Measurement Anomaly
Systematic errors in optical fiber testing occur when fibers do not align perpendicular to the scanning light source. This phenomenon, known as major axis orientation bias, arises when fibers are tilted during transit through the measuring cell. It leads to an overestimation of the average fiber diameter.
Optical Distortion
Automated instruments measure the shadow or light scatter of fibers to calculate their thickness. When a fiber is oriented at an angle rather than flat against the sensor, its projected width appears larger than its true diameter. This distortion is particularly problematic for non-circular fibers.
Calibration Correction
Modern testing equipment uses specialized flow cells to minimize this orientation effect. The carrier fluid is passed through a narrow nozzle that stretches and aligns the fibers parallel to the direction of flow. This fluid dynamic action ensures that most fibers cross the optical sensor in a consistent orientation.
Accuracy Improvement
Correcting for this alignment bias is essential for the accurate grading of high-value fibers like cashmere. A small error in diameter measurement can classify a batch into a lower price bracket. By implementing advanced image filtering algorithms, instruments can identify and reject misaligned fibers from the final dataset.
This selective filtering ensures that only correctly aligned fiber profiles are used to generate the distribution curve, leading to highly reliable test results that protect both the buyer and seller.
