Scanning Optical System Asymmetric Aberration Compensation

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Solution Overview

Problem

Conventional miniaturized scanning optical systems face challenges with asymmetric aberration and reduced allowable margins for positional errors of optical elements due to the use of polygon mirrors and converging lenses, leading to sensitive optical performance and increased astigmatism.

Innovation Solution

A scanning optical system is designed with specific conditions to widen the allowable margin for positional errors, including a converging element, deflector, and scanning speed controlling element, configured to satisfy equations that maintain symmetric scanning trajectories and reduce aberration, allowing for favorable optical performance even in a compact size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a polygon mirror is employed as a deflector in a miniaturized scanning optical system, then the system size is reduced, but asymmetric aberration occurs due to deflection point shift during scanning

Engineering Contradiction:

Improvesystem sizeVSAvoidscanning trajectory symmetry

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent applies asymmetry by intentionally designing the fθ lens group with asymmetric power allocation to compensate for the symmetric scanning trajectory distortion caused by the polygon mirror. Specifically, the lens group has different refractive powers in different directions to counterbalance the deflection point shift effect, thereby achieving symmetric scanning performance despite the asymmetric nature of the polygon mirror deflection geometry.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes optical parameters by adjusting the power allocation of the fθ lens group and optimizing the incident angle of laser light on the polygon mirror. By modifying these parameters, the system compensates for the asymmetric aberration caused by the polygon mirror while maintaining a compact size. The specific parameter optimization includes adjusting lens curvature, glass composition, and incident angles to achieve the desired scanning symmetry.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the fθ lens group is designed with asymmetric power allocation to compensate for asymmetric aberration, then scanning trajectory symmetry is improved, but the allowable margin of positional error for optical elements is narrowed

Engineering Contradiction:

Improvescanning trajectory symmetryVSAvoidtolerance to positional error

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by pre-compensating for positional errors through the asymmetric power allocation design of the fθ lens group. The lens group is designed with built-in error compensation capabilities that cushion against the effects of minor misalignments and positional errors in optical elements. This design margin allows the system to maintain scanning trajectory symmetry even when optical elements are not perfectly positioned during assembly.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Length of stationary object

If converging light is used instead of parallel light in a miniaturized scanning optical system, then the back focus is shortened and system size is reduced, but asymmetric aberration is caused by deflection point shift

Engineering Contradiction:

Improveback focus lengthVSAvoidscanning trajectory symmetry

Core Design Contradiction:

Length of stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies asymmetry by designing the fθ lens group with asymmetric power allocation to compensate for the symmetric scanning trajectory distortion caused by the polygon mirror. The lens group has different refractive powers in different directions to counterbalance the deflection point shift effect, thereby achieving symmetric scanning performance despite the asymmetric nature of the polygon mirror deflection geometry.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

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 system achieves stable and symmetric scanning trajectories with reduced aberration and increased tolerance for positional errors, maintaining high optical performance while minimizing the impact of element misalignment, similar to systems using parallel light.

Implementation Method 1

a converging element configured to converge the laser light emitted by the light source in the predetermined scanning direction

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

a deflector configured to deflect the laser light converged by the converging element so as to scan the laser light on the scanned surface

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS7477436B2Scanning optical system

Publication Date: 2009.01.13 HOYA CORPORATION

AI summary

A scanning optical system configured to scan laser light on a scanned surface in a scanning direction, includes a light source emitting the laser light, a converging element converging the emitted laser light in the predetermined scanning direction, a deflector deflecting the converged laser light to scan the laser light on the scanned surface, and a scanning speed controlling element controlling the deflected laser light to be scanned at a constant scanning speed. The scanning optical system is configured to satisfy predetermined conditions.