Lens Meter Refractive Power Measurement Using Dynamic Positioning
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Solution Overview
Problem
Conventional lens meters face challenges in accurately and efficiently measuring refractive power distribution of progressive power lenses, particularly in the distance and near portions, due to increased costs and reliability issues with multi-position measurement systems.
Innovation Solution
A lens meter with a lens rest, measurement optical system, two-dimensional image sensor, calculation part, detection part, guiding device, storage part, and display control part that allows for the measurement and display of refractive power distribution across a wide range, including distance, progressive, and near portions, using a low-cost structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens meter measures optical characteristics in multiple measurement positions within a wide measurement region, then the refractive power distribution of progressive power lens can be obtained, but the cost of production increases due to extensive requirements for screen, image forming lens, photo-receiving surface size, and calculation part performance
Solution Approach 1:
The measurement region is divided into multiple positions (distance portion, progressive portion, near portion) and measured sequentially by moving the lens rest, rather than attempting to capture all positions simultaneously. This segmentation allows use of a simple single-point measurement system while still obtaining comprehensive refractive power distribution data across the entire lens area.
Solution Approach 2:
The lens rest is made movable in the optical axis direction to dynamically shift the measurement position. By moving the lens rest to different positions (distance, progressive, near portions) and performing measurements sequentially, the system obtains refractive power distribution across the entire lens without requiring a complex multi-position static optical system.
2Measurement precision
If a lens meter uses a wide measurement region covering distance, progressive, and near portions, then refractive power distribution can be obtained, but measurement reliability decreases because heights to rear surface cannot be kept constant in peripheral parts
Solution Approach 1:
The lens rest is moved dynamically in the optical axis direction to position the lens at different heights corresponding to distance, progressive, and near portions. This dynamic positioning allows the measurement system to maintain constant height relative to the lens rear surface at each measurement position, ensuring measurement reliability while still covering the entire lens area through sequential positioning.
3Device complexity
If a lens meter measures optical characteristics at one measurement position, then the structure remains simple, but it takes a lot of trouble to find distance and near portions and takes much time to obtain refractive power distribution
Solution Approach 1:
The lens rest is moved automatically or manually in the optical axis direction to sequentially position the lens at distance, progressive, and near portions. This dynamic positioning enables the simple single-point measurement system to obtain refractive power distribution across the entire lens area efficiently, eliminating the need for complex multi-position optical systems while maintaining high measurement productivity.
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 efficient and reliable measurement of refractive power distribution across a wide range, reducing costs and improving measurement accuracy and reliability by shifting the measurement region to capture optical characteristics in multiple positions.
Implementation Method 1
a light source (12) projecting a measurement light bundle along the measurement optical axis (L1), a target plate (14) having a plurality of measurement targets (20), and a two-dimensional image sensor (15) detecting images of the targets, the target images being formed by the measurement light bundle having passed through the subject lens (LE)
Data Source
AI summary
A lens meter for measuring refractive power distribution of a progressive power lens and displaying its distribution map, has a lens rest having an aperture, an optical system including an axis, a source projecting a light bundle along the axis, a plate having targets and a two-dimensional image sensor detecting images by the bundle passing through the lens, aperture and plate, a part calculating the distribution within a measurement region from detection results, a part detecting a lens-position in a two-dimensional direction orthogonal to the axis, a device guiding movement on the rest to shift the measurement region and obtaining the distribution within an analysis region including distance, progressive and near portions, a part storing the distribution in the measurement region in association with the detected position, a display part, and a part controlling to display the distribution map within the analysis region based on the stored distribution and position.