GB2601501A - Optical fiber coupling in a real-time thermal cycler - Google Patents

Abstract

A coupling comprises two optical ball lenses 1, arranged next to each other and between two optical fibers 5 arranged on both sides of the two ball lenses. The coupling may be used with a thermal cycler with a movable cycler cover (11, figure 2) (in a closed state) which couples light between the separable and fiber-based optical paths. Excitation, emission fibers (2, 3, figure 2) respectively, which end in close proximity to a cover or foil used as a cover (8, figure 2) that is arranged between a top heater (7, figure 2) and polymerase chain reactor (PCR) consumables (9, figure 2). The PCR consumable is arranged in a thermal block (13, figure 2) which heats and cools the PCR consumable. A thermoelectric element (15, figure 2) like a Peltier element, may be arranged below the thermal block.

Description

OPTICAL FIBER COUPLING IN A REAL-TIME THERMAL CYCLER

DESCRIPTION

Field of the Invention

[0001] The invention relates to an optical fiber coupling.

Brief description of the related art

[0002] Automated analyser systems for use in clinical diagnostics and life sciences are produced by a number of companies For example, STRATEClu SE, Birkenfeld, Germany, produces a number of devices for specimen handling and detection for use in automated analyser systems and other laboratory instrumentation [0003] STRATEC designs and manufactures diagnostic instruments with functional modules that allow for loading and potentially on-board storage of e.g. consumables, reagents and controls. In many cases, a compartment for that is actively cooled to a specific temperature range to allow for longer on-board stability of these loaded goods. Relative humidity inside of such a compartment is typically not controlled and due to cooling relatively high when compared to ambient. Flexible usage with individual thermal or humidity settings in sub-compartments has not been realized so far.

[0004] Real-time PCR thermal cyclers (also called thermocyclers) are specific instruments for the amplification and simultaneous (real-time) detection of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) within a sample of cells. According to this such systems combine the functionalities of a thermal cycler and a fluorimeter which are explained below: Thermal cycler Cycled heating and cooling of a sample in a disposable reaction vessel or cavity (so called consumables) with a defined thermal profile (thermal treatment).

Fluorimeter (also called fluorometer): Device to measure fluorescence parameters, in particular intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. The parameters are used to identify the presence and number of specific molecules in a sample.

[0005] The functional combination enables the processing of a real-time PCR, also known as quantitative PCR (qPCR), in order to perform diverse analysis in the field of molecular diagnostics. Relevant applications include quantitative gene expression analysis, SNP analysis, drug target validation and genotyping.

[0006] For the purpose of consumable loading or sequential / stepwise scanning of reaction wells a movement of cycler components is required. Depending on specific concept and design of the system, also the relative motion of optical components is mandatory.

[0007] Several RT (real-time) thermal cyclers use flexible optical fibers (glass or plastic) for the transmission / transfer of excitation or emission light between two spots (fiber ends) within a device. Fiber optics provide specific advantages regarding the design of optical system: - Design flexibility due to fiber routing options (flexible optical path design) Simultaneous and concentrated measurement via one or only a few detection units at: - Decentralized reaction vessel / cycler positions High number of reaction cavities with simultaneous large spatial expansion / distribution Light transmission and component motion at the same time [0008] Moved optical fibers can also provide some essential drawbacks, for example, fluorescence intensity variations or reduced system reliability caused by fiber breakage. Because of the direct influence on the measurement result, system designers try to avoid according architectures [0009] With regard to fiber optics-based qPCR cyclers it is possible to distinguish between systems with and without moved optical fibers. The general structure and functionality of such systems is identical or quite similar.

[0010] Fluorescence excitation is provided by high-intensity light sources (usually LEDs) filtered to generate light at defined wavelengths, capable of exciting all fluorophores used in the according real-time PCR. The light is transmitted from the source via optical fibers to the sample containing reaction vessel which is located in the thermal treatment unit / block. A heated lid prevents changes in reaction volume and optical artifacts due to condensation. The emitted fluorescence light from the reaction sample will be captured and transmitted via also fiber-based optics (including inline filter device for spectral separation) to the responsible detection unit in order to measure the light intensity of different colors.

[0011] Certain system set-ups require moving and the associated bending, rolling, twisting / torsion etc. of fiber optic cables before and after or even during fluorescence measurement. In contrast, optical systems where the concept and set-up do not require a relative movement of the fibers are also known. This may be related to the complete optical system being moved together with the fibers, or in general a movement of the optical structure. The need to move fibers or the entire optics can be caused by the following exemplary technical aspects: - Loading and unloading of sample holding consumables (reaction vessels), - Positioning and fixation of optics, thermal units and consumable with respect to each other, - Measurement process / procedure (e.g. simultaneous measurement of all reaction vessels in comparison to stepwise scanning) [0012] In the following, examples of corresponding fiber-based optical systems are described which are known from the prior art.

[0013] The prior art describes a multi-well plate qPCR cycler that consists of an upper part with fluorescence photometer and a lower part containing the thermal cycler. The fluorometer is based on moved optical fibers due to the measuring process arid the sequential scanning of the well plate rows.

[0014] Published German Patent Application No, DE 10 2006 036 171 Al shows an optical system with three differently colored LEDs as light source which are producing the required light for the excitation of fluorescent dyes. The multiplexer unit consists of a rotating wheel with up to six color filter modules. By the rotation of the filter wheel, the color filter modules pass subsequently each of the eight light fibers that transmit fluorescent light from the source to the multiplexer. An array of optical fibers is arranged in the measuring head in a shuttle system which scans the sample block row-wise transmitting fluorescent light for the excitation of samples to each single well and for collecting emitted light. Emitted light is detected by a Channel Photo Multiplier (CPM) after it has passed emission filters in the color modules. Optical fibers are used for the transmittance of light between the light source, multiplexer and measuring head [0015] Another example for a ciPCR cycler without moving optical fibers is disclosed in published European Patent Application No, EP 2 463 661 A] . It basically comprises the thermal block cycler which is part of an extendable drawer and the optical system for the fluorescence measurement. The optical system consists of an optic module containing 2 x 96 glass fibers for providing the excitation light and collecting the emitted light to and from each well, and one fiber for the reference channel. It comprises further a LED light source, wherein the instrument uses a white high-power LED as the excitation light source. The actual wavelength used for excitation of fluorophores in the reaction is determined by the chosen excitation filter. The instruments comprise also a filter module containing the filter wheel with four excitation and four emission filters and a CCD camera for measuring the intensity of the emitted light.

[0016] Fiber optics provide the optical coupling between the excitation source, PCR, emission source, and CCD camera. The glass fibers in the optic module distribute the excitation light to the 96 wells of the multi-well plate and collect the emitted light. After passing through the excitation filter, the light is projected via the glass fibers in the optic module onto the wells in the multi-well plate. In the same way, light emitted by the fluorophores is passed vertically into the optic module. This ensures that there are no shading effects within the plate wells and no distortions or variations in the signals coming from wells located at the edges of the PCR multi-well plate compared to center wells, enabling homogeneous sensitivity over the complete plate. The fluorescent signals are then guided to the emission filter contained in the filter module and detected using the CCD camera.

[0017] Following multi-well plate loading and insertion of the thermal block cycler, the entire optical system performs a vertical movement so that the heated lid presses onto the consumable. This improves the thermal contact between the block cycler mount and well plate and ensures a reliable / repeatable positioning of the fiber ends in reference to the reaction sample. The heated cover prevents changes in reaction volume and optical artifacts due to condensation.

[0018] Published European Patent Applications EP 2 879 981 Al and EP 2 972 222 Al describe another device comprising an integrated measurement module which processes single PCR tubes / vials with a system specific design. Multiple individually controllable cyclers allow the thermal treatment of the prepared reaction samples within the PCR consumables. A gripper inserts or places the tubes from above into one of five positions of a cycler bank. The excitation and detection of the fluorescence is achieved through the vial bottom having a measurement window at the bottom's tip by means of a single optical fiber. Each vial position is equipped with one fiber which transmits excitation light from the light source to the sample as well as emission light from the sample to the photodetector.

[0019] The fiber ends, which do not face the consumables, are connected to two multi-channel fluorometer (so called "detector head"). Each fluorescence channel is formed by an optical assembly (so called "signal detectors") consisting of the following main functional elements: LED light source: Colored LEDs for generation of excitation light Lenses and mirros: Directing of light (focusing, dispersion, reflection etc.) Fluorescence filters: Filtering / wavelength depending selection of light Dichroic mirrors: Spectral separation between excitation and emission light Photodi ode: Detection of emission light [0020] The detector heads perform the sequential excitation and detection at the connected vial positions by turning of the signal detectors and the consecutive optical coupling to the circular arranged fibers. The coupling takes place at the interface between fiber and signal detector.

[0021] There are also fiber-based systems without any moving optical parts with tradeoffs regarding handling, functional scope etc. [0022] The disadvantages related to systems known from the prior art can be summarized as follows: - Moved fibers and resulting stresses can cause negative effects like: o Excitation and emission light (signal) variations o Reliability and performance issues due to potential fiber breakage - Efforts to minimize or eliminate the above outlined negative effects affect the design of consumables and devices, if no fibers should be moved and a separation of the according optical fibers / path is not acceptable / feasible: o Concept and design limitations and / or o Higher requirements and efforts Object of the Invention 100231 It is therefore the object of this invention to provide a system and device avoiding the disadvantages related to systems known from the prior art

Summary of the Invention

[0024] The present invention provides a coupling for optical elements, wherein the coupling comprises two optical ball lenes arranged next to each other and between two optical fibers arranged on both sides of the two ball lenses.

[0025] In another aspect of the present invention, each one of the two optical ball lenses comprise an adapter for fixation of the two optical fibers.

[0026] In a further embodiment, both other optical fibers of the two optical fibers connected to the two optical ball lenses are excitation fibers or light emitting fibers [0027] It is also intended that the two ball-lenses are separably arranged next to each other.

[0028] Another object of the present invention is a device comprising a coupling for optical elements as described above.

[0029] In another aspect of the present invention, a first part of the coupling of a device may comprises a first one of the two optical fibers and a first ball lens of the two ball lenses and a second part of the coupling comprises the other one of the two optical fibers and a second ball lens of the two ball lenses.

[0030] The first part can be a movable cover, and the second part may be a housing of an analytical or diagnostic device [0031] The device according to the present invention may be an analytical or diagnostic device, like a thermocycler.

[0032] It is further intended that an opposite end of an optical fiber to the end which is connected to a ball lens is either arranged next to a receptacle, a cover of a receptacle, an excitation unit or a detection unit [0033] Another object of the present invention is a method for coupling light from a first optical fiber into a second optical fiber, comprising the steps of - Connecting the first optical fiber to a first optical ball lens; - Connecting the second optical fiber to a second optical ball lens; - Arranging first and second optical ball lens next to each other sharing a common central optical axis.

[0034] A further object of the present invention relates to the use of a coupling according to any one of claims 1 to 4 or a device according to any one of claims 5 to 9 for coupling light from a first optical fiber into a second optical fiber.

[0035] Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating preferable embodiments and implementations. The present invention is also capable of other and different embodiments and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention.

Summary of the Figures

[0036] The invention will be described based on figures. It will be understood that the embodiments and aspects of the invention described in the figures are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects of other embodiments of the invention, in which: [0037] FIG. 1 shows a pair of ball lenses arranged between two fiber ends [0038] FIG. 2 shows a schematic drawing of a thermocycler with a movable cycler cover having a coupling according to the present invention arranged between cover and housing of the thermocycler.

[0039] FIG. 3 shows the movable cycler cover in an open position.

Detailed Description of the Invention and the Figures [0040] The technical problem is solved by the independent claims The dependent claims cover further specific embodiments of the invention.

[0041] The term receptacle shall be understood within the meaning of the present invention as a container, bottle or any other vessel which is suitable for taking up a rection mixture or samples. A reaction mixture may comprise liquids and/or solid particles. A sample refers for instance to body fluids like whole blood, plasma or any other liquid sample that may be obtained from a patient prior to its use in chemical reaction for analyzing or diagnosing it.

[0042] The invention provides an optical coupling for a real-time thermal cycler that allows an efficient light transfer and transmission between separable optical pathways (e.g. two interfacing fibers) which perform temporary relative movements during processing and measurements. The design avoids mechanical stress to optical fibers (e.g. by twisting or bending) in any way. Note: The light transfer is only implemented at an initial state before or after the relative movement.

[0043] The invention relates to an optical fiber coupling which is an integrated part of a real-time PCR thermal cycler system The entire system consists of a cluster of thermal cyclers connected via fibers with common fluorescence optics responsible for excitation and emission. Fibers are used for the light transmission and transfer of light between the optical units and sample wells due to the high number of individually controllable cyclers, the decentralized arrangement and the cost effectiveness of the design.

[0044] The cycler block can be covered by a moveable heated lid. The removal of the lid is required for the loading and unloading of prepared PCR consumables containing reaction samples. In the context of a cycler concept according to the present invention, the fluorescence measurement is performed from above through sealed openings of the consumable reaction cavities. It is therefore necessary to move not only the top heaters but also the optical elements (e.g. fiber or light guide) to allow the insertion and removal of the consumables manually, from above by a three-axis portal gripper or by any other gripper which may be also part of another device. Mechanical stress on fibers and the associated disadvantages and negative effects (e.g. fiber breakage or signal variations) should be avoided. The design of the following described real-time PCR cycler optics addresses these requirements. By means of an optical coupling and the resulting temporary separation of the optical path, appropriate processing is possible.

[0045] FIG. 1 shows a pair of ball lenses 1 which is used to couple two optical fibers 5 (or a fiber and a light guide) of an excitation or emission path. These pair of ball lenses 1 will be located between two facing fiber ends 6 for collimation and focusing of the light (lines through ball lenses) at the interface.

[0046] Basically, there are five key parameters needed to understand and use ball lenses (comp. Figure 1): Diameter of input source (d), diameter of ball lens (D), effective focal length of ball lens (EFL), back focal length of ball lens (BFL) and index of refraction of ball lens (n; not shown). The key feature of the ball lens is its short back focal length (BFL) which reduces the distance required from the lens to the optical fiber. This allows for precision coupling, which is particularly useful where space or size is a limiting factor within the application or device. Ball lenses are according to the present invention generally used in pairs as shown in FIG. 1. One lens acts as a collimator for collimating the output of a first optical fiber or diode, whilst the second ball lens focuses the light back into the coupled second optical fiber. For smaller applications, half ball lenses may offer a more compact solution.

[0047] FIG 2 provides a schematic drawing of a thermal cycler with a movable cycler cover 11(in a closed state) which couples light between the separable and fiber-based optical paths via ball lenses 1. Next to each ball lens 1 of the pair of ball lenses are optical fibers 5 which are connected excitation, emission fibers 2, 3, respectively, which end in close proximity to a cover or foil used as a cover 8 that is arranged between a top heater 7 and PCR consumables 9.

[0048] The fibers 2, 3 and the cover/foil 8 are separate parts. It is to be noted that the cover 8 may have optical properties relating to the transmission of light (in different directions). It is within the scope of the present invention to arranged optical elements either as part of the fiber's 2, 3 ends, as part of the cover/foil 8 or as separate parts for improving, coupling or modeling light into or out of the PCR consumables 9.

[0049] The PCR consumable 9 is arranged in a thermal block 13 which heats and cools the PCR consumable 9. A thermoelectric element 15, like a Pelletier element, may be arranged below the thermal block 13. The thermocycler shown in FIG. 2 further comprises a fan 17 and a heat sink 21 at the bottom of housing 18. Excitation fibers 2 are connected to an excitation unit 19 and are further connected to one ball lens of the pair of ball lenses 1 which is arranged on top of housing 18. Emission fibers 3 are connected to a detection unit 20 and extend to another connection to a first ball lens of a coupling according to the present invention. The respective second ball lens for the excitation fiber 2 and the emission fiber 3, respectively, are located in the movable cycler cover 11. By closing the movable cycler 11, the ball lenses belonging to coupling will be arranged next to each other so that an optical coupling is achieved.

[0050] The design allows temporary separation of the optical path for opening and closing of the module while maintaining high coupling efficiency in closed / aligned state. Only in the opened state consumables can be loaded or unloaded from the device (comp. FIG. 3).

[0051] Furthermore, the optical coupling allows the movement of the cycler cover which provides additional advantages relevant for the module performance: - Pressing of PCR consumable into / against the thermal block to improve the contact between the two parts in order increase the heat transfer (cycler performance) - Reliable and repeatable positioning of the top heating in reference to the consumable to prevent changes in reaction volume and optical artifacts due to condensation -Reliable and repeatable positioning of the fiber ends very close to the reaction volume [0052] The Advantages of the invention can be summarized as follows: - Relative movements of main functional elements (e.g.heated lid) of the thermal cycler are possible for achieving high coupling efficiency between separable (and fiber-based) optical pathways - Design is very robust against mechanical / positioning tolerances - Small / compact size of ball lenses and according optical coupling interfaces / designs - Rotational symmetry provides advantages regarding mounting, positioning and alignment - Focal length of the ball lens is less sensitive to climatic / thermal conditions, ball lenses are more efficient for applications that are subject to significant variations in temperature - Higher system reliablility in comparision to other coupling designs or moved fibers [0053] Alternative approaches to realize or to circumvent the invention relate to: Different options for fiber-to-fiber coupling i. Direct coupling of fibers without other / additional optical elements Optical coupling via one ball lens only Optical coupling via half-ball / hemispherical lenses iv. Lensed optical fibers (LOF), fiber end with integrated / applied lens geometry (e.g. ball lens end or end with curvature) v Optical coupling via (ball) lens array vi Optical coupling via collimation and focusing lens (spherical or aspherical) vii. Optical coupling via gradient index (GRIN) lenses viii. Optical coupling via Fresnel lenses ix. Optical coupling via diffractive optical elements/ lenses Coupling between fiber and light guide - Coupling to cycler cover with integrated lens / mirror-based optical system Hinge with integrated ball lenses and fiber interfaces / mounting points [0054] The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment was chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.

Reference Numerals 1 ball lens 2 excitation fiber 3 emission fiber optical fiber 6 fiber end 7 top heater 8 cover/foil 9 PCR consumable 11 movable cycler cover 13 thermal block thermoelectric element 17 fan 18 housing 19 excitation unit detection unit 21 heat sink

Claims (5)

2. A coupling for optical elements, wherein the coupling comprises two optical ball lenes arranged next to each other and between two optical fibers arranged on both sides of the two ball lenses.
3. The coupling of claim 1, wherein each one of the two optical ball lenses comprise an adapter for fixation of the two optical fibers 3. The coupling of claim 2, wherein both other optical fibers of the two optical fibers connected to the two optical ball lenses are excitation fibers or light emitting fibers.
4. The coupling of any one of claims 1 to 3, wherein the two ball-lenses are separable arranged next to each other.
5. 5. A device comprising a coupling for optical elements of any one of claims 1 to 4 The device of claim 5, wherein a first part of the coupling comprises a first one of the two optical fibers and a first ball lens of the two ball lenses and a second part of the coupling comprises the other one of the two optical fibers and a second ball lens of the two ball lenses.The device of claim 6, wherein the first part is a movable cover, and the second part is a housing of an analytical or diagnostic device The device of any one of claims 5 to 7, wherein the analytical or diagnostic device is a therm ocycler The device of any one of claims 5 to 8, wherein an opposite end of an optical fiber to the end which is connected to a ball lens is either arranged next to a receptacle, a cover of a receptacle, an excitation unit or a detection unit.A method for coupling light from a first optical fiber into a second optical fiber, comprising the steps of - Connecting the first optical fiber to a first optical ball lens; - Connecting the second optical fiber to a second optical ball lens; - Arranging first and second optical ball lens next to each other sharing a common central optical axis.11 The use of a coupling according to any one of claims 1 to 4 or a device according to any one of claims 5 to 9 for coupling light from a first optical fiber into a second optical fiber.