A phase-shift triangulation gageHarding, Kevin
doi: 10.1117/12.3052293pmid: N/A
Triangulation gages are one of the most commonly used optical metrology tools in use in many industries from primary metals production to process control. However, little has changed in the basic operation of triangulation gages which are known to have limitations due to surface reflectivity and surface texture. This paper presents a new design of point triangulation that isolates the surface noise limitation of using the center of a noisy spot seen on a surface to allow a wide range of surfaces from rough to glossy without loss of performance. The extensive study conducted includes considerations of source noise, analysis methods and speed to provide the means for a viable alternative to traditional sensor limitations.
Characterization of window materials using out-of-plane BSDF measurements, combining resolution of small-angle scattering and low level background scatteringApian-Bennewitz, Peter
doi: 10.1117/12.3054183pmid: N/A
The Bidirectional-Scatter-Distribution-Function (BSDF) is well established in research and engineering to describe scattering in terms of radiometry and geometrical optics. Two extreme cases of the BSDF are applicable to windows: First, the near Dirac-delta BSDF of transparent materials, whose imperfections govern the visual clarity. This requires high angular resolution of small-angle scattering and mandates a very ’sharply’ localised light-source. Secondly, measurements of low background scattering of transparent materials, commonly associated with haze, requires a maximum of incident power, with reduced requirements on angular resolution. We present results using our PG2 scanning gonio-photometer that uses the same servo-driven out-of-plane mechanics with different light-sources and sensor opening angles to measure these two extremes of the BSDF and combine them into a common data-set. Aspects of combing high-power incoherent sources with low-power/high-radiance coherent sources are discussed, as well as the influence of optical elements in the source beam-path.
A mapping autocollimator using phase measurementHarding, Kevin
doi: 10.1117/12.3052294pmid: N/A
One of the common tools used in the alignment of precision optics as well as industrial production tools is the autocollimator which provides a point measurement of surface slope. The design and mechanism of these instruments have changed little over the years, which systems such as interferometry have seen big improvements with the use of phase shift measurements. This paper presents an autocollimator that uses phase shift analysis to improve performance as well as provide the means to map the slope of a continuous curved surface. This capability has the potential to provide both translations and tilt information over a large area without the need for scanning point measurements.
Investigating the factors that influence 3D stereo depth sensor noisePierce, Terrence; Rachakonda, Prem
doi: 10.1117/12.3052823pmid: N/A
3D stereo depth sensors have a variety of applications, including sensing for autonomous vehicles, reverse engineering, and manufacturing automation. The performance of these sensors can be affected by various factors, such as sensor* construction, sensor technology, sensor settings, environment, etc. Understanding parameters that affect sensor output is needed to characterize them and to develop standards. As machine learning (ML) with 3D point clouds and depth data becomes increasingly prevalent, understanding the data used with these models becomes crucial for improving the adoption rates of such depth sensors. In certain domains, sensor noise and transient effects can become dominant. Reducing noise before using sensor data with ML algorithms is necessary for increased algorithm accuracy. To characterize depth sensors, we conducted experiments using targets with varying gloss, color, and texture/pattern. Additionally, we studied sensor data quality and noise by exploring sensor parameters such as exposure, gain, and laser power. We found transient effects in both 2D images and depth data captured by sensors. These experiments help inform the operating conditions that could be advised for specific applications and future standards addressing these sensors.
High-resolution tactile sensor for 3D surface measurement using structured light systemYeo, Ingu; Hyun, Jae-Sang
doi: 10.1117/12.3052185pmid: N/A
In the digital fringe projection system, attempts have been made to overcome the reflection or transmission of the structured pattern from the digital projector on the object, such as adjusting the camera focus or camera exposure time. However, these adjustments did not resolve the fundamental limitations of the object. In this study, we develop a contact-based surface measurement method using silicone. By bringing the object into contact with a specially coated silicone layer, fringe patterns are projected onto the opposite surface, enabling the acquisition of 3-D information. This method allows for the capture of highly accurate 3-D data, making it applicable for real-time surface measurements. The experimental results have validated the effectiveness of the proposed approach.
Line-scan hyperspectral 4D imaging across visible to shortwave infrared spectral rangeLi, Jiaqiong; Li, Beiwen
doi: 10.1117/12.3055415pmid: N/A
We present a line-scan hyperspectral 4D (x, y, z, spectrum λ ) imaging system capable of capturing 3D data and hyperspectral images across visible to short-wave infrared (SWIR) wavelengths. The system employs two line-scan sensors to simultaneously acquire Visible and Near-Infrared (VNIR) and short-wave infrared (SWIR) hyperspectral images, while a fringe projection profilometry (FPP) subsystem captures 3D data. Alignment of the hyperspectral images is achieved using a line-scan homography method, and a transformation technique registers the 3D spatial data with the hyperspectral images. The experimental results demonstrate the effectiveness and potential of our system for various applications.
3-dimensional plenoptic microscopy using a stacked microlens arrayLee, Munseob; Kim, Chihoon; Lim, Hyungjun
doi: 10.1117/12.3053579pmid: N/A
Microlens array-based plenoptic technology enables precise 3D imaging by providing various parallax information. Among different plenoptic techniques, the multifocal method, which uses two or more focal lengths, offers a greater depth of field (DoF) compared to the single focal length method. In this paper, we designed and fabricated a stacked skip-bound microlens array to achieve three distinct focal lengths. The skip-bound microlens array is composed of two microlenses and empty spaces arranged in a repeated structure. By stacking three skip-bound microlens arrays and shifting each to have different optical paths, we achieved three focal lengths. The microlens array has a diameter of 200μm, numerical apertures (NA) of 0.02, 0.056, and 0.037, and was implemented in a hexagonal structure. This system was applied to a 10x microscope and a 25M-class camera, achieving micron-scale depth resolution. Additionally, we verified its ability to inspect defects, such as wire bending or broken wires, and perform quantitative measurements in packaging processes.
Front Matter: Volume 13462doi: 10.1117/12.3074937pmid: N/A
This PDF file contains the front matter associated with SPIE Proceedings Volume 13462, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.
Single-shot 3D surface reconstruction with dual frequency composite pattern and multiview systemSeok, Jin-Hyuk; Hyun, Jae-Sang
doi: 10.1117/12.3053763pmid: N/A
In structured light systems, phase unwrapping is necessary to convert wrapped phase measurements into continuous phase values for accurate 3D reconstruction. While prior studies have addressed phase ambiguity using binocular setups and geometric constraints, they often incorporate additional reference information such as speckle patterns or stereo intensity cues. Although these methods reduce the number of required patterns compared to conventional approaches, they still depend on multiple images. We propose a novel transform-based 3D reconstruction method that operates with a single-shot composite pattern using a binocular camera–projector system. The composite pattern simultaneously encodes low- and high-frequency components, and a tailored score function that integrates phase periodicity and intensity cues enables correspondence estimation without requiring absolute phase recovery. Experimental results demonstrate that the proposed approach successfully resolves phase ambiguity even in scenes with multiple isolated objects.
Enhanced absolute phase unwrapping method for multiview structured-light system using deep learningKim, Wonhoe; Hyun, Jae-Sang
doi: 10.1117/12.3053770pmid: N/A
Fringe Projection Profilometry (FPP) system offers high accuracy and resolution compared to other 3D reconstruction techniques. The multi-view FPP systems can restore 3D information at a faster speed compared to a typical single-view system. These systems rely on geometric relationships across multiple views to restore absolute phase information, but they require high system complexity and cost. In this study, we propose a framework leveraging two neural networks to perform phase unwrapping using only four images. WPNet predicts the wrapped phase from fringe images, while MVPUNet utilizes multi-view wrapped phases and their geometric relationships to estimate the unwrapped phase. To train the framework, we constructed a synthetic dataset within a virtual environment. The experimental results demonstrate both the accuracy and structural validity of the proposed method.