Measurement of dissolved oxygen using optical radiation to induce luminescence

Abstract

The present invention relates to the measurement of dissolved oxygen using optical radiation to induce luminescence, providing a method and apparatus for analyzing the optical measurement to determine whether the liquid includes dissolved oxygen, to determine a predicted concentration of dissolved oxygen in the liquid, and / or to determine additional or alternative characteristics related to dissolved oxygen in the liquid. A light source can be controlled to emit optical radiation into a container containing a liquid. The light source can be located outside the container, and the optical radiation includes, for example without limitation, radiation conforming to the dissolved oxygen absorption band. The optical radiation can be pulsed, or can be periodically intensity modulated. A light detector located outside the container but in optical communication with the interior of the container can produce an optical measurement for analysis.

Description

Technical Field

[0001] This invention relates to the measurement of dissolved oxygen that emits light using optical radiation. Background Technology

[0002] Organic liquids can dissolve oxygen when they come into contact with air. Dissolved oxygen in organic liquids can affect one or more downstream processes utilizing the organic liquid and / or can affect one or more properties of the final product produced using the organic liquid. As a non-limiting example, organic liquid precursors can be used to produce chemical products such as plastics. The presence of dissolved oxygen in the organic liquid precursor (e.g., at least at a threshold concentration) can affect the polymerization process producing the chemical product, can affect the color of the final chemical product, and / or can affect other properties of the final chemical product. Therefore, monitoring the dissolved oxygen level in organic liquids used in chemical processes can be important for enabling remedial action when dissolved oxygen is present and / or at least at a threshold concentration.

[0003] Various techniques have been proposed for measuring dissolved oxygen in organic liquids. However, these different techniques may require one or more components (e.g., one or more probes and / or one or more semi-permeable membranes) to be in direct contact with the organic liquid during the measurement, may require the addition of chemicals to the organic liquid, and / or may only be utilized with a limited subset of the organic liquid. Contact between components and the organic liquid can lead to contamination of the organic liquid and / or damage to the components over time. Adding chemicals to the organic liquid can adversely affect its performance. In some cases, this may necessitate the wasteful removal of the organic liquid sample in order to be able to analyze the sample without adversely affecting the overall organic liquid. Summary of the Invention

[0004] The embodiments described herein relate to methods and apparatus for inducing luminescence of dissolved oxygen in a liquid and analyzing the emitted light detected from the luminescence to determine measurements related to dissolved oxygen in the liquid (if present). For example, analyzing the detected emitted light to determine whether the liquid contains dissolved oxygen (e.g., including at least a threshold concentration), determining a predicted concentration of dissolved oxygen in the liquid, and / or determining other measurements related to dissolved oxygen in the liquid.

[0005] In some embodiments, a method includes controlling a light source to emit optical radiation into a container containing a liquid. The light source is located outside the container and the optical radiation includes radiation of wavelengths that conform to the dissolved oxygen absorption band. The method also includes generating optical measurements. The optical measurements are generated by a photodetector located outside the container but in optical communication with the interior of the container. The method further includes analyzing the optical measurements to determine whether the liquid contains dissolved oxygen.

[0006] These and other implementations of the technology disclosed herein may include one or more of the following features.

[0007] In some embodiments, the optical radiation comprises multiple pulses. In some pulsed optical radiation embodiments, the method further includes determining the desired duration of each pulse based on one or more properties of the liquid. In those embodiments, controlling the light source includes controlling the light source to generate a sequence of pulses based on the desired duration. One or more properties may include one or more of the following: the classification of the liquid, one or more chemicals contained in the liquid, or the temperature of the liquid.

[0008] In some implementations of pulsed optical radiation, the method further includes determining a subset of optical measurements based on a subset detected during non-pulsed periods. In those implementations, analyzing the optical measurements involves analyzing only a subset of the optical measurements. A non-pulsed period is a time during which pulses of optical radiation do not occur.

[0009] In some pulsed optical radiation implementations, the method also includes generating optical measurements based solely on detections by a photodetector that occur during non-pulsed periods.

[0010] In some embodiments, the optical radiation is periodically intensity-modulated. In some embodiments of periodically intensity-modulated optical radiation, analyzing the optical measurements includes analyzing the orthogonal harmonic components of the optical measurements (i.e., a phase shift of π / 2 relative to the excitation modulation) when determining whether the liquid contains dissolved oxygen. In some of those embodiments, the method further includes using a lock-in amplifier to determine the orthogonal components and / or determining an optimal modulation frequency based on the liquid-specific luminescence lifetime for dissolved oxygen.

[0011] In some implementations of periodically intensity-modulated optical radiation, the optical radiation is sinusoidally intensity-modulated.

[0012] In some implementations of periodically intensity-modulated optical radiation, the optical radiation is transmitted through a short-pass filter, a band-pass filter, and / or a polarizer before entering the container. For example, the optical radiation may be transmitted through only a band-pass filter. As another example, the optical radiation may be transmitted through only a short-pass filter and a polarizer.

[0013] In some periodically intensity-modulated optical radiation implementations, any emitted light that is emitted by any dissolved oxygen in the liquid in response to the excitation of optical radiation and that encounters the photodetector is transmitted through a long-pass filter or a band-pass filter after leaving the container and before encountering the photodetector.

[0014] In some implementations, the optical radiation passes through at least a portion of the container's optical surface after being emitted by the light source and before entering the container.

[0015] In some implementations, analytical optical measurements include determining the predicted concentration of dissolved oxygen in the liquid.

[0016] In some embodiments, a dissolved oxygen measurement system is provided and includes a container for temporarily storing liquid for analysis. The container includes an outer surface having one or more transparent or translucent optical windows. The system also includes a light source that emits optical radiation. The light source is located outside the container and positioned to emit optical radiation through at least one of the one or more optical windows and into the interior of the container. The optical radiation includes radiation of wavelengths that correspond to the absorption band of dissolved oxygen. The system also includes a photodetector located outside the container. The photodetector optically communicates with the interior of the container via one or more optical windows and optional other optical elements such as lenses and / or filters.

[0017] These and other implementations of the technology disclosed herein may include one or more of the following features.

[0018] In some implementations, the system also includes one or more processors to process the optical measurements of the photodetector and, based on that processing, determine the predicted concentration of any dissolved oxygen in the liquid.

[0019] In some implementations, the optical radiation comprises multiple pulses or is periodically intensity-modulated.

[0020] In some embodiments, the system further includes a short-pass filter located outside the container and positioned in the optical path of the optical radiation, a band-pass filter located outside the container and positioned in the optical path of the optical radiation, and / or a polarizer located outside the container and positioned in the optical path of the optical radiation. For example, the system may include a short-pass filter or a band-pass filter, and may also include a polarizer. As another example, the system may include only a short-pass filter.

[0021] In some embodiments, the system further includes a long-pass filter located outside the container and positioned between the container and the photodetector, a band-pass filter located outside the container and positioned between the container and the photodetector, and / or a spatial filter located outside the container and positioned between the container and the photodetector. For example, the system may include only a long-pass filter or only a band-pass filter.

[0022] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail herein are considered part of the subject matter disclosed herein. For example, all combinations of the claimed subject matter appearing at the end of this disclosure are considered part of the subject matter disclosed herein. Attached Figure Description

[0023] Figure 1 An example dissolved oxygen measurement system, which may employ selected aspects of this disclosure according to various embodiments, is schematically depicted.

[0024] Figure 2 This is a flowchart of example methods based on the various implementations described in this article.

[0025] Figure 3 An example of a certain amount of excited oxygen molecules over time and an example of pulsed optical radiation are shown.

[0026] Figure 4 An example of periodically intensity-modulated optical radiation is illustrated, along with an example of optical measurements detected from the modulated optical radiation. Detailed Implementation

[0027] The embodiments described herein relate to methods and apparatus for inducing emission of a target dissolved molecule in a liquid and analyzing the emitted light detected from the emission to determine measurements associated with the dissolved molecule in the liquid, if present. For example, analyzing the detected emitted light to determine whether the liquid contains the target molecule (e.g., including at least a threshold concentration), to determine a predicted concentration of the target molecule in the liquid, and / or to determine other measurements associated with the target molecule in the liquid. In various embodiments, the dissolved molecule is dissolved oxygen, and many examples provided herein will be described with respect to dissolved oxygen. However, embodiments of the methods and apparatus described herein can be utilized for other target molecules in fluids or solids.

[0028] The luminescence of the target dissolved molecules can be induced using lasers and / or other light sources that emit optical radiation, including (e.g., limited to) radiation with wavelengths matching the absorption band of the dissolved molecules. For example, the absorption band of dissolved oxygen includes 755-775 nm and 1263-1283 nm. Radiation matching the absorption band of dissolved oxygen can include radiation within the absorption band or within 2 nm, 5 nm, or other thresholds at the center of the absorption band.

[0029] The emitted light can be detected using photodetectors such as photodiodes or photomultiplier tubes (PMTs). For example, the photodetector can be in the optical path of the emitted light (if any, it is generated by the emission of light from target molecules in response to optical radiation). Furthermore, the photodetector can generate optical measurements, and these optical measurements are affected by the emitted light during their generation.

[0030] In many embodiments, the light source emitting optical radiation and the photodetector detecting the cold light (if any) caused by the optical radiation can be completely non-contact with the liquid being analyzed. In some versions of those embodiments, the light source and photodetector are external to the container temporarily storing the liquid for analysis (e.g., including inlets and outlets for liquid passage). In those versions, the container may include one or more optical windows, and one or more windows allow optical radiation to enter the container and one or more windows (the same and / or different windows) allow the emitted light to exit the container. For example, at least a portion of the container shell may be made of an optical material (e.g., acrylic, glass, polycarbonate) and this portion may form an optical window (e.g., a single optical window or one of multiple optical windows).

[0031] In some versions of the container that include an optical window, the light source is positioned such that the emitted optical radiation is directed through the optical window of the container and enters the container through the optical window. Lenses and / or reflectors may optionally be inserted between the light source and the optical window through which the optical radiation passes, and may guide and / or focus the optical radiation toward the optical window. Furthermore, optical filters (e.g., short-pass, long-pass, band-pass, and / or spatial) and / or optical polarizers may additionally or alternatively be inserted between the light source and the optical window.

[0032] Furthermore, in some versions of the container that include an optical window, the photodetector is positioned such that the emitted light, emitted by the luminescence of the target dissolved molecules and exiting the container through the optical window, is directed toward the photodetector. Optical lenses and / or optical reflectors may optionally be inserted between the light source and the optical window through which the emitted light exits the container, and may guide and / or focus the emitted light toward the photodetector. Optical filters and / or polarizers may additionally or alternatively be inserted between the photodetector and the optical window.

[0033] In some embodiments disclosed herein, the light source is controlled such that the optical radiation has discontinuous excitation. In some versions of those embodiments, the optical radiation is pulsed. In some other versions of those embodiments, the optical radiation is periodically intensity modulated (e.g., sinusoidal intensity modulation).

[0034] In some implementations of pulsed optical radiation, the duration of each pulse can be determined based on the lifetime of the excited target dissolved molecules, which can vary between different liquids. For example, for dissolved oxygen, the duration of each pulse can be determined based on the lifetime of singlet O2 in the analyte, which varies between different liquids. For example, the lifetime of singlet O2 in tetrachloromethane is approximately 17 milliseconds, while in acetone it is 0.051 milliseconds. In some versions of those implementations, the duration can be determined based on multiplying the lifetime by a factor (such as three, or a value of two to four). For example, by making the duration of each pulse three times the lifetime of singlet O2 in the liquid analyte, approximately 95% of the maximum possible number of excited O2 molecules in the liquid will be reached at the end of the pulse.

[0035] Utilizing a pulse duration based on the liquid being analyzed and aiming to reach a threshold percentage of excited molecules (e.g., 95%, 90%, or other thresholds) ensures that the pulse duration is long enough but not exceeding the necessary duration. A sufficiently long duration ensures that the threshold percentage of the target dissolved molecules is excited, so that the emitted light can be detected and / or used to resolve dissolved concentrations and / or other dissolution measurements. Preventing the duration from exceeding the time required to reach the threshold percentage allows for the analysis of a larger amount of emitted light occurring during non-pulsed periods over a period of time. This enables faster resolution measurements of the target dissolved molecules, which can be based on the analysis of multiple instances of emitted light detected during non-pulsed periods.

[0036] In some implementations, one or more characteristics of the liquid analyte may be received (e.g., based on human operator input or input from a control system), and these characteristics are used to determine the duration of each pulse. These characteristics may include the liquid's classification and / or its temperature. The liquid classification may be a genus classification encompassing multiple liquids (e.g., "hydrogen-containing") or a more refined classification including only a specific solvent (e.g., "acetone"). As a particular example, a memory or other computer-readable medium may store the association between one or more specific characteristics and their corresponding pulse durations. The received characteristics can be used to determine the corresponding pulse duration from the memory. The light source can then be controlled based on the corresponding pulse duration. For example, a driver for the light source can be configured based on the corresponding pulse duration.

[0037] In some implementations where optical radiation is pulsed, time-resolved measurements and / or analysis are utilized. In other words, the emitted light being analyzed (e.g., in determining the predicted concentration of a target dissolved molecule) can be limited to the emitted light detected by a photodetector during each non-pulse period following the corresponding pulse. The emission of dissolved oxygen and other dissolved molecules has a non-zero lifetime, meaning it continues after the corresponding pulse and can therefore be detected during the non-pulse period. For example, the lifetime of dissolved oxygen emitting light in acetone could be approximately 0.051 milliseconds, while the lifetime of dissolved oxygen emitting light in tetrachloromethane could be approximately 17 milliseconds. Furthermore, Rayleigh scattering of optical radiation is instantaneous, meaning it only occurs during the pulse. Therefore, analyzing the emitted light detected during the non-pulse period following the pulse can prevent (or at least mitigate) the adverse effects of Rayleigh-scattered light on the analysis of the dissolved target molecules, since Rayleigh scattering does not occur during the non-pulse period and therefore does not affect the emitted light detected during the non-pulse period. In some other implementations, emitted light from the pulse period may optionally be considered during the analysis, but the analysis may be weighted more heavily toward emitted light detected during the non-pulse period.

[0038] In some embodiments where the analysis is limited to the emitted light detected by the photodetector during non-pulsed periods or is more heavily weighted toward the emitted light detected by the photodetector during non-pulsed periods, the photodetector can only be activated and detect the emitted light during such non-pulsed periods. In some other embodiments, the photodetector may also be activated during pulsed periods, but the analysis is based on a subset of the emitted light determined by its occurrence during non-pulsed periods, and only that subset is analyzed (or that subset is more heavily weighted in the analysis). When determining non-pulsed periods, signals from the light source can be used to indicate when the light source produces optical radiation and / or does not produce optical radiation. Additionally or alternatively, a common or synchronous clock can be used to distinguish between pulsed and non-pulsed periods. In some embodiments, the duration of each non-pulsed period can be determined based on the properties of the liquid being analyzed. For example, if dissolved oxygen is being analyzed and the characteristics include a fine classification indicating a particular liquid, the duration can be based on the lifetime of the luminescent singlet O2 in the liquid. For example, the lifetime in acetone can be approximately 0.051 milliseconds, and the non-pulse time period can be equal to or within a threshold (e.g., within 10%, within 5%, or within other threshold percentages).

[0039] In some embodiments where optical radiation is periodically intensity modulated (e.g., sinusoidal modulation), the fixed modulation frequency can optionally be determined based on the properties of the liquid being analyzed. For example, if the properties include a fine classification indicating a particular liquid, the duration can be based on the lifetime of the luminescent dissolved molecules in the liquid. For example, for dissolved oxygen, a first frequency can be used with acetone (lifetime approximately 0.051 ms), while a lower second frequency can be used with tetrachloromethane (lifetime approximately 17 ms). It should be noted that when optical radiation is periodically intensity modulated, the luminescence of the dissolved target molecules will also be periodically intensity modulated. However, the amplitude of the modulated luminescence can differ from the amplitude of the optical radiation and can be phase-shifted relative to the amplitude of the optical radiation. Variations in amplitude and / or phase can depend on the lifetime of the luminescent target molecules in the liquid analyte and the amplitude and frequency of the optical radiation.

[0040] Furthermore, in some embodiments where the optical radiation is periodically intensity-modulated, the optical measurements generated by the photodetector may be affected by light from Rayleigh scattering. In some of those embodiments, analyzing the optical measurements may include analyzing the orthogonal (90-degree phase shift) component of the optical measurements in the measurement to determine the target dissolved molecule. Analyzing the orthogonal component, rather than the in-phase component, can effectively suppress (or even completely eliminate) the light caused by Rayleigh scattering in the analysis. Optionally, a lock-in amplifier is used to measure the orthogonal component of the probe light when processing the optical measurements. The reference signal of the lock-in amplifier may be based on the periodically intensity-modulated optical radiation or the electrical signal causing the modulation, optionally taking into account the phase shift of the modulated emission, which, as mentioned above, may depend on the lifetime of the irradiated target dissolved molecule in the liquid analyte and optionally on the properties of the optical radiation.

[0041] Furthermore, in some embodiments where the optical radiation is periodically intensity modulated, one or more optical components and / or optical techniques can be additionally or alternatively utilized to suppress probe light as a result of Rayleigh scattering. As an example, an optical polarizer can be used in the path of the optical radiation (e.g., inserted between the light source and the optical window of the container) and is selected to mitigate Rayleigh scattering. As another example, spectral filters selected to filter out certain wavelengths can be additionally or alternatively utilized. For example, a short-pass filter can be used in the path of the optical radiation and / or a long-pass filter can be inserted between the optical window and the photodetector. This can be effective because the emitted light is redshifted relative to the optical radiation, while the background light from Rayleigh scattering conforms to the spectrum of the optical radiation. As yet another example, spatial filters, such as those inserted between the optical window and the photodetector, can be additionally or alternatively utilized.

[0042] Now turn to the attached diagram. Figure 1An example dissolved oxygen measurement system 100, which may employ selected aspects of this disclosure according to various embodiments, is schematically depicted. Figure 1 The components depicted are not drawn to scale. For illustrative purposes, the dimensions of various components and the spatial relationships between them have been exaggerated.

[0043] The dissolved oxygen measurement system 100 includes a container 120, which includes an interior 122 that at least temporarily contains a liquid for dissolved oxygen analysis. The container 120 includes a housing 124, which... Figure 1 The interior 122 is shown in shaded lines and defines the interior. The outer shell 124 can take various forms depending on the shape of the container 120. For example, in Figure 1 In this context, container 120 can have a cylindrical shape (in...) Figure 1 (As shown in the cross-section). In other embodiments where the optical container 120 has other shapes, the shape of the container 120 may be different.

[0044] exist Figure 1 In this case, the entire outer casing 124 is made of optical materials, such as acrylic or glass, and is either transparent or translucent. Therefore, in Figure 1 In this embodiment, the housing 124 effectively forms a single optical window through which optical radiation can enter the interior 122 and / or through which emitted light can exit. In some other embodiments, a portion of the housing 124 may be opaque, while other portions of the housing 124 may be transparent or translucent. Thus, in those embodiments, less than the entire housing 124 allows light to enter and / or exit, and the housing 124 may include multiple optical windows through which light can enter and / or exit.

[0045] The container 120 may contain a variety of organic liquids, such as those used in various chemical processes. In various embodiments, the optical container 120 may be hermetically sealed, for example through the housing 124, such that the liquid contained within the interior 122 cannot escape except at selected locations. For example, the container 120 may optionally include one or more channels 126A, 126B through the housing 124, these channels being selected locations provided for introducing liquid samples into the interior 122 of the container 120 for analysis, and for removing liquid samples from the interior 122. Figure 1 In this design, the first channel 126A is used to introduce liquid into the interior 122, while the second channel 126B is used to remove liquid from the interior 122, but this does not imply limitation. For example, channels 126A and 126B can take various forms, such as valves operable to allow and / or prevent liquid from entering / exiting the interior 122. As another example, a single channel could be provided for both introducing liquid into and draining liquid from the interior.

[0046] The dissolved oxygen measurement system 100 also includes a light source 110 and a photodetector, both of which are outside the container 120 and therefore do not come into contact with any liquid introduced into the container 120.

[0047] Light source 110 emits optical radiation 111. The optical radiation 111 emitted by light source 110 may include (e.g., limited to) radiation of wavelengths conforming to the absorption band of dissolved oxygen. Light source 110 may take various forms, such as a laser source or an optical fiber transmitting laser light emitted from an external laser source. Light source 110 may emit coherent or incoherent light. As described herein, in various embodiments, light source 110 (e.g., via logic unit 101 described below) is controlled such that the optical radiation 111 has discontinuous excitation, such as pulsed excitation, or periodically intensity-modulated excitation.

[0048] exist Figure 1 In the illustration, various optical elements are shown outside the container 120 and positioned within the optical path of optical radiation 111. More specifically, Figure 1 The illustration shows a short-pass filter 112, a polarizer 114, and a positive lens 116. In various embodiments, one or more of the illustrated optical components in the optical path may be omitted. Furthermore, additional and / or alternative optical components, such as mirrors or other reflectors that redirect optical radiation 111 along alternative optical paths, may be provided.

[0049] In embodiments providing a short-pass filter 112, it can be selected to filter out radiation wavelengths longer than those included in the optical radiation 111, such as those close to (e.g., within 5 nm, 10 nm, or other thresholds), whose wavelengths correspond to the absorption band of dissolved oxygen. For example, in the case where such radiation is from 1263–1283 nm, the short-pass filter 112 can filter out wavelengths longer than 1283 nm. In embodiments providing a polarizer 114, it can be used to mitigate Rayleigh scattering in the optical path entering the photodetector 130. In various embodiments, the short-pass filter 112 and / or polarizer 114 are provided when the optical radiation 111 is periodically intensity-modulated radiation. In embodiments providing a positive lens 116, it can narrow the optical radiation 111 through a portion of the housing 124 to focus it onto the interior 122 of the container 120.

[0050] Because the optical radiation 111 emitted by the light source 110 includes radiation with wavelengths matching the absorption band of dissolved oxygen, any dissolved oxygen present in the liquid contained within the container 120 will emit light upon excitation by the optical radiation 111. For simplicity, the liquid contained within the container 120 is not shown in the image. Figure 1As shown in the diagram. However, the emission 105 is schematically shown as concentric circles of dots. The emission 105 represents the emission of dissolved oxygen in response to the excitation of optical radiation 111, with a wavelength matching the absorption band of dissolved oxygen. Also shown in the diagram. Figure 1 Some of the emitted light 106A is shown in the optical path that is emitted from the interior 122, passes through the housing 124 and enters the photodetector 130.

[0051] exist Figure 1 In the illustration, various optical elements are shown outside the container 120 and positioned within the optical path of the photodetector 130. More specifically, Figure 1 The diagram illustrates a collimator 132, a long-pass filter 134, and a positive lens 136. In various embodiments, one or more of the optical components shown in the optical path may be omitted. Furthermore, additional and / or alternative optical components, such as mirrors or other reflectors, may be provided to redirect the emitted light 106A along an alternative optical path of the photodetector 130.

[0052] In embodiments providing a long-pass filter 136, it can be selected to filter out radiation wavelengths shorter than those included in the optical radiation 111. For example, if the wavelength of the optical radiation 111 is 1269 nm, the long-pass filter 136 can filter out wavelengths shorter than 1270 nm. This is beneficial for filtering out light as a result of Rayleigh scattering, while allowing emitted light to pass through, since the emitted light can be redshifted relative to the radiation included in the optical radiation 111, and its wavelength matches the absorption band of dissolved oxygen (which is not the case for light as a result of Rayleigh scattering). In various embodiments, a long-pass filter 134 is provided when the optical radiation 111 is periodically intensity-modulated radiation. In embodiments providing a positive lens 136, it can narrow the emitted light 106A (and any other light emitted from the container 120, such as light as a result of Rayleigh scattering) to focus it toward the photodetector 130. In embodiments providing a collimator 132, it can collimate the emitted light 106A (and any other light emitted from the container 120, such as light as a result of Rayleigh scattering).

[0053] Also there Figure 1 The diagram shows additional emitted light 106B that can be emitted from container 120 but is not directed to the photodetector (i.e., not in the optical path of the photodetector). Note that additional emitted light may be emitted, but for simplicity only emitted light 106A and 106B are shown. In some embodiments, one or more reflectors may optionally be provided to redirect emitted light 106B and / or other emitted light along the optical path of photodetector 130.

[0054] The photodetector 130 may be, for example, a photodiode or a PMT. The photodetector 130 is positioned such that at least some of the emitted light (e.g., emitted light 106A) that is emitted by dissolved oxygen and exits the container 120 through an optical window in the housing 124 is directed towards the photodetector 130. The photodetector 130 generates optical measurements, each based on the light detected by the photodetector 130 at a given moment. Some of these optical measurements may be influenced by emitted light such as emitted light 106A, and optionally, some of these optical measurements may be influenced by other light, such as light from Rayleigh scattering.

[0055] Logic unit 101 may be provided and operatively coupled to light source 110 and / or photodetector 130. Logic unit 101 may take various forms, such as executing instructions (transient and / or non-transient) stored in memory (not depicted) to perform all or aspects of one or more of the methods described herein, by one or more processors. For example, one or more processors may analyze optical measurements to determine one or more measurements related to dissolved oxygen based on the optical measurements. As another example, one or more processors may additionally or alternatively receive characteristics 103 of the liquid to be analyzed and, based on characteristics 103 (e.g., based on data in memory mapped to characteristics), determine how to control light source 110 (e.g., determine pulse duration), the time period during which photodetector 130 should detect optical measurements, and / or how to analyze optical measurements to determine measurements related to dissolved oxygen. Characteristics 103 may be based, for example, on user input, such as input specifying characteristics. Characteristics 103 may additionally or alternatively be based on input, for example, from a control system (such as a control system in a chemical processing plant).

[0056] The processor that may be included in logic unit 101 may include, for example, a microprocessor, an application-specific integrated circuit (ASIC), and / or a field-programmable gate array (FPGA). Logic unit 101 may additionally or alternatively include one or more discrete components, which may be analog or digital and may optionally include one or more processors. For example, logic unit 101 may include a lock-in amplifier that can be used to process optical measurements from photodetector 130 to extract the quadrature components of the probe light from the optical measurements. As another example, logic unit 101 may include a driver for light source 110, and the driver may optionally be configured (e.g., dynamically) to generate pulsed or modulated optical radiation with desired characteristics. For example, the driver may be configured to generate pulsed optical radiation, wherein the pulse has a desired pulse duration as determined herein.

[0057] It should be noted that the liquid within the container may possess characteristics such as temperature, particles, and acidity, which can corrode or otherwise damage the light source 110, photodetector 130, and / or optical components 112, 114, 116, 132, 134, and / or 136. The arrangement of the light source 110, photodetector 130, and / or optical components 112, 114, 116, 132, 134, and / or 136 allows such components to be located outside the container and not in contact with the liquid, while still enabling effective dissolved oxygen analysis.

[0058] Figure 2 A flowchart illustrating an example method 200 for practicing selected aspects of this disclosure is shown. Other embodiments may include, in addition to... Figure 2 Additional operations beyond those shown can be performed in a different order and / or in parallel. Figure 2 The steps, and / or can be omitted. Figure 2 One or more operations. Figure 2 The steps are described in terms of a system for implementing the steps. Such a system may include, for example, Figure 1 One or more components.

[0059] At step 202, the system controls the light source to emit optical radiation, including radiation of wavelengths that correspond to the absorption band of dissolved oxygen, into the interior of the container containing the liquid. For example, the light source can be controlled to emit optical radiation along an optical path, through an optical window in the container shell, and into the container.

[0060] In some implementations, step 202 may include step 202A or step 202B.

[0061] At step 202A, the system controls the light source to emit optical radiation with multiple pulses. In some embodiments, the duration of each pulse is based on the singlet O2 lifetime in the analyte liquid, which varies between different liquids. In some versions of those embodiments, the system determines the pulse duration based on inputs indicating liquid properties. In some additional or alternative versions, the duration may be determined based on multiplying the singlet O2 lifetime in the analyte liquid by a factor (such as three or a value from two to four). For example, by making the duration of each pulse three times the singlet O2 lifetime of the liquid analyte, approximately 95% of the maximum possible (at a given radiation power) number of O2 molecules in the liquid will be excited until the pulse ends. More specifically, with the intensity of the optical radiation constant, the number N of excited molecules can be described by a kinetic equation: Where A is the excitation rate and τ is the singlet O2 lifetime in the analyte. Assuming there are initially no excited molecules, the solution to this differential equation is... Based on this solution, it can be determined that 95% of the maximum possible number of excited molecules is achieved when the pulse duration is three times the singlet O2 lifetime (τ). Other factors (besides three times) can be chosen to achieve another desired percentage of excited molecules.

[0062] At step 202B, the system controls the light source to emit periodically intensity-modulated (e.g., sinusoidal) optical radiation. In some embodiments, the fixed modulation frequency may optionally be determined based on the properties of the liquid being analyzed. For example, a first frequency may be used with acetone (lifetime approximately 0.051 ms), while a lower second frequency may be used with tetrachloromethane (lifetime approximately 17 ms).

[0063] At step 204, the system generates optical measurements using a photodetector that communicates optically with the interior of the container. For example, the photodetector may be external to the container, but positioned such that at least some of any light emitted by dissolved oxygen in response to the excitation of optical radiation in step 202, exiting the container through its optical window, points towards the photodetector. All optical measurements are based on the light detected by the photodetector at the corresponding time. If the emitted light was generated at the corresponding time, some of those optical measurements may be affected by the emitted light. Alternatively, some of those optical measurements may be affected by other light, such as light from Rayleigh scattering (if it was generated at the corresponding time).

[0064] In some implementations, step 204 may include step 204A or step 204B.

[0065] In some embodiments, step 204A may optionally be performed during step 202A. At step 204A, the system generates optical measurements only during the non-pulse time period. That is, the system generates optical measurements only for at least a portion of the duration during which the light source does not generate pulses. This can mitigate (or prevent) any detection of scattered light, while still enabling the detection of emitted light that continues to emit light after the corresponding pulse has ended.

[0066] In some embodiments, step 204B may optionally be performed during step 202B. At step 204B, the system generates an optical measurement that includes only the orthogonal components of the probe light. In some embodiments, a lock-in amplifier is used to process the light initially detected by the photodetector to generate an optical measurement that includes only the orthogonal components of the detected light. As described herein, this can help suppress light from the optical measurement as a result of Rayleigh scattering.

[0067] At step 206, the system analyzes the optical measurements of step 204 to determine whether the liquid contains dissolved oxygen and / or to determine the predicted concentration of dissolved oxygen. These determinations may be based on, for example, the time-resolved amplitude and / or amplitude of one or more optical measurements. In some embodiments, when determining measurements related to dissolved oxygen in the analyte, the system determines the measurements based on the optical measurements and on the radiative lifetime of dissolved oxygen in the analyte. For example, a shorter radiative lifetime anticipates stronger luminescence, while a longer radiative lifetime anticipates weaker luminescence.

[0068] In some implementations, step 206 may include step 206A or step 206B.

[0069] In some embodiments, step 206A may optionally be performed during step 202A. At step 206A, the system analyzes only optical measurements from non-pulse time periods, and not measurements from pulse time periods (if any). In some embodiments (e.g., during step 204A), the optical measurements generated by the photodetector are limited to those from non-pulse time periods. In other embodiments, the optical measurements include both those from pulse and non-pulse time periods. In those other embodiments, a subset of optical measurements from non-pulse time periods can be identified and analyzed. For example, timestamps from the measurements and signals from the light source (e.g., its driver) can be used to identify the subset of optical measurements from non-pulse time periods.

[0070] In some embodiments, step 206B may optionally be performed during step 202B. At step 206B, the system analyzes only the quadrature components of the optical measurements. In some embodiments (e.g., during step 204B), the optical measurements generated by the photodetector are limited to quadrature component measurements. In other embodiments, the optical measurements include both quadrature and in-phase components. In those other embodiments, the quadrature components can be determined and analyzed. For example, the phase shift between the optical radiation and the optical measurements can be used to distinguish the quadrature components.

[0071] Figure 3 Examples of the change of a certain amount of excited oxygen molecules over time and examples of pulsed optical radiation are shown. Specifically, line 305 represents the number of excited oxygen molecules, dashed line 311A ​​represents the first pulse of pulsed optical radiation, and dashed line 311B represents a portion of the second pulse of pulsed optical radiation. The pulse time interval corresponding to the first pulse is also annotated as the non-pulse time interval between the first and second pulses.

[0072] from Figure 3It can be seen that the number of excited oxygen molecules increases throughout the first pulse. When the first pulse stops, the number of excited oxygen molecules decreases. However, it is noteworthy that the excited oxygen molecules (and the resulting luminescence) persist after the pulse stops and at least for part of the non-pulse period. Furthermore, Rayleigh scattering ceases when the first pulse stops. Therefore, analyzing optical measurements occurring during the non-pulse period mitigates or eliminates the influence of light from Rayleigh scattering from the analysis. This allows for accurate and / or precise determination of the presence and / or concentration of dissolved oxygen. For example, the concentration can be determined based on time-resolved measurements of optical radiation during all or part of the non-pulse period.

[0073] Figure 4 An example of periodically intensity-modulated optical radiation 410 and an example of optical measurement 430 detected from the modulated optical radiation are illustrated. Specifically, line 412 represents the amplitude of optical radiation 410 over time, and line 432 represents the amplitude of optical measurement 430 over time. Note that in Figure 4 In the example, the frequency of optical radiation 410 is the same as the frequency of optical measurement 430. However, the amplitude of optical measurement 430 is reduced relative to the amplitude of optical radiation 410. Furthermore, optical measurement 430 is phase-shifted by ninety degrees relative to optical radiation 410. This can be observed, for example, by looking at vertical lines 414 and 434, which reflect the start of the corresponding periods of optical measurement 430 and optical radiation 410.

[0074] While several embodiments have been described and illustrated herein, various other means and / or structures may be utilized to achieve the functionality and / or obtain the results and / or one or more advantages described herein, and each such variation and / or modification is considered to be within the scope of the implementations described herein. More generally, all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and actual parameters, dimensions, materials, and / or configurations will depend on the specific application or the application using the teachings. Those skilled in the art will recognize or be able to determine many equivalents of the particular embodiments described herein using only conventional experimentation. Therefore, it should be understood that the foregoing embodiments are presented by way of example only, and that embodiments may be practiced in ways different from the specific descriptions and claims within the scope of the appended claims and their equivalents. Implementation of this disclosure relates to each individual feature, system, article, material, kit, and / or method described herein. Furthermore, any combination of two or more such features, systems, articles, materials, kits, and / or methods, provided that such features, systems, articles, materials, kits, and / or methods do not contradict each other, is included within the scope of this disclosure.

Claims

1. A method comprising: The light source is controlled to emit optical radiation into the interior of a container containing a liquid. The light source is located outside the container, and The optical radiation is discontinuously excited and includes radiation with wavelengths that conform to the dissolved oxygen absorption band. Optical measurements are generated by a photodetector located outside the container but in optical communication with the liquid inside the container, and the optical measurements include at least one optical measurement based on the detection of emitted light derived from the luminescence of dissolved oxygen in the liquid caused by the optical radiation; and The optical measurements are analyzed to determine whether the liquid contains dissolved oxygen.

2. The method according to claim 1, wherein, The optical radiation includes multiple pulses.

3. The method according to claim 2, further comprising: The desired duration of each of the pulses is determined based on one or more properties of the liquid; Controlling the light source includes controlling the light source to generate a sequence of pulses based on the desired duration, and The one or more characteristics include one or more of the following: The classification of the liquids, The liquid contains one or more chemicals, or The temperature of the liquid.

4. The method according to claim 2, further comprising: The subset of optical measurements is determined based on a subset detected during a non-pulse period, which is a period during which the pulse of the optical radiation does not occur; The analysis of the optical measurements includes analyzing only the subset of the optical measurements.

5. The method according to claim 2, wherein, Generating the optical measurement includes generating the optical measurement solely based on detections occurring by the photodetector during a non-pulse period, which is a period during which the pulse of the optical radiation does not occur.

6. The method according to claim 1, wherein, The optical radiation is periodically intensity-modulated.

7. The method according to claim 6, wherein, The analysis of the optical measurements includes: The orthogonal components of the optical measurements were analyzed in determining whether the liquid contained dissolved oxygen.

8. The method according to claim 7, further comprising: The quadrature components are determined using a lock-in amplifier.

9. The method according to claim 7, further comprising: The orthogonal components are determined based on the specific radiative lifetime of the liquid for dissolved oxygen.

10. The method according to claim 6, wherein, The optical radiation is sinusoidally periodically intensity-modulated.

11. The method according to claim 6, wherein, Before entering the container, the optical radiation is transmitted through one or more of a short-pass filter, a band-pass filter, or a polarizer.

12. The method according to claim 6, wherein, Any light emitted by any dissolved oxygen in the liquid in response to the excitation of the optical radiation and encountering the photodetector is transmitted through one or both of the long-pass filter and the band-pass filter after leaving the container and before encountering the photodetector.

13. The method according to claim 1, wherein, The optical radiation, after being emitted by the light source, passes through at least a portion of the optical surface of the container before entering the container.

14. The method according to claim 1, wherein, Analyzing the optical measurements includes determining the predicted concentration of dissolved oxygen in the liquid.

15. A dissolved oxygen measurement system, comprising: A container for temporarily storing a liquid for analysis, the container including an outer surface having one or more optical windows that are transparent or translucent; A light source for emitting optical radiation with discontinuous excitation, the light source being located outside the container and positioned to emit the optical radiation to pass through at least one of the one or more optical windows and into the interior of the container, and the optical radiation comprising radiation of wavelengths conforming to the absorption band of dissolved oxygen, wherein the optical radiation emitted by the light source causes the dissolved oxygen in the liquid to emit light; as well as A photodetector located outside the container, the photodetector optically communicating with the liquid inside the container via one or more of the optical windows.

16. The dissolved oxygen measurement system according to claim 15, further comprising: One or more processors are used to process optical measurements of the photodetector and, based on the processing, determine the predicted concentration of any dissolved oxygen in the liquid.

17. The dissolved oxygen measurement system according to claim 15, wherein, The optical radiation includes multiple pulses or periodically modulated intensity.

18. The dissolved oxygen measurement system according to claim 15, further comprising one or more of the following: A short-pass filter located outside the container and positioned in the optical path of the optical radiation. A bandpass filter located outside the container and positioned in the optical path of the optical radiation, or A polarizer located outside the container and positioned in the optical path of the optical radiation.

19. The dissolved oxygen measurement system according to claim 18, further comprising one or more of the following: A long-pass filter located outside the container and positioned between the container and the photodetector. A bandpass filter located outside the container and positioned between the container and the photodetector, or A spatial filter located outside the container and positioned between the container and the photodetector.

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