Method and apparatus for measuring speed of vehicle

• US 6,628,804 B1
• Filed: 02/17/2000
• Issued: 09/30/2003
• Est. Priority Date: 02/19/1999
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Edanami, Takafumi
• Primary Examiner(s): Werner, Brian
• Assistant Examiner(s): Miller, Ryan J.
• Application Number:
  US09/505,536
• Time in Patent Office: 1,321 Days
• Field of Search: 382/107, 382/103, 382/104, 382/105, 382/168, 348/149, 348/169, 340/936
• US Class Current: 382/107
• CPC Class Codes: G01P 3/806 in devices of the type to be classified in G01P3/68
• CPC Class Codes: G06T 7/246 using feature-based methods, e.g. the tracking of corners or segments
• CPC Class Codes: G08G 1/052 with provision for determining speed or overspeed speed measuring in general G01P

Abstract

A method for measuring the speed of a vehicle which enables measurement of the speed of a vehicle with a high accuracy by an image pickup camera mounted to a single simple supporting pole installed at the side of a field, including capturing a vehicle in motion by an image pickup unit mounted on a support provided at the side of a field, calculating an amount of movement in the vertical direction by an image of the vehicle captured by the image pickup unit on a display screen displaying the image, calculating an amount of movement in the horizontal direction by the image of the vehicle captured by the image pickup unit on the display screen displaying the image, converting the calculated amount of vertical movement and amount of horizontal movement based on information of the capture location of the image pickup unit in the real space of the vehicle and information of the attitude of the image pickup camera to an amount of vertical movement and amount of horizontal movement in that real space, and computing the speed of the vehicle from the amount of vertical movement and amount of horizontal movement in the real space of the vehicle and the movement time.

Claims

1. A method for measuring the speed of a vehicle comprising:

a first step of capturing a vehicle in motion by an image pickup unit mounted on a support provided at the side of a field,

a second step of calculating an amount of movement in the vertical direction by an image of the vehicle captured by the image pickup unit on a display screen displaying the image,

a third step of calculating an amount of movement in the horizontal direction by the image of the vehicle captured by the image pickup unit on the display screen displaying the image;

a fourth step of converting the calculated amount of vertical movement and amount of horizontal movement based on information of the capture location of the image pickup unit in the real space of the vehicle and information of the attitude of the image pickup unit to an amount of forward and backward direction movement and an amount of left and right direction movement in that real space; and

a fifth step of computing the speed of the vehicle from the amount of forward and backward direction movement and an amount of left and right direction movement in the real space of the vehicle and the movement time;

further comprising the additional steps of;

defining the information of the attitude of the image pickup unit by a directional angle (θ

) comprising an angle of offset from a first axis corresponding to a direction of travel of the vehicle in a three-dimensional coordinate system defining the real space and a dip angle (Φ

) comprising an angle of offset from a plane defined by the first axis in the real space and a second axis orthogonal to it and, at that time,

using a predetermined coordinate conversion using a 3D first rotational matrix having the directional angle (θ

) as a parameter, a 3D second rotational matrix having the dip angle (Φ

) as a parameter, a camera coefficient (f) determined by the amount of vertical movement (u) and the amount of horizontal movement (v) on the display screen, a focal distance of the image pickup unit, and properties of the image pickup unit, and information of a location of the image pickup unit to calculate the amount of forward and backward direction movement and the amount of left and right direction movement of the vehicle in real space,

so as to enable a computation of a speed of an object moving in an inclined direction within the image captured by the image pickup unit.

2. A method for measuring the speed of a vehicle as set forth in claim 1, wherein the predetermined coordinate conversion is expressed by the following coordinate conversion equation:

$\begin{array}{cc}\left(\begin{array}{c}{x}^{\mathrm{\prime <br><br>}}\\ y^{\mathrm{\prime <br><br>}}\\ z^{\mathrm{\prime <br><br>}}\end{array}\right)=\left(\begin{array}{ccc}\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}& \sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}& 0\\ -\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}& \cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}& 0\\ 0& 1& 1\end{array}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\begin{array}{ccc}-\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}& 0& \cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\phi <br><br>}\\ 0& 1& 0\\ \cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\phi <br><br>}& 0& \sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\phi <br><br>}\end{array}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\begin{array}{c}f\\ u\\ v\end{array}\right)+\left(\begin{array}{c}\mathrm{x0}\\ \mathrm{y0}\\ \mathrm{z0}\end{array}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\begin{array}{c}\mathrm{where}\\ \mathrm{\theta <br><br>}={\cos }^{-1}<br><br>\left\{\mathrm{x0}<br><br>\text{/}<br><br>{\left({\mathrm{x0}}^2+{\mathrm{y0}}^2\right)}^{1<br><br>\text{/}<br><br>2}\right\}\\ \mathrm{\phi <br><br>}={\cos }^{-1}<br><br>\left\{{\left({\mathrm{x0}}^2+{\mathrm{y0}}^2\right)}^{1<br><br>\text{/}<br><br>2}<br><br>\text{/}<br><br>d\right\}\\ d={\left({\mathrm{x0}}^2+{\mathrm{y0}}^2+{\mathrm{z0}}^2\right)}^{1<br><br>\text{/}<br><br>2}\end{array}\right)& \left(1\right)\end{array}$

where the coordinates expressing the location of the image of the vehicle on the display screen in terms of a 3D coordinate system defining the real space are made (x′

, y′

, z′

) and the coordinates expressing the location of the image pickup unit, from which the vehicle is viewed, in terms of a 3D coordinate system defining the real space are made (x0, y0, z0).

3. A method for measuring the speed of a vehicle as set forth in claim 1, further comprising creating a horizontal direction histogram obtained by cumulatively adding only the elements of the horizontal edges present in the image of the vehicle on the display screen for the image frame (Pn) of a certain time, creating a similar horizontal direction histogram for the image frame (Pn−

1) of a predetermined time before that time, finding the correlation between these two horizontal direction histograms, and detecting a peak of the correlation so as to calculate the amount of vertical movement on the display screen in the second step.

4. A method for measuring the speed of a vehicle as set forth in claim 3, further comprising a step of tracking a change in contrast surrounding the vehicle and averaging the contrast for finding the elements of the horizontal edges when creating the horizontal histograms for the image of the vehicle.

5. A method for measuring the speed of a vehicle as set forth in claim 4, wherein the step for averaging the contrast includes processing for creating a brightness histogram on the display screen and then averaging it.

6. A method for measuring the speed of a vehicle as set forth in claim 3, wherein the amount of vertical movement is calculated by motion compensation image coding for a predetermined feature area including the image of the vehicle on the display screen found when calculating the amount of vertical movement by the horizontal direction histograms.

7. A method for measuring the speed of a vehicle as set forth in claim 1, further comprising creating a vertical direction histogram obtained by cumulatively adding only the elements of the vertical edges present in the image of the vehicle on the display screen for the image frame (Pn) of a certain time, creating a similar vertical direction histogram for the image frame (Pn−

1) of a predetermined time before that time, finding the correlation between these two vertical direction histograms, and detecting the peak of the correlation so as to calculate the amount of horizontal movement on the display screen in the third step.

8. A method for measuring the speed of a vehicle as set forth in claim 7, further comprising a step of tracking a change in contrast surrounding the vehicle and averaging the contrast for finding the elements of the vertical edges when creating the vertical histograms for the image of the vehicle.

9. A method for measuring the speed of a vehicle as set forth in claim 8, wherein the step of averaging the contrast includes processing for creating a brightness histogram on the display screen and then averaging it.

10. A method for measuring the speed of a vehicle as set forth in claim 7, wherein the amount of horizontal movement is calculated by motion compensation image coding for a predetermined feature area including the image of the vehicle on the display screen found when calculating the amount of horizontal movement by the vertical direction histograms.

11. A method for measuring the speed of a vehicle as set forth in claim 1, wherein the amount of vertical movement and the amount of horizontal movement is calculated by the second step and third step based on motion compensation image coding for a feature area containing the image of the vehicle on the display screen.

12. A method for measuring the speed of a vehicle as set forth in claim 11, further comprising extracting by filter processing an image signal having a signal component appearing at a predetermined period in an image signal, forming an image of the vehicle on the display screen, and using the image of the portion corresponding to the extracted image signal as the feature area.

13. A method for measuring the speed of a vehicle as set forth in claim 11, further comprising performing one-dimensional DCT or FFT on an image signal of a portion believed to be a feature area in the image signal of the vehicle on the display screen and designating the portion corresponding to a peak in the values obtained by the processing as a feature area.

14. An apparatus for measuring the speed of a vehicle comprising:

an image pickup unit mounted on a support provided at a side of a field and capturing a vehicle in motion,

a unit for calculating an amount of movement in the vertical direction by an image of the vehicle output by the image pickup unit on a display screen displaying the image,

a unit for calculating an amount of movement in the horizontal direction by the image on the display screen,

a unit for converting the amount of vertical movement and amount of horizontal movement on the display screen calculated by the vertical movement calculating unit and horizontal movement calculating unit based on information of the location of the image pickup unit in the real space of the vehicle and information of the attitude of the image pickup unit to an amount of forward and backward direction movement and an amount of left and right direction movement in that real space, and

a unit for computing the speed of the vehicle from the amount of forward and backward direction movement and an amount of left and right direction movement in the real space of the vehicle and the movement time;

wherein information of the attitude of the image pickup unit is defined by a directional angle (θ

) comprising an angle of offset from a first axis corresponding to a direction of travel of the vehicle in a three-dimensional coordinate system defining the real space and a dip angle (Φ

) comprising an angle of offset from a plane defined by the first axis in the real space and a second axis orthogonal to it and, at that time,

said unit for converting using a predetermined coordinate conversion using a 3D first rotational matrix having the directional angle (θ

) as a parameter, a 3D second rotational matrix having the dip angle (Φ

) as a parameter, a camera coefficient (f) determined by the amount of vertical movement (u) and the amount of horizontal movement (v) on the display screen, a focal distance of the image pickup unit, and properties of the image pickup unit, and information of a location of the image pickup unit to calculate the amount of forward and backward direction movement and the amount of left and right direction movement in real space,

so as to enable a computation of a speed of an object moving in an inclined direction within the image captured by the image pickup unit.