Optical Position Sensing Grating Layout for Harmonic Suppression
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Solution Overview
Problem
Existing position measurement systems face challenges in achieving high accuracy due to signal-distorting influences such as unwanted subharmonics, harmonics, and 2D spatial frequencies, particularly when using binary gratings instead of ideal sinusoidal gratings.
Innovation Solution
A position measuring system with a detector arrangement and scanning grating design that includes mirror-symmetrical detector regions, phase-shifted detector elements, and a combined amplitude-phase grating to suppress undesirable diffraction orders, ensuring reliable 2D angle measurement over a large distance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional detector arrangements are used in position measurement systems, then the system structure is simple, but signal distortion occurs due to unwanted subharmonics, harmonics, and 2D spatial frequencies
Solution Approach 1:
The detector arrangement is divided into multiple detector regions (first and second detector regions) with specific geometric configurations. Each region contains detector elements arranged in a structured pattern, allowing separate processing of different spatial frequency components to eliminate signal distortion while maintaining measurement precision.
Solution Approach 2:
The detector regions are designed with asymmetric geometric configurations relative to the scanning grating lines. The first detector region has a specific arrangement of detector elements that creates an asymmetric response pattern, which when combined with the scanning grating, selectively filters out unwanted harmonics and subharmonics from the measurement signal.
2Reliability
If the detector arrangement uses complex mirror-symmetrical regions with multiple axes of symmetry, then signal distortion is suppressed, but the device complexity increases
Solution Approach 1:
Multiple detector regions with different geometric configurations are merged into a single integrated detector arrangement. The first and second detector regions are combined in such a way that their combined response provides both harmonic suppression and maintains sufficient signal strength, achieving reliable measurement without requiring separate complex detection systems.
Solution Approach 2:
The detector arrangement is designed to perform multiple functions simultaneously: detecting the primary measurement signal, filtering out harmonics and subharmonics, and maintaining signal strength across varying distances. The mirror-symmetrical configuration with multiple axes of symmetry enables the same structure to achieve both signal quality improvement and distortion suppression.
3Object-generated harmful factors
If the scanning grating uses combined amplitude-phase structure, then unwanted diffraction orders are suppressed, but manufacturing precision requirements increase
Solution Approach 1:
The scanning grating is designed with local variations in its structure, where different regions have different amplitude and phase characteristics. The combined amplitude-phase structure creates local zones that selectively suppress specific diffraction orders while maintaining transmission of the desired measurement signal, achieving harmful factor suppression with manageable manufacturing precision requirements.
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 system significantly enhances measurement accuracy by filtering out signal distortions, maintaining sufficient signal strength over a wide distance range, and enabling precise 2D spatial position determination.
Implementation Method 1
a scanning grating and an optoelectronic detector arrangement, the light-sensitive surfaces of which are oriented towards the scanning grating
Implementation Method 2
an optoelectronic detector arrangement whose light-sensitive surfaces are oriented in the direction of the scanning grating
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The present invention relates to a position measurement system for determining spatial position information. It comprises at least one light source and at least one optical receiving unit, the receiving unit having a scanning grating and an optoelectronic detector arrangement whose light-sensitive surfaces are oriented towards the scanning grating. The detector arrangement has two detector regions arranged in a detection plane in a mirror-symmetrical manner with respect to a first axis of symmetry which passes through the center of the detector arrangement in the detection plane, the first axis of symmetry being orthogonal to the longitudinal direction of the detector regions. The two detector regions each have the shape of an isosceles acute-angled triangle, the vertices of which are oriented with the apex angle towards the center of the detector arrangement (Fig. 2a).