Rotation detector

Abstract

To provide a rotation detector that can easily reduce power consumption and improve its versatility.SOLUTION: A rotation detector comprises: a single light source that emits diverging bundles of rays toward a rotation unit; three or more photodetectors for detecting incident light; and a lens array having a light source-side surface facing the light source and an object-side surface facing the rotation unit. The light source-side surface is composed of three or more inner convex surfaces in contact with each other in the circumferential direction of an optical axis of the light source, boundaries of which intersect at the single center point while denting toward the other boundaries. Each of the inner convex surfaces has a positive refractive power. The bundles of rays emitted from the light source are divided into three or more branched bundles of rays by entering the three or more inner convex surfaces at the area including the center point, and then the branched bundles of rays are projected toward the rotation trajectory of the rotation unit. The three or more photodetectors are aligned at the points to which each of the branched bundles of rays projected onto the rotation trajectory is individually made incident.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a rotation detection device that can easily reduce power consumption and improve versatility. [Background technology]

[0002] For example, a technology is known in which a rotation detection device that electrically detects the rotation of a rotating part that rotates according to the flow rate of tap water is built into or retrofitted to a water meter. The rotation detection device in Patent Document 1 detects the position of the rotating part using three optical sensors, and detects (calculates) the rotation direction and number of rotations of the rotating part from the timing at which each optical sensor detects the rotating part. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-003012 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned Patent Document 1, since the three optical sensors each have a light source and a light receiving element, the power consumption of the rotation detection device is high. Also, since the detection range of the optical sensor in Patent Document 1 is narrow, for example, when the rotation detection device in Patent Document 1 is used for another device such as a water meter or a gas meter, even a slight deviation in the position of the rotating part relative to the optical sensor makes it difficult to detect the rotating part. In other words, the rotation detection device in Patent Document 1 has a problem of low versatility.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a rotation detection device that can easily reduce power consumption and improve versatility. [Means for solving the problem]

[0006] In order to achieve this object, the rotation detection device of the present invention is provided in an apparatus having a rotating part that rotates around a rotation axis, and comprises a single light source that emits a diverging bundle of rays toward the rotating part, three or more light receiving elements that detect the incident light, and a lens array having a light source side surface facing the light source and an object side surface facing the rotating part, wherein the light source side surface has three or more inner convex surfaces that are in contact with each other in a circumferential direction centered on the optical axis of the light source and are concave toward each other's boundaries while the boundaries intersect at a central point, each of the inner convex surfaces having a positive refractive power, the bundle of rays emitted from the light source is incident on the three or more inner convex surfaces at a position including the central point, thereby being split into three or more branched bundles of rays, and the branched bundles of rays are projected toward the rotation locus of the rotating part, and the three or more light receiving elements are positioned at positions where each of the branched bundles of rays projected onto the rotation locus is individually incident on each of the three or more light receiving elements. Effect of the Invention

[0007] According to the rotation detection device of claim 1, the light source side of the lens array has three or more inner convex surfaces that are in contact with each other in the circumferential direction centered on the optical axis of the light source. These inner convex surfaces are recessed toward their boundaries, with their boundaries intersecting at one central point, and each has a positive refractive power. When a bundle of rays emitted from a single light source is incident on the three or more inner convex surfaces at a position including the central point, it is split so as to move away from the boundaries between the inner convex surfaces, becoming three or more branched bundles of rays. That is, each of the branched bundles of rays deflects from the central point outward in the radial direction of the optical axis and moves away from each other in the circumferential direction.

[0008] Such branched light beams are projected toward the rotation locus of the rotating part, and three or more light receiving elements are arranged at positions where each branched light beam is incident individually. This makes it possible to detect the rotation direction, number of rotations, position, etc. of the rotating part from the fluctuation in the detection value of each light receiving element depending on whether or not the branched light beam is incident on the rotating part. Since the light beams projected to three or more points on the rotation locus of the rotating part for this detection can be projected from a single light source by a lens array, power consumption can be reduced compared to when multiple light sources are provided.

[0009] The light beam from the light source diverges and is incident on a relatively wide range of the inner convex surface. This light beam is divided by the inner convex surface, and the divergence is weakened to become branched light beams, which are projected toward the rotation trajectory of the rotating part. This allows each branched light beam to illuminate a wide area of ​​the rotation trajectory, while ensuring the light intensity (illuminance) within that area, and reducing the light beams that do not contribute to rotation detection. As a result, even if the size and position of the rotating part vary, the rotation detection device can easily detect the rotating part, and the light intensity of the light beam from the light source required for detection can be weakened. This makes it easier to reduce the power consumption of the rotation detection device and improves versatility.

[0010] The rotation detection device described in claim 2 is detachably attached to an instrument that is an instrument with a needle-shaped rotating part rotating on a dial. The rotation detection device projects a branched light beam split by an inner convex surface onto the dial, and causes each of the branched light beams reflected by the dial to be incident individually on a light receiving element. As described above, since the branched light beams can illuminate a wide area of ​​the dial, which is the rotation trajectory of the rotating part, the rotation detection device can easily detect the rotating part even if there is variation in the size and position of the rotating part due to the type of instrument or an installation error on the instrument. Thus, in addition to the effect of claim 1, the versatility of the rotation detection device that can be detachably attached to an instrument can be improved.

[0011] According to the rotation detector of claim 3, each of the inner convex surfaces is a part of a convex surface that slopes radially downward from the apex. As a result, the light beam incident on each of the inner convex surfaces is refracted toward the axis passing through the apex of the inner convex surface, and the divergence of the light beam is weakened in the circumferential and radial directions of the optical axis. Therefore, the light intensity in the illumination area by each of the split branch light beams can be improved, so that the detection value of the light receiving element can be ensured even if the light intensity of the light beam emitted from the light source is weak. Therefore, in addition to the effects of claim 1 or 2, the power consumption of the rotation detector can be further reduced.

[0012] According to the rotation detector described in claim 4, the full width at half maximum region of the light beam emitted from the light source is incident on the central point side of the vertices of the three or more inner convex surfaces. This makes it difficult for coma aberration to occur in the branched light beams, making it easier to obtain uniformity in light intensity for each illumination area by the branched light beams. As a result, in addition to the effect of claim 3, the rotation detector can ensure the detection accuracy of the rotating part.

[0013] According to the rotation detection device of claim 5, the light receiving element is disposed on the light source side with respect to the lens array, at a position where the branched light beams reflected from the rotating part side are incident. The light source side of the lens array has three or more outer convex surfaces provided at positions facing each of the light receiving elements individually. As a result, each of the branched light beams heading toward the light receiving element passes through the outer convex surface. Since each of the outer convex surfaces has a positive refractive power, the branched light beams incident on the light receiving element can be focused by the outer convex surface. As a result, even if the light intensity of the light beam emitted from the light source is weak, the detection value of the light receiving element can be ensured, and in addition to the effect of claim 1 or 2, the power consumption of the rotation detection device can be further reduced.

[0014] According to the rotation detection device of claim 6, the branched light beams projected onto the rotation locus through the inner convex surface and the object side surface are parallel light beams. This makes it possible to equalize the size of the illumination area by the branched light beams and the light intensity within that area even if the distance from the lens array to the rotation locus of the rotating part varies. This makes it possible to suppress variations in the range and light intensity of the branched light beams incident on the light receiving element that are caused by such variations, thereby achieving the effects of claim 1 or 2, and suppressing a decrease in the detection accuracy of the rotating part by the rotation detection device.

[0015] According to the rotation detection device of claim 7, the central point where the boundaries of three or more inner convex surfaces intersect is located on the optical axis of the light source, so that the light beam emitted from the light source is deflected radially from the optical axis and is divided in the circumferential direction of the optical axis to become branched light beams. Since the light beam from the light source is basically axially symmetric with respect to the optical axis, the width of the illumination area and the light intensity of the branched light beams after division can be made uniform to each other. Therefore, in addition to the effect of claim 1 or 2, the detection accuracy of the rotating part by the rotation detection device can be improved.

[0016] The rotation detection device described in claim 8 is installed in a device having a rotating part so that the center point is located on the optical axis and the optical axis is coaxial with the rotation axis. This makes it easier to guide the branched light beams split and deflected by the inner convex surface to the outside in the radial direction of the rotation axis, and allows the branched light beams to efficiently illuminate three or more points on the rotation trajectory of the rotating part. As a result, in addition to the effect of claim 7, the detection accuracy of the rotating part by the rotation detection device can be further improved.

[0017] According to the rotation detection device of claim 9, the light receiving element is disposed on the light source side with respect to the lens array, at a position where the branched light beams reflected from the rotating part side are incident. The object side surface has an outer inclined surface provided outside the rear side of each inner convex surface in the radial direction of the optical axis. The branched light beams split by the inner convex surface are deflected outside the radial direction of the optical axis, so that they are incident on this outer inclined surface when reflected on the rotating part side. The outer inclined surface inclines toward the light source side as it moves away from the optical axis in the radial direction, so that the branched light beams can be refracted toward the optical axis side. This allows the light receiving element to be disposed close to the optical axis (light source) so that the branched light beams that have passed through the outer inclined surface are incident on the light receiving element. As a result, in addition to the effects of claim 1 or 2, the rotation detection device can be made smaller in the radial direction of the optical axis.

[0018] According to the rotation detector of claim 10, the object side surface has an inner inclined surface provided on the back side of each of the inner convex surfaces. A branched light beam from the inner convex surface toward the rotation locus of the rotating part passes through the inner inclined surface. This inner inclined surface inclines toward the light source side as it moves away from the optical axis in the radial direction, so that the branched light beam toward the rotation locus can be refracted toward the optical axis side, compared to when the part corresponding to the inner inclined surface is a plane perpendicular to the optical axis. This allows the light receiving element onto which the branched light beam is incident to be disposed closer to the optical axis, compared to when the part corresponding to the inner inclined surface is a plane perpendicular to the optical axis. As a result, in addition to the effects of claim 1 or 2, the rotation detector can be made smaller in the radial direction of the optical axis. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is an exploded perspective view of the rotation detection device and the water meter according to the embodiment. [Diagram 2] 1 is a cross-sectional view of a rotation detection device and a water meter. [Diagram 3] FIG. 2 is a block diagram showing an electrical configuration of the rotation detection device. [Figure 4] 1A is a top view of the optical element, and FIG. 1B is a bottom view of the optical element. [Diagram 5] 4(a) is a cross-sectional end view of the rotation detection device and the water meter, including a cross section of the optical element taken along line VV in FIG. [Figure 6] 6 is a cross-sectional end view of the rotation detection device and the water meter including a cross section of the optical element taken along line VI-VI in FIG. 4(a). [Figure 7] FIG. 2 is a schematic diagram showing an illumination area of ​​the rotation detection device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is an exploded perspective view of a rotation detection device 30 and a water meter 10 in one embodiment. Fig. 2 is a cross-sectional view of the rotation detection device 30 and the water meter 10. In the following description, the upper side of the paper in Figs. 1 and 2 refers to the upper side of the rotation detection device 30, etc., and the lower side of the paper in Figs. 1 and 2 refers to the lower side of the rotation detection device 30, etc.

[0021] The water meter 10 is a known instrument for measuring the flow rate of tap water. A rotation detection device 30 is detachably attached to the water meter 10 via a mounting fixture 20. The water meter 10 includes a piping section 11 through which tap water flows, a case 12 provided on the upper part of the piping section 11, and a measurement section 13 provided inside the case 12. Basically, tap water flows inside the piping section 11 from the upper left to the lower right in FIG. 1.

[0022] Case 12 is a cylindrical metal member, the lower end of which is connected to piping section 11 and the upper end of which is open. This upper opening is covered by cover 12a made of a transparent material such as glass or synthetic resin. Cover 12a is not shown in Fig. 1. The cross section of Fig. 2 is a cross section that includes the central axis of case 12 and is taken along the direction in which tap water flows through piping section 11.

[0023] Rectangular parallelepiped protrusions 12b protrude radially outward from each of the four sides of the outer circumferential surface of case 12. A lid 12c that opens and closes the opening at the top end of case 12 is attached to one of the four protrusions 12b.

[0024] The measuring unit 13 is a part that measures the flow rate of tap water flowing through the piping unit 11. On the upper surface of the measuring unit 13, a plurality of integrating counters and a water flow pilot 13a are provided so that the integrated value (measured value) of the flow rate can be visually confirmed through the cover 12a from the opening at the top end of the case 12. The water flow pilot 13a rotates when tap water is flowing through the piping unit 11.

[0025] Multiple accumulators include 100 liter (0.1 m 3The first counter 13b displays an integrated value in units of 10 liters, and the third counter displays an integrated value in units of 1 liter. The first counter 13b is a drum-type counter and can display an integrated value in units of 0 to 9999.9 m. 3 A number between is displayed.

[0026] The second counter includes a dial 13c on which numbers from 0 to 9 are marked clockwise together with a scale, and a needle-shaped rotating part 13d that rotates on the dial 13c. The tip of the needle of the rotating part 13d advances one scale clockwise for every 10 liters of flow rate, and the rotating part 13d makes one rotation at 100 liters.

[0027] The third counter includes a dial 13e on which numbers from 0 to 9 are marked clockwise along with a scale, and a needle-shaped rotating part 13f that rotates on the dial 13e. The tip of the needle of the rotating part 13f advances one scale clockwise for every 1 liter of flow rate, and the rotating part 13f makes one rotation at 10 liters. Note that the numbers and scales on the dials 13c and 13e are omitted from FIG. 1.

[0028] The mounting fixture 20 is a tool for mounting the rotation detection device 30 to the water meter 10, and is mainly made of metal. The mounting fixture 20 includes a cylindrical upper portion 21, an annular plate-shaped lower portion 22, a fixing portion 23 for fixing the lower portion 22 to the upper portion 21, and an attachment portion 24 for attaching the rotation detection device 30 to the upper portion 21.

[0029] The upper part 21 is a cylindrical member that covers the entire outer circumferential surface of the case 12. An upper end 21a of the upper part 21 is bent radially inward to form an annular plate, and is placed on the upper end of the case 12. The upper part 21 is provided with through holes 21b that penetrate in the radial direction on all four sides. The through holes 21b also open at the lower end of the upper part 21, and the protrusions 12b of the case 12 are housed in the through holes 21b.

[0030] The lower part 22 is formed in the shape of an annular plate coaxial with the upper part 21, and the upper part 21 fits onto the inner circumferential side of the lower part 22. A protruding part 22a that fits into a through hole 21b of the upper part 21 protrudes from the inner circumferential edge of the lower part 22. This protruding part 22a comes into contact with the lower surface of the protrusion 12b inside the through hole 21b, so that the case 12 is sandwiched vertically between the protruding part 22a and the upper end part 21a of the upper part 21.

[0031] The fixing portion 23 is an annular plate-shaped member for fixing the upper portion 21 and the lower portion 22 in a state in which the case 12 is sandwiched between them. The lower surface of the lower portion 22 is placed on the upper surface of the fixing portion 23, and a plurality of protruding plates 23a capable of contacting the outer periphery of the lower portion 22 protrude from the fixing portion 23. This restricts radial deviation between the fixing portion 23 and the lower portion 22. In addition, since the protruding plates 23a protrude from both the upper and lower surfaces of the fixing portion 23, the fixing portion 23 can be used upside down.

[0032] An internal thread 23b is formed on the inner peripheral edge of the fixing portion 23 to fit into an external thread 21c provided on the outer peripheral surface of the lower end side of the upper portion 21. By hooking a finger onto a hook portion 23c protruding radially from the outer peripheral edge of the fixing portion 23 and manually turning the fixing portion 23 to fit the internal thread 23b into the external thread 21c, the upper portion 21 and the lower portion 22 are fixed together with the case 12 sandwiched between them. As a result, the mounting fixture 20 is fastened and fixed to the water meter 10.

[0033] The fixed position between the upper part 21 and the lower part 22 can be adjusted in the vertical direction by the male thread 21c and the female thread 23b, and the through hole 21b is larger in the circumferential direction than the protrusion 12b. Therefore, the mounting fixture 20 can be attached to various water meters 10 having different sizes of the protrusions 12b.

[0034] The mounting portion 24 includes a cylindrical tube portion 24a formed coaxially with the upper portion 21, and an annular plate-like flange portion 24d extending vertically from the lower end of the tube portion 24a outward in the radial direction. A male thread 24b is formed on the outer circumferential surface of the tube portion 24a. The tube portion 24a is divided into approximately half a circumference by two notches 24c. The notches 24c are provided to extend to the inner circumferential side of the flange portion 24d.

[0035] Flange portion 24d has arc holes 24e that penetrate in the plate thickness direction and extend in the circumferential direction. Flange portion 24d is placed on the upper surface of upper end portion 21a, and the shanks of screws 25 inserted into arc holes 24e are fitted into screw holes 21d provided in upper end portion 21a, thereby fixing flange portion 24d to upper portion 21. Because arc holes 24e are arc-shaped about the axes of upper portion 21 and cylindrical portion 24a, the circumferential position of notch 24c relative to water meter 10 and upper portion 21 can be adjusted by loosening screws 25.

[0036] The rotation detection device 30 is attached to the water meter 10 by the mounting fixture 20, and is a device for reading the measurement value of the water meter 10 and transmitting the same to an external server or the like. The rotation detection device 30 includes a cylindrical lower case 31 that is inserted into the tube portion 24a of the mounting unit 24, and an upper case 32 that is connected to an upper portion of the lower case 31. Note that the internal structure of the upper case 32 is not shown in FIG. 2.

[0037] A rectangular parallelepiped protrusion 31a that fits into the cutout 24c of the mounting portion 24 protrudes from the outer circumferential surface of the lower case 31. A portion of the lower case 31 above the protrusion 31a is inserted into the inner circumferential side of a circular plate-shaped fixing ring 33. An internal thread 33a that fits into the external thread 24b of the mounting portion 24 is formed on the inner circumferential edge of the fixing ring 33.

[0038] The fixing ring 33 is manually rotated by hooking the hook portions 33b radially protruding from the outer periphery of the fixing ring 33 with fingers, and the female threads 33a are fitted into the male threads 24b. This brings the lower surface of the fixing ring 33 into contact with the upper surface of the protruding portions 31a, restricting the upward movement of the lower case 31 and the upper case 32 relative to the mounting fixture 20. Furthermore, since the protruding portions 31a are fitted into the cutout portions 24c, the circumferential rotation of the lower case 31 and the upper case 32 relative to the mounting fixture 20 is restricted. As a result of the above, the rotation detection device 30 is fixed to the mounting fixture 20, i.e., the rotation detection device 30 is attached to the water meter 10 via the mounting fixture 20.

[0039] Unless otherwise specified, the following describes the state in which the rotation detection device 30 is attached to the water meter 10. A seal member 34 is provided around the entire periphery of the lower end of the lower case 31 of the rotation detection device 30. This seal member 34 comes into close contact with the cover 12a of the water meter 10 around the entire periphery, sealing the gap between the rotation detection device 30 and the lower end of the lower case 31.

[0040] The internal space of the lower case 31 of the rotation detector 30 is divided by a partition wall 35 along the axial direction of the lower case 31 into a space facing the first counter 13b and a space facing the third counter (dial 13e and rotating portion 13f). The upper end of the space facing the first counter 13b is closed by a light-transmitting portion 36 made of a transparent material. The gap between the lower case 31 and the partition wall 35 and the light-transmitting portion 36 is sealed by a seal member 37 all around.

[0041] The upper case 32 connected to the lower case 31 has a through hole 32a that penetrates vertically at a position facing the light-transmitting portion 36. A cover 38 made of a transparent material and having a half-moon shaped hole is fitted into the upper end of this through hole 32a. Therefore, even when the rotation detection device 30 is attached to the water meter 10, the first counter 13b of the water meter 10 can be seen from above through the cover 38, the through hole 32a, and the light-transmitting portion 36.

[0042] Of the internal space of lower case 31, the space facing the third counter etc. is closed at the lower end by bottom plate 39, and a part of upper case 32 is inserted from the upper end side to close the upper end as well. A base plate 40 and an annular mounting member 41 that is superimposed on the upper surface of base plate 40 are attached to this bottom plate 39 in a state spaced apart upward from the bottom plate 39.

[0043] A rotation detection circuit 50 (see FIG. 3) for detecting the rotation of the rotating part 13f of the third counter is provided on the substrate 40. The rotation detection circuit 50 includes a light source 51 and light receiving elements 52a to 52c (see FIGS. 5 and 6). An optical element 60 for projecting the light beam R emitted from the light source 51 onto a predetermined range of the third counter is attached to the upper surface of the bottom plate 39 via a mounting member (not shown) and exposed on the lower surface of the bottom plate 39.

[0044] The mounting member 41 is a member for fixing the substrate 40 to the lower case 31. A part of the upper case 32 is inserted into the space facing the third counter or the like until the upper case 32 abuts against the upper end of the mounting member 41. The substrate 40 and the internal structure of the upper case 32 are electrically connected through the inner periphery of the mounting member 41. In addition, the gap between the outer periphery of the mounting member 41 and the lower case 31 and the partition wall 35 is sealed by the seal member 42 all around.

[0045] The surroundings of the substrate 40 and the optical element 60, and the upper surface side of the cover 12a of the water meter 10 are sealed spaces by the sealing members 34, 37, and 42. This makes it possible to prevent a decrease in the detection accuracy of the rotation of the third counter (rotating portion 13f) by the rotation detection device 30 due to adhesion of water, dust, etc. to the optical element 60 or the upper surface of the cover 12a. Although not shown, a moisture absorbent is provided in the sealed space. This makes it difficult for condensation to occur in the sealed space, and makes it possible to prevent a decrease in the detection accuracy of the rotation of the third counter due to the condensation.

[0046] Next, the electrical configuration of the rotation detection device 30 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the electrical configuration of the rotation detection device 30. The rotation detection device 30 includes a battery 43, a power supply circuit 44, a control circuit 45, a wireless communication circuit 46, a wireless communication antenna 47, and a rotation detection circuit 50, and each part is connected to each other. Note that all parts except the rotation detection circuit 50 are provided inside the upper case 32.

[0047] The battery 43 is for operating the rotation detection device 30 without connecting it to an external power source. The power supply circuit 44 is a circuit for converting the power input from the battery 43 into power suitable for output to the control circuit 45.

[0048] The control circuit 45 is a circuit for controlling the operation of each circuit 44, 46, 50, and outputs the power input from the power supply circuit 44 to the wireless communication circuit 46, the rotation detection circuit 50, etc. The wireless communication circuit 46 is a circuit for transmitting the detection results by the rotation detection circuit 50 to an external server, etc. via a wireless communication antenna 47. This makes it possible to remotely monitor the flow rate of the water meter 10 equipped with the rotation detection device 30.

[0049] Next, a method for detecting the rotation of the third counter by the rotation detection device 30 (rotation detection circuit 50) will be described with reference to Fig. 4(a) to Fig. 7. Fig. 4(a) is a top view of the optical element 60. Fig. 4(b) is a bottom view of the optical element 60. Fig. 5 is a cut-away end view of the rotation detection device 30 and the water meter 10, including a cross section of the optical element 60 taken along line VV in Fig. 4(a). Fig. 6 is a cut-away end view of the rotation detection device 30 and the water meter 10, including a cross section of the optical element 60 taken along line VI-VI in Fig. 4(a). Fig. 7 is a schematic diagram showing illumination areas Aa to Ac by the rotation detection device 30. Note that Figs. 5 and 6 show an enlarged view of the vicinity of the optical element 60.

[0050] 5 and 6, the rotation detection device 30 includes a single light source 51, three light receiving elements 52a, 52b, and 52c, and one optical element 60. The light source 51 and the light receiving elements 52a to 52c are provided on a substrate 40.

[0051] The light source 51 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 light beam R toward the dial 13e and rotating part 13f of the third counter. The light beam R diverges from the light source 51 toward the dial 13e, etc. The light beam R is symmetrical with respect to the optical axis O of the light source 51 (the central axis of the lens-shaped sealing resin).

[0052] The light intensity of the light beam R is maximum on the optical axis O and decreases radially outward from the optical axis O. The light beams of the light beam R at positions where the light intensity is half of the maximum value are shown by solid lines in Figs. 5 and 6. 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 light beam R in this embodiment is between 5 degrees and 30 degrees.

[0053] The light source 51 is disposed so that the optical axis O is perpendicular to the dial 13e. Here, the rotating part 13f rotates about a rotation axis 13g perpendicular to the dial 13e. The light source 51 is disposed so that the rotation axis 13g and the optical axis O are coaxial.

[0054] The light receiving elements 52a to 52c are elements that convert the light intensity of the light beam R (branched light beams Ra to Rc described later) incident thereon into an electric signal and output the signal. The light receiving elements 52a to 52c are configured to be able to detect the wavelength of the light beam R emitted from the light source 51. A filter that cuts wavelengths that can be detected by the light receiving elements 52a to 52c is provided on the surface of the light transmitting portion 36. This makes it possible to prevent sunlight, etc., incident on the dial 13e side from affecting the detection values ​​of the light receiving elements 52a to 52c.

[0055] The three light receiving elements 52a to 52c are disposed spaced apart from one another in the circumferential direction of the optical axis O. When viewed from above in the axial direction of the optical axis O as shown in Fig. 7, with the optical axis O as the reference, the light receiving element 52a is disposed on the upper side of the paper in Fig. 7, the light receiving element 52b is disposed on the left side, and the light receiving element 52c is disposed on the right side.

[0056] Furthermore, the light receiving elements 52b and 52c are disposed on the substrate 40 at positions rotated 90 degrees about the optical axis O with respect to the light receiving element 52a. Therefore, the light receiving elements 52a to 52c and the light source 51 may be disposed on the substrate 40 so that the optical axis O is located at the midpoint of the line segment connecting the light receiving elements 52b and 52c, and the light receiving element 52a is located on the perpendicular bisector to the line segment. Therefore, the positional accuracy of the light receiving elements 52a to 52c and the light source 51 on the substrate 40 can be easily ensured.

[0057] 4(a) to 6, the optical element 60 is a lens array made of a transparent material such as glass or synthetic resin, and is arranged on the optical axis O. The optical element 60 has a light source side surface 61 facing the light source 51 and the light receiving elements 52a to 52c, and an object side surface 62 facing the dial 13e and the rotating portion 13f.

[0058] The light source side surface 61 has three inner convex surfaces 63a, 63b, and 63c. The three inner convex surfaces 63a to 63c are in contact with one another in the circumferential direction of the optical axis O. The boundaries between the inner convex surfaces 63a to 63c intersect at a single center point O1. In this embodiment, this center point O1 is located on the optical axis O.

[0059] When viewed from above in the axial direction of optical axis O, inner convex surface 63a is disposed on the upper side of the paper in Fig. 4(a), inner convex surface 63b is disposed on the left side, and inner convex surface 63c is disposed on the right side with respect to optical axis O. The upper side, right side, and left side of the paper in Fig. 4(a) respectively correspond to the upper side, right side, and left side of the paper in Fig. 7. That is, inner convex surfaces 63a to 63c are provided at positions corresponding to light receiving elements 52a to 52c, respectively.

[0060] The inner convex surface 63a is a 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 62 (the rotating part 13f side). Similarly, the inner convex surface 63b is a 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 62. The inner convex surface 63c is a 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 62.

[0061] The central axes Ca to Cc are parallel to one another and to the optical axis O, and are disposed apart from one another in the radial direction. In addition, since the inner convex surfaces 63a to 63c are parts of an axially symmetric convex surface, it is easy to form the inner convex surfaces 63a to 63c.

[0062] Each of the inner convex surfaces 63a-63c having such a shape has a positive refractive power. Furthermore, the three inner convex surfaces 63a-63c are concave toward their boundaries. As a result, when the light beam R emitted from the light source 51 is incident on the inner convex surfaces 63a-63c at a position including the center point O1, it is split away from the boundaries between the inner convex surfaces 63a-63c and becomes three branched light beams Ra, Rb, and Rc.

[0063] That is, each of the branched ray bundles Ra to Rc is deflected radially outward from 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 substantially the same.

[0064] The branched ray bundle Ra is the ray bundle R that is incident on the inner convex surface 63a and tends to be focused toward the central axis Ca compared to the ray bundle R before it is incident. Similarly, the branched ray bundle Rb is the ray bundle R that is incident on the inner convex surface 63b 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 convex surface 63c and tends to be focused toward the central axis Cc.

[0065] The branched branched light beams Ra to Rc pass through the object side surface 62 and the cover 12a, and are projected onto the dial 13e which is the rotation locus of the rotating part 13f, illuminating the dial 13e. As shown in Fig. 7, an illumination area Aa which is the range illuminated by the branched light beam Ra is between the marks 0 and 9 on the dial 13e. An illumination area Ab by the branched light beam Rb is in the vicinity of the mark 7 on the dial 13e. An illumination area Ac by the branched light beam Rc is in the vicinity of the mark 2 on the dial 13e.

[0066] 5 and 6, when the rotating part 13f is located in the illumination area Ac, the branched light beams Ra and Rb specularly reflected by the dial 13e pass through the cover 12a and the object side surface 62 again, and further through the light source side surface 61, and are incident on the light receiving elements 52a and 52b individually. The light receiving element 52a is disposed at the position where the branched light beam Ra is incident, and the light receiving element 52b is disposed at the position where the branched light beam Rb is incident. Note that even when the branched light beam Rc is specularly reflected by the dial 13e, the light receiving element 52c is disposed at the position where the branched light beam Rc that has passed through the object side surface 62, the light source side surface 61, etc. is incident.

[0067] However, a part of the branched light beam Rc is reflected by the rotating part 13f, not by the dial 13e. The upper surface of the rotating part 13f is not parallel to the dial 13e, and is inclined downward toward the dial 13e as it moves radially outward. Therefore, the branched light beam Rc reflected by the rotating part 13f does not enter the light receiving element 52c. As a result, the detection value of the light receiving element 52c becomes smaller when the branched light beam Rc is reflected by the rotating part 13f, compared to when the entire branched light beam Rc is reflected by the dial 13e. Therefore, the rotation detection device 30 (rotation detection circuit 50) can detect that the rotating part 13f is located in the illumination area Ac when the detection value of the light receiving element 52c becomes smaller.

[0068] Similarly, when the detection value of light receiving element 52a becomes small, rotation detection device 30 can detect that rotating part 13f is located in illumination area Aa. When the detection value of light receiving element 52b becomes small, rotation detection device 30 can detect that rotating part 13f is located in illumination area Ab.

[0069] Furthermore, for example, when the rotation detector 30 detects that the rotating part 13f is located in the lighting area Aa, the lighting area Ac, the lighting area Ab, and the lighting area Aa in this order as the rotating part 13f rotates, it can determine that the rotating part 13f has rotated once clockwise. That is, the rotation detector 30 can detect the rotation direction and the number of rotations of the rotating part 13f by illuminating three places on the dial 13e and detecting the reflections from each of the lighting areas Aa to Ac individually with the light receiving elements 52a to 52c. In addition, the rotation speed of the rotating part 13f can also be detected from the time it takes to move through each of the lighting areas Aa to Ac.

[0070] According to such a rotation detection device 30, branched light beams Ra-Rc to be projected onto each of the three illumination areas Aa-Ac in order to detect the number of rotations, etc., can be projected from a single light source 51 by the inner convex surfaces 63a-63c of the optical element 60. As a result, compared to a case in which a plurality of light sources are provided to individually project light beams onto each of the illumination areas Aa-Ac, the single light source 51 can reduce the power consumption of the rotation detection device 30. In particular, since the rotation detection device 30 operates on the battery 43, the reduced power consumption can reduce the frequency of replacing the battery 43.

[0071] The light beam R from the light source 51 diverges and is incident on a relatively wide range of the inner convex surfaces 63a to 63c. The light beam R is divided by the inner convex surfaces 63a to 63c, and the divergence is weakened to become branched light beams Ra to Rc, which illuminate the illumination areas Aa to Ac of the dial 13e. This allows each of the illumination areas Aa to Ac to be widened in the circumferential direction and radial direction of the optical axis O, and the light intensity (illuminance) in the illumination areas Aa to Ac is ensured, and the light beam R that does not contribute to the detection of the rotation can be reduced. As a result, even if the size and position of the rotating part 13f in the water meter 10 vary, the rotating part 13f can be easily detected, and the light intensity of the light beam R from the light source 51 required for the detection can be weakened. This makes it easier to reduce the power consumption of the rotation detection device 30 and improves versatility. Furthermore, the ambient light caused by the light beam R that does not contribute to the detection can be suppressed, and the detection accuracy of the rotating part 13f by the rotation detection device 30 can be improved.

[0072] In particular, because the rotation detection device 30 is detachably attached to the water meter 10, the position of the rotating part 13f may vary with respect to the illumination areas Aa to Ac due to individual differences and types of water meters 10, installation errors on the water meter 10, etc. For example, during this installation, the circumferential position of the mounting part 24 with respect to the upper part 21 of the mounting fixture 20 is adjusted by visual inspection so that the optical axis O of the rotation detection device 30 and the rotation axis 13g of the water meter 10 are coaxial. However, there may be a slight misalignment between the optical axis O and the rotation axis 13g, causing the position of the rotating part 13f to be misaligned with respect to the illumination areas Aa to Ac. Even in such a case, the rotation detection device 30 can easily detect the rotating part 13f by widening the illumination areas Aa to Ac.

[0073] Since each of the inner convex surfaces 63a-63c is a part of a convex surface that slopes radially downward from the vertices V1a-V1c, the light beam R incident on each of the inner convex surfaces 63a-63c is refracted toward the central axes Ca-Cc, and the divergence of the light beam R is weakened in the circumferential and radial directions of the optical axis O. Therefore, the light intensity in the illumination areas Aa-Ac by each of the split branch light beams Ra-Rc can be improved, so that the detection values ​​of the light receiving elements 52a-52c can be ensured even if the light intensity of the light beam R emitted from the light source 51 is weak. Therefore, the power consumption of the rotation detection device 30 can be further reduced.

[0074] The light source 51 emits a light beam R with a half-maximum half angle 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 light beams Ra to Rc incident on the light receiving elements 52a to 52c via the optical element 60 can be further improved.

[0075] The full width at half maximum region of the light beam R emitted from the light source 51 is incident on the center point O1 (optical axis O) side of the vertices V1a to V1c of the inner convex surfaces 63a to 63c. This makes it possible to prevent coma aberration and the like from occurring in the branched light beams Ra to Rc.

[0076] 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 optical axis O direction. In this case, it is possible to make it more difficult for coma aberration and the like to occur in the branched ray bundles Ra to Rc. As a result, it is possible to easily obtain uniformity in light intensity for each of the illumination areas Aa to Ac onto which the branched ray bundles Ra to Rc are projected. As a result, it is possible to ensure the detection accuracy of the rotating part 13f by the rotation detection device 30.

[0077] Since the center point O1 where the boundaries of the inner convex surfaces 63a to 63c intersect is located on the optical axis O, the ray bundle R emitted from the light source 51 is deflected radially (outward in the radial direction) from the optical axis O and is divided 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 51 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 division can be made uniform to each other. This improves the detection accuracy of the rotating part 13f by the rotation detection device 30.

[0078] Furthermore, since the center point O1 is located on the optical axis O, which is coaxial with the rotation axis 13g, the branched light beams Ra to Rc split and deflected by the inner convex surfaces 63a to 63c can be easily guided outward in the radial direction of the rotation axis 13g. As a result, the branched light beams Ra to Rc can efficiently illuminate three locations on the dial 13e around the rotation axis 13g. As a result, the detection accuracy of the rotation detector 30 for the rotating part 13f can be further improved.

[0079] The branched light beams Ra to Rc that are split by the inner convex surfaces 63a to 63c and travel toward the dial 13e pass through an inner inclined surface 64 provided on the object side surface 62 of the optical element 60. The inner inclined surface 64 is provided on the back side of each of the inner convex surfaces 63a to 63c of the optical element 60.

[0080] The inner inclined surface 64 is a convex surface symmetrical about the optical axis O, and inclines toward the light source side surface 61 (light source 51) as it moves away from the optical axis O. Therefore, compared to a case where the portion corresponding to the inner inclined surface 64 is a plane perpendicular to the optical axis O, the branched light beams Ra to Rc passing through the inner inclined surface 64 toward the dial 13e can be refracted toward the optical axis O. This allows the light receiving elements 52a to 52c onto which the branched light beams Ra to Rc reflected from the dial 13e are incident, and each portion of the optical element 60 through which they pass (the outer inclined surface 65 and the outer convex surfaces 66a to 66c described later) to be disposed closer to the optical axis O. As a result, the vicinity of the optical element 60 of the rotation detection device 30 and the optical element 60 itself can be made smaller in the radial direction of the optical axis O.

[0081] The refractive power of the inner convex surfaces 63a-63c is adjusted with respect to the degree of divergence of the light beam R so that the branched light beams Ra-Rc projected onto the dial 13e through the inner convex surfaces 63a-63c and the inner inclined surface 64 become parallel light beams. Note that in this specification, a parallel light beam refers to a branched light beams Ra-Rc with a half-maximum angle of 4 degrees or less. In addition, the shape of the inner inclined surface 64 is set so that the branched light beams Ra-Rc are incident on the inner inclined surface 64 approximately perpendicularly, so that the refractive power of the inner inclined surface 64 has almost no effect on the half-maximum angle of the branched light beams Ra-Rc.

[0082] By making the branched light beams Ra-Rc parallel, the size of the illumination areas Aa-Ac illuminated by the branched light beams Ra-Rc and the light intensity within the illumination areas Aa-Ac can be made uniform even if the distance from the optical element 60 to the dial 13e varies. This makes it possible to suppress variation in the light intensity of the branched light beams Ra-Rc incident on the light receiving elements 52a-52c due to the variation, thereby suppressing a decrease in the detection accuracy of the rotation detection device 30 for the rotating part 13f.

[0083] An outer inclined surface 65 is provided on the object side surface 62 of the optical element 60, radially outward of the inner inclined surface 64. The branched light beams Ra to Rc split by the inner convex surfaces 63a to 63c are deflected radially outward of the optical axis O, and are therefore incident on the outer inclined surface 65 when reflected by the dial 13e.

[0084] The outer inclined surface 65 is a part of a convex surface symmetrical about the optical axis O, and inclines toward the light source side surface 61 as it moves away from the optical axis O. Therefore, the branched ray bundles Ra to Rc incident on the outer inclined surface 65 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 52a to 52c to be disposed close to the optical axis O and the light source 51 so that the branched ray bundles Ra to Rc that have passed through the outer inclined surface 65 are incident on the light-receiving elements 52a to 52c. As a result, the vicinity of the optical element 60 of the rotation detection device 30 can be made compact in the radial direction of the optical axis O.

[0085] The outer peripheral edge of the inner inclined surface 64 and the inner peripheral edge of the outer inclined surface 65 are connected by a connecting surface 67 that inclines toward the light source side surface 61 as it moves radially inward. In other words, the object side surface 62 is formed of a Fresnel lens surface. This makes it possible to reduce the thickness of the optical element 60 (the dimension in the axial direction of the optical axis O) compared to a case in which the inner inclined surface 64 and the outer inclined surface 65 are formed by a continuous convex surface.

[0086] The light source side surface 61 of the optical element 60 includes an outer convex surface 66a disposed on the opposite side of the center point O1 from the inner convex surface 63a and facing the light receiving element 52a, an outer convex surface 66b disposed on the opposite side of the center point O1 from the inner convex surface 63b and facing the light receiving element 52b, and an outer convex surface 66c disposed on the opposite side of the center point O1 from the inner convex surface 63c and facing the light receiving element 52c. As a result, each of the branched light beams Ra to Rc split by the inner convex surfaces 63a to 63c and reflected from the dial 13e passes through the outer convex surfaces 66a to 66c and enters the light receiving elements 52a to 52c.

[0087] Each of the outer convex surfaces 66a-66c has a positive refractive power. This allows each of the branched ray bundles Ra-Rc incident on the light receiving elements 52a-52c to be condensed by the outer convex surfaces 66a-66c. As a result, even if the light intensity of the ray bundle R emitted from the light source 51 is weak, the detection values ​​of the light receiving elements 52a-52c can be ensured, and the power consumption of the rotation detection device 30 can be further reduced.

[0088] More specifically, the outer convex surface 66a is a part of a convex surface that slopes radially downward from the apex V2a toward the object-side surface 62. The outer convex surface 66b is a part of a convex surface that slopes radially downward from the apex V2b toward the object-side surface 62. The outer convex surface 66c is a part of a convex surface that slopes radially downward from the apex V2c toward the object-side surface 62. This allows the outer convex surfaces 66a to 66c to condense each of the branched light beams Ra to Rc incident on the light-receiving elements 52a to 52c in the circumferential and radial directions of the optical axis O, thereby further reducing the power consumption of the rotation detection device 30. In addition, the outer convex surfaces 66a to 66c are parts of an axisymmetric convex surface with respect to an axis that passes through the apexes V2a to V2c and is parallel to the optical axis O, making it easier to form the outer convex surfaces 66a to 66c.

[0089] As shown in FIG. 4(a), in the axial view of the optical axis O, the center point O1, the vertex V1a of the inner convex surface 63a, and the vertex V2a of the outer convex surface 66a are aligned on a straight line. Similarly, the center point O1, the vertices V1b and V1c of the inner convex surfaces 63b and 63c, and the vertices V2b and V2c of the outer convex surfaces 66b and 66c are aligned on a straight line. As a result, in the axial view of the optical axis O, each of the branched beams Ra to Rc is aligned along the straight line. Therefore, by arranging the light receiving elements 52a to 52c at positions overlapping with the straight line in the axial view of the optical axis O, it is possible to easily make the branched beams Ra to Rc enter the light receiving elements 52a to 52c. That is, the positional relationship of each part for making the branched beams Ra to Rc enter the light receiving elements 52a to 52c can be easily determined.

[0090] 5 and 6, the focal points of the outer convex surfaces 66a-66c are located closer to the optical element 60 than the light receiving elements 52a-52c, and closer to the light receiving elements 52a-52c than half the distance from the vertices V2a-V2c to the light receiving elements 52a-52c. Therefore, when the branched light beams Ra-Rc made substantially parallel to the optical axis O by the outer inclined surface 65 pass through the outer convex surfaces 66a-66c, they are condensed at the focal points of the outer convex surfaces 66a-66c and then diverge slightly on the light receiving elements 52a-52c side. This makes it easier for the branched light beams Ra-Rc to be incident on the light receiving elements 52a-52c even if the light receiving elements 52a-52c are misaligned in the radial or circumferential direction of the optical axis O with respect to the outer convex surfaces 66a-66c due to an assembly error of the rotation detection device 30 or the like.

[0091] The optical element 60 has, in a single member, inner convex surfaces 63a-63c and inner inclined surface 64 (illumination means) that form branched beams Ra-Rc from the beam R and project them onto the dial 13e, and outer convex surfaces 66a-66c and outer inclined surface 65 (light-collecting means) that individually guide the branched beams Ra-Rc reflected from the dial 13e to the light-receiving elements 52a-52c. This makes it possible to make the rotation detection device 30 smaller and easier to assemble, compared to a case in which the illumination means and the light-collecting means are provided separately.

[0092] Although the above description is based on the above embodiment, the present invention is not limited to the above embodiment, and it can be easily assumed that various improvements and modifications are possible within the scope of the present invention. For example, the type and size of the light source 51 and the light receiving elements 52a to 52c may be appropriately changed. The light intensity of the light beam R emitted from the light source 51 is not limited to the case where it decreases with increasing distance from the optical axis O, and may be approximately constant in the vicinity of the optical axis O.

[0093] Also, for example, the inner inclined surface 64, the outer inclined surface 65, and the outer convex surfaces 66a-66c may be omitted, and the surfaces corresponding thereto may be flat surfaces perpendicular to the optical axis O. When both the outer inclined surface 65 and the outer convex surfaces 66a-66c are omitted, the branched light beams Ra-Rc reflected from the dial 13e do not need to be incident on the optical element 60. In this case, the light receiving elements 52a-52c may be disposed closer to the dial 13e than the optical element 60.

[0094] In the above embodiment, the case where three of each of the inner convex surfaces 63a-63c, the outer convex surfaces 66a-66c, and the light receiving elements 52a-52c are provided corresponding to each other has been described, but this is not necessarily limited to this. Four or more of each of these may be provided, and four or more points on the dial 13e may be illuminated with branched light beams that are divided into four or more beams. Even when four or more of the inner convex surfaces 63a-63c are provided, it is sufficient that the boundaries between all of the inner convex surfaces 63a-63c intersect at one center point O1.

[0095] In the above embodiment, the light receiving elements 52b and 52c are arranged at positions rotated 90 degrees around the optical axis O relative to the light receiving element 52a, and the inner convex surfaces 63a-63c and the outer convex surfaces 66a-66c are also arranged at 90 degrees offset from each other around the center point O1 (optical axis O) in a corresponding manner. However, this is not necessarily limited to this. The intervals between the light receiving elements 52a-52c, the inner convex surfaces 63a-63c, and the outer convex surfaces 66a-66c around the optical axis O or the center point O1 may be other than 90 degrees, for example, 120 degrees.

[0096] In the above embodiment, the rotation of the rotating part 13f of the third counter that displays the integrated value in 1-liter units in the water meter 10 is detected by the rotation detection device 30, but this is not necessarily limited to the above. For example, the rotation of the rotating part 13d of the second counter may be detected by the rotation detection device 30. Also, 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) may be detected by the rotation detection device 30. Furthermore, the rotation detection device 30 may be provided in an instrument having a rotating part that rotates around a rotation axis, and the rotation of the rotating part may be detected by the rotation detection device 30, not limited to an instrument.

[0097] The rotation detection device 30 may be provided not only in devices with a rotating part that rotates once, but also in devices (such as an automobile speedometer) with a rotating part that rotates back and forth within a predetermined range, and the rotation of the rotating part may be detected by the rotation detection device 30. When the rotation detection device 30 is provided in a speedometer, the position where the dial is illuminated by the branched light beams can be subdivided, so that the position of the rotating part can be detected by the rotation detection device 30, and the speed of the automobile can be calculated from that position.

[0098] Furthermore, the rotation detection device 30 is not limited to being detachably attached to an apparatus such as the water meter 10 by the mounting fixture 20, but may also be built into an apparatus such as the water meter 10. In this case of being built-in or depending on the type of apparatus, 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 instead of the dial 13e, or there may be neither the dial 13e nor the incident surface. The method of detecting the rotating part by the rotation detection device 30 may be changed as appropriate depending on the type of rotating part and the presence or absence of the dial 13e, etc.

[0099] For example, the rotation detector 30 may be configured to vary the detection values ​​of the light receiving elements 52a-52c when the branched light beams Ra-Rc are incident on the incident surface and when they are incident on the rotating part by making the degree of scattering or light absorption (regular reflectance) different between the incident surface (including the dial 13e) and the rotating part, and to detect the rotation of the rotating part from these variations. Alternatively, the rotating part may be configured as a through hole provided on the incident surface, and the rotation of the rotating part may be detected based on the fact that the branched light beams Ra-Rc are not reflected by the rotating part and are not incident on the light receiving elements 52a-52c. Conversely, the light receiving elements 52a-52c may be provided at positions where the branched light beams Ra-Rc that have passed through the through hole are incident, and the rotation of the rotating part may be detected.

[0100] Furthermore, when there is neither the dial 13e nor the incidence surface, the rotation detector 30 may be configured such that the optical element 60 (inner convex surfaces 63a-63c) is disposed between the light source 51 and the light receiving elements 52a-52c, and the detection values ​​of the light receiving elements 52a-52c are smaller when the branched light beams Ra-Rc enter the rotating part than when they pass through the rotation locus of the rotating part. Furthermore, the branched light beams Ra-Rc may be configured such that the reflected branched light beams Ra-Rc enter the light receiving elements 52a-52c only when they are reflected by the rotating part. In either case, the detection values ​​of the light receiving elements 52a-52c vary depending on whether the branched light beams Ra-Rc enter the rotating part, and the rotation of the rotating part can be detected from these variations.

[0101] In the above embodiment, the inner convex surfaces 63a-63c are axially symmetrical 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 convex surfaces 66a-66c are not limited to being part of an axially symmetrical convex surface that slopes downward radially from the vertices V2a-V2c. For example, the inner convex surfaces 63a-63c and the outer convex surfaces 66a-66c may be formed of Fresnel lens surfaces. Furthermore, the inner convex surfaces 63a-63c and the outer convex surfaces 66a-66c may be part of a non-axially symmetrical convex surface such as a cylindrical surface or a toric surface, or may be free curved surfaces.

[0102] In the above embodiment, the inner inclined surface 64 and the outer inclined surface 65 are at least a part of a convex surface symmetrical about the optical axis O, but the present invention is not limited to this. The inner inclined surface 64 and the outer inclined surface 65 may be configured, for example, as at least a part of a conical surface or a pyramidal surface as long as they are inclined toward the light source side surface 61 as they move away from the optical axis O. The inner inclined surface 64 and the outer inclined surface 65 may be provided at a position on the object side surface 62 through which the branched light beam bundles Ra to Rc pass, and may be provided intermittently in the circumferential direction of the optical axis O. Furthermore, the connecting surface 67 may be omitted, and the inner inclined surface 64 and the outer inclined surface 65 may be formed by a continuous surface. The inner inclined surface 64 and the outer inclined surface 65 may be configured by a Fresnel lens surface. [Explanation of symbols]

[0103] 10 Water meters (equipment, gauges) 13e dial 13f Rotating section 13g Rotating shaft 30 Rotation detection device 51 Light source 52a~52c Photodetector 60 Optical Elements 61 Light source side 62 Object side 63a~63c Inner convex surface 64 Inner inclined surface 65 Outer slope 66a~66c Outer convex surface O optical axis O1 center point R ray flux Ra~Rc Branched ray bundle V1a~V1c Vertex of the inner convex surface

Claims

1. A rotation detection device provided in a device having a rotating part that rotates around a rotation axis, A single light source that emits a diverging light beam toward the rotating part; Three or more light receiving elements for detecting incident light; a lens array having a light source side surface facing the light source and an object side surface facing the rotating portion; The light source side surface includes three or more inner convex surfaces that are in contact with each other in a circumferential direction centered on the optical axis of the light source, are recessed toward each other's boundaries, and each of the boundaries intersect at a single center point, each of the inner convex surfaces has positive optical power; the light beam emitted from the light source is incident on three or more of the inner convex surfaces at a position including the center point, and is thereby split into three or more branched light beams, and the branched light beams are projected toward a rotation locus of the rotating part, A rotation detection device, characterized in that the three or more light receiving elements are arranged at positions where each of the branched light beams projected onto the rotation locus is individually incident thereon.

2. The device is an instrument in which the needle-shaped rotating part rotates on a dial, 2. The rotation detection device according to claim 1, wherein the rotation detection device is detachably attached to the instrument, projects the branched light beams split by the inner convex surface onto the dial, and causes each of the branched light beams reflected by the dial to be individually incident on the light receiving element.

3. 3. The rotation detector according to claim 1, wherein each of said inner convex surfaces is a part of a convex surface that slopes radially downward from an apex.

4. 4. The rotation detection device according to claim 3, wherein a full width at half maximum region of said light beam is incident on three or more of said inner convex surfaces on the side of said center point relative to said vertices.

5. the light receiving element is disposed on the light source side with respect to the lens array at a position where the branched light beam reflected from the rotating portion side is incident, the light source side surface includes three or more outer convex surfaces provided at positions facing the light receiving elements individually, 3. A rotation detector according to claim 1, wherein each of said outer convex surfaces has a positive refractive power.

6. 3. The rotation detection device according to claim 1, wherein the branched light beams that pass through the inner convex surface and the object side surface and are projected onto the rotation locus are parallel light beams.

7. 3. The rotation detection device according to claim 1, wherein the central point is located on the optical axis.

8. 8. The rotation detection device according to claim 7, wherein the rotation detection device is provided on the equipment so that the optical axis is coaxial with the rotation axis.

9. the light receiving element is disposed on the light source side with respect to the lens array at a position where the branched light beam reflected from the rotating portion side is incident, 3. The rotation detection device according to claim 1, wherein the object side surface is provided radially outward of the optical axis relative to the back sides of the inner convex surfaces, and comprises an outer inclined surface that inclines toward the light source as it moves away from the optical axis in the radial direction.

10. 3. The rotation detection device according to claim 1, wherein the object side surface is provided on the back side of each of the inner convex surfaces and includes an inner inclined surface that inclines toward the light source as it moves away from the optical axis in the radial direction.

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