Observation device and observation method

Abstract

An observation device according to the present disclosure is for observing the state of a cell population comprising of a plurality of cells. The observation device comprises: at least one irradiating unit which is disposed in a position facing the cell population, and which irradiates at least one irradiation region set in the cell population with irradiating light having at least one wavelength included in the ranges of 650 to 850 nm and 1060 to 1090 nm; at least one light receiving unit which is disposed in a position facing the cell population and which receives emitted light emitted from the cell population as a result of the irradiation of the irradiation region with the irradiating light; and an analyzing unit which is communicably connected to the light receiving unit, and which obtains, on the basis of the intensity of the emitted light, a parameter that includes at least one of the number of cells and the cell density of the cell population in the irradiation region.

Description

Observation device and observation method

[0001] This application claims priority to Japanese Application No. 2024-005452, filed on January 17, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] In recent years, research has progressed on the application of planar or three-dimensional cell populations, such as cell colonies, cell sheets, spheroids, or organoids, to drug discovery and regenerative medicine. Known methods for non-invasive optical observation of the state of such cell populations include, for example, a method of observing the intensity of transmitted light from a cell population using a transmission microscope. Other known methods for non-invasive optical observation of the state of a cell population include those disclosed in Patent Documents 1 to 4. Patent Documents 1 and 2 disclose methods for observing the intensity distribution of transmitted or reflected light from a cell population. Patent Documents 3 and 4 disclose methods for observing the internal structure of a cell population using optical coherence tomography (OCT).

[0003] JP 2018-004594 A JP 2020-094925 A International Publication No. 2015 / 004762 International Publication No. 2017 / 216930

[0004] The observation device disclosed herein is an observation device for observing the state of a cell population composed of a plurality of cells. The observation device includes at least one irradiation unit positioned opposite the cell population and irradiating at least one irradiation region set in the cell population with irradiation light having at least one wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, at least one light receiving unit positioned opposite the cell population and receiving output light emitted from the cell population in response to the irradiation of the irradiation region with the irradiation light, and an analysis unit communicably connected to the light receiving unit and configured to determine parameters including at least one of the number of cells and the cell density of the cell population in the irradiation region based on the intensity of the output light.

[0005] FIG. 1 is a diagram showing the configuration of an observation device according to a first embodiment. FIG. 2 is an enlarged view of a portion of the observation device shown in FIG. 1. FIG. 3 is a diagram showing the hardware configuration of the analysis unit shown in FIG. 1. FIG. 4 is a diagram showing the functional configuration of the analysis unit shown in FIG. 1. FIG. 5 is a graph showing a spectrum of change in light intensity of a cell. FIG. 6 is a graph showing a spectrum of change in light intensity of a culture solution. FIG. 7 is a flowchart showing an example of an observation method performed using the observation device shown in FIG. 1. FIG. 8 is a diagram showing a modified example of the observation device shown in FIG. 1. FIG. 9A is a diagram showing a modified example of the observation device shown in FIG. 1. FIG. 9B is a diagram showing a modified example of the observation device shown in FIG. 1. FIG. 10 is a diagram showing a modified example of the observation device shown in FIG. 1. FIG. 11 is a diagram showing the configuration of an observation device according to a second embodiment. FIG. 12 is an enlarged view of a portion of the observation device shown in FIG. 11. FIG. 13 is a diagram showing the functional configuration of the analysis unit shown in FIG. 11. FIG. 14 is a graph explaining how to determine the Rayleigh scattering coefficient and reflection intensity in the analysis unit shown in FIG. 11. FIG. 15 is a graph explaining a wavelength range suitable for observing the state of a cell population. Fig. 16 is a diagram showing a modified example of the observation apparatus of Fig. 11. Fig. 17 is a diagram showing a modified example of the observation apparatus of Fig. 11. Fig. 18A is a diagram showing a modified example of the observation apparatus of Fig. 11. Fig. 18B is a diagram showing a modified example of the observation apparatus of Fig. 11. Fig. 19 is a graph for explaining how to determine the Rayleigh scattering coefficient and reflection intensity in the observation apparatuses of Figs. 18A and 18B. Fig. 20 is a diagram showing a modified example of the observation apparatus of Fig. 11. Fig. 21 is a diagram showing a modified example of the observation apparatus of Fig. 11.

[0006] [Problem to be Solved by the Present Disclosure] The above-described cell population is formed, for example, by cell proliferation, resulting in the formation of a planar population of multiple cells or a multi-layered population. In such cell populations, the number of cells and cell density may vary depending on the location. Information such as the number of cells and cell density at each location in the cell population is an important indicator for detailed evaluation of the state of the cell population. When light is irradiated onto a cell population, the intensity of light scattered and reflected by the cell population depends on the number and cell density of the cells in the cell population. Therefore, by observing the intensity of light emitted from the cell population, it is possible to obtain information including the number of cells and cell density. When light is irradiated onto a cell population, in addition to light scattering and reflection from the cell population, light absorption by the cell population and culture medium also occurs. Therefore, the intensity of light emitted from the cell population reflects a mixture of multiple phenomena, including light scattering and reflection and light absorption.

[0007] In the above-mentioned method using a transmission microscope, the obtained microscope image reflects a mixture of multiple phenomena, such as light scattering, reflection, and absorption. It is difficult to distinguish the effects of scattering and reflection by the cell population from the effects of light absorption by the cell population, etc., from such an observation image (i.e., the emitted light). Therefore, it is difficult to obtain detailed information, including cell number and cell density, using this method. The same can be said for the methods disclosed in Patent Documents 1 and 2. In addition, while the methods disclosed in Patent Documents 1 and 2 can evaluate the quality of cell populations on a population-by-population basis using the light intensity distribution, it is difficult to obtain detailed information, such as cell number and cell density at specific locations within the cell population.

[0008] The techniques disclosed in Patent Documents 3 and 4 (techniques using OCT) utilize optical interference to scan a cell population three-dimensionally, which takes time to observe the state of the cell population. This technique requires observation of the cell population after it has been removed from a culture vessel in which the temperature, atmospheric gas, and other environmental conditions are controlled and maintained to be suitable for culturing the cell population. Therefore, considering the invasiveness of the technique, it is difficult to use OCT for quality control or 100% inspection of cell populations during culture.

[0009] The present disclosure provides an observation device and an observation method that enable detailed and efficient observation of the state of a cell population.

[0010] [Effects of the Present Disclosure] According to the present disclosure, an observation device and an observation method are provided that allow for detailed and efficient observation of the state of a cell population.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] (1) The observation device disclosed herein is an observation device for observing the state of a cell population composed of a plurality of cells. The observation device includes at least one irradiation unit positioned opposite the cell population and irradiating at least one irradiation region set in the cell population with irradiation light having at least one wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, at least one light receiving unit positioned opposite the cell population and receiving output light emitted from the cell population in response to the irradiation of the irradiation region with the irradiation light, and an analysis unit communicably connected to the light receiving unit and configured to determine a parameter including at least one of the number of cells and the cell density of the cell population in the irradiation region based on the intensity of the output light.

[0013] Generally, when a cell population is irradiated with light, phenomena such as scattering, reflection, and absorption of light can occur in the cell population and its surroundings. The intensity of light emitted from the cell population in response to light irradiation reflects a mixture of these phenomena. Therefore, the intensities of scattering, reflection, and absorption can be observed by observing the change or relative value of the emitted light intensity relative to the irradiated light intensity (hereinafter, the "change or relative value of the emitted light intensity relative to the irradiated light intensity" will be referred to as the "light intensity change"). Hereinafter, "absorption intensity" and "absorption intensity" refer to the "change in light intensity due to absorption." "Scattering intensity" and "scattering intensity" refer to the "change in light intensity due to scattering." "Reflection intensity" and "reflection intensity" refer to the "change in light intensity due to reflection." Of these phenomena, the change in light intensity due to scattering and reflection depends on parameters including at least one of the number of cells and cell density in the cell population. The change in light intensity due to absorption depends on chemical reactions in the cell population and its surroundings. Therefore, in order to quantitatively determine parameters such as cell number and cell density, the amount of change in light intensity due solely to scattering and reflection may be acquired. The inventors have conducted extensive research into methods for acquiring the amount of change in light intensity due solely to scattering and reflection, and have found that irradiating a cell population with irradiation light having at least one wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm is effective. For example, in a culture medium in which a cell population can be placed, the wavelength ranges of 650 nm to 850 nm and 1060 nm to 1090 nm are ranges in which light absorption by the culture medium is sufficiently small relative to the scattering and reflection of light by the cells, so the effect of light absorption by the culture medium on the intensity of the emitted light can be ignored. In cells, the wavelength ranges of 650 nm to 850 nm and 1060 nm to 1090 nm are also ranges in which light absorption by the cells is sufficiently small relative to the scattering and reflection of light by the cells, so the effect of light absorption by the cells on the intensity of the emitted light can be ignored.Therefore, when a cell population is irradiated with irradiation light having at least one wavelength in the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, parameters including at least one of cell number and cell density can be quantitatively determined as indicators of the state of the cell population based on the amount of change in light intensity due solely to scattering and reflection. With the above-described observation device, each irradiation region of the cell population is irradiated with irradiation light, and parameters including at least one of cell number and cell density can be determined for each irradiation region based on the intensity of light emitted from the irradiation region of the cell population. This allows the state of a specific location in the cell population to be observed. Therefore, the above-described observation device enables detailed observation of the state of a cell population. Unlike techniques using OCT, the above-described observation device allows the state of a cell population to be observed efficiently in a short time by simply irradiating the cell population with irradiation light.

[0014] (2) In the observation device described in (1) above, the irradiation unit may include a laser light source using a semiconductor optical element that emits light having a wavelength within the range of 650 nm to 850 nm and 1060 nm to 1090 nm as irradiation light. In this case, by using a semiconductor light-emitting element with stable light intensity as the light source, the risk of fluctuations in the intensity of the emitted light due to factors other than the state of the cell population (e.g., instability in the intensity of the irradiation light) can be reduced. This allows for more reliable observation of the state of the cell population based on the intensity of the emitted light.

[0015] (3) In the observation device described in (1) or (2) above, the light-receiving unit may be disposed on the opposite side of the cell population from the irradiation unit, and may receive, as emitted light, a portion of the irradiation light that is emitted from the irradiation unit and transmitted through the cell population. In this case, the position of the light-receiving unit relative to the irradiation unit can be easily adjusted.

[0016] (4) In the observation device described in any one of (1) to (3) above, the irradiating unit may include one or more light sources that emit irradiation light, and may irradiate each of a plurality of irradiation regions set in the cell population with the irradiation light. The light receiving unit may include one or more optical sensors onto which the emitted light is incident, and may receive a plurality of irradiation light beams that have passed through the cell population as a plurality of emitted light beams. In this way, when the irradiation light is simultaneously irradiated onto each irradiation region of the cell population, it is possible to efficiently observe the state of each irradiation region of the cell population in a short time, compared to when the irradiation light is sequentially irradiated onto each irradiation region of the cell population.

[0017] (5) In the observation device described in any one of (1) to (4) above, the irradiation unit may irradiate the irradiation region of the cell population with first irradiation light having a first wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, and second irradiation light having a second wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, but different from the first wavelength. The light-receiving unit may receive first exit light and second exit light having different wavelengths emitted from the cell population by irradiation with the first irradiation light and second irradiation light. The analysis unit may determine the number of cells and the cell density in the irradiation region based on the intensities of the first exit light and the second exit light, respectively. Among the light scattering, reflection, and absorption phenomena that occur in cell populations, light scattering and reflection can be broadly divided into Rayleigh scattering, which occurs due to the internal molecular structure of the cells constituting the cell population, and reflection, which occurs due to density fluctuations within the cell population. The amount of change in light intensity due to Rayleigh scattering depends on the number of cells in a cell population. The amount of change in light intensity due to reflection depends on the cell density of a cell population. The amount of change in light intensity due to Rayleigh scattering is wavelength dependent. The amount of change in light intensity due to reflection is not wavelength dependent. Therefore, when observing the state of a cell population using light of multiple wavelengths, it is possible to distinguish and determine the amount of change in light intensity due to Rayleigh scattering, which is wavelength dependent, and the amount of change in light intensity due to reflection, which is not wavelength dependent, by utilizing the differences in wavelength dependency. In other words, it is possible to distinguish and quantitatively determine the number of cells and cell density. This makes it possible to observe the state of a cell population in more detail.

[0018] (6) In the observation device described in (5) above, the irradiation unit may include a first light source that emits first irradiation light, a second light source that emits second irradiation light, and a switching unit that switches the optical path of the first irradiation light and the optical path of the second irradiation light so that the first irradiation light and the second irradiation light are selectively irradiated onto the irradiation region of the cell population. The light receiving unit may include an optical sensor that selectively receives the first output light and the second output light emitted from the cell population. In this case, a single optical sensor can be used to distinguish and detect the intensities of the first output light and the second output light. As a result, there is no need to provide separate optical sensors for detecting the intensity of the first output light and the second output light, thereby avoiding a complex configuration of the light receiving unit.

[0019] (7) In the observation device described in (5) above, the irradiation unit may include a first light source that emits first irradiation light, a second light source that emits second irradiation light, and a combining unit that combines the first irradiation light and the second irradiation light to generate combined irradiation light and irradiates the irradiation area of ​​the cell population with the combined irradiation light. The light receiving unit may include a spectroscopic unit that separates, by wavelength, the combined output light emitted from the cell population by irradiation with the combined irradiation light, a first optical sensor that detects the intensity of the first output light separated from the combined output light, and a second optical sensor that detects the intensity of the second output light separated from the combined output light. In this case, the intensities of the first output light and the second output light can be detected simultaneously using the combined irradiation light and the combined output light, thereby making it possible to more efficiently observe the state of the cell population based on the intensities of the first output light and the second output light in a shorter time.

[0020] (8) In the observation device described in (5) above, the irradiation unit may include a light source that emits light including the first irradiation light and the second irradiation light, a first filter that transmits only the first irradiation light, and a second filter that transmits only the second irradiation light, and a filter switching unit that switches the position of the first filter and the position of the second filter so that the first filter or the second filter is positioned on the optical path of the light between the light source and the cell population. The light receiving unit may include an optical sensor that selectively receives the first emitted light and the second emitted light emitted from the cell population. In this case, for example, by using an inexpensive lamp light source as the light source, the cost of the observation device can be reduced compared to when an expensive laser light source is used as the light source.

[0021] (9) The presently disclosed observation method is a method for observing the state of a cell population composed of a plurality of cells. The observation method includes the steps of: irradiating at least one irradiation region set in the cell population with irradiation light having at least one wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm; receiving output light emitted from the cell population upon irradiation of the irradiation region with the irradiation light; and determining, based on the intensity of the output light, a parameter including at least one of the number of cells and the cell density of the cell population in the irradiation region. This observation method can achieve the same effects as the observation device described above.

[0022] (10) In the observation method described in (9) above, the step of irradiating the irradiation area may include irradiating the irradiation area with first irradiation light having a first wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, and second irradiation light having a second wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, but different from the first wavelength. The step of receiving the emitted light may include receiving first emitted light and second emitted light having different wavelengths emitted from the cell population upon irradiation with the first irradiation light and second irradiation light. The step of calculating parameters may include calculating the number of cells and the cell density in the irradiation area based on the intensities of the first emitted light and the second emitted light, respectively. In this case, the same effect as in (5) above can be achieved.

[0023] [Details of the embodiments of the present disclosure] Specific examples of the observation device and observation method of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0024] [First Embodiment] FIG. 1 is a diagram showing the configuration of an observation device 1 according to a first embodiment. The observation device 1 is a device for observing the state of a cell population 2. The cell population 2 is a mass formed by the aggregation of multiple cells, i.e., a mass in which multiple cells aggregate. The cell population 2 can also be described as a cell population in which multiple cells are aggregated in a single-layer planar or multi-layered three-dimensional configuration. The cell population 2 includes various forms of cells, such as aggregates of multiple cells called colonies, aggregates arranged in a two-dimensional sheet-like form, two-dimensional aggregates, and three-dimensional aggregates called spheroids, organoids, and assembloids, as well as tissues and organs. The cells contained in the cell population 2 include cells collected from animals or humans, stem cells collected from animals or humans, stem cells created from cells collected from animals or humans, or cells differentiated from stem cells. A single cell population 2 may contain a mixture of multiple cell types.

[0025] The "state" of the cell population 2 observed by the observation device 1 is represented by a parameter indicating at least one of the "cell number" and "cell density" of the cell population 2. In this embodiment, a parameter called "aggregation degree," which collectively represents the "cell number" and "cell density" of the cell population 2, is used as an index indicating the "state" of the cell population 2. The "aggregation degree" is defined as "cell number" x "cell density" (i.e., the value obtained by multiplying the "cell number" and "cell density").

[0026] The observation device 1 irradiates each irradiation region R set in the cell population 2 with irradiation light L1, and determines the "aggregation degree" of the cell population 2 for each irradiation region R based on the intensity of the emitted light L2 from the cell population 2. As a result, information including the "cell number" and "cell density" is obtained for each irradiation region R. The "cell number" in the irradiation region R refers to the total number of cells contained in the irradiation region R. The "cell density" in the irradiation region R refers to the number of cells present in a unit volume of the irradiation region R. The cell population 2 is formed, for example, by the proliferation of a single cell, resulting in multiple layers of cells stacked one on top of the other. In the cell population 2 formed in this manner, the "cell number" and "cell density" vary depending on the position (region). Therefore, obtaining information on the "cell number" and "cell density" for each irradiation region R is important for detailed evaluation of the state of the cell population 2.

[0027] 1, the observation device 1 includes, for example, an irradiation module 10, a light-receiving module 20, and an analysis unit 30. The irradiation module 10 is disposed in a position facing the cell population 2. The light-receiving module 20 is disposed, for example, on the opposite side of the cell population 2 from the irradiation module 10. The cell population 2 is contained in a container 5 together with, for example, a culture solution 7. The container 5 is cylindrical with an opening 5b at one end. The observation device 1 may also include a mounting table on which the container 5 is placed.

[0028] The cell population 2 is placed on the bottom surface 5a of the container 5 while immersed in the culture solution 7. The cell population 2 may be in contact with the bottom surface 5a or may be separated from the bottom surface 5a. The container 5 is formed, for example, from a glass material or a resin material that is transmissive to the emitted light L2 emitted from the cell population 2. Hereinafter, within the vertical direction A1 along the normal to the bottom surface 5a, the direction from the bottom surface 5a toward the opening 5b may be referred to as "up," and the direction from the opening 5b toward the bottom surface 5a may be referred to as "down." The direction perpendicular to the vertical direction A1 is referred to as the horizontal direction A2. A transmissive material is, for example, a material that has a transmittance of 20% or more for light of 650 nm to 850 nm and 1060 nm to 1090 nm when the material has a thickness of 1 mm.

[0029] The irradiation module 10 includes, for example, a plurality of irradiation units 11 arranged two-dimensionally when viewed from above. The plurality of irradiation units 11 are arranged in a plane, for example, along a left-right direction A2 perpendicular to the up-down direction A1 and a front-back direction (depth direction relative to the paper surface of FIG. 1 ) perpendicular to both the up-down direction A1 and the left-right direction A2. A plurality of irradiation regions R are set in the cell population 2. The plurality of irradiation regions R are multiple regions set by dividing the cell population 2 when viewed from above, and are regions to be irradiated with irradiation light L1. The plurality of irradiation regions R are arranged two-dimensionally when viewed from above. For example, the plurality of irradiation regions R are arranged in a plane along the left-right direction A2 and the front-back direction (depth direction relative to the paper surface of FIG. 1 ). The plurality of irradiation units 11 are respectively arranged above the plurality of irradiation regions R. In other words, the plurality of irradiation units 11 are arranged in positions facing the plurality of irradiation regions R in a one-to-one relationship in the up-down direction A1. The plurality of irradiation units 11 irradiate the irradiation light L1 to the plurality of irradiation regions R, respectively. The irradiation units 11 have, for example, the same configuration as each other. The irradiation units 11 may also have different configurations from each other.

[0030] The light-receiving module 20 includes, for example, multiple light-receiving units 21 arranged two-dimensionally when viewed from above. The multiple light-receiving units 21 are arranged, for example, in a planar manner along the left-right direction A2 and the front-back direction (the depth direction relative to the paper surface of FIG. 1 ). The multiple light-receiving units 21 are arranged below the multiple irradiation regions R. The multiple light-receiving units 21 are arranged in positions facing the multiple irradiation units 11 in the up-down direction A1, one-to-one, with the cell population 2 in between. Each light-receiving unit 21 receives output light L2 emitted from the cell population 2 when the irradiation region R of the cell population 2 is irradiated with the irradiation light L1. In this embodiment, the output light L2 is transmitted light of the irradiation light L1 that has passed through the cell population 2. Each light-receiving unit 21 outputs an electrical signal S corresponding to the intensity of the output light L2 to the analysis unit 30. The multiple light-receiving units 21 have, for example, the same configuration as each other. The multiple light-receiving units 21 may also have different configurations.

[0031] FIG. 2 is an enlarged view of a portion of the observation device 1. As shown in FIG. 2, the irradiation unit 11 includes, for example, a light source 13 and a lens 15. The light source 13 is disposed above the irradiation region R of the cell population 2. That is, the light source 13 is disposed in a position facing the irradiation region R of the cell population 2 in the vertical direction A1. The light source 13 emits irradiation light L1 toward the irradiation region R. The optical axis of the irradiation light L1 emitted from the light source 13 is aligned along the vertical direction A1. In one example, the optical axis of the irradiation light L1 is perpendicular to the bottom surface 5a and parallel to the vertical direction A1. The light source 13 is, for example, a laser light source using a laser diode (LD). The irradiation light L1 has a wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. The ranges of 650 nm to 850 nm and 1060 nm to 1090 nm refer to ranges that include both the range of 650 nm to 850 nm and the range of 1060 nm to 1090 nm. Therefore, it can be said that the irradiation light L1 has one wavelength that is included in at least one of the ranges of 650 nm to 850 nm and the range of 1060 nm to 1090 nm.

[0032] The light source 13 is not limited to a laser light source using a laser diode. For example, the light source 13 may be a light source using a semiconductor light-emitting element such as a laser diode, a light-emitting diode (LED), or a superluminescent diode (SLD), a laser light source using an element other than a semiconductor light-emitting element, or a lamp light source. For example, when a broadband light source such as a lamp light source is used, the irradiation light L1 may have one or more wavelengths in addition to wavelengths in the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. In this case, the one or more wavelengths in addition to the wavelengths in the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm may be wavelengths in the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, or wavelengths outside the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm.

[0033] The lens 15 is disposed on the optical path of the irradiation light L1 between the light source 13 and the cell population 2. The lens 15 is, for example, a condensing lens that condenses the irradiation light L1 from the light source 13. The lens 15 may be a collimating lens that collimates the irradiation light L1. The irradiation light L1 emitted from the light source 13 passes through the lens 15 and is irradiated onto the irradiation region R of the cell population 2. A portion of the irradiation light L1 passes through the cell population 2 and is emitted as emitted light L2.

[0034] The light receiving unit 21 includes, for example, an optical sensor 23 and a lens 25. The optical sensor 23 is disposed below the irradiation region R of the cell population 2. In other words, the optical sensor 23 is disposed on the vertical opposite side of the light source 13 across the irradiation region R of the cell population 2. Therefore, the light receiving unit 21 faces the light source 13 in the vertical direction A1, sandwiching the cell population 2 therebetween. The optical sensor 23 is disposed on the optical path of the emitted light L2 emitted from the cell population 2, i.e., on an extension of the optical axis of the irradiated light L1. The optical axis of the emitted light L2 is, for example, perpendicular to the bottom surface 5a on which the cell population 2 is placed and parallel to the vertical direction A1. The size of the field of view of the optical sensor 23 is suitably, for example, the same as or smaller than the size of the cells constituting the cell population 2. For example, the diameter of the field of view of the optical sensor 23 may be 20 μm or less.

[0035] The lens 25 is disposed on the optical path of the emitted light L2 between the cell population 2 and the optical sensor 23. The lens 25 is, for example, an objective lens. The lens 25 may be a collimating lens. The emitted light L2 emitted from the cell population 2 passes through the lens 25 and enters the optical sensor 23. The optical sensor 23 receives the emitted light L2 and outputs an electrical signal S according to the intensity of the emitted light L2. If the illumination light L1 includes multiple wavelengths, a filter that transmits light of a specific wavelength may be disposed at any position between the light source 13 and the optical sensor 23.

[0036] 1 , the analysis unit 30 is communicatively connected to a plurality of light receiving units 21 of the light receiving module 20. The analysis unit 30 may be communicatively connected to a plurality of irradiation units 11 of the irradiation module 10. The analysis unit 30 receives an electrical signal S from each optical sensor 23. Based on the received electrical signal S, the analysis unit 30 determines the "cell count" and the "degree of aggregation" representing the "cell density" of the cell population 2.

[0037] 3 is a diagram showing the hardware configuration of the analysis unit 30. The analysis unit 30 is physically one or more computers. As shown in FIG. 3, the analysis unit 30 physically includes hardware such as one or more processors 301, a main memory device 302, an auxiliary memory device 303, an input device 304, an output device 305, and a communication device 306. The analysis unit 30 is configured by one or more physical computers configured by these physical hardware devices and software such as programs.

[0038] 4 is a diagram showing the functional configuration of the analysis unit 30. The analysis unit 30 includes, as functional components, an acquisition unit 31, a storage unit 33, and a conversion unit 35. Each functional component of the analysis unit 30 is implemented by executing a program on the hardware of the physical computer described above.

[0039] The acquisition unit 31 acquires the intensity of the emitted light L2 indicated by the electrical signal S from the light-receiving module 20 for each irradiation region R of the cell population 2. The acquisition unit 31 provides the conversion unit 35 with light intensity information D1 indicating the intensity of the emitted light L2 for each irradiation region R of the cell population 2.

[0040] The storage unit 33 stores conversion information D2 for determining the "aggregation degree" of the cell population 2 based on the intensity of the emitted light L2. The conversion information D2 includes, for example, a calibration curve G1 showing the relationship between the amount of change in light intensity obtained from the light intensity information D1 and the "aggregation degree" of the cell population 2. The calibration curve G1 is a graph plotting the relationship between the amount of change in light intensity and the "aggregation degree" of the cell population 2. The amount of change in light intensity is the relative ratio between the intensity of the emitted light L2 and the intensity of the irradiated light L1, and is a value obtained by standardizing the intensity of the emitted light L2. The amount of change in light intensity is defined as the value obtained by dividing the intensity of the emitted light L2 by the intensity of the irradiated light L1 (-10 Log (intensity of emitted light L2 / intensity of irradiated light L1)).

[0041] As shown in the calibration curve G1 in Figure 4, the amount of change in light intensity decreases as the "aggregation" of the cell population 2 decreases, and increases as the "aggregation" increases. Therefore, if the magnitude of the amount of change in light intensity is known, the "aggregation" can be estimated. By preparing a sample of the cell population 2 with a known "aggregation" (or a sample with a reference "aggregation") in advance and irradiating the sample with irradiation light L1 using the observation device 1, it is possible to create in advance a calibration curve G1 that shows the relationship between the amount of change in light intensity and the "aggregation" of the sample.

[0042] The storage unit 33 stores the calibration curve G1 thus prepared in advance and provides the conversion information D2 including the calibration curve G1 to the conversion unit 35. The conversion information D2 may include a conversion formula (conversion formula) showing the relationship between the amount of change in light intensity and the "degree of agglutination" of the cell population 2, instead of or in addition to the calibration curve G1. In addition to the calibration curve G1, the conversion information D2 may include information necessary for converting the amount of change in light intensity into the "degree of agglutination" of the cell population 2. For example, the conversion information D2 may include the intensity of the irradiated light L1 necessary to derive the amount of change in light intensity.

[0043] The conversion unit 35 calculates the "aggregation degree" of the cell population 2 for each irradiation region R using the light intensity information D1 and the conversion information D2. First, the conversion unit 35 calculates the amount of change in light intensity, which is the relative ratio between the intensity of the emitted light L2 and the intensity of the irradiated light L1. Next, the conversion unit 35 converts the calculated amount of change in light intensity into the "aggregation degree" of the cell population 2 by referring to the calibration curve G1. As described above, the "aggregation degree" of the cell population 2 is a parameter including the "cell number" and "cell density" of the cell population 2, and serves as an index indicating the state of the cell population 2. Therefore, by calculating the "aggregation degree" for each irradiation region R of the cell population 2, it is possible to quantitatively evaluate the state of each irradiation region R of the cell population 2. The analysis unit 30 may output the observation results, including the "aggregation degree" of the cell population 2 calculated by the conversion unit 35, using an output device 305, such as a monitor or printer.

[0044] The reason why irradiation light L1 in the wavelength ranges of 650 nm to 850 nm and 1060 nm to 1090 nm is used to irradiate the cell population 2 will be explained below with reference to FIGS. 5 and 6.

[0045] Figure 5 is a graph showing the spectrum of change in light intensity of cell population 2. In Figure 5, the vertical axis represents the change in light intensity of cell population 2, and the horizontal axis represents wavelength [nm]. The vertical axis of Figure 5 can also be said to represent the scattering intensity, reflection intensity, and absorption intensity of cell population 2. Figure 6 is a graph showing the spectrum of change in light intensity of culture solution 7. In Figure 6, the vertical axis represents the change in light intensity of culture solution 7, and the horizontal axis represents wavelength [nm]. Since no scattering or reflection occurs in culture solution 7, the vertical axis of Figure 6 can also be said to represent the absorption intensity of culture solution 7.

[0046] When light is irradiated onto the cell population 2 in the culture solution 7, light absorption occurs in the cell population 2 and the culture solution 7, resulting in scattering and reflection of the light from the cell population 2. The intensity of light (transmitted light or reflected light) emitted from the cell population 2 when light is irradiated onto the cell population 2 reflects a mixture of multiple phenomena, including light scattering and reflection, and light absorption. Of these phenomena, the light intensity caused by scattering and reflection depends on parameters such as the "cell number" and "cell density" of the cell population 2. Therefore, if the light intensity caused only by scattering and reflection can be obtained, it becomes possible to quantitatively determine the "degree of aggregation" of the cell population 2, which is a parameter that includes the "cell number" and "cell density."

[0047] As shown in graph G2 of FIG. 5 , in the wavelength range of 1300 nm or more, there are many peaks where the change in light intensity of the cell population 2 changes sharply. These peaks are caused by light absorption by the cell population 2. Therefore, in wavelength ranges where many peaks exist, the influence of light absorption on the intensity of light emitted from the cell population 2 is significant, making it difficult to obtain the change in light intensity due solely to scattering and reflection. It can be seen that in the wavelength range R1 of 1300 nm or less, there are no peaks and the change in light intensity changes extremely gradually. In such wavelength range R1, the influence of light absorption on the intensity of light emitted from the cell population 2 is sufficiently small compared to the influence of scattering and reflection that it can be ignored, making it easy to obtain the change in light intensity due solely to scattering and reflection.

[0048] As shown in graph G3 of FIG. 6 , within the wavelength range R1 of 1300 nm or less, in the wavelength ranges R2 of 650 nm to 850 nm and 1060 nm to 1090 nm, the amount of change in light intensity due solely to light absorption by the culture solution 7 is significantly smaller than the amount of change in light intensity due to light scattering and reflection by the cells shown in FIG. 5 . Therefore, by irradiating the cell population 2 in the culture solution 7 with light in the wavelength ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, the influence of light absorption by the culture solution 7 can be ignored. In other words, the intensity of light emitted from the cell population 2 can be prevented from being influenced by light absorption by the culture solution 7. The culture solution 7 may contain water, amino acids, vitamins, salts, and glucose. An indicator such as phenol red may be added to the culture solution 7. If the influence of light absorption by the culture solution 7 can be ignored, it is possible to obtain a change in light intensity that reflects only scattering and reflection by the cell population 2. Ultraviolet light having a wavelength shorter than 400 nm is not suitable as light to irradiate the cell population 2 because it may damage the cell population 2 .

[0049] Therefore, when the cell population 2 is irradiated with irradiation light L1 having wavelengths within the wavelength ranges R2 of 650 nm to 850 nm and 1060 nm to 1090 nm, as described above, the influence of absorption of the irradiation light L1 by the cell population 2 and the culture solution 7 can be ignored, making it possible to obtain the intensity of the output light L2 that reflects only the scattering and reflection of the irradiation light L1 by the cell population 2. As a result, it is possible to quantitatively determine the "aggregation degree" of the cell population 2 based on the intensity of the output light L2 obtained. Thus, in this embodiment, the wavelength ranges R2 of 650 nm to 850 nm and 1060 nm to 1090 nm are selected as wavelength ranges in which the influence of absorption of the irradiation light L1 by the cell population 2 and the culture solution 7 can be ignored, based on the light intensity change spectrum of the cells and the light intensity change spectrum of the culture solution 7.

[0050] The steps of the observation method carried out using the observation device 1 described above will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the steps of the observation method.

[0051] First, each of the irradiation units 11 arranged two-dimensionally above the cell population 2 irradiates each irradiation region R of the cell population 2 with irradiation light L1 in the wavelength ranges of 650 nm to 850 nm and 1060 nm to 1090 nm (step S11). A portion of the irradiation light L1 irradiated to each irradiation region R of the cell population 2 passes through the cell population 2 and is emitted from the cell population 2 as emitted light L2.

[0052] Next, each of the light receiving units 21 arranged two-dimensionally below the cell population 2 receives each of the emitted light beams L2 emitted from the cell population 2 (step S12). Each of the light receiving units 21 outputs an electrical signal S to the analysis unit 30 according to the intensity of each of the received emitted light beams L2.

[0053] Next, the analysis unit 30 determines the "degree of aggregation," which is a parameter including the "cell number" and "cell density" of the cell population 2, as an index indicating the state of the cell population 2, based on the intensity of the emitted light L2 indicated by each electrical signal S (step S13). Specifically, the conversion unit 35 of the analysis unit 30 first calculates the amount of change in light intensity by dividing the intensity of the emitted light L2 by the intensity of the irradiated light L1. The conversion unit 35 then converts the calculated amount of change in light intensity into the "degree of aggregation" of the cell population 2 by referring to the calibration curve G1 shown in FIG. 4. Using the "degree of aggregation" determined in this manner, it becomes possible to quantitatively observe the state of each irradiation region R of the cell population 2.

[0054] The effects obtained by the first embodiment described above will be explained. As described above, in the light intensity change spectrum of the culture solution 7, the wavelength ranges R2 (see FIG. 6 ) of 650 nm to 850 nm and 1060 nm to 1090 nm are ranges in which light absorption by the culture solution 7 in which the cell population 2 is placed is sufficiently small compared to the scattering and reflection of light by the cells shown in FIG. 5 . Therefore, when irradiation light L1 having wavelengths within the wavelength ranges R2 of 650 nm to 850 nm and 1060 nm to 1090 nm is used to irradiate the cell population 2, the effect of light absorption by the culture solution 7 on the intensity of the output light L2 can be ignored. In the light intensity change spectrum of cell population 2, the wavelength ranges R2 from 650 nm to 850 nm and from 1060 nm to 1090 nm are included in the wavelength range R1 (see Figure 5) in which there are no sharp peaks caused by light absorption by cells, and therefore the effect of light absorption by cell population 2 on the intensity of output light L2 is sufficiently small compared to the scattering and reflection that occurs in cell population 2 and can be ignored.

[0055] Therefore, when the cell population 2 is irradiated with irradiation light L1 having at least wavelengths included in the wavelength ranges R2 of 650 nm to 850 nm and 1060 nm to 1090 nm, the intensity of the emitted light L2 resulting only from scattering and reflection can be obtained. Therefore, based on the intensity of the emitted light L2, the "aggregation degree," a parameter including the "cell number" and "cell density," can be quantitatively determined as an index indicating the state of the cell population 2. In this embodiment, the irradiation light L1 is irradiated to each irradiation region R of the cell population 2, so that the intensity of the emitted light L2 can be obtained separately for each irradiation region R. In other words, the "aggregation degree" can be quantitatively determined for each irradiation region R of the cell population 2. This makes it possible to obtain information including the "cell number" and "cell density" at a specific position of the cell population 2, thereby enabling detailed observation of the state of the cell population 2.

[0056] According to the present embodiment, unlike the technique using OCT, it is possible to observe the state of the cell population 2 efficiently in a short time by the simple task of irradiating the cell population 2 with irradiation light L1. As a result, it becomes possible to perform a 100% inspection in which all cell populations 2 to be observed are observed, and it becomes possible to avoid complicated process management for observing the cell population 2.

[0057] As in this embodiment, the irradiation unit 11 may include a light source 13 using a laser diode that emits light having a wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm as the irradiation light L1. The light source 13 may also be a light source using a semiconductor light-emitting element such as a laser diode, a light-emitting diode, or a superluminescent diode. In this case, by using light from a light source using a semiconductor light-emitting element with stable light intensity as the irradiation light L1, the risk of fluctuations in the intensity of the emitted light L2 due to factors other than the state of the cell population 2 (e.g., instability in the intensity of the irradiation light) can be reduced. This allows for more reliable observation of the state of the cell population 2 based on the intensity of the emitted light L2.

[0058] As in the present embodiment, the light receiving unit 21 may be disposed on the opposite side of the cell population 2 from the irradiation unit 11, and may receive as emitted light L2 a portion of the irradiation light L1 that is emitted from the irradiation unit 11 and transmitted through the cell population 2. In this case, the position of the light receiving unit 21 relative to the irradiation unit 11 can be easily adjusted.

[0059] As in the present embodiment, the plurality of irradiating units 11 may irradiate the irradiation light L1 onto each of the plurality of irradiation regions R. The plurality of light receiving units 21 may receive, as a plurality of emitted light beams L2, a portion of the irradiation light L1 that has been emitted from each of the plurality of irradiating units 11 and passed through the cell population 2. In this way, when the irradiation light L1 is simultaneously irradiated onto each irradiation region R of the cell population 2, it becomes possible to observe the state of each irradiation region R of the cell population 2 efficiently in a short time, compared to when the irradiation light L1 is sequentially irradiated onto each irradiation region R of the cell population 2.

[0060] The observation device and observation method of the present disclosure are not limited to the first embodiment described above, and various other modifications are possible.

[0061] <Modification 1> Figure 8 is a diagram showing a modification of the observation device 1. As in the observation device 1A shown in Figure 8, the irradiation module 10A may include only one irradiation unit 11, and the light-receiving module 20A may include only one light-receiving unit 21. In this case, the irradiation unit 11 is disposed above one of the irradiation regions R of the cell population 2 and irradiates the irradiation region R with irradiation light L1. The light-receiving unit 21 is disposed on the opposite side of the cell population 2 from the irradiation unit 11. In other words, the light-receiving unit 21 is disposed below the irradiation region R to which irradiation light L1 is irradiated, and faces the irradiation unit 11 in the up-down direction A1, with the cell population 2 in between.

[0062] The irradiating unit 11 and the light-receiving unit 21 are configured to be movable in a left-right direction A2 perpendicular to the up-down direction A1 and in a front-rear direction (the depth direction relative to the plane of the paper in FIG. 1 ) perpendicular to both the up-down direction A1 and the left-right direction A2. The irradiating unit 11 sequentially irradiates each irradiation region R of the cell population 2 with irradiation light L1 while moving in the left-right direction A2 and the front-rear direction. The light-receiving unit 21 similarly moves in the left-right direction A2 and the front-rear direction in accordance with the movement of the irradiating unit 11, sequentially receiving each emitted light L2 emitted from the cell population 2 as a result of irradiation of each irradiation region R with irradiation light L1.

[0063] The irradiation unit 11 and the light receiving unit 21 may be configured to be movable relative to the container 5 that contains the cell population 2. Therefore, the irradiation unit 11 and the light receiving unit 21 may be configured to move along the left-right direction A2 and the front-back direction while the position of the container 5 is fixed. Conversely, the irradiation unit 11 and the light receiving unit 21 may be configured to move along the left-right direction A2 and the front-back direction while the positions of the irradiation unit 11 and the light receiving unit 21 are fixed.

[0064] 8 also makes it possible to quantitatively determine the "aggregation degree," a parameter including the "cell number" and "cell density," for each irradiation region R of the cell population 2 based on the intensity of each light beam L2 emitted from the cell population 2, thereby achieving the same effect as in the first embodiment. With the observation device 1A, each irradiation region R for the cell population 2 can be set more precisely in accordance with the movement width of the irradiation unit 11 in the left-right direction A2, making it possible to determine the "aggregation degree" in more irradiation regions R of the cell population 2. In other words, it becomes possible to observe the state of the cell population 2 in more detail.

[0065] <Modification 2> Figures 9A and 9B are diagrams showing a modification of the observation device 1. The observation device 1B shown in Figure 9A and the observation device 1C shown in Figure 9B each include, for example, the irradiation module 10A and the light-receiving module 20A shown in Figure 8 described above. The observation devices 1B and 1C may each include the irradiation module 10 and the light-receiving module 20 of the first embodiment. In the observation devices 1B and 1C, the light-receiving module 20A is disposed above the cell population 2, similar to the irradiation module 10A. In other words, the light-receiving module 20A is disposed in the same region as the irradiation module 10A, of the two regions sandwiching the cell population 2.

[0066] 9A , the optical axis of the irradiation light L1 emitted from the irradiation module 10A is inclined with respect to the vertical direction A1. A portion of the irradiation light L1 irradiated onto the irradiation region R of the cell population 2 is reflected on the surface or inside of the cell population 2. The reflected light reflected by the cell population 2 is emitted from the cell population 2 as emitted light L2. The optical axis of the emitted light L2 is inclined with respect to the vertical direction A1.

[0067] The light-receiving module 20A is disposed on the optical path of the emitted light L2. The light-receiving module 20A is disposed, for example, at a position adjacent to the irradiation module 10A in the left-right direction A2. The light-receiving module 20A receives the emitted light L2 and detects the intensity of the emitted light L2. The observation device 1B can also quantitatively determine the "aggregation degree," which is a parameter including the "cell number" and "cell density," for each irradiation region R of the cell population 2 based on the intensity of each emitted light L2 from the cell population 2, thereby achieving the same effect as in the first embodiment.

[0068] In the observation device 1C shown in FIG. 9B , a circulator 41 is disposed above the irradiation region R of the cell population 2. The irradiation module 10A is disposed further above the circulator 41. The light-receiving module 20A is disposed at a position spaced apart from the circulator 41 in the left-right direction A2. The circulator 41 is disposed at the intersection of the optical axis of the irradiation light L1 emitted from the irradiation module 10A and the optical axis of the emitted light L2 incident on the light-receiving module 20A. The circulator 41 may be optically coupled to the irradiation module 10A and the light-receiving module 20A using a lens and an optical fiber. A collimating lens or an objective lens may be disposed between the circulator 41 and the cell population 2.

[0069] The circulator 41 is an optical component for separating two beams of light traveling in opposite directions, and has three ports P1, P2, and P3 for the light. The irradiation light L1 emitted from the irradiation module 10A enters port P1 of the circulator 41 and is emitted from port P2 toward the irradiation region R of the cell population 2. The emitted light L2 emitted from the cell population 2 toward port P2 is emitted from port P3 to the light-receiving module 20A. The observation device 1C can also quantitatively determine the "aggregation degree," a parameter including the "cell number" and "cell density," for each irradiation region R of the cell population 2 based on the intensity of each emitted light L2 from the cell population 2, thereby achieving the same effect as the first embodiment.

[0070] <Modification 3> FIG. 10 is a diagram showing a modification of the observation device 1. As in the observation device 1D shown in FIG. 10, the irradiation module 10B may include only one irradiation unit 11A, and the light-receiving module 20B may include only one light-receiving unit 21A. In the example shown in FIG. 10, the irradiation unit 11A includes one light source 13 and one lens 15. The light source 13 is configured to uniformly irradiate a wide area with irradiation light L1. The light source 13 is disposed above the cell population 2 and uniformly irradiates a wide area that spreads two-dimensionally when viewed from above with irradiation light L1. The range of irradiation light L1 irradiated from the light source 13 may be a region that spreads in a planar manner along the left-right direction A2 and the front-back direction (the depth direction relative to the paper surface of FIG. 10). The light source 13 simultaneously and uniformly irradiates multiple irradiation areas R that are set in the cell population 2 and are arranged along the left-right direction A2 and the front-back direction.

[0071] The lens 15 is disposed on the optical path of the illumination light L1 between the light source 13 and the cell population 2. The lens 15 is, for example, a collimating lens that collimates the illumination light L1 emitted over a wide range from the light source 13. The lens 15 extends in a planar shape along the left-right direction A2 and the front-rear direction so as to face the light source 13 in the up-down direction A1 and to face all of the illumination regions R set on the cell population 2 in the up-down direction A1. The illumination light L1 emitted in a divergent manner from the light source 13 is collimated by the lens 15 and irradiated onto each illumination region R of the cell population 2. A portion of each of the multiple illumination light beams L1 passes through the cell population 2 and is emitted as multiple emitted light beams L2.

[0072] The light receiving unit 21A includes a plurality of optical sensors 23 and one lens 25. The plurality of optical sensors 23 are respectively disposed below a plurality of irradiation regions R of the cell population 2. The light receiving unit 21A receives emitted light L2 emitted from the cell population 2 when irradiation light L1 is applied to the irradiation region R of the cell population 2.

[0073] The lens 25 is disposed on the optical path of the multiple output light beams L2 between the cell population 2 and the multiple optical sensors 23. The lens 25 is, for example, an objective lens. The lens 25 may be a collimating lens. The lens 25 extends in a planar shape along the left-right direction A2 and the front-rear direction so as to face all irradiation regions R set in the cell population 2 in the up-down direction A1 and all optical sensors 23 in the up-down direction A1. The lens 25 faces the lens 15 in the up-down direction A1, sandwiching the cell population 2 therebetween. Each output light beam L2 emitted from the cell population 2 passes through the lens 25 and enters each optical sensor 23. Each optical sensor 23 receives the output light beam L2 and outputs an electrical signal S corresponding to the intensity of the output light beam L2.

[0074] 10 also makes it possible to quantitatively determine the "aggregation degree," which is a parameter including the "cell number" and "cell density," for each irradiation region R of the cell population 2 based on the intensity of each emitted light L2 from the cell population 2, thereby achieving the same effect as in the first embodiment. In the observation device 1D, a single light source 13 can be used to irradiate each irradiation region R with the irradiation light L1, which allows for a reduction in the number of light sources and simplification of the device configuration compared to when multiple light sources are used to irradiate each irradiation region R with the irradiation light L1.

[0075] In the observation device 1D, the irradiation unit 11A may include, instead of one lens 15, a plurality of lenses individually provided for the plurality of irradiation regions R. The light receiving unit 21A may include, instead of one lens 25, a plurality of lenses individually provided for the plurality of irradiation regions R. In this case, each lens may be disposed in a position facing each optical sensor 23 in a one-to-one relationship in the up-down direction A1.

[0076] Second Embodiment An observation device according to a second embodiment will be described below. In the following description of the second embodiment, descriptions of parts that overlap with the first embodiment will be omitted as appropriate, and differences from the first embodiment will be mainly described.

[0077] Fig. 11 is a diagram showing the configuration of an observation device 101 of the second embodiment. Fig. 12 is an enlarged view of a portion of the observation device 101 of Fig. 11. The observation device 101 of this embodiment includes an irradiation module 110, a light-receiving module 120, and an analyzing unit 130. Each of the multiple light-receiving units 121 included in the light-receiving module 120 has the same configuration as the light-receiving unit 21 of the first embodiment, for example. That is, as shown in Fig. 12, the light-receiving unit 121 includes a lens 125 having the same configuration as the lens 25, and an optical sensor 123 having the same configuration as the optical sensor 23.

[0078] As in the first embodiment, the plurality of light receiving units 121 are arranged in a plane along, for example, the left-right direction A2 perpendicular to the up-down direction A1 and the front-rear direction (the depth direction relative to the paper surface of FIG. 1 ) perpendicular to both the up-down direction A1 and the left-right direction A2. As in the first embodiment, the plurality of irradiation units 111 included in the irradiation module 110 are also arranged in a plane along, for example, the left-right direction A2 and the front-rear direction.

[0079] Each of the multiple irradiation units 111 included in the irradiation module 110 has a different configuration from the irradiation unit 11 of the first embodiment. As shown in FIG. 12 , the irradiation unit 111 includes a first light source 113A, a second light source 113B, a lens 115, and a switching unit 117. The lens 115 has the same configuration as the lens 15 of the first embodiment. The first light source 113A and the second light source 113B are disposed above one irradiation region R of the cell population 2. Each of the first light source 113A and the second light source 113B is, for example, a laser light source using a laser diode (LD). Each of the first light source 113A and the second light source 113B may be a light source using a semiconductor light-emitting element such as a laser diode, a light-emitting diode (LED), or a super luminescent diode (SLD), or may be a laser light source or a lamp light source using an element other than a semiconductor light-emitting element.

[0080] The first light source 113A emits first irradiation light L1A having a first wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. The second light source 113B emits second irradiation light L1B having a second wavelength different from the first wavelength. The second wavelength is, for example, a wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm that is different from the first wavelength. The first irradiation light L1A and the second irradiation light L1B may each have multiple wavelengths. That is, the first irradiation light L1A may have a wavelength different from the first wavelength, and the second irradiation light L1B may have a wavelength different from the second wavelength.

[0081] The switching unit 117 is disposed between the first light source 113A and the second light source 113B and the lens 115. The switching unit 117 is optically coupled to the first light source 113A, the second light source 113B, and the lens 115 using optical fibers and lenses. The switching unit 117 switches between the optical paths of the first irradiation light L1A and the second irradiation light L1B so that the first irradiation light L1A from the first light source 113A and the second irradiation light L1B from the second light source 113B are selectively irradiated onto the irradiation region R of the cell population 2. For example, the switching unit 117 sequentially irradiates the irradiation region R of the cell population 2 with the first irradiation light L1A and the second irradiation light L1B. The switching unit 117 is, for example, an optical switch in which a mirror or a prism slides to change the direction in which light travels. The switching unit 117 may be an optical switch that switches the direction in which light travels by using a dielectric material having an electro-optic effect, such as LiON3 (lithium nitrate) or LiTaO3 (lithium tantalate).

[0082] When the cell population 2 is irradiated with the first irradiation light L1A, a portion of the first irradiation light L1A passes through the cell population 2 and is emitted from the cell population 2 as first outgoing light L2A. The first outgoing light L2A has the same wavelength as the first wavelength of the first irradiation light L1A. When the cell population 2 is irradiated with the second irradiation light L1B, a portion of the second irradiation light L1B passes through the cell population 2 and is emitted from the cell population 2 as second outgoing light L2B. The second outgoing light L2B has a second wavelength that is the same as the wavelength of the second irradiation light L1B.

[0083] The optical sensor 123 selectively receives the first emitted light L2A and the second emitted light L2B emitted from the cell population 2. For example, the optical sensor 123 sequentially receives the first emitted light L2A and the second emitted light L2B. The optical sensor 123 outputs to the analysis unit 130 a first electrical signal SA corresponding to the intensity of the first emitted light L2A and a second electrical signal SB corresponding to the intensity of the second emitted light L2B.

[0084] The analysis unit 130 quantitatively determines the "cell number" and "cell density" of the cell population 2 based on the intensities of the first emitted light L2A and the second emitted light L2B. Generally, when light is irradiated onto the cell population 2 in the culture solution 7, light is absorbed by the cell population 2 and the culture solution 7, causing scattering and reflection of the light from the cell population 2. Of these phenomena, light scattering and reflection can be broadly divided into Rayleigh scattering, which occurs due to the internal molecular structure of the cells that make up the cell population 2, and reflection, which occurs due to density fluctuations within the cell population 2.

[0085] The Rayleigh scattering intensity generated by irradiating the irradiation region R of the cell population 2 with light depends on the "cell number" in the irradiation region R. The reflection intensity generated in the irradiation region R depends on the "cell density" in the irradiation region R. "Rayleigh scattering intensity" means the "amount of change in light intensity caused by Rayleigh scattering." Rayleigh scattering intensity depends on the wavelength of light, whereas reflection intensity does not depend on the wavelength of light. Therefore, when observing the state of the cell population 2 using light of multiple wavelengths, the difference in wavelength dependency can be utilized to separately determine the wavelength-dependent Rayleigh scattering intensity and the wavelength-independent reflection intensity. In other words, the "cell number" can be quantitatively determined based on the Rayleigh scattering intensity, and the "cell density" can be quantitatively determined based on the reflection intensity.

[0086] 13 is a diagram showing the functional configuration of the analysis unit 130. The analysis unit 130 includes, as functional components, an acquisition unit 131, a storage unit 133, and a conversion unit 135, for example. The acquisition unit 131 acquires the intensity of the first emitted light L2A indicated by the first electrical signal SA and the intensity of the second emitted light L2B indicated by the second electrical signal SB for each irradiation region R of the cell population 2. The acquisition unit 131 provides the conversion unit 135 with first light intensity information D11 indicating the intensity of the first emitted light L2A for each irradiation region R of the cell population 2 and second light intensity information D12 indicating the intensity of the second emitted light L2B for each irradiation region R of the cell population 2.

[0087] The storage unit 133 stores first conversion information D21 for determining the "cell number" of the cell population 2 based on the intensities of the first and second emitted light beams L2A and L2B, and second conversion information D22 for determining the "cell density" of the cell population 2 based on the intensities of the first and second emitted light beams L2A and L2B. The first conversion information D21 includes a first calibration curve G11 showing the relationship between the "cell number" of the cell population 2 and the Rayleigh scattering coefficient obtained from the first and second light intensity information D11 and D12. The "Rayleigh scattering coefficient" is a parameter that indicates the relationship between Rayleigh scattering intensity and wavelength, and can be determined from the wavelength dependence of the Rayleigh scattering intensity. There is a proportional relationship in which the larger the Rayleigh scattering coefficient, the greater the Rayleigh scattering intensity. Therefore, the "cell number" can be quantitatively determined by determining either the Rayleigh scattering intensity or the Rayleigh scattering coefficient. In this embodiment, a case in which the "cell number" is determined using the Rayleigh scattering coefficient is illustrated. The first calibration curve G11 is a graph plotting the relationship between the Rayleigh scattering coefficient and the "cell number." The second conversion information D22 includes a second calibration curve G12 showing the relationship between the reflection intensity obtained from the first light intensity information D11 and the second light intensity information D12 and the "cell density" of the cell population 2. The second calibration curve G12 is a graph plotting the relationship between the reflection intensity and the "cell density." At least one of the first conversion information D21 and the second conversion information D22 may include the intensity of the first irradiation light L1A for calculating the first light intensity change amount from the first light intensity information D11, or may include the intensity of the second irradiation light L1B for calculating the second light intensity change amount from the second light intensity information D12.

[0088] FIG. 14 is a graph illustrating how to calculate the Rayleigh scattering coefficient and reflection intensity. Graph G13 in FIG. 14 shows the relationship between the amount of change in light intensity and wavelength λ when there is no absorption and only Rayleigh scattering and reflection. In FIG. 14, the vertical axis represents the amount of change in light intensity, and the horizontal axis represents wavelength λ divided by the fourth power. FIG. 14 also shows a plot P11 illustrating the relationship between the first amount of change in light intensity P(A) and the first wavelength λ(A), and a plot P12 illustrating the relationship between the second amount of change in light intensity P(B) and the second wavelength λ(B). The first amount of change in light intensity P(A) is the relative ratio between the intensity of the first emitted light L2A and the intensity of the first irradiation light L1A, and is defined as −10 Log (intensity of first emitted light L2A / intensity of first irradiation light L1A). The second light intensity change amount P(B) is the relative ratio between the intensity of the second emitted light L2B and the intensity of the second irradiation light L1B, and is defined as −10 Log (intensity of the second emitted light L2B / intensity of the second irradiation light L1B).

[0089] In Figure 14, the amount of change in light intensity is represented by the sum of the Rayleigh scattering intensity and the reflection intensity. The reflection intensity that is not wavelength-dependent is represented by the intercept of the line connecting plot P11 and plot P12 (i.e., the intensity P(C) indicated by the intersection of the line and the vertical axis of the graph). The Rayleigh scattering intensity that is wavelength-dependent is represented by the product of the slope of the line connecting plot P11 and plot P12 (i.e., the Rayleigh scattering coefficient) and one-fourth power of the wavelength λ. Therefore, the Rayleigh scattering coefficient Pr1 can be calculated using the following equation (1), and the reflection intensity Pr2 can be calculated using the following equation (2). Once the Rayleigh scattering coefficient Pr1 is calculated, it is also possible to calculate the Rayleigh scattering intensity using the above relationship.

[0090] 13 , the storage unit 133 pre-stores first conversion information D21 including a first calibration curve G11 showing the relationship between the Rayleigh scattering coefficient and the “cell number,” and second conversion information D22 including a second calibration curve G12 showing the relationship between the reflection intensity and the “cell density.” A sample of the cell population 2 whose “cell number” and “cell density” are known (or a sample having a reference “cell number” and “cell density”) is prepared in advance, and the sample is irradiated with the first irradiation light L1A and the second irradiation light L1B using the observation device 101, thereby making it possible to pre-create the first calibration curve G11 showing the relationship between the Rayleigh scattering coefficient and the “cell number” of the sample, and the second calibration curve G12 showing the relationship between the reflection intensity and the “cell density.”

[0091] The conversion unit 135 uses the first light intensity information D11 and second light intensity information D12 from the acquisition unit 131 and the first conversion information D21 and second conversion information D22 from the storage unit 133 to determine the "cell number" and "cell density" for each irradiation region R of the cell population 2. Specifically, the conversion unit 135 first calculates a first light intensity change P(A), which is the relative ratio between the intensity of the first emitted light L2A and the intensity of the first irradiation light L1A, and calculates a second light intensity change P(B), which is the relative ratio between the intensity of the second emitted light L2B and the intensity of the second irradiation light L1B. Next, the conversion unit 135 uses the first light intensity change P(A) and the second light intensity change P(B) to determine the Rayleigh scattering coefficient Pr1 shown in Equation (1). The conversion unit 135 uses the Rayleigh scattering coefficient Pr1 to determine the reflection intensity Pr2 shown in Equation (2).

[0092] Thereafter, the conversion unit 135 converts the Rayleigh scattering coefficient Pr1 into a "cell number" by referring to the first calibration curve G11. The conversion unit 135 converts the reflection intensity Pr2 into a "cell density" by referring to the second calibration curve G12. This makes it possible to separately determine the "cell number" and "cell density" for each irradiation region R of the cell population 2.

[0093] FIG. 15 is a graph illustrating wavelength ranges suitable for observing the state of the cell population 2. Graph G14, represented by a solid line in FIG. 15, shows the wavelength dependence of the amount of change in light intensity, reflecting the influence of light absorption by the cells and the culture solution 7. Graph G15, represented by a dotted line in FIG. 15, shows the wavelength dependence of the amount of change in light intensity, when there is no influence of light absorption by the cells and the culture solution 7. As shown in FIG. 15, graph G14 includes wavelength ranges R11 and R12, where there is a peak where the amount of change in light intensity increases sharply, and wavelength ranges R21 and R22, where there is no such peak. In the wavelength ranges R11 and R12, where such peaks exist, it may be difficult to accurately determine the Rayleigh scattering coefficient due to the influence of the peaks. Therefore, in order to accurately determine the Rayleigh scattering coefficient, it is appropriate to use wavelengths included in the wavelength ranges R21 and R22, where there are no peaks.

[0094] In this embodiment, the first wavelength λ(A) of the first irradiation light L1A and the second wavelength λ(B) of the second irradiation light L1B are both included in the wavelength ranges R2 (see FIG. 6 ) of 650 nm to 850 nm and 1060 nm to 1090 nm. In graph G14 of FIG. 15 , wavelengths of 1060 nm to 1090 nm are included in the wavelength range R21 where no peak exists, and wavelengths of 650 nm to 850 nm are included in the wavelength range R22 where no peak exists. Therefore, when the above-described first irradiation light L1A and second irradiation light L1B are irradiated onto the irradiation region R of the cell population 2, a change in light intensity is obtained that is not affected by absorption of the irradiation light by the cell population 2 and the culture solution 7, and therefore the Rayleigh scattering coefficient can be accurately determined based on the change in light intensity.

[0095] The effects obtained by the second embodiment described above will be explained. As described above, when light is irradiated onto the cell population 2, Rayleigh scattering due to the internal molecular structure of the cells constituting the cell population 2 and reflection due to density fluctuations within the cell population 2 occur. The Rayleigh scattering intensity depends on the "cell number." The reflection intensity depends on the "cell density." The Rayleigh scattering intensity is wavelength dependent. The reflection intensity is not wavelength dependent. Therefore, when observing the state of the cell population 2 using light of multiple wavelengths, it is possible to distinguish and determine the wavelength-dependent Rayleigh scattering intensity from the wavelength-independent reflection intensity by utilizing the differences in wavelength dependency. In other words, it is possible to distinguish and quantitatively determine the "cell number" and the "cell density." This makes it possible to observe the state of the cell population 2 in more detail.

[0096] As in the present embodiment, the irradiation unit 111 may include a first light source 113A, a second light source 113B, and a switching unit 117. The light receiving unit 121 may include an optical sensor 123. In this case, the intensity of the first emitted light L2A and the intensity of the second emitted light L2B can be distinguished and detected using a single optical sensor 123. As a result, it is not necessary to separately prepare an optical sensor for detecting the intensity of the first emitted light L2A and an optical sensor for detecting the intensity of the second emitted light L2B, which can avoid complicating the configuration of the light receiving unit 121.

[0097] The observation device and observation method of the present disclosure are not limited to the second embodiment described above, and various other modifications are possible.

[0098] <Modification 1> Figure 16 is a diagram showing a modification of the observation device 101. As in the observation device 101A shown in Figure 16, the irradiation module 110A may include only one irradiation unit 111, and the light-receiving module 120A may include only one light-receiving unit 121. In this case, the irradiation unit 111 is disposed above one of the irradiation regions R of the cell population 2 and irradiates the irradiation region R with the first irradiation light L1A and the second irradiation light L1B. The light-receiving unit 121 is disposed on the opposite side of the cell population 2 from the irradiation unit 111. In other words, the light-receiving unit 121 is disposed below the irradiation region R irradiated with the first irradiation light L1A and the second irradiation light L1B, and faces the irradiation unit 111 in the up-down direction A1, with the cell population 2 interposed therebetween.

[0099] The irradiation unit 111 and the light receiving unit 121 are configured to be movable in a left-right direction A2 perpendicular to the up-down direction A1 and in a front-rear direction (the depth direction relative to the plane of the paper in FIG. 16 ) perpendicular to both the up-down direction A1 and the left-right direction A2. The irradiation unit 111 sequentially irradiates each irradiation region R of the cell population 2 with the first irradiation light L1A and the second irradiation light L1B while moving in the left-right direction A2 and the front-rear direction. The light receiving unit 121 similarly moves in the left-right direction A2 and the front-rear direction in accordance with the movement of the irradiation unit 111, sequentially receiving the first emission light L2A and the second emission light L2B emitted from the cell population 2 as a result of the irradiation of each irradiation region R with the first irradiation light L1A and the second irradiation light L1B.

[0100] The irradiation unit 111 and the light receiving unit 121 may be configured to be movable relative to the container 5 that contains the cell population 2. Therefore, the irradiation unit 111 and the light receiving unit 121 may be configured to move along the left-right direction A2 and the front-back direction while the position of the container 5 is fixed. Conversely, the irradiation unit 111 and the light receiving unit 121 may be configured to move along the left-right direction A2 and the front-back direction while the positions of the irradiation unit 111 and the light receiving unit 121 are fixed.

[0101] 16 also allows the "cell count" and "cell density" to be quantitatively determined for each irradiation region R of the cell population 2 based on the intensity of the first emitted light L2A and the intensity of the second emitted light L2B, thereby achieving the same effect as in the second embodiment. In the observation device 101A, each irradiation region R for the cell population 2 can be set more precisely in accordance with the movement width of the irradiation unit 111 in the left-right direction A2, making it possible to determine the "cell count" and "cell density" in more irradiation regions R of the cell population 2. In other words, it becomes possible to observe the state of the cell population 2 in more detail.

[0102] <Modification 2> Fig. 17 is a diagram showing a modification of the observation device 101. As in the observation device 101B shown in Fig. 17, the irradiation unit 111A may include a multiplexing unit 119 instead of the switching unit 117. The multiplexing unit 119 is optically coupled to the first light source 113A, the second light source 113B, and the lens 115 using optical fibers and lenses. The multiplexing unit 119 is disposed between the first light source 113A and the second light source 113B and the lens 115. The multiplexing unit 119 multiplexes the first irradiation light L1A from the first light source 113A and the second irradiation light L1B from the second light source 113B, and irradiates the irradiation region R of the cell population 2 with the multiplexed irradiation light L3. The multiplexed irradiation light L3 is multiplexed light including the first irradiation light L1A and the second irradiation light L1B, and has a first wavelength λ(A) and a second wavelength λ(B). When the combined irradiation light L3 is irradiated onto the irradiation region R of the cell population 2, a portion of the combined irradiation light L3 passes through the cell population 2 and is emitted from the cell population 2 as combined output light L4. The combined output light L4 has a wavelength corresponding to the first wavelength λ(A) and the second wavelength λ(B) (e.g., the same wavelength as the first wavelength λ(A) and the second wavelength λ(B)). The multiplexing unit 119 is, for example, a dichroic mirror. The multiplexing unit 119 may also be an optical fiber multiplexer such as a WDM coupler.

[0103] The light receiving unit 121A includes a spectroscopic unit 129, a first optical sensor 123A, and a second optical sensor 123B instead of the optical sensor 123. The first optical sensor 123A and the second optical sensor 123B are disposed below the cell population 2 and adjacent to each other in the left-right direction A2. The spectroscopic unit 129 is disposed between the cell population 2 and the first optical sensor 123A and the second optical sensor 123B. The spectroscopic unit 129 splits the combined output light L4 into a first output light L2A having a first wavelength λ(A) and a second output light L2B having a second wavelength λ(B). The first optical sensor 123A receives the first output light L2A split from the combined output light L4 by the spectroscopic unit 129 and outputs a first electrical signal SA indicating the intensity of the first output light L2A. The second optical sensor 123B receives the second output light L2B separated from the combined output light L4 by the spectroscopic unit 129 and outputs a second electrical signal SB indicating the intensity of the second output light L2B. The spectroscopic unit 129 is, for example, a dichroic mirror. The spectroscopic unit 129 may also be an optical fiber spectrometer such as a WDM coupler.

[0104] 17 , the "cell count" and "cell density" can also be quantitatively determined for each irradiation region R of the cell population 2 based on the intensities of the first emitted light L2A and the second emitted light L2B, thereby achieving the same effect as in the second embodiment. According to the observation device 101B, the intensities of the first emitted light L2A and the second emitted light L2B can be detected simultaneously using the combined irradiation light L3 and the combined emitted light L4, so that the state of each irradiation region R of the cell population 2 based on the intensities of the first emitted light L2A and the second emitted light L2B can be observed more efficiently in a shorter time.

[0105] <Modification 3> Figures 18A and 18B are diagrams showing a modification of the observation device 101. The observation device 101C shown in Figure 18A and the observation device 101D shown in Figure 18B each include, for example, the irradiation module 110A and the light-receiving module 120A shown in Figure 16. The observation devices 101C and 101D may each include the irradiation module 110 and the light-receiving module 120 of the second embodiment. In the observation devices 101C and 101D, the light-receiving module 120A is disposed above the cell population 2, similar to the irradiation module 110A. In other words, the light-receiving module 120A is disposed in the same region as the irradiation module 110A, of the two regions sandwiching the cell population 2.

[0106] In the observation device 101C shown in FIG. 18A , the optical axes of the first irradiation light L1A and the second irradiation light L1B (hereinafter simply referred to as "irradiation light L1A, L1B") emitted from the irradiation module 110A are inclined with respect to the vertical direction A1. A portion of the first irradiation light L1A irradiated onto the irradiation region R of the cell population 2 is reflected on the surface or inside of the cell population 2. The reflected light reflected on the cell population 2 is emitted from the cell population 2 as the first emitted light L2A. A portion of the second irradiation light L1B irradiated onto the irradiation region R of the cell population 2 is reflected on the surface or inside of the cell population 2. The reflected light reflected on the cell population 2 is emitted from the cell population 2 as the second emitted light L2B. The optical axes of the first emitted light L2A and the second emitted light L2B are inclined with respect to the vertical direction A1.

[0107] The light-receiving module 120A is disposed on the optical paths of the emitted light beams L2A and L2B. The light-receiving module 120A is disposed, for example, at a position adjacent to the irradiation module 110A in the left-right direction A2. The light-receiving module 120A receives the first emitted light beam L2A and the second emitted light beam L2B (hereinafter simply referred to as "emitted light beams L2A and L2B") and detects the intensities of the emitted light beams L2A and L2B. Similar to the observation device 101 of the second embodiment, the observation device 101C calculates the Rayleigh scattering coefficient and the reflection intensity based on the intensities of the emitted light beams L2A and L2B.

[0108] Fig. 19 is a graph illustrating how to determine the Rayleigh scattering coefficient and the reflection intensity. In Fig. 19, the vertical axis represents the amount of change in light intensity, and the horizontal axis represents the wavelength λ divided by the fourth power. Fig. 19 also shows a plot P21 illustrating the relationship between the first amount of change in light intensity P(A) and the first wavelength λ(A) of the first emitted light L2A, and a plot P22 illustrating the relationship between the second amount of change in light intensity P(B) and the second wavelength λ(B) of the second emitted light L2B. The first amount of change in light intensity P(A) is the relative ratio between the intensity of the first emitted light L2A and the intensity of the first illumination light L1A, and is defined as -10 Log (intensity of the first emitted light L2A / intensity of the first illumination light L1A). The second light intensity change amount P(B) is the relative ratio between the intensity of the second emitted light L2B and the intensity of the second irradiation light L1B, and is defined as −10 Log (intensity of the second emitted light L2B / intensity of the second irradiation light L1B).

[0109] In graph G23 of FIG. 19 , the change in light intensity is represented by the sum of the Rayleigh scattering intensity and the reflection intensity. The reflection intensity, which is not wavelength-dependent, is represented by the intercept of the line connecting plots P21 and P22 (i.e., the intensity P(C) indicated by the intersection of the line with the vertical axis of the graph). The Rayleigh scattering intensity, which is wavelength-dependent, is represented by the product of the slope of the line connecting plots P21 and P22 (i.e., the Rayleigh scattering coefficient) and one-fourth power of the wavelength λ. Therefore, the Rayleigh scattering coefficient Pr1 can be calculated using the above-mentioned formula (1). The reflection intensity Pr3 can be calculated using the following formula (3). Then, by converting the Rayleigh scattering coefficient Pr1 to the "cell number" and the reflection intensity Pr3 to the "cell density," the "cell number" and the "cell density" can be quantitatively calculated. Therefore, the observation device 101C can also achieve the same effects as those of the second embodiment.

[0110] 18B, a circulator 141 is disposed above the irradiation region R of the cell population 2. The irradiation module 110A is disposed further above the circulator 141. The light-receiving module 120A is disposed at a position spaced apart from the circulator 141 in the left-right direction A2. The circulator 141 is disposed at the intersection of the optical axes of the irradiation light beams L1A and L1B emitted from the irradiation module 110A and the optical axes of the emitted light beams L2A and L2B incident on the light-receiving module 120A.

[0111] The circulator 141 is an optical component for separating two beams of light traveling in opposite directions, and has three ports P1, P2, and P3 for the light. The irradiation beams L1A and L1B emitted from the irradiation module 110A enter port P1 of the circulator 141 and are emitted from port P2 toward the irradiation region R of the cell population 2. The emitted beams L2A and L2B emitted from the cell population 2 toward port P2 are emitted from port P3 to the light-receiving module 120A. The observation device 101D can also quantitatively determine the "cell number" and "cell density" of the cell population 2 for each irradiation region R of the cell population 2 based on the intensities of the emitted beams L2A and L2B from the cell population 2, thereby achieving the same effect as the second embodiment.

[0112] <Modification 4> Figure 20 is a diagram showing a modification of the observation device 101. As in the observation device 101E shown in Figure 20, the irradiation module 110B may include only one irradiation unit 111B, and the light-receiving module 120B may include only one light-receiving unit 121B. In the example shown in Figure 20, the irradiation unit 111B includes one light source unit 114 and one lens 115. The light source unit 114 is configured to uniformly irradiate a wide area with irradiation light L1A, L1B. The light source unit 114 is disposed above the cell population 2 and uniformly irradiates a wide area that spreads two-dimensionally when viewed from above with irradiation light L1A, L1B. The range of irradiation light L1A, L1B irradiated from the light source unit 114 may be a region that spreads in a planar manner along the left-right direction A2 and the front-back direction (the depth direction relative to the paper surface of Figure 20). The light source unit 114 simultaneously and uniformly irradiates irradiation light L1A or L1B onto a plurality of irradiation regions R that are set in the cell population 2 and that are arranged along the left-right direction A2 and the front-back direction.

[0113] The light source unit 114 may be configured to include, for example, a first light source 113A, a second light source 113B, and a switching unit 117 (see FIG. 12 ), or may be configured to include a first light source 113A, a second light source 113B, and a multiplexing unit 119 (see FIG. 17 ). Alternatively, the light source unit 114 may be configured to include a light source 113C, a lens 115, and a filter switching unit 118 (described later) (see FIG. 21 ). The light source unit 114 is not limited to these configurations and may have other configurations as long as it is capable of irradiating the illumination light beams L1A and L1B over a wide area that spreads two-dimensionally when viewed from above.

[0114] The lens 115 is disposed on the optical path of the irradiation light L1A, L1B between the light source unit 114 and the cell population 2. The lens 115 is, for example, a collimating lens that collimates the irradiation light L1A, L1B emitted over a wide range from the light source unit 114. The lens 115 extends in a planar shape along the left-right direction A2 and the front-rear direction so as to face the light source unit 114 in the up-down direction A1 and to face all irradiation regions R set on the cell population 2 in the up-down direction A1. The irradiation light L1A, L1B emitted in a divergent manner from the light source unit 114 are collimated by the lens 115 and irradiated onto each irradiation region R of the cell population 2. A portion of the irradiation light L1A passes through the cell population 2 and is emitted as emitted light L2A, and a portion of the irradiation light L1B passes through the cell population 2 and is emitted as emitted light L2B.

[0115] The light receiving unit 121B includes a plurality of optical sensors 123 and one lens 125. The plurality of optical sensors 123 are respectively disposed below a plurality of irradiation regions R of the cell population 2. Each optical sensor 123 selectively receives emitted light L2A, L2B emitted from the cell population 2 in response to irradiation of the irradiation region R of the cell population 2 with irradiation light L1A, L1B.

[0116] The lens 125 is disposed on the optical path of the multiple emitted light beams L2A and L2B between the cell population 2 and the multiple optical sensors 123. The lens 125 is, for example, an objective lens. The lens 125 extends in a planar shape along the left-right direction A2 and the front-rear direction so as to face all irradiation regions R set on the cell population 2 in the up-down direction A1 and all optical sensors 123 in the up-down direction A1. The lens 125 faces the lens 115 in the up-down direction A1, sandwiching the cell population 2 therebetween. The emitted light beams L2A and L2B emitted from the cell population 2 pass through the lens 125 and enter the respective optical sensors 123. Each optical sensor 123 selectively receives the emitted light beams L2A and L2B and outputs electrical signals SA and SB corresponding to the intensities of the emitted light beams L2A and L2B.

[0117] 20 also allows the "cell count" and "cell density" to be quantitatively determined for each irradiation region R of the cell population 2 based on the intensities of the emitted light beams L2A and L2B from the cell population 2, thereby achieving the same effect as in the second embodiment. In the observation device 101E, a single light source unit 114 can be used to irradiate each irradiation region R with the irradiation light beams L1A and L1B, which allows the number of light source units to be reduced and the device configuration to be simplified compared to when multiple light source units are used to irradiate each irradiation region R with the irradiation light beams L1A and L1B.

[0118] In the observation device 101E, the irradiation unit 111B may include, instead of one lens 115, a plurality of lenses individually provided for the plurality of irradiation regions R. The light receiving unit 121B may include, instead of one lens 125, a plurality of lenses individually provided for the plurality of irradiation regions R. In this case, each lens is disposed in a position facing each optical sensor 123 in a one-to-one relationship in the up-down direction A1.

[0119] <Modification 5> FIG. 21 is a diagram showing a modification of the observation device 101. As shown in FIG. 21 , the observation device 101F may include an irradiation unit 111C instead of the irradiation unit 111. The irradiation unit 111C includes a light source 113C, a lens 115, and a filter switching unit 118. The light source 113C is a halogen lamp (lamp light source) that emits irradiation light L1 including multiple wavelengths. At least one wavelength included in the irradiation light L1 is included in the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. Other wavelengths included in the irradiation light L1 may be included in the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm, or may be outside the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm.

[0120] The lens 115 is optically coupled to the light source 113C using an optical fiber such as a fiber bundle. The filter switching unit 118 is disposed on the optical path of the illumination light L1 between the lens 115 and the cell population 2. The filter switching unit 118 holds a first filter 118A and a second filter 118B, and positions either the first filter 118A or the second filter 118B in the optical path of the illumination light L1. The first filter 118A is a bandpass filter that transmits only a first wavelength λ(A) among the multiple wavelengths contained in the illumination light L1. The second filter 118B is a bandpass filter that transmits only a second wavelength λ(B) among the multiple wavelengths contained in the illumination light L1. As shown in the upper right portion of FIG. 21 , when the filter switching unit 118 is viewed in the up-down direction A1, each of the first filter 118A and the second filter 118B is, for example, circular.

[0121] 21 , when the filter switching unit 118 places the first filter 118A in the optical path of the irradiation light L1, the cell population 2 is irradiated with first irradiation light L1A having a first wavelength λ(A) that has passed through the first filter 118A. When the filter switching unit 118 places the second filter 118B in the optical path of the irradiation light L1, the cell population 2 is irradiated with second irradiation light L1B having a second wavelength λ(B) that has passed through the second filter 118B. The filter switching unit 118 swaps the positions of the first filter 118A and the second filter 118B so that the first filter 118A or the second filter 118B is placed on the optical path of the irradiation light L1 between the light source 113C and the cell population 2. In this way, the filter switching unit 118 selectively irradiates the cell population 2 with the first irradiation light L1A or the second irradiation light L1B.

[0122] When the cell population 2 is irradiated with the first irradiation light L1A, a portion of the first irradiation light L1A passes through the cell population 2 and is emitted from the cell population 2 as first emitted light L2A. When the cell population 2 is irradiated with the second irradiation light L1B, a portion of the second irradiation light L1B passes through the cell population 2 and is emitted from the cell population 2 as second emitted light L2B. The light receiving unit 121 selectively receives the first emitted light L2A and the second emitted light L2B emitted from the cell population 2. The light receiving unit 121 outputs a first electrical signal SA corresponding to the intensity of the first emitted light L2A and a second electrical signal SB corresponding to the intensity of the second emitted light L2B to the analysis unit 130.

[0123] 21 also makes it possible to quantitatively determine the "cell number" and "cell density" for each irradiation region R of the cell population 2 based on the intensity of the first emitted light L2A and the intensity of the second emitted light L2B, thereby achieving the same effect as in the second embodiment. By using the light source 113C, which is an inexpensive lamp light source, as in the observation device 101F, the cost of the observation device 101F can be reduced compared to when an expensive laser light source is used.

[0124] The present disclosure is not limited to the above-described embodiments and modifications, and various other modifications are possible. For example, the above-described embodiments and modifications may be combined with each other to a consistent extent depending on the required purpose and effect. In the above-described embodiments and modifications, a case in which one cell population is contained in a container has been described, but multiple cell populations may also be contained in a container. The cell population may be suspended in a culture medium. In the above-described embodiments and modifications, a case in which an irradiation module is disposed above a cell population and a light-receiving module is disposed below the cell population has been mainly described, but the irradiation module and the light-receiving module may be interchanged. In other words, the irradiation module may be disposed below the cell population, and the light-receiving module may be disposed above the cell population.

[0125] In the above-described embodiments and modifications, the irradiating light irradiated onto the cell population includes at least one wavelength within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. However, all wavelengths of the irradiating light may be within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. That is, the irradiating light may only have wavelengths within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm. In this case, a decrease in measurement accuracy due to the inclusion of wavelengths outside the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm in the irradiating light can be avoided. The analysis unit may only handle information (irradiating light intensity or emitted light intensity) obtained from wavelengths within the ranges of 650 nm to 850 nm and 1060 nm to 1090 nm.

[0126] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D, 101, 101A, 101B, 101C, 101D, 101E, 101F... Observation device 2... Cell population 5... Container 5a... Bottom surface 5b... Opening 7... Culture solution 10, 10A, 10B, 110, 110A, 110B... Irradiation module 11, 11A, 111, 111A, 111B, 111C... Irradiation unit 13... Light source (laser light source) 15, 25, 115, 125... Lens 20, 20A, 20B, 120, 120A, 120B... Light receiving module 21, 21A, 121, 121A, 121B... Light receiving unit 23, 123... Optical sensor 30, 130... Analysis unit 31, 131... Acquisition unit 33, 133...storage unit 35, 135...conversion unit 41, 141...circulator 113A...first light source 113B...second light source 113C...light source 114...light source unit 117...switching unit 118...filter switching unit 118A...first filter 118B...second filter 119...combining unit 123A...first optical sensor 123B...second optical sensor 129...spectrometry unit 301...processor 302...main memory device 303...auxiliary memory device 304...input device 305...output device A1...up and down direction A2...left and right direction D1...light intensity information D2...conversion information D11...first light intensity information D12...second light intensity information D21...first conversion information D22...second conversion information G1...calibration curve G11...first calibration curve G12...second calibration curve L1...Irradiation light L1A...First irradiation light L1B...Second irradiation light L2...Outgoing light L2A...First outgoing light L2B...Second outgoing light L3...Combined irradiation light L4...Combined outgoing light P1, P2, P3...Port P(A)...First light intensity change amount P(B)...Second light intensity change amount Pr1...Rayleigh scattering coefficient Pr2, Pr3...Reflection intensity R...Irradiation area R1, R2, R11, R21, R22...Wavelength range λ...Wavelength λ(A)...First wavelength λ(B)...Second wavelength S...Electrical signal SA...First electrical signal SB...Second electrical signal

Claims

1. An observation apparatus for observing the state of a cell population composed of a plurality of cells, comprising: at least one irradiation unit disposed at a position facing the cell population and irradiating at least one irradiation region set in the cell population with irradiation light having at least one wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less; at least one light receiving unit disposed at a position facing the cell population and receiving the emitted light emitted from the cell population by the irradiation of the irradiation light to the irradiation region; and an analysis unit communicably connected to the light receiving unit and obtaining a parameter including at least one of the number of cells and the cell density of the cell population in the irradiation region based on the intensity of the emitted light.

2. The observation apparatus according to claim 1, wherein the irradiation unit includes a light source using a semiconductor light emitting element that emits light having one wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less as the irradiation light.

3. The observation apparatus according to claim 1 or 2, wherein the light receiving unit is disposed at a position on the opposite side of the irradiation unit with the cell population interposed therebetween, and receives a part of the irradiation light emitted from the irradiation unit and transmitted through the cell population as the emitted light.

4. The observation apparatus according to any one of claims 1 to 3, wherein the irradiation unit includes one or more light sources that emit the irradiation light, and irradiates each of the plurality of irradiation regions set in the cell population with the irradiation light; and the light receiving unit includes one or more light sensors into which the emitted light is incident, and receives the plurality of irradiation lights transmitted through the cell population as the plurality of emitted lights.

5. The irradiation unit irradiates the irradiation region of the cell population with first irradiation light having a first wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less, and second irradiation light having a second wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less and different from the first wavelength. The light receiving unit receives first emitted light and second emitted light having different wavelengths, which are emitted from the cell population by the irradiation of the first irradiation light and the second irradiation light. The analysis unit obtains the number of cells and the cell density in the irradiation region based on the intensity of the first emitted light and the intensity of the second emitted light. The observation device according to any one of claims 1 to 4.

6. The irradiation unit includes: a first light source that emits the first irradiation light; a second light source that emits the second irradiation light; and a switching unit that switches the optical path of the first irradiation light and the optical path of the second irradiation light so that the first irradiation light and the second irradiation light are selectively irradiated on the irradiation region of the cell population. The light receiving unit includes an optical sensor that selectively receives the first emitted light and the second emitted light emitted from the cell population. The observation device according to claim 5.

7. The irradiation unit includes: a first light source that emits the first irradiation light; a second light source that emits the second irradiation light; and a multiplexing unit that multiplexes the first irradiation light and the second irradiation light to generate multiplexed irradiation light and irradiates the multiplexed irradiation light on the irradiation region of the cell population. The light receiving unit includes: a spectroscopic unit that spectroscopically analyzes the multiplexed emitted light emitted from the cell population by the irradiation of the multiplexed irradiation light for each wavelength; a first optical sensor that detects the intensity of the first emitted light spectroscopically analyzed from the multiplexed emitted light; and a second optical sensor that detects the intensity of the second emitted light spectroscopically analyzed from the multiplexed emitted light. The observation device according to claim 5.

8. The irradiation unit includes a light source that emits light including the first irradiation light and the second irradiation light, a first filter that transmits only the first irradiation light, and a second filter that transmits only the second irradiation light, and a filter switching unit that switches the position of the first filter and the position of the second filter so that the first filter or the second filter is disposed on the optical path of the light between the light source and the cell population. The light receiving unit includes a photosensor that selectively receives the first emitted light and the second emitted light emitted from the cell population. The observation apparatus according to claim 5.

9. An observation method for observing the state of a cell population composed of a plurality of cells, the method comprising: irradiating at least one irradiation region set in the cell population with irradiation light having at least one wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less; receiving emitted light emitted from the cell population by the irradiation of the irradiation light on the irradiation region; and obtaining a parameter including at least one of the number of cells and the cell density of the cell population in the irradiation region based on the intensity of the emitted light.

10. In the step of irradiating the irradiation region, the irradiation region is irradiated with first irradiation light having a first wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less, and second irradiation light having a second wavelength included in the range of 650 nm or more and 850 nm or less and 1060 nm or more and 1090 nm or less and different from the first wavelength. In the step of receiving the emitted light, the first emitted light and the second emitted light having different wavelengths, which are emitted from the cell population by the irradiation of the first irradiation light and the second irradiation light, are received. In the step of obtaining the parameter, the number of cells and the cell density in the irradiation region are respectively obtained based on the intensity of the first emitted light and the intensity of the second emitted light. The observation method according to claim 9.

Images