Infrared Sensor Shading Layer for Stable Temperature Calibration
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Solution Overview
Problem
Uncooled infrared focal plane arrays face challenges in accurately calibrating images due to ambient temperature drift, as infrared optical blind reference pixels do not effectively absorb incident infrared radiation, leading to signal drift and reduced sensitivity.
Innovation Solution
The infrared sensor incorporates a substrate with an active pixel array and a reference pixel array, featuring a light absorbing layer, sidewall spacer, and a shading layer to prevent light leakage and improve sensitivity by using a conformally deposited light shielding metal layer to reflect light at various angles, thereby stabilizing temperature-related signal drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared optical blind reference pixels are used to determine ambient temperature for calibration, then temperature drift correction is achieved, but light leakage occurs and sensitivity is reduced
Solution Approach 1:
The reference pixel structure is segmented into multiple functional layers: a light blocking layer divided into blocking portions positioned over the reference pixel, and a light absorbing layer with light receiving portions positioned over the active pixel array. This segmentation allows the reference pixel to block light (preventing leakage) while still enabling temperature measurement through thermal conduction via the platform and resistor structure.
Solution Approach 2:
A platform structure with a resistor is introduced as an intermediary between the substrate and the reference pixel's light blocking layer. The platform conducts heat from the substrate to the reference pixel, enabling temperature sensing without requiring the reference pixel to directly receive infrared radiation. This mediator allows temperature calibration while maintaining light blocking capability.
2Object-affected harmful factors
If the light absorbing layer is extended to cover the reference pixel, then light leakage is prevented, but infrared radiation absorption is reduced
Solution Approach 1:
The light absorbing layer is configured with spatially varying properties: it has light receiving portions positioned only over the active pixel array where infrared detection is needed, and blocking portions positioned over the reference pixel where light must be prevented. This local differentiation allows the same layer to simultaneously perform both light absorption for detection and light blocking for reference pixel protection.
Solution Approach 2:
The problem is solved by transitioning from a two-dimensional planar coverage to a three-dimensional structured arrangement. The light absorbing layer is positioned at specific heights and configurations, with light receiving portions aligned with active pixels and blocking portions aligned with reference pixels, creating vertical and horizontal differentiation that enables simultaneous light absorption and blocking functions.
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 enhances the infrared sensor's sensitivity and accuracy by preventing light leakage and temperature-related signal drift, allowing for precise thermal imaging with improved response times.
Implementation Method 1
The light absorbing layer is over the reference pixel
Implementation Method 2
the shading layer is conformally formed over the light absorbing layer and the sidewall spacer
Implementation Method 3
The infrared sensing material layer is over the resistor
Data Source
AI summary
An infrared sensor includes a substrate, an active pixel array, a reference pixel array, a light absorbing layer, a sidewall spacer, and a shading layer. The active pixel array is over the substrate. The reference pixel is over the substrate, adjacent to the active pixel array, and having a reference pixel. The reference pixel includes a platform, a resistor, and an infrared sensing material layer. The resistor is on the platform. The infrared sensing material layer is over the resistor. The light absorbing layer is over the reference pixel. The sidewall spacer is over the reference pixel and extends along a sidewall of the light absorbing layer. The shading layer is conformally formed over the light absorbing layer and the sidewall spacer.