Lighting device and method of using the lighting device

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

Technical Field

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

Background Art

[0002] In order to measure the color or gloss of an object, it is desirable to satisfy the lighting and light-receiving conditions defined by Japanese Industrial Standards, and many contact-type colorimeters and gloss meters compliant with the Japanese Industrial Standards are commercially available. For an object capable of creating a flat and uniform sample surface, the color and gloss of the target object can be measured by commercially available contact-type colorimeters and gloss meters. However, in order to measure a sample with a complex shape as it is, a color luminance meter and a camera are used to observe the target object non-contact, and lighting needs to be provided separately. Then, variations are likely to occur in the lighting and light-receiving conditions, making it difficult to ensure measurement accuracy.

[0003] The inventors of the present case proposed a lighting device capable of achieving both high measurement accuracy and improved measurement convenience in Patent Document 1 below. Specifically, an example of the lighting device according to the proposal includes a casing, a plurality of plate materials, 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, and the observation unit is arranged at intervals in the circumferential direction along the inner surface from the apex. Each plate material is arranged in the internal space and covers a part of the inner surface when viewed from the center. The surface facing the center of each plate material is made of a material that absorbs light. The plurality of plate materials includes a first plate material, a second plate material arranged symmetrically with the first plate material with respect to the center, and a third plate material not arranged symmetrically with any other plate material with respect to the center. The second plate material and the third plate material each have a transmission port arranged at a position corresponding to the observation unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The inventors of this case conducted further investigations and found that the lighting device proposed in Patent Document 1 has a problem in that the measurement accuracy may decrease due to the reasons described below.

[0006] The first reason is that the proposed lighting device uses a two-right-angled spherical triangle-shaped light trap (optical absorber) as an example, configured so that the entire surface facing the center absorbs light. However, such a light trap blocks all diffuse light from the azimuth angle in which the light trap is located, regardless of the size of the vertex angle of the two right-angled spherical triangles. Therefore, when using a two-right-angled spherical triangle-shaped light trap, depending on the shape of the object being measured, shadows may appear, potentially increasing measurement errors and reducing measurement accuracy.

[0007] A second reason is that if a portion of the bottom surface of the hemispherical internal space is blocked with a reflector, depending on the shape of the object being measured, there may be areas where specular reflection (halation) cannot be removed, potentially reducing the measurement accuracy in those areas.

[0008] Figure 17 shows an example in a conventional lighting device where, when a portion of the bottom surface of the hemispherical internal space is blocked by a reflector, a portion of the specular reflection component cannot be removed. As illustrated in Figure 17, when a portion of the bottom surface of the hemispherical internal space is blocked by a reflector, the specular reflection component shown by the dashed line reaches the observation area, meaning that for convex objects to be measured, a portion of the specular reflection component cannot be removed.

[0009] In one respect, this invention has been made in view of the above circumstances, and its purpose is to provide an illumination device that prevents a decrease in measurement accuracy caused by at least one of the generation of shadows on the object to be measured and the persistence of specular reflection components, thereby enabling highly accurate measurements. [Means for solving the problem]

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

[0011] In other words, 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, wherein the inner surface is made of a material that defines the internal space and reflects light, the internal space has a center, a zenith, and an axis, the axis passes through the center and the zenith, and the observation section is provided for observing an object placed in the internal space and is positioned at the zenith or at a position spaced circumferentially apart from the zenith along the inner surface, and a plate material positioned in the internal space opposite the inner surface, which covers a part of the inner surface when viewed from the center and is configured to be adjustable in position around the axis, having a first surface facing the inner surface and a second surface facing the center The device comprises a plate material having a second surface and a light source positioned to irradiate the internal space with light, wherein the upper portion of the plate material, which is the side of the plate material on which the observation section is positioned relative to the equatorial plane, includes a plurality of thin plates arranged so as not to overlap each other, the plurality of thin plates configured such that the second surface absorbs light, and by moving at least one of the plurality of thin plates arranged so as not to overlap each other in the upper portion at an angle smaller than 360 degrees around the axis and rearranging it, a single curved plate in the shape of a two-right-angled spherical triangle can be formed by all of the plurality of thin plates, corresponding to the region of the inner surface that connects three points: the point on the inner surface corresponding to the zenith and two points on the line of intersection of the equatorial plane and the inner surface.

[0012] In this configuration, the plurality of thin plates are configured so that the second surface absorbs light, and are arranged in the upper portion so as not to overlap each other. By rearranging the position of at least one of the plurality of thin plates by moving it around the axis by an angle smaller than 360 degrees, all of the plurality of thin plates can be used to form one curved plate. In other words, the area of ​​each of the plurality of thin plates included in the upper portion and configured so that the second surface absorbs light is smaller than the area of ​​the curved plate. Furthermore, if the upper portion and the curved plate are arranged so that one side of each (for example, the bottom edge) overlaps, the area of ​​the overlapping portion of the two is smaller than the area of ​​the curved plate.

[0013] Therefore, compared to conventional light traps in which the entire second surface of the two right-angled spherical triangular curved plate is configured to absorb light, the upper portion allows diffused light from the azimuth angle corresponding to the curved plate to reach the object more easily, and shadows are less likely to occur on the object. Accordingly, the illumination device according to one aspect of the present invention can prevent a decrease in measurement accuracy caused by the occurrence of shadows and realize highly accurate measurements.

[0014] In the lighting device relating to the above-described aspect, the area of ​​each of the plurality of thin plates may be less than or equal to half the area of ​​the curved plate. In this configuration, the upper portion can secure at least twice the amount of diffused light reaching the object from the azimuth angle corresponding to the curved plate, compared to a conventional light trap configured to absorb light across the entire second surface of the two right-angled spherical triangular curved plate.

[0015] In the lighting device relating to one aspect described above, the plurality of thin plates do not have to be in contact with each other. In this configuration, the upper portion can be made up of the plurality of thin plates that are not in contact with each other.

[0016] Each lighting device relating to the above aspect may further include an extraction unit that extracts from a plurality of measurement data showing the object in its brightest state and the object in its darkest state from among a plurality of measurement data showing the object observed while the plate material is moved around the axis in the observation unit, and a storage unit that stores the two measurement data extracted by the extraction unit as observation results of the object. In this configuration, the measurement data showing the object in its brightest state and the measurement data showing the object in its darkest state are extracted from the plurality of measurement data, and these two measurement data are stored as observation results of the object. Therefore, compared to the case where all of the plurality of measurement data are stored 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 when measuring at high speed, and by adopting this configuration, for example, it becomes easy to measure an object in water while suppressing specular reflection from a rippling water surface.

[0017] In the illumination device relating to one aspect of the present invention, the internal space is spherical, and the plate material includes the upper portion and the lower portion which extends to the side opposite to the side on which the observation section is positioned relative to the equatorial plane, 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. Accordingly, the illumination device relating to one aspect of the present invention can prevent a decrease in measurement accuracy due to the residual specular reflection component and achieve high-precision measurement.

[0018] In the illumination device relating to one aspect described above, the internal space is hemispherical, and the device further comprises a reflector configured such that the surface facing the internal space specularly reflects light, and is positioned to cover a part of the bottom surface of the internal space. The plate material may include the upper portion and a horizontal portion which is configured such that the second surface absorbs light, covers a part of the surface of the reflector facing the internal space, and extends along the equatorial plane. In this configuration, the horizontal portion covers a part of the surface of the reflector facing the internal space and extends along the equatorial plane, 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, for example, even if the object has a convex shape. Thus, the illumination device relating to one aspect of the present invention can prevent a decrease in measurement accuracy due to the residual specular reflection component and achieve high-precision measurement.

[0019] The lighting device relating to the above-described 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, which is measurement data obtained in advance by observing a white diffuse object of the same shape as the object in the observation unit. In this configuration, the measurement data is corrected using the reference measurement data. Therefore, even if shading occurs in the object for some reason, high-precision measurement can be performed by correcting the part where shading occurs using the reference measurement data.

[0020] In the lighting device relating to one aspect described above, the casing and the plate material may be integrated by forming a part of the inner surface with a light-absorbing material. In this configuration, the casing and the plate material are integrated by forming a part of the inner surface with a light-absorbing material. Therefore, the lighting device relating to one aspect of the present invention can be made smaller than a lighting device in which the casing and the plate material are separate components, and can be installed in environments with limited space, such as factory production lines.

[0021] In the lighting device relating to one aspect described above, the plurality of thin plates may be formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. As described above, by rearranging at least one of the plurality of thin plates by moving it around the axis at an angle smaller than 360 degrees, a single curved plate in the shape of two right-angled spherical triangles can be formed from all of the plurality of thin plates. Therefore, the plurality of thin plates may be formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. Thus, in the lighting device relating to one aspect of the present invention, it is possible to easily prepare the plurality of thin plates that can form a single curved plate in the shape of two right-angled spherical triangles by rearranging them.

[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 section, wherein the inner surface is made of a material that defines the internal space and reflects light, the internal space has a center, a zenith, and an axis, the axis passes through the center and the zenith, and the observation section is provided for observing an object placed in the internal space and is positioned at the zenith or at a position spaced circumferentially apart from the zenith along the inner surface, and the casing and the inner surface facing the internal space A plate material arranged facing the center, which covers a part of the inner surface when viewed from the center and is configured to be adjustable in position about the axis, and has a first surface facing the inner surface and a second surface facing the center, and includes an upper portion which is the part that extends toward the side where the observation part is arranged relative to the equatorial plane and a lower portion which is the part that extends toward the side opposite to the side where the observation part is arranged relative to the equatorial plane, and a light source arranged to irradiate the internal space with light, wherein 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, by the second surface of the lower portion, for example, even when the object has a convex shape, the specular reflection component can be removed. Thus, 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 and realize highly accurate measurement.

[0024] The lighting device according to the above aspect may further include an extraction unit that extracts, from a plurality of measurement data each indicating the object observed while the plate material is moved around the axis in the observation unit, the measurement data in which the object in the brightest state is observed and the measurement data in which the object in the darkest state is observed, and a storage unit that stores the two measurement data extracted by the extraction unit as an observation result 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, which is measurement data previously obtained by observing a white diffusing object having the same shape as the object in the observation unit.

[0026] In the lighting device according to the above aspect, the casing and the plate material may be integrated by forming a part of the inner surface with a material that absorbs light.

[0027] In the lighting device according to the above aspect, the upper portion includes a plurality of thin plates arranged so as not to overlap each other. The plurality of thin plates are configured such that the second surface absorbs light. By moving and rearranging at least one of the plurality of thin plates that are arranged so as not to overlap each other in the upper portion at an angle smaller than 360 degrees around the axis, it may be possible to form a single curved plate in the shape of a right spherical triangle 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 of the equatorial plane and the inner surface by all of the plurality of thin plates.

[0028] In the lighting device relating to one aspect described above, the plurality of thin plates may be formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. As described above, by rearranging at least one of the plurality of thin plates by moving it around the axis at an angle smaller than 360 degrees, a single curved plate in the shape of two right-angled spherical triangles can be formed from all of the plurality of thin plates. Therefore, the plurality of thin plates may be formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. Thus, in the lighting device relating to one aspect of the present invention, it is possible to easily prepare the plurality of thin plates that can form a single curved plate in the shape of two right-angled spherical triangles by rearranging them. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide an illumination device that prevents a decrease in measurement accuracy caused by at least one of the generation of shadows on the object to be measured and the persistence of specular reflection components, thereby achieving high-precision measurement. [Brief explanation of the drawing]

[0030] [Figure 1] Figure 1 is a schematic side view illustrating a lighting device according to the first embodiment. [Figure 2] Figure 2 is a schematic plan view illustrating the main body according to the first embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view illustrating the main body according to the first embodiment. [Figure 4] Figure 4 is a diagram illustrating how the multiple thin plates included in the upper plate material according to the first embodiment are arranged within the upper plate material. [Figure 5] Figure 5 is a schematic diagram illustrating an example of the software configuration of the controller according to the first embodiment. [Figure 6] Figure 6 shows the movement of the plate material whose position is controlled by the controller in Figure 5. [Figure 7A] Figure 7A is a diagram illustrating how the multiple thin plates included in the modified upper plate are arranged within the modified upper plate. [Figure 7B] Figure 7B is a diagram illustrating how the multiple thin plates included in the modified upper plate are arranged within the modified upper plate. [Figure 7C] Figure 7C is a diagram illustrating how the multiple thin plates included in the modified upper plate are arranged within the modified upper plate. [Figure 7D] Figure 7D is a diagram illustrating how the multiple thin plates included in the modified upper plate are arranged within the modified upper plate. [Figure 7E] Figure 7E is a diagram illustrating how the multiple thin plates included in the modified upper plate are arranged within the modified upper plate. [Figure 8] Figure 8 is a schematic diagram illustrating an example of the software configuration of a controller related to a modified example. [Figure 9] Figure 9 is a schematic diagram illustrating an example of the software configuration of a controller related to a modified example. [Figure 10] Figure 10 is a diagram illustrating the outline of an experiment to verify how much the illuminance is improved by the lighting device according to the embodiment compared to a conventional lighting device. [Figure 11] Figure 11 shows the results of the experiment outlined in Figure 10. [Figure 12] Figure 12 is a schematic side view illustrating a lighting device according to the second embodiment. [Figure 13] Figure 13 is a schematic cross-sectional view illustrating the main body according to the second embodiment. [Figure 14] Figure 14 is a schematic side view illustrating an example of the configuration of a lighting device according to the third embodiment. [Figure 15] Figure 15 is a schematic cross-sectional view illustrating an example of the configuration of the main body according to the third embodiment. [Figure 16]Figure 16 is a diagram illustrating the shape of the upper plate material according to the third embodiment. [Figure 17] Figure 17 shows an example in a conventional lighting device where, when a portion of the bottom surface of the hemispherical internal space is blocked with a reflector, a portion of the specular reflection component cannot be removed. [Figure 18] Figure 18 illustrates the configuration of the upper plate material according to yet another modified example. [Figure 19] Figure 19 illustrates the configuration of the upper plate material in a different modification than that shown in Figure 18. [Modes for carrying out the invention]

[0031] Hereinafter, an embodiment relating to one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described based on the drawings. However, this embodiment described below is merely illustrative in all respects of the present invention. Needless to say, 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 adopted as appropriate. For the convenience of explanation, the following description will be based on the orientation in the drawings.

[0032] <First Embodiment> Conventional lighting devices use a two-right-angled spherical triangle-shaped light trap configured so that the entire surface facing the center absorbs light. However, such conventional light traps block all diffuse light from the azimuth angle in which the light trap is located, regardless of the size of the vertex angle of the two right-angled spherical triangles. Therefore, when using a two-right-angled spherical triangle-shaped light trap configured so that the entire surface facing the center absorbs light, depending on the shape of the object being measured, shadows may appear, potentially increasing measurement errors and reducing measurement accuracy.

[0033] In contrast, the lighting device according to this embodiment utilizes a plurality of thin plates, each configured to absorb light on its center-facing side, arranged so as not to overlap, as a light trap. By rearranging at least one of these plates by moving it at an angle smaller than 360 degrees around an axis passing through the zenith and center of the spherical observation space (internal space), it is possible to form a single curved plate of the following shape using all of these plates. That is, by rearranging at least one plate, it is possible to form a single curved plate with a two-right-angled spherical triangle shape, similar to that of conventional lighting devices, where the entire surface facing the center absorbs light.

[0034] In other words, the area of ​​each of these multiple thin plates is smaller than the area of ​​the single curved plate in the shape of two right-angled spherical triangles described above. Therefore, the light trap provided in 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 a conventional light trap configured to absorb light across the entire second surface of the curved plate in the shape of two right-angled spherical triangles. In other words, the light trap provided in the lighting device according to this embodiment is less likely to cast shadows on the object. Consequently, the lighting device according to this embodiment can prevent a decrease in measurement accuracy caused by the occurrence of shadows and achieve high-precision measurements.

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

[0036] §1 Example Configuration An example of the configuration of the lighting device L1 according to this embodiment will be explained using Figures 1 to 11. Figure 1 is a schematic side view illustrating an example of the configuration of the lighting device L1 according to this embodiment. The lighting device L1 according to this embodiment is used for color measurement of an object S. As illustrated in Figure 1, the lighting device L1 comprises a spherical body B1, a support column 5, and a controller 100 that is communicatively connected to the body B1. Figures 2 and 3 are schematic plan view and cross-sectional view illustrating an example of the configuration of the body B1. As shown in each figure, the body B1 comprises a casing 1, a plate material 2, a light source 3, and a sample stage 4.

[0037] (Casing) The casing 1 according to this embodiment is spherical and consists of a hemispherical upper casing 1h(u) and a hemispherical lower casing 1h(d), which have substantially the same shape, as illustrated in Figures 1 and 3. In the following description, when referring to the upper casing 1h(u) and the lower casing 1h(d) collectively without distinction, the term "hemispherical casing 1h" will be used. Furthermore, when distinguishing between the configuration of the upper casing 1h(u) and the configuration of the lower casing 1h(d), the configuration of the upper casing 1h(u) will be marked with "(u)" after the component number, and the configuration of the lower casing 1h(d) will be marked with "(d)" after the component number.

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

[0039] The hemispherical outer surface 11h faces outward from the hemispherical casing 1h, and the hemispherical inner surface 12h faces inward from the hemispherical casing 1h. In this embodiment, the hemispherical inner surface 12h is made of a material that diffusely reflects light. The material that diffusely reflects light is not particularly limited as long as it is capable of diffusely reflecting light, and may be, for example, a white painted member or a member made of a white material. Specific examples of the material that diffusely reflects light may be barium sulfate, porous PTFE resin, etc. Furthermore, 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, a vertex 132h, a base 133h, and an axis 134h. The center 131h is located in the middle of the sphere containing the hemisphere of the hemispherical internal space 13h. The vertex 132h is located vertically above (or vertically below) the center 131h. The axis 134h passes through the center 131h and the vertex 132h. The base 133h contains the center 131h and is formed in a circular shape. The hemispherical casing 1h is open to the base 133h side of the hemispherical internal space 13h and has an annularly formed open end 15h. Hereinafter, the vertex 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 specifically referred to as the zenith 132. Furthermore, 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 integrally. Alternatively, the hemispherical casing 1h may be divided into multiple parts around the axis. Furthermore, the material of the hemispherical casing 1h 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 hemispherical casing 1h. It is desirable that the material of the hemispherical casing 1h be a material that has excellent workability and can ensure strength.

[0042] A spherical casing 1 is formed by arranging two hemispherical casings 1h, as described above, such that their respective centers 131h coincide and their respective open ends 15h face each other. Specifically, a spherical casing 1 is formed by arranging an upper casing 1h(u) and a lower casing 1h(d) such that their respective centers 131h coincide and their respective open ends 15h face each other.

[0043] Therefore, as illustrated in Figure 3, the casing 1 comprises 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 fatally affect 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] Up to this point, we have described an example of constructing a spherical casing 1 from a hemispherical upper casing 1h(u) and a hemispherical lower casing 1h(d). However, it is not essential to use an upper casing 1h(u) and a lower casing 1h(d) to construct the casing 1. The casing 1 may be divided into multiple parts around an axis, that is, it may be divided into multiple parts by multiple planes passing through the axis 134. The lighting device L1 (main body B1) only needs to have 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 Figure 3, the casing 1 (particularly the upper casing 1h(u)) is equipped with a light-receiving port 14. The light-receiving port 14 is provided for observing an object S placed in the internal space 13. The light-receiving port 14 is an example of the "observation section" of the present invention. In the examples shown in Figures 1 to 3, the light-receiving port 14 is positioned at a location corresponding to the zenith 132 of the internal space 13. However, the position of the light-receiving port 14 is not particularly limited and may be set as appropriate depending on the embodiment. For example, the light-receiving port 14 may be positioned spaced apart from the zenith 132 in the circumferential direction along the inner surface 12. Specifically, to be suitable for measuring specular reflection, the light-receiving port 14 may be positioned such that the angle between the line connecting the light-receiving port 14 and the center 131 and the axis 134 is 20 degrees, 45 degrees, 60 degrees, or 85 degrees. Furthermore, for example, to be suitable for measuring diffuse reflectance, the light-receiving aperture 14 may be positioned such that the angle between the line connecting the light-receiving aperture 14 and the center 131 and the axis 134 is 45 degrees. Also, for example, to be suitable for measuring retroreflection, the light-receiving aperture 14 may be positioned such that the angle between the line connecting the light-receiving aperture 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 can transmit light, and may be appropriately determined depending on the embodiment. For example, the light-receiving opening 14 may be made of a transparent material such as a resin material. Alternatively, for example, the light-receiving opening 14 may be made of 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 port 14 may be configured to be open, allowing light to pass through, and closed, blocking light transmission. The configuration for making the light-receiving port 14 open and closed is not particularly limited and may be determined appropriately depending on the embodiment. For example, a closing member (not shown), such as a cap, which can be attached to the light-receiving port 14, may be provided. By blocking the light-receiving port 14 with this closing member, the light-receiving port 14 may be in a closed state. On the other hand, by removing this closing member from the light-receiving port 14, the light-receiving port 14 may be in an open state.

[0048] As described above, the outer surface 11 of the casing 1 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 appropriately selected depending on the embodiment.

[0049] (Light source, sample stage, and support column) Next, the light source 3 will be described. As shown in Figure 3, the light source 3 is positioned to irradiate the internal space 13 with light. In this embodiment, the light source 3 is attached to the support column 5. The support column 5 is a member that supports the sample stage 4 on which the object S is placed, and for example, it has the shape of a long, slender rod extending along its longitudinal direction (axial direction), and its axis is configured to coincide with the axis 134 passing through the center 131 of the spherical internal space 13. As illustrated in Figure 3, the support column 5 may be configured to be able to adjust its height so that the object S placed on the sample stage 4 is positioned near the center 131 of the internal space 13.

[0050] (plate material) The plate material 2 is positioned in the internal space 13 facing the inner surface 12. In particular, as illustrated in Figure 3, in the lighting device L1 (main body B1), the plate material 2 comprises an upper plate material 2h(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 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 material 2h(u) is composed of 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 each other.

[0051] In the plate material 2 illustrated in Figure 3, the upper plate material 2h(u) and the lower plate material 2h(d) are in contact with each other in the equatorial plane (a plane passing through the center 131 and perpendicular to the axis 134). That is, in the plate material 2, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is located is the upper plate material 2h(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is located is the lower plate material 2h(d). For example, the lengths of contact with the equatorial plane (arc length in the equatorial plane) of the upper plate material 2h(u) and the lower plate material 2h(d) are equal, and they are arranged such that the surface of the upper plate material 2h(u) that is in contact with the equatorial plane and the surface of the lower plate material 2h(d) that is in contact with the equatorial plane face each other. In the plate material 2, the upper plate material 2h(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2h(u) around the axis 134, the lower plate material 2h(d) also rotates around the axis 134.

[0052] In the following description, when referring to the upper plate 2h(u) and the lower plate 2h(d) collectively without distinction, the term "plate 2" will be used. Plate 2 covers a portion of the inner surface 12 as viewed from the center 131 and is configured to be adjustable in position around the axis 134. Plate 2 has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131. Below, we will first describe the upper plate 2h(u) using Figure 4.

[0053] (Upper board) Figure 4 schematically illustrates the relationship between the upper plate material 2h(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and also illustrates how the multiple thin plates 210 contained within the upper plate material 2h(u) are arranged within the upper plate material 2h(u). The upper plate material 2h(u) contains multiple thin plates 210, and in the example shown in Figure 4, it includes thin plate 210(1) and thin plate 210(2). In the following explanation, when referring to the multiple thin plates 210 collectively without distinguishing between them, the term "thin plate 210" will be used. When distinguishing between the multiple thin plates 210, they will be distinguished by adding "(1)", "(2)", ..., "(n)" (where "n" is a natural number greater than or equal to 2), etc.

[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 can absorb light, and may be, for example, a black painted component or a component made of black material. Specific examples of light-absorbing materials include carbon black and non-reflective brushed cloth. On the other hand, the composition of the surface of the thin plate 210 facing the inner surface 12 (first surface 21h(u)) is not particularly limited and may be appropriately selected depending on the embodiment. The first surface 21h(u) of the thin plate 210 may be made of a material that diffusely 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 other materials.

[0055] The material of the thin sheet 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 sheet 210. It is desirable that the material of the thin sheet 210 be one that has excellent workability and can ensure strength.

[0056] The left side of Figure 4 shows an example of how the thin plates 210(1) and 210(2) are arranged on the upper plate material 2h(u). The right side of Figure 4 shows an example of how the thin plates 210(1) and 210(2) are rearranged after moving the thin plate 210(1) around axis 134, compared to the arrangement shown on the left side of Figure 4. In other words, the left side of Figure 4 shows an example of the arrangement of the thin plates 210(1) and 210(2) on the upper plate material 2h(u) before the rearrangement change. The right side of Figure 4 shows an example of the arrangement of the thin plates 210(1) and 210(2) after the rearrangement change.

[0057] Here, as shown in Figure 4, in this embodiment, the hemispherical inner surface 12h(u) is virtually divided equally into multiple right-angled spherical triangular regions A1 around an axis 134 by a plane passing through the zenith 132 and the center 131h. In the example in Figure 4, the hemispherical inner surface 12h(u) is divided into 12 equal parts, and the vertex angle of each of the 12 regions A1 is 30 degrees. However, the number of divisions is not limited to this example and may be determined as appropriate depending on the embodiment.

[0058] Thin plates 210(1) and thin plate 210(2) are arranged in the upper plate material 2h(u) so as not to overlap each other. In particular, as illustrated on the left side of Figure 4, thin plates 210(1) and thin plate 210(2) before the arrangement change are each arranged so as not to overlap each other, facing only one of the multiple (two in the example shown in Figure 4) regions A1. That is, the multiple thin plates 210 included in the upper plate material 2h(u) are each arranged in the upper plate material 2h(u) so as not to overlap each other, facing only one of the multiple regions A1 of equal area that are virtually provided on the hemispherical inner surface 12h(u).

[0059] As illustrated on the right side of Figure 4, by moving and rearranging at least one of the multiple thin plates 210 included in the upper plate material 2h(u) (in the example of Figure 4, thin plate 210(1)) around the axis 134, one curved plate can be formed as follows. That is, one curved plate having a shape corresponding to a virtual two-right-angled spherical triangular region A1 that evenly divides the inner surface 12 can be formed. On the right side of Figure 4, an example is shown in which thin plate 210(1) and thin plate 210(2) are used to form one curved plate with a two-right-angled spherical triangular shape corresponding to region A1 by moving and rearranging thin plate 210(1) around the axis 134 at an angle smaller than 360 degrees. Specifically, an example is shown in which a curved plate in the shape of two right-angled spherical triangles corresponding to region A1 is formed by moving the thin plate 210(1) (thin plate 210(1) before rearrangement), as exemplified on the left side of Figure 4, 30 degrees clockwise around axis 134.

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

[0061] As has been explained using Figures 1 to 4, the lighting device L1 comprises a casing 1, a plate material 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 opening 14 (observation section). 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, the axis 134 passing through the center 131 and the zenith 132. The light-receiving opening 14 is provided for observing an object S placed in the internal space 13 and is positioned at a location corresponding to the zenith 132, or at a position spaced circumferentially apart from the zenith 132 along the inner surface 12.

[0062] The light source 3 is positioned to irradiate light into the internal space 13. The plate material 2 is positioned in the internal space 13 facing the inner surface 12, covering a portion of the inner surface 12 when viewed from the center 131, and is configured to be adjustable in position around the axis 134. The plate material 2 has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131.

[0063] The upper plate material 2h(u) (upper portion) of the plate material 2, which is the part on the side of the plate material 2 where the light-receiving aperture 14 is positioned 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 the second surface 22h(u) absorbs light.

[0064] By rearranging at least one of the multiple thin plates 210, which are arranged in the upper plate material 2h(u) so as not to overlap each other, by moving it around the axis 134 at an angle smaller than 360 degrees, the following curved plate can be formed by all of the multiple thin plates 210. That is, by rearranging at least one thin plate 210, one curved plate in the shape of a two-right-angled spherical triangle can be formed by all of the multiple thin plates 210, which corresponds to "region A1 of the inner surface 12, which connects three points consisting of the point corresponding to the zenith 132 of the inner surface 12 and two points on the line of intersection of the equatorial plane and the inner surface 12".

[0065] In this configuration, the multiple thin plates 210 are configured such that their second surface 22h(u) absorbs light, and are arranged in the upper plate material 2h(u) so as not to overlap each other. By rearranging the position of at least one of the multiple thin plates 210 by moving it around the axis 134 at an angle smaller than 360 degrees, all of the multiple thin plates 210 can form one "bent 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 material 2h(u) and configured so that their second surface 22h(u) absorbs light is smaller than the area of ​​the "bent plate in the shape of two right-angled spherical triangles corresponding to region A1". Furthermore, if the upper plate 2h(u) and the "two right-angled spherical triangular curved plate corresponding to region A1" are placed so that one side of each (for example, the bottom side) overlaps, the area of ​​the overlapping portion of the two is smaller than the area of ​​the "two right-angled spherical triangular curved plate corresponding to region A1".

[0066] Therefore, compared to conventional light traps in which the entire second surface (the surface facing the center 131) of the "two right-angled spherical triangular curved plate corresponding to region A1" is configured to absorb light, the upper plate material 2h(u) allows diffused light from the azimuth angle corresponding to the "two right-angled spherical triangular curved plate corresponding to region A1" to reach the object S more easily, and shadows are less likely to occur on the object S. Consequently, the illumination device L1 can prevent a decrease in measurement accuracy caused by the occurrence of shadows and achieve high-precision measurements.

[0067] Furthermore, in the upper plate material 2h(u), the multiple thin plates 210 may be connected to each other via a frame or the like. Also, in the upper plate material 2h(u), the multiple thin plates 210 may be connected to each other via a "white plate configured so that the first and second surfaces reflect light" or via a "transparent plate that transmits light".

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

[0069] (Lower board) As illustrated in Figure 3, in the lighting device L1 (main body B1), the plate material 2 includes a lower plate material 2h(d) that faces the hemispherical inner surface 12h(d) of the lower casing 1h(d). In other words, the plate material 2 includes a lower plate material 2h(d) (lower portion) which is the part that extends on the side opposite to the side where the light receiving opening 14 is positioned relative to the equatorial plane. As described above, the upper plate material 2h(u) (in particular, the thin plate 210(2)) and the lower plate material 2h(d) have equal lengths in contact with the equatorial plane (arc length in the equatorial plane). The thin plate 210(2) and the lower plate material 2h(d) are arranged such that the surface of the thin plate 210(2) that contacts the equatorial plane and the surface of the lower plate material 2h(d) that contacts the equatorial plane face each other.

[0070] The lower plate material 2h(d) has a shape that corresponds to (opposes) at least a part of one of a plurality of regions A1 of equal area that are virtually provided on the hemispherical inner surface 12h(d) of the lower casing 1h(d). For example, the lower plate material 2h(d) is constructed as a strip-shaped (approximately trapezoidal) plate material (curved plate) formed by removing a curved plate in the shape of two right-angled spherical triangles that is within a predetermined range from the vertex angle, from a curved plate in the shape of two right-angled spherical triangles that corresponds to (opposes) the entire region A1. That is, the lower plate material 2h(d) is constructed as a strip-shaped curved plate formed by removing a curved plate in the shape of two right-angled spherical triangles that is below a predetermined longitude (a predetermined plane parallel to the equatorial plane), from a curved plate in the shape of two right-angled spherical triangles that corresponds to the entire region A1.

[0071] However, it is not essential that the lower plate material 2h(d) be configured as a strip-shaped plate material; the lower plate material 2h(d) may be a plate material (curved plate) in the shape of two right-angled spherical triangles corresponding to the entire region A1. The lower plate material 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 (especially the hemispherical inner surface 12h(d)) as illustrated in Figure 3, and is reflected by the object S to reach the light receiving opening 14 (observation section). The shape of the lower plate material 2h(d) may be appropriately selected depending on the embodiment. Depending on the shape and size of the object S, the lower plate material 2h(d) may be configured so that the latitude of the lower end of the lower plate material 2h(d) extending along the hemispherical inner surface 12h(d) towards the vertex 132h(d) (the angle between the straight line from the lower end to the center 131 and the axis 134) can be adjusted.

[0072] The surface of the lower plate material 2h(d) facing the center 131 (second surface 22h(d)) is made of a light-absorbing material. The light-absorbing material is not particularly limited as long as it can absorb light, and may be, for example, a black painted material, a black material, etc. Specific examples of light-absorbing materials include, for example, carbon black, non-reflective brushed cloth, etc. On the other hand, the composition of the surface of the lower plate material 2h(d) facing the inner surface 12 (first surface 21h(d)) is not particularly limited and may be appropriately selected depending on the embodiment. The first surface 21h(d) of the lower plate material 2h(d) may be made of a light-diffusing and reflecting material, similar to the inner surface 12 (hemispherical inner surface 12h). Alternatively, the first surface 21h(d) of the lower plate material 2h(d) may be made of other materials.

[0073] In this configuration, the second surface 22h(d) of the lower plate material 2h(d) is configured to absorb light. Therefore, as illustrated in Figure 3, the second surface 22h(d) of the lower plate material 2h(d) can remove the specular reflection component, even if the object S has a convex shape. Consequently, the illumination device L1 can prevent a decrease in measurement accuracy caused by the residual specular reflection component and achieve high-precision measurement.

[0074] Similar to the thin plate 210, the material of the lower plate material 2h(d) 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 lower plate material 2h(d). It is desirable that the material of the lower plate material 2h(d) is one that has excellent workability and can ensure strength.

[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 (especially the plate material 2) and performs color measurement of the object S based on measurement data such as each reflection component of the object S measured by the lighting device L1. The controller 100 is implemented by a general-purpose or dedicated computer and has at least the following functional components as illustrated in Figure 5, which are implemented by its CPU, memory, etc. Specifically, 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] Figure 5 is a schematic diagram illustrating an example of the software configuration of the controller 100. The position control unit 110 controls the position of the plate material 2 (position around the axis 134). That is, the position control unit 110 controls the position of the plate material 2 so that it moves a predetermined angle (for example, 30 degrees) clockwise (or counterclockwise) around the axis 134 in a predetermined period. For example, the position control unit 110 grasps the current position of the plate material 2 (current period) and determines the position of the plate material 2 in the next period (target position). The target position is the position obtained by moving a predetermined angle clockwise (or counterclockwise) around the axis 134 from the current position of the plate material 2. The position control unit 110 notifies the drive unit 120 and the data acquisition unit 130 of the position of the plate material 2 in each period (for example, the current position and the target position in the next period).

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

[0078] The data acquisition unit 130 acquires various measurement data for the object S measured by sensors, etc., located in the light receiving port 14 (observation unit) when the plate material 2 reaches the position of the plate material 2 in each cycle, as notified by the position control unit 110. In other words, the data acquisition unit 130 acquires measurement data for 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, along with the position of the plate material 2 in each cycle, as notified by the position control unit 110.

[0079] The data storage unit 150 stores the measurement data for each cycle acquired by the data acquisition unit 130 in the memory unit 140, associating it with the position of the plate material 2 in each cycle. In other words, the data storage unit 150 stores "measurement data 141 for each position of the plate material 2" in the memory unit 140. By analyzing this "measurement data 141 for each position of the plate material 2," color measurement of the target object S can be performed.

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

[0081] First, as preparation for color measurement, the user places the object to be measured 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, illuminating the internal space 13 with light from the light source 3. As a result, the internal space 13 is in a state where light is diffusely reflected by the inner surface 12 of the casing 1. Then, the user places the light sensor on the outer surface 11 of the casing 1, aligned with the light receiving opening 14, and begins measuring each reflective component of the object S placed in the internal space 13 using the light sensor.

[0082] The type of object S is not particularly limited and may be appropriately selected depending on the embodiment. The object S may be a flat and uniform sample surface, or, for example, an uneven building material (e.g., tile, stone, etc.), food or ingredients (e.g., bread, chocolate, etc.), a plant, a living thing (e.g., an insect, etc.). The type of light sensor is not particularly limited as long as it can measure the color of the object S and may be appropriately selected depending on the embodiment. For example, a colorimeter, digital camera, CCD (Charge Coupled Device), CMOS (Complementary Metal-Oxide-Semiconductor), etc. may be used as the light sensor.

[0083] For example, in the 0th cycle (i.e., the start time), the plate material 2 (upper plate material 2h(u)) is in the position shown on the left side of the paper in Figure 6. Specifically, at the start time, the thin plate 210(2) of the upper plate material 2h(u) is at the 6 o'clock position (bottom side of the paper). The position control unit 110 recognizes that "in the 0th cycle, the thin plate 210(2) is at the 6 o'clock position" and notifies the data acquisition unit 130 that "in the 0th cycle, the thin plate 210(2) is at the 6 o'clock position". In addition, the light sensor measures each reflection component of the object S in the 0th cycle, and the measurement results, i.e., the measurement data, are sent to the data acquisition unit 130. The data storage unit 150 associates the "measurement data in the 0th cycle" acquired by the data acquisition unit 130 with the "position of the plate material 2 (upper plate material 2h(u)) in the 0th cycle" 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 material 2 (upper plate material 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 plate material 2 in the first cycle". In the example in Figure 6, the "target position of plate material 2 in the first cycle" is the position obtained by moving 30 degrees counterclockwise around the axis 134 from the position of plate material 2 in the 0th cycle.

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

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

[0087] In this way, the measurement data for each cycle is associated with the position of the plate material 2 in each cycle and stored in the storage unit 140 as "measurement data 141 for each position of the plate material 2". When the entire inner surface 12 (hemispherical inner surface 12h(u)) faces at least one of the thin plates 210(1) and 210(2) at least once, the acquisition of the measurement data necessary for measuring the color of the object S is completed. In the example shown in Figure 6, the measurement data for each cycle from the 0th cycle to the 11th cycle is associated with the position of the plate material 2 in each cycle and stored in the storage unit 140 as "measurement data 141 for each position of the plate material 2", thereby completing the acquisition of the measurement data necessary for measuring the color of the object S.

[0088] §3 Features As described above, in the lighting device L1 according to this embodiment, the multiple thin plates 210 including the upper plate material 2h(u) are configured such that the second surface 22h(u) absorbs light. By moving at least one of the multiple thin plates 210, which are arranged in the upper plate material 2h(u) so as not to overlap each other, around the axis 134 at an angle smaller than 360 degrees and rearranging them, the following curved plate can be formed by all of the multiple thin plates 210. That is, one curved plate in the shape of two right-angled spherical triangles corresponding to region A1 can be formed. In the upper plate material 2h(u), the multiple thin plates 210 are arranged so as not to overlap each other, for example, so as to face only one of the multiple regions A1.

[0089] In other words, in the lighting device L1, the area of ​​each of the multiple thin plates 210 included in the upper plate material 2h(u) and configured so that the second surface 22h(u) absorbs light is smaller than the area of ​​the "two right-angled spherical triangular curved plate corresponding to region A1". Therefore, compared to conventional light traps in which the entire second surface (the surface facing the center 131) of the "two right-angled spherical triangular curved plate corresponding to region A1" is configured to absorb light, the upper plate material 2h(u) allows diffused light from the azimuth angle corresponding to the "two right-angled spherical triangular curved plate corresponding to region A1" to reach the object S more easily, and shadows are less likely to occur on the object S. Consequently, the lighting device L1 can prevent a decrease in measurement accuracy caused by the occurrence of shadows and achieve high-precision measurements.

[0090] Furthermore, in the illumination device L1 according to this embodiment, the plate material 2 includes a lower plate material 2h(d) which is a portion extending from the equatorial plane to the side opposite to the side where the light receiving opening 14 is positioned, and the second surface 22h(d) of the lower plate material 2h(d) is made of a light-absorbing material. Therefore, the second surface 22h(d) of the lower plate material 2h(d) can remove specular reflection components, for example, even when the object S has a convex shape. Thus, the illumination device L1 can prevent a decrease in measurement accuracy caused by the residual specular reflection component and achieve high-precision measurement.

[0091] As is clear from the above explanation, if we focus solely on suppressing the occurrence of shadows to prevent a decrease in measurement accuracy, it is not essential for the illumination device L1 according to this embodiment to be equipped with a lower plate material 2h(d) as a light trap (plate material 2). In other words, in order to suppress the occurrence of shadows, the illumination device L1 only needs to be equipped with an upper plate material 2h(u) as a light trap (plate material 2). By equipping the illumination device L1 with an upper plate material 2h(u) as a light trap (plate material 2), it is possible to suppress the occurrence of shadows, prevent a decrease in measurement accuracy caused by the occurrence of shadows, and achieve high-precision measurements. Furthermore, by equipping the illumination device L1 with a lower plate material 2h(d) as a light trap (plate material 2) in addition to the upper plate material 2h(u), it is possible to further prevent a decrease in measurement accuracy caused by the residual specular reflection component and achieve high-precision measurements.

[0092] §4 Variant Although one embodiment of the present invention has been described above, the above description is merely illustrative in all respects of the present invention. Needless to say, various improvements and modifications can be made without departing from the scope of the present invention. For example, the following modifications are possible. In the following, the same reference numerals are used for components similar to those in the above embodiment, and explanations of points similar to those in the above embodiment have been omitted as appropriate. The following modifications can be combined as appropriate.

[0093] <4.1> About the structure of the observation section In the above embodiment, the casing 1 is equipped with a light-receiving port 14 as an example of an observation unit. However, the configuration of the observation unit is not limited to this example and may be appropriately selected depending on the embodiment. For example, the observation unit may be composed of the light sensor itself.

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

[0095] Figure 7A is a diagram illustrating the configuration of the upper portion of the plate material 2a (i.e., the upper plate material 2ah(u)) of the modified lighting device L1a (main body B1a). In other words, Figure 7A schematically illustrates the relationship between the upper plate material 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 material 2ah(u) are arranged on the upper plate material 2ah(u). The lighting device L1a is the same as the lighting device L1, except that it is equipped with plate material 2a instead of plate material 2.

[0096] In the plate material 2a, the upper plate material 2ah(u) (in particular, the thin plate 210a(4) described later) and the lower plate material 2h(d) are in contact at the equatorial plane. That is, in the plate material 2a, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is positioned is the upper plate material 2ah(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is positioned is the lower plate material 2h(d). For example, the length of the upper plate material 2ah(u) (in particular, the thin plate 210a(4) described later) and the lower plate material 2h(d) in contact with the equatorial plane is equal to that of the two, and they are arranged such that the surface of the thin plate 210a(4) in contact with the equatorial plane and the surface of the lower plate material 2h(d) in contact with the equatorial plane face each other. In the plate material 2a, the upper plate material 2ah(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2ah(u) around the axis 134, the lower plate material 2h(d) also rotates around the axis 134.

[0097] The plate material 2a is positioned in the internal space 13 facing the inner surface 12. The plate material 2a comprises an upper plate material 2ah(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate material 2h(d) of plate material 2a is the same as the lower plate material 2h(d) of plate material 2, so its description is omitted.

[0098] As illustrated in Figure 7A, the upper plate material 2ah(u) includes multiple thin plates 210a, and in the example shown in Figure 7A, it includes thin plate 210a(1), thin plate 210a(2), thin plate 210a(3), and thin plate 210a(4). In the following description, when referring to the multiple thin plates 210a collectively without distinguishing between them, the term "thin plate 210a" will be used. When distinguishing between the multiple thin plates 210a, "(1)", "(2)", ..., "(n)", etc. will be added to distinguish them. The thin plates 210a included in the upper plate material 2ah(u) are the same as the thin plates 210 included in the upper plate material 2h(u), except for their number and arrangement. For example, the surface of the thin plate 210a facing the center 131 (the 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 Figure 7A, the thin plates 210a(1), 210a(2), 210a(3), and 210a(4) included in the upper plate material 2ah(u) are each arranged in the upper plate material 2ah(u) so as not to overlap with each other. In particular, as illustrated in Figure 7A, these four thin plates 210a are each arranged in the upper plate material 2ah(u) so as not to overlap with each other, facing only one of the multiple (two in the example shown in Figure 7A) regions A1. That is, the multiple thin plates 210a included in the upper plate material 2ah(u) are each arranged in the upper plate material 2ah(u) so as not to overlap with each other, facing only one of the multiple regions A1 virtually provided on the hemispherical inner surface 12h(u).

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

[0101] In the upper plate material 2ah(u), the multiple thin plates 210a may be connected to each other via a frame or the like. Alternatively, in the upper plate material 2ah(u), the multiple thin plates 210a may be connected to each other via a "white plate configured so that the first and second surfaces reflect light" or via a "transparent plate that transmits light".

[0102] Figure 7B illustrates the configuration of the upper portion of the plate material 2b (i.e., the upper plate material 2bh(u)) of the modified lighting device L1b (main body B1b). In other words, Figure 7B schematically illustrates the relationship between the upper plate material 2bh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and also explains how the multiple thin plates 210 included in the upper plate material 2bh(u) are arranged on the upper plate material 2bh(u). The lighting device L1b is the same as the lighting device L1, except that it includes plate material 2b instead of plate material 2.

[0103] In the plate material 2b, the upper plate material 2bh(u) (in particular, the thin plate 210b(3) described later) and the lower plate material 2h(d) are in contact at the equatorial plane. That is, in the plate material 2b, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is positioned is the upper plate material 2bh(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is positioned is the lower plate material 2h(d). For example, the upper plate material 2bh(u) (in particular, the thin plate 210b(3) described later) and the lower plate material 2h(d) have equal lengths in contact with the equatorial plane, and they are arranged such that the surface of the thin plate 210b(3) in contact with the equatorial plane and the surface of the lower plate material 2h(d) in contact with the equatorial plane face each other. In the plate material 2b, the upper plate material 2bh(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2bh(u) around the axis 134, the lower plate material 2h(d) also rotates around the axis 134.

[0104] The plate material 2b is positioned in the internal space 13 facing the inner surface 12. The plate material 2b comprises an upper plate material 2bh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate material 2h(d) of plate material 2b is the same as the lower plate material 2h(d) of plate material 2, so its description is omitted.

[0105] As illustrated in Figure 7B, the upper plate material 2bh(u) includes multiple thin plates 210b, and in the example shown in Figure 7B, it includes thin plate 210b(1), thin plate 210b(2), and thin plate 210b(3). In the following description, when referring to the multiple thin plates 210b collectively without distinguishing between them, the term "thin plate 210b" will be used. When distinguishing between the multiple thin plates 210b, prefixes such as "(1)", "(2)", ..., "(n)" will be added to distinguish them.

[0106] The thin plates 210b included in the upper plate material 2bh(u) are the same as the thin plates 210 included in the upper plate material 2h(u), except for their number and position. For example, the surface of the thin plate 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 plate 210. As illustrated in Figure 7B, the thin plates 210b(1), 210b(2), and 210b(3) included in the upper plate material 2bh(u) are each arranged in the upper plate material 2bh(u) so as not to overlap with each other. In particular, as illustrated in Figure 7B, these three thin plates 210b are each arranged in the upper plate material 2bh(u) so as not to overlap with each other, facing only one of the multiple (three in the example shown in Figure 7B) regions A1. In other words, the multiple thin plates 210b included in the upper plate material 2bh(u) are arranged so as not to overlap with each other, so that each of them faces only one of the multiple regions A1 virtually provided on the hemispherical inner surface 12h(u) of the upper plate material 2bh(u).

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

[0108] In the upper plate material 2bh(u), the multiple thin plates 210b may be connected to each other via a frame or the like. Alternatively, in the upper plate material 2bh(u), the multiple thin plates 210b may be connected to each other via a "white plate configured so that the first and second surfaces reflect light" or via a "transparent plate that transmits light".

[0109] Figure 7C illustrates the configuration of the upper portion of the plate material 2c (i.e., the upper plate material 2ch(u)) of the modified lighting device L1c (main body B1c). In other words, Figure 7C schematically illustrates the relationship between the upper plate material 2ch(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and also explains how the multiple thin plates 210 included in the upper plate material 2ch(u) are arranged on the upper plate material 2ch(u). The lighting device L1c is the same as the lighting device L1 except that it is equipped with plate material 2c instead of plate material 2.

[0110] In the plate material 2c, the upper plate material 2ch(u) (in particular, the thin plate 210c(3) described later) and the lower plate material 2h(d) are in contact at the equatorial plane. That is, in the plate material 2c, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is positioned is the upper plate material 2ch(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is positioned is the lower plate material 2h(d). For example, the length of the upper plate material 2ch(u) (in particular, the thin plate 210c(3) described later) and the lower plate material 2h(d) in contact with the equatorial plane is equal to that of the two, and they are arranged such that the surface of the thin plate 210c(3) in contact with the equatorial plane and the surface of the lower plate material 2h(d) in contact with the equatorial plane face each other. In the plate material 2c, the upper plate material 2ch(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2ch(u) around the axis 134, the lower plate material 2h(d) also rotates around the axis 134.

[0111] The plate material 2c is positioned in the internal space 13 facing the inner surface 12. The plate material 2c comprises an upper plate material 2ch(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate material 2h(d) of plate material 2c is the same as the lower plate material 2h(d) of plate material 2, so its description is omitted.

[0112] As illustrated in Figure 7C, the upper plate material 2ch(u) includes multiple thin plates 210c, and in the example shown in Figure 7C, it includes thin plate 210c(1), thin plate 210c(2), and thin plate 210c(3). In the following description, when referring to the multiple thin plates 210c collectively without distinguishing between them, the term "thin plate 210c" will be used. When distinguishing between the multiple thin plates 210c, prefixes such as "(1)", "(2)", ..., "(n)" will be added to distinguish them.

[0113] The thin plates 210c included in the upper plate material 2ch(u) are the same as the thin plates 210 included in the upper plate material 2h(u), except for their number and position. For example, the surface of the thin plate 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 plate 210. As illustrated in Figure 7C, the thin plates 210c(1), 210c(2), and 210c(3) included in the upper plate material 2ch(u) are each arranged in the upper plate material 2ch(u) so as not to overlap with each other. In particular, as illustrated in Figure 7C, these three thin plates 210c are each arranged in the upper plate material 2ch(u) so as not to overlap with each other, facing only one of the multiple (two in the example shown in Figure 7C) regions A1. In other words, the multiple thin plates 210c included in the upper plate material 2ch(u) are arranged so as not to overlap with each other, so that each of them faces only one of the multiple regions A1 virtually provided on the hemispherical inner surface 12h(u) of the upper plate material 2ch(u).

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

[0115] In the upper plate material 2ch(u), multiple thin plates 210c may be connected to each other via a frame or the like. Alternatively, in the upper plate material 2ch(u), multiple thin plates 210c may be connected to each other via a "white plate configured so that the first and second surfaces reflect light" or via a "transparent plate that transmits light".

[0116] Figure 7D illustrates the configuration of the upper portion of the plate material 2d (i.e., the upper plate material 2dh(u)) of the modified lighting device L1d (main body B1d). In other words, Figure 7D schematically illustrates the relationship between the upper plate material 2dh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and also explains how the multiple thin plates 210 included in the upper plate material 2dh(u) are arranged on the upper plate material 2dh(u). The lighting device L1d is the same as the lighting device L1 except that it is equipped with plate material 2d instead of plate material 2. The plate material 2d is arranged in the internal space 13 facing the inner surface 12. The plate material 2d comprises an upper plate material 2dh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate material 2h(d) of plate material 2d is the same as the lower plate material 2h(d) of plate material 2, so its description is omitted.

[0117] In the plate material 2d, the upper plate material 2dh(u) (in particular, the thin plate 210d(6) described later) and the lower plate material 2h(d) are in contact at the equatorial plane. That is, in the plate material 2d, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is positioned is the upper plate material 2dh(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is positioned is the lower plate material 2h(d). For example, the length of the upper plate material 2dh(u) (in particular, the thin plate 210d(6) described later) and the lower plate material 2h(d) in contact with the equatorial plane is equal to that of the two, and they are arranged such that the surface of the thin plate 210d(6) in contact with the equatorial plane and the surface of the lower plate material 2h(d) in contact with the equatorial plane face each other. In the plate material 2d, the upper plate material 2dh(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2dh(u) around the axis 134, the lower plate material 2h(d) also rotates around the axis 134.

[0118] As illustrated in Figure 7D, the upper plate material 2dh(u) includes multiple thin plates 210d, and in the example shown in Figure 7D, it includes thin plate 210d(1), thin plate 210d(2), thin plate 210d(3), thin plate 210d(4), thin plate 210d(5), and thin plate 210d(6). In the following description, when referring to multiple thin plates 210d collectively without distinguishing between them, the term "thin plate 210d" will be used. When distinguishing between multiple thin plates 210d, prefixes such as "(1)", "(2)", ..., "(n)" will be added to distinguish them.

[0119] The thin plates 210d included in the upper plate material 2dh(u) are the same as the thin plates 210 included in the upper plate material 2h(u), except for their number and position. For example, the surface of the thin plate 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 plate 210. As illustrated in Figure 7D, the thin plates 210d(1), 210d(2) to 210d(6) included in the upper plate material 2dh(u) are each arranged in the upper plate material 2dh(u) so as not to overlap with each other. In particular, as illustrated in Figure 7D, these six thin plates 210d are each arranged in the upper plate material 2dh(u) so as not to overlap with each other, facing only one of the multiple (three in the example shown in Figure 7D) regions A1. In other words, the multiple thin plates 210d included in the upper plate material 2dh(u) are arranged so as not to overlap with each other, so that each of them faces only one of the multiple regions A1 virtually provided on the hemispherical inner surface 12h(u) of the upper plate material 2dh(u).

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

[0121] In the upper plate material 2dh(u), the multiple thin plates 210d may be connected to each other via a frame or the like. Alternatively, in the upper plate material 2dh(u), the multiple thin plates 210d may be connected to each other via a "white plate configured so that the first and second surfaces reflect light" or via a "transparent plate that transmits light".

[0122] The area of ​​each of the multiple thin plates (thin plates 210a to thin plates 210d) included in the upper portion (upper plate material 2ah(u) to 2dh(u)) of the plate material (plate material 2a to 2d) as explained 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 secure more than twice the amount of diffused light reaching the object 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 across the entire second surface (the surface facing the center 131) of the "two right-angled spherical triangular curved plate corresponding to region A1".

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

[0124] Figure 7E illustrates the configuration of the upper portion of the plate material 2e (i.e., the upper plate material 2eh(u)) of the modified lighting device L1e (main body B1e). In other words, Figure 7E schematically illustrates the relationship between the upper plate material 2eh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and also explains how the multiple thin plates 210e included in the upper plate material 2eh(u) are arranged on the upper plate material 2eh(u). The lighting device L1e is the same as the lighting device L1 except that it is equipped with plate material 2e instead of plate material 2. The plate material 2e is arranged in the internal space 13 facing the inner surface 12. The plate material 2e comprises an upper plate material 2eh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d). The lower plate material 2h(d) of plate material 2e is the same as the lower plate material 2h(d) of plate material 2, so its description is omitted.

[0125] In the plate material 2e, the upper plate material 2eh(u) (in particular, the thin plate 210e(2) described later) and the lower plate material 2h(d) are in contact at the equatorial plane. That is, in the plate material 2e, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is positioned is the upper plate material 2eh(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is positioned is the lower plate material 2h(d). For example, the upper plate material 2eh(u) (in particular, the thin plate 210e(2) described later) and the lower plate material 2h(d) have equal lengths in contact with the equatorial plane, and they are arranged such that the surface of the thin plate 210e(2) in contact with the equatorial plane and the surface of the lower plate material 2h(d) in contact with the equatorial plane face each other. In the plate material 2e, the upper plate material 2eh(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2eh(u) around the axis 134, the lower plate material 2h(d) also rotates around the axis 134.

[0126] As illustrated in Figure 7E, the upper plate material 2eh(u) includes multiple thin plates 210e, and in the example shown in Figure 7E, it includes thin plate 210e(1) and thin plate 210e(2). In the following explanation, when referring to the multiple thin plates 210e collectively without distinguishing between them, the term "thin plate 210e" will be used. When distinguishing between the multiple thin plates 210e, "(1)", "(2)", ..., "(n)", etc. will be added to distinguish them.

[0127] The thin plate 210e included in the upper plate material 2eh(u) is the same as the thin plate 210 included in the upper plate material 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 Figure 7E, the thin plates 210e(1) and 210e(2) included in the upper plate material 2eh(u) are each arranged in the upper plate material 2eh(u) so as not to overlap each other. In particular, as illustrated in Figure 7E, these two thin plates 210e are each arranged in the upper plate material 2eh(u) so as not to overlap each other, facing only one of the multiple (two in the example shown in Figure 7E) regions A1. In other words, the multiple thin plates 210e included in the upper plate material 2eh(u) are arranged so as not to overlap with each other, so that each of them faces only one of the multiple regions A1 virtually provided on the hemispherical inner surface 12h(u) of the upper plate material 2eh(u).

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

[0129] As explained using Figure 7E, in the lighting device L1e, the multiple thin plates (thin plates 210e) included in the upper portion (upper plate material 2eh(u)) of the plate material (plate material 2e) do not have to be in contact with each other. In this configuration, the upper portion can be made up of the multiple thin plates that are not in contact with each other.

[0130] <4.4> Regarding the number of boards Up to this point, we have described examples in which each of the lighting devices L1 to L1e (main bodies B1 to B1e) is equipped with one plate material (specifically, each of plate materials 2 to 2e). However, it is not essential that the lighting devices according to the above embodiments are equipped with only one plate material, and may be equipped with multiple plate materials. For example, the lighting devices according to the above embodiments may be equipped with two plate materials (a first plate material and a second plate material) arranged symmetrically with respect to the center 131, similar to the lighting device described in Patent Document 1 (Japanese Patent Application Publication No. 2020-202119). Furthermore, the lighting devices according to the above embodiments may be equipped with a third plate material in addition to these two plate materials, which is not positioned symmetrically with respect to the center 131 with respect to either of the two plate materials. Furthermore, the lighting devices according to the above embodiments may be equipped with a fourth plate material which is not positioned symmetrically with respect to the center 131 with respect to any of the first plate material, the second plate material, and the third plate material. Among these multiple plate materials, at least one plate material may have an upper portion (i.e., the upper plate material facing the hemispherical inner surface 12h(u) of the upper casing 1h(u)) that is one of the upper plate materials 2h(u) to 2eh(u) described above.

[0131] The information described so far can be summarized as follows: 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 with each other, with each facing only one of two or more regions A1 (or a part of any one of regions A1), so that diffused light is secured from the azimuthal direction corresponding to each region A1 by at least half. For example, the upper portion is formed by dividing a single curved plate in the shape of two right-angled spherical triangles corresponding to region A1 into a plurality of thin plates on one or more planes parallel to the equator, and arranging each of these plurality of thin plates so as to face only one of two or more regions A1. Therefore, the upper portion makes it possible to secure diffused light from the azimuthal direction corresponding to each region A1 by at least half.

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

[0133] Here, if the number of exposures (cycles) required to completely obscure the inner surface 12 using the conventional "single curved plate in the shape of two right-angled spherical triangles corresponding to region A1" is a multiple of 2, the following relationship holds: That is, the number of cycles required to completely obscure the inner surface 12 using the upper portion, which is "formed by dividing the 'single curved plate in the shape of two right-angled spherical triangles corresponding to region A1' and arranging multiple thin plates so that each of them faces only one of the two regions A1," is the same as the number of cycles required in the conventional method. Furthermore, similar to the lighting device described in Patent Document 1, the lighting devices according to each of the above embodiments may also be equipped with multiple plate materials (in particular, multiple upper portions). By providing multiple upper portions, the lighting devices according to each of the above embodiments can reduce the number of exposures (cycles) required to completely obscure the hemispherical inner surface 12h(u) with the upper portions, while preventing a decrease in diffusivity.

[0134] Furthermore, if the number of exposures (cycles) required to completely block the inner surface 12 using the conventional "one curved plate in the shape of two right-angled spherical triangles corresponding to region A1" is a multiple of 3, then the upper portion may be made by "dividing the "one curved plate in the shape of two right-angled spherical triangles corresponding to region A1" and arranging multiple thin plates so that each plate faces only one of the three regions A1." The upper portion, which includes multiple thin plates each arranged to face only one of the three regions A1, can ensure that diffused light from the directional direction corresponding to each region A1 is at least 2 / 3. In other words, in the lighting device according to each of the above embodiments, the upper portion of the plate material used as a light trap may be made by dividing the "one curved plate in the shape of two right-angled spherical triangles corresponding to region A1" and arranging multiple thin plates so that each plate faces only one of the "n" regions A1. By adopting such a configuration (arrangement), the upper portion can ensure that diffused light from the directional direction corresponding to each region A1 is at least "(n-1) / n".

[0135] <4.5> About the controller (Reducing the amount of data to be stored) Each of the above embodiments of the lighting device may include a controller 100A instead of the controller 100, as described below with reference to Figure 8. Note that the modified lighting device L1f described below has components that share the same operation and function as the components of the lighting device L1 described with reference to Figure 1, etc. Such components are denoted by the same reference numerals as the corresponding components shown in Figure 1, etc., and detailed descriptions are omitted unless necessary.

[0136] Controller 100A, like Controller 100, is implemented by a general-purpose or dedicated computer, and its functional components, such as its CPU and memory, include at least the following functional units illustrated in Figure 8. Specifically, Controller 100A includes at least a position control unit 110, a drive unit 120, a data acquisition unit 130, and a storage unit 140, similar to Controller 100, and further includes a data extraction unit 160 (extraction unit) and a data update unit 170 (storage unit).

[0137] Figure 8 schematically illustrates an example of the software configuration of the controller 100A included in the modified lighting device L1f. The position control unit 110 of the controller 100A controls the position (position around the axis 134) of the plate material (plate material 2 to 2e) in each cycle, similar to the position control unit 110 of the controller 100. For the sake of ease of understanding, the following explanation will describe an example where the plate material is "plate material 2". The drive unit 120 of the controller 100A changes the position (position around the axis 134) of the plate material 2 in each cycle according to the target position in each cycle notified by the position control unit 110, similar to the drive unit 120 of the controller 100. The data acquisition unit 130 of the controller 100A acquires measurement data in each cycle, similar to the data acquisition unit 130 of the controller 100. The data acquisition unit 130 of the controller 100A notifies the data extraction unit 160 of the acquired "measurement data for each cycle" along with the "position of the plate material 2 in each cycle (target position)" notified by the position control unit 110.

[0138] The memory unit 140 has pre-stored the "darkest data (for example, data showing solid black)" as the initial value for the brightest measurement data 142, and the "brightest data (for example, data showing solid white)" as the initial value for the darkest measurement data 143. When the data extraction unit 160 is notified by the data acquisition unit 130 of "measurement data for a certain period C(x)" and "the position of the plate material 2 in a certain period C(x)", it performs the following processing. That is, the data extraction unit 160 first refers to the memory unit 140 to obtain the brightest measurement data 142 and the darkest measurement data 143. Then, the data extraction unit 160 compares the "measurement data for a certain period C(x)" notified by the data acquisition unit 130 with the brightest measurement data 142 and the darkest measurement data 143, respectively. The data extraction unit 160 determines whether the "measurement data for a certain period C(x)" is "brighter" than the "brightest measurement data 142". Furthermore, the data extraction unit 160 determines whether the "measurement data for a certain period C(x)" is "darker" than the "darkest measurement data 143". For example, the data extraction unit 160 may perform the above determination using the "brightness (luminosity), luminance, light intensity, etc." of the "measurement data for a certain period C(x)", the "brightest measurement data 142", and the "darkest measurement data 143".

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

[0140] The data update unit 170 updates at least one of the "brightest measurement data 142" and the "dimest measurement data 143" stored in the storage unit 140 in accordance with the notification from the data extraction unit 160. That is, if the data update unit 170 determines that the "measurement data for a certain period C(x)" is brighter than the "brightest measurement data 142", it updates the "brightest measurement data 142" stored in the storage unit 140 with the "measurement data for a certain period C(x)". Also, if the data update unit 170 determines that the "measurement data for a certain period C(x)" is darker than the "dimest measurement data 143", it updates the "dimest measurement data 143" stored in the storage unit 140 with the "measurement data for a certain period C(x)".

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

[0142] As explained 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 of each period the measurement data in which the brightest object S is observed and the measurement data in which the darkest object S is observed. The measurement data of each period is measurement data that shows the object S observed at the light receiving opening 14 (observation unit) while the plate material (plate material 2 to 2e) is moved around the axis 134. The data update unit 170 stores the "measurement data in which the brightest object S is observed" and the "measurement data in which the darkest object S is observed" extracted by the data extraction unit 160 as observation results of the object S.

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

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

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

[0146] (Correction based on pre-measurement of mockups) Each of the above embodiments of the lighting device may include a controller 100B, as described below with reference to Figure 9, instead of controller 100 or controller 100A. Note that the modified lighting device L1g described below has components that share the same operation and function as the components of the lighting device L1 described with reference to Figure 1, etc. Such components are denoted by the same reference numerals as the corresponding components shown in Figure 1, etc., and detailed descriptions are omitted unless necessary.

[0147] Controller 100B, like Controller 100, is implemented by a general-purpose or dedicated computer, and its functional components, such as its CPU and memory, include at least the following functional units illustrated in Figure 9. Specifically, Controller 100B includes at least a position control unit 110, a drive unit 120, a data acquisition unit 130, and a storage unit 140, similar to Controller 100, and further includes a data correction unit 180 (correction unit) and a data storage unit 190.

[0148] Figure 9 schematically illustrates an example of the software configuration of the controller 100B of the lighting device L1g according to a modified example. The position control unit 110 of the controller 100B controls the position (position around the axis 134) of the plate material (plate material 2 to 2e) in each cycle, similar to the position control unit 110 of the controller 100. For the sake of ease of understanding, the following explanation will describe an example where the plate material is "plate material 2". The drive unit 120 of the controller 100B changes the position (position around the axis 134) of the plate material 2 in each cycle according to the target position in each cycle notified by the position control unit 110, similar to the drive unit 120 of the controller 100. The data acquisition unit 130 of the controller 100B acquires measurement data in each cycle, similar to the data acquisition unit 130 of the controller 100. The data acquisition unit 130 of the controller 100B notifies the data correction unit 180 of the acquired "measurement data for each cycle" along with the "position of the plate material 2 in each cycle (target position)" notified by the position control unit 110.

[0149] When the data correction unit 180 receives notification from the data acquisition unit 130 of "measurement data for each period" and "position of the plate material 2 in each period," it performs the following processing. Specifically, the data correction unit 180 first refers to the storage unit 140 and obtains the reference measurement data 144 that has been previously stored in the storage unit 140. The reference measurement data 144 is measurement data that has been previously obtained by observing a white diffuse object (mock-up) of the same shape as the target object S at the light receiving port 14 (observation unit). The reference measurement data 144 may, for example, be measurement data that has been previously obtained by observing the above-mentioned mock-up at 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 the calculation "(corrected measurement data) = {(measurement data for each period) / (reference measurement data 144)} × (luminance of white)". 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 material 2 in each period.

[0151] The data storage unit 190 stores the "corrected measurement data for each cycle" and the "position of the plate material 2 in each cycle" notified by the data correction unit 180 in the storage unit 140 as "corrected measurement data 145". In other words, 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 plate material 2 in each cycle", in the storage unit 140. By analyzing this "corrected measurement data 145", the color measurement of the object S can be performed with precision.

[0152] As explained above, the lighting device L1g includes a data correction unit 180 that corrects the measurement data acquired by observing the object S at 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 of the same shape as the object S at the light receiving port 14 (observation unit). In this configuration, the measurement data acquired by observing the object S is corrected using the reference measurement data 144. Therefore, even if shading occurs in the object S for some reason, high-precision measurement can be performed by correcting the part where shading occurs using the reference measurement data 144.

[0153] <4.6> Relationship between casing and sheet metal In the lighting devices according to each of the above embodiments, the inner surface 12 of the casing 1 was made of a material that diffusely reflects light, and the second surface 22 of the plate material (plate material 2 to 2e) was made of a material that absorbs light. In other words, in each of the above embodiments, the inner surface 12 of the casing 1 played the role of diffusing and reflecting light, and the second surface 22 of the plate material (plate material 2 to 2e) played the role of a light trap. However, the configuration of the lighting devices according to each of the above embodiments is not limited to such examples.

[0154] For example, in the modified lighting device, the casing 1 and the plate material (plate material 2-2e) may be integrated by forming a part of the inner surface 12 with a light-absorbing material. The light-absorbing material is not particularly limited as long as it can absorb light, and may be, for example, a black painted component or a component made of black material. As a specific example, the light-absorbing material may be, for example, carbon black or non-reflective brushed cloth. In this configuration, the casing 1 and the plate material (plate material 2-2e) are integrated by forming a part of the inner surface 12 with a light-absorbing material. Therefore, the lighting device according to this modified version can be made smaller 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 integrating the casing 1 and the plate material (plate material 2-2e), instead of rotating the plate material around the axis 134, the casing 1 may be rotated around the axis 134. In other words, instead of controlling the position (position around axis 134) of the plate material (plate material 2 to 2e), the rotation of the casing 1 around axis 134 may be controlled.

[0155] <4.7> About Light Sources Furthermore, in each of the above embodiments, the light source 3 was attached to the support column 5. However, the arrangement of the light source 3 is not limited to these examples, as long as it is possible to illuminate the internal space 13 with light, and may be determined as appropriate depending on the embodiment.

[0156] Furthermore, although the above embodiments describe examples in which the light source 3 and the plate material (plate material 2 to 2e) are provided separately, it is not essential for the lighting device according to the above embodiments to provide the light source 3 and the plate material separately. For example, the light source 3 may be placed on the first surface 21 (the surface facing the inner surface 12) of the plate material (plate material 2 to 2e), thereby integrating the light source 3 and the plate material. By adopting such a configuration, miniaturization can be achieved compared to a lighting device in which the light source 3 and the plate material (plate material 2 to 2e) are separate components.

[0157] <4.8> Regarding the shape of thin plates Figure 18 illustrates the configuration of the upper plate material 2fh(u) according to a modified example. In other words, Figure 18 schematically illustrates the relationship between the upper plate material 2fh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and is also a diagram to explain how the multiple thin plates 210 (in the example shown in Figure 18, thin plates 210f(1) and thin plates 210f(2)) included in the upper plate material 2fh(u) are arranged on the upper plate material 2fh(u). The lighting device L1f (overall view not shown) is the same as the lighting device L1, except that it is equipped with an upper plate material 2fh(u) instead of the upper plate material 2h(u).

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

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

[0160] In the lighting device according to this embodiment, the multiple thin plates included in the upper portion of the plate material may be formed by dividing a single right-angled spherical triangular curved plate with a plane "inclined" to the equatorial plane. For example, as illustrated in Figure 18, the upper plate material 2fh(u) includes multiple thin plates 210f, and in the example shown in Figure 18, it includes thin plate 210f(1) and thin plate 210f(2). In the following description, when referring to the multiple thin plates 210f collectively without distinguishing between them, the term "thin plate 210f" will be used. When distinguishing between the multiple thin plates 210f, "(1)", "(2)", ..., "(n)", etc. will be added to distinguish them.

[0161] The thin plate 210f included in the upper plate material 2fh(u) is the same as the thin plate 210 included in the upper plate material 2h(u), except that it is formed by dividing a single right-angled spherical triangular curved plate with a plane "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 Figure 18, the thin plates 210f(1) and 210f(2) included in the upper plate material 2fh(u) are arranged in the upper plate material 2fh(u) so as not to overlap each other. In particular, as illustrated in Figure 18, these two thin plates 210f are arranged in the upper plate material 2fh(u) such that they do not overlap with each other, so that each faces only one of the multiple (two in the example shown in Figure 18) regions A1. That is, the multiple thin plates 210f included in the upper plate material 2fh(u) are arranged in the upper plate material 2fh(u) such that each faces only one of the multiple regions A1 virtually provided on the hemispherical inner surface 12h(u), so that they do not overlap with each other.

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

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

[0164] <4.9> Regarding the placement of thin plates Figure 19 illustrates the configuration of the upper plate material 2gh(u) according to a modified example. In other words, Figure 19 schematically illustrates the relationship between the upper plate material 2gh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131, and also explains how the multiple thin plates 210 (in the example shown in Figure 19, thin plates 210g(1) to 210g(16)) contained in the upper plate material 2gh(u) are arranged on the upper plate material 2gh(u). The lighting device L1g (overall view not shown) is the same as the lighting device L1, except that it is equipped with an upper plate material 2gh(u) instead of an upper plate material 2h(u).

[0165] As illustrated in Figure 19, the upper plate material 2gh(u) includes multiple thin plates 210g, and in the example shown in Figure 19, it includes thin plates 210g(1) to 210g(16). In the following explanation, when referring to multiple thin plates 210g collectively without distinguishing between them, the term "thin plate 210g" will be used. When distinguishing between multiple thin plates 210g collectively, "(1)", "(2)", ..., "(n)", etc. will be added to distinguish them.

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

[0167] As illustrated in Figure 19, the thin plates 210g(1) to 210g(16) included in the upper plate material 2gh(u) are arranged in such a way that they do not overlap each other in the upper plate material 2gh(u). In particular, in the upper plate material 2gh(u) illustrated in Figure 19, each of the thin plates 210g(1) to 210g(16) is arranged such that the meridians of each thin plate 210g(1) to 210g(16) as a whole form a curve extending from the zenith 132 to the equatorial plane on a sphere. As each of the thin plates 210g(1) to 210g(16) is arranged as described above, the upper plate material 2gh(u) is a spherical isosceles triangle containing two sides of equal length that curvely extend from the zenith 132 to the equatorial plane on a sphere.

[0168] Regarding the thin plates 210, 210a to 210e described so far, the multiple thin plates were arranged so as not to overlap with each other, with each facing only one of the multiple regions A1. For example, the thin plates 210(1) and 210(2) before the arrangement change were arranged so as not to overlap with each other, with each facing only one of the multiple (two in the example shown in Figure 4) regions A1. However, in the lighting device according to this embodiment, it is not essential that the multiple thin plates included in the upper portion of the plate material (upper plate material) are arranged so as not to overlap with each other, with each facing only one of the multiple regions A1. As illustrated in Figure 19, one of the multiple thin plates 210g (for example, thin plate 210g(10)) may be arranged so as to span two adjacent regions A1 among the multiple regions A1.

[0169] By rearranging some of the thin plates 210g contained in the upper plate material 2gh(u) by moving them around the axis 134 at an angle smaller than 360 degrees, one "bent plate in the shape of two right-angled spherical triangles corresponding to region A1" can be formed. In addition, the multiple thin plates 210g in the upper plate material 2gh(u) may be connected to each other via a frame or the like.

[0170] As explained with reference to Figure 19, in the lighting device according to this embodiment, the upper portion of the plate material (upper plate material 2gh(u)) may be a spherical isosceles triangle shape including "two sides of equal length that extend curvedly 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 material (upper plate material) only need to be arranged so as not to overlap each other, for example, they may be arranged on the same spherical surface. In the lighting device according to this embodiment, the shape of the upper portion composed of the multiple thin plates is not particularly limited, and the arrangement of each of the multiple thin plates can be appropriately determined according to the usage form of the lighting device, etc.

[0171] [Examples] The inventors of this case verified, through the following experiment, how much the amount of diffused light (illuminance) reaching the object S is improved by the lighting device according to the above embodiment compared to a conventional lighting device that uses a single curved plate in the shape of two right-angled spherical triangles corresponding to region A1 as a light trap.

[0172] Figure 10 is a diagram illustrating the outline of the experiment. In the experiment, the illuminance near the center 131 was measured for two cases: when the upper plate material 2bh(u), explained using Figure 7B, was used as a light trap, and when the conventional "single curved plate in the shape of two right-angled spherical triangles corresponding to region A1" was used as a light trap. Specifically, a light sensor (illuminance meter) was placed near the center 131, and the illuminance near the center 131 was measured for two cases: when the "single curved plate in the shape of two right-angled spherical triangles corresponding to region A1" was used as a light trap, and when the upper plate material 2bh(u) was used. In the experiment, as the "single curved plate in the shape of two right-angled spherical triangles corresponding to region A1," a single curved plate in the shape of two right-angled spherical triangles corresponding to (opposite) region A1, where the vertex angle is "30," was used. Also, as the upper plate material 2bh(u), an upper plate material 2bh(u) with a vertex angle of "90" was used. In other words, in the upper plate material 2bh(u) used in the experiment, each of the multiple thin plates 210b contained within the upper plate material 2bh(u) is positioned to face only one of three adjacent regions A1 (the vertex angles of each of the three regions A1 are 30 degrees).

[0173] In the following explanation, the azimuth angle is defined as follows, as shown on the left side of Figure 10: the top of the page is "0" degrees, the left side is "90" degrees, the bottom is "180" degrees, and the right side is "270" degrees, when viewed from directly above the main body (casing) (the side with the zenith 132). The right side of Figure 10 also shows the arrangement of the light sensors as viewed from the side (specifically, in the direction of an azimuth angle of "90" degrees).

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

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

[0176] Figure 11 shows the illuminance measured by the above-mentioned optical sensor when the upper plate material 2bh(u) is used as the optical trap and when the conventional "single right-angled spherical triangular curved plate corresponding to region A1" is used as the optical trap. In Figure 11, the dotted line shows the illuminance measured when the conventional "single right-angled spherical triangular curved plate corresponding to region A1" is used as the optical trap. The solid line shows the illuminance measured when the upper plate material 2bh(u) is used as the optical trap.

[0177] Furthermore, in Figure 11, the "azimuth angle (position)" of "a single right-angled spherical triangular curved plate corresponding to region A1" indicates the "azimuth angle (position)" of the center of latitude of this curved plate (the line that bisects the vertex angle ("30" degrees) of this curved plate). Also, the "azimuth angle (position)" of the upper plate material 2bh(u) indicates the "azimuth angle (position)" of the center of latitude of the upper plate material 2bh(u) (the line that bisects the vertex angle ("90" degrees) of the upper plate material 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 at an azimuth angle of approximately 180 degrees. In contrast, when the upper plate material 2bh(u) is used as the light trap, the change in illuminance becomes smoother, and the minimum illuminance is also slightly improved. Specifically, when the light trap is positioned at an azimuth angle of approximately 180 degrees, the illuminance becomes 305 [lx].

[0179] Here, the reduction in illuminance due to light trapping can be mitigated by performing brightness correction (illuminance correction) after measurement. However, the smaller the reduction in illuminance, the less correction is needed. Also, since performing correction increases measurement error (noise), it is desirable to minimize the amount of correction.

[0180] As shown in Figure 11, experiments confirmed that when the upper plate material 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 in the shape of two right-angled spherical triangles 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 required compared to a conventional lighting device that uses a single curved plate in the shape of two right-angled spherical triangles corresponding to region A1 as the light trap, and as a result the measurement error can be reduced. In other words, the lighting device according to the above embodiment can prevent a decrease in measurement accuracy and realize highly accurate measurements.

[0181] <Second Embodiment> Hereinafter, the lighting device L2 according to the second embodiment will be described with reference to Figures 12 and 13. The lighting device L2 described below has components that have the same operation and function as the components of the lighting devices L1 to L1g described so far. Such components are denoted by the same reference numerals as the corresponding components shown in Figure 1, etc., and detailed explanations will be omitted unless necessary.

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

[0183] (Casing) The upper casing 1h(u) of the lighting device L2 (particularly the main body B2) is the same as the upper casing 1h(u) of the lighting device L1 (particularly the main body B1), so details are omitted. Similarly, 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 the same as the hemispherical internal space 13h(u) defined by the upper casing 1h(u) of the main body B1, so details are omitted. Furthermore, as illustrated in Figures 12 and 13, the upper casing 1h(u) is equipped with a light-receiving port 14. The light-receiving port 14 is provided for observing an 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 the same as the light-receiving port 14 provided in the casing 1 of the lighting device L1, so the details are omitted.

[0184] (Light source and frame material) As shown in Figure 13, the light source 3 is positioned to irradiate light onto the hemispherical internal space 13h(u). In this embodiment, the light source 3 is attached to the frame member 7. The frame member 7 is formed in an annular shape and is configured to support the open end 15h(u) of the upper casing 1h(u). In this embodiment, the frame member 7 comprises 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 periphery side of the main body portion 70 and is positioned on the outside (hemispherical outer surface 11h(u) side) of the upper casing 1h(u). On the other hand, the inner peripheral wall 72 is provided on the inner periphery side of the main body portion 70 and is positioned 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 circumferential wall 72 has an outer circumferential surface 721 that faces the hemispherical inner surface 12h(u) of the upper casing 1h(u). In this embodiment, the light source 3 is positioned on the outer circumferential surface 721 of the inner circumferential 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 appropriately selected depending on the embodiment. In this embodiment, since the light source 3 is attached to the frame material 7, it is desirable to use a material with good thermal conductivity that can effectively dissipate the heat generated from the light source 3 for the frame material 7. From this viewpoint, it is desirable to use aluminum, for example, for the frame material 7. Also, the type and number of light sources 3 are not particularly limited and may be appropriately selected depending on the embodiment. For example, LEDs (light emitting diodes), fluorescent tubes, organic EL (electro-luminescence), etc. may be used for the light sources 3. In addition, multiple light sources 3 may be arranged on the cylindrical outer surface 721 at intervals around the axis 134 (for example, at equal intervals).

[0186] (Reflector and support member) The reflector 6 is positioned to cover a portion of the bottom surface 133h of the hemispherical internal space 13h(u). In the example shown in Figure 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 around the center 131h. In this case, when performing color measurement, at least the portion of the object S to be measured is housed within the hemispherical internal space 13h(u) of the upper casing 1h(u). That is, in the example shown in Figure 13, the reflector 6 is formed so that the hemispherical internal space 13h(u) and the outside are in communication near the center 131h, by removing the portion near the center 131h. In this case, when performing color measurement, the object S is positioned at least partially outside the hemispherical internal space 13h(u), and can access the hemispherical internal space 13h(u) from its connecting portion.

[0187] However, the shape and dimensions of the reflector 6 are not limited to these examples and may be determined as appropriate depending on the embodiment. The reflector 6 may be configured to completely block the bottom surface 133h of the hemispherical internal space 13h(u) rather than partially blocking it.

[0188] The reflector 6 has a surface (upper surface) facing the hemispherical internal space 13h(u), and this upper surface is configured to specularly reflect light. The material of the reflector 6 is not particularly limited and may be appropriately selected depending on the embodiment. The reflector 6 may be made of a resin material with aluminum vapor deposition, stainless steel, etc. Accordingly, the upper surface of the reflector 6 may be made of a surface with aluminum vapor deposition, a stainless steel surface, etc. The reflector 6 may be divided into multiple parts.

[0189] The support member 8 is a member that supports the reflector 6 from the side of the bottom surface of the reflector 6 (the surface opposite the top surface of the reflector 6). For example, it supports the reflector 6 from below by being in contact with the bottom surface of the reflector 6. The material of the support member 8 is not particularly limited and may be appropriately selected depending on the embodiment. The support member 8 should be made of a material and structure that has sufficient strength to support the reflector 6.

[0190] (plate material) As illustrated in Figure 13, the plate material 2X is arranged in the hemispherical internal space 13h(u) and comprises an upper plate material 2h(u) that faces the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a horizontal plate material 2h(h) that faces at least a portion of the upper surface of the reflector 6. The plate material 2X is arranged in the hemispherical internal space 13h(u) facing the hemispherical inner surface 12h(u). In particular, the plate material 2X is arranged in the hemispherical internal space 13h(u) such that the upper plate material 2h(u) faces the hemispherical inner surface 12h(u) and the horizontal plate material 2h(h) faces at least a portion of the upper surface of the reflector 6.

[0191] In plate material 2X, the horizontal plate material 2h(h) and the upper plate material 2h(u) are in contact. For example, the lowest surface of the upper plate material 2h(u) is in contact with the upper surface of the horizontal plate material 2h(h) on the side closest to the hemispherical inner surface 12h(u). The lowest surface of the upper plate material 2h(u) is the surface of the upper plate material 2h(u) closest to the equatorial plane and parallel to the equatorial plane. In Figure 13, it is the surface of the upper plate material 2h(u) closest to the upper surface of the reflector 6 and parallel to the equatorial plane. For example, the arc length of the lowest surface of the upper plate material 2h(u) is equal to the arc length of the outermost surface of the horizontal plate material 2h(h) (the surface closest to the hemispherical inner surface 12h(u) and parallel to the hemispherical inner surface 12h(u)). In the plate material 2X, the upper plate material 2h(u) and the horizontal plate material 2h(h) are arranged such that the lowest surface of the upper plate material 2h(u) and the upper surface of the horizontal plate material 2h(h) closest to the hemispherical inner surface 12h(u) face each other. In the plate material 2X, the upper plate material 2h(u) and the horizontal plate material 2h(h) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate material 2h(u) around the axis 134, the horizontal plate material 2h(h) also rotates around the axis 134.

[0192] In the plate material 2X illustrated in Figure 13, the upper plate material 2h(u) is defined as "the portion extending from the contact point between the horizontal plate material 2h(h) and the upper plate material 2h(u) towards the zenith 132 side along the hemispherical inner surface 12h(u)." That is, in plate material 2X, the upper plate material 2h(u) is defined as "the portion extending from the contact point between the horizontal plate material 2h(h) and the upper plate material 2h(u) toward the side where the light-receiving aperture 14 is positioned relative to the equatorial plane, facing the hemispherical inner surface 12h(u)." Furthermore, in plate material 2X, the horizontal plate material 2h(h) is defined as "the portion extending from the contact point between the horizontal plate material 2h(h) and the upper plate material 2h(u) toward the center 131h side along the equatorial plane." In other words, in the plate material 2X, the horizontal plate material 2h(h) is the portion that extends from the contact point between the horizontal plate material 2h(h) and the upper plate material 2h(u) along the upper surface of the reflector 6 toward the center 131h.

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

[0194] (Upper board) The upper plate material 2h(u) of the lighting device L2 (main body B2) is the same as the upper plate material 2h(u) of the lighting device L1 (main body B1). That is, the upper plate material 2h(u) of the main body B2 is configured to cover a part of the hemispherical inner surface 12h(u) of the upper casing 1h(u) when viewed from the center 131h. The upper plate material 2h(u) is composed of 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 each other. In particular, the plurality of thin plates 210 are arranged so as not to overlap each other, with each of them facing only one of a plurality of regions A1 of equal area that are virtually provided on the inner surface 12 of the upper plate material 2h(u). 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 (that is, the surface facing the hemispherical inner surface 12h(u)) is not particularly limited.

[0195] (Horizontal plate material) As illustrated in Figure 13, in the lighting device L2 (main body B2), the plate material 2X includes a horizontal plate material 2h(h) (horizontal portion). The horizontal plate material 2h(h) is a portion that covers a part of the upper surface of the reflector 6 (the surface facing the hemispherical internal space 13h(u)) and extends along the equatorial plane. As mentioned above, the arc length of the lowest surface of the upper plate material 2h(u) (in particular, the thin plate 210(2)) is equal to the arc length of the outermost surface of the horizontal plate material 2h(h). The thin plate 210(2) and the horizontal plate material 2h(h) are arranged such that the lowest surface of the thin plate 210(2) and the upper surface of the horizontal plate material 2h(h) on the side closest to the hemispherical inner surface 12h(u) face each other.

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

[0197] The horizontal plate material 2h(h) has a shape that corresponds to at least a part of the upper surface of the reflector 6. For example, the horizontal plate material 2h(h) is configured as a strip-shaped (approximately trapezoidal) plate material formed by removing a fan-shaped curved plate within a predetermined range from the central angle from a fan-shaped plate material corresponding to region F1. However, it is not essential that the horizontal plate material 2h(h) is configured as a strip-shaped plate material; the horizontal plate material 2h(h) may be a fan-shaped plate material corresponding to the entire region F1. The horizontal plate material 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 reflector 6, is reflected by the object S, and reaches the light receiving opening 14 (observation section), as illustrated in Figure 13. The shape of the horizontal plate material 2h(h) may be appropriately selected depending on the embodiment. Depending on the shape and size of the object S, the horizontal plate material 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.

[0198] The horizontal plate 2h(h) extends towards the center 131h along the equatorial plane, above the reflecting mirror 6 (closer to the center 131h). Therefore, the first surface 21h(h) of the horizontal plate 2h(h) faces the upper surface of the reflecting mirror 6, and in the example shown in Figure 13, it faces the bottom of the paper. Also, the second surface 22h(h) of the horizontal plate 2h(h) (the surface opposite the first surface 21h(h)) faces the hemispherical internal space 13h(u), and in the example shown in Figure 13, it faces the top of the paper.

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

[0200] §2 Features

[0201] As has been explained using Figures 12 and 13, the illumination device L2 comprises a hemispherical upper casing 1h(u), a plate material 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 opening 14 (observation section). The hemispherical inner surface 12h(u) defines the hemispherical internal space 13h(u) and is made of a material that reflects light. The hemispherical internal space 13h(u) has a center 131h, a zenith 132 (vertex 132h(u)), and an axis 134h, the axis 134h passing through the center 131h and the zenith 132. The light-receiving aperture 14 is provided for observing an object S placed in the hemispherical internal space 13h(u), and is positioned at a location corresponding to the zenith 132, or at a position spaced circumferentially away from the zenith 132 along the hemispherical inner surface 12h(u).

[0202] The light source 3 is positioned to irradiate light onto the hemispherical internal space 13h(u). The plate material 2X is positioned (at least a portion thereof) in the hemispherical internal space 13h(u) facing the hemispherical inner surface 12h(u). That is, the plate material 2X is positioned in the hemispherical internal space 13h(u), and the upper portion of the plate material 2X (upper plate material 2h(u)) faces the hemispherical inner surface 12h(u). In addition, the plate material 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 material 2X (upper plate material 2h(u)) covers a portion of the hemispherical inner surface 12h(u) when viewed from the center 131h. The plate material 2X is configured to be adjustable in position around the axis 134h and comprises a first surface 21h(u) and a second surface 22h(u). The first surface 21h(u) of the upper part of plate material 2X (upper plate material 2h(u)) faces the hemispherical inner surface 12h(u), and the second surface 22h(u) of the upper part faces the center 131h.

[0203] The upper plate material 2h(u) (upper portion) of the plate material 2X, which is the part on the side of the plate material 2X where the light-receiving aperture 14 is positioned 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 the second surface 22h(u) absorbs light.

[0204] By rearranging at least one of the multiple thin plates 210, which are arranged in the upper plate material 2h(u) so as not to overlap each other, by moving it around the axis 134 at an angle smaller than 360 degrees, a single curved plate in the shape of two right-angled spherical triangles corresponding to region A1 can be formed by all of the multiple thin plates 210.

[0205] In this configuration, the multiple thin plates 210 are configured such that their second surface 22h(u) absorbs light, and are arranged in the upper plate material 2h(u) so as not to overlap each other. By rearranging the position of at least one of the multiple thin plates 210 by moving it around axis 134h at an angle smaller than 360 degrees, 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 material 2h(u) and configured so that their second surface 22h(u) absorbs light is smaller than the area of ​​the curved plate in the shape of two right-angled spherical triangles corresponding to region A1. Furthermore, if the upper plate 2h(u) and the "two right-angled spherical triangular curved plate corresponding to region A1" are placed so that one side of each (for example, the bottom side) overlaps, the area of ​​the overlapping portion of the two is smaller than the area of ​​the "two right-angled spherical triangular curved plate corresponding to region A1".

[0206] Therefore, compared to conventional light traps in which the entire second surface (the surface facing the center 131h) of the "two right-angled spherical triangular curved plate corresponding to region A1" is configured to absorb light, the upper plate material 2h(u) allows diffused light from the azimuth angle corresponding to the "two right-angled spherical triangular curved plate corresponding to region A1" to reach the object S more easily, and shadows are less likely to occur on the object S. Consequently, the illumination device L2 can prevent a decrease in measurement accuracy caused by the occurrence of shadows and achieve high-precision measurements.

[0207] Furthermore, in the upper plate material 2h(u), the multiple thin plates 210 may be connected to each other via a frame or the like. Also, in the upper plate material 2h(u), the multiple thin plates 210 may be connected to each other via a "white plate configured so that the first and second surfaces reflect light" or via a "transparent plate that transmits light".

[0208] Furthermore, the lighting device L2 includes a reflector 6 whose surface (upper surface) facing the hemispherical internal space 13h(u) is configured to specularly reflect light, and which is positioned to cover a portion of the bottom surface 133h of the hemispherical internal space 13h(u). In addition, the plate material 2X in the lighting device L2 includes a horizontal plate material 2h(h) in addition to the upper plate material 2h(u). The horizontal plate material 2h(h) is configured so that its second surface 22h(h) (i.e., the surface facing the hemispherical internal space 13h(u)) absorbs light, and it is a portion that extends along the equatorial plane, covering a portion of the surface of the reflector 6 that faces the hemispherical internal space 13h(u).

[0209] In this configuration, the horizontal plate material 2h(h) extends along the equatorial plane, covering a portion of the surface facing the hemispherical internal space 13h(u) of the reflecting mirror 6, and the second surface 22h(h) of the horizontal plate material 2h(h) is configured to absorb light. Therefore, as shown in Figure 13, the second surface 22h(h) of the horizontal plate material 2h(h) can remove the specular reflection component, for example, even if the object S has a convex shape. Thus, the illumination device L2 can prevent a decrease in measurement accuracy due to the residual specular reflection component and achieve high-precision measurement.

[0210] As is clear from the above explanation, if we focus solely on suppressing the occurrence of shadows to prevent a decrease in measurement accuracy, it is not essential for the illumination device L2 according to this embodiment to be equipped with a horizontal plate material 2h(h) as a light trap (plate material 2X). In other words, in order to suppress the occurrence of shadows, the illumination device L2 only needs to be equipped with an upper plate material 2h(u) as a light trap (plate material 2X). By equipping the illumination device L2 with an upper plate material 2h(u) as a light trap (plate material 2X), the occurrence of shadows can be suppressed, preventing a decrease in measurement accuracy caused by the occurrence of shadows, and enabling high-precision measurements. Furthermore, by equipping the illumination device L2 with a horizontal plate material 2h(h) as a light trap (plate material 2X) in addition to the upper plate material 2h(u), it is possible to further prevent a decrease in measurement accuracy caused by the residual specular reflection component and enable high-precision measurements.

[0211] §3 Variant Example <3.1> About the structure of the observation section The configuration of the observation unit of the lighting device according to the second embodiment may be appropriately selected according to the embodiment, as described in <4.1> of the first embodiment. For example, the observation unit may be composed of the light sensor itself.

[0212] <3.2> Regarding the shape of the upper part of the board material The lighting device according to the second embodiment may be equipped with any of the upper plate material 2ah(u) to 2dh(u) instead of the upper plate material 2h(u), as described in <4.2> of the first embodiment. Alternatively, the lighting device according to the second embodiment may be equipped with an upper plate material 2fh(u) or an upper plate material 2gh(u) instead of the upper plate material 2h(u). By equipping any of the upper plate material 2ah(u) to 2gh(u) instead of the upper plate material 2h(u), the lighting device according to the second embodiment can secure more than twice the amount of diffused light reaching the object 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 across the entire second surface (the surface facing the center 131) of the "two right-angled spherical triangular curved plate corresponding to region A1".

[0213] <3.3> Whether or not contact between thin plates is necessary The lighting device according to the second embodiment may, in the same manner as described in <4.3> of the first embodiment, include an upper plate material 2eh(u) which includes a plurality of thin plates (thin plates 210e) that are not in contact with each other, instead of or together with the upper plate material 2h(u).

[0214] <3.4> Regarding the number of boards The lighting device according to the second embodiment may include a plurality of plate members 2X, similar to those described in <4.4> of the first embodiment. At least one of the plurality of plate members 2X may include one of the upper plate members 2h(u) to 2dh(u).

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

[0216] <3.6> Relationship between casing and sheet metal In the lighting device according to the second 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) with a light-absorbing material, similar to the method described in <4.6> of the first embodiment.

[0217] <3.7> About frame materials In the above embodiment, the lighting device L2 was equipped with a frame member 7. However, the configuration of the lighting device according to the second embodiment is not limited to this example. The frame member 7 may be omitted. Furthermore, the shape of the frame member 7 is not limited to the above example, as long as it can support the upper casing 1h(u), and may be appropriately determined according to the embodiment.

[0218] <3.8> About the light source In the above embodiment, the light source 3 was positioned on the outer 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 positioning of the light source 3 is not limited to this example, as long as it is possible to irradiate the hemispherical internal space 13h(u) with light, and may be determined appropriately depending on the embodiment.

[0219] Furthermore, although the above embodiment described an example in which the light source 3 and the plate material 2X are provided separately, it is not essential for the lighting device according to the second embodiment to provide the light source 3 and the plate material 2X separately. For example, the light source 3 may be placed on the first surface 21 of the plate material 2X (in particular, the first surface 21h(u) of the upper plate material 2h(u)) thereby integrating the light source 3 and the plate material. By adopting such a configuration, miniaturization can be achieved compared to a lighting device in which the light source 3 and the plate material 2Y are separate components.

[0220] <3.9> Regarding the shape of thin plates The lighting device according to the second embodiment may include an upper portion (upper plate material) of a plate material, which includes "a plurality of thin plates formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane," similar to the description in <4.8> of the first embodiment. As described above, by rearranging at least one of the plurality of thin plates by moving it around an axis at an angle smaller than 360 degrees, a single curved plate in the shape of two right-angled spherical triangles can be formed from all of the plurality of thin plates. Therefore, the plurality of thin plates may be formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. Thus, in the lighting device according to one aspect of the present invention, it is possible to easily prepare the plurality of thin plates that can form a single curved plate in the shape of two right-angled spherical triangles by rearranging them.

[0221] <3.10> Regarding the placement of thin plates The lighting device according to the second embodiment may include a spherical isosceles triangular upper plate (e.g., upper plate 2gh(u)) that includes "two sides of equal length that curvely extend from the zenith 132 to the equatorial plane on the spherical surface," similar to the upper plate 2gh(u) described in <4.9> of the first embodiment. In the lighting device according to this embodiment, the multiple thin plates included in the upper portion of the plate (upper plate) only need to be arranged so as not to overlap each other, for example, they may be arranged 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 can be appropriately determined according to the usage form of the lighting device, etc.

[0222] <Third Embodiment> Hereinafter, the lighting device L3 according to the third embodiment will be described with reference to Figures 14 to 16. The lighting device L3 described below has components that have the same operation and function as the components of the lighting devices according to the above embodiments. Such components are denoted by the same reference numerals as the corresponding components shown in Figure 1, etc., and detailed descriptions will be omitted unless necessary.

[0223] §1 Example Configuration Figure 14 is a schematic side view illustrating 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 Figure 14, the illumination device L3 comprises a spherical body B3, a support column 5, and a controller 100 that is communicatively connected to the body B3. The controller 100 of the illumination device L3 is the same as the controller 100 of the illumination device L1, so its details are omitted. Similarly, the support column 5 of the illumination device L3 is the same as the support column 5 of the illumination device L1, so its details are omitted. Figure 15 is a schematic cross-sectional view illustrating an example of the configuration of the body B3. As shown in each figure, the body B3 comprises a casing 1, a plate material 2Y, a light source 3, and a sample stage 4.

[0224] The casing 1, light source 3, and sample stage 4 of main unit B3 are the same as those of main unit B1, so details are omitted.

[0225] (plate material) The plate material 2Y differs from plate material 2 in that it has an upper plate material 2yh(u) instead of an upper plate material 2h(u), but is otherwise the same as plate material 2. That is, plate material 2Y is positioned in the internal space 13 facing the inner surface 12. In particular, as illustrated in Figure 15, in the lighting device L3 (main body B3), plate material 2Y comprises an upper plate material 2yh(u) facing the hemispherical inner surface 12h(u) of the upper casing 1h(u), and a lower plate material 2h(d) facing the hemispherical inner surface 12h(d) of the lower casing 1h(d).

[0226] In the plate material 2Y illustrated in Figure 15, the upper plate material 2yh(u) and the lower plate material 2h(d) are in contact at the equatorial plane. That is, in the plate material 2Y, the portion extending from the equatorial plane toward the side where the light-receiving aperture 14 is positioned is the upper plate material 2yh(u), and the portion extending from the equatorial plane toward the side opposite to the side where the light-receiving aperture 14 is positioned is the lower plate material 2h(d). For example, the lengths of the upper plate material 2yh(u) and the lower plate material 2h(d) that are in contact with the equatorial plane (arc lengths at the equatorial plane) are equal, and they are arranged such that the surface of the upper plate material 2yh(u) that is in contact with the equatorial plane and the surface of the lower plate material 2h(d) that is in contact with the equatorial plane face each other. In the plate material 2Y, the upper plate material 2yh(u) and the lower plate material 2h(d) may be formed integrally, that is, they may be connected to each other. For example, by rotating the upper plate 2yh(u) around axis 134, the lower plate 2h(d) also rotates around axis 134.

[0227] In the following explanation, when referring to the upper plate material 2yh(u) and the lower plate material 2h(d) collectively without distinction, the term "plate material 2Y" will be used. Plate material 2Y covers a portion of the inner surface 12 when viewed from the center 131 and is configured to be adjustable in position around the axis 134. Plate material 2Y has a first surface 21 facing the inner surface 12 and a second surface 22 facing the center 131. Below, we will first describe the upper plate material 2yh(u) using Figure 16.

[0228] (Upper board) Figure 16 is a diagram illustrating the shape of the upper plate material 2yh(u). In particular, Figure 16 schematically illustrates the relationship between the upper plate material 2yh(u) and the hemispherical inner surface 12h(u) as viewed from the center 131. The upper plate material 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 material 2yh(u) is made of a light-absorbing material. As a result, the upper plate material 2yh(u) functions as a light trap. The light-absorbing material is not particularly limited as long as it can absorb light, and may be, for example, a black painted member or a member made of black material. Specific examples of light-absorbing materials include, for example, carbon black or non-reflective napped 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 diffusely reflects light. Alternatively, the first surface 21h(u) may be made of other materials.

[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 the vertex 132 and the center 131. The upper plate material 2yh(u) has a shape corresponding to one region A1 of the inner surface 12. The shape corresponding to one region A1 can be any shape that occludes the region A1 of the object S as seen from the object S, for example, it may be a two-right-angled spherical triangle. In the example in 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 as appropriate depending on the embodiment.

[0230] The material of the upper plate 2yh(u) 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 upper plate 2yh(u). It is desirable that the material of the upper plate 2yh(u) is one that has excellent workability and can ensure strength.

[0231] (Lower board) As illustrated in Figure 15, in the lighting device L3 (main body B3), the plate material 2Y includes a lower plate material 2h(d) that faces the hemispherical inner surface 12h(d) of the lower casing 1h(d). In other words, the plate material 2Y includes a lower plate material 2h(d) (lower portion) which is the part that extends on the side opposite to the side where the light receiving opening 14 is located with respect to the equatorial plane (i.e., the plane passing through the center 131 and perpendicular to the axis 134).

[0232] The lower plate material 2h(d) has a shape that corresponds to (opposes) at least a part of one of a plurality of regions A1 of equal area that are virtually provided on the hemispherical inner surface 12h(d) of the lower casing 1h(d). For example, the lower plate material 2h(d) is constructed as a strip-shaped (approximately trapezoidal) plate material (curved plate) formed by removing two right-angled spherical triangular curved plates that are within a predetermined range from the vertex angle from two right-angled spherical triangular curved plates that correspond to (oppose) the entire region A1. That is, the lower plate material 2h(d) is constructed as a strip-shaped curved plate formed by removing two right-angled spherical triangular curved plates that are below a predetermined latitude (a predetermined plane parallel to the equatorial plane) from two right-angled spherical triangular curved plates that correspond to the entire region A1.

[0233] However, it is not essential that the lower plate material 2h(d) be configured as a strip-shaped plate material; the lower plate material 2h(d) may be a plate material (curved plate) in the shape of two right-angled spherical triangles corresponding to the entire region A1. The lower plate material 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 (especially the hemispherical inner surface 12h(d)) as illustrated in Figure 15, and is reflected by the object S to reach the light receiving opening 14 (observation section). The shape of the lower plate material 2h(d) may be appropriately selected depending on the embodiment. Depending on the shape and size of the object S, the lower plate material 2h(d) may be configured so that the latitude of the lower end of the lower plate material 2h(d) extending along the hemispherical inner surface 12h(d) toward the vertex 132h(d) can be adjusted.

[0234] The surface of the lower plate material 2h(d) facing the center 131 (second surface 22h(d)) is made of a light-absorbing material. The light-absorbing material is not particularly limited as long as it can absorb light, and may be, for example, a black painted material, a black material, etc. Specific examples of light-absorbing materials include, for example, carbon black, non-reflective brushed cloth, etc. On the other hand, the composition of the surface of the lower plate material 2h(d) facing the inner surface 12 (first surface 21h(d)) is not particularly limited and may be appropriately selected depending on the embodiment. The first surface 21h(d) of the lower plate material 2h(d) may be made of a light-diffusing and reflecting material, similar to the inner surface 12 (hemispherical inner surface 12h). Alternatively, the first surface 21h(d) of the lower plate material 2h(d) may be made of other materials.

[0235] In this configuration, the second surface 22h(d) of the lower plate material 2h(d) is configured to absorb light. Therefore, as illustrated in Figure 15, the second surface 22h(d) of the lower plate material 2h(d) can remove the specular reflection component, even if the object S has a convex shape. Consequently, the illumination device L3 can prevent a decrease in measurement accuracy caused by the residual specular reflection component and achieve high-precision measurement.

[0236] Similar to the upper plate material 2yh(u), the material of the lower plate material 2h(d) 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 lower plate material 2h(d). It is desirable that the material of the lower plate material 2h(d) is one that has excellent workability and can ensure strength.

[0237] §2 Features As described above, the lighting device L3 according to this embodiment comprises 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 opening 14 (observation section). 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, the axis 134 passing through the center 131 and the zenith 132. The light receiving opening 14 is provided for observing an object S placed in the internal space 13 and is positioned at a location corresponding to the zenith 132, or at a position spaced circumferentially apart from the zenith 132 along the inner surface 12.

[0238] The light source 3 is positioned to irradiate light into the internal space 13. The plate material 2Y is positioned in the internal space 13 facing the inner surface 12, covering a portion of the inner surface 12 when viewed from the center 131, and is configured to be adjustable in position around the axis 134. 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 material 2Y includes an upper plate material 2yh(u) (upper portion) and a lower plate material 2h(d) (lower portion). The upper plate material 2yh(u) is the portion that extends toward the side where the light-receiving aperture 14 is positioned relative to the equatorial plane. The lower plate material 2h(d) is the portion that extends toward the side opposite to the side where the light-receiving aperture 14 is positioned relative to the equatorial plane. The second surface 22h(d) of the lower plate material 2h(d) is configured to absorb light.

[0240] In this configuration, the second surface 22h(d) of the lower plate material 2h(d), which is configured to absorb light, can remove the specular reflection component even when the object S has a convex shape, as illustrated in Figure 15. Therefore, the illumination device L3 can prevent a decrease in measurement accuracy caused by the residual specular reflection component and achieve high-precision measurement.

[0241] §3 Variant Example <3.1> About the structure of the observation section The configuration of the observation unit of the lighting device according to the third embodiment may be appropriately selected according to the embodiment, as described in <4.1> of the first embodiment. For example, the observation unit may be composed of the light sensor itself.

[0242] <3.2> Regarding the number of boards The lighting device according to the third embodiment may include a plurality of plate materials 2Y, similar to those described in section 4.4 of the first embodiment.

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

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

[0245] <3.5> About the light source In the above embodiment, the light source 3 is attached to the support column 5. However, the arrangement of the light source 3 is not limited to this example, as long as it can illuminate the internal space 13 with light, and may be determined appropriately depending on the embodiment.

[0246] Furthermore, although the above embodiment described an example in which the light source 3 and the plate material 2Y are provided separately, it is not essential for the lighting device according to the third embodiment to provide the light source 3 and the plate material 2Y separately. For example, the light source 3 may be placed on the first surface 21 of the plate material 2Y (the surface facing the inner surface 12), thereby integrating the light source 3 and the plate material. By adopting such a configuration, miniaturization can be achieved compared to a lighting device in which the light source 3 and the plate material 2Y are separate components. [Explanation of Symbols]

[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 board 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...hemispherical inner surface (inner surface), 13...Internal space, 13h...Semispherical internal space (internal space), 14…Light receiving port (observation section), 131, 131h...center, 132...zenith, 132h...peak, 133h...Bottom, 134, 134h...axis, 21, 21h...first page, 22, 22h…Second side, 142...Brightest measurement data (measurement data where the object is observed in its brightest state), 143...Darkest measurement data (measurement data where the object is observed in its 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 plates, A1…field, L1, L1a, L1b, L1c, L1d, L1e, L1f, L1g, L2, L3, ... lighting devices S…object

Claims

1. A casing having an outer surface, an inner surface, a spherical or hemispherical internal space, and an observation section, The aforementioned inner surface is composed of a material that defines the internal space and 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 positioned at the zenith or at a position spaced circumferentially from the zenith along the inner surface. Casing and, A plate material arranged in the aforementioned internal space opposite to the inner surface, It covers a portion of the inner surface when viewed from the center, and is configured to be adjustable in position around the axis. It comprises a first surface facing the inner surface and a second surface facing the center, Board material and, A light source is arranged to irradiate the aforementioned internal space with light, Equipped with, The upper portion of the aforementioned plate material, which is the side on which the observation section is positioned relative to the equatorial plane, which is a plane passing through the center and perpendicular to the axis, includes a plurality of thin plates arranged so as not to overlap each other. The plurality of thin plates are configured such that the second surface absorbs light. By rearranging at least one of the multiple thin plates, which are arranged in the upper portion so as not to overlap each other, by moving it around the axis at an angle smaller than 360 degrees, it is possible to form a single curved plate in the shape of a two-right-angled spherical triangle using the multiple thin plates, which corresponds to the region of the inner surface that connects three points: the point on the inner surface corresponding to the zenith, and two points on the line of intersection of the equatorial plane and the inner surface. Lighting device.

2. The area of ​​each of the aforementioned plurality of thin plates is less than or equal to half the area of ​​the curved plate. The lighting device according to claim 1.

3. The aforementioned plurality of thin plates are not in contact with each other. The lighting device according to claim 1 or 2.

4. From among a plurality of measurement data, each of which indicates 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, Measurement data in which the object is observed in its darkest state, An extraction unit that extracts, A storage unit stores the two measurement data extracted by the extraction unit as observation results of the object, Furthermore, The lighting device according to claim 1 or 2.

5. The aforementioned internal space is spherical, The aforementioned plate material is The aforementioned upper portion and, The lower portion is the part that extends on the side opposite to the side on which the observation unit is positioned relative to the equatorial plane, Includes, The second surface of the lower portion is configured to absorb light. The lighting device according to claim 1 or 2.

6. The aforementioned internal space is hemispherical, A reflecting mirror in which the surface facing the internal space is configured to specularly reflect light, It is positioned to cover a portion of the bottom surface of the aforementioned internal space, Equipped with additional reflectors, The aforementioned plate material is The aforementioned upper portion and, The second surface is configured to absorb light and covers a portion of the surface of the reflector facing the internal space, and has a horizontal portion that extends along the equatorial plane, including, The lighting device according to claim 1 or 2.

7. The device further includes a correction unit that corrects the measurement data obtained by observing the object in the observation unit using reference measurement data, which is measurement data obtained in advance by observing a white diffuse object having the same shape as the object in the observation unit. The lighting device according to claim 1 or 2.

8. By forming a portion of the inner surface with a light-absorbing material, the casing and the plate material are integrated. The lighting device according to claim 1 or 2.

9. The plurality of thin plates are formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. The lighting device according to claim 1 or 2.

10. A casing having an outer surface, an inner surface, a spherical internal space, and an observation section, The aforementioned inner surface is composed of a material that defines the internal space and 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 positioned at the zenith or at a position spaced circumferentially from the zenith along the inner surface. Casing and, A plate material arranged in the aforementioned internal space opposite to the inner surface, It covers a portion of the inner surface when viewed from the center, and is configured to be adjustable in position around the axis. It comprises a first surface facing the inner surface and a second surface facing the center, It includes an upper portion which extends toward the side where the observation unit is positioned relative to the equatorial plane, which is a plane passing through the center and perpendicular to the axis, and a lower portion which extends toward the side opposite to the side where the observation unit is positioned relative to the equatorial plane, Board material and, A light source is arranged to irradiate the aforementioned internal space with light, Equipped with, The second surface of the lower portion is configured to absorb light. Lighting device.

11. From among a plurality of measurement data, each of which indicates 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, Measurement data in which the object is observed in its darkest state, An extraction unit that extracts, A storage unit stores the two measurement data extracted by the extraction unit as observation results of the object, Furthermore, The lighting device according to claim 10.

12. The device further includes a correction unit that corrects the measurement data obtained by observing the object in the observation unit using reference measurement data, which is measurement data obtained in advance by observing a white diffuse object having the same shape as the object in the observation unit. The lighting device according to claim 10 or 11.

13. By forming a portion of the inner surface with a light-absorbing material, the casing and the plate material are integrated. The lighting device according to claim 10 or 11.

14. The aforementioned upper portion includes a plurality of thin plates arranged so as not to overlap each other, The plurality of thin plates are configured such that the second surface absorbs light. By rearranging at least one of the multiple thin plates, which are arranged in the upper portion so as not to overlap each other, by moving it around the axis at an angle smaller than 360 degrees, it is possible to form a single curved plate in the shape of a two-right-angled spherical triangle using the multiple thin plates, which corresponds to the region of the inner surface that connects three points: the point on the inner surface corresponding to the zenith, and two points on the line of intersection of the equatorial plane and the inner surface. The lighting device according to claim 10 or 11.

15. The plurality of thin plates are formed by dividing a single curved plate in the shape of two right-angled spherical triangles with a plane parallel to or inclined to the equatorial plane. The lighting device according to claim 14.

16. A method of using the lighting device described in Claim 1, A step of placing the object in the internal space of the casing and irradiating the internal space with light from the light source, After the step of irradiating light from the light source, the observation unit measures the reflection component of the object at the starting point, and stores the measurement result as measurement data in the storage unit, corresponding to the position of the plate material at the starting point. A method for using a lighting device, comprising the steps of: after storing measurement data at the starting point, changing the position of the plate material, measuring the reflective component of the object with the observation unit, and storing the measurement result as measurement data in the storage unit in correspondence with the changed position of the plate material, repeating this until all of the inner surfaces of the internal space face at least one of the plurality of thin plates at least once.

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