Fig .... 1-Type 520 .NTSC Vectorscope

!NTRODUCT!ON of picture quality are readily made. How­ ever, certain signal distortions-particularly Color TV has caused Television Broadcast differential rihase may he difficult to iden­ facilities to expand at a rapid rate. The tify or diagnose. The push-button operating controls are ar­ resulting increase in the quantity and com­ ranged into two groups-one for signal se­ plexity of studio equipment has created a lection and one for measurement display need for more versatile, easier to use, meas­ mode. All controls unnecessary for specific uring equipment. Oscilloscopes are exten­ A new V ectorscope was developed, to measurement are automatically disconnected sively used in the TV Broadcast industry assist the Broadcast Engineer and Tech­ from use to eliminate front-panel confusion. as program monitors to measure picture nician in making these color measurements. Controls such as the CRT display focus and levels, as troubleshooting devices to isolate The new Tektronix 520 NTSC Veclorscope pos1t10ning controls which require only equipment malfunctions, and as a measure­ (Fig 1) was designed with emphasis as an periodic adjustment are located behind front­ ment tool to determine waveform compli­ "operating" instrument rather than a special panel doors. ance with FCC Standards. test oscilloscope used only to identify or Fig 2 shows the typical vector display of The studio operator now routinely veri­ solve special video problems. a 75 % saturated color bar test signal. Note fies or adjusts a variety of parameters that the sharply defined spots which permit in­ The new oscilloscope is designated as a were not required with black and white creased phase-angle resolution, particularly "vectorscope", however, the addition of a equipment; burst phase, I, Q, burst level, useful for detecting phase jitter or very luminance channel has extended the meas­ color bar phase, luminance to chrominance small phase errors. urement versatility to include most of the level and others. routine checks required in a color camera Fig 3 illustrates the comparison of two chain. signals on a time-shared basis. Channel A In addition to the variety of color system is displayed for two scanning lines and setup requirements, greater emphasis is being \.Vhile measurement versatility is important channel B displayed on the next successive placed on in-service monitoring of picture when considering the purchase of any piece two scanning lines. The time-shared signals quality. Signal distortion limits which de­ of equipment, ease of operation and long appear as if they were being displayed fine acceptable picture quality arc well es­ term reliability are equally important. on a dual-beam oscilloscope. The time dif­ tablished. Suitable test signals have been Through special design efforts the Type ference between the two input signals nor­ developed to check distortion; i.e. NTSC 520 Vectorscope provides the user with sta­ mally causes a phase-angle displacement be­ Color Bar Test Signal, Linearity siair-step, ble drift-free displays at the touch of a t ween the two displays (Note Fig 3). This etc. Using these standard test signals as button, without sacrificing measurement res­ condition is normal and is due to subcarrier reference values, quantitative measurements olution or accuracy. reference in the instrument being locked

2 © 1967, Tektronix, Inc. All Rights Reserved to only one of the signals. By adding a sec­ oml phase-control knob to the front panel and time sharing its operation with the first phase control, the burst of each input signal One of the more familiar applications can be independently rotated to the X axis of the vectorscope is the measurement of permitting an overlay of the vectors for differential phase and differential gain. The direct comparison. For example, Fig 4 Type 520 Vectorscope provides these meas­ illustrates the input and output waveforms urement capabilities quickly and accurately of a distribution amplifier, with intentional at the touch of a button. Fig 5 illustrates distortion, applied to Channel A and Chan­ the Differential Gain operating mode using nel B inputs respectively. Differential phase a modulated stairstep waveform. A dif­ and differential gain can easily be seen to ferent graticule is used to measure dif­ exist on the yellow, cyan and to a lesser ex­ ferential gain than \1·as used to m

Fig 2-Vector display of 7 5 % saturated color bar test signal Fig 3-Vector display with channel A and B time-shared

100 - dA - 80 ·= 10" II ~ 80 = 8 11, 1=. ll 4 \ 40 I r= ,·n• I" 0 ,,:::: 2.0 -2 ••• 11i I= ui: -4 7.5..,. - ~ ...,. ;- 0 II -6 -8 II -20 -10"

-40

Fig 4-Vector display of input and output waveforms from a distri­ Fig 5-Differential Gain display using a modulated stairstep wave­ bution amplifier form 3 When the d ¢ (differential phase) button MEASUREMENT from viewer to viewer making con­ is depressed, the display is automatically The Type 520 Vectorscope utilizes the sistent readings difficult. repositioned to the center of the CRT and luminance portion of the composite color the graticule illumination removed. The 3) Picture monitor characteristcis may signal to permit measurement of the trans­ measurment is then taken from the calibrated vary. formed reel, green and blue picture values phase shift dial and the CRT display now which normally appear at the picture tube 4) Small error differences between the serves only as a null indicator. Since con­ of a color monitor. The Y (or M) luminance and chrominancc waveform siderable amplifier gain is required to re­ luminance signal and the chrominance sig­ amplitudes are almost impossible to solve phase differences of 0.2 degree or nal are transformed at the receiver into detect without using picture compari­ less, small amounts of noise existing on reel, green and blue picture components. son techniques. either the applied signal or in the vector­ Currently, the only means by which the scope will make display interpretation diffi­ transformation can be verified is by ob­ cult. Display interpretation is simplified by serving the display from the color picture Measurement of the transformed signal alternately inverting the display to produce tube itself. Subjective evaluations of pic­ is made by selecting one of four buttons the mirror image observed in Fig 6. Any ture quality made from color bars viewed labeled Y, R, G, B. These buttons corre­ noise on the display (as evidence by a wide directly on a color monitor are influenced spond to luminance, red, green and blue trace) can then be averaged out by simply by several variables : video displays. adjusting the overlayed traces for minimum trace width. In Fig 6 each step has a phase l) Phosphor light output efficiency is ·when saturated colors (75% or 100%) transient in the middle amounting to about reduced with age or usage. arc displayed on a picture monitor, the 0.09°. 2) Color response of the human eye varies monitor electron guns arc either on or

Fig 6. Differential Phase measurement using a modulated stair-step signal. Dial reading A to dial reading B indicates 2.1 ° differential phase.

Fig 7-Red values of NTSC Color Bar Test Signal with magenta Fig 8-Red values of the NTSC Color Bar Test Signal with luminance and red bars oversaturated amplifier nonlinearity in the white region 4 Fig 9-Green values of NTSC Color Bar Test Signal Fig 10-Blue values of NTSC Color Bar Test Signal

off as primary and complementary colors to the eye (because reel is a primary color) are reproduced. During the primary color the magenta error would be more difficult to "Reel", for instance, the reel gun is on and detect in the reproduced picture. green and blue guns are off. The comple­ n1entary color of "Reel" is "Cyan", which Fig 10 shows the blue picture display is reproduced by the green and blue guns which is not as seriously affected by lumi­ with the red gun held off. nance errors. In Fig 7 the reel (R) "image" is displayed on the vectorscope using the "standanl" cle­ coclecl color bar signal. The colors are ar­ ranged from the left of the display to the right in order of descending luminance­ grey, yellow, cyan, green, magenta, reel, and blue. Note that the magenta and reel Push-button controls provide new operat­ bars arc over-saturated, however, the error ing convenience and permit rapid selection is not easily detected by the eye on the pic­ of displays for quick analysis of television ture monitor because the error is not too color signal characteristics. Amplitude cali­ large. Observing the vector display of the brated displays of chroma and luminance same signal in Fig 2 indicates that the are assured with internal calibration test chrominance portions of the encoclccl color signals to verify amplifier accuracy. The bars are correct. Therefore the luminance luminance component of the composite color levels for magenta and reel must be incorrect signal is derived for displaying separately -too high in this case. In this illustration, or in combination with the reel (R), green since only two color bars are affected, the ( G), or blue ( B) components. error is not due to non-linear luminance gain but simply because the luminance ped­ Two 0° to 360° phase-shifters provide A parallax-free vector graticule, or IRE estal levels of the color bar generator are independent phase control of channel A graticule, is automatically selected and edge­ incorrectly adjusted. and B. Phase differences caused by unequal lighted concurrent with operating mode se­ signal paths are easily cancelled. A precision lection. All silicon solid-state design provides Fig 8 shows the same display except calibrated phase shifter with a range of 30°, long-term reliability and cool, quiet opera­ that the luminance amplifier is non linear spread over 30 inches of dial length pro­ tion. in the white region. The effect however, vides excellent resolution for making small The Type 520 NTSC Vectorscope 1s is not apparent on the grey and yellow bars phase angle measurements. Video cable available in electrically identical cabinet or but on the magenta, reel and blue bars lengths can be accurately matched for time rackmount models. and is clue to the luminance amplifier gain delay at the color subcarrier frequency to having been adjusted with a white pedestal. less than 0.5 ° phase difference. Differential A more complete description of this in­ gain and differential phase measurement strument is found in the Tektronix New Fig 9 illustrates the green ( G) display capabilities are provided with accuracies Products Catalog Supplement recently dis­ of the same waveform. Note the luminance within 1% for gain and 0.2° for phase. tributed. distortion previously observed affects the green more seriously. Green should he A digital line selector permits the display TYPE 520 NTSC VECTORSCOPE $1850 off during the last three bars. \Vhile the of a single line Vertical Interval Test Sig­ TYPE R520 RACK.MOUNT ..... $1850 slight presence of green during the red bar nal from a selected line of either field 1 will cause the displayed reel to appear orange or field 2. U.S. Sales Price FOB Beaverton, Oregon 5 TYPE 611

INTRODUCTION (3) Techniques to improve computer time are to be presented, the Tektronix simpli­ utilization were developed. fied direct-view bistable-storage CRT pro­ The Type 564 Storage Oscilloscope, a vides an economic solution to the memory/ measuring instrument, served as an excel­ ( 4) Computer time-sharing appeared to display problem. lent exploratory tool to determine the ad­ be a solution to efficient use of computer vantages of bistable-storage cathode-ray time but because of input-output limitations, tubes as computer readout devices. Sev­ many parallel or time-shared users are re­ The interested groups who experimented eral groups experimented with the bistable quired in order to keep the computer busy. with the Ty11e 564 Storage Oscilloscope storage tube in this application and the (5) Time-sharing a central computer re­ as a computer remote-terminal readout de­ results show that a bistable storage tube quires remote terminals convenient to the vice were encouraged by the results obtained when used with the appropriate periphal and indicated the need for an instrument equipment provides high-resolution, non­ users. optimized for computer display rather than refreshed, alpha-numeric and graphics dis­ ( 6) The cost per remote terminal for measuring applications. Producing an in­ plays without flicker or fade. time-sharing application must be sensibly strument specifically for computer readout low. A sequence of events occurred as the purposes required different design objec­ tives than those for measuring devices. computer market developed that contributed (7) A major economic consideration of toward the development of .the bistable stor­ remote terminals is local memory cost, es­ ( 1) ·writing-speed parameters could be age tube as a computer display device. pecially if arbitrary format alpha-numeric traded off for more uniform and smaller and graphic capabilities are required. It is spot size. ( 1) Computer usage was being discour­ not economically wise to provide display (2) Plug-ins replaced with built-in am­ aged by man-to-machine interface problems, refreshing from the computer memory, and plifiers resulting in a more compact unit. that is, a problem is submitted through a even with a buffer memory the communica­ programmer, a misunderstanding is found tion link bandwidth may be too narrow to (3) The Z axis modified for "on-off" after a period of time, the problem is re­ allow refreshing a display at above flicker operation. submitted, etc. rates. ( 4) The CRT target modified for im­ (2) Larger and faster computers were (8) For applications where flexible for­ proved isolated stroke or dot appearance (a developed to help offset computation costs. mat is required and large amounts of data key contribution). 6 ABSOLUTE OIFF. TO VERT. GEOM. The recently announced Types 601 and VALUE OF MULTI SINGLE CORRECTION SQUARE PLIER >-----...~O FEEDBACK ENDED 611 Storage Display Units were designed to x OF. VERT. be used as integral parts of computer remote ±y terminals. vVhen driven by the appropriate periphal equipment these units will present non-refreshed displays of alpha-numerics and graphics without flicker or fade. xz The Type 601 and 611 are intended for xz + yz SUM >----....- DYNAMIC individual use, not group viewing. The high y2 FOCUS resolution of the 601 and 611, require the viewer to sit fairly close to the instruments in order to resolve the displayed informa­ tion. Y SIGNAL :x HOR!Z. GEOM. ABSOLUTE DIFF. TO 2 The Type 601 Storage Display Unit fea­ ----+-i>-l VALUE OF SQUARE MUL Tl PLIER SINGLE >--Y~~x-~~CORRECT ION y ENDED TO cEEDBACK tures a new, Tektronix developed, 5-inch OF HORIZ. bistable-storage display tube, providing clear, non-fading presentations. Resolution in an Fig 1-Block diagram of Type 611 pincushion and dynamic focus correction. 8-cm x 10-cm display area is 100 stored line pairs in the vertical axis and 125 stored line pairs in the horizontal axis providing an ic focus summing circuit gets its input from the multipliers, rather than the squaring information capacity of about 400 alpha­ Compatibility between the Types 601 and circuits directly, because of the signal levels numerics. The information storage rate is 611 is maintained with regard to the input involved; that is, the output of the multiplier 100-thousand dots per second and time re­ connectors and selection of common func­ is at a more convenient level than the squar­ quired to erase the stored information is tions, such as erase. However there are ing circuit. This combination of corrections 200 ms. All solid-state modular circuit de­ differences which should be kept in mind. appears to be new, and unexpectedly simple. sign insures long-term stable performance. The Type 601 has ± 6 cm continuously The operating functions are remotely pro­ variable position controls for X & Y, while The Type 601 with an electrostatically grammable by simply grounding program the Type 611 has three position switches deflected tube has a itnique method of cor­ lines at a rear-panel connector. Access to X, that permit the operator to select one of rection ; instead of the usual rotation coil, Y and Z inputs is through rear-panel BNC nine beam resting positions. Variable con­ signals are independently mixed from the connectors or a remote program connector. trols provide a ± 10% range for small ad­ X and/or Y amplifiers into the Y and/or justments of each position. The limited var­ X amplifier, thus introducing tilt and/or iable range was chosen because of the more slant as necessary to correct trace alignment and/or orthogonality. Because of this cross­ The Type 611 Storage Display Unit fea­ stringent drift requirements of the Type 611. Both units have internal gain calibration ad­ mixing, the use of the Type 601 as a wave­ tures an 11-inch 1rn1gnetically deflected, form monitor should be restricted to appli­ bistable-storage display tube developed by justments to set the full screen deflection voltage within 2% of 1 volt. Both units cations involving bandwidths below 100 kHz. Tektronix. This new storage tube offers The smaller deflection angle and lower res­ high information density and excellent res­ have provision for other less-sensitive de­ flection factors. olution requirement of the Type 601 make olution on a 21-cm x 16.3-cm display screen. dynamic scan or focus corrections unnec­ The information capacity of the Type 611 Trace alignment of the two instruments essary. is about 4000 alpha-numerics. Dot settling is different. The Type 611, using an elec­ time is 3.5 µs/cm plus S µs and clot writing tromagnetrically-deflectecl tube, has an ex­ time is 20 µs. The time required to erase ternal deflection yoke which may be rotated The first instrument to use the Tektronix and return to ready-to-write status is 0.5 to align the traces; orthogonality is a func­ developed bistable storage tube was the Type seconds. tion of how well the yoke was manufactured. 564 Storage Oscilloscope, introduced in the The operating functions are remotely pro­ The larger screen requirement of the Type spring of 1962. Since that time, the Type grammable through a rear-panel connector 611 requires magnetic deflection through 564 has found extensive use in a multiplic­ with access to X, Y and Z inputs through an angle of 70°, in order to keep the length ity of applications including information rear BNC connectors or the remote pro­ of the instrument reasonable (the Type 611 display. Early experiments with the Type gram connector. A "Write-Through Cur­ is about 20% longer than the Type 601). 564 as an information display device proved sor" feature permits positioning the writing The wide magnetic deflection angle of the the validity of the concept and helped define beam to any point on the display area with­ Type 611 CRT, together with the flat face­ new storage tube requirements ; the Type out storing the cursor or destroying pre­ plate, requires correction to the deflection 601 and 611 Storge Display Units are the viously stored information. Write through geometry, linearity and focus. vVithout go­ first display instruments to employ these for alpha-numerics and graphics can be done ing into the mathematical details, it can be new storage tubes. said that both pincushion and dynamic focus by shortening the unblank pulse duration A more complete description of these new from the normal value of 9 µs (Type 601) require squared deflection terms. Figure 1 instruments is found in the Tektronix New shows the block diagram. The squaring cir­ or 20 µs (Type 611). This mode of opera­ Products Catalog Supplement recently dis­ tion is useful for manual graphics, with the cuit is a single FET. The multiplier is a tributed. aid of equipment like the Rand Tablet or differential pair driven from a current with ~n SRI Mouse. An internal test signal source. Thus with comparatively simple Type 601 Storage Display Unit $1050 provides a quick check of focus, storage circuitry, the circuit generates the required and general performance status of the in­ X'Y and Y'X for pincushion correction, and Type 611 Storage Display Unit $2500 strument. X' + Y' for focus correction. The dynam- U.S. Soles Prices FOB Beaverton, Oregon

Printed in U.S.A. TPD A-2372 7 Tektronix, Inc. P.O. Box 500 Beaverton, Oregon, U.S.A. 97005

/ s·L--­ )

( 11/~t F~ANKGRt~~ rtPT. ~R~~~~~~v l~ & Svsrt~sLAa~ OTTAWA lNTERNATDONAL Al~PO~T OTTAWA, ()NTAR&O, (ANAOA