Television System and Method

This invention relates to a television broadcasting and receiving system and method wherein higher than standard resolution television picture signals are generated and transmitted in a manner whereby they are compatible with both standard television receivers and receivers which are designed and constructed to provide high resolution images on their viewing screens to provide improved picture quality. Such improved picture quality may be particularly applied in projection television systems wherein the image generated on the screen of a television cathode ray tube or the like is projected to many times its size and the imperfections and shortcomings in the lower resolution images generated on standard television viewing screens are more easily discernible when the image field is so enlarged.

Conventional television short wave broadcasting in the United States employs a beam scanning resolution of 525 horizontal lines scanned to define the image field or frame. Picture resolution improves as the number of horizontal scanning lines is increased permitting the image to be viewed in greater detail. By doubling or tripling the number of horizontal lines scanned per screen, substantial improvements are experienced in the images so generated with resulting greater image detail. For example, the image of a page of conventional typewriter printed material occupying an entire television receiver screen which is in the range of 14"-19" in diameter or measured diagonally may be easily read by eye but finer type requires increasing the resolution to perhaps 1050 lines per screen, or greater.

In a preferred form of the invention, a high resolution television camera, say 1050 line resolution, is employed and operated to effect frame scanning wherein each frame is defined by four fields of interlaced scanning of the camera's scanning by its read-beam and the picture signals generated thereby are transmitted with corresponding synchronizing signals which synchronizing signals may be utilized by both high and standard resolution receivers to control the write-beam scanning to generate standard television images at their 525 line resolution with two fields of interlaced scanning while higher resolution television receivers may receive the same signals and effect 1050 line scanning of their image fields or frame using four interlaced field scannings per frame of video information displayed.

Accordingly, it is a primary object of this invention to provide a new and improved television broadcasting and receiving system.

Another object is to provide a television system in which television images are generated at either or both high and lower resolution depending on the receivers employed.

Another object is to provide a high resolution television broadcasting system which is compatible with lower resolution or standard television receivers.

Another object is to provide a television broadcasting system employing a high resolution television camera for generating television signals and special code signals which may be utilized by both high and lower resolution television receivers to generate respective high and lower resolution pictures on their viewing screens.

Another object is to provide a new and improved method for broadcasting and receiving television signals and displaying the information broadcast.

Another object is to provide a method for simultaneously broadcasting high and lower resolution television information and displaying such information on both high and lower resolution television viewing screens.

Another object is to provide a method of coding television signals so that when they are broadcast, they may be employed by television receivers to display the same information at different resolutions.

Another object is to provide a method of generating, coding and transmitting high resolution television signals and receiving such signals by both high and low resolution television receivers and utilizing same to generate images on the screens of both such receivers at their respective resolutions.

With the above and such other objects in view as may hereinafter more fully appear, the invention consists of the novel constructions, combinations and arrangements of parts and method for generating, transmitting, receiving and utilizing high resolution television signals to display both high and low resolution television information as will be more fully described and illustrated in the accompanying drawings but it is to be understood that changes, variations and modifications may be resorted to which fall within the scope of the invention as claimed.

In the drawings:

FIG. 1 is a plan or face view of a television scanning frame displayed by a television receiver.

FIG. 1A is a face view of a portion of the field shown in FIG. 1 wherein the scanning lines and fields thereof are generated at conventional resolution for use by conventional home television set owners.

FIG. 1B is a face view of a portion of the frame shown in FIG. 1 wherein the scanning lines and fields thereof are generated and displayed at a higher resolution and contain twice the number of lines scanned to generate images or frames as the lines employed in the frame shown in FIG. 1A.

FIG. 2 is a schematic diagram showing electronic components and circuits for a standard television system modified to permit the generation and transmission of both conventional and higher resolution television signals and their display.

In FIG. 1 is shown details of a video image field or frame such as the image field or frame scanned by the read-beam of a television camera, or one which is generated by the write-beam of a television receiver cathode ray tube. FIGS. 1A and 1B show respective portions or a portion of such image field frame F enlarged so as to permit comparison between a frame in which standard 525 line scanning is effected and one in which a higher resolution scanning, such as a frame containing 1050 scanning lines, or double that of the standard frame, is generated.

In standard television scanning of the type which is employed to transmit conventional television programs by short wave transmission within the United States, scanning lines of picture information are generated in which two separate scanning sweeps or field are effected with the scanning lines of one field interposed between those of the other so as to provide a so called interlaced scanning system wherein the spaces between lines of one field of such interlace scanning are occupied by the horizontal scanning beam traces or lines of the next field in order to provide suitable resolution and to eliminate so called flicker in the picture or image so generated. U.S. Pat. Nos. 4,251, Eriksen and 3,116,436, Sweeney set forth the standard television transmission system which uses two interlaced fields, each having 2621/2 lines or 525 lines per frame. The fields are at 60 hertz and the frames are at 30 hertz. The frame shown in FIG. 1A is one which is generated by interlacing two successive field scans, which two field scanning constitutes a complete picture frame defining a complete image. In the representation of the higher resolution enlargement shown in FIG. 1B, the same image field scanned in FIG. 1A is defined by four full-frame interlaced scannings or fields rather than the conventional two interlaced scannings or fields. Each full-frame scan in FIG. 1B is composed of scanning lines scanned wherein each beam trace covers one-half of the width covered by the beam trace of a beam scanning a standard 525 line field. With reference to the scanning lines of each frame, the following comparisons of line traces for the herein provided system for standard and high resolution scanning the same image field, may be made:

Thus it is seen that for each frame of high resolution video picture information which is generated by the high resolution television camera or reproduced from a recorder, two frames of transmitted television image information are written on the screen of the standard television receiver.

In other words, conventional television receivers may, without modification, process and reproduce the incoming high resolution television signals as though they were conventional low resolution signals in the following manner:

Each line of the first field of the transmitted four field interlaced frame of video picture information is generated along the horizontal scanning line area of the conventional television receiver screen which would ordinarily be scanned in generating the first field of a frame consisting of two fields of interlaced scanning. Each line of the second field defined by such higher resolution video signal is generated along the horizontal scanning area which ordinarily would be scanned in generating the second field of such two-field interlaced frame. Each line of the third field defined by the received high resolution video signal is generated along the line area of the display screen which is ordinarily scanned in generating the first field of a received frame while each line of the fourth field of the frame of the higher resolution video signal is generated along the line area of the display screen which is ordinarily scanned to generate the second field of the two-field interlaced scanning system frame.

Thus one full frame, which is composed of video picture signals derived from four interlaced scannings of the field by the video camera is properly processed and displayed by a conventional (525 line) television receiver as though the picture frame received were composed of two frames of conventional video information, each defined by two interlaced fields.

The time required to transmit each field of high resolution video information is consistent with the time required to transmit a single field of conventional video information. However, a complete high resolution frame is transmitted and received in twice the time it takes to transmit and receive the lower resolution conventional frame.

In FIG. 2 is shown a schematic diagram defining electronic components employed in a standard television transmission system which is modified to permit its performance as described, wherein scanning control of the signal or picture generating beam may define either the described high or low resolution scanning systems illustrated in FIGS. 1A and 1B. System 10 of FIG. 2 includes a standard television transmission set, the design and operation of which are well known in the art. A sync generator 11 produces signals for controlling operation of a horizontal pulse generator 12 and a vertical pulse generator 13 at standard frequencies for whatever television system is used, such as a 525 line scanning system. The output of the vertical pulse generator 13 applies clock pulses, one for each frame scanned, to a counter circuit 14. Counter 14 may comprise, for example, a BCD counter which resets at the count of five to provide scanning of the type illustrated in FIG. 1B, and which sequentially steps through its outputs upon receipt of each pulse from the pulse generator 13 (e.g., one pulse for each complete vertical frame). The scan sequence for four sequential fields, which are interlaced to form a complete video frame or picture, may be described as follows:

On receipt of the initial horizontal sync pulse from pulse generator 12, the horizontal sweep generator 15 outputs the horizontal sweep signal to the television camera 16, thereby effecting controlled horizontal scanning of the image field by such camera in a conventional manner. Simultaneously, as such signals are generated, the first vertical pulse from generator 13 is generated for controlling the read-beam of the television camera in attaining vertical scanning movement through its scanning field by controlling the vertical deflection control circuit 17 of the camera. Deflection control circuit 17 is additionally energized with a bias voltage from a variable bias supply 18, the bias output of which is determined by which of the outputs of the connected BCD counter 14 is activated. The particular bias value determines the degree the field being scanned is offset from its initial position.

Upon receipt of each subsequent vertical frame pulse from generator 13, counter 14 will step through its sequence causing the proper bias to be output from the variable bias supply 18 to the sweep circuit 17 to properly position the scanning lines of the sequentially generated scanning fields so as to effect the nesting arrangement illustrated in FIG. 1B.

Camera 16, which may be a vidicon, charge coupled device or other imaging device, outputs color and luminance signals which are processed by color and luminance circuits 19 and the signals resulting from such processing are conducted to a modulator 20 together with sound signals, such as voice and music signals, which are picked up by a microphone 21 or are reproduced from a source of such sound signals such as a record tape. Such signals are amplified by amplifier 22 and conducted to modulator 20 which also receives the necessary horizontal and vertical signals from the respective sync generators 12 and 13. All of such signals input to the modulator 20 are processed and integrated to form a composite video picture signal together with audio signals which are transmitted by a short wave transmitter 23 as radiated by an antenna 24 in a form permitting such signals to be received by a television receiver or home set in a conventional manner. Such signals may also be transmitted through a cable television system.

A suitable power supply 25 is provided which is connected to supply proper electrical energy at the correct polarities and magnitudes for appropriately operating the various illustrated components and circuits as described above.

Also shown in FIG. 2 are two television receivers, a high resolution receiver 26 and a conventional home television receiver 29. The conventional receiver 29 has a video image generating screen 31 with a write-beam operable to generate a full-frame image of a television picture by interlaced scanning of the type illustrated in FIG. 1A, say at a horizontal scanning line resolution of 525 lines scanned per frame while the high resolution receiver 26 has a video image generating screen 28 with a write-beam controlled to generate a full-frame video image by interlaced scanning of the type illustrated in FIG. 1B. Notations 27 and 30 refer respectively to receiving antennas for the television receivers 26 and 29. In general, the lower resolution closed circuit or short wave television scanning systems will operate in the range of 250-600 horizontal lines scanned per image screen or full frame of video display while the higher resolution system will operate in the range of 500-1200 horizontal lines scanned per full frame of video image displayed on the screen of the higher resolution receiver, the latter having twice the number of interlaced lines scanned per full frame scanned than the former lower resolution system, it being noted that both the low and high resolution receivers shown in FIG. 2 may display picture information transmitted by a single high resolution scanner or television camera having circuits of the type shown in FIG. 2.