3D Measurement Device DMD Black Pattern Timing
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Solution Overview
Problem
Three-dimensional measurement devices using the phase shift method face challenges in maintaining measurement accuracy due to difficulties in projecting a striped pattern with a highly accurate, ideal sinusoidal light intensity distribution, particularly when using digital micromirror devices (DMDs), which can lead to reduced accuracy in reflecting luminance values during image capture.
Innovation Solution
A three-dimensional measurement device configuration that employs a reflective optical modulator like a DMD to project a striped pattern, with image data acquisition synchronized to include full black pattern projection periods to prevent light exposure during non-measurement times, ensuring accurate reflection of luminance values and maintaining high measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DMD is used to project striped patterns at high frame rates, then the ability to express intermediate tones and improve measurement accuracy is enhanced, but charge accumulation in imaging elements occurs during non-measurement periods, reducing measurement accuracy
Solution Approach 1:
The patent implements periodic projection of full black patterns (non-measurement periods) alternating with striped pattern projection (measurement periods). This periodic action allows the imaging elements to clear accumulated charges during black pattern periods, ensuring that only light from intended striped patterns is captured during measurement periods, thereby maintaining luminance value accuracy while using high-frame-rate DMD projection
Solution Approach 2:
The patent applies preliminary anti-action by projecting full black patterns before and after striped pattern sequences. These black patterns preemptively clear any charge accumulation that might occur during transitions or idle periods, preventing contamination of subsequent measurement data. This anticipatory clearing ensures that each measurement period starts with a clean state in the imaging elements
2Productivity
If continuous imaging is performed during DMD projection, then all projected frames are captured, but luminance values from non-measurement periods are incorrectly included in measurement data
Solution Approach 1:
The patent segments the imaging process into distinct measurement periods (during striped pattern projection) and non-measurement periods (during full black pattern projection). By controlling the imaging unit to operate only during measurement periods, the system captures image data exclusively when valid striped patterns are projected, excluding data from non-measurement periods while maintaining high overall imaging throughput
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 configuration enhances measurement accuracy by ensuring that only the light projected during the striped pattern period is imaged, preventing charge accumulation in imaging elements and accurately reflecting luminance values, thereby improving the reliability of three-dimensional measurements.
Implementation Method 1
a reflective optical modulator configured to convert the light emitted from the light source into a predetermined striped pattern
Implementation Method 2
an imaging unit configured to take an image of at least the measurement object which the striped pattern is projected onto
Data Source
AI summary
A three-dimensional measurement device includes: a projector that includes: a light source that emits predetermined light; and a reflective optical modulator that converts the predetermined light into a predetermined striped pattern, wherein the projector projects the predetermined striped pattern onto a measurement object at a predetermined number of frames per unit time; an imaging device that takes an image of the measurement object projected with the predetermined striped pattern; a processor that: controls the projector and the imaging device to sequentially project a plurality of different ones of the predetermined striped pattern and take images of the plurality of different ones of the predetermined striped pattern to obtain a plurality of image data having different light intensity distributions; and executes three-dimensional measurement of the measurement object based on the plurality of image data.