JPH0237176Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention is an access device for a CD player, particularly a compact disk (hereinafter referred to as a CD), which uses a pick-up to pick up signals at a predetermined position written in a spiral shape. The present invention relates to an access device for a CD player that quickly and accurately moves a pick-up to a predetermined position during reading.

(Technical Background and Problems) By setting a disc on which bits are recorded in a spiral shape with or without bits into a CD player, the absolute time information recorded on each track is read out using a pick-up. Current pick
You can know the exact location of the app.

Furthermore, it takes a long time to set the position based on absolute time information read out by a pick-up. For this purpose, a potentiometer that moves in conjunction with the pick-up is provided, and servo control is performed so that the voltage generated at the potentiometer is equal to the DC voltage obtained by converting the instructed digital value into an analog signal. I did this and roughly set the position.

However, it is difficult to completely correspond the output voltage at each position of the potentiometer to each position of the CD, that is, to finely adjust the characteristics of the potentiometer during manufacturing. The displacement becomes large, and it takes a long time to accurately set the predetermined position based on the absolute time information read by the pick-up after the above-mentioned approximate position setting;
As a result, there was a problem that the access time became long.

(Purpose and structure of the invention) The purpose of the invention is to solve the above-mentioned problems, and by providing a circuit that compensates for the output voltage characteristics of a potentiometer that detects the pick-up position of a CD. By correlating with absolute time information read out by pick-up, extremely accurate position setting can be performed and access time can be shortened. Therefore, the access device for a CD player of the present invention includes a pick-up that detects the presence or absence of a predetermined bit recorded on a disc, a drive device that moves the pick-up in a direction substantially perpendicular to the rotational direction of the disc. a position detector for detecting the position of the pick-up moved by the drive device; a designated time input section for inputting a digital value for moving the pick-up to a predetermined position; comprising a conversion unit that converts a digital value input to an input unit into an analog value, and a subtraction unit that calculates a difference between the analog value from the conversion unit and the analog value obtained by the position detector, In an access device for a CD player that performs negative feedback control of the drive device using an output signal from the subtraction section, a pickup position detection signal detected by the position detector is detected by a pickup. It is characterized in that it includes a position detection signal compensation circuit that matches the detected absolute time information.

(Embodiments of the invention) The invention will be described in detail below with reference to the drawings.

Fig. 1 is an embodiment of the present invention, Fig. 2 is an explanatory diagram explaining the operation of the embodiment of the invention shown in Fig. 1, Fig. 3 is a specific example of the main part of the invention, and Fig. 4 is FIG. 3 is an explanatory diagram illustrating the characteristics of a specific example of the main part of the present invention.

In the figure, 1 is a CD player, 2 is a CD (compact disc), 3 is a drive motor, and 4 is a pick-up.
5 is a potentiometer, 6 is an amplifier,
7 is a specified time input section, 8 is a D/A converter, 9
is a subtraction unit, 10 is a selector, 11 is a motor drive circuit, 12 is an access control unit, 13 is a fine adjustment servo,
Reference numeral 14 represents a fine adjustment control section, 15 a check section, and 16 a correction control section.

In FIG. 1, a CD 2 set in a CD player 1 is rotated at a high speed at a predetermined speed by a spindle motor (not shown). A pick-up 4, which is moved by a drive motor 3 transversely to the direction of rotation of the CD 2, reads the presence or absence of bits spirally formed on the CD 2. The position of the pick-up 4 can be accurately known from the absolute time information among the read information.
On the other hand, in order to quickly move the pick-up 4 to a predetermined position, a potentiometer 5 is provided which moves in conjunction with the position of the pick-up 4. The voltage generated at the potentiometer 5 is amplified by an amplifier 6. Also, pick up 4
In order to set the D/A converter 8 to a predetermined position, the D/A converter 8
A predetermined digital value is supplied to the converter and converted into a DC voltage. Then, the subtracting section 9 is connected to the D/A converter 8.
A voltage e corresponding to the difference (A-B) between the output voltage A from the amplifier 6 and the output voltage B from the amplifier 6 is determined, and the voltage e is supplied to the motor drive circuit 11 via the a side of the selector 10. The drive circuit 11 is connected to the drive motor 3
to quickly move the pick-up 4 to a predetermined position.

In this way, the digital value for setting the pick-up 4 at a predetermined position is input to the designated time input section 7.
By inputting , the pick-up 4 is automatically set to approximately a predetermined position, that is, coarsely adjusted, by the servo system that performs the above-described operations.

Further, after the pick-up 4 is coarsely adjusted, the check section 15 in the access control section 12 selects the selector 1.
0 to the b side, the fine adjustment control section 14 extracts absolute time information from the signal read out by the pick-up 4, and outputs the absolute time information to the motor drive circuit 11 via the fine adjustment servo 13 and the b side of the selector 10. A predetermined voltage corresponding to the difference between the absolute time information and the current position is supplied to. The motor drive circuit 11 is connected to the drive motor 3
to accurately set the pick-up 4 at a predetermined position.

When performing the coarse adjustment described above, conventionally a potentiometer 5 was used to detect the position of the pick-up 4.
It would be good if the output voltage characteristics at each position of the potentiometer 5 corresponded completely to the absolute time information read out by the pick-up 4, but in reality they will deviate.
Therefore, after the rough adjustment mentioned above, the pick up 4
There is a problem in that the position setting amount based on the absolute time information read out by the method, that is, the fine adjustment amount becomes large, and as a result, the access time becomes long.

Therefore, in the present invention, the output voltage characteristics of the potentiometer 5 for detecting the position of the pick-up 4 are made to match the absolute time information read out by the pick-up 4. This will be explained below.

In FIG. 2, the horizontal axis shows the absolute time on CD2 read out from CD2 by pick-up 4, and the vertical axis shows the output voltage of potentiometer 5 that detects the position of pick-up 4. .

The figure and the example of the characteristics of the potentiometer 5 are shown. Since the relationship between the absolute time on the CD 2 and the output voltage of the potentiometer 5 is not proportional, the setting accuracy of the pick-up 4 due to the rough adjustment described above is Deteriorate. Therefore, it takes time for the fine adjustment based on the absolute time information to be performed after the coarse adjustment, and the access time for the above-mentioned coarse adjustment and fine adjustment becomes long.

The illustration shows the characteristics after being compensated by the present invention. For example, a potentiometer 5 having convex characteristics as shown may be passed through a circuit having concave characteristics as shown, or a potentiometer 5 having concave characteristics as shown may be passed through a circuit having convex characteristics as shown. By passing , it is possible to provide the proportional characteristic shown in the figure. This improves the coarse adjustment accuracy mentioned above,
The total access time for coarse adjustment and fine adjustment is reduced.

For example, a case in which the potentiometer 5 having the concave characteristic shown in FIG. 2 is compensated for having the proportional characteristic shown in the drawing will be explained in detail with reference to FIGS. 3 and 4.

The circuit shown in FIG. 3 is called a broken line approximation circuit using a diode clamp, and is a specific example of the amplifier 6 shown in FIG. The voltage Vo has a convex characteristic.

In the broken line approximation circuit using the diode clamp shown in FIG. 3, when the voltage applied to the input terminal 17 is gradually increased, the applied voltage is
As the voltage divided by 2 and 2 becomes higher than each voltage value obtained by dividing the reference voltage Vcc for the diode clamp by resistance, the diodes D1, D2, and D3 become conductive in sequence, and the positive polarity terminal (10 terminal) of the operational amplifier becomes higher. ), the output voltage Vo at the output terminal 18 of the operational amplifier has a convex characteristic (FIG. 4).

Therefore, when the output voltage from the potentiometer 5 having the concave characteristic shown in FIG. 2 is input to a circuit having the convex characteristic shown in FIG. 3, it can have the proportional characteristic shown in FIG. 2. . At this time, in order to have a completely proportional characteristic, the reference voltage for the diode clamp in the circuit shown in Figure 3 must be
Just adjust Vcc. In addition, if the proportional characteristic cannot be obtained only by adjusting the reference voltage Vcc,
The resistor for the diode clamp can be selected appropriately. Furthermore, in order to cope with the potentiometer 5 having convex characteristics shown in FIG. 2, a circuit having concave characteristics can be realized by providing a diode clamp circuit at the negative polarity terminal (-terminal) of the operational amplifier.

(Effect of the invention) As explained above, according to the invention, the pick
Potentiometer 5 detects the position of up 4
Since a circuit is provided to compensate for the output voltage characteristics of the pick-up 4 to match the absolute time information read out by the pick-up 4, it is possible to coarsely adjust the pick-up 4 extremely accurately, and fine adjustment is possible. The time required for accessing is reduced, and the overall access time can be reduced.

[Brief explanation of the drawing]

Fig. 1 is an embodiment of the present invention, Fig. 2 is an explanatory diagram explaining the operation of the embodiment of the invention shown in Fig. 1, Fig. 3 is a specific example of the main part of the invention, and Fig. 4 is FIG. 3 is an explanatory diagram illustrating the characteristics of a specific example of the main part of the present invention. In the figure, 1 is a CD player, 2 is a CD (compact disc), 3 is a drive motor, and 4 is a pick-up.
5 is a potentiometer, 6 is an amplifier,
7 is a specified time input section, 8 is a D/A converter, 9
is a subtraction unit, 10 is a selector, 11 is a motor drive circuit, 12 is an access control unit, 13 is a fine adjustment servo,
Reference numeral 14 represents a fine adjustment control section, 15 a check section, and 16 a correction control section.

Claims (1)

[Scope of utility model registration request] a pick-up for detecting the presence or absence of a predetermined bit recorded on a disk; a drive device for moving the pick-up in a direction substantially perpendicular to the rotational direction of the disk; and a drive device for moving the pick-up by the drive device. a position detector for detecting the position of the pick-up, a specified time input section for inputting a digital value for moving the position of the pick-up to a predetermined position, and a specified time input section for converting the digital value input to the specified time input section into an analog value. A conversion unit that performs conversion, and a subtraction unit that calculates a difference between an analog value from the conversion unit and an analog value obtained by the position detector, and uses an output signal from the subtraction unit to perform the drive. In an access device for a CD player that performs negative feedback control of the device, a position detection signal that matches a pick-up position detection signal detected by the position detector with absolute time information detected by the pick-up. An access device for a CD player characterized by being equipped with a compensation circuit.