Image Sensor Pixel Crosstalk Characterization via Segmented Illumination
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Solution Overview
Problem
Existing methods for characterizing image sensor pixels are inadequate for small pixels, as they face difficulties in illumination and are prone to diffraction phenomena, which prevent accurate characterization, especially when the pixel size decreases below a certain threshold.
Innovation Solution
A method involving a test image sensor with specific arrangements of color filters, where a central pixel is surrounded by peripheral pixels of different colors, allowing for measurement and comparison of electron detection across various wavelengths to determine crosstalk, enabling characterization of image sensor pixels of any size and type without modifying the device structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin local beam is used to illuminate a single pixel for crosstalk characterization, then the crosstalk measurement can be performed, but the method becomes impossible or inaccurate when pixel size becomes very small due to diffraction phenomena
Solution Approach 1:
The pixel array is divided into a central pixel region and peripheral pixels region. The method separately characterizes the central pixel and peripheral pixels by illuminating them independently and comparing their responses, enabling accurate crosstalk measurement without requiring complex illumination setups that would cause diffraction in small pixels
Solution Approach 2:
The method changes the illumination parameters by using variable wavelengths and illuminating different portions (central vs peripheral) of the pixel array. This allows characterization to be performed across different spectral ranges and spatial configurations, avoiding the diffraction limitations of fixed thin beam illumination while maintaining measurement accuracy
2Measurement precision
If a thin local beam illumination method is used, then crosstalk can be measured in all directions, but the method is not representative of normal pixel operation and becomes impractical for small pixels
Solution Approach 1:
The patent creates a test image sensor structure that can perform multiple characterization functions: measuring crosstalk in all directions, evaluating spectral response across different wavelengths, and characterizing both central and peripheral pixels. This universal test structure replaces the need for multiple separate measurement setups and is applicable to both small and large pixels
Solution Approach 2:
The invention creates a test copy of the pixel array with specific configurations (central pixel surrounded by peripheral pixels with different color filters) that replicates real operational conditions. This test copy allows characterization without modifying the actual production pixels, providing accurate representation of normal pixel behavior including crosstalk patterns
3Measurement precision
If the pixel array is characterized by illuminating individual pixels with a thin beam, then directional crosstalk can be measured, but the device structure must be modified and the process becomes complex
Solution Approach 1:
The test image sensor structure is designed to self-characterize its own pixels. The central pixel and peripheral pixels are illuminated and measured in a configuration that automatically reveals crosstalk patterns without requiring external modification or complex measurement systems. The structure itself provides the measurement capability
Solution Approach 2:
The patent combines multiple characterization capabilities into a single test structure: crosstalk measurement, spectral response evaluation, and multi-directional analysis are all integrated into one pixel array configuration. This merged approach eliminates the need for separate measurement systems for each parameter, reducing 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 approach allows for accurate characterization of image sensor pixels, including small ones, by simulating real operational conditions, providing comprehensive crosstalk analysis and spectral response data, and is adaptable to both front- and back-illuminated sensors, without causing interference or stray capacitances.
Implementation Method 1
a first portion of the array formed of pixels associated with a color filter of a first color; illuminating a first portion of the array formed of pixels associated with a color filter of a first color
Implementation Method 2
elementary photodetection cells, called pixels, are formed at the surface of a semiconductor substrate. Each pixel generally comprises an area where photogenerated charges are collected
Data Source
AI summary
A method for characterizing image sensor pixels arranged in an array, including the steps of: (a) illuminating a first portion of the array formed of pixels associated with a color filter of a first color; (b) measuring the detection performed by a central pixel of the first portion; (c) illuminating a second portion of the array formed of a central pixel associated with a color filter of a second color and of peripheral pixels associated with a color filter of the first color; (d) measuring the detection performed by the central pixel and the peripheral pixels of the second portion; (e) comparing the measurements of steps (b) and (d).