Photon Counting Device Pixel Gain Offset Correction
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Solution Overview
Problem
Photon counting accuracy is degraded in CMOS image sensors due to variations in gain and offset values among pixels, especially when binning is performed, leading to incorrect detection rates and reduced accuracy.
Innovation Solution
A photon counting device and method that includes a correction unit to adjust digital values from A/D converters across multiple pixels, accounting for variations in gain and offset values, allowing for accurate summation and conversion of photon counts, with a readout noise of less than 0.2 e-rms to minimize incorrect detection rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If binning of pixels is performed to improve signal-to-noise ratio, then detection sensitivity is improved, but photon counting accuracy is degraded due to variations in gain and offset values among pixels
Solution Approach 1:
The patent applies preliminary action by performing correction of digital values before binning operation. The correction unit corrects digital values from multiple pixels based on their individual gain and offset variations prior to summation, ensuring that photon counting accuracy is maintained even when binning is performed to improve detection sensitivity.
Solution Approach 2:
The patent applies parameter changes by introducing correction parameters (gain and offset values) that are specific to each pixel. These parameters are used to adjust the digital values from individual pixels before binning, compensating for manufacturing variations and enabling accurate photon counting despite pixel-to-pixel differences.
2Measurement precision
If readout noise is reduced to improve photon counting accuracy, then measurement precision is improved, but device complexity increases due to additional correction circuits
Solution Approach 1:
The patent introduces an intermediary correction unit that mediates between the A/D converter output and the binning operation. This correction unit uses stored gain and offset parameters to adjust digital values, effectively reducing the impact of readout noise and pixel variations without requiring fundamental changes to the sensor architecture.
3Reliability
If gain is increased to improve signal amplification, then detection sensitivity is improved, but variation in gain and offset values among pixels increases leading to reduced accuracy
Solution Approach 1:
The patent applies local quality by assigning individual correction parameters (gain and offset values) to each pixel based on its specific characteristics. This allows the system to account for local variations in amplification across different pixels, enabling high gain operation while maintaining overall photon counting accuracy through pixel-specific correction.
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
The solution effectively curbs the degradation of photon counting accuracy, achieving an incorrect detection rate of 1% or less, and allows for accurate reproduction of analog values with a gain of 10 DN/e or higher, enhancing the precision of photon counting.
Implementation Method 1
a photoelectric conversion element configured to convert input light to charge
Data Source
AI summary
A photon counting device includes a plurality of pixels each including a photoelectric conversion element configured to convert input light to charge, and an amplifier configured to amplify the charge converted by the photoelectric conversion element and convert the charge to a voltage, an A/D converter configured to convert the voltage output from the amplifier of each of the plurality of pixels to a digital value and output the digital value, a correction unit configured to correct the digital value output from the A/D converter so that an influence of a variation in a gain and an offset value among the plurality of pixels is curbed, a calculation unit configured to output a summed value obtained by summing the corrected digital values corresponding to at least two pixels, and a conversion unit configured to convert the summed value output from the calculation unit to a number of photons.