Optical Needle Tip Detection in Autoinjectors
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Solution Overview
Problem
Automated handheld injection devices (autoinjectors) face challenges in accurately determining the location of a hypodermic needle tip within the device, leading to potential errors in injection depth due to manufacturing tolerances and variable placement of medicament containers.
Innovation Solution
An optical detector system using two LEDs and a photodiode detector positioned on a printed circuit board, with light emitted by the LEDs being guided by a lens to create distinct light planes along the needle path, allowing for precise determination of the needle tip position through ratiometric measurement and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional mechanical or visual methods are used to determine needle tip location, then the device structure remains simple, but measurement precision deteriorates due to manufacturing tolerances and variable container placement
Solution Approach 1:
The patent replaces mechanical or visual methods for determining needle tip location with an optical detection system. Two light sources illuminate the needle path, and a light detector measures light absorption or reflection changes as the needle moves, enabling precise measurement of needle tip position without mechanical contact or complex visual alignment.
Solution Approach 2:
The patent introduces light as an intermediary medium to detect needle tip position. Light sources emit light through the needle path, and the needle itself acts as an intermediary object that modulates the light signal based on its position. The light detector measures these modulated signals to determine needle tip location, using light as a non-contact measurement intermediary.
2Manufacturing precision
If manufacturing tolerances and variable container placement are not compensated, then the device structure remains simple, but injection depth accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the optical detector continuously monitors needle tip position during injection. The processor analyzes the detected light signals to determine actual needle position in real-time, comparing it against the intended injection depth. This feedback enables dynamic adjustment and compensation for manufacturing tolerances and container placement variations, ensuring accurate injection depth despite these variations.
Solution Approach 2:
The patent uses changes in light absorption or reflection parameters as the needle moves through different positions. By measuring these optical parameter changes, the system can determine needle tip location with high precision. The processor analyzes these parameter variations to compensate for manufacturing tolerances and achieve consistent injection depth accuracy across different devices and operators.
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 accurate detection of the needle tip position, mitigating errors associated with manufacturing tolerances and ensuring precise injection depths, even with variable placement of medicament containers.
Implementation Method 1
a light detector arranged to receive light reflected by the needle
Implementation Method 2
produce a first signal when reflected light emitted by the first light source is detected, and produce a second signal when reflected light emitted by the second light source is detected
Data Source
AI summary
A system determines the location of a tip of a hypodermic needle by moving a needle along a path, shining light from two sources onto respective portions of the path, and analysing signals received from the respective light sources that have been reflected by the needle.