CN105654084A - Laser-based vehicle license plate positioning method, device and system - Google Patents

Abstract

The invention relates to a laser-based vehicle license plate positioning method, device and system. The method includes the following steps that: when it is detected that a vehicle triggers laser scanning lines, the vehicle head position of the vehicle is obtained from the updated historical frame data of the vehicle; the left and right positions as well as the upper and lower positions of a vehicle license plate in a captured photo are calculated according to the vehicle head position, so that a vehicle head position region in the captured photo can be obtained; comprehensive confidence weight and comprehensive left and right boundaries are calculated according to all historical frame data of the vehicle; the comprehensive left and right boundaries are shrunk inwards according to the comprehensive confidence weight, so that the left and right positions of the vehicle license plate can be obtained, and y-axis pixel values of the triggered laser scanning lines on the captured photo are expanded upwards and downwards according to a first preset pixel expansion amount, so that the upper and lower positions of the vehicle license plate in the captured photo can be obtained, and therefore, a vehicle license plate position region can be obtained. The device is implemented based on the above method. With the method adopted, the position of the vehicle license plate can be accurately positioned; and the positioning of the vehicle license plate is not affected by light conditions such as vehicle license plate light receiving and light shielding.

Description

License plate locating method based on laser instrument, Apparatus and system

Technical field

The present invention relates to multilane Free-flow technical field, be specifically related to a kind of based on laser instrumentLicense plate locating method, Apparatus and system.

Background technology

Multilane Free-flow (Multi-LaneFreeFlow is called for short MLFF) technology is extensively usedIn fields such as city congestion-pricing, city tolls on the road and bridge. Increasingly block up in urban transportation, atmosphereToday that pollution is on the rise, the importance of MLFF technology highlights increasingly.

MLFF need to use the information interaction system based on bus or train route communication conventionally. Vehicle-mounted when being provided withThe vehicle of electronic tag (OnboardUnit, be called for short OBU) is during through control area, MLFFRoadside device and OBU carry out information interaction after safety certification, complete transaction and form transaction record.Simultaneously vehicle locating device completes vehicle location, trigger vehicle image candid photograph equipment capture,The identification number-plate number. Transaction record, vehicle location and vehicle identifying information, vehicle image and carBoard recognition result is uploaded to track computer. Track computer is as track logic coordinating control coreThe heart, carries out informix coupling. Then this track computer, according to matching result, forms completeCross car transaction record as a result of foundation, or carry out artificial illegal vehicle payment and pressure is heldMethod.

MLFF positioner is realized location and the following function of vehicle, triggering when camera this carCapture and identify car plate, in the time recognizing car plate, camera need to be to given vehicle positionPut region and carry out car plate search identification. Because car plate is under different light condition, its texture spyLevy, the characteristic signal such as color characteristic is easily submerged in environment, thereby makes the frequent mistake of cameraCar plate is navigated to errors present in photo by ground, causes camera identification car plate to lose efficacy. As Fig. 1 instituteShow the first half, in situation backlight, this roof brightness ratio is higher, and headstock position presents ashLook, shade on the ground presents dark color. When whole automobile carried out to binaryzation, due to car plateVery approaching in the binaryzation data of the shade on ground with vehicle, make the contrast of car plate very not clearAobvious, thus cause car plate texture to disappear, make camera can not locate this car plate, cause car plate to be knownNot failed. On urban road main road, the vehicular traffic of a day is generally at train numbers up to ten thousand, whenWhen the success rate of camera discrimination car plate significantly reduces, can affect the complete of multilane Free-flow systemWeather ability to work, also can affect to Fare Collection System, monitoring system. Therefore,Need badly a kind of accurate license plate locating method is provided, to improve camera identification car plate success rate.

Summary of the invention

For defect of the prior art, the invention provides a kind of car plate based on laser instrument locationMethod, Apparatus and system, can solve the frequent location of mistake car plate of camera position in prior art,Improve all weather operations ability of multilane Free-flow system.

First aspect, the invention provides a kind of license plate locating method based on laser instrument, its spyLevy and be, comprising:

In the time having detected that vehicle triggers laser scans line, the history from the renewal of this vehicleIn frame data, obtain the headstock position of this vehicle;

Position, left and right and upper-lower position according to this this headstock of headstock position calculation in candid photograph photographThereby obtain in the headstock band of position of capturing in photograph;

Calculate limit, the heavy and comprehensive left and right of comprehensive confidence weighting according to all historical frames data of this vehicleBoundary; And heavily this border, comprehensive left and right is inwardly shunk and obtained this car plate according to described comprehensive confidence weightingPosition, left and right, and according to the first presetted pixel propagation, triggered laser scans line is existedY axle pixel value on described candid photograph photograph is expanded up and down and is obtained this car plate in described candid photograph phaseUpper-lower position in sheet, thus the car plate band of position obtained.

Second aspect, the embodiment of the present invention also provides a kind of car plate location side based on laser instrumentMethod, the method comprises:

Obtain the laser scans line data of vehicle at laser instrument surveyed area, thereby obtain car plateCharacteristic information Sample Storehouse;

In the time having vehicle to trigger laser scans line, if the beam pattern information of trigger position and instituteA vehicle license plate characteristic information stating vehicle license plate characteristic message sample storehouse is consistent, and obtains this hot spot positionPut the pixel coordinate at described candid photograph photograph;

According to the second presetted pixel propagation, this facula position is sat in the pixel of described candid photograph photographNear mark, carry out left and right and expand to obtain up and down car plate position.

The third aspect, the embodiment of the present invention provides again a kind of car plate based on laser instrument location dressPut, comprising:

Headstock position acquisition unit, in the time having detected that vehicle triggers laser scans line,In historical frames data from the renewal of this vehicle, obtain the headstock position of this vehicle;

Headstock band of position acquiring unit, for capturing according to this this headstock of headstock position calculationThereby the position, left and right in photograph and upper-lower position obtain in the headstock lane place of capturing in photographTerritory;

Car plate band of position acquiring unit, calculates for all historical frames data according to this vehicleBorder, the heavy and comprehensive left and right of comprehensive confidence weighting; And heavily comprehensively left to this according to described comprehensive confidence weightingRight margin inwardly shrinks the position, left and right that obtains this car plate, and according to the first presetted pixel propagationY axle pixel value to triggered laser scans line on described candid photograph photograph expands up and downThereby exhibition obtains the upper-lower position of this car plate in described candid photograph photograph and obtains the car plate band of position.

Fourth aspect, the embodiment of the present invention provides a kind of car plate based on laser instrument location dress againPut, when position, car plate left and right is positioned at the center of headstock, car plate height is fixed value H₁Time, this dressPut and comprise:

Sample Storehouse acquiring unit, for obtaining the laser scans of vehicle at laser instrument surveyed areaLine data, thus vehicle license plate characteristic message sample storehouse obtained;

Facula position coordinate acquiring unit, in the time having vehicle to trigger laser scans line, ifA vehicle license plate characteristic in the beam pattern information of trigger position and described vehicle license plate characteristic message sample storehouseInformation is consistent, and obtains the pixel coordinate of this facula position at described candid photograph photograph;

Car plate band of position acquiring unit, for according to the second presetted pixel propagation to this hot spotPosition is carried out left and right and is expanded to obtain up and down car plate near the pixel coordinate of described candid photograph photographThe band of position.

The 5th aspect, the embodiment of the present invention also provides a kind of car plate positioning systems based on laser instrumentSystem, comprises license plate positioning device mentioned above and at least one laser instrument;

Described at least one laser instrument is for sending laser scans line to surveyed area, and receptionThe laser scans line returning offers license plate positioning device;

Described license plate positioning device is for detecting the headstock position of triggering vehicle according to laser scans linePut and determine the headstock band of position and the car plate band of position in candid photograph photograph.

The 6th aspect, the embodiment of the present invention also provides a kind of car plate positioning systems based on laser instrumentSystem, comprises license plate positioning device mentioned above and at least one laser instrument;

Described at least one laser instrument is for sending laser scans line to surveyed area, and receptionThe laser scans line returning offers license plate positioning device;

Described license plate positioning device is for detecting the headstock position of triggering vehicle according to laser scans linePut and determine the car plate band of position in candid photograph photograph.

The present invention utilizes the continuous multiple frames data of at least one laser instrument, accurately obtains multilane certainlyBy the car plate band of position of vehicle that enters transaction scene in streaming system, and then accurately provide candid photographThe pixel coordinate of car plate in picture, to improve the car plate stationkeeping ability of capturing camera, especially improvesCamera is met the success rate of car plate location in light, the not enough situation of light filling at backlight and night at car plate.

Brief description of the drawings

Can more clearly understand the features and advantages of the present invention by reference to accompanying drawing, accompanying drawing is to showMeaning property and should not be construed as the present invention is carried out to any restriction, in the accompanying drawings:

Fig. 1 is that the correspondence of the overall binaryzation of car plate picture in situation backlight and local binarization is shownIntention;

Fig. 2 is a kind of license plate locating method flow process based on laser instrument that the embodiment of the present invention providesFigure;

Fig. 3 is the laser scans line coordinates conversion schematic diagram that the embodiment of the present invention provides;

Fig. 4 is scan-data waveform signal after laser scans line coordinates conversion as shown in Figure 3Figure;

Fig. 5 is that the vehicle that the embodiment of the present invention provides enters laser instrument surveyed area schematic diagram;

Fig. 6 is the candid photograph photograph pixel coordinate schematic diagram that the embodiment of the present invention provides;

Fig. 7 is the reparation car plate up-and-down boundary coordinate schematic diagram that the embodiment of the present invention provides;

Fig. 8 is a kind of Position System of automobile license plate location block diagram based on laser instrument that the embodiment of the present invention provides;

Fig. 9 is the car plate location block diagram of the another kind that provides of the embodiment of the present invention based on laser instrument.

Detailed description of the invention

For making object, technical scheme and the advantage of the embodiment of the present invention clearer, will tie belowClose the accompanying drawing in the embodiment of the present invention, to the technical scheme in the embodiment of the present invention carry out clear,Intactly describe, obviously, described embodiment is the present invention's part embodiment, instead ofWhole embodiment. Based on the embodiment in the present invention, those of ordinary skill in the art are not havingMake the every other embodiment obtaining under creative work prerequisite, all belong to the present invention's protectionScope.

Embodiment mono-

The embodiment of the present invention provides a kind of license plate locating method based on laser instrument, as Fig. 2 instituteShow, comprising:

S1, when having detected that vehicle triggers laser scans line, from the renewal of this vehicleIn historical frames data, obtain the headstock position of this vehicle;

S2, according to this this headstock of headstock position calculation capturing position, left and right in photograph with upper and lowerThereby position obtains in the headstock band of position of capturing in photograph;

S3, calculate the heavy and comprehensive left and right of comprehensive confidence weighting according to all historical frames data of this vehicleBorder; And heavily this border, comprehensive left and right is inwardly shunk and obtained this car according to described comprehensive confidence weightingThe position, left and right of board, and according to the first presetted pixel propagation to triggered laser scans lineY axle pixel value on described candid photograph photograph is expanded up and down and is obtained this car plate in described candid photographThereby the upper-lower position in photograph obtains the car plate band of position.

Below with 6 laser instruments and Fig. 2～Fig. 7 to the car plate based on laser instrument provided by the inventionLocalization method is elaborated.

First, introduce S1, in the time having detected that vehicle triggers laser scans line, from this vehicleRenewal after historical frames data in obtain the step of the headstock position of this vehicle.

The embodiment of the present invention comprises obtains laser scans line data, laser data coordinate transformWith judged whether that vehicle triggers laser scans line.

1, obtain laser scans line data and comprise data receiver, Data Analysis and data framing.Wherein, license plate positioning device receives at least one laser instrument biography with polling mode or interrupt modeDefeated laser scans line data of coming. This license plate positioning device is swept received laser instrumentRetouch line data carry out verification and reject frame head and postamble after extracted valid data. Then by extractValid data mate framing according to time sequencing, form a frame scan contextual data.

It should be noted that, laser scans line refers to, laser scans to carriageway surfacing orPoint (this point is test point) on vehicle body, connects successively according to the order of the scanning element of laser instrumentThe virtual line getting up. The corresponding laser scans line of each laser instrument.

It should be noted that, laser scans line data comprise distance value in each scanning element echo,Pwm value and peak value of pulse, also comprise the width of vehicle in surveyed area, highly, speed, realityTime the information such as position.

2, laser data coordinate transform. By each scanning element in obtained laser scans line dataThe distance value (laser instrument is to the distance between sensing point) calculating carries out coordinate transform, withObtain the coordinate system data (track as shown in Figure 3, track of each scanning element and corresponding sensing pointCoordinate system xyz). That is to say, according to the distance value of laser scans line data acquisition be onlyLaser instrument, to the distance of sensing point, be converted into distance value the positional information in the coordinate system of trackThereby get current frame data.

In practical application, scanning angle is 0～180 degree, every k degree run-down, and k value exists0.1 degree is between 2 degree. As shown in Figure 3, put corresponding track for m laser dataCoordinate M_x、M_y、M_z, Coordinate Conversion process is as follows: known laser device is under the coordinate system of trackCoordinate be L_x、L_y、L_z, the angle of inclination of laser instrument is β, the laser distance of m pointData are S:

$L_x=M_x-S\·sin(\frac{m\·k\mathrm{\π}}{180}-\frac{\mathrm{\π}}{2}),$

$L_y=M_y+S\·cos(\frac{m\·k\mathrm{\π}}{180}-\frac{\mathrm{\π}}{2})\·sin\mathrm{\β},$

$L_z=M_z+S\·cos(\frac{m\·k\mathrm{\π}}{180}-\frac{\mathrm{\π}}{2})\·cos\mathrm{\β},$

In formula, L_x、L_y、L_zRepresent x axle, y axle and the z of laser instrument under the coordinate system of trackAxial coordinate; M_x、M_y、M_zRepresent that m test point of laser scans line is at track coordinate systemUnder x-axis, y-axis and z-axis coordinate; S represents the laser distance of laser instrument to m test pointFrom, k represents laser scans interval angle, inclination angle when β represents laser scans.

3, in the present invention, also comprise Data Matching process. This matching process comprises: to present frameData are mated with the historical frames data of the vehicle under current scene. If Data Matching success,This current frame data is deposited in the historical data base of corresponding vehicle, this current frame data becomesFor the historical frames data after upgrading in historical data base. In the present invention, all historical frames data are notBut comprise the corresponding laser instrument data of vehicle (position coordinates of laser instrument, scanning angle and sharpLight data etc.), also comprise test point after the Coordinate Conversion position letter under the coordinate system of trackBreath, and intermediate data (time, a vehicle left side that car number, vehicle are detected for the first timeRight position and headstock coordinate etc.). In practical application, when historical frames data are carried out to index, adoptIndex mark by car number as historical frames data.

It should be noted that, in the present invention, coupling refers to, two frame data under contrast same scene,If these two frame data comprise close positional information, explanation in identical or certain threshold rangeThese two frame data conform to. As shown in Figure 4, if represent historical frames data in Fig. 4, if currentFrame data with comprise vehicle V1 in Fig. 4 and the waveform of vehicle V2, current frame data is describedIdentical with historical frames data. If current frame data only comprises the ripple of vehicle V1 and vehicle V2Shape, explanation does not have new vehicle to trigger laser scans line; If removed containing car in current frame dataOutside the waveform of V1 and vehicle V2, also produce distortion, explanation at first via scan-data placeThere is new vehicle to trigger laser scans line.

As shown in Fig. 3 and Fig. 5, in Fig. 3, a laser instrument is fixed on portal frame, along sweepingRetouching line scans to the left from the right side of direction of traffic. It should be noted that this scan line bagDraw together multiple test points, laser instrument scans a test point at every turn. As shown in Figure 5, multiple when havingWhen laser instrument, the arrangement position of laser scans line as shown in Figure 5, on direction of traffic according toLine 1, line 2 ... the order of line N (representative has N laser instrument) distributes successively, last line 1And between line N and the left margin of runway and right margin form the detection zone of this N laser instrumentTerritory. 4, judged whether that vehicle newly triggers laser rays. If not having vehicle newly to enter laser instrument sweepsRetouch line, this current frame data processing procedure finishes, and again receives laser scans line data.As shown in Figure 4, the right bossing is vehicle V1 position, and left side bossing is vehicleV2 position. According to the data characteristics of present frame, to car in current frame data and current sceneHistorical frames data mate. After the match is successful, deposit current frame data in current sceneIn the historical data of middle vehicle. Vehicle in current scene is carried out to poll, if the history of this vehicleIn frame data, except current frame data has the data of n article of laser rays, historical number beforeAccording in all there is no n article of laser rays, think that this vehicle laser rays that newly sets out need to calculate headstockPosition, trigger position is headstock position.

Secondly, introduce S2, according to this this headstock of headstock position calculation in the left and right of capturing in photographThereby position and upper-lower position obtain in the step of capturing the headstock band of position in photograph.

The coordinate information that triggers the trigger position of laser scans line according to vehicle obtains headstock positionPut. Then in capturing photograph, historical frames data determine one according to headstock position and this vehicleThe individual headstock band of position. This headstock band of position needs frame to live the headstock of this vehicle, and car plate alsoBe comprised in this headstock band of position. In practical application, the height of this headstock band of position andBetween 1.1～3 times of the value car plate actual size of width. The complete frame of the very big probability of license plate areaLive car plate, but because each link error or car plate be not in reasons such as headstock centers, few situationUnder there will be license plate area to live car plate by frame segment.

As shown in Figure 6, make photo pixel coordinate initial point in the upper left corner, X-axis from left to right, YAxle from top to bottom. Represent respectively the left margin of the headstock band of position with X1, X2, Y1 and Y2Pixel value, right margin pixel value, coboundary pixel value and lower boundary pixel value.

1, determining of the left margin of the headstock band of position and right margin:

Trigger laser scans line trigger position according to vehicle and obtain headstock under the coordinate system of trackPosition, left and right. Then, according to camera conversion table, linear interpolation is made to also in the position, left and right of this headstockThereby map to capture in photograph and obtain headstock in the X1He You position, left position of capturing in photographX2。

Linear difference method is illustrated: known certain laser perpendicular to direction of trafficOn device scan line, 3 P1, P2, P3 are at track plane coordinate system (track coordinate system in Fig. 3Xyz, obtains track plane coordinate system after removing z axle) lower coordinate for (Ppx1, Ppy), (Ppx2,And (Ppx3, Ppy) Ppy), and know the pixel coordinate value of P1, P2 point in photo for (Px1,Py), (Px2, Py). From geometrical relationship:

$\frac{Px3-Px1}{Px2-Px1}=\frac{Ppx3-Ppx1}{Ppx2-Ppx1}.$

Thereby can obtain pixel coordinate system (in Fig. 6 pixel coordinate system of P3 in photo according to above formulaXY) coordinate under is (Px3, Py), wherein:

$Px3=Px1+\frac{Ppx3-Ppx1}{Ppx2-Ppx1}\·(Px2-Px1).$

2, determining of the coboundary of the headstock band of position and lower boundary:

Look into camera conversion table, the corresponding pixel value of laser scans line that finds vehicle to triggerY3. On the basis of pixel value Y3, expand up and down, propagation is made as pixel value Y4,There is Y1=Y3 – Y4, Y2=Y3+Y4.

Again, introduce S3, calculate comprehensive confidence weighting weight according to all historical frames data of this vehicleWith border, comprehensive left and right; And heavily this border, comprehensive left and right is inwardly received according to described comprehensive confidence weightingContracting obtains the position, left and right of this car plate, and according to the first presetted pixel propagation to triggered swashingThe y axle pixel value of light device scan line on described candid photograph photograph expanded up and down and obtained this car plateThereby the upper-lower position in described candid photograph photograph obtains the step of the car plate band of position.

As shown in Figure 6, make photo pixel coordinate initial point in the upper left corner, X-axis from left to right, YAxle from top to bottom. Represent respectively the left margin pixel of the car plate band of position with x1, x2, y1, y2Value, right margin pixel value, coboundary pixel value, lower boundary pixel value.

1, determining of the left margin of the car plate band of position and right margin:

Obtain whole historical frames data of this vehicle, the limit, left and right of calculating its each historical frames dataBoundary and corresponding confidence weighting weight, adopt average weighted mode calculate border, comprehensive left and right and comprehensively putLetter weight; The size being heavily worth according to comprehensive confidence weighting, inwardly receives border, comprehensive left and rightContracting, obtains position, car plate left and right.

Access method is recaptured to comprehensive confidence weighting in border, comprehensive left and right to be illustrated:

The new total n frame historical frames data of vehicle, the left and right boundary bit of every frame historical frames data of triggeringPut LX_jAnd RX_jThe heavy LF of respectively corresponding confidence weighting_jAnd RF_j. Wherein subscript j is data number,Value is from 1 to n. The appraisal procedure that confidence weighting is heavy can or be used warp with reference to correlation engineering definitionTest formula.

Lx represents the comprehensive left margin position of vehicle, and Rx represents the comprehensive right margin position of vehicle,Lf represents the comprehensive left confidence weighting weight of vehicle, and Rf represents the comprehensive right confidence weighting weight of vehicle; These are four years oldThe account form of individual amount is:

$L_x=\frac{{\mathrm{\Σ}}_{j=1}^n({\mathrm{LX}}_j\×{\mathrm{LF}}_j)}{{\mathrm{\Σ}}_{j=1}^n{\mathrm{LF}}_j},$

$L_f={\mathrm{\Σ}}_{j=1}^n{\mathrm{LF}}_j,$

$R_x=\frac{{\mathrm{\Σ}}_{j=1}^n({\mathrm{RX}}_j\×{\mathrm{RF}}_j)}{{\mathrm{\Σ}}_{j=1}^n{\mathrm{RF}}_j},$

$R_f={\mathrm{\Σ}}_{j=1}^n{\mathrm{RF}}_j.$

According to camera conversion table, by the comprehensive left margin position of vehicle and comprehensive right margin position profitBe converted to pixel coordinate Lp and Rp by linear difference method. Track coordinate is utilized to linear differenceBe converted to the method for pixel coordinate in narration above, repeat no more herein. Lp and Rp warpInwardly cross and shrink, can obtain the pixel value of camera position, car plate left and right used: x1=Lp+Xp, x2=Rp – Xp. The heavy Lf of comprehensive left confidence weighting of the big or small Xp of amount of contraction and vehicle is with comprehensiveThe size of closing the heavy Rf of left confidence weighting is directly proportional, and Lf and Rf value are larger, and amount of contraction Xp is larger.The value of amount of contraction Xp has certain limitation requirement, makes the license plate area left and right width after shrinking largeIn the width value of true car plate.

2, determining of the coboundary of the car plate band of position and lower boundary:

Obtain the y axle pixel of the corresponding pixel value Y3 of laser scans line that vehicle triggersValue. Under normal circumstances, using this y axle pixel value as the corresponding pixel value in car plate center, soAfterwards this y axle pixel value is expanded up and down, propagation is the first presetted pixel propagation, thisSample can obtain this car plate at the upper-lower position of capturing in photograph.

In practical application, directly using the corresponding pixel value meeting as car plate center of y axle pixel valueProduce certain error. In the time requiring accurately to determine the car plate band of position, described in should repairing as far as possibleError. For this reason, in the embodiment of the present invention, also comprise the step that this y axle pixel value is repairedSuddenly.

As shown in Figure 7, get off when extract triggered laser scans line from current frame dataHeadstock height be H_V; Suppose that car plate height is fixed value H₁; Laser scans inclination angleβ; Laser instrument setting height(from bottom) H_j; α angle is exactly error angle, and unit is radian, this angleBe multiplied by coefficient A and can obtain the pixel of repairing. Wherein A is the parameter relevant to camera, need to carryFront demarcation or according to empirical value setting, its physical significance is: when certain point in camera perspective along yWhen direction moves, radian of every movement, correspondence is mobile y axle pixel in candid photograph photographValue, unit is: pixel/radian. In the time that α angle is very little, α angle can equal H approx_yWith H₀Ratio. Can try to achieve figure middle conductor H according to geometrical relationship_yWith H₀Length:

H_y＝(H₁-H_V)·cosβ，

H₀＝(H_j-H₁)/cosβ。

The error calculating formula of y axle pixel value is:

$\mathrm{\α}\·A\≈\frac{H_y}{H_0}\·A=A\·\frac{H_1-H_v}{H_j-H_1}\·{\cos }^2\mathrm{\β}.$

The y axle pixel value of the car plate center after repairing is:

In the embodiment of the present invention, this y axle pixel value is carried out according to the first presetted pixel propagation Y5Expansion up and down, thus coboundary pixel value and the lower boundary pixel of the car plate band of position can be obtainedValue:

$y_1=Y_3+A\·\frac{H_1-H_v}{H_j-H_1}\·{\cos }^2\mathrm{\β}-Y_5,$

$y_2=Y_3+A\·\frac{H_1-H_v}{H_j-H_1}\·{\cos }^2\mathrm{\β}+Y_5.$

Along with vehicle progresses into laser instrument surveyed area, the relevant historical frames data of vehicle can be byCumulative adding, thus the degree of accuracy of the car plate center of calculating progressively promotes, car plate left sideThe inside amount of contraction in right position progressively increases, and the propagation of car plate upper-lower position gradually reduces, i.e. carThe size of the board band of position (x1, x2, y1, y2) is progressively dwindled.

It should be noted that, the present invention determines that the method for x1, x2, y1, y2 is based on hypothesis:The position, left and right of car plate is at the left and right of headstock place-centric; The height under the coordinate system of track of car plateDegree is fixed value H₁。

In the embodiment of the present invention, by the continuous multiple frames data place at least one laser instrumentReason, in conjunction with at least one laser parameter and at least one camera parameter etc., can provide car plateThe accurate car plate band of position in camera. By the accurate car plate band of position and headstock positionPutting region can be in different light rays situation, first at car plate band of position search car plate, at thisWhen the car plate band of position is searched for less than car plate, search for again car plate from the headstock band of position, thereby realizeThe accurate location of car plate. The latter half as shown in Figure 1, the present invention is by adopting above-mentioned partAfter the method for range searching car plate, this headstock band of position or the car plate band of position are being carried outWhat after binaryzation, can be perfectly clear obtains license board information.

Embodiment bis-

For the superiority of the license plate locating method that provides of the embodiment of the present invention one, the present invention are providedEmbodiment also provides a kind of license plate positioning device based on laser instrument, as shown in Figure 8, and bagDraw together:

Headstock position acquisition unit, in the time having detected that vehicle triggers laser scans line,In historical frames data from the renewal of this vehicle, obtain the headstock position of this vehicle;

Headstock band of position acquiring unit, for capturing according to this this headstock of headstock position calculationThereby the position, left and right in photograph and upper-lower position obtain in the headstock lane place of capturing in photographTerritory;

Car plate band of position acquiring unit, calculates for all historical frames data according to this vehicleBorder, the heavy and comprehensive left and right of comprehensive confidence weighting; And heavily comprehensively left to this according to described comprehensive confidence weightingRight margin inwardly shrinks the position, left and right that obtains this car plate, and according to the first presetted pixel propagationY axle pixel value to triggered laser scans line on described candid photograph photograph expands up and downThereby exhibition obtains the upper-lower position of this car plate in described candid photograph photograph and obtains the car plate band of position.

In practical application, headstock band of position acquiring unit adopts following steps to obtain headstock and is grabbingClap the position, left and right in photograph:

Determine the left and right position of headstock under the coordinate system of track;

According to camera conversion table, the position, left and right of this headstock is made linear interpolation and mapped to candid photograph phaseThereby in sheet, obtain headstock in the position, left and right of capturing in photograph;

Wherein, this camera conversion table refers to, the track of the test point in track under the coordinate of trackCoordinate with it at the corresponding table of conversion of capturing the pixel coordinate under pixel coordinate system in photograph.

Need to further illustrate, camera conversion table adopts following calculating formula by described laser instrumentThe coordinate information of scan line under the coordinate of track is transformed into the respective pixel in described candid photograph photographValue:

$Px3=Px1+\frac{Ppx3-Ppx1}{Ppx2-Ppx1}\·(Px2-Px1).$

In practical application, be quick obtaining license board information, car plate lane place in the embodiment of the present inventionThe height and the width value in territory is between 1.1～3 times of car plate actual size. Certainly this area,Technical staff also can arrange car plate band of position height and the width according to concrete use scenesValue, the present invention is not construed as limiting.

More preferably, above-mentioned headstock position acquisition unit comprises historical frames data update module, and this is gone throughHistory frame data more new module are used for carrying out following steps and comprise:

Gather laser scans line data and process to obtain a frame scan contextual data;

Laser data to each test point in this frame scan scene is carried out coordinate transform, to obtainThe current frame data of this scanning scene under the coordinate system of track;

When this current frame data and historical frames data are carried out location matches success, to historical frames dataUpgrade, form the historical frames data after upgrading.

It should be noted that, in the present invention, all historical frames data not only comprise that vehicle institute is correspondingLaser instrument data (position coordinates, scanning angle and the laser data etc. of laser instrument), also bagDraw together test point after the Coordinate Conversion positional information under the coordinate system of track, and intermediate data(time, left and right vehicle wheel position and headstock coordinate that car number, vehicle are detected for the first timeDeng). In practical application, when the index of historical frames data, adopt car number as historical framesThe index mark of data.

For realizing the accurate location to car plate center, car plate band of position acquiring unit comprisesPixel value is repaired module, for the laser scans line to triggered on described candid photograph photographY axle pixel value carries out error adjustment. Described pixel value is repaired module and is adopted following error calculating formulaThis y axle pixel value is repaired:

$\mathrm{\α}\·A-A\·\frac{H_1-H_V}{H_j-H_1}\·{\cos }^2\mathrm{\β},$

In practical application, car plate band of position acquiring unit adopts following calculating formula to obtain a comprehensive left sideRight margin and comprehensive confidence weighting weight:

$L_x=\frac{{\mathrm{\Σ}}_{j=1}^n({\mathrm{LX}}_j\×{\mathrm{LF}}_j)}{{\mathrm{\Σ}}_{j=1}^n{\mathrm{LF}}_j},$

$L_f={\mathrm{\Σ}}_{j=1}^n{F}_j,$

$R_x=\frac{{\mathrm{\Σ}}_{j=1}^n(X_j\×F_j)}{{\mathrm{\Σ}}_{j=1}^n{F}_j},$

$R_f={\mathrm{\Σ}}_{j=1}^n{F}_j.$

Embodiment tri-

The embodiment of the present invention provides again a kind of Position System of automobile license plate location based on laser instrument, as Fig. 5Shown in, comprise the license plate positioning device described in embodiment bis-and at least one laser instrument;

At least one laser instrument is for sending laser scans line to surveyed area, and reception is returnedLaser scans line offer license plate positioning device;

License plate positioning device is used for according to the headstock position of laser scans line detection triggering vehicle alsoIn candid photograph photograph, determine the headstock band of position and the car plate band of position.

As seen from the above, the license plate positioning device that the embodiment of the present invention two provides and embodiment tri-The Position System of automobile license plate location providing is all realized based on the license plate locating method described in embodiment mono-, therebyCan solve same technical problem, and obtain identical technique effect, superfluous no longer one by one at thisState.

Embodiment tetra-

In the time that vehicle newly triggers laser scans line, laser scans line has certain probability just to sweepAbove car plate, now can determine in another way x1, x2, y1, y2. For this reason, originallyInvention also provides the another kind of license plate locating method based on laser instrument.

The embodiment of the present invention provides a kind of license plate locating method based on laser instrument, comprising:

Obtain the laser scans line data of vehicle at laser instrument surveyed area, thereby obtain car plateCharacteristic information Sample Storehouse;

In the time having vehicle to trigger laser scans line, if the beam pattern information of trigger position and instituteA vehicle license plate characteristic information stating vehicle license plate characteristic message sample storehouse is consistent, and obtains this hot spot positionPut the pixel coordinate at described candid photograph photograph;

According to the second presetted pixel propagation, this facula position is sat in the pixel of described candid photograph photographNear mark, carry out left and right and expand to obtain up and down car plate position.

It should be noted that, vehicle license plate characteristic message sample storehouse refers to, different vehicle is by least oneWhen the scanning area of individual laser instrument, this laser instrument after car plate is just arrived by laser scans line sweepThe characteristic information of the car plate comprising in scan line, this characteristic information comprises the reflectance signature of material,The reflection pulsewidth of zones of different etc. The laser scans line feature of for example same car plate diverse location,The laser scans line feature of same car plate under varying environment light, the different car plates of same positionLaser scans line feature. It should be noted that, this vehicle license plate characteristic message sample storehouse is through excessiveThe set of the laser scans feature with statistical property that amount experiment is obtained, along with sample sizeIncrease, just more accurate to the precision of car plate location.

It should be noted that, beam pattern information conforms to and refers to vehicle license plate characteristic information, to hot spotThe laser scans line data of position carry out obtaining the distance in echo after Data Analysis and data framingIdentical or close with the analog value in above-mentioned Sample Storehouse from value, pwm value and peak value of pulse. ItsIn close referring to, the characteristic information value of facula position and corresponding vehicle license plate characteristic in Sample Storehouse letterBreath value in certain error range, and do not affect to car plate position determine.

The embodiment of the present invention, can be in laser scans by setting up vehicle license plate characteristic message sample storehouseWhen line directly scans car plate, realize location fast. Along with by the increase of vehicle, car plate spySample size in reference breath Sample Storehouse can continue to increase, thereby expands the identification energy of error rangePower, further improves the success rate of license plate locating method in the present embodiment.

For example: the echo that laser instrument hot spot is got on different materials has certain feature, laser instrumentThe echo character that hot spot is got to car plate is included among distance value, pwm value, pulsewidth peak value, profitAfter given data being trained by statistical method, can carry out vehicle license plate characteristic extraction. Due to laserDevice scans according to certain hour interval, in the time that vehicle newly triggers laser rays, and laser scansLine has certain probability just to sweep to above car plate.

Therefore, in the time that each vehicle newly triggers laser rays, if trigger position detected withVehicle license plate characteristic information conforms to constantly, thinks that the facula position that this feature occurs is exactly car plate position.The track coordinate system coordinate of facula position is become to pixel coordinate Xb according to camera translation table,Yb. Then in the big or small expansion that fixes of this pixel coordinate, making left and right expanding value is Xe, upper and lowerExpanding value is Ye:

x1＝Xb–Xe，

x2＝Xb+Xe，

y1＝Yb–Ye，

y2＝Yb+Ye。

It should be noted that, if corresponding vehicle license plate characteristic information do not detected, utilize embodiment mono-The license plate locating method providing is determined the car plate band of position.

Embodiment five

For the superiority of the license plate locating method that provides of the embodiment of the present invention four is provided, the present invention is realExecute example the another kind of license plate positioning device based on laser instrument is also provided, as shown in Figure 9, bagDraw together:

Sample Storehouse acquiring unit, for obtaining the laser scans of vehicle at laser instrument surveyed areaLine data, thus vehicle license plate characteristic message sample storehouse obtained;

Facula position coordinate acquiring unit, in the time having vehicle to trigger laser scans line, ifA vehicle license plate characteristic in the beam pattern information of trigger position and described vehicle license plate characteristic message sample storehouseInformation is consistent, and obtains the pixel coordinate of this facula position at described candid photograph photograph;

Car plate band of position acquiring unit, for according to the second presetted pixel propagation to this hot spotPosition is carried out left and right and is expanded to obtain up and down car plate near the pixel coordinate of described candid photograph photographThe band of position.

Embodiment six

The embodiment of the present invention also provides the another kind of Position System of automobile license plate location based on laser instrument, as figureShown in 7, comprise license plate positioning device described in embodiment, at least one camera and at least oneLaser instrument;

At least one laser instrument is for sending laser scans line to surveyed area, and reception is returnedLaser scans line offer license plate positioning device;

License plate positioning device is used for according to the headstock position of laser scans line detection triggering vehicle alsoIn candid photograph photograph, determine the car plate band of position.

As seen from the above, the license plate positioning device that the embodiment of the present invention five provides and embodiment sixThe Position System of automobile license plate location providing is all realized based on the license plate locating method described in embodiment tetra-, therebyCan solve same technical problem, and obtain identical technique effect, superfluous no longer one by one at thisState.

In the present invention, term " first ", " second ", " the 3rd " be only for describing object,And can not be interpreted as instruction or hint relative importance. Term " at least one " refers to one or oneMore than individual, unless separately there is clear and definite restriction. Term " multiple " refers to two or more, removesNon-separately have a clear and definite restriction.

Although described by reference to the accompanying drawings embodiments of the present invention, those skilled in the art canTo make without departing from the spirit and scope of the present invention various modifications and variations, like thisAmendment and modification all fall into by within claims limited range.

Claims (13)

1. the license plate locating method based on laser instrument, is characterized in that, comprising:

In the time having detected that vehicle triggers laser scans line, the history from the renewal of this vehicleIn frame data, obtain the headstock position of this vehicle;

Position, left and right and upper-lower position according to this this headstock of headstock position calculation in candid photograph photographThereby obtain in the headstock band of position of capturing in photograph;

Calculate limit, the heavy and comprehensive left and right of comprehensive confidence weighting according to all historical frames data of this vehicleBoundary; And heavily this border, comprehensive left and right is inwardly shunk and obtained this car plate according to described comprehensive confidence weightingPosition, left and right, and according to the first presetted pixel propagation, triggered laser scans line is existedY axle pixel value on described candid photograph photograph is expanded up and down and is obtained this car plate in described candid photograph phaseUpper-lower position in sheet, thus the car plate band of position obtained.

2. license plate locating method according to claim 1, is characterized in that, to historical framesThe step that data are upgraded comprises:

Gather laser scans line data and process to obtain a frame scan contextual data;

Laser data to each test point in this frame scan scene is carried out coordinate transform, to obtainThe current frame data of this scanning scene under the coordinate system of track;

When this current frame data and historical frames data are carried out location matches success, to historical frames dataUpgrade, form the historical frames data after upgrading.

3. license plate locating method according to claim 2, is characterized in that, described historyFrame data comprise: distance value, pwm value and peak value of pulse in each test point echo, respectively detectThe positional information of point under the coordinate system of track, car number, vehicle be detected for the first time timeBetween, left and right vehicle wheel position and headstock coordinate; Adopt car number to carry out rope to historical frames dataDraw.

4. license plate locating method according to claim 1, is characterized in that, described basisThe first presetted pixel propagation is the y on described candid photograph photograph to triggered laser scans lineAxle pixel value is expanded the step that obtains the upper-lower position of this car plate in described candid photograph photograph up and downBefore rapid, comprise the step that this y axle pixel value is repaired; And adopt following error calculating formulaThis y axle pixel value is repaired:

$\mathrm{\α}\·A=A\·\frac{H_1-H_V}{H_j-H_1}\·{\cos }^2\mathrm{\β},$

In formula, α represents error angle, and unit is radian; A represents to put in camera perspective when certainWhile movement along y direction of principal axis, a radian of every movement y axle pixel value in corresponding photo, singlePosition is pixel/radian; H₁Represent car plate height; H_VHeadstock while representing to trigger laser scans lineHighly; H_jRepresent laser instrument setting height(from bottom); Inclination angle when β represents laser scans.

5. license plate locating method according to claim 1, is characterized in that, described car plateThe height and the width value of the band of position is between 1.1～3 times of car plate actual size.

6. license plate locating method according to claim 1, is characterized in that, according to this carThis headstock of position calculation adopts following steps in the time of the position, left and right of capturing in photograph:

Determine the left and right position of headstock under the coordinate system of track;

According to camera conversion table, the position, left and right of this headstock is made linear interpolation and mapped to candid photograph phaseThereby in sheet, obtain headstock in the position, left and right of capturing in photograph;

Wherein, this camera conversion table refers to, the track of the test point in track under the coordinate of trackCoordinate with it at the corresponding table of conversion of capturing the pixel coordinate under pixel coordinate system in photograph.

7. license plate locating method according to claim 6, is characterized in that, described cameraConversion table adopt following calculating formula by described laser scans line the coordinate information under the coordinate of trackBe transformed into the respective pixel value in described candid photograph photograph:

$Px3=Px1+\frac{Ppx3-Ppx1}{Ppx2-Ppx1}\·(Px2-Px1)$

In formula, Ppx1, Ppx2 and Ppx3 are illustrated in same laser instrument under the plane coordinate system of trackThe abscissa of 3 P1, P2 and P3 on scan line; Ppy represents P1, P2 and P3 tool at 3There is identical ordinate; Px1, Px2, Px3 represent respectively pixel coordinate system lower P1, P2, P3The abscissa of point; Py represents that pixel coordinate system lower P1, P2, P3 point have identical ordinate.

8. license plate locating method according to claim 1, is characterized in that, below employingCalculating formula is obtained border, comprehensive left and right and comprehensive confidence weighting weight:

$L_x=\frac{{\mathrm{\Σ}}_{j=1}^n({\mathrm{LX}}_j\×{\mathrm{LF}}_j)}{{\mathrm{\Σ}}_{j=1}^n{\mathrm{LF}}_j},$

$L_f={\mathrm{\Σ}}_{j=1}^n{\mathrm{LF}}_j,$

$R_x=\frac{{\mathrm{\Σ}}_{j=1}^n({\mathrm{RX}}_j\×{\mathrm{RF}}_j)}{{\mathrm{\Σ}}_{j=1}^n{\mathrm{RF}}_j},$

$R_f={\mathrm{\Σ}}_{j=1}^n{\mathrm{RF}}_j,$

In formula, L_xRepresent the comprehensive left margin position of vehicle; R_xRepresent the comprehensive right margin of vehiclePosition; L_fRepresent the comprehensive left confidence weighting weight of vehicle; R_fRepresent the comprehensive right confidence weighting of vehicleHeavy; J represents data number, value 1～n, and wherein n represents total n frame historical frames data;Represent to ask for the heavy sum of n confidence weighting; LX_jAnd RX_jRepresent respectively the left side of vehicleBoundary and right margin; LF_jAnd RF_jThe left margin confidence weighting that represents respectively vehicle weighs and right confidence weightingHeavy.

9. the license plate locating method based on laser instrument, is characterized in that, the method bagDraw together:

Obtain the laser scans line data of vehicle at laser instrument surveyed area, thereby obtain car plateCharacteristic information Sample Storehouse;

In the time having vehicle to trigger laser scans line, if the beam pattern information of trigger position and instituteA vehicle license plate characteristic information stating vehicle license plate characteristic message sample storehouse is consistent, and obtains this hot spot positionPut the pixel coordinate at described candid photograph photograph;

According to the second presetted pixel propagation, this facula position is sat in the pixel of described candid photograph photographNear mark, carry out left and right and expand to obtain up and down car plate position.

10. the license plate positioning device based on laser instrument, is characterized in that, comprising:

Headstock position acquisition unit, in the time having detected that vehicle triggers laser scans line,In historical frames data from the renewal of this vehicle, obtain the headstock position of this vehicle;

Headstock band of position acquiring unit, for capturing according to this this headstock of headstock position calculationThereby the position, left and right in photograph and upper-lower position obtain in the headstock lane place of capturing in photographTerritory;

Car plate band of position acquiring unit, calculates for all historical frames data according to this vehicleBorder, the heavy and comprehensive left and right of comprehensive confidence weighting; And heavily comprehensively left to this according to described comprehensive confidence weightingRight margin inwardly shrinks the position, left and right that obtains this car plate, and according to the first presetted pixel propagationY axle pixel value to triggered laser scans line on described candid photograph photograph expands up and downExhibition obtains the upper-lower position of this car plate in described candid photograph photograph, thereby obtains the car plate band of position.

11. 1 kinds of license plate positioning devices based on laser instrument, is characterized in that, this device bagDraw together:

Sample Storehouse acquiring unit, for obtaining the laser scans of vehicle at laser instrument surveyed areaLine data, thus vehicle license plate characteristic message sample storehouse obtained;

Facula position coordinate acquiring unit, in the time having vehicle to trigger laser scans line, ifA vehicle license plate characteristic in the beam pattern information of trigger position and described vehicle license plate characteristic message sample storehouseInformation is consistent, and obtains the pixel coordinate of this facula position at described candid photograph photograph;

Car plate band of position acquiring unit, for according to the second presetted pixel propagation to this hot spotPosition is carried out left and right and is expanded to obtain up and down car plate near the pixel coordinate of described candid photograph photographThe band of position.

12. 1 kinds of Position System of automobile license plate locations based on laser instrument, is characterized in that, comprise that right willAsk license plate positioning device and at least one laser instrument described in 10;

Described at least one laser instrument is for sending laser scans line to surveyed area, and receptionThe laser scans line returning offers license plate positioning device;

Described license plate positioning device is for detecting the headstock position of triggering vehicle according to laser scans linePut and determine the headstock band of position and the car plate band of position in candid photograph photograph.

13. 1 kinds of Position System of automobile license plate locations based on laser instrument, is characterized in that, comprise that right willAsk license plate positioning device and at least one laser instrument described in 11;

Described at least one laser instrument is for sending laser scans line to surveyed area, and receptionThe laser scans line returning offers license plate positioning device;

Described license plate positioning device is for detecting the headstock position of triggering vehicle according to laser scans linePut and determine the car plate band of position in candid photograph photograph.