Optical Shape Measuring Method for Lens Surface Accuracy
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Solution Overview
Problem
Current shape measuring methods for lenses face challenges such as the need for large apparatuses and measurement errors due to axis deviations, especially when measuring both top and bottom surfaces of miniaturized camera lenses with high accuracy and resolution.
Innovation Solution
A shape measuring method using a light source, periodic pattern application, objective lens, focus drive unit, photodetector, and face shape calculation unit to acquire and analyze top and bottom surface data of light-transmitting objects, allowing for accurate shape data collection without flipping the lens and reducing measurement errors by aligning the focal point with the bottom surface through the top surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a contact type probe is used to measure lens surface shape, then measurement accuracy can be maintained, but the apparatus size increases and measurement efficiency decreases
Solution Approach 1:
The patent replaces the mechanical contact type probe with an optical measurement system using a light source, objective lens, and photodetector. This substitutes mechanical scanning with optical field-based measurement, achieving non-contact measurement that eliminates the need for large apparatus while maintaining measurement accuracy through optical focusing and light intensity detection.
Solution Approach 2:
The patent creates an optical copy of the lens surface shape by focusing light onto the surface and detecting the reflected or transmitted light patterns. The photodetector captures the optical image information which is then processed to reconstruct the surface shape, effectively using light as a copy mechanism to obtain measurement data without physical contact.
2Loss of information
If the lens is flipped to measure both top and bottom surfaces, then complete shape data can be obtained, but measurement axis deviation occurs causing measurement errors
Solution Approach 1:
The patent makes the measurement system universal by enabling it to measure both the top and bottom surfaces of the lens without requiring the lens to be flipped. The optical system is configured to illuminate and detect light from both surfaces through the lens material, allowing a single fixed-position measurement apparatus to acquire complete shape data from multiple surfaces simultaneously.
Solution Approach 2:
The patent uses the lens itself as an intermediary medium. By transmitting light through the lens material, the system can access and measure the bottom surface without physical contact or repositioning. The lens material acts as a mediator that allows optical penetration from one side to the other, enabling measurement of both surfaces through a single optical path.
3Measurement precision
If miniaturized camera lenses are measured with contact type probes, then shape inspection can be performed, but measurement accuracy approaches the limit due to extreme miniaturization
Solution Approach 1:
The patent replaces mechanical probing with optical field-based measurement, which is not limited by the physical size of the measuring instrument. The optical system can focus light to extremely small spots and detect subtle variations in light intensity, enabling measurement of miniaturized lenses with resolutions beyond the capabilities of mechanical probes.
Solution Approach 2:
The patent changes the measurement parameter from mechanical displacement to optical light intensity. By detecting changes in light intensity patterns as the objective lens focuses and defocuses on the miniaturized lens surface, the system achieves high-resolution measurement without being constrained by mechanical probe dimensions or contact forces.
4Measurement precision
If the focal point is aligned precisely with the measurement surface, then measurement accuracy improves, but the measurement process becomes more complex
Solution Approach 1:
The patent implements feedback control by continuously monitoring the light intensity detected by the photodetector and using this information to determine when the focal point is optimally aligned with the measurement surface. The system automatically identifies the peak intensity condition as the focal point, providing real-time feedback that simplifies the focusing process while maintaining high measurement precision.
Solution Approach 2:
The measurement system performs self-alignment by automatically detecting the focal point position through light intensity variations. The objective lens and photodetector configuration enables the system to self-determine the optimal focus position without requiring complex external alignment mechanisms, as the light intensity peak inherently indicates proper focal alignment.
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 high-accuracy, high-throughput shape data acquisition for both top and bottom surfaces of lenses, eliminating the need for large apparatuses and minimizing measurement errors, while maintaining the lens in a stable position.
Implementation Method 1
an objective lens that irradiates an object to be measured with the light beam
Implementation Method 2
a focus drive unit that displaces a focal point of the objective lens relatively to the object to be measured
Implementation Method 3
a photodetector that detects the light beam reflected by the object to be measured
Implementation Method 4
by transmitting through the top surface of the object to be measured and aligning the focal point of the objective lens on the bottom surface
Data Source
AI summary
A shape measuring apparatus applies, to a light beam, a periodic pattern having periodicity in a direction perpendicular to an optical axis and displaceable in the direction perpendicular to the optical axis, relatively displaces a focal point of an objective lens in a direction parallel to the optical axis, and calculates, based on amplitude of intensity of the light beam detected by a photodetector, face shape data on the object to be measured. Then, a top surface measuring step of acquiring face shape data on a top surface of the object to be measured, and a bottom surface measuring step of acquiring face shape data on a bottom surface of the object to be measured by transmitting through the top surface of the object to be measured and aligning the focal point of the objective lens on the bottom surface of the object to be measured are performed.