JPH05166300A - Information playback device - Google Patents

Abstract

(57) [Abstract] [Purpose] The reproduction reliability is further enhanced by controlling the amplitude level of the reproduction signal with higher accuracy. A means for amplifying a reproduction signal read from an information recording medium, a means for measuring an amplitude level value of a reproduction signal in a predetermined recording area for each sector of the recording medium, and a means for measuring the amplitude level value. Means for accumulating data of the amplitude level value, means for averaging or weighted averaging the accumulated data, and varying the gain of the amplifying means based on the obtained averaged data. , Means for controlling the amplitude level of the reproduction signal to a target value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reproducing apparatus for reproducing information recorded on an information recording medium such as an optical disc.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of a reproduction signal processing system in a general information recording / reproducing apparatus. In the figure,
50 is a detector that detects a signal from a recording medium such as an optical pickup, 51 is an amplifier that amplifies the signal, 52 is a noise filter that cuts noise in an unnecessary signal band, 5
Reference numeral 3 is a binarization circuit that binarizes the reproduced signal by a method such as differentiating the signal and detecting a zero-cross point. Also, 54
Is a PLL circuit for generating a synchronous clock, 55 is a discriminator for discriminating whether or not data is present in the detection window obtained by the synchronous clock, and 56 is for decoding the data encoded at the time of recording. Is the decoder of. In addition to this, a waveform equalizer may be provided at the output of the noise filter 52. In the reproduction signal processing system described above, the amplification factor of the amplifier 51 is fixed, and therefore the influence of the amplitude change of the detected signal is absorbed by the binarization circuit 53. That is, since the binarization circuit 53 has a configuration in which the signal is differentiated and then input to the comparator to detect the zero-crossing point as described above, even if the amplitude of the signal fluctuates a little, there is little effect. Further, strict design and adjustment are made so that the amplitude of the detection signal does not vary more than the allowable value.

By the way, there is a difficult problem in trying to provide common compatibility among various types of recording media, various types of recording devices and reproducing devices. That is, the amplitude of the reproduction signal changes due to factors such as variations in the recording sensitivity of the recording medium, environmental conditions such as temperature, dirt and scratches on the medium, and aging. Further, the amplitude of the reproduction signal also changes due to variations in characteristics of individual reproducing apparatuses, variations in characteristics of apparatuses that record information, and compatibility between the recording medium and the reproducing apparatus. When the amplitude of the reproduced signal changes due to various factors as described above, if the amplification factor of the amplifier 51 is constant, the noise filter 52 and the binarization circuit 53 are not operated when the input signal is too large or too small. It will not work properly. Therefore, the AGC (Auto Gain
Control) function is desirable.

[0004]

However, when this AGC function is added to the amplifier, the following problems occur. That is, the normal recording medium is divided into a plurality of sectors and
The format of one sector is decided. In order to absorb the variation in the reproduction speed with respect to the recording speed, the boundary portion of this sector contains GAP or BUFFE.
An area called R, in which data is not recorded, is provided. Since the level of the reproduction signal should be close to 0 in this area, if the AGC circuit is operated in this area, the amplification factor increases sharply, which hinders the data reproduction immediately thereafter. In addition, the write-once type recording medium and the rewritable type recording medium,
Since there is a sector in which no data is recorded, if the AGC circuit operates in the unrecorded area of the data, there is a problem in that the reproduction of the data is hindered when the data is transferred from the unrecorded area to the recorded area. ..

Therefore, the inventor of the present application has previously applied for an information reproducing apparatus that solves the above problems as Japanese Patent Application No. 3-250247 and Japanese Patent Application No. 3-248469. In the former information reproducing device, a fixed pattern was recorded for each sector,
For example, the amplitude level of the reproduction signal is measured using a VFO pattern or the like, and the amplification factor of the reproduction signal is adjusted based on the value. The latter information reproducing apparatus adjusts the amplification factor of the reproduction signal for every reproduction operation during the information reproduction or the reproduction preparation operation before the reproduction. Further, according to these information reproducing apparatuses, the problems caused by the AGC function can be solved and the signal processing can be performed after the amplitude level of the reproduced signal is made constant. Therefore, the type of recording medium, the type of recording apparatus, or the reproducing There is an effect that a signal can be stably processed regardless of the type of device and compatibility can be guaranteed in all combinations.
Although the above information reproducing apparatus can stabilize the amplitude level of the reproduced signal that fluctuates due to various causes, further stable amplitude control is desired in order to further improve the reproduction reliability of the apparatus.

An object of the present invention is to provide an information reproducing apparatus which improves the above-mentioned prior art and further improves the reproduction reliability.

[0007]

The object of the present invention is to provide means for amplifying a reproduction signal read from an information recording medium, and an amplitude level of the reproduction signal in a predetermined recording area for each sector of the recording medium. Means for measuring the value, means for accumulating data of this measured amplitude level value,
Means for averaging or weighted averaging the accumulated data, and varying the gain of the amplifying means based on the obtained averaging data to control the amplitude level of the reproduction signal to a target value. And an information reproducing device.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the information reproducing apparatus of the present invention. In FIG. 1, reference numeral 1 is a gain control amplifier having a function of changing an amplification factor according to an instruction from the outside, and 2 is a signal amplitude level measuring circuit for measuring an amplitude level of a reproduction signal amplified by the amplifier 1. The reproduction signal is a signal read from an information recording medium such as an optical disk (not shown) by a photodetector such as an optical pickup. As the measurement circuit 2, any one of a sample hold circuit, a peak hold circuit, a bottom hold circuit, a rectifier circuit, an envelope circuit, or a circuit combining them can be used. As an example of the combination, for example, a peak hold circuit and a bottom hold circuit may be used to detect the peak value and the bottom value of the reproduction signal, and the difference may be taken to measure the amplitude level. In any case, it is assumed here that any measurement circuit measures one of the maximum amplitude value and the average amplitude value of the reproduction signal, the maximum peak value in a specific section of the information recording medium (not shown), and the like. Although there are various definitions of the measured value as described above, in the present embodiment, the measured value such as the maximum amplitude value or the average amplitude value will be referred to as an amplitude level value. 3 is the measurement circuit 2
The AD converter for converting the amplitude level value measured in 1. into a digital value, 4 is a microcomputer for controlling the amplification factor of the gain control amplifier 1 based on the obtained amplitude level value, and 5 is the measured amplitude A history memory for accumulating history data of level values, and a DA converter 6 for analog-converting an instruction value for the gain control amplifier 1 of the microcomputer 4.

Next, the operation of this embodiment will be described. First,
Recording information is sequentially read from the information recording medium, and the read reproduction signal is sequentially input to the gain control amplifier 1. The gain control amplifier 1 amplifies the input reproduction signal by the amplification factor at that time and outputs it to the measurement circuit 2. The measuring circuit 2 measures the amplitude level value of the reproduction signal as described above and outputs it to the AD converter 3. In this case, the measurement circuit 2 measures the amplitude level value of the reproduction signal in the specific area for each sector of the information recording medium according to an instruction from the timing control circuit (not shown). For example, VF for each sector
Signals of O pattern and SM pattern are measured. The amplitude level value measured by the measurement circuit 2 is digitized by the AD converter 3 and then output to the microcomputer 4.

The control operation of the microcomputer 4 will now be described. In addition, in order to facilitate the description in FIG.
The flow of processing is shown in the microcomputer 4. In the microcomputer 4, first, an arithmetic process of dividing the amplitude level value by the amplification factor of the gain control amplifier 1 at that time is performed to calculate the amplitude level value of the actual reproduction signal (S1). Then, it is determined whether the measured amplitude level value is within a predetermined allowable range, and if it is outside the allowable range, the data is discarded (S
2). If it is within the allowable range, it is stored in the history memory 5 as history data (S3). At this time, if the storage capacity of the history memory 5 is exhausted, the oldest data is erased and new data is accumulated (S3). That is,
Since the capacity of the history memory 5 is limited, when the number of data exceeds a predetermined number, the oldest data is erased sequentially and the newest data is replaced. Next, the microcomputer 4 executes a process of averaging or weighted averaging the data accumulated in the history memory 5 as described above (S4). The weighted average means, for example, that newer data is weighted as more reliable, or that measurement data obtained when an error occurs in the device is lightly handled and averaged.

The microcomputer 4 calculates the amplification factor of the gain control amplifier 1 based on the average value thus obtained so that the amplitude level value of the reproduction signal becomes the target value (S5). And the microcomputer 4
The instruction value calculated by is converted into an analog signal by the DA converter 6, and then input to the gain control amplifier 1 to be adjusted to the instructed amplification factor. Since no data is initially stored in the history memory 5, an incorrect average value may be calculated or the average value may become unstable. Therefore, in order to prevent such a problem, a predetermined default value is initially substituted in the history memory 5. Further, in the information reproducing apparatus, the history data becomes invalid when the recording medium is replaced or activated, and therefore, in such a case, a predetermined default value is substituted in the history memory 5. As described above, a more stable reproduction signal having a constant amplitude can be obtained from the gain control amplifier 1.

FIG. 2 is a block diagram showing another embodiment of the present invention. This embodiment is an example in which the amplitude level value of the reproduction signal is measured on the input side of the gain control amplifier 1. Further, while the embodiment of FIG. 1 is feedback type control, this embodiment is open type control, but the processing of the microcomputer 4 is simpler in this embodiment than in the embodiment of FIG. become. Even in the present embodiment, it is possible to obtain a stable reproduction signal having a constant amplitude as in the embodiment of FIG. In the embodiments of FIGS. 1 and 2, an example in which various processes are performed by software using a microcomputer is shown, but similar processes can be performed by hardware.

[0013]

As described above, according to the present invention, the history data of the measured amplitude level values is accumulated, and the history data is averaged or weighted to be used to further reproduce the reproduced signal. The amplitude level can be controlled accurately, and a more stable reproduction signal with a constant amplitude can be obtained. Therefore, since the amplitude level of the reproduction signal can be further stabilized, there is an effect that the reproduction reliability of the information reproducing apparatus can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an information reproducing apparatus of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a reproduction signal processing system of a general information reproducing apparatus.

[Explanation of symbols]

 1 gain control amplifier 2 signal amplitude level measurement circuit 3 AD converter 4 microcomputer 5 history memory 6 DA converter

Claims (4)

[Claims] 1. A means for amplifying a reproduction signal read from an information recording medium, a means for measuring an amplitude level value of the reproduction signal in a predetermined recording area for each sector of the recording medium, and Means for accumulating the data of the measured amplitude level value, means for averaging or weighted averaging the accumulated data, and gain of the amplifying means based on the obtained averaged data. And a means for controlling the amplitude level of the reproduction signal to be a target value. 2. The information reproducing apparatus according to claim 1, wherein the history data of the data accumulating means is erased and a predetermined default value is substituted when the apparatus is activated or the recording medium is exchanged. 3. The method according to claim 1, wherein when the number of history data of the amplitude level value of the data storage means exceeds a predetermined number, the old history data is sequentially erased and replaced with new data. Information reproduction device. 4. The information reproducing apparatus according to claim 1, wherein when the measured amplitude level value is out of a predetermined allowable range, it is not stored in the data storage means.