CN103714551B - Method for calibrating camera external parameters of automatic motormeter detection visual system on basis of interval elimination - Google Patents

Abstract

The invention relates to a method for calibrating camera external parameters of an automatic motormeter detection visual system on the basis of interval elimination, which relates to a method for calibrating camera external parameters, and aims at solving the problems that as camera external parameters of an existing automatic motormeter detection visual system can be only adjusted depending on personal experience, the parameter precision is low, the parameter adjustment process is complicated and the detection precision of the automatic motormeter detection visual system is low. The method for calibrating the camera external parameters of the automatic motormeter detection visual system is characterized in that all to-be-calibrated camera external parameters are iterated to obtain a minimal value of the iteration result and an optimal camera external parameter, the optimal camera external parameter of the iteration result at the present time is compared with that of the iteration result at the previous time, so that the parameter range is narrowed to 0.618 of an original interval, and the detection precision of the automatic motormeter detection visual system can be improved by 60 percent. The method is suitable for calibration on the camera external parameters.

Description

Camera extrinsic number mark based on the interval automobile instrument automatic detection visual system eliminating Determine method

Technical field

The present invention relates to a kind of Camera extrinsic number scaling method.

Background technology

In automobile instrument automatic detecting platform, visual system is the core of platform, and most detection use-case is all Relevant with image procossing, image recognition., as the core component of visual system, its parameter is fine or not, directly for wherein camera Have impact on the accuracy of detection of detection platform, this requires to find a kind of side being capable of quick and precisely calibration for cameras parameter optimal value Method.

Camera has intrinsic parameter and outer parameter, and intrinsic parameter cannot change after camera dispatches from the factory again, and outer parameter is can With adjust at any time, these parameters include aperture time, camera gain, contrast etc..In actual applications, these Camera extrinsic Number does not have a standard, rational algorithm to determine these parameters, is essentially all empirically to pass through continuous debugging Find one group of relatively reasonable parameter.In automobile instrument automatic detecting platform, the algorithm of image procossing is often to determine, calculates Method realize programming after the completion of be not intended to change, but when light in detection platform, the brightness of automobile instrument itself, When color changes, we must make corresponding change again, at this moment just can reach it is desirable that only changing Camera extrinsic number Algorithm requires.But because the camera of detection platform has the outer parameter of many, if only to debug outer parameter by experience, often look for not To one group of satisfied parameter, this is unfavorable to the reusability of automobile instrument automatic detection algorithm, therefore finds a kind of quick Accurately scaling method is very necessary.

Interval cancellation is a kind of by constantly reducing siding-to-siding block length thus the one kind gradually approaching object function extreme point is excellent Change method, that is, in each iterative process, all eliminates a part and does not contain the interval of extreme point, until remaining interval according to one Fixed required precision converges to extreme point.

The outstanding algorithm at present the adjustment neither one of Camera extrinsic number generally acknowledged, major part is all using the most direct " test method(s) ", personnel empirically carry out adjusting parameter with subjective sensation.The thought of " test method(s) " is：Given one group of initial parameter values, Empirically change a parameter every time, judge whether new parameter value is more reasonable by subjective sensation, if under reasonable change One parameter value, if unreasonable continue to change this parameter, constantly modification parameter feels reasonable until subjective.This method Shortcoming the most fatal is that it has very big randomness, and whether the parameter finally demarcated is reasonable and do not know.This shortcoming is in vapour Embody clearly in car instrument automatic detecting platform, the camera parameter of detection platform is a lot, the process of debugging camera parameter Very complicated, and be difficult to find the parameter of one group of satisfaction.

Content of the invention

The present invention is can only to rely on individual to solve the Camera extrinsic number of existing automobile instrument automatic detection visual system Experience is adjusted, and makes that parameters precision is low, parameter testing process complicated, and then leads to automobile instrument automatic detection visual system detection essence Spend low problem, the Camera extrinsic number scaling method based on the interval automobile instrument automatic detection visual system eliminating now is provided.

Based on the Camera extrinsic number scaling method of the interval automobile instrument automatic detection visual system eliminating it is：

All Camera extrinsic numbers to be calibrated are iterated, obtain the minima f (X of iteration result^j)_minWith this minima f (X^j)_minCorresponding optimum Camera extrinsic number X^j, wherein j is iterationses, and initial value is 1；As j=2, execute following step：

Minima f (the X of contrast current iteration result^j)_minCorresponding optimum Camera extrinsic number X^jWith last iteration result Minima f (X^j-1)_minCorresponding optimum Camera extrinsic number X^j-1If, | | X^j-X^j-1| |≤δ, then current iteration result is Little value f (X^j)_minCorresponding optimum Camera extrinsic number X^jFor optimum Camera extrinsic number, δ is 0, otherwise, j=j+1, carry out next time Iteration.

The method that all Camera extrinsic numerical value to be calibrated are iterated comprises the steps：

Step one：Minima f (X according to last iteration result^j-1)_min, in all Camera extrinsic numbers to be calibrated, profit With Fibonacci method, obtain Camera extrinsic numerical intervals to be calibratedAnd utilize golden cut algorithm to select in this interval Take two groups of iterative parameter valuesWithWherein i ∈ [1, n], n are the number of Camera extrinsic number, then execution step two；

Step 2：Using two groups of iterative parameter valuesWithSet camera, and obtain the image shot by camera under this parameter, Then execution step three；

Step 3：Camera shooting figure step 2 being obtained using the standards of grading of automobile instrument automatic detection visual system As being scored, obtain 2ⁿIndividual appraisal resultWherein k=1,2 ..., 2ⁿ, then execution step four；

Step 4：2 that step 3 is obtainedⁿIndividual appraisal resultIt is compared, obtain 2ⁿIn individual appraisal result Little value f (X^j)_min, thus obtaining minima f (X^j)_minCorresponding Camera extrinsic number X^j.

Above-mentioned iterative parameterFor：

$x_{1i}^j=a_{1i}^j+0.382(b_{1i}^j-a_{1i}^j).$

Above-mentioned iterative parameterFor：

$x_{2i}^j=a_{2i}^j+0.618(b_{2i}^j-a_{2i}^j).$

Above-mentioned Camera extrinsic number X^jFor：

$X^j={\[x_{1i}^j,x_{2i}^j\]}^T.$

Above-mentioned parameterFor camera gain.

Above-mentioned parameterFor shutter speed.

Camera extrinsic number demarcation side based on the interval automobile instrument automatic detection visual system eliminating of the present invention Method, the optimal result using last iteration carries out next iteration, so that parameter area narrows down to the 0.618 of former interval, And optimum camera parameter just be can determine by the iteration within 15 times, compare existing dependence personal experience and judge parameter Faster, parameter value is more accurate for speed, and automobile instrument automatic detection visual system accuracy of detection can be made to improve 60%.Simultaneously The present invention, for single-point parameter, can converge to optimized parameter；Local optimum parameter can be converged to for multiple spot parameter.

Camera extrinsic number demarcation side based on the interval automobile instrument automatic detection visual system eliminating of the present invention Method is it is adaptable to demarcate to Camera extrinsic number.

Brief description

Fig. 1 is the image scoring figure of two groups of parameters, and wherein solid-line curve is shutter speed, and imaginary curve is camera gain；

Fig. 2 is the plane angle figure of iterative process；

Fig. 3 is the equal pitch contour visual angle figure of iterative process；

Fig. 4 is the parameter value scattergram of primary iteration；

Fig. 5 is iterative process schematic diagram when two parameters are iterated.

Specific embodiment

Specific embodiment one：The automobile instrument automatic detection visual system based on interval cancellation described in present embodiment Camera extrinsic number scaling method be：

All Camera extrinsic numbers to be calibrated are iterated, obtain the minima f (X of iteration result^j)_minWith this minima f (X^j)_minCorresponding optimum Camera extrinsic number X^j, wherein j is iterationses, and initial value is 1；As j=2, execute following step：

Minima f (the X of contrast current iteration result^j)_minCorresponding optimum Camera extrinsic number X^jWith last iteration result Minima f (X^j-1)_minCorresponding optimum Camera extrinsic number X^j-1If, | | X^j-X^j-1| |≤δ, then current iteration result is Little value f (X^j)_minCorresponding optimum Camera extrinsic number X^jFor optimum Camera extrinsic number, δ is 0, otherwise, j=j+1, carry out next time Iteration.

Specific embodiment two：Present embodiment is to the automotive meter based on interval cancellation described in specific embodiment one The Camera extrinsic number scaling method of table automatic detection visual system is described further, in present embodiment, to all to be calibrated The method that Camera extrinsic numerical value is iterated comprises the steps：

Step one：Minima f (X according to last iteration result^j-1)_min, in all Camera extrinsic numbers to be calibrated, profit With Fibonacci method, obtain Camera extrinsic numerical intervals to be calibratedAnd utilize golden cut algorithm to select in this interval Take two groups of iterative parameter valuesWithWherein i ∈ [1, n], n are the number of Camera extrinsic number, then execution step two；

Step 2：Using two groups of iterative parameter valuesWithSet camera, and obtain the image shot by camera under this parameter, Then execution step three；

Step 3：Camera shooting figure step 2 being obtained using the standards of grading of automobile instrument automatic detection visual system As being scored, obtain 2ⁿIndividual appraisal resultWherein k=1,2 ..., 2ⁿ, then execution step four；

Step 4：2 that step 3 is obtainedⁿIndividual appraisal resultIt is compared, obtain 2ⁿIn individual appraisal result Little value f (X^j)_min, thus obtaining minima f (X^j)_minCorresponding Camera extrinsic number X^j.

Specific embodiment three：Present embodiment is to the automotive meter based on interval cancellation described in specific embodiment two The Camera extrinsic number scaling method of table automatic detection visual system is described further, in present embodiment, described iterative parameterFor：

$x_{1i}^j=a_{1i}^j+0.382(b_{1i}^j-a_{1i}^j).$

Specific embodiment four：Present embodiment is to the automotive meter based on interval cancellation described in specific embodiment two The Camera extrinsic number scaling method of table automatic detection visual system is described further, in present embodiment, iterative parameterFor：

$x_{2i}^j=a_{2i}^j+0.618(b_{2i}^j-a_{2i}^j).$

Specific embodiment five：Present embodiment is to the automotive meter based on interval cancellation described in specific embodiment two The Camera extrinsic number scaling method of table automatic detection visual system is described further, in present embodiment, described Camera extrinsic Number X^jFor：

$X^j={\[x_{1i}^j,x_{2i}^j\]}^T.$

Specific embodiment six：Present embodiment is to the automotive meter based on interval cancellation described in specific embodiment two The Camera extrinsic number scaling method of table automatic detection visual system is described further, in present embodiment, parameterFor camera Gain.

Specific embodiment seven：Present embodiment is to the automotive meter based on interval cancellation described in specific embodiment two The Camera extrinsic number scaling method of table automatic detection visual system is described further, in present embodiment, parameterFor shutter Speed.

As shown in figure 1, according to automobile instrument automatic detection algorithm, two camera parameters obtain figure in the case of different value As the scoring of quality, scoring lower expression picture quality is better.

In conjunction with shown in Fig. 2 and Fig. 3, in all Camera extrinsic numbers to be calibrated, choose camera gain and two groups of shutter speed Parameter, and set the scope of camera gain value as [0,100], the scope of shutter speed value is [0,100]；

Using Fibonacci method, obtaining two groups of primary iteration parameters is：

$\left\{\begin{array}{c}{x}_{11}^0=a_{11}+0.382(b_{11}-a_{11});x_{21}^0=a_{21}+0.618(b_{21}-a_{21})\\ x_{12}^0=a_{12}+0.382(b_{12}-a_{12});x_{22}^0=a_{22}+0.618(b_{22}-a_{22})\end{array}\right.;$

Standards of grading using automobile instrument automatic detection visual system score to above-mentioned two groups of image shot by cameras, Obtain 4 appraisal resultAs shown in Figure 4；Two camera gain parameters and two shutter speed parameters Four parameter value intervals are marked off, four points represent the value condition of four kinds of camera parameters.

Iterative process as shown in figure 5, each square frame represent be each iteration shutter speed and camera gain data point, Numerical value in square frame represents the result of which time iteration, and plus sige represents the optimized parameter of each iteration.Pass through as seen from Figure 4 Method of the present invention, camera parameter constantly approaches to optimal location, has arrived the position of local optimum through 11 iteration convergences Put, now camera gain is 62, shutter speed is 18, parameter scores are 101, approximately close to optimized parameter scoring 100.Thus demonstrate,prove The bright present invention have found the local optimum of parameter by iteration, and achieve multiple parameters and adjust simultaneously, compares artificial operation Not only more rapid but also more accurate, effectively increase the accuracy of detection of automobile instrument automatic detection visual system.

Claims (6)

1. the Camera extrinsic number scaling method based on the interval automobile instrument automatic detection visual system eliminating it is characterised in that The method is：

All Camera extrinsic numbers to be calibrated are iterated, obtain the minima f (X of iteration result^j)_minWith this minima f (X^j)_minCorresponding optimum Camera extrinsic number X^j, wherein j is iterationses, and initial value is 1；As j=2, execute following step：

Minima f (the X of contrast current iteration result^j)_minCorresponding optimum Camera extrinsic number X^jWith last iteration result Little value f (X^j-1)_minCorresponding optimum Camera extrinsic number X^j-1If, | | X^j-X^j-1| |≤δ, then minima f of current iteration result (X^j)_minCorresponding optimum Camera extrinsic number X^jFor optimum Camera extrinsic number, δ is 0, otherwise, j=j+1, carry out next iteration；

The method that all Camera extrinsic numerical value to be calibrated are iterated comprises the steps：

Step one：Minima f (X according to last iteration result^j-1)_min, in all Camera extrinsic numbers to be calibrated, using Huang Golden split-run, obtains Camera extrinsic numerical intervals to be calibratedAnd utilize golden cut algorithm to choose two in this interval Group iterative parameter valueWithWherein i ∈ [1, n], n are the number of Camera extrinsic number, then execution step two；

Step 2：Using two groups of iterative parameter valuesWithSet camera, and obtain the image shot by camera under this parameter, then Execution step three；

Step 3：Entered using the image shot by camera that the standards of grading of automobile instrument automatic detection visual system obtain to step 2 Row scoring, obtains 2ⁿIndividual appraisal resultWherein k=1,2 ..., 2ⁿ, then execution step four；

Step 4：2 that step 3 is obtainedⁿIndividual appraisal resultIt is compared, obtain 2ⁿMinima in individual appraisal result f(X^j)_min, thus obtaining minima f (X^j)_minCorresponding Camera extrinsic number X^j.

2. the Camera extrinsic number mark based on the interval automobile instrument automatic detection visual system eliminating according to claim 1 Determine method it is characterised in that described iterative parameterFor：

$x_{1i}^j=a_{1i}^j+0.382(b_{1i}^j-a_{1i}^j);$

WithRepresent iterative parameter respectivelyInterval parameter endpoint value.

3. the Camera extrinsic number mark based on the interval automobile instrument automatic detection visual system eliminating according to claim 1 Determine method it is characterised in that described iterative parameterFor：

$x_{2i}^j=a_{2i}^j+0.618(b_{2i}^j-a_{2i}^j);$

WithRepresent iterative parameter respectivelyInterval parameter endpoint value.

4. the Camera extrinsic number mark based on the interval automobile instrument automatic detection visual system eliminating according to claim 1 Determine method it is characterised in that described Camera extrinsic number X^jFor：

$X^j={\[x_{1i}^j,x_{2i}^j\]}^T.$

5. the Camera extrinsic number mark based on the interval automobile instrument automatic detection visual system eliminating according to claim 1 Determine method it is characterised in that parameterFor camera gain.

6. the Camera extrinsic number mark based on the interval automobile instrument automatic detection visual system eliminating according to claim 1 Determine method it is characterised in that parameterFor shutter speed.