CN2856928Y - Device of adopting double wavelength structural light for measuring object outline - Google Patents

Abstract

The utility model relates to a device for measuring object profile by using dual wavelength structured light, which belongs to the field of optical measurement technology. The device comprises a projector connected for generating a sinusoidal-modulated beam white light, a camera the computer for picking up the image of the object to be measured in the white light optical field, a computer for controlling the white light with special structure generated by the projector and receiving the image from the camera to process, wherein the projector and the camera are connected to the computer, and the connection line between the camera and the projector is parallel with the reference plane, the distance of the projector and the camera to the reference plane is L, and the distance between the projector and the camera is d. Compared to prior technique, the device in the utility model can be used for measuring an object which is provided with more complicated surface shape with higher measurement accuracy.

Description

A kind of device that adopts double wavelength structural light Measuring Object profile

Technical field

The utility model relates to a kind of device that adopts double wavelength structural light Measuring Object profile, belongs to optics (three-dimensional) and measures

Technical field.

Background technology

Optical projection formula profilometry can be divided into two big classes: direct trigonometry and phase measurement.Directly trigonometry comprises laser point by point scanning method, binocular stereo vision method, structured light method (also claiming light cross-section method) etc.Phase measurement projects to the phase place of the grid picture on the object based on measurement, and Moire technique, phase-shifting method, Fourier transform method or the like are arranged.

The binocular stereo vision method is obtained two width of cloth images of Same Scene from different perspectives, as people's eyes observing scene.Computing machine obtains the depth information of this point of object by detection and coupling to same object point two picture points on two width of cloth images.The principle of binocular vision imaging is simple, but owing to will match corresponding point in the image of the left and right sides, the actual calculation process is very complicated, and three-dimensional matching problem is the main difficult point that binocular vision is measured all the time.Lot of domestic and foreign scholar studies coupling, a lot of matching algorithms has been proposed, for example utilize conditions such as outer polar curve constraint, consistency constraint, unique constraints shape continuity constraint to dwindle matching range, and the MPG algorithm of extensive influence and multi-channel structure algorithm.KanadeT. wait the iteration matching algorithm that has proposed based on selecting template window shape, size adaptively, also have matching algorithm in addition, based on the multiple dimensioned coupling of wavelet transformation etc. based on the pyramid picture structure.

The basic thought of method of structured light is exactly the geological information in the geological information help extraction scenery that utilizes in the illumination.For surf zone smooth, that do not have obvious gray scale, texture and change of shape, can form tangible striations with structured light, make things convenient for the analysis and the processing of image.Method of structured light calculates simply, measuring accuracy is higher, is widely used in actual vision measurement system.The measuring process of method of structured light mainly comprises two steps: earlier throw controllable laser to form unique point according to measuring needs to body surface by projection light source, and obtain surface image.Press the geometric shape characteristic explain projection mode of body surface projection light pattern then, utilize the triangulation principle can try to achieve distance between unique point and the camera lens principal point, the i.e. depth information of unique point.After calibrating direction in space in world coordinate system of light source and video camera, location parameter again, can try to achieve the three-dimensional coordinate of unique point in world coordinate system.

The plot of light intensity that phase measurement adopts Sine Modulated to cross looks like to be projected on the object, and image projection then deforms along with the variation of object height to object, and the light image after the distortion has formed two-dimentional bar graph, and it has comprised the three-dimensional information of object.The light intensity representation of distortion is: I _i(x, y, δ _i)=a (x, y)+b (x, y) cos[ (x, y)+δ _i], according to result data repeatedly, the autocorrelation of using Sine Modulated solves , and (x, y), (x, y), process is separated the 3D shape that envelope obtains actual object to calculate h then.Autocorrelation can be got rid of the interference of the dry sound of high frequency, so the phase-shift method precision is very high, changes the uncertain situation of separating that exists but separate the envelope process for step.

In sum, prior art is owing to adopt proprietary projection arrangement at present, and the 3-D scanning mode is confined to monotechnics, and precision index exists the barrier that is difficult to go beyond aspect indivedual.Binocular method matching problem is very complicated, causes error to be difficult to control.The striped distance of structured light method can not be infinitely small, and precision is restricted.Phase method is owing to exist the arc tangent conversion in the computation process, obtaining one group separates, under the body surface continuity constraint, can find unique suitable separating, but the scope that this step that has limited the object under test surface consecutive point degree of depth changes, the applicability of product is restricted bigger.

Summary of the invention

The purpose of this utility model is to propose a kind of device that adopts double wavelength structural light Measuring Object profile, the light of crossing by the Sine Modulated of liquid crystal projection apparatus projection different wave length is to body surface, obtain to have the two-dimensional image data of projected light information by video camera, restore the depth information of object again according to the projected image Pixel Information.

The device of the employing double wavelength structural light Measuring Object profile that the utility model proposes comprises:

(1) projector is used to produce a branch of white light after Sine Modulated, and the brightness value of this white light is: ${\mathrm{Iout}}_i(m,n,{\mathrm{\δ}}_i)=\cos [\frac{m}{p}\×2\mathrm{\π}+{\mathrm{\δ}}_i],$ p ₁Be the wavelength of Sine Modulated, m, n are the coordinate of light field on reference planes, δ _iBe phase-shift phase, ${\mathrm{\δ}}_i\∈(-\frac{\mathrm{\π}}{2},\frac{\mathrm{\π}}{2}),$ , computing machine is connected;

(2) camera, be used for taking the image at the illumination light field object under test of above-mentioned white light, camera is parallel with described reference planes with the line of projector, and the distance between projector and camera and the reference planes is L, distance between projector and the camera is d, is connected with computing machine;

(3) computing machine is used to control projector and produces the white light with ad hoc structure, and handles behind the image of reception camera.

The device of the employing double wavelength structural light Measuring Object profile that the utility model proposes has following characteristics and advantage:

1, in the utility model device, the calculating of phase differential is easy to the influence of unfavorable factor such as filtering environmental light to measurement result, therefore the algorithm stability that relates to is good.

2, in the utility model device computing machine to treatment of picture, very strong to the correct reducing power of object surfaces step situation to be measured, thus this device can the surface measurements shape complex objects more.

3, use device of the present utility model, 3D shape that can clear reproduction object under test, measuring accuracy is higher than prior art.

Description of drawings

Fig. 1 is the principle schematic of the device that the utility model proposes.

Fig. 2 is the light path synoptic diagram in the utility model device.

Fig. 3 be relate in the utility model device separate the envelope synoptic diagram.

Fig. 4 is the structural representation of the utility model device.

Among Fig. 1～Fig. 4, the 1st, projector, the 2nd, camera, the 3rd, object under test, 3a is the lip-deep observation station of object under test, the 4th, reference planes, the 5th, the face such as y such as grade at light path place, the 6th, observation station 3a is at the phase place equivalent point before the object under test modulation on the reference planes 4, the 7th, observation station 3a arrives the intersection point of reference planes 4, and the 8th, observation station 3a is at the phase place equivalent point after the object under test modulation on the reference planes 4, the 9th, computing machine, the 10th, projector is to the connecting line of computing machine, and the 11st, camera is to the connecting line of computing machine.D among Fig. 2 is the distance between the entrance pupil of of projector and camera, l be projector and camera go out the distance of entrance pupil to reference planes.Among Fig. 3, A is the object under test surface configuration, and B is the surface configuration that main value that phase-shifting method is obtained differs calculating, and C is the object that there is the step situation on another surface, and D is the surface configuration that object C obtains through phase-shifting method.

Embodiment

The device of the employing double wavelength structural light Measuring Object profile that the utility model proposes, its structure comprises as shown in Figure 4: projector 1, be used to produce a branch of white light after Sine Modulated, the brightness value of this white light is: ${\mathrm{Iout}}_i(m,n,{\mathrm{\δ}}_i)=\cos [\frac{m}{p}\×2\mathrm{\π}+{\mathrm{\δ}}_i],$ P is the wavelength of Sine Modulated, and m, n are the coordinate of light field on reference planes, δ _iBe phase-shift phase, ${\mathrm{\δ}}_i\∈(-\frac{\mathrm{\π}}{2},\frac{\mathrm{\π}}{2});$ Camera 2 is used for taking the image at the illumination light field object under test of white light, and camera is parallel with described reference planes with the line of projector, and the distance between projector and camera and the reference planes is l, and the distance between projector and the camera is d; Computing machine 3 is used to control projector and produces the white light with ad hoc structure, and handles behind the image of reception camera.

Among the embodiment of the present utility model, the model of used projector is: PB2245, to produce by BenQ company, and the model of used camera is: DH-HV series colorful digital output video camera, to produce by company of Daheng, used computing machine is the P4 compatible.

Below in conjunction with an embodiment of the present utility model, introduce the course of work and the principle of this device in detail:

At first, as shown in Figure 1, projector 1 projection Sine Modulated is crossed the white light of brightness.The brightness value of this illumination light field as shown in the formula, be known, by 1 output of computing machine 3 control projector. ${\mathrm{Iout}}_i(x,y,{\mathrm{\δ}}_i)=\cos [\frac{x}{p}\×2\mathrm{\π}+{\mathrm{\δ}}_i],$ As can be seen, light intensity value and y are irrelevant from formula, and the y direction is first-class bright.P is a wavelength, δ _iBe phase-shift phase, ${\mathrm{\δ}}_i\∈(-\frac{\mathrm{\π}}{2},\frac{\mathrm{\π}}{2}).$

After illumination light arrived on the object, light field was modulated, the image after camera is taken, brightness value as shown in the formula:

I _i(x，y，δ _i)＝a(x，y)+b(x，y)cos[(x，y)+δ _i]

Phase shift scanning is continuously repeatedly taken, and each frame phase shift 2 π/N gathers the N frame altogether.Use I ₁, I ₂, I ₃... I _NExpression then can observe the image calculating from N phase shift to the N frame brightness value of same point according to correlation method:

Use correlation method and can greatly eliminate I _i(x, y, δ _i)=a (x, y)+b (x, y) cos[ (x, y)+δ _i] a in the formula (and x, y) and b (x, y) for the adverse effect of measuring, the phase differential that extracts can have very high precision.Obtain Δ  (x, y) after, then can obtain observation station 3a to the distance of reference planes 4 this depth information just, as shown in Figure 2, some 3a for body surface, when reference planes are not placed object, then the same point on the image is a point 6, then putting 6 phase place is this phase place before the testee modulation on the image, and has placed after the object, and the phase place of putting 3a changes, produced phase shift, it is identical to put 8 phase place on phase place after some 3a changes and the reference surface, so phase differential has: Δ  (x, y)= (x ₈, y)- (x ₆, y),  (x in the formula ₆, y),  (x ₈, y) be respectively the phase place of the light field of Sine Modulated at point 6, point 8, so can get:

Δ  (x, y)=2 π | x ₆₈|/p, p is the wavelength of Sine Modulated in the formula, x ₆₈For putting 6 to the distance of putting 8.Can draw by the triangle similarity relation:

Z in the formula _3a7Be the depth information value of a 3a to reference planes 4.

In the superincumbent solution procedure, separating of phase differential to separating set, if get the calculating that main value carries out the back, then the result needs phase place to remove parcel, as shown in Figure 3, A is a cross section of object under test real surface shape among the figure, and B gets the surface configuration that the phase difference calculating behind the main value obtains, separating of depth information is fixed in the scope as can be seen, so just need wait according to the constraint condition of the continuous character in object under test surface and recover.But when step taking place,, shown in C among Fig. 3, separate the depth information that calculates before the envelope so shown in D at 2, then can't correctly restore true form as C if adjacent degree of depth difference surpasses the upper limit of span in the reality for the surface.In order to avoid the appearance of this situation as far as possible, a feasible method is to enlarge span, actual step is within the scope gets final product.But the size of span is relevant with wavelength, and p is big more, and span is big more, but p is big more, and the illumination light field is even more, is unfavorable for error control, and this also is to enlarge the drawback that wavelength causes merely.The utility model proposes the dual wavelength method, use twice close illumination light field of wavelength to obtain two cover phase-shifting method data, carry out certain reorganization, do not influence the quality of light field under the prerequisite of increase span.

By Δ  (x, y)=2 π | x ₆₈|/p

Obtain 2 π | x ₆₈|=Δ  (x, y) p

Dual wavelength can get: 2 π | x ₆₈|=Δ  ₁(x, y) p ₁

2π·|x ₆₈|＝Δ ₂(x，y)·p ₂

Two formulas comprehensively have:

So can remember work: Δ  (x, y)=Δ  ₂(x, y)-Δ  ₁(x, y)

$p=\frac{p_1{p}_2}{p_1-{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="Y20052014705200092.png"\; state="\{\{state\}\}">p</figure-callout>}}_2}$

I.e. 2 π | x ₆₈|=Δ  (x, y) p

At this moment, if p ₁, p ₂Very approaching, then Zu He wavelength p is just very big, uses the calculation of parameter depth information of combination.Then for finding the solution It is big that the span of the degree of depth becomes, and the illumination light field remains the small wavelength Sine Modulated, does not have the uniform problem of light field, well solved the problem that the depth information step of consecutive point overruns and can't reduce.Through separating the actual three-dimensional shape data that to obtain object behind the envelope.

Claims (1)

1, a kind of device that adopts double wavelength structural light Measuring Object profile is characterized in that this device comprises:

(1) projector is used to produce a branch of white light after Sine Modulated, and the brightness value of this white light is: ${\mathrm{Iout}}_i(m,n,{\mathrm{\&delta;}}_i)=\cos [\frac{m}{p}\&times;2\mathrm{\&pi;}+{\mathrm{\&delta;}}_i],$ p ₁Be the wavelength of Sine Modulated, m, n are the coordinate of light field on reference planes, δ _iBe phase-shift phase, ${\mathrm{\&delta;}}_i\&Element;(-\frac{\mathrm{\&pi;}}{2},\frac{\mathrm{\&pi;}}{2}),$ Be connected with computing machine;

(2) camera, be used for taking the image at the illumination light field object under test of above-mentioned white light, camera is parallel with described reference planes with the line of projector, and the distance between projector and camera and the reference planes is L, distance between projector and the camera is d, is connected with computing machine;

(3) computing machine is used to control projector and produces the white light with ad hoc structure, and handles behind the image of reception camera.

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