Microbolometer Line Switching for Noise Reduction
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Solution Overview
Problem
Uncooled microbolometer thermal imaging systems face challenges with noise degradation due to random, fixed pattern, and banding noise, particularly in rolling shutter mode, which affects the signal-to-noise ratio (SNR) and thermal response times.
Innovation Solution
A method and system that alternates between generating target and reference image frames by switching individual lines of microbolometer pixels between exposed and shielded states using an optical chopper, allowing each line to reach a stabilized temperature before readout in the next state, and adjusting target frames using reference frames to reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uncooled microbolometer arrays operate in rolling shutter mode, then device complexity and power consumption are reduced, but noise degradation increases due to random noise, fixed pattern noise, and banding noise
Solution Approach 1:
The detector array is divided into multiple independently controllable zones or regions, allowing different integration times for different portions of the array. This segmentation enables the system to maintain rolling shutter operation for most pixels while providing extended integration time for specific regions of interest, thereby improving signal-to-noise ratio without significantly increasing overall device complexity
Solution Approach 2:
The system dynamically adjusts the integration time of individual pixels or regions based on scene requirements, transitioning between standard rolling shutter mode and extended integration mode as needed. This dynamic adaptability allows the system to optimize noise performance for specific scenarios while maintaining the simplicity of standard operation during normal conditions
2Ease of manufacture
If uncooled microbolometer arrays use rolling shutter readout scheme, then manufacturing cost and device robustness are improved, but thermal response time increases causing banding noise
Solution Approach 1:
The system performs preliminary thermal equilibration of the microbolometer pixels before the actual measurement integration period. By allowing the detectors to reach thermal equilibrium with the incoming radiation in advance, the system reduces thermal transients and banding artifacts during the rolling shutter readout, thereby improving thermal response characteristics without changing the fundamental rolling shutter architecture
Solution Approach 2:
The system employs periodic reset or reference measurements interspersed with the rolling shutter readout sequence. These periodic actions allow the system to compensate for thermal drift and response time variations by comparing current measurements against reference states, thereby reducing banding noise while maintaining the cost-effective rolling shutter approach
3Use of energy by moving object
If uncooled microbolometer arrays operate at room temperature, then device size and power consumption are reduced, but noise performance deteriorates compared to cooled detectors
Solution Approach 1:
The system continuously accumulates thermal energy from the target scene over extended integration periods, maximizing the useful signal accumulation before readout. By maintaining continuous exposure and integration for as long as possible within each frame cycle, the system improves the signal-to-noise ratio through temporal averaging, compensating for the higher noise floor inherent in uncooled operation
Solution Approach 2:
The system incorporates real-time noise characterization and adaptive integration time adjustment based on measured signal quality. By continuously monitoring the noise levels and scene brightness, the system dynamically optimizes the integration time to maximize signal-to-noise ratio, thereby improving noise performance while maintaining low power consumption and room temperature operation
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 enhances the signal-to-noise ratio and reduces performance issues related to thermal response times, resulting in improved thermal imaging quality by maximizing the time for microbolometers to reach steady-state temperatures.
Implementation Method 1
an optical chopper disposed in the intermediate image plane, the optical chopper being configured to cause each line of microbolometer pixels to individually switch between an exposed state, where the line is exposed to electromagnetic radiation from the target scene, and a shielded state, where the line is shielded from electromagnetic radiation from the target scene
Implementation Method 2
thermal imaging systems based on arrays of uncooled microbolometer detectors... configured to detect electromagnetic radiation, typically infrared radiation, emitted by the objects and living bodies present in a scene being viewed. The detected radiation is converted into electrical signals on a per-detector basis
Data Source
AI summary
A method and system for imaging a target scene using a microbolometer array having multiple lines of microbolometer pixels are disclosed. Each line is switchable between an exposed state and a shielded state, where the line is exposed to the target scene and a reference scene, respectively. The method may include alternating between generating a target frame of the target scene and generating a reference frame of the reference scene, each of which in a rolling shutter mode. The method may also include, concurrently with the generating steps, alternating between sequentially shielding each line after its readout in the exposed state for its next readout in the shielded state, and sequentially exposing each line after its readout in the shielded state for its next readout in the exposed state. The method may also include adjusting the target frames using the reference frames to generate thermal images of the target scene.