Optical Scanner Slit Aspect Ratio for Angle Resolution
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Solution Overview
Problem
Conventional optical scanning devices experience reduced resolution in pivot-angle detection when the distance between the mirror unit and the photoreflector is decreased, as a wider range of pivot angles are incident on the photoreflector, leading to lower detection accuracy.
Innovation Solution
The optical scanning device incorporates a light-blocking unit with a slit having an increased aspect ratio, where the length of the slit in the optical path direction is greater than or equal to a predetermined value, allowing only detection light at a specific angle to pass through and be detected, while attenuating light at other angles, thereby enhancing resolution even at short distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between the mirror unit and the photoreflector is decreased, then the device size is reduced, but the resolution of pivot-angle detection deteriorates
Solution Approach 1:
The patent applies local quality by giving different dimensional characteristics to different parts of the slit. Specifically, the slit length in the optical path direction is made significantly larger than the slit width in the pivot angle direction, creating an asymmetric aspect ratio. This local dimensional differentiation allows the slit to selectively pass light at specific angles while blocking others, thereby maintaining high detection resolution even when the overall device size is reduced through shorter distances between components.
Solution Approach 2:
The patent changes the geometric parameters of the slit, specifically setting the aspect ratio (length in optical path direction divided by width in pivot angle direction) to be equal to or greater than a predetermined value. This parameter change transforms the slit from a simple opening into an angular filter that maintains detection precision regardless of the distance between the mirror unit and photoreflector, thus resolving the contradiction between compact size and measurement precision.
2Device complexity
If the distance between the slit and the mirror unit is decreased, then the device structure is simplified, but the angle range of light that can pass through the slit increases, causing lower detection resolution
Solution Approach 1:
The patent resolves this contradiction by applying local quality to the slit geometry. By making the slit length in the optical path direction much larger than the slit width in the pivot angle direction (aspect ratio ≥ predetermined value), the slit creates a localized angular acceptance window. This allows the device to maintain simple structure with short distances while the asymmetric slit geometry locally filters light angles, preventing the angle range from increasing excessively and maintaining detection resolution.
Solution Approach 2:
The patent employs asymmetry by designing the slit with a specific aspect ratio where the length in the optical path direction is significantly greater than the width in the pivot angle direction. This asymmetric geometry creates different light-passing characteristics in different directions: it allows light from a wide range of positions to pass through the long dimension while restricting the angular range through the narrow dimension, thus maintaining resolution despite simplified device structure.
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 enables high-resolution pivot-angle detection by suppressing detection light at angles other than the predetermined angle, improving the accuracy and intensity of the detected signal, even when the distance between the reflector and detector is short.
Implementation Method 1
The slit of the light-blocking unit has an aspect ratio where a length, in a direction along which the optical path extends, of the slit relative to a length, in a width direction along a pivoting direction of a reflector, of an opening end portion of the slit is equal to or greater than a predetermined value. The detecting unit is configured to detect a pivot angle of the reflector by receiving the detection light that passes through the slit.
Implementation Method 2
a pivotable reflecting unit, a light-emitting unit that emits a detection light toward the reflector, a detection unit that receives the detection light, which is reflected at the reflecting unit
Data Source
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AI summary
An optical scanning device (100) includes a reflector (101) that is pivotable, a light-emitter (102) that emits a detection light toward the reflector, a detector (103) that receives the detection light reflected at the reflector, and a light-blocking unit (104) that includes a slit (s) wherethrough the detection light passes. The light-blocking unit (104) is disposed on an optical path whereby the detection light reflected from the reflector advances to the detector. The slit (s) has an aspect ratio where a length of the slit in a direction in which the optical path extends relative to a length of the slit in a width direction is equal to or greater than a predetermined value. The width direction is along a pivoting direction of the reflector, of an opening end portion of the slit. The detector (103) is configured to detect a pivot angle of the reflector (101) by receiving the detection light that passes through the slit (s).