Evaluation of a moiré imaging system

Moiré fringe techniques can be used to measure surface topography. The factors that affect the formation of the fringes have been assessed theoretically by developing models of gratings and light sources of finite dimensions. In this way the effect of parameters such as the intensity distribution of the light source, the viewing aperture function, the lateral displacement of the source relative to the viewing axis, the viewing distance, the grating spacing and grating ratio have been evaluated. Other factors, related to the physical properties and geometry of the reflecting surface, are also investigated. Suggestions are made for the design of an optimum moiré imaging system.

Theoretical aspects and practical applications of moiré topography

When a surface is observed at a distance through a parallel line grating which is illuminated by a source of light laterally displaced to the viewing axis, the grating is superimposed on its shadow and this gives rise to a moiré fringe pattern. The fringes represent cross-sections of the surface parallel to the grating plane. The principle of the formation of the contour map has been studied assuming a grating represented by a Fourier series, a source of light represented by a 3D intensity distribution and a viewing aperture of finite dimensions. The experimental system used for illumination and observation of the moiré fringes consists of an equispaced parallel-lined glass grating and two small light sources positioned symmetrically about the imaging device. The arrangement constitutes a 3D imaging system with an accuracy of the order of 1 mm. The technique has been applied in radiotherapy problems such as the design of contour compensators and the measurement of body contours. Moiré patterns have been analysed with the aid of a PDP-8 computer, and have been used to calculate surface areas and volumes such as in breast studies and superficial tumour measurements.

Thermography of the female breast: a five-year study in relation to the detection and prognosis of cancer

More than 12,000 women have been examined thermographically in the Breast Unit of the Royal Marsden Hospital, London. Of these women 1,464 had biopsy and histology; 363(25 per cent) were found to have carcinoma and of these 68 per cent had abnormal thermograms, 13 per cent has some thermal asymmetry of doubtful significance and 19 per cent had normal thermal patterns. Fifty-seven per cent and 62 per cent of patients with Stage I and Stage II cancer, respectively, had abnormal thermograms whereas 83 per cent of patients with Stage III cancer had abnormal thermograms. Of 1,101 women who had benign lesions, 63 per cent had normal thermal patterns, 15 per cent had thermal asymmetry of doubtful significance and 22 per cent had abnormal thermograms. The subsequent histories of 172 cancer patients examined thermographically have been analysed and three-year survival rates have been correlated with thermography report, the clinical stage of the disease and the histotogical grade (Bloom, 1950) of the excised tumour. The mean three-year survival rates for patients with Stage II or Stage III cancer are 84 per cent for those with normal and 61 per cent for those with abnormal thermograms.

Haemolytic-uraemic syndrome. A report of an outbreak

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