DISTANCE MEASURING SYSTEM

• US 20130278917A1
• Filed: 03/15/2013
• Published: 10/24/2013
• Est. Priority Date: 03/21/2012
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: KOREKADO, Keisuke, KAMIYAMA, Tomoyuki, OHASHI, Nobuyuki
• Granted Patent: US 9,109,888 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• 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 7/484 Transmitters
• 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
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A light emission reference signal, the timing of which is adjusted by a first delay time control circuit, is input as a timing adjustment signal to a light emitter driver. The light emission reference signal, which is delayed by a second delay time control circuit, is output as an offset signal. The offset signal and a light emission timing signal from the light emitter driver are input to a timing correction phase comparator, and a phase comparison result is output from the timing correction phase comparator. The phase comparison result is input to a timing correction control logic circuit, and a delay adjusting signal based on the phase comparison result is output from the timing correction control logic circuit. The delay adjusting signal is input to the first delay time control circuit, whereby the timing of the light emission reference signal is adjusted.

Claims

1. A distance measuring system comprising:

a light emitter that emits light toward a target object;

a light receiver that receives reflected light of the emitted light from the target object and produces an output corresponding to an amount of light received;

a controller for controlling the light emitter and the light receiver; and

a distance calculating unit that calculates a distance to the target object by means of a time-of-flight method using the output of the light receiver,

wherein the controller further comprises;

a sequencer that regulates a light emission timing at which light is emitted from the light emitter and a light reception timing at which light is received by the light receiver;

a reference clock signal generating unit that generates a reference clock signal and outputs the reference clock signal to the sequencer;

a light emitter driver for driving the light emitter;

a light receiver driver for driving the light receiver; and

a timing correction unit interposed in a previous stage of the light emitter driver for correcting the light emission timing,

wherein the timing correction unit includes a first delay time control circuit, a second delay time control circuit, a timing correction phase comparator, and a timing correction control logic circuit;

the sequencer generates a reference signal synchronized with the reference clock signal, and inputs the reference signal to the first delay time control circuit and the second delay time control circuit;

the second delay time control circuit receives the reference signal, which is input thereto, and outputs an offset signal in which timing of the reference signal is delayed;

the timing correction phase comparator receives the offset signal and an output signal from the light emitter driver, which are input thereto, and outputs a phase comparison result;

the timing correction control logic circuit reads the phase comparison result, and outputs a delay adjusting signal based on the phase comparison result; and

the first delay time control circuit reads the delay adjusting signal, adjusts the timing of the reference signal, and outputs the same as a light emission timing adjustment signal to the light emitter driver.

2. The distance measuring system according to claim 1, wherein the timing correction unit further comprises a first delay locked loop and a second delay locked loop;

the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator each include, respectively, a first delay line and a second delay line;

a first delay adjusting bias generated by the first delay locked loop is applied to each of the first delay lines; and

a second delay adjusting bias generated by the second delay locked loop is applied to each of the second delay lines.

3. The distance measuring system according to claim 1, wherein the timing correction unit further comprises a first delay locked loop and a second delay locked loop;

the first delay locked loop includes a first delay line;

the second delay locked loop includes a second delay line; and

the timing correction phase comparator shares the first delay line and the second delay line.

4. The distance measuring system according to claim 1, wherein the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator each include, respectively, a first delay locked loop and a second delay locked loop;

each of the first delay locked loops includes a first delay line;

each of the second delay locked loops includes a second delay line; and

the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator each share the respective first delay lines and the respective second delay lines.

5. The distance measuring system according to claim 1, wherein at least one of the first delay time control circuit and the second delay time control circuit comprises:

a first delay adjusting circuit having a variable number of delay stages;

a second delay adjusting circuit having a variable number of delay stages; and

a third delay adjusting circuit equipped with a first delay line and a second delay line and having a variable path between the first delay line and the second delay line,

wherein the timing correction control logic circuit generates a first delay adjusting signal for adjusting the number of the delay stages of the first delay adjusting circuit, a second delay adjusting signal for adjusting the number of the delay stages of the second delay adjusting circuit, and a third delay adjusting signal for setting the path of the third delay adjusting circuit;

the first delay adjusting circuit generates a first delay signal from the reference signal based on the reference clock signal and the first delay adjusting signal;

the second delay adjusting circuit generates a second delay signal from the first delay signal based on the second delay adjusting signal; and

the third delay adjusting circuit generates a third delay signal from the second delay signal based on the third delay adjusting signal.

6. The distance measuring system according to claim 1, wherein the timing correction phase comparator converts a phase difference between the offset signal and the output signal from the light emitter driver into a digital signal, and outputs the digital signal as the phase comparison result.

7. The distance measuring system according to claim 6, wherein the timing correction phase comparator comprises:

a first delay line constituted by connecting in series a plurality of first delay elements, and to which the output signal from the light emitter driver is input to a first stage of the first delay elements;

a second delay line constituted by connecting in series a plurality of second delay elements such that the second delay elements correspond to the first delay elements one by one, and to which the offset signal is input to a first stage of the second delay elements; and

a phase detector having at least a plurality of flip-flop circuits,

wherein each of the flip-flop circuits generates a phase detecting signal responsive to outputs from a corresponding first delay element and a corresponding second delay element; and

the phase detector outputs the phase detecting signals from the respective flip-flop circuits as a phase difference value.

8. The distance measuring system according to claim 7, wherein the phase detector further includes a decoder, and the decoder generates the phase difference value based on the phase detecting signals from each of the flip-flop circuits.

9. The distance measuring system according to claim 7, wherein the phase detector further includes a decoder, and from among the phase detecting signals from the flip-flop circuits, the decoder determines a number of bits having logical values of “

1”

or a number of bits having logical values of “

0”

, and outputs the same as the phase difference value.

10. A distance measuring system comprising:

a light emitter that emits light toward a target object;

a light receiver that receives reflected light of the emitted light from the target object and produces an output corresponding to an amount of light received;

a controller for controlling the light emitter and the light receiver; and

a distance calculating unit that calculates a distance to the target object by means of a time-of-flight method using the output of the light receiver,

wherein the controller further comprises;

a sequencer that regulates a light emission timing at which light is emitted from the light emitter and a light reception timing at which light is received by the light receiver;

a reference clock signal generating unit that generates a reference clock signal and outputs the reference clock signal to the sequencer;

a light emitter driver for driving the light emitter;

a light receiver driver for driving the light receiver; and

a timing correction unit interposed in a previous stage of the light emitter driver for correcting the light emission timing,

wherein the timing correction unit includes a circuit startup sequence generator, a delay time control and timing correction phase comparator, and a timing correction control logic circuit;

the circuit startup sequence generator, at the time of system startup, outputs a startup trigger signal to the timing correction control logic circuit, to thereby start up driving of the timing correction control logic circuit;

the timing correction control logic circuit sets an initial value in the delay time control and timing correction phase comparator based on the startup trigger signal; and

the circuit startup sequence generator outputs a startup signal to the delay time control and timing correction phase comparator, to thereby start up driving of the delay time control and timing correction phase comparator.

11. The distance measuring system according to claim 10, wherein:

the delay time control and timing correction phase comparator includes a first delay time control circuit, a second delay time control circuit, and a timing correction phase comparator; and

the timing correction control logic circuit sets an initial value of the first delay time control circuit based on input thereto of the startup trigger signal, and starts up driving of the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator.

12. The distance measuring system according to claim 11, wherein the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator each include, respectively, a first delay line and a second delay line;

the timing correction unit further comprises a first delay locked loop that generates a first delay adjusting bias for adjusting a delay time of each of the first delay lines, and a second delay locked loop that generates a second delay adjusting bias for adjusting a delay time of each of the second delay lines; and

the timing correction control logic circuit starts up driving of the first delay locked loop and the second delay locked loop prior to starting up driving of the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator, and starts up driving of the first delay time control circuit, the second delay time control circuit, and the timing correction phase comparator after the first delay adjusting bias and the second delay adjusting bias have become stabilized.

13. The distance measuring system according to claim 11, wherein the sequencer generates a reference signal, which is synchronized with the reference clock signal, and inputs the reference signal to the first delay time control circuit and the second delay time control circuit;

the first delay time control circuit outputs a signal to the light emitter driver, in which the reference signal is delayed based on the initial value;

the second delay time control circuit outputs an offset signal, in which the delay time is offset from the reference signal;

the timing correction phase comparator carries out phase comparison between the offset signal and the output signal from the light emitter driver, and outputs a phase comparison result; and

the timing correction control logic circuit generates an offset adjusting signal based on the phase comparison result, and updates an offset value in the second delay time control circuit.

14. The distance measuring system according to claim 13, wherein the timing correction control logic circuit updates the offset value and sets the offset value as an updated offset value, when the phase comparison result has reached a median within a detection range of the timing correction phase comparator.

15. The distance measuring system according to claim 14, wherein the updated offset value is held in memory in the second delay time control circuit.

16. The distance measuring system according to claim 14, wherein the timing correction control logic circuit:

generates a delay adjusting signal based on the phase comparison result, which is read after the offset value is updated and set, and controls the first delay time control circuit using the delay adjusting signal to thereby delay the reference signal; and

correctively controls the first delay time control circuit so as to make the offset signal and the output signal from the light emitter driver have the same phase.

17. The distance measuring system according to claim 16, wherein the timing correction control logic circuit measures a jitter value per each sampling period from the phase comparison result over an arbitrary number of sampling periods, and adjusts at least a sampling interval based on the jitter value.

18. The distance measuring system according to claim 17, wherein:

the sampling interval is shortened in accordance with an increase in the jitter value; and

the sampling interval is lengthened in accordance with a decrease in the jitter value.

19. The distance measuring system according to claim 17, wherein, in the event that the jitter value lies within an allowable range, the sampling interval is regarded as appropriate, and adjustment of the sampling interval is not carried out.

20. The distance measuring system according to claim 16, wherein the timing correction control logic circuit adjusts an update interval of an adjustment in timing performed by the first delay time control circuit, based on an amount of variation of the phase comparison result within a fixed time period.

21. The distance measuring system according to claim 20, wherein the update interval of the adjustment in timing is shortened in accordance with an increase in the amount of variation.

22. The distance measuring system according to claim 20, wherein, in the event that the update interval lies within an allowable range, the update interval is regarded as appropriate, and adjustment of the update interval is not carried out.

23. A distance measuring system comprising:

a light emitter that emits light toward a target object;

a light receiver that receives reflected light of the emitted light from the target object and produces an output corresponding to an amount of light received;

a controller for controlling the light emitter and the light receiver; and

a distance calculating unit that calculates a distance to the target object by means of a time-of-flight method using the output of the light receiver,

wherein the controller further comprises;

a sequencer that regulates a light emission timing at which light is emitted from the light emitter and a light reception timing at which light is received by the light receiver;

a reference clock signal generating unit that generates a reference clock signal and outputs the reference clock signal to the sequencer;

a light emitter driver for driving the light emitter; and

a light receiver driver for driving the light receiver,

wherein the sequencer outputs a control signal, by which the light emission timing and the light reception timing are regulated, to the light emitter driver and the light receiver driver, via a timing correction unit that carries out adjustment of a delay time based on a transition timing of the reference clock signal, and at a time resolution that is higher than the time resolution of the reference clock signal.

24. The distance measuring system according to claim 23, wherein the timing correction unit includes a light emission side timing correction unit and a light reception side timing correction unit;

and

the sequencer outputs a first control signal to the light emitter driver via the light emission side timing correction unit, and outputs a second control signal to the light receiver driver via the light reception side timing correction unit.

25. The distance measuring system according to claim 24, wherein:

the light emission side timing correction unit generates the first control signal based on a phase comparison result between a first offset signal, in which a light emission reference signal from the sequencer is delayed, and an output signal from the light emitter driver, and then outputs the same to the light emitter driver; and

the light reception side timing correction unit generates the second control signal based on a phase comparison result between a second offset signal, in which a light reception reference signal from the sequencer is delayed, and an output signal from the light receiver driver, and then outputs the same to the light receiver driver.

26. The distance measuring system according to claim 25, wherein:

the light emission side timing correction unit includes a first delay time control circuit, a second delay time control circuit, a first timing correction phase comparator, and a first timing correction control logic circuit;

the light emission reference signal from the sequencer is input to the first delay time control circuit and the second delay time control circuit;

the first delay time control circuit outputs a signal, in which the light emission reference signal is delayed, to the light emitter driver as the first control signal;

the second delay time control circuit outputs as a first offset signal a signal in which the light emission reference signal is delayed, so as to offset a delay time from generation of the light emission reference signal until the output of the light emitter driver;

the first timing correction phase comparator carries out phase comparison between the first offset signal and the output signal from the light emitter driver, and outputs the same as a first phase comparison result;

the first timing correction control logic circuit outputs a first delay adjusting signal based on the first phase comparison result;

the first delay time control circuit inputs the first delay adjusting signal, and adjusts timing of the light emission reference signal;

the light reception side timing correction unit includes a third delay time control circuit, a fourth delay time control circuit, a second timing correction phase comparator, and a second timing correction control logic circuit;

the light reception reference signal from the sequencer is input to the third delay time control circuit and the fourth delay time control circuit;

the third delay time control circuit outputs a signal, in which the light reception reference signal is delayed, to the light receiver driver as the second control signal;

the fourth delay time control circuit outputs as a second offset signal a signal in which the light reception reference signal is delayed, so as to offset a delay time from generation of the light reception reference signal until the output of the light receiver driver;

the second timing correction phase comparator carries out phase comparison between the second offset signal and the output signal from the light receiver driver, and outputs the same as a second phase comparison result;

the second timing correction control logic circuit outputs a second delay adjusting signal based on the second phase comparison result; and

the third delay time control circuit inputs the second delay adjusting signal, and adjusts timing of the light reception reference signal.

27. A distance measuring system comprising:

a light emitter that emits light toward a target object;

a light receiver that receives reflected light of the emitted light from the target object and produces an output corresponding to an amount of light received;

a controller for controlling the light emitter and the light receiver; and

a distance calculating unit that calculates a distance to the target object by means of a time-of-flight method using the output of the light receiver,

wherein the controller further comprises;

a sequencer that regulates a light emission timing at which light is emitted from the light emitter and a light reception timing at which light is received by the light receiver;

a reference clock signal generating unit that generates a reference clock signal and outputs the reference clock signal to the sequencer;

a light emitter driver for driving the light emitter; and

a light receiver driver for driving the light receiver,

wherein the sequencer outputs a control signal, by which the light emission timing is regulated, to the light emitter driver, via a timing correction unit that carries out adjustment of a delay time based on a transition timing of the reference clock signal, and at a time resolution that is higher than the time resolution of the reference clock signal.

28. The distance measuring system according to claim 27, wherein the timing correction unit generates the control signal based on a phase comparison result between an offset signal, in which the light emission reference signal from the sequencer is delayed, and an output signal from the light emitter driver, and then outputs the same to the light emitter driver.

29. The distance measuring system according to claim 27, further comprising a light receiving element that receives direct light from the light emitter and outputs a light emission timing observation signal,

wherein the timing correction unit generates the control signal based on a phase comparison result between an offset signal, in which the light emission reference signal from the sequencer is delayed, and the light emission timing observation signal from the light receiving element, and then outputs the same to the light emitter driver.

30. The distance measuring system according to claim 28, wherein:

the timing correction unit includes a first delay time control circuit, a second delay time control circuit, a timing correction phase comparator, and a timing correction control logic circuit;

the light emission reference signal from the sequencer is input to the first delay time control circuit and the second delay time control circuit;

the first delay time control circuit outputs a signal, in which the light emission reference signal is delayed, to the light emitter driver as the control signal;

the second delay time control circuit outputs as an offset signal a signal in which the light emission reference signal is delayed, so as to offset a delay time from generation of the light emission reference signal until the output of the light emitter driver;

the timing correction phase comparator carries out phase comparison between the offset signal and the output signal from the light emitter driver, and outputs the same as a phase comparison result;

the timing correction control logic circuit outputs a delay adjusting signal based on the phase comparison result; and

the first delay time control circuit inputs the delay adjusting signal, and adjusts timing of the light emission reference signal.

31. The distance measuring system according to claim 27, wherein the light receiver driver is installed in a single device together with at least the sequencer.