Tilted Lens Optical System for Compact Wide-Angle Imaging

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Solution Overview

Problem

Conventional optical systems for wearable cameras face challenges in compactness and the generation of invalid imaging regions when attempting to achieve a wide-angle view with a single viewpoint, particularly due to the geometric constraints of hyperboloidal mirrors and the need for additional mirrors to reduce size.

Innovation Solution

An optical system comprising a main convex paraboloid mirror, a second-reflection concave paraboloid mirror, and a lens group where the lens's optical axis is tilted relative to the mirrors' rotational axes, allowing for a compact design that captures a full angle of view without invalid regions and maintains a single viewpoint during zooming and pan-tilt motions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If a hyperboloidal mirror is used to achieve a wide angle of view with a single viewpoint, then the angle of view is improved, but the distance between the mirror and lens becomes large, compromising compactness

Engineering Contradiction:
Improveangle of viewVSAvoiddistance between mirror and lens
Core Design Contradiction:
Area of moving objectVSLength of stationary object

Solution Approach 1:

The patent introduces a second reflection mirror to deflect the light path in the radius direction, adding another dimension to the optical path folding. This allows the light to travel a longer effective distance within a compact physical footprint, achieving both wide angle of view and compact size simultaneously

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Length of stationary object

If the curvature of the hyperboloid is increased to reduce the distance between mirror and lens, then compactness is improved, but image focus deteriorates due to out-of-focus images

Engineering Contradiction:
Improvedistance between mirror and lensVSAvoidimage focus
Core Design Contradiction:
Length of stationary objectVSManufacturing precision

Solution Approach 1:

The patent divides the reflection function into two separate mirrors: a first reflection mirror (hyperboloidal portion) and a second reflection mirror. This segmentation allows each mirror to have optimized curvature for its specific function, maintaining proper image focus while achieving compact overall size through the folded optical path

Inventive Principle:
Principle #1Segmentation

3Ease of operation

If the optical axis of the lens coincides with the axis of the convex mirror, then the alignment is simplified, but an invalid imaging region is generated within the angle of view

Engineering Contradiction:
Improvealignment simplicityVSAvoidvalid imaging region
Core Design Contradiction:
Ease of operationVSArea of moving object

Solution Approach 1:

The patent intentionally tilts the optical axis of the lens relative to the axis of the convex mirror, creating an asymmetric configuration. This asymmetry eliminates the invalid imaging region that would otherwise be generated, ensuring the entire angle of view is effectively utilized while maintaining a compact design

Inventive Principle:
Principle #4Asymmetry

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 solution enables a compact optical system capable of wide-angle image capture with a single viewpoint, reducing the size of the mirror-radius direction and minimizing invalid imaging areas, while maintaining image quality and viewpoint consistency across zooming and pan-tilt operations.

Implementation Method 1

a main mirror having a shape of a portion of a convex paraboloid which includes an opening in a center and is rotationally symmetric

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 2

a second-reflection mirror which further reflects light reflected by the main mirror, the second-reflection mirror having a shape of a portion of a concave paraboloid

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 3

at least one lens which forms an image of the light reflected by the second-reflection mirror

Methodology Applied
Scientific EffectRefraction: Refraction

Data Source

PatentEP2418530B1Optical system and imaging device
Publication Date: 2015.03.11 PANASONIC HOLDINGS CORP
  • EP2418530B1 patent drawingFigure 1
  • EP2418530B1 patent drawingFigure 2A~2B
  • EP2418530B1 patent drawingFigure 3A~3B

AI summary

An optical system includes: a main mirror (11) having a shape of a portion of a convex paraboloid which includes an opening in a center and is rotationally symmetric; a second-reflection mirror (12) which further reflects light reflected by the main mirror (11), and has a shape of a portion of a concave paraboloid which is rotationally symmetric; at least one lens which forms an image of the light reflected by the second-reflection mirror (12); and a lens barrel (14) holding the at least one lens, and a position of a front principal point of the at least one lens coincides with a focal position of the second-reflection mirror (12), and an optical axis of the at least one lens is tilted with respect to a rotational axis of each of the convex paraboloid and the concave paraboloid.