Distance Measuring Apparatus Noise Suppression

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Solution Overview

Problem

Distance measuring apparatuses face challenges in increasing measurement range while maintaining a high signal-to-noise ratio due to noise light incidence on the condenser lens, especially when using wide-angle lenses, which leads to distorted irradiated areas and reduced accuracy in selecting photodetectors.

Innovation Solution

A distance measuring apparatus that includes a projector, a photodetector array, a condenser lens, and a selector. The selector chooses the appropriate photodetectors based on the distortion of the irradiated area, determined by the angle of incidence of the reflected laser beam, to improve accuracy and suppress noise light, even when using wide-angle lenses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a wide-angle lens is used as a condenser lens to increase measurement range, then the light projection range is increased, but noise light incident on the condenser lens increases and signal-to-noise ratio decreases

Engineering Contradiction:

Improvemeasurement rangeVSAvoidnoise light incidence

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent divides the photodetector array into multiple regions corresponding to different projection angles. The selection unit selectively reads out signals from specific photodetector regions that correspond to the current projection angle, thereby segmenting the detection process to exclude noise light from regions not currently being measured.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different selection strategies for different regions of the photodetector array based on the projection angle. By adjusting which photodetector regions are actively read out based on the current measurement direction, the system optimizes signal quality locally for each projection angle while maintaining wide-angle coverage capability.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If a photodetector array is used to selectively use outputs from specific photodetectors, then noise light is suppressed, but distortion of the irradiated area on the photodetector array occurs when projection angle is large, reducing selection accuracy

Engineering Contradiction:

Improvenoise light suppressionVSAvoidphotodetector selection accuracy

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent pre-calculates and stores the correspondence relationships between projection angles and photodetector array regions in a table during the design phase. This preliminary action accounts for optical distortions that occur at large projection angles, allowing the selection unit to accurately identify which photodetectors to read out even when distortion occurs during actual measurement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses pre-stored correspondence data that reflects the actual optical path and distortion characteristics of the specific hardware configuration. This feedback mechanism ensures that the selection unit can compensate for distortion effects by referencing the pre-characterized relationship between projection angles and photodetector positions.

Inventive Principle:

Principle #23Feedback

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 solution enhances the accuracy of selecting photodetectors and maintains a high signal-to-noise ratio by accounting for distortion and noise suppression, allowing for extended measurement ranges without deteriorating the signal quality.

Implementation Method 1

a condenser lens configured to concentrate, on the photodetector array, the laser beam reflected by the object

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

a photodetector array in which a plurality of photodetectors are arranged; a detector configured to detect an output of at least one of the photodetectors

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS10444358B2Distance measuring apparatus, distance measuring method, and table creating method

Publication Date: 2019.10.15 FUJITSU LTD

AI summary

A distance measuring apparatus includes a projector configured to project laser beam at a projection angle to an object; a photodetector array in which a plurality of photodetectors are arranged; a condenser lens configured to concentrate, on the photodetector array, the laser beam reflected by the object positioned on a direction of the projection angle; a detector configured to detect an output of at least one of the photodetectors of the photodetector array; and a selector configured to select the photodetector from which the detector receives the output, depending on a distortion of an area on the photodetector array irradiated with the reflected laser beam when the projection angle is large, the area being determined by an angle of incidence of the reflected laser beam to the condenser lens, the angle of incidence being associated with the projection angle.