Veli-Pekka Putila

Prototyping of miniature plastic imaging lens

The prototyping process of miniaturized plastic imaging lens is described. The sequence is divided into five phases: specification, optics design, optomechanical design, manufacturing and characterization. During specification, the optical and mechanical requirements of the lens are defined. In the optical design phase, the lens is optimized, and a tolerance analysis is carried out. Simulation tools, especially, an image quality simulator, can be used to visualize and verify the performance of the design. Mechanical design is performed considering the geometrical specifications and optical tolerances of the system. In addition, stray light analysis is carried out to verify the optical performance of the optomechanics. Plastic optics are particularly vulnerable to stray light due to the integrated mountings, which provide additional paths for unwanted light. If the prototype is used for preliminary performance evaluation of a future product, the differences between prototype and mass manufacturing methods need to be considered carefully. After the lenses are manufactured they are characterized, and the experimental results are compared with the original specifications and estimations obtained from the previous design verification simulations. New error analysis simulations can be performed in order to pinpoint faults in manufactured modules. If the performance of the prototype is not sufficient, a new prototyping iteration circle is needed. The whole process is described and analyzed using a miniature, plastic imaging lens as an example, but it can also be applied to other optical prototyping tasks.

Laser profilometer module based on a low-temperature cofired ceramic substrate

We realized a laser profilometer module using low tempera- ture cofired ceramics technology. The device consists of a vertical-cavity surface-emitting laser as the light source and a complementary metal oxide semiconductor image sensor as the detector. The laser transmitter produces a thin light stripe on the measurable object, and the receiver calculates the distance profile using triangulation. Because the design of optoelectronic modules, such as the laser profilometer, is usually carried out using specialized software, its electronic compatibility is very impor- tant. We developed a data transmission network using commercial opti- cal, electrical, and mechanical design software, which enabled us to electronically transfer data between the designers. The module electron- ics were realized with multilayer ceramics technology that eases compo- nent assembly by providing precision alignment features in the sub- strate. The housing was manufactured from aluminum using electronic data transfer from the mechanical design software to the five-axis milling workstation. Target distance profiles were obtained from 100 points with an accuracy varying from 0.1 mm at a 5-cm distance to 2 cm at 1.5 m. The module has potential for distance measurement in portable devices where small size, light weight, and low power consumption are important.