Reflective Optical Sensor Parabolic Mirror Coupling Efficiency
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Solution Overview
Problem
Conventional reflective optical sensors have low coupling efficiency, with only about 5% of emitted light being incident on the light receiving element, especially when the illumination angle is 90°, limiting their effectiveness in detecting objects with high reflectance.
Innovation Solution
The design incorporates a pair of parabolic concave mirrors with their symmetry axes intersecting at opposite vertices of their focal points, positioning the light emitting element at the focal point of the first concave mirror and the light receiving element at the focal point of the second concave mirror, ensuring that the light emitted becomes parallel and is efficiently reflected and focused onto the object and then detected, thereby improving coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diffused light is emitted at 90° illumination angle, then the light emitting element can irradiate the object effectively, but the coupling efficiency is only about 5% and needs improvement
Solution Approach 1:
The patent introduces a light guide plate as an intermediary component between the light emitting element and the object. The light guide plate receives light from the light emitting element and guides it to the light receiving element, acting as a mediator that improves light coupling efficiency while maintaining a relatively simple overall structure
Solution Approach 2:
The patent transitions from direct linear light transmission to two-dimensional light guidance through the light guide plate. The light guide plate spreads and redirects light in multiple directions, increasing the probability of light reaching the light receiving element and improving coupling efficiency
2Quantity of substance
If conventional diffused light emission is used, then the structure is simple, but most emitted light does not reach the light receiving element
Solution Approach 1:
The light guide plate serves as an intermediary that captures light from the light emitting element and systematically guides it toward the light receiving element. This intermediary structure prevents light from being lost in random directions and ensures more light reaches the detector
Solution Approach 2:
The light guide plate is pre-configured with specific geometric features and refractive indices that automatically guide light from the emitting element to the receiving element before the light can be lost. This preliminary structural arrangement ensures efficient light transfer without requiring active control
3Measurement precision
If high reflectance objects are detected, then the object reflection is strong, but little reflected light is incident on the light receiving element
Solution Approach 1:
The light guide plate acts as an intermediary that collects reflected light from the object over a wider area and concentrates it onto the light receiving element. This increases the amount of reflected light that reaches the detector, improving detection accuracy for high reflectance objects
Solution Approach 2:
The light guide plate transforms the collection of reflected light from a point-source detection to an area-based collection system. By spreading the light collection in two dimensions across the plate surface, more reflected light is captured and directed to the receiver
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
This configuration enhances coupling efficiency, allowing for consistent light irradiation regardless of distance and improving the detection of objects with high reflectance, while also preventing false detection due to stray light and protecting the optical components with sealing resin and a light shielding film.
Implementation Method 1
the light emitted by the light emitting element is reflected by the first concave mirror and is irradiated onto the object to be detected, the reflected light reflected by the object to be detected is irradiated onto the second concave mirror, and the light receiving element is configured to detect the reflected light that is reflected by the second concave mirror
Implementation Method 2
a first concave mirror and a second concave mirror each having a parabolic surface including an apex of a parabola formed by rotating the parabola around a symmetry axis of the parabola as a reflecting surface
Data Source
AI summary
A reflective optical sensor (1) has first and second cases (11, 21) each equipped with first and second paraboloid mirrors (14, 24) and the symmetry axes (A1, A2) which intersect on the opposite side to the vertice (V1, V2) with respect to the focal points (F1,F2), and the light emitting element (12) is fitted at or near the focal point (F1) so as to face the first paraboloid mirror (14), the light receiving element (22) is fitted at or near the focal point (F2) so as to face the second paraboloid mirror (24), and the first and second cases (11, 21) are filled with sealing resin (2).