Distance measurement device

Abstract

This distance measurement device (1) comprises: a lens (10) that condenses reflected light from a measurement target object (2); a light-receiving element (20) that receives the light condensed by the lens (10); and a housing (30) for preventing external ambient light from hitting the light-receiving element (20). At least one light-shielding groove (34) having two inclined surfaces facing each other is provided in the housing (30). The two inclined surfaces of the light-shielding groove (34) face the lens (10).

Description

Distance measuring device

[0001] The present disclosure relates to distance measurement devices.

[0002] Distance measurement devices that measure the distance to a measurement object using the TOF (Time Of Flight) method are known. TOF distance measurement devices project laser light toward the measurement object and receive the laser light reflected by the measurement object, thereby detecting the delay time between the projection of the laser light and the reception of the light. This allows the distance from the distance measurement device to be calculated.

[0003] This type of distance measurement device includes, for example, a lens that collects reflected light from the object to be measured, a light receiving element that receives the light collected by the lens, and a housing that houses the lens and the light receiving element.

[0004] In a distance measurement device, if unwanted light such as stray light enters the light receiving element, the distance to the measurement object cannot be measured correctly, which means that the accuracy of the distance measurement by the distance measurement device decreases.

[0005] Therefore, in the past, a distance measurement device has been proposed in which a conical light-blocking plate is placed between the lens and the light-receiving element in order to prevent stray light from entering the light-receiving element (Patent Document 1).

[0006] Japanese Patent Application Publication No. 6-74763

[0007] However, the distance measurement device disclosed in Patent Document 1 uses a light-blocking plate that is inversely tapered with respect to the optical axis, making it impossible to integrally mold the light-blocking plate with other components. Therefore, in the distance measurement device disclosed in Patent Document 1, it is necessary to separately manufacture the light-blocking plate and combine it with other components such as a lens or a housing. This not only increases the number of components and increases costs, but also leads to assembly errors such as misalignment of the optical axes between components during assembly, which can result in an inaccurate measurement of the distance to the object to be measured.

[0008] Furthermore, in distance measurement devices that measure distances over a wide range from very close to long distances, the degree of parallelism of reflected light entering the lens differs between measuring long distances and measuring very close distances. Therefore, when measuring long distances or very close distances, light that does not focus on the light receiving element is generated, and this light is reflected by the inner surface of the housing that houses the light receiving element, becoming stray light with an unknown optical path length. Furthermore, natural light such as sunlight or artificial light from illumination enters the housing and becomes stray light. When such stray light enters the light receiving element, the accuracy of distance measurement by the distance measurement device decreases.

[0009] The present disclosure has been made in response to such problems, and aims to provide a distance measurement device that can suppress stray light from entering a light receiving element without increasing the number of parts.

[0010] In order to achieve the above-mentioned object, one aspect of a distance measuring device according to the present disclosure comprises a lens that focuses reflected light from an object to be measured, a light receiving element that receives the light focused by the lens, and a housing that prevents external ambient light from entering the light receiving element, wherein the housing has at least one light-shielding groove having two opposing inclined surfaces, and the two inclined surfaces face toward the lens.

[0011] Another aspect of the distance measuring device according to the present disclosure comprises a lens that focuses reflected light from an object to be measured, a light receiving element that receives the light focused by the lens, and a housing that contains the lens, wherein the housing has at least one light-shielding groove having two opposing inclined surfaces, and the two inclined surfaces face toward the lens.

[0012] According to the present disclosure, it is possible to prevent stray light from entering a light receiving element without increasing the number of parts.

[0013] FIG. 1 is a diagram showing the appearance of a distance measurement device and a measurement object according to an embodiment. FIG. 2 is a cross-sectional view showing the configuration of the distance measurement device according to the embodiment. FIG. 3 is a perspective view of a lens in the distance measurement device according to the embodiment. FIG. 4 is a front view of the lens in the distance measurement device according to the embodiment. FIG. 5 is a diagram showing the state in which reflected light is collected by the lens when using a distance measurement device of a comparative example. FIG. 6 is a diagram for explaining the effects of the distance measurement device according to the embodiment. FIG. 7 is an enlarged view of a light-shielding groove in the distance measurement device according to the embodiment. FIG. 8 is an enlarged view of a light-shielding groove in a distance measurement device according to Modification 1. FIG. 9 is an enlarged view of a light-shielding groove of a light-receiving element and its surroundings in a distance measurement device according to Modification 2. FIG. 10 is an enlarged view of a light-shielding groove in a distance measurement device according to Modification 3. FIG. 11 is an enlarged view of a light-shielding groove in a distance measurement device according to Modification 4.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present disclosure will be described as optional components.

[0015] Note that each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, the scales and the like do not necessarily match in each figure. Furthermore, in each figure, substantially the same configuration is assigned the same reference numeral, and duplicate explanations are omitted or simplified. Furthermore, in this specification, the terms "up" and "down" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition.

[0016] (Embodiment) The configuration of a distance measurement device 1 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a diagram showing the appearance of the distance measurement device 1 according to the embodiment and a measurement target 2. Fig. 2 is a cross-sectional view showing the configuration of the distance measurement device 1 according to the embodiment.

[0017] As shown in FIG. 1, the distance measurement device 1 is a distance measuring device that can measure the distance between the distance measurement device 1 and a measurement object 2 using light such as a laser beam. The distance measurement device 1 in this embodiment is a TOF sensor that measures the distance between the distance measurement device 1 and the measurement object 2 using a TOF method. The distance measurement device 1 is also a reflective 1D (one-dimensional) TOF sensor. Specifically, the distance measurement device 1 projects laser light toward the measurement object 2 and receives the laser light reflected by the measurement object 2 (reflected light), thereby detecting the delay time from when the laser light is projected to when it is received. This makes it possible to calculate the distance from the distance measurement device 1 to the measurement object 2.

[0018] The distance measurement device 1 can measure distances over a wide range from short distances to long distances. That is, the distance measurement device 1 can measure the distance when the measurement object 2 is located at a short distance from the distance measurement device 1, and can also measure the distance when the measurement object 2 is located at a long distance from the distance measurement device 1. Furthermore, the distance measurement device 1 can measure the distance when the measurement object 2 is located at an extremely short distance from the distance measurement device 1, even within short distances.

[0019] Here, "short distance" refers to a distance within 500 mm from the distance measurement device 1, and "long distance" refers to a distance exceeding 500 mm from the distance measurement device 1. Furthermore, "ultra-short distance" refers to a distance of about 50 mm even within the short distance.

[0020] As shown in FIG. 2, the distance measurement device 1 includes a lens 10 that focuses incident light, a light receiving element 20 that receives the light focused by the lens 10, and a housing 30.

[0021] The distance measurement device 1 in this embodiment is of a reflective type, and therefore projects light for measuring the distance to the measurement object 2 toward the measurement object 2. Specifically, the distance measurement device 1 includes a light projecting unit 40 that projects laser light onto the measurement object 2 as light for measuring the distance to the measurement object 2.

[0022] The distance measurement device 1 may also include a light receiving circuit, a light projecting circuit, a control unit, an output unit, etc. The circuit elements constituting each of the light receiving circuit, the light projecting circuit, the control unit, and the output unit are mounted on one or more mounting boards (for example, printed wiring boards).

[0023] The lens 10 is a light-receiving lens that receives the laser light (reflected light) that is projected from the light-projecting unit 40 and reflected by the measurement object 2. In other words, the laser light (reflected light) that is reflected by the measurement object 2 is incident on the lens 10.

[0024] The lens 10 is a condenser lens that condenses the light reflected from the measurement object 2. In this embodiment, the lens 10 condenses the light reflected from the measurement object 2 onto the light receiving surface 21 of the light receiving element 20.

[0025] The lens 10 is formed into a predetermined shape using a light-transmitting material. Specifically, the lens 10 is formed using a transparent material such as a transparent resin material, such as acrylic or polycarbonate, or a transparent material, such as a glass material.

[0026] The lens 10 is formed to be a convex lens. As an example, the lens 10 is a plano-convex lens as a whole. As shown in Figures 3 and 4, in this embodiment, the lens 10 has a lens surface area S1 including a lens surface 11 that collects incident light, and a non-lens surface area S2 where the lens surface 11 is not present. Figure 3 is a perspective view of the lens 10 in the distance measurement device 1 according to the embodiment. Figure 4 is a front view of the lens 10.

[0027] 3 and 4, reflected light from the measurement object 2 is incident on the lens surface region S1. Specifically, the reflected light from the measurement object 2 is incident on the lens surface 11. In other words, the lens surface 11 is the incident surface onto which the reflected light from the measurement object 2 is incident. The non-lens surface region S2 is a region in the lens 10 where a cutout portion 12 is provided. The cutout portion 12 is a through-hole that penetrates the lens 10 in the direction of the lens optical axis J1.

[0028] The lens surface 11 in the lens surface region S1 has a first lens surface 11a which is a convex lens surface configured as a convex curved surface including a vertex P1, and a second lens surface 11b which is an aspheric surface having a different curvature from that of the first lens surface 11a.

[0029] First lens surface 11a is a long-distance lens surface that transmits reflected light from measurement object 2 when measurement object 2 is located at a long distance. First lens surface 11a is compatible with not only long distances but also medium distances. As an example, the medium to long distance refers to a distance from lens 10 to measurement object 2 of approximately 500 mm to 5000 mm.

[0030] The second lens surface 11b is a lens surface for short distances through which reflected light from the measurement object 2 passes when the measurement object 2 is located at a short distance. As an example, the short distance is a distance from the lens 10 to the measurement object 2 of 500 mm or less.

[0031] When viewed from the lens optical axis J1 passing through the vertex P1, the second lens surface 11b is disposed between the first lens surface 11a and the non-lens surface region S2 so as to follow at least a portion of the boundary between the lens surface region S1 and the non-lens surface region S2. The area occupied by the second lens surface 11b on the lens surface 11 is smaller than the area occupied by the first lens surface 11a on the lens surface 11.

[0032] As described above, lens 10 in this embodiment is provided with first lens surface 11 a and second lens surface 11 b, which allows for improved focusing accuracy of light incident on lens 10 over a wider distance range.

[0033] 2 and 3 , the lens 10 has an exit surface 13 through which light incident on the lens 10 exits the lens 10. The exit surface 13 faces away from the lens surface 11, which is the incident surface through which reflected light from the measurement object 2 enters. In this embodiment, the exit surface 13 is a flat surface. Therefore, the lens optical axis J1 of the lens 10 is perpendicular to the exit surface 13 of the lens 10.

[0034] 2, the lens 10 configured as above is disposed in the housing 30 with the lens surface 11 exposed so that reflected light from the measurement object 2 is incident thereon. Therefore, the exit surface 13 of the lens 10 faces the light receiving element 20.

[0035] The light receiving element 20 receives the light focused by the lens 10. In this embodiment, the lens 10 focuses the laser light, and therefore the light receiving element 20 receives the laser light focused by the lens 10.

[0036] The light receiving element 20 is a photoelectric conversion element that receives the laser light focused by the lens 10 and converts it into an electrical signal. Since the distance measurement device 1 in this embodiment is a 1D-TOF sensor, the light receiving element 20 does not receive light that provides two-dimensional information like a camera or the like, but receives light that provides one-dimensional information. For example, the light receiving element 20 is a photodiode, a photo IC diode, a phototransistor, a photomultiplier tube, or the like.

[0037] The light receiving element 20 has a light receiving surface 21 that receives light. The light receiving surface 21 is a flat surface. Therefore, the light receiving axis J2 of the light receiving element 20 is perpendicular to the light receiving surface 21 of the light receiving element 20.

[0038] The light receiving element 20 is disposed opposite the exit surface 13 of the lens 10 so that the light receiving axis J2 passes through the vertex P1 of the first lens surface 11a of the lens 10. In other words, the light receiving element 20 is disposed so that the light receiving axis J2 coincides with the lens optical axis J1. Therefore, the light receiving axis J2 of the light receiving element 20 is perpendicular to the exit surface 13 of the lens 10. In other words, the light receiving surface 21 of the light receiving element 20 is parallel to the exit surface 13 of the lens 10.

[0039] The light-receiving axis J2 of the light-receiving element 20 and the light-projecting axis J4 of the light-projecting unit 40 are parallel to each other but not coaxial with each other. The light-receiving axis J2 and the light-projecting axis J4 do not have to be strictly parallel to each other and may be misaligned by, for example, about ±10°.

[0040] The light receiving element 20 is disposed at the focal position of the lens 10. Specifically, the light receiving element 20 is disposed at the focal position of the first lens surface 11a of the lens 10.

[0041] The light-receiving element 20 outputs the converted electrical signal to the light-receiving circuit. The light-receiving circuit includes, for example, an A / D conversion circuit. In this case, the light-receiving circuit converts an analog light-receiving signal corresponding to the amount of received light output from the light-receiving element 20 into a digital light-receiving signal using the A / D conversion circuit and outputs the digital light-receiving signal to the control unit. Based on the light-receiving signal from the light-receiving circuit, the control unit calculates the time from when the light-emitting unit 40 emits laser light to when the laser is reflected by the measurement object 2 and the reflected light is received by the light-receiving element 20. In other words, the control unit calculates the time required for light to travel back and forth between the distance measurement device 1 and the measurement object 2. Based on the calculation result, the control unit calculates distance data (distance measurement result) indicating the distance from the distance measurement device 1 to the measurement object 2 and outputs it to the outside from the output unit. The control unit is, for example, an IC. The control unit is electrically connected to and controls the light-emitting circuit, the light-receiving circuit, and the output unit.

[0042] The light receiving element 20 is mounted on a substrate. The substrate is a mounting substrate such as a printed wiring board. Circuit elements constituting the light receiving circuit may be mounted on this substrate. Circuit elements constituting the light projecting circuit, the control unit, and the output unit may also be mounted on the substrate. The substrate on which the light receiving element 20 and the like are mounted may be fixed to a base provided in the distance measurement device 1.

[0043] The housing 30 is a member for preventing external ambient light from being incident on the light receiving element 20. The housing 30 surrounds the light receiving element 20. In this embodiment, the housing 30 is an outer housing member that forms the outer casing of the distance measurement device 1. Note that the housing 30 is not an outer housing member, and the distance measurement device 1 may be provided with another outer housing member that surrounds the housing 30.

[0044] In the present embodiment, the housing 30 also functions as a support member that supports the lens 10. In other words, the housing 30 is a lens housing that holds the lens 10. Therefore, the housing 30 not only surrounds the light receiving element 20, but also surrounds the lens 10. The housing 30 contains the lens 10 and the light receiving element 20.

[0045] The housing 30 has a lens support portion 31 that supports the lens 10. The lens support portion 31 has a cylinder 31a with an opening. In this embodiment, the cylinder 31a is cylindrical. The lens support portion 31 is provided so that the opening of the lens support portion 31 exposes the exit surface 13 of the lens 10. The lens support portion 31 supports the flange portion of the lens 10. The lens support portion 31 is made of a resin material. Specifically, the lens support portion 31 is a resin molded product formed into a predetermined shape using an injection molding die. Note that the lens support portion 31 may be made of a metal material instead of a resin material. In this case, the lens support portion 31 may be made of a metal die-cast made of an aluminum alloy or the like.

[0046] The housing 30 also has a plurality of concentrically formed annular zones 32. Each of the plurality of annular zones 32 is an annular protrusion having a different diameter size. The plurality of annular zones 32 is provided so as to surround the light receiving element 20. The plurality of annular zones 32 is formed so as to protrude from the light receiving element 20 toward the lens 10. The cross-sectional shape of each of the plurality of annular zones 32 is triangular. Specifically, the cross-sectional shape of each of the plurality of annular zones 32 is a wedge-shaped, tapered triangle.

[0047] The multiple annular portions 32 are located inside the cylindrical body 31a of the lens support portion 31. Specifically, the multiple annular portions 32 are surrounded by the cylindrical body 31a. In other words, the cylindrical body 31a is located outside the multiple annular portions 32 and surrounds the multiple annular portions 32.

[0048] The multiple annular portions 32 are made of a resin material. In this embodiment, the multiple annular portions 32 are integrally formed with the housing 30. Specifically, the multiple annular portions 32 are integrally formed with the lens support portion 31 using a resin material. That is, the multiple annular portions 32 and the lens support portion 31 are a resin-molded product formed integrally using an injection molding die. Note that in this embodiment, not only the multiple annular portions 32 and the lens support portion 31 are integrally formed with a resin material, but the entire housing 30 is integrally formed with a resin material. Note that the entire housing 30 may be integrally formed with a metal material. For example, the housing 30 may be a metal part made of a die-cast metal such as an aluminum alloy. In this case, the multiple annular portions 32 and the lens support portion 31 are made of a die-cast metal.

[0049] The cylindrical body 31a of the lens support part 31 and the multiple annular parts 32 form a light trap 33. The light trap 33 has a function of trapping unwanted light such as stray light. The light trap 33 traps unwanted light such as stray light by attenuating or absorbing the unwanted light. For example, by painting the surfaces of the light trap 33 (the cylindrical body 31a and the annular parts 32 of the lens support part 31) black, the light trap 33 can absorb light.

[0050] The lens support portion 31 and the plurality of annular portions 32 are made of a black resin material. In this embodiment, the entire housing 30 is made of a black resin material. For example, the entire surface of the housing 30 can be made black by adding a black pigment or a black dye to the resin material that makes up the housing 30. Note that the surface of the housing 30 may also be made black by applying a black paint or the like to the housing 30 after injection molding to form a black film.

[0051] Furthermore, a surface treatment such as a graining process may be performed on the surface of the housing 30 to form an uneven structure on the surface of the housing 30. This allows the uneven structure to also scatter and absorb light.

[0052] The light trap 33 has at least one light-shielding groove 34. In this embodiment, the light trap 33 has a plurality of light-shielding grooves 34. The plurality of light-shielding grooves 34 includes grooves between two adjacent ring-shaped portions 32 among the plurality of ring-shaped portions 32. In this embodiment, the plurality of light-shielding grooves 34 includes not only grooves between two adjacent ring-shaped portions 32, but also grooves between the ring-shaped portion 32 (outermost ring-shaped portion) located on the outermost side among the plurality of ring-shaped portions 32 and the cylindrical body 31 a of the lens support unit 31. The groove between the ring-shaped portion 32 (outermost ring-shaped portion) and the cylindrical body 31 a of the lens support unit 31 is the light-shielding groove 34 located on the outermost side among the plurality of light-shielding grooves 34.

[0053] Each of the plurality of light-shielding grooves 34 has two opposing inclined surfaces, a first inclined surface 34 a and a second inclined surface 34 b. The first inclined surface 34 a is an inclined surface located more inward than the second inclined surface 34 b, and the second inclined surface 34 b is an inclined surface located more outward than the first inclined surface 34 a.

[0054] The cross-sectional shape of each of the multiple light-shielding grooves 34 is triangular. That is, each light-shielding groove 34 is a V-groove. In the light trap 33, the depth of the multiple light-shielding grooves 34 increases with increasing distance from the lens optical axis J1 of the lens 10. That is, the depth of the multiple light-shielding grooves 34 increases toward the outside. Specifically, the height of the multiple annular portions 32 increases with increasing distance from the lens optical axis J1 of the lens 10. Note that the height of the cylindrical body 31a of the lens support portion 31 is greater than the height of any of the multiple annular portions 32.

[0055] The first inclined surface 34a and the second inclined surface 34b (two inclined surfaces) in each light-shielding groove 34 do not face the light-receiving element 20 side, but face the lens 10 side. Therefore, the first inclined surface 34a and the second inclined surface 34b are both inclined with a forward taper rather than a reverse taper, and face directly toward the lens 10. In this embodiment, the first inclined surface 34a and the second inclined surface 34b in all of the multiple light-shielding grooves 34 face the lens 10 side.

[0056] The light-projecting unit 40 projects light to be irradiated onto the object to be measured. In this embodiment, the light-projecting unit 40 projects laser light as the light to be irradiated onto the object to be measured. The light-projecting unit 40 has a light-projecting element which is a light source, a light-projecting lens disposed in front of the light-projecting element, and a cylindrical case that houses the light-projecting element and the light-projecting lens.

[0057] The light-emitting element is, for example, a semiconductor laser element that emits laser light. The wavelength of the laser light emitted from the light-emitting element is not particularly limited. As an example, the laser light emitted from the light-emitting element may be visible light with a wavelength of 660 nm (red), or may be infrared light, etc. The light-emitting element is electrically connected to the light-emitting circuit and emits the laser light in accordance with a drive command from the light-emitting circuit. The light-emitting circuit outputs a drive signal to the light-emitting element that adjusts the emission intensity or emission time of the laser light based on a control command from the control unit. The light-emitting element emits pulsed laser light based on the drive signal.

[0058] As shown in FIG. 4 , the light-projecting unit 40 is disposed in the non-lens surface region S2 of the lens 10. Specifically, the light-projecting unit 40 is inserted into the cutout 12. For example, the case of the light-projecting unit 40 is press-fit into the cutout 12. By disposing the light-projecting unit 40 in the non-lens surface region S2 (cutout 12) in this manner, the light-projecting axis J4 and the light-receiving axis J2 can be brought closer together. This improves the light-focusing accuracy of the lens 10 and prevents the distance measurement device 1 from becoming larger even if the distance measurement device 1 includes the light-projecting unit 40. In particular, by disposing the light-projecting unit 40 adjacent to the second lens surface 11b of the lens 10, the amount of light received by the light-receiving element 20 can be ensured while minimizing the area occupied by the second lens surface 11b. As a result, the amount of reflected light received by the light-receiving element 20 increases. This improves the distance measurement accuracy of the distance measurement device 1.

[0059] Next, the effects of the distance measurement device 1 configured as above will be described in comparison with a distance measurement device 1X of a comparative example using Figures 5 and 6. Figure 5 is a diagram showing the state in which reflected light is collected by the lens 10 when using the distance measurement device 1X of the comparative example. Figure 6 is a diagram for explaining the effects of the distance measurement device 1 according to the embodiment. In Figures 5 and 6, the dotted areas indicate reflected light L2.

[0060] As shown in FIG. 5, in the distance measurement device 1X of the comparative example, the degree of parallelism of the reflected light incident on the lens 10 differs between when measuring a long distance and when measuring an extremely short distance.

[0061] Specifically, when measuring the distance to the object to be measured using the comparative distance measuring device 1X, as shown in (a) and (b) of Figures 5A and 5B, laser light is emitted from the light-emitting unit 40 toward the object to be measured as emitted light L1, and the laser light reflected by the object to be measured enters the lens 10 as reflected light L2.

[0062] 5A, when measuring a long distance (for example, when the distance to the measurement object is 5000 mm), the reflected light L2 is incident on the lens 10 as parallel light. In other words, the angle of incidence of the reflected light L2 on the lens 10 is approximately zero. Therefore, the reflected light L2 is condensed by the lens 10 so as to be focused on the light receiving surface 21 of the light receiving element 20.

[0063] On the other hand, as shown in FIG. 5B, when measuring a short distance (for example, when the distance to the measurement target is 50 mm), the reflected light L2 is incident on the lens 10 as non-parallel light. Therefore, the reflected light L2 is condensed by the lens 10 so as not to be focused on the light-receiving surface 21 of the light-receiving element 20. In other words, the reflected light L2 forms a blurred spot on the light-receiving surface 21 of the light-receiving element 20. In this case, light L3 that cannot be fully condensed by the lens 10 and does not enter the light-receiving element 20 is reflected by the inner surface of the housing (not shown) that houses the light-receiving element 20, becoming stray light with an unknown optical path length and entering the light-receiving element 20. As a result, the accuracy of distance measurement by the distance measurement device 1X decreases.

[0064] In contrast, in the distance measurement device 1 according to the present embodiment, as shown in FIGS. 6A and 6B, reflected light L2 from the measurement target is incident on the lens 10, similar to the distance measurement device 1X of the comparative example. That is, as shown in FIG. 6A, when measuring a long distance, the reflected light L2 is incident on the lens 10 as parallel light, and is collected by the lens 10 so as to be focused on the light receiving surface 21 of the light receiving element 20. On the other hand, as shown in FIG. 6B, when measuring a short distance, the reflected light L2 is incident on the lens 10 as non-parallel light, and is collected by the lens 10 so as not to be focused on the light receiving surface 21 of the light receiving element 20. That is, light L3 is generated that cannot be completely collected by the lens 10 and travels a trajectory that does not enter the light receiving element 20.

[0065] However, in the distance measurement device 1 of this embodiment, the housing 30 is provided with a light-shielding groove 34, which has two opposing inclined surfaces: a first inclined surface 34a and a second inclined surface 34b. As a result, light L3 that is not fully focused by the lens 10 and does not enter the light-receiving surface 21 of the light-receiving element 20 enters the light-shielding groove 34 and is attenuated by repeatedly reflecting and scattering at the first inclined surface 34a and the second inclined surface 34b. That is, light L3 that enters the light-shielding groove 34 is specularly reflected by the first inclined surface 34a and the second inclined surface 34b, and is scattered and reflected with each specular reflection, repeatedly attenuating the light. In this way, the light-shielding groove 34 functions as a labyrinth that attenuates and traps stray light L3. This prevents stray light from entering the light-receiving surface 21 of the light-receiving element 20, thereby preventing a decrease in distance measurement accuracy.

[0066] Furthermore, the light-shielding groove 34 is provided in the existing housing 30 (i.e., the light-shielding groove 34 is part of the housing 30), and the first inclined surface 34a and the second inclined surface 34b of the light-shielding groove 34 both face the lens 10 side and are not reverse tapered. Therefore, the housing 30 having the light-shielding groove 34 can be easily manufactured using an injection molding die, or the light-shielding groove 34 can be easily formed in the housing 30 by cutting.

[0067] Furthermore, by providing the shading groove 34 in the housing 30, there is no need to combine a separately manufactured shading plate with other parts such as a lens, as in the distance measuring device disclosed in Patent Document 1, so the number of parts does not increase and problems such as misalignment of the optical axes between parts during assembly do not occur.

[0068] In this way, the distance measurement device 1 according to the present embodiment can suppress stray light from entering the light receiving element 20 without increasing the number of parts, thereby improving the accuracy of distance measurement by the distance measurement device 1.

[0069] Furthermore, in the distance measuring device 1 according to this embodiment, in the cross-sectional view shown in Figure 7, if the angle between a straight line A1 passing through the vertex of the first inclined surface 34a of the light-shielding groove 34 and parallel to the lens optical axis J1 of the lens 10 and the first inclined surface 34a of the light-shielding groove 34 is α, and the angle between a straight line A2 passing through the vertex of the second inclined surface 34b of the light-shielding groove 34 and parallel to the lens optical axis J1 of the lens 10 and a straight line A3 connecting the vertex of the second inclined surface 34b of the light-shielding groove 34 and the center of the light-receiving surface 21 of the light-receiving element 20 is θ, then it is preferable that the relationship α<90°-θ is satisfied.

[0070] As a result, light L3 (stray light) that is not completely focused by the lens 10 and travels along a trajectory that does not enter the light-receiving element 20 is reflected two or more times by the inclined surfaces (first inclined surface 34a and second inclined surface 34b) of the light-shielding groove 34. Therefore, light that enters the light-shielding groove 34 can be efficiently attenuated. Note that in Figure 7, the apex of the second inclined surface 34b may be the effective outer diameter of the lens 10. Also, in Figure 7, the area indicated by dotted hatching indicates the optical path area.

[0071] As shown in FIG. 7, the vertices of the first inclined surface 34a and the second inclined surface 34b may be located on the boundary of the optical path area or outside the optical path area.

[0072] Furthermore, as shown in Figure 8, if the angle formed between a straight line A2 that passes through the vertex of the second inclined surface 34b of the light-shielding groove 34 and is parallel to the lens optical axis J1 of the lens 10 and the second inclined surface 34b of the light-shielding groove 34 is β, it is preferable that the relational expression α + 2β < 90° - θ is satisfied.

[0073] As a result, light L3 (stray light) that is not completely focused by the lens 10 and travels along a trajectory that does not enter the light-receiving element 20 is reflected four or more times by the inclined surfaces (first inclined surface 34a and second inclined surface 34b) of the light-shielding groove 34. Therefore, stray light that has entered the light-shielding groove 34 can be attenuated even more efficiently. Note that β is preferably 0° or an angle close to 0 (for example, 10° or less). Also, in Figure 8, the area indicated by dotted hatching indicates the optical path area.

[0074] Also, as shown in Figure 2, in the distance measuring device 1 of this embodiment, the housing 30 has a plurality of annular portions 32 formed concentrically, and the light-shielding groove 34 is a groove between two adjacent annular portions 32 among the plurality of annular portions 32.

[0075] With this configuration, the multiple annular portions 32 can be configured concentrically and continuously like a Fresnel lens, so that a compact distance measuring device 1 can be realized even if multiple annular portions 32 are provided in the housing 30. In other words, it is possible to save space within the housing 30, and to maximize the effect of trapping stray light in the limited space within the housing 30.

[0076] In particular, by painting the surfaces of the multiple annular portions 32 (i.e., the first inclined surfaces 34a and the second inclined surfaces 34b) black, stray light that enters the light-shielding groove 34 can not only be attenuated by being reflected and scattered by the first inclined surfaces 34a and the second inclined surfaces 34b, but also can be absorbed by the first inclined surfaces 34a and the second inclined surfaces 34b each time the light is reflected by them. This makes it possible to effectively attenuate stray light that enters the light-shielding groove 34. In this way, the multiple annular portions 32 can be used as a light-shielding wall that absorbs light.

[0077] Furthermore, in the distance measurement device 1 according to this embodiment, there are a plurality of light-shielding grooves 34, and the depth of the plurality of light-shielding grooves 34 increases with increasing distance from the lens optical axis J1 of the lens 10. In other words, the depth of the plurality of light-shielding grooves 34 increases toward the outer periphery.

[0078] The deeper the light-shielding grooves 34, the more times stray light that enters the light-shielding grooves 34 can be reflected. The farther away from the lens optical axis J1 of the lens 10, the more stray light there is, while it is desirable to ensure an optical path area in the portion close to the lens optical axis J1 of the lens 10. Therefore, by making the depth of the light-shielding grooves 34 deeper the farther away from the lens optical axis J1 of the lens 10, it is possible to efficiently attenuate stray light by the light-shielding grooves 34 while ensuring an optical path area. Furthermore, because the light-shielding grooves 34 can be provided in necessary locations where stray light is to be attenuated, the amount of resin required to form the annular portion 32 can be reduced, leading to cost savings.

[0079] In the distance measuring device 1 according to this embodiment, the housing 30 is made of a resin material, and the plurality of ring portions 32 are integrally formed with the housing 30 .

[0080] This allows the housing 30 and the plurality of ring portions 32 to be molded integrally using an injection molding die, thereby eliminating assembly errors and reducing manufacturing costs.

[0081] Also, as shown in Figures 3 and 4, in the distance measuring device 1 of this embodiment, the lens 10 has a lens surface area S1 having a lens surface 11 that focuses incident light, and a non-lens surface area S2 where the lens surface 11 is not present, and the lens surface 11 has a first lens surface 11a which is a convex lens surface configured as a convex curved surface including a vertex, and a second lens surface 11b which is an aspheric surface having a different curvature from that of the first lens surface 11a.

[0082] As described above, lens 10 in this embodiment is a two-point focal lens having first lens surface 11a and second lens surface 11b, and therefore generates more stray light than a normal lens with a single focal point. In particular, a large amount of stray light is generated by second lens surface 11b, which is a lens surface for close distances. However, in this embodiment, housing 30 is provided with light-shielding groove 34, and therefore, even when lens 10, which is a two-point focal lens, is used, stray light can be effectively attenuated by entering light-shielding groove 34.

[0083] Furthermore, as shown in Figure 9, it is desirable that the vertex P2 (the vertex of the first inclined surface 34a and the second inclined surface 34b) of the annular portion 32 that is closest to the light receiving element 20 among the multiple annular portions 32 be located as close as possible to the light receiving element 20 and as close as possible to the boundary line of the optical path area.

[0084] This configuration can further suppress stray light from entering the light receiving element 20. This can further improve the accuracy of distance measurement by the distance measurement device 1.

[0085] (Modification) Although the distance measurement device 1 according to the present disclosure has been described above based on the embodiment, the present disclosure is not limited to the above embodiment.

[0086] For example, in the above embodiment, the first inclined surface 34a and the second inclined surface 34b of the light-shielding groove 34 are flat, but this is not limited thereto. That is, in a cross-sectional view, the inclined lines of the first inclined surface 34a and the second inclined surface 34b are straight, but this is not limited thereto. For example, the first inclined surface 34a and the second inclined surface 34b may be curved. Specifically, in a cross-sectional view, the inclined lines of the first inclined surface 34a and the second inclined surface 34b may be curved, such as an arc. In this case, as shown in FIG. 10 , the inclined lines of the first inclined surface 34a and the second inclined surface 34b may be arcs that convex outward from the light-shielding groove 34, or as shown in FIG. 11 , the inclined lines of the first inclined surface 34a and the second inclined surface 34b may be arcs that convex inward from the light-shielding groove 34. In addition, it is not limited to the case where both the inclined lines of the first inclined surface 34a and the second inclined surface 34b are arcs that convex outward or inward from the light-shielding groove 34, but one of the inclined lines of the first inclined surface 34a and the second inclined surface 34b may be an arc that convex outward from the light-shielding groove 34, and the other inclined line of the first inclined surface 34a and the second inclined surface 34b may be an arc that convex inward from the light-shielding groove 34.

[0087] In the above embodiment, the plurality of annular portions 32 are annular with the lens optical axis J1 of the lens 10 as the center, but this is not limiting. For example, the plurality of annular portions 32 may be polygonal, such as rectangular, annular with the lens optical axis J1 of the lens 10 as the center.

[0088] In the above embodiment, the vertices of the annular zone 32 are angular, but this is not limiting. For example, the vertices of the annular zone 32 may be rounded to remove the corners.

[0089] In the above embodiment, the angles of the first inclined surfaces 34a in the light-shielding grooves 34 may be the same or different from each other. Similarly, the angles of the second inclined surfaces 34b in the light-shielding grooves 34 may be the same or different from each other.

[0090] In the above embodiment, the lengths of the first inclined surfaces 34a in the light-shielding grooves 34 are different from one another, but this is not limiting. Specifically, the lengths of the first inclined surfaces 34a may be the same. Similarly, the lengths of the second inclined surfaces 34b in the light-shielding grooves 34 are different from one another, but may also be the same.

[0091] In the above embodiment, the distance measurement device 1 is a reflective TOF sensor, but is not limited to this. For example, the distance measurement device 1 may be a transmissive TOF sensor.

[0092] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that would occur to those skilled in the art, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. Furthermore, the present disclosure also includes any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing, within the scope of technical compatibility. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of technical compatibility, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims.

[0093] The present disclosure is suitable for distance measurement devices that measure the distance to an object, and is particularly suitable for TOF distance measurement devices.

[0094] REFERENCE SIGNS LIST 1 Distance measuring device 2 Measurement object 10 Lens 11 Lens surface 11a First lens surface 11b Second lens surface 12 Notch 13 Emission surface 20 Light receiving element 21 Light receiving surface 30 Housing 31 Lens support portion 31a Cylinder 32 Annular portion 33 Light trap 34 Light shielding groove 34a First inclined surface 34b Second inclined surface 40 Light projecting portion S1 Lens surface area S2 Non-lens surface area J1 Lens optical axis J2 Light receiving axis J4 Light projecting axis

Claims

1. A distance measuring device comprising: a lens that focuses light reflected from an object to be measured; a light receiving element that receives the light focused by said lens; and a housing that prevents external ambient light from entering said light receiving element, said housing having at least one light-shielding groove with two opposing inclined surfaces that face towards said lens.

2. The distance measuring device according to claim 1, wherein one of the two inclined surfaces is a first inclined surface, and the other of the two inclined surfaces is a second inclined surface located outward of the first inclined surface, and the angle formed between the first inclined surface and a line passing through the vertex of the first inclined surface and parallel to the optical axis of the lens in a cross-sectional view is defined as α, and the angle formed between the first inclined surface and a line passing through the vertex of the second inclined surface and parallel to the optical axis of the lens in a cross-sectional view is defined as θ, and the angle formed between the vertex of the second inclined surface and a line connecting the vertex of the second inclined surface and the center of the light-receiving surface of the light-receiving element satisfies the relational expression α<90°-θ.

3. A distance measuring device according to claim 2, wherein, in a cross-sectional view, the angle formed between the second inclined surface and a straight line passing through the vertex of the second inclined surface and parallel to the optical axis of the lens is defined as β, and the angle satisfies the relational expression α + 2β < 90° - θ.

4. A distance measuring device according to any one of claims 1 to 3, wherein the housing has a plurality of ring-shaped portions formed concentrically, and the light-shielding groove is a groove between two adjacent ring-shaped portions of the plurality of ring-shaped portions.

5. The distance measuring device according to claim 4, wherein the housing is made of a resin material or a metal material, and the plurality of ring portions are integrally formed with the housing.

6. A distance measuring device according to any one of claims 1 to 3, wherein there are a plurality of light-shielding grooves, and the depths of the plurality of light-shielding grooves increase with increasing distance from the optical axis of the lens.

7. A distance measuring device according to any one of claims 1 to 3, wherein the lens has a lens surface region having a lens surface that focuses incident light, and a non-lens surface region where the lens surface is not present, and the lens surface has a first lens surface that is a convex lens surface configured as a convex curved surface including a vertex, and a second lens surface that is an aspheric surface and has a different curvature from that of the first lens surface.

8. The distance measuring device according to any one of claims 1 to 3, further comprising a light projecting unit that projects laser light onto the object to be measured.

9. A distance measuring device comprising: a lens that collects reflected light from an object to be measured; a light receiving element that receives the light collected by said lens; and a housing that contains said lens, wherein said housing is provided with at least one light-shielding groove having two opposing inclined surfaces, and said two inclined surfaces face towards said lens.

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