Optical MTF Measurement with Single-Sensor Full-Field Imaging
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Solution Overview
Problem
Existing apparatuses for measuring optical properties, such as modulation transfer function (MTF), struggle to efficiently capture images at multiple field positions, especially for optical systems with variable focal lengths, requiring time-consuming realignment of cameras and limiting their use in high-volume production.
Innovation Solution
An apparatus using a two-dimensional image sensor and collecting optics with a focal length f, where the image sensor is positioned at a distance a within 0.9·f ≤ a ≤ 1.1·f, allowing simultaneous imaging of multiple structures across the entire field of view, eliminating the need for multiple cameras and reducing realignment during focal length changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple independent cameras are arranged to capture images at multiple field positions, then measurement coverage increases, but device complexity and arrangement difficulty increase
Solution Approach 1:
The patent combines multiple camera functions into a single image sensor by using a light field lens to simultaneously direct light from multiple field positions to different regions of the same sensor. This merging approach achieves multi-position measurement coverage while eliminating the complexity of arranging and synchronizing multiple independent cameras.
Solution Approach 2:
The light field lens serves multiple functions: it acts as a collecting lens to gather light, a beam splitter to direct light from different field positions, and an imaging element. This multi-functional component enables a single camera system to perform what previously required multiple specialized cameras, reducing overall system complexity.
2Measurement precision
If cameras are arranged densely to measure more field positions, then measurement precision improves, but light entry difficulty increases
Solution Approach 1:
The light field lens utilizes angular information in addition to spatial information, creating a four-dimensional light field mapping. By encoding both position and angle information in the light distribution, the system can distinguish between different field positions without requiring physically dense camera arrangements, thus maintaining light entry ease while achieving high measurement precision.
3Measurement precision
If cameras are realigned when focal length changes, then measurement accuracy is maintained, but measurement time increases
Solution Approach 1:
The optical system is pre-configured with the light field lens positioned at a specific location in the Fourier plane where it can accommodate focal length changes without requiring realignment. This preliminary positioning allows the system to maintain accurate measurements across different focal lengths, enabling rapid quality control of zoom lenses without time-consuming realignment procedures.
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-precision measurement of optical properties across a large number of field points without realignment, suitable for rapid quality control of optical systems like smartphone cameras and afocal systems, with improved measurement accuracy and efficiency.
Implementation Method 1
a two-dimensional image sensor, collecting optics with a focal length f, where the image sensor is positioned at a distance a within 0.9·f ≤ a ≤ 1.1·f
Data Source
AI summary
An apparatus for measuring the MTF or another optical property of an optical system includes an object to be imaged, which has a plurality of structures arranged in a plane and separated from one another, a two-dimensional image sensor, and collecting optics having a focal length f. The image sensor has a distance a from the collecting optics with 0.94·f≤a≤1.1·f. A holder for the optical system is arranged such that the optical system is located in a beam path between the object and the collecting optics. The image sensor and the collecting optics are configured such that all structures can be imaged by the optical system and the collecting optics onto the image sensor simultaneously.