TOF Sensor Optical Cross-Talk Reduction via Light Barrier
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Solution Overview
Problem
Integrating time-of-flight (TOF) sensors into handheld devices like smartphones is challenging due to space constraints and the need for accurate distance measurements that are robust against thermal drifting effects, which can be exacerbated by optical cross-talk between active and reference pixels.
Innovation Solution
The implementation of an optoelectronic module with a light barrier and micro lenses to separate and reduce optical cross-talk between active detection pixels and reference pixels, using a combination of coatings and optical filters to direct light to reference pixels without affecting active pixels, and embedding sensor chips within a printed circuit board (PCB) to minimize size and prevent mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference pixels are provided to perform self-calibration of TOF distance measurement, then measurement precision is improved, but device complexity increases due to need for optical separation between reference pixels and active pixels
Solution Approach 1:
The patent combines reference pixels and active pixels onto the same sensor chip without requiring separate optical paths. The light barrier structure integrates both pixel types in a unified optical detection path, eliminating the need for complex optical separation mechanisms while maintaining self-calibration capability through the reference pixels.
Solution Approach 2:
The patent segments the sensor chip into distinct regions: active pixels for distance measurement, reference pixels for self-calibration, and light barrier structures for optical isolation. This segmentation allows each component to perform its specific function while maintaining overall system integration on a single chip.
2Measurement precision
If light barrier structures are added to reduce optical cross-talk, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs thin film light barrier structures that can be deposited or formed directly on the sensor chip surface. These thin film barriers provide effective optical isolation while being more tolerant to manufacturing variations compared to thick rigid light blocking structures, reducing alignment precision requirements.
3Volume of moving object
If TOF sensor size is reduced to meet space constraints, then device compactness is improved, but reliability decreases due to increased susceptibility to thermal drifting effects
Solution Approach 1:
The patent implements self-calibration functionality through reference pixels that automatically compensate for thermal drifting effects. The reference pixels measure the illumination source characteristics and enable real-time correction of thermal drift, allowing compact sensor design without sacrificing reliability against environmental variations.
4Measurement precision
If micro lenses are added to direct light to reference pixels, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent designs micro lenses that serve dual functions: directing illumination source light to reference pixels for self-calibration and guiding reflected scene light to active pixels for distance measurement. This multi-functionality reduces the need for separate optical components for each pixel type, minimizing overall device complexity.
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 enables accurate and robust distance measurements by reducing optical cross-talk and thermal drifting effects, allowing for smaller, more efficient TOF sensor modules that can be effectively integrated into handheld devices.
Implementation Method 1
a light barrier and micro lenses to separate and reduce optical cross-talk between active detection pixels and reference pixels
Implementation Method 2
micro lenses to separate and reduce optical cross-talk between active detection pixels and reference pixels
Implementation Method 3
distance is determined by tallying the time for emitted light to reflect back onto the sensor
Implementation Method 4
The reflected light is imaged onto a sensor, and the photo-generated electrons are demodulated in the sensor
Data Source
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AI summary
The present disclosure describes optical imaging and optical detection modules that include sensors such as time-of-flight (TOF) sensors. Various implementations are described that, in some instances, can help reduce the amount of optical cross-talk between active detection pixels and reference pixels and/or can facilitate the ability of the sensor to determine an accurate phase difference to be used, for example, in distance calculations.