CN105066906A - Fast high dynamic range three-dimensional measurement method - Google Patents

Abstract

The invention provides a fast high dynamic range three-dimensional measurement method. The method comprises the steps that a four-amplitude grating strip is generated by a computer; two polarizer are respectively placed on the optical axis of a projector and the optical axis of a camera; any one polarizer is rotated; the angle between the optical axis of the projector and the optical axis of the camera is set to be 90 degrees; the projector is used to project the generated four-amplitude grating strip to an object to be measured; the camera is used to synchronously shoot a four-amplitude strip image generated by the reflection of the object to be measured; the four-amplitude strip image is analyzed to acquire a high frequency wrapped phase and low frequency phase; the high frequency wrapped phase is unwrapped to acquire a high frequency unwrapped phase; and according to the unwrapped phase, the three-dimensional scene of the measured object is reconstructed. The fast high dynamic range three-dimensional measurement method provided by the invention can carry out high dynamic range three-dimensional measurement on a dynamic scene.

Description

A kind of high dynamic range method for three-dimensional measurement fast

Technical field

The invention belongs to field of optical measuring technologies, be specifically related to a kind of high dynamic range method for three-dimensional measurement fast.

Background technology

Optical three-dimensional measuring method becomes with noncontact, high precision, the advantage such as easy to implement a kind of important means that people obtain three-D profile data day by day.According to the difference of means of illumination, usually optical three-dimensional measurement is divided into active and three-dimensional measurement that is passive type.Passive type three-dimensional measurement is taken measured object from different perspectives by two or more cameras, from the two dimensional image obtained, recover measured surface three-dimensional information.This class methods advantage is that measuring system is simple and data acquisition convenient, so it has a wide range of applications in machine vision.Binocular vision method is a kind of exemplary process of these class methods, and it is similar to the function of human eye according to bionical thing principles of construction, from the two dimensional image of different visual angles, determine distance.It is in airborne survey field, utilizes aircraft to load large visual field high resolution camera and takes image sequence along heading, thus obtain topography and geomorphology.Although passive type method effectively can obtain measured object surface three dimension information, it mainly contains two shortcomings: operand is very huge, usually needs high speed processor to realize to measure; Article surface vein is too relied on, makes the method be not suitable for measuring smooth or that unique point is less surface.

Active three-dimensional measurement adopts the method for Structured Illumination to measured object projection optical signal on one's own initiative, then according to taking the three-dimensional information demodulating measured object in the modulation light field that obtains.These class methods are initiatively modulated tested surface owing to utilizing light modulated, so which solve the problem relied on object its own face texture, and avoid the use of related algorithm, thus reduce data operation quantity.Conventional proactive comprises fringe projection method, time-of-flight method, degree of modulation consistency profiles etc.Wherein fringe projection method uses a kind of measuring method the most general at present.The method, by projecting grating fringe to measured object, the grating fringe that video camera is modulated from another angle shot through measured object, through striped decoding, demodulates measured surface three-D profile.Along with the development of digital projection device, this technology is increasingly being used to dynamic scene three-dimensional scene and measures.Along with striped is projected to measured surface and video camera synchronous acquisition two-dimensional grating pattern at high speed, eventually through high-speed data process, the high speed three-dimensional that can realize for motion changing object is measured.

High speed three-dimensional is measured has very significance for fields such as on-line checkingi, biologic medical, deformation analysiss.But in actual measurement process, researchist is still encountered by a lot of urgent problem.One of them problem the most often run into is exactly that the high speed how realizing high dynamic range is measured.Because at present object under test surface due to reflectivity high, be easy to form local Gao Guang.Particularly alloying metal workpiece, the high light on its surface is particularly evident.The Gao Guang on surface, due to camera pixel can be caused saturated, so make video camera cannot obtain the useful light signal at high light place, is finally difficult to the three-D profile recovering this region.Meanwhile, although traditional many exposure techniques can realize the three-dimensional measurement of high dynamic range, due to needs multiexposure, multiple exposure, so be only suitable for the measurement with static scene.

Summary of the invention

The object of the present invention is to provide a kind of high dynamic range method for three-dimensional measurement fast, the three-dimensional measurement of high dynamic range can be realized dynamic scene.

In order to solve the problems of the technologies described above, the invention provides a kind of high dynamic range method for three-dimensional measurement fast, using Practical computer teaching four amplitude grating striped; On projector optical axis and camera optical axis, place one piece of polariscope respectively, rotate any one piece of polariscope, the angle between projector optical axis and camera optical axis is adjusted to 90 degree; Use projector that the four amplitude grating stripeds generated are projected to measured object, use the four spoke print images that video camera sync pulse jamming is generated by measured object reflection; Four spoke print images are analyzed, obtains high frequency wrapped phase and low frequency phase; Parcel is gone to high frequency wrapped phase, obtaining high frequency and go to wrap up rear phase place, wrapping up rear Phase Build Out testee three-dimensional scenic according to going.

Further, four amplitude grating striped I of Practical computer teaching ^p ₁~ I ^p ₄optics expression formula as follows,

I ^p ₁(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πfx ^p)

I ^p ₂(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p)

I ^p ₃(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p+2π/3)

I ^p ₄(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p+4π/3)

Wherein, (x ^p, y ^p) be projector pixel coordinate, A ^pfor DC component, B ^pfor degree of modulation, A ^p=B ^p=127.5, the image pixel degree of depth is 8 bits, and f is the frequency of the first width sinusoidal grating striped.

Further, four spoke print image I of video camera sync pulse jamming ^c ₁~ I ^c ₄intensity distributions expression formula as follows,

I ^c ₁(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _h)

I ^c ₂(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l)

I ^c ₃(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l+2π/3)

I ^c ₄(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l+4π/3)

Wherein, (x ^c, y ^c) be camera pixel coordinate, A ^cfor background light intensity, B ^cfor phase-modulation degree, φ _hfor the first spoke print image of shooting in the high-frequency phase that comprises, φ _lfor the second width of shooting is to the 4th spoke print image in the low frequency phase that comprises.

Further, to the first spoke print image I ^c ₁carry out two-dimensional Fourier transform, in the frequency spectrum obtained, use Hanning window to align one-level frequency spectrum carry out filtering, then carry out two-dimentional inverse Fourier transform, obtain high frequency wrapped phase φ _h.

Further, to the second width to the 4th spoke print image I ^c ₂, I ^c ₃and I ^c ₄use three step phase-shift method analyses, obtain low frequency phase φ _l, computing formula is as follows,

${\mathrm{\φ}}_l(x^c,y^c)={\tan }^{-1}\frac{\sqrt{3}\left(I_1^c\right(x^c,y^c)-I_3^c(x^c,y^c\left)\right)}{2I_2^c(x^c,y^c)-I_1^c(x^c,y^c)-I_3^c(x^c,y^c)}.$

Further, acquisition goes the concrete grammar wrapping up rear phase place Φ to be shown below:

$\mathrm{\Φ}(x^c,y^c)={\mathrm{\φ}}_h(x^c,y^c)+2\mathrm{\π}\×Round\[\frac{{\mathrm{f\φ}}_l(x^c,y^c)-{\mathrm{\φ}}_h(x^c,y^c)}{2\mathrm{\π}}\]$

Wherein, Round is for asking for nearest integer.

Compared with prior art, its remarkable advantage is in the present invention, and the present invention uses polariscope to solve the high optical issue of prior art existence well, makes the three-dimensional measurement that just can realize high dynamic range when single exposure.In addition, according to classic method, such as double frequency three step phase-shift method, dynamic scene is measured needs six spoke lines usually, and the inventive method only needs use four amplitude grating striped, so the present invention is applicable to the measurement of rapid movement changing object very much.

Below in conjunction with accompanying drawing, the present invention is described in further detail.

Accompanying drawing explanation

Fig. 1 is the present invention's quick high dynamic range method for three-dimensional measurement schematic flow sheet.

Fig. 2 is the measuring object and scene image thereof that use in the embodiment of the present invention, and measuring object is the white water tumbler with local Gao Guang in image.

Fig. 3 in the embodiment of the present invention to measuring object shown in Fig. 2 shooting four spoke print images, wherein, (a) be take the first spoke print image b () is the second spoke print image of shooting c () is the 3rd spoke print image of shooting d () is the 4th spoke print image of shooting

Fig. 4 is the phase place schematic diagram solved in the embodiment of the present invention, and wherein (a) is high-frequency phase φ _h, (b) is low frequency phase φ _l.

Fig. 5 is the three-dimensional reconstruction image contrast that the embodiment of the present invention obtains, and wherein (a) uses classic method to rebuild the 3-D view obtained, and (b) uses the inventive method to rebuild the 3-D view obtained.

Embodiment

Easy understand, according to technical scheme of the present invention, when not changing connotation of the present invention, one of ordinary skill in the art can imagine the numerous embodiments the quick high dynamic range method for three-dimensional measurement of the present invention.Therefore, following embodiment and accompanying drawing are only the exemplary illustrations to technical scheme of the present invention, and should not be considered as of the present invention all or the restriction be considered as technical solution of the present invention or restriction.

Composition graphs 1, quick high dynamic range method for three-dimensional measurement of the present invention, step is as follows:

Step one, uses four amplitude grating stripeds needed for Practical computer teaching.Example is generated as, four amplitude grating striped I with vertical striped ^p ₁~ I ^p ₄, four amplitude grating striped I ^p ₁~ I ^p ₄generate in the following manner:

I ^p ₁(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πfx ^p)

I ^p ₂(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p)

I ^p ₃(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p+2π/3)

I ^p ₄(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p+4π/3)

Wherein, (x ^p, y ^p) be projector pixel coordinate, A ^pfor DC component, B ^pfor degree of modulation, A ^p=B ^p=127.5, the image pixel degree of depth is 8 bits, and f is the frequency of the first width sinusoidal grating striped.

Step 2, places polariscope.On projector optical axis and camera optical axis, place one piece of polariscope respectively, rotate wherein any one piece of polariscope, the angle between projector optical axis and the light transmission shaft of camera optical axis is adjusted to 90 degree.

Step 3, gathers grating fringe and phase solution.

First, use projector that the four amplitude grating stripeds generated are projected to measured object, the four spoke print images that video camera synchronous acquisition is generated by measured object reflection, four spoke print image I of video camera sync pulse jamming ^c ₁(x ^c, y ^c) ~ I ^c ₄(x ^c, y ^c) can be represented as:

I ^c ₁(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _h)

I ^c ₂(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l)

I ^c ₃(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l+2π/3)

I ^c ₄(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l+4π/3)

Wherein, (x ^c, y ^c) be camera pixel coordinate, A ^cfor background light intensity, B ^cfor phase-modulation degree, φ _hfor the first spoke print image of shooting in the high-frequency phase that comprises, φ _lfor the second width of shooting is to the 4th spoke print image in the low frequency phase that comprises.

Secondly, to the first spoke print image use Fourier Transform Profilomery to analyze, obtain high frequency wrapped phase φ _h.Use two-dimensional Fourier transform, in the frequency spectrum obtained, the Hanning window that use size is M × N aligns one-level frequency spectrum and carries out filtering, finally carries out two-dimentional inverse Fourier transform, obtains high frequency wrapped phase φ _h.

Finally, to the second width to the 4th spoke print image use three step phase-shift method analyses, obtain low frequency phase φ _l.Low frequency phase φ _lspecifically obtained by following formula:

${\mathrm{\φ}}_l(x^c,y^c)={\tan }^{-1}\frac{\sqrt{3}\left(I_1^c\right(x^c,y^c)-I_3^c(x^c,y^c\left)\right)}{2I_2^c(x^c,y^c)-I_1^c(x^c,y^c)-I_3^c(x^c,y^c)}$

Step 4, tested scene three-dimensional reconstruction.To high frequency wrapped phase φ _hremove parcel, obtaining high frequency and go to wrap up rear phase place Φ, rebuilding tested three-dimensional scenic according to going to wrap up rear phase place Φ.Obtaining goes the concrete grammar wrapping up rear phase place Φ to be shown below:

$\mathrm{\Φ}(x^c,y^c)={\mathrm{\φ}}_h(x^c,y^c)+2\mathrm{\π}\×Round\[\frac{{\mathrm{f\φ}}_l(x^c,y^c)-{\mathrm{\φ}}_h(x^c,y^c)}{2\mathrm{\π}}\]$

Wherein, Round is for asking for nearest integer.Try to achieve wrap up after after phase place Φ, according to go to wrap up rear phase place Φ rebuild tested three-dimensional scenic can list of references " Automaticidentificationandremovalofoutliersforhigh-speed fringeprojectionprofilometry " (OptEng2013; Phase depth conversion method 52013605-013605).

Embodiment

In the present embodiment, measurand is illustrated in figure 2 the water tumbler that there is high light reflectivity on a surface.The four amplitude grating striped projections using step one of the present invention to generate are measured, when not adding polariscope, three-dimensional measuring result is as shown in Fig. 5 (a), obviously can find out that pit has appearred in the surface of highlight area, illustrate that the existence of Gao Guang affects the measurement of this part surface.After adding polariscope by step 2 according to the inventive method on projector optical axis and camera optical axis, the four spoke print images gathered are successively as shown in (a) to (d) in Fig. 3, be not difficult to find from Fig. 3, original high light is weakened.Subsequently, utilize Fourier Transform Profilomery in step 3 to analyze the stripe pattern in Fig. 3 shown in (a), obtain high frequency wrapped phase φ _h, high frequency wrapped phase φ _has shown in Fig. 4 (a).Then use three step phase-shift methods in step 3 to process three spoke print images in Fig. 4 shown in (b) to (d), obtain low frequency phase φ _l, low frequency phase φ _las shown in Fig. 4 (b).Finally, adopt the method for three-dimensional reconstruction in step 4 to obtain the three-D profile of tested water tumbler, three-D profile is as shown in Fig. 5 (b), and wherein mm represents millimeter, and Pixel represents pixel.Can find out, utilize the method for the invention, also can be measured properly reconstruction of three-dimensional images at the body surface that there is Gao Guang.

Claims (6)

1. a quick high dynamic range method for three-dimensional measurement, is characterized in that,

Use Practical computer teaching four amplitude grating striped;

On projector optical axis and camera optical axis, place one piece of polariscope respectively, rotate any one piece of polariscope, the angle between projector optical axis and camera optical axis is adjusted to 90 degree;

Use projector that the four amplitude grating stripeds generated are projected to measured object, use the four spoke print images that video camera sync pulse jamming is generated by measured object reflection; Four spoke print images are analyzed, obtains high frequency wrapped phase and low frequency phase;

Parcel is gone to high frequency wrapped phase, obtaining high frequency and go to wrap up rear phase place, wrapping up rear Phase Build Out testee three-dimensional scenic according to going.

2. quick high dynamic range method for three-dimensional measurement as claimed in claim 1, is characterized in that, four amplitude grating striped I of Practical computer teaching ^p ₁~ I ^p ₄optics expression formula as follows,

I ^p ₁(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πfx ^p)

I ^p ₂(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p)

I ^p ₃(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p+2π/3)

I ^p ₄(x ^p,y ^p)＝A ^p(x ^p,y ^p)+B ^p(x ^p,y ^p)cos(2πx ^p+4π/3)

Wherein, (x ^p, y ^p) be projector pixel coordinate, A ^pfor DC component, B ^pfor degree of modulation, A ^p=B ^p=127.5, the image pixel degree of depth is 8 bits, and f is the frequency of the first width sinusoidal grating striped.

3. quick high dynamic range method for three-dimensional measurement as claimed in claim 2, is characterized in that, four spoke print image I of video camera sync pulse jamming ^c ₁~ I ^c ₄intensity distributions expression formula as follows,

I ^c ₁(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _h)

I ^c ₂(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l)

I ^c ₃(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l+2π/3)

I ^c ₄(x ^c,y ^c)＝A ^c(x ^c,y ^c)+B ^c(x ^c,y ^c)cos(φ _l+4π/3)

Wherein, (x ^c, y ^c) be camera pixel coordinate, A ^cfor background light intensity, B ^cfor phase-modulation degree, φ _hfor the first spoke print image of shooting in the high-frequency phase that comprises, φ _lfor the second width of shooting is to the 4th spoke print image in the low frequency phase that comprises.

4. quick high dynamic range method for three-dimensional measurement as claimed in claim 3, is characterized in that, to the first spoke print image I ^c ₁carry out two-dimensional Fourier transform, in the frequency spectrum obtained, use Hanning window to align one-level frequency spectrum carry out filtering, then carry out two-dimentional inverse Fourier transform, obtain high frequency wrapped phase φ _h.

5. quick high dynamic range method for three-dimensional measurement as claimed in claim 4, is characterized in that, to the second width to the 4th spoke print image I ^c ₂, I ^c ₃and I ^c ₄use three step phase-shift method analyses, obtain low frequency phase φ _l, computing formula is as follows,

${\mathrm{\φ}}_l(x^c,y^c)={\tan }^{-1}\frac{\sqrt{3}\left(I_1^c\right(x^c,y^c)-I_3^c(x^c,y^c\left)\right)}{2I_2^c(x^c,y^c)-I_1^c(x^c,y^c)-I_3^c(x^c,y^c)}.$

6. quick high dynamic range method for three-dimensional measurement as claimed in claim 5, is characterized in that, obtain and go the concrete grammar wrapping up rear phase place Φ to be shown below:

$\mathrm{\Φ}(x^c,y^c)={\mathrm{\φ}}_h(x^c,y^c)+2\mathrm{\π}\×Round\[\frac{{\mathrm{f\φ}}_l(x^c,y^c)-{\mathrm{\φ}}_h(x^c,y^c)}{2\mathrm{\π}}\]$

Wherein, Round is for asking for nearest integer.