Dispersive lens arrangement, microscope system, method of use and method of manufacture of the dispersive lens arrangement

Abstract

Aspects concern a dispersive lens arrangement comprising: a plurality of lenses, at least one of the plurality of lenses comprising a geometric parameter that is individually and independently adjustable; wherein an adjustment of the geometric parameter is configured to cause an axial dispersion of electromagnetic radiation passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the electromagnetic radiation passing through the plurality of lenses. A chromatic confocal microscope system utilizing the dispersive lens arrangement, a method of use, and a method of manufacture, are also disclosed.

Description

DISPERSIVE LENS ARRANGEMENT, MICROSCOPE SYSTEM, METHOD OF USE AND METHOD OF MANUFACTURE OF THE DISPERSIVE LENSARRANGEMENTCROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims the benefit of priority of Singapore patent application No. 10202402319S, filed on 2 August 2024, the content of it being hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The disclosure relates to a dispersive lens arrangement, a microscope system comprising the dispersive lens arrangement, method of use, and method of manufacture of the dispersive lens arrangement.BACKGROUND

[0003] The following discussion of the background is intended to facilitate an understanding of the present disclosure only. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known, or is part of the common general knowledge of the person skilled in the art in any jurisdiction as of the priority date of the di closure.

[0004] A dispersive lens is an optical lens that exhibits chromatic dispersion, that is, the optical lens refracts or bends different wavelengths (colors) of light by different amounts along an optical axis. This results in each wavelength focusing at a different position along the optical axis, leading to a separation of colors (spectral dispersion). Dispersive lenses arc often used in various applications where chromatic separation is required, such as chromatic confocal microscopy, chromatic confocal sensors, or displacement sensors.

[0005] In the utilization of dispersive lens to chromatic confocal microscopy related applications, the optical phenomenon of axial chromatic aberrations is typically made use of to achieve the said chromatic separation. However, dispersive lens arrangements may also result in lateral chromatic aberrations. The axial and lateral chromatic aberrations may be interrelated and increasing one may inevitably lead to an increase in the other.

[0006] A challenge exists in the development of a chromatic confocal technology that effectively utilizes axial dispersion to establish a relationship between spatial position and wavelength at the axial focal point, and to ensure that all fields within the region of interest (both on-axis and off-axis fields) are in good reasonable focus.

[0007] Accordingly, there exists a need to provide an improved solution to address the challenge, at least in part.SUMMARY

[0008] A technical solution comprising a dispersive lens arrangement specifically crafted to introduce axial chromatic aberration while minimizing all other optical aberrations, such as, but not limited to, lateral chromatic aberrations, is disclosed.

[0009] In some embodiments, the dispersive lens arrangement may be incorporated into a chromatic confocal system. In some embodiments, the dispersive lens arrangement can be inserted or incorporated into an infinity -corrected microscope system that aims to minimize all the other optical aberrations apart from axial chromatic aberration to achieve consistent and geometrically accurate depth measurements.

[0010] According to an aspect of the present disclosure, there is provided a dispersive lens arrangement including: a plurality of lenses, at least one of the plurality of lenses comprising a geometric parameter that is individually and independently adjustable; wherein an adjustment of the geometric parameter is configured to cause an axial dispersion of electromagnetic radiation passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the electromagnetic radiation passing through the plurality of lenses.

[0011] In some embodiments, the dispersive lens arrangement includes a first triplet lens arrangement, the first triplet lens arrangement comprising three lenses.

[0012] In some embodiments, the dispersive lens arrangement includes a second triplet lens arrangement, the second triplet lens arrangement comprising three further lenses.

[0013] In some embodiments, the first triplet lens arrangement and the second triplet lens arrangement comprise a total of eight optical surfaces.

[0014] In some embodiments, the dispersive lens arrangement further comprises one or more spacers separating the first triplet lens arrangement and the second triplet lens arrangement.

[0015] In some embodiments, the at least one of the plurality of lenses comprising the geometric parameter that is individually and independently adjustable is the third lens of the second triplet lens arrangement.

[0016] In some embodiments, the geometric parameter comprises at least one of a surface curvature and / or a thickness.

[0017] In some embodiments, the lens thickness of at least one of the lenses in the dispersive element is individually and independently adjustable. In particular, the lens thickness of the third lens of the second triplet lens arrangement may be individually and independently adjustable. In some embodiments, the lens thickness is adjustable in a range from 1 millimetres (mm) to 7 mm.

[0018] In some embodiments, wherein the geometric par ameter is the surface curvature, the surface curvature may be adjustable via a radius of curvature, the radius of curvature adjustable in a range from 26 mm to 31 mm.

[0019] In some embodiments, the at least one of the plurality of lenses is arranged or configured to be a primary source to cause axial chromatic aberration.

[0020] In some embodiments, one or more other lens of the plurality of lenses are configured to rectify a lateral chromatic aberration caused by the at least one of the plurality of lenses.

[0021] According to another aspect of the present disclosure there is provided a chromatic confocal microscope system comprising the dispersive lens arrangement as described, an objective lens configured to focus electromagnetic radiation passing through the dispersive lens arrangement into a sample; a detector; and a tube lens configured to direct the electromagnetic radiation reflected from the sample to the detector.

[0022] According to another aspect of the present disclosure there is provided a method for using the dispersive lens arrangement as described, the method comprising: adjusting the surface curvature of the at least one of the plurality of lenses; and / or adjusting a lens thickness of the at least one of the plurality of lenses.

[0023] In some embodiments, the dispersive lens arrangement includes a first triplet lens system comprising three lenses, and a second triplet lens arrangement comprising three further lenses.

[0024] In some embodiments, the method further comprises selecting the third lens of the second triplet lens arrangement for adjustment of the surface curvature and / or the lens thickness.

[0025] In some embodiments, the lens thickness is adjustable in a range from 1 millimeter (mm) to 7 mm.

[0026] In some embodiments, the adjustment of the surface curvature of the lens includes adjusting a radius of curvature of the surface of the lens, the radius of curvature adjustable in a range from 26 mm to 31 mm.

[0027] In some embodiments, the adjustment of the surface curvature and / or the lens thickness is performed dynamically during operation.

[0028] In some embodiments, the adjustment of the surface curvature and / or the lens thickness is performed dynamically during an optical design simulation.

[0029] According to another aspect of the present disclosure there is provided a method for manufacturing a dispersive lens arrangement comprising: providing a plurality of lenses, selecting at least one of the plurality of lenses comprising a geometric parameter that is individually and independently adjustable; and adjusting the geometric parameter of the selected at least one of the plurality of lenses such as to cause an axial dispersion of electromagnetic radiation passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the electromagnetic radiation passing through the plurality of lenses.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The disclosure will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:- FIG. 1 shows a dispersive lens arrangement according to various embodiments of the present disclosure.- FIG. 2A to FIG. 2D collectively illustrate the optical performance characteristics of the dispersive lens arrangement of FIG. 1, spanning visible wavelengths from 400 nanometers (nm) to 700 nm.- FIG. 3 illustrates a chromatic confocal microscope system incorporating the dispersive lens arrangement of FIG. 1.- FIG. 4A and FIG. 4B show the simulation results of adjusting a geometric parameter, in the form of the thickness, and the surface curvature, of a selected lens.- FIG. 5 is a flow chart of a method for adjusting the dispersive lens arrangement according to various embodiments of the present disclosure.- FIG. 6 is a flow chart of a method for manufacturing the dispersive lens arrangement according to various embodiments of the present disclosure.DETAILED DESCRIPTION roo3n The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure. Other embodiments may be utilized and structural, logical changes may be made without departing from the scope of the disclosure. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0032] Embodiments described in the context of one of the systems or methods are analogously valid for the other systems or methods.

[0033] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0034] In the context of some embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0035] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0036] As used herein, the term “at least substantially” may include “exactly” and a reasonable variance.

[0037] As used herein, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance.

[0038] As used herein, the term “processor” refers to, or forms part of, or include an Application Specific Integrated Circuit (ASIC); an electrical / electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a computer server (shared, dedicated, or group) that executes code; other suitable hardware components (e.g. controller) that provide the described functionality; or a combination of some or all of the above, such as in a systemon-chip. The term processor may include memory (shared, dedicated, or group) that stores code executed by the processor.

[0039] As used herein, the term “device” may be understood to refer to any apparatus, equipment, or component, whether standalone or integrated, that performs a specific function or set of functions. This includes, but is not limited to, mechanical, electrical, electronic, optical, or electromechanical systems, subsystems, and assemblies. A device may comprise one or more components, modules, or units that arc designed to interact with each other to achieve a particular- purpose.

[0040] As used herein, the term “configured to” broadly refers to the design, arrangement, or adaptation of a system, device, component, or module to perform a specific function or achieve a particular outcome. The term includes both hardware and softw are implementations wherein in a hardware implementation, the physical components are arranged, programmed, or structured to carry out the intended function(s), and in the context of programming and software, a device is operable under executable instructions (e.g., software, firmware) to perform the specified function(s) when executed by one or more processors. The resultant configuration allows the system or component to perform the stated function, either inherently or after suitable programming or activation, without requiring substantial modifications to its structure or operational logic.

[0041] As used herein, the term “triplet lens arrangement” may be a lens arrangement comprising three lens, the same can be adapted to maximize chromatic dispersion for use in chromatic confocal setups. In some embodiments, three selected glass types may be used to enhance chromatic axial dispersion of electromagnetic radiation, such as visible light, passing through the three lens. In some embodiments, the material of each of the lens in the triplet lens system may be carefully selected or designed, with each having tailored dispersive properties to create the required chromatic focal shift over one or more spectral range of interest.

[0042] In the following, embodiments will be described in detail.

[0043] FIG. 1 shows an embodiment of a dispersive lens arrangement 100 according to the present disclosure. The dispersive lens arrangement 100 may include a plurality of lenses 110A, HOB, HOC, HOD, HOE, HOF, at least one of the plurality of lenses 1 10F comprising a geometric parameter that is individually and independently adjustable.

[0044] The adjustment of the geometric parameter may be based on the principle to cause an axial dispersion of visible light passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the visible light passing through the plurality of lenses.

[0045] The dispersive lens arrangement 100 shown in FIG. 1 comprises a first triplet lens arrangement 120, and a second triplet lens arrangement 130. The first triplet lens arrangement 120 comprises three lenses 110A, 110B, HOC. The dispersive lens arrangement 100 also includes a second triplet lens arrangement 130, the second triplet lens arrangement 130 comprising three further lenses 110D, 110E, 110F.

[0046] The first triplet lens arrangement 120 and the second triplet lens arrangement 130 comprise a total of eight optical surfaces. The lens in the first triplet lens arrangement 120 and the lens in the second triplet lens arrangement 130 may be configured or selected based on an optimization of surface curvatures and material properties of each of the plurality of lenses 110A, HOB, HOC, 110D, 110E, 110F. In some embodiments, the glass type or glass types of each of the plurality of lenses 110A, 110B, HOC, HOD, 110E, 110F may be selected and paired based on each of their refractive index and Abbe number to control how each lens contributes to chromatic separation. The optical surfaces may be oriented and spaced to balance axial dispersion and lateral aberration effects while preserving overall image quality. This approach allows for design flexibility while maintaining performance, and is central to achieving a scalable dispersion tuning.

[0047] In some embodiments, the dispersive lens arrangement 100 may further comprises one or more spacers 150 separating the first triplet lens arrangement 120 and the second triplet lens arrangement 130. Such one or more spacers 150 may be included to adjust the overall magnification, working distance, and / or field of view.

[0048] The at least one of the plurality of lenses comprising the geometric parameter that is individually and independently adjustable may be the third lens 110F of the second triplet lens arrangement 130. The geometric parameter that is adjustable may be at least one of a surface curvature and / or a thickness parameter of the lens 110F.

[0049] In some embodiments, the lens thickness of the at least one of the plurality of lenses 110F in the dispersive element is individually and independently adjustable. In particular, the lens thickness (denoted as ‘T’ in FIG. 1) of the third lens 1 1 OF of the second triplet lens arrangement 130 may be individually and independently adjustable. In some embodiments, the lens thickness T is adjustable in a range from 1 millimeters (mm) to 7 mm.

[0050] In some embodiments, wherein the geometric parameter is the surface curvature, the surface curvature may be adjustable via a radius, also referred to as the radius of curvature, the radius of curvature (denoted as ‘R’ in FIG. 1) adjustable in a range from 26 mm to 31 mm.

[0051] In some embodiments, the at least one of the plurality of lenses 110F is arranged or configured to be a primary source to cause axial chromatic aberration.

[0052] In some embodiments, one or more other lens of the plurality of lenses are configured to rectify a lateral chromatic aberration caused by the at least one of the plurality of lenses 110F.

[0053] In some embodiments, the selection of glass matcrial(s) for each of the plurality of lenses 110A, HOB, HOC, 110D, 110E, and 110F will be based on a measure of a transparent material's dispersion of light. The measure may be an Abbe number, a V-number, or constringence.

[0054] In some embodiments, by selecting transparent materials (e.g. glass) with lower Abbe number, which corresponds to transparent materials that exhibit higher dispersion, axial chromatic aberration can be induced in the design of the dispersive lens arrangement 100. Through a suitable combination of different glass types having different Abbe number, the design of the dispersive lens arrangement 100 can be optimized to produce a chromatic focal shift that is linear with the wavelength. For example, the first triplet lens arrangement 120, which comprises three lens 110A, 110B, 110C, may be a combination of a low-dispersion glass (e.g. glass types D-FK61-25 and H-LAF54) for reducing other aberrations, such as lateral color aberration or spherical aberration. The curvature and spacing of the first triplet lens arrangement 120 may be adj u stab le / optimized to maintain collimation. The second triplet lens arrangement 130, which comprises three lens 110D, 110E, 110F, may be configured to produce higher dispersion than the first triplet lens arrangement 120. The second triplet lens arrangement 130 may be configured to exhibit relatively higher refractive index and relatively lower Abbe number (e.g. glass types LASF35 and H-ZLAF92) so as to provide a chromatic focal shift. A crown-type glass, such as glass type H-QK1, may also be employed to controlbeam profile uniformity and suppress lateral chromatic aberration. The curvatures and spacing of the second triplet lens arrangement 130 may be optimized to keep the dispersion predominantly along the axial direction.

[0055] In some embodiments, in addition to causing axial dispersion and reducing lateral chromatic aberration, the dispersive lens arrangement 100 may be configured to correct one or more other forms of optical aberrations, including, but not limited to, spherical aberration, at each imaging plane. The correction may be accomplished by precisely designing or adjusting one or more of the lenses 1 10, such that the path of electromagnetic radiation (e.g. visible light) across a range of wavelengths may be modified to minimize the degree of aberration present at the corresponding imaging surface.

[0056] As a result, for each wavelength of electromagnetic radiation utilized by the system, the image of a point source remains as nearly focused (i.c., confined in size) as possible at the respective, intended location on the imaging plane. In some embodiments, one or more of the following quantitative metrics may be employed:

[0057] Spot size: The diameter or area where the majority of electromagnetic radiation from a point source focuses on the imaging plane. In some embodiments, the spot size may be quantified as a root-mean-square (RMS) or a geometric spot size. The spot size may be used to represent how tightly the optical system can focus light and is a metric of resolution.

[0058] Modulation transfer function (MTF): MTF quantifies how well an optical system preserves image contrast at different spatial frequencies. MTF is calculated or measured for multiple spatial frequencies and wavelengths to evaluate system resolution. Design changes may be iteratively introduced to optimize MTF performance within application-specific requirements, for example, by maximizing MTF values within the range required by the application, across all relevant wavelengths.

[0059] Seidel aberration values: Each of the five classical Seidel aberrations — spherical aberration, coma, astigmatism, field curvature, and distortion — may be quantified during simulation and design to assess system performance. Tolerance analyses may be used to ensure these values remain within predefined acceptable limits, such as acceptable design limits under manufacturing variation.

[0060] The spot size, MTF, and seidel aberrations values may be used as the evaluation criteria in the design optimization process.

[0061] In some embodiments, the lens 110F having a geometric parameter that is adjustable may be a single lens, or more than one lens, or may be a composite lens. In some embodiments, the lens 1 10F may be a smart or adaptive lens, with at least one geometric parameter, such as curvature or thickness, being adjustable. In some embodiments, the smart lens may be equipped with, or may be arranged in data communication with a controller or processor, or may be operatively coupled to a controller or processor, to adjust the geometric parameter dynamically in operation.

[0062] In some embodiments, the lens 11 OF may include aspheric lens, variable lens groupings, or adaptive optical elements that can be adjusted through either mechanical, electro- optical, or software control methods to correct aberrations dynamically or in a predetermined configuration.

[0063] Spherical aberration and potentially other Seidel aberrations (coma, astigmatism, field curvature, distortion) may be assessed and reduced during both the design and assembly process of the optical system, cither by ray tracing methodologies, optimization algorithms, or empirical fine-tuning. In some embodiments, the aberration analysis may include identifying surfaces contributing significantly to lateral chromatic aberration via optical analysis tools such as Seidel diagrams. Once identified, these surfaces are re-optimized to reduce their contribution, either through changes in curvature, thickness, or substitution with glass types of different Abbe numbers or partial dispersions.

[0064] At each imaging plane, corrective efforts ensure that the wavefront error for each wavelength is minimized within the required tolerance for intended imaging performance.

[0065] In some embodiments, one or more additional lens may be added to the dispersive lens arrangement 100. The one or more additional lens may provide more optical surfaces made available for aberration balancing, compensation, and correction.

[0066] FIG. 2A to FIG. 2D collectively illustrate the optical performance characteristics of the dispersive lens arrangement 100, spanning visible wavelengths from 400 nm to 700 nm.

[0067] FIG. 2A illustrates a full-field dispersion effect in area-based imaging, in the form of a ray-tracing diagram. The ray-tracing diagram visualizes how electromagnetic radiation, in the form of visible light, across multiple wavelengths (indicated by various shades 201 , 202, 203 etc.) propagates through the optical system. The spread of the rays demonstrates the dispersion effect occurring at the system's full field, highlighting the need for aberration correction and control to maintain image fidelity across the field of view.

[0068] FIG. 2B shows a graph depicting axial linearity over 400 nanometres (nm) to 700 nm wavelength range. The graph plots the axial, or longitudinal, chromatic focal shift as a function of wavelength within the working range of 400 nm to 700 nm. The relatively linear relationship indicates the dispersive lens arrangement’s ability to maintain focus across the full spectrum. The minimal deviation confirms that axial color correction strategies are effective.

[0069] FIG. 2C indicates the spot size diagrams for on-axis and off-axis fields across the entire field-of-view (FOV). This set of spot size diagrams quantify the performance at multiple field positions (both on-axis and off-axis) across the entire FOV. The compact spot sizes, with profiles shown to be closely confined and nearly circular, demonstrate that the aberration correction ensures the system is diffraction-limited across the field. Achieving relatively small spot sizes at all field points is evidence of superior correction of both monochromatic and chromatic aberrations.

[0070] FIG. 2D shows a modulation transfer function (MTF) plot for diffraction-limited quality. The MTF plot displays the modulation transfer function as a function of spatial frequency. The high MTF values at low and intermediate spatial frequencies, progressively tapering off at higher frequencies, are consistent with diffraction-limited performance. The overlap of the measured (or calculated) MTF with the theoretical diffraction limit indicates that the imaging system preserves fine image details up to the physical limits imposed by diffraction.

[0071] Together, the figures FIG. 2A to FIG. 2D establish that the optical design of the dispersive lens arrangement 100 may be optimized for various applications, including, but not limited to, broadband, high-resolution imaging, achieving tight chromatic focus, minimal aberrations, and high imaging quality both on-axis and off-axis throughout the full field of view.

[0072] The dispersive lens arrangement 100 is shown to obtain good axial linearity in the working wavelength range of 400 nm to 700 nm with the imaging quality reaching diffraction limit.

[0073] It may be appreciable that the dispersive lens arrangement 100 may be designed to be incremental. In some embodiments, the dispersion range can be altered by modifying one of its lens surfaces. More specifically, by adjusting the lens thickness T of one of the lenses (e.g. the lens 1 10F), in the dispersive element, the axial chromatic aberration can be increasedincrementally without significant impact on the overall optical performance of the dispersive lens arrangement 100.

[0074] FIG. 3 illustrates a chromatic confocal microscope system 300. The chromatic confocal microscope system 300 comprises the dispersive lens arrangement 100, an objective lens 310 configured to focus the visible light 390 passing through the dispersive lens arrangement into a sample 1000; a detector 320; and a tube lens 330 configured to direct the visible light reflected from the sample 1000 to the detector 320. The visible light 390 may be directed from a light source (not shown).

[0075] In some embodiments, the lens surface of the lens 110F may be specially designed to be the major contributor of axial chromatic aberration. Other optical aberrations were corrected and compensated by the other optical surfaces in the dispersive element.

[0076] It may be appreciable that the variation and adjustments of the geometric parameters) of the lens 110F, i.e. the third lens element of the second triplet lens arrangement 130, may affect the performance of the dispersive lens arrangement.

[0077] FIG. 4A shows the simulation result when the thickness of the lens 110F is varied between 1 mm to 7 mm. The optimal axial dispersion of 304.85 pm is achieved while other forms of optical aberrations are minimized. The thickness corresponding to the optimal axial dispersion is 3 nun. The corresponding depth measurement may range between 1 pm to 300 pm.

[0078] FIG. 4B shows the simulation result when the radius of curvature R of the lens 110F is varied between 26 mm to 31 mm. The optimal axial dispersion of 304.85 pm is achieved while other forms of optical aberrations are minimized. The radius of curvature R corresponding to the optimal axial dispersion of 304.85 pm is 27.6 mm.

[0079] It may be appreciable that the simulation of how the lens will perform under varying environmental conditions may be used to obtain design parameters, such as focal point of lens design. In this context, the need for traditional experimentation may be eliminated because the simulation itself may function as the experiment. In some embodiments used in the creation of commercial optical systems, software tools like Zcmax may be used. These software tools may be configured to provide modeling, analysis, and optimization of the performance of complex optical systems in a virtual environment before physical prototyping.

[0080] In particular, Zemax specializes in lens design, optical system simulation, and ray tracing. It may be used in imaging, medical devices, aerospace, and consumer electronics.Zemax may be configured to emulate a wide range of environmental conditions, such as temperature, humidity, and mechanical tolerances, for creating high-fidelity virtual prototypes. Additionally, it offers a robust experimental framework, allowing for detailed exploration and optimization of lens configurations.

[0081] It may be appreciable that lens characteristics may be meticulously identified and evaluated via simulation, thus achieving time efficiency. This includes critical parameters such as data analysis, resolution, aberration, focal length, and transmission - aspects that would typically require experimental methods to ascertain. The incremental adjustment and isolation to a lens (e.g. lens 110F) for adjustment is such that once an adjusted geometric parameter is aligned with the simulation's outcomes and meets the desired criteria, it may be primed for manufacturing, with no necessity for additional experimentation or verification using alternative software tools. The streamlined approach may accelerate the design process and enhances the precision, ensuring that the final product conforms closely to the intended technical specifications.

[0082] In some embodiments, an additional element can be introduced into any infinity- corrected microscope system to induce axial chromatic effects for depth measurements without affecting the overall optical performance of the confocal microscope.

[0083] It may be appreciable that the incremental dispersive element design based on the identification and isolation of a lens (e.g. lens 110F) may be used to achieve smaller or larger dispersion range based on application requirements. More specifically, by adjusting the lens thickness of one of the lenses in the dispersive element, the axial chromatic aberration can be increased incrementally without significant impact on the overall optical performance of the chromatic confocal microscope system. This lens surface was specially designed to be the major contributor of axial chromatic aberration.

[0084] In some embodiments, a set of interchangeable lens elements associated with the adjustable lens 11 OF can be fabricated with identical surface geometry but different center thicknesses (e.g., 1 mm, 3 mm, 5 mm, 7 mm).

[0085] By swapping only the lens 110F, the axial chromatic dispersion range can be incrementally tuned (e.g., from 219 pm to 508 pm) while maintaining high image quality and minimal lateral chromatic aberration.

[0086] Such an approach may provide a method for system customization without requiring full optical redesign, thus providing a straightforward, modular route to scalability — supporting different system use cases with minimal redesign.

[0087] It may be appreciable that without the modular, scalable approach, any change in dispersion range would necessitate a complete re-design of all six lenses (i.e., both triplets) — which may be a highly time-consuming and resource-intensive process. The present disclosure seeks to isolate dispersion control to a single lens component, enabling flexibility and scalability while preserving optical performance.

[0088] It may be appreciable that a dispersive element design that induces only axial chromatic effects while minimizing lateral chromatic effects and other optical aberrations- achieved through (a) the identification of major contributors of lateral chromatic aberrations coupled together with re-optimization of the surface curvature, lens thickness or the glass material of these surfaces while introducing design constraints that limit these surfaces from further increasing their lateral chromatic aberration; (b) introduction of new surfaces that corrects the lateral chromatic aberration of the current design through the proper selection of appropriate glass material based on its Abbe number and refractive index together with further optimization for aberration correction and balancing. Where lateral chromatic effects cannot be minimized through re-optimization alone, one or more new corrective surfaces (e.g. additional lens) may be introduced into the optical path. These are designed to produce opposing (negative) lateral chromatic aberrations that offset those of the original system. The glass material and refractive index are carefully chosen to balance aberrations without degrading image quality. By way of example, Table 1 below provides a set of refractive indices and Abbe number for each optical surface of the first triplet lens arrangement 120 and the second triplet lens arrangement 130. Table 1 also include the “type of surface” which refer to the mathematical model that defines the shape and optical behavior of the surface in the lens system, and may include, for example, a standard (spherical) surface characterized by a single radius of curvature. The “Radius” in Table 1 denotes the surface radius of curvature (i.e., the inverse of curvature). The “Thickness” in Table 1 represents the axial distance between the vertex of the current surface and the vertex of the subsequent surface. The “Mechanical Semi-Diameter” in Table 1 corresponds to the physical extent of the optical element, including areas that may not be part of the clear aperture and might be used for mounting or other purposes. The “Clear' Semi -Di meter” in Table 1 refers to the radius of the area on an opticalsurface through which light rays are allowed to pass. The “Radius”, “Thickness”, “Mechanical Semi-Diameter” and “Clear Semi -Diameter” may each be expressed in lens unit, which define the length measurement used for all dimensional parameters in the optical system. The lens unit may be specified, for example, in millimeters (mm), centimeters (cm), inches (in) or meters (m). For the purposes of Table 1, millimeters are used.

[0089] [Table 1]

[0090] According to another aspect of the present disclosure and with reference to FIG. 5, there is provided a method 500 for using the dispersive lens arrangement, the method comprising the steps of:

[0091] Step S501: adjusting the surface curvature of the at least one of the plurality of lenses; and / or adjusting a lens thickness of the at least one of the plurality of lenses.

[0092] In the case where the dispersive lens arrangement comprises the first triplet lens arrangement and the second triplet lens arrangement: -

[0093] Step S502: selecting the third lens of the second triplet lens arrangement for adjustment of the surface curvature and / or the lens thickness.

[0094] In some embodiments, the step S501 includes adjusting the surface curvature of at least one of the lenses, specifically the third lens element 110F of the second triplet lens arrangement 130.

[0095] In some embodiments, the step S502 includes adjusting the lens thickness, specifically the center thickness of a designated lens element, e.g. lens 110F.

[0096] According to another aspect of the present disclosure there is provided a method 600 for manufacturing a dispersive lens arrangement comprising the steps of:

[0097] Step S601: providing a plurality of lenses,

[0098] Step S602: selecting at least one of the plurality of lenses comprising a geometric parameter that is individually and independently adjustable; and

[0099] Step S603: adjusting the geometric parameter of the selected at least one of the plurality of lenses such as to cause an axial dispersion of electromagnetic radiation passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the electromagnetic radiation passing through the plurality of lenses.

[0100] In some embodiments, the manufacture of the dispersive lens arrangement 100 may be performed using established precision optical fabrication processes. The lenses 110A, 110B, 110C, 110D, 110E, and 110F may be manufactured via standard optical grinding and polishing methods. For scalability, the adjustable dispersive element or lens 110F (e.g., the third lens in the second triplet) can be fabricated in variants with different center thicknesses or curvature radii (e.g., radius of curvature ranging from 26 mm to 31 mm) to produce specific dispersion ranges.

[0101] In some embodiments, the two triplet groups, i.e. the first triplet lens arrangement 120, and the second triplet lens arrangement 130, can be assembled separately and joined with a fixed air gap using precision spacers 150. Such a modular approach may simplify alignment and offers flexibility in scaling production. The lenses may be mounted using opto-mechanical holders with alignment tolerances optimized for minimal sensitivity. The system tolerancing may be designed to remain robust even with slight deviations in spacer distance.

[0102] It may be appreciable that the present disclosure seeks to provide a dispersive lens arrangement that isolates dispersion contribution to a specific surface or element. The design localizes the contribution to axial dispersion within a designated lens element, e.g. lens 110F, allowing for adjustments (e.g., in center thickness or curvature) to vary the dispersion range without disturbing the overall optical performance or introducing additional lateral chromatic aberration.

[0103] It may be appreciable that constraints and multi-configuration optimization may be applied to ensure that adjustments made to increase axial dispersion (e.g., increased thicknessor surface curvature) do not lead to unacceptable increases in off-axis aberrations (coma, field curvature, etc.). A multi-configuration optimization strategy across wavelength and field points ensures uniform image quality and spot size across the full FOV.

[0104] While the disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims. The scope of the disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1 . A dispersive lens arrangement comprising: a plurality of lenses, at least one of the plurality of lenses comprising a geometric parameter that is individually and independently adjustable; wherein an adjustment of the geometric parameter is configured to cause an axial dispersion of electromagnetic radiation passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the electromagnetic radiation passing through the plurality of lenses.

2. The dispersive lens arrangement according to claim 1, further comprising a first triplet lens arrangement, the first triplet lens arrangement comprising three lenses.

3. The dispersive lens arrangement according to claim 2, further comprising a second triplet lens arrangement, the second triplet lens arrangement comprising three further lenses.

4. The dispersive lens arrangement according to claim 3, wherein the first triplet lens arrangement and the second triplet lens arrangement comprises a total of eight optical surfaces.

5. The dispersive lens arrangement according to claim 3 or 4, further comprising one or more spacers separating the first triplet lens arrangement and the second triplet lens arrangement.

6. The dispersive lens arrangement according to any one of claims 1 to 5, wherein the at least one of the plurality of lenses comprising the geometric parameter that is individually and independently adjustable is the third lens of the second triplet lens arrangement.

7. The dispersive lens arrangement according to any one of claims 1 to 6, wherein the geometric parameter comprises at least one of a surface curvature and / or a lens thickness.

8. The dispersive lens arrangement according to claim 6 or 7, wherein the lens thickness of at least one of the lenses in the dispersive element is individually and independently adjustable.

9. The dispersive lens arrangement according to claim 8, wherein the lens thickness of the third lens of the second triplet lens arrangement may be individually and independently adjustable.

10. The dispersive lens arrangement according to claim 9, wherein the lens thickness is adjustable in a range from 1 millimeter (mm) to 7 mm.

11. The dispersive lens arrangement according to any one of claims 7 to 10, wherein the geometric parameter is the surface curvature, the surface curvature may be adjustable via a radius of curvature, the radius of curvature adjustable in a range from 26 mm to 31 mm.

12. The dispersive lens arrangement according to any one of claim 1 to claim 11, wherein the at least one of the plurality of lenses is arranged or configured to be a primary source to cause axial chromatic aberration.

13. The dispersive lens arrangement according to claim 12, wherein one or more other lens of the plurality of lenses are configured to rectify a lateral chromatic aberration caused by the at least one of the plurality of lenses.

14. A chromatic confocal microscope system comprising the dispersive lens arrangement of any one of claims 1 to 13, an objective lens configured to focus electromagnetic radiation passing through the dispersive lens arrangement onto a sample; a detector; and a tube lens configured to direct the electromagnetic radiation reflected from the sample to the detector.

15. A method for using the dispersive lens arrangement according to any one of claim 7 to claim 13, the method comprising: adjusting the surface curvature of the at least one of the plurality of lenses; and / or adjusting the lens thickness of the at least one of the plurality of lenses.

16. The method according to claim 15, wherein the dispersive lens arrangement includes a first triplet lens system comprising three lenses, and a second triplet lens arrangement comprising three further lenses.

17. The method according to claim 16, further comprising selecting the third lens of the second triplet lens arrangement for adjustment of the surface curvature and / or the lens thickness.

18. The method according to claim 17, wherein the lens thickness is adjustable in a range from 1 millimeter (mm) to 7 mm.

19. The method according to claim 18, wherein the adjustment of the surface curvature of the lens includes adjusting a radius of curvature of the surface of the lens, the radius of curvature adjustable in a range from 26 mm to 31 mm.

20. The method according to any one of claim 15 to claim 19, wherein the adjustment of the surface curvature and / or the lens thickness is performed dynamically during operation.

21. The method according to any one of claim 15 to claim 19, wherein the adjustment of the surface curvature and / or the lens thickness is performed dynamically during an optical design simulation.

22. A method of manufacturing a dispersive lens arrangement comprising: providing a plurality of lenses, selecting at least one of the plurality of lenses comprising a geometric parameter that is individually and independently adjustable; and adjusting the geometric parameter of the selected at least one of the plurality of lenses such as to cause an axial dispersion of electromagnetic radiation passing through the plurality of lenses; and at least partially correct for or reduce a lateral chromatic aberration of the electromagnetic radiation passing through the plurality of lenses.

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