 Image processing apparatus using inclined line screens to reduce Moire |
| An object of the present invention is to eliminate the above-explained drawbacks. Another object of ... |
|
| Image pick-up device and system |
| The present invention has been made ro further improve the image pick-up system and device of the ... |
|
| Solid state television camera |
| Accordingly, an object of the present invention relates to a dots sequential gain control amplifier ... |
|
| Solid state color imaging apparatus |
| The object of the present invention is to provide a color imaging apparatus not associated with the ... |
|
| Color information detecting device |
| A color information detecting device including a plurality of color sensing means for sensing ... |
|
| Color video signal recording and reproducing apparatus |
| Accordingly, it is a general object of the present invention to provide a novel and useful color ... |
|
| Method and apparatus for transforming PRESTEL codes to NAPLPS codes |
| Accordingly, it is an object of the invention to provide an apparatus for converting PRESTEL codes ... |
|
|
Method and apparatus for composite wobbled and push-pull tracking servo system
| Details |
Inventors: Yonezawa, Seiji; Ohtake, Masatoshi; Ito, Masaru; Tsuyoshi, Toshiaki; Ichino, Kazuo; Nakagaki, Harushige;
Assignee: Hitachi, Ltd. (Tokyo, JP)
Primary Examiner: Cardillo; Raymond F.
Assistant Examiner: Young; Wayne R.
Attorney, Agent or Firm: Antonelli, Terry & Wands
A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in each of the header fields in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted from the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot passing the wobbled track marks. After attenuating the gain of the wobbled tracking error signal by a low-pass filter so that the gain of the wobbled tracking error signal becomes equal to that of the push-pull tracking error signal at a frequency fe satisfying the relation 1/50.multidot.N.multidot.fd<fe<1/5.multidot.N.multidot.fd where N is the number of the header fields included in one complete revolution of the disc, and fd is the frequency of rotation of the disc, the attenuated wobbled tracking error signal is combined with the push-pull tracking error signal to provide a composite tracking error signal which is used for the tracking control. |
|
DETAILED DESCRIPTION With a view to solve the prior art problem of the offset pointed out above, it is a primary object of the present invention to provide an optical tracking method and apparatus which can eliminate the undesirable offset (the error component) thereby ensuring more accurate tracking.
The present invention utilizes the so-called track wobbling method in which an optical disc is previously formed with one or more sets of wobbled pits disposed in a relation wobbled relative to the center of a track, and the relative amounts of light reflected from these pits as a result of irradiation with a light spot are compared to detect a track error, if any.
This track wobbling method is already known per se and disclosed in, for example, U.
S.
Pat.
No.
4,223,187.
According to this track wobbling method, the true position of light spot passed through the wobbled pits can be detected.
Therefore, a more accurate servo system can be provided as compared to a servo system utilizing the push-pull method based on the distribution of diffraction by the pregrooves.
On the other hand, however, the track wobbling method requires provision of 1,000 or more wobbled pits per track, resulting in a correspondingly reduced data efficiency.
The track wobbling method has such another problem that it is not compatible with the push-pull method.
In view of the above prior art problems, the present invention provides a tracking system of high utility which has such features that (1) the merit of the wobbled tracking method is maintained; (2) the data efficiency is not degraded; and (3) it is compatible with the push-pull tracking system which is a prior art system most widely employed in this field.
The tracking servo system according to the present invention is a composite of the push-pull tracking system using the pregrooves and the wobbled tracking system using the wobbled track marks, and has a dual structure so that an offset component of low-frequency from the dc level, which tends to occur in the push-pull servo system, can be suppressed in the wobbling servo system
|
| Related patents |
|
|
Method of recording and reproducing digital information and apparatus therefor
It is an object of the present invention to solve the above-mentioned prior art problems and provide a method and apparatus for recording and reproducing digital ...
|
|
|
Digital selective calling receiver having a selectively attachable device for multiple independent address decoding capability
I claim: 1. In a digital selective call receiver including a receiver circuit for receiving transmitted signals, and a decoder for decoding said received signals, said ...
|
|
|
Portable transfer apparatus
Accordingly, an object of the present invention is to provide a portable transfer apparatus that may achieve a transfer operation with a desired time lag and an spatial ...
|
|
|
Positioning and control apparatus that is interactively programmable using a display
The first positioning apparatus of the conventional art requires machine mechanisms, such as a long connecting shaft and cam, taking much time and labor in manufacturing ...
|
|
|
Information transmission system having collective data transmission and collection devices
It is an object of the present invention to provide a communication control method and an information transmission system for collectively transmitting and collecting ...
|
|
|
Teletext receiver
The object of the present invention is to obviate this disadvantage by giving the teletext receivers means making it possible to simplify the tests, particularly by ...
|
|
|
Rotary head assembly
The principal object of the present invention is to provide a novel head assembly for use in a rotary scan type multitrack recording apparatus, wherein a plurality of ...
|
|
|
Abnormal separation detecting circuits of chromatic signals of SECAM systems
Accordingly, it is an object of this invention to provide a novel abnormal separation detecting circuit of chromatic signals utilized in a SECAM system which can check ...
|
|
|
Color video signal recording and reproducing apparatus
Accordingly, it is a general object of the present invention to provide a novel and useful color video signal recording and reproducing apparatus in which the problems ...
|
|
|
Method for recording and reproducing a digital color video signal
Accordingly, it is an object of this invention to provide a method and apparatus for recording a digital color video signal that avoids the above-described difficulties ...
|
|
|
TV Signal 
