Recently, the development of IoT technologies such as for autonomous driving and factory automation has been thriving. Both imaging devices and sensing devices that use optics are the most important devices among IoT technologies. When developing these devices, controlled light source is one of most important parts. There are not many reports of the development of single illumination optics with a super-wide-angle light distribution compared to camera lenses. Single illumination optics with super-wide-angle light distribution is desired for cost reduction and space saving of IoT device. However, it was difficult to make it with high efficiency and high uniformity due to severe requirement of geometrical tolerance and an increase of Fresnel reflection in large angle region. We report development and manufacturing of micro lens array diffuser with super-wide-angle distribution and high efficiency. Our optical design including an antireflection coating for super-wide-angle region could make the curvature of the lenslet low and enable us to manufacture this optics. In our design, it is achieved a super-wide-angle light distribution of about 170 degrees and high efficiency of about 80% using a micro-lens-array diffuser consisting of about 100-micron lenslet. And, we have realized a mass-produced product with high similarity between the micro lens array and the mold by using the technology to transfer the mold shape to the resin with high precision.
We fabricated transmissive optical diffusers with a randomized concavo-convex surface that was designed to control the irradiation distribution and can be fabricated easily. The diffusers were molded from acrylic using the mold cores machined by ultraprecision cutting or milling. Less stray light was observed from the diffuser molded with the cutting core compared with the milling core. As the Fourier optics simulation was consistent with the measured distribution, it was beneficial for the design evaluation of diffusers. Furthermore, we molded a Penrose-tiling micro-lens-array to generate uniform light distribution without random displacement of each lens. The measurement results showed the feasibility of the Penrosetiling micro-lens-array as a diffuser.
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