GB2137799A - Dirt Detection and Display System for an Information Read-Out System - Google Patents
Dirt Detection and Display System for an Information Read-Out System Download PDFInfo
- Publication number
- GB2137799A GB2137799A GB08406780A GB8406780A GB2137799A GB 2137799 A GB2137799 A GB 2137799A GB 08406780 A GB08406780 A GB 08406780A GB 8406780 A GB8406780 A GB 8406780A GB 2137799 A GB2137799 A GB 2137799A
- Authority
- GB
- United Kingdom
- Prior art keywords
- signal
- detection
- dirt
- level
- output 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.)
- Granted
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 131
- 230000002159 abnormal effect Effects 0.000 claims abstract description 3
- 230000010354 integration Effects 0.000 claims description 4
- 238000010586 diagram Methods 0.000 description 10
- 238000010276 construction Methods 0.000 description 4
- 241001422033 Thestylus Species 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 230000007257 malfunction Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B33/00—Constructional parts, details or accessories not provided for in the other groups of this subclass
- G11B33/10—Indicating arrangements; Warning arrangements
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
- G11B23/50—Reconditioning of record carriers; Cleaning of record carriers ; Carrying-off electrostatic charges
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
- G11B27/34—Indicating arrangements
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/36—Monitoring, i.e. supervising the progress of recording or reproducing
Landscapes
- Optical Recording Or Reproduction (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
The present invention provides a dirt detection and display system for an information read-out system comprising dirt detection means (2, 3, 6 to 10) for detecting an abnormal condition of a read-out signal produced at a pickup device and for producing a dirt detection signal. The dirt detection signal is then applied to a holding means (4) which produces an output signal for a predetermined period of time after receipt of the dirt detection signal and a display device (5) is operated according to the output signal of the holding means (4). <IMAGE>
Description
SPECIFICATION
Dirt Detection and Display System for an
Information Read-out System
The present invention relates to a dirt detection and display system for an information read-out system, and more specifically to a system for detecting dirt, for example on the recording medium and being a cause of drop-out, and for displaying the presence of dirt to an operator of the information read-out system.
In an information read-out system such as a system for playing back a video information and/or a sound information, the presence of dirt on a recording medium, on a pickup device, or on a read-out head causes a temporary absence, i.e., drop-out, of the playback rf (radio frequency) signal which results in relatively large noise in reproduced picture or reproduced sound.
Therefore, a system for compensating for the drop-out is indispensable in those systems for reading out, recorded information.
In the case of usual systems for compensating for the drop-out, an average value between the data immediately before the occurence of a dropout and a data immediately after the drop-out is utilized for the compensation. In other cases, a data immediately before the drop-out or a data a predetermined time before the drop-out is used for the compensation. However, in those drop-out compensation systems, if dirt is present along a long range of recording track of recording medium, for example, then it becomes difficult to compensate for the drop-out of such a long period of time. Generally, the occurence of drop-out for such a period has resulted in the deterioration of the playback picture information and/or sound information.Further, in some cases, the long time drop-out has resulted in the malfunction of a servo system which is provided for adjusting a read-out position of the pickup device. Therefore, it is desirable to provide a system which detects and displays the presence of dirt so that an operator of the read-out system can remove the dirt on the recording medium, the pickup device and so on.
An object of the present invention is to provide a dirt detection and playback system for an information read-out system, by which an operator the read-out system can remove the dirt for the better reproduction of a recorded picture information or sound information, and further preventing the malfunction of the servo system.
According to the present invention, a dirt detection and display system includes a dirt detection means for detecting abnormal conditions of the read-out signal and producing a dirt detection signal, a holding means for holding the dirt detection signal, and the detection of dirt is displayed in accordance with an output signal of the holding means.
The foregoing and other objects and advantages of the invention will become more clearly understood from the following description taken in conjunction with the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
Fig. 1 is a block diagram of a first embodiment of the dirt detection and display system according to the present invention;
Fig. 2 is a block diagram of a second embodiment in which an integrator is provided in the means for generating the dirt detection signal;
Fig. 3 is a block diagram of a third embodiment of the dirt detection and display system in which an envelope of the playback rf signal is detected;
Fig. 4 is a block diagram of a fourth embodiment in which the level of the playback rf signal is detected;;
Fig. 5 is a block diagram of a fifth embodiment in which an envelope of a focus error signal produced by the pickup device is detected;
Fig. 6 is a block diagram of a sixth embodiment in which the level of the focus error signal and a tracking error signal are compared to provide the dirt detection signal;
Fig. 7 is a block diagram of a seventh embodiment in which an error of reproduced information in the form of coded data is detected; and
Fig. 8 is a block diagram of an eighth embodiment in which an integrator for integrating the frequency of error signal is provided to the system of Fig. 7.
Reference is first made to Fig. 1, in which the first embodiment of the dirt detection and display system according to the present invention is illustrated.
As shown, there is provided a pickup 1 for picking up an rf (radio frequency) signal component representing an information recorded on a recording disc and providing an output signal which at the same time has a focus error signal component representative of the distance between a point of convergence of the read-out laser beam and a surface of the recording disc, and a tracking error signal component representative of the deviation of the spot of the read-out laser beam from a center of the recording track. The rf signal component produced by the pickup 1 is supplied to a drop-out detector 2.The drop-out detector 2 is constructed, for instance, in a manner that a positive pulse and a negative pulse are produced in synchronism with the zero cross points of the rf signal and either one of those pulses are used for triggering a retriggerable monostable multivibrator (referred to as r-mmvbr hereinafter) having a predetermined time constant, 207ns for example. This time constant of the r-mmvbr is subsantiallly corresponding to the maximum period of the rf signal. When the rf signal is absent for more than the predetermined time period, such a condition causes an inversion of the state of the output signal of the r-mmvbr. Therefore, a drop-out detection signal, for example, consisting of a negative pulse can be produced at a Q output terminal of the r-mmvbr. The thus produced dropout detection signal is then applied to a counter circuit 3.The counter circuit 3 is, for example, made up of a binary counter which counts up the drop-out signal, a pulse generator for generating a pulse train of a constant interval and supplying the same to a reset terminal of the binary counter, and a plurality of interconnected logic gates which are responsive to the output signal of the binary counter and adapted to produce a high level output signal when the count value of the binary counter has reached a predetermined value. The counter circuit 3, together with the drop-out detector 2, forms the dirt detection means which provides a high level output signal from the counter circuit 3 as the dirt detection signal, when the drop-out has occured more than a predetermined number of times within the predetermined time period.
This dirt detection signal is then applied to a timer circuit 4 acting as a holding means. The timer circuit 4 is constructed, for example, to produce a high level output signal for a predetermined time period T2 after the generation of the dirt detection signal. The output signal of the timer circuit 4 is then supplied to a display device 5 which, for example, consists of a light emitting diode.
Turning to the block diagram of Fig. 2, the second embodiment of the present invention will be explained. The construction of this embodiment is basically identical with the construction of the first embodiment shown in
Fig. 1, except for the structure of the means for generating the dirt detection signal according to the number of the occurence of the drop-out within the predetermined time period.
Specifically, the system includes the pickup device 1, the drop-out detector 2, the timer circuit 4, and the display device 5. However, in the case of this embodiment, the drop-out detection signal generated from the drop-out detector 2 is applied to an integrator 6. In the integrator 6, the dropout detection signal is integrated to produce an output signal whose level is proportional to the frequency of the occurence of the drop-out within the predetermined time period. The output signal of the integrator 6 is compared with a reference signal at a compatator 7. The drop-out detector 2, the integrator 6 and comparator 7, as a whole, form the dirt detection means which produces the high level dirt detection signal when the number of occurence of the drop-out signals is greater than the predetermined number during a predetermined unit time period.By supplying this dirt detection signal to the timer circuit 4, the detection of the dirt of the recordng medium, for example, is displayed in the same manner as the system of Fig. 1.
Figs. 3 and 4 show the other embodiments of dirt detection and display system according to the present invention. In both embodiments shown in
Figs. 3 and 4, the construction of the system is substantially identical with the construction of the system of Fig. 1 except in that the dirt detection is performed by detecting the variation of the amplitude of the rf signal picked up by means of the pickup device 1. More specifically, in the embodiment of
Fig. 3, the rf signal obtained from the pickup device 1 is supplied to an envelope detector 8 which, for instance, is made up of an AM detector circut. An output signal of this envelope detector 8 is then compared with a reference signal in a comparator 9.When a drop-out occurs, i.e., when the output signal level of the envelope detector 8 becomes lower than the reference voltage instantly, the comparator 9 produces an output pulse signal whose pulse width corresponds to the time period in which the output signal level of the envelope detector 8 drops. This output pulse signal of the comparator 9 is in turn supplied to a pulse width detector 10 which is constructed to count up a clock signal during the presence of the pulse signal supplied from the comparator 9, and produces a high level output signal when it is determined from the count value that the pulse width is greater than a predetermined value.The envelope detector 8, the comparator 9, and pulse width detector 10, altogether form the dirt detection means which provides the high level output signal of the pulse width detector 10 to the timer circuit 4 as the dirt detection signal when the level drop of the envelope signal due to the absence of the rf signal has continued for more than the predetermined time period. After that, the detection of the dirt is displayed on the display device in the same manner as the embodiment of Fig. 1.
In the case of the embodiment of Fig. 4, the rf signal from the pickup device is supplied to the level detector 1 1 which, for example, is made up of a half-wave rectifier circuit for receiving the rf signal, and an integration circuit for integrating the output signal of the half-wave rectifier circuit.
Thus, the level detector 11 produces an output signal whose level is proportional to the level of the rf signal, and this output signal of the level detector 1 1 is supplied to a comparator 12 in which the output signal of the level detector is compared with a predetermined reference voltage signal. Thus, the level detector 11 and the comparator 12 form the dirt detection means which produces a high level output signal from the comparator 12 and supplys the same to the timer circuit 4 as the dirt detection signal when the output signal level of the rf signal drops. Then, the detection of the dirt of the recording medium is displayed on the display device in the same manner as the embodiment of Fig. 1.
Figs. 5 and 6 show the other embodiments of the dirt detection and display system according to the present invention which are constructed in the same manner as the embodiment of Fig. 1 except in that the detection of dirt is performed by utilizing an error signal produced by the pickup device 1.
In Fig. 5, a focus error signal produced from the pickup device 1 is supplied to an envelope detector 13. The envelope detector 13 is constructed to detect an envelope of a low frequency component of the focus error signal.
The envelope detector 13, together with the comparator 14 and the pulse width detector 15, forms the dirt detection means which provides the high level output signal of the pulse width detector 10 to the timer circuit 4 as the dirt detection signal when the level drop of the low envelope signal of the low frequency component of the focus error signal for more than the predetermined time period. Then the detection of the dirt on the recording medium is displayed on the display device 5 as previous cases.
In the case of the embodiment of Fig. 6, the focus error signal and a tracking error signal produced from the pickup device are compared with each other in the comparator 16. Therefore, the comparator 16 produces a noise signal in the pulse form when the level difference between the focus error signal and the tracking error signal has changed abruptly due to the dirt on the recoding medium. This pulse like output signal of the comparator 16 is then applied to a counter circuit 17, which, for example, is made up in the same manner as the counter circuit 3 of the previous embodiment, and provides a high level output signal to the timer circuit 4 when the pulse like output signals are produced from the comparator more than a predetermined number of times within a predetermined time period.Then the detection of the dirt is displayed on the display device 5 in the same manner as the previous embodiments.
Figs. 7 and 8 are block diagrams of the other embodiments of the dirt detection system according to the present invention which are identical with the first embodiment of the invention except in that the dirt dection is performed by means of an error of the coded data contained in the rf signal, which is the case when recording of the information is performed by the
PCM (pulse code modulation) system.
In the case of the system of Fig. 7, a coded data contained in the rf signal is supplied to the code error detection circuit 18. When an error of the coded data is detected by the code error detection circuit 18, signals such as an error detection signal and an interpolation command signal are produced and supplied to the counter circuit 19. The counter circuit 19 is, for example, constructed in the same manner as the counter circuit 3 and in which the number of occurence of the error detection signal or the interpolation command signal during the predetermined time period is counted. When the count value has reached a predetermined number, a high level output signal is produced and supplied to the timer circuit 4 as the dirt detection signal. After that, the detection of the dirt is displayed on the display device 5 in the same manner as the previous embodiments.
In the case of the embodiment of Fig. 8, the error detection signal or the interpolation detection signal produced from the code error detection circuit 18 is applied to an integrator 20.
The integrator 20, in turn, produces a voltage signal whose level corresponds to the number of occurence of the code error detection signal or the interpolation command signal. The output signal of the integrator 20 is then compared with a predetermined reference voltage in a comparator 21, and consequently, the comparator produces a dirt detection signal when the code error detection signal or the interpolation command signal is generated more than the predetermined number of times during a unit time. The dirt detection signal from the comparator 21 is then applied to the timer circuit 4 and the detection of the dirt is displayed in the display device in the same manner as the previous embodiments.
It will be understood from the foregoing, according to the present invention the detection of the dirt of the recording medium, for example is displayed. Therefore, the stable operation of the playback system such as the video and/or sound information playback system can be maintained by cleaning the surface of the recording medium, a playback magnetic head, or mirrors which are provided as the part of the pickup device, in accordance with the state indicated in the display device. Thus, it becomes possible to obtain good picture and/or sound from the playback system, and also, an erroneous operation of servo system of the playback system can be prevented for maintaining the stable state of the playback operation.
It will be appreciated that the foregoing description is for illustrative purpose only, and is not intended to limit the scope of the invention.
Rather, there are numerous equivalents to the preferred embodiments, and such are intended to be covered by the appended claims.
As an example, instead of the timer circuit used in the preferred embodiments, a monostable multivibrator or a flip-flop circuit can be used as the holding means. In addition, instead of the photo emitting diode, a vacuum fluorescent tube, a liquid crystal device, or an alarm device using a buzzar can be used as the display or indicator device. Further, instead of displaying the detection of dirt, other methods such as to stop or pause the playback operation, or to eject the recording medium can be adopted.
Moreover, in the case of an information playback device having an electro-static type pickup device, the remaining life of the stylus of the pickup device can be displayed along with the detection of dirt on the recording device. This is because the wear of the stlylus causes a change in the frequency characteristics of the output signal of the pickup device whch will result in respective change in the amplitudes of the carriers of the video information and the sound information, and the remaining life time of the stylus can be estimated by the difference between the amplitudes of the carriers.
Claims (14)
1. A dirt detection and display system for an information read-out system comprising:
a dirt detection means for detecting an abnormal condition of a read-out signal picked up from a recording medium, and producing a dirt detection signal;
a holding means for holding said dirt detection signal for a predetermined period of time and producing an output signal for said predetermined period of time after a last reception of said dirt detection signal; and
a display means for displaying detection of dirt according to the output signal of said holding means.
2. A dirt detection and display system as set forth in claim 1, wherein said dirt detection means includes a drop-out detection means for detecting an absence of said read-out signal and producing a drop-out detection signal, and means responsive to said drop-out detection signal for producing said dirt detection signal according to a frequency of said drop-out detection signal within a predetermined period of time.
3. A dirt detection and display system as set forth in claim 2, wherein said means responsive to the drop-out detecton signal is a counter for counting up said drop-out signal and producing said dirt detection signal when said drop-out detection signal is generated more than a predetermined number of times within a predetermined time period.
4. A dirt detection and display system as set forth in claim 2, wherein said means responsive to the drop-out detection signal is an integrator for integrating said drop-out detection signal and a comparator for comparing an output signal of said integrator with a predetermined reference level and producing said dirt detection signal when said output signal of integrator becomes greater than the reference level.
5. A dirt detection and display device as set forth in claim 1, wherein said dirt detection means includes an amplitude detectoin means responsive to said read-out signal for generating an output signal indicative of an amplitude of said read-out signal, and means responsive to said output signal of amplitude detection means, for producing said dirt detection signal according to an instant level of said output signal of amplitude detection means.
6. A dirt detection and display system as set forth in claim 5, wherein said#ampIitude detection means is an envelope detector for generating an envelope signal of said read-out signal, and said means responsive to the output signal of amplitude detection means is a comparator for comparing a level of said envelope signal with a predetermined reference level and producing a comparator output signal when the level of the envelope signal becomes higher than said reference level and a pulse width detector for producing said dirt detection signal when said comparator output signal is produced for more than a predetermined period of time.
7. A dirt detectoin and display device as set forth in claim 5, wherein said amplitude detection means is a level detection means for detecting a level of said read-out signal and said means responsive to the output signal of the amplitude detection means is a comparator for comparing an output signal of said level detection means with a predetermined reference level and producing said dirt detection signal when the output signal of the level detection means becomes greater than the reference level.
8. A dirt detection and display system as set forth in claim 1, wherein said dirt detection means induces a level detection means for detecting a change in the level of an error signal component representing an error of a read-out position and contained in said read-out signal, and producing an output signal indicative of said change of level, and means responsive to said output signal of level detection means for producing said dirt detection signal according to the generation of said output signal of level detection means.
9. A dirt detection and display system as set forth in claim 8, wherein said level detection means is an envelope detector for generating an envelope signal of a focus signal component contained in said read-out signal and said means responsive to the output signal of level detection means is a comparator for comparing said envelope signal with a predetermined reference level and producing a comparator output signal when the level of said envelope signal becomes greater than the reference level, and a pulse width detector for producing said dirt detection signal when said comparator output signal is produced for more than a predetermined period of time.
10. A dirt detection and display system as set forth in claim 8, wherein said level detection means is a comparator for comparing a level of a focus error signal component and a level of a tracking error signal component contained in said read-out signal and producing a compartor output signal when a difference between the levels of the error signals becomes greater than a predetermined value, and said means responsive to the output signal of the level detection means is a counter for counting up said comparator output signal and produces said dirt detection signal when said comparator output signal has generated more than a predetermined number of times within a predetermined time period.
1 A dirt detection and display system as set forth in claim 1, wherein said dirt detection means includes an error detection means for detecting an error of coded data contained in said read-out signal and generating an error detection signal upon detection of said error, and means responsive to said error detection signal for providing said dirt detection signal according to a frequency of generation of said error detection signal within a predetermined period of time.
12, A dirt detection anddisplay system as set forth in claim 11, wherein said means responsive to the error detection signal is a counter for counting up said error detection signal and producing said dirt detection signal when said error detection signal is generated more than a predetermined number of times within a predetermined period of time.
13. A dirt detection and display system as set forth in claim 11, wherein said means responsive to the error detection signal is an integrator for integrating said error detection signal and producing an integration signal, and a comparator (21) for comparing said integration signal with a reference signal and producing said dirt detection signal when a level of said integration signal becomes greater than the reference level.
14. A dirt detection and display system for an information read-out system, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1983037275U JPH0643901Y2 (en) | 1983-03-15 | 1983-03-15 | Optical information reader with dirt detection display function |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8406780D0 GB8406780D0 (en) | 1984-04-18 |
| GB2137799A true GB2137799A (en) | 1984-10-10 |
| GB2137799B GB2137799B (en) | 1986-07-02 |
Family
ID=12493133
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08406780A Expired GB2137799B (en) | 1983-03-15 | 1984-03-15 | Dirt detection and display system for an information read-out system |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH0643901Y2 (en) |
| DE (1) | DE3409557A1 (en) |
| FR (1) | FR2547097A1 (en) |
| GB (1) | GB2137799B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4750163A (en) * | 1985-03-14 | 1988-06-07 | Olympus Optical Co., Ltd. | Pick-up head abnormality detector for optical recording/reproducing apparatus |
| EP0491563A2 (en) * | 1990-12-18 | 1992-06-24 | Pioneer Electronic Corporation | Information recording/reproducing apparatus |
| EP0517099A1 (en) * | 1991-06-07 | 1992-12-09 | Deutsche Thomson-Brandt Gmbh | Error motive signalling of optical information carriers |
| US5485444A (en) * | 1991-06-07 | 1996-01-16 | Deustsche Thomson-Brandt Gmbh | Signalization of types of defects of an optical information carrier |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0816982B2 (en) * | 1984-09-28 | 1996-02-21 | 株式会社東芝 | Drop-out control device for optical recording / reproducing apparatus |
| JPS6371930A (en) * | 1986-09-16 | 1988-04-01 | Matsushita Electric Ind Co Ltd | Optical information recording and reproducing device |
| JP2009170019A (en) * | 2008-01-15 | 2009-07-30 | Taiyo Yuden Co Ltd | Surface evaluating method for optical disk and optical disk recording and playback device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2413318A1 (en) * | 1974-03-20 | 1975-10-02 | Agfa Gevaert Ag | Marking drop-outs in flexible magnetic tapes - by recording electronic marks in separate track as drop-outs are registered |
| DE2611539C3 (en) * | 1976-03-18 | 1982-09-09 | Agfa-Gevaert Ag, 5090 Leverkusen | Method for recognizing and locating defects extending in the longitudinal direction of a moving material web |
| GB1535022A (en) * | 1976-08-09 | 1978-12-06 | Caterpillar Tractor Co | Vehicle wheel having radially movable impact absorbing rims |
| JPS54156610A (en) * | 1978-05-31 | 1979-12-10 | Tdk Corp | Inspecting method of magnetic recording tapes |
-
1983
- 1983-03-15 JP JP1983037275U patent/JPH0643901Y2/en not_active Expired - Lifetime
-
1984
- 1984-03-15 DE DE19843409557 patent/DE3409557A1/en not_active Withdrawn
- 1984-03-15 FR FR8404009A patent/FR2547097A1/en not_active Withdrawn
- 1984-03-15 GB GB08406780A patent/GB2137799B/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4750163A (en) * | 1985-03-14 | 1988-06-07 | Olympus Optical Co., Ltd. | Pick-up head abnormality detector for optical recording/reproducing apparatus |
| EP0491563A2 (en) * | 1990-12-18 | 1992-06-24 | Pioneer Electronic Corporation | Information recording/reproducing apparatus |
| EP0491563A3 (en) * | 1990-12-18 | 1992-10-28 | Pioneer Electronic Corporation | Information reproducing apparatus |
| EP0517099A1 (en) * | 1991-06-07 | 1992-12-09 | Deutsche Thomson-Brandt Gmbh | Error motive signalling of optical information carriers |
| WO1992022064A1 (en) * | 1991-06-07 | 1992-12-10 | Deutsche Thomson-Brandt Gmbh | Signalization of types of defects of an optical information carrier |
| EP0671742A1 (en) * | 1991-06-07 | 1995-09-13 | Deutsche Thomson-Brandt Gmbh | Signalization of types of defects of an optical information carrier |
| US5485444A (en) * | 1991-06-07 | 1996-01-16 | Deustsche Thomson-Brandt Gmbh | Signalization of types of defects of an optical information carrier |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2547097A1 (en) | 1984-12-07 |
| JPH0643901Y2 (en) | 1994-11-14 |
| DE3409557A1 (en) | 1984-09-20 |
| GB2137799B (en) | 1986-07-02 |
| GB8406780D0 (en) | 1984-04-18 |
| JPS59142989U (en) | 1984-09-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 746 | Register noted 'licences of right' (sect. 46/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19950315 |