JPH01146169A - Optical information reproducing device - Google Patents

Abstract

PURPOSE:To reduce the phase error and to obtain an accurate signal resulting in few read errors by separating an analog MFM reproducing signal into a low band component and a high band component and latching a binarizing signal of the low band component from a data pulse of the high band component. CONSTITUTION:An information reproducing signal (b) as a result of the filtration of an unnecessary DC component from the analog MFM (Modified Frequency Modulation) signal (a) by a high pass filter 1 is separated into a low band component signal (c) and a high band component signal (d) by a low pass filter 2 and a high pass filter 3 respectively, whereas a low band component binarized signal (e) is obtained by a binarization circuit 4 from the low band component signal (c), while a delayed high band component data pulse (g) is outputted by a pulse shaper 5 and a delay circuit 6 from the high band component signal (d). Then, the low band component binarized signal (e) is converted into a digital MFM signal (h) by a flip-flop 7 in accordance with the delayed high band component data pulse (g). By this method, an accurate binarization signal (h) with few phase errors can be outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information reproducing device, and more particularly to a circuit for binarizing a reproduced signal of an optical information reproducing device.

[Background of the Invention] In recent years, many optical information recording and reproducing devices using information recording carriers such as optical files and compact discs have been proposed. Card-shaped optical information storage RMU with capacity
Proposals for optical cards (hereinafter referred to as optical cards) are also beginning to be made.

FIG. 3 is a schematic plan view showing the recording format of the optical card, and FIG. 4 is a partially enlarged view thereof.

In both figures, a recording area 12 is provided on an optical card 11 that is an information recording carrier, and the recording area 12 is formed by a plurality of bands 13 arranged. Further, the bunt 13 is formed by arranging a large number of information tracks 14, and the information tracks 14 have an information capacity of about several tens to 100 bits. In addition, each band is a reference line (hereinafter referred to as R
It is called a line. ), and a home position IP, which is an access reference position, is provided at a corner of the optical cart 11.

Note that arrow A is the moving direction of the optical card 11 during reproduction, and arrow C is the moving direction of the optical head, which will be described later.

FIG. 5 is a schematic diagram of the optical cart reproducing device.

In the figure, the optical card 11 is movable in the direction of arrow A by a rotation mechanism 16. Information recorded on the optical card 11 is read and reproduced by the optical head 21 for each information track 14. First, light from a light source 17 such as an LED is focused by a lens system 18 and illuminates a certain information track 14 on which information is recorded. The image of the illuminated information track 14 is formed on the sensor array 2o by the imaging optical system 19, and an electrical signal corresponding to the information recorded on the information track 14 is output from the sensor array 2o. Optional information track 14 on optical card II
To access, first, the optical head 21 is moved in the direction of arrow C with the home position HP as a reference. The optical head 21 selects the band 13 to which the target information track to be read belongs by counting the R lines 15, and stops when reaching the band. Subsequently, the optical card 11 is moved in the direction of arrow A by the rotation mechanism 16, and when it reaches the target information track, the information is read. However, in an actual system, it is rare that only one information track is accessed, and in order to facilitate information management, the minimum access unit (usually called a sector or block) consisting of a plurality of information tracks is usually used. ) is accessed.

[Problems to be Solved by the Invention] In the optical card reproducing device as described above, a binarization circuit that converts a reproduction input signal from the optical card into a binary signal is often used in optical information recording and reproducing devices. ing.

FIG. 6 is a circuit diagram showing an example of a conventional binarization circuit.

As shown in FIG. 6, the binarization circuit of this example has a reference voltage source 3
7, and a comparator 36 to which a reference voltage is input from the reference voltage source 37 to an inverting input terminal, and to which an input signal 38 is input to a non-inverting input terminal.

When an input signal 38 is input to this binarization circuit, a binary signal 39 is outputted which is at a high level in a signal range of a voltage higher than the reference voltage value and at a low level in a signal range of a lower voltage.

FIG. 7 is a circuit diagram showing another example of the conventional binarization circuit.

In the binarization circuit of this example, the potential of the inverting input terminal of the comparator 41 is set to Ov, and an input signal is applied to the non-inverting input terminal via an HPF (high pass filter) 40.
When the low frequency component of the input signal 38 is cut by the HPF 40 and input to the non-inverting input terminal, a binary signal 39 is output which is high level in the positive voltage signal range and low level in the negative voltage signal range.

In the above binarization circuit, when an input signal with fluctuations in the DC voltage component as shown in FIG. 8(a) is input, in the former binarization circuit, the signal range of the voltage 43 exceeding the reference voltage 44 is Since it is not detected, an undetected area may occur, or a phase error may occur in the detected binary signal, making it difficult to obtain accurate binary signals.
A problem arises in which a value signal cannot be obtained.

FIG. 8(b) is a waveform diagram showing a binary signal. The part corresponding to the center of the input signal has been binarized almost correctly, but the parts on both sides are lower than the reference voltage of the input signal. The low signal range is reduced due to variations in the DC voltage component, resulting in large phase errors.

Also, in the latter binarization circuit, although the DC voltage fluctuation of low frequency components can be removed, when the frequency of the DC voltage fluctuation approaches the frequency of the modulation signal component of the input signal, the HPF cannot remove the DC voltage component. This was difficult and caused similar problems.

[Object of the present invention] An object of the present invention is to provide a binarization circuit that can extract only the modulated signal component of an input signal and output an accurate binary signal with little phase error.

[Means for solving the problem] The above problem is solved by separating the input signal into a high frequency component and a low frequency component and converting the input signal into a binary signal using a binary signal of the low frequency component and a pulse signal of the high frequency component. This problem is solved by a binarization circuit that performs the following.

[Examples] Examples of the present invention will be described in detail below. Before explaining the binarization circuit of the optical information reproducing apparatus of the present invention, the optical information reproducing apparatus will be briefly explained.

FIG. 9 is a partially enlarged schematic diagram of the recording format of the optical card shown in FIG. 3. However, the shaded area 53a in the figure indicates information "l".

In the figure, the information track 14 is separated from adjacent information tracks in the direction in which the bits of the information track 14 are arranged by a separation area 52. Further, a plurality of tracks each consisting of the information track 14 and the separation area 52 are arranged to form the hand 13. Bands 13 are arranged in multiple rows,
The row of separation regions 52 in the hand 13 serves as R lines for separating adjacent information tracks.

Information on the R line is recorded with a length shorter than the track width of other data areas.

The ratio of the track width of the data area to the information recording width of the R line is about 1:1/2.

The data stored in each unit data area 13 is M F M
(Modified Frequency Mod
lation) is modulated and recorded. The signal recorded by the MFM modulation method has T, 1.5 T, 2
Only a signal of length T is included. Here, T is the minimum inversion interval of the signal, and corresponds to 1 bit in the recording format shown in FIG. That is, the information track 14
The information recorded in does not include reversal intervals of 4 or more guns.

Therefore, a region having an inversion interval of 4T is used as a separation region 52 for separating information tracks. for example,
A separation signal of "011110" is recorded in the reading direction or arrangement direction of the information track. Of course, the information is not limited to this, and any information may be used as long as it can be recorded so that it can be distinguished when read.

Further, the information track 14 has 16 unit data areas 13.
It has a total of 80 bits.

As described above, since the one-separation area 52 includes consecutive identical codes that do not appear in the information track 14, the R line can be detected reliably.

Next, a method for reproducing the information recording carrier will be explained.

Here, an optical cart is used as an information recording carrier having the recording format shown in FIG. 9, and a reproducing apparatus shown in FIG. 5 is used as a device for reading information from the optical cart. Furthermore, as shown in FIG. 1O, one bit 115 in the recording area of the optical card is connected to
The optical magnification is selected so that the image is formed on four cells 116. For example, if the size of one bit 115 of the optical card is 10 pm and the size of the cell 116 of the sensor array 10 is 154 m, then the imaging optical system 19 has a magnification of 4X l 5/10 = 6 (times). Bye.

FIG. 11 is an explanatory diagram showing a method for reproducing an information recording carrier.

In the figure, in the recording area on the optical card, band 3 and
Bands 3a and 3b adjacent to band 3, information tracks 14a and 14b of each band, and separation areas 52, 52a and 52b for separating each information track are formed in the format shown in FIG. There is. Here, the L-band track is formed of one separation area (6 bits) and an information track (80 bits), totaling 86 bits. Therefore, the track of the l hand is sensor array 1.
00, images are formed on 344 cells 116.

Therefore, here, a CC having 512 cells 116 is used.
D is used as the sensor array 100, and the reading area 57 is set so that part of the information tracks 14a and 14b adjacent to the information track 14 to be read is also imaged on the sensor array 100.

From the time when the separation area 52 is detected, the information recorded on the information track 14 is reproduced using the extracted clock, and the information reproduction operation is stopped when the separation area 52b is detected.

FIG. 12 is a block diagram of an optical card reproducing apparatus that implements the above reproducing method.

In the figure, a sensor array 1 having a reading area 57 is shown.
00 is driven by a drive clock 119 from a sensor array driver 118, and its output signal 120 is also amplified by the driver 118 and output as an analog MFM signal 121.
The signal is input to the binarization circuit 122 as a signal.

The analog MFM signal binarized by the binarization circuit 122 is converted into an NRZI signal 123 by a clock regeneration circuit 124,
The signals are output to MFM demodulation circuit 126 and R line detection circuit 128, respectively.

Clock regeneration circuit 124 extracts clock signal 125 from NRZI signal 123 and outputs it to MFM demodulation circuit 126 . The MFM demodulation circuit 126 receives the clock signal 125
and the NRZI signal 123, the demodulated signal N
Outputs RZ signal 127. On the other hand, R line detection circuit 1
2B is a clock signal 130 obtained by frequency-dividing the drive clock 119 from the 4-frequency divider circuit 129 and N from the binarization circuit 122.
Input RZ I signal 123 and R line detection signal 13
1 is output to the MFM demodulation circuit 126. MFM demodulation circuit 126 outputs NRZ signal 127 according to R line detection signal 131.

FIG. 13 is a block diagram of the R line detection circuit 128. In the figure, an NRZI signal 123 is input to a serial input terminal of a shift register 132, and a clock signal 130 whose frequency has been divided by four is input to a clock input terminal.

Also.

The 6-bit parallel output terminal of the shift register 132 is “
011110" are respectively connected to the input terminals of the minus number circuit 133. The coincidence signal of the minus number circuit 133 is outputted as a line detection signal 131 to the MFM demodulation circuit 126.

The specific operation of the reproducing apparatus having such a configuration will be explained with reference to FIG. 3 and FIG. 11.

When the sensor array 100 scans the reading area 117 in the direction of arrow B using the drive clock 119, first the NRZI
The signal 123 serves as a signal for reading information from a portion of the adjacent information track 14a. As mentioned above, since the inversion intervals for this signal are only T, 1.5 T, and 2T in principle, the minimum inversion interval T is extracted by the clock regeneration circuit 124 using a PLL circuit, etc., and the clock signal 125 is regenerated. can do. Depending on this clock signal 125, the NRZ I signal 123 or the N
It is demodulated into an RZ signal 127. However, unless the first R line detection signal 131 is input, the MFM demodulation circuit 126
doesn't work. That is, the shift register 132 of the R line detection circuit 128 is sequentially inputted with each bit signal in the reading area 57, and is always filled with signals for 6 bits.

Therefore, the contents stored in the shift register 132 are the recorded contents of the separation area 52 or 52b, that is, 011110''.
The R line detection signal 131 is not output unless it matches.

When the 6-bit information of the first separation area 52 is stored in the shift register 132, the R line detection signal 131 is outputted from the minus number circuit 133, whereby the MFM demodulation circuit 126 starts demodulating operation. Therefore, the NRZ signal 127 for the information of the information track 14 to be read is
is output as a playback signal.

Then, the information of the next separation area 52b is transferred to the shift register 1.
32, the R line detection signal 131 is output from the minus number circuit 133, and the MFM demodulation circuit 126 stops outputting the reproduced signal.

In this way, information reproduction of the information track 14 to be read is performed by the self-clock. Similarly, moving the optical card in the direction of the arrow or sensor array 1
By moving the optical head 21 equipped with 00 in the direction of arrow C, a desired information track is selected as a reading target, and that information is reproduced.

Next, the binarization circuit of the present invention used in the above-mentioned optical card reproducing device will be explained.

FIG. 1 is a block diagram for explaining the binarization circuit of the present invention. In the same figure, an analog MFM which is an input signal
The signal a is an information reproduction signal obtained by removing unnecessary C components from the analog MFM signal a by a bypass filter (HPF) 1 that passes the band of the MFM signal. The information reproduction signal S is further provided with a low-pass filter (L) for the low-frequency component signal C and the high-frequency component signal d of the information reproduction signal.
PF) 2 and a bypass filter (IPF) 3. The low frequency component signal C is converted into a low frequency component binary signal e by the binarization circuit 4. Further, the pulse shaper 5 which performs waveform shaping of the high frequency component signal d generates a high frequency component data pulse f at the binarization level point of the high frequency component. The play circuit 6 outputs the high frequency component data pulse f as a delayed high frequency component data pulse g. Digital M
A flip-flop 7 serving as FM signal generating means converts the low frequency component binary signal e into a digital MFM signal using the delayed high frequency component data pulse g.

The operation of the binarization circuit will be explained below.

FIG. 2 is a waveform diagram of output signals of each constituent means of the binarization circuit.

The analog information signal is a reproduced signal obtained by removing a DC component from an MFM modulation signal corresponding to the intensity of light incident on the sensor array 10. In the figure, the amount of light incident on the sensor array 10 is greater in the portion where the voltage of the analog information reproduction signal is lower. Therefore, the peak on the negative side of the AC voltage component indicates a high reflectance portion of the optical cart, and the peak on the positive side indicates a low reflectance portion. That is, the unevenness of the AC voltage component indicates the content of recorded information. The binary signal of the low frequency component of this analog information reproduction signal is digitized as shown in FIG. 2e. Further, the high-frequency component signal of the analog information reproduction signal is outputted by a pulse shaper as a pulse as shown in FIG. 2(f) at the rise and fall of the binary signal in the high-frequency component. This high-frequency component data pulse is converted into a delayed high-frequency component data pulse by the play circuit as shown in FIG. 2g.

The play time t of this play circuit is the minimum interval T of the playback signal.
It is necessary to make the delay time shorter and longer than the delay time of the low frequency component binary signal. By the rising edge trigger of this delayed high-frequency component data pulse g, the flip-flop shown in FIG. 1 takes in the low-frequency component binary signal e and outputs it as a digital MFM signal.

Digital MFM signals have no phase error and can effectively utilize the entire area illuminated by the illumination optical system.
The entire area of the information track imaged on the sensor array 10 can be used as an effective recording area. Further, as a result, the optical design of the illumination optical system and the imaging optical system is facilitated, and the alignment between the optical head and the information track is facilitated. Furthermore, digital M
Since there is no phase error in the FM signal, there is also the effect that the probability of reading errors is very low.

Although one embodiment of the binarization circuit of the present invention has been described above, the circuit configuration is not limited to that of this embodiment, and other circuit configurations that function similarly may be used.

[Effects of the Invention] As explained in detail above, according to the binarization circuit of the present invention, the analog information reproduction signal is separated into a low frequency component and a high frequency component. The phase error of the binary signal can be reduced with a simple configuration by capturing the binary signal of Accurate signals with fewer errors can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the binarization circuit of the present invention, and FIG. 2 is an output signal waveform diagram of each constituent means of the binarization circuit. Fig. 3 is a schematic plan view showing the recording format of an optical card, Fig. 4 is a partially enlarged view of the above format, Fig. 5 is a schematic configuration diagram of an optical card reproducing device, and Fig. 6 is a conventional binary FIG. 7 is a diagram showing an example of a conventional binarizing circuit; FIG. 8 is a waveform diagram illustrating the operation of the conventional binarizing circuit. Fig. 9 is a partial schematic diagram of the recording format of the optical card, Fig. 10 is an explanatory diagram of the optical magnification of the optical head, Fig. 11 is an explanatory diagram showing the reproducing method of the optical card, and Fig. 12 is the optical A block diagram of an optical cart playback device that implements the card playback method. FIG. 13 is a circuit diagram showing an example of an R line detection circuit. b...Analog information reproduction signal e...Low frequency component binary signal f...High frequency component data pulse g...Delayed high frequency component data pulse h...Digital MFM signal

Claims (1)

[Scope of Claims] In a binary circuit that converts an output signal from a photodetector of an optical information reproducing device into a binary value, the output signal is separated into a high frequency component and a low frequency component, and the low frequency component is separated into a high frequency component and a low frequency component. 2 of the output signal by the binary signal and the pulse signal of the high frequency component.
An optical information reproducing device characterized by performing value conversion.