Retroreflector Elements for Multi-Axis Position Detection
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Solution Overview
Problem
Existing optical position measuring devices require optical scanning from multiple sides to detect an object's position in multiple spatial degrees of freedom, which is not always feasible due to structural constraints and increases the object's mass with the need for deflection mirrors, and complex calculations are required for single-direction scanning solutions.
Innovation Solution
An optical position measuring device that uses a scanning plate with integrated diffractive retroreflector elements and scales on the object, allowing optical scanning from a single direction to detect movement in multiple degrees of freedom by superimposing partial beams of rays, eliminating the need for heavy deflection mirrors and complex calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical probing is performed from multiple sides to detect position in multiple degrees of freedom, then measurement precision is improved, but device complexity and manufacturing difficulty increase due to the need for deflecting mirrors and complex alignment
Solution Approach 1:
The patent combines multiple measurement functions into a single retroreflector element that integrates both the retroreflection function and the beam deflection function. The retroreflector contains multiple retroreflective surfaces arranged to deflect beams along different measurement directions, eliminating the need for separate deflecting mirrors and reducing system complexity while maintaining the capability to measure multiple degrees of freedom
Solution Approach 2:
The retroreflector element is designed to perform multiple functions simultaneously: it provides retroreflection to return the measurement beam to the source, and it contains multiple retroreflective surfaces that deflect the beam along different measurement directions. This multi-functional design eliminates the need for multiple separate components and simplifies the overall system architecture
2Measurement precision
If deflecting mirrors are added to the object for multi-directional scanning, then measurement capability is improved, but the object's mass increases
Solution Approach 1:
The patent merges the deflecting mirror functionality into the retroreflector element itself. The retroreflector contains multiple retroreflective surfaces that perform the beam deflection function that would otherwise require separate deflecting mirrors. This integration eliminates additional heavy components while maintaining the capability to detect motion in multiple directions
3Measurement precision
If optical scanning is performed from multiple sides, then complete position detection is achieved, but accessibility requirements increase making the solution inapplicable to certain designs
Solution Approach 1:
Instead of requiring multiple scanning directions as in conventional solutions, the patent inverts the approach by using a single scanning direction with a retroreflector that contains multiple retroreflective surfaces. These surfaces deflect the single incoming beam along different measurement directions, achieving complete spatial position detection while maintaining a single-sided scanning configuration that is adaptable to various design constraints
4Adaptability or versatility
If single-direction optical scanning is used to improve accessibility, then adaptability is improved, but calculation complexity increases to determine position signals
Solution Approach 1:
The retroreflector element is designed to automatically provide the correct beam deflection geometry through its physical structure. The multiple retroreflective surfaces are arranged in specific orientations that inherently encode the measurement direction information. This geometric encoding simplifies the calculation process compared to systems requiring complex software-based reconstruction from arbitrary multi-directional measurements
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 precise detection of an object's position in multiple spatial degrees of freedom with a compact system, reducing the need for complex adjustments and increasing accessibility, as only one side of the object needs to be optically accessible.
Implementation Method 1
a scanning plate (20), into which at least first and second retroreflector elements (21, 22) are integrated, wherein the first retroreflector element (21) extends parallel to the first direction of extension and the second retroreflector element (22) extends parallel to the second direction of extension and undergoes back reflection in the direction of the respective measuring scale via the partial beams incident on it from the first and second scales
Implementation Method 2
The retroreflector elements are designed as diffractive retroreflector elements, wherein several diffractive elements are arranged on a first side of the scanning plate and at least one reflector element is arranged on the opposite second side of the scanning plate
Data Source
Figure 1
Figure 2a~2b
Figure 2c
AI summary
The optical position measuring device has a light source and a material measure arranged at object (10), which extends along an extension direction and comprises division regions periodically arranged along the extension direction. Another material measure is arranged at the object and extends along another extension direction. A scanning plate (20) is provided, in which three retroreflector elements (21,22,23) are integrated. The former retroreflector element extends parallel to former extension direction and the later retroreflector element extends parallel to later extension direction.