Time-of-Flight Sensor Crosstalk Calibration Using Earliest Peak
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Solution Overview
Problem
Time of flight sensors suffer from optical crosstalk due to light reflections off the transparent cover or contaminants, leading to inaccurate distance measurements, especially when targets are close to the sensor, and existing calibration methods become inaccurate with changes in cover contamination.
Innovation Solution
A method to measure optical crosstalk by emitting a series of pulses and analyzing the distribution of photon detection times, allowing for separate peak identification and calibration during normal use, even when targets are present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration measurements are performed with no target present or with cover blocked, then optical crosstalk can be measured, but the calibration becomes inaccurate when cover contamination changes
Solution Approach 1:
The patent performs optical crosstalk calibration measurements during normal sensor operation with targets present, rather than requiring separate preliminary calibration steps. The system continuously monitors the histogram distribution and identifies the cover reflection peak in real-time, automatically compensating for contamination changes without user intervention.
Solution Approach 2:
The sensor system performs its own calibration by automatically detecting and measuring optical crosstalk from the cover reflection during normal operation. The processing circuitry identifies the earliest peak in the histogram distribution and uses this information to compensate for crosstalk, making the system self-calibrating without external equipment or user actions.
2Measurement precision
If light blocking material is used to measure optical crosstalk, then crosstalk level can be determined, but additional measurement steps and materials are required
Solution Approach 1:
The patent extracts and isolates the cover reflection signal from the overall histogram distribution by identifying the earliest peak. This separates the optical crosstalk measurement from target detection, allowing the system to measure crosstalk using the same sensor hardware without additional blocking materials or separate measurement procedures.
Solution Approach 2:
The sensor system performs multiple functions using the same hardware: it simultaneously detects targets and measures optical crosstalk by analyzing different regions of the histogram distribution. The earliest peak provides crosstalk information while later peaks provide target distance information, eliminating the need for separate calibration equipment.
3Measurement precision
If targets are close to the sensor, then useful distance measurements can be obtained, but optical crosstalk from cover reflections overlaps with target reflections
Solution Approach 1:
The patent segments the histogram distribution into distinct components: the earliest peak represents cover reflection (optical crosstalk) while subsequent peaks represent target reflections. By separating these components in the time domain, the system can independently analyze and compensate for crosstalk without affecting close target measurements.
Solution Approach 2:
The system uses the measured optical crosstalk from the earliest peak as feedback to compensate for interference in target distance measurements. The processing circuitry adjusts the interpretation of later peaks based on the crosstalk level determined from the first peak, enabling accurate measurements even when targets are close to the sensor.
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 accurate calibration and compensation for optical crosstalk without additional user-specific measurements, maintaining sensor accuracy even with changing cover contamination levels.
Implementation Method 1
Time of flight sensors are sensors which determine the distance to a target by emitting light and detecting reflections of the light from the target
Implementation Method 2
a major source of optical crosstalk is light from the emitter which is reflected off the cover, or off contamination on the cover
Implementation Method 3
using the one or more photodetectors to obtain a distribution of times at which at least one photodetector of the one or more photodetectors detected photons
Data Source
AI summary
Time of Flight Sensor A method of measuring optical crosstalk in a time of flight sensor, which comprises a substantially transparent cover covering a light emitter and one or more photodetectors. The method comprises emitting a series of pulses of light from the light emitter; and using the one or more photodetectors to obtain a distribution of times at which at least one photodetector of the one or more photodetectors detected photons after each emission of the series of pulses of light. The method further comprises recording one or more parameters of the earliest peak if the distribution comprises two or more separate peaks.