Imager Optical Systems With Front Aperture Stops for Better SNR
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Solution Overview
Problem
Conventional lens systems with aperture stops positioned behind the front lens element require large, thick windows to maintain mechanical stability and wide field of view, leading to reduced signal-to-noise ratio due to increased absorption of long-wave infrared radiation.
Innovation Solution
Positioning the aperture stop between the window and the front lens element, allowing for a smaller and thinner window that minimizes the impact on signal-to-noise ratio while enabling miniaturization and cost-effective integration, with full system calibration performed at the factory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the aperture stop is positioned behind the front lens element, then the mechanical stability and wide field of view are maintained, but the signal-to-noise ratio is reduced due to increased absorption of long-wave infrared radiation by large, thick windows
Solution Approach 1:
The aperture stop is repositioned from behind the front lens element to in front of it, between the window and the first lens element. This inversion of the conventional arrangement allows the window to be made smaller and thinner, reducing absorption of long-wave infrared radiation and improving signal-to-noise ratio while maintaining mechanical stability through the lens barrel structure
Solution Approach 2:
The positioning change of the aperture stop enables modification of the window parameters (size and thickness), transforming it from a large, thick window that absorbs radiation to a smaller, thinner window that minimizes absorption and improves thermal imaging performance
2Strength
If large, thick windows are used to maintain mechanical stability and wide field of view, then structural integrity is ensured, but the absorption of long-wave infrared radiation increases, reducing signal-to-noise ratio
Solution Approach 1:
By inverting the position of the aperture stop to be in front of the front lens element rather than behind it, the design enables the window to be reduced in size and thickness, thereby minimizing infrared radiation absorption while the lens barrel provides the necessary structural support
Solution Approach 2:
The function of providing structural stability is extracted from the window and transferred to the lens barrel assembly. This allows the window to be optimized for minimal radiation absorption (smaller and thinner) while the lens barrel maintains the mechanical strength and wide field of view requirements
3Loss of energy
If the aperture stop is repositioned between the window and the front lens element, then the window size and thickness are reduced improving signal-to-noise ratio, but the device complexity increases requiring full system calibration
Solution Approach 1:
Full system calibration is performed in advance at the factory during manufacturing. This preliminary action ensures that the repositioned aperture stop and modified optical path are properly calibrated, allowing the device to be shipped as a ready-to-use unit without requiring field calibration and simplifying deployment
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 configuration enhances the signal-to-noise ratio and facilitates miniaturization, enabling cost-effective and interchangeable imaging devices suitable for automotive applications with improved vehicle detection capabilities.
Implementation Method 1
a window configured to transmit electromagnetic radiation associated with a scene
Implementation Method 2
a first lens element configured to receive the electromagnetic radiation from the window and transmit the electromagnetic radiation... a second lens element adjacent to the first lens element and configured to receive the electromagnetic radiation and direct the electromagnetic radiation to the detector array
Implementation Method 3
Each detector is configured to receive the electromagnetic radiation from the lens system and generate a thermal image based on the electromagnetic radiation
Data Source
AI summary
Imager optical systems and methods are provided. In one example, an imaging device includes a window configured to transmit electromagnetic radiation associated with a scene. The imaging device further includes a lens system. The lens system includes a first lens element configured to receive the electromagnetic radiation from the window and transmit the electromagnetic radiation. An aperture stop is positioned between the window and a surface of the first lens element adjacent to the window. The lens system further includes a second lens element adjacent to the first lens element and configured to receive the electromagnetic radiation and direct the electromagnetic radiation to the detector array. The imaging device further includes a detector array including detectors. Each detector is configured to receive the electromagnetic radiation from the lens system and generate a thermal image based on the electromagnetic radiation. Related methods and systems are also provided.