MEASUREMENT APPARATUS

• US 20150153452A1
• Filed: 11/11/2014
• Published: 06/04/2015
• Est. Priority Date: 11/29/2013
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: YAMAMOTO, Hirofumi, TAGUCHI, Shinichirou, MIKI, Akira
• Granted Patent: US 9,753,127 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487

Abstract

A measurement apparatus measuring a flight time of a search wave corresponding to a time after the search wave is emitted and before a reflected wave is received is provided. The measurement apparatus includes a transceiver, a memory portion, a sampling portion, a measurement portion, and a determination portion. The transceiver emits the search wave and receives the reflected wave. The sampling portion generates a sampling data and causes the memory portion to store the sampling data. The sampling portion includes a first processing unit and a second processing unit. The first processing unit causes the memory portion to store the sampling data as a first signal data. The second processing unit causes the memory portion to store the sampling data as a second signal data. The measurement portion measures the flight time and generates a measurement value of the flight time. The determination portion determines a sampling period.

Claims

1. A measurement apparatus measuring a flight time of a search wave corresponding to a time after the search wave is emitted and before a reflected wave of the search wave is received, the measurement apparatus comprising:

a transceiver emitting the search wave, receiving the reflected wave, and outputting a receiving signal;

a memory portion;

a sampling portion generating a sampling data of the receiving signal and causing the memory portion to store the sampling data, wherein the sampling portion includes

a first processing unit causing the memory portion to store the sampling data generated by sampling the receiving signal at a first sampling frequency as a first signal data, and

a second processing unit causing the memory portion to store the sampling data generated by sampling the receiving signal at a second sampling frequency, which is lower than the first sampling frequency, as a second signal data;

a measurement portion measuring the flight time based on the first signal data and the second signal data and generating a measurement value of the flight time; and

a determination portion determining a sampling period of the receiving signal corresponding to the first signal data based on the measurement value of the flight time, wherein

the first processing unit causes the memory portion to selectively store the sampling data of the receiving signal in a specific period with an emission event of the search wave as a reference, as the first signal data, and

the specific period corresponds to the sampling period determined by the determination portion.

2. The measurement apparatus according to claim 1, wherein

the measurement portion outputs a distance from the measurement apparatus to a front object reflecting the search wave based on the measurement value of the flight time.

3. The measurement apparatus according to claim 1, wherein

the measurement portion calculates the measurement value of the flight time based on the first signal data and the second signal data, and

the measurement portion selectively refers to the second signal data and calculates the measurement value of the flight time based on the second signal data when a difference between the flight time represented by the first signal data and the flight time represented by the second signal data is equal to or more than a reference value.

4. The measurement apparatus according to claim 1, wherein

the measurement portion calculates a first candidate of the flight time based on the first signal data,

the measurement portion calculates a second candidate of the flight time based on the second signal data,

the measurement portion selects the first candidate of the flight time as the measurement value of the flight time when a difference between the first candidate of the flight time and the second candidate of the flight time is less than a reference value, and

the measurement portion selects the second candidate of the flight time as the measurement value of the flight time when the difference between the first candidate of the flight time and the second candidate of the flight time is equal to or more than the reference value.

5. The measurement apparatus according to claim 1, wherein

the sampling portion includes an output circuit, which samples the receiving signal at the first sampling frequency and outputs the sampling data corresponding to the receiving signal,

the first processing unit extracts a data part corresponding to the specific period from the sampling data outputted from the output circuit as the first signal data, and

the second processing unit thins out the sampling data outputted from the output circuit as the second signal data.

6. The measurement apparatus according to claim 1, wherein

the determination portion determines the sampling period including an estimated time when the transceiver receives the reflected wave, which corresponds to the search wave emitted at a next measurement, based on the measurement value of the flight time.

7. The measurement apparatus according to claim 1, wherein

the first processing unit causes the memory portion to store the first signal data,

the first signal data is generated by accumulating a receiving intensity represented by the sampling data for each time with the emission event of the search wave as a reference,

the sampling data for the first signal data is obtained by sampling the receiving signal in the specific period at the first sampling frequency at a plurality of emission operations of the search wave,

the second processing unit causes the memory portion to store the second signal data,

the second signal data is generated by accumulating the receiving intensity represented by the sampling data for each time with the emission event of the search wave as a reference,

the sampling data for the second signal data is obtained by sampling the receiving signal at the second sampling frequency at the plurality of the emission operations of the search wave, and

the measurement portion refers to the receiving intensity represented by the first signal data and the receiving intensity represented by the second signal data at each time and measures the flight time each time when the plurality of the emission operations are completed.

8. The measurement apparatus according to claim 7, wherein

the second processing unit generates an intermediate data each time when an emission operation of the search wave is performed from an initiation to a completion of the plurality of the emission operations,

the intermediate data is generated by accumulating the receiving intensity represented by the sampling data obtained from an initial emission operation to a current emission operation for each time with the emission event of the search wave as a reference,

the measurement portion corrects the sampling period including the receiving time when the reflected wave is received in a case where the measurement portion detects that the reflected wave is received based on the receiving intensity represented by the intermediate data of each time at a prescribed time in a period of the plurality of the emission operations,

the first processing unit causes the memory portion to store the first signal data when the sampling period is corrected in the period of the plurality of the emission operations,

the first signal data is generated by accumulating the receiving intensity represented by the sampling data for each time with the emission event of the search wave as a reference, and

the sampling data is generated by a remaining emission operation performed after the prescribed time, and obtained by sampling the receiving signal corresponding to a corrected sampling period corrected by the measurement portion at the first sampling frequency.

9. The measurement apparatus according to claim 8, wherein

the measurement portion stops operating the second processing unit considering the intermediate data as the second signal data, which is completed, when the measurement portion detects that the reflected wave is received at the prescribed time.

10. The measurement apparatus according to claim 1, wherein

the transceiver emits a light pulse as the search wave,

the transceiver receives a reflected light of the light pulse for each pixel defined by dividing a front visual field receiving the reflected light,

the first processing unit causes the memory portion to store the first signal data generated based on the receiving signal received by the transceiver for each pixel,

the second processing unit causes the memory portion to store the second signal data generated based on the receiving signal received by the transceiver for each pixel,

the measurement portion measures the flight time of the light pulse based on the first signal data and the second signal data for each pixel, and

the determination portion determines the sampling period for each pixel based on the measurement value of the flight time obtained by each pixel.

11. The measurement apparatus according to claim 10, wherein

the determination portion predicts a motion of a front object reflecting the light pulse based on the measurement value of the flight time of each pixel,

the determination portion determines the sampling period of each pixel based on a prediction result of the motion of the front object, and

the determination portion causes the memory portion to store the sampling data corresponding to the receiving signal of the light pulse reflected by the front object as the first signal data.

12. The measurement apparatus according to claim 11, wherein

when a plurality of front objects are predicted to overlap in a pixel, the determination portion determines the sampling period of the pixel and causes the memory portion to store the sampling data as the first signal data, and

the sampling data corresponds to the receiving signal of the light pulse reflected by the front object positioned to a nearest position to the measurement apparatus among the plurality of the front objects predicted to overlap.

13. The measurement apparatus according to claim 11, wherein

the determination portion prevents the first processing unit from operating with respect to a pixel in which the front object is not predicted to exist.