Ralph E Frazee

High-speed noncontact fiber-diameter measurement using forward light scattering

The forward scattering of light by an optical fiber produces an interference fringe pattern, and the fringe period is inversely proportional to the fiber diameter. An electrooptic system has been developed to produce and detect this scattering pattern to provide an instrument which will measure fiber diameter during the drawing operation. The system measures the fiber diameter at a 1-kHz rate with a precision of 0.25 microm and an accuracy of +/-0.25 microm over a range of 50-150-microm diams. The instrument allows the fiber to move laterally in a 1-cm diam window maintaining the above accuracy. The system can be calibrated optically and does not need a standard fiber for this procedure. The instrument has been used for months without the need for recalibration. In addition to the digital diameter output, the system employs a microprocessor to compute mean and standard deviation values for various sample lengths and provides suitable signals for feedback control of fiber diameter.

An Optical Fiber Diameter Measurement System Using Forward Scattered Light

Forward scattering of light by an optical fiber produces an interference fringe pattern in which the fringe spacing is inversely proportional to the fiber diameter. An electrooptic system has been developed to produce and detect this scattering pattern, thus providing a measure of fiber diameter.

A Microprocessor-Based Statistical Analysis Subsystem

This paper describes a microprocessor-based subsystem which was developed to provide a statistical description of the diameter of an arbitrary length of wire during the drawina or insulation process. The instrument, built around a 4-bit Intel microprocessor, computes the mean and standard deviation of 1000 data samples over a length of wire determined by the setting on a Binary-Coded Decimal (BCD) thumbwheel switch. The sample period may be varied from 2 milliseconds to 10 seconds. The statistical quantities are output on analog channels as well as digital displays. In addition to the statistical computation, the instrument has the option of playing back the data at arbitrary speeds and generatinq histograms of the data samples. The techniques described in this paper can be inexpensively implemented to provide a statistical description of many laboratory or production processes with a minimum of operator intervention.

High speed measurement of the core diameter of a step-index optical fiber: errata.

The forward scattering light pattern from a clad optical fiber illuminated perpendicular to its axis is characteristic of the outer diameter, the core diameter, and their respective refractive indices. This pattern is detected by a diode array detector to produce a video signal representation of the scattering pattern. Electronic circuits have been developed to analyze the scattering pattern and detect the angular position of the modulation characteristics of the pattern. This provides a determination of the core to outer diameter ratio of the fiber. Using linearization circuits and the outer diameter measurement signal, linear measurement signal voltages of both core ratio and core diameter are derived. The measurement of core ratio refers to a particular radius vector and means that determinations of circularity and concentricity can also be made.

Gold Contact Inspection Using a Scanning Laser Beam

A laser scanner inspection machine was built to detect defects on printed wiring board gold contact fingers. The scanner sweeps a focused laser beam in raster fashion across the contacts at 60 scans/sec and the scattered beam is detected and electronically analyzed to yield the defects. Marking is accomplished with a relay-driven felt tip pen which marks the back of the board under the defective contact. The inspection of a board about four inches on a side can be done in a few seconds. A range of defects can be detected with this machine, including pinholes, gradual indentations, scratches, discolored gold, etc. The detection levels can be adjusted to pass imperfections which are not considered serious. This advantage makes the machine programmable in an objective manner, easily accommodating revisions in specifications. In this report, the operation of the machine is described including a detailed account of alignment procedures and electronic processing. Results of a preliminary test of the system effectiveness are discussed and it is shown that the level of detection must be empirically determined.