Monolithic IR-Visible Sensor Layout for Laser Spot Registration
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Solution Overview
Problem
Conventional imagers used in laser designator systems struggle to capture both the reflected laser pulse energy and surrounding scenery simultaneously, leading to registration errors when trying to merge images from separate sensors, which is problematic for applications requiring high accuracy.
Innovation Solution
A monolithic sensor capable of detecting both infrared and visible light is developed, featuring a semiconductor substrate with integrated visible and infrared photodiodes, along with a textured region to enhance light absorption, allowing for simultaneous capture and integration of both light types to create a composite image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional imager is gated in time to capture the reflected laser pulse, then the laser spot detection is improved, but the surrounding scenery capture is lost
Solution Approach 1:
The sensor array is segmented into multiple pixel types within the same physical array, with each pixel type optimized for different wavelength ranges (visible and infrared). This allows simultaneous capture of laser spots (infrared) and surrounding scenery (visible) without temporal gating, resolving the contradiction between laser detection accuracy and scenery information retention.
Solution Approach 2:
The sensor array is designed with multi-functional pixels that can detect both visible and infrared light. By integrating different photodiode types (silicon for visible, InGaAs for infrared) within the same sensor array, the system achieves universal detection capability across multiple wavelength ranges, enabling simultaneous laser spot and scenery capture.
2Adaptability or versatility
If separate sensors are used to capture laser spots and surrounding scenery, then both imaging functions are achieved, but registration errors occur
Solution Approach 1:
The patent merges multiple sensor functions into a single integrated sensor array where visible and infrared photodiodes are physically co-located at the same positions. This spatial merging eliminates the field-of-view misalignment and registration errors that occur with separate sensors, while maintaining the versatility to capture both laser spots and surrounding scenery simultaneously.
Solution Approach 2:
The sensor array employs a nested structure where infrared photodiodes (InGaAs) and visible photodiodes (silicon) are integrated within the same pixel architecture. Each pixel location contains both types of photodiodes, with the infrared detection capability nested within the visible detection framework, ensuring perfect spatial correspondence between different wavelength images.
3Speed
If the gate time is limited to capture the laser pulse, then the laser detection speed is improved, but the background video imagery quality deteriorates
Solution Approach 1:
The system uses periodic laser pulsing combined with synchronized infrared detection. The infrared photodiodes are gated to detect only during the brief laser pulse periods, while the visible photodiodes continuously capture background video. This periodic action approach maintains fast laser detection speed while preserving background imagery quality through parallel continuous visible light capture.
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 monolithic sensor enables accurate and simultaneous imaging of laser spots and surrounding scenery without registration errors, improving aiming accuracy by providing a single composite image with enhanced light absorption and reduced noise.
Implementation Method 1
A visible light photodiode can be formed at the device surface
Implementation Method 2
An infrared photodiode can be formed at the device surface in proximity to the visible light photodiode
Implementation Method 3
A light diffusing region can be coupled to the infrared photodiode and positioned to interact with electromagnetic radiation
Data Source
AI summary
A monolithic sensor for detecting infrared and visible light according to an example includes a semiconductor substrate and a semiconductor layer coupled to the semiconductor substrate. The semiconductor layer includes a device surface opposite the semiconductor substrate. A visible light photodiode is formed at the device surface. An infrared photodiode is also formed at the device surface and in proximity to the visible light photodiode. A textured region is coupled to the infrared photodiode and positioned to interact with electromagnetic radiation.