Optical videodisk player

Abstract: A video disc player and the method of its operation are such that in a so-called scan playback mode a track jump is completed at the central eccentricity point of the optical video disc so that various characteristics relating to timebase correction are improved.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to optical video disc players and, more particularly, is directed to an optical video disc player in which an optical video disc recorded according to a constant linear velocity format is reproduced in a so-called scan playback mode. Description of the Prior Art In order to understand the present invention more clearly, let us first describe an example of a prior-art optical video disc player with reference to Fig. 1. A similar optical video disc player is disclosed in figure 4 of the patent document FR-A-2 603 149. Referring to Fig. 1, there is provided a microcomputer 70 which generally controls the operation of this video disc player. An optical video disc 10 is provided, on which there is recorded a signal, FM-modulated by a color composite video signal, in a predetermined format, for example, CLV (constant linear velocity) format. The optical video disc 10 is rotated by a spindle motor 51 which is servo-controlled in rotation by a spindle servo circuit 50 as will be described later. In a reproducing circuit 20, there is provided an optical pickup head 21 which is comprised of a laser light emitting element, a receiving element for receiving a laser light emitted from the laser light emitting element, an objective lens, a tracking coil for moving the optical axis of the objective lens in the radial direction of the disc 10, et cetera. The optical pickup head 21 is moved in the radial direction of the optical video disc 10 by a sled motor 43. In a tracking servo circuit 30, one portion of an output signal from the optical pickup head 21 is supplied to a detecting circuit 31 by which a tracking error voltage Vt is derived. This voltage Vt is supplied through an amplifier 32 to the tracking coil of the optical pickup head 21 so that the objective lens (not shown) is servo-controlled in tracking. In a sled servo circuit 40, the tracking error voltage Vt from the detecting circuit 31 is supplied to a low-pass filter 41 from which there is derived a DC component of the tracking error voltage Vt. This DC component is supplied through an amplifier 42 to the sled motor 43 so that a sled servo is performed. Accordingly, in the normal reproduction mode, the tracking servo circuit 30 and the sled servo circuit 40 enable the optical pickup head 21 to correctly follow the tracks of the optical video disc 10 so that a reproduced signal is obtained from the optical pickup head 21. The reproduced signal is supplied through a playback amplifier 22 and a limiter 23 to an FM demodulating circuit 24, in which it is FM-demodulated to provide a color composite video signal Sc. The color composite video signal Sc is supplied to a time base corrector (TBC) 25, in which any timebase fluctuation of the video signal Sc is removed. The signal Sc from the FM demodulating circuit 24 is supplied to a charge coupled device (CCD) 251, and the signal Sc from the CCD 251 is supplied to a synchronizing separating circuit 252, from which there are derived a vertical synchronizing pulse PBV and a horizontal synchronizing pulse PBH2. The horizontal synchronizing pulse PBH2 is supplied to a phase comparing circuit 253. A master sync. (synchronizing) pulse generating circuit 61 generates a synchronizing pulse REFH having a reference horizontal frequency. This synchronizing pulse REFH is also supplied to the phase comparing circuit 253. The phase comparing circuit 253 derives a phase-compared output of the pulses PBH2 and REFH. The phase-compared output is supplied to a low-pass filter 254 which derives a times base error voltage TBCE. The time base error voltage TBCE changes level in accordance with the phase difference between the pulses PBH2 and REFH. This time base error voltage TBCE is supplied to a voltage controlled oscillator (VCO) 255 as a control signal, and an oscillation signal from the VCO 255 is supplied to the CCD 251 as a clock signal. Accordingly, the synchronizing pulse PBH2 has a constant phase synchronized with the reference pulse REFH so that when the video signal Sc from the CCD 251 has time base fluctuation caused by a jitter component, the eccentricity of the optical video disc 10 or the like, this time fluctuation is removed. This video signal Sc is supplied through a memory circuit 26 and an amplifier 27 to an output terminal 28. The memory circuit 26 is utilized to effect a special playback or the like, and is comprised of an analog-to-digital (A/D) converter for converting the input signal Sc to a digital signal, a field memory in which the digitized signal Sc is written, a digital-to-analog (D/A) converter for converting the digital signal Sc read-out from the field memory to an analog signal and a controller for controlling the above-described circuits, though not shown. In the normal reproduction mode, the memory circuit 26 is by-passed so that the input signal Sc is directly outputted. Further, the video signal Sc from the FM demodulating circuit 24 is supplied to a synchronizing separating circuit 52 which derives a horizontal synchronizing pulse PBH1. The horizontal synchronizing pulse PBH1 is supplied to the servo circuit 50, and the pulse REFH from the reference signal generating circuit 61 is supplied to the servo circuit 50, whereby the rotation of the spindle motor 51 is controlled so that the pulse PBH1 can be synchronized with the pulse REFH, and thus the aforementioned spindle servo is carried out. With the employment of the spindle servo utilizing the pulses PBH1 and REFH, the lock range is narrow so that, for example, when the optical video disc 10 starts rotating or the like, the servo operation can not be properly carried out. Therefore, a frequency generator 53 is coupled to the spindle motor 51 and an output signal of the frequency generator 53 is supplied to the servo circuit 50 to thereby back-up the spindle servo utilizing the pulses PBH1 and REFH. The video disc player is operated in the normal playback mode as described above. In the aforementioned video disc player, if the optical pickup head 21 is moved in the radial direction of the optical video disc 10 at a speed higher than that of the normal playback mode while the objective lens within the optical pickup head 21 is servo-controlled in tracking, then the objective lens tends to stay in the original track by the action of the tracking servo circuit 30 against the movement of the photo pickup head 21. When the photo pickup head 21 is moved to the controllable limit of the tracking servo, the objective lens is caused to make a track jump to a new track (in practice, at that time, the tracking servo is turned OFF and the track jump is forcibly effected) and the tracking servo is again performed so that the photo pickup head 21 is tracked to the new track. Accordingly, regardless of the movement of the optical pickup head 21 at the speed higher than that in the normal playback mode, a normal video signal Sc having no noise component due to mistracking can be intermittently produced. Therefore, utilizing the video signal Sc thus normally reproduced, it is possible to obtain a fast forward or fast rewind reproduced picture. In the following description, this operation mode will hereinafter be referred to as a scan mode or scan playback mode. In the scan playback mode, the microcomputer 70 supplies the amplifier 42 with a control signal SCN to cause the photo pickup head 21 to move in the inner peripheral or outer peripheral direction of the optical video disc 10 at a speed higher than that of the normal playback mode. Also, the microcomputer 70 supplies the tracking displacement amount detecting circuit 31 with a jump control signal so that a track jump of the objective lens of the optical pickup head 21 is performed. The tracking displacement amount detecting circuit 31 detects the tracking condition by detecting the amplitude of the output video signal from the optical pickup head 21. When a jump signal Si (which will be described later) is forcibly supplied by the microcomputer 70 to the detecting circuit 31, then the jump operation of the optical pickup head 21 becomes possible. Therefore, at that time, the aforementioned normal video signal Sc can be intermittently obtained. The synchronizing pulses PBH2 and PBV are supplied to the memory circuit 26 as signals indicative of the timing at which the video signal Sc is supplied to the memory circuit 26. The pulse PBV is supplied to the microcomputer 70 as a signal indicative of the timing of the video signal Sc, thereby generating a write request signal WTRQ. The write request signal WTRQ is supplied to the memory circuit 26. The sync. generating circuit 61 generates synchronizing pulses REFH and REFV having reference horizontal and vertical frequencies, respectively. These synchronizing pulses REFH and REFV are also supplied to the memory circuit 26. As described above, when the normal video signal Sc is obtained, one field of the video signal Sc is written in the field memory of the memory circuit 26 in synchronism with the pulses PBH2 and PBV. Until the next normal video signal Sc is obtained, the video signal Sc written in the field memory is repeatedly read-out therefrom in synchronism with the pulses REFH and REFV. The thus read-out video signal Sc is supplied to the output terminal 28. Therefore, the scan playback is carried out so that a desired picture can be monitored in the fast forward or fast rewind mode, if necessary. However, if the scan playback is carried out as described above, it causes trouble in the TBC 25, and this will be described hereinunder with reference to Figs. 2A to 2F. Figs. 2A to 2F are timing charts to which reference will be made in explaining the present invention, respectively. As shown by the time period before the time point t1 in Figs. 2A to 2C, in the normal playback mode, the reference synchronizing pulse REFH and the reproduced synchronizing pulse PBH1 are substantially the same in phase. Accordingly, as shown by the time period before the time point t₁ in Fig. 2E, the time base error voltage TBCE more or less fluctuates around a central value Ec thereof in response to a fluctuation of the time base. If a track jump is carried out from the time point t₁ to the time point t₂ in order to effect a scan playback, then the pulses PBH1 and PBH2 derived from the sync. separating circuit 252 become noise components during the period between the time points t₁ and t₂. In practice, the jitter component is compensated for by the CCD 251 so that the pulse PBH2 is delayed in phase from the pulse PBH1 by a predetermined delay time. This is negligible in the following description. Further, the microcomputer 70 controls the low-pass filter 254 so as to hold the value of the time base error voltage TBCE at time point t₁ from the time point t₁. If the track jump is ended at the time point t₂ and the tracking is stabilized at the time point t₃, then the normal pulses PBH1 and PBH2 are again obtained from the next time point t₄. The durations of the periods of t₁ to t₂ and t₂ to t₃ are, for example, 8 milliseconds and 2 milliseconds, respectively, and the time point t₄ is the time point at which the first pulse PBH1 is generated after the time point t₃. Accordingly, as compared with the duration of t₁ to t₃, t₃ ≈ t₄ is satisfied. The time point t₄ at which the pulse PBH1 is obtained is random relative to the time point whereat the reference synchronizing pulse REFH is obtained, and these two time points are generally not coincident with each other as shown in Figs. 2A and 2B. If the time points of the two pulses PBH1 and REFH are not coincident, then the TBC 25 must compensate for the time base fluctuation while incessantly absorbing a phase difference between the two pulses PBH1 and REFH. Consequently, a wide compensation range is required by the TBC 25. Therefore, when the pulse PBH1 is obtained at the time point t₄, a control signal HSFT from the microcomputer 70 is supplied to the sync. generating circuit 61, whereby as shown in Fig. 2D a pulse REFH′ is reset at the time point t₄ and is made the same in phase as the pulse PBH1. Thereafter, the pulse REFH′ is generated at every horizontal period, and the holding operation of the TBC 25 is released from the time point t4. Accordingly, after the time point t₄, the TBC 25 compensates for the time base fluctuation similarly to the time period before the time point t₁ so that, when the next vertical synchronizing pulse PBV is obtained, a video signal Sc of one field succeeding to the pulse PBV is written in the memory circuit 26. In practice, it is frequently observed that the time point t₂ must be extended until the response of the spindle servo circuit 50 becomes satisfactory after the track jump. For the sake of simplicity, this will not be described herein. The optical video disc 10 has an eccentricity so that while the phase ϑ REF of the reference horizontal synchronizing pulse REFH is constant as shown in Figs. 3A and 3B, the phase ϑ PBH of the reproduced horizontal synchronizing pulse PBH1 fluctuates around the phase ϑ REF and has a period coinciding with the rotation of the optical video disc 10. In the rotation cycle of the CLV disc 10, one rotation corresponds with a period of 2 fields in the innermost periphery of the disc 10 and about 5.3 fields in the outermost periphery of the disc 10. In the scan playback mode, the pulse REFH is reset so that it can coincide in phase with the pulse PBH1 at the time point t₄ as described above. Assuming now that this reset time point is the time point at which a delay of the phase ϑ PBH of the pulse PBH1 becomes maximum as shown by a cross mark in Fig. 3A, then the TBC 25 must become capable of compensating for the time base of the output video signal Sc in the advanced direction by a peak-to-peak value Δϑ in the range in which the phase ϑ PBH of the reproduced pulse PBH1 is changed. Conversely, assuming that the reset time point t₄ is the time point at which the advance of the phase ϑ PBH of the reproduced pulse PBH1 is maximized as shown by a solid circle in Fig. 3A, then the TBC 25 must become capable of compensating for the time base of the output video signal Sc in the delayed direction by a value Δϑ. Therefore, because the optical video disc 10 has the eccentricity, the TBC 25 needs a time base compensation range of a value 2Δϑ as shown in Fig. 3C, which unavoidably increases the number of coupling stages of the CCD 251. Alternatively, as shown in Fig. 2E, if the time base compensation range of the TBC 25 for the eccentricity of the optical video disc 10 is smaller than the value of 2Δϑ, the time base error voltage TBCE of the TBC 25 is fixed to a maximum value Eu or minimum value Ed of the error output, whereby the TBC 25 can not operate normally, and thus a disturbed picture is reproduced. OBJECTS AND SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved optical video disc player which can eliminate the defects encountered with the prior art. More specifically, it is an object of the present invention to provide an optical video disc player, and a scan mode reproduction method for use with such an optical video disc player, respectively, in which the compensation range of the time base fluctuation can be reduced by one-half. It is another object of the present invention to provide an optical video disc player, and a scan mode reproduction method for use with such an optical video disc player, respectively, in which the number of stages of a charge coupled device in the time base corrector can be reduced. It is still another object of the present invention to provide an optical video disc player, and a scan mode reproduction method for use with such an optical video disc player, respectively, in which a reproduced picture during the scan mode can be prevented from being disturbed. Concerning the optical video disc player, the invention is defined by the teaching of appended claim 1, whereas concerning said method, the invention is defined by the teaching of appended claim 7. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing an example of a prior-art optical video disc player; Figs. 2A to 2F are timing charts to which reference will be made in explaining the present invention; Figs. 3A to 3C are waveform diagrams to which reference will be made in explaining the defects inherent in the prior-art optical video disc player; Fig. 4 is a block diagram showing an embodiment of an optical video disc player according to the present invention; Figs. 5A to 5L are timing charts to which reference will be made in explaining the operation of the embodiment of Fig. 4; Fig. 6 is a block diagram showing an example of a phase shifter circuit used in the present invention; and Figs. 7 to 10 are waveform diagrams to which reference will be made in explaining an operation of the phase shifter circuit of Fig. 6. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings in detail, and initially to Fig. 4 and Figs. 5A to SD, an embodiment of the optical video disc player according to the present invention will now be described. Fig. 4 is a block diagram showing an overall arrangement of the instant embodiment, and in Fig. 4, like parts corresponding to those of Fig. 1 are marked with the same references and therefore need not be described in detail. It will be seen in Fig. 4 that, in the scan playback mode, the microcomputer 70 supplies a switching circuit 81 with a control signal SSW, whereby the switching circuit 81 is turned ON to permit the reproduced horizontal synchronizing pulse PBH1 from the horizontal synchronizing pulse separating circuit 52 to be supplied therethrough to a counter 82 as a reset input. A timing chart of this pulse PBH1 is represented in Fig. 5A. The sync. generating circuit 61 generates a clock pulse CLCK (see Fig. 5B) having a frequency, for example, as high as 455 times the normal reference horizontal frequency. This clock pulse CLCK is supplied to the counter 82 as a count input. A count output of the counter 82 is supplied to a decoder 83 so that when the count value of the counter 82 becomes "455" the decoder 83 generates a pulse Pd (see Fig. 5C) indicative of this count value. The pulse Pd is supplied to one input terminal of an AND circuit 84 which is supplied at its other input terminal with the synchronizing pulse PBH1. Accordingly, the pulse Pd is generated from the decoder 83 at every 455th clock pulse CLCK after the counter 82 is reset by the reproduced horizontal synchronizing pulse PBH1. At that time, the frequency of the clock pulse CLCK is as high as 455 times the normal horizontal frequency so that 455 clock pulses CLCK exist in a normal horizontal period. Since the pulse Pd and the reproduced horizontal synchronizing pulse PBH1 are supplied to the AND circuit 84, the AND circuit 84 generates an AND output Pa (see Fig. 5D) when the cycle of the pulse PBH1 is equal to that of the normal horizontal synchronizing period. In other words, as shown in Figs. 5E and 5F, the pulse Pa is derived from the AND circuit 84 each time the phase ϑ PBH of the reproduced horizontal synchronizing pulse PBH1 coincides with the phase ϑ REF of the reference horizontal synchronizing pulse REFH which occurs at or near the time point of the video disc's center of eccentricity after the track jump is completed. The pulse Pa is supplied to a mask circuit 85, in which it is masked to provide a pulse Pb for every other pulse Pa as shown in Fig. 5G. Thus the period of the pulses Pb is synchronized with and equal to the period of the video disc's eccentricity. This pulse Pb is supplied to a counter 92 as a reset input. The counter 32 might be, for example, 32-scale counter. The frequency generator 53 is formed to have a number of teeth so as to generate by optical or magnetic detection, for example, 32 pulses Pf per revolution of the optical video disc 10. The waveform of the pulse Pf is represented in Fig. 5H, and this pulse Pf is supplied through a waveform-shaping circuit 91 to the counter 92 as a count input. Accordingly, the counter 92 counts the pulse Pf, and is reset by the pulse Pb, whereby a count output signal MSB from the counter 92 becomes "0" in response to each pulse Pb and which becomes "1" at the central time point of the period before the next pulse Pb as shown in Fig. 5I. Therefore, the phase of the eccentricity of the disc 10 is effectively stored by the counter 92. The signal MSB from the counter 92 is supplied to a phase shifter circuit 93, in which it is phase-shifted to provide a signal Ss whose trailing edge is advanced in phase, for example, by 10 milliseconds as shown in Fig. 5J. This signal Ss is supplied to the microcomputer 70. The microcomputer 70 generates a pulse Pj in response to the trailing edge of the signal Ss as shown in Fig. 5K and also generates a signal Sj which becomes "1" (high level) in response to the trailing edge of the signal Ss and which becomes "0" (low level) at the time point of the pulse Pb with a delay time of 10 milliseconds. In that case, the leading edges of the pulse Pj and the signal Sj correspond to the time point t₁ of Fig. 2, and a track jump is performed by these signals Pj and Sj so that the scan playback is carried out. Further, the trailing edge of the signal Sj corresponds to the time point t₃ of Fig. 2, and on the basis of the trailing edge of the signal Sj, the reference horizontal synchronizing pulse REFH is reset via the control signal HSFT from the microcomputer to the master sync. pulse generator circuit 61 at the next time point t₄ of Fig. 2. As described above, according to the present invention, in the scan playback mode, the time point of the center of the eccentricity of the disc 10 (t₃ ≈ t₄) is detected and the reference horizontal synchronizing pulse REFH is reset substantially at the time point of the center of the eccentricity of the disc 10 thereby being synchronized with the reproduced horizontal synchronizing pulse PBH1 so that, when the TBC 25 compensates for the time base fluctuation presented by the eccentricity of the disc 10, the compensation range of the time base fluctuation is Δϑ, which is one-half of 2Δϑ in Fig. 3C. Therefore, according to the present invention, it is possible to reduce the number of stages of the CCD 251. Furthermore, even if the time base compensation range of the TBC 25 relative to the eccentricity of the disc 10 is small, the time base error voltage TBCE of the TBC 25 can be prevented from being fixed to the maximum value Eu or minimum value Ed. Therefore, the reproduced picture can be prevented from being disturbed. Fig. 6 shows in more detail an example of the phase shifter circuit 93 (Fig. 4). In this example, the signal Ss is formed from the signal MSB by a negative feedback control operation and the signal Sj is generated by the phase shifter circuit 93 instead of the microcomputer 70. Referring to Fig. 6, there are provided a variable monostable multivibrator 101 and a stationary monostable multivibrator 102, wherein the signal MSB is supplied to the monostable multivibrator 101 which then generates the signal Ss. This signal Ss is supplied to the monostable multivibrator 102 from which there is derived the signal Sj. D-type flip-flop circuits 103 and 104 and a charge and discharge circuit 105 are respectively provided. These circuits 103, 104 and 105 perform a negative feedback by which the period of "1" of the monostable multivibrator 101 is controlled so that the trailing edge of the signal Ss coincides with the time point t₁. As shown in Fig. 7, when the trailing edge of the signal Ss is located before the time point t₁, a signal S6 is an AND signal of inverted signals of the signals Ss and Sj so that the signal S6 becomes "1" from the trailing edge of the signal Sj to the leading edge of the signal Ss. This signal S6 is supplied to the charge and discharge circuit 105 and the charge and discharge circuit 105 is thereby charged. Then, an output voltage Vc of the charge and discharge circuit 105 is supplied to a time constant portion of the monostable multivibrator 101, whereby the period of "1" of the signal Ss is gradually extended. Thus, the signal Sj is shifted in the delay direction (in the right-hand side of Fig. 7) while keeping a pulse width of 10 milliseconds. As shown in Fig. 8, when the trailing edge of the signal Ss is behind the time point t₁, the signal S3 is cleared by the trailing edge of the signal Sj and is inverted by the trailing edge of the signal MSB with the result that the signal S3 becomes "0" from the time point t3 to the trailing edge of the signal Sj. This signal S3 is supplied to the charge and discharge circuit 105, whereby the charge and discharge circuit 105 discharges so that the period of "1" of the signal Sj is gradually reduced. Therefore, the signal Sj is shifted in the advance direction (in the left-hand direction of Fig. 8) while maintaining a pulse width of 10 milliseconds. As shown in Fig. 9, when the trailing edge of the signal Ss is delayed from the time point t₃, the signal S6 is formed similarly to Fig. 7, whereby the charging is performed by the charge and discharge circuit 105. Further, the signal S4 is cleared by the trailing edge of the signal Ss and is inverted by the trailing edge of the signal MSB so that the signal S4 remains "0" from the time point t₃ to the leading edge of the signal Sj. Therefore, the charge and discharge circuit 105 is discharged by the signal 54. Accordingly, in the case of Fig. 9, the charge and discharge circuit 105 is alternately charged and discharged by the signals S6 and S4. In that case, if the resistance values of resistors R3 and R4 through which the signals S6 and S4 (see Fig. 6) flow are selected so as to satisfy R3 >> R4, for example, an equality of R3 = 100·R4, then the discharge becomes superior to the charge. As a result, the period of "1" of the signal Ss is gradually reduced, and the signal Sj is shifted in the advance direction while maintaining a pulse width of 10 milliseconds. Thus, the signal Sj is placed in the state shown in Fig. 8. Therefore, in the steady state, as shown in Fig. 10, the signal Ss falls at the time point t₁ and the signal Sj becomes "1" during the period of t₁ to t₃. As described above, in the scan playback mode, the video signal Sc stored in the memory circuit 26 is read-out therefrom during the period in which the video signal Sc can not be normally reproduced. Alternatively, during the period in which the video signal Sc can not be normally reproduced, the video signal Sc can be muted and replaced with a signal which presents, for example, a gray picture. As described above, according to the present invention, in the scan playback mode, the time point of the center of the eccentricity of the disc 10 is detected and the reference horizontal synchronizing pulse REFH is reset substantially at the time point of the center of the eccentricity of the disc 10 thereby being synchronized with the reproduced horizontal synchronizing pulse PBH1 so that, when the TBC 25 compensates for the time base fluctuation presented by the eccentricity of the disc 10, the compensation range of the time base fluctuation is Δϑ, which is one-half of 2Δϑ. Therefore, according to the present invention, it is possible to reduce the number of stages of the CCD 251. Furthermore, even if the time base compensation range of the TBC 25 relative to the eccentricity of the disc 10 is small, the time base error voltage TBCE of the TBC 25 can be prevented from being fixed to the maximum value Eu or minimum value Ed. Therefore, the reproduced picture can be prevented from being disturbed.

Claims: An optical video disc player for reproducing a video signal from constant linear velocity (CLV) formatted signals recorded on an eccentric optical video disc (10), the video disc player including: an optical pickup head (21), an optical pickup head tracking servo circuit (31, 41, 42, 43), time base corrector means (25) supplied with the reproduced video signal and including a synchronizing pulse separator (52) for separating a horizontal synchronizing pulse (PBH1) from the reproduced video signal for correcting its time base and generating a time base error voltage, and scan reproduction mode means (32, 81) for moving the pickup head (21) in the radial direction of the optical video disc (10) at a speed higher than that of a normal playback mode so as to reproduce a signal and to further cause the pickup head (21) to effect a track jump of a plurality of tracks in the radial direction of the optical video disc (10), the video disc player being characterized in that it further comprises: (a) eccentricity detecting means (61, 82 - 85) for detecting the eccentricity condition of the optical video disc (10) and producing a corresponding output signal (Pb); and (b) synchronizing means (53, 91 - 93) responsive to the output signal of the eccentricity detecting means (61, 82 - 85) for generating a reference horizontal frequency synchronizing pulse (REFH) for application to the time base corrector means (25), and synchronizing the said reference horizontal frequency synchronizing pulse (REFH) with the horizontal synchronizing pulse (PBH1) of the reproduced video signal at the time when the said eccentricity signal (Pb) crosses its center value. An optical video disc player according to Claim 1, wherein (a) the eccentricity detecting means (61, 82-85) detects the time point of the center of the eccentricity of the optical video disc (10) to produce the corresponding output signal; and (b) the synchronizing means (53, 91-93) in response to the output signal of the eccentricity detecting means (61, 82-85) generates and supplies to the time base corrector means (25) the reference horizontal frequency synchronizing pulse (REFH) and synchronizes it with the horizontal synchronzing pulse (PBH1) of the reproduced video signal at or near the time point of the center of the eccentricity after the track jump is completed. An optical video disc player according to Claim 2, wherein the synchronizing means (61, 82-85) includes central time point computing means (61, 82-84) for detecting the horizontal synchronizing pulse (PBH1) in the reproduced video signal and for generating a clock signal pulse (CLCK) synchronized with the reference horizontal frequency synchronizing pulse (REFH). An optical video disc player according to Claim 3, wherein the central time point computing means (61, 82-84) is comprised of a first counter (82) for counting the clock signal pulses (CLCK) and producing a corresponding output value, a decoder (83) for decoding the output value of the first counter (82) and an AND gate (84) for producing an output signal (Pa) when the output of the decoder (83) and the reproduced horizontal synchronizing pulse (REFH) coincide with each other. An optical video disc player according to Claim 4, wherein the synchronizing means (53, 91-93) is comprised of video disc rotation sensing means (53) for generating a pulse output (Pf) synchronized with the rotation of the optical video disc (10). An optical video disc player according to Claim 5, wherein the synchronizing means (53, 91-93) is further comprised of a second counter (92) supplied with the pulse output of the disc rotation sensing means (53) and which starts its counting on the basis of the output from the AND gate (84). A scan mode reproduction method for use with an optical video disc player for reproducing a video signal recorded according to a constant linear velocity (CLV) format on an eccentric optical video disc (10) the method comprising the steps of: reproducing a recorded video signal from the optical video disc (10) by a pickup head (21), servo controlling the tracking of the pickup head (21), time base correcting the reproduced video signal, including the step of separating a horizontal synchronizing pulse (PBH1) from the reproduced video signal, and moving the pickup head (21) in the radial direction of the optical video disc (10) at a speed higher than that of a normal playback mode to jump a plurality of tracks during a scan reproduction mode so as to reproduce a signal, the method being characterized in that it further comprises the steps of: producing an eccentricity signal representing the eccentricity condition of the optical video disc; detecting the time point of the center of the eccentricity of the optical video disc (10); and generating and synchronizing a reference horizontal frequency synchronizing pulse (REFH) with the said horizontal synchronizing pulse (PBH1) of the reproduced video signal at the time when the said eccentricity signal crosses its center value after the track jump is completed and using the reference horizontal frequency synchronizing pulse (REFH) in time base correcting the reproduced video signal.

Inventors: YAMASHITA NORIYUKI, YAMASHITA, NORIYUKI
Applicants: SONY CORP, SONY CORPORATION
Application year: 1990
Main classification: G11B7
IPC codes: G11B7, G11B19, G11B27, H04N5