Scanning Optical Apparatus Diffractive Refractive Thermal Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Scanning optical apparatuses face challenges in maintaining focal point stability due to temperature changes, particularly when using plastic lenses, leading to undesirable image plane shifts, which affect the performance of electrophotographic image forming systems.
Innovation Solution
The apparatus incorporates a housing with a specific coefficient of linear expansion and an illumination optical system with a combination of refractive and diffractive surfaces, ensuring a balanced ratio of refractive to diffractive power, along with a scan lens that focuses the beam into a dot-like image, to minimize image plane shifts caused by temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plastic lens is used in the illumination optical system, then cost is reduced, but the focal point shifts due to temperature changes
Solution Approach 1:
The patent applies parameter changes by combining refractive and diffractive surfaces with specific power ratios that compensate for thermal expansion. The diffractive surface has a negative thermal expansion coefficient that counteracts the positive thermal expansion of the plastic lens, maintaining focal point stability across temperature changes while using cost-effective plastic materials.
Solution Approach 2:
The illumination optical system uses a composite structure combining refractive surfaces and diffractive surfaces in a single lens element. This composite approach allows the lens to simultaneously provide focusing power and temperature compensation, achieving both cost reduction through plastic construction and reliability through thermal stability.
2Reliability
If the ratio of refractive power to diffractive power is optimized for temperature compensation, then image plane shift is reduced, but the optical system design becomes more complex
Solution Approach 1:
The patent merges the functions of temperature compensation and optical focusing into a single illumination optical system element. By integrating both refractive and diffractive surfaces in one component, the design achieves image plane stability without requiring separate compensation mechanisms, thereby limiting complexity while maintaining reliability.
3Ease of manufacture
If a resin housing with high coefficient of linear expansion is used, then manufacturing cost is reduced, but temperature compensation performance deteriorates
Solution Approach 1:
The patent utilizes thermal expansion principles by selecting a resin housing with a specific coefficient of linear expansion that works synergistically with the diffractive surface's negative thermal expansion. This combination creates a balanced thermal response that maintains optical performance while using cost-effective resin materials for the housing.
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 effectively limits image plane shifts to within ±1 mm in the main scanning direction and ±4 mm in the sub-scanning direction, even with temperature variations of ±30°C, ensuring stable performance across a range of temperatures.
Implementation Method 1
The illumination optical system has at least one rotation-symmetric diffractive surface
Implementation Method 2
The illumination optical system has at least one anamorphic refractive surface
Data Source
AI summary
In a scanning optical apparatus, an illumination optical system has a diffractive power φdM and a refractive power φnM in a main scanning direction, and a ratio φnM/φdM in the main scanning direction for a focal length fi in a range of 10-22 mm satisfies: g2(fi)≤φnM/φdM≤g1(fi), where A(Z)=(1.897×107)Z2+6744Z+0.5255, B(Z)=(2.964×107)Z2+5645Z+0.6494, C(Z)=(3.270×107)Z2+3589Z+0.5250, D(Z)=(5.016×107)Z2+4571Z+0.8139, g1(fi)=fi{D(Z)−B(Z)}/12−5D(Z)/6+11B(Z)/6, g2(fi)=fi{C(Z)−D(Z)}/12−5C(Z)/6+11A(Z)/6g2(fi)=fi{C(Z)−A(Z)}/12−5C(Z)/6+11A(Z)/6.