Inmould integration of a microscope add-on systemto a 1.3 Mpix camera phone

摘要

A microscope add-on device to a 1.3 Mpix camera phone was selected as a demonstrator system for testing inmould integration of electronic substrates and plastic optics. Optical design of the device was quite challenging due to the fact that illumination system needed to be integrated with a double aspheric singlet lens structure as a single optical piece. The designed imaging lens resolution was adequate to resolve 10 μm features with a mobile phone camera. In the illumination optics the light from LEDs embedded into the plastic structure was collected and guided to the surface that was imaged. Illumination was designed to be uniform and adequately bright to achieve high resolution images with the camera phone. Lens mould design was tested by using injection moulding simulation software. The critical mould optical surfaces were designed as separate insert parts. Final shapes producing lens surfaces were tooled by diamond turning on nickel coatings. Electronic circuit board inserts with bonded bare LED chips and packaged SMD LEDs were assembled to the mould and then overmoulded with optical grade PMMA. Experiences proved that inmould integration of electronic substrates, bare LED chips and high resolution imaging optics in injection-compression moulding process is feasible. The yield of embedded packaged and also bare chip components was close to 100% after the right injection moulding process parameters were found. Prototype add-on system was characterized by testing the imaging properties of the device with a camera phone.