Lighting device and observation system

Abstract

Provided is a lighting device comprising: a main body part having a concave mirror facing an object to be observed; and a light source part that emits light toward the mirror. A second observation hole for observing the object in a first direction from an observation position is formed in the mirror. The concave shape of the mirror is shaped as a curved surface that causes parallel light components parallel to the first direction to be greater than diffused light components reflected in a plurality of directions different from the first direction among reflected light reflected by the mirror from the light emitted by the light source part.

Description

Lighting equipment and observation system 【0001】 This invention relates to a lighting device and an observation system. 【0002】 It is known that by irradiating an object to be observed with diffused light using a dome-shaped lighting device, etc., and imaging the reflected light that is reflected by the object, scratches, cracks, chips, foreign matter adhesion, etc. on the surface of the object to be observed can be detected (see, for example, Patent Document 1). 【0003】 Japanese Patent Publication No. 2024-134474 【0004】 However, when illuminating an object with diffused light using such lighting devices and observing the object itself with an imaging device, the intensity of the reflected light from a part of the object becomes so high that at least a part of the object becomes invisible due to the reflected light. 【0005】 Therefore, the present invention has been made in view of these points, and aims to make it easier to observe an object from an observation position while irradiating the object with light. 【0006】 In a first embodiment of the present invention, there is a lighting device for irradiating an object to be observed with light, comprising: a main body having a concave-shaped reflector facing the object to be observed; and a light source that irradiates light toward the reflector, wherein the main body has a first observation hole formed therein for observing the object to be observed in a first direction from an observation position opposite to the object to the main body, and the reflector has a second observation hole formed therein for observing the object to be observed in the first direction from the observation position, and the concave shape of the reflector has a curved surface that makes the parallel light component parallel to the first direction greater than the diffuse light component reflected in a plurality of directions other than the first direction among the reflected light reflected by the reflector from the light source, wherein the lighting device is provided. 【0007】 The concave shape of the reflecting mirror may have a parabolic shape in a first cross-section parallel to the first direction of the main body. The concave shape of the reflecting mirror may have a quadratic curve shape in a first cross-section parallel to the first direction of the main body. 【0008】 The concave shape of the reflecting mirror may have an elliptical shape in the first cross-section parallel to the first direction of the main body. 【0009】 The concave shape of the reflecting mirror may have a straight line in a second cross-section that is parallel to the first direction of the main body and perpendicular to the first cross-section, and parallel to the second direction perpendicular to the first cross-section. 【0010】 The concave shape of the reflecting mirror may have the shape of an inverse hyperbolic function, which is the inverse function of a hyperbolic function, in a first cross section parallel to the first direction of the main body and a second cross section perpendicular to the first cross section. 【0011】 The inverse hyperbolic function is one of the following functions: the inverse hyperbolic sine, the inverse hyperbolic cosine, and the inverse hyperbolic tangent. With x and y as variables, the inverse hyperbolic sine is given by: hyperbolic sine sinh(x) = (e ｘ -e －ｘ The inverse function of ) / 2, which is arcsinh(x) or sinh －１ (x) is expressed as y = arcsinh(x) = x = sinh(y), and the inverse hyperbolic cosine is the hyperbolic cosine cosh(x) = (e ｘ +e －ｘ The inverse function of ) / 2, which is arccosh(x) or cosh －１ (x) is expressed as (x≧1), y=arccosh(x) is y that satisfies x=cosh(y), and the inverse hyperbolic tangent is the inverse function of the hyperbolic tangent tanh(x)=sinh(x) / cosh(x), and is arctanh(x) or tanh －１ It can be expressed as (x) (-1 < x < 1), and y = arctanh(x) may also be y that satisfies x = tanh(y). 【0012】 The light source unit may have a plurality of LEDs arranged in a second direction perpendicular to the first cross-section. 【0013】The plurality of LEDs form an LED row arranged in two columns in the second direction, and the LED row arranged in two columns may be positioned to straddle a straight line connecting at least a portion of the first observation hole and at least a portion of the second observation hole to at least a portion of the object to be observed. 【0014】 The multiple LEDs are positioned closer to the object to be observed than the second observation hole in the first direction, and may irradiate a predetermined light in a direction inclined toward the second observation hole with respect to the first direction in the first cross-section. 【0015】 In a second embodiment of the present invention, an observation system is provided comprising the illumination device according to the first embodiment, and an imaging device positioned at the observation location, which is further from the object to be observed than the main body in the first direction, for observing the object to be observed through the first observation hole and the second observation hole. 【0016】 According to the present invention, the effect is achieved that the object to be observed can be illuminated with light while making it easier to observe the object from the observation position. 【0017】 This shows an example of the configuration of the observation system S according to this embodiment. This shows an example of the configuration of the lighting device 10 according to this embodiment. This shows a cross-section A-A' of the lighting device 10 shown in Figure 2. This shows a cross-section B-B' of the lighting device 10 shown in Figure 2. This shows a first example of the observation results of the object to be observed 30. This shows a second example of the observation results of the object to be observed 30. This shows a third example of the observation results of the object to be observed 30. This shows a fourth example of the observation results of the object to be observed 30. This shows a modified version of the lighting device 10 according to this embodiment. This shows a cross-section B-B' of the lighting device 10 shown in Figure 9. 【0018】 <Example of Observation System S Configuration> Figure 1 shows an example of the configuration of the observation system S according to this embodiment. In Figure 1, the three orthogonal axes are defined as the X, Y, and Z axes. The observation system S comprises an illumination device 10 and an imaging device 20. The observation system S is a system for observing an object 30 illuminated by the light of the illumination device 10 using the imaging device 20. The object 30 may have parts made of a material that easily reflects light, and may also have fine parts or parts that have undergone fine processing. 【0019】 The illumination device 10 irradiates the object 30 being observed with light. Figure 1 shows an example in which the illumination device 10 irradiates the object 30 being observed, which is positioned in the Z direction. In this embodiment, the direction substantially parallel to the Z direction is defined as the first direction. Details of the illumination device 10 will be described later. 【0020】 The imaging device 20 images the object to be observed 30. The imaging device 20 captures still images or moving images of the object to be observed 30. The imaging device 20 may have, for example, a display unit, and the captured still images or moving images may be displayed on the display unit. In this embodiment, the operation of the imaging device 20 imaging the object to be observed 30, the operation of the imaging device 20 displaying the captured images on the display unit, etc., are expressed as "the imaging device 20 observing the object to be observed 30". 【0021】 The imaging device 20 is positioned at an observation location further from the object to be observed 30 than the illumination device 10 in the first direction. In other words, the imaging device 20, illumination device 10, and object to be observed 30 are arranged in the order of imaging device 20, illumination device 10, and object to be observed 30 in the first direction. The illumination device 10 is provided with an observation hole, and the imaging device 20 observes the object to be observed 30 through the observation hole. 【0022】 Conventionally, dome-shaped and ring-shaped illumination devices that irradiate the object to be observed 30 with diffused light were known. Such conventional illumination devices irradiated the object to be observed 30 with light from various directions, reducing shadows, halation, etc., caused by the unevenness and curved surfaces of the object to be observed 30. In other words, conventional illumination devices functioned to illuminate the object to be observed 30 with indirect light. 【0023】 In this case, for example, if an observation hole or the like is formed in the dome to observe the object 30, the amount of diffused light irradiated onto the object 30 from the position of the observation hole is reduced, which can cause a bias in the diffused light and result in shadows being cast on the object 30. Also, if diffused light is irradiated onto the object 30 from various directions, the direction of the light reflected by a part of the object 30 may coincide in a specific direction, resulting in constructive interference. 【0024】When such reflected light reaches the imaging device 20, the amount of reflected light reflected from a part of the object being observed becomes large in the image obtained by the imaging device 20, making it difficult to observe the object being observed 30. For example, if the object being observed 30 has parts that easily reflect light, such as metal, fine parts, or parts that have undergone fine processing, the reflected light from these parts becomes large, making observation difficult. 【0025】 Therefore, the illumination device 10 according to this embodiment irradiates the object to be observed 30 with light while reducing the variation in the distribution of reflected light reaching the observation position of the imaging device 20, thereby making it easier to observe the object from the observation position. Such an illumination device 10 will be described next. 【0026】 <Example of the configuration of the lighting device 10> Figure 2 shows an example of the configuration of the lighting device 10 according to this embodiment. In Figure 2, the three orthogonal axes are defined as the X, Y, and Z axes. Figure 3 shows a cross-section of the lighting device 10 shown in Figure 2 along the line A-A'. Figure 4 shows a cross-section of the lighting device 10 shown in Figure 2 along the line B-B'. The lighting device 10 comprises a main body 11 and a light source 15. 【0027】 The main body 11 has a reflector 12. The main body 11 is the part for fixing the reflector 12 and the light source 15. Figure 2 shows an example in which the main body 11 and the reflector 12 are formed integrally, but instead, the main body 11 and the reflector 12 may be formed separately. 【0028】 The reflecting mirror 12 is a concave mirror facing the object to be observed 30. The light source unit 15 shines light towards the reflecting mirror 12. As will be described later, the light source unit 15 is a light source that emits light that diffuses in multiple directions. The reflecting mirror 12 reflects the light emitted by the light source unit 15 and illuminates the object to be observed 30. The concave shape of the reflecting mirror 12 is such that, of the reflected light reflected by the reflecting mirror 12 from the light source unit 15, the parallel light component parallel to the first direction is greater than the diffuse light component reflected in multiple directions other than the first direction. 【0029】In other words, unlike conventional illumination devices that illuminate the object to be observed 30 with diffused light that diffuses in multiple directions, the reflecting mirror 12 reflects the light emitted by the light source unit 15 so that it becomes parallel light parallel to a first direction, and illuminates the object to be observed 30 with this parallel light. Such a reflecting mirror 12 can be realized by having various concave shapes. 【0030】 For example, the concave shape of the reflector 12 has a parabolic shape in a first cross-section (see Figure 3) parallel to the first direction of the main body 11. Alternatively, the concave shape of the reflector 12 may have a quadratic curve shape in the first cross-section. Furthermore, the concave shape of the reflector 12 may have an elliptical shape in the first cross-section. 【0031】 Thus, by having a concave shape of the reflecting mirror 12 that is a parabola, quadratic curve, or ellipse, the reflecting mirror 12 can increase the amount of parallel light component parallel to the first direction compared with the diffuse light component scattered in multiple directions, and illuminate the object to be observed 30 with the parallel light component parallel to the first direction. Since such a concave shape can be easily optically designed from the positional relationship between the reflecting mirror 12 and the light source unit 15, a detailed explanation of the design values ​​and precise shape is omitted here. 【0032】 The concave shape of the reflector 12 shown in Figure 2 may be the same in multiple cross-sections parallel to the first cross-section, for example. In other words, the concave shape of the reflector 12 has a straight line parallel to the second direction perpendicular to the first cross-section in a second cross-section (see Figure 4) that is parallel to the first direction of the main body 11 and perpendicular to the first cross-section. Thus, the reflector 12 has a mirror surface formed in a concave shape, for example, as if the main body 11 had been hollowed out in a crescent shape. Such a reflector 12 can be easily manufactured at low cost by, for example, cutting the main body 11, forming the main body 11 from casting, or forming a plate-shaped member and then providing a reflective film on the resulting part. 【0033】Alternatively, the concave shape of the reflecting mirror 12 may have the same concave shape in a second cross-section parallel to the first direction of the main body portion 11 and perpendicular to the first cross-section as in the concave shape of the first cross-section. In this case, the reflecting mirror 12 has a mirror surface formed in a concave shape, for example, as if the main body portion 11 had been hollowed out in a hemispherical shape. Such a reflecting mirror 12 can convert more light into parallel light parallel to the first direction, and can efficiently irradiate the object to be observed 30 with parallel light. 【0034】 As explained in Figure 1, the main body 11 is positioned closer to the object to be observed 30 than the imaging device 20 in the first direction. The main body 11 has a first observation hole 13 formed therein for observing the object to be observed 30 in the first direction from an observation position opposite to the object to be observed 30 relative to the main body 11. Similarly, the reflecting mirror 12 also has a second observation hole 14 formed therein for observing the object to be observed 30 in the first direction from the observation position. 【0035】 It is desirable that the first observation hole 13 and the second observation hole 14 are formed to be approximately the same size and shape. The size and shape of the first observation hole 13 and the second observation hole 14 should be such that the imaging device 20 can observe the object to be observed 30 from the imaging position. The first observation hole 13 and the second observation hole 14 are, for example, circular through holes with a diameter of several millimeters to several centimeters. 【0036】 As described above, the illumination device 10 illuminates the object to be observed 30 with parallel light, so the amount of parallel light reaching areas other than the area directly below the second observation hole 14 hardly changes even when the second observation hole 14 is formed in the reflecting mirror 12. In addition, the area directly below the second observation hole 14 receives light that is a mixture of light spreading from the parallel light around the second observation hole 14 and external light passing through the second observation hole 14 and traveling in the first direction. In this way, even when the second observation hole 14 for observation is formed in the reflecting mirror 12, the illumination device 10 does not significantly change the distribution of light intensity illuminating the object to be observed 30, thus making it less likely for shadows to be cast on the object to be observed 30. 【0037】The light source unit 15 includes, for example, one or more LEDs that output light in the visible light band. It is desirable for the light source unit 15 to irradiate light that diffuses in a plurality of directions and irradiate a wider area of the reflector 12 with light. Also, it is desirable for the light source unit 15 to include a plurality of LEDs. Thereby, the lighting device 10 can irradiate parallel light to a wider area. 【0038】 FIG. 2 shows an example in which the light source unit 15 has a plurality of LEDs arranged in a second direction perpendicular to the first cross section. Also, in FIG. 2, the plurality of LEDs form an LED array arranged in two rows in the second direction, and the LED array arranged in two rows is arranged so as to sandwich a straight line connecting at least a part of the observation object 30 from at least a part of the first observation hole 13 and at least a part of the second observation hole 14. Thereby, the light source unit 15 can irradiate the entire reflector 12 with light, and the lighting device 10 can irradiate parallel light to a wider area. 【0039】 Note that it is desirable for the plurality of LEDs to be arranged at a position closer to the observation object 30 than the second observation hole 14 in the first direction. Also, it is desirable for the plurality of LEDs to be arranged so as to irradiate predetermined light in a direction inclined toward the side of the second observation hole 14 with respect to the first direction in the first cross section. Thereby, the light source unit 15 can efficiently irradiate the reflector 12 with light. 【0040】 As described above, in the observation system S according to the present embodiment, the lighting device 10 irradiates the observation object 30 with light from the first direction, and the imaging device 20 observes the observation object 30 located in the first direction through the first observation hole 13 and the second observation hole 14 of the lighting device 10. Since the lighting device 10 irradiates the observation object 30 with light having a larger component of light traveling in the first direction than the component of diffused light irradiating in a plurality of directions, it is possible to reduce the concentration of the irradiated light on a specific part of the observation object 30. Therefore, it is possible to reduce the concentration of the reflected light reflected from a specific part of the observation object 30 in a specific direction. 【0041】Therefore, while irradiating the observation object 30 with light by the illumination device 10, the observation system S can reduce the generation of strong reflected light at a specific part of the observation object 30, and make it easier for the imaging device 20 to observe the observation object 30. According to such an observation system S, even if the observation object 30 has a part that easily reflects light such as metal, a fine part, or a part where fine processing has been performed, etc., the illumination device 10 can illuminate the observation object 30 and observe the observation object 30. 【0042】 In the observation system S according to the above-described embodiment, an example has been described in which the direction in which the imaging device 20 observes the observation object 30 and the direction in which the illumination device 10 irradiates the observation object 30 with light coincide in the first direction, but it is not limited thereto. If the illumination device 10 irradiates the observation object 30 with light in a predetermined one direction, the concentration of reflected light in a specific direction can be reduced. Therefore, the direction in which the imaging device 20 observes the observation object 30 does not have to coincide with the predetermined one direction. 【0043】 For example, it is sufficient that the imaging device 20 can observe the observation object 30 through the first observation hole 13 and the second observation hole 14. And when the direction in which the imaging device 20 observes the observation object 30 is the first direction, the illumination device 10 may increase the component in the direction toward the observation object 30 rather than the diffused light components reflected in a plurality of directions. In this case, the reflected light toward the observation object 30 can be decomposed into components in the first direction. In other words, the illumination device 10 may reflect so as to increase the parallel light component parallel to the first direction rather than the diffused light components reflected in a plurality of directions different from the first direction. 【0044】 In the observation system S according to the above-described embodiment, an example has been described in which the first direction, which is the direction in which the imaging device 20 observes the observation object 30, is a direction substantially parallel to the Z direction, but it is not limited thereto. As described above, it is sufficient that the imaging device 20 can observe the observation object 30 through the first observation hole 13 and the second observation hole 14. For example, the first direction may be a direction having a deflection angle within a predetermined range in at least one of the X direction and the Y direction with respect to the Z direction. 【0045】<Examples of observation results by observation system S> Figures 5 to 8 show examples of observation results of the object to be observed 30. Figures 5(a), 6(a), 7(a), and 8(a) show comparative images of observation results obtained by observing the object to be observed 30 using a conventional lighting device. Figures 5(b), 6(b), 7(b), and 8(b) show the observation results by observation system S according to this embodiment. The object to be observed 30 in Figure 5 is the tip of a drill bit, the object to be observed 30 in Figure 6 is a screw, the object to be observed 30 in Figure 7 is a pen tip, and the object to be observed 30 in Figure 8 is a round metal rod. 【0046】 From the first example of the observation results for the object 30 shown in Figure 5, it can be seen that the comparison image shows that some parts are dark, while other parts have strong reflected light, making it difficult to observe the entire tip of the drill. In contrast, the observation results from the observation system S show that there are no parts with extremely strong or extremely weak reflected light, and the entire tip of the drill can be clearly observed. Similar results were obtained from the second example of the observation results for the object 30 shown in Figure 6, the third example of the observation results for the object 30 shown in Figure 7, and the fourth example of the observation results for the object 30 shown in Figure 8. 【0047】 In the observation system S according to this embodiment, an example has been described in which the illumination device 10 illuminates the object to be observed 30 and the imaging device 20 observes the object to be observed 30, but the system is not limited to this. The observation system S may further include, for example, a processing device for processing a predetermined part of the observed object to be observed 30. 【0048】 In the observation system S according to this embodiment, examples have been described in which the concave shape of the reflecting mirror 12 is a parabola, a quadratic curve, or an ellipse, but the system is not limited to these. The concave shape of the reflecting mirror 12 may have the shape of an inverse hyperbolic function, which is the inverse function of a hyperbolic function, in a first cross section parallel to the first direction of the main body 11 and a second cross section perpendicular to the first cross section. 【0049】FIG. 9 shows a modified example of the lighting device 10 according to the present embodiment. FIG. 9 shows an example of a view through the main body portion 11 of the lighting device 10 so that the concave shape of the reflecting mirror 12 can be confirmed. FIG. 10 shows a perspective view of a C-C' cross section of the lighting device 10 shown in FIG. 9. The C-C' cross section of the lighting device 10 is an example of the first cross section. In the present embodiment, in the first cross section and the second cross section, the concave shape of the reflecting mirror 12 having the shape of an inverse hyperbolic function is called an inverse hyperbolic paraboloid. 【0050】 The inverse hyperbolic function is any one of the inverse hyperbolic sine, inverse hyperbolic cosine, and inverse hyperbolic tangent functions. When x and y are variables, the inverse hyperbolic sine is the inverse function of the hyperbolic sine sinh(x) = (e ｘ - e －ｘ ) / 2, and is expressed as arcsinh(x) or sinh －１ (x), and y = arcsinh(x) is y that satisfies x = sinh(y). 【0051】 The inverse hyperbolic cosine is the inverse function of the hyperbolic cosine cosh(x) = (e ｘ + e －ｘ ) / 2, and is expressed as arccosh(x) or cosh －１ (x) (x ≥ 1), and y = arccosh(x) is y that satisfies x = cosh(y). The inverse hyperbolic tangent is the inverse function of the hyperbolic tangent tanh(x) = sinh(x) / cosh(x), and is expressed as arctanh(x) or tanh －１ (x) (-1 < x < 1), and y = arctanh(x) is y that satisfies x = tanh(y). 【0052】 The reflecting mirror 12 of the lighting device 10 in the above modified example can also make more light into parallel light parallel to the first direction, and can efficiently irradiate the observation object 30 with parallel light. The inverse hyperbolic paraboloid has a shape like a horse's saddle. When the light irradiated by the light source unit 15 is reflected as the concave shape of the reflecting mirror 12, the light distribution becomes superior with respect to the observation object 30 having many irregularities, and uniform light can be irradiated. Therefore, the lighting device 10 of the modified example is considered to be effective for observing an observation object 30 having a shell structure or the like. 【0053】Furthermore, the shape of an inverse hyperbolic paraboloid can be formed by combining two sets of distinct straight lines. Therefore, a curved surface can be formed using linear members without dealing with complex curved sections. Such an inverse hyperbolic paraboloid shape can have higher rigidity compared to concave shapes having the shapes of parabolas, quadratic curves, or ellipses. Moreover, an inverse hyperbolic paraboloid has the duality of being a complex curved surface yet composed of simple straight lines, which can create visually unique and beautiful designs. 【0054】 Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments. 【0055】 10 Illumination device 11 Main body 12 Reflecting mirror 13 First observation hole 14 Second observation hole 15 Light source unit 20 Imaging device 30 Object to be observed

Claims

1. An illumination device for irradiating an object to be observed with light, comprising: a main body having a concave-shaped reflecting mirror facing the object to be observed; and a light source unit that irradiates light toward the reflecting mirror, wherein the main body has a first observation hole formed therein for observing the object to be observed in a first direction from an observation position opposite to the object to the main body; the reflecting mirror has a second observation hole formed therein for observing the object to be observed in the first direction from the observation position; and the concave shape of the reflecting mirror has a curved surface that makes the parallel light component parallel to the first direction greater than the diffuse light component reflected in multiple directions other than the first direction among the reflected light reflected by the reflecting mirror from the light source unit.

2. The lighting device according to claim 1, wherein the concave shape of the reflecting mirror has a parabolic shape in a first cross section parallel to the first direction of the main body.

3. The lighting device according to claim 1, wherein the concave shape of the reflecting mirror has the shape of a quadratic curve in a first cross section parallel to the first direction of the main body.

4. The lighting device according to claim 1, wherein the concave shape of the reflecting mirror has an elliptical shape in a first cross section parallel to the first direction of the main body.

5. The lighting device according to claim 2, wherein the concave shape of the reflector is parallel to the first direction of the main body and, in a second cross-section perpendicular to the first cross-section, has the shape of a straight line parallel to the second direction perpendicular to the first cross-section.

6. The illumination device according to claim 1, wherein the concave shape of the reflecting mirror has the shape of an inverse hyperbolic function, which is the inverse function of a hyperbolic function, in a first cross section parallel to the first direction of the main body and a second cross section perpendicular to the first cross section.

7. The inverse hyperbolic function is one of the inverse hyperbolic sine, inverse hyperbolic cosine, and inverse hyperbolic tangent functions, where x and y are variables, and the inverse hyperbolic sine is given by the hyperbolic sine sinh(x) = (e ｘ -e －ｘ The inverse function of ) / 2, which is arcsinh(x) or sinh －１ (x) is expressed as y = arcsinh(x), and y = arcsinh(x) is y that satisfies x = sinh(y), and the inverse hyperbolic cosine is the hyperbolic cosine cosh(x) = (e ｘ +e －ｘ The inverse function of ) / 2, which is arccosh(x) or cosh －１ (x) is expressed as (x≧1), and y=arccosh(x) is y that satisfies x=cosh(y), and the inverse hyperbolic tangent is the inverse function of the hyperbolic tangent tanh(x)=sinh(x) / cosh(x), and is arctanh(x) or tanh －１ The lighting device according to claim 6, wherein (x) is expressed as (-1 < x < 1), and y = arctanh(x) is y that satisfies x = tanh(y).

8. The lighting device according to claim 5, wherein the light source unit has a plurality of LEDs arranged in a second direction perpendicular to the first cross-section.

9. The illumination device according to claim 8, wherein the plurality of LEDs form an LED row arranged in two columns in the second direction, and the LED row arranged in two columns is positioned to straddle a straight line connecting at least a portion of the first observation hole and at least a portion of the second observation hole to at least a portion of the object to be observed.

10. The illumination device according to claim 9, wherein the plurality of LEDs are positioned closer to the object to be observed than the second observation hole in the first direction, and irradiate a predetermined light in a direction inclined toward the second observation hole with respect to the first direction in the first cross-section.

11. An observation system comprising: the illumination device according to any one of claims 1 to 10; and an imaging device positioned at the observation position, which is further from the object to be observed than the main body in the first direction, for observing the object to be observed through the first observation hole and the second observation hole.

Images