JPH064413Y2 - Focusing device for optical disk player - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing device for an optical disc player, and more particularly to a focusing device that enables quick and reliable high-precision focusing. .

(Prior Art) A conventional focus device for an optical disk player is configured as shown in FIGS. 3 and 4. Incidentally, FIG. 3 is an overall block diagram, and FIG. 4 is a circuit diagram of a focus switching circuit for opening and closing the focus loop.

In the figure, 16 is a zero-cross detection comparator that outputs a zero-cross detection signal by comparing the signal output from the detection signal processing circuit 12 that processes the signal read from the optical disc 10 with a reference voltage, and 15 is the R of the detection signal processing circuit 12.
A low-pass filter that removes the low-frequency component from the F signal 14 by removing the RF component, 17 is a comparator that compares the output from the low-pass filter 15 and a reference voltage set by dividing resistors +4 and R5 from + Vcc, and 18 is a zero-cross It is a focus switching circuit that switches focus drive according to a zero-cross detection signal from the detection comparator 16 and a servo permission signal from the comparator 17.

The focus switching circuit 18 includes NAND1 and NAN.
It is composed of a flip-flop circuit in which D2 is combined.

(Problems to be solved by the invention) However, in such a focus device, since the flip-flop circuit as shown in FIG. 4 is used, the focus signal is close to the comparison reference voltage as shown in FIG. The phenomenon that the pickup is sluggish and the focus switch is switched by the error signal before the true focus zero-cross detection signal when the focus error signal is offset near the comparison reference voltage as shown in Fig. 7 and focus is not applied. was there.

That is, in FIG. 6, the focus switch is switched at the point A, which is noise, so that the focus cannot be properly applied.

(Means for Solving the Problem) A focusing device for an optical disc player according to the present invention comprises a pickup for reading a signal from a recording medium, a detection signal processing circuit for processing the signal from the pickup,
An optical system composed of a focus zero-cross detection circuit that outputs a focus zero-cross detection signal by comparing the signal from the detection signal processing circuit with a reference voltage, and a focus switching circuit that opens and closes a focus servo loop by the zero-cross detection signal. A focus device of a disc player is provided with a noise removal circuit that delays the output of the focus zero-cross detection signal.

(Operation) Since the noise removal circuit delays the output of the focus zero-cross detection signal, the true focus zero-cross detection signal can be output.

(Embodiment) An embodiment according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a circuit diagram showing a first embodiment according to the present invention, and FIG. 2 is a circuit diagram showing a second embodiment according to the present invention. The basic overall configuration is based on FIG. 3 described above.

In FIG. 1, the noise removal circuit is composed of a shift register composed of flip-flops F _{1 to} F _n, and an AND circuit 3 for AND-inputting outputs from the respective flip-flops.
It is composed of and. In addition, each flip-flop F
₁ with the clock to F _n noise rejection clock 2, focus zero cross detection signal is inputted to the data. Reference numeral 5 in the drawing is a focus switching circuit, which is composed of a servo permission signal 4 and a flip-flop to which a signal from the noise removing circuit is input and which outputs a switching signal.

In the focus switching circuit, the servo permission signal is H level.
Level and focus zero cross detection signal 1 is H
The focus servo is closed when the level becomes L level.

With the above configuration, the focus zero-cross detection signal 1 is input to the flip-flops F _{1 to} F _n , but until the predetermined number of noise removal clocks are input, that is, the predetermined time T
The AND circuit 3 does not become the H level until the time elapses. Then, after the elapse of the predetermined time T, the focus zero-cross detection signal becomes H level, and when the focus zero-cross detection signal changes from H level to L level, the focus servo is closed.

That is, in the noise portion of FIG. 6, the focus zero-cross signal accompanying the focus error signal is input to the noise removing circuit, but the focus zero-cross detection signal 1 changes from the H level to the L level until the predetermined time T elapses. Therefore, the AND circuit 3 does not become the H level, and the focus servo is not applied at the point A in the figure. Therefore, it becomes possible to close the focus servo at the point B which is the true zero-cross detection signal.

Next, a second embodiment will be described. In FIG. 2, 7 is a retriggerable counter and 8 is a flip-flop. The noise removal clock 2 is input to the clock of the re-triggerable counter 7, and the focus zero-cross detection signal 1 is input to the counter. The flip-flop 8 is configured so that the output from the retriggerable counter 7 and the focus zero-cross detection signal 1 are input and output to the focus switching circuit 5.

Therefore, the focus zero-cross detection signal 1 is input to the re-triggerable counter 7, but the flip-flop does not become H level until a predetermined number of noise removal clocks are input, that is, until the predetermined time T elapses. In addition,
When the noise removal clock reaches a predetermined number and a predetermined time T elapses, the flip-flop circuit 8 becomes H level and
Latches the level state and the focus zero cross signal is H
When the level changes from the L level to the L level, the output of the flip-flop circuit 8 is reset and the output signal becomes the L level.

Therefore, as in the case of the first embodiment, A in FIG.
The focus servo is not applied at the point, and the focus servo can be closed at the point B which is the true zero-cross detection signal.

(Effect of the Invention) According to the focus device of the optical disc player according to the present invention, since the noise removing circuit configured to delay the output of the focus zero-cross detection signal is provided, the pickup does not rattle. Further, there is an excellent feature that there is no malfunction of switching of the focus switch and the switching is appropriately performed so that the focus is not applied.

[Brief description of drawings]

1 is a circuit diagram showing a first embodiment according to the present invention, FIG. 2 is a circuit diagram showing a second embodiment according to the present invention, and FIG.
FIG. 4 is a block diagram showing a focusing device of an optical disc player, FIG. 4 is a circuit diagram of a conventional focus switching circuit, FIG. 5 is a signal waveform diagram, and FIGS. 6 to 7 are focus error signals and focus zero cross detection. It is explanatory drawing which shows the relationship of a signal. F _{1 to} F _n : Shift register 3: AND circuit 5, 8: Flip-flop circuit 7: Counter 15: Low-pass filter 17: Comparator 18: Focus switching circuit 19: Focus device

Claims (3)

[Scope of utility model registration request] 1. A pickup for reading a signal from a recording medium, a detection signal processing circuit for processing the signal from the pickup, and a signal from the detection signal processing circuit is compared with a reference voltage to output a focus zero-cross detection signal. In a focus device for an optical disc player, which comprises a focus zero-cross detection circuit and a focus switching circuit that opens and closes a focus servo loop according to the zero-cross detection signal, a noise removal circuit for delaying the output of the focus zero-cross detection signal is provided. A focusing device for an optical disc player. 2. A noise removing circuit includes a shift register and an AN.
A focus device for an optical disc player according to claim 1, characterized in that the focus device comprises a D circuit. 3. A focus device for an optical disc player according to claim 1, wherein the noise removing circuit is composed of a retriggerable counter and a flip-flop circuit.