CN105301279B - A kind of speed measurement method based on camera, device and mobile terminal - Google Patents

Abstract

The invention discloses a camera-based speed measurement method, device and mobile terminal, wherein the method includes: after the camera is focused and its position is fixed, acquiring two imaging images of the object to be measured on the photosensitive surface of the camera, and the photosensitive surface is parallel Based on the travel route of the object to be measured; according to the position of the two images on the photosensitive surface, calculate the distance between the two images as the imaging displacement of the object to be measured; calculate the object distance according to the image distance and the focal length of the lens; The actual displacement of the object to be measured is calculated by imaging displacement, image distance and object distance; the speed of the object to be measured is calculated according to the actual displacement and the time interval between two imaging. Based on the built-in camera of the mobile terminal, the present invention measures the speed of moving objects without adding hardware equipment, and solves the problem of complex structure of the speed measuring device. The speed measuring device of the present invention has a simple structure and low cost.

Description

A camera-based speed measurement method, device and mobile terminal

technical field

The invention belongs to the technical field of mobile terminals, and relates to a camera-based speed measurement method, device and mobile terminal.

Background technique

In traffic engineering, speed is one of the basic important data for measuring and evaluating road performance and traffic conditions. There are many ways to collect speed data, including manual measurement of fixed distance travel time, pressure tube method, coil method, image processing method, radar speed measurement method and laser speed measurement method. Among them, the radar speed measurement method is a method with high accuracy, so it is widely used.

However, radar is a complex electromechanical mechanism, which includes antenna, radome, feeder, antenna base, radar servo mechanical transmission, radar transmitter, radar case, cabinet and its accessories, special electromechanical devices, in order to ensure radar performance and The quality and the requirements for the radar manufacturing process are also very strict. Therefore, the manufacturing cost of radar speed measuring equipment is relatively high.

Contents of the invention

In view of this, the object of the present invention is to propose a camera-based speed measurement method, device and mobile terminal to solve the problem of complex structure of speed measurement equipment and reduce manufacturing costs.

To achieve the above object, the present invention adopts the following technical solutions:

In a first aspect, an embodiment of the present invention provides a camera-based speed measurement method, including:

After the camera is focused and the position is fixed, two images of the object to be measured are obtained on the photosensitive surface of the camera, and the photosensitive surface is parallel to the traveling route of the object to be measured;

According to the positions of the two imagings on the photosensitive surface, calculate the distance between the two imagings as the imaging displacement of the object to be measured;

Calculate the object distance according to the image distance and the focal length of the lens;

calculating the actual displacement of the object to be measured according to the imaging displacement, image distance and object distance;

The velocity of the object to be measured is calculated according to the actual displacement and the time interval between the two imagings.

In a second aspect, an embodiment of the present invention provides a camera-based speed measurement device, including:

An imaging acquisition module, configured to obtain two images of the object to be measured on the photosensitive surface of the camera after the camera focuses and the position is fixed, and the photosensitive surface is parallel to the traveling route of the object to be measured;

An imaging displacement calculation module, configured to calculate the distance between the two imagings according to the positions of the two imagings on the photosensitive surface as the imaging displacement of the object to be measured;

The object distance calculation module is used to calculate the object distance according to the image distance and the focal length of the lens;

An actual displacement calculation module, configured to calculate the actual displacement of the object to be measured according to the imaging displacement, image distance and object distance;

A velocity calculation module, configured to calculate the velocity of the object to be measured according to the actual displacement and the time interval between the two imagings.

In a third aspect, an embodiment of the present invention provides a mobile terminal, where the mobile terminal includes the camera-based speed measurement device and a camera described in the second aspect above.

The beneficial effect of the present invention is: a camera-based speed measurement method, device and mobile terminal provided by the present invention, when measuring the speed of the object to be measured, make the camera mirror surface of the mobile terminal parallel to the travel route of the object to be measured, and Carry out focusing, after finishing focusing, quickly take continuous shooting of the object to be measured, and the mobile terminal is fixed during the shooting process, and obtain two imaging images of the object to be measured on the photosensitive surface of the camera; according to the calculated imaging displacement, object distance, and image distance And the continuous shooting time interval that can be set in advance, that is, the time interval between two imaging, calculates the speed of the object to be measured, solves the problem of complex structure of the speed measuring equipment, does not need to increase the hardware device, and reduces the manufacturing cost.

Description of drawings

Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those of ordinary skill in the art will be more aware of the above-mentioned and other features and advantages of the present invention. In the accompanying drawings:

FIG. 1 is a schematic flowchart of a camera-based speed measurement method provided in Embodiment 1 of the present invention;

FIG. 2 is a schematic diagram of speed measurement using a camera of a mobile terminal provided by Embodiment 1 of the present invention;

Fig. 3 is a schematic diagram of displacement changes of the motor in the camera provided by Embodiment 1 of the present invention under force;

4 is a schematic diagram of the positional relationship between the lens and the photosensitive surface provided by Embodiment 1 of the present invention;

Fig. 5 is a schematic diagram of the imaging of the object to be measured provided by Embodiment 1 of the present invention;

Fig. 6 is a structural block diagram of a camera-based speed measuring device provided in Embodiment 2 of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, only some structures related to the present invention are shown in the drawings but not all structures.

Embodiment one

FIG. 1 is a schematic flowchart of a camera-based speed measurement method provided by Embodiment 1 of the present invention. The method is suitable for measuring the linear moving speed of an object within a visible distance, and the method can be executed by a camera-based speed measuring device set in a mobile terminal. The device can be realized by software and/or hardware. As shown in Figure 1, the method includes:

Step 110 , after the camera is focused and its position is fixed, acquire two images of the object to be measured on the photosensitive surface of the camera, wherein the photosensitive surface is parallel to the traveling route of the object to be measured.

Exemplarily, when measuring the speed of the object to be measured, click the icon of speed measurement on the mobile terminal, and the mobile terminal automatically turns on the camera; referring to FIG. The small angular deviation between the travel routes of 15 has little influence on the measurement results. Therefore, in actual operation, the plane of the mobile terminal should be as close as possible to the travel route of the object to be measured 15 (the arrow passing through the object to be measured 15 in the figure line) parallel to ensure that the photosensitive surface of the camera is as parallel as possible to the traveling route of the object 15 to be measured; when the object 15 to be measured enters the field of view of the lens and after focusing is completed, keep the mobile terminal fixed and quickly connect the object 15 to be measured. The above-mentioned speed measurement device acquires two images of the object to be measured 15 on the photosensitive surface of the camera.

Step 120 , according to the positions of the two imagings on the photosensitive surface, calculate the distance between the two imagings as the imaging displacement of the object to be measured.

Since the photosensitive surface remains still, for a moving object to be measured, its imaging position on the photosensitive surface is different at different times. At the position on the photosensitive surface, the distance between the two imaging is calculated, and the distance is taken as the imaging displacement of the object to be measured.

Preferably, this step may include: analyzing and comparing the two imagings, selecting image points at corresponding positions of the two imagings as two reference points; calculating the distance between the two reference points as the imaging displacement of the object to be measured. Perform image processing on the two imaging, select an image point in one of the imaging as a reference point, compare and analyze the other imaging with the above-mentioned one of the imaging, select the image point at the corresponding position as another reference point, and calculate two The distance between the reference points is used to obtain the imaging displacement of the object to be measured. The imaging displacement is calculated through the reference point, which makes the measurement result more accurate.

Step 130, calculate the object distance according to the image distance and the focal length of the lens.

Wherein, the image distance can be calculated according to the magnitude of the driving current. In this embodiment, referring to Fig. 3 and Fig. 4, the motor 10 is arranged in the bracket 12 of the camera, and is pulled by a spring 11 to balance the magnetic field force F received by the motor 10, so that the motor 10 can be fixed at a certain position of the bracket 12, This drives the lens 13 in the camera to expand and contract. Wherein, the position and length of the bracket 12 limit the distance from the lens 13 to the photosensitive surface 14 ie the minimum value x _min and maximum value x _max of the image distance, and the initial position of the lens 13 is at the minimum value of the image distance.

Specifically, a small magnetic field is distributed in the camera bracket 12, and the controller in the mobile terminal controls the drive circuit to provide the motor 10 with a drive current of 1 through the drive circuit, and the drive current passes through the coil of the motor 10, so that the energized coil is subjected to Magnetic field force F, and the magnitude of the magnetic field force F=KBI, wherein, K is a constant, B is the magnetic field strength, and I is the driving current. At this time, the motor 10 is also affected by the spring traction force F _spring opposite to the direction of the magnetic field force, and the magnitude of the spring traction force F _spring =kX, where k is the spring coefficient, and X is the displacement of the motor 10 . When the F _bullet and F balance, the motor 10 is fixed in the bracket 12, and the lens 13 stops moving, thus, F _bullet =F, it can be obtained image distance Therefore, the image distance can be calculated by obtaining the magnitude of the driving current based on the speed measuring device of the camera.

Specifically, after the camera-based speed measurement device obtains the image distance and focal length, the object distance is calculated based on the following formula:

Among them, u is the object distance, which means the distance from the object to be measured to the camera lens; v is the image distance, which means the distance from the lens to the photosensitive surface; f is the focal length, which means the distance from the lens center to the focal point.

In this embodiment, the focal length of the lens of the mobile terminal may be a constant.

It should be noted that the image distance in this embodiment can also be self-tested by the camera module, and the measurement result can be directly obtained by the camera-based speed measurement device.

Step 140, calculate the actual displacement of the object to be measured according to the imaging displacement, image distance and object distance.

Further, the camera-based speed measurement device can calculate the actual displacement of the object to be measured according to the imaging displacement, image distance and object distance. Referring to Fig. 5, when taking a photo for the first time, the object to be measured 15 passes through the lens 13 and forms an image 16 on the photosensitive surface 14 for the first time, and when taking a photo for the second time, the object to be measured 15 passes through the lens 13 and forms an image 16 on the photosensitive surface 14. The second imaging 17, the displacement from the first imaging 16 to the second imaging 17 is the imaging displacement. Since the photosensitive surface 14 is parallel to the travel path of the object to be measured 15, the imaging displacement y is parallel to the actual distance of the object to be measured 15. The displacement x is determined by the similar triangle theorem, and the actual displacement of the object to be measured can be calculated based on the following formula:

Among them, x is the actual displacement of the object to be measured; y is the imaging displacement of the object to be measured.

Step 150, calculate the velocity of the object to be measured according to the actual displacement and the time interval between two imagings.

Exemplarily, the time interval of continuous shooting can be set before the continuous shooting, the time interval between two imaging is determined according to the time interval of continuous shooting, and finally the speed of the object to be measured is calculated according to the actual displacement and the time interval between two imaging, Specifically, the speed of the object to be measured can be calculated based on the following formula:

Among them, V is the speed of the object to be measured, and Δt is the time interval between two imaging.

In the camera-based speed measurement method provided by Embodiment 1 of the present invention, when measuring the speed of the object to be measured, the camera mirror surface of the mobile terminal is parallel to the traveling route of the object to be measured, and the focus is performed when the object to be measured enters the field of view of the camera lens. After the focus is completed, the object to be measured is quickly taken continuously, and the mobile terminal is fixed during the shooting process to obtain two images of the object to be measured on the photosensitive surface of the camera; according to the calculated imaging displacement, object distance, image distance and The set continuous shooting time interval, that is, the time interval between two imagings, calculates the speed of the object to be measured, which solves the problem of complex structure of the speed measuring device, does not need to increase hardware devices, and reduces the manufacturing cost.

Embodiment two

Fig. 6 is a structural block diagram of a camera-based speed measuring device provided in Embodiment 2 of the present invention. As shown in FIG. 6 , the device includes: an imaging acquisition module 20 , an imaging displacement calculation module 21 , an object distance calculation module 22 , an actual displacement calculation module 23 and a speed calculation module 24 .

Wherein, the imaging acquisition module 20 is used to obtain two imaging images of the object to be measured on the photosensitive surface of the camera after the camera is focused and the position is fixed, wherein the photosensitive surface is parallel to the traveling route of the object to be measured;

The imaging displacement calculation module 21 is used to calculate the distance between the two imagings according to the positions of the two imagings on the photosensitive surface as the imaging displacement of the object to be measured;

The object distance calculation module 22 is used to calculate the object distance according to the focal length of the image distance and the lens;

The actual displacement calculation module 23 is used to calculate the actual displacement of the object to be measured according to the imaging displacement, image distance and object distance;

The velocity calculation module 24 is used to calculate the velocity of the object to be measured according to the actual displacement and the time interval between two imagings.

Preferably, in the above scheme, the imaging displacement calculation module 21 includes:

The reference point selection unit is used to analyze and compare the two imagings, and select the image points at the corresponding positions of the two imagings as two reference points;

The imaging displacement calculation unit is used to calculate the distance between two reference points as the imaging displacement of the object to be measured.

Further, in the above scheme, the object distance calculation module 22 is specifically used for:

The object distance is calculated based on the following formula:

Among them, u is the object distance, indicating the distance from the camera lens to the traveling route of the object to be measured; v is the image distance, indicating the distance from the lens to the photosensitive surface; f is the focal length, indicating the distance from the lens center to the focal point.

Further, in the above scheme, the actual displacement calculation module 23 is specifically used for:

Calculate the actual displacement of the object to be measured based on the following formula:

Among them, x is the actual displacement of the object to be measured; y is the imaging displacement of the object to be measured.

The camera-based speed measurement device provided in Embodiment 2 of the present invention can be used to execute the camera-based speed measurement method provided in the embodiment of the present invention, and has corresponding functions and beneficial effects.

Embodiment Three

The mobile terminal provided in the third embodiment of the present invention includes the camera-based speed measuring device and the camera provided in the second embodiment of the present invention. The mobile terminal can use the camera-based speed measurement device provided by the present invention to measure the moving speed of objects within the visible range by using a corresponding speed measurement method.

Wherein, the mobile terminal may be a smart phone, a tablet computer, or a personal digital assistant.

The mobile terminal provided by Embodiment 3 of the present invention includes the camera-based speed measuring device provided by the embodiment of the present invention, and has corresponding functions and beneficial effects.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the present invention The scope is determined by the scope of the appended claims.

Claims (9)

1. a kind of speed measurement method based on camera, which is characterized in that including：

Camera focusing and position it is fixed after, obtain twice imaging of the object under test on camera photosurface, it is described Photosurface is parallel to the travelling route of the object under test；

According to the position being imaged on twice on the photosurface, described the distance between imaging twice is calculated, as institute State the imaging displacement of object under test；

Object distance is calculated according to the focal length of image distance and camera lens；

The actual displacement of the object under test is calculated according to the imaging displacement, image distance and object distance；

The speed of the object under test is calculated according to the actual displacement and the time interval being imaged twice；

Wherein, the time interval of continuous shooting, the time interval for determining to be imaged twice according to the time interval of continuous shooting are set before continuous shooting.

2. it according to the method described in claim 1, it is characterized in that, is imaged on twice on the photosurface described in the basis Position calculates described the distance between imaging twice, as the imaging displacement of the object under test, including：

It is imaged twice described in analysis comparison, is imaged the picture point of corresponding position described in selection twice as two reference points；

The distance between described two reference points are calculated, the imaging displacement as the object under test.

3. according to the method described in claim 1, it is characterized in that, the focal length according to image distance and camera lens calculates object distance, Including：

Object distance is calculated based on following formula：

Wherein, u is object distance, represents cam lens to the distance of object under test travelling route；V is image distance, represents that photosurface arrives The distance of lens；F is focal length, represents focus to the distance of lens centre.

4. according to the method described in claim 3, it is characterized in that, described calculate according to the imaging displacement, image distance and object distance Go out the actual displacement of the object under test, including：

The actual displacement of object under test is calculated based on following formula：

Wherein, x is the actual displacement of object under test；Y is the imaging displacement of object under test.

5. a kind of velocity measuring device based on camera, which is characterized in that including：

Be imaged acquisition module, for camera focusing and position it is fixed after, obtain object under test in camera photosurface On imaging twice, the photosurface is parallel to the travelling route of the object under test；

Imaging displacement computing module, for described according to the position being imaged on twice on the photosurface, calculating twice The distance between imaging, the imaging displacement as the object under test；

Object distance computing module, for calculating object distance according to the focal length of image distance and camera lens；

Actual displacement computing module, for calculating the reality of the object under test according to the imaging displacement, image distance and object distance Displacement；

Speed calculation module, for calculating the determinand according to the actual displacement and the time interval being imaged twice The speed of body；

Wherein, the time interval of continuous shooting, the time interval for determining to be imaged twice according to the time interval of continuous shooting are set before continuous shooting.

6. device according to claim 5, which is characterized in that the imaging displacement computing module includes：

Reference point chooses unit, is imaged twice described in comparison for analyzing, is imaged the picture point of corresponding position described in selection twice As two reference points；

Imaging displacement computing unit, for calculating the distance between described two reference points, as the object under test into Image displacement.

7. device according to claim 5, which is characterized in that the object distance computing module is specifically used for：

Object distance is calculated based on following formula：

Wherein, u is object distance, represents cam lens to the distance of object under test travelling route；V is image distance, represents lens to sense The distance of smooth surface；F is focal length, represents lens centre to the distance of focus.

8. device according to claim 7, which is characterized in that the actual displacement computing module is specifically used for：

The actual displacement of object under test is calculated based on following formula：

Wherein, x is the actual displacement of object under test；Y is the imaging displacement of object under test.

9. a kind of mobile terminal, which is characterized in that the mobile terminal includes claim 5-8 any one of them and is based on camera shooting The velocity measuring device and camera of head.