Miniature Phase-Corrected THz Antennas for High Resolution Imaging Arrays
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Solution Overview
Problem
Current THz imaging systems face limitations in achieving high-resolution, compact detector layouts and supporting a large number of detector elements without using expensive and bulky lenses, due to issues like reflection losses at the lens/air boundary and the need for local oscillator signals and large low-pass IF filters.
Innovation Solution
Integration of dual slot antennas with zero-biased Sb-heterostructure backward diodes for direct detection of THz radiation, along with improved antenna layouts that support tilted radiation patterns to increase the number of detectors and reduce reflection losses, allowing for a more compact and efficient THz imaging array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an extended hemispherical lens is used to focus the image on the array elements, then the coupling efficiency of pixels positioned away from the lens axis is significantly reduced due to reflections at the lens/air boundary, but the number of detector elements is limited by the lens diameter and cannot support imaging for scan angles beyond ±20°
Solution Approach 1:
The patent divides the imaging system into multiple focal plane arrays, each covering a specific angular range. By segmenting the detection field into multiple zones with dedicated detector arrays, the system can support a larger total number of detector elements without requiring a single large lens, thereby resolving the contradiction between coupling efficiency and the number of detector elements.
Solution Approach 2:
The patent introduces optical elements such as mirrors or additional lenses as intermediaries to redirect THz radiation onto the detector elements. This intermediary approach allows pixels positioned away from the lens axis to maintain high coupling efficiency while expanding the field of view beyond ±20°, effectively increasing the number of usable detector elements without requiring a larger primary lens.
2Measurement precision
If Schottky diodes monolithically integrated within double slot antennas are employed in heterodyne THz detectors settings, then the Gaussian beam coupling efficiency and diffraction limited patterns are achieved, but the need for local oscillator signal and relatively large low-pass IF filter sections does not allow for tightly packed array development
Solution Approach 1:
The patent extracts and eliminates the local oscillator signal requirement and large low-pass IF filter sections from the detector design. By using direct detection heterojunction detector diodes instead of heterodyne detection, the system achieves high Gaussian beam coupling efficiency without the bulky additional components, thereby enabling tightly packed array development.
Solution Approach 2:
The patent replaces complex heterodyne detection components (local oscillator sources and large filter sections) with simpler, more compact direct detection diodes. This substitution with simpler components achieves the same detection function with significantly reduced size, allowing for high-density array packing while maintaining diffraction-limited performance.
3Device complexity
If a mechanical raster scan of the object is used to generate medical images using THz radiation, then the imaging can be performed with simple detector setups, but long image acquisition times constitute a major bottleneck
Solution Approach 1:
The patent segments the detection function into multiple parallel detector elements arranged in focal plane arrays. Instead of using a single detector performing mechanical raster scanning, multiple detectors simultaneously capture different spatial positions, thereby dramatically reducing image acquisition time while maintaining the simplicity of the detector design through parallel operation.
Solution Approach 2:
The patent transitions from one-dimensional mechanical raster scanning to two-dimensional parallel detection using focal plane arrays. By adding the spatial dimension of multiple simultaneous detectors, the system achieves rapid imaging without complex mechanical movement, resolving the contradiction between simple detector setups and long acquisition times.
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 the development of high-resolution, compact THz imaging arrays with increased detector density and improved off-axis detection capabilities, reducing the need for large lenses and enhancing the sensitivity and efficiency of THz imaging systems.
Implementation Method 1
dual slot antenna element integrated with a zero-biased Sb-heterostructure backward diode for direct detection of THz radiation
Implementation Method 2
When an extended hemispherical lens is used to focus the image on the array elements
Implementation Method 3
reflections at the lens/air boundary significantly reduce coupling efficiency of the pixels positioned away from the lens axis
Data Source
AI summary
An imaging/detection device includes a hemispherical lens having a surface opposite a curvature of the hemispherical lens, where the hemispherical lens defines an optical axis. The imaging/detection device also includes a plurality of detectors arranged on a focal plane array that is positioned near the surface of the hemispherical lens. Each of the detectors respectively includes a diode and an antenna monolithically integrated with the diode. Additionally, at least one of the detectors is offset by a distance from the optical axis of the hemispherical lens and is configured such that a radiating pattern of the respective antenna is tilted by an angle and directed toward the optical axis of the hemispherical lens. A maximum direction of the radiating pattern of the respective antenna is related to the distance by which the detector is offset from the optical axis of the hemispherical lens.