Liquid level determination device and liquid level determination method

Abstract

The present invention provides a liquid level determination device and liquid level determination method that can accurately determine the liquid level of a sample even if a barcode label or the like is attached to the sample container. [Solution] The present invention provides a liquid level determination device comprising: a light source that irradiates light onto a sample container containing a sample; an imaging unit that acquires an image using light irradiated from the light source and transmitted through the sample container; a drive unit that tilts at least the sample container; an operation control unit that controls the operation of the light source, the imaging unit and the drive unit; and a liquid level determination unit that determines the liquid level of the sample based on the image acquired by the imaging unit, wherein the liquid level determination unit determines whether or not there is a change in brightness for each height of the sample container based on the image acquired by the imaging unit while the sample container is tilted, and determines the boundary between a height region where the change in brightness decreases and a height region where the change in brightness increases as the liquid level of the sample.

Description

Technical Field

[0001] The present invention relates to a liquid level determination device and a liquid level determination method.

Background Art

[0002] In the inspection of specimens represented by blood and the like, automatic inspection devices are widespread. On the other hand, when an appropriate amount of the specimen has not been obtained, the reliability of the inspection result is lost. Therefore, before inputting the specimen into the automatic inspection device, an operation of visually checking the properties including the amount of the specimen is required. As the number of specimens increases, the burden on the inspector increases, so automation is desired. For example, in Patent Document 1, a specimen container storing a specimen is rotated from a first state to a second state, the specimen in the specimen container that has moved along with this rotation is imaged, and based on an image obtained by subjecting the imaged image to binarization processing, a technique for determining the presence or absence of coagulated matter in the specimen is disclosed (Claim 3 of the same document).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since a barcode label or the like is generally attached to the specimen container, it may be difficult to directly image the liquid level of the specimen. In such a case, there is also a possibility of misdetecting the liquid level.

[0005] An object of the present invention is to provide a liquid level determination device and a liquid level determination method that can accurately determine the liquid level of a specimen even when a barcode label or the like is attached to the specimen container.

Means for Solving the Problems

[0006] To solve the aforementioned problems, the present invention provides a liquid level determination device comprising: a light source that irradiates light onto a sample container containing a sample; an imaging unit that acquires an image using light irradiated from the light source and transmitted through the sample container; a drive unit that tilts at least the sample container; an operation control unit that controls the operation of the light source, the imaging unit, and the drive unit; and a liquid level determination unit that determines the liquid level of the sample based on the image acquired by the imaging unit, wherein the liquid level determination unit determines whether or not there is a change in brightness for each height of the sample container based on the image acquired by the imaging unit while the sample container is tilted, and determines the boundary between a height region where the change in brightness decreases and a height region where the change in brightness increases as the liquid level of the sample. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a liquid level determination device and liquid level determination method that can accurately determine the liquid level of a sample even if a barcode label or the like is attached to the sample container. [Brief explanation of the drawing]

[0008] [Figure 1] Overall configuration diagram of the liquid level determination device [Figure 2] A diagram showing an example of an image acquired by the imaging unit. [Figure 3] Functional block diagram of the liquid level determination device [Figure 4] A flowchart showing the process by which the control unit estimates the sample volume. [Figure 5] This figure shows a method for determining the presence or absence of brightness fluctuations using a threshold. [Figure 6A] This diagram shows the brightness fluctuations (initial values) for each height, which are stored in the brightness fluctuation memory unit. [Figure 6B] This figure shows the brightness fluctuations for each height (an example of the final value) stored in the brightness fluctuation memory unit. [Figure 7] This figure shows an example of the liquid level determination result output to the output unit. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described based on the drawings.

[0010] Figure 1 is an overall diagram of the liquid level determination device. As shown in Figure 1, the liquid level determination device comprises a light source 1, an imaging unit 2, a support unit 10, a drive unit 3, a control unit 4, an input unit 5, and an output unit 6.

[0011] Light source 1 illuminates the sample container 7 containing the sample. If the sample is blood (e.g., whole blood), it is desirable to use an LED as light source 1 that emits near-infrared light, which is easily absorbed by red blood cells. However, other liquids with a uniform composition and varying transmitted light intensity may be used as samples; in such cases, an appropriate light source 1 should be selected according to the type of sample. Furthermore, it is desirable that light source 1 emits light of a wavelength that is less affected by disturbances caused by the material of the sample container 7 or the material of the label attached to the sample container 7.

[0012] The imaging unit 2 acquires an image using light that is irradiated from the light source 1 and transmitted through the sample container 7; for example, it is a CCD camera. The support unit 10 grips the sample container 7 and also supports the light source 1 and the imaging unit 2.

[0013] The drive unit 3 rotates the support unit 10 around a horizontal rotation axis, thereby tilting the sample container 7 from an upright position (0 degrees) to a predetermined angle (e.g., 135 degrees), and is composed of, for example, a motor. The tilt angle of the sample container 7 should preferably be 90 degrees or more, as too small an angle makes it difficult to determine the liquid level, and 180 degrees or less, as too large an angle reduces throughput. In this embodiment, the common drive unit 3 drives (tilts) not only the sample container 7 but also the light source 1 and the imaging unit 2 as a single unit, which has the advantage of requiring only one drive unit 3 and maintaining a constant positional relationship between the sample container 7 and the light source 1 and imaging unit 2 while driving (tilting).

[0014] The control unit 4 controls the operations of the light source 1, the imaging unit 2, the drive unit 3, etc., and determines the liquid level of the specimen contained in the specimen container 7 and estimates the amount of the specimen. Details of the control unit 4 will be described later with reference to FIG. 3.

[0015] The input unit 5 is for inputting control parameters for controlling the operations of each mechanism, setting information such as the inner diameter of the specimen container, and threshold values (the first threshold value and the second threshold value described later) used for determining the liquid level, and is, for example, a keyboard or a mouse. The output unit 6 is for outputting the determination result of the liquid level, the estimation result of the amount of the specimen, etc., and is, for example, a display or a speaker. Note that the input unit 5 and the output unit 6 may be integrally configured as a touch panel type operation display unit or the like.

[0016] FIG. 2 is a diagram showing an example of an image acquired by the imaging unit. As shown in FIG. 2, a barcode label 8 is attached to the specimen container 7. Note that what is attached to the specimen container 7 is not limited to the barcode label 8, and other labels (seals) or tags may be used. Further, as the structure of the specimen container 7, a transparent cylindrical container (for example, a blood collection tube) is mainly assumed, but containers of other shapes may be used.

[0017] Further, the support unit 10 of the present embodiment can hold five specimen containers 7. For this reason, the liquid levels of the specimens 9 in the five specimen containers 7 can be determined simultaneously, and the throughput can be improved. Note that the number of specimen containers 7 that the support unit 10 can hold is not limited to five.

[0018] FIG. 3 is a functional block diagram of the liquid level determination device. As shown in FIG. 3, the control unit 4 of the liquid level determination device includes a processor 41, a memory 42, and a storage 43. The storage 43 has an image storage unit 431, a setting storage unit 432, a luminance variation storage unit 433, and a determination result storage unit 434. Note that the storage 43 may be an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a storage device on a network.

[0019] In FIG. 3, the functions conceptually executed by the processor 41 are shown as an operation control unit 421, a preprocessing unit 422, a liquid level determination unit 423, and a sample amount estimation unit 424, and programs for realizing each function are stored in a memory. Note that the programs may be provided by being pre - incorporated in a ROM or the like, or recorded on a computer - readable recording medium in an installable or executable file format and provided or distributed. Further, the programs may be stored on a computer connected to a network and provided or distributed by being downloaded via the network.

[0020] The operation control unit 421 controls the operations of the light source 1, the imaging unit 2, the drive unit 3, etc. The preprocessing unit 422 performs preprocessing for analysis to determine the liquid level, such as dynamically adjusting the range of the image acquired by the imaging unit 2 or extracting an analysis range from the image acquired by the imaging unit 2. The liquid level determination unit 423 determines the liquid level of the sample 9 contained in the sample container 7 based on the image of the analysis range extracted by the preprocessing unit 422. The sample amount estimation unit 424 estimates the sample amount by calculating the volume of the sample 9 contained in the sample container 7 using the liquid level determined by the liquid level determination unit 423 and information such as the inner diameter of the sample container 7 stored in the setting storage unit 432.

[0021] FIG. 4 is a flowchart showing the process by which the control unit 4 estimates the sample amount. The sample amount estimation process is mainly divided into the following three flows. The first flow is a step of determining the presence or absence of luminance variation for each height of the sample container 7. The second flow is a step of determining the liquid level of the sample 9 as the point where the direction of the luminance variation changes, that is, the boundary between the height region where the luminance variation decreases and the height region where the luminance variation increases. The third flow is a step of estimating the amount of the sample from the liquid level of the sample 9.

[0022] First, let's explain the first flow. The preprocessing unit 422 reads out the image to be determined from the transmission images acquired by the imaging unit 2 and stored in the image storage unit 431, that is, the first image (frame) acquired when the sample container 7 begins to tilt from an upright position (step S401). The frame rate of the images acquired by the imaging unit 2 should be commensurate with the speed at which the sample container 7 tilts as the drive unit 3 rotates.

[0023] Next, the preprocessing unit 422 specifies an analysis range (for example, the rectangular area enclosed by the dashed line in Figure 2, with a width of M pixels and a height of N pixels) that follows the shape of the sample container 7 as an ROI (Region of Interest) from the read image, and calculates the average brightness in the width direction (radial direction of the sample container 7) within that range (step S402). Note that the analysis range specified as the ROI is not limited to a rectangle, but may be other shapes corresponding to the structure of the sample container, such as an ellipse. Then, the liquid level determination unit 423 calculates the difference between the average brightness in the frame in the initial state (when the sample container 7 is upright) and the average brightness in the frame to be determined (step S403).

[0024] Here, the average brightness of each frame is calculated first, and then the difference between the average brightness of each frame is calculated. However, it is also possible to calculate the difference in brightness of each frame first, and then calculate the average brightness of the difference. Furthermore, when calculating the average brightness or the difference in brightness, a smoothing filter may be applied to suppress the influence of disturbances such as barcode labels 8. Examples of smoothing filters include known filters such as moving average filters, Gaussian filters, and median filters.

[0025] Next, the liquid level determination unit 423 specifies the starting height (i=0) within the ROI as the target for determining whether or not there is a change in brightness (step S404). In this embodiment, the starting height is the uppermost position within the ROI, but it may also be the lowermost position within the ROI. Furthermore, the liquid level determination unit 423 determines whether the difference between the average brightness of the initial state frame (initial frame) and the average brightness of the frame to be determined (target frame) at the starting height exceeds the first threshold or the second threshold (step S405). The first threshold and the second threshold are stored in the setting storage unit 432. The first threshold is a negative value and the second threshold is a positive value, but their absolute values ​​may be the same.

[0026] Figure 5 shows a method for determining the presence or absence of brightness fluctuations using a threshold. According to Figure 5, the sample that was gathered at the bottom of the sample container 7 when the sample container 7 was in an upright position (initial frame) gradually moves upward as the tilting motion progresses, and is no longer present at the bottom of the sample container 7 when the tilting motion is completed (final frame).

[0027] Furthermore, focusing on the height H1, it can be seen that the brightness is relatively high in the initial frame when the sample container 7 is upright, but as the sample container 7 tilts and the number of frames progresses, the brightness decreases, so the difference in brightness gradually decreases from 0 to negative. However, in order to prevent misjudgment due to the influence of barcode labels 8, etc., a decrease in brightness is only determined when the decrease exceeds the first threshold.

[0028] Similarly, focusing on the height H2, the brightness is relatively low in the initial frame when the container 7 is upright, but as the sample container 7 tilts and the number of frames progresses, the brightness increases, so the brightness difference gradually increases from 0 to a positive value. However, in order to prevent misjudgments due to the influence of barcode labels 8, etc., an increase in brightness is only determined when it exceeds a second threshold.

[0029] Returning to the flowchart in Figure 4, in step S405, if the difference in brightness does not exceed either the first or second threshold, the liquid level determination unit 423 specifies the next height (i=1) as the target for determining whether or not there is a brightness fluctuation (step S408).

[0030] On the other hand, in step S405, if the difference in brightness exceeds the first or second threshold, the liquid level determination unit 423 refers to the brightness fluctuation storage unit 433 and determines whether the brightness fluctuation at that height is 0 or not (step S406). Since the target frame here is the first frame acquired after tilting begins from the upright state, the brightness fluctuation storage unit 433 stores an initial value of 0 as the brightness fluctuation at height i=0, as shown in Figure 6A.

[0031] Figure 6A shows the brightness fluctuations (initial values) for each height stored in the brightness fluctuation memory unit 433. For example, if the brightness difference decreases beyond the first threshold, the liquid level determination unit 423 overwrites "-1" as the brightness fluctuation at height i=0 and stores it in the brightness fluctuation memory unit 433 (step S407). Subsequently, the liquid level determination unit 423 specifies the next height (i=1) as the target for determining whether or not there is a brightness fluctuation (step S408).

[0032] In step S406, if a value other than 0 is already stored as the luminance variation at height i, the system proceeds to step S408 without changing the stored luminance variation. For example, if "-1" is already stored as the luminance variation at height i, even if the luminance difference increases beyond the second threshold in step S405, the luminance variation remains "-1" and the system proceeds to step S408. Conversely, if "+1" is already stored as the luminance variation at height i, even if the luminance difference decreases beyond the first threshold in step S405, the luminance variation remains "+1" and the system proceeds to step S408. Therefore, even if the liquid level darkens and then brightens again midway down the slope, or brightens and then darkens again midway down the slope, the system can determine the liquid level based on the first luminance variation that occurred, thus suppressing misjudgments.

[0033] Next, the liquid level determination unit 423 determines whether the height i has exceeded the endpoint height (the lowest position within the ROI) (step S409). If it is determined that the height i has not exceeded the endpoint height, the process returns to step S405 and the same process is repeated.

[0034] Then, in step S409, if it is determined that the height i has exceeded the endpoint height, the liquid level determination unit 423 determines whether the target frame is the final frame or not (step S410). If it is determined that it is not the final frame, the process returns to step S401, and the preprocessing unit 422 reads from the image storage unit 431 the frame acquired when the sample container 7 is tilted further as the next target frame. From there, the same process as steps S402 to S410 described above is repeated. On the other hand, if it is determined in step S410 that the target frame is the final frame, the process moves to the second flow.

[0035] The second flow will now be explained. The liquid level determination unit 423 specifies the starting height (i=0) within the ROI as the target for determining whether or not the luminance fluctuation is in a region of decreasing brightness (step S411). Next, the liquid level determination unit 423 refers to the luminance fluctuation storage unit 433 and determines whether or not the luminance fluctuation at the starting height is "-1" (step S412). If the luminance fluctuation at the starting height is determined to be "-1", the liquid level determination unit 423 stores that height (i=0) in the determination result storage unit 434 as a candidate for the liquid level (step S413). Subsequently, the liquid level determination unit 423 specifies the next height (i=1) as the target for determining whether or not the luminance fluctuation is in a region of decreasing brightness (step S414). Note that if in step S412 it is determined that the luminance fluctuation at that height is not "-1", then that height is not a candidate for the liquid level, and the process proceeds directly to step S414.

[0036] Next, the liquid level determination unit 423 determines whether the height i has exceeded the endpoint height (the lowest position within the ROI) (step S415). If it is determined that the height i has not exceeded the endpoint height, the process returns to step S412 and the same process is repeated.

[0037] Then, in step S415, if it is determined that the height i has exceeded the endpoint height, the liquid level determination unit 423 determines the maximum (the one located at the bottom) of the candidate liquid levels, i.e., the height i at which the brightness fluctuation is "-1", as the liquid level (step S416).

[0038] Figure 6B shows an example of the luminance fluctuation for each height (final value) stored in the luminance fluctuation memory unit 433. In the example shown in Figure 6B, the largest height i at which the luminance fluctuation is "-1" is t, so height t is determined to be the liquid level. Note that if the barcode label 8 is thick or a meniscus is formed on the liquid surface of the sample 9, the difference in luminance from the initial frame may not exceed either the first or second threshold, resulting in a luminance fluctuation of "0". In such cases, the largest height i at which the luminance fluctuation is "0" may be determined to be the liquid level. Alternatively, the smallest height i at which the luminance fluctuation is "+1" (the one located at the top) may be determined to be the liquid level. Furthermore, to mitigate the effects of calculation errors in the luminance average, the liquid level may be determined only when the direction of the luminance fluctuation is consecutive for a certain number of times or more. When the liquid level determination unit 423 determines the liquid level in step S416, it stores the liquid level height in the determination result memory unit 434 and proceeds to the third flow.

[0039] The third flow will now be explained. The sample volume estimation unit 424 estimates the sample volume by calculating the volume of the sample 9 contained in the sample container 7 using information such as the liquid level height determined in step S416, the inner diameter of the sample container 7 stored in the setting storage unit 432, and the position of the sample container 7 (step S417). If the sample container 7 has a complex shape, the sample volume may be estimated by defining an approximate calculation formula or by pre-calculating the cross-sectional area for each height. The sample volume estimation unit 424 stores the estimated sample volume in the determination result storage unit 434 and the third flow ends.

[0040] Figure 7 shows an example of the liquid level determination results output to the output unit. As shown in Figure 7, the output unit 6 displays the position where the sample container 7 is held, the liquid level height, the sample volume, the evaluation result, etc., for each sample 9. If the liquid level height or sample volume falls outside the predetermined normal range, the evaluation result will be either too low or too high. In that case, the output unit 6 may notify the higher-level system of the liquid level determination device (e.g., an automated analyzer) of the abnormality. Note that if the liquid level height is known, it may be possible to evaluate the sample 9, in which case the third flow described above (step S417) and the display of the sample volume on the output unit 6 may be omitted.

[0041] This embodiment provides the following advantages. When barcode labels or the like are attached to the blood collection tube, it can sometimes be difficult to visually confirm whether the correct amount of sample is contained in the tube. However, in this embodiment, the liquid level of the sample can be determined with high accuracy even in such cases. Furthermore, it is possible to determine the liquid level at a lower cost compared to methods such as opening the blood collection tube, inserting a probe, and detecting the liquid level height with a pressure sensor, or irradiating the blood collection tube with a laser to detect the liquid level height.

[0042] The present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the embodiments described above, the liquid level determination unit 423 referred to the luminance fluctuations for each height stored in the luminance fluctuation memory unit 433 and determined the largest height i at which the luminance fluctuation is "-1" to be the liquid level. However, the liquid level height may be determined by other methods. For example, the relationship between the luminance fluctuations for each height and the liquid level height may be learned in advance, and the liquid level height may be output by inputting the luminance fluctuations for each height (e.g., Figure 6B). The data used for learning is not limited to the luminance fluctuations for each height, but may also be data used to determine the presence or absence of luminance fluctuations, such as the difference between the average luminance of the initial frame and the average luminance of each frame. Furthermore, any known learning method may be used, such as deep learning methods like SVM (Support Vector Machine), gradient boosting, or CNN (Convolutional Neural Network). [Explanation of Symbols]

[0043] 1...Light source, 2...Imaging unit, 3...Drive unit, 4...Control unit, 5...Input unit, 6...Output unit, 7...Sample container, 8...Barcode label, 9...Sample, 41...Processor, 42...Memory, 43...Storage, 421...Motion control unit, 422...Preprocessing unit, 423...Liquid level determination unit, 424...Sample volume estimation unit, 431...Image storage unit, 432...Setting storage unit, 433...Brightness fluctuation storage unit, 434...Judgment result storage unit

Claims

1. A light source that illuminates the specimen container containing the specimen, An imaging unit that acquires an image using light irradiated from the light source and transmitted through the sample container, At least a drive unit for tilting the sample container, An operation control unit that controls the operation of the light source, the imaging unit, and the drive unit, A liquid level determination device comprising: a liquid level determination unit that determines the liquid level of the sample based on an image acquired by the imaging unit, The liquid level determination unit is, Based on the image acquired by the imaging unit while the sample container is tilted, the presence or absence of brightness fluctuations is determined for each height of the sample container. A liquid level determination device that determines the boundary between a height region where brightness fluctuations decrease and a height region where brightness fluctuations increase as the liquid level of the sample.

2. In the liquid level determination device according to claim 1, The liquid level determination unit is, If the brightness of the sample container at a predetermined height decreases by more than a first threshold compared to when the sample container is in an upright position, the brightness fluctuation at that height is determined to be a decrease. A liquid level determination device that determines an increase in brightness fluctuation at a given height if the brightness at a predetermined height of the sample container increases by more than a second threshold compared to when the sample container is in an upright position.

3. In the liquid level determination device according to claim 2, When the sample container is tilted from an upright position to a predetermined angle, if it is determined that the brightness fluctuation at a predetermined height of the sample container has decreased, Even if the brightness fluctuation at that height increases when the sample container is further tilted, the liquid level determination unit keeps the brightness fluctuation at that height decreasing. When the sample container is tilted from an upright position to a predetermined angle, if it is determined that the brightness fluctuation at a predetermined height of the sample container is increasing, A liquid level determination device in which, even if the brightness fluctuation at a given height decreases when the sample container is further tilted, the liquid level determination unit keeps the brightness fluctuation at that height increasing.

4. In the liquid level determination device according to claim 1, The liquid level determination unit determines the lowest height in the height range where brightness fluctuations decrease as the liquid level of the sample.

5. In the liquid level determination device according to claim 1, The drive unit is a liquid level determination device that integrally tilts the light source and the imaging unit together with the sample container.

6. The process involves the following steps: while the drive unit tilts the sample container, a light source irradiates the sample container with light, and the imaging unit acquires an image using the transmitted light; A liquid level determination method comprising the steps of: a liquid level determination unit determining, based on an image acquired by the imaging unit, whether or not there is a change in brightness for each height of the sample container, and determining the boundary between a height region where the change in brightness decreases and a height region where the change in brightness increases as the liquid level of the sample.

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