JPH05151590A - Focal position controller - Google Patents

Abstract

PURPOSE:To provide the controller capable of facilitating and automatically execusing the adjustment of a focal position signal. CONSTITUTION:This controller is provided with a position detecting means 1 with receives a reflected light beam that is reflected at a reflection surface and outputs two signals that very in accordance with the distance between the focus position of the light beam and the reflection surface, a means which obtains a difference signal between these two signals and a signal adjustment means. As an adjustment means, the device is provided with offset compensating means 31 and 32 which individually compensate for offsets to the two signals outputted by the means 1 and gain compensating means 21 and 22 which individually compensate for gains to the two signals in which offsets are compensated for. Since the signals, which enter into the means 21 and 22, are beforehand compensated to an offset zero condition by the means 31 and 32, there is no effect on the offsets and an adjustment, which only requires a gain change, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus position control device for controlling the focusing of a light beam used in an optical recording / reproducing device or the like, and particularly, the focus control position can be easily adjusted. It is configured as follows.

[0002]

2. Description of the Related Art An optical recording / reproducing apparatus, as shown in FIG. 5, rotates a disk-shaped recording medium A by a spindle motor B, and emits light from a light source C onto a concentric or spiral track of the recording medium A. The light beam is irradiated through the objective lens D to record / reproduce information. This light beam needs to be always focused on the surface of the recording medium A. Therefore, in the optical recording / reproducing apparatus, the objective lens D is arranged so that the light beam is correctly focused on the recording medium A. And a focus position control device for automatically controlling the distance between the recording medium A and the recording medium A.

In the conventional focus position control device, the position detecting means 1 for receiving the light beam reflected by the surface of the recording medium A via the objective lens D and the half mirror E, and the position detecting means 1 outputs 2 Gain correction means 2 for correcting the gain for one of the two signals, offset correction means 3 for correcting the offset for the difference signal between the one signal after gain correction and the other signal, and the received difference signal The phase compensating means 4 for sending a signal for controlling the distance between the objective lens D and the recording medium A to the objective lens driving means 5 is provided.

As is well known, the position detecting means 1 has two (or four) symmetrically arranged photosensors, and when the focus of the light beam is located deeper than the surface of the recording medium. Is configured such that the output of one optical sensor exhibits a maximum, and conversely, when the output of the other optical sensor is present in front of the surface of the recording medium, the output of the other optical sensor exhibits a maximum.

The respective outputs of these optical sensors are output as two signals of the position detecting means 1, and the difference signal between these signals is corrected by the gain and offset, and the difference signal between them is shown in FIG.
It is adjusted so that the characteristic curve shown in FIG. On this drawing,
The horizontal axis represents the distance between the recording medium A and the objective lens D, and the intersection of the curve of the difference signal and the line of output 0 is the objective lens D when the light beam is focused on the surface of the recording medium A. Indicates the position.

When these adjustments are completed, the focus position can be automatically controlled. In this control, the light beam reflected by the surface of the rotating recording medium A is detected by the position detecting means 1, and the difference signal between the two signals output from the position detecting means 1 is "shifted" from the state of no output. If so, a signal for compensating for the “deviation” is sent from the phase compensating means 4 to the objective lens driving means 5 and the objective lens D is moved so that the focal point of the light beam coincides with the surface of the storage medium A.

The adjustment of the difference signal is performed as follows.

FIG. 6 shows a change in signal output at each point (a, b, c, d, e) of the focus position control device when the position of the objective lens D moves. In order to balance the two signals (a and b in FIG. 6) output by the position detecting means 1, the gain of one signal is corrected by the gain correcting means 2 (c in FIG. 6). When the differential of the two balanced signals is taken, the difference signal has an offset (residual deviation) with respect to the line of output 0 as shown in d of FIG. This is corrected by the offset correction means 3 and the center line of the difference signal is set to 0 (e in FIG. 6). In this state, it becomes possible to detect the information signal from the rotating recording medium A while controlling the focus at a fixed position.

Therefore, as a fine adjustment of the control target position, the intensity of the information signal obtained from the rotating recording medium A is measured while moving the focus control position by changing the gain balance, and the intensity is maximized. Set the gain balance to.

In this way, the focus control target position is adjusted correctly.

[0011]

However, in the conventional focus position control apparatus, when the gain balance of one signal is adjusted to change the gain balance, the offset of the difference signal also changes, and the gain Only the balance cannot be adjusted independently.

Therefore, when finely adjusting the control target,
It is necessary to alternately repeat the operation of adjusting the gain balance by changing it and the operation of adjusting the offset caused by changing the gain by the correction means, which requires a long time for the adjustment and the experience of the adjuster. And needed technology.

Further, since the conventional focus position control device requires repeated judgment and a long adjustment time in the adjustment as described above, there is a drawback that the device becomes too complicated when the adjustment is automated. , Therefore, the adjustment is not automated.

The present invention is intended to improve these drawbacks of the conventional apparatus, and the focus position signal can be easily adjusted, and the focus position control can be automatically performed. The purpose is to provide a device.

[0015]

Therefore, according to the present invention, a position for receiving a light beam reflected by a reflecting surface and outputting two signals that fluctuate depending on the distance between the focal position of the light beam and the reflecting surface. In a focus position control device provided with a detecting means, a means for obtaining a difference signal between these two signals, and a signal adjusting means, as the adjusting means, an offset is individually applied to the two signals output from the position detecting means. Offset correction means for correcting and gain correction means for individually correcting the gain for at least one of the two signals whose offsets have been corrected are provided.

Further, the detecting means for detecting the reflection intensity of the light beam reflected by the reflecting surface, and the gain for receiving the detection result from the detecting means and setting the correction amount of the gain correcting means in a state where the reflection intensity becomes maximum.・ Balance setting means is provided.

Further, the position detecting means is configured to receive the light beam reflected by the signal recording surface of the recording medium in the optical recording / reproducing apparatus.

Further, the gain balance setting means sets the gain correction amount of the gain correction means so that the signal strength of the information signal reproduced from the signal recording surface of the recording medium becomes maximum.

[0019]

Therefore, in the focus position control device of the present invention, since the signal input to the gain correction means can be corrected in advance to the state of offset 0 by the offset correction means, the gain balance can be achieved without affecting the offset. It only allows adjustments that change.

By setting the gain balance so that the reflection intensity is maximized while detecting the reflection intensity, it is possible to finely adjust the focus control target position.

[0021]

【Example】

(First Embodiment) As shown in FIG. 1, the focus position control device of the first embodiment of the present invention is an offset correction means 31 for correcting the offset for each of the two signals output by the position detection means 1. , 32 and gain correction means 2 for correcting the gain
1 and 22 are provided, and the difference signal between the two signals is formed by taking the differential of the signals after correcting the gain and the offset. Other configurations are the same as those of the conventional device (FIG. 5).

In this focus position control device, the difference signal is adjusted as follows.

FIG. 3 shows a change in signal output at each point (a, b, c, d, e, f, g) of the focus position control device when the position of the objective lens D is moved. The two signals (a and b in FIG. 3) output by the position detecting means 1 are corrected by the offset correcting means 31 and 32 so that the offset becomes 0, and the characteristics shown in c and d in FIG. 3 are obtained. obtain.
With respect to one of the two signals whose offsets have been corrected, the gain correction means 21 performs correction for gain balance. As a result, the two signals have the characteristics shown in e and f of FIG. The difference signal shown in FIG. 3g is formed by taking the differential of these two signals.

In the fine adjustment of the control target position, the difference signal is calculated as shown in FIG.
After adjusting to the state of g, while measuring the intensity of the information signal detected from the rotating recording medium A, the gain correction means 2
Use 1 and 22 to change the gain balance and move the focus control position to set the gain
Set the balance.

In this case, the offsets of the signals input to the gain correction means 21 and 22 have already been adjusted to 0.
Even if the gain is changed, the offset does not change.

As described above, in the focus position control device of the first embodiment, it is possible to change the gain balance without affecting the offset, so that the fine adjustment to the control target position can be easily performed. You can

Either one of the gain correction means 21 and 22 may be omitted.

(Second Embodiment) A focus position control device according to a second embodiment of the present invention is configured so that fine adjustment of a control target position can be automatically performed. This device is shown in FIG. As shown, in addition to the configuration of the focus position control device of the first embodiment, offset correction means 31, 32 and gain correction means
Gain / balance setting means 6 for setting the correction amounts of 21 and 22
And an information signal strength detecting means 7 for transmitting a signal relating to the strength of the information signal to the gain / balance setting means 6.

Adjustment of the difference signal is performed in the following order.

The position detecting means 1 is maintained in a state in which the light beam reflected by the recording medium A is not incident, the outputs of the two signals of the position detecting means 1 at this time are measured, and the measured values are offset-corrected. The amount is input to the gain / balance setting means 6, and the offset correction amount of the offset correction means 31, 32 is set.

Then, the light beam reflected from the recording medium A is returned to a state where the position detecting means 1 can receive the light beam, and the gain balance is set so that the maximum amplitudes of the two signals output from the position detecting means 1 may coincide with each other. The means 6 sets the gain correction amounts of the gain correction means 21 and 22.

Then, in order to finely adjust the control target position, the gain / balance setting means 6 includes the gain correction means 2
By changing the gain correction amounts of 1 and 22, the information signal strength detecting means 7 detects the information signal strength at that time. In this case, the information signal strength fluctuates in the curve shown in FIG. 4 according to the change in the gain / balance correction amount. The gain / balance setting means 6 receives the detection signal of the information signal detection means 7 and sets the gain correction amounts of the gain correction means 21 and 22 in a state where the information signal strength is maximized.

As described above, in the focus position control device of the second embodiment, the gain correction amount is changed so that the information signal amplitude is detected while moving the focus control position, so that the information signal amplitude becomes maximum. By automatically performing each operation of finding the position and setting the gain correction amount, the adjustment of the gain / balance correction amount is automated.

The focus position control device of the present invention can be used not only as an optical recording / reproducing device but also as a focus position control device for other devices.

[0035]

As is apparent from the above description of the embodiment, the focus position control device of the present invention can easily adjust the focus control position.

With the ease of this adjustment, the gain / balance correction amount can be automatically adjusted.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a focus position control device of the present invention,

FIG. 2 is a block diagram of a second embodiment of the focus position control device of the present invention,

FIG. 3 is an operation explanatory view of the focus position control devices of the first and second embodiments,

FIG. 4 is a diagram showing the relationship between gain / balance correction amount and information signal strength in the device of the present invention,

FIG. 5 is a block diagram showing an example of a conventional focus position control device,

FIG. 6 is an operation explanatory diagram of a conventional focus position control device.

[Explanation of symbols]

 A recording medium B spindle motor C light source D objective lens E half mirror 1 position detection means 2, 21, 22 gain correction means 3, 31, 32 offset correction means 4 phase compensation means 5 objective lens drive means 6 gain balance setting Means 7 Information signal strength detection means

Claims (4)

[Claims] 1. A position detecting means for receiving a light beam reflected by a reflecting surface and outputting two signals that fluctuate depending on a distance between a focal position of the light beam and the reflecting surface, and the two signals. In the focus position control device including a means for obtaining the difference signal of the above and an adjusting means for the signal, as the adjusting means, an offset correcting means for individually correcting the offset for the two signals output by the position detecting means. And a gain correction unit that individually corrects the gain of at least one of the two signals whose offsets have been corrected. 2. A detection means for detecting the reflection intensity of the light beam reflected by the reflection surface, and a correction amount of the gain correction means for receiving the detection result from the detection means to maximize the reflection intensity. The focus position control device according to claim 1, further comprising: a gain / balance setting means for setting. 3. The focus position control device according to claim 1, wherein the position detection means receives the light beam reflected by the signal recording surface of the recording medium in the optical recording / reproducing device. .. 4. The focus position control device according to claim 2, wherein a signal intensity of an information signal reproduced from a signal recording surface of a recording medium is detected as the reflection intensity.