Optical device

Abstract

To provide an optical device that can emit light efficiently with a compact structure.SOLUTION: An optical device 1 of the present invention includes: a light source 100; a first reflection surface 101 for reflecting light from the light source 100 to an object 103; and a second reflection surface 102 for reflecting part of the light from the object 103 to the object 103, the first and second reflection surfaces having different shapes.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0005]

[0001] The present invention relates to an optical device.

Background Art

[0002] Conventionally, an optical device that detects substances contained in an object by receiving light reflected or scattered by the object is known. Patent Document 1 discloses an optical device that irradiates a gas with light from a light source and then receives the light scattered by the gas with a light receiving element to detect particles contained in the gas.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the optical device disclosed in Patent Document 1, since the light source and the light receiving element are provided on different sides with respect to the gas flow path, the device has become large-sized.​​​​​​​​​​​​​​​​ [Brief explanation of the drawing]

[0007] [Figure 1] A schematic cross-sectional view of the optical device according to the first embodiment. [Figure 2] A schematic diagram showing how light is reflected by an object in an optical device according to the first embodiment. [Figure 3] A schematic diagram showing how light is reflected by an object in an optical device according to the first embodiment. [Figure 4] A graph comparing the relative light intensity of reflected light in the optical device according to the first embodiment. [Figure 5] A schematic diagram showing how light is reflected by an object in an optical device according to the first embodiment. [Figure 6] A graph comparing the detection amounts in the optical device according to the first embodiment. [Figure 7] A partial projection view, a partial top view, and a cross-sectional view of the optical device according to the second embodiment. [Figure 8] A graph showing the breakdown of the amount of light received in the optical device according to the second embodiment, based on the number of reflections. [Figure 9] A partial projection view, a partial top view, and a cross-sectional view of the optical device according to the third embodiment. [Figure 10] A partial projection view, a partial top view, and a cross-sectional view of an optical device according to the fourth embodiment. [Figure 11] A partial projection view, a partial top view, and a cross-sectional view of the optical device according to the fifth embodiment. [Figure 12] A partial projection view, a partial top view, and a cross-sectional view of an optical device according to the sixth embodiment. [Figure 13] A partial projection view, a partial top view, and a cross-sectional view of an optical device according to the seventh embodiment. [Figure 14] A partial projection view and cross-sectional view of an optical device according to the eighth embodiment. [Figure 15] A schematic diagram showing how light is reflected and transmitted in the optical device according to the eighth embodiment. [Figure 16] A partial projection view and cross-sectional view of an optical device according to the ninth embodiment. [Figure 17] Schematic cross-sectional view of a measuring device including an optical device according to the present embodiment. [Figure 18] Main part sub-scanning cross-sectional view of an image forming apparatus according to an embodiment.

Mode for Carrying Out the Invention

[0008] Hereinafter, the optical device according to the present embodiment will be described in detail based on the attached drawings. Note that the drawings shown below may be drawn at scales different from the actual ones in order to facilitate understanding of the present embodiment.

[0009] [First Embodiment] Conventionally, an optical device has been proposed that efficiently condenses diffused light from an illuminated object using a spherical reflecting surface and an ellipsoidal reflecting surface onto a light receiving element. For example, a detection device that detects fine particles contained in the atmosphere using an optical system in which the foci of an ellipsoidal reflecting surface and the center of a spherical reflecting surface are at the same position is known. In addition, an inspection device that inspects the surface of an object by irradiating the object with light from a light source using a spherical reflecting surface is known.

[0010] In the conventional optical devices as described above, another device is required to efficiently illuminate the light from the light source, which causes the device to become large, or it is difficult to efficiently irradiate the object with the light from the light source because the light reflected on the inner surface of the spherical reflecting surface is used, resulting in problems. Therefore, an object of the present embodiment is to provide an optical device that can efficiently irradiate an object with light from a light source with a compact configuration.

[0011] FIG. 1 shows a schematic cross-sectional view of an optical device 1 according to the first embodiment. The optical device 1 according to the present embodiment includes a light source 100, a first reflecting surface 101, and a second reflecting surface 102.

[0012] The light source 100 is a light-emitting means such as a light-emitting diode (LED), which emits light toward the first reflective surface 101. As the light source 100, instead of a light-emitting diode, a light-emitting element or light-emitting device such as a laser light source or a spectroscopic light source may be used.

[0013] The first reflective surface 101 is a reflective means such as a mirror, and in order to efficiently illuminate the object 103, it includes the center of the light source 100 and has a concave curvature, i.e., convex power (refractive force), in a cross section perpendicular to a reference plane parallel to the object 103 (a cross section parallel to the plane of the paper). The second reflective surface 102 is a reflective means such as a mirror, and includes the center of the light source 100. It also has a linear shape in a cross section perpendicular to a reference plane parallel to the object 103 (a cross section parallel to the plane of the paper).

[0014] In other words, the first reflective surface 101 and the second reflective surface 102 have different shapes from each other. Also, the first reflective surface 101 and the second reflective surface 102 are spaced apart from each other. The light-receiving element 104 is a light-receiving means such as a photodiode (PD), and receives a portion of the light reflected by the second reflective surface 102.

[0015] As shown in Figure 1, in the optical device 1 according to this embodiment, light emitted from the light source 100 is incident on the first reflective surface 101. Then, the light reflected by the first reflective surface 101 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 102.

[0016] Next, the light reflected by the second reflective surface 102 is incident on the object 103 again. Then, a portion of the light reflected again by object 103 is again incident on the second reflective surface 102. Then, a portion of the light reflected again by the second reflective surface 102 enters the light-receiving element 104.

[0017] In other words, in the optical device 1 according to this embodiment, the first reflective surface 101 is defined as a reflective region that reflects light from the light source 100 toward the object 103, and the second reflective surface 102 is also defined as a reflective region that reflects a portion of the light from the object 103 toward the object 103.

[0018] Figures 2(a) and 2(b) are schematic diagrams showing how light is reflected by objects 103a and 103b in the optical device 1 according to this embodiment, respectively.

[0019] In the optical device 1 according to this embodiment, the object 103 that is illuminated is, for example, a light-reflecting member such as a white plate. Object 103 may be replaced with paper, powder, liquid, or gaseous material instead of the white plate.

[0020] Object 103 generally contains a main substance 1031, which is the main component of object 103, and impurities 1032 other than the main substance 1031. Here, for example, the main substance 1031 could be a substance that reflects a portion of the incident light according to its reflectivity, such as barium sulfate, while the impurity 1032 could be a substance that absorbs a portion of the incident light according to its absorptivity, such as graphite.

[0021] Furthermore, the main substance 1031 can be a material that reflects a portion of the incident light depending on its reflectivity, such as cellulose or fluororesin, and the impurity 1032 can be a material that absorbs a portion of the incident light depending on its absorptivity, such as water. In the optical device 1 according to this embodiment, the object 103 illuminated is composed of a main substance 1031 that reflects a portion of the incident light according to its reflectivity and an impurity 1032 that absorbs a portion of the incident light according to its absorptiveness. As long as the object 103 is composed of these two components, the above combination is not limited to any particular combination, and a wide variety of combinations are possible.

[0022] As shown in Figure 2(a), assume that object 103a contains only the main substance 1031 and no impurities 1032. At this time, when light A reflected by the first reflective surface 101 is incident on object 103a, light A interacts with the main material 1031 inside object 103a, causing light B to be diffusely reflected from the surface of object 103a.

[0023] On the other hand, as shown in Figure 2(b), let's assume that object 103b contains impurities 1032 in addition to the main substance 1031. At this time, when light A reflected by the first reflective surface 101 is incident on object 103b, light A interacts with the main substance 1031 and impurities 1032 inside object 103b, causing light C to be diffusely reflected from the surface of object 103b.

[0024] Therefore, in the optical device 1 according to this embodiment, the light B reflected by object 103a and the light C reflected by object 103b are received by the light receiving element 104, and the respective light quantities are compared with each other. This makes it possible to detect the ratio of impurities 1032 to the main substance 1031 in object 103b.

[0025] Figures 3(a), (b), and (c) are schematic diagrams showing how light reflected by object 103b in the optical device 1 according to this embodiment is re-entered onto object 103b via the second reflective surface 102.

[0026] First, as shown in Figure 3(a), when light A reflected by the first reflective surface 101 is incident on object 103b, light A interacts with the main substance 1031 and impurities 1032 inside object 103b, causing light C to be diffusely reflected from the surface of object 103b. Next, the light C diffusely reflected from the surface of object 103b is reflected by the second reflective surface 102 as described above, and as shown in Figure 3(b), it enters object 103b again.

[0027] Then, when light C reflected by the second reflective surface 102 is incident on object 103b, light C interacts with the main substance 1031 and impurities 1032 inside object 103b, causing light D to be diffusely reflected from the surface of object 103b. Next, the light D diffusely reflected from the surface of object 103b is reflected by the second reflective surface 102 as described above, and enters object 103b again, as shown in Figure 3(c). Then, when light D reflected by the second reflective surface 102 is incident on object 103b, light D interacts with the main substance 1031 and impurities 1032 inside object 103b, causing light E to be diffusely reflected from the surface of object 103b.

[0028] Thus, in the optical device 1 according to this embodiment, the number of interactions between the light and the main substance 1031 and impurities 1032 contained in the object 103 can be increased by causing the light to be re-incident to the object 103 by the second reflective surface 102. Furthermore, as described above, since impurity 1032 absorbs a portion of the incident light, the amount of light reflected by object 103b decreases as the number of interactions increases.

[0029] Figure 4 shows a graph comparing the relative luminous intensity (RI) of each light source in the examples shown in Figures 2 and 3.

[0030] In Figure 4, the relative light intensity RI is set to 1 when the light receiving element 104 receives light B reflected from the surface of object 103a, which does not contain the impurity 1032 as shown in Figure 2(a). Then, as shown in Figure 3(a), when light A reflected by the first reflective surface 101 is incident on object 103b containing impurity 1032, a portion of light A is absorbed through interaction with the impurity 1032 (first time), and then light C is diffusely reflected from the surface of object 103b. At this time, the relative luminous intensity RI of light C is assumed to have decreased to 0.90.

[0031] Then, as shown in Figure 3(b), when light C is reflected by the second reflective surface 102 and enters object 103b again, light C interacts with the impurity 1032 again (for the second time), and after some of it is absorbed, light D is diffusely reflected from the surface of object 103b. At this time, the relative luminous intensity RI of light D decreases to 0.81.

[0032] Next, as shown in Figure 3(c), when light D is reflected by the second reflective surface 102 and enters object 103b again, light D interacts with the impurity 1032 again (for the third time), and after some of it is absorbed, light E is diffusely reflected from the surface of object 103b. As a result, the relative luminous intensity RI of light E decreases to 0.73.

[0033] Figures 5(a), (b), and (c) are schematic diagrams showing how light A reflected by the first reflective surface 101 in the optical device 1 according to this embodiment is incident on objects 103c, 103d, and 103b, respectively.

[0034] As shown in Figures 5(a) to (c), objects 103c, 103d, and 103b each have different content levels of impurity 1032. Specifically, in object 103c, the content of impurity 1032 is 1% relative to the main substance 1031; in object 103d, the content of impurity 1032 is 2% relative to the main substance 1031; and in object 103b, the content of impurity 1032 is 3% relative to the main substance 1031.

[0035] Then, as shown in Figure 5(a), when light A reflected by the first reflective surface 101 is incident on object 103c, a portion of light A is absorbed by interacting with the impurity 1032, and then light F is diffusely reflected from the surface of object 103c. Furthermore, as shown in Figure 5(b), when light A reflected by the first reflective surface 101 is incident on object 103d, a portion of light A is absorbed due to interaction with the impurity 1032, and then light G is diffusely reflected from the surface of object 103d.

[0036] Furthermore, as shown in Figure 5(c), when light A reflected by the first reflective surface 101 is incident on object 103b, a portion of the light A is absorbed due to interaction with the impurity 1032, and then the remaining light H is diffusely reflected from the surface of object 103b. In other words, in this case, light H is identical to light C shown in Figure 3(a).

[0037] Figure 6(a) is a graph comparing the detected amounts T of impurity 1032 in each of the objects 103c, 103d, and 103b shown in Figure 5. Here, the detected amount T for the content of impurity 1032 is defined as the difference between the relative light quantity RI (=1) of light B reflected from the surface of object 103a that does not contain impurity 1032, as shown in Figure 2(a), and the relative light quantity RI of light reflected from the surface of the corresponding object, i.e., as shown in equation (1) below. T=1-RI ···(1)

[0038] First, the relative light intensity RI of the light H (i.e., light C) reflected from the surface of object 103b, which contains 3% impurity 1032, is 0.90, as shown in Figure 4. Therefore, the detected amount T when the light receiving element 104 receives light H can be calculated from equation (1) as 0.10. Furthermore, the amount of light detected when the light receiving element 104 receives light F reflected from the surface of object 103c, which contains 1% impurity 1032, is calculated to be 0.10 × (1 / 3) = 0.03.

[0039] Furthermore, the amount of light detected when the light receiving element 104 receives light G reflected from the surface of object 103d, which contains 2% impurity 1032, is calculated to be 0.10 × (2 / 3) = 0.07. In other words, when the incident light in each of objects 103c, 103d, and 103b interacts with the impurity 1032 only once, the detection amount T shown in Figure 6(a) is obtained.

[0040] Next, as shown in Figure 3(c), consider the case where light that has already interacted twice with the impurity 1032 contained in each object is incident again on object 103c, object 103d, and object 103b. In this case, the light H reflected from the surface of object 103b, which contains 3% impurity 1032, is the same as the light E shown in Figure 3(c). Furthermore, since the relative light intensity RI of light E is 0.73 as shown in Figure 4, the detected amount T when light H is received by the light-receiving element 104 can be calculated from equation (1) as 0.27.

[0041] Furthermore, the amount detected T when the light receiving element 104 receives light F reflected from the surface of object 103c, which contains 1% impurity 1032, is calculated to be 0.27 × (1 / 3) = 0.09. Furthermore, the amount of light detected when the light receiving element 104 receives light G reflected from the surface of object 103d, which contains 2% impurity 1032, is calculated to be 0.27 × (2 / 3) = 0.18.

[0042] Figure 6(b) shows a graph comparing the detected amounts T for impurity 1032 in such cases. As shown in Figures 6(a) and (b), the detection amount T can be increased by increasing the number of interactions between light and impurities 1032 inside object 103. As the detection amount T increases, the amount of impurities 1032 in object 103 can be determined with greater accuracy.

[0043] As described above, in the optical device 1 according to this embodiment, by providing a first reflective surface 101 and a second reflective surface 102, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, by reflecting the light from object 103 with the second reflective surface 102, object 103 can be illuminated multiple times, thereby increasing the number of interactions between the light and the main substance 1031 and impurities 1032 that make up object 103.

[0044] [Second Embodiment] Figures 7(a) and 7(b) show a partial projection view and a partial top view, respectively, of the optical device 2 according to the second embodiment. Figure 7(c) also shows a cross-sectional view of the optical device 2 according to the second embodiment, cut along the line 7C-7C in Figure 7(a).

[0045] The optical device 2 according to this embodiment includes a light source 100, a reflective element 200, and a substrate 105.

[0046] The light source 100 is a light-emitting means such as a light-emitting diode (LED), which emits light toward the first reflective surface 202. As the light source 100, instead of a light-emitting diode, a light-emitting element or light-emitting device such as a laser light source or a spectroscopic light source may be used.

[0047] The light-receiving element 104 is a light-receiving means such as a photodiode (PD), and receives a portion of the light reflected by the third reflective surface 203. The substrate 105 is a component that holds the light source 100 and the light receiving element 104, and has an opening 105a (first opening) formed therein.

[0048] The reflective element 200 has the function of reflecting light from the light source 100 and light from the object 103, and is made of resin. In addition, various materials such as metal may be used instead of resin for the material of the reflective element 200.

[0049] Furthermore, in the optical device 2 according to this embodiment, the reflective element 200 is a mirror surface that has been coated with metal vapor deposition, and has a second reflective surface 201, a first reflective surface 202, and a third reflective surface 203 that are connected to each other. Instead of applying metal vapor deposition to the second reflective surface 201, the first reflective surface 202, and the third reflective surface 203, various reflective means such as total internal reflection or gloss coating may be provided.

[0050] The second reflective surface 201, the first reflective surface 202, and the third reflective surface 203 each have a curved surface defined by the following equation (2), where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section.

[0051]

number

[0052] The first reflective surface 202 and the third reflective surface 203 are aspherical surfaces that satisfy the condition -1.0 ≤ K < 0.0 with respect to the conic coefficient K, as shown by the shaded areas in Figure 7(a). Specifically, the first reflective surface 202 and the third reflective surface 203 are part of a spheroidal ellipsoid with a radius of curvature R of 7.5 mm and a conic coefficient K of -0.444.

[0053] Furthermore, the optical axis O1 that passes through (includes) the vertex of the ellipsoidal surface forming the first reflective surface 202 on the light source 100 side and the focal point is tilted by θ = 20.964° with respect to the reference plane RP. Furthermore, the optical axis O2 that passes through (includes) the vertex of the ellipsoidal surface forming the third reflective surface 203 on the side of the photodetector 104 and the focal point is tilted by θ = 20.964° with respect to the reference plane RP. In other words, the optical axes O1 and O2 are non-parallel to the surface (substrate plane) of the substrate 105.

[0054] Here, the optical axis O1 is parallel to the major axis of the ellipsoidal spheroid that forms the first reflective surface 202, and the optical axis O2 is parallel to the major axis of the ellipsoidal spheroid that forms the third reflective surface 203. Furthermore, the second reflective surface 201 is part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0. In other words, the first reflective surface 202 and the second reflective surface 201 have different shapes. Specifically, the first reflective surface 202 and the second reflective surface 201 have different curvatures.

[0055] As shown in Figure 7(c), the light source 100 is positioned to include one of the focal points (first focal point) of the first reflective surface 202. Furthermore, the light-receiving element 104 is positioned to include one of the focal points (the first focal point) of the third reflective surface 203.

[0056] Furthermore, the second reflective surface 201, the first reflective surface 202, and the third reflective surface 203 are formed in the reflective element 200 such that the other focal point (second focal point) of each of the first reflective surface 202 and the third reflective surface 203 is located near the center of the second reflective surface 201. Preferably, the focal points of the other of the first reflective surface 202 and the third reflective surface 203 are located at the same position as the center of the second reflective surface 201. The object 103 is positioned to include at least one of the other focal points of the first reflective surface 202 and the third reflective surface 203.

[0057] As shown in Figure 7(c), in the optical device 2 according to this embodiment, a portion of the light emitted from the light source 100 is incident on the first reflective surface 202. Then, the light reflected by the first reflective surface 202 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 201 and the third reflective surface 203.

[0058] Next, the light that has entered the second reflective surface 201 is reflected by the second reflective surface 201 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 201 and the third reflective surface 203. Then, a portion of the light reflected by the third reflective surface 203 enters the light-receiving element 104.

[0059] In other words, in the optical device 2 according to this embodiment, the first reflective surface 202 is defined as a reflective region that reflects light from the light source 100 toward the object 103, and the second reflective surface 201 is defined as a reflective region that reflects a portion of the light from the object 103 toward the object 103. Furthermore, the third reflective surface 203 is defined as a reflective region that reflects a portion of the light from the object 103 toward the photodetector 104.

[0060] Figures 8(a) and 8(b) are graphs showing the breakdown of the amount of light received by the light-receiving element 104 in the optical device 2 according to this embodiment, according to the number of times it was reflected by the object 103. Here, the total amount of light received by the light-receiving element 104 is defined as 100%.

[0061] As shown in Figures 8(a) and (b), in the optical device 2 according to this embodiment, it can be seen that the amount of received light also includes light that has traveled back and forth between the object 103 and the second reflective surface 201 10 or more times, that is, light that has been reflected by the object 103 10 or more times. In other words, by adopting the above configuration, the optical device 2 according to this embodiment makes it possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 201 more than 10 times, that is, light that has been reflected by the object 103 more than 10 times, to the light-receiving element 104.

[0062] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0063] As described above, in the optical device 2 according to this embodiment, by providing the first reflective surface 202 and the second reflective surface 201, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 200. Furthermore, by adopting the above configuration, the number of times light travels back and forth between object 103 and the second reflective surface 201, that is, the number of times light is reflected by object 103, can be further increased.

[0064] [Third Embodiment] Figures 9(a) and 9(b) show a partial projection view and a partial top view, respectively, of the optical device 3 according to the third embodiment. Figure 9(c) also shows a cross-sectional view of the optical device 3 according to the third embodiment, cut along the line 9C-9C in Figure 9(a). In this embodiment, the optical device 3 has the same configuration as the optical device 2 according to the second embodiment, except that a reflective element 300 is provided instead of the reflective element 200. Therefore, the same reference numerals are used for the same components and their descriptions are omitted.

[0065] The optical device 3 according to this embodiment includes a light source 100, a reflective element 300, and a substrate 105.

[0066] The reflective element 300 has the function of reflecting light emitted from the light source 100 and light reflected by the object 103, and resin is used as the material. Furthermore, various materials such as metal may be used instead of resin for the material of the reflective element 300.

[0067] Furthermore, in the optical device 3 according to this embodiment, the reflective element 300 has a second reflective surface 301, a first reflective surface 302, and a third reflective surface 303, all of which are mirror surfaces coated with metal vapor deposition. Instead of applying metal vapor deposition to the second reflective surface 301, the first reflective surface 302, and the third reflective surface 303, various reflective means such as total internal reflection or gloss coating may be provided.

[0068] The first reflective surface 302 and the third reflective surface 303 each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section. Specifically, the first reflective surface 302 and the third reflective surface 303 are aspherical surfaces with a conic coefficient K in the range of -1.0 ≤ K < 0.0, as shown by the shaded area in Figure 9(a). More specifically, the first reflective surface 302 and the third reflective surface 303 are part of a spheroidal ellipsoid with a radius of curvature R of 7.5 mm and a conic coefficient K of -0.444.

[0069] Furthermore, the optical axes passing through the vertices and focal points of the first reflective surface 302 and the third reflective surface 303 are tilted by 20.964° with respect to the reference plane.

[0070] Furthermore, the second reflective surface 301 has a retroreflective function, that is, it is a retroreflective surface, and specifically has a shape in which a large number of minute corner cubes are arranged. Furthermore, as the second reflective surface 301, a retroreflective surface having various shapes with retroreflective properties may be used, such as a surface with a large number of small spheres arranged on it instead of a large number of small corner cubes.

[0071] As shown in Figure 9(c), the light source 100 is positioned to include one of the focal points of the first reflective surface 302. Furthermore, the light-receiving element 104 is positioned to include one of the focal points of the third reflective surface 303.

[0072] Furthermore, the first reflective surface 302 and the third reflective surface 303 are formed in the reflective element 300 such that the focal points of the other of the first reflective surface 302 and the third reflective surface 303 are positioned close to each other. The object 103 is positioned to include at least one of the other focal points of the first reflective surface 302 and the third reflective surface 303.

[0073] As shown in Figure 9(c), in the optical device 3 according to this embodiment, a portion of the light emitted from the light source 100 is incident on the first reflective surface 302. Then, the light reflected by the first reflective surface 302 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 301 and the third reflective surface 303.

[0074] Next, the light incident on the second reflective surface 301 is retroreflected by the second reflective surface 301 and incident on the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 301 and the third reflective surface 303. Then, a portion of the light reflected by the third reflective surface 303 enters the light-receiving element 104.

[0075] In the optical device 3 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 301 more than 10 times, that is, light that has been reflected by the object 103 more than 10 times, to the light-receiving element 104.

[0076] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0077] As described above, in the optical device 3 according to this embodiment, by providing the first reflective surface 302 and the second reflective surface 301, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 300. In addition, by forming the second reflective surface 301 to have retroreflective properties, the thickness of the reflective element 300 can be reduced compared to the optical device 2 according to the second embodiment.

[0078] [Fourth Embodiment] Figures 10(a) and 10(b) show a partial projection view and a partial top view of the optical device 4 according to the fourth embodiment, respectively. Figure 10(c) also shows a cross-sectional view of the optical device 4 according to the fourth embodiment, cut along the line 10C-10C in Figure 10(a). In this embodiment, the optical device 4 has the same configuration as the optical device 2 according to the second embodiment, except that a reflective element 400 is provided instead of the reflective element 200. Therefore, the same reference numerals are used for the same components and their descriptions are omitted.

[0079] The optical device 4 according to this embodiment includes a light source 100, a reflective element 400, and a substrate 105.

[0080] The reflective element 400 has the function of reflecting light emitted from the light source 100 and light reflected by the object 103, and is made of resin. Furthermore, various materials such as metal may be used instead of resin for the material of the reflective element 400.

[0081] Furthermore, in the optical device 4 according to this embodiment, the reflective element 400 has a second reflective surface 401, a first reflective surface 402, and a third reflective surface 403, all of which are mirror surfaces coated with metal vapor deposition. Instead of applying metal vapor deposition to the second reflective surface 401, the first reflective surface 402, and the third reflective surface 403, various reflective means such as total internal reflection or gloss coating may be provided.

[0082] The first reflective surface 402 and the third reflective surface 403 each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section. Specifically, the first reflective surface 402 and the third reflective surface 403 are aspherical surfaces with a conic coefficient K in the range of -1.0 ≤ K < 0.0, as shown by the shaded area in Figure 10(a). More specifically, the first reflective surface 402 and the third reflective surface 403 are part of a spheroidal ellipsoid with a radius of curvature R of 7.5 mm and a conic coefficient K of -0.444.

[0083] Furthermore, the optical axes passing through the vertices and focal points of the first reflective surface 402 and the third reflective surface 403 are tilted by 20.964° with respect to the reference plane.

[0084] Furthermore, the second reflective surface 401 is composed of a first partial reflective surface 4011, a second partial reflective surface 4012, and a third partial reflective surface 4013. The first partial reflective surface 4011 is part of a sphere with a radius of curvature R of 15 mm and a conic coefficient K of 0.

[0085] Furthermore, the second partial reflective surface 4012 is part of a sphere with a radius of curvature R of 16.5 mm and a conic coefficient K of 0. Furthermore, the third partial reflective surface 4013 is part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0. Furthermore, the centers of the first partial reflective surface 4011, the second partial reflective surface 4012, and the third partial reflective surface 4013 are located at the same position relative to each other.

[0086] As shown in Figure 10(c), the light source 100 is positioned to include one of the focal points of the first reflective surface 402. Furthermore, the light-receiving element 104 is positioned to include one of the focal points of the third reflective surface 403.

[0087] Furthermore, the second reflective surface 401, the first reflective surface 402, and the third reflective surface 403 are formed in the reflective element 400 such that the focal points of the other of the first reflective surface 402 and the third reflective surface 403 are located near the center of the second reflective surface 401, that is, near the center of the first partial reflective surface 4011, the second partial reflective surface 4012, and the third partial reflective surface 4013, respectively. The object 103 is positioned to include at least one of the other focal points of the first reflective surface 402 and the third reflective surface 403.

[0088] As shown in Figure 10(c), in the optical device 4 according to this embodiment, a portion of the light emitted from the light source 100 is incident on the first reflective surface 402. Then, the light reflected by the first reflective surface 402 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 401 and the third reflective surface 403.

[0089] Next, the light that has entered the second reflective surface 401 is reflected by the second reflective surface 401 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 401 and the third reflective surface 403. Then, a portion of the light reflected by the third reflective surface 403 enters the photodetector 104.

[0090] In the optical device 4 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 401 more than 10 times, that is, light that has been reflected by the object 103 more than 10 times, to the light-receiving element 104.

[0091] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0092] As described above, in the optical device 4 according to this embodiment, by providing the first reflective surface 402 and the second reflective surface 401, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 400.

[0093] In addition, by providing a first partial reflective surface 4011, a second partial reflective surface 4012, and a third partial reflective surface 4013, which are parts of a sphere with different radii of curvature R, as the second reflective surface 401, the thickness of the reflective element 400 can be reduced compared to the optical device 2 according to the second embodiment. Furthermore, even if the radii of curvature R of the first partial reflective surface 4011, the second partial reflective surface 4012, and the third partial reflective surface 4013 are made the same, that is, the second reflective surface 401 is designed to have the shape of a Fresnel surface, the same effect as the optical device 4 according to this embodiment can be obtained.

[0094] [Fifth Embodiment] Figures 11(a) and (b) show a partial projection view and a partial top view of the optical device 5 according to the fifth embodiment, respectively. Furthermore, Figures 11(c), (d), and (e) show cross-sectional views of the optical device 5 according to the fifth embodiment, cut along the lines 11C-11C, 11D-11D, and 11E-11E in Figure 11(a), respectively.

[0095] The optical device 5 according to this embodiment includes a first light source 1001, a second light source 1002, a reflecting element 500, and a substrate 1005.

[0096] The first light source 1001 and the second light source 1002 are light-emitting means such as light-emitting diodes (LEDs). Instead of light-emitting diodes, light-emitting elements or devices such as laser light sources or spectral light sources may be used as the first light source 1001 and the second light source 1002. The light-receiving element 1003 is a light-receiving means such as a photodiode (PD). The substrate 1005 is a component that holds the first light source 1001, the second light source 1002, and the light receiving element 1003, and has an opening 1005a formed therein.

[0097] The reflective element 500 has the function of reflecting light from the first light source 1001 and the second light source 1002, as well as light from the object 103, and is made of resin. Furthermore, various materials such as metal may be used instead of resin for the material of the reflective element 500.

[0098] Furthermore, in the optical device 5 according to this embodiment, the reflective element 500 has a second reflective surface 501, a first reflective surface 502, a fourth reflective surface 503 (first reflective surface), and a third reflective surface 504, all of which are mirror surfaces coated with metal vapor deposition. Instead of applying metal vapor deposition to the second reflective surface 501, the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504, various reflective means such as total internal reflection or gloss coating may be provided.

[0099] The second reflective surface 501, the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504 each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section.

[0100] The first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504 are aspherical surfaces with a conic coefficient K in the range of -1.0 ≤ K < 0.0, as shown by the shaded areas in Figure 11(a). Specifically, the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504 are part of a spheroidal ellipsoid with a radius of curvature R of 7.5 mm and a conic coefficient K of -0.444.

[0101] Furthermore, the optical axes passing through the vertices and focal points of the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504 are tilted by 20.964° with respect to the reference plane. Furthermore, the second reflective surface 501 is part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0.

[0102] As shown in Figure 11(c), the first light source 1001 is positioned to include one of the focal points of the first reflective surface 502. Furthermore, as shown in Figure 11(d), the second light source 1002 is positioned to include one of the focal points of the fourth reflective surface 503. Furthermore, as shown in Figure 11(e), the light-receiving element 1003 is positioned to include one of the focal points of the third reflective surface 504.

[0103] The second reflective surface 501, the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504 are formed in the reflecting element 500 such that the focal points of the other surfaces of the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504 are positioned near the center of the second reflective surface 501. Furthermore, object 103 is positioned to include at least one of the other focal points of the first reflective surface 502, the fourth reflective surface 503, and the third reflective surface 504.

[0104] As shown in Figure 11(c), in the optical device 5 according to this embodiment, a portion of the light emitted from the first light source 1001 is incident on the first reflective surface 502. Then, the light reflected by the first reflective surface 502 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 501 and the third reflective surface 504.

[0105] Next, the light that has entered the second reflective surface 501 is reflected by the second reflective surface 501 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 501 and the third reflective surface 504. As shown in Figure 11(e), some of the light reflected by the third reflective surface 504 is incident on the photodetector 1003.

[0106] Furthermore, as shown in Figure 11(d), in the optical device 5 according to this embodiment, a portion of the light emitted from the second light source 1002 is incident on the fourth reflective surface 503. Then, the light reflected by the fourth reflective surface 503 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 501 and the third reflective surface 504.

[0107] Next, the light that has entered the second reflective surface 501 is reflected by the second reflective surface 501 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 501 and the third reflective surface 504. As shown in Figure 11(e), some of the light reflected by the third reflective surface 504 is incident on the photodetector 1003.

[0108] In the optical device 5 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 501 10 or more times, that is, light that has been reflected by the object 103 10 or more times, to the light-receiving element 1003.

[0109] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0110] As described above, in the optical device 5 according to this embodiment, by providing the first reflective surface 502, the fourth reflective surface 503, and the second reflective surface 501, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 500.

[0111] In addition, the optical device 5 according to this embodiment can interact with various impurities 1032 in the object 103 by making the wavelengths of light emitted from the first light source 1001 and the second light source 1002 different from each other. In that case, multiple light-receiving elements 1003 may be provided so that they can receive light of multiple wavelengths. Furthermore, by providing a filter on the light-receiving element 1003, it is possible to select the wavelength of the light to be received.

[0112] [Sixth Embodiment] Figures 12(a) and 12(b) show a partial projection view and a partial top view of the optical device 6 according to the sixth embodiment, respectively. Furthermore, Figures 12(c), (d), and (e) show cross-sectional views of the optical device 6 according to the sixth embodiment, cut along the lines 12C-12C, 12D-12D, and 12E-12E in Figure 12(a), respectively. In this embodiment, the optical device 6 has the same configuration as the optical device 5 according to the fifth embodiment, except that a reflective element 600 is provided instead of the reflective element 500. Therefore, the same reference numerals are used for the same components and their descriptions are omitted.

[0113] The optical device 6 according to this embodiment includes a first light source 1001, a second light source 1002, a reflecting element 600, and a substrate 1005.

[0114] The reflective element 600 has the function of reflecting light from the first light source 1001 and the second light source 1002, as well as light from the object 103, and is made of resin. Furthermore, various materials such as metal may be used instead of resin for the material of the reflective element 600.

[0115] Furthermore, in the optical device 6 according to this embodiment, the reflective element 600 has a second reflective surface 601, a first reflective surface 602, a fourth reflective surface 603 (first reflective surface), and a third reflective surface 604, all of which are mirror surfaces coated with metal vapor deposition. Instead of applying metal vapor deposition to the second reflective surface 601, the first reflective surface 602, the fourth reflective surface 603, and the third reflective surface 604, various reflective means such as total internal reflection or gloss coating may be provided.

[0116] The second reflective surface 601, the first reflective surface 602, the fourth reflective surface 603, and the third reflective surface 604 each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section.

[0117] The first reflective surface 602, the fourth reflective surface 603, and the third reflective surface 604 are aspherical surfaces with a conic coefficient K in the range of -1.0 ≤ K < 0.0, as shown by the shaded areas in Figure 12(a). Specifically, the first reflective surface 602, the fourth reflective surface 603, and the third reflective surface 604 are part of a paraboloid of revolution with a radius of curvature R of 9 mm and a conic coefficient K of -1.

[0118] Furthermore, the optical axes passing through the vertices and focal points of the first reflective surface 602, the fourth reflective surface 603, and the third reflective surface 604 are tilted by 20° with respect to the reference plane. Furthermore, the second reflective surface 601 is part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0.

[0119] As shown in Figure 12(c), the first light source 1001 is positioned to include the focal point (first focal point) of the first reflective surface 602. Furthermore, as shown in Figure 12(d), the second light source 1002 is positioned to include the focal point (first focal point) of the fourth reflective surface 603.

[0120] Furthermore, as shown in Figure 12(e), the light-receiving element 1003 is positioned to include the focal point of the third reflective surface 604. The object 103 is then positioned to include the vicinity of the center of the second reflective surface 601.

[0121] As shown in Figure 12(c), in the optical device 6 according to this embodiment, a portion of the light emitted from the first light source 1001 is incident on the first reflective surface 602. Then, the light reflected by the first reflective surface 602 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 601 and the third reflective surface 604.

[0122] Next, the light that has entered the second reflective surface 601 is reflected by the second reflective surface 601 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 601 and the third reflective surface 604. Then, as shown in Figure 12(e), some of the light reflected by the third reflective surface 604 enters the light-receiving element 1003.

[0123] Furthermore, as shown in Figure 12(d), in the optical device 6 according to this embodiment, a portion of the light emitted from the second light source 1002 is incident on the fourth reflective surface 603. Then, the light reflected by the fourth reflective surface 603 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 601 and the third reflective surface 604.

[0124] Next, the light that has entered the second reflective surface 601 is reflected by the second reflective surface 601 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 601 and the third reflective surface 604. Then, as shown in Figure 12(e), some of the light reflected by the third reflective surface 604 enters the light-receiving element 1003.

[0125] In the optical device 6 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 601 10 or more times, that is, light that has been reflected by the object 103 10 or more times, to the light-receiving element 1003.

[0126] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0127] As described above, in the optical device 6 according to this embodiment, by providing the first reflective surface 602, the fourth reflective surface 603, and the second reflective surface 601, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 600.

[0128] In addition, in the optical device 6 according to this embodiment, the object 103 can be uniformly illuminated by designing the first reflective surface 602, the fourth reflective surface 603, and the third reflective surface 604 to be part of a paraboloid of revolution. This makes it possible to minimize the change in the amount of light received by the light-receiving element 1003, i.e., the detected amount T, even when the position of the object 103 changes.

[0129] [Seventh Embodiment] Figures 13(a) and 13(b) show a partial projection view and a partial top view of the optical device 7 according to the seventh embodiment, respectively. Figure 13(c) also shows a cross-section of the optical device 7 according to the seventh embodiment, perpendicular to the reference plane.

[0130] The optical device 7 according to this embodiment includes a light source unit 703, a reflective element 700, and a substrate 105.

[0131] The light source unit 703 consists of a light source 7031 and an illumination lens 7032. The light source 7031 is a light-emitting means such as a light-emitting diode (LED). Alternatively, instead of a light-emitting diode, other light-emitting elements or devices such as a laser light source or a spectroscopic light source may be used as the light source 7031. Furthermore, the illumination lens 7032 applies a predetermined refractive effect to the light emitted from the light source 7031.

[0132] The light-receiving unit 704 consists of a light-receiving element 7041 and an imaging lens 7042. The light-receiving element 7041 is a light-receiving means such as a photodiode (PD). The imaging lens 7042 also focuses the incident light onto the photodetector 7041.

[0133] The substrate 105 is a component that holds the light source unit 703 and the light receiving unit 704, and has an opening 105a formed therein.

[0134] The reflective element 700 has the function of reflecting light from the light source unit 703 and light from the object 103, and is made of resin. Furthermore, various materials such as metal may be used instead of resin for the material of the reflective element 700.

[0135] Furthermore, in the optical device 7 according to this embodiment, the reflective element 700 has a second reflective surface 701 and a first reflective surface 702, both of which are mirror surfaces coated with metal vapor deposition. Instead of applying metal vapor deposition to the second reflective surface 701 and the first reflective surface 702, various reflective means such as total internal reflection or gloss coating may be provided. As shown below, in the optical device 7 according to this embodiment, the first reflective surface 702 also functions as the third reflective surface in the optical devices according to the first to sixth embodiments.

[0136] The second reflective surface 701 and the first reflective surface 702 each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section.

[0137] The first reflective surface 702 is an aspherical surface with a conic coefficient K in the range of -1.0 ≤ K < 0.0, as shown by the shaded area in Figure 13(a). Specifically, the first reflective surface 702 is part of a paraboloid of revolution with a radius of curvature R of 28.8 mm and a conic coefficient K of -1.

[0138] Furthermore, the optical axis passing through the vertex and focal point of the first reflective surface 702 is tilted by 90° with respect to the reference plane. Furthermore, the second reflective surface 701 is part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0.

[0139] As shown in Figure 13(c), the light source unit 703 is positioned such that the light emitted from the light source 7031 is focused via the first reflective surface 702 towards the vicinity of the center of the second reflective surface 701. Furthermore, the light receiving unit 704 is positioned so that light (divergent light) from near the center of the second reflective surface 701 is focused onto the light receiving element 7041 via the first reflective surface 702.

[0140] Furthermore, the second reflective surface 701 and the first reflective surface 702 are formed in the reflective element 700 such that the center of the second reflective surface 701 and the focal point of the first reflective surface 702 are close to each other. The object 103 is positioned to include at least one of the center of the second reflective surface 701 and the focal point of the first reflective surface 702.

[0141] As shown in Figure 13(c), in the optical device 7 according to this embodiment, light emitted from the light source 7031 passes through the illumination lens 7032 and then enters the first reflective surface 702. Then, the light reflected by the first reflective surface 702 toward the object 103 is reflected by the object 103, and a portion of it then enters the second reflective surface 701 and the first reflective surface 702.

[0142] Next, the light that has entered the second reflective surface 701 is reflected by the second reflective surface 701 and enters the object 103 again. Then, a portion of the light reflected again by object 103 is incident on the second reflective surface 701 and the first reflective surface 702. Then, a portion of the light reflected by the first reflective surface 702 passes through the imaging lens 7042 and enters the photodetector 7041.

[0143] In the optical device 7 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 701 more than 10 times, that is, light that has been reflected by the object 103 more than 10 times, to the light-receiving element 7041.

[0144] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0145] As described above, in the optical device 7 according to this embodiment, by providing the first reflective surface 702 and the second reflective surface 701, light from the light source 7031 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 700.

[0146] In addition, in the optical device 7 according to this embodiment, the first reflective surface 702 is designed to be part of a paraboloid of revolution, and the optical axis of the first reflective surface 702 is tilted by 90° with respect to the reference plane, thereby increasing the area (reflection area, effective area) to which light is incident on the first reflective surface 702. This makes it possible to expand the area in which the light source 7031 and the light receiving element 7041 can be placed.

[0147] [Eighth Embodiment] Figure 14(a) shows a partial projection view of the optical device 8 according to the eighth embodiment. Figure 14(b) also shows a cross-sectional view of the optical device 8 according to the eighth embodiment, cut along the line 14B-14B in Figure 14(a).

[0148] The optical device 8 according to this embodiment includes a light source 100, a first reflective element 800a, a second reflective element 800b, and a first substrate 1051.

[0149] The light source 100 is a light-emitting means such as a light-emitting diode (LED). Alternatively, instead of a light-emitting diode, a light-emitting element or light-emitting device such as a laser light source or a spectroscopic light source may be used as the light source 100. The light-receiving element 104 is a light-receiving means such as a photodiode (PD). The first substrate 1051 and the second substrate 1052 are components that hold the light source 100 and the light receiving element 104, respectively.

[0150] The first reflective element 800a has the function of reflecting light emitted from the light source 100 and light reflected by the object 103, and is made of resin. The second reflective element 800b has the function of reflecting light that has passed through object 103, and resin is used as the material for this element. Furthermore, instead of resin, various materials such as metal may be used for the first reflector element 800a and the second reflector element 800b.

[0151] Furthermore, in the optical device 8 according to this embodiment, the first reflective element 800a has a second reflective surface 801a and a first reflective surface 802a formed on it, both of which are mirror surfaces coated with metal vapor deposition. Furthermore, the second reflective element 800b has a fourth reflective surface 801b (second reflective surface) and a third reflective surface 802b formed on it, both of which are mirror surfaces coated with metal vapor deposition. In addition, instead of applying metal vapor deposition to the second reflective surface 801a, the first reflective surface 802a, the fourth reflective surface 801b, and the third reflective surface 802b, various reflective means such as total internal reflection or gloss coating may be provided.

[0152] The second reflective surface 801a, the first reflective surface 802a, the fourth reflective surface 801b, and the third reflective surface 802b each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section.

[0153] The first reflective surface 802a and the third reflective surface 802b are aspherical surfaces, as shown by the shaded areas in Figure 14(a), where the conic coefficient K is in the range of -1.0 ≤ K < 0.0. Specifically, the first reflective surface 802a and the third reflective surface 802b are part of a spheroidal ellipsoid with a radius of curvature R of 7.5 mm and a conic coefficient K of -0.444.

[0154] Furthermore, the optical axes passing through the vertices and focal points of the first reflective surface 802a and the third reflective surface 802b are tilted by 20.964° with respect to the reference plane. Furthermore, the second reflective surface 801a and the fourth reflective surface 801b are part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0.

[0155] As shown in Figure 14(b), the light source 100 is positioned to include one of the focal points of the first reflective surface 802a. Furthermore, the light-receiving element 104 is positioned to include one of the focal points of the third reflective surface 802b.

[0156] Furthermore, the first reflective surface 802a and the second reflective surface 801a are formed in the first reflective element 800a, and the third reflective surface 802b and the fourth reflective surface 801b are formed in the second reflective element 800b, such that the focal points of the other of the first reflective surface 802a and the third reflective surface 802b are located near the center of the second reflective surface 801a and the fourth reflective surface 801b, respectively. The object 103 is positioned to include at least one of the other focal points of the first reflective surface 802a and the third reflective surface 802b.

[0157] As shown in Figure 14(b), in the optical device 8 according to this embodiment, a portion of the light emitted from the light source 100 is incident on the first reflective surface 802a. The light reflected by the first reflective surface 802a toward the object 103 is then either reflected by the object 103 or transmitted through the object 103.

[0158] Next, a portion of the light reflected by object 103 is incident on the second reflective surface 801a. Meanwhile, a portion of the light that has passed through object 103 is incident on the fourth reflective surface 801b.

[0159] Next, the light incident on the second reflective surface 801a is reflected by the second reflective surface 801a and incident on the object 103 again, after which it is either reflected by the object 103 or transmitted through the object 103. Furthermore, the light reflected by the fourth reflective surface 801b toward the object 103 is either reflected by the object 103 toward the fourth reflective surface 801b or the third reflective surface 802b, or transmitted through the object 103. Then, a portion of the light reflected by the third reflective surface 802b enters the photodetector 104.

[0160] Figure 15(a) is a schematic diagram showing how light is reflected by or transmitted through object 103a in the optical device 8 according to this embodiment. Figure 15(b) is a schematic diagram showing how light is reflected by or transmitted through object 103b in the optical device 8 according to this embodiment.

[0161] As shown in Figure 15(a), assume that object 103a contains only the main substance 1031 and no impurities 1032. At this time, when light A reflected by the first reflective surface 802a is incident on object 103a, light A interacts with the main material 1031 inside object 103a, causing light B to be diffusely reflected from the surface of object 103a and light I to be diffusely transmitted from the back surface of object 103a. Here, the front and back surfaces of object 103a are defined as the surfaces facing the second reflective surface 801a and the fourth reflective surface 801b of object 103a, respectively.

[0162] On the other hand, as shown in Figure 15(b), let's assume that object 103b contains impurities 1032 in addition to the main substance 1031. At this time, when light A reflected by the first reflective surface 802a is incident on object 103b, light A interacts with the main substance 1031 and impurities 1032 inside object 103b, causing light C to be diffusely reflected from the surface of object 103b and light J to be diffusely transmitted from the back surface of object 103b.

[0163] Therefore, in the optical device 8 according to this embodiment, the light I transmitted through object 103a and the light J transmitted through object 103b are detected using the light-receiving element 104, and the respective light quantities are compared with each other. This makes it possible to detect the ratio of impurities 1032 to the main substance 1031 in object 103b.

[0164] In the optical device 8 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 801a and the fourth reflective surface 801b 10 or more times, that is, light that has been reflected by the object 103 10 or more times, to the light-receiving element 104.

[0165] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0166] As described above, in the optical device 8 according to this embodiment, by providing a first reflective surface 802a, a second reflective surface 801a, and a fourth reflective surface 801b, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the first reflecting element 800a and the second reflecting element 800b. In addition, the optical device 8 according to this embodiment can also detect light that has passed through the object 103.

[0167] In the optical device 8 according to this embodiment, the first reflective element 800a and the second reflective element 800b are provided as separate components, but they are not limited to this arrangement and may be provided as a single integrated unit. Furthermore, in the optical device 8 according to this embodiment, the first substrate 1051 and the second substrate 1052 are provided as separate components, but the device is not limited to this and may be provided as a single integrated unit.

[0168] [Ninth Embodiment] Figure 16(a) shows a partial projection view of the optical device 9 according to the ninth embodiment. Figure 16(b) also shows a cross-sectional view of the optical device 9 according to the ninth embodiment, cut along the line 16B-16B in Figure 16(a).

[0169] The optical device 9 according to this embodiment includes a light source 100, a reflective element 900, and a first substrate 1051.

[0170] The light source 100 is a light-emitting means such as a light-emitting diode (LED). Alternatively, instead of a light-emitting diode, a light-emitting element or light-emitting device such as a laser light source or a spectroscopic light source may be used as the light source 100. The light-receiving element 104 is a light-receiving means such as a photodiode (PD). The first substrate 1051 and the second substrate 1052 are components that hold the light source 100 and the light receiving element 104, respectively.

[0171] The reflective element 900 has the function of reflecting light emitted from the light source 100 and light reflected by the object 103, and resin is used as the material. Furthermore, various materials such as metal may be used instead of resin for the material of the reflective element 900.

[0172] Furthermore, in the optical device 9 according to this embodiment, the reflective element 900 has a second reflective surface 901 and a first reflective surface 902, both of which are mirror surfaces coated with metal deposition. Instead of applying metal vapor deposition to the second reflective surface 901 and the first reflective surface 902, various reflective means such as total internal reflection or gloss coating may be provided. Furthermore, a portion of the reflective element 900, including the second reflective surface 901, has an opening 905 (second opening) through which some of the light reflected by the object 103 passes, as shown in Figures 16(a) and (b).

[0173] The second reflective surface 901 and the first reflective surface 902 each have a curved surface defined as shown in equation (2) above, where the point of intersection with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, and the cross section perpendicular to the optical axis is the YZ cross section.

[0174] The first reflective surface 902 is an aspherical surface with a conic coefficient K in the range of -1.0 ≤ K < 0.0, as shown by the shaded area in Figure 16(a). Specifically, the first reflective surface 902 is part of a spheroidal ellipsoid with a radius of curvature R of 7.5 mm and a conic coefficient K of -0.444.

[0175] Furthermore, the optical axis passing through the vertex and focal point of the first reflective surface 902 is tilted by 20.964° with respect to the reference plane. Furthermore, the second reflective surface 901 is part of a sphere with a radius of curvature R of 18 mm and a conic coefficient K of 0.

[0176] As shown in Figure 16(b), the light source 100 is positioned to include one of the focal points of the first reflective surface 902. On the other hand, the light-receiving element 104 is located outside the reflecting element 900.

[0177] Furthermore, the first reflective surface 902 and the second reflective surface 901 are formed in the reflecting element 900 such that the focal point of the other side of the first reflective surface 902 is located near the center of the second reflective surface 901. The object 103 is then positioned to include the other focal point of the first reflective surface 902.

[0178] Furthermore, in the optical device 9 according to this embodiment, the distance between the center of the light source 100 and the center of the light-receiving element 104 within the reference plane is equal to the distance between the focal points of the first reflective surface 902.

[0179] As shown in Figure 16(b), in the optical device 9 according to this embodiment, a portion of the light emitted from the light source 100 is incident on the first reflective surface 902. The light reflected by the first reflective surface 902 toward the object 103 is then reflected by the object 103, and a portion of it then enters the second reflective surface 901 or passes through the aperture 905 before entering the light-receiving element 104.

[0180] Next, the light that has entered the second reflective surface 901 is reflected by the second reflective surface 901 and enters the object 103 again. Then, a portion of the light reflected again by object 103 either enters the second reflective surface 901 again, or enters the light-receiving element 104 after passing through the aperture 905.

[0181] In the optical device 9 according to this embodiment, by adopting the above configuration, it becomes possible to guide light that has traveled back and forth between the object 103 and the second reflective surface 901 10 or more times, that is, light that has been reflected by the object 103 10 or more times, to the light-receiving element 104.

[0182] As a result, compared to the optical device 1 according to the first embodiment, the number of reflections by the object 103 increases, and as explained with reference to Figure 6, the amount T of the impurity 1032 content in the object 103 can be further increased. Furthermore, by increasing the detection amount T, the amount of impurities 1032 in object 103 can be determined with even greater accuracy.

[0183] As described above, in the optical device 9 according to this embodiment, by providing the first reflective surface 902 and the second reflective surface 901, light from the light source 100 can be efficiently irradiated onto the object 103. Furthermore, it is possible to efficiently illuminate the object 103 located outside the reflective element 900. In addition, in the optical device 9 according to this embodiment, the second substrate 1052 and the object 103 are spaced apart from each other, which increases the degree of freedom in their arrangement.

[0184] [Measuring device] Figures 17(a) and (b) show schematic cross-sectional views of the measuring device 50 according to this embodiment, respectively.

[0185] The measuring device 50 according to this embodiment includes a light source 100, a reflecting element 200, a light receiving element 104, a substrate 105, a light emission control device 1000 (light emission control unit), a computing device 2000 (calculation unit), a storage device 3000 (storage unit), and an output device 4000 (output unit). Note that the configuration of the light source 100, reflective element 200, and substrate 105 provided in the measuring device 50 according to this embodiment is the same as that of the optical device 2 according to the second embodiment, so a description will be omitted.

[0186] The light emission control device 1000 controls the amount of light emitted from the light source 100, the timing of light emission, and other related parameters. The computing device 2000 performs various calculations to determine the detected amount T, and consequently the content of impurities 1032 in object 103, based on the output of the light-receiving element 104, specifically the amount of light received by the light-receiving element 104.

[0187] The memory device 3000 stores the calculation results of the arithmetic unit 2000 and also outputs the stored calculation results to the arithmetic unit 2000. The output device 4000 is, for example, a monitor or an external output terminal, and outputs various calculation results calculated by the arithmetic unit 2000.

[0188] In the measuring device 50 according to this embodiment, first, measurements are taken on the standard object 113, as shown in Figure 17(a). Here, the standard object 113 is one whose properties are known in advance, specifically, whose impurity content is known, such as a standard white plate.

[0189] Specifically, by illuminating the standard object 113 with light set by the light emission control device 1000 to emit light from the light source 100 at a predetermined amount, the light receiving element 104 detects light having a predetermined amount, as shown in the second embodiment. Then, the arithmetic unit 2000 performs averaging processing on the detected light quantity to obtain the light quantity I1, and then stores the light quantity I1 in the storage device 3000 as the detection result for the standard object 113.

[0190] Next, the measuring device 50 according to this embodiment performs measurements on the object to be measured 123, as shown in Figure 17(b). Here, the object under test 123 is an object containing impurities that are to be tested.

[0191] Specifically, by illuminating the object under test 123 with light set by the light emission control device 1000 to emit light from the light source 100 at a predetermined amount, the light receiving element 104 detects light having a predetermined amount, as shown in the second embodiment. Next, the arithmetic unit 2000 performs averaging processing on the detected light intensity to obtain the light intensity I2.

[0192] The arithmetic unit 2000 then reads the detection result for the standard object 113, i.e., the light intensity I1, from the storage device 3000, and calculates the relative light intensity RI and thus the detected amount T from the ratio between the light intensity I1 and the light intensity I2, thereby calculating the impurity content in the object under test 123. Then, the result calculated by the arithmetic unit 2000 is output by the output unit 4000.

[0193] [Image forming apparatus] Figure 18 shows a sub-scanning cross-sectional view of the main part of an image forming apparatus 60 equipped with the measuring device 50 according to this embodiment.

[0194] The image forming apparatus 60 is a tandem-type color image forming apparatus in which four optical scanning devices are arranged in parallel, and each records image information on the surface of a photosensitive drum, which is an image carrier. The image forming apparatus 60 includes optical scanning devices 61, 62, 63, and 64, and photoreceptor drums 81, 82, 83, and 84 as image carriers. The image forming apparatus 60 also includes developing units 31, 32, 33, and 34, a measuring device 50, a transport belt 51, a printer controller 53, a fuser 54, and a paper cassette 95.

[0195] The image forming apparatus 60 receives R (red), G (green), and B (blue) color signals (code data) from an external device 52 such as a personal computer. These color signals are converted into C (cyan), M (magenta), Y (yellow), and K (black) image data by the printer controller 53 within the apparatus. These image data are input as image signals and image information to the optical scanning devices 61, 62, 63, and 64, respectively. These optical scanning devices 61, 62, 63, and 64 then emit modulated light beams 71, 72, 73, and 74 according to the image data of each color. These light beams scan the photosensitive surfaces (scanned surfaces) of the photoreceptor drums 81, 82, 83, and 84 in the main scanning direction.

[0196] In the image forming apparatus 60, for example, the optical scanning device 61 receives a C (cyan) image signal, the optical scanning device 62 receives a M (magenta) image signal, the optical scanning device 63 receives a Y (yellow) image signal, and the optical scanning device 64 receives a K (black) image signal. These image signals are then recorded in parallel on the photosensitive surfaces of the photosensitive drums 81, 82, 83, and 84, respectively, and a color image is printed at high speed.

[0197] As described above, the image forming apparatus 60 uses light beams based on the respective image data from the four optical scanning devices 61, 62, 63, and 64 to form electrostatic latent images of each color on the photosensitive surfaces of the corresponding photosensitive drums 81, 82, 83, and 84. Subsequently, the electrostatic latent images of each color are developed into toner images of each color by the developers 31, 32, 33, and 34, and the developed toner images of each color are transferred in multiple layers by the transfer unit to the transfer material conveyed by the transport belt 51. Then, the transferred toner images are fixed by the fuser 54 to form a single full-color image.

[0198] Furthermore, in the image forming apparatus 60, the measuring device 50 according to this embodiment is provided near the paper cassette 95. Furthermore, the amount of moisture contained in the transfer material fed from the paper cassette 95 can be measured using the measuring device 50 according to this embodiment, and various adjustments can be made in the image forming apparatus 60 based on the measurement results.

[0199] Furthermore, as the external device 52, for example, a color image reading device equipped with a CCD sensor may be used. In this case, the color digital copier is configured with this color image reading device and the color image forming apparatus 60. Furthermore, the image forming apparatus 60 is not limited to a configuration of four optical scanning devices and four photoreceptor drums. For example, it may consist of only one optical scanning device and one photoreceptor drum. Alternatively, it may consist of two, three, or five or more optical scanning devices and photoreceptor drums.

[0200] Although preferred embodiments have been described above, the invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its essence.

[0201] For example, in the optical apparatus according to the second to ninth embodiments, the shape of each reflective surface is defined as shown in equation (2) above, but the apparatus is not limited to this, and higher-order aspherical shapes may be added to further improve optical aberrations. Furthermore, while the optical devices according to the second to ninth embodiments formed all aspherical surfaces as either ellipsoids of revolution or parabolas of revolution, the invention is not limited to these configurations. That is, even if some aspherical surfaces are formed as ellipsoids of revolution and the remaining aspherical surfaces are parabolas of revolution, or if higher-order aspherical shapes are added to some aspherical surfaces, the same effects as those of this embodiment can be obtained.

[0202] Furthermore, even if the first reflective surface and the second reflective surface in the optical apparatus according to the second to ninth embodiments are formed to be part of a sphere and to have different curvatures, the same effects as in this embodiment can be obtained. Furthermore, in the optical apparatus according to the second to ninth embodiments, even if the first reflective surface is formed to be part of a spherical surface and the second reflective surface is formed to be part of an aspherical surface, the same effects as in this embodiment can be obtained. Furthermore, in the optical apparatus according to the first to ninth embodiments, the area and number of light sources and light-receiving elements can also be changed within the scope of the gist of this embodiment.

[0203] Furthermore, in the optical apparatus according to the first to ninth embodiments, by using light sources that emit multiple lights with different wavelengths, it is possible to calculate the content of multiple types of substances contained in an object, in other words, the content of at least one type of substance. In this case, the light-receiving elements may also be configured to independently detect multiple lights with different wavelengths. [Explanation of symbols]

[0204] 1 Optical device 100 light sources 101 First reflective surface 102 Second reflective surface 103 Object

Claims

1. A light source; a first reflecting surface that reflects light from the light source toward an object; a second reflecting surface having a shape different from that of the first reflecting surface and configured to reflect a portion of the light from the object toward the object; and a third reflecting surface that reflects a portion of the light that has been reflected by the second reflecting surface and then by the object toward a light receiving element.

2. 2. The optical device according to claim 1, wherein the first and second reflecting surfaces have different curvatures.

3. The intersection point with the optical axis is the origin, the axis parallel to the optical axis is the X-axis, the cross section perpendicular to the optical axis is the YZ cross section, the radius of curvature is R, and the conic coefficient is K. The shapes of the first, second, and third reflecting surfaces are [0010] When expressed as above, at least one of the first, second and third reflecting surfaces is −1.0≦K<0.0 3. The optical device according to claim 1, wherein the following condition is satisfied:

4. The first reflecting surface is −1.0≦K<0.0 4. The optical device according to claim 3, wherein the following condition is satisfied:

5. 5. The optical device according to claim 4, wherein the light source is disposed so as to include a first focal point of the first reflecting surface.

6. 6. The optical device according to claim 4, wherein the first reflecting surface is a part of an ellipsoid of revolution.

7. 7. The optical device of claim 6, wherein the object is positioned to include a second focal point of the first reflecting surface.

8. the second reflecting surface is a portion of a sphere; 8. The optical device according to claim 6, wherein the second focal point of the first reflecting surface and the center of the second reflecting surface are located at the same position.

9. 6. The optical device according to claim 4, wherein the first reflecting surface is a part of a paraboloid of revolution.

10. 10. The optical device according to claim 1 , further comprising a substrate for holding the light source, the substrate having a first opening through which the light reflected by the first reflecting surface passes.

11. 11. The optical device according to claim 10, wherein the optical axis of the first reflecting surface is non-parallel to the surface of the substrate.

12. 12. The optical device according to claim 1, wherein the second reflecting surface is a part of a spherical surface.

13. 12. The optical device according to claim 1, wherein the second reflecting surface has a shape in which a large number of minute corner cubes are arranged.

14. 14. The optical device according to claim 1, wherein the first and second reflecting surfaces are connected to each other.

15. 15. The optical device according to claim 1, wherein the light source emits a plurality of light beams having different wavelengths.

16. An optical device according to any one of claims 1 to 15, and a light receiving element that receives light from the optical device.

17. 17. The measuring device according to claim 16, further comprising a calculation unit that performs calculations based on an output from the light receiving element.

18. The measuring device according to claim 17 , wherein the calculation unit calculates a content of at least one type of substance in the object.

19. A measuring device described in any one of claims 16 to 18, characterized in that the light receiving element is arranged to include a first focal point of the third reflecting surface.

20. a second opening is formed in the second reflecting surface, through which a portion of the light reflected by the object passes; 19. The measurement apparatus according to claim 16, wherein the light receiving element is disposed so as to receive the light that has passed through the second opening.

21. the first reflecting surface is a portion of an ellipsoid of revolution; 21. The measurement apparatus of claim 20, wherein in a reference plane of the optical device, a distance between a center of the light source and a center of the light receiving element is equal to a distance between a first and second focal point of the first reflecting surface.

22. 22. The measuring apparatus according to claim 16, wherein the light receiving element detects a plurality of light beams having different wavelengths.

23. 23. An image forming apparatus comprising: an optical scanning device that scans a surface to be scanned; a developing unit that develops an electrostatic latent image formed on the surface to be scanned by the optical scanning device into a toner image; a transfer unit that transfers the developed toner image to a transfer material; a fixing unit that fixes the transferred toner image to the transfer material; and a measuring device according to any one of claims 16 to 22 that measures the content of a substance contained in the transfer material.

24. An image forming apparatus comprising: an optical scanning device for scanning a surface to be scanned; a printer controller for converting a signal output from an external device into image data and inputting the image data to the optical scanning device; and a measuring device according to any one of claims 16 to 22 for measuring the content of a substance contained in a material to be transferred.

Images