Luminance Attenuation Research Articles

A life testing system design and life prediction for plant lighting LED-based luminaires

With the increasing demand for plant lighting LED-based luminaires, the reliability is facing a severe test, and the collection and the research of their life information is imminent. Firstly, the life testing system of plant lighting LED-based luminaires is constructed independently by conducting the preliminary tests of samples. Secondly, the test steps are designed to collect the luminance attenuation data of samples. Finally, the data pretreatment scheme is proposed to optimize the test data under conventional stress, and the life prediction is achieved by three-parameter Weibull right approximation method (TPWRAM). The results indicate that the collected test data well reflect the luminance attenuation characteristics of plant lighting LED-based luminaires, and the developed life test system has higher feasibility. The self-designed data preprocessing scheme is scientific and reasonable, and the processed test data objectively describe the luminance attenuation trend. In addition, the most important thing is that three-parameter Weibull function fits well with test data, which can accurately predict the normal life of plant lighting LED-based luminaires. The above results can provide technical reference for engineers to improve the performance of plant lighting LED-based luminaire.

Online Projector Deblurring Using a Convolutional Neural Network.

Projector deblurring is an important technology for dynamic projection mapping (PM), where the distance between a projector and a projection surface changes in time. However, conventional projector deblurring techniques do not support dynamic PM because they need to project calibration patterns to estimate the amount of defocus blur each time the surface moves. We present a deep neural network that can compensate for defocus blur in dynamic PM. The primary contribution of this paper is a unique network structure that consists of an extractor and a generator. The extractor explicitly estimates a defocus blur map and a luminance attenuation map. These maps are then injected into the middle layers of the generator network that computes the compensation image. We also propose a pseudo-projection technique for synthesizing physically plausible training data, considering the geometric misregistration that potentially happens in actual PM systems. We conducted simulation and actual PM experiments and confirmed that: (1) the proposed network structure is more suitable than a simple, more general structure for projector deblurring; (2) the network trained with the proposed pseudo-projection technique can compensate projection images for defocus blur artifacts in dynamic PM; and (3) the network supports the translation speed of the surface movement within a certain range that covers normal human motions.

Explore Luminance Attenuation and Optical Crosstalk of RGB Mini Light-Emitting Diode via Microscopic Hyperspectral Imaging

In this article, we experimentally and quantitatively investigate the luminance attenuation for red, green, and blue mini light-emitting diodes (LEDs), and the optical crosstalk in the RGB mini-LED array under different working currents via the microscopic hyperspectral imaging technique. The evaluation metrics of luminance attenuation for one single mini-LED subpixel and luminance in?uence among all three colored mini-LEDs are well defined to quantitatively describe the optical crosstalk among three mini-LED subpixels in the array. We also compare the size-dependent behaviors of luminance attenuation for blue and green mini-LEDs with an emission peak of about 465 nm and 529 nm, respectively. The minimum pixel pitch of blue and green mini-LEDs with different chip sizes is obtained through optical simulation based on LightTools software, so that the optical crosstalk can be reduced. Finally, we believe that this study could provide a useful guidance for selecting suitable working current conditions while driving the mini-LED display with suitable pixel size and pixel pitch to reduce both the optical and color crosstalk in the mini-LED display.

MEASUREMENT OF HALF-VALUE LAYER IN COMPUTED TOMOGRAPHY SCANNERS USING LUMINESCENCE OF POLYETHERSULFONE RESIN BY X-RAY IRRADIATION.

In this study, a method for estimating the half-value layer (HVL) and effective energy (Eeff) by imaging the luminescence from a polyethersulfone (PES) resin with rotating irradiation of X-rays in a computed tomography scanner was developed. The luminescence of the PES resin was imaged using a charge-coupled device camera. The PES-HVL was determined from the luminance attenuation profile corresponding to the X-ray attenuation within the resin. The PES-HVLs for tube potentials of 80-135 kVp were converted into Eeff values and were compared to those of a conventional lead-covered case method. The Eeff obtained using the proposed luminescence imaging method agreed within ~3.9% of that obtained using the conventional method. Moreover, dose simulations based on the X-ray spectrum calculated from the HVLs were performed using a poly(methyl methacrylate) phantom with a diameter of 16 cm. The simulated doses based on the luminescence imaging method agreed with the in-phantom dosimetry within ~9%.

P‐4.3: A Timekeeping Compensation Algorithm for OLED Luminance Attenuation

As we know, OLED has a short lifetime compared with LCD, due to its material characteristic[1], which leads to a fact that improved performance of lifetime in OLED display , especially vehicle OLED products is one of the most important factors in display market development of OLED. In this paper, a novel algorithm for luminance attenuation in OLED was proposed, using the method of statistical regularity.

Two life prediction models for optoelectronic displays without conventional life tests.

To precisely predict the life of optoelectronic displays over a short time, two life prediction models were established based on the three-parameter Weibull right approximation method (TPWRAM). In Model I, the acceleration life under each stress was obtained using TPWRAM, the data points formed by acceleration life and acceleration stress were, respectively, fitted by three extrapolation functions and the optimal extrapolation function was determined by comparing the fitting determination coefficient and root-mean-square error. In Model II, after introducing an acceleration parameter, the luminance attenuation data under conventional stress were calculated directly by combining the ones obtained using TPWRAM under each acceleration stress. The luminance attenuation test data from the vacuum fluorescent display (VFD) were collected through four groups of constant-stress accelerated degradation tests (ADT), and the two models were applied to the life prediction of VFD. The results indicated that the designed ADT scheme was feasible, Model I revealed the changing law of life with stress and simplified the process of life prediction, and Model II made it possible to obtain the luminance attenuation formula at conventional stress without conducting a conventional life test, overcoming the shortcomings of long time-consuming traditional life tests. It was verified by comparing the life prediction values that the two models had very high precision, and both of these not only achieve the accurate estimation of optoelectronic product life without resorting to conventional life test, but also improved the method of life prediction and perfect its theoretical system.

Visual and non-visual properties of filters manipulating short-wavelength light.

PurposeOptical filters and tints manipulating short‐wavelength light (sometimes called ‘blue‐blocking’ or ‘blue‐attenuating’ filters) are used in the management of a range of ocular, retinal, neurological and psychiatric disorders. In many cases, the only available quantification of the optical effects of a given optical filter is the spectral transmittance, which specifies the amount of light transmitted as a function of wavelength.MethodsWe propose a novel physiologically relevant and retinally referenced framework for quantifying the visual and non‐visual effects of these filters, incorporating the attenuation of luminance (luminous transmittance), the attenuation of melanopsin activation (melanopsin transmittance), the colour shift, and the reduction of the colour gamut (gamut reduction). Using these criteria, we examined a novel database of spectral transmittance functions of optical filters (n = 121) which were digitally extracted from a variety of sources.ResultsWe find a large diversity in the alteration of visual and non‐visual properties. The spectral transmittance properties of the examined filters vary widely, in terms of shapes and cut‐off wavelengths. All filters show relatively more melanopsin attenuation than luminance attenuation (lower melanopsin transmittance than luminous transmittance). Across the data set, we find that melanopsin transmittance and luminous transmittance are correlated.ConclusionsWe suggest that future studies and examinations of the physiological effects of optical filters quantify the visual and non‐visual effects of the filters beyond the spectral transmittance, which will eventually aid in developing a mechanistic understanding of how different filters affect physiology. We strongly discourage comparing the downstream effects of different filters on, e.g. sleep or circadian responses, without considering their effects on the retinal stimulus.

SHAPE ESTIMATION OF BOWTIE FILTERS BASED ON THE LUMINESCENCE FROM POLYETHYLENE TEREPHTHALATE RESIN BY X-RAY IRRADIATION.

In this study, we devised a novel method estimating the bowtie filter shapes by imaging luminescence from a polyethylene terephthalate (PET) resin with X-ray irradiation in a computed tomography (CT) scanner. The luminescence distribution of the PET resin corresponding to the thickness of bowtie filter was imaged using a charge-coupled device camera. On the assumption that the material of bowtie filter is aluminium (Al), the shape of bowtie filters was estimated from the correlation between Al attenuation curves and the angular-dependent luminance attenuation profiles according to the thickness of bowtie filters. Dose simulations based on the estimated bowtie filter shapes were performed using head and body PMMA phantoms with 16 and 32 cm in diameter. The simulated values of head and body weighted CT dose index (CTDIw) based on bowtie filter shape by the luminescence imaging method agreed within ~9% with the measured values by a dosemeter.

A 2D/3D Switchable Directional-Backlight Autostereoscopic Display Using Polymer Dispersed Liquid Crystal Films

A 2D/3D switchable autostereoscopic display with spatial and sequential hybrid control (SSHC) using polymer dispersed liquid crystal (PDLC) films is studied. The light propagation in the SSHC system is simulated with a Monte Carlo ray-tracing method. Relationship between the 2D uniformity and anisotropy factor as well as mean free path is obtained by a series of simulation cases. The uniformity reaches over 85% in simulation. As well, a two-viewpoint prototype is built to give the experimental result. Measurements show that a highly transparent PDLC film can maintain the high-quality 3D performance while a strongly diffusive one can enhance the uniformity in 2D mode. By increasing the driving duty cycle of the backlight units, the issue of luminance attenuation in 2D mode can be addressed. Our technique offers a practical solution for 2D/3D switch in autostereoscopic displays.

Color correction for tiled projection with irregularly shaped, overlapping region

In this Letter, a new, constrained color-matching algorithm that removes the color variations is presented, in which all the color gamut of the projectors is mapped into a common gamut that can be produced by all the devices in the system. The smoothness constraints on the difference between two adjacent pixels are taken into account to calculate the luminance attenuation map of each pixel in the overlapping region to achieve luminance seamlessness. The experimental results demonstrate the validity and superiority of this correction algorithm.

Investigation and assessment of photoluminescent embroidered elements

Purpose – The purpose of this paper is to determine conformity of geometrical parameters between the elements embroidered with photoluminescent threads and their digital images as well as to explore the change in photoluminescent radiation. Design/methodology/approach – Using some different methodologies and apparatus, analysis shape of embroidered elements conformity and photoluminescent luminance attenuation are analysed. Findings – The provided methodologies allow assessing the quality of embroidered elements area and photoluminescent properties. Originality/value – The proposed approach can be adjusted to investigate photoluminescent properties of embroidered elements of different filling types.

Investigation of LED Light Attenuation in Fog

In fog, visibility reduces and the illuminance levels of street surface and objects that are in the observer’s field of view alter. In order to establish the technical characteristics of intelligent street lighting with the effect of fog taken into account, the peculiarities of light propagation and luminance of objects in fog are to be known. In this work, a fog chamber that allowed for the experimental investigation of the transmittance and luminance attenuation for white and coloured LEDs in fog with variable density was developed. The obtained dependences of transmittance and relative luminance on relative fog density were described by exponential regression functions. The dependence of the illuminance and luminance attenuation coefficients on light colour (dominant wavelength) was investigated. Light of shorter wavelengths (blue and green) was found to be scattered by about 1.5 times weaker than that of longer wavelengths (yellow and red). When additional foreground light was applied, a high fog density resulted in that the main contribution to luminance in the field view was due to the luminance of the foreground light scattered in fog rather than due to the luminance of the object itself. An increase of the correlated colour temperature of the white LED was observed due to the dependence of light scattering on wavelength. Ill. 7, bibl. 5, tabl. 4 (in English; abstracts in English and Lithuanian).DOI: http://dx.doi.org/10.5755/j01.eee.121.5.1651

22.3: Viewing Angle‐Aware Color Correction for LCDs

AbstractViewing angle‐dependent color shift is one of the major drawbacks of liquid crystal displays (LCD). As the viewing angle increases, not only the luminance but also the color saturation reduces and compromises the image quality. In this paper, we characterize the viewing angle‐dependent color shift of an LCD and propose a compensation method of adjusting the backlights and panel transmittance simultaneously. By increasing the panel transmittance, the color shift and luminance attenuation can be minimized. By increasing or decreasing the backlight intensity, the original luminance can be preserved or the power consumption can be reduced. Similar to previous approaches, the proposed method requires a video camera to capture the user's location for calculating the viewing angle. We have also implemented an emulator for reproducing the viewing angle‐dependent visual effects.