Small Light Source Research Articles

A method to improve reconstruction of the distribution of hemoglobin, oxygenation, and MLu concentration in the human prostate before and after photodynamic therapy.

Explicit dosimetry of photodynamic therapy requires detailed knowledge of the light, drug, and oxygenation distributions within the target tissue. We present a method for the optical detection and three-dimensional reconstruction of hemoglobin concentration and oxygenation and sensitizer concentration within the human prostate. Spectrally resolved diffuse transmission measurements were made using a small isotropic fiber-based white light source and an isotropic detector inserted into the prostate via parallel closed transparent catheters. The spectra were modeled using the diffusion approximation appropriate for infinite media. The optical absorption of the prostate was assumed to be a linear combination of the absorption spectra of oxy- and deoxyhemoglobin and MLu, and the scattering was assumed to be of the form A(λ/λ0)-b. The separation of absorption and scattering coefficients was accomplished based on the spectral shape of the diffuse transmission, rather than the spatial variation in intensity. By making multiple measurements at various source-detector separations, we investigate the signal-to-noise sensitivity of our algorithm. In addition, the redundancy in our source-detector position matrix creates several positions in which the tissue parameters can be reconstructed from multiple independent measurements, allowing an assessment of the repeatability of the algorithm. We find significant heterogeneity in the reconstructed optical properties; however the recovery of spectrally consistent absorption and scattering spectra is improved compared to wavelength-wise reconstruction algorithms.

地域性と横道認知を考慮した交差点の光環境整備の提案 : 富山市八尾町を対象として

This research focused on the advance perception of nighttime intersections in Yatsuo Town in Toyama City. The research considered an ideal street lighting method taking into consideration danger avoidance and regional characteristics. First, the present situation regarding the perception of intersections in the town was evaluated. The result showed that many narrow crossroads were not perceived easily at night, and it was found that the visibility of the crossroad outline and the corner buildings was important in perceiving crossroads in advance. Next, a new lighting environment at an intersection was created experimentally using small light sources, and it was found that these lights harmonized with the streetscape and also succeeded in helping drivers to perceive the intersection earlier.

The illuminated surface areas of high-intensity discharge and tungsten halogen headlamps in the USA

,!This study was designed to compare the illuminated surface areas of high-intensity discharge (HID) and tungsten halogen low-beam headlamps in the USA. A sample of 20 tungsten halogen lamps and 17 HID lamps for model year 2000 vehicles in the US was examined. The illuminated surface area was determined using a modified version of an Economic Commission for Europe (ECE) method for evaluating the illuminated surface of signalling devices. The main finding is that the HID low (passing) beams generally have smaller illuminated surface areas than do the tungsten halogen low beams. Because smaller light sources result in more discomfort glare (presumably via greater luminance), the present finding suggests that the smaller illuminated area is one reason for drivers reporting more discomfort from HID lamps. An implication is that the increased discomfort from HID lamps could be reduced by increasing their illuminated surface area.

Real‐time Light Animation

Abstract Light source animation is a particularly hard field of real‐time global illumination algorithms since moving light sources result in drastic illumination changes and make coherence techniques less effective. However, the animation of small (point‐like) light sources represents a special but practically very important case, for which the reuse of the results of other frames is possible. This paper presents a fast light source animation algorithm based on the virtual light sources illumination method. The speed up is close to the length of the animation, and is due to reusing paths in all frames and not only in the frame where they were obtained. The possible applications of this algorithm are the lighting design and systems to convey shape and features with relighting.

Evaluation of new organic pigments as laser-active media for a solid-state dye laser

Solid-state dye lasers are small, low-cost, simple, and coherent light sources. These lasers can output a laser beam at many wavelengths by changing the organic dyes or pigments. Photodegradation of the laser-active medium, however, is difficult with this type of laser. Research regarding new fluorescent materials that are not easily degraded by exposure to the pump light is therefore important in developing practical applications for solid-state dye lasers. In the present study, six new organic pigments were synthesized and evaluated as the active medium of the solid-state dye laser. The issues evaluated were: (1) whether the pigments can oscillate as laser medium or not; and (2) degradation by exposure to UV light. As a result of the evaluation, each of the six pigments oscillated as laser medium and green and yellow laser oscillations were obtained. The pigments were also found to have degradation characteristics similar to those of Rhodamine B.

A geometry-based soft shadow volume algorithm using graphics hardware

Most previous soft shadow algorithms have either suffered from aliasing, been too slow, or could only use a limited set of shadow casters and/or receivers. Therefore, we present a strengthened soft shadow volume algorithm that deals with these problems. Our critical improvements include robust penumbra wedge construction, geometry-based visibility computation, and also simplified computation through a four-dimensional texture lookup. This enables us to implement the algorithm using programmable graphics hardware, and it results in images that most often are indistinguishable from images created as the average of 1024 hard shadow images. Furthermore, our algorithm can use both arbitrary shadow casters and receivers. Also, one version of our algorithm completely avoids sampling artifacts which is rare for soft shadow algorithms. As a bonus, the four-dimensional texture lookup allows for small textured light sources, and, even video textures can be used as light sources. Our algorithm has been implemented in pure software, and also using the GeForce FX emulator with pixel shaders. Our software implementation renders soft shadows at 0.5--5 frames per second for the images in this paper. With actual hardware, we expect that our algorithm will render soft shadows in real time. An important performance measure is bandwidth usage. For the same image quality, an algorithm using the accumulated hard shadow images uses almost two orders of magnitude more bandwidth than our algorithm.

A noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator–based stereotactic radiotherapy of uveal melanoma

Purpose To introduce a noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator-based stereotactic radiotherapy for uveal melanoma. Methods and materials At the Department of Radiotherapy and Radiobiology, University of Vienna, stereotactic radiotherapy is offered to patients with uveal melanoma considered unsuitable for 106Ru brachytherapy or local resection. For the present feasibility study, 8 patients were carefully selected according to their ability to fixate a small light source with the diseased eye and whether they had a rather small head to meet the limited geometric space available. A polymethyl methacrylate tube was attached to a stereotactic mask system in craniocaudal orientation supporting a 45° mirror, which was placed in front of the diseased eye. At the other end of the tube, the patient was given a small fixation light, and a small camera was positioned beneath, which was shielded for use during MRI. A computer interface calculated and visualized the spatial difference of the actual and a given reference pupil position, which was defined before CT scanning, during the MRI sequences, and during treatment delivery at the linear accelerator. Results The described system can be attached to a conventional stereotactic mask system with minor modifications. Because of the large distance between the eye and the fixation light, the optical fixation system was well tolerated by all patients, and a stable position of the eye was obtained. The camera system can be used during CT and MRI without interference. Absorption of the 6-MV photon beam by the mirror and the polymethyl methacrylate tube was negligible. The computer interface designed to determine the pupil position uses an image-processing algorithm that correlates a template of the reference image with the actual image of the eye. Provided sufficient illumination of the pupil, the correlation function showed a pronounced minimum at the reference position. The precision of the algorithm was tested by phantom measurements. For a given 1 mm or 2 mm displacement, the interface reported a mean shift of 0.96 ± 0.18 mm or 2.07 ± 0.11 mm, respectively. Conclusion The results of this study demonstrated the feasibility of a new optical fixation system for linear accelerator-based stereotaxis. The artifact-free application of the camera system during image acquisition and irradiation and the use of the computer interface, which automatically monitored eye movements with submillimeter precision, provided large improvements compared with existing techniques. Given well-defined interruption criteria and accelerated image processing, the described system has a high potential to perform automatically gated treatment beam delivery in the near future.

Isoprene production by Prochlorococcus, a marine cyanobacterium, and other phytoplankton

The oceans are a small source of light (C 2–C 6) non-methane hydrocarbons (NMHC), which influence the photo-oxidant chemistry of the remote marine atmosphere. Previous work has shown that water column sources of alkenes include photochemical processes, and that various phytoplankton species can produce isoprene. However, only a few phytoplankton species have been studied, and no assessment has been performed of the effects of other pelagic microorganisms on NMHC cycling. The dependence of phytoplanktonic isoprene production on light, temperature, and organism size has also not been investigated. In this work, laboratory cultures of five different marine phytoplankton species ( Prochlorococcus, Synechococcus, Micromonas pusilla, Pelagomonas calceolata, and Emiliania huxleyi) were examined for NMHC production capabilities. All species were found to produce isoprene at constant rates during the balanced exponential growth phase; rates ranged from 1×10 −21 to 4×10 −19 mol cell −1 day −1 over all cell species and growth conditions tested. No other NMHC was consistently produced or consumed by these cells. The presence of heterotrophic bacteria in phytoplankton cultures had no effect on isoprene production rates per phytoplankton cell. A positive allometric relationship was observed between isoprene production rate and cell volume; highest production rates were found for the largest cell, E. huxleyi, and lowest rates for Prochlorococcus, the smallest cell. Isoprene production was a function of light intensity and temperature in Prochlorococcus, with patterns that were similar to those between growth rate and these environmental variables. The maximum production with light intensity occurred in the photoinhibited regime, and the maximum with temperature was at the maximum of growth rate for this species, near 23 °C. Nanoflagellate grazing by Cafeteria roenbergensis on, and phage infection of, Prochlorococcus controlled total isoprene produced in the flask by controlling cell abundances. Phage infection also decreased the isoprene production rate per cell during latent period of infection as compared to healthy cells. With certain assumptions, combining the measured laboratory isoprene production rates with observed water column phytoplankton abundances resulted in a maximum estimated sea-to-air flux of isoprene that was on the same order of magnitude as previously reported values determined using in situ measured seawater and atmospheric measurements.

Simple device for quantifying the influence of halos after lasik surgery

We present a simple device (called a halometer) to detect and quantify the phenomenon of halos after certain surgical procedures, such as refractive surgery. The task of the subject consists basically of discriminating, after dark adaptation, a small light source around a central high-luminance stimulus. The device, which is connected to a computer, provides a disturbance index to measure the effect of halos on the observer's vision. Tested with normal subjects and patients after LASIK (laser in situ keratomileusis) surgery, this apparatus proved sufficiently sensitive to quantify the halos in subjects who had undergone surgery.

Tailored freeform optical surfaces.

Freeform optical surfaces embedded in three-dimensional space, without any symmetry, are tailored so as to solve the archetypal problem of illumination design: redistribute the radiation of a given small light source onto a given reference surface, thus achieving a desired irradiance distribution on that surface. The shape of the optical surface is found by solving a set of partial nonlinear differential equations. For most cases, a few topologically distinct solutions exist, given suitable boundary conditions.

Probing Biological Samples with Near-Field Optics

Abstract Near-field scanning optical microscopy (NSOM) is an emerging optical technique capable of probing samples at the nanometric level. With the NSOM technique, high spatial resolution is achieved by scanning a small light source (or collector) close to a sample surface. The light source is usually formed with special fiber optic probes that funnel light down to an aperture that is smaller than the optical wavelength. By positioning the aperture close to a sample, the emerging radiation is forced to interact with the sample before diffracting out. Therefore, the spatial resolution in NSOM is only limited by the size of the aperture and its proximity to the sample, and not the wavelength of the light as in conventional optical microscopy. Recently, we have been using the single molecule detection limits combined with the unique nature of the electric fields present near the NSOM tip aperture to probe molecular level structure in model lipid membranes.

Autostereoscopic 3-D video display using multiple light beams with scanning

An autostereoscopic 3-D displaying technique that uses fan-likely placed multiple light beams in a light array with 2-D raster scanning is proposed. This technique is capable of displaying multiple perspective views at high resolution because the number of views only depends on the number of light beams, while the number of light beams does not depend on the resolution of each view. Moreover, dozens or hundreds of perspective views at an angular interval narrower than one degree can be produced if small light sources are used. On the basis of this technique, an experimental 3-D display system capable of producing 45-view video images at an angular interval of 0.5 degrees at a time is developed. Furthermore, the effectiveness of the technique is demonstrated by using this system.

Lighted stylet tracheal intubation: a review.

Tracheal intubation is older than the recognized his-tory of general anesthesia itself. In the late 18th cen-tury, The Royal Humane Society of London used tra-cheal intubation for resuscitating the near-drowned.Approximately 100 years later, MacEwan (1) per-formed a digital tracheal intubation in an awake pa-tient before a chloroform and air general endotrachealanesthetic for the resection of a tongue tumor, and in1928, Magill (2) incorporated blind nasal tracheal in-tubation as a part of a general anesthetic. Althoughlaryngoscopes were invented in the 19th century, tra-cheal intubation under direct visualization was greatlyenhanced by the development of a special laryngo-scope blade by Macintosh (3) in 1943.The first reported use of a lighted stylet used tofacilitate intubation came in 1957 when (by now SirRobert) Macintosh (4) described an 18-inch illumi-nated tracheal tube introducer, which was designed tostiffen the tube and better illuminate the cords bysupplementing the light of the laryngoscope. Berman(5) described a similar device in 1959 and said it wasuseful “when the fickle light of the laryngoscope hasgone out at the most inopportune time.” In the sameyear, Yamamura et al. (6) described a light bulb-tippedwire that was inserted into the tracheal tube beforeblind nasal intubation in awake patients. The tubeposition was then determined by the medial transillu-mination of the external throat and neck.In 1977, Foster (7) used a transilluminating fiberop-tic bundle to facilitate tracheal intubation in a youngchild with trismus, and Ducrow (8), in the followingyear, used a flexible surgical light (Flexi-lum™, Con-cept Corporation, Clearwater, FL) to achieve the sameend by first passing a guide (two plastic suction cath-eters connected end-to-end) into the trachea followedby passage of the tracheal tube over the guide. In acorrespondence to the latter article, Rayburn (9) com-mented that the Flexi-lum™ could be positioned in-side the tracheal tube, thereby shortening the intuba-tion sequence and claimed that the technique,nicknamed “lightwand intubation,” had been used forsome years at the Brooke Army Medical Center.

ＬＥＤの温度上昇が光合成有効光量子束に及ぼす影響および送風による除熱の試み

Recently, LED is being used as a light source for the cultivation of plants. However, the temperature rise of LED due to heat generation reduces the photosynthetic photon flux (PPF) of LED. Therefore, it is important to develop a method for heat removal. We report the effects of temperature rise in LED and heat removal by passing air either to the LED lamps or to the space between two circuit boards on PPF.We found that the PPF of LED is reduced by more than 30% in half an hour after lighting under the condition without heat removal. Thus, the method of heat removal attempted in this study seems to be effective for small scale light sources.

Observations on the optical effects of a cataract

Purpose To describe and measure the optical effects seen by a person with a cataract and to use these observations to deduce physical changes in the crystalline lens caused by the cataract formation. Setting Humphrey Systems, Dublin, California, USA. Methods Caustic patterns created on the retina by a bright point source of white light as that source is viewed at various far-point distances ranging from the anterior focal point of the eye to +15.00 diopters were observed. The subtended retinal angle of a diffractive ring of light created by a small bright source of white light was observed and measured. Results Three optical effects were seen and measured: multiple-image formation at certain far-point positions; a diffractive light ring surrounding small bright sources; a radial needle of bright light surrounding a small bright-white source. With a point source of light positioned at the anterior focal point of the eye, the Y sutures of the lens could be visualized. With the point source at other distances, characteristic caustic patterns could be visualized, allowing assessment of the lens’ optical character. The subtended retinal angle of the diffractive ring was measured so the periodic lens structure could be evaluated. Conclusions The lens acted refractively as if it were divided into 3 elements with noncoincident optical axes. These 3 segments were associated with areas defined by the Y sutures, causing 3 images to be formed at certain distances. The caustic patterns indicate that each segment is slightly toroidal with axes at about 120 degrees apart combined with overcorrected spherical aberration. The period structure creating the diffractive ring had a period of 10 μm, approximately the width of a cortical lens cell, indicating that fluid between the cells likely creates a diffractive phase grating.

Discomfort glare from small light sources

Glare from very small sources is grossly overrated by the UGR (Unified Glare Rating) formula. Experiments were carried out on glare from small sources at interior lighting distances. Results varied widely but were of adequate statistical accuracy. They showed that a small glare source is characterised by a constant projected area of 0.005 m2, not a constant solid angle; that glare from a source below 0.005 m2 is determined by its intensity, not by its luminance; and that the UGR formula is applicable to small sources if it is suitable modified (L2ω becomes 200I 2/R2).

High pressure discharges in cavities formed by microfabrication techniques

High pressure discharges are the basis of small high intensity light sources. In this work, we demonstrate the formation of high pressure discharges, in cavities formed by applying micromachining and integrated circuit techniques to quartz substrates. Cavities containing varying amounts of mercury and argon were fabricated to obtain high pressure discharges. A high pressure mercury discharge was formed in the electrodeless cavities by exciting them with a microwave source, operating at 2.45 GHz and in the electroded cavities by applying a dc voltage. The contraction of the discharge into a high pressure arc was observed. A broad emission spectrum due to self-absorption and collisions between excited atoms and normal atoms, typical of high pressure mercury discharges, was measured. The light output and efficacy increased with increasing pressure. The measured voltage was used to estimate the pressure within the electroded cavities, which is as high as 127 atm for one of the two cavities discussed in this work. Efficacies over 40 lumens per watt were obtained for the electrodeless cavities and over 50 ℓm/W for the electroded cavities.

Consultation with the specialist. Eye examinations in infants and children.

1. Joseph H. Calhoun, MD* 1. 2. *Director, Pediatric Ophthalmology and Strabismus, Wills Eye Hospital, Philadelphia, PA. Typically the pediatrician is the first physician who recognizes the signs or symptoms of possible eye disease in children. Therefore, it is incumbent upon him or her to be cognizant of those signs or symptoms that merit referral to an ophthalmologist for further evaluation and treatment. As in many other diseases in the field of pediatrics, appropriate examination and evaluation vary with the age of the child. In the first several days of life, examination of the eyes can be difficult. The lids may be swollen from the birthing process and from chemical conjunctivitis caused by the required gonococcal prophylaxis. The newborn usually will be sleeping and the eyes closed at the time of examination. In spite of these difficulties, it is important to exclude any major anomalies of eye development. The examination should include an inspection of the external surface of the eyeball, using any direct source of light, such as a penlight, a flashlight, or room light in the nursery. If the lids are closed and cannot be opened by active movement or twirling of the infant, cotton-tipped applicators may be used to open them. The applicators are placed on the lid margins, at the lashes, and are directed so as to push each lid margin against the cornea while at the same time separating the lids. This should allow a view of at least half of the cornea and the iris. This lid separation may be manipulated to view most of the front surface of the eyeball. If the applicators are placed away from the lid margins in the middle of each lid, the lids will evert, revealing only their back surfaces. The examiner should determine that each eye is the same and has a transparent cornea that provides a clear view of each iris (usually blue) …

ガス分析計用ＳｉＣウイスカー強化ＭｏＳｉ２小型赤外高輝度光源の開発

ガス分析計用ＳｉＣウイスカー強化ＭｏＳｉ２小型赤外高輝度光源の開発

QUANTITATIVE OPTICAL SPECTROSCOPY FOR TISSUE DIAGNOSIS

The interaction of light within tissue has been used to recognize disease since the mid-1800s. The recent developments of small light sources, detectors, and fiber optic probes provide opportunities to quantitatively measure these interactions, which yield information for diagnosis at the biochemical, structural, or (patho)physiological level within intact tissues. However, because of the strong scattering properties of tissues, the reemitted optical signal is often influenced by changes in biochemistry (as detected by these spectroscopic approaches) and by physiological and pathophysiological changes in tissue scattering. One challenge of biomedical optics is to uncouple the signals influenced by biochemistry, which themselves provide specificity for identifying diseased states, from those influenced by tissue scattering, which are typically unspecific to a pathology. In this review, we describe optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and then provide a descriptive framework for light interaction based upon tissue absorption and scattering properties. Finally, we review important endogenous and exogenous biological chromophores and describe current work to employ these signals for detection and diagnosis of disease.