Microscope arrays are arrays of miniature high power objectives, each of a similar size to a miniature endoscope1
capable of imaging biological specimens, such as histology slides, sputum smears, or cell cultures. Such arrays have already been put to use in the field of pathology,2
but have not yet become widespread in clinical use or in biomedical research. There is still great potential for array microscopes in biology, but the high cost of developing these devices remains a hurdle. Techniques currently used to make lens arrays include UV lithography, thermal reflow, compression molding, microforging, diamond machining, and often combinations of multiple techniques.3–8
These technologies have provided the ability to fabricate lens arrays designed for a wide variety of uses, but not all of these techniques are capable of producing the size lenses needed for an array microscope at the quality needed for at least a prototype system. Diamond machining technology is among the best at producing surfaces with the sag, radius, and diameter needed of miniature microscope lenses. This technology is often used to fabricate a master that can then be used in a replication process, such as plastic injection molding.9
3-D diamond milling, or micromilling, has been shown effective in producing these masters in metal.10
Using a lens array mold to produce a finished product of state of the art optical quality is not trivial, however. Obtaining a single finished prototype from a mold can be difficult and therefore expensive. Molding may only be economical in the case of microscope arrays at the commercial production phase, not at the development phase, unless the researchers have both mold-making and molding equipment at their disposal. For many research and development laboratories, especially academic laboratories, such a complete facility can be prohibitively expensive, as would be the cost of outsourcing the production of a single prototype by molding. The ability to produce a finished part on one machine in one step brings this cost of development down significantly.
Lens arrays have been produced in this single-step fashion in poly(methly methacrylate) (PMMA) using a plunge milling method, but the method of fabrication error correction is etching of the tool, and it is only good for lenses with a diameter of 1 mm or less.8
Diamond micromilling, since it is capable of producing state of the art lens molds, is a logical choice for direct fabrication. It is therefore the goal of this study to show the capability of 3-D diamond milling to produce high power lens arrays directly in plastic with state of the art form accuracy and optical quality surface roughness. Both types of lens shapes, concave and convex, are shown to fully demonstrate the ability of this process to produce all of the lenses needed in any array microscope design.