JPS60171637A - Circuit for counting number of traversed track - Google Patents

Abstract

PURPOSE:To count accurately the titled number even whe a light spot moves at a high speed, by counting the output of a pulse generating circuit which generates different pulses when the track traversing speed of the minute light spot is low and high in response to the output of a movement detecting circuit, and detecting the number of traversing tracks. CONSTITUTION:It is discriminated that whether the track traversing speed of a light spot is high or low by respectively inputting the two input signals of a reversible counter CNT in an F/V converter 10 through an OR gate 9 and inputting the output of the converter 10 in a comparator 11 where the output is compared with a threshold E. When the speed is low, the k1 and k2 of a multiplexer (MPX)12 are respectively connected with the contacts l1 and l2 of another MPX13 and track deviating quantity signals (d) and (c) from a counting section TC are counted at the counter CNT through an AND circuit. When the speed is high, the contacts k1 and k3 of the MPX12 are respectively connected with the contacts l1 and l3 of the MPX13 and a track traversed signal (h) from the counting section TC is directly counted at the counter CNT.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an optical recording/reproducing device, and particularly to a circuit for counting the number of traversed tracks for random access control thereof.

(bJ Prior Art and Problems In optical recording and reproducing devices such as optical disk devices or magneto-optical disk devices capable of additional writing, it is necessary to position a minute light spot formed by a lens at a predetermined position on the recording medium. .

For this purpose, positioning grooves (hereinafter referred to as tracks) are formed in advance on the recording medium (the pre-group method is common. Figure 1 shows the principle of the pre-group method, and Figure 2 shows tracking using the circumferential method. A diagram for explaining an error detection method is shown.

In FIG. 1, numeral 1 indicates a medium surface, and numeral 2 indicates a track provided at a recording position, and the depth of the track is λ/8 (λ is the optical wavelength). When the minute light spot (hereinafter referred to as the light spot) focused by the objective lens 3 is moved in the direction across the track 2 as shown in the figure, the intensity distribution of the amount of reflected light from the track 2 is calculated at the corresponding position. Shown above.

In FIG. 2, 4 is a reflecting mirror, 5 is a two-split photodetector, and its output is composed of P and P2.

6a is a differential amplifier (track deviation amount detection circuit);

61) is a summing amplifier (reflected light amount detection circuit), a waveform (FL
) is the output waveform of the differential amplifier 6a, the waveform (fl shows the output waveform of the summing amplifier 6b. The difference signal shown by the output waveform (a) shows zero at the center of the track, and the area before and after that is linear) In addition, a step occurs in the waveform at the intermediate position between the track and the trunk.Also, the sum signal indicated by the output waveform (fl) has a minimum value at the center of the track and a maximum at the intermediate position between the track and the adjacent track. It has characteristics that indicate value.

If this difference signal is fed back to the optical spot moving device, the optical spot can always be aligned above the target track with respect to the eccentricity of the medium disk. This is a so-called tracking servo, and this difference signal is called a positional deviation signal. - In a multi-optical disk device, in addition to the above-mentioned tiger and king servos that follow the light spot onto the track, it is also necessary to quickly move the light spot across the track to the target track. To complete this movement, it is necessary to know the area of movement, and if the number of traversed tracks can be accurately counted, the movement device does not need to have a dedicated scale, which is convenient.

Figure 3 is a circuit diagram of a conventional cross track counting device.
! Figure g4 shows a time chart of the signal waveform of the third section. In the top view, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and explanations thereof will be omitted.

The circuit of FIG. 3 will be explained with reference to FIG.

The difference in Figure 4 (with respect to the X point shown in No. 8 (a)), the left side shows that the light spot is moving from the outside of the track to the inside, and the right side shows that the light spot is moving from the inside of the track to the outside. The point X is the inverted value I6t.

In FIG. 3, TC shown in a chain line frame indicates a track counting section, and counting section T (3 is a comparator (3, and 02 are thresholds) connected to the difference signal (a) in FIG. 2 in opposite phases. A monostable multi-vibrator (hereinafter referred to as "mono-multi") that is triggered at each rising edge of this waveform (IJ) and <c+, which obtains waveforms (b) and (C) by comparing with the voltage scream, respectively. ΔH! and 4111M2 are used to form pulses of the required width to obtain waveforms (d) and (e). However, with this alone, pulses are generated even at zero crosses between tracks in the difference signal (a). It ends up.

The pulses generated at the time of zero crossing between tracks are called pseudo pulses, and the pulses shown in waveforms (d) and (e) are shown with an X mark attached to them.

Therefore, the sum signal (f) outputted by the summing amplifier 6b is compared with the comparator C8, and when the signal level of the sum signal (f) is high, the peak holder circuit P Judging that it is located between the tracks, AND gate ■D and AND2 are closed. However, if one tries to differentiate simply by setting the threshold value of the comparator C3, it will not be possible to differentiate unless the medium reflectance and the irradiated laser beam are very constant.

Therefore, the high level (waveform f') at the middle of the track is memorized by the peak holder circuit PH, and the value and the actual reflection intensity (waveform (f)) are subtracted by the differential amplifier JJ2, and the output waveform is As shown in (g), the threshold value Cv is determined depending on whether the difference is large or small, so-called automatic threshold control (ATO) is used to distinguish whether it is on a track or between tracks.

If the peak holder circuit PH is ideal and the medium reflectance gradually decreases, there is a risk that the output of the peak holder circuit PH will deviate from the actual reflected light intensity at the middle of the track unless the peak holder circuit Pfi is cleared. There is a time constant in the peak holder circuit PH, and the hold value gradually decreases as shown in the waveform (crocodile), so if you set the time constant appropriately,
The edge of the peak holder circuit PH always indicates approximately the intensity of the medium reflected light. In addition, the threshold value q can be set based on the intensity of reflected light between tracks.
This is more reliable than setting an absolute value, and even if there is some variation in medium reflectance or irradiation laser power, it can be reliably distinguished.

The threshold value set in this way and the output of the differential amplifier D2 are compared by the comparator C3, and the output waveform (
h), and the H level of the waveform (h) and the waveform (d) and ([1
) and the output waveform of the AND gate mD (i) and the subtraction (DOWN) of the reversible counter CNT.
Connected to the side, AND gate 1lJ2 output waveform (j)
By connecting to the addition (UP) side, the number of traversed tracks can be accurately counted. In the waveform (h) #, a pulse marked xX is generated at the position corresponding to the inversion position Not counted.

Normally, the track pitch of an optical disk device is much smaller than the medium eccentricity, so even if the light spot is moving from the inner track to the outer side of the medium, if the speed is slow, it will be relatively indicated at the reversal position X point. Although there are cases where a truck crosses from an outside track to the inside as shown in FIG. 3, since the direction can be detected in the example shown in FIG.

However, in the example shown in Figure I$3, the high-frequency characteristics of the differential amplifier 6a cannot be sufficiently improved, so there is a drawback that it is impossible to count track crossings when the optical spot moves at high speed. In other words, if the frequency characteristics are increased to a higher band, the positional deviation error signal Cu) will become larger.

Miscounts occur because information recorded previously is mixed in.

FIG. 5 shows a diagram for explaining the problems of the conventional example.

In the figure, 7 indicates the information written in 2, and 8
shows the trajectory in which the light spot crosses Tora, 7ri2. The positional deviation signal waveform in this case is shown at the corresponding position on track 2. In other words, an ideal error signal is obtained as shown by the broken line on a track where no information is written, but
If information such as 7 is recorded on the track or track, there will be no reflection in this part, and the error signal will also become zero as shown by the solid line. If the frequency band of the differential amplifier is low, it will be integrated and will not appear in the output, but if the frequency band can be amplified to high frequencies, it will appear as a solid line. , and when attempting to detect zero crosses from this output, there is a drawback that many zero crosses appear other than at the center of the track, causing miscounts.

(C) Object of the Invention In view of the above-mentioned drawbacks of the conventional art, an object of the present invention is to provide a circuit for counting the number of traversal tracks that can accurately count even when a light spot moves at high speed.

According to the present invention, an optical recording/reproducing method for recording and reproducing information by forming a scanned light spot by optical means on a disc-shaped recording medium having a positioning track in advance. A track crossing pulse counting circuit for moving the minute light spot onto the target track in the device, the circuit comprising at least a track deviation detection circuit, a circuit for detecting the amount of reflected light from a medium, and a circuit for moving the minute light spot onto the target track. a first pulse generation circuit that generates a pulse by detecting the crossing of the track by the track deviation amount detection circuit; and a second pulse generation circuit that generates a pulse by detecting the crossing of the track by the reflected light amount detection circuit. a pulse generating circuit and a circuit for detecting the moving speed of the minute light spot;
This is achieved by providing a traversal track number counting circuit characterized in that the number of traversed tracks is detected by counting the output of the second pulse generating circuit in the case of high speed, and the output of the second pulse generating circuit in the case of high speed. .

<8) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

Note that this embodiment can be constructed in addition to the track counting section T (3) in the conventional example shown in FIG. 3, so the intermediate section To is omitted, and the same parts as in FIG. 3 are denoted by the same reference numerals. 8th
It is necessary to increase the bandwidth from the summing amplifier 6b to the comparator C3 in the figure.

FIG. 6 shows a circuit diagram of a circuit for counting the number of tracks traversed according to the present invention.

In the figure, the two input signals of CNT (reversible Curran) are
Each signal is input via an OR gate 9 to an F/V converter 10 that converts the pulse rate into a voltage. The output is input to the comparator 11, and a threshold value E for determining whether the pulse rate of the output of the OR gate 9 is high or low is set in the comparator 11. and comparator 11
When the output of is low speed, the contact of multiplexer 12 is
2 and the contacts 111 and 12 of the multiplexer 13 are connected to perform the same operation as the conventional example shown in FIG. When the output of the comparator 11 is high speed, the contacts 1 and 3 of the multiplexer 12 and the contacts 11 and 1 of the multiplexer 18 are connected.
3 are connected and the pulse of the waveform (h) shown in FIG. 4 is directly input to the counter. Since it is known in advance whether the access command is input to the addition side or the subtraction side of the counter UNT, whether the access command is from the inside to the outside of the track or from the outside to the inside, the external signal 8 is used to input the access command to the multiplexers 14 and 15. All you have to do is switch between the two.

Furthermore, as is clear from the waveform (h) shown in Fig. 4, the output of waveform (h) not only occurs regardless of the direction, but also at the reversal position
Pulses are generated as shown by the marks, but if the light spot moves at high speed, the pulses marked by Xx cannot be generated. Therefore, Hikari Nobo 1. It is possible to accurately count the number of tracks crossed by distinguishing between when the track is moving at low speed and when it is moving at high speed.

(f) Effects of the Invention As explained in detail above, according to the cross-trunk counting circuit of the present invention, the number of tracks crossed by a light spot can be counted even when moving at high speed, and can be accurately counted even when moving at low speed. can.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the pregroup method, Fig. 2 is a diagram for explaining the tracking error detection method using the same method, Fig. 3 is a circuit diagram of a conventional transverse track counting circuit, and Fig. 4 is a diagram of the tracking error detection method using the pregroup method. Time chart of signal waveforms of each part of the circuit shown in the figure,
FIG. 5 is a diagram for explaining the problems of the conventional example, and FIG. 6 is a circuit diagram of a cross track counting circuit according to the present invention. In the figure, 2 is a track, 5 is a two-split photodetector 6a is a differential amplifier, 6b is a summing amplifier, 8 is a trajectory of a light spot, 9 is an OR gate, 10 is an F/V converter, 11 is a comparator, and 12 to 15 are A multiplexer is shown. Figure 1 Figure 3 Figure 4 Figure 5 Weight Go-171G37 (5)

Claims (1)

[Claims] In order to form a minute light spot by optical means (on a disk-shaped recording medium having a positioning track in advance) and move the minute light spot onto a target track in an optical recording and reproducing apparatus that records and reproduces information. The track crossing pulse counting circuit includes at least a track deviation amount detection circuit, a reflected light amount detection circuit from a medium, and a track deviation amount detection circuit that detects that the minute light spot crosses the track. a first pulse generating circuit that generates a pulse by detecting the crossing of the track by the reflected light amount detecting circuit; a circuit that responds to the output of the moving speed detecting circuit to generate the minute skip)/) when the rack crossing speed is low, the output of the first pulse generating circuit, and when the rack crossing speed is high, the second pulse. A circuit for counting the number of crossing tracks, characterized in that the number of crossing tracks is detected by counting the outputs of respective generation circuits.