Tiny 3D printed compound lenses of unprecedented optical quality can now be printed directly onto small structures including image sensors, or even the tip of an optical fibre - just two hairs wide - for use as an endoscope (used to explore the body cavity or hollow organs). Described in a paper published online this week in Nature Photonics, the high-performance compound lenses are only about 0.1 mm in size and enable multi-lens and microscale imaging systems around the size of a grain of salt.
Current lens manufacturing processes limit the size and shape of lenses, hampering their optical performance. Multi-lens elements with non-spherical shapes are required for high optical performance and to correct for aberrations. Timo Gissibl and colleagues used a femtosecond direct laser writing system to 3D print multi-lens systems that are about 0.1 mm in size. The multi-lens systems feature multiple singlet (simple) lenses that are combined into a compound lens within a supporting shell, and the systems can be printed at a rate of centimetres per second.
The authors print a triplet lens system directly onto the end of an optical fibre that is so thin it fits inside a typical syringe needle and show that objects 3 mm from the lens can be successfully imaged at the other end of the 1.7-m-long optic fibre. Finally, they show that arrays of lens systems with four refractive interfaces can be printed onto 5-megapixel CMOS image sensors (used in digital cameras). The authors conclude that their method paves the way towards printed optical miniature instruments such as next-generation endoscopes and high-quality imaging elements directly on CMOS sensors for miniaturized robots and drones.