Optical element and light projection / reception system

Abstract

Provided is an optical element that readily reduces power consumption while being able to improve the accuracy of detection of a state of a reflecting object. The optical element (10) comprises: an illumination means (13a to 13c, 14) that, while causing a light beam (R) emitted from a light source (21) to be refractively or diffractively deflected radially in at least three directions different from each other, divides same in the circumferential direction around the center of this radiation to form at least three branch light beams (Ra to Rc) and projects the branch light beams towards a reflecting object; and a light condensing means (15, 16a to 16c), which is provided to the outside, with respect to the illumination means, in the radiation direction in which the branch light beams are deflected, and which refractively or diffractively individually guides, to respectively corresponding light receiving elements (22a to 22c), the branch light beams that have been projected from the illumination means and reflected from the reflecting object.

Description

Optical elements and light-emitting / receiving system

[0001] The present invention relates to an optical element and a light emitting / receiving system that can easily reduce power consumption and improve the accuracy of detecting the state of a reflective object.

[0002] A light projecting and receiving system is known in which a light beam emitted from a light source is projected onto a reflective object through an optical element, the light beam reflected from the reflective object is incident on a plurality of light receiving elements through the optical element, and the state of the reflective object is detected from the detection values ​​of the plurality of light receiving elements. The optical element of the light projecting and receiving system disclosed in Patent Document 1 includes a plurality of light projecting lenses (illumination means) that project light beams onto a plurality of areas on the reflective object side, and a plurality of condensing lenses (condensing means) that individually condense the light beams reflected from the plurality of areas onto a plurality of light receiving elements, all of which are mounted on a dome-shaped cover. In this way, forming the light projecting lenses and the condensing lenses within a single member facilitates miniaturization and assembly of the light projecting and receiving system.

[0003] Japanese Patent Application Publication No. 07-043450

[0004] However, in Patent Document 1, since the multiple projection lenses are provided at a distance from each other, the light beams emitted from the light source that enter the cover between the projection lenses do not contribute to detecting the state of the reflective object, and power is wasted for the light beams that do not contribute. Furthermore, the light beams that enter the cover between the projection lenses become disturbance light and affect the detection value of the light receiving element, which may adversely affect the detection result of the state of the reflective object.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide an optical element and a light-emitting / receiving system that can easily reduce power consumption and improve the accuracy of detecting the state of a reflective object.

[0006] In order to achieve this object, the optical element of the present invention is arranged between a light source, the light-receiving elements, and the reflecting object so that a bundle of rays emitted from the light source is reflected by the reflecting object and enters three or more light-receiving elements, and comprises: an illumination means that radially deflects the bundle of rays emitted from the light source in three or more mutually different directions by refraction or diffraction, and splits the bundle of rays in a circumferential direction around the center of radiation to form three or more branched bundles of rays, and projects the branched bundles of rays toward the reflecting object; and a focusing means that is arranged outside the radial direction in which the branched bundles of rays are deflected relative to the illumination means, and that individually guides the branched bundles of rays projected from the illumination means and reflected from the reflecting object to the corresponding light-receiving elements by refraction or diffraction.

[0007] The optical element according to claim 1 comprises an illumination means and a focusing means. The illumination means deflects a light beam emitted from a light source radially in three or more different directions by refraction or diffraction, while splitting the light beam in a circumferential direction around the center of radiation. The illumination means forms three or more branched light beams, which are projected toward the reflecting object. The focusing means, located outside the direction of the deflection of the branched light beams relative to the illumination means, guides the branched light beams projected from the illumination means and reflected from the reflecting object to corresponding light receiving elements by refraction or diffraction. The detected values ​​of the light receiving elements indicate the state of reflection from three or more points on the reflecting object, respectively, and the state of the reflecting object can be detected based on the detected values.

[0008] As described above, the light beam emitted from the light source is deflected radially and split in the circumferential direction, and the split light beams are guided to the light-receiving element by the light-collecting means, so that the light beams that do not contribute to the detection of the state of the reflective object can be reduced. Therefore, the light intensity of the light beam from the light source required for the detection can be weakened, making it easier to reduce the power consumption of the light-emitting and receiving system in which the optical element is provided, and the ambient light caused by the light beams that do not contribute to the detection can be suppressed, thereby improving the accuracy of detecting the reflective object.

[0009] According to an optical element described in claim 2, the surface of the illumination means facing the light source includes three or more inner positive power surfaces that are tangent to each other in the circumferential direction, recessed toward their boundaries, and whose boundaries intersect at a single central point. Each of these inner positive power surfaces has positive power. When a bundle of rays emitted from the light source is incident on the three or more inner positive power surfaces at a position including the central point, the bundle of rays is split away from the boundaries between the inner positive power surfaces, resulting in three or more branched bundles of rays. In other words, the bundle of rays emitted from the light source is radially deflected by the three or more inner positive power surfaces.

[0010] Furthermore, the positive power can cause the branched ray bundles traveling from the inner positive power surface toward the reflecting object to tend to converge, thereby reducing the ray bundles that do not contribute to detecting the state of the reflecting object. Thus, in addition to the effect of claim 1, the light intensity of the ray bundle from the light source necessary for detecting the state of the reflecting object can be weakened, making it easier to reduce the power consumption of the light projecting and receiving system in which the optical element is provided.

[0011] According to the optical element of claim 3, each of the inner positive power surfaces is part of a convex surface that slopes radially downward from the apex. This causes a bundle of rays incident on each inner positive power surface to refract toward the axis passing through the apex of that inner positive power surface, and the branched bundle of rays tends to converge in the radial and circumferential directions. Therefore, even if the light intensity of the bundle of rays emitted from the light source is weak, the detection value of the light-receiving element can be ensured, thereby achieving the effect of claim 2 and further reducing the power consumption of the light-emitting and receiving system in which the optical element is installed.

[0012] According to an optical element described in claim 4, the surface of the illumination means facing the reflecting object includes an inner inclined surface provided on the back side of each of the inner positive power surfaces. Because this inner inclined surface slopes toward the light source as it extends outward in the radiation direction, the branched ray bundles traveling from the inner positive power surface toward the reflecting object can be refracted toward the center in the radiation direction, compared to when the portion corresponding to the inner inclined surface is flat. As a result, the branched ray bundles reflected from the reflecting object and incident on the focusing means are closer to the center in the radiation direction, compared to when the portion corresponding to the inner inclined surface is flat, and the focusing means can be positioned closer to the center. As a result, in addition to the effect of claim 2, the optical element can be made smaller in size in the radiation direction.

[0013] According to the optical element of claim 5, the surface of the focusing means facing the light source includes three or more outer positive power surfaces, each of which faces a corresponding one of the light-receiving elements. This allows each of the branched ray bundles reflected from the reflecting object and traveling toward the light-receiving element to pass through the outer positive power surface. Because the outer positive power surface has positive power, the branched ray bundles incident on the light-receiving element can be focused by the outer positive power surface. Therefore, even if the light intensity of the ray bundle emitted from the light source is weak, the detection value of the light-receiving element can be ensured. In addition to the effect of claim 1, this also allows for further reduction in the power consumption of the light-emitting and receiving system in which the optical element is provided.

[0014] According to the optical element of claim 6, the surface of the focusing means facing the reflecting object has an outer inclined surface that inclines toward the light source as it extends outward in the radiation direction. This causes the branched ray bundle reflected from the reflecting object and traveling toward the light receiving element to be refracted toward the center in the radiation direction when it passes through the outer inclined surface. This allows the light receiving element to be positioned closer to the center in the radiation direction so that the branched ray bundle that has passed through the outer inclined surface is incident on the light receiving element. As a result, in addition to the effect of claim 1, the light projecting and receiving system in which the optical element is provided can be made smaller in the radiation direction.

[0015] According to the optical element of claim 7, the illumination means converts the branched ray bundle into a parallel ray bundle and projects it toward the reflecting object. This makes it possible to uniformize the size of the illumination area onto which the branched ray bundle is projected and the light intensity within that area, even if the distance from the optical element to the reflecting object varies. This makes it possible to suppress variations in the range and light intensity of the branched ray bundle incident on the light-receiving element due to such variations, thereby achieving the effect of claim 1 and suppressing a decrease in the accuracy of detecting the state of the reflecting object.

[0016] A light projecting and receiving system according to claim 8 includes the optical element according to any one of claims 1 to 7, a light source that emits a light beam toward the optical element, and three or more light receiving elements that are arranged closer to the light source than the optical element, and the light beam emitted from the light source is reflected by a reflective object and made to enter the light receiving elements. Since only one light source is provided, in addition to the effects of any one of claims 1 to 7, the power consumption of the light projecting and receiving system can be reduced compared to when multiple light sources are provided.

[0017] A light projecting and receiving system according to claim 9 includes the optical element according to any one of claims 1 to 7, a light source that emits a light beam toward the optical element, and three or more light receiving elements that are arranged closer to the light source than the optical element, and the light beam emitted from the light source is reflected by a reflective object and made to enter the light receiving elements. Since the light source emits a light beam with a half-width at half maximum of 30 degrees or less, in addition to the effects of any one of claims 1 to 7, the light intensity of the light beam that enters the light receiving elements via the optical element can be increased.

[0018] A light projecting and receiving system according to claim 10 includes the optical element according to claim 3, a light source that emits a ray bundle toward the optical element, and three or more light receiving elements arranged on the light source side of the optical element, and the ray bundle emitted from the light source is reflected by a reflective object and incident on the light receiving elements. The full width at half maximum region of the ray bundle emitted from the light source is incident on the center point side of the vertices of the three or more inner positive power surfaces. This makes it difficult for coma aberrations and the like to occur in the branched ray bundle, making it easier to achieve uniformity in light intensity for each illumination area illuminated by the branched ray bundle. Therefore, in addition to the effect of claim 3, the light projecting and receiving system can ensure high accuracy in detecting the state of the reflective object.

[0019] 1A is a top view of an optical element according to an embodiment, and FIG. 1B is a bottom view of the optical element. FIG. 1A is a cross-sectional end view of a light projecting and receiving system including a cross section of the optical element taken along line II-II in FIG. 1A. FIG. 1B is a cross-sectional end view of a light projecting and receiving system including a cross section of the optical element taken along line III-III in FIG. 1A. FIG. 1C is a schematic diagram showing an area illuminated by the light projecting and receiving system. FIG. 1D is a schematic diagram showing a case where the light projecting and receiving system is applied to tilt measurement. FIG. 1A is a top view of an optical element according to a modified example, and FIG. 1B is a cross-sectional view of the optical element taken along line VIb-VIb in FIG. 6A.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1(a) is a top view of an optical element 10 according to one embodiment. Fig. 1(b) is a bottom view of the optical element 10. Fig. 2 is a cross-sectional end view of the light projecting and receiving system 1, including a cross section of the optical element 10 taken along line II-II in Fig. 1(a). Fig. 3 is a cross-sectional end view of the light projecting and receiving system 1, including a cross section of the optical element 10 taken along line III-III in Fig. 1(a). Fig. 4 is a schematic diagram showing illumination areas Aa to Ac illuminated by the light projecting and receiving system 1.

[0021] 2 and 3, the light projecting and receiving system 1 includes a single light source 21, three light receiving elements 22a, 22b, and 22c, and one optical element 10. The light projecting and receiving system 1 projects a light beam R emitted from the light source 21 onto a detection target via the optical element 10, and causes the light beam R reflected from the detection target (branched light beams Ra to Rc, described below) to be incident on the light receiving elements 22a to 22c via the optical element 10. The light projecting and receiving system 1 detects the state of the detection target based on the detection values ​​of the light receiving elements 22a to 22c.

[0022] The detection target in this embodiment is a rotating part 25 of a water meter 23. The light emitting and receiving system 1 is configured to detect the rotation of this rotating part 25. The water meter 23 is a known instrument for measuring the flow rate of tap water. The water meter 23 includes a counter that displays the flow rate of tap water, and is configured so that the counter can be seen through a cover 27 made of a transparent material such as glass or synthetic resin.

[0023] As shown in Figure 4, the counter of water meter 23 includes a dial 24 on which numbers from 0 to 9 are marked clockwise along with a scale, and a needle-shaped rotating part 25 that rotates on dial 24. Rotating part 25 rotates around a rotation axis 26 that is perpendicular to dial 24. The tip of the needle of rotating part 25 moves one scale clockwise for every liter of tap water flow rate, and rotating part 25 makes one rotation at 10 liters.

[0024] 2 and 3, the light source 21 is a bullet-shaped LED (light-emitting diode) in which a light-emitting element is sealed with a lens-shaped sealing resin, and emits a beam of light R toward the dial 24 and the rotating part 25. The beam of light R diverges from the light source 21 toward the dial 24, etc. The beam of light R is axially symmetrical with respect to the optical axis O of the light source 21 (the central axis of the lens-shaped sealing resin).

[0025] The light intensity of the ray bundle R is maximum on the optical axis O and decreases radially outward from the optical axis O. The ray of the ray bundle R at a position where the light intensity is half of the maximum value is shown by a solid line in Figures 2 and 3. The area inside this solid line is called the full width at half maximum region, and the angle between one side of this solid line and the optical axis O in a cross section including the optical axis O is called the half angle at half maximum. The half angle at half maximum of the ray bundle R in this embodiment is between 5 degrees and 30 degrees.

[0026] The light source 21 is disposed so that the optical axis O is perpendicular to the dial 24. Furthermore, the light source 21 is disposed so that the rotation axis 26 of the rotating part 25 and the optical axis O are coaxial.

[0027] The light receiving elements 22a to 22c are elements that convert the light intensity of the ray bundle R (branched ray bundles Ra to Rc) incident thereon into an electrical signal and output the signal. The three light receiving elements 22a to 22c are arranged spaced apart from one another in the circumferential direction of the optical axis O.

[0028] When viewed from above in the axial direction of the optical axis O as shown in Figure 4, the light receiving element 22a is arranged on the upper side of the paper in Figure 4, the light receiving element 22b is arranged on the left side, and the light receiving element 22c is arranged on the right side, with the optical axis O as the reference.

[0029] Furthermore, light receiving elements 22b and 22c are disposed at positions rotated 90 degrees around optical axis O relative to light receiving element 22a. Therefore, light receiving elements 22a to 22c and light source 21 can be disposed so that optical axis O is located at the midpoint of the line segment connecting light receiving elements 22b and 22c, and light receiving element 22a is located on the perpendicular bisector to that line segment. Therefore, the positional accuracy of light receiving elements 22a to 22c and light source 21 can be easily ensured.

[0030] 1(a) to 3, the optical element 10 is a lens array made of a transparent material such as glass or synthetic resin, and is arranged on an optical axis O. The optical element 10 has a light source side surface 11 facing the light source 21 and the light receiving elements 22a to 22c, and an object side surface 12 facing the dial 24 and the rotating portion 25.

[0031] The light source side surface 11 includes three inner positive power surfaces 13a, 13b, and 13c. The three inner positive power surfaces 13a to 13c are in contact with one another in the circumferential direction of the optical axis O. The boundaries between the inner positive power surfaces 13a to 13c intersect at a single center point O1. In this embodiment, this center point O1 is located on the optical axis O.

[0032] When viewed from above in the axial direction of optical axis O, inner positive power surface 13a is arranged on the upper side of the paper in FIG. 1A, inner positive power surface 13b is arranged on the left side, and inner positive power surface 13c is arranged on the right side, with optical axis O as the reference. The upper side, right side, and left side of the paper in FIG. 1A correspond to the upper side, right side, and left side of the paper in FIG. 4, respectively. That is, inner positive power surfaces 13a to 13c are provided at positions corresponding to light-receiving elements 22a to 22c, respectively.

[0033] The inner positive power surface 13a is part of a convex surface formed axisymmetrically with respect to the central axis Ca, and is inclined radially downward from a vertex V1a on the central axis Ca toward the object-side surface 12 (the rotating portion 25 side). Similarly, the inner positive power surface 13b is part of a convex surface formed axisymmetrically with respect to the central axis Cb, and is inclined radially downward from a vertex V1b on the central axis Cb toward the object-side surface 12. The inner positive power surface 13c is part of a convex surface formed axisymmetrically with respect to the central axis Cc, and is inclined radially downward from a vertex V1c on the central axis Cc toward the object-side surface 12.

[0034] The central axes Ca to Cc are parallel to each other and to the optical axis O, and are spaced apart from each other in the radial direction. Furthermore, since the inner positive power surfaces 13a to 13c are part of an axially symmetric convex surface, it is easy to form the inner positive power surfaces 13a to 13c.

[0035] Each of the inner positive power surfaces 13a to 13c having such a shape has positive power (refracting power). Furthermore, the three inner positive power surfaces 13a to 13c are concave toward their respective boundaries. As a result, when the ray bundle R emitted from the light source 21 is incident on the inner positive power surfaces 13a to 13c at a position including the center point O1, it is split into three branch ray bundles Ra, Rb, and Rc, moving away from the boundaries between the inner positive power surfaces 13a to 13c.

[0036] That is, the branched ray bundles Ra to Rc are deflected radially outward in the radial direction of the optical axis O (center point O1), while moving away from each other in the circumferential direction of the optical axis O. When the optical axis O coincides with the center point O1, the radial direction in which the branched ray bundles Ra to Rc are deflected coincides with the radial direction of the optical axis O, and the circumferential direction around the center of the radiation coincides with the circumferential direction of the optical axis O. Even if the optical axis O and the center point O1 are slightly misaligned, these directions can be said to be approximately the same.

[0037] The branched ray bundle Ra is the ray bundle R that is incident on the inner positive power surface 13a and tends to be focused toward the central axis Ca compared to the ray bundle R before incidence. Similarly, the branched ray bundle Rb is the ray bundle R that is incident on the inner positive power surface 13b and tends to be focused toward the central axis Cb. The branched ray bundle Rc is the ray bundle R that is incident on the inner positive power surface 13c and tends to be focused toward the central axis Cc.

[0038] The branched beams of rays Ra to Rc pass through the object side surface 12 and the cover 27, and are projected onto the dial 24, which is the rotation locus of the rotating part 25, illuminating the dial 24. As shown in Figure 4, an illumination area Aa, which is the range illuminated by the branched beam of rays Ra, is between the 0 and 9 marks on the dial 24. An illumination area Ab, which is illuminated by the branched beam of rays Rb, is near the 7 mark on the dial 24. An illumination area Ac, which is illuminated by the branched beam of rays Rc, is near the 2 mark on the dial 24.

[0039] 2 and 3 , when rotating unit 25 is located in illumination area Ac, branched ray bundles Ra and Rb specularly reflected by dial 24 pass again through cover 27 and object-side surface 12, and further through light-source-side surface 11, to be incident individually on light-receiving elements 22a and 22b. Light-receiving element 22a is disposed at the position where branched ray bundle Ra is incident, and light-receiving element 22b is disposed at the position where branched ray bundle Rb is incident. Note that even when branched ray bundle Rc is specularly reflected by dial 24, light-receiving element 22c is disposed at the position where branched ray bundle Rc is incident after passing through object-side surface 12, light-source-side surface 11, etc.

[0040] However, part of the branched beam Rc is reflected by the rotating part 25, not by the dial 24. The upper surface of the rotating part 25 is not parallel to the dial 24, and is inclined downward toward the dial 24 as it moves radially outward. Therefore, the branched beam Rc reflected by the rotating part 25 does not enter the light-receiving element 22c. As a result, the detection value of the light-receiving element 22c is smaller when the branched beam Rc is reflected by the rotating part 25, compared to when the entire branched beam Rc is reflected by the dial 24. Therefore, the light-emitting and receiving system 1 can detect that the rotating part 25 is located in the illumination area Ac when the detection value of the light-receiving element 22c becomes smaller.

[0041] Similarly, when the detection value of the light receiving element 22a becomes small, the light projecting and receiving system 1 can detect that the rotating part 25 is located in the illumination area Aa. When the detection value of the light receiving element 22b becomes small, the light projecting and receiving system 1 can detect that the rotating part 25 is located in the illumination area Ab.

[0042] Furthermore, for example, if the light projecting and receiving system 1 detects that the rotating part 25 is positioned in the order of illumination area Aa, illumination area Ac, illumination area Ab, and illumination area Aa as the rotating part 25 rotates, it can determine that the rotating part 25 has rotated one full rotation clockwise. That is, the light projecting and receiving system 1 illuminates three locations on the dial 24 and detects the reflections from each of the illumination areas Aa to Ac individually using the light receiving elements 22a to 22c, thereby detecting the rotation direction and number of rotations of the rotating part 25. The rotational speed of the rotating part 25 can also be detected from the time it takes to move through each of the illumination areas Aa to Ac.

[0043] With this light projecting and receiving system 1, branched ray bundles Ra to Rc that are projected onto three illumination areas Aa to Ac for detecting the number of rotations and the like can be projected from a single light source 21 by the inner positive power surfaces 13a to 13c of the optical element 10. As a result, the single light source 21 can reduce the amount of power consumed by the light projecting and receiving system 1 compared to when a plurality of light sources are provided that individually project ray bundles onto each of the illumination areas Aa to Ac.

[0044] Because the ray bundle R from the light source 21 diverges, it is incident on a relatively wide range of the inner positive power surfaces 13a-13c. This ray bundle R is split by the inner positive power surfaces 13a-13c, weakening its divergence and becoming branched ray bundles Ra-Rc, which illuminate the illumination areas Aa-Ac of the dial 24. This allows each of the illumination areas Aa-Ac to be widened in the circumferential and radial directions about the optical axis O, while ensuring sufficient light intensity (illuminance) within the illumination areas Aa-Ac, thereby reducing the ray bundle R that does not contribute to rotation detection. As a result, even if the size and position of the rotating part 25 of the water meter 23 vary, the rotating part 25 can be easily detected, and the light intensity of the ray bundle R from the light source 21 required for detection can be weakened. This facilitates reducing the power consumption of the light-emitting / receiving system 1 and improves versatility. Furthermore, disturbance light due to the light beam R that does not contribute to detection can be suppressed, and the detection accuracy of the rotating part 13f by the light projecting and receiving system 1 can be improved.

[0045] Because each of the inner positive power surfaces 13a to 13c is part of a convex surface that slopes radially downward from vertices V1a to V1c, the ray bundle R incident on each of the inner positive power surfaces 13a to 13c is refracted toward the central axes Ca to Cc, and the divergence of the ray bundle R is weakened in the circumferential and radial directions about the optical axis O. This improves the light intensity within the illumination areas Aa to Ac of each of the split branch ray bundles Ra to Rc, so that the detection values ​​of the light-receiving elements 22a to 22c can be ensured even if the light intensity of the ray bundle R emitted from the light source 21 is weak. This allows for further reduction in the power consumption of the light projecting and receiving system 1.

[0046] The light source 21 emits a ray bundle R with a half-angle at half maximum of 5 degrees or more and 30 degrees or less. Therefore, the illumination areas Aa to Ac can be made sufficiently wide, and the light intensity of the branched ray bundles Ra to Rc incident on the light receiving elements 22 a to 22 c via the optical element 10 can be further improved.

[0047] The full width at half maximum region of the ray bundle R emitted from the light source 21 is incident on the inner positive power surfaces 13 a to 13 c closer to the center point O1 (optical axis O) than the vertices V1 a to V1 c, thereby making it difficult for coma aberrations and the like to occur in the branched ray bundles Ra to Rc.

[0048] In particular, it is preferable that the full width at half maximum region of the ray bundle R is incident on the center point O1 side of the line segment connecting the vertices V1a to V1c when viewed from the direction of the optical axis O. In this case, coma aberration and the like are less likely to occur in the branched ray bundles Ra to Rc. As a result, uniformity in light intensity can be easily achieved for each of the illumination areas Aa to Ac onto which the branched ray bundles Ra to Rc are projected. As a result, the detection accuracy of the rotating part 25 by the light projecting and receiving system 1 can be ensured.

[0049] Since the center point O1 where the boundaries of the inner positive power surfaces 13a to 13c intersect is located on the optical axis O, the ray bundle R emitted from the light source 21 is deflected radially (outward in the radial direction) from the optical axis O and is split in the circumferential direction of the optical axis O into branched ray bundles Ra to Rc. Since the ray bundle R from the light source 21 is axially symmetric with respect to the optical axis O, the widths and light intensities of the illumination areas Aa to Ac by the branched ray bundles Ra to Rc after splitting can be made closer to each other. This improves the detection accuracy of the rotating part 25 by the light projecting and receiving system 1.

[0050] Furthermore, because center point O1 is located on optical axis O, and optical axis O is coaxial with rotation axis 26, branched ray bundles Ra to Rc split and deflected by inner positive power surfaces 13a to 13c can be easily guided radially outward from rotation axis 26. As a result, branched ray bundles Ra to Rc can efficiently illuminate three locations on dial 24 around rotation axis 26. As a result, the detection accuracy of rotating part 25 by light-emitting / receiving system 1 can be further improved.

[0051] The branched ray bundles Ra to Rc that are split by the inner positive power surfaces 13 a to 13 c and travel toward the dial 24 pass through inner inclined surfaces 14 provided on the object-side surface 12 of the optical element 10. The inner inclined surfaces 14 are provided on the back sides of the inner positive power surfaces 13 a to 13 c of the optical element 10.

[0052] The inner inclined surface 14 is a convex surface symmetrical about the optical axis O, and inclines toward the light source side surface 11 (light source 21) as it moves away from the optical axis O. Therefore, compared to when the portion corresponding to the inner inclined surface 14 is a flat surface perpendicular to the optical axis O, the branched ray bundles Ra to Rc passing through the inner inclined surface 14 and proceeding toward the dial 24 can be refracted toward the optical axis O. This allows the light-receiving elements 22a to 22c onto which the branched ray bundles Ra to Rc reflected from the dial 13e are incident, and the various portions of the optical element 10 through which they pass (the outer inclined surface 15 and the outer positive power surfaces 16a to 16c, described below), to be positioned closer to the optical axis O. As a result, the vicinity of the optical element 10 in the light-emitting and receiving system 1 and the optical element 10 itself can be made smaller in the radial direction of the optical axis O.

[0053] The power of the inner positive power surfaces 13a to 13c is adjusted with respect to the degree of divergence of the ray bundle R so that the branched ray bundles Ra to Rc that pass through the inner positive power surfaces 13a to 13c and the inner inclined surface 14 and are projected onto the dial 24 are parallel ray bundles. Note that in this specification, parallel ray bundles refer to branched ray bundles Ra to Rc whose half-maximum angles are 4 degrees or less. Furthermore, the shape of the inner inclined surface 14 is set so that the branched ray bundles Ra to Rc are incident on the inner inclined surface 14 substantially perpendicularly, and therefore the power of the inner inclined surface 14 has almost no effect on the half-maximum angles of the branched ray bundles Ra to Rc.

[0054] By making the branched ray bundles Ra to Rc into parallel ray bundles, it is possible to uniformize the size of the illuminated areas Aa to Ac illuminated by the branched ray bundles Ra to Rc and the light intensity within the illuminated areas Aa to Ac, even if there is variation in the distance from the optical element 10 to the dial 24. This makes it possible to suppress variation in the light intensity of the branched ray bundles Ra to Rc incident on the light-receiving elements 22 a to 22 c that occurs due to the variation, and therefore suppresses a decrease in the detection accuracy of the rotating part 25 by the light-emitting and receiving system 1.

[0055] An outer inclined surface 15 is provided on the object-side surface 12 of the optical element 10, radially outward of the inner inclined surface 14. The branched ray bundles Ra to Rc split by the inner positive power surfaces 13 a to 13 c are deflected radially outward of the optical axis O, and are therefore incident on the outer inclined surface 15 after being reflected by the dial 24.

[0056] The outer inclined surface 15 is part of a convex surface symmetrical about the optical axis O, and is inclined toward the light source side surface 11 as it moves away from the optical axis O. Therefore, the branched ray bundles Ra to Rc incident on the outer inclined surface 15 can be refracted toward the optical axis O, and in this embodiment, the branched ray bundles Ra to Rc can be made substantially parallel to the optical axis O. This allows the light-receiving elements 22a to 22c to be disposed close to the optical axis O and the light source 21 so that the branched ray bundles Ra to Rc that have passed through the outer inclined surface 15 are incident on the light-receiving elements 22a to 22c. As a result, the area near the optical element 10 of the light-projecting and receiving system 1 can be made compact in the radial direction of the optical axis O.

[0057] The outer peripheral edge of inner inclined surface 14 and the inner peripheral edge of outer inclined surface 15 are connected by connecting surface 17, which slopes radially inward toward light source side surface 11. In other words, object-side surface 12 is formed of a Fresnel lens surface. This allows the thickness of optical element 10 (the dimension in the axial direction of optical axis O) to be reduced compared to when inner inclined surface 14 and outer inclined surface 15 are formed with continuous convex surfaces.

[0058] The light-source-side surface 11 of the optical element 10 includes an outer positive power surface 16a that is disposed on the opposite side of the center point O1 from the inner positive power surface 13a and faces the light-receiving element 22a, an outer positive power surface 16b that is disposed on the opposite side of the center point O1 from the inner positive power surface 13b and faces the light-receiving element 22b, and an outer positive power surface 16c that is disposed on the opposite side of the center point O1 from the inner positive power surface 13c and faces the light-receiving element 22c. As a result, each of the branched ray bundles Ra to Rc that are split by the inner positive power surfaces 13a to 13c and reflected from the dial 24 passes through the outer positive power surfaces 16a to 16c and is incident on the light-receiving elements 22a to 22c.

[0059] Each of the outer positive power surfaces 16a to 16c has a positive power. This allows the branched ray bundles Ra to Rc incident on the light-receiving elements 22a to 22c to be condensed by the outer positive power surfaces 16a to 16c. As a result, even if the light intensity of the ray bundle R emitted from the light source 21 is weak, the detection values ​​of the light-receiving elements 22a to 22c can be ensured, thereby further reducing the power consumption of the light-emitting and receiving system 1.

[0060] More specifically, the outer positive power surface 16a is part of a convex surface that slopes radially downward from the vertex V2a toward the object-side surface 12. The outer positive power surface 16b is part of a convex surface that slopes radially downward from the vertex V2b toward the object-side surface 12. The outer positive power surface 16c is part of a convex surface that slopes radially downward from the vertex V2c toward the object-side surface 12. This allows the outer positive power surfaces 16a-16c to focus each of the branched ray bundles Ra-Rc incident on the light-receiving elements 22a-22c in the circumferential and radial directions about the optical axis O, further reducing the power consumption of the light projection and reception system 1. Furthermore, because the outer positive power surfaces 16a-16c are part of a convex surface that is axially symmetric with respect to an axis that passes through the vertices V2a-V2c and is parallel to the optical axis O, the outer positive power surfaces 16a-16c can be easily formed.

[0061] As shown in FIG. 1A , when viewed in the axial direction of the optical axis O, the center point O1, the vertex V1a of the inner positive power surface 13a, and the vertex V2a of the outer positive power surface 16a are aligned on a straight line. Similarly, the center point O1, the vertices V1b and V1c of the inner positive power surfaces 13b and 13c, and the vertices V2b and V2c of the outer positive power surfaces 16b and 16c are aligned on a straight line. As a result, when viewed in the axial direction of the optical axis O, each of the branched ray bundles Ra to Rc lies along the straight line. Therefore, when viewed in the axial direction of the optical axis O, by arranging the light-receiving elements 22a to 22c at positions that overlap the straight line, it is possible to easily cause the branched ray bundles Ra to Rc to be incident on the light-receiving elements 22a to 22c. In other words, the positional relationship of each component for causing the branched ray bundles Ra to Rc to be incident on the light-receiving elements 22a to 22c can be easily determined.

[0062] 2 and 3, the focal points of the outer positive power surfaces 16a-16c are located closer to the optical element 10 than the light-receiving elements 22a-22c and closer to the light-receiving elements 22a-22c than half the distance from the vertices V2a-V2c to the light-receiving elements 22a-22c. Therefore, when the branched ray bundles Ra-Rc are made substantially parallel to the optical axis O by the outer inclined surface 15, they are focused at the focal points of the outer positive power surfaces 16a-16c and then diverge slightly on the light-receiving elements 22a-22c side after passing through the outer positive power surfaces 16a-16c. This makes it possible to easily direct the branched ray bundles Ra-Rc to the light-receiving elements 22a-22c even if the light-receiving elements 22a-22c are misaligned in the radial or circumferential direction of the optical axis O relative to the outer positive power surfaces 16a-16c due to, for example, an assembly error in the equipment that provides the light projection and reception system 1.

[0063] Optical element 10 has, within a single member, inner positive power surfaces 13a-13c and inner inclined surface 14 (illumination means) that form branched ray bundles Ra-Rc from ray bundle R and project them onto dial 24, and outer positive power surfaces 16a-16c and outer inclined surface 15 (light-collecting means) that individually guide branched ray bundles Ra-Rc reflected from dial 24 to light-receiving elements 22a-22c. This makes it possible to reduce the size of light-projecting and receiving system 1 and facilitate assembly, compared to when the illumination means and light-collecting means are provided separately.

[0064] While the above description has been based on the above embodiment, the present invention is not limited to the above embodiment, and it is readily apparent that various improvements and modifications are possible within the spirit and scope of the present invention. For example, the type and size of the light source 21 and the light-receiving elements 22a to 22c may be changed as appropriate. Multiple light sources 21 may be provided. The light intensity of the ray bundle R emitted from the light source 21 does not necessarily decrease with increasing distance from the optical axis O, but may be substantially constant near the optical axis O. Furthermore, for example, the inner inclined surface 14, the outer inclined surface 15, and the outer positive power surfaces 16a to 16c may be omitted, and the corresponding surfaces may be flat surfaces perpendicular to the optical axis O.

[0065] In the above embodiment, the case where three inner positive power surfaces 13a-13c, three outer positive power surfaces 16a-16c, and three light receiving elements 22a-22c are provided correspondingly has been described, but this is not necessarily limited to this. Four or more of each may be provided, and four or more locations on the dial 24 may be illuminated with branched light beams split into four or more beams. Even when four or more inner positive power surfaces 13a-13c are provided, it is sufficient that the boundaries between all of the inner positive power surfaces 13a-13c intersect at a single center point O1.

[0066] In the above embodiment, the light-receiving elements 22b and 22c are arranged at positions rotated 90 degrees around the optical axis O relative to the light-receiving element 22a, and the inner positive power surfaces 13a-13c and the outer positive power surfaces 16a-16c are also arranged at 90-degree intervals around the center point O1 (optical axis O). However, this is not necessarily limited to this. The intervals around the optical axis O or the center point O1 between the light-receiving elements 22a-22c, the inner positive power surfaces 13a-13c, and the outer positive power surfaces 16a-16c may be other than 90 degrees, for example, 120 degrees.

[0067] In the above embodiment, the light emitting and receiving system 1 detects the rotation of the rotating part 25 of the water meter 23, but this is not necessarily limited to this. For example, the light emitting and receiving system 1 may detect the rotation of a needle-shaped rotating part on a dial of an instrument other than a water meter (for example, a gas meter or a clock-type tachometer). Furthermore, the light emitting and receiving system 1 may be provided in any device that has a rotating part that rotates around a rotation axis, and the light emitting and receiving system 1 may detect the rotation of the rotating part.

[0068] The light emitting and receiving system 1 may be provided not only in devices with a rotating part that rotates once, but also in devices with a rotating part that rotates back and forth within a predetermined range (for example, an automobile speedometer), and the rotation of the rotating part may be detected by the light emitting and receiving system 1. When the light emitting and receiving system 1 is provided in a speedometer, the position of the rotating part can be detected by the light emitting and receiving system 1 by dividing the position where the dial is illuminated by the branched light beam into smaller positions, and the speed of the automobile can be calculated from that position.

[0069] Furthermore, the light emitting and receiving system 1 may be detachably attached to a device such as the water meter 23, or may be built into a device such as the water meter 23. In this case, depending on the type of device or when it is built into the device, the rotating part may be formed in a shape other than a needle, an incident surface onto which the branched light beams Ra to Rc are incident may be provided in place of the dial 24, or there may be no dial 24 or incident surface. The method for detecting the rotating part by the light emitting and receiving system 1 may be changed as appropriate depending on the type of rotating part and whether or not there is a dial 24 or the like.

[0070] For example, the light projecting and receiving system 1 may be configured so that by varying the degree of scattering and absorption (regular reflectance) between the incident surface (including the dial 24) and the rotating part, the detection values ​​of the light receiving elements 22a to 22c change when the branched light beams Ra to Rc are incident on the incident surface and when they are incident on the rotating part, and the rotation of the rotating part is detected from these changes.

[0071] Alternatively, the rotating portion may be a through hole provided on the incident surface, and the rotation of the rotating portion may be detected based on the branched ray bundles Ra to Rc not being reflected by the rotating portion and not being incident on the light-receiving elements 22 a to 22 c. The branched ray bundles Ra to Rc may be incident on the light-receiving elements 22 a to 22 c only when they are reflected by the rotating portion. In this case as well, the detection values ​​of the light-receiving elements 22 a to 22 c vary depending on whether the branched ray bundles Ra to Rc are incident on the rotating portion, and the rotation of the rotating portion can be detected from these variations.

[0072] Furthermore, the object to be detected by the light projecting and receiving system 1 is not limited to the rotation of the rotating part. For example, the object to be detected may be the color or fluorescence intensity of reagents placed in multiple reaction vessels. In this case, the branched light beams Ra to Rc are incident individually on the reaction vessels, and the branched light beams Ra to Rc reflected from the reaction vessels are incident individually on the light receiving elements 22a to 22c. Therefore, the light receiving elements 22a to 22c can detect the light intensity of a specific color obtained through an optical filter or the light intensity of reflected fluorescent light. Therefore, the light projecting and receiving system 1 can simultaneously detect the color or fluorescence intensity of the reagents in each reaction vessel using the light beam R from the single light source 21.

[0073] 5, the light projecting and receiving system 1 can detect the tilt of a reflecting surface 32. FIG. 5 is a schematic diagram showing the application of the light projecting and receiving system 1 to tilt measurement. In FIG. 5, to facilitate comparison with FIG. 2, a cover 33 identical to the cover 27 is provided on the light projecting and receiving system 1, but the cover 33 may be omitted. The light receiving elements 22a to 22c in this light projecting and receiving system 1 are area sensors capable of detecting the incidence range of the branched light beams Ra to Rc incident thereon.

[0074] In Fig. 5, a reference state in which the reflecting surface 32 is perpendicular to the optical axis O is shown by a broken line, and the branched beams of rays Rb and Rc reflected by the reflecting surface 32 are shown by a two-dot chain line. Furthermore, in Fig. 5, the reflecting surface 32 is tilted downward from the reference state to the right side of the paper in Fig. 5, and the branched beams of rays Rb and Rc reflected by the reflecting surface 32 are shown by solid lines. For ease of explanation, the light projecting and receiving system 1 in Fig. 5 shows a case in which the branched beams of rays Rb and Rc are focused at one point on the light-receiving elements 22b and 22c, but this is not necessarily limited to this, and the beams may be focused over a predetermined range.

[0075] As shown in Figure 5, when the reflecting surface 32 is tilted downward to the right with respect to the reference state, the center of gravity of the incident range of the branched ray bundles Rb and Rc on the light-receiving elements 22b and 22c shifts to the right. Similarly, when the reflecting surface 32 is tilted downward to the left with respect to the reference state, the center of gravity of the incident range of the branched ray bundles Rb and Rc on the light-receiving elements 22b and 22c shifts to the left. Furthermore, when the reflecting surface 32 is tilted in the front-to-back direction of the paper surface of Figure 5 with respect to the reference state, the center of gravity of the incident range of the branched ray bundle Ra on the light-receiving element 22a (see Figure 3) shifts in the front-to-back direction. With the light-projecting and receiving system 1, the tilt angle and tilt direction from the reference state can be detected (calculated) by calculating the amount of deviation of the reflected light from three points on the reflecting surface 32 that are not on a straight line.

[0076] In the above embodiment, the inner positive power surfaces 13a-13c are axisymmetric with respect to the central axes Ca-Cc and are part of a convex surface that slopes downward radially from the vertices V1a-V1c. However, this is not necessarily limited to this. Similarly, the outer positive power surfaces 16a-16c are not limited to being part of an axisymmetric convex surface that slopes downward radially from the vertices V2a-V2c. For example, the inner positive power surfaces 13a-13c and the outer positive power surfaces 16a-16c may be part of a non-axisymmetric convex surface, such as a cylindrical surface or a toric surface, or may be free-form surfaces.

[0077] FIG. 6( a) is a top view of an optical element 40 according to a modified example. FIG. 6( b) is a cross-sectional view of the optical element 40 taken along line VIb-VIb in FIG. 6( a). The optical element 40 is configured similarly to the optical element 10, with the inner positive power surfaces 13a-13c replaced with inner positive power surfaces 43a-43c and the outer positive power surfaces 16a-16c replaced with outer positive power surfaces 46a-46c. The inner positive power surfaces 13a-13c and the outer positive power surfaces 46a-46c may be provided in a single optical element, or the inner positive power surfaces 43a-43c and the outer positive power surfaces 16a-16c may be provided in a single optical element.

[0078] The inner positive power surfaces 43a to 43c and the outer positive power surfaces 46a to 46c are configured as Fresnel lens surfaces with sawtooth cross sections, in which a radially continuous, axially symmetric convex surface is divided into concentric regions and the thickness of each region is reduced. This allows the thickness of the optical element 40 to be reduced compared to the optical element 10.

[0079] Each of the inner positive power surfaces 43a-43c and the outer positive power surfaces 46a-46c has positive power. The inner positive power surfaces 43a-43c and the outer positive power surfaces 46a-46c have a surface inclination (the inclination angle of a cross section including the central axes Ca-Cc) of each region that slopes radially downward. The inner positive power surfaces 43a-43c are in contact with each other in the circumferential direction and are recessed toward their respective boundaries, with their respective boundaries intersecting at a single center point O1. The surface inclination of each region of the inner positive power surfaces 43a-43c increases toward their respective boundaries. Because these configurations function similarly to the inner positive power surfaces 13a-13c and the outer positive power surfaces 16a-16c, the optical paths of the branched ray bundles Ra-Rc when the optical element 40 is used are substantially the same as those when the optical element 10 is used.

[0080] Furthermore, the number of divisions of the inner positive power surfaces 43a-43c and the outer positive power surfaces 46a-46c may be increased, and the inner positive power surfaces 43a-43c and the outer positive power surfaces 46a-46c may be made into blazed diffractive surfaces. In the case of a diffractive surface, the diffraction pitch of each region of the inner positive power surfaces 43a-43c decreases toward the boundary between the surfaces. This diffractive surface does not use refraction like the inner positive power surfaces 13a-13c, the outer positive power surfaces 16a-16c, or Fresnel lens surfaces, but rather uses diffraction to split the ray bundle R into branched ray bundles Ra-Rc and guide the branched ray bundles Ra-Rc to the light receiving elements 22a-22c. However, because this diffraction functions similarly to refraction, the diffractive surface can also be said to have positive power (diffractive power). The optical paths of the branched ray bundles Ra to Rc when a diffractive surface is used are also substantially the same as the optical paths when the optical element 10 is used. Note that, because the diffracted branched ray bundles Ra to Rc become parallel ray bundles, it is easy to design the optical element 10 so that the parallel ray bundles are projected onto the detection target, such as the rotating part 25.

[0081] Furthermore, the diffractive surface is not limited to a blazed type, and may be a binary type in which light-transmitting and light-blocking areas alternate, as long as it can split the light beam R into branched light beams Ra to Rc by diffraction and guide the branched light beams Ra to Rc to the light-receiving elements 22 a to 22 c by diffraction.

[0082] In the above embodiment, the inner inclined surface 14 and the outer inclined surface 15 are at least part of a convex surface symmetrical about the optical axis O, but this is not necessarily limited to this. The inner inclined surface 14 and the outer inclined surface 15 may be formed, for example, as at least part of a conical or pyramidal surface, as long as they slope toward the light source-side surface 11 with increasing distance from the optical axis O. Furthermore, the inner inclined surface 14 and the outer inclined surface 15 may be formed at a position on the object-side surface 12 through which the branched ray bundles Ra to Rc pass, and may be formed intermittently in the circumferential direction of the optical axis O. The inner inclined surface 14 and the outer inclined surface 15 may be formed as a Fresnel lens surface or a diffractive surface. Each region of this Fresnel lens surface or diffractive surface slopes toward the light source-side surface 11 with increasing distance from the optical axis O.

[0083] 6(b), the connecting surface 17 may be omitted, and the inner inclined surface 44 and the outer inclined surface 45 may be formed as a continuous convex surface. The inner inclined surface 44 and the outer inclined surface 45 are configured substantially identically to the inner inclined surface 14 and the outer inclined surface 15 in the above embodiment. By omitting the connecting surface 17, the inner inclined surface 44 and the outer inclined surface 45 can be easily formed.

[0084] DESCRIPTION OF SYMBOLS 1 Light projecting and receiving system 10, 40 Optical element 13a to 13c, 43a to 43c Inner positive power surface (part of illumination means) 14, 44 Inner inclined surface (part of illumination means) 15, 45 Outer inclined surface (part of focusing means) 16a to 16c, 46a to 46c Outer positive power surface (part of focusing means) 21 Light source 22a to 22c Light receiving element 24 Dial (part of reflecting object) 25 Rotating portion (part of reflecting object) 32 Reflecting surface (reflecting object) O Optical axis O1 Center point R Ray bundle Ra to Rc Branched ray bundle V1a to V1c Vertex of inner positive power surface

Claims

1. An optical element arranged between a light source, the light receiving element and the reflecting object so that a light beam emitted from the light source is reflected by the reflecting object and enters three or more light receiving elements, comprising: an illumination means which radially deflects the light beam emitted from the light source in three or more different directions by refraction or diffraction, while splitting the light beam in the circumferential direction around the center of radiation to form three or more branched light beams, and projects the branched light beams towards the reflecting object; and a focusing means which is arranged outside the radial direction in which the branched light beams are deflected with respect to the illumination means, and which individually guides the branched light beams projected from the illumination means and reflected from the reflecting object to the corresponding light receiving elements by refraction or diffraction.

2. The optical element according to claim 1, characterized in that the surface of said illumination means facing said light source is provided with three or more inner positive power surfaces which are in contact with each other in the circumferential direction and recessed toward each other's boundaries with each boundary intersecting at a single center point, and each of said inner positive power surfaces has positive power.

3. The optical element according to claim 2, wherein each of said inner positive power surfaces is a part of a convex surface that slopes radially downward from an apex.

4. An optical element according to claim 2, characterized in that the surface of said illumination means facing the reflecting object is provided on the back side of each of said inner positive power surfaces and has an inner inclined surface that inclines towards the light source as it moves outward in the radiation direction.

5. An optical element as described in claim 1, characterized in that the surface of said focusing means facing the light source has three or more outer positive power surfaces provided in positions facing each of said light receiving elements individually, and each of said outer positive power surfaces has a positive power.

6. The optical element according to claim 1, wherein the surface of said focusing means facing said reflecting object is provided with an outer inclined surface that inclines toward said light source as it moves outward in the radiation direction.

7. The optical element according to claim 1, wherein said illumination means converts said branched light beams into parallel light beams and projects the parallel light beams toward said reflecting object.

8. A light-projecting and receiving system comprising an optical element as described in any one of claims 1 to 7, a light source which emits a bundle of rays toward said optical element, and three or more light-receiving elements which are arranged closer to the light source than said optical element, said light-projecting and receiving system reflecting the bundle of rays emitted from said light source onto said reflective object and causing it to enter said light-receiving elements, characterized in that only one light source is provided.

9. A light-projecting and receiving system comprising an optical element as described in any one of claims 1 to 7, a light source which emits a bundle of rays toward said optical element, and three or more light-receiving elements which are arranged closer to the light source than said optical element, wherein the bundle of rays emitted from said light source is reflected by said reflecting object and made to enter said light-receiving elements, wherein said light source emits the bundle of rays with a half-width at half maximum of 30 degrees or less.

10. A light projecting and receiving system comprising the optical element of claim 3, a light source which emits the light beam toward the optical element, and three or more light receiving elements which are arranged closer to the light source than the optical element, wherein the light beam emitted from the light source is reflected by the reflecting object and made to enter the light receiving elements, characterized in that a full width at half maximum region of the light beam emitted from the light source is incident on the side of the center point relative to the vertices of three or more of the inner positive power surfaces.

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