Shape Measurement Apparatus Using Grating Projection and Reliability Indices
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Solution Overview
Problem
Existing shape measurement techniques, such as the shadow Moire method, face limitations in measuring three-dimensional shapes due to the requirement for a grating larger than the measurement target, and struggle to enhance measurement resolution and accuracy, especially for inspecting defects in electronic devices like printed circuit boards.
Innovation Solution
A shape measurement apparatus and method that projects grating patterns onto a target, captures images, and calculates reliability indices and phases to determine the quality of pads and surfaces, using a weight function based on brightness, visibility, and signal-to-noise ratio to enhance measurement accuracy and detect defects without requiring additional two-dimensional shape data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shadow Moire method is used to measure three-dimensional shape, then non-contact measurement is achieved, but the grating must be larger than the measurement target which limits applicability
Solution Approach 1:
The patent transitions from the shadow Moire method to the projection Moire method, fundamentally changing the measurement dimensionality. Instead of projecting shadows onto a screen (2D projection), the invention directly projects grating patterns onto the measurement target surface and captures the deformed patterns reflected from the target. This dimensional change allows the grating size to be independent of the target size, resolving the contradiction between measurement capability and adaptability to different target sizes
2Measurement precision
If phase shifting method is applied to Moire technique, then measurement resolution is enhanced, but measurement accuracy and reliability need further improvement
Solution Approach 1:
The patent introduces a reliability index calculation mechanism that provides feedback on measurement quality. The control section calculates reliability indices based on the captured grating images and uses this information to assess measurement accuracy. This feedback loop allows the system to identify and correct potential measurement errors, thereby improving overall measurement reliability while maintaining the high resolution achieved through phase shifting
Solution Approach 2:
The patent employs multiple parameter changes to enhance measurement reliability. It uses multi-directional projection of grating patterns with different orientations, captures images at multiple phase shifts, and calculates reliability indices based on various parameters including pattern recognition accuracy and consistency across different measurements. These parameter changes enable the system to achieve both high resolution and high reliability
3Measurement precision
If existing Moire techniques are used for printed circuit board inspection, then three-dimensional shape can be measured, but two-dimensional shape measurement requires additional data and processes
Solution Approach 1:
The patent creates a universal measurement system that simultaneously provides both two-dimensional and three-dimensional shape information through the same projection Moire process. By analyzing the grating pattern deformations in multiple directions and combining the results, the system extracts both planar (2D) and elevation (3D) information from the same set of images. This multi-functional approach eliminates the need for separate measurement processes or additional data acquisition for 2D shape inspection
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 enables accurate measurement of both two-dimensional and three-dimensional shapes, effectively inspecting defects on printed circuit boards by improving measurement resolution and reliability, and enhancing inspection accuracy through the use of reliability indices and weight functions.
Implementation Method 1
a pattern-projecting section including a light source, a grating part transmitting and blocking light generated by the light source to generate a grating image
Implementation Method 2
a projecting lens part making the grating image on a measurement target of the target substrate
Implementation Method 3
an image-capturing section capturing the grating image reflected by the measurement target of the target substrate
Data Source
AI summary
A shape measurement apparatus includes a work stage supporting a target substrate, a pattern-projecting section including a light source, a grating part partially transmitting and blocking light generated by the light source to generate a grating image and a projecting lens part making the grating image on a measurement target of the target substrate, an image-capturing section capturing the grating image reflected by the measurement target of the target substrate, and a control section controlling the work stage, the pattern-projecting section and the image-capturing section, calculating a reliability index of the grating image and phases of the grating image, which is corresponding to the measurement target, and inspecting the measurement target by using the reliability index and the phases. Thus, the accuracy of measurement may be enhanced.