22 - LEDs for projectors

ObjectiveTissue injuries caused by the thermal effects of xenon light microscopes have previously been reported. Due to this, the development of a safe microscope light source became a necessity. A newly developed laser light source is evaluated regarding its effectiveness and safety as an alternative to conventional xenon light source.MethodsWe developed and tested a new laser light source for surgical microscopes. Four experiments were conducted to compare xenon and laser lights: 1) visual luminance comparison, 2) luminous and light chromaticity measurements, 3) examination and analysis of visual fatigue, and 4) comparison of focal temperature elevation due to light source illumination using porcine muscle samples.ResultsResults revealed that the laser light could be used at a lower illumination value than the xenon light (p < 0.01). There was no significant difference in visual fatigue status between the laser light and the xenon light. The laser light was superior to the xenon light regarding luminous intensity and color chromaticity. The focal temperature elevation of the muscle samples was significantly higher when irradiated with xenon light in vitro than with laser light (p < 0.01).ConclusionThe newly developed laser light source is more efficient and safer than a conventional xenon light source. It lacks harmful ultraviolet waves, has a longer lifespan, a lower focal temperature than that of other light sources, a wide range of brightness and color production, and improved safety for the user’s vision. Further clinical trials are necessary to validate the impact of this new light source on the patient’s outcome and prognosis.

A light source has been built at the simulation chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) at the Karlsruhe Institute of Technology, simulating solar radiation at ground level. Instead of full spectra light sources, it uses a combination of LEDs with a narrow emission spectrum, resulting in a combined spectrum similar to the solar spectrum between 300 and 530 nm. The use of LEDs leads to an energy-efficient, robust and versatile illumination concept. The light source can be used over a wide temperature range down to −90 °C, is adjustable in intensity and spectral width as well as easily adjustable to new technological developments or scientific needs. Characterization of the illumination conditions shows a vertical intensity gradient in the chamber. The integral intensity corresponds to a NO2 photolysis frequency j(NO2) of (1.58 ± 0.21 (1σ)) x 10−3 s−1 for temperatures between 213 and 295 K. At constant temperature, the light intensity is stable within ±1 %. While the emissions of the different LEDs change with temperature, they can be adjusted, thus it is possible to adapt the spectrum for different temperatures. Although, the illumination of the simulation chamber leads to an increase of 0.7 K h−1 of the mean gas temperature, it is possible to perform experiments with aqueous droplets at relative humidities up to ≤ 95 % and also above water or ice saturation with corresponding clouds. Additionally, temperature and wavelength dependent photolysis experiments with 2,3-pentanedione have been conducted. The photolysis of 2,3-pentanedione occurs mainly between 400 and 460 nm resulting in a mean photolysis frequency of (1.03 ± 0.15) x 10−4 s−1 independent of temperature in the range 213–298 K with a quantum yield of 0.36 ± 0.04. In contrast the yield of the two main photolysis products, acetaldehyde and formaldehyde, decreases with temperature. Furthermore, the light source was applied to study the photochemistry of aerosol particles. For the atmospheric brown carbon proxy compound 3,5-diacetyl-2,4,6-trimethyl-1,4-dihydropyridine photochemical reaction products were identified. In aerosol particles containing iron oxalate as photosensitizer the photosensitized degradation of organic acids (pinic and pinonic acid) was studied. Although, the light source only generates about 1/3 of the maximum solar irradiation at ground level with a substantial intensity gradient throughout the simulation chamber it could be shown that this type of light source allows reproducible experiments over a wide range of simulated atmospheric conditions and with a large flexibility and control of the irradiation spectrum.

See-through head-up 3D display is being reported, which uses a commercial projector as the light source and a lens array in the form of holographic optical element (HOE). By introducing novel technique in the fabrication process of the HOE based lens array, we have significantly simplified the display system by not using any collimation optics. Light field reconstructions of a 3D scene of size 20cm (Width) × 10cm (Height) × 5 cm (Depth) is successfully demonstrated with a view angle of 10-degrees.

LCD projection-based cockpit displays are beginning to make entry into military and commercial aircraft. Customers for commercial Head-Up Displays (HUDs)(including airframe manufacturers) are now interested in the adaptation of the technology into existing and future HUD optical systems. LCD projection can improve mean-time-between-failure rates because the LCDs are very robust and the light sources can be replaced with scheduled maintenance by the customer without the need for re-calibration. LCD projectors promise to lower the cost of the HUD because the cost of these displays continues to drop while the cost of CRTs remain stable. LCD projectors provide the potential for multi-colors, higher brightness raster, and all-digital communication between the flight computer and display unit. Another potential benefit of LCD projection is the ability to increase field of view and viewing eyebox without exceeding existing power budgets or reducing display lifetime and reliability compared to the capabilities provided by CRTs today. This paper describes the performance requirements and improved performance of a third-generation LCD projection image source for use in a wide field of view head-up display (HUD) optical system. This paper will focus on new HUD requirements and the application of various technologies such as LCOS microdisplays, arc lamps, and rear-projection screens. Measured performance results are compared to the design requirements.

An understanding of light and its interaction with matter is essential to produce images. As the modeling of light sources, light transport and light reflection improves, it becomes possible to render images with increasing realism. The central motivation behind this thesis is to improve realism in computer graphics images by more accurate local shading models and to assist the user to obtain the desired lighting effects with these more complex models. The first part of the thesis addresses the problem of rendering surfaces illuminated by extended (linear and area) light sources. To compute the light reflected by a surface element in a given direction, one needs to determine the unoccluded regions (shadowing) of each light source and then to compute the light reflection (shading) from each of these regions. Traditionally, point light sources are distributed on the lights to approximate both the shadowing and the shading. Instead, an efficient analytical solution is developed for the shading. Shadowing from extended light sources is a fairly expensive process. To give some insights on the complexity of computing shadows, some properties of shadows and algorithms are presented. To reduce the cost of computing shadows from linear light sources, two acceleration schemes, extended from ray tracing, are introduced and evaluated. The second part of this thesis addresses the problem of achieving a desired shading effect by building up systems of constraints. This approach is called inverse shading. It allows a user to obtain a desired lighting effect by interacting directly with the scene model. An interactive modeling system has been built to study the introduction of rendering issues into the modeling process itself. Two rendering aspects are considered: shading and shadows. By specifying a highlight position and size, the unique direction of a directional light source as well as the surface glossiness are determined. Interactively moving this highlight on the surface redefines the light direction while changing its size redefines the surface glossiness. By manipulating shadow volumes (the volume within which a particular light cannot be completely seen), the light source definition and position can be modified. By assigning colours to various points in a 3D scene, information about the colour of a surface as well as other surface characteristics can be deduced. This relatively new concept of defining the causes by manipulating the effects is expected to have a major impact on the design of future computer graphics modeling systems. It begins a new family of tools for the design of more intuitive user interfaces.

Cymer continues to address several areas of sustainability within the semiconductor industry by reducing or eliminating consumption of power and specific types of gas (i.e. neon, helium) required by DUV light sources in order to function. Additionally, Cymer introduced a new recycling technology to reduce the dependence on production of raw gases. In this paper, those initiatives that reduce the operational cost, environmental footprint, and business continuity risk will be discussed. Cymer has increased the efficiency of its light sources through improvements that have resulted in energy output increase while maintaining the same or requiring less power consumption. For both KrF and ArF systems, there have been component [1], system, and architecture improvements [2] that allowed customers to increase energy efficiency and productivity. An example of module improvements is the latest MO chamber that helped reduce power consumption by ~15%. Future improvements aim to continue reducing the power consumption and cost of operation of the install base and new systems. The neon supply crisis in 2015 triggered an intensive effort by the lithography light source suppliers to find ways to minimize the use of neon, a main consumable of the light source used in DUV photolithography. Cymer delivered a multi-part support program to reduce natural resource usage, decrease overall cost of operation, and ensure that chipmaker’s business continuity risk is minimized. The methods used to minimize the use of neon for 248 nm and 193 nm photolithography that offered significant relief from supply constraints and reduction of business continuity risk for chipmakers were described in previous work [3]. In this paper, results from the program will be presented. In addition, techniques to capture the neon effluent and re-purify it within the semiconductor fabs have been pursued. For example, Cymer has developed and validated a neon recycling system for ArF light sources that resides within the chipmaker’s fab. Cymer has partnered with a global gas supplier to develop a system capable of capturing, recycling and delivering <90% of the total neon gas required by multiple ArF light sources through automated operation, including online analysis. In this paper, the neon recycle system performance as demonstrated by a quantitative analysis of facility-supplied gas versus the recycled neon in ArF light source performance will be discussed. Similarly, DUV light sources have historically used helium as a purge gas in the critical line narrowing module (LNM) to achieve stable wavelength and bandwidth control. Helium has a low coefficient of index of refraction change vs. temperature relative to nitrogen and provides efficient cooling and purging of critical optics in the LNM. Previous work demonstrated how helium consumption can be reduced and still achieve stable performance under all operating conditions [1]. In this paper, results of eliminating the use of helium will be described.

This paper presents and investigates methods for fast and accurate illumination of scenes containing many light sources that have limited spatial influence, e.g. point light sources. For speeding up the computation, current graphics applications use an assumption that the light sources range can be limited using bounding spheres due to their limited spatial influence and illumination is computed only if a surface lies within the sphere. Therefore, we explore the differences in illumination between scenes illuminated with spatially limited light sources and physically more correct computation where the light radius is infinite. We show that the difference can be small if we add appropriate ambient lighting. The contribution of the paper is the method for fast estimation of ambient lighting in scenes illuminated by numerous light sources. We also propose a method for elimination of color discontinuities at the edges of the bounding spheres. Our solution is tested on two different scenes: a procedurally generated city and the Sibenik cathedral. Our approach allows for correct lighting computation in scenes with numerous light sources without any modification of the scene graph or other data structures or rendering procedures. It thus can be applied in various systems without any structural modifications.

Light-Source Modeling Using Pyramidal Light Maps

A very fast (- 10 psec) laser light source has been constructed which can be used tomake shadowgraph, interferometry, and other diagnostic photographs useful in laser fusionstudies. To produce this pulsed light source, a portion of the 100 psec main Nd:glasslaser pulse is split off, sent through CS2 cells to produce a frequency chirp, and thenoptically compressed by diffraction gratings. By frequency converting the output pulse,one can perform studies at frequencies other than the fundamental (i.e., harmonic orRaman -shifted frequencies). The compressed pulse is absolutely time -synchronized with themain laser pulse. Shadowgrams taken using this technique are shown.IntroductionA very important diagnostic technique in laser fusion studies is the use ofsubnanosecond optical observations of laser produced plasmas. Optical techniques utilizinga pulsed light source such as shadowgraphy, Schlieren photography, and interferometry l'2 have proven particularly valuable for measuring the plasma density, shape, and velocity;while the Faraday rotations method has been used to measure the magnetic field generatedin the plasma. These plasmas often have velocities greater than 107 cm /sec, densitiesgreater than 1021 particles /cm3, and steep density gradients, particularly in the vicinityof the critical surface. Thus the use of such techniques usually requires a spatial -resolution of less than 10 u.m and a time -resolution of less than 10 picosec.In this paper we describe a technique by which a very short light pulse can be producedby compressing a portion of the main laser pulse.4 Moreover, the frequency of thecompressed pulse can be modified to serve a particular diagnostic purpose. Although atechnique of synchronizing two independent oscillators to within 100 psec has beenreported, the pulse compression system has the advantage that the probe light signal isabsolutely time -synchronized with the main laser pulse, and has a pulse duration shortenough to prevent time -smearing in the photograph.Pulse CompressionThe technique of pulse compression to reduce optical pulse duration and increase laserpeak power has been used for some time. 8'7 In this technique a relatively long laserpulse is passed through a liquid with a large nonlinear index of refraction to produce afrequency ; i.e., an actual optical carrier frequency variation within a singlelaser pulse. The chirped pulse can then be temporally compressed by passing it through apair of diffraction gratings.° Compression will take place if those frequencies thatappear earliest in the long pulse are forced to undergo the greatest delay. This isindicated in Fig. 1 where an incoming chirped pulse of FWHM duration At is dispersed sothat the higher frequency component (wo + Aw) is seen to follow a shorter path (AS) afterreflection from the second grating than the lower frequency component (wo - Aw), whichappeared earlier in the incident pulse. The recollimated exiting beam is then time -compressed to width Atc « At if the chirp bandwidth is large and if AS - c(At - Atc),The frequency chirp with initial pulsewidths up to about 100 psec is best produced byself phase modulation in a liquid with a high nonlinear index of refraction,i.e., for CS2n2 = 1.3 x 10 -11 esu. For example, an intense laser pulse passing through a CS2 cell under-goes self phase modulation, which results in an instantaneous frequency displacementfrom the original laser frequency given byHere

Development of a new multi-mode NIR laser system for photodynamic therapy

Monochromatic wavelength identification never had such significance as today when several lighting applications favor the use of light emitting diodes as light sources. People with normal color vision designing the color appearance of a monochromatic lighting solution usually do not consider the different appearance of these stimuli for color blind. In our study we have measured the monochromatic color identification of more than 100 observers with different types of color vision and we have found significant differences in their color identification. The results should be implemented in all illumination design where the use of LEDs is considered.

Free-space optical communications hold promising advantages, including a large bandwidth, access to license-free spectrum, high data rates, quick and simple deployment, low power consumption, and relaxed quality requirements. Nevertheless, key technical challenges remain, such as a higher transmission efficiency, a lower transmission loss, and a smaller form factor of optical systems. Here, we demonstrate the viability of circular-polarization-multiplexed multi-channel optical communication using metasurfaces alongside a photonic-crystal surface-emitting laser (PCSEL) light source at wavelength of 940 nm. Through the light manipulation with metasurface, we split the linearly polarized incidence into left and right circular polarizations with desired diffraction angles. Such orthogonal polarization states provide a paradigm of polarization division multiplexing technique for light communication. The PCSEL light source maintains a low divergence angle of about 0.373 degrees after passing through an ultra-thin metasurface without further bulky collimator or light guide, making end-to-end (E2E) and device-to-device (D2D) communications available in a compact form. Both light source and modulated polarized light exhibit a − 3 dB bandwidth over 500 MHz, with successful 1 Gbit/s transmission demonstrated in eye diagrams. Our results affirm that metasurface effectively boosts transmission capacity without compromising the light source's inherent properties. Future metasurface designs could expand channel capacity, and its integration with PCSEL monolithically holds promise for reducing interface losses, thereby enhancing efficiency.

Inverse rendering, a technique for reconstructingthree-dimensional (3D) geometric structures and surface materials from two-dimensional (2D) images, is of great significance in fields such as robotic manipulation, virtual reality, and augmented reality. However, existing inverse rendering methods based on neural implicit representations are primarily suitable for scenarios with fixed light sources and struggle with dynamic point lighting. This paper introduces a novel 3D inverse rendering method that estimates the positions of point light sources, facilitating the 3D reconstruction of geometrical structures and the determination of light source locations from a collection of images captured from various perspectives, even under dynamic illumination conditions from an unknown point light source.

A light source based on blue laser and phosphor wheel is developed for portable projection displays. The phosphor wheel has multiple phosphor segments that can convert the blue laser to different color light. When the phosphor wheel is rotating, sequential color light will be generated. A color filter set is integrated with the phosphor wheel; therefore the color coordinates of each color light can be controlled to fulfill the requirements such as Rec. 709 standard. Thermal quenching of the phosphor is studied and improved to enhance the energy efficacy of this light source. Engineering samples were made to do performance, lifetime and reliability tests.

Photocatalytic decompositions of gaseous HCHO over thin films of anatase titanium oxide converted from amorphous in a heated air and in an aqueous solution of hydrogen peroxide