Variable Refractive Lens for High-Speed Ophthalmic Laser Focus Displacement
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Solution Overview
Problem
Current ophthalmic laser systems face challenges in achieving fast and precise three-dimensional incision guidance due to limitations in focal displacement speed and accuracy, particularly in corneal lenticular extraction, where conventional mechanical drives are not suitable for high-speed and precise z-focus repositioning required for efficient refractive corrections.
Innovation Solution
An ophthalmic laser apparatus featuring a controllable lens of variable refractive power, such as a liquid or liquid-crystal lens, is used to displace the laser focus in the z-direction without mechanical repositioning, enabling high-speed and precise focus adjustments through electrical control, allowing for faster and more accurate three-dimensional incision guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional mechanical drives are used to reposition the focusing objective or zoom lens for z-focus displacement, then the system structure is simple and reliable, but the repositioning speed is too slow (1-5 mm/s) to meet the requirements of high-speed laser surgery (needing at least 10 mm/s)
Solution Approach 1:
The patent replaces the conventional mechanical drive system with an acoustic radiation pressure system. Ultrasonic waves are focused onto the zoom lens to generate acoustic radiation pressure that drives the lens for z-focus displacement. This substitution eliminates mechanical contact and friction, enabling repositioning speeds of at least 10 mm/s while maintaining positioning accuracy, thus resolving the speed limitation of mechanical drives without sacrificing control precision.
2Measurement precision
If the focusing objective is displaced mechanically in the z-direction, then the focus location is repositioned with 1:1 accuracy, but the mechanical displacement speed is insufficient for fast focus switching between consecutive laser pulses
Solution Approach 1:
The patent replaces mechanical displacement of the focusing objective with acoustic radiation pressure acting on a zoom lens. The ultrasonic waves generate contactless acoustic pressure that moves the lens elements, achieving both high speed (10+ mm/s) and high precision focus repositioning. This eliminates the speed-accuracy trade-off inherent in mechanical systems by using a non-contact actuation mechanism.
Solution Approach 2:
The patent employs periodic ultrasonic waves at specific frequencies to generate acoustic radiation pressure. By controlling the frequency and duration of these periodic acoustic cycles, the system can precisely control the lens displacement timing and magnitude, enabling synchronized fast focus switching with the laser pulse sequence while maintaining accurate focus positioning.
3Weight of moving object
If a beam expander with displaceable input lens is used to shift the focus location, then the mass to be moved is reduced improving repositioning speed, but the maximum speed is still limited by conventional linear drives to 1-5 mm/s which is insufficient for three-dimensional incision
Solution Approach 1:
The patent replaces the conventional linear drive system with an acoustic radiation pressure system for moving the beam expander's input lens. The ultrasonic waves generate contactless acoustic pressure that can accelerate the lightweight lens elements to speeds of at least 10 mm/s, overcoming the speed limitation of linear drives while maintaining the advantage of moving only small-mass lens elements.
Solution Approach 2:
The patent changes the actuation parameter from mechanical force (linear drive) to acoustic radiation pressure. By adjusting the ultrasonic wave parameters (frequency, power, focal position), the system can dynamically control the lens repositioning speed and position, achieving speeds of 10+ mm/s that are necessary for three-dimensional corneal incision while keeping the moving mass small.
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 faster and more precise three-dimensional incision guidance, reducing treatment time and improving the accuracy of refractive corrections, such as corneal lenticular extraction, by allowing focus displacement in the high two-digit μm range within a few milliseconds, thus minimizing patient discomfort and enabling precise incision profiles matched to individual sight defects without the need for excimer lasers.
Implementation Method 1
a controllable lens of variable refractive power, such as a liquid or liquid-crystal lens, is used to displace the laser focus in the z-direction
Implementation Method 2
A variable refractive index of the lens of variable refractive power is changed by means of an applied electrical driver voltage
Implementation Method 3
a scanner downstream of the telescope, for deflecting the laser beam in a plane (x-y plane) perpendicular to the beam path
Implementation Method 4
an at least single-lens focusing objective, in particular f-theta objective, downstream of the scanner, for focusing the laser beam
Implementation Method 5
Laser systems that emit short-pulse radiation within the femtosecond range are employed in ophthalmic surgery... The effect that is utilised in this connection is optical breakthrough, which results in a so-called photodisruption of the irradiated tissue
Data Source
AI summary
An apparatus for ophthalmic laser surgery comprises a source (28) for a pulsed femtosecond laser beam, a telescope (32) expanding the laser beam, a scanner (36) downstream of the telescope, for deflecting the laser beam in a plane perpendicular to the beam path, and also an f-theta objective (44) downstream of the scanner, for focusing the laser beam. In accordance with the invention, an entrance lens (52) of the telescope (32) takes the form of a controllable lens of variable refractive power. The entrance lens (52) is preferentially constituted by an electrically controllable liquid lens or liquid-crystal lens.