Time-of-Flight Sensor Demodulation Using Segmented Photoelectron Transfer

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Solution Overview

Problem

Depth sensors face inefficiencies in demodulation due to photoelectron loss from thermal diffusion, which affects the accuracy of distance measurement using the time-of-flight principle.

Innovation Solution

The sensor employs a method involving packets with distinct intervals for signal demodulation, using oscillation signals with phase differences to form depletion layers under photogates, and applying a DC voltage during the second interval to transfer residual photocharges, enhancing photoelectron transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If photoelectrons are collected during the entire packet period, then the number of collected photoelectrons increases, but thermal diffusion causes photoelectron loss and reduces demodulation efficiency

Engineering Contradiction:

Improvenumber of collected photoelectronsVSAvoiddemodulation efficiency

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The packet period is divided into two distinct intervals: a first interval for collecting photoelectrons generated by the modulated photon signal, and a second interval for transferring residual photocharges to floating diffusion nodes. This segmentation allows the system to collect photoelectrons efficiently while managing thermal diffusion losses through controlled transfer operations in separate time windows.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sensor operates by periodically repeating the two-interval packet structure, where oscillation signals are applied during the first interval to collect photoelectrons, and DC voltages are applied during the second interval to transfer residual photocharges. This periodic action maintains demodulation efficiency while continuously collecting photoelectron signals.

Inventive Principle:

Principle #19Periodic action

2Productivity

If oscillation signals are applied to photogates, then photoelectrons are collected efficiently, but residual photocharges remain and cause interference

Engineering Contradiction:

Improvephotoelectron collection efficiencyVSAvoidinterference from residual photocharges

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

Residual photocharges are extracted from the photogate region and transferred to floating diffusion nodes during the second interval by applying DC voltages. This extraction removes the harmful residual photocharges that would otherwise interfere with subsequent measurements, while preserving the beneficial photoelectron collection from the first interval.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The transfer of residual photocharges is performed as a preliminary action before the next packet begins, ensuring that the photogate region is cleared of interfering charges. This preliminary cleanup action prepares the system for the next cycle of efficient photoelectron collection without interference.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If the light source is continuously enabled, then photoelectron generation is maximized, but thermal diffusion increases and reduces measurement accuracy

Engineering Contradiction:

Improvephotoelectron generation rateVSAvoiddistance measurement accuracy

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The light source is enabled periodically during the first interval of each packet to generate photoelectrons, then disabled during the second interval while DC voltages transfer residual photocharges. This periodic operation maximizes photoelectron generation when needed while reducing thermal diffusion effects during the transfer phase, thereby maintaining measurement accuracy.

Inventive Principle:

Principle #19Periodic action

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 increases demodulation efficiency and accuracy of distance measurement by separately defining intervals for collection and transfer, thereby improving the overall performance of the sensor.

Implementation Method 1

providing a plurality of packets, each packet including a first interval and a second interval, to demodulate a modulated photon signal output from a light source

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

When each of the plurality of oscillation signals oscillates between a first level and a second level, a first depletion layer may be formed in a semiconductor substrate under each of the photogates when the plurality of oscillation signals are provided respectively to the plurality of photogates at the first level

Methodology Applied

Scientific EffectDepletion layer formation:

Implementation Method 3

disabling the light source and providing a direct current (DC) voltage to the plurality of photogates during the second interval of each of the plurality of packets

Methodology Applied

Scientific EffectElectric field: Electric Field

Data Source

PatentUS9046358B2Sensor, method of operating the same, and system including the same

Publication Date: 2015.06.02 SAMSUNG ELECTRONICS CO LTD

AI summary

A method includes providing packets to demodulate a modulated photon signal output from a light source, wherein each packet includes a first interval and a second interval, and providing oscillation signals respectively having different phases from one another to photogates during the first interval of each of the packets. The light source is disabled and a direct current (DC) voltage is provided to the photogates during the second interval of each of the packets.