High dynamic range

About: High dynamic range is a research topic. Over the lifetime, 4280 publications have been published within this topic receiving 76293 citations. The topic is also known as: HDR.

Quantitative analysis of infrared contrast enhancement algorithms

Abstract: Dynamic range reduction and contrast enhancement are two image-processing methods that are required when developing thermal camera systems. The two methods must be performed in such a way that the high dynamic range imagery output from current sensors are compressed in a pleasing way for display on lower dynamic range monitors. This research examines a quantitative analysis of infrared contrast enhancement algorithms found in literature and developed by the author. Four algorithms were studied, three of which were found in literature and one developed by the author: tail-less plateau equalization (TPE), adaptive plateau equalization (APE), the method according to Aare Mallo (MEAM), and infrared multi-scale retinex (IMSR). TPE and APE are histogram-based methods, requiring the calculation of the probability density of digital counts within an image. MEAM and IMSR are frequency-domain methods, methods that operate on input imagery that has been split into components containing differing spatial frequency content. After a rate of growth analysis and psychophysical trial were performed, MEAM was found to be the best algorithm.

Design and Self-Noise of MET Closed-Loop Seismic Accelerometers

Abstract: Molecular electronic transfer (MET) technology offers an alternative approach for the development of accelerometers with high dynamic range and low self-noise. The best performance is achieved by using a force-balancing feedback. However, the operating principles of the feedback sensors has not been reporting yet, also, there is not any comprehensive theoretical model describing sensor noise in the complete operating frequency range. This paper reports on the development of the feedback system for an MET seismic accelerometer, a feedback stability analysis, and an optimization of the signal conditioning feedback electronics to get the highest dynamic range. Also, both the theoretical model and experimental results of such sensors self-noise are presented in the range of 0.1–120 Hz. According to the model and the experimental observation, there are two major contributors into self-noise: convective processes in the electrolyte and electronic noise of the signal operational amplifiers. The research results give better understanding of the molecular electronic accelerometers noise nature and suggest ways to reduce it.

A DC-Coupled High Dynamic Range Biomedical Radar Sensor With Fast-Settling Analog DC Offset Cancelation

Abstract: One challenge of designing a dc-coupled biomedical radar sensor is dealing with the dc offset voltage presented in its receiver. The undesired dc offset is mainly caused by clutter reflection and hardware imperfection. It may saturate the baseband amplifier and limit the maximum dynamic range that a biomedical radar sensor can achieve. AC-coupling the signal can eliminate dc offset but it will also distort the signal, and thus may not be acceptable for high precision applications. In this paper, a dc-coupled biomedical radar sensor is proposed incorporating an analog dc offset cancelation circuit with fast start-up feature. It can automatically remove any dc offset in the baseband signal and emulates an ac-coupling system. It can also be easily reconfigured into a dc-tracking mode when application requires. When entering this mode, the initial dc offset will be removed, whereas future dc change can be recorded. The proposed solution only uses analog components without requiring any digital signal processing nor software programing. Therefore, compared with the existing digitized dc offset calibration techniques, the proposed method has the advantage of low cost, easy implementation, short delay, and high resolution. The experiment results demonstrated that a wide range of dc offset can be successfully removed from the biomedical radar sensor, and its dynamic range can be maximized. The reconfiguration of the dc-tracking mode has also been tested and verified. Furthermore, the proposed dc offset cancelation circuit has the potential to be easily adopted by other systems that also face the dc offset problem.

Optimal shutter speed sequences for real-time HDR video

Abstract: A technique to create High Dynamic Range (HDR) video frames is to capture Low Dynamic Range (LDR) images at varying shutter speeds. They are then merged into a single image covering the entire brightness range of the scene. While shutter speeds are often chosen to vary by a constant factor, we propose an adaptive approach. The scene's histogram together with functions judging the contribution of an LDR exposure to the HDR result are used to compute a sequence of shutter speeds. This sequence allows for the estimation of the scene's radiance map with a high degree of accuracy. We show that, in comparison to the traditional approach, our algorithm achieves a higher quality of the HDR image for the same number of captured LDR exposures. Our algorithm is suited for creating HDR videos of scenes with varying brightness conditions in real-time, which applications like video surveillance benefit from.