JPH06267084A - Track counting circuit in cd player - Google Patents

Abstract

PURPOSE:To solve counting errors of the number of tracks and improve the accessing accuracy when an optical pickup of a CD player makes access. CONSTITUTION:A count signal and a tracking error pulse generated in accordance with the movement of an optical pickup 12 along a track are input to an exclusive-OR circuit 17. An AND output of tone logic output and the count signal is input to a downloading counter circuit 23. The output of the exclusive-OR circuit 17 is inverted and, an AND output of the inverted output and the count signal is input to an uploading counter circuit 22. Since the phase of the tracking error pulse is reversed depending on the traversing direction of the track, the count signal is output to the uploading counter circuit 22 when the pickup moves from the inner circumference to the outer circumference. In the case where the pickup moves in the opposite direction, the count signal is generated to the downloading counter 23. Accordingly, the correct number of tracks where the pickup moved can be detected from the counting numbers at both times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track counting circuit in a CD player, and more particularly to a track counting circuit with improved counting accuracy.

[0002]

2. Description of the Related Art A conventional track counting circuit is shown in FIGS.
Follow the instructions below. In FIG. 5, reference numeral 1 indicates a CD (compact disc), and 2 indicates an optical pickup. The optical pickup 2 is driven by a feed motor (not shown) to C
It moves between the inner circumference and the outer circumference of D1. Optical pickup 2
The three-spot laser beam emitted from CD to CD1 is C
The light is reflected by the surface of D1 and is received by the photodiode in the optical pickup 2, and is amplified by the preamplifiers 3 and 3.

The RF signal received by the digital signal reading photodiode of the optical pickup 2 is shaped into a pulse waveform by the mirror surface detection signal generating circuit 4 which is a comparator, and is received by the left and right tracking beam reading photodiodes. The tracking error signal T · E is shaped into a pulse waveform by the tracking error comparator 5. Then, the count signal creating circuit 6 outputs a count signal obtained by latching the mirror surface detection signal at the rising and falling edges of the tracking error pulse, and the counter circuit 7 integrates the number of moving tracks.

FIG. 6 is a timing chart of each of the above-mentioned parts. (A) is an RF signal received, (b) is a mirror surface detection signal obtained by shaping the RF signal, and (c) is a photodiode for reading left and right tracking errors. Is a differential output of the tracking error signal, (d) is a tracking error pulse that is formed by shaping the tracking error signal, and (e) is a count signal that latches the mirror surface detection signal of (b) at the rising and falling edges of the tracking error pulse. is there. Also,
In addition to the above-mentioned configuration, there is a configuration in which a simple means for directly counting the mirror surface detection signal (b) is adopted.

[0005]

Since the CD track pitch is as narrow as 1.6 .mu.m, lateral deviation of about several tens of tracks occurs due to the eccentricity accuracy of the CD, but during normal reproduction, the lateral deviation is caused by the tracking servo. Has no effect. However, when accessing another track by an operation such as a search, when the moving speed of the pickup at the start of access and immediately before the stop is slow, that is, when the moving amount of the optical pickup per one rotation of the CD is less than the eccentric amount, The track once traversed may cross the laser beam in the opposite direction again due to eccentricity. Further, such overlapping crossing is also caused by vibration of the optical pickup.

Conventionally, since all the count signals generated by the track crossing are counted, when the same track is crossed over, an error occurs between the actual number of moving tracks and the measured number of tracks, and the access accuracy is lowered. There is a problem. Therefore, there is a technical problem to be solved in order to eliminate the duplicate count of tracks and improve the access accuracy, and an object of the present invention is to solve the above problem.

[0007]

DISCLOSURE OF THE INVENTION The present invention is proposed to achieve the above-mentioned object, and detects the mirror surface portion between tracks of a CD by changing the level of incident light when accessing the optical pickup of a CD player. A track count circuit that generates a count signal from the mirror surface detection signal and counts the count signal, a circuit that outputs an exclusive OR of the count signal and a tracking error detection signal, and an exclusive OR output The present invention provides a track counting circuit in a CD player including a counter circuit for adding or subtracting the count signal according to the above.

[0008]

When the optical pickup accesses one track of the CD to another track, the tracking error signal by the three-spot tracking servo method has a phase difference of 180 ° depending on the moving direction of the optical pickup. The moving direction of the optical pickup is discriminated by taking the exclusive OR of the tracking error signal and the count signal indicating the track crossing, and the actual number of track movements is obtained by integrating the count signals for each moving direction. To be

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a track counting circuit. Reference numeral 11 is a CD, 12 is an optical pickup, 13 and 13 are preamplifiers, and 14 is an RF signal envelope obtained by photoelectrically converting the reflected light of a beam for reading a digital signal into a pulse. A mirror surface detection signal generation circuit for determining whether the beam is in the pit row of the CD or on the mirror surface portion between the tracks, 15 is a tracking error comparator for converting the tracking error signal into a pulse by performing zero cross comparison, 16 Is a count signal generation circuit which latches the mirror surface detection signal at the rising and falling edges of the tracking error pulse and outputs a count signal. The tracking error pulse is further input to the exclusive OR circuit 17 together with the count signal, the logical output is output to the two AND circuits 19 and 20 through the low pass filter 18, and one of the A
An inverted signal is input to the ND circuit 19 via the inverter 21. The count signal is input to the two AND circuits 19 and 20, and the AND outputs of the count signal and the tracking error pulse are input to the counter circuits 22 and 23, respectively.

The AND output of the inversion tracking error pulse and the count signal output from one AND circuit 19 is input to the up counter circuit 22 which counts the number of track movements from the inner circumference to the outer circumference of the CD, and the other AND.
The output of the circuit 20 is input to a down counter circuit 23 that counts the number of reverse track movements, and finally the actual number of track movements and the movement direction are calculated from the number of track movements in both the forward and reverse directions.

The low-pass filter 18 is for removing a tracking error pulse that may occur even when the track is being followed during CD reproduction. FIG. 2 shows the relationship between the laser beam of the optical pickup 12 and the track of the CD 11. A central digital signal reading beam C and tracking servo beams I and O are emitted to the left and right thereof. In the case of an on-track where the central beam C covers the center of the pit row of the track T ₂ , the left and right tracking servo beams I and O respectively hit the inner track T ₁ and the outer track T ₃ and reflect light. The amount of received light is almost equal. And
When the central beam C is moved from the track T ₂ to the mirror surface portion M between the tracks by moving the optical pickup 12, the amount of reflected light received by the central beam C is increased, and when the track is continuously traversed, as shown in FIG. An RF signal as shown in a) is generated. FIG. 2B shows a mirror surface detection signal obtained by pulse shaping the envelope of this RF signal by the mirror surface detection signal generating circuit 14.

When the optical pickup 12 traverses the track in the outer peripheral direction (up direction), first, as the central beam C deviates from the track T ₂ (ON → OFF), the outer tracking servo beam shown in FIG. O is applied more to the pit row of the outer track T _{3 and} the amount of received light decreases, and the inner tracking servo beam I goes out of the pit row of the inner track T ₁ to increase the amount of received light and cause a tracking error. The signal changes as shown in FIG. This is a tracking error comparator 15
The pulse shaped by (d) in the same figure,
(E) is a count signal in which the count signal generation circuit 16 latches the mirror surface detection signal (b) at the rising and falling edges of the tracking error pulse (d).

At this time, the exclusive OR circuit 1 shown in FIG.
The logic output of the count signal and the tracking error pulse output from 7 is Lo as shown in FIG. 3 (f) because the input is 0, 0 or 1, 1 and the logic output of the up counting side shown in FIG. The AND circuit 19 outputs a count signal to the up counter circuit 22 each time the count signal is input, and the up counter circuit 22 counts the count signal.

In FIG. 4, the optical pickup 12 has a track inside.
Shows the case of crossing in the circumferential direction (down direction).
Since the movement direction of Up 12 is opposite,
At this time, the tracking servo beam on the inner peripheral side shown in FIG.
Track I on the inner circumference side ₁More in the pit row of
However, the tracking servo beam O on the outer peripheral side is the outer peripheral side.
Truck T₃To the mirror surface part M. Therefore figure
As shown in (c) and (d) of 4,
Signal and tracking error pulse are shown in Fig. 3 (c) and
(D) and the opposite phase.

Therefore, the tracking error pulse (d)
And the exclusive OR output (f) of the count signal (e)
When the input becomes 0, 1 or 1, 0, it becomes Hi, the count signal is output from the AND circuit 20 on the down side shown in FIG. 1, and the down counter circuit 23 integrates. In this way, the track crossing direction is discriminated, and the actual track movement number is calculated from the integrated values of up (inner circumference → outer circumference) and down (outer circumference → inner circumference). As a result, even if the same track is crossed a plurality of times, an accurate number of track movements can be obtained.

In the above embodiment, two counter circuits 2 are used.
Up / down is separately counted by 2 and 23, but the technical scope of the present invention is such that one up / down counter circuit is used and the exclusive OR output is used as the up / down control signal. Various modifications are possible within the scope of the invention, and it goes without saying that the present invention extends to those modifications.

[0017]

As described in detail in the above one embodiment, the present invention determines the transverse direction of the CD track with respect to the optical pickup, counts the number of track movements in both forward and reverse directions, and calculates the actual number of track movements. Therefore, the duplicate count of tracks due to the eccentricity of the CD, the vibration of the optical pickup, and the like is eliminated, a highly accurate count result is obtained, and the access accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a track counting circuit of the present invention.

FIG. 2 is an explanatory view showing a relationship between a CD track and a laser beam of an optical pickup.

FIG. 3 is a timing chart when a track is crossed from the inner circumference to the outer circumference.

FIG. 4 is a timing chart when a track is traversed from the outer circumference to the inner circumference.

FIG. 5 is a circuit block diagram of a conventional track counting circuit.

FIG. 6 is a timing chart of a conventional track counting circuit.

[Explanation of symbols]

 11 track counting circuit 12 optical pickup 13 preamplifier 17 exclusive OR circuit 19, 20 AND circuit 21 inverter

Claims (1)

[Claims] 1. A track for detecting a mirror surface portion between tracks of a CD by changing a level of incident light when an optical pickup of a CD player is accessed, generating a count signal from the mirror surface portion detection signal, and counting the count signal. A track in a CD player including a circuit for outputting an exclusive OR of the count signal and the tracking error detection signal in a counting circuit, and a counter circuit for adding or subtracting the count signal according to the exclusive OR output. Counting circuit.