Review of Display Technologies Focusing on Power Consumption

Producción CientíficaThis paper provides an overview of the main manufacturing technologies of displays, focusing on those with low and ultra-low levels of power consumption, which make them suitable for current societal needs. Considering the typified value obtained from the manufacturer’s specifications, four technologies—Liquid Crystal Displays, electronic paper, Organic Light-Emitting Display and Electroluminescent Displays—were selected in a first iteration. For each of them, several features, including size and brightness, were assessed in order to ascertain possible proportional relationships with the rate of consumption. To normalize the comparison between different display types, relative units such as the surface power density and the display frontal intensity efficiency were proposed. Organic light-emitting display had the best results in terms of power density for small display sizes. For larger sizes, it performs less satisfactorily than Liquid Crystal Displays in terms of energy efficiency.Junta de Castilla y León (Programa de apoyo a proyectos de investigación-Ref. VA036U14)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA013A12-2)Ministerio de Economía, Industria y Competitividad (Grant DPI2014-56500-R

Low-Overhead Adaptive Brightness Scaling for Energy Reduction in OLED Displays

Organic Light Emitting Diode (OLED) is rapidly emerging as the mainstream mobile display technology. This is posing new challenges on the design of energy-saving solutions for OLED displays, specifically intended for interactive devices such as smartphones, smartwatches and tablets. To this date, the standard solution is brightness scaling. However, the amount of the scaling is typically set statically (either by the user, through a setting knob, or by the system in response to predefined events such as low-battery status) and independently of the displayed image. In this work we describe a smart computing technique called Low-Overhead Adaptive Brightness Scaling (LABS), that overcomes these limitations. In LABS, the optimal content-dependent brightness scaling factor is determined automatically for each displayed image, on a frame-by-frame basis, with a low computational cost that allows real-time usage. The basic form of LABS achieves more than 35% power reduction on average, when applied to different image datasets, while maintaining the Mean Structural Similarity Index (MSSIM) between the original and transformed images above 97%

Focus: A Usable & Effective Approach to OLED Display Power Management

Singapore under its Academic Research Funding Tier 2; National Research Foundation (NRF) Singapore under IDM Futures Funding Initiativ

Power Minimization in a Backlit TFT-LCD Display by Concurrent Brightness and Contrast Scaling

This paper presents a Concurrent Brightness and Contrast Scaling (CBCS) technique for a cold cathode fluorescent lamp (CCFL) backlit TFT-LCD display. The proposed technique aims at conserving power by reducing the backlight illumination while retaining the image fidelity through preservation of the image contrast. First, we explain how CCFL works and show how to model the non-linearity between its backlight illumination and power consumption. Next, we propose the contrast distortion metric to quantify the image quality loss after backlight scaling. Finally, we formulate and optimally solve the CBCS optimization problem with the objective of minimizing the fidelity and power metrics. Experimental results show that an average of 3.7X power saving can be achieved with only 10% of contrast distortion

LAPSE: Low-Overhead Adaptive Power Saving and Contrast Enhancement for OLEDs

Organic Light Emitting Diode (OLED) display panels are becoming increasingly popular especially in mobile devices; one of the key characteristics of these panels is that their power consumption strongly depends on the displayed image. In this paper we propose LAPSE, a new methodology to concurrently reduce the energy consumed by an OLED display and enhance the contrast of the displayed image, that relies on image-specific pixel-by-pixel transformations. Unlike previous approaches, LAPSE focuses specifically on reducing the overheads required to implement the transformation at runtime. To this end, we propose a transformation that can be executed in real time, either in software, with low time overhead, or in a hardware accelerator with a small area and low energy budget. Despite the significant reduction in complexity, we obtain comparable results to those achieved with more complex approaches in terms of power saving and image quality. Moreover, our method allows to easily explore the full quality-versus-power tradeoff by acting on a few basic parameters; thus, it enables the runtime selection among multiple display quality settings, according to the status of the system

Adaptive display power management for mobile games

Ministry of Education, Singapore under its Academic Research Funding Tier

Låga ljusintensiteters påverkan på mjölkkors beteende

The animal welfare act in Sweden states that dairy cows need to have at least a dim light present at night, but there are no recommendations for what intensity the light should have. It is unknown how cows perceive and react to low light intensities and earlier studies on this topic are limited. Red light as night light has also been suggested, based on the cows’ inability to perceive red light. This have however been questioned. The aim with this study was to investigate how four different light intensities affect dairy cows behavior. The aim was also to investigate how red light affects the cows’ behavior. In the study, twelve cows’ behavior and locomotion pattern were observed at the different light intensities 0, 5, 20 and 50 lux in presence or absence of red light. The cows were asked to pass through an obstacle course and perform a novel object test (NOT) in the different treatments. The study design was following a change-over design with four groups of cows and four different light intensity treatments. The experiment prolonged for four weeks and each treatment period lasted one day. Based on results in this study, it can be concluded that dairy cows can perceive light intensities down to 5 lux. It is further hypothesized that cows may be affected of a light intensity as low as 0.2 lux. This study also show that behavior is significantly affected by a light intensity since step frequency, number of stops, time taken for passing the obstacle course as well as step length and step rate were different at 0 lux compared to 5, 2 and 50 lux. In the NOT, time taken to the first interaction with an object was prolonged at 0 lux compared to the other light intensities. The cows’ behavior was not affected by the presence of red light in light intensities at 5, 20 and 50 lux. At 0 lux with presence of red light the cows had a higher frequency of steps, interacted less with the surrounding and knocked down fewer obstacles in the obstacle course compared to the other three tested light intensities. In the NOT, time taken for the cows to first interact with the objects was longer at 0 lux accompanied by red light compared to the other light intensities and compared to 0 lux in absence of red light. It is unclear if this is a result of a light intensity of 0.2 lux emitted by the red light or due to the precipitation of red light.Enligt Sveriges djurskyddslag ska mjölkkor ha tillgång till dämpad belysning under natten, men det finns inga rekommendationer för hur stark belysningen bör vara. Hur kor uppfattar och reagerar på låga ljusintensiteter är ännu inte känt och det finns endast ett begränsat antal studier inom området. Nattbelysning som ger ifrån sig ett rött sken har introducerats i flera företag, med förklaringen att kor inte uppfattar det röda ljuset. Detta har dock ifrågasatts. Syftet med denna studie var att undersöka hur fyra olika ljusintensiteter påverkar kors beteende. Syftet var även att undersöka om röd belysning påverkar deras beteende. I studien observerades tolv kors beteenden i fyra olika ljusintensiteter, 0, 5, 20 och 50 lux i närvarande eller frånvarande av röd belysning. Korna manades igenom en hinderbana varefter ett novel object test utfördes i de olika behandlingarna. Utformningen av studien följde en change-over design av de fyra olika behandlingarna, där korna var indelade i fyra grupper om tre i varje. Experimentet pågick under fyra veckor, varav varje enskild behandling pågick under en dag. Slutsatsen av studien är att kor kan uppfatta ljusintensiteter ner till 5 lux och troligtvis också ända ner till 0.2 lux. Deras beteende ändrades tydligt i 0 lux, jämfört med 5, 20 och 50 lux. Korna tog fler steg, stannade oftare, tog längre tid på sig i hinderbanan, minskade sin steglängd och steghastighet i hinderbanan i 0 lux jämfört med i de andra testade ljusintensiteterna. I novel object testet så tog det längre tid för dem att interagera med objekten i 0 lux jämfört med i de andra testade ljusintensiteterna. Kornas beteende påverkades inte av den röda belysningen i de högre ljusintensiteterna 5, 20, och 50 lux. I röd belysning vid 0 lux tog korna fler antal steg, interagerade mindre med omgivningen, slog ner färre hinder i hinderbanan, medan det i NOT testet tog längre tid för dem att interagera med objekten jämfört med i 0 lux utan röd belysning. Om detta beror på att den röda belysningen ger ifrån sig en ljusintensitet på 0.2 lux eller att korna uppfattar den röda belysningen går inte att avgöra

FINE-GRAINED DYNAMIC VOLTAGE SCALING ON OLED DISPLAY

Organic Light Emitting Diode (OLED) has emerged as a new generation of display techniques for mobile devices. Emitting light with organic fluorescent materials OLED display panels are thinner, brighter, lighter, cheaper and more power efficient, compared to other display technologies such as Liquid Crystal Displays (LCD). In present mobile devices, due to the battery capacity limitation and increasing daily usage, the power efficiency significantly affect the general performance and user experience. However, display panel even built with OLEDs is still the biggest contributor to a mobile device’s total power consumption. In this thesis, a fine-grained dynamic voltage scaling (FDVS) technique is proposed to reduce the OLED display power consumption. In bottom level, based on dynamic voltage scaling (DVS) power optimization, a DVS-friendly AMOLED driver design is proposed to enhance the color accuracy of the OLED pixels under scaled down supply voltage. Correspondingly, the OLED panel is partitioned into multiple display sections and each section’s supply voltage is adaptively adjusted to implement fine-grained DVS with display content. When applied to display image, some optimization algorithm and methods are developed to select suitable scaled voltage and maintain display quality with Structural Similarity Index (SSIM), which is an image distortion evaluation criteria based on human vision system (HVS). Experimental results show that, the FDVS technique can achieve 28.44%~39.24% more power saving on images. Further analysis shows FDVS technology can also effectively reduce the color remapping cost when color compensation is required to improve the image quality of an OLED panel working at a scaled supplied voltage

Image Processing for Machine Vision Applications

L'abstract è presente nell'allegato / the abstract is in the attachmen