Time-of-Flight Sensor Pixel Circuit for Compact 3D Imaging

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Solution Overview

Problem

Existing 3D imaging technologies using the triangulation technique require large devices and significant computer processing power, limiting their size and efficiency in capturing real-time three-dimensional images.

Innovation Solution

A time-of-flight sensor with an array of pixel circuits that accumulate and process image charges in response to projection light pulses, using a processing circuit to calculate distance information signals for 3D imaging, allowing for smaller device sizes and improved processing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If triangulation technique is used to create 3D images, then 3D imaging capability is achieved, but device size becomes large due to minimum separation distance between camera units

Engineering Contradiction:

Improve3D imaging capabilityVSAvoiddevice size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent replaces the mechanical/optical triangulation system with a time-of-flight measurement system. Instead of using multiple camera units separated by a minimum distance to achieve 3D imaging, the invention uses a single sensor that measures the time for light to travel to and from the object, thereby determining distance. This substitution of the measurement principle eliminates the need for large physical separation between camera units while maintaining 3D imaging capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If triangulation technique is used to create 3D images, then 3D imaging capability is achieved, but computer processing power requirement becomes significant

Engineering Contradiction:

Improve3D imaging capabilityVSAvoidcomputer processing power

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The patent replaces the computationally intensive triangulation algorithm with direct time-of-flight measurement. The distance to the object is obtained directly from the measured time delay between emitted and reflected light pulses, eliminating the need for complex image processing and mathematical computations required by triangulation methods. This reduces the computational burden and power requirements for real-time 3D imaging.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If first sum and second sum of image charges are calculated separately, then accuracy is maintained, but processing time increases

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent merges the calculation of the first sum and second sum of image charges into a single simultaneous operation. The processing circuit is designed to compute both sums in parallel during the same accumulation period, rather than sequentially. This combining of operations maintains the accuracy required for precise distance measurement while reducing the total processing time, as both calculations are performed concurrently rather than one after the other.

Inventive Principle:

Principle #5Merging (Combining)

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

Enables the capture of 3D images with reduced device size and enhanced processing efficiency, effectively addressing the limitations of prior art by simultaneously calculating image charge sums to generate accurate distance information signals.

Implementation Method 1

a photodiode, which is configured to operably accumulate the image charges in the accumulation periods in response to the reflection light pulse

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

a light source, which is configured to operably emit projection light pulses at the object according to a projection signal

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Data Source

PatentUS11768277B2Time-of-flight sensor and control method thereof

Publication Date: 2023.09.26 PIXART IMAGING INC

AI summary

A time-of-flight sensor for capturing a three-dimensional (3D) image of an object, includes: a light source for emitting projection light pulses at the object according to a projection signal; an array of pixel circuits for sensing reflection light pulses and storing image charges according to the reflection light pulses; and a processing circuit for calculating a first sum of first portions of the image charges and a second sum of second portions of the image charges to generate a distance information signal of the 3D image of the object simultaneously, wherein in one accumulation period, the first portion of the image charges is generated during a first time period, and the second portion of the image charges is generated during a second time period, wherein the second time period is directly following the first time period in the accumulation period.