Angular Filter for Fiber Optic Phosphor Screen Stray Light
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fiber optic phosphor screens in image intensifier tubes suffer from significant stray light due to the mismatch between the light ray transmission cone and numerical aperture of optical fibers, leading to reduced image contrast and efficiency.
Innovation Solution
Incorporating an angular filter between the thin film phosphor layer and the fiber optic plate, ensuring that any light ray emitted by the phosphor layer enters the core of the optical fiber with a refraction angle less than or equal to π/2-arcsin(nG/nC), thereby reducing stray light and improving image contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin film phosphor layer is used without an angular filter, then the structure is simple and manufacturing is easier, but stray light increases and image contrast deteriorates
Solution Approach 1:
An angular filter layer is introduced as an intermediary component between the phosphor layer and the optical fiber plate. This filter selectively transmits light rays within a specific angular range (numerical aperture) while blocking stray light at larger angles, thereby improving image contrast without significantly complicating the manufacturing process
Solution Approach 2:
The angular filter is designed with specific optical parameters (refractive index, thickness, angular transmission characteristics) that are optimized to match the numerical aperture of the optical fibers. By controlling these parameters, the system maximizes light transmission within the desired cone angle while minimizing stray light, achieving better image quality
2Use of energy by moving object
If the transmission cone angle is larger than the numerical aperture, then more light is collected from the phosphor layer, but light rays are refracted into the sheath causing stray light and reducing image contrast
Solution Approach 1:
The angular filter acts as a mediator that reconciles the conflict between light collection efficiency and stray light prevention. It allows broad angular acceptance from the phosphor layer while selectively directing only the appropriate angular range into the optical fibers, blocking excessive angles that would cause sheath refraction
Solution Approach 2:
The angular filter provides different transmission properties for different angular ranges of incident light. It exhibits high transmission for rays within the numerical aperture cone and low transmission for rays at larger angles, creating a localized quality variation that optimizes both light collection and stray light rejection
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
The angular filter significantly reduces stray light within the sheath of optical fibers, enhancing the efficiency and contrast of the output image formed by the phosphor screen.
Implementation Method 1
any light ray emitted by the phosphor layer enters the core of the optical fiber with a refraction angle less than or equal to π/2-arcsin(nG/nC)
Implementation Method 2
The numerical aperture of the optical fibers forms a second angular aperture at the interface between the thin film phosphor layer and the core of the optical fibers... a light ray which penetrates the core of the fiber and whose angle of incidence at said phosphorus layer/core of the fiber interface is less than or equal to this second critical angle remains localized in the core of the fiber, due to the phenomenon of total internal reflection
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a fibre optic phosphor screen comprising a thin-film phosphor layer (10) and a fibre optic faceplate (20), allowing the interfering light in the cladding (22) of the optical fibres to be reduced. To this end, the phosphor screen comprises an angular filter (30) having at least one layer (31; 32) arranged between the thin-film phosphor layer (10) and the fibre optic faceplate (20).