Centroid-Locating Sensor Circuits for Low-Light Angle Detection

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Solution Overview

Problem

Conventional optical sensors, such as 4-quadrant detectors, face challenges in achieving high-resolution and high-accuracy angle-of-arrival sensing for low-intensity light while maintaining a large angular field of view and fast response time, due to noise issues and the need for serial multiplexed readout of signals.

Innovation Solution

A centroid-locating sensor with a plurality of photo-diode detector elements, digitization comparators, and spatial filtering logic circuits that reject noise and generate binary outputs, allowing for real-time centroid location determination with reduced noise and increased sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a large detector active area is used to achieve a large angular field of view, then the field of view is improved, but the response speed is limited

Engineering Contradiction:

Improvedetector active areaVSAvoidresponse speed

Core Design Contradiction:

Area of stationary objectVSSpeed

Solution Approach 1:

The detector is divided into multiple photodiode elements arranged in an array, where each element can be read out independently or in parallel groups. This segmentation allows the large detector area to maintain fast response speed by enabling parallel readout of multiple elements simultaneously, rather than reading out the entire large area sequentially.

Inventive Principle:

Principle #1Segmentation

2Reliability

If thresholding circuit is used to block low-magnitude noise inputs, then false pulse interpretation is prevented, but noise in photocurrent pulse magnitude cannot be reduced

Engineering Contradiction:

Improvepulse detection accuracyVSAvoidnoise in photocurrent

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system changes the parameter being thresholded from the raw photocurrent signal to the integrated charge signal. By integrating the photocurrent first and then applying the threshold to the integrated value, the system achieves better noise rejection because the integration process averages out high-frequency noise while preserving the pulse signal, allowing more effective threshold-based noise filtering.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If serial multiplexed readout is used for PD array elements, then the number of output channels is reduced, but the output rate becomes slow

Engineering Contradiction:

Improveoutput channel countVSAvoidoutput rate

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The system uses periodic scanning of the PD array elements in a systematic sequence, repeatedly cycling through all elements. This periodic readout approach allows the system to maintain a high overall output rate by continuously cycling through elements, while still using a single or reduced number of output channels. The periodic nature ensures that each element is read out at regular intervals, maintaining productivity despite the multiplexed architecture.

Inventive Principle:

Principle #19Periodic action

4Measurement precision

If the number of illuminated PD elements is increased to reduce location-estimation error, then centroid accuracy is improved, but higher light intensity is required

Engineering Contradiction:

Improvecentroid location accuracyVSAvoidlight intensity

Core Design Contradiction:

Measurement precisionVSIllumination intensity

Solution Approach 1:

The system replaces the requirement for high light intensity with an electronic signal processing approach. Instead of relying on high photon flux to illuminate more PD elements, the system uses low-noise preamplifiers and integration circuits to amplify and accumulate the weak signals from illuminated elements. This substitution of electronic amplification for optical intensity allows accurate centroid determination with lower light levels, as the electronic gain compensates for the lower signal levels from each element.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 sensor achieves high-resolution and high-accuracy angle-of-arrival estimation for lower light intensities with a large instantaneous field of view and fast response, reducing noise and enabling real-time processing.

Implementation Method 1

a plurality of photo-diode (PD) detector elements... configured to receive a spot of light and generate corresponding output signals

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS9274203B1Centroid locating sensors having plural spatial filtering logic circuits connected to plural digitization comparators and methods for locating an illuminated spot on a detector

Publication Date: 2016.03.01 THE BOEING CO

AI summary

Centroid locating sensors and methods for locating an illuminated spot on a detector are provided. One sensor includes a plurality of photo-diode (PD) detector elements connected to the PD detector elements. The sensor also includes a plurality of digitization comparators connected to the plurality of PD detector elements and configured to receive output signals from the plurality of PD detector elements and generate a binary 1 output when the output from the PD detector element exceeds a threshold set point and generate a binary 0 output when the output is below the threshold set point. The sensor further includes a plurality of spatial filtering logic circuits connected to the digitization comparators and are configured to receive outputs from a plurality of the PD detector elements and to reject noise for one of the PD detector elements.