JP2014238383A - Water drop detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water drop detection sensor which has uniform detection sensitivity and for which an area of a detection region is secured.SOLUTION: A water drop detection sensor (100) comprises; a light-emitting element (10) emitting detection light; a refraction part (30) refracting detection light and causing the detection light to enter a transparent plate; a light receiving element (70) receiving the detection light totally reflected on a boundary face between an outer face of the transparent plate and the air; and a detection part (90) detecting a water droplet attached on an outer face of the transparent plate by detecting an increase and decrease of the detection light entering the light receiving element. The refraction part has a plurality of divided incidence planes (31b, 32b) that are aligned from the light-emitting element toward the light receiving element on an inner surface of the transparent plate. A distance connecting each of the plurality of incidence planes and the light-emitting element is set so as to uniformize the intensity of the detection light entering each of the plurality of incidence planes.

Description

  The present invention includes a light emitting element that irradiates a transparent plate with detection light, a refracting portion that refracts the detection light, a light receiving element that receives the detection light reflected at the interface between the outer surface of the transparent plate and air, It is related with the water-drop detection sensor which has a detection part which detects the increase / decrease in the detection light which injects into water, and detects the water droplet adhering to the outer surface of a transparent plate.

  Conventionally, as disclosed in, for example, Patent Document 1, a light emitting element that irradiates light from the light emitting element on the inner wall side of the windshield and a light receiving element that measures light reflected by the windshield, A raindrop detection device that detects the amount of raindrops adhering to a wall surface has been proposed. This raindrop detection device has a light guide mounted on the inner wall side of the windshield. The light guide has a plurality of incident-side inclined surfaces that transmit light from the light-emitting element, and an incident-side step surface that connects ends of adjacent incident-side inclined surfaces.

Japanese Patent No. 4215553

  By the way, in the raindrop detection apparatus disclosed in Patent Document 1, a first lens that makes incident light parallel light is formed on the incident-side inclined surface. The first lens has an incident-side divided plano-convex lens obtained by dividing one plano-convex lens into a plurality of pieces. The dividing surface of the incident side divided plano-convex lens is disposed along the optical axis of the incident side divided plano-convex lens.

  However, the split surface of the incident side split plano-convex lens is not arranged so that the light intensity of the light emitting element incident thereon is uniform. Therefore, the intensity of light incident on each of the split surfaces of the incident side split plano-convex lens is non-uniform. Therefore, the intensity of the light that is refracted by the incident side split plano-convex lens and irradiates the outer surface of the windshield where raindrops adhere is also uneven, and the detection sensitivity of the light irradiation area (raindrop detection area) on the outer surface of the windshield Becomes uneven. As a result, there is a problem that the detection sensitivity is lowered in a specific region, and the area of the detection region cannot be sufficiently secured.

  In view of the above problems, an object of the present invention is to provide a water droplet detection sensor in which the detection sensitivity is uniform and the area of the detection region is ensured.

  In order to achieve the above object, the present invention comprises a light emitting element (10) that irradiates detection light toward the inner surface (110a) of the transparent plate (110), and refracts the detection light so as to enter the transparent plate. The refraction part (30) that totally reflects at the interface between the outer surface (110b) of the transparent plate and the air, and the total reflection at the interface between the outer surface of the transparent plate and the air, and the detection light emitted from the transparent plate is received. A light receiving element (70) and a detection unit (90) for detecting water droplets adhering to the outer surface of the transparent plate by detecting an increase or decrease in detection light incident on the light receiving element due to water droplets adhering to the outer surface of the transparent plate; The refraction part has a plurality of incident surfaces (31b, 32b) as incident surfaces on which detection light is mainly incident, and the plurality of divided incident surfaces are transparent. Projection part of light emitting element and light receiving element on inner surface of plate The plurality of incident surfaces, the light emitting elements, and the light emitting elements are arranged between the light emitting elements and the light receiving elements, and the intensity of the detection light incident on each of the plurality of incident surfaces is uniform. The distance connecting is set.

  As described above, according to the present invention, detection light having a uniform intensity is incident on each of the plurality of incident surfaces (31b, 32b). Therefore, the intensity of the detection light that is refracted by the incident surfaces (31b, 32b) and irradiates the outer surface (110b) of the transparent plate (110) to which water droplets adhere is uniform. Thereby, the detection sensitivity of the detection light irradiation region (water droplet detection region) on the outer surface (110b) of the transparent plate (110) becomes uniform. And it is suppressed that a detection sensitivity falls in a specific area | region, and it becomes suppressed that the area of a detection area | region becomes narrow. As a result, the area of the detection region is ensured.

It is sectional drawing which shows schematic structure of the water droplet detection sensor which concerns on 1st Embodiment. It is a conceptual diagram for showing the separation distance from the light emitting element in az direction. It is a graph which shows the light intensity of detection light. It is a graph which shows the optical relative intensity of detection light. It is sectional drawing for demonstrating a refractive part. It is a top view which shows the shape of the xy plane of the refractive part seen from the white arrow shown in FIG. It is sectional drawing of the refractive part in the yz plane for demonstrating an entrance plane. It is sectional drawing of the refractive part in the yz plane which shows the modification of an entrance plane. It is sectional drawing of the refractive part in the yz plane which shows the modification of an entrance plane. It is sectional drawing which shows the modification of a refractive part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
Based on FIGS. 1-7, the water droplet detection sensor which concerns on this embodiment is demonstrated. In addition, in FIG. 5, the connection part 60 and the film 61 which are mentioned later are abbreviate | omitted.

  In the following, the three directions that are orthogonal to each other are referred to as an x direction, a y direction, and a z direction. A plane defined by the x direction and the y direction is an xy plane, a plane defined by the y direction and the z direction is a yz plane, and a plane defined by the z direction and the x direction is z−. Shown as x-plane. The x direction is the “direction from the light emitting element to the light receiving element” and the y direction is “the direction perpendicular to both the direction from the light emitting element to the light receiving element and the height direction” and the z direction is “ This corresponds to the “height direction perpendicular to the outer surface of the transparent plate”.

  As shown in FIG. 1, the water droplet detection sensor 100 includes a light emitting element 10, a refracting unit 30, a light collecting unit 50, a light receiving element 70, and a detecting unit 90. The light emitting element 10 and the light receiving element 70 are separated from each other in the x direction, and the refraction part 30 and the light collecting part 50 are located therebetween. As indicated by solid line arrows and broken line arrows in FIG. 1, detection light is irradiated from the light emitting element 10 toward the inner surface 110 a of the transparent plate 110, and the detection light is incident on the refraction part 30. The detection light is refracted by the refracting unit 30 and enters the transparent plate 110. Then, the detection light is reflected at the interface between the outer surface 110 b of the transparent plate 110 and the air (hereinafter simply referred to as the interface) and is emitted from the inner surface 110 a of the transparent plate 110. The detection light emitted from the inner surface 110 a enters the light collecting unit 50 and is collected by the light collecting unit 50. Then, the collected detection light is incident on the light receiving element 70. The detection light is converted into an electrical signal corresponding to the amount of light by the light receiving element 70, and the electrical signal is input to the detection unit 90.

  If no water droplets are attached to the outer surface 110b, the amount of detection light reflected at the interface is the largest. For this reason, the output of the electrical signal converted by the light receiving element 70 is the largest. However, if a water droplet is attached to the detection light irradiation region (water droplet detection region) on the outer surface 110b, the detection light that is normally reflected at the interface is not reflected at the interface but is transmitted to the outside. Therefore, the amount of detection light reflected at the interface is reduced, and the output of the electrical signal converted by the light receiving element 70 is also reduced. As described above, the detection light incident on the light receiving element 70 increases or decreases according to the adhesion of water droplets on the outer surface 110b, and the electrical signal output from the light receiving element 70 to the detection unit 90 increases or decreases accordingly. Therefore, the detection unit 90 detects the presence or absence of water droplets adhering to the outer surface 110b and the amount of adhesion thereof by detecting the increase or decrease of the electrical signal input to itself.

  The water droplet detection sensor 100 includes a case 91, a fixing member 92, a wiring board 93, a connecting portion 60, and a film 61 in addition to the above-described components 10 to 90. The components 10 to 90 are accommodated in the case 91. The case 91 has a box shape having one opening, and the opening is closed by the inner surface 110 a of the transparent plate 110. A wiring substrate 93 on which the elements 10 and 70 and the detection unit 90 are mounted is provided on the inner surface of the case 91 via a fixing member 92. In addition, a connecting portion 60 that integrally connects the refracting portion 30 and the light collecting portion 50 is provided via a film 61 in a region of the inner surface 110 a that closes the opening of the case 91.

  The connecting portion 60 is provided in a plate shape, and has one surface to which the refracting portion 30 and the light collecting portion 50 are fixed, and a back surface that is opposite to the one surface and contacts the film 61. Further, the connecting part 60 is made of glass, like the refracting part 30 and the light collecting part 50.

  The film 61 has adhesiveness to fix the refraction part 30, the light collecting part 50, and the connecting part 60 to the transparent plate 110, and is interposed between the transparent plate 110 and the connecting part 60. The film 61 has one surface that contacts the inner surface 110 a of the transparent plate 110 and a back surface that is opposite to the one surface and contacts the connecting portion 60. The film 61 may have a refractive index with little reflection loss at the interface with the connecting portion 60 and the interface with the transparent plate 110. Specifically, the film 61 has a refractive index close to that of the connecting portion 60 and the transparent plate 110. The film 61 according to the present embodiment is made of a silicon sheet having the above adhesiveness and refractive index.

  The light emitting element 10 emits detection light having directivity characteristics. The light emitting element 10 according to this embodiment is an LED, and one surface 10a of the light emitting element 10 is fixed to the transparent plate 110 side of the wiring board 93, and the back surface thereof is a light emitting surface 10b. Detection light having an elliptical directivity indicated by a two-dot chain line in FIG. 1 is emitted from the light emitting surface 10b, but the intensity decreases as the distance from the light emitting surface 10b increases. More specifically, the intensity of the detection light falls in inverse proportion to the square of the distance from the light emitting surface 10b.

  As shown in FIGS. 3 and 4, when the planes along the xy plane that are intermittently separated from the light emitting element 10 in the z direction are A, B, and C planes, as shown in FIGS. The intensity of the detection light changes depending on the separation intensity from 10. 3 and 4, the curve indicated by the solid line is the A plane, the curve indicated by the broken line is the B plane, and the curve indicated by the alternate long and short dash line is the intensity of the detection light corresponding to the C plane. The vertical axis in FIG. 3 indicates the light intensity, and the unit is an arbitrary unit. The vertical axis | shaft shown in FIG. 4 shows the light relative intensity | strength on the basis of the value with the highest light intensity, and a unit is%. 3 and 4 indicate the distance from the light emitting element 10 in one direction along the xy plane, and the unit is mm.

  As shown in FIG. 3, the intensity of the detection light decreases from the A surface to the B surface and from the B surface to the C surface. As indicated by solid arrows in FIG. 4, the detection light spreads in one direction along the xy plane from the A plane to the B plane and from the B plane to the C plane. Therefore, the intensity of the detection light emitted from the light emitting element 10 decreases as it approaches the inner surface 110a from the light emitting element 10, and decreases as it approaches the light receiving element 70 side.

  The refracting unit 30 refracts the detection light so that the detection light incident on the transparent plate 110 is totally reflected at the interface. The transparent plate 110 is made of glass. When the incident angle from the transparent plate 110 to the interface is approximately 40 ° or more, the detection light is totally reflected at the interface. Therefore, the refracting unit 30 according to the present embodiment refracts the detection light so that the detection light enters the interface at an incident angle of 45 °. In the following, the direction along the detection light having an incident angle of 45 ° is referred to as a total reflection direction. Incidentally, in the drawing shown in FIG. 5, the incident angle is the counterclockwise direction from the reference line to the detection light among the angles formed by the reference line along the z direction indicated by the alternate long and short dash line and the detection light indicated by the broken line. An acute angle is shown.

  As shown in FIG. 1, the refracting portion 30 is located between the projected portion of the light emitting element 10 and the projected portion of the light receiving element 70 along the z direction on the inner surface 110a. As shown in FIGS. 5 and 6, the refracting section 30 is divided into a plurality of parts, and includes a plurality of first refracting lenses 31 and second refracting lenses 32. The plurality of refractive lenses 31 and 32 are arranged from the light emitting element 10 toward the light receiving element 70 in the x direction so that the second refractive lens 32 is positioned closer to the light receiving element 70 than each of the plurality of first refractive lenses 31. It is out.

  Each of the plurality of refractive lenses 31 and 32 includes inclined surfaces 31a and 32a that are inclined along the total reflection direction, and incident surfaces 31b and 32b that are connected to the inclined surfaces 31a and 32a and on which detection light is mainly incident. Have. And the distance which connects each of the some incident surfaces 31b and 32b and the light emitting element 10 is set so that the intensity | strength of the detection light which injects into each of the some incident surfaces 31b and 32b may become uniform. The distance is determined based on the intensity distribution of the detection light shown in FIGS. Specifically, when considering a plurality of incident surfaces 31b and 32b arranged in the x direction, the respective heights of the plurality of refractive lenses 31 and 32 formed from the incident surfaces 31b and 32b in the z direction are light emitting elements. As the distance from 10 approaches the light receiving element 70, it gradually increases. Thereby, the intensity | strength of the detection light which injects into each of the several entrance planes 31b and 32b is uniform.

  As shown in FIG. 6, each of the plurality of refractive lenses 31 and 32 has a symmetrical shape via a symmetric line indicated by a one-dot chain line. The width (the length in the y direction) of each of the plurality of refractive lenses 31 and 32 may be determined based on the relative position with respect to the light emitting element 10 and the intensity distribution of the detection light shown in FIGS. good. For example, the widths of the refractive lenses 31 and 32 may be gradually increased as the distance from the light emitting element 10 in the x direction is increased.

  Each of the incident surfaces 31b and 32b is curved so as to be convex toward the light emitting element 10 in the total reflection direction, and the detection light incident on the refractive lenses 31 and 32 has the same inclination as that of each of the inclined surfaces 31a and 32a. Refracted to an angle (45 °). Specifically, each of the incident surfaces 31b and 32b has a hyperboloid shape.

  As shown in FIGS. 1 and 5, the inclined surface 31 a of the first refractive lens 31 located on the light emitting element 10 side among the two first refractive lenses 31 adjacent to each other is located on the light receiving element 70 side. The first refraction lens 31 is connected to the incident surface 31b. The inclined surface 31 a of the first refractive lens 31 adjacent to the second refractive lens 32 is connected to the incident surface 32 b of the second refractive lens 32. In addition, the inclined surface 31a of the first refractive lens 31 adjacent to the second refractive lens 32 is a principal axis along the total reflection direction among the axes connecting the light emitting element 10 and the transparent plate 110 (a line indicated by a broken line arrow in FIG. 5). ).

  The plurality of divided incident surfaces 31b and 32b are arranged in the y direction in addition to the x direction. Specifically, as shown in FIG. 7, the incident surfaces 31b and 32b are divided into five so as to be formed side by side in the y direction. The central portion of the incident surfaces 31b and 32b has a lower height in the z direction than the annular portion located outside of itself. In addition, the annular part adjacent to the central part has a lower height in the z direction than the annular part located on the outermost side. The curved surface shape of each of these five parts is a hyperboloid shape. The broken line shown in FIG. 7 has shown the notch which arises because height was provided in the entrance planes 31b and 32b.

  The condensing part 50 condenses the detection light reflected from the interface and emitted from the transparent plate 110 onto the light receiving element 70. As shown in FIG. 1, the condensing unit 50 includes a condensing lens 51 that is divided into a plurality of parts. It is located between 70 projection parts. Each of the plurality of condenser lenses 51 has the same height in the z direction, and is equal to or less than the height of the second refractive lens 32 having the highest height in the z direction among the plurality of refractive lenses 31 and 32. Yes. The condensing unit 50 and the refraction unit 30 are made of the same material (glass), and are integrally formed via the connecting unit 60. And the condensing part 50 and the refraction | bending part 30 are arrange | positioned so that it may become symmetrical via the central axis CA (dot-dash line shown in FIG. 1) of the water droplet detection sensor 100 in the x direction.

  The light receiving element 70 converts detection light into an electrical signal. The electrical signal converted by the light receiving element 70 is input to the detection unit 90. As shown in FIG. 1, one surface 70a of the light receiving element 70 is fixed to the surface of the wiring board 93 on the transparent plate 110 side, and the back surface thereof is the light receiving surface 70b. Detection light that is totally reflected at the interface and collected by the light collecting unit 50 is incident on the light receiving surface 70b.

  The detection unit 90 detects water droplets adhering to the outer surface 110b by detecting increase / decrease of detection light incident on the light receiving element 70 due to water droplets adhering to the outer surface 110b of the transparent plate 110. As described at the beginning, if a water droplet adheres to the outer surface 110b, the output of the electrical signal input to the detection unit 90 increases or decreases accordingly. The detection unit 90 stores the output value (expected value) of the electric signal input to itself when nothing is attached to the outer surface 110b, and how much the electric signal is output from the stored expected value. Detects if has fallen. By doing so, the detection unit 90 detects the presence or absence of water droplets and the amount of water droplets.

  Next, the effect of the water droplet detection sensor 100 according to the present embodiment will be described. As described above, detection light with uniform intensity is incident on each of the plurality of incident surfaces 31b and 32b. Therefore, the intensity of the detection light that is refracted by the plurality of incident surfaces 31b and 32b and irradiates the outer surface 110b of the transparent plate 110 to which water droplets adhere is uniform. Thereby, the detection sensitivity of the detection light irradiation region (water droplet detection region) on the outer surface 110b becomes uniform. And it is suppressed that a detection sensitivity falls in a specific area | region, and it becomes suppressed that the area of a detection area | region becomes narrow. As a result, the area of the detection region is ensured.

  As described above, the plurality of divided incident surfaces 31b and 32b are arranged in the y direction in addition to the x direction. That is, the incident surfaces 31b and 32b of the refracting unit 30 are three-dimensionally divided. And the distance which connects self and the light emitting element 10 is set so that the intensity | strength of the detection light which injects into several divided entrance surfaces 31b and 32b may become uniform. According to this, it is suppressed that the intensity | strength of the detection light which injects into each of several incident surface 31b and 32b becomes non-uniform | heterogenous. As a result, the detection sensitivity of the water droplet detection region becomes more uniform, and the area of the detection region is further secured.

  The refracting unit 30 includes a plurality of first refracting lenses 31 and one second refracting lens 32 having a larger physique than each of the plurality of first refracting lenses 31. Each of the plurality of refractive lenses 31 and 32 includes inclined surfaces 31a and 32a inclined along the total reflection direction, and incident surfaces 31b and 32b connected to the inclined surfaces 31a and 32a, on which detection light is mainly incident. Have. The inclined surface 31a of the first refractive lens 31 adjacent to the second refractive lens 32 is a principal axis (a line indicated by a one-dot chain line in FIG. 5) along the total reflection direction among the axes connecting the light emitting element 10 and the transparent plate 110. ).

  When there are a plurality of second refraction lenses 32, the incident angle of the detection light incident on each of the plurality of second refraction lenses 32 is wider than the total reflection direction. That is, it becomes wider than the inclination angle of the inclined surface 32a. Therefore, in the direction from the light emitting element 10 to the second refractive lens 32, the incident surface 32b of the second refractive lens 32 adjacent to each other and positioned on the light emitting element 10 side and the inclination of the second refractive lens 32 positioned on the light receiving element 70 side. The surface 32a overlaps, and a blind spot where no detection light is incident on the inclined surface 32a is generated. On the other hand, in the present embodiment, as described above, one second refractive lens 32 is provided. Accordingly, the generation of blind spots in the second refractive lens 32 is suppressed.

  Each of the plurality of condenser lenses 51 has the same height in the z direction, and is equal to or less than the height of the second refractive lens 32 having the highest height in the z direction among the plurality of refractive lenses 31 and 32. Yes. According to this, an increase in the physique of the water droplet detection sensor 100 is suppressed as compared with a configuration in which each of the plurality of condensing lenses 51 is higher than the second refractive lens 32.

  The condensing part 50 and the refracting part 30 are made of the same material and are integrally formed via the connecting part 60. According to this, the increase in the number of parts is suppressed and the mounting of the condensing unit 50 and the refracting unit 30 on the transparent plate 110 is simplified as compared with a configuration in which the condensing unit 50 and the refracting unit 30 are separate. It becomes. Therefore, the manufacturing cost is reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In this embodiment, the example in which the light emitting element 10 is LED was shown. However, the light emitting element 10 is not limited to the above example, and any light emitting element can be used as long as it emits light.

  In the present embodiment, an example has been described in which the refracting unit 30 refracts the detection light so that the detection light enters the interface at an incident angle of 45 °. However, the angle at which the refracting unit 30 refracts is not limited to the above example, and may be an angle at which the detection light is totally reflected at the interface. For example, 50 ° can be employed.

  In the present embodiment, an example in which each of the incident surfaces 31b and 32b is curved to be convex toward the light emitting element 10 in the total reflection direction is shown. However, the shapes of the incident surfaces 31b and 32b are not limited to the above example. For example, the shapes of the incident surfaces 31b and 32b facing the total reflection direction may be employed.

  In the present embodiment, as an example in which the distances between the light incident elements 10 and the plurality of incident surfaces 31b and 32b are set so that the intensity of the detection light incident on the respective incident surfaces 31b and 32b is uniform. The configuration shown in FIG. 7 was shown. However, the configuration in which the distance connecting each of the incident surfaces 31b and 32b and the light emitting element 10 is set is not limited to the above example. For example, the configuration shown in FIGS. 8 and 9 may be employed. In the modification shown in FIGS. 8 and 9, the incident surfaces 31b and 32b are divided into three in the y direction, and the central portion of the incident surfaces 31b and 32b is in the z direction as compared with the annular portion located outside of itself. The height at is low.

  In FIG. 8, the central portion has a flat shape along the xy plane, and in FIG. 9, the central portion is curved so as to be concave toward itself in the incident direction connecting itself and the light emitting element 10. ing. Needless to say, the incident surfaces 31b and 32b of the refracting unit 30 may be divided into a plurality of parts at least in the x direction. That is, it is possible to adopt a configuration that is divided only in the x direction and not divided in the y direction.

  In the present embodiment, the refracting unit 30 includes a plurality of first refractive lenses 31 and one incident surface 32b, and one second refractive lens 32 having a larger physique than each of the plurality of first refractive lenses 31; An example consisting of However, as shown in FIG. 10, the refracting unit 30 may include a plurality of first refracting lenses 31 and a single second refracting lens 32 having a plurality of incident surfaces 32 b. Although not shown, the refracting unit 30 may be composed of only the plurality of first refractive lenses 31.

  In this embodiment, the condensing part 50 showed the example which consists of the condensing lens 51 divided | segmented into plurality. However, the condensing unit 50 may include one condensing lens 51.

  In the present embodiment, an example in which the height in the z direction of each of the plurality of condenser lenses 51 is the same is shown. However, the height of each of the plurality of condenser lenses 51 may be different.

  In the present embodiment, an example in which the height of each of the plurality of condenser lenses 51 is equal to or less than the height of the second refractive lens 32 having the highest height has been described. However, the height of each of the plurality of condenser lenses 51 can be determined without depending on the height of the second refractive lens 32 or the height of the first refractive lens 31.

  In the present embodiment, the example in which the light collecting unit 50 and the refraction unit 30 are made of the same material (glass) and are integrally formed via the connection unit 60 is shown. However, the condensing part 50 and the refractive part 30 may be formed separately or may be formed of different materials.

  In the present embodiment, an example in which the detection unit 90 is mounted on the wiring board 93 and provided in the case 91 is shown. However, the detection unit 90 may not be mounted on the wiring board 93 and may not be provided in the case 91.

  In the present embodiment, an example in which the refracting portion 30 is formed by a plurality of refracting lenses 31 and 32 having inclined surfaces 31a and 32a and incident surfaces 31b and 32b is shown. However, the refraction part 30 can be adopted as long as it has a plurality of divided incident surfaces 31b and 32b. For example, the refractive lenses 31 and 32 may be formed by injection molding and configured as a single refractive part 30.

DESCRIPTION OF SYMBOLS 10 ... Light emitting element 30 ... Refraction part 31 ... 1st refraction lens 32 ... 2nd refraction lens 70 ... Light receiving element 90 ... Detection part 100 ... Water drop detection sensor 110 ...・ Transparent plate 110a ... inner surface 110b ... outer surface

Claims (9)

A light emitting element (10) for irradiating detection light toward the inner surface (110a) of the transparent plate (110);
A refracting part (30) that refracts the detection light and makes it incident on the transparent plate and totally reflects it at the interface between the outer surface (110b) of the transparent plate and air;
A light receiving element (70) that receives the detection light that is totally reflected at the interface between the outer surface of the transparent plate and air and emitted from the transparent plate;
A water droplet having a detection unit (90) for detecting water droplets adhering to the outer surface of the transparent plate by detecting increase / decrease of the detection light incident on the light receiving element due to the water droplets adhering to the outer surface of the transparent plate A detection sensor,
The refracting portion has an incident surface (31b, 32b) divided into a plurality as an incident surface on which the detection light is mainly incident,
The plurality of divided incident surfaces (31b, 32b) are located between the projected portion of the light emitting element and the projected portion of the light receiving element on the inner surface of the transparent plate, and from the light emitting element to the light receiving element. The distance between each of the plurality of incident surfaces and the light emitting element is set so that the intensity of the detection light incident on each of the plurality of incident surfaces is uniform. Water drop detection sensor.   The plurality of divided incident surfaces are arranged in a direction perpendicular to both the direction from the light emitting element toward the light receiving element and the height direction orthogonal to the outer surface of the transparent plate. The water droplet detection sensor described in 1. The refraction part (30) is composed of a plurality of refraction lenses (31, 32), so that the incident surface is divided into a plurality of parts,
From the light emitting element to the light receiving element, the height of each of the plurality of refractive lenses in the height direction orthogonal to the outer surface of the transparent plate is uniform so that the intensity of the detection light incident on each of the incident surfaces is uniform. The water drop detection sensor according to claim 1, wherein the water drop detection sensor is gradually higher as it goes to. As the plurality of refractive lenses, a plurality of first refractive lenses (31) and one second refractive lens (32) positioned closer to the light receiving element than each of the plurality of first refractive lenses,
In each of the first refractive lens and the second refractive lens, an angle formed with the height direction is a direction in which the detection light is totally reflected at an interface between the outer surface of the transparent plate and air. An inclined surface (31a, 32a) inclined along the total reflection direction, and the incident surface connected to the inclined surface and on which the detection light is mainly incident,
Of the two first refractive lenses adjacent to each other, the inclined surface of the first refractive lens located on the light emitting element side is connected to the incident surface of the first refractive lens located on the light receiving element side. The inclined surface of the first refractive lens adjacent to the second refractive lens is connected to the incident surface of the second refractive lens;
The inclined surface of the first refractive lens adjacent to the second refractive lens is along a main axis along the total reflection direction among the axes connecting the light emitting element and the transparent plate. Item 4. The water droplet detection sensor according to Item 3.   The light collecting part (50) for condensing the detection light, which is totally reflected at an interface between the outer surface of the transparent plate and air and emitted from the transparent plate, on the light receiving element. Or the water droplet detection sensor of Claim 4. The condensing unit comprises a condensing lens (51) divided into a plurality of parts,
6. The water droplet detection sensor according to claim 5, wherein the plurality of condensing lenses are positioned between a projection site of the light emitting element and a projection site of the light receiving element on the inner surface of the transparent plate. .   The height in the height direction orthogonal to the outer surface of the transparent plate in each of the plurality of condenser lenses is the height of the refractive lens (32) having the highest height in the height direction among the plurality of refractive lenses. The water droplet detection sensor according to claim 6, wherein   The water droplet detection sensor according to claim 6 or 7, wherein each of the plurality of condensing lenses has the same height in a height direction orthogonal to the outer surface of the transparent plate.   The water droplet detection sensor according to any one of claims 5 to 8, wherein the condensing unit and the refracting unit are made of the same material, and the condensing unit and the refracting unit are integrated.

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