Dynamic range

About: Dynamic range is a research topic. Over the lifetime, 7576 publications have been published within this topic receiving 101739 citations. The topic is also known as: DNR & DR.

A Linear Time-Over-Threshold Digitizing Scheme and Its 64-channel DAQ Prototype Design on FPGA for a Continuous Crystal PET Detector

Abstract: We propose a practical general method, called the linear time-over-threshold (linear TOT) scheme, for nuclear pulse amplitude digitization aiming at providing a high degree of integration for a high-channel count detector system. The most critical technique in the scheme is that for a different particle detector and diverse pulse shaping, how to produce the time-varying dynamic threshold voltage, which enables the linear conversion from the peak amplitude of nuclear pulse to the TOT time width. Compared with the normal time-over-threshold method for pulse height digitizing, the linear TOT has a strict linearity, large measurable signal dynamic range, and good signal-to-noise ratio. Using the scheme, we design a prototype of a field-programmable gate-array (FPGA)-based 64-channel data-acquisition (DAQ) system for a continuous crystal poistron emission tomography detector. The system only consists of 64-channel active RC integrators and voltage comparators, a shared dynamic threshold generating circuit, and an FPGA. The physical size of the system is so small that it could be attached on the base of the PMT. The preliminary test results show that the nonlinearity between pulse amplitude and TOT time width is about 0.01%, and the prototype could achieve an energy resolution of 12.3% by 22Na coincident spectrum measurement, which is better than the result (14.6%) obtained using our previous homemade DAQ system designed with a normal analog-to-digital converter technique. The design proves that the linear TOT scheme is an effective solution for a high-channel count digitizing system in nuclear detection, not only for its high performance, but also for a high degree of integration.

Micro-optical sensor system for pressure, acceleration, and pressure gradient measurements

Abstract: A micro-optical fiber tip based sensor system for pressure, acceleration, and pressure gradient measurements in a wide bandwidth, the design of which allows for multiplexity of the input side of the system is based on micro-electromechanical fabrication techniques. The optical portion of the system is based on low coherence fiber-optic interferometry techniques which has a sensor Fabry-Perot interferometer and a read-out interferometer combination that allows a high dynamic range and low sensitivity to the wavelength fluctuation of the light source. A phase modulation and demodulation scheme takes advantage of the Integrated Optical Circuit phase modulator and multi-step phase-stepping algorithm for providing high frequency and real time phase signal demodulation. The system includes fiber tip based Fabry-Perot sensors each of which has a diaphragm that is used as a transducer.

An optimal tone reproduction curve operator for the display of high dynamic range images

Abstract: We present a new tone mapping method for the display of high dynamic range images in low dynamic range devices. We formulate high dynamic range image tone mapping as an optimisation problem. We introduce a two-term cost function, the first term favours linear scaling mapping, the second term favours histogram equalisation mapping, and jointly optimising the two terms optimally maps a high dynamic range image to a low dynamic range image. We control the mapping results by adjusting the relative weightings of the two terms in the objective function. We also present a fast and simple implementation for solving the optimisation problem. We present results to demonstrate that our method works very effectively.

Methods and apparatuses for encoding an HDR images, and methods and apparatuses for use of such encoded images

Abstract: A method of encoding a high dynamic range image (M_HDR), comprising the steps of: - converting the high dynamic range image into a low luminance dynamic range image (LDR_o) by applying: a) normalization of the image of high dynamic range at a luma axis scale that is [0, 1] giving a high normalized dynamic range image with normalized colors that have normalized luminance (Yn_HDR), b) calculate a gamma function on normalized luminance giving converted luminance with gamma (xg), c) apply a first tone mapping that gives lumas (v) that is defined as ** Formula **, with RHO having a predetermined value, and d) apply a monotonously increasing arbitrary tone mapping function that maps the lumas with output lumas (Yn_LDR) of the lower dynamic range image (LDR_o); and - emit, in an image signal (S_im), an encoding of the pixel colors of the lower luminance dynamic range image (LDR_o), and - emit, in the image signal (S_im), values encoding the function forms of previous color conversions bad as metadata, or values for their inverse functions, metadata that allow a receiver to reconstruct a reconstructed high dynamic range image (Rec_HDR) from the low luminance dynamic range image (LDR_o ), where RHO or a value that is a function of RHO is issued in the metadata.

A compact time-resolved system for near infrared spectroscopy based on wavelength space multiplexing.

Abstract: We designed and developed a compact dual-wavelength and dual-channel time-resolved system for near-infrared spectroscopy studies of muscle and brain. The system employs pulsed diode lasers as sources, compact photomultipliers, and time-correlated single photon counting boards for detection. To exploit the full temporal and dynamic range of the acquisition technique, we implemented an approach based on wavelength space multiplexing: laser pulses at the two wavelengths are alternatively injected into the two channels by means of an optical 2×2 switch. In each detection line (i.e., in each temporal window), the distribution of photon time-of-flights at one wavelength is acquired. The proposed approach increases the signal-to-noise ratio and avoids wavelength cross-talk with respect to the typical approach based on time multiplexing. The instrument was characterized on tissue phantoms to assess its properties in terms of linearity, stability, noise, and reproducibility. Finally, it was successfully tested in preliminary in vivo measurements on muscle during standard cuff occlusion and on the brain during a motor cortex response due to hand movements.