Phase-Sensitive Image Sensor Pixels for Time-of-Flight Depth Mapping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Film-based image sensors face limitations in efficiently converting incident photons into charge carriers and accurately estimating the time of flight of radiation, which affects their performance in constructing depth maps and distinguishing between ambient and modulated radiation.
Innovation Solution
The implementation of a photosensitive medium with a bias electrode and pixel circuits that apply varying potentials to control charge carrier collection, along with readout circuitry to output signals responsive to charge carriers, and control circuitry to synchronize with modulated radiation, facilitating the estimation of time of flight and reducing ambient light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pixel electrode is used to collect charge carriers, then the device structure is simple, but the ability to estimate time of flight and distinguish radiation phases is limited
Solution Approach 1:
The pixel electrode is divided into two spatially separated electrodes (first pixel electrode and second pixel electrode) positioned at different locations across the pixel. This segmentation enables differential charge collection that encodes time of flight information, allowing the system to distinguish between early-arriving and late-arriving charge carriers without requiring complex temporal gating circuitry.
Solution Approach 2:
The invention transitions from temporal discrimination (using transfer gates to gate charge carriers in time) to spatial discrimination (using two pixel electrodes at different positions to collect charge carriers based on their drift distance). This dimensional change simplifies the circuit structure while maintaining time of flight measurement capability.
2Measurement precision
If transfer gates are used to control charge carrier collection, then time of flight information can be captured, but ambient light interference increases
Solution Approach 1:
The invention employs periodic modulation of the bias electrode potential in synchronization with modulated illumination. This periodic action creates time-gated collection windows that preferentially collect charge carriers generated during specific phases of the modulation cycle, thereby rejecting ambient light that is not synchronized with the modulation and improving signal-to-noise ratio.
3Productivity
If the photosensitive medium has high charge mobility, then charge carrier collection efficiency is improved, but charge carrier diffusion increases reducing measurement accuracy
Solution Approach 1:
The invention dynamically adjusts the bias electrode potential to create time-varying electric fields that control charge carrier drift velocity. By modulating the bias potential in synchronization with illumination, the system optimizes charge carrier collection during signal phases while minimizing diffusion effects during ambient light phases, thereby maintaining both collection efficiency and measurement precision.
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
Enhances image sensor performance by accurately estimating time of flight and constructing depth maps, while effectively suppressing ambient light interference, thereby improving imaging accuracy and reducing noise.
Implementation Method 1
a photosensitive medium configured to convert incident photons into charge carriers
Data Source
AI summary
Imaging apparatus (100, 200) includes a photosensitive medium (302) configured to convert incident photons into charge carriers. A bias electrode (304) overlies the photosensitive medium and applies a bias potential to the photosensitive medium. One or more pixel circuits (306) are formed on a semiconductor substrate. Each pixel circuit defines a respective pixel (300) and includes first and second pixel electrodes (316, 318) coupled to collect the charge carriers from the photosensitive medium at respective first and second locations, and first and second transfer gates (326, 328) in respective proximity to the first and second pixel electrodes. Circuitry (700) is coupled to apply different, respective first and second potentials to the first and second transfer gates and to vary the first and second potentials so as to control relative proportions of the charge carriers that are collected by the first and second electrodes.