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.

Continuous-Time Trajectory Estimation for Event-based Vision Sensors

Abstract: Event-based vision sensors, such as the Dynamic Vision Sensor (DVS), do not output a sequence of video frames like standard cameras, but a stream of asynchronous events. An event is triggered when a pixel detects a change of brightness in the scene. An event contains the location, sign, and precise timestamp of the change. The high dynamic range and temporal resolution of the DVS, which is in the order of micro-seconds, make this a very promising sensor for high-speed applications, such as robotics and wearable computing. However, due to the fundamentally different structure of the sensor's output, new algorithms that exploit the high temporal resolution and the asynchronous nature of the sensor are required. In this paper, we address ego-motion estimation for an event-based vision sensor using a continuous-time framework to directly integrate the information conveyed by the sensor. The DVS pose trajectory is approximated by a smooth curve in the space of rigid-body motions using cubic splines and it is optimized according to the observed events. We evaluate our method using datasets acquired from sensor-in-the-loop simulations and onboard a quadrotor performing flips. The results are compared to the ground truth, showing the good performance of the proposed technique.

A Fiber-Optic Fabry-Perot Accelerometer Based on High-Speed White Light Interferometry Demodulation

Abstract: A fiber-optic Fabry-Perot (F-P) accelerometer with high resolution, high dynamic range, high speed, and absolute measurement capability was developed and demonstrated in elevator health monitoring. The sensor element is based on a mesh diaphragm mass-loaded compact structure, and the F-P cavity interrogation was achieved by utilizing a high-speed white light interferometry demodulation algorithm. The displacement of inertial mass representing the change of F-P cavity was measured and translated to acceleration in real time. The results indicate a resonance frequency of 270 Hz and axial sensitivity of 3.86 μm/g within the frequency bandwidth of 10-120 Hz for the sensor. In experimental tests, the acceleration resolution achieved 8.5 μg within a ± 30 g maximum measurement range. The performance of the sensing system was compared with a commercialized piezoelectric accelerometer in monitoring the acceleration of an elevator.

A 1K×1K high dynamic range CMOS image sensor with on-chip programmable region of interest readout

Abstract: An integrated 1024×1024 CMOS image sensor with programmable region of interest (ROI) readout and multi-exposure technique has been developed and successfully tested. Size and position of the ROI is programmed based on multiples of a minimum readout kernel of 32×32 pixels. Since the dynamic range of the irradiance normally exceeds the electrical dynamic range of the imager that can be covered using a single integration time a multi exposure technique has been implemented in the imager. Subsequent sensor images are acquired using different integration times and recomputed to form a single composite image. A newly developed algorithm performing the recomputation is presented. The chip has been realized in a 0.5µm n-well standard CMOS process. The pixel pitch is 10µm × 10µm and the total chip area is 164mm2.

Spectrophotometry and Spectrofluorometry with the Self-Scanned Photodiode Array:

Abstract: A state-of-the-art self-scanned photodiode array, utilized as a spectrometric multichannel detector, was studied for its applicability to molecular absorption and molecular fluorescence spectrometry. Molecular absorption spectrophotometry requires detectors with high UV to near IR response, high dynamic range, linear response, low noise, and temporal as well as thermal stability. Molecular fluorescence spectrometry requires, in addition, sensitivity to low-light level signals. These requirements were satisfied by the systems under study. Other parameters that govern the overall performance of diode array-based spectrophotometers and spectrofluorometers include: photometric range, stray energy radiation and its effect on photometric accuracy, photometric precision, spectral resolution sensitivity, and signal-to-noise considerations. Various readout methods for the array detectors were examined including: real time, in-memory signal integration, on-target signal integration, variable integration time (VIT), diode grouping, and diode fast access (a pseudorandom access readout). Performance demonstrations of these multichannel spectrometers were made with a few typical chemical systems. The spectrophotometric performance of the diode array system was excellent, practically equal to that of conventional single-channel systems. Exceptions were higher amenability to the adverse effects of stray radiation energy and a dependency of the geometric (wavelength) accuracy on spatial fluctuations (wander) in the light source. Potential long-term UV degradation of diode arrays may present an inherent problem, but was not discussed here because data accumulated up-to-date was considered inconsequential. As a spectrofluorometer multichannel detector, the diode array showed an "unexpected" signal-to-noise (detectability) performance, closely matching that of conventional high gain detectors. However, this performance was achieved only if sufficiently long signal integration times (20 to 160 s) were feasible. Overall performance of the diode array has demonstrated that theoretical multiplex advantages are achievable, resulting in either a considerable improvement in signal-to-noise or a corresponding shortening in observation time.

Experimental investigation of the nonlinear optical loop mirror with twisted fiber and birefringence bias

Abstract: We examine the transmission characteristics of a NOLM device using a symmetrical coupler, highly twisted fiber, and a quarter-wave (QW) retarder plate introducing a polarization asymmetry in the loop. We demonstrate high dynamic range with controllable transmissivity, and good stability over long times. We experimentally study the transmission behavior for different input polarization states and distinguish between different polarization components of the output beam. Experiments are in good agreement with our theoretical approach previously published. Appropriate choice of the input and output polarizations allows a very high dynamic range. The adjustment of the QW retarder and input polarization enables tuning the critical power over a wide range.