JPH05109093A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To easily discriminate a land and group from each other by calculating a medium value of the peak vale and bottom value for discriminating the land and group from each other by fetching the value of a total sum signal at the zero-crossing point of a tracking error signal. CONSTITUTION:A CPU 7 detects the rise and fall of a tracking error signal binarized at a zero-cross comparator 5 by using a timing signal. At the timing of the rising and falling edges of the binarized signal, the value of an A/D converter 6 obtained by digitizing the total sum signal is stored in memories. At the time of storing the value, a CPU 7 stores the value in a memory A when the rising edge of the binarized signal is detected and in another memory B when the falling edge of the binarized signal is detected. Then the CPU 7 discriminates a land and group from each other by comparing the values of the memories A and B with the value of a memory C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording or reproducing information on an optical recording medium by irradiating a light beam, and more particularly, to land and groove of the recording medium by reflection or transmission of the light beam. It relates to a device for determining.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing a configuration example of a conventional optical information recording / reproducing apparatus. In the figure, reference numeral 10 denotes an optical disk, on which a plurality of tracks are arranged in a spiral or concentric form. This optical disc 1
0 is rotationally driven by a spindle motor 11, and information is recorded or reproduced by irradiating a light beam from an optical head 21. The optical head 21 has a built-in semiconductor laser 12, which is a light source, and its light beam is focused on the optical disk 10 through a collimator lens 13, a beam splitter 14, and an objective lens 15. The light reflected by the optical disk 10 passes through the objective lens 15 again, is separated from the incident light beam by the beam splitter 14, and is detected by the photodetector 18 via the sensor lens 17. The photodetector 18 has a light-receiving surface divided into a plurality of areas, and based on the output of each area, auto-tracking (AT) / auto-focusing (A).
F) The control circuit 19 detects the focusing signal and the tracking signal by using a well-known method such as an astigmatism method or a push-pull method. These detected control signals are fed back to the lens actuator 16, and AT / AF is performed by moving the objective lens 15 in the optical axis direction and in the direction perpendicular to the optical axis and across the track.

In the apparatus as described above, when the light beam is to access a desired track, the entire optical head 21 is moved by the linear motor 22 in the disk radial direction, that is, the direction traversing the track, and the lens actuator 16 is used. Input a track jump signal to and move the objective lens across the track. At this time, an on-track / off-track signal is used to determine the position and the moving direction of the light beam. This on-track off-track signal is obtained by processing the sum signal of the outputs of all areas of the photodetector 18 by the on-track off-track detection circuit 20.

Conventionally, as the on-track / off-track detection circuit, it has been general to obtain an on-track / off-track signal by comparing the sum signal of the optical sensor with a constant reference voltage using a comparator. However, this apparatus cannot obtain an on-track / off-track signal with sufficient accuracy due to the influence of the change in the reflectance of the disk and the change in the laser power. Therefore, as an apparatus that solves the above problems, for example, Japanese Patent Application No. 2-1
An information recording / reproducing apparatus disclosed in Japanese Patent Application No. 01637 and Japanese Patent Application No. Hei 2-161912 has been proposed. FIG. 5 is the above-mentioned Japanese Patent Application No. 2
It is an on-track off-track detection circuit shown in No. 101637. This detection circuit includes a peak hold circuit including a differential amplifier 22, a diode D1, resistors R1 and R5, and a capacitor C1, and a bottom hold circuit including a differential amplifier 23, a diode D2, resistors R2 and R6, and a capacitor C2. The hold circuit holds the peak value and the bottom value of the sum signal 21 of the optical sensor, respectively. And the differential amplifiers 24, 2
5, a circuit composed of the resistors R3 and R4 determines an intermediate value M between the peak value and the bottom value.
The on-track / off-track signal 27 is generated by comparing the sum signal 21 from the optical sensor with the comparator 26 by the comparator 26.

According to the above detection circuit, when the offset or the modulation degree of the sum signal of the optical sensor changes, the intermediate value changes accordingly, so that it is not affected by the offset or the change after the modulation. , You can always get accurate on-track and off-track signals. However, in the detection circuit of FIG. 5, since the convergence value of the hold circuit is set to the average level of the summation signal, if the amount of detected light is greatly reduced due to dirt on the objective lens or the like, it may not be able to function sufficiently. ..

FIG. 6 shows an on-track / off-track detection circuit disclosed in the above-mentioned Japanese Patent Application No. Hei 2-161912. The peak hold value is divided by resistors R7 and R8, and the converged value of the bottom hold signal is divided by this divided value. Is to be set. According to this detection circuit, the convergence value changes depending on the peak hold value, and the voltage is always lower than the peak hold value. Therefore, even if the amount of light received by the optical sensor decreases, or even after the tracking pull-in, It becomes possible to detect on-track and off-track signals in
The problem of the detection circuit can be solved.

[0007]

However, in the detection circuit of FIG. 6, since the sum signal is peak-held and bottom-held, the reflected light or noise from the high-reflectance portion due to a defect of the disk causes
There was a risk of holding the wrong peak value or bottom value. Therefore, in such a case, since the hold time constant is long, a normal on-track / off-track signal cannot be obtained for a while. Further, there is a problem that the device becomes large in size because a relatively large number of hardware circuits such as a peak hold circuit, a bottom hold circuit, or a circuit for outputting an intermediate value are required.

The present invention provides an optical information recording / reproducing apparatus which is an improvement of this prior art and can detect on-track and off-track more accurately regardless of a disk defect or noise and also has a simple device configuration. Especially.

[0009]

It is an object of the present invention to irradiate an optical information recording medium having a plurality of tracks with a light beam, and to move the light beam relatively in a direction transverse to the tracks. And a means for detecting reflected light or transmitted light of a light beam which is modulated by traversing the track, in an optical information recording / reproducing apparatus, a tracking error signal obtained from an output signal of the detecting means. A means for fetching the value of the sum signal of the detection means at the timing of the zero-cross point and calculating an intermediate value between the peak value and the bottom value of the sum signal, and comparing the intermediate value and the value of the sum signal obtained for each zero-cross point. However, the optical information recording / reproducing apparatus is provided with a means for discriminating the land and the groove of the recording medium according to the comparison result.

[0010]

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 optical information recording / reproducing apparatus of the present invention. In FIG. 1, reference numeral 1 is a four-division sensor for receiving a light beam reflected from an optical disk (not shown) which is an information recording medium. The four-division sensor 1 is provided in an optical head (not shown) together with a semiconductor laser which is a light source for recording / reproducing information and other optical lenses. The optical disc may be either a reflection type or a transmission type. Reference numeral 2 denotes a current-voltage conversion circuit for converting each photocurrent of the four-division sensor 1 into a voltage signal, and reference numeral 3 denotes a tracking error signal for performing a predetermined calculation process using the four outputs of the current-voltage conversion circuit 2. Is an arithmetic circuit for generating. Further, 4 is an arithmetic circuit for calculating the sum of the four outputs of the current-voltage conversion circuit 2 and generating a sum signal,
Reference numeral 5 is a zero-cross comparator for binarizing the tracking error signal at zero level, and 6 is an A / D converter for digitizing the sum signal. Further, 7 is a CPU that performs processing for discriminating between the land and groove of the optical disc and the direction of the light beam when the light beam crosses a track. A timing signal for notifying the preformat section is input to the CPU 7 from a signal processing system (not shown). In response to this timing signal, the CPU 7 prohibits the land / groove discrimination and the light beam direction discrimination in the preformat section, and executes the discrimination processing only in the other regions.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG. 2 and the time chart shown in FIG. First, the CPU 7 initializes the memories A, B and C as shown in FIG. 2 (S1). Memories A, B, C
Is an internal memory of the CPU 7 and is a memory for recording the digital value of the summation signal obtained by the arithmetic circuit 4. When the memory initialization is completed, the CPU 7 confirms that the tracking servo lube is off (S2), and confirms that it is not the pre-formatted portion of the optical disc by the timing signal sent from the signal processing system (not shown) (S2).
3). The reason why the land and the groove are discriminated in the parts other than the pre-format part is based on the reason that the light amount of the total signal changes in the pre-format part and an accurate value cannot be obtained.
Also, during this determination operation, the focus servo lube is on. In this way, the CPU 7 detects the rising edge and the falling edge of the binarized signal of the tracking error signal binarized by the zero-cross comparator 5 in the area other than the preformat section by the timing signal (S4).

FIG. 3 shows the signal waveform of each part of the embodiment of FIG. 1, and FIG. 3 (a) shows the tracking error signal.
(B) is a binarized signal of the tracking error signal binarized by the comparator 5. The CPU 7 digitizes the sum signal (FIG. 3C) at the timing of the rising and falling edges of the binarized signal binarized as described above.
The value of the / D converter 6 is stored in the memory. At this time, the CPU 7 stores the value in the memory A when the rising edge of the binary signal is detected (S5), and stores it in the memory B when the falling edge is detected (S6). Next, the CPU 7 compares the values of the memories A and B with the values of the memory C (S7), and determines the land and the groove according to the comparison result. That is, the memory C stores a value (A + B) / 2 (an intermediate value between the peak value and the bottom value of the summation signal) obtained by dividing the addition value of the memories A and B one time before by 2 and this value. The land and the groove are discriminated by comparing the values of the memories A and B. Specifically, first, when the value of the memory A is smaller than the value of the memory C at the rising edge of the binarized signal, it is determined to be a groove (S8), and conversely, the value of the memory A is larger than the value of the memory C. When it is large, it is determined to be land (S9). Further, even when the binarized signal falls, if the value of the memory B is smaller than the value of the memory C, it is determined to be a groove (S11), and conversely, if the value of the memory B is larger than the value of the memory C. Is determined as land (S12).

The CPU 7 is thus provided with the comparator 5-2.
At the rising and falling edges of the digitized signal, the value of the sum signal is compared with the intermediate value of the previous values of the memories A and B, and the land or groove is determined from the comparison result. That is, when the light beam travels in one direction, if the comparison result by the value of the memory A is a land, it becomes a groove in the next memory B, and the land and the groove are inevitably distinguished alternately. .. Therefore, if the determination result changes and the land and the groove are not alternately determined, it may be determined that the direction of the light beam is reversed. Therefore, the CPU 7 monitors the above determination result and determines whether or not the land or groove is alternately determined (S13). In this case, if lands or grooves are alternately identified,
An intermediate value between the values of the memories A and B is calculated (S14), this is stored in the memory C, and the value of the memory C is updated. Then, returning to S2 again, at the next rising edge and falling edge of the binarized signal, the value of the summation signal is fetched in the same manner as above,
The land and the groove are determined by comparing this with the value of the memory C updated last time. In this way, the land and groove determination processing is repeatedly performed at each rising and falling edge of the binarized signal, and when the light beam is traveling in one direction, the CPU 7 proceeds as shown in FIG. A direction determination signal (here, a high level signal) corresponding to the direction is continuously output. On the other hand, when the land and the groove are not discriminated alternately, the CPU 7 inverts the direction discriminating signal to the low level as shown in FIG. 3E, and notifies the external control unit that the direction of the light beam has been inverted. To do. After that, the process returns to S2 and the land / groove discrimination processing is repeated for each rising edge and falling edge of the binarized signal as described above. If the direction of the light beam is reversed, the value in the memory C is not updated.

In the above embodiments, the discrimination of the land and the groove and the discrimination of the direction are processed inside the CPU. However, the value of the memory C is analog-converted by the D / A converter, and the sum signal is used as the comparator level. A signal for discriminating between land and groove (on-track / off-track signal) as shown in FIG.
Can also be generated. In the embodiment, the direction is determined when the tracking servo loop is off, but when the tracking servo loop is on, the above direction determination is not performed, and the last value is stored in the memories A, B, and C. Keep it. These values are used as initial values when the servo loop is turned off next time. Further, when the speed of track crossing is fast due to seeking, etc., there is no need to discriminate the direction, the land, and the groove, and because of the hardware restrictions of the CPU and the A / D converter, the discrimination of the land and the groove and the direction can be performed. It is better not to perform discrimination processing. The present embodiment does not require a hard circuit such as peak hold and bottom hold as in the related art, and is a relatively inexpensive CP.
A simple circuit using a U or A / D converter can discriminate between the land and the groove and discriminate the direction. Also, A
If a CPU having a built-in / D converter is used, the configuration can be further simplified.

[0015]

As described above, according to the present invention, the value of the summation signal is taken in at the zero crossing point of the tracking error signal, and the intermediate value between the peak value and the bottom value for discriminating between land and groove is calculated. By doing so, it is possible to easily determine the land and the groove without requiring special hardware. Moreover, since the sum signal is captured only at the zero-cross points of the tracking error signal, there is little effect of defects or scratches on the disc or noise, and there is the effect that the land and groove can be detected more accurately.

[Brief description of drawings]

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

2 is a land / groove discrimination process according to the embodiment of FIG. 1;
9 is a flowchart showing a light beam direction determination process.

FIG. 3 is a time chart showing signal waveforms of various parts of the embodiment of FIG.

FIG. 4 is a block diagram showing a configuration example of an optical information reproducing device.

FIG. 5 is a circuit diagram showing a conventional on-track / off-track detection circuit.

FIG. 6 is a circuit diagram showing another conventional on-track / off-track detection circuit.

[Explanation of symbols]

 1 Optical sensor 2 Current-voltage conversion circuit 3,4 Arithmetic circuit 5 Zero cross comparator 6 A / D converter 7 CPU

Claims (3)

[Claims] 1. A means for irradiating an optical information recording medium having a plurality of tracks with a light beam, a means for relatively moving the light beam in a direction crossing the track, and a modulation by crossing the track. In an optical information recording / reproducing apparatus comprising means for detecting reflected light or transmitted light of a received light beam, the sum of the detecting means at the timing of the zero cross point of the tracking error signal obtained from the output signal of the detecting means. Means for taking the value of the signal and calculating an intermediate value between the peak value and the bottom value of the sum signal,
An optical information recording / reproducing apparatus provided with means for comparing an intermediate value obtained for each zero-cross point and a value of a sum signal and discriminating a land and a groove of the recording medium according to a comparison result. .. 2. A direction discriminating means for discriminating the direction of the light beam based on the discrimination result of the discriminating means, wherein the discriminating means, when the land and the groove are not discriminated alternately,
The optical information recording / reproducing apparatus according to claim 1, wherein it is determined that the direction of the light beam is reversed. 3. The optical information recording / reproducing apparatus according to claim 1, wherein the discrimination between the land and the groove is prohibited when the light beam crosses the preformatted portion of the recording medium.