Optical Sensor Crosstalk Compensation via Segmented Light Reception
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Solution Overview
Problem
Time-of-flight (TOF) sensors face challenges in accurately measuring distance due to crosstalk from cover panels, especially when detection targets are present, leading to incorrect distance calculations and poor resolution, as existing methods struggle to update crosstalk values in real-time.
Innovation Solution
An optical sensor configuration that includes a reference pulse generation circuit, a light emitting element, photo-count type light receiving elements, a time difference extraction circuit, and a determination circuit to calculate crosstalk values based on time differences and reference cycles, allowing for accurate distance measurement even with cover panels present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cover panel is added to protect the optical sensor, then the sensor is protected from environmental damage, but crosstalk from cover panel reflection light causes incorrect distance measurements
Solution Approach 1:
The patent divides the light receiving elements into two separate groups: first light receiving elements positioned to receive target reflection light, and second light receiving elements positioned to receive cover panel reflection light. This spatial segmentation allows the system to separately measure and compensate for crosstalk signals, resolving the contradiction between sensor protection and measurement accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the crosstalk value calculated from the second light receiving elements is continuously fed back to correct the distance measurements from the first light receiving elements. This feedback loop enables real-time compensation for cover panel crosstalk, maintaining measurement accuracy while the cover panel remains in place.
2Device complexity
If traditional TOF measurement is used without crosstalk correction, then the system is simple, but distance measurement is incorrect when detection targets are present
Solution Approach 1:
The patent segments the light receiving function into two distinct pathways: one for measuring target reflection light and another for measuring cover panel reflection light. This segmentation enables the system to distinguish between valid measurement signals and crosstalk signals, achieving accurate distance measurement without overly complicating the overall system architecture.
Solution Approach 2:
The patent introduces an intermediary calculation process that uses the second light receiving elements as mediators to measure and quantify the crosstalk component. This intermediary measurement allows the system to mathematically subtract the crosstalk influence from the total signal, achieving accurate measurements while maintaining relatively simple hardware.
3Loss of information
If the optical sensor measures distance to detection targets, then useful distance information is obtained, but crosstalk from cover panel reflection light cannot be distinguished from target reflection light
Solution Approach 1:
The patent applies spatial segmentation by arranging first light receiving elements and second light receiving elements at different positions relative to the light emitting element. The first elements are positioned to primarily receive target reflection light, while the second elements are positioned to primarily receive cover panel reflection light. This segmentation enables the system to separately measure both components without requiring complex additional hardware.
Solution Approach 2:
The patent applies local quality by giving different functional characteristics to different regions of the light receiving array. Specific light receiving elements are optimized for detecting target reflection light while others are optimized for detecting cover panel reflection light, allowing each element to perform its specialized function effectively without requiring the entire system to be overly complex.
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
Enables correct distance measurement and updates crosstalk values in real-time, improving resolution and accuracy by distinguishing between target and cover panel reflection light components.
Implementation Method 1
a light emitting element 3 that emits light toward a target 19 based on the reference pulse signal TX
Implementation Method 2
a photo-count type first light receiving element 5 that is provided so as to receive target reflection light L1 reflected by the target 19 and cover panel reflection light L2 reflected by the cover panel 4
Implementation Method 3
a time difference extraction circuit 7 that extracts a time difference based on a distance on a spatial light path to the target 19
Data Source
AI summary
An optical sensor includes a time difference extraction circuit for extracting a time difference based on the distance to a target on the basis of a first received light pulse signal from a first light receiving unit, a reference cycle, and a second received light pulse signal from a second light receiving unit, and a determination circuit for determining whether a crosstalk value can be calculated on the basis of the time difference extracted by the time difference extraction circuit and the reference cycle.