Particle diameter distribution measuring device, particle diameter distribution measuring method, and program for particle diameter distribution measurement

Abstract

To provide a particle diameter distribution measuring device that can automatically adjust a focus position in a short time in particle diameter distribution measurement using a PTA method.SOLUTION: A particle diameter distribution measuring device comprises imaging means 3 that picks up an image of particles in a cell 1, and an analysis unit that, on the basis of imaging data obtained by the imaging means, calculates the rate of diffusion of the particles caused by the Brownian motion to calculate a particle diameter distribution. The particle diameter distribution measuring device further comprises: an upper and lower limit focus position determination unit that determines a lower limit focus position that is a focus position at which the particles are started to be captured in a process of moving the focus of the imaging means from a near side to a depth side of the cell, and an upper limit focus position that is a focus position at which the particles are started to be captured in a process of moving the focus of the imaging means from the depth side to the near side of the cell; a focus position for measurement calculation unit that calculates a focus position for measurement that is a focus position between these positions and used during the measurement; and an auto-focusing unit that adjusts the focus of the imaging means to the focus position for measurement during the measurement.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a particle size distribution measuring device, a particle size distribution measuring method, and a program for measuring particle size distribution. [Background technology]

[0002] Conventional particle size distribution measuring devices include those that use a measuring method called the particle trajectory analysis method (PTA method).

[0003] Specifically, this measurement method measures particle size distribution by calculating the diffusion speed of particles due to Brownian motion based on image data obtained by imaging particles in a cell.

[0004] In such particle size distribution measuring devices, in order to ensure measurement accuracy, it is desirable to obtain imaging data with many particles in focus. However, currently, operators must manually adjust the focus position, which is a time-consuming and labor-intensive task.

[0005] Therefore, the present inventors attempted to apply an existing autofocus function installed in cameras and the like to provide the device with a function for automatically adjusting the focus.

[0006] One such existing autofocus function is one that adjusts the focus to the position where the image contrast is maximized.

[0007] However, the PTA method has characteristics such as a large number of particles appearing in the image, the boundaries between particles being unclear due to scattering phenomena, and the particles being constantly moving due to Brownian motion, which can cause contrast to change in a short period of time. Therefore, even if the above-mentioned existing autofocus function is used, the operation to maximize contrast often does not converge.

[0008] As a result, even if existing focus functions are applied to the PTA method, the focus position is often not determined, and in reality, this does not lead to a reduction in time. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication 2020-204604 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, the present invention is intended to solve all of the above-mentioned problems at once, and its main objective is to enable the focus position to be automatically adjusted in a short time with a high success rate in particle size distribution measurement by the PTA method. [Means for solving the problem]

[0011] That is, the particle size distribution measuring device according to the present invention is a particle size distribution measuring device comprising: an imaging means for imaging particles in a cell; and an analysis unit for calculating a particle size distribution by calculating a diffusion speed due to Brownian motion of the particles based on imaging data obtained by the imaging means, and is characterized by comprising: an upper and lower limit focus position determination unit for determining a lower limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the front side to the back side of the cell, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the back side to the front side of the cell; a measurement focus position calculation unit for calculating a measurement focus position to be used during measurement, which is a focus position between the lower limit focus position and the upper limit focus position, based on the lower limit focus position and the upper limit focus position; and an autofocus unit for adjusting the focus of the imaging means to the measurement focus position during measurement.

[0012] According to the particle size distribution measuring device configured in this manner, the lower focus position and the upper focus position are determined by moving the focus of the imaging means relative to the cell, and the measurement focus position is calculated based on these positions. Therefore, the measurement focus position can be calculated in a shorter time with a higher success rate than with existing autofocus functions. This makes it possible to automatically adjust the focus position in a short time when measuring particle size distribution using the PTA method, eliminating the need for manual focus adjustment as has been required up until now.

[0013] It is desirable to further include a number-related value acquisition unit that acquires a number-related value regarding the number of particles from the imaging data, and the upper and lower limit focus position determination unit determines the lower limit focus position and the upper limit focus position by comparing the number-related value acquired by the number-related value acquisition unit with a predetermined threshold value. According to this configuration, the lower limit focus position and the upper limit focus position are determined using the number-related value obtained from the imaging data, so that the calculation of the measurement focus position is not influenced by, for example, the subjective opinion of the operator, thereby improving reproducibility, etc.

[0014] It is preferable that the imaging device further includes an image processing unit that performs image processing on the imaging data, and the number-related value acquisition unit acquires the number-related value from the imaging data that has been binarized by the image processing unit. According to this configuration, the number-related value is obtained using binarized imaging data, so the amount of calculation required in the process of obtaining the number-related value is small, and processing speed can be improved. As a result, it is possible to automatically adjust the focus position in a shorter time.

[0015] In order to be able to image a large enough number of particles to ensure measurement accuracy, it is desirable that the measurement focus position calculated by the measurement focus position calculation unit falls within a central region of a predetermined length that includes the midpoint between the lower limit focus position and the upper limit focus position.

[0016] Incidentally, in the measurement by the PTA method, after measuring the particle size distribution, the particles in the cell may be stirred or the imaging position may be changed, and then the particle size distribution may be measured again. In this manner, the number of measurements may be increased (i.e., the number of particles to be measured) to improve the measurement accuracy. In this case, it is currently believed that the focus is not significantly off after stirring, and measurements are continued without changing the focus position before stirring. However, in order to further improve measurement accuracy, it is preferable to readjust the focus position even after stirring. However, manually adjusting the focus every time you mix would take an enormous amount of time and effort.

[0017] Therefore, if the particle size distribution measuring device is configured to further include a stirring means for stirring the particles in the cell, the effects of the present invention will be more pronounced, and the measurement accuracy can be further improved in a short time and without hassle.

[0018] In the configuration including the stirring means described above, in order to automate the measurement, it is preferable to include a control unit that repeats stirring of the particles in the cell by the stirring means, alignment of the focus of the imaging means by the autofocus unit, and measurement of the particle size distribution.

[0019] The particle size distribution measuring method according to the present invention is a particle size distribution measuring method using a particle size distribution measuring device including an imaging means for imaging particles in a cell and an analysis unit for calculating a particle size distribution by calculating a diffusion rate due to Brownian motion of the particles based on imaging data obtained by the imaging means, and is characterized by comprising: an upper and lower limit focus position determining step for determining a lower limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the front side to the back side of the cell, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the back side to the front side of the cell; a measurement focus position calculating step for calculating a measurement focus position used during measurement, which is a focus position between the lower limit focus position and the upper limit focus position, based on the lower limit focus position and the upper limit focus position; and an autofocus step for adjusting the focus of the imaging means to the measurement focus position during measurement.

[0020] Further, a particle size distribution measurement program according to the present invention is a particle size distribution measurement program used in a particle size distribution measurement device including an imaging means for imaging particles in a cell, and an analysis unit for calculating a particle size distribution by calculating a diffusion rate due to Brownian motion of the particles based on imaging data obtained by the imaging means, the program being characterized in that it causes a computer to execute functions as an upper and lower limit focus position determination unit for determining a lower limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the front side to the back side of the cell, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the back side to the front side of the cell, a measurement focus position calculation unit for calculating a measurement focus position used during measurement, which is a focus position between the lower limit focus position and the upper limit focus position, and an autofocus unit for adjusting the focus of the imaging means to the measurement focus position during measurement.

[0021] Such a particle size distribution measuring method and program for measuring particle size distribution can provide the same effects as those of the above-mentioned particle size distribution measuring device. Effect of the Invention

[0022] According to the present invention as described above, in particle size distribution measurement by the PTA method, it is possible to automatically adjust the focus position in a short time, thereby eliminating the need for manual focus adjustment as in the conventional method. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic diagram showing a particle size distribution measuring device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a functional block diagram showing functions of the information processing apparatus according to the embodiment. [Diagram 3] FIG. 4 is a schematic diagram for explaining an autofocus function in the embodiment. [Figure 4] 4 is a flowchart showing the operation of the particle size distribution measuring device of the embodiment. [Diagram 5] FIG. 13 is a schematic diagram showing a particle size distribution measuring device in another embodiment. [Figure 6] 10 is a flowchart showing the operation of a particle size distribution measuring device in another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of a particle size distribution measuring device according to the present invention will be described with reference to the drawings.

[0025] <Device configuration> As shown in FIG. 1 , the particle size distribution measuring device 100 in this embodiment includes a light irradiating unit 2 that irradiates particles in a cell 1 with light of an excitation wavelength, an imaging means 3 that images the particles by detecting scattered light by the particles in the cell 1, and an information processing device 4 that analyzes the imaging data obtained by the imaging means 3.

[0026] The light irradiation unit 2 has a plurality of light sources 21, 22, 23 that irradiate light of different excitation wavelengths. The light sources 21, 22, 23 are, for example, laser light sources. Here, when detecting scattered light by a particle and imaging the particle, it is necessary to irradiate light of an appropriate excitation wavelength according to the particle diameter. In this embodiment, three light sources 21, 22, 23 are provided to handle particles of various particle diameters. Note that one light source may irradiate light including three excitation wavelengths. The number of light sources may be three or more, or may be one.

[0027] The first light source 21 irradiates light of a predetermined first excitation wave λ1, the second light source 22 irradiates light of a predetermined second excitation wavelength λ2, and the third light source 23 irradiates light of a predetermined third excitation wavelength λ3. The light emitted from each of the light sources 21, 22, and 23 is guided to the cell 1 via an irradiation optical system 24 including reflection mirrors 241 and 242, half mirrors 243 and 244, and a condenser lens 245.

[0028] These light sources 21, 22, and 23 are controlled by a control unit (not shown) so as to simultaneously irradiate light of the respective excitation wavelengths λ1, λ2, and λ3. Note that these light sources 21, 22, and 23 can also be controlled so as to simultaneously irradiate light.

[0029] The imaging means 3 detects scattered light by the particles in the cell 1 to capture images of the particles, and in this embodiment is an imaging camera such as a CCD camera, and outputs, for example, video image data as imaging data. Note that, in Fig. 1, the light irradiation direction of the light irradiation unit 2 and the imaging direction of the imaging means 3 are set perpendicular to each other, but this is not limited thereto.

[0030] The information processing device 4 is a computer equipped with a CPU, a memory, a display, various input / output devices, etc., and is connected to the imaging means 3 by wire or wirelessly.

[0031] The information processing device 4 performs at least the function of an analysis section 41 as shown in FIG. 2 by executing a particle size distribution measuring program stored in the memory.

[0032] The analysis unit 41 acquires imaging data from the imaging means 3 and calculates the particle size distribution by the PTA method based on the imaging data. More specifically, the analysis unit 41 calculates the particle size distribution by calculating the diffusion speed of the particles due to Brownian motion based on the imaging data.

[0033] Thus, the particle size distribution measuring device 100 of this embodiment is provided with an autofocus function for automatically adjusting the focus of the imaging means 3 described above on the particles in the cell 1.

[0034] Specifically, the above-mentioned information processing device 4 is configured to function as an autofocus unit 42, an image processing unit 43, a number-related value acquisition unit 44, an upper and lower limit focus position determination unit 45, and a measurement focus position calculation unit 46, as shown in FIG. 2.

[0035] The autofocus unit 42 moves the focus of the imaging means 3 according to a predetermined rule, and specifically, is configured to move the focus of the imaging means 3 toward and away from the cell 1.

[0036] As shown in FIG. 3(a), the autofocus unit 42 moves the focus of the imaging means 3 from the front side of the cell 1 to the back side, or from the back side of the cell 1 to the front side.

[0037] More specifically, the autofocus unit 42 here moves the focus of the imaging means 3 from the front end face A of the cell 1 or from further in front of the end face A to the back side, or moves the focus from the back end face B of the cell 1 or from further in back of the end face B to the front side. However, the autofocus unit 42 may be configured to move from slightly behind the front end face A of the cell 1 to further back, or to move from slightly in front of the rear end face B of the cell 1 to further forward.

[0038] The autofocus unit 42 of this embodiment is configured to move the focus of the imaging means 3 relative to the cell 1 by a predetermined distance at each focus position, and the imaging means 3 captures an image of the inside of the cell 1 at each of the focus positions to which it is moved, and the image data is sent to the image processing unit 43.

[0039] The image processing unit 43 processes the imaging data transmitted by the imaging means 3, and more specifically, processes the imaging data so that particles captured in the image represented by the imaging data can be distinguished from particles other than those captured in the image.

[0040] The image processing unit 43 of this embodiment is configured to binarize each piece of imaging data successively sent from the imaging means 3, so that in the image represented by the imaging data, for example, particles appear white and everything else appears black.

[0041] The number-related value acquiring unit 44 acquires a number-related value related to the number of particles included in the image represented by the imaging data. Note that the number-related value is a concept including not only a value related to the number of particles but also a value indicating the number of particles itself.

[0042] The number-related value acquisition unit 44 of the present embodiment acquires a number-related value from image data processed by the image processing unit 43, and here acquires the number-related value from binarized image data.

[0043] To explain in more detail, the number-related value acquisition unit 44 here is configured to acquire the number-related value using pixels that represent particles (white pixels) from among the numerous pixels that make up the binarized image data.

[0044] One specific embodiment of the number-related value acquisition unit 44 is one in which pixels representing particles (white pixels) are counted and the number of counted pixels or a value obtained from the number of pixels (for example, the ratio of the number of pixels to the total number of pixels) is acquired as the number-related value.

[0045] As another embodiment of the number-related value acquiring unit 44, when pixels (white pixels) representing particles are gathered in a predetermined number or more, the group of pixels may be counted as one particle, and the number of particles thus counted may be acquired as the number-related value.

[0046] The number-related value thus acquired is output from the number-related value acquisition unit 44 to the upper and lower limit focus position determination unit 45 .

[0047] The upper and lower limit focus position determining unit 45 determines a lower limit focus position, which is a focus position at which particles begin to be captured in the process in which the autofocus unit 42 moves the focus of the imaging means 3 from the front side to the back side of the cell 1, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process in which the autofocus unit 42 moves the focus of the imaging means 3 from the back side to the front side of the cell 1. Note that the focus position at which particles begin to be captured here is a focus position at which particles completely disappear when the focus movement direction is reversed.

[0048] It should be noted that the lower limit focus position and the upper limit focus position determined by the upper and lower limit focus position determination unit 45 do not necessarily have to be the focus positions at the moment when the particle begins to be captured, but may be focus positions that are slightly displaced after the particle begins to be captured.

[0049] These lower limit focus position and upper limit focus position are positions used in the calculation of a measurement focus position used during measurement, which will be described later, and are, so to speak, reference positions for the measurement focus position.

[0050] The upper and lower limit focus position determiner 45 of this embodiment determines the lower limit focus position and the upper limit focus position by comparing the number-related value acquired by the number-related value acquirer 44 with a predetermined threshold value. Note that the threshold value used to determine the lower limit focus position and the threshold value used to determine the upper limit focus position may be the same value or different values.

[0051] Here, referring to Figure 3(b), we consider the image represented by the imaging data obtained during the focus of the imaging means 3 being moved from the front side to the back side of the cell 1, or from the back side to the front side.

[0052] As shown in Figure 3(b), in the images shown by these imaging data, no particles are captured for a while after the focus starts to be moved (X in Figure 3), then at a certain point, particles start to be captured (Y in Figure 3), and thereafter the number of captured particles should increase.

[0053] In other words, there will be no change in the quantity-related value for a while after the focus starts to move, but at a certain point in time, a change will occur in the quantity-related value. This is true whether the focus is moved from the front side to the back side of cell 1 or the back side to the front side of cell 1.

[0054] Therefore, the upper and lower limit focus position determination unit 45 sequentially compares the number-related values ​​obtained from each image data with a predetermined threshold value, and when the number-related value exceeds the threshold value, determines the focus position corresponding to the image data from which the number-related value was obtained as the lower limit focus position or the upper limit focus position.

[0055] The lower limit focus position and the upper limit focus position thus determined are output from the upper / lower limit focus position determining unit 45 to the measurement focus position calculating unit 46 .

[0056] The measurement focus position calculation section 46 calculates, based on the lower limit focus position and the upper limit focus position, a measurement focus position that is between these positions and is used during measurement.

[0057] This measurement focus position calculation unit 46 is configured to calculate the measurement focus position using, for example, a predetermined calculation formula, and is configured so that the calculated measurement focus position falls within an intermediate region of a predetermined length that includes the midpoint between the lower limit focus position and the upper limit focus position. The length occupied by the intermediate region is preferably equal to or less than half the length from the lower limit focus position to the upper limit focus position, and more preferably equal to or less than one-third thereof.

[0058] The measurement focus position calculation section 46 of this embodiment calculates the midpoint between the lower limit focus position and the upper limit focus position as the measurement focus position. However, the measurement focus position calculation section 46 may, for example, weight the lower limit focus position or the upper limit focus position, and calculate a position shifted from the midpoint between these positions as the measurement focus position.

[0059] The measurement focus position calculated by the measurement focus position calculation unit 46 is output to the above-mentioned autofocus unit 42, and the autofocus unit 42 adjusts the focus of the imaging means 3 to the measurement focus position before measuring the particle size distribution.

[0060] Next, the operation of the information processing device 40 before measurement by the particle size distribution measuring device 100 will be described with reference to FIG.

[0061] First, when an autofocus button displayed on a display or the like is operated, the autofocus unit 42 moves the focus of the imaging means 3 toward and away from the cell 1.

[0062] The autofocus unit 42 of this embodiment first moves the focus of the imaging means 3 from the front side to the back side of the cell 1 by, for example, a predetermined distance (S1).

[0063] Then, the imaging data obtained at the destination is sent from the imaging means 3 to the image processing section 43, which then binarizes the imaging data (S2).

[0064] Next, the number-related value acquisition unit 44 acquires a number-related value from the binarized imaging data, for example, by counting the number of pixels representing particles (S3).

[0065] Next, the upper and lower limit focus position determining unit 45 compares each number-related value acquired by the number-related value acquiring unit 44 with a threshold value (S4).

[0066] In S4, if the number-related value does not reach the threshold value, the process returns to S1, and the focus is again moved a predetermined distance from the front side of cell 1 to the back side.

[0067] On the other hand, if the number-related value exceeds the threshold in S4, the upper / lower limit focus position determination unit 45 determines the focus position corresponding to the imaging data from which the number-related value was obtained as the lower limit focus position (S5).

[0068] This completes the operation of moving the focus in S1 from the front side to the back side of cell 1.

[0069] Next, the autofocus unit 42 moves the focus of the imaging means 3 from the back side to the front side of the cell 1 by, for example, a predetermined distance (S6).

[0070] Then, the imaging data obtained at the destination is sent from the imaging means 3 to the image processing section 43, and the image processing section 43 binarizes the imaging data (S7).

[0071] Next, the number-related value acquisition unit 44 acquires a number-related value from the binarized imaging data, for example, by counting the number of pixels representing particles (S8). Note that, in order to adjust the focus position with higher accuracy, processing such as object recognition may be performed.

[0072] Next, the upper and lower limit focus position determining unit 45 compares each of the number-related values ​​acquired by the number-related value acquiring unit 44 with a threshold value (S9).

[0073] In S9, if the number-related value does not reach the threshold value, the process returns to S6, and the focus is again moved a predetermined distance from the back side of cell 1 to the front side.

[0074] On the other hand, if the number-related value exceeds the threshold in S9, the upper / lower limit focus position determination unit 45 determines the focus position corresponding to the imaging data from which the number-related value was obtained as the upper limit focus position (S10).

[0075] This completes the operation of moving the focus from the back side of cell 1 to the front side in S6.

[0076] Thereafter, the lower limit focus position and the upper limit focus position determined by the upper and lower limit focus position determination unit 45 are sent to the measurement focus position calculation unit 46, which calculates the midpoint between the lower limit focus position and the upper limit focus position as the measurement focus position (S11).

[0077] Then, this measurement focus position is output again to the autofocus unit 42, and the autofocus unit 42 moves the focus of the imaging means 3 to the measurement focus position (S12).

[0078] By utilizing the above-mentioned autofocus function to adjust the focus of the imaging means 3 to the measurement focus position, and measuring the particle size distribution in this state (S13), it is possible to perform a highly accurate measurement.

[0079] <Effects of this embodiment> According to the particle size distribution measuring apparatus 100 of this embodiment configured as described above, the lower and upper focus positions are determined by moving the focus of the imaging means 3 relative to the cell, and the measurement focus position is calculated based on these positions. Therefore, the measurement focus position can be calculated in a shorter time with a higher success rate than with existing autofocus functions. This makes it possible to automatically adjust the focus position in a short time when measuring particle size distribution using the PTA method, eliminating the need for manual focus adjustment as has been required up until now.

[0080] Furthermore, since the quantity-related value acquisition unit 44 acquires the quantity-related value using the binarized imaging data, the amount of calculation required to acquire the quantity-related value is small, and the processing speed can be improved. As a result, it becomes possible to automatically adjust the focus position in a short period of time.

[0081] Furthermore, the information processing device 40 of this embodiment automatically determines the upper and lower focus positions, calculates the measurement focus position, and adjusts the focus to the measurement focus position, thereby further reducing the workload of the operator.

[0082] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0083] For example, the particle size distribution measuring device 100 may further include a stirring means 5 for stirring the particles in the cell 1 as shown in FIG. In this case, the information processing device 4 may be equipped with a control unit that repeats each of the following operations multiple times: adjusting the focus position of the imaging means 3 using an autofocus function (T1), calculating the particle size distribution using the analysis unit 41 (T2), and stirring the particles in the cell 1 using the stirring means 7 (T3), as shown in Figure 6. With this configuration, the number of measurements can be increased (i.e., the number of particles to be measured can be increased) in measurements using the PTA method, and the focus of the imaging means 3 can be automatically adjusted each time stirring is performed, thereby further improving the measurement accuracy in a short time and without hassle.

[0084] In addition, in this embodiment, the number-related value acquisition unit 44 acquires the number-related value based on binarized image data, but it may also acquire the number-related value based on image data that has undergone image processing other than binarization.

[0085] Furthermore, the number-related value acquisition unit 44 may acquire the number-related value based on imaging data that has not been subjected to image processing. In this case, the information processing device 4 can omit the function of the image processing unit 43.

[0086] Moreover, the information processing device 4 does not necessarily need to include the upper and lower focus limit position determining unit 45 . In this case, an example of an embodiment of the information processing device 4 is one in which the lower limit focus position and the upper limit focus position can be input via an input means or the like, and the measurement focus position calculation unit 46 calculates the measurement focus position using the input lower limit focus position and upper limit focus position.

[0087] In addition, in the above embodiment, the upper and lower limit focus position determination unit 45 determines the upper limit focus position after determining the lower limit focus position, but it may be configured to determine the lower limit focus position after determining the upper limit focus position.

[0088] Furthermore, in the above embodiment, the lower limit focus position and the upper limit focus position were determined by moving the focus of the imaging means 3 a predetermined distance relative to the cell 1, but the focus of the imaging means 3 may be moved continuously relative to the cell 1, and the lower limit focus position and the upper limit focus position may be determined based on the imaging data captured by the imaging means 3 during the movement.

[0089] In addition, the particle size distribution measuring device 100 may further include a display unit that displays the actual focus position of the imaging means 3 on a display or the like using, for example, a numerical value. Specifically, the display unit may display the focus position in real time as the focus is being moved. Furthermore, the display unit may be configured to display an image represented by the imaging data obtained by the imaging means 3 on a display or the like while the focus is being moved and / or after the autofocus operation is completed.

[0090] Furthermore, the particle size distribution measuring device 100 may be configured so that the focus of the imaging means 3 can be manually changed so that the focus position can be finely adjusted, for example, after the completion of an autofocus operation. In this case, for example, a focus position change button may be displayed on a display or the like, and the focus of the imaging means 3 can be manually changed by operating this button.

[0091] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0092] 100...Particle size distribution measuring device 1 cell 2. Light irradiation unit 3. Imaging Method 4. Information processing device 41...Analysis Department 42 Autofocus section 43 Image processing section 44 Number-related value acquisition unit 45 Upper and lower limit focus position determining section 46 Measurement focus position calculation unit

Claims

1. An imaging means for imaging particles in the cell; and an analysis unit that calculates a particle size distribution by calculating a diffusion speed due to Brownian motion of particles based on the imaging data obtained by the imaging means, an upper and lower limit focus position determining unit that determines a lower limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the front side to the back side of the cell, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the back side to the front side of the cell; a measurement focus position calculation unit that calculates, based on the lower limit focus position and the upper limit focus position, a measurement focus position to be used during measurement, which is a focus position between the lower limit focus position and the upper limit focus position; and an autofocus unit that adjusts the focus of the imaging means to the measurement focus position during measurement.

2. a number-related value acquiring unit that acquires a number-related value related to the number of particles from the imaging data, 2. The particle size distribution measuring device according to claim 1, wherein the upper and lower limit focus position determining unit determines the lower limit focus position and the upper limit focus position by comparing the number-related value acquired by the number-related value acquiring unit with a predetermined threshold value.

3. An image processing unit that processes the imaging data is further provided, 3. The particle size distribution measuring device according to claim 2, wherein the number-related value acquiring unit acquires the number-related value from the imaging data binarized by the image processing unit.

4. 4. The particle size distribution measuring device according to claim 1, wherein the measurement focus position calculated by the measurement focus position calculation unit falls within a central region of a predetermined length including a midpoint between the lower limit focus position and the upper limit focus position.

5. 5. The particle size distribution measuring apparatus according to claim 1, further comprising a stirring means for stirring the particles in the cell.

6. 6. The particle size distribution measuring device according to claim 5, further comprising a control unit that repeats stirring of the particles in the cell by the stirring means, alignment of the focus of the imaging means by the autofocus unit, and measurement of the particle size distribution.

7. A particle size distribution measuring method using a particle size distribution measuring device including: an imaging means for imaging particles in a cell; and an analysis unit for calculating a particle size distribution by calculating a diffusion speed due to Brownian motion of the particles based on imaging data obtained by the imaging means, an upper and lower limit focus position determination step for determining a lower limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the front side to the back side of the cell, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the back side to the front side of the cell; a measurement focus position calculation step of calculating, based on the lower limit focus position and the upper limit focus position, a measurement focus position to be used during measurement, which is a focus position between the lower limit focus position and the upper limit focus position; and an autofocus step of adjusting the focus of the imaging means to the measurement focus position during measurement.

8. An imaging means for imaging particles in the cell; and an analysis unit that calculates a particle size distribution by calculating a diffusion rate due to Brownian motion of particles based on imaging data obtained by the imaging means, an upper and lower limit focus position determining unit that determines a lower limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the front side to the back side of the cell, and an upper limit focus position, which is a focus position at which particles begin to be captured in the process of moving the focus of the imaging means from the back side to the front side of the cell; a measurement focus position calculation unit that calculates, based on the lower limit focus position and the upper limit focus position, a measurement focus position to be used during measurement, which is a focus position between the lower limit focus position and the upper limit focus position; A program for measuring particle size distribution, which causes a computer to execute a function as an autofocus unit that adjusts the focus of the imaging means to the measurement focus position during measurement.

Images