WO2018101226A1 - Measuring device - Google Patents

Abstract

A measuring device (1) is provided with a light source (10), a translucent member (12), and a light receiver (16). The translucent member (12) is a flat board-type member that is disposed such that light outputted from the light source (10) is diagonally inputted. The light receiver (16) is disposed on the opposite side to the light source (10) by having the translucent member as reference. The measuring device (1) is, for instance, a measuring device, which outputs light from an output port (32), and receives light reflected by an object (60), said measuring device measuring the distance from the measuring device (1) to the object (60).

Description

measuring device

The present invention relates to a measuring apparatus.

In recent years, non-contact distance measuring devices that can be used for automatic driving of automobiles have been developed. The non-contact distance measuring device measures the distance from the surrounding object by measuring the time until the emitted light is reflected by the object and returns.

In such a measuring apparatus, it is necessary to place a light receiver on the optical path of the reflected light in order to detect the reflected light from the object. In addition, it is necessary to configure the optical system so that the reflected light can be selectively received without hindering the emission of light.

Patent Document 1 describes that light from a light source is emitted through a hole of a perforated reflection mirror, and the returned light is reflected by a reflection surface of the perforated reflection mirror and guided to a light receiving element.

JP 2004-170965 A

However, in the technique of Patent Document 1, light that reaches the hole of the perforated reflection mirror among the returned light is not detected by the light receiving element. Therefore, the loss which cannot be detected among the returned light becomes large.

Also, although it is conceivable to use a beam splitter that can separate the optical path by polarization, a large loss may occur if the polarization state of the received light is unknown.

An example of a problem to be solved by the present invention is to realize a measuring apparatus that can transmit and receive light with high efficiency.

The invention described in claim 1
A light source;
A flat plate-shaped translucent member arranged so that light emitted from the light source is incident obliquely;
It is a measuring apparatus provided with the light receiver arrange | positioned on the opposite side to the said light source on the basis of the said translucent member.

The above-described object and other objects, features, and advantages will be further clarified by a preferred embodiment described below and the following drawings attached thereto.

It is a figure which illustrates the composition of the measuring device concerning an embodiment. It is a figure which illustrates the relationship between incident angle (theta) ₁ with respect to a translucent member, and the reflectance of each light of P polarized light and S polarized light. 1 is a block diagram illustrating a functional configuration of a measurement apparatus according to Example 1. FIG. It is a figure which illustrates the hardware constitutions of a measuring device. It is a figure for demonstrating reflection and permeation | transmission of the light in a translucent member. (A) it is, when the refractive index n of the light transmitting member is 1.4, a diagram showing the relationship between the incident angle theta ₁ and the reflectance _{E 1 (S), (b} ) , the light-transmitting member when the refractive index n is 1.4, a diagram showing the relationship between the incident angle theta ₁ and the transmittance E _2, (c), the refractive index n of the light transmitting member is, when the 1.4, it is a view showing the relationship between the incident angle theta ₁ and _{E 1 (S) × E 2} . (A) it is, when the refractive index n of the light transmitting member is 1.6, a diagram showing the relationship between the incident angle theta ₁ and the reflectance _{E 1 (S), (b} ) , the light-transmitting member when the refractive index n is 1.6, a diagram showing the relationship between the incident angle theta ₁ and the transmittance E _2, (c), the refractive index n of the light transmitting member is, when the 1.6, it is a view showing the relationship between the incident angle theta ₁ and _{E 1 (S) × E 2} . (A) it is, when the refractive index n of the light transmitting member is 1.8, a diagram showing the relationship between the incident angle theta ₁ and the reflectance _{E 1 (S), (b} ) , the light-transmitting member when the refractive index n is 1.8, a diagram showing the relationship between the incident angle theta ₁ and the transmittance E _2, (c), the refractive index n of the light transmitting member is, when the 1.8, it is a view showing the relationship between the incident angle theta ₁ and _{E 1 (S) × E 2} . (A) it is, when the refractive index n of the light transmitting member is 2.0, a diagram showing the relationship between the incident angle theta ₁ and the reflectance _{E 1 (S), (b} ) , the light-transmitting member when the refractive index n is 2.0, a diagram showing the relationship between the incident angle theta ₁ and the transmittance E _2, (c), the refractive index n of the light transmitting member is, when the 2.0, it is a view showing the relationship between the incident angle theta ₁ and _{E 1 (S) × E 2} . FIG. 6 is a diagram illustrating a configuration of a measuring apparatus according to a second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

FIG. 1 is a diagram illustrating a configuration of a measurement apparatus 1 according to the embodiment. In this figure, the light path of the first light 71 that is light transmitted toward the object 60 is indicated by a dashed arrow, and the second light 72 that is received light after being reflected by the object 60. The light path is indicated by a dotted arrow.

The measuring apparatus 1 according to the present embodiment includes a light source 10, a translucent member 12, and a light receiver 16. The translucent member 12 is a flat plate member that is arranged so that light emitted from the light source 10 is incident obliquely. The light receiver 16 is disposed on the side opposite to the light source 10 with respect to the light transmitting member. This will be described in detail below.

The measuring device 1 is a measuring device that emits light from the emission port 32 and receives reflected light reflected by the object 60, and is a measuring device that measures the distance from the measuring device 1 to the object 60. Specifically, in the measuring apparatus 1, for example, the distance from the measuring apparatus 1 to the object 60 is calculated based on the difference between the light emission timing and the reflected light reception timing. The light is, for example, infrared light. However, the wavelength of light is not particularly limited and may be visible light. The light source 10 is, for example, a laser diode. The light output from the light source 10 is, for example, pulsed light, which is linearly polarized light. The light receiver 16 is a light receiving element such as a photodiode.

The light output from the light source 10 of the measuring device 1 and emitted through the emission port 32 is reflected by the external object 60 and returns at least partially toward the measuring device 1. Then, the reflected light enters the measuring apparatus 1. At least a part of the reflected light incident on the measuring device 1 is detected by the light receiver 16. Here, in the measuring apparatus 1, the time from when the light is emitted from the light source 10 to when the reflected light is detected by the light receiver 16 is measured. Then, the distance between the measuring apparatus 1 and the object 60 is calculated using the measured time and the light propagation speed. The measuring device 1 is, for example, a rider (LIDAR: Laser Imaging Detection and Ranging, Laser Illuminated Detection and Ranging) or a LiDAR (Light Detection and Ranging) device or a radar device. Moreover, the measuring apparatus 1 can be mounted on a moving body, for example. The moving body is, for example, a vehicle such as an automobile or a train.

The translucent member 12 is a flat plate member having translucency. The translucent member 12 is, for example, glass or resin. Specifically, examples of the glass include BK (BK7), SF-3, and SK-16. Examples of the resin include ZEONEX, APL, and PC. Both the first light 71 and the second light 72 are incident on the translucent member 12 from the first surface 121. The first surface 121 is a surface of the translucent member 12 on the light source 10 side, and the second surface 122 is a surface opposite to the first surface 121 of the translucent member 12. The translucent member 12 reflects a part of the first light 71 and transmits the rest. The translucent member 12 reflects a part of the second light 72 and transmits the rest. The first light 71 reflected by the translucent member 12 is emitted from the emission port 32. Then, only the second light 72 transmitted through the translucent member 12 is received by the light receiver 16.

The shape viewed from the direction perpendicular to the main surface of the translucent member 12 is not particularly limited, and may be, for example, a circle, a rectangle, or a polygon. Moreover, although the thickness of the translucent member 12 is not specifically limited, For example, they are 1 mm or more and 10 mm or less. In order to increase the amount of the first light 71 emitted from the emission port 32 by increasing the reflectance, it is preferable that the first surface 121 which is the surface of the light transmitting member 12 on the light source 10 side does not have a coating film. Moreover, it is preferable that the translucent member 12 has an antireflection film on the second surface 122 that is the surface on the light receiver 16 side. Then, stray light and the like incident on the light receiver 16 can be reduced, and the transmittance on the second surface 122 can be ensured to the maximum.

The measuring apparatus 1 according to the present embodiment further includes a movable reflecting portion 14. The movable reflecting portion 14 is, for example, a MEMS mirror whose angle of the reflecting surface with respect to the emission port 32 is variable. The movement of the MEMS mirror may be uniaxial or biaxial. The movable reflecting portion 14 is disposed on the same side as the light source 10 with the translucent member 12 as a reference. The measuring apparatus 1 includes the movable reflecting portion 14, so that the light emission direction from the emission port 32 can be made variable. For example, the position and shape of the object 60 around the measuring device 1 can be grasped by scanning the surroundings of the measuring device 1 with light.

The measuring apparatus 1 according to this embodiment further includes a collimating lens 11 and a condensing lens 19. The collimating lens 11 makes light from the light source 10 substantially parallel. The condensing lens 19 condenses the second light 72 on the light receiving surface of the light receiver 16. In the example of this figure, the collimating lens 11 is provided between the light source 10 and the translucent member 12, and the condenser lens 19 is provided between the second surface 122 and the light receiver 16. However, the positions of the collimating lens 11 and the condensing lens 19 are not limited to the example of this figure.

In the present embodiment, the measuring apparatus 1 further includes a housing 30. The light source 10, the collimating lens 11, the translucent member 12, the movable reflecting portion 14, the condensing lens 19, and the light receiver 16 are accommodated in the housing 30. The housing 30 is provided with an opening as an emission port 32. For example, a light-transmitting window may be fitted in the emission port 32.

In the example of FIG. 1, the light path will be described in detail below. However, the light path is not limited to the example of this figure. In the example of this figure, first, the light output from the light source 10 passes through the collimating lens 11 as the first light 71 and then enters the first surface 121 of the translucent member 12. Then, at least a part of the first light 71 is reflected by the translucent member 12 and travels toward the movable reflecting portion 14. Further, the first light 71 reflected by the reflecting surface of the movable reflecting portion 14 is emitted to the outside of the housing 30 through the emission port 32. The emitted first light 71 is reflected by the external object 60.

At least part of the light reflected by the object 60 enters the inside of the housing 30 again through the emission port 32. Here, it is assumed that the second light 72 incident from the emission port 32 is approximately coaxial with the first light 71 emitted through the emission port 32. The second light 72 incident on the inside of the housing 30 is incident on the first surface 121 of the translucent member 12 again via the movable reflector 14. At least a part of the second light 72 incident on the first surface 121 is transmitted to the second surface 122 side of the translucent member 12 and is incident on the light receiving surface of the light receiver 16 through the condenser lens 19. Note that the angle of the reflecting surface of the movable reflecting portion 14 may be the same when reflecting the first light 71 and when reflecting the second light 72, or may be slightly different. That is, the incident angle of the first light 71 to the translucent member 12 and the incident angle of the second light 72 to the translucent member 12 may be the same or may be slightly different.

Note that the measuring apparatus 1 may further include a mirror or the like that guides the reflected light that has passed through the translucent member 12 to the light receiver 16. If it does so, the design and arrangement | positioning freedom degree of the optical system in the housing | casing 30 can be raised, and size reduction of the measuring apparatus 1 can be achieved.

FIG. 2 is a diagram illustrating the relationship between the incident angle θ ₁ with respect to the translucent member 12 and the reflectance of each of P-polarized light and S-polarized light. With reference to this figure, the transmission / reception of the light by the measuring apparatus 1 is demonstrated.

The incident light from the light source 10 to the translucent member 12 is not particularly limited, but is preferably S-polarized light. Then, the reflectance of the first light 71 on the first surface 121 can be increased, and the emission efficiency can be increased. In the following description, it is assumed that the incident light from the light source 10 to the translucent member 12 is S-polarized light.

Further, it is assumed that the first light 71 is incident on the first surface 121 of the translucent member 12 at an incident angle θ ₁ . When θ ₁ = 75 °, the reflectance of the first light 71 on the first surface 121 is the size represented by the arrow α in the figure, specifically 0.5. That is, approximately 50% of the light emitted from the light source 10 is output from the emission port 32.

Then, the second light 72 reflected by the object 60 enters the emission port 32 and enters the first surface 121 of the translucent member 12 at θ ₁ = 75 °. Here, the polarization direction of the second light 72 depends on the reflection surface of the object 60. Assuming that the intensity ratio of P-polarized light and S-polarized light in the second light 72 is P-polarized light: S-polarized light = 100: 0, the transmittance of the translucent member 12 is represented by an arrow β _{1 in} the figure. The specific size is 0.91. That is, approximately 91% of the light incident on the exit port 32 can be received by the light receiver 16. In the second light 72, the intensity ratio of the P polarized light and S-polarized light, P-polarized light: Table when it is 100, the transmittance of a translucent member 12 in the arrow in the figure beta _3: S-polarized light = 0 The size is 0.50, specifically 0.50. That is, approximately 50% of the light incident on the exit port 32 can be received by the light receiver 16. Then, in the second optical 72, the intensity ratio of the P polarized light and S-polarized light, P-polarized light: S-polarized light = 50: when it is 50, the table by the arrows in transmittance in this drawing beta ₂ of a translucent member 12 Specifically, it is 0.71, which is an average value of β ₁ and β ₃ . That is, approximately 71% of the light incident on the exit port 32 can be received by the light receiver 16.

Although the polarization direction of the second light 72 incident on the exit port 32 is unknown, at least 50% of the light can be received by the light receiver 16 in this way.

As described above, according to the present embodiment, the measuring apparatus 1 includes the flat plate-shaped translucent member 12 arranged so that the light emitted from the light source 10 is incident obliquely. Therefore, light can be transmitted and received with high efficiency even when the polarization direction of the received light is unknown. As a result, distance measurement with high sensitivity becomes possible.

Example 1
FIG. 3 is a block diagram illustrating the functional configuration of the measuring apparatus 1 according to the first embodiment. The measuring apparatus 1 according to Example 1 has the same configuration as the measuring apparatus 1 according to the embodiment.

The measuring apparatus 1 according to the present embodiment further includes a drive circuit 20, a drive circuit 24, a detection circuit 26, a control unit 50, and a calculation unit 52. The drive circuit 20 is a drive circuit for the light source 10. The drive circuit 20 inputs a drive signal for outputting light to the light source 10 based on control by the control unit 50. The drive circuit 24 is a drive circuit for the movable reflector 14. The drive circuit 24 inputs a drive signal to the movable reflection unit 14 based on control by the control unit 50. The movable reflection unit 14 changes the emission direction of the light from the measuring device 1 based on the drive signal.

In the measuring apparatus 1, for example, the light source 10 repeatedly emits pulsed light at regular intervals. The movable reflector 14 is controlled so that the light emission direction is changed to a uniaxial or biaxial direction and a predetermined range is scanned with the light. By doing so, the object 60 existing around the measuring apparatus 1 can be detected.

The detection circuit 26 is a detection circuit of the light receiver 16. The detection circuit 26 can be configured to include, for example, a current-voltage conversion circuit and an amplifier circuit. For example, when the light receiver 16 is a photodiode, a current generated when light enters the light receiver 16 is converted into a detection signal by the detection circuit 26.

The control unit 50 controls the light source 10 via the drive circuit 20 and controls the movable reflection unit 14 via the drive circuit 24. And the control part 50 implement | achieves the measurement of a distance by controlling the light source 10 and the movable reflection part 14. FIG.

The calculating unit 52 calculates the distance between the measuring device 1 and the object 60 based on the detection result of the light receiver 16. That is, the calculation unit 52 calculates the distance between the measuring apparatus 1 and the object 60 using the time from when the light is emitted from the light source 10 until the reflected light is detected by the light receiver 16 and the light propagation speed. To do. Specifically, the calculation unit 52 receives a trigger signal indicating the output timing of the light source 10 from the control unit 50. The calculation unit 52 receives a signal indicating the light reception timing from the detection circuit 26 of the light receiver 16. And the calculation part 52 measures the time from an output timing to a light reception timing based on each received signal. Next, the calculation unit 52 calculates the distance between the measurement apparatus 1 and the object 60 using the measured time and the light propagation speed. The calculation unit 52 may receive a trigger signal indicating the output timing of the light source 10 from the light source 10 or the drive circuit 20 instead of receiving from the control unit 50. The information indicating the light propagation speed can be read from, for example, the storage device 108 described later and used by the calculation unit 52.

FIG. 4 is a diagram illustrating a hardware configuration of the measuring apparatus 1. In this figure, the measuring apparatus 1 is mounted using an integrated circuit 100. The integrated circuit 100 is, for example, a SoC (System On Chip).

The integrated circuit 100 includes a bus 102, a processor 104, a memory 106, a storage device 108, an input / output interface 110, and a network interface 112. The bus 102 is a data transmission path through which the processor 104, the memory 106, the storage device 108, the input / output interface 110, and the network interface 112 transmit / receive data to / from each other. However, the method of connecting the processors 104 and the like is not limited to bus connection. The processor 104 is an arithmetic processing device realized using a microprocessor or the like. The memory 106 is a memory realized using a RAM (Random Access Memory) or the like. The storage device 108 is a storage device realized using a ROM (Read Only Memory) or a flash memory.

The input / output interface 110 is an interface for connecting the integrated circuit 100 to peripheral devices. In this figure, the input / output interface 110 is connected to the drive circuit 20 of the light source 10, the drive circuit 24 of the movable reflector 14, and the detection circuit 26 of the light receiver 16.

The network interface 112 is an interface for connecting the integrated circuit 100 to a communication network. This communication network is, for example, a CAN (Controller Area Network) communication network. Note that a method of connecting the network interface 112 to the communication network may be a wireless connection or a wired connection.

The storage device 108 stores program modules for realizing the functions of the control unit 50 and the calculation unit 52, respectively. The processor 104 reads out the program module to the memory 106 and executes it, thereby realizing the functions of the control unit 50 and the calculation unit 52.

The hardware configuration of the integrated circuit 100 is not limited to the configuration shown in the figure. For example, the program module may be stored in the memory 106. In this case, the integrated circuit 100 may not include the storage device 108.

FIG. 5 is a diagram for explaining the reflection and transmission of light in the translucent member 12. θ ₁ is an incident angle of light with respect to the translucent member 12, and the translucent member 12 is arranged so that light from the light source 10 is incident at an incident angle θ ₁ . The second light 72 is also incident on the translucent member 12 at an incident angle θ ₁ . θ ₂ is the refraction angle of the light incident on the translucent member 12. n ₁ is the refractive index of air, and n ₂ is the refractive index of the translucent member 12. In addition, although the example in which the 1st surface 121 and the 2nd surface 122 are parallel is shown in this figure, the 1st surface 121 and the 2nd surface 122 do not necessarily need to be parallel, and the 2nd surface 122 is shown. Is preferably formed so as to be perpendicular to the light beam passing through the inside of the translucent member 12.

The reflectance of the S-polarized light with respect to the first surface 121 on the light source 10 side of the translucent member 12 is E ₁ (S), the transmittance of the S-polarized light is E ₂ (S), and When the transmittance is E ₂ (P), the following formulas (1) to (3) hold. In addition, n ₁ sin θ ₁ = n ₂ sin θ ₂ holds.

Assuming the refractive index n ₂ of the translucent member 12, the following relationships of FIGS. 6 (a) to 9 (c) are obtained from these equations.

FIG. 6 (a), the FIG. 7 (a), the FIG. 8 (a), the and FIG. 9 (a) respectively, the refractive index n ie _{n 2} of the light transmitting member 12, 1.4,1.6,1. when the 8 and 2.0, is a view showing the relationship between the incident angle theta ₁ and the reflectance _E 1 (S). FIG. 6 (b), the FIG. 7 (b), the FIG. 8 (b), the and 9 (b) respectively, the refractive index n ie _{n 2} of the light transmitting member 12, 1.4,1.6,1. when the 8 and 2.0, is a view showing the relationship between the incident angle theta ₁ and the transmittance E _2. FIG. 6 (c), the FIG. 7 (c), the FIG. 8 (c), the and FIG. 9 (c) respectively, the refractive index n ie _{n 2} of the light transmitting member 12, 1.4,1.6,1. when the 8 and 2.0, is a view showing the relationship between the incident angle theta ₁ and _{E 1 (S) × E 2} . In these figures, E ₂ indicates the transmittance for S-polarized light and the transmittance for P-polarized light.

When the incident light from the light source 10 to the translucent member 12 is S-polarized light, a preferable refractive index n and incident angle θ ₁ of the translucent member 12 will be described below.

From the viewpoint of increasing the reception efficiency while ensuring a sufficient amount of light transmission, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.60 and E ₁ (S) ≧ 0.15 may be satisfied. preferable. Moreover, it is more preferable that {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.70 holds, and it is further preferable that {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.80 holds. preferable. And it is more preferable that E ₁ (S) ≧ 0.20 holds.

When the refractive index n of the translucent member 12 is 1.6 or more and 2.0 or less, specifically, as can be seen from FIGS. 7B, 8B, and 9B, the incident angle. When θ ₁ is 75 ° or less, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.60 holds, and when the incident angle θ ₁ is 72 ° or less, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.70 holds, and when the incident angle θ ₁ is 62 ° or less, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.80 holds. Further, as can be seen from FIGS. 7A, 8A, and 9A, when the incident angle θ ₁ is 50 ° or more, E ₁ (S) ≧ 0.15 holds and the incident angle When the angle θ ₁ is 60 ° or more, E ₁ (S) ≧ 0.20 holds. Therefore, when the refractive index n of the translucent member 12 is 1.6 or more and 2.0 or less and the incident angle θ ₁ is 50 ° or more and 75 ° or less, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.60 and E ₁ (S) ≧ 0.15 hold.

When the refractive index n of the translucent member 12 is 1.6 or more and 1.8 or less, when the incident angle θ ₁ is 77 ° or less, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0.60 And when the incident angle θ ₁ is 50 ° or more, E ₁ (S) ≧ 0.15 holds. When the refractive index n of the translucent member 12 is 1.8 or more and 2.0 or less, when the incident angle θ ₁ is 75 ° or less, {E ₂ (S) + E ₂ (P)} / 2 ≧ 0 .60 and E ₁ (S) ≧ 0.15 holds when the incident angle θ ₁ is 42 ° or more.

On the other hand, it is preferable that E ₁ (S) × E ₂ (P) ≧ 0.30 holds from the viewpoint of improving the transmission / reception efficiency as a total by balancing transmission efficiency and reception efficiency, and E ₁ (S) × It is more preferable that E ₂ (P) ≧ 0.35 is satisfied, and it is further preferable that E ₁ (S) × E ₂ (P) ≧ 0.40 is satisfied.

When the refractive index n of the translucent member 12 is 1.6 or more, specifically, as can be seen from FIGS. 7C, 8C, and 9C, the incident angle θ ₁ is 67. E ₁ (S) × E ₂ (P) ≧ 0.30 holds when the angle is not less than 87 ° and not more than 87 °. When the incident angle θ ₁ is not less than 72 ° and not more than 86 °, E ₁ (S) × E ₂ When (P) ≧ 0.35 holds and the incident angle θ ₁ is not less than 75 ° and not more than 85 °, E ₁ (S) × E ₂ (P) ≧ 0.40 holds.

When the refractive index n of the translucent member 12 is 1.4 or more, E ₁ (S) × E ₂ (P) ≧ 0.30 holds when the incident angle θ ₁ is 74 ° or more and 86 ° or less. When the refractive index n of the translucent member 12 is 1.8 or more, E ₁ (S) × E ₂ (P) ≧ 0.30 holds when the incident angle θ ₁ is 62 ° or more and 87 ° or less. .

Further, from the viewpoint of increasing the transmission / reception efficiency as a total, it is preferable that E ₁ (S) × E ₂ (S) ≧ 0.20 holds.

When the refractive index n of the translucent member 12 is 1.6 or more and 2.0 or less, specifically, as can be seen from FIGS. 7C, 8C, and 9C, the incident angle. When θ ₁ is 65 ° or more and 82 ° or less, E ₁ (S) × E ₂ (S) ≧ 0.20 holds. Therefore, when the incident angle θ ₁ is 67 ° or more and 82 ° or less, E ₁ (S) × E ₂ (P) ≧ 0.30 and E ₁ (S) × E ₂ (S) ≧ 0.20 hold. .

When the refractive index n of the translucent member 12 is 1.6 or more and 1.8 or less, when the incident angle θ ₁ is 67 ° or more and 84 ° or less, E ₁ (S) × E ₂ (P) ≧ 0.30 And E ₁ (S) × E ₂ (S) ≧ 0.20 holds. Further, when the refractive index n of the translucent member 12 is 1.8 or more and 2.0 or less, when the incident angle θ ₁ is 62 ° or more and 82 ° or less, E ₁ (S) × E ₂ (P) ≧ 0 .30 and E ₁ (S) × E ₂ (S) ≧ 0.20.

As described above, according to the present example, as in the embodiment, the measuring apparatus 1 includes the flat plate-shaped translucent member 12 arranged so that the light emitted from the light source 10 is incident obliquely. Therefore, light can be transmitted and received with high efficiency even when the polarization direction of the received light is unknown. As a result, distance measurement with high sensitivity becomes possible.

(Example 2)
FIG. 10 is a diagram illustrating the configuration of the measuring apparatus 1 according to the second embodiment. The measuring apparatus 1 of the present example has the same configuration as the measuring apparatus 1 according to the embodiment, and is the same as the measuring apparatus 1 according to the example 1 except that the quarter wavelength plate 13 is provided.

The quarter-wave plate 13 is disposed on the same side as the light source 10 with respect to the translucent member 12. In the example of this figure, by passing through the quarter wavelength plate 13, linearly polarized light becomes circularly polarized light, and circularly polarized light becomes linearly polarized light. In this embodiment, the S-polarized first light 71 output from the light source 10 and reflected by the translucent member 12 is converted into circularly-polarized light by passing through the quarter-wave plate 13. Then, circularly polarized first light 71 is emitted from the emission port 32 and reflected by the object 60.

When the polarization characteristics of the light reflected by the object 60 do not change significantly, the circularly polarized second light 72 enters the exit port 32 and passes through the quarter-wave plate 13. Here, the second light 72 transmitted through the quarter-wave plate 13 is converted into P-polarized light (or the P-polarized component becomes larger than the S-polarized component), and enters the translucent member 12. Then, the second light 72 transmitted through the translucent member 12 is detected by the light receiver 16. As can be seen from FIG. 6B and the like, since E ₂ (P) is larger than E ₂ (S), the translucent member 12 transmits the second light 72 with a high transmittance, and in the light receiver 16. The light receiving efficiency can be increased.

As described above, according to the present example, as in the embodiment, the measuring apparatus 1 includes the flat plate-shaped translucent member 12 arranged so that the light emitted from the light source 10 is incident obliquely. Therefore, light can be transmitted and received with high efficiency even when the polarization direction of the received light is unknown. As a result, distance measurement with high sensitivity becomes possible.

In addition, according to the present embodiment, the measuring apparatus 1 includes the quarter wavelength plate 13. Therefore, the translucent member 12 can transmit the second light 72 with a high transmittance, and the light receiving efficiency of the light receiver 16 can be increased. In addition, if the light applied to the object 60 is circularly polarized light, for example, when the object 60 has a polarization characteristic in the reflection of the object 60, for example, the object 60 has an angle or it is difficult to reflect light in a specific polarization direction. The reflected light can be received with high efficiency.

As mentioned above, although embodiment and the Example were described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

This application claims priority based on Japanese Patent Application No. 2016-2331096 filed on November 29, 2016, the entire disclosure of which is incorporated herein.

Claims (12)

A light source;
A flat plate-shaped translucent member arranged so that light emitted from the light source is incident obliquely;
A measuring apparatus comprising: a light receiver disposed on a side opposite to the light source with respect to the translucent member. The measuring apparatus according to claim 1,
A measuring apparatus further comprising a movable reflecting portion disposed on the same side as the light source with respect to the light transmitting member. The measuring apparatus according to claim 1 or 2,
A measuring apparatus having no coating film on the light source side surface of the translucent member. In the measuring device according to any one of claims 1 to 3,
The translucent member is a measuring apparatus having an antireflection film on a surface on the light receiver side. In the measuring device according to any one of claims 1 to 4,
Incident light from the light source to the light transmissive member is S-polarized light. The measuring apparatus according to claim 5, wherein
The translucent member is arranged so that light from the light source is incident at an incident angle θ ₁ ,
The reflectance of S-polarized light with respect to the light source side surface of the translucent member is E ₁ (S), the transmittance of S-polarized light is E ₂ (S), and the transmittance of P-polarized light is when the E ₂ (P), the incident angle _{θ 1, {E 2 (S} ) + E 2 (P)} / 2 ≧ 0.60 and _E 1 (S) ≧ 0.15 is satisfied measuring device. The measuring apparatus according to claim 6, wherein
The light transmitting member has a refractive index n of 1.6 or more,
A measuring apparatus having an incident angle θ ₁ of 50 ° or more and 75 ° or less. The measuring apparatus according to claim 5, wherein
The translucent member is arranged so that light from the light source is incident at an incident angle θ ₁ ,
The reflectance of S-polarized light with respect to the light source side surface of the translucent member is E ₁ (S), the transmittance of S-polarized light is E ₂ (S), and the transmittance of P-polarized light is when E ₂ and (P), the incident angle _{θ 1, E 1 (S)} × E 2 (P) ≧ 0.30 is satisfied measuring device. The measuring apparatus according to claim 8, wherein
The light transmitting member has a refractive index n of 1.6 or more,
The incident angle theta ₁ is 67 ° or more 87 ° or less measuring device. The measuring device according to claim 8 or 9,
A measuring apparatus in which E ₁ (S) × E ₂ (S) ≧ 0.20 holds at an incident angle θ ₁ . The measuring device according to claim 10,
The light transmitting member has a refractive index n of 1.6 or more and 2.0 or less,
The incident angle theta ₁ is 67 ° or more 82 ° or less measuring device. In the measuring device according to any one of claims 1 to 11,
A measuring apparatus further comprising a quarter-wave plate disposed on the same side as the light source with respect to the translucent member.

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