Bolometer Bias Circuit Topology for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bolometer circuits are hindered by increased size, cost, complexity, noise, and power consumption due to additional transistors or control mechanisms required for bias generation and control, which also reduce sensitivity and usable signal range for infrared radiation detection.
Innovation Solution
A bolometer circuit design that utilizes a bias circuit to set and maintain biases across active bolometers, incorporating thermally shorted bolometers as temperature-compensated loads and feedback resistors, and a CMOS DAC for precise voltage control, reducing the need for extra circuitry and noise sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional transistors or control mechanisms are used for bias generation and control, then the bias can be maintained at a desired level, but the size, cost, complexity, and power consumption of the bolometer circuit increase
Solution Approach 1:
The patent removes transistors and control mechanisms from the bolometer conduction path, extracting only the essential biasing function. The bias is generated directly through circuit topology (series connection of bolometers to supply voltage) without intermediate active components, eliminating the need for complex control while maintaining bias stability
Solution Approach 2:
The patent combines multiple bolometers in series within the same conduction path, merging their functions to achieve self-biasing. The series connection allows the bolometers to share the supply voltage, providing stable bias without requiring separate control circuitry for each device
2Reliability
If additional transistors or control mechanisms are placed in the bolometer conduction path, then bias control is improved, but noise in the sensitive bolometer conduction path increases
Solution Approach 1:
The patent extracts all active control components (transistors, switches) from the bolometer conduction path, leaving only passive elements. This removal eliminates the primary noise sources while maintaining the ability to control bias through circuit topology and timing
3Reliability
If transistors limit the current flow and voltage on the bolometer conduction path to control bias, then bias control is achieved, but the voltage and current available for biasing the bolometer are reduced, reducing sensitivity
Solution Approach 1:
The patent removes current-limiting transistors from the conduction path, allowing the full supply voltage and current to be applied directly to the bolometer. Bias control is achieved through timing and circuit topology rather than active current limiting, preserving maximum signal strength for detection
Solution Approach 2:
The patent employs periodic pulsing of the bolometer conduction path to achieve bias control. By applying voltage in controlled pulses rather than continuous DC, the system maintains bias stability while allowing peak voltage and current levels to remain high during the active detection phase
4Reliability
If conventional bias generation and control circuits are used, then bias stability is maintained, but the usable signal range for representing IR radiation intensity is reduced due to self-heating effects
Solution Approach 1:
The patent uses periodic pulsing of the bolometer with controlled duty cycles to manage self-heating. By applying bias voltage in pulses rather than continuously, the system maintains stability during measurement while allowing thermal dissipation during off-periods, thereby extending the usable signal range before saturation occurs
Solution Approach 2:
The patent dynamically adjusts the pulsing parameters (frequency, duty cycle) of the bolometer conduction path to optimize performance. This dynamic control allows the system to adapt to changing conditions and maintain both stability and extended signal range across different operating scenarios
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 achieves reduced complexity, noise, and cost while providing a larger bias range and improved sensitivity for infrared radiation detection, enabling higher performance and lower power consumption.
Implementation Method 1
A bolometer, which changes its resistance in response to optical heating
Implementation Method 2
changes its resistance in response to optical heating
Implementation Method 3
incorporating thermally shorted bolometers as temperature-compensated loads
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A bolometer circuit includes a substrate on which a focal plane array (FPA) of active bolometers is provided. Each active bolometer is configured to receive external infrared (IR) radiation and substantially thermally isolated from the substrate. The bolometer circuit also includes one or more blind arrays of blind bolometers shielded from the external IR radiation and substantially thermally isolated from the substrate. Noises in outputs from each column and/or each row of the FPA are corrected, reduced, or suppressed based on a statistical property of outputs from a corresponding column or row of the one or more blind arrays. Noise in each frame of IR image captured by the FPA may also be corrected, reduced, or suppressed using the one or more blind arrays.