Image Intensifier Power Supply Duty Factor Control
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Solution Overview
Problem
Conventional image intensifiers face challenges in regulating their Figure of Merit (FOM) and signal-to-noise ratio (SNR) effectively, particularly in varying light conditions, which affects their performance and compliance with regulatory standards.
Innovation Solution
The solution involves controlling the duty factor of the power supply to the image intensifier by using a series of voltage sources and switches, along with a timer/driver circuit, to adjust the photocathode and micro-channel plate voltages, thereby regulating the effective photoresponse and ultimately the FOM and SNR. This is achieved through a power supply system that includes multiple voltage sources, switches, and a timing control mechanism to manage the duty cycle and reduce peak voltages in high light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the image intensifier operates continuously at high gain to maintain superior image quality, then the Figure of Merit and signal-to-noise ratio are improved, but the device cannot comply with regulatory FOM thresholds and generates excessive noise in varying light conditions
Solution Approach 1:
The patent implements periodic gating of the photocathode voltage, switching it between active and inactive states in controlled cycles. This periodic action allows the system to achieve compliance with regulatory FOM thresholds by reducing average electron emission, while still maintaining superior image quality during active periods when high gain is needed for low-light conditions.
Solution Approach 2:
The system dynamically adjusts the photocathode voltage and duty factor based on operating conditions and regulatory requirements. By making the voltage application dynamic rather than static, the image intensifier can adapt its FOM and SNR characteristics to meet different regulatory thresholds while maintaining optimal performance across varying light conditions.
2Measurement precision
If the photocathode voltage is continuously applied to maintain high photoresponse, then image quality is improved, but the device cannot regulate FOM to meet export restrictions
Solution Approach 1:
The patent applies periodic gating to the photocathode voltage, creating pulsed operation cycles. During active periods, full voltage is applied to maintain high photoresponse and image quality. During inactive periods, voltage is reduced or eliminated, reducing average electron emission to comply with export FOM restrictions. This periodic application resolves the contradiction between maintaining high image quality and regulating FOM for export compliance.
Solution Approach 2:
The system changes the temporal parameter of voltage application by introducing duty factor control. Instead of continuous voltage application, the system varies the proportion of time the photocathode receives full voltage versus reduced or zero voltage. This parameter change enables FOM regulation to meet export restrictions while preserving image quality during active periods.
3Power
If the image intensifier operates at high gain in high light conditions, then signal amplification is maximized, but noise and image quality deteriorate
Solution Approach 1:
The patent incorporates automatic gain control that responds to light level conditions. When high light conditions are detected, the system reduces the photocathode voltage duty factor or magnitude, providing negative feedback to prevent excessive signal amplification that would cause noise and image quality deterioration. This feedback mechanism dynamically optimizes the balance between signal amplification and image quality across varying light conditions.
Solution Approach 2:
The system dynamically adjusts operating parameters based on real-time light level detection. In high light conditions, the photocathode voltage duty factor is reduced to lower gain and prevent noise. In low light conditions, full duty factor is applied to maximize amplification. This dynamic adaptation resolves the contradiction between signal amplification power and image quality measurement precision.
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 adjustable FOM and SNR, ensuring optimal image quality while complying with regulatory requirements by effectively managing the duty factor and peak voltages, thereby maintaining superior image quality across different light conditions.
Implementation Method 1
The photocathode 14, e.g., a photoemissive semiconductor heterostructure that is extremely sensitive to low-radiation levels of light in the 580-900 nm spectral range, provides a spatially coherent emission of electrons in response to the electromagnetic radiation
Implementation Method 2
Electrons impinging on interior sides of the holes through the MCP 20 result in the emission of a number of secondary electrons each of which, in turn, causes the emission of more secondary electrons
Implementation Method 3
Electrons emerging from an output plane of the MCP 20 are accelerated toward a phosphor screen 16 (anode), which is maintained at a higher positive potential than the output of the MCP 20. The phosphor screen 16 converts the emitted electrons into visible light
Data Source
AI summary
Power supplies and methods for regulating performance of image intensifiers are disclosed. Performance is regulated by controlling the duty factor of the image intensifiers.