securely retained and properly aligned with the correct optical path through the optical element holder320, consequently resulting in a properly aligned light beam370. Subsequently, the optical element124may be removed by any suitable technique in which the optical element124is able to be grasped and moved out from the optical element receptacle356while overcoming the biasing force imparted by the pusher component374.

FIG. 3also illustrates an additional embodiment in which the optical element holder320further includes a retaining or cornering feature382. Generally, the cornering feature382is positioned such that the optical element124contacts the cornering feature382at the final operative position. Generally, the cornering feature382is configured to apply a reaction force384to the optical element124in response the optical element124contacting the cornering feature382. The reaction force384is oriented such that the reaction force384pushes the optical element124against a desired surface of the optical element holder320, thereby assisting or supplementing the operation of the pusher component374in ensuring proper alignment of the optical element124(i.e., minimizing angular tilt of the optical element124). The reaction force384has a force component in a direction along the central axis342and a force component in a direction along the transverse or radial axis344. The directions of the respective force components of the reaction force384along the central axis342and along the transverse or radial axis344may be opposite to the corresponding force components of the biasing force376applied by the pusher component374. For example, the resultant reaction force384may be oriented at an angle to both the central axis342and to the transverse or radial axis344that is complementary or substantially complementary to (shifted by or about ninety degrees from) the angle of the pushing or biasing force376. In some embodiments, the cornering feature382is an angled section of one of the surfaces of the optical element holder320. For example, in the illustrated embodiment the cornering feature382is an angled section of the longitudinal receptacle surface366. In some embodiments, the pusher component374and the cornering feature382cooperate to bias the optical element124into contact with a single surface or side of the optical element receptacle356. For example, in the illustrated embodiment the optical element124in its operative (aligned) position is biased into contact with the first transverse receptacle surface362, which is perpendicular to the central axis342.

FIG. 4Ais a perspective view of an example of an optical element holder420according to another embodiment.FIG. 4Bis a cutaway perspective view of the optical element holder420. Specifically, a portion of the optical element holder420inFIG. 4Bis cut away along a plane parallel with the central axis and orthogonal to the transverse (or radial) axis, which axes are defined above and illustrated inFIGS. 2 and 3.FIGS. 4A and 4Balso illustrate an optical element124loaded in the optical element holder420.FIGS. 4A and 4Bfurther illustrate an example of a different type of optical element125loaded in the optical element holder420. For instance, the optical element124may be a filter and the other optical element125may be a lens such as a phase alignment lens. In the illustrated embodiment, the optical element holder420is configured as a disk or wheel that can be rotated about its central axis to select an optical element124for use in a given experiment. Thus, the optical element holder420may include a centrally located coupling486configured to be coupled to a motor to drive rotation of the optical element holder420about the central axis. In the illustrated example, the coupling486includes a shaft and a belt drive pulley that may be operatively linked to a suitable motor.

The body of the optical element holder420includes a plurality of optical element receptacles456for holding a like number of optical elements124. Eight optical element receptacles456are shown by example only, with the understanding that more or less than eight optical element receptacles456may be provided. The optical element receptacles456are each positioned at a radial distance from the central axis, and are circumferentially spaced from each other about the central axis. In the present embodiment, the optical element holder420is configured for radial loading of the optical elements124, and thus includes radial openings436leading into the respective optical element receptacles456. Also in present embodiment, the optical element holder body includes a first body portion452and a second body portion454. In this embodiment, the first body portion446is the structure that primarily defines or forms the optical element receptacles456, including the radial openings436and the openings at the optical input side and the optical output side, i.e., the openings communicating with the optical element receptacles456that enable a light path to be established through a selected optical element124(e.g., openings358and360shown inFIG. 3). The optical element holder420further includes a plurality of pusher components474. The boundaries of the optical element receptacles456(or the optical element receptacles456and the radial openings436) may be at least partially defined by the pusher components474. In this embodiment, the pusher components474generally extend outward in radial directions from the central axis. The pusher components474may be considered as being radial extensions of the second body portion454. In the illustrated example, the pusher components474are fastened to the second body portion454by screws. In other embodiments, however, the pusher components474may be attached to the second body portion454by other means, or may be integral parts of the second body portion454.

As described above, the pusher components474are provided to address the problem of optical element misalignment. Each pusher component474may be configured for pushing or biasing the corresponding optical element124at an angle to both axes of the optical element holder420, i.e., at an angle to the central axis and to the transverse (or radial) axis, such that the optical element124is forced or biased into contact with (i.e., the optical element124bears against) at least one surface of the optical element holder420such as a surface of the optical element receptacle456. The pushing or biasing force thus has a force component in a direction along the central axis and a force component in a direction along the transverse axis. The pusher component474is positioned so as to contact the optical element124, and thereby apply the biasing force to the optical element124, at some point while the optical element124is inserted into the optical element receptacle456. In the present embodiment, each pusher component474includes a spring member480and at least two contact elements488extending from the spring member480. The spring member480in this embodiment is a deflectable structure capable of storing potential energy and applying the angled pushing or biasing force. The contact elements488may be integrally formed with the spring member480or may be attached to the spring member480such as by fastening, bonding, welding, brazing, riveting, etc.

In some embodiments and as illustrated, each spring member480may include two arms that terminate at ends spaced apart from each other, and each contact element488may be positioned at the end of one of the arms. By this configuration, the two arms of each spring member480are individually deflectable, and the contact elements488are independently movable. Each pusher component474, and thus each spring member480, is positioned between two adjacent optical element receptacles456. By this configuration, two contact elements488are associated with each optical element receptacle456. Thus, the present embodiment is an example of dual-point biasing of each optical element124mounted to the optical element holder420. The contact elements488associated with each optical element receptacle456are spaced from each other so as to be positioned generally on opposing sides of the perimeter of the optical element124. In the present context, “opposing sides” refers to two sides (or halves) of the optical element124demarcated by a diametrical line that is located between the two contact elements488, resulting in one contact element488being positioned on one side of that diametrical line and the other contact element488being positioned on the other side of that diametrical line. Hence, as shown, the two contact elements488do not need to be positioned diametrically opposite to each other relative to the corresponding optical element124, but more generally are circumferentially spaced from each other relative to the optical element124by some arc length along the perimeter of the optical element124.

As best shown inFIG. 4B, each contact element488includes an outer contact surface478for contacting the optical element124. The contact surface478may be rounded or curved so as to facilitate sliding contact with the optical element124as the optical element124is moved into and out from the optical element receptacle456, and to minimize the contact area between the contact surface478and the optical element124. For example, the contact surface478may be generally spherical, conical, or the like. The contact surfaces478associated with each optical element receptacle456are positioned generally on “opposing sides” of the perimeter of the optical element124, and both contact surfaces478apply an angled biasing force to the optical element124. Each angled biasing force has a force component in a direction along the central axis and a force component in a direction along the transverse (or radial) axis. Due to the contact surfaces478being at different locations, the angle (or orientation) of the resultant biasing forces of the respective contact surfaces478are different. The magnitudes of the two biasing forces may be the same or substantially the same. Consequently, the two pusher components474associated with each optical element receptacle456cooperate to bias the optical element124into contact with at least one surface of the optical element holder420, such as a transverse surface462(or both the transverse surface462and a longitudinal surface466) of the first body portion452(FIG. 4A).

FIG. 4Cis a perspective view of the optical element holder420with the pusher components474removed. As shown, surfaces of the optical element holder body facing the optical element receptacles456, such as surfaces of the first body portion452, may include recesses or pockets490that are sized, shaped, and positioned to accommodate the presence and movement of the contact elements488.

The operation of the optical element holder420may be similar to that described above in conjunction withFIG. 3. Each optical element124is loaded into one of the optical element receptacles456generally along the radial direction. As each optical element124is loaded, the optical element124comes into contact with the contact surfaces478of the contact elements488positioned at the corresponding optical element receptacle456(two contact elements488per optical element receptacle456in the illustrated example). The optical element124may slide along the contact surfaces478for a small distance (and against the biasing force imparted by the pusher components474) before being urged by the pusher components474(via contact with the contact surfaces478) into its final operative position in the optical element receptacle456. As in other embodiments disclosed herein, the pusher components474(particularly the contact elements488) are configured, and positioned relative to the optical element receptacle456, such that the final operative position of the optical element124in the optical element receptacle456is a distinct, repeatable position that does not vary from one iteration of loading and removing the optical element124to another iteration. Moreover, at the operative position, the optical element124is securely retained and properly aligned with the correct optical path through the optical element holder420, consequently resulting in a properly aligned light beam through the selected optical element124. Subsequently, the optical element124may be removed by any suitable technique.

FIG. 5Ais a perspective view of an example of an optical element holder520according to another embodiment.FIG. 5Bis a cutaway perspective view of the optical element holder520, in which a portion of the optical element holder520is cut away along a plane similar to that shown inFIG. 4B. Specifically, along a plane parallel with the central axis and orthogonal to the transverse (or radial) axis, which axes are defined above and illustrated inFIGS. 2 and 3.FIGS. 5A and 5Balso illustrate an optical element124loaded in the optical element holder520.FIGS. 5A and 5Bfurther illustrate an example of a different type of optical element125loaded in the optical element holder420. For instance, the optical element124may be a filter and the other optical element125may be a lens such as a phase alignment lens. As in the embodiment described above and illustrated inFIGS. 4A to 4C, the optical element holder520is configured as a disk or wheel that can be rotated about its central axis to select an optical element124for use in a given experiment.

The optical element holder520may include many of the same or similar components as those described above and illustrated inFIGS. 4A to 4C. Thus, the optical element holder520may include a centrally located coupling586. The body of the optical element holder520includes a plurality of optical element receptacles556for holding a like number of optical elements124. The optical element receptacles556are each positioned at a radial distance from the central axis, and are circumferentially spaced from each other about the central axis. The optical element holder520includes radial openings536leading into the respective optical element receptacles556. The body of the optical element holder520includes a first body portion552and a second body portion554. The first body portion446may be the structure that primarily defines or forms the optical element receptacles556, including the radial openings536and the openings at the optical input side and the optical output side. The optical element holder520further includes a plurality of pusher components574, which may at least partially define the boundaries of the optical element receptacles556(or the optical element receptacles556and the radial openings536). The pusher components574generally extend outward in radial directions from the central axis, and may be attached to the second body portion554or may be integral parts of the second body portion554.

As in other embodiments, the pusher components574function to retain the optical elements124in fixed, repeatable operating (or aligned) positions in the respective optical element receptacles556, such that each optical element124when moved into the optical path is correctly aligned with the optical path. For this purpose, each pusher component574may be configured for pushing or biasing the corresponding optical element124at an angle to both axes of the optical element holder520, i.e., at an angle to the central axis and to the transverse (or radial) axis (as defined above), such that the optical element124is forced or biased into contact with (i.e., the optical element124bears against) at least one surface of the optical element holder520such as a surface of the optical element receptacle556. The pusher component574is positioned so as to contact the optical element124, and thereby apply the biasing force to the optical element124, at some point while the optical element124is inserted into the optical element receptacle556. Each pusher component574includes a spring member580(e.g., a deflectable structure) and a contact element588extending from the spring member580. Surfaces of the optical element holder body facing the optical element receptacles556, such as surfaces of the first body portion552, may include recesses or pockets590that are sized, shaped, and positioned to accommodate the presence and movement of the contact elements588.

Each pusher component574, and thus each spring member580, is generally positioned between two adjacent optical element receptacles556. However, the contact element588extending from the spring member580of each pusher component574is positioned such that the contact element588extends into (or is present in) only one optical element receptacle556. Thus, in this embodiment only one pusher component574(and only one spring member580and corresponding contact element588of that pusher component574) is associated with each optical element receptacle556. The present embodiment is thus an example of single-point biasing of each optical element124mounted to the optical element holder520. As best shown inFIG. 5B, each contact element588includes an outer contact surface578for contacting the optical element124. As described above, the contact surface578applies an angled biasing force to the optical element124that has a force component in a direction along the central axis and a force component in a direction along the transverse (or radial) axis. Consequently, the pusher component574associated with each optical element receptacle556biases the optical element124into contact with at least one surface of the optical element holder520, such as a transverse surface562(or both the transverse surface562and a longitudinal surface566) of the first body portion552(FIG. 5A).

Other than the single-point biasing, the operation of the optical element holder520may be generally the same as that described above in conjunction withFIGS. 4A to 4C.

FIG. 6is a cutaway perspective view of an example of an optical element holder620according to another embodiment, in which a portion of the optical element holder620is cut away along a plane similar to that shown inFIGS. 4B and 5B.FIG. 6also illustrates optical elements124loaded in respective optical element receptacles656of the optical element holder620. As in other embodiments described above, the optical element holder620is configured as a disk or wheel that can be rotated about its central axis to select an optical element124for use in a given experiment.

The optical element holder620may include many of the same or similar components as those described above and illustrated inFIGS. 4A to 5B. Thus, the body of the optical element holder620includes a plurality of optical element receptacles656for holding a like number of optical elements124. The optical element receptacles656are each positioned at a radial distance from the central axis, and are circumferentially spaced from each other about the central axis. The optical element holder620includes radial openings636leading into the respective optical element receptacles656. The body of the optical element holder620includes at least a first body portion652that primarily defines or forms the optical element receptacles656, including the radial openings636and the openings at the optical input side and the optical output side. The holder body may also include a second body portion (not shown), which may be similar to the second body portions described above and illustrated inFIGS. 4A to 5B. The optical element holder620further includes a plurality of pusher components, which may at least partially define the boundaries of the optical element receptacles656(or the optical element receptacles656and the radial openings636). The pusher components (or portions thereof) may be configured generally as described above and illustrated inFIGS. 4A to 5B, and thus may generally extend outward in radial directions from the central axis, and may be attached to the second body portion or may be integral parts of the second body portion.

As in other embodiments, the pusher components function to retain the optical elements124in fixed, repeatable operating (or aligned) positions in the respective optical element receptacles656, such that each optical element124when moved into the optical path is correctly aligned with the optical path. For this purpose, each pusher component may be configured for pushing or biasing the corresponding optical element124at an angle to both axes of the optical element holder620, i.e., at an angle to the central axis and to the transverse (or radial) axis (as defined above), such that the optical element124is forced or biased into contact with (i.e., the optical element124bears against) at least one surface of the optical element holder620such as a surface of the optical element receptacle656. The pusher component is positioned so as to contact the optical element124, and thereby apply the biasing force to the optical element124, at some point while the optical element124is inserted into the optical element receptacle656. Each pusher component includes a spring member (e.g., a deflectable structure, not shown) and two or more contact elements688positioned to be biased by the spring member. The spring member may be configured generally as described above and illustrated inFIGS. 4A to 5B. Surfaces of the optical element holder body facing the optical element receptacles656, such as surfaces of the first body portion652, may include recesses or pockets690that are sized, shaped, and positioned to accommodate the presence and movement of the contact elements688.

As described above and illustrated inFIGS. 4A and 4B, each spring member may include two arms that terminate at ends spaced apart from each other, and each contact element688may be positioned at the end of one of the arms. By this configuration, the two arms of each spring member are individually deflectable, and the contact elements688are independently movable. Each pusher component, and thus each spring member, is positioned between two adjacent optical element receptacles656. By this configuration, two contact elements688are associated with each optical element receptacle656. Thus, the present embodiment is an example of dual-point biasing of each optical element124mounted to the optical element holder620. The contact elements688associated with each optical element receptacle656are spaced from each other so as to be positioned generally on “opposing sides” of the perimeter of the optical element124, as described above. In the present embodiment, the contact elements688are shaped as balls or spheres, which may be attached or integrated with the spring members, or may be separate components contacted by the spring members. As described above, the contact element688applies an angled biasing force to the optical element124that has a force component in a direction along the central axis and a force component in a direction along the transverse (or radial) axis. Consequently, the pusher components associated with each optical element receptacle656bias the corresponding optical element124into contact with at least one surface of the optical element holder620, such as a transverse surface662(or both the transverse surface662and a longitudinal surface666) of the first body portion652.

As an alternative to each spring member having two arms that terminate at ends where respective contact elements688are located, two spring members may be provided generally between each pair of adjacent receptacles656. In this case, each spring member may terminate at an end at which at least one contact element688is located.

FIG. 7is a cutaway perspective view of an example of an optical element holder720according to another embodiment, in which a portion of the optical element holder720is cut away along a plane similar to that shown inFIGS. 4B, 5B, and 6.FIG. 7also illustrates optical elements124loaded in respective optical element receptacles756of the optical element holder720. As in other embodiments described above, the optical element holder720is configured as a disk or wheel that can be rotated about its central axis to select an optical element124for use in a given experiment.

The optical element holder720may include many of the same or similar components as those described above and illustrated inFIGS. 4A to 6. Thus, the body of the optical element holder720includes a plurality of optical element receptacles756for holding a like number of optical elements124. The optical element receptacles756are each positioned at a radial distance from the central axis, and are circumferentially spaced from each other about the central axis. The optical element holder720includes radial openings736leading into the respective optical element receptacles756. The body of the optical element holder720includes at least a first body portion752that primarily defines or forms the optical element receptacles756, including the radial openings736and the openings at the optical input side and the optical output side. The holder body may also include a second body portion (not shown), which may be similar to the second body portions described above and illustrated inFIGS. 4A to 5B. The optical element holder720further includes a plurality of pusher components, which may at least partially define the boundaries of the optical element receptacles756(or the optical element receptacles756and the radial openings736). The pusher components (or portions thereof) may be configured generally as described above and illustrated inFIGS. 4A to 5B, and thus may generally extend outward in radial directions from the central axis, and may be attached to the second body portion or may be integral parts of the second body portion.

As in other embodiments, the pusher components function to retain the optical elements124in fixed, repeatable operating (or aligned) positions in the respective optical element receptacles756, such that each optical element124when moved into the optical path is correctly aligned with the optical path. For this purpose, each pusher component may be configured for pushing or biasing the corresponding optical element124at an angle to both axes of the optical element holder720, i.e., at an angle to the central axis and to the transverse (or radial) axis (as defined above), such that the optical element124is forced or biased into contact with (i.e., the optical element124bears against) at least one surface of the optical element holder720such as a surface of the optical element receptacle756. The pusher component is positioned so as to contact the optical element124, and thereby apply the biasing force to the optical element124, at some point while the optical element124is inserted into the optical element receptacle756. Each pusher component includes a spring member (e.g., a deflectable structure, not shown) and at least one contact element788positioned to be biased by from the spring member. The spring member may be configured generally as described above and illustrated inFIGS. 4A to 5B. Surfaces of the optical element holder body facing the optical element receptacles756, such as surfaces of the first body portion752, may include recesses or pockets790that are sized, shaped, and positioned to accommodate the presence and movement of the contact elements788.

As described above and illustrated inFIGS. 4A to 5B, each contact element688may be positioned at the end of each spring member. In the present embodiment, each contact element688is sized and positioned such that at least two portions of each contact element688face respective adjacent optical element receptacles756, as shown inFIG. 7. These two portions may be portions of a single contact surface (i.e., a single outer surface) of the contact element688, or the two portions may be two distinct contact surfaces of the contact element688. In either case, the contact elements688associated with each optical element receptacle756are spaced from each other so as to be positioned generally on “opposing sides” of the perimeter of the optical element124, as described above. By this configuration, at least two portions of respective contact elements688face each receptacle756on opposing sides thereof. Thus, the present embodiment is an example of dual-point biasing of each optical element124mounted to the optical element holder720. In the present embodiment, the contact elements788are shaped as balls or spheres, which may be attached or integrated with the spring members, or may be separate components contacted by the spring members. As illustrated, the balls or spheres may be truncated, e.g., have flat top surfaces, which are contacted by (or attached to or integrated with) the corresponding spring members. As described above, the contact element788applies an angled biasing force to the optical element124that has a force component in a direction along the central axis and a force component in a direction along the transverse (or radial) axis. Consequently, the pusher components associated with each optical element receptacle756bias the corresponding optical element124into contact with at least one surface of the optical element holder720, such as a transverse surface762(or both the transverse surface762and a longitudinal surface766) of the first body portion752.

Other embodiments of an optical element holder as described herein may include different combinations of features described above and illustrated inFIGS. 1 to 7. For example, an optical element holder such as described above and illustrated inFIGS. 4A to 4C,FIGS. 5Aand5B,FIG. 6, orFIG. 7may include retaining or cornering features such as described above and illustrated inFIG. 3.

It will be understood that terms such as “communicate” and “in . . . communication with” (for example, a first component “communicates with” or “is in communication with” a second component) are used herein to indicate a structural, functional, mechanical, electrical, signal, optical, magnetic, electromagnetic, ionic or fluidic relationship between two or more components or elements. As such, the fact that one component is said to communicate with a second component is not intended to exclude the possibility that additional components may be present between, and/or operatively associated or engaged with, the first and second components.