Mixed-mode depth detection using TOF and structured light

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Solution Overview

Problem

Current time-of-flight (TOF) depth detection methods face limitations in achieving high-resolution depth maps due to cumulative latencies in IR pulsing and detector circuitries, which can impede low-latency gesture recognition and 3D image capture.

Innovation Solution

A MEMS laser beam display utilizing mixed-mode depth detection, combining TOF and structured light depth detection, where TOF provides coarse depth and structured light offers fine depth, enabling a composite 3D image and gesture recognition with reduced latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple IR laser diodes or duplicated components in receive circuitry are used to obtain higher resolution depth map, then spatial resolution is improved, but device complexity increases

Engineering Contradiction:

Improvespatial resolution of depth mapVSAvoidnumber of IR laser diodes and receive circuitry components

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the depth detection process into two distinct modes: TOF mode for coarse depth detection and structured light mode for fine depth detection. This segmentation allows each mode to operate independently with optimized components, avoiding the need for multiple full-depth-detection systems while achieving high overall resolution.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent merges TOF depth detection and structured light depth detection into a unified mixed-mode system. The TOF detector and structured light detector share common components including the IR laser beam source, scanning mechanism, and processing circuitry, reducing overall device complexity while maintaining high measurement precision.

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If oversampling with a single IR laser beam is used to obtain higher resolution depth map, then spatial resolution is improved, but processing latency increases

Engineering Contradiction:

Improvespatial resolution of depth mapVSAvoidprocessing latency and frame rate

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent employs periodic action by alternating between TOF mode and structured light mode at different time intervals within a scanning cycle. This time-division multiplexing allows the system to collect data from both modes without requiring oversampling, thereby maintaining high spatial resolution while minimizing processing latency and maximizing frame rate.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If TOF mode is used for depth detection, then device complexity is reduced, but measurement precision deteriorates due to cumulative latencies

Engineering Contradiction:

Improvesimpler circuitry and single IR laser beamVSAvoidspatial resolution of depth map

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the depth detection task into coarse detection (TOF mode) and fine detection (structured light mode). The TOF mode handles the bulk of the depth detection with simpler circuitry, while the structured light mode provides high-resolution details only where needed, thus maintaining low device complexity while achieving high overall measurement precision.

Inventive Principle:

Principle #1Segmentation

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 allows for high-resolution depth maps with low latency, enhancing gesture recognition and 3D image capture by integrating TOF and structured light depth detection for improved spatial resolution and reduced processing overhead.

Implementation Method 1

Time of flight (TOF) methods for depth detection may be utilized to determine a depth or a distance of a target from a display or other device

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Implementation Method 2

The round trip distance may be calculated using the speed of light so that the depth or distance to the target may be determined

Methodology Applied

Scientific EffectSpeed of light: Light

Implementation Method 3

A spatial light modulator (SLM) and a stack of optical sensors

Methodology Applied

Scientific EffectSpatial light modulation:

Data Source

PatentEP3347738B1Mixed-mode depth detection

Publication Date: 2020.11.25 MICROVISION INC

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AI summary

Briefly, in accordance with one or more embodiments, a MEMS laser beam display to implement mixed-mode depth detection comprises an imaging engine to project an image in a field of view of the MEMS laser beam display, a time of flight (TOF) depth detector (114) to determine a distance to a target within the field of view in a first mode of depth detection, wherein the TOF depth detector determines coarse depth data of the target, and a structured light depth detector (116) to determine a distance to the target in a second mode of depth detection, wherein the structured light depth detector determines fine depth data of the target. Depth processing circuitry may generate a composite three-dimensional (3D) image of the target, or may identify a gesture region of the target for gesture recognition.