JPH03116452A - Memory device for optical disk - Google Patents

Abstract

PURPOSE:To obtain the best focus at recording and reproducing times by recording the offset value of the best focus and generating the offset voltage corresponding to this offset value. CONSTITUTION:An optical detector 10, adding circuits 16, 15, a subtraction circuit 17, an offset generation circuit 19, a photo coupler 19a and D/A convertor circuit 20 are provided. A preset focus offset value is outputted from an offset value output means(e.g. an external part control circuit), when a device becomes a recording motion. In the offset generation means 19 the current corresponding to the offset value thereof is flowed to the light emitting diode of the photocoupler 19a, the variable resistance value of the photocoupler becomes at the value corresponding to the current thereof and the voltage corresponding to the variable resistance value is obtd. A preset focus offset value is output from an offset value output means similarly to the device becoming a reproduction motion. The best focus point can be obtd. in the respective state at the time of the recording and reproducing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc memory device capable of recording information on an optical disc and reading information from the optical disc. The present invention relates to an optical disk memory device that changes the focus offset value at the position of the head and provides the best focus during recording, reproduction, and focus control at the position of the optical head.

[Conventional Example] Recently, optical discs have significantly developed from read-only and write-once types to rewritable types, and various devices have been proposed for recording information on optical discs and reproducing information, such as optical disc memory devices. ing.

Incidentally, the optical disc memory device has the configuration shown in FIG. 2, for example, and is equipped with an optical head that irradiates the optical disc 1 with a laser beam and detects reflected light from the optical disc 1. This optical head has
Laser light output device 2, collimator lens 3, prism 4, polarizing beam splitter (Pus) 5, and λ74
Wave plate (QWP) 6, objective lens 7, detection lens 8, cylindrical lens 9, and photodetector (PD)
10 are provided. That is, the laser light output device 2
The laser light from is focused on the recording surface 1a of the optical disc 1 through the collimator lens 3, prism 4, polarizing beam splitter 5, λ/4 wavelength plate 6, and objective lens 7, and
The reflected light from this optical disk 1 is reflected by the objective lens 7, λ/4
Wave plate 6. The light passes through the polarizing beam splitter 5, the detection lens 8, and the cylindrical lens 9, enters the photodetector 10, and is converted into an electrical signal.

Further, the optical disk memory device is provided with a focus error detection circuit for obtaining a focus error signal as shown in FIG. 3, a tracking error detection circuit for obtaining a tracking error signal (not shown), etc., and the error signal is focus control and tracking control are performed. That is, if the laser light from the laser light output device 2 is focused on the recording surface 1a of the optical disc 1 and does not accurately follow the track of the optical disc 1, information will not be recorded.
This is because playback is not performed accurately. In order to control the optical head, the focus servo uses an astigmatism method, and the tracking servo uses a push-pull method.
(Pull) method is adopted.

By the way, the focus error detection circuit described above is based on the photodetector 1.
0 is a four-division photodetector, an amplifier (buffer circuit) 11.12.13. that converts the detected current by the detection lights ia, b, c, and d of these photodetectors into a voltage and amplifies this converted voltage to a predetermined value. 14, its detection light fta,
It is provided with operational amplifier circuits 15, 16, and 17 that calculate the detection voltages of b, c, and d by the astigmatism method. Further, an offset voltage 18 for focus offset is supplied to the operational amplifier circuit 17 via its inverting input terminal. Furthermore, since the operational amplifier circuits 15 and 16 are addition circuits, and the operational amplifier circuit 17 is a subtraction circuit, (a
+c) - (b+d) addition/subtraction processing is performed, and the result of this calculation becomes the focus error signal (F's). In other words, when the recording surface 1a of the optical disc 1 is in the focal plane of the optical system, the above calculation result is becomes zero, and as the optical disk 1 approaches or retreats from the objective lens 7, the imaging plane of the reflected light becomes farther or closer, so that the reflected light that forms an image on the four-part photodetector becomes an ellipse. Then, a focus error signal is obtained in the form of a minus or plus, and the optical head is moved in the direction of the arrow in FIG. 2 based on this focus error signal, and the focus is controlled so that the error signal becomes zero.

[Problems to be Solved by the Invention] In the above-mentioned optical disc memory device, when determining a focus point during a recording operation, for example, focus control is performed on an unrecorded optical disc 1, and a tracking error signal is monitored to determine the amplitude of the signal. at the maximum value and so that its envelope is flat.

When the focus offset is adjusted (when the offset voltage 18 is adjusted), the optical disc 1
There is a problem in that when a signal is recorded on a computer and this recorded information is reproduced, it is not possible to reproduce the best signal. That is, for example, the maximum amplitude value of the tracking error signal and the maximum amplitude value of the reproduced RF signal are different between the recording operation and the reproduction operation (in addition, depending on the optical disc, the maximum amplitude value of the reproduction RF signal is different)
This is because there are cases where the maximum value of the signal and the maximum value of the RF multiplied signal match.

This invention was made in view of the above-mentioned problems, and its purpose is to automatically change the focus offset during recording operation, playback operation, and the position of the optical head to obtain the best focus during recording and playback. An object of the present invention is to provide an optical disk device which is configured as follows.

[Means for Solving the Problems] In order to achieve the above object, the present invention stores information on an optical disc and when reading information from the optical disc, obtains a tracking error signal by a push-pull method and An optical disk memory device that obtains a focus error signal by a point aberration method, and in obtaining the focus error signal, 8] offset value output means for outputting an offset value according to the operating state of the optical disk memory device; and offset generation means for generating an offset voltage corresponding to the value.

The gist is that the focus offset is adjusted using the offset voltage.

[Function] With the above configuration, when the optical disk memory device starts a recording operation, the offset value output means (for example, an external control circuit) outputs a preset focus offset value (during the recording operation). Ru. Then, in the offset generating means, a current corresponding to the offset value flows through the light emitting diode of the photocoupler, the variable resistance value of the photocoupler becomes a value corresponding to the current, and a voltage (offset voltage) corresponding to the variable resistance value is generated. is obtained. Furthermore, when the optical disk memory device starts a playback operation, the offset value output means outputs a preset focus offset value (for the playback operation), similarly to the above recording operation. Therefore, the offset generating means outputs a voltage (offset voltage) corresponding to the offset value. Further, the offset value output means outputs a preset focus offset value depending on the position of the optical head of the optical disk memory device, that is, the inner circumferential side or the outer circumferential side. Therefore, the offset generating means outputs a voltage (offset voltage) corresponding to the offset value.

In this way, the offset voltage for focus control can be changed in the recording/playback state of the optical disk memory device, so for example, when recording information and reproducing that information, the best focus control can be achieved in each state. You can get a focus point.

[Example] Hereinafter, an example of the present invention will be explained based on FIG.
In the figure, the same parts as in FIG. 3 are given the same reference numerals, and redundant explanation will be omitted.

In this figure, the focus error detection circuit generates an offset voltage corresponding to the offset value from the external control circuit (offset value output means), and outputs this offset voltage to the inverting input terminal of the operational circuit (subtraction circuit) 17. An offset generation circuit (offset generation means) 19 is provided.

The external control circuit 1 is, for example, a main control circuit (microcomputer) of an optical disk memory device, and this main control circuit is designed in advance to enable the best focus control during recording operation, playback operation, and position of the optical head. An offset value is stored for this purpose. Further, the offset generating circuit 19 has voltages +V, -V, resistors R,,R
2 and a photocoupler 19a for variable resistance control. Then, a current corresponding to the offset value from the external control circuit flows through the light emitting element of the photocoupler, and the resistance value of the variable resistor is changed by the light from the light emitting element. The voltage divided by the variable resistance value and the resistors R□ and R2 is outputted to the inverting input terminal of the operational amplifier circuit 17 as an offset voltage.

Next, offset voltages at the time of the recording operation, the reproduction operation, and the position of the optical head will be explained.

First, in the case of focus offset during recording operation, focus is controlled on the optical disc 1 to be used, and information can be recorded in the best possible manner by aiming at the point where the tracking error/signal amplitude is maximum and the envelope is flat. Obtain the offset voltage.

On the other hand, in the case of focus offset during playback operation, when the l (F signal) of the information recorded on the optical disc 1 is played back, the offset voltage that will give the best RF multiplied signal is obtained. For example, in EFM, the center of the eye pattern is automatically detected, so the maximum amplitude of the RF multiplied signal is at the center.

Further, when the focus point of the base 1- differs between the position of the optical head, that is, between the inner circumference and the outer circumference of the optical disc 1, the offset is adjusted at the position of the optical head to obtain an offset pressure. Then, offset values that can be generated by these offset voltages are determined in the offset generation circuit 19, and these offset values are stored in advance in a memory or the like of an external control circuit. Note that if the optical disc 1 is of the same type, the above offset value can be used, and there is no need to record on the optical disc 1 to be used again and adjust it to obtain the offset value.

Here, when the optical disk memory device starts a recording operation, focus and tracking control are performed, and a tracking error detection circuit (not shown) (push-pull method) outputs a tracking error signal, and the focus error detection circuit (not shown) shown in FIG. A focus error signal (Fe) is output from the astigmatism method. At this time, the external control circuit outputs a pre-stored offset value during the recording operation, and based on this offset value, the focus offset generation circuit 19 supplies an offset voltage to the operating eye amplifier circuit 17. There is.

Therefore, offset adjustment is performed in the operational amplifier circuit 17, and focus control is performed at the best focus during recording, so that focus control is performed at the best focus when information is recorded on the optical disc 1.

Also, when the optical disk memory device starts playing,
The external control circuit outputs a pre-stored offset value during the recording operation, and based on this offset value, the focus offset generation circuit j8 supplies the offset voltage for reproduction to the operational amplifier circuit 17. Therefore, the offset adjustment of the focus error detection circuit is performed, and the focus control during reproduction is made to be the best, so that the focus control is performed at the best focus when information is reproduced from the optical disc 1.

Further, since the external control circuit outputs an offset value of a predetermined position of the optical head that is stored in advance, focus control is performed at the best focus in the same manner as described above.

Thus, the operating status of the optical disk memory device.

For example, the focus offset is changed during the recording operation, during the reproducing operation, and at the position of the optical head, and the best focus point in each operating state is provided, so that better signal recording/reproduction is possible. This is particularly useful for optical discs in which the focus offset cannot be fixed during recording/reproduction.

The broken line in FIG. 1 shows a modified embodiment of the invention, in which a D/A converter circuit 20 is used in place of the offset generation circuit 19 of the above embodiment.

This D/A converter circuit 20 converts the offset value (digital data) from the external control circuit described above into an analog offset voltage, and outputs this offset voltage to the inverting input terminal of the operational amplifier circuit 17 described below. Therefore, similarly to the above embodiment, it is possible to obtain an offset voltage depending on the operating state of the optical disk memory device.

[Effects of the Invention] As explained above, according to the optical disc memory device of the present invention, the offset value 1-output means stores the offset value of the best focus in the state of the optical disc memory device and outputs the offset value. and an offset generation circuit that generates an offset voltage according to this offset value, it is possible to provide the best focus point during recording operation, playback operation, and focus control at position 1a of the optical head, making it possible to Able to record/play back good signals.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram of an optical disk focus error detection circuit showing an embodiment of the present invention, FIG. 2 is a schematic block diagram of an optical head of an optical disk memory device, and FIG. 3 is a schematic block diagram of a conventional optical disk memory device. FIG. 3 is a schematic circuit diagram of a focus error detection circuit. In the figure, 10 is a photodetector (quadrant photodetector), 16.15 is an addition circuit (operational amplifier circuit M), 17 is a subtraction circuit (operational amplifier circuit #), 19 is an offset generation circuit, and 19a
A photocoupler (variable resistance control type), 20 is a D/A converter circuit, R and R2 are resistors, and +V and -V are voltage sources.

Claims (4)

[Claims] (1) An optical disk memory device that stores information on an optical disk and, when reading information from the optical disk, obtains a tracking error signal by a push-pull method and obtains a focus error signal by an astigmatism method, comprising: When obtaining a focus error signal, the method further comprises: an offset value output means for outputting an offset value according to an operating state of the optical disk memory device; and an offset generation means for generating an offset voltage corresponding to the offset value; An optical disk memory device characterized in that a focus offset is adjusted by adjusting the focus offset. (2) The offset value output means is configured in advance to
2. The optical disc memory device according to claim 1, wherein offset values that enable the best focus control during a reproduction operation and at the position of the optical head of the optical disc memory device are stored. (3) The optical disc memory device according to claim 1, wherein the offset generating means comprises variable resistance means that varies the resistance value according to the offset value, and a voltage source divided by the variable resistance means. (4) The optical disc memory device according to claim 1, wherein the offset generating means is a D/A converter circuit that outputs a voltage corresponding to the offset value.