Avalanche Photodiode Line Array for Scanning Microscope Light Detection
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Solution Overview
Problem
Scanning microscopes face challenges with low signal-to-noise ratio and limited time for light quantum collection due to dye saturation and noise in CCD detectors, particularly at high speeds, which affects image quality and data processing speed.
Innovation Solution
A line scanning microscope with a light detector featuring a line array of avalanche semiconductor diodes and an electronic drive circuit that operates in Geiger mode, allowing for simultaneous recording of all pixels in a line and reducing noise through parallel counter technology and active quenching circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche photodiode detectors are used to increase sensitivity and reduce dead time, then the signal-to-noise ratio is improved, but the device complexity and data processing requirements increase
Solution Approach 1:
The detector is divided into multiple independent line arrays, where each line array can be read out independently in parallel. This segmentation allows the system to process data from different spatial regions simultaneously, reducing the overall data processing burden while maintaining high sensitivity through avalanche photodiode technology
Solution Approach 2:
The patent transitions from point-by-point scanning to line-by-line scanning by arranging photodiodes in linear arrays. This dimensional change from 0D (point) to 1D (line) allows simultaneous detection of multiple points along a line, reducing the total number of sequential measurements needed and thereby reducing data processing complexity
2Productivity
If the scanning speed is increased to improve productivity, then the image acquisition speed is improved, but the signal-to-noise ratio deteriorates due to reduced photon collection time
Solution Approach 1:
By dividing the detection task across multiple line arrays that can be read out in parallel, the system can maintain high scanning speeds while allocating sufficient integration time to each line. The parallel readout architecture ensures that data from all lines is captured simultaneously without sequential bottlenecks
Solution Approach 2:
The patent employs avalanche photodiodes operating in Geiger mode, which fundamentally changes the detection parameter from analog intensity measurement to single-photon counting. This parameter change enables extremely sensitive detection with very short integration times, allowing high scanning speeds to be maintained without sacrificing signal-to-noise ratio
3Productivity
If multiple line arrays are used to reduce dead time and increase detection capacity, then the productivity is improved, but the device complexity increases
Solution Approach 1:
Multiple line arrays are combined into a single integrated detector assembly that functions as a unified detection system. The parallel architecture merges the detection capabilities of individual line arrays while sharing common control and readout infrastructure, thereby increasing total detection capacity without proportionally increasing overall device complexity
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
This configuration enhances sensitivity, reduces noise, and increases data acquisition speed, enabling the detection of single photons and improving image quality by multiplying the time available for photon detection across multiple pixels.
Implementation Method 1
A light detector is proposed which is particularly suitable for use in a scanning microscope... The light detector includes a line array of semiconductor photodiodes, the line array including a plurality of avalanche semiconductor diodes
Implementation Method 2
APDs can be operated in a linear range, in which the current signal runs at least approximately linearly with the number of photons radiated in, and, above a breakdown voltage, in a non-linear range in which the avalanche effect mentioned occurs and which is also called the Geiger area
Data Source
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AI summary
Disclosed is a light detector (110) for use in a scanning microscope (142), especially a line scanning microscope. Said light detector (110) comprises a linear array (112) of avalanche semiconductor detectors (114) and an electronic control circuit (116) which is designed to operate the avalanche semiconductor detectors (114) in Geiger mode with internal charge gain and/or in a linear mode. The control circuit (116) is equipped with a parallel meter (118) which is designed to read in parallel light pulses that are detected by the avalanche semiconductor detectors (114). Furthermore, the parallel meter (118) is designed to add up the light pulses detected by the avalanche semiconductor detectors (114) during a predefined counting period.