JPH0715760B2 - Focus control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reproducing device, and more particularly to a focus control device thereof.

2. Description of the Related Art As a conventional focus control device, for example, Japanese Patent Laid-Open No. 59-
There is one disclosed in Japanese Patent No. 168940. This will be described below with reference to FIG.

A light beam generated from a light source 1 such as a semiconductor laser is collimated by a coupling lens 2 and then reflected by a polarization beam splitter 3 to pass a λ / 4 plate 4 (λ is the wavelength of the light beam). After being focused by the focusing lens 5, the rotating disk 7 is irradiated by the motor 6.
The reflected light of the light beam from the disk 7 is focused by the focusing lens 5,
The light passes through the λ / 4 plate 4 again, passes through the polarization beam splitter 3, and is irradiated onto the photodetector 8 having a three-divided structure.

The direction of the dividing line of the photodetector 8 having the three-divided structure is set so as to coincide with the tangential direction of the spiral (or concentric) track on the disk 7 irradiated with the light beam in a predetermined focused state.

The output B of the photodetector 8 and the sum of the output A and the output C are amplified by the preamplifiers 9a and 9b, respectively, and then the differential amplifier 1
The differential amplifier 10 obtains the difference output of both preamplifiers, that is, the focus shift signal.

Further, if the differential output between the output A and the output C of the photodetector 8 is taken, it is possible to obtain the track deviation signal for controlling the light beam on the disk 7 to scan the track correctly. The description is omitted because it is not directly related to the present invention.

The focus shift signal is input to the focus control element 13 via the phase compensation circuit 11 for compensating the phase of the focus control system, the switch 14 for closing the loop of the control system, and the drive circuit 12 for power amplification. There is.

Therefore, the focus control element 13 is controlled so that the light beam on the disk 7 is always in a predetermined focused state.

The switch 14 is turned on by the output of a command signal (hereinafter referred to as the FCON signal) from the microcomputer 15 that constitutes the system of this control device, and closes the loop of the focus control system as described above.

The preamplifiers 9a and 9b, the differential amplifier 10, the phase compensation circuit 11, the switch 14 and the drive circuit 12 are bipolar (power supply voltage ± Vcc).
It is operated by the power supplies 17a and 17b.

Problems to be Solved by the Invention In the conventional control device, since the drive circuit of the control element is operated by the bipolar power supply, the device power is turned on and off.
When FF occurs, there is a time difference between the rising and falling of the two power supplies, and a voltage is instantaneously generated at the output of the drive circuit. An overcurrent flows through the control element due to the voltage,
There was a problem of damage.

The present invention has been made in view of the above problems, the operation of the drive circuit is stopped until the loop of the control system is closed, and the overcurrent does not flow to the control element when the power is turned on and off. To prevent damage to the control element,
The goal is to provide a highly reliable device.

Means for Solving the Problems The present invention relates to a focusing means for focusing a light beam generated from a light source on a record carrier, a detecting means for detecting a signal according to a focusing state of the light beam on the record carrier, and Moving means for moving the light beam focused by the focusing means in a direction perpendicular to the surface of the record carrier; and, according to a signal from the detecting means,
Focus control means for driving the moving means and a signal of the detecting means to the drive means and driving the drive means to control the light beam on the record carrier to a predetermined focusing state. And a protector for disabling the drive means in response to the signal from the signal open / close means, and a focus open / close means for transmitting / blocking the signal from the detector.

Action The present invention, with the above-described configuration, stops the operation of the drive circuit until the loop of the control system is closed.
Overcurrent does not flow through the control element due to N and OFF, damage to the control element can be prevented, and the reliability and maintainability of the device can be improved.

EXAMPLES Examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the focus control apparatus according to this embodiment. The same parts as those of the conventional focus control device are designated by the same reference numerals, and the description thereof will be omitted.

The microcomputer 15 that constitutes the system of this focus control device switches the command signal, that is, the FCON signal.
Input to 14 to close the loop of the focus control system, and also to protect circuit 16.

When the FCON signal is input, the protection circuit 16 transmits a protection release signal to the drive circuit 12, operates the drive circuit 12, and drives the control element 13.

FIG. 2 is a detailed diagram showing an embodiment of the protect circuit 16. This embodiment will be described in more detail with reference to FIG.

For example, when a high-level FCON signal is input from the microcomputer 15, the transistor 25 is turned on, the transistor 26 is turned off, and the collector of the transistor 26, that is, the output of the protection circuit 16 becomes high level. The output of the protect circuit 16 is input to the drive circuit 12 as a protect release signal, and the drive circuit 12 can supply a current to the control element 13 to drive it.

When the power is turned on and off, in this control system, the FCON signal is not output, the input from the microcomputer 15 to the protection circuit 16 is low level, the transistor 25 is off, the transistor 26 is off, and the transistor 26 is off.
, That is, the output of the protect circuit 16 becomes low level. The output of the protect circuit 16 is the drive circuit 12
To the control element 13, and the operation of the drive circuit 12 is stopped at this time, and no current flows through the control element 13.

As described above, according to the present embodiment, even if a pseudo control signal to be input to the drive circuit is generated by turning on and off the power supplied to the control device, the overcurrent does not flow in the drive element. It is possible to prevent the control element from being damaged.

Further, the present embodiment can be similarly applied to the tracking control device, and if the output of the protection circuit 16 is input to the drive circuit of the tracking control element, not only the focus control element described above but also the tracking control element Damage can also be prevented.

As described above, according to the present invention, a pseudo signal generated in the drive circuit due to ON / OFF of the power supply supplied to the present control device can prevent the overcurrent flowing in the conventional control element. The control element can be protected by eliminating the flow, and a highly reliable device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a focus control device according to an embodiment of the present invention, FIG. 2 is a detailed diagram of the protect circuit portion of FIG. 1, and FIG. 3 is a configuration of a conventional tracking control device. It is a block diagram showing. 1 ... Semiconductor laser, 2 ... Coupling lens, 3 ...
... Polarizing beam splitter, 4 ... λ / 4 plate, 5 ... Focusing lens, 6 ... Motor, 7 ... Disk, 8 ... Photodetector, 9a, 9b ... Preamplifier, 10 ... Differential amplifier, 11 ……
Phase compensation circuit, 12 ... Drive circuit, 13 ... Control element, 14 ...
… Switch, 15 …… Microcomputer, 16 …… Protect circuit, 17a, 17b …… Power supply.

Claims (1)

[Claims] 1. Focusing means for focusing a light beam generated from a light source on a record carrier, detection means for detecting a signal according to a focus state of the light beam on the record carrier, and light focused by the focusing means. Moving means for moving the beam in a direction perpendicular to the surface of the record carrier; driving means for driving the moving means in response to a signal from the detecting means; and transmitting a signal from the detecting means to the driving means, Focus control means for driving the driving means to control the light beam on the record carrier to a predetermined focusing state, signal opening / closing means for transmitting / blocking the signal of the detecting means, and signal for the signal opening / closing means A focus control device for disabling the drive means according to the above, and operating the protect means in response to opening and closing of the signal opening / closing means.