Multi-wavelength absorption water sensor

Abstract

The invention relates to a multi-wavelength absorption water sensor. An apparatus and method are provided for measuring the absorption of a liquid at a plurality of high resolution wavelengths in the ultraviolet spectrum, as well as in the visible and / or near infrared light spectrum, of an additional wavelength or set of wavelengths. The device comprises a housing immersible in a liquid, the housing comprising a broadband light source emitting ultraviolet light, visible light and near-infrared light, an optical window defining a measurement area of the liquid, optical chopper units alternating between a reference beam and a measurement beam, an optical system includes a broadband light source, an optical sensor that detects a particular wavelength or set of wavelengths in the spectrum of visible light or near infrared light from the broadband light source, a slit that defines broadband light geometry onto a diffraction grating, the diffraction grating that modifies the broadband light beam to a wavelength of ultraviolet light at high wavelength resolution, and a line sensor that detects ultraviolet light at high wavelength resolution.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 541,179, filed on September 28, 2023, entitled “MULTIWAVELENGTH ABSORPTION WATERSENSOR WITH HIGH UV WAVELENGTH RESOLUTION AND EXTENDED VISIBLE AND NIRMEASUREMENT RANGE,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of water quality monitoring using light absorption measurements in the ultraviolet spectrum. In general, the present disclosure relates to measuring nitrogen compounds and organic compounds in water. Background Art

[0004] The measurement of organic and nitrogen compounds is required in many applications in industrial and municipal water and wastewater as well as in environmental or surface water monitoring.

[0005] Various types of instruments are available for measuring these compounds in the laboratory. However, these laboratory instruments typically use measurement methods that require the use of reagents and often involve multiple hours of reaction time per measurement before the test is complete.

[0006] In order to measure organic compounds and nitrogen compounds in real time on site, the instrument must utilize a more practical measurement method. Specifically, a method that does not require reagents and can be performed quickly with negligible reaction time is more suitable for field applications.

[0007] Prior art instruments for measuring organic and nitrogen compounds include instruments that measure the absorption spectrum of water in the UV and visible light regions, and sometimes in the near infrared (NIR) light region. Specifically, in order to detect and distinguish different groups of organic and nitrogen compounds, such as nitrates, nitrites, and aromatic organics, wavelengths of 200nm to 350nm must be measured, while wavelengths above 350nm and into the visible light region of the spectrum are used to detect particles, colloids, and other compounds that cause turbidity in water. The measurement of particles, colloids, and other compounds that cause turbidity is usually best accomplished by dedicated instruments, such as instruments based on turbidimeters, or absorbance instruments using visible or NIR wavelengths. In the context of instruments designed to measure organic and nitrogen-based compounds, visible light (VIS) and / or NIR wavelengths are primarily used to compensate for measurements in the ultraviolet (UV) light region to compensate for interference from particles, colloids, and other compounds that cause turbidity, thereby ensuring more accurate measurement of organic and nitrogen compounds.

[0008] As a result of the above requirements for absorption spectroscopic instruments for measuring organic compounds and nitrogen compounds in water, a variety of instruments are available on the market that combine a variety of key optical components, including a broadband light source such as a xenon flash lamp, a dispersive element such as a transmission or reflection diffraction grating, and a line imaging sensor such as a CCD or photodiode array. Light emitted from the light source is transmitted through the water region under test toward the diffraction grating, which resolves the transmitted broadband light into different wavelengths or wavelength groups. The line sensor detects the wavelength resolved light and provides a measurement of the light intensity of each wavelength or wavelength group. The instrument can be configured primarily depending on the design of the diffraction grating, which determines the potential wavelength range of the instrument as well as the wavelength resolution of the instrument.

[0009] Typically, for practical field instruments, there is a design compromise between wavelength resolution and wavelength range. For many applications, such as surface water detection of nitrogen compounds as radicals, the requirement for wavelength resolution of the instrument is about 5nm, which allows the use of a diffraction grating design that includes a full UV / VIS wavelength range while still maintaining a sufficient wavelength resolution of 5nm. However, for applications that require the distinction of compounds with similar absorption spectra, such as distinguishing nitrate and nitrite compounds in wastewater, a wavelength resolution of less than 1nm is required. In this case, the spectral region associated with measuring nitrate and nitrate is primarily less than two hundred and fifty nm, and the wavelength resolution of less than one nm that can be measured in the UV light region less than two hundred and fifty nm takes precedence over the wavelength range. Therefore, the available instruments for this application must use a diffraction grating with a high wavelength resolution of less than 250nm, so due to the compromise of the grating design, they cannot provide any significant absorption measurements in the visible light region or the NIR light region. This means that these instruments cannot usually fully compensate for the UV absorption measurements of nitrate and nitrite, which come from interference caused by particles, colloids and other compounds that cause turbidity.

[0010] Existing instrument designs do not adequately compensate for the measurement of organic and nitrogen compounds of particulates, colloids and other turbidity causing compounds, which is particularly problematic because some of the most valuable applications require wavelength resolutions of less than 1 nm in the UV region, and there are large amounts of these interfering compounds. This results in poor measurement performance of prior art instruments in these more challenging applications. Therefore, there is a need for an improved instrument design that is capable of measuring in UV light with a wavelength resolution of less than 1 nm, while also providing measurements in visible or NIR wavelengths. Summary of the invention

[0011] In one embodiment, an immersible device for measuring light absorption of a liquid sample around the device is provided. The device includes a broadband light source, a measurement area, a light sensor, an optical slit, a diffraction grating, and a line sensor array. The broadband light source is configured to output broadband light in the ultraviolet light spectrum and light in one or more of the visible light spectrum and the near infrared light spectrum. The measurement area includes a liquid sample that propagates the broadband light emitted from the broadband light source. The light sensor is configured to detect the intensity of visible light or near infrared light from the broadband light emitted by the broadband light source. The optical slit is configured to generate an approximate point light source from the broadband light emitted by the broadband light source. The diffraction grating is configured to decompose the broadband light propagated from the optical slit into a plurality of decomposed and substantially adjacent narrow ultraviolet bandwidth regions, and the line sensor array is configured to detect a plurality of individual light intensities corresponding to the ultraviolet bandwidth regions generated by the diffraction grating.

[0012] In another embodiment, a method operable by a controller of an immersion device is provided for measuring light absorption of a liquid sample surrounding the device. The device includes a broadband light source, a measurement region, a light sensor, an optical slit, a diffraction grating, and a line sensor array. The broadband light source is configured to output broadband light in an ultraviolet light spectrum and light in one or more of a visible light spectrum and a near infrared light spectrum. The measurement region includes a liquid sample that propagates the broadband light emitted from the broadband light source. The light sensor is configured to detect the intensity of visible light or near infrared light from the broadband light emitted by the broadband light source. The optical slit is configured to generate an approximate point light source from the broadband light emitted by the broadband light source. The diffraction grating is configured to decompose the broadband light propagated from the optical slit into a plurality of decomposed and substantially adjacent narrow ultraviolet bandwidth regions, and the line sensor array is configured to detect a plurality of individual light intensities corresponding to the ultraviolet bandwidth regions generated by the diffraction grating. The method includes recording and outputting intensity measurements of visible or near infrared light detected by the light sensor, recording and outputting intensities of a plurality of individual light intensities corresponding to an ultraviolet bandwidth region detected by the line sensor array, and calculating light absorbance of a liquid sample using the recorded intensity measurements of ultraviolet and visible or near infrared light. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, which form a part of this application and in which:

[0014] Figure 1 depicts an immersible device for measuring water quality parameters in an exemplary embodiment; and

[0015] Figure 2 A block diagram of a method operable by a controller of an immersible device for measuring light absorption of a liquid sample surrounding an immersible device is depicted. DETAILED DESCRIPTION

[0016] In the following specification and claims, reference will be made to a number of terms which shall be defined to have the following meanings.

[0017] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0018] "Optional" or "optionally" means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not.

[0019] Approximate language used throughout the specification and claims can be used to modify any quantitative representation that can be allowed to vary without causing a change in the basic function associated with it. Therefore, the values ​​modified by one or more terms such as "about", "approximately" and "substantially" are not limited to the specified precise values. In at least some cases, approximate language can correspond to the accuracy of the instrument used to measure the value. In this article and throughout the specification and claims, range limitations can be combined and / or interchanged, unless the context or language indicates otherwise, such ranges are determined and include all subranges contained therein.

[0020] As used herein, the terms "processor" and "computer" and related terms (e.g., "processing device," "computing device," and "controller") are not limited to those integrated circuits referred to as computers in the art, but broadly refer to microcontrollers, microcomputers, analog computers, programmable logic controllers (PLCs), application specific integrated circuits (ASICs), and other programmable circuits, and these terms are used interchangeably herein. In the embodiments described herein, "memory" may include, but is not limited to, computer-readable media such as random access memory (RAM), computer-readable non-volatile media such as flash memory. Alternatively, a floppy disk, a compact disk-read only memory (CD-ROM), a magneto-optical disk (MOD), and / or a digital versatile disk (DVD) may also be used. In addition, in the embodiments described herein, the additional input channels may be, but are not limited to, computer peripherals associated with an operator interface such as a touch screen, a mouse, and a keyboard. Alternatively, other computer peripherals may also be used, which may include, for example, but not limited to, a scanner. In addition, in exemplary embodiments, additional output channels may include, but are not limited to, an operator interface monitor or a heads-up display. Some embodiments involve the use of one or more electronic or computing devices. Such devices typically include a processor, a processing device or a controller, such as a general-purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a reduced instruction set computer (RISC) processor, an ASIC, a programmable logic controller (PLC), a field programmable gate array (FPGA), a digital signal processing (DSP) device and / or any other circuit or processing device capable of performing the functions described herein. The methods described herein may be encoded as executable instructions contained in a computer-readable medium, which may include, but is not limited to, a storage device and / or a memory device. When executed by a processing device, such instructions cause the processing device to perform at least a portion of the method described herein. The above examples are not intended to limit the definition and / or meaning of the terms processor and processing device in any way.

[0021] Without limitation, most of the systems described herein relate to devices and methods for measuring optical properties of liquids (e.g., water). Various embodiments of the present disclosure are described herein. However, the disclosed embodiments are merely exemplary, and it should be understood that the present disclosure may be implemented in many different and alternative forms.

[0022] The figures are not drawn to scale, and some features may be exaggerated or minimized to show details of particular elements, while related elements may be eliminated to prevent obscuring novel aspects. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure. For purposes of teaching and not limitation, the illustrated embodiments relate to real-time industrial and municipal water and liquid quality monitoring.

[0023] As used herein, the coordinate conjunction "and / or" means a choice between logical separation and logical connection of adjacent words, phrases or clauses. Specifically, the phrase "X and / or Y" is intended to be interpreted as "one or both of X and Y", where X and Y are any words, phrases or clauses.

[0024] As used herein, the term "fluid" refers to any liquid, gas, or substance that continuously deforms under an applied shear stress.

[0025] As used herein, the term "light" refers to any electromagnetic radiation and is not limited to wavelengths of visible light. For example, "light" may refer to radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, or gamma rays.

[0026] Parts List

[0027]

[0028]

[0029] Figure 1 An immersible device 100 for measuring a water quality parameter in an exemplary embodiment is shown. Test water 1 is the liquid in which the device 100 is immersed and measured by the device 100. The test water 1 is intended to flow freely into a water measurement area 6 of the device 100, as defined by an optical window 2 of the device 100.

[0030] The broadband light beam 5 of the device 100 is defined as a light beam having a bandwidth that includes the ultraviolet, visible, and near-infrared regions of the spectrum. Alternatively, the broadband light beam 5 may include only broadband light in the ultraviolet region, and at least one narrowband light source in the visible or near-infrared region. Alternatively, the broadband light beam 5 may include broadband light in the ultraviolet region and the visible region, omitting light in the near-infrared region.

[0031] The broadband light source 3 of the device 100 is used as a UV, visible and infrared light source. In one embodiment, the broadband light source 3 is a xenon flash lamp. Alternatively, the broadband light source 3 may consist of a plurality of narrowband light sources, such as light emitting diodes (LEDs), or a combination of a broadband light source and at least one narrowband light source. The main requirement is that the broadband light source 3 provides broadband light in the UV spectrum and some bandwidth in the visible or near-UV spectrum.

[0032] The broadband light beam 5 emitted by the broadband light source 3 is split 22 into two broadband light beams: the first part includes the reference beam 24 and the second part includes the measuring beam 25. The reference beam 24 and the measuring beam 25 ideally include the same optical bandwidth. In one embodiment, each of the reference beam 24 and the measuring beam 25 ideally has a similar amplitude, but this is not required. In an embodiment, the reference beam 24 and the measuring beam 25 are guided via ultraviolet transmitting fused silica fiber optics using total internal reflection. A plurality of free space optical components can be used to guide the reference beam 24 and the measuring beam 25. Broadband beam splitting 22 can be achieved using fiber fusion technology or other collimating optical devices.

[0033] The reference beam 24 is directed around the water measurement area 6 to the shutter actuator and assembly 7 of the device 100. The measuring beam 25 is directed through the water measurement area 6 via two opposing optical windows 2 that define a path therethrough. The measuring beam 25 leaves the water measurement area 6 and is directed to the shutter actuator and assembly 7.

[0034] The shutter actuator assembly 7 includes a shutter 29 connected to an actuator (not shown) that provides the shutter 29 with the ability to move alternately between two positions. The first position 8 of the shutter 29 physically blocks the measurement beam 24, while the second position 9 of the shutter 29 physically blocks the reference beam 25. Therefore, the shutter actuator assembly 7 ultimately allows the reference beam 24 and the measurement beam 25 to be measured alternately at different times. This alternation between the reference beam 24 and the measurement beam 25 allows the device 100 to effectively compensate the measurement of the light absorption of the test water 1 for changes in the output of the broadband light source 3. Such changes may be due to aging of the broadband light source 3 or due to the influence of changes in ambient temperature or water temperature that affect the broadband light source 3 and the power supply 4 of the broadband light source 3.

[0035] In one embodiment, the reference beam 24 and the measuring beam 25 are combined at the beam combiner 23 of the device 100. It should be understood that the combination of the beams is in the sense of the optical directions of the beams. Note that the reference beam 24 and the measuring beam 25 cannot propagate beyond the shutter actuator assembly 7 at the same time.

[0036] In another embodiment, the combined broadband beam is then split again at the beam second beam splitter 26 of the device 100 in a similar manner to the beam first beam splitter 22, whereby the bandwidth of each split beam 27, 28 is ideally the same. In one embodiment, each of the two beams 27, 28 ideally has a similar amplitude, but this is not required.

[0037] The broadband light split beam A27 is directed to the filter 20 of the device 100. The filter 20 enables filtering the broadband light split beam A27 into a narrower band of visible light or near infrared light. The generated narrowband light beam 19 continues to propagate toward the photodiode sensor 18. The photodiode sensor 18 detects the intensity of the filtered narrowband light beam 19. In some embodiments, the photodiode sensor 18 may be referred to as a light sensor. In some embodiments, the device 100 does not include the filter 20. In these embodiments, the photodiode sensor 18 detects the intensity of the narrowband light directly from the broadband light split beam A27 without using the filter 20. For example, the photodiode sensor 18 may have a specific wavelength sensitivity range that is suitable for measuring a narrower band of visible or near infrared light directly from the broadband light split beam A27.

[0038] The broadband light split beam B28 is directed to the optical slit 10 of the device 100. The optical slit is configured to generate an approximate point light source from the broadband light beam 5 emitted by the broadband light source 3. The light propagating from the light split beam B28 through the optical slit 10 continues toward the diffraction grating 12 of the device 100. In one embodiment, the diffraction grating 12 is a reflective diffraction grating. However, a transmission grating can be used instead of a reflective grating, with some changes to the geometry of the arrangement of the optical components in the device 100. The device 100 utilizes the diffraction grating 12 to decompose the incident broadband light 11 into substantially separate wavelengths of light, so that in some embodiments, the resulting wavelength optical resolution is no greater than 1 nm in the ultraviolet region, and the resolution is mainly required in the ultraviolet spectrum of 200 nm to 300 nm. In some embodiments, the diffraction grating 12 is configured to decompose the light split beam B28 propagating from the optical slit into at least ten resolved and substantially adjacent narrow ultraviolet bandwidth regions, wherein each bandwidth region is no greater than two nanometers.

[0039] The wavelength-decomposed light 13 propagates toward the line sensor array 15 of the device 100, whereby individual pixels in the line sensor array 15 are configured to individually detect light of a bandwidth less than 1 nm in the ultraviolet light spectrum. In one embodiment, the line sensor array 15 is a charge coupled device (CCD). However, the line sensor array 15 may be a photodiode array (PDA) or other equivalent line sensor array device. The line sensor array 15 is configured to detect a plurality of individual light intensities corresponding to the ultraviolet bandwidth region generated by the diffraction grating 12. In some embodiments, the line sensor array 15 is configured to detect at least ten individual light intensities corresponding to the ultraviolet bandwidth region generated by the diffraction grating 12.

[0040] The controller 14 of the device 100 is connected to the electronic and electromechanical components of the device 100, including the shutter actuator and assembly 7, the power supply 4 for the broadband light source 3, the photodiode sensor 18 and the line sensor array 15, via internal control and power lines 17. External control and power lines 16 are connected to the controller 14 and allow external control, power supply and communication with external devices.

[0041] Figure 2 A block diagram of a method 200 operable by the controller 14 of the device 100 for measuring light absorption of a liquid sample surrounding the device 100 is depicted.

[0042] In one embodiment, the controller 14 records and outputs 202 intensity measurements of visible or near infrared light detected by the photodiode sensor 18. The controller 14 records and outputs 204 intensities corresponding to a plurality of individual light intensities (e.g., at least ten individual light intensities) of the ultraviolet bandwidth region detected by the line sensor array 15. The controller 14 then uses the recorded intensity measurements of ultraviolet and visible or near infrared light to calculate 206 the light absorbance of the test water 1. In some embodiments, the controller 14 records the intensity measurements during the period when the shutter 29 is in the first position 8 and during the period when the shutter 29 is in the second position 9, respectively, and calculates the absorbance of the test water 1 using compensation for changes in the raw light output of the broadband light source 3.

[0043] The above description of the embodiments of the present disclosure has been presented to illustrate the principles of the present disclosure and is not intended to limit the present disclosure to the particular embodiments illustrated. The scope of the present disclosure is intended to be defined by all embodiments encompassed by the appended claims and their equivalents.

Claims

1. An immersible device for measuring light absorption of a liquid sample surrounding the immersible device, the immersible device comprising: a broadband light source configured to output broadband light in the ultraviolet spectrum and light in one or more of the visible spectrum and the near infrared spectrum; a measurement region configured to include the liquid sample, the measurement region propagating the broadband light emitted from the broadband light source; a light sensor configured to detect intensity of visible light or near infrared light from the broadband light emitted by the broadband light source; an optical slit configured to generate an approximate point light source from the broadband light emitted by the broadband light source; a diffraction grating configured to decompose the broadband light propagating from the optical slit into a plurality of decomposed and substantially adjacent narrow ultraviolet bandwidth regions; as well as A line sensor array is configured to detect a plurality of individual light intensities corresponding to substantially adjacent narrow ultraviolet bandwidth regions generated by the diffraction grating.

2. The immersible device of claim 1 , further comprising an optical beam splitter configured to substantially split the broadband light emitted from the broadband light source, wherein: a first portion of the emitted light is directed to propagate through the measurement region containing the liquid sample and constitute a measurement beam; and A second portion of the emitted light is directed around the measurement area and constitutes a reference beam.

3. The submersible device of claim 2, wherein: The measuring beam and the reference beam include substantially the same optical bandwidth.

4. The submersible device of claim 2, wherein: The measuring beam and the reference beam comprise substantially the same amplitude.

5. The submersible device of claim 2, wherein: The optical beam splitter includes UV-transmissive fused silica fiber optics.

6. The immersible device of claim 2, further comprising an actuator and a shutter assembly, wherein the actuator and shutter assembly are configured to move alternately between: a first position whereby the shutter substantially blocks propagating light of the measurement beam; and a second position whereby the shutter substantially blocks propagating light of the reference beam.

7. The immersible device of claim 6, further comprising a controller connected to the broadband light source, the light sensor, and the line sensor array, wherein the controller is configured to: recording and outputting said intensity measurements of visible light or near infrared light detected by said light sensor; recording and outputting intensities corresponding to the plurality of individual light intensities in the ultraviolet bandwidth region detected by the line sensor array; and The recorded intensity measurements of the UV and visible or near-IR light are used to calculate the absorbance of the liquid sample.

8. The immersion device of claim 7, wherein the controller is further configured to: recording intensity measurements during a period when the shutter is in the first position and during a period when the shutter is in the second position, respectively; and The absorption of the liquid sample is calculated using compensation for variations in raw light output of the broadband light source.

9. The immersible device according to any one of claims 1 to 6, further comprising a controller connected to the broadband light source, the light sensor and the line sensor array, wherein the controller is configured to: recording and outputting the intensity measurements of visible or near infrared light detected by the light sensor, and recording and outputting intensities of the plurality of individual light intensities corresponding to the ultraviolet bandwidth region detected by the line sensor array; and The recorded intensity measurements of the ultraviolet and visible or near infrared light are used to calculate the absorbance of light passing through the liquid sample.

10. An immersible device according to any one of claims 1 to 8, wherein: The diffraction grating is further configured to decompose the broadband light propagating from the optical slit into at least ten resolved and substantially adjacent narrow ultraviolet bandwidth regions, wherein each bandwidth region is no larger than two nanometers, and The line sensor array is also configured to detect at least ten individual light intensities corresponding to the ultraviolet bandwidth region generated by the diffraction grating.

11. An immersible device according to any one of claims 1 to 8, wherein: The broadband light source is further configured to output the broadband light only in the ultraviolet light spectrum and to output at least one narrowband light in the visible light spectrum or the near infrared light spectrum.

12. An immersible device according to claim 11, wherein: The at least one narrow band of light is in the visible light spectrum.

13. The submersible device according to any one of claims 1 to 8, further comprising: an optical filter configured to generate a narrow band of visible or infrared light from the broadband light emitted by the broadband light source, Wherein, the light sensor is configured to detect the intensity of the visible light or near infrared light generated by the filter.

14. A method operable by a controller of an immersible device for measuring light absorption of a liquid sample surrounding the immersion device, wherein: The submersible device comprises: a broadband light source configured to output broadband light in the ultraviolet spectrum and light in one or more of the visible spectrum and the near infrared spectrum; a measurement region, the measurement region including the liquid sample and the measurement region propagating the broadband light emitted from the broadband light source; a light sensor configured to detect intensity of visible light or near infrared light from the broadband light emitted by the broadband light source; an optical slit configured to generate an approximate point light source from the broadband light emitted by the broadband light source; a diffraction grating configured to decompose the broadband light propagating from the optical slit into a plurality of resolved and substantially adjacent narrow ultraviolet bandwidth regions; and a line sensor array configured to detect a plurality of individual light intensities corresponding to the ultraviolet bandwidth region generated by the diffraction grating, and The method comprises: recording and outputting intensity measurements of visible light or near infrared light detected by the light sensor; recording and outputting intensities corresponding to a plurality of individual light intensities in the ultraviolet bandwidth region detected by the line sensor array; and The recorded intensity measurements of the ultraviolet and visible or near infrared light are used to calculate the absorbance of the liquid sample.

15. The method of claim 14, wherein the immersible device further comprises an optical beam splitter configured to substantially split the broadband light emitted from the broadband light source, and wherein: A first portion of the emitted light is directed to propagate through a measurement region containing the liquid sample and constitutes a measurement beam; and A second portion of the emitted light is directed around the measurement region and constitutes a reference beam.

16. The method of claim 15, wherein: The submersible device further comprises an actuator and a shutter assembly, The actuator and shutter assembly are configured to move alternately under the direction of the controller between: a first position whereby the shutter substantially blocks propagating light of the measurement beam; as well as a second position whereby the shutter substantially blocks propagation of the reference beam, and The method further comprises: recording intensity measurements during a time period when the shutter is in the first position and during a time period when the shutter is in the second position; as well as The absorption of the liquid sample is calculated using compensation for variations in raw light output of the broadband light source.

17. The method of claim 15, wherein: The diffraction grating is further configured to decompose the broadband light propagating from the optical slit into at least ten resolved and substantially adjacent narrow ultraviolet bandwidth regions, wherein each bandwidth region is no larger than two nanometers, and The line sensor array is also configured to detect at least ten individual light intensities corresponding to the ultraviolet bandwidth region generated by the diffraction grating.

18. A method according to any one of claims 15 to 17, wherein: The broadband light source is further configured to output the broadband light only in the ultraviolet light spectrum and to output at least one narrowband light in the visible light spectrum or the near infrared light spectrum.

19. A method according to any one of claims 15 to 17, wherein: The at least one narrow band of light is in the visible light spectrum.

20. The method according to any one of claims 15 to 17, wherein: The submersible device further comprises: an optical filter configured to generate a narrow band of visible or infrared light from the broadband light emitted by the broadband light source, Wherein, the light sensor is configured to detect the intensity of the visible light or near infrared light generated by the filter.

Images