Method and assembly for measuring particle size of particles suspended in fluid

Abstract

The present disclosure relates to a method for measuring particle size of particles suspended in a fluid, the method comprising: modulating (S1) radiation with a periodic wave optical mask; irradiating (S2) the fluid with the modulated radiation; detecting scattered radiation and / or transmitted radiation with a 2D detector capturing an image at the first modulation frequency (S3-1); detecting scattered radiation and / or transmitted radiation with a 2D detector capturing an image at a second modulation frequency (S3-2); extracting (S4) a first image of the first modulation frequency and a second image of the second modulation frequency, respectively; calculating (S5) a second modulation frequency and a first extinction coefficient of the first modulation frequency, respectively, based on the extracted first image and the extracted second image, respectively; a size of the suspended particles is determined based on a relationship between the calculated first extinction coefficient and the calculated second extinction coefficient (S7). The present disclosure also relates to an assembly for measuring the particle size of particles suspended in a fluid.

Description

Technical Field

[0001] The present disclosure relates to a method for measuring the particle size of particles suspended in a fluid and an assembly for measuring the particle size of particles suspended in a fluid as defined in the preambles of the independent claims. Background Art

[0002] Measuring the amount of particles suspended in water is very important for determining the quality of water in different situations. Total Suspended Solids (TSS) is the amount of fine particles suspended in water. TSS is an indication of whether the water is pure. In many cases, unclear water is unwanted and / or unhealthy. In order to monitor water quality, TSS needs to be measured regularly. However, in order to study particles suspended in water, a cumbersome measurement process is required. Usually, the sample is diluted and the measurement is slow, demanding and expensive. Therefore, there is a need for an improved way to measure the amount and size of particles suspended in water. Summary of the invention

[0003] The purpose of the present disclosure is to mitigate, alleviate or eliminate one or more of the defects and shortcomings in the prior art pointed out above, and at least solve the problems mentioned above. According to a first aspect, a method for measuring the particle size of particles suspended in a fluid is provided, the method comprising: modulating radiation using a periodic wave optical mask; irradiating the fluid with spatially modulated radiation; detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a first modulation frequency; detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a second modulation frequency; extracting a first image of the first modulation frequency and a second image of the second modulation frequency respectively; calculating first extinction coefficients of the second modulation frequency and the first modulation frequency respectively based on the extracted first image and the extracted second image; determining the size of the suspended particles based on the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient.

[0004] The advantage of this measurement is that it is fast and does not require any intervention on the measured sample, such as dilution or waiting for sedimentation. The measurement can also be carried out on site where it is needed and can be used as an online solution for regular monitoring of water volumes.

[0005] The entire measurement is completed quickly since only two images need to be captured at two different modulation frequencies.

[0006] The example of a measurement for which the method is particularly useful is a measurement for measuring water quality. However, the method can be applied to suspended particles in any fluid that is transparent to the radiation used. The radiation is light used to measure suspended particles in water. However, for other fluids, other radiation types can be considered based on the absorption spectrum of the fluid in question. The fluid can be a liquid or a gas, and the particle will be interpreted broadly and can be a droplet, a microdroplet or an aerosol of any small solid entity or liquid.

[0007] According to some embodiments, the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient is a difference. The determination is performed by comparing the difference to a pre-calibrated table or calibration curve.

[0008] According to some embodiments, the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient is a ratio. The determination is performed by comparing the ratio to a pre-calibrated table or calibration curve.

[0009] According to some embodiments, the measurements are performed at multiple frequencies instead of two frequencies corresponding to the following steps. An advantage is that the accuracy and / or precision of determining the size of the suspended particles may be improved.

[0010] According to some embodiments, the method further comprises: calculating a true extinction coefficient based on the calculated extinction coefficient; and estimating a number density of the suspended particles based on the determined size of the suspended particles and the true extinction coefficient.

[0011] An advantage of this embodiment is that the number density can be estimated, thereby providing additional information required to determine the mass of the fluid from the suspended particles.

[0012] According to some embodiments, the method further comprises calculating a total suspended solids amount of the suspended particles based on the estimated number density and the determined size of the suspended particles.

[0013] An advantage of this embodiment is that it provides a value for the total suspended solids volume (TSSV), which is an important value for estimating the quality of a fluid in terms of suspended particles.

[0014] According to some embodiments, the method comprises calculating the dry weight based on the TSSV and the density of the particle.

[0015] This embodiment has the advantage of providing a value for dry weight, which is an important value for estimating the mass of a fluid based on suspended particles.

[0016] According to some embodiments, the method includes repeating the method a plurality of times over time to measure particle settling and estimating density based on the particle settling.

[0017] The advantage of this embodiment is that the accuracy of density measurement is further improved.

[0018] According to some embodiments, the periodic wave optical mask is included in the group comprising: a square wave mask / pattern; a sinusoidal wave mask / pattern or a diffractive optical element.

[0019] According to some embodiments, the method further comprises generating a plurality of modulation frequencies by sequentially illuminating a plurality of masks with different frequencies (two or more frequencies).This is a relatively simple and fast way to implement the measurement method and produce measurement results.

[0020] According to some embodiments, a plurality of masks are placed on the same substrate, and the method further comprises: moving the substrate so that the masks for modulating radiation are sequentially shifted.

[0021] This has the advantage that it is a simple, robust and fast way of achieving multiple frequencies of modulated radiation with which to illuminate the fluid.

[0022] According to some embodiments, the method further comprises generating a plurality of modulation frequencies by extracting different harmonics in the modulation using a Fast Fourier Transform method.

[0023] An advantage of this embodiment is that moving parts can be avoided, so that the measurement setup can be made more robust, since the measurement is performed with a single recording and no movement of the optical mask is required.

[0024] According to some embodiments, the scattering is side scattering detected by a 2D detector from the side.

[0025] An advantage of this embodiment is that a two-dimensional (2D) image can be captured and the extinction of the signal along the x-axis can be observed in the captured image.

[0026] According to some embodiments, the mask is a square wave mask and wherein the harmonics are separated by a one-dimensional power spectrum and spatial locking analysis.

[0027] An advantage of this embodiment is that multiple frequencies of the modulated radiation used to illuminate the fluid can be measured in one image without the need for sequential measurements, making the measurement truly instantaneous.

[0028] According to some embodiments, the scattering is forward scattering detected by the 2D detector behind the liquid along the direction of radiation propagation.

[0029] An advantage of this embodiment is that measurements can be taken along the line without having to measure from the side.

[0030] According to some embodiments, the mask is a square wave mask and wherein the harmonics are separated by two-dimensional power spectrum (Fourier transform) and spatial locking analysis.

[0031] An advantage of this embodiment is that multiple frequencies of the modulated radiation used to illuminate the fluid can be measured in one image without the need for sequential measurements, making the measurement truly instantaneous.

[0032] According to a second aspect, a method for measuring the particle size of particles suspended in a fluid is provided, the method comprising: modulating radiation using a periodic wave optical mask; irradiating the fluid with the modulated radiation; detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a first radiation wavelength; detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a second radiation wavelength; extracting a first image of the first radiation wavelength and a second image of the second radiation wavelength, respectively; calculating a first extinction coefficient of the radiation wavelength and the first radiation wavelength, respectively, based on the extracted first image and the extracted second image, respectively; and determining the size of the suspended particles based on the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient.

[0033] The second aspect is intended to measure particle sizes below about one micron. Then, rather than using two modulation frequencies similar to the method according to the first aspect, two or more wavelengths can be used and only one modulation frequency can be used. Rayleigh scattering will vary depending on the wavelength compared to how the Lorenz-Mie scattering from larger particles differs depending on the modulation frequency as described in conjunction with the first aspect. By combining radiation of two wavelengths or colors in the same modulated light sheet (e.g., the upper half has a long wavelength in the red or IR region, and the lower half has a short wavelength in the blue or UV region), it is possible to measure in one single camera shot of the side scattering.

[0034] According to a second aspect, a component for measuring the particle size of particles suspended in a fluid is provided, the component comprising: a radiation distribution generator, the radiation distribution generator being configured to provide a radiation distribution, wherein the radiation distribution has a propagation path in a second spatial dimension; a periodic wave optical mask, the periodic wave optical mask being arranged to modulate the radiation distribution; a holder for a sample of the medium, the holder being configured to enable an intensity modulated radiation sheet to irradiate the sample; and a 2D detector, the 2D detector being arranged to capture at least one 2D image for each of a plurality of modulation frequencies; wherein the component is arranged to perform a method according to the first aspect.

[0035] The advantage of the assembly is that it is robust and enables rapid (and according to some embodiments also instantaneous), accurate measurement of the size, density or TSSV of particles suspended in a fluid.

[0036] According to some embodiments, the radiation distribution generator is configured to provide a polychromatic radiation sheet comprising a radiation spectrum extending in a first spatial dimension. The advantage is that a 2D image can be recorded from the side to observe and measure the extinction of radiation as it propagates through a fluid with suspended particles. This is particularly useful when measuring particle sizes below about one micron. Then, two or more wavelengths can be used and only one modulation frequency is used, rather than using two modulation frequencies similar to the method according to the first aspect. Compared to how the Lorenz-Mie scattering from larger particles depends on the modulation frequency as described in conjunction with the first aspect, the Rayleigh scattering will vary depending on the wavelength.

[0037] The effects and features of the second and third aspects are largely similar to those described above in conjunction with the first aspect. The embodiments mentioned with respect to the first aspect are largely compatible with the second and third aspects.

[0038] The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the present disclosure only by way of illustration. Those skilled in the art will appreciate from the guidance of the detailed description that changes and modifications may be made within the scope of the present disclosure.

[0039] Therefore, it should be understood that the disclosure disclosed herein is not limited to the specific components of the described devices or the steps of the described methods, as such devices and methods may vary. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above objects and other objects, features and advantages of the present disclosure will be more fully understood by referring to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure when taken in conjunction with the accompanying drawings.

[0041] Figure 1a Shown are schematic side views illustrating example assemblies according to some implementations of the present disclosure.

[0042] Figure 1b Shows Shows Figure 1a Schematic top view of an example assembly of .

[0043] Figure 2a Shown are the signal intensity as a function of the penetration length through a sample with suspended particles of three different sizes and at two different frequencies.

[0044] Figure 2b Shows Figure 3a The signal strengths disclosed in , but are shown on a logarithmic scale for two different frequencies.

[0045] Figure 2c For two different frequencies, Figure 3b A graph of the linear regression coefficients for the lines disclosed in FIG.

[0046] Figure 3a The method of the present disclosure is shown for measuring the extinction coefficient at two different frequencies by sequential phase shifting, 2D imaging of side scattering, and subtraction of the images.

[0047] Figure 3b The method of the present disclosure is shown for measuring the extinction coefficient at two different frequencies by a single mask with two frequencies, 2D imaging of the side scatter, and FFT analysis to extract the extinction coefficient from the first harmonic.

[0048] Figure 3c is used for Figure 3a and Figure 3b Schematic diagram of the setup of the embodiment disclosed in .

[0049] Figure 3d is a schematic diagram of the present disclosure for measuring the extinction coefficient at a single frequency and phase by a single mask, 2D imaging of side scattering, and FFT analysis to extract the extinction coefficient from the first and second harmonics.

[0050] Figure 4a The method of the present disclosure is shown for measuring the extinction coefficient at two different frequencies by sequential phase shifting, imaging of the transmitted light and forward scattered light, and subtraction of the images.

[0051] Figure 4b The method of the present disclosure is shown for measuring the extinction coefficient at two different frequencies by a single mask for each frequency, imaging of the transmitted and forward scattered light, and FFT analysis to extract the extinction coefficient from the first harmonic.

[0052] Figure 4c is used for Figure 4b Schematic diagram of the setup of the embodiment disclosed in .

[0053] Figure 5 The method of the present disclosure is shown for measuring the extinction coefficient using modulated light of a single frequency but with two different wavelengths, 2D imaging of the side scattering, and calculation of the extinction for each wavelength.

[0054] Figure 6 is a flow chart illustrating example method steps according to some implementations. DETAILED DESCRIPTION

[0055] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the present disclosure are shown. However, the present disclosure may be implemented in other forms and should not be construed as being limited to the embodiments disclosed herein. The disclosed embodiments are provided to fully convey the scope of the present disclosure to the skilled person.

[0056] Many conventional methods of spectrophotometric measurement use a continuously applied monochromatic light beam to illuminate a sample of the medium being inspected. In order to obtain information at more than one wavelength, a scan through all wavelengths of interest needs to be performed. Such an approach can be inefficient for performing measurements.

[0057] In the following, embodiments that enable efficient and accurate measurements will be described. In addition, some embodiments provide increased flexibility when measuring the optical properties of the inspected medium. Thus, accurate measurements can be performed by the same component for media with a wide range of various optical properties.

[0058] Furthermore, in general, the term "optical parameter" may refer to any suitable optical parameter describing an optical property; for example, an absorption coefficient, an attenuation coefficient (also called an extinction coefficient), a scattering coefficient, a fluorescence quantum yield (QY), a phosphorescence quantum yield (QY), etc. The extinction coefficient is equal to the sum of the absorption coefficient and the scattering coefficient. Other examples of optical properties include properties associated with one or more of the following: concentration, average cross section, and particle size (if particles are present in the medium). Therefore, these parameters may also be derived. Therefore, measuring an optical parameter may be defined as measuring the (corresponding) optical property.

[0059] Furthermore, generally, illustration of scattering is meant to also relate to emission from a photoluminescent medium, and vice versa.

[0060] Furthermore, in general, the term "light" refers to electromagnetic radiation having a wavelength within a certain range. This range may include what is commonly referred to as visible light (i.e., the portion of the electromagnetic radiation spectrum visible to the human eye). Alternatively or additionally, this range may include what is commonly referred to as invisible light (i.e., the portion of the electromagnetic radiation spectrum invisible to the human eye), such as infrared (IR) light and / or ultraviolet (UV) light. The term "irradiation" refers to irradiation with light as defined above.

[0061] Furthermore, in general, the term "polychromatic" describes an electromagnetic radiation spectrum that includes two or more (visible or invisible) wavelengths of the electromagnetic radiation spectrum.

[0062] Furthermore, in general, the term (single) optical sensor may refer to an array / matrix of constituent optical sensors (e.g. a digital camera in which each pixel has a corresponding constituent optical sensor; an optical detector) or to a single optical sensor element (single optical detector) configured to scan across a recording area.

[0063] Figure 1 schematically illustrates an example assembly for measuring one or more optical parameters of a medium according to some embodiments. Part (a) shows a side view of a variation of the assembly, and part (b) shows a top view of the assembly.

[0064] The components include a light sheet generator (LSG) 110 , a light intensity modulator (LIM) 130 , a holder (HOLD) 145 for a sample of a medium (SAMP) 140 , and optical sensors (SENS) 161 , 162 .

[0065] The light sheet generator 110 is configured to provide a monochromatic or polychromatic light sheet 192 and has a propagation path in the second spatial dimension 102 .

[0066] The second spatial dimension is not parallel to (usually orthogonal to) the first spatial dimension (e.g., in Euclidean coordinates). The first spatial dimension and the second spatial dimension span the three-dimensional space together with the third spatial dimension 103 (which is not parallel to, and is generally orthogonal to, the first spatial dimension and the second spatial dimension). The terms "spatial dimension" and "dimension" will be used interchangeably herein.

[0067] For example, a light sheet may be defined as light propagating along two or more paths in a single plane (eg, in Euclidean coordinates).

[0068] The extension of the spectrum in the first spatial dimension may be understood as a light wavelength variation having the property that each coordinate along the path in the first spatial dimension experiences at most one light wavelength.

[0069] The light intensity modulator (LIM) 130 comprises an optical holder 180 holding a grating 1 for modulating a light sheet 192. The light intensity modulator 130 is configured to provide an intensity modulated light sheet 193, 193a by applying an intensity modulation having a periodic or substantially periodic pattern in a first spatial dimension.

[0070] Examples of periodic patterns include patterns defined by Ronchi rulings - i.e., constantly spaced bars and spatial square waves as shown in FIG2 (e.g., equal to a when 2kb≤x<(2k+1)b, ​​and equal to c when (2k+1)b≤x<(2k+2)b, k∈Z) - and patterns defined by sinusoidal functions. Examples of substantially periodic patterns include any pattern that changes between values ​​below its average and values ​​above its average within a certain period on x, but where the values ​​below its average and / or the values ​​above its average may be different for different periods. Another example of a substantially periodic pattern is a pattern with a slight periodic shift along x. Thus, other periodic patterns may be triangular masks or any periodic pattern masks.

[0071] Refer again Figure 1a and Figure 1b A second aspect of the present disclosure shows a component for measuring one or more optical parameters of a medium, the component comprising: a light distribution generator of the first aspect, the light distribution generator being configured to provide a light distribution, wherein the light distribution has a propagation path in a second spatial dimension 102; a light intensity modulator 130, the light intensity modulator being configured to provide an intensity modulated light distribution 193, 193a by applying an intensity modulation having a periodic or substantially periodic pattern in the first spatial dimension to the light distribution; a holder 140 for a sample 140 of the medium; 5, the holder being configured to enable an intensity modulated light sheet to illuminate the sample; and optical sensors 161, 162, configured to spectrally record the intensity of light 194, 195 leaving the sample for providing one or more optical parameters; wherein the light intensity modulator 130 comprises: an optical holder 180 for a grating, the optical holder being electronically controlled and movable in a third spatial dimension 103; and a grating 1 according to the first aspect, the grating being arranged in the optical holder for providing intensity modulation to the light distribution.

[0072] Typically, two or more phases are applied to different recordings to achieve the determination of the optical parameters. Furthermore, typically, each phase shift corresponds to a displacement of the modulation by a distance corresponding to the modulation period divided by the number of recordings n.

[0073] It may be preferable to position the light intensity modulator as close to the sample as possible, in order to maintain the spatial modulation until the modulated light sheet enters the sample. This is essentially achieved by a method where the light intensity modulator is an imprint on the container of the sample.

[0074] The holder 145 for the sample 140 of the medium is configured to enable the intensity modulated light sheet to illuminate the sample. For example, the holder may be positioned relative to the light intensity modulator and the light sheet generator such that when the sample is provided at the holder, the intensity modulated light sheet illuminates the sample.

[0075] Typically, the entire intensity modulated light sheet illuminates the sample, but some embodiments may employ solutions where only a portion of the intensity modulated light sheet illuminates the sample.

[0076] Preferably, the holder is configured so that illumination of the sample is close to the side 141 of the sample facing the optical sensor 162. This reduces the distance that the main scattered light (ie single light scatter) travels through the sample to reach the optical sensor.

[0077] The holder may be, for example, a rack for receiving the sample.The sample may be provided in a container, for example a cuvette that is transparent to the light / radiation used.

[0078] The optical sensor 162 is configured to record (spectrally) the intensity of the light leaving the sample. The recorded intensity can then be used to determine one or more optical parameters.

[0079] Typically, the optical sensor may be a camera (eg, a charge coupled device (CCD) camera or a scientific complementary metal oxide semiconductor (sCMOS) camera).

[0080] The optical sensor 162 is configured to record the intensity of light leaving the sample relative to the illumination (so-called transmitted light, shown as 194 in Figure 1) and / or the intensity of light leaving the sample substantially orthogonal to the light sheet (scattered light or photoluminescent light, shown as 195 in Figure 1).

[0081] By placing the optical sensor so that a straight line through the sample and the optical sensor is substantially normal to the light sheet - ie extends in the third dimension - it is possible to record the intensity of light 195 leaving the sample substantially normal to the light sheet. Figure 1b The optical sensor arrangement 162 is shown in FIG.

[0082] Recording the intensity of light 194 leaving the sample relative to the illumination can be achieved by having the assembly further include an optical reflector 150 in the propagation path of the light sheet along the second spatial dimension, wherein the optical reflector is configured to reflect the light 194 of the intensity modulated light sheet leaving the sample relative to the illumination towards the optical sensor 162. Such a method is Figure 1b The reflector can be, for example, a mirror or a diffusing glass layer.

[0083] According to this method, a single fixed optical sensor may be used to record the intensity of light leaving the sample opposite to the illumination and the intensity of light leaving the sample substantially orthogonal to the light sheet; possibly in a single recording.

[0084] In some embodiments, the method may further include an attenuator (e.g., a neutral density filter) or amplifier in the light path between the reflector and the optical sensor to provide light leaving the sample relative to the illumination and light leaving the sample substantially orthogonal to the light sheet at similar intensities at the optical sensor. This avoids saturating the optical sensor while enabling recording of relatively small intensity changes. Other methods of avoiding saturating the optical sensor while enabling recording of relatively small intensity changes include recording the intensity of light leaving the sample relative to the illumination and the intensity of light leaving the sample substantially orthogonal to the light sheet in different recordings, and varying the light source intensity and / or optical sensor exposure time between recordings.

[0085] When recording the intensity of light 195 leaving the sample substantially orthogonal to the light sheet (optical sensor arrangement 162), the optical sensor is typically able to measure light intensity variations along the entire "width" 142 of the sample ("width" being the extension in the second dimension).

[0086] In some embodiments, the optical sensor that records the intensity of light leaving the sample substantially orthogonal to the light sheet can also be configured to switch between recording changes in light intensity along the entire width 142 of the sample and recording changes in light intensity along a portion of the width of the sample. The portion is typically the illuminated portion closest to the sample. In some embodiments, the optical sensor can be configured to change the size of the portion. For example, this feature can be achieved by using a zoom function of the optical sensor (e.g., an objective lens, a telecentric objective lens, a zoom lens, etc.).

[0087] With respect to this method of recording light intensity variations along a portion of the width of the sample, it may be beneficial for the assembly to include a light sheet resizer (RS) 135 that is configured to provide an intensity modulated light sheet in one of a plurality of available extensions in a first spatial dimension (e.g., in one of a plurality of available sizes or ratios). This is illustrated in part (a) of FIG. 1 as a light sheet resizer that shrinks an initial intensity modulated light sheet 193 to provide a resized intensity modulated light sheet 193a having a smaller extension in the first spatial dimension. Thus, when the optical sensor zooms in to a portion of the width of the sample (and inherently zooms in to a portion of the "height" of the sample, "height" being the extension in the second dimension), the resized intensity modulated light sheet 193a can be formed such that it can still be fully recorded by the optical sensor. For example, the light sheet resizer 135 can be implemented by appropriately applying one or more lenses and Fourier filtering.

[0088] Reference Figure 2a to Figure 2c , the principle behind the method disclosed in this article will be further explained. In order to determine the particle size in a suspension, two different modulation frequencies are used to determine the size. This is possible due to the different scattering properties of particles of different sizes. Figure 2a The signal intensity is shown as a function of the penetration length through a sample having three different sizes of suspended particles suspended in a fluid. Figure 2a to Figure 2c In the figure, the relationship between the three particle sizes is d3>d2>d1. The frequency fq2 is higher than fq1. The solid line is the theoretical extinction of the signal according to Beer-Lambert's law. It can be seen that the larger the particle, the greater the deviation from Beer-Lambert's law at lower frequencies fq1, but for high frequencies fq2, large particles are also close to the theoretical value according to Beer-Lambert's law. By using a sufficiently high frequency, Figure 2c The line at fq2 may be nearly horizontal, indicating that for all particle sizes, the extinction follows Beer-Lambert's law. To increase accuracy, measurements may be made at more than two frequencies.

[0089] Figure 2b Shows Figure 2a The signal strengths disclosed in , but are shown on a logarithmic scale for both frequencies. Figure 2c yes Figure 2b A graph of the linear regression coefficients of the line disclosed in . Based on the linear regression coefficients at two different frequencies, a size calibration can be performed using particles of known size in the suspension. Then, in the method disclosed in this article, the calibration is used to determine the size of the particles in the suspension.

[0090] Figure 3a The method of the present disclosure is shown for measuring the extinction coefficient at two different frequencies by using a first mask 31, 33 and a second mask 32, 34 through sequential phase shifting of the first mask 31, 33 and the second mask 32, 34, respectively. Figure 3c The camera arrangement shown in images the side scatter. The two phase recorded images are subtracted to reveal only the scattered light, and the extinction of the light passing through the sample can be calculated, as depicted in the resulting graph 36. Figure 3a In the image I captured 1 ,I 2 The upper half of the image has a first modulation frequency v1, and the lower half of the image has a second modulation frequency v2. In the graph 36, two extinctions from each of the two frequencies are shown. As discussed above, the lower curve (with higher extinction) is the higher modulation frequency with a curve that is closer to the theoretical Beer-Lambert law, and the upper curve is the extinction measured at the lower modulation frequency. The first measured extinction of the first mask 31, 33 for the first frequency v1 (image I 1) and the second measured extinction of the second mask 32, 34 at the second frequency v2 (image I 2 ) (Image 35) is used to calculate the extinction and particle size, such as by combining Figure 2a to Figure 2c discussed.

[0091] Figure 3b The method of the present disclosure is shown for measuring the extinction coefficient at two different frequencies by a single mask for each frequency, 2D imaging of the side scatter, and FFT analysis 39 to extract the extinction coefficient from, for example, the first harmonic.

[0092] Figure 3d Schematic diagram of the present disclosure of measuring the extinction coefficient at a single frequency and phase by a single mask, 2D imaging of the side scatter, and FFT analysis to extract the extinction coefficient from the first and second harmonics. Since a single mask is used, no moving parts are required. The measurement can be performed nearly instantaneously. A 2D image 51 of the side scatter from modulated light propagating through a suspended particle is captured by a camera device. The harmonics are extracted using a one-dimensional Fast Fourier Transform, as shown in image 52. Each of the first, third, and fifth harmonics are isolated and inverse Fast Fourier Transformed back into an image, where the extinction of the three different frequencies can be calculated, as shown in image 53, and used to calculate the extinction coefficient based on the combined image. Figure 2a to Figure 2c The theoretical calculation of the particle size of a sample of suspended particles is described.

[0093] Figure 4a A method of the present disclosure for measuring the extinction coefficient at two different frequencies by sequential phase shifting, imaging of transmitted light and forward scattered light, and subtraction of the images is shown. As shown, the method uses two phases for each frequency of masks 41, 42, 43, 44, wherein the phases are shifted 180 degrees (or pi radians) between 41 and 42 and between 43 and 44, respectively. The light distribution of the transmitted light through the sample for a single measurement is depicted in graph 45, wherein the light is modulated using a first mask 41. A subsequent second measurement is then performed using a second mask 42, and the second measurement is subtracted from the first measurement to calculate the extinction coefficient for the first frequency. The same operation is repeated for masks 43 and 44 of the second frequency in the modulation to be able to estimate the particle size. In order to calculate the extinction, the measurement is compared with a reference image (not shown) without particles.

[0094] Figure 4b and Figure 4cThe method of the present disclosure for measuring the extinction coefficient at two different frequencies by imaging and FFT analysis of a single mask for each frequency, transmitted light and forward scattered light to extract the extinction coefficient from the first harmonic is shown. Masks 43, 44 are used sequentially. However, the camera can be kept in exposure mode for capturing the transmission using two masks 43, 44 so that the measurement can be made in one shot and the particle count can be made using only one camera exposure. Nearly instantaneous measurements of particle size in suspension can thereby be made, with the delay depending only on the speed of the calculation and the time to shift the masks 43, 44.

[0095] Figure 5 The method of the present disclosure for measuring the extinction coefficient for particles smaller than 1 micron using modulated light of a single frequency but with two different wavelengths is shown. Small particles will scatter light by Rayleigh scattering. A 2D image 52 of the side scatter is recorded. The setup used is similar to Figure 3c The sample and the camera are provided in the same manner. Figure 5 In the example, a light sheet separated into two colors (where, for example, the upper half is red and the lower half is blue) propagates through a mask 51, which is a Ronchi grating with one frequency. The light sheet propagates through the sample and an image 52 of the side scatter is recorded with a camera. An example of a 2D image 52 of the side scatter is shown in the figure, where the upper half is red λ 1 , and the lower part is blue λ 2 The extinction for each half of the image is calculated and displayed in the extinction image 53, which shows the extinction of the light with the longer wavelength λ 1 The light has a relatively short wavelength λ 2 As shown by the intensity I of the side scattering at shorter wavelengths, λ 1 (e.g. blue) decreases more rapidly with distance through the sample.

[0096] Now refer to Figure 6 , the first aspect of the present disclosure will be described. A method for measuring the particle size of particles suspended in a fluid, the method comprising: modulating S1 radiation using a periodic wave optical mask; irradiating S2 the fluid using the modulated radiation; detecting S3-1 the scattered radiation and / or the transmitted radiation using a 2D detector that captures an image at a first modulation frequency; detecting S3-2 the scattered radiation and / or the transmitted radiation using a 2D detector that captures an image at a second modulation frequency; extracting S4 a first image of the first modulation frequency and a second image of the second modulation frequency, respectively; calculating S5 a first extinction coefficient of the second modulation frequency and the first modulation frequency, respectively, based on the extracted first image and the extracted second image; determining S7 the size of the suspended particles based on the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient.

[0097] The variation between the extinction coefficients at different frequencies is determined by the size of the suspended particles.

[0098] The frequency used in the optical mask is selected after a rough estimate of the size of the particles. Small particles require a higher frequency than large particles.

[0099] The method is based on the fact that small particles blur the modulation faster with distance than large particles. The method "sees" this as if the extinction is greater. By changing the modulation frequency, it is observed how the extinction coefficient changes; if the extinction coefficient remains the same, the particle is small, if the extinction coefficient changes, the particle is large. The size can then be estimated based on the change in extinction coefficient with modulation frequency and a pre-calibrated calibration curve or calibration table.

[0100] The detected side scatter is preferably measured from the side, e.g. Figure 3c As shown in , and may also include fluorescence. Figure 4c As shown in , the transmitted radiation is preferably measured in the forward direction of the illumination radiation, and may also include forward scattered radiation.

[0101] exist Figure 5 The following method steps S6 to S12 are drawn with dashed lines, which indicate that the steps are optional and refer to different detailed implementations.

[0102] According to some embodiments, the method further comprises: calculating a true extinction coefficient based on the calculated first extinction coefficient and the calculated second extinction coefficient S8; estimating a number density of the suspended particles based on the determined size of the suspended particles and the true extinction coefficient S9.

[0103] According to some embodiments, the method further comprises calculating a total suspended solids volume TSSV S10 of the suspended particles based on the estimated number density and the determined size of the suspended particles.

[0104] According to some embodiments, the method further comprises: calculating a dry weight based on the TSSV and the density of the particles S11.

[0105] According to some embodiments, the method further comprises: repeating the S12 method a plurality of times over time to measure particle settling and estimating density based on the particle settling.

[0106] Reference Figure 3a , Figure 3b , Figure 3c , Figure 4a , Figure 4b and Figure 4c , the periodic wave optical mask is included in the group comprising: a square wave mask; a sinusoidal wave mask or a diffractive optical element.

[0107] According to some embodiments, the method further comprises: generating S6-1 multiple modulation frequencies by sequentially irradiating multiple masks with different modulation frequencies. Multiple masks 31 to 34, 41 are placed on the same substrate 2, wherein the method further comprises: moving the substrate S6-2 so that the masks for modulating radiation are sequentially shifted.

[0108] According to an alternative embodiment, the method further comprises: generating S6-3 a plurality of modulation frequencies by extracting different harmonics in the modulation. When measuring side scattering detected from the side by a 2D detector, the mask is a square wave mask, and wherein the harmonics are separated by a one-dimensional power spectrum and spatial locking analysis, such as Figure 3b and 4b As disclosed in.

[0109] Reference Figure 4c When measuring forward scattering detected by a 2D detector behind a liquid in the direction of radiation propagation, the mask is a square wave mask 41, 49 and the harmonics are separated by two-dimensional power spectrum and spatial locking analysis. Figure 4c The bottom graph 51 shows the 2D power spectrum and lock-in analysis. Figure 4c As shown in , gratings 41, 49 are placed perpendicular to each other to effectively form a square mask. In some embodiments, grating 41 and grating 49 are integrated into one square mask grating. The result is that the diffraction due to the different gratings will be in the vertical direction, so that when the image is analyzed by FFT, the first harmonic of mask 49 will end up in the horizontal plane, while the first harmonic from the vertical mask 41 will end up in the vertical plane, as depicted by graph 51.

[0110] As discussed above, the disclosed methods of measuring particle size of particles suspended in a fluid may be performed by measuring side scattered or transmitted radiation.

[0111] When measuring side scatter, Figure 3a to Figure 3c As shown in , the method can be performed by sequential illumination of a mask that is shifted so that the frequencies used to implement the disclosed method are sequentially shifted. Alternatively, multiple frequencies can be recorded from a single captured picture by extracting the harmonics produced by a square wave mask. The harmonics are separated by spatial locking and locking analysis of the resulting 1D power spectrum.

[0112] When measuring transmitted radiation, such as Figures 4a to 4c As shown, the method can be performed by sequential illumination of a mask that is shifted so that the frequencies used to implement the disclosed method are sequentially shifted. Alternatively, multiple frequencies can be recorded from a single captured picture by extracting the harmonics produced by a square wave mask. Harmonics are separated by spatial locking and locking analysis of the resulting 2D power spectrum.

[0113] Reference Figure 1a, Figure 1b , Figure 3c and Figure 4c , a second aspect of the disclosure shows an assembly for measuring the particle size of particles suspended in a fluid 140, the assembly comprising: a radiation distribution generator of the first aspect, the radiation distribution generator being configured to provide a radiation distribution, wherein the radiation distribution has a propagation path in a second spatial dimension 102; a periodic wave optical mask, the periodic wave optical mask being arranged to modulate the radiation distribution; a holder 145 for a sample of suspended particles 140, the holder being configured to enable an intensity modulated radiation sheet to illuminate the sample; and a 2D detector 162, the 2D detector being arranged to capture at least one 2D image for each of a plurality of modulation frequencies; wherein the assembly is arranged to perform a method according to the first aspect. The radiation distribution generator is configured to provide a radiation sheet 192 comprising a radiation spectrum extending in the first spatial dimension 101.

[0114] Those skilled in the art recognize that the present disclosure is not limited to the preferred embodiments described above. Those skilled in the art also recognize that modifications and variations are possible within the scope of the appended claims. For example, in Figure 3c and Figure 4c In the embodiments, the detector is disclosed as a camera, but those skilled in the art recognize that any equivalent sensor may be used. Those skilled in the art also recognize that the disclosed example equations may be changed in various ways with similar results and still perform the method as described in the claims. In addition, variations of the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed disclosure based on a study of the drawings, the present disclosure, and the appended claims.

Claims

1. A method for measuring the particle size of particles suspended in a fluid, the method comprising: include: modulating (S1) radiation using a periodic wave optical mask; irradiating (S2) the fluid with modulated radiation; detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a first modulation frequency (S3-1); detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a second modulation frequency (S3-2); extracting (S4) a first image of the first modulation frequency and a second image of the second modulation frequency respectively; Calculating (S5) first extinction coefficients of the second modulation frequency and the first modulation frequency based on the extracted first image and the extracted second image, respectively; The size of the suspended particles is determined based on the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient (S7).

2. The method according to claim 1, in, The method further comprises: Calculating a true extinction coefficient based on the calculated first extinction coefficient and the calculated second extinction coefficient (S8); Based on the determined size of the suspended particles and the true extinction coefficient, the number density of the suspended particles is estimated (S9).

3. The method according to claim 2, in, The method further includes calculating a total suspended solid volume (TSSV) of the suspended particles based on the estimated number density and the determined size of the suspended particles ( S10 ).

4. The method according to claim 3, further comprising: include: The dry weight is calculated based on the TSSV and density of the particles (S11).

5. The method according to any one of the preceding claims, further comprising: include: The method is repeated (S12) multiple times over time to measure particle settling and estimate density based on the particle settling.

6. The method according to any one of the preceding claims, in, The method further includes generating (S6-1) a plurality of modulation frequencies by sequentially irradiating a plurality of masks having different modulation frequencies.

7. The method according to claim 6, in, The plurality of masks are placed on the same substrate, and the method further includes: moving the substrate (S6-2) so that the masks for modulating the radiation are sequentially shifted.

8. The method according to any one of claims 1 to 5, in, The method further comprises generating (S6-3) the plurality of modulation frequencies by extracting different harmonics in the modulation.

9. The method according to any one of the preceding claims, in, The scattering is side scattering detected by the 2D detector from the side.

10. The method according to claim 10, in, The mask is a square wave mask and wherein the harmonics are separated by one-dimensional power spectrum and spatial locking analysis.

11. The method according to any one of claims 1 to 8, in, The scatter is forward scatter detected by the 2D detector behind the liquid along the direction of radiation propagation.

12. The method according to claim 11, in, The mask is a square wave mask and wherein the harmonics are separated by two-dimensional power spectrum and spatial locking analysis.

13. A method for measuring the particle size of particles suspended in a fluid, the method include: modulating (S1) radiation using a periodic wave optical mask; irradiating (S2) the fluid with modulated radiation; detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a first radiation wavelength (S3-1); detecting scattered radiation and / or transmitted radiation using a 2D detector that captures an image at a second radiation wavelength (S3-2); extracting (S4) a first image of the first radiation wavelength and a second image of the second radiation wavelength respectively; Calculating (S5) a radiation wavelength and a first extinction coefficient of the first radiation wavelength based on the extracted first image and the extracted second image, respectively; The size of the suspended particles is determined based on the relationship between the calculated first extinction coefficient and the calculated second extinction coefficient (S7).

14. A component for measuring the particle size of particles suspended in a fluid, the component include: a radiation distribution generator (110) configured to provide a radiation distribution, wherein the radiation distribution has a propagation path in a second spatial dimension (102); a periodic wave optical mask arranged to modulate the radiation distribution; a holder (145) for a sample (140) of a medium, the holder being configured to enable a sheet of intensity modulated radiation to illuminate the sample; and a 2D detector arranged to capture at least one 2D image of the illuminated sample; Wherein the assembly is arranged to perform a method according to any one of claims 1 to 13.

15. The assembly according to claim 12, in, The radiation distribution generator is configured to provide a polychromatic radiation sheet (192, 292) comprising a radiation spectrum extending in a first spatial dimension (101).

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