Surface Profile Measurement for Transparent Objects
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Solution Overview
Problem
Conventional surface profile measuring apparatuses struggle to accurately measure the profiles of objects made of optically transparent materials due to back surface reflection interference.
Innovation Solution
A surface profile measuring apparatus using a measuring head with a distance detector and an angle detector, where the first and second probe light beams are obliquely incident on the surface, allowing the separation of front and back surface reflections, and a controller to derive the surface profile based on the detected positions and angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional profile measuring apparatuses use light reflection measurement, then they can accurately measure reflective surfaces like mirrors, but they cannot accurately measure transparent materials like lenses due to back surface reflection interference
Solution Approach 1:
The invention segments the measurement process by using two separate probe light beams with different incident angles. The first probe light beam measures the front surface profile, while the second probe light beam measures the back surface profile. By separating the measurement of front and back surfaces into distinct operations, the interference from back surface reflection on front surface measurement is eliminated, enabling accurate measurement of transparent materials.
2Device complexity
If a single probe light beam is used for measurement, then the device structure is simple, but it cannot separate front and back surface reflections for transparent material measurement
Solution Approach 1:
The measurement function is segmented into two independent measurement systems: one for the front surface and one for the back surface. Each system uses a probe light beam with a specific incident angle optimized for its target surface. This segmentation allows the device to handle transparent materials by measuring each surface separately, while maintaining a relatively simple overall structure through modular design.
Solution Approach 2:
Each probe light beam is configured with specific local qualities - different incident angles optimized for their respective measurement targets. The first probe light beam has an incident angle suitable for front surface measurement, while the second probe light beam has an incident angle optimized for back surface measurement through transparent materials. This local optimization enables precise measurement of both surfaces despite the different optical properties involved.
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 stable measurement of transparent objects by separating front and back surface reflections, ensuring accurate surface profile derivation.
Implementation Method 1
a distance detector configured to detect a distance to a surface under measurement of an object under measurement using a first probe light beam
Implementation Method 2
an angle detector configured to detect an angle of the surface under measurement using a second probe light beam
Data Source
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AI summary
A surface profile measuring apparatus LMS includes a measuring head 25 having therein a distance detector and an angle detector, a workstage unit 10 configured to move an object under measurement W, a head stage unit 30 configured to swing the measuring head 25, and a controller 50 configured to control operations of the units. A first probe light beam provided by the distance detector and a second probe light beam provided by the angle detector are configured to be both obliquely incident on a surface under measurement. The controller 50 moves the measuring head 25 and the object under measurement W relative to each other in such a manner that the applied positions of the first and second probe light beams move along a measurement line and derives the profile of the surface under measurement along the measurement line based on the distance to the surface under measurement detected by the distance detector 21 and the angle of the surface under measurement detected by the angle detector 22.