@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Applied Science, Faculty of"@en, "Electrical and Computer Engineering, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Yusuf, Tundey"@en ; dcterms:issued "2011-05-24T22:22:48Z"@en, "1970"@en ; vivo:relatedDegree "Master of Applied Science - MASc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """This is an instrumentation thesis. The interface system discussed is a link between an ordinary TV camera and a computer for storage of visual data. The same system can also be used as a link between the computer and a display monitor. Because of its wide bandwidth, a video signal cannot be sampled at the Nyquist rate and presented to a computer. Previous interface systems overcame the problem by scanning slowly on an element-by-element basis using a special scanner and then presenting the samples to the computer. After processing, the data would be read out at the same slow rate and displayed on a special display monitor. The interface described in this thesis will accept material obtained from an ordinary TV camera scanning at standard rate. By using a "stroboscope" sampling technique the samples are presented to the computer slowly enough for it to process. After processing, the data is displayed in a similar manner on a normally scanned monitor for evaluation. Basically the interface operates as follows: A TV camera video signal is sampled at a rate slow enough for computer acceptance. The camera scans the same picture several hundred times until all the points representing the picture have been sampled and stored, the sampling is controlled such that all the points are each sampled only once. Because of the sampling method consecutive samples in the computer do not correspond to adjacent points on the picture being stored. It may therefore be necessary to programme the computer to arrange the samples such that adjacent data in the computer represent consecutive picture points before processing. After processing, the samples may be rearranged and read out for display in the same order they were stored. The horizontal resolution of the picture being stored can be varied quite easily in steps. For example, a system designed to have a maximum of 480 points/line will also have the ability to provide such lower resolutions as 60, 120 and 240 points/lines. This variation is made possible by the design of the hardware. By software the vertical resolution can be varied between an upper limit of 525 lines per picture and such near submultiples of this as 263 and 131 lines/picture. The thesis is discussed in relation to the PDP-9 computer on which most of the work described was done. However, the system interfaces readily with other computers."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/34777?expand=metadata"@en ; skos:note "A TELEVISION CAMERA TO COMPUTER INTERFACE by TUNDEY YUSUF B.Sc. U n i v e r s i t y o f W a l e s , Swansea, 1968 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n t h e Department o f E l e c t r i c a l E n g i n e e r i n g We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d R e s e a r c h S u p e r v i s o r Members o f t h e Committee A c t i n g Head o f the Department Members o f t h e Department o f E l e c t r i c a l E n g i n e e r i n g THE UNIVERSITY OF BRITISH COLUMBIA A u g u s t , 1970 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my Depar tment o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l no t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Depa r tment The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, Canada ABSTRACT . This i s an instrumentation t h e s i s . The i n t e r f a c e system discussed i s a l i n k between an ordinary TV camera and a computer f o r storage of v i s u a l data. The same system can also be used as a l i n k between the computer and a d i s p l a y monitor. Because of i t s wide bandwidth, a video s i g n a l cannot be sampled at the Nyquist rate and presented to a computer. Previous i n t e r f a c e systems overcame the problem by scanning slowly on an .element-by-element basis using a s p e c i a l scanner and then presenting the samples to the computer. A f t e r processing, the data would be read out at the same slow rate and displayed on a s p e c i a l d i s p l a y monitor. The i n t e r f a c e described i n t h i s thesis w i l l accept material obtained from an ordinary TV camera scanning at standard rate. By using a \"stroboscope\" sampling technique the samples are pre-sented to the computer slowly enough f o r i t to process. A f t e r processing, the data i s displayed i n a s i m i l a r manner on a normally scanned monitor f o r evaluation. B a s i c a l l y the i n t e r f a c e operates as follows: A TV camera vid-ao s i g n a l i s sampled at a rate slow enough f or i computer acceptance. The camera scans the same p i c t u r e several hundred times u n t i l a l l the points representing the p i c t u r e have been sampled and stored, the sampling i s c o n t r o l l e d such that a l l the points are each sampled only once. Because of the sampling method consecutive samples i n the computer do not correspond to adjacent points on the p i c t u r e being stored. I t may therefore be necessary to programme the computer to arrange the samples such that adjacent data i n the computer represent consecutive p i c t u r e points before processing. A f t e r processing, the samples may be rearranged and read out f o r dis p l a y i n the same order they were stored. i i The h o r i z o n t a l r e s o l u t i o n of the p i c t u r e being stored can be var i e d quite e a s i l y i n steps. For example, a system designed to have a maximum of 480 p o i n t s / l i n e w i l l also have the a b i l i t y to provide such lower r e s o l u t i o n s as 60, 120 and 240 p o i n t s / l i n e s . This v a r i a t i o n i s made po s s i b l e by the design of the hardware. By software the v e r t i c a l r e s o l u t i o n can be va r i e d between an upper l i m i t of 525 l i n e s per p i c t u r e and such near submultiples of t h i s as 263 and 131 l i n e s / p i c t u r e . The thesis i s discussed i n r e l a t i o n to the PDP-9 computer on which most of the work described was done. However, the system i n t e r f a c e s r e a d i l y with other computers. i i i TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i v LIST OF ILLUSTRATIONS v 1. INTRODUCTION 1 1.1 Previous Interface Systems 1 1.2 The New Interface System 2 2. HARDWARE REALIZATION . . 7 2.1 The Storage System 7 2.2 The Display System 15 3. PROGRAMMING TECHNIQUES . 23 3.1 Coarse Quantization 24 3.2 Storage Programme f o r 7-bit Quantization 26 3.3 The Display Prograjnme 28 4. PERFORMANCE TESTS 31 4.1 Q u a l i t a t i v e Tests 31 4.2 Quantitative Tests 35 5. SUMMARY AND CONCLUSIONS 36 5.1 Limitations 36 5.2 Methods of Improvements 37 5.3 Possible Uses 40 APPENDICES 41 BIBLIOGRAPHY 47 i v LIST OF ILLUSTRATIONS Page 1.1 A T y p i c a l V i s u a l Data-Computer Interface . . . . . 3 1.2 The New System Interface « 3 1.3a P i c t u r e being Scanned 5 b Video Signal Showing Points where Samples Have been Taken • 5 2.1 The Storage System 8 2.2 The Frequency M u l t i p l i e r 10 2.3a,b,c,d M u l t i p l i e r Waveforms 11 2.4 Pulse A m p l i f i e r . 12 2.5a,b Sample and Hold C i r c u i t s 13 2.6a Sample and Hold Input 14 b Sample and Hold Output 14 2.7 The Display System . 16 2.8 Computer D/A Output 18 2.9 M u l t i v i b r a t o r Delay 19 2.10 Pulse A m p l i f i e r 20 2.11 Gated Operational A m p l i f i e r 21 2.12 Sawtooth Generators 22 3.1 Flow Chart f o r Programme to Store and Display a P i c t u r e at. 4 bits/sample 25 3.2 Flow Chart of Programme to Store a 7-bit Quantization P i c t u r e on PDP-9 Tapes 27 3.3 Flow Chart of Programme to Continuously Display.the 7-bit P i c t u r e 29 v Page 4.1a O r i g i n a l \"Test Pattern\" P i c t u r e 32 b Output from Computer at 138 usec/sample 32 c Output from Computer at 69 ysec/sample 32 5.1 Phase Locked Loop Scheme 38 5.2 * Generation of a Narrow Pulse 38 v i ACKNOWLEDGEMENT I wish, to express my gratitude to the National Research Council of Canada for the f i n a n c i a l assistance i n carrying out the research and to Dr. Micheal Beddoes f o r very u s e f u l ideas and advice. I would also l i k e to thank Dr. J.S. MacDonald for reading the thesis and making useful suggestions and to Rodney. George, Joan Kushner and Heather DuBois f o r the preparation and typing of the manuscript. v i i 1 1. INTRODUCTION The use of computers to process v i s u a l data has been i n existence f o r some time. The f i r s t problem that researchers i n the f i e l d had to solve was how to get the v i s u a l data information into the computer. This was done by scanning the p i c t u r e on a point-by-point basis i n a TV camera-like manner to obtain an e l e c t r i c a l s i g n a l equivalent of the v i s u a l information. An ordinary TV camera was not used to act as the l i n k between the p i c t u r e and the computer because of the wide bandwidth of the r e s u l t i n g video s i g n a l . This would have caused a data presentation rate greater than the computer could accept. Instead s p e c i a l cameras and display systems were designed to i n t e r f a c e the v i s u a l information to the computer. This thesis presents the re s u l t s of an i n v e s t i g a t i o n i n t o the p o s s i b i l i t y of using an ordinary TV camera and display monitor i n v i s u a l data processing. As a prelude to discussing this and some of the e a r l i e r i n t e r f a c e s , a b r i e f d e s c r i p t i o n of the way a TV p i c t u r e i s obtained w i l l f i r s t be presented. A TV p i c t u r e i s made up of l i n e s which are se q u e n t i a l l y scanned and presented to the viewer. Standard TV presents one l i n e of p i c t u r e i n about 67 usees. A t o t a l of 525 l i n e s are used to complete a p i c t u r e . Just as each p i c t u r e i s made up of l i n e s , each l i n e i s made up of poi n t s . The number of points per l i n e i s determined by the r e s o l u t i o n of the camera. This r e s o l u t i o n varies from about 100 to 650 points per l i n e . Thus a TV p i c t u r e i s made up of points and any system required to store the p i c t u r e information w i l l only need to have the a b i l i t y to store the information of the poi n t s . 1.1 Previous Interface Systems In previous picture-computer i n t e r f a c e systems, the points making up a p i c t u r e were scanned s e q u e n t i a l l y . The rate of scanning was slowed down 2 so that the computer could accept the information. A t y p i c a l system i s shown i n F i g . 1.1 and operates as follows: A transparency of the p i c t u r e i s scanned by a slow moving f l y i n g spot scanner. The resultant e l e c t r i c a l s i g n a l s , representing the brightness of successive p i c t u r e elements are A/D converted and recorded on magnetic tape. This provides a d i g i t a l v ersion of the input p i c t u r e for computer processing. A f t e r the p i c t u r e has been processed according to some algorithms, the computer i n s t r u c t s a microfilm p r i n t e r to generate the new product. This i s done i n a manner which i s the inverse of the o r i g i n a l scanning. A TV-like tube paints the p i c t u r e with a moving spot of l i g h t and a camera records i t on f i l m to provide a photographic end product There are v a r i a t i o n s of t h i s b a s ic method. One such v a r i a t i o n eliminates the need f o r tape recording by i n p u t t i n g the d i g i t a l data s t r a i g h t i n t o the computer memory. In such a case the f l y i n g spot scanner may be required to wait at each p i c t u r e point so as to give the computer s u f f i c i e n t time to accept the data. E i t h e r way the system i s complex and c o s t l y . 1.2 The New Interface System We are here i n t e r e s t e d i n being able to use an ordinary TV camera, scanning at standard speed. Obviously the points on the p i c t u r e cannot be sampled s e q u e n t i a l l y since t h i s rate of presentation i s too f a s t f or any computer. The problem i s overcome t h i s way. A point at the beginning of the p i c t u r e , say, i s sampled and stored i n the computer. Assuming i t takes N Liseconds to store t h i s and a r e s o l u t i o n of 120 p o i n t s / l i n e i s required, at the scanning rate of 67 useconds per l i n e , the time between successive p i c t u r e points i s ^ useconds. Therefore ^57^ points away from the f i r s t point w i l l correspond to a time of N useconds. This i s sampled as the next point for the computer. Another In PUT TRANSPARENCY FLYING--SPOT \\ • A/r> CONVERTER DIGITAL TAPE RECOVER COMPUTE^ TAPE RECORDER PICTURE PHOTO&MPHIC EHLfjRGER, MitROFlLN] PRINTER F i g . 1.1 A t y p i c a l Visual Data-Computer Interface, OPVINAR. y PICTURE OR ST/^T/ONSRY OBTEC-T V SYSTEM INTERFACE CofAPOTELR i T>iSPLfiy FROCESSEI) MaNITOR^ gs- PHOTOGRAPH F i g . 1.2 The New System Interface. 4 p o i n t s away, a sample i s . a g a i n t a k e n and t h e v a l u e s t o r e d . The p r o c e s s 67 i s r e p e a t e d u n t i l t h e b o t t o m o f t h e p i c t u r e i s r e a c h e d . When t h e s c a n n e r , ., t . t • 120N . . r e t u r n s t o t h e t o p , a sample i s t a k e n a t a p o x n t t h a t i s ^ p o i n t s away from t h e l a s t one t a k e n a t t h e b o t t o m o f t h e p i c t u r e . As can be seen f r o m F i g u r e 1 . 3 , c o n s e c u t i v e l y numbered p o i n t s , w h i c h r e p r e s e n t a d j a c e n t l y s t o r e d samples i n t h e computer, a r e n o t a d j a c e n t p i c t u r e p o i n t s . T h e r e f o r e , t h e camera must s c a n t h e same p i c t u r e r e p e a t e d l y s e v e r a l hundred t i m e s u n t i l a l l t h e p o i n t s making up t h e p i c t u r e have each been sampled and s t o r e d . The s a m p l i n g i s c o n t r o l l e d s u c h t h a t a l l t h e p o i n t s a r e e a c h sampled o n l y once. I t can be e a s i l y shown by i n d u c t i o n t h a t t h i s c an be done i f a number p i s chosen as t h e number o f p i c t u r e p o i n t s between s u c c e s s i v e samples where p i s n o t a f a c t o r o f and does n o t have a common f a c t o r w i t h t h e t o t a l number o f p i c t u r e p o i n t s , p must a l s o , • 120N be g r e a t e r t h a n . 6 / The i n t e r f a c e s t o r e s t h e d a t a i n t h e computer under programme c o n t r o l . When a l l t h e samples r e p r e s e n t i n g t h e p i c t u r e have been s t o r e d , t h e computer may have t o a r r a n g e them so t h a t a d j a c e n t samples i n s t o r a g e a r e a d j a c e n t p i c t u r e p o i n t s b e f o r e t h e . d a t a , c a n be p r o c e s s e d as d e s i r e d . When t h e d a t a has been p r o c e s s e d and i s re a d y t o be d i s p l a y e d , a r e v e r s e p r o c e s s t o t h e one d e s c r i b e d above now t a k e s p l a c e . The samples must be i n t h e same p o s i t i o n s t h e y were when f i r s t b r o u g h t i n t o t h e computer. The d a t a i s t h e n r e a d o u t i n the same way i t was s t o r e d . The f i r s t i n f o r m a t i o n o u t o f t h e computer goes t o t h e b e g i n n i n g o f t h e s c r e e n d i s p l a y . The s e c o n d sample i s a c t u a l l y \"^32^ p o i n t s away, so t h e s c r e e n must be b l a n k e d u n t i l b I t h i s p o i n t i s r e a c h e d . When the p o i n t i s r e a c h e d , the s c r e e n i s u n b l a n k e d and the p o i n t d i s p l a y e d . The n e x t sample i s d i s p l a y e d a g a i n \"^y^\" p o i n t s away f r o m t h e l a s t one. The p r o c e s s goes on u n t i l t he b o t t o m o f t h e s c r e e n i s L I N E 1 _ _ _ LINE 2 LINE 3 LIME -4 /./NE 525 Fig.1.3a P i c t u r e being scanned (0 07) SAMPLING-PULSES F i g . 1.3fc.Video s i g n a l showing p o i n t s where samples have been taken. 6 r e a c h e d . The s c a n n e r r e t u r n s t o the top and d i s p l a y s the n e x t sample a t p o i n t s away f r o m t h e l a s t one a t t h e b o t t o m o f the s c r e e n . These s t e p s a r e r e p e a t e d u n t i l a l l the p o i n t s have been d i s p l a y e d . I f t h e t i m e between samples i s 69 u s e e , a t o t a l t i m e o f about 3.8 seconds w o u l d be r e q u i r e d to b u i l d a p i c t u r e r e p r e s e n t e d by 63,000 p o i n t s . T h i s i s the same time i t t a k e s t o s t o r e t h e p i c t u r e . An o r d i n a r y p h o t o g r a p h i c camera f o c u s e d on t h e d i s p l a y s c r e e n and opened f o r 3.8 seconds w i l l g i v e a p h o t o g r a p h o f t h e p r o c e s s e d v i s u a l i n f o r m a t i o n . A b l o c k d i a g r a m o f the i n t e r f a c e s y s t e m i s shown i n F i g u r e 1.2. Because o f i t s d u a l r o l e the s y s t e m has two p a r t s : a s t o r a g e p a r t and a d i s p l a y p a r t . The s t o r a g e p a r t c o n s i s t s e s s e n t i a l l y o f a sample and h o l d c i r c u i t and c o n t r o l u n i t . The c o n t r o l u n i t d e c i d e s the time a t w h i c h s a m p l i n g o f t h e v i s u a l i n f o r m a t i o n i s t o s t a r t and t h e time between s a m p l e s . I t i s made up o f a f r e q u e n c y m u l t i p l i e r , c o u n t e r and p u l s e s h a p i n g d i g i t a l c i r c u i t s . The d i s p l a y p a r t c o n s i s t s o f a s e t o f m o n o s t a b l e m u l t i v i b r a t o r s , s a w t o o t h g e n e r a t o r s and a g a t e d a m p l i f i e r i n a d d i t i o n t o the c o n t r o l u n i t m e n t i o n e d e a r l i e r . T h i s i n t e r f a c e s y s t e m has s e v e r a l a d v a n t a g e s o v e r some o f t h e e x i s t i n g o n e s . Among t h e s e a r e the a b i l i t y t o use an o r d i n a r y p h o t o g r a p h o r even a s t i l l o b j e c t as t h e v i s u a l i n f o r m a t i o n s o u r c e i n s t e a d o f a t r a n s p a r e n c y , the p o s s i b l i t y o f w o r k i n g w i t h e x i s t i n g o r d i n a r y TV camera and d i s p l a y e q u i p -ment, t h e ease o f v a r y i n g the p i c t u r e r e s o l u t i o n and the low c o s t o f t h e h a r d w a r e . The l i m i t a t i o n s o f t h e s y s t e m and methods f o r i m p r o v i n g i t s p e r -formance w i l l be d i s c u s s e d i n C h a p t e r 5. The n e x t C h a p t e r w i l l be c o n c e r n e d w i t h a d e t a i l e d d e s c r i p t i o n o f the h a r d w a r e w h i l e C h a p t e r 3 w i l l g i v e a r e v i e w o f t h e programming t e c h n i q u e s r e q u i r e d t o o p e r a t e t h e i n t e r f a c e . R e s u l t s o f p e r f o r m a n c e t e s t s on t h e s y s t e m w i l l be p r e s e n t e d i n C h a p t e r 4. / 2. HARDWARE REALISATION 2.1 The Storage System The scheme presented here requires the knowledge of the exact number of points making up a p i c t u r e . Since the manufacturers only give an approxi-mate value with t h e i r cameras, i t i s necessary to f i n d a way of obtaining an exact value. I t i s also necessary to count the points so as to know when to take a sample during storage and when to unblank during display. In order to know the exact number of points making up a p i c t u r e , i t would have to be made up by the designer. The 67 useconds l i n e scanning rate of standard TV camera corresponds to a l i n e frequency of 15.5 Khz i n a 525 l i n e per frame system. There i s an o s c i l l a t o r i n the camera going at t h i s frequency and causing the l i n e scan. I f t h i s frequency i s m u l t i p l i e d by 120, say, an e f f e c t i v e l i n e r e s o l u t i o n of 120 points i s automatically given to the p i c t u r e under observation; each cycle corresponding to a point. A c t u a l l y a TV camera has a master o s c i l l a t o r going at twice the l i n e frequency. In the system described here, a \"multiply by s i x t y \" c i r c u i t was used to get the desired 120 points per l i n e . The m u l t i p l i e r output was used as a clock to a counter, each clock cycle corresponding to a p i c t u r e point. The counter had a module p-1, so each output of i t corresponded to a point to be sampled on the video s i g n a l . Since the camera w i l l scan the same p i c t u r e repeatedly, i t i s only necessary to keep a count of the number of samples already taken to know when s u f f i c i e n t data has been stored to represent the p i c t u r e completely. This was done by software. The camera also provides a synchronising pulse each time the scanner goes back to the top of the p i c t u r e . I f the computer waits for one of these before s t a r t i n g to store, the f i r s t sample taken w i l l be at the beginning of the p i c t u r e . r MULTIVIBRATOR ' 1 I START OF I S7-otf « S W I T C H SWITCH M E M O R Y PUL$t5 F i g . 2.5b Sampling Scope Sample and Hold block diagram. VJHEN THE SWITCH » S C t O S E i V 0 y T = V,H 14 FIG. 2.6a TV Camera video signal (input to sample & hold) FIG. 2.6b Sample and Hold output hold time up to 500 usee with n e g l i g i b l e decay. I t was designed using valve a m p l i f i e r s . To save time, a s i m i l a r design was not b u i l t , instead a sampling scope \"plug-in\" unit was used as the sample and hold i n the i n t e r f a c e system. The block diagram of the unit i s shown i n F i g . 2.5b. Normally the scope generates i t s own sampling pulses but i n t h i s system i t was provided with sampling pulses by the counter. The system worked w e l l as can be seen from the pi c t u r e s of F i g . 2.6 which shows the video input and the sample and hold output. The s i g n a l i s now ready f o r input i n t o the computer. 2.2 The Display System When the v i s u a l data has been processed according to the desired algorithms, i t i s required to be read out of the computer and displayed f o r evaluation. The system i n t e r f a c e w i l l act as a l i n k between the computer and a display monitor. I t s operation i n t h i s mode i s the reverse of that described i n the previous se c t i o n . The block diagram f o r the display part of the i n t e r f a c e i s shown i n F i g . 2.7. The m u l t i p l i e r and counter from the storage system are also part of t h i s . In ad d i t i o n , there are 2 sawtooth generators, a gated operational a m p l i f i e r and some m u l t i v i b r a t o r s . The counter output pulses are now used to i n s t r u c t the computer to display the corresponding point on a monitor instead of s t o r i n g . We wish to display the points on the monitor i n the same order that they were stored. The d i g i t a l b i t s i n the computer, representing the samples, were f i r s t D/A converted. Each D/A output was an analog s i g n a l l a s t i n g u n t i l the next sample. The waveform shown i n F i g . 2.8 was obtained from the com-puter. This i s s i m i l a r to the output of the sample and hold, F i g . 2.6b. In order to get point display f o r each analog l e v e l , the l e v e l s were sampled with r ~ FRAME P U L S E S o MyLTivieR/)To« M U L T I P L I E R C O U N T E R . 1 PULSE MULTIVIgfi/^ PULSE r r — 4 LINE puisrs. FRAME ftVLTlVIBRfiTdk PBLfiy SfiVJTooTH GENERATOR X I PROCESSED I V _1 si eiv/rtL. C R T L J F i g 2 . 7 The Display System a narrow pulse by passing them through the gated operational a m p l i f i e r . The gate of the a m p l i f i e r was c o n t r o l l e d by the sampling pulses from the counter. The short duration analog s i g n a l s obtained were then used as the \"video\" input to the CRT. Since the signals had no synchronizing pulses, unlike a normal composite video s i g n a l from a TV camera, external pulses were provided to cause h o r i z o n t a l and v e r t i c a l d e f l e c t i o n s . These pulses were obtained d i r e c t from the camera. A TV monitor was not a v a i l a b l e during the design and b u i l d i n g of the i n t e r f a c e . The system was therefore designed for display on an ordinary o s c i l l o s c o p e . The amplifiers were used as \"plug-ins\" to the scope and each a m p l i f i e r had a sawtooth waveform applied to i t . One sawtooth was generated from the h o r i z o n t a l camera d e f l e c t i o n pulses and the other from the v e r t i c a l pulses. There i s usually a few microseconds delay between the time a computer receives the pulse i n s t r u c t i n g i t to output a stored sample and the time the sample i s a c t u a l l y received. Since the i n s t r u c t i n g pulse i s also used to control the gate of the gated operational a m p l i f i e r to allow a converted s i g n a l through, i t was delayed by the few microseconds before being applied to the gate so as to give the computer time to output the value. The v e r t i c a l and h o r i z o n t a l pulses were delayed by the same amount before being applied to the sawtooth generators so as to preserve the r e l a t i v e p o s i t i o n s of the points on the screen. , The exact value of the computer delay i s not known but i s about 5 useconds f o r a PDP-9. A delay of 10 usee was given to each pulse. This gave the computer plenty of time to convert a value and s e t t l e down. The delays were provided by monostable m u l t i v i b r a t o r c i r c u i t s . These c i r c u i t s also acted as shapers of the various pulses. F i g . 2.8 Computer D/A Output F i g . 2.9 M u l t i v i b r a t o r Delay £80 / ^ - W A -IN our 0 OUT F i g . 2.10 Pulse Amplfier The s a w t o o t h waveforms a p p l i e d t o t h e scope c a u s e d a r a s t e r t o appear on t h e s c r e e n . The o u t p u t o f t h e g a t e d o p e r a t i o n a l a m p l i f i e r was a p p l i e d t o t h e CRT b l a n k i n g and th u s z-modulated t h e s c r e e n . The i n t e n s i t y due t o t h e s i g n a l was s u p e r i m p o s e d on t h e r a s t e r . The i n t e n s i t y was t u r n e d down u n t i l t h e r a s t e r d i s a p p e a r e d . The o n l y t h i n g s t h e n v i s i b l e were t h e random p o i n t s t h a t add up t o make t h e p i c t u r e . By t a k i n g a t i m e - e x p o s u r e p h o t o g r a p h o f th e p o i n t s , a p i c t u r e was o b t a i n e d . Most o f t h e components making up t h i s d i s p l a y p a r t o f t h e i n t e r f a c e s y s t e m a r e o f f - t h e - s h e l f I-C modules. The m u l t i v i b r a t o r d e l a y s were made fro m M o t o r o l a MC 799 d u a l v b u f f e r g a t e s . The c i r c u i t f o r one s u c h d e l a y i s shown i n F i g . 2.9. The o n l y e x t e r n a l components a r e r e s i s t o r s and c a p a c i t o r s . The o u t p u t o f t h e f i r s t m u l t i v i b r a t o r was d i f f e r e n t i a t e d . The p o s i t i v e h a l f was t h e n used as i n p u t t o t h e se c o n d m u l t i v i b r a t o r . The w i d t h o f t h e f i r s t p u l s e t h u s d e t e r m i n e d t h e amount o f d e l a y a p p l i e d t o the i n p u t p u l s e . A M o t o r o l a MC 1545 g a t e d o p e r a t i o n a l a m p l i f i e r was used t o o b t a i n t h e n a r r o w a n a l o g s i g n a l s w h i c h z-modulated t h e sc o p e . The a m p l i f i e r works as f o l l o w s . A s i g n a l a p p l i e d t o i t s i n p u t a p p e ars a t t h e o u t p u t i f t h e g a t e 4.7 K O U T + 5 ' F i g . - £••// Gated operational amplifier has 5v o r more a p p l i e d t o i t . I f t h e g a t e v o l t a g e i s l e s s t h a n t h i s t h e i n p u t i s i n h i b i t e d . I n o u r sys t e m t h e g a t e was c o n t r o l l e d by t h e d e l a y e d c o u n t e r o u t p u t p u l s e s . The p u l s e s were f i r s t d i f f e r e n t i a t e d and t h e n a m p l i f i e d by t h e common e m i t t e r c i r c u i t shown i n F i g . 2.10 b e f o r e b e i n g a p p l i e d t o t h e g a t e . The d i f f e r e n t i a t i o n was n e c e s s a r y i n o r d e r t o o b t a i n t h e r e q u i r e d n a rrow a n a l o g s a m p l e s . The c i r c u i t f o r the s a w t o o t h g e n e r a t o r s a r e shown i n F i g . 2.12. They a r e s t a n d a r d s a w t o o t h c i r c u i t s and t h e r e f o r e need no d e s c r i p t i o n . The i n p u t and o u t p u t systems have now been d e s c r i b e d . I n t h e n e x t c h a p t e r t h e s o f t w a r e t h a t c o n t r o l s t h e o p e r a t i o n o f t h e s y s t e m by t h e computer w i l l be d i s c u s s e d . 560-IN 0,1'fuF 2Z0 MPS 637 .00/ 4 70ff -h25v OV7 F i g . Z-f2.°-Hor i z o n t a l Sawtooth Generator OOJ 1— —i i—. %— Fig.z./z'b V e r t i c a l Sawtooth Generator 3. PROGRAMMING TECHNIQUES The philosophy behind the programme that operates with the computer w i l l be presented i n th i s chapter. The systems in t e r f a c e s r e a d i l y with other computers but the actual programme presented here are f o r the PDP-9 machine on which most of the work was done. Any computer that i s to be li n k e d to a TV camera through the i n t e r -face system must have A/D and D/A conversion c a p a b i l i t y , a large core memory or a f a s t mass storage f a c i l i t y . The computer must also be able to sense when to s t a r t s t o r i n g the v i s u a l data and at what rate. Since the sampling speed of the i n t e r f a c e i s geared to the rate of input of data into the computer, a large core memory or a d i s c i n the computer would be i d e a l . When the s i g n a l i s given by the i n t e r f a c e (see F i g . 2.1),' the computer s t a r t s to sample the v i s u a l data. Every sample i s A/D converted and stored i n the memory. Each time a sample i s stored, a count i s taken and when th i s count reaches the number of required samples, sampling ceases. Since consecutive samples stored i n the computer are not consecutive elements on the pi c t u r e being stored, the computer may have to arrange the points so that adjacent samples are adjacent points of the p i c t u r e . The data can then be processed to simulate a desired system (a separate programme i s required to do t h i s ) . A f t e r processing, the samples must be i n the same r e l a t i v e p o s i t i o n s they were when f i r s t brought i n t o the computer. The computer then performs a D/A conversion on the samples and outputs them for display through the i n t e r f a c e system. The computer i s programmed to s t a r t storage or display only when the camera i s at the top of the p i c t u r e scan. With a large core memory v i r t u a l l y any computer can be programmed to carry out the steps described above. A PDP-9 f o r example can have a core memory o f 32,000 w o r d s , each word 18 b i t s l o n g . I f each p i c t u r e sample i s c o n v e r t e d t o 7 b i t s , s a y , f i v e samples can be p a c k e d i n 2 computer words. Thus o n l y 25k words o f memory w o u l d be r e q u i r e d t o s t o r e a c o m p l e t e p i c t u r e o f 525 x 120 i . e . 63,000 p o i n t s . From the memory the d a t a can be s t o r e d on an a u x i l l i a r y s t o r a g e f a c i l i t y f o r l a t e r p r o c e s s i n g . The t y p i c a l t ime f o r A/D c o n v e r s i o n and s t o r a g e o f a sample i s 20 u s e e , t h e r e f o r e t o t a l t i m e t o s t o r e a p i c t u r e w o u l d be about 1.3 s e c o n d s . W i t h a f a s t e r A/D, t h i s t i m e w o u l d be r e d u c e d . 3.1 C o a r s e Q u a n t i z a t i o n More o f t e n t h a n n o t , s m a l l and medium s c a l e computers do n o t have a l a r g e c o r e memory. The PDP-9 u s e d , f o r example had o n l y 16k o f memory. W i t h c o a r s e q u a n t i z a t i o n (4 b i t s / s a m p l e ) , i t was p o s s i b l e to s t o r e the i n f o r m a t i o n o f a p i c t u r e i n t h i s memory. N i n e samples were p a c k e d i n two computer words. Thus o n l y 10.5k words o f the memory were needed f o r t h e 63,000 sam p l e s . The optimum s a m p l i n g speed o f 50Khz c o u l d have been a c h i e v e d . However the i n t e r f a c e s y s t e m was d e s i g n e d f o r o n l y two s a m p l i n g s p e e d s : a p p r o x i m a t e l y 7.25 Khz and 14.5 Khz c o r r e s p o n d i n g t o 253 and 121 p o i n t s r e s p e c t -i v e l y between s a m p l e s . I n t h e case o f 7.25 Khz s a m p l i n g r a t e , about 3.8 seconds a r e r e q u i r e d to s t o r e a c o m p l e t e p i c t u r e as opposed t o t w i c e t h a t f o r 14.5 Khz. The programme f l o w c h a r t e d i n F i g . 3.1 ( a c t u a l programme i s i n c l u d e d i n t h e a p p e n d i x ) was used t o s t o r e the p i c t u r e i n f o r m a t i o n i n t h e computer. When s u f f i c i e n t samples have b e e n s t o r e d i n the memory, t h e d a t a was t r a n s f e r r e d to a t a p e . The computer t h e n went to a subprogramme w h i c h a r r a n g e d the samples as d e s c r i b e d p r e v i o u s l y and p r o c e s s e d them as f o l l o w s : Each sample was com-p a r e d w i t h the one b e f o r e i t . I f the f i r s t t h r e e b i t s were e q u a l , t h e samples were t a k e n as b e i n g o f e q u a l a m p l i t u d e . I f the t h r e e b i t s were u n e q u a l , the v a l u e o f t h e p r e s e n t sample was r e t a i n e d and compared w i t h the n e x t one. S E T UP TAPE TO ITS BEGINNING-f Wfi/T FOrX TOP OF F / C T d * £ POLSE FO/Q, SfiMPLtNG-PUL&E SbmpLE ^ ft /j> CONVERT SHIFT E 1 T» IH7EZRUPT OCCURS IAJHEM /^EAi/M(^ COAlPAETEt) Wr»T FoR. Top of-' PICTURE SCAN UWPflCK SAMPLES, F * O M CsmPPTS-% WORI>S. D/A CON v EAT A.wt> OUTPUT r o INTERFACE SE\"F T/)f£ 1 MoViWG- S/)CK . ST/}/?T TAPE Z . THTZRROPT M/IIN p«as«/lM ENTER. STOP T/=)P£\" MOTIONS. S E T U^3 TO START REPi2>ltJG- F&OtA ONE TAPE AND OTHER TAPE B / } C K W H E W IH$TKUCTEI> By MAIN PROG-RAM I RETURN TO M/lfA/ pftoCxRAitA r>C-TUR.E HAS BEEN 2\\S.f>lfWEb ONCE. ReTUft.N TO TOP To START VISPLfiy 1N G- THE\" WfW 12-5 K 8/rrcH OF 2>AT* '4.5 K. 'AVPITIOHPIL DlSPLfiy^i P U W P A C K . MORE W O R - D S ^ O M M E M o f t y ^ 2/SP2/iy T H E P O I N T S F i g 3 - 3 Flow c h a r t of program t o c o n t i n u o u s l y d i s p l a y a p i c t u r e . nately reading from the tapes the v i s u a l data was continuously a v a i l a b l e f o r displa y . S i m i l a r programmes to the : ones described here can be w r i t t e n when other types of computers are involved. However great care i s required i n programming e s p e c i a l l y when tapes are used f o r storage, otherwise synchroni-s a t i o n between the computer data and the camera d e f l e c t i o n pulses may be l o s t f o r much of the time. 4. PERFORMANCE TESTS Q u a l i t a t i v e and q u a n t i t a t i v e tests were performed on the i n t e r f a c e system to check i t s performance as a u s e f u l camera-computer l i n k . The r e s u l t s of these tests are presented here. 4.1 Q u a l i t a t i v e Tests In the q u a l i t a t i v e t e s t s , a TV camera was focused on an object and the output of the camera displayed on an o s c i l l o s c o p e . A photograph of the display i s shown i n F i g . 4.1a (Because of the l i m i t a t i o n s imposed by the scope, a very simple p i c t u r e pattern c o n s i s t i n g of l e t t e r s w r i t t e n on a white background was used as the object ). The video s i g n a l from the TV camera was stored i n the computer using the i n t e r f a c e system and the programme of F i g . 3.1. At a sampling rate of 1 sample about every 138 psec, (about 7.25 kHz), a t o t a l time of about 7.6 seconds was required to store the p i c t u r e . The data i n the computer was arranged and processed by the subprogramme mentioned i n s e c t i o n 3.1. A second subprogramme rearranged the samples a f t e r processing then read them out for display as previously described. A time exposure photograph of the display was taken by opening the p o l a r o i d camera shutter f o r 7.6 seconds. F i g . 4.1b shows the r e s u l t obtained. The r e l a t i v e p o s i t i o n s of the points making up the p i c t u r e were maintained despite the \"stroboscope\" sampling method. If this was not true the p r i n t e d words would not have come out as they d i d . The v a l i d i t y of the method i s therefore e s t a b l i s h e d . The sampling speed was increased to 1 sample every 69 usee. A t o t a l of about 3.8 seconds was required to store or display the p i c t u r e pattern. A photograph of the scope display i s shown i n F i g . 4.1c. A diagonal scanning pattern i s seen to be superimposed on the p i c t u r e . This a r i s e s as 33 f o l l o w s . The s t r o b o s c o p i c s a m p l i n g scheme r e s u l t s i n a d i a g o n a l p a t t e r n d u r i n g s a m p l i n g and d i s p l a y (see F i g . 1.3). F o r f a s t s a m p l i n g the time t o d i s p l a y a d i a g o n a l i s v e r y s h o r t . Thus i f the p o l a r o i d camera used t o t a k e a p i c t u r e o f t h e p o i n t s i s opened by a few m i l l i s e c o n d s l e s s t h a n t h e e x a c t t i m e r e q u i r e d , some p o i n t s w o u l d be m i s s e d . T h i s w o u l d g i v e r i s e t o the d i a g o n a l p a t t e r n seen i n F i g . 4.1c. F o r s l o w s a m p l i n g t h e t i m e t o d i s p l a y each d i a g o n a l i s l o n g so i n a d v e r t a n t l y s h o r t e n t h e e x p o s u r e t i m e by a few m i l l i s e c o n d s w o u l d n o t impose a n o t i c e a b l e p a t t e r n . The q u a l i t y o f the p i c t u r e s i s due e n t i r e l y t o the scope on w h i c h th e d i s p l a y s were done. T h i s a s s e r t i o n i s b o r n e o u t by t h e p o o r q u a l i t y o f the o r i g i n a l p i c t u r e s ( F i g . 4.1a). N o n - u n i f o r m i l l u m i n a t i o n o f t h e s c r e e n , the v e r y low r e s o l u t i o n o f the scope and t h e n o n - l i n e a r i t y o f the z - a x i s m o d u l a t i o n a r e l a r g e l y r e s p o n s i b l e f o r t h i s . F o u r b i t q u a n t i z a t i o n was used i n the d i s p l a y o f the p r o c e s s e d s i g n a l s . F o r t h e i n p u t p i c t u r e p a t t e r n s u s e d , t h i s q u a n t i z a t i o n l e v e l was q u i t e a d e q u a t e . Any h i g h e r r e s o l u t i o n w o u l d n o t be too m e a n i n g f u l on t h e s c o p e d i s p l a y . However i t i s p o s s i b l e t o q u a n t i z e up to s e v e n b i t s u s i n g t h e programmes d e s c r i b e d i n s e c t i o n s 3.2 and 3.3. The o u t p u t from t h e computer D/A c o n v e r t e r f o r s u c h q u a n t i z a t i o n was p a s s e d t h r o u g h t h e i n t e r f a c e and the c o r r e s p o n d i n g p i c t u r e d i s p l a y e d on t h e s c o p e . W h i l e the s i g n a l i t s e l f l o o k e d l i k e t he sample and h o l d o u t p u t p r e s e n t e d to the computer, d i s p l a y i n g t h e p i c t u r e on t h e sco p e p r e s e n t e d some p r o b l e m . F o r much o f the t i m e , t h e r e was l o s s o f s y n c h r o n i s a t i o n , as a r e s u l t the p i c t u r e was s p l i t up, p a r t . o f i . i t a p p e a r i n g on one s i d e o f the sco p e and the r e s t on t h e o t h e r s i d e . T h i s l o s s o f s y n c h r o n i s a t i o n was due t o t h e few m i l l i s e c o n d s l o s t by t h e computer i r i . s t a r t i n g and t u r n i n g the t a p e s a r o u n d . The p r o b l e m was s o l v e d by making the computer check f o r \"top of p i c t u r e \" p u l s e a f t e r each c o m p l e t e p i c t u r e d i s p l a y . I f synchronization was .lo s t , i t would be re-established before the display began 'again. 4.2 Quantitive Test The i n t e r f a c e was tested f o r noise and j i t t e r . The most l i k e l y source of noise i n the system would be the sample and hold. The unit i s supposed to sample the input video s i g n a l and hold the analog s i g n a l u n t i l the next sample. I f another sample i s taken before the output a m p l i f i e r s e t t l e s down, j i t t e r i n g w i l l r e s u l t . This j i t t e r e f f e c t was tested for i n the following manner. The camera was focused on a white sheet of paper and the s i g n a l due to this stored on tape through the memory using the program of F i g . 3.2. The 63,000 7-bit samples were then compared (by the computer) with each other to see how many samples have d i f f e r e n t values from the r e s t . I t was found that only 100 samples were d i f f e r e n t . T h i r t y nine of these samples were out by 2 b i t s , the re s t by only 1 b i t . 5. SUMMARY AND CONCLUSIONS A s y s t e m has been p r e s e n t e d w h i c h can be used as a l i n k i n P i c t u r e P r o c e s s i n g by Computer. The i n t e r f a c e makes i t p o s s i b l e to use o r d i n a r y TV camera and d i s p l a y m o n i t o r i n such p r o c e s s e s i n s t e a d o f b u i l d i n g s p e c i a l o n e s . R e s u l t s were p r e s e n t e d t o p r o v e t h e v a l i d i t y o f t h e method. The advantage o f the s y s t e m o v e r p r e v i o u s i n t e r f a c e s were a l s o p r e s e n t e d . The l i m i t a t i o n s o f the i n t e r f a c e w i l l be d i s c u s s e d h e r e as w e l l as methods o f i m p r o v i n g the s y s t e m t o imp r o v e i t s r e l i a b i l i t y . Some o f the uses t h a t t h e i n t e r f a c e may be p u t t o w i l l a l s o be b r i e f l y m e n t i o n e d . 5.1 L i m i t a t i o n s Because o f t h e arrangement t h a t may be n e c e s s a r y b e f o r e a v i s u a l d a t a s t o r e d i n the computer u s i n g t h i s i n t e r f a c e can be p r o c e s s e d , i t i s n o t p o s s i b l e t o use t h e i n t e r f a c e as a l i n k f o r r e a l time o n - l i n e computer p i c t u r e p r o c e s s i n g . F o r t h e same r e a s o n i t i s n o t p o s s i b l e to p r o c e s s a p o r t i o n o f t h e p i c t u r e and d i s p l a y i t i n d e p e n d e n t l y o f the r e s t o f the p i c t u r e . I f a p o r t i o n o f the v i s u a l d a t a i s p r o c e s s e d , the whole p i c t u r e w i l l have t o be d i s p l a y e d i n o r d e r t o be a b l e to o b s e r v e t h e e f f e c t o f the p r o c e s s i n g on the p o r t i o n o f i n t e r e s t . F o r some o p e r a t i o n s t h e s e l i m i t a t i o n s may make the i n t e r -f a c e s y s t e m u n a c c e p t a b l e . An example o f t h i s i s c o n t o u r t r a c i n g i n p a t t e r n r e c o g n i t i o n computer p r o c e s s i n g . Where t h i s l i m i t a t i o n i s n o t i m p o r t a n t , t h e r e i s a n o t h e r p r o b l e m t h a t may a r i s e . T h i s i s the f a c t t h a t a c o n t i n u o u s d i s p l a y o f t h e p r o c e s s e d d a t a f o r a l o n g p e r i o d o f ti m e may n o t be p o s s i b l e on computers w i t h s m a l l o r s l o w s t o r a g e f a c i l i t y . T h i s i s b e c a u s e o f t h e l o s s o f s y n c h r o n i s a t i o n m e n t i o n e d i n S e c t i o n 4.1. F o r example t h e t a p e t u r n around t i m e on a PDP-12 i s so l o n g as t o p r e c l u d e t h e two tape s t o r a g e and d i s p l a y method d e s c r i b e d i n C h a p t e r 3. The b e s t t h a t can be done on a PDP-12 t h a t has o n l y m a g n e t i c t a p e f o r mass s t o r a g e i s t o s t o r e t h e v i s u a l i n f o r -m a t i o n s e v e r a l t i m e s on t h e t a p e . The tape has a - c a p a c i t y o f about 1.6 m i l l i o n b i t s . T h i s can s t o r e f o u r 63,000 sample p i c t u r e i n f o r m a t i o n i f each sample i s q u a n t i z e d t o 6 b i t s . By s t o r i n g the same p i c t u r e on the tape f o u r t i m e s , i t w i l l be p o s s i b l e t o g e t t h e p r o c e s s e d i n f o r m a t i o n d i s p l a y e d f o u r t i m e s c o n t i n u o u s l y . A f t e r t h a t ^ the t a p e has t o r e w i n d b a c k to i t s b e g i n n i n g ( a b o u t 30 s econds a r e r e q u i r e d f o r t h i s ) b e f o r e t h e d i s p l a y can be r e s t a r t e d . T h i s may n o t be a s e r i o u s l i m i t a t i o n i f a l l t h a t i s r e q u i r e d i s f o r t h e d i s p l a y to l a s t l o n g enough f o r a p h o t o g r a p h t o be t a k e n . A n o t h e r p r o b l e m t h a t may a r i s e w i t h the i n t e r f a c e s y s t e m i s t h e l i m i t o f v a r i a t i o n o f t h e v e r t i c a l r e s o l u t i o n . The 525 l i n e s / p i c t u r e o f t h e TV camera i s t h e maximum r e s o l u t i o n p o s s i b l e . T h i s s h o u l d n o t be a s e r i o u s drawback however s i n c e f o r most a p p l i c a t i o n s t h i s r e s o l u t i o n i s q u i t e ade-q u a t e . The l o w e r r e s o l u t i o n s e a s i l y o b t a i n e d a r e l i m i t e d t o s u c h n e a r s u b m u l t i p l e s of 525 as 263 and 131. These a r e o b t a i n e d by u s i n g the i n t e r l a c e f a c i l i t y i n the camera. F o r i n s t a n c e , to o b t a i n 263 l i n e s / p i c t u r e , the computer i s programmed t o s t o r e the samples f r o m e v e r y o t h e r f i e l d o n l y . These t h e n a r e the l i m i t a t i o n s o f t h i s i n t e r f a c e s y s t e m , i n s p i t e o f them i t s h o u l d s t i l l be u s e f u l as a v i s u a l d a t a - c o m p u t e r l i n k . 5.2 Methods o f Improvement The p h i l o s o p h y b e h i n d t h e d e s i g n o f t h e i n t e r f a c e i s t h a t ,the s a m p l i n g p u l s e s be l o c k e d ( i e w e l l s y n c h r o n i s e d ) w i t h t h e d e f l e c t i o n p u l s e s g e n e r a t e d by t h e camera. I f t h i s i s n o t so t h e n i t i s q u i t e p o s s i b l e t h a t t h e samples t a k e n d u r i n g t h e s t o r a g e of t h e v i s u a l d a t a w i l l n o t be d i s p l a y e d i n t h e i r r e l a t i v e p o s i t i o n s a f t e r p r o c e s s i n g . I n a d d i t i o n some samples may be m i s s e d a l t o g e t h e r . The use of the m u l t i p l i e r - d i v i d e r scheme i s t o a v o i d t h i s p r o b l e m . I f t h e m u l t i p l i e r i s w e l l d e s i g n e d , t h e p r o b l e m i s n o t s e r i o u s . However even a m u l t i p l i e r o f the b e s t d e s i g n may sometime b u r s t i n t o o s c i l l a t i o n i n d e p e n d e n t l y o f t h e camera m a s t e r o s c i l l a t o r and s y n c h r o n i s a t i o n may be l o s t f o r a t i m e . An a l t e r n a t i v e and more s t a b l e way t o l o c k the s a m p l i n g p u l s e s t o the d e f l e c t i o n p u l s e s w o u l d be t o use the p h a s e - l o c k e d l o o p method. I n t h i s method, a waveform i s g e n e r a t e d by a c r y s t a l o s c i l l a t o r a t t h e r e q u i r e d h i g h f r e q u e n c y , e.g. 1.85 MHz o f t h e p r o t o t y p e . T h i s f r e q u e n c y i s t h e n d i v i d e d down by d i g i t a l c o u n t e r s (a v e r y much s i m p l e r o p e r a t i o n t h a n m u l t i p l y i n g ) to t h e d e f l e c t i o n f r e q u e n c y . The camera d e f l e c t i o n f r e q u e n c y i s compared w i t h t h e e x t e r n a l l y g e n e r a t e d one and t h e e r r o r s i g n a l i s u s e d t o c o n t r o l t h e f r e q u e n c y o f t h e c r y s t a l o s c i l l a t o r i n a f e e d b a c k c o n t r o l l o o p method. F i g . 5.1 shows t h i s d i a g r a m m a t i c a l l y . I f e i t h e r t h e camera o r the o s c i l l a t o r d r i f t s f rom the p r e s c r i b e d f r e q u e n c y , t h e o t h e r f o l l o w s a u t o m a t i c a l l y and the s a m p l i n g p u l s e s w i l l be p e r m a n e n t l y l o c k e d to t h e d e f l e c t i o n p u l s e s . I t was m e n t i o n e d i n S e c t i o n 2.2 t h a t t h e s a m p l i n g p u l s e s must be v e r y n a rrow so t h a t t h e d e s i r e d h o r i z o n t a l r e s o l u t i o n may be a c h i e v e d . The n a r r o w p u l s e s were g e n e r a t e d by u s i n g d i f f e r e n t i a t o r s . F o r t h e low r e s o l u t i o n o f 120 p o i n t s / l i n e , t h i s was q u i t e a d e q u a t e . F o r h i g h e r r e s o l u t i o n s however where s a m p l i n g p u l s e s o f 50ns o r l e s s a r e r e q u i r e d a l t e r n a t i v e methods may be n e c e s s a r y . One s i m p l e way o f o b t a i n i n g a v e r y n a r r o w p u l s e i s shown i n F i g . 5.2. The d u r a t i o n o f t h e p u l s e i s g i v e n by the d e l a y of t h e l o g i c g a t e . F o r a TTL g a t e f o r i n s t a n c e t h i s d e l a y i s u n d e r 10 n s . The p r o t o t y p e s y s t e m was d e s i g n e d t o have 2 s a m p l i n g s p e e d s , 69 y s e c / s a m p l e and 138 y s e c / s a m p l e . I t i s q u i t e easy t o have s e v e r a l s a m p l i n g speeds by s i m p l y h a v i n g s e v e r a l c o u n t d e c o d e r s i n s t e a d o f two. As can be CflMERFf f : £ — PULSES f F i g . 5.1 P h a s e l o c k e d l o o p s c h e m e T T — ^ T J O U T F i g . 5.2 G e n e r a t i o n o f a narrov/- p u l s e . seen from the photographs i n Chapter 4 however a high sampling rate tends to superimpose an unacceptable sampling pattern on the p i c t u r e . I t would be better to f i n d the f a s t e s t sampling rate at which the sampling pattern : disappears and use th i s i n a f i n a l design. In the l a s t few months, I.C and d i s c r e t e component a m p l i f i e r s of required c h a r a c t e r i s t i c s to b u i l d a sample and hold to the following s p e c i f i c a t i o n s have become a v a i l a b l e : sampling window 50 ns, hold time up to 1 usee. I t was mentioned i n the i n t r o d u c t i o n that the sample and hold i n the i n t e r f a c e would be required to hold a sample u n t i l the next sample i s taken. This i s a r i g i d s p e c i f i c a t i o n which i s not r e a l l y necessary. The computer A/D converter needs the signal -'to be a v a i l a b l e f o r l e s s than 1 usee. Therefore a sample and hold with the s p e c i f i c a t i o n s mentioned above w i l l be quite adequate. With these modifications i t should be p o s s i b l e to b u i l d a completely r e l i a b l e system. Some of the uses to which such a system can be put w i l l be described i n the next s e c t i o n . 5.3 P o s s i b l e Uses The f i e l d of TV bandwidth compression was one of the f i r s t areas of p i c t u r e processing where computers were applied. A pi c t u r e would be stored i n the computer, the v i s u a l data would then be processed according to some algorithms so as to simulate various schemes proposed f o r reducing TV bandwidth. The processed data would be read out and displayed to see what e f f e c t the simulation has had on the q u a l i t y of the p i c t u r e . The i n t e r f a c e system described i n t h i s thesis can be used as the l i n k between the p i c t u r e information and the computer. Some of the processing f o r the simulation of TV bandwidth compression however require adjacent samples i n the computer to correspond to consecutive p i c t u r e points. This i s - t h e r e f o r e an area where arrangement of data a f t e r storage would be required. While a l o t of work i s s t i l l being done on TV bandwidth compression, much att e n t i o n i s now being paid to the r e l a t i v e l y newer area of image processing by computer, pattern recognition. This t i t l e covers a wide area i n c l u d i n g such diverse topics as f i n g e r p r i n t i d e n t i f i c a t i o n , spacecraft image evaluation and biomedical image processing. The one thing these have i n common i s that the computer i s usually only required to recognize c e r t a i n c h a r a c t e r i s t i c s of the pi c t u r e information stored i n i t . Display of the processed data i s very seldom required. Thus i n the case of f i n g e r p r i n t i d e n t i f i c a t i o n f o r example, several f i n g e r p r i n t p i c t u r e information are entered into the computer, the computer i s required to compare them and f i n d which two are i d e n t i c a l . Weather forecasting by computer i s another f i e l d of pattern recognition. The processing required to be done by the computer i s s i m i l a r to the one j u s t described. S a t e l l i t e weather photographs are fed into the computer, information i s then extracted from t h i s to p r e d i c t the weather. Since i n these and many other areas of pattern r e c o g n i t i o n there i s no necessity f o r disp l a y i n g the processed information, the i n t e r f a c e system should be more r e a d i l y acceptable as a l i n k between the photographic information and the computer. This i s because the possible loss of syn-chronization during the display that was mentioned i n Section 4.1 w i l l not a r i s e . . T I T L E STORE MO. 1 (STORED .GLOBL BACK /THIS PROGRAM STORES A TV PICTURE ON TAPE THROUGH MEMORY. /EACH SAMPLE IS CONVERTED TO 11 BITS 7 0F WHICH ARE MOT /USED. 9 SAMPLES ARE PACKED IN 2 WORDS. AFTER STORING, THE /COMPUTER GOES TO ANOTHER PROGRAM TO MAKE USE OF THE DATA. / / SKPFRFr705301 CLRFRF=705302 SKPSAF=705401 C L R S A F r 7 0 5 4 0 2 SKPADF :705601 CLRADF=705602 CLRBUF :701104 LRS 1 1 = 640511 ADRB=701117 ADSC=701304 ALS3=640703 ALS7=643707 L R S D 6 4 0 5 0 1 ' • ' ' LRS7=640507 LRS5=640505 DTLA=707545 DTDF:707601 DTXA=707544 DAL 1 = 703 107 GO JMP START /THIS PART OF THE PROGRAM SETS OVER LAC (CBLK /UP THE TAPE TO ITS BEGINNING. DAC* (31 DZM* (30 . LAC (221000 DTLA WAIT DTDF JMP . - 1 SEARCH LAC RBLK CMA TAD (1 TAD CBLK SMA JMP REV DAC* (30 LAC (010000 DTXA JMP WAIT REV SZA JMP INVT LAC (020000 DTXA JMP START INVT CMA TAD (1 DAC* (30 LAC (050000 DTXA JMP WAIT /THE STORING OF THE PICTURE IN /MEMORY BEGINS HERE. THE INPUT /SIGNAL IS SAMPLED AND A/D CONVERTED. /NEGATIVE SAMPLES ARE IGNORED SINCE. /THEY ONLY REPRESENT THE SYNC PART /OF THE ORIGINAL VIDEO SIGNAL. / / / START CLRBUF CLRADF LAC (163S DAC* (13 LAC ( - 1 5 5 3 0 . DAC COUNT* ' CLRFRF CLRSAF SKPFRF JMP . - 1 • SKPSAF JMP . - I ADSC SKPADF JMP . - 1 CLRFRF CLRSAF DZM TEMP# CLA JMS SAMPLE JMP SI 0 ADD TEMP DAC TEMP ADRB SKPSAF JMP . - 1 ADSC DAC HOLD# AND (004000 SAD (004000 JMP IGNORE LAC HOLD CMA TAD (1 DAL I LAC HOLD CLRSAF JMP * SAMPLE IGNORE DZM HOLD JMP LOOP / / / / / / SAMPLE LOOP / 'TOP OF PICTURE ° PULSE PRESENT? ./NO. TEST AGAIN / Y E S . WAIT FOR PRESENCE OF SAMPLING /PULSE THEN START SAMPLING AND /A/D CONVERTING. . -/SAMPLING PULSE PRESENT? /NO. TEST AGAIN /YES . SAMPLE AND A/D CONVERT / /THIS PART OF THE PROGRAM WILL MASK /OUT THE LAST 7 BITS OF EACH CONVERTED /SAMPLE AND PACK 9 SAMPLES IN 2 WORDS. / / 51 ALS7 AND (740300 JMS SAMPLE 52 ALS3 AMD (036000 JMS SAMPLE 53 LRS1 AND (001700 JMS SAMPLE 54 LRS5 AND (000074 JMS SAMPLE . - . 55 LRS11 , AND (000003 ADD TEMP DAC* 10 LAC HOLD LRS7 AMD (000003 . DZM TEMP JMS SAMPLE 56 ALS7 AND (740000 JMS SAMPLE 57 ALS3 AND (036300 JMS SAMPLE 58 LRS1 AND (001700 JMS SAMPLE 59 LRS5 AND (000074 ADD TEMP DAC* 10 1SZ COUNT * JMP .+2 JMS* BACK / / / / / / / / / CLA DZM TEMP ' JMS SAMPLE JMP SI /SUFFICIENT SAMPLES TAKEN? /NO. GO AND TAKE MORE /YES . GO TO SUBROUTINE TO /TRANSFER DATA TO TAPE /SUBROUTINE TO DEPOSIT DATA ON TAPE . /THE DAT IS STORED ON TAPE SO THAT /IT CAN BE PROCESSED LATER. / / WRITE LAC ( - 2 DAC* (30 • - • . LAC (CBLK DAC* (31 ; LAC (231300 DTLA DTDF JMP . - 1 . LAC CBLK • • . • DAC SAVE# . LAC (1636 DAC* (31 LAC ( - 1 5 5 3 0 DAC* (30 LAC (005000 DTXA DTDF JMP . - 1 LAC (020000 DTXA JMS* BACK /EXIT TO ANOTHER PROGRAM. RBLK I CBLK 0 .END GO . T I T L E D I S P L A Y .NO. 1 ( D S P L Y 1 ) .GLOBL BACK / T H I S PROGRAM P R O V I D E S A D I S P L A Y OF A T V P I C T U R E , /STORED IN MEMORY BY T H E P R E V I O U S PROGRAM, ON AN / O S C I L L O S C O P E . T H E S A M P L E S R E P R E S E N T I N G THE P I C T U R E /ARE U N P A C K E D , D/A C O N V E R T E D AND P R E S E N T E D TO T H E / I N T E R F A C E S Y S T E M . / • / / S K P F R F = 7 0 5 3 8 1 C L R F R F : 7 0 5 3 3 2 S K P S A F = 7 0 5 4 3 1 • C L R S A F : 7 0 5 4 3 2 A L S 1 1 : 6 4 0 7 1 1 A L S 1 : 6 4 0 7 0 1 -A L S 5 : 6 4 0 7 0 5 A L S 7 : 6 4 0 7 0 7 L R S 3 : 6 4 0 5 0 3 L R S 7 : 6 4 0 5 0 7 DAL 1 : 7 0 3 1 0 7 D T L A : 7 0 7 5 4 5 D T D F : 7 3 7 6 0 1 . D T X A : 7 0 7 5 4 4 / S E T UP FOR T H E D I S P L A Y T A K E S P L A C E H E R E . T H E COMPUTER /WAITS FOR A 'TOP OF P I C T U R E ' P U L S E B E F O R E S T A R T I N G TO /OUTPUT TH E D A T A . / / BACK 0 AWAY L A C ( - 1 5 5 3 0 DAC COUNT* L A C ( 1 6 3 6 D A C * ( 1 0 P L A C E L A C * 10 DAC T E M P * L R S 7 AND ( 0 0 3 6 0 0 CM A TAD (1 L A C ( J M P D l DAC P L A C E C L R F R F C L R S A F S K P F R F JMP .-2 S K P S A F JMP .-1 DAL 1 L A C (-3 TAD (1 S Z A JMP .-2 C L R S A F L A C TEMP JMP D2 /THE U N P A C K I N G AND D I S P L A Y / I N T H I S S U B R O U T I N E . / / P R O C E S S T A K E P L A C E D S P L Y 0 AND ( 0 0 3 6 0 0 CMA TAD (1 S K P S A F JMP .-1 DAL 1 L A C (-2 TAD (1 S Z A JMP .-2 C L R S A F L A C TEMP J M P * D S P L Y D l L A C * 10 DAC TEMP L R S 7 JMS D S P L Y D2 L R S 3 JMS D S P L Y D3 A L S 1 JMS D S P L Y DA A L S 5 JMS D S P L Y D5 A L S 1 1 AND ( 0 0 3 0 0 0 DAC K E E P # L A C * 10 DAC TEMP A L S 7 AND ( 0 0 0 6 0 0 TAD K E E P JMS D S P L Y D6 L R S 7 JMS D S P L Y D.7. L R S 3 . JMS D S P L Y D8 A L S 1 JMS D S P L Y D9 A L S 5 JMS D S P L Y I S Z COUNT JMP D l , JMP AWAY / D I S P L A Y P U L S E P R E S E N T ? /NO. T E S T A G A I N / Y E S . D I S P L A Y THE C O R R E S P O N D I N G / S A M P L E . / A L L S A M P L E S D I S P L A Y E D ? /NO. GO AND D I S P L A Y R E M A I N D E R . / Y E S . GO BACK TO T H E TOP AND / S T A R T D I S P L A Y I N G T H E P I C T U R E / A G A I N . .END BACK BIBLIOGRAPHY 1. W.F. Schreiber and D.N. Graham, \"A D i g i t a l Scanner f o r Computer Image Processing\". Indian I n s t i t u t e of Technology, Dept. of E.E., A p r i l 1966. 2. A z r i e l Rosenfeld, \"P i c t u r e Processing by Computer\". New York Academic Press, 1969. 3. L.D. Harmon and K.C. Knowlton, \"Picture Processing by Computer\". Science Vo l . 164, pp. 19-29, A p r i l 1969. 4. Tektronix, Inc., \"Sampling Notes\". Beaverton, Oregon, 1969. 5. Louis Nashelsky, \" D i g i t a l Computer Theory\". New York, John Wiley & Sons Inc., 1966. 6. O.J. Tratiak, The \"SCAD\", M.I.T. Research Lab of E l e c t r o n i c s . Quarterly Progress Report 83, Oct. 15, 1966. 7. T.S. Huang and O.J. Tretiak, \"Research i n Pi c t u r e Processing\" i n o p t i c a l and E l e c t r o - O p t i c a l Information Processing. Chapter 3, M.I.T. Press, 1965. 8. H.U. Malmstadt and C.G. Enke, \" D i g i t a l E l e c t r o n i c s f o r S c i e n t i s t s \" , New York, W.A. Benjamin Inc., 1969. 9. S p e c i a l Issue on \"Redundancy Reduction\", Proceedings of the IEEE V o l . 55, March 1967. 10. J.G. Cossalter, \"A Computer Visual-Input System f o r the Automatic Recognition of Blood C e l l s \" , M.A.Sc. Thesis, U.B.C, August 1970. 11. E. Renschler and B. Welling, \"An Integrated C i r c u i t Phase-Locked Loop D i g i t a l Frequency Synthesizer\". A p p l i c a t i o n Note AN-463. Motorola Semiconductor Products. Inc. "@en ; edm:hasType "Thesis/Dissertation"@en ; edm:isShownAt "10.14288/1.0102116"@en ; dcterms:language "eng"@en ; ns0:degreeDiscipline "Electrical and Computer Engineering"@en ; edm:provider "Vancouver : University of British Columbia Library"@en ; dcterms:publisher "University of British Columbia"@en ; dcterms:rights "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en ; ns0:scholarLevel "Graduate"@en ; dcterms:title "A television camera to computer interface"@en ; dcterms:type "Text"@en ; ns0:identifierURI "http://hdl.handle.net/2429/34777"@en .