Photodetector Drift Compensation via Dark Pixel Shielding
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Solution Overview
Problem
Existing photodetectors for measuring optical radiation, particularly in the infrared range, face challenges such as strong temperature dependency and long-time drift due to factors like electron-hole pairs, leading to inaccurate measurements and the need for costly stabilization systems.
Innovation Solution
A photodetector design incorporating both active and dark pixels, where the dark pixel is shielded from optical radiation using a temperature equalizing cover to maintain thermal equilibrium with the active pixel, allowing for self-calibration against drifts without external stabilization, thereby reducing costs and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermoelectric cooling system is used to stabilize photodetector temperature, then measurement stability is improved, but device complexity and cost increase
Solution Approach 1:
The photodetector uses itself to compensate for its own drift through the dark pixel measurement. The dark pixel provides a reference signal that captures the drift, which is then used to correct the active pixel measurements, eliminating the need for external stabilization systems.
Solution Approach 2:
The invention extracts the drift component from the total signal by using the dark pixel as a reference. By separating the drift signal (from dark pixel) from the measurement signal (from active pixel), the drift can be compensated without affecting the measurement stability.
2Object-affected harmful factors
If dark pixel is covered with absorbing material to block radiation, then dark pixel shielding is improved, but self-heating occurs causing thermal imbalance
Solution Approach 1:
The patent introduces an intermediary substance - the infrared-transparent material - that allows infrared radiation to pass through while blocking visible light. This material acts as a mediator that achieves the shielding function without causing the harmful self-heating effect.
Solution Approach 2:
The cover material has different optical properties for different wavelengths: it is opaque to visible light (blocking stray light) but transparent to infrared radiation (allowing thermal equilibrium). This local quality differentiation resolves the contradiction between shielding and thermal balance.
3Measurement precision
If multiple pixels are used for drift compensation, then measurement accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
The invention merges the measurement function and the reference function into a single integrated photodetector structure. The dark pixel is formed by simply covering part of the photosensitive area, combining the benefits of drift compensation with ease of manufacturing.
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 design enables precise, cost-effective optical measurements by compensating for temperature and long-time drifts, enhancing the reliability and stability of the photodetector without the need for complex stabilization systems.
Implementation Method 1
The photodetectors based on the photoconductive effect are known as photoresistors, photosensitive resistors, photoconductors, or photoconductive detectors. A photodetector comprises at least one photosensitive region, which changes at least one of its physical quantities proportional to electromagnetic radiation. In case of the photoconductors, this physical quantity is the resistance.
Implementation Method 2
the absorption of the electromagnetic radiation, especially of the IR radiation leads to a self-heating. Since such materials absorb more energy than the other detectors in the system, the heating of the dark pixel is stronger than the heating of any other active pixel.
Data Source
AI summary
Disclosed herein is a photodetector for measuring optical radiation. The photodetector includes:at least one active pixel including an active photosensitive region, where the active pixel is configured for generating at least one active signal by using the active photosensitive region, where the active signal is dependent on an illumination of the active pixel by the optical radiation; andat least one dark pixel including:a dark photosensitive region, where the dark pixel is configured for generating at least one dark signal by using the dark photosensitive region, where the dark signal is independent on an illumination of the dark pixel by the optical radiation; anda temperature equalizing cover configured for covering the dark photosensitive region at least against the optical radiation.