Display Optical System Diffractive Surface Chromatic Aberration Correction

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Solution Overview

Problem

Existing display optical systems for electronic viewfinders struggle to effectively correct lateral chromatic aberration and astigmatism, particularly in peripheral areas distant from the optical axis.

Innovation Solution

Incorporating a diffractive surface with a controlled wavelength dispersion characteristic, specifically a metasurface, between the observation surface and the display surface, which controls the optical path difference functions to correct chromatic aberrations and astigmatism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a lens with strong positive refractive power is used to enable magnified image observation, then magnification capability is improved, but lateral chromatic aberration and astigmatism are generated

Engineering Contradiction:

Improvemagnification capabilityVSAvoidlateral chromatic aberration and astigmatism

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

A diffractive surface is introduced as an intermediary optical element between the positive and negative lenses. This diffractive surface acts as a mediator that provides negative dispersion to counteract the positive dispersion from the refractive lenses, thereby correcting lateral chromatic aberration while maintaining the magnification capability of the strong positive lens

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The optical system combines different optical mechanisms (refraction and diffraction) into a composite structure. The diffractive surface with its periodic microstructure creates diffractive optical effects that complement the refractive effects of the lenses, forming a hybrid optical system that achieves both magnification and aberration correction

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If conventional diffractive surfaces are used, then some chromatic aberration correction is achieved, but the wavelength dispersion characteristic cannot be sufficiently controlled

Engineering Contradiction:

Improvechromatic aberration correctionVSAvoidwavelength dispersion control

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent modifies the diffractive surface parameters by introducing a specific periodic structure with controllable pitch and depth. By changing these geometric parameters, the wavelength dispersion characteristic can be precisely controlled to achieve optimal correction of lateral chromatic aberration across different wavelength ranges, providing adaptability for various optical design requirements

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 display optical system achieves satisfactory correction of lateral chromatic aberration and astigmatism, improving optical performance across the entire field of view while maintaining a strong positive refractive power.

Implementation Method 1

a diffractive surface (or a metasurface) with a controlled wavelength dispersion characteristic

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a lens having strong positive refractive power for enabling the observer to observe a magnified image

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS20250076736A1Display optical system and display apparatus

Publication Date: 2025.03.06 CANON KK

AI summary

A display optical system includes a diffractive surface with a controlled wavelength dispersion characteristic. A predetermined inequality is satisfied.