Light source assembly, optical fiber atomic absorption spectrometer and double-beam optical fiber atomic absorption spectrometer

Abstract

A light source assembly for a fiber optic atomic absorption spectrometer, the light source assembly comprising: a plurality of light sources arranged about an axis; an arm arranged to rotate about the axis; an optical cable; a focusing element configured to couple light from a selected light source of the plurality of light sources into one end of the optical cable; wherein the optical cable and the focusing element are arranged on the arm such that the arm can rotate with respect to the plurality of light sources in order to select a light source for the optical cable. The invention further relates to an optical fiber atomic absorption spectrometer and a double-beam optical fiber atomic absorption spectrometer.

Description

[0001] This application is a divisional application of a patent application with an application date of May 24, 2019, application number 201980035931.6 (international application number PCT / EP2019 / 063469), and invention name “Atomic Absorption Spectrometer”. Technical Field

[0002] The present invention relates to spectroscopy. In particular, the present invention relates to atomic absorption spectroscopy (AAS) and apparatus for performing AAS. Background Art

[0003] The technique of AAS relies on the following principle: electrons of elements in atomic form have discrete energy levels and will absorb specific wavelengths of energy corresponding to those discrete energy levels. Each atomic element has a unique arrangement of discrete electron energy levels. Therefore, the wavelength or wavelengths of light absorbed by the atoms will indicate the discrete energy levels and can be used to identify the specific element. Furthermore, the amount of light absorbed is proportional to the number of atoms present, and therefore the amount of atoms present can also be determined.

[0004] A typical AAS system includes a light source for providing light of known wavelength, an atomizer for atomizing the sample to be measured, a monochromator, and a light detector.

[0005] Typically, the light source is a hollow cathode lamp (HCL). The HCL is typically composed of a glass tube containing a cathode, an anode, and a buffer gas (typically an inert gas). Applying a large voltage across the anode and cathode will ionize the buffer gas, thereby generating a plasma. The cathode can be composed of the element to be analyzed in the AAS measurement. Then, the buffer gas ions will be accelerated into the cathode, thereby sputtering atoms from the cathode. The electrons of both the buffer gas ions / atoms and the sputtered cathode ions / atoms will then be excited by colliding with other particles in the plasma. When these excited electrons subsequently drop to a lower state, the excited electrons will emit photons with a wavelength specific to the element to be analyzed in the AAS measurement.

[0006] The light emitted from the HCL source can pass through an atomizer containing the atomized sample to be analyzed, where a portion of the light is absorbed. The light that is not absorbed by the atomized sample is then filtered by a monochromator to separate the wavelength or wavelengths of interest for the element to be detected from other wavelengths. The resulting light signal is focused on a photodetector to measure the signal.

[0007] To improve the accuracy of AAS measurements, a secondary light source is often used together with an element-specific HCL light source. For example, the secondary light source can be a deuterium lamp that produces light with a continuous broadband spectrum, typically in the range of 180 nm to 370 nm. The effects of background absorbance in analytical measurements can be corrected by first measuring the atomized sample with a hollow cathode lamp to determine the analyte plus background signal, and subsequently using a broadband light source to determine only the background signal.

[0008] Another source of error in AAS measurements can be caused by variations in the light intensity produced by the HCL and deuterium light sources. Typically, a portion of the light from each light source is not directed through the sample and is measured at the detector as a reference beam in order to improve the accuracy of the AAS measurement. Such AAS systems are often referred to as dual-beam (sample beam and reference beam) spectrometers.

[0009] Known AAS systems typically use a series of mirrors and lenses to transmit light from a light source through an atomizer and a monochromator to a detector. Figure 1 A schematic diagram of a typical double beam spectrometer known in the prior art is shown. A double beam spectrometer uses a chopper to transfer the light source between the reference beam path and the sample beam path. The chopper is essentially a circular reflector with many segments (usually 4) cut around the circumference. When the beam is aligned with the cut-off segment, the beam passes along the sample beam path to the flame. When the beam is aligned with the remaining reflective segment on the reflector, the beam is reflected around the flame and becomes the reference beam.

[0010] The beam combiner combines the two paths together to focus on the monochromator. The beam combiner can be a circular mirror with a series of holes in it. The sample beam can pass through the holes in the mirror, while the reference beam is reflected via the mirror surface of the beam combiner.

[0011] Known double beam spectrometers include Figure 1 The exemplary system shown includes multiple mirrors and focusing lenses to transmit light from one or more light sources through the sample and the monochromator to the detector. Such systems using multiple optical components are highly sensitive to small changes in the relative alignment of these components. Small changes in the translational or rotational position of one or more optical components (e.g., mirrors) may introduce errors in the alignment of downstream optical components, thereby reducing signal strength and / or increasing noise in the measurement system. Therefore, such optical systems generally require calibration of the relative alignment of the optical components to ensure that the system operates as expected.

[0012] WO 2011 / 062630 discloses a photon measurement instrument using non-solarizing fibre optics. A set of optical cables is used to guide light from one or more light sources to each of at least two analysis chambers of a sample holding module. Another set of optical fibres is used to guide light from the analysis chamber to a detector. Summary of the invention

[0013] According to a first aspect of the present invention, an adjustable slit mechanism for a monochromator is provided. The adjustable slit mechanism comprises a first slit member and a second slit member, the first slit member comprising a first slit edge, the second slit member comprising a second slit edge, wherein the first slit edge is arranged relative to the second slit edge to define an adjustable slit of the adjustable slit mechanism. The adjustable slit mechanism also comprises a slit adjustment cam having a variable radius. Further, a first arm is connected to the first slit member, and a second arm is connected to the second slit member. The first arm and the second arm are biased against the slit adjustment cam, so that the rotation of the slit adjustment cam causes the first arm and the second arm to be adjustably separated to adjust the width of the adjustable slit.

[0014] Thus, an adjustable slit mechanism is provided, which is configured to adjust the slit width (i.e., the opening between the first slit edge and the second slit edge) of the monochromator. By means of controlling the slit width by rotating a cam having a variable radius, the slit width can be repeatedly and accurately adjusted to a desired width by controlling the rotational position of the slit adjustment cam. Advantageously, the adjustable slit mechanism according to the present invention can adjust the position of the first slit edge and the second slit edge because both the first arm and the second arm are biased against the slit adjustment cam. Therefore, the position of the slit center can be accurately controlled according to the variable radius of the slit adjustment cam.

[0015] In a particularly preferred embodiment, the variable radius of the slit adjustment cam is configured to adjust the separation of the first arm and the second arm by moving each of the first arm and the second arm substantially equally. In this way, the center of the slit can be maintained in substantially the same position for a plurality of different slit sizes. Therefore, the center of the slit can be maintained in a central position of the sample light path and / or the reference light path for a range of different slit sizes without requiring any additional calibration of the sample light path or the reference light path between adjustments to the slit. In this way, the adjustable slit mechanism can be incorporated into a robust fiber optic AAS system with minimal calibration.

[0016] Preferably, the point at which the first arm abuts against the slit adjustment cam offset is opposite to the point at which the second arm abuts against the slit adjustment cam offset. In this way, a change in the diameter of the slit adjustment cam can be used to adjust the separation of the first arm from the second arm. Such adjustment of the separation of the first arm from the second arm can provide a corresponding adjustment of the separation of the first slit edge from the second slit edge (i.e., adjustment of the slit width). Thus, a mechanically robust system for adjusting the slit width of a monochromator can be provided.

[0017] A resilient biasing element may be provided, the resilient biasing element being connected between the first arm and the second arm to bias the first arm and the second arm against the slit adjustment cam. By elastically biasing the first arm and the second arm together, the relative position of the first arm and the second arm can be accurately positioned against the slit adjustment cam, so that the separation of the first arm and the second arm is accurately controlled by rotating the slit adjustment cam. Preferably, a pair of resilient biasing elements are connected between the first arm and the second arm. The pair of resilient biasing elements are respectively connected to the first arm and the second arm at the two side points and the arms contact the slit adjustment cam at the points of their respective connection sides. Such an arrangement improves the stability of the adjustable slit assembly because the pair of resilient biasing elements provide resistance to the relative rotation of the first arm or the second arm around the slit adjustment cam.

[0018] Preferably, each of the first arm and the second arm is supported by a plurality of guide members configured to align the first slit edge parallel to the second slit edge. For example, the guide members may be provided by positioning washers configured to support and position the first arm and the second arm.

[0019] Preferably, each of the first arm and the second arm comprises an alignment portion, each alignment portion being configured to engage with a plurality of guide members. Thus, when modifying the slit width of the adjustable slit, the alignment portions of the first arm and the second arm are positioned to prevent relative rotation of the first slit edge and the second slit edge when in contact with the guide members. In this way, the alignment portions of the first arm and the second arm restrict movement of the respective arms to a single axis of movement. Thus, the width of the adjustable slit can be accurately controlled for a range of different slit widths.

[0020] Preferably, the first and second arms each include a cam engagement portion, each cam engagement portion being configured to provide a surface that engages with the slit adjustment cam. The cam engagement portion may further preferably be composed of a sliding bearing material, or may include a component composed of a sliding bearing material, which is integrated into the cam engagement portion, thereby providing a surface that engages with the slit adjustment cam. In particular, cast iron and babbitt can be used as sliding bearing materials. The use of sliding bearing materials to provide a surface that engages with the slit adjustment cam can reduce the friction between the surface and the slit adjustment cam, thereby reducing the wear on the slit adjustment cam over time. This is particularly advantageous because the increase in wear on the slit adjustment cam over time will reduce the accuracy of the adjustable slit mechanism.

[0021] Also in a preferred embodiment, the slit adjustment cam may consist of a sliding bearing material, or may include at least one component, in particular two components, consisting of a sliding bearing material integrated into the slit adjustment cam, thereby providing a surface that engages with the cam engagement portion of the first arm and the second arm. In particular, cast iron and babbitt alloys may be used as sliding bearing materials. Providing a surface that engages with the cam engagement portion of the first arm and the second arm using a sliding bearing material may reduce friction between the surface and the cam engagement portion of the first arm and the second arm, thereby reducing wear on the cam engagement portion of the first arm and the second arm over time. This is particularly advantageous because increased wear on the cam engagement portion of the first arm and the second arm over time may reduce the accuracy of the adjustable slit mechanism.

[0022] Preferably, each cam engagement portion is configured to engage with the slit adjustment cam in a plane substantially parallel to the first slit edge and the second slit edge. Thus, any adjustment of the separation of the cam engagement portions by rotating the slit adjustment cam will be directly reflected in an equivalent adjustment of the separation of the first slit edge and the second slit edge. In this way, a robust but highly accurate adjustable slit mechanism can be provided.

[0023] In a particularly preferred embodiment, the cam engaging portion and the alignment portion of each of the first arm and the second arm are connected to form a substantially L-shaped portion.

[0024] Preferably, the first slit edge and the second slit edge of the adjustable slit are configured to provide an entrance slit and an exit slit for the monochromator. Thus, both the width of the entrance slit and the width of the exit slit can be adjusted using a single mechanism, thereby improving the robustness of the monochromator while also reducing manufacturing costs.

[0025] Preferably, the first slit member and the second slit member are connected to the first arm and the second arm respectively by fasteners. As such, the first slit member and the second slit member can be formed of different materials and / or by different manufacturing methods compared to the first arm and the second arm and subsequently coupled together. For example, a relatively high accuracy forming method can be used to manufacture the first slit edge and the second slit edge of the first slit member and the second slit member, respectively, while an alternative manufacturing technique can be used to form the first arm and the second arm. Of course, in some embodiments of the present invention, the first slit member and the first arm can be formed from the same body using the same manufacturing technique.

[0026] Preferably, the first slit edge and the second slit edge are each vertically aligned. Therefore, gravity acting on the first slit member and the second slit member may not cause the relative alignment of the first slit edge and the second slit edge to change over time. Therefore, a stable adjustable slit mechanism is provided.

[0027] Preferably, the adjustable slit of the adjustable slit mechanism according to the first aspect is adjustable within a range of 0.025 mm to 2 mm, or more preferably within a range of 0.025 mm to 0.5 mm.

[0028] According to a second aspect of the present invention, a slit assembly (monochromator slit assembly) for a monochromator of a fiber atomic absorption spectrometer is provided. The slit assembly comprises: a sample optical fiber for conveying sample light; a reference optical fiber for conveying reference light; and a slit of the monochromator. One end of each of the sample optical fiber and the reference optical fiber is arranged to guide light through the slit along the respective sample optical path and reference optical path. The slit assembly also comprises: a rotatable chopper, the rotatable chopper is arranged downstream of the entrance slit, and the rotatable chopper is configured to alternatively close the sample optical path and the reference optical path by rotating the rotatable chopper.

[0029] The slit assembly of the present invention includes slits for both sample light and reference light. In this way, the slit of the monochromator can provide an entrance slit. Since each end of the sample fiber and the reference fiber is configured to guide light directly to the slit, additional alignment optical devices (e.g., reflectors) may not be required to guide the light into the monochromator. By providing a rotatable chopper downstream of the slit, all light from the sample fiber and the reference fiber can be guided to the slit. Therefore, the slit is arranged to filter all light transmitted by both the sample fiber and the reference fiber. By providing a chopper downstream of the slit, only the light filtered by the slit is incident on the rotatable chopper.

[0030] The rotatable chopper according to the first aspect is advantageously configured to alternatively close the sample light path and the reference light path. Thus, the rotatable chopper provides a way to temporally separate the sample light and the reference light integrated with the slit of the monochromator. Thus, a more compact and robust monochromator slit assembly for a fiber optic dual beam AAS system is provided.

[0031] Preferably, the slit of the monochromator according to the second aspect of the invention is provided by an adjustable slit assembly according to the first aspect of the invention. As such, it will be appreciated that the rotatable chopper can also be accurately aligned with the center of the (adjustable) slit, so that the alignment of the rotatable chopper with the sample light and the reference light can be maintained securely over time.

[0032] Preferably, the rotation axis of the rotatable chopper is aligned with the slit (i.e., the central axis of the slit). By aligning the rotation axis of the rotatable chopper with the slit, the rotatable chopper can be accurately positioned in the sample light path and the reference light path downstream of the slit. Therefore, the chopper assembly according to the present invention can be easily calibrated and controlled and is robust to external environmental disturbances.

[0033] Preferably, the rotatable chopper, when in use, has its axis of rotation generally vertical. Thus, gravity will act according to the axis of rotation of the rotatable chopper, so that the rotatable chopper will maintain its alignment in the sample light path and the reference light path over time. Thus, the generally vertical alignment reduces and / or eliminates any lever forces that may act on the rotatable chopper, which may cause the alignment of the rotatable chopper with the entrance slit to change over time. Thus, slight changes in the alignment over time that may affect the intensity of light transmitted by the chopper assembly can be reduced and / or eliminated. Thus, the rotatable chopper according to the present invention is stable and does not experience changes in alignment over time due to gravity.

[0034] Preferably, the chopper has a substantially circular (ring-shaped) shape perpendicular to its axis. Preferably, the chopper may have a polygonal shape (ie, a regular polygon) with the same side length. Specifically, the polygon may have a number of equal sides.

[0035] Also preferably, the center of mass of the rotatable chopper is generally aligned with the axis of rotation. Thus, the rotatable chopper will rotate about its center of mass when in use, thereby reducing and / or eliminating centripetal forces so that the rotatable chopper will maintain its alignment in the sample and reference optical paths over time.

[0036] Preferably, the rotatable chopper is further configured to define at least one sample channel for transmitting sample light. Preferably, the rotatable chopper is further configured to define at least one reference channel for transmitting reference light. Preferably, the sample channel and the reference channel are free space channels through the rotatable chopper for transmitting sample light or reference light through the thickness of the rotatable chopper. Preferably, the sample channel is spaced apart from the reference channel along the rotation axis of the chopper. By providing a sample channel and a reference channel for transmitting light through the rotatable chopper, the rotatable chopper provides a mechanically stable device for transmitting and / or closing the sample light path and the reference light path independently of each other. Further, by providing the chopper with a free space channel for transmitting light, the rotatable chopper does not utilize any additional optical elements to supply the monochromator with sample light and reference light, thereby resulting in time-dependent measurement of the light intensity of the two light sources.

[0037] Specifically, the rotatable chopper can be configured to define at least two sample channels and at least two reference channels, the at least two sample channels being arranged transversely relative to each other around the rotation axis of the chopper, and the at least two reference channels being arranged transversely relative to each other around the rotation axis of the chopper. Preferably, when the reference channel is offset from the sample channel around the rotation axis, the rotatable chopper is configured to alternatively block the sample light and the reference light. Thus, in a single rotation of the rotatable chopper, the sample light path can be transmitted four times, and the reference light path can be transmitted four times. By offsetting the sample channel from the reference channel around the rotation axis, the transmission of the sample light path and the reference light path can be temporally spaced (time resolved) when the rotatable chopper rotates.

[0038] Preferably, the chopper assembly includes a sensor configured to detect the rotational position of the chopper assembly. Thus, the position of the rotatable chopper can be accurately determined and calibrated over time to reduce or prevent minor changes in alignment over time that may affect the intensity of light transmitted by the chopper assembly.

[0039] Preferably, the chopper assembly includes a stepper motor configured to drive the rotatable chopper. Specifically, preferably, the stepper motor has a step angle of no more than 10°, or more preferably 8°. By using a stepper motor with a relatively small step angle, the rotational position of the rotatable chopper can be accurately controlled. In addition, the detent torque of the stepper motor ensures that the position accuracy of the rotatable chopper is maintained when the chopper is held in a fixed position, such as during an AAS experiment.

[0040] In an alternative embodiment of the present invention, a slit assembly may be provided as part of an optical system. As such, the slit assembly may include: a slit, a device for delivering sample light to the slit; and a device for delivering reference light to the slit. The device for delivering sample light and reference light may be arranged to guide light along respective sample light paths and reference light paths through the slit. The slit assembly further includes: a rotatable chopper, the rotatable chopper being arranged downstream of the slit, the rotatable chopper being configured to alternatively close the sample light path and the reference light path by rotating the rotatable chopper.

[0041] For example, the means for delivering sample and reference light may be provided by sample and reference optical fibres, or may be provided by an arrangement comprising one or more optical components including mirrors and / or lenses.

[0042] According to a third aspect of the present invention, a monochromator assembly is provided. The monochromator assembly comprises the monochromator slit assembly according to the second aspect of the present invention, a collimator element and a diffraction element. The collimator element is arranged downstream of the rotatable chopper to guide sample light or reference light from a first position of the slit to the diffraction element. The diffraction element is arranged to reflect light incident on the diffraction element from the collimator element back to the collimator element. The collimator element is further configured to guide the sample light and the reference light from the diffraction element along the slit to respective second positions, which are spatially separated from the first position.

[0043] Preferably, the collimating element is arranged downstream of the rotatable chopper. Thus, the collimating element and the diffraction element guide only the light (reference light and sample light) which is not blocked by the rotatable chopper.

[0044] Preferably, the monochromator assembly according to the third aspect is combined with the adjustable slit mechanism of the first aspect. Therefore, the diffraction element can be rotatably adjusted so that the monochromator combined with the adjustable slit mechanism can selectively output sample light or reference light with a bandwidth in the range of 0.1nm to 2nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0046] - Figure 1 A schematic diagram of an exemplary dual beam spectrometer known in the prior art is shown.

[0047] - Figure 2 A schematic diagram of an optical fiber AAS according to an embodiment of the present invention is shown;

[0048] - Figure 3 shows an isometric representation of a lamp socket assembly according to an embodiment of the present invention;

[0049] - Figure 4 shows another isometric representation of a lamp socket assembly according to an embodiment of the present invention;

[0050] - Figure 5A shows an isometric representation of an optical fiber assembly according to an embodiment of the present invention;

[0051] - Figure 5B shows a top-down representation of an optical fiber assembly according to the present invention;

[0052] - Figure 6 An isometric view of an adjustable slit mechanism of a monochromator according to an embodiment of the present invention is shown;

[0053] - Figure 7 A plan view showing an adjustable slit mechanism of a monochromator according to an embodiment of the present invention;

[0054] - Figure 8 Shows Figure 6 Additional isometric views of the adjustable slit mechanism are shown with the optical sensor assembly hidden from view;

[0055] - Fig. 9 It shows that Figure 7 A plan view of the adjustable slit mechanism of the monochromator shown with the optical sensor assembly hidden from view;

[0056] - Fig.10 shows an additional isometric view of the mechanism for driving and controlling the rotational position of the slit adjustment cam, with a portion of the optical sensor assembly and mounting plate shown in transparent outline;

[0057] - Fig.11 A diagram showing an exemplary slit adjustment cam having a variable radius according to an embodiment of the present invention;

[0058] - Fig.12 Shows Fig.11 A three-dimensional view of an exemplary slit adjustment cam is shown;

[0059] - Fig.13 A rear plan view of an adjustable slit mechanism according to an embodiment of the present invention is shown;

[0060] - Fig.14A , Fig. 14B and Fig. 14C illustrative views of a sample optical fiber, a reference optical fiber, and a combined optical fiber connector are shown (front view, side view, and cross-sectional view along line H-H, respectively);

[0061] - Fig.15 Shown along Fig. 14B A cross-sectional view along line E-E of ;

[0062] - Fig.16A , Fig. 16B and Fig. 16C It shows that Fig.14A and Fig. 14B Detailed views of the sample fiber, reference fiber, and combined fiber connectors as indicated C, D, and A;

[0063] - Fig.17 A detailed view F of the end of a combined fiber optic connector is shown. DETAILED DESCRIPTION

[0064] The present invention relates to atomic absorption spectroscopy (AAS), in particular to fiber optic AAS. However, the present invention is not limited to AAS. It will be appreciated that fiber optic AAS is an AAS in which optical fibers are used to guide light between at least some of the optical components of the AAS, for example, the optical fibers may be used to transport light from one or more light sources to a sample chamber, or to transport light from a sample chamber to an entrance aperture of a monochromator.

[0065] However, the adjustable slit mechanism of the invention can be used in any kind of optical devices and / or optical instruments, in particular optical spectrometers, when light from different sources should be detected. The use is not limited to visible light and can also be used for electromagnetic radiation of various wavelengths of the electromagnetic spectrum.

[0066] The present invention also relates to an AAS using a light source that emits light. It should be understood that in this disclosure, the use of the term light refers to electromagnetic radiation of any suitable wavelength for use in the AAS. Thus, it should be understood that light as referred to in this disclosure is not limited to only visible light wavelengths (i.e., approximately 400-800nm), but also includes electromagnetic radiation of other wavelengths both shorter and longer than visible light. For example, light as used in this disclosure is intended to include at least ultraviolet and infrared. Thus, light as used in this disclosure may include UV visible light, which may include wavelengths ranging from 200nm to 1000nm.

[0067] According to an embodiment of the present invention, an atomic absorption spectrometer (AAS) 1 is disclosed.

[0068] Figure 2 FIG. 4 shows a schematic diagram of an AAS 1 according to an embodiment of the present invention. Figure 2 As shown, the AAS 1 includes at least one hollow cathode lamp 10 housed in a lamp holder assembly 20, a broadband light source 12, an optical cable assembly 30, a sample chamber 40, a sample atomizer 50, a sample optical fiber 60, a reference optical fiber 70, a monochromator assembly 80 and a detector 90.

[0069] like Figure 2 As shown, the fiber assembly 30 is connected to the lamp holder assembly 20, the broadband light source 12 and to the focusing elements 32, 34 of the sample chamber 40. The fiber assembly 30 is configured to combine and transport light from the lamp holder assembly 20 and the broadband light source 12 along the sample light path and the reference light path. Light from each of the lamp holder assembly and the broadband light source is coupled into each of the sample light path and the reference light path. Additional details of the fiber assembly 30 are provided below.

[0070] The optical fiber assembly 30 outputs the light on the sample optical path and the reference optical path to a plurality of first focusing elements 32 and 34. Figure 2 As shown, two focusing elements 32, 34 are provided to direct sample light on a sample light path and reference light on a reference light path. The focusing elements 32, 34 are configured to direct light output from the fiber optic assembly 30 into the sample chamber (40).

[0071] The sample chamber 40 accommodates at least one sample atomizer 50. Figure 2 The sample atomizer 50 shown is a burner. The burner is configured to atomize the sample contained therein and expose the atomized sample to the sample light of the sample light path. Therefore, the sample light of the sample light path can be absorbed by the atoms of the atomized sample in the burner to perform the AAS experiment.

[0072] The sample chamber 40 is also configured to provide free space for the reference light of the reference light path to travel through the sample chamber without further interference. As part of a dual beam spectrometer, a suitable sample chamber 40 and sample atomizer 50 for accommodating the sample atomizer 50 can be provided by a 100 mm universal burner as part of an iCE 3300 dual beam AA spectrometer provided by Thermo Fisher Scientific Inc. In other embodiments, the sample atomizer 50 can be another type of sample atomizer known in the art, such as a graphite furnace or a steam generation unit.

[0073] like Figure 2 As shown, the sample chamber 40 provides outputs for the sample optical path and the reference optical path. A plurality of second focusing elements 36, 38 are positioned at the output of the sample chamber 40 to focus the light of the sample optical path and the reference optical path into the first end of the sample optical fiber 60 and the first end of the reference optical fiber 70, respectively.

[0074] A sample optical fiber 60 and a reference optical fiber 70 are provided for conveying light from the sample chamber 40 to the monochromator assembly 80. Figure 2 As shown, the sample fiber 60 and the reference fiber 70 may be bent to provide a more compact arrangement for the AAS 1. Figure 2 As shown, the direction of travel of the sample and reference light runs through 180° through bends in optical fibers 60, 70. Using optical fibers to change the direction of travel of the sample and reference light is advantageous because it reduces or avoids the use of many mirrors and lenses that may be sensitive to vibrations and environmental disturbances.

[0075] The sample fiber 60 and the reference fiber 70 may each be a multi-core fiber, or they may be a single-core fiber. Preferably, the sample fiber 60 and the reference fiber 70 are optimized to be highly transparent to light having a wavelength typically used for AAS. For example, a preferred wavelength range of about 190-800 nm may be a typical wavelength range for AAS. Preferably, the sample fiber 60 and the reference fiber 70 are optimized to reduce and / or prevent overexposure.

[0076] Preferably, the optical fiber used in the present invention (i.e., optical fiber assembly 30, sample optical fiber 60, reference optical fiber 70) utilizes an optical fiber core comprising silica. Therefore, the operating range of the optical cable of the present invention can be 190nm to 1100nm. The optical fiber can also be resistant to overexposure, thereby improving the long-term optical performance of the optical fiber. For example, the optical fiber CF01493-43 produced by OFS, Georgia, USA, with a core size of at least 550 μm can be a suitable optical fiber for the present invention.

[0077] The second ends of the sample optical fiber 60 and the reference optical fiber 70 are arranged in a fixed positional relationship with the entrance slit of the monochromator assembly 80. The entrance slit can be provided by an adjustable slit assembly 81 ( Figure 6 , 8 , 9 and 13 in 300) as further described below.

[0078] The monochromator assembly 80 is configured to filter the sample light and / or reference light incident on the entrance slit and output a relatively narrow wavelength band at the exit slit 89. In this way, the function of the monochromator assembly 80 is to select the light of the narrow wavelength band. Preferably, the selected light includes a light of a specific wavelength, and the specific wavelength is related to the photons absorbed by the specific elements contained in the sample under study. This wavelength is isolated by the monochromator assembly 80. The exit slit 89 is coupled to the detector 90 to detect the intensity of the light of the narrow wavelength band passing through the exit slit 89. The monochromator assembly 80 can also include a rotatable chopper 500 in the monochromator assembly 80 for separating the reference light from the sample light in time when the reference light and the sample light travel to the detector 90. The rotatable chopper 500 will be described in more detail below.

[0079] like Figure 2As shown, the monochromator assembly 80 is arranged in an Ebert-type configuration. As such, the skilled person will appreciate that the monochromator uses a single collimating mirror 82 to direct light incident from the entrance slit to a grating 84. The grating 84 is provided with a blaze angle so that the reflected light path is directed to the exit slit 89. In an exemplary embodiment, according to the Ebert-type configuration, the grating 84 is configured to diffract the light incident thereon and reflect the light back onto the single collimating mirror 82. The light reflected back from the single collimating mirror is focused on the exit slit 89, which is spatially separated from the entrance slit. Figure 2 In the exemplary embodiment shown, both the entrance slit and the exit slit of the monochromator are provided by separate (spatially separated) portions of the adjustable slit assembly 81. Figure 2 In the embodiment shown, the grating is arranged with a blaze angle so that the angle of the incident light path is the same as the angle of the reflected light path (i.e., a Littrow-type grating). A suitable grating 84 is a diffraction grating having a line density of 1800 lines / mm supplied by Richardson Gratings. Such gratings are well known in the art, as is the arrangement of such gratings in an Ebert-type monochromator, and therefore these gratings are not further described herein.

[0080] The diffracted light from the grating 84 is reflected back to the collimating mirror 82, which in turn reflects the light back to the exit slit of the adjustable slit assembly 81. The diffraction grating 84 causes a wavelength-dependent diffusion in the light reflected back toward the exit slit 89. The angle of the grating 84 relative to the collimating mirror 82 can be adjusted to change one or more narrow wavelength bands of the diffracted light aligned with the exit slit. In this way, the relative angle of the grating 84 can be adjusted to provide a narrow band light output at the exit slit, wherein the wavelength range can be adjusted.

[0081] Thus, monochromator assembly 80 may be configured to separate specific wavelengths of reference light and / or sample light to be measured from other wavelengths of light that may be emitted by other emission sources, such as a flame.

[0082] Light emitted from the exit slit of the adjustable slit assembly can be coupled to a detector 90 where it can be converted into a photocurrent and integrated. Figure 2 As shown, a further mirror 86 is provided to couple light into a detector 90. Figure 2 In the embodiment shown, the detector is a photomultiplier tube. It should be understood that other photodetectors such as avalanche photodiodes may also be suitable for use as detector 90.

[0083] Despite Figure 2In the embodiment of the present invention, an Ebert type monochromator assembly 80 is shown, but it should be understood that the AAS1 of the present invention is not limited to such a monochromator. For example, in other embodiments, a Czerny-Turner type monochromator including multiple collimating mirrors may be used. In addition, different (i.e., separate) adjustable slit assemblies may be used for one or more of the entrance slit and / or exit slit.

[0084] Therefore, AAS1 can be used to guide light from the lamp holder assembly 20 or light from the broadband light source 12 to the sample atomizer 50, whereby the light can interact with the atomized sample. According to the present invention, the light traveling through the sample atomizer 50 is sample light. Due to the absorption of photons by the atoms of the atomized sample, the intensity of the sample light guided through the sample atomizer 50 is reduced. The sample light can be delivered by the sample optical fiber 60 to the entrance slit provided by the adjustable slit assembly 81. The sample light passing through the entrance slit is reflected by the collimating reflector 82 and the grating 84, so that the sample light is diffracted and dispersed in space. Therefore, a small (narrow) wavelength band of the sample light can be aligned with the exit slit 89 of the adjustable slit assembly 81. Therefore, the monochromator assembly can be used to select a small bandwidth of the sample light to be detected by the detector 90. A similar function is provided for guiding light on the reference light path, wherein the reference light is not exposed to the atomized sample. Therefore, the light intensity of the reference light on the reference light path will not be reduced due to absorption by the sample elements. Specifically, only one specific wavelength of light can be associated with the absorption of photons by a specific element of the sample.

[0085] Next, we will refer to Figure 3 and Figure 4 The lamp socket assembly 20 is described in detail.

[0086] Figure 3 FIG. 2 shows a schematic diagram of a lamp holder assembly 20 according to an embodiment of the present invention. Figure 3 As shown, the lamp holder assembly 20 includes two hollow cathode lamps 102 , 104 , a fiber optic cable 106 , a focusing element 108 , an arm 110 , a drive shaft 112 , a first stepper motor 114 , a counterweight 116 , a support member 118 , and a housing assembly 120 .

[0087] like Figure 3 The illustrated lamp holder assembly 20 includes two hollow cathode lamps 102, 104. Each hollow cathode lamp is mounted on a hollow cathode lamp base 130a, 130b. Each hollow cathode lamp base 130a, 130b is configured to provide a power connection for the hollow cathode lamp 102, 104 and to fixedly support the hollow cathode lamp 102, 104 in a generally vertical / generally upright position. Figure 3As shown, the output windows of the hollow cathode lamps 102, 104 are arranged to face generally upward so that relative to Figure 3 The housing is shown to output light from the hollow cathode lamp in a generally upward direction.

[0088] The lamp holder assembly 20 is provided with a plurality of lamp holder bases 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j to support a plurality of hollow cathode lamps 102, 104. More specifically, Figure 2 The illustrated lamp holder assembly 20 includes ten lamp holder bases for ten hollow cathode lamps 102, 104. It should be understood that the number of hollow cathode lamps and hollow cathode lamp bases is not limited to this number, and in other embodiments, there may be less than 10 or more than 10 hollow cathode lamps and corresponding hollow cathode lamp bases. Figure 2 As shown, some of the hollow cathode lamp bases in the hollow cathode lamp base may not have a hollow cathode lamp installed. By providing the lamp holder assembly 20 with the option of installing multiple hollow cathode lamps 102, 104, a selection of different hollow cathode lamps can be provided for use with the atomic absorption spectrometer 1. Specifically, the hollow cathode lamps installed in the lamp holder assembly 20 can have different emission profiles, so that light of different wavelengths can be provided by a series of hollow cathode lamps for use with one or more AAS experiments. It should be understood that hollow cathode lamps and devices for installing hollow cathode lamps are well known in the art, and therefore the hollow cathode lamps 102, 104 and hollow cathode lamp bases 130a, 130b are not further discussed herein. It should be further understood that any light source configured to produce light with a suitable narrow bandwidth for AAS can be used as a substitute for the HCL lamp, such as an electrodeless discharge lamp or a boost hollow cathode lamp.

[0089] like Figure 3 As shown, one end of the optical cable 106 is connected to one end of the arm 110 at a fiber optic base 122. The end of the optical cable 106 is connected to the fiber optic base 122 by a fastener 124. The optical fiber 106 is also supported at a point along its length by a support member 118. The support member 118 provides a support point for the optical fiber 106 at one or more points along the length of the optical fiber, thereby positioning the optical fiber 106 relative to the support arm 110.

[0090] An arm 110 is provided to rotatably position the optical fiber 106 and the focusing element 108 above one of the hollow cathode lamps 102, 104 mounted in the lamp holder assembly 20. As such, the arm 110 is rotatable (rotatable arm) and can be rotated to selectively couple light from one of the hollow cathode lamps 102, 104 into the fiber optic cable 106.

[0091] In order to maximize the amount of light focused from the hollow cathode lamps 102, 104 into the optical fiber 106, a focusing element 108 is disposed within the optical fiber base 122 in a fixed positional relationship with the end of the optical cable 106 at the end of the arm 110. The optical fiber 106 can be a single core optical fiber or can be a multi-core optical fiber. Optical fibers with multiple cores can be produced to cover a larger area, thereby increasing the total power of light that can be transmitted down the optical fiber. For example, the optical fiber 106 can have at least five optical fiber cores; more preferably, the optical fiber has at least seven optical fiber cores or at least nine optical fiber cores. As such, it should be understood that the optical fiber 106 according to the present invention can be a single optical fiber or a multi-core optical fiber.

[0092] The focusing element 108 is configured to couple light incident on the focusing element over a wide area to a smaller area and coupled by total internal reflection at an acceptable angle for transmission down the optical fiber 106. The focusing element 108 may be mounted within a hollow portion of an optical fiber base (not shown). The focusing element 108 may be a lens, or a reflector, or a combination thereof, suitable for focusing light incident on a portion of the focusing element into the optical fiber 106. Figure 3 In the embodiment shown in FIG. 1 , the focusing element 108 is preferably only a lens. It is advantageous to use only a lens as the focusing element 108 of the fiber mount 122 to focus light into the optical fiber in order to provide a robust means for consistently focusing light into the optical fiber 106. In contrast, a focusing element combined with a mirror may be more susceptible to changes in alignment over time, which may require repeated calibration to compensate for the alignment changes.

[0093] Preferably, the focusing element 108 is a lens that is spaced apart from the end of the optical fiber 106 and is held in a fixed position relative to the end of the optical fiber 106 within the fiber base 122. The focusing element 108 and the end of the optical fiber 106 are arranged on the end of the support arm 110 so that the fiber base 122 can be rotatably positioned above the output window of each of the one or more hollow cathode lamps 102, 104. When the fiber base 122 of the support arm 110 is positioned above the hollow cathode lamp 102, the light output passing through the window of the hollow cathode lamp 102 can be directed onto the focusing element 108. The focusing element 108 then focuses the substantial portion of the light onto the end of the optical fiber 106 so that the substantial portion of the light can be transmitted along the optical fiber by total internal reflection. In this way, the rotatable support arm 110 of the lamp holder assembly 20 is configured to selectively couple light from each of the plurality of hollow cathode lamps 102, 104 into the optical cable 106.

[0094] The support arm 110 is also attached to the drive shaft 112 to change the rotational position of the support arm 110. In this way, the support arm 110 can rotate around the rotation axis determined by the axis of the drive shaft 112. Figure 3 As shown, the drive shaft 112 and the rotational axis are at least substantially vertical (generally upright), preferably vertical. Substantially vertical can mean a deviation from vertical of less than 5°, preferably less than 2°, more preferably less than 1°, still more preferably less than 0.5°, yet more preferably less than 0.2°, and even more preferably less than 0.1°. By providing the drive shaft 112 in this orientation relative to the housing 120 (and the intended orientation of the lamp holder assembly in use), the drive shaft 112 and the rotational axis therein are not subject to leverage forces due to gravity, which can cause the alignment of the rotational axis to vary over time through the alignment of the drive shaft 112. The alignment stability of the rotational axis of the support arm allows the support arm to be accurately and consistently positioned over a plurality of different hollow cathode lamps 102, 104 arranged about the rotational axis. It should be understood that variations in the alignment of the focusing element 108 of the fiber mount 122 relative to the direction of the light output of the output window of the hollow cathode lamp may cause variations in the intensity of light coupled into the optical fiber from the hollow cathode lamps 102, 104 located in different positions about the axis of rotation. Preferably, the light output of the hollow cathode lamp is focused in the direction of the axis of rotation by the focusing element 108. Thus, variations in the relative alignment of the light output of the hollow cathode lamp to the axis of rotation should preferably be less than 2°, more preferably less than 1°, still more preferably less than 0.5°, yet more preferably less than 0.2°, and even more preferably less than 0.1°.

[0095] The support arm is also connected to a counterweight 116 at an end of the support arm 110 opposite the fiber mount 122. The counterweight 116 is disposed at an end of the support arm opposite the fiber mount 122. The counterweight 116 is configured to counteract the leverage forces on the support arm 110 about the drive shaft 112 on which the support arm 110 is supported, generated by the weight of the support arm 110, the optical fiber 106, the focusing element 108, the fiber mount 122, and the support member 118. Thus, the counterweight 116 ensures that no additional leverage forces are acting on the drive shaft due to the weight of the support arm and components attached thereto. Thus, the effects of gravity over time (leverage forces acting on the support arm 110 due to gravity) can be reduced and / or eliminated, such that changes in the alignment of the rotational axis of the support arm over time can be reduced or eliminated.

[0096] To further increase the accuracy of the rotational position of the support arm 110, the support arm 110 may further include a position sensor 126. The position sensor 126 is configured to detect at least one rotational position of the support arm 110 relative to the lamp holder assembly 20. Figure 3As shown, position sensor 126 comprises an optical sensor mounted on housing assembly 120, but any sensor suitable for measuring rotational position may be used. When the support arm is in a particular rotational position (the "home" position), position sensor 126 detects the presence of mark 128 on support arm 110. Thus, the position of support arm 110 may be repeatedly calibrated using position sensor 126 so that the accuracy of the rotational position of support arm 110 may be maintained.

[0097] The lamp holder assembly 20 further includes a housing assembly 120, such as Figure 3 As shown. The housing 120 includes an upper support plate 142, a base plate 144, and a connecting portion 146. The connecting portion 146 connects the upper plate 142 to the base plate 144. The drive shaft 112 may be supported by the housing assembly 120 at two or more points. Figure 3 As shown, the drive shaft 112 is supported by the upper support plate 142 at a first upper end and by the base plate 142 at a second lower end.

[0098] 144 supports. Thus, the housing assembly 120 provides at least two fixed support points for the drive shaft to ensure that the rotational axis of the drive shaft is accurately maintained relative to the housing assembly 120 over time.

[0099] Figure 4 Another schematic diagram of the lamp holder assembly 20 is shown, wherein Figure 3 Compared with the figure, only one of the plurality of hollow cathode lamps 102 and one of the plurality of lamp holder bases 130a are shown. Figure 4 The support arm 110 and the drive mechanism of the drive shaft 112 are shown in greater detail.

[0100] The driving mechanism for the rotational movement of the support arm 110 is provided by a first stepper motor 114. The first stepper motor 114 is connected to the support arm and the drive shaft via a worm gear 150 and a worm 152. Figure 4 As shown, the worm wheel 150 is connected around the drive shaft 112, and the worm 152 is fixed to the axle of the first stepper motor 114. The worm 152 is rotatably driven by rotating the axle 154 of the first stepper motor 114. The rotation of the worm 152 rotates the worm wheel 150 attached to the drive shaft 112 so as to transfer the rotational movement from the axis of the first stepper motor 114 to the axis of the drive shaft 112. By using the first stepper motor 114 to drive the movement of the support arm 110, when the first stepper motor 114 is not driven, the positioning torque of the first stepper motor 114 can be used to ensure that the support arm is kept in a fixed position. Therefore, without the need for additional mechanical components, the rotational position of the support arm 110 can be firmly maintained in a simple manner by the first stepper motor 114.

[0101] like Figure 3 and Figure 4 14. As shown in the embodiment of the present invention, the first stepper motor 114 is mounted on a mounting plate 156, and the axle 154 of the first stepper motor 114 extends through the mounting plate. The mounting plate 156 is then mounted on the base plate 144 by fasteners to provide a safe attachment point for the first stepper motor 114. It should be understood that the arrangement of the worm 152 and the worm wheel 150 for connecting the first stepper motor 114 to the drive shaft 112 is only a possible arrangement for driving the drive shaft 112 with the first stepper motor 114. The technician will understand that other drives (drive devices), specifically gear drives (gear drive devices) may also be suitable. The technician will also understand that the orientation of the axle of the stepper motor and / or the mounting plate 156 is not limited to any specific orientation, and the arrangement of the stepper motor can be changed in the housing in this way.

[0102] like Figure 4 As shown, the base plate 144 includes a plurality of attachment points 148 for attaching the lamp holder bases 130a, 130b, 130c, etc. to the base plate. Similar attachment points are arranged at fixed radial distances around the rotation axis of the drive shaft. Therefore, it should be understood that when the lamp holder assembly 20 is fully assembled, the plurality of hollow cathode lamps 102, 104 will be arranged at fixed radial distances around the rotation axis. By providing the plurality of hollow cathode lamps 102, 104 at fixed radial distances around the rotation axis, the fiber optic base 122 of the support arm 110 can be accurately positioned above each of the hollow cathode lamps 102, 104 in the same relative position.

[0103] Preferably, the housing of the lamp holder assembly 20 is constructed of aluminum, for example, aluminum plate. The aluminum plate provides a lightweight yet rigid structure for fixing the alignment of the drive shaft. It should be understood that the housing assembly 120 is shaped to provide two fixing points for supporting the drive shaft at opposite distal ends. Therefore, the present invention contemplates various modifications to the base plate 144, the connecting member 146, and the upper plate 142, which can also provide the necessary fixing points for the drive shaft 112 and the support arm 110.

[0104] The lamp holder assembly may also include a controller (not shown) configured to control the operation of the first stepper motor 114 and the position sensor 126 to position the arm over one of the hollow cathode lamps. The controller may also control the operation of the hollow cathode lamp. The functionality of the controller of the lamp holder assembly may be incorporated into the controller of the AAS.

[0105] As described above, the lamp support arm 110 can rotate about the drive axis 112 so that the optical fiber base 122 can be positioned above (or relative to) one of the plurality of hollow cathode lamps 102, 104 to couple light from one hollow cathode lamp 102 into the optical cable 106. The bases of the hollow cathode lamps 130a, 130b, 130c are arranged in a circular pattern about the drive axis, corresponding to the path of rotation of the end of the support arm about the drive axis. This allows the end of the support arm to be positioned above each of the hollow cathode lamp bases 130a, 130b, 130c. Therefore, light from the lamp mounted on the hollow cathode lamp base positioned below the end of the support arm can be coupled into the optical fiber 106. Therefore, the rotation of the support arm 110 can be used to select one of the hollow cathode lamps for use in the AAS experiment. Light from the selected hollow cathode lamp 102, 104 is focused into the optical fiber, while the other lamps remain unused. Preferably, the entire lamp holder assembly is enclosed in an additional common housing (not shown) to prevent ambient light from being inadvertently focused into the optical fiber, thereby reducing the accuracy of the experiment.

[0106] Next, we will refer to Figure 2 , Figure 3 and Figure 4 A method of operating the lamp socket assembly 20 is described.

[0107] In a particularly preferred embodiment of the method for operating the lamp socket assembly 20, the support arm 110 is first sent to a starting position to calibrate the rotational position of the support arm 110. The starting position of the support arm 110 can be set with reference to the position sensor 126, which is configured to detect a fixed rotational position of the support arm 110.

[0108] Next, the user can select a desired hollow cathode lamp 102, 104 for use by specifying a lamp holder base position to be used. The desired lamp holder base position can be selected by the user through a user interface to the controller. The controller (not shown) is configured to drive the first stepper motor 114 from a starting position a predetermined number of steps to a rotational position corresponding to the desired hollow cathode lamp base position. Optionally, once the support arm 110 reaches the desired predetermined position, the rotational position of the support arm 110 can be further calibrated to find the optimal rotational position of the hollow cathode lamp using a calibration routine.

[0109] For the calibration routine, fine step adjustments of the first stepper motor 114 can be used to provide relatively small angles of rotational adjustment via the gear arrangement on the worm 152 and worm wheel 150. As a result of the adjustment, changes in the intensity of light (e.g., light of a particular wavelength emitted by an HCL lamp) coupled into the optical fiber 106 can be detected by the detector 90 of the AAS system 1. Intensity measurements can be performed by measuring the intensity of the light as a reference light in the AAS 1. By performing a number of such intensity measurements at different angular positions, the optimal rotational position of the support arm relative to the hollow cathode lamp can be determined. Thus, the predetermined number of steps to the desired rotational position can be updated based on the optimal position determined by the calibration routine.

[0110] The optimal rotational position of the support arm 110 can be stored by the controller for the selected hollow cathode lamp 102. Therefore, when the user of the lamp holder assembly 20 reselects the lamp, the support arm 110 can be directly returned to the optimal position. The above calibration method can be repeated for one or more of the hollow cathode lamps 102, 104 in the lamp holder assembly 20. For example, a calibration procedure can be performed at startup of the AAS1, wherein the optimal position of the support arm for each of the hollow cathode lamps 102, 104 in the lamp holder assembly 20 is recorded. Alternatively, the optimal position of the hollow cathode lamp can be determined at the first use after startup of the AAS1.

[0111] Thus, during an AAS experiment, the support arm can quickly select a hollow cathode lamp 102 and move to the optimal position of the hollow cathode lamp without further calibration. Preferably, the support arm can be moved to the starting position between each adjustment of the position of the support arm 106, so that the number of steps to the desired optical position is always counted from the starting position to ensure that the support arm is accurately moved to the desired position. Thus, for any hollow cathode lamp of the lamp holder assembly 20, the support arm can be firmly and accurately positioned in the optimal position.

[0112] As discussed above, a fiber assembly 30 of the optical fiber AAS1 is provided according to an embodiment of the present invention. The fiber assembly 30 is configured to provide a fiber optical path between the lamp holder assembly 20, the broadband light source 12, and the focusing elements 32, 34 of the sample chamber 40. The fiber assembly 30 is configured to couple light from the lamp holder assembly 20 (first light source) to the focusing elements 32, 34 to form a sample optical path and a reference optical path. The fiber assembly is also configured to couple light from the broadband light source 12 (second light source) to the focusing elements 32, 34 along the sample optical path and the reference optical path. In this way, light from each of the lamp holder assembly 20 and the broadband light source 12 is coupled into each of the sample optical path and the reference optical path.

[0113] Figure 5AAn isometric view of a fiber optic assembly 200 is shown in accordance with an embodiment of the present invention. Figure 5B An additional top-down view of a fiber assembly 200 is shown. The fiber assembly 200 includes a first light source input 202 and a second light source input 204, as well as a sample light output 206 and a reference light output 208. The first light source input 202 is connected to the sample light output 206 through a first sample fiber 210. The first light source input 202 is connected to the reference light output 208 through a first reference fiber 212. The second light source input 204 is connected to the sample light output 206 through a second sample fiber 214. The second light source input 204 is connected to the reference light output 208 through a second reference fiber 216.

[0114] The first light source input 202 includes a connecting element 220 for connecting the sample light input 202 to the first light source. For example, the connecting element can be a fastener configured to connect the optical fiber 106 to the lamp holder assembly as described above, such as the fastener 122. The first light source input 202 also includes a first coupling assembly 222, which is configured to couple light incident on the first light source input 202 into the first sample optical fiber 210 and the first reference optical fiber 212.

[0115] The coupling assembly 222 includes a plurality of optical cores 224 (224a, 224b, 224c, 224d, 224e, 224f, 224g) disposed at the end of the coupling assembly 222 exposed to the light from the first light source. The optical core is typically provided as a UV-resistant optical core for optical fiber known in the art. Thus, the plurality of optical cores are arranged to be able to couple the light from the first light source into the coupling assembly 222 by total internal reflection. The coupling assembly 222 also includes a splitting element 226 configured to split the light coupled in the plurality of optical cores 224 into the first sample fiber 210 and the first reference fiber 212. Preferably, the splitting element 226 couples the light equally into the first sample fiber 210 and the first reference fiber 212, but other ratios of light coupling may also be provided. For example, it may be advantageous to couple a larger portion of the light into the first sample fiber 210 for use in the sample optical path.

[0116] The coupling assembly 222 may be housed in a protective layer 228 to connect and hold all components in place and to prevent external radiation from coupling into the optical fiber.

[0117] Similarly, the second light source input 204 also includes a connecting element 220a, a coupling assembly 222a (including a dividing element 226a) and a protective housing 228a for connecting the second light source input 204 to the second light source. The coupling assembly 222a in the second light source input 204 is configured to couple the light incident on the second light source input 204 into the second sample optical fiber 214 and the second reference optical fiber 216. As such, the coupling assembly 222a can be substantially the same as the coupling assembly 222 of the first light source input 202.

[0118] Each of the first sample optical fiber 210, the first reference optical fiber 212, the second sample optical fiber 214 and the reference optical fiber 216 can be provided as a UV-resistant optical fiber. In this way, it should be understood that the optical fiber is configured to be resistant to overexposure. Each of the optical fibers 210, 212, 214, 216 can be provided as a single-core optical fiber, or more preferably a multi-core optical fiber. Preferably, the diameter of each of the optical cores is 0.55 mm. In one embodiment, the multi-core optical fiber includes 7 optical fiber cores, each of which has a diameter of 0.55 mm, which preferably allows the optical fiber to have suitable flexibility (i.e., it can have a bending radius of less than 15 cm without the risk of micro-fracture). Of course, it should be understood that optical fibers with different core numbers or different core diameters can be equally suitable for use in the optical fiber assembly 200.

[0119] exist Figure 5A and Figure 5B In the illustrated embodiment, the first sample fiber 210 and the first reference fiber 212 may each have a length of approximately 450 mm, while the second sample fiber 214 and the second reference fiber 216 may each have a length of 250 mm.

[0120] The sample light output 206 is configured to output light coupled from the first sample optical fiber 210 and the second sample optical fiber 214. The sample light output 206 may include a connecting element 220b for connecting the output to the focusing element 32. By using the connecting element 220b, the end of the sample light output 206 may be held in a fixed position arrangement with the focusing element 32, thereby providing a stable arrangement for guiding the sample light path. In order to couple light from the first sample optical fiber 210 and the second sample optical fiber 214 to the output, a coupling assembly 222b may be provided substantially as described above, wherein light travels from the first sample optical fiber 210 and the second sample optical fiber 214 to the sample light output 206. In contrast to the splitting element 226, the combining element 226b is configured to combine light from the first sample optical fiber 210 and the second sample optical fiber 214 into a plurality of optical cores 224. The plurality of optical cores 224 then couple light to the end of the sample light output 206.

[0121] Similarly, reference light output 208 also includes a connection element 220c, a coupling assembly 222c, and a protective housing 228c for connecting reference light output 208 to focusing element 34. Coupling assembly 222c in reference light output 208 is configured to couple and combine light from first reference fiber 212 and second reference fiber 216 in a manner similar to sample light output 206 as described above.

[0122] It should be understood that Figure 5A and Figure 5B The optical fibers 210, 212, 214, 216 of the illustrated fiber assembly 200 are not limited to the lengths or dimensions described above. In practice, the lengths of the respective optical fibers and the relative alignment of the first light source input 202, the second light source input 204, the sample light output 206, and the reference light output 208 may vary, not least due to the inherent flexibility of the optical fibers. Thus, the fiber assembly 30, 200 according to the present invention may be a robust device for providing sample and reference light paths for a fiber optic AAS system in combination with a secondary light source.

[0123] According to another embodiment of the present invention, Figure 6 An isometric view of an adjustable slit mechanism 300 of a monochromator is shown. For example, Figure 6 The embodiment of the adjustable slot mechanism 300 shown can provide Figure 2 The adjustable slit assembly 81 of the monochromator assembly 80 is shown. As such, the adjustable slit assembly 81 is arranged to receive sample light and reference light from the sample optical fiber 60 and the reference optical fiber 70, respectively.

[0124] The adjustable slit mechanism includes a first slit member 302 and a second slit member 304 , a slit adjustment cam 306 , a first arm 308 , a second arm 310 , and an optical sensor assembly 311 .

[0125] The first slit member 302 provides a first slit edge 312 for the adjustable slit mechanism 300. The second slit member 304 provides a second slit edge 314 for the adjustable slit mechanism 300. The second slit member 304 is arranged opposite to the first slit member 302 so that the first slit edge 312 and the second slit edge 314 are opposite to each other to define the slit of the monochromator. The first slit member 302 and the second slit member 304 are configured to provide the first slit edge 312 and the second slit edge 314 as straight edges suitable for defining the precise slit width of the monochromator.

[0126] The first slit member 302 is mounted on the first arm 308. Figure 7As shown, the first slit member 302 is mounted on the first arm 308 by a plurality of (two) fasteners 316. By mounting the first slit member 302 on the first arm 308 using the plurality of fasteners 316, the first slit member 302 can be mounted at a precise location on the first arm 308. Therefore, the position (alignment) of the first slit edge 312 relative to the first arm 308 can be precisely controlled. Similarly, the second slit member 314 is mounted on the second arm 310 by the plurality of fasteners 316.

[0127] In order to provide the first slit member 302 and the second slit member 304 of the first slit edge 312 and the second slit edge 314, a (relatively) high accuracy forming process is used to form the first slit member 302 and the second slit member 304. In this context, a high accuracy forming process is considered to be a forming process configured to form a shape with an accuracy of ± 0.05mm or less. Preferably, the accuracy of the chemical etching process is ± 0.025mm. In a preferred embodiment, the first slit member and the second slit member are formed by spring steel and further formed using a chemical etching process. In the chemical etching process, a photoresist mask is applied to the component to be etched in a desired pattern, and then the unmasked area of ​​the component is subsequently exposed to a chemical etchant. The chemical etching process of spring steel is known in the art and is therefore not described in further detail herein. Since the first slit member 302 and the second slit member 304 are formed separately from the first arm 308 and the second arm 310, the size of the component to be chemically etched is reduced. Of course, the skilled artisan will appreciate that alternative high accuracy forming processes, such as laser machining or micro-polishing, may also be used to form the first and second slit members.

[0128] Figure 8 The first arm 308 is shown in more detail in FIG. 3 , which shows an additional isometric view of the adjustable slit mechanism 300 with the optical sensor assembly 311 hidden from view. Fig. 9 Also shown is a plan view of the adjustable slit mechanism 300, with the optical sensor assembly 311 hidden from view. Figure 8 and Fig. 9 As shown, the first arm 308 includes a first mounting portion 320 , a first alignment portion 322 , and a first cam engagement portion 324 .

[0129] The first mounting portion 320 of the first arm is configured to provide a mounting location for attaching a fastener 316 so as to mount and precisely position the first slit member 302 on the first arm 308. The first alignment portion 322 of the first arm 308 is connected to the first mounting portion 320 at one end of the first alignment portion and extends away from the mounting portion. The first alignment portion 322 of the first arm 308 provides a device for adjusting the position of the first slit member 302 and aligning the adjustment direction of the first slit member 302. The first alignment portion 322 includes one or more straight edges, which are provided to align the first arm, as discussed in more detail below. The first cam engagement portion 324 is connected to the first alignment portion 322 at its end opposite to the first mounting portion 320. The first cam engagement portion 324 is configured to provide a surface for engaging with the slit adjustment cam 306. As Fig. 9 As shown, the cam engagement portion 324 preferably includes a sliding bearing material 326 mounted thereon to provide a surface for engaging the slit adjustment cam 306. In the illustrated embodiment, a ring of sliding bearing material is disposed on the cam engagement portion 324. The ring of sliding bearing material may be fixed by a screw 327, or may be pivoted on the cam engagement portion 324 by the screw 327. The surface for engaging the slit adjustment cam 306 will be discussed in more detail below.

[0130] like Figure 8 324, the combination of the first alignment portion 322 and the first cam engagement portion 324 provides a substantially L-shaped portion of the first arm 308. The combination of the first mounting portion 320, the first alignment portion 322, and the first cam engagement portion 324 provides a substantially U-shaped first arm 308. Of course, it should be understood that the shapes of the first mounting portion 320, the first alignment portion 322, and / or the first cam engagement portion 324 of the first arm 308 may vary, and thus the present invention is not limited to the above. Figure 8 For example, as known in the art, the nature of the mounting and fasteners can vary, and thus the shape of the first mounting portion 320 can vary accordingly. Further, the shape of the cam engagement portion 324 can vary depending on the shape and relative position of the slit adjustment cam 306.

[0131] Similarly, the second arm 310 is Figure 8 and Fig. 9 As shown. The second arm 310 includes a second mounting portion 328, a second alignment portion 330, and a second cam engagement portion 332, which are connected in a U-shape similar to the first arm 308. As such, the features of the second arm 310 are similar to the features of the first arm 310 as discussed above. As with the first arm 308, the shape of the second arm 310 is not limited to the shape of the first arm 308. Figure 8 The shape shown in the embodiment.

[0132] from Figure 8 The illustrated embodiment will appreciate that the second cam engagement portion 332 and the first cam engagement portion 324 each extend in a direction aligned with the first slit edge 312 and the second slit edge 314. As such, the surfaces of the first cam engagement portion 324 and the second cam engagement portion 332 that engage the slit adjustment cam 306 may be parallel to the first slit edge 312 and the second slit edge 314. In the case where the surfaces of the first cam engagement portion 324 and the second cam engagement portion 332 that engage the slit adjustment cam 306 are provided by the sliding bearing material 326, it will be appreciated that the points on the sliding bearing material 326 that contact the slit adjustment cam 306 may be considered to be arranged tangentially to the slit adjustment cam 306. The plane formed by such tangents will be substantially parallel to the first slit edge 312 and the second slit edge 314. As such, it will be appreciated that the separation of the first cam engagement portion 324 and the second cam engagement portion 332 may be adjusted in a direction substantially normal to the first slit edge 312 and the second slit edge 314.

[0133] The first arm 308 and the second arm 310 can each be formed of stainless steel. As such, each of the first mounting portion 320 and the second mounting portion 328, the first alignment portion 322 and the second alignment portion 330, and the first cam engagement portion 324 and the second cam engagement portion 332 can each be formed of stainless steel. Preferably, the stainless steel used is SAE grade 316 stainless steel.

[0134] The adjustable slit mechanism 300 further includes a mounting plate 340 on which the adjustable slit mechanism 300 is mounted. The first arm 308 and the second arm 310 are mounted on the mounting plate 340 via a plurality of positioning washers (guide members) 342. Each of the first arm 308 and the second arm 310 is mounted on the mounting plate 340 using at least two positioning washers 342.

[0135] The mounting plate 340 on which the first arm 308 and the second arm 310 are mounted is made of a stainless steel component. The mounting plate 340 includes a plurality of threaded holes for attaching the positioning washers 342 to the mounting plate 340. The mounting plate 340 also includes a hole for mounting the second stepper motor 360. The various threaded holes for positioning the positioning washers 342 and the holes for mounting the second stepper motor 360 are manufactured using a high-precision fixture to provide accurate positioning of the components. Of course, it should be understood that other relatively high-precision processing techniques, such as laser processing, may also be used.

[0136] like Figure 8 and Fig. 9As shown, the first arm 308 is mounted on the mounting plate 340 using two locating washers 342. The locating washers 342 are arranged on the mounting plate 340 to engage with the first alignment portion 322 of the first arm 308. The locating washers 342 are each mounted on the mounting plate 340 by a fastener. The fastener is preferably a spring-loaded bolt. The spring-loaded bolt is connected to the mounting plate 340 at the desired position of the locating washer 342 through a threaded hole in the mounting plate 340. The locating washer 342 is then installed around the bolt threads, and the spring applies tension between the bolt head and the locating washer 342 to position the washer against the mounting plate 340.

[0137] The positioning washers 342 each include an arm retaining portion 344 and an arm alignment portion 346. The arm retaining portion 344 is configured to retain the arm it contacts against the mounting plate 340. The arm alignment portion 346 is configured to provide alignment for the arm it contacts so that the first slit edge 312 is aligned with the second slit edge 314. Further, the arm alignment portions 346 of the fasteners are aligned with each other so that the relative alignment of the first slit edge 312 with the second slit edge 314 is maintained when the width of the adjustable slit is adjusted. Of course, it should be understood that the guide member of the present invention is not limited to the positioning washers 342, and the guide member can be provided in a range of different shapes and sizes to locate and guide each of the first arm 308 and the second arm 310 on the mounting plate 340.

[0138] like Figure 8 and Fig. 9 As shown, the arm alignment portion 346 of the positioning washer 342 is provided as an annular washer of a first diameter, which is provided to engage with the edge of the first arm or the second arm to align and position the edge against the washer. Preferably, the thickness of the arm alignment portion 346 is the same as the thickness of the first arm 308 and / or the second arm 310. The arm retaining portion 344 is connected to the arm alignment portion 346 and has a second diameter that is larger than the first diameter of the arm alignment portion 346, so that the arm retaining portion 344 overlaps with the respective arm (at Fig. 9 308 and 310 relative to the mounting plate 340. The spring of the spring-loaded bolt tensions the locating washer 342 against the mounting plate 340, so that the locating washer and the respective first arm 308 and second arm 310 are securely held in place.

[0139] like Fig. 9As shown, the first arm 308 is mounted on the mounting plate 340 by two locating washers 342. The locating washers 342 are arranged to engage with the edge of the first alignment portion 322. The locating washers 342 are arranged on the lower edge of the first alignment portion 322 so that when the first alignment assembly is oriented upward in its intended upright orientation, the locating washers 342 support the first arm 308. The two locating washers 342 of the first arm 308 are also positioned so that in combination with the substantially straight edge of the first alignment portion 322, the first arm is free to move in a substantially horizontal direction. Additional details of the movement of the first arm 308 will be discussed below.

[0140] The second arm 310 is mounted on the mounting plate 340 by using four positioning washers 342. Fig. 9 As shown, three positioning washers 342 are arranged to contact the substantially straight edge of the second alignment portion 330 of the second arm 310. A fourth positioning washer 342 is provided at the lower end of the second cam engagement portion 332 to provide vertical support for the second arm 310, thereby subsequently preventing the second arm 310 from rotating about the positioning washer 342 in contact with the second cam engagement portion 332. In this way, the positioning washer 342 is configured to position and align the second arm 310 on the mounting plate 340.

[0141] exist Figures 6 to 10 In the illustrated embodiment, the first arm 308 and the second arm 310 are mounted on the mounting plate 340 using a positioning washer 342 so that there is a small vertical separation (not shown) between the first alignment portion 322 and the second alignment portion 330. The alignment portions do not need to contact each other because the positioning washer 342 can accurately position each of the first arm 308 and the second arm 310 of the mounting plate 340 without any additional support. Of course, in other embodiments, it should be understood that the two arms can be provided in contact to provide additional alignment. In such embodiments, lubrication between the components can be provided to reduce friction. Sliding bearing material can be provided at the contact area of ​​at least one of the first alignment portion 322 and the second alignment portion 330 to reduce friction.

[0142] To further position the first arm 308 and the second arm 310, the first arm 308 and the second arm 310 are each elastically biased against the slit adjustment cam 306. Fig. 9 As shown, the first cam engagement portion 324 is elastically biased against the slit adjustment cam 306 at a first point on the circumference of the slit adjustment cam 306, and the second cam engagement portion 332 is elastically biased against the slit adjustment cam 306 at a second point on the circumference of the slit adjustment cam 306. Fig. 9, the first point is opposite to the second point. In this way, the point at which the first arm 308 is elastically biased against the slit adjustment cam 306 is opposite to the point at which the second arm 310 is elastically biased against the slit adjustment cam 306 (i.e., on the opposite side of the slit adjustment cam). The first arm 308 and the second arm 310 are elastically biased against the slit adjustment cam 306 by the first elastic element 350 and the second elastic element 352 respectively. Preferably, the first elastic element 350 and the second elastic element 352 are respectively connected to the first arm 308 and the second arm 310 and can be arranged between the two arms 308 and 310. The first elastic element 350 and the second elastic element 352 are spaced apart from each other on the first arm 308 and the second arm 310. The elastic elements 350 and 352 are configured to elastically bias the first arm 308 and the second arm 310 toward the slit adjustment cam 306. In an alternative embodiment, each elastic element can be connected to and arranged between the mounting plate 340 and the first arm 308 or the second arm 310.

[0143] like Fig. 9 As shown, the first elastic member 350 is connected to the first cam engagement portion 324 of the first arm 308 at one end of the elastic member 350. The other opposite end of the first elastic member 350 is connected to the second cam engagement portion 332 of the second arm 310. Similarly, the second elastic member 352 is connected to the first cam engagement portion 324 and the second cam engagement portion 332 at opposite ends. The first elastic member 350 and the second elastic member 352 are spaced apart along the respective lengths of the first cam engagement portion 324 and the second cam engagement portion 332. The first elastic member 350 and the second elastic member 352 are preferably spaced apart to be on both sides of the first point and the second point where the cam engagement portions 324, 332 contact the slit adjustment cam 306.

[0144] Therefore, the first elastic member 350 and the second elastic member 352 are connected to the first arm 308 and the second arm 310, so that the slit adjustment cam 306 (adjustably) tightens the first elastic member 350 and the second elastic member 352 by separating the first arm 308 from the second arm 310. Therefore, the first elastic member 350 and the second elastic member 352 elastically bias the first arm 308 toward the second arm 310 so that both arms are kept in contact with the slit adjustment cam 306. Therefore, the slit width of the adjustable slit mechanism can be accurately controlled by the slit adjustment cam 306.

[0145] like Fig. 9As shown in the embodiment of FIG. 1 , the first elastic element 350 and the second elastic element 352 are springs (helical springs). The springs are each attached to the first arm 308 and the second arm 310 by a fastener. Of course, it should be understood that the first elastic element 350 and the second elastic element 352 are not limited to helical springs, and any other type of elastic element or its equivalent known to a skilled person that is suitable for elastically biasing the first arm 308 and the second arm 310 toward each other is suitable.

[0146] The first arm 308 and the second arm 310 can be made of, for example, stainless steel, and other suitable materials similar to stainless steel are well known to those skilled in the art. The first arm 308 and the second arm 310 can be manufactured into their desired shapes using milling and grinding processes. Such known processes can provide the components with the desired shape and smoothness to provide suitable alignment surfaces as discussed above.

[0147] As discussed above, the slit adjustment cam 306 is positioned between the first cam engagement portion 324 of the first arm and the second cam engagement portion 332 of the second arm 310. The slit adjustment cam 306 is mounted on an axle connected to the stepper motor 360 so that the slit adjustment cam can rotate about an axis of rotation. The slit adjustment cam 306 has a variable radius about its axis of rotation. The variable radius of the slit adjustment cam is provided so as to provide a means for adjusting the separation of the first cam engagement portion 324 of the first arm 308 and the second cam engagement portion 332 of the second arm 308. Reference Figure 8 and Fig. 9 It will be appreciated that changing the relative separation of the first cam engagement portion 324 from the second cam engagement portion 332 will cause a corresponding change in the separation of the first slit edge 312 from the second slit edge 314. In this manner, rotation of the slit adjustment cam 306 will cause the (adjustable) separation of the first slit edge 312 from the second slit edge 314.

[0148] Preferably, the variable radius of the slit adjustment cam 306 is provided such that for at least one rotational position of the slit adjustment cam 306, the diameter of the slit adjustment cam 306 is such that the separation between the first arm 308 and the second arm 310 provided by the slit adjustment cam 306 is sufficient to allow the first slit edge 312 to contact the second slit edge 314. As such, the variable radius of the slit adjustment cam 306 around its circumference includes a portion configured to allow the adjustable slit of the monochromator to be fully closed. Such a portion may preferably be the minimum radius of the variable radius of the slit adjustment cam 306. The slit adjustment cam 306 further includes one or more portions around the circumference where the variable radius increases such that rotation of the slit adjustment cam 306 increases the separation of the first arm 308 from the second arm 310. Thus, rotating the slit adjustment cam 306 adjustably separates the first slit edge 312 from the second slit edge 314. Preferably, the variable radius of the slit adjustment cam 306 is provided so that at a first point where the slit adjustment cam contacts the first cam engagement portion 324, the radius is the same as the radius of the slit adjustment cam 306 at a second point where the slit adjustment cam contacts the second cam engagement portion 332. In this way, the slit adjustment cam 306 equally separates the first arm 308 and the second arm 310 in opposite directions (relative to its rotation axis). Advantageously, by equally separating the first arm 308 and the second arm 310, the center position of the adjustable slit remains unchanged. By providing a mechanism in which the center of the adjustable slit remains unchanged, incident light on the adjustable slit can be aligned with the center of the adjustable slit of one slit width, and since the center position of the slit will remain unchanged, no additional alignment is required. Therefore, a stable adjustable slit mechanism of a monochromator can be provided.

[0149] like Figure 8 As shown, preferably, the slit adjustment cam 306 is engaged with the first arm 308 and the second arm 310 through the ring 326, 326'. Preferably, the ring 326, 326' is made of a sliding bearing material, or at least the outer surface of the ring 326, 326' is composed of a sliding bearing material. The ring 326, 326' is mounted on each of the first arm 308 and the second arm 310 at the respective cam engagement portion 324, 332. Figure 8In the embodiment shown, preferably, the rings 326, 326' are mounted on the first arm 308 and the second arm 310 by fasteners 327, 327'. The rings 326, 326' provide a contact point for the slit adjustment cam 306, which reduces the friction between the rotating slit adjustment cam 306 and the first arm 308 and the second arm 310, especially if the surface of the ring is composed of a sliding bearing material. In an alternative embodiment, the slit adjustment cam can directly contact the first arm 308 and the second arm 310. Advantageously, the use of the rings 326, 326' reduces the friction caused by the rotation of the slit adjustment cam 306 so as to reduce the wear of the slit adjustment cam 306.

[0150] Fig.10 An additional isometric view of the mechanism for driving and controlling the rotational position of the slit adjustment cam 306 is shown. Fig.10 In the cross-sectional view of FIG. 3 , a portion of the optical sensor assembly 311 and the mounting plate 340 are shown in transparent outline to show a more detailed view of the adjustable slit mechanism. The optical sensor assembly 311 includes an optical disc 370 and an optical sensor 372. The optical disc 370 includes one or more levels configured to provide an indication of the rotational position of the optical disc. The optical sensor 372 is configured to sense the one or more levels on the optical disc 370 so as to output information about the rotational position of the slit adjustment cam 306. By sensing the rotational position of the slit adjustment cam 306 using the optical sensor assembly 370, the second stepper motor 360 can control the rotational position of the slit adjustment cam 306 by a precisely controlled number of steps, so that the slit width of the adjustable slit mechanism 300 can be precisely controlled. A controller (not shown) is provided, which is configured to control the second stepper motor 360 using the information provided by the optical sensor assembly 311 to provide the desired rotational position of the slit adjustment cam 306 in response to the slit width required by the user. Using the second stepper motor 360 to rotate the slit adjustment cam 306 means that when the second stepper motor 360 is not driven, the detent torque of the stepper motor ensures that the slit adjustment cam 306 remains in a fixed rotational position. Therefore, the adjustable slit mechanism 300 can be robust and vibration-resistant.

[0151] Fig.11 A diagram illustrating an exemplary slit adjustment cam 306 having a variable radius in accordance with an embodiment of the present invention is shown. Fig.12 Shows Fig.11 3D view of an exemplary slit adjustment cam 306 is shown. The exemplary slit adjustment cam 306 has an inner diameter 380 for mounting on the axle of the second stepper motor 360. In the exemplary embodiment, the inner diameter is 8 mm in size. The slit adjustment cam 306 also has an outer diameter 382 having a variable radius around the circumference of the slit adjustment cam. Fig.11As shown, the size of the variable radius increases from a minimum value at a first point around the circumference at a nominal 0° to a maximum value at a second point around the circumference 160° from the nominal 0° point. This variable radial profile around the circumference repeats from a point 180° around the circumference to a point 360° around the circumference. Thus, in a preferred embodiment, the radius at any given point of the circumference of the slit adjustment cam 306 is the same as the radius of the opposite point of the circumference of the slit adjustment cam (i.e., the point on the opposite side of the central axis). Thus, the slit adjustment cam has a variable radius, wherein the diameter (variable diameter) of the slit adjustment cam has a midpoint that is aligned with the axis of rotation of the cam around the slit adjustment cam. In an exemplary embodiment, the variable radius increases from a minimum of 7.5 mm at the nominal 0° point at a rate of 1 μm per degree. Thus, after a rotation of 10°, the radius of the slit adjustment cam 306 increases by 10 μm. Since the variable radial profile repeats 180° around the circumference, the diameter of the slit adjustment cam 306 will increase by 20 μm after a 10° rotation. After a 160° rotation, in order for the variable radial profile to reach its maximum value, the diameter of the slit adjustment cam will increase by 320 μm.

[0152] As mentioned above, Fig.11 The slit adjustment cam 306 shown is configured to provide the adjustable slit mechanism with an adjustable slit width from 0 μm (i.e., the slit is fully closed) to 320 μm. Fig.11 and 12 In the drawings, only the base diameter of the outer diameter is indicated to provide a clearer indication of the variable profile, and in practice, this base circumference is not necessarily distinguishable in the finished cam 306. It should also be understood that Fig.11 The variable radial profile shown is exemplary only and the profile may be adapted depending on the desired range of slit widths required for the adjustable slit mechanism of the monochromator.

[0153] For example, the diameter of the slit adjustment cam 306 can increase by at least 2 mm from the minimum diameter to the maximum diameter. Therefore, a slit adjustment cam can be provided, which is configured to provide an adjustable slit width ranging from at least 0.025 mm to no more than 2 mm, or more preferably ranging from, for example, at least 0.025 mm to no more than 0.5 mm.

[0154] according to Fig.11 and 12The slit adjustment cam 306 of the exemplary embodiment shown is made of spring steel. More specifically, the slit adjustment cam 306 can be made of oil hardened non-deformed (OHNS) steel. The slit adjustment cam 306 is first cut into a wide outer diameter and a desired inner diameter 380 using standard machining techniques. Then, a wire cutting machine is used to cut the variable radial profile of the slit adjustment cam 306 from the wider outer diameter. Then, a heat treatment process, such as an oil hardening process, is used to harden the wire-cut slit adjustment cam 306. Preferably, the slit adjustment cam is hardened to at least 30HRC (Rockwell hardness), more preferably at least 35HRC, more preferably at least 40HRC, and most preferably at least 45HRC. Since the wire cutting process produces a sufficiently accurate and smooth finish on the variable radial profile of the cam, no additional machining or polishing of the component is required. A press-fit bushing can be installed in the inner diameter of the slit adjustment cam 306 so that the slit adjustment cam 306 is adapted to be installed on the axle of the second stepper motor 360. Of course, other high precision machining techniques for producing a cam having a desired radial profile are known to the skilled person.

[0155] Fig.13 A rear plan view of an exemplary embodiment of an adjustable slit mechanism 300 is shown. Fig.13 As shown, the adjustable slit mechanism 300 provides both the entrance slit 88 and the exit slit 89 of the monochromator assembly 80 (see also Figure 2 , wherein the entrance slit 88 is provided by the adjustable slit assembly 81). To further define the entrance slit 88 and the exit slit 89, the mounting plate 340 further includes an entrance hole 390 for the sample light and the reference light to pass through the mounting plate 340 and an exit hole 392 for the sample light to pass through the mounting plate 340 in the opposite direction. Fig.13 As shown, the first slit edge 312 and the second slit edge 314 of the adjustable slit mechanism are visible through each of the inlet aperture 390 and the outlet aperture 392 .

[0156] In an exemplary embodiment, the adjustable slit is used as both the entrance slit 88 and the exit slit 89. At least 11 mm of the length of the adjustable slit is provided as the exit slit 89, wherein the length of the sample light path is about 4 mm, and the length of the reference light path is about 4 mm, and (by the optical device of the system) a spacing of about 3 mm is provided between the light paths. The portion of the adjustable slit mechanism that forms the exit slit 89 is separated from the portion of the adjustable slit mechanism that forms the entrance slit by a gap of about 24 mm. The entrance slit 88 can also be provided using an adjustable slit mechanism of about 11 mm length.

[0157] Next, the operation will be described Figures 6 to 10A method of operating the adjustable slit mechanism 300 is shown. After assembling the adjustable slit mechanism 300 as described above, an initial setup and calibration of the machine may be performed. The first slit edge 312 and the second slit edge 314 may be aligned in the adjustable slit mechanism 300 such that the slit edges 312, 314 are in contact along their lengths (i.e., the slit may be completely closed along its length). Figures 6 to 10 In the illustrated embodiment, the first slit edge 312 and the second slit edge 314 are aligned parallel to each other so that both slit edges are vertical. The alignment of the first slit edge 312 and the second slit edge 314 is provided by the first arm 308 and the second arm 310 in contact with the positioning washer 342. The positioning washer 342 is provided to limit the movement of the first slit member 302 and the second slit member 304 to a single axis of movement. In this way, when the width of the slit is adjusted by the slit adjustment cam 306, the first slit edge 312 and the second slit edge 314 remain parallel to each other.

[0158] The alignment of the first slit edge 312 and the second slit edge 314 can be confirmed by checking that the adjustable slit can be completely closed so that no light passes through the slit. Figure 2 The calibration of the slit adjustment cam 306 can be checked by using a slit adjustment mechanism in a monochromator system such as the monochromator 80 shown. By rotating the slit adjustment cam 306 to a known angular position that provides a desired slit width, incident light (sample light or reference light) can be imaged on the adjustable slit, and the light can be measured using the detector 90. As is known in the art, the slit width of the monochromator can be inferred based on the bandwidth of the detected light. Therefore, the system can be simply calibrated to confirm that the actual slit width of the monochromator 80 at the known angular position of the slit adjustment cam 306 corresponds to the expected slit width and produces the desired optical performance. Once this initial setup is performed, due to the stable nature of the adjustable slit mechanism 300, no additional calibration of the adjustable slit mechanism is required. For example, no further calibration of the width of the adjustable slit mechanism is required when the system is started, because the controller is configured to adjust the angular position of the slit adjustment cam 306 based on information from the optical sensor assembly 311.

[0159] The second stepper motor 360 is used to adjust the angular position of the slit adjustment cam 306 in response to a request from the controller to change the slit width. The controller may include a memory that stores information about the variable radial profile of the slit adjustment cam, for example, which angular positions of the slit adjustment cam correspond to a specific slit width of the adjustable slit mechanism. The controller is configured to use the information to instruct the second stepper motor 360 to rotate the slit adjustment cam 306 to a desired angular position corresponding to the desired slit width (i.e., corresponding to the diameter of the slit adjustment cam 306).

[0160] In order to deliver the sample light and the reference light to the adjustable slit mechanism 81, 300, optical fibers may be used. Figure 2 As shown as a portion of an optical fiber AAS, sample fiber 60 and reference light 70 can be used to deliver light to entrance hole 390. Fig.14A , Fig. 14B and Fig. 14C Illustrative views of a sample optical fiber 60 and a reference optical fiber 70 used for such purposes are shown.

[0161] Fig.14A A front view of a sample optical fiber 60, a reference optical fiber 70, and a combined optical fiber connector 400 for focusing sample light and reference light onto an adjustable slit is shown. Fig. 14B As shown, the sample optical fiber 60 and the reference optical fiber 70 can each be connected at one end to, for example, Figure 2 The sample light source and the reference light source of the second focusing elements 36, 38 are shown. Fig. 14C Shown along the Fig. 14B A detailed view of section H-H is shown.

[0162] Fig.15 Shown along Fig. 14B Detailed view of section E-E. Fig.15 A cross-sectional view of reference optical fiber 70 is shown.

[0163] Fig.16A , Fig. 16B and Fig. 16C It shows that Fig.14A , Fig. 14B and Fig. 14C Further detailed views of the fiber core arrangements at respective ends of the sample optical fiber 60 and the reference optical fiber 70 are indicated. Fig.16A A detailed view of the multiple fiber cores within reference fiber 70 is shown. Fig.16A As indicated, there are seven optical fiber cores within reference optical fiber 70. Similarly, Fig. 16B A detailed view of a sample optical fiber 60 is shown which also has seven optical fiber cores. Fig. 16C It shows that Fig. 14B and Fig. 14C A detailed view "A" of one embodiment of the arrangement of the fiber cores of the sample fiber 60 and the reference fiber 70 from section H-H is indicated. Fig. 16C As shown, the combined fiber optic connector 400 is arranged to direct the fiber core of each of the reference fiber 70 and the sample fiber 60 into an arrangement suitable for injecting light into the entrance aperture 390 of the adjustable slit mechanism 300 .

[0164] Preferably, the combined fiber optic connector 400 is shaped to separate the fiber core of the reference fiber 70 from the fiber core of the sample fiber 60 and also to align each of the fiber core groups in a single plane. Fig.17 An example of such alignment is shown, which provides an example of Fig.14A End view indicated by detail "F" in FIG. Fig.17 As indicated, Fig.16A and 16B Each of the labeled optical fiber cores shown is aligned by the combined optical fiber connector 400 along a plane, which can then be aligned with the center of the slit of the adjustable slit mechanism 300. Therefore, the combined optical fiber connector 400 is configured to output sample light on the sample optical path and to output reference light on the reference optical path, the sample optical path and the reference optical path being separated by a spacing portion of the combined optical fiber connector 400.

[0165] According to another embodiment of the present invention, a monochromator slit assembly for a fiber optic atomic absorption spectrometer is provided. The monochromator slit assembly comprises a sample optical fiber, a reference optical fiber, a slit of a monochromator and a rotatable chopper. In a particularly preferred embodiment of the present invention, the monochromator slit assembly comprising a rotatable chopper can be incorporated into the adjustable slit mechanism 300 as described above.

[0166] For example, Figure 6 FIG. 4 shows a monochromator slit assembly according to an embodiment of the present invention. Figure 6 As shown, the monochromator slit assembly includes a sample fiber 60 for delivering sample light, a reference fiber 70 for delivering reference light, a slit of the monochromator provided by an adjustable slit mechanism 300, and a rotatable chopper 500 also shown in a separate detailed view.

[0167] like Figure 6 As shown, the rotatable chopper 500 is arranged downstream of the adjustable slit mechanism 300, so that the light output from the sample optical fiber 60 and the reference optical fiber 70 can travel through the adjustable slit mechanism 300, so that the light is incident on the rotatable chopper 500. As such, the rotatable chopper 500 is understood to be arranged downstream of the adjustable slit mechanism 300. The rotatable chopper 500 is configured to alternatively block the light output from the sample optical fiber 60 and the light output from the reference optical fiber 70. As explained above, due to the arrangement of the combined optical fiber connector 400 that spatially separates the sample optical path from the reference optical path, the light output from the sample optical fiber 60 on the sample optical path is spatially separated from the light output from the reference optical fiber 70 on the reference optical path.

[0168] The rotatable chopper 500 includes a plurality of sample channels 502, 504 and a plurality of reference channels 506, 508, each of which is configured to transmit a sample light path when one of the sample channels is aligned with the adjustable slit, and each of which is configured to transmit a reference light path when one of the reference light channels is aligned with the reference light path. Each of the sample channels 502, 504 and the reference light channels 506, 508 is provided as a through hole of the rotatable chopper 500, which runs through the central axis of the rotatable chopper.

[0169] The rotatable chopper 500 is provided as an elongated member that may be substantially tubular and may have a rotation axis aligned with the central axis of the adjustable slit of the adjustable slit mechanism 300. Figure 6 As shown, the rotatable chopper is provided so that the axis of rotation of the rotatable chopper 500 is generally vertical when in use. This is advantageous because the gravitational force acting on the rotatable chopper 500 will act according to the axis of rotation of the rotatable chopper 500 so that the alignment of the axis of rotation of the chopper (relative to the adjustable slit mechanism) will remain aligned with the central axis of the adjustable slit of the adjustable slit mechanism 300 over time. Thus, a stable monochromator slit assembly for fiber optic AAS is provided.

[0170] like Figure 6 As shown in the embodiment of FIG. 5 , the rotatable chopper 500 includes two sample channels 502, 504 and two reference channels 506, 508. The sample channels 502, 504 are spaced apart from the reference channels 506, 508 according to the spacing between the sample light path incident on the adjustable slit and the reference light path. Therefore, it should be understood that when the rotatable chopper 500 rotates about its rotation axis, the sample light channel 502 can be aligned with the sample light path at a first angular position, so that the sample light path passes along the sample light channel 502, while the reference light on the reference light path is blocked by the rotatable chopper because there is no reference light channel aligned with the reference light path. The rotatable chopper can be moved to a second position by rotating the rotatable chopper clockwise by about 45°. In the second position, the reference light channel 508 can be aligned with the reference light path output by the reference optical fiber 70 through the adjustable slit. In such a second position, the reference light on the reference light path will be transmitted by the rotatable chopper 500 through the reference light channel 508. In the second position, the sample light will be blocked by the rotatable chopper 500 since no sample channel is aligned with the sample light path.

[0171] Thus, when each of the sample light channels 502, 504 and the reference light channels 506, 508 are aligned with the adjustable slit, rotation of the rotatable chopper 500 causes the rotatable chopper to alternatively block the sample light path and the reference light path. It should be understood that in an intermediate position, such as at a rotation (e.g., 45°) between the first position and the second position, the rotatable chopper can be provided to block both the sample light path and the reference light path such that interference between the sample light and the reference light is not possible (i.e., the sample light and the reference light are not transmitted simultaneously).

[0172] In order to control the rotational position of the rotatable chopper 500, the rotatable chopper is mounted on a Figure 6 The third stepper motor 510 below the rotatable chopper 500 shown is driven. The rotatable chopper 500 and the third stepper motor 510 are mounted on a mounting platform 512, which provides a stable base for the rotatable chopper 500 and ensures that the rotatable chopper 500 is aligned with the adjustable slit of the adjustable slit mechanism 300. In order to control the rotational position of the rotatable chopper 500, the third stepper motor 510 is controlled by a controller (not shown). The controller can be the same controller used to control the first stepper motor 114 and / or the second stepper motor 360. The controller is configured to receive information about the rotational position of the rotatable chopper 500 from a sensor. Figure 6 In the illustrated embodiment, the sensor is an optical sensor 514. The optical sensor 514 is configured to detect an optical strip 516 attached to the rotatable chopper 500 when the optical strip passes through the optical sensor 514. Therefore, the optical sensor 514 can be configured to detect the starting position of the rotatable chopper 500. The controller can then control the third stepper motor 510 to rotate the rotatable chopper 500 by the desired number of steps of the third stepper motor 510 to reach a desired angular position, so as to align the sample channel or the reference channel with the adjustable slit as needed, depending on the measurement to be performed by the monochromator. For example, Figure 6 As shown, the rotatable chopper 500 is oriented so that the reference light (R) of the reference fiber 70 is transmitted by the rotatable chopper 500, while the sample light of the sample fiber 60 is blocked by the rotatable chopper 500. In order to precisely control the rotation of the third stepper motor 510, the step angle of the third stepper motor 510 is preferably less than 10°.

[0173] It should be understood that Figure 6 In the embodiment, the rotatable chopper only extends about half the length of the adjustable slit. This is because the upper portion of the adjustable slit serves as the exit slit for the reference and sample light. Preferably, the rotatable chopper 500 is positioned directly downstream of the adjustable slit (i.e., at Figure 2The collimating mirror 82 is disposed before the grating 84 so that at any one time, only one of the sample light or the reference light but not both can be incident on the optical device of the monochromator (ie, the collimating mirror 82 and the grating 84).

[0174] So, reference Figures 6 to 9 The adjustable slit mechanism shown and Figure 2 The monochromator 80 shown may provide a monochromator assembly. Figure 2 As shown, such a monochromator assembly includes an adjustable slit mechanism 300, a rotatable chopper 500, a collimating element (e.g., a collimating mirror 82), and a diffraction element (e.g., a diffraction grating 84). Specifically, the adjustable slit mechanism 300 is provided to serve as both the entrance slit and the exit slit (i.e., a common entrance slit and exit slit) of the monochromator assembly.

[0175] One advantage of such a monochromator assembly is that the monochromator assembly is robust because the sample and reference optical paths output from the respective sample and reference optical fibers 60, 70 remain aligned with the center of the adjustable slit mechanism and the central axis of the rotatable chopper 500. Thus, the light output through the exit aperture 392 of the monochromator can be accurately controlled for a range of different adjustable slit sizes because the central axis of the adjustable slit remains aligned with the sample and reference optical fibers 60, 70 for a range of different slit widths. Thus, the need to calibrate the monochromator for a range of different slit widths can be reduced and / or eliminated.

[0176] In a particularly preferred embodiment, the adjustable slit mechanism 81, 300 can provide both an entrance slit and an exit slit for the monochromator assembly 80, so that the monochromator can output light with a bandwidth in the range of 0.1nm to 2nm. For example, such a bandwidth range can be achieved by: a slit width with an adjustable range between 25μm and 2mm combined with a suitable diffraction grating, or a slit width that can be adjusted between 25μm and 320μm combined with a suitable diffraction grating. In both exemplary cases, it should be understood that the adjustable slit can also be completely closed (i.e., a slit width of 0μm). The design of suitable diffraction gratings and collimating mirrors in combination with common entrance slits and exit slits is well known in the art, and therefore will not be discussed further herein. As such, any component of this monochromator can be replaced by any component having the same physical effect.

[0177] Therefore, according to the present invention, an optical fiber AAS1 is provided. The optical fiber AAS1 includes many components described according to embodiments of the present invention. A particularly advantageous embodiment is a lamp holder assembly 20. The lamp holder assembly 20, in combination with a rotatable arm and an optical fiber connection, allows light to be focused from one of a plurality of sample light sources into an optical cable in a robust and highly repeatable manner.

[0178] In a further advantageous embodiment of the present invention, an adjustable slit mechanism 300 is provided. The adjustable slit mechanism can provide an entrance slit and / or an exit slit (common adjustable slit) for the monochromator 80. Such an adjustable slit mechanism can be used in various types of monochromators, but is particularly advantageous when used in conjunction with an optical cable as part of a fiber optic AAS. Fiber optic AAS systems reduce complexity and improve robustness by reducing mirror-based focusing elements, which may require repeated calibration before use to ensure adequate alignment of various optical components. Fiber optic AAS systems can include optical fibers for guiding sample light and reference light, which can maintain a fixed positional relationship with the entrance slit of the monochromator. Therefore, an adjustable slit mechanism with a constant slit center axis is particularly advantageous because the center position of the adjustable slit mechanism will maintain the position of the adjustable slit mechanism relative to the sample fiber 60 and the reference fiber 70 during an extended period of time, so that further calibration of the slit alignment can be reduced and / or avoided. Therefore, a stable but highly accurate adjustable slit mechanism for fiber optic AAS can be provided.

[0179] In addition, the adjustable slit mechanism can form a monochromator slit assembly including a rotatable chopper 500. In this assembly, advantageously, the rotatable chopper 500 has a rotation axis that can be aligned with the central axis of the adjustable slit. Thus, as part of a dual-beam AAS system, the monochromator can filter sample light and / or reference light. The alignment (vertical alignment) of the rotatable chopper can ensure that the relative alignment of the monochromator slit assembly is stable over time and does not require repeated calibration.

[0180] According to another embodiment of the present invention, a fiber optic cable assembly is provided. Such an assembly provides an efficient and robust means for delivering light from a first light source and a second light source to a sample housing 40 as part of a dual beam fiber optic AAS.

[0181] Embodiments of the present invention can be summarized in the following clauses:

[0182] 1. An adjustable slit mechanism for a monochromator, the adjustable slit mechanism comprising:

[0183] a first slit member, the first slit member comprising a first slit edge;

[0184] a second slit member, the second slit member comprising a second slit edge;

[0185] The first slit edge is arranged opposite to the second slit edge to define an adjustable slit of the adjustable slit mechanism;

[0186] a slit adjustment cam having a variable radius;

[0187] a first arm connected to the first slit member;

[0188] a second arm connected to the second slit member;

[0189] The first arm and the second arm are elastically biased against the slit adjustment cam, so that rotation of the slit adjustment cam adjustably separates the first arm and the second arm to adjust the width of the adjustable slit.

[0190] 2. An adjustable slit mechanism according to clause 1, wherein the point at which the first arm is resiliently biased against the slit adjustment cam is opposite to the point at which the second arm is resiliently biased against the offset slit adjustment cam.

[0191] 3. The adjustable slit mechanism according to clause 1 or 2, further comprising a resilient biasing element connected between the first arm and the second arm to bias the first arm and the second arm against the slit adjustment cam.

[0192] 4. An adjustable slit mechanism according to claim 3, wherein a pair of elastic biasing elements are connected between the first arm and the second arm, the pair of elastic biasing elements are respectively connected to the first arm and the second arm at the two side points and the arms contact the slit adjusting cam at the points on their corresponding connection sides respectively.

[0193] 5. An adjustable slit mechanism according to any of the preceding clauses, wherein the variable radius of the slit adjustment cam is configured to adjust the separation of the first arm and the second arm by moving each of the first arm and the second arm substantially equally.

[0194] 6. An adjustable slit mechanism according to any of the preceding clauses, wherein each of the first arm and the second arm is supported by a plurality of guide members configured to align the first slit edge parallel to the second slit edge.

[0195] 7. An adjustable slit mechanism according to clause 6, wherein each of the first arm and the second arm includes an alignment portion, each alignment portion being configured to engage with a plurality of guide members.

[0196] 8. An adjustable slit mechanism according to any of the preceding clauses, wherein the first arm and the second arm each include a cam engagement portion, each cam engagement portion being configured to provide a surface for engagement with the slit adjustment cam.

[0197] 9. An adjustable slit mechanism according to clause 8, wherein each cam engagement portion further comprises a sliding bearing material configured to provide the surface for engagement with the slit adjustment cam.

[0198] 10. An adjustable slit mechanism according to clause 8 or 9, wherein each cam engagement portion is configured to engage with the slit adjustment cam in a plane substantially parallel to the first slit edge and the second slit edge.

[0199] 11. An adjustable slit mechanism according to any one of clauses 8 to 10, when dependent on any one of clauses 6 or 7, wherein the cam engaging portion and the alignment portion of each of the first arm and the second arm are connected together to form a substantially L-shaped portion.

[0200] 12. An adjustable slit mechanism according to any of the preceding clauses, wherein the first slit edge and the second slit edge of the adjustable slit are configured to provide entrance and exit slits for the monochromator.

[0201] 13. An adjustable slit mechanism according to any of the preceding clauses, wherein the first slit member and the second slit member are connected to the first arm and the second arm respectively by fasteners.

[0202] 14. An adjustable slit mechanism according to any of the preceding clauses, wherein the slit width is adjustable in the range of 0.025 mm to 2 mm or in the range of 0.025 mm to 0.5 mm.

[0203] 15. A slit assembly for a monochromator of an optical fiber atomic absorption spectrometer, the slit assembly comprising:

[0204] a sample optical fiber for delivering sample light;

[0205] a reference optical fiber for delivering reference light;

[0206] an adjustable slit provided by an adjustable slit mechanism according to any one of clauses 1 to 14,

[0207] wherein one end of each of the sample optical fiber and the reference optical fiber is arranged to direct light along the respective sample optical path and reference optical path through the adjustable slit;

[0208] as well as

[0209] A rotatable chopper is disposed downstream of the adjustable slit mechanism and is configured to alternatively close the sample light path and the reference light path by rotation.

[0210] 16. The slit assembly of clause 15, wherein the rotation axis of the rotatable chopper is aligned with the adjustable slit.

[0211] 17. A slit assembly according to clause 15 or 16, wherein the axis of rotation of the rotatable chopper is generally vertical when in use.

[0212] 18. The slit assembly according to any one of clauses 15 to 17, wherein the rotatable chopper is further configured to define:

[0213] at least one sample channel configured to transmit the sample light; and

[0214] at least one reference channel, the at least one reference channel configured to transmit the reference light;

[0215] The sample channel is spaced apart from the reference channel along the rotation axis of the chopper.

[0216] 19. The slit assembly according to clause 18, wherein the rotatable chopper is configured to further define:

[0217] at least two sample channels, the at least two sample channels being arranged transversely relative to each other about the axis of rotation of the chopper; and

[0218] At least two reference channels are arranged transversely relative to each other about the rotation axis of the chopper.

[0219] 20. The slit assembly according to any of clauses 15 to 19, comprising a sensor configured to detect the rotational position of the rotatable chopper.

[0220] 21. The slit assembly according to any one of clauses 15 to 20, comprising:

[0221] a stepper motor configured to rotate the rotatable chopper,

[0222] The stepping angle of the stepping motor is less than 10°.

[0223] 22. A monochromator assembly comprising:

[0224] A slit assembly according to any one of clauses 15 to 21;

[0225] Collimation element;

[0226] Diffractive elements;

[0227] wherein the collimating element is configured to guide the sample light and the reference light path incident on the collimating element from the respective first positions along the slit to the diffraction element;

[0228] The diffraction element is arranged to reflect the sample light and the reference light incident on the diffraction element from the collimation element back to the collimation element; and

[0229] The collimating element is further configured to direct the sample light and the reference light from the diffraction element along the adjustable slit to respective second positions, the respective second positions being spatially separated from the first position.

[0230] 23. The monochromator assembly of clause 22, wherein the collimating element is arranged downstream of the rotatable chopper.

[0231] 24. A monochromator assembly according to claim 22 or claim 23 and combined with the adjustable slit mechanism described in any one of claims 1 to 14, wherein the diffraction element is rotatably adjustable so that the monochromator, in combination with the adjustable slit mechanism, can selectively output sample light or reference light with a bandwidth in the range of 0.1 nm to 2 nm.

[0232] 25. A monochromator slit assembly for a fiber-optic atomic absorption spectrometer, the monochromator slit assembly comprising:

[0233] a sample optical fiber for delivering sample light;

[0234] a reference optical fiber for delivering reference light;

[0235] The slit of the monochromator,

[0236] wherein one end of each of the sample optical fiber and the reference optical fiber is arranged to direct light along the respective sample optical path and reference optical path through the slit; and

[0237] A rotatable chopper is disposed downstream of the slit and is configured to alternatively block the sample light path and the reference light path.

[0238] 26. The monochromator slit assembly of clause 25, wherein the rotation axis of the rotatable chopper is aligned with the slit.

[0239] 27. A monochromator slit assembly according to clause 25 or 26, wherein the axis of rotation of the rotatable chopper is generally vertical when in use.

[0240] 28. The monochromator slit assembly according to any one of clauses 25 to 27, wherein the rotatable chopper is further configured to define:

[0241] at least one sample channel configured to transmit the sample light; and

[0242] at least one reference channel, the at least one reference channel configured to transmit the reference light;

[0243] The sample channel is spaced apart from the reference channel along the rotation axis of the chopper.

[0244] 29. The monochromator slit assembly of clause 28, wherein the rotatable chopper is configured to further define:

[0245] at least two sample channels, the at least two sample channels being arranged transversely relative to each other about the axis of rotation of the chopper; and

[0246] At least two reference channels are arranged transversely relative to each other about the rotation axis of the chopper.

[0247] 30. A monochromator slit assembly according to any one of clauses 25 to 29, comprising a sensor configured to detect a rotational position of the chopper assembly.

[0248] 31. A monochromator slit assembly according to any one of clauses 25 to 30, comprising:

[0249] a stepper motor configured to rotate the chopper assembly,

[0250] The stepping angle of the stepping motor is less than 10°.

[0251] 32. The monochromator slit assembly according to any one of clauses 25 to 31, wherein the slit is an entrance slit of a monochromator.

[0252] 33. A monochromator assembly comprising:

[0253] A monochromator slit assembly according to any one of clauses 25 to 32;

[0254] Collimation element;

[0255] Diffractive elements;

[0256] wherein the collimating element is configured to guide the sample light and the reference light path incident on the collimating element from the respective first positions along the slit to the diffraction element;

[0257] The diffraction element is arranged to reflect the sample light and the reference light incident on the diffraction element from the collimation element back to the collimation element; and

[0258] The collimating element is further configured to direct the sample light and the reference light from the diffraction element along the slit to respective second positions, the respective second positions being spatially separated from the first position.

[0259] 34. The monochromator assembly of clause 33, wherein the collimating element is arranged downstream of the rotatable chopper.

[0260] 35. A monochromator assembly according to clause 33 or 34, wherein the slit of the monochromator is provided by an adjustable slit mechanism, the adjustable slit mechanism comprising:

[0261] a first slit member, the first slit member comprising a first slit edge;

[0262] a second slit member, the second slit member comprising a second slit edge;

[0263] The first slit edge is arranged opposite to the second slit edge to define an adjustable slit of the adjustable slit mechanism;

[0264] a slit adjustment cam having a variable radius;

[0265] a first arm connected to the first slit member;

[0266] a second arm connected to the second slit member;

[0267] wherein the first arm and the second arm are elastically biased against the slit adjustment cam so that rotation of the slit adjustment cam adjustably separates the first arm and the second arm to adjust the width of the adjustable slit,

[0268] The diffraction element is rotatably adjustable, so that the monochromator combined with the adjustable slit mechanism can selectively output sample light or reference light with a bandwidth ranging from 0.1 nm to 2 nm.

[0269] 36. A monochromator assembly according to clause 35, wherein the point at which the first arm is resiliently biased against the slit adjustment cam is opposite the point at which the second arm is resiliently biased against the slit adjustment cam.

[0270] 37. The monochromator assembly of clause 35 or 36, further comprising a resilient biasing element connected between the first arm and the second arm to bias the first arm and the second arm against the slit adjustment cam.

[0271] 38. A monochromator assembly according to any one of clauses 35 to 37, wherein the variable radius of the slit adjustment cam is configured to adjust the separation of the first arm and the second arm by moving each of the first arm and the second arm substantially equally.

[0272] 39. A monochromator assembly according to any one of clauses 35 to 38, wherein

[0273] Each of the first arm and the second arm is supported by a plurality of guide members configured to align the first slit edge parallel to the second slit edge; and

[0274] The first arm and the second arm each include:

[0275] cam engaging portions, each cam engaging portion being configured to provide a surface for engaging with the slit adjusting cam; and

[0276] alignment portions, each alignment portion being configured to engage with the plurality of guide members,

[0277] Wherein the cam engaging portion and the alignment portion of each of the first arm and the second arm are connected together to form a substantially L-shaped portion.

[0278] 40. A light source assembly (AAS) for a fiber optic atomic absorption spectrometer, the light source assembly comprising:

[0279] a plurality of light sources, the plurality of light sources being arranged around an axis;

[0280] an arm arranged to rotate about the axis;

[0281] Optical cables;

[0282] a focusing element configured to couple light from a selected one of the plurality of light sources into one end of the optical cable;

[0283] The optical cable and the focusing element are arranged on the arm so that the arm can be rotated relative to the plurality of light sources to select a light source for the optical cable.

[0284] 41. A light source assembly according to clause 40, wherein

[0285] The axis of rotation of the arm is generally vertical when the arm is in use.

[0286] 42. A light source assembly according to clause 40 or 41, wherein

[0287] The arm includes a counterweight at an end of the arm opposite the focusing element.

[0288] 43. A light source assembly according to any one of clauses 40 to 42, wherein

[0289] The focusing element is a lens.

[0290] 44. A light source assembly according to any one of clauses 40 to 43, wherein

[0291] The focusing element is arranged on the arm with respect to the optical cable to couple light directly into the optical cable.

[0292] 45. A light source assembly according to any one of clauses 40 to 44, wherein

[0293] The focusing element and the one end of the optical cable are aligned with a direction in which light is output from the selected light source.

[0294] 46. ​​A light source assembly according to clause 45, wherein

[0295] The optical fibre, the focusing element and the selected light source are arranged to be substantially vertically aligned in use.

[0296] 47. A light source assembly according to any one of clauses 40 to 46, comprising:

[0297] A drive shaft is connected to the arm at one end, the drive shaft being aligned with the rotational axis.

[0298] 48. A light source assembly according to clause 47, comprising

[0299] A stepper motor is configured to drive the drive shaft at the opposite end of the arm.

[0300] 49. A light source assembly according to clause 47 or 48, comprising

[0301] A housing is configured to support the drive shaft at both ends.

[0302] 50. A light source assembly according to any one of clauses 40 to 49, comprising:

[0303] A controller is configured to calibrate a rotational position of the arm relative to the light source in response to a signal indicative of optical power focused into the fiber optic cable from the light source.

[0304] 51. A light source assembly according to any one of clauses 40 to 50, wherein

[0305] The plurality of light sources includes a plurality of hollow cathode lamps.

[0306] 52. A light source assembly according to any one of clauses 40 to 51, wherein

[0307] The plurality of light sources comprises at least 5 light sources, preferably at least 10 light sources.

[0308] 53. A fiber optic atomic absorption spectrometer, comprising:

[0309] A light source assembly according to any one of clauses 40 to 52;

[0310] Sample atomizer;

[0311] Sample optical cables;

[0312] Monochromator; and

[0313] Detector,

[0314] The light source assembly is configured to output sample light to the monochromator through the sample atomizer and the sample optical cable, and the monochromator is configured to filter the sample light and output the filtered light to the detector.

[0315] 54. A dual-beam fiber-optic atomic absorption spectrometer, comprising:

[0316] A light source assembly according to any one of clauses 40 to 52;

[0317] Reference light source;

[0318] a sample atomizer configured to receive a sample to be analyzed;

[0319] Sample optical cables;

[0320] Reference optical cable;

[0321] Monochromator; and

[0322] Detector,

[0323] The light source assembly and the reference light source are configured to output light to the monochromator on the following optical path:

[0324] i) a sample optical path passing through the sample atomizer and the sample optical cable; and

[0325] ii) a reference optical path passing through the reference optical cable;

[0326] The monochromator is configured to filter the sample light and the reference light and output the filtered light to the detector.

[0327] It will be appreciated by those skilled in the art that the present invention is not limited to the embodiments described above and shown in the accompanying drawings and that numerous additions and modifications are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A light source assembly for a fiber optic atomic absorption spectrometer, the light source assembly comprising: a plurality of light sources, the plurality of light sources being arranged around an axis; an arm arranged to rotate about the axis; Optical cables; a focusing element configured to couple light from a selected one of the plurality of light sources into one end of the optical cable; The optical cable and the focusing element are arranged on the arm so that the arm can be rotated relative to the plurality of light sources to select a light source for the optical cable.

2. The light source assembly according to claim 1, characterized in that: The axis of rotation of the arm is generally vertical when the arm is in use.

3. The light source assembly according to claim 1 or 2, characterized in that: The arm includes a counterweight at an end of the arm opposite the focusing element.

4. The light source assembly according to any one of claims 1 to 3, characterized in that: The focusing element is a lens.

5. The light source assembly according to any one of claims 1 to 4, characterized in that: The focusing element is arranged on the arm with respect to the optical cable to couple light directly into the optical cable.

6. The light source assembly according to any one of claims 1 to 5, characterized in that: The focusing element and the one end of the optical cable are aligned with a direction in which light is output from the selected light source.

7. The light source assembly according to claim 6, characterized in that: The optical fibre, the focusing element and the selected light source are arranged to be substantially vertically aligned in use.

8. The light source assembly according to any one of claims 1 to 7, characterized in that It includes: A drive shaft is connected to the arm at one end, the drive shaft being aligned with the rotational axis.

9. The light source assembly according to claim 8, characterized in that: It includes A stepper motor is configured to drive the drive shaft at the opposite end of the arm.

10. The light source assembly according to claim 8 or 9, characterized in that: It includes A housing is configured to support the drive shaft at both ends.

11. The light source assembly according to any one of claims 1 to 10, characterized in that It includes A controller is configured to calibrate a rotational position of the arm relative to the light source in response to a signal indicative of optical power focused into the fiber optic cable from the light source.

12. The light source assembly according to any one of claims 1 to 11, characterized in that The plurality of light sources includes a plurality of hollow cathode lamps.

13. The light source assembly according to any one of claims 1 to 12, characterized in that The plurality of light sources comprises at least 5 light sources, preferably at least 10 light sources.

14. A fiber optic atomic absorption spectrometer, comprising: A light source assembly according to any one of claims 1 to 13; Sample atomizer; Sample optical cables; Monochromator; as well as Detector, The light source assembly is configured to output sample light to the monochromator through the sample atomizer and the sample optical cable, and the monochromator is configured to filter the sample light and output the filtered light to the detector.

15. A dual-beam fiber-optic atomic absorption spectrometer, comprising: A light source assembly according to any one of claims 1 to 13; Reference light source; a sample atomizer configured to receive a sample to be analyzed; Sample optical cables; Reference optical cable; Monochromator; as well as Detector, The light source assembly and the reference light source are configured to output light to the monochromator on the following optical path: iii) a sample optical path passing through the sample atomizer and the sample optical cable; as well as iv) a reference optical path passing through the reference optical cable; The monochromator is configured to filter the sample light and the reference light and output the filtered light to the detector.

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