In-Vehicle Optical Projection Layout for Wide View and Central Magnification
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Solution Overview
Problem
Existing optical systems for in-vehicle cameras struggle to achieve a wide angle of view equivalent to fisheye lenses while maintaining a large imaging magnification in the central angle of view area, leading to larger image sensors and cameras.
Innovation Solution
An optical system comprising a front unit and a rear unit with multiple lenses, including aspherical lenses, that satisfies the inequality 1 < f × sin(θmax) / y(θmax) ≤ 1.9, with a local maximum differential value in the projection characteristic, to balance wide angle of view and high imaging magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a fisheye lens with equidistant projection or stereographic projection is used to achieve a wide angle of view, then the maximum angle of view is increased, but the imaging magnification in the central angle of view area becomes too small to serve as a rearview mirror substitute
Solution Approach 1:
The patent applies local quality by implementing different projection characteristics in different angular regions. The optical system provides high imaging magnification (foveal projection) in the central angle of view area where d²y/dθ² > 0, and transitions to wide-angle coverage (fisheye projection) in the peripheral areas. This spatially varying projection property allows the single optical system to simultaneously satisfy both requirements: wide overall angle of view and sufficient central magnification for rearview mirror application.
2Area of moving object
If the image sensor size is increased to achieve a wider angle of view, then the angle of view is improved, but the camera size becomes larger
Solution Approach 1:
The patent changes the projection characteristic parameter from conventional fisheye projections to a foveal projection where the relationship between image height y and angle θ satisfies d²y/dθ² > 0 in the central region. This parameter change in the projection function allows achieving a wide angle of view (90° or more half angle of view) while maintaining sufficient central magnification, thereby avoiding the need to increase image sensor size and consequently reducing camera overall size.
3Measurement precision
If an optical system with high imaging magnification in the central area is designed, then the central resolution is improved, but the maximum angle of view becomes insufficient for wide-area monitoring
Solution Approach 1:
The patent segments the angle of view into different functional zones: a central foveal region (0° to approximately 30°) where d²y/dθ² > 0 provides high magnification and resolution for detailed observation, and peripheral regions where the projection characteristic transitions to provide wide-angle coverage. This segmentation of functional requirements across different angular zones enables the optical system to achieve both high central magnification and wide maximum angle of view simultaneously.
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 provides a wide angle of view equivalent to fisheye lenses with improved central resolution and reduced optical distortion, enabling better detection accuracy and natural perspective without electronic correction.
Implementation Method 1
an optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a front unit including a plurality of lenses, an aperture stop, and a rear unit including a plurality of lenses
Implementation Method 2
at least one of the lenses in the front unit and the rear unit is an aspherical lens
Data Source
AI summary
An optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a front unit including a plurality of lenses, an aperture stop, and a rear unit including a plurality of lenses. A projection characteristic of the optical system representing a relationship between a half angle of view and an image height on an image plane satisfies a predetermined condition.