3D Measurement Method Research Articles

Novel 3D shape measurement method with lower occlusion for the bottom of cavity

Because the bottom of the cavity has the shadow and occlusion, the angle between the projection system and imaging system is limited. So the traditional fringe projection technique based on the principle of optical triangulation is inapplicable. This Letter presents a 3D shape measurement method of using the light tube for the cavity. The method can measure an object from two opposite views at the same time, which means it will obtain two different groups of 3D data for the same object in a single measurement. The experimental results show the feasibility and validity of the 3D shape measurement method.

３Ｄ内視鏡光プローブ式精密測定方法の開発

We developed an optical OCT endoscope, which consists of ϕ1.5 mm quartz pipe with built-in two micro motors and conduct the helical 3D scanning. The method of 3D measurement of inner wall of the object is inserting the optical probe with rotating emission of the light in the hole of the object and measuring based on the outer diameter of quartz pipe. In this way, we enabled to high precision 3D measurement of under 0.2 μm variability by eliminating influence of the rotary vibration of the scanning motor and the fluctuation of the optical system of OCT. This measuring method can conduct the 3D measurement of inner wall of thin (small diameter) or deep hole, which has been conventionally impossible. In addition, calculating the eccentricity amount and the incline angle between the optical probe and an object, using the 3D shape data captured by the optical probe, and conducting the autocorrecting has allowed setting-free, and good operatability has been realized.

単眼カメラと透明平板による屈折を利用したスケール復元が可能なStructure from Motion

Structure from Motion is a popular 3D measurement method. This technique uses images captured by a single camera with motion. Structure from Motion can calculate the 3D position of objects and the camera motion simultaneously. Because of its simplicity, Structure from Motion has been implemented in various ways. However, there is an essential problem that the scale of the objects cannot be calculated by Structure from Motion. In this paper, we propose a method which solves this problem using refraction. Refraction induced by introducing a different medium results in a change in the path of a light ray. This method is implemented using only a refractive plate and a single camera. The refractive plate is placed in front of the camera. We can obtain the refractive images using this system. The results of simulations show the effectiveness of the proposed method. It is also shown that the precision of reconstruction in the proposed method is improved when the thicker refractive plate is used.

Development of 3D Measurement System Using Phase Shift Digital Holography

SUMMARYThe demand for three‐dimensional (3D) measurement technology has been increasing, but in many of the traditional 3D measurement methods, such as the method using phase shift pattern projection, it is difficult to measure the shape of specular‐reflective and transparent objects, because the power of the light reflected from specular reflective objects is too high and that from transparent objects is too low. Consequently, digital cameras cannot acquire accurate information from reflected light. Digital holography has been used as a means of resolving this problem. In traditional digital holography, the interference fringes of the light from the object being measured and the reference light can be captured by a digital camera. Using the Fresnel diffraction principle, the phase information in the light from the object being measured can be acquired and the shape of the object can be calculated by interferometry. Digital holography can be used to measure reflective and transparent objects. However, by the principle of Fresnel diffraction, dc and conjugate components exist in the calculated phase information a noises, so that the accuracy of measurements is reduced. Phase shift digital holography can remove noise by using special devices to change the phase of the reference light, but the devices are costly and the systems are complex, so that practical application of phase shift digital holography has been difficult. In this paper, we propose a new method of phase shift digital holography using the light detection principle. We also propose a digital holography reconstruction method using the convolution approach rather than the traditional Fresnel approach. The proposed method results in a compact phase shift holography system with lower cost and greater accuracy than the 3D measurement method. Therefore, the practical applications of digital holography can be realized less expensively and more accurately.

Definition of anatomical zero positions for assessing shoulder pose with 3D motion capture during bilateral abduction of the arms.

BackgroundSurgical interventions at the shoulder may alter function of the shoulder complex. Clinically, the outcome can be assessed by universal goniometry. Marker-based motion capture may not resemble these results due to differing angle definitions.MethodsThe clinical inspection of bilateral arm abduction for assessing shoulder dysfunction is performed with a marker based 3D optical measurement method. An anatomical zero position of shoulder pose is proposed to determine absolute angles according to the Neutral-0-Method as used in orthopedic context. Static shoulder positions are documented simultaneously by 3D marker tracking and universal goniometry in 8 young and healthy volunteers. Repetitive bilateral arm abduction movements of at least 150° range of motion are monitored. Similarly a subject with gleno-humeral osteoarthritis is monitored for demonstrating the feasibility of the method and to illustrate possible shoulder dysfunction effects.ResultsWith mean differences of less than 2°, the proposed anatomical zero position results in good agreement between shoulder elevation/depression angles determined by 3D marker tracking and by universal goniometry in static positions. Lesser agreement is found for shoulder pro-/retraction with systematic deviations of up to 6°. In the bilateral arm abduction movements the volunteers perform a common and specific pattern in clavicula-thoracic and gleno-humeral motion with maximum shoulder angles of 32° elevation, 5° depression and 45° protraction, respectively, whereas retraction is hardly reached. Further, they all show relevant out of (frontal) plane motion with anteversion angles of 30° in overhead position (maximum abduction). With increasing arm anteversion the shoulder is increasingly retroverted, with a maximum of 20° retroversion. The subject with gleno-humeral osteoarthritis shows overall less shoulder abduction range of motion but with increased out-of-plane movement during abduction.ConclusionsThe proposed anatomical zero definition for shoulder pose fills the missing link for determining absolute joint angles for shoulder elevation/depression and pro-/retraction. For elevation-/depression the accuracy suits clinical expectations very well with mean differences less than 2° and limits of agreement of 8.6° whereas for pro-/retraction the accuracy in individual cases may be inferior with limits of agreement of up to 24.6°. This has critically to be kept in mind when applying this concept to shoulder intervention studies.

Wire bonding 자동 전단력 검사를 위한 wire의 3차원 위치 측정 시스템 개발

The bond pull test is the most widely used technique for the evaluation and control of wire bond quality. The wire being tested is pulled upward until the wire or bond to the die or substrate breaks. The inspector test strength of wire by manually and it takes around 3 minutes to perform the test. In this paper, we develop a 3D vision system to measure 3D position of wire. It gives 3D position data of wire to move a hook into wires. The 3D measurement method to use here is a confocal imaging system. The conventional confocal imaging system is a spot scanning method which has a high resolution and good illumination efficiency. However, a conventional confocal systems has a disadvantage to perform XY axis scanning in order to achieve 3D data in given FOV (Field of View) through spot scanning. We propose a method to improve a parallel mode confocal system using a micro-lens and pin-hole array to remove XY scan. 2D imaging system can detect 2D location of wire and it can reduce time to measure 3D position of wire. In the experimental results, the proposed system can measure 3D position of wire with reasonable accuracy.

Unidirectional Fabric Drape Testing Method

In most cases, fabrics such as curtains, skirts, suit pants and so on are draped under their own gravity parallel to fabric plane while the gravity is perpendicular to fabric plane in traditional drape testing method. As a result, it does not conform to actual situation and the test data is not convincing enough. To overcome this problem, this paper presents a novel method which simulates the real mechanical conditions and ensures the gravity is parallel to the fabric plane. This method applied a low-cost Kinect Sensor device to capture the 3-dimensional (3D) drape profile, thus we obtained the drape degree parameters and aesthetic parameters by 3D reconstruction and image processing and analysis techniques. The experiment was conducted on our self-devised drape-testing instrument by choosing different kinds of weave structure fabrics as our testing samples and the results were compared with those of traditional method and subjective evaluation. Through regression and correlation analysis we found that this novel testing method was significantly correlated with the traditional and subjective evaluation method. We achieved a new, non-contact 3D measurement method for drape testing, namely unidirectional fabric drape testing method. This method is more suitable for evaluating drape behavior because it is more in line with actual mechanical conditions of draped fabrics and has a well consistency with the requirements of visual and aesthetic style of fabrics.

Measuring the 3D shape of high temperature objects using blue sinusoidal structured light

The visible light radiated by some high temperature objects (less than 1200 °C) almost lies in the red and infrared waves. It will interfere with structured light projected on a forging surface if phase measurement profilometry (PMP) is used to measure the shapes of objects. In order to obtain a clear deformed pattern image, a 3D measurement method based on blue sinusoidal structured light is proposed in this present work. Moreover, a method for filtering deformed pattern images is presented for correction of the unwrapping phase. Blue sinusoidal phase-shifting fringe pattern images are projected on the surface by a digital light processing (DLP) projector, and then the deformed patterns are captured by a 3-CCD camera. The deformed pattern images are separated into R, G and B color components by the software. The B color images filtered by a low-pass filter are used to calculate the fringe order. Consequently, the 3D shape of a high temperature object is obtained by the unwrapping phase and the calibration parameter matrixes of the DLP projector and 3-CCD camera. The experimental results show that the unwrapping phase is completely corrected with the filtering method by removing the high frequency noise from the first harmonic of the B color images. The measurement system can complete the measurement in a few seconds with a relative error of less than 1 : 1000.

A two-level space-time color-coding method for 3D measurements using structured light

Color-coding methods have significantly improved the measurement efficiency of structured light systems. However, some problems, such as color crosstalk and chromatic aberration, decrease the measurement accuracy of the system. A two-level space-time color-coding method is thus proposed in this paper. The method, which includes a space-code level and a time-code level, is shown to be reliable and efficient. The influence of chromatic aberration is completely mitigated when using this method. Additionally, a self-adaptive windowed Fourier transform is used to eliminate all color crosstalk components. Theoretical analyses and experiments have shown that the proposed coding method solves the problems of color crosstalk and chromatic aberration effectively. Additionally, the method guarantees high measurement accuracy which is very close to the measurement accuracy using monochromatic coded patterns.

Measurement in the angiography suite: evaluation of vessel sizing techniques

BackgroundAccurate vessel size measurement is important for neurointervention. Modern angiographic equipment offers various two-dimensional (2D) and 3D measurement methods that have not been systematically evaluated for accuracy and reliability.ObjectiveTo evaluate...

Large-scale three-dimensional measurement via combining 3D scanner and laser rangefinder.

This paper presents a three-dimensional (3D) measurement method of large-scale objects by integrating a 3D scanner and a laser rangefinder. The 3D scanner, used to perform partial section measurement, is fixed on a robotic arm which can slide on a guide rail. The laser rangefinder, used to compute poses of the 3D scanner, is rigidly connected to the 3D scanner. During large-scale measurement, after measuring a partial section, the 3D scanner is straightly moved forward along the guide rail to measure another section. Meanwhile, the poses of the 3D scanner are estimated according to its moved distance for different partial section alignments. The performance and effectiveness are evaluated by experiments.

Precise measurement of three-dimensional positions of transparent ellipsoidal particles using digital holographic microscopy.

The dynamic motions of various particles suspended in microscale flows are essential phenomena in the scientific and engineering fields. These motions can be precisely measured by using 3D quantitative flow visualization techniques. Moreover, most cells and particles in nature possess a nonspherical shape. Digital holographic microscopy (DHM) is employed to measure the 3D positional information of transparent ellipsoidal particles. Both in-plane and out-of-plane positional information are obtained by analyzing the distinctive light scattering from the microsized ellipsoidal particles. The performance of the 3D position measurement method is experimentally verified for ellipsoidal particles seeded in a planar surface and a microtube. This DHM technique exhibits promising potential in the dynamic analysis of ellipsoidal particles and cells suspended in various microscale fluid flows.

Simultaneous 3D temperature and velocity field measurements of micro-flow with laser-induced fluorescence and micro-digital holographic particle tracking velocimetry: Numerical study

We propose a method for simultaneous 3D temperature and velocity measurement of a micro-flow field. The 3D temperature field is characterized with two-color laser-induced fluorescence particles which are tracked with micro-digital holographic particle tracking velocimetry. A diffraction-based model is applied to analyze defocused particles to determine the intensity ratio of two fluorescent dyes on the particle. The model is validated with experimental images. As the result shows that the intensity ratio nearly remains unchanged with respect to depth positions, defocused particles can be used as 3D temperature sensors. Numerical work is carried out to check the method, and 3D temperature and velocity field in a 120 \mu m \times 120 \mu m \times 80 \mu m test volume are retrieved.

ワンショットデジタルホログラフィによる赤血球の三次元計測

In these years, because of applications for medical analysis, such as biopsy, demand of 3D microscope is arising. Typical existing 3D microscopes are Scanning Electron Microscope (SEM) and confocal laser scanning microscopy (CLSM). SEM is a type of electron microscope that produces images of an object by scanning it with a focused beam of electrons. The electrons interact with atoms in the object, producing various signals that can be detected and that contain information about the sample’s surface topography and composition. However, SEM needs a vacuum system during measurement, and it is big size and price high. CLSM is a technique for obtaining high-resolution optical images with depth selectivity. It is its ability to acquire in-focus images from selected depths, a process known as optical sectioning. Images are acquired point-by-point and reconstructed with a computer, allowing 3D reconstructions of topologically complex objects. However, 3D measurement using CLSM is time consuming because it has to scan an object point-by-point, and 3D measurement accuracy of CLSM is about 1μm which is difficult to measure nano-structure objects. To resolve problems in existing 3D microscopes, 3D microscope using single-shot phase-shift digital holography is proposed in this paper. In proposal 3D microscope, at first, a Michelson interferometer and general optical components are used, so reduction in system size and price-down can be realized easily. Second, the proposal 3D measurement method, single-shot phase-shift digital holography, uses Fourier-transform method of fringe-pattern which has been used for interferometry originally. Using the proposal method, 3D shape of an object can be measured in real-time(60ms) with 5.5nm accuracy in height direction and 0.59μm resolution in XY plane. Finally, 3D shapes of human red blood cells are measured in measurement experiment. According to result of experiment, we conclude that the proposed 3D microscope can be applied to the field of precision medical analysis.

2A1-R04 透明平板による屈折を利用した単眼力メラでのスケール復元が可能なStructure from Motion

Structure from Motion is one of the 3D measurement methods. This technique requires only a single camera, and reconstructs the objects from pictures obtained by the camera with moving. However there is an essential problem that the scale of the objects cannot be computed by Structure from Motion. In order to solve this problem, we have proposed scale-reconstructable Structure from Motion using refraction. The refractive plate is placed in front of a camera to generate the refraction. The nomal of the refractive plate is required to be the same direction of the camera axis in the previous study. This is a limitation when the camera and the refractive plate are set. In this paper, we propose the method that the plate is not required to be placed orthogonal to the optical axis of camera. Therefore the setting of a camera and a refractive plate is more flexible than previous method.

Measurement of 3D Printed Structure Using a Peak Detection Method in Dispersive Interferometry

We describe an optical three dimensional (3D) measurement method using white-light dispersive interferometry in the range of 5 μm–150 μm. A spectrometer was employed for real-time wavelength scanning and the distance information was obtained using a simple peak detection method in the spectral domain. Fast measurement time enabled us real-time distance measurement of the specimen. The piezoelectric actuator and capacitance distance sensor was employed for nanometer positioning and measuring distance reference value. This technique can be implemented as a distance measurement unit in white-light scanning interferometry by simply attaching a spectrometer to the conventional system. The results showed an accuracy of better than 60 nm for any position within 5 μm–150 μm. The proposed technique can be used as shape-measuring tool for 3D printed products. Measurement results using the proposed method are also presented. These experimental results show that pthe roposed method can be used as a measurement tool for 3D printed products.

Application of the digital phase-shifting method in 3D deformation measurement at micro-scale by SEM

There have been many approaches for three-dimensional (3D) deformation measurement at the macro-scale, but these methods are mostly not applicable to 3D deformation measurement at the micro-scale due to the low resolution. With the broad application of the scanning electron microscope (SEM) at micro-scale measurement, in-situ deformation measurement under SEM has been made feasible. The 3D deformation measurement method based on digital phase shifting and the SEM system is proposed in this paper. In the proposed method, two SEM images of a specimen grating at different tilting angles are required to solve the in-plane and out-of-plane displacement. The digital generated reference grating is superimposed with the SEM images of a the specimen grating at different tilting angles to form the digital moiré. Using the digital phase-shifting method, the phase information of the grating at different tilting angles can be acquired. With the derived relationship between the phase of the grating at different tilting angles and the in-plane and out-of-plane displacement, 3D displacement can be obtained. To verify the feasibility and assess the accuracy, a numerical experiment is conducted to reverse the given in-plane and out-of-plane deformation. The proposed method is used to measure the out-of-plane deformation of aluminum film on a soft substrate. The successful results indicate that this method is feasible and has the potential to be applied in 3D deformation measurement at micro-scale.

Novel approach to development of direct volume rendering algorithms based on visualization quality assessment

A novel approach to the development of direct volume rendering algorithms is proposed. The approach is based on the assessment of the visualization quality. Analysis of rendering artifacts and various assessment methods is done using 3D reconstructed medical tomograms as test datasets. Analysis of the previous research on methods of 3D visualization quality assessment and quality improvement is presented. 3D visualization artifacts and quality measurement method (quantitative estimation) is proposed. The method does not require any ground truth image; hence, it is a universal approach to measure the quality of the 3D-reconstruction by any ray casting technique. The method is based on generation of the reference image as a mathematical expectation for a set of 3D visualizations obtained via the jittering technique. Start position of the rays are being shifted randomly towards their directions. To estimate the deviation of a pixel value from mathematical expectation, we use PSNR metrics, which is traditional metrics in signal and image processing and measures deviation in the decibel scale. The conditions of a proper use of the technique are discussed. A new virtual samplings method with preintegration is proposed to reduce sampling artifacts in the ray casting algorithm. The novelty of the method consists in using pre-integrated classification instead of post-classification in the virtual sampling method. A novel approach to 3D visualization algorithms development based on analysis of a ray casting method in quality-performance space is demonstrated by comparing the state-of-the-art ray casting methods and the proposed method. The comparative analysis revealed an advantage of the classical pre-integrated method in the case of using trilinear filtering without local shading. It also showed the advantage of the proposed virtual sampling method with pre-integration in the case of using tricubic filtering with local lighting.

Three-dimensional inline inspection for substrate warpage and ball grid array coplanarity using stereo vision.

We present a method for full-field 3D measurement of substrate warpage and ball grid array coplanarity, which is suitable for inline back-end inspection and process monitoring. For evaluating the performance of the proposed system, the linearity between our system and a reference confocal microscope is studied by repeating measurements 35 times with a particular substrate sample (38 mm×28.5 mm). The point-to-point correlation coefficient with 1σ between two methods is 0.968±0.002, and the 2σ difference is 25.15±0.20 μm for warpage measurement. 1σ repeatability of the substrate warpage is 4.2 μm. For BGA coplanarity inspection the bump level correlation coefficient is 0.957±0.001 and the 2σ difference is 28.79±0.14 μm. 1σ repeatability of BGA coplanarity is 3.7 μm. Data acquisition takes about 0.2 s for full field measurements.

An Out-of-Plane Motion Compensation Strategy for Improving Material Parameter Estimation Accuracy with 2D Field Measurements

In-plane surface displacements, when measured with 2D Digital Image Correlation (2D-DIC), are very sensitive to out-of-plane displacement components. Any out-of-plane motion of the surface can pollute the measured field by introducing artificial displacements. These displacements are difficult to separate from the underlying response of the surface and thereby limit the application of 2D-DIC in inverse problems where the test specimen has significant motion in the out-of-plane direction. In the context of inverse problems, we propose to partially relax this condition of no out-of-plane motion in 2D-DIC. With this approach, only the out-of-plane rigid-body motion of the specimen surface, which is initially in-plane, needs to be avoided while the requirement of surface deformations to be primarily in-plane is essentially waived. Compensation, based on the pinhole camera model, for out-of-plane displacements of the surface in response to applied load is included within the error function of the minimization problem. The improvements in material parameter estimation, obtained by using the proposed compensation strategy, are demonstrated by an example. The proposed technique makes it possible to utilize 2D-DIC with a simple conventional lens for an increased number of inverse problems; and in the process avoiding the computational and experimental difficulties associated with 3D measurement methods as well as the high cost and magnification limitations of a telecentric lens.