CN105157612A - Three-dimensional measurement method based on pulse width modulation fringe - Google Patents
Three-dimensional measurement method based on pulse width modulation fringe Download PDFInfo
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- CN105157612A CN105157612A CN201510252609.2A CN201510252609A CN105157612A CN 105157612 A CN105157612 A CN 105157612A CN 201510252609 A CN201510252609 A CN 201510252609A CN 105157612 A CN105157612 A CN 105157612A
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Abstract
The invention discloses a three-dimensional measurement method based on a pulse width modulation fringe. The three-dimensional measurement method consists of three key parts of pulse fringe encoding, pulse fringe defocusing and three-dimensional reconstructing. A pulse fringe is generated from a computer and then moderately defocused through a projector to generate a sine fringe on a reference face for three-dimensional measurement. The invention is advantageous in that (1) as the pulse fringe is a binary fringe, the grayscale value thereof can only be two values (0 and 1), so the measurement is quick; (2) since the nonlinear gamma of the projector can be eliminated simply by slight defocusing the projector, phase errors can be reduced without complex nonlinear calibration; and (3) thanks to less reduction in fringe contrast after the pulse fringe is slightly defocused, the measurement depth problem is overcome.
Description
Technical field
The present invention relates to a kind of optical three-dimensional measuring method, belong to photoelectric detection technology field.Particularly relate to a kind of method for three-dimensional measurement based on pulse-length modulation striped.
Background technology
Along with staggered form and the development of many fusion types of science and technology, the method for three-dimensional measurement based on optics, electricity, image procossing and computer vision has become the industrial nondestructive testing method having more broad prospect of application.The structured light three-dimensional measurement system that the method is formed is because of advantages such as high speed, high precision, noncontact, measurement of full field, snap information acquisitions; be widely used in the numerous areas such as industry manufacture, historical relic's protection, medical treatment, played an important role in commercial production and daily life.For meeting the fast rhythm of productive life, three-dimensional measurement speed becomes the important indicator weighing measuring system; Meanwhile, along with the fast development of science and technology, producing senior, accurate, most advanced and sophisticated product becomes inevitable, proposes requirements at the higher level to the measuring accuracy of 3-D measuring apparatus.Therefore, the product three-dimensional data that the three-dimension measuring system of people to structure based light obtains, not only needs measuring speed fast, and measuring accuracy also wants high.
But the factor of both impacts but has a lot, comprise the feature (type, intensity, sine, periodicity etc.) of striped, the attribute (equipment quality, nonlinear effect etc.) of electronic equipment, phase unwrapping package method etc.In striped type, due to traditional sine streak, be the gray scale picture of 8, its grey value profile is between 0-255, and projection speed is limited within 120HZ, constrains measuring speed; In electronic equipment attribute, due to present three-dimension measuring system, be all by the striped of DLP projection zone characteristic information, therefore, the higher hamonic wave caused by the non-linear gamma effect of electronic equipment and the measuring error caused is an inevitable problem.Pulse-length modulation striped of the present invention is scale-of-two striped, only has two gray-scale values, and its projection speed can reach 10KZH, greatly improves measuring speed; Pulse-length modulation striped of the present invention, as long as slight out of focus, the gamma that just can overcome projector is non-linear, effectively reduces phase error, improves measuring accuracy.The present invention produces based on above thinking.
Three-dimension measuring system of the present invention as shown in Figure 1, comprises DLP projector 1, CCD2, workstation 3, measures support 4, reference planes 5 and object under test 6; DLP projector 1 and CCD2 are placed on and measure on support 4; DLP projector 1, CCD2 connect workstation 3 respectively by data line; Object under test 6 is placed in reference planes 5; Image pick-up card, projection software, Survey Software is comprised in workstation 3.Striped with characteristic information focuses on and projects testee 6 surface by DLP projector 1, gathers stripe information, extract characteristic information, and carry out three-dimensional reconstruction according to special algorithm after workstation 3 processes by CCD2.DLP projector 1 optical axis and CCD2 optical axis intersect at O point.DLP projector 1 and CCD2 are sustained height, and the distance between them is
d, they to the distance of reference planes are
l 0 .The high computational formula of testee 6 is:
（1）
The frequency of sine streak wherein for reference planes generate is the continuous phase potential difference of body surface image and reference planes image corresponding point.
Summary of the invention
The present invention proposes a kind of method for three-dimensional measurement based on pulse-length modulation striped, be made up of the large key component of the coding of pulse striped, the out of focus of pulse striped and three-dimensional reconstruction three, it is characterized in that: pulse striped coding principle: generate desirable one-period by computer sinusoidal wave, frequency is f
s; Meanwhile, in same period, generate one group of trapezoidal wave, frequency is designated as f
t; These two kinds of wave modes are carried out judgement compare, generate the pulse width modulation wave of a two-value; The pulse width modulation wave of one-period is carried out the multicycle to copy; Finally, one-dimensional wave is converted to Two-dimensional Pulsed bar graph.
In one-period of the present invention, sinusoidal wave and trapezoidal wave frequency ratio is: f
s: f
t=1:10.
Trapezoidal wave in one-period of the present invention, its dutycycle and positive pulse are 0.1 with the ratio in pulse total cycle.
Value mode when sine wave of the present invention and trapezoidal wave two kinds of waveform comparison, when sine wave is less than trapezoidal wave, gets 1; When sine wave is greater than trapezoidal wave, get 0.
Of the present invention one dimension pulse width modulation wave is converted to Two-dimensional Pulsed bar graph, refers to that one dimension pulsating wave carries out periodic repetitions by row in programming.
Advantage of the present invention: (1) due to pulse striped be two-value striped, its gray-scale value only has two values (0 and 1), therefore measuring speed is fast.(2) because projector only needs slight out of focus, just can eliminate the non-linear gamma of projector, therefore not need complicated nonlinear calibration just can reduce phase error.(3) because pulse striped is by after slight out of focus, fringe contrast reduces less, therefore overcomes the problem fathomed.
Accompanying drawing explanation
Fig. 1 is three-dimension measuring system schematic diagram of the present invention.
Fig. 2 is that monocycle impulse ripple of the present invention produces schematic diagram.
Fig. 3 is monocycle impulse bar graph of the present invention.
Fig. 4 is 12 recurrent pulse bar graphs of the present invention.
Fig. 5 is 12 recurrent pulse striped out of focus figure of the present invention.
Embodiment
Illustrate below in conjunction with accompanying drawing and be described in further detail embodiments of the invention, but the present embodiment is not limited to the present invention, every employing analog structure of the present invention and similar change thereof, all should list protection scope of the present invention in.
Based on the method for three-dimensional measurement of pulse-length modulation striped, comprise the following steps:
(1) coding of pulse striped.
A. generate by computer the ideal sine wave that has four-step phase-shifting function:
(2)
Wherein, T is periodicity, and y is sinusoidal wave pixel, and s is step-length, and m is phase shift step number (=1,2,3,4).As shown in red line in Fig. 2 (a), periodicity is 1, phase shift step number is the phase shifted sinusoids of 1, and frequency is designated as f
s.
B. in same period, one group of trapezoidal wave is generated, being allocated as follows of each section of pixel in an one trapezoidal wave:
(3)
Wherein, dutycycle
zthe ratio of pulse total cycle (positive pulse with) is set to 0.1, p is a trapezoidal cycle total pixel number.
A trapezoidal wave is carried out row copy, form one group of trapezoidal wave, frequency is designated as ft(ft=10fs), its intensity is:
(4)
As shown in green line in Fig. 2 (a).
C. these two kinds of wave modes are carried out judgement by following formula to compare, generate the pulse width modulation wave of a two-value, its intensity is:
（5）
As shown in blue line in Fig. 2 (b), it is the pulse width modulation wave of one-period.
D. the pulse width modulation wave of one-period is carried out in column direction the multicycle to copy:
(6)
Here, n is the self-defined columns copied.
E. last, one-dimensional wave is converted to Two-dimensional Pulsed bar graph:
(7)
Here, n is the self-defined line number copied.
As Fig. 3, it is the pulse striped of one-period.For the pulse striped of four-step phase-shifting, only need by sine wave phase shift as stated above, trapezoidal wave does not need phase shift, can generate required pulse striped.
(2) out of focus of pulse striped.As Fig. 4, by the pulse striped in 13 cycles through projector projects on reference surface, paired pulses striped carries out appropriate out of focus, with CCD gather striped go forward side by side line frequency spectrum and sine analysis, judge that out of focus is appropriately spent.As Fig. 5, after the suitable out of focus of pulse striped, carry out the deforming stripe shooting of referenced and object modulation, and be sent in computing machine.
(3) three-dimensional reconstruction is carried out in a computer.For the striped on reference surface, obtained blocking phase place by pulse striped
, obtain reference surface continuous phase by phase unwrapping algorithm
; For the deforming stripe on object, obtained blocking phase place by pulse striped
, obtain object continuous phase by phase unwrapping algorithm
; By following formula:
(8)
Obtain continuous phase potential difference, thus utilize phase height formula:
(1)
Finally obtain the elevation information of body surface every bit.
Claims (5)
1. the method for three-dimensional measurement based on pulse-length modulation striped, be made up of the large key component of the coding of pulse striped, the out of focus of pulse striped and three-dimensional reconstruction three, it is characterized in that: pulse striped coding principle: the standard sine wave being generated one-period by computer, frequency is designated as f
s; Meanwhile, in same period, generate one group of trapezoidal wave, frequency is designated as f
t; These two kinds of wave modes are carried out judgement compare, generate the pulse width modulation wave of a two-value; The pulse width modulation wave of one-period is carried out the multicycle to copy; Finally, one dimension pulse width modulation wave is converted to Two-dimensional Pulsed bar graph.
2. a kind of method for three-dimensional measurement based on pulse-length modulation striped according to claim 1, is characterized in that: in one-period, and sinusoidal wave and trapezoidal wave frequency ratio is: f
s: f
t=1:10.
3. a kind of method for three-dimensional measurement based on pulse-length modulation striped according to claim 1, is characterized in that: the trapezoidal wave in one-period, and its dutycycle and positive pulse are 0.1 with the ratio in pulse total cycle.
4. a kind of method for three-dimensional measurement based on pulse-length modulation striped according to claim 1, is characterized in that: value mode when sine wave and trapezoidal wave two kinds of waveform comparison, when sine wave is less than trapezoidal wave, gets 1; When sine wave is greater than trapezoidal wave, get 0.
5. a kind of method for three-dimensional measurement based on pulse-length modulation striped according to claim 1, is characterized in that: one dimension pulse width modulation wave is converted to Two-dimensional Pulsed bar graph, refers to that one dimension pulsating wave carries out periodic repetitions by row in programming.
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| CN110057319A (en) * | 2019-02-20 | 2019-07-26 | 西安理工大学 | A kind of high speed three-dimensional measurement method of a wide range of reflectivity changes object |
| CN111060028A (en) * | 2019-12-23 | 2020-04-24 | 广东工业大学 | Composite sinusoidal trapezoidal stripe structured light three-dimensional measurement method |
| CN114279356A (en) * | 2021-12-09 | 2022-04-05 | 南京信息工程大学 | Gray scale stripe pattern design method for three-dimensional measurement |
| CN116858130A (en) * | 2023-05-30 | 2023-10-10 | 中国空气动力研究与发展中心低速空气动力研究所 | Three-dimensional ice shape measurement method based on pi/2 complementary double pulse width modulation mode |
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| CN114279356A (en) * | 2021-12-09 | 2022-04-05 | 南京信息工程大学 | Gray scale stripe pattern design method for three-dimensional measurement |
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| CN116858130A (en) * | 2023-05-30 | 2023-10-10 | 中国空气动力研究与发展中心低速空气动力研究所 | Three-dimensional ice shape measurement method based on pi/2 complementary double pulse width modulation mode |
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