JP2662876B2 - Detector for digital information reproduction of optical information recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The device of the present invention records (writes) data information in a pit shape along a track by focusing a laser beam on an information recording medium, and records the information. An optical information recording / reproducing apparatus capable of irradiating information on the information recording medium with the laser beam and reproducing (reading) the information from the information recording medium, for example, an effective RF signal applied at the time of reading information data in a reader / writer of a laser card. And a peak value detector.

"Prior art" In a reader / writer that records digital data on the laser card and reproduces the data, the output of laser light is increased when writing data, and the output of laser light is used for reading recorded data. It is controlled according to the command of the CPU so as to reduce it.

Conventionally, a control signal for focusing on an information recording medium by irradiating a laser beam to a laser card and for moving a pickup along a track is detected by a photoelectric detector. The pit information RF signal on the information recording medium is detected by a detection device as shown in FIG.
Although this can detect the vicinity of the RF peak value, it does not reduce the read-out (omission) or jitter of the information to be read, but has good tracking of the RF signal and the RF peak at the center of the information pit. The values were not exactly detectable.

"Problems to be Solved by the Invention" However, the present invention can detect the RF peak value at the pit center of the write information and can minimize the jitter even if noise is superimposed on the information recording medium and minimize the jitter. It is trying to get.

"Means to solve the problem" After amplification of the RF signal processed by the low-pass filter,
Follow the falling region of the wave with a width equivalent to the threshold voltage of the diode, and set the point beyond the peak value of RF as the origin.
It is configured to add a time constant for obtaining a slope having a constant slope crossing the RF wave.

One embodiment of the present invention will be described with reference to FIGS.

Embodiment FIG. 1 is a circuit configuration diagram of a detection device according to the present invention. In IN, reflected light from a disk enters via a photoelectric detector.
RF signal input terminal, 1 is a high-pass filter for blocking DC, 2 is a low-pass filter for removing high-frequency noise,
Reference numeral 3 denotes an amplifier, 4 denotes a comparator input level determination circuit used for detection, and OUT denotes a detection output terminal.

Next, looking at the conventional circuit of FIG. 3 before explaining the circuit characteristics of FIG. 1, when the time constants due to R3 and C3 are made sufficiently small, as shown in FIG. and transition to follow the forward voltage drop that is Suresshuyorudo voltage as high RF waveform of the diode D ₁ in the downlink region, discharged at a tilt determined by the discharge time constant R _4, C ₃ reaches a peak value lower. When connecting only diode D ₂ in parallel with the level determining circuit as Figure 1, comparator as shown in FIG. (B)
Although the falling region of the RF waveform to transition to follow the upper by Suresshuyorudo voltage of the D _1, the RF waveform reaches the lower peak point, and discharge according to the time constant by R _4, C _3, the terminal When the input voltage reaches downward by Suresshuyorudo voltage of D ₂ from the RF wave applied to the input terminal, the terminal now moves to follow the lower only Suresshuyorudo voltage than the input voltage or RF. At this time, R ₄ , C of the discharge time constant circuit 6
Voltage RF waveform applied ₃ to the large very comparator terminal is applied to the terminal when it reaches the lower peak draw large discharge curve time constant the voltage of the pin reaches Suresshuyorudo voltage of D ₂ when following a terminal transition Therefore, detection can be performed in the vicinity of the lower peak point, and the effect of suppressing jitter is exhibited as much as possible.

However the only but about parallel only D ₂ as the wound in the total reflection range of the unrecorded portion or the information recording medium of the information recording medium attached to the information recording medium surface, the noise component based on the dust or the like Because there are many, following up to this noise, the regular output of the comparator
A normal detection signal is not output to OUT, and incorrect information different from the signal read from the pit is sent to the CPU.

Therefore the addition of R ₅ to a second diode resistor cascade element clogging D ₂ in parallel with the first diode resistor cascade element in FIG. 1, the lower peak point RF signal voltage as an input voltage When the input voltage reaches the discharge time constant circuit 6
Of R _4, a slope that is, the second diagram determined by the time constant of C ₃ of _{^{(A) ▲ S '1 ▼}} , ▲ S' 2 ▼, ▲ S '3 ▼ and such discharge x ₁ region of FIG. (D) Although the characteristics are shown, when the input voltage shifts below the RF voltage applied to the terminal by the threshold voltage of D _{2 by} the threshold voltage of D ₂ , discharge starts based on the time constant of R ₄ / R ₅ × C ₃ (FIG. 2) A) S ₁ , S ₂ , S ₃ and FIG.
The following characteristics can be obtained.

It can be variously changed the slope of its discharge characteristics by the value of R ₅ in this case to the second cascaded body, even the noise N as in FIG. 2 (A) is included in the RF signal, the discharge It can be seen that the time constant should be selected within a range where the slope of the time does not catch.

To supplement explanation by FIG. 2 (C), in the fall range of RF waves to reach a -P ₁ follow offset by Suresshuyorudo voltage based on the diode D ₁ to the upper side of the RF, the lower peak point -P ₁ After passing, the slope determined by the time constant of R ₄ and C ₃ ▲
Discharge occurs at S ^″ ₁ ▼, ▲ S ^″ ₂ ▼, ▲ S ^″ ₃ ▼.

If the discharge time constant circuit is increased, the slope of the slope will be slower and the responsiveness will worsen.If the time constant is reduced, jitter will be reduced.If the time constant is reduced, the RF waveform will follow. Performance is improved, but jitter is increased. Therefore, by adopting the circuit of the present invention shown in FIG. 1, the discharge characteristics as shown in FIG.
It is possible to select a time constant that improves the followability of the waveform and reduces the jitter.

[Effect] At the center of the information pit recorded on the information recording medium, a diode corresponding to both the positive and negative directions of the RF signal so as to match the lower peak value of the photoelectric detection signal of the reflected beam.
By providing an anti-parallel circuit of resistor series connection and a discharge time constant circuit on the input side of the comparator, it is possible to select a combined time constant according to the RF wave, so that jitter can be eliminated, noise information can be read out, and error information can be avoided. Accurate and faithful reproduction of information from the read laser reflected signal, such as avoidance of detection, is possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a detector for digital information reproduction in an optical information recording / reproducing apparatus according to the present invention, and FIGS. 2 (A), (B), (C) and (D). 3) are detection graphs for explaining RF waveforms and discharge characteristics, and FIG. 3 is a circuit configuration diagram of a conventional detection device. 1: high-pass filter, 2: low-pass filter, 3: amplifier,
4: level determining circuit, 5: _{comparator, S 1, S 2, S} 3 ...: discharge _{slope, + P 1, -P 2 ...} : positive, negative peak point, N: noise, x _1, x _2:
Jitter generation area.

Claims (1)

(57) [Claims] 1. An apparatus for recording digital data in the form of pits by irradiating a laser beam on the surface of an information recording medium, and converting the recorded information into a reflected light amount due to the laser beam irradiation into an electric signal. At times, a signal reproduced by discriminating information using the difference in brightness between the reflection portion of the recording medium and the pit is input as an RF signal to a low-pass filter and an amplifier via a coupling capacitor, and the amplifier An output terminal is provided with a comparator connected to an input terminal via an anti-parallel circuit including two sets of resistors and a diode, and the output terminal of the amplifier is connected to the input terminal. A terminal is provided with a parallel discharge circuit of a capacitor and a resistor, and the peak value of the RF signal is taken out from the output terminal of the comparator in accordance with the center of the pit. A detecting device at the time of digital information reproduction of an optical information recording / reproducing device.