Micro lens arrays (MLA) can be utilized in various applications of light sensitive devices such as digital cameras or objective free microscopes, and 3D imaging because of their good light collection efficiencies. Many of the fabrication methods used today require heat or expensive equipment or molds and that is why there is a need for a simple and cost effective fabrication method for MLAs. An inkjet printing based production method for low-cost micro lenses is presented here. By pre-patterning the used substrate the printing accuracy and the shape of the lenses is improved. The surface patterning is done with photolithography to fabricate round, shallow reservoirs for the lenses to be printed in. The liquid lens material is then inkjet printed into them. The pattern edges prevent the spreading of the ink outside the wanted area increasing the tolerance for printing inaccuracy and resulting to the uniform array of micro lenses. By depositing the ink to the reservoir, the ink forms a convex surface a.k.a. a lens. The used lens material is negative photoresist, so after printing it is cured with UV-light and baked in a hot plate to solidify the lens matrix. By placing different amount of ink in a reservoir the height of the lenses changes and thus the focus of the lens can be adjusted making the proposed method versatile tool for MLA fabrication.
We present the use of sub-micron resolution optical coherence tomography (SMR SD-OCT) in volumetric
characterization of ink- jet printed color filters, aimed for electronic paper display (EPD). The device used in the study is based on supercontinuum light source, Michelson interferometer centered at 600 nm and employs 400-800 nm spectral region. Spectra are acquired at a continuous rate of 140,000 per second. Color filter array of 143 μm x 141 μm sized and 6 rtm deep ink pools was studied. The volumetric OCT reconstruction was done using the experimental SMR SD-OCT device and a commercial SD-OCT imaging system. The ink layer in the pools was estimated to be 2μm thin. The optical profilometer was used for reference measurements.