Hierarchical Binary Structured Light Patterns for Depth Mapping

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Solution Overview

Problem

Structured light imaging devices face limitations in capturing both detailed scenes and extending depth range, as they typically rely on single spatial frequency patterns that are either better for details or depth, but not both simultaneously, and require stationary scenes.

Innovation Solution

The generation and use of hierarchical binary structured light patterns, which are formed by iteratively scaling a lower resolution binary pattern to multiple successively higher resolutions, allowing for improved detail capture and extended depth range while maintaining pattern structure, enabling more accurate and comprehensive depth mapping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single high spatial frequency pattern is used, then detail capture is improved, but depth range is reduced

Engineering Contradiction:

Improvedetail capture accuracyVSAvoiddepth range

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The single pattern is segmented into multiple binary patterns with different spatial frequencies. Each binary pattern captures depth information at different ranges, and their combinations enable both fine detail capture and extended depth range simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple binary patterns with different spatial frequencies are combined into a composite structured light pattern. This composite pattern integrates the advantages of both high-frequency (detail capture) and low-frequency (depth range) patterns, resolving the trade-off between the two parameters.

Inventive Principle:

Principle #40Composite materials

2Length of stationary object

If a single low spatial frequency pattern is used, then depth range is extended, but detail capture is reduced

Engineering Contradiction:

Improvedepth rangeVSAvoiddetail capture accuracy

Core Design Contradiction:

Length of stationary objectVSMeasurement precision

Solution Approach 1:

The low-frequency pattern is segmented and combined with high-frequency binary patterns. The segmentation allows the system to process different spatial frequency components separately and combine them to achieve both extended depth range and fine detail capture.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The structured light pattern is formed as a composite of multiple binary patterns with varying spatial frequencies. This composite structure enables the system to simultaneously achieve the depth range extension benefit of low-frequency patterns and the detail capture benefit of high-frequency patterns.

Inventive Principle:

Principle #40Composite materials

3Length of stationary object

If dynamic multi-pattern projection is used, then both detail capture and depth range are improved, but the scene must be stationary

Engineering Contradiction:

Improvedepth rangeVSAvoiddynamic environment capability

Core Design Contradiction:

Length of stationary objectVSAdaptability or versatility

Solution Approach 1:

Multiple binary patterns are merged into a single composite structured light pattern that can be projected in one shot. This merging eliminates the need for sequential projection of multiple patterns, thereby eliminating motion artifacts and enabling operation in dynamic environments while maintaining both detail capture and depth range.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The multiple binary patterns are pre-computed and combined into a single projected pattern before execution. This preliminary preparation allows the system to capture all necessary depth information in a single shot, making the system adaptable to dynamic scenes where objects may move during capture.

Inventive Principle:

Principle #10Preliminary action

4Length of stationary object

If fixed pattern projection is used, then dynamic scenes are handled, but either detail capture or depth range must be compromised

Engineering Contradiction:

Improvedepth rangeVSAvoiddetail capture accuracy

Core Design Contradiction:

Length of stationary objectVSMeasurement precision

Solution Approach 1:

The fixed projected pattern is designed as a composite of multiple binary patterns with different spatial frequencies. This composite structure enables the single-shot fixed pattern system to simultaneously achieve both detail capture and extended depth range, eliminating the need to compromise between these parameters while maintaining compatibility with dynamic scenes.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS10542248B2Hierarchical binary structured light patterns

Publication Date: 2020.01.21 TEXAS INSTRUMENTS INC

AI summary

A method of image processing in a structured light imaging device is provided that includes receiving a captured image of a scene, wherein the captured image is captured by a camera of a projector-camera pair in the structured light imaging system, and wherein the captured image includes a pre-determined hierarchical binary pattern projected into the scene by the projector, wherein the pre-determined hierarchical binary pattern was formed by iteratively scaling a lower resolution binary pattern to multiple successively higher resolutions, rectifying the captured image to generated a rectified captured image, extracting a binary image from the rectified captured image at full resolution and at each resolution used to generate the pre-determined hierarchical binary pattern, and using the binary images to generate a depth map of the captured image.