Quality-based 2D phase unwrapping algorithms provide one of the best tradeoffs between speed and quality of results. Their robustness depends on a quality map, which is used to build a path that visits the most reliable pixels first. Unwrapping then proceeds along this path, delaying unwrapping of noisy and inconsistent areas until the end, so that the unwrapping errors remain local. We propose a novel quality measure that is consistent, technically sound, effective, fast to compute, and immune to the presence of a carrier signal. The new measure combines the benefits of both the quality-guided and the residue-based phase unwrapping approaches. The quality map is justified from the two different theoretical points of view. Exhaustive tests on a variety of artificially generated and real 2D wrapped phase signals illustrate its potential usefulness in the field of fringe projection profilometry.

All atomic force microscope (AFM) images suffer from distortions, which are principally produced by the interaction between the measured sample and the AFM tip. If the three-dimensional shape of the tip is known, the distorted image can be processed and the original surface form `restored', typically by deconvolution approaches. This restored image gives a better representation of the real 3D surface of the measured sample than the original distorted image. In this paper, we propose a method for estimating the three-dimensional shape of the AFM tip by measuring a micro-cylinder with a-priori known dimensions. The estimated tip shape is then used to restore subsequent AFM images, when measured with the same tip, under similar measurement conditions. Significantly, the impulse response of the AFM can be deduced using this method. The suitability of this novel approach for restoring AFM images has been confirmed using both computer simulation and also with real experimental AFM images. The proposed method is compared with standard restoration techniques and is shown to provide superior performance to such approaches.

There has recently been a significant growth in interest in determining the mechanical properties of living human cells. Much of this work has centred around the application of the Hertz Contact Stress model to force/displacement curves that are obtained from atomic force microscopy. However, it is widely recognised that the conventional Hertzian approach, that is based upon a linear elastic model for the stress strain relationship of the material, is inadequate for accurately modelling and describing the behaviour of living cells under load. This paper presents a new non-linear extension of the Hertzian model and shows results that provide excellent agreement with experimentally obtained force/displacement data from a range of different cell types. Furthermore the paper goes on to show the way in which the model can be used as a tool to distinguish between different populations of cells of different types, morphologies, or pathological status.

An investigation into orientation preferences shown by actin fibres within ex-situ actin as imaged by Atomic Force Microscopy (AFM) is described. Actin is a primary cytoskeletal component and is believed to play a vital role in cell structure. Actin structure images measured by AFM were analysed using automated pre-processing steps. These steps were identical for the production of an initial binary image, which was then processed by both Hough transformation and thinning. Results obtained question the validity of using the Hough transform approach, as bias could not easily be eliminated, and hence the Hough transform method was deemed to be unsuitable for this application and instead the thinning technique was used to identify and locate actin orientation within the AFM images. The results show that polymerised ex-situ actin fibres appears to display a bimodal distribution of orientation, with a 90 degree separation, with a significant co-efficient of bimodality of 0.656.