Optical device

Abstract

The optical device (1) includes: a light source unit (20) that projects illumination light (L1) toward a sensing area; a light detector (40) that receives the reflected light (R1) of the illumination light (L1) reflected in the sensing area; and a condenser lens (30) that condenses the reflected light (R1) onto the light detector (40). The condenser lens (30) has a through-hole (30b) that allows the illumination light (L1) emitted from the light source unit (20) to pass through and aligns the optical axis (A1) of the light source unit (20) with the optical axis (A2) of the condenser lens (30). The reflecting surface (30a) of the condenser lens (30) has a shape obtained by cutting a cylinder extending in the projection direction of the illumination light (L1) with a rotational ellipsoidal surface having its major axis as the rotation axis. The light detector (40) is arranged in the direction of the first focal position (FP1) with respect to the condenser lens (30) and facing the condenser lens (30), and the sensing area is set in the direction of the second focal position (FP2) with respect to the condenser lens (30) and facing the condenser lens (30).

Description

Technical Field

[0001] The present invention relates to an optical device having an emission optical system and a light-receiving optical system, and is suitable for, for example, sensing the state of moisture in a sensing area. Background Art

[0002] Conventionally, a road surface sensing device for sensing the state of a road surface has been known. For example, Patent Document 1 below describes the following road surface state sensing device: illumination light is irradiated onto a sensing area on the road surface, and based on the reflected light, it is determined whether a detected object such as ice or water exists in the sensing area. In this device, as the illumination light, detection light and reference light having different wavelengths are sequentially switched and irradiated onto the sensing area. In addition, in synchronization with the switching of each light, the reflected light of each light is received and an electrical signal is generated. Then, these electrical signals are compared and calculated, and based on the calculation result, it is determined whether a sensed object such as water or ice exists in the sensing area.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-216592 Summary of the Invention

[0006] In the structure of the above Patent Document 1, the illumination light and the reflected light pass through respective optical systems and are separately irradiated and received in mutually different directions. Therefore, it is necessary to adjust the irradiation angle of the illumination light and the light-receiving angle of the reflected light according to the distance between the road surface sensing device and the sensing area. Such adjustment work is extremely complicated.

[0007] In view of this problem, an object of the present invention is to provide an optical device that can appropriately receive the reflected light from a sensing area without performing complicated adjustment work.

[0008] -Means for Solving the Problem-

[0009] The optical device according to the first aspect of the present invention includes: a light source unit that projects illumination light onto a sensing area; a light detector that receives the reflected light of the illumination light reflected in the sensing area; and a condenser lens that condenses the reflected light onto the light detector. Here, the condenser lens has a through-hole that allows the illumination light emitted from the light source unit to pass through, and matches the optical axis of the light source unit with the optical axis of the condenser lens. In addition, the reflecting surface of the condenser lens has a shape obtained by cutting a cylinder extending in the projection direction of the illumination light with a rotational ellipsoid having a major axis as the rotation axis. Further, the light detector is disposed in a direction toward the first focal position of the condenser lens with respect to the condenser lens, and the sensing area is set in a direction toward the second focal position of the condenser lens with respect to the condenser lens.

[0010] In the optical device according to this aspect, since the optical axis of the light source unit matches the optical axis of the condenser lens, among the reflected light reflected in the sensing area, the reflected light traveling in the reverse direction of the matched optical axis can pass through the condenser lens and be condensed onto the light detector. Therefore, it is not necessary to adjust the angles of the illumination light and the reflected light with respect to the sensing area according to the distance between the device and the sensing area, and even without such adjustment, the light detector can appropriately receive the reflected light from the sensing area.

[0011] In addition, since the reflecting surface of the condenser lens has a shape obtained by cutting a cylinder extending in the projection direction of the illumination light with a rotational ellipsoid having a major axis parallel to the projection direction as the rotation axis, by disposing the light detector in a direction toward the first focal position of the condenser lens with respect to the condenser lens and setting the sensing area in a direction toward the second focal position of the condenser lens with respect to the condenser lens, the reflected light from the sensing area can be effectively guided to the light detector.

[0012] The optical device according to the second aspect of the present invention includes: a light source unit that projects illumination light onto a sensing area; a light detector that receives the reflected light of the illumination light reflected in the sensing area; and a condenser lens that condenses the reflected light onto the light detector. Here, the reflecting surface of the condenser lens has a shape obtained by cutting a cylinder extending in the projection direction of the illumination light with a rotational ellipsoid having a major axis parallel to the projection direction as the rotation axis. Further, the light detector is disposed in a direction toward the first focal position of the condenser lens with respect to the condenser lens, and the sensing area is set in a direction toward the second focal position of the condenser lens with respect to the condenser lens.

[0013] In the optical device according to this embodiment, since the reflecting surface of the condenser has a shape obtained by cutting a cylinder extending in the projection direction of the illumination light with a rotational ellipsoid having a major axis parallel to the projection direction as the rotation axis, by disposing a light detector in the direction of the first focal position of the condenser facing the condenser and setting a sensing area in the direction of the second focal position of the condenser facing the condenser, the reflected light from the sensing area can be efficiently guided to the light detector. Therefore, the reflected light from the sensing area can be appropriately received by the light detector.

[0014] The optical device according to the second embodiment can include an optical element that matches the optical axis of the light source unit with the optical axis of the condenser.

[0015] According to this structure, since the optical axis of the light source unit and the optical axis of the condenser match each other, among the reflected light reflected in the sensing area, the reflected light traveling in the reverse direction of the matched optical axis can be condensed by the condenser onto the light detector. Therefore, it is not necessary to adjust the angles of the illumination light and the reflected light with respect to the sensing area according to the distance between the device and the sensing area, and even without performing the above adjustments, the reflected light from the sensing area can be appropriately received by the light detector.

[0016] -Advantages of the Invention-

[0017] As described above, according to the present invention, an optical device capable of appropriately receiving the reflected light from the sensing area without performing complicated adjustment operations can be provided.

[0018] The effects and significance of the present invention will become clearer through the description of the embodiments shown below. However, the embodiments shown below are merely examples when implementing the present invention, and the present invention is not limited to the forms described in the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a perspective view showing the external structure of the moisture sensing device according to Embodiment 1.

[0020] Figure 2 It is a perspective view showing the external structure of the moisture sensing device with the front housing removed according to Embodiment 1.

[0021] Figure 3 It is a cross-sectional view of the moisture sensing device according to Embodiment 1.

[0022] Figure 4 (a) and (b) are diagrams showing the structure of the light source unit according to Embodiment 1.

[0023] Figure 5It is a block diagram showing the structure of the circuit section of the moisture sensing device according to Embodiment 1.

[0024] Figure 6 It is a graph showing the absorption coefficient of light in water according to Embodiment 1.

[0025] Figure 7 It is a flowchart showing the determination process of the moisture sensing device according to Embodiment 1.

[0026] Figure 8 It is a diagram for explaining the method of forming the reflecting surface according to Embodiment 1.

[0027] Figure 9 (a) to (c) of are respectively ray diagrams obtained by simulation for obtaining the appearance of the reflected light rays incident on the light receiving surface of the photodetector when the reflecting surface and the light receiving surface of the photodetector are configured according to the conditions of Adjustment Method 1 according to Embodiment 1. Figure 9 (d) of is a graph showing the relationship between the distance to the sensing area and the relative light receiving amount of the photodetector when the reflecting surface and the light receiving surface are set according to the conditions of Adjustment Method 1 according to Embodiment 1.

[0028] Figure 10 (a) to (c) of are respectively ray diagrams obtained by simulation for obtaining the appearance of the reflected light rays incident on the light receiving surface of the photodetector when the reflecting surface and the light receiving surface of the photodetector are configured according to the conditions of Adjustment Method 2 according to Embodiment 1. Figure 10 (d) of is a graph showing the relationship between the distance to the sensing area and the relative light receiving amount of the photodetector when the reflecting surface and the light receiving surface are set according to the conditions of Adjustment Method 2 according to Embodiment 1.

[0029] Figure 11 (a) to (c) of are respectively ray diagrams obtained by simulation for obtaining the appearance of the reflected light rays incident on the light receiving surface of the photodetector when the reflecting surface and the light receiving surface of the photodetector are configured according to the conditions of Adjustment Method 3 according to Embodiment 1. Figure 11 (d) of is a graph showing the relationship between the distance to the sensing area and the relative light receiving amount of the photodetector when the reflecting surface and the light receiving surface are set according to the conditions of Adjustment Method 3 according to Embodiment 1.

[0030] Figure 12 It is a diagram schematically showing the structure of the road surface information distribution system according to Embodiment 1.

[0031] Figure 13It is a perspective view of the external structure of the moisture sensing device showing the state where the front housing is removed, which pertains to a modification example of Embodiment 1.

[0032] Figure 14 For (a) and (b) of , they are side views of the condenser lens when viewed from the exit side of the illumination light, which pertain to Embodiment 1 and the modification example respectively. Figure 14 For (c) of Figure 14 , it is a diagram showing the condensing range at the position of the light-shielding mask for the reflected light condensed by the reflecting surface in Embodiment 1 and the modification example.

[0033] Figure 15 It is a perspective view of the external structure of the moisture sensing device showing the state where the front housing is removed, which pertains to Embodiment 2.

[0034] Figure 16 It is a cross-sectional view of the moisture sensing device which pertains to Embodiment 2.

[0035] Figure 17 For (a) and (b) of , they are the rear view and the rear perspective view of the condenser lens which pertain to Embodiment 2 respectively.

[0036] Figure 18 It is a structural diagram of the optical system of the moisture sensing device which pertains to Embodiment 3.

[0037] Among them, the drawings are only for illustration and do not limit the scope of the present invention. Detailed Embodiments

[0038] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0039] In the present embodiment, as an example of the optical device according to the present invention, a moisture sensing device for sensing moisture (such as water, snow, ice, etc.) accumulated on the road surface as a sensing area is shown. For convenience, in each drawing, mutually orthogonal XYZ axes are appropriately assigned. The X-axis direction, the Y-axis direction, and the Z-axis direction are the width direction, the height direction, and the front-rear direction of the moisture sensing device 1 respectively. The positive direction of the Z-axis is the projection direction of the illumination light.

[0040] <Structure of the Device>

[0041] Figure 1 It is a perspective view of the external structure of the moisture sensing device 1.

[0042] As Figure 1As shown, the moisture sensing device 1 has a box shape approximately like a rectangular parallelepiped. By combining the front and rear housings 11 and 12, the outer contour of the moisture sensing device 1 is formed. On the front side surface of the housing 11, a substantially square opening 11a is formed. The opening 11a is blocked by the window member 13. The window member 13 is a band-pass filter that blocks visible light and transmits infrared light. The illumination light L1 is projected from the inside of the housings 11 and 12, through the window member 13, onto the road surface (sensing area). In addition, the reflected light R1 of the illumination light L1 is taken into the inside of the housings 11 and 12 through the window member 13.

[0043] Figure 2 is a perspective view showing the external structure of the moisture sensing device 1 with the front housing 11 removed. Figure 3 is at the intermediate position in the X-axis direction, by a plane parallel to the Y-Z plane, Figure 2 of the moisture sensing device 1 when cut.

[0044] Refer to Figure 2 and Figure 3 , the moisture sensing device 1 includes: a light source unit 20, a condenser lens 30, a light detector 40, a circuit board 50, and a light shielding member 60. The light source unit 20 projects infrared light of three wavelengths in the positive Z-axis direction. Through these infrared lights, the illumination light L1 is constituted. The illumination light L1 is projected onto the road surface (sensing area).

[0045] Figure 4 of (a) and (b) are respectively diagrams showing the structure of the light source unit 20.

[0046] The light source unit 20 includes 3 light sources 21a, 21b, and 21c with different wavelengths. The light sources 21a, 21b, and 21c are, for example, laser light sources such as semiconductor lasers. The light sources 21a, 21b, and 21c can also be constituted by LEDs or white light sources with filters for specific wavelengths. The light source 21a emits near-infrared light with a wavelength of 980 nm (hereinafter referred to as "reference wavelength"). The light source 21b emits near-infrared light with a wavelength of 1450 nm (hereinafter referred to as "absorption wavelength 1"). The light source 21c emits near-infrared light with a wavelength of 1550 nm (hereinafter referred to as "absorption wavelength 2"). The light sources 21a, 21b, and 21c emit the illumination light L1 in the same direction (positive X-axis direction). The emission optical axes of the light sources 21a, 21b, and 21c are included in the same plane parallel to the X-Y plane.

[0047] The light source unit 20 further includes collimating lenses 22a, 22b, 22c, a reflecting mirror 23, dichroic mirrors 24, 25. The collimating lenses 22a, 22b, 22c respectively convert the illumination light L1 emitted from the light sources 21a, 21b, 21c into parallel light. The reflecting mirror 23 reflects the illumination light L1 emitted from the light source 21a in the positive Y-axis direction. The dichroic mirror 24 allows the illumination light L1 emitted from the light source 21a to pass through and reflects the illumination light L1 emitted from the light source 21b in the positive Y-axis direction. Thus, the emission optical axes of the light sources 21a and 21b are matched.

[0048] The dichroic mirror 25 allows the two illumination lights L1 incident from the side of the dichroic mirror 24 to pass through and reflects the illumination light L1 emitted from the light source 21c in the positive Y-axis direction. Thus, the emission optical axes of the light sources 2Ia, 21b, 21c are matched to form a single optical axis A1. The reflecting mirror 23 and the dichroic mirrors 24, 25 constitute a matching optical system 20a that matches the emission optical axes of the light sources 21a, 21b, 21c with each other. The optical axis A1 is bent in the positive Z-axis direction by the reflecting mirror 26. Thus, the illumination lights L1 respectively emitted from the light sources 21a, 21b, 21c are emitted from the light source unit 20 in the positive Z-axis direction.

[0049] Return to Figure 2 and Figure 3 , the condenser lens 30 is made of a metal material such as aluminum. The condenser lens 30 may also include a resin material. The condenser lens 30 has a reflecting surface 30a on the surface opposite to the light source unit 20. The reflecting surface 30a is a curved surface that is recessed inward of the condenser lens 30. The reflecting surface 30a is formed by mirror-finishing the inwardly recessed curved surface and then vapor-depositing a material with a high reflectivity such as gold on the curved surface. The shape of the reflecting surface 30a is a shape obtained by cutting a prism-shaped column extending in the projection direction of the illumination light L1 with a rotational ellipsoidal surface having a major axis parallel to the projection direction as the rotation axis. Refer to Figure 8 for a description of the method for setting the shape of the reflecting surface 30a.

[0050] In the condenser lens 30, a through-hole 30b for allowing the illumination light L1 emitted from the light source unit 20 to pass through is further formed. The through-hole 30b is formed along the central axis of the columnar portion 30d. The illumination light L1 passes through the opening 14c and the through-hole 30b and is projected onto the road surface (detection area) ahead. The condenser lens 30 matches the optical axis A1 of the light source unit 20 with the optical axis A2 of the condenser lens 30 itself within the range on the road surface side (the range in the projection direction of the illumination light L1 of the condenser lens 30). That is, these two optical axes A1, A2 are made the same as a common optical axis A10 through the condenser lens 30. The optical axis A2 of the condenser lens 30 is perpendicular to the optical axis A1 of the light source unit 20.

[0051] The condenser lens 30 reflects the reflected light R1 incident from the road surface onto the reflecting surface 30a in the negative Y-axis direction, and condenses the reflected light R1 onto the light-receiving surface of the light detector 40. The light detector 40 includes, for example, a photodiode. As the light detector 40, a photodiode having detection sensitivity in the infrared band (for example, 900 to 1800 nm) can be used. When the light detector 40 also has detection sensitivity in the visible light band, a filter that transmits the emission wavelengths of the light sources 21a, 21b, 21c, namely the reference wavelength, the absorption wavelength 1, and the absorption wavelength 2, and blocks the visible light band can be arranged in front of the light detector 40. The light detector 40 may also include an avalanche photodiode.

[0052] The light detector 40 receives the reflected light R1 obtained by reflecting the illumination light L1 emitted from the light sources 21a, 21b, 21c by the road surface, and outputs an electrical signal based on the received light amount. The light detector 40 is provided on the upper surface of the circuit board 50. The light detector 40 is arranged below the outlet of the through hole 30b.

[0053] In the present embodiment, the light sources 21a, 21b, 21c are driven to emit pulsed light in a time-division manner. Therefore, the light detector 40 receives the reflected light R1 based on the illumination light L1 from the light sources 21a, 21b, 21c in a time-division manner, and outputs an electrical signal corresponding to the received light amount of each reflected light R1. Based on the electrical signals corresponding to the respective reflected lights R1 output from the light detector 40, the type of the deposit (moisture state) on the road surface is determined. The determination process of the deposit will be described later with reference to Figure 7 to explain the determination process of the deposit.

[0054] The light-shielding member 60 has a circular light-shielding mask 60a at a position directly above the light detector 40. The light-shielding mask 60a is supported by the light-shielding member 60 through four beam portions 60b. In a plan view, the size of the light-shielding mask 60a is substantially equal to the size of the outlet of the through hole 30b formed in the condenser lens 30. An infrared absorber 60c that absorbs infrared light is attached to the upper surface of the light-shielding mask 60a. For example, a coating containing the infrared absorber 60c is applied to the upper surface of the light-shielding mask 60a. Alternatively, a sheet coated with the infrared absorber 60c is attached to the upper surface of the light-shielding mask 60a.

[0055] When a part of the illumination light L1 emitted from the light source unit 20 reaches the outlet of the through hole 30b and scatters, the light-shielding mask 60a shields the scattered light from the light detector 40. That is, the scattered light from the outlet of the through hole 30b to the light detector 40 is incident on the upper surface of the light-shielding mask 60a and is absorbed by the infrared absorber 60c. In addition, the infrared absorber 60c may not be attached to the upper surface of the light-shielding mask 60a. In this case, the scattered light from the outlet of the through hole 30b to the light detector 40 is blocked by the light-shielding mask 60a.

[0056] The beam portion 60b that supports the light-shielding mask 60a is preferably formed into a thin linear shape so as to minimize the obstruction of the reflected light R1 that is condensed onto the light-receiving surface of the photodetector 40 through the outside of the light-shielding mask 60a. In addition, the light-shielding mask 60a does not necessarily have to be supported by the beam portion 60b. For example, a transparent plate may be disposed on the upper surface of the light-shielding member 60, and the light-shielding mask 60a may be attached to the transparent plate. In this case, it is preferable to apply an AR coating to the upper surface and the lower surface of the transparent plate.

[0057] In Figure 2 and Figure 3 In the structure of, the condenser lens 30, the circuit board 50, and the light-shielding member 60 are provided on the support member 14 fixed to the housing 12. That is, the condenser lens 30 is fixed to the front surface of the wall plate portion 14a of the support member 14 through the back plate portion 30c and is provided on the support member 14. In addition, the circuit board 50 is fixed to the lower surface of the front frame 14b of the support member 14, and the light-shielding member 60 is fixed to the front surface of the wall plate portion 14a of the support member 14. Further, the light source unit 20 is fixed to the back surface of the wall plate portion 14a of the support member 14 while being held by the holder. A circular opening 14c for passing the illumination light L1 is formed in the wall plate portion 14a. In this way, the assembly of the internal structure of the moisture sensing device 1 is completed.

[0058] <Structure of the circuit portion>

[0059] Figure 5 is a block diagram showing the structure of the circuit portion of the moisture sensing device 1.

[0060] In addition to Figure 1 the light sources 21a, 21b, 21c and the photodetector 40 shown, the moisture sensing device 1 further includes a control unit 110, a storage unit 120, an output unit 130, three drive units 141, 142, 143, and a processing unit 150.

[0061] The control unit 110 includes, for example, a CPU and a microcomputer. The control unit 110 controls each part in the moisture sensing device 1 according to the control program stored in the storage unit 120. As a function based on the control program, a determination unit 111 is provided in the control unit 110. The determination unit 111 determines the type of deposit (water, snow, ice) on the road surface based on the detection signal from the photodetector 40. The determination unit 111 may not be configured as a function based on the control program but may be configured as hardware.

[0062] The storage unit 120 includes a memory that stores a control program and serves as a working area during control processing. The output unit 130 outputs the determination result of the determination unit 111. The output unit 130 can be a display unit such as a monitor configured in the moisture sensing device 1, or can also be a communication module for sending the determination result of the determination unit 111 to an external processing device such as a server.

[0063] The drive units 141, 142, and 143 drive the light sources 21a, 21b, and 21c respectively according to the control from the control unit 110. The processing unit 150 converts the electrical signal input from the light detector 40 into a digital signal, takes the logarithm, and outputs it to the control unit 110. The control unit 110 determines the type of the accumulation on the road surface (the state of moisture) based on the detection signal input from the processing unit 150. This determination is made by the determination unit 111 as described above.

[0064] <Determination method>

[0065] Next, a method for determining the type of accumulation will be described.

[0066] Figure 6 is a graph showing the absorption coefficients of light in water and ice.

[0067] In Figure 6 the reference wavelength, absorption wavelength 1, and absorption wavelength 2 of the emission wavelengths respectively set for the light sources 21a, 21b, and 21c are represented by arrows.

[0068] As Figure 6 shown, the absorption coefficients of the reference wavelength for water and ice are smaller than those of absorption wavelength 1 and absorption wavelength 2. That is, the illumination light L1 of the reference wavelength is less absorbed based on water or ice compared to the illumination lights L1 of absorption wavelength 1 and absorption wavelength 2. Therefore, even if there is moisture (water, ice, snow) in the irradiation area on the road surface, the illumination light L1 (reference wavelength) emitted from the light source 21a is easily reflected by the road surface, and the light receiving amount of the reflected light R1 of this illumination light L1 (reference wavelength) by the light detector 40 increases. On the other hand, the absorption coefficients of absorption wavelength 1 and 2 emitted from the light sources 21b and 21c based on water or ice are larger. Therefore, when there is moisture in the irradiation area, the illumination lights L1 of absorption wavelength 1 and 2 are absorbed by the moisture, and the light amount of the reflected lights R1 of absorption wavelength 1 and 2 received by the light detector 40 decreases.

[0069] Therefore, by using the detection signal of the illumination light L1 of the reference wavelength that is hardly affected by moisture to standardize the detection signals of the illumination lights L1 of absorption wavelength 1 and 2, it is possible to suppress noise components such as scattering based on the shape of the road surface.

[0070] In the present embodiment, water and ice are discriminated by utilizing the difference in the absorption coefficients of absorption wavelength 1 and absorption wavelength 2. That is, at absorption wavelength 1 (1450 nm), the absorption coefficient in water is larger than that in ice, and at absorption wavelength 2 (1550 nm), the absorption coefficient in ice is larger than that in water. Therefore, by obtaining the ratio of the detection signals at absorption wavelength 1 and absorption wavelength 2, it is possible to discriminate whether it is water or ice when moisture exists at the irradiation position.

[0071] Figure 7 It is a flowchart showing the determination process of the type of deposit based on the control unit 110 (determination unit 111).

[0072] First, the control unit 110 drives the light source unit 20 (S11). Specifically, the control unit 110 causes the illumination light L1 to be emitted from the light sources 21a, 21b, and 21c in a time-division manner via the drive units 141, 142, and 143. Then, the control unit 110 obtains, via the processing unit 150, the detection signal output from the photodetector 40 according to the drive of the light source 21a, the detection signal output from the photodetector 40 according to the drive of the light source 21b, and the detection signal output from the photodetector 40 according to the drive of the light source 21c.

[0073] Next, the determination unit 111 of the control unit 110 determines the state of the irradiation position based on the intensity of the detection signal at the reference wavelength, the intensity of the detection signal at absorption wavelength 1, and the intensity of the detection signal at absorption wavelength 2.

[0074] Specifically, when the value R11 obtained by logarithmically transforming the ratio of the intensity of the detection signal at absorption wavelength 1 to the intensity of the detection signal at the reference wavelength is equal to or greater than the threshold value Rth1, and the value R12 obtained by logarithmically transforming the ratio of the intensity of the detection signal at absorption wavelength 2 to the intensity of the detection signal at the reference wavelength is equal to or greater than the threshold value Rth2 (S12: Yes), it is determined that there is no moisture (dry) at the irradiation position (S13).

[0075] Here, the threshold value Rthl is obtained by subtracting the absorption coefficient value at the absorption wavelength 1 (1450 nm) for water from the absorption coefficient value at the reference wavelength (980 nm) for water and multiplying the resulting value by twice the thickness determined to have water. For example, when sensing water with a thickness of 10 μm or more, the value of Rthl is -0.062. In addition, the threshold value Rth2 is obtained by subtracting the absorption coefficient value at the absorption wavelength 2 (1550 nm) for ice from the absorption coefficient value at the reference wavelength (980 nm) for ice and multiplying the resulting value by twice the thickness determined to have ice. For example, when sensing ice with a thickness of 10 μm or more, the value of Rth2 is -0.069.

[0076] In the case where the determination in step S12 is negative, the determination unit 111 determines that there is moisture at the irradiation position, and the process proceeds to step S14.

[0077] In step S14, the determination unit 111 calculates the ratio of the value R11 to the value R12, and determines whether this value is equal to or less than the threshold value Ri. Here, the value of the threshold value Ri is the ratio of the value obtained by subtracting the absorption coefficient of the reference wavelength (980 nm) from the absorption coefficient of the absorption wavelength 1 (1450 nm) in ice to the value obtained by subtracting the absorption coefficient of the reference wavelength (980 nm) from the absorption coefficient of the absorption wavelength 2 (1550 nm) in ice.

[0078] In the case where the ratio of the value R11 to the value R12 is equal to or less than the threshold value Ri (S14: Yes), the determination unit 111 determines that only ice or snow exists at the irradiation position, and the process proceeds to step S15. In the case where the ratio of the value R11 to the value R12 exceeds the threshold value Ri (S14: No), the determination unit 111 determines that water or water and ice exist at the irradiation position, and the process proceeds to step S18.

[0079] In step S15, the determination unit 111 determines whether the received light intensity Ir of the reference wavelength is equal to or greater than the threshold value Ith. Here, in the case where the received light intensity Ir is equal to or greater than the threshold value Ith (S15: Yes), the determination unit 111 determines that snow exists at the irradiation position (S16). On the other hand, in the case where the received light intensity Ir is less than the threshold value Ith (S15: No), the determination unit 111 determines that ice exists at the irradiation position (S17). Here, after the determination unit 111 determines that snow or ice exists, the control unit 110 may also measure the thickness thereof based on the values of the detection signals of the reference wavelength and the absorption wavelength 1.

[0080] In step S18, the determination unit 111 calculates the ratio of the value R11 to the value R12, and determines whether this value is equal to or greater than the threshold value Rw. In the case where the ratio of the value R11 to the value R12 is equal to or greater than the threshold value Rw (S18: Yes), the determination unit 111 determines that water exists at the irradiation position (S19). Here, after the determination unit 111 determines that water exists at the irradiation position, the control unit 110 may also further measure the thickness of the water based on the values of the detection signals of the reference wavelength and the absorption wavelength 2.

[0081] On the other hand, when the ratio of the value R11 to the value R12 is less than the threshold value Rw (S18: No), that is, when Ri < R11 / R12 < Rw, the determination unit 111 determines that there is a mixture of water and ice at the irradiation position (S20). Here, the control unit 110 calculates the ratio of water to ice present at the irradiation position by comparing the value of (R11 / R12 - Ri) with the value of (Rw - R11 / R12), and based on this ratio and the detection signal values of the reference wavelength, absorption wavelength 1, and absorption wavelength 2, the film thickness of the water-ice mixture can also be measured.

[0082] <Method for forming the reflecting surface>

[0083] Next, a method for forming the reflecting surface 30a of the condenser lens 30 will be described.

[0084] Figure 8 It is a diagram for explaining the method for forming the reflecting surface 30a.

[0085] As Figure 8 shown, when one ridge line of the reflecting surface 30a is in the shape of a part along a specified ellipse E0, the light emitted from the first focal position FP1 on the major axis AX1 of the ellipse E0 passes through the reflecting surface 30a and converges at the second focal position FP2 on the major axis AX1. Conversely, the light emitted from the second focal position FP2 passes through the reflecting surface 30a and converges at the first focal position FP1.

[0086] Here, the optical axis A21 from the reflecting surface 30a to the first focal position FP1 and the optical axis A22 from the reflecting surface 30a to the second focal position FP2 are perpendicular to each other. In addition, according to the ratio of the major axis AX1 to the minor axis AX2 of the ellipse E0, the first focal distance FD1 to the first focal position FP1 and the second focal distance FD2 to the second focal position FP2 change. In other words, according to the lengths of the first focal distance FD1 and the second focal distance FD2, the ratio of the major axis AX1 to the minor axis AX2 changes, and the shape of the ellipse E0 also changes. Correspondingly, the shape of the ridge line of the reflecting surface 30a also changes.

[0087] In the first embodiment, the road surface (sensing surface) is set in the direction from the reflecting surface 30a to the second focal position FP2, and the detection surface of the light detector 40 is set in the direction from the reflecting surface 30a to the first focal position FP1. Therefore, the first focal distance FD1 is set near the distance between the reflecting surface 30a and the light detector 40 in the moisture sensing device 1, and the second focal distance FD2 is set near the distance between the reflecting surface 30a and the road surface (sensing area). For example, the first focal distance FD1 is set to about 50 mm, and the second focal distance FD2 is set to about several meters to more than ten meters. In this case, the ellipse E0 compared to Figure 8In the case where the ratio of the major axis AX1 to the minor axis AX2 is significantly increased.

[0088] In Embodiment 1, the shape of the reflecting surface 30a is set to be a cross-sectional shape obtained by cutting a quadrangular prism (cylinder) P0 extending in the direction along the optical axis A22 from a rotational ellipsoidal surface having the major axis AX1 passing through the first focal position FP1 and the second focal position FP2 as the rotation axis. The two opposed side surfaces of the quadrangular prism P0 are parallel to the plane including the optical axes A21 and A22, and the other two opposed side surfaces of the quadrangular prism P0 are perpendicular to the plane including the optical axes A21 and A22. The central axis of the quadrangular prism P0 coincides with the optical axis A22 directed toward the second focal position FP2. Figure 8 The optical axis A21 and the optical axis A22 respectively correspond to Figure 3 the optical axis A2 and the optical axis A10.

[0089] By setting the shape of the reflecting surface 30a in this way, it is possible to effectively condense the reflected light R1 generated near the second focal position FP2 onto the light-receiving surface of the photodetector 40 disposed near the first focal position FP1. That is, compared with the case where the reflecting surface 30a is set to a parabolic surface that condenses parallel light from infinity onto the light-receiving surface of the photodetector 40, more light amount of the reflected light R1 can be condensed onto the photodetector 40.

[0090] <Adjustment method of reflecting surface and light-receiving surface>

[0091] Next, an adjustment method for the reflecting surface 30a and the light-receiving surface of the photodetector 40 will be described.

[0092] Here, it is assumed that the measurement distance range is set to 2 to 15 m. The measurement distance range refers to the variation range of the distance to the sensing area. For example, when the moisture sensing device 1 is installed on a utility pole or the like, the range of the distance to the sensing area (road surface) that can vary according to the installation state (height of the installation position, orientation of the projection direction) of the moisture sensing device 1 is the measurement distance range.

[0093] The inventors of the present application have studied, from various viewpoints, a preferable adjustment method for the reflecting surface 30a and the light-receiving surface of the photodetector 40 with respect to the measurement distance range based on simulation. Hereinafter, together with the simulation results, an adjustment method for the reflecting surface 30a and the light-receiving surface of the photodetector 40 based on this study will be described.

[0094] (1) Adjustment method 1

[0095] In adjustment method 1, Figure 8The second focal position FP2 shown is set at a distance position (e.g., 4 m) between the farthest distance position (15 m) and the nearest distance position (2 m) of the measurement distance range, and the light-receiving surface of the light detector 40 is positioned at the position of the first focal position FP1. In addition, the size of the light-receiving surface is set such that the spot size on the light-receiving surface of the reflected light R1 reflected at the farthest distance position is smaller than the size of the light-receiving surface.

[0096] Figure 9 (a) to (c) of FIG. are ray diagrams obtained by simulation to obtain the appearance of the rays of the reflected light R1 incident on the light-receiving surface 40a of the light detector 40 when the reflecting surface 30a and the light-receiving surface 40a of the light detector 40 are configured according to the conditions of adjustment method 1.

[0097] In Figure 9 (a) to (c) of FIG., the points at positions 15 m, 4 m, and 2 m from the reflecting surface 30a (including the positions on the straight line of the optical axis A22) are respectively shown, and the rays of the reflected light R1 that are reflected and diffused and are captured by the reflecting surface 30a and condensed on the light detector 40 are shown. Figure 8 In this simulation, the first focal distance FD1 and the second focal distance FD2 shown in FIG. are set to 50 mm and 4 m respectively to form the shape of the reflecting surface 30a. In addition, in

[0098] In this simulation, Figure 8 the first focal distance FD1 and the second focal distance FD2 shown are set to 50 mm and 4 m respectively to form the shape of the reflecting surface 30a. In addition, in Figure 2 FIG., the left-right and up-down widths of the reflecting surface 30a when viewed from the positive Z-axis side are set to 52 mm respectively. That is, the widths of the four side surfaces of the columnar portion 30d of the quadrangular prism are all set to 52 mm. In addition, the diameter of the through hole 30b when viewed from the positive Z-axis side is set to 5 mm. Further, the light-receiving surface 40a of the light detector 40 is set to a circle with a diameter of 1 mm. In addition, the light-receiving surface 40a of the light detector 40 is set at the position of the first focal position FP1.

[0099] Under this condition, as shown in Figure 9 (b) of FIG., the reflected light R1 from the reflection position at a distance of 4 m is focused on the light-receiving surface 40a. In addition, in this case, as shown in Figure 9 (a) of FIG., the position where the reflected light R1 from the reflection position at a distance of 15 m (the farthest distance of the measurement distance range) converges to the minimum beam diameter is closer to the reflecting surface 30a side than the light-receiving surface 40a, but all of the reflected light R1 captured by the reflecting surface 30a is incident on the light-receiving surface 40a. Further, in this case, as shown in Figure 9As shown in (c), the position where the reflected light R1 from the reflection position at a distance of 2 m (the closest distance in the measurement distance range) converges to the minimum beam diameter is farther from the reflection surface 30a than the light-receiving surface 40a, but all of the reflected light R1 captured by the reflection surface 30a enters the light-receiving surface 40a.

[0100] Thus, if the reflection surface 30a and the light-receiving surface 40a are set according to the conditions of adjustment method 1 respectively, when a sensing area is set at any distance position within the measurement distance range, all of the reflected light R1 captured by the reflection surface 30a can enter the light-receiving surface 40a. Therefore, the reflected light R1 can be efficiently condensed on the light-receiving surface 40a.

[0101] Figure 9 (d) is a graph showing the relationship between the distance to the sensing area and the light-receiving light amount of the light detector 40 based on the above simulation when the reflection surface 30a and the light-receiving surface 40a are set according to the conditions of adjustment method 1.

[0102] In Figure 9 (d), the horizontal axis is the distance to the sensing area (the distance between the reflection surface 30a and the sensing area), and the vertical axis is the relative light-receiving light amount of the reflected light R1 with the light-receiving light amount when the distance to the sensing area is 15 m (the farthest distance in the measurement distance range) set to 1.

[0103] Since the reflected light of the illumination light L1 spreads in the sensing area, the light amount of the reflected light R1 captured by the reflection surface 30a is inversely proportional to the square of the distance to the sensing area. On the other hand, according to the conditions of adjustment method 1, as Figure 9 (a) to (c) show, at any distance position within the measurement distance range, all of the reflected light R1 captured by the reflection surface 30a enters the light-receiving surface 40a. Therefore, the light amount of the reflected light R1 entering the light-receiving surface 40a (light-receiving light amount) is inversely proportional to the square of the distance to the sensing area.

[0104] Therefore, as Figure 9 (d) shows, the light-receiving light amount of the reflected light increases sharply as the distance to the sensing area becomes shorter. Here, the relative light-receiving light amount at the closest distance position (2 m) is about 56 times that at the farthest distance position (15 m). Therefore, the processing unit 150 (refer to Figure 5 ) that processes the signal from the light detector 40 needs to have a detection circuit capable of covering a range Rn1 of about 56 times. In this case, the detection circuit needs to include a gain switching circuit, a gain adjustment circuit, etc.

[0105] Here, according to the conditions of adjustment method 1, as Figure 9As shown in (d), in the short-distance range, the relative received light amount is significantly higher. Therefore, when the moisture sensing device 1 is used in the short-distance range, the output of the light sources 21a, 21b, and 21c can be reduced compared to when measuring the long-distance range. Thereby, the power consumption of the moisture sensing device 1 can be suppressed, and the range Rn1 can be compressed. Therefore, the gain switching circuit and the gain adjustment circuit can be omitted from the detection circuit.

[0106] In addition, in the above inspection confirmation, as Figure 9 shown in (a) and (c), the second focal length FD2 and the size of the light receiving surface 40a are set such that the spot size of the reflected light R1 on the light receiving surface 40a reflected at the farthest distance position and the spot size of the reflected light R1 on the light receiving surface 40a reflected at the nearest distance position are both smaller than the size of the light receiving surface 40a. In contrast, the second focal length FD2 and the size of the light receiving surface 40a can also be set such that the spot size of the reflected light R1 reflected at the nearest distance position is larger than the light receiving surface 40a. In this way, in the short-distance range, a part of the reflected light R1 can be separated from the light receiving surface 40a, and the received light amount in the short-distance range can be reduced. Thereby, the range Rn1 that the detection circuit should cover can be narrowed, and simplification of the detection circuit can be achieved.

[0107] (2) Adjustment method 2

[0108] In adjustment method 2, Figure 8 the second focal position FP2 shown in is set at the farthest distance position (15 m) of the measurement distance range, and the light receiving surface of the photodetector 40 is positioned at the position of the first focal position FP1. In addition, the light receiving surface is set such that the size of the light receiving surface is smaller than the spot size of the reflected light R1 on the light receiving surface reflected at the nearest distance position.

[0109] Figure 10 Figures (a) to (c) are ray diagrams obtained by simulation to obtain the appearance of the rays of the reflected light R1 incident on the light receiving surface 40a of the photodetector 40 when the reflecting surface 30a and the light receiving surface 40a of the photodetector 40 are configured according to the conditions of adjustment method 2.

[0110] Figure 10 Figures (a) to (c) respectively show the reflected light R1 that is reflected and diffused at positions 15 m, 4 m, and 2 m from the reflecting surface 30a (including Figure 8 the positions on the straight line of the optical axis A22 of ) and is obtained by the reflecting surface 30a and condensed on the photodetector 40.

[0111] In this simulation, Figure 8The first focal length FD1 and the second focal length FD2 shown are set to 50 mm and 15 m, respectively, to form the shape of the reflecting surface 30a. Other simulation conditions are set in the same manner as in Figure 9 cases (a) to (c).

[0112] In this case, as shown in Figure 10 (a), the reflected light R1 from the reflection position at a distance of 15 m (the farthest distance in the measurement distance range) is focused on the light receiving surface 40a. Further, as shown in Figure 10 (b), the position where the reflected light R1 from the reflection position at a distance of 4 m (the distance between the farthest distance and the nearest distance) converges to the minimum beam diameter is shifted downward with respect to the light receiving surface 40a, but all the reflected light R1 captured by the reflecting surface 30a is incident on the light receiving surface 40a. Further, as shown in Figure 10 (c), the position where the reflected light R1 from the reflection position at a distance of 2 m (the nearest distance in the measurement distance range) converges to the minimum beam diameter is further shifted with respect to the light receiving surface 40a, so that a part of the reflected light R1 captured by the reflecting surface 30a deviates from the light receiving surface 40a.

[0113] Figure 10 (d) is a graph showing the relationship between the distance to the sensing area and the received light amount of the photodetector 40 based on the above simulation when the reflecting surface 30a and the light receiving surface 40a are set according to the conditions of adjustment method 2. The vertical axis and the horizontal axis are the same as in Figure 9 (d).

[0114] According to the conditions of adjustment method 2, as shown in Figure 10 (c), when the reflection position is the nearest distance position, a part of the reflected light R1 captured by the reflecting surface 30a deviates from the light receiving surface 40a. Therefore, as shown in Figure 10 (d), the degree of increase in the received light amount of the reflected light R1 in the short distance range is slower than that in Figure 9 (d). Here, the relative received light amount at the nearest distance position (2 m) is compressed to about 37 times the relative received light amount at the farthest distance position (15 m). Therefore, the processing unit 150 (refer to Figure 5 ) that processes the signal from the photodetector 40 only needs a detection circuit capable of covering a range Rn2 of about 37 times. In this case, there is a possibility of omitting a gain switching circuit, a gain adjustment circuit, etc. from the detection circuit.

[0115] In addition, under the conditions of adjustment method 2, similar to the case of adjustment method 1, when the moisture sensing device 1 is used in a short distance range, adjustment can also be made to reduce the outputs of the light sources 21a, 21b, and 21c. Thereby, the power consumption of the moisture sensing device 1 can be suppressed, and the range Rn2 can be compressed. Therefore, the gain switching circuit and the gain adjustment circuit can be omitted from the detection circuit.

[0116] In addition, under the conditions of adjustment method 2, the reflected light R1 reflected from the farthest distance position (15 m) is focused on the light receiving surface 40a of the photodetector 40. Therefore, compared with adjustment method 1, the size of the light receiving surface 40a can be reduced. That is, even if the size of the light receiving surface 40a is set small, the reflected light R1 that is reflected in the long distance range and has a small acquisition amount relative to the light receiving surface 40a can be reliably incident on the light receiving surface 40a of the photodetector 40 without remainder.

[0117] In addition, when the size of the light receiving surface 40a is adjusted small in this way, the light amount of the reflected light R1 that escapes from the light receiving surface 40a among the reflected lights R1 from the short distance range increases. Thereby, the relative light receiving amount in the short distance range can be reduced, and the range Rn2 can be further compressed. Therefore, the gain switching circuit and the gain adjustment circuit can be omitted from the detection circuit.

[0118] In addition, if the light receiving surface 40a is reduced, the detection accuracy of the photodetector 40 can be improved, and the cost of the photodetector 40 can be reduced.

[0119] (3) Adjustment method 3

[0120] In adjustment method 3, Figure 8 the second focal position FP2 shown is set to the farthest distance position (15 m) of the measurement distance range, and the light receiving surface of the photodetector 40 is positioned at a position shifted toward the reflection surface 30a side with respect to the first focal position FP1. In addition, the light receiving surface is set such that the spot size on the light receiving surface of the reflected light R1 reflected at the farthest distance position is equal to the size of the light receiving surface, and the size of the light receiving surface is smaller than the spot size on the light receiving surface of the reflected light R1 reflected at the closest distance position.

[0121] Figure 11 (a) to (c) are ray diagrams for obtaining the appearance of the rays of the reflected light R1 incident on the light receiving surface 40a of the photodetector 40 when the reflection surface 30a and the light receiving surface 40a of the photodetector 40 are configured according to the conditions of adjustment method 3 through simulation.

[0122] Figure 11 In (a) to (c), the positions at distances of 15 m, 4 m, and 2 m from the reflection surface 30a are shown (including Figure 8Among the point-reflected and diffused reflected light R1 at a position on the straight line of the optical axis A22), the light beam of the reflected light R1 obtained by the reflecting surface 30a and condensed on the light detector 40.

[0123] In this simulation, compared with Figure 10 the simulation conditions of (a) to (c), the position of the light detector 40 is different. In Figure 11 (a) to (c) of Figure 10 the light detectors arranged in (a) to (c) of

[0124] That is, in Figure 11 the simulations of (a) to (c) of Figure 10 a light-receiving surface 40a is arranged at a position shifted in a direction approaching the reflecting surface 30a with respect to the first focal position FP1. More specifically, the light detector 40 is arranged such that the spot size (beam diameter) W1 on the light-receiving surface 40a of the reflected light R1 reflected at the farthest distance position (15 m) is equal to the size (diameter) of the light-receiving surface 40a. Other simulation conditions are set in the same manner as in

[0125] In this case, as shown in Figure 11 (a) of Figure 11 all the reflected light R1 from the reflection position at a distance of 15 m (the farthest distance in the measurement distance range) is condensed on the light-receiving surface 40a. Further, as shown in Figure 11 (b) of

[0126] Figure 11 as the position where the reflected light R1 from the reflection position at a distance of 41 n (the distance between the farthest distance and the nearest distance) converges to the minimum beam diameter moves away from the light-receiving surface 40a, the spot size W1 becomes larger than the size of the light-receiving surface 40a, and a part of the reflected light R1 obtained by the reflecting surface 30a detaches from the light-receiving surface 40a. Further, as shown in Figure 11 (c) of

[0126] Figure 11 as the position where the reflected light R1 from the reflection position at a distance of 2 m (the nearest distance in the measurement distance range) converges to the minimum beam diameter moves further away from the light-receiving surface 40a, the spot size W1 further increases, and a larger part of the reflected light R1 obtained by the reflecting surface 30a detaches from the light-receiving surface 40a.

[0126] Figure 11 Figure (d) shows a graph of the relationship between the distance to the sensing area and the received light amount of the light detector 40 based on the above simulation when the reflecting surface 30a and the light-receiving surface 40a are set according to the conditions of adjustment method 3. The vertical axis and the horizontal axis are the same as in Figure 9 (d) of

[0127] According to the conditions of adjustment method 3, as in Figure 11 (b) of Figure 11As shown in (c), as the reflection position approaches the closest distance position, the amount of reflected light R1 departing from the light-receiving surface 40a increases. Therefore, as shown in Figure 11 (d), the degree of increase in the received light amount of the reflected light R1 in the short-distance range further becomes slow. Here, the relative received light amount at the closest distance position (2 m) is compressed to about 11 times the relative received light amount at the farthest distance position (15 m). Therefore, the processing unit 150 (refer to Figure 5 ) that processes the signal from the light detector 40 only needs to have a detection circuit capable of covering a range Rn3 of about 11 times. In this case, a gain switching circuit, a gain adjustment circuit, etc. can be omitted from the detection circuit.

[0128] In addition, by adjusting the conditions of Method 3, all of the reflected light R1 reflected from the farthest distance position (15 m) is also condensed onto the light-receiving surface 40a of the light detector 40. Therefore, it is possible to reliably make the reflected light R1, which is reflected at the farthest distance position and has a small acquisition amount relative to the light-receiving surface 40a, enter the light-receiving surface 40a of the light detector 40 without remainder. Therefore, moisture sensing at the farthest distance position can be performed more accurately.

[0129] In addition, in the above simulation conditions, the light detector 40 is arranged such that the spot size W1 on the light-receiving surface 40a of the reflected light R1 reflected at the farthest distance position (15 m) is equal to the size of the light-receiving surface 40a. However, the position of the light detector 40 or the size of the light-receiving surface 40a can also be set so that the spot size W1 on the light-receiving surface 40a of the reflected light R1 reflected at the farthest distance position (15 m) is slightly smaller than the size of the light-receiving surface 40a. Thereby, it is possible to reliably make the reflected light R1 enter the light-receiving surface 40a of the light detector 40 in the long-distance range, and moisture sensing in the long-distance range can be accurately performed.

[0130] <System Structure Example>

[0131] Next, a system structure example using the moisture sensing device 1 according to the above-described Embodiment 1 will be described.

[0132] Figure 12 FIG. schematically shows the structure of the road surface information distribution system 200.

[0133] The road surface information distribution system 200 includes the moisture sensing device 1 and the management server 2. In the Figure 12 example, the road 3 passes through the exit 5a of the bridge 4 and the tunnel 5 and is connected to the inside of the tunnel 5.

[0134] The moisture sensing device 1 is provided not only on the side of the road 3 via a pole portion or the like, but also on an external lamp, a wall surface, etc. provided on the side of the road 3. The moisture sensing device 1 senses the state of the road surface 3a of the road 3.Figure 12 In the figure, there are two moisture sensing devices 1. The moisture sensing device 1 at the front side senses the state of the sensing area 3a1 of the road surface 3a on the bridge 4, and the moisture sensing device 1 at the inner side detects the state of the sensing area 3a2 of the road surface 3a near the exit 5a of the tunnel 5. The distances between each moisture sensing device 1 and the sensing areas 3al and 3a2 are different from each other. Any distance is within the range of the measurement distance range. The moisture sensing device 1 judges the state of the moisture (type of deposit, thickness, etc.) in each sensing target area of the road surface 3a, and sends the judgment result to the management server 2 via the base station 6 and the network 7.

[0135] The base station 6 is set to include the moisture sensing device 1 within the communicable range, and is configured to be able to communicate with the moisture sensing device 1 wirelessly. In this case, Figure 3 the output unit 130 includes a communication module. The base station 6 is connected to the network 7. The network 7 is, for example, the Internet.

[0136] The management server 2 is set in the road surface condition distribution center 8 or the like and is connected to the network 7. Based on the information related to the road surface state distributed by the moisture sensing device 1, the management server 2 generates map information for reporting the state of the road surface 3a, and distributes the generated map information to vehicles and the like via the network 7 and the base station 6. The distributed map information is displayed on the display unit of the vehicle navigation system mounted on the vehicle. The driver can confirm the display content and grasp the state of the road surface 3a of the driving path. Thereby, the safety when driving on the road surface 3a can be improved.

[0137] In addition, the moisture sensing device 1 can also be mounted on the vehicle. In this case, the moisture sensing device 1 is provided on the vehicle so that, for example, the illumination light L1 irradiates the road surface in the forward direction of the vehicle and in the inclined direction. The moisture sensing device 1 senses the road surface state in front of the vehicle and displays the sensing result on the navigation system of the vehicle. The sensing of the road surface state is also performed when the vehicle is driving and is displayed on the navigation system at any time. Thereby, the driver can reliably grasp the state of the road surface currently being driven on.

[0138] In this case, further, based on the sensing result of the road surface of the moisture sensing device 1 together with the information indicating the current driving position, it can be sent from the navigation system to Figure 8 the management server 2 and aggregated to the management server 2. Thereby, the management server 2 can generate finer map information indicating the state of the road based on the sensing results of the road surfaces aggregated from each vehicle. The driver can more reliably grasp the state of the road that can be the driving path.

[0139] <Effects of the Embodiment>

[0140] By Embodiment 1, the following effects are obtained.

[0141] As shown Figure 3 in the figure, the optical axis A1 of the light source unit 20 and the optical axis A2 of the condenser lens 30 match each other in the range on the road surface side (the sensing area side). Therefore, among the reflected lights reflected by the road surface (sensing area), the reflected light R1 traveling in the reverse direction of the matched optical axis A10 can be condensed onto the light detector 40 by the condenser lens 30. Therefore, it is not necessary to adjust the angles of the illumination light L1 and the reflected light R1 with respect to the road surface according to the distance between the moisture sensing device 1 and the road surface. Even without such adjustment, the light detector 40 can appropriately receive the reflected light R1 from the road surface.

[0142] In addition, as described with reference to Figure 8 , since the reflecting surface 30a of the condenser lens 30 has a shape obtained by cutting a cylinder (quadrangular prism P0) extending in the projection direction of the illumination light L1 with a rotational ellipsoid having the major axis as the rotation axis, by arranging the light detector 40 in the direction of the first focal position FP1 with respect to the condenser lens 30 and setting the sensing area in the direction of the second focal position FP2 with respect to the condenser lens 30, the reflected light R1 from the sensing area can be efficiently guided to the light detector 40. Therefore, the state of moisture in the sensing area can be sensed with higher precision.

[0143] In addition, as Figure 3 shown in the figure, a light-shielding mask 60a for shielding the illumination light L1 scattered at the outlet of the through-hole 30b is provided between the outlet of the through-hole 30b and the light detector 40. Thereby, it is possible to suppress the incidence of unnecessary light other than the reflected light R1 onto the light detector 40. As a result, the moisture sensing accuracy can be improved.

[0144] In addition, in Figure 10 the adjustment method 2 shown in (a) to (d) and Figure 11 the adjustment method 3 shown in (a) to (d), the second focal position FP2 is set at the farthest distance position in the measurement distance range. Thereby, the reflected light R1 from the farthest distance position with a small received light amount can be efficiently condensed onto the light receiving surface 40a of the light detector 40 by the reflecting surface 30a. Therefore, the moisture sensing accuracy can be improved.

[0145] In addition, in Figure 10 the adjustment method 2 shown in (a) to (d), the light receiving surface 40a of the light detector 40 is arranged at the first focal position FP1. Thereby, all of the reflected light R1 from the farthest distance position can be reliably condensed onto the light receiving surface 40a of the light detector 40. Therefore, the moisture sensing accuracy can be improved.

[0146] In addition, in Figure 11In the adjustment method 3 shown in (a) to (d) thereof, the spot size W1 of the reflected light R1 reflected at the farthest distance position is arranged at a position having the same size as the light receiving surface 40a of the light detector 40. Thereby, all of the reflected light R1 reflected at the farthest distance position can be condensed onto the light receiving surface 40a, and as the reflection position (detection area) approaches the closest distance position, the amount of the reflected light R1 that escapes from the light receiving surface 40a can be increased. Therefore, as shown in Figure 11 (d) thereof, the range Rn3 of the received light amount can be significantly compressed, and the structure of the detection circuit that processes the signal from the light detector 40 can be simplified.

[0147] In addition, in Figure 9 the adjustment method 1 shown in (a) to (d) thereof, the second focal point position FP2 is set at a distance position between the farthest distance position and the closest distance position of the measurement distance range (here, the distance position of 4 m), and the size of the light receiving surface 40a of the light detector 40 is set such that the spot size on the light receiving surface 40a of the light detector 40 of the reflected light R1 reflected at the farthest distance position (here, the distance position of 15 m) is equal to or smaller than the size of the light receiving surface 40a. Thereby, as shown in Figure 9 (d) thereof, the reflected light R1 can be efficiently received over the entire range of the measurement distance range. Therefore, in the case where the detection area is in the short distance range, a corresponding measure of reducing the emission power of the light sources 21a to 21c can be taken, and suppression of power consumption can be achieved.

[0148] In addition, in Figure 10 the adjustment method 2 shown in (a) to (d) thereof and Figure 11 the adjustment method 3 shown in (a) to (d) thereof, the light receiving surface 40a of the light detector 40 is smaller than the spot size on the light receiving surface 40a of the reflected light reflected at the closest distance position in the measurement distance range. Thereby, in the short distance range where the acquisition amount with respect to the reflection surface 30a is large, a part of the reflected light R1 escapes from the light receiving surface 40a. Therefore, as shown in Figure 10 (d) thereof and Figure 11 (d) thereof, the ranges Rn2 and Rn3 of the relative received light amount can be compressed, and the structure of the detection circuit that processes the signal from the light detector 40 can be simplified.

[0149] In addition, as shown in Figure 4 (a) and (b) thereof, the light source unit 20 includes: a plurality of light sources 21a to 21c that emit lights having mutually different wavelengths, and a matching optical system 20a (mirrors 23, dichroic mirrors 24, 25) that makes the emission optical axes of these light sources 21a to 21c match each other. Thus, by making the emission optical axes of the light sources 21a to 21c match the optical axis A1, the optical axis A1 can be easily made to match the optical axis A2 of the condenser lens 30 by the condenser lens 30.

[0150] In addition, the moisture sensing device 1 includes a determination unit 111 that determines deposits in the sensing area based on the detection signal of the optical detector 40. And, as Figure 7 shown, the determination unit 111 determines deposits (snow, ice, water) on the road surface based on values R11 and R12 obtained by normalizing the detection signals of two detection illumination lights L1 for absorption wavelengths 1 and 2 using the detection signal of the reference illumination light L1 for the reference wavelength. In this way, by using the detection signal of the illumination light L1 for the reference wavelength that is hardly affected by moisture, the detection signals of the illumination lights L1 for absorption wavelengths 1 and 2 are normalized, and noise components such as scattering caused by the shape of the road surface can be suppressed. Therefore, the state of moisture (type of deposit) on the road surface can be accurately determined.

[0151] <Modified Example>

[0152] Figure 13 is a perspective view showing the structure of the moisture sensing device 1 according to the modified example of Embodiment 1.

[0153] In Figure 13 the structure, compared with the structure of Figure 2 , the shape of the condenser lens 31 is changed. That is, in the structure of Figure 13 , the columnar portion 31d of the condenser lens 31 is cylindrical. The columnar portion 31d protrudes in the projection direction of the illumination light L1. In the columnar portion 31d, a through hole 31b is formed along the central axis. The reflecting surface 31a is formed by the method shown in Figure 2 in the same manner as in the structure of Figure 8 . That is, by using a rotating ellipsoid with the major axis AX1 as the rotation axis and cutting a cylinder with the same diameter as the columnar portion 31d, the reflecting surface 31a is formed. The functions of the through hole 31b and the back plate portion 31c are the same as those of the through hole 30b and the back plate portion 30c formed in Figure 2 . The structure other than the condenser lens 31 is the same as the structure of Figure 2 .

[0154] Through Figure 13 the structure, as in the above-described Embodiment 1, by adjusting Methods 1 to 3, the reflecting surface 31a and the light receiving surface 40a of the optical detector 40 are set. Thus, the same effects as those of the above-described Embodiment 1 can be achieved.

[0155] In addition, through Figure 13In terms of the structure, similar to the above-described Embodiment 1, the optical axis A1 of the light source unit 20 and the optical axis A2 of the condenser lens 30 match each other in the range on the road surface side (detection area side). Therefore, among the reflected lights reflected by the road surface (detection area), the reflected light R1 traveling in the reverse direction of the matched optical axis A10 can be condensed onto the light detector 40 by the condenser lens 30. Therefore, it is not necessary to adjust the angles of the illumination light L1 and the reflected light R1 with respect to the road surface according to the distance between the moisture detection device 1 and the road surface. Even without such adjustment, the light detector 40 can appropriately receive the reflected light R1 from the road surface.

[0156] In addition, with Figure 13 the structure, it is also possible to achieve the same effect as Figure 2 the corresponding structure.

[0157] Furthermore, in Figure 13 the structure, since the reflecting surface 31a is formed by cutting a cylinder with a rotational ellipsoid, the area of the reflecting surface 31a is reduced compared to the case where the reflecting surface 30a is formed by cutting a quadrangular prism with a rotational ellipsoid as in the above-described Embodiment 1.

[0158] Figure 14 (a) and (b) of

[0159] are side views of the condenser lenses 30 and 31 when viewed from the positive Z-axis side. Figure 14 In (a) and (b) of

[0160] the widths of the columnar part 30d in the X-axis direction and the Y-axis direction and the widths of the columnar part 31d in the X-axis direction and the Y-axis direction are respectively the same. In the above-described Embodiment 1, since the columnar part 30d has a quadrangular prism shape, the area S0 of the reflecting surface 30a when viewed from the positive Z-axis side is approximately equal to the value obtained by multiplying the width of the columnar part 30d in the Y-axis direction by the width in the X-axis direction. Here, since the cross-section of the quadrangular prism when viewed from the positive Z-axis side is approximately square, if the width of the columnar part 30d in the X-axis direction is set as D, the area S0 is obtained by the following formula.

[0160] S0 = D 2 ...(1)

[0161] On the other hand, in the modified example, since the columnar part 31d has a cylindrical shape, the area S1 of the reflecting surface 30a when viewed from the positive Z-axis side is approximately equal to the area of a circle with the width D of the columnar part 31d in the X-axis direction as the diameter. In this case, the area S1 is obtained by the following formula.

[0162] S1 = πD 2 / 4...(2)

[0163] According to the above formulas (1) and (2), the area S0 is 127% of the area S1. Therefore, compared with Figure 13 the structure of the modified example shown, in Figure 2 the structure of Embodiment 1 shown, the condensing area of the condenser 30 can be increased by about 1.2 times. Thus, in the structure of Embodiment 1, the reflected light R1 can be condensed on the light detector 40 more efficiently. As a result, the accuracy of moisture sensing can be improved.

[0164] Figure 14 FIG. (c) is a diagram showing the condensing ranges S10 and S11 of the reflected light R1 condensed by the reflecting surface 30a of Embodiment 1 and the reflecting surface 31a of the modified example at the position of the light-shielding mask 60a. In Figure 14 FIG. (c), in the top view of the moisture sensing device 1 in which the condensers 30 and 31 are omitted, the condensing ranges S10 and S11 are added.

[0165] As Figure 14 shown in FIG. (c), in the structure of the above Embodiment 1, compared with the structure of the modified example, the area of the reflecting surface 30a is larger. Therefore, the condensing range S10 of the reflected light R1 at the position of the light-shielding mask 60a is larger than the condensing range S11 in the case of the modified example. Therefore, in the structure of Embodiment 1, the ratio of the reflected light blocked by the light-shielding mask 60a to the reflected light condensed in the condensing range S10 is smaller than that of Modified Example 1. Therefore, in the structure of Embodiment 1, compared with the structure of the modified example, more reflected light can be condensed on the light-receiving surface 40a of the light detector 40.

[0166] As described above, preferably, the columnar portion 30d of the condenser 30 is a quadrangular prism shape as in Embodiment 1 above. That is, preferably, the reflecting surface 30a is a shape obtained by cutting a quadrangular prism by a rotational ellipsoidal surface. Thus, when the widths of the columnar portions in the X-axis direction and the Y-axis direction are the same, more reflected light R1 can be condensed on the light-receiving surface 40a of the light detector 40.

[0167] In other words, when condensing the reflected light R1 with the same amount of light on the light-receiving surface 40a of the light detector 40, preferably, the shape of the columnar portion 30d is a quadrangular prism shape. Thus, the widths of the columnar portions 30d in the X-axis direction and the Y-axis direction can be made smaller than the case where the columnar portion is circular. As a result, the external dimensions of the moisture sensing device 1 can be reduced.

[0168] <Embodiment 2>

[0169] In the above-described Embodiment 1, the illumination light L1 scattered at the exit of the through-hole 30b is blocked by the light-shielding mask 60a of the light-shielding member 60. In contrast, in Embodiment 2, by providing a notch on the inner side surface of the through-hole facing the light detector 40, the incidence of scattered light on the light detector 40 can be suppressed.

[0170] Figure 15 FIG. 4 is a perspective view showing the external structure of the moisture sensing device 1 with the front housing 11 removed, which relates to Embodiment 2. Figure 16 At the intermediate position in the X-axis direction, by a plane parallel to the Y-Z plane, Figure 15 FIG. 5 is a cross-sectional view when the moisture sensing device 1 is cut. Figure 17 FIGS. 6(a) and 6(b) are a rear view and a rear perspective view of the condenser lens 32 according to Embodiment 2, respectively.

[0171] Compared with Embodiment 1, in Embodiment 2, the structure of the condenser lens 32 is different. The structures other than the condenser lens 32 are the same as those in Embodiment 1.

[0172] As Figure 17 shown in FIGS. 6(a) and 6(b), the condenser lens 32 has a concave portion 32e with a square contour that is recessed toward the positive Z-axis direction on the back surface. The through-hole 32b penetrates from this concave portion 32e to the reflecting surface 32a in the Z-axis direction. On the positive Y-axis side of the through-hole 32b, a notch 32f extending in the positive Y-axis direction is formed. Here, as Figure 17 shown in FIG. 6(a), the bottom surface of the concave portion 32e is recessed into a runway shape toward the positive Z-axis direction, and the through-hole 32b and the notch 32f are formed in this recess. The through-hole 32b and the notch 32f are connected in a direction parallel to the Y-Z plane.

[0173] Similar to the above-described Embodiment 1, the columnar portion 32d has a shape obtained by cutting a quadrangular prism extending in the positive Z-axis direction with a rotational ellipsoidal surface. Similar to the above-described Embodiment 1, the reflecting surface 32a has a shape obtained by cutting a quadrangular prism having the same width as the columnar portion 32d with a rotational ellipsoidal surface. The functions of the reflecting surface 32a, the through-hole 32b, and the back plate portion 32c are the same as the functions of the reflecting surface 30a, the through-hole 30b, and the back plate portion 30c in the above-described Embodiment 1, respectively.

[0174] As Figure 16 shown, in the structure of Embodiment 2, the illumination light L1 scattered at the exit of the through-hole 32b travels in the direction toward the concave portion 32e. The scattered light of the illumination light L1 incident on the concave portion 32e is attenuated by being repeatedly reflected on the inner side surface of the space surrounded by the concave portion 32e and the wall plate portion 14a. An infrared light absorber may be coated on the inner side surface of the space surrounded by the concave portion 32e and the wall plate portion 14a.

[0175] Thus, in the structure of the second embodiment, by providing the notch 32f on the inner side surface of the through hole 32b facing the photodetector 40, it is possible to prevent the illumination light L1 scattered at the outlet of the through hole 32b from traveling in the direction of the photodetector 40. As a result, it is possible to suppress the incident of the scattered light on the light receiving surface 40a of the photodetector 40. Therefore, as Figure 15 and Figure 16 shown, it is possible to omit the light shielding member 60, and it is possible to simplify the structure and reduce the cost.

[0176] In addition, in the second embodiment, similar to the modification example of the first embodiment described above, the shape of the columnar portion 32d may be a cylindrical shape. However, as described above, in order to condense more reflected light R1 on the photodetector 40, preferably as Figure 15 such, the shape of the columnar portion 32d is a quadrangular prism shape.

[0177] Furthermore, in the above structure, the notch 32f is formed to extend in the Y-axis direction, but the formation method of the notch 32f is not limited thereto. As long as it is possible to prevent the illumination light L1 scattered at the outlet of the through hole 30b from traveling in the direction of the photodetector 40, the notch 32f may be formed to extend in a direction inclined with respect to the Y-axis. In addition, the width of the notch 32f may not be constant. For example, the notch 32f may be formed to be wider on the positive Y-axis side.

[0178] <Embodiment 3>

[0179] In the above-described first and second embodiments, by forming the through hole 30b in the condenser lens 30, the optical axis A1 of the light source unit 20 is matched with the optical axis A2 of the condenser lens 30. In contrast, in the third embodiment, a smaller mirror is used to match the optical axis A1 of the light source unit 20 with the optical axis A2 of the condenser lens 30.

[0180] Figure 18 is a diagram showing the structure of the optical system of the moisture sensing device 1 according to the third embodiment.

[0181] In Figure 18In the structure, compared with the structure of Embodiment 1, an optical element 27 is added. The optical element 27 is a flat mirror. The reflecting surface 27a of the optical element 27 is slightly larger than the beam size of the illumination light L1 collimated by the collimating lenses 22a to 22c of the light source unit 20. The shape of the optical element 27 is a shape corresponding to the beam shape of the illumination light L1 incident on the optical element 27. The optical element 27 reflects the illumination light L1 and guides the reflected light R1 passing around the optical element 27 to the condenser lens 33. The optical element 27 bends the optical axis A1 of the light source unit 20 in a direction parallel to the optical axis A2 of the condenser lens 33 to match the optical axes A1 and A2. The optical element 27 is disposed at a position where the optical axis A1 of the light source unit 20 intersects the optical axis A2 of the condenser lens 33.

[0182] Similar to the above-described Embodiments 1 and 2, the condenser lens 33 has a reflecting surface 33a having a shape of a quadrangular prism obtained by cutting a rotating ellipsoid with the same width as the columnar portion 33b. The method of forming the reflecting surface 33a is the same as the method described with reference to Figure 8 Similar to the modification example of the above-described Embodiment 1, the reflecting surface 33a may also have a shape of a cylinder obtained by cutting a rotating ellipsoid. The setting method of the reflecting surface 33a and the light receiving surface 40a of the photodetector 40 is the same as the adjustment methods 1 to 3 described in the above-described Embodiment 1.

[0183] By Figure 18 With the structure of, it is also possible to use the optical element 27 to match the optical axis A1 of the light source unit 20 and the optical axis A2 of the condenser lens 30 to a common optical axis A10. Therefore, similar to the above-described embodiments, it is not necessary to adjust the angles of the illumination light L1 and the reflected light R1 with respect to the road surface according to the distance between the moisture sensing device 1 and the road surface. Even without such adjustment, the reflected light R1 from the road surface can be appropriately received by the photodetector 40.

[0184] In addition, since the reflecting surface 33a of the condenser lens 33 has a shape of a quadrangular prism obtained by cutting a rotating ellipsoid with its major axis as the rotation axis and extending in the projection direction of the illumination light L1, similar to the above-described Embodiments 1 and 2, the reflected light R1 from the sensing area can be efficiently guided to the photodetector 40. Therefore, the state of moisture in the sensing area can be sensed with higher accuracy.

[0185] In addition, Figure 18 In the structure of, a light shielding mask 60a may be disposed to prevent the illumination light L1 scattered at the edge portion of the optical element 27 from entering the light receiving surface 40a of the photodetector 40. Thereby, it is possible to suppress the incidence of unnecessary light other than the reflected light R1 on the photodetector 40, and as a result, the accuracy of moisture sensing can be improved.

[0186] <Other modification examples>

[0187] In the above-described Embodiments 1 to 3 and the modification examples, light of three wavelengths is used as the illumination light L1. However, the number of types of wavelengths used as the illumination light L1 is not limited to three. For example, two light sources that respectively emit the illumination light L1 of the reference wavelength and the illumination light L1 of the absorption wavelength, and a radiation temperature sensor that detects the temperature of the road surface may be used to determine the type of the deposit. In this case, either the dichroic mirrors 24 or 25 are omitted from the light source unit 20.

[0188] In addition, in Figure 4 In the structures of (a) and (b), two dichroic mirrors 24 and 25 are used to align the optical axes of the light sources 21a to 21c. However, the structure for aligning the optical axes is not limited to this. For example, the optical axes of the light sources 21a to 21c may be aligned by replacing one of the dichroic mirrors 24 and 25 with a polarization beam splitter and adjusting the polarization directions of the laser lights emitted from the respective light sources. For example, when the dichroic mirror 25 is replaced with a polarization beam splitter, the light sources 21a to 21c are arranged such that the laser lights emitted from the light sources 21a and 21b are P-polarized light with respect to the polarization beam splitter, and the laser light emitted from the light source 21c is S-polarized light with respect to the polarization beam splitter.

[0189] In addition, in the above-described Embodiments 1 to 3 and the modification examples, the light of the reference wavelength emitted from the light source 21a is near-infrared light with a wavelength of 980 nm. However, the reference wavelength is not limited to 980 nm, and may be other wavelengths with less absorption by water. In addition, the light of the reference wavelength is not limited to near-infrared light, and may be visible light with a wavelength of 750 nm or less. However, if the light of the reference wavelength is visible light, since there is a concern that the road surface 3a is irradiated and the traffic on the road 3 is obstructed, it is preferable that the light of the reference wavelength is near-infrared light.

[0190] In addition, the shapes and sizes of the optical components constituting the optical system are not limited to the forms shown in the above-described Embodiments 1 to 3 and the modification examples, and can be appropriately changed.

[0191] In addition, the measurement distance range is not limited to the ranges shown in the above-described adjustment methods 1 to 3, and can be appropriately changed. In addition, the first focal distance FD1 and the second focal distance FD2 for setting the shape of the reflecting surface, the major axis AX1 of the ellipse, and the minor axis AX2 are not limited to the values shown in the above-described adjustment methods 1 to 3, and can be appropriately changed. The adjustment methods for the reflecting surface and the light receiving surface do not have to be limited to the above-described adjustment methods 1 to 3.

[0192] In addition, in Figure 7 In the determination process shown, the type of the deposit on the road surface is determined. However, the determination object is not limited to this, and the thickness, ease of slipping, etc. of the deposit may be further determined.

[0193] In addition, in the above-described Embodiments 1 to 3 and the modification example, the state of moisture on the road surface (water, ice, snow) is detected, but the detection area for detecting the state of moisture does not have to be limited to the road surface. For example, the present invention can also be applied to a moisture detection device that detects the state of moisture on the surface of a floor or a table, or a moisture detection device that detects the moisture of leaves. In this case, the number and type of light used for detection can be adjusted according to the type of moisture to be detected and the like.

[0194] Furthermore, the application examples of the moisture detection device 1 are not limited to Figure 8 the road surface information distribution system 200 shown, or the application example of mounting the moisture detection device 1 on a vehicle. As long as it is a structure that uses illumination light and reflected light to detect the state of moisture of an object, the moisture detection device 1 can also be used for other structures.

[0195] In addition, in the above-described embodiment, as one mode of the optical device according to the present invention, a moisture detection device that detects moisture (water, snow, ice, etc.) in the detection area is exemplified, but it is not limited thereto. The optical device according to the present invention can also be other modes of optical devices having an emission optical system and a light receiving optical system.

[0196] For example, the present invention can also be applied to a lidar that projects light onto a detection area, receives the light reflected in the detection area, and detects the presence or absence of an object in the detection area. In this case, the light source unit 20 does not necessarily have to project illumination light of multiple wavelengths onto the detection area. For example, it can also project illumination light in only the infrared wavelength band onto the detection area. In addition, the lidar can also measure the distance to an object existing in the detection area based on the time difference between the projection timing of the illumination light and the light receiving timing of the reflected light.

[0197] In addition, the embodiments of the present invention can be appropriately modified within the scope of the technical idea shown in the claims.

[0198] -Symbol Explanation-

[0199] 1 Moisture detection device

[0200] 3a1, 3a2 Detection area

[0201] 20 Light source unit

[0202] 20a Matching optical system

[0203] 27 Optical element

[0204] 21a, 21b, 21c Light source

[0205] 30, 31, 32, 33 Condensing lens

[0206] 30a, 31a, 32a, 33a reflecting surfaces

[0207] 30b, 31b, 32b through holes

[0208] 30d, 31d, 32d, 33b columnar parts

[0209] 32f notch

[0210] 40 photodetector

[0211] 40a light-receiving surface

[0212] 60a light-shielding mask

[0213] 111 judgment unit

[0214] FP1 first focal position

[0215] FP2 second focal position

[0216] AX1 major axis

[0217] A1, A2, A10 optical axes

[0218] L1 illumination light

[0219] R1 reflected light

[0220] P0 quadrangular prism (prism).

Claims

1. An optical device comprising: a light source unit that projects illumination light onto a sensing area; a light detector that receives the reflected light of the illumination light reflected in the sensing area; and a condenser lens that condenses the reflected light onto the light detector, the condenser lens having a through hole that allows the illumination light emitted from the light source unit to pass through, and that matches the optical axis of the light source unit with the optical axis of the condenser lens, the reflecting surface of the condenser lens having a shape obtained by cutting a cylinder extending in the projection direction of the illumination light with a rotational ellipsoid having a major axis as the rotation axis, the light detector is arranged in a direction toward the first focal position with respect to the condenser lens, and the sensing area is set in a direction toward the second focal position with respect to the condenser lens.

2. The optical device according to claim 1, wherein, the cylinder is a quadrangular prism.

3. The optical device according to claim 1 or 2, wherein, the through hole has a notch on the inner side surface facing the light detector.

4. The optical device according to claim 1 or 2, wherein, between the exit of the through hole and the light detector, a light-shielding mask is provided for shielding the illumination light scattered at the exit of the through hole.

5. The optical device according to claim 1 or 2, wherein, the second focal position is set at the farthest distance position within the measurement distance range.

6. The optical device according to claim 5, wherein, the light-receiving surface of the light detector is arranged at the first focal position.

7. The optical device according to claim 5, wherein, the light detector is arranged at a position where the spot size of the reflected light reflected at the farthest distance position is the same size as the light-receiving surface of the light detector.

8. The optical device according to claim 1 or 2, wherein, the second focal position is set at a distance position between the farthest distance position and the nearest distance position within the measurement distance range, the size of the light-receiving surface of the light detector is set such that the spot size of the reflected light reflected at the farthest distance position on the light-receiving surface of the light detector is a size equal to or smaller than the light-receiving surface.

9. The optical device according to claim 1 or 2, wherein, the light-receiving surface of the light detector is smaller than the spot size of the reflected light on the light-receiving surface at the nearest distance position within the measurement distance range.

10. The optical device according to claim 1 or 2, wherein, the light source unit comprises: a plurality of light sources that emit light of mutually different wavelengths; and a matching optical system that matches the emission optical axes of the respective light sources.

11. The optical device according to claim 10, wherein, the optical device comprises: a determination unit that determines deposits in the sensing area based on the detection signal of the light detector.

12. The optical device according to claim 11, wherein, the light source unit comprises: a first light source, a second light source, and a third light source that respectively emit light of mutually different first, second, and third wavelengths, Two of the first light source, the second light source, and the third light source respectively emit light for detection having a wavelength with a relatively high absorption coefficient for water and ice, and the remaining one light source emits light for reference having a wavelength with a relatively low absorption coefficient for water and ice. The determination unit determines the deposit based on a signal obtained by normalizing the detection signals for the two detection lights using the detection signal for the reference light.

13. The optical device according to claim 12, wherein, as the deposit, the determination unit determines water, ice, and snow.

14. An optical device comprising: a light source unit that projects illumination light onto a sensing area; a light detector that receives the reflected light of the illumination light reflected in the sensing area; and a condenser lens that condenses the reflected light onto the light detector, the reflecting surface of the condenser lens has a shape obtained by cutting a cylinder extending in the projection direction of the illumination light with a rotational ellipsoid having a major axis parallel to the projection direction as the rotation axis, the light detector is arranged in a direction toward the first focal position of the condenser lens with respect to the condenser lens, and the sensing area is set in a direction toward the second focal position of the condenser lens with respect to the condenser lens.

15. The optical device according to claim 14, wherein, the optical device includes an optical element that aligns the optical axis of the light source unit with the optical axis of the condenser lens.

Images