Method and device for measuring the shortest distance of the front visual field of a vehicle

Abstract

The present invention provides a device for measuring the shortest distance of the front visual field of a vehicle, comprising: a calibration pole, a wide-angle objective lens, a camera, and a host computer; the calibration pole is vertically installed on the ground; a calibration reference point A and a correction auxiliary point B are provided on the calibration pole; the height of the calibration reference point A is equal to the vertical height H from the driver's eye point position to the ground projection point; the correction auxiliary point B is located directly below the calibration reference point A, and the distance between the calibration reference point A and the correction auxiliary point B is h; the wide-angle objective lens and the camera are arranged along a horizontal optical path, and the wide-angle objective lens is arranged in front of the camera; the calibration reference point A is located in the horizontal optical path where the center of the wide-angle objective lens and the center of the imaging element of the camera are located; the camera is connected to the host computer; the distance between the calibration reference point A and the center of the wide-angle objective lens 4 is L; the distance between the center of the wide-angle objective lens and the center of the imaging element of the camera is one times the focal length f' of the wide-angle objective lens. The present invention is simple to operate, accurate in measurement, and highly practical.

Description

Technical Field

[0001] The invention relates to the field of photogrammetry, and in particular to a method and a device for measuring the shortest distance of a vehicle's front field of vision. Background Art

[0002] The closest distance is the distance between the projection point of the driver's eye position on the ground and the closest point where the driver can just see the ground. The closest distance is one of the measurement items required by the national military standard GJB 59.33-91 "Armored Vehicle Test Procedure Vision Measurement". The national military standard is mandatory. The closest distance is also related to whether the driver can timely and accurately find and avoid obstacles on the road ahead. The measurement of the closest distance is of great significance to the driving safety and maneuverability of the vehicle.

[0003] The traditional measuring device is a horizon light stand. The method of use is to place the horizon light stand at the driver's position in a moonless environment at night, turn on the horizon light, observe the horizon light lighting conditions, and measure the distance from the nearest point on the ground illuminated by the horizon light to the projection point of the driver's position on the ground as the closest distance. The measurement process using this device is simple, but it needs to be measured in a dark environment and is greatly affected by environmental factors. It is necessary to manually observe the nearest point of lighting, which is greatly affected by human factors. There are also measurement errors during measurement, so the overall measurement result has a large error. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a method and device for measuring the shortest distance to the front field of view of a vehicle, which has the characteristics of simple operation, accurate measurement and strong practicality.

[0005] The embodiment of the present invention provides a device for measuring the shortest distance of the front field of vision of a vehicle, comprising: a calibration pole, a wide-angle objective lens, a camera, and a host computer;

[0006] The calibration pole is vertically mounted on the ground; a calibration reference point A and a correction auxiliary point B are provided on the calibration pole; the height of the calibration reference point A is equal to the vertical height H from the driver's eye point to the ground projection point; the correction auxiliary point B is located directly below the calibration reference point A, and the distance between the calibration reference point A and the correction auxiliary point B is h;

[0007] The wide-angle objective lens and the camera are arranged along a horizontal optical path, and the wide-angle objective lens is arranged in front of the camera; the calibration reference point A is located in the horizontal optical path where the center of the wide-angle objective lens and the center of the imaging element of the camera are located; the camera is connected to a host computer;

[0008] The distance between the calibration reference point A and the center of the wide-angle objective lens 4 is L;

[0009] The distance between the center of the wide-angle objective lens and the center of the imaging element of the camera is one times the focal length f' of the wide-angle objective lens.

[0010] Preferably, the calibration rod is made of a material that can be attracted by a magnet and is provided with scales; the calibration reference point A and the correction auxiliary point B use magnetic marking points of different colors that are adsorbed on the calibration rod.

[0011] An embodiment of the present invention further provides a method for measuring the shortest distance of a vehicle's front horizon, comprising the following steps:

[0012] S1, install the calibration pole, wide-angle objective lens, camera, and connect the camera to the host computer;

[0013] The calibration pole is installed vertically on the ground; the wide-angle objective lens and the camera are arranged along the horizontal optical path, the wide-angle objective lens is located in front of the camera, and the distance between the center of the wide-angle objective lens and the center of the imaging element of the camera is one times the focal length f′ of the wide-angle objective lens;

[0014] Find a scale on the calibration pole that corresponds to the vertical height H from the driver's eye point to the projection point on the ground, align the center of the wide-angle objective lens and the camera with the scale, observe the image through the host computer, and adjust the wide-angle objective lens and the camera at the same time until the scale is imaged at the center of the image; set the calibration reference point A on the scale, and set the correction auxiliary point B at a distance h below the calibration reference point A; the distance between the calibration reference point A and the center of the wide-angle objective lens is L;

[0015] S2, since the focal length f' of the wide-angle objective lens is known, let the theoretical image height after the correction auxiliary point B is imaged be d1. From the triangle similarity theorem, we can know that:

[0016]

[0017] Get the theoretical image height:

[0018]

[0019] The imaging position of the correction auxiliary point B is observed by the host computer 6, and the actual image height is d2. According to the first-order radial distortion correction formula, we get:

[0020] d1=d2(1+k1r d 2 )

[0021] where r d 2 =d2 2 , the distortion parameter k1 can be obtained by combining:

[0022]

[0023] S3, the closest point on the ground that the camera can observe through the wide-angle objective lens is the closest point C of the horizon, and the closest point C of the horizon is located in the plane determined by the calibration reference point A, the correction auxiliary point B and the center of the wide-angle objective lens;

[0024] The image height of the closest point C in the observation horizon on the host computer is s1, and the corrected image height s2 is obtained according to the first-order radial distortion correction formula, that is:

[0025]

[0026] The shortest distance of the front field of view of the vehicle is X, which can be obtained from the triangle similarity principle:

[0027]

[0028] The shortest distance X of the vehicle's front field of view is:

[0029]

[0030] Furthermore, the first-order radial distortion correction formula is:

[0031] x c =x d (1+k1r d 2 )

[0032] y c =y d (1+k1r d 2 )

[0033] Among them, x d ,y d is the actual image coordinate of the image point, x c ,y c is the coordinate of the image point after distortion correction, k1 is the order radial distortion parameter, r d is the distortion radius, and

[0034] Preferably, the calibration rod is made of a material that can be attracted by a magnet and is provided with scales; the calibration reference point A and the correction auxiliary point B use magnetic marking points of different colors that are adsorbed on the calibration rod.

[0035] The advantages of the present invention are:

[0036] 1) The method proposed in the present invention corrects the first-order radial distortion of the wide-angle objective lens and improves the measurement accuracy.

[0037] 2) In the present invention, each measuring point: point A, point B and point C are located on the same two-dimensional plane in the three-dimensional world, and the distance can be directly calculated without solving the spatial three-dimensional coordinates of the points, thereby simplifying the calculation process.

[0038] 3) It can realize automatic measurement of the shortest distance, which is very practical.

[0039] 4) Camera imaging measurement is less affected by human and environmental factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the shortest distance X of the vehicle's front field of view according to an embodiment of the present invention.

[0041] Figure 2 Schematic diagram of a measuring device according to an embodiment of the present invention.

[0042] Figure 3 Schematic diagram of first-order radial distortion correction of a wide-angle objective lens according to an embodiment of the present invention.

[0043] Figure 4 Schematic diagram of measuring the shortest distance X of the vehicle's front field of view according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with specific drawings and embodiments.

[0045] An embodiment of the present invention provides a device for measuring the shortest distance of a vehicle's front visual field.

[0046] The closest distance to the front view of the vehicle is Figure 1 As shown, Figure 1 The distance X between the projection point of the driver's eye point on the ground and the closest point where the driver can just see the ground is the closest distance of the vehicle's front field of vision;

[0047] In this embodiment, the device for measuring the shortest distance of the front field of view of the vehicle comprises a calibration pole 3, a wide-angle objective lens 4, a camera 5, and a host computer 6;

[0048] The calibration pole 3 is vertically mounted on the ground 1; a calibration reference point A and a correction auxiliary point B are provided on the calibration pole 3; the height of the calibration reference point A is equal to the vertical height H from the driver's eye point to the ground projection point; the correction auxiliary point B is located directly below the calibration reference point A, and the distance between the calibration reference point A and the correction auxiliary point B is h;

[0049] As a preferred solution, the calibration rod 3 is made of a material that can be attracted by a magnet, such as an iron rod, and is provided with a scale; the calibration reference point A and the correction auxiliary point B can use magnetic marking points 2 of different colors, which are adsorbed on the calibration rod 3; when measuring the closest distance of the front field of view of different vehicles, the calibration reference point A can adjust the height H accordingly;

[0050] In other embodiments, the calibration reference point A and the calibration auxiliary point B may also be directly marked on the calibration rod 3 using a color pen; the calibration rod 3 may also not be scaled, and a tape measure may be used to determine the height H and the distance h;

[0051] The wide-angle objective lens 4 and the camera 5 are arranged along a horizontal optical path, and the wide-angle objective lens 4 is arranged in front of the camera 5; the calibration reference point A is located at the horizontal optical path where the center of the wide-angle objective lens 4 and the center of the imaging element of the camera 5 are located; the camera 5 is connected to the host computer 6;

[0052] The distance between the calibration reference point A and the center of the wide-angle objective lens 4 is L;

[0053] The distance between the center of the wide-angle objective lens 4 and the center of the imaging element of the camera 5 is one times the focal length f′ of the wide-angle objective lens 4;

[0054] The measuring device uses a wide-angle objective lens 4, which inevitably produces distortion, which affects the readability of the image and further reduces the measurement accuracy. Optical distortion is mainly divided into three categories: radial distortion, eccentric distortion and thin prism distortion. According to the optical imaging principle of the lens, the distortion model is:

[0055] D x (x,y)=k1x(x 2 +y 2 )+(p1(3x 2 +y 2 )+2p2xy)+s1(x 2 +y 2 )

[0056] D y (x,y)=k2x(x 2 +y 2 )+(p2(3x 2 +y 2 )+2p1xy)+s2(x 2 +y 2 )

[0057] Among them, D x , D y is the nonlinear distortion value, D x , D y The first term is called radial distortion, the second term is called eccentric distortion, and the third term is called thin prism distortion, where k1, k2, p1, p2, s1, s2 are called nonlinear distortion parameters;

[0058] Considering that in this embodiment, radial distortion has the greatest impact on the image; therefore, in this embodiment, the first-order radial distortion of the image is corrected by measuring and calculating the first-order radial distortion correction formula to improve the measurement accuracy; the first-order radial distortion correction formula can be written as:

[0059] x c =x d (1+k1r d 2 )

[0060] yc =y d (1+k1r d 2 )

[0061] Among them, x d ,y d is the actual image coordinate of the image point, x c ,y c is the coordinate of the image point after distortion correction, k1 is the order radial distortion parameter, r d is the distortion radius, and

[0062] The method for measuring the shortest distance of the vehicle's front horizon proposed in this embodiment includes the following steps:

[0063] S1, install the calibration pole 3, the wide-angle objective lens 4, the camera 5, and connect the camera 5 to the host computer 6;

[0064] The calibration rod 3 is made of a material that can be attracted by a magnet, such as an iron rod, and is provided with a scale. The calibration rod 3 is vertically mounted on the ground 1. The wide-angle objective lens 4 and the camera 5 are arranged along a horizontal optical path, the wide-angle objective lens 4 is located in front of the camera 5, and the distance between the center of the wide-angle objective lens 4 and the center of the imaging element of the camera 5 is one times the focal length f′ of the wide-angle objective lens 4.

[0065] Find a scale corresponding to the vertical height H from the driver's eye point to the ground projection point on the calibration pole 3, align the center of the wide-angle objective lens 4 and the camera 5 with the scale, observe the image through the host computer 6, and adjust the wide-angle objective lens 4 and the camera 5 at the same time until the scale is imaged at the center of the image; set the calibration reference point A on the scale, and set the correction auxiliary point B at a distance h below the calibration reference point A. For example, the calibration reference point A and the correction auxiliary point B can use magnetic marking points 2 of different colors, which are adsorbed on the calibration pole 3; the distance between the calibration reference point A and the center of the wide-angle objective lens 4 is L;

[0066] S2, since the focal length f' of the wide-angle objective lens is known, let the theoretical image height after the correction auxiliary point B is imaged be d1. From the triangle similarity theorem, we can know that:

[0067]

[0068] Get the theoretical image height:

[0069]

[0070] The imaging position of the correction auxiliary point B is observed by the host computer 6, and the actual image height is d2. According to the first-order radial distortion correction formula, we get:

[0071] d1=d2(1+k1r d 2)

[0072] where r d 2 =d2 2 , the distortion parameter k1 can be obtained by combining:

[0073]

[0074] S3, the closest point on the ground that the camera 5 can observe through the wide-angle objective lens 4 is the closest point C of the field of view, and the closest point C of the field of view is located in the plane determined by the calibration reference point A, the correction auxiliary point B and the center of the wide-angle objective lens 4;

[0075] The image height of the closest point C in the observation horizon on the host computer 6 is s1, and the corrected image height s2 is obtained according to the first-order radial distortion correction formula, that is:

[0076]

[0077] The shortest distance of the front field of view of the vehicle is X, which can be obtained from the triangle similarity principle:

[0078]

[0079] The shortest distance X of the vehicle's front field of view is:

[0080]

[0081] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A device for measuring the shortest distance of a vehicle's front field of vision, characterized in that: include: Calibration rod (3), wide-angle objective lens (4), camera (5), host computer (6); The calibration pole (3) is vertically mounted on the ground (1); a calibration reference point A and a correction auxiliary point B are provided on the calibration pole (3); the height of the calibration reference point A is equal to the vertical height H from the driver's eye point to the ground projection point; the correction auxiliary point B is located directly below the calibration reference point A, and the distance between the calibration reference point A and the correction auxiliary point B is h; The wide-angle objective lens (4) and the camera (5) are arranged along a horizontal optical path, and the wide-angle objective lens (4) is arranged in front of the camera (5); the calibration reference point A is located in the horizontal optical path where the center of the wide-angle objective lens (4) and the center of the imaging element of the camera (5) are located; the camera (5) is connected to a host computer (6); The distance between the calibration reference point A and the center of the wide-angle objective lens (4) is L; The distance between the center of the wide-angle objective lens (4) and the center of the imaging element of the camera (5) is one times the focal length f′ of the wide-angle objective lens (4).

2. The device for measuring the shortest distance to the front visual field of a vehicle according to claim 1, characterized in that: The calibration rod (3) is made of a material that can be attracted by a magnet and is provided with scales; the calibration reference point A and the correction auxiliary point B are made of magnetic marking points (2) of different colors, which are adsorbed on the calibration rod (3).

3. A method for measuring the shortest distance of a vehicle's front horizon, characterized in that: The following steps are involved: S1, installing a calibration rod (3), a wide-angle objective lens (4), and a camera (5), and connecting the camera (5) to a host computer (6); Install the marking rod (3) vertically on the ground (1); Wide Angle The objective lens (4) and the camera (5) are arranged along a horizontal optical path, the wide-angle objective lens (4) is located in front of the camera (5), and the distance between the center of the wide-angle objective lens (4) and the center of the imaging element of the camera (5) is one times the focal length f′ of the wide-angle objective lens (4); A scale corresponding to the vertical height H from the driver's eye point to the ground projection point is found on the calibration pole (3), the center of the wide-angle objective lens (4) and the camera (5) are aligned with the scale, the imaging image is observed through the host computer (6), and the wide-angle objective lens (4) and the camera (5) are adjusted at the same time until the scale is imaged at the center of the image; the calibration reference point A is set at the scale, and the correction auxiliary point B is set at a distance h below the calibration reference point A; the distance between the calibration reference point A and the center of the wide-angle objective lens (4) is L; S2, since the focal length f' of the wide-angle objective lens is known, let the theoretical image height after the correction auxiliary point B is imaged be d1. From the triangle similarity theorem, we can know that: Get the theoretical image height: The imaging position of the correction auxiliary point B is observed by the host computer (6). The actual image height is d2. According to the first-order radial distortion correction formula, we get: d1=d2(1+k1r d 2 , where r d 2 =d2 2 , the distortion parameter k1 can be obtained by combining: S3, the closest point on the ground that can be observed by the camera (5) through the wide-angle objective lens (4), that is, the closest point C of the horizon, and the closest point C of the horizon is located in the plane determined by the calibration reference point A, the correction auxiliary point B and the center of the wide-angle objective lens (4); The image height of the image of the closest point C in the field of view observed on the host computer (6) is s1, and the corrected image height s2 is obtained according to the first-order radial distortion correction formula, that is: The shortest distance of the front field of view of the vehicle is X, which can be obtained from the triangle similarity principle: The shortest distance X of the vehicle's front field of view is: The first-order radial distortion correction formula is: x c =x d (1+k1r d 2 ) and c =and d (1+k1r d 2 ) Among them, x d ,y d is the actual image coordinate of the image point, x c ,y c is the coordinate of the image point after distortion correction, k1 is the order radial distortion parameter, r d is the distortion radius, and 4. The method for measuring the shortest distance of the vehicle's front visual field as claimed in claim 3, characterized in that: The calibration rod (3) is made of a material that can be attracted by a magnet and is provided with scales; the calibration reference point A and the correction auxiliary point B are made of magnetic marking points (2) of different colors, which are adsorbed on the calibration rod (3).

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