Inkjet Spectacle Lens Printing With Dithered Layer Smoothing
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Solution Overview
Problem
Existing methods for inkjet printing spectacle lenses result in visible steps on the lens surfaces, requiring additional processing steps like polishing to compensate for these steps, which complicates the manufacturing process.
Innovation Solution
A computer-implemented method for calculating a digital twin of a spectacle lens, which involves positioning volume elements in specific patterns to avoid surface steps during inkjet printing, using a dithering algorithm to ensure smooth surfaces by controlling the placement of ink droplets based on a digital twin representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If multiple layers are inkjet printed successively to create a curved-form spectacle lens, then the lens can be manufactured with complex curvature, but visible steps appear on the surface requiring additional polishing processing
Solution Approach 1:
The patent applies local quality by varying the droplet distribution density across different regions of each layer. Specifically, the inner peripheral region has a first droplet distribution density while the outer peripheral region has a second droplet distribution density that is lower than the first. This non-uniform local quality compensates for the step formations that would otherwise occur at layer transitions, achieving smooth surface curvature without additional polishing.
Solution Approach 2:
The patent changes the parameter of droplet distribution density to control surface morphology. By adjusting the droplet distribution density in different radial regions of each printed layer, the method controls the local thickness and curvature of the lens material. This parameter variation eliminates visible steps between layers while maintaining the desired overall curved-form shape.
2Manufacturing precision
If additional processing steps like polishing are applied to remove surface steps, then surface smoothness is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent performs preliminary action by pre-compensating for step formations during the inkjet printing process itself. Instead of adding material uniformly across each layer, the method预先 (in advance) adjusts the droplet distribution density in the inner and outer peripheral regions of each layer. This preliminary compensation ensures that when layers are stacked, the surface remains smooth without requiring subsequent polishing or corrective processing steps.
3Ease of manufacture
If uniform droplet distribution is used across each layer, then printing process is simple, but visible steps form on the lens surface
Solution Approach 1:
The patent implements local quality by dividing each layer into distinct radial regions (inner peripheral and outer peripheral) with different droplet distribution densities. This regional differentiation allows the printing process to maintain relative simplicity while achieving smooth surfaces, as the density variation is systematically applied based on position rather than requiring complex real-time adjustments.
Data Source
AI summary
A computer-implemented method for generating printing instructions for inkjet printing a spectacle lens, wherein the printing instructions are based on a digital twin of the spectacle lens, the digital twin being sliced into a layer stack. The method includes the steps of 1) positioning a volume element in a discrete xm+1, ym+1, zm+1 . . . xn+1, yn+1, zn+1 position of a layer of the layer stack, based on a positioning of a volume element in a discrete xm, ym, zm . . . xn, yn, zn position of an adjacent layer of the layer stack; or 2) not positioning a volume element in a discrete xm+1, ym+1, zm+1 . . . xn+1, yn+1, zn+1 position of a layer of the layer stack, based on a positioning of a volume element in a discrete xm, ym, zm . . . xn, yn, zn position of an adjacent layer of the layer stack.