Photoelectric Encoder Scheimpflug Alignment Compact Design
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Solution Overview
Problem
Photoelectric encoders with telecentric optical systems face issues with reduced light transmission and non-uniform contrast due to the insertion of a half mirror and optical axis inclination, leading to blurring and reduced signal detection efficiency.
Innovation Solution
A photoelectric encoder design where three planes from the main scale, the lens principal plane, and the light receiving element image plane intersect at a single point, satisfying the Scheimpflug rule, with equal angles between the main scale and lens planes and lens and image planes, and optionally using a second lens to adjust magnification and compensate for aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a half mirror is inserted in the telecentric optical system to redirect light, then the optical path can be folded to reduce system size, but the light transmission is reduced to 1/4 causing insufficient signal intensity
Solution Approach 1:
The patent removes the half mirror from the optical system entirely. Instead of folding the optical path with a half mirror, the system uses a direct linear arrangement of optical components (collimator lens, main lens, aperture) that achieves compactness without light loss. This extraction of the problematic component resolves the contradiction by eliminating the source of light attenuation while maintaining system compactness through optimized component spacing and arrangement.
Solution Approach 2:
The patent introduces an aperture as a key intermediary element positioned at the focal point of the main lens. This aperture serves multiple functions: it defines the telecentric optical path, controls light transmission uniformly across the field, and enables compact system design without requiring a half mirror. The aperture acts as a mediator that achieves both compactness and adequate light transmission by precisely controlling the optical path geometry.
2Volume of moving object
If the optical axis is inclined to reduce the air gap and make the optical system smaller, then the system size is reduced, but focus cannot be obtained uniformly across the entire image plane causing blurring and contrast reduction
Solution Approach 1:
The patent addresses the focus uniformity problem by carefully controlling the positional relationships and orientations of optical components in three-dimensional space. The collimator lens, main lens, and aperture are positioned with precise spacing and angular relationships that maintain uniform focus across the entire image plane even with reduced air gaps. This dimensional control allows compact system design without sacrificing image quality.
Solution Approach 2:
The patent optimizes specific optical parameters including the air gap distances, lens focal lengths, and aperture positioning to achieve both compact system size and uniform focus. By carefully adjusting these parameters - particularly the spacing between the collimator lens and main scale, the focal length of the main lens, and the position of the aperture at the focal point - the system achieves compact dimensions while maintaining focus uniformity and image contrast across the entire field of view.
3Volume of moving object
If the air gap between the main scale and lens is reduced to make the system smaller, then the optical system size is reduced, but the telecentric optical path control becomes difficult affecting measurement precision
Solution Approach 1:
The aperture positioned at the focal point of the main lens serves as a critical intermediary that maintains telecentric optical path accuracy even with reduced air gaps. The aperture physically constrains the light rays to pass through the correct optical path, ensuring that the principal rays remain parallel to the optical axis. This intermediary element compensates for the reduced spacing and maintains measurement precision.
Solution Approach 2:
The patent optimizes the air gap parameter to a specific value that balances system compactness with telecentric path control. By carefully selecting the distance between the main scale and the lens assembly, and positioning the aperture at the precise focal point, the system achieves compact dimensions while maintaining accurate telecentric optical paths for high-precision 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
This design ensures focus over the entire image plane, prevents contrast reduction, and allows for a smaller optical system while maintaining signal detection efficiency by aligning planes according to the Scheimpflug rule and using a second lens to compensate for distortions.
Implementation Method 1
a lens optical system including a lens (42) inserted between a main scale (20) and a light receiving element (34)
Implementation Method 2
three planes extended from a surface of the main scale (20), a principal plane of the lens (42), and an image plane of the light receiving element (34) satisfy the Scheimpflug rule
Implementation Method 3
a telecentric optical system including a lens and an aperture arranged at the focal position of the lens
Data Source
AI summary
A photoelectric encoder that has a lens optical system including a lens inserted between a main scale and a light receiving element. In the photoelectric encoder, three planes extended from a surface of the main scale, a principal plane of the lens, and an image plane of the light receiving element are disposed so as to intersect at a single point and satisfy the Scheimpflug rule. Focus can thereby be obtained over the entire image plane, so that a reduction in contrast is prevented, even if the optical axis is inclined to make an optical system smaller.