1、- EIA TEPL05-9 87 m 323LIbOO 0007390 m r- o I u3 O e W I- r TEPAC PU B L I CAT I ON Line Profile Measurements in Shadow Mask and Other Structured Screen Cathode Ray Tubes TEPl05-9 JANUARY 1987 ELECTRONIC INDUSTRIES ASSOCIATION ENGINEERING DEPARTMENT _ EIA TEPL05-9 7 m 3234600 0007393 T m NOTICE EIA
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4、ons preclude their voluntary use by those other then EIA members, whether the atandard 13 to be used either domestically or internatienelly. Recommended Standarda and Publicatisna aro adopted by EM wltheut regard te whether or not their adoption may lnvelve patents on art!&, materkh 8F processes. By
5、 such action, $IA doe8 net 888ume any liability te my patent 8Wn&r8 nor does it essume any ebligsition whatever to partie8 8dQpflflg the Rooem= mended Standard or Publicetien, Pcrbllehed by EIA TEPL05-9 7 m 3234600 0007392 II m INDUSTRIAL CATHODE RAY TUBE TEST HETHOD 105-9 This publication was formu
6、lated under the cognizance of the JT-20 Committee on Electro-optic Devices and approved by the Tube Engineering Panel Advisory Council (TEPAC). developed for industrial cathode ray tubes. useful in evaluating cathode ray tubes with respect to parameters which are of interest to useks of these device
7、s. The TEP-105 series of publications comprise a set of test methods They are intended to be It is expected that, at an appropriate time, this material will be forwarded to the US National Committee (USNC) of the IEC as a proposed revision, in part, of IEC 151-14. 0 i - EIA TEP105-7 7 m 3234600 0007
8、393 3 m TEP105-9 Page 1 LINE PROFILE MEASUREMENTS IN SHADOW MASK AND OTHER STRUCTURED SCREEN CATHODE RAY TUBES 1.0 SCOPE The purpose of this test is to measure the profile of a line on the face of a shadow mask or other structured screen cathode ray tube (CRT) in order to estimate the resolution cap
9、acity of the CRT. Since the display on a CRT usually consists of a series of lines or line segments forming alphanumeric characters or graphics patterns the line width is an important parameter in the determination of the resolution. For this reason, the test method discussed below measures the hori
10、zontal and vertical (and possibly diagonal) profiles of the lines produced by the electron beam or beams. From these profiles, the line widths can be determined. Only one gun of a mutiple gun CRT is measured at a time. Such a test for determining the size of the CRT . spot is the first step in any r
11、esolution calculation. Note that line profiles can also be determined from measurements of the intensity contours of the CRT spot. This method of determining the line profile is not discussed in this document. The line profile of the CRT spot is dependent on a number of factors in addition to the fo
12、cused electron beam distribution at the screen. Some of these factors are: 1. Electron scattering in the screen and support structure 2. Light scattering due to the granular nature of the phosphor and the aluminum backing of the screen 3. Saturation of the phosphor 4. Internal reflections and absorp
13、tion of light in the faceplate and panels mounted onto the faceplate 5. Optical coatings, etches, etc., on the faceplate or panel TEP 105-9 Page 2 6. Static or dynamic convergence of the beams in multiple beam tubes External influnces on the resolution of the CRT, including ambient light, are not di
14、scussed in this method. These include the the transfer character- istics of the viewing sestem, .in .particular, the non- linear response of a human observer. Determination of the resolution of a structured screen CRT is a complex problem which is not completely solved at the present time. The limit
15、ing resolution of the tube can, in some cases, be estimated by referring to the conclusions reported in recent papers. For a shadow mask color CRT, the resolution is strongly dependent on the pitch of the shadow mask. Kojima and Barten2y3 suggest that for a dot screen CRT the spot diameter at 5% of
16、peak brightness should be 2.5-2.6 times the shadow mask pitch( the center to center distance between nearest neighbor mask holes ). The same relation seems to hold for line screen tubes where the pitch is the horizontal distance between the mask slots. For beams smaller than this, moire patterns are
17、 produced. In addition to the references above, a short bibliography is attached. The reader io urged to consult these references and the current literature before making any conclusions about the resolution of a structured screen display. 2.0 TEST EQUIPMENT 2.1 Power supplies are required to operat
18、e the CRT under the specified conditions of voltage, current and regulation. 2.2 2.3 . Deflection supplies providing linear sweeps in each deflection coil axis are required to generate the scan lines to be measured. The supplies should be capable of producing a single horizontal or vertical line at
19、the scan velocity and repetition rate specified for the CRT. If the CRT is to be used in other than a raster display, the deflection supplies should be capable of generating the scan type used in the final display. A microscope-analyzer consisting of optics, aperture, detector(s) and the necessary p
20、ower supplies for %he system must be provided. It is recommended that a round or square aperture be used. The effective aperture diameter should be smaller than the projected TEP 105-9 Page 3 3.0 2.4 2.5 -image of the phosphor element. The detector system must operate in a linear response mode over
21、the full range of light intensities involved. Complete units available from Celco, EG&G Gamma Scientific and Photo Research (or equivalent) may be used if sui table. TEST SETUP An oscilloscope, chart recorder, storage oscilloscope or computerized data acquisition system is necessary to display and a
22、rchive the line profile. The test should be conducted in facilities where ambient light levels can be reduced adequately to prevent interference with the measurements. The background, both elect- ronic noise and any ambient light not specif- ically accounted for in the measurement, should be as low
23、as possible. It is recom- mended that this background be less than one percent (1%) of the peak intensity. If the line width at 1% of peak height is desired, the background should be significantly lower than this recommended level. 3.1 The CRT shall be operated at the conditions specified. They shal
24、l include all tube elec- trode voltages as well as an operating condi- tion based on either drive, current, luminous output or radiant output. Purity and conver- gence should be adjusted. Deflection param- eters such as yoke type, neck hardware type, raster size, writing speed, retrace blanking inte
25、rval and repetition rate shall be specified if applicable. Specifications should realistically represent the conditions of use of the CRT. 3.2 The microscope-analyzer is adjusted so that the image of the scan line is focused on the plane containing the aperture. The image of a single phosphor elemen
26、t (dot or stripe) should completely cover the aperture. It is recommended that the characteristic dimension of the aperture be a maximum of one tenth ( 0.1) of the width of the projected scan line image in the aperture plane measured at 50% of the peak intensity. If this condition is not met, it may
27、 be necessary to correct the measured profile for the finite aperture TEP105-9 Page 4 3.3 3.4 4.0 EIA TEP105-9 87 3234600 O007396 9 size. The optical system should be such that all the light passing through the aperture is collected by the detector. On high light output tubes one must be care- ful t
28、o operate- the detector in a linear response mode. This may be accomplished through the use of neutral density filters or a variable aperture objective lens. The diffraction limit of the lens must not be exceeded when using small apertures in the objective lens. It is important that the optical aber
29、ations in the microscope do not appreciably affect the image. The depth of field of the microscope should be considered in evaluating the data. Line profile measurements are generally per- formed at the center of the tube face. It may be desirable to perform the measurements at the edges, corners or
30、 other locations on the CKT face. In these cases, it is important to ensure that the line profile is measured in a direction perpendicular to the scan line. At all points on the tube face, the aperture plane should be perpendicular to the axis of the tube parallel to the neck. Profiles of vertical l
31、ines should be taken to measure the horizontal dimensions of the CRT spot. These lines should be produced by driving the vertical coil of the yoke in a manner to provide the proper scan velocity and repetition rate. This technique elim- inates the effects of the finite width of the drive pulse and o
32、f the finite bandwidth of the video amplifier. In some special cases, it may be possible to make a valid measurement by rotating the deflection yoke by 90 degrees. TEST PROCEDURE 4.1 The line profile is measured by slowly moving the image of a single scan line (generated by a single gun in a mutiple
33、 gun CRT) across the aperture in the direction perpendicular to the scan direction. This motion must be provided by an electrical signal supplied to a deflection coil for the axis perpendicular to the scan line. This coil can be either the main deflection coil for this perpen- Y EIA TEP105-9 87 m 32
34、34600 0007397 O m 5.0 4.2 TEP105-9 Page 5 dicular direction or a separate special purpose coil. Calibration of this slow sweep can be achieved in many ways, Several possi- bilities are: 1) The scan line can be deflected a large distance which can be measured with either a ruler or a special gauge. 2
35、) The microscope can be translated to a second phosphor dot a known distance from the first. The deflection current required to move the beam this distance will provide a calibration. 3) A second aperture in the image plane will give two line profiles separated by a known distance. In this case, the
36、 spacing of the apertures must be commensurate with the phos- phor structure. 4) A large external mask containing two comparatively large slits a known distance apart can be used to determine the relation- ship between distance and deflection current. In this case, the slits could be large enough th
37、at the phosphor structure does not influence the calibration measurement. 5) The gain of the deflection amplifier may be changed by a known factor and the larger of the deflection amplitudes measured. A peak detector, sample and hold electronics, or an integrating voltmeter should be used to eiminat
38、e the effects of the phosphor decay and the periodic nature of the signal. The line profile is plotted or otherwise stored for further processing. DATA 5.1 Aminimum set of data shall consist of hori- zontal and vertical line widths at 50% and 5% of the peak intensity for all beams of the CRT measure
39、d at the center of the screen. Measurements at the 1% level are particularly useful for comparisons of gun designs and for evaluation of the perceptual characteristics , TEP105-9 Page 6 5.2 EIA TEPL05-9 87 323YbUU UUUiiY e W of the resulting display. Plots of the measured line profiles may be suppli
40、ed and modulation transfer functions (MTF) or just noticable difference (JND) analyses may be performed. It is recornmen-ded that the line widths be reported as a function of focus voltage over the nominal focus range of the CRT. The criteria used to determine the optimum focus must be carefully spe
41、cified. In addition, line width measurements at other than the center of the screen allow better evaluation of the quality and suitability of the CRT. 6.0 PRECAUTIONS 6.1 Care must be taken not to saturate the detector system such that its response becomes nonlinear. 6.2 Optical focusing of the scan
42、 line image onto the aperture plane is critical. Visual focus is operator dependent and may not correspond to optimum photometric focus. A useful method of optimizing the photometric focus is to maximize the detector signal when the image of the maximum intensity portion of the scan line is directly
43、 over the aperture. 6.3 6.4 6.5 Measurements taken at locations other than the center of the tube are dependent on the deflection yoke, convergence hardware, beam shaping coils, and geometry correction used. Although not specified in this document, the following items should be considered as they af
44、fect the accuracy and repeatability of the measurements: 1) Power supply stability and accuracy 2) Deflection and video jitter 3) Mechanical stability of the apparatus 4) Static and dynamic electromagnetic fields in the area of the CRT, including those intentionally used for geometry correction. Eac
45、h gun should be measured on its corres- ponding color phosphor to include phosphor EIA TEPL05-9 87 W 3234600 0007399 4 - -$ TEP 105-9 Page 7 saturation and/or phosphor grain limitations . in the measurement. REFERENCES AND SELECTED BIBLIOGRAPHY 1) Kojima, Ahikiro, Digest of Technical Papers, SID Int
46、ernational Symposium, - 14, 66 (1983). 2) Barten, Peter G. J., Digest of Technical Papers, SID International Symposium, - 14, 64 (1983). 3) Barten, Peter G. J., Proc. SID, - 25, 35 (1984). 4) Infante, Carlo, Seminar Lecture Notes, SID International Symposium, - 15, S.2b-2 (1984). 5) Rogowitz, B. E.,
47、 Proc. SID, - 24, 235 (1983). 6) Carlson, C. R. and Cohen, R. W., Proc. SID, 21, 229 (1980). N0TE:This entire issue of the Proc. SID isdevoted to the problem of image quality and resolution. 7) Carlson, C. R. and Cohen, R. W., Tech. Report to the Office of Naval Research, Contract No. N00014-74-C-01
48、84, July, 1978. 8) Klopfendtein, R, W., and Carlson, C. R., Digest of Technical Papers, SID International Symposium, 15, 56 (1983). 9) Griffis, P. D. and Shefer, J., IEEE Trans. Consumer Elect., - CE23 14 (1977). 10) Keller, Peter, “A Survey of Data-Display Resolution“, TEPAC Engineering Bulletin No
49、. 25, June 1985. This is a partial list of the papers dealing with the determina- tion of the resolution of a display system. It is not intended to be complete. The order in which the papers are listed is arbitary and is not intended to suggest the relative importance of the papers. The articles by Infante and Rogowitz are review articles which contain substantial l.ists of additional references.
