Profile Measuring Apparatus for Inclined Surface Precision
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Solution Overview
Problem
Conventional profile measuring apparatuses face challenges in achieving high measurement precision due to the reduction in numerical aperture (NA) of the optical imaging system when the object surface is inclined, leading to decreased focal depth and accuracy in detecting the focus position.
Innovation Solution
A profile measuring apparatus that includes an imaging element, an image formation optical system with an objective lens, a measuring direction changing unit to adjust the object's inclination based on surface information, and a measuring unit to measure the object's profile by ensuring a light flux enters the objective lens with a predetermined aperture angle, thereby maintaining or increasing the focal depth equivalent to the NA of the optical imaging system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the object surface is inclined with respect to the objective lens, then the measurement can be performed on inclined surfaces, but the numerical aperture (NA) of the optical imaging system is reduced
Solution Approach 1:
Instead of adjusting the optical system to accommodate inclined surfaces, the patent inverts the approach by adjusting the inclination of the object surface itself. The measuring direction changing unit tilts the object surface to match the incident light direction, allowing the optical imaging system to maintain its optimal numerical aperture while measuring inclined surfaces.
Solution Approach 2:
The patent introduces a dynamic adjustment mechanism (measuring direction changing unit) that can change the inclination of the object surface based on the measured inclination angle. This dynamic adaptation allows the system to maintain optimal measurement conditions for surfaces with varying inclinations while preserving the numerical aperture of the optical system.
2Adaptability or versatility
If the object surface is inclined, then inclined surfaces can be measured, but the focal depth of the optical imaging system decreases
Solution Approach 1:
The patent reverses the conventional approach by not tilting the optical system to measure inclined surfaces. Instead, it tilts the object surface to match the fixed optical axis direction, thereby maintaining the original focal depth of the optical imaging system while enabling measurement of inclined surfaces.
Solution Approach 2:
The measuring direction changing unit provides dynamic adjustment of the object surface inclination, allowing the system to adapt to different surface angles while maintaining optimal focal depth. This dynamic reconfiguration ensures that the focal depth remains determined by the numerical aperture rather than being reduced by inclination.
3Adaptability or versatility
If the object surface is inclined, then inclined surfaces can be measured, but the accuracy of detecting the focus position deteriorates
Solution Approach 1:
The patent inverts the conventional solution by not adjusting the optical system's inclination to match the surface. Instead, it adjusts the object surface inclination to match the optical system's fixed axis, thereby maintaining optimal focus detection accuracy while enabling measurement of inclined surfaces.
Solution Approach 2:
The measuring direction changing unit dynamically adjusts the object surface inclination based on detected surface angles, ensuring that the light flux from the object surface always enters the objective lens at the optimal aperture angle. This dynamic adjustment maintains high focus detection accuracy across various surface inclinations.
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 solution enhances the precision of profile measurement by adjusting the object's inclination to maintain the focal depth determined by the numerical aperture, improving the accuracy of focus detection and profile measurement.
Implementation Method 1
an image formation optical system which is arranged to form an image of the pattern, projected on the object, on the imaging element and which includes an objective lens that condenses a light flux from the object on which the pattern is projected
Implementation Method 2
a measuring direction changing unit which is configured to change inclination of a surface of the object with respect to the objective lens based on information of the inclination of the surface of the object so that a light flux from a position of the object, reaching the imaging element through the objective lens
Data Source
AI summary
There is provided a profile measuring apparatus which measures a profile of an object, including an imaging element; an image formation optical system including an objective lens; a measuring direction changing unit which is configured to change inclination of a surface of the object with respect to the objective lens based on information of the inclination of the surface of the object so that a light flux enters the objective lens with an aperture angle not less than a predetermined degree; and a measuring unit which is configured to measure the profile of the object based on the image, of the object on which the pattern is projected, obtained by the imaging element.