Optical Sensor Cavity Segmentation for Time-of-Flight Crosstalk Reduction
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Solution Overview
Problem
Current optical sensor arrangements for time-of-flight measurement face challenges in achieving precise distance measurements due to limitations in determining start and stop times, often resulting in reduced accuracy and increased optical crosstalk between the emitter and photodetectors.
Innovation Solution
The proposed optical sensor arrangement features a housing with optically separated cavities, utilizing a translucent cover plate with opaque coatings and strategically positioned apertures to isolate the emitter and photodetectors, allowing for precise determination of start and stop times by separating the reference and measurement paths, thereby reducing unwanted optical crosstalk and improving measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the emitter and photodetectors are placed in the same cavity, then the device structure is simpler, but optical crosstalk increases and measurement precision deteriorates
Solution Approach 1:
The housing is divided into multiple cavities (first cavity for emitter, second cavity for photodetectors) separated by an optical barrier. This segmentation physically isolates the light source from the detectors, preventing optical crosstalk while maintaining a relatively simple integrated housing structure.
Solution Approach 2:
An optical barrier is introduced as an intermediary element between the emitter and photodetectors. This barrier allows the measurement of light from external objects while blocking direct light from the emitter, thus enabling precise TOF measurement without crosstalk interference.
2Measurement precision
If optical crosstalk is reduced by separating emitter and photodetectors, then measurement precision improves, but device complexity increases
Solution Approach 1:
Multiple functional components (emitter, measurement photodetector, reference photodetector, optical barrier, and cover plate with apertures) are merged into a single integrated housing structure. This combining approach achieves precise TOF measurement functionality while avoiding the complexity of multiple separate modules.
3Use of energy by moving object
If apertures are enlarged to improve light transmission, then signal strength increases, but optical crosstalk between cavities increases
Solution Approach 1:
The cover plate features locally optimized aperture arrangements with specific sizes and positions. The apertures are sized and positioned to maximize light transmission for measurement and reference paths while maintaining optical isolation between cavities, achieving local optimization of light transmission without compromising overall crosstalk rejection.
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 configuration enhances the precision of time-of-flight measurements by accurately controlling beam intensity, position, and direction, leading to improved accuracy in determining start and stop times and reducing undesired optical interactions, thus enhancing the overall measurement precision.
Implementation Method 1
The cavities are optically separated by an optical barrier
Implementation Method 2
a translucent cover plate with an opaque coating having two outer apertures for light emission by the emitter and respective detection of light reflected from an object
Implementation Method 3
The emitter is configured and arranged, in particular, the emitter and the first aperture are mutually arranged, to emit light through the first aperture
Implementation Method 4
The measurement photodetector is configured and arranged, in particular, the measurement photodetector and the fourth aperture are mutually arranged, to detect light entering the second cavity through the fourth aperture
Implementation Method 5
The second and the third aperture establish a reference path for light from the emitter to the reference photodetector
Data Source
AI summary
An optical sensor arrangement for time-of-flight comprises a first and a second cavity separated by an optical barrier and covered by a cover arrangement. An optical emitter is arranged in the first cavity, a measurement and a reference photodetector are arranged in the second cavity. The cover arrangement comprises a plate and layers of material arranged on an inner main surface thereof. The layers comprise an opaque coating with a first and second aperture above the first cavity, and with a third and fourth aperture above the second cavity. The measurement photodetector is configured to detect light entering the second cavity through the fourth aperture. The second and the third aperture establish a reference path for light from the emitter to the reference photodetector.