Optical Interface Interferometry for Multi-Lens Geometry
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Solution Overview
Problem
Existing methods struggle to accurately distinguish and measure geometric parameters of interfaces in optical elements, particularly for multi-lens assemblies, especially when interfaces are close or buried, leading to mixed measurement results and increased centering errors, especially in small optical components like smartphone lenses.
Innovation Solution
A method and device using interferometric measurement with a low-coherence light source and optical sensors to selectively detect interference signals from individual interfaces by positioning a coherence zone and rotating the optical element, allowing for precise discrimination and correction of decentering errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a measurement beam is propagated through multi-lens assemblies to measure interface geometric information, then the measurement can cover multiple interfaces, but the reflected beams from multiple interfaces superpose and mix, leading to loss of measurement precision
Solution Approach 1:
The patent divides the measurement process into sequential steps, measuring each interface individually by positioning the coherence zone at each interface in turn. This segmentation prevents signal superposition and allows precise measurement of each interface's geometric information, including centering errors, while still covering multiple interfaces through the systematic measurement sequence.
Solution Approach 2:
The patent introduces a coherence zone as an intermediary spatial region that selectively interacts with individual interfaces. By positioning this coherence zone at specific interfaces during different measurement steps, the system enables selective detection of reflected beams from individual interfaces, preventing mixing of signals from multiple interfaces while maintaining comprehensive measurement capability.
2Measurement precision
If the measuring head is moved along the measuring axis to position the focal point near the surface to be measured, then the measurement can focus on specific interfaces, but variations of the measuring beam axis around the reference axis occur, introducing additional alignment errors
Solution Approach 1:
The patent replaces mechanical movement of the measuring head with optical field positioning. Instead of physically moving the measuring head to focus on different interfaces, the system uses a coherence zone that can be positioned at different interfaces through optical means. This substitution eliminates mechanical-induced axis variations and maintains both focal point positioning accuracy and reference axis alignment.
3Measurement precision
If the depth of field of imaging optics is increased to improve discrimination power, then interfaces can be distinguished more reliably, but the system size increases, which is problematic for mobile devices
Solution Approach 1:
The patent extracts the discrimination function from the imaging optics depth of field and implements it through selective coherence zone positioning. By using a coherence zone that can be independently positioned at different interfaces, the system achieves high discrimination power without relying on increased depth of field, thereby maintaining a compact device size suitable for mobile applications.
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 reliable and precise measurement of geometric parameters of optical element interfaces, including centering errors, without additional steps, and allows for high-precision geometric information determination and correction, suitable for optical assemblies during production.
Implementation Method 1
interferometric measuring means with at least one optical sensor and at least one low coherence light source configured to direct a measuring beam along the measuring axis towards the optical element so as to pass through at least one of the at least two interfaces and to be reflected by the interface to be measured and generate a reflected measuring beam, and to selectively detect an interference signal resulting from interference between the reflected measuring beam and a reference beam
Data Source
Figure 1~2
Figure 3
Figure 4(a)~5(c)
AI summary
The invention relates to a method (10) for determining information relating to an interface (103) of an optical element comprising a plurality of interfaces, the method being implemented by a device comprising at least one optical sensor (602) and at least one light source (612) in order to make a beam (606) pass through at least one of the interfaces and be reflected by the interface to be measured, and to detect an interference signal between the reflected beam and a reference beam; the method comprising: - positioning (12) a coherence zone at an interface; - at least two measurements (14, 16) of the interface in order to produce an interference image by measurement on the basis of respective interference signals; - rotating (15) the optical element about a reference axis of the device between the measurements; and - processing (17) the at least two images in order to obtain information relating to the interface.