CCD Sensor Laser Detection via Pixel Thresholding
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Solution Overview
Problem
Existing methods for detecting pulsed laser radiation, such as those from beamrider missiles, face challenges in distinguishing low-intensity signals from ambient brightness, particularly during the day, and struggle to achieve precise 2-dimensional directional resolution due to limitations in detector design and complexity, leading to reduced sensitivity and delayed detection.
Innovation Solution
A method utilizing a CCD sensor with high sampling frequency and on-chip signal processing to compare each pixel with a threshold value, enabling fast and efficient separation of pulsed laser signals from background noise, and achieving high sensitivity and directional resolution through pixel-by-pixel analysis and adaptive threshold adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large-area photodiodes are used to increase signal intensity, then the total signal intensity incident on the detector is increased, but the capacitance increases and the cut-off frequency of the detection decreases
Solution Approach 1:
The patent divides the detector into multiple small detector elements arranged in an array, where each element has a small active area. This segmentation allows each element to maintain low capacitance and high cut-off frequency while the array collectively provides sufficient signal detection capability through spatial distribution of detection elements.
2Device complexity
If the number of detection sectors is kept small to limit technical complexity, then device complexity is reduced, but precise direction detection is not possible
Solution Approach 1:
The patent employs an array of multiple detector elements that can be arranged to cover the required detection angle. Each element contributes to directional information, and through signal processing combining outputs from multiple elements, high angular resolution is achieved without requiring a mechanically complex system with many discrete detection sectors.
Solution Approach 2:
The patent transitions from a single-detector or few-sector approach to a two-dimensional array of detector elements. This spatial arrangement in multiple dimensions enables precise direction determination through the spatial distribution of detected signals, achieving high angular resolution without increasing mechanical complexity.
3Reliability
If background light is accumulated over the entire detection sector to increase signal collection, then more background signal is collected, but suppression of background signal is only possible to a limited extent
Solution Approach 1:
The patent divides the detection field into multiple small detector elements, each with a limited field of view. This segmentation allows for more selective background rejection because each element collects less background light while maintaining sensitivity to the laser signal. The spatial distribution enables discrimination between signal and background through pattern recognition across the array.
Solution Approach 2:
The patent applies different characteristics to different parts of the detection system by using an array of detector elements with specific spatial arrangements and potentially different spectral responses. This allows optimization of signal-to-background ratio for different regions of the detection field, with each element tailored to its specific viewing direction and background conditions.
4Measurement precision
If an array of approx. 27,000 detector elements is used to achieve 1° angular resolution, then directional accuracy is improved, but the effort required increases immensely
Solution Approach 1:
The patent designs a detector array where each element serves multiple functions: detecting laser signals, providing directional information, and contributing to background rejection. The shared readout electronics and signal processing architecture allow the system to achieve high angular resolution without requiring completely independent processing channels for each element, thereby reducing overall 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 sensitive detection of pulsed laser threats with high 2-dimensional directional resolution of at least 1°, even in daylight conditions, without mechanical delays, and with a compact design that effectively suppresses background noise.
Implementation Method 1
A CCD sensor with high sampling frequency and on-chip signal processing to compare each pixel with a threshold value
Data Source
AI summary
The method involves generating single images by comparing pixels of a CCD sensor (1) to a respective threshold value. A mean- or peak value of stored pixel values of a single image pixel-by-pixel is ascertained over 10 samples during signal processing. A signal image obtained in the signal processing is forwarded for image processing at an image frequency of 10-500 Hz. A signal pixel representing incident laser radiation (10) is identified from the image in an image processing. A direction of incidence of the laser radiation is determined from a position of the signal pixels on the image. Independent claims are also included for the following: (1) a CCD sensor (2) an imaging laser alerter.