Multi-Tap iToF Sensor Pixel for Depth Resolution
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Solution Overview
Problem
Current indirect Time-of-Flight (iToF) systems face challenges in achieving high depth resolution and low depth noise, particularly at longer distances, due to limitations in phase shift measurement and tap mismatch.
Innovation Solution
The implementation of an indirect Time-of-Flight sensor with a pixel array comprising multiple taps (three or more) and a read-out circuit to manage charges collected at these taps, allowing for greater phase shift measurement and reduced depth noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 2-tap sensor system is used, then the device complexity is low, but the depth resolution and measurement precision deteriorate at longer distances
Solution Approach 1:
The sensor is divided into multiple taps (three or more) instead of using a single 2-tap structure. Each tap corresponds to a different phase sampling point, allowing the system to measure greater phase shifts and achieve higher depth resolution without excessive complexity increase
Solution Approach 2:
The patent transitions from temporal sampling (2-tap sequential measurement) to spatial sampling (multiple taps simultaneously), adding a spatial dimension to the measurement process. This allows parallel phase sampling at multiple points, improving depth resolution while maintaining manageable device complexity
2Reliability
If the modulation frequency is reduced for longer distance measurement, then the measurement range increases, but the depth resolution and phase shift precision deteriorate
Solution Approach 1:
The patent changes the sampling parameter from 2 taps to 3 or more taps, which effectively increases the phase measurement precision. With N taps, the system can measure phase shifts up to (N-1)π, providing finer phase resolution and reducing depth noise even when operating at lower modulation frequencies for long-distance measurements
3Measurement precision
If the number of taps is increased to three or more, then the phase shift measurement precision improves, but the device complexity and pixel structure complexity increase
Solution Approach 1:
The patent designs a universal pixel structure where multiple taps share common components such as the photodiode, read-out circuit, and control logic. This multi-functional design allows the same hardware infrastructure to support N-tap operation, improving phase measurement precision while limiting complexity growth through component sharing
Solution Approach 2:
The patent merges multiple phase sampling functions into a single integrated pixel structure. Instead of separate circuits for each tap, the design combines multiple taps around shared resources (photodiode, capacitors, switches), reducing overall complexity while achieving N-tap measurement capability
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 approach enhances the depth imaging capabilities of iToF cameras by increasing the effective modulation frequency, thereby improving depth resolution and reducing noise in distance measurements.
Implementation Method 1
A Time-of-Flight (ToF) camera is a range imaging camera system that determines the distance of objects by measuring the time of flight of a light signal between the camera and the object for each point of the image
Implementation Method 2
A pixel array in the ToF camera collects the light reflected from the scene and measures phase-shift which provides information on the travelling time of the light
Implementation Method 3
The pixels of a ToF camera typically comprise one or more photosensitive elements (e.g. photodiodes). A photosensitive element converts the incoming light into a current
Data Source
AI summary
An indirect Time-of-Flight sensor having a pixel array which includes a plurality of pixels, each pixel having three or more taps and a read-out circuit configured to read-out charges collected at the respective three or more taps.