JPS60170074A - Information reproducer - Google Patents

Abstract

PURPOSE:To read accurately and stably the information even from a reproduction signal having a change of the duty ratio by giving the digital control to said duty ratio. CONSTITUTION:The 1st and 2nd reversible counters 20 and 21 counts forwardly the clocks phi when a reproduced digital signal is kept at level H and then count adversely those clocks when said digital signal is kept at level L respectively. If the duty ratio of the digital signal is larger than the normal value with a longer time set for level H than level L, the counter 20 increases its number on an average and produces a carry signal at an output terminal C. This signal C is supplied to the counter 21 as a ripple clock through an input terminal RC. The output signals Qi, Qj and Qk given from the counter 21 undergo the D/A conersion and are immediately fed back to threshold. This can improve the shift of the duty ratio of the reproduction digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an information reproducing apparatus for reading information from a tie information record carrier on which a digital signal is recorded, and in particular, an information reproducing apparatus for reading information from a tie information record carrier on which a digital signal is recorded, and in particular, the deity ratio of the reproduced digital signal is higher than that of the original digital signal. The tjf has a duty ratio control means that allows correct information to be read even when the information is different from that of the tjf.
This is related to the t@playback device 1. --Conventional configuration and problems thereof Figure 1 shows a block diagram of a duty ratio control means in a conventional information reproducing device, where 1 is a comparator, ``N'' is a low-pass filter, and ``A'' is a low-pass filter. The differential amplifier 4 is a reference voltage generator.

・Hereinafter, ・The operation will be explained with reference to the drawings.

- If the irregular information is properly digitally modulated, the output ratios of logic 0 and logic J11 are tl and 60, respectively. In addition, even in the case of information that has O or 1, if it is digitally modulated so that the probability of occurrence of logic 0 and logic 1 is 60 times each, then in most cases, the modulated signal will have logic. 0 and logical 1 appear with equal probability. As such digital modulation methods, for example, F iVL, PE, M'h' iVl, etc. are known. Ushita. Examples of information that can be considered irregular include digitized music signals and the like. There is also a digital modulation method in which the probability of appearance of logic 0 and logic 1 is equal for any information, regardless of regularity or irregularity. In this way, logic 0 and logic i! If 4!1 appears with a high probability, it is a logic 0 cumulative time; Flil
The integrated times should be approximately equal. Therefore, comparator 1 outputs the reproduced signal (HN) at an appropriate threshold. If you reshape it, you will get a reproduced digital (i) that is the same as the original digital No.
4- is obtained, and the DC component of this reproduced digital signal has a voltage approximately halfway between the logic 0 voltage and the logic 1 voltage. However, if the threshold value deviates, the voltage of the DC component of the reproduced digital signal also deviates. Therefore, the intermediate voltage is generated by the reference voltage generator 4, and the low-frequency component extracted from the output signal of the comparator 1 is compared with the voltage generated by the reference voltage generator 4 by the low-pass filter 2. An error in the threshold value of comparator 1 can be detected. Therefore, by amplifying this error with the differential amplifier 3 and feeding it back to the country 1L of the comparator 1, it is possible to suppress the comparator 1 to correctly shape the waveform. However, in this configuration, the low-pass filter 2 includes elements such as capacitors, so when an integrated circuit is used, external circuit components are required, and temperature drift and changes over time occur. It also had the disadvantage of being easy.

Purpose of the Invention The present invention eliminates the above conventional drawbacks by controlling the duty ratio digitally, and makes it possible to accurately and stably read information even from a reproduced signal with a changed duty ratio. It is something.

Structure of the Invention The information reproducing apparatus of the present invention comprises: a waveform shaping means for obtaining a reproduced digital signal by waveform shaping a reproduced signal read from an information recording carrier on which a digital signal is recorded; and a waveform shaping means having a variable threshold value; a clock generator that generates clock pulses at a cycle sufficiently shorter than the length of the element waveform; a first counting means that increases or decreases the clock pulses in accordance with the reproduced digital signal; a second counting means for increasing or counting the carry signal from the first counting means; and a digital/analog conversion means (hereinafter referred to as D/A converting means), and the D/A converting means is
The output signal of the A conversion means is fed back to the 14 values of the waveform shaping means, and the first counting means is configured to be preset to a predetermined value when a carry signal is generated.

As a result, even if the duty ratio of the reproduced signal is shifted, the information μ can be read accurately, there is almost no temperature drift or change over time, and when using an integrated circuit, there is no need to worry about external circuit components. This means that less is needed.

Description of an Actual Example An actual example of the present invention will be described below with reference to Box 1.

FIG. 2 shows a block diagram of the duty ratio control means in one embodiment of the present invention. In FIG. 2, 1o is a waveform shaping means, 11 is a clock generator, 12 is a first counting means, 13 is a second counting means, 14
is L)/A change means.

Duty ratio 11 for this case configured as above
1J The operation of the four means will be explained below.

The waveform shaping means 1 converts the reproduced signal (HF) into an appropriate aperture.
When waveform shaping is performed at o, a reproduced digital signal similar to the original recorded digital signal is obtained. If the level of this threshold 1 shift is not excessive, then the theory of reproduction digital 1 JiJ! The average value of the length of 0 and the length of logical 1 will be different. Therefore, the clock generator 11 generates a tack pulse whose cycle is sufficiently shorter than the cycle of the recorded digital signal 1N element waveform, and when the reproduced digital signal 1 is logic 1, this pulse is sent to the first counting means. If the first counting means 12 counts forward n at 12 and counts backward when the axis layer is 0, the first counting means 12 will increase the count formula on average and output a carry signal. The second counting means 13 counts this carry signal forward, and the count value changes. Conversely, when the length of the level L of the reproduced digital signal is longer than the length of the level h, the first counting means 12 outputs a carry (borrow) signal, and the second counting means 13 performs backward counting. . By configuring a closed loop so that this count value is D/A converted by the D/A conversion means 14 and fed back to I@1m of the waveform shaping means 10, the duty ratio
The ratio can be controlled to be correct. However, when the level of the reproduced digital signal is a, Ii! When the J10 counting means 12 outputs a carry signal, it outputs a carry signal again when the reproduced digital signal becomes level L, and this is repeated several times to start the second count. Chattering may occur in the count value of the means 13. When this chattering occurs, glitches occur frequently in the D/A converter 14iJ, causing many hazards in the reproduced digital signal, and there is a possibility that the fh information may be read incorrectly. Regarding Honji Tsumugi Shiri,
When the first counting means 12 generates a carry signal,
The count value of the first counting means 12 is configured to be preset to a predetermined if approximately halfway between the maximum value and the minimum value, thereby making it possible to prevent the above-mentioned chattering.

Next, the present invention will be explained in more detail with reference to specific circuit examples.

FIG. 3 shows a circuit diagram of the first counting means 12 and the second counting means 13 in an embodiment of the present invention, in which 20 is a first reversible counter, 21 is a second reversible counter, 22ijO: IT gate, 23 is NAND
A gate, 24 is an AiD gate, and 25 and 26 are inverters.

The operation will be explained below. In the following explanation, it will be assumed that logic f#0 has a low potential and is considered to be level L, and theory 1 has a high potential and is considered to be level L. 1st 61
through counter 20 and second reversible counter 21rfi,
, the switching between forward counting and backward counting is 1lrIl@ by the reproduction digital signal (5), and when the reproduction digital signal is at level H, □1 clock (φ) is counted forward, and when it is at level L, the same Now, if the data resistance of the reproduced digital signal is the normal 111 (which is larger than the time of level L, the time of rettle, ', R is longer than the time of level L, then the first reversible counter 2o' is the average value. , the count increases and a carry signal is generated at the output terminal CK.

This carry 1 digit C is input to the input terminal hc of the second reversible counter 21 as a ripple clock.

In the case of the present example, the signal C is normally generated in a forward counting state (because the time at level H is much longer than the time at level L), and the second reversible counter 211 , y 7' /l/pnk 0y)l, and the counting means adds the output signal WQ from the second reversible counter 21. and Qk as E
)/A conversion and returning this to the south, the above-mentioned duty ratio deviation can be improved.

Furthermore, when the carry signal C from the first reversible counter 20 is output, this carry signal C is delayed by the inverters 26 and 26 and is applied to the input terminal, so that the carry signal C is outputted from the first reversible counter 20. Qa, Qb, , Qc of
, Q(1, Qe v, tJf , QCJ and Qhu
o, o, o, o, o, o, respectively.

and preset to 1. This is to prevent the first reversible counter 20 from repeatedly generating a carry, a carry, and a borrow in synchronization with each state inversion of the reproduced digital signal. 2
It is possible to prevent the count value of the counting means 13 from frequently changing and the D/A converting means 14 from generating many glitches each time. Also, the AND gate 23 is set to 7 (when) the second reversible counter 21 reaches a maximum of 11 sections.
The OR gate 22 is the one that stops the counting.
This is to stop the inverse counting when the oJ inverse counter 21 of the oJ inverse counter 21 reaches the minimum value.

In addition, how accurate are the slant-shaped rock-shaped means and the first counting means in the present invention? 11', and any type of device having similar functions may be purchased. For example, a comparator can be used as the waveform shaping means, and when the first counting device and the reproduced digital signal are at level H, the clock φ1
A counter that counts φ and a clock φ when the level is L.
Two counters, one counting 1, may be used, and after these koi/kori nana sotoshi are counted, the counts within the ichiganjishi may be compared.

Effects of the Invention As is clear from the above description, the present invention has the advantage of waveform shaping a reproduced signal taken from an information recording carrier on which a digital signal is recorded, and converts the reproduced digital signal to 1↓11 so that the threshold value is h. a clock generator that generates clock pulses with the same JvJ sufficiently shorter than the length of the element drum shape of the digital signal, and a clock pulse that is counted forward or backward in accordance with the reproduced digital signal. A first counting means for counting, a second counting means JM for forward or backward counting of the carry signal from the first counting means, and this 20th counting means.
Changing the count number of the counting means to analog IchikawaD
/A converting means, the output signal of the L)/A converting means is directly fed back to the threshold of the waveform shaping means, and the first
The counting means is constructed so that it is preset to a predetermined value when a signal is generated, so it can be processed entirely digitally. This has the effect of reducing the number of external circuit components and reducing fb'ML drift and changes over time.Furthermore, chattering occurs in the count value of the second counting means 13, which causes 1J/A conversion. The advantage can also be obtained that the means can be prevented from generating frequent glitches and causing a number of hazards in the reproduced digital signal.

[Brief explanation of drawings]

Figure 1 is a block diagram of duty ratio control means in a conventional information reproducing device, Figure 2 is a block diagram of duty ratio control means in an embodiment of the present invention, and Figure 3 is an example of an actual gun of the present invention. (/il: is a specific circuit diagram of the first counting means and the second counting means. 10... waveform" K-shaped stage, 11-... clock generator, 12...first counting means,
13...Second counting means, 14...
- D/A conversion means, 2o. 21... Tsukasa reverse counter, 22... OR
Gate, 23...N A N D gate, 24
...Ha NO Gate, 25.26... Name of inverter agent Patent attorney Toshio Nakao and 1 other person 1st
figure

Claims (1)

[Claims] A waveform shaping means which obtains a reproduced digital signal by waveform shaping a reproduced signal read from an information recording carrier on which the digital signal is recorded, and whose threshold value is variable, and a waveform shaping means having a sufficiently short period than the length of the element waveform of the digital signal. a clock generator that generates clock pulses, a counting means of 5FS1 that counts the clock pulses forward or backward according to the reproduced digital signal, and a count means of 5FS1 that counts the carry signal from the first counting means forward a second counting means for counting or backward counting; and this M2
digital/analog converting means converting the count number of the counting means into an analog voltage, and converting the output signal of the digital/analog converting means into
1. An information reproducing device characterized by a circuit configured to be reset to a predetermined unit when the first counting means returns to the first count and generates an upgrade signal.