CN102692183A - Measurement method of initial positions and poses of multiple cameras - Google Patents

Abstract

The invention provides a measurement method of initial positions and poses of multiple cameras. The method comprises the following steps of: setting a sighting target at a proper position, aligning an optical axis of each movable camera whose initial position is needed to be measured to the sighting target simultaneously, and measuring a rotation angle between the optical axis and the initial position and a distance from the camera to the sighting target. The above process is repeated more than 4 times for sighting targets at different positions, by utilizing the measured optical rotation angle and the distance from the camera to the sighting target, a relation between initial coordinate systems of movable cameras is deduced, and by utilizing the relation, a coordinate of a specially arbitrary point in an initial coordinate system of a camera can be converted into a coordinate in an initial coordinate system of other cameras.

Description

Method for measuring initial positions and postures of multiple cameras

Technical Field

The invention relates to a method for measuring initial positions and postures of a plurality of cameras. Specifically, the present invention relates to a method for measuring an initial position and a posture in order to obtain relative positions of a plurality of moving cameras or fixed cameras.

Background

There are now some methods for finding the initial position of a camera by measuring the relative position between multiple cameras. For example, in patent document 1 (japanese patent application laid-open No. 2009-094724), a device capable of transmitting and receiving radio waves, ultrasonic waves, infrared rays, and the like is attached to each camera, and data such as the distance and inclination of each camera is transmitted between the cameras to determine the relative position. However, in the technique disclosed in patent document 1, radio waves, ultrasonic waves, infrared rays, and the like used for communication are blocked by the influence of the installation position of the camera, and thus cannot be used.

Further, as shown in patent document 2 (japanese patent application laid-open No. 2008-209354), initial positions and initial directions of respective cameras are obtained using corresponding points of images captured by the plurality of cameras, and relative positions between the cameras are obtained. However, the accuracy of the relative position measurement using the corresponding point is not high, and a problem arises in practical use, and particularly when the shooting directions of the cameras are greatly different, it is difficult to find the corresponding point because different sides of the optotype are shot.

Disclosure of Invention

The invention aims to provide a method for measuring initial positions and postures of a plurality of cameras, which is simple and has high precision.

In order to achieve the above object, the present invention provides a method for measuring initial positions and postures of a plurality of movable cameras, comprising the steps of: a process of providing optotypes at different locations; a process of simultaneously aligning the same visual target provided by a plurality of tested movable cameras arranged at the required positions and shooting; the process that the optical axis of each movable camera aligns each sighting mark; a process of establishing an initial coordinate system of each movable camera based on the initial position and the initial optical axis angle of the movable camera, and measuring the angle of the optical axis of each movable camera rotating from the initial position; a process of measuring the distance from the position of each movable camera to each optotype; calculating the correlation of the initial coordinate systems of the movable cameras by using the rotation angle of the optical axis of the movable camera and the distance between the movable camera and the sighting mark; and calculating the process of converting the coordinates of each sighting mark in the initial coordinate system of one movable camera into the coordinates in the initial coordinate systems of other movable cameras by utilizing the mutual relation among the initial coordinate systems of the movable cameras.

In the method for measuring the initial positions and postures of the plurality of movable cameras, the optotypes are provided at least at 3 or more different positions in the process of providing the optotypes at the different positions.

The method for measuring the initial positions and postures of the plurality of movable cameras, wherein the coordinate conversion process utilizes the following conversion determinant:^l0T_r0＝^loP·^roP^-1wherein^l0p refers to the coordinates of each optotype in the initial coordinate system of a moving camera,^r0p refers to the coordinates of each optotype in the initial coordinate system of the other active cameras,^loT_rothe method refers to a transformation determinant for transforming the coordinates in the initial coordinate system of one movable camera to the initial coordinate systems of other movable cameras.

In the method for measuring the initial positions and postures of the plurality of movable cameras, each movable camera is provided with a zoom lens, in the shooting process of the sighting target, the sighting target is firstly identified in the wide-angle state of the zoom lens, the optical axis is aligned with the identified sighting target, the sighting target is identified again in the telescopic state of the zoom lens, the optical axis is aligned with the identified sighting target again, and finally the rotation angle of the movable camera is measured through a rotation angle sensor.

In the method for measuring the initial positions and postures of the plurality of movable cameras, the deviation of the optical axis of each movable camera with the zoom lens is measured at different zooming positions.

The invention provides another technical scheme that the method for measuring the initial positions and postures of the plurality of fixed cameras comprises the following steps: a process of providing optotypes at different locations; shooting the same sighting target by a plurality of tested fixed cameras arranged at required positions; a process of recognizing the position of the optotype on the image through the images photographed by the respective fixed cameras; a process of measuring the distance from each sighting mark to each fixed camera; measuring the angle between each sighting mark and each fixed camera in a coordinate system established by the position of the fixed camera and the sight angle by using the position of the sighting mark on the image and the measured distance between the sighting mark and the camera; calculating the relationship between the initial coordinate systems of the fixed cameras by using the obtained angle and the distance from the sighting target to the fixed cameras; and converting the coordinates of each sighting mark in the initial coordinate system of one fixed camera into the coordinates in the initial coordinate systems of other fixed cameras by utilizing the relationship among the initial coordinate systems.

The invention provides another technical scheme that the method for measuring the initial positions and postures of the plurality of movable cameras and the fixed cameras comprises the following steps: a process of providing optotypes at different locations; shooting the same sighting target by a plurality of movable cameras and fixed cameras which are arranged at required positions; an alignment procedure for each sighting mark by each movable rotatable camera in relation to the movable camera; a process of establishing an initial coordinate system in relation to each of the movable cameras from the initial position and the initial optical axis angle of each of the movable cameras, and measuring the rotation angle of the optical axis of each of the movable cameras after aligning the optotype in this coordinate system; a process of separate metering of distances from each sighting mark to each movable camera in relation to the movable rotary camera; a process of identifying, in association with each of the fixed cameras, a position of the optotype from the images taken by each of the fixed cameras; a process of measuring distances from the respective optotypes to the respective fixed cameras, respectively, in association with the respective fixed cameras; a process of measuring an angle between each optotype and each fixed camera in a coordinate system established by the position of the fixed camera and the sight angle, using the position of the optotype on the image and the measured distance of the optotype to the camera, in relation to each fixed camera; a process of calculating a relationship between the initial coordinate systems of the respective movable cameras and the initial coordinate systems of the fixed cameras by using the obtained angles and distances from the optotypes to the respective movable cameras and the fixed cameras; and converting the coordinates of each sighting mark in the initial coordinate system of one movable camera or fixed camera into the coordinates in the initial coordinate systems of other movable cameras or fixed cameras by utilizing the relationship among the initial coordinate systems.

The invention provides a method for measuring initial positions and postures of a plurality of cameras, which can simply and accurately measure the relative positions of the plurality of cameras.

Drawings

The method for measuring the initial positions and postures of a plurality of cameras according to the present invention is described in the following embodiments and accompanying drawings.

Fig. 1 is a schematic diagram of initial coordinate systems of two movable cameras in the method for measuring initial positions and postures of multiple cameras according to the invention.

Fig. 2 is a schematic diagram of a coordinate system when the Z-axis of the initial coordinate system of two movable cameras is used as the optical axis and the Z-axis is aligned with the view standard in the method for measuring the initial positions and postures of multiple cameras according to the present invention.

Detailed Description

The method for measuring the initial positions and postures of the plurality of cameras according to the present invention will be described in further detail with reference to fig. 1 to 2.

The method for measuring the initial positions and postures of the plurality of cameras comprises the following steps:

installing a plurality of movable cameras at required positions, and enabling the cameras to shoot sighting marks at different positions, wherein the sighting marks can be formed by placing a plurality of arbitrary objects at different positions, or sequentially placing any object at different positions, or taking the existing object as the sighting mark, and in addition, when the relative position of the movable cameras is to be measured, the same sighting mark is arranged at the position where all the cameras can shoot;

the optical axis of each movable camera is respectively aligned with each sighting mark, wherein the optical axis generally refers to the optical central axis of the lens and generally coincides with the rotation symmetry axis of the lens;

establishing an initial coordinate system based on the initial position and the initial optical axis angle of the movable camera, and measuring the optical axis angle of each movable camera aligned with the sighting target in the coordinate system, wherein the initial position and the initial optical axis angle refer to the reference position coordinate of each camera and the direction opposite to the camera when the movable camera is installed at the specified position, and determining the initial coordinate system (individual coordinate system) of the movable camera on the basis;

measuring the distance from each target to each movable camera, wherein the distance is obtained by using a common laser or ultrasonic distance meter or by measuring the phase difference and contrast of a focusing mechanism of the movable camera, specifically, the distance from the target to the optical center of each movable camera;

calculating the relationship between the initial coordinate systems of the movable cameras by using the measured optical axis angles and the distances from the sighting marks to the movable cameras, wherein the relationship between the initial coordinate systems is explained in detail later;

by converting the coordinates of each optotype in the initial coordinate system of one of the moving cameras into the coordinates in the initial coordinate systems of the other moving cameras using the relationship between the initial coordinate systems, the mutual position between the moving cameras can be obtained (one coordinate system is converted into the other coordinate system) without knowing the distance between the moving cameras.

The relationship between the initial coordinate systems is explained in more detail below:

when two movable cameras are installed at a designated position and the position of a sighting target or a target is measured according to the triangulation principle, the precision of the distance (base line) between the movable cameras can have a great influence on the measurement of the position of the sighting target. If several cameras are not far apart, it is not a great problem if the distance between the cameras can be measured completely. However, when the cameras are far away from each other, for example, on the back of a building, and the distance cannot be measured accurately, the method of measuring the position of the optotype by using the triangulation principle based on the baseline cannot be used. The method adopted in the invention is to determine the relation between the initial coordinate systems through the installation position and the installation angle of the movable camera, and carry out coordinate conversion.

First, a conversion matrix of each coordinate system is explained: fig. 1 shows the coordinate systems of two moving cameras, where in fig. 1 the coordinate system of the first camera is on the left and the coordinate system of the second camera is on the right, assuming that the initial coordinate system of the first camera is Σ_loThe initial coordinate system of the second camera is sigma_roSetting the coordinate system sigma of the sighting mark P in the first camera_loThe coordinate value of (1) is^l0P, coordinate values in the coordinate system of the second camera are^r0In this case, the position vector of the optotype P can be expressed as follows:

[ EQUATION 1 ]

^l0P＝[^l0x_p ^l0y_p ^l0z_p 1]^T

^r0P＝[^r0x_p ^r0y_p ^r0z_p 1]^T

Wherein T in the above formula represents a transposition of the matrix;

in addition, the coordinate system Σ_loOrigin O of_roIn a coordinate system Σ_loThe above table is as follows:

for letting the coordinate system sigma_roOrigin O of_roAnd coordinate system sigma_loOrigin O of_loIs consistent with the handle ∑_roThe new coordinate system obtained after translation is set as sigma'_roAt this time, #'_roRelative to Σ_loThe Euler angles of (a, beta, gamma),^l0p and^r0p has the following relationship:

[ equation 2 ]

^l0P＝^l0T_r0·^r0Pz

Wherein the conversion matrix^loT_roIs represented as follows:

$T_{r0}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}$

<math> <mrow> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mi>cos</mi> <mi></mi> <mi>&alpha;</mi> <mi>cos</mi> <mi></mi> <mi>&beta;</mi> <mi>cos</mi> <mi>&gamma;</mi> <mo>-</mo> <mi>sin</mi> <mi></mi> <mi>&alpha;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mo>-</mo> <mi>sin</mi> <mi></mi> <mi>&alpha;</mi> <mi>cos</mi> <mi>&gamma;</mi> <mo>-</mo> <mi>cos</mi> <mi></mi> <mi>&alpha;</mi> <mi>cos</mi> <mi></mi> <mi>&beta;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mi>cos</mi> <mi></mi> <mi>&alpha;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mmultiscripts> <mi>x</mi> <mrow> <mi>Or</mi> <mn>0</mn> </mrow> <mi>l</mi> </mmultiscripts> </mtd> </mtr> <mtr> <mtd> <mi>sin</mi> <mi></mi> <mi>&alpha;</mi> <mi>cos</mi> <mi></mi> <mi>&beta;</mi> <mi>cos</mi> <mi>&gamma;</mi> <mo>+</mo> <mi>cos</mi> <mi></mi> <mi>&alpha;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mi>cos</mi> <mi></mi> <mi>&alpha;</mi> <mi>cos</mi> <mi>&gamma;</mi> <mo>-</mo> <mi>sin</mi> <mi></mi> <mi>&alpha;</mi> <mi>cos</mi> <mi></mi> <mi>&beta;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mi>sin</mi> <mi></mi> <mi>&alpha;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mmultiscripts> <mi>y</mi> <mrow> <mi>Or</mi> <mn>0</mn> </mrow> <mi>l</mi> </mmultiscripts> </mtd> </mtr> <mtr> <mtd> <mo>-</mo> <mi>sin</mi> <mi></mi> <mi>&beta;</mi> <mi>cos</mi> <mi>&gamma;</mi> </mtd> <mtd> <mi>sin</mi> <mi></mi> <mi>&beta;</mi> <mi>sin</mi> <mi>&gamma;</mi> </mtd> <mtd> <mi>cos</mi> <mi>&beta;</mi> </mtd> <mtd> <mmultiscripts> <mi>z</mi> <mrow> <mi>Or</mi> <mn>0</mn> </mrow> <mi>l</mi> </mmultiscripts> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> <mtd> <mn>1</mn> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

using this transformation matrix^loT_roOne coordinate system can be converted to the other coordinate system and therefore the initial position and attitude of each of the moving cameras can be measured.

The transformation matrix is described in detail below:

the visual mark is set as P_n(n 1, 2, 3.) two moving cameras are aimed at the same sighting target P_nWhen shooting is carried out, the optical axis of each movable camera is respectively aligned with the sighting mark. Setting the Z axis of the coordinate system of each movable camera as the optical axis, rotating the first camera to make the Z axis of the first camera align with the sighting mark P_nThen, this coordinate system is set to be ∑_itRotating the second camera to align the Z-axis of the second camera with the sighting mark P_nThen, this coordinate system is set to be ∑_rtThe coordinate system at this time is as shown in fig. 2, and in fig. 2, the initial coordinate system Σ_lo、∑_roIndicated by solid lines, Z-axis and optotype P_nAligned coordinate system sigma_it、∑_rtIndicated by a dotted line;

thus, the optotype P_nThe position vectors of (a) can be expressed in the following form, respectively:

[ equation 3 ]

^ltP＝[0 0 ^ltz_p 1]^T

^rtP＝[0 0 ^rtz_p 1]^T

As in the case of the above-mentioned formula 2,^ltp and^rtp and^lop and^rop has the following relationship:

[ EQUATION 4 ]

^l0P＝^l0T_lt·^ltP

^r0P＝^r0T_rt·^rtP

Here, the^loT_ltAnd^roT_rtis a transformation matrix;

substituting equation 4 into equation 2, and transforming with equation 3, the following equation is obtained:

[ EQUATION 5 ]

<math> <mrow> <mmultiscripts> <mi>T</mi> <mi>lt</mi> <mrow> <mi>l</mi> <mn>0</mn> </mrow> </mmultiscripts> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <msub> <mi>z</mi> <mi>lt</mi> </msub> </mtd> </mtr> <mtr> <mtd> <mn>1</mn> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mmultiscripts> <mi>T</mi> <mrow> <mi>r</mi> <mn>0</mn> </mrow> <mrow> <mi>l</mi> <mn>0</mn> </mrow> </mmultiscripts> <mo>&CenterDot;</mo> <mmultiscripts> <mi>T</mi> <mi>rt</mi> <mrow> <mi>r</mi> <mn>0</mn> </mrow> </mmultiscripts> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <msub> <mi>z</mi> <mi>rt</mi> </msub> </mtd> </mtr> <mtr> <mtd> <mn>1</mn> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

Here, the^loT_lt、^roT_rt、^roT_roAre respectively defined as follows:

[ EQUATION 5 ]

$\mathrm{<figure-callout\; id="0"\; label="T\; lt\; l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">T</figure-callout>}_{\mathrm{lt}l}^0=\left[\begin{array}{cccc}t_{\mathrm{lt}-11}^{l0}& t_{\mathrm{lt}-12}^{l0}& t_{\mathrm{lt}-13}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}& 0\\ t_{\mathrm{lt}-21}^{l0}& t_{\mathrm{lt}-22}^{l0}& t_{\mathrm{lt}-23}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}& 0\\ t_{\mathrm{lt}-31}^{l0}& t_{\mathrm{lt}-32}^{l0}& t_{\mathrm{lt}-33}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}& 0\\ 0& 0& 0& 1\end{array}\right]$

$\mathrm{<figure-callout\; id="0"\; label="T\; rt\; r"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">T</figure-callout>}_{\mathrm{rt}r}^0=\left[\begin{array}{cccc}t_{\mathrm{rt}-11}^{r0}& t_{\mathrm{rt}-12}^{r0}& t_{\mathrm{rt}-13}^{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">r</figure-callout>}0}& 0\\ t_{\mathrm{rt}-21}^{r0}& t_{\mathrm{rt}-22}^{r0}& t_{\mathrm{rt}-23}^{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">r</figure-callout>}0}& 0\\ t_{\mathrm{rt}-31}^{r0}& t_{\mathrm{rt}-32}^{r0}& t_{\mathrm{rt}-33}^{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">r</figure-callout>}0}& 0\\ 0& 0& 0& 1\end{array}\right]$

$T_{r0}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}=\left[\begin{array}{cccc}t_{r0-11}^{l0}& t_{r0-12}^{l0}& t_{r0-13}^{l0}& t_{r0-14}^{l0}\\ t_{r0-21}^{l0}& t_{r0-22}^{l0}& t_{r0-23}^{l0}& t_{r0-24}^{l0}\\ t_{r0-31}^{l0}& t_{r0-32}^{l0}& t_{r0-33}^{l0}& t_{r0-34}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}\\ 0& 0& 0& 1\end{array}\right]$

At this time, equation 5 becomes the following form:

[ EQUATION 7 ]

$\left[\begin{array}{c}t_{\mathrm{lt}-13}^{l0}{Z}_{\mathrm{lt}}\\ t_{\mathrm{lt}-23}^{l0}{Z}_{\mathrm{lt}}\\ t_{\mathrm{lt}-33}^{l0}{Z}_{\mathrm{lt}}\\ 1\end{array}\right]=\left[\begin{array}{cccc}t_{r0-11}^{l0}& t_{r0-12}^{l0}& t_{r0-13}^{l0}& t_{r0-14}^{l0}\\ t_{r0-21}^{l0}& t_{r0-22}^{l0}& t_{r0-23}^{l0}& t_{r0-24}^{l0}\\ t_{r0-31}^{l0}& t_{r0-32}^{l0}& t_{r0-33}^{l0}& t_{r0-34}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}\\ 0& 0& 0& 1\end{array}\right]\left[\begin{array}{c}t_{\mathrm{rt}-13}^{l0}{Z}_{\mathrm{rt}}\\ t_{\mathrm{rt}-23}^{l0}{Z}_{\mathrm{rt}}\\ t_{\mathrm{rt}-33}^{l0}{Z}_{\mathrm{rt}}\\ 1\end{array}\right]$

From equation 7, one optotype can obtain three equations, and from equation 2, six unknowns are required, i.e., α, β, γ, y,Thus, theoretically, the relationship between the initial coordinate systems of the two moving cameras can be obtained when the two targets are photographed.

However, in order to simplify the calculation process, it is considered to capture more optotypes and to obtain the relationship between the initial coordinate systems.

It is assumed here that the optotype P_nThere are four, each is (P)₁，P₂，P₃，P₄) The position vector of each optotype is as follows:

[ EQUATION 8 ]

^rtP₁＝[0 0 ^rtz_p1 1]^{T lt}P₁＝[0 0 ^ltz_p1 1]^T

^rtP₂＝[0 0 ^rtz_p2 1]^{T lt}P₂＝[0 0 ^ltz_p2 1]^T

^rtP₃＝[0 0 ^rtz_p3 1]^{T lt}P₃＝[0 0 ^ltz_p3 1]^T

^rtP₄＝[0 0 ^rtz_p4 1]^{T lt}P₄＝[0 0 ^ltz_p4 1]^T

These equations are used to transform equation 7 as follows:

[ equation 9 ]

$\left[\begin{array}{cccc}t_{l1-13}^{l0}{Z}_{l1}& t_{l2-13}^{l0}{Z}_{l2}& t_{l3-13}^{l0}{Z}_{l3}& t_{l4-13}^{l0}{Z}_{l4}\\ t_{l1-23}^{l0}{Z}_{l2}& t_{l2-23}^{l0}{Z}_{l2}& t_{l3-23}^{l0}{Z}_{l3}& t_{l4-23}^{l0}{Z}_{l4}\\ t_{l1-33}^{l0}{Z}_{l3}& t_{l2-33}^{l0}{Z}_{l2}& t_{l3-33}^{l0}{Z}_{l3}& t_{l4-33}^{l0}{Z}_{l4}\\ 1& 1& 1& 1\end{array}\right]$

$=\left[\begin{array}{cccc}t_{r0-11}^{l0}& t_{r0-12}^{l0}& t_{r0-13}^{l0}& t_{r0-14}^{l0}\\ t_{r0-21}^{l0}& t_{r0-22}^{l0}& t_{r0-23}^{l0}& t_{r0-24}^{l0}\\ t_{r0-31}^{l0}& t_{r0-32}^{l0}& t_{r0-33}^{l0}& t_{r0-34}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}\\ 0& 0& 0& 1\end{array}\right]\left[\begin{array}{cccc}t_{r1-13}^{r0}{Z}_{r1}& t_{r2-13}^{r0}{Z}_{r2}& t_{r3-13}^{r0}{Z}_{r3}& t_{r4-13}^{r0}{Z}_{r4}\\ t_{r1-23}^{r0}{Z}_{r1}& t_{r2-23}^{r0}{Z}_{r2}& t_{r3-23}^{r0}{Z}_{r3}& t_{r4-23}^{r0}{Z}_{r4}\\ t_{r1-33}^{r0}{Z}_{r1}& t_{r2-33}^{r0}{Z}_{r2}& t_{r3-33}^{r0}{Z}_{r3}& t_{r4-33}^{r0}{Z}_{r4}\\ 1& 1& 1& 1\end{array}\right]$

This equation can be transformed into the following form:

$\left[\begin{array}{cccc}t_{r0-11}^{l0}& t_{r0-12}^{l0}& t_{r0-13}^{l0}& t_{r0-14}^{l0}\\ t_{r0-21}^{l0}& t_{r0-22}^{l0}& t_{r0-23}^{l0}& t_{r0-24}^{l0}\\ t_{r0-31}^{l0}& t_{r0-32}^{l0}& t_{r0-33}^{l0}& t_{r0-34}^{\mathrm{<figure-callout\; id="0"\; label="l"\; filenames="HDA0000051625110000021.png"\; state="\{\{state\}\}">l</figure-callout>}0}\\ 0& 0& 0& 1\end{array}\right]$

$=\left[\begin{array}{cccc}t_{l1-13}^{l0}{Z}_{l1}& t_{l2-13}^{l0}{Z}_{l2}& t_{l3-13}^{l0}{Z}_{l3}& t_{l4-13}^{l0}{Z}_{l4}\\ t_{t1-23}^{l0}{Z}_{l2}& t_{l2-23}^{l0}{Z}_{l2}& t_{l3-23}^{l0}{Z}_{l3}& t_{14-23}^{l0}{Z}_{l4}\\ t_{l1-33}^{l0}{Z}_{l3}& t_{l2-33}^{l0}{Z}_{l2}& t_{l3-33}^{l0}{Z}_{l3}& t_{l4-33}^{l0}{Z}_{l4}\\ 1& 1& 1& 1\end{array}\right]\left[\begin{array}{cccc}t_{r1-13}^{r0}{Z}_{r1}& t_{r2-13}^{r0}{Z}_{r2}& t_{r3-13}^{r0}{Z}_{r3}& t_{r4-13}^{r0}{Z}_{r4}\\ t_{r1-23}^{r0}{Z}_{r1}& t_{r2-23}^{r0}{Z}_{r2}& t_{r3-23}^{r0}{Z}_{r3}& t_{r4-23}^{r0}{Z}_{r4}\\ t_{r1-33}^{r0}{Z}_{r1}& t_{r2-33}^{r0}{Z}_{r2}& t_{r3-33}^{r0}{Z}_{r3}& t_{r4-33}^{r0}{Z}_{r4}\\ 1& 1& 1& 1\end{array}\right]$

if the right side of equation 10 is known, the relative relationship of the first camera and the second camera, i.e., the transformation matrix^loT_roIt can be found. If the first camera and the second camera are aligned with the sighting mark P₁，P₂，P₃，P₄The right-hand side of equation 10 can be determined using equation 4, if the temporal optical axis angle and the distance from the individual sighting marks to the individual cameras are known, so that the transformation matrix on the left-hand side of equation 10 is obtained^loT_roCan also be found. This transformation matrix is the relationship between the initial coordinate systems of the individual active cameras.

The relationship between the initial coordinate systems is thus determined, with which the coordinate values of the optotype in the initial coordinate system of one of the moving cameras can be converted into coordinate values in the initial coordinate systems of the other cameras. Through the conversion, each movable camera can be operated under the same coordinate system, and the initial position and the attitude of each movable camera can be measured.

In addition, the initial position and orientation measuring method of the present invention is not limited to photographing four optotypes. If more targets can be provided and the respective optical axis angles and distances to the targets are found by the method of the present invention, the initial position and attitude with higher accuracy can be obtained by fitting with the least square method.

The plurality of moving cameras used herein are not limited to single focus lenses, and zoom lenses are also possible. If the zoom lens is used, when the sighting target is shot, the wide-angle part of the zoom lens is firstly used for identifying the sighting target, then the optical axis is aligned to the sighting target, then the telescopic part of the zoom lens is used for identifying the sighting target again, and the optical axis is aligned to the identified sighting target.

In addition, when a zoom lens is used, there is a deviation of the optical axis due to a difference in zoom position, and in order to compensate for the deviation, a deviation of the moving optical axis corresponding to the zoom position is measured, and when an angle of the optical axis aligned with the optotype is measured, if the deviation is taken into consideration, a more accurate initial position and posture can be obtained.

In addition, although the above example describes the measurement method of the initial position and orientation with respect to the moving camera, the present invention is not limited to this, and the initial position and orientation of the fixed camera may be measured in the same manner, that is, the relative positions of the plurality of fixed cameras may be determined by the measurement method of the initial position and orientation of the present invention.

The following describes a case of finding relative positions of a plurality of fixed cameras:

the visual target is provided, so that several fixed cameras shoot the same visual target, as in the case of a moving camera, although the optical axis of the fixed camera cannot be aligned with the sighting mark, with the image processing method, in the initial coordinate system of the fixed camera, measuring the angle between the sight line (optical central axis) of each fixed camera and the sighting mark, namely, establishing an initial coordinate system based on the initial position and the initial sight line angle when the fixed camera is arranged, calculating the position of the sighting mark on the shot image on the coordinate system, then, the distance between each sighting mark and each fixed camera is measured, and then, by using the position of the sighting mark on the image and the distance between the sighting mark and the camera, measuring the angle between the sighting target and each fixed camera on an initial coordinate system established by the initial position and the initial sight angle of each fixed camera;

the next process is the same as the case of the moving camera, the relationship between the initial coordinate systems is derived using the known angle of the optotype and the distance to the optotype to find the transformation matrix, and then the coordinate values of the optotype in the initial coordinate system of one camera are transformed into coordinate values in the initial coordinate systems of the other cameras using the transformation matrix representing the relationship between the initial coordinate systems, and the initial positions and attitudes of the plurality of fixed cameras can be measured.

Furthermore, the movable camera and the fixed camera may be used in combination, that is, the relative positions of the plurality of movable cameras and the fixed camera may be determined, and the optotypes may be converted on the respective initial coordinate systems by using this relationship. As in the case of the above-described movable camera and fixed camera, the relationship between the initial coordinate systems can be obtained by using the angles of the targets with respect to the optical axis or the sight line and the distances from the respective targets to the cameras, and then the coordinates on the initial coordinate system of one movable camera or fixed camera can be converted by using this relationship.

It should be noted that the method for measuring the initial positions and postures of the plurality of cameras according to the present invention is not limited to the above-described example, and various applications are possible without departing from the scope of the present invention, and it goes without saying that, for example, a camera and a laser range finder may be mounted on the rotary table to measure the initial position and posture of the rotary table.

Claims (7)

1. A method for measuring initial positions and poses of a plurality of moving cameras, the method comprising:

a process of providing optotypes at different locations;

a process of simultaneously aligning the same visual target provided by a plurality of tested movable cameras arranged at the required positions and shooting;

the process that the optical axis of each movable camera aligns each sighting mark;

a process of establishing an initial coordinate system of each movable camera based on the initial position and the initial optical axis angle of the movable camera, and measuring the angle of the optical axis of each movable camera rotating from the initial position;

a process of measuring the distance from the position of each movable camera to each optotype;

calculating the correlation of the initial coordinate systems of the movable cameras by using the rotation angle of the optical axis of the movable camera and the distance between the movable camera and the sighting mark;

and a process of converting the coordinates of each sighting mark in the initial coordinate system of one movable camera into the coordinates in the initial coordinate systems of other movable cameras by utilizing the mutual relation among the initial coordinate systems of the movable cameras.

2. The method of claim 1, wherein the visual target is provided at least 3 different positions in the process of providing the visual target at the different positions.

3. The method of claim 1, wherein the coordinate transformation process uses the following transformation determinant:

^l0T_r0＝^loP·^roP^-1

wherein,^l0p refers to the coordinates of each optotype in the initial coordinate system of a moving camera,^r0p refers to the coordinates of each optotype in the initial coordinate system of the other active cameras,^loT_rothe transformation matrix is a transformation matrix for transforming the coordinates in the initial coordinate system of one movable camera to the initial coordinate systems of other movable cameras.

4. The method as claimed in claim 1, wherein each of the plurality of movable cameras has a zoom lens, and the moving target is captured by recognizing the target in a wide angle state of the zoom lens, aligning an optical axis with the recognized target, recognizing the target again in a telephoto state of the zoom lens, aligning the optical axis with the recognized target again, and measuring a rotation angle of the movable camera by a rotation angle sensor.

5. The method of claim 1, wherein the deviation of the optical axis of each of the movable cameras with the zoom lens is measured at a different zoom position.

6. A method for measuring initial positions and poses of a plurality of fixed cameras, the method comprising:

a process of providing optotypes at different locations;

shooting the same sighting target by a plurality of tested fixed cameras arranged at required positions;

a process of recognizing the position of the optotype on the image through the images photographed by the respective fixed cameras;

a process of measuring the distance from each sighting mark to each fixed camera;

measuring the angle between each sighting mark and each fixed camera in a coordinate system established by the position of the fixed camera and the sight angle by using the position of the sighting mark on the image and the measured distance between the sighting mark and the camera;

calculating the relationship between the initial coordinate systems of the fixed cameras by using the obtained angle and the distance from the sighting target to the fixed cameras;

and converting the coordinates of each sighting mark in the initial coordinate system of one fixed camera into the coordinates in the initial coordinate systems of other fixed cameras by utilizing the relationship among the initial coordinate systems.

7. A method for measuring initial positions and poses of a plurality of moving cameras and a fixed camera, the method comprising:

a process of providing optotypes at different locations;

shooting the same sighting target by a plurality of movable cameras and fixed cameras which are arranged at required positions;

an alignment procedure for each sighting mark by each movable rotatable camera in relation to the movable camera;

a process of establishing an initial coordinate system in relation to each of the movable cameras from the initial position and the initial optical axis angle of each of the movable cameras, and measuring the rotation angle of the optical axis of each of the movable cameras after aligning the optotype in this coordinate system;

a process of separate metering of distances from each sighting mark to each movable camera in relation to the movable rotary camera;

a process of identifying, in association with each of the fixed cameras, a position of the optotype from the images taken by each of the fixed cameras;

a process of measuring distances from the respective optotypes to the respective fixed cameras, respectively, in association with the respective fixed cameras;

a process of measuring an angle between each optotype and each fixed camera in a coordinate system established by the position of the fixed camera and the sight angle, using the position of the optotype on the image and the measured distance of the optotype to the camera, in relation to each fixed camera;

a process of calculating a relationship between the initial coordinate systems of the respective movable cameras and the initial coordinate systems of the fixed cameras by using the obtained angles and distances from the optotypes to the respective movable cameras and the fixed cameras;

and converting the coordinates of each sighting mark in the initial coordinate system of one movable camera or fixed camera into the coordinates in the initial coordinate systems of other movable cameras or fixed cameras by utilizing the relationship among the initial coordinate systems.

Images