Asymmetric Five-Lens Optical System for Extended Depth of Field
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Solution Overview
Problem
Current optical systems for compact electronic devices, such as camera phones, face challenges in achieving extended depth of field (EDoF) with high resolution and a compact form factor, particularly in maintaining image sharpness for objects near the optical system while minimizing distortion and chromatic focal shift.
Innovation Solution
A five-lens or four-lens optical system design with specific refractive indices and aspheric surfaces, optimized for a total track length of less than 5.3 mm and f-numbers around 2.4 or 2.8, providing asymmetric modulation transfer functions and extended near-field resolution, which allows for improved image sharpness and reduced distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact optical system is designed for small electronic devices, then the device size is reduced, but the depth of field and image sharpness deteriorate
Solution Approach 1:
The optical system is divided into multiple lens elements (typically 5-7 elements) with different optical powers and functions. This segmentation allows each element to contribute to specific optical corrections, enabling compact size while maintaining image quality through distributed optical functionality across multiple components.
Solution Approach 2:
The patent employs asymmetric lens configurations where lens elements have different shapes, curvatures, and positions relative to the optical axis. This asymmetry enables optimized light path control for near-field objects while keeping the overall system compact, addressing both the size constraint and image sharpness requirement simultaneously.
2Device complexity
If the focal length is fixed for compact design, then the device complexity is reduced, but the depth of field range is limited
Solution Approach 1:
The patent utilizes changes in optical parameters such as refractive index, curvature radius, and lens spacing to achieve extended depth of field. By carefully selecting and adjusting these parameters in the fixed focal length system, the optical design maintains simplicity while expanding the acceptable focus range through optimized optical path control.
Solution Approach 2:
The optical system incorporates intermediary elements such as aspheric surfaces and specific lens configurations that act as mediators to extend the depth of field. These intermediary optical features modify light paths to maintain image sharpness across a broader range of object distances without requiring complex focusing mechanisms.
3Measurement precision
If high resolution sensors are used, then the image quality is improved, but the optical system precision requirements increase
Solution Approach 1:
The patent applies local quality optimization by designing specific lens elements with specialized characteristics (such as aspheric surfaces, specific refractive indices, or particular curvature profiles) at critical positions in the optical path. This localized optimization allows high-resolution imaging without requiring uniform high precision across all optical elements, thereby reducing overall manufacturing complexity.
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 proposed optical systems achieve significant improvements in image sharpness and resolution over traditional fixed focus camera optics, maintaining high performance across a range of focal shifts and wavelengths, making them suitable for small electronic devices.
Implementation Method 1
A five lens system can be provided having an f-number of about 2.4, and can result in an asymmetric modulation transfer function (MTF) that provides extended image sharpness or EDoF for objects relatively near to the optical system
Data Source
AI summary
Providing for a fixed focus optical system exhibiting extended depth of field is provided herein. By way of example, a compact and fast optical system that yields an asymmetric modulation transfer function (MTF) is disclosed. In some aspects, the asymmetric MTF results in extended depth of field for near field objects. Such a response can be particularly beneficial for small handheld cameras or camera modules having high resolution. According to some disclosed aspects, the resolution can be about 8 mega pixels. Additionally, the optical system can comprise four lenses in one aspect and five lenses in another, while remaining below about 5.3 mm total track length (TTL) for the respective systems. In at least one application, the disclosed optical systems can be employed for a high resolution compact camera, for instance in conjunction with an electronic computing device, communication device, display device, surveillance equipment, or the like.