Technical Field

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 in- formation includes a directly viewable reproduction of the image.

Background Art

Many types of sensing equipment produce TV video sig¬ nals of images which images are normally displayed by cathode ray tubes (CRT)s. Ultrasonic scanning systems used for con¬ ducting medical examinations such as the one disclosed and claimed in an application entitled "High Resolution Rotating Ultrasonic Scanner" by Robert L. Metz et al, Serial No. 922,185, filed July 5, 1978, which application is assigned to the same assignee as this invention, produce large num¬ bers of such images for each patient examined. The abun¬ dance 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, ate 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 in¬ terpret 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 or¬ gan in the viewer's mind. it is also desirable that the record on which the im¬ ages are stored be compact so that the record of an examin¬ ation of a patient can be stored in a relatively small spac preferably in the patient's file. It is obviously desirabl that the cost of such records be minimized and that the records have the capability of reproducing images of sub¬ stantially the same quality and detail as the originals whe displayed on a TV monitor, for example. It is a great adva tage 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. Th capability of being directly viewable is particularly usefu 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 mediu such as on magnetic tape or on a magnetic disc. Such mag¬ netic recordings and reproduction systems have the disadvan tage of being relatively high in cost, and are characterize by the fact that the images recorded are not directly view¬ able 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 pro¬ duced in examining one patient, for example, so that all

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relevant records of the patient are stored in one location and only the records of that patient are stored there.

Disclosure of 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 on which it is recorded 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 signals from an image recorded as described above in a sector of the film, the beam of a laser of substantially constant inten¬ sity, 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 substan¬ tially 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 yideo 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 sig- nals produced by an ultrasonic scanning system, for example.

It is, therefore, an object of this invention to pro¬ vide 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.

It is another object of this invention to provide me¬ thod 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 record 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 reproduced 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 com¬ bination of an acousto-optical deflector to provide the rapi deflections required for TV horizontal sweep, and galvanomet

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driven mirrors to provide TV vertical sweep and the larger deflections required for recording and reproducing multiple images on photographic ilm without sacrificing the resolu¬ tion 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 anaappropriate rate to create a three dimensional im¬ age of the organ in the viewer's mind. It is a still further object of this invention to pro¬ vide 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.

Brief Description of Drawings

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

Fig. 1 is a block diagram of the system of the invention; Fig. 2 is a block diagram of the recording subsystem;

Fig. 3 is a block diagram of the reproducing subsystem;

Fig. 4 illustrates waveforms useful in describing the invention;

Fig. 5 is a schematic view of the optical subsystem of the invention;

Fig. 6 is a schematic block diagram of the components for deflecting and positioning a laser beam;

Fig. 7 is a schematic circuit diagram of a portion of the feedback circuit of the invention;

Fig. 8 is a schematic view of a film on which images have been recorded; and

Fig. 9 is a truth table describing the function of the feedback loop.

Best Mode ^: for C&rrying Out the Invention

In Fig. 1 recording and reproducing system 10 is pro¬ vided with a user interface control panel 12 which is used by the operator of system 10 to determine or set the opera¬ ting 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 reply subsystem 16 accordingly. Each time a new image is available for record¬ ing, 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 re¬ corded on photographic film 20 if system 10 is in its record ing, or write, mode. The input video signals applied to recording and replay subsystem 16 are the typical or stand¬ ard 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 appro¬ priate devices for deflecting the laser beam horizontally and vertically, as well as a device for modulating the inten sity of the write laser beam. The horizontal and vertical deflections of the write laser beam are synchronized with th

TV video sychronization signals tp perform or conduct the standard TV raster sca,n in the preferred example. The inten¬ sity of the write laser beam is modulated primarily by the camera signal portion of a TV video signals. The devices or components of recording and reply 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 ad 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.

Fig. 2 is a block diagram of recording or write sub¬ system 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 pro¬ duces 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 expos¬ ing film 20. Intensity modulator 28 and TV raster deflector 30 are preferably acousto-optical devices (Bragg cells) , de¬ vices in which ultrasonic standing waves are used to modu¬ late 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 inten¬ sity 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 deflec- tor 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 function of the frequency of the standing waves in deflec- tor 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 _n , Y _Q 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 con¬ vert an image selector digital code from control logic 14 into analog voltages corresponding to the coordinates X_ and Y 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 sub¬ system, 50 of recording and reproducing subsystem 16 of sys- tern 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 synchroni¬ zation signals, or sync pulses, causes the read laser beam

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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 _Q , Y _Q 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 sig¬ nal 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 re¬ corded 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 hori zontal 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 extend ing the horizontal sweep 60 as illustrated in Fig. 4C so that a portion 58a of sync pulse 58 can be applied to modu lator 28 so that the intensity of the write laser beam whi passes through modulator 28 is substantially at its maximu intensity which results, in the preferred embodiment, in a horizontal black sync bar 62 being written, or recorded, o the right-hand border of the raster of each image recorded in each sector 22 of film 20. During flyback the video, o camera, signal 63 applied to modulator 28, which is illu- strated in Fig. 4D has a value such that in the preferred embodiment essentially no light from laser 26 passes throu modulator 28, or to describe it another way, camera signal 63 includes a blanking pulse 65 which is applied to modu¬ lator 28 during flyback. Sync bar 62 will in the preferre embodiment be blacker than the normal video black level an will extend into the nonlinear region of the gamma curve o film 20. During a read, the video signals produced by pho detector 52 will include an abbreviated sync pulse produce when the intensity of the read beam is modulated by a blac 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 ras by causing the horizontal mirror deflector 38 to move so that the horizontal sync pulses detected by photodetector occur at the proper time with respect to the horizontal sy pulses applied to TV sweep generator 34 as will be describ later.

A similar technique can be used to cause a black yertical sync bar 64 to be recorded at the bottom of each raster 23 of the image recorded in each sector 22 by caus¬ ing 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 verti¬ cal 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 .8 millimeters in diameter. This beam is essentially sta¬ tionary and of substantially constant intensity. The output beam of laser 26 passes through the acousto-optical modula- tor 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 ener¬ gized 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 apread out into a beam of light that is approximately 4Q millimeters wide and 1.6 millimeters high. The beam is

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recolli ated in the X, or horizontal plane and focused in the Y, or vertical plane by lens 7Q. The beam from lens 70 which is still stationary then enters acousto-optical defle tor 32. Deflector 32 has applied it to .-horizontal sweep or scanning waves produced by raster generator 34 in response to synchronization 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 len 74 and cylindrical lens 76 into a cylindrical collimated beam of light again approximately 1.6 millimeters in dia¬ meter. 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 stationar in the vertical or Y direction. The beam is again enlarged by lenses 78,80 into a circular beam of light 6.3 milli¬ meters 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 hori zontally 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 micropro- cessor 14 to D/A converter 48 which converts the binary signals, or numbers, to corresponding dc voltages to proper position mirror 38. Lenses 82, 84 serve to reimage the signals from horizontal deflector mirror 38 onto the vertic deflector mirror 35. Light reflected from mirror 35 which positioned by dc motor 36, a typical galvanometer, is direc ted 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 2Q 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 6 1/2 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 6 1/2 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 Holo¬ graphic 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 appratus and method of this invention is directly viewable and preferably has the same contrast or appearance when directly viewed .as when the same image is produced on a black and white TV moni¬ tor for example, by applying the TV video signals of the image to the monitor. It is within the scope of this inven¬ tion 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 inten¬ sity 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 out¬ put of photodetector 52 is a video signal which when com¬ bined with synchronization signals can be applied to stand- ard TV monitor 18 for the production of an image by the typical CRT of TV monitor 18. The elctrical 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 synchroniza- . tion 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 verti cal 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 illu¬ strated in Fig. 6, passes through Bragg cell 32 which will deflect beam 90 horizontally as described above as a functio 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

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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 horizon-, tal 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 posi- tioned 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

-S level which is approximately 0.0 volts in a preferred embodi¬ ment. 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 "O", 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 to the D terminal of flip- flop 96. The first signal BBAR or HD to have a 0 to transi tion 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 produ ces a logical 1 at its Q output terminal for 1/2 microsecon which logical 1 is applied to the input terminal D of flip- flop 98. If the horizontal drive HD pulse occurs within th 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 O 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 pro- grammable 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 wit in a half microsecond. Using the truth table of Fig. 9, the binary numbers applied to D/A converter 48 is increment or decremented by microprocessor 14 which causes DC motor 40 for example to change the position of mirror 39 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 substan¬ tially the same as the circuit illustrated in Fig. 7 except that it uses the vertical drive pulses VD from sync generat 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 rea

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laser beam. The pulser for the vertical feedback circuit provides a 150 microsecond pulse instead of the half micro¬ second pulse provided by pulser 100 for horizontal synchro¬ nization. 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 coin¬ cides 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 record¬ ing 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.

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