Reflective Optical Sensor

Abstract

[Problem] To provide a reflective optical sensor capable of improving coupling efficiency. [Solution] In the present invention, a reflective optical sensor (1A) senses an object (OB) to be sensed by sensing, using a light-receiving element (4), light from a light-emitting element (3) that is reflected by the object (OB) to be sensed, and has a case (2), shaped like an open box, in which first and second concave mirrors (5, 6) are formed, each having as a reflective surface a partial concave surface of a rotated elliptical surface of an ellipse that is rotated about the longitudinal axis thereof. The first and second concave mirrors (5, 6) are formed so as to be open toward the open side of the case (2), such that one focal point of the first concave mirror (5) matches one focal point of the second concave mirror (6) as a common focal point (F0), and such that another first focal point (F1) of the first concave mirror (5) and another second focal point (F2) of the second concave mirror (6) do not overlap. Light emitted by the light-emitting element (3) from the position of the first focal point (F1) toward the first concave mirror (5) is reflected by the first concave mirror (5) and irradiated onto the common focal point (F0) or the object (OB) to be sensed in the vicinity of the common focal point (F0), reflected light that is reflected by the object (OB) to be sensed is reflected by the second concave mirror (6), and the reflected light is sensed by the light-receiving element (4) at the position of the second focal point (F2).

Description

[Technical field]

[0001] The present invention relates to a reflective optical sensor that detects an object by irradiating light and detecting the light reflected by the object. [Background technology]

[0002] Reflective optical sensors have been widely used in the past to detect objects by irradiating light and detecting the light reflected by a nearby object. Reflective optical sensors are capable of detecting objects without contact, and are therefore commonly used in applications such as detecting rotation angles and object edges.

[0003] A reflective optical sensor, as in Patent Document 1, for example, has a light-emitting element, a light-receiving element, and a light-shielding wall disposed between them, and is configured so that light emitted by the light-emitting element is reflected by the object to be detected and this reflected light is received by the light-receiving element. The output of the light-receiving element fluctuates depending on the presence or absence of reflected light and the intensity of the reflected light, and this is utilized to detect the object to be detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-308372 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the reflective optical sensor of Patent Document 1, the light-emitting element irradiates diffuse light to a nearby object to be detected. Therefore, most of the light emitted by the light-emitting element is irradiated to the object to be detected, but even if the object to be detected has a high reflectance, only a small amount of the light reflected by the object to be detected enters the light-receiving element. For example, when the ratio of the light emitted by the light-emitting element to the light that enters the light-receiving element is defined as the coupling efficiency, the result of a ray tracing simulation of the reflective optical sensor of Patent Document 1 shows that the coupling efficiency is about 3%, and there is a demand for an improvement in the coupling efficiency.

[0006] An object of the present invention is to provide a reflective optical sensor capable of improving coupling efficiency. [Means for solving the problem]

[0007] The reflective optical sensor of the invention of claim 1 comprises a light-emitting element and a light-receiving element, and detects an object by the light-receiving element detecting light reflected from the object, the reflective optical sensor having an open box-like case integrally formed with a first concave mirror and a second concave mirror, each of which has a reflective surface that is a partial concave surface of an ellipsoid obtained by rotating an ellipse around its major axis, the first concave mirror and the second concave mirror are common focal points formed by matching one focus of the first concave mirror with one focus of the second concave mirror, and the first focus, which is the other focus of the first concave mirror, and the second focus, which is the other focus of the second concave mirror, do not overlap. The common focus is located on the same line without any The light emitting element is formed in an open shape toward the open side of the case as shown in FIG. 1, the light emitting element irradiates light from the position of the first focal point toward the first concave mirror, the light reflected by the first concave mirror is irradiated onto the common focal point or the object to be detected in the vicinity of the common focal point, and the reflected light is reflected by the second concave mirror, and the light receiving element detects the reflected light reflected by the second concave mirror at the position of the second focal point.

[0008] According to the above configuration, the reflective optical sensor has a case in which the first and second concave mirrors, each of which has a partial concave surface of an ellipsoid of revolution as a reflective surface, are integrally formed. The first and second concave mirrors have one focal point of each mirror as a common focal point, and the other focal points of each mirror do not overlap. The common focus is located on the same line without anyThe light emitting element at the position of the first focal point, which is not the common focal point of the first concave mirror, emits light toward the first concave mirror, and the light reflected by the first concave mirror is irradiated onto the object to be detected, which is located at the common focal point or in the vicinity thereof. The light reflected by the object to be detected is reflected by the second concave mirror and enters the light receiving element at the position of the second focal point, which is not the common focal point of the second concave mirror. Since the light emitted from the position of the first focal point is focused at the common focal point by the first concave mirror, most of the light from the light emitting element is irradiated onto the object to be detected and is reflected by the object to the second concave mirror. Since this reflected light is reflected at the common focal point or in the vicinity thereof, most of the reflected light is reflected by the second concave mirror and focused at the second focal point of the second concave mirror, and enters the light receiving element at the position of the second focal point. Therefore, the diffuse light irradiated from the light-emitting element is collected and irradiated onto the detected object, and the reflected light is collected and detected by the light-receiving element, so that the coupling efficiency can be improved when the ratio of light incident on the light-receiving element to the light emitted by the light-emitting element is defined as the coupling efficiency. Furthermore, since the first focal point and the second focal point are on the same straight line with the common focal point in between, when the light-emitting element and the light-receiving element are arranged, the detection position of the object to be detected is set between the light-emitting element and the light-receiving element, and the object to be detected can be easily aligned with the detection position.

[0011] Claim 2 The reflective optical sensor of the present invention is as follows: 1 In the invention, the light emitting element and the light receiving element are housed in the case, and the case is filled with a sealing resin through which light from the light emitting element passes. According to the above configuration, the light emitting element, the light receiving element, and the reflecting surfaces of the first and second concave mirrors are protected by the sealing resin, making it possible to prevent damage to the reflective optical sensor due to a collision with an object to be detected.

[0012] Claim 3 The reflective optical sensor of the present invention is as follows: 1 The invention is characterized in that there is a light-shielding wall between the first concave mirror and the second concave mirror, which prevents light from the light-emitting element from directly entering the second concave mirror. According to the above configuration, light from the light-emitting element is prevented from being reflected by the object to be detected and entering the light-receiving element, thereby making it possible to prevent erroneous detection of the object to be detected. Effect of the Invention

[0013] According to the reflective optical sensor of the present invention, the coupling efficiency can be improved. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view of a reflective optical sensor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. [Figure 4] FIG. 2 is an explanatory diagram for assembling a reflective optical sensor. [Diagram 5] 4 is an example of a ray tracing simulation result in the reflective optical sensor according to the first embodiment. [Figure 6] 4 is a diagram showing the relationship between the distance h to a detection object and coupling efficiency in the reflective optical sensor according to the first embodiment. FIG. [Figure 7] 5 is a cross-sectional view corresponding to FIG. 2 of a reflective optical sensor according to a second embodiment of the present invention. [Figure 8] 13 is an example of a ray tracing simulation result in the reflective optical sensor according to the second embodiment. [Figure 9] 13 is a diagram showing the relationship between the distance h to a detection object and coupling efficiency in the reflective optical sensor according to the second embodiment. FIG. [Figure 10] 13 is a diagram showing, in the form of contour lines, the relationship between the distance h to a detected object in the reflective optical sensor according to Example 2, the tilt angle of the major axes of the first and second concave mirrors, and the maximum value of the obtained coupling efficiency. FIG. [Figure 11] FIG. 4 is a plan view showing a modified example of the reflective optical sensor in accordance with the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the mode for carrying out the present invention will be described based on examples. EXAMPLES

[0016] 1 and 2, the reflective optical sensor 1A has an open box-shaped case 2 with an open top surface of a rectangular parallelepiped, a light-emitting element 3, and a light-receiving element 4. Although the open side of the case 2 will be described as being above the reflective optical sensor 1A, the reflective optical sensor 1A can be used in various positions depending on the application, etc.

[0017] A first concave mirror 5 and a second concave mirror 6 are integrally formed on the inside bottom of the case 2 in an open shape with their reflective surfaces facing the open side of the case 2. The first concave mirror 5 is formed with its reflective surface being a partial concave surface of an ellipsoid of revolution obtained by rotating an ellipse E1 around its major axis. The second concave mirror 6 is formed with its reflective surface being a partial concave surface of an ellipsoid of revolution obtained by rotating an ellipse E2 around its major axis.

[0018] Ellipses E1 and E2 are x on the xy plane as shown in Figure 3. 2 / a 2 +y 2 / b 2 In the ellipse E represented by a = 1, for example, a = 4 mm, b = 3.5 mm, and the ellipses are the same size, but they may be of different sizes. 2 -b 2 ) 1 / 2 As a result, (x The positions (c, 0), (-c, 0) are the two foci of the ellipse E.

[0019] As shown in Figs. 1 and 2, one focus of the ellipse E1 forming the first concave mirror 5 is aligned with one focus of the ellipse E2 forming the second concave mirror 6 to form a common focus F0. The first concave mirror 5 and the second concave mirror 6 are formed so that the first focus F1 and the second focus F2 do not overlap when the other focus of the ellipse E1 is the first focus F1 and the other focus of the ellipse E2 is the second focus F2. At this time, the first concave mirror 5 and the second concave mirror 6 are formed so that a plane including the common focus F0 and passing between the first focus F1 and the second focus F2 is the boundary. Here, the first concave mirror 5 and the second concave mirror 6 are arranged so that the first focus F1 and the second focus F2 are located on the same straight line (on the straight line L) with the common focus F0 in between, and the boundary between the first concave mirror 5 and the second concave mirror 6 is perpendicular to the straight line L.

[0020] The case 2 is formed, for example, by resin molding, into a box shape with an open top surface of a rectangular parallelepiped, and partial concave surfaces of the ellipsoids of revolution E1, E2 corresponding to the first and second concave mirrors 5, 6 are formed on the inside bottom. Reflective films 5a, 6a containing a metal such as gold or titanium are formed on at least these partial concave surfaces, and the first and second concave mirrors 5, 6 are formed integrally with the case 2. At the boundary between the first concave mirror 5 and the second concave mirror 6, a light-shielding wall 7 is formed extending from the inside bottom of the case 2 toward the open side so as to separate the first concave mirror 5 and the second concave mirror 6.

[0021] At the open end of the case 2, recesses 2a to 2d are formed by recessing from the open end face 2e of the case 2 toward the bottom side in order to position a pair of first lead frames 8a, 8b and a pair of second lead frames 9a, 9b. The light-emitting element 3 is fixed to one side of the tip of the first lead frame 8a, which is placed and fixed in the recess 2a. The first lead frame 8a is fixed to the recess 2a so that the light-emitting surface from which the light of the light-emitting element 3 is emitted faces the first concave mirror 5 and the light-emitting element 3 is positioned at the position of the first focal point F1. At this time, the light-emitting element 3 is accommodated in the case 2. Note that the recesses 2a to 2d may not be formed and positioning may be performed by another method.

[0022] The light receiving element 4 is fixed to one surface of the tip of the second lead frame 9a, which is placed and fixed in the recess 2c. The second lead frame 9a is fixed to the recess 2c so that the light receiving surface of the light receiving element 4, which receives light, faces the second concave mirror 6 and so that the light receiving element 4 is located at or near the second focal point F2. At this time, the light receiving element 4 is accommodated in the case 2.

[0023] As shown in FIG. 2, the case 2 housing the light-emitting element 3 and the light-receiving element 4 is filled with a sealing resin 10, and the light-emitting element 3 and the light-receiving element 4 are covered with the sealing resin 10. The first lead frames 8a, 8b and the second lead frames 9a, 9b may also be covered with the sealing resin 10. The sealing resin 10 is a translucent resin that transmits the light of the light-emitting element 3, for example, an epoxy-based synthetic resin that transmits visible light or infrared light. The sealing resin 10 protects the reflecting surfaces of the light-emitting element 3, the light-receiving element 4, and the first and second concave mirrors 5, 6, and regulates the oscillation of the light-emitting element 3 and the light-receiving element 4. If vibrations are not transmitted from the outside to the light-emitting element 3 and the light-receiving element 4, the sealing resin 10 may be omitted.

[0024] The surface 10a of the sealing resin 10 is formed flat so as to coincide with the open end surface 2e of the case 2, except for the portions of the first lead frames 8a, 8b and the second lead frames 9a, 9b. The surface 10a of the sealing resin 10 coincides with a plane including the first focal point F1, the second focal point F2, and the common focal point F0, or is a plane parallel to this plane and in the vicinity of the common focal point F0. The position of the common focal point F0 or the vicinity (above) of the common focal point F0 becomes the detection position of the detected object.

[0025] Since the first lead frames 8a, 8b and the second lead frames 9a, 9b are elongated members made of, for example, kovar (an alloy containing iron, nickel, and cobalt), it is not easy to attach them to the case 2 individually. Therefore, as shown in FIG. 4, the light emitting element 3 and the light receiving element 4 are fixed to the first lead frames 8a, 8b and the second lead frames 9a, 9b formed integrally with a rectangular frame 11, and are electrically connected by, for example, bonding wires. Then, the first lead frames 8a, 8b and the second lead frames 9a, 9b are simultaneously placed together with the frame 11 in the corresponding recesses 2a to 2d. Then, after sealing with the sealing resin 10, the base ends of the first lead frames 8a, 8b and the second lead frames 9a, 9b are cut, for example, as shown by the dashed lines, to separate and remove the frame 11.

[0026] The frame 11 having the first lead frames 8a, 8b and the second lead frames 9a, 9b can be formed in a tape or sheet shape so that the frame 11 is connected in a plane. In this case, the light emitting element 3 and the light receiving element 4 can be easily fixed and electrically connected, and they can be attached consecutively or simultaneously to a plurality of cases 2 arranged at predetermined intervals, for example, improving manufacturing efficiency.

[0027] 5, due to the nature of the ellipse, a part of the light i1 emitted from the light-emitting element 3 at the position of the first focal point F1 is reflected by the first concave mirror 5 and collected at the position of the common focal point F0 like light i2. The light-shielding wall 7 prevents the light emitted from the light-emitting element 3 from directly entering the second concave mirror 6. The light-emitting element 3 is a light-emitting diode with an illumination angle of 150°.

[0028] When the object to be detected OB is located at or near the common focal point F0, the light i2 is reflected by the object to be detected OB, and the reflected light i3 is reflected by the second concave mirror 6 and collected at the second focal point F2 as the reflected light i4. The reflected light i4 is then incident on the light receiving element 4 at the second focal point F2, and a photocurrent is output. On the other hand, when the object to be detected OB is not present, the light i2 reflected by the first concave mirror 5 from the light of the light-emitting element 3 does not enter the second concave mirror 6 but goes out, and does not enter the light receiving element 4. Therefore, the second concave mirror 6 reflects the reflected light i3 from the light-emitting element 3 reflected by the object to be detected OB, and the light receiving element 4 detects the reflected light i4 reflected by the second concave mirror 6, thereby making it possible to detect the object to be detected OB.

[0029] When the ratio of light irradiated by the light-emitting element 3 that is incident on the light-receiving element 4 is taken as the coupling efficiency, the higher the coupling efficiency, the larger the photocurrent output. Therefore, it is desirable to achieve a high coupling efficiency, since it is possible to easily prevent erroneous detection of the object OB due to the influence of stray light, for example, and it is also possible to reduce power consumption by reducing the amount of light from the light-emitting element 3, for example. Here, based on the ray tracing simulation shown in FIG. 5, the coupling efficiency (Coupling Efficiency) when the object OB is separated from the common focus F0 is shown in FIG. 6, with the distance h between the common focus F0 and the object OB as a parameter.

[0030] When the distance h=0 mm where the object to be detected is at the common focal point F0, the coupling efficiency exceeds 60%. As the distance h increases, the coupling efficiency tends to decrease, but even when the distance h=2 mm, the coupling efficiency is about 10%. Even if a certain distance h is secured to prevent damage to the reflective optical sensor 1A and the object to be detected OB due to contact between the reflective optical sensor 1A and the object to be detected OB, a high coupling efficiency can be ensured. Also, a high coupling efficiency can be obtained even when the common focal point F0 is located inside the sealing resin 10. EXAMPLES

[0031] A description will be given of a reflective optical sensor 1B which is a partial modification of the reflective optical sensor 1A of the above-mentioned embodiment 1. The same parts as those in the above-mentioned embodiment 1 are given the same reference numerals as those in the above-mentioned embodiment 1, and the description thereof will be omitted.

[0032] 7, the reflective optical sensor 1B has a rectangular box-shaped case 2 with an open top, a light-emitting element 3, and a light-receiving element 4. A first concave mirror 15 and a second concave mirror 16 are integrally formed on the inside bottom of the case 2 with their reflective surfaces facing the open side of the case 2. As with the reflective optical sensor 1A, one focus of the ellipse E1 that forms the first concave mirror 15 coincides with one focus of the ellipse E2 that forms the second concave mirror 16 to form a common focus F0.

[0033] When the other focal point of the ellipse E1 is the first focal point F1 and the other focal point of the ellipse E2 is the second focal point F2, the first concave mirror 15 and the second concave mirror 16 are arranged so that the first focal point F1 and the second focal point F2 do not overlap. In this case, the first concave mirror 15 and the second concave mirror 16 are formed so that the boundary between them is a plane that includes the common focal point F0 and passes between the first focal point F1 and the second focal point F2.

[0034] Here, in the reflective optical sensor 1B, compared to the reflective optical sensor 1A, the major axes of the ellipses E1 and E2 are each rotated by an angle θ around the common focal point F0, so that the major axes of the ellipses E1 and E2 are each inclined. As a result, the first focal point F1 and the second focal point F2 are located below the common focal point F0 (toward the bottom of the case 2). The major axis of the ellipse E1 inclined by an angle θ is a straight line L1 that passes through the first focal point F1 and the common focal point F0. The major axis of the ellipse E2 inclined by an angle θ is a straight line L2 that passes through the second focal point F2 and the common focal point F0. Since the major axes are inclined, the ellipses E1 and E2 are each inclined.

[0035] A reflective film 5a serving as a reflective surface is formed on the partial concave surface of an ellipsoid obtained by rotating an ellipse E1 around its inclined major axis (straight line L1), thereby forming a first concave mirror 15. Similarly, a reflective film 6a serving as a reflective surface is formed on the partial concave surface of an ellipsoid obtained by rotating an ellipse E2 around its inclined major axis (straight line L2), thereby forming a second concave mirror 16. Here, the first focal point F1, the second focal point F2, and the common focal point F0 are included in one plane (the cross section shown in FIG. 7), the angle θ of the inclination of the major axis is, for example, 10°, and the angle 2θ is set as a predetermined intersection angle between the major axes of the two ellipses E1 and E2.

[0036] At the boundary between the first concave mirror 15 and the second concave mirror 16, a light-shielding wall 7 extending from the bottom of the case 2 toward the open side is formed so as to separate the first concave mirror 15 and the second concave mirror 16.

[0037] Of the recesses 2a to 2d formed at the open end of the case 2, the light-emitting element 3 is fixed to one surface of the tip of the first lead frame 8a fixed to the recess 2a. The first lead frame 8a is placed and fixed in the recess 2a so that the light-emitting surface from which light of the light-emitting element 3 is emitted faces the first concave mirror 15 and the light-emitting element 3 is disposed at the position of the first focal point F1, and the light-emitting element 3 is accommodated in the case 2.

[0038] The light receiving element 4 is fixed to one surface of the tip of the second lead frame 9a fixed in the recess 2c. The second lead frame 9a is placed in the recess 2c so that the light receiving surface of the light receiving element 4, which receives light, faces the second concave mirror 16 and the light receiving element 4 is located at the position of the second focal point F2, and the light receiving element 4 is housed in the case 2. Although not shown in the figure, power for light emission is supplied to the light emitting element 3 via the corresponding pair of first lead frames 8a, 8b, and a photocurrent is output from the light receiving element 4 via the corresponding pair of second lead frames 9a, 9b.

[0039] 7, the case 2 housing the light-emitting element 3 and the light-receiving element 4 is filled with sealing resin 10, and the light-emitting element 3 and the light-receiving element 4 are covered with the sealing resin 10. The sealing resin 10 is translucent to allow the light from the light-emitting element 3 to pass therethrough, and is, for example, an epoxy-based synthetic resin that allows visible light or infrared light to pass therethrough. The first lead frames 8a, 8b and the second lead frames 9a, 9b may also be covered with the sealing resin 10.

[0040] The surface 10a of the sealing resin 10 is formed flat so as to coincide with the open end surface 2e of the case 2, except for the portions of the first lead frames 8a, 8b and the second lead frames 9a, 9b. The surface 10a of the sealing resin 10 coincides with a plane including the first focal point F1 and the second focal point F2, or is a plane in the vicinity of the first and second focal points F1, F2 parallel to this plane. The position of the common focal point F0, which is spaced apart from the surface 10a of the sealing resin 10, or the vicinity of the common focal point F0, becomes the detection position of the object to be detected.

[0041] As shown in Fig. 8, due to the nature of the ellipse, a part of the light i1 emitted from the light-emitting element 3 at the position of the first focal point F1 is reflected by the first concave mirror 15 and collected at the position of the common focal point F0 like light i2. The light-shielding wall 7 prevents the light emitted from the light-emitting element 3 from directly entering the second concave mirror 16. The light-emitting element 3 is a light-emitting diode with an illumination angle of 150°.

[0042] When the object to be detected OB is located at or near the common focal point F0, the light i2 is reflected by the object to be detected OB, and reflected light i3 is reflected by the second concave mirror 16 and collected at the second focal point F2 as reflected light i4. Then, the reflected light i4 is incident on the light receiving element 4 at the second focal point F2, and a photocurrent is output. On the other hand, when the object to be detected OB is not present, the light i2 reflected by the first concave mirror 15 from the light of the light-emitting element 3 does not enter the second concave mirror 16 but goes out, and does not enter the light receiving element 4. Therefore, the second concave mirror 16 reflects the reflected light i3 from the light-emitting element 3 reflected by the object to be detected OB, and the light receiving element 4 detects the reflected light i4 reflected by the second concave mirror 16, thereby detecting the object to be detected OB.

[0043] When the coupling efficiency is defined as the proportion of light emitted by the light-emitting element 3 that is incident on the light-receiving element 4, it is desirable to achieve a high coupling efficiency. Based on a ray tracing simulation as shown in FIG. 8, FIG. 9 shows the coupling efficiency when the object OB to be detected is separated from the reflective optical sensor 1B, with the distance h between the object OB and a plane including the straight line L3 passing through the first and second focal points F1 and F2 as a parameter. The inclination angle (ellipse) of the first and second concave mirrors 15 and 16 is set to 1 / 2. The angle θ of inclination of the major axes of circles E1 and E2 is 10°.

[0044] When the object OB is moved away from the reflective optical sensor 1B and the distance h is increased, a coupling efficiency of 58% is obtained when the distance h is 0.6 mm, which corresponds to the position of the common focal point F0. The coupling efficiency tends to decrease as the object OB is moved away from the common focal point F0, but even when the distance h is 2 mm, the coupling efficiency is about 16%. Therefore, even if a certain distance h is secured to prevent damage to the reflective optical sensor 1B and the object OB due to contact between the reflective optical sensor 1B and the object OB, a high coupling efficiency can be obtained. Furthermore, since the coupling efficiency peaks at a position away from the reflective optical sensor 1B, the object OB can be detected without contact in a wide range including the distance h at which the coupling efficiency peaks.

[0045] The coupling efficiency when the distance h and the inclination angle θ of the first and second concave mirrors 15, 16 (the inclination angle of the major axes of the ellipses E1, E2) are used as parameters is shown in the form of contour lines in Fig. 10. As the angle θ increases, the common focal point F0 is positioned higher relative to the first and second focal points F1, F2, so the range of distance h where high coupling efficiency is obtained shifts toward the side where the distance h increases as the angle θ increases. Therefore, a larger angle θ is advantageous for non-contact detection of the object OB.

[0046] The functions and effects of the reflective optical sensors 1A and 1B will now be described. The reflective optical sensor 1A (1B) has a case 2 in which first and second concave mirrors 5, 6 (15, 16) are integrally formed, each of which has a partial concave surface of an ellipsoid of revolution as a reflective surface. The first and second concave mirrors 5, 6 (15, 16) are formed so that one of their focal points is a common focal point F0, and the other focal points (the first focal point F1 and the second focal point F2) do not overlap. The light emitting element 3 at the position of the first focal point F1 of the first concave mirror 5 (15) irradiates light i1 toward the first concave mirror 5 (15), and the light reflected by the first concave mirror 5 (15) is irradiated to the object to be detected OB located at or near the common focal point F0. The reflected light i3 reflected by the object to be detected OB is reflected by the second concave mirror 6 (16) and enters the light receiving element 4 at the position of the second focal point F2.

[0047] The light i1 emitted from the position of the first focal point F1 is collected by the first concave mirror 5 (15) at the common focal point F0, so that most of the light from the light-emitting element 3 is irradiated onto the object to be detected OB and is reflected by the object to be detected OB toward the second concave mirror 6 (16). Since this reflected light i3 is reflected at or near the common focal point F0, most of the reflected light i3 is reflected by the second concave mirror 6 (16) and collected at the second focal point F2 of the second concave mirror 6 (16), and enters the light-receiving element 4 at the position of the second focal point F2. Therefore, the diffuse light irradiated from the light-emitting element 3 can be collected and irradiated onto the object to be detected OB, and the reflected light can be collected and detected by the light-receiving element 4, so that the coupling efficiency can be improved.

[0048] The first concave mirror 5 and the second concave mirror 6 of the reflective optical sensor 1A are formed so that the first focal point F1 and the second focal point F2 are located on the same straight line (on the straight line L) with the common focal point F0 in between. Because the first focal point F1 and the second focal point F2 are on the same straight line with the common focal point F0 in between, when the light-emitting element 3 and the light-receiving element 4 are disposed, the detection position of the object to be detected OB is set between the light-emitting element 3 and the light-receiving element 4, and the object to be detected OB can be easily aligned with the detection position.

[0049] The first concave mirror 15 and the second concave mirror 16 of the reflective optical sensor 1B are formed so that the long axis (straight line L1) of the first concave mirror 15 passing through the first focal point F1 and the common focal point F0 and the long axis (straight line L2) of the second concave mirror 16 passing through the second focal point F2 and the common focal point F0 intersect at a predetermined intersection angle at the common focal point F0. When the light-emitting element 3 and the light-receiving element 4 are disposed in the case 2, the detection position of the object OB to be detected can be set at a position outside the case 2 away from the reflective optical sensor 1B, and the object to be detected can be detected without contact. Therefore, damage to the object OB and damage to the reflective optical sensor 1B due to collision between the object OB and the reflective optical sensor 1B can be prevented.

[0050] The reflective optical sensor 1A (1B) has a light-emitting element 3 and a light-receiving element 4 housed in a case 2, and the case 2 is filled with a sealing resin 10 through which the light of the light-emitting element 3 passes. The sealing resin 10 protects the light-emitting element 3, the light-receiving element 4, and the reflective surfaces of the first and second concave mirrors 5, 6 (15, 16), and can prevent damage to the reflective optical sensor 1A (1B) due to collision with a detected object OB.

[0051] The reflective optical sensor 1A (1B) has a light-shielding wall 7 between the first concave mirror 5 (15) and the second concave mirror 6 (16) to prevent light from the light-emitting element 3 from directly entering the second concave mirror 6 (16). The light-shielding wall 7 blocks light that is not reflected by the object to be detected OB and enters the light-receiving element 4, thereby preventing erroneous detection of the object to be detected OB.

[0052] The reflective optical sensor 1A may be modified to form a reflective optical sensor 1C by forming first and second concave mirrors 25 and 26 in the case 2, in which the major axes (straight lines L4 and L5) of ellipses E1 and E2 intersect at the common focal point F0 on a plane including the first focal point F1, the second focal point F2, and the common focal point F0, as shown in FIG. 11. Although not shown, instead of the first lead frames 8a and 8b and the second lead frames 9a and 9b, the light-emitting element 3 and the light-receiving element 4 may be fixed to a cover member transparent to the light of the light-emitting element 3, and multiple wirings may be formed to electrically connect these elements, and the cover member may be fixed to the case 2. In the above ray tracing simulation, refraction at the surface 10a of the sealing resin 10 is omitted, but when the refractive index n of the sealing resin 10 with respect to air is taken into consideration, the distance h may be multiplied by 1 / n. In addition, a person skilled in the art may implement the above embodiment in various modified forms without departing from the spirit of the present invention, and the present invention also includes such modified forms. [Explanation of symbols]

[0053] 1A, 1B, 1C: Reflective optical sensor 2: Case 2a~2d: Concave part 2e: Open side end surface 3: Light emitting element 4: Light receiving element 5,15,25: 1st concave mirror 6,16,26:Second concave mirror 7: Shading wall 8a, 8b: first lead frame 9a, 9b: second lead frame 10: Sealing resin 10a: surface 11: Frame F0 :Common focus F1: 1st focal point F2: 2nd focal point

Claims

1. A reflective optical sensor includes a light emitting element and a light receiving element, and detects an object by detecting light emitted from the light emitting element and reflected by the object using the light receiving element, The present invention has an open box-like case in which a first concave mirror and a second concave mirror are integrally formed, the first concave mirror and the second concave mirror each having a reflecting surface that is a partial concave surface of an ellipsoid obtained by rotating an ellipse around its major axis, the first concave mirror and the second concave mirror are formed in an open manner toward the open side of the case such that one focal point of the first concave mirror coincides with one focal point of the second concave mirror to form a common focal point, and a first focal point which is the other focal point of the first concave mirror and a second focal point which is the other focal point of the second concave mirror are not overlapped but are on the same straight line on either side of the common focal point, the light emitting element emits light from the position of the first focal point toward the first concave mirror, the light reflected by the first concave mirror is irradiated onto the common focal point or the object to be detected in the vicinity of the common focal point, and the reflected light is reflected by the second concave mirror; a light receiving element that detects the reflected light reflected by the second concave mirror at the position of the second focal point;

2. A reflective optical sensor as described in claim 1, characterized in that the light-emitting element and the light-receiving element are housed within the case, and the case is filled with a sealing resin through which light from the light-emitting element can pass.

3. A reflective optical sensor as described in claim 1, characterized in that there is a light-shielding wall between the first concave mirror and the second concave mirror, which prevents light from the light-emitting element from directly entering the second concave mirror.

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