27,612 research outputs found
Stent optical inspection system calibration and performance
Implantable medical devices, such as stents, have to be inspected 100% so no defective ones are implanted into a human body. In this paper, a novel optical stent inspection system is presented. By the combination of a high numerical aperture microscope, a triple illumination system, a rotational stage, and a CMOS camera, unrolled sections of the outer and inner surfaces of the stent are obtained with high resolution at high speed with a line-scan approach. In this paper, a comparison between the conventional microscope image formation and this new approach is shown. A calibration process and the investigation of the error sources that lead to inaccuracies of the critical dimension measurements are presented.Postprint (author's final draft
An optically actuated surface scanning probe
We demonstrate the use of an extended, optically trapped probe that is capable of imaging surface topography with nanometre precision, whilst applying ultra-low, femto-Newton sized forces. This degree of precision and sensitivity is acquired through three distinct strategies. First, the probe itself is shaped in such a way as to soften the trap along the sensing axis and stiffen it in transverse directions. Next, these characteristics are enhanced by selectively position clamping independent motions of the probe. Finally, force clamping is used to refine the surface contact response. Detailed analyses are presented for each of these mechanisms. To test our sensor, we scan it laterally over a calibration sample consisting of a series of graduated steps, and demonstrate a height resolution of ∼ 11 nm. Using equipartition theory, we estimate that an average force of only ∼ 140 fN is exerted on the sample during the scan, making this technique ideal for the investigation of delicate biological samples
Extrinsic Parameter Calibration for Line Scanning Cameras on Ground Vehicles with Navigation Systems Using a Calibration Pattern
Line scanning cameras, which capture only a single line of pixels, have been
increasingly used in ground based mobile or robotic platforms. In applications
where it is advantageous to directly georeference the camera data to world
coordinates, an accurate estimate of the camera's 6D pose is required. This
paper focuses on the common case where a mobile platform is equipped with a
rigidly mounted line scanning camera, whose pose is unknown, and a navigation
system providing vehicle body pose estimates. We propose a novel method that
estimates the camera's pose relative to the navigation system. The approach
involves imaging and manually labelling a calibration pattern with distinctly
identifiable points, triangulating these points from camera and navigation
system data and reprojecting them in order to compute a likelihood, which is
maximised to estimate the 6D camera pose. Additionally, a Markov Chain Monte
Carlo (MCMC) algorithm is used to estimate the uncertainty of the offset.
Tested on two different platforms, the method was able to estimate the pose to
within 0.06 m / 1.05 and 0.18 m / 2.39. We also propose
several approaches to displaying and interpreting the 6D results in a human
readable way.Comment: Published in MDPI Sensors, 30 October 201
Use of stereo camera systems for assessment of rockfish abundance in untrawlable areas and for recording pollock behavior during midwater trawls
We describe the application of two types of stereo camera
systems in fisheries research, including the design, calibration, analysis techniques, and precision of the data
obtained with these systems. The first is a stereo video system deployed by using a quick-responding winch with a
live feed to provide species- and size- composition data adequate to produce acoustically based biomass estimates
of rockfish. This system was tested on the eastern Bering Sea slope where rockfish were measured. Rockfish sizes were similar to those sampled with a bottom trawl and the relative error in multiple measurements of the same rockfish in multiple still-frame images was small. Measurement errors of up to 5.5% were found on a calibration target of known size. The second system consisted of a pair of still-image digital cameras mounted
inside a midwater trawl. Processing of the stereo images allowed fish length, fish orientation in relation to the camera platform, and relative distance of the fish to the trawl netting to be determined. The video system was useful for surveying fish in Alaska, but it could also be used
broadly in other situations where it is difficult to obtain species-composition or size-composition information.
Likewise, the still-image system could be used for fisheries research to obtain data on size, position, and
orientation of fish
Data reduction methods for single-mode optical interferometry - Application to the VLTI two-telescopes beam combiner VINCI
The interferometric data processing methods that we describe in this paper
use a number of innovative techniques. In particular, the implementation of the
wavelet transform allows us to obtain a good immunity of the fringe processing
to false detections and large amplitude perturbations by the atmospheric piston
effect, through a careful, automated selection of the interferograms. To
demonstrate the data reduction procedure, we describe the processing and
calibration of a sample of stellar data from the VINCI beam combiner. Starting
from the raw data, we derive the angular diameter of the dwarf star Alpha Cen
A. Although these methods have been developed specifically for VINCI, they are
easily applicable to other single-mode beam combiners, and to spectrally
dispersed fringes.Comment: Accepted for publication in Astronomy & Astrophysics, 17 pages, 19
figure
The QUEST Data Processing Software Pipeline
A program that we call the QUEST Data Processing Software Pipeline has been
written to process the large volumes of data produced by the QUEST camera on
the Samuel Oschin Schmidt Telescope at the Palomar Observatory. The program
carries out both aperture and PSF photometry, combines data from different
repeated observations of the same portion of sky, and produces a Master Object
Catalog. A rough calibration of the data is carried out. This program, as well
as the calibration procedures and quality checks on the output are described.Comment: 17 pages, 1 table, 8 figure
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