A 55 - 6 233 & - - 1 P - i) XR 3 574, 325 1 - UUed Stati r Heckman, Jr. X is 3,674,925 (45) July 4, 1972 . A (54) CABLE-LESS TELEVISION systEM (57 ABSTRACT (72) inventor: Paul J. Heckman, Jr., Rancho Santa Fe, Calif. This invention relates to apparatuses and methods for enabling surveillance of a distant target from a remote viewing 73) Assignee: The United States of America as point which does not require a cable or acoustic signals represented by the Secretary of the Navy between the target and the viewing point. The apparatus at the target includes a light source, for example, a laser, for illu 22) Filed: Dec. 3, 1970 minating the target, and which may be modulated by any of (21) Appl. No.: 94,659 various known techniques, at a frequency in the range of 3 kHz or more. A TV camera tube, which observes the target, generates a conventional composite video signal, including 52 U.S.C...................... 178/6.8, 178/DIG. 1, 178/DIG. 8, horisontal and vertical blanking pulses, the bandwidth of the 178/DIG. 38,250/199 video system being at least 50 kHz. A light source modulator (51) int-Cl........................................................... H04n 7/02 connected between the light source and the TV camera tube, (58) Field of Search...........250/199; 178/DIG. 1, 29, DIG. 8, modulates the light source in accordance with the variation in 178/DIG. 38, 6.8 amplitude of the composite video signal. (56) References Cited The apparatus at the remote viewing point includes a lens for focusing the light from the target, remote light source, and any UNITED STATES PATENTS scattered light from the medium in which the target is located, and a photodetector for receiving the light focused by the lens. 3,578,907 5/1971 Stock et al............................ 178/7.88 A frequency-compensating amplifier, connected to the 3,258,595 6/1966 Galante................................. 250/199 photodetector, compensates for any drop in high-frequency 2,472,889 6/1949 Du Mont..... .250/199 X response to the photodetector. A demodulator, connected to 1984,673 12/1934. Du Mont............................ 250/199 X the output of the frequency-compensating amplifier, demodu Primary Examiner-Robert L. Griffin lates the modulated composite video signal, and, in effect, Assistant Examiner-Richard K. Eckert, Jr. decodes the video information. A TV monitor, connected to Attorney-Richard S. Sciascia, Ervin F. Johnston and John the output of the pulse-time demodulator, permits observing Stan the target at the viewing point remote from the target. 12 Claims, 4 Drawing Figures Aaaag, Sca?ew14 rve 4awaarasar 246aam--------- - - - ---oaf aayaaaaa Caaza Alese 71 aavaysAWrseem eaeza, at aceweato. aaeeanas ar. assaertar aasaawayaea/ away AMeowzamf (seawarafe) 46 a scamawas Apafear/Year 7e/ae aara apaveday savaaaf afeevaagaa 2 waaaaap ame-reparaserae 72 aaafa. ama aafa 2 Aatas Y womree n...S. 42 ----- - - . PATENTED JUL 4 197 3, S74,925 SHEET 2 OF 2 A2.2 Aaaa, EF till 42m-taaaaar. Sca/aa-1477 ar Ola eaa-M1 da AMAvalae Caesale -zess 7/ 322 Seva YazAAAA/eaf se 7/ M72Av/722a J Sysza1. Zaamsa1saaay Capaza, a 52 afépowaa.o. afaeae areas 47. 42 atazaza (26sarazzaay A2.W.7 M7AFore/M/ (sata wazaa) 4a ra is cavatma Aaaaaapr2/5 avr Aafeevyear release a 77aea 7 - (22 Za Agao/a/7OMy saveata AfeelAarza 2. Zayaraa Aead 172, 4. A/o-72zdaraaczea Aa crowava/sea weaf Syzszew Z/s/w2 Waaaaad aago / a7/epay. 72 Aaas Jaafapuza7243 a2 3,674,925 1. 2 CABLE-LESSTELEVISIONSYSTEM directly to a modulator unit, where frequency-compensating circuitry coupled to modulating networks are used to vary the STATEMENT OF GOVERNMENT INTEREST input voltage to the lightsource. The invention described herein may be manufactured and The light source is thus used for two distinct purposes. First, used by or for the Government of the United States of Amer it is used to illuminate the target area. This is the normal func ica for governmental purposes without the payment of any tion of a light source. Secondly, it is used as the transmitter of royalties thereon or therefor. the composite video signal. The modulated light is not a hin drance to the observing capabilities of the TV camera because BACKGROUND OF THE INVENTION the modulated signal is integrated by the photosensitive sur This invention relates to apparatuses and methods for 10 face of the TV camera. Thus, any flicker of the light caused by enabling surveillance of a target from a remote viewing point, the modulated signal is not seen on the camera output signal. which does not require a cable or acoustic signals between the In this invention, advantage is taken of the fact that the image target and the viewing point. The apparatus at the target in target of the camera tube is an integrating mechanism, but the cludes a light source, a TV camera tube, and a light source 15 photodetector is not. modulator connected between the camera tube and the light The video bandwidth may range between 50 kHz and 4 SOCC. MHz, with the lower end of the range requiring a much lower The apparatus at the remote viewing point includes a lens line scanning rate. for focusing the light from the target and a photodetector for A filament-type light source cannot be used with the inven receiving the light focused by the lens. A frequency-compen 20 tion because of the considerable time lag between the applica sating amplifier is connected to the high-gain photodetector tion of power to the light source and the corresponding circuit to compensate for high-frequency roll-off of video in change in light intensity, unless an external optical modulator formation. A TV monitor connected to the output of the am were provided. However, the concept in back of the invention plifier permits viewing the target at the remote viewing point. is easier to understand if we assume the existence of an ideal 25 light source of the filament type where there is no time delay DESCRIPTION OF THE PRIOR ART between the application of energy to the light source and the In the prior art apparatus of this type, usually the ocean consequent change in light intensity. In such an instance, the floor is surveyed, searched, or photographed by means of an light source would vary in power output only, and therefore in optical system comprising a TV camera and a light source, intensity, the variation being similar in form to the variation which is often remote from the TV monitor readout. The TV 30 shown by a conventional video signal as used in a standard TV camera may be connected by hundreds, even thousands, of system. This variation in intensity is what the phototube feet of cable between the viewing point and the target ob located on the support ship must detect, and the positioning or served by the camera tube. Use of the cable creates drag, orientation of the photodetector is not at all critical. A lens weight and cable-handling problems. system focused upon the combined light source and target There are presently in use underwater surveillance systems 35 area would, in turn, focus the received light upon the sensitive using a cable between a surface ship and a vehicle which views area of the photodetector. The required accuracy in focusing the target. Significant degradation of TV data signals take is well within the present state of the art. place at depths of 7,000 feet. Attempts to design systems for With the present state of the art, it may not be possible to much greater depths have been unsuccessful, due either to modulate a non-laser light source at a 4 MHz rate. However, prohibitive increases in the size of the cable or loss of resolu this rate is not essential, inasmuch as satisfactory video tion to the point of precluding satisfactory operational per response may be obtained at a much lower rate. formance. While a laser light source may be amplitude-modulated, for Other approaches to long-line underwater TV transmission example, with the aid of a Kerr cell or Pockels cell, however, exist, but the state of the art is not sufficiently advanced. 45 pulse-time modulation (PTM) may be preferable, including Transmission is accomplished by (1) reducing the scan rate of pulse-duration modulation (PDM) or pulse-position modula the picture to present a non-real time picture, which is often a tion (PPM). A pulse-type modulation must be employed in poor quality picture; and (2) reducing transmission loss by most cases, since the energy of the light source commonly using large coaxial cables. used, whether an argon or xenon bulb, or a laser light source, Another solution to the problem is by transmitting video 50 must be turned on and off more or less instantaneously, due to acoustic signals from the target to the remote monitoring loca their characteristics of operation. tion, or remote viewing point. This is not possible, however, The video signal may then be picked up at a remote viewing with the present state of technology, because of the 4 point, for example, at a surface support ship, by placing a megahertz bandwidth required for the video signals. The photomultiplier, or other type of photodetector, beneath the higher frequencies would be too greatly attenuated in the 55 surface of the ocean, and focusing, by means of a lens, the en water to allow a practical reconstruction of the original data. tire area encompassing the illuminator and the illuminated tar In addition, a sophisticated acoustic array, and a tremendous get area.