 Method and system for interference suppression in a color television system |
| FIG. 1 collectively, illustrates the system which is known in accordance with the prior art. In FIG... |
|
| Interface for a video display processor arranged to provide an overlay on a video display |
| The foregoing and additional objects are achieved in accordance with the present invention by an ... |
|
| Method and apparatus for overlaying digitally generated graphics over an analog video signal |
| It is to be understood that corresponding elements having the same function in the several views ... |
|
| Auto-master pedestal control circuit |
| It is an object of the present invention to provide an auto-master pedestal control circuit which ... |
|
| Method and circuit for recovering a logic signal from a band limited signal channel |
| The foregoing objects are achieved by passing the VITC or other distorted bi-level logic signal ... |
|
| Signal processing circuit for a solid-state image pickup device |
| It is an object of the present invention to provide a signal processing circuit in the multi-plate ... |
|
| Comb filter arrangement having delay time compensation and load matching in all circuit paths |
| We claim: 1. A comb filter arrangement in which signals A, B, and C of three picture lines, made ... |
|
|
Device for controlling focus of an optical disk apparatus
| Details |
Inventors: Nomura, Masaru;
Assignee: Sharp Kabushiki Kaisha (Osaka, JP)
Primary Examiner: Tran; Thang V.
Assistant Examiner:
Attorney, Agent or Firm: Conlin; David G., Oliver; Milton
A focusing control device for use in an optical disk apparatus of the present invention is provided with: an error-signal generation circuit for generating a focus error signal; a detection circuit for detecting the quantity of light derived from a light beam reflected from an optical disk in order to form a light signal; a voltage-generating circuit for generating an offset signal whose polarity is suitable for an out-focus state based on the difference between a reference signal and the light signal, only when the light signal is smaller than the reference signal, that is, only during the out-focus state; an addition amplifier for adding the offset signal to the focus error signal; and a control circuit for controlling the position of a lens in response to the output of the addition amplifier. With this arrangement, the focus error signal is added by the offset signal so as to be shaped only during the out-focus state. The lens is always driven toward the just-focus position by the use of the focus error signal thus shaped; this eliminates failure in the focus pull-in operation. |
|
DETAILED DESCRIPTION The object of the present invention is to provide a focusing control device used for an optical disk apparatus, which is capable of improving the accuracy of the focus pull-in operation by the use of a simple circuit configuration.
In order to achieve the above object, the focusing control device used for an optical disk apparatus of the present invention is provided with the following means: (1) error-signal generation means for generating a focus error signal (for example, error-signal generation circuit).
(2) detection means for detecting the quantity of light derived from a light beam reflected from an optical disk or transmitted through the optical disk (for example, photodetector).
(3) voltage-generating means for generating an offset signal for moving a lens toward a just-focus position which allows the light beam to be focused onto the optical disk only when the quantity of light is smaller than a predetermined value (for example, error-direction detection circuit, storage circuit, light-difference detection circuit, and polarity-switching circuit).
(4) addition means for adding the offset signal to the focus error signal (for example, addition amplifier).
(5) control means for controlling the position of the lens in response to the output of the addition means (for example, driver, focus actuator).
With the above arrangement, the quantity of light derived from the reflected light beam or the transmitted light beam becomes smaller than the predetermined value in the out-focus state, and only in this state, the voltage-generating means generates the offset signal for shaping the focus-error signal.
Therefore, the output of the addition means becomes equal to the focus error signal in the proximity of the just-focus position, and is represented by the addition of the focus error signal and the offset signal in the out-focus position.
As a result, even if the focus error signal becomes almost zero in the out-focus position, the lens is always driven toward the just-focus position in accordance with the offset signal; this eliminates failure in the focus pull-in operation
|
| Related patents |
|
|
Method of pre-editing an original video tape in combination of scene numbers with a card and systems for carrying out the method
What is claimed is: 1. A method of rearranging a sequence of first scenes into a sequence of second scenes by the use of a first and a second video tape and a television ...
|
|
|
Apparatus for synchronizing two video pictures by controlling vertical synchronization of a video camera
Accordingly, it is an object of this invention to provide an apparatus for synchronizing separate object images by generating a signal for controlling the vertical ...
|
|
|
Apparatus for reproducing a color video signal
Accordingly, it is an object of this invention to provide an improved color video signal reproducing apparatus which overcomes the above-described disadvantages. It is ...
|
|
|
Periodical signal detection circuit within a variable window length
Accordingly, it is a general object of the present invention to provide a novel and useful periodical signal detection circuit in a reproducing apparatus, in which the ...
|
|
|
Image signal selector for television receiver combined with video cassette recorder
OF THE INVENTION Referring to the drawing, the invention shall be described in details. According to the invention, inputs A0 and A1 of IC 1 for switch No. 1 ...
|
|
|
Automatic sharpness control circuit for a television receiver
It is an object of the present invention to provide an automatic control of the degree of picture sharpness, thus avoiding the noise accentuation in the case of low ...
|
|
|
NTSC color television transmission without chroma crawl
In accordance with the present invention, the upward moving pattern at the edges of luminance is eliminated by control of the vertical scan rate to end each scan line ...
|
|
|
Color burst phase detection system for use in a video disk player system
The present invention is made to avoid the above mentioned problem, and an object of the present invention is therefore to provide a burst phase detection system which ...
|
|
|
Television receiver which includes a memory for storing a field image which can be periodically displayed as a still picture
Accordingly, it is an object of the present invention to provide an improved television apparatus which can remove the defects encountered with the prior art television ...
|
|
|
Engine idling speed sensing system
Accordingly, it is an object of this invention to provide an engine idling speed sensing system. It is another object of this invention to provide an engine idling speed ...
|
|
|
TV Signal 
