Optical Scanning Device Light Blocking Member Ghost Light
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Solution Overview
Problem
In optical scanning devices, especially in image forming apparatuses like laser beam printers, unwanted light (ghost light) from one imaging lens system can pass through another, causing image density fluctuations due to installation errors, which existing solutions like antireflection films are difficult to apply on plastic lenses and light blocking members may fail to intercept effectively.
Innovation Solution
The optical scanning device is designed with two scanning units where one unit includes a light blocking member to intercept unwanted light, and the other unit has an imaging optical element with positive refracting power in the sub-scan section, ensuring effective blocking of unwanted light even with installation errors, by positioning the light blocking member strategically between the deflecting means and the imaging optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light blocking member is used to intercept unwanted light, then unwanted light can be blocked, but installation errors cause the unwanted light to deviate from the predicted light path and reach the scan surface
Solution Approach 1:
The patent introduces a new dimension (the third imaging optical element with positive refracting power) to redirect the unwanted light path. By adding this optical element, the system creates an additional light path modification that ensures unwanted light is blocked even when installation errors occur, effectively solving the problem in a higher-dimensional optical space.
Solution Approach 2:
The third imaging optical element acts as an intermediary between the fourth imaging optical element and the light blocking member. This intermediary element with positive refracting power modifies the light path of unwanted light, ensuring it reaches the light blocking member for effective interception, thereby mediating the interaction between the blocking member and unwanted light.
2Object-affected harmful factors
If antireflection film is deposited on lens surfaces to reduce unwanted light, then reflection can be reduced, but this is difficult to apply to plastic lenses used for light-weighting
Solution Approach 1:
The patent extracts the antireflection function from the lens coating process and replaces it with a structural solution using the third imaging optical element and light blocking member combination. This extraction allows the system to achieve unwanted light reduction without requiring antireflection film deposition on plastic lenses, thus solving the manufacturing difficulty.
Solution Approach 2:
The patent replaces the chemical process of antireflection film deposition with a mechanical/optical structural solution involving the third imaging optical element and light blocking member. This substitution eliminates the need for complex film deposition processes on plastic lenses while achieving the same effect of reducing unwanted light.
3Volume of moving object
If the structure is made more complicated to reduce size, then the overall system size is reduced, but installation precision of optical elements decreases
Solution Approach 1:
The patent incorporates the third imaging optical element with positive refracting power as a preemptive measure to compensate for potential installation errors. This element is designed in advance to handle deviations in unwanted light paths caused by installation inaccuracies, providing a buffer that maintains system performance despite reduced precision in compact configurations.
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 ensures high-quality image formation by effectively blocking unwanted light, reducing image density fluctuations, and maintaining image quality despite installation errors, without the need for antireflection films on plastic lenses.
Implementation Method 1
unwanted light reflected at an optical surface of a fourth imaging optical element
Implementation Method 2
an optical surface of a third imaging optical element through which unwanted light reflected at the optical surface of the fourth imaging optical element and directed to the scan surface at the one scanning unit side passes has a positive refracting power in the sub-scan section
Data Source
AI summary
An optical scanning device includes two scanning units which are disposed opposed to each other with a scanning deflector arranged therebetween, wherein one scanning unit has first and second imaging optical elements while the other scanning unit has third and fourth imaging optical elements, wherein the one scanning unit includes a light blocking member for intercepting unwanted light reflected at an optical surface of the fourth imaging optical element, wherein the third imaging optical element is provided at a light path between the fourth imaging optical element and the first light blocking member, and wherein the third imaging optical element has a positive refracting power in the sub-scan section through which unwanted light reflected at the optical surface of the fourth imaging optical element passes.