Laser-based Scanner Research Articles

Three Birds, One Stone: Unified Laser-Based 3-D Reconstruction Across Different Media

The laser-based 3-D reconstruction is crucial for autonomous manipulation and resource exploration in both the air and underwater scenarios, due to its accurate precision and robustness to disturbances. However, most current laser-based 3-D reconstruction sensors cannot be applied across different media without recalibration directly, e.g., air, air$\rightarrow $ glass$\rightarrow $ air, and air$\rightarrow $ glass$\rightarrow $ water, which is called killing three birds with one stone. This is because the variation of the medium density could change the sensor calibration parameters and further make the sensor suffer from a systematic geometric bias. To address these challenges, a unified laser-based 3-D reconstruction method is proposed in order that the laser-based scanner could be used across different media without recalibration, where we first explicitly model the refraction of the underwater vision systems and transform it across different media into a unified sensor reference frame. More specifically, an underwater refractive camera calibration model is designed to calibrate the orientation and position of the refractive interface, which can improve the accuracy of underwater reconstruction for the laser-based scanner, and we then present a refractive pose estimation model with a unified sensor reference frame, which can help the sensor to be applied across different scenarios directly. For the experiments, we validate the performance of our method on our underwater 3-D scanner prototype. Several reconstruction results on different objects and scenarios demonstrate the effectiveness of our proposed method and the practicality of our designed sensor.

Three-dimensional scanning of soil surface and furrow profiles using a portable and affordable unit

Soil surface and furrow profiles in soil dynamics research and applications are usually measured using manual profile meters and laser-based scanners. Manual profile meters are laborious to use, and laser-based scanners could be expensive and not portable. An approach was developed for measuring soil surface and furrow profiles using a portable and affordable 3D scanner. The developed approach was validated by using the 3D scanner to measure the width and depth of a V-groove (with known dimensions) created in three types of soils (coarse sand, Black Vertosol and Red Ferrosol) at different soil water contents moulded in a soil box. Average error of ±1.83% was found for all the three soil types and soil water contents. Results from the 3D scanner were also validated in the field by comparison to profiles measured with a pinned profile meter. In terms of percentage difference in readings, the 3D scanner results showed 16, 5 and 4% greater furrow width, ridge height and cross-sectional area, respectively, and 1% less furrow backfill. These differences were partly due to profile meter pins digging into loose soil and limitation with accurate width measurement. Data acquisition and processing with the 3D scanner unit were significantly faster than with the pinned profile meter. In general, it could be concluded that the developed methodology has the level of accuracy required for soil surface and furrow profile measurements. Furthermore, this approach is a cost-effective alternative to using laser-based scanners.

IN GEL DETECTION OF A HIS-TAGGED TRANSGENE FOLLOWING THE SEPARATION OF CRUDE PLANT PROTEIN EXTRACTS WITH SDS PAGE

In the present study, we visualised sundew His6-tagged chitinase protein in crude protein extracts of transgenic tobacco plants following protein separation with sodium dodecyl sulfate polyacrylamide gel electrophoresis by detecting chitinase activity as well as the His-tag. A short sequence encoding six histidines was fused downstream of the DNA sequence encoding the last amino acid of the mature protein. Following binary vector construction and plant transformation, a set of 10 transgenic plants was analysed for transgene expression. Except for one, all transgenic plants exhibited the presence of sundew chitinase protein of ~52 kDa, which was different from the calculated molecular weight of ~32 kDa. Clear identification of DrChitHis protein was performed with a Ni2+:NTA complex conjugated to a fluorescent dye and visualized using light laser-based scanner. A subsequent endochitinolytic activity assay using a N-fluorescein-labelled chitin substrate confirmed that the two transgenic lines with the strongest expression of DrChitHis protein had endochitinolytic activity 6.4 and 6.7 times higher than non-transgenic control.

Validation of a novel Kinect-based device for 3D scanning of the foot plantar surface in weight-bearing

BackgroundAdvancements in additive manufacturing, along with new 3D scanning tools, are increasingly fulfilling the technological need for custom devices in personalized medicine. In podiatry and in the footwear industry, custom orthotic and footwear solutions are often required to address foot pathologies or morphological alterations which cannot be managed with standard devices. While laser scanners are the current gold-standard for 3D digitization of the foot shape, their costs limit their applications and diffusion, therefore traditional operator-dependent casting methods are still in use. The aim of this study was to design and validate a novel 3D foot scanner based on the Microsoft Kinect sensor, allowing a 3D scan of the plantar shape of the foot to be acquired in weight-bearing.MethodsThe accuracy and repeatability of the prototypal foot scanner were investigated in a population of 14 asymptomatic healthy subjects, with no history of foot or lower limb injuries. The accuracy was estimated by comparing the Kinect foot scans with those obtained with a high-resolution laser scanner used as reference. The repeatability was assessed by comparing scans of the same foot acquired in different sessions.ResultsThe inter-subject average Root Mean Square Error (RMSE) of the Kinect scans was lower than 3 mm for the whole plantar surface, and lower than 1.6 mm for the arch region alone, both in left and right feet. The repeatability, quantified as the average RMSE of pairwise comparisons between sessions, was 1.2 ± 0.4 mm.ConclusionsThe present Kinect-based 3D foot scanner showed optimal intra-operator repeatability and its accuracy appears adequate to obtain 3D scans of the foot plantar surface suitable for different clinical applications. This device could represent a valid low-cost alternative to expensive laser-based scanners and could be used for automatic foot measurements, supporting the design of custom insoles and footwear.

On the influence of scanning factors on the laser scanner-based 3D inspection process

3D inspection process is getting more and more interest for manufacturing industries as it helps to carefully check the expected quality of the released products. Much more attention is oriented to optical devices able to quickly capture the whole shape of the product providing many useful information on the process variability and the deliverability of the key characteristics linked to the quality of the product/process. Although the optical control of 3D scanners is mature enough, many factors may influence the quality of the scanned data. These factors may be strictly related to internal elements to the acquisition device, such as scanner resolution and accuracy, and external to it, such as proper selection of scanning parameters, ambient lighting and characteristics of the object surface being scanned (e.g. surface colour, glossiness, roughness, shape), as well as the sensor-to-surface relative position. For the 3D laser-based scanners, the most common on the market, it would be of great industrial interest to study some scanning factors mainly affecting the quality of the 3D surface acquisitions and provide users with guidelines in order to correctly set them so to increase the massive usage of these systems in the product inspection activities. In this context, by using a commercial triangulation 3D laser scanner, the effects of some scanning factors that may affect the measurement process were analysed in the present paper. Working on a sheet metal test part, more complex than the ones commonly used in laboratory and documented in the literature, the scanner-to-object relative orientation and the ambient lighting, as well as an internal scanner parameter, were tested. Through a Design of Experiments (DoE) approach, and setting root mean square error (RMSE) as response function, the outcomes of the tests mainly pointed out that the scanner-to-object relative orientation as well as its position within the field of view of the measurement device are the key factors mostly influencing the accuracy of the measurement process.

Assessment of the accuracy and reliability of new 3-dimensional scanning devices

The primary objective of this study was to assess the accuracy and the reliability of the SureSmile OraScanner (Orametrix, Richardson, Tex) by comparing it with other desktop 3-dimensional scanners: VIVID910 (Konica Minolta, Tokyo, Japan) and R700 (3Shape, Copenhagen, Denmark). A laser-based scanner, the SLP250 Laser Probe (Laser Design, Detroit, Mich), served as the gold standard. Five sets of dental casts were used. First, the accuracy of each scanner was studied by comparing the 3-dimensional models created by OraScanner, VIVID910, and R700 with the gold standard 3-dimensional models of the SLP250. To assess the reliability of the 3-dimensional models, the shell/shell deviation of each model was calculated based on the same surface-based registrations for all 5 sets of dental casts. OraScanner, VIVID910, and R700 were sufficiently accurate when compared with the gold standard. In the assessment of reliability, there were no significant differences between all comparisons. The results showed that the OraScanner system has a sophisticated algorithm for 3-dimensional surface registration and can be used to generate accurate and reliable 3-dimensional digital models for use by clinicians.

A Symbol-Based Algorithm for Decoding Bar Codes

We investigate the problem of decoding a bar code from a signal measured with a hand-held laser-based scanner. Rather than formulating the inverse problem as one of binary image reconstruction, we instead incorporate the symbology of the bar code into the reconstruction algorithm directly, and search for a sparse representation of the Universal Product Code bar code with respect to this known dictionary. Our approach significantly reduces the degrees of freedom in the problem, allowing for accurate reconstruction that is robust to noise and unknown parameters in the scanning device. We propose a greedy reconstruction algorithm and provide robust reconstruction guarantees. Numerical examples illustrate the insensitivity of our symbology-based reconstruction to both imprecise model parameters and noise on the scanned measurements.

Combinatorial Signaling Microenvironments for Studying Stem Cell Fate

Extracellular matrix (ECM) and growth factor signaling networks are known to interact in a complex manner. Therefore, reductionist approaches that test the cellular response to individual ECM components and growth factors cannot be used to predict the response to more complex mixtures without knowledge of the underlying signaling network. To address this challenge, we have developed a technology platform to experimentally probe the interactions of ECM components and soluble growth factors on stem cell fate. We present a multiwell microarray platform that allows 1200 simultaneous experiments on 240 unique signaling environments. Mixtures of extracellular matrix (fibronectin, laminin, collagen I, collagen III, collagen IV) are arrayed using a robotic spotter and arranged in a multiwell format. Embryonic stem (ES) cells adhere to ECM spots and are cultured in mixtures of soluble factors [wnt3a, activin A, bone morphogenetic protein-4 (BMP-4), and fibroblast growth factor-4 (FGF-4)]. Differentiation along the cardiac lineage is monitored by myosin heavy chain-alpha-green fluorescent protein (MHC alpha-GFP) reporter expression as compared to growth by monitoring nuclear DNA, and both signals are quantified using a confocal microarray scanner. In developing the platform, we characterized the amount of deposited protein, the fluorescent readout of GFP expression and DNA content, and the use of a laser-based scanner as compared to fluorescent microscopy for data acquisition. The effects of growth factors on growth and differentiation are consistent with previously reported literature, and preliminary evidence of interactive signaling is illuminated. This versatile technique is compatible with virtually any set of insoluble and soluble cues, leverages existing software and hardware, and represents a step toward developing the 'systems biology' of stem cells.

Colorimetric silver detection of methylation using DNA microarray coupled with linker-PCR

Background: Aberrant DNA methylation of CpG site is among the earliest and most frequent alterations in cancer. Detection of promoter hypermethylation of cancer-related genes may be useful for cancer diagnosis or the detection of recurrence. Recently, several DNA microarray methods have been developed to detect the methylation status of the multiple genes. However, the microarrays are currently detected in fluorescence using a sophisticated laser-based scanner. These methods are limited by their lower sensitivity. Methods: We present a sensitive colorimetric silver method coupled with linker-PCR to detect methylation status of four genes, including p16, E-cadherin, VHL, and hMLH1. The signal generated with this method results from the precipitation of silver onto nanogold particles bound to streptavidin used to detect biotinylated DNA. Results: We show that p16, E-cadherin, VHL, and hMLH1 were all methylated in the positive control. However, no methylation was found in these genes for the negative control. P16 gene was only methylated in the sample, whereas others were not methylated. Furthermore, as little as 0.1 fmol of target DNA amplicons could be detected on the arrays. The results were further validated by methylation-specific PCR (MSP) and bisulfite DNA sequencing. Conclusions: The colorimetric silver detection of DNA microarray could be used as an inexpensive, useful, and sensitive tool to detect methylation status of the multiple genes in the future.

Imaging technologies for the detection of multiple stains in proteomics.

Laser-based scanners and charge-coupled device (CCD) camera systems are evolving to have greater functional capabilities for capturing images from a range of staining technologies used in gel electrophoresis and electroblotting. Digitizing Coomassie Brilliant Blue (CBB) stained gels and silver stained gels has now become possible using a laser-based gel scanner, the FLA-5000 fluorescent image analyzer system. Also, a simultaneous dual fluorescent imaging function has been incorporated into the FLA-5000 system, utilizing dichroic mirrors with both the optical system and the emission filter. In the workflow of routine proteomics research, the relationship between SYPRO dye staining and fluorescent detection using the FLA-5000 system have become symbiotic. Additionally in many cases, subsequent staining of the gel with CBB is useful for future research, and thus imaging instruments should be able to handle both staining formats. Digitizing the CBB stained gel can now be easily performed by the FLA-5000 fluorescent image analyzer system using a fluorescent board as an epi-illumination background. A cooled CCD camera system has the potential of imaging not only chemiluminescent membranes but also digitizing molecular weight markers and fluorescent detection of SYPRO dye-stained gels. With Multi Gauge software version 2.0 it is now a simple task to combine two images into one, as commonly required in dual detection experiments. The LAS-3000 system was designed to capture chemiluminescent images and to digitize the images automatically. Thus, new capabilities added to gel imaging systems make them capable of detecting and displaying multiple signals more conveniently.

Speckle noise in bar-code scanning systems--power spectral density and SNR.

Laser-based flying-spot scanners are strongly affected by speckle that is intrinsic to coherent illumination of diffusing targets. In such systems information is usually extracted by processing the derivative of a photodetector signal that results from collecting over the detector's aperture the scattered light of a laser beam scanning a bar code. Because the scattered light exhibits a time-varying speckle pattern, the signal is corrupted by speckle noise. In this paper we investigate the power spectral density and total noise power of such signals. We also analyze the influence of speckle noise on edge detection and derive estimates for a signal-to-noise ratio when a laser beam scans different sequences of edges. The theory is illustrated by applying the results to Gaussian scanning beams for which we derive closed form expressions.

Colorimetric Silver Detection of DNA Microarrays

Development of microarrays has revolutionized gene expression analysis and molecular diagnosis through miniaturization and the multiparametric features. Critical factors affecting detection efficiency of targets hybridization on microarray are the design of capture probes, the way they are attached to the support, and the sensitivity of the detection method. Microarrays are currently detected in fluorescence using a sophisticated confocal laser-based scanner. In this work, we present a new colorimetric detection method which is intented to make the use of microarray a powerful procedure and a low-cost tool in research and clinical settings. The signal generated with this method results from the precipitation of silver onto nanogold particles bound to streptavidin, the latter being used for detecting biotinylated DNA. This colorimetric method has been compared to the Cy-3 fluorescence method. The detection limit of both methods was equivalent and corresponds to 1 amol of biotinylated DNA attached on an array. Scanning and data analysis of the array were obtained with a colorimetric-based workstation.

A whole new way of looking at things: the use of Dark Reader technology to detect fluorophors.

The Dark Reader optical system (Clare Chemical Research, Denver, CO, USA) uses relatively low intensity broad-band visible blue light in combination with broad-band optical filters to detect fluorescence with a level of sensitivity that often surpasses that of UV transilluminators and can rival that of laser-based scanners. Applications of DR (Clare Chemical Research) devices include the detection of DNA and SYBR-stained protein samples following, and also during, electrophoresis. Unlike laser-based imaging systems, the fluorescence is directly visible to the user as well as being fully compatible with charge-coupled device (CCD) and Polaroid camera-based detection and imaging. Additionally, the DR optical system functions well in multicolor fluorophor environments. Because the Dark Reader does not emit any UV light, the extent of DNA damage incurred when visualizing DNA samples is drastically reduced compared to the damage produced by a UV device and this can have a significant benefit on downstream cloning protocols. Furthermore, dye photobleaching is minimal, extending the length of time that a fluorescent sample is visible. The inherent flexibility of the DR optical system allows many different configurations of the Dark Reader to be constructed such as transilluminators, hand lamps and integrated transilluminator-electrophoresis units.

Optical density changes of Gafchromic MD-55 film resulting from laser light exposure at wavelengths of 671 nm and 633 nm.

Laser-based scanners provide a sensitive means for measuring optical density (OD) of Gafchromic films. Such instruments were reviewed in a recent AAPM report (task group 55) which provided recommendations and information on OD measurements (effect of wavelength, temperature, etc.). The present article reports that variable rate scanners and spot densitometers using laser diodes (671 nm) and HeNe lasers (633 nm) can cause polymerization of Gafchromic film. The light induced polymerization depends on light power, wavelength, beam spot size, dwell time, and prior radiation dose of the film. Measurements were made with a custom built scanner that provided accurate control of light power, light polarization, dwell time, and film position in relation to the beam focus. The results demonstrate that lasers operating with powers of 0.1, 0.5, 1.0, and 1.5 mW produce a nonlinear increase in OD of Gafchromic film. The measured change in OD after 1 min of exposure ranges from 0.150 to 0.244 for a laser diode operating at 0.5 and 1.5 mW, respectively. Tables are included that tabulate the increase in OD for laser power, dwell time, and prior dose. Laser light induced polymerization can have a significant impact on dosimetry measurements acquired using these laser-based systems.

A comparison of the response of storage phosphor and film radiography to small variations in X-ray exposure.

To determine the response to small repeated variations in X-ray exposure of storage phosphor (SP) plates compared with Ektaspeed Plus dental film. Exposure of SP plates and Ektaspeed Plus dental film was varied within a small range [8.62 microC kg-1 to 9.03 microC kg-1, (5%)]. Radiographs were digitized and SP plates read with a laser-based scanner. Nested analysis of variance, analysis of covariance, and regression analysis were used to test the relationship between exposure and the resulting signal. The relationship between exposure and signal for digital images of film radiographs was not significant whereas the corresponding relationship for SP images was highly significant (P < 0.001, R2 = 0.44). Over the narrow range of X-ray exposures studied there was a significant direct linear relationship between exposure and digital gray-scale values for SP images but not for digital images of Ektaspeed Plus films.

Reverse Engineering of Quadric Surfaces Employing Three-Dimensional Laser Scanning

A software package for the reverse engineering of surface forms commonly found in manufactured objects is presented. An object's surface is digitized using a three-dimensional, laser-based scanner that produces accurate and copious data files. Complex surface forms are reconstructed by interactively segmenting the multiple-surface patches, invoking the appropriate surface modelling routine and transferring the resulting surfaces to a CAD package via a standard IGES entity. Examples of the accuracy of the laser scanner data, and software algorithms for modelling planes, cylinders, cones and spheres, are presented by performing comparisons with results generated by a coordinate measuring machine. The paper concentrates on the novel software process to model the principal quadric forms; however, the program's capabilities do extend to free-form surfaces.