Optical information recording and reproducing apparatus

The optical information recording and reproducing apparatus of the present invention comprises a detecting device detecting that an optical disc-like recording medium, having a spiral track, has made one rotation. A track jump circuit moves the position of a light beam, radiated on one segment of the spiral track of the optical disc-like recording medium, to an objective track segment. A track jump correcting circuit corrects the position of the light beam by the number of tracks which is equal to the number of one-rotation detecting signals obtained from the detecting device during the movement by the track jump circuit. A kick back circuit holds the light beam to always be radiated on the objective track segment.

FIELD OF THE INVENTION 
This invention relates to an optical information recording and reproducing 
apparatus provided with a track access means for an optical recording 
medium having a spiral track. 
BACKGROUND OF THE INVENTION 
Recently, an optical information recording and reproducing apparatus is 
used whereby information can be recorded and reproduced at a high density 
on an optical recording medium using a light beam from an optical pickup 
instead of recording and reproducing information using a magnetic head. 
A disc-like recording medium (which shall be mentioned as a disc 
hereinafter) has tracks which are formed concentrically or spirally. 
Now, as disclosed, for example, in a Japanese patent application laid open 
No. 37743/1982, conventionally, in case the number of tracks from the 
present track to an objective track (or desired track) is several tens of 
tracks, the optical pickup will access the objective track by a track 
jump. First of all, the controller will read the address number of the now 
held track (i.e., present track), will calculate a difference in address 
number from the address number of the objective track and will designate 
the value of the difference as a track jump command. When the track jump 
of the designated number ends, the coincidence of the address number of 
that track with the address number of the objective track will be 
confirmed and the access operation (seeking operation) will end. 
Now, as shown in FIG. 1, in a spiral disc 1, as the track continues 
spirally, a different track number (address number) will be alotted in the 
position where one rotation has been made and the recording region is 
distinguished. 
In a spiral disc, when a predetermined track is to be maintained, a 
mechanical index, provided in response to a position at which the track 
number is different, will be detected. The track will be maintained by 
making a kick back operation 2 of returning the pickup to the previous 
track position for each rotation as shown in FIG. 1. 
However, in a spiral disc, when passing a region of a kick back while a 
track jump is being carried out, since the track jump is preferred to be 
made witout making a kick back, the number of tracks to reach the 
objective track will be different from the first designated number of 
tracks. For example, in FIG. 1, when seeking tracks Nos. 1 to 4, the 
number of jump commands will be 3. In such a case, as shown by a reference 
symbol A, in case a track jump is made outside a region in which a kick 
back is made, that is, a boundary in which the track number varies, an 
access to the objective track No. 4 will be able to be made but, as shown 
by a reference symbol B, if a track jump is made while passing through the 
region in which the track number varies, the track number will be 5 
(rather than track number 4) after the track jump. Therefore, after the 
track jump ends, when the controller confirms the track address number, it 
will be different from that of the objective track and therefore a track 
jump command will have to be issued again to make a track jump. Therefore, 
there is a defect that a long time can occur until an access to the 
objective track is made. 
OBJECT AND SUMMARY OF THE INVENTION 
The present invention has as an object to provide an optical information 
recording and reproducing apparatus whereby a seek operation by a track 
jump can be ended within a short time without repeating a track jump 
command. 
The optical information recording and reproducing apparatus of the present 
invention comprises a device for detecting the number of passages through 
a boundary region in which the track number of a spiral track changes 
while the present track is moving to an objective track by a track jump 
and a device for correcting a kick back by the number of passages during a 
track jump in the direction of a kick back after the above mentioned track 
jump. Thus, an objective track can be sought by one track seeking process 
irrespective of the passage through the track number changing point and 
without repeating the seeking process. 
The other features and advantages of the present invention will be apparent 
with the following explanation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention shall be explained with reference to the drawings: 
FIGS. 2 to 5(d) show an embodiment of the present invention. 
As shown in FIG. 2, in an optical information recording and reproducing 
apparatus 11 of the present invention, an optical pickup 13 is arranged 
opposed to one disc surface of a spiral disc 12 rotated by a spindle motor 
(not illustrated) and is made movable in a radial direction R of the 
spiral disc 12, (that is, in the direction of intersecting the spiral disc 
12) together with a carriage 14 by a coarsely moving means such as a VCM 
(voice coil motor) motor. A spiral track is formed also on the surface to 
which the optical pickup 13 is opposed. 
By the above mentioned pickup 13, light of a laser diode 17 is made into a 
parallel light beam by a collimator lens 18 and enters a polarized light 
beam splitter 19 as p-polarized light. The light, having substantially 
100% passed through this polarized beam splitter 19, is made into circular 
polarized light by a 1/4-wavelength plate 21, is further condensed by the 
condenser lens 22 and is radiated onto the spiral disc 12. The light 
reflected by the disc 12 passes through the lens 22 and is made into 
S-polarized light through the 1/4-wavelength plate 21. The S-polarized 
light is substantially 100% reflected by the polarized light beam splitter 
19 and enters a critical angle prism 23. The light reflected by the slope 
of the prism 23 is received by a photodetector 24 arranged in a far field 
position as opposed to the exit surface of the prism 23. The photodetector 
24 is formed of a quarterly-divided light receiving device. A DC SUM 
signal, as a reproduced signal, is produced through an addition circuit 
26. By passing the light through a reduction circuit, not illustrated, a 
tracking error signal or focus error signal is produced. 
By applying a track jump pulse to a tracking coil 27 forming a lens 
actuator, the above mentioned objective lens 22 is made movable 
(track-jumpable) to the next track from the present track position in 
which the light beam is on-track. 
The above mentioned track jump pulse is applied to the tracking coil 27 
through a track jump circuit part 32 and lens driving circuit 33 based 
upon a command by a controller 31. By the controller 31, a light is 
radiated by the optical pickup 13 and is read out of a reproduced signal 
demodulating circuit 41. The difference between the present track number 
and the objective track number is calculated and the difference and 
direction are output to the track jump circuit part 32. The track jump 
circuit part 32 is a timing circuit wherein, in order that the number of 
tracks given by a track jump command may be jumped in a predetermined 
direction (that is, in an inner peripheral side or outer peripheral side 
direction), a track jump pulse is generated and is output to the lens 
driving circuit 33. 
The lens driving circuit 33 is formed of an analogue driving circuit for 
driving the objective lens 22. 
The above mentioned spiral disc 12 is provided with an index as, for 
example, a high reflection pattern 34. The index is used for detecting 
that the disc 12 has made one rotation, by a position sensor 35 such as a 
photoreflector. In case the disc 12 has made one rotation, when the 
pattern 34 is just below the position sensor 35, the sensor 35 will be 
able to detect the pattern. The output of the position sensor 35 is input 
into a mechanical index detecting circuit 36 so that, when the pattern 34 
passes just below the position sensor 35, the mechanical index detecting 
circuit 36 will output a mechanical index pulse. 
The above mentioned position sensor 35 is arranged so as to be just above 
the pattern 34 when the boundary region, i.e., where the track number on 
the disc 12 varies, is in the state of being read out by the optical 
pickup 13. That is to say, when the optical pickup 13 reads out that the 
track number has varied, the position sensor 35 will detect the high 
reflection pattern 34. 
The mechanical index pulse output from the above mentioned mechanical index 
detecting circuit 36 is input into the track jump circuit part 32 through 
an AND-gate 37 and into a kick back circuit 39 through a second AND-gate 
38. 
With the kick back circuit 39, a kick back pulse for the kick back 
operation, which is synchronized with the input mechanical index pulse, is 
generated and is output to the lens driving circuit 33. With the lens 
driving circuit 33, using the track jump pulse output from the track jump 
circuit part 32, the objective lens 22 is moved and the beam spot 
condensed and radiated by the objective lens 22 is jumped and moved from 
the present track to another desired track. When a kick back pulse is 
input from the kick back circuit 39, the beam spot will be moved from the 
adjacent track and will be returned to the original track. (In the 
tracking state in this embodiment, as shown in FIG. 4, the beam spot is 
moved in the outer peripheral direction which is determined by the spiral 
direction and rotating direction. Therefore, in order to correct the 
moving direction, after one rotation, the beam spot is moved to the inner 
peripheral side track.) 
With the kick back operation, the beam spot will be held in the state of 
always following the same track number. However, when the kick back 
operation is stopped the beam spot will spirally scan the track with the 
rotation of the disc 12. 
During the track jump operation, the above mentioned track jump circuit 32 
will output an ON-JUMP signal of an "H" level. The ON-JUMP signal is input 
into the AND gate 37 so that, while the ON-JUMP signal is being output, a 
mechanical index pulse will be input and a track jump will be made by 
taking the number of pulses of the mechanical index pulse into 
consideration (by increasing or decreasing the correcting track jump 
pulses). 
The ON-JUMP signal is also input into the kick back circuit 39 through an 
inverter 40 and the AND gate 38 so that, during the ON-JUMP signal, no 
kick back operation will be made. 
That is to say, during the ON-JUMP signal, the kick back operation will be 
suspended, the number of pulses of the mechanical index pulse during the 
suspension, that is, the number of variations of the track number, will be 
counted by the track jump circuit 32, the number of track jump pulses will 
be increased or decreased (added or reduced in response to the direction 
of the track jump or the like) by the number of variations of the track 
number and an access to the objective or desired track may be made by one 
lens seeking command. 
A reproduced signal output from the above mentioned adding circuit 26 is 
input into a reproduced signal demodulating circuit 41. The encoded 
reproduced signal is demodulated and a track number signal of an ID part 
of the disc 12 is input into the controller 31. That is to say, using the 
track number signal, the controller 31 detects the present track number 
and outputs to the track jump circuit part 32 a lens seeking command when 
an access to the objective track is input. 
A formation of the above mentioned track jump circuit part 32 is shown in 
FIG. 3. 
The track jump circuit part 32 comprises a track jump circuit 51 making a 
track jump in response to a lens seeking command from the controller 31 
and a track jump correcting circuit 52. The number of variations of the 
track number during the track jump operation is detected by using a 
mechanical index pulse. A kick back correcting pulse is output as a jump 
pulse following the track jump by the above mentioned track jump circuit 
51 and a jump operation for making a kick back correction is made. 
A lens seeking direction command 53, in the lens seeking command from the 
above mentioned controller 31, is input into a seeking direction setting 
circuit 54. The controller determines whether the difference between the 
objective track number and the present track number is positive or 
negative. For example, in case the difference is positive, the lens 
seeking direction command will output an outside track jump pulse 
(directed toward the outer periphery) through an AND gate 55. On the other 
hand, if the difference is negative, the controller will output an inside 
track jump pulse (directed toward the inner periphery) through an AND gate 
56 and OR gate 57. 
A track jump pulse is formed from the above mentioned outside track jump 
pulse and inside track jump pulse. On the other hand, a lens seeking 
number command 58 is determined by the absolute value of the difference 
between the present track number and the objective track number and is 
input into the first jump counter 59. The number of tracks to be moved is 
then set as a counted value and the counted value is input into a first 
coincidence circuit 61 which senses whether the counted value coincides 
with the counted value of the second jump counter 62. The first 
coincidence circuit 61 will be "H" for coincidence but will be "L" when no 
coincidence. The output of the coincidence circuit 61 is output as an 
ON-JUMP signal through an OR gate 75. The output of the coincidence 
circuit 61 is also input into an AND gate 63 and into an AND gate 65 and 
3-input NAND gate 66 through an inverter 64 and is applied to a switch 67 
at the ON-OFF controlling end. The switch 67 will close when the output of 
the first coincidence circuit 61 is "L", that is, at the time of no 
coincidence but will open at the time of coincidence. When the switch 67 
is closed, the track jump pulse from a track jump pulse generating circuit 
68 will be input into the jump counter 62. With the track jump pulse 
generating circuit 68, a track jump pulse is generated at regular 
intervals and is input into the AND gates 63 and 65 and NAND gate 66. The 
output of the AND gate 63 is input into the AND gates 55 and 56 and the 
output of the AND gate 65 is input into the OR gate 57. The AND gate 65 is 
to output a kick back correcting pulse (output as an inside track jump 
pulse output through the OR gate 57) successively after the lens seeking 
number command 58 is carried out. (See the track jump pulse in FIG. 5.) 
The above mentioned 3-input NAND gate 66 will output a down pulse to a 
mechanical index counter 69 only when the output of the coincidence 
circuit 61 coincides. The output of the AND gate 37, that is, a mechanical 
index pulse in the ON-JUMP signal is applied to the mechanical index 
counter 69 at the up count input end. The counted output of the mechanical 
index counter 69 is applied to the second coincidence circuit 71 at one 
input end which senses whether the counted output coincides with the "O" 
value applied at the other input end thereof. The output of the 
coincidence circuit 71 is input into the 3-input AND gate 65, 3-input NAND 
gate 66 and an OR gate 75. When the respective output signals of the two 
coincidence circuits 61 and 71 are input into the OR gate 75, the gate 75 
will continue to output ON-JUMP signals until these coincidence circuits 
61 and 71 coincide with each other. The above mentioned index counter 69 
counts up the mechanical index pulses through the AND gate 37 and makes an 
inside track jump for the number of tracks corresponding to the pulses to 
correct the kick back operation. Even if the mechanical index pulse is 
input while the kick back correcting pulse is being output, when the 
pulses are counted down at the rear edge of the pulse, the counter 69 will 
be able to be up until the correcting pulse is output to the end. 
In the 3-input AND gate 65, after the end of the track jump of the lens 
seeking command number, when the output of the inverter 64 becomes "H", 
the output of the second coincidence circuit 71 will be "H", that is to 
say, the mechanical index pulse will continue to make the inside track 
jump pulse of the counted number of tracks. 
The operation of the thus formed first embodiment shall be explained in the 
following: 
In case there is no access command from the controller 31, a tracking servo 
system will be making a kick back by moving one track to the inner 
peripheral side of the disc 12 once in one rotation in order to hold the 
track at the present point. This is shown in FIG. 4. The timing of the 
kick back is made by a kick back pulse output by the kick back circuit 39 
from the mechanical index pulse output by the mechanical index detecting 
circuit 36 by sensing the pattern 34 after the position sensor 35 shown in 
FIG. 2. In this state, the lens driving circuit 33 will be switched from 
the output end of the track jump circuit part 32 to the tracking servo 
system side by a switch (not illustrated) and will scan the same track. In 
such a case, a two-step servo state will be set by the VCM 15 and the 
tracking servo system. 
When an access mode seeking an objective track is set, in case the 
objective track is far away from the present track position, a coarse 
access will be made by the VCM 15. In case the objective track is near the 
present track position, the lens 22 will be moved to make a close access. 
This close access is made according to this first embodiment. 
For example, with a lens seeking command, the number of lens seekings is 10 
and there is a timing of making a kick back while the lens seeking is 
being carried out. A timing chart of this example is shown in FIG. 5(a-d). 
The timing of making a kick back is synchronized with the mechanical index 
pulse, is generated once in one rotation and is not synchronized with the 
lens seeking. 
Shown in FIG. 5(a) is a lens seeking command output from the controller 31. 
As shown in FIG. 5(b), the track jump circuit part 32 outputs a number of 
track jump pulse (that is, 10) commands which are delivered to the lens 
driving circuit 33. At the same time, as shown in FIG. 5(c), an ON-JUMP 
signal is output. In the lens driving circuit 33, according to the track 
jump pulse, a voltage for moving one track is output to the lens 22 to 
carry out a track jump. When the ON-JUMP signal is at a "H" level, it will 
pass through the AND gate 37 and the mechanical index pulse will be able 
to be input into the track jump circuit part 32. For example, when passing 
through a track position in which the track number varies while the track 
jump is being carried out, as shown in FIG. 5(d), a mechanical index pulse 
will be output and will be counted and held in the track jump circuit part 
32. Track jump pulses of the above mentioned set number will be delivered, 
and track jumps equal to the number of the counted and held mechanical 
index pulses will be made to the inner peripheral side of the disc. Then, 
the above mentioned counted value will be set and the ON-JUMP signal will 
be on an "L" level. While a track jump by the lens seeking is thus being 
carried out, even if passing through the position in which a mechanical 
index pulse is output, the number of the passages of the mechanical index 
pulse will be detected, a kick back correction will be made by track jumps 
by the number of passages following the ordinary track jump and therefore, 
after this track jump is carried out, an access to the objective track 
will be able to be made. Therefore, it is not necessary that, in the 
conventional example, after the lens seeking, the track number of the ID 
part of the track is read out, the residual part to make a track jump by 
the mechanical index pulse part is recognized and a track jump must be 
made again. 
When the above mentioned ON-JUMP signal is at the "H" level, the AND gate 
37 will be closed and no mechanical index pulse will be input into the 
track jump circuit part 32. At the same time, the mechanical index pulse 
can be input into the kick back circuit 39 through the AND gate 38. When 
the mechanical index pulse is input, a kick back operation will be made. 
According to this first embodiment, by one lens seeking command, following 
the ordinary track jump, a track jump for the kick back correction can be 
made (successively) and therefore an access can be made to the objective 
track without repeating the lens seeking operation. Therefore, an access 
can be made to the objective track within a short time. 
In the above mentioned first embodiment, in case, as shown in FIG. 4, the 
optical disc 12 is rotated and driven clockwise from the inner periphery 
to the outer periphery and, on the other hand, the spiral is 
counter-clockwise from the inner periphery to the outer periphery, a track 
jump will be made to the inner peripheral side to make a kick back 
correction. Even in case the spiral direction is different, a correction 
pulse will be made in the direction of making the kick back. In case the 
kick back is made in the outer peripheral direction, the OR gate 57 in the 
track jump correcting circuit 52 in FIG. 3 may be interposed on the output 
side of the AND gate 55 instead of the output side of the AND gate 56. 
FIG. 3 shows an embodiment of the track jump circuit part 32 which may be 
made of a different formation. When a mechanical index pulse is sensed by 
using a CPU, the number of pulses may be held and a kick back correcting 
pulse may be output following the ordinary track jump. 
The formation of the optical pickup is not limited to that shown in FIG. 2. 
The position sensor 35 setting position may be arranged on the somewhat 
front side from the boundary in which the track number varies so that, 
when the position sensor 35 senses the pattern 34, the track jump 
operation will be suspended, a kick back operation will be made and, after 
the kick back operation, the remaining track jump operation may be made 
again. 
As described above, according to the present invention, during lens 
seeking, the passages of the mechanical index will be counted and, after 
the jumps by the number set by the lens seeking command end, the lens 
seeking will be made in the same direction as the kick back by the number 
of passages of the mechanical index and therefore the access can be 
completed without the recognition of the ID.