Diffractive Lens Thermal Compensation for Optical Scanning
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Solution Overview
Problem
Conventional optical scanning devices face challenges in maintaining temperature stability due to uneven temperature distributions within the device, which disrupt the balance between wavelength changes of the light source and the scanning optical system, leading to geometric aberrations and focus deviations.
Innovation Solution
The optical scanning device incorporates a diffractive lens with a diffractive surface configured to provide excessive correction power for the scanning optical system, ensuring that the deviation amount of the in-focus position by the diffractive optical element is larger or smaller than that of the scanning optical system, thereby compensating for temperature-induced focus deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a diffractive lens is used to achieve high precision and reduced size, then the optical characteristic precision is improved and device size is reduced, but the device becomes more sensitive to temperature changes causing geometric aberrations and focus deviations
Solution Approach 1:
The patent applies parameter changes by intentionally designing the diffractive lens with specific parameters (diffraction angle, focal length) that create a compensatory effect. The diffractive lens is designed to have a focal length that changes in opposition to the scanning optical system's focal length change with temperature, thereby compensating for thermal aberrations and focus deviations.
Solution Approach 2:
The patent converts the harmful temperature-induced focus deviation into a beneficial compensatory effect. By designing the diffractive lens with specific parameters, the wavelength change caused by temperature increase is transformed from a harmful factor into a useful compensation mechanism that counteracts the focal length change of the scanning optical system.
2Stability of the object's composition
If the diffractive lens is designed with strong negative dispersion to compensate for wavelength changes, then temperature stability is improved, but the focus position deviation from the scanning optical system increases
Solution Approach 1:
The patent carefully adjusts the parameters of the diffractive lens, specifically the diffraction angle and focal length, to achieve the optimal balance. The diffractive lens is designed with a focal length that is a specific fraction (1/2 to 2 times) of the scanning optical system's focal length, creating a compensatory effect that stabilizes focus position across temperature variations.
Solution Approach 2:
The patent applies partial action by providing just enough correction power in the diffractive lens to compensate for the scanning optical system's temperature-induced focus deviation. The diffractive lens is designed with a focal length that provides sufficient compensation without over-correcting, maintaining precise focus position while achieving temperature stability.
3Device complexity
If conventional optical elements are used to maintain simplicity, then device complexity is reduced, but temperature stability deteriorates due to inability to compensate for wavelength changes
Solution Approach 1:
The patent applies multi-functionality by designing the diffractive lens to perform multiple functions simultaneously: it acts as both a focusing element and a temperature compensation mechanism. The diffractive lens with its specific parameters (diffraction angle, focal length) provides both optical focusing and compensates for wavelength changes due to temperature, eliminating the need for separate compensation components.
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 enhances the temperature stability of the optical scanning device, reducing residual focus position deviations and enabling stable optical scanning without increasing component count or cost, even under uneven temperature distributions.
Implementation Method 1
at least one surface of the lenses is formed with a diffractive optical surface
Implementation Method 2
a first optical system that converts the light flux from the coupling optical system in a main scanning direction into a parallel light and that converges the light flux in a sub-scanning direction onto a deflecting unit
Implementation Method 3
a scanning optical system that concentrates the light flux deflected by the deflecting unit
Implementation Method 4
a scanning optical system that concentrates the light flux deflected by the deflecting unit on the scanning surface
Data Source
AI summary
A temperature of a scanning optical system is different from a temperature of a light source when an optical scanning device is in operation, and when the both temperatures are assumed to be equal, a diffractive surface of a diffractive optical element is set according to a magnitude relationship between both temperatures when the optical scanning device is in operation such that a deviation amount of an in-focus position of the light flux by the diffractive optical element becomes larger or smaller than a deviation amount for canceling a deviation amount of an in-focus position of the light flux by the scanning optical system.