Rolling Shutter CMOS Sensor Pulse Detection
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Solution Overview
Problem
Existing low-cost detectors for pulsed radiation are limited by the Nyquist Theorem, restricting their ability to detect pulse repetition frequencies above a certain threshold due to the minimum predetermined integration period of rolling shutter cameras, making them unsuitable for high-frequency events.
Innovation Solution
A computer-implemented method using a rolling shutter operation with sensor arrays, where each element line is addressed consecutively for a predetermined integration period, extracts a beat signal and calculates a peak-to-trough ratio to determine the pulse repetition frequency, allowing detection beyond the Nyquist limit by combining beat frequency and peak-to-trough ratio in a pulse repetition frequency function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rolling shutter operation with a predetermined integration period is used to detect pulsed radiation, then the device cost is reduced, but the detectable pulse repetition frequency is limited by the Nyquist Theorem
Solution Approach 1:
The patent changes the integration period dynamically for different element lines rather than using a fixed predetermined integration period. By varying the integration period across element lines, the system can detect pulse repetition frequencies that would otherwise exceed the Nyquist limit imposed by a fixed integration period, thus resolving the contradiction between low cost and high frequency detection capability
Solution Approach 2:
The patent divides the sensor array into multiple element lines, each with different integration periods. This segmentation allows different portions of the array to capture different frequency ranges simultaneously, enabling the detection of high-frequency pulsed radiation while maintaining the use of low-cost rolling shutter cameras
2Measurement precision
If the integration period is reduced to increase the maximum detectable frequency, then the detectable pulse repetition frequency increases, but the signal integration time decreases leading to reduced signal quality
Solution Approach 1:
By dividing the sensor array into multiple element lines with different integration periods, the system allows some element lines to use longer integration periods for better signal quality while other element lines use shorter integration periods to capture higher frequencies. This segmentation resolves the contradiction between signal quality and maximum detectable frequency
Solution Approach 2:
The system dynamically assigns different integration periods to different element lines based on the pulse repetition frequency being detected. This dynamic adjustment allows the system to optimize both signal quality and frequency detection capability simultaneously, rather than being constrained by a single fixed integration period
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
Enables the detection of pulse repetition frequencies above the apparent limitation related to the predetermined integration period, enhancing the capability of low-cost rolling shutter devices to detect high-frequency pulsed radiation, including pulsed laser radiation.
Implementation Method 1
addressing the sensor array of sensor elements using a rolling shutter operation, wherein the rolling shutter operation comprises addressing each element line consecutively for a predetermined integration period
Implementation Method 2
extracting a beat signal from the pixel values of the radiation image in a sensor array direction corresponding to the direction of the rolling shutter operation; calculating a beat frequency from the beat signal
Data Source
AI summary
Techniques for detecting pulsed radiation. A CMOS sensor array being irradiated across at least a portion of the array with pulsed radiation is addressed using a rolling shutter operation. The sensor array is read to extract the integrated energy from each sensor element and convert the integrated energy into a pixel value for a pixel in a radiation image. A pulse detection operation is then applied to the radiation image to obtain a pulse repetition frequency of the pulsed radiation. The pulse detection operation includes extracting a beat signal, calculating a beat frequency and peak to trough ratio from the beat signal, and determining the pulse repetition frequency therefrom. Particularly suited to the technical field of pulsed laser detection. Also relates to a pulse detector for the same.