CA1103351A - Binary coded digital optical record - Google Patents
Binary coded digital optical recordInfo
- Publication number
- CA1103351A CA1103351A CA293,421A CA293421A CA1103351A CA 1103351 A CA1103351 A CA 1103351A CA 293421 A CA293421 A CA 293421A CA 1103351 A CA1103351 A CA 1103351A
- Authority
- CA
- Canada
- Prior art keywords
- data
- bit
- spots
- track
- signal
- 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
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
- G11B7/24085—Pits
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/14—Digital recording or reproducing using self-clocking codes
- G11B20/1403—Digital recording or reproducing using self-clocking codes characterised by the use of two levels
- G11B20/1407—Digital recording or reproducing using self-clocking codes characterised by the use of two levels code representation depending on a single bit, i.e. where a one is always represented by a first code symbol while a zero is always represented by a second code symbol
- G11B20/1419—Digital recording or reproducing using self-clocking codes characterised by the use of two levels code representation depending on a single bit, i.e. where a one is always represented by a first code symbol while a zero is always represented by a second code symbol to or from biphase level coding, i.e. to or from codes where a one is coded as a transition from a high to a low level during the middle of a bit cell and a zero is encoded as a transition from a low to a high level during the middle of a bit cell or vice versa, e.g. split phase code, Manchester code conversion to or from biphase space or mark coding, i.e. to or from codes where there is a transition at the beginning of every bit cell and a one has no second transition and a zero has a second transition one half of a bit period later or vice versa, e.g. double frequency code, FM code
Abstract
Abstract A digital optical record with a data track of data spots and spaces arranged in an improved binary code is described along with a playback apparatus for such record which produces an electrical readout signal of narrow frequency band width. A greater bit storage density is achieved on the record because the minimum length of the data spots and spaces is increased to the width, W, of a single bit data zone, thereby enabling a readout light beam of a larger diameter. In addition, the electrical readout signal has an increased signal-to-noise ratio because the maximum length of the data spots and of the data spaces between spots is reduced to 2W
reducing the dynamic range over which the signal must be extracted. The improved code accomplishes these ad-vantages for optical recording by providing data spot to space light transitions in the middle of the bit data zones for "1" bits and by spot to space light transitions at the trailing boundaries of the data zones for "0" bits, except that not light transition occurs at the boundary when the "0" bit is followed by a "1" bit.
reducing the dynamic range over which the signal must be extracted. The improved code accomplishes these ad-vantages for optical recording by providing data spot to space light transitions in the middle of the bit data zones for "1" bits and by spot to space light transitions at the trailing boundaries of the data zones for "0" bits, except that not light transition occurs at the boundary when the "0" bit is followed by a "1" bit.
Description
JC:srd 20789-94 11/30/77 ~U335~
The subject matter of the present invention relates to digital optical recording with binary coded data spots and spaces, to improved binary coded digital optical records and to playback apparatus for such records.
In particular, the digital optical records of the present invention employ an improved binary code so that the length of the data spots and the spaces between such spots is reduced to a narrower range with a higher mini-mum length and a lower maximum length. As a result, a readout signal of narrower frequency band width is pro-duced when such records are played back. Also, the size of the readout light beam is increased relative to the width of the data zone for a single bit, thereby enabling higher density storage of optical data. The present in-vention is especially useful for digital optical records which store video television signals, in digital optical data tracks on such records, and for playback apparatus producing an electrical readout signal of the data track on such records. However, it can be used for storing and playing back any type of data on digital optical records.
In recording binary coded digital signals on an optical record, a light beam is turned on and off or modulated by the data signal to be recorded as such beam is scanned across a photosensitive surface of the record.
As a result, an optical data track of binary coded data spots and spaces between such spots is recorded on the record, as shown in U. S. Patent 3,501,586 of Russell, granted March 17, 1970. The data spots may be of light reflective material, or of light opaque material, in which case the spaces between such spots are light transparent.
JC:srd 20789-94 11/30/77 ~1~33Sl The playback apparatus scans an unmodulated light beam along the data track, and thereby causes light to be re-flected from the data spots in the first case, or light to be transmitted through the spaces between spots in the second case, to a photoelectric light detector which pro-duces a corresponding electrical readout signal.
When using optical records, the amplitude of the readout signal produced by the photodetector is pro-portional to the area of the light beam diameter and the area of the data spots or the spaces between spots or both.
Thus, the amplitude of the readout signal increases with both the length of the spots and the length of the spaces between spots. In addition, the frequency band width of the readout signal is also dependent upon the length of the data spots and the spaces between such spots. A
narrow band width readout signal is produced by reducing the maximum length of the spots and the spaces. In ad-dition, the minimum length of the data spots and spaces between spots determines the size of the light beam which can be used during recording and playback since it must be slightly smaller than such minimum spots and spaces.
Conversely, the size of the light beam limits the minimum size of the data spots and spaces. l'herefore, for maxi-mum storage density the smallest data spot or space should be the same size as the space occupied by a single data bit, hereafter referred to as a "data zone."
The two most commonly used binary codes for digital optical recording are the non-return to zero (NRZ~
code and the Manchester code, both of which suffer from one or more of the above-described defects when such codes are applied to optical recording. Both the NRZ and liQ3351 Manchester codes, which were developed for and have been used extensively in magnetic recording, are described in United States Patent 3,108,261 of Miller, granted October 22, 1963. Also described in this patent are the re+urn to zero binary code and another code similar to that of the present invention that was developed many years ago to solve some of the problems which are unique to magnetic recording and playback, but do not occur in optical record-ing and playback. Magnetic recording and playback depends upon detection of changes in magnetic flux, usually a reversal of polarity, and is proportional to a derivative of the magnetic flux, rather than the area of the recorded magnetic spot. ~hus, in magnetic recording and playback, storage density is limited by the maximum number of flux changes per unit length of magnetic tape or other magnetic medium which can be recorded, stored and detected.
Because of the fundamental differences between the principles involved in magnetic recording and playback and optical recording and playback, the binary code of this patent has not been used previously for optical recording, even though such code has long been used for magnetic recording, as shown in United States Patent 3,235,855 of Woo, granted February 15, 1966; United States Patent 3,774,178 of Curtis, granted October 20, 1973; and United States Patent 3,864,735 of Davis et al, granted February 4, 1975.
In accordance with the present invention, there is provided a binary coded digital optical data record comprising:
an optical data storage medium;
at least one optical data track recorded on said storage medium to provide a plurality of laterally spaced track positions;
said data track being divided into a plurality of successive bit data zones which have binary digital coded data spots and data spaces of di~ferent light transmission or light reflection characteristics recorded therein, each bit data zone having a width measured longitudinally along the track equal to a single binary bit, at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at i~3351 intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
and said data spots having a length in a range of between a minimum of one times and a maximum of two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range for greater bit storage density and less dynamic range of change in spot length thereby enabling a record playback signal of higher signal to noise ratio.
In accordance with another aspect of the invention, there is provid-ed playback apparatus including scanner means for scanning an optical data track on a digital optical data record with a light beam in which the improve-ment comprises:
said record having at least one optical data track including binary coded data spots and spaces forming a plurality of successive binary bit data zones at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at an intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
said data spots having a length in a range of between one and two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range; and said scanner means including a photoelectric light detector means which upon receipt of the scanned light beam produces an electrical readout signal corresponding to said first and second spot-space tr~nsitions in said data track, said readout signal being amplitude modulated in accordance with the length of said data spots and data spaces.
- 3a -J
11(133Sl It is an object of the present invention to provide a digital optical record having an improved data track of binary coded data spots and data spaces recorded thereon, which is capable of high data storage density and which produces an electrical readout JC:srd 20789-94 11/30/77 ~103;~Sl signal of narrow frequency band width upon playback.
Another object of the invention is to provide such a digital optical record using an improved binary code in which the maximum lengths of the data spots and the data spaces are reduced to provide the electrical readout signal of narrow band width and of higher signal-to-noise ratio.
A further object of the invention is to pro-vide such an improved digital optical record in which the minimum length of the data spots and data spaces is in-creased to enable greater data storage density and the use of a readout light beam of larger diameter relative to the width of a bit data zone.
An additional object of the present invention is to provide such an improved digital optical record in which the optical data track is self-clocking.
Still another object of the present invention is to provide an improved playback apparatus for scanning such optical record with a light beam to produce an electrical readout signal of narrower band width and in-creased signal-to-noise ratio.
A still further object of the invention is to provide such a playback apparatus which employs a band pass filter at the output of the photoelectric detector to transmit the readout signal through such filter so that the following electrical circuits of the playback apparatus need not be D.C. coupled.
Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof and from the attached drawings, of which:
JC:srd 20789-94 11/30/77 11033Si Fig. 1 shows the light readout signals pro-duced during playback of digital optical records having binary coded data tracks using the improved binary code in accordance with the present invention and using two other codes transmitting the same binary data;
Fig. 2 is a schematic diagram showing two data tracks of different digital optical records, one using the binary code of the present invention and the other an NRZ code, together with the electrical readout signals produced by scanning each of such data tracks with a light beam during playback; and Fig. 3 is a block diagram of a playback ap-paratus in accordance with the present invention.
The differences between the binary coded digi-tal optical record of the present invention and those using conventional binary codes is clear from their light readout signals of Fig. 1. ~s shown in Fig. lC, a digi-tal optical record having a data track of binary coded data spots and data spaces arranged in the present code produces a readout light signal 10. This light signal varies between a minimum or no light level A and a max-imum light level B, corresponding to the binary data re-corded in the data track on such record, such data being indicated in Fig. lB. The binary data includes "1" and "0" bits which are each provided in one of the fifteen bit data zones of Fig. lA. Each of the bit data zones has a width "W" corresponding to the width of a single bit. The light signal 10 produced by the present binary code has intermediate light transitions 12 in an inter-mediate position between the end boundaries of the "1"bits which are substantially in the center of the data JC:srd 20789-94 11/30/77 11033~1 zones corresponding to such "1" bits. In addition, the readout light signal 10 is provided with boundary light transitions 14 at the trailing edge boundaries of the "0"
bits except when such "0" bit is followed by a "1" bit.
Thus, the "0" bit in the second data zone does not pro-duce a boundary light transition because it is followed by a "1" bit in the third data zone, while the "0" bit in the fifth data zone produces a boundary light trans-ition 14, because it is followed by another "0" bit in the sixth data zone.
Fig. lD shows a readout light signal 16 of a data track having data spots and spaces arranged in the non-return to zero, or NRZ, binary code. The NRZ read-out signal 16 has boundary light transitions 14 at the ends of both the "1" bits and the "0" bits unless such bits are followed immediately by a bit of the same type.
Thus, for light signal 16, the "1" bit in the third data zone does not produce a boundary light transition at its trailing edge because it is immediatel,7 followed by another "1" bit in the fourth data zone. However, the "1" bit in the fourth data zone is provided with a boundary light transition 14 at its trailing edge be-cause it is followed by a "0" bit. It should be noted that the NRZ readout light signal has no intermediate light transitions 12 in the middle of the data zones of either type of bit. As a result, the maximum length of the longest light pulse or longest space between light pulses is 3W or more, and is greater than the maximum length 2W of the longest light pulses and spaces of the light signal 10. While the maximum light pulse length in the NRZ readout signal 16 of Fig. lD is shown to be JC:srd 20789-94 11/30/77 ~1()3;3SI
3W, it can actually be much greater, as hereafter dis-cussed with reference to Fig. 2. This is a disadvantage because the electrical readout signals of NRZ coded data tracks, produced by such light signals, have a greater amplitude variation or swing and a wider frequency band width.
Fig. lE shows the readout light signal 18 for a digital optical record having a data track of binary coded data spots and data spaces using the Manchester binary code. As shown, the Manchester code readout signal 18 includes intermediate light transitions 12 in the centers of both the "0" and "1" bits, and also in-cludes boundary light transitions 14 at the ends of "0"
and "1" bits. In the Manchester code light signal 18 the intermediate light transitions 12 in the center of the "0" bits and the "1" bits extend in opposite direc-tions in order to distinguish such bits. Thus, in Fig.
lE, positive going intermediate light transitions 12 indicate "0" bits, while negative going intermediate transitions 12 indicate "1" bits. This has the dîsad-vantage that the minimum data spot length or minimum data space length is equal to W/2 or 1/2 the width of a single bit data zone. Since the readout light beam which plays back such minimum length spot or space must be of small~r size than such spot or space, such beam is slightly less than W/2 in diameter in the case of a circular beam. This reduces data storage density.
The minimum useful diameter of a readout light beam currently possible is approximately one micron.
This means that when using the Manchester code, the bit data zones must be two microns in width, W, or twice that JC:srd 20789-94 11/30/77 . ~
liO3351 of the bit data zones used in either the NRZ code signal or the present coded signal. Thus, the minimum length data spot or space using either the NRZ or the present code is equal to W, not W/2, as is clearly shown in Figs. lC and lD.
It should be noted that in Fig. 1 the light level B of each of the readout light signals 10, 16 and 18 corresponds to either the presence of a spot when a light reflecting data spot is employed, or the presence of a data space when light transparent spaces and opaque spots are employed. However, in either case the length of the light pulses corresponds to the length of either the data spot or the data space, as the case may be.
As shown in Fig. 2C, a data track recorded on a digital optical record in accordance with the present binary code includes three types of data spots 20, 22 and 24 of three different lengths, W, 3/2W and 2W, re-spectively. Similarly, such data track includes three types of data spaces 26, 28 and 30 of three different lengths, W, 3/2W and 2W, respectively, where W is the width of a single bit data zone. An electrical readout signal 32, produced by scanning the data track of Fig.
lC longitudinally with a reading light beam 34, is shown in Fig. 2D. The signal amplitude of the electrical read-out signal 32 varies between a minimum voltage V of one unit and a maximum voltage 3V of three units. Thus, the dynamic range of the amplitude swing of readout signal 32 is 2V, or the difference between its maximum amplitude and the minimum amplitude. It should be noted that these are relative voltage units and not actual voltages.
In contrast, a data track of NRZ binary coded JC:srd 20789-94 11/30/77 ~lQ3351 data spots and spaces on a digital optical record is shown in Fig. 2A. This track includes extremely large data spots 36 having a maximum length equal to 7W or seven times the width of a single bit data zone. Thus, the large data spot 36 is produced when seven successive "1" bits are recorded using the NRZ code. Similarly, a large data space 38 having a length equal to 6W, or six times the width of a single bit data zone, is recorded when six consecutive "0" bits occur in the NRZ coded track. Thus, it can be seen that the longest data spots and data spaces necessary to record binary information using the NRZ code greatly exceed the maximum length 2W
of the longest data spots 24 and the longest data spaces 30 in the data track of Fig. lC, using the present code.
As a result, an electrical readout signal 40 in Fig. 2B
of much larger amplitude swing is produced when the reading light beam 34 is scanned along the NRZ coded data track of Fig. 2A.
As shown in Fig. 2B, the readout signal 40 varies from a minimum amplitude having a voltage V of one unit to a maximum amplitude having a voltage lOV of ten units. Thus, the dynamic range of the amplitude swing of the electrical readout signal 40 is equal to 9V. This is much greater than the amplitude swing of the readout signal 32 produced by the data track of the present invention shown in Fig. 2C. For the two examples of data tracks shown in Figs. 2A and 2C, the dynamic range of a readout signal 32 produced when playing back the data track of the present invention is less than 1/4 that of the dynamic range produced by the NRZ coded data track. This also means that the frequency band width of JC:srd 20789-94 11/30/77 liO33Sl the electrical readout signal 32 is much narrower than that of readout signal 40. The different band widths are due to the lower frequency limit of the readout signal 40 of the NRZ data track being much less than that of the readout signal 32 because of the long flat amplitude signal portions corresponding to the large data spot 36 and the large data space 38. In one ex-ample, the frequency band width of the electrical read-out signal 32 produced by the data track of the present invention is in a range between a lower limit of 6.25 megahertz and an upper limit of 12.5 megahertz, while the frequency band width of the NRZ coded data track readout signal 40 is in a range from a lower limit of 15 kilohertz to an upper limit of 12.5 megahertz. Thus the upper limit frequency is only twice the lower limit frequency for the band width of the electrical readout signal 32 produced by the data track of the present in-vention. However, the ratio of the upper limit frequency to the lower limit frequency of the band width of the NRZ
coded track readout signal 40 is over 800 to 1.
Fig. 3 shows a block diagram of one type of record playback apparatus which can be employed with the digital optical record of the present invention. Such playback apparatus includes a light source 42, which may be a laser or other suitable focused light source device, for producing a narrow beam of light that can be used as the playback light beam 34 for scanning the data track of the optical record. The light beam is transmitted through a scanner mechanism 44 which deflects such beam to scan it along the data track. The scanner 44 may be like that disclosed in the above-mentioned U. S. Patent JC:srd 20789-g4 11/30/77 ~103351 3,501,586 of Russell when a fixed data record is em-ployed, or it may be like that shown in Canadian patent application No. 232,631 , when a moving data record is employed. A digital optical data record 46, having a data track of data spots and data spaces which are binary coded in accordance with the present invention, is pro-vided in the path of the light beam 34 emitted from scanner 44. This light beam 34 is scanned longitudinally along the data track so it is modulated by the spots and spaces in such data track as it is transmitted through the record, to produce a modulated light beam 48 which is transmitted to a photoelectric detector 50. This light beam 48 is modulated in accordance with the binary coded data ln the form of the readout light signal 10 of Fig. 1.
The photoelectric detector 50 converts the readout light signal into an electrical readout signal similar to signal 32 shown in Fig. 2D. The electrical readout signal is transmitted through a band pass filter 52 having an upper limit frequency Fl which is approxi-mately twice that of its lower limit frequency F2. Thus for electrical readout signal 32 of the frequency band width given in the above example, Fl is 12.5 megahertz and F2 is 6.25 megahertz. The output of the filter 52 is transmitted through an A.C. coupling capacitor 53 to an amplifier 54 having an automatic gain control. After amplification, the electrical readout signal is trans-mitted from amplifier 54 through another coupling capa-citor 55 to one input of a threshold circuit 56 whose other input is connected to a D.C. reference voltage on the movable contact 58 of a potentiometer which may be JC:srd 20789-94 12/1/77 ~IQ33Sl varied to control the output of such threshold circuit.
The threshold circuit is a bistable switchlng circuit which converts the analog readout signal 32 into a binary level output signal. The output of the thres-hold circuit switches positive when signal 32 exceeds the reference voltage and switches negative when such signal goes below such reference voltage, thereby pro-ducing output voltage levels corresponding to the "0"
and "1" bits of the electrical readout signal 32. The threshold output signal is transmitted to a clock sync generator and digital decoder logic circuit 60, which produces a sync pulse output 62 and a digital data out-put 64, in the form of binary coded digital pulses suitable for transmission to an electronic computer.
The data output signal at 64 may be of the same binary code as the optical data on record 46, or it may be converted by the circuit 60 into another code which is more easily processed by the digital computer to which it is connected. Of course, the sync pulses at output 62 are fed to a clock in order to synchro-nize such clock to the digital data output pulses at output 64 for transmit~ing such data pulses into the computer. It should be noted that the presence of the band pass filter 52 greatly simplifies the remainder of the playback circuitry 54, 56 and 60 connected to the output of such filter, since these circuits do not have to be D.C. coupled.
It will be obvious to those having ordinary skill in the art that many changes may be ma2e in the above described details of the preferred embodiment of the present invention without departing from the spirit JC:srd 20789-94 12/1~77 ~1~3351 of the invention. For example, a light reflecting op-tical data record can be employed rather than the trans-missive data record 46 shown in the playback system of Fig. 3, in which case the photodetector is positioned on the same side of the data record as the light source 42 and scanner 44, and other appropriate changes are made in the apparatus. Therefore, the scope of the present invention should only be determined by the following claims.
The subject matter of the present invention relates to digital optical recording with binary coded data spots and spaces, to improved binary coded digital optical records and to playback apparatus for such records.
In particular, the digital optical records of the present invention employ an improved binary code so that the length of the data spots and the spaces between such spots is reduced to a narrower range with a higher mini-mum length and a lower maximum length. As a result, a readout signal of narrower frequency band width is pro-duced when such records are played back. Also, the size of the readout light beam is increased relative to the width of the data zone for a single bit, thereby enabling higher density storage of optical data. The present in-vention is especially useful for digital optical records which store video television signals, in digital optical data tracks on such records, and for playback apparatus producing an electrical readout signal of the data track on such records. However, it can be used for storing and playing back any type of data on digital optical records.
In recording binary coded digital signals on an optical record, a light beam is turned on and off or modulated by the data signal to be recorded as such beam is scanned across a photosensitive surface of the record.
As a result, an optical data track of binary coded data spots and spaces between such spots is recorded on the record, as shown in U. S. Patent 3,501,586 of Russell, granted March 17, 1970. The data spots may be of light reflective material, or of light opaque material, in which case the spaces between such spots are light transparent.
JC:srd 20789-94 11/30/77 ~1~33Sl The playback apparatus scans an unmodulated light beam along the data track, and thereby causes light to be re-flected from the data spots in the first case, or light to be transmitted through the spaces between spots in the second case, to a photoelectric light detector which pro-duces a corresponding electrical readout signal.
When using optical records, the amplitude of the readout signal produced by the photodetector is pro-portional to the area of the light beam diameter and the area of the data spots or the spaces between spots or both.
Thus, the amplitude of the readout signal increases with both the length of the spots and the length of the spaces between spots. In addition, the frequency band width of the readout signal is also dependent upon the length of the data spots and the spaces between such spots. A
narrow band width readout signal is produced by reducing the maximum length of the spots and the spaces. In ad-dition, the minimum length of the data spots and spaces between spots determines the size of the light beam which can be used during recording and playback since it must be slightly smaller than such minimum spots and spaces.
Conversely, the size of the light beam limits the minimum size of the data spots and spaces. l'herefore, for maxi-mum storage density the smallest data spot or space should be the same size as the space occupied by a single data bit, hereafter referred to as a "data zone."
The two most commonly used binary codes for digital optical recording are the non-return to zero (NRZ~
code and the Manchester code, both of which suffer from one or more of the above-described defects when such codes are applied to optical recording. Both the NRZ and liQ3351 Manchester codes, which were developed for and have been used extensively in magnetic recording, are described in United States Patent 3,108,261 of Miller, granted October 22, 1963. Also described in this patent are the re+urn to zero binary code and another code similar to that of the present invention that was developed many years ago to solve some of the problems which are unique to magnetic recording and playback, but do not occur in optical record-ing and playback. Magnetic recording and playback depends upon detection of changes in magnetic flux, usually a reversal of polarity, and is proportional to a derivative of the magnetic flux, rather than the area of the recorded magnetic spot. ~hus, in magnetic recording and playback, storage density is limited by the maximum number of flux changes per unit length of magnetic tape or other magnetic medium which can be recorded, stored and detected.
Because of the fundamental differences between the principles involved in magnetic recording and playback and optical recording and playback, the binary code of this patent has not been used previously for optical recording, even though such code has long been used for magnetic recording, as shown in United States Patent 3,235,855 of Woo, granted February 15, 1966; United States Patent 3,774,178 of Curtis, granted October 20, 1973; and United States Patent 3,864,735 of Davis et al, granted February 4, 1975.
In accordance with the present invention, there is provided a binary coded digital optical data record comprising:
an optical data storage medium;
at least one optical data track recorded on said storage medium to provide a plurality of laterally spaced track positions;
said data track being divided into a plurality of successive bit data zones which have binary digital coded data spots and data spaces of di~ferent light transmission or light reflection characteristics recorded therein, each bit data zone having a width measured longitudinally along the track equal to a single binary bit, at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at i~3351 intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
and said data spots having a length in a range of between a minimum of one times and a maximum of two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range for greater bit storage density and less dynamic range of change in spot length thereby enabling a record playback signal of higher signal to noise ratio.
In accordance with another aspect of the invention, there is provid-ed playback apparatus including scanner means for scanning an optical data track on a digital optical data record with a light beam in which the improve-ment comprises:
said record having at least one optical data track including binary coded data spots and spaces forming a plurality of successive binary bit data zones at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at an intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
said data spots having a length in a range of between one and two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range; and said scanner means including a photoelectric light detector means which upon receipt of the scanned light beam produces an electrical readout signal corresponding to said first and second spot-space tr~nsitions in said data track, said readout signal being amplitude modulated in accordance with the length of said data spots and data spaces.
- 3a -J
11(133Sl It is an object of the present invention to provide a digital optical record having an improved data track of binary coded data spots and data spaces recorded thereon, which is capable of high data storage density and which produces an electrical readout JC:srd 20789-94 11/30/77 ~103;~Sl signal of narrow frequency band width upon playback.
Another object of the invention is to provide such a digital optical record using an improved binary code in which the maximum lengths of the data spots and the data spaces are reduced to provide the electrical readout signal of narrow band width and of higher signal-to-noise ratio.
A further object of the invention is to pro-vide such an improved digital optical record in which the minimum length of the data spots and data spaces is in-creased to enable greater data storage density and the use of a readout light beam of larger diameter relative to the width of a bit data zone.
An additional object of the present invention is to provide such an improved digital optical record in which the optical data track is self-clocking.
Still another object of the present invention is to provide an improved playback apparatus for scanning such optical record with a light beam to produce an electrical readout signal of narrower band width and in-creased signal-to-noise ratio.
A still further object of the invention is to provide such a playback apparatus which employs a band pass filter at the output of the photoelectric detector to transmit the readout signal through such filter so that the following electrical circuits of the playback apparatus need not be D.C. coupled.
Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof and from the attached drawings, of which:
JC:srd 20789-94 11/30/77 11033Si Fig. 1 shows the light readout signals pro-duced during playback of digital optical records having binary coded data tracks using the improved binary code in accordance with the present invention and using two other codes transmitting the same binary data;
Fig. 2 is a schematic diagram showing two data tracks of different digital optical records, one using the binary code of the present invention and the other an NRZ code, together with the electrical readout signals produced by scanning each of such data tracks with a light beam during playback; and Fig. 3 is a block diagram of a playback ap-paratus in accordance with the present invention.
The differences between the binary coded digi-tal optical record of the present invention and those using conventional binary codes is clear from their light readout signals of Fig. 1. ~s shown in Fig. lC, a digi-tal optical record having a data track of binary coded data spots and data spaces arranged in the present code produces a readout light signal 10. This light signal varies between a minimum or no light level A and a max-imum light level B, corresponding to the binary data re-corded in the data track on such record, such data being indicated in Fig. lB. The binary data includes "1" and "0" bits which are each provided in one of the fifteen bit data zones of Fig. lA. Each of the bit data zones has a width "W" corresponding to the width of a single bit. The light signal 10 produced by the present binary code has intermediate light transitions 12 in an inter-mediate position between the end boundaries of the "1"bits which are substantially in the center of the data JC:srd 20789-94 11/30/77 11033~1 zones corresponding to such "1" bits. In addition, the readout light signal 10 is provided with boundary light transitions 14 at the trailing edge boundaries of the "0"
bits except when such "0" bit is followed by a "1" bit.
Thus, the "0" bit in the second data zone does not pro-duce a boundary light transition because it is followed by a "1" bit in the third data zone, while the "0" bit in the fifth data zone produces a boundary light trans-ition 14, because it is followed by another "0" bit in the sixth data zone.
Fig. lD shows a readout light signal 16 of a data track having data spots and spaces arranged in the non-return to zero, or NRZ, binary code. The NRZ read-out signal 16 has boundary light transitions 14 at the ends of both the "1" bits and the "0" bits unless such bits are followed immediately by a bit of the same type.
Thus, for light signal 16, the "1" bit in the third data zone does not produce a boundary light transition at its trailing edge because it is immediatel,7 followed by another "1" bit in the fourth data zone. However, the "1" bit in the fourth data zone is provided with a boundary light transition 14 at its trailing edge be-cause it is followed by a "0" bit. It should be noted that the NRZ readout light signal has no intermediate light transitions 12 in the middle of the data zones of either type of bit. As a result, the maximum length of the longest light pulse or longest space between light pulses is 3W or more, and is greater than the maximum length 2W of the longest light pulses and spaces of the light signal 10. While the maximum light pulse length in the NRZ readout signal 16 of Fig. lD is shown to be JC:srd 20789-94 11/30/77 ~1()3;3SI
3W, it can actually be much greater, as hereafter dis-cussed with reference to Fig. 2. This is a disadvantage because the electrical readout signals of NRZ coded data tracks, produced by such light signals, have a greater amplitude variation or swing and a wider frequency band width.
Fig. lE shows the readout light signal 18 for a digital optical record having a data track of binary coded data spots and data spaces using the Manchester binary code. As shown, the Manchester code readout signal 18 includes intermediate light transitions 12 in the centers of both the "0" and "1" bits, and also in-cludes boundary light transitions 14 at the ends of "0"
and "1" bits. In the Manchester code light signal 18 the intermediate light transitions 12 in the center of the "0" bits and the "1" bits extend in opposite direc-tions in order to distinguish such bits. Thus, in Fig.
lE, positive going intermediate light transitions 12 indicate "0" bits, while negative going intermediate transitions 12 indicate "1" bits. This has the dîsad-vantage that the minimum data spot length or minimum data space length is equal to W/2 or 1/2 the width of a single bit data zone. Since the readout light beam which plays back such minimum length spot or space must be of small~r size than such spot or space, such beam is slightly less than W/2 in diameter in the case of a circular beam. This reduces data storage density.
The minimum useful diameter of a readout light beam currently possible is approximately one micron.
This means that when using the Manchester code, the bit data zones must be two microns in width, W, or twice that JC:srd 20789-94 11/30/77 . ~
liO3351 of the bit data zones used in either the NRZ code signal or the present coded signal. Thus, the minimum length data spot or space using either the NRZ or the present code is equal to W, not W/2, as is clearly shown in Figs. lC and lD.
It should be noted that in Fig. 1 the light level B of each of the readout light signals 10, 16 and 18 corresponds to either the presence of a spot when a light reflecting data spot is employed, or the presence of a data space when light transparent spaces and opaque spots are employed. However, in either case the length of the light pulses corresponds to the length of either the data spot or the data space, as the case may be.
As shown in Fig. 2C, a data track recorded on a digital optical record in accordance with the present binary code includes three types of data spots 20, 22 and 24 of three different lengths, W, 3/2W and 2W, re-spectively. Similarly, such data track includes three types of data spaces 26, 28 and 30 of three different lengths, W, 3/2W and 2W, respectively, where W is the width of a single bit data zone. An electrical readout signal 32, produced by scanning the data track of Fig.
lC longitudinally with a reading light beam 34, is shown in Fig. 2D. The signal amplitude of the electrical read-out signal 32 varies between a minimum voltage V of one unit and a maximum voltage 3V of three units. Thus, the dynamic range of the amplitude swing of readout signal 32 is 2V, or the difference between its maximum amplitude and the minimum amplitude. It should be noted that these are relative voltage units and not actual voltages.
In contrast, a data track of NRZ binary coded JC:srd 20789-94 11/30/77 ~lQ3351 data spots and spaces on a digital optical record is shown in Fig. 2A. This track includes extremely large data spots 36 having a maximum length equal to 7W or seven times the width of a single bit data zone. Thus, the large data spot 36 is produced when seven successive "1" bits are recorded using the NRZ code. Similarly, a large data space 38 having a length equal to 6W, or six times the width of a single bit data zone, is recorded when six consecutive "0" bits occur in the NRZ coded track. Thus, it can be seen that the longest data spots and data spaces necessary to record binary information using the NRZ code greatly exceed the maximum length 2W
of the longest data spots 24 and the longest data spaces 30 in the data track of Fig. lC, using the present code.
As a result, an electrical readout signal 40 in Fig. 2B
of much larger amplitude swing is produced when the reading light beam 34 is scanned along the NRZ coded data track of Fig. 2A.
As shown in Fig. 2B, the readout signal 40 varies from a minimum amplitude having a voltage V of one unit to a maximum amplitude having a voltage lOV of ten units. Thus, the dynamic range of the amplitude swing of the electrical readout signal 40 is equal to 9V. This is much greater than the amplitude swing of the readout signal 32 produced by the data track of the present invention shown in Fig. 2C. For the two examples of data tracks shown in Figs. 2A and 2C, the dynamic range of a readout signal 32 produced when playing back the data track of the present invention is less than 1/4 that of the dynamic range produced by the NRZ coded data track. This also means that the frequency band width of JC:srd 20789-94 11/30/77 liO33Sl the electrical readout signal 32 is much narrower than that of readout signal 40. The different band widths are due to the lower frequency limit of the readout signal 40 of the NRZ data track being much less than that of the readout signal 32 because of the long flat amplitude signal portions corresponding to the large data spot 36 and the large data space 38. In one ex-ample, the frequency band width of the electrical read-out signal 32 produced by the data track of the present invention is in a range between a lower limit of 6.25 megahertz and an upper limit of 12.5 megahertz, while the frequency band width of the NRZ coded data track readout signal 40 is in a range from a lower limit of 15 kilohertz to an upper limit of 12.5 megahertz. Thus the upper limit frequency is only twice the lower limit frequency for the band width of the electrical readout signal 32 produced by the data track of the present in-vention. However, the ratio of the upper limit frequency to the lower limit frequency of the band width of the NRZ
coded track readout signal 40 is over 800 to 1.
Fig. 3 shows a block diagram of one type of record playback apparatus which can be employed with the digital optical record of the present invention. Such playback apparatus includes a light source 42, which may be a laser or other suitable focused light source device, for producing a narrow beam of light that can be used as the playback light beam 34 for scanning the data track of the optical record. The light beam is transmitted through a scanner mechanism 44 which deflects such beam to scan it along the data track. The scanner 44 may be like that disclosed in the above-mentioned U. S. Patent JC:srd 20789-g4 11/30/77 ~103351 3,501,586 of Russell when a fixed data record is em-ployed, or it may be like that shown in Canadian patent application No. 232,631 , when a moving data record is employed. A digital optical data record 46, having a data track of data spots and data spaces which are binary coded in accordance with the present invention, is pro-vided in the path of the light beam 34 emitted from scanner 44. This light beam 34 is scanned longitudinally along the data track so it is modulated by the spots and spaces in such data track as it is transmitted through the record, to produce a modulated light beam 48 which is transmitted to a photoelectric detector 50. This light beam 48 is modulated in accordance with the binary coded data ln the form of the readout light signal 10 of Fig. 1.
The photoelectric detector 50 converts the readout light signal into an electrical readout signal similar to signal 32 shown in Fig. 2D. The electrical readout signal is transmitted through a band pass filter 52 having an upper limit frequency Fl which is approxi-mately twice that of its lower limit frequency F2. Thus for electrical readout signal 32 of the frequency band width given in the above example, Fl is 12.5 megahertz and F2 is 6.25 megahertz. The output of the filter 52 is transmitted through an A.C. coupling capacitor 53 to an amplifier 54 having an automatic gain control. After amplification, the electrical readout signal is trans-mitted from amplifier 54 through another coupling capa-citor 55 to one input of a threshold circuit 56 whose other input is connected to a D.C. reference voltage on the movable contact 58 of a potentiometer which may be JC:srd 20789-94 12/1/77 ~IQ33Sl varied to control the output of such threshold circuit.
The threshold circuit is a bistable switchlng circuit which converts the analog readout signal 32 into a binary level output signal. The output of the thres-hold circuit switches positive when signal 32 exceeds the reference voltage and switches negative when such signal goes below such reference voltage, thereby pro-ducing output voltage levels corresponding to the "0"
and "1" bits of the electrical readout signal 32. The threshold output signal is transmitted to a clock sync generator and digital decoder logic circuit 60, which produces a sync pulse output 62 and a digital data out-put 64, in the form of binary coded digital pulses suitable for transmission to an electronic computer.
The data output signal at 64 may be of the same binary code as the optical data on record 46, or it may be converted by the circuit 60 into another code which is more easily processed by the digital computer to which it is connected. Of course, the sync pulses at output 62 are fed to a clock in order to synchro-nize such clock to the digital data output pulses at output 64 for transmit~ing such data pulses into the computer. It should be noted that the presence of the band pass filter 52 greatly simplifies the remainder of the playback circuitry 54, 56 and 60 connected to the output of such filter, since these circuits do not have to be D.C. coupled.
It will be obvious to those having ordinary skill in the art that many changes may be ma2e in the above described details of the preferred embodiment of the present invention without departing from the spirit JC:srd 20789-94 12/1~77 ~1~3351 of the invention. For example, a light reflecting op-tical data record can be employed rather than the trans-missive data record 46 shown in the playback system of Fig. 3, in which case the photodetector is positioned on the same side of the data record as the light source 42 and scanner 44, and other appropriate changes are made in the apparatus. Therefore, the scope of the present invention should only be determined by the following claims.
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A binary coded digital optical data record comprising:
an optical data storage medium;
at least one optical data track recorded on said storage medium to provide a plurality of laterally spaced track positions;
said data track being divided into a plurality of successive bit data zones which have binary digital coded data spots and data spaces of dif-ferent light transmission or light reflection characteristics recorded there-in, each bit data zone having a width measured longitudinally along the track equal to a single binary bit, at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at an intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
and said data spots having a length in a range of between a minimum of one times and a maximum of two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range for greater bit storage density and less dynamic range of change in spot length thereby enabling a record playback signal of higher signal to noise ratio.
an optical data storage medium;
at least one optical data track recorded on said storage medium to provide a plurality of laterally spaced track positions;
said data track being divided into a plurality of successive bit data zones which have binary digital coded data spots and data spaces of dif-ferent light transmission or light reflection characteristics recorded there-in, each bit data zone having a width measured longitudinally along the track equal to a single binary bit, at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at an intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
and said data spots having a length in a range of between a minimum of one times and a maximum of two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range for greater bit storage density and less dynamic range of change in spot length thereby enabling a record playback signal of higher signal to noise ratio.
2. A data record in accordance with claim 1 in which the data spots are all of the same width, and are of different lengths equal to 1, 3/2 or 2 times the data zone width.
3. A data record in accordance with claim 1 in which the data spots are light opaque and the data spaces are light transparent.
4. A data record in accordance with claim 1 in which the data spots are light reflective and the data spaces are nonreflective.
5. A data record in accordance with claim 1 in which the first spot-space transitions are in the middle of the data zones.
6. Playback apparatus including scanner means for scanning an optical data track on a digital optical data record with a light beam in which the improvement comprises:
said record having at least one optical data track including binary coded data spots and spaces forming a plurality of successive binary bit data zones at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at an intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
said data spots having a length in a range of between one and two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range; and said scanner means including a photoelectric light detector means which upon receipt of the scanned light beam produces an electrical readout signal corresponding to said first and second spot-space transitions in said data track, said readout signal being amplitude modulated in accordance with the length of said data spots and data spaces.
said record having at least one optical data track including binary coded data spots and spaces forming a plurality of successive binary bit data zones at least some of said data spots having a length longitudinally along the track greater than its height laterally of said track;
said data track including first spot-space transitions each at an intermediate position between the opposite ends of a bit data zone correspond-ing to one type of bit and including second spot-space transitions each at the trailing end of a data zone corresponding to the other type of bit except where said other type of bit is immediately followed by said one type of bit;
said data spots having a length in a range of between one and two times the width of a single data zone, and successive data spots being spaced apart by a spacing distance also in said range; and said scanner means including a photoelectric light detector means which upon receipt of the scanned light beam produces an electrical readout signal corresponding to said first and second spot-space transitions in said data track, said readout signal being amplitude modulated in accordance with the length of said data spots and data spaces.
7. Playback apparatus in accordance with claim 6 in which the readout signal is amplitude modulated and has increased signal-to-noise ratio with the maximum amplitude portion of the signal being about three times the minimum amplitude portion.
8. Playback apparatus in accordance with claim 6 in which the output of the light detector is connected to a narrow frequency band pass filter.
9. Playback apparatus in accordance with claim 8 in which the upper frequency limit of the filter is about twice the lower frequency limit of said filter.
10. Playback apparatus in accordance with claim 7 in which the output of the filter is A.C. coupled to subsequent circuits.
11. Playback apparatus in accordance with claim 6 in which the light beam has a diameter substan-tially equal to the width of one data zone.
12. Playback apparatus in accordance with claim 6 in which the light detector integrates the light signal corresponding to the area of the data spot or data space to produce the readout signal.
13. Playback apparatus in accordance with claim 7 in which the output of the filter is connected to a threshold circuit which converts the analog light detector readout signal into a binary coded digital data output signal.
14. Playback apparatus in accordance with claim 13 in which the output of the threshold circuit is connected to a clock pulse generator circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US76356777A | 1977-01-28 | 1977-01-28 | |
| US763,567 | 1977-01-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1103351A true CA1103351A (en) | 1981-06-16 |
Family
ID=25068187
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA293,421A Expired CA1103351A (en) | 1977-01-28 | 1977-12-19 | Binary coded digital optical record |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5395603A (en) |
| CA (1) | CA1103351A (en) |
| DE (1) | DE2803603A1 (en) |
| FR (1) | FR2379129A1 (en) |
| GB (1) | GB1570799A (en) |
| NL (1) | NL7800613A (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7811003A (en) * | 1978-11-06 | 1980-05-08 | Philips Nv | DISC-SHAPED, OPTICALLY READABLE RECORD CARRIER, AS A STORAGE MEDIUM FOR DATA INFORMATION. |
| NL8000121A (en) * | 1980-01-09 | 1981-08-03 | Philips Nv | DISC-SHAPED, OPTICALLY READABLE RECORD CARRIER AS A STORAGE MEDIUM FOR DATA INFORMATION, DEVICE FOR MANUFACTURING SUCH RECORD CARRIER, DEVICE FOR RECORDING DATA INFORMATION RECORDER AND RECORD. |
| NL8000122A (en) * | 1980-01-09 | 1981-08-03 | Philips Nv | DISC-SHAPED, OPTICALLY-READABLE RECORD CARRIER AS A STORAGE MEDIUM FOR DATA INFORMATION, DEVICE FOR MANUFACTURING SUCH REGISTRATION CARRIER, DEVICE FOR RECORDING AND / OR DISPLAYING DATA INFORMATION IN C.Q. OF SUCH REGISTRATION CARRIER. |
| NL8000124A (en) * | 1980-01-09 | 1981-08-03 | Philips Nv | DEVICE FOR DISPLAYING DIGITALLY-CODED INFORMATION APPLIED ON AN OPTICALLY READABLE DISC REGISTRATION CARRIER. |
| US5253244A (en) * | 1980-07-16 | 1993-10-12 | Discovision Associates | System for recording digital information in a pulse-length modulation format |
| US5553047A (en) * | 1980-07-16 | 1996-09-03 | Discovision Associates | System for recording digital information in a pulse-length modulation format |
| US5577015A (en) * | 1980-07-16 | 1996-11-19 | Discovision Associates | System for recording digital information in a pulse-length modulation |
| US4532616A (en) * | 1982-06-03 | 1985-07-30 | News Log International, Inc. | Method for optically encoding digital data on a substrate and the data record carrier formed thereby |
| DE10224372A1 (en) * | 2002-05-24 | 2003-12-11 | Jenoptik Automatisierungstech | Code-reading method for applying/reading out encoding of any length on moving material uses a laser beam switched on and off by controlling electronics |
| DE102009039808A1 (en) | 2009-07-06 | 2011-01-13 | GM Global Technology Operations, Inc., Detroit | Rear floor assembly and frame structure of a self-supporting vehicle body |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3108261A (en) * | 1960-04-11 | 1963-10-22 | Ampex | Recording and/or reproducing system |
| FR1437760A (en) * | 1964-04-15 | 1966-05-06 | Itek Corp | Method and device for data processing |
| US3365706A (en) * | 1964-04-15 | 1968-01-23 | Gilbert W. King | Photo-optical data storage and retrieval system employing error detection and error location identification components |
| US3501586A (en) * | 1966-09-01 | 1970-03-17 | Battelle Development Corp | Analog to digital to optical photographic recording and playback system |
| DE2132512A1 (en) * | 1971-06-30 | 1973-02-15 | Licentia Gmbh | DEVICE FOR RECORDING BITS BY A BEAM ON A RECORDING MEDIUM |
| NL7413162A (en) * | 1974-10-07 | 1976-04-09 | Philips Nv | DEVICE FOR READING A DISK-SHAPED RECORDING CARRIER. |
-
1977
- 1977-12-16 GB GB52536/77A patent/GB1570799A/en not_active Expired
- 1977-12-19 CA CA293,421A patent/CA1103351A/en not_active Expired
-
1978
- 1978-01-13 FR FR7800965A patent/FR2379129A1/en not_active Withdrawn
- 1978-01-18 NL NL7800613A patent/NL7800613A/en not_active Application Discontinuation
- 1978-01-26 JP JP781978A patent/JPS5395603A/en active Pending
- 1978-01-27 DE DE19782803603 patent/DE2803603A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FR2379129A1 (en) | 1978-08-25 |
| DE2803603A1 (en) | 1978-08-03 |
| JPS5395603A (en) | 1978-08-22 |
| NL7800613A (en) | 1978-08-01 |
| GB1570799A (en) | 1980-07-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5128916A (en) | Optical disc with alternating servo patterns and driving apparatus therefor | |
| KR100606255B1 (en) | Information recording apparatus | |
| EP0245511A4 (en) | Optical card reader. | |
| CA1103351A (en) | Binary coded digital optical record | |
| US5796692A (en) | Data reproducing method and apparatus for determining the interval between pits on a recording medium from a modulated read-out signal | |
| US5410527A (en) | Information recording/reproducing apparatus including setting optimum recording condition or reproducing condition | |
| AU705350B2 (en) | Method and apparatus for retreiving data from a storage device | |
| JP2602493B2 (en) | Optical data recording device | |
| US5027339A (en) | Optical card analyzing apparatus | |
| JPS6038765A (en) | Signal shaping method and apparatus | |
| CA2242195C (en) | Method and device for recording data in an optical memory card | |
| EP0817180B1 (en) | Optical data storage and retrieval system and method | |
| US5053610A (en) | Reading apparatus and photodetector for optical recording medium | |
| US5327410A (en) | Direction-determination logic as for a signal pickup in recorded signal recovery apparatus | |
| JP2637603B2 (en) | Optical information recording / reproducing method | |
| JP2598146B2 (en) | Optical information recording / reproducing method | |
| KR950020296A (en) | Optical reader | |
| US5473591A (en) | Method for recording and reproducing data on recording mediums | |
| AU6418690A (en) | Detector circuit | |
| JP2637595B2 (en) | Optical information recording / reproducing method | |
| US4189783A (en) | Mass storage of books | |
| JPS60160067A (en) | Information reproducer | |
| US5181196A (en) | Erase mark detecting circuit for detecting an erase mark superimposed on data recorded on a sector of an optical recording medium | |
| EP0302507A2 (en) | Optical card recording/playing back apparatus | |
| JPH01204226A (en) | Data recording system for optical disk device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |