Photoelectric Encoder Telecentric Mirror System
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Solution Overview
Problem
Photoelectric encoders with imaging optical systems face issues such as reduced light intensity and aberrations in regions distant from the optical axis due to increased curvature of lens surfaces when trying to reduce the overall size of the optical system, and existing reflective systems like the Offner relay suffer from contamination and complex assembly requirements.
Innovation Solution
A reflective both-side telecentric optical system is implemented using a spherical concave main mirror and a spherical convex sub-mirror with a specific radius ratio, along with light-restricting means to control the incident light and prevent contamination by integrating the optical surfaces, allowing for reduced size and improved optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the focal length of the lens is reduced to decrease the overall length of the optical system, then the size of the optical system is reduced, but the curvature of the lens surface is increased causing degradation of optical performance and reduction in light amount
Solution Approach 1:
The patent replaces the refractive lens system with a reflective optical system using mirrors. Specifically, it uses a combination of a concave mirror and a convex mirror to achieve the imaging function without requiring high-curvature lens surfaces, thereby maintaining optical performance while reducing system length.
Solution Approach 2:
The patent employs a folded optical path design where the light path is bent back on itself using mirrors. This allows the optical system to achieve a compact form factor in one dimension while maintaining the necessary optical path length through folding the path in perpendicular dimensions.
2Length of stationary object
If the focal length of the lens is reduced to decrease the overall length of the optical system, then the size of the optical system is reduced, but the amount of light in regions distant from the optical axis is reduced
Solution Approach 1:
The patent replaces the refractive lens with a reflective mirror system. Mirrors reflect light without absorbing it, and the reflective surfaces can be designed to maintain uniform illumination across the field of view, preventing the light reduction that occurs with high-curvature lenses in off-axis regions.
3Length of stationary object
If the Offner relay optical system is used to reduce the overall length of the optical system, then the size is reduced and light reduction is suppressed, but the mirror surfaces are exposed making them easily contaminated and requiring high-accuracy assembly
Solution Approach 1:
The patent integrates the light-restricting function directly into the mirror assembly structure. The mirrors are positioned and configured within a housing that provides both structural support and contamination protection, eliminating the need for separate exposed mirror components that require precise assembly.
Solution Approach 2:
The patent employs a housing structure that encloses the mirror surfaces, protecting them from contamination while allowing the optical path to function. This encapsulation approach prevents direct exposure of the mirrors to the environment.
4Length of stationary object
If the Offner relay optical system is used, then the overall length is reduced, but multiple separate components require high-accuracy assembly
Solution Approach 1:
The patent combines the light-restricting function with the mirror mounting structure into a single integrated assembly. This reduces the number of separate components that need to be aligned and assembled with high precision, simplifying the overall assembly process while maintaining the compact optical path.
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 solution prevents light reduction and aberrations in the field of view, specifies the numerical aperture, and simplifies assembly by integrating the optical components, reducing contamination risks and system size.
Implementation Method 1
a main mirror, which is a spherical concave mirror
Implementation Method 2
the main mirror and the sub-mirror fold an optical path of the light from the first planar reflective surface by reflecting the light from the first planar reflective surface 2n-1 times between the main mirror and the sub-mirror
Implementation Method 3
a sub-mirror, which is a spherical convex mirror and has a center that coincides with a center of the main mirror
Implementation Method 4
a first planar reflective surface, a main mirror, which is a spherical concave mirror, a sub-mirror, which is a spherical convex mirror and has a center that coincides with a center of the main mirror, and a second planar reflective surface
Data Source
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AI summary
A photoelectric encoder (1) includes a light source (2) that emits collimated light, a scale (3) on which the collimated light emitted by the light source (2) is incident, an imaging optical system (4) on which the collimated light that has passed through the scale (3) is incident and which emits the incident light as collimated light, and a light receiver (5) that receives the collimated light emitted by the imaging optical system (4). The imaging optical system (4) includes a main mirror (42), which is a spherical concave mirror, and a sub-mirror (43), which is a spherical convex mirror. The center of the spherical surface of the main mirror (42) coincides with the center of the spherical surface of the sub-mirror (43), and the ratio between the radii of the spherical surfaces is n:n-1 (n is an integer that is greater than or equal to 2). An optical path is folded by repeating reflection 2n-1 times between the main mirror (42) and the sub-mirror (43), and the reflection system constitutes a both-side telecentric optical system.