Electron Counter with Charge Splitting for Single-Photon Detection
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Solution Overview
Problem
Current imaging technologies face challenges in achieving both high sensitivity and wide dynamic range, particularly in urban imaging where light intensity varies significantly, as existing devices either sacrifice sensitivity for dynamic range or vice versa.
Innovation Solution
The development of electron counters that combine a charge-coupled device (CCD) register with Geiger-mode avalanche diodes, enabling noiseless charge splitting and digital output at low light levels, and a nondestructive readout amplifier for high light levels, allowing for sensitive single photoelectron detection across a wide dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photomultiplier tubes or intensified solid-state imagers are used for single photoelectron detection, then sensitivity is improved, but dynamic range is limited
Solution Approach 1:
The invention segments the detection process into two distinct pathways: a charge domain segmentation that splits charge packets into single-electron packets for digital counting at low light levels, and an analog domain pathway for high light levels. This segmentation allows the system to optimize for sensitivity in the digital pathway while maintaining dynamic range through the analog pathway.
Solution Approach 2:
The invention dynamically switches between two detection modes based on signal level: at low light levels, it operates in digital electron counting mode with charge splitting for maximum sensitivity; at high light levels, it transitions to analog readout mode. This dynamic adaptation resolves the contradiction by allowing the system to optimize performance for the current operating conditions.
2Measurement precision
If avalanche-register CCD imagers or Geiger-mode avalanche photodiodes are used, then single photon detection capability is improved, but dynamic range is sacrificed
Solution Approach 1:
The invention merges the advantages of CCD technology (high dynamic range, low readout noise) with the advantages of Geiger-mode avalanche photodiodes (single photon sensitivity) into a hybrid system. The CCD register provides noiseless charge storage and transfer, while the Geiger-mode photodiodes provide single electron detection capability, and the charge splitter integrates both functions.
Solution Approach 2:
The charge splitter acts as an intermediary device that receives charge packets from the CCD register and conditionally routes them: single-electron packets are directed to Geiger-mode photodiodes for digital counting, while larger charge packets are directed to analog readout amplifiers. This intermediary function enables the system to achieve both high sensitivity and wide dynamic range.
3Measurement precision
If charge splitting is performed to achieve single-electron detection, then sensitivity is improved, but readout noise increases in conventional systems
Solution Approach 1:
The invention replaces conventional analog readout electronics with a charge domain processing approach. Instead of using noisy analog amplifiers to detect single electrons, the system performs charge splitting and routing in the charge domain using CCD technology, which has inherently low readout noise. This substitution eliminates the readout noise problem that plagues conventional single-electron detection systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These electron counters provide high sensitivity and dynamic range, capable of detecting photoelectrons from single to hundreds of thousands, overcoming the limitations of existing devices by merging CCD performance with digital electron counting.
Implementation Method 1
a p+-doped barrier layer is formed adjacent to the n+-doped region in the substrate to create a Geiger-mode avalanche diode
Implementation Method 2
a charge-coupled device (CCD) register configured to transfer electrons
Implementation Method 3
The nondestructive readout amplifier senses the charge at the output of the CCD register and provides an analog output whose amplitude represents the amount of the charge sensed
Data Source
AI summary
Embodiments of the present invention include an electron counter with a charge-coupled device (CCD) register configured to transfer electrons to a Geiger-mode avalanche diode (GM-AD) array operably coupled to the output of the CCD register. At high charge levels, a nondestructive amplifier senses the charge at the CCD register output to provide an analog indication of the charge. At low charge levels, noiseless charge splitters or meters divide the charge into single-electron packets, each of which is detected by a GM-AD that provides a digital output indicating whether an electron is present. Example electron counters are particularly well suited for counting photoelectrons generated by large-format, high-speed imaging arrays because they operate with high dynamic range and high sensitivity. As a result, they can be used to image scenes over a wide range of light levels.