EBAPS Star Camera Resolution and Noise Control
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Solution Overview
Problem
Conventional star imaging technologies face challenges in capturing high-resolution images of stars due to sensitivity to thermal noise, cosmic rays, and limited gain adjustment range, especially when observing stars outside the visible light spectrum, and are hindered by atmospheric interference such as ozone and gas/dust clouds.
Innovation Solution
The system employs an electron bombarded active pixel sensor (EBAPS) with a photocathode and anode in a vacuum, generating an electric field to direct electrons from the photocathode to the anode, providing high gain and increased image resolution through electron multiplication, and allows for movement of the collector relative to the optical system to enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CCD imagers are used for star imaging, then image capturing capability is provided, but thermal noise and cosmic rays cause shifts or hot spots degrading the star image
Solution Approach 1:
The patent extracts the harmful thermal noise by taking multiple exposures with the shutter closed to create a baseline, then subtracts this baseline from the open-shutter image to remove image defects caused by thermal noise and cosmic rays
Solution Approach 2:
The patent performs preliminary action by capturing multiple baseline images with the shutter closed before capturing the actual star image, allowing thermal noise to be characterized and removed in advance
2Illumination intensity
If ICCD with image intensifier is used to amplify photons, then sensitivity to low light is improved, but image resolution remains low and gain adjustment range is limited
Solution Approach 1:
The patent replaces the mechanical electron multiplication system (micro-channel plate) with an electronic gain system using readout amplifiers and analog-to-digital converters, enabling precise electronic gain adjustment without the resolution limitations of physical electron multiplication
3Adaptability or versatility
If electron-bombarded CCD is used, then gain adjustment is provided, but image resolution remains low and the system is not widely used
Solution Approach 1:
The patent replaces the electron-bombardment mechanical system with an electronic gain control system implemented through readout amplifiers, allowing precise gain adjustment through electronic means while maintaining high image resolution
4Ease of manufacture
If CMOS imager is used, then cost is reduced and integration is improved, but sensitivity to low light levels is insufficient
Solution Approach 1:
The patent applies dynamic gain adjustment to the CMOS imager, allowing the system to optimize sensitivity for low-light conditions by electronically adjusting the gain of readout amplifiers, thereby maintaining cost-effectiveness while improving low-light performance
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 enables improved low-light imaging and increased resolution for celestial navigation, allowing observation of stars in various wavelengths, including ultraviolet and infrared, by reducing noise and overcoming atmospheric obstructions.
Implementation Method 1
When the star is focused by the optical system onto the photocathode in the vacuum, the photocathode releases electrons into the vacuum
Implementation Method 2
the electric field directs the electrons toward the active pixel sensor anode to generate a star image
Implementation Method 3
The EBAPS includes a voltage source that is connected to both the photocathode and the anode to generate an electric field within the vacuum between the photocathode and the anode
Data Source
AI summary
A star camera system that includes an optical system configured to focus radiation from a star to be imaged onto a collector that is in the form of an electron bombarded active pixel sensor (EBAPS) configured to provide high gain. The EBAPS comprising a photocathode disposed in a vacuum is configured to release electrons into the vacuum when exposed to radiation focused thereon by the optical system. The EBAPS includes an active pixel sensor anode disposed distant from the photocathode in the vacuum. An electric field is generated by a voltage source to direct the electrons from the photocathode to the active pixel sensor anode. Furthermore, the collector is mounted on a translation device configured to move the collector relative to the optical system by a predetermined amount of less than pixel size in the focal plane of the optical system to increase image resolution of a plurality of images.