Wide-Angle Projector Optics With Telecentric Reduction

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Solution Overview

Problem

Existing projection systems suffer from chromatic aberration and difficulty in achieving a wide angle of view due to the placement of a positive lens adjacent to the aperture diaphragm, leading to issues with luminous flux distribution and chromatic aberration.

Innovation Solution

A projection system design with a first lens group having negative and positive sub-groups, featuring a wide air gap between them, and a second lens group with a cemented lens configuration of negative, positive, and negative lenses, ensuring telecentric reduction and suppressing chromatic aberration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a positive lens is placed adjacent to the aperture diaphragm at the enlargement side, then the luminous flux output is widened and beam enlargement is facilitated, but chromatic aberration occurs in the positive lens

Engineering Contradiction:

Improveluminous flux outputVSAvoidchromatic aberration

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The first lens group is divided into two sub-groups: a first sub-lens group with negative power and a second sub-lens group with positive power. This segmentation allows the positive lens to be positioned at the reduction side rather than adjacent to the aperture diaphragm, thereby widening luminous flux output while avoiding chromatic aberration at the aperture location.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of placing the positive lens adjacent to the aperture diaphragm at the enlargement side (conventional approach), the patent inverts the arrangement by placing the positive lens at the reduction side and using negative lenses at the enlargement side. This inversion resolves the chromatic aberration issue while maintaining beam enlargement capability.

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If a wide air gap is provided between lenses at the enlargement side, then beam enlargement is facilitated, but the system length increases

Engineering Contradiction:

Improvebeam enlargementVSAvoidsystem length

Core Design Contradiction:

ProductivityVSLength of moving object

Solution Approach 1:

The patent redistributes the air gap distribution along the optical axis by placing the widest air gap at the reduction side rather than concentrating it at the enlargement side. This dimensional redistribution allows beam enlargement while maintaining a more compact overall system length.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If the half angle of view is increased beyond 40°, then wide angle projection is achieved, but optical aberration increases

Engineering Contradiction:

Improvehalf angle of viewVSAvoidoptical aberration

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different optical properties to different regions of the lens system: negative power lenses at the enlargement side for wide angle coverage, and positive power lenses at the reduction side for aberration control. This local differentiation enables half angle of view >40° while managing optical aberration through the cemented lens configuration.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The cemented lens at the reduction side combines multiple lens elements with different refractive indices and Abbe numbers (positive and negative lenses cemented together). This composite lens structure corrects chromatic aberration and other optical aberrations while maintaining the wide half angle of view capability.

Inventive Principle:

Principle #40Composite materials

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 a half angle of view greater than 40° while effectively managing chromatic aberration and maintaining compact size, with improved imaging performance and reduced chromatic aberration.

Implementation Method 1

a first lens group having refractive power, an aperture diaphragm, and a second lens group having refractive power sequentially from an enlargement side toward a reduction side

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

the second lens group includes a cemented lens, the cemented lens includes a first lens having negative power, a second lens having positive power, and a third lens having negative power sequentially from the enlargement side toward the reduction side

Methodology Applied

Scientific EffectChromatic aberration correction:

Data Source

PatentUS12443008B2Projection system and projector

Publication Date: 2025.10.14 SEIKO EPSON CORP

AI summary

A projection system includes a first lens group, an aperture diaphragm, and a second lens group. A reduction side of the second lens group is telecentric. The first lens group includes a first sub-lens group having negative power and a second sub-lens group having positive power. Between a lens located at the most reduction side of the first sub-lens group and a lens located at the most enlargement side of the second sub-lens group, an air gap wider than air gaps between the other lenses adjacent to each other is provided. A lens located at the most reduction side in the first lens group is a positive lens. A cemented lens of the second lens group includes a first lens having negative power, a second lens having positive power, and a third lens having negative power from an enlargement side toward a reduction side. ω>40.