Fast fluorescence dynamics in non-ratiometric calcium indicators

A fluorescence decay of high-affinity non-ratiometric Ca2+ indicator Oregon Green BAPTA-1 (OGB-1) is analyzed with unprecedented temporal resolution in the two-photon excitation regime. A triple exponential decay is shown to best fit the fluorescence dynamics of OGB-1. We provide a new model for accurate measurements of the free Ca2+ concentration and dissociation constants of non-ratiometric calcium indicators.Comment: 3 pages, 2 figures, figures revised, added chi-square goodness of fi

Quanta Burst Photography

Single-photon avalanche diodes (SPADs) are an emerging sensor technology capable of detecting individual incident photons, and capturing their time-of-arrival with high timing precision. While these sensors were limited to single-pixel or low-resolution devices in the past, recently, large (up to 1 MPixel) SPAD arrays have been developed. These single-photon cameras (SPCs) are capable of capturing high-speed sequences of binary single-photon images with no read noise. We present quanta burst photography, a computational photography technique that leverages SPCs as passive imaging devices for photography in challenging conditions, including ultra low-light and fast motion. Inspired by recent success of conventional burst photography, we design algorithms that align and merge binary sequences captured by SPCs into intensity images with minimal motion blur and artifacts, high signal-to-noise ratio (SNR), and high dynamic range. We theoretically analyze the SNR and dynamic range of quanta burst photography, and identify the imaging regimes where it provides significant benefits. We demonstrate, via a recently developed SPAD array, that the proposed method is able to generate high-quality images for scenes with challenging lighting, complex geometries, high dynamic range and moving objects. With the ongoing development of SPAD arrays, we envision quanta burst photography finding applications in both consumer and scientific photography.Comment: A version with better-quality images can be found on the project webpage: http://wisionlab.cs.wisc.edu/project/quanta-burst-photography

Sensor Network Architecture for a Fully Digital and Scalable SPAD based PET System

Digital SiPMs in the recent past have emerged as a viable low cost alternative to PMTs providing higher granularity and MRI compatibility. The rich dataset generated by digital SiPM sensors have posed a challenge, especially at the system level when a multitude of such sensors are to be used. In this paper we present a sensor network based solution for data acquisition, scalable to multi-ring based pre-clinical, clinical and brain PET

3D Imaging based on Single Photon Detectors

This paper introduces a mathematical model to evaluate fast and cost-effective 3D image sensors based on single photon detectors. The model will help engineers evaluate design parameters based on operating conditions and system performance. Ranging is based on the time-of-flight principle using TCSPC techniques. Two scenarios are discussed: (i) short-distance range indoors and (ii) medium-distance range outdoors. The model predicts an accuracy of 0.25cm at 5m with 0.5W of illumination and 1klux of background light. In the medium-range scenario, a precision of 0.5cm is predicted at 50m with 20W of illumination and 20klux of background light

3D Near-infrared Imaging based on a Single-photon Avalanche Diode Array Sensor

A new imager for 3D near-infrared imaging has been designed based on a single-photon avalanche diode (SPAD) imager with 128x128 pixels capable of performing time-resolved measurements with a resolution of 97ps. The imager linearity has been improved to make more accurate measurements. A new optical setup has been imple- mented in order to prove the suitability of this kind of sensors for this application

A Disdrometer based on Ultra-Fast SPAD Cameras

We present a new environmental application of SPAD imagers, namely the continuous and real-time measurement of size and shapes of hydrometeors. Details of the set-up and results obtained with a first 32x32 pixel prototype based on the RADHARD2 chip [1] are illustrated. Real-time operation at very low light levels, 6000 frames per second and 1:100 average data reduction are amongst the most significant achievements

Industrial application for the Los Alamos Materials Modeling Platform

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Casting and solidification of molten metals and metal alloys is a critical step in the production of high-quality metal stock and in the fabrication of finished parts. Control of the casting process can be the determining factor in both the quality and cost of the final metal product. Major problems with the quality of cast stock or finished parts can arise because of the difficulty of preventing variations in the alloy content, the generation of porosity or poor surface finish, and the loss of microstructure controlled strength and toughness resulting from the poor understanding and design of the mold filling and solidification processes. In this project, we sought to develop a new set of applications focused on adding the ability to accurately model solidification and grain growth to casting simulations. We implemented these applications within the Los Alamos Materials Modeling Platform, LAMMP, a graphical-based materials, and materials modeling environment being created at the Computational Testbed for Industry