Abstract
The micro lens array (MLA) has played an important role in optical systems for the past few years, and the precision of pressing dies has dominated the quality of MLAs in glass molding. Few studies have covered the transcription effects on surface roughness of pressing dies for this technology. Therefore, this research utilized pressing dies to produce a sine-wave lens array on glass molding, to transform the Gauss-distributed spotlight into a uniform straight one and then characterize the transcription effects of these lenses. Pressing dies with a sine-wave shape were firstly cut by wire electrical discharge machining (WEDM), and then ultrasonic polishing using diamond abrasives was applied to finish the sine-wave surface with an original roughness of 0.2 μm Ra. Next, the sine-wave lens arrays were pressed by glass molding at the appropriate pressure and temperature, before evaluating the transcription effects of transforming the Gauss-distributed spotlight into a uniform straight one. The result showed that the sine-wave lens array stuck easily to the pressing die and then ruptured during glass molding due to the poor surface roughness of pressing tool. However, the diamond abrasive with appropriate sizes could establish good surface roughness on pressing dies via ultrasonic polishing, and the pressing die with a low surface roughness of 0.08 μm Ra was able to successfully perform MLA in the glass molding. However, only pressing dies with a surface roughness smaller than 0.023 μm Ra could produce precision glass lenses to transform the Gauss-distributed spotlight into a uniform straight one.
Highlights
Introduction iationsIn recent years, the micro lens array (MLA) has become a vital part of optical systems [1,2].One of the main applications of MLAs is to make the distribution of light energy uniform, and shapes of the lens are applicable to precision measurements, calibration, robot visual systems, light source control of optical systems, etc
A good transcription effect was obtained if the surface roughness of the glass lens and the pressing die were the same
The results show that regardless of the mesh of diamond abrasive utilized in the pressing die polishing, the surface roughness of pressing dies decreased with an increase in polishing time; the material removal increased with an increase in working time
Summary
One of the main applications of MLAs is to make the distribution of light energy uniform, and shapes of the lens are applicable to precision measurements, calibration, robot visual systems, light source control of optical systems, etc. Precise metal lenses and glass lenses are usually made using the diamond grinding process [3]; the grinding machine is very expensive and has high requirements in terms of operators and the environment. The long grinding time in making precise lenses is a high manufacturing cost. The precise glass molding (PGM) technique is an ideal processing method for fabricating highprecision glass elements because of its short cycle time, high accuracy, and high freedom; Licensee MDPI, Basel, Switzerland
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