JPH0748255B2 - Focus search control method for optical disc player - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a focus search control method for an optical disc player that can be installed vertically or horizontally, and particularly relates to a focus servo pull-in regardless of the installation angle. The present invention relates to a focus search control method for an optical disc player that can be stabilized.

<Prior Art> In an optical disc player such as a CD player, for example, the depth of focus of the objective lens that focuses the laser beam on the disc surface is only about ± 1.0 μm. Therefore, when the disc is placed on the turntable of the CD player, it is hardly expected that the pit will be in focus. Even when the disc is placed on the turntable of the CD player, even if the disc is in focus, the distance between the disc and the lens constantly changes due to the warp of the disc and the surface wobbling caused by the machining accuracy, and the next moment Is out of focus. For this reason, a focus servo control device is usually provided in a CD player to generate a focus error signal having a voltage value according to the distance between the objective lens and the disc, and perform the servo control using the focus error signal to perform the servo control. Focusing is performed by controlling the position of the objective lens with respect to the disk surface so that the distance is constant, in other words, the disk surface is always the focal plane.

By the way, in order to activate the focus servo control device, the distance between the objective lens and the disc reflection surface must be close to the depth of focus to some extent. Therefore, immediately after the disc is mounted on the turntable, the objective lens must be moved by the focus actuator to a position where the focus servo can be applied. Therefore, normally, as shown in FIG. 4 (a), a focus search signal (triangular wave signal of 1 to 2 Hz) FS of a low frequency is applied to a position where focus servo can be applied, for example, a focal point (the focus is aligned with the reflection surface of the disk). The objective lens is moved to (the position of the objective lens at the time of the movement) (hereinafter, such control is referred to as “focus search control”), and then the focus error signal FE (fourth position) having an amplitude according to the distance between the objective lens and the focal point is obtained. The focus servo is performed so that the objective lens is located at the focal point, as shown in FIG. Whether or not the objective lens reaches the in-focus point is detected by whether or not the focus error signal FE crosses the zero level.

<Problems to be Solved by the Invention> However, the movement of the objective lens that follows a constant focus search signal FS changes by changing the installation angle of the CD player. That is, as shown in FIG.
When the CD player is installed vertically, the focus servo system is not affected by the weight of the objective lens and the actuator itself.
Respond immediately to FS. However, when the CD player is installed horizontally as shown in FIG. 5B, the focus servo system repels the own weight of the objective lens and the focus actuator to move the objective lens. The focus search signal FS when moving the objective lens in the direction (direction to bring the objective lens closer to the disc)
(Moving speed becomes slower than the dotted line),
The stroke amount to the maximum moving point decreases. On the other hand, when the objective lens is moved in the-direction of the focus servo system (the direction in which the objective lens is moved away from the disk), the focus search signal FS is rapidly lowered to reach the lowest point.

As described above, in the conventional focus search control method of the optical disc player, the movement of the objective lens, that is, the stroke of the objective lens and the lens are determined by the relationship between the weight of the objective lens and the focus actuator depending on the installation angle of the optical disc player. There is a problem in that the speed changes, the conditions under which the objective lens passes the focal point are not constant, and the pulling of the focus servo is hindered.

In view of the above, an object of the present invention is to provide a focus search control method for an optical disc player, which can stabilize pull-in to the focus servo regardless of the installation angle of the optical disc player.

<Means for Solving the Problems> According to the present invention, the above-mentioned problems are achieved by a means for storing in advance a table of the correspondence relationship between the installation angle of the optical disc player main body and the rising and falling slopes of the focus search signal, Means for obtaining the rising and falling slopes of the focus search signal according to the actual installation angle of the optical disc player body from the table, and generating the focus search signal having the rising and falling slopes to focus the objective lens. And means for moving to the position where the servo is applied.

<Operation> The correspondence relationship between the installation angle of the optical disc player main body and the rising and falling inclinations of the focus search signal is stored as a table in advance, and the focus according to the actual installation angle of the optical disc player main body is stored. The rising and falling slopes of the search signal are obtained from the table, a focus search signal having the rising and falling slopes is generated, and the objective lens is moved to a position where the focus servo can be applied.

<Embodiment> FIG. 1 is a block diagram of a focus search circuit according to the present invention.

2 is an optical pickup, 2a is an objective lens, 2b is a focus actuator, 11 is a focus servo circuit, 12 is a focus driver, 13 is a focus search circuit, 13a is a correspondence table, 13b is a focus search signal generator, and 14b.
Is an angle sensor.

The rising and falling slopes of the focus search signal FS corresponding to the installation angle of the CD player body are stored in the correspondence table 13a, and the focus search signal having the rising and falling slopes according to the angle detected by the angle sensor 14 is stored. FS is generated by the focus search signal generation unit 13b, the focus search signal FS is output to the focus driver 12, the objective lens 2a is moved to a position where the focus servo can be applied by the focus actuator 2b, and then the focus error signal FE is output. The focus servo circuit 11 is used to perform focus servo.

FIG. 2 is a block diagram of a CD player embodying the present invention.

In the figure, 1 is a CD (compact disc), 2 is an optical pickup, 2a is an objective lens, and 2b is a focus actuator, which optically reads digital information recorded on CD1 and outputs a signal via an RF amplifier 3. Input to the processing circuit 4. The signal processing circuit 4 demodulates the EFM signal input from the RF amplifier 3, separates acoustic data and subcode, and performs error detection / correction processing on the acoustic data.
Information is input to the D / A converter 5, and the information read from the lead-in area of the subcode and the CD is also input to the system controller 6. The D / A converter 5 D / A converts the 16-bit sound data input from the signal processing circuit 4, inputs the output to the audio circuit 7, and the audio circuit 7 outputs sound from a speaker (not shown).

The system controller 6 stores the lead-in area information input from the signal processing circuit 4 in the memory 6a,
Similarly, the Q channel of the input subcode is analyzed to extract data indicating the song number of the current song, the elapsed time for each song, the total elapsed time, and the like, and the data is appropriately displayed on the display unit 8. Also,
The system controller 6 performs various processes such as play and search based on the information input from the operation unit 9.

11 is a focus servo circuit, 12 is a focus driver,
Reference numeral 13 is a focus search circuit, 14 is an angle sensor, and these circuits constitute a focus servo system.
Focus the light on the signal surface of. In focus servo control, the switch circuit is activated when the focus servo is activated.
Switch the SW to the focus search circuit 13 side, move the objective lens 2a by the focus actuator 2b to a position close to the depth of focus where servo control is possible, and then switch the switch circuit SW to the focus servo circuit 11 side to output the focus error signal FE. Perform the focus servo used.

Reference numeral 21 is a tracking servo circuit, and 22 is a tracking driver. These circuits form a tracking servo system and make the optical pickup 2 follow the eccentricity of the CD 1.

31 is a sled servo circuit, 32 is a sled driver, and these circuits constitute a sled servo system.
The sled motor 33 is driven along with the reproduction to move the optical pickup position.

Reference numeral 41 is a spindle servo circuit, and 42 is a spindle driver, which rotates a spindle motor 43 at a constant linear velocity.

As shown in FIG. 1, the focus search circuit 13 according to the present invention includes a correspondence table 13a for storing the rising and falling inclinations of the focus search signal FS corresponding to the installation angle of the CD player body, and the correspondence table. The focus search signal generator 13b, which generates a focus search signal FS having rising and falling slopes stored in 13a, has rising and falling slopes according to the angle detected by the angle sensor 14. Outputs focus search signal FS. The inclination of the focus search signal FS will be described with reference to FIG.

When the CD player is installed vertically, the weight of the objective lens 2a and the focus actuator 2b has no influence, and the movement of the objective lens 2a immediately responds to the focus search signal FS. Therefore, the slope of the focus search signal FS is the third
As shown in FIG. 7A, both the rising and falling edges are set to be equal and symmetrical above and below the focal point.

If the CD player is installed horizontally, the objective lens
It is necessary to repel the weight of 2a and the focus actuator 2b to move the objective lens 2a. Therefore, as shown in FIG. 3 (b), the rising edge of the focus search signal FS for moving the focus servo system in the + direction (direction in which the objective lens 2a is brought closer to CD1) is made steeper, and the-direction of the focus servo system is decreased. The slope of the trailing edge of the focus search signal FS for moving the objective lens 2a away from CD1 is set gently. It should be noted that the amplitude of the focus search signal FS is set to be large along with the setting of the inclination. By controlling the rising and falling slopes of the focus search signal FS in this way, the movement of the objective lens 2a (shown by the dotted line) regardless of the installation angle of the CD player, in other words, as shown in FIG. 3 (c). As shown, the condition that the focus error signal FE crosses the zero level can be made constant, and thus the pull-in operation to the focus servo can be stabilized.

Although the method of automatically detecting the installation angle of the CD player using the angle sensor 14 has been described in the present embodiment, a switch may be provided instead of the angle sensor and the switch may be set according to the installation angle. I don't care.

In the present embodiment, the CD player is exemplified as the optical disc player, but the present invention can be easily implemented with any optical disc player such as CD-V, CD-I, LD (laser disc).

<Advantages of the Invention> As described above, according to the present invention, the inclination of the rising edge and the falling edge of the focus search signal is controlled based on the installation angle of the main body of the optical disc player. However, the movement of the objective lens during focus search becomes constant near the in-focus point,
It has an excellent advantage that the pulling into the focus servo can be stabilized.

[Brief description of drawings]

FIG. 1 is a block diagram of a focus search circuit according to the present invention, FIG. 2 is a block diagram of a CD player embodying the present invention, FIG. 3 is a waveform diagram of a focus search signal according to an installation angle, FIG. FIG. 5 is a waveform diagram for explaining the background of the present invention. 2 ... Optical pickup, 2a ... Objective lens, 2b ... Focus actuator, 11 ... Focus servo circuit, 12 ... Focus driver, 13 ... Focus search circuit, 13a ... Corresponding table, 13b ... Focus search signal Generator, 14 ... Angle sensor.

Claims (1)

[Claims] 1. A focus search control method for an optical disc player, wherein an objective lens is moved to a position where a focus servo can be applied by a focus search signal having a triangular wave shape, and then the focus servo is performed. The correspondence between the angle and the rising and falling slopes of the focus search signal is tabulated and stored, and the rising and falling slopes of the focus search signal according to the actual installation angle of the optical disc player body are recorded as described above. A focus search control method for an optical disc player, characterized by generating a focus search signal having the rising and falling slopes obtained from a table and moving the objective lens to a position where a focus servo can be applied.