Patent Description:
As apparatus for measuring particle characteristics, such as shapes of particles, a particle size distribution, and a molecular weight, there are known light scattering measuring apparatus for detecting light scattered from a sample including the particles. When a particle size distribution of a sample in which particles of different particle sizes are mixed is analyzed, it is required to perform not only forward measurement or side measurement, in which a scattering angle formed by incident light and scattered light is small, but also back measurement, in which a scattering angle is large.

For example, in <CIT>, there is disclosed a light scattering measuring apparatus in which an optical element is arranged between a light source and a sample. The optical element modifies light from the light source to create a modified beam, and the modified beam diverges in the far field. As a result, a dark region that is substantially not illuminated is produced at a distance from the sample position along the illumination axis. Then, the light scattering measuring apparatus characterizes particle by a light receiver at a distance from the sample position detecting forward scattered light or back scattered light.

Further, in <CIT>, there is disclosed a light scattering measuring apparatus, which is an apparatus for detecting scattered light from a gel particle, and includes means for separating reflected light from a mechanism for stirring a sample and a reagent in a sample cell and a surface of the cell, and the scattered light from the sample. Still further, in <CIT>, there is disclosed a particle measuring apparatus, in which incident light beams of different wavelengths are irradiated from two or more different directions, and the incident light beams can be deflected with a light deflector.

<CIT> describes a particle size distribution analysis apparatus comprising a sample measurement zone adapted to define a sample of particles, a light emitting means adapted to provide a source of light incident upon the sample measurement zone, a second source of light, and at least a first detection means adapted to measure light levels in the apparatus at particular scattering angles and output a signal to a computation means enabling the particle size distribution of particles contained within the sample to be determined. The computation means is adapted, in use, to calculate a particle size distribution taking into account reflections by the measurement zone of light scattered off the particles, e.g., reflections by cell walls at large scattering angles.

In recent years, it is required to downsize and reduce cost of apparatus. As a method for downsizing and reducing cost, there is a method of sharing a light receiver used for forward measurement or side measurement and back measurement. However, when the back measurement is performed with use of a light scattering apparatus that can perform the forward measurement or the side measurement, a reduction in measurement accuracy caused by a component (so-called stray light) other than scattered light occurs. Accordingly, when the back measurement is performed, it is required to take countermeasures so that the stray light (mainly the component resulting from incident light being reflected on a surface of a cell) does not enter the light receiver.

As the countermeasures, there is a method involving inclining the cell when the back measurement is performed. With this method, it is possible to prevent the light reflected on the surface of the cell from entering the light receiver. However, when the cell is inclined, a deviation occurs in an optical path in performing the forward measurement or the side measurement, and hence the apparatus that inclines the cell to perform the back measurement cannot perform the forward measurement or the side measurement.

The present disclosure has been made in view of the above-mentioned situation, and therefore has an object to provide a light scattering measuring apparatus, with which at least one of forward measurement or side measurement, and the back measurement can be performed, and which is downsized and reduced in cost with a single light receiver, and a measuring jig to be used in the light scattering measuring apparatus.

This object is solved by a light scattering measuring apparatus and a measuring jig comprising the light scattering measuring apparatus having the features of claims <NUM> and <NUM>, respectively. Additional embodiments are defined in claims <NUM> to <NUM>.

At least one embodiment of the present disclosure is described below with reference to the drawings.

<FIG> is a view for schematically illustrating a light scattering measuring apparatus <NUM> according to the at least one embodiment of the present disclosure. As illustrated in <FIG>, the light scattering measuring apparatus <NUM> includes light sources <NUM>, a half mirror <NUM>, mirrors <NUM>, a cell <NUM>, a sample holder, a moving mechanism <NUM>, and a light receiver <NUM>.

The light sources <NUM> generate light to irradiate a sample. Specifically, for example, the light sources <NUM> generate laser beams with use of, for example, a He-Ne laser or a semiconductor laser. Further, in the example illustrated in <FIG>, the light sources <NUM> include a first light source 102A and a second light source 102B.

The first light source 102A generates light on a first optical path. In this example, the first optical path is an optical path used for the at least one measurement of forward measurement or side measurement. A path of light used in performing the forward measurement is hereinafter referred to as "forward measurement optical path. " Further, a path of light used in performing the side measurement is referred to as "side measurement optical path. " Still further, the light to irradiate the sample is referred to as "incident light," and light scattered by the sample is referred to as "scattered light.

The first optical path includes the forward measurement optical path and the side measurement optical path. The forward measurement and the side measurement are measurement performed under a condition in which a scattering angle formed by the incident light and the scattered light is <NUM>° or less. For example, the scattering angle of the forward measurement exceeds <NUM>° and is <NUM>° or less, and the scattering angle of the side measurement exceeds <NUM>° and is <NUM>° or less.

The second light source 102B generates light on a second optical path. In this example, the second optical path is an optical path used for the back measurement. A path of light used in performing the back measurement is hereinafter referred to as "back measurement optical path. " Further, the back measurement is measurement performed under a condition in which a scattering angle exceeds <NUM>°. For example, the scattering angle of the back measurement exceeds <NUM>° and is less than <NUM>°. The forward measurement optical path, the side measurement optical path, and the back measurement optical path are described later in detail. Still further, it is assumed that positions in a Z-axis direction of the first light source 102A and the second light source 102B are the same.

In the example illustrated in <FIG>, a light source is shared as a light source used for the forward measurement and a light source used for the side measurement, but the light source used for the forward measurement and the light source used for the side measurement may be provided individually.

The half mirror <NUM> separates the light emitted by the first light source 102A into light used on the forward measurement optical path and light used on the side measurement optical path. When the light source used for the forward measurement and the light source used for the side measurement are provided individually, the half mirror <NUM> may be omitted.

The mirrors <NUM> reflect light. Specifically, the mirrors <NUM> are arranged on the forward measurement optical path, the side measurement optical path, and the back measurement optical path, and reflect light on the optical paths. The mirrors <NUM> are arranged so that light on the optical paths, which is emitted by the light sources, is guided to the cell <NUM>. Further, optical path lengths of the optical paths are adjusted by positions at which the mirrors <NUM> are arranged.

The cell <NUM> has a cavity in which the sample is to be contained. Specifically, for example, the cell <NUM> has a cuboid shape, and has the cavity formed of inner side surfaces that are parallel to outer surfaces. In the cavity, a liquid sample serving as an object to be measured is to be contained. The cell <NUM> having the sample contained therein is arranged in the sample holder.

The sample holder includes a frame body and an optical element <NUM>. The sample holder, which is a member for holding the sample, is a jig used for light scattering measurement, and hence is hereinafter also referred to as "measuring jig <NUM>. " Specifically, description is given with reference to, for example, <FIG>. <FIG> are perspective views of the measuring jig <NUM> according to the at least one embodiment of the present disclosure as viewed from different directions. <FIG> are side views of the measuring jig <NUM> according to the at least one embodiment of the present disclosure. Further, the measuring jig <NUM> may be formed of only the frame body excluding the optical element <NUM>, or may include the frame body, the optical element <NUM>, and the cell <NUM>.

Specifically, for example, the frame body includes a bottom surface portion <NUM>, a first side surface portion <NUM>, a second side surface portion <NUM>, and an upper surface portion <NUM>, and has a holding space. The bottom surface portion <NUM> is a platelike member that is parallel to an XY plane. The first side surface portion <NUM> and the second side surface portion <NUM> are members erected on a surface on a Z-axis side of the bottom surface portion <NUM>. A space corresponding to a shape of the cell <NUM> is formed between the first side surface portion <NUM> and the second side surface portion <NUM>. The upper surface portion <NUM> is arranged on the Z-axis side of the first side surface portion <NUM> and the second side surface portion <NUM>, and has an opening corresponding to the shape of the cell <NUM>. The space between the first side surface portion <NUM> and the second side surface portion <NUM>, and the opening form the holding space. The holding space is a space surrounded by the frame body, and is a space in which the cell <NUM> is to be arranged. The cell <NUM> arranged in the holding space is supported in an X-axis direction and a Y-axis direction by the frame body. Further, the cell <NUM> is supported in the Z-axis direction by the bottom surface portion <NUM>.

Further, the frame body has a first opening <NUM> and a second opening <NUM>. Specifically, the first opening <NUM> is an opening formed by a notched portion that is formed in the first side surface portion <NUM>, and an end portion of the second side surface portion <NUM>. The first opening <NUM> is formed in an incident portion of the first optical path, which is to be described later. The second opening <NUM> is a hole that penetrates from an outer side surface of the first side surface portion <NUM> to the holding space. The second opening <NUM> is formed in an incident portion of the second optical path, and in an exit portion of the first optical path and the second optical path. As illustrated, the second opening <NUM> has a larger diameter in the Z-axis direction as compared to the first opening <NUM>.

The optical element <NUM> has a first surface <NUM> that forms a certain angle with a side surface of the cavity. Further, the optical element <NUM> has a portion having a triangular prism shape including the first surface <NUM> and a second surface <NUM>, which is opposed in parallel to the cell <NUM> on a side opposite to the first surface <NUM>. The optical element <NUM> is arranged in at least one of the incident portion or the exit portion of at least one optical path of the first optical path or the second optical path. In other words, it is only required that the optical element <NUM> be arranged in at least one of the incident portion of the first optical path, the exit portion of the first optical path, the incident portion of the second optical path, or the exit portion of the second optical path. For example, in the example illustrated in <FIG>, the optical element <NUM> is arranged in the incident portion of the second optical path and the exit portion of the second optical path. The optical element <NUM> may have another shape as long as the optical element <NUM> includes a portion having a triangular prism shape.

The light receiver <NUM> is arranged at a position at which the scattered light that is output from the sample is received, and measures an intensity of the scattered light. Specifically, the light receiver <NUM> is a measuring instrument that measures the intensity of the scattered light at predetermined time intervals, and acquires a change with time of the intensity of the scattered light. The light receiver <NUM> is arranged in exit portions of the forward measurement optical path, the side measurement optical path, and the back measurement optical path. The light sources, the mirrors <NUM>, the half mirror <NUM>, and the measuring jig <NUM> are arranged so that the exit portions of the forward measurement optical path, the side measurement optical path, and the back measurement optical path have the same optical path. In other words, the light receiver <NUM> is shared among the forward measurement, the side measurement, and the back measurement. Accordingly, a single light receiver <NUM> is provided in the light scattering measuring apparatus. As a result, the light scattering measuring apparatus <NUM> can be downsized.

The moving mechanism <NUM> moves the measuring jig <NUM> in a vertical direction. Specifically, when the at least one measurement of the forward measurement or the side measurement is to be performed, the moving mechanism <NUM> moves the first opening <NUM> to a position of the incident portion of the first optical path. Further, when the back measurement is to be performed, the moving mechanism <NUM> moves the second opening <NUM> to a position of the incident portion of the second optical path.

With the moving mechanism <NUM> moving the measuring jig <NUM> in the vertical direction, a switch can be made between the measurement (one or both of forward scattering measurement and side scattering measurement) using the first optical path, and the measurement (back scattering measurement) using the second optical path without moving the light sources <NUM>, the mirrors <NUM>, the half mirror <NUM>, or other such components. When the cell <NUM> is inclined to perform the back scattering measurement as in the related art, it is required to perform the measurement using the first optical path and the measurement using the second optical path in different XY planes. However, with the measuring jig <NUM> being moved in the vertical direction, the measurement using the first optical path and the measurement using the second optical path can be performed in the same XY plane. Thus, it is not required to move the light sources <NUM>, the mirrors <NUM>, the half mirror <NUM>, or other such components. Further, in the case in which the cell <NUM> is inclined, it is required to strictly control an inclination angle for adjustment of the optical path lengths, but in the case in which the measuring jig <NUM> is moved in the vertical direction, measurement accuracy is not affected even when some error occurs in a movement distance. Consequently, the measurement accuracy can be increased.

The light scattering measuring apparatus <NUM> conducts analysis by an information processing unit (not shown) based on the intensity of the scattered light measured by the light receiver <NUM>. Specifically, the light scattering measuring apparatus <NUM> calculates a zeta potential, a particle diffusion coefficient, particle sizes, a particle size distribution, and the like based on the intensity of the scattered light through use of a photon correlation method. The information processing unit is a personal computer included in the light scattering measuring apparatus <NUM> or an external personal computer for use with the light scattering measuring apparatus <NUM>, and performs computation required to calculate the zeta potential, the particle diffusion coefficient, the particle sizes, the particle size distribution, and the like.

Next, the forward measurement optical path, the side measurement optical path, and the back measurement optical path are described with reference to <FIG> and <FIG> to <FIG>. <FIG> is a perspective view of the measuring jig <NUM> showing the forward measurement optical path, the side measurement optical path, and the back measurement optical path. <FIG> are views for illustrating the cell <NUM>, and the forward measurement optical path, the side measurement optical path, and the back measurement optical path in the sample arranged in the cavity of the cell <NUM> as viewed from the Z-axis direction. <FIG> is a view of the back measurement optical path of <FIG> as viewed from a side surface. Each solid line illustrated in <FIG> and <FIG> to <FIG> is the forward measurement optical path. Each chain line is the side measurement optical path. Each one dot chain line is the back measurement optical path.

As illustrated in <FIG>, the forward measurement optical path is a path of light that starts at the first light source 102A, is transmitted through the half mirror <NUM>, is reflected by a mirror 106A, is scattered by the sample, and reaches the light receiver <NUM>. The side measurement optical path is a path of light that starts at the first light source 102A, is reflected by the half mirror <NUM> and a mirror 106B, is scattered by the sample, and reaches the light receiver <NUM>. The back measurement optical path is a path of light that starts at the second light source 102B, is reflected by a mirror 106C and a mirror 106D, is scattered by the sample, and reaches the light receiver <NUM>. A portion of each optical path until the light enters the sample is referred to as "incident portion," and a portion after the light is output from the sample is referred to as "exit portion.

As illustrated in <FIG>, the light on the forward measurement optical path and the side measurement optical path passes through the first opening <NUM> and irradiates the sample. The light on the back measurement optical path passes through the second opening <NUM> and irradiates the sample. Further, output light on the forward measurement optical path, the side measurement optical path, and the back measurement optical path passes through the second opening <NUM> and enters the light receiver <NUM>. Still further, the first optical path and the second optical path are separated from each other in the vertical direction. Specifically, the back measurement optical path is located on the side of the Z-axis direction of the forward measurement optical path and the side measurement optical path.

As illustrated in <FIG>, the light on the forward measurement optical path is scattered by the sample. Of the scattered light on the forward measurement optical path, light having a scattering angle θ of <NUM>° passes through the second opening <NUM> and enters the light receiver <NUM>.

As illustrated in <FIG>, the light on the side measurement optical path is scattered by the sample. Of the scattered light on the side measurement optical path, light having the scattering angle θ of <NUM>° passes through the second opening <NUM> and enters the light receiver <NUM>.

As illustrated in <FIG>, the light on the back measurement optical path is scattered by the sample. Of the scattered light on the back measurement optical path, light having the scattering angle θ of <NUM>° passes through the second opening <NUM> and enters the light receiver <NUM>. Further, as illustrated in <FIG> and <FIG>, in the exit portion of the back measurement optical path, the optical element <NUM> is arranged. In the at least one embodiment of the present disclosure, the optical element <NUM> has a triangular prism shape arranged so as to have a triangular shape as viewed from the side surface. A surface that is opposed to the cell <NUM> and is parallel to a Z-axis is the second surface <NUM>. A surface on the side opposite to the second surface <NUM>, which forms a certain angle with a side surface of the cell <NUM>, is the first surface <NUM>. The optical element <NUM> prevents stray light, for example, light reflected on a surface of the cell <NUM>, from entering the light receiver <NUM>.

The arrows depicted with the one dot chain lines of <FIG> indicate directions of travel of light in the incident portion of the back measurement optical path, and the light entering the light receiver <NUM> of the scattered light. The arrows depicted with the two dot chain lines indicate directions of travel of the stray light. In this specification, the stray light is a component that does not contribute to the measurement, of the light entering the light receiver <NUM>. Refractive indices of air, the optical element <NUM>, the cell <NUM>, and the sample are different, and hence intensities of light reflected on interfaces of the air, the optical element <NUM>, the cell <NUM>, and the sample are high. Accordingly, a main element of the stray light is the light reflected on surfaces of the optical element <NUM> and the cell <NUM>.

Specifically, as illustrated in <FIG>, the first surface <NUM> of the optical element <NUM> and the side surface of the cell <NUM> have the certain angle. Thus, the stray light reflected on the first surface <NUM> of the optical element <NUM> travels in a direction different from the direction in which the light receiver <NUM> exists. Similarly, the stray light transmitted through the optical element <NUM> and reflected on a surface (including the surface opposed to the optical element <NUM> and a surface on a side opposite to the surface) of the cell <NUM> travels in a direction different from the direction in which the light receiver <NUM> exists due to the difference in refractive index of the optical element <NUM> and the air. Consequently, an intensity of the stray light that enters the light receiver <NUM> is reduced by the optical element <NUM> so that the measurement accuracy can be increased.

With the light being refracted on the interface between the air and the cell <NUM>, and the interface between the cell <NUM> and the sample, the direction of travel of the light is changed. Thus, in <FIG>, specifically, the direction of travel is changed at the interface between the air and the cell <NUM>, and the interface between the cell <NUM> and the sample, but depiction of the change is omitted. Further, the optical element <NUM> may be arranged to be in contact with the cell <NUM>, or may be arranged via an interval with the cell <NUM>.

Next, a method of light scattering measurement using the light scattering measuring apparatus <NUM> is described with reference to a flow chart of <FIG>. First, determination is made as to whether to perform multiangle measurement (Step S702). Specifically, with a user operating the light scattering measuring apparatus <NUM>, the light scattering measuring apparatus <NUM> receives information indicating whether to perform the multiangle measurement. When it is determined that the multiangle measurement is to be performed, the process proceeds to Step S704.

Next, the measuring jig <NUM> is placed (Step S704). Specifically, the measuring jig <NUM>, which is formed of the frame body and the optical element <NUM>, is placed in the light scattering measuring apparatus <NUM>. Then, the cell <NUM> is placed in the holding space of the measuring jig <NUM> (Step S706). In the cavity of the cell <NUM>, the sample serving as the object to be measured is placed in advance. There is no particular order for Step S704 and Step S706, and after the cell <NUM> is first placed in the holding space of the measuring jig <NUM>, the measuring jig <NUM> may be placed in the light scattering measuring apparatus <NUM>.

Next, the moving mechanism <NUM> moves the measuring jig <NUM> so that the second opening <NUM> is positioned in the incident portion of the second optical path (Step S708). Specifically, the moving mechanism <NUM> adjusts the position in the Z-axis direction of the measuring jig <NUM> so that the back measurement optical path illustrated in <FIG> is positioned in the second opening <NUM>.

Next, the light scattering measuring apparatus <NUM> performs the back scattering measurement (Step S710). Specifically, the second light source 102B emits light, and the light on the back measurement optical path passes through the optical element <NUM> and irradiates the sample. The light receiver <NUM> measures the intensity of the scattered light that has been scattered by the sample.

Next, the moving mechanism <NUM> moves the measuring jig <NUM> so that the first opening <NUM> is positioned in the incident portion of the first optical path (Step S712). Specifically, the moving mechanism <NUM> adjusts the position in the Z-axis direction of the measuring jig <NUM> so that the forward measurement optical path and the side measurement optical path illustrated in <FIG> are positioned in the first opening <NUM>.

Next, the light scattering measuring apparatus <NUM> performs the forward scattering measurement and the side scattering measurement (Step S714). Specifically, the first light source 102A emits light, and the light on the forward measurement optical path irradiates the sample. The light receiver <NUM> measures the intensity of the scattered light that has been scattered by the sample. Similarly, the light scattering measuring apparatus <NUM> performs the side scattering measurement. Then, the light scattering measuring apparatus <NUM> calculates the particle size distribution with use of the intensities of the scattered light measured in Step S710 and Step S714, and the photon correlation method. The measurement performed in Step S714 may be only one of the forward scattering measurement and the side scattering measurement.

When it is determined in Step S702 that the multiangle measurement is not to be performed, the process proceeds to Step S716. In Step S716, the measuring jig <NUM> is placed. Then, the cell <NUM> is placed in the holding space of the measuring jig <NUM> (Step S718). Step S716 and Step S718 are similar to Step S704 and Step S706.

Next, the moving mechanism <NUM> moves the measuring jig <NUM> so that the first opening <NUM> is positioned in the incident portion of the first optical path or the second optical path (Step S720). Step S720 is similar to Step S712. Then, the light scattering measuring apparatus <NUM> performs the forward, side, or back scattering measurement (Step S722). For example, when the forward scattering measurement is performed in Step S722, the first light source 102A emits light, and the light on the forward measurement optical path irradiates the sample. The light receiver <NUM> measures the intensity of the scattered light that has been scattered by the sample. Then, the light scattering measuring apparatus <NUM> calculates the particle size distribution with use of the photon correlation method. The position to which the measuring jig <NUM> is moved in Step S720, and the measurement performed in Step S722 may be selected in accordance with an instruction from the user as appropriate.

Through the steps described above, measurement by the three methods of the forward scattering measurement, the side scattering measurement, and the back scattering measurement, or measurement by one method of only the forward scattering measurement is performed in accordance with the instruction from the user.

<FIG> shows an example of measurement results obtained through Step S716 to Step S722 of <FIG>. <FIG> shows an example of measurement results obtained through Step S704 to Step S714 of <FIG>. The measurement results of <FIG> are measurement results for the same sample.

As shown in <FIG>, in the analysis results obtained by one method of only the forward scattering measurement, a scattering intensity distribution with a peak at particle size values of from <NUM> to <NUM> is obtained. In contrast, as shown in <FIG>, in the analysis results obtained by the three methods of the forward scattering measurement, the side scattering measurement, and the back scattering measurement, a scattering intensity distribution with two peaks at particle size values of <NUM> and <NUM> is obtained. In other words, through the analysis by the three methods, for a sample in which particles with different particle sizes but with a small difference between the particle sizes are mixed, a distribution separated for each particle of a different particle size was successfully obtained. In contrast, when it is sufficient to obtain an approximate particle size distribution, the analysis by one method can be performed to reduce time required for the measurement.

Claim 1:
A light scattering measuring apparatus, comprising:
light sources (<NUM>) configured to generate incident light to irradiate a sample;
a single light receiver (<NUM>), which is arranged at a position at which scattered light output from the sample is received, and is configured to measure an intensity of the scattered light;
a sample holder including:
a cell (<NUM>) having a cavity in which the sample is to be contained;
a frame body having a holding space in which the cell (<NUM>) is to be arranged, a first opening (<NUM>) formed in an incident portion of a first optical path used for at least one measurement of forward measurement or side measurement, in which a scattering angle formed by the incident light and the scattered light is <NUM>° or less, and a second opening (<NUM>) formed in an incident portion of a second optical path used for back measurement, in which a scattering angle exceeds <NUM>°; and
an optical element (<NUM>) having a first surface that forms a certain angle with a side surface of the cavity; and
a moving mechanism (<NUM>) configured to move the sample holder in a vertical direction,
the optical element (<NUM>) being arranged in at least one of the incident portion or an exit portion of at least one optical path of the first optical path or the second optical path,
the first optical path and the second optical path being separated from each other in the vertical direction,
the moving mechanism (<NUM>) being configured to move the first opening (<NUM>) to a position of the incident portion of the first optical path when the at least one measurement of forward measurement or side measurement is to be performed, and to move the second opening (<NUM>) to a position of the incident portion of the second optical path when the back measurement is to be performed.