JPS58166538A - Optical reader - Google Patents

Abstract

PURPOSE:To improve the reliability of data reproduction, by detecting the amplitude of a specific pattern in a specific area of the recording data in each sector on a disk in the form of a sampled value, and setting a gain to some value only while the sector is handled. CONSTITUTION:From the output of a sector mark area SM in a preformat part 1, a sector head (SM) signal 10 is generated on the basis of this signal, a timing circuit generates an envelope detection gate signal 7; and the amplitude of a read signal 6 when said signal has a true value is held by an envelope circuit, whose output voltage level is used as the gain adjusting signal 8 of a readout amplifying circuit. The envelope circuit holds this voltage level until the envelope detection gate signal of the next sector has a true value and fixes the gain of one sector by the control voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention The present invention is an optical reading device that detects a reproduced signal using a laser beam or the like, which depends on the size of a read signal waveform from each sector of an optical disk device. This invention relates to an optical reading device that applies an AGO.

BACKGROUND ART Conventionally, an automatic gain adjustment method for a magnetic disk drive has been provided with a gain adjustment circuit having a large time constant in order to detect the amplitude difference between the inner circumference and the outer circumference of the disk and correct the amplitude difference.

The premise of this method is that since there is little amplitude change in the early cycles of the same track, a gain*S with good response characteristics can be obtained.
That means it's unnecessary.

Further, in the case of magnetic tape, the amplitude of a burst signal near the beginning of the tape is detected, the gain is automatically set according to the amplitude, and reproduction is performed with a fixed gain for one roll of the tape.

By the way, optical disc information #i1! When additional recording is performed to a sector that has not been previously recorded, the difference between the previously recorded signal and the newly recorded signal is that the recording sensitivity of the disc deteriorates over time and the optical disc device's recording speed increases. The amplitude of the reproduced signal will change depending on the characteristics and the like. For this reason, the output chain changes stepwise to different sectors on the disk, making it impossible to track with a method with a large time constant such as a magnetic disk device. It is also impossible to maintain the reproduced signal constant with a set gain.
There is a problem in that the conventional method as described above cannot be applied as it is as the automatic gain #11 method of an optical disk device.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and its purpose is to read a specific area of recorded data in each sector of a disk in an optical signal reading device such as an optical disk device. Detects the amplitude of a specific pattern as a sample value L
7. An optical reader that improves the reliability of data reproduction by setting the gain to a certain value only while corresponding to the sector and keeping the reproduction amplitude of the sector constant. Our goal is to provide the following.

That is, the present invention provides an optical signal reading device that detects information on a rotating disk using a laser beam or the like, in which the gain when reading each sector is determined by the value of the signal amplitude of the first specific area of recorded data for each sector. The present invention relates to an optical signal reading AT which is capable of extracting the data as a sample value and increasing the gain for each sector, and the reliability of data reproduction is significantly improved by the present invention.

EXAMPLES OF THE INVENTION Hereinafter, the present invention will be explained in detail with reference to examples. 1st
11 shows an example of the sector format of an optical disc and the second
2 is a block diagram illustrating an embodiment of the present invention. FIG. An example of the sector format of an optical disc shown in FIG. 1 includes a preformat section 1 including a sector mark area 8M for detecting the start end of a sector, and a signal for synchronizing the glue when reading an additionally recorded signal. It consists of a data area section 2 including areas VIFO87MO2 and the like.

Now, considering the case of reading out a sector that has already been recorded, although the successive signal 6 contains various data patterns, the area 7708 in the data area section 2
Ylf02 has 11 to wealth! Since the data pattern is recorded, l1iI in this area is recorded.
Using the yi1 data pattern, the gain is adjusted so that the amplitude of the reproduced signal is constant. That is, a sector start fi (SM) signal 10 is generated from the output of the sector mark area SM in the preformat section 1, and an envelope detection gate signal 7 is generated by the timing circuit based on this signal. The amplitude of the readout signal 6 during the period in which it is true is held by the envelope (gl&3), and this output voltage level is applied to the output voltage level of the amplifying circuit 6.
Used as I& signal 8. The envelope circuit δ holds this voltage level until the envelope 1 detection gate signal of the next sector becomes the true value, and fixes the gain for one sector by this control voltage.

In this way, the gain of the successive widening circuit is corrected based on the fixed width value of the first part of the data area of a certain sector on the disk, and this operation is repeated for each sector. The gain adjustment for recording and reproduction of the entire disk is performed for each sector, and the effect is that the reproduction level is kept almost constant.

As described in detail, according to the present invention, even if information is written to an optical disc at certain intervals for each sector, the amplitude of the reproduced signal does not change from sector to sector. However, the reliability of data reproduction is significantly improved.

[Brief explanation of the drawing]

@1wi shows an example of the sector format of an optical disc and various signals in the block diagram of FIG. 2, and FIG. 2 shows a plotter diagram of an embodiment of the present invention. 1 nibrifuo 1! 2: Data area section, 3: Envelope circuit, 4: Timing circuit, δ: Successive expansion width.
Road. Patent applicant: Hitachi, Ltd.

Claims (1)

[Claims] In an optical reading device that detects information recorded in a sector on an optical disk using a laser beam or the like, the gain obtained by successively recording data recorded in each sector is determined by first identifying the data recorded in the sector. An optical reading device characterized in that the amplitude value of a fixed signal in a region is extracted as a sample, and the gain is adjusted using this as a reference for the sector.