Multi-Beam Optical Scanning Diffractive Lens Temperature Compensation
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Solution Overview
Problem
Multi-beam optical scanning devices face challenges in maintaining stable beam spots and scanning line intervals due to ambient temperature variations and wavelength differences between light sources, leading to degraded image quality, especially when using resin lenses which exhibit larger changes in curvature, thickness, and refractive index compared to glass lenses.
Innovation Solution
The implementation of a multi-beam optical scanning device with a specific optical system configuration, including a first and second lens, where the second lens is an anamorphic element with a diffracting surface, and a housing design that stabilizes the optical axis, along with aperture positioning and focal length relationships, to minimize beam spot shifts and maintain consistent scanning line intervals across different wavelengths and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resin lenses are used to reduce cost, then manufacturing cost decreases, but beam spot size stability deteriorates due to larger changes in curvature, thickness, and refractive index caused by temperature variation and wavelength changes
Solution Approach 1:
The patent applies parameter changes by introducing a diffracting surface with specific power characteristics that compensates for temperature-induced parameter changes in resin lenses. The diffracting surface power is designed to vary with wavelength in a manner that counteracts the refractive index and curvature changes of the resin lens, thereby maintaining beam spot size stability despite using cost-effective resin materials.
Solution Approach 2:
The patent employs composite materials by combining resin lens material with a diffracting surface structure. This composite approach leverages the cost and fabrication advantages of resin while the diffracting surface component provides temperature compensation functionality, achieving both low cost and stable beam spot characteristics.
2Reliability
If the number of lenses is increased to compensate for temperature variations, then beam spot stability improves, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into a single optical element by integrating a diffracting surface directly onto the lens. This combined structure provides both focusing functionality and temperature compensation, eliminating the need for separate compensation lenses and reducing overall system complexity while maintaining beam spot stability.
Solution Approach 2:
The lens with the diffracting surface serves multiple functions simultaneously: it performs the primary focusing function of the lens while also providing temperature compensation for beam spot size. This multi-functionality reduces the total number of components needed in the optical system.
3Reliability
If a diffracting surface is provided on a scanning lens for correction, then temperature-induced beam spot changes are reduced, but fabrication time and cost increase due to the broad region requiring the diffracting surface
Solution Approach 1:
The patent applies local quality by concentrating the diffracting surface fabrication on a localized region rather than requiring it across the entire lens surface. The diffracting surface is applied only in the specific area where light beams pass through, reducing fabrication complexity and cost while maintaining effective temperature compensation.
4Ease of manufacture
If resin optical elements are used in the scanning optical system, then manufacturing cost decreases, but beam spot position shift due to temperature change of the optical system behind the deflector cannot be sufficiently reduced
Solution Approach 1:
The patent applies preliminary anti-action by designing the diffracting surface power to preemptively counteract the beam spot position shifts that would occur due to temperature changes in downstream optical elements. The diffracting surface is configured to produce an opposing effect that compensates for anticipated thermal drift, maintaining beam spot position stability despite using inexpensive resin optical elements.
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 achieves stable and small beam spots and consistent scanning line intervals, enhancing image quality by effectively compensating for temperature and wavelength-induced changes, while reducing costs associated with glass lenses and simplifying fabrication.
Implementation Method 1
at least the second lens includes a diffracting surface having a power
Implementation Method 2
a second lens that guides the light beams from the first lens to the deflection unit, the second lens being an anamorphic element having power at least in a sub scanning direction
Data Source
AI summary
A multi-beam scanning device is disclosed that is able to realize a stable and small beam spot and realize stable scanning line intervals between plural light beams. The multi-beam optical scanning device includes a first optical system which has a first lens for coupling the light beams from the light sources, and a second lens which is an anamorphic element having power at least in a sub scanning direction and for guiding the light beams from the first lens to the deflection unit; and a second optical system. At least the second lens includes a diffracting surface having power. Magnifications of the whole optical system in a main scanning direction (βm0) and in a sub scanning direction (βs0), and a magnification of the second optical system (βs2) in a sub scanning direction satisfy |βm0|>|βs0|, and |βs0|>|βs2|, and the power of the diffracting surface of the first lens in the main scanning direction (P1m), that in the sub scanning direction (P1s), and the power of the diffracting surface of the second lens in the sub scanning direction (P2s) satisfy |P2s|>|P1m| and |P2s|>|P1s|.