Radar device

• US 20050200833A1
• Filed: 03/09/2005
• Published: 09/15/2005
• Est. Priority Date: 03/10/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Morikawa, Katsuhiro, Nakamura, Mitsuo
• Granted Patent: US 7,602,477 B2
• Time in Patent Office: Days
• US Class Current: 356/4.70
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 2007/4975 of sensor obstruction by, e.g. dirt- or ice-coating, e.g. by reflection measurement on front-screen
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A laser radar sensor includes a light emitting circuit, a light receiving circuit, an object detection circuit, and a CPU. The object detection circuit has a summation block, a noise reference determination block, a noise reference storing block, and a differentiation block. The summation block sums up photoreception signals outputted from a photoreceptor also included in the radar sensor and produces a summation signal. The noise reference determination block determines the summation signal outputted in a condition that no object is present in a detection area as a noise reference signal. The noise reference storing block stores the noise reference signal. The differentiation block calculates a subtraction signal by subtracting the noise reference signal from the summation signal for removing a noise component from the summation signal. Object detection is performed based on the subtraction signal. With this configuration, an object is properly detected even when a protection cover of the radar sensor has a duty spot on its surface.

Claims

1. A radar device comprising:

radar means that emits an outgoing wave in a predetermined detection area and outputs a reception signal according to intensity of a reflected wave of the outgoing wave, the reflected wave being reflected by an object;

determination means that determines a condition in which no object is present in the detection area;

storing means that stores a noise reception signal corresponding to a noise outputted from the radar means in association with emission of an outgoing wave by the radar means when the condition in which no object is present in the detection area is determined and the outgoing wave is emitted by the radar means;

differentiation means that calculates a subtraction signal by subtracting the noise reception signal stored by the storing means from the reception signal outputted by the radar means; and

object detection means that compares the subtraction signal with a predetermined reference value and detects the object reflecting the outgoing wave based on the subtraction signal equal to or larger than the reference value.

2. The radar device according to claim 1, wherein:

the radar means emits a plurality of outgoing waves in different directions in the detection area;

the storing means stores each noise reception signal outputted from the radar means in response to corresponding emission of the outgoing waves;

the differentiation means uses the noise reception signal that corresponds to the outgoing wave emitted in the same direction as a source outgoing wave of the reception signal that is under the calculation for subtracting the noise reception signal from the outgoing signal.

3. The radar device according to claim 1, wherein the determination means determines the condition in which no object is present in the detection area when a shape of the reception signal matches a waveform that indicates a condition in which no object is present in the detection area.

4. The radar device according to claim 1, wherein the radar means emits a plurality of outgoing waves in different directions in the detection area, further comprising:

summation range specification means that determines a plurality of summation ranges by specifying a number of reception signals corresponding to a number of outgoing waves emitted adjacent to each other and by shifting adjacent summation ranges by a number of reception signals smaller than the specified number of reception signals such that some of the reception signals are included in a plurality of the summation ranges; and

summation means that sums up the reception signals for each range determined by the summation range specification means, wherein

the storing means stores a noise component of each summation signal, and

the differentiation means calculates the subtraction signal by subtracting the noise component from the summation signal.

5. The radar device according to claim 4, wherein the determination means determines the condition in which no object is present in the detection area when a shape of the reception signal matches a waveform that indicates a condition in which no object is present in the detection area.

6. The radar device according to claim 4, wherein the object detection means sets a reference value in a range lower than a peak value of the subtraction signal, and detects an object based on a comparison between the subtraction signal and the reference value.

7. The radar device according to claim 1, wherein the storing means updates the noise reception signal every time when the condition in which no object is present in the detection area is determined by the determination means.

8. A radar device for a vehicle comprising:

radar means that emits an outgoing wave in a predetermined detection area located ahead of the vehicle and outputs a reception signal corresponding to intensity of a reflected wave of the outgoing wave, the reflected wave being reflected by an object;

determination means that determines a condition in which no object is present in the detection area;

storing means that stores a noise reception signal corresponding to a noise outputted from the radar means in association with emission of an outgoing wave by the radar means when the condition in which no object is present in the detection area is determined and the outgoing wave is emitted by the radar means;

differentiation means that calculates a subtraction signal by subtracting the noise reception signal stored by the storing means from the reception signal outputted by the radar means; and

object detection means that compares the subtraction signal with a predetermined reference value and detects the object reflecting the outgoing wave based on the subtraction signal equal to or larger than the reference value.

9. The radar device according to claim 8, wherein:

the radar means emits a plurality of outgoing waves in different directions in the detection area;

the storing means stores each noise reception signal outputted from the radar means at each emission of the outgoing waves;

the differentiation means uses the noise reception signal that corresponds to the outgoing wave emitted in the same direction as the outgoing wave that is a source wave of the reception signal under the calculation for subtracting the noise reception signal from the outgoing signal.

10. The radar device according to claim 8, wherein the determination means determines the condition in which no object is present in the detection area when a shape of the reception signal match a specific pattern obtained in a condition that no object is present in the detection area.

11. The radar device according to claim 8, wherein the radar means emits a plurality of outgoing waves in different directions in the detection area, further comprising:

summation range specification means that determines a plurality of summation ranges by specifying a number of reception signals corresponding to a number of outgoing waves emitted adjacent to each other and by shifting adjacent summation ranges by a number of reception signals smaller than the specified number of reception signals such that some of the reception signals are included in a plurality of the summation ranges; and

summation means that sums up the reception signals for each range determined by the summation range specification means, wherein

the storing means stores a noise component of each summation signal, and

the differentiation means calculates the subtraction signal by subtracting the noise component from the summation signal.

12. The radar device according to claim 11, wherein the determination means determines the condition in which no object is present in the detection area when a shape of the summation signal match a specific pattern obtained in a condition that no object is present in the detection area.

13. The radar device according to claim 8, wherein the object detection means sets a reference value in a range lower than a peak value of the subtraction signal, and detects an object based on a comparison between the subtraction signal and the reference value.

14. The radar device according to claim 8, wherein the storing means updates data on the noise reception signal by every time when the condition in which no object is present in the detection area is determined by the determination means.