Infrared F-theta Lens for Large-Format Telecentric Laser Marking
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Solution Overview
Problem
Conventional Fθ lenses for large-format telecentric systems are bulky and difficult to correct for aberrations due to the need for a large optical aperture and long focal lengths, making them impractical for infrared large-format telecentric laser marking.
Innovation Solution
An Fθ lens design comprising a sequence of negative biconcave, positive meniscus, and plane lens elements arranged along the incident ray axis, with specific curvature radii and thicknesses, which reduces the volume and simplifies the system by using a retrofocus structure to minimize entrance pupil and system distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical aperture is increased to meet large-format telecentric requirements, then the imaging quality and telecentric performance are improved, but the lens volume and system size increase proportionally
Solution Approach 1:
The lens is divided into multiple lens elements (first lens element, second lens element, third lens element, and optionally fourth lens element) with different optical functions. Each element has specific curvature radii and thicknesses that contribute to the overall telecentric performance while keeping individual element sizes manageable, thus resolving the contradiction between large aperture requirements and volume constraints.
Solution Approach 2:
The patent introduces a retrofocus structure that changes the spatial arrangement of optical components. By positioning the entrance pupil at a specific distance from the focal point and using a combination of positive and negative lens elements, the system achieves large-format telecentric imaging with a more compact overall configuration, effectively utilizing dimensional optimization to reduce volume.
2Measurement precision
If the focal length is increased to achieve large-format imaging, then the field of view and imaging quality are improved, but the entrance pupil position moves to a distant point increasing system volume
Solution Approach 1:
The patent employs a retrofocus structure that inverts the conventional lens arrangement. Instead of having the entrance pupil close to the lens, the design positions it at a specific distance by using a negative lens element followed by positive lens elements. This inversion allows the system to achieve long effective focal length for large-format imaging while keeping the physical system length and entrance pupil distance manageable.
Solution Approach 2:
The optical system is segmented into multiple elements with specific functions: the first lens element (negative) controls the entrance pupil position, while subsequent positive lens elements contribute to the focal length and imaging quality. This segmentation allows independent optimization of each element to achieve both long effective focal length and compact physical dimensions.
3Use of energy by moving object
If the optical aperture is increased for large-format imaging, then the light gathering ability is improved, but the difficulty of correcting optical aberrations increases
Solution Approach 1:
The lens is divided into multiple elements, each with specific curvature radii and thicknesses designed to correct particular types of optical aberrations. The first lens element (negative) and subsequent positive lens elements work together to balance and correct aberrations that would be difficult to control in a single large-aperture lens, thus reducing the complexity of aberration correction while maintaining large aperture for light gathering.
Solution Approach 2:
The patent introduces intermediate lens elements between the object and the image plane that act as mediators to control and correct optical aberrations. These intermediate elements with specific optical properties help manage the complex aberration patterns that arise in large-aperture telecentric systems, making the overall system more manageable despite the large aperture requirement.
4Measurement precision
If the entrance pupil position is moved to the front focus for conventional telecentric design, then the chief ray perpendicularity is achieved, but the system volume and working distance increase
Solution Approach 1:
The patent inverts the conventional telecentric design by using a retrofocus structure. Instead of placing the entrance pupil at the front focus, the design positions it at a specific distance from the focal point by using a negative lens element followed by positive lens elements. This inversion maintains chief ray perpendicularity for telecentric imaging while reducing the working distance and system volume.
Solution Approach 2:
The patent optimizes specific parameters including the curvature radii (e.g., -143 mm, 330 mm, -1100 mm, -160 mm, 320 mm) and thicknesses (e.g., 6 mm, 16 mm, 12 mm) of each lens element to achieve the desired entrance pupil position. By carefully adjusting these parameters, the system maintains telecentric performance with reduced working distance and 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 design achieves a compact optical system with improved aberration correction capabilities, meeting telecentric requirements for large-format laser marking while maintaining high imaging quality.
Implementation Method 1
a first lens element, which is a negative biconcave lens element... a second lens element, which is a positive meniscus lens element... a third lens element, which is a positive meniscus lens element... arranged sequentially around a same axis along the propagation direction of an incident ray
Data Source
AI summary
An Fθ lens for infrared large-format telecentric laser marking is disclosed, including a first lens element, a second lens element, a third lens element and a fourth lens element arranged sequentially along the propagation direction of an incident ray. The first lens element is a negative biconcave lens element including a first curved surface and a second curved surface. The second lens element is a positive meniscus lens element including a third curved surface and a fourth curved surface. The third lens element is a positive meniscus lens element including a fifth curved surface and a sixth curved surface. The fourth lens element is a plane lens adapted to play a role in protecting other lens elements. The first to third lens elements are arranged around a same axis along the propagation direction of the incident ray. The first to sixth curved surfaces are arranged sequentially along the propagation direction of the incident ray. The above Fθ lens for infrared large-format telecentric laser marking can be used as an Fθ lens for infrared laser marking, which can meet the telecentric requirement of the large-format laser marking, and control the volume of the lens within an acceptable and applicable range, to achieve miniaturizing of the whole optical system.