Telecentric Optical System for Robot Encoder Accuracy
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Solution Overview
Problem
Existing encoder systems in robots with turnable joint sections face accuracy issues due to fluctuations in the distance between the imaging element and the pattern, leading to deterioration in detection accuracy, especially when there is asymmetrical weight distribution.
Innovation Solution
Incorporating a telecentric optical system between the imaging element and the mark, which maintains consistent image forming magnification even if the distance fluctuates, and using oblique illumination to improve contrast and durability of the mark.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical system is used in the encoder, then the structure is simple and cost is low, but image forming magnification changes when the distance between the imaging element and the mark fluctuates, causing deterioration in detection accuracy
Solution Approach 1:
The patent applies a telecentric optical system which changes the optical parameters (magnification characteristics) to be insensitive to distance fluctuations. The telecentric design ensures that the chief rays are parallel to the optical axis, making the magnification constant regardless of object distance changes, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent addresses the dynamic nature of the distance fluctuation caused by asymmetrical weight distribution and robot arm movement. By using a telecentric optical system, the design accommodates these dynamic distance changes without requiring active compensation mechanisms, maintaining detection accuracy throughout the range of motion
2Measurement precision
If the distance between the imaging element and the mark is kept constant, then detection accuracy is maintained, but this is difficult to achieve when there is asymmetrical weight distribution in the robot arm
Solution Approach 1:
Instead of trying to maintain constant distance (mechanical solution), the patent changes the optical parameter (magnification) to be invariant with respect to distance changes. The telecentric optical system achieves this by making the magnification dependent on the focal length rather than the object distance, thereby eliminating the need for precise mechanical positioning
3Measurement precision
If a telecentric optical system is used, then image forming magnification remains consistent despite distance fluctuations, but the optical system becomes more complex and costly
Solution Approach 1:
The patent changes the optical design parameters to achieve telecentricity, which provides consistent magnification. While this does increase optical complexity, it eliminates the need for expensive active compensation mechanisms, precision mechanical assemblies, and frequent calibration procedures, making the overall system more cost-effective in the long term
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 reduces detection accuracy deterioration, allows for a smaller and less costly optical system, and enhances image quality by maintaining consistent magnification and improving contrast.
Implementation Method 1
The encoder includes a telecentric optical system disposed between the imaging element and the mark
Data Source
AI summary
A robot includes a base, a robot arm provided to be turnable around a turning axis with respect to the base, and an encoder including a mark configured to turn around the turning axis according to the turning of the robot arm and an imaging element configured to image the mark, the encoder detecting a state of the turning of the robot arm using a signal output from the imaging element. The encoder includes a telecentric optical system disposed between the imaging element and the mark.