JPH01220227A - Focusing servo controller - Google Patents

Abstract

PURPOSE:To perform focus pull-in in a comparatively short time by storing a focusing position at the first time of performing focusing search in a comparatively wide range, and performing search in a comparatively narrow range centering a stored focusing position from the next focusing search. CONSTITUTION:A focusing error detecting means 5 to generate an error signal corresponding to the relative distance of an objective lens for an optical information recording medium, a means 3 to control the position of the objective lens for the information recording medium based on a focusing error signal, and a means 7 to store the focusing position after the pull-in of focusing servo are provided. Also, a means 4 to generate a focusing search signal to vary the relative distance actively between the information recording medium and the objective lens based on a memory device in a storage means is provided. And the focusing position at the first time of performing the focusing search is stored, and the focusing search is performed based on the above stored position at the next time of performing the focusing search. In such a way, the focusing search can be performed at high speed and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus servo control device for reliably pulling in focus at high speed in an optical information recording/reproducing device.

[Prior Art] Fig. 2 is a block diagram of a conventional focus servo control device. (2) is a focus actuator that drives the objective lens of the pickup (1) in the focus control direction; (3) is a focus actuator (2) that drives the objective lens of the pickup (1) in the focus control direction; A focus actuator drive circuit that supplies a control current, (4) a focus search circuit that supplies a control signal to the focus actuator drive circuit (3), and (5) a signal output from the big up (1). A focus error signal detection circuit (6) detects a focus error based on the focus error signal and generates an error signal, and a focus actuator drive circuit (3) detects a focus error based on the error signal obtained by the focus error signal detection circuit (5).
) is a focus servo pull-in circuit that controls the focus servo.

Next, the operation will be explained. Always check the relative distance between the pickup (1) and the information recording/reproducing medium.
In order to maintain the in-focus position of the objective lens built in 1), a search for the in-focus position is first performed. The focus search circuit (4) drives the focus actuator (2) via the focus actuator drive circuit (3) to actively adjust the relative distance between the pickup (1) and the information recording/reproducing medium. It is done by changing. As a result of this focus search, the laser beam that returns from the information recording and reproducing medium to the pickup (1) contains a focus error, and when this is manually input to the focus error signal detection circuit (5), the in-focus position is determined. An error signal is detected and generated. The error signal generated by the focus error signal p detection circuit (5) is manually input to the focus servo pull-in circuit (6), and when the objective lens of the pickup (1) comes near the in-focus position, focus search is performed. The search signal of circuit (4) is stopped and the focus servo system is closed. From then on, the focus error signal detected by the focus error signal detection circuit (5) automatically maintains the relative distance between the pickup (1) and the information recording/reproducing medium at the in-focus position of the objective lens. controlled by.

[Problems to be Solved by the Invention] Since the conventional focus servo control device is configured as described above, in order to reliably move the objective lens of the pickup (1) to the in-focus position of the objective lens, it is necessary to The search range of the focus search circuit (4) is set as wide as possible. However, there is a limit to the ability of the focus actuator (2) to follow the drive signal, and as a result, there is a problem that it takes a long time to pull the focus.

This invention was made to solve the above-mentioned problems, and the focus search time can be reduced by determining the focus search range based on the stored position of the in-focus position during the previous focus search. It is an object of the present invention to provide a focus servo control device that shortens the time and performs focus servo pull-in at high speed.

[Means for Solving the Problems] In order to solve the above problems, there is provided a focus error detection means that generates an error signal according to the relative distance of the objective lens to the optical information recording medium, and a focus error detection means that generates an error signal based on the focus error signal. means for controlling the position of the objective lens with respect to the information recording medium; means for storing the in-focus position after focus servo retraction; and storage means for actively changing the relative distance between the information recording medium and the objective lens. The present invention provides a focus servo control device comprising means for generating a focus search signal based on a storage device.

[Operation] In the above means, the focus servo control device of the present invention stores the in-focus position at the time of the first focus search, and performs the in-focus search based on the previously stored position at the time of the next focus search. This enables fast and reliable focus search.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a focus servo $116 device according to an embodiment of the present invention. In the figure, (7)
is a focus position memory circuit that stores the level of the focus pull-in signal from the focus servo pull-in circuit (6), that is, the signal level for moving and holding the objective lens of the pickup (1) to the focus position. A control signal is supplied to the focus actuator drive circuit (3) based on the signal.

The operation of this configuration will be explained next.

In order to always maintain the relative distance between the pickup (1) and the information recording/reproducing medium at the focal point position of the objective lens built into the pickup (1), a search for the focal point position is first performed. This is carried out by outputting a search signal from the focus search circuit (4) and supplying this search signal to the focus actuator (2) via the focus actuator drive circuit (3).

As a result, the focus actuator (2) is driven to actively change the relative distance between the objective lens of the pickup (1) and the information recording/reproducing medium. This search operation is performed in a relatively wide preset range near the focal point position of the objective lens.

As a result of this search operation, the focus actuator (
2) is supplied with a current to drive the objective lens;
The relative distance between the pickup (1) and the information recording medium changes in synchronization with the search signal of the focus search circuit (4). This search signal is generated by the focus error signal detection circuit (5) and the focus servo pull-in circuit (6) at a predetermined speed in the direction of moving the objective lens of the pickup (1) closer to the information recording medium over time. It's going to change. When the objective lens of the pickup (1) comes near the focal point, the return light from the information recording medium is reflected by the pickup.
From up (1) to focus error signal detection circuit (5)
), where an error signal for the in-focus position is detected and generated. Focus error signal detection circuit (5
) is input to the focus servo pull-in circuit (6), which stops the search signal of the focus search circuit (4) when the objective lens approaches the in-focus position, and the focus servo system closes. focus
The relative distance between the pickup (1) and the information recording medium is automatically controlled by the error signal so as to be at the in-focus position.

After the focus servo pull-in circuit (6) stops the search signal of the focus search circuit (4), the pick
The focus search circuit (4) is used as the level of the signal to move and hold the up (1) objective lens to the focused position
) is stored in the focus position storage circuit (7). Next, focus again.
When performing a search, the search signal output from the focus search circuit (4) is searched in a relatively narrow range centered around the focused position stored in the focused position memory circuit (7). The focus servo can be pulled in.

Therefore, even though it may take some time during the initial focus search, it is possible to reliably perform a focus search over a relatively wide range.
When performing the next focus search, a relatively narrow focus range is selected based on the memorized position of the in-focus point during the previous search.
By performing a search, you can focus and focus at high speed.
It becomes possible to perform servo pull-in.

In the above embodiment, the first search position in the focus search circuit (4) is stored in the focus position memory circuit (7), and from the next search onwards, the memory in the focus position memory circuit (7) is stored. Although we have illustrated a configuration in which focus search is performed based on position, the focus position memory circuit (7) is provided with a backup battery, and the focus position is set in advance at the time of factory shipment or during the first focus search. Of course, it is also possible to do so.

[Effects of the Invention] As described above, according to the present invention, the in-focus position is memorized during the initial focus search over a relatively wide range,
From the next focus search, a search is performed in a relatively narrow range centered around the memorized in-focus position, which has the effect of making it possible to pull in focus in a relatively short time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a focus servo control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional focus servo control device. In the figure, (1) is a pickup, (2) is a focus actuator, (3) is a focus actuator drive circuit, (4) is a focus search circuit, (
5) is a focus error signal detection circuit, (6) is a focus servo pull-in circuit, and (7) is a focus position storage circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent: Patent attorney Masuo Oiwa (and 2 others) Conventional control device Diagram 2

Claims (1)

[Claims] (1) Focus error detection means for generating an error signal according to the relative distance of the objective lens with respect to the optical information recording medium, and means for controlling the position of the objective lens with respect to the information recording medium based on the focus error signal. , means for storing a focused position after focus servo retraction, and means for generating a focus search signal based on the storage device of the storage means to actively change the relative distance between the information recording medium and the objective lens. A focus servo control device comprising: