Optical Angle Detector Using Freeform Beam Shaping
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Solution Overview
Problem
Optical angular position detectors face challenges in achieving high signal-to-noise ratio and linearity due to the limited homogeneity of wide-angle LEDs and increased sensitivity to radial and axial movements, leading to reduced measurement accuracy.
Innovation Solution
The use of a beam shaping element with a non-planar, non-spherical surface, such as a truncated cone, to redirect and reflect light onto photo sensors, optimizing light utilization and reducing sensitivity to axial and radial shifts, while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wide-angle LED is positioned close to photo sensors to maximize light incidence, then the signal-to-noise ratio is improved, but the detector becomes more sensitive to radial and axial movements of the shaft
Solution Approach 1:
A beam shaping element is introduced as an intermediary component between the LED light source and the photo sensors. This element redirects and shapes the light beams, allowing the LED to be positioned at a distance from the sensors while still achieving effective light coupling. The beam shaping element mediates the optical path, resolving the contradiction between maximizing light incidence and minimizing sensitivity to shaft movements.
Solution Approach 2:
The patent changes the spatial parameters of the optical system by using a beam shaping element to redirect light at specific angles. This allows optimization of the light path geometry, enabling the LED to be positioned optimally relative to the sensors while maintaining stable illumination conditions that are less sensitive to shaft movements.
2Reliability
If the LED is positioned far from photo sensors, then sensitivity to radial and axial movements is reduced, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The beam shaping element serves as a mediator that enables effective light transmission over larger distances. By shaping and redirecting the light beams, it maintains high light intensity at the sensors even when the LED is positioned farther away, thus preserving the signal-to-noise ratio while reducing sensitivity to shaft movements.
Solution Approach 2:
The beam shaping element introduces a new dimension to the optical path by redirecting light at controlled angles. This spatial manipulation allows the system to achieve effective light coupling without requiring minimal distance between LED and sensors, thereby decoupling the relationship between positioning and sensitivity.
3Measurement precision
If multiple optical elements are introduced to improve light homogeneity, then measurement accuracy is improved, but the device complexity and overall size increase
Solution Approach 1:
The beam shaping element is designed to perform multiple functions simultaneously: it shapes the light beams, redirects them at optimal angles, and contributes to the compact mechanical structure of the detector. This multi-functionality allows the system to achieve improved measurement accuracy without proportionally increasing device complexity.
Solution Approach 2:
The beam shaping element is integrated into the mechanical structure of the detector, merging optical and mechanical functions. By combining the beam shaping functionality with the structural support and positioning mechanisms, the patent reduces the number of separate optical elements needed while maintaining measurement accuracy.
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 approach enhances the signal-to-noise ratio and linearity of the position detector, ensuring accurate angular position measurement with improved insensitivity to shaft movements and maintaining a compact, space-saving setup.
Implementation Method 1
a beam shaping element (7), in particular a freeform beam shaping element, having a non-planar, non-spherical surface, by which the light is reflected on its way to the detector element
Data Source
AI summary
A position detector for determining the rotation angle of an element which is rotatable around an axis of rotation (A) comprises a light source (3), a detector element (18, 19, 20, 21) arranged around the axis of rotation (A) for detecting light radiation emitted by the light source (3), a beam reshaping element (7, 207) arranged between the light source (3) and the detector element (18, 19, 20, 21) such that light from the light source (3) is directed towards the detector element (18, 19, 20, 21), and a light-blocking element (5) positioned between the beam reshaping element (7, 207) and the detector element (18, 19, 20, 21) such that it can rotate around the axis of rotation (A) together with the rotatable element whereby, depending on the rotation angle, the incidence of light on different partial regions of the detector element (18, 19, 20, 21) is prevented. The beam reshaping element (7, 207) comprises a freeform surface (6, 206) at which the light from the light source (3) is reflected on its way to the detector element (18, 19, 20, 21).