Structured Light Distance Measurement via Shadow Brightness Ratios
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Solution Overview
Problem
Current structured-light based measurement methods for video inspection devices face limitations such as restricted baseline spacing, difficulty in determining object distance on surfaces lacking unique features, and the need for interchanging probe tips, which reduces efficiency and accuracy.
Innovation Solution
A method using two light emitters and shadow-forming elements to capture images with and without projected shadows, determining object distance by analyzing brightness ratios of pixel luminance values, allowing for automatic and precise distance measurement without the need for tip interchanging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If stereoscopic systems use a special optic system with limited baseline spacing, then the apparatus can be compact, but the resolution and accuracy of object distance determination are reduced
Solution Approach 1:
The patent replaces the mechanical/optical baseline spacing system with an electronic/image processing system. Instead of physically separating light sources to create stereoscopic depth cues, the invention uses a single light source with shadow-forming elements and processes the resulting shadow images computationally to determine object distance, thereby achieving high measurement precision without requiring large baseline spacing.
Solution Approach 2:
The patent transitions from using spatial baseline separation (one dimension) to using shadow projection and image analysis (adding temporal and computational dimensions). By projecting shadows from known geometries and analyzing their distortion in captured images, the system determines object distance through computational methods rather than direct optical triangulation.
2Device complexity
If shadow measurement methods use a single opaque element positioned at an angle, then the measurement can be taken with simple optics, but only one specific area is measured and surface irregularity over the field of view cannot be detected
Solution Approach 1:
The patent divides the single shadow measurement function into multiple shadow-forming elements arranged in different positions and orientations. Each element casts shadows that illuminate different portions of the object's field of view, allowing comprehensive surface inspection while maintaining relatively simple optical hardware.
Solution Approach 2:
The patent combines multiple shadow-forming elements into a single integrated measurement system. By merging the functionality of multiple opaque elements positioned at different angles into one apparatus, the system achieves broad field of view coverage and surface irregularity detection while avoiding the complexity of multiple separate optical systems.
3Measurement precision
If two sets of optics are used for viewing and measurement, then specialized measurement can be performed, but the probe tips must be interchanged which consumes additional time and reduces efficiency
Solution Approach 1:
The patent integrates measurement functionality directly into the viewing probe tip. The same probe tip that captures images for visual inspection also contains light emitters and shadow-forming elements for automated measurement, eliminating the need to interchange probe tips and thereby improving inspection efficiency without sacrificing measurement accuracy.
Solution Approach 2:
The patent merges the viewing optics and measurement optics into a single integrated probe tip assembly. By combining image capture, light emission, and shadow projection functionalities in one unit, the system allows simultaneous or sequential viewing and measurement without requiring physical interchange of components.
4Measurement precision
If shadow measurement optics are used, then object distance can be determined, but the field of view is less well illuminated which limits the viewing distance
Solution Approach 1:
The patent uses sequential activation of different light emitters - alternating between general viewing illumination and shadow-forming measurement illumination. This periodic switching allows the system to provide full illumination during viewing phases and perform measurements during dedicated measurement phases, ensuring both good illumination and accurate measurement capability.
Solution Approach 2:
The patent implements dynamic control of multiple light sources, switching between different illumination modes as needed. The system can activate general viewing lights for optimal illumination during inspection phases and switch to shadow-forming light emitters during measurement phases, adapting illumination characteristics to the current operational requirement.
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 accurate and efficient determination of object distance across a larger field of view, improving resolution and reducing human subjectivity, while maintaining a compact probe design for versatile applications.
Implementation Method 1
a first light emitter and a second light emitter for emitting light through an opening with at least one shadow-forming element onto the object forming a plurality of shadows on the object
Implementation Method 2
capturing at least one first emitter image of the object with the first light emitter activated and the second light emitter deactivated
Data Source
AI summary
A method of determining the distance to an object can use a video inspection device comprising a first light emitter and a second light emitter, wherein the first light emitter can emit light through an opening with at least one shadow-forming element. The method can comprise capturing at least one first emitter image with the first light emitter activated and the second light emitter deactivated, capturing at least one second emitter image with the second light emitter activated and the first light emitter deactivated, determining a first plurality of luminance values of the pixels in the at least one first emitter image, determining a second plurality of luminance values of the pixels in the at least one second emitter image, determining the brightness ratios of the second plurality of luminance values to the first plurality of luminance values, and determining an object distance using the brightness ratios.