1、1 I in O e, W b - - STD-EIA TEPLOS-Lb-A-ENGL ZOO0 323Lib00 Ob57717 Tb TEPAC PUBLICATION Test Method for Phosphor Linearity TEP 105- 1 6-A (Revision of TEP105-16) JNE 2000 ELECTRONIC COMPONENTS, ASSEMBLIES I is the beam current in milliamperes; width of scan line is given in centimeters; use the full
2、 beam width defined by the half maximum intensity writing speed is given in centimeters per microsecond. points. EXAMPLE-A typical high drive condition for entertainment CRTs would be five milliamperes beam current per gun at a writing speed of about one centimeter per microsecond. Assuming a typica
3、l beam diameter of 0.2 centimeters, one obtains E (typical entertainment) = 5 mA I ( 0.2 cm) x ( 1 cm/ps ) = 25 nC/cm2. This excitation density is sufficiently high that it reduces the luminous efficacy of ZnS:Ag blue phosphor and ZnS:Cu green phosphor to about 80% of their “normal” values. Sublinea
4、r effects known as “saturation” become quite evident at this level. White colors acquire a reddish hue due to the more constant linearity of the red primary, and the green primary itself may shift in spectral distribution towards shorter wavelengths. The latter phenomenon has been reported in severa
5、l studies. Some authors express the per unit area excitation density, E, in units of energy (joules) rather than electric charge (coulombs). To do this they multiply the expression in equation 2 by the anode potential in volts. Their results in energy vs. charge densities are shown in table I where
6、the beam current, spot diameter, and writing speed are taken from example 1. A 1 STD-EIA TEPLOS-Lb-A-ENGL 2000 E 3234bUO b59922 Yb3 E 5 5 TEP-105-16-A Test method for phosphor linearity Page 2 w 0.2 1 30 5 25 0.75 1500 0.2 1 15 2 25 0.38 1900 Phosphor linearity test Anode voltage, kV 30 Average beam
7、 current, pA 1 O Peak beam current, mA 1.8 Width of scan line, cm 0.15 The last column in table 1 points out a peculiar feature of the per unit volume energy density. It actually is higher at lower anode voltage because the assumed beam penetration depth into phosphor particles is superlinear with a
8、node voltage, .e., varies by a power of the anode voltage greater than one. The effect upon the volume energy density is to make it increase by 23% in halving the anode voltage. The per unit area energy density varies in the opposite direction (increases) by 100% as the anode voltage is halved. Whic
9、h measure should one use for characterizing phosphor linearity? Linearity of luminescence should be governed by the volume energy density and not the area energy density if significant variations in the anode voltage occur. Moreover the volume energy density is more closely related to the area charg
10、e density than to the area energy density. One may therefore profitably choose to use the area charge density as the most significant parameter in phosphor linearity studies. We have done this in equation 2. Phosphor type: XXD-green Date: 511 9/99 CRT type: A68ADT19XOl Horizontal scan time, ps 53 Fi
11、eld repetition rate, Hz 60 Phosphor at low drive, CdNV 20.7 CRT shadow mask transmission 0.2 2 Definitions Glass transmittance excitation density: The per unit area per pulse charge density. pulse duration: Typically 100 ns, the dwell time of the scanning beam on a phosphor particle. 0.5 pulse inter
12、val: Typically 16 ms, the time between consecutive pulses. luminous efficacy: luminous flux in candelas per watt incident beam power. phosphor linearity: Luminous efficacy at a given excitation density expressed as a percent of the asymptotic maximum value at low excitation density. 3 Typical CRT te
13、st conditions for measuring phosphor linearity 3.1 A video pattern should be imposed to reduce the average beam current to a value less than 10% of the peak current. Crosshatch patterns consisting of horizontal and vertical lines are preferred, where a 10 fi average beam current typically correspond
14、s to 1.8 mA peak current. 3.2 Align a luminance detector such as a spectroradiometer to focus on the center part of the horizontal line where it crosses the minor axis of the tube so that when the horizontal scan is collapsed the detector will still see a segment of the line. 3.3 The data sheet head
15、er should contain information about the test conditions similar to that in the following example: - - STD-EIA TEPLOS-Lb-A-ENGL 2000 e 3234b00 b59923 3TT IPI Writing speed Excitation density, nC/cmL Horizontal scan size (cm) I53 ps I .8 * 53 / (0.1 5 * horizontal scan size in cm ) 3.4 record the lumi
16、nance and the CIE x and y coordinates of the viewed segment of the line. Generate a data table resembling table 2 in which at least ten such sets of luminance readings vs. excitation densities are recorded. The excitation densities are computed from equation 2. Vary the horizontal scan size in discr
17、ete steps until it collapses to a centimeter. At each setting The input power density in W/m2 is obtained by multiplying the excitation density Q in nC/cm2 by the field repetition rate (60 Hz), the anode voltage (30 kV), and by 0.01 to convert from microwatts per square centimeter to watts per squar
18、e meter: Input power density (W/m2 ) = V/ft/ hw where (3) V i Is the anode current: f Is the refresh rate; t h Is the horizontal length; w Is the screen anode voltage; Is the horizontal sweep time: Is the beam spot diameter The luminances in candelas per square meter are assumed to be the results of
19、 measurements using a spectroradiometer focused on the central one centimeter section of a horizontal scan line in the crosshatch pattern. If the width of the scan line does not completely fill the vertical dimension of the sampling window of the spectroradiometer, the luminance reading should be sc
20、aled by a correction factor. The phosphor linearity according to 2.5 is the luminous efficacy in candelas per watt expressed as a percent of the maximum value of luminous efficacy at low excitation density. Phosphor linearity = 1 O0 0 luminance/(input power density) 0 20.7 0 glass mask (4) where one
21、 takes into account the glass transmittance and the mask transmission factors. If the sampling window of the luminance detector is not completely filled by the width of the scan line some false reduction in the luminance measurements will result and be carried over to the phosphor linearity values.
22、Since luminance detectors are usually equipped with reflex viewers which allow the operator to see TEP-105-16-A Test method for phosphor linearity Page 4 whether the sampling window is filled, some estimate can be made of the degree to which incomplete filling occurs. Numerical corrections can be ap
23、plied to the luminance readings to compensate for the sampling error. To roughly check the accuracy of the phosphor linear2y test examine the linearity value for the lowest excitation density (in this example 91.5% for Q =12.7 nC/cm ). Make another determination at half the anode current; if the sam
24、e linearity value results then the linearity values for all excitation densities need to be corrected by 100 divided by the maximum linearity value obtained in the test. Energy conversion efficiency of XXD green phosphor 0.0 i I I I I I Excitation density, nC/cm2 O 100 200 300 400 500 600 700 Figure
25、 I-Phocphor linearity vc excitation density EIA Document Improvement Proposal Document No. If in the review or use of this document, a potential change is made evident for safety, health or technical reasons, please fill in the appropriate information below and mail or FAX to: Document Title: Electr
26、onic Industries Alliance Engineering Department - Publications Office 2500 Wilson Blvd. Arlington, VA 2220 1 FAX: (703) 907-7501 Signature: Date: Submitters Name: I Telephone No.: FAX No.: e-mail: Address: I Urgency of Change: Immediate: At next revision: 0 Problem Area: a. Clause Number and/or Drawing: I I FOR EU USE ONLY Responsible Committee: Chairman: Date comments forwarded to Committee Chairman:
