Smartphone SLAM Eyeglass Measurement Using Frame Dimensions
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Solution Overview
Problem
Smartphone-based systems struggle to obtain accurate measurements for fitting prescription eyewear due to scale inconsistencies in three-dimensional mapping, particularly when using a single camera, which affects the precise fitting of eyeglasses to an individual's face.
Innovation Solution
A method utilizing a smartphone camera to image a person wearing eyeglass frames from multiple positions, leveraging autofocus and SLAM systems to determine three-dimensional coordinates with a known scale, allowing for accurate calculation of fabrication measurements without requiring a physical scale in the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single camera is used for depth mapping, then device complexity is reduced, but measurement precision deteriorates due to scale inconsistencies in three-dimensional mapping
Solution Approach 1:
The patent introduces an intermediary scaling process that uses known physical dimensions of the eyeglass frame (such as lens width, bridge width, or temple length) as a reference standard. This reference dimension acts as a mediator to convert the relative scale measurements from single-camera SLAM into absolute real-world dimensions, thereby resolving the scale inconsistency problem while maintaining single-camera simplicity
Solution Approach 2:
The patent changes the scaling parameter from unknown to known by incorporating predetermined dimensional information about the eyeglass frame into the measurement process. By using these known parameters as reference standards, the system transforms the output of SLAM from relative coordinate space to absolute measurement space, achieving both simplicity and precision
2Device complexity
If SLAM is used for three-dimensional mapping from a single camera position, then device complexity remains low, but manufacturing precision deteriorates due to inability to obtain accurate scale information
Solution Approach 1:
The patent applies preliminary action by pre-storing dimensional information about standard eyeglass frame components (lens width, bridge width, temple length) before the actual measurement process. This pre-known information is then used to calibrate and scale the SLAM-generated three-dimensional model, ensuring that fabrication measurements are obtained with accurate scale information without adding complex hardware
3Ease of operation
If autofocus system is used to determine camera-object distance, then ease of operation is improved, but measurement precision may worsen due to focus-based distance estimation limitations
Solution Approach 1:
The patent employs feedback by using the autofocus distance measurement as an initial estimate, then refining this distance value through the SLAM process that tracks feature points across multiple frames. The known scale information from eyeglass frame dimensions provides additional feedback to correct and validate the distance measurements, combining the ease of autofocus with the precision of multi-frame analysis
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 the generation of accurate measurements for fabricating prescription lenses that fit comfortably and aesthetically, accounting for anatomical features and posture, improving the fitting process by providing reliable scale information for eyeglass frames.
Implementation Method 1
By sensing the time of flight of the emitted energy between transmission and reception, the distance of the object could be calculated
Implementation Method 2
In a structured light system, a known light pattern such as a grid is projected onto an object in front of the camera. This is typically accomplished using infrared light that is not visible to the naked eye. The projected grid will be distorted by the shape of the object it hits.
Implementation Method 3
SLAM systems track a set of targeted pixel points through successive camera frames and using these tracks to triangulate a value for position in real space
Data Source
AI summary
A system and method for determining the measurements needed to fabricate prescription eyeglasses. A person is imaged wearing the eyeglass frames, from a first camera position and a subsequent camera position. This produces images having differing perspectives from known distances. Common measurement points are identified within at least some of the images. The common measurement points undergo positional changes between the images having said differing perspectives. The positional changes of the common measurement points and the known distance to the imaging camera are utilized to map three dimensional coordinates for the measurement points using an actual measurement scale. Fabrication measurements are calculated between the various three-dimensional coordinates in the same scale.