Four-Lens Folded-Path Imaging for Thin Telephoto Modules
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Solution Overview
Problem
The challenge of integrating high-resolution and high-performance camera modules into miniaturized mobile electronic devices is hindered by the increased total track length of telephoto lenses, which in turn increases the device's size.
Innovation Solution
An optical imaging system with a configuration of four lenses and a reflecting member, where the lenses are spaced apart along the optical axis, and specific optical characteristics are defined to maintain a narrow field of view and long total track length without increasing the device's thickness, using plastic materials with varying optical characteristics for the lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a telephoto lens with long focal length is used to achieve high resolution and high performance, then the total track length increases, but the device thickness increases
Solution Approach 1:
The patent introduces a reflecting member (mirror) to change the optical path from a straight line to a folded path. Light enters the objective lens, reflects off the mirror at an angle, and returns through the lens system to the image sensor. This dimensional change in the optical path allows the total track length to be achieved without increasing the device thickness in the direction perpendicular to the sensor plane.
Solution Approach 2:
The reflecting member is positioned within the space between the objective lens and the image sensor, effectively nesting the reflection function within the existing optical path volume. This allows the long focal length required for telephoto imaging to be accommodated within the limited thickness of the mobile device by folding the optical path back on itself.
2Measurement precision
If the total track length is increased to achieve higher resolution, then the device size increases, but miniaturization is required
Solution Approach 1:
By using a reflecting member to fold the optical path, the patent achieves a long total track length (TTL) within a compact volume. The light path is extended in the optical dimension while the physical footprint in the device volume is minimized through the folded configuration.
Solution Approach 2:
The patent employs plastic lens materials that can be molded with precise aspherical surfaces, allowing dynamic optimization of the optical path lengths and angles. The plastic material enables complex curved surfaces that efficiently guide light through the folded path while maintaining compact dimensions.
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 effectively maintains a narrow field of view and long total track length while preventing an increase in device thickness, enabling miniaturization without compromising imaging performance.
Implementation Method 1
a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses
Data Source
AI summary
An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by preset distances along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.