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1、Q W I - a TEPAC PU B L I CAT I ON Measurement of Phosphor Persistence of CRT Screens TEP105-14 ELECTRONIC INDUSTRIES ASSOCIATION ENGINEERING DEPARTMENT Copyright Electronic Components, Assemblies S,C=O FOR Ta0 TO T i a. D=D*VCT) S-S+VCT)nSINCP2nT) C*C +VCf)eCOS CP2xt3 NEXT T _ . R=SQRCCnC+SSS)/ PRIN
2、T USING 1770 5 F.R NEXT I Ripple ratio! PRINT o PRINT e PRIHT e P I I H T TEPlO5-14 Page 11 Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 01:45:56 MDTNo reprod
3、uction or networking permitted without license from IHS -,-,- TEP105- 14 Page 12 ADDENDUM II E I A TEPLOS-14 87 3234600 0007354 4 . Alternate Pulsed Raster Method The note in section IV.D.2 refers to a possible effect of excitation mode and duration upon the duration of the phosphor persistence sign
4、al. The field of view of the photodetector is cited as a factor in this interaction. This addendum illustrates a useful application of increasinq the field of view of the photodetector while measuring the persistence of a pulsed raster. I. Move the detector at least a raster dimension away from the
5、phosphor screen, so that it views the entire raster. 2. Excite the raster with a pulse longer than 33 milliseconds, or simply bias on the beam without applying a periodic pulse. 3. When the pulse or bias switch turns off the beam, the detector will rewrd a decaying signal elongated in time compared
6、to the impulse response of the phosphor under test. A. An exception occurs for a material having an exponential impulse response: no time elongation will occur in the pulsed raster decay in this case. B. The inpulse response IR(t) is defined as the decay signal resulting from a very narrow excftatio
7、n pulse as approximated in the pulsed spot technique. See Section IV.A.5. C. The recorded pulsed raster decay signal is identical to the integrated light remaining function I ( T ) which is defined in Section i, provided L ( t ) equals the impulse response IR(t). This provision is satisfied if L(t)
8、is the result of the pulsed spot measurement, or of the pulsed line measuremenc with the detector viewing a small portion of the line. We demonstrate this useful axiom by considering a snapshot of an excited raster. The snapshot shows the beam Landing on a spot within the raster, where the intensity
9、 is at its maximum. Immediately to the right of the landing spot the intensity falls abruptly, while to the left the fall-off in intensity is very gradual. We assign the following values to these in t ens it i e s : IR(t) , IR(O), IR(P-t) + IR(P+t), IR(P), IR(2P-t) + IR(ZP+t),. IR(ZP), IR(3P-t) +. +
10、 IR(NP+t), IR(NP), IR(M+IP-t) where t, on the order of microseconds9 is the scan time between the point to the left of the londing spot and the landing spot. P is the raster frame Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS
11、Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 01:45:56 MDTNo reproduction or networking permitted without license from IHS -,-,- E I A TEPLOS-14 87 323YbUU ijhh b m TEP10 5 - 14 Page 13 time, usually 33 milliseconds, and (N*L)P is the pulse width or raster excitation time. If a
12、photodetector integrated the intensities from all raster points, the integration becomes, in effect, a time integral of the Form, pulsed raster, within - f R ( t ) d t detector viewing angle o The integral from O to infinity of the impulse response must be finite and is well epproxinated by choosing
13、 N sufficiently large. Pulse widths on the order of seconds would achieve a steady raster signal even in the slowest phosphors prior to gur. cut-off. For fast phosphors, equally long pulses may be used, giving in any case a very close approximation to excited raster at steady state intensity 2 IR(t)
14、dt = finite constant (Finite because of finite energy in excitation puise.) O At time T after gun cut-off O pulsed raster persistence totally within detector viewing angle By letting 2 = T+t the integral becomes which is identically the integrated light remaining, Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 01:45:56 MDTNo reproduction or networking permitted without license from IHS -,-,-