Headlamp Illumination Research Articles

A New Lighting System for Surgical Vision Optimization in Barbed Pharyngoplasty for OSA.

Obstructive sleep apnea (OSA) surgery is now a viable solution in selected patients and the "remodeling" palatopharyngeal surgery is the most common one. Recently, it has become less invasive with the introduction of barbed sutures (BS). An optimization of surgical techniques is represented by barbed pharyngoplasty (BP), which requires surgical precision and needs efficient and precise oropharyngeal visualization. Consequently, the lighting system is of pivotal importance in BP. The aim of this work is to describe the first experience on the use of a new lighting system, called KLAROTM in BP for OSA. We evaluated the KLARO™ system in 15 consecutives BP for OSA in comparison with conventional headlamp illumination. The visualization of palatopharyngeal muscle in the bottom of the tonsillar fossa, entry and exit needle, such as needle tip, were statistically better with KLAROTM than headlamp illumination for both the surgeon and resident (p < 0.05). No significant differences for the visualization of the posterior pharyngeal wall and uvula were reported. The KLAROTM lighting system allows a satisfied illumination of oral cavity and oropharynx in the majority of cases. We encourage the use of KLAROTM not only in BP for OSA, but in all oral and pharyngeal surgeries, including tonsillectomy and oncological surgery.

Evaluation of quantitative glare technique based on the analysis of bio-signals

This laboratory study evaluated the effect of glare source (halogen, HID and LED) and its illumination levels (0.7, 2 and 5 lx) using a quantitative methodology. Pupil diameter and electroencephalography were measured using FaceLab and Biopac systems, respectively. The discomfort glare was assessed subjectively with Borg’s CR-10 scale. Twenty healthy subjects participated. Pupil size was significantly affected by the headlamp type and illumination condition. Pupil size was smaller when exposed to the LED headlamp than other headlamps (Halogen > HID > LED). In addition, when the illumination increased, pupil size decreased (0.7 lx > 2 lx > 5 lx). Also, driver’s discomfort increased when pupil size was small, and theta waves were high. This discomfort may cause reduced attention and safety of the driver. These results can be applied to design and development of headlamps. Further investigation is necessary with adopted methodology to evaluate other headlamps in different illumination conditions.Practitioner Summary: This study evaluated pupil size and electroencephalography under different glare source (halogen, HID and LED) and illumination levels (0.7, 2 and 5 lx). Driver’s discomfort increased when pupil size was small, and theta waves were high. This discomfort may cause reduced attention and safety of the driver.

Human Factors Techniques in the Analysis of Low Illumination Accidents

The primary goal of this paper is to present a case study and several human factors methodologies useful for investigations of accidents occurring during low light, nighttime situations. Classical vehicular accident reconstruction approaches seldom consider the potential contribution of low visibility. However, visual acuity can be enormously impacted by low ambient illumination. It is therefore important to consider visibility to fully understand the perceptual and cognitive limitations of drivers. In order for the most likely cause of an accident to be identified, appropriate human factors techniques should be applied to facilitate the determination of how and why a nighttime collision occurred. With the help of a specific case study, this paper will discuss human visual limitations at night, techniques to measure headlamp luminance and illuminance, validated photographic approaches, and how to translate the results into a format that can subsequently be used as the bases for engineering and scientific animations and demonstrative exhibits.

From headlamp illumination to headlamp performance: a critical review of the Ford motor company 'detect' model

This article reviews a range of issues relevant to evaluating visibility provided by automobile headlamps, with emphasis on the driver visibility model DETECT that was developed by the Ford Motor Company. The first section of the article discusses general issues concerning evaluation of headlamp performance. The main sections of the article review the major failures of DETECT, its limitations, and suggested improvements. Finally, it is argued that further progress in the development of headlighting models and their increased acceptability is contingent on reaching a consensus regarding what good headlighting should be able to do. Consequently, a worldwide survey of experts in industry, academia, and government on desirable aspects of headlamp performance is advocated.

Differences in Nighttime Luminance of Work Zone Drums with and without Steady-Burn Warning Lights

Research was performed to explore the differences in the nighttime luminance of drums, with and without steady-burn warning lights, that are used in work zones to channelize traffic. Two evaluations were performed: one in the field, which included luminance measurements of 372 drums in 15 freeway work zones throughout Michigan, and another, controlled evaluation, which included luminance measurements of 24 common drum scenarios in a vacant parking lot. Drums with and without steady-burn lights were considered in both evaluations. All luminance measurements were performed from the passenger seat of a vehicle under low-beam headlamp illumination. The results of the controlled evaluation showed that the addition of a steady-burn warning light increased the average luminance of drums with high-intensity sheeting by 0.165 candelas per square meter (cd/m2) (2.6%). The added light increased the average luminance of drums with microprismatic sheeting by 0.50 cd/m2 (3.9%). Similar results were obtained during the field evaluation. It was concluded that drums with high-intensity sheeting and without steady-burn warning lights typically provided adequate levels of nighttime luminance when viewed from a vehicle under low-beam headlamp illumination. If additional nighttime brightness was desired, however, microprismatic sheeting offered far greater luminance than a steady-burn warning light.

전조등 조도변동에 대한 운전자의 인식연구 : 2. 운전자의 시인 특성

전조등 조도변동에 대한 운전자의 인식연구 : 2. 운전자의 시인 특성

Recent Changes in Headlamp Illumination Directed toward Traffic Signs

This study examined the differences in sign light between 1997 tungsten-halogen and 2004 high-intensity discharge (HID) low-beam headlamps manufactured for use on U.S. vehicles. The results indicate that the HIDs tended to deliver less light above the horizontal straight ahead and to the left of the vertical, and less light to the right of the vertical above about 1.5° up. The consequences of the changed beam pattern were analyzed in detail for three typical sign locations: center overhead, right shoulder, and left shoulder. The most frequent geometric conditions were modeled: a straight road, and very large-radius left and right curves, all with no vertical curvature. Viewing distances between 50 m and 300 m were considered.The results imply that with current HID low beams, sign retro-reflectivity would need to be increased to maintain the effectiveness that a given sign had a decade ago with tungsten-halogen low beams. This applies to overhead signs on straight roads and on very large-radius left and right curves, and to right and left shoulder-mounted signs on straight roads and on very large-radius left curves.

Development of a Model to Calculate Roadway Luminance Induced by Fixed Roadway Lighting

Overhead luminaires often provide illumination on pavement, pavement markings, and nearby objects for nighttime drivers. Earlier studies have characterized the bidirectional reflectivity distribution functions of typical roadway surfaces. The luminaire spatial photometric beam distributions and relative spectral distributions have been investigated in part by the Illumination Engineering Society (IES). Mathematical models for luminance calculations are also established by the Commission Internationale de l'Eclairage (CIE; the International Commission on Illumination) and IES. Yet no computer models integrate such data to determine roadway luminance induced by overhead luminaires in conjunction with headlamp illumination for any given roadway geometry for the nighttime driver. Furthermore, existing models are limited to photopic vision, whereas nonphotopic (i.e., mesopic) vision prevails at night. With the Tarvip model being a suitable platform, work was undertaken under the sponsorship of FHWA to develop a computer model that would combine the available data and assess the performance characteristics of different overhead luminaires under different configurations and roadway characteristics for the nighttime driver. The model accommodates horizontal and vertical curves; custom luminaire configurations; and the CIE standard photopic, mesopic, and scotopic observers. With such a model, it is possible to analyze the visual benefits of existing or fictitious overhead luminaires under different configurations (i.e., different heights and gaps) on various roadway surfaces and geometries while oncoming vehicle glare is factored in without the need for field studies. The fixed overhead lighting module that was developed has been verified and validated in the field.

Development of a Model to Calculate Roadway Luminance Induced by Fixed Roadway Lighting

Overhead luminaires often provide illumination on pavement, pavement markings, and nearby objects for nighttime drivers. Earlier studies have characterized the bidirectional reflectivity distribution functions of typical roadway surfaces. The luminaire spatial photometric beam distributions and relative spectral distributions have been investigated in part by the Illumination Engineering Society (IES). Mathematical models for luminance calculations are also established by the Commission Internationale de l'Eclairage (CIE; the International Commission on Illumination) and IES. Yet no computer models integrate such data to determine roadway luminance induced by overhead luminaires in conjunction with headlamp illumination for any given roadway geometry for the nighttime driver. Furthermore, existing models are limited to photopic vision, whereas non-photopic (i.e., mesopic) vision prevails at night. With the Tarvip model being a suitable platform, work was undertaken under the sponsorship of FHWA to develop...

Photometric Measurements of Traffic Signs as a Function of Pavement Reflectance at Grazing Angles

A supply vs. demand luminance concept is currently employed to provide a metric to set minimum retroreflectivity levels. Supply luminance depends on reliable modeled estimates of luminance directed back toward the driver. A small pocket of literature shows inconsistent relationships between measured and modeled illuminance and luminance levels. One of the possible sources of error identified was the lack of consideration of pavement reflectance. A literature review resulted in insufficient evidence to assess the effect of pavement reflection. Therefore, the objective of this research was to determine the effect of indirect illuminance as function of pavement reflectance on the sign luminance returned to the driver.Measurements of headlamp illuminance falling on a sign and the returned sign luminance were simultaneously recorded on typical sections of dry concrete and dry asphalt pavement. The sign luminance measurements that included the headlamp illuminance reflecting off the pavement were only 0.6 to 2.4 percent higher that those made without the headlamp illuminance reflecting off the pavement surface. Therefore, it is recommended that effect of pavement reflection be neglected when modeling sign luminance at night as a function of headlamp illumination.

Validation of Photometric Modeling Techniques for Retroreflective Traffic Signs

Recent research in the United States has focused on the development of minimum retroreflectivity levels for traffic signs. The engineered approach uses a supply luminance versus demand luminance concept to achieve a metric that can be used to set minimum retroreflectivity levels. The supply luminance depends on reliable modeled estimates of headlamp illuminance reaching traffic signs and the resultant luminance directed back toward the driver. While the science behind the photometric modeling process is fundamentally sound, a small pocket of literature shows inconsistent relationships between measured and modeled illuminance and luminance levels. A systematic validation study of photometric modeling was done with field measurements made under conditions identical to those that were modeled. A set of headlamps were photometrically measured along with three different samples of retroreflective sign sheeting materials. Illuminance and luminance levels were then modeled for nine sign positions and three vehicle types. Then field illuminance and luminance were measured using the same scenarios, headlamps, and retroreflective sign sheeting materials. The field measurements were recorded once on a concrete pavement and once on an asphalt pavement. Both sets of field measurements also included baffled and unbaffled measurements so the impact of pavement reflection could be considered. Photometric modeling techniques of nighttime traffic sign performance compared well with field measurements made under identical conditions. The maximum illuminance difference was 16% and was attributed to the pavement reflection properties. The maximum luminance difference was only 2.4%. The retroreflective performance of traffic signs redirects most of the pavement reflection back toward the pavement. Therefore, estimates and measurements of luminance are less affected than illuminance.

Retroreflective Material Specifications and On-Road Sign Performance

Retroreflective materials for traffic control devices are designed to return light from a vehicle’s headlamps back to the driver. Recent advances in material technology have created prismatic retroreflective sheeting. This type of material does not have the predictability in its retroreflective performance of the older, glass-bead material. The ASTM recently recognized three new types of prismatic material for traffic control devices. The on-road performance of these new material types was examined through the use of computer simulation of sign luminance. Inputs to the computer model included vehicle dimensions, headlamp illumination data, material retroreflectivity data, sign placement, and roadway geometry. A variety of sign positions and roadway types was included to illustrate the similarities and differences among the three new types of material. The ranking of the three materials in terms of sign-luminance performance depends on the roadway configuration and the viewing distance. ASTM Type VII is shown to be comparable to Type VIII at long distances with small entrance angles but superior to Type VIII and IX in large entrance-angle situations. ASTM Type IX is shown to have higher luminance at shorter distances associated with sign-legibility distance ranges. Engineers and specifiers are encouraged to evaluate on-road sign performance at night before making material choices.

Sign Retroreflectivity: Comparing Results of Nighttime Visual Inspections with Application of Minimum Retroreflectivity Values

In 1993, FHWA published research recommendations for minimum levels of retroreflectivity for traffic signs. These values were later revised in a 1998 FHWA report. The minimum values were developed as part of a process to add end-of-service life retroreflectivity values to the Manual on Uniform Traffic Control Devices. There have been few or no comparisons between the use of minimum retroreflectivity values to define end-of-service life and the results of typical nighttime visual inspections. Researchers at the Texas Transportation Institute conducted such an evaluation as part of a Texas Department of Transportation (TxDOT) sign workshop. In the evaluation, TxDOT sign crews evaluated 49 signs on an 8-km (5-mi) closed course. Each sign was rated as “acceptable,” “marginal,” or “unacceptable.” Vehicle headlamp illuminance was also measured. The results of the evaluations were compared with the application of the FHWA minimum values. The results show that whereas one sign did not meet the low-speed FHWA minimum values, the average ratings for the TxDOT sign crews indicated that 26 signs were not acceptable. The researchers identified several factors that affected the average sign ratings. These factors included the uniformity of the sign face, the type of sheeting material, and the retroreflectivity. The findings indicate that among the TxDOT sign crews participating in the evaluation, visual nighttime inspections result in a higher failing rate than does the application of the FHWA research recommendations for minimum levels of retroreflectivity. This finding indicates that visual sign inspections should be an important component of assessing the nighttime visibility of traffic signs.

Advanced Vehicle Navigation applied in the BMW Real Time Light Simulation

Advanced vehicle navigation based on the US Global Positioning Systems (GPS) will play a major role in future vehicle control systems. Contemporary vehicle navigation systems generally consist of vehicle positioning using satellites and location and orientation of the vehicle with respect to the roadway geometry using a digitised map on a CD-ROM. The standard GPS (with Selective Availability) enables positioning with an accuracy of at least 100 m and is sufficiently accurate for most route guidance tasks. More accurate, precision navigation can be obtained by Differential GPS techniques. A new light concept called Adaptive Light Control (ALC) has been developed with the aim to improve night-time traffic safety. ALC improves the headlamp illumination by means of continuous adaptation of the headlamps according to the current driving situation and current environment. In order to ensure rapid prototyping and early testing, the step from offline to online (real-time) simulation of light distributions has been successfully completed in the driving simulator. The solutions are directly ported to real vehicles to allow further testing with natural road conditions.

Visibility of Road Markings as a Function of Age, Retroreflectivity Under Low-Beam and High-Beam Illumination at Night

A study was conducted to obtain visibility data for old and young subjects performing a pavement marking end detection task on a fully marked road under headlamp illumination conditions. A total of 20 healthy subjects (10 old and 10 young) were used. It was found that observer age had a highly significant effect on pavement marking visibility. The effect of headlamp illumination (high-beam versus lowbeam) was found to be rather weak, probably because of the low-beam headlamp pattern, which favors the right-edge line. Pavement marking retroreflectivity was found to be significant at the levels investigated in the experiment. The new yellow dashed centerlines (tape) with a gapto-stripe ratio of 9.1/3 had a retroreflectivity of RL = 222 mcd/m2/lx and RL = 399 mcd/m2/lx under the medium and high conditions, respectively. The new white edge lines (tape) had a retroreflectivity of RL = 268 mcd/m2/lx and RL = 706 mcd/m2/lx under the medium and high conditions, respectively. The average end detection distances ranging from 124.8 m (average preview time 5.1 s for 88.5 km/h) for the old group under low-beam illumination on the medium retroreflectivity road to 237.3 m (average preview time 9.7 s for 88.5 km/h) for the young group under high-beam illumination on the high retroreflectivity road may appear to be rather long. However, the reader should be aware that markings as bright as the ones used in this research are the exception instead of the rule in real-world driving situations. The aim of this study was to determine the end detection distances obtainable under fairly favorable pavement marking material conditions.

Visual Target Detection Models for Civil Twilight and Night Driving Conditions

A luminance contrast-based computer visibility model is discussed and compared with the civil twilight method, which has recently been introduced. The civil twilight method attempts to predict the visibility of ordinary objects (reflectance 3 to 79 percent, average size) by using only the headlamp illuminance at the target. It is suggested that the one-factor approach used by the civil twilight method is insufficient to satisfactorily address target visibility in the field. Developers of more advanced visibility models generally attempt to design models based on the current state of the visibility research and with enough capability to obtain a reasonable degree of realism. The level of the benchmark illuminance (3.2 lx) used in the civil twilight method is considered by the authors to be too high, leading to very short detection distances for pedestrians under automobile headlamp illumination at night. The developers of the civil twilight method claim that the 3.2-lx visibility benchmark is based on systematic visual observations made by astronomers over a century ago. The use of the civil twilight method for pedestrian detection under automobile headlamp illumination at night is strongly discouraged by the authors of this paper, because the method may be misused by forensic experts if there is a need to produce arbitrarily short pedestrian detection distances, regardless of factors such as clothing reflectance, contrast, pedestrian size, windshield transmittance, and atmospheric transmissivity.

Reflective Properties of Selected Road Surfaces for an Automobile Headlamp Geometry

Luminance-contrast-based pavement marking visibility models are widely used in the design of street and automobile lighting systems, the design and evaluation of retroreflective sheeting materials and pavement-marking materials, and in the establishment of minimum visibility requirements for nighttime motorists. Computer-based visibility models usually determine the visibility of pavement markings by comparing the available luminance contrast formed between the pavement marking and the immediate surrounding road surface with a human threshold contrast value. However, to be able to calculate the luminance contrast between a pavement marking and the road surface, a pavement-marking visibility model needs matrices of retroreflectance as a function of the entrance angle and the observation angle, both for the pavement and the pavement markings. However, no extensive field data are available on the reflective properties of road surfaces under an automobile headlamp geometry (observation angles less than 1°). Retroreflectance matrices were developed for old asphalt, new asphalt, old concrete, and new concrete road surfaces. The road surface retroreflectance was measured with a specially designed apparatus in the field. Multiple linear regression models were developed with the retroreflectance data obtained for each measured road surface. Traffic sign luminance measurements under automobile headlamp illumination conditions were conducted in the field at night to determine the degree to which a post-mounted traffic sign (sign center 1.98 m above the ground) receives indirect light reflected from the road surface.

A technique for endoscopic pituitary tumor removal

A number of milestones have marked the development of transsphenoidal pituitary tumor resection this century. The introduction of headlamp illumination, followed by the use of the operating microscope and fluoroscopy have allowed neurosurgeons to perform this surgery in a safe and highly effective manner. With the aid of a case report, we describe the incorporation of endoscopic techniques in pituitary tumor resection. The technique described is minimally invasive, avoiding septal dissection and allowing unsurpassed, unobstructed, and panoramic visualization of the region of interest to the surgeon and operative team.

Phacoemulsification in the standing position with loupe magnification and headlamp illumination

A patient who could not recline from the seated position because of myotonic dystrophy and advanced interstitial lung disease presented to the UCLA Department of Ophthalmology Inpatient Consultation Service complaining of poor vision in both eyes as a result of corticosteroid-induced cataracts. We performed phacoemulsification and posterior chamber intraocular lens implantation in the standing position using magnifying loupes and fiber optic headlamp illumination. The excellent red reflex provided by the coaxial headlamp and the surgical control provided by bracing the operating hand against the cheek made this approach a viable option for this severely compromised patient. We discuss the surgical technique and its limitations.

Instrumentation for mapping light intensity contours

Automobile headlamp illumination is of concern because uniformity and shape of the beam pattern are quite important for optimum road visibility and safety for oncoming drivers. The Society of Automotive Engineers' specification on headlamp illumination [1] designates the maximum and minimum intensities at several spots within the beam. Many states require inspection of vehicle-mounted headlamps for illumination and aiming, and this test is commonly performed using a device which clamps on the headlamp lens. This clamp-on device is limited to checking the maximum intensity at beam center, rather than checking the overall beam pattern to the SAE-J579a specifications. In addition, mechanical limitations of this device have often resulted in the mis-aiming of vehicle headlamps. Present instrumentation available for measuring light intensity per SAE-J579a is primarily of the photo-cell type device, and the point-to-point measurement of light intensities is quite tedious and time consuming. A technique is described in this paper which incorporates electronic signal processing into a closed-circuit television system for displaying contours of constant illumination intensity. The technique is capable of rapidly performing vehicle-mounted headlamp testing per SAE-J579a and could be adapted for use at state inspection stations.