LEPSD AOA Sensor with Focusing Lens and Low Sheet Resistance
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Solution Overview
Problem
Conventional optical angle of arrival (AOA) sensors face limitations due to speckle and occlusions in the input aperture, leading to non-uniform optical intensity distributions and erroneous angle estimates, and are not sensitive to eye-safe laser wavelengths, requiring complex achromatic designs or limited response bandwidth.
Innovation Solution
An AOA sensor configuration using a focusing lens and an array of lateral-effect position sensing detector (LEPSD) elements, where each LEPSD includes an absorber region for specific wavelengths and lateral current conducting layers with low sheet resistance, allowing for improved sensitivity and response bandwidth, and an in-line configuration with an image detecting array to share the same optical axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large defocused spot is used on the 4-quadrant detector, then the angle of arrival can be determined by comparing relative optical energy across quadrants, but speckle and aperture occlusions produce non-uniform intensity distribution resulting in erroneous centroid estimates
Solution Approach 1:
The patent changes the spot size parameter from large/defocused to small/focused, transforming the illumination pattern to be resistant to speckle and occlusion effects. This parameter change fundamentally alters how the detector responds to incoming light, making the measurement immune to the previously problematic non-uniform intensity distributions.
Solution Approach 2:
The patent replaces the conventional 4-quadrant detector system with a lateral-effect position sensing detector (LEPSD) that uses lateral current flow to determine spot position. This substitution of the detection mechanism eliminates the need to compare relative optical energy across quadrants and instead directly measures the centroid position through lateral current distribution, which is inherently resistant to speckle and occlusion effects.
2Ease of manufacture
If silicon material is used for the LEPSD, then the device can be fabricated with standard processes, but the light-absorbing layer must be very thick (30-100 μm) resulting in small capacitance per unit area and limited sensitivity to eye-safe laser wavelengths
Solution Approach 1:
The patent employs compound semiconductor materials such as InGaAs, InAs, InAsSb, InSb, or HgCdTe that possess direct-bandgap properties. These composite materials enable the LEPSD to detect eye-safe laser wavelengths (>1.4 μm) with high sensitivity while maintaining practical capacitance values, overcoming the limitations of silicon material for this specific wavelength range.
3Speed
If the I-layer in an InGaAs LEPSD is made thin (1-3 μm) to reduce capacitance, then the response bandwidth and rise time are limited due to high capacitance per unit area
Solution Approach 1:
The patent optimizes the I-layer thickness parameter to achieve an optimal balance between capacitance and absorption efficiency. By carefully controlling the thickness and doping profile of the InGaAs I-layer, the device achieves both low capacitance for fast response and sufficient absorption for high sensitivity, resolving the trade-off between speed and measurement precision.
4Measurement precision
If multiple photodiode detectors are arranged in a linear array with resistive combining, then the device can function like a single-axis LEPSD, but the number of distinguishable spatial locations is limited to the number of photodiodes requiring a very large number of photodiodes for high resolution
Solution Approach 1:
The patent replaces the discrete photodiode array with continuous LEPSD elements that use lateral current flow to provide continuous position information. This substitution transforms the system from one requiring discrete sampling (multiple photodiodes) to one providing continuous measurement (lateral effect detector), achieving high spatial resolution without proportionally increasing device complexity.
5Object-affected harmful factors
If a focusing lens is used to focus light on the LEPSD array, then the spot size is reduced minimizing speckle and occlusion effects, but the optical system becomes more complex
Solution Approach 1:
The patent changes the optical focusing parameter to create a small focused spot at the LEPSD detector plane. By adjusting the focal length and aperture settings, the system produces a tightly focused spot that minimizes the impact of speckle and occlusion effects while maintaining a relatively simple optical configuration.
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 solution enhances the accuracy of angle-of-arrival detection, particularly for eye-safe wavelengths, and enables a compact dual-mode sensor with a large instantaneous field of view and fast response, reducing noise and improving angle-estimation resolution.
Implementation Method 1
each of the LEPSD elements includes an absorber region that absorbs light of a first wavelength range that is focused on the LEPSD elements
Implementation Method 2
The aperture projects an illuminated spot onto a 4-quadrant detector... a focusing lens and an array of lateral-effect position sensing detector (LEPSD) elements
Implementation Method 3
Each of the LEPSD elements further includes at least one lateral current conducting layer that has a relatively low sheet resistance
Data Source
AI summary
Optical angle of arrival sensors and methods for determining an angle of arrival of incident light are provided, wherein one sensor includes a focusing lens and an array of lateral-effect position sensing detector (LEPSD) elements. The focusing lens is configured to focus light on the array, wherein each of the LEPSD elements includes an absorber region that absorbs light of a first wavelength range that is focused on the LEPSD elements. Each of the LEPSD elements further includes at least one lateral current conducting layer that has a relatively low sheet resistance.