Optical Sensor Housing Panel Reflection Correction

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Solution Overview

Problem

Existing optical sensors face challenges in maintaining measurement accuracy at both short and long distances when a housing panel is present between the sensor and the detection target, due to errors caused by housing panel reflections, particularly on the long distance side.

Innovation Solution

The optical sensor employs a dual light-receiving configuration with a first light-receiving portion for reflected light from the target and a second for internal reflections, using a time difference extracting circuit and a period changing circuit to adjust the light-emitting period and reference clock based on the digital value output, ensuring accurate distance measurement by distinguishing between short and long distances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the light-emitting width is increased to cope with long distance measurement, then the measurement range is extended, but the signal deviation increases leading to larger measurement errors

Engineering Contradiction:

Improvemeasurement rangeVSAvoidmeasurement error

Core Design Contradiction:

Length of moving objectVSMeasurement precision

Solution Approach 1:

The patent segments the light-receiving function into two separate portions: a first light-receiving portion for detecting reflected light from the target object, and a second light-receiving portion for detecting reflected light from the housing panel. This segmentation allows independent optimization of each portion's characteristics and enables separate processing of the corresponding signals, thereby reducing measurement errors while maintaining extended measurement range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a housing panel reflection signal as an intermediary element to correct measurement errors. By detecting the reflection from the housing panel using the second light-receiving portion, the system can calculate a correction value that compensates for the error introduced by the housing panel's reflective properties, thereby improving measurement precision without sacrificing range.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the light-emitting width is increased to secure overlapping signal portions for correction, then the correction capability is improved, but the measurement time increases and accuracy decreases

Engineering Contradiction:

Improvecorrection capabilityVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs preliminary detection of the housing panel reflection signal during the same measurement period using the second light-receiving portion. This preliminary action allows the system to calculate correction values in advance or simultaneously with the main measurement, eliminating the need for separate correction measurement phases and thereby reducing total measurement time while maintaining correction capability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent continues the light-emitting operation throughout the measurement period, with both light-receiving portions actively detecting signals simultaneously. This continuous operation ensures that correction information is gathered without interrupting the main measurement process, thereby maintaining measurement accuracy while reducing the overall measurement time compared to intermittent or sequential measurement approaches.

Inventive Principle:

Principle #20Continuity of useful action

3Device complexity

If a housing panel is present between the optical sensor and detection target, then the sensor structure is completed, but reflection errors are introduced particularly on the long distance side

Engineering Contradiction:

Improvesensor structureVSAvoiddistance measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful housing panel reflection into a useful correction signal. By using the second light-receiving portion to detect the housing panel reflection, the system extracts correction information from what would otherwise be an error source. This corrected information is then used to adjust the distance measurement, thereby transforming the harmful reflection into a beneficial correction mechanism that improves measurement accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 optical sensor to maintain high measurement accuracy at both short and long distances by effectively correcting for housing panel reflections, reducing errors and optimizing measurement time.

Implementation Method 1

avalanche photodiodes that utilize the avalanche amplification (avalanche) effect of photodiodes have been used

Methodology Applied

Scientific EffectAvalanche effect: Avalanche Breakdown

Implementation Method 2

reflected light from a body

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 3

time-of-flight measurement (TOF)

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS11287518B2Optical sensor and electronic device

Publication Date: 2022.03.29 SHARP KK

AI summary

An optical sensor of the present invention changes a light-emitting period of a light-emitting element and a period of a reference clock that is used by a time difference extracting circuit, depending on whether or not a digital value that is output from a first digital calculating portion exceeds a reference value in a determination period. With this, there is achieved an optical sensor capable of maintaining both of measurement accuracy at short distance and measurement accuracy at long distance when a housing panel is present between the optical sensor and a detection target.