1,888,245 research outputs found
Front Matter: Volume 6583
No full textThis PDF file contains the front matter associated with SPIE Proceedings Volume 6878, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing
Front Matter for Volume 7738
No full textThis PDF file contains the front matter associated with SPIE Proceedings volume 7550, including Title page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing
Front Matter: Volume 6457
No full textThis PDF file contains the front matter associated with SPIE Proceedings Volume 6457, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing
Front Matter: Volume 6565
No full textThis PDF file contains the front matter associated with SPIE Proceedings Volume 6426, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing
Front Matter: Volume 7950
No full textIt has been nearly twenty years since the conception of photonic crystal fibers, as
devised by Philip St. J. Russell in unpublished work dating to 1991. That work was a
development of the photonic crystal ideas of Yablonovich and John who
published two milestone papers on photonic crystals in 1987. The photonic crystal
fiber (PCF) has given the field of fiber optics a newfound resurgence, resulting in
revolutionary research and practical breakthroughs that would have proven
otherwise impossible with conventional optical fibers; these include octavespanning
light continua, air guidance of light with low loss over several kilometers,
and endlessly single-mode fiber operating over several hundred nanometers. The
unusual confinement characteristics of PCF have resulted in their use in
applications such as fiber-optic communications and sensing, fiber lasers,
nonlinear devices, high-power transmission, and highly sensitive gas sensors,
amongst others.The Society of Photo-Optical Instrumentation Engineers (SPIE), Brussels Photonics Team (B-PHOT), Brussels-Capital Region, Fonds Wetenschappelijk Onderzoek (FWO), International Commission for Optics (ICO), Ville de Bruxelle
Proceedings of SPIE - The International Society for Optical Engineering: Introduction
No full textThis PDF file contains the front matter associated with SPIE Proceedings Volume 8351, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)
Proceedings of SPIE - The International Society for Optical Engineering: Introduction
No full textThis PDF file contains the front matter associated with SPIE Proceedings Volume 8423, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)
Multiple return separation for a full-field ranger via continuous waveform modelling
No full textWe present two novel Poisson noise Maximum Likelihood based methods for identifying the individual returns within mixed pixels for Amplitude Modulated Continuous Wave rangers. These methods use the convolutional relationship between signal returns and the recorded data to determine the number, range and intensity of returns within a pixel. One method relies on a continuous piecewise truncated-triangle model for the beat waveform and the other on linear interpolation between translated versions of a sampled waveform. In the single return case both methods provide an improvement in ranging precision over standard Fourier transform based methods and a decrease in overall error in almost every case. We find that it is possible to discriminate between two light sources within a pixel, but local minima and scattered light have a significant impact on ranging precision. Discrimination of two returns requires the ability to take samples at less than 90 phase shifts
Toward-1mm depth precision with a solid state full-field range imaging system
No full textPreviously, we demonstrated a novel heterodyne based solid-state full-field range-finding imaging system. This system is comprised of modulated LED illumination, a modulated image intensifier, and a digital video camera. A 10 MHz drive is provided with 1 Hz difference between the LEDs and image intensifier. A sequence of images of the resulting beating intensifier output are captured and processed to determine phase and hence distance to the object for each pixel. In a previous publication, we detailed results showing a one-sigma precision of 15 mm to 30 mm (depending on signal strength). Furthermore, we identified the limitations of the system and potential improvements that were expected to result in a range precision in the order of 1 mm. These primarily include increasing the operating frequency and improving optical coupling and sensitivity. In this paper, we report on the implementation of these improvements and the new system characteristics. We also comment on the factors that are important for high precision image ranging and present configuration strategies for best performance. Ranging with sub-millimeter precision is demonstrated by imaging a planar surface and calculating the deviations from a planar fit. The results are also illustrated graphically by imaging a garden gnome
Characterization of modulated time-of-flight range image sensors
No full textA number of full field image sensors have been developed that are capable of simultaneously measuring intensity and distance (range) for every pixel in a given scene using an indirect time-of-flight measurement technique. A light source is intensity modulated at a frequency between 10–100 MHz, and an image sensor is modulated at the same frequency, synchronously sampling light reflected from objects in the scene (homodyne detection). The time of flight is manifested as a phase shift in the illumination modulation envelope, which can be determined from the sampled data simultaneously for each pixel in the scene. This paper presents a method of characterizing the high frequency modulation response of these image sensors, using a pico-second laser pulser. The characterization results allow the optimal operating parameters, such as the modulation frequency, to be identified in order to maximize the range measurement precision for a given sensor. A number of potential sources of error exist when using these sensors, including deficiencies in the modulation waveform shape, duty cycle, or phase, resulting in contamination of the resultant range data. From the characterization data these parameters can be identified and compensated for by modifying the sensor hardware or through post processing of the acquired range measurements
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