Shape measurement of long microbores applying photon counting method

New technology, especially in the field of microelectronics and mechatronics, created the need for making, positioning and inspection techniques of long microbore-holes and gaps (defined by length/width to diameter ratio l/d > 10 for d < 200 μm). The technological aspect is, in principle, subdued but the metrological one is still unsolved.In Zosel et al. Zosel J, Guth U, Thies A, Reents B. Flow measurements in micro holes with electrochemical and optical methods. Electrochim Acta 2003;48:3299–305] the properties (power loss and phase distortion) of focused laser microbeam penetrating extremely long through microbores is described; it was proved that the measurement information is distorted depending on the microbore geometry. The samples were prepared of glass–resin laminate with microbore diameter ranging from 35 to 200 μm.In present research an adjustable 100 μm microbore is used as a master. It is formed of mutually accurately adjusted 20 metal plates 100 μm thick set of coaxially in pile. Precise positioning of each plate enables creating free-shaped microbore.The photon batching device emitting 2.5 million photons per second is used as a generator of incident photon beam. The measured transmission efficiency is understood as a relation between outgoing and incoming light energy. The outgoing energy, for particular microbore, was determined by scanning linearly and angularly the bore with photon beam and integrating the results. Experiments were performed in dark room with background 2/5 photons per second (including dark current of photomultiplier).These changes describe the relationship between the shape of the microbore and the transmission energy and can be considered as a measure of microbore cylindricity deviation.