Figure - available from: Optics Express
This content is subject to copyright. Terms and conditions apply.
The result of reconstructed model. (a) The measured 3D-printed model; (b) The measured 3D-printed model with stripe; (c) The reconstructed model.
Source publication
Micro-Electro-Mechanical System (MEMS) scanning is increasingly popular in 3D surface measurement with the merits of the compact structure and high frame-rate. In this paper, we achieve real-time fringe structured 3D reconstruction by using a uniaxial MEMS-based projector. To overcome the limitations on uniaxial MEMS-based projector of lensless str...
Similar publications
Microelectromechanical system (MEMS) mirror based laser beam scanning (LBS) projectors for fringe projection profilometry (FPP) are becoming increasingly popular attributing to their small size and low cost. However, the initial phase of the scanning MEMS mirror employed in an LBS projector may vary over time, resulting in unstable and distorted fr...
Citations
... There are numerous ways to generate sinusoidal fringes in PSP. Such as mechanically moving gratings [11][12][13], laser interferometric fringe [14][15][16][17], digital fringe projection [18][19][20][21][22], optical channel switching [23][24][25], and MEMS scanning [26][27][28][29], and additional methods proposed in recent years [30][31][32]. A common technique is proposed to generate fringe patterns that are free of speckle noise and have a long depth of field by utilizing a beam splitter cube and LED sources, However, the effective distance for interference is limited by the tilt angle of the beam splitter cube [33]. ...
Among numerous mature optical 3D measurement techniques, phase-shift profilometry (PSP) has been widely used because of its high precision and insensitivity to ambient light, and high-speed PSP has become a research hotspot in recent years. Current mainstream high-frame rate PSP projection techniques employ binary defocusing projection schemes, which limit the available measurement depth. We propose a high-frame rate, large-depth-range sinusoidal fringe projection technique based on step-designed LED chips array. In principle, on the one hand, the LED chips array still produces a binary pattern, so high-frame rate switching can be achieved, on the other hand, whether focusing or defocusing can generate sinusoidal fringes, avoiding the limit of defocusing projection on the depth range of measurement. A PSP projector is designed and manufactured, and 3D reconstruction of static human face mask and dynamic rotating fan is carried out at 1 kHz frame rate. In another experiment, the PSP projector projected the fringes at a 100kHz frame rate and detected the fringes with a single point photodetector, and the output waveform showed that the projection technique had the potential to be much higher than the 100 kHz frame rate. These results show that the PSP projection technology has the advantages of high-frame rate and large-depth-range, and is very useful for three-dimensional measurement of moving targets.
... Since the calibration of a FPP system determines in which form the 3D reconstruction is carried out, it is closely related to the accuracy of the reconstruction and can affect the range of measurement to a certain extent. Different calibration strategies [14][15][16][17][18] have been widely and deeply investigated. Currently, there are mainly two classical calibration technology routes, including the stereo-vision-based calibration method and the phasecoordinate mapping model-based calibration method [16]. ...
... In addition, this type of method requires more computational resources for homologous point matching, which limits the extended use of this method. In the phase-coordinate mapping model [14,15,21,22], the coordinates X, Y, and Z can be directly obtained by bringing the absolute phase into a pre-calibrated function, which does not require orthogonal phases and thus is still applicable in FPP systems composed of MEMS-mirror-based projectors. ...
... Initially, the coordinates of these known points were represented in the world coordinate system, which meant that precise translation stages were needed to control the transformation of their coordinates, and these points were clearly always on the calibration board. Some existing methods [14,15] have relaxed restrictions and do not require precision translation stages or gage blocks for calibration. The coordinates of these points appear in the camera coordinate system, and they need to provide raw calibration data for the fitting of the phase-coordinate mapping model together with the phase of the corresponding pixels on the calibration board plane. ...
Currently, 3D reconstruction methods in structured light are generally implemented in a pre-calibrated area. To realize a full-field reconstruction, the calibration plate can be moved to multiple positions in a time-consuming manner, or the whole field can be calibrated with the help of a large calibration plate, which is more costly. In this paper, we address this problem by proposing a method for obtaining a global phase-angle model under a locally calibrated region, and based on this relationship, we investigate and analyze the reconstruction inside and outside of the calibrated zone. The results show that the method can reconstruct the object outside of the calibration zone completely, and can keep the planarity error around 0.1 mm and the sphericity error below 0.06 mm. The method only requires local calibration of the projected fringes at the two calibration positions to realize the 3D reconstruction of the full-field, which makes the method more advantageous.
... MEMS projector mainly consists of a laser diode, a Powell lens and a MEMS mirror. It is a typical optical micro-electro-mechanical device that allows the incident beam to be reflected in a specific manner and time sequence to achieve scanning imaging on the image plane [8]. Since MEMS mirror can form two-dimensional structured light field with alternating light and dark through the one-dimensional oscillation and scanning, most phase-based algorithms using the DFP projector can be easily reproduced by it [9][10][11]. ...
In this paper, a compact, cost-effective, and fast translational online-switchable phase-shifting fringe (TOPF) projector is designed and fabricated for high accuracy three-dimensional (3D) face imaging. Compared with the conventional mechanical projectors, the main difference is that it utilizes a translational approach instead of a rotational one to achieve a better balance in terms of size, speed, accuracy, and cost. To mitigate the inconsistency of the motor's step size and ensure the stability of phase-shifting, an optical encoder-based feedback control mechanism is employed. Additionally, to address the random phase shift errors induced by mechanical motion, a fast, generalized phase-shifting algorithm with unknown phase shifts (uPSAs) that can calculate arbitrary phase shifts is proposed. Finally, a 3D imaging system consisting of the TOPF projector and two cameras is constructed for experimental validation. The feasibility, effectiveness, and precision of our proposed method are substantiated through the reconstruction of a static facial model and a dynamic real face.
... With remarkable advantages of non-contact, high accuracy, high speed, and dense data capture, binocular structured light three-dimensional (3D) measurement has found widespread applications in diverse fields such as industrial inspection, intelligent manufacturing, cultural heritage preservation, and medical diagnostics [1][2][3][4][5][6]. Phase encoding information from fringe projection is often used to generate active features for robust and accurate 3D reconstruction [7,8]. Traditionally, unidirectional phase information is combined with the epipolar geometry to guarantee uniform constraints for corresponding point searching [9][10][11][12]. ...
The binocular structured light 3D measurement system is widely used in situ industrial inspection and shape measurement, where the system structure is generally unstable due to mechanical loosening or environmental disturbance. Timely corrections to the changing structural parameters thus is an essential task for online high-accuracy measurement, which is difficult for traditional unidirectional fringe projection methods to self-correct the structural change. To this end, we propose an online self-correction method based on the investigation that orthogonal fringe projection can intrinsically relax the constraint on the epipolar geometry relationship and provide bidirectional phases for accurate corresponding point searching. Since orthogonal fringe projection may sacrifice the measurement efficiency, we further design a searching strategy by locally unwrapping one directional phase to reduce the number of projection patterns. Experimental results demonstrate that the proposed method is effective for online self-correction of unstable system structure to achieve high-accuracy 3D measurement under complex measurement environments.
... To meet that demand, as a key component in PSP, the projector used to generate the phase-shifting sinusoidal fringes must be ultra-small (several millimeters in size), low-cost, and simple-to-control. Reviewing the history of PSP research, various phase-shifted fringe projection techniques have been employed, including mechanically moving gratings [16][17][18], laser interferometric fringe [19][20][21][22], digital fringe projection [23][24][25][26][27][28], optical channel switching [29][30][31], and MEMS scanning [32][33][34][35], etc. In these projection techniques, although some projectors have ultra-small projection optical device, the supporting control components are relatively complex, resulting in large overall sizes and elevated costs. ...
Demand for ultra-small, inexpensive, and high-accurate 3D shape measurement devices is growing rapidly, especially in the industrial and consumer electronics sectors. Phase shifting profilometry (PSP) is a powerful candidate due to its advantages of high accuracy, great resolution, and insensitivity to ambient light. As a key component in PSP, the projector used to generate the phase-shifting sinusoidal fringes must be ultra-small (several millimeters), low-cost, and simple to control. However, existing projection methods make it difficult to meet these requirements simultaneously. In this paper, we present a modern technique that can be used to fabricate the desired projector. A specifically designed device based on segmented liquid crystal display (SLCD) technology is used to display the projected patterns, and a cylindrical lens is used as the projection lens. The SLCD device can display four sets of specific filled binary patterns, each yielding a sinusoidal fringe, and all four sinusoidal fringes satisfy the four-step phase shift relation. 3D shape measurement experiments verify the performance of the projector. Considering that the size of SLCD devices can be reduced to a few millimeters, the proposed technique can be easily used to manufacture ultra-small, low-cost, and simple-to-control PSP projectors.
... Microelectromechanical system (MEMS) scanning micromirrors have recently attracted broad interest due to their potential applications in LiDAR 1,2 , 3D cameras [3][4][5] , and VR/AR [6][7][8] . Several types of MEMS micromirrors exist, including electromagnetic, electrostatic, and electrothermal micromirrors 9,10 . ...
Electrothermal bimorph-based scanning micromirrors typically employ standard silicon dioxide (SiO 2 ) as the electrothermal isolation material. However, due to the brittle nature of SiO 2 , such micromirrors may be incapable to survive even slight collisions, which greatly limits their application range. To improve the robustness of electrothermal micromirrors, a polymer material is incorporated and partially replaces SiO 2 as the electrothermal isolation and anchor material. In particular, photosensitive polyimide (PSPI) is used, which also simplifies the fabrication process. Here, PSPI-based electrothermal micromirrors have been designed, fabricated, and tested. The PSPI-type micromirrors achieved an optical scan angle of ±19.6° and a vertical displacement of 370 μm at only 4 Vdc. With a mirror aperture size of 1 mm × 1 mm, the PSPI-type micromirrors survived over 200 g accelerations from either vertical or lateral directions in impact experiments. In the drop test, the PSPI-type micromirrors survived falls to a hard floor from heights up to 21 cm. In the standard frequency sweeping vibration test, the PSPI-type micromirrors survived 21 g and 29 g acceleration in the vertical and lateral vibrations, respectively. In all these tests, the PSPI-type micromirrors demonstrated at least 4 times better robustness than SiO 2 -type micromirrors fabricated in the same batch.
... Microelectromechanical system (MEMS) scanners offer high resolution, with unprecedented speed, and form factor in comparison to other scanning counterparts such as galvanometers and polygon mirrors [1,2]. Such inherent advantages have leveraged the use of MEMS scanners in display systems [3,4], spectrometers [5][6][7], profilometry [8][9][10], and biomedical imaging devices [11][12][13]. ...
We present and demonstrate a cascaded laser scan architecture to achieve a threefold gain in scan angle. We cascaded multiple piezoelectric MEMS scanners using a high numerical aperture relay lens pair in between scanners, which are located at optical conjugate planes. The cascaded scan architecture comprising 3 scanners is simulated using ray-tracing software. Finally, we conduct experiments using the folded architecture, where the incoming laser beam bounces off the first scan mirror (twice) and the second scan mirror, having nearly identical resonant frequencies of 27.59 kHz, yielding a total optical scan angle of 90 •. The observed scan angle exceeds the angle achieved by any single MEMS scanner. One can exploit the use of the back surface of the mirrors, as well as higher numerical aperture lenses to improve the achievable total optical scan to more than double, up to 210 •. With further development, the proposed architecture can be integrated into LiDAR systems to achieve high number of resolvable spots on the target, with unprecedented speed and form factor, far beyond what can be achieved with rotating motor or polygon mirror-based architectures.
... Taking advantage of this characteristic, several new mathematical models have been proposed for the uniaxial MEMS mirror. In [15], the authors proposed an isophase plane model, where the laser beam is treated as an isophase plane, and then a laser SL-alike model is used to obtain 3D information. To address the assembly error in MEMS mirrors, a curved light surface model was proposed in [16] to supersede the ideal isophase plane model for calibration and reconstruction. ...
... However, in the perspective projection model of the camera, all lights come from a single point, which is the camera optical center. This is why some works [15,17] claim that MEMS cannot be directly viewed as an anti-camera. In Figure 2 (b), plane 1 2 1 2 is the center iso-phase plane emitted from line 2 2 . ...
Benefiting from the small size and low driven voltage of the Micro Electro Mechanical Systems (MEMS) mirror, MEMS-based structured light (SL) 3D reconstruction has recently attracted much attention. In this paper, we propose a novel triangular stereo model for uniaxial MEMS-based 3D reconstruction. Existing SL methods based on MEMS mirrors often require the construction of a look-up table(LUT), but the proposed method only requires 34 parameters for accurate reconstruction. By analyzing the anatomy of the MEMS mirror, we put forward a transition function that allows the MEMS mirror to be regarded as an inverse camera model. Then, the triangular stereo principle can be directly employed to calculate 3D information. Furthermore, we present a calibration method to obtain the parameters of our model, since MEMS mirrors can only perform unidirectional fringe projection. Extensive experiments are performed to verify the feasibility and accuracy of our proposed mathematical model and calibration method.
... Among the existing fringe projection profilometry (FPP), there are three main types: the method based on phase-height mapping [6], the method based on binocular stereo vision [7], and the hybrid method combining the first two methods [8][9][10][11]. The first method uses moving the reference plane to establish the phase-height mapping relationship and calculates the remaining x and y coordinates through the imaging parameters. In the second method, the projector is regarded as a reverse camera, and x, y, and z coordinates are calculated through the fringe phase matching relationship and stereo vision. ...
... where f undis is a distortion-free function used to transfer x M id to x M in , P ij is the projection matrix with three rows and four columns. Only when the image point u M id and z M j is determined, the other two coordinates, x M j and y M j can be obtained according to equation (10). Let the subscript i = c and j = g and z M g = 0, we can calculate x M g . ...
... On the contrary, in the virtual moiré model, we can place any number of parallel plates, that is, set any preset value of z Mi w . According to the Weierstrass approximation theorem and similar to [9,10], since the mapping relationship between z M w and Φ d in the local area is continuous, we can directly use a polynomial function to fit the mapping function. In addition, as the virtual moiré system can obtain enough phase point pairs, the moiré model in the form of a polynomial function has sufficient precision, and the specific expression is as follows ...
The projection moiré method is a high-precision optical topography measurement method. The existing moiré models calibrate the phase-height mapping relationship by setting and moving the reference plane, which introduces many system errors and reduces the usability and scanning scalability of the methods. This paper proposes a moiré model based on virtual reality bridging and the corresponding scanning method. First, we use the imaging parameters of the real moiré system and the derived moiré phase correspondence to build a virtual moiré model matching the real system. Then we use a variety of phase optimization algorithms to improve the coincidence between the virtual and the reality. In addition, we propose a method to calculate the pose between views to facilitate the reconstruction of the corresponding virtual moiré model during scanning measurement. Finally, we use the virtual moiré model and scanning method to conduct fixed position and scanning measurements. The results show that the proposed virtual moiré model has high accuracy and robustness, and the scanning method can achieve high-precision full-field 3D shape measurement.
... To improve the performance of the classical phase-coordinate polynomial fitting model, Miao [24] used the Light Plane Model (LPM) to directly establish a reciprocal polynomial between phase and space coordinates for each pixel point. However, this method only ensures that the pixels projected from the structured light to the calibration board are valid values. ...
Projectors based on Micro-Electro-Mechanical System (MEMS) have the advantages of small size and low cost. Moreover, uniaxial MEMS projectors have high projection accuracy, and have been widely used in structured light 3D reconstruction. However, the existing calibration methods for uniaxial MEMS projectors are not effective in large-scale scenes. To solve this problem, this paper proposes a novel efficient large-scale calibration method, which is easily implemented. The proposed method first calibrates a partial light plane for a fixed sampling period, then obtains the rest of the light plane by exploiting a non-fixed rotating shaft linear interpolation method. Experimental results verify that the proposed method attains high accuracy in a large depth field with only 11 sets of calibration data. Specifically, at a distance of 3000mm, the standard deviation of the plane fitting error reaches 0.2584mm on the standard plane, and the measurement accuracy attains 0.9124mm on the standard step object with 200mm interval.
