Lateral Lens Actuation in Folded Optic Autofocus
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Solution Overview
Problem
Traditional autofocus mechanisms are challenging to implement in folded optic image sensor arrays due to height limitations and the need for ultra-high resolution across a small form factor, especially in mobile devices, where the focal length and field of view requirements are stringent, and existing methods can increase the system height and alter optical axis positions.
Innovation Solution
The implementation of a two-part lens system with a movable portion that can move laterally within the mechanical tolerances of the folded optic system, using a guide rail and actuator to focus light onto the image sensor while maintaining the relative positioning of optical elements, allowing for optical zoom and increased resolution across the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional autofocus mechanisms are used in folded optic image sensor arrays, then focusing capability is achieved, but system height increases and optical axis positioning is altered
Solution Approach 1:
The lens assembly is divided into two distinct parts: a stationary portion that remains fixed relative to the image sensor, and a movable portion that can be independently actuated for focusing. This segmentation allows the movable portion to be positioned and controlled without increasing the overall system height, as it operates within the existing optical path geometry rather than requiring axial movement of the entire lens assembly.
Solution Approach 2:
The stationary portion of the lens assembly is integrated with the folded optic structure, combining the focusing mechanism with the existing optical elements. This merging allows the movable portion to be actuated independently while maintaining stable optical axis positioning, as the stationary portion provides a fixed reference frame for the optical path.
2Length of moving object
If the focal length is shortened to maintain low profile, then device thickness is reduced, but image circle diameter decreases and resolution is compromised
Solution Approach 1:
The lens assembly incorporates a movable portion that can be dynamically actuated to adjust focus, enabling the system to achieve proper focus with a shorter focal length lens. This dynamic adjustment compensates for the reduced image circle diameter that results from the shorter focal length, maintaining image resolution despite the low-profile design.
3Manufacturing precision
If more optical elements are added to increase resolution, then image quality improves, but system complexity and space requirements increase
Solution Approach 1:
The patent introduces lateral movement of the movable lens portion as a new degree of freedom for focusing, rather than relying solely on axial movement. This dimensional change allows the system to achieve focus adjustment without adding multiple optical elements along the optical axis, reducing system complexity while maintaining the ability to incorporate multiple lenses for increased resolution.
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
This solution enables the creation of low-profile image capture devices with improved autofocus capabilities, maintaining high image performance and allowing for more complex optics, such as multiple lenses, without increasing the system height, and achieving effective focal lengths and resolution across the entire field of view.
Implementation Method 1
a lens assembly including at least one stationary lens positioned between the secondary light folding surface and the image sensor, the at least one stationary lens having a first surface mechanically coupled to the optical element and a second surface mechanically coupled to the image sensor, and at least one movable lens positioned between the primary light folding surface and the optical element
Implementation Method 2
an actuator configured to move the at least one movable lens to focus light propagating through the lens assembly onto the image sensor
Implementation Method 3
The lens system additionally includes a stationary portion of the lens assembly. In some embodiments, two or more movable lens assembles can be incorporated to implement Zoom and AF. The stationary portion of the lens assembly comprises a field corrector lens placed in close proximity to the image sensor
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Embodiments of imaging systems and methods of autofocusing are disclosed, for example, using a folded optics configuration. One system includes at least one camera configured to capture a target image scene, including an image sensor comprising an array of sensor elements, a primary light folding surface configured to direct a portion of received light in a first direction, and an optical element having a secondary light folding surface directing light in a second direction. The system can also include a lens assembly having at least one stationary lens positioned between the secondary light folding surface and the image sensor, the at least one stationary lens having a first surface mechanically coupled to the optical element and a second surface mechanically coupled to the image sensor, at least one movable lens positioned between the primary light folding surface and the optical element, and an actuator configured to move the at least one movable lens to focus light propagating through the lens assembly onto the image sensor.