Optical Imaging Assembly for Infusion Pump Distortion Correction
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Solution Overview
Problem
Existing optical imaging systems for measuring fluid flow in medical infusion pumps face challenges due to coarse measurement granularity, optical distortion from cylindrical drip chambers, and issues with splashes and condensation, which affect the accuracy of droplet volume measurement and fluid flow rate calculation.
Innovation Solution
An optical imaging assembly that corrects for optical distortion using a combination of cylindrical, acylindrical, and spherical or aspherical lens elements, is telecentric in object space, and has an f-number of 1.5 or less, ensuring that droplets on the infusion tube walls are out of focus and the measurement is independent of the object-to-lens distance, thereby improving the accuracy of fluid flow rate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple lens is used for imaging the pendant drop, then the device complexity is reduced, but optical distortion from the cylindrical drip chamber cannot be corrected
Solution Approach 1:
The optical system is divided into multiple lens elements (first lens element with cylindrical surface, second lens element with aspherical surface, third lens element with spherical surface) arranged in sequence. Each lens element addresses specific optical aberrations introduced by the cylindrical drip chamber, progressively correcting distortion while maintaining manageable system complexity through modular design.
Solution Approach 2:
The patent employs lens elements with specifically curved surfaces including cylindrical and aspherical geometries. The first lens element has a cylindrical surface to correct meridional distortion, while the second and third elements have aspherical and spherical surfaces respectively to address other optical aberrations, thereby achieving comprehensive distortion correction.
2Measurement precision
If the imaging system uses a fast aperture to resolve droplet details, then measurement precision improves, but splashes and condensation on the infusion tube walls become more prominent
Solution Approach 1:
The second lens element incorporates an aspherical surface that works in conjunction with the cylindrical surface of the first lens element to correct optical aberrations. This aspherical surface specifically addresses field curvature and distortion issues that would otherwise cause splashes and condensation artifacts to appear prominent in the image.
Solution Approach 2:
The optical system adjusts parameters including the f-number (set to 1.5 or less for fast aperture) and the curvature radii of lens surfaces to optimize the balance between resolving droplet details and minimizing the visibility of harmful artifacts. The specific combination of lens parameters allows the system to achieve both high measurement precision and reduced artifact impact.
3Device complexity
If the imaging assembly is not telecentric, then the device complexity is reduced, but measurement accuracy changes with varying object-to-lens distance
Solution Approach 1:
The optical system uses multiple lens elements arranged in sequence, with the third lens element specifically positioned and configured to provide telecentricity. This segmented approach allows the telecentric property to be achieved through the combined optical power and geometry of the lens sequence rather than requiring a single complex telecentric lens.
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
The solution provides accurate and precise measurement of fluid flow rates by effectively correcting optical distortions and maintaining image quality, even with varying object distances and presence of artifacts, enhancing the reliability of fluid flow monitoring in medical infusion systems.
Implementation Method 1
The imaging assembly employs combinations of cylindrical or acylindrical, and spherical or aspherical lens elements to correct optical distortion and other aberrations
Data Source
AI summary
An optical imaging assembly configured to obtain an image of an object. The assembly includes a light-transmissive sleeve arranged on an optical axis and configured to enclose the object. Four refractive elements are arranged in series on the optical axis and each have an input surface and an output surface. An aperture stop is disposed on the optical axis between the third and fourth refractive elements. The input surface of the third refractive element, the output surface of the third refractive element, the input surface of the fourth refractive element, the output surface of the fourth refractive element, of a combination of the foregoing have radial symmetry.