Laser Scanning Unit Aperture Layout for Mirror Surface Detection
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Solution Overview
Problem
Existing laser scanning units in electrophotographic image forming apparatuses face issues with erroneous detection of beam light reflected by the polygon mirror, leading to incorrect identification of target mirror surfaces and subsequent scanning errors.
Innovation Solution
The laser scanning unit incorporates a reflective optical sensor and a light receiving element, with a detection aperture positioned to avoid internally reflected light, ensuring accurate detection of the target mirror surface by employing a cover with strategically placed apertures to minimize interference from internally reflected light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection aperture is positioned to detect reflected light from the rotation shaft, then the reflective optical sensor can identify the target mirror surface, but internally reflected light from the beam light may reach the sensor and cause erroneous detection
Solution Approach 1:
The patent extracts and removes the harmful internally reflected light from the detection path by strategically positioning the detection aperture in an area where such light cannot reach after multiple reflections. This separates the useful detection function from the harmful interference, allowing accurate detection without erroneous signals.
Solution Approach 2:
The cover with its specifically positioned detection aperture acts as an intermediary element that mediates between the beam light and the reflective optical sensor. The aperture's placement in a region avoiding internally reflected light paths allows it to transmit only the desired detection light while blocking harmful reflections.
2Object-affected harmful factors
If the cover completely encloses the polygon mirror and motor, then external contaminants are blocked, but detection light and reflected light paths may be blocked preventing sensor operation
Solution Approach 1:
The cover is segmented with specifically positioned apertures - a detection aperture for the reflective optical sensor and a scanning aperture for the beam light. This segmentation allows the cover to provide overall protection while maintaining necessary optical pathways, balancing enclosure benefits with operational requirements.
Solution Approach 2:
The cover exhibits local quality variations through strategically positioned apertures with specific characteristics. The detection aperture is located in an area avoiding internally reflected light, while the scanning aperture accommodates beam light paths. Each aperture's local properties are optimized for its specific function while maintaining overall protective enclosure.
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 prevents erroneous processing by effectively distinguishing between detection light and internally reflected light, ensuring precise control over the scanning beam light and accurate formation of electrostatic latent images.
Implementation Method 1
a reflective optical sensor... emits detection light toward the rotation shaft through the detection aperture and detects reflected light of the detection light
Implementation Method 2
a plurality of mirror surfaces configured to reflect the beam light emitted from the light source
Implementation Method 3
a light receiving element... detects scanning beam light, which is the beam light sent for scanning through the scanning aperture
Data Source
AI summary
A cover covers the periphery of a polygon mirror and a motor, and has a detection aperture formed at a specific position around a portion of a rotation shaft where a to-be-detected portion is formed. An reflective optical sensor is disposed outside the cover so as to face the detection aperture. The detection aperture is formed in an area where internally reflected light, which is the beam light reflected toward the inner surface of the cover on each of the plurality of mirror surfaces, can reach after at least two specular reflections on the inner surface of the cover when viewed in an axial direction along the rotation shaft.