ECA 300-1964 3 Image Orthicons Methods of Test for《3》.pdf

1、EIA 300 64 m 3234b00 00b5301 9 m ,- Il Il . II EIA STANDARD for METHODS OF TEST FOR 3“ IMAGE ORTHICONS ELECTRONIC INDUSTRIES ASSOCIATION STANDARD RS-300 APRIL, 1964 Formulated by JEDEC bleciren Tube Council EIA 300 b4 W 3234b00 00b5302 O W NOTICE These standards, adopted and issued by the Electronic

2、 Industries Association, were formulated by the Electron Tube Council of the Joint Electron Device Engineering Councils. EIA engineering standards are designed to serve the public interest through eliminating mis- understandings between manufacturers and purchasers, facilitating interchangeability a

3、nd improve- ment of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such standards shall not in any respect preclude any member or non-member of EIA from manufacturing or selling products not conforming to s

4、uch standards. Recommended standards adopted by EIA are without any regard to whether or not their adop- tion may in any way involve patents on articles, materials, or processes. By such action, EIA dqes not assume any liability to any patent owner, nor does it assume any obligation whatever to part

5、ies adopting the recommended standards. Published by ELECTRONIC IIYDUSTRIES ASSOCIATION Engineering Department 11 West 42nd Street, New York 36, N. Y. 0 Electronic Industries Association 1964 A11 rights reserved Price $.i0 - - Printed in U.S.A. , EIA 300 64 m 3234600 0065303 2 m RS-300 Page 1 METHOD

6、S OF TEST FOR 3” IMAGE ORTHICONS (From Standards Proposal No. 81 7 formulated under the cognizance of JEDEC Committee JTS-4 on Photosensitive Devices) 1. GENERAL 1.1 Reference: IEEE Standard 158, Electron Tubes, Methods of Testing, Part 8, Camera Tubes. 1.2 The results of any test on a camera tube t

7、hat utilizes magnetic deflection or focus or alignment are dependent on the design of the components used to produce the magnetic fields. The subject of any test must be considered to be the combination of the tube and these field-producing components. These components must be specified in the descr

8、iption of the test. 1.3 Considerable care is required in the design, construction, adjustment, and operation of test equipment in order that the results obtained will be characteristic of the camera tube only and further, that the results will be measurements which can be reproduced on a test equipm

9、ent of differ- ent design. Ordinarily the practical accuracy of these tests is limited to somewhere between 1 and 10%. 2. TEST EQUIPMENT Critical attention must be given to the uniformity of illumination of the test pattern, to the quality of the lens used for imaging the test pattern on the tube fa

10、ce, to the frequency dependence of amplification and phase shift in signal amplifiers, and to the linearity of amplifiers and oscilloscopes. 2.1 The Picture Monitor Scanning Amplitudes for test purposes are set so as not to overscan the face of the monitor tube in order that the whole raster may be

11、visible at all times. 2.2 The Dimensions of the Image Area on the Photocathode of the image orthicon may be set to the desired size by the following procedure: The desired scanned area is marked off on a sheet: of translucent paper. The lens to be used is removed from the camera and is used to image

12、 a rectangu- lar test pattern having the desired aspect ratio on the translucent paper. The lens-to-test pattern distance required to make the image of the test pattern fit the marked area on the translucent paper is determined. The lens iris should be fully open for minimum depth of focus during th

13、is determina- tion. The lens is replaced on the test camera, care being taken not to change its focal length and the test pattern set at the determined distance. Any point on the lens barrel may be used as the reference point for these measurements as long as it is used consistently. The Dimensions

14、of the Image Area on the Photocathode Equivalent to the Scanned Area on the Target will depend not only upon the design of the focusing and deflecting coils, but the relative positions of the tube and the coils. In determining these dimensions the proper target scanning area (in accordance with 3.1

15、under TEST CONDITIONS below) is first established by adjusting the lens to test-pattern distance so that the corners of the 3 x 4 rectangle test pattern just touch the inside of the image-orthicon target ring as viewed on the monitor with the camera tube operating in the over- scanned condition. The

16、 corresponding image area dimensions on the photocathode is then detei- mined by reversing the procedure of the method given above in The Dimensions of the Image Area on the Photocathode. With the camera tube in both optical and electrical focus, and with the scan directions rotated to align with th

17、e test rectangle, the scan amplitudes are set to scan the test rectangle by watching the picture monitor. 2.3 The Linearity of Scan is particularly important when measuring the signal uniformity because the signal is proportional to the rate of scanning. The deflection circuits may be adjusted to gi

18、ve a linear scan on the camera tube by means of the EIA Linearity Chart as described in the IEEE Stand- ards on Television : Methods of Measurement of Aspect Ratio and Geometric Distortion, 1954. (IEEE Publication 202). Since lens distortion of the barrel or pin cushion type affects this adjust- men

19、t, it should be determined that this is not a significant factor. EIA 300 b4 m 3234b00 0065304 4 m RS-300 Page 2 2.4 Determination of the Number of Loops of Focus in the Beam may be made based on the fact that this number is proportional to the magnetic focus field strength and inversely proportiona

20、l to the square root of the potential of the space through which the beam passes. 2.4.1 With fixed voltages on the tube electrodes, the focusing coil current is varied and its value determined for two or more successive conditions of electron beam focus. If the coil currents for these focus points a

21、re plotted against their numbers, the straight line so deter- mined may be extrapolated to zero current. This point identified the zeroth loop of focus, and the ordinal number of all the focus points is then determined. 2.4.2 In an alternate method the focusing field is maintained constant and the v

22、oltage varied to obtain two or more points of focus. In this method it is important that the persuader (G3), decelerator (G5), and beam-focus electrode (G4) voltages be proportionally varied to main- tain constant relative electrostatic field conditions. The reciprocal of the square root of the volt

23、age, preferably the beam focus electrode (G4) voltage, is plotted against focus-point number and extrapolated to zero (infinite voltage) to determine the zeroth loop. NOTE: Because of the relative complexity of the electrostatic field in the image orthicon, the method outlined in 2.4.1 is preferred.

24、 3. TEST CONDITIONS ExceDt where sDecificalls noted to do otherwise, the following parameters and test conditions should be esiablished as indicafed below : 3.1 Raster dimension relative to target size. 3.2 Photocathode illumination relative to illumination at the knee of the trans- fer characterist

25、ic. 3.3 Focusing field. 3.4 Number of loops of focus in the scan section of the tube. 3.5 Beam focus (G4) voltage. 3.6 3.7 3.8 Accelerator (G6) voltage. 3.9 Image focus voltage. Target voltage above target cut-off. Number of loops in the image section. 3.10 Beam current. 3.11 Decelerator (G5) voltag

26、e. 3.12 Persuader (G3) voltage. 3.13 Bulb temperature near target. 3.14 Scan rate. 3.15 Response characteristic of test equip- ment as a function of frequency. 3.16 Test Charts. Maximum diagonal dimension at the target (diagonal of raster = diameter of the target) using a 4 :3 aspect ratio of horizo

27、ntal to vertical picture dimensions. Twice the Knee (one f stop greater than that corre- sponding to the knee), or at the knee, or one half of that at the knee (one f stop less than that correspond- ing to the knee), as specified for the particular test. NOTE: In the case of image orthicons in which

28、 the knee is not well defined (such as wide spaced image orthicons) a specific photocathode illumination is used. 75 gauss, center of the field. 6 loops. Voltage on beam focus electrode necessary to obtain conditions (3.3.) and (3.4.) simultaneously ; between 140 and 180 volts. 2 volts. 1 loop. Adju

29、st for minimum S-distortion and ghost images ; between -300 and -450 volts. Voltage on photocathode necessary to obtain condi- tions (3.3.), (3.7.), and (3.8.) simultaneously ; be- tween -400 and -540 volts. Minimum required to discharge highlights of picture. Adjust for maximum signal output in the

30、 corners (minimum portholing) at a photocathode illumination corresponding to twice that of the knee of the transfer characteristic ; between O and 125 volts. Adjust for best compromise between maximum signal output and the flattest lens-capped background ; be tween 225 and 330 volts. 40“ f 2C. 30 f

31、rames per sec with 2 :1 interlace, 525 lines. Flat up to 10MC f 1 db. Resolution, linearity and gray scale test charts are ob- tainable from : Electronic Industries ASSOC., Engi- neering Office-11 West 42nd St., Room 2260, New York 36, New York. EIA 300 64 m 3234600 0065305 b m RS-300 Page 3 4. METH

32、ODS OF TEST 4.1 Beam-Control-Grid (Gl) Cut-Off Voltage 4.1.1 With illumination on the photocathode, overscan target so that the target ring is visible in the picture. 4.1.2 Decrease G1 potential until the highest light level in the scene is reduced to the black of the target ring. This potential is

33、the G1 cut-off voltage. NOTE 1: The beam-control-grid cut-off voltage measured above is not necessarily the same as the cut-off voltage determined by reducing the cathode current to zero. 4.2 Beam-Control-Grid (Gl) Operating Voltage 4.2.1. Set photocathode highlight illumination to twice that of the

34、 knee using the standard resolution test chart. 4.2.2 Increase G1 potential until the beam just discharges the highlights in the picture. This potential corresponds to the G1 operating voltage. 4.3 G1 Modulation is the difference between the GI operating voltage and G1 cut-off. 4.4 Target Cut-Off Vo

35、ltage 4.4.1 Set photocathode highlight illumination to twice that of the knee using a standard reso- lution test chart. 4.4.2 Remove blanking, if any, from the target. 4.4.3 Reduce target potential until the picture just disappears. Target potential should be reduced until the last portion of the pi

36、cture disappears. This reading is the target cut-off voltage. 4.5 Alignment 4.5.1 Method A 4.5.1.1 Set photocathode highlight illumination at twice that of the knee using the standard resolution test chart. 4.5.1.2 For alignment coils with two mutually perpendicular fields: Vary the beam focus (G4)

37、voltage while simultaneously adjusting the current through the two align- ment coils at 90“ to each other and normal to the focusing field. Correct alignment is obtained when the information near the central area of the test chart is observed to undergo no rotation or displacement as the focus field

38、 is varied through the point of focus. The magnitude of the alignment field is expressed in terms of the currents in the alignment coils. The vector sum of the two currents measured is taken as an indi- cation of the alignment field necessary to align the tube. 4.5.1.3 For an alignment coil consisti

39、ng of one coil mechanically rotated around the tube : Vary the beam focus (G4) voltage while simultaneously adjusting the current and mechanical position of the single coil normal to the longitudinal focusing field. Correct alignment is obtained when the information near the central area of the test

40、 pattern is observed to undergo no rotation or displacement as the focusing field is varied through the point of focus. The alignment field is expressed in terms of the coil current and its angular mechanical position relative to the jumbo pin in the image section. 4.5.2 Method B 4.5.2.1 Cap lens. 4

41、.5.2.2 Same as 4.5.1.1 and 4.5.1.2 except that at correct alignment the image of the dynode aperture is observed to undergo no displacement as the focusing field is varied. NOTE : Because of the very diffuse nature of the dynode image obtained with field-mesh image orthicons, only Method A is applic

42、able for this image orthicon type. EIA 300 64 m 3234600 0065306 B m RS-300 Page 4 4.6 Transfer Characteristics (below the knee) 4.6.1 Use a horizontally mounted, calibrated linear gray-scale step chai-t. The background for this scale corresponds to step #9. The step of lowest brightness, step #lo, s

43、hould be black; a swatch of clean black velvet or an opaque strip in the tube face may be used with a reflectance step chai-t. 4.6.2 The linear gray-scale should correspond to 10% of the total raster area, the gray back- ground comprising the remainder. 4.6.3 Set photocathode illumination so that th

44、e highlight (step #1 of the scale) is at 1/2 that of the knee. NOTE : For tubes without a well defined knee (such as wide-spaced image orthicons) the high- light illumination is set to a specified value. 4.6.4 Line select through the gray scale. Measure the signal amplitude on the oscilloscope for e

45、ach step. The camera should be panned so that each measurement is made at the same point on the photocathode of the image orthicon. A plot of signal amplitude as a function of its associated step brightness gives a graphical representation of the transfer characteristic. 4.7 Knee of Transfer Charact

46、eristic 4.7.1 Set up the linear gray-scale and line selection as in 4.6. 4.7.2 Increase the light level (by opening the lens iris) until the brightest step of the gray- scale chart no longer increases in amplitude at the same rate as the others. The brightest step is then considered to be at the kne

47、e of the transfer characteristic. NOTE: For image orthicons with wide target-mesh spacing the slope of the transfer charac- teristic decreases slowly over a wide range of photocathode illumination. Because of its poorly defined nature, the knee of the transfer characteristic is normally not consider

48、ed in such tubes. 4.8 Spectral Response, Photocathode Luminous Sensitivity, and Photocathode Radiant Sensitivity : Treat image orthicon as a phototube with accelerator electrode (G6) and target assembly tied together as anode. See “Methods of Test for Phototubes.” 4.9 Signal-to-Noise Ratio 4.9.1 Met

49、hod A 4.9.1.1 Set photocathode highlight illumination at twice that of the knee using a stand- ard resolution test chart. For tubes without a well-defined knee, such as the wide-spaced image orthicons, the highlight illumination is set to a specified value. 4.9.1.2 Line select through a region containing an adjacent black and white. 4.9.1.3 Record the peak-to-peak black-to-white signal as measured from the mid-point of the black noise to the mid-point of the white noise. 4.9.1.4 Measure and record the peak-to-peak noise in the black and the peak-to-peak noise in the white. Obtain an average