Scanning Optical Apparatus Temperature Compensation
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Solution Overview
Problem
Scanning optical apparatuses face challenges in maintaining focal point stability due to temperature changes, particularly when using plastic lenses, leading to image plane shifts that affect image quality in electrophotographic image forming systems.
Innovation Solution
The apparatus incorporates an illumination optical system with distinct refractive and diffractive powers in both main and sub-scanning directions, along with a holding member with a controlled coefficient of linear expansion, to minimize image plane shifts caused by temperature changes. This system includes a diffraction lens with a focal length between 10 to 30 mm, and specific power ratios to optimize temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plastic lens is used in the illumination optical system to reduce cost, then manufacturing cost is reduced, but the focal point shifts due to temperature changes
Solution Approach 1:
The patent changes the material parameter from conventional plastic to a resin with a specific coefficient of linear expansion (3.0×10^-5 to 9.5×10^-5). This parameter change allows the lens to compensate for temperature-induced focal shifts while maintaining the cost benefits of using a molded resin lens instead of glass
Solution Approach 2:
The patent employs a composite optical system combining the illumination optical system with the scanning optical system, where the holding member made of specific resin material works in conjunction with the plastic lens to achieve temperature compensation. This composite approach allows the system to benefit from both low-cost plastic lens manufacturing and stable focal point positioning
2Reliability
If the coefficient of linear expansion of the holding member is too high, then temperature compensation is improved, but the dimensions of the apparatus change excessively
Solution Approach 1:
The patent specifies a precise range for the coefficient of linear expansion (3.0×10^-5 to 9.5×10^-5) of the holding member resin. This controlled parameter change ensures sufficient temperature compensation capability while preventing excessive dimensional changes that would occur with higher expansion coefficients
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
The solution effectively suppresses image plane shifts within ±3 mm across varying temperatures, ensuring stable image formation and improved performance by balancing refractive and diffractive powers and managing linear expansion coefficients.
Implementation Method 1
The illumination optical system focuses the beam of light near the deflector in a sub-scanning direction and makes the same into a parallel or nearly parallel beam in the main scanning direction
Implementation Method 2
the illumination optical system may include a refractive surface and a diffractive surface so that an undesirable shift of the focal point (image plane shift) due to change in temperature is suppressed
Data Source
AI summary
In a scanning optical apparatus, an illumination optical system has a diffractive power φdM in a main scanning direction, a diffractive power φdS in a sub-scanning direction, a refractive power φnM in the main scanning direction, and a refractive power φnS in the sub-scanning direction. A ratio φnM/φdM in the main scanning direction for a focal length fi in a range of 10-30 mm satisfies: g2(fi)≦φnM/φdM≦g1(fi), where A(Z)=(3.532×107)Z2+3023Z+0.7010, B(Z)=(5.719×107)Z2+4169Z+0.7678, C(Z)=(1.727×107)Z2+3244Z+0.4217, D(Z)=(1.373×108)Z2+3232Z+1.224, g1(fi)=fi{D(Z)−B(Z)}/20−0.5D(Z)+1.5B(Z), g2(fi)=fi{C(Z)−D(Z)}/20−0.5C(Z)+1.5A(Z), and a ratio φnS/φdS in the sub-scanning direction satisfies: φnS/φdS<1.3.