1、7- I EIA TEP175 87 3234b00 0QOki727 O : TEPAC P U B L I CAT I ON Method for Calculating Refractive Gain for Color TV Picture Tube and Color Monitor Tube Screens TEP195 DECEMBER 1987 ELECTRONIC INDUSTRIES ASSOCIATION ENGINEERING DEPARTMENT EIA TEP395 87 8% 3234680 0008728 2 I NOTICE EIA Engineering S
2、tandards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product fo
3、r his particular need. Existence of such Standards and Pub- lications shall not in any respect preclude any member or non-member of EIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their
4、voluntary use by those other than EIA members, whether the standard is to be used either domestically or internationally. Recommended Standards and Publications are adopted by EIA without regard to whether or not their adoption may involve patents on articles, materials, or processes. By such action
5、, EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Recom- mended Standard or Publication. This document was developed by the JT-6 Committee on Tri-Color Cathode Ray Tubes of the Tube Ehgineering Panel Advisory Council (TEPAC).
6、Published by ELECTRONIC INDUSTRIES ASSOCIATION Engineering Department 2001 Eye Street, N.W. Washington, D.C 20006 PRICE: $5.00 Published in U.S.A. EIA TEP195 87 3234600 0008729 4 I 3 TEP195 Page 1 Method for Calculatina Refractive Gain For Color TV Picture Tube and Color M0nito.r Tube Screens The si
7、ze of TV picture tubes and monitor tubes is determined by the minimum viewable screen diagonal in the Worldwide Type Designation System. For color TV picture tubes and color monitor tubes, the actual screen size (on the inside surface of the face panel) is calculated from the specified minimum viewa
8、ble screen (as viewed from the outside surface of the face panel). Therefore, it takes into account the refractive gain of .the glass face panel of the tube (See EIA Recommended Standard EIA-527). However, there are different methods of determining the refractive gain. This TEPAC Publication describ
9、es the two methods of calculating the refractive gain that are to be used for color TV picture tubes and color monitor tubes. The first method is for face panels that are described by a polynomial, and the second method is for face panels that are described by annular segments of spheres. FOE Face P
10、anels Described by a Polynomial This method is to be used when the outside and inside surfaces of 0 the face panel are described by the following general polynomial: z=A, + Al*X2 + A, *X4 + A3 *X6 (1) + A4*Y2 + A5 *X2 *y2 + A6*X4*y2 + A, *X6 *Y2 + A,*Y4 + A, *Xz *Y4 + Alo*X4*Y4 + A, ,*X6 *Y4 + Alz*Y
11、6 + A,*X2*Y6 + A14*X4*Y6 + A15*X6*Y6 Where: Z = Sagittal height at the desired location X = Horizontal distance to the desired location Y = Vertical distance to the desired location The radial distance W from the 2 axis of the tube to the location of the desired sagittal height is calculated as foll
12、ows: w = (X“ + (2) For the horizontal axis of the screen, Y = O; therefore, W = X and formula (i) becomes: z = A, + A,*X2 + A, *X4 + A3 *X6 (3) Likewise, for the vertical axis of the screen, X = O; therefore, W = Y and formula (i) becomes: Z = A, + A4*Y2 + A,*Y4 + A, *Y6 (4) EIA TEPIS5 87 3234600 00
13、08730 Il W L TEP195 Page 2 A ray emitted through the outside surface of the panel parallel CO the Z axis of the tube (and a distance, Wo from the 2 axis) will have an angle (p) with the normal to the surface. In passing through the glass it will be refracted according to Snells Law, making an angle
14、(9) with the normal to the surface. The index of refraction M for glass panels is 1.52; therefore: 1.52 * sin (4) = sin (p) (5) The slope of the panel surface, tan (p), is determined by differentiating Z with respect to X, Y, or W. This approach assumes the slope in the t direction (normal to W) is
15、zero, which is exactly true for spherical segments and approximately true for the aspheric surfaces under consideration. . The refractive gain of the panel will be the difference between I W, and the point at which this ray will intercept the inside surface of the panel. The point of interception ca
16、n be calculated by successive approximations as follows (see Figure 1): For the first approximation, assume that the ray is not refracted; therefore: w, = wo Then evaluate Z, and Zil using formula (i), (3), or (4), as required. The first approximation for the refractive gain can be calculated as fol
17、lows: G1 = TI * tan (p-q) = (To + Zil - 2,) * tan (a-b) The second approximation is determined by evaluating Z, at: W, = Wo - GI The second approximation for the refractive gain can be calculated as follows: G, = T, * tan (p-q) = (To + Z, - Z,) * tan (p-q) The third approximation is determined by ev
18、aluating Z, at: The third approximation for the refractive gain can be calculated as follows: G3 = T, * tan (p-q) = (To + Z, - Z,) * tan (p-q) d) a TEP195 Page 3 Three iterations are usually sufficient; however, the procedure can be repeated until the difference from the previous approximation 0 mee
19、ts the required accuracy. An example using this method is included as Appendix A. It is described for calculation on a personal computer using the Lotus 1-2-3 program. For Face Panels Described by Annular Segments of Spheres This method is to be used when the outside surface is described by compound
20、 radii and the inside surface is spherical. More specifically, the outside surface is described by a central radius and a second radius which is offset from the tube axis producing annular spherical segments. The crossover (d, in Figure 2) between the spherical segments can be calculated by similar
21、triangles using the following formula: For sagittal heights at d.istances from the tube axis that are less than the crossover, the following formula can be used: 7) 2 = Rl - (RIZ - W2)o.5 For sagittal heights beyond the crossover, the following formula can be used: The refractive gain of the panel c
22、an be calculated in a similar manner as above except using formulas (7) and (8) for the sagittal heights. An example using this method is included as Appendix B. It is described for calculation on a personal computer using the Lotus 1-2-3 program. Sumnary The methods of calculating refractive gain d
23、escribed in this recommended standard are intended for use in determining the screen dimensions of color TV picture tubes and color monitor tubes in the Worldwide Type Designation System. EIA TEP195 7 3234b00 0008732 4 sl I d w, = w, - TEP195 Page 4 . T I Figure 1 EIA- TEP195 87 323qb00 0008733 h r r h .% a TEP195 Page 5 f wo - I Figure 2 TEP195 Page 6 u! EIA TEP195 87 E 3234600 0008734 B Appendix A CI CT I a Y & a CI o 8 W 3 - t EIA TEP195 87 W 3234b00 0008735 T : c TEP195 Page 7 Appendix B s c I h 51 si -I Y w I P 2 n A p. a I Y R O O 9 3
