Abstract:
Multibeam optical disk record and reproduction apparatus and method, in which at least two light beams generated are concentrated in different positions of on recording tracks of a recording medium to record or reproduce data to or from the recording medium on the different positions at the same time. The light beams are moved independently of each other across the recording tracks so that any one light beam is movable during the recording or reproducing of data by another light beam. This allows parallel recording/reproducing with a plurality of light beams without producing areas unaccessed due to the jumps of the light beams.

Description:
This application is a continuation of application Ser. No. 07/697,603, filed May 9, 1991 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a multibeam optical disk record and reproduction apparatus and method in which data is recorded onto or reproduced from an optical disk with a plurality of light beams in parallel. 
     2. Description of the Background Art 
     A conventional optical disk record and reproduction method is known in which data are recorded onto or reproduced from an information recording medium such as an optical disk in parallel by using a plurality of light beams in order to increase READ/WRITE operation speed. An apparatus of this kind is reported in “Digest of Papers”, 7th IEEE Symposium on Mass Storage Systems (1985), pp. 17-21. 
     In the conventional optical disk record and reproduction system, a particular recording disk dedicated for parallel recording using a plurality of light beams is required. Also, the system does not work effectively with a common optical disk for a single light beam. 
     Now referring to FIGS. 3 and 4, problems will briefly be described which arise when the reproducing of data from a conventional common recording disk is carried out by using a plurality of light beams. FIG. 3 shows a positional relationship between recording tracks T of a conventional recording disk and light spots of light beams such as beam  1  and beam  2  focused on the recording tracks T for recording and reproducing. Data is recorded on the spiral recording tracks T and a part of the spiral traced by a head H in one rotation of the recording disk is designated one track. A pair of light beams, i.e., beam  1  and beam  2  carry out recording and reproducing of adjacent two tracks, for example, with the head H on the tracks while the recording disk is turned in a direction indicated by an arrow A in FIG.  3 . 
     FIG. 4 shows positions of beam  1  and beam  2  moving along the tracks with reference to elapsed time in the reproducing operation of a conventional system. As shown in FIG. 4, beam  1  starts the reproducing from the leading edge of the track n at the time t 1  while beam  2  also starts the reproducing from the leading edge of the track n+1 at the time t 1 . At the time t 2 , beam  1  reaches the end of the track n and beam  2  reaches the end of the track n+1. Then, since the track n+1 is already reproduced by beam  2 , beam  1  is jumped to the track n+2 and beam  2  is also jumped to the track n+3. However, it takes approximately several hundreds of μs (microsecond) for the jumps, and beam  1  and beam  2  start to the reproducing of the tracks n+2 and n+3 from the time t 3 . Accordingly, the head portions (indicated by hatching in FIG. 4) of the tracks n+2 and n+3 can not be reproduced between the times t 2  and t 3  during the jumps. In recording operation, the same problem arises. In case of three light beams or more light beams used, some areas remain unreproduced or unrecorded in jumping between the tracks in the same manner as described above. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a multibeam optical disk record and reproduction apparatus, free from the drawbacks of the prior art, which is capable of preventing causing of not recorded or reproduced portions on a conventional recording disk, enabling data parallel processing in recording and reproducing operations, and improving an operation speed of the recording and reproducing. 
     It is another object of the present invention to provide a multibeam optical disk record and reproduction apparatus which is capable of carrying out an effective reproducing operation even for a recording disk which is apt to cause misreading. 
     In accordance with one aspect of the present invention, there is provided an optical disk record and reproduction apparatus, comprising means for generating at least two light beams, means for concentrating the light beams in at least two different positions of an information recording medium having at least one recording track for recording and reproducing data to and from the recording medium, and means for moving the positions of the light beams independently of each other across recording tracks on the recording medium, any one of the light beams being movable during recording or reproducing of data by another light beam. 
     In accordance with another aspect of the present invention, there is provided a multibeam optical disk record and reproduction method, comprising the steps of generating at least two light beams, concentrating the light beams on different positions of a plurality of recording tracks formed in a spiral line on a recording medium to record or reproduce data to or from the recording medium on the different positions at the same time, and moving the light beams independently of each other on the recording track. 
     In operation, one of a pair of recording/reproducing light spots is movable independently of the other light spot. This allows one light spot to continue, during a jump at by the other light spot, to reproduce or record data on a track, which precedes by one track the destination track of the jumping light spot so as to cover the area which the jumping light spot has left unreproduced or unrecorded. If this operation is applied to the example of FIG. 4, beam  2  continues to reproduce during a jumping of beam  1  so as to reproduce data of the area which otherwise beam  1  would leave unreproduced. 
     Thus, parallel recording/reproducing with a plurality of light spots can be achieved without producing areas unaccessed due to the jumps of the beams, thereby providing higher speed of recording/reproducing. 
     Further, when an error is detected in data reproduced by one light spot, the other light spot is jumped to the erroneous position of the recording disk to retry the reproducing, thereby providing effective reproduction even for a recording disk which is apt to cause misreading. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and advantages of the present invention will more fully appear from the following description of the preferred embodiments with reference to the accompanying drawings, in which. 
     FIG. 1 is a schematic view showing a movement of two light beams along the tracks with reference to elapsed time in a recording operation in a first embodiment of an optical disk record and reproduction apparatus according to the present invention; 
     FIG. 2 is a schematic side view of a essential mechanical part of the first embodiment of an optical disk record and reproduction apparatus according to the present invention; 
     FIG. 3 is a schematic elevation of a conventional recording disk having tracks and light beams positioned thereon: 
     FIG. 4 is a schematic view showing movement of two light beams along the tracks with reference to elapsed time in a reproducing operation of a conventional optical disk record and reproduction apparatus; 
     FIG. 5 is a schematic block diagram of the first embodiment of an optical disk record and reproduction apparatus according to the present invention; 
     FIG. 6 is a schematic view showing a structure of a buffer memory shown in FIG. 5; 
     FIG. 7 is a schematic view showing one track having sectors therein of the recording disk; 
     FIG. 8 is a flow chart of light beam movement in normal recording and reproducing operations according to the present invention: 
     FIG. 9 is a flow chart of light beam movement in a reproducing operation including an error data detection processing according to the present invention; 
     FIG. 10 is a schematic view showing movement of two light beams along the tracks with reference to elapsed time in a reproducing operation including an error data detection processing in the first embodiment of an optical disk record and reproduction apparatus according to the present invention; 
     FIG. 11 is a schematic top view of a modified optical head used in the first embodiment; 
     FIG. 12 is a schematic block diagram of the second embodiment of an optical disk record and reproduction apparatus according to the present invention; 
     FIG. 13 is a schematic top view of a further optical head used in a second embodiment of an optical disk record and reproduction apparatus according to the present invention; 
     FIG. 14 is a schematic view showing movement of three light beams along the tracks with reference to elapsed time in a reproducing operation in the second embodiment; and 
     FIG. 15 is a schematic view showing another movement of three light beams along the tracks with reference to elapsed time in a reproducing operation in the second embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views and thus the repeated description thereof can be omitted for the brevity, there is shown in FIGS. 1,  2 ,  5  to  10  the first embodiment of an optical disk record and reproduction apparatus according to the present invention. 
     As shown in FIG. 2, an information recording medium such as a recording disk  101  is rotated by a spindle motor  102 , and an optical head  104  for recording or reproducing the information onto or from the recording disk  101  is moved in a radial direction of the recording disk  101  by a coarse actuator  103 . 
     In FIG. 5, there are shown components inside the optical head  104  and associated electronic circuits therefor. The optical head  104  includes a focus optical system  10 , a first beam optical system  20  and a second beam optical system  30 . The focus optical system  10  is composed of an objective lens  110  and two fixed mirrors  112  and  113 . The first beam optical system  20  for outputting and detecting a first light beam (hereinafter referred to as beam  1  in short) is composed of a first galvanomirror  114 , a first beam splitter  115 , a first wavelength filter  116 , a second beam splitter  117 , a first coupling lens  118 , a first laser diode  119 , a first reproduction signal detector  120 , a third beam splitter  121 , a first position signal detector  122  and a focal point signal detector  123 . The second beam optical system  30  for outputting and detecting a second light beam (hereinafter referred to as beam  2  in short) is composed of a second galvanomirror  124 , a fourth beam splitter  125 , a second wavelength filter  126 , a fifth beam splitter  127 , a second coupling lens  128 , a second laser diode  129 , a second reproduction signal detector  130  and a second position signal detector  131 . 
     The first laser diode  119  emits a light beam having a wavelength of 0.78 μm, and the first wavelength filter  116  passes the light beam having the wavelength of 0.78 μm but does not pass a light beam having a wavelength of 0.83 μm. The second laser diode  129  emits a light beam having a wavelength of 0.83 μm, and the second wavelength filter  126  passes the light beam having the wavelength of 0.83 μm but does not pass a light beam having a wavelength of 0.78 μm. It is so controlled that beam  2  outputted by the second beam optical system  30  may be focused on the recording disk when beam  1  outputted by the first beam optical system  20  is focused on the recording disk. Thus, the light beams having the wavelength of0.78 μm or 0.83 μm are dominated in the first and second beam optical system  20  and  30 , respectively. 
     The whole electronic circuit is divided into a servo system circuit and a recording/reproducing system circuit. The servo system circuit includes two fine position control circuits  144  and  148  for driving the galvanomirrors  114  and  124  according to the position signals outputted by the position signal detectors  122  and  131  to carry out fine position controls of the light spots on the recording disk and jumping controls of the light spots between the tracks, a coarse position control circuit  145  for driving the coarse actuator  103  to carry out a movement control of the optical head  104 , and a focal point control circuit  141  for driving the objective lenses  110  according to the signal outputted by the focal point signal detector  123  to focus the light beam on the recording disk  101  and a seek control circuit  150  for controlling seek operation and starting operation of jumps. 
     The recording/reproducing system circuit includes two writing modulation circuits  142  and  146  for modulating the digital data into recording data to drive the laser diodes  119  and  129 , two reading demodulation circuits  143  and  147  for converting the signals outputted by the reproduction signal detectors  120  and  130  into digital data, a sector detection circuit  149  for checking up ID (identification) of the reproduced sectors, an error detection and correction circuit  152  for adding an error detection code to the recording data and carrying out an error detection and correction of the reproduced data, a buffer memory  155  for temporarily storing the recording or reproduced data, a host connection circuit  154  for communicating data and instructions with a host computer (not shown), a buffer memory control circuit  153  for controlling the communication of data among the buffer memory  155  and the host connection circuit  154  and the writing modulation circuits  142  and  146  and the reading demodulation circuits  143  and  147 , and a main control circuit  151  for interpreting the instructions fed from the host computer and controlling the entire system. 
     In FIG. 6, there is shown a structure of the buffer memory  155  which is divided into four equal areas such as first, second, third and fourth buffer areas (hereinafter referred to as BAs)  161 ,  162 ,  163  and  164 . Each BA has a capacity for storing one track of data and all the BAs act as a ring buffer for a host. 
     In FIG. 7, there is shown one example of one track which is divided into n sectors from SCT 0  to SCTn−1. Each sector is divided into an ID part, a DATA part, a GAP between the ID part and DATA part, and a GAP or ISG between the sectors. The ID part and the DATA part each is provided with a SYNC in their head portion. In the ID part, the SYNC is followed by an IDAM for representing the ID part, a TRK# for representing the track number, a SCT# for representing the sector number, and a CRC for use in detecting an error of reproduction. In the DATA part, the SYNC is followed by a DTAM for representing the DATA part, DATA for recording data therein and an ECC for carrying out error detection and correction of data in reproducing. 
     Then, the recording operation of the optical disk record and reproduction apparatus according to the present invention will now be described in detail in connection with FIGS. 1 and 8. FIG. 1 schematically illustrates the movement of the light beams and the flow of the data outputted from the data buffer in the recording operation. FIG. 8 shows a flow chart exhibiting an algorithm of the movement of the light beams. 
     As shown in FIG. 8, upon receipt of an instruction from the host computer in step  171 , the main control circuit  151  decodes the instruction in step  172 . When the instruction is neither a read nor write instruction, the instruction is executed in step  173 . If the instruction is a write instruction, the main control circuit  151  gives track numbers to be sought to the seek control circuit  150 , and the seek control circuit  150  causes the coarse position control circuit  145  to actuate the coarse actuator  103  for seek operation of beam  1  and beam  2  in step  174 . For example, for the explanation, this instruction is assumed to be an instruction for writing data to tracks from the track n to the track n+6 shown in FIG.  1 . As shown in FIG. 1, at time t 10  beam  1  starts to seek the track n−1 and beam  2  starts to seek the track n from the track k+1. The seek control circuit  150  continues the seeking until beam  1  reaches the track n−1 in step  175 . When beam  1  reaches the track n−1, the seek control circuit  150  checks if beam  2  has reached the track n in step  176 . If beam  2  has not reached to the track n yet, the seek control circuit  150  makes the fine position control circuit  148  to actuate the second galvanomirror  124  so as to jump beam  2  to the track n in step  177 . 
     From time t 11  (FIG. 1) in the course of the seeking operation, the receiving of data outputted from the host computer is started, and the recording data is stored sequentially from the first BA  161  to the last BA  164  in the buffer memory  155 . 
     When beam  1  reaches the track n−1 and beam  2  reaches the track n, the sector detection circuit  149  starts to search a recording start sector by using the output signals from the reading demodulation circuits  143  and  147  in step  178 . When the recording start sector is detected at time t 12  in FIG. 1, the data recording is started in step  179 . The data stored in the first BA  161  of the buffer memory  155  is transferred to the writing modulation circuit  142  by the buffer memory control circuit  153  and are recorded on the track n by beam  1  through the first laser diode  119 . In parallel with this, the data stored in the second BA  162  of the buffer memory  155  is transferred to the writing modulation circuit  146  and is recorded on the track n+1 by beam  2  through the second laser diode  129 . 
     At time t 13 , beam  1  finishes the recording of one track of data in step  181  to reach the track n+1 on which beam  2  has already recorded the data, in step  183 . Then, the seek control circuit  150  causes the fine position control circuit  144  to actuate the first galvanomirror  114  so as to jump beam  1  two tracks ahead to the track n+3 beyond the track on which beam  2  has recorded the data, in step  185 . At the same time, at the time t 13 , the buffer memory control circuit  153  switches the source of the data to be sent to the writing modulation circuit  146  from the second BA  162  to the third BA  163  of the buffer memory  155  in step  182  while beam  2  continues to record data on the track n+2. 
     When the recording data transfer from the host computer to the fourth BA  164  has been finished, the recording data is stored again sequentially from the first BA  161 . At this moment, the data firstly stored in the first and second BAs  161  and  162  have been recorded on the recording disk  101 . 
     At time t 14 , when beam  1  finishes the jumping from the track n+1 to the track n+3 and detects the head or leading edge of any sector on the track n+3 in step  186 , beam  1  starts to record the data from the sector whose head is detected, in step  187 . At this time, the buffer memory control circuit  153  starts to transfer the data stored in the fourth BA  164  from a part corresponding to the first detected sector for beam  1  to the writing modulation circuit  143 . 
     At time t 15 , when beam  2  has finished the recording of the data on the track n+2 in step  181 , the buffer memory control circuit  153  starts to transfer data stored in the fourth BA  164  from its head to the writing modulation circuit  143  in step  182  while beam  2  still continues to record data on a portion  40  of the track n+3, which is left or not recorded by beam  1  during the jumping from the track n+1 to the track n+3. 
     At time t 16 , when beam  2  has reached the head of the area on which beam  1  finished recording, in step  183 , the seek control circuit  150  causes the fine position control circuit  148  to actuate the second galvanomirror  124  so as to jump beam  2  two tracks ahead to the track n+5 in step  185 . 
     At time t 17 , when beam  2  has finished the jumping from the track n+3 to the track n+5 and detects the head of any sector on the track n+5 in step  186 , beam  2  starts to record the data from the sector whose head is detected, in step  187 . At this time, like in the time t 14 , the buffer memory control circuit  153  starts to transfer the data stored in the fourth BA  164  from its part corresponding to the detected sector for beam  2  to the writing modulation circuit  143 . Even after having finished the recording of data on the track n+4, beam  1  still continues to record the data on another portion  50  of the track n+5, which is left or not recorded by beam  2  during the jumping from the track n+3 to the track n+5. 
     At time t 18 , when beam  1  has reached the head of the area on which beam  2  finished recording, in step  183 , since the track n+7 of two tracks ahead is out of the areas to be recorded in step  184 , no jumping of beam  1  is carried out to stop the writing or recording operation of beam  1  in step  188 . 
     At time t 19 , beam  2  finishes the recording of data on the track n+6. Thus, the recording of all seven tracks from the track n to the track n+6 is finished in step  189 , and the writing or recording operation of beam  2  is finished in step  190  to finish the processing of the write instruction. In case of an even number of tracks to be recorded, a preceding beam reaches earlier out of the recording areas to be recorded in step  180  and finishes earlier the writing operation in step  191 , and then the following beam reaches the recording end area in step  192 . Then, the following beam finishes the writing operation in step  193 , and thus the write instruction operation is all finished. 
     Although the moving operation of the light beams in the recording operation has been described as above, when no error occurs, the moving operation of the light beams such as beam  1  and beam  2  in the reproducing operation can be carried out in the same manner as the recording operation except that the direction of the data transfer is reversed, and thus the description of the reproducing operation is omitted for brevity. Although the recording has been carried out from the areas starting from the head of the track, however, of course, the recording as well as the reproducing can be carried out to start from the head of any sector of any track. 
     Referring next to FIGS. 9 and 10, the movement of the light beams in a reproducing operation including an error data detection in the optical disk record and reproduction apparatus according to the present invention will be described in detail. FIG. 9 is a flow chart showing an algorithm of the movement of light beams when an error is detected. FIG. 10 illustrates the movement of the light beams and the flow of data outputted from the data buffer in the reproducing operation including an error data detection. In the drawings, at time t 21 , data reproduction is started such that data is reproduced by beam  1  from the track n and is transferred to the first BA  161  of the buffer memory  155  while another data is reproduced by beam  2  from the track n+1 and is transferred to the second BA  162  of the buffer memory  155 . Then, beam  1  jumps from the track n+1 to the track n+3 in the same manner as shown in FIG.  1 . 
     At time t 22 , when an error of the reproduced data is detected by the error detection and correction circuit  152 , a data error processing is started. If the error detection and correction circuit  152  discriminates that the error correction is possible in step  201 , the error of the reproduced data is corrected in step  202 , and the reading operation is continued in step  203  to return to the normal operation. If the error correction is impossible, the data is read again as follows. Firstly, it is discriminated on which one of beam  1  and beam  2  the error occurred in the data reproduced in step  204 . In this instance, since the data having an error detected at the time t 22  is reproduced by the preceding beam  1  in step  204 , the reading by beam  1  is continued in step  207 . The following beam or beam  2  continues the reading until it reaches the head of the area which beam  1  finished its reproducing, in step  208 . Having reached the head of the area which beam  1  finished the reproducing, beam  2  does not jump and temporarily stop the reading in step  209 . 
     At time t 23 , when beam  2  has reached the sector including the error of the reproduced data in step  210 , beam  2  rereads the error sector in step  211 . If no error is detected in the rereading of the sector in step  212 , beam  2  is returned to the normal operation. When the error is detected again by rereading the error sector in step  212  and the error correction is possible in step  213 , the error correction of the reproduced data is carried out in step  202 , and beam  2  continues the reading in step  203  to return to the normal operation. If the error correction is still impossible in step  213 , the data error processing is continued. However, when an incorrigible error is still detected in step  214  even after the rereading is repeated at the predetermined number of times of retries, the reading is stopped in step  215 . Then, abnormal termination is reported to the host through the host connection circuit  154  at step  216 , and the reading instruction operation is stopped. When an incorrigible error is detected in the data reread at the time t 23  in step  213  and the number of times of the retries is less than the predetermined number in step  214 , the rereading by beam  2  is continued in step  205 , and beam  1  jumped to return to the track n+3 in step  206 . At this moment, although the data of the tracks n+4 and n+5 has already been reproduced by beam  1  and are stored in the first and second BAs  161  and  162 , the BAs are rewritten with the data reproduced by beam  2 . 
     At time t 24 , beam  1  reaches the track n+3, and waits until it reaches the error sector in step  210 . At time t 25 , beam  1  reads again the error sector, and the reproduced data is transferred to the corresponding portion of the first BA  161 . If no error is detected in the reproduced data in step  212 , beam  1  is returned to the normal operation. Since the data reproducing of the track n+4 has already been finished, at the time t 26 , beam  1  is jumped to the track n+6 to continue the reading. 
     In FIGS. 11 and 12, there is shown another optical disk record and reproduction apparatus according to the present invention, having the same structure as the first embodiment shown in FIGS. 2 and 5 except an optical head device. FIG. 11 shows a recording disk  101  fitted on a spindle motor  102  and the optical head device having first and second optical heads  221  and  222  which are moved by a common coarse actuator  220 . FIG. 12 shows components inside the first and second optical heads  221  and  222  and associated electronic circuits therefor. 
     As shown in FIG. 12, the first optical head  221  comprises a first objective lens  231 , a first galvanomirror  232 , a first beam splitter  233 , a first coupling lens  234 , a first laser diode  235 , a second beam splitter  236 , a first reproduction signal detector  237 , a third beam splitter  238 , a first position signal detector  239  and a first focal point signal detector  240 . The second optical head  222  comprises a second objective lens  241 , a second galvanomirror  242 , a fourth beam splitter  243 , a second coupling lens  244 , a second laser diode  245 , a fifth beam splitter  246 , a second reproduction signal detector  247 , a sixth beam splitter  248 , a second position signal detector  249  and a second focal point signal detector  250 . 
     The electronic circuits have the same structure as that shown in FIG. 5 except that a second focal point control circuit  251  for driving the second objective lens  241  according to the signal output by the second focal point signal detector  250  to focus the second light beam on the recording disk  101  is added to the servo system circuit. 
     As described above, in the first embodiment, data can be recorded onto or reproduced from a conventional recording disk having one spiral recording track by using two light beams in parallel, and the recording and reproducing operation speed can be increased almost twice as compared with the conventional apparatus. Further, when the error of reproduced data is detected, in parallel with the reproducing operation of normal data, the error detected sector can be reread to ensure the reliability of the data and to improve the reproducing speed. 
     In FIGS. 13 to  15 , there is shown a second embodiment of an optical disk record and reproduction apparatus according to the present invention, having the same construction as the embodiment shown in FIGS. 11 and 12 except that an optical head device includes three optical heads for three light beams. FIG. 13 shows a recording disk  101  fitted on a spindle motor  102  and the optical head device having first, second and third optical heads  301 ,  302  and  303  which are moved by a common coarse actuator  304 . A structure of the component inside the three optical heads  301  to  303  and associated electronic circuits is the same as that shown in FIG. 12 except that the third optical head is added. FIGS. 14 and 15 show the moving operations of the three light beams and the flow of data outputted from the data buffer in the recording or reproducing operation. 
     The first moving method of the three light beams will be described in connection with FIG.  14 . At time t 40 , beam  1 , beam  2  and beam  3  start to read the tracks n, n+1 and n+2, respectively, at the same time. At time t 41 , when beam  1  and beam  2  finish the reading of the tracks n and n+1, respectively, at the same time, beam  1  and beam  2  are jumped from the tracks n+1 and n+2 to the tracks n+5 and n+4, respectively, while beam  3  continues the reading of the track n+3. At time t 42 , when the jumping of beam  1  and beam  2  is completed, beam  1  and beam  2  restart to read the tracks n+5 and n+4, respectively. 
     At time t 43 , when beam  3  reaches the head of the area that beam  2  has finished reading and beam  2  reaches the head of the area that beam  1  has finished reading, beam  3  and beam  2  jump to the tracks n+8 and n+7, respectively, while beam  1  continues the reading of the track n+6. At time t 44 , when the jumping of beam  3  and beam  2  is finished, beam  3  and beam  2  restart to read the tracks n+8 and n+7, respectively. Then, the reading and jumping are repeated in the same manner as described above to read the areas to be read. The writing operation is also carried out in the same manner as described above, and the explanation thereof is omitted for brevity. 
     FIG. 15 shows the second moving method of the three light beams. At time t 50 , beam  1 , beam  2  and beam  3  start to read the tracks n, n+1 and n+2, respectively, at the same time. At time t 51 , beam  1 , beam  2  and beam  3  finish the reading of one track of data and reach the tracks n+1, n+2 and n+3, respectively, but the tracks n+1 and n+2 are already read by beam  2  and beam  3 , respectively. 
     At the time t 51 , beam  1  jumps to the n+4, and beam  2  temporarily stops the reading of the track n+2 while beam  3  continues the reading of the, track n+3. After completion of the jumping of beam  1 , at time t 52 , beam  2  jumps to the track n+5. Then, the reading and jumping are repeated in the same manner as described above. The writing operation is also performed in the same manner as described above. In this manner of jumping, the jumping timings of the light beams are changed or shifted so as not to carry out jumping of two or more beams at the same time to reduce the maximum electric power consumption. 
     As described above, in the second embodiment, data can be recorded or reproduced in parallel onto or from a conventional recording disk having one spiral recording track by using three light beams, and the recording and reproducing operation speed can be increased approximately thrice as compared with the conventional apparatus. 
     As described above, according to the present invention, an area not recorded or reproduced during jumping of one light beam can be recorded or reproduced by another light beam on a conventional optical recording disk, and hence an optical disk recording and reproducing operation speed can be largely increased. 
     Further, when there is an error in data reproduced by one light beam, the read operation can be retried to such an error by another light beam moved to an error sector while other light beam can continue the processing in parallel. Hence, a recording disk which is apt to cause errors can be recorded or reproduced with improved operation efficiency and operation speed. 
     Although the present invention has been described in its preferred embodiments with reference to the accompanying drawings, it readily understood that the present invention is not restricted to the preferred embodiments and that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention.