CN103411535A - Variable weight image point location method for return light reflection marker - Google Patents

Abstract

The invention discloses a variable weight image point location method for a return light reflection marker. The method comprises the following steps of a, setting a plurality of object space mark points, b, shooting the object space mark points from different positions to obtain the gray levels of a plurality of position points on imaging light spots, c, acquiring a second weight factor beta related to background noise, d, acquiring a first weight factor alpha related to a measurement field environment variable, e, calculating point center coordinates (x0, y0) of an measured oval image point according to the first acquired weight factor alpha and the second acquired weight factor beta. Compared with an existing method, the center location method for the return light reflection marker is more general, is suitable for different site environments, eliminates effects caused by the site environments and improves the location accuracy of the center of the return light reflection mark point.

Description

But a kind of picture point of variable weight for light echo reflective marker localization method

Technical field

The present invention relates to the photogrammetric technology field.Particularly, the present invention relates to a kind of for light echo reflective marker (Retro-Reflective Targets, be called for short RRT) but variable weight picture point localization method.

Background technology

Photogrammetric utilization photography obtains the two dimensional image of measured object, obtains the three-dimensional information of measured object.20th century the mid-80, close-range photogrammetry succeeds in commercial Application, it utilizes large format grid camera, many picture convergences are calculated, digital picture scans, processes, relatively waits technology, and 000 relative accuracy is provided up to 1:500, the precision that can surpass transit to the measurement of large sized object (as, diameter > 10 meters).The mid-90, combine digital sensor (CCD& COMS) after technology, close-range photogrammetry is called as the off-line Digital Photogrammetric System.By the high resolving power slr camera, light echo reflective marker point, and the technology of pixel location, it can provide very high precision level.Its typical measuring accuracy is 1:100,000 to 1:200,000 relative accuracy (1 times of standard deviation), the former corresponding 10 meters target sizes are issued to the absolute precision of 0.1mm, and generally by the absolute precision of linear measure longimetry, characterize the relative accuracy of three-dimensional reconstruction, generally than spot placement accuracy low 2 to 3 times (for example,, to the about 0.05mm of the object of 2m).

The light echo reflective marker is widely used a kind of artificial target in the high-precision industrial photogrammetry of recent domestic, and it adopts the special glass microballoon material structure with high index of refraction.For example, when ad-hoc location is used light source (flashlamp) to irradiate, RRT can reflex to the light source place according to original path by incident light, as shown in Figure 1.It has high reflectivity, is generally even thousands of times of the hundred times of common sign reflectivity, and the accurate bianry image " separated " to reach impact point and background, help the accurate location of impact point and extraction and the identification of unique point.

After having obtained accurate bianry image, can position RRT.Usually RRT is a circle that a certain size is arranged, and its home position i.e. the coordinate position of this RRT representative.For extracting this position, for different situations, diverse ways is arranged.At the camera photo-sensitive cell, be the epoch of film, normally film be placed under the high magnification magnifier, obtain a RRT image after amplification, then by method of geometry, find the center of RRT.

Development along with modern science and technology and manufacturing technology, especially take CCD and COMS development and the develop rapidly as the solid state image sensor technology of important representative, adopt digital camera to obtain digitized video more and more universal, basically be substituted traditional film type camera.Digital camera is unlike film camera, sensing element can be taken out to amplify position RRT, and due to the restriction of CCD and COMS sensor development level, its spatial resolution can not show a candle to the height of film.Circular light echo reflective marker is generally ellipse after lens imaging, the schematic diagram of imaging facula as shown in Figure 2.

Be subjected to the restriction of optical system and imageing sensor manufacturing process, the resolution relative accuracy of image is no more than 1:10, and 000, for reaching higher relative accuracy, need to carry out other accurate location of sub-pixel to the light echo reflection spot, namely need the center of imaging ellipse light spot is positioned.In order to reach the hi-Fix to elliptical center, two kinds of methods are arranged usually.One class methods are to ask for the RRT edge, then simulate elliptic equation, thereby try to achieve RRT elliptical point center; Another kind of method is based on the half-tone information of RRT, tries to achieve RRT elliptical point center by centroid method.Wherein the accuracy requirement of extracting of edge fitting method edge point is very high, when the monumented point size is less, and can be because the edge extracting error cause the elliptical point center to be had a strong impact on.And the precision that the centroid method edge point of intensity-based extracts is insensitive, extraction accuracy changes not quite under the monumented point of different size, and its shortcoming is easily to be subject to the inhomogeneous impact of intensity profile.

Sub-pixel positioning algorithm commonly used has fitting process, digital correlation, centroid method.The prerequisite of using fitting process is that target property meets functional form known or supposition, so the general very high sub-pixel precision of more difficult acquisition.Digital correlation has that principle is simple, strong adaptability and precision advantages of higher, but to rolling target or in rotating abandoned target localization, seldom using relevant method, because this makes the selection of template be difficult to realize, and in close-range photogrammetry, RRT is always inevitably with rotation, so correlation method can not be located for RRT dot center.The grey scale centre of gravity method, be based on the grey scale centre of gravity method of threshold value, square weighting method etc. the sub-pix algorithm that centroid method forms, the advantage of these algorithms is to take full advantage of the gray-scale value of every bit in RRT, usually can obtain the sub-pixel precision higher than centroid method, precision at 1/20px to 1/50 about pixel.But according to the experimental result of different documents, show, the point center distill precision quality of these methods is not absolute, but, under different occasions, obtains different point center distill precision.Therefore because these methods are subject to the impact of Different field environment, thereby show inconsistent performance level, in the situation that environmental change, it is very inconvenient to use.

Therefore, need a kind of more general center positioning method for the light echo reflective marker, go for different site environments, eliminate as much as possible the impact that site environment causes, to improve the positioning precision of light echo reflective marker dot center.

Summary of the invention

The object of the present invention is to provide a kind of variable weighting centroid method for light echo reflective marker location, to improve the positioning precision of dot center.

According to an aspect of the present invention, but provide a kind of picture point of variable weight for light echo reflective marker localization method, described method comprises the steps: a) to arrange a plurality of object space monumented points; B) at different erect-positions, described a plurality of object space monumented points are taken, obtained the gray-scale value at a plurality of location points place on imaging facula; C) obtain the second weight factor β relevant with ground unrest; D) obtain the first weight factor α relevant to the measurement field environmental variance; E), according to the first weight factor α obtained and the second weight factor β, based on following formula, calculate the coordinate (x of dot center of measured oval picture point ₀, y ₀),

${\mathrm{<figure-callout\; id="0"\; label="x"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">x</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}$

${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}$

X wherein _iAnd y _jCoordinate (x for the specific location point on imaging facula _i, y _j), g (x _i, y _j) be (x _i, y _j) locate the gray-scale value of imaging facula, [w ₁, w ₂] be the width range of imaging facula, [h ₁, h ₂] be the altitude range of imaging facula.

Preferably, described object space monumented point is the circular RRT sign that utilizes retroreflecting material to make.

Preferably, the diameter range of described RRT sign is at 3-12mm.

Preferably, the diameter of described RRT sign is 6mm.

Preferably, described object space monumented point is evenly distributed in tested.

Preferably, described the second weight factor β is the average gray value of captured image.

Preferably, described the second weight factor β is 0.

Preferably, [w ₁, w ₂] and [h ₁, h ₂] span is slightly larger than the width w of imaging facula ₀With height h ₀.

Preferably, in described step d), the computing method of the optimal value of the first weight factor α are as follows: d1) measure the coordinate of obtaining each imaging point on captured picture, extract the two-dimensional points centre coordinate (x tried to achieve _I0, y _I0) as true value; D2) use the algorithm that comprises described formula to obtain each point coordinate (x on picture _i, y _i) as measured value; D3) obtain the average of the residual error of described measured value and described true value; D4) getting α corresponding to minimum mean is optimal value.

Preferably, the value of described the first weight factor α is integer.

Center positioning method for the light echo reflective marker according to the present invention is more general than previous methods, goes for different site environments, has eliminated as much as possible the impact that site environment causes, and has improved the positioning precision of light echo reflective marker dot center.

The description and the follow-up detailed description that should be appreciated that aforementioned cardinal principle are exemplary illustration and explanation, should not use the restriction of doing the claimed content of the present invention.

The accompanying drawing explanation

Describe by reference to the accompanying drawings above and other of the present invention aspect in detail, in accompanying drawing:

Fig. 1 shows the light path schematic diagram that RRT reflects the incident light when ad-hoc location is used light source irradiation;

Fig. 2 shows the schematic diagram of the imaging facula of circular light echo reflective marker after lens imaging;

But Fig. 3 shows the process flow diagram according to variable weight picture point localization method of the present invention;

Fig. 4 shows the experiment controlling filed schematic diagram of checking the inventive method;

Fig. 5 shows the picture point photo that the experiment that utilizes Fig. 4 is taken with controlling filed;

Fig. 6 shows the relation curve of weight coefficient α and two-dimensional coordinate residual error in the plane of delineation.

Embodiment

But the present invention proposes a kind of picture point of variable weight for light echo reflective marker localization method.By the relevant environment variable in conjunction with measurement field, correlative factor by measurement field, the for example distribution of angle, illumination and monumented point, and thereby the ground unrest of taking etc. is set as the weight factor that can change and comprehensively considers, but a kind of localization method with calculating light echo reflective marker center of variable weight has been proposed.Therefore the method according to this invention can be applicable to different measurement environment, thereby obtain optimum weight coefficient based on the corresponding weight of environment variable settings, experimental results show that the positioning precision that can reach higher than prior art.

But Fig. 3 shows the process flow diagram according to variable weight picture point localization method of the present invention.

In step 301, a plurality of object space monumented points are set.The object space monumented point is the circular RRT sign that utilizes retroreflecting material to make, and the diameter range of RRT sign, at 3-12mm, preferably is about 6mm.Preferably, the object space monumented point should be evenly distributed in tested as far as possible.

In step 302, at different erect-positions, set a plurality of object space monumented points to be measured are taken, obtain a plurality of location point (x on imaging facula _i, y _j) gray-scale value located.Erect-position refers to device for shooting, residing position during the camera pictures taken for example, and erect-position can point to corresponding three rotation angle (θ, ω, κ) at the optical axis of the coordinate (x, y, z) of global coordinate system and filming apparatus by filming apparatus and mean.The coordinate of filming apparatus erect-position distributes and should be evenly distributed on to survey on the ball conical surface that object centers is the centre of sphere as far as possible, and cone angle, between 75 °～105 °, is generally got 90 °, and optical axis should point to the centre of sphere as far as possible.

In step 303, obtain the parameter of camera, namely obtain the second weight factor β relevant with ground unrest.Usually can use the average gray value of captured image as the second weight factor β.In some occasion, for example work as the RRT size very greatly and, in the uniform situation of brightness, also can ignore β.

In step 304, obtain the first weight factor α relevant to the measurement field environmental variance, make (x ₀, y ₀) be dot center's coordinate of the measured oval picture point of trying to achieve, (x ₀, y ₀) and the first weight factor α and the second weight factor β between relation derivation as follows:

At first, order

${\mathrm{<figure-callout\; id="0"\; label="x"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">x</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_{i}F(x_i,y_j,k_1,k_2,...k_n)}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}F(x_i,y_j,k_1,k_2,...k_n)}$

${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_{i}F(x_i,y_j,k_1,k_2,...k_n)}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}F(x_i,y_j,k_1,k_2,...k_n)}---\left(1\right)$

Wherein, F (x _i, y _j, k ₁, k ₂... k _n) be with imaging facula on specific location point (x _i, y _j) locate the function that gray-scale value is relevant.K ₁, k ₂... k _nFor the coefficient of function, the scope of asking for is x _i∈ [w ₁, w ₂], y _j∈ [h ₁, h ₂], [w wherein ₁, w ₂] be the width range of imaging facula, [h ₁, h ₂] be the altitude range of imaging facula.Preferably, [w ₁, w ₂] and [h ₁, h ₂] span is slightly larger than the width w of imaging facula ₀With height h ₀, generally get the spot width absolute value, i.e. Shu w ₁-w ₂Shu=w ₀+ 4, facular height absolute value, i.e. Shu h ₁-h ₂Shu=h ₀The unit of+4(4 is pixel).

Make (x _i, y _j) to locate gray-scale value be g (x _i, y _j), can be by the F (x in (1) formula _i, y _j, k ₁, k ₂... k _n) the writing polynomial form, namely

$F(x_i,y_j,k_1,k_2,...k_n)=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{k}_i\&times;g{(x_i,y_i)}^{n-i}---\left(2\right)$

While after formula (2) right side is launched, getting two rank, have

F(x _i,y _j,k ₁,k ₂,…k _n)=k ₁·g(x _i,y _j) ²+k ₂·g(x _i,y _j) ¹+k ₃ (3)

Be out of shape,

F(x _i,y _j,k ₁,k ₂,…k _n)=K ₁(g(x _i,y _j)+K ₂) ²+K ₃ (4)

K wherein ₂=k ₁, $K_2=\frac{k_2}{4k_1}$ $K_3=\frac{4k_1{k}_3-k_2^2}{4k_1}.$

As can be known by (1) formula, K ₁Value does not affect result, therefore get 1.Again from the actual measurement experience, obtaining K ₂And K ₃Impact on the dot center location is basic identical, therefore for shortcut calculation can merge it, so have

F(x _i,y _j,k ₁,k ₂,…k _n)=(g(x _i,y _j)-β) ^α (5)

Wherein α is the highest n-1 of polynomial expression, β=K ₂, α ∈ N ₊, β>=-g (x _i, y _j), namely

${\mathrm{<figure-callout\; id="0"\; label="x"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">x</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}$

${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}---\left(6\right)$

In step 305, according to the first weight factor α obtained and the second weight factor β, based on formula (6), calculate the coordinate (x of dot center of measured oval picture point ₀, y ₀), the location that has namely completed picture point.

The first weight factor α according to the present invention has reflected the various variablees relevant with the measurement field environment, can select different α values for different environment fields, thereby obtains the highest localization method of precision.The calculating of the optimal value of the first weight factor α can be in the following way.

Can measure the coordinate (for example utilizing VSTARS software) of obtaining each imaging point on captured picture, extract the two-dimensional points centre coordinate (x tried to achieve _I0, y _I0) as true value; Use comprises the algorithm routine of variable weight model (being above-mentioned formula (6)) and obtains each point coordinate (x on picture _i, y _i) as measured value; Average with the residual error of measured value and true value

As evaluation criterion, because α ∈ is Q, so the residual error average

Should be along with α changes continuously, and must obtain minimum value at specific α place, this α value is optimal weights.

According to formula of the present invention (6), not only can comprise the factor of environmental change, namely the value by α and β reflects different measurement field situations, can also compatible existing method for calculating and locating.For example, when α=1, β=0 o'clock, formula (6) is traditional gray scale centroid method, that is,

$x_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_{i}f(x_i,y_j)}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}f(x_i,y_j)}$ ${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_{i}f(x_i,y_j)}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}f(x_i,y_j)}---\left(7\right)$

F (x wherein _i, y _j) be that coordinate is (x _i, y _j) locate gray-scale value a little, the scope of asking for is x _i∈ [w ₁, w ₂], y _j∈ [h ₁, h ₂], (x ₀, y ₀) be dot center's coordinate of trying to achieve.

When α=1, β=th(th means threshold value) time, formula (6) is the gray scale centroid method with threshold value, that is,

$x_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_i[f(x_i,y_j)-\mathrm{th}]}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}[f(x_i,y_j)-\mathrm{th}]}$ ${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_i[f(x_i,y_j)-\mathrm{th}]}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}[f(x_i,y_j)-\mathrm{th}]}---\left(8\right)$

F (x wherein _i, y _j) be that coordinate is (x _i, y _j) locating gray-scale value a little, th is threshold constant.

When α=2, β=0 o'clock.Formula (6) is gray scale square weighting centroid method, namely

$x_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_{i}f{(x_i,y_j)}^2}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}f{(x_i,y_j)}^2}$ ${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_{i}f{(x_i,y_j)}^2}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}f{(x_i,y_j)}^2}---\left(9\right)$

F (x wherein _i, y _j) be that coordinate is (x _i, y _j) locate gray-scale value a little, the scope of asking for is x _i∈ [w ₁, w ₂], y _j∈ [h ₁, h ₂], grey scale pixel value has been done to a square processing here.

As can be seen here, can adapt to different situations according to the variation of environment according to localization method of the present invention, when the RRT size is very large, in the uniform situation of brightness, can ignore β, make β=0, and get α=1; When image that shooting obtains has in the situation of certain background Gaussian noise, can set β is certain threshold value; And little when the RRT size, in the situation that the impact of pixel disc of confusion can not be ignored, can by the size of setting α, reflect the impact of pixel disc of confusion, for example get α=2 or α=3 etc.

In above method, the α value is integer, therefore corresponding different measurement environment.More preferably, under the measurement environment of reality more complicated and changeable, the α value can not be also integer.Can make α ∈ Q.To different measurement environment, the optimal value of weight α is not fixed value, but along with the relevant environment variable of measurement field determines, angle for example, illumination, the distribution of monumented point etc.Namely

$\left\{\begin{array}{cc}{x}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}& {\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_i{(g(x_i,y_i)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}\\ \mathrm{\&alpha;}=F(k_1,k_2\&CenterDot;\&CenterDot;\&CenterDot;,k_n)& \end{array}\right.---\left(10\right)$

Wherein, α ∈ Q, β>=-g (x _i, y _j), k ₁, k ₂, k _nRelevant environment variable for measurement field.Formula (10) has namely reflected the picture point localization method that weight factor is variable.

Experimental result

1. data acquisition

But variable weight localization method of the present invention is carried out to experimental verification.As shown in Figure 4, its size is 4m*3m*1.5m to the schematic diagram of controlling filed.In controlling filed shown in Figure 4, arranging several RRT, is equally distributed as shown in Figure 4.Fig. 4 just schematically shows a part and layouts.Use the industrial digital up short coordinate measuring machine V-STARS E4X of U.S. GSI company development to take.Filming apparatus adopts Nikon D2Xs, and 1,200 ten thousand pixels, resolution are 4288 * 2848, and pixel size is 6 μ m, uses doughnut-shaped flash lamp to expose.Process software is V-STARS4.3, and its dot center's positioning precision can reach 1/50px.

With Nikon D2Xs camera, take multiple pictures at different erect-positions, amount to 67.The picture part that shooting obtains as shown in Figure 5.

2. data are processed

Under controlling filed environment shown in Figure 4, owing to having used high-quality photographic goods, can control ground unrest is 0 substantially, β=0 now.Like this (6) but the formula abbreviation be

$x_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_i{\left(g(x_i,y_j)\right)}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{\left(g(x_i,y_j)\right)}^{\mathrm{\&alpha;}}}$ ${\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA00003631625400011.png"\; state="\{\{state\}\}">y</figure-callout>}}_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_i{\left(g(x_i,y_j)\right)}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{\left(g(x_i,y_j)\right)}^{\mathrm{\&alpha;}}}---\left(10\right)$

For example, because the optimal weights factor alpha is determined by some correlative factors of measurement field, the distribution of angle, illumination, monumented point, i.e. α=F (k ₁, k ₂..., k _n)

Funtcional relationship F wherein is at present also indefinite, therefore the method for usage comparison is found the optimal weights factor alpha under current checkout area environment.When asking optimal weights, use following methods:

Use VSTARS software to obtain each point coordinate on picture, extract the two-dimensional points centre coordinate (x that VSTARS tries to achieve _I0, y _I0) as true value; Use comprises the algorithm routine of variable weight model, obtains each point coordinate (x on picture _i, y _i) as measured value; Average with the residual error of measured value and true value As evaluation criterion, because α ∈ is Q, so the residual error average

Should be along with α changes continuously.And must obtain minimum value at specific α place, this α value is optimal weights.Data processed result as shown in Figure 6.

As seen from Figure 6, residual error average

In interval in [1.0,2.0] with weight coefficient α, change, and at α, be about at 1.6 o'clock and obtain minimum value.With traditional centroid method of α=1.0 and the gray scale square weighting centroid method of α=2.0, compare, improved at least 25%.By the optimal weights α that said method is tried to achieve, when getting optimal weights, evaluation index all is better than classic method, illustrates that the precision of using variable weight gray scale centroid method to extract dot center is better than classic method.

But by above-mentioned experimental verification according to variable weight localization method of the present invention, its point center distill precision is better than traditional centroid method and gray scale square weighting centroid method, standard deviation by calculating residual error is as the standard of estimating localization method, residual error wherein refers to that the method according to this invention tries to achieve the coordinate Coord of dot center (u, v) and coordinate true value Coord0 (u ₀, v ₀) between the mould of difference || Coord-Coord0||.The experimental result surface, the standard deviation of residual error can improve more than 25% at least.Therefore, use according to after the variable weight model, dot center asks for the method that precision is relatively traditional and is improved.According to the variable weight model, optimal weights α is not fixed value, is and changes with different measurement field.Concrete optimal weights factor alpha is determined by some correlative factors of measurement field, for example distribution of angle, illumination, monumented point.

Should be understood that, under the prerequisite that does not deviate from the described spirit of the present invention of appended claim, the present invention can have multiple combination, correction, change and alternative.The foregoing is only the embodiment in the present invention; but protection scope of the present invention is not limited to this; anyly be familiar with the people of this technology in the disclosed technical scope of the present invention; can understand conversion or the replacement expected; all should be encompassed in of the present invention comprise scope within; therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.In conjunction with the explanation of the present invention and the practice that disclose here, other embodiment of the present invention are apparent for those skilled in the art.Illustrate with embodiment and only be considered to exemplary, true scope of the present invention and purport limit by claim.

Claims (10)

1. but the picture point of the variable weight for light echo reflective marker localization method, described method comprises the steps:

A) a plurality of object space monumented points are set;

B) at different erect-positions, described a plurality of object space monumented points are taken, obtained the gray-scale value at a plurality of location points place on imaging facula;

C) obtain the second weight factor β relevant with ground unrest;

D) obtain the first weight factor α relevant to the measurement field environmental variance;

E), according to the first weight factor α obtained and the second weight factor β, based on following formula, calculate the coordinate (x of dot center of measured oval picture point ₀, y ₀),

$x_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{x}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}$

$y_0=\frac{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{y}_i{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}{\underset{i=h_1}{\overset{h_2}{\mathrm{\&Sigma;}}}\underset{j=w_1}{\overset{w_2}{\mathrm{\&Sigma;}}}{(g(x_i,y_j)-\mathrm{\&beta;})}^{\mathrm{\&alpha;}}}$

X wherein _iAnd y _jCoordinate (x for the specific location point on imaging facula _i, y _j), g (x _i, y _j) be (x _i, y _j) locate the gray-scale value of imaging facula, [w ₁, w ₂] be the width range of imaging facula, [h ₁, h ₂] be the altitude range of imaging facula.

2. picture point localization method as claimed in claim 1, wherein said object space monumented point are the circular RRT sign that utilizes retroreflecting material to make.

3. picture point localization method as claimed in claim 2, the diameter range of wherein said RRT sign is at 3-12mm.

4. picture point localization method as claimed in claim 3, the diameter of wherein said RRT sign is 6mm.

5. picture point localization method as claimed in claim 1, wherein said object space monumented point are evenly distributed in tested.

6. picture point localization method as claimed in claim 1, wherein said the second weight factor β is the average gray value of captured image.

7. picture point localization method as claimed in claim 1, wherein said the second weight factor β is 0.

8. picture point localization method as claimed in claim 1, wherein [w ₁, w ₂] and [h ₁, h ₂] span is slightly larger than the width w of imaging facula ₀With height h ₀.

9. picture point localization method as claimed in claim 1, in wherein said step d), the computing method of the optimal value of the first weight factor α are as follows:

D1) measure the coordinate of obtaining each imaging point on captured picture, extract the two-dimensional points centre coordinate (x tried to achieve _I0, y _I0) as true value;

D2) use the algorithm that comprises described formula to obtain each point coordinate (x on picture _i, y _j) as measured value;

D3) obtain the average of the residual error of described measured value and described true value;

D4) getting α corresponding to minimum mean is optimal value.

10. picture point localization method as claimed in claim 1, the value of wherein said the first weight factor α is integer.

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