Method and apparatus for recording and reproducing on film directly viewable TV video signals

Method and apparatus for optically recording and reproducing video signals. The intensity of a laser beam is modulated as a function of the amplitude of the video signals. The modulated laser beam is caused to conduct a raster scan synchronized by standard TV sync pulses and used to expose photographic film. Horizontal and vertical sync bars of contrasting optical density are recorded beyond the borders of the raster. The developed film is a directly viewable reproduction of the image scanned to produce the video signals recorded. To reproduce the video signals, an unmodulated laser beam conducts a raster scan of the developed image recorded on the film. The intensity of the scanning beam is modulated by the optical density of the film and converted to amplitude modulated electrical signals, a reproduction of the video signals recorded. The optically recorded sync bars are also detected and are used to produce electrical sync pulses to position the raster scan conducted by the unmodulated beam to substantially overlie the image recorded on the film being scanned.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is in the field of methods and apparatus for recording TV 
video signals of an image on photographic film and for reproducing the 
recorded TV video signals from the information recorded on the film, which 
information includes a directly viewable reproduction of the image. 
2. Description of the Prior Art 
Many types of sensing equipment produce TV video signals of images which 
images are normally displayed by cathode ray tubes (CRT)s. Ultrasonic 
scanning systems used for conducting medical examinations such as the one 
disclosed and claimed in an application entitled "High Resolution Rotating 
Ultrasonic Scanner" by Robert L. Metz et al, Ser. No. 922,185, filed July 
5, 1978 application is assigned to the same assignee as this invention, 
produce large numbers of such images for each patient examined. The 
abundance of such data creates problems in how to view and properly 
comprehend the information contained in the images. To do so effectively 
and efficiently requires that some or all of the images be recorded and 
retained for an indefinite time. Obviously there is a need to be able to 
reproduce any images so recorded and retained when desired and to be able 
to reproduce the images so recorded in any order. These problems are 
particularly applicable to the medical field where a physician may not be 
present when the images, cross-sections through an organ of a patient such 
as a breast, are produced by an ultrasonic scanning system or when the 
opinion of several specialists may be desired to confirm or establish a 
diagnosis. Obviously reproducible records from earlier examinations, if 
available, are particularly helpful in preparing a medical diagnosis as 
such earlier information can confirm if there has been any observable 
change and the nature of the change since the last examination or from any 
earlier examinations. The amount of information available also makes it 
desirable to reduce the time necessary to interpret individual 
cross-sectional images of an organ. One way of doing this is by displaying 
a set of adjacent images sequentially to create a three-dimensional image 
of the organ in the viewer's mind. 
It is also desirable that the record on which the images are stored be 
compact so that the record of an examination of a patient can be stored in 
a relatively small space, preferably in the patient's file. It is 
obviously desirable that the cost of such records be minimized and that 
the records have the capability of reproducing images of substantially the 
same quality and detail as the originals when displayed on a TV monitor, 
for example. It is a great advantage if the records are directly viewable 
by appropriate optical equipment, similar to a microfiche viewer, so that 
the image or images so recorded can be viewed and studied other than by 
displaying them on a CRT of a TV monitor. The capability of being directly 
viewable is particularly useful in comparing current information displayed 
on a TV monitor for example with images of the same cross-section obtained 
in prior examinations. 
Prior art devices for recording TV video signals have generally recorded 
the TV video signals on a magnetic medium such as on magnetic tape or on a 
magnetic disc. Such magnetic recordings and reproduction systems have the 
disadvantage of being relatively high in cost, and are characterized by 
the fact that the images recorded are not directly viewable or perceivable 
by the human eye or through relatively simple and low cost purely optical 
viewers. In addition the magnetic media on which such images are stored 
does not lend itself to the recording of a limited number of images nor 
for the filing or storing of the records of the images produced in 
examining one patient, for example, so that all relevant records of the 
patient are stored in one location and only the records of that patient 
are stored there. 
SUMMARY OF THE INVENTION 
The present invention provides both method and apparatus for recording on 
photographic film TV video signals of an image such as a cross-sectional 
view through an organ of a patient, by modulating the intensity of a laser 
beam with an acousto-optical modulator and by deflecting the beam so that 
it conducts a standard TV raster scan. The beam is focused on and 
positioned on the film which is fixed or nonmoving and the film when 
developed is a transparency. The film is divided into sectors so that a 
relatively large number of rasters, or images, up to 100 in a preferred 
example, can be optically recorded on a single piece of standard film. The 
apparatus will position the write laser beam so that the raster which 
exposes the film will be positioned in a predetermined one of the sectors 
of the film. Recorded in the sector with the video signals are the optical 
sync bars, the equivalent of the video horizontal and vertical 
synchronization signals or sync pulses. The optical image recorded on the 
film when the film is exposed by the write beam, when developed, is the 
equivalent of the image of the TV video signals and is directly viewable 
on the film. To reproduce the TV video signals from an image recorded as 
described above in a sector of the film, the beam of a laser of 
substantially constant intensity, or one which is unmodulated, is 
deflected so that the read beam conducts a standard TV raster scan of the 
image or raster recorded in a sector. The intensity of the read beam is 
modulated by the optical density, or transmissivity, of the image recorded 
on the film as well as by the sync bars of contrasting optical density. A 
feedback loop is provided so that the raster scan conducted by the read 
beam substantially coincides with the raster of the image recorded in the 
sector. The read laser beam after its intensity is modulated by the film 
is converted into electrical signals, which signals are substantially an 
accurate reproduction of the TV video signals used to create the image 
recorded in the sector. The TV video signals can be manipulated and 
displayed in the same manner as the original of such signals produced by 
an ultrasonic scanning system, for example. 
It is, therefore, an object of this invention to provide method and 
apparatus for recording on photographic film TV video signals of an image 
and reproducing the TV video signals recorded on the film when needed, and 
in which the record on the film is an optical reproduction of the image; 
i.e., the scan lines of the image are substantially contiguous. 
It is another object of this invention to provide method and apparatus for 
recording on film optical signals which are the substantial equivalent of 
TV video signals of images including synchronization signals in which the 
recorded optical signals produce a directly viewable record of the image 
on the film and for reproducing from such optically recorded signals TV 
video signals. 
It is yet another object of this invention to record on film directly 
viewable images produced from standard TV video signals and to reproduce 
the standard electronic TV video signals from such images. 
It is a further object of this invention to provide method and apparatus 
for recording on photographic film TV video signals and to reproduce the 
TV video signals which automatically center the scanning raster on replay 
so that any change in film size due to developing the film or other causes 
does not require the user to adjust the position of each image obtained 
from reroduced TV video signals during replay where the recorded image is 
displayed on the screen of a TV monitor so that rapid replay of recorded 
images is possible while maintaining each image in the center of the 
screen of the TV monitor. 
It is another object of this invention to use a combination of an 
acousto-optical deflector to provide the rapid deflections required for TV 
horizontal sweep, and galvanometer driven mirrors to provide TV vertical 
sweep and the larger deflections required for recording and reproducing 
multiple images on photographic film without sacrificing the resolution of 
each individual image so recorded and reproduced. 
It is also an object of this invention to reduce the time required to 
interpret cross-sectional images of an organ by displaying a group, or 
set, of such images sequentially and at an appropriate rate to create a 
three dimensional image of the organ in the viewer's mind. 
It is a still further object of this invention to provide a compact record 
of TV video signals of a large number of images which can be stored in a 
relatively small space, is relatively economical to use, is capable of 
reproducing the recorded TV signals, the reproduced TV video signals 
having substantially the same quality as those of the original, and which 
is directly viewable.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 recording and reproducing system 10 is provided with a user 
interface control panel 12 which is used by the operator of system 10 to 
determine or set the operating parameters for the system; for example, to 
place system 10 in its reproduction, or read mode; or in its record, or 
write mode. If system 10 is in its read mode, the operator can select 
which image is to be read, or reproduced, as well as the next image to be 
read, for example. System 10 can also be set to create sequentially and at 
an appropriate rate a three dimensional image in the viewer's mind of an 
organ or to reproduce the recorded images in substantially any manner or 
order that the operator desires. Mode control logic, or microprocessor, 14 
interprets the operator's requests and controls the recording and replay 
subsystem 16 accordingly. Each time a new image is available for 
recording, a logic signal (new image present) is applied to mode control 
logic 14 from the source of the signal such as the ultrasonic scanning 
system referred to above. The new image present signal will cause the 
video signals of the image applied to recording and reproducing subsystem 
16 to be recorded on photographic film 20 if system 10 is in its 
recording, or write, mode. The input video signals applied to recording 
and replay subsystem 16 are the typical or standard TV video signals such 
as are applied to a cathode ray tube of a conventional television set or 
monitor such as TV monitor 18. Recording and replay subsystem 16 includes 
a laser as a source of coherent monochromatic light and appropriate 
devices for deflecting the laser beam horizontally and vertically, as well 
as a device for modulating the intensity of the write laser beam. The 
horizontal and vertical deflections of the write laser beam are 
synchronized with the TV video synchronization signals to perform or 
conduct the standard TV raster scan in the preferred example. The 
intensity of the write laser beam is modulated primarily by the camera 
signal portion of a TV video signal. The devices or components of 
recording and replay subsystem 16 also have the capability of positioning 
the raster scanned by the write laser beam so that it is recorded in a 
predetermined sector of film segment 20. Film 20 in a preferred embodiment 
is divided into an array of 100 sectors 22 as illustrated schematically in 
FIG. 8, with each sector 22 having the capability of storing a raster 23 
of an image by having film 20 exposed by the write beam and thereafter 
developed. It should be noted that during recording and reproducing of TV 
video signals, the position of film 20 relative to laser 26 is 
substantially fixed. 
FIG. 2 is a block diagram of recording or write subsystem 24 of recording 
and reproducing subsystem 16 of system 10. An unblank signal produced by 
mode control logic 14 when no new image is present is used to keep the 
intensity of the light beam from conventional helium neon laser 26 that 
produces a continuous beam of coherent monochromatic light of 
substantially uniform or constant intensity that may reach film 20 below 
the threshold necessary for writing or exposing film 20. Intensity 
modulator 28 and TV raster deflector 30 are preferably acousto-optical 
devices (Bragg cells), devices in which ultrasonic standing waves are used 
to modulate the intensity of the write beam produced by laser 26 or to 
deflect the beam as is well known in the art. While one Bragg cell can 
both deflect a laser beam to provide horizontal sweep and to modulate the 
intensity of the beam passing through the cell, in the preferred 
embodiment intensity modulator 28 and horizontal deflector 32, seen in 
FIG. 6, are separate devices. The intensity of the write laser beam after 
passing through modulator 28 is determined by the amplitude of the 
standing acoustic waves in modulator 28. The write beam is deflected to 
conduct a standard TV raster scan, in the preferred embodiment, by raster 
deflector 30 in response to horizontal and vertical scanning waves 
produced by conventional TV sweep generator 34 in response to the TV sync 
signals applied to it which synchronization signals are stripped, or 
separated, from the standard TV video signals. The horizontal deflection 
of the raster scan is produced by acousto-optical horizontal deflector 32 
and is a functon of the frequency of the standing waves in deflector 32. 
Vertical scan, or deflection, of the writing beam to produce the raster 
scan is accomplished by vertical mirror deflector 35 which is positioned 
by a small dc motor 36 of a conventional galvanometer. While the vertical 
sweep could be performed by an acousto-optical cell, the use of a motor 
driven mirror to provide the slower vertical scan has the advantage of 
reducing the cost of system 10. 
Motor 36 and mirror 35 and horizontal mirror deflector 38 and dc motor 40 
of a second conventional galvanometer are components of position deflector 
42. Position generator 44 provides signals X.sub.0, Y.sub.0 which are the 
coordinates of the origin of raster 23a, for example, on film 20 where 
raster 23a is to be recorded. In the Y, or vertical, direction both the 
vertical sweep associated with a TV raster scan, and the positioning of 
the raster on film 20 is accomplished by motor 36 and vertical mirror 
deflector 35, as will be explained later. Position generator 44 is, in the 
preferred embodiment, a pair of digital to analog converters (D/A) 46, 48 
that convert an image selector digital code from control logic 14 into 
analog voltages corresponding to the coordinates X.sub.0 and Y.sub.0 that 
drive motors 36, 40 to position raster 23 in sector 22a of film 20. 
When an image recorded on film 20 is to be reproduced or converted into 
video signals, the read, or reproducing subsystem, 50 of recording and 
reproducing subsystem 16 of system 10 which is illustrated in FIG. 3 is 
utilized. In the read, or replay, mode the intensity of the light beam 
from laser 26 is not modulated by modulator 28 except during retrace when 
essentially no light from laser 26 is permitted to pass through modulator 
28 in the preferred embodiment. TV sweep generator 34 in response to 
standard TV synchronization signals, or sync pulses, causes the read laser 
beam to be deflected to conduct a standard TV raster scan by raster 
deflector 30 with the fast horizontal sweep provided by horizontal 
deflector 32 and the vertical sweep by mirror 35. Position generator 44 
will cause raster 23 scanned by the read beam to substantially coincide 
with the raster of an image recorded in a sector 22 as the result of 
position generator 44 supplying X.sub.0, Y.sub.0 coordinates of the origin 
of the raster to position deflector 42. The amount of the scanning read 
beam passing through raster 23 is measured by photodetector 52 which 
produces electrical signals which are a function of the film density 
scanned by the read laser beam. The output of detector 52 is a standard TV 
video signal which can be used in the conventional way to produce an image 
on a CRT of a TV monitor. 
Any change in the dimension of film 20 as a function of time, or any change 
in position between the time data, images are recorded on film 20 and when 
film 20 is positioned to be read to reproduce the recorded TV signals can 
result in the raster scan conducted by the read beam not substantially 
coinciding with the raster photographically recorded in a sector 22 of 
film 20. It is therefore necessary to provide some form of feedback so 
that the raster scan conducted by the read beam coincides with, or is 
congruent with, the raster of the recorded image. To provide appropriate 
feedback, TV synchronization signals, or sync pulses, are recorded in the 
sector of film 20 during the time a raster 23 is being recorded by a write 
laser beam in the sector. 
To do this the horizontal scanning wave or horizontal sweep is extended so 
that it is longer than usual. Referring to FIG. 4, in FIG. 4A the normal, 
or standard horizontal scanning wave or sweep which is not to scale is 
illustrated. The time between the beginning of horizontal sweep 56a and 
its end is substantially 53 microseconds. The period between sweeps is 
approximately 10 microseconds to permit flyback. In FIG. 4B typical video 
signals are illustrated. The video, or camera, signals 54 used to modulate 
the intensity of an electron beam in a CRT, for example, essentially 
terminate at the end of each horizontal sweep 56. There is a 1.3 
microsecond period between the end of the video signal 54 and the 
beginning of horizontal sync pulse 58 which is 5 microseconds in width and 
approximately 3.7 microseconds until the video signal 54b appears, at 
which time the horizontal sweep 56b begins as can be seen by comparing 
FIGS. 4A and 4B. 
To record synchronization information on film 20, a portion 58a, 
illustrated in FIG. 4D of the horizontal sync signal 58 is used to 
modulate the intensity of the laser beam produced by laser 26. This is 
accomplished by extending the horizontal sweep 60 as illustrated in FIG. 
4C so that a portion 58a of sync pulse 58 can be applied to modulator 28 
so that the intensity of the write laser beam which passes through 
modulator 28 is substantially at its maximum intensity which results, in 
the preferred embodiment, in a horizontal black sync bar 62 being written, 
or recorded, on the right-hand border of the raster of each image recorded 
in each sector 22 of film 20. During flyblack the video, or camera, signal 
63 applied to modulator 28, which is illustrated in FIG. 4D has a value 
such that in the preferred embodiment essentially no light from laser 26 
passes through modulator 28, or to describe it another way, camera signal 
63 includes a blanking pulse 65 which is applied to modulator 28 during 
flyback. Sync bar 62 will in the preferred embodiment be blacker than the 
normal video black level and will extend into the nonlinear region of the 
gamma curve of film 20. During a read, the video signals produced by 
photodetector 52 will include an abbreviated sync pulse produced when the 
intensity of the read beam is modulated by a black sync bar 62, for 
example. The sync pulses can be detected and the image location code 
produced by microprocessor 14 can be modified to change the position of 
the scanning raster by causing the horizontal mirror deflector 38 to move 
so that the horizontal sync pulses detected by photodetector 52 occur at 
the proper time with respect to the horizontal sync pulses applied to TV 
sweep generator 34 as will be described later. 
A similar technique can be used to cause a black vertical sync bar 64 to be 
recorded at the bottom of each raster 23 of the image recorded in each 
sector 22 by causing the lower or bottom three horizontal scan lines of 
the raster to have voltages corresponding to the vertical sync pulses 
applied to modulator 28 so that a heavy black bar 64 will be written on 
the bottom border of the raster 23 of each image which vertical black sync 
bar 64 can be detected and used to modify the position of the vertical 
deflector mirror 38 by causing microprocessor 14 to change the vertical 
address or location applied to the position generator 44 until the 
vertical sync pulses applied to the TV sweep generator 34 and those 
detected by photodetector 52 are occurring at the right times. 
Referring to FIG. 5, the output of laser 26 is a narrow beam of coherent 
monochromatic light that is approximately 0.8 millimeters in diameter. 
This beam is essentially stationary and of substantially constant 
intensity. The output beam of laser 26 passes through the acousto-optical 
modulator 28. TV video signals 63 during write mode are applied to 
acousto-optical modulator 28 to vary the intensity of the beam transmitted 
through modulator 28 as a function of the amplitude of the video signals 
applied thereto. Modulator 28 is turned off so that the full intensity of 
laser beam from laser 26 passes through it when system 10 is in its read 
mode except during flyback when modulator 28 is energized to essentially 
prevent light from laser 26 reaching photodetector 52. The output of 
modulator 28 is a narrow beam of light that is unmodulated except during 
flyback as described above during the read mode of system 10 and is 
modulated by TV video signals 63 during the write mode of system 10. The 
beam is spread out by lenses 65 and 66 to a cylindrical beam approximately 
1.6 millimeters in diameter. That beam then passes through cylindrical 
lens 68 and is spread out into a beam of light that is approximately 40 
millimeters wide and 1.6 millimeters high. The beam is recollimated in the 
X, or horizontal plane and focused in the Y, or vertical plane by lens 70. 
The beam from lens 70 which is still stationary then enters 
acousto-optical deflector 32. Deflector 32 has applied to it horizontal 
sweep or scanning waves produced by raster generator 34 in response to 
sychronization signals from TV sync generator 72. The output of horizontal 
deflector 32 is a sheet of light which is approximately 40 millimeters 
wide and somewhat less than 1.6 millimeters high in a preferred embodiment 
and which beam has been deflected through a small angle. As a result the 
laser beam is deflected horizontally to perform the horizontal sweep of 
the standard TV raster scan. The beam of light after leaving deflector 32 
is reformed through lens 74 and cylindrical lens 76 into a cylindrical 
collimated beam of light again approximately 1.6 millimeters in diameter. 
This beam of light after passing through lens 76 contains intensity 
information during the write mode, is sweeping in the horizontal or X 
direction, and is stationary in the vertical or Y direction. The beam is 
again enlarged by lenses 78, 80 into a circular beam of light 6.3 
millimeters in diameter. This beam of light sweeps only in the horizontal 
direction and is deflected at the horizontal sweep rate of the standard TV 
raster. The beam of light is then deflected by mirror 38 which positions 
the raster horizontally and in the preferred embodiment will deflect the 
beam of light through an angle of approximately 8 degrees depending upon 
the angle of mirror 38. Motor 40 positions mirror 38 and is controlled by 
digital numbers, twelve bits in the preferred embodiment, which are 
applied by microprocessor 14 to D/A converter 48 which converts the binary 
signals, or numbers, to corresponding dc voltages to properly position 
mirror 38. Lenses 82, 84 serve to reimage the signals from horizontal 
deflector mirror 38 onto the vertical deflector mirror 35. Light reflected 
from mirror 35 which is positioned by dc motor 36, a typical galvanometer, 
is directed straight up out of the horizontal plane in which all of the 
optical elements preceding, or before mirror 35, are located; and is thus 
swept in two directions, horizontally and vertically. The laser beam after 
being reflected by the vertical mirror deflector 35 as illustrated in FIG. 
5 is focused onto film 20 by lens 86 to expose the film, which film when 
developed is a substantially permanent record of the images so recorded. 
As seen in FIG. 8, film 20 is divided into an array of sectors 22, 10 in 
each column or row, for a total of 100 in a preferred embodiment. In the 
preferred embodiment, each image or raster 23 recorded in sector 22 is 
approximately 61/2 millimeters wide and has a 1/2 millimeter border which 
provide a total of 10 sectors in 70 millimeters, the width of the film. 
The vertical dimensions of the rasters 23 are also 61/2 millimeters high 
with a 1/2 millimeter border to provide 10 sectors in the 70 millimeters 
of film 20 available vertically. A suitable type of film for use in 
recording and reproducing system 10 is Kodak High Speed Holographic film 
type SO-253, a product of the Eastman Kodak Co. 
In the preferred embodiment, film 20 when developed produces a transparency 
on which the image whose TV signals are recorded in a sector of the film 
by the apparatus and method of this invention is directly viewable and 
preferably has the same contrast or appeareance when directly viewed as 
when the same image is produced on a black and white TV monitor for 
example, by applying the TV video signals of the image to the monitor. It 
is within the scope of this invention to use film which when exposed and 
developed is either a positive or negative transparency and to 
appropriately modulate the intensity of the write laser beam to produce a 
directly viewable record of the image having substantially the same 
appearance as that produced by a TV monitor. 
In the read mode a piece of exposed and developed film 20 is placed as 
illustrated in FIG. 5. The read beam from laser 26 is positioned by 
position generator 44 and position deflector 42 so that the read beam 
scans a raster 23 of an image recorded in a sector 22 of film 20 and has 
its intensity modulated by the transmissivity, or optical density, of the 
recorded raster 23. The intensity modulated read beam is focused by lens 
87 onto photodetector 52. The output of photodetector 52 is a video signal 
which when combined with synchronization signals can be applied to 
standard TV monitor 18 for the production of an image by the typical CRT 
of TV monitor 18. The electrical output signals of photodetector 52 are 
also applied to a standard sync detector 88 to detect the location of the 
sync bars 60, 62 recorded on a raster 23 of an image on film 20. The 
output of sync detector 88 is applied to the feedback circuit illustrated 
in FIG. 7. 
In FIG. 6, the components that deflect laser beam 90 produced by laser 26 
so that it conducts a standard TV raster scan and which will position the 
raster so that it can be recorded in a predetermined sector, such as 
sector 22a, of film 20 which is schematically illustrated in FIG. 8. 
Conventional TV sync generator 72 produces the synchronization signals, or 
sync pulses, having the characteristics of standard TV sync pulses. These 
sync pulses are applied to TV sweep generator 34 which produces horizontal 
and vertical scanning waves, or sweep signals. Beam 90 from laser 26 after 
passing through modulator 28 which does not modulate laser beam 90 except 
on flyback and is therefore not illustrated in FIG. 6, passes through 
Bragg cell 32 which will deflect beam 90 horizontally as described above 
as a function of the horizontal sweep signal applied to it so that the 
beam of light from laser 26 will conduct a horizontal linear sweep in 
synchronization with the horizontal sweep signals produced by generator 
34. The positioning of a raster 23 in a sector 22 is controlled by 
microprocessor 14 which provides the "X" and "Y" coordinates of the 
origin of the raster 23a, for example, as 12 bit binary numbers which are 
converted to dc voltages by D/A converters 46, 48. The voltage from D/A 
converter 46 has added to it the vertical sweep wave form produced by TV 
sweep generator 34 which voltages are combined by summing amplifier 92. 
The output of amplifier 92 is applied to dc motor 36 to control the 
position of vertical mirror deflector 35. The X or horizontal position of 
the raster scanned by beam 90 is controlled by microprocessor 14 by 
providing the location of the X coordinate of the origin of the raster 
23a, for example, as a 12 bit binary number in the preferred embodiment, 
which origin is located in the sector 22a in which the raster 23a is to be 
recorded. In response to the binary numbers applied to it D/A converter 48 
produces a dc output which will cause dc motor 40 to position horizontal 
mirror deflector 38 to deflect beam 90 so that it is properly positioned 
to scan raster 23a in sector 22a, for example. 
As mentioned before, the possibility exists of changes in the dimensions of 
film 20 or in its position so that it is necessary to provide feedback so 
that the raster 23 scanned by beam 90 as determined by the sweep signals 
of generator 34 and the positioning signals from microprocessor 14 during 
the read mode of system 10 will be properly positioned to overlie, and be 
congruent with, the recorded raster 23. To provide such feedback control, 
the output of sync detector 88, which is illustrated in FIG. 5, is applied 
to the negative input terminal of comparator 94 illustrated in FIG. 7. The 
positive terminal of comparator 94 has applied to it a voltage 
corresponding to the black video level which is approximately 0.0 volts in 
a preferred embodiment. The signal BBAR, the output of comparator 94, will 
go positive, or be a logical 1, when the output of sync detector 88 
corresponds to one of the black sync bars 62, 64 on the right or bottom 
sides of a raster 23. The signal BBAR is applied to the clock input 
terminal C of BBFIRST flip-flop 96 and the horizontal drive signal or sync 
pulse HD is applied to the clock terminal C of HDFIRST flip-flop 98. Both 
flip-flops 96 and 98 are standard delay type flip-flops. The ARM signal a 
negative pulse, or a logical "0", initially resets both flip-flops 96, 98 
since the ARM signal, which is produced by microprocessor 14, when 
programmed to do so, is applied to the reset terminals of flip-flops 96, 
98. When flip-flop 96 resets the output of terminal Q of flip-flop 96, a 
logical 1 is applied through or gate 99 to the D terminal of flip-flop 98, 
and the output of the Q terminal of flip-flop 98 which is also a logical 1 
is applied to the D terminal of flip-flop 96. The first signal BBAR or HD 
to have a 0 to 1 transition sets the corresponding flip-flop HDFIRST 98 or 
BBFIRST flip-flop 96. If HDFIRST is set first, its output at the output 
terminal Q goes low so that a following BBAR pulse will not set flip-flop 
96. If flip-flop 96 is set first, it triggers the one-half microsecond 
pulser 100 which produces a logical 1 at its Q output terminal for 1/2 
microsecond, which logical 1 is applied to the input terminal D of 
flip-flop 98. If the horizontal drive HD pulse occurs within the half 
microsecond interval following the production of BBAR, then flip-flop 98 
will also set. If the horizontal drive sync pulse occurs later than this, 
a logical 0 is applied to terminal D of flip-flop 98 through or gate 99 
and flip-flop 98 will no longer set. 
The two signals HDFIRST and BBFIRST are applied to microprocessor 14 
through a commercially available programmable interface 104 (PIA). 
Microprocessor 14 will interpret the signals according to the table set 
forth in FIG. 9. The desired result is for the signal BBAR to come first 
with the horizontal drive pulse HD following BBAR within a half 
microsecond. Using the truth table of FIG. 9, the binary numbers applied 
to D/A converter 48 is incremented or decremented by microprocessor 14 
which causes DC motor 40 for example to change the position of mirror 38 
until such time as the desired relationship between BBAR and HD is 
achieved. 
The vertical feedback circuit which positions the scanning raster 
vertically during the read mode is substantially the same as the circuit 
illustrated in FIG. 7 except that it uses the vertical drive pulses VD 
from sync generator 72 instead of HD pulses and a similar BBAR signal 
produced by a comparator 94 when sync detector 88 detects a vertical sync 
bar 64 of a raster as the raster is scanned by the read laser beam. The 
pulser for the vertical feedback circuit provides a 150 microsecond pulse 
instead of the half microsecond pulse provided by pulser 100 for 
horizontal synchronization. Thus the circuit illustrated in FIG. 7 and a 
similar circuit for the vertical synchronization, provides feedback 
control of the X or horizontal position of the scanning raster and 
feedback control for the Y or vertical position so that the location of 
the raster during the read mode scanned by laser beam 90 can be adjusted 
by appropriate modifications of the signals applied to the A/D converters 
46, 48 by microprocessor 14 with the result that the scanning read raster 
conducted by laser beam 90 substantially coincides with the recorded 
raster 23 on film 20. The feedback circuits permit the scanning raster on 
replay, or read, to center quickly and accurately on the recorded raster 
so that there is no need for the user, or operator, to adjust the position 
of each image as reproduced on a TV monitor for example. As a result, 
rapid replay of recorded images is possible while maintaining each image 
in the center of the TV screen. 
From the foregoing, it is believed apparent that it is obvious that 
Applicants have provided apparatus for recording on photographic film TV 
video signals of an image that can be viewed directly and which images can 
be scanned by a beam of light to reproduce the recorded TV video signals. 
The film record 20 is small, relatively inexpensive, and can be stored 
substantially indefinitely in the patient's records. A big advantage of 
the system of the invention is that it reduces the time necessary to 
interpret the individual cross-sectional images of an organ in conducting 
medical screening and diagnosis by displaying a group or set of images 
sequentially and at an appropriate rate to create effectively a 
three-dimensional image in the viewer's mind. Such an effect is 
accomplished by having the last image displayed in a sequence immediately 
following the next to last rather than starting over with the first image. 
This eliminates interruptions in the continuity of the organ as perceived 
by the viewer and thus the system enhances the ability of a physician to 
recognize abnormalities, for example. 
It should be evident that various modifications can be made to the 
described embodiment without departing from the scope of the present 
invention.