Reflective Optical Sensor With Elliptical Mirrors for Light Coupling
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Solution Overview
Problem
Conventional reflective optical sensors have low coupling efficiency due to the majority of emitted light being diffused, resulting in a small amount of reflected light being incident on the light receiving element, even when the object has high reflectance.
Innovation Solution
The reflective optical sensor employs a configuration with a first and second concave mirror, each with a partial rotational ellipse surface, where one focal point of each mirror serves as a common focal point, and the other focal points do not overlap, focusing the emitted light onto the object and then onto the light receiving element, thereby enhancing the coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diffused light is emitted onto the object, then the object can be illuminated, but most of the light is wasted and coupling efficiency is low
Solution Approach 1:
The patent employs a concave mirror with an elliptical cross-section (rotational ellipse surface) to focus diffused light. The curved reflective surface redirects scattered light rays toward the focal point where the light receiving element is positioned, converting wasted diffused light into concentrated detectable signals and improving coupling efficiency.
Solution Approach 2:
The concave mirror acts as an intermediary optical element between the light source and the light receiving element. It mediates the light path by collecting diffused light from the object and redirecting it to the focal point, enabling efficient light transfer without direct line-of-sight between emitter and receiver.
2Reliability
If a light blocking wall is used to prevent direct light from reaching the receiver, then false detection is prevented, but the structure becomes more complex
Solution Approach 1:
The patent replaces the light blocking wall with a concave mirror having an elliptical cross-section. The curved geometry naturally blocks direct light paths while simultaneously focusing reflected light to the focal point. This single curved element performs both functions (blocking and focusing) that previously required separate components, reducing structural complexity.
Solution Approach 2:
The concave mirror serves multiple functions: it acts as a light blocking barrier to prevent direct illumination of the receiver, and simultaneously functions as a focusing element to concentrate reflected light at the focal point. This multi-functionality eliminates the need for separate light blocking walls and focusing mirrors, simplifying the overall structure.
3Productivity
If the light emitting element directly illuminates the object, then simple detection is possible, but coupling efficiency remains low at about 3%
Solution Approach 1:
The patent introduces a concave mirror with rotational ellipse surface geometry to focus diffused light onto the light receiving element positioned at the focal point. This curved optical element concentrates scattered light rays, dramatically improving coupling efficiency from 3% to significantly higher levels while maintaining a relatively simple single-component structure.
Solution Approach 2:
The patent changes the optical parameters by introducing a focusing element that alters the light path geometry. The elliptical mirror transforms the diffused light distribution into a concentrated beam at the focal point, changing the effective coupling parameter from low (3%) to high efficiency without fundamentally redesigning the entire optical system.
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 significantly improves the coupling efficiency, allowing for higher photocurrent output and preventing misdetection by focusing the diffused light and reflected light effectively, while also enabling non-contact detection and protection against collisions.
Implementation Method 1
the first concave mirror reflects the light to the object to be detected which is positioned at or near the common focal point
Implementation Method 2
The light emitted from the first focal point is focused on the common focal point by the first concave mirror
Implementation Method 3
the second concave mirror reflects light reflected by the object to be detected, and the light receiving element is configured to detect light reflected by the second concave mirror at the second focal point
Implementation Method 4
most of this reflected light is reflected and focused at the second focal point of the second concave mirror
Data Source
AI summary
A reflective optical sensor (1A) having a light emitting element (3) and a light receiving element (4) detects an object (OB) to be detected by reflected light reflected by the object (OB), and the sensor(1A) has an case (2) in which first and second concave mirrors (5, 6) are fitted, each of which has a reflective surface comprising a partial concave surface of a rotational ellipse surface rotated around a major axis, one focal point of the first concave mirror (5) and one focal point of the second concave mirror (6) are coincide to be a common focal point (F0), and the light emitting element (3) is fitted at the focal point (F1), the light receiving element is fitted at the focal point (F2).