EP1946041A1 - Système de mesure pour objets en trois dimensions - Google Patents

Système de mesure pour objets en trois dimensions

Info

Publication number
EP1946041A1
EP1946041A1 EP06829021A EP06829021A EP1946041A1 EP 1946041 A1 EP1946041 A1 EP 1946041A1 EP 06829021 A EP06829021 A EP 06829021A EP 06829021 A EP06829021 A EP 06829021A EP 1946041 A1 EP1946041 A1 EP 1946041A1
Authority
EP
European Patent Office
Prior art keywords
light
light modulator
switching
control circuit
dark
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06829021A
Other languages
German (de)
English (en)
Inventor
Jörg FRIEMEL
Frank Fuhrmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ASMPT GmbH and Co KG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP1946041A1 publication Critical patent/EP1946041A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G01B11/2513—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object with several lines being projected in more than one direction, e.g. grids, patterns
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/02—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the intensity of light
    • G02B26/04—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the intensity of light by periodically varying the intensity of light, e.g. using choppers

Definitions

  • the invention relates to a three-dimensional object measurement system with a strip projector for generating a strip-shaped light pattern on an object to be measured, the strip projector comprising a light source and a liquid crystal light modulator with a matrix-shaped arrangement of light and dark controllable pixels, and with an electronic camera for recording Images of the illuminated object with the light pattern.
  • Such surveying systems are used for the three-dimensional measurement of the shape of surfaces of arbitrary measuring objects.
  • Such craver horrssysteme which are also referred to as a 3D scanner, work according to the triangulation method, as z. B. in DE 195 11 160 A1 is described.
  • an optical sensor is an arrangement of a strip projector with a liquid crystal element (LCD) and an electronic camera is used.
  • a strip projector By means of the strip projector, a light pattern consisting of a plurality of light stripes is projected onto the object to be measured. At a predeterminable angle with respect to the direction of projection, a two-dimensional image of the object illuminated with the stripe pattern is recorded by means of the electronic camera.
  • the three-dimensional profile of the object is then deduced by evaluating the image by means of a computer.
  • a computer In order to be able to determine the three-dimensional shape of the object in a unique manner, it is often necessary to take a plurality of images, wherein the object is illuminated with different stripe patterns.
  • Commercially available LCD microdisplays such as are also used in video projectors, are used as light modulators in known object measurement systems. Such LCD elements can disadvantageously only produce a few gray scale levels. In addition, the precision and reproducibility in the generation of gray levels often leaves much to be desired. The accuracy in generating the gray value levels is sufficient for video projection purposes. In the three-dimensional object measurement, however, the achievable measurement accuracy depends directly on the precision of the intensity distribution of the light pattern generated by means of the strip projector. Thus, known three-dimensional object measurement systems that work with LCD microdisplays have the disadvantage of low measurement accuracy.
  • Image the pixels of the light modulator are switched between light and dark, the timing of the switching of the pixels is synchronized with the image recording.
  • the pixels of the light modulator are driven binary by means of the control circuit. This means that each pixel is only switched between the states light and dark. Different gray levels are generated by switching between light and dark during the exposure time of an image by means of the electronic camera. During the exposure time, the electronic camera integrates the light intensity so that the gray value for each pixel results from the ratio of the respective bright and dark times.
  • the switching times of the liquid-crystal light modulator play a decisive role. With switching times those times are meant that pass from light to dark or from dark to light when switching a pixel of the light modulator.
  • the pixels do not change their state abruptly from light to dark or from dark to light, instead the pixels have an asymptotic switching process.
  • the switching times of modern LCD elements are in the range of a few milliseconds.
  • the long switching times are based on the comparatively high viscosity of the liquid crystals.
  • the viscosity in turn depends strongly on the ambient temperature.
  • the time profile of the switching of the image dots is synchronized with the image recording. In this way a good reproducibility in the generation of the gray values is ensured.
  • the reproducibility is not affected by the highly dependent on environmental influences switching times of the pixels.
  • control circuit according to the invention is arranged in such a way that each pixel of the light modulator is in a predetermined switching state at the beginning of each image acquisition. It is known that in LCD light modulators the switching times for switching from light to dark and for switching from dark to bright can be very different. In view of the desired reproducibility in the generation of the gray values, it is therefore useful if the pixels of the light modulator at the beginning of each image recording in the same predetermined switching state (light or dark) are.
  • a switching time for switching between light and dark is determined by means of the control circuit for each pixel of the light modulator in accordance with a given gray value for this pixel taking into account the switching times of the light modulator.
  • the gray value for each pixel results from the ratio of the light and dark times. This relationship can be through appropriate Specification of the changeover time to be influenced. Since during the exposure time the light intensity for each pixel is integrated by means of the electronic camera, the exact gray value also depends on the switching times of the light modulator due to the described asymptotic switching course of the pixels.
  • each pixel of the light modulator is switched after the beginning of the exposure time when reaching the switching between light and dark. This is then the synchronization according to the invention of the time course of the switching of the pixels with the image recording.
  • the switching times of the light modulator depend, as mentioned above, on environmental influences, such as temperature. It therefore makes sense to provide a light sensor connected to the control circuit in the system according to the invention, wherein the control circuit is adapted to calibrate the switching times of the light modulator based on the sensor signal of the light sensor.
  • the light sensor enables a comparison of the actually emitted light intensity with the respectively desired gray value. From this comparison can be deduced the switching times of the light modulator. These can then be taken into account in the actual measurement process for determining the switching times of the pixels.
  • control circuit of the object measuring system is expediently set up in such a way that a strip-shaped light pattern with sinusoidal gray value profile is generated transversely to the strip direction by means of the strip projector. From such a light pattern can be particularly close to the three-dimensional shape of the object to be measured according to the principle of triangulation.
  • Phase of the sinusoidal gray value curve be variable. It can then be taken several pictures with different phase angles to to obtain clear information regarding the three-dimensional shape of the object.
  • the light modulator of the object measurement system may be a so-called LCOS microdisplay.
  • LCOS means "liquid crystal on silicon”.
  • LCOS microdisplays consist of a support made of silicon, which also serves as a light-reflecting mirror. On this support is a thin coating of liquid crystals. The arrangement is covered by a thin pane of glass.
  • LCOS microdisplays are commercially available as mass products at relatively low cost and can be used with advantage according to the invention.
  • the functional principle of the object measuring system according to the invention with regard to the synchronization of the time profile of the switching of the pixels with the image recording is independent of whether the pixels are switched from light to dark or dark to light during image acquisition. Switching between light and dark therefore, in the context of the invention, involves both switching from light to dark and from dark to light. Multiple switching operations during the exposure time are also possible.
  • FIG. 1 representation of a rever horrssystems invention as a block diagram
  • Fig. 2 temporal course of the control of the light modulator according to the invention.
  • the three-dimensional object measurement system is designated overall by the reference numeral 1.
  • An essential element of the object measurement system 1 is a strip projector 2 for producing a strip-shaped light pattern on an object 3 to be measured.
  • the strip projector 2 comprises a light source 4, from whose light a liquid crystal light modulator 5 is illuminated.
  • the liquid crystal light modulator 5 is an LCOS microdisplay with a matrix-like arrangement of light and dark controllable pixels.
  • the object measurement system 1 has an electronic camera 6. By means of the electronic camera 6, images of the object 3 illuminated with the light pattern are recorded.
  • An evaluation computer 7 evaluates the recorded images and calculates therefrom the three-dimensional shape of the object 3. As can also be seen in FIG.
  • the fringe projector 2 and the electronic camera 6 are controlled by means of a control circuit 8.
  • This is according to the invention set up such that during the exposure time of an image, the pixels of the light modulator 5 are switched between light and dark, wherein the timing of the switching of the pixels is synchronized with the image recording. This is done z. B. in such a way that all pixels of the light modulator 5 by means of the control circuit 8 in a predetermined switching state (eg bright) are switched before the start of image acquisition.
  • a predetermined switching state eg bright
  • the strip projector 2 is assigned a light sensor 9. This is connected to the control circuit 8.
  • the light sensor 9 is used to calibrate the switching times of the light modulator 5. The switching times of the light modulator 5 can then be taken into account when determining the switching times corresponding to the gray values desired for the individual pixels.
  • the temporal switching course S is a
  • Pixel of the light modulator 5 shown as an example.
  • the diagram shows the time course of the control signal B of the electronic camera 6.
  • the image recording begins at the time T A entered in the diagram.
  • the pixel is switched to light.
  • the signal B is activated. It begins the exposure of the image and the camera 6 integrates the light intensity of the pixel.
  • the pixel is switched from light to dark according to the desired gray value.
  • the brightness of the pixel does not change abruptly, but falls during the switching time t
  • a time interval t d elapses.
  • the gray value of the pixel thus depends on the four time values th, ti, t d and t b .
  • the control signal B of the camera 6 drops.
  • the pixel is switched back to the bright state.
  • the pixel approaches the bright state asymptotically during the switching time t 2 .
  • the next image is taken, the gray value being different according to a now changed light pattern.
  • any desired gray value can be generated for each pixel by appropriate specification of the light and dark times t h and t d .

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Optics & Photonics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

L’invention concerne un système (1) de mesure d’objet en trois dimensions pourvu d’un projecteur à bande (2) permettant de réaliser un modèle de lumière en forme de bande sur un objet (3) à mesurer, le projecteur à bande (2) comportant une source de lumière (4) et un modulateur de lumière (5) à cristaux liquides de configuration matricielle de pixels pouvant être clairs et sombres, et d’une caméra électronique (6) pour prendre les images de l’objet (3) éclairé par le modèle de lumière. Pour obtenir une grande précision de mesure, le projecteur à bande (2) et la caméra électronique (6) sont commandes selon l'invention par un circuit de commande (8), configuré de telle sorte que pendant le temps d’éclairage d’une image les pixels du modulateur de lumière (5) passent de clairs à sombres et vice-versa, la séquence temporelle de commutation des pixels étant synchronisée à la prise de vue.
EP06829021A 2005-11-11 2006-11-13 Système de mesure pour objets en trois dimensions Withdrawn EP1946041A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102005054337A DE102005054337A1 (de) 2005-11-11 2005-11-11 Dreidimensionales Objektvermessungssystem
PCT/EP2006/010855 WO2007054351A1 (fr) 2005-11-11 2006-11-13 Système de mesure pour objets en trois dimensions

Publications (1)

Publication Number Publication Date
EP1946041A1 true EP1946041A1 (fr) 2008-07-23

Family

ID=37734357

Family Applications (1)

Application Number Title Priority Date Filing Date
EP06829021A Withdrawn EP1946041A1 (fr) 2005-11-11 2006-11-13 Système de mesure pour objets en trois dimensions

Country Status (5)

Country Link
EP (1) EP1946041A1 (fr)
KR (1) KR20080068111A (fr)
CN (1) CN101305260A (fr)
DE (1) DE102005054337A1 (fr)
WO (1) WO2007054351A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100947463B1 (ko) * 2007-08-31 2010-03-17 에스엔유 프리시젼 주식회사 엘시디를 이용한 삼차원 형상 측정장치
CN101451826B (zh) * 2008-12-17 2010-06-09 中国科学院上海光学精密机械研究所 物体三维轮廓测量装置及测量方法
WO2012091238A1 (fr) * 2010-12-29 2012-07-05 주식회사 포디컬쳐 Système d'analyse tridimensionnelle
CN103649677A (zh) * 2011-07-13 2014-03-19 法罗技术股份有限公司 利用空间光调制器来查找物体的三维坐标的装置和方法
CN105783712B (zh) * 2014-12-26 2018-11-27 北京中电科电子装备有限公司 一种检测刀痕的方法及装置
EP3101383A1 (fr) * 2015-06-01 2016-12-07 Canon Kabushiki Kaisha Appareil de mesure de forme, procédé de calcul de forme, système et procédé de fabrication d'articles
CN108982502B (zh) * 2018-07-30 2021-03-02 华中科技大学苏州脑空间信息研究院 一种基于梯度反射的多层信号共面并行探测装置
CN109831598B (zh) * 2019-02-13 2021-08-31 盎锐（上海）信息科技有限公司 用于投影光栅建模的相机设置方法及装置

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DE9301901U1 (de) * 1993-02-11 1993-04-01 Fa. Carl Zeiss, 7920 Heidenheim Vorrichtung zur Topographiemessung mittels projizierter Muster
DE19641168A1 (de) * 1996-10-08 1998-04-09 Wolf Henning Vorrichtung zur Erfassung der Form von Objekten
DE19749435B4 (de) * 1997-11-09 2005-06-02 Mähner, Bernward Verfahren und Vorrichtung zur dreidimensionalen, flächenhaften, optischen Vermessung von Objekten
DE19753246C2 (de) * 1997-12-01 2002-11-28 Roland Seifert Vorrichtung zur Bestimmung von dreidimensionalen Daten von Objekten
US20040125205A1 (en) * 2002-12-05 2004-07-01 Geng Z. Jason System and a method for high speed three-dimensional imaging
US20040184653A1 (en) * 2003-03-20 2004-09-23 Baer Richard L. Optical inspection system, illumination apparatus and method for use in imaging specular objects based on illumination gradients

Non-Patent Citations (1)

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Title
See references of WO2007054351A1 *

Also Published As

Publication number Publication date
WO2007054351A1 (fr) 2007-05-18
CN101305260A (zh) 2008-11-12
KR20080068111A (ko) 2008-07-22
DE102005054337A1 (de) 2007-05-16

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