JPH01166377A - Error rate reducing circuit for cd signal - Google Patents

Abstract

PURPOSE:To prevent a noise from being leaked into the neighborhood of a slice level by deciding asymmetry according to an error rate or the quantity of a synchronizing error and causing an equalize characteristic to be variable. CONSTITUTION:The output of an equalizer circuit 2 is inputted to a demodulating circuit 3 and demodulated. Next, this demodulating output signal is inputted to an error detecting section 4 and an error is detected. Then, this error signal is inputted to an integrator 5 and compared with a certain threshold value by a comparator 6. When the error signal is over the threshold value, the equalizer circuit 2 is controlled. Since amplitude correction is generally main for the equalizer circuit 2, it is enough to turn off the equalizer 2 to the increase of the error. Thus, the leaking-in noise due to a ringing, etc., can be reduced to a slice level position.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a player that also plays back various types of discs such as LD/CD/CDV, and particularly relates to a CD signal (playback signal) suitable for reducing the error rate during playback. This invention relates to an error rate reduction circuit.

[Conventional technology]

Conventionally, the error rate of CD signals has been reduced by using an equalizer to compensate for deterioration of frequency characteristics, etc.

As a method of this type, for example, the one described on page 129 of the book "Compact Disc Reader" published by Ohmsha is known.

[Problem that the invention seeks to solve]

The above conventional technology is for playing back CD discs with a CD player, and in a player that plays different types of discs, such as CNV/X and N discs, it is difficult to avoid an increase in asymmetry caused by differences in lens aperture ratio, tilt angle of the pickup system, etc. No consideration was given to this point, and there was a problem that if an asymmetrical disc was tried to be played on a dual-purpose player, it would become unplayable.6 The object of the present invention is to solve the above problems and make it possible to play the disc. An object of the present invention is to provide an error rate reduction circuit for CD signals.

[Means for solving problems]

The above object is achieved by determining asymmetry based on the error rate or the amount of synchronization error and varying the equalization characteristics.

[Effect]

In the case of large asymmetry, passing through an equalizer makes it impossible to detect the slice level position, resulting in an increase in errors. Therefore, when the error amount exceeds a certain threshold value, the equalization characteristic is varied to make it easier to detect the slice level position and reduce the error.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

The figure is a block diagram showing one embodiment of the present invention.

Reference numeral 1 denotes a pickup section that extracts an EFM signal from a disk (not shown). 2 is an equalizer circuit and pickup section 1
Since the output has a one-frequency characteristic, this is corrected.

The output of the equalizer circuit 2 is input to a demodulation circuit 3 and demodulated. The demodulated output signal is input to the error detection section 4 to detect errors. The error signal is input to an integrator 5, compared with a certain threshold value by a comparator 6, and if it exceeds the threshold value, the equalizer circuit 2 is controlled.

Since the equalizer circuit 2 generally mainly performs amplitude correction, the equalizer 2 may be configured to be turned off in response to an increase in errors. In other words, by stopping the amplitude length in the high range, noise leaking into the slice level position due to ringing etc. is reduced.

According to this embodiment, the equalizer has the effect of preventing noise from leaking into the vicinity of the slice level.

〔Effect of the invention〕

According to the present invention, in a dual-purpose player, by varying the equalizer, it is possible to prevent noise from seeping into the vicinity of the slice level, even for highly asymmetrical discs.

[Brief explanation of the drawing]

The figure is a professional diagram of one embodiment of the present invention. 1...Pickup section 2...
・−・・Equalizer circuit 3・・・・・・・・・・
... Demodulation circuit 4 ...... Error detection section 5 ...
......Integrator 6...Comparator agent Patent attorney Masaru Ogawa 5

Claims (1)

[Claims] 1. A pickup unit that reproduces and extracts an EFM signal from a disk, an equalizer circuit that corrects the frequency characteristics of the EFM signal extracted from the pickup unit, and an output signal from the equalizer circuit that is input. A CD signal reproducing device having a demodulation circuit that reproduces and demodulates the pit clock, an error detection circuit that detects a signal error from a demodulated output from the demodulation circuit, and an error amount detected by the detection circuit that is constant a correction characteristic variable circuit that changes the correction characteristic of the equalizer circuit to reduce the error when the limit is exceeded;
A CD signal error rate reduction circuit characterized by comprising: