EP4652564A1

EP4652564A1 - A method and apparatus for determining an amount of a material present in a mixture of at least two materials

Info

Publication number: EP4652564A1
Application number: EP24701468.1A
Authority: EP
Inventors: Jack East; Akinwande Olanrewaju COLE; Robert Holland; Ali RAMEZANI
Original assignee: Nicoventures Trading Ltd
Current assignee: Nicoventures Trading Ltd
Priority date: 2023-01-17
Filing date: 2024-01-15
Publication date: 2025-11-26
Also published as: GB202300670D0; JP2026501026A; WO2024153917A1

Abstract

The invention provides a method and apparatus for determining an amount of a first material present in a mixture of at least a first material and a second material, each material comprising a plurality of discrete portions of material. First and second images of a mixture sample are obtained, wherein the second image is different from the first image. The boundaries of the first material are determined in each image, from which the total area of the first material present in each image is determined. The amount of first material present in the mixture can be determined from the total area of the first material present in each image. The second image being different from the first image may be achieved by varying the image conditions or by varying the physical configuration, if the sample is the same in each image. Varying the physical configuration may be achieved by varying the relative positions of the discrete portions of material, for example by physically rearranging the sample through disturbing, agitating or remixing. If the sample is different in each image (e.g. if passing on a conveyor), the image conditions may be maintained.

Description

A Method and Apparatus for Determining an Amount of a Material Present in a Mixture of At Least Two Materials

Technical Field

The present invention relates to a method and apparatus for determining an amount of a material present in a mixture of at least two materials, each material comprising a plurality of discrete portions of material.

Background

Certain products may comprise a mixture of two or more materials, each material comprising a plurality of discrete portions of material such as strands or strips. For example, in an aerosol provision system such as a heated tobacco product, the aerosol-producing article may include a mixture of tobacco or tobacco-containing strips and strips of an amorphous solid such as a dried gel. The mixture is heated during use to generate the aerosol.

During the manufacturing process, it is important to monitor an amount of at least one of the materials in the mixture for quality control purposes. This may be necessary to determine the absolute amount of one or more of the materials in the mixture, the relative amounts of the materials in the mixture, or for determining the uniformity of the mixture. Depending on the result, further action may be necessary such as adjusting a process parameter, e.g. the amount of a material in the mixture, mixing time, etc.

It may be necessary to analyse the mixture at different places in the manufacturing process, for example to analyse the mixture feed prior to manufacture of the product, and/or the mixture in the manufactured product itself.

A traditional method for determining the amount of a material present in a mixture is to obtain a sample of the mixture from the desired place in the process and to separate the materials by hand. The amount of one or more of the materials (e.g. weight) can then be determined by standard methods. If the strips of material are relatively small (e.g. in the case of the tobacco/gel mixture, the strips may be 1mm wide, 0.1-lmm thick, and 20-40mm long), the separation method may require the use of tweezers and a magnifier. Such a method is labour-intensive and relatively slow. If the materials in the mixture are of contrasting colours, hand separation, even though timeconsuming, may produce results within an acceptable level of accuracy depending on the skill of the operator. However, for some products at least, it is desirable for the materials to have the same colour. For example, in the case of the tobacco/gel mixture referred to above, it may be desirable to disguise the presence of the gel in the finished product by colouring the gel to match the tobacco material. In this case, it becomes more difficult to recognise the different materials by eye and to separate them with acceptable accuracy.

Summary of the Invention

According to a first aspect, the invention provides a method for determining an amount of a first material present in a mixture of at least a first material and a second material, each material comprising a plurality of discrete portions of material, the method comprising: obtaining a first image of a mixture sample; obtaining a second image of a mixture sample, wherein the second image is different from the first image; determining boundaries of the first material in each image; determining the total area of the first material present in each image; and determining the amount of first material present in the mixture from the total area of the first material present in each image.

The method is not limited to the specific order of steps claimed, but the skilled person will understand that steps can be carried out in any logical order, such as obtaining a first image, determining the boundaries/area for that image, obtaining a second image, determining boundaries/area for that image, etc. or alternatively obtaining all images first and then determining the boundaries/areas for all images.

The second image being different from the first image may be achieved by:

• for the same sample in each image, by varying the image conditions or by varying the physical configuration;

• for different samples in each image, by maintaining the image conditions.

Varying the image conditions may include varying one or more of: position, angle, magnification, image area, camera settings (focus point, depth of field, shutter speed, aperture, zoom), lighting properties, background properties. Varying the physical configuration may include varying the relative positions of the discrete portions of material, for example by physically rearranging the sample through disturbing, agitating, remixing, etc.

If the sample is different in each image (e.g. if passing on a conveyor for example), it should be ensured that the sample properties are consistent so that the amount of material visible in the image is the same (e.g. a consistent area, depth, volume, weight etc.). The image conditions may be consistent between images.

In some embodiments, the method may further comprise: determining boundaries of the second material in each image; determining the total area of the second material present in each image; and determining the amount of second material present in the mixture from the total area of the second material present in each image. The method may further comprise determining the relative amounts of the first material and the second material present in the mixture, such as proportion, ratio, etc.

In some embodiments, the step of determining boundaries comprises determining the boundaries of each individual material portion in each image.

In some embodiments, the method further comprises obtaining one or more further images of a mixture sample different from the first and second images and performing the determining steps for each further image. As discussed below, a higher number of images reduces the likely statistical error.

In some embodiments, determining the amount of material present in the mixture comprises calculating the average of the total areas of material in each image to obtain an area of material in the mixture. In some embodiments, determining the amount of material present in the mixture comprises, based on the total areas of material in each image or the area of material in the mixture, calculating one or more of: volume, length, width, thickness, weight, relative weight. If a required parameter of the material is known, e.g. density, basis weight (gsm), thickness/width/length, the desired "amount" (volume, length, width, thickness, weight/mass, relative weight/mass) can be calculated from the area. In some embodiments, the area of material in the mixture is calibrated with a known sample. This is discussed further below. The calibration process may also convert the area into, for example, a volume or weight/mass measurement, assuming the required parameter(s) is/are known and are fed into the calibration calculation.

In some embodiments, the mixture sample is the same sample for each image. In this embodiment, one or more image conditions of each image may be different. As discussed above, varying the image conditions may include varying one or more of: position, angle, magnification, image area, camera settings (focus point, depth of field, shutter speed, aperture, zoom), lighting properties, background properties. Lighting properties may include: wavelength, colour, intensity. Lighting may for example be white, coloured, ultra-violet or infra-red. The light source may be any conventional light source to provide the desired wavelength, colour or intensity, including LED for example. It may be desirable to include an additive in one of the materials in the sample which reacts to the incident electromagnetic radiation (e.g. fluorescence) more visibly than the other material, thus enhancing visibility and increasing differentiation between the materials. For example, a tobacco material may absorb infra-red radiation and therefore an additive could be included in a gel strip formulation which causes this material to fluoresce or reflect the infra-red radiation more than the tobacco. Background properties may include: brightness, colour. The background may be a non- reflective black colour for example. In this embodiment, the physical configuration of the mixture sample may be the same for each image.

In embodiments where the mixture sample is the same sample for each image, the physical configuration of the mixture sample may be different for each image. As discussed above, varying the physical configuration may include varying the relative positions of the discrete portions of material, for example by physically rearranging the sample through disturbing, agitating, remixing, etc. In some embodiments therefore, the method may further comprise physically rearranging the mixture sample prior to obtaining the second image and prior to obtaining each further image. In some embodiments, the rearrangement may be achieved by agitating or shaking a container which contains the mixture. In such embodiments, the image conditions of each image may be the same.

In some embodiments, the mixture samples are different for each image. The image conditions for each image may be the same however. In such embodiments, the images may be obtained from a moving mixture, such as one which is passing on a conveyor for example. In the first aspect, each material comprises a plurality of discrete portions of material. Discrete portions may comprise pieces or sections of material, or strands or strips of material. One or more of the materials may comprise shredded strands or strips of material. The discrete portions of each material may be uniform, i.e. of generally the same dimensions, or the discrete portions may comprise two or more different groups of portions, for example a group of portions of a first length and a group of portions of a second length.

In the first aspect, the first material is different from the second material. The materials may differ in one or more of the following properties: physical dimensions of the discrete portions, appearance, colour, composition. However, the invention is more relevant for a method for determining an amount of a first material present in a mixture of at least a first material and a second material, when the first material is a different composition from the second material.

In some embodiments, the first material is a first aerosolisable material and the second material is a second aerosolisable material, having a different composition from the first aerosolisable material.

In some embodiments, one of the aerosolisable materials may comprise an amorphous solid, a gel or a dried gel. The amorphous solid, gel or dried gel may be substantially free from botanical material. The amorphous solid, gel or dried gel may be substantially tobacco free. The other of the aerosolisable materials may comprise tobacco, reconstituted tobacco or paper reconstituted tobacco.

In some embodiments, the mixture is for use as or in an aerosol provision system

In some embodiments, the method is a computer-implemented method.

According to a second aspect, the invention provides a method of adjusting the relative proportions of a first material and a second material present in a mixture, comprising the steps of: determining the amount of first material present in the mixture in accordance with the method described above, and adjusting the amount of first material present in the mixture.

According to a third aspect, the invention provides a method of manufacturing an article for use as or in an aerosol provision system, wherein the article includes a mixture of a first material and a second material, the method comprising the steps of: determining the amount of first material present in the mixture in accordance with the method described above, and adjusting the amount of first material present in the mixture.

According to a fourth aspect, the invention provides apparatus configured to carry out the method described above, comprising: imaging means configured to obtain the images, and processing means configured to carry out the determining steps.

In some embodiments the imaging means is a digital camera.

In some embodiments, the apparatus further comprises a light source to illuminate the mixture sample. The properties of the light source may be variable or adjustable for specific materials or image conditions. Lighting properties may include: wavelength, colour, intensity. The light source may for example emit white, coloured, ultra-violet or infra-red electromagnetic radiation. The light source may be any conventional light source to provide the desired wavelength, colour or intensity, including LED for example.

In some embodiments, the apparatus further comprises a background for locating behind the mixture sample during image acquisition. "Behind" in this sense is from the viewpoint of the image. The background may comprise a screen. The properties of the background may be adjustable for specific materials or image conditions. Background properties may include: brightness, colour, reflectivity. The background property may be non-reflective black.

In some embodiments, the apparatus further comprises means to change the physical configuration of the mixture sample. The means to change the physical configuration of the mixture sample may change the configuration of the mixture sample from a first configuration to a second configuration which is different from the first configuration. Changing the physical configuration may include varying the relative positions of the discrete portions of material, for example by physically rearranging the sample through disturbing, agitating, remixing, etc. In some embodiments, the means to change the physical configuration of the mixture sample is configured to rearrange the sample. In some embodiments, the means to change the physical configuration may comprise an agitation mechanism, a vibration mechanism, a stirrer, a shaker or an air blower. Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic diagram of apparatus suitable for carrying out the method of the embodiment in accordance with an embodiment;

Fig. 2 shows a schematic diagram of an image analysis process in accordance with an embodiment; Fig. 3 shows an image of a mixture of brown tobacco strips and white gel strips;

Fig. 4 shows the image of Fig. 3 with boundary conditions identified;

Fig. 5 shows an image of a mixture of brown tobacco strips and brown-coloured gel strips;

Fig. 6 shows an image of brown tobacco strips and brown-coloured gel strips with enhanced contrast using near infra-red illumination;

Fig. 7 shows a raw image of brown tobacco strips and brown-coloured gel strips illuminated with near infra-red illumination; and

Fig. 8 shows the image of Fig. 7 processed to show tobacco strips in green and gel strips in blue.

Detailed Description of Embodiments of the Invention

Embodiments of the invention relate to a method for detecting and measuring the area or volume of gel strips and tobacco strips in a gel/tobacco mixture or matrix.

Embodiments of the invention utilise a camera system with variable lighting capability. An image of the gel and tobacco is taken against a suitable background. The areas of gel strips and tobacco strips within the image are measured. The sample is physically agitated, a further image taken and areas remeasured. This is repeated until a statistically significant number of images have been taken. This is because, in a given image, strips may overlie other strips or may be curled or curved, such that a single area measurement is skewed. The use of multiple images each with a different physical arrangement of the strips minimises the effects of strip orientation or configuration in a single image.

However, calibration with a known sample of the mixture may still be necessary because there may always be some strips in every image which are not fully visible. Calibration may also allow a direct correlation between the observed area (averaged over multiple images) and a different property such as a calibrated weight of the material present in the sample. This would require knowledge of the basis weight or density and thickness of the material, which could be pre-programmed into the calibration calculation.

The background upon which the strips are placed may be chosen to enhance the contrast of the strips with respect to the background, which can improve the accuracy of measurement. It has been found that a suitable background is non-reflective black in the range of spectral response of the camera and lens system deployed.

Lighting of the sample under examination can be varied both in intensity and in colour (spectral range) to enhance the contrast between gel and tobacco strips. For example, if the gel strips are white and contain menthol, white light may be suitable for providing sufficient contrast between the tobacco strips and the gel strips. If on the other hand the gel strips have been coloured brown to match the tobacco strips, white light may not be able to provide sufficient contrast between the gel and tobacco. In this case, alternative lighting schemes can be used in the form of coloured LEDs or lights or even extending the spectral response beyond the visible spectrum using ultraviolet- or infrared-rich lighting sources. It is known that tobacco absorbs light in the infrared spectrum and this can provide enhanced image contrast. Alternatively, additives to the gel strips could fluoresce under ultra violet light, again increasing contrast if a suitable lighting system is deployed.

The camera and lens system would be designed to match the field of view over which the tobacco/gel sample is distributed and have sufficient resolution, spectral range and magnification to allow effective analysis of the image. The image is preferably digital. A computer system or processor may be needed for image capture and processing.

Image processing determines the areas or relative areas of the gel and/or tobacco strips in each image. If the thickness of a material is known (e.g. from the thickness of the sheet from which the strips were cut), an area can be converted into a volume. If the basis weight is known (e.g. in gsm), an area can be converted into weight/mass. Similarly, if the density is known, the volume can be converted into weight/mass. The weight/mass of one or both materials may then be expressed as weight percent.

If additional information about the material is known, other parameters of the material or mixture can be determined. For example, if the strips of material are a uniform width which is known, and the number of strips in the sample can be determined, the average length of the strips in the sample can be calculated. This information may be helpful if the material comprises a mix of "short" and "long" strips, e.g. strips of 20mm length and strips of 40mm length, for example to provide information on the proportion of "short" to "long" gel strips. Determining the distribution of the length of strips within the sample may provide information about the mixing of strips and also the damage that may be caused to the strips during processing. It is known that specific proportions of strips of certain lengths has an influence of the sensory perception of the THP user and so a clear process control understanding is helpful.

The analysis may be carried out on images of a single sample of the mixture, which may be taken from the mixture feed prior to manufacture of the product or which may be harvested from one or more manufactured products. Multiple images of the single sample may then be taken for analysis, for example by changing the physical configuration of the sample (e.g. by means of agitation) between each image, or by changing the image conditions between each image, as discussed above.

In some embodiments, the invention could be used in a standalone mode for quality assurance purposes. It could be used within equipment that would take a formed tobacco heated product (THP) rod, extract the tobacco gel mixture, either through slitting, blowing, sucking or by some other means, place in the field of view of the area for imaging to take place. The sample would be periodically agitated by means of controlled air blasts, mechanical/air stirrers, vibration or similar between image capture. Images thus taken would be analysed and the weight of gel determined for each image and the results statistically processed to produce a representative value for the area, volume or weight of the gel in the tobacco mixture. At the end of a controlled set of measurements, the sample of gel and tobacco strips would be automatically dispensed with, thereby preparing the field of view for the next sample. This data could be processed in the form of a batch of a controlled number of THP rods to provide useful information on the acceptability of the batch either for control purposes or as part of a batch release process.

In other embodiments, the analysis may be carried out on images of a different sample each time, for example by taking a different sample of mixture for each image, or by taking images of the mixture passing on a conveyor. In this case, the image conditions (field of view, illumination, etc.) can stay the same for each image. Other parameters, such as the quantity of mixture present in each image (e.g. weight, volume, area) may need to be kept as uniform as possible between images, although the higher the number of images are employed, the less the effect of any variations will be. Small batch sampling from a tobacco/gel hopper feeding a THP manufacturing machine or the blend fed into the hopper would be possible. This could employ a portioning mechanism that ensures that approximately the same quantity of mixture is examined each time. This could be achieved through a pocket in a rotating drum situated over the hopper, the pocket being the volume of the required sample. The pocket would fill from the hopper and then be rotated to deposit the sample gathered onto the field of view of the camera. After analysis, a second pocket full of tobacco/gel mixture can be collected and deposited and so on. A further sophistication would be to provide an agitator in the hopper to ensure uniformity of mixture. An alternative method would be to advance a sample of known size from a hopper by means of an Archimedes screw that is rotated for a controlled interval which deposits the required sample size.

Although the hopper feed/blend may well characterise the mixture in the finished product, the mixture delivered to the THP manufacturing machine could differ in a subtle manner from the bulk properties of the mixture. In this case it would be possible to use the invention in a "single image" mode to sequentially image a moving bed of gel/tobacco mixture as it is fed to the THP manufacturing machine. Images taken with high shutter speeds at a high rate can be analysed for the proportion of gel weight in tobacco and so a constant stream of data concerning the control of the mix can be obtained in the form of a moving average of data thus removing the need for agitation and repeat measurements of a single sample. This data could be deployed for process control functions and also it can be envisaged that it may be possible to provide a control function to the hopper/blend that increases the relative proportion of gel or reconstituted tobacco.

Fig. 1 shows a schematic diagram of apparatus 10 suitable for carrying out the method of the invention in accordance with an embodiment. The apparatus comprises a digital camera 1, a lens 2 and an illumination system 3. The mixture sample is placed on sample holder 4 and the configuration of the sample can be changed by means of sample agitation system 5. Images of the sample in different configurations are acquired by the digital camera 1 and are sent to the image processing unit 6. The apparatus also includes a control system/processor 7 and a display 8. The image processing unit 6 and the control system/processor 7 enhance the images as required and determine the visible area of one or more of the materials in the mixture. Calibration may be performed as described above and any further calculations carried out (either as part of the calibration process or subsequently) and the required data is provided via data output 9. Fig. 2 shows a schematic diagram of an image analysis process in accordance with an embodiment, which is carried out by the image processing unit 6 and the control system/processor 7 of Fig. 1.

Fig. 3 shows an image of a mixture of brown tobacco strips and white gel strips and Fig. 4 shows the image of Fig. 3 with boundary conditions identified (brown tobacco strips bordered in green and white gel strips bordered in red). In this example, because of the natural contrast between the tobacco strips and the gel strips, it is relatively straightforward to identify the areas of gel and/or tobacco with proprietary image-processing software. Image enhancement may not be required in this case, and the image may simply be fed in as the input image for the process of Fig. 2 (either as a colour or as a monochrome image). Multiple images similar to Fig. 3 may therefore be taken and analysed to determine the amount of one or both materials present, as discussed herein.

Fig. 5 shows an image of a mixture of brown tobacco strips and brown-coloured gel strips. There is very little contrast between the two materials, and therefore image enhancement is carried out prior to analysis by the method of Fig. 2. Fig. 6 shows an image of brown tobacco strips and browncoloured gel strips, illuminated using near infra-red illumination to enhance the contrast between the materials. The tobacco strips appear lighter than the gel strips in this enhanced image. This enhanced image is employed as the input image for the process of Fig. 2.

Fig. 7 shows a raw image of brown tobacco strips and brown-coloured gel strips illuminated with near infra-red illumination; and Fig. 8 shows the image of Fig. 7 processed to show tobacco strips in green and gel strips in blue. This enhanced image is employed as the input image for the process of Fig. 2.

The boundary tools used to identify the separate materials in the enhanced images and so determine the strip areas in view are known to one skilled in the art. It is the combination of these tools with the statistical approach of analysing multiple images, together with image enhancement by illumination or other means which drives the desired repeatability and accuracy of measurement.

Embodiments of the invention are described above with reference to a mixture of tobacco and gel strips. However, the invention is not limited to such materials and the invention may be employed to determine amounts or relative amounts of materials in any mixture suitable for analysis by this process. The invention may relate to a method of determining the relative amounts of substrate in a mixture comprising:

1) capturing an image of a mixture of two different substrates (e.g. tobacco and thin film);

2) determining the area of at least one of the substrates from the images; and

3) determining the mass of at least one of the substrates using the determined area.

Conventionally, in order to determine the amount of thin film in a THP rod, it is necessary to cut the rod open, separate the thin film from the tobacco, and then weigh the separated thin film. The new method does not require the materials to be separated from each other, hence allowing fast online (or offline) thin film weight measurement.

Additional features of the method may include:

• irradiating the mixture with different wavelengths of light depending on the reflective properties of the substrate (e.g. NIR, visible, UV etc.), and a detector configured to detect those wavelengths

• changing the background upon which substrate is placed for test;

• performing a substrate mixing/agitation step after step 1), repeating step 1) after mixing (to provide two or more images), performing step 2) on both mixture images captured under step 1) and then performing statistical analysis (e.g. average) to obtain a more accurate measurement

• a calibration step may be carried out between steps 2) and 3) with a known sample to improve accuracy and convert the area information into another property such as mass.

Claims

Claims:

1. A method for determining an amount of a first material present in a mixture of at least a first material and a second material, each material comprising a plurality of discrete portions of material, the method comprising: obtaining a first image of a mixture sample; obtaining a second image of a mixture sample, wherein the second image is different from the first image; determining boundaries of the first material in each image; determining the total area of the first material present in each image; and determining the amount of first material present in the mixture from the total area of the first material present in each image.

2. The method of claim 1, further comprising: determining boundaries of the second material in each image; determining the total area of the second material present in each image; determining the amount of second material present in the mixture from the total area of the second material present in each image.

3. The method of claim 2, further comprising determining the relative amounts of the first material and the second material present in the mixture.

4. The method of claim 1, 2 or 3, wherein the step of determining boundaries comprises determining the boundaries of each individual material portion in each image.

5. The method of any of claims 1 to 4, further comprising obtaining one or more further images of a mixture sample different from the first and second images and performing the determining steps for each further image.

6. The method of any of claims 1 to 5, wherein determining the amount of material present in the mixture comprises calculating the average of the total areas of material in each image to obtain an area of material in the mixture.

7. The method of any of claims 1 to 6, wherein determining the amount of material present in the mixture comprises, based on the total areas of material in each image or the area of material in the mixture, calculating one or more of: volume, length, width, thickness, weight, relative weight.

8. The method of any of claims 1 to 7, wherein the mixture sample is the same sample for each image.

9. The method of claim 8, wherein one or more image conditions of each image are different.

10. The method of claim 9, wherein the image conditions include: position, angle, magnification, camera settings (focus point, depth of field, shutter speed, aperture), lighting properties, background properties.

11. The method of claim 9 or 10, wherein the physical configuration of the mixture sample is the same for each image.

12. The method of claim 8, wherein the physical configuration of the mixture sample is different for each image.

13. The method of claim 12, further comprising physically rearranging the mixture sample prior to obtaining the second image and prior to obtaining each further image.

14. The method of claim 12 or 13, wherein the image conditions of each image are the same.

15. The method of any of claims 1 to 7, wherein the mixture samples are different for each image.

16. The method of claim 15, wherein the image conditions for each image are the same.

17. The method of claim 15 or 16, wherein the images are obtained from a moving mixture.

18. The method of any of claims 1 to 17, wherein the first and second materials comprise strands or strips of material.

19. The method of claim 18, wherein the first and second materials are selected from: aerosolisable material, amorphous solid, gel, dried gel, tobacco, reconstituted tobacco, paper reconstituted tobacco.

20. The method of any of claims 1 to 19, wherein the mixture is for use as or in an aerosol provision system.

21. The method of any of claims 1 to 20, wherein the method is a computer-implemented method.

22. A method of adjusting the relative proportions of a first material and a second material present in a mixture, comprising the steps of: determining the amount of first material present in the mixture in accordance with the method of any of claims 1 to 21, and adjusting the amount of first material present in the mixture.

23. A method of manufacturing an article for use as or in an aerosol provision system, wherein the article includes a mixture of a first material and a second material, the method comprising the steps of: determining the amount of first material present in the mixture in accordance with the method of any of claims 1 to 21, and adjusting the amount of first material present in the mixture.

24. Apparatus configured to carry out the method of any of claims 1 to 23 comprising: imaging means configured to obtain the images, and processing means configured to carry out the determining steps.

25. The apparatus of claim 24, wherein the imaging means is a digital camera.

26. The apparatus of claim 24 or 25, further comprising a light source to illuminate the mixture sample.

27. The apparatus of claim 24, 25 or 26, further comprising a background for locating behind the mixture sample during image acquisition.

28. The apparatus of any of claims 24 to 27, further comprising means to change the physical configuration of the mixture sample.

29. The apparatus of claim 28, wherein the means to change the physical configuration of the mixture sample is configured to rearrange the sample.

30. The apparatus of claim 28 or 29 wherein the means to change the physical configuration of the mixture sample comprises a container containing the mixture sample and means for agitating the container to change the physical configuration of the mixture sample.