Multi-Photowell Depth Sensor for Low-Dark-Current Photon Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional 3D imagers and depth sensors using solid-state light sensors with electron avalanche gain suffer from high dark current, low quantum efficiency, low spatial resolution, and impractically long read-out latency, limiting their accuracy and applicability.
Innovation Solution
The development of low-latency, multi-photowell light sensors with pinned photodiodes and JFET-based devices, which reduce readout latency to sub-nanosecond levels and enhance sensitivity and resolution by allowing multiple photocarriers to be stored and detected simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche-gain photodetectors (SPADs, SiPMs) are used, then sensitivity to single photons is improved, but dark current increases and quantum efficiency decreases
Solution Approach 1:
The photodetector is divided into multiple independent photowells (e.g., first photowell for storing first photocarriers, second photowell for storing second photocarriers) instead of using a single avalanche-gain photodetector. This segmentation allows each photowell to operate independently without avalanche gain, reducing dark current while maintaining sensitivity through multi-carrier detection capability.
2Ease of manufacture
If pinned photodiode read-out is used, then manufacturing yield and quantum efficiency are improved, but read-out latency increases to hundreds of nanoseconds
Solution Approach 1:
Photocarriers are pre-stored in dedicated photowells during the integration period, and multiple photocarriers accumulate simultaneously in each photowell. This preliminary accumulation of multiple carriers allows the read-out process to complete much faster (sub-nanosecond to nanosecond range) because the signal is already prepared and amplified through multi-carrier storage rather than requiring slow sequential read-out of single electrons.
3Power
If single-electron well capacity is used, then avalanche gain is achieved, but spatial resolution and manufacturing yield decrease
Solution Approach 1:
The invention transitions from single-electron detection in the vertical dimension to multi-carrier storage across multiple photowells in the horizontal dimension. By distributing photocarrier storage across multiple photowells (first photowell, second photowell, etc.), the system achieves both high spatial resolution through precise carrier localization and high signal capacity through multi-carrier accumulation, eliminating the need for avalanche gain.
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 dramatically improves depth sensing capabilities by achieving higher sensitivity, finer resolution, and significantly reduced readout latency, overcoming the limitations of conventional avalanche-gain sensors.
Implementation Method 1
a light sensor in a pulse-based system intended measure a distance/depth with 5 mm accuracy will need to resolve the round-trip flight time of the light pulse
Implementation Method 2
JFET-based devices, which reduce readout latency to sub-nanosecond levels and enhance sensitivity and resolution
Data Source
AI summary
A sensing device includes a light source to emit light, a light sensor to detect reflection of the emitted light and distance determination circuitry responsive to reflected-light detection within the light sensor. The light sensor includes a photodetector having a photocharge storage capacity in excess of one electron and an output circuit that generates an output signal responsive to light detection within the photodetector with sub-hundred nanosecond latency. The distance determination circuitry measures an elapsed time based on transition of the output signal in response to photonic detection within the photodetector and determines, based on the elapsed time, a distance between the sensing device and a surface that yielded the reflection of the emitted light.