Camera Distance Measurement Using Body-Part Image Calibration
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Solution Overview
Problem
Existing methods for measuring distance between a camera and a user face, especially using a smartphone, are inaccurate in far-field vision due to blurring and reflection issues, and require complex setups or professional assistance.
Innovation Solution
A method involving multiple positional adjustments and image analysis to measure distance using a single device with a camera and display, utilizing body part features for calibration and reference lengths to compensate for blurring and reflection, enabling accurate measurements in both near- and far-field vision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a reference object displayed on a smartphone screen is used for distance measurement in far-field vision, then the measurement can be performed with a simple setup, but the reflection in the mirror becomes blurry and obscured, reducing measurement precision
Solution Approach 1:
The patent introduces a camera as an intermediary device to capture the reflection in the mirror, separating the measurement function from the display device. This allows the reference object to be displayed on the smartphone screen while the camera records the reflection, enabling far-field vision testing without direct observation of the blurry screen reflection.
Solution Approach 2:
The patent divides the measurement system into separate functional components: the smartphone displays the reference object, the camera captures the reflection, and the processing system analyzes the images. This segmentation allows each component to perform its function optimally without the limitations of using a single device for all functions.
2Measurement precision
If the smartphone is held close to the eyes for near-field vision testing, then accurate measurement of short distances is possible, but the device cannot be held at arm's length as required for proper near-field vision testing
Solution Approach 1:
The camera acts as an intermediary that allows the smartphone to be positioned at arm's length while still capturing the reference object reflection. This resolves the contradiction by separating the display function from the measurement function, enabling proper vision testing positioning.
3Device complexity
If existing distance measurement methods are used with smartphone cameras, then equipment complexity is reduced, but the focal length of the smartphone camera causes inaccuracies in distance measurement
Solution Approach 1:
The patent uses feedback by capturing images with the camera and processing them to determine the actual distance. The system measures the apparent size of the reference object in the captured image and uses this feedback to calculate and correct the distance, compensating for the smartphone camera's short focal length limitations.
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 precise distance measurement in various vision conditions with minimal equipment and user-friendly implementation, reducing the impact of blurring and reflection, and allowing for continuous adjustment during testing.
Implementation Method 1
acquiring a first image comprising the reference object and at least one body part of the user with the camera
Data Source
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AI summary
The invention relates to a method for measuring a test distance (DT) separating a camera (CAM) from a user (1), comprising steps of: - prompting the user to get in a first position, - displaying a reference object, - acquiring a first image comprising the reference object and at least one body of the user, - detecting and measuring a calibration length from the reference and obtaining a calibration distance separating the camera and the reference object, - detecting and measuring at least one first reference length relative to the at least one body part, - prompting the user to get in a second position, - acquiring a second image comprising the at least one body part, - detecting and measuring at least one second reference length (PL') in the second image, and - obtaining the test distance (DT).