CN106017357A - Defocused projection three-dimensional measuring method based on colorful triangular wave fringes - Google Patents

Abstract

The invention discloses a defocused projection three-dimensional measuring method based on colorful triangular wave fringes. The method includes four key parts including the colorful triangular wave fringe encoding principle, a defocused projection system, the principle of eliminating color crosstalk between channels and the three-dimensional measuring principle. The method has the advantages that compared with a traditional fringe projection method needing to project three frames of fringes (phase shift of each frame is 120 degrees), only one frame of colorful triangular wave fringes needs to be projected in the method, and three-dimensional measuring speed is greatly increased; the triangular wave fringes are subjected to slight defocused projection, and ideal sine fringes can be obtained on a reference plane; the colorful triangular wave fringe defocusing method is adopted, so high-order harmonics can be filtered out, the gamma effect can be reduced, and accordingly measuring precision is further improved. The method has potential application prospects and practical value in quick and real-time three-dimensional measuring of dynamic objects.

Description

Based on color triangle ripple striped out of focus projection three-dimensional measurement method

Technical field

The present invention relates to a kind of method for three-dimensional measurement, be specifically related to measure based on color triangle ripple striped out of focus projection three-dimensional Method.

Background technology

Fringe projection technology of profiling due to noncontact, measurement of full field, measuring speed is fast, precision is high and it is excellent to be prone to information processing etc. Point, significant in three-dimensional measurement.Three-dimension measuring system as it is shown in figure 1, include projector 1, colorful CCD camera 2, work Make station 3, measurement bracket 4, reference plane 5, object under test 6；Projector 1 and colorful CCD camera 2 are placed in measurement bracket 4 and divide It is not connected to work station 3 by data wire；Image pick-up card, projection software, Survey Software is comprised in work station 3.Projector 1 will Project reference plane 5 after becoming sine streak with the suitable out of focus of striped of characteristic information, colorful CCD camera 2 gather striped Information, obtains fixed phase after work station 3 processes.Then object under test 6 is placed on same position, obtains through work station 3 To corresponding deforming stripe picture, calculate phase place, deduct the phase place change that fixed phase i.e. obtains being caused by determinand dignity shape, Thus carry out three-dimensional reconstruction according to the corresponding relation of phase place Yu object surface appearance.DLP projector 1 optical axis and colorful CCD camera 2 Optical axis intersects at O point.Projector 1 and colorful CCD camera 2 are sustained height, and the distance between them is d, and they are to reference to flat The distance in face is l₀.The high computational formula of testee 6 is:

$h=\frac{l_0\mathrm{\Δ}\mathrm{\φ}}{2{\mathrm{\πf}}_{0}d+\mathrm{\Δ}\mathrm{\φ}}---\left(3\right)$

Wherein f₀For the sine streak frequency in reference plane, Δ φ is that body surface image is corresponding with reference plane image The continuous phase potential difference of point.

By domestic and international present Research and developments are analyzed and researched, high speed, real-time, high accuracy three-dimensional survey in recent years Measure and suffer from being widely applied at aspects such as medical diagnosis, On-line Product detection, face and fingerprint recognition.Both at home and abroad for object The quick three-dimensional of surface topography is measured and has been done a series of research, generally the three-dimensional measurement side to dynamic scene theoretical in application Method has Fourier transform profilometry and color coding approach.Fourier transform profilometry based on fringe projection is utilized to realize dynamic State process three dimension profile measurement.Utilize color coding approach can realize personage's expression to flutter and catch.The advantage of both the above method is to survey The striped quantity needing projection during amount is few, drastically increases measuring speed.Traditional method for three-dimensional measurement needs projection at least Three frame bar print images, the longest, directly affect measuring speed, the measurement technology of this single channel cannot meet need now Want faster speed, more precisely this development trend of Measuring Object three-dimensional appearance.The present invention proposes a kind of based on color triangle Ripple striped out of focus projection three-dimensional measurement method, the method only need to project a frame color triangle ripple striped, the shortest, thus improves survey Amount speed, is suitable for quick, the occasion of real-time three-dimensional measurement.Use triangular wave striped out of focus projecting method simultaneously, reduce gamma The impact of effect, improves certainty of measurement.In addition, the present invention can reduce interchannel crosstalk by adding algorithm, and And the intensity of compensation passage is unbalanced, thus revise the error blocking phase place, further increase certainty of measurement.

In a lot of industrial automations detect, need to measure the three-dimensional information data obtaining object, therefore realize object Surface topography high speed, high accuracy three-dimensional measuring method are increasingly paid attention to by vast researcher.Owing to coloured image is more grey Degree image has more abundant information and preferably identifies feature, it is possible to reduce projection frame number, therefore, utilizes color fringe Colouring information carries out quick, real-time, high accuracy three-dimensional measurement and becomes a kind of new method.The present invention propose based on colour Triangular wave striped out of focus projection three-dimensional measurement method will play a significant role in high speed, high precision three-dimensional measurement.

Summary of the invention

The present invention proposes a kind of based on color triangle ripple striped out of focus projection three-dimensional measurement method, and the method is more traditional The method for three-dimensional measurement of sine stripe projection, reduces gamma effect, improves certainty of measurement and speed.

The present invention propose based on color triangle ripple striped out of focus projection three-dimensional measurement method, it is characterized in that: color triangle Ripple striped coding principle, out of focus optical projection system, elimination interchannel color cross-talk principle, three-dimensional measurement principle；

Described color triangle ripple striped coding principle, by being respectively embedded into same frequency in tri-passages of RGB and phase place depends on Secondary is-120 °, 0 °, the triangular wave striped of 120 °, then by synthesis, obtains color triangle ripple striped；

Described out of focus optical projection system, by triangular wave striped being carried out Fourier analysis:

$x\left(t\right)=\frac{A}{2}+\frac{4A}{{\mathrm{\π}}^2}\underset{k=1}{\overset{N}{\Σ}}\frac{1}{{(2k+1)}^2}\cos (2k+1){\mathrm{\ω}}_{0}t---\left(4\right)$

In above formula, A is range value, and k is overtone order, w₀For fundamental frequency.Understand in triangular wave striped humorous containing multinomial high order Ripple, by it is carried out appropriateness out of focus, can filter higher hamonic wave, obtain the sine streak of standard；

Described three-dimensional measurement principle, by the color triangle three kinds of colors of the isolated red, green, blue of ripple striped after elimination crosstalk Colored sine streak, use three step phase shift methods to obtain blocking phase value:

$\mathrm{\φ}(x,y)={\tan }^{-1}\left(\sqrt{3}\frac{I_R-I_B}{2I_G-I_R-I_B}\right)---\left(2\right)$

Use quality guidance method to carry out Phase-un-wrapping again, obtain continuous phase place value, thus utilize phase height formula (3) elevation information of body surface every bit is obtained.

The invention have the advantage that (1) is compared with traditional sine stripe projection method: traditional method need to project three frames respectively Sine streak (every frame phase shift 120 °)；This method has only to use projection arrangement by single width color triangle ripple fringe projection to object Surface just can realize three-dimensional measurement, can preferably meet requirement of real-time；(2) triangular wave striped projects through out of focus, in ginseng Examining and obtain sine streak in plane, compared with binary system fringe projection out of focus situation, triangular wave striped out of focus degree is more shallow, only needs Just preferable sine streak is can get under slight out-of-focus appearance；(3) have employed color triangle ripple striped out of focus projecting method, can To filter higher hamonic wave, high-frequency noise and to overcome the non-linear Gamma effect of projector, it is greatly enhanced three-dimensional measurement essence Degree, the method has the highest practical value in high speed, high precision three-dimensional measurement.

Accompanying drawing explanation

Fig. 1 is the three-dimension measuring system schematic diagram of the present invention.

Fig. 2 is the triangular wave bar graph one of the three step phase shifts of the present invention.

Fig. 3 is the triangular wave bar graph two of the three step phase shifts of the present invention.

Fig. 4 is the triangular wave bar graph three of the three step phase shifts of the present invention.

Fig. 5 is the color triangle ripple fringe intensity figure after the red, green, blue triple channel synthesis of the present invention.

Fig. 6 is the color triangle ripple bar graph of the present invention.

Fig. 7 is the triangular wave striped spectrogram of the present invention.

Fig. 8 is the sine streak figure obtained after the triangular wave striped out of focus of the present invention.

In the drawings, 1 is projector, 2, colorful CCD camera, 3, work station, 4, measurement bracket 5, reference plane, 6, determinand Body.

Detailed description of the invention

Illustrate below in conjunction with the accompanying drawings the enforcement of the present invention is described in further detail, but the present embodiment is not limited to The present invention, the analog structure of every employing present invention and similar change thereof, protection scope of the present invention all should be listed in.

The present invention is such to work and enforcement, based on color triangle ripple striped out of focus projection three-dimensional measurement method, its Feature is: by color triangle ripple striped coding principle, out of focus optical projection system, eliminate interchannel color cross-talk principle, three-dimensional measurement The big key component of principle four forms.

One, traditional colored sine streak

Traditional colored sine streak is to be adopted by the sine streak of red (Red), green (Green), blue (Blue) three passages Obtaining phase value with three step phase shift methods, in three kinds of colouramas, the phase contrast between each two is all 120 °, red, green, blue three kinds Color each pixel (x, light intensity y) is as follows:

I_R(x, y)=I'(x, y)+I " (x, y) cos [φ (x, y)-2 π/3] (5)

I_G(x, y)=I'(x, y)+I " (x, y) cos [φ (x, y)] (6)

I_B(x, y)=I'(x, y)+I " (x, y) cos [φ (x, y)+2 π/3] (7)

I_R(x,y)、I_G(x,y)、I_B(x y) is the light intensity value on three kinds of Color Channels of red, green, blue respectively.I'(x, y) be Background intensity, I " (x, y) is modulate intensity, and (x y) is PHASE DISTRIBUTION to φ.

Two, color triangle ripple striped coding principle

Tradition RGB color strip encoding uses sinusoidal model, there is non-linear Gamma effect and the height of projector Subharmonic, directly influences certainty of measurement.So it is commonly used in the measurement of low required precision.To this end, the present invention proposes Problem above is solved based on color triangle ripple striped out of focus projecting method, will three passages of red, green, blue in RGB image Triangular wave striped coding, phase place is separated by 120 °, as shown in Figure 2, Figure 3 and Figure 4 successively；Again by synthesis, obtain color triangle Ripple striped, as shown in Figure 5 and Figure 6.

Three, color triangle ripple striped out of focus is projected

By triangular wave striped being carried out Fourier analysis:

$x\left(t\right)=\frac{A}{2}+\frac{4A}{{\mathrm{\π}}^2}\underset{k=1}{\overset{N}{\Σ}}\frac{1}{{(2k+1)}^2}\cos (2k+1){\mathrm{\ω}}_{0}t---\left(8\right)$

Fourier spectrum represents such as formula (9):

X(f_t)=Csinc (f_t/2f₀)comb(f_t/f₀) (9)

In formula (9), c is a constant, f₀Fundamental frequency for triangular wave striped.

Projection optics transmission function such as following formula (10):

H(f_t)=J₁(2πf_tr₀)/πf_tr₀ (10)

Wherein J₁For being first-order bessel function, r₀It it is the discrete radius of circle that formed of out of focus.

Work as f_t=kf₀, when wherein k takes natural number, out of focus system OTF can be re-written as:

$H\left(k\right)=\frac{J_1(2pkb/2)}{pkb/2}---\left(11\right)$

In formula (11), b is a defocus parameter,

Optical defocus system is used for filtering the high fdrequency component of triangular wave striped (such as Fig. 7 as a gauss low frequency filter Shown in).It addition, along with the intensification of out of focus degree, Dispersive spot radius r₀Will increase, come therewith is the increase of b, and this is the most logical Cross out of focus suitable to triangular wave striped, filter higher hamonic wave, obtain the sine streak (as shown in Figure 8) of standard.

So, by color triangle ripple striped is carried out suitable out of focus, respond well colored sine streak can be obtained.

Four, colored sine streak interchannel color cross-talk principle is eliminated

Color triangle ripple striped in (two) is eliminated by compensation formula the crosstalk of each passage, then corrects each and lead to The intensity in road.

Five, three-dimensional measurement principle

Eliminate the red, green, blue three kinds that the color triangle ripple striped after crosstalk has been obtained separating by the method in (three) The colored sine streak of color.Obtained it by three step phase shift methods and block phase value:

$\mathrm{\φ}(x,y)={\tan }^{-1}\left(\sqrt{3}\frac{I_R-I_B}{2I_G-I_R-I_B}\right)---\left(2\right)$

Use quality guidance method to carry out Phase-un-wrapping again, obtain its continuous phase place value, thus utilize phase height formula (3) height of object is obtained.

Claims (1)

1. based on color triangle ripple striped out of focus projection three-dimensional measurement method, it is characterized in that: former by color triangle ripple striped coding Reason, out of focus optical projection system, elimination interchannel color cross-talk principle, three-dimensional measurement principle four big key component composition；

Described color triangle ripple striped coding principle, by by tri-passages of RGB are respectively embedded into same frequency and phase place be followed successively by- 120 °, 0 °, the triangular wave striped of 120 °, then by synthesis, obtain color triangle ripple striped；

Described out of focus optical projection system, by triangular wave striped being carried out Fourier analysis:

$x\left(t\right)=\frac{A}{2}+\frac{4A}{{\mathrm{\π}}^2}\[cos\mathrm{\ω}t+\frac{1}{3^2}cos3\mathrm{\ω}t+\frac{1}{5^2}cos5\mathrm{\ω}t+\mathrm{...}+\frac{1}{{(2k+1)}^2}cos(2k+1)\mathrm{\ω}t+\mathrm{...}\]---\left(1\right)$

Understand in triangular wave striped containing higher hamonic wave, higher hamonic wave can be filtered by it is carried out suitable out of focus, be marked Accurate sine streak；

Described three-dimensional measurement principle is to be obtained by the method in out of focus optical projection system by the color triangle ripple striped after eliminating crosstalk The colored sine streak of isolated three kinds of colors of red, green, blue, uses three step phase shift methods to obtain blocking phase value:

$\mathrm{\φ}(x,y)={\tan }^{-1}\left(\sqrt{3}\frac{I_R-I_B}{2I_G-I_R-I_B}\right)---\left(2\right)$

Use quality guidance method to carry out Phase-un-wrapping again, obtain continuous phase place value, thus utilize phase height formula:

$h=\frac{l_0\mathrm{\Δ}\mathrm{\φ}}{2{\mathrm{\πf}}_{0}d+\mathrm{\Δ}\mathrm{\φ}}---\left(3\right)$

Obtain the elevation information of body surface every bit.