Optical Scanning Unit Thermal Focus Compensation
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Solution Overview
Problem
Temperature variations cause focus movement issues in electro-photographic image forming apparatuses due to changes in refractive indexes and light wavelengths, leading to improper focusing and reduced image quality.
Innovation Solution
An optical scanning unit is designed with a first optical device comprising a refraction unit and a diffraction unit, where the power ratio of the refraction unit to the diffraction unit satisfies 0.5<φr/φd<1.3, and the thermal expansion coefficients of the optical device and supporting unit are optimized to compensate for focus movement, using a plastic injection molding method for manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical devices are used without temperature compensation, then the device complexity is low, but focus movement occurs due to temperature changes causing improper focusing and reduced image quality
Solution Approach 1:
The patent combines a refraction unit and a diffraction unit into a single integrated first optical device. The refraction unit has power φr and the diffraction unit has power φd, with their power ratio φr/φd satisfying 0.5<φr/φd<1.3. This merged structure compensates for focus movement caused by temperature changes while maintaining a relatively simple overall device structure.
Solution Approach 2:
The first optical device uses a composite optical structure combining refractive and diffractive elements. The refraction unit and diffraction unit work together with their powers in a specific ratio range to compensate for thermal focus shifts, effectively using composite optical principles to resolve the contradiction between reliability and complexity.
2Reliability
If the power ratio of refraction unit to diffraction unit is not optimized, then the manufacturing process is simpler, but focus movement compensation is insufficient leading to reduced image quality
Solution Approach 1:
The patent specifies a parameter range for the power ratio φr/φd between the refraction unit and diffraction unit, where 0.5<φr/φd<1.3. By controlling this parameter within the specified range, the system achieves effective focus movement compensation. The supporting unit's thermal expansion coefficient A2 is also controlled relative to the first optical device's coefficient A1, with (1−(f1/f2))×0.182/A11/f2))×0.25, to further optimize temperature compensation.
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 compensates for focus movement caused by temperature changes, ensuring accurate focusing and improved image quality by maintaining the power balance between the refraction and diffraction units within specific ratios, thereby minimizing print movement.
Implementation Method 1
a refraction unit and a diffraction unit, a ratio of φr/φd satisfies the equation: 0.5<φr/φd<1.3
Implementation Method 2
a refraction unit and a diffraction unit, a ratio of φr/φd satisfies the equation: 0.5<φr/φd<1.3
Implementation Method 3
a first optical device that collimates light radiated from the light source
Implementation Method 4
a first optical device that collimates light radiated from the light source
Data Source
AI summary
An optical scanning unit that includes a first optical device that forms collimated light from light radiated from a light source, a second optical device that focuses the collimated light onto a deflector, and an imaging optical device that focuses light deflected by the deflector onto an exposure object. The optical scanning unit further includes a refraction unit and a diffraction unit, and the power of the refraction unit is φr, the power of the diffraction unit is φd, and the ratio φr/φd is such that 0.5<φr/φd<1.3.