1、 FORD LABORATORY TEST METHOD BF 103-01 Date Action Revisions 2001 03 02 Revised Editorial no technical change A. Cockman 2000 05 31 Revised Updated R. Surowiec 1991 08 29 Printed copies are uncontrolled Page 1 of 4 Copyright 2001, Ford Global Technologies, Inc. GLASS-VISIBILITY DISTORTION, ZEBRA TES
2、T PROCEDURE Application This procedure involves measuring distortion by placing the glass sample between the eye of the viewer and a diagonally striped (Zebra) examining screen. The glass is placed on a vertical plane with the principal distortions running in a vertical direction. Optical irregulari
3、ties in the glass cause the normally regular and parallel lines of the Zebra board to appear distorted. The glass is rotated about a vertical axis until these Zebra line distortions are on the verge of disappearance. Apparatus Required Zebra Board* The zebra board size must cover the maximum length
4、and height of the parts to be inspected, typically 2.0 x 2.0 meter or greater. The zebra board shall have a pattern of alternating 25 +/- 1mm wide black and white lines 45 +/- 2.5 clockwise from the vertical. Zebra board light intensity shall be measured facing the center of the zebra board from the
5、 sample glass position. The illumination shall be 200 +/- 100 lux. During zebra readings, the only light in the examination area is the light illuminating the zebra board. Lighting Guidelines For front-lit boards: . Lights are to be placed between the glass sample and the zebra board outside the fie
6、ld of view. . The type and number of lighting lamps is not important. . Avoid direct illumination to the viewer by using shielded or hooded lights. . The goal is to illuminate the zebra board as uniformly as possible while achieving the required illumination. . Types of lamps that have been used are
7、 hooded 400-watt Mercury Vapor lamps and hooded fluorescent lamps. For back-lit boards: . Avoid non-uniform light areas by placing the lamps too close behind the translucent zebra screen. Sample Holder* Holder includes an angle indicator. The sample holder is located 4.6 +/- 0.2 meters from the zebr
8、a board. The sample holder must be capable of holding rectangular pieces of glass in the vertical position. The sample holder can be designed to either hold one piece of glass or two for side-to-side comparison of a sample to a reference. FORD LABORATORY TEST METHOD BF 103-01 Page 2 of 4 Copyright 2
9、001, Ford Global Technologies, Inc. Observer Control Cabinet* The observer control cabinet does not have to be a literal cabinet but an indicated area for the location of the observer. The sample holder pivot controls need to be located near the observer. The observer location is located 9.2 +/- 0.2
10、 meters from the zebra board. The observer location and the sample holder are located on the same plane perpendicular to the zebra board center (+/- 0.2 meters). Conditioning and Test Conditions There are no requirements for material conditioning. Procedure 1. Place the sample in the sample holder (
11、with the line of glass draw vertical) and set the angle of incidence at 90 (i.e., the surface of the glass is parallel to the line of sight); then position yourself so that only the glass thickness edge can be seen. (Refer to Figure 1) 2. Using the sample holder pivot control, rotate the glass slowl
12、y and observe the distortion lines. The angle of incidence is reduced until the most objectionable distortion lines are about to disappear. This angle is the figure quoted as the “Zebra Angle“ of the glass. (Refer to Figure 2) Note: To assure minimum variability in the test results, avoid moving you
13、r head while rotating the glass. Materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. *Drawings: Visteon Glass Division Quality Control 17333 Federal Drive Allen Park, MI 48
14、101-3614 FORD LABORATORY TEST METHOD BF 103-01 Page 3 of 4 Copyright 2001, Ford Global Technologies, Inc. FORD LABORATORY TEST METHOD BF 103-01 Page 4 of 4 Copyright 2001, Ford Global Technologies, Inc. Angle 2 = Angle 4 = 90 Angle 1 = Angle 3 = Angle of incidence = Zebra Angle Angle 1 is measured with a degree indicator Figure 2
