Infrared Reference Pixel Shielding 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 shading layer to enhance light absorption and shielding, ensuring accurate temperature calibration by preventing light leakage and improving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared optical blind reference pixels are used for temperature calibration, then ambient temperature calibration is enabled, but light absorption capability is insufficient leading to signal drift
Solution Approach 1:
The patent applies local quality by differentiating the optical properties of reference pixels from active pixels. The reference pixels are configured with light blocking structures (metal layers, shading layers, sidewall spacers) that prevent infrared radiation absorption, while active pixels maintain full light absorption capability. This localized structural differentiation ensures reference pixels accurately track ambient temperature without experiencing signal drift from infrared exposure, thereby resolving the contradiction between calibration accuracy and signal stability.
Solution Approach 2:
The patent introduces intermediary structures (light blocking metal layers, shading layers, and sidewall spacers) between the infrared radiation source and the reference pixels. These intermediary elements act as mediators that selectively block infrared radiation from reaching reference pixels while allowing ambient temperature effects to pass through. This intermediary approach enables reference pixels to serve as stable temperature references without direct infrared exposure, resolving the signal drift issue while maintaining calibration functionality.
2Measurement precision
If reference pixels are exposed to infrared radiation, then they can track temperature changes, but light absorption causes signal drift
Solution Approach 1:
The patent extracts the harmful light absorption function from reference pixels by introducing dedicated light blocking structures. The metal layers, shading layers, and sidewall spacers are specifically designed to remove or block infrared radiation paths to reference pixels. This extraction of the light absorption function from reference pixels allows them to track temperature changes through thermal conduction without being contaminated by direct infrared radiation, thereby eliminating signal drift while preserving temperature tracking capability.
Solution Approach 2:
The patent converts the potentially harmful effect of infrared radiation exposure into a beneficial configuration by deliberately designing reference pixels with light blocking structures. Instead of allowing reference pixels to absorb infrared radiation (which causes signal drift), the patent uses the same infrared radiation that hits active pixels to create a contrast effect. The light blocking structures transform the harmful infrared exposure into a design feature that highlights the difference between active and reference pixels, improving calibration accuracy while preventing signal drift in reference pixels.
3Reliability
If light blocking structures are added to reference pixels, then signal drift is prevented, but device complexity increases
Solution Approach 1:
The patent merges multiple light blocking functions into a unified reference pixel structure. The metal layers, shading layers, and sidewall spacers are integrated together to form a comprehensive light blocking system for reference pixels, rather than treating each element separately. This merging approach consolidates the complexity into a standardized reference pixel design that can be replicated across the array, reducing overall device complexity while maintaining signal stability through the combined effect of multiple protective structures.
Solution Approach 2:
The patent addresses light blocking from multiple dimensional perspectives by implementing structures at different spatial levels. The sidewall spacers provide lateral dimension blocking, while metal layers and shading layers provide vertical dimension blocking. This multi-dimensional approach to light blocking ensures comprehensive protection of reference pixels without requiring excessive material or complex single-dimension structures, thereby managing device complexity while achieving reliable signal stability.
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 prevents signal drift and enhances sensitivity by ensuring accurate temperature calibration, allowing for precise thermal imaging and improved operational accuracy.
Implementation Method 1
The light absorbing layer is over the reference pixel
Implementation Method 2
The infrared sensor includes a substrate, an active pixel array, a reference pixel array
Implementation Method 3
The shading layer is conformally formed over the light absorbing layer and the sidewall spacer
Data Source
AI summary
An infrared sensor includes a substrate, a reference pixel array, a light absorbing layer, a first spacer, and a light shielding metal layer. The reference pixel array is disposed over the substrate and has a first reference pixel and a second pixel adjacent to the first reference pixel. The light absorbing layer extends across the first and second reference pixels and has a lateral strip and a protruding strip on the lateral strip. The first spacer extends along a first sidewall of the protruding strip of the light absorbing layer. The light shielding metal layer is conformally formed over the protruding strip of the light absorbing layer and the first spacer.