APPLICATION OF 3-D TOPOGRAPHY TO BIOENGINEERING

Traditionally, quantitative measurement of surface texture has been ca rried out using contacting stylus instruments yielding purely 2-dimens ional topographical information. Recently, there has been a great expa nsion in this field through developments in instrumentation and comput ers which now make 3-dimensional surface measurement a routine procedu re. The latest instruments measure roughness ranges from nanometers up to millimetres. In conjunction with the development of these new tech niques a new range of numerical parameters are currently being develop ed in an attempt to establish a basis for new international 3-dimensio nal surface measurement standards avoiding the ''parameter rash'' prob lems encountered in the development of 2-dimensional surface measureme nt. Primarily the new measurement techniques can be divided into conta ct (employing styli) or non-contact measurement (employing mostly inte rferometers or focus detection systems) regimes. Despite the commercia l availability of many of these new systems they all possess certain i mportant drawbacks as far as their wide applicability is concerned. Tr ue quantitative 3D surface measurement has meant that the field of app lications of these techniques. has expanded enormously, from the tradi tional 2-dimensional area of quality monitoring of machined surfaces i nto 3-dimensional measurement fields ranging from ultra-fine thin film measurement of dermatological cancer studies. A relatively new and de veloping field of application of 3D analysis is that of bio-engineerin g where the surface topography is of extreme importance in areas such as joint prosthesis surfaces replacement heart valve seal quality and contact lens quality. The present study presents a review of a number of the new measuring systems available and their associated numerical characterisation methods. A number of bio-engineered surfaces are give n as examples covering four decades of vertical measurement range in o rder to illustrate the data sampling techniques, measurement strategie s, range to resolution and instrument selection issues.