Optical information recording/reproducing apparatus

Abstract: An optical recording and/or reproducing apparatus is operable to transmit at a high speed a long-play program comprising video and/or audio signals and has a capability of recording the program during a playback mode at a normal reproducing speed of the program. At a transmitter side, a digital data of the program is divided on a time-sharing basis and is then reproduced from an optical disc at a high transfer rate simultaneously with a plurality of channels of optical read/write heads so that, when the digital data is transmitted, the length of time which the transmission occupies a transmission line can be reduced. On the other hand, at a receiver side, the transmitted signals are recorded on the optical disc at a high transfer rate simultaneously with the plural channels of optical read/write heads. When a subscriber wishes to look the program, only one channel of the optical head is used to sequentially reproduce the data at the normal reproducing speed to reproduce the program while maintaining the sequence and speed of the original program. In this way, the optical recording and/or reproducing apparatus capable of reducing the time during which the transmission occupies the transmission line can be realized.

Description: BACKGROUND OF THE INVENTION (Field of the Invention) The present invention generally relates to an optical information recording and/or reproducing apparatus and, more particularly, to a video on demand device. (Description of the Prior Art) The prior art optical information recording and/or reproducing apparatus, or an optical disc player for short, selectively recording or reproducing information, such as one or a combination of video and audio signals, on or from an optical disc, respectively, is generally designed to have a record transfer rate equal to a playback transfer rate. In other words, in the prior art optical disc player, the speed at which information are recorded on an optical disc by means of an optical recording/reproducing head during a recording mode, that is, the record transfer rate, is equal to the speed at which information are reproduced from an optical disc by means of an optical recording/reproducing head during a playback mode, that is, the playback transfer rate. Accordingly, the structure of recording channels and the speed of rotation of the optical disc during the recording mode are identical with those during the playback mode. The prior art optical disc player has, however, a problem in that, after a long-play program such as, for example, one or both of long-play video and audio signals, have been recorded on an optical disc in a short space of time, the recorded long-play program cannot be reproduced at a normal speed of reproduction of the program. By way of example, where a relatively small number of sample optical discs are prepared, they will not be prepared by the use of a stamper, and it often occurs that information is recorded on the recordable optical discs. In this case, since in the case of a long-play program such as one or a combination of the video and audio signals the time required to accomplish the recording of such long-play program must be equal to that required to accomplish the playback of such long-play program, the preparation of the sample optical discs requires a substantial length of time. Also, even where a viewer or subscriber of a cable television system selects one of video and/or audio programs for reproduction thereof, the programs must be transmitted at a high speed. While it is a recent trend to increasingly substitute optical fiber cables for wirings for television transmission, the speed of transmission of information through the optical fiber cable is sufficiently higher than the playback transfer rate of the optical disc during the playback mode and the video and/or audio program can be transmitted in a short space of time. Unless the program is transmitted at a high speed comparable to the speed of transmission of information through the optical fiber cable, the transfer rate of the optical disc during the recording or playback mode will impose a limitation on the speed of transmission of the information. EP-A-082 077 discloses a transmission system wherein music data are transmitted at high speed via a fibre optic cable to a consumer's VCR. Compressed data is stored on a master video disk, the data is then read out at a high rate and transmitted at this high rate to the remote VCR, where it is recorded at a high rate. The data is then expanded in a deceleration circuit prior to output. JP-A-620 84441 discloses a multi-beam disk recording/reproduction apparatus where high speed recording/reproduction is achieved by simultaneously accessing sequential portions of a track with multiple beams. SUMMARY OF THE INVENTION Accordingly, the present invention has been devised to eliminate the foregoing problems inherent in the prior art optical disc player and is intended to provide an improved optical disc player simple in structure and capable of transmitting a long-play video and/or audio program at a high speed and reproducing the program at a normal speed during a playback mode. In order to accomplish the above described object, a video on-demand device according to claim 1 is proposed. With the foregoing construction, after the long-play video and/or audio program has been recorded on the optical disc in a short space of time using a simplified structure, the playback of the recorded program can be effected at the same normal reproducing speed as used for reproducing the original program. Therefore, the length of time during which the transmission of the program occupies the transmission line can advantageously be reduced. Therefore, the transmitter side can make the transmission line available to other subscribers, making it possible to maximize the use of the transmission line. On the other hand, the receiver side can reduce the time required to connect with the transmission line, making it possible to reduce the cost incurred by the utilization of the transmission line. BRIEF DESCRIPTION OF THE DRAWINGS This and other objects and features of the present invention will become clear from the following description taken in conjunction with a preferred embodiment thereof with reference to the accompanying drawings, in which like parts are designated by like reference numerals and in which: Fig. 1 is a schematic diagram showing a transmission system for transmitting video and/or audio signals in one embodiment of an optical disc player; Fig. 2 is a timing chart showing a relationship among various optical heads employed in the apparatus shown in Fig. 1; Fig. 3 is schematic diagrams showing the optical heads that can be employed in the optical disc player according to the present invention; Fig. 4 is a schematic diagram showing a relationship between the optical disc and the optical heads; and Fig. 5 is a timing chart showing the sequence of operation of the optical heads shown in Fig. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 3 illustrates a structure of an optical disc player according to an embodiment. An optical disc, identified by 1, is adapted to be driven by a disc motor 2 for rotation in one direction about an axis of a motor drive shaft at a predetermined speed appropriate to a recording or playback of information on or from the optical disc 1. Reference characters A and B represent optical read/write heads disposed above the optical disc 1 for recording or reproducing information on or from A and B channels on an upper surface of the optical disc, respectively, whereas reference characters C and D represent optical read/write heads disposed beneath the optical disc 1 for recording or reproducing information on or from C and D channels on a lower surface of the optical disc 1, respectively. It is to be noted that the status of operation of each of the optical read/write heads A to D (i.e., either a recording mode or a playback mode) is shown by a small reference character depicted within the framework of a schematic representation of the associated optical read/write head A to D, wherein R and P represent the recording mode and the playback mode, respectively. Of Fig. 3, Fig. 3(a) illustrates the system in a high transfer rate recording operation in which information transmitted at a high transfer rate is multi-channel recorded on the optical disc 1. As shown therein, the optical read/write heads A to D are all in the recording mode to accomplish the multi-channel recording of the information transmitted at the high transfer rate. A program consisting of a series of video and/or audio signals are, in this instance, divided into four channel segments which are simultaneously recorded on the optical disc 1 by means of the associated optical read/write heads A to D by modulating light beams emerging therefrom. Fig. 4 illustrates the optical disc 1 shown in Fig. 3(a) as viewed from above. The optical read/write heads A and B are oriented downwards, as viewed in Fig. 3, so as to direct respective beams of light downwards towards the upper surface of the optical disc 1 whereas the optical read/write heads C and D are oriented upwards so as to direct respective beams of light upwardly towards the lower surface of the optical disc 1. The optical read/write head A is used to record a first data of the video and/or audio program, which has been divided into four segments, on an outer peripheral portion 3 of the upper surface of the optical disc 1; the optical read/write head B is used to record a second data of the video and/or audio program, which has been divided into the four segments, on an inner peripheral portion of the upper surface of the optical disc 1; the optical read/write head C is used to record a third data of the video and/or audio program, which has been divided into the four segments, on an outer peripheral portion 5 of the lower surface of the optical disc 1; and the optical read/write head D is used to record a fourth data of the video and/or audio program, which has been divided into the four segments, on an inner peripheral portion of the lower surface of the optical disc 1. By recording the information on the four channels on the optical disc 1 simultaneously, the program consisting of the video and/or audio signals can be recorded on the optical disc 1 at a high speed. Figs. 3(b) and 3(c) illustrates the system in a low transfer rate playback operation in which information recorded on the optical disc 1 is reproduced at a low transfer rate, i.e., on a single channel basis. Specifically, Fig. 3(b) illustrates a condition in which only one channel of the optical read/write head A above the optical head 1 is used to reproduce information from the outer and inner peripheral portions 3 and 4 of the upper surface of the optical disc 1. In this case, accordingly, the optical read/write head A reproduces continuously the first and second data of the four-divided program at a normal reproducing speed equal to that of the original program. Similarly, as shown in Fig. 3(c), only one channel of the optical read/write head C beneath the optical head 1 is used to reproduce information from the outer and inner peripheral portions 5 and 6 of the lower surface of the optical disc 1. Accordingly, the optical read/write head C reproduces continuously the third and fourth data of the four-divided program at a normal reproducing speed equal to that of the original program. Thus, if the information recorded on the upper and lower surfaces of the optical disc 1 as shown in Figs. 3(b) and 3(c), respectively, are continuously reproduced in sequential fashion without the reproduced information being interrupted, the four-divided program segments can be reproduced in a sequence identical with that of the original video and/or audio program at a normal reproducing speed. As a matter of course, if the number of revolutions of the disc motor 2 during the recording mode is N times that during the playback mode (N being an integer), a high transfer rate of 4·N can be realized. Fig. 5 illustrates the operation of the optical read/write heads accomplished when the number of revolutions of the disc motor 2 during the recording mode is chosen to be twice that during the playback mode. It is to be noted that the operation shown in Fig. 5(b) corresponds to that shown in Fig. 3(a) and the operation shown in Fig. 5(c) corresponds to that shown in each of Figs. 3(b) and 3(c). The length of time required to reproduce the program consisting of the video and/or audio signals during the normal playback mode is indicated by 7. As shown in Fig. 5(a), this video and/or audio program is divided into four program segments 7a, 7b, 7c and 7d. Then, as shown in Fig. 5(b), the four program segments 7a to 7d are recorded on the optical disc 1 by means of the respective optical read/write heads A to D. Since in this case the number of revolutions of the disc motor 2 during the recording mode is chosen to be twice that during the playback mode, the instance of Fig. 5(b9 makes it possible to record the program as a whole at a speed which is equal to eight times the normal reproducing speed. Fig. 5(c) illustrates a condition in which the program segments 7a and 7b are reproduced from the upper surface of the optical disc 1 by means of the optical read/write head A at the normal reproducing speed whereas the program segments 7c and 7d are reproduced from the lower surface of the optical disc 1 by means of the optical read/write head C at the normal reproducing speed. Accordingly, the total time 8 required for the optical read/write heads A and C to reproduce the program segments 7a to 7c is equal to the length of time 7 required to reproduce the original program. While the description made with reference to each of Figs. 3 and 5 applies where the information is recorded at the high transfer rate or the information is reproduced at the low transfer rate, respectively, the respective status of operation of the optical read/write heads A to D, shown by R and P in Fig. 3(a), may be reversed and the respective status of operation of the optical read/write heads A and C, shown by P in Figs. 3(b) and 3(c) may be reversed. In such case, the information can be reproduced at a high transfer rate and recorded at a low transfer rate. Fig. 1 illustrates a preferred embodiment of the invention in which a number of the optical disc players of the present invention are combined together to transmit at a long-play program consisting of video and/or audio signals at a high speed through a cable television transmission system. Referring to Fig. 1, the video and/or audio program is transmitted at a high speed through a transmission line 9 which may comprise an optical fiber. Figs. 1(a), 1(b) and 1(c) illustrate a system set-up and an operation of the optical disc player on a transmitter side whereas Figs. 1(d), 1(e) and 1(f) illustrate a system set-up and an operation of the optical disc player on a receiver side. On the other hand, intervals T1, T2, T3, T4, T5 and T6 shown in Fig. 2 correspond to recording and playback timings of the optical read/write heads held in respective status (either recording or playback modes) shown in Figs. 1(a) to 1(f). As is the case with Fig. 1, the characters R and P represent the recording and playback modes of the optical read/write heads. A signal outputted from a data generator 10 for video and/or audio signals is utilized to modulate a beam of light emitted from the respective optical read/write head. In the first place, as shown in Fig. 1(a), the first and second program segments 7a and 7b of the original program 7 are entirely recorded on the upper surface of the optical disc 1 using only one channel, i.e., the optical read/write head A. The recording timing is shown by T1 in Fig. 2. Thereafter, a signal outputted from the data generator 10 is used to cause the third and fourth program segments 7c and 7d of the original program 7 entirely on the lower surface of the optical disc using only one channel, i.e., the optical read/write head C. The recording timing is shown by T2 in Fig. 2. In this way, the program of the video and/or audio signals are recorded on both surfaces of the optical disc 1 and the optical disc 1 having a number of video and/or audio programs recorded thereon is stored at the transmitter side. The optical disc 1 having the programs recorded thereon and stored at the transmitter side may include not only those recorded according to the operation described with reference to Figs. 1(a) and 1(b), but also those which have been recorded with the use of any other recording apparatus or those which have been duplicated by means of any known method using a stamper. In the event that a subscriber selects a particular one of the programs and requests that it should be transmitted through the transmission line 9, the optical read/write head A reproduces, as shown in Fig. 1(c), the first data of the video and/or audio program, which has been divided into the four program segments, from the outer peripheral portion 3 of the upper surface of the optical disc 1. At the same time, the optical read/write head B reproduces the second data of the four-divided program from the inner peripheral portion 4 of the upper surface of the optical disc 1; the optical read/write head C reproduces the third data of the four-divided program from the outer peripheral portion 5 of the lower surface of the optical disc 1; and the optical read/write head D reproduces the third data of the four-divided program from the inner peripheral portion 6 of the lower surface of the optical disc 1. By reproducing the four channels simultaneously in this way, the video and/or audio program can be reproduced and transmitted at a high speed. In the example shown by T3 in Fig. 2, the program is reproduced and transmitted at a speed which is eight times the normal reproducing speed. On the other hand, the operation of the optical disc player owned by a cable television subscriber, which receives and records the video and/or audio program transmitted at a high speed through the transmission line 9, is shown in Fig. 1(d). As shown therein, the optical read/write head A records the first data of four-divided the video and/or audio program, which has been transmitted through the transmission line 9, on the outer peripheral portion 3 of the upper surface of the optical disc 1. At the same time, the optical read/write head B records the second data of the four-divided program on the inner peripheral portion 4 of the upper surface of the optical disc 1; the optical read/write head C records the third data of the four-divided program on the outer peripheral portion 5 of the lower surface of the optical disc 1; and the optical read/write head D records the third data of the four-divided program on the inner peripheral portion 6 of the lower surface of the optical disc 1. By recording the four channels simultaneously in this way, the video and/or audio program can be recorded on the optical disc at a high speed. In the example shown by T4 in Fig. 2, the program is received and recorded at a speed which is eight times the normal reproducing speed, completing a recording in a short space of time one or some of the programs transmitted through the transmission line 9. Thus, it will readily be seen that if the subscriber makes a recording of some of the transmitted programs which he or she wishes to view, he or she can look them at any time by reproducing the programs at the normal reproducing speed. Fig. 1(e) illustrates a condition in which using only one channel, i.e., the optical read/write head A, information recorded on the outer and inner peripheral portions 3 and 4 of the upper surface of the optical disc 1 is reproduced. In this condition, the optical read/write head A reproduces the first and second data of the four-divided program continuously and at the same normal reproducing speed as used for reproducing the original program. The operational timing is shown by T5 in Fig. 2. The reproduced data are inputted to an image data processing and reproducing device 11 so that the subscriber can view the program reproduced at the normal reproducing speed. Similarly, Fig. 1(f) illustrates a condition in which using only one channel, i.e., the optical read/write head C, information recorded on the outer and inner peripheral portions 5 and 6 of the lower surface of the optical disc 1 is reproduced. In this condition, the optical read/write head C reproduces the third and fourth data of the four-divided program continuously and at the same normal reproducing speed as used for reproducing the original program. The operational timing is shown by T6 in Fig. 2. The reproduced data are inputted to the image data processing and reproducing device 11 so that the subscriber can view the program reproduced at the normal reproducing speed. Thus, if the information recorded on the upper and lower surfaces of the optical disc 1 as shown in Figs. 1(e) and 1(f), respectively, are continuously reproduced in sequential fashion without the reproduced information being interrupted, the four-divided program segments can be reproduced in a sequence identical with that of the original video and/or audio program at the normal reproducing speed 8. With the construction described above, after the long-play video and/or audio program has been recorded on the optical disc in a short space of time using a simplified structure, the playback of the recorded program can be effected at the same normal reproducing speed as used for reproducing the original program. Therefore, the length of time during which the transmission of the program occupies the transmission line can advantageously be reduced. Therefore, the transmitter side can make the transmission line available to other subscribers, making it possible to maximize the use of the transmission line. On the other hand, the receiver side can reduce the time required to connect with the transmission line, making it possible to reduce the cost incurred by the utilization of the transmission line. In other words, where a cable television subscriber selects and reproduces the video and/or audio program, the program can be transmitted at a high speed and in a short length of time and can, when being reproduced, be reproduced at the normal reproducing speed, and therefore, a cable television system by which subscribers can enjoy looking programs they wish to view can be realized. Although the present invention has fully been described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention, as defined by the appended claims, unless they depart therefrom.

Claims: A video on-demand device comprising a receiver-side optical disk recording and reproducing apparatus and a transmitter-side optical disk recording and reproducing apparatus interconnected by a data transmission line (9), said transmitter-side optical disk recording and reproducing apparatus comprising: (a) a low transfer rate recording means (10) having an optical recording head (R) for recording a digital program onto a first optical disk (1) at a data record transfer rate of r bits per second, wherein r is a positive number and wherein the digital program denotes at least one of video signals, audio signals and video game software, said low transfer rate recording means including means for sequentially modulating a beam of light from the optical recording head (R) on N divided surface regions (3 to 6) of opposite surfaces of the first optical disk (1) in accordance with the digital program to sequentially record N portions (7a to 7d) of the digital program at the respective N divided surface regions (3 to 6) of the opposite surfaces of the first optical disk (1) wherein N is an integer greater than 1; (b) a high transfer rate reproducing means (11) having N optical reproducing heads (P) for simultaneously reproducing the recorded N portions (7a to 7b) of the digital program from the respective N divided surface regions (3 to 6) of the first optical disk (1) at a data playback transfer rate of p bits per second, wherein p is a positive number which is greater than r, said high transfer rate reproducing means including means for simultaneously applying N reproduction light beams respectively from said N optical reproducing heads to the respective N divided surface regions (3 to 6) of the opposite surfaces of the first optical disk (1) to simultaneously reproduce the recorded N portions (7a to 7d) of the digital program, wherein a ratio of a time for recording the digital program data by said low transfer rate recording means (10) to a time for reproducing the digital program by said high transfer rate reproducing means (11) is p/r; and (c) means for transmitting the digital program reproduced by said high transfer rate reproducing means on the data transmission line (9) at a rate of p bits per second; said receiver-side optical disk recording and reproducing apparatus comprising: (a) means for receiving the digital program from the data transmission line (9) at a rate of r' bits per second, where p = r'; (b) a high transfer rate recording means (10) having N' optical recording heads (R) for recording the digital program onto a second optical disk (1) at a data record transfer rate of r' bits per second, said high transfer rate recording means (10) including means for simultaneously modulating N' beams of light respectively from said N' optical recording heads (R) on the second optical disk (1) in accordance with the digital program to simultaneously record N' portions (7a to 7d) of the digital program at respective N' divided surface regions of opposite surfaces of the second optical disk, wherein N' is an integer greater than 1; and, (c) a low transfer rate reproducing means (11) having an optical reproducing head (P) for sequentially reproducing the recorded N' portions (7a to 7d) of the digital program form the respective N' divided surface regions (3 to 6) of the second optical disk (1) at a data playback transfer rate of p' bits per second during a normal reproduction mode, wherein p' is a positive number which is less than r', said low transfer rate reproducing means (11) including means for sequentially applying a reproduction light beam from said reproducing optical head (P) to the N' divided surface regions of the opposite surfaces (3 to 6) of the second optical disk (1) to sequentially reproduce the recorded N' portions (7a to 7d) of the digital program, wherein a ratio of a time for reproducing the digital program data by said low transfer rate reproducing means (11) to a time for recording the digital program by said high transfer rate recording means (10) is r'/p'. The device as claimed in claim 1, wherein said high transfer rate recording means (10) includes means for rotating the optical disk (1) at a first rotation rate A' during recording of the digital program at the data record transfer rate of r' bits per second, and wherein said low transfer rate reproducing means (11) includes means for rotating the optical disk at a second rotation rate B' during reproduction of the digital program at the data reproduction transfer rate of p' bits per second, wherein the first rotation rate A' is faster than the second rotation rate B'; and said low transfer rate recording means (10) includes means for rotating the optical disk (1) at a third rotation rate A' during recording of the digital program at the data record transfer rate of r bits per second, and wherein said high transfer rate reproducing means (11) includes means for rotating the optical disk at a fourth rotation rate B' during reproduction of the digital program at the data reproduction transfer rate of p bits per second, wherein the third rotation rate A' is slower than the fourth rotation rate B'. The device as claimed in claim 2, wherein the ratio of r/p is equal to N times A/B, and wherein the ratio of p'/r' is equal to N' times B'/A'. The device as claimed in anyone of the preceding claims, wherein said data transmission line (9) comprises an optical fiber.

Inventors: KOISHI KENJI, KOISHI, KENJI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1992
Main classification: G11B7
IPC codes: G11B7, H04N5, G11B20, G11B27