CA1202720A - Apparatus for reproducing designated information from a recorded disc - Google Patents
Apparatus for reproducing designated information from a recorded discInfo
- Publication number
- CA1202720A CA1202720A CA000435187A CA435187A CA1202720A CA 1202720 A CA1202720 A CA 1202720A CA 000435187 A CA000435187 A CA 000435187A CA 435187 A CA435187 A CA 435187A CA 1202720 A CA1202720 A CA 1202720A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- designated
- disc
- location
- count
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B21/00—Head arrangements not specific to the method of recording or reproducing
- G11B21/02—Driving or moving of heads
- G11B21/08—Track changing or selecting during transducing operation
- G11B21/081—Access to indexed tracks or parts of continuous track
- G11B21/083—Access to indexed tracks or parts of continuous track on discs
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for reproducing designated information from a digitally recorded disc uses a stepping motor which moves an optical pick-up device radially across the disc to the designated location using a predetermined number of stepping pulses representing the distance of the optical head to the designated location. A motor control circuit generates the stepping pulses in response to a driving signal comprising a predetermined number of driving pulses and a direction signal, the polarity of which corresponds to radially inward or outward movement of the pick-up device relative to the disc. A counter counts the driving pulses so that the actual count in the counter represents the distance of the optical head from a reference location, typically the beginning of the recorded track on the disc. A designating signal is used to generate a designated count of driving pulses required to reach the designated location from the same reference location. The difference between the actual count and the designated count is used to provide the driving signal for moving the pick-up device. When the pick-up device is within a certain distance of the designated location, address information read from the disc by the optical head is used to provide a fine-adjustment signal to precisely locate the optical head.
An apparatus for reproducing designated information from a digitally recorded disc uses a stepping motor which moves an optical pick-up device radially across the disc to the designated location using a predetermined number of stepping pulses representing the distance of the optical head to the designated location. A motor control circuit generates the stepping pulses in response to a driving signal comprising a predetermined number of driving pulses and a direction signal, the polarity of which corresponds to radially inward or outward movement of the pick-up device relative to the disc. A counter counts the driving pulses so that the actual count in the counter represents the distance of the optical head from a reference location, typically the beginning of the recorded track on the disc. A designating signal is used to generate a designated count of driving pulses required to reach the designated location from the same reference location. The difference between the actual count and the designated count is used to provide the driving signal for moving the pick-up device. When the pick-up device is within a certain distance of the designated location, address information read from the disc by the optical head is used to provide a fine-adjustment signal to precisely locate the optical head.
Description
~2~'~7~ S83P154 APPARATUS FOR RF,PRODUCING DESIGNATED
INFORMATIOM FROM A RECORDED DISC
BACKGROUND OF THE INVENTION
Field of the Invention The presen~ invention relates to apparatus for reproducing information from a disc-shaped recording medium and, more particularly, to apparatus for reproducinq designated information from such a medium.
Description of the Prior Art Disc-shaped recording mediums contalning program information recorded in diyital form enable very high Eidelty sound reproduction. The many problems inherent in analog records are eliminated with discs recorded in digital form. However, digital discs do no~ as easily lend themselves to finding particular parts of the recorded program information as do analo~ discs, which provide a visual indication of the beginnings of different program sections.
A convenient and well-known form of digitally recorded disc uses a series of microscopic pits in the disc surface to represent the recorded information. The pi~s are arranged in a spiral track and, as the disc rotates, a laser beam is focussed on the spiral track. Variations in the re1ected or transmitted laser beam cau6ed by the pits are sensed and the digital information thus derived is supplied to suitable decoding circuitry to convert the digital
INFORMATIOM FROM A RECORDED DISC
BACKGROUND OF THE INVENTION
Field of the Invention The presen~ invention relates to apparatus for reproducing information from a disc-shaped recording medium and, more particularly, to apparatus for reproducinq designated information from such a medium.
Description of the Prior Art Disc-shaped recording mediums contalning program information recorded in diyital form enable very high Eidelty sound reproduction. The many problems inherent in analog records are eliminated with discs recorded in digital form. However, digital discs do no~ as easily lend themselves to finding particular parts of the recorded program information as do analo~ discs, which provide a visual indication of the beginnings of different program sections.
A convenient and well-known form of digitally recorded disc uses a series of microscopic pits in the disc surface to represent the recorded information. The pi~s are arranged in a spiral track and, as the disc rotates, a laser beam is focussed on the spiral track. Variations in the re1ected or transmitted laser beam cau6ed by the pits are sensed and the digital information thus derived is supplied to suitable decoding circuitry to convert the digital
-2-~ z ~ S~3P154 information into the signal's original analog form for supply to headphones or loudspeakers.
A common ~echnique for digital recording employs pulse code modulation, or PCM. PCM recording "samples" the original signal and converts each sample in~o digital form.
Error correction and other digltal inforrnation is added to the PCM data and recorded on the disc. A typical ormat for arranging the digital data employs a series of frames, each of which contains~ among other information, program information (the original signal) and address information.
The address information included in the digital data recorded on the d sc identifies par~icular program information. For example, the address information might contain data identifying the particular section of program information, data identifying the particular part of that section and data representing the playing time required to reach that part of the program information from the beginning of that particular program section when the disc player is opexating in the normal reproducing mode.
In any case, the digital data is reproduced from the disc by tracing the spiral track of pits in the disc outwardly from the radially innermost end of the ~rack. At the beginning of the spiral track a 7'table of contents" is provided. The table of contents~ contains in digital form, the running time in the normal playback mode of the disc player to the beginning of each segment of program information.
To find a designated part of the progxam information in prior art devices~ the laser picX-up device moved transverse to the track a given amount and -then traced --3~
~2~7Z~ S83P154 the trackO The address information at that point was reproduced and used to determine how far the pick~up was ~rom the designated location. That searching operation would then be repeated until the reproduced address information matched the designated address information.
That approach inherentlv requires repeated reproduction, at the normal playback speed, of address information from the disc. As a resul~, the search time can be lengthy. The resulting inconvenience will be even greater when the designated program information is n~arer the end of the track because it will take even longer to reach it.
SUMl!lARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for reproducing information from a designated location on a recorded disc that avoids the aforementioned shortcomings of the prior art.
It is a further object of the present invention to move the pick-up means of the reproducing apparatus transversely across adjacent tracks using driving pulses provided in a number proportional to the distance across adjacent tracks to the designated location~ /
In accordance with an aspect of the present in~ention/ an apparatus is provided for reproducing program information from a designated location on a disc having recorded thereon program information in a spiral track using a pick-up means movable along the track in a normal playback mode for reproducing the program information and transversely across adjacent tracks generally radially of -~ ~ ~'~ S01~22 ~ ~ S83P154 the disc. The apparatus comprises driving means for moving the pick-up means from a reerence location transversely across adjacent tracks on the disc in response to driving pulses supplied thereto, counter means for providing an actual count of driving pulses supplied to the driving means, and system control means for providing a designated count of driving pulses representing the distance transversely across adjacent tracks between -the reference loca~ion and the designated location and producing a driving signal including a predetermined number of driving pulses representing the difference between the designated count and the actual count for supply to the driving means.
The above and other objects, features and advantages of the present invention will be apparent when the following detailed description of a preferred embodiment of the invention is considered in connection with the accompanying drawings.
BRIEF DESCRXPTION OF THE DRAWINGS
Fig. 1 i5 a schematic block diagram of a disc player incorporating an embodiment of the present invention.
Fig. 2 is a flow chart illustrating the opexation of the disc player shown in Fig. 1~
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Fig. 1 shows a digitally rec~rded disc 1 loaded on a disc player for rotation. The disc 1 has program, address and other informatlon recorded on it by means of a series of pits Inot shown) formed in a spiral track in the surface of the disc. The track is traced by an optical pick-up head 2.
S0182~
~2~ S83P15~
The spiral track begins radially inwardly of the edye of the disc 1 and is traced as the di~c 1 rotates by xadial].y outward movement of the pick-up head 2. The program informat~.on on the disc 1 .is arranged in segments and -the spiral track begl.ns with a table of conten-ts which contains data indicating the running time, in minutes and seconds, to the beginning of each segment. Typically, the information .in the table of contents is also printed on the disc in human-readable form.
The pick-up head 2 ~irects a laser beam agalnst ~he disc 1. The head ~ includes a photodetector -that detects the modulation by the pits of the laser's reflection. ~lternatively, the laser can be transmit~ed through the disc, in which case the photodetector detects the modulation by the pits of the laser beam as it is transmitted t'nrough the disc. The photodetector in either case provides an electrical output that represents the digital information on the disc 1, in a well-known fashion.
The point where the laser beam impinges on the disc 1 must be precisely controlled so that the pits are read in the proper order. The optical head 2 thus includes a tracking device that directs the laser beam against the surface of the disc. The disc player includes a tracking error detection circuit 3 that provides an error signal which indicates mistracking of the l.aser beam in response to the output of the photodetectorO The error signal is fed to a tracking control circuit 4 which positions the optical head using the tracking device. The direction in which the laser beam i.s pointed is thus controlled by a servo-control ~-6-~ 2~ S01~22 system to maintain proper tracing of the spiral track of pits in the disc 1.
For larger movement of the optical head 2, a stepping motor 5 moves the optical head 2 radially lnwardly and outwardly relatlve to the disc 1, depending on the direction of rotation of the motor 5. A system control circui~ 6 provides the input signals to a motor con~rol circuit 7 which in turn provides signals to actlvate the stepping motor 5. The motor actuation signals from the motor control circuit 7 take the form of stepping pulses which drive the stepping motor 5 a predetermined number of steps either radially inwardly or outwardly relative to the disc 1 depending on the polarity of the stepping pulses. In the embodiment shown, each s~epwise rotation of the stepping motor 5 moves the optical head 2 a constant distance radially of the disc 1.
A counter 8 has three input terminals, U/D~ CK and CR, and a single output terminal CO. The clock terminal CK
receives pulses and adds or subtracts them to the number already in the counter 8. The up/down terminal U/D receives a signal the polarity of which determines whether the pulses received by the terminal CX will be added or subtracted from the number in the counter~ The clear terminal CR sets the number in the coun*er to a reference value, typically 2ero, when it receives a signal. ~he output terminal CO provides a signal that represents the number in t~e counter 8.
A start detector 9 provides a start signal when the optical head ~ is at the beginning of the spiral track on the disc 1. The start detector can either be a mechanical device that provides a signal when contacted by . -7 ~2~2~%~ S83P15~
~he op-tical head 2 or can be arranged to operate optically.
:~n any case, the start signal is provided to the CR terminal of the counter 8 to set the counter to the zero reference count when the optical. head 2 is set to begln tracing the spiral track. As shown in Fi.g. 1, the system control circuit 6 has two output termlnals tl and t2 at which are provided signals Ps and Pd, respectively/ which together comprise a driving signal. The signal Ps is applied to the CK terminal of the counter 8 and the motor control circuit 7. The signal PD is applied to the U/D terminal of the counter and also to the motor control circuit 7. The signal Ps comprises driving pulses that are used by the motor control circuit 7 to provide the stepping pulses to the stepping motor 5 to cause it to rotate a predetermined number of steps depending on, for example, the number of pulses comprising the signal Ps. The signal PD is a direction signal, the state (here its polarity) of which is sensed by the motor control circuit 7 to determlne in which direction the motor 5 is to be rotated. For example, if PD
is negative, the motor 5 is actuated in a directi~n that moves the optical head 2 radially inwardly toward the beginning of the spiral track and, if PD is posltive, the motor 5 is rotated in the other direction.
: Meanwhile, the number stored in the counter 8 indicates the position of the optical head 2 relative to a reference location, which in the illustrated embodiment is the beginning of the spiral track, because the number of driving pulses in the signal P~ is added to or subtracted from, depending the polarity of the direction signal PD, the number in the counter 8~ Thus, the signal dp at the output ~2~27Z~ S83P154 ~erminal CO of the counter 8 comprises the actual count in the counter 8 and represents the distance of the optical head 2 from the reference location. The ac-tual count signal dp is provided to an input ~erminal nl of the system control circuit 6~
The output of the optical head 2 is supplied to a digital signal detection circui~ 10 that conditions the digital signal reproduced from the disc 1 for further use.
The conditioned digital signal is provided ~o a decoder ll.
The decoder 11 provides three outputs. ~irst, the program information Sp is provided by the decoder 11 to a program information processing circuit 12 that provides the program information as an analog signal A corresponding to the original signal. The analog signal A can be used in the conventional manner to drive loudspeakers or headphones.
The decoder 11 also provides address in~ormation Q' reproduced from the disc. The address information Ql is converted by a deciphering circuit 13 into a resulting time signal TQ. The resulting time signal TQ represents the resulting time that would be required for the optical head 2 to reach the particular address represented by the signal Q' when operated fxom the beginning of the splral track in the normal playback mode. The resulting time signal TQ is provided to a second input terminal n2 of the system control circuit 6 .
Finally, the decoder 11 provides the table of contents as a signal Toc to an input terminal n3 of the system control circuit 6, which stores the information represented by the signal Toc.
.._9_ ~z~7~ S~3P154 As Fig. 1 shows, the system control circuit 6 has a third output -terminal t3 which provides jump signal J to a jumping pulse generating circuit 14. In response to the signal J the circuit 14 provides a jumping pulse Pj to the tracking control circuit 4. The -tracki.ng control circuit 4 moves the optical head 2 radially of the disc 1 in response to the jumping pulse Pj, The output of the tracking control c.ircuit 4 is also provided through a low pass filter 15 to a fourth input terminal n4 of ~he system control circuit 6.
The disc player incorporating -~he present invention also includes a command signal generating circuit 16 that provldes a designating .signal I to a f.ifth lnput terminal n5 of the system control circuit 6. An operator uses the generating circuit 16 as a designating means to select a position on the disc 1 from which the reproduction of program information is to begin. For example, by using the printed table of contents on the disc, the operato.r can choose the desired time, in minutes and seconds from the beginning of a parti.cular program segment, from which .reproduction is to begin. The generating circuit 16 provides the designating signal I representing that designated information to the system control circuit 6.
The operation of the apparatus of the presen~
.Lnvention can be understood by referring to both F.igs. 1 and .
Assume that the operator wishes reproduction of program information from the disc 1 to begin at x minutes and ~ seconds from the beginning of the Mth program segment.
Assume also that the disc 1 has been loaded on the disc player and that the table of contents has been read from the --10~
~ z~ , S01822 2~ S83P154 disc and provided to the system control circuit 6 as the slgnal Toc and is stored therein.
The operator provides the informatlon concerning the clesignated location from which reproduction is to begin.
As shown in Fig. 2, the first calculation step C1, performed by the system control circuit 6, converts the designating signal I into time data in the proper form. The system control circuit 6 has, in the table of contents inEormation stored ~herein, sufficient data to calculate the -time, in xO
minutes and yO seconds, irom the heginning of the spiral track to the beginning of the Mth prograrn section. With that information, the system control circuit 6 calculates the normal reproducing time T in X minutes Ix ~ x ) and Y
~ o seconds (y -~ yO) it would require to reach the designated ]o~ation from the beginning of the spiral track.
In calculation step C2, the time Ti is converted into a signal dil so that the time Ti actually represents the radial distance from the beginning of the spiral ~rack to the designated location. Generally,`the radial distance dr fron the beginning of the spiral track to any given point, which takes the optical head 2 a time Tx to ~each when in a normal playback mode, can be expressed:
dr = flTX) ~ a constank.
Thusl if the function f(Tx) is known and programmed into the system control circuit 6, the signal di can be calculated from Ti.
The signal di calculated by skep C2 is in the same form as the actual count dp provided from the counter 8 output terminal CO. That is, di is expressed as a number that corresponds to the distance represented by Ti, can be :~Z~7~0 S83P154 time regarded as a designated count. So, if di and dp have the same value, the actual radial distance (dp) of the optical head 2 from the beginning of ~he spiral track is the same as the dlstance calcu].ated uslng the time Tl.
In steps C4 and C5 the system control circuit 6 uses a difference signal di to generat.e the pulse signal Ps and the direction signal Pd, which are provided to the motor control circuit 7 and the counter 8. The pulse signal Ps comprises a predetermined number of driving pulses and the direction signal Pd has a polarity which depends on the comparison of di and dp. The motor control circuit 7 generates the stepping pulses with the pro~er polarity to move the optical head 2 radially of the disc 1 and, at the same time, the count in the counter 8 changes to provide a different actual count dp which represents the new position of the optical head 2. That movement of the optical head is shown in the block in Fig. 2 following step C5.
The optical head 2 is then operated momentarilv in the normal playback mode long enough to obtain address information Q from the disc 1. That address information Q
is converted by the deciphering circuit 13 into the resulting time signal TQ representing the time required to reach that particular location on the disc in a normal playhack modeO In step C6 the resulting time TQ is compared with the designated time Ti to obtain a time difference signal Ui Q (= Ti ~ TQ)' The time difference signal Ui_Q is compared with a first coarse-reference time Ul. The decision step Dl depicts that comparison. If Ui Q is less than or equal to Ul~ steps -~2-~Z~272~ S~3P154 C7, C8 and Cg are omitted and the next calculation step that takes place is C10.
If Ui Q is greater than Ul, indicating that it woulcl take longer than the coarse-reference time Ul of playing time to reach the designated position on the disc from the optical head's actual position, the step C7 is performed. In step C~ the system control circuit 6 again calculates the number of steps and the direction of rotation required for the motor S to move the optical head 2 from the location of the address information Q to the designated location di, by using the resulting time TQ. The pulse and direction signals Ps and Pd, as shown by step C8, again cause the optical head 2.
Ps and Pd are also supplied to the counter 8, so that the actual count dp provided by the counter output CO
still has a value that corresponds to the radial distance from the reference location at the beginning of the spiral track.
The disc 1 is again read long enough to obtain again address information Q that represents the actual position of the optical head 2 relative to the beginning of the track on the disc 1. The time data TQ thus obtained from Q by the deciphering circuit 13 is used to calculate Ti TQ, as represented by step Cg. The magnitude of that difference is used by the system control circuit 6 to provide the signal J to the jumping pulse generating circuit 14, which pr~vides a jumping pulse Pj to the tracking control circuit 4, as depicted by the step C10 in Fig. 2.
The tracking control circuit 4 generates a fine-adjustment signal using the jumping pulse Pj. The SOl~22 ~2~27~ S83P154 fine-adjustment signal is in a form identical to the signal provided by the tracklng con~rol circuit 4 in response to the tracking error cletection circuit , that is, a direct current signal. The fine-adjustment signal is provided with a voltage which is proportional to the difference between the designated time Ti and the resulting time T~ last read from the disc.
The tracking device used to change the position of the laser in the optical head 2 relative to the disc 1 has a conventional and well-known configuration. For example, the optical head 2 may be rotably mounted on an axis substantially normal to the disc surface. The laser is directed at the disc from a location on the optical head displaced from that axis. A coil surrounds the optical head such that the magnitude and polarity of a dc signal supplied to the coil causes the optical head to rotate about the axis and thereby move the location of the laser relative to the disc surface.
In any case, the fine-adjustment signal causes the optical head to direct the laser against the disc at a track that is displaced from the location of the last-provided address information Q, which is the track-jumping operation depicted in Fig. 2. ~he address in_ormation Q is read from the disc at that location and is converted by the deciphering circuit 13 into another resulting time signal r TQ.
At the same time, the fine-adjustment signal is provided through the low-pass filter 15 to the input terminal n4 of the system control circuit 6. The system control circuit 6 generates the driving signal (Ps and Pd~
1~2~ S83Pl5~
which causes ~he stepping motor 5 to move the optical head 2 and increments the counter 8 to change dpo As shown in step C11, the designated time Ti and ~he result,ing time TQ are compa,red. The resul-t Ui Q of that comparison is checked against a fine-reference time UO. If the time difference signal Ui Q is less than or equal to UO, then the search operation is ended. However, if Ui Q is greater than UO, steps C10, C11 and D2 are repeated.
Thus, a ine~adjustment process is accomplished by direct use of the address information aftex a coarse~
adjustment which initially uses driving pulses to quickly move the optical head to a loca-~ion very close -to the designated location and then indirectly uses address information driving pulses if the initial movement of the optical head is not to within an acceptable distance from the designated location.
The present invention has been described by reerring to a specific embodiment thereof. Those skilled in -the art will recognize that modifications other than those specifically referred to can be made in that embodiment without departing from the spirit of the invention. For that reason the scope of the in~ention is not to be limited by the above description but instead is defined solely by the claims which follow.
~ -15-.;
A common ~echnique for digital recording employs pulse code modulation, or PCM. PCM recording "samples" the original signal and converts each sample in~o digital form.
Error correction and other digltal inforrnation is added to the PCM data and recorded on the disc. A typical ormat for arranging the digital data employs a series of frames, each of which contains~ among other information, program information (the original signal) and address information.
The address information included in the digital data recorded on the d sc identifies par~icular program information. For example, the address information might contain data identifying the particular section of program information, data identifying the particular part of that section and data representing the playing time required to reach that part of the program information from the beginning of that particular program section when the disc player is opexating in the normal reproducing mode.
In any case, the digital data is reproduced from the disc by tracing the spiral track of pits in the disc outwardly from the radially innermost end of the ~rack. At the beginning of the spiral track a 7'table of contents" is provided. The table of contents~ contains in digital form, the running time in the normal playback mode of the disc player to the beginning of each segment of program information.
To find a designated part of the progxam information in prior art devices~ the laser picX-up device moved transverse to the track a given amount and -then traced --3~
~2~7Z~ S83P154 the trackO The address information at that point was reproduced and used to determine how far the pick~up was ~rom the designated location. That searching operation would then be repeated until the reproduced address information matched the designated address information.
That approach inherentlv requires repeated reproduction, at the normal playback speed, of address information from the disc. As a resul~, the search time can be lengthy. The resulting inconvenience will be even greater when the designated program information is n~arer the end of the track because it will take even longer to reach it.
SUMl!lARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for reproducing information from a designated location on a recorded disc that avoids the aforementioned shortcomings of the prior art.
It is a further object of the present invention to move the pick-up means of the reproducing apparatus transversely across adjacent tracks using driving pulses provided in a number proportional to the distance across adjacent tracks to the designated location~ /
In accordance with an aspect of the present in~ention/ an apparatus is provided for reproducing program information from a designated location on a disc having recorded thereon program information in a spiral track using a pick-up means movable along the track in a normal playback mode for reproducing the program information and transversely across adjacent tracks generally radially of -~ ~ ~'~ S01~22 ~ ~ S83P154 the disc. The apparatus comprises driving means for moving the pick-up means from a reerence location transversely across adjacent tracks on the disc in response to driving pulses supplied thereto, counter means for providing an actual count of driving pulses supplied to the driving means, and system control means for providing a designated count of driving pulses representing the distance transversely across adjacent tracks between -the reference loca~ion and the designated location and producing a driving signal including a predetermined number of driving pulses representing the difference between the designated count and the actual count for supply to the driving means.
The above and other objects, features and advantages of the present invention will be apparent when the following detailed description of a preferred embodiment of the invention is considered in connection with the accompanying drawings.
BRIEF DESCRXPTION OF THE DRAWINGS
Fig. 1 i5 a schematic block diagram of a disc player incorporating an embodiment of the present invention.
Fig. 2 is a flow chart illustrating the opexation of the disc player shown in Fig. 1~
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Fig. 1 shows a digitally rec~rded disc 1 loaded on a disc player for rotation. The disc 1 has program, address and other informatlon recorded on it by means of a series of pits Inot shown) formed in a spiral track in the surface of the disc. The track is traced by an optical pick-up head 2.
S0182~
~2~ S83P15~
The spiral track begins radially inwardly of the edye of the disc 1 and is traced as the di~c 1 rotates by xadial].y outward movement of the pick-up head 2. The program informat~.on on the disc 1 .is arranged in segments and -the spiral track begl.ns with a table of conten-ts which contains data indicating the running time, in minutes and seconds, to the beginning of each segment. Typically, the information .in the table of contents is also printed on the disc in human-readable form.
The pick-up head 2 ~irects a laser beam agalnst ~he disc 1. The head ~ includes a photodetector -that detects the modulation by the pits of the laser's reflection. ~lternatively, the laser can be transmit~ed through the disc, in which case the photodetector detects the modulation by the pits of the laser beam as it is transmitted t'nrough the disc. The photodetector in either case provides an electrical output that represents the digital information on the disc 1, in a well-known fashion.
The point where the laser beam impinges on the disc 1 must be precisely controlled so that the pits are read in the proper order. The optical head 2 thus includes a tracking device that directs the laser beam against the surface of the disc. The disc player includes a tracking error detection circuit 3 that provides an error signal which indicates mistracking of the l.aser beam in response to the output of the photodetectorO The error signal is fed to a tracking control circuit 4 which positions the optical head using the tracking device. The direction in which the laser beam i.s pointed is thus controlled by a servo-control ~-6-~ 2~ S01~22 system to maintain proper tracing of the spiral track of pits in the disc 1.
For larger movement of the optical head 2, a stepping motor 5 moves the optical head 2 radially lnwardly and outwardly relatlve to the disc 1, depending on the direction of rotation of the motor 5. A system control circui~ 6 provides the input signals to a motor con~rol circuit 7 which in turn provides signals to actlvate the stepping motor 5. The motor actuation signals from the motor control circuit 7 take the form of stepping pulses which drive the stepping motor 5 a predetermined number of steps either radially inwardly or outwardly relative to the disc 1 depending on the polarity of the stepping pulses. In the embodiment shown, each s~epwise rotation of the stepping motor 5 moves the optical head 2 a constant distance radially of the disc 1.
A counter 8 has three input terminals, U/D~ CK and CR, and a single output terminal CO. The clock terminal CK
receives pulses and adds or subtracts them to the number already in the counter 8. The up/down terminal U/D receives a signal the polarity of which determines whether the pulses received by the terminal CX will be added or subtracted from the number in the counter~ The clear terminal CR sets the number in the coun*er to a reference value, typically 2ero, when it receives a signal. ~he output terminal CO provides a signal that represents the number in t~e counter 8.
A start detector 9 provides a start signal when the optical head ~ is at the beginning of the spiral track on the disc 1. The start detector can either be a mechanical device that provides a signal when contacted by . -7 ~2~2~%~ S83P15~
~he op-tical head 2 or can be arranged to operate optically.
:~n any case, the start signal is provided to the CR terminal of the counter 8 to set the counter to the zero reference count when the optical. head 2 is set to begln tracing the spiral track. As shown in Fi.g. 1, the system control circuit 6 has two output termlnals tl and t2 at which are provided signals Ps and Pd, respectively/ which together comprise a driving signal. The signal Ps is applied to the CK terminal of the counter 8 and the motor control circuit 7. The signal PD is applied to the U/D terminal of the counter and also to the motor control circuit 7. The signal Ps comprises driving pulses that are used by the motor control circuit 7 to provide the stepping pulses to the stepping motor 5 to cause it to rotate a predetermined number of steps depending on, for example, the number of pulses comprising the signal Ps. The signal PD is a direction signal, the state (here its polarity) of which is sensed by the motor control circuit 7 to determlne in which direction the motor 5 is to be rotated. For example, if PD
is negative, the motor 5 is actuated in a directi~n that moves the optical head 2 radially inwardly toward the beginning of the spiral track and, if PD is posltive, the motor 5 is rotated in the other direction.
: Meanwhile, the number stored in the counter 8 indicates the position of the optical head 2 relative to a reference location, which in the illustrated embodiment is the beginning of the spiral track, because the number of driving pulses in the signal P~ is added to or subtracted from, depending the polarity of the direction signal PD, the number in the counter 8~ Thus, the signal dp at the output ~2~27Z~ S83P154 ~erminal CO of the counter 8 comprises the actual count in the counter 8 and represents the distance of the optical head 2 from the reference location. The ac-tual count signal dp is provided to an input ~erminal nl of the system control circuit 6~
The output of the optical head 2 is supplied to a digital signal detection circui~ 10 that conditions the digital signal reproduced from the disc 1 for further use.
The conditioned digital signal is provided ~o a decoder ll.
The decoder 11 provides three outputs. ~irst, the program information Sp is provided by the decoder 11 to a program information processing circuit 12 that provides the program information as an analog signal A corresponding to the original signal. The analog signal A can be used in the conventional manner to drive loudspeakers or headphones.
The decoder 11 also provides address in~ormation Q' reproduced from the disc. The address information Ql is converted by a deciphering circuit 13 into a resulting time signal TQ. The resulting time signal TQ represents the resulting time that would be required for the optical head 2 to reach the particular address represented by the signal Q' when operated fxom the beginning of the splral track in the normal playback mode. The resulting time signal TQ is provided to a second input terminal n2 of the system control circuit 6 .
Finally, the decoder 11 provides the table of contents as a signal Toc to an input terminal n3 of the system control circuit 6, which stores the information represented by the signal Toc.
.._9_ ~z~7~ S~3P154 As Fig. 1 shows, the system control circuit 6 has a third output -terminal t3 which provides jump signal J to a jumping pulse generating circuit 14. In response to the signal J the circuit 14 provides a jumping pulse Pj to the tracking control circuit 4. The -tracki.ng control circuit 4 moves the optical head 2 radially of the disc 1 in response to the jumping pulse Pj, The output of the tracking control c.ircuit 4 is also provided through a low pass filter 15 to a fourth input terminal n4 of ~he system control circuit 6.
The disc player incorporating -~he present invention also includes a command signal generating circuit 16 that provldes a designating .signal I to a f.ifth lnput terminal n5 of the system control circuit 6. An operator uses the generating circuit 16 as a designating means to select a position on the disc 1 from which the reproduction of program information is to begin. For example, by using the printed table of contents on the disc, the operato.r can choose the desired time, in minutes and seconds from the beginning of a parti.cular program segment, from which .reproduction is to begin. The generating circuit 16 provides the designating signal I representing that designated information to the system control circuit 6.
The operation of the apparatus of the presen~
.Lnvention can be understood by referring to both F.igs. 1 and .
Assume that the operator wishes reproduction of program information from the disc 1 to begin at x minutes and ~ seconds from the beginning of the Mth program segment.
Assume also that the disc 1 has been loaded on the disc player and that the table of contents has been read from the --10~
~ z~ , S01822 2~ S83P154 disc and provided to the system control circuit 6 as the slgnal Toc and is stored therein.
The operator provides the informatlon concerning the clesignated location from which reproduction is to begin.
As shown in Fig. 2, the first calculation step C1, performed by the system control circuit 6, converts the designating signal I into time data in the proper form. The system control circuit 6 has, in the table of contents inEormation stored ~herein, sufficient data to calculate the -time, in xO
minutes and yO seconds, irom the heginning of the spiral track to the beginning of the Mth prograrn section. With that information, the system control circuit 6 calculates the normal reproducing time T in X minutes Ix ~ x ) and Y
~ o seconds (y -~ yO) it would require to reach the designated ]o~ation from the beginning of the spiral track.
In calculation step C2, the time Ti is converted into a signal dil so that the time Ti actually represents the radial distance from the beginning of the spiral ~rack to the designated location. Generally,`the radial distance dr fron the beginning of the spiral track to any given point, which takes the optical head 2 a time Tx to ~each when in a normal playback mode, can be expressed:
dr = flTX) ~ a constank.
Thusl if the function f(Tx) is known and programmed into the system control circuit 6, the signal di can be calculated from Ti.
The signal di calculated by skep C2 is in the same form as the actual count dp provided from the counter 8 output terminal CO. That is, di is expressed as a number that corresponds to the distance represented by Ti, can be :~Z~7~0 S83P154 time regarded as a designated count. So, if di and dp have the same value, the actual radial distance (dp) of the optical head 2 from the beginning of ~he spiral track is the same as the dlstance calcu].ated uslng the time Tl.
In steps C4 and C5 the system control circuit 6 uses a difference signal di to generat.e the pulse signal Ps and the direction signal Pd, which are provided to the motor control circuit 7 and the counter 8. The pulse signal Ps comprises a predetermined number of driving pulses and the direction signal Pd has a polarity which depends on the comparison of di and dp. The motor control circuit 7 generates the stepping pulses with the pro~er polarity to move the optical head 2 radially of the disc 1 and, at the same time, the count in the counter 8 changes to provide a different actual count dp which represents the new position of the optical head 2. That movement of the optical head is shown in the block in Fig. 2 following step C5.
The optical head 2 is then operated momentarilv in the normal playback mode long enough to obtain address information Q from the disc 1. That address information Q
is converted by the deciphering circuit 13 into the resulting time signal TQ representing the time required to reach that particular location on the disc in a normal playhack modeO In step C6 the resulting time TQ is compared with the designated time Ti to obtain a time difference signal Ui Q (= Ti ~ TQ)' The time difference signal Ui_Q is compared with a first coarse-reference time Ul. The decision step Dl depicts that comparison. If Ui Q is less than or equal to Ul~ steps -~2-~Z~272~ S~3P154 C7, C8 and Cg are omitted and the next calculation step that takes place is C10.
If Ui Q is greater than Ul, indicating that it woulcl take longer than the coarse-reference time Ul of playing time to reach the designated position on the disc from the optical head's actual position, the step C7 is performed. In step C~ the system control circuit 6 again calculates the number of steps and the direction of rotation required for the motor S to move the optical head 2 from the location of the address information Q to the designated location di, by using the resulting time TQ. The pulse and direction signals Ps and Pd, as shown by step C8, again cause the optical head 2.
Ps and Pd are also supplied to the counter 8, so that the actual count dp provided by the counter output CO
still has a value that corresponds to the radial distance from the reference location at the beginning of the spiral track.
The disc 1 is again read long enough to obtain again address information Q that represents the actual position of the optical head 2 relative to the beginning of the track on the disc 1. The time data TQ thus obtained from Q by the deciphering circuit 13 is used to calculate Ti TQ, as represented by step Cg. The magnitude of that difference is used by the system control circuit 6 to provide the signal J to the jumping pulse generating circuit 14, which pr~vides a jumping pulse Pj to the tracking control circuit 4, as depicted by the step C10 in Fig. 2.
The tracking control circuit 4 generates a fine-adjustment signal using the jumping pulse Pj. The SOl~22 ~2~27~ S83P154 fine-adjustment signal is in a form identical to the signal provided by the tracklng con~rol circuit 4 in response to the tracking error cletection circuit , that is, a direct current signal. The fine-adjustment signal is provided with a voltage which is proportional to the difference between the designated time Ti and the resulting time T~ last read from the disc.
The tracking device used to change the position of the laser in the optical head 2 relative to the disc 1 has a conventional and well-known configuration. For example, the optical head 2 may be rotably mounted on an axis substantially normal to the disc surface. The laser is directed at the disc from a location on the optical head displaced from that axis. A coil surrounds the optical head such that the magnitude and polarity of a dc signal supplied to the coil causes the optical head to rotate about the axis and thereby move the location of the laser relative to the disc surface.
In any case, the fine-adjustment signal causes the optical head to direct the laser against the disc at a track that is displaced from the location of the last-provided address information Q, which is the track-jumping operation depicted in Fig. 2. ~he address in_ormation Q is read from the disc at that location and is converted by the deciphering circuit 13 into another resulting time signal r TQ.
At the same time, the fine-adjustment signal is provided through the low-pass filter 15 to the input terminal n4 of the system control circuit 6. The system control circuit 6 generates the driving signal (Ps and Pd~
1~2~ S83Pl5~
which causes ~he stepping motor 5 to move the optical head 2 and increments the counter 8 to change dpo As shown in step C11, the designated time Ti and ~he result,ing time TQ are compa,red. The resul-t Ui Q of that comparison is checked against a fine-reference time UO. If the time difference signal Ui Q is less than or equal to UO, then the search operation is ended. However, if Ui Q is greater than UO, steps C10, C11 and D2 are repeated.
Thus, a ine~adjustment process is accomplished by direct use of the address information aftex a coarse~
adjustment which initially uses driving pulses to quickly move the optical head to a loca-~ion very close -to the designated location and then indirectly uses address information driving pulses if the initial movement of the optical head is not to within an acceptable distance from the designated location.
The present invention has been described by reerring to a specific embodiment thereof. Those skilled in -the art will recognize that modifications other than those specifically referred to can be made in that embodiment without departing from the spirit of the invention. For that reason the scope of the in~ention is not to be limited by the above description but instead is defined solely by the claims which follow.
~ -15-.;
Claims (19)
1. Apparatus for reproducing program information from designated location on a disc having recorded thereon program information in a spiral track using a pick-up means movable along the track in a normal playback mode for reproducing the program information and transversely across adjacent tracks generally radially of the disc the apparatus comprising:
driving means for moving the pick-up means from a reference location transversely across adjacent tracks on the disc in response to driving pulses supplied thereto;
counter means for providing an actual count of driving pulses supplied to said driving means; and system control means for providing a designated count of driving pulses representing the distance transversely across adjacent tracks between said reference location and said designated location and producing a driving signal including a predetermined number of driving pulses representing the difference between said designated count and said actual count for supply to said driving means.
driving means for moving the pick-up means from a reference location transversely across adjacent tracks on the disc in response to driving pulses supplied thereto;
counter means for providing an actual count of driving pulses supplied to said driving means; and system control means for providing a designated count of driving pulses representing the distance transversely across adjacent tracks between said reference location and said designated location and producing a driving signal including a predetermined number of driving pulses representing the difference between said designated count and said actual count for supply to said driving means.
2. Apparatus as in claim 1; wherein said reference location is disposed substantially at the beginning of the spiral track and said apparatus further comprises clearing means for setting said actual count to a reference count when said pick-up means is in said reference location.
3. Apparatus as in claim 2; wherein said reference count is zero.
4. Apparatus as in claim 2; wherein said clearing means is contacted by said pick-up means when said pick-up means is disposed substantially at the beginning of the track for providing a clearing signal for setting said counter means to zero.
5. Apparatus as in claim 3; wherein said driving signal further includes a direction signal having two states for respectively moving the pick-up means generally radially outwardly and inwardly.
6. Apparatus as in claim 5; wherein said actual count increases and decreases in response to said respective states of said direction signal.
7. Apparatus as in claim 6; wherein states of said direction signal correspond to the polarity thereof and said actual count increases when said direction signal has a positive polarity and thereby provides generally radially outward movement of said pick-up means and decreases when said direction signal has a negative polarity and thereby provides generally radially inward movement of said pick-up means.
8. Apparatus as in claim 7; wherein said driving means includes:
a stepping motor for moving said pick-up means in discrete steps in response to stepping pulses supplied thereto; and a motor control circuit for providing one said stepping pulse to said stepping motor in response to each said driving pulse and moving said stepping motor in a first direction in response to one said state of said direction signal and in a second direction in response to the other said state of said direction signal.
a stepping motor for moving said pick-up means in discrete steps in response to stepping pulses supplied thereto; and a motor control circuit for providing one said stepping pulse to said stepping motor in response to each said driving pulse and moving said stepping motor in a first direction in response to one said state of said direction signal and in a second direction in response to the other said state of said direction signal.
9. Apparatus as in claim 8; wherein the disc is digitally recorded with program information recorded in segments in the spiral track and the pick up means comprises an optical head operable in a normal reproducing mode in which the spiral track is traced generally radially outwardly.
10. Apparatus as in claim 9; further comprising designating means for providing a designating signal representing the radial distance from the beginning of the spiral track to the designated location, wherein said system control means generates said designated count using said designating signal.
11. Apparatus as in claim 10; wherein:
the disc includes a digitally recorded table of contents at the beginning of the spiral track, which table of contents comprises data representing the normal playback time required to reach the start of each program segment from the beginning of the spiral track;
said designating signal identifies to said system control means the particular program segment containing the designated program information and the normal playback time from the beginning of the particular program segment to the designated location; and said system control means stores the table of contents received from the optical head and provides said designated count of driving pulses in response to the table of contents and the designating signal.
the disc includes a digitally recorded table of contents at the beginning of the spiral track, which table of contents comprises data representing the normal playback time required to reach the start of each program segment from the beginning of the spiral track;
said designating signal identifies to said system control means the particular program segment containing the designated program information and the normal playback time from the beginning of the particular program segment to the designated location; and said system control means stores the table of contents received from the optical head and provides said designated count of driving pulses in response to the table of contents and the designating signal.
12. An apparatus as in claim 11; wherein said system control means compares said actual count and said designated count and provides said predetermined number of driving pulses and said direction signal in response to said comparison.
13. An apparatus as in claim 12; further comprising a deciphering circuit for converting address information recorded on the disc for identifying particular program information and provided by said optical head into a resulting normal playback time required by said optical head to reach the resulting address information from the beginning of the spiral track, wherein:
said system control means converts said designating signal into a designated time representing the normal playback time from the beginning of the track to the designated location; and said deciphering circuit provides said resulting time to said system control means after the optical head has been moved in response to said driving signal and has read said resulting address information for comparison with said designated time to obtain a time difference signal representing the difference between said resulting time and said designated time.
said system control means converts said designating signal into a designated time representing the normal playback time from the beginning of the track to the designated location; and said deciphering circuit provides said resulting time to said system control means after the optical head has been moved in response to said driving signal and has read said resulting address information for comparison with said designated time to obtain a time difference signal representing the difference between said resulting time and said designated time.
14. Apparatus as in claim 13; wherein, if said time difference signal is greater than a coarse-reference signal, said system control means provides a resulting count representing the distance between said resulting address information and the beginning of the spiral track, compares said resulting count and said designated count and provides a plurality of driving pulses and a direction signal in response to said comparison.
15. Apparatus as in claim 14; wherein the optical head includes means for directing a light beam in a predetermined location on the disc and a tracking means for changing said location in response to a tracking signal, and, if said time difference signal is less than said coarse-reference signal, said system control means actuates said tracking means to change said location an amount proportional to said time difference signal.
16. Apparatus as in claim 15; further comprising:
a jumping pulse generating circuit for providing a jumping pulse in response to a jump signal provided by said system control means representing said time difference signal; and a tracking control circuit for providing a tracking signal in response to said jumping pulse for actuating said tracking means.
a jumping pulse generating circuit for providing a jumping pulse in response to a jump signal provided by said system control means representing said time difference signal; and a tracking control circuit for providing a tracking signal in response to said jumping pulse for actuating said tracking means.
17. Apparatus as in claim 16; further comprising a low pass filter, wherein:
said tracking means changes the location of said light beam an amount proportional to the dc voltage supplied thereto;
said tracking control circuit provides said tracking signal as a dc pulse with a voltage proportional to said time difference signal;
said dc pulse is provided to said system control means for generation of a driving signal for moving said optical head an amount corresponding to the change in location caused by said tracking signal.
said tracking means changes the location of said light beam an amount proportional to the dc voltage supplied thereto;
said tracking control circuit provides said tracking signal as a dc pulse with a voltage proportional to said time difference signal;
said dc pulse is provided to said system control means for generation of a driving signal for moving said optical head an amount corresponding to the change in location caused by said tracking signal.
18. Apparatus as in claim 17; wherein said optical head provides resulting address information to said deciphering circuit after the location of said light beam has been changed, and said deciphering circuit provides said resulting time to said system control means for comparison with said designated time to obtain said time difference signal.
19. Apparatus as in claim 18; wherein, if said time difference signal is greater than a fine-reference signal, said system control means provides said jumping pulse and, if said time difference is less than or equal to said fine-reference signal, said optical head is operated in is normal playback mode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP148094/82 | 1982-08-25 | ||
| JP57148094A JPS5938976A (en) | 1982-08-25 | 1982-08-25 | Disk reproducer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1202720A true CA1202720A (en) | 1986-04-01 |
Family
ID=15445101
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000435187A Expired CA1202720A (en) | 1982-08-25 | 1983-08-23 | Apparatus for reproducing designated information from a recorded disc |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5938976A (en) |
| KR (1) | KR910006076B1 (en) |
| AU (1) | AU563615B2 (en) |
| CA (1) | CA1202720A (en) |
| DE (1) | DE3330544A1 (en) |
| FR (1) | FR2532460B1 (en) |
| GB (1) | GB2127176B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5012460A (en) * | 1985-05-31 | 1991-04-30 | Information Storage, Inc. | RAM head positioning and tracking system |
| JP2624698B2 (en) * | 1987-08-07 | 1997-06-25 | 株式会社東芝 | Disc playback device |
| JP2716226B2 (en) * | 1989-11-28 | 1998-02-18 | 出光石油化学株式会社 | Articulators and packaging bags with articulators |
| ATE172407T1 (en) * | 1993-01-19 | 1998-11-15 | Canon Kk | RECORDING DEVICE |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3789378A (en) * | 1971-05-24 | 1974-01-29 | Olivetti & Co Spa | Transducer positioning mechanism |
| JPS559355B2 (en) * | 1972-05-17 | 1980-03-10 | ||
| US3956766A (en) * | 1974-11-25 | 1976-05-11 | International Business Machines Corporation | Counter resetting circuitry for magnetic disk system |
| FR2349191A1 (en) * | 1976-04-23 | 1977-11-18 | Thomson Brandt | OPTICAL INFORMATION DISC READER INCLUDING AN AUTOMATIC INFORMATION ACCESS DEVICE |
| JPS5916348B2 (en) * | 1977-11-29 | 1984-04-14 | 日本ビクター株式会社 | Information truck position search control method |
| FR2409572B1 (en) * | 1977-11-22 | 1985-10-04 | Victor Company Of Japan | SELECTIVE ACCESS DEVICE FOR REPRODUCING APPARATUS WITH ROTATING RECORDING MEDIUM |
| DE2949015A1 (en) * | 1979-12-06 | 1981-06-11 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Position finding system for video or sound disc - uses data stored in memory to compare distance between reference signal along track and required position |
| JPS5737744A (en) * | 1980-08-20 | 1982-03-02 | Teac Co | Retrieving method of disk device |
| JPS5760540A (en) * | 1980-09-30 | 1982-04-12 | Fujitsu Ltd | Track accessing system for optical disc |
-
1982
- 1982-08-25 JP JP57148094A patent/JPS5938976A/en active Pending
-
1983
- 1983-08-23 CA CA000435187A patent/CA1202720A/en not_active Expired
- 1983-08-24 AU AU18380/83A patent/AU563615B2/en not_active Ceased
- 1983-08-24 DE DE3330544A patent/DE3330544A1/en active Granted
- 1983-08-24 GB GB08322706A patent/GB2127176B/en not_active Expired
- 1983-08-25 FR FR838313720A patent/FR2532460B1/en not_active Expired - Lifetime
- 1983-08-25 KR KR1019830003985A patent/KR910006076B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2532460A1 (en) | 1984-03-02 |
| FR2532460B1 (en) | 1992-03-27 |
| DE3330544C2 (en) | 1992-03-05 |
| JPS5938976A (en) | 1984-03-03 |
| KR910006076B1 (en) | 1991-08-12 |
| GB2127176A (en) | 1984-04-04 |
| AU563615B2 (en) | 1987-07-16 |
| GB8322706D0 (en) | 1983-09-28 |
| GB2127176B (en) | 1986-04-30 |
| AU1838083A (en) | 1984-03-01 |
| KR840005870A (en) | 1984-11-19 |
| DE3330544A1 (en) | 1984-03-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |