CA1235500A - Apparatus for reading a disc-shaped record carrier - Google Patents
Apparatus for reading a disc-shaped record carrierInfo
- Publication number
- CA1235500A CA1235500A CA000462123A CA462123A CA1235500A CA 1235500 A CA1235500 A CA 1235500A CA 000462123 A CA000462123 A CA 000462123A CA 462123 A CA462123 A CA 462123A CA 1235500 A CA1235500 A CA 1235500A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- jump
- address code
- light beam
- record carrier
- 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
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
-
- 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
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
- G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
- G11B7/08517—Methods for track change, selection or preliminary positioning by moving the head with tracking pull-in only
-
- 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
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
- G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
- G11B7/08529—Methods and circuits to control the velocity of the head as it traverses the tracks
- G11B7/08535—Methods and circuits to control the velocity of the head as it traverses the tracks to maintain constant velocity during the traverse
-
- 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
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
- G11B7/08547—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements
- G11B7/08564—Arrangements for positioning the light beam only without moving the head, e.g. using static electro-optical elements using galvanomirrors
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/76—Television signal recording
- H04N5/7605—Television signal recording on discs or drums
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S358/00—Facsimile and static presentation processing
- Y10S358/907—Track skippers, i.e. "groove skippers"
Abstract
ABSTRACT:
"Apparatus or reading a disc-shaped record carrier"
The invention relates to a video-disc player in which by controlling a pivotal mirror rapid jumps over a large number of tracks can be made substantially within the field-blanking interval. In order to minimize the picture disturbance the jump is always started at the instant at which the duration of the remaining period until just before the address code within the next field blanking interval is equal to the anticipated duration of the jump to be per-formed, in particular by measuring the time which has elapsed since the previous read-out of an address code.
"Apparatus or reading a disc-shaped record carrier"
The invention relates to a video-disc player in which by controlling a pivotal mirror rapid jumps over a large number of tracks can be made substantially within the field-blanking interval. In order to minimize the picture disturbance the jump is always started at the instant at which the duration of the remaining period until just before the address code within the next field blanking interval is equal to the anticipated duration of the jump to be per-formed, in particular by measuring the time which has elapsed since the previous read-out of an address code.
Description
~355~
PUN 10.766 l 1.1~1983 Apparatus for reading a disc-shaped record carrier The invention relates to an apparatus for reading a disc-shaped record carrier in which video signals are recorded in substantially spiral tracks in such a way that corresponding picture elements of consecutive pictures are situated at substantially the same circumferential position on said record carrier, an address code being contained in at least one of the-two fields of each video picture in said video signals at a predetermined position in the field blanking interval lo after the field-synchronizing pulse, which apparatus comprises:
an optical system -for aiming a light beam at the record carrier, said light beam being modulated by the record carrier, and -for converting said modulated light beam into an electric signal, a converter for converting said electric signal into a radial tracking-error signal which corresponds to the radial position of the landing spot of the light beam relative to a desired track, positioning means for controlling the position o-f the landing spot o-f the light beam as a function of the radial tracking-error signal, a jump-signal generator for generating a control signal for causing the landing spout of the light beam to be shifted over a predetermined distance in response to a jump signal, and means for applying said control signal to the positioning means during said jump.
Such apparatus is inter aria the video-disc player which is commercially available from No Phillips' Gl~ilampenfabrieken under the designation "Laser vision"
and which its described inter aria in the magazine "Phillips Technical Review", Vol. 33, 1973, No. 7, pages 177-193 and - ~3~5C~
PUN 10.766 2 1.12~1983 United States Patent Specification No RYE 29,9630 In this known apparatus a jump of one or a few tracks is made in order to obtain still picture, slow motion etc.
In said apparatus a predetermined signal is applied via the field synchronizing pulse during the field-blanking interval in order to obtain a jump of the positioning means over a specific distance.
For some use 9 such as in interactive video disc players which cooperate with a game computer, it is lo desirable to have the possibility of changing the scene being reproduced, for which purpose the landing spot of the laser beam must be changed very rapidly over a large number of tracks in a radial direction by the positioning means, for example a pivotal mirror, though it is also possible to use other actuators such as linearly moving actuators. In particular because in such a case a plurality of scenes may have been recorded in parallel and may change prom -track to track, it is essential that such a jump in a radial direction ends at the desired track, because otherwise a scene other than -the desired scene it reached. In order to be able to ascertain immediately whether a jump is correct, it is therefore necessary that the address code can be read aster the jump and that consequently the jump is always terminated before said address code is read, It is the object of -the invention to provide an apparatus of the type specified in -the opening paragraph by means of which said jumps can be effected in such a manner that -they always terminate before said address code 30 and in such a manner that the disturbance of the picture is minimal To this end the inven~on is characterized by means or generating a first signal which is a continuous measure of the duration of the period of time 35 up to a reference point in the field blanking interval which point precedes said address code, means for generating a second signal under commend of the jump signal, which second signal is a measure of KIWI
PUN 10,766 3 1012019c3 the anticipated duration of the jump to be performed in response to said command, and means for continuously comparing said first and said second signet and, in relation to the instant at which the two durations correspond, generating a start signal for the jump-signal generator at least if said instant appears prior to the field-synchronizing pulse preceding said address code, The steps in accordance with the invention ensure lo that the jumps always terminate prior to the read-out of the address code. Maximum jumps longer than the field blanking interval are permissible without the picture being disturbed significantly because the video signal of the preceding field is disturbed only and not to more than lo the necessary extent if the jumps are longer than the field blanking intervals 9 said disturbance then appearing in the lower lines of the picture in only one field during a change of scene.
With respect to the means for generating the 20 first signal the apparatus may further be characterized in that said means for generating the first signal comprise counting means which are started each time -that an address code appears.
The invention will now be described in more 25 detail, by way of example with reference to the drawings in which:
Fig, 1 shows an apparatus in accordance with the invention, Fig. 2 shows some diagrams to explain the 30 operation of the apparatus shown in Fig. 1, Fig, 3 shows a version of the jump-signal generator 14 in the apparatus shown in Fig. 1, Fig, 4 shows some diagrams to explain the operation of a part of the generator shown in Fig, 3, and Fig shows some diagrams representing the various signals which appear when a jump is performed by means of the jump-signal generator shown in Fig. 30 `" i~355~)~
PUN 10.766 4 Fig 1 shows an apparatus in accordance with the invention for reading a rotating optically readable record carrier 1. For the purpose of reading a light beam emitted by a laser 2 is projected on the record carrier via a pivotal mirror 3 and an objective 4, the beam which is reflected by this record carrier being pro-jetted on a detector 6 via a semi-transparent mirror 5.
Specifically in the case of ALP the laser beam comprises one main beam two sub-beams and the detector comprises 3 sub-de~ectors, so that by means of one tracking-error signal generator 15 a signal can be obtained which is a measure of the position of the landing spot of the laser beam relative to information tracks on the record carrier 1. By means of this signal the position of said spot is controlled in that the entire optical system 16 can be moved in a radial direction by means of a mechanism 22, ` shown symbolically, and in that the mirror 3 can be tilted by means of a motor 7, enabling the landing spot of the beam to be moved over a limited number of tracks in a rapid and accurate manner. This is described comprehend lively in inter aria the magazine Phillips Technical Review, Vol. 33, 1973, No. 7, pages 186,189, United States Patent Specification 4,037,252, and German Patent Apply-cation no. 31.21.013, which has been laid open to public inspection.
Fig. pa schematically represents the structure of a video signal which has been read from the record car-nor 1. For each picture said signal comprises two field synchronizing pulses So and So, which after 16 picture lines are each followed by two picture lines (17 and 18) containing an address code tin principle it is also posy sidle to use only one address code per picture. The visible part of the picture extends from line 21 up to line 262.5 (NTSC).
For some uses such as interactive players which cooperate with a game computer, it is desirable to be able to change the scene being reproduced without disturb-in the field sequence, for which purpose the landing .... .
I
PUN 10.766 5 1.1201983 spot of the laser beam must be shifted radially over a plurality of` tracks by means of the pivotal mirror 3.
In particular since for such a use a plurality of` scenes may have been recorded in parallel and may change from track to track it is essential that such a radial jump ends on the desired track because otherwise a scene other than the desired scene may be reached. In order to be able to ascertain directly whether such a jump is correct J
it is therefore necessary that the address code contained lo in lines 17 and 18 is read after -the jump and that the jump therefore always terminates before line 17 of the next field.
Since a picture disturbance of a few lines in the lower part of the picture during one field just before 15 a change of scene is not very annoying, the maximum number of tracks to be jumped can be selected in such a way that -the maximum jump starts a specific number offense before the last line of the visible video picture and terminates just before line 17 of the next field. In order to minimize 20 the picture disturbance the instant at which the jump begins is always selected so that a minimal number of`
lines of the visible video picture is disturbed, jumping being effected in such a way that, if possible, a jump is made before the next address code after receipt ox a jump 25 command. This is possible by continuously measuring the time still available until the next address code appears.
In the embodiment shown in Fig. 1 this is achieved as follows. A detection circuit 8 derives a signal for example shown in Fig 2b, which is synchronous with 30 the address code, or with line 17, from the video signal recovered by means of the detector 6. This signal each time starts a counter 99 which counts a counting signal supplied by a clock-signal generator loo This counter 9 then supplies a signal which is a continuous measure ox the 35 time which has elapsed after the read-out of the last address code and consequently of the time available until the appearance of the next address code, The jump command ~;~3~5~)~
PUN 10.766 6 1.12.1983 is applied to an input 11 as a signal which is a measure of the number of tracks to be jumped, for example in the form of a digital signal, In a circuit 12 this signal is converted into a signal which is a measure of the time required for this jump. By means of a comparator lo the time required is compared with the running time and a signal is generated when the time available until the appearance of the next address code corresponds to the time required. Fig. 2c shows an example of such a signal.
lo By means of this signal a jump-signal generator 14 is started, This jump-signal generator 14 controls a switch 23 which interrupts the connection between the tracking-error signal generator 15 and the motor 7, so that the motor 7 is controlled ho this jump-signal generator 14 lo until a jump of the desired number of tracks is obtained, For this purpose the jump-signal generator 14 receives a signal indicating the number of tracks to be jumped from input 11 and a signal which indicates the passage of the tracks and which is supplied by a tracking-signal generator 15, of which examples are described in the publications referred to.
In its simplest form the circuit 12 for generating a signal which is a measure of the time required for the jump can establish a linear relationship between the time required and the number of tracks to be jumped, If a more accurate relationship is required, the circuit 12 may perform an algorithm which defines said relation-ship or may contain a conversion table based on this relationship For example, allowance can be made for the 30 non-linearity of this relationship as a result of starting and braking the movement of the pivotal mirror 3. It it also possible to select a fixed jumping instant ho starting those jumps which require a time shorter than a specific time, for example all jumps requiring time 35 which is shorter than the time between the last visible picture line of the relevant field and the next address code, at the end of said last visible picture line, an -~.35~
PUN 10.766 7 1.12.1983 extreme jumping instant being defined only for longer jumps.
The -tracking-signal generator 157 in known manner, supplies a control signal to the drive motor via the 5 switch 23 9 in order to keep the laser beam aimed at the track to be followed when no jump is performed.
Fig. 3 shows a version of the jump-signal generator 14 D It comprises a control-signal generator 24 on whose input 25 a signal appears which via input 11 10 indicates the number of tracks to be jumped and on whose input 26 a starting signal from a comparator 13 (jig. 1) appears. On an output 28 a signal appears which sets the switch 23 to the position shown in Fig 1 for the duration of the jump. On an output 29 a signal appears which lo indicates -the direction of the jump. The radial tracking-error signal generator 15 is applied to an input 270 By means of a limiter 32 the signal is converted into a scurvy signal which when the laser beam moves over the tracks in the radial direction exhibits a period 23correspondirlg to the time interval between the consecutive track passages and has edges appearing in the centre of the tracks and midway between the tracks By means of an exclusive-OR-circuit 33 the signal is logically combined with the direction signal on output 29, so that a 25signal is obtained which is independent of the direction of -the jump. This signal is applied to input 34 of the control-signal generator 24 which counts the number of tracks passed by means of this signal. On output 30 the control-signal generator 24 supplies a logic signal from Ann ill~tant which appears a fixed time, for example 350/usecsO
after the start of the jump until the end of lie jump, and on output 31 the control-signal generator supplies a logic signal from the beginning of -the jump until an instant at which the number oil tracks to be jumped (n) minus a predetermined number of tracks (x) has been passed.
The jump-signal generator further comprises a first monostable multi vibrator circuit 35 which receives a I
PUN 10.766 8 1,12,1983 trigger signal T on an inverted trigger input To and a second monostable multi vibrator circuit 36 which receives the trigger signal T on the trigger input T, Via an exclusive-or-gate 37 this trigger signal To is supplied by the output of the exclusive-or-gate 33~ the gate 37 transferring this signal when a logic "1" appears on the other input of this gate 37. The monostable multi-vibrator circuits 35 and 36 are triggered by the signal on output 30 of the control signal generator 24 and their lo lime constant, i.e. the length of the pulse supplied, is changed over by the signal on the output 31 of the control circuit. The monos-table multi vibrators 35 and 36 supply signals To and To, respectively, which are combined with the trigger signal To in the logic circuit 48 to form 15 the signals To and To in conformity with the relationships :
To = Sty Sty To = Sty + To- 1 The operation of the two multi vibrators 35 and 36 and the circuit 48 will he described with reference to Fig. 4, which shows the signals To, To, To, To and Thy When ignoring a possible inversion depending on the direction of the jump, the signal To is the limited -tracking signal whose period is inversely proportional to the jumping speed. As it is triggered on its inverting trigger input, the rnul-tivibrator 35 supplies pulses of a fixed duration each starting at the trailing edges of the signal T , whilst the multi vibrator 36 supplies the same pulses starting at -the leading edges. The resulting signal To then has a relative pulse width which is proportional to the positive difference between the pulse width of the signal To and the pulse width of the signals To and To, determined by the time constant ox the multi vibrators, or a relative pulse width which is a measure of the extent to which the jumping speed deviates in a negative sense prom a nominal speed defined by the time constant of the 5Q~
Ply 100766 9 1.12.1983 multi vibrators. Similarly, the relative pulse width of the signal To is a measure of the extent to which the jumping speed deviates from said nominal speed in a positive sense.
The signals To and To are applied -to a commutator 38, which exchanges these signals depending on the jump direction indicated by the signal on output 29 Said signals To and To control switches 39 and 40 which supply a positive or a negative supply voltage -to output lo 29 or which makes the output floating, so that the motor 7 accelerates decelerates and freewheels,respectively.
The operation of the entire jump-signal generator 14 is explained with reference to Fig. 5, in which Fig. pa represents the jumping speed v as a function of time. Figs. 5b, 5c and Ed represent the signals on outputs 289 30 and 31 of the control-signal generator AL
Fig. ye shows the limited radial tracking-error signal, and Fig. of shows a control signal for the motor 7 on output 29.
At an instant to the comparator 13 supplies the starting command to input 26. Via output I (signal shown in Fig 5b) switch 23 is changed over Via output 31 (signal shown in Fin Ed) the time consent of the multi vibrators 35 and 36 is set to a small value 25 corresponding to a high nominal jumping speed, Until an instant if the signal on output 30 (signal shown in Fig 5c) remains low so that the two multi vibrators are inoperative, the signals To and To are low, the signal To is high and the signal To is low. During the period to 30 to if the motor 7 is then accelerated continuously (see Fig. pa). At the instant to the two multi vibrators are started and the signals To and To corresponding to the diagram shown in Fig. 4 are generated The jump is then performed with a substantially constant speed.
35 After the passage of the number of tracks to be jumped (n) minus a predetermined number of tracks (x) at the instant to the signal on output 31 (Fig Ed) switches so PUN 10.766 10 1,12~1983 the time Canaanite ox the multi vibrators to a high value corresponding to a low nominal speed, The circuit then also generates a train of braking pulses To until at instant to this lower nominal speed is reached Subset quaintly, the jump continues with said constant lower speed until a-t the instant to the number of tracks to be jumped minus half a -track is reached. A-t this instant the signal on output 28 resets the switch 23 (jig. 1) and locking-in to the desired track is effected via the tracking mechanism.
Since at the lower nominal speed the repetition frequency of the limited tracking error signal decreases substantially a signal on an input 42 is combined with the output signal of the exclusive-or-gate 33 by means ox the signal on output 31 via an or-gate 41 and an exclusive-or-gate 37. A signal which is 90 phase-shi~ted relative to the limited radial error signal is applied to this input 42. when the signal on output 31 is low, which is the case at the lower nominal speed, this signal is added to the limited radial tracking-error signal in the exclusive-or-gate 37, yielding a signal of twice the repetition frequency.
The device shown in Fig 3 may be designed so that or a jump ox less than a predetermined number of tracts (or example 25) the signal on output 31 go Ed) is kept low -throughout Jumping period, so that -the mirror is controlled directly towards -the lower ox the two speeds It is to be noted that the apparatus described herein may be wormed portly in particularly parts 9, 12, 13 and 24, by a microprocessor
PUN 10.766 l 1.1~1983 Apparatus for reading a disc-shaped record carrier The invention relates to an apparatus for reading a disc-shaped record carrier in which video signals are recorded in substantially spiral tracks in such a way that corresponding picture elements of consecutive pictures are situated at substantially the same circumferential position on said record carrier, an address code being contained in at least one of the-two fields of each video picture in said video signals at a predetermined position in the field blanking interval lo after the field-synchronizing pulse, which apparatus comprises:
an optical system -for aiming a light beam at the record carrier, said light beam being modulated by the record carrier, and -for converting said modulated light beam into an electric signal, a converter for converting said electric signal into a radial tracking-error signal which corresponds to the radial position of the landing spot of the light beam relative to a desired track, positioning means for controlling the position o-f the landing spot o-f the light beam as a function of the radial tracking-error signal, a jump-signal generator for generating a control signal for causing the landing spout of the light beam to be shifted over a predetermined distance in response to a jump signal, and means for applying said control signal to the positioning means during said jump.
Such apparatus is inter aria the video-disc player which is commercially available from No Phillips' Gl~ilampenfabrieken under the designation "Laser vision"
and which its described inter aria in the magazine "Phillips Technical Review", Vol. 33, 1973, No. 7, pages 177-193 and - ~3~5C~
PUN 10.766 2 1.12~1983 United States Patent Specification No RYE 29,9630 In this known apparatus a jump of one or a few tracks is made in order to obtain still picture, slow motion etc.
In said apparatus a predetermined signal is applied via the field synchronizing pulse during the field-blanking interval in order to obtain a jump of the positioning means over a specific distance.
For some use 9 such as in interactive video disc players which cooperate with a game computer, it is lo desirable to have the possibility of changing the scene being reproduced, for which purpose the landing spot of the laser beam must be changed very rapidly over a large number of tracks in a radial direction by the positioning means, for example a pivotal mirror, though it is also possible to use other actuators such as linearly moving actuators. In particular because in such a case a plurality of scenes may have been recorded in parallel and may change prom -track to track, it is essential that such a jump in a radial direction ends at the desired track, because otherwise a scene other than -the desired scene it reached. In order to be able to ascertain immediately whether a jump is correct, it is therefore necessary that the address code can be read aster the jump and that consequently the jump is always terminated before said address code is read, It is the object of -the invention to provide an apparatus of the type specified in -the opening paragraph by means of which said jumps can be effected in such a manner that -they always terminate before said address code 30 and in such a manner that the disturbance of the picture is minimal To this end the inven~on is characterized by means or generating a first signal which is a continuous measure of the duration of the period of time 35 up to a reference point in the field blanking interval which point precedes said address code, means for generating a second signal under commend of the jump signal, which second signal is a measure of KIWI
PUN 10,766 3 1012019c3 the anticipated duration of the jump to be performed in response to said command, and means for continuously comparing said first and said second signet and, in relation to the instant at which the two durations correspond, generating a start signal for the jump-signal generator at least if said instant appears prior to the field-synchronizing pulse preceding said address code, The steps in accordance with the invention ensure lo that the jumps always terminate prior to the read-out of the address code. Maximum jumps longer than the field blanking interval are permissible without the picture being disturbed significantly because the video signal of the preceding field is disturbed only and not to more than lo the necessary extent if the jumps are longer than the field blanking intervals 9 said disturbance then appearing in the lower lines of the picture in only one field during a change of scene.
With respect to the means for generating the 20 first signal the apparatus may further be characterized in that said means for generating the first signal comprise counting means which are started each time -that an address code appears.
The invention will now be described in more 25 detail, by way of example with reference to the drawings in which:
Fig, 1 shows an apparatus in accordance with the invention, Fig. 2 shows some diagrams to explain the 30 operation of the apparatus shown in Fig. 1, Fig, 3 shows a version of the jump-signal generator 14 in the apparatus shown in Fig. 1, Fig, 4 shows some diagrams to explain the operation of a part of the generator shown in Fig, 3, and Fig shows some diagrams representing the various signals which appear when a jump is performed by means of the jump-signal generator shown in Fig. 30 `" i~355~)~
PUN 10.766 4 Fig 1 shows an apparatus in accordance with the invention for reading a rotating optically readable record carrier 1. For the purpose of reading a light beam emitted by a laser 2 is projected on the record carrier via a pivotal mirror 3 and an objective 4, the beam which is reflected by this record carrier being pro-jetted on a detector 6 via a semi-transparent mirror 5.
Specifically in the case of ALP the laser beam comprises one main beam two sub-beams and the detector comprises 3 sub-de~ectors, so that by means of one tracking-error signal generator 15 a signal can be obtained which is a measure of the position of the landing spot of the laser beam relative to information tracks on the record carrier 1. By means of this signal the position of said spot is controlled in that the entire optical system 16 can be moved in a radial direction by means of a mechanism 22, ` shown symbolically, and in that the mirror 3 can be tilted by means of a motor 7, enabling the landing spot of the beam to be moved over a limited number of tracks in a rapid and accurate manner. This is described comprehend lively in inter aria the magazine Phillips Technical Review, Vol. 33, 1973, No. 7, pages 186,189, United States Patent Specification 4,037,252, and German Patent Apply-cation no. 31.21.013, which has been laid open to public inspection.
Fig. pa schematically represents the structure of a video signal which has been read from the record car-nor 1. For each picture said signal comprises two field synchronizing pulses So and So, which after 16 picture lines are each followed by two picture lines (17 and 18) containing an address code tin principle it is also posy sidle to use only one address code per picture. The visible part of the picture extends from line 21 up to line 262.5 (NTSC).
For some uses such as interactive players which cooperate with a game computer, it is desirable to be able to change the scene being reproduced without disturb-in the field sequence, for which purpose the landing .... .
I
PUN 10.766 5 1.1201983 spot of the laser beam must be shifted radially over a plurality of` tracks by means of the pivotal mirror 3.
In particular since for such a use a plurality of` scenes may have been recorded in parallel and may change from track to track it is essential that such a radial jump ends on the desired track because otherwise a scene other than the desired scene may be reached. In order to be able to ascertain directly whether such a jump is correct J
it is therefore necessary that the address code contained lo in lines 17 and 18 is read after -the jump and that the jump therefore always terminates before line 17 of the next field.
Since a picture disturbance of a few lines in the lower part of the picture during one field just before 15 a change of scene is not very annoying, the maximum number of tracks to be jumped can be selected in such a way that -the maximum jump starts a specific number offense before the last line of the visible video picture and terminates just before line 17 of the next field. In order to minimize 20 the picture disturbance the instant at which the jump begins is always selected so that a minimal number of`
lines of the visible video picture is disturbed, jumping being effected in such a way that, if possible, a jump is made before the next address code after receipt ox a jump 25 command. This is possible by continuously measuring the time still available until the next address code appears.
In the embodiment shown in Fig. 1 this is achieved as follows. A detection circuit 8 derives a signal for example shown in Fig 2b, which is synchronous with 30 the address code, or with line 17, from the video signal recovered by means of the detector 6. This signal each time starts a counter 99 which counts a counting signal supplied by a clock-signal generator loo This counter 9 then supplies a signal which is a continuous measure ox the 35 time which has elapsed after the read-out of the last address code and consequently of the time available until the appearance of the next address code, The jump command ~;~3~5~)~
PUN 10.766 6 1.12.1983 is applied to an input 11 as a signal which is a measure of the number of tracks to be jumped, for example in the form of a digital signal, In a circuit 12 this signal is converted into a signal which is a measure of the time required for this jump. By means of a comparator lo the time required is compared with the running time and a signal is generated when the time available until the appearance of the next address code corresponds to the time required. Fig. 2c shows an example of such a signal.
lo By means of this signal a jump-signal generator 14 is started, This jump-signal generator 14 controls a switch 23 which interrupts the connection between the tracking-error signal generator 15 and the motor 7, so that the motor 7 is controlled ho this jump-signal generator 14 lo until a jump of the desired number of tracks is obtained, For this purpose the jump-signal generator 14 receives a signal indicating the number of tracks to be jumped from input 11 and a signal which indicates the passage of the tracks and which is supplied by a tracking-signal generator 15, of which examples are described in the publications referred to.
In its simplest form the circuit 12 for generating a signal which is a measure of the time required for the jump can establish a linear relationship between the time required and the number of tracks to be jumped, If a more accurate relationship is required, the circuit 12 may perform an algorithm which defines said relation-ship or may contain a conversion table based on this relationship For example, allowance can be made for the 30 non-linearity of this relationship as a result of starting and braking the movement of the pivotal mirror 3. It it also possible to select a fixed jumping instant ho starting those jumps which require a time shorter than a specific time, for example all jumps requiring time 35 which is shorter than the time between the last visible picture line of the relevant field and the next address code, at the end of said last visible picture line, an -~.35~
PUN 10.766 7 1.12.1983 extreme jumping instant being defined only for longer jumps.
The -tracking-signal generator 157 in known manner, supplies a control signal to the drive motor via the 5 switch 23 9 in order to keep the laser beam aimed at the track to be followed when no jump is performed.
Fig. 3 shows a version of the jump-signal generator 14 D It comprises a control-signal generator 24 on whose input 25 a signal appears which via input 11 10 indicates the number of tracks to be jumped and on whose input 26 a starting signal from a comparator 13 (jig. 1) appears. On an output 28 a signal appears which sets the switch 23 to the position shown in Fig 1 for the duration of the jump. On an output 29 a signal appears which lo indicates -the direction of the jump. The radial tracking-error signal generator 15 is applied to an input 270 By means of a limiter 32 the signal is converted into a scurvy signal which when the laser beam moves over the tracks in the radial direction exhibits a period 23correspondirlg to the time interval between the consecutive track passages and has edges appearing in the centre of the tracks and midway between the tracks By means of an exclusive-OR-circuit 33 the signal is logically combined with the direction signal on output 29, so that a 25signal is obtained which is independent of the direction of -the jump. This signal is applied to input 34 of the control-signal generator 24 which counts the number of tracks passed by means of this signal. On output 30 the control-signal generator 24 supplies a logic signal from Ann ill~tant which appears a fixed time, for example 350/usecsO
after the start of the jump until the end of lie jump, and on output 31 the control-signal generator supplies a logic signal from the beginning of -the jump until an instant at which the number oil tracks to be jumped (n) minus a predetermined number of tracks (x) has been passed.
The jump-signal generator further comprises a first monostable multi vibrator circuit 35 which receives a I
PUN 10.766 8 1,12,1983 trigger signal T on an inverted trigger input To and a second monostable multi vibrator circuit 36 which receives the trigger signal T on the trigger input T, Via an exclusive-or-gate 37 this trigger signal To is supplied by the output of the exclusive-or-gate 33~ the gate 37 transferring this signal when a logic "1" appears on the other input of this gate 37. The monostable multi-vibrator circuits 35 and 36 are triggered by the signal on output 30 of the control signal generator 24 and their lo lime constant, i.e. the length of the pulse supplied, is changed over by the signal on the output 31 of the control circuit. The monos-table multi vibrators 35 and 36 supply signals To and To, respectively, which are combined with the trigger signal To in the logic circuit 48 to form 15 the signals To and To in conformity with the relationships :
To = Sty Sty To = Sty + To- 1 The operation of the two multi vibrators 35 and 36 and the circuit 48 will he described with reference to Fig. 4, which shows the signals To, To, To, To and Thy When ignoring a possible inversion depending on the direction of the jump, the signal To is the limited -tracking signal whose period is inversely proportional to the jumping speed. As it is triggered on its inverting trigger input, the rnul-tivibrator 35 supplies pulses of a fixed duration each starting at the trailing edges of the signal T , whilst the multi vibrator 36 supplies the same pulses starting at -the leading edges. The resulting signal To then has a relative pulse width which is proportional to the positive difference between the pulse width of the signal To and the pulse width of the signals To and To, determined by the time constant ox the multi vibrators, or a relative pulse width which is a measure of the extent to which the jumping speed deviates in a negative sense prom a nominal speed defined by the time constant of the 5Q~
Ply 100766 9 1.12.1983 multi vibrators. Similarly, the relative pulse width of the signal To is a measure of the extent to which the jumping speed deviates from said nominal speed in a positive sense.
The signals To and To are applied -to a commutator 38, which exchanges these signals depending on the jump direction indicated by the signal on output 29 Said signals To and To control switches 39 and 40 which supply a positive or a negative supply voltage -to output lo 29 or which makes the output floating, so that the motor 7 accelerates decelerates and freewheels,respectively.
The operation of the entire jump-signal generator 14 is explained with reference to Fig. 5, in which Fig. pa represents the jumping speed v as a function of time. Figs. 5b, 5c and Ed represent the signals on outputs 289 30 and 31 of the control-signal generator AL
Fig. ye shows the limited radial tracking-error signal, and Fig. of shows a control signal for the motor 7 on output 29.
At an instant to the comparator 13 supplies the starting command to input 26. Via output I (signal shown in Fig 5b) switch 23 is changed over Via output 31 (signal shown in Fin Ed) the time consent of the multi vibrators 35 and 36 is set to a small value 25 corresponding to a high nominal jumping speed, Until an instant if the signal on output 30 (signal shown in Fig 5c) remains low so that the two multi vibrators are inoperative, the signals To and To are low, the signal To is high and the signal To is low. During the period to 30 to if the motor 7 is then accelerated continuously (see Fig. pa). At the instant to the two multi vibrators are started and the signals To and To corresponding to the diagram shown in Fig. 4 are generated The jump is then performed with a substantially constant speed.
35 After the passage of the number of tracks to be jumped (n) minus a predetermined number of tracks (x) at the instant to the signal on output 31 (Fig Ed) switches so PUN 10.766 10 1,12~1983 the time Canaanite ox the multi vibrators to a high value corresponding to a low nominal speed, The circuit then also generates a train of braking pulses To until at instant to this lower nominal speed is reached Subset quaintly, the jump continues with said constant lower speed until a-t the instant to the number of tracks to be jumped minus half a -track is reached. A-t this instant the signal on output 28 resets the switch 23 (jig. 1) and locking-in to the desired track is effected via the tracking mechanism.
Since at the lower nominal speed the repetition frequency of the limited tracking error signal decreases substantially a signal on an input 42 is combined with the output signal of the exclusive-or-gate 33 by means ox the signal on output 31 via an or-gate 41 and an exclusive-or-gate 37. A signal which is 90 phase-shi~ted relative to the limited radial error signal is applied to this input 42. when the signal on output 31 is low, which is the case at the lower nominal speed, this signal is added to the limited radial tracking-error signal in the exclusive-or-gate 37, yielding a signal of twice the repetition frequency.
The device shown in Fig 3 may be designed so that or a jump ox less than a predetermined number of tracts (or example 25) the signal on output 31 go Ed) is kept low -throughout Jumping period, so that -the mirror is controlled directly towards -the lower ox the two speeds It is to be noted that the apparatus described herein may be wormed portly in particularly parts 9, 12, 13 and 24, by a microprocessor
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for reading a disc-shaped record carrier in which video signals are recorded in substan-tially spiral tracks in such a way that corresponding picture elements of consecutive pictures are situated at substantially the same circumferential position on said record carrier, an address code being contained in at least one of the two fields of each video picture in said video signals at a predetermined position in the field blanking interval after the field-synchronizing pulse which apparatus comprises:
an optical system for aiming a light beam at the record carrier, said light beam being modulated by the record carrier, and for converting said modulated light beam into an electric signal, a converter for converting said electric signal into a radial tracking-error signal which corresponds to the radial position of the landing spot of the light beam relative to a desired track, positioning means for controlling the position landing spot of the light beam as a function of the radial tracking error signal, a jump-signal generator for generating a control signal for causing the landing spot of the light beam to be shifted over a predetermined distance in response to a jump signal, and means for applying said control signal to the positioning means during said jump, characterized by means for generating a first signal which is a continuous measure of the duration of the period of time up to a reference point in the field-blanking interval, which point precedes said address code, means for generating, a second signal under command of the jump signal, which second signal is a measure of the anticipated duration of the jump to be performed in response to said command, and means for continuously comparing said first and said second signal and, in relation to the instant at which the two durations coincide, generating a starting signal for the jump-signal generator at least if said instant appears prior to the field-synchronizing pulse preceding said address code.
an optical system for aiming a light beam at the record carrier, said light beam being modulated by the record carrier, and for converting said modulated light beam into an electric signal, a converter for converting said electric signal into a radial tracking-error signal which corresponds to the radial position of the landing spot of the light beam relative to a desired track, positioning means for controlling the position landing spot of the light beam as a function of the radial tracking error signal, a jump-signal generator for generating a control signal for causing the landing spot of the light beam to be shifted over a predetermined distance in response to a jump signal, and means for applying said control signal to the positioning means during said jump, characterized by means for generating a first signal which is a continuous measure of the duration of the period of time up to a reference point in the field-blanking interval, which point precedes said address code, means for generating, a second signal under command of the jump signal, which second signal is a measure of the anticipated duration of the jump to be performed in response to said command, and means for continuously comparing said first and said second signal and, in relation to the instant at which the two durations coincide, generating a starting signal for the jump-signal generator at least if said instant appears prior to the field-synchronizing pulse preceding said address code.
2. An apparatus as claimed in Claim 1, characteri-zed in that the means for generating the first signal comprise counting means which are started each time that an address code appears.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8303046 | 1983-01-09 | ||
| NL8303046A NL8303046A (en) | 1983-09-01 | 1983-09-01 | DEVICE FOR READING A DISC REGISTRATION CARRIER. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1235500A true CA1235500A (en) | 1988-04-19 |
Family
ID=19842334
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000462123A Expired CA1235500A (en) | 1983-09-01 | 1984-08-30 | Apparatus for reading a disc-shaped record carrier |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US4567534A (en) |
| EP (1) | EP0138245B1 (en) |
| JP (1) | JPH0783461B2 (en) |
| KR (1) | KR920005261B1 (en) |
| AT (1) | ATE40486T1 (en) |
| AU (1) | AU572885B2 (en) |
| CA (1) | CA1235500A (en) |
| DE (1) | DE3476480D1 (en) |
| ES (1) | ES8505486A1 (en) |
| HK (1) | HK82991A (en) |
| NL (1) | NL8303046A (en) |
| SG (1) | SG51190G (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61104337A (en) * | 1984-10-24 | 1986-05-22 | Hitachi Ltd | Optical information recording and reproducing device |
| JPS6273430A (en) * | 1985-09-26 | 1987-04-04 | Canon Inc | Optical information recording and reproducing device |
| US5166805A (en) * | 1985-06-18 | 1992-11-24 | Pioneer Electronic Corporation | Disk player with a blanking during fast scanning |
| US4819219A (en) * | 1986-03-25 | 1989-04-04 | Kabushiki Kaisha Toshiba | Track jump control system for optical disk apparatus |
| US4862291A (en) * | 1986-11-14 | 1989-08-29 | Pioneer Electronic Corporation | Scanning system in information reproducing apparatus |
| DE3887126T2 (en) * | 1987-08-29 | 1994-04-28 | Fujitsu Ltd | METHODS TO ACCESS AN OPTICAL RECORDING TRACK. |
| US4897827A (en) * | 1987-12-12 | 1990-01-30 | U.S. Philips Corporation | Video disc player with rapid track access means |
| CZ289474B6 (en) * | 1990-09-19 | 2002-01-16 | Koninklijke Philips Electronics N. V. | Picture retrieval system comprising a record carrier and a read device |
| NL9002111A (en) * | 1990-09-19 | 1992-04-16 | Koninkl Philips Electronics Nv | METHOD FOR RECORDING IMAGE INFORMATION, AND A REGISTRATION CARRIER, AND AN IMAGE SEARCH AND DISPLAY DEVICE FOR READING THE REGISTRATION CARRIER. |
| US5473584A (en) * | 1992-01-29 | 1995-12-05 | Matsushita Electric Industrial Co., Ltd. | Recording and reproducing apparatus |
| USRE40957E1 (en) | 1992-01-29 | 2009-11-10 | Panasonic Corporation | Medium, apparatus, and method related to encryption resultant information |
| EP0637016B1 (en) * | 1993-07-27 | 2001-03-07 | Matsushita Electric Industrial Co., Ltd. | Recording and reproducing apparatus |
| JP3826856B2 (en) * | 2002-08-05 | 2006-09-27 | ソニー株式会社 | REPRODUCTION CONTROL DEVICE, REPRODUCTION CONTROL METHOD, AND REPRODUCTION CONTROL PROGRAM |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2349191A1 (en) * | 1976-04-23 | 1977-11-18 | Thomson Brandt | OPTICAL INFORMATION DISC READER INCLUDING AN AUTOMATIC INFORMATION ACCESS DEVICE |
| FR2396379A1 (en) * | 1977-07-01 | 1979-01-26 | Thomson Brandt | OPTICAL INFORMATION DISC READER EQUIPPED WITH AN AUTOMATIC INFORMATION ACCESS DEVICE |
| JPS576443A (en) * | 1980-06-13 | 1982-01-13 | Matsushita Electric Ind Co Ltd | Recorder and reproducer |
| JPS5753880A (en) * | 1980-09-12 | 1982-03-31 | Victor Co Of Japan Ltd | Detector of periodic signal |
| JPS5765075A (en) * | 1980-10-08 | 1982-04-20 | Trio Kenwood Corp | High speed reproduction method of video disc |
| JPS57104386A (en) * | 1980-12-19 | 1982-06-29 | Trio Kenwood Corp | Video disc playback device |
| JPS57120272A (en) * | 1981-01-14 | 1982-07-27 | Victor Co Of Japan Ltd | Reproducing device for discoid information recording medium |
| JPS57150173A (en) * | 1981-03-12 | 1982-09-16 | Victor Co Of Japan Ltd | Reproducer for disc shape information recording medium |
| JPS5862868A (en) * | 1981-10-09 | 1983-04-14 | Pioneer Video Corp | High speed address information searching system of information reproducing device |
| JPS5896474A (en) * | 1981-12-04 | 1983-06-08 | Matsushita Electric Ind Co Ltd | Video disc reproducer |
| JPS58171730A (en) * | 1982-03-31 | 1983-10-08 | Sony Corp | Disc reproducing device |
| US4536863A (en) * | 1982-04-15 | 1985-08-20 | Discovision Associates | Method and apparatus for recovering information from a videodisc |
| JPS58196047U (en) * | 1982-06-18 | 1983-12-27 | 日立精機株式会社 | reduction gear |
-
1983
- 1983-09-01 NL NL8303046A patent/NL8303046A/en not_active Application Discontinuation
- 1983-12-07 US US06/559,064 patent/US4567534A/en not_active Expired - Fee Related
-
1984
- 1984-08-28 EP EP84201240A patent/EP0138245B1/en not_active Expired
- 1984-08-28 DE DE8484201240T patent/DE3476480D1/en not_active Expired
- 1984-08-28 AT AT84201240T patent/ATE40486T1/en active
- 1984-08-29 ES ES535485A patent/ES8505486A1/en not_active Expired
- 1984-08-30 CA CA000462123A patent/CA1235500A/en not_active Expired
- 1984-08-31 AU AU32585/84A patent/AU572885B2/en not_active Ceased
- 1984-08-31 JP JP59182520A patent/JPH0783461B2/en not_active Expired - Lifetime
- 1984-09-01 KR KR1019840005382A patent/KR920005261B1/en not_active IP Right Cessation
-
1990
- 1990-07-04 SG SG511/90A patent/SG51190G/en unknown
-
1991
- 1991-10-24 HK HK829/91A patent/HK82991A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE3476480D1 (en) | 1989-03-02 |
| AU572885B2 (en) | 1988-05-19 |
| ATE40486T1 (en) | 1989-02-15 |
| ES535485A0 (en) | 1985-05-16 |
| EP0138245A1 (en) | 1985-04-24 |
| KR920005261B1 (en) | 1992-06-29 |
| SG51190G (en) | 1990-08-31 |
| JPH0783461B2 (en) | 1995-09-06 |
| EP0138245B1 (en) | 1989-01-25 |
| ES8505486A1 (en) | 1985-05-16 |
| JPS6090480A (en) | 1985-05-21 |
| NL8303046A (en) | 1985-04-01 |
| AU3258584A (en) | 1985-03-07 |
| KR850002535A (en) | 1985-05-13 |
| HK82991A (en) | 1991-11-01 |
| US4567534A (en) | 1986-01-28 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |