Dual-Detector Laser Retroreflection Discrimination

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Solution Overview

Problem

Existing methods for detecting magnifying optical systems, such as telescopes and eyes, face ambiguity due to the presence of other retroreflective objects like vehicle reflectors, as they all reflect light and create similar luminous spots, making it difficult to distinguish between them.

Innovation Solution

A dual-detector system is employed, where a first detector is closely adjacent to a laser emitter and takes images of the scene, while a second detector, separated transversely, captures a second image. By comparing these images, the system determines if the object is a magnifying optical system based on the narrowness of its retroreflection cone, distinguishing it from wider-angle reflectors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single detector is used to detect retroreflected light from the scene, then the detection system is simple, but it cannot distinguish between magnifying optical systems and standard reflectors

Engineering Contradiction:
Improvedetection system structureVSAvoidobject identification accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The detection system is segmented into two separate detectors: a first detector positioned adjacent to the laser emitter that receives all retroreflected light, and a second detector positioned at a transverse distance that only receives light from wide-angle reflectors. This segmentation allows the system to differentiate between magnifying optical systems (narrow retroreflection cone) and standard reflectors (wide retroreflection cone) by comparing the presence or absence of signals in each detector.

Inventive Principle:
Principle #1Segmentation

2Reliability

If the second detector is positioned close to the laser emitter, then it can receive retroreflected light from all objects, but it cannot discriminate magnifying optical systems from standard reflectors

Engineering Contradiction:
Improvelight reception capabilityVSAvoidobject type discrimination
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The solution moves the second detector from the longitudinal position (close to the emitter) to a transverse dimension, positioning it at a specific lateral distance from the laser emitter. This dimensional change exploits the angular characteristics of retroreflection: the narrow retroreflection cone of magnifying optical systems does not reach the transverse detector, while the wide retroreflection cone of standard reflectors does, enabling automatic discrimination based on geometric optics.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 effectively discriminates magnifying optical systems from standard reflectors by ensuring only the first detector receives the narrow retroreflected light, allowing accurate detection even at various distances, with a transverse gap of at least 200 mm to 400 mm between detectors.

Implementation Method 1

magnifying optical systems (such as telescopes and eyes) have the property of retroreflecting light

Methodology Applied
Scientific EffectRetroreflection: Retroreflector

Implementation Method 2

said scene is illuminated by at least one pulse laser emitted by a laser emitter

Methodology Applied
Scientific EffectLaser: Laser

Data Source

PatentEP2137549A2Method and single laser device for detecting magnifying optical systems
Publication Date: 2009.12.30 CIE IND DES LASERS CILAS ALCATEL

AI summary

The invention comprises illuminating a scene where said magnifying optical system (OP) may occur with at least one pulse generated by first laser transmitter (E). The laser transmitter (E) and a first detector of the scene thus illuminated (D1) are adjacent, while a second detector (D2) is remote from said transmitter (E) transversally to the direction (d) of said scene.