Single-Fold Optical Systems with Power Prisms for Compact Imaging

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Solution Overview

Problem

Conventional small cameras in mobile devices struggle to capture high-resolution, high-quality images due to limitations in optical systems, requiring larger image sensors while maintaining a compact form factor.

Innovation Solution

The implementation of a single fold optical system with a power prism and a lens stack, including anamorphic lenses to correct aberrations, reduces the Z-axis height and X-axis length, utilizing optical plastic or glass materials and total internal reflection to enhance imaging quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional double folded optical systems are used, then imaging quality can be maintained, but Z-axis height and X-axis length increase

Engineering Contradiction:
Improveimaging qualityVSAvoidZ-axis height and X-axis length
Core Design Contradiction:
Manufacturing precisionVSLength of stationary object

Solution Approach 1:

The patent combines the light-folding function and the optical power function into a single prism. The prism incorporates both a light-folding surface (reflective or refractive) and a power surface (curved surface providing optical convergence/divergence) integrated into one optical element, eliminating the need for separate folding elements and reducing overall system size while maintaining imaging quality

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The single prism performs multiple functions simultaneously: it folds the optical path (changing light direction) and provides optical power (converging or diverging light). This multi-functional design replaces what would traditionally require multiple separate optical components, achieving compactness without sacrificing imaging performance

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Manufacturing precision

If image sensor size is increased for higher resolution, then image quality improves, but camera form factor increases

Engineering Contradiction:
Improveimage resolutionVSAvoidcamera form factor
Core Design Contradiction:
Manufacturing precisionVSVolume of moving object

Solution Approach 1:

The patent uses folded optical paths to change the spatial arrangement of optical components. By folding the light path in non-linear dimensions, the optical system achieves longer effective focal lengths and larger imaging circles without increasing the linear dimensions of the camera module, enabling higher resolution sensors to be accommodated in compact form factors

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

3Manufacturing precision

If more optical elements are added to correct aberrations, then imaging quality improves, but device complexity increases

Engineering Contradiction:
Improveaberration correctionVSAvoidnumber of optical elements
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines multiple optical functions (light folding, power provision, and aberration correction) into a single integrated prism design. The prism's complex surface geometry (including both reflective/refractive folding surfaces and curved power surfaces) is optimized to correct aberrations such as astigmatism and field curvature while maintaining a compact single-element structure, reducing complexity compared to multi-element conventional designs

Inventive Principle:
Principle #5Merging (Combining)

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 single fold optical system achieves reduced thickness and length, enabling high brightness and high-resolution imaging in compact cameras, suitable for smartphones and tablets, while correcting aberrations caused by prism surfaces.

Implementation Method 1

a power prism with an aspherical object side surface to provide refractive power

Methodology Applied
Scientific EffectRefraction: Refraction

Implementation Method 2

utilizing optical plastic or glass materials and total internal reflection to enhance imaging quality

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

at least one anamorphic lens that is oriented to correct for aberrations including astigmatism caused by surface errors of the reflective surface of the prism(s)

Methodology Applied
Scientific EffectAstigmatism correction:

Data Source

PatentEP4158407B1Folded optical systems
Publication Date: 2025.10.08 APPLE INC
  • EP4158407B1 patent drawingFigure 1
  • EP4158407B1 patent drawingFigure 2
  • EP4158407B1 patent drawingFigure 3

AI summary

Single fold optical systems that include a power prism and a lens stack including two or more refractive lens elements. The single fold optical system may provide a long mechanical back focus without increasing the Z-height of the optical system. Providing power on the prism may reduce the optical total length and reduce the X-length of the optical system. The single folded optical systems may provide reduced Z-axis height and reduced X-axis length when compared to conventional double folded optical systems with similar optical characteristics. In addition, the optical systems may include an anamorphic lens that is oriented to correct for astigmatism caused by surface errors of the reflective surface of the prism.