Lateral Lens Motion 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, making it difficult to achieve both height constraints and performance requirements, especially with wide Field of View (FoV) lenses.
Innovation Solution
The implementation of a two-part lens system with a movable portion and a stationary field corrector lens, coupled with an actuator and guide rail, allows for lateral motion of the lens assembly within the folded optic system, maintaining image performance and enabling optical zoom and increased resolution across the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional autofocus mechanism is implemented in a folded optic image sensor array, then focusing capability is improved, but the height of the system increases and the optical axis positioning becomes unstable
Solution Approach 1:
The patent transitions from vertical lens movement (along the optical axis) to lateral lens movement (parallel to the imaging plane). This dimensional change allows the lens assembly to move sideways between the primary and secondary light folding surfaces, achieving focus adjustment without increasing the vertical height of the camera module. The guide rail mechanism constrains the motion to this lateral dimension, preventing tilt, roll, pitch, and yaw while maintaining stable optical axis positioning.
2Reliability
If the lens assembly is moved vertically to achieve focus, then focusing is improved, but the position of the optical axis changes relative to other cameras in the array
Solution Approach 1:
The patent changes the movement dimension from vertical (affecting optical axis position) to lateral (parallel to imaging plane). This ensures that during focusing, the optical axis remains vertically aligned and its position relative to other cameras in the array remains constant. The lateral motion along the guide rail does not alter the vertical projection of the optical axis, maintaining stable composition and alignment across the camera array.
Solution Approach 2:
The guide rail acts as an intermediary mechanism that mediates between the actuator and the lens assembly. It translates the actuator's motion into constrained lateral movement of the lens assembly, preventing unwanted rotational movements (tilt, roll, pitch, yaw) and ensuring that the optical axis remains stable. The guide rail structure with engagement surfaces provides this constraining function, maintaining precise optical alignment during focusing operations.
3Measurement precision
If more optical elements are added to increase resolution, then image quality is improved, but the focal length increases and the device height increases
Solution Approach 1:
The patent enables the inclusion of multiple optical elements (such as zoom lenses and focus lenses) by utilizing lateral space between the light folding surfaces. Instead of stacking optical elements vertically, they are arranged along the lateral optical path where space is available. The guide rail mechanism provides the necessary lateral movement range to accommodate these additional elements while maintaining a compact vertical profile.
Solution Approach 2:
The patent implements a dynamic lens assembly that can laterally move along the guide rail to adjust focus. This dynamic positioning capability allows the lens assembly to accommodate multiple optical elements while maintaining proper focus at different distances. The actuator-driven lateral motion enables the system to dynamically adjust the effective optical path, achieving high resolution imaging without increasing device height.
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 efficient autofocus in folded optic arrays by maintaining image quality and allowing for more complex optics, such as multiple lenses, while constraining motion to prevent tilt, roll, pitch, and yaw, thus achieving high modulation transfer function (MTF) values across the entire field of view.
Implementation Method 1
an actuator configured to move the movable portion of the lens assembly laterally along the optical axis and at least one guide rail coupled between the actuator and the movable portion of the lens assembly, the at least one guide rail positioned to slidably engage another surface within the folded optic imaging system to constrain motion of the movable portion of the lens assembly away from the optical axis or rotating around the optical axis
Implementation Method 2
a lens assembly comprising a stationary portion having a first surface connected to the output surface of the optical element and a second surface connected to the image sensor, wherein the stationary portion of the lens assembly comprises a field corrector lens, and a movable portion positioned in an optical path between the image sensor and the primary light folding surface
Implementation Method 3
an optical element having an input surface configured to receive light from the primary light folding surface, a secondary light folding surface configured to redirect the received light in a second direction toward an image sensor
Data Source
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AI summary
An image capturing system and a method of autofocusing are disclosed such that, for example, when a folded optics configuration is used, a field corrector lens can be placed on the image sensor of the system and a plurality of lenses can be placed perpendicular to the image sensor. The plurality of lenses can be movable relative to the image sensor such that acceptable MTF curve performances can be obtained when the image capturing system is focused at reference distances..