JPS6138476A - Apparatus for detecting flaw of recording medium - Google Patents

Abstract

PURPOSE:To reduce the erroneous ratio in the reading of data as the whole of an apparatus, by setting a flaw detection level having to judge the presence or absence of a flaw by the comparison with the reading voltage of a data track. CONSTITUTION:The recording content of a recording medium 10 is read by a magnetic head 1 while peak voltage is held by a peak hold circuit 4 through an amplifier 2 and a rectifier circuit 3 and the output signal (c) is averaged in one track by an average output level detection circuit 8 to be inputted to a flaw level setting circuit 9 along with the output of a flaw count circuit 7. Further, the signal (c) and the signal of the circuit 9 are compared by a flaw detection circuit 5 and the signal (c) equal to or less than the signal of the circuit 9 is set as a flaw signal while the pulse number thereof is stored in a flaw position memory circuit 6. At this time, the flaw signal of the circuit 5 is counted by the circuit 7 and the flaw detection level of the circuit 9 is set so that the counted value is brought to the max. number of flaws to be accommodated in one track and flaw avoiding function is utilized to the max. possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a recording medium defect detection device δ for a rotary data recording device having a defect avoidance function.

(Prior Art) In general, in a rotating data 8C recording device, such as a magnetic disk device, as the recording density increases, the area of the magnetic disk required to record one bit becomes extremely small, and the entire surface of the magnetic disk is covered. It has become difficult to stably manufacture disks that contain no (or very few) surface defects. Conventionally, a method was used in which a data track containing such surface defects was treated as a defective track and a replacement trunk was provided, but in recent years, defect position information has been recorded in advance in front of the data section, and the defect position information is recorded during recording and playback. f. A method has been proposed in which the defect is avoided (jumped) when the magnetic head reaches the defective position during reading. Recently, the number of defects allowed in one track has increased to about 4 to 7 and can now be used.

However, when actually saving the recording medium, a constant value of the average read voltage within one track (iin is usually 50 to
60%) is set as the defect detection level, and the defect detection level is set so that the maximum allowable number of defects is achieved for trunks with poor characteristics.In most trunks, no defects are detected, and even if defects are detected, only one defect is detected. However, there was a drawback that the utilization rate of the defect avoidance replacement area secured in advance was extremely low.

(Objective of the Invention) The object of the present invention is to eliminate such drawbacks and improve the entire system by feeding back the number of detected defects to the total defect detection level setting circuit and effectively utilizing the defect avoidance alternation area secured in advance. An object of the present invention is to provide a recording medium defect detection device that can greatly reduce the error rate of data reading.

(Configuration of the Invention) The configuration of the present invention provides a recording medium defect detection device for an oral data recording device that avoids defects in a small recording medium by storing a defective portion of a data track in a replacement track.
a defect detection circuit that outputs a defect signal when the read voltage of the data track becomes less than a predetermined defect detection level; a defect counting circuit that counts the defect signal from the defect detection circuit and outputs it as defect number information; an average output level detection circuit that detects an average read voltage within one track from the read voltage of the data track, and a number of recording defects allowed within the previous 6c: 1- track from the average read voltage and the defect number information; The present invention is characterized by comprising a defect detection level setting circuit that sets the defect detection level so as to have a maximum number of defects.

(Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of a medium defect detection device according to an embodiment of the present invention, and FIGS. 2(a-1) to (f) are time charts showing the operation of FIG. is read by a magnetic head 1 and amplified by an amplifier 2,
A readout waveform as shown in Fig. 2 (al) is output. In order to obtain the output level from this output waveform, it is rectified by the rectifier circuit 3 (Fig. 2 (b)), and the obtained rectified waveform is peaked. Input to hold circuit 4. This peak hold circuit 4
holds the peak voltage of the rectified output 1.8g2 (C1
Set the readout output level as shown in ! do. On the other hand, the average output level detection circuit 8 detects this readout output level (FIG. 2(C)
)) within one track is determined and input to the defect detection level setting circuit 9 as the average output level.

Conventionally, a fixed ratio of this average output level (usually 50 to 60
%) and the readout output level using a comparator (, "・f
However, in this embodiment, the defect detection level setting circuit 9 initially detects the average output level. A fixed ratio of the defect detection level is outputted to the defect detection circuit 5 as a defect detection level. That is, j:F E! in Figure 2 (C)! The defect detection level (E+) is the minimum level (E+)f required to find a position where a read error can occur with a probability greater than the read error rate of the device.

This defect detection circuit 5 generates a defect signal as shown in FIG. get information.

Here, assuming that the maximum number of defects allowed in one track is 4, the defect number information of the defect counting circuit 7 will never be 4 in most tracks.

Therefore, the defect detection level setting circuit 9 sets the defect number information to 4.
If the defect detection level is less than
The detection level is set more strictly from the first time, such as level E2 of No. 1. As a result, the defect signal can detect minor defects that were overlooked the first time, as shown in Figure 2 (el).In this case, the defect number information is 3, and the maximum allowable defect number is 4. Therefore, the defect detection level setting circuit 9 sets the defect detection level t=i2 to a more severe level as level E3 in FIG.
As a result, the defect number information is 4, which is the maximum allowable number of defects, so four defect positions are stored in the defect position storage circuit 6 as shown in FIG. 11. The information is recorded at the beginning of the track as information for defect avoidance, and the medium defect detection test is completed. Defects are counted by a defect counting circuit, and based on the result, the defect detection level is set to a stricter level, and the number of defects allowed within one track is increased.
By discovering even minor defects before reaching the number of major defects, the defect avoidance function can be utilized to the fullest and the overall error rate of the device can be lowered.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a medium defect detection device according to an embodiment of the present invention, and the 21st pieces (aJ to (f) are time charts showing the operations of FIG. A1.

Claims (1)

[Claims] In a recording medium defect detection device for a rotary data recording device that avoids defects in a recording medium by storing a defective portion of a data track in a replacement track, a defect signal is generated when the read voltage of the data track becomes below a predetermined defect detection level. a defect detection circuit that counts the defect signals from this defect detection circuit and outputs it as defect number information; and an average output level that detects the average read voltage within one track from the read voltage of the data track. comprising a detection circuit and a defect detection level setting circuit that sets the defect detection level based on the average read voltage and the defect number information so that the number of recording defects becomes the maximum number of defects allowed in one track. A recording medium defect detection device characterized by: