Coherent optical signal processing methods for screening Pap smears were evaluated and are presented in a three-part sequence. In Part 1, 2-D Fourier spectra of normal and abnormal cells generated from many high resolution cell photographs are presented. Each cell spectrum was measured with a coherent optical data processing system containing a special geometry detector and automated data collection capability. Several parameters, determined from weighted measures of the cell transform intensity variations, were tested as feature discriminators to separate normal from abnormal cells. An analysis of the experimental data demonstrates that several transform features are good discriminators of normal/abnormal cells (using standard Baysian decision algorithms with quadratic decision rules). In Part 2, mathematical model studies to guide and validate the experimental work show certain transform parameters to be functionally related to cell and nucleus diameter and optical density. Other parameters appear to be related to cell characteristics such as clumping of nuclear deoxyribonucleic acid (DNA). The model studies also show that the photographic variables play a key role in cell image preprocessing prior to Fourier analysis. Part 3 discusses an optical transducer that was used as a film replacement to modulate a laser beam spatially with a cell image. Several of the feature discriminators used in Part 1 with photographic film images served also to separate normal and malignant cell types when the cell Fourier spectrum was obtained from a transducer image. Based on an understanding of the procedure from the model studies and the demonstrated ability to separate normal and malignant cells using certain transform features, a coherent optical processing system to screen Pap smears from cell or slide photographs is feasible and appears practical in terms of the number of cells to be processed. A high-speed optical transducer would be required for processing large numbers of cells without photography in a reasonable time interval.
This paper describes a new experimental procedure for measuring sinusoidal vibration displacement amplitudes by means of a laser homodyne system. Advantages that include a self-checking feature to validate the measurement and a direct readout capability are discussed. Unambiguous displacement amplitude measurements for amplitude values greater than the optical wavelength employed are also shown to be possible. With a calibrated system, rotational vibration amplitudes can be measured.
Earlier research using a very limited data base gave encouraging results for the automated screening of exfoliated cytologic samples using coherent optical processing techniques to examine individual isolated cells. A more thorough investigation involving a larger data base has confirmed our initial results. This investigation was performed using a specially designed Fourier spectrum analyzer and a solid state optical detector array. An analysis was made to determine the performance of a screening system using such a cell-by-cell discriminating device. This analysis indicated that less than 20,000 cells would have to be examined to obtain a system performance level of 1% false negative and 10% false positive error rates with a 1% probability of occurrence of malignant cells in a malignant sample. This performance figure was inferred from measured statistical performance characteristics of a laboratory cell-by-cell screening device using optically generated Fourier transfrom techniques for cell discrimination. The performance of the system was shown to be much more sensitive to cell-by-cell false error rates than false negative error rates. It was also found that the majority of false positive errors were due to misclassifying parabasal cells as malignant. By eliminating parabasal cells, which comprised more than 25% of our normal cell data base, the number of cells needed to be screened dropped by an order of magnitude. It was also shown that there is an inverse quadratic relationship between the percentage of malignant cells in a malignant sample and the number of cells that must be screened to achieve any desired system performance.
The far-field pattern of light scattered by a small rough metallic surface area is obtained with a coherent optical system and used to quantify roughness measurements of machined surfaces. The distribution is usually anisotropic due to tooling marks. A cylinder lens forms a 1-D transform at favorable angular orientations about the optic axis to circumvent this problem and provides useful spectrum averaging. The integrated Gaussian curve fits to experimentally observed scattered light patterns from individual roughness samples yield an empirical linear relation between a Gaussian width parameter and average roughness height.
A 1-D optical Fourier spectrum analyzer system is used to detect fatigue cracks as small as 0.5 microm in titanium test samples. Signatures obtained from scans of reflected laser light diffraction patterns show features linked to the presence of surface cracks. Signature characteristics are preserved without a need for critical focusing or optics-to-sample positioning. Analytic modeling of a crack surface profile is used to explain the primary cause of the observed signature properties.
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