Object sensing device

An object sensing device has a radiation part that radiates an exploring wave forward, a sensing part having a first sensing element and a second sensing element, wherein the first sensing element and the second sensing element sense a reflected wave of the exploring wave radiated by the radiation part; and a determination part. The determination part determines a rainfall state ahead based on an intensity of the reflected wave sensed by the first sensing element. The determination part determines existence or non-existence of an object positioned forward based on an intensity of the reflected wave sensed by the second sensing element. A visual-field restricting member is disposed in front of the first sensing element. The visual-field restricting member causes a visual field, in which the first sensing element senses the reflected wave, to differ from a visual field, in which the second sensing element senses the reflected wave.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an object sensing device, which radiates a laser beam and the like forward as an exploring wave and senses a reflected wave of the laser beam to sense an object positioned ahead.

2. Related Art

In some conventional radar devices mounted to a vehicle, exploring waves, such as a laser beam and a radio wave, are radiated in front of an own vehicle, a reflected wave of the exploring wave is sensed to sense objects, such as a car ahead, which are positioned in front of the own vehicle, and a distance to the sensed object is measured. A sensing result of the radar device can be applied to vehicle running control, such as Adaptive Cruise Control (ACC) in which the distance to the car ahead is kept constant and Low Speed Following (LSF) during backup (during a low speed). The radar device can also be applied to a pre-crush safety system that brakes the own vehicle to reduce a damage at the time of a collision when sensing the car ahead or a stopped object, which is positioned in front of the own vehicle and hardly avoids the collision with the own vehicle.

In some radar devices, a raindrop sensing function of determining a rainfall state, which can be used in automatic control of a wiper of the vehicle, is integrally configured (for example, see Japanese Unexamined Patent Publication No. 10-329653). The radar device of Japanese Unexamined Patent Publication No. 10-329653 includes a light receiving element (stain sensing PD) and a light receiving element (ranging PD). The stain sensing PD receives light randomly reflected from a light projecting/light receiving surface (a transmission window made of glass or synthetic resin) through which a laser beam radiated forward is transmitted. The ranging PD receives light, which is transmitted through the light projecting/light receiving surface and reflected by the object positioned forward. In each predetermined period (for example, ten minutes), the radar device of Japanese Unexamined Patent Publication No. 10-329653 repeats processing of sensing a situation in which the raindrop adheres to the light projecting/light receiving surface, namely, rainfall amount to sense the rainfall state based on a change in light receiving amount of the stain sensing PD. The radar device of Japanese Unexamined Patent Publication No. 10-329653 also senses the object positioned forward and the distance to the object by receiving the reflected light using the ranging PD.

SUMMARY

However, a conventional radar device may not accurately sense the rainfall state unless the stain sensing PD sufficiently suppresses the reception of the light reflected from the object positioned forward. That is, in order to improve the sensing accuracy of the rainfall state in the radar device, the stain sensing PD may reduce the reception of the light reflected from the object and the like positioned forward.

One or more embodiments of the present invention improves the sensing accuracy of the rainfall state by reducing the influence of the reception of the light reflected from the object ahead, in the object sensing device having both the function of sensing the object positioned forward and the function of sensing the rainfall state.

In accordance with one or more embodiments of the present invention, an object sensing device includes: an radiation part that radiates an exploring wave forward; a sensing part that includes a first sensing element and a second sensing element, the first sensing element and the second sensing element sensing reflected wave of the exploring wave radiated by the radiation part; and a determination part that determines a rainfall state ahead based on an intensity of the reflected wave sensed by the first sensing element, and determines existence or non-existence of an object positioned forward based on an intensity of the reflected wave sensed by the second sensing element, wherein a visual-field restricting member is disposed in front of the first sensing element, the visual-field restricting member causing a visual field, in which the first sensing element senses the reflected wave, to differ from a visual field, in which the second sensing element senses the reflected wave.

According to one or more embodiments of the present invention, the radiation part radiates the exploring wave forward. According to one or more embodiments of the present invention, the exploring wave is a laser beam or a millimeter wave.

According to one or more embodiments of the present invention, the sensing part includes the first sensing element and the second sensing element, and the first sensing element and the second sensing element sense reflected wave of the exploring wave radiated by the radiation part.

According to one or more embodiments of the present invention, the determination part determines the rainfall state ahead based on the intensity of the reflected wave sensed by the first sensing element. The determination part also determines the existence or non-existence of the object positioned forward based on the intensity of the reflected wave sensed by the second sensing element.

According to one or more embodiments of the present invention, the visual-field restricting member is disposed in front of the first sensing element. The visual-field restricting member causes the visual field, in which the first sensing element senses the reflected wave, to differ from the visual field, in which the second sensing element senses the reflected wave. According to one or more embodiments of the present invention, the visual-field restricting member restricts the sensing visual fields of the first sensing element and the second sensing element such that the first sensing element senses the wave reflected from the raindrop in the surrounding range of tens of centimeters, and such that the second sensing element senses the wave reflected from the object positioned in the range of several meters to tens of meters. Thus, the first sensing element differs from the second sensing element in the object that reflects the sensed reflected wave.

According to one or more embodiments of the present invention, the visual-field restricting member restricts the sensing visual fields of the first sensing element and the second sensing element such that the first sensing element accurately senses the wave reflected from the raindrop and such that the second sensing element senses the wave reflected from the object positioned forward, so that the object positioned forward and the rainfall state can accurately be sensed.

The wave reflected from the raindrop may be extremely small compared to the wave reflected from the object. Therefore, according to one or more embodiments of the present invention, the visual-field restricting member restricts the visual field of the first sensing element to a visual field in which the wave reflected from a position closer to the radiation part than the visual field of the second sensing element is sensed.

According to one or more embodiments of the present invention, the visual-field restricting member forms a window in each of the first sensing element and the second sensing element, the reflected wave sensed by each of the first sensing element and the second sensing element passing through the window.

According to one or more embodiments of the present invention, the object positioned ahead and the rainfall state can accurately be sensed.

DETAILED DESCRIPTION

FIG. 1is a block diagram illustrating a configuration of a main portion of a radar device according to one or more embodiments of the present invention. A radar device1includes a controller2, a radiation part3, a sensing part4, a solar radiation sensor5, and an input/output unit6. The radar device1is mounted on a vehicle. The radar device1radiates a laser beam in front of the vehicle, on which the radar device1is mounted, (hereinafter referred to as an own vehicle) as an exploring wave, and senses reflected light of the laser beam to sense an object positioned in front of the own vehicle. The radar device1also has a rainfall state sensing function of sensing the light, which is reflected from a raindrop around the own vehicle, to sense a rainfall state around the own vehicle.

The controller2controls an operation of each part of a main body of the radar device1. The controller2has a function of the determination part according to one or more embodiments of the present invention.

The radiation part3includes a laser diode31(hereinafter referred to as an LD31) and an LD driving circuit32. In response to an instruction from the controller2, the LD driving circuit32causes the LD31to emit the light to radiate the pulsed laser beam in front of the own vehicle.

The sensing part4includes a raindrop sensing photodiode41(hereinafter referred to as a raindrop sensing PD41), a first object sensing photodiode42(hereinafter referred to as a first object sensing PD42), a second object sensing photodiode43(hereinafter referred to as a second object sensing PD43), and a light receiving circuit44.

The raindrop sensing PD41corresponds to the first sensing element according to one or more embodiments of the present invention. According to one or more embodiments of the present invention, an APD (avalanche photodiode) is used as the raindrop sensing PD41. The APD outputs a signal according to a light receiving amount in a region where the light receiving amount is relatively small.

The first object sensing PD42is a light receiving element in which a light receiving region is horizontally divided into n regions (in this case, ten regions). The second object sensing PD43is a light receiving element in which the light receiving region is not divided (one light receiving region). According to one or more embodiments of the present invention, a PIN photodiode is used as the first object sensing PD42and the second object sensing PD43. The PIN photodiode outputs the signal according to the light receiving amount in a region where the light receiving amount is relatively large. Each of the divided regions of the first object sensing PD42receives the light reflected from a reflector (reflective plate), which is attached to both sides of a car positioned about 7 m to about 20 m ahead of the own vehicle. The second object sensing PD43receives the light reflected from objects, such as the car ahead, which is positioned within about 7 m ahead of the own vehicle.

One of the first object sensing PD42and the second object sensing PD43corresponds to a second sensing element according to one or more embodiments of the present invention.

The light receiving circuit44integrates and amplifies an output signal in each of the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43. For the first object sensing PD42, the light receiving circuit44integrates and amplifies the output signal in each divided light receiving region.

The solar radiation sensor5senses a solar radiation amount.

For example, the input/output unit6outputs object sensing information indicating a position and the like (a relative position to the own vehicle) of the object, such as the detected car ahead, rainfall state sensing information indicating the rainfall state around the own vehicle, and solar radiation amount sensing information indicating the solar radiation amount around the own vehicle and the like to a control device (not illustrated) of the own vehicle. The input/output unit6receives an input of vehicle state information, such as a running speed of the own vehicle, from the control device of the own vehicle.

The control device of the own vehicle performs braking control, wiper control, light control, air conditioning control, and the like. In the braking control, the running speed of the vehicle is controlled based on the object sensing information inputted from the radar device1. In the wiper control, operation/stop of a wiper is controlled based on the rainfall state sensing information. In the light control, lighting/light shutoff of a light of the own vehicle is controlled based on the solar radiation amount sensing information. In the air conditioning control, the operation of an automatic air conditioner is controlled.

In the radar device1, for example, as illustrated inFIG. 2, the LD31, the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43are attached onto an in-car side of an upper portion of a windshield in the own vehicle.

FIG. 3Ais a view illustrating a positional relationship among the LD, the raindrop sensing PD, the first object sensing PD, and the second object sensing PD. As illustrated inFIG. 3A, the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43are gathered on one side with respect to the LD31. The raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43are not divided into two sides while the LD31is interposed between the two sides. Therefore, a space necessary to dispose the LD31, the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43is suppressed to achieve downsizing.

The first object sensing PD42is disposed substantially immediately below the second object sensing PD43. The raindrop sensing PD41is disposed closer to the side of the LD31than the first object sensing PD42and the second object sensing PD43.

As illustrated inFIGS. 3B,3C, and3D, a visual-field restricting member50is disposed in front of the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43.FIG. 3Bis a plan view of the visual-field restricting member50when the visual-field restricting member50is viewed from front.FIG. 3Cis a plan view of the visual-field restricting member50when the visual-field restricting member50is viewed from above.FIG. 3Dis a plan view of the visual-field restricting member50when the visual-field restricting member50is viewed from the side. InFIG. 3C, the first object sensing PD42and the second object sensing PD43are overlapped in a direction perpendicular to a paper plane. InFIG. 3D, the LD31and the raindrop sensing PD41are overlapped in the direction perpendicular to the paper plane.

Windows51,52, and53are formed in the visual-field restricting member50. The visual-field restricting member50restricts a sensing visual field that receives the reflected light of the laser beam emitted from the LD31with respect to each of the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43.

The window51is formed into a horizontally long slit shape, and located at the substantially same level as the raindrop sensing PD41. A center of the window51is horizontally deviated toward the side of the LD31with respect to the position facing the light receiving surface of the raindrop sensing PD41. As illustrated inFIG. 3B, when viewed from the front, the window51and the light receiving surface of the raindrop sensing PD41are configured not to be overlapped with each other. The raindrop sensing PD41receives the light passing through the window51. The sensing visual field of the raindrop sensing PD41is defined by the relationship between the light receiving surface of the raindrop sensing PD41and the window51.

The center of the window52faces the center of the light receiving surface of the first object sensing PD42. InFIGS. 3C and 3D, an imaging lens55forms an image on the light receiving surface of the first object sensing PD42using the reflected light that passes through the window52from the object. The sensing visual field of the first object sensing PD42is defined by a relationship between the light receiving surface of the first object sensing PD42and the imaging lens55.

The center of the window53faces the center of the light receiving surface of the second object sensing PD43. InFIGS. 3C and 3D, a collective lens56collects the reflected light, which passes through the window52from the object, to the light receiving surface of the second object sensing PD43. The sensing visual field of the second object sensing PD43is defined by a relationship between the light receiving surface of the second object sensing PD43and the collective lens56.

It is to be noted that inFIG. 3C, the collective lens56and the imaging lens55be overlapped in the direction perpendicular to the paper plane, and the window52and the window53are overlapped in the direction perpendicular to the paper plane. The window51located between the window52and the window53is not illustrated inFIG. 3C. The sensing visual fields of the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43are indicated by broken lines inFIG. 3C. The sensing visual fields of the first object sensing PD42and the second object sensing PD43are indicated by broken lines inFIG. 3D. InFIG. 3D, the sensing visual field of the raindrop sensing PD41is omitted because the sensing visual field of the raindrop sensing PD41is overlapped with the sensing visual fields of the first object sensing PD42and the second object sensing PD43in the direction perpendicular to the paper plane.

A relationship between an irradiation region of the laser beam emitted from the LD31and the sensing visual fields, which receive the reflected light, of the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43will be described below.

FIGS. 4A and 4Bare views illustrating the relationship between an irradiation region of the laser beam of the LD and the sensing visual fields of the raindrop sensing PD, the first object sensing PD, and the second object sensing PD.FIG. 4Ais a view in the horizontal direction, andFIG. 4Bis a view in the vertical direction. A region indicated by a broken line inFIG. 4is irradiated with the laser beam emitted from the LD31using a light projecting lens (not illustrated), which is disposed opposite the light emitting surface of the LD31. For example, using the light projecting lens, the region is irradiated with the laser beam at a spread angle of 16° in the horizontal direction and 26° in the vertical direction. As illustrated inFIG. 4B, the light projecting lens spreads the laser beam downward while suppressing upward spread of the laser beam, whereby the light projecting lens suppresses the irradiation of display boards, such as a road traffic sign, which are placed above the road, with the laser beam (suppresses the reception of the light reflected from the display board placed above the road).

The sensing visual field of the raindrop sensing PD41is a hatched region inFIG. 4A. That is, the positional relationship between the light receiving surface of the raindrop sensing PD41and the window51of the visual-field restricting member50is set such that the hatched region inFIG. 4Abecomes the sensing visual field of the raindrop sensing PD41. According to one or more embodiments of the present invention, the light receiving surface of the raindrop sensing PD41is obliquely attached to the direction of the sensing visual field because the light receiving surface of the raindrop sensing PD41suppresses the reception of the light reflected from the front. The raindrop sensing PD41receives the light reflected from the raindrop in a region (hereinafter referred to as a raindrop sensing region) where the sensing visual field of the raindrop sensing PD41and the irradiation region of the laser beam of the LD31are overlapped with each other. The visual-field restricting member50restricts the sensing visual field of the raindrop sensing PD41such that a space on a hood of the own vehicle becomes the raindrop sensing region.

As illustrated inFIG. 4A, the sensing visual fields of the first object sensing PD42and the second object sensing PD43are substantially overlapped in the horizontal direction. The second object sensing PD43senses objects, such as the vehicle, which are positioned closer than the first object sensing PD42. Therefore, as illustrated inFIG. 4B, the sensing visual field of the second object sensing PD43is oriented downward compared with the sensing visual field of the first object sensing PD42. The hatched region inFIG. 4Bis the sensing visual field of the first object sensing PD42, and the region surrounded by a solid line is the sensing visual field of the second object sensing PD43.

InFIG. 4B, the sensing visual field of the raindrop sensing PD41is omitted because the sensing visual field of the raindrop sensing PD41is overlapped with the sensing visual fields of the first object sensing PD42and the second object sensing PD43in the direction perpendicular to the paper plane.

The positional relationship between the light receiving surface of the first object sensing PD42and the imaging lens55is set such that the sensing visual field of the first object sensing PD42becomes the region inFIGS. 4A and 4B. For example, the sensing visual field of the first object sensing PD42is spread at an angle of 13° in the horizontal direction and 12° in the vertical direction. The positional relationship between the light receiving surface of the second object sensing PD43and the collective lens56is set such that the sensing visual field of the second object sensing PD43becomes the region inFIGS. 4A and 4B. For example, the sensing visual field of the second object sensing PD43is spread at an angle of 13° in the horizontal direction and 10° in the vertical direction.

The first object sensing PD42receives the light reflected from the object in a region (hereinafter referred to as a first object sensing region) where the sensing visual field of the first object sensing PD42and the irradiation region of the laser beam of the LD31are overlapped with each other. The second object sensing PD43receives the light reflected from the object in a region (hereinafter referred to as a second object sensing region) where the sensing visual field of the second object sensing PD43and the irradiation region of the laser beam of the LD31are overlapped with each other.

As illustrated inFIGS. 4A and 4B, the first object sensing region and the second object sensing region are partially overlapped with each other. On the other hand, the raindrop sensing region is not overlapped with each of the first object sensing region and the second object sensing region.

Here, sensing of the object with the raindrop sensing PD41, the first object sensing PD42, and the second object sensing PD43will be described below. As described above, the LD31radiates the laser beam having a predetermined pulse width forward.

As described above, the raindrop sensing region is the space on the hood of the own vehicle. Accordingly, the reflected light received by the raindrop sensing PD41is the light, in which the laser beam emitted from the LD31is reflected from the raindrop in the raindrop sensing region. The amount of reflected light received by the raindrop sensing PD41is increased because the number of raindrops is increased with increasing rainfall amount around the own vehicle. The controller2determines one of non-existence of the rainfall, a small amount of rainfall, a middle amount of rainfall, and a large amount of rainfall based on the mount of light reflected from the raindrop, which is received by the raindrop sensing PD41. A determination result of the rainfall state in the controller2is outputted from the input/output unit6to the control device (not illustrated) of the own vehicle.

Thus, the raindrop sensing PD41accurately senses the light reflected from the raindrop around the own vehicle using the visual-field restricting member50, so that the rainfall state can accurately be sensed around the own vehicle.

Next, sensing of the object with the first object sensing PD42will be described below.FIGS. 5A to 5Care schematic diagrams illustrating the car ahead in which an image is formed on the light receiving surface of the first object sensing PD and an acceptance light amount of each light receiving region depending on the distance to the car ahead. The distance to the car ahead is about 20 m inFIG. 5A, the distance to the car ahead is about 10 m inFIG. 5B, and the distance to the car ahead is about 3 m inFIG. 5C.

As illustrated inFIG. 5A, for the long distance to the car ahead, the image of the entire car ahead is formed on the light receiving surface of the first object sensing PD42. The LD31radiates the laser beam having the predetermined pulse width forward. For the long distance to the car ahead, the entire car ahead is irradiated with the laser beam emitted from the LD31, and the first object sensing PD42can receive the light reflected from the car ahead. As illustrated inFIGS. 5A and 5B, the light reflected from the reflectors attached to both the sides of the car ahead is received in the region where the acceptance light amount is large in the light receiving region of the first object sensing PD42.

The controller2calculates a distance D to the car ahead by
D=(t2−t1)×c/2 (wherecis a light speed)

using a clock time t1when the LD31emits the laser beam and a clock time t2when the first object sensing PD42receives the reflected light.

The controller2calculates a horizontal position X of the object with respect to the own vehicle in each of the divided light receiving regions (ten light receiving regions) of the first object sensing PD42that receives the reflected light by
X=α×Dtan θ (where θ is the spread angle in the horizontal direction of the sensing visual field of the first object sensing PD 42)

using coefficients α (α1to α10) that are previously fixed with respect to the light receiving regions of the first object sensing PD42.

The coefficients α (α1to α10) that are previously fixed with respect to the light receiving region of the first object sensing PD42may be fixed based on the relatively positional relationship between the irradiation region of the laser beam of the LD31and the sensing visual field of the first object sensing PD42.

Accordingly, the radar device1senses the distance to the object positioned in front of the own vehicle and the horizontal position of the object without horizontally scanning the laser beam emitted from the LD31.

On the other hand, as illustrated inFIG. 5C, for the short distance to the car ahead, the image of the upper portion (surroundings of a rear window of the car ahead) of the car ahead is formed on the light receiving surface of the first object sensing PD42. The rear window of the car ahead has a low reflectance to the laser beam emitted from the LD31. Therefore, the first object sensing PD42cannot sense the light reflected from the rear window of the car ahead, and possibly the first object sensing PD42cannot sense the car ahead as the object.

However, as illustrated inFIG. 4B, because the sensing visual field of the second object sensing PD43is oriented downward compared with the sensing visual field of the first object sensing PD42, the second object sensing PD43receives the light reflected from the reflector of the car ahead for the short distance to the car ahead. The controller2calculates the distance D to the car ahead by
D=(t3−t1)×c/2 (wherecis the light speed)

using the clock time t1when the LD31emits the laser beam and a clock time t3when the second object sensing PD43receives the reflected light.

Accordingly, even for the short distance to the car ahead, the radar device1senses the distance to the car ahead by receiving the reflected light using the second object sensing PD43.

As described above, the radar device1can accurately sense the light reflected from the raindrop around the own vehicle using the raindrop sensing PD41, and also accurately sense objects, such as the car ahead, which are positioned in front of the own vehicle, using the first object sensing PD42and the second object sensing PD43.

In one or more embodiments of the present invention, by way of example, the laser beam is used as the exploring wave. However, the exploring wave is not limited to the laser beam. For example, a millimeter wave may be used as the exploring wave.