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In our latest tech talk, Thomas Tessnow talked about how to design a Light Carpet Projector using Micro-Lens Arrays (MLA). He demonstrated how MLAs are used in automotive projection applications such as symbol projectors or light carpets.
This article outlines the process of designing the lens array using the Macro Focal Lens tool and the optimizer in LucidShape software. Since the MLAs are made of more than one material, the ability to solve a multi-material lens problem is showcased. This includes a mask calculation method, which creates a high number of mask images with minimal additional CAD effort.
Figure 1: Light carpet example
(? Driving Vision News 2022)
Micro Lens Arrays in Automotive Projection Applications
Micro Lens Arrays, also known as MLA, are arrays of tiny lenses, typically 1mm in diameter or less. These arrays are often made up of a glass substrate and a plastic lens array on each side. They are primarily used in the automotive industry for projection applications such as symbol projectors or light carpets. Their small size and the ability to project images onto target surfaces make them ideal for these applications.
MLAs are constructed by a semiconductor-style wafer batch process and then cut into individual pieces. This process allows for a high alignment accuracy between the optics and mask, which is important, as the images projected by the lenses are all superimposed in the far field.
Designing the Optics for the MLA
The design process for the MLA optics is detailed using the LucidShape software. The software allows for the design of one lens and the generation of a rectangular pattern automatically. This is advantageous as the size and spacing of the lens array can easily be changed in the MF-Lens dialog.
A process is outlined using a 5x5 lens array as an example, where each lens is 1x1mm in size. The lens layers are 0.2 mm thick and made of plastic, with a glass layer of 3mm thickness. The mask is on top of the glass layer inside the plastic lens material.
Figure 2: Example of a 5x5 Micro Lens Array with mask projecting a symbol onto the ground
Calculating and Processing a Mask Surface
After designing the optics and defining the available projected area, an image is chosen and a mask for it is calculated. This involves creating a CAD surface in the shape of the desired image in the LucidShape coordinate system. This surface is then imported into LucidShape and a ray file sensor is attached to it.
A ray trace is run and all the rays reaching the image surfaces are collected. These rays are then inverted and traced back until they reach the mask plane. An illumination sensor in the mask plane collects the lux distribution, which is then converted into a surface and exported to CAD. After processing the exported surface into a usable mask surface, it is re-imported into LucidShape and verified by simulation.
Figure 3: Mask for a 10x10 MLA with different images in each quadrant for animations
Conclusion
Micro Lens Arrays are a vital component in automotive projection applications. With the help of LucidShape software, the design and optimization of these arrays can be done efficiently and effectively. The software also allows for the calculation of a mask for a target image on an arbitrary projection plane. Despite certain limitations, there are possibilities for further expansion such as the use of multiple masks and LEDs for creating small animations. This technology continues to evolve, and with it, the possibilities for its application continue to expand.
Watch the full tech talk online either on-demand or on SolvNetPlus (account required, log in to first to view link).