Speed detection methods and devices

• US 7,242,462 B2
• Filed: 03/21/2005
• Issued: 07/10/2007
• Est. Priority Date: 12/21/2004
• Status: Expired due to Fees

• Current Assignee: Asia Optical Company Incorporated
• Original Assignee: Asia Optical Company Incorporated
• Inventors: Huang, Dong
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): BRAINARD, TIMOTHY A
• Application Number:
  US11/085,426
• Publication Number:
  US 20060132755A1
• Time in Patent Office: 841 Days
• Field of Search: 356/28
• US Class Current: 356/27
• CPC Class Codes: G01S 17/50 Systems of measurement based on relative movement of target

Abstract

A speed detection method. A range finder acquires a specific number of distance measurement samples of an object during a period of time. A new unit of measurement larger than respective movement distances of the object in a first period and a second period is acquired. Rough measured distances D1 and D2 respectively corresponding to the locations of the object in the first period and the second period are calculated by comparing portions of the distance measurement samples corresponding to the first period and the second period utilizing the new unit of measurement. A scope is determined based on the D1 and D2 for filtering the distance measurement samples. The speed of the object is calculated based the filtered distance measurement samples.

Claims

1. A speed detection method, implemented in a speed detector comprising a range finder, comprising:

acquiring by the range finder a specific number of distance measurement samples of an object during a period of time utilizing an original unit of distance measurement supported by the range finder;

acquiring a new unit of distance measurement larger than respective movement distances of the object in a first period and a second period;

calculating rough measured distances D1 and D2 respectively corresponding to the locations of the object in the first period and the second period by comparing portions of the distance measurement samples corresponding to the first period and the second period utilizing the new unit of measurement;

determining a scope based on the distances D1 and D2 for filtering the distance measurement samples;

utilizing the scope to filter the distance measurement samples; and

calculating a speed of the object based on the filtered distance measurement samples.

2. The method as claimed in claim 1, wherein each of the distance measurement samples comprises a sequence of reflected pulses of a distance measurement laser pulse emitted by the range finder, each of the reflected pulses corresponds to a scale measured with the new unit of measurement, the D1 is a distance represented by a scale to which the most reflected pulses within the first period correspond, and the D2 is a distance represented by a scale to which the most reflected pulses within the second period correspond.

3. The method as claimed in claim 1, wherein each of the distance measurement samples comprises a sequence of reflected pulses of a distance measurement laser pulse emitted at a received pulse order by the range finder, each of the reflected pulses corresponds to a distance measured with the original unit of distance measurement smaller than the new unit and is distributed in a planar coordinate system spanned by a time axis and a distance axis, and the time-axis and distance-axis coordinates of each reflected pulse comprise the corresponding received pulse order and distance thereof respectively, further comprising determining a first line on the planar coordinate system based on the first period, the second period, the D1, and the D2, wherein the scope is based on the first line.

4. The method as claimed in claim 3, wherein the scope comprises two parallel lines based on the first line, reflected pulses between the two parallel lines are reserved as the filtered distance measurement samples, and the other reflected pulses are filtered out.

5. The method as claimed in claim 4, wherein the first period comprises received pulse order Ti˜

Tj, the second period comprises received pulse order Tk˜

Tl, the first line is determined by coordinates (Tn, D1) and (Tm, D2) on the planar coordinate system Ti≦

Tn≦

Tj and Tk≦

Tm≦

Tl the two parallel lines comprise a line determined by coordinates (Tn, D1+D) and (Tm, D2+D) and another line determined by coordinates (Tn, D1-D) and (Tm, D2-D), and D is a distance offset.

6. The method as claimed in claim 5, wherein Tj−

Ti=Tl−

Tk and |Tk−

Ti|=|Tm−

Tn|.

7. The method as claimed in claim 1, wherein the speed is calculated utilizing the method of least square or the method of weighted mean.

8. A speed detection method, implemented in a speed detector comprising a range finder, comprising:

acquiring by the range finder a specific number of distance measurement samples of an object utilizing an original unit of distance measurement supported by the range finder, wherein each of the distance measurement samples comprises a sequence of reflected pulses of a distance measurement laser pulse emitted by the range finder in a received pulse order, each of the reflected pulses corresponds to a distance and is distributed in a planar coordinate system spanned by a time axis and a distance axis, and the time-axis and distance-axis coordinates of each reflected pulse respectively comprise the corresponding received pulse order and distance thereof;

calculating a rough measured distances D1 and D2 respectively corresponding to the locations of the object in a first period and a second period by sampling portions of the distance measurement samples corresponding to the first period and the second period;

determining a first line on the planar coordinate system based on the first period, the second period, the distance D1, and the distance D2;

determining a scope based on the first line for filtering the distance measurement samples;

utilizing the score to filter the distance measurement; and

calculating a speed of the object based on the filtered distance measurement samples.

9. The method as claimed in claim 8, wherein the scope comprises two parallel lines based on the first line, reflected pulses between the two parallel lines are reserved as the filtered distance measurement samples, and the other reflected pulses are filtered out.

10. The method as claimed in claim 9, wherein the first period comprises received pulse order Ti˜

Tj, the second period comprises received pulse order Tk˜

Tl, the first line is determined by coordinates (Tn, D1) and (Tm, D2) on the planar coordinate system Ti≦

Tn≦

Tj and Tk≦

Tm≦

Tl the two parallel lines comprise a line determined by coordinates (Tn, D1+D) and (Tm, D2+D) and another line determined by coordinates (Tn, D1−

D) and (Tm, D2−

D), and D is a distance offset.

11. The method as claimed in claim 10, wherein Tj−

Ti=Tl−

Tk and |Tk−

Ti|=|Tm−

Tn|.

12. The method as claimed in claim 8, wherein the speed is calculated utilizing the method of least square or the method of weighted mean.

13. A speed detector, comprising:

a range finder acquiring a specific number of distance measurement samples of an object during a period of time using an original unit of distance measurement of the range finder; and

a processor coupled to the range finder, acquiring a new unit of distance measurement larger than the movement distances of the object in a first period and a second period respectively, calculating a rough measured distance D1 and D2 respectively corresponding to the locations of the object in the first period and the second period by comparing portions of the distance measurement samples corresponding to the first period and the second period utilizing the new unit of measurement, determining a scope based on the distance D1 and distance D2 for filtering the distance measurement samples, filtering the distance measurement samples based on the scope and calculating a speed of the object based on the filtered distance measurement samples.

14. The device as claimed in claim 13, wherein each of the distance measurement samples comprises a sequence of reflected pulses of distance measurement laser pulses emitted by the range finder, each of the reflected pulses corresponds to a scale measured with the new unit of measurement, the D1 is a distance represented by a scale to which the most reflected pulses within the first period correspond, and the D2 is a distance represented by a scale to which the most reflected pulses within the second period correspond.

15. The device as claimed in claim 13, wherein each of the distance measurement samples comprises a sequence of reflected pulses of a distance measurement laser pulse emitted in a received pulse order by the range finder, each of the reflected pulses corresponds to a distance measured with the original unit of distance measurement smaller than the new unit and is distributed in a planar coordinate system spanned by a time axis and a distance axis, the time-axis and distance-axis coordinates of each reflected pulse comprise the corresponding received pulse order and distance thereof respectively, the processor determines a first line on the planar coordinate system based on the first period, the second period, the D1, and the D2, wherein the scope is based on the first line.

16. The device as claimed in claim 15, wherein the scope comprises two parallel lines based on the first line, the processor reserves reflected pulses between the two parallel lines as the filtered distance measurement samples and filters out the other reflected pulses.

17. The device as claimed in claim 16, wherein the first period comprises received pulse order Ti˜

Tj, the second period comprises received pulse order Tk˜

Tl, the first line is determined by coordinates (Tn, D1) and (Tm, D2) on the planar coordinate system, Ti≦

Tn≦

Tj and Tk≦

Tm≦

Tl, the two parallel lines comprise a line determined by coordinates (Tn, D1+D) and (Tm, D2+D) and another line determined by coordinates (Tn, D1−

D) and (Tm, D2−

D), and D is a distance offset.

18. The device as claimed in claim 17, wherein Tj−

Ti=Tl−

Tk and |Tk−

Ti|=|Tm−

Tn|.

19. The device as claimed in claim 13, wherein the processor calculates the speed utilizing the method of least square or the method of weighted mean.