Display Illumination Research Articles

Sunny with a Chance of Servos: Solar-Powered Arduinos

The Arduino microcontroller is finding its way into labs throughout undergraduate physics curricula, from introductory courses to a variety of beyond-the-first-year laboratory classes. At Davidson College, we use Arduinos in a gateway STEM course for students who are interested in energy and the environment. Students learn to build simple circuits and write the accompanying Arduino code to control the temperature in solar-powered model buildings. To make the models fully solar powered, the Arduino itself must be powered by the Sun—no batteries allowed! Hence, we replace the 9-V battery that is usually used to power an Arduino with a 13.5 cm × 12.5 cm 9-V solar panel (DFRobot part #FIT0330), which can generate a maximum short-circuit current of approximately 200 mA. We find that the solar panel works well for most tasks, including temperature measurements, liquid-crystal display (LCD) illumination, and SD card module operation, but cannot generate enough power to drive a servo motor, which needs several hundred milliamps. For these situations, a 9-V, 1-F capacitor connected in parallel with the solar panel can store energy during the rest period between brief high-current operations and supplement the solar panel when higher power is required.

P‐7.10: Display illumination with tailored viewing volume

Display technology has been developing rapidly in recent decades and the basic principle is related to the way that the image is illuminated and light is emanated. This work proposes and demonstrates a novel display illuminating scheme which is capable of providing display viewing only in certain spatial regions. For a viewer close and away from the designated regions, the display content becomes invisible. The scheme is associated with an axicon lens [1] and four lenses that enables to view only in designated continuous region, as shown in the Fig. 1. The longitudinal depth‐designed display illumination with the advantages of no lighting‐noise will have impact on intelligent lighting display in the future.

Wide Bandgap Perovskite Photovoltaic Cells for Stray Light Recycling in a System Emitting Broadband Polarized Light

AbstractPerovskite based photovoltaic (PV) cells are unique in combining low open‐circuit voltage losses with a broad bandgap tunability. This makes them an ideal PV cell to recycle photons back into electrical power in a variety of illumination systems or light emitting devices. Here, advantage of these features is taken and wide bandgap (WBG) perovskite PV cells are incorporated in devices suitable for display illumination and demonstrate a high yield in stray light recycling back into electricity with up to a 37.5% power conversion efficiency. The specific device considered is a modified half‐cylinder photonic plate designed to emit diffused broadband polarized light using a nonabsorbing reflective polarizer based on a random dielectric layer distribution. It is experimentally demonstrated that light recycling using appropriately tuned WBG perovskite PV cells becomes very efficient when implemented in systems where the light is emitted from narrowband sources, even if the emission spans a broad wavelength range.

Affordable and Adaptable Oled Display Illumination for One-Shot Multimodal Imaging Both on Smartphone and Optical Microscope

Affordable and Adaptable Oled Display Illumination for One-Shot Multimodal Imaging Both on Smartphone and Optical Microscope

Display illumination with modulated directional backlight

AbstractIllumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution.

P‐8.2: Display Illumination with Modulated Directional Backlight

P‐8.2: Display Illumination with Modulated Directional Backlight

Doubling the Signal Quality of Smartphone Camera Pulse Oximetry Using the Display Screen as a Controllable Selective Light Source.

Recent smartphones have the potential to bring camera oximetry to everyone using their powerful sensors and the capability to process measurements in real-time, potentially augmenting people's lives through always-available oximetry monitoring everywhere. The challenge of camera oximetry on smartphones is the low contrast between reflections from oxyhemoglobin and deoxyhemoglobin. In this paper, we show that this is the result of using the camera flash for illumination, which illuminates evenly across bands than thus leads to the diminished contrast in reflections. Instead, we propose capturing pulse using the front-facing camera and illuminating with the phone's display, a selective illuminant in the red, green, and blue band. We evaluate the spectral characteristics of the phone display using a spectroradiometer in a controlled experiment, convolve them with the sensitivity curves of the phone's camera, and show that the screen's narrow-band display illumination increases the contrast between the reflections in the desired bands by a factor of two compared to flash illumination. Our preliminary evaluation showed further support for our approach and findings.

Study on uniform irradiance of micro curved-light-emitting diode array

The curved light-emitting diode (LED) array has so many advantages over conventional planar micro LED array such as wider viewing angles, and convenience in its actual applications:curved mobile phone screen, curved smart watch screen, and wide-angle communication illumination light source, etc. Irradiance uniformity is considered to be one of the momentous parameters for evaluating the degree of display or communication lighting devices. In order to improve the untilization of micro-curved LED array in display illumination, we focus on uniform irradiance of cylindrical and spherical micro-LED array by the method of ray-tracing. The calculation results show that the curved radius R and LED radiation parameter m are main factors affecting the uniform irradiance of the cylindrical array. We can improve the energy utilization efficiency by arranging the array pixel positions rationally. The simulation of 1010 cylindrical array with bending radius R=5 cm shows that the uniformity of maximum irradiance can reach 90.5% when detection distance z=300 cm and the detection area is defined as {(x, y)|-100 x 100, -100 y 100}. Furthermore, the irradiance distribution of spherical array is calculated and the results show that the irradiance uniformity of the single spherical array is unrelated to the number of pixels when it surpasses three. The main factors that affect the irradiance distribution of the multi-ring LED array are the ring distribution coefficient K, the normal angle 0, and the luminous flux ratio of each ring . Also the two-ring LED array model is calculated when the pixel number of the first ring is set to be 6 and the second ring is assumed to be 12. And the simulation results show that the maximum irradiance uniformity of the two-ring LED array can reach 94.8% in which the value of 0 is set to be 20, the ring distribution coefficient K=0.5 and the two ring pixel unit luminous flux ratio =20. Experimentally, we adopt the approach of the two micro LEDs to confirm the accuracy of the theory. And the results show that the irradiance distributions of two LEDs with the values of angle =13, 15 and 17 are consistent with the theoretical calculations. Thus, the theoretical and the experimental results in the paper can offer references for curved-LED display and multi-mode intelligent illumination.

基于自由曲面阵列的激光投影显示照明系统设计

基于自由曲面阵列的激光投影显示照明系统设计

Impact of different visible light spectra on oxygen absorption and surface discoloration of bologna sausage

The objective of this study was to evaluate the influence of several visible light spectra in various intensities on the oxygen absorption and surface color of sliced bologna. Sausage samples were stored in a gastight model packaging system and illuminated at 5°C with six single-colored LEDs covering the main part of the visible light spectrum. The initial oxygen level was set at 0.5% in order to simulate common residual oxygen amounts in conventional packaging. The oxygen absorption and the discoloration measured as changes in CIE a*-value were dependent from the applied light intensity. The color stability of bologna was differently affected by light of various wavelengths. The results show that the use of suitable LEDs with specific spectra for display illumination can help to reduce the light induced deterioration of cured sausages in retail markets.

65-5L:Late-News Paper: Sparkle Evaluation with Visual Weighting

We introduce a new method for evaluation of sparkle of the combination of display and AG-layer by application of a weighting of the Fourier amplitudes of the random luminance modulations that are perceived as sparkle, according to the contrast sensitivity function of the human visual system. This new approach provides improved sensitivity to small sparkle variations, better control of parasitic low frequency components caused by non-uniformities of display illumination and an improved match to visual ratings with subtle differences in the low sparkle region.

The Research of LED Arrays for Uniform Illumination

Nowadays, light emitting diodes (LEDs) are becoming a natural source choice for display illumination due to their small size, lower power consumption as well as lower heat generation. To be useful in practical display applications and to further improve the performance of LED-based illumination system, a secondary optical design for LED illumination is required to rearrange the direct output of LEDs so as to achieve a desired illumination. In this paper, a numerical modeling based on the direct datasheet fit is used to optimize and analyze the uniform illumination system designs, and close attention is paid to the LED source model. The uniformity of typical square and circular array distributions are analyzed for a commercial non-perfect Lambertian LED model.

Roll-to-roll pilot nanoimprinting process for backlight devices

► We demonstrate a pilot scale roll-to-roll manufacturing process for backlight devices. ► Backlight device (28 × 28) mm 2 consist more than 78,000 binary elements with different orientation. ► Each element has 40 trenches with 5 μm width and 1.3 μm thick, totally 3.1 million trenches in one device. ► Quality of printed devices are good and devices can be used for display illumination. A pilot scale roll-to-roll manufacturing process for backlight devices was demonstrated using Poly(methyl methacrylate) (PMMA) film. Backlight device (28 × 28) mm 2 consist more than 78,000 binary elements with different orientation. Each element has 40 trenches with 5 μm width and 1.3 μm thick, totally 3.1 million trenches in one device. These devices can be used for display illumination in various applications when three LED is connected on the other end of the device. More than 1000 device was printed on 50 mm wide 375 μm thick PMMA web using custom made nanoimprinting equipment. These devices demonstrate a high throughput and a low cost production possibility for micron- and submicron optical structures. The printed patterns were analysed by using optical microscopy, atomic force microscopy (AFM) and confocal microscopy. The backlight device after LED integration was characterized using luminescence measurements. The three surface mounted LED is connect to the upper side of printed PMMA device to give light in the polymer film. To collect statistics, every 50th sample was analysed. The pattern replication is good and the depth of the imprinted structure is typically in the range of 1.2–1.4 μm when limits for working device is ca. 1.0 μm. The optical properties of the analysed devices show good homogeneity inside one device. The standard deviation for the measured luminescence values for all devices was within 17% which is still acceptable for final production. No drastic wearing of the stamp can be seen after pilot manufacturing.

Integration of a fuzzy neural network and multi-objective genetic algorithm for optimisation of BLU light guide plate injection moulding parameters

Backlight module unit (BLU) is a key component of LCD, and thinning of the BLU light guide plate is the focus of development. Most light guide plates are manufactured using the injection moulding process. The experimental design in this study is the most common research approach applied in the setting of light guide plate parameters. However, the parameter interaction and system non-linearity can easily result in prediction errors of parameters. Meanwhile, since the optimal moulding conditions have not been achieved, the best effects of display illumination and brightness cannot be achieved. Hence, this study first applied the grey relational sorting method to determine the major control factors influencing the BLU light guide plate, and then built the approximate model of a fuzzy neural network, according to experimental planning samples, before using the multi-objective genetic algorithm to determine the optimal manufacturing parameter design. The results suggested that the process capability index Cpk value of the light guide plate X-axis size is improved from 0.43 to 1.56, and has stabilised product quality and enhanced process capability. This study proved that the prediction model of process optimisation, as obtained by using this research method, is effective.

Performance of High Power Light Emitting Diodes in Display Illumination Applications

The performance of liquid crystal displays and micro display projection systems is for a large part determined by the lamps and illumination optics they are using. Traditionally, gas discharge lamps are used, but light-emitting diode lamps are gradually taking over because of their attractive characteristics. We will discuss how the transfer to light-emitting diodes in the various display architectures changes the key performance parameters, remaining technical challenges, and prospects for future improvement

Efficient Polarized Backlight for Transflective Liquid Crystal Display Illumination

A collimated backlight was designed for high-efficiency transflective liqud crystal display (LCD) illumination. Additionally, polarization separation was achieved by selective total internal reflection at microgrooves in polymeric foils, which were stretched to be anisotropic materials for easy fabrication and tunable birefringence. A lenticular lens array was then utilized to collect the collimated light of the polarized backlight to further improve light utilization efficiency. Therefore, gains of 2.91 and 1.37 in light utilization efficiency were obtained for transmissive and reflective modes, respectively.

Younger and Older Adults' Perception of the Wundt-Hering Illusion as a Function of Display Illumination and Reflectance Contrast

Reflectance contrast (i.e., black as compared to grey figures on white ground) and display illumination were manipulated to vary the brightness contrast of Wundt-Hering figures. 16 college students and 16 older adults were presented with high, medium, and low reflectance contrast figures. For half the participants, display illumination was manipulated by covering the figures with a .5 yellow neutral density filter. Magnitude of the illusion increased significantly with increased reflectance contrast for college students, and college students were significantly more susceptible to the high contrast figures than were older adults. Display illumination had no effect on the performance of either group.

The locus of the word-priority effect in a target-detection task

When subjects are required to monitor verbal displays for predesignated targets, their reaction time for word targets is less than that for subcomponents of words, such as letters. One explanation for this word-priority effect is that encoding of words is completed prior to encoding of their constituent letters. An alternative explanation is that it takes longer to compare letter targets with encoded displays than it does word targets. In this experiment, target set size and display illumination were independently manipulated during word and letter target-detection tasks, and interactions between factors were examined using the assumptions of Sternberg's (1969) additive factor approach. It was found that the magnitude of the word-priority effect increased with an increase in target set size, but not with a decrease in display illumination. This suggested that the effect occurs at a comparison stage rather than at an encoding stage in the information processing chain.

Lighting factors affecting the visibility of a moving display

Compensatory tracking performance was shown to be substantially degraded by oscillation of the visual display at both 1.0 and 2.0 Hz. The severity of this decrement was altered significantly by changes in both the color and the intensity of the display illumination. Performance was significantly better with red light illuminating the display at 0.05 mL than with blue light at the equivalent luminance. This improvement in performance was similar in magnitude to that found for an increase in broad-band illumination of the display where luminance was increased from 1/2 log unit below to 1/2 log unit above 0.05 mL. Visual mechanisms that may have been responsible for these findings are suggested.