Diffraction Grating Optical Beam Scanning Temperature Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical beam scanning devices face challenges in correcting optical characteristics due to temperature changes, leading to color shift and registration issues, particularly in the sub scanning direction, which are not adequately addressed by existing techniques.
Innovation Solution
The implementation of a rotary deflector and a post-deflection optical system with a shared optical device configuration, including fθ lenses and a diffraction grating on at least one optical device, allows for proper alignment and correction of optical characteristics by adjusting the incident positions of luminous fluxes in the sub scanning direction, thereby reducing temperature-induced shifts and aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffractive optics is provided to correct chromatic aberration of magnification in a pre-deflection optical system, then the length of scanning line in the main scanning direction is prevented from being varied by wavelength change, but color shift occurs due to temperature rise in the image forming apparatus
Solution Approach 1:
The patent moves the diffractive optics from the pre-deflection optical system to the post-deflection optical system, changing the spatial dimension and timing of where chromatic aberration correction is applied. This allows the diffractive optics to work on already-deflected beams from multiple light sources, enabling simultaneous correction of chromatic aberration and compensation for thermal expansion effects in the sub-scanning direction
Solution Approach 2:
The patent utilizes the wavelength-dependent diffraction effect to change beam spacing dynamically. By designing the diffractive optics with specific diffraction powers in both main-scanning and sub-scanning directions, the system adjusts beam positions to compensate for thermal expansion, transforming the harmful wavelength variation into a useful correction mechanism
2Object-affected harmful factors
If lenses with negative power are provided in a pre-deflection optical system to change beam spacing, then color shift in the main scanning direction is restrained, but the number of lenses must be increased
Solution Approach 1:
The patent combines multiple functions into a single diffractive optics component in the post-deflection system. This single element simultaneously corrects chromatic aberration of magnification, adjusts beam spacing in the sub-scanning direction, and compensates for thermal expansion effects, replacing what would otherwise require multiple separate lenses and correction elements
Solution Approach 2:
The patent replaces the mechanical approach of using multiple physical lenses with a diffractive optical element that achieves the same beam spacing adjustment through diffraction. This substitution reduces the number of components while maintaining or improving correction effectiveness
3Stability of the object's composition
If correction of color shift due to thermal expansion is focused on the sub scanning direction, then beam alignment in that direction is improved, but color shift occurs due to temperature rise in the image forming apparatus
Solution Approach 1:
The patent applies different diffraction powers to different directions: negative diffraction power in the main-scanning direction to correct chromatic aberration of magnification, and positive diffraction power in the sub-scanning direction to compensate for thermal expansion. This directional differentiation allows simultaneous correction of both types of color shift without interference
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 minimizes color shift and registration errors due to temperature changes, improving the stability and accuracy of the optical beam scanning process, and reduces the number of optical components required, leading to cost and manufacturing efficiency gains.
Implementation Method 1
a diffraction grating is formed at least on one of an incident surface and an exit surface of the luminous flux in the optical device
Implementation Method 2
a rotary deflector configured to reflect and deflect an incident luminous flux by plural reflection surfaces arrayed in a direction of rotation
Data Source
AI summary
A technique is provided which enables proper correction of optical characteristics in accordance with change in ambient temperature.An optical beam scanning device capable of causing a luminous flux from a light source to scan a photoconductive surface of each of plural photoconductors in a main scanning direction, includes: a polygon mirror 80 which reflects and deflects an incident luminous flux by plural reflection surfaces arrayed in a direction of rotation, and thereby causes the incident luminous flux to scan in the main scanning direction; and a post-deflection optical system A which includes plural optical devices and which guides the luminous flux reflected and deflected by each of the plural reflection surfaces in the polygon mirror 80, to a photoconductive surface of a photoconductor to which the luminous flux should be guided. Of the plural optical devices forming the post-deflection optical system A, in at least one optical device on which a principal ray of the luminous flux which should be guided to each of the plural photoconductors becomes incident at different incident positions from each other in a sub scanning direction orthogonal to the main scanning direction, a diffraction grating is formed at least on one of an incident surface and an exit surface of the luminous flux in the optical device.