Craig A. Williamson

Nominal ocular dazzle distance (NODD)

A simple model for laser eye dazzle is presented together with calculations for laser safety applications based on the newly defined Maximum Dazzle Exposure (MDE) and Nominal Ocular Dazzle Distance (NODD). A validated intraocular scatter model has been combined with a contrast threshold target detection model to quantify the impact of laser eye dazzle on human performance. This allows the calculation of the MDE, the threshold laser irradiance below which a target can be detected, and the NODD, the minimum distance for the visual detection of a target in the presence of laser dazzle. The model is suitable for non-expert use to give an estimate of anticipated laser eye dazzle effects in a range of civilian and military scenarios.

Simple computer visualization of laser eye dazzle

A technique is presented to simulate visually the appearance of laser dazzle to the human eye. This can reduce the need for human laser exposures in applications such as laser awareness training and laser dazzler effectiveness testing. The benefits of reduced human exposures include the reduced time and cost for experimentation, the ability to explore more complex parameter spaces, and the potential to simulate non-eye-safe laser exposures. In this implementation, an adapted version of the CIE general disability glare equation, which has been validated with human subject laser experiments, is used to determine the dazzle extent across the visual field. Simple image manipulation then permits the resulting dazzle field to be superimposed upon scene imagery to give a visualization of the severity of the dazzle in a given environment. Examples are presented that illustrate the increased dazzle field experienced with reduced ambient luminance and increased laser irradiance, including non-eye-safe levels. The a...

Optical eye simulator for laser dazzle events.

An optical simulator of the human eye and its application to laser dazzle events are presented. The simulator combines optical design software (ZEMAX) with a scientific programming language (MATLAB) and allows the user to implement and analyze a dazzle scenario using practical, real-world parameters. Contrary to conventional analytical glare analysis, this work uses ray tracing and the scattering model and parameters for each optical element of the eye. The theoretical background of each such element is presented in relation to the model. The overall simulators calibration, validation, and performance analysis are achieved by comparison with a simpler model based uponCIE disability glare data. Results demonstrate that this kind of advanced optical eye simulation can be used to represent laser dazzle and has the potential to extend the range of applicability of analytical models.

Mode locking of semiconductor laser with curved waveguide and passive mode expander

Active mode locking is reported for a 1.55 μm semiconductor laser with a curved waveguide and passive mode expander, placed in a wavelength tunable external cavity. One facet with a very low reflectivity of 8×10−6 is achieved through a curved active region that tapers into an underlying passive waveguide, thus expanding the mode to give reduced divergence. 10 GHz pulses of 3.1 ps duration have been generated, with a linewidth of 0.81 nm.

Simulating the impact of laser eye protection on color vision

Laser eye protection (LEP) imparts coloration to the visual scene observed by the wearer, which can make interpreting color information problematic. A model has been developed to allow rapid visualization of the impact of LEP on the appearance of reflective color patches and emissive displays. This model uses the transmission spectra of LEP and spectral information of color stimuli, in conjunction with an implementation of the CIECAM02 model to account for complex aspects of human vision including chromatic adaptation. Applications include training LEP users of anticipated color shifts and iterative testing of LEP and display designs to optimize color presentation. (DSTL/JA87054)

Mode locking of a novel split-contact semiconductor Laser-experiment and theory

A novel semiconductor laser, with a curved and tapered active region and a split contact, has been experimentally and theoretically mode-locked for the first time. An innovative yet simple traveling-wave rate-equation model has been developed to incorporate the tapered waveguide structure together with external-cavity grating effects and the reverse biased saturable absorber region. Both the experiment and model have demonstrated pulsewidths of around 5.5 ps at a repetition frequency of 2.5 GHz and a tunable emission wavelength around 1550 nm. The model has been used to demonstrate optimized operation of the device with a predicted reduction in pulsewidths down to 1 ps.

Laser event recorder

The primary objective of this effort is to develop a low-cost, self-powered, and compact laser event recorder and warning sensor for the measurement of laser events. The target requirements are to measure the wavelength, irradiance, pulse length, pulse repetition frequency, duration and scenery image for each event and save the information in a time and location stamped downloadable file. The sensor design is based on a diffraction grating, low-cost optics, CCD array technology, photodiodes, integral global positioning sensor, and signal processing electronics. The sensor has applications in laser safety, video surveillance and pattern recognition.

Scaling laser disability glare functions with "K" factors to predict dazzle

With the increasing availability of higher power laser pointers, there is growing coneem about disability glare or dazzle from laser illumination and the safe operation of aireraft and vehicles. A study was condueted to determine the ability of observers to discriminate targets over three log units of laser irradiance (from 0.6 μW·cm−2 to 600 μW·cm−2) and at adaptation levels that simulated twilight (3 cd·m−2), low daytime (30 cd·m−2) and daytime (3,400 cd·m−2) conditions. Other factors that were varied included: target size (0.7°-12°), laser exposure angle (0°-55°), and the presence or absence of an aireraft windscreen. The dazzle effect increased with laser irradiance and decreased as target size increased. The dazzle effect was also greater with a windscreen than without a windscreen, and dazzle increased as ambient luminance decreased. The glare obscuration with eccentricity from the laser source was subsequently used to calibrate the Commission Internationale de l’Eclairage (CIE) disability glare function with appropriate “K” factors, thus allowing a more accurate predietion of dazzle effects across other irradiances and adaptation levels.With the increasing availability of higher power laser pointers, there is growing coneem about disability glare or dazzle from laser illumination and the safe operation of aireraft and vehicles. A study was condueted to determine the ability of observers to discriminate targets over three log units of laser irradiance (from 0.6 μW·cm−2 to 600 μW·cm−2) and at adaptation levels that simulated twilight (3 cd·m−2), low daytime (30 cd·m−2) and daytime (3,400 cd·m−2) conditions. Other factors that were varied included: target size (0.7°-12°), laser exposure angle (0°-55°), and the presence or absence of an aireraft windscreen. The dazzle effect increased with laser irradiance and decreased as target size increased. The dazzle effect was also greater with a windscreen than without a windscreen, and dazzle increased as ambient luminance decreased. The glare obscuration with eccentricity from the laser source was subsequently used to calibrate the Commission Internationale de l’Eclairage (CIE) disability glare fun...

Determination of a laser eye dazzle safety framework

A simple safety framework for laser eye dazzle, based on a complex model developed from human subject experiments, is proposed to address the urgent need for guidance within international laser safety standards. Maximum Dazzle Exposure (MDE) safety limits are derived that set the laser irradiance at the eye above which an object cannot be visually detected. A newly defined concept of dazzle level accounts for the extent of visual obscuration, and different ambient light levels are accommodated by determining safety limits for night, dusk/dawn, and day conditions. The resulting table of MDE values allows dazzle effects to be quantified in simple safety calculations across a wide range of scenarios. This safety framework is intended to empower the laser safety community to understand and quantify the impacts of laser eye dazzle, specify protection measures for those at risk, and assure the safety and effectiveness of laser dazzle devices.A simple safety framework for laser eye dazzle, based on a complex model developed from human subject experiments, is proposed to address the urgent need for guidance within international laser safety standards. Maximum Dazzle Exposure (MDE) safety limits are derived that set the laser irradiance at the eye above which an object cannot be visually detected. A newly defined concept of dazzle level accounts for the extent of visual obscuration, and different ambient light levels are accommodated by determining safety limits for night, dusk/dawn, and day conditions. The resulting table of MDE values allows dazzle effects to be quantified in simple safety calculations across a wide range of scenarios. This safety framework is intended to empower the laser safety community to understand and quantify the impacts of laser eye dazzle, specify protection measures for those at risk, and assure the safety and effectiv...

Laser eye dazzle safety framework

A safety framework for laser eye dazzle has been constructed to address the urgent need for dazzle advice within international laser safety standards. Simple calculations are presented to permit dazzle effects to be quantified, based upon the new concepts of Dazzle Level (DL), Maximum Dazzle Exposure (MDE) and Nominal Ocular Dazzle Distance (NODD).A safety framework for laser eye dazzle has been constructed to address the urgent need for dazzle advice within international laser safety standards. Simple calculations are presented to permit dazzle effects to be quantified, based upon the new concepts of Dazzle Level (DL), Maximum Dazzle Exposure (MDE) and Nominal Ocular Dazzle Distance (NODD).