Illumination device and method for using the same

Abstract

In an aspect of this invention, the lighting device includes multiple thin plates, the surface of each of which oriented to the center is configured to absorb light. The thin plates may be rearranged by moving at least one thin plate through a <360 angle about the axis; as a result, by the entirety of the thin plates, it is possible to form a curved plate formed from double right-angled spherical triangles.

Description

lighting equipment

[0001] The present invention relates to a lighting device.

[0002] To measure the color or gloss of an object, it is desirable to meet the lighting and light-receiving conditions specified by the Japanese Industrial Standards (JIS), and many contact colorimeters and glossmeters that comply with these standards are commercially available. If a flat, uniform sample surface can be created, the color and gloss of the object can be measured using commercially available contact colorimeters and glossmeters. However, to measure a sample with a complex shape in its original form, a color luminance meter and a camera must be used to observe the object without contact, requiring separate lighting. This can lead to variations in lighting and light-receiving conditions, making it difficult to ensure measurement accuracy.

[0003] The present inventors proposed an illumination device capable of achieving both high measurement accuracy and improved measurement convenience in Patent Document 1 listed below. Specifically, one example of the proposed illumination device includes a casing, multiple plates, and a light source. The inner surface of the casing defines a hemispherical internal space and is made of a material that diffusely reflects light. Observation sections are arranged circumferentially along the inner surface from the vertex, spaced apart from one another. Each plate is arranged in the internal space and covers a portion of the inner surface when viewed from the center. The surface of each plate facing the center is made of a light-absorbing material. The multiple plates include a first plate, a second plate arranged symmetrically with the first plate about the center, and a third plate not arranged symmetrically with any of the other plates about the center. The second plate and the third plate each have a transmission opening arranged at a position corresponding to the observation section.

[0004] Japanese Patent Application Laid-Open No. 2020-202119

[0005] After further investigation, the inventors of the present invention found that the lighting device proposed in Patent Document 1 has a problem in that measurement accuracy may be reduced due to the causes explained below.

[0006] The first reason is that the proposed lighting device uses a bi-rectangular spherical triangular light trap (optical absorber) as an example of a light trap, in which the entire surface facing the center absorbs light. However, such a light trap blocks all diffused light from the azimuth angle at which the light trap is located, regardless of the size of the apex angle of the bi-rectangular spherical triangular light trap. Therefore, when using a bi-rectangular spherical triangular light trap, depending on the shape of the object being measured, shadows may appear, which may increase measurement errors and reduce measurement accuracy.

[0007] The second reason is that if part of the bottom surface of the hemispherical internal space is covered with a reflecting mirror, depending on the shape of the object to be measured, there may be areas where the regular reflection component (halation) cannot be removed, which could reduce the measurement accuracy in these areas.

[0008] Fig. 17 is a diagram showing an example in which, when a part of the bottom surface of the hemispherical internal space is blocked with a reflecting mirror in a conventional lighting device, a part from which the specular reflection component cannot be removed is generated. As shown in Fig. 17, when a part of the bottom surface of the hemispherical internal space is blocked with a reflecting mirror, the specular reflection component indicated by the dashed dotted line reaches the observation part, that is, a part from which the specular reflection component cannot be removed is generated for a convex measurement object.

[0009] In one aspect, the present invention has been made in consideration of the above-described circumstances, and its object is to provide an illumination device that prevents a decrease in measurement accuracy due to at least one of the occurrence of shadows on the object to be measured and the remaining specular reflection component, thereby achieving high-precision measurements.

[0010] In order to solve the above-mentioned problems, the present invention employs the following configuration.

[0011] That is, an illumination device according to one aspect of the present invention is a casing having an outer surface, an inner surface, a spherical or hemispherical internal space, and an observation section, the inner surface defining the internal space and being made of a material that reflects light, the internal space having a center, a zenith, and an axis, the axis passing through the center and the zenith, and the observation section being provided for observing an object placed in the internal space and being located at a position spaced apart from the zenith or the zenith in a circumferential direction along the internal surface, and a plate member arranged opposite the internal surface in the internal space, covering a portion of the internal surface when viewed from the center, and configured so that its position around the axis can be adjusted, the casing having a first surface facing the internal surface and a second surface facing the center. and a light source arranged to irradiate light into the internal space, wherein an upper portion of the plate, which is the side on which the observation unit is arranged with respect to the equatorial plane, includes a plurality of thin plates arranged so as not to overlap one another, the plurality of thin plates being configured so that the second surface thereof absorbs light, and by moving and repositioning at least one of the plurality of thin plates arranged so as not to overlap one another in the upper portion around the axis by an angle smaller than 360 degrees, it is possible to form, with all of the plurality of thin plates, a single curved plate in the shape of a two right-angled spherical triangle, which corresponds to a region of the inner surface connecting three points consisting of a point corresponding to the zenith of the inner surface and two points on the intersection line between the equatorial plane and the inner surface.

[0012] In this configuration, the second surfaces of the plurality of thin plates are configured to absorb light, and the plurality of thin plates are arranged in the upper portion so as not to overlap one another. By shifting the position of at least one of the plurality of thin plates around the axis by an angle smaller than 360 degrees and repositioning it, all of the plurality of thin plates can form a single curved plate. In other words, the area of ​​each of the plurality of thin plates included in the upper portion and configured to absorb light is smaller than the area of ​​the curved plate. Furthermore, when the upper portion and the curved plate are arranged so that one side (e.g., the bottom side) of each overlap, the area of ​​the overlapping portion is smaller than the area of ​​the curved plate.

[0013] Therefore, compared to conventional light traps that are configured to absorb light from the entire second surface of the curved plate in the shape of a two-right-angled spherical triangle, the upper portion allows diffused light from the azimuth angle corresponding to the curved plate to more easily reach the object, making it less likely that a shadow will be cast on the object. Therefore, the lighting device according to one aspect of the present invention can prevent a decrease in measurement accuracy due to the generation of a shadow, thereby achieving high-precision measurements.

[0014] In the lighting device according to the above aspect, the area of ​​each of the plurality of thin plates may be equal to or less than half the area of ​​the curved plate. In this configuration, the upper portion can ensure at least twice the amount of diffused light reaching the target from an azimuth angle corresponding to the curved plate, compared to a conventional light trap configured to absorb light from the entire second surface of the curved plate having a birectangular spherical triangular shape.

[0015] In the lighting device according to the above aspect, the plurality of thin plates may not be in contact with each other. In this configuration, the upper portion can be configured to include the plurality of thin plates that are not in contact with each other.

[0016] The lighting device according to the above aspect may further include an extraction unit that extracts, from a plurality of measurement data pieces showing the object observed while the plate is moved around the axis in the observation unit, measurement data pieces in which the object is observed in the brightest state and measurement data pieces in which the object is observed in the darkest state, and a storage unit that stores the two measurement data pieces extracted by the extraction unit as observation results of the object. In this configuration, the measurement data pieces in which the object is observed in the brightest state and measurement data pieces in which the object is observed in the darkest state are extracted from the plurality of measurement data pieces, and these two measurement data pieces are stored as observation results of the object. Therefore, compared to storing all of the plurality of measurement data pieces as observation results of the object, the amount of data to be stored can be reduced, and the amount of measurement data stored as observation results of the object can be kept constant. This is particularly effective when increasing the number of measurements or performing high-speed measurements. For example, employing this configuration makes it easy to measure an object underwater while suppressing specular reflection from a rippling water surface.

[0017] In the illumination device according to the above aspect, the internal space may be spherical, the plate member may include the upper portion and a lower portion extending on the opposite side of the equatorial plane from the side on which the observation unit is disposed, and the second surface of the lower portion may be configured to absorb light. In this configuration, the second surface of the lower portion is configured to absorb light. Therefore, the second surface of the lower portion can remove specular reflection components, for example, even when the object has a convex shape. Therefore, the illumination device according to one aspect of the present invention can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurement.

[0018] In the lighting device according to the above aspect, the internal space may be hemispherical, and the lighting device may further include a reflector whose surface facing the internal space is configured to specularly reflect light and which is arranged to cover a portion of the bottom surface of the internal space. The plate may include the upper portion and a horizontal portion whose second surface is configured to absorb light, covering a portion of the surface of the reflector facing the internal space and extending along the equatorial plane. In this configuration, the horizontal portion extends along the equatorial plane, covering a portion of the surface of the reflector facing the internal space, and the second surface of the horizontal portion is configured to absorb light. Therefore, the second surface of the horizontal portion can remove specular reflection components, even when the object has a convex shape. Therefore, the lighting device according to one aspect of the present invention can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurements.

[0019] The illumination device according to the above aspect may further include a correction unit that corrects measurement data acquired by observing the object with the observation unit using reference measurement data, which is measurement data acquired in advance by observing a white diffusing object having the same shape as the object with the observation unit. In this configuration, the measurement data is corrected using the reference measurement data. Therefore, even if a shadow occurs on the object for some reason, high-precision measurement can be performed by correcting the shadowed portion using the reference measurement data.

[0020] In the lighting device according to the above aspect, the casing and the plate may be integrated by forming a portion of the inner surface using a light-absorbing material. In this configuration, the casing and the plate are integrated by forming a portion of the inner surface using a light-absorbing material. Therefore, the lighting device according to the above aspect can be made more compact than a lighting device in which the casing and the plate are separate components, and can be installed in environments with limited space, such as a factory production line.

[0021] In the lighting device according to the above aspect, the plurality of thin plates may be formed by dividing a single curved plate having the two right-angled spherical triangular shape along a plane parallel to or inclined to the equatorial plane. As described above, by moving and rearranging at least one of the plurality of thin plates around the axis by an angle smaller than 360 degrees, all of the plurality of thin plates can form a single curved plate having the two right-angled spherical triangular shape. Therefore, the plurality of thin plates may be formed by dividing a single curved plate having the two right-angled spherical triangular shape along a plane parallel to or inclined to the equatorial plane. Therefore, the lighting device according to one aspect of the present invention makes it possible to easily prepare a plurality of thin plates whose rearrangement can form a single curved plate having the two right-angled spherical triangular shape.

[0022] Furthermore, an illumination device according to one aspect of the present invention is a casing having an outer surface, an inner surface, a spherical internal space, and an observation portion, the inner surface defining the internal space and being made of a material that reflects light, the internal space having a center, a zenith, and an axis that passes through the center and the zenith, and the observation portion being provided for observing an object placed in the internal space and being disposed at a position spaced apart from the zenith or the zenith in a circumferential direction along the internal surface, the casing and a light source that faces the internal surface in the internal space. the plate is arranged facing the inner surface, covering a portion of the inner surface when viewed from the center, and configured to be able to adjust its position around the axis, and has a first surface facing the inner surface and a second surface facing the center, and includes an upper portion that extends toward the side where the observation unit is arranged with respect to the equatorial plane, and a lower portion that extends toward the side opposite the side where the observation unit is arranged with respect to the equatorial plane; and a light source arranged to irradiate light into the internal space, and the second surface of the lower portion is configured to absorb light.

[0023] In this configuration, the second surface of the lower portion is configured to absorb light. Therefore, the second surface of the lower portion can remove specular reflection components, even when the object has a convex shape. Therefore, the illumination device according to one aspect of the present invention can prevent a decrease in measurement accuracy due to the remaining specular reflection components, thereby achieving high-precision measurements.

[0024] The lighting device according to the above aspect may further include an extraction unit that extracts, from a plurality of measurement data showing the object observed while the plate material is moved around the axis in the observation unit, measurement data in which the object is observed in the brightest state and measurement data in which the object is observed in the darkest state, and a storage unit that stores the two measurement data extracted by the extraction unit as observation results of the object.

[0025] The lighting device according to the above aspect may further include a correction unit that corrects the measurement data obtained by observing the object in the observation unit using reference measurement data that is measurement data that has been obtained in advance by observing a white diffuse object having the same shape as the object in the observation unit.

[0026] In the lighting device according to the aforementioned aspect, the casing and the plate may be integrated by forming a part of the inner surface using a light-absorbing material.

[0027] In the lighting device according to the above aspect, the upper portion may include a plurality of thin plates arranged so as not to overlap one another, and the plurality of thin plates may be configured such that the second surfaces thereof absorb light. At least one of the plurality of thin plates arranged so as not to overlap one another in the upper portion may be moved around the axis by an angle smaller than 360 degrees and rearranged, so that all of the plurality of thin plates may form a single curved plate in the shape of a two right-angled spherical triangle, which corresponds to a region of the inner surface connecting three points consisting of a point on the inner surface corresponding to the zenith and two points on the intersection line between the equatorial plane and the inner surface.

[0028] In the lighting device according to the above aspect, the plurality of thin plates may be formed by dividing a single curved plate having the two right-angled spherical triangular shape along a plane parallel to or inclined to the equatorial plane. As described above, by moving and rearranging at least one of the plurality of thin plates around the axis by an angle smaller than 360 degrees, all of the plurality of thin plates can form a single curved plate having the two right-angled spherical triangular shape. Therefore, the plurality of thin plates may be formed by dividing a single curved plate having the two right-angled spherical triangular shape along a plane parallel to or inclined to the equatorial plane. Therefore, the lighting device according to one aspect of the present invention makes it possible to easily prepare a plurality of thin plates whose rearrangement can form a single curved plate having the two right-angled spherical triangular shape.

[0029] According to the present invention, it is possible to provide an illumination device that prevents a decrease in measurement accuracy due to at least one of the occurrence of shadows on the object to be measured and the remaining specular reflection component, thereby achieving highly accurate measurements.

[0030] FIG. 1 is a side view schematically illustrating an illumination device according to a first embodiment. FIG. 2 is a plan view schematically illustrating a main body according to the first embodiment. FIG. 3 is a cross-sectional view schematically illustrating a main body according to the first embodiment. FIG. 4 is a diagram for explaining how a plurality of thin plates included in an upper plate according to the first embodiment are arranged on the upper plate. FIG. 5 is a diagram for explaining an example of the software configuration of a controller according to the first embodiment. FIG. 6 is a diagram showing the movement of a plate whose position is controlled by the controller of FIG. 5. FIG. 7A is a diagram for explaining how a plurality of thin plates included in an upper plate according to a modified example are arranged on the upper plate according to the modified example. FIG. 7B is a diagram for explaining how a plurality of thin plates included in an upper plate according to a modified example are arranged on the upper plate according to the modified example. FIG. 7C is a diagram for explaining how a plurality of thin plates included in an upper plate according to a modified example are arranged on the upper plate according to the modified example. FIG. 7D is a diagram for explaining how a plurality of thin plates included in an upper plate according to a modified example are arranged in the upper plate according to the modified example. FIG. 7E is a diagram for explaining how a plurality of thin plates included in an upper plate according to a modified example are arranged in the upper plate according to the modified example. FIG. 8 is a diagram schematically illustrating an example of a software configuration of a controller according to a modified example. FIG. 9 is a diagram schematically illustrating an example of a software configuration of a controller according to a modified example. FIG. 10 is a diagram for explaining an outline of an experiment verifying how much the illumination device according to the embodiment improves illuminance compared to a conventional illumination device. FIG. 11 is a diagram showing the results of the experiment outlined in FIG. 10. FIG. 12 is a side view schematically illustrating an illumination device according to a second embodiment. FIG. 13 is a cross-sectional view schematically illustrating a main body according to the second embodiment. FIG. 14 is a side view schematically illustrating an example of the configuration of an illumination device according to a third embodiment. FIG. 15 is a cross-sectional view schematically illustrating an example of the configuration of a main body according to the third embodiment. FIG. 16 is a diagram for explaining the shape of the upper plate according to the third embodiment.Fig. 17 is a diagram showing an example in which, when a part of the bottom surface of the hemispherical internal space in a conventional lighting device is blocked with a reflecting mirror, a part of the bottom surface from which the specular reflection component cannot be removed is generated. Fig. 18 is a diagram showing an example of the configuration of an upper plate according to yet another modified example. Fig. 19 is a diagram showing an example of the configuration of an upper plate according to another modified example different from that shown in Fig. 18.

[0031] An embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described below with reference to the drawings. However, the present embodiment described below is merely an example of the present invention in all respects. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention. In other words, when implementing the present invention, specific configurations according to the embodiment may be appropriately adopted. For convenience of explanation, the following description will be made based on the orientation in the drawings.

[0032] First Embodiment Conventional lighting devices use a light trap with a shape of two right-angled spherical triangles, each of which is configured so that the entire surface facing the center absorbs light. However, such a conventional light trap blocks all diffused light from the azimuth angle at which the light trap is located, regardless of the size of the apex angle of the two right-angled spherical triangles. Therefore, when using a light trap with a shape of two right-angled spherical triangles, each of which is configured so that the entire surface facing the center absorbs light, shadows may appear depending on the shape of the object to be measured, which may increase measurement errors and reduce measurement accuracy.

[0033] In contrast, the lighting device according to the present embodiment uses multiple thin plates, each with a surface facing the center that absorbs light, arranged so that they do not overlap each other and used as a light trap. By moving and repositioning at least one of these thin plates around an axis passing through the zenith and center of the spherical observation space (internal space) by an angle smaller than 360 degrees, all of these thin plates can be used to form a single curved plate with the following shape: That is, by repositioning at least one thin plate, all of these thin plates can be used to form a curved plate with a two-right-angled spherical triangle shape, as in conventional lighting devices, with the entire surface facing the center configured to absorb light.

[0034] In other words, the area of ​​each of these multiple thin plates is smaller than the area of ​​the single curved plate with the aforementioned two-right-angled spherical triangular shape. Therefore, the light trap provided by the lighting device according to this embodiment allows diffused light from the azimuth angle corresponding to the curved plate to reach the object more easily than conventional light traps configured to absorb light from the entire second surface of the curved plate with the two-right-angled spherical triangular shape. In other words, the light trap provided by the lighting device according to this embodiment is less likely to cast shadows on the object. Therefore, the lighting device according to this embodiment can prevent a decrease in measurement accuracy due to the generation of shadows, thereby achieving high-precision measurements.

[0035] These thin plates can be obtained, for example, by dividing a single curved plate having the shape of two right-angled spherical triangles. An example of a lighting device having such a configuration will be described below.

[0036] §1 Configuration Example An example of the configuration of the illumination device L1 according to this embodiment will be described using FIGS. 1 to 11. FIG. 1 is a side view that schematically illustrates an example of the configuration of the illumination device L1 according to this embodiment. The illumination device L1 according to this embodiment is used for measuring the color of an object S. As illustrated in FIG. 1, the illumination device L1 includes a spherical main body B1, a support 5, and a controller 100 that is communicatively connected to the main body B1. FIGS. 2 and 3 are a plan view and a cross-sectional view that schematically illustrate an example of the configuration of the main body B1. As shown in each figure, the main body B1 includes a casing 1, a plate 2, a light source 3, and a sample stage 4.

[0037] (Casing) The casing 1 according to this embodiment is spherical and is composed of a hemispherical upper casing 1h(u) and a hemispherical lower casing 1h(d), which have substantially the same shape, as shown in, for example, Figures 1 and 3. In the following description, when the upper casing 1h(u) and the lower casing 1h(d) are referred to collectively without distinction, they will simply be referred to as the "hemispherical casing 1h." Furthermore, when distinguishing between the components of the upper casing 1h(u) and the lower casing 1h(d), the components of the upper casing 1h(u) are indicated by adding "(u)" after the component number, and the components of the lower casing 1h(d) are indicated by adding "(d)" after the component number.

[0038] The hemispherical casing 1h has a hemispherical outer surface 11h, a hemispherical inner surface 12h, and a hemispherical inner space 13h.

[0039] The hemispherical outer surface 11h faces the outside of the hemispherical casing 1h, and the hemispherical inner surface 12h faces the inside of the hemispherical casing 1h. In this embodiment, the hemispherical inner surface 12h is made of a material that diffusely reflects light. The material that diffuses and reflects light is not particularly limited as long as it can diffusely reflect light, and may be, for example, a white-painted member or a member made of a white material. Specific examples of the material that diffuses and reflects light include barium sulfate and porous PTFE resin. The hemispherical inner surface 12h is formed in a hemispherical shape, thereby defining a hemispherical internal space 13h.

[0040] The hemispherical internal space 13h has a center 131h, an apex 132h, a bottom surface 133h, and an axis 134h. The center 131h is located in the middle of the sphere that includes the hemisphere of the hemispherical internal space 13h. The apex 132h is located vertically above (or vertically below) the center 131h. The axis 134h passes through the center 131h and the apex 132h. The bottom surface 133h includes the center 131h and is formed in a circular shape. The hemispherical casing 1h is open to the bottom surface 133h of the hemispherical internal space 13h and has an annular open end 15h. Hereinafter, the apex 132h of the upper hemispherical internal space 13h(u), defined by the hemispherical inner surface 12h(u) of the upper casing 1h(u), may be referred to as the zenith 132. The shape of the hemispherical internal space 13h does not have to be a perfect hemisphere as long as it does not have a fatal effect on the color measurement of the object S.

[0041] Here, the hemispherical casing 1h may be formed as a single unit. Alternatively, the hemispherical casing 1h may be divided into a plurality of sections around the axis. The material of the hemispherical casing 1h is not particularly limited and may be selected appropriately depending on the embodiment. For example, acrylic resin, stainless steel, etc. may be used for the hemispherical casing 1h. A material that is easy to process and can ensure strength is desirable for the material of the hemispherical casing 1h.

[0042] Two hemispherical casings 1h described above are arranged so that their centers 131h coincide with each other and their open ends 15h face each other, thereby forming a spherical casing 1. Specifically, the spherical casing 1 is formed by arranging an upper casing 1h(u) and a lower casing 1h(d) so that their centers 131h coincide with each other and their open ends 15h face each other.

[0043] Therefore, as illustrated in FIG. 3 and other figures, the casing 1 has a spherical outer surface 11, a spherical inner surface 12, and a spherical internal space 13. The spherical internal space 13 has a center 131, a zenith 132, and an axis 134. The center 131 is located in the middle of the spherical internal space 13. The zenith 132 is located vertically above the center 131. The axis 134 passes through the center 131 and the zenith 132. Note that the shape of the internal space 13 does not have to be a perfect sphere as long as it does not have a fatal impact on the color measurement of the object S. When performing color measurement, the object S is placed near the center 131 in the internal space 13.

[0044] So far, an example has been described in which the spherical casing 1 is configured from a hemispherical upper casing 1h(u) and a hemispherical lower casing 1h(d). However, it is not necessary to use the upper casing 1h(u) and the lower casing 1h(d) to configure the casing 1. The casing 1 may be divided into multiple parts around the axis, that is, divided into multiple parts by multiple planes passing through the axis 134. The lighting device L1 (main body B1) may simply include a casing 1 that defines a spherical internal space 13 and has an inner surface 12 made of a light-reflecting material.

[0045] As illustrated in FIG. 3 and other figures, the casing 1 (particularly the upper casing 1h(u)) includes a light receiving opening 14. The light receiving opening 14 is provided for observing an object S placed in the internal space 13. The light receiving opening 14 is an example of an "observation unit" in the present invention. In the example illustrated in FIGS. 1 to 3, the light receiving opening 14 is disposed at a position corresponding to the zenith 132 of the internal space 13. However, the position of the light receiving opening 14 is not particularly limited and may be set appropriately depending on the embodiment. For example, the light receiving opening 14 may be disposed at a distance from the zenith 132 in the circumferential direction along the inner surface 12. Specifically, to be suitable for measuring specular reflection, the light receiving opening 14 may be disposed so that the angle between the axis 134 and a line connecting the light receiving opening 14 and the center 131 is 20 degrees, 45 degrees, 60 degrees, or 85 degrees. Furthermore, for example, to suit the measurement of diffuse reflection, the light receiving port 14 may be arranged so that the angle between the line connecting the light receiving port 14 and the center 131 and the axis 134 is 45 degrees. Furthermore, for example, to suit the measurement of retroreflection, the light receiving port 14 may be arranged so that the angle between the line connecting the light receiving port 14 and the center 131 and the axis 134 is 5 degrees, 30 degrees, or 40 degrees.

[0046] In this embodiment, the light receiving opening 14 is configured to transmit light from the inner surface 12 to the outer surface 11. The configuration of the light receiving opening 14 is not particularly limited as long as it is capable of transmitting light, and may be determined appropriately depending on the embodiment. For example, the light receiving opening 14 may be made of a transparent material such as a resin material. Furthermore, for example, the light receiving opening 14 may be configured as a through hole that penetrates from the inner surface 12 to the outer surface 11. The through hole may be filled with a transparent material such as a resin material.

[0047] Furthermore, the light receiving opening 14 may be configured to be capable of being in an open state that transmits light and a closed state that blocks light transmission. The configuration for opening and closing the light receiving opening 14 is not particularly limited and may be determined appropriately depending on the embodiment. For example, a blocking member (not shown) such as a cap configured to be attachable to the light receiving opening 14 may be provided. By blocking the light receiving opening 14 with this blocking member, the light receiving opening 14 may be in a closed state. On the other hand, by removing this blocking member from the light receiving opening 14, the light receiving opening 14 may be in an open state.

[0048] The outer surface 11 of the casing 1 described above is formed in a spherical shape, similar to the internal space 13. However, the shape of the outer surface 11 of the casing 1 is not limited to this example, and may be selected appropriately depending on the embodiment.

[0049] (Light Source, Sample Stage, and Support) Next, the light source 3 will be described. As shown in FIG. 3 , the light source 3 is arranged to irradiate the internal space 13 with light. In this embodiment, the light source 3 is attached to a support 5. The support 5 is a member that supports the sample stage 4 on which the object S is placed, and is configured, for example, to have a long, thin rod shape extending along the longitudinal direction (axial direction), with its axis coinciding with an axis 134 passing through the center 131 of the spherical internal space 13. As exemplified in FIG. 3 , the support 5 may be configured so that its height is adjustable so that the object S placed on the sample stage 4 is positioned near the center 131 of the internal space 13.

[0050] (Plate) The plate 2 is disposed in the internal space 13, facing the inner surface 12. In particular, as illustrated in Fig. 3, in the lighting device L1 (main body B1), the plate 2 includes an upper plate 2h(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). As will be described in detail later, the upper plate 2h(u) is configured to include a plurality of thin plates 210, each facing the hemispherical inner surface 12h(u) of the upper casing 1h(u) and arranged so as not to overlap one another.

[0051] 3, the upper plate 2h(u) and the lower plate 2h(d) are in contact with each other on the equatorial plane (a plane that passes through the center 131 and is perpendicular to the axis 134). That is, in the plate 2, the portion that extends from the equatorial plane toward the side where the light receiving port 14 is located relative to the equatorial plane is the upper plate 2h(u), and the portion that extends from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving port 14 is located is the lower plate 2h(d). For example, the upper plate 2h(u) and the lower plate 2h(d) have the same length of contact with the equatorial plane (the length of the arc at the equatorial plane), and the upper plate 2h(u) and the lower plate 2h(d) are arranged so that the surface of the upper plate 2h(u) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2, the upper plate 2h(u) and the lower plate 2h(d) may be integrally formed, i.e., may be connected to each other. For example, by rotating the upper plate 2h(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0052] In the following description, when the upper plate 2h(u) and the lower plate 2h(d) are referred to collectively without distinction, they will simply be referred to as "plate 2." The plate 2 covers a portion of the inner surface 12 when viewed from the center 131, and is configured so that its position around the axis 134 can be adjusted. The plate 2 has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131. First, the upper plate 2h(u) will be described below using Figure 4.

[0053] (Upper Plate) FIG. 4 is a diagram illustrating a schematic example of the relationship between the upper plate 2h(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2h(u) are arranged in the upper plate 2h(u). The upper plate 2h(u) includes multiple thin plates 210, and in the example shown in FIG. 4, they include thin plate 210(1) and thin plate 210(2). In the following description, when the multiple thin plates 210 are referred to collectively without being distinguished from one another, they are simply referred to as "thin plates 210." When distinguishing between the multiple thin plates 210, they are distinguished from one another by adding a designation such as "(1)," "(2)," ..., "(n)" (where "n" is a natural number greater than or equal to 2).

[0054] The surface of the thin plate 210 facing the center 131 (second surface 22h(u)) is made of a light-absorbing material. The light-absorbing material is not particularly limited as long as it is capable of absorbing light, and may be, for example, a black-painted material or a material made of black material. Specific examples of light-absorbing materials include carbon black and non-reflective raised fabric. On the other hand, the configuration of the surface of the thin plate 210 facing the inner surface 12 (first surface 21h(u)) is not particularly limited, and may be selected appropriately depending on the embodiment. The first surface 21h(u) of the thin plate 210 may be made of a material that diffuses and reflects light, similar to the inner surface 12 (hemispherical inner surface 12h). Alternatively, the first surface 21h(u) of the thin plate 210 may be made of another material.

[0055] The material of the thin plate 210 is not particularly limited and may be appropriately selected depending on the embodiment. For example, acrylic resin, stainless steel, etc. may be used for the thin plate 210. It is desirable that the material of the thin plate 210 be a material that is easy to process and can ensure strength.

[0056] The left side of Fig. 4 shows an example of how the thin plates 210(1) and 210(2) are arranged in the upper plate 2h(u). The right side of Fig. 4 shows an example of the arrangement of the thin plates 210(1) and 210(2) after the thin plate 210(1) has been moved around the axis 134 and rearranged from the arrangement of the thin plates 210(1) and 210(2) illustrated on the left side of Fig. 4. That is, the left side of Fig. 4 shows an example of the arrangement of the thin plates 210(1) and 210(2) in the upper plate 2h(u) before the rearrangement. The right side of Fig. 4 shows an example of the arrangement of the thin plates 210(1) and 210(2) after the rearrangement.

[0057] As shown in Fig. 4, in this embodiment, the hemispherical inner surface 12h(u) is virtually equally divided into a plurality of two-right-angled spherical triangular regions A1 around an axis 134 on a plane passing through the zenith 132 and the center 131h. In the example of Fig. 4, the hemispherical inner surface 12h(u) is equally divided into 12 regions, each with an apex angle of 30 degrees. However, the number of divisions is not limited to this example and may be determined appropriately depending on the embodiment.

[0058] The thin plates 210(1) and 210(2) are arranged in the upper plate member 2h(u) so as not to overlap each other. In particular, as illustrated on the left side of the page in Fig. 4 , the thin plates 210(1) and 210(2) before the rearrangement are arranged so as not to overlap each other, so as to face only one area A1 of a plurality of areas A1 (two areas in the example shown in Fig. 4 ). In other words, the multiple thin plates 210 included in the upper plate member 2h(u) are arranged in the upper plate member 2h(u) so as not to overlap each other, so as to face only one area A1 of a plurality of areas A1 that are virtually provided on the hemispherical inner surface 12h(u) and have the same area.

[0059] As illustrated on the right side of Figure 4, by moving and rearranging at least one thin plate 210 (thin plate 210(1) in the example of Figure 4) among the multiple thin plates 210 included in the upper plate material 2h(u) around the axis 134, it is possible to form one curved plate as follows. That is, it is possible to form one curved plate having a shape corresponding to an imaginary two-right-angled spherical triangular region A1 that equally divides the inner surface 12. The right side of Figure 4 shows an example in which a curved plate having a two-right-angled spherical triangular shape corresponding to region A1 is formed by moving and rearranging the thin plate 210(1) around the axis 134 by an angle smaller than 360 degrees, using the thin plates 210(1) and 210(2). Specifically, an example is shown in which a thin plate 210(1) (thin plate 210(1) before rearrangement) illustrated on the left side of the page in Figure 4 is moved 30 degrees clockwise around axis 134 to form a curved plate with a two-right-angled spherical triangle shape corresponding to area A1.

[0060] As explained using FIG. 4 , the multiple thin plates 210 included in the upper plate member 2h(u) are obtained, for example, by dividing a single curved plate having two right-angled spherical triangular shapes corresponding to region A1. Specifically, the multiple thin plates 210 included in the upper plate member 2h(u) are obtained by dividing the single curved plate having two right-angled spherical triangular shapes corresponding to region A1 along one or more planes parallel to the equatorial plane (a plane passing through the center 131 and perpendicular to the axis 134). The multiple thin plates 210 thus obtained are then arranged so that each plate faces only one of the multiple regions A1 and does not overlap with each other, thereby forming the upper plate member 2h(u). That is, the thin plates 210(1) and 210(2) illustrated in FIG. 4 are obtained by dividing the single curved plate having two right-angled spherical triangular shapes corresponding to region A1 along one plane parallel to the equatorial plane. The thin plate 210(1) and thin plate 210(2) obtained in this manner are arranged so that they do not overlap each other and each faces only one of the multiple areas A1, thereby forming the upper plate material 2h(u) illustrated on the left side of the paper in Figure 4.

[0061] As described above with reference to FIGS. 1 to 4 , the lighting device L1 includes a casing 1, a plate 2, and a light source 3. The casing 1 has an outer surface 11, an inner surface 12, a spherical internal space 13, and a light receiving port 14 (observation portion). The inner surface 12 defines the internal space 13 and is made of a material that reflects light. The internal space 13 has a center 131, a zenith 132, and an axis 134, with the axis 134 passing through the center 131 and the zenith 132. The light receiving port 14 is provided for observing an object S placed in the internal space 13, and is located at a position corresponding to the zenith 132 or at a position spaced apart from the zenith 132 in the circumferential direction along the inner surface 12.

[0062] The light source 3 is arranged to irradiate light into the internal space 13. The plate 2 is arranged in the internal space 13 facing the inner surface 12, covers a part of the inner surface 12 when viewed from the center 131, and is configured so that its position around the axis 134 is adjustable. The plate 2 has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131.

[0063] The upper plate 2h(u) (upper portion), which is the portion of the plate 2 on the side where the light receiving port 14 is located relative to the equatorial plane, includes a plurality of thin plates 210 that are arranged so as not to overlap each other. The plurality of thin plates 210 are configured so that their second surfaces 22h(u) absorb light.

[0064] Of the multiple thin plates 210 arranged so as not to overlap one another on the upper plate member 2h(u), by moving and rearranging at least one thin plate 210 around the axis 134 by an angle smaller than 360 degrees, it is possible to form the following curved plate using all of the multiple thin plates 210. That is, by rearranging at least one thin plate 210, it is possible to form one curved plate in the shape of two right-angled spherical triangles using all of the multiple thin plates 210, which corresponds to "area A1 of the inner surface 12 connecting three points consisting of a point corresponding to the zenith 132 of the inner surface 12 and two points on the intersection line between the equatorial plane and the inner surface 12."

[0065] In this configuration, the multiple thin plates 210 have second surfaces 22h(u) configured to absorb light, and are arranged on the upper plate member 2h(u) so as not to overlap one another. By moving the position of at least one of the multiple thin plates 210 around the axis 134 by an angle smaller than 360 degrees and rearranging it, all of the multiple thin plates 210 can form a single "curved plate in the shape of two right-angled spherical triangles corresponding to region A1." In other words, the area of ​​each of the multiple thin plates 210 included in the upper plate member 2h(u) and having second surfaces 22h(u) configured to absorb light is smaller than the area of ​​the "curved plate in the shape of two right-angled spherical triangles corresponding to region A1." Furthermore, when the upper plate material 2h(u) and the "curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1" are arranged so that one side (for example, the bottom side) of each overlaps, the area of ​​the overlapping portion between the two is smaller than the area of ​​the "curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1".

[0066] Therefore, compared to conventional light traps configured to absorb light from the entire second surface (the surface facing the center 131) of the "curved plate in the shape of a double right-angled spherical triangle corresponding to area A1," the upper plate 2h(u) makes it easier for diffused light from the azimuth angle corresponding to the "curved plate in the shape of a double right-angled spherical triangle corresponding to area A1" to reach the object S, making it less likely that a shadow will be cast on the object S. Therefore, the lighting device L1 can prevent a decrease in measurement accuracy due to the generation of a shadow, and achieve high-precision measurements.

[0067] The plurality of thin plates 210 in the upper plate member 2h(u) may be connected to one another via a frame, etc. The plurality of thin plates 210 in the upper plate member 2h(u) may be connected to one another via "white plates whose first and second surfaces are configured to reflect light" or "transparent plates that transmit light."

[0068] In the upper plate 2h(u) illustrated on the left side of FIG. 4 , the thin plate 210(1) and the thin plate 210(2) are connected to each other via a frame. That is, in the upper plate 2h(u) illustrated on the left side of FIG. 4 , no components such as thin plates are arranged in either the region 211(1) or the region 211(2). However, a "white plate having first and second surfaces configured to reflect light" or a "transparent plate that transmits light" may be arranged in the region 211(1) and the region 211(2) on the left side of FIG. 4 . That is, the thin plate 210(1) and the thin plate 210(2) may be connected to each other via a "white plate having first and second surfaces configured to reflect light" or a "transparent plate that transmits light" arranged in the region 211(1) and the region 211(2) on the left side of FIG. 4 .

[0069] (Lower Plate) As illustrated in FIG. 3 , in the lighting device L1 (main body B1), the plate 2 includes a lower plate 2h(d) that faces the hemispherical inner surface 12h(d) of the lower casing 1h(d). That is, the plate 2 includes a lower plate 2h(d) (lower portion) that extends toward the side opposite the side where the light receiving port 14 is located with respect to the equatorial plane. As described above, the upper plate 2h(u) (particularly, the thin plate 210(2)) and the lower plate 2h(d) have the same length tangent to the equatorial plane (the length of the arc at the equatorial plane). The thin plate 210(2) and the lower plate 2h(d) are arranged so that the surface of the thin plate 210(2) that faces the equatorial plane faces the surface of the lower plate 2h(d) that faces the equatorial plane.

[0070] The lower plate member 2h(d) has a shape corresponding to (facing) at least a portion of one of a plurality of equal-area regions A1 virtually defined on the hemispherical inner surface 12h(d) of the lower casing 1h(d). For example, the lower plate member 2h(d) is configured as a belt-shaped (approximately trapezoidal) plate member (curved plate) formed by removing two right-angled spherical triangular curved plates within a predetermined range from the apex angle from a two-right-angled spherical triangular curved plate corresponding to (facing) the entire region A1. That is, the lower plate member 2h(d) is configured as a belt-shaped curved plate formed by removing two right-angled spherical triangular curved plates below a predetermined longitude (a predetermined plane parallel to the equatorial plane) from a two-right-angled spherical triangular curved plate corresponding to (facing) the entire region A1.

[0071] However, it is not essential that the lower plate member 2h(d) be configured as a strip-shaped plate member. The lower plate member 2h(d) may be a plate member (curved plate) with a shape of two right-angled spherical triangles corresponding to the entire region A1. The lower plate member 2h(d) only needs to have a shape (area) that can absorb the "specular reflection component that reaches the object S from the inner surface 12 (particularly the hemispherical inner surface 12h(d)), reflects off the object S, and reaches the light receiving port 14 (observation unit)" as illustrated in FIG. 3. The shape of the lower plate member 2h(d) may be appropriately selected depending on the embodiment. The lower plate member 2h(d) may be configured so that the latitude of the lower end of the lower plate member 2h(d) extending along the hemispherical inner surface 12h(d) toward the vertex 132h(d) (the angle between the axis 134 and the straight line from the lower end to the center 131) can be adjusted depending on the shape and size of the object S.

[0072] The surface (second surface 22h(d)) of the lower plate 2h(d) facing the center 131 is made of a light-absorbing material. The light-absorbing material is not particularly limited as long as it is capable of absorbing light, and may be, for example, a black-painted material or a material made of black material. Specific examples of light-absorbing materials include carbon black and non-reflective raised fabric. On the other hand, the configuration of the surface (first surface 21h(d)) of the lower plate 2h(d) facing the inner surface 12 is not particularly limited and may be selected appropriately depending on the embodiment. The first surface 21h(d) of the lower plate 2h(d) may be made of a material that diffuses and reflects light, similar to the inner surface 12 (hemispherical inner surface 12h). Alternatively, the first surface 21h(d) of the lower plate 2h(d) may be made of another material.

[0073] In this configuration, the second surface 22h(d) of the lower plate 2h(d) is configured to absorb light. Therefore, as illustrated in Fig. 3, the second surface 22h(d) of the lower plate 2h(d) can remove the specular reflection component, even when the target object S has a convex shape. Therefore, the illumination device L1 can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurements.

[0074] As with the thin plate 210, the material of the lower plate 2h(d) is not particularly limited and may be selected appropriately depending on the embodiment. For example, acrylic resin, stainless steel, etc. may be used for the lower plate 2h(d). A material that is easy to process and can ensure strength is desirable for the material of the lower plate 2h(d).

[0075] (Controller) Next, the functions of the controller 100 will be described in detail. The controller 100 controls the operation of each part of the lighting device L1 (particularly the board 2), and performs color measurement of the object S based on measurement data of each reflection component of the object S measured by the lighting device L1. The controller 100 is realized by a general-purpose or dedicated computer, and includes at least the following functional units, exemplified in FIG. 5, as functional components realized by the CPU, memory, etc. That is, the controller 100 includes at least a position control unit 110, a drive unit 120, a data acquisition unit 130, and a storage unit 140.

[0076] FIG. 5 is a diagram illustrating a typical software configuration of the controller 100. The position control unit 110 controls the position of the plate 2 (position around the axis 134). That is, the position control unit 110 controls the position of the plate 2 so that the plate 2 moves clockwise (or counterclockwise) around the axis 134 by a predetermined angle (e.g., 30 degrees) in a predetermined cycle. The position control unit 110, for example, determines the current position (current cycle) of the plate 2 and determines the position (target position) of the plate 2 in the next cycle. The target position is a position obtained by moving the plate 2 clockwise (or counterclockwise) around the axis 134 by a predetermined angle from the current position of the plate 2. The position control unit 110 notifies the drive unit 120 and the data acquisition unit 130 of the position of the plate 2 in each cycle (e.g., the current position and the target position in the next cycle).

[0077] The driving unit 120 changes the position of the plate 2 (position around the axis 134) according to the position of the plate 2 in each cycle (particularly, the target position in the next cycle) notified by the position control unit 110. That is, the driving unit 120 changes the position of the plate 2 so that the plate 2 reaches the target position in the next cycle. The driving unit 120 may be realized by a servo motor or the like.

[0078] The data acquisition unit 130 acquires, from a sensor or the like arranged in the light receiving port 14 (observation unit), "various measurement data about the object S" measured by the sensor or the like at the time when the plate 2 reaches the "position of the plate 2 in each cycle" notified by the position control unit 110. In other words, the data acquisition unit 130 acquires the measurement data about the object S in each cycle. The data acquisition unit 130 notifies the data storage unit 150 of the acquired measurement data for each cycle together with the "position of the plate 2 in each cycle" notified by the position control unit 110.

[0079] The data storage unit 150 associates the measurement data for each period acquired by the data acquisition unit 130 with the position of the board 2 for each period and stores the data in the memory unit 140. That is, the data storage unit 150 stores "measurement data 141 for each position of the board 2" in the memory unit 140. By analyzing this "measurement data 141 for each position of the board 2", it is possible to perform color measurement of the object S.

[0080] §2 Method of Use Next, a method of use of the lighting device L1 according to this embodiment will be described using Fig. 6. Fig. 6 is a diagram showing the movement of the plate 2, the position of which (position around the axis 134) is controlled by the controller 100. In particular, Fig. 6 schematically illustrates the relationship between the upper plate 2h(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and shows how the position of the upper plate 2h(u) moves as viewed from the center 131.

[0081] First, in preparation for color measurement, the user places the measurement object S (hereinafter abbreviated as "object S") near the center 131 of the internal space 13 of the casing 1. Next, the user turns on the light source 3, causing the light source 3 to irradiate light into the internal space 13. This places the internal space 13 in a state where light is diffusely reflected by the inner surface 12 of the casing 1. Then, the user positions the optical sensor on the outer surface 11 of the casing 1, aligning it with the light receiving opening 14, and begins measuring each reflection component of the object S placed in the internal space 13 with the optical sensor.

[0082] The type of object S may not be particularly limited and may be selected appropriately depending on the embodiment. The object S may have a flat and uniform sample surface, or may be, for example, uneven building materials (e.g., tile, stone, etc.), food or ingredients (e.g., bread, chocolate, etc.), plants, living things (e.g., insects, etc.). The type of optical sensor may not be particularly limited as long as it is capable of measuring the color of the object S, and may be selected appropriately depending on the embodiment. For example, a color luminance meter, a digital camera, a charge-coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS), etc. may be used as the optical sensor.

[0083] For example, in the 0th period (i.e., the start point), the plate 2 (upper plate 2h(u)) is in the position shown on the left side of the paper in FIG. 6 . Specifically, at the start point, the thin plate 210(2) of the upper plate 2h(u) is in the 6 o'clock position (lower side of the paper). The position control unit 110 determines that "in the 0th period, the thin plate 210(2) is in the 6 o'clock position" and notifies the data acquisition unit 130 that "in the 0th period, the thin plate 210(2) is in the 6 o'clock position." In addition, the optical sensor measures each reflection component of the object S in the 0th period, and the measurement results, i.e., measurement data, are sent to the data acquisition unit 130. The data storage unit 150 associates the "measurement data at the 0th period" acquired by the data acquisition unit 130 with the "position of the plate material 2 (upper plate material 2h(u)) at the 0th period" and stores it in the memory unit 140 as "measurement data 141 for each position of the plate material 2."

[0084] Furthermore, the position control unit 110 determines the position (target position) of the plate 2 (upper plate 2h(u)) in the next cycle (i.e., the first cycle), and notifies the drive unit 120 and the data acquisition unit 130 of the determined "target position of the plate 2 in the first cycle." In the example of Fig. 6, the position moved 30 degrees counterclockwise around the axis 134 from the plate 2 in the 0th cycle is the "target position of the plate 2 in the first cycle."

[0085] The driving unit 120 changes the position of the plate 2 in accordance with the "target position of the plate 2 in the first period" notified by the position control unit 110. As a result, in the first period, the plate 2 (upper plate 2h(u)) is at a position moved 30 degrees counterclockwise around the axis 134 from the plate 2 in the 0th period. The gray area in the upper plate 2h(u) in the first period indicates the area of ​​the inner surface 12 (hemispherical inner surface 12h(u)) facing the thin plate 210(1) or the thin plate 210(2) up to that point (that period).

[0086] Then, the optical sensor measures each reflection component of the object S in the first period, and the measurement results, that is, measurement data, are sent to the data acquisition unit 130. The data storage unit 150 associates the "measurement data in the first period" acquired by the data acquisition unit 130 with the "position of the plate 2 (upper plate 2h(u)) in the first period," and stores this in the memory unit 140 as "measurement data 141 for each position of the plate 2."

[0087] In this way, the measurement data for each period is associated with the position of the plate 2 for each period and stored in the storage unit 140 as "measurement data 141 for each position of the plate 2." Then, when all of the inner surfaces 12 (hemispherical inner surfaces 12h(u)) face at least one of the thin plates 210(1) and 210(2) at least once, acquisition of the measurement data necessary for colorimetry of the object S is completed. In the example shown in FIG. 6 , the measurement data for each period from the 0th period to the 11th period is associated with the position of the plate 2 for each period and stored in the storage unit 140 as "measurement data 141 for each position of the plate 2," thereby completing acquisition of the measurement data necessary for colorimetry of the object S.

[0088] §3 Features As described above, in the lighting device L1 according to this embodiment, the plurality of thin plates 210 included in the upper plate member 2h(u) are configured so that the second surface 22h(u) absorbs light. Among the plurality of thin plates 210 arranged so as not to overlap one another in the upper plate member 2h(u), at least one thin plate 210 can be moved around the axis 134 by an angle smaller than 360 degrees and rearranged to form the following curved plate using all of the plurality of thin plates 210. That is, a single "curved plate in the shape of two right-angled spherical triangles corresponding to region A1" can be formed. In the upper plate member 2h(u), the plurality of thin plates 210 are arranged so as not to overlap one another, for example, so as to face only one of the plurality of regions A1.

[0089] In other words, in the illumination device L1, the area of ​​each of the plurality of thin plates 210 included in the upper plate member 2h(u) and configured with the second surface 22h(u) to absorb light is smaller than the area of ​​the "two right-angled spherical triangular curved plate corresponding to region A1." Therefore, compared to a conventional light trap configured to absorb light over the entire second surface (the surface facing toward the center 131) of the "two right-angled spherical triangular curved plate corresponding to region A1," the upper plate member 2h(u) allows diffused light from the azimuthal angle corresponding to the "two right-angled spherical triangular curved plate corresponding to region A1" to more easily reach the target S, and shadows are less likely to be cast on the target S. Therefore, the illumination device L1 can prevent a decrease in measurement accuracy due to the generation of shadows, thereby achieving high-precision measurements.

[0090] Furthermore, in the illumination device L1 according to this embodiment, the plate 2 includes a lower plate 2h(d), which is a portion extending on the side opposite the side where the light receiving port 14 is located with respect to the equatorial plane, and the second surface 22h(d) of the lower plate 2h(d) is made of a light-absorbing material. Therefore, the second surface 22h(d) of the lower plate 2h(d) can remove the specular reflection component, even when the target object S has a convex shape, for example. Therefore, the illumination device L1 can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurements.

[0091] As is clear from the above description, when focusing only on the viewpoint of suppressing the occurrence of shadows to prevent a decrease in measurement accuracy, it is not essential that the illumination device L1 according to this embodiment include the lower plate 2h(d) as the light trap (plate 2). In other words, to suppress the occurrence of shadows, the illumination device L1 only needs to include the upper plate 2h(u) as the light trap (plate 2). By including the upper plate 2h(u) as the light trap (plate 2), the illumination device L1 can suppress the occurrence of shadows, prevent a decrease in measurement accuracy due to the occurrence of shadows, and achieve high-precision measurements. Furthermore, by including the lower plate 2h(d) as the light trap (plate 2) in addition to the upper plate 2h(u), the illumination device L1 can further prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurements.

[0092] §4 Modifications Although one embodiment of the present invention has been described above, the above description is merely an example of the present invention in every respect. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention. For example, the following modifications are possible. Note that, in the following, the same reference numerals are used for components similar to those in the above embodiment, and descriptions of similar points to those in the above embodiment are omitted where appropriate. The following modifications can be combined as appropriate.

[0093] <4.1> Configuration of the Observation Unit In the above embodiment, the casing 1 includes the light receiving port 14 as an example of the observation unit. However, the configuration of the observation unit is not limited to this example and may be selected appropriately depending on the embodiment. For example, the observation unit may be configured by the optical sensor itself.

[0094] <4.2> Shape of the Upper Part of the Plate In the above embodiment, the upper part of the plate (upper plate 2h(u)) functioning as a light trap included thin plate 210(1) and thin plate 210(2). However, the upper part of the plate included in the lighting device according to this embodiment is not limited to this example and may be selected appropriately depending on the embodiment. The upper part of the plate included in the lighting device according to this embodiment may include multiple thin plates that can all form a "curved plate with a two-right-angled spherical triangular shape corresponding to region A1" by moving and repositioning at least one thin plate around axis 134 by an angle smaller than 360 degrees.

[0095] FIG. 7A is a diagram illustrating the configuration of the upper portion of the plate 2a (i.e., the upper plate 2ah(u)) for the lighting device L1a (main body B1a) according to a modified example. In other words, FIG. 7A is a diagram illustrating a schematic example of the relationship between the upper plate 2ah(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2ah(u) are arranged in the upper plate 2ah(u). The lighting device L1a is similar to the lighting device L1 except that it includes a plate 2a instead of the plate 2.

[0096] In the plate 2a, the upper plate 2ah(u) (particularly, the thin plate 210a(4) described later) and the lower plate 2h(d) are in contact with each other at the equatorial plane. That is, in the plate 2a, the portion extending from the equatorial plane toward the side where the light receiving port 14 is disposed relative to the equatorial plane is the upper plate 2ah(u), and the portion extending from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving port 14 is disposed relative to the equatorial plane is the lower plate 2h(d). For example, the upper plate 2ah(u) (particularly, the thin plate 210a(4) described later) and the lower plate 2h(d) have the same length of contact with the equatorial plane, and are arranged so that the surface of the thin plate 210a(4) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2a, the upper plate 2ah(u) and the lower plate 2h(d) may be integrally formed, i.e., they may be connected to each other. For example, by rotating the upper plate 2ah(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0097] The plate member 2a is disposed in the internal space 13 facing the inner surface 12. The plate member 2a includes an upper plate member 2ah(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate member 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate member 2h(d) included in the plate member 2a is similar to the lower plate member 2h(d) included in the plate member 2, and therefore will not be described further.

[0098] As illustrated in FIG. 7A , the upper plate 2ah(u) includes a plurality of thin plates 210a, and in the example shown in FIG. 7A , the thin plates 210a include a thin plate 210a(1), a thin plate 210a(2), a thin plate 210a(3), and a thin plate 210a(4). In the following description, when the plurality of thin plates 210a are collectively referred to without distinguishing between them, they will be simply referred to as "thin plates 210a." When distinguishing between the plurality of thin plates 210a, they will be distinguished by adding "(1)," "(2)," ..., "(n)," etc. The thin plates 210a included in the upper plate 2ah(u) are similar to the thin plates 210 included in the upper plate 2h(u) except for their number and arrangement positions. For example, the surface of the thin plate 210a facing the center 131 (second surface 22h(u)) is made of a light-absorbing material, similar to the second surface 22h(u) of the thin plate 210.

[0099] As illustrated in Fig. 7A, the thin plates 210a(1), 210a(2), 210a(3), and 210a(4) included in the upper plate member 2ah(u) are arranged so as not to overlap one another in the upper plate member 2ah(u). In particular, as illustrated in Fig. 7A, these four thin plates 210a are arranged so as not to overlap one another in the upper plate member 2ah(u) so as to face only one area A1 of a plurality of areas A1 (two areas in the example shown in Fig. 7A). In other words, the multiple thin plates 210a included in the upper plate member 2ah(u) are arranged so as not to overlap one another in the upper plate member 2ah(u) so as to face only one area A1 of a plurality of areas A1 virtually provided on the hemispherical inner surface 12h(u).

[0100] By moving and rearranging at least one of the thin plates 210a included in the upper plate member 2ah(u) by an angle smaller than 360 degrees around the axis 134, it is possible to form one "curved plate in the shape of two right-angled spherical triangles corresponding to the region A1." In the example shown in Figure 7A, by moving the thin plates 210a(1) and 210a(3) in the upper plate member 2ah(u) by 30 degrees clockwise around the axis 134, it is possible to form one curved plate in the shape of two right-angled spherical triangles corresponding to the region A1.

[0101] The plurality of thin plates 210a in the upper plate member 2ah(u) may be connected to each other via a frame, etc. Also, the plurality of thin plates 210a in the upper plate member 2ah(u) may be connected to each other via "white plates whose first and second surfaces are configured to reflect light" or "transparent plates that transmit light."

[0102] FIG. 7B is a diagram illustrating the configuration of the upper portion of the plate 2b (i.e., the upper plate 2bh(u)) for the lighting device L1b (main body B1b) according to a modified example. In other words, FIG. 7B is a diagram illustrating a schematic example of the relationship between the upper plate 2bh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2bh(u) are arranged in the upper plate 2bh(u). The lighting device L1b is similar to the lighting device L1 except that it includes a plate 2b instead of the plate 2.

[0103] In the plate 2b, the upper plate 2bh(u) (particularly, the thin plate 210b(3) described later) and the lower plate 2h(d) are in contact with each other at the equatorial plane. That is, in the plate 2b, the portion extending from the equatorial plane toward the side where the light receiving opening 14 is disposed relative to the equatorial plane is the upper plate 2bh(u), and the portion extending from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving opening 14 is disposed relative to the equatorial plane is the lower plate 2h(d). For example, the upper plate 2bh(u) (particularly, the thin plate 210b(3) described later) and the lower plate 2h(d) have the same length of contact with the equatorial plane, and are arranged so that the surface of the thin plate 210b(3) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2b, the upper plate 2bh(u) and the lower plate 2h(d) may be integrally formed, i.e., they may be connected to each other. For example, by rotating the upper plate 2bh(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0104] The plate member 2b is disposed in the internal space 13 facing the inner surface 12. The plate member 2b includes an upper plate member 2bh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate member 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate member 2h(d) included in the plate member 2b is similar to the lower plate member 2h(d) included in the plate member 2, and therefore will not be described further.

[0105] As illustrated in Fig. 7B, the upper plate 2bh(u) includes a plurality of thin plates 210b, and in the example shown in Fig. 7B, these include a thin plate 210b(1), a thin plate 210b(2), and a thin plate 210b(3). In the following description, when the plurality of thin plates 210b are collectively referred to without distinguishing between them, they will simply be referred to as "thin plates 210b." When distinguishing between the plurality of thin plates 210b, they will be distinguished by adding "(1)," "(2)," ..., "(n)," etc.

[0106] The thin plates 210b included in the upper plate member 2bh(u) are similar to the thin plates 210 included in the upper plate member 2h(u) except for their number and arrangement positions. For example, the surface of the thin plates 210b facing the center 131 (second surface 22h(u)) is made of a light-absorbing material, similar to the second surface 22h(u) of the thin plates 210. As illustrated in FIG. 7B , the thin plates 210b(1), 210b(2), and 210b(3) included in the upper plate member 2bh(u) are arranged so as not to overlap each other in the upper plate member 2bh(u). In particular, as illustrated in FIG. 7B , these three thin plates 210b are arranged so as not to overlap each other in the upper plate member 2bh(u) so as to face only one of the multiple (three in the example shown in FIG. 7B ) regions A1. That is, the multiple thin plates 210b included in the upper plate material 2bh(u) are arranged in the upper plate material 2bh(u) so as not to overlap each other and so as to face only one area A1 out of multiple areas A1 virtually provided on the hemispherical inner surface 12h(u).

[0107] By moving and rearranging at least one of the thin plates 210b included in the upper plate member 2bh(u) by an angle smaller than 360 degrees around the axis 134, it is possible to form one "curved plate in the shape of two right-angled spherical triangles corresponding to the region A1." In the example shown in Figure 7B, by moving the thin plate 210b(1) in the upper plate member 2bh(u) by 60 degrees clockwise and the thin plate 210b(2) by 30 degrees clockwise around the axis 134, it is possible to form one curved plate in the shape of two right-angled spherical triangles corresponding to the region A1.

[0108] The plurality of thin plates 210b in the upper plate member 2bh(u) may be connected to one another via a frame or the like. Also, the plurality of thin plates 210b in the upper plate member 2bh(u) may be connected to one another via "white plates whose first and second surfaces are configured to reflect light" or "transparent plates that transmit light."

[0109] FIG. 7C is a diagram illustrating the configuration of the upper portion of the plate 2c (i.e., the upper plate 2ch(u)) for a lighting device L1c (main body B1c) according to a modified example. In other words, FIG. 7C is a diagram illustrating a schematic example of the relationship between the upper plate 2ch(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2ch(u) are arranged in the upper plate 2ch(u). The lighting device L1c is similar to the lighting device L1 except that it includes a plate 2c instead of the plate 2.

[0110] In the plate 2c, the upper plate 2ch(u) (particularly, the thin plate 210c(3) described later) and the lower plate 2h(d) are in contact with each other at the equatorial plane. That is, in the plate 2c, the portion extending from the equatorial plane toward the side where the light receiving port 14 is disposed relative to the equatorial plane is the upper plate 2ch(u), and the portion extending from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving port 14 is disposed relative to the equatorial plane is the lower plate 2h(d). For example, the upper plate 2ch(u) (particularly, the thin plate 210c(3) described later) and the lower plate 2h(d) have the same length of contact with the equatorial plane, and are arranged so that the surface of the thin plate 210c(3) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2c, the upper plate 2ch(u) and the lower plate 2h(d) may be integrally formed, i.e., they may be connected to each other. For example, by rotating the upper plate 2ch(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0111] The plate member 2c is disposed in the internal space 13 facing the inner surface 12. The plate member 2c includes an upper plate member 2ch(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate member 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate member 2h(d) included in the plate member 2c is similar to the lower plate member 2h(d) included in the plate member 2, and therefore will not be described further.

[0112] As illustrated in Fig. 7C, the upper plate material 2ch(u) includes a plurality of thin plates 210c, and in the example shown in Fig. 7C, these include a thin plate 210c(1), a thin plate 210c(2), and a thin plate 210c(3). In the following description, when the plurality of thin plates 210c are collectively referred to without distinguishing between them, they will simply be referred to as "thin plates 210c." When distinguishing between the plurality of thin plates 210c, they will be distinguished by adding "(1)," "(2)," ..., "(n)," etc.

[0113] The thin plates 210c included in the upper plate 2ch(u) are similar to the thin plates 210 included in the upper plate 2h(u) except for their number and arrangement. For example, the surface of the thin plates 210c facing the center 131 (second surface 22h(u)) is made of a light-absorbing material, similar to the second surface 22h(u) of the thin plates 210. As illustrated in FIG. 7C , the thin plates 210c(1), 210c(2), and 210c(3) included in the upper plate 2ch(u) are arranged so as not to overlap each other in the upper plate 2ch(u). In particular, as illustrated in FIG. 7C , these three thin plates 210c are arranged so as not to overlap each other in the upper plate 2ch(u) so as to face only one of the multiple (two in the example shown in FIG. 7C ) regions A1. That is, the multiple thin plates 210c included in the upper plate material 2ch(u) are arranged in the upper plate material 2ch(u) so as not to overlap each other and so as to face only one of the multiple areas A1 virtually provided on the hemispherical inner surface 12h(u).

[0114] By moving and rearranging at least one of the thin plates 210c included in the upper plate member 2ch(u) by an angle smaller than 360 degrees around the axis 134, it is possible to form one "curved plate having a shape of two right-angled spherical triangles corresponding to the region A1." In the example shown in Figure 7C, by moving the thin plate 210c(2) in the upper plate member 2ch(u) by 30 degrees clockwise around the axis 134, it is possible to form one curved plate having a shape of two right-angled spherical triangles corresponding to the region A1.

[0115] The plurality of thin plates 210c in the upper plate member 2ch(u) may be connected to each other via a frame, etc. Also, the plurality of thin plates 210c in the upper plate member 2ch(u) may be connected to each other via "white plates whose first and second surfaces are configured to reflect light" or "transparent plates that transmit light."

[0116] FIG. 7D is a diagram illustrating the configuration of the upper portion of the plate 2d (i.e., the upper plate 2dh(u)) for a lighting device L1d (main body B1d) according to a modified example. In other words, FIG. 7D is a diagram illustrating a schematic example of the relationship between the upper plate 2dh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2dh(u) are arranged in the upper plate 2dh(u). The lighting device L1d is similar to the lighting device L1 except that it includes a plate 2d instead of the plate 2. The plate 2d is arranged facing the inner surface 12 in the internal space 13. The plate 2d includes an upper plate 2dh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate 2h(d) included in the plate 2d is similar to the lower plate 2h(d) included in the plate 2, and therefore will not be described further.

[0117] In the plate 2d, the upper plate 2dh(u) (particularly, the thin plate 210d(6) described later) and the lower plate 2h(d) are in contact with each other at the equatorial plane. That is, in the plate 2d, the portion extending from the equatorial plane toward the side where the light receiving port 14 is disposed relative to the equatorial plane is the upper plate 2dh(u), and the portion extending from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving port 14 is disposed relative to the equatorial plane is the lower plate 2h(d). For example, the upper plate 2dh(u) (particularly, the thin plate 210d(6) described later) and the lower plate 2h(d) have the same length of contact with the equatorial plane, and are arranged so that the surface of the thin plate 210d(6) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2d, the upper plate 2dh(u) and the lower plate 2h(d) may be integrally formed, i.e., they may be connected to each other. For example, by rotating the upper plate 2dh(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0118] As illustrated in Fig. 7D , the upper plate member 2dh(u) includes a plurality of thin plates 210d, including a thin plate 210d(1), a thin plate 210d(2), a thin plate 210d(3), a thin plate 210d(4), a thin plate 210d(5), and a thin plate 210d(6) in the example shown in Fig. 7D . In the following description, when the plurality of thin plates 210d are collectively referred to without distinguishing between them, they will be simply referred to as "thin plates 210d." When distinguishing between the plurality of thin plates 210d, they will be distinguished from one another by adding a suffix such as "(1)," "(2)," ..., "(n)," etc.

[0119] The thin plates 210d included in the upper plate member 2dh(u) are similar to the thin plates 210 included in the upper plate member 2h(u) except for their number and arrangement. For example, the surface of the thin plates 210d facing the center 131 (second surface 22h(u)) is made of a light-absorbing material, similar to the second surface 22h(u) of the thin plates 210. As illustrated in FIG. 7D , the thin plates 210d(1), 210d(2) to 210d(6) included in the upper plate member 2dh(u) are arranged so as not to overlap one another in the upper plate member 2dh(u). In particular, as illustrated in FIG. 7D , these six thin plates 210d are arranged so as not to overlap one another in the upper plate member 2dh(u) so as to face only one of the multiple (three in the example shown in FIG. 7D ) regions A1. That is, the multiple thin plates 210d included in the upper plate material 2dh(u) are arranged in the upper plate material 2dh(u) so as not to overlap each other and so as to face only one of the multiple areas A1 virtually provided on the hemispherical inner surface 12h(u).

[0120] By moving and rearranging at least one of the thin plates 210d included in the upper plate member 2dh(u) by an angle smaller than 360 degrees around the axis 134, it is possible to form one "curved plate in the shape of two right-angled spherical triangles corresponding to the region A1." In the example shown in Figure 7D, by moving the thin plates 210d(1) and 210d(4) in the upper plate member 2dh(u) by 60 degrees clockwise and the thin plates 210d(2) and 210d(5) by 30 degrees clockwise around the axis 134, it is possible to form one curved plate in the shape of two right-angled spherical triangles corresponding to the region A1.

[0121] The plurality of thin plates 210d in the upper plate member 2dh(u) may be connected to each other via a frame, etc. Also, the plurality of thin plates 210d in the upper plate member 2dh(u) may be connected to each other via "white plates whose first and second surfaces are configured to reflect light" or "transparent plates that transmit light."

[0122] The area of ​​each of the multiple thin plates (thin plates 210a to 210d) included in the upper portions (upper plate members 2ah(u) to 2dh(u)) of the plate members (plate members 2a to 2d) described using Figures 7A to 7D is less than half the area of ​​the "two right-angled spherical triangular curved plate corresponding to region A1." In this configuration, the upper portion can ensure more than twice the amount of diffused light reaching the target S from the azimuth angle corresponding to the "two right-angled spherical triangular curved plate corresponding to region A1," compared to a conventional light trap configured to absorb light over the entire second surface (the surface facing toward center 131) of the "two right-angled spherical triangular curved plate corresponding to region A1."

[0123] <4.3> Regarding the necessity of contact between thin plates In the above embodiment, the multiple thin plates (thin plates 210 to 210d) included in the upper portions (upper plate members 2h(u) to 2dh(u)) of the plate members (plate members 2 to 2d) were in contact with each other. For example, the thin plates 210(1) and 210(2) included in the upper plate member 2h(u) are arranged in the upper plate member 2h(u) so as not to overlap each other but to be in contact with each other. However, in the lighting device according to this embodiment, it is not essential that the multiple thin plates included in the upper portions of the plate members are in contact with each other. In the lighting device according to this embodiment, the multiple thin plates included in the upper portions of the plate members may be arranged in the upper portions of the plate members without being in contact with each other, that is, they may be arranged spaced apart from each other.

[0124] FIG. 7E is a diagram illustrating the configuration of the upper portion of the plate 2e (i.e., the upper plate 2eh(u)) of the lighting device L1e (main body B1e) according to a modified example. In other words, FIG. 7E is a diagram illustrating a schematic example of the relationship between the upper plate 2eh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210e included in the upper plate 2eh(u) are arranged in the upper plate 2eh(u). The lighting device L1e is similar to the lighting device L1 except that it includes a plate 2e instead of the plate 2. The plate 2e is arranged facing the inner surface 12 in the internal space 13. The plate 2e includes an upper plate 2eh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate 2h(d) included in the plate 2e is similar to the lower plate 2h(d) included in the plate 2, and therefore will not be described further.

[0125] In the plate 2e, the upper plate 2eh(u) (particularly, the thin plate 210e(2) described later) and the lower plate 2h(d) are in contact with each other at the equatorial plane. That is, in the plate 2e, the portion extending from the equatorial plane toward the side where the light receiving port 14 is disposed relative to the equatorial plane is the upper plate 2eh(u), and the portion extending from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving port 14 is disposed relative to the equatorial plane is the lower plate 2h(d). For example, the upper plate 2eh(u) (particularly, the thin plate 210e(2) described later) and the lower plate 2h(d) have the same length of contact with the equatorial plane, and are arranged so that the surface of the thin plate 210e(2) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2e, the upper plate 2eh(u) and the lower plate 2h(d) may be integrally formed, i.e., they may be connected to each other. For example, by rotating the upper plate 2eh(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0126] As illustrated in Fig. 7E, the upper plate 2eh(u) includes a plurality of thin plates 210e, and in the example shown in Fig. 7E, the upper plate 2eh(u) includes a thin plate 210e(1) and a thin plate 210e(2). In the following description, when the plurality of thin plates 210e are collectively referred to without distinguishing between them, they will be simply referred to as "thin plates 210e." When distinguishing between the plurality of thin plates 210e, they will be distinguished by adding "(1)," "(2)," ..., "(n)," etc.

[0127] The thin plate 210e included in the upper plate 2eh(u) is similar to the thin plate 210 included in the upper plate 2h(u) except for its position. For example, the surface of the thin plate 210e facing the center 131 (second surface 22h(u)) is made of a light-absorbing material, similar to the second surface 22h(u) of the thin plate 210. As illustrated in FIG. 7E, the thin plates 210e(1) and 210e(2) included in the upper plate 2eh(u) are arranged so as not to overlap each other in the upper plate 2eh(u). In particular, as illustrated in FIG. 7E, these two thin plates 210e are arranged so as not to overlap each other in the upper plate 2eh(u) so as to face only one region A1 of the multiple regions A1 (two in the example shown in FIG. 7E). That is, the multiple thin plates 210e included in the upper plate material 2eh(u) are arranged in the upper plate material 2eh(u) so as not to overlap each other and so as to face only one of the multiple areas A1 virtually provided on the hemispherical inner surface 12h(u).

[0128] By moving and rearranging at least one of the thin plates 210e included in the upper plate member 2eh(u) by an angle smaller than 360 degrees around the axis 134, it is possible to form a single "curved plate in the shape of two right-angled spherical triangles corresponding to the region A1." In the example shown in Figure 7E, by moving the thin plate 210e(1) in the upper plate member 2eh(u) by 180 degrees clockwise around the axis 134, it is possible to form a single curved plate in the shape of two right-angled spherical triangles corresponding to the region A1. The multiple thin plates 210e in the upper plate member 2eh(u) may be connected to each other via a frame or the like.

[0129] 7E, in the lighting device L1e, the upper portion (upper plate 2eh(u)) of the plate (plate 2e) includes a plurality of thin plates (thin plates 210e) that do not need to be in contact with each other. In this configuration, the upper portion can be configured to include the plurality of thin plates that are not in contact with each other.

[0130] <4.4> Number of Plates Up to this point, examples have been described in which each of the lighting devices L1 to L1e (main bodies B1 to B1e) includes one plate (specifically, each of the plates 2 to 2e). However, the lighting devices according to the above embodiments do not necessarily include one plate; they may include multiple plates. For example, the lighting devices according to the above embodiments may include two plates (a first plate and a second plate) arranged symmetrically about the center 131, similar to the lighting device according to Patent Document 1 (JP 2020-202119 A). Furthermore, the lighting devices according to the above embodiments may further include a third plate that is not arranged symmetrically about the center 131 with either of the first, second, or third plates. Furthermore, the lighting devices according to the above embodiments may include a fourth plate that is not arranged symmetrically about the center 131 with either of the first, second, or third plates. Of these multiple plate materials, the upper portion of at least one plate material (i.e., the upper plate material facing the hemispherical inner surface 12h(u) of the upper casing 1h(u)) may be any of the upper plate materials 2h(u) to 2eh(u) described above.

[0131] The above description can be summarized as follows. That is, in the lighting device according to each of the above embodiments, the upper portion of the plate material used as a light trap includes a plurality of thin plates. In the upper portion, the plurality of thin plates are arranged so as not to overlap each other and so as to face only one of two or more regions A1 (a part of one of the regions A1), thereby ensuring at least half of the diffused light from the azimuthal direction corresponding to each region A1. For example, the upper portion is formed by dividing a "single curved plate having a shape of two right-angled spherical triangles corresponding to region A1" into a plurality of thin plates by one or more planes parallel to the equator, and arranging each of the plurality of thin plates so as to face only one of the two or more regions A1. Therefore, the upper portion can ensure at least half of the diffused light from the azimuthal direction corresponding to each region A1.

[0132] For example, the upper plate members 2h(u) and 2eh(u) are formed by dividing a "single curved plate with a two-right-angled spherical triangular shape corresponding to region A1" into two upper and lower sections, each of which is arranged so that each of the two thin plates faces only one of the two regions A1. For example, the upper plate members 2ah(u) and 2ch(u) are formed by dividing a "single curved plate with a two-right-angled spherical triangular shape corresponding to region A1" into three or more upper and lower sections, each of which is arranged so that each of the three thin plates faces only one of the two regions A1. As a result, the upper portion of each of the above embodiments can efficiently block the entire hemispherical inner surface 12h(u) by simply rotating it around axis 134, just like a conventional light trap (a curved plate with a two-right-angled spherical triangular shape).

[0133] Here, when the number of times (number of periods) required to completely block the inner surface 12 using a conventional "single curved plate in the shape of a right-angled spherical triangle corresponding to region A1" is a multiple of two, the following relationship holds: That is, the number of times required to completely block the inner surface 12 using the upper portion of the "multiple thin plates obtained by dividing a single curved plate in the shape of a right-angled spherical triangle corresponding to region A1" is the same as the conventional number of periods. Furthermore, similar to the lighting device described in Patent Document 1, the lighting device according to each of the above embodiments may include multiple plate members (particularly, multiple upper portions). By including multiple upper portions, the lighting device according to each of the above embodiments can reduce the number of times (number of periods) required to completely block the hemispherical inner surface 12h(u) using the upper portions while preventing a decrease in diffusion.

[0134] Furthermore, if the number of times (number of periods) required to completely block the inner surface 12 using a conventional "single curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1" is a multiple of three, an upper portion may be used that includes multiple thin plates obtained by dividing "a single curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1" and arranged so that each thin plate faces only one of the three regions A1. An upper portion including multiple thin plates arranged so that each thin plate faces only one of the three regions A1 can ensure at least two-thirds of the diffused light from the azimuthal direction corresponding to each region A1. That is, in the lighting device according to each of the above embodiments, the upper portion of the plate material used as a light trap may include multiple thin plates obtained by dividing "a single curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1" and arranged so that each thin plate faces only one of the "n" regions A1. By adopting such a configuration (arrangement), the upper portion can ensure at least "(n-1) / n" diffused light from the azimuthal direction corresponding to each region A1.

[0135] <4.5> Regarding the Controller (Reduction of the Amount of Data to be Stored) The lighting device according to each of the above embodiments may include a controller 100A as described below using FIG. 8, instead of the controller 100. Note that the lighting device L1f according to the modified example described below has components that share actions and functions with the components of the lighting device L1 described using FIG. 1, etc. Such components are denoted by the same reference numerals as the corresponding components shown in FIG. 1, etc., and detailed description thereof will be omitted unless necessary.

[0136] Like controller 100, controller 100A is realized by a general-purpose or dedicated computer, and includes at least the following functional units illustrated in Fig. 8 as functional components realized by its CPU, memory, etc. That is, like controller 100, controller 100A includes at least a position control unit 110, a drive unit 120, a data acquisition unit 130, and a storage unit 140, and further includes a data extraction unit 160 (extraction unit) and a data update unit 170 (storage unit).

[0137] FIG. 8 is a diagram illustrating an example of the software configuration of a controller 100A included in a lighting device L1f according to a modified example. Similar to the position control unit 110 included in the controller 100, the position control unit 110 included in the controller 100 controls the position (position around the axis 134) of the plate (plates 2 to 2e) in each cycle. For ease of understanding, the following description will be given assuming that the plate is "plate 2." Similar to the drive unit 120 included in the controller 100, the drive unit 120 included in the controller 100 changes the position (position around the axis 134) of the plate 2 in each cycle according to the target position for each cycle notified by the position control unit 110. Similar to the data acquisition unit 130 included in the controller 100, the data acquisition unit 130 included in the controller 100 acquires measurement data for each cycle. The data acquisition unit 130 included in the controller 100A notifies the data extraction unit 160 of the acquired “measurement data for each cycle” together with the “position (target position) of the plate material 2 in each cycle” notified by the position control unit 110.

[0138] The storage unit 140 stores in advance "darkest data (e.g., data indicating solid black)" as the initial value of the brightest measurement data 142, and "brightest data (e.g., data indicating solid white)" as the initial value of the darkest measurement data 143. When the data extraction unit 160 is notified of "measurement data of a certain period C(x)" and "the position of the plate material 2 in the certain period C(x)" from the data acquisition unit 130, the data extraction unit 160 executes the following process. That is, the data extraction unit 160 first refers to the storage unit 140 and acquires the brightest measurement data 142 and the darkest measurement data 143. Then, the data extraction unit 160 compares the "measurement data of a certain period C(x)" notified by the data acquisition unit 130 with each of the brightest measurement data 142 and the darkest measurement data 143. The data extraction unit 160 determines whether the "measurement data of a certain period C(x)" is "brighter" than the "brightest measurement data 142." Furthermore, the data extraction unit 160 determines whether the "measurement data of a certain cycle C(x)" is "darker" than the "darkest measurement data 143." For example, the data extraction unit 160 may make the above-described determination using the "brightness (luminosity), luminance, light amount, etc." of each of the "measurement data of a certain cycle C(x)," "the brightest measurement data 142," and "the darkest measurement data 143."

[0139] When the data extraction unit 160 determines that the "measurement data of a certain period C(x)" is "brighter" than the "brightest measurement data 142," it notifies the data update unit 170 of the determination result, the "measurement data of a certain period C(x)," and the "position of the plate 2 in the certain period C(x)." Furthermore, when the data extraction unit 160 determines that the "measurement data of a certain period C(x)" is "darker" than the "darkest measurement data 143," it notifies the data update unit 170 of the determination result, the "measurement data of a certain period C(x)," and the "position of the plate 2 in the certain period C(x)."

[0140] The data updating unit 170 updates at least one of the "brightest measurement data 142" and the "darkest measurement data 143" stored in the storage unit 140 in accordance with the notification from the data extracting unit 160. That is, when the data updating unit 170 obtains a determination result that the "measurement data of a certain cycle C(x)" is brighter than the "brightest measurement data 142," the data updating unit 170 updates the "brightest measurement data 142" stored in the storage unit 140 with the "measurement data of a certain cycle C(x)." Furthermore, when the data updating unit 170 obtains a determination result that the "measurement data of a certain cycle C(x)" is darker than the "darkest measurement data 143," the data updating unit 170 updates the "darkest measurement data 143" stored in the storage unit 140 with the "measurement data of a certain cycle C(x)."

[0141] When all of the inner surfaces 12 (hemispherical inner surfaces 12h(u)) have faced one of the multiple thin plates (thin plates 210) included in the upper portion (upper plate 2h(u)) of the plate 2 at least once, acquisition of the measurement data necessary for color measurement of the object S is completed. At the point when acquisition of the measurement data is completed, only the "brightest measurement data 142" and the "darkest measurement data 143" are stored in the memory unit 140. By analyzing this "brightest measurement data 142" and "darkest measurement data 143," color measurement of the object S can be performed.

[0142] As described above, the lighting device L1f includes a data extraction unit 160 (extraction unit) and a data update unit 170 (storage unit). The data extraction unit 160 extracts, from the measurement data for each cycle, measurement data in which the object S is observed in the brightest state and measurement data in which the object S is observed in the darkest state. Each of the measurement data for each cycle is measurement data indicative of the object S observed at the light receiving port 14 (observation unit) while the plate (plates 2 to 2e) is moved around the axis 134. The data update unit 170 stores the "measurement data in which the object S is observed in the brightest state" and the "measurement data in which the object S is observed in the darkest state" extracted by the data extraction unit 160 as observation results of the object S.

[0143] In this configuration, the measurement data in which the object S is observed in the brightest state and the measurement data in which the object S is observed in the darkest state are extracted from the multiple measurement data, and these two measurement data are saved as the observation results of the object S. Therefore, compared to saving all of the multiple measurement data as the observation results of the object S, the amount of data to be saved can be reduced, and the amount of measurement data saved as the observation results of the object S can be kept constant. This is particularly effective when increasing the number of measurements or taking measurements at high speeds, and by adopting this configuration, for example, it becomes easy to measure an object underwater while suppressing specular reflection from a rippling water surface.

[0144] For example, as described above, in the controller 100 that stores the measurement data for each cycle in the memory unit 140 in association with the position of the plate 2 for each cycle, the following measurement data is stored in the memory unit 140 to perform color measurement of the object S. That is, the "measurement data for each cycle associated with the position of the plate 2 for each cycle" is stored in the memory unit 140 for the number of cycles required for "all of the inner surfaces 12 to face any one of the plurality of thin plates 210 at least once." Therefore, if the number of cycles required for "all of the inner surfaces 12 to face any one of the plurality of thin plates 210 at least once" increases, the amount of data stored in the memory unit 140 will become enormous.

[0145] In contrast, in the controller 100A, only the following data is stored in the memory unit 140 in order to perform color measurement of the object S, regardless of the number of cycles required for "all of the inner surfaces 12 to face any of the plurality of thin plates 210 at least once." That is, only the "brightest measurement data 142 (measurement data in which the object S is observed in the brightest state)" and the "darkest measurement data 143 (measurement data in which the object S is observed in the darkest state)" are stored in the memory unit 140.

[0146] (Correction by Prior Measurement of Mockup) The lighting device according to each of the above embodiments may include a controller 100B as described below with reference to FIG. 9, instead of the controller 100 or the controller 100A. Note that the lighting device L1g according to the modified example described below has components that share actions and functions with the components of the lighting device L1 described with reference to FIG. 1, etc. Such components are denoted by the same reference numerals as the corresponding components shown in FIG. 1, etc., and detailed description thereof will be omitted unless necessary.

[0147] Like controller 100, controller 100B is realized by a general-purpose or dedicated computer, and includes at least the following functional units exemplified in Fig. 9 as functional components realized by its CPU, memory, etc. That is, like controller 100, controller 100B includes at least a position control unit 110, a drive unit 120, a data acquisition unit 130, and a storage unit 140, and further includes a data correction unit 180 (correction unit) and a data storage unit 190.

[0148] FIG. 9 is a diagram illustrating a schematic example of the software configuration of a controller 100B included in a lighting device L1g according to a modified example. Similar to the position control unit 110 included in the controller 100, the position control unit 110 included in the controller 100 controls the position (position around the axis 134) of the plate (plates 2 to 2e) in each cycle. For ease of understanding, the following description will be given assuming that the plate is "plate 2." Similar to the drive unit 120 included in the controller 100, the drive unit 120 included in the controller 100 changes the position (position around the axis 134) of the plate 2 in each cycle according to the target position for each cycle notified by the position control unit 110. Similar to the data acquisition unit 130 included in the controller 100, the data acquisition unit 130 included in the controller 100 acquires measurement data for each cycle. The data acquisition unit 130 provided in the controller 100B notifies the data correction unit 180 of the acquired “measurement data for each cycle” together with the “position (target position) of the plate material 2 in each cycle” notified by the position control unit 110.

[0149] When the data correction unit 180 is notified of the "measurement data for each period" and the "position of the board 2 in each period" by the data acquisition unit 130, the data correction unit 180 executes the following process. That is, the data correction unit 180 first refers to the storage unit 140 and acquires reference measurement data 144 that has been stored in advance in the storage unit 140. The reference measurement data 144 is measurement data that has been acquired in advance by observing a white diffuse object (mockup) having the same shape as the target object S at the light receiving port 14 (observation unit). The reference measurement data 144 may be, for example, measurement data that has been acquired in advance by observing the above-mentioned mockup in each period.

[0150] The data correction unit 180 then corrects the "measurement data for each period" notified by the data acquisition unit 130 using the reference measurement data 144. If the measurement data is luminance, the correction may be performed by calculating "(corrected measurement data) = {(measurement data for each period) / (reference measurement data 144)} × (white luminance)." For example, the data correction unit 180 may correct the "measurement data for a certain period C(x)" notified by the data acquisition unit 130 using the "reference measurement data 144 for a certain period C(x)." In other words, the data correction unit 180 may correct the "measurement data acquired by observing the object S in a certain period C(x)" using the "measurement data acquired by observing the above-mentioned mockup in a certain period C(x)." The data correction unit 180 notifies the data storage unit 190 of the corrected measurement data for each period, along with the position of the plate 2 in each period.

[0151] The data storage unit 190 stores the "corrected measurement data for each cycle" and the "position of the board 2 for each cycle" notified by the data correction unit 180 as "corrected measurement data 145" in the memory unit 140. That is, the data storage unit 190 stores the "corrected measurement data 145," which is the "corrected measurement data for each cycle" associated with the "position of the board 2 for each cycle," in the memory unit 140. By analyzing this "corrected measurement data 145," it is possible to perform precise color measurement of the object S.

[0152] As described above, the lighting device L1g includes a data correction unit 180 that corrects measurement data acquired by observing the object S through the light receiving port 14 using reference measurement data 144. The reference measurement data 144 is measurement data acquired in advance by observing a white diffuse object having the same shape as the object S through the light receiving port 14 (observation unit). In this configuration, the reference measurement data 144 is used to correct the measurement data acquired by observing the object S. Therefore, even if a shadow occurs on the object S for some reason, high-precision measurement can be performed by performing correction using the reference measurement data 144 for the portion where the shadow occurs.

[0153] <4.6> Relationship between the Casing and the Plates In the lighting devices according to the above embodiments, the inner surface 12 of the casing 1 is made of a material that diffuses and reflects light, and the second surfaces 22 of the plates (plates 2 to 2e) are made of a material that absorbs light. In other words, in the above embodiments, the inner surface 12 of the casing 1 serves to diffuse and reflect light, and the second surfaces 22 of the plates (plates 2 to 2e) serve to trap light. However, the configuration of the lighting devices according to the above embodiments need not be limited to this example.

[0154] For example, in a lighting device according to a modified example, the casing 1 and the plate material (plate material 2-2e) may be integrated by forming a portion of the inner surface 12 from a light-absorbing material. The light-absorbing material is not particularly limited as long as it is capable of absorbing light, and may be, for example, a black-painted material or a material made of black material. Specific examples of the light-absorbing material include carbon black and non-reflective raised fabric. In this configuration, the casing 1 and the plate material (plate material 2-2e) are integrated by forming a portion of the inner surface 12 from a light-absorbing material. Therefore, the lighting device according to this modified example can be more compact than a lighting device in which the casing 1 and the plate material (plate material 2-2e) are separate components, and can be installed in environments with limited space, such as a factory production line. When the casing 1 and the plate material (plate material 2-2e) are integrated, the casing 1 may rotate around the axis 134 instead of rotating the plate material around the axis 134. That is, instead of controlling the positions (positions around the axis 134) of the plates (plates 2 to 2e), the rotation of the casing 1 around the axis 134 may be controlled.

[0155] <4.7> Regarding the Light Source Furthermore, in each of the above embodiments, the light source 3 is attached to the support 5. However, the arrangement of the light source 3 is not limited to this example as long as it is possible to irradiate light into the internal space 13, and may be determined appropriately depending on the embodiment.

[0156] Furthermore, in each of the above embodiments, an example has been described in which the light source 3 and the plate (plates 2 to 2e) are provided separately, but providing the light source 3 and the plate separately is not essential for the lighting device according to each of the above embodiments. For example, the light source 3 may be integrated with the plate (plates 2 to 2e) by arranging the light source 3 on the first surface 21 (the surface facing the inner surface 12) of the plate. By adopting such a configuration, it is possible to achieve a more compact lighting device than a lighting device in which the light source 3 and the plate (plates 2 to 2e) are separate components.

[0157] <4.8> Regarding the Shape of the Thin Plates FIG. 18 is a diagram illustrating the configuration of an upper plate 2fh(u) according to a modified example. In other words, FIG. 18 is a diagram illustrating a schematic example of the relationship between the upper plate 2fh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2fh(u) (in the example shown in FIG. 18, thin plates 210f(1) and thin plates 210f(2)) are arranged in the upper plate 2fh(u). The lighting device L1f (not shown in its entirety) is similar to the lighting device L1, except that it includes an upper plate 2fh(u) instead of the upper plate 2h(u).

[0158] For example, the multiple thin plates (thin plates 210a to 210e) included in the upper portions (upper plate members 2ah(u) to 2eh(u)) of the plate members (plate members 2a to 2e) described using Figures 7A to 7E are formed as follows. That is, thin plates 210a to 210e are each formed by dividing a single curved plate in the shape of two right-angled spherical triangles (for example, "a curved plate in the shape of two right-angled spherical triangles corresponding to one region A1") along a plane parallel to the equatorial plane. For example, thin plates 210a(1), 210a(2), 210a(3), and 210a(4) are formed by dividing "a curved plate in the shape of two right-angled spherical triangles corresponding to one region A1" into four along a plane parallel to the equatorial plane. Similarly, thin plate 210b(1), thin plate 210b(2), and thin plate 210b(3) are formed by dividing "a curved plate having two right-angled spherical triangular shapes corresponding to one region A1" into three along planes parallel to the equatorial plane. That is, thin plate 210a to thin plate 210e are each formed by dividing "a curved plate having two right-angled spherical triangular shapes corresponding to one region A1" into multiple parts along planes parallel to the equatorial plane.

[0159] However, in the lighting device according to this embodiment, it is not necessary for the multiple thin plates included in the upper portion (upper plate) of the plate to be formed by dividing a single curved plate with a two-right-angled spherical triangular shape along a plane “parallel” to the equatorial plane. In the lighting device according to this embodiment, the multiple thin plates included in the upper portion of the plate may be formed by dividing a single curved plate with a two-right-angled spherical triangular shape along a plane parallel to or inclined to the equatorial plane. As described above, by moving and rearranging at least one of the multiple thin plates around an axis by an angle smaller than 360 degrees, all of the multiple thin plates can form a single curved plate with a two-right-angled spherical triangular shape. Therefore, the multiple thin plates may be formed by dividing a single curved plate with a two-right-angled spherical triangular shape along a plane parallel to or inclined to the equatorial plane. Therefore, the lighting device according to one aspect of the present invention makes it possible to easily prepare the multiple thin plates that can be rearranged to form a single curved plate with a two-right-angled spherical triangular shape.

[0160] In the lighting device according to this embodiment, the multiple thin plates included in the upper portion of the plate may be formed by dividing a single curved plate having a two-right-angled spherical triangular shape by a plane "inclined" to the equatorial plane. For example, as illustrated in FIG. 18 , the upper plate 2fh(u) includes multiple thin plates 210f, and in the example shown in FIG. 18 , the multiple thin plates 210f include a thin plate 210f(1) and a thin plate 210f(2). In the following description, when the multiple thin plates 210f are referred to collectively without distinguishing between them, they will be simply referred to as "thin plates 210f." When distinguishing between the multiple thin plates 210f, they will be distinguished by adding a prefix such as "(1)," "(2)," ..., or "(n)."

[0161] The thin plate 210f included in the upper plate member 2fh(u) is similar to the thin plate 210 included in the upper plate member 2h(u), except that it is formed by dividing a single curved plate shaped like two right-angled spherical triangles by a surface "inclined" to the equatorial plane. For example, the surface of the thin plate 210f facing the center 131 (second surface 22h(u)) is made of a light-absorbing material, similar to the second surface 22h(u) of the thin plate 210. As illustrated in FIG. 18 , the thin plate 210f(1) and the thin plate 210f(2) included in the upper plate member 2fh(u) are arranged so as not to overlap each other in the upper plate member 2fh(u). In particular, as illustrated in Figure 18, these two thin plates 210f are arranged in the upper plate 2fh(u) so as not to overlap each other and so as to face only one area A1 of the plurality of areas A1 (two areas in the example shown in Figure 18). That is, the plurality of thin plates 210f included in the upper plate 2fh(u) are arranged in the upper plate 2fh(u) so as not to overlap each other and so as to face only one area A1 of the plurality of areas A1 virtually provided on the hemispherical inner surface 12h(u).

[0162] By moving and repositioning at least one of the thin plates 210f included in the upper plate member 2fh(u) by an angle smaller than 360 degrees around the axis 134, a single "curved plate with two right-angled spherical triangles corresponding to region A1" can be formed. In the example shown in FIG. 18 , by moving the thin plate 210f(1) in the upper plate member 2fh(u) by 30 degrees clockwise around the axis 134, a single curved plate with two right-angled spherical triangles corresponding to region A1 can be formed. The multiple thin plates 210f in the upper plate member 2fh(u) may be connected to each other via a frame or the like. The thin plates 210f(1) and 210f(2) are formed, for example, by dividing a "curved plate with two right-angled spherical triangles corresponding to one region A1" into two at a plane inclined toward the equatorial plane.

[0163] As explained using Figure 18, in the lighting device according to this embodiment, the multiple thin plates (thin plates 210f) included in the upper part of the plate (upper plate 2fh(u)) may be formed by dividing a single curved plate having a shape of two right-angled spherical triangles (for example, "a curved plate having a shape of two right-angled spherical triangles corresponding to one area A1") by a surface "inclined" to the equatorial plane.

[0164] <4.9> Regarding the Arrangement of Thin Plates FIG. 19 is a diagram illustrating the configuration of an upper plate 2gh(u) according to a modified example. In other words, FIG. 19 is a diagram illustrating a schematic example of the relationship between the upper plate 2gh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram for explaining how the multiple thin plates 210 included in the upper plate 2gh(u) (in the example shown in FIG. 19, thin plates 210g(1) to 210g(16)) are arranged in the upper plate 2gh(u). The lighting device L1g (not shown in its entirety) is similar to the lighting device L1, except that it includes an upper plate 2gh(u) instead of the upper plate 2h(u).

[0165] As illustrated in Figure 19, the upper plate material 2gh(u) includes a plurality of thin plates 210g, and in the example shown in Figure 19, these include thin plates 210g(1) to 210g(16). In the following description, when the plurality of thin plates 210g are referred to collectively without distinguishing between them, they will simply be referred to as "thin plates 210g." When distinguishing between the plurality of thin plates 210g, they will be distinguished by adding "(1)," "(2)," ..., "(n)," etc.

[0166] The thin plate 210g included in the upper plate member 2gh(u), like each of the thin plates 210a to 210e, is formed by dividing a curved plate in the shape of two right-angled spherical triangles (for example, "a curved plate in the shape of two right-angled spherical triangles corresponding to one region A1") along a plane parallel to the equatorial plane. As illustrated in FIG. 19, the upper plate member 2gh(u) as a whole has a spherical isosceles triangle shape including "two sides of equal length that extend in a curved manner from the zenith 132 to the equatorial plane on the spherical surface." The thin plate 210g included in the upper plate member 2gh(u) is similar to the thin plate 210 included in the upper plate member 2h(u), except that the upper plate member 2gh(u) is arranged so as to have a spherical isosceles triangle shape including "two sides of equal length that extend in a curved manner from the zenith 132 to the equatorial plane on the spherical surface." For example, the surface of the thin plate 210g facing the center 131 (second surface 22h(u)), like the second surface 22h(u) of the thin plate 210, is made of a light-absorbing material.

[0167] As illustrated in Figure 19, the thin plates 210g(1) to 210g(16) included in the upper plate member 2gh(u) are arranged so as not to overlap each other in the upper plate member 2gh(u). In particular, in the upper plate member 2gh(u) illustrated in Figure 19, the thin plates 210g(1) to 210g(16) are arranged so that the meridians of the thin plates 210g(1) to 210g(16) as a whole form a "curved line extending from the zenith 132 to the equatorial plane on the spherical surface." By arranging the thin plates 210g(1) to 210g(16) as described above, the upper plate member 2gh(u) has a spherical isosceles triangle shape including "two sides of equal length that curve from the zenith 132 to the equatorial plane on the spherical surface."

[0168] In the thin plates 210, 210a to 210e described so far, the multiple thin plates were arranged so as not to overlap each other and to face only one of the multiple regions A1. For example, before the rearrangement, the thin plates 210(1) and 210(2) were arranged so as not to overlap each other and to face only one of the multiple regions A1 (two in the example shown in FIG. 4). However, in the lighting device according to this embodiment, it is not necessary for the multiple thin plates included in the upper portion (upper plate) of the plate to be arranged so as not to overlap each other and to face only one of the multiple regions A1. As illustrated in FIG. 19, among the multiple thin plates 210g, a certain thin plate 210g (e.g., thin plate 210g(10)) may be arranged so as to straddle two adjacent regions A1 among the multiple regions A1.

[0169] By moving and rearranging some of the thin plates 210g included in the upper plate member 2gh(u) by an angle smaller than 360 degrees around the axis 134, it is possible to form a single "curved plate in the shape of two right-angled spherical triangles corresponding to the region A1." Note that the thin plates 210g in the upper plate member 2gh(u) may be connected to each other via a frame or the like.

[0170] As described with reference to FIG. 19 , in the lighting device according to this embodiment, the upper portion of the plate (upper plate 2gh(u)) may have the shape of a spherical isosceles triangle including two sides of equal length that curve from the zenith 132 to the equatorial plane on the spherical surface. In the lighting device according to this embodiment, the multiple thin plates included in the upper portion of the plate (upper plate) may be arranged so as not to overlap each other, for example, on the same spherical surface. In the lighting device according to this embodiment, the shape of the upper portion formed by the multiple thin plates is not particularly limited, and the arrangement of each of the multiple thin plates may be determined appropriately depending on the usage mode of the lighting device, etc.

[0171] [Example] The inventors conducted the following experiment to verify how much the illumination device according to the above embodiment improves the amount of diffused light (illuminance) reaching the target S compared to a conventional illumination device that uses "a single curved plate in the shape of a two right-angled spherical triangle corresponding to area A1" as a light trap.

[0172] FIG. 10 is a diagram illustrating an outline of the experiment. In the experiment, the illuminance near the center 131 was measured for the case where the upper plate member 2bh(u) described with reference to FIG. 7B was used as the light trap, and for the case where a conventional "single curved plate with a two-right-angled spherical triangular shape corresponding to region A1" was used as the light trap. Specifically, an optical sensor (illuminance meter) was placed near the center 131, and the illuminance near the center 131 was measured for the case where the "single curved plate with a two-right-angled spherical triangular shape corresponding to region A1" was used as the light trap, and for the case where the upper plate member 2bh(u) was used. In the experiment, a single curved plate with a two-right-angled spherical triangular shape corresponding to (opposing) region A1 with a 30-degree apex angle was used as the "single curved plate with a two-right-angled spherical triangular shape corresponding to region A1." In addition, the upper plate member 2bh(u) used had a 90-degree apex angle. That is, in the upper plate material 2bh(u) used in the experiment, each of the multiple thin plates 210b included in the upper plate material 2bh(u) is arranged so as to face only one of the three adjacent areas A1 (the apex angles of the three areas A1 are each 30 degrees).

[0173] In the following description, the azimuth angle is defined as "0" degrees on the upper side of the paper, "90" degrees on the left side of the paper, "180" degrees on the lower side of the paper, and "270" degrees on the right side of the paper, as viewed from directly above the main body (casing) (the zenith 132 side), as shown on the left side of Fig. 10. Also, the right side of Fig. 10 shows the arrangement of the optical sensors as viewed from the horizontal direction (specifically, the direction of an azimuth angle of "90" degrees).

[0174] In the experiment, as shown on the left side of Fig. 10, an optical sensor covered on three sides by a light shielding plate and open in the azimuth angle direction of "180" degrees was placed near the center 131 of the main body of the lighting device. In addition, as shown on the right side of Fig. 10, the optical sensor was installed in the azimuth angle direction of "180" degrees, tilted by 20 degrees from the vertical direction.

[0175] Then, using this optical sensor, the illuminance near the center 131 was measured when the upper plate material 2bh(u) was used as the light trap and when the conventional "single curved plate in the shape of two right-angled spherical triangles corresponding to area A1" was used as the light trap.

[0176] 11 is a diagram showing the illuminance measured by the above-mentioned optical sensor when the upper plate 2bh(u) is used as the light trap and when a conventional "single curved plate in the shape of two right-angled spherical triangles corresponding to area A1" is used as the light trap. The dotted line in FIG. 11 shows the illuminance measured when the conventional "single curved plate in the shape of two right-angled spherical triangles corresponding to area A1" is used as the light trap. The solid line shows the illuminance measured when the upper plate 2bh(u) is used as the light trap.

[0177] 11, the "azimuth angle (position)" of "one curved plate in the shape of a two right-angled spherical triangle corresponding to area A1" indicates the "azimuth angle (position)" of the center of latitude of this curved plate (the line that bisects the apex angle (30 degrees) of this curved plate). Also, the "azimuth angle (position)" of the upper plate member 2bh(u) indicates the "azimuth angle (position)" of the center of latitude of the upper plate member 2bh(u) (the line that bisects the apex angle (90 degrees) of the upper plate member 2bh(u)).

[0178] As shown in Figure 11, when "a single curved plate in the shape of two right-angled spherical triangles corresponding to region A1" is used as the light trap, the illuminance drops to 272 [lx] when the light trap is positioned near an azimuth angle of 180 degrees. In contrast, when the upper plate material 2bh(u) is used as the light trap, the change in illuminance becomes gentler, and the minimum illuminance is improved slightly. Specifically, when the light trap is positioned near an azimuth angle of 180 degrees, the illuminance is 305 [lx].

[0179] Here, the impact of the reduction in illuminance due to light trapping on the measurement value can be reduced by performing brightness correction (illuminance correction) after measurement. However, the smaller the reduction in illuminance, the less correction is required. Furthermore, since performing correction also increases measurement error (noise), it is desirable to keep the amount of correction as small as possible.

[0180] As shown in Figure 11, experiments have confirmed that when the upper plate member 2bh(u) is used as the light trap, the decrease in illuminance can be suppressed and the change in illuminance can be made smoother compared to when a "single curved plate with two right-angled spherical triangular surfaces corresponding to region A1" is used as the light trap. Therefore, the lighting device according to the above embodiment can reduce the decrease in illuminance and the amount of correction compared to a conventional lighting device that uses a "single curved plate with two right-angled spherical triangular surfaces corresponding to region A1" as the light trap, thereby reducing measurement errors. In other words, the lighting device according to the above embodiment can prevent a decrease in measurement accuracy and achieve high-precision measurements.

[0181] Second Embodiment An illumination device L2 according to a second embodiment will be described below with reference to Figures 12 and 13. The illumination device L2 described below has components that share actions and functions with the components of the illumination devices L1 to L1g described so far. Such components are denoted by the same reference numerals as the corresponding components shown in Figure 1 and the like, and detailed description thereof will be omitted unless necessary.

[0182] §1 Configuration Example FIG. 12 is a side view that schematically illustrates an example of the configuration of the lighting device L2 according to this embodiment. The lighting device L2 according to this embodiment is used to measure the color of an object S, similar to the lighting device L1 and the like described above. As illustrated in FIG. 12, the lighting device L2 includes a hemispherical main body B2 and a controller 100 that is communicatively connected to the main body B2. FIG. 13 is a cross-sectional view that schematically illustrates an example of the configuration of the main body B2. As shown in each figure, the main body B2 includes a hemispherical upper casing 1h(u), a plate member 2X, a light source 3, a reflector 6, a frame member 7, and a support member 8.

[0183] (Casing) The upper casing 1h(u) of the lighting device L2 (particularly, the main body B2) is similar to the upper casing 1h(u) of the lighting device L1 (particularly, the main body B1), and therefore a detailed description thereof will be omitted. Furthermore, the hemispherical internal space 13h(u) defined by the hemispherical inner surface 12h(u) of the upper casing 1h(u) of the main body B2 is similar to the hemispherical internal space 13h(u) defined by the upper casing 1h(u) of the main body B1, and therefore a detailed description thereof will be omitted. Furthermore, as illustrated in FIGS. 12 and 13 , the upper casing 1h(u) has a light receiving opening 14. The light receiving opening 14 is provided for observing the object S placed in the hemispherical internal space 13h(u). In other respects, the light receiving port 14 provided in the upper casing 1h(u) is similar to the light receiving port 14 provided in the casing 1 of the lighting device L1, and therefore a detailed description thereof will be omitted.

[0184] (Light Source and Frame Material) As shown in FIG. 13 , the light source 3 is disposed so as to irradiate the hemispherical internal space 13h(u). In this embodiment, the light source 3 is attached to a frame material 7. The frame material 7 is formed in an annular shape and configured to support the open end 15h(u) of the upper casing 1h(u). In this embodiment, the frame material 7 includes a main body portion 70, an outer peripheral wall 71, and an inner peripheral wall 72. The main body portion 70 is formed in an annular shape. The outer peripheral wall 71 is provided on the outer peripheral side of the main body portion 70 and is disposed outside the upper casing 1h(u) (on the hemispherical outer surface 11h(u) side). On the other hand, the inner peripheral wall 72 is provided on the inner peripheral side of the main body portion 70 and is disposed spaced apart from the hemispherical inner surface 12h(u) of the upper casing 1h(u) toward the center 131 (131h). The outer peripheral wall 71 and the inner peripheral wall 72 are each formed in a cylindrical shape. The inner peripheral wall 72 has an outer peripheral surface 721 that faces the hemispherical inner surface 12h(u) of the upper casing 1h(u). In this embodiment, the light source 3 is disposed on the outer peripheral surface 721 of the inner peripheral wall 72, facing toward the hemispherical inner surface 12h(u) of the upper casing 1h(u).

[0185] The material of the frame material 7 is not particularly limited and may be selected appropriately depending on the embodiment. In this embodiment, since the light sources 3 are attached to the frame material 7, it is desirable to use a material with good thermal conductivity for the frame material 7 that can effectively dissipate heat generated from the light sources 3. From this perspective, it is desirable to use aluminum, for example, for the frame material 7. The type and number of light sources 3 are not particularly limited and may be selected appropriately depending on the embodiment. For example, LEDs (light emitting diodes), fluorescent tubes, organic EL (electroluminescence), etc. may be used as the light sources 3. Furthermore, multiple light sources 3 may be arranged at intervals (e.g., at equal intervals) around the axis 134 on the cylindrical outer circumferential surface 721.

[0186] (Reflector and Support Member) The reflector 6 is positioned so as to cover a portion of the bottom surface 133h of the hemispherical internal space 13h(u). In the example of FIG. 13, the reflector 6 is formed in a rectangular shape larger than the open end 15h(u) of the upper casing 1h(u) and is configured to cover the bottom surface 133h of the hemispherical internal space 13h(u) except for the area around the center 131h. In this case, when performing color measurement, at least the portion of the object S to be measured is contained within the hemispherical internal space 13h(u) of the upper casing 1h(u). That is, in the example shown in FIG. 13, the portion of the reflector 6 near the center 131h is removed, thereby connecting the hemispherical internal space 13h(u) to the outside near the center 131h. In this case, when performing color measurement, the object S is placed at least partially outside the hemispherical internal space 13h(u), and the hemispherical internal space 13h(u) can be accessed through the communicating portion.

[0187] However, the shape and dimensions of the reflecting mirror 6 are not limited to this example and may be determined appropriately depending on the embodiment. The reflecting mirror 6 may be configured to completely cover the bottom surface 133h of the hemispherical internal space 13h(u) rather than partially covering the bottom surface 133h.

[0188] The reflecting mirror 6 has a surface (top surface) facing the hemispherical internal space 13h(u), and this top surface is configured to mirror-reflect light. The material of the reflecting mirror 6 is not particularly limited and may be selected appropriately depending on the embodiment. The reflecting mirror 6 may be made of an aluminum-deposited resin material, a stainless steel material, or the like. Accordingly, the top surface of the reflecting mirror 6 may be made of an aluminum-deposited surface, a stainless steel surface, or the like. The reflecting mirror 6 may be divided into multiple sections.

[0189] The support member 8 is a member that supports the reflecting mirror 6 from the bottom surface side (the surface opposite to the top surface of the reflecting mirror 6), and for example, it contacts the bottom surface of the reflecting mirror 6 and supports the reflecting mirror 6 from below. The material of the support member 8 is not particularly limited and may be selected appropriately depending on the embodiment. The support member 8 may be made of a material and structure that has the strength to support the reflecting mirror 6.

[0190] 13 , the plate 2X is disposed in the hemispherical internal space 13h(u), and includes an upper plate 2h(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a horizontal plate 2h(h) facing at least a portion of the upper surface of the reflecting mirror 6. The plate 2X is disposed in the hemispherical internal space 13h(u) facing the hemispherical inner surface 12h(u). In particular, the plate 2X is disposed in the hemispherical internal space 13h(u) such that the upper plate 2h(u) faces the hemispherical inner surface 12h(u) and the horizontal plate 2h(h) faces at least a portion of the upper surface of the reflecting mirror 6.

[0191] In the plate 2X, the horizontal plate 2h(h) and the upper plate 2h(u) are in contact with each other. For example, the bottom surface of the upper plate 2h(u) is in contact with the top surface of the horizontal plate 2h(h) closest to the hemispherical inner surface 12h(u). The bottom surface of the upper plate 2h(u) is the surface of the upper plate 2h(u) closest to the equatorial plane and parallel to the equatorial plane. In FIG. 13, this is the surface of the upper plate 2h(u) closest to the top surface of the reflector 6 and parallel to the equatorial plane. For example, the arc length of the bottom surface of the upper plate 2h(u) is equal to the arc length of the outermost surface of the horizontal plate 2h(h) (the surface closest to the hemispherical inner surface 12h(u) and parallel to the hemispherical inner surface 12h(u)). In the plate 2X, the upper plate 2h(u) and the horizontal plate 2h(h) are arranged so that the bottom surface of the upper plate 2h(u) faces the top surface of the horizontal plate 2h(h) closest to the hemispherical inner surface 12h(u). In the plate 2X, the upper plate 2h(u) and the horizontal plate 2h(h) may be integrally formed, i.e., connected to each other. For example, by rotating the upper plate 2h(u) about the axis 134, the horizontal plate 2h(h) also rotates about the axis 134.

[0192] 13 , the upper plate 2h(u) is the "portion extending from the contact position between the horizontal plate 2h(h) and the upper plate 2h(u) toward the zenith 132 along the hemispherical inner surface 12h(u)." That is, in the plate 2X, the upper plate 2h(u) is the "portion extending from the contact position between the horizontal plate 2h(h) and the upper plate 2h(u) toward the side where the light receiving port 14 is located relative to the equatorial plane, facing the hemispherical inner surface 12h(u)." Also, in the plate 2X, the horizontal plate 2h(h) is the "portion extending from the contact position between the horizontal plate 2h(h) and the upper plate 2h(u) toward the center 131h along the equatorial plane." That is, in the plate 2X, the "portion extending from the contact position between the horizontal plate 2h(h) and the upper plate 2h(u) along the upper surface of the reflector 6 toward the center 131h" is the horizontal plate 2h(h).

[0193] In the following description, when the upper plate 2h(u) and the horizontal plate 2h(h) are referred to collectively without distinction, they will be simply referred to as "plate 2X." The plate 2X covers a portion of the hemispherical inner surface 12h(u) when viewed from the center 131h, and is configured so that its position around the axis 134h is adjustable. In particular, the plate 2X is configured so that the upper plate 2h(u) covers a portion of the hemispherical inner surface 12h(u) when viewed from the center 131h, and the horizontal plate 2h(h) covers at least a portion of the upper surface of the reflector 6. The plate 2X has a first surface 21h(u) facing the hemispherical inner surface 12h(u) and a second surface 22h(u) facing the center 131h. In particular, the plate member 2X includes an upper plate member 2h(u) having a first surface 21h(u) and a second surface 22h(u), and a horizontal plate member 2h(h) having the first surface 21h(h) facing the upper surface of the reflecting mirror 6 and the second surface 22h(h) facing the hemispherical internal space 13h(u). That is, in the upper plate member 2h(u), the first surface 21h(u) and the second surface 22h(u) face each other and face in opposite directions (opposite directions). In addition, in the horizontal plate member 2h(h), the first surface 21h(h) and the second surface 22h(h) face each other and face in opposite directions (opposite directions).

[0194] (Upper Plate) The upper plate 2h(u) of the lighting device L2 (main body B2) is similar to the upper plate 2h(u) of the lighting device L1 (main body B1). That is, the upper plate 2h(u) of the main body B2 is configured to cover a portion of the hemispherical inner surface 12h(u) of the upper casing 1h(u) when viewed from the center 131h. The upper plate 2h(u) includes a plurality of thin plates 210, each of which faces the hemispherical inner surface 12h(u) of the upper casing 1h(u) and is arranged so as not to overlap one another. In particular, the plurality of thin plates 210 are arranged so as not to overlap one another on the upper plate 2h(u) and so as to face only one of a plurality of regions A1 having equal areas that are virtually provided on the inner surface 12. The second surface 22h(u) of the thin plate 210 (i.e., the surface facing the center 131h) is configured to absorb light. The configuration of the first surface 21h(u) of the thin plate 210 (i.e., the surface facing the hemispherical inner surface 12h(u)) is not particularly limited.

[0195] (Horizontal Plate) As illustrated in FIG. 13 , in the lighting device L2 (main body B2), the plate 2X includes a horizontal plate 2h(h) (horizontal portion). The horizontal plate 2h(h) is a portion that extends along the equatorial plane and covers a portion of the upper surface of the reflector 6 (the surface facing the hemispherical internal space 13h(u)). As described above, the arc length of the bottom surface of the upper plate 2h(u) (particularly, the thin plate 210(2)) is equal to the arc length of the outermost surface of the horizontal plate 2h(h). The thin plate 210(2) and the horizontal plate 2h(h) are arranged so that the bottom surface of the thin plate 210(2) faces the top surface of the horizontal plate 2h(h) closest to the hemispherical inner surface 12h(u).

[0196] In this embodiment, the bottom surface 133h is virtually equally divided into a plurality of sector-shaped regions F1. For example, the bottom surface 133h is equally divided into the same number of regions F1 as the number of regions A1 formed by virtually equally dividing the hemispherical inner surface 12h(u), and in this embodiment, the number of divisions is 12. However, the number of divisions is not limited to this example and may be determined appropriately depending on the embodiment.

[0197] The horizontal plate 2h(h) has a shape corresponding to at least a portion of the upper surface of the reflecting mirror 6. For example, the horizontal plate 2h(h) is configured as a strip-shaped (approximately trapezoidal) plate formed by removing a curved portion of the fan-shaped plate within a predetermined range from the central angle from a fan-shaped plate corresponding to the region F1. However, the horizontal plate 2h(h) does not necessarily have to be configured as a strip-shaped plate; the horizontal plate 2h(h) may be a fan-shaped plate corresponding to the entire region F1. The horizontal plate 2h(h) only needs to have a shape (area) that can absorb the "specular reflection component that reaches the object S from the upper surface of the reflecting mirror 6, is reflected by the object S, and reaches the light receiving opening 14 (observation unit)," as shown in FIG. 13. The shape of the horizontal plate 2h(h) may be selected appropriately depending on the embodiment. The horizontal plate member 2h(h) extending along the equatorial plane toward the center 131h may be configured so that the distance to the center 131h can be adjusted depending on the shape and size of the object S.

[0198] The horizontal plate 2h(h) extends above the reflecting mirror 6 (closer to the center 131h) along the equatorial plane toward the center 131h. Therefore, the first surface 21h(h) of the horizontal plate 2h(h) faces toward the upper surface of the reflecting mirror 6, and faces downward on the paper in the example shown in Fig. 13. Furthermore, the second surface 22h(h) of the horizontal plate 2h(h) (the surface opposite the first surface 21h(h)) faces toward the hemispherical internal space 13h(u), and faces upward on the paper in the example shown in Fig. 13.

[0199] The second surface 22h(h) of the horizontal plate member 2h(h) is made of a light-absorbing material. The light-absorbing material is not particularly limited as long as it is capable of absorbing light, and may be, for example, a black-painted material or a material made of black material. Specific examples of the light-absorbing material include carbon black and non-reflective raised fabric. On the other hand, the configuration of the first surface 21h(h) of the horizontal plate member 2h(h) is not particularly limited, and may be selected appropriately depending on the embodiment. The first surface 21h(h) of the horizontal plate member 2h(h) may be made of a material that diffuses and reflects light. Alternatively, the first surface 21h(h) of the horizontal plate member 2h(h) may be made of other materials.

[0200] §2 Features

[0201] As described above with reference to FIGS. 12 and 13 , the lighting device L2 includes a hemispherical upper casing 1h(u), a plate 2X, and a light source 3. The upper casing 1h(u) has a hemispherical outer surface 11h(u), a hemispherical inner surface 12h(u), a hemispherical internal space 13h(u), and a light receiving port 14 (observation section). The hemispherical inner surface 12h(u) defines the hemispherical internal space 13h(u) and is made of a light-reflecting material. The hemispherical internal space 13h(u) has a center 131h, a zenith 132 (vertex 132h(u)), and an axis 134h, and the axis 134h passes through the center 131h and the zenith 132. The light receiving port 14 is provided for observing an object S placed in the hemispherical internal space 13h(u), and is positioned at a position corresponding to the zenith 132 or at a position circumferentially spaced apart from the zenith 132 along the hemispherical inner surface 12h(u).

[0202] The light source 3 is positioned to irradiate light into the hemispherical internal space 13h(u). The plate 2X is positioned (at least a portion thereof) facing the hemispherical inner surface 12h(u) in the hemispherical internal space 13h(u). That is, the plate 2X is positioned in the hemispherical internal space 13h(u), and the upper portion of the plate 2X (the upper plate 2h(u)) faces the hemispherical inner surface 12h(u). Furthermore, the plate 2X (at least a portion thereof) covers a portion of the hemispherical inner surface 12h(u) when viewed from the center 131h. That is, the upper portion of the plate 2X (the upper plate 2h(u)) covers a portion of the hemispherical inner surface 12h(u) when viewed from the center 131h. The plate 2X is configured so that its position around the axis 134h can be adjusted, and has a first surface 21h(u) and a second surface 22h(u). A first surface 21h(u) of the upper portion of the plate 2X (upper plate 2h(u)) faces the hemispherical inner surface 12h(u), and a second surface 22h(u) of the upper portion faces the center 131h.

[0203] The upper plate 2h(u) (upper portion), which is the portion of the plate 2X on the side where the light receiving port 14 is located with respect to the equatorial plane, includes a plurality of thin plates 210 that are arranged so as not to overlap each other. The plurality of thin plates 210 are configured so that their second surfaces 22h(u) absorb light.

[0204] Of the multiple thin plates 210 arranged so as not to overlap each other in the upper plate material 2h(u), by moving and repositioning at least one thin plate 210 around the axis 134 at an angle smaller than 360 degrees, it is possible to form one "curved plate in the shape of two right-angled spherical triangles corresponding to region A1" using all of the multiple thin plates 210.

[0205] In this configuration, the multiple thin plates 210 have second surfaces 22h(u) configured to absorb light and are arranged on the upper plate member 2h(u) so as not to overlap one another. By moving the position of at least one of the multiple thin plates 210 around the axis 134h by an angle smaller than 360 degrees and rearranging it, all of the multiple thin plates 210 can form a single "curved plate in the shape of two right-angled spherical triangles corresponding to region A1." In other words, the area of ​​each of the multiple thin plates 210 included in the upper plate member 2h(u) and having second surfaces 22h(u) configured to absorb light is smaller than the area of ​​the "curved plate in the shape of two right-angled spherical triangles corresponding to region A1." Furthermore, when the upper plate material 2h(u) and the "curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1" are arranged so that one side (for example, the bottom side) of each overlaps, the area of ​​the overlapping portion between the two is smaller than the area of ​​the "curved plate in the shape of a two-right-angled spherical triangle corresponding to region A1".

[0206] Therefore, compared to conventional light traps configured to absorb light from the entire second surface (the surface facing the center 131h) of the "curved plate in the shape of a two-right-angled spherical triangle corresponding to area A1," the upper plate 2h(u) makes it easier for diffused light from the azimuth angle corresponding to the "curved plate in the shape of a two-right-angled spherical triangle corresponding to area A1" to reach the object S, and shadows are less likely to appear on the object S. Therefore, the lighting device L2 can prevent a decrease in measurement accuracy due to the occurrence of shadows, and achieve high-precision measurements.

[0207] The plurality of thin plates 210 in the upper plate member 2h(u) may be connected to one another via a frame, etc. The plurality of thin plates 210 in the upper plate member 2h(u) may be connected to one another via "white plates whose first and second surfaces are configured to reflect light" or "transparent plates that transmit light."

[0208] The lighting device L2 also includes a reflector 6 whose surface (upper surface) facing the hemispherical internal space 13h(u) is configured to specularly reflect light and which is arranged to cover a portion of the bottom surface 133h of the hemispherical internal space 13h(u). In the lighting device L2, the plate 2X further includes a horizontal plate 2h(h) in addition to the upper plate 2h(u). The horizontal plate 2h(h) has a second surface 22h(h) (i.e., the surface facing the hemispherical internal space 13h(u)) configured to absorb light, and extends along the equatorial plane, covering a portion of the surface of the reflector 6 facing the hemispherical internal space 13h(u).

[0209] In this configuration, the horizontal plate 2h(h) extends along the equatorial plane, covering a portion of the surface of the reflector 6 facing the hemispherical internal space 13h(u), and the second surface 22h(h) of the horizontal plate 2h(h) is configured to absorb light. Therefore, as shown in FIG. 13 , the second surface 22h(h) of the horizontal plate 2h(h) can remove the specular reflection component, even when the target object S has a convex shape. Therefore, the illumination device L2 can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurements.

[0210] As is clear from the above description, when focusing only on the viewpoint of suppressing the occurrence of shadows to prevent a decrease in measurement accuracy, it is not essential that the illumination device L2 according to this embodiment include the horizontal plate 2h(h) as the light trap (plate 2X). In other words, to suppress the occurrence of shadows, the illumination device L2 only needs to include the upper plate 2h(u) as the light trap (plate 2X). By including the upper plate 2h(u) as the light trap (plate 2X), the illumination device L2 can suppress the occurrence of shadows, prevent a decrease in measurement accuracy due to the occurrence of shadows, and achieve high-precision measurements. Furthermore, by including the horizontal plate 2h(h) as the light trap (plate 2X) in addition to the upper plate 2h(u), the illumination device L2 can further prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurements.

[0211] §3 Modifications <3.1> Configuration of the Observation Unit The configuration of the observation unit provided in the illumination device according to the second embodiment may be selected as appropriate depending on the embodiment, as explained in <4.1> of the first embodiment. For example, the observation unit may be composed of the optical sensor itself.

[0212] <3.2> Regarding the Shape of the Upper Portion of the Plate As described in <4.2> of the first embodiment, the lighting device according to the second embodiment may include any of the upper plates 2ah(u) to 2dh(u) instead of the upper plate 2h(u). Furthermore, the lighting device according to the second embodiment may include any of the upper plates 2fh(u) or 2gh(u) instead of the upper plate 2h(u). By including any of the upper plates 2ah(u) to 2gh(u) instead of the upper plate 2h(u), the lighting device according to the second embodiment can ensure more than twice the amount of diffused light reaching the target S from the azimuth angle corresponding to the "curved plate shaped like two right-angled spherical triangles corresponding to the region A1" compared to a conventional light trap configured to absorb light from the entire second surface (the surface facing toward the center 131) of the "curved plate shaped like two right-angled spherical triangles corresponding to the region A1."

[0213] <3.3> Regarding the necessity of contact between thin plates As explained in <4.3> of the first embodiment, the lighting device according to the second embodiment may be provided with an upper plate 2eh(u) including a plurality of thin plates (thin plates 210e) that are not in contact with each other, instead of or together with the upper plate 2h(u).

[0214] <3.4> Number of Plates As described in <4.4> of the first embodiment, the lighting device according to the second embodiment may include a plurality of plate members 2X. At least one of the plurality of plate members 2X may include any one of the upper plate members 2h(u) to 2dh(u).

[0215] <3.5> Regarding the Controller The lighting device according to the second embodiment may include a controller 100A or a controller 100B instead of the controller 100, as described in <4.5> of the first embodiment.

[0216] <3.6> Relationship between the casing and the plate material In the lighting device according to the second embodiment, as explained in <4.6> of the first embodiment, the upper casing 1h(u) and the plate material 2X may be integrated by forming a part of the hemispherical inner surface 12h(u) from a light-absorbing material.

[0217] <3.7> Regarding the Frame Material In the above embodiment, the lighting device L2 includes the frame material 7. However, the configuration of the lighting device according to the second embodiment need not be limited to this example. The frame material 7 may be omitted. Furthermore, the shape of the frame material 7 need not be limited to the above example, as long as it can support the upper casing 1h(u), and may be determined appropriately depending on the embodiment.

[0218] <3.8> Regarding the Light Source In the above embodiment, the light source 3 is disposed on the outer peripheral surface 421 of the inner peripheral wall 42 of the frame material 7, facing the inner surface 12 of the upper casing 1h(u). However, the arrangement of the light source 3 is not limited to this example, and may be determined appropriately depending on the embodiment, as long as it is possible to irradiate light into the hemispherical internal space 13h(u).

[0219] Furthermore, in the above embodiment, an example in which the light source 3 and the plate 2X are provided separately has been described, but providing the light source 3 and the plate 2X separately is not essential for the lighting device according to the second embodiment. For example, the light source 3 may be integrated with the plate 2X by arranging the light source 3 on the first surface 21 of the plate 2X (particularly the first surface 21h(u) of the upper plate 2h(u)). By adopting such a configuration, it is possible to achieve a more compact lighting device than one in which the light source 3 and the plate 2Y are separate components.

[0220] <3.9> Regarding the Shape of the Thin Plates As described in <4.8> of the first embodiment, the lighting device according to the second embodiment may include an upper plate portion (upper plate) including "plural thin plates formed by dividing a single curved plate having a two-right-angled spherical triangular shape along planes parallel to or inclined to the equatorial plane." As described above, by moving and rearranging at least one of the plurality of thin plates around an axis by an angle smaller than 360 degrees, all of the plurality of thin plates can form a single curved plate having a two-right-angled spherical triangular shape. Therefore, the plurality of thin plates may be formed by dividing a single curved plate having a two-right-angled spherical triangular shape along planes parallel to or inclined to the equatorial plane. Therefore, the lighting device according to one aspect of the present invention can easily prepare a plurality of thin plates whose rearrangement can form a single curved plate having a two-right-angled spherical triangular shape.

[0221] <3.10> Regarding the Position of Thin Plates As described in <4.9> of the first embodiment, the lighting device according to the second embodiment may include an upper plate (e.g., upper plate 2gh(u)) in the shape of a spherical isosceles triangle including two sides of equal length that curve from the zenith 132 to the equatorial plane on the spherical surface. In the lighting device according to this embodiment, the multiple thin plates included in the upper portion (upper plate) of the plate may be arranged so as not to overlap each other, for example, on the same spherical surface. In the lighting device according to this embodiment, the shape of the upper portion formed by the multiple thin plates is not particularly limited, and the arrangement of each of the multiple thin plates may be determined appropriately depending on the usage mode of the lighting device, etc.

[0222] Third Embodiment An illumination device L3 according to a third embodiment will be described below with reference to Figures 14 to 16. The illumination device L3 described below has components that share actions and functions with the components of the illumination devices according to the above embodiments. Such components are denoted by the same reference numerals as the corresponding components shown in Figure 1 and the like, and detailed description thereof will be omitted unless necessary.

[0223] §1 Configuration Example FIG. 14 is a side view that schematically illustrates an example of the configuration of the illumination device L3. The illumination device L3 is used for color measurement of an object S. As illustrated in FIG. 14, the illumination device L3 includes a spherical main body B3, a support 5, and a controller 100 that is communicatively connected to the main body B3. The controller 100 included in the illumination device L3 is similar to the controller 100 included in the illumination device L1, and therefore a detailed description thereof will be omitted. The support 5 included in the illumination device L3 is also similar to the support 5 included in the illumination device L1, and therefore a detailed description thereof will be omitted. FIG. 15 is a cross-sectional view that schematically illustrates an example of the configuration of the main body B3. As shown in each figure, the main body B3 includes a casing 1, a plate 2Y, a light source 3, and a sample stage 4.

[0224] The casing 1, light source 3, and sample stage 4 of the main body B3 are similar to the casing 1, light source 3, and sample stage 4 of the main body B1, respectively, and therefore will not be described in detail.

[0225] (Plate) The plate 2Y differs from the plate 2 in that it includes an upper plate 2yh(u) instead of the upper plate 2h(u), but is otherwise similar to the plate 2. That is, the plate 2Y is disposed opposite the inner surface 12 in the internal space 13. In particular, as illustrated in Fig. 15 , in the lighting device L3 (main body B3), the plate 2Y includes an upper plate 2yh(u) that faces the hemispherical inner surface 12h(u) of the upper casing 1h(u) and a lower plate 2h(d) that faces the hemispherical inner surface 12h(d) of the lower casing 1h(d).

[0226] In the plate 2Y illustrated in FIG. 15 , the upper plate 2yh(u) and the lower plate 2h(d) are in contact with each other at the equatorial plane. That is, in the plate 2Y, the portion extending from the equatorial plane toward the side where the light receiving port 14 is located relative to the equatorial plane is the upper plate 2yh(u), and the portion extending from the equatorial plane toward the opposite side of the equatorial plane from the side where the light receiving port 14 is located relative to the equatorial plane is the lower plate 2h(d). For example, the upper plate 2yh(u) and the lower plate 2h(d) have the same length of contact with the equatorial plane (arc length at the equatorial plane), and are arranged such that the surface of the upper plate 2yh(u) that is in contact with the equatorial plane faces the surface of the lower plate 2h(d) that is in contact with the equatorial plane. In the plate 2Y, the upper plate 2yh(u) and the lower plate 2h(d) may be integrally formed, that is, they may be connected to each other. For example, by rotating the upper plate 2yh(u) about the axis 134, the lower plate 2h(d) also rotates about the axis 134.

[0227] In the following description, when the upper plate 2yh(u) and the lower plate 2h(d) are referred to collectively without distinction, they will simply be referred to as "plate 2Y." The plate 2Y covers a portion of the inner surface 12 when viewed from the center 131, and is configured so that its position around the axis 134 can be adjusted. The plate 2Y has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131. First, the upper plate 2yh(u) will be described below using FIG. 16 .

[0228] (Upper Plate) FIG. 16 is a diagram illustrating the shape of the upper plate 2yh(u). In particular, FIG. 16 schematically illustrates the relationship between the upper plate 2yh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131. The upper plate 2yh(u) has a first surface 21h(u) facing the hemispherical inner surface 12h(u) and a second surface 22h(u) facing the center 131. The second surface 22h(u) of the upper plate 2yh(u) is made of a light-absorbing material. This allows the upper plate 2yh(u) to function as a light trap. The light-absorbing material is not particularly limited as long as it is capable of absorbing light, and may be, for example, a black-painted material or a material made of black material. Specific examples of the light-absorbing material include carbon black and non-reflective brushed fabric. On the other hand, the configuration of the first surface 21h(u) is not particularly limited and may be appropriately selected depending on the embodiment. The first surface 21h(u) may be made of a material that diffuses and reflects light. Alternatively, the first surface 21h(u) may be made of another material.

[0229] As shown in Figure 16, in this embodiment, the hemispherical inner surface 12h(u) is virtually divided equally into multiple regions A1 around an axis 134 by a plane passing through a vertex 132 and a center 131. The upper plate member 2yh(u) has a shape corresponding to one region A1 of the inner surface 12. The shape corresponding to one region A1 may be any shape that shields the target region A1 as viewed from the target object S, and may be, for example, a two-right-angled spherical triangle. In the example of Figure 16, the inner surface 12 is divided into 12 equal parts. However, the number of divisions is not limited to this example and may be determined appropriately depending on the embodiment.

[0230] The material of the upper plate member 2yh(u) is not particularly limited and may be selected appropriately depending on the embodiment. For example, acrylic resin, stainless steel, etc. may be used for the upper plate member 2yh(u). A material that is easy to process and can ensure strength is desirable for the material of the upper plate member 2yh(u).

[0231] 15 , in the lighting device L3 (main body B3), the plate 2Y includes a lower plate 2h(d) that faces the hemispherical inner surface 12h(d) of the lower casing 1h(d). That is, the plate 2Y includes a lower plate 2h(d) (lower portion) that is a portion that extends on the side opposite to the side on which the light receiving port 14 is located with respect to the equatorial plane (i.e., the plane that passes through the center 131 and is perpendicular to the axis 134).

[0232] The lower plate member 2h(d) has a shape corresponding to (facing) at least a portion of one of a plurality of equal-area regions A1 virtually defined on the hemispherical inner surface 12h(d) of the lower casing 1h(d). For example, the lower plate member 2h(d) is configured as a belt-shaped (approximately trapezoidal) plate member (curved plate) formed by removing two right-angled spherical triangular curved plates within a predetermined range from the apex angle from a two-right-angled spherical triangular curved plate corresponding to (facing) the entire region A1. That is, the lower plate member 2h(d) is configured as a belt-shaped curved plate formed by removing two right-angled spherical triangular curved plates below a predetermined latitude (a predetermined plane parallel to the equatorial plane) from a two-right-angled spherical triangular curved plate corresponding to (facing) the entire region A1.

[0233] However, it is not essential that the lower plate member 2h(d) be configured as a strip-shaped plate member. The lower plate member 2h(d) may be a plate member (curved plate) with a shape of two right-angled spherical triangles corresponding to the entire region A1. The lower plate member 2h(d) only needs to have a shape (area) that can absorb the "specular reflection component that reaches the object S from the inner surface 12 (particularly the hemispherical inner surface 12h(d)), reflects off the object S, and reaches the light receiving port 14 (observation unit)" as illustrated in FIG. 15. The shape of the lower plate member 2h(d) may be selected appropriately depending on the embodiment. The lower plate member 2h(d) may be configured so that the latitude of the lower end of the lower plate member 2h(d) extending along the hemispherical inner surface 12h(d) toward the vertex 132h(d) can be adjusted depending on the shape and size of the object S.

[0234] The surface (second surface 22h(d)) of the lower plate 2h(d) facing the center 131 is made of a light-absorbing material. The light-absorbing material is not particularly limited as long as it is capable of absorbing light, and may be, for example, a black-painted material or a material made of black material. Specific examples of light-absorbing materials include carbon black and non-reflective raised fabric. On the other hand, the configuration of the surface (first surface 21h(d)) of the lower plate 2h(d) facing the inner surface 12 is not particularly limited and may be selected appropriately depending on the embodiment. The first surface 21h(d) of the lower plate 2h(d) may be made of a material that diffuses and reflects light, similar to the inner surface 12 (hemispherical inner surface 12h). Alternatively, the first surface 21h(d) of the lower plate 2h(d) may be made of another material.

[0235] In this configuration, the second surface 22h(d) of the lower plate 2h(d) is configured to absorb light. Therefore, as illustrated in Fig. 15, the second surface 22h(d) of the lower plate 2h(d) can remove the specular reflection component, even when the target object S has a convex shape. Therefore, the illumination device L3 can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurement.

[0236] As with the upper plate 2yh(u), the material of the lower plate 2h(d) is not particularly limited and may be selected appropriately depending on the embodiment. For example, acrylic resin, stainless steel, etc. may be used for the lower plate 2h(d). A material that is easy to process and can ensure strength is desirable for the material of the lower plate 2h(d).

[0237] §2 Features As described above, the lighting device L3 according to this embodiment includes a casing 1, a plate material 2Y, and a light source 3. The casing 1 has an outer surface 11, an inner surface 12, a spherical internal space 13, and a light receiving port 14 (observation portion). The inner surface 12 defines the internal space 13 and is made of a material that reflects light. The internal space 13 has a center 131, a zenith 132, and an axis 134, with the axis 134 passing through the center 131 and the zenith 132. The light receiving port 14 is provided for observing an object S placed in the internal space 13, and is disposed at a position corresponding to the zenith 132 or at a position spaced apart from the zenith 132 in the circumferential direction along the inner surface 12.

[0238] The light source 3 is disposed so as to irradiate light into the internal space 13. The plate material 2Y is disposed in the internal space 13 facing the inner surface 12, covers a portion of the inner surface 12 when viewed from the center 131, and is configured so that its position around the axis 134 can be adjusted. The plate material 2Y has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131.

[0239] The plate 2Y includes an upper plate 2yh(u) (upper portion) and a lower plate 2h(d) (lower portion). The upper plate 2yh(u) is a portion that extends toward the side of the equatorial plane where the light receiving opening 14 is located. The lower plate 2h(d) is a portion that extends toward the opposite side of the equatorial plane from the side where the light receiving opening 14 is located. A second surface 22h(d) of the lower plate 2h(d) is configured to absorb light.

[0240] In this configuration, the second surface 22h(d) of the lower plate member 2h(d) is configured to absorb light, so that the specular reflection component can be removed even when the target object S has a convex shape, as illustrated in Fig. 15. Therefore, the illumination device L3 can prevent a decrease in measurement accuracy due to the remaining specular reflection component, thereby achieving high-precision measurement.

[0241] §3 Modifications <3.1> Configuration of the Observation Unit The configuration of the observation unit provided in the illumination device according to the third embodiment may be selected as appropriate depending on the embodiment, as explained in <4.1> of the first embodiment. For example, the observation unit may be composed of the optical sensor itself.

[0242] <3.2> Number of Plates The lighting device according to the third embodiment may include a plurality of plate members 2Y, as explained in <4.4> of the first embodiment.

[0243] <3.3> Regarding the Controller The lighting device according to the third embodiment may include a controller 100A or a controller 100B instead of the controller 100, as described in <4.5> of the first embodiment.

[0244] <3.4> Relationship between the casing and the plate material In the lighting device according to the third embodiment, the casing 1 and the plate material 2Y may be integrated by forming a part of the inner surface 12 from a light-absorbing material, as described in <4.6> of the first embodiment.

[0245] <3.5> Regarding the Light Source In the above embodiment, the light source 3 is attached to the support 5. However, the arrangement of the light source 3 is not limited to this example as long as it is possible to irradiate light into the internal space 13, and may be determined appropriately depending on the embodiment.

[0246] Furthermore, in the above embodiment, an example in which the light source 3 and the plate 2Y are provided separately has been described, but providing the light source 3 and the plate 2Y separately is not essential for the lighting device according to the third embodiment. For example, the light source 3 may be integrated with the plate 2Y by arranging the light source 3 on the first surface 21 (the surface facing the inner surface 12) of the plate 2Y. By adopting such a configuration, it is possible to achieve a more compact lighting device than a lighting device in which the light source 3 and the plate 2Y are provided as separate components.

[0247] 1... Casing, 1h (u)... Upper casing (casing), 2, 2a, 2b, 2c, 2d, 2e, 2X, 2Y... Plate material, 2h(u), 2ah(u), 2bh(u), 2ch(u), 2dh(u), 2eh(u), 2fh(u), 2gh(u), 2yh(h)...Upper plate material (upper part), 2h(d)...Lower plate material (lower part), 2h(h)...Horizontal plate material (horizontal part), 3...Light source, 6...Reflector, 11...Outer surface, 11h...Semispherical outer surface (outer surface), 12...Inner surface, 12h...Semispherical inner surface (inner surface), 13...Inner space, 13h...Semispherical inner space (inner space), 14...Light receiving port (observation part), 131, 131h...Center, 132...Zenith, 132h...Vertex, 133h...bottom surface, 134, 134h...axis, 21, 21h...first surface, 22, 22h...second surface, 142...brightest measurement data (measurement data in which the object is observed in the brightest state), 143...darkest measurement data (measurement data in which the object is observed in the darkest state), 144...reference measurement data, 160...data extraction unit (extraction unit), 170...data update unit (storage unit), 180...data correction unit (correction unit), 210, 210a, 210b, 210c, 210d, 210e, 210f, 210g...thin plate, A1...area, L1, L1a, L1b, L1c, L1d, L1e, L1f, L1g, L2, L3...lighting device, S...object

Claims

1. A casing having an outer surface, an inner surface, a spherical or semi-spherical interior space, and an observation portion, the inner surface defines the interior space and is constructed from a material that reflects light; The internal space has a center located in the middle of the internal space, a zenith located vertically above the center, and an axis passing through the center and the zenith, The observation unit is provided for observing an object placed in the internal space, and is disposed at the zenith or at a position spaced apart from the zenith in a circumferential direction along the inner surface. A casing; A plate material disposed opposite the inner surface in the internal space, A portion of the inner surface is covered when viewed from the center, and the position around the axis is adjustable; a first surface facing the inner surface and a second surface facing the center; A board and A light source arranged to irradiate light into the interior space; Equipped with an upper portion of the plate member on a side where the observation unit is disposed with respect to an equatorial plane that is a plane that passes through the center and is perpendicular to the axis, the upper portion including a plurality of thin plates that are disposed so as not to overlap each other; The plurality of thin plates are configured such that the second surface absorbs light; At least one of the thin plates arranged so as not to overlap each other in the upper portion can be moved around the axis by an angle smaller than 360 degrees and rearranged, whereby a curved plate having a shape of two right-angled spherical triangles can be formed by the thin plates, the curved plate corresponding to a region of the inner surface connecting three points consisting of a point corresponding to the zenith of the inner surface and two points on the intersection line between the equatorial plane and the inner surface. Lighting equipment.

2. The area of ​​each of the plurality of thin plates is half or less of the area of ​​the curved plate.

10. The lighting device of claim 1.

3. The plurality of thin plates are not in contact with each other.

3. The lighting device according to claim 1 or 2.

4. from among a plurality of measurement data each showing the object observed while the plate material is moved around the axis in the observation unit, Measurement data in which the object is observed in its brightest state; and Measurement data in which the object is observed in its darkest state; and An extraction unit for extracting a storage unit that stores the two pieces of measurement data extracted by the extraction unit as observation results of the object; Further comprising:

3. The lighting device according to claim 1 or 2.

5. The interior space is spherical; The plate material is the upper portion; a lower portion extending on a side opposite to a side on which the observation unit is disposed with respect to the equatorial plane; Including, The second surface of the lower portion is configured to absorb light.

3. The lighting device according to claim 1 or 2.

6. The interior space is hemispherical; A reflector configured such that a surface facing the interior space is specularly reflective of light, The inner space is provided with a bottom wall. Further comprising a reflector; The plate material is the upper portion; a horizontal portion, the second surface being configured to absorb light, covering a portion of the surface of the reflector facing the interior space and extending along the equatorial plane; Including, 3. The lighting device according to claim 1 or 2.

7. and a correction unit that corrects the measurement data acquired by observing the object with the observation unit, using reference measurement data that is measurement data acquired in advance by observing a white diffusing object having the same shape as the object with the observation unit.

3. The lighting device according to claim 1 or 2.

8. The casing and the plate material are integrated by forming a part of the inner surface with a light-absorbing material.

3. The lighting device according to claim 1 or 2.

9. The plurality of thin plates are formed by dividing one curved plate having a shape of two right-angled spherical triangles along a plane parallel to or inclined to the equatorial plane.

3. The lighting device according to claim 1 or 2.

10. A casing having an outer surface, an inner surface, a spherical interior space, and an observation portion, the inner surface defines the interior space and is constructed from a material that reflects light; The internal space has a center located in the middle of the internal space, a zenith located vertically above the center, and an axis passing through the center and the zenith, The observation unit is provided for observing an object placed in the internal space, and is disposed at the zenith or at a position spaced apart from the zenith in a circumferential direction along the inner surface. A casing; A plate material disposed opposite the inner surface in the internal space, A portion of the inner surface is covered when viewed from the center, and the position around the axis is adjustable; a first surface facing the inner surface and a second surface facing the center; an upper portion which extends toward a side where the observation unit is disposed with respect to an equatorial plane which is a plane that passes through the center and is perpendicular to the axis, and a lower portion which extends toward a side opposite to the side where the observation unit is disposed with respect to the equatorial plane, A board and A light source arranged to irradiate light into the interior space; Equipped with The second surface of the lower portion is configured to absorb light. Lighting equipment.

11. from among a plurality of measurement data each showing the object observed while the plate material is moved around the axis in the observation unit, Measurement data in which the object is observed in its brightest state; and Measurement data in which the object is observed in its darkest state; and An extraction unit for extracting a storage unit that stores the two pieces of measurement data extracted by the extraction unit as observation results of the object; Further comprising:

11. The lighting device of claim 10.

12. and a correction unit that corrects the measurement data acquired by observing the object with the observation unit, using reference measurement data that is measurement data acquired in advance by observing a white diffusing object having the same shape as the object with the observation unit.

12. An illumination device according to claim 10 or 11.

13. The casing and the plate material are integrated by forming a part of the inner surface with a light-absorbing material.

12. An illumination device according to claim 10 or 11.

14. the upper portion includes a plurality of thin plates arranged so as not to overlap one another; The plurality of thin plates are configured such that the second surface absorbs light; At least one of the thin plates arranged so as not to overlap each other in the upper portion can be moved around the axis by an angle smaller than 360 degrees and rearranged, whereby a curved plate having a shape of two right-angled spherical triangles can be formed by the thin plates, the curved plate corresponding to a region of the inner surface connecting three points consisting of a point corresponding to the zenith of the inner surface and two points on the intersection line between the equatorial plane and the inner surface.

12. An illumination device according to claim 10 or 11.

15. The plurality of thin plates are formed by dividing one curved plate having a shape of two right-angled spherical triangles along a plane parallel to or inclined to the equatorial plane.

15. An illumination device according to claim 14.

16. A method of using the lighting device of claim 1, comprising: placing the object in the internal space of the casing and irradiating light from the light source into the internal space; a step of measuring a reflected component of the object by the observation unit at a start point after the step of irradiating light from the light source, and storing the measurement result in a storage unit as measurement data in association with the position of the plate material at the start point; a step of storing measurement data at the starting point, followed by a step of changing the position of the plate, measuring the reflected component of the object using the observation unit, and storing the measurement result in the memory unit as measurement data in association with the position of the plate after the change, the step being repeated until all of the inner surfaces of the internal space are opposed to at least any of the plurality of thin plates at least once.