JP2502494Y2 - Pickup speed detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a moving speed detection device for a pickup,
In particular, the present invention relates to a pickup moving speed detecting device in a device for reading recorded information on a recording disc such as a video disc.

BACKGROUND ART An information reading device reads a recorded information by using a pickup that detects information by reflected light obtained by irradiating a recording surface of a recording disk (hereinafter abbreviated as a disk) with a light beam. Is configured. In such an information reading device, the focus servo device controls the position of the focal point of the light beam of the pickup, and an information detecting light spot (information detecting point) is formed on the recording surface of the disc. At the same time, the tracking servo device controls the light spot so as to accurately follow a recording track formed, for example, in a spiral shape on the recording surface of the disk.

In such an information reading apparatus, the carriage carrying the pickup is moved in the radial direction of the disk to search information. As a device for detecting the speed of the carriage movement speed at this time, a volume, potentiometer, etc. are rotated according to the movement distance of the carriage to generate a signal having a level according to the position of the carriage in the disk radial direction. A moving speed detecting device configured to convert to a speed signal is well known.

Further, a device having a structure in which the tracking servo loop is opened and the moving speed is detected by counting the pulses generated every time the light spot crosses the track when the carriage is moved is also known.

However, in the former case, not only a member such as a volume and a potentiometer is required but also a mechanical load is applied, which has a drawback that it hinders stability of movement and speeding up. In the latter case, the moving speed cannot be detected when the tracking servo loop is closed.
At the time of so-called visual scanning, that is, when the carriage is forcibly moved and the tracking actuator reaches the limit of the movable range, the tracking servo loop is opened and the tracking actuator returns to the vicinity of the middle point of the movable range by mechanical force such as a spring. In this case, there is a drawback that the moving speed control during high speed reproduction, which is performed by repeating the operation of turning on the tracking servo loop again, cannot be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a moving speed detecting device capable of detecting the moving speed of a pickup when the tracking servo loop is closed without disturbing the stability and speeding up of the movement.

The pickup moving speed detecting device according to the present invention generates a tracking error signal according to a distance and a distance of an information detecting point of the pickup with respect to a center of a recording track of a recording disk, and is arranged in the pickup to detect the tracking error signal. Tracking servo means for controlling a tracking state of the information detection point by driving a tracking actuator for biasing the information detection point in the radial direction of the recording disk, and relative to the pickup and the recording disk in response to a command. In an information reading apparatus comprising a pickup position changing means for changing the position in the radial direction of the recording disk, the pick-up position moved by the pickup position changing means while a tracking servo loop is closed. A moving speed detecting device for detecting a relative speed of the recording disk with respect to the recording disk, the driving force detecting means generating a driving force detecting signal according to the driving force for driving the tracking actuator, and a predetermined driving force detecting signal. It has a change rate detecting means for generating a signal according to the change rate of a component below the frequency as a moving speed detection signal.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, laser light emitted from a laser light source 2 such as a laser diode in a pickup 1 is collimated by a collimator lens 3 into a parallel light beam, and then a beam splitter 4 and a quarter wavelength plate 5 for changing a polarization direction. Then, the light is focused on the recording surface of the disk 7 through the objective lens 6 and becomes a light spot for information detection.

Recording tracks (pit rows) 8 on the recording surface of the disk 7
Are formed. The reflected light from the recording surface of the disk 7 passes through the objective lens 6 and the quarter-wave plate 5 and then enters the beam splitter 4 to separate the incident light and the reflected light containing information. The reflected light separated by the beam splitter 4 enters the four-division detector 11 via the convex lens 9 and the cylindrical lens 10.

Each output of the four-division detector 11 is amplified by the RF amplifier 15 and then supplied to the tracking error signal generation circuit 16. The tracking error signal generation circuit 16 generates a tracking error signal according to the deviation of the information detection light spot from the recording track center by a so-called one-beam method such as a so-called push-pull method or a heterodyne method. The method of generating the tracking error signal in the tracking error signal generation circuit 16 is not limited to this one-beam method, but a so-called three-beam method can be used.

The tracking error signal generated by the tracking error signal generation circuit 16 represents the relative positional relationship between the information detection point of the pickup 1 and the track 8 as shown in FIG. It has a so-called S-shaped curve characteristic, and is normally adjusted by the RF amplifier 15 or the tracking error signal generation circuit 16 so as to have a positive / negative symmetrical waveform with respect to the zero cross point. This tracking error signal is sent to the analog switch 17 and amplifier.
A tracking actuator (not shown), which is supplied to a drive coil 19 in the pickup 1 via 18 and displaces the objective lens 6 in a direction perpendicular to its optical axis, is driven to perform tracking control of an information detection point. The analog switch 17 is supplied with the detection output of a detection circuit (not shown) that detects that the tracking actuator has been driven to the limit of the movable range by the drive signal supplied to the drive coil 19, for example. Switch 17
Are configured to be opened by this detection output. This analog switch 17 periodically opens the tracking servo loop during visual scanning.

A resistor R is connected in series to the drive coil 19. A signal corresponding to the current flowing through the drive coil 19 is generated by the resistor R and supplied to the LPF (low pass filter) 20. L
The output of PF20 is supplied to the differentiating circuit 21. These resistors R, LPF 20 and differentiating circuit 21 form a moving speed detecting device 22 according to the present invention, and the output of the differentiating circuit 21 is supplied to each part as a moving speed detecting signal.

A carriage motor 23 drives a carriage (not shown) on which the pickup 1 is mounted. The carriage motor 23 is drive-controlled by a motor drive circuit 24. The motor drive circuit 24 detects the amount of deviation of the tracking actuator based on the output of the LPF 20, and controls the position of the pickup 1 in the disk radial direction so that the amount of deviation is zero, that is, the tracking actuator is located at the midpoint of the movable range. Along with this, the motor drive circuit 24 responds to a visual scan command output from a system controller (not shown) or the like by a moving speed detection signal output from the differentiating circuit 21, and the relative speed of the pickup 1 in the disk radial direction. Is detected and a drive signal corresponding to the relative speed is supplied to the carriage motor 23.

In the above configuration, since the drive current corresponding to the tracking error signal is supplied to the drive coil 19, when the tracking actuator is an electrodynamic actuator, a drive force proportional to the drive current of the drive coil 19 is generated. The value of the drive current of the drive coil 19 depends on the relative position between the pickup 1 and the track 8. Therefore, the output of the differentiating circuit 21 for differentiating the low-frequency component of the signal according to the drive current is in accordance with the rate of change in the relative position between the pickup 1 and the track 8, that is, the relative speed of the pickup 1 with respect to the track 8. Therefore, the moving speed of the pickup 1 is detected.

When the pickup 1 is moved in the radial direction of the disc during visual scanning or the like, the tracking loop closing time is much longer than the tracking loop opening time, and therefore the moving speed information is obtained over almost the entire moving period. be able to.

Effect of the Invention As described in detail above, the pickup moving speed detecting device according to the present invention is a driving force detection signal according to a driving force for driving the biasing means for biasing the information detection point of the pickup in the radial direction of the disk by the tracking error signal. Is generated and a signal corresponding to the rate of change of a component of the driving force detection signal equal to or lower than a predetermined frequency is output as a moving speed detection signal. Therefore, it is necessary to provide a member for detecting such as a potentiometer on the carriage. Therefore, the mechanical load is not increased, and the stability and speed of movement are not hindered. At the same time, since the moving speed is detected by detecting the driving force applied to the biasing means such as the tracking actuator by the tracking error signal, the moving speed can be detected when the tracking servo loop is closed. . Therefore, the pickup moving speed detecting device according to the present invention is
When a carriage is driven by a linear motor, speed feedback is required especially for feeding at a constant speed at a low speed, and therefore it is suitable for use in moving speed detection during visual scanning.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a relationship between a recording track and a tracking error signal. Description of main part code 1 …… Pickup 19 …… Drive coil 20 …… LPF 21 …… Differentiation circuit

Claims (2)

(57) [Scope of utility model registration request] 1. A tracking error signal is generated in accordance with a distance and a distance of an information detection point of a pickup with respect to a center of a recording track of a recording disk, and the tracking error signal is arranged in the pickup to detect the information detection point by the tracking error signal. A tracking servo unit that drives a tracking actuator that deviates in the radial direction of the recording disc to control the tracking state of the information detection point; and a relative position between the pickup and the recording disc in response to a command, In an information reading apparatus including a pickup position changing means for changing in a radial direction, a relative movement of the pickup moved by the pickup position changing means with respect to the recording disk while a tracking servo loop is closed. And a rate of change of a component of the driving force detection signal having a frequency equal to or lower than a predetermined frequency, the driving force detecting device generating a driving force detection signal according to a driving force for driving the tracking actuator. And a change rate detecting means for generating a signal corresponding to the moving speed detection signal as a moving speed detection signal. 2. The tracking servo means includes means for supplying a drive signal corresponding to the tracking error signal to the tracking actuator, and the drive force detection means includes the drive force detection signal based on the drive signal. The moving speed detecting device for a pickup according to claim 1, wherein: