Photon Counting Thresholds for CMOS Read Noise Compensation
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Solution Overview
Problem
Existing CMOS image sensors experience reading noise that broadens the probability distribution of photon counts, leading to a decrease in counting accuracy, particularly in pixels with large noise fluctuations.
Innovation Solution
A method and system for determining threshold values by calculating first and second probability distributions based on observation probabilities for each photoelectron number, allowing for accurate sorting of provisional photon numbers into integers, thereby mitigating the impact of reading noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reading noise is reduced to improve photon counting accuracy, then measurement precision improves, but device complexity increases due to additional threshold value determination processes
Solution Approach 1:
The patent calculates threshold value data in advance based on probability distributions before actual photon counting occurs. This preliminary determination of thresholds allows the system to compensate for reading noise effects without adding complexity during the main measurement process, as the thresholds are pre-computed and stored for use during photon counting operations
Solution Approach 2:
The patent introduces threshold value data as an intermediary element between the raw signal and the final photon count determination. This intermediary threshold data, derived from probability distributions of reading noise, mediates the relationship between noisy measurements and accurate photon counting, allowing the system to achieve high measurement precision without directly increasing processing complexity
2Measurement precision
If threshold value determination is performed to improve photon number resolution, then measurement precision improves, but calculation time increases
Solution Approach 1:
The patent performs threshold value determination as a preliminary action before actual photon counting measurements. By pre-calculating thresholds based on probability distributions and storing them for later use, the system avoids time-consuming calculations during the measurement process, thereby improving photon number resolution without significantly increasing total calculation time
Solution Approach 2:
The patent creates and stores threshold value data as a copy of the complex probability distribution calculations. This copied threshold data can be rapidly retrieved and applied during photon counting without reperforming the complex calculations, enabling high measurement precision while minimizing time loss during actual measurements
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 approach improves the accuracy of photon number resolution by reducing the influence of reading noise on the derived values, enhancing the precision of photon counting in CMOS image sensors.
Implementation Method 1
a photoelectric conversion element for converting input light to electric charges
Data Source
AI summary
A threshold value determination method includes a step of calculating a probability distribution of a provisional value for each photon number of a target pixel based on an observation probability for each photoelectron number based on a probability distribution of the photon number and an observation probability for each photoelectron number based on a probability distribution of the photoelectron number accompanying reading noise of the target pixel and a step of calculating threshold value data for sorting the provisional value into a corresponding photon number based on the probability distribution for each photon number.