Resin Lens Diffractive Surface Beam Waist Stabilization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional optical scanning devices face challenges in maintaining high-density, high-speed image formation due to issues like increased power consumption, noise, heat generation, and durability degradation, particularly with resin lenses that exhibit significant fluctuations in surface curvature, thickness, and refractive index with temperature changes and wavelength variations, leading to image degradation and increased beam-spot diameter.

Innovation Solution

The optical scanning device incorporates a first and second optical system, where at least one of the systems includes a resin lens with a diffractive surface, where the power of the diffractive portion and refractive portion cancel each other out, stabilizing the beam waist position and reducing temperature-induced fluctuations, and employs a diffractive surface with a step structure to simplify machining and reduce heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If resin lenses are used to reduce cost, then manufacturing cost is reduced, but image quality degrades due to large fluctuations in surface curvature, thickness, and refractive index with temperature and wavelength changes

Engineering Contradiction:

Improvemanufacturing costVSAvoidimage quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent combines resin lens material with diffractive optical surfaces to create a composite optical element. The resin provides cost advantages and flexibility, while the diffractive surface structure compensates for temperature-induced refractive index changes, maintaining image quality across varying conditions.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces diffractive surface structures with specific groove patterns and depths that create wavelength-dependent optical path differences. These structural parameters are designed to counteract the temperature-dependent refractive index changes of the resin material, stabilizing the focal position across temperature variations.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If glass lenses are used to maintain image quality, then image quality is maintained, but manufacturing cost increases

Engineering Contradiction:

Improveimage qualityVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive glass lenses with resin lenses that have diffractive surfaces, achieving similar optical performance at lower cost. The resin material allows for more economical manufacturing processes while the diffractive structure provides the necessary temperature compensation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the inherent thermal stability of glass with an active optical compensation mechanism using diffractive surfaces. Instead of relying on material properties alone, the optical path is controlled through structured surface features that actively compensate for thermal effects.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If polygon mirror rotates at high speed to increase scanning speed and density, then image formation speed and density increase, but power consumption, noise, heat generation, and durability degradation increase

Engineering Contradiction:

Improveimage formation speedVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent modifies the optical parameters of the scanning system by introducing diffractive surfaces that alter the optical path length and focusing characteristics. This allows for optimized beam waist positions and reduced sensitivity to rotational speed variations, enabling effective scanning at lower speeds with reduced power consumption and heat generation.

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

This configuration achieves stable beam-spot diameter and reduces image degradation by canceling temperature-induced changes in the beam waist position, enhancing the durability and cost-effectiveness of the optical scanning device while maintaining high-resolution image formation.

Implementation Method 1

the diffractive surface includes a diffractive portion and a refractive portion, and is in a shape so that a power of the diffractive portion and a power of the refractive portion cancel each other

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

the diffractive surface includes a diffractive portion and a refractive portion, and is in a shape so that a power of the diffractive portion and a power of the refractive portion cancel each other

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS8077369B2Optical scanning device, optical writing device, and image forming apparatus

Publication Date: 2011.12.13 RICOH CO LTD

AI summary

An optical scanning device includes a first optical system for guiding light beams emitted from a plurality of light emitting units to an optical deflector, and a second optical system for focusing the light beams to optically scan a surface to be scanned. At least one of the first optical system and the second optical system includes a resin lens having a diffractive surface. The diffractive surface includes a diffractive portion and a refractive portion. A power of the diffractive portion and a power of the refractive portion cancel each other.