Three-Mirror Telecentric Panel Inspection for Chromatic Aberration Control
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Solution Overview
Problem
Conventional optical systems for machine vision applications, particularly in inspecting OLED displays, face challenges with chromatic aberrations, especially when magnification exceeds 1×, leading to difficulties in detecting small defects and requiring complex glass lens designs that are logistically challenging and prone to significant aberrations.
Innovation Solution
A panel inspection device using a combination of first, second, and third mirrors with specific curvatures, arranged to provide a magnification factor greater than one, reduces chromatic aberrations by employing a planar folded mirror system with aspherical surfaces to correct aberrations and maintain telecentricity, allowing for high-resolution inspection of panels with a broad wavelength spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional glass lenses are used to achieve magnification greater than 1×, then the inspection resolution is improved, but chromatic aberrations increase significantly
Solution Approach 1:
The patent replaces the conventional glass lens optical system with a mirror-based optical system. Mirrors reflect light without refracting it, thereby eliminating chromatic aberrations entirely while maintaining the required magnification capability greater than 1× for high-resolution inspection
Solution Approach 2:
The patent changes the fundamental optical parameter from refraction-based imaging (glass lenses) to reflection-based imaging (mirrors). This parameter change transforms the optical path so that light rays of different wavelengths follow the same path, eliminating longitudinal chromatic aberration while achieving the needed magnification
2Object-affected harmful factors
If multiple lens elements are added to correct chromatic aberrations, then the aberration control is improved, but the device complexity increases
Solution Approach 1:
The patent eliminates the need for multiple corrective lens elements by substituting the entire glass lens system with a mirror system. This substitution inherently corrects chromatic aberrations without requiring additional optical elements, thereby reducing device complexity
Solution Approach 2:
The patent extracts and removes the problematic glass lens elements from the optical system. By taking out the refractive components that cause chromatic aberration, the system achieves aberration control without the complexity of multiple corrective elements
3Measurement precision
If magnification is increased to detect smaller defects, then the measurement precision is improved, but the axial color aberration becomes more prominent
Solution Approach 1:
The patent substitutes glass lenses with mirrors in the high-magnification optical system. Since mirrors reflect rather than refract light, axial color aberration is eliminated even at magnifications greater than 1×, enabling precise detection of small defects without the harmful effects of chromatic aberration
Solution Approach 2:
The patent employs curved mirror surfaces with specific radii of curvature to achieve the required magnification greater than 1×. The spherical or aspherical mirror geometry provides the necessary optical power while maintaining chromatic aberration-free imaging at high magnification
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 system achieves diffraction-limited imaging with reduced longitudinal and lateral chromatic aberrations, enabling high-resolution inspection of large panel areas simultaneously, while maintaining telecentricity and correcting for various aberrations, thus enhancing inspection efficiency and accuracy.
Implementation Method 1
The first mirror, the second mirror, and the third mirror are arranged to display a section of the panel to be inspected on the sensor with a magnification factor M greater than one
Data Source
AI summary
An inspection device for inspecting a panel, in particular a display, or a PCB, includes a first mirror, a second mirror, a third mirror, and a sensor. The first mirror, the second mirror, and the third mirror are arranged to display a section of the panel to be inspected on the sensor with a magnification factor greater than one. At least two of the group of the first mirror, the second mirror, and the third mirror, have both a first type of curvature, and a remaining mirror has a second type of curvature, opposite to the first type of curvature. The first mirror, the second mirror, and the third mirror form a telecentric system which is telecentric on a panel facing side and/or on a sensor facing side.