Diamond Pattern DMD for Compact 3D Shape Measuring Apparatus
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Solution Overview
Problem
Conventional three-dimensional shape measuring apparatuses with digital mirror devices in a lattice pattern require a light source to be arranged at an oblique interval, leading to an enlargement of the external dimensions of the light source unit, which increases the installation width and reduces measurement accuracy.
Innovation Solution
A three-dimensional shape measuring apparatus with a digital mirror device arranged in a diamond pattern, where the light source is positioned within the installation width and orthogonal to the swing axes of the mirrors, allowing for the projection of stripe pattern light without enlarging the light source unit's dimensions, and enabling improved measurement accuracy by reducing the pitch between light portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital mirror device in a lattice pattern is used with the light source arranged at an oblique interval, then the stripe pattern light can be projected, but the external dimension of the light source unit is enlarged
Solution Approach 1:
The patent changes the mirror arrangement from a conventional lattice pattern to a diamond pattern, where the swing axes are rotated 45 degrees relative to the lattice pattern. This asymmetric transformation allows the light source to be positioned within the installation width of the DMD rather than requiring an oblique arrangement, thereby reducing the external dimension of the light source unit while maintaining stripe pattern projection capability
Solution Approach 2:
The patent reorients the swing axes of the mirrors from being inclined at 45 degrees to the side edges (lattice pattern) to being parallel to the side edges (diamond pattern). This dimensional reconfiguration of the mirror swing axes enables the light source to be positioned in a different spatial relationship to the DMD, allowing it to fit within the installation width while still achieving the required optical path for stripe pattern projection
2Length of stationary object
If the light source is arranged within the installation width of the DMD, then the external dimension is reduced, but the traveling direction of light may not be orthogonal to the swing axes
Solution Approach 1:
By rotating the mirror swing axes by 45 degrees to create a diamond pattern from the conventional lattice pattern, the patent achieves a configuration where the light source can be positioned within the installation width of the DMD while maintaining orthogonality between the light traveling direction and the swing axes. This asymmetric reconfiguration of the mirror arrangement resolves the conflict between compact positioning and optical precision
3Measurement precision
If the pitch between light portions is reduced, then measurement accuracy is improved, but the light source unit dimension may need to be increased
Solution Approach 1:
The diamond pattern arrangement of mirrors with swing axes parallel to the side edges, rather than the conventional lattice pattern with 45-degree inclined axes, enables a more efficient use of the DMD surface area. This asymmetric configuration allows for reduced pitch between light portions (improving measurement accuracy) while keeping the light source within the installation width, thus avoiding an increase in overall unit dimension
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
The solution suppresses the increase in the outer dimension of the light source unit, enhances measurement accuracy by generating accurate stripe patterns, and improves resolution by reducing the pitch between light portions, while maintaining the Scheimpflug principle for focused projection.
Implementation Method 1
a digital mirror device including a plurality of mirrors arranged in a diamond pattern... the light emitted from the light source is reflected by the digital mirror device, whereby the stripe pattern light alternately including the light portion and the dark portion can be projected on the inspection target portion
Data Source
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AI summary
A three-dimensional shape measuring apparatus (100) a pluraluty of projectors each comprising a light source (323), a digital mirror device, DMD, (326) for applying stripe pattern light to an inspection target including light portions and dark portions, and an objective lens (327). An imaging device (31) images the inspection target portion to which the stripe pattern light is applied, with which information about the height of an inspection target portion (110) can be acquired. Each DMD includes a plurality of mirrors (326a) arranged in a diamond pattern. Inside each projector the DMD and the source may be rotatable about the normal to the reflection surface of the DMD, which is non parallel to the optical axis of the objective lens. The projection lens may be configured to be relatively movable in a direction parallel to the reflecting surface of the DMD. The DMD may be configured to apply the stripe pattern light to the inspection target portion such that light intensity is larger on a farther side from the projector than on a closer side therefrom.