JPS59186143A - Optical disc device - Google Patents

Abstract

PURPOSE:To prevent deformation, deterioration, destruction or the like of a recording film by shifting forcibly a focus of beam light at the stand-by state. CONSTITUTION:When no recording information exists and the mode is brought into the recording stand-by state or the reproducing stand-by state between recordings while one recording is finished before the next recording is performed, a control signal is inverted into a high level and a switch 16 is turned on. Then, an offset signal from a focus adjusting signal generating section 15 is applied, and the focus of the optical beam of an optical head 3 is shifted forcibly from a face of a disc 1, thereby preventing deformation, deterioration, destruction or the like of the recording film of the disc 1 due to the intensified amount of light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an optical disk device that records or reproduces multiple information by, for example, irradiating a rotating optical disk with a laser beam.

(Technical background of the invention and its problems) This type of optical disk device rotates an optical disk on which a recording track is formed in advance in the form of a spiral array of pre-pits on its surface, and emits a single laser beam into a reproduction beam. By switching between the light and the recording beam light, information is recorded by tracking the pre-pit row with the reproduction beam light and forming data bits according to the recording information between the bits with the recording beam light,
Furthermore, when reproducing recorded information, the information is reproduced by detecting data bits while tracking the recording track in which the data bits are formed with the reproduction beam light.

In such an optical disk device, the width of a recording track formed on an optical disk is approximately 1 μm, and a beam of light is focused onto such a narrow recording track by an objective lens.

Therefore, it is necessary to accurately focus the beam light so that it always forms a spot of about 1 μmφ on the optical disk. However, due to tilting or eccentricity of the optical disk or vibration of the optical system, the distance between the optical disk and the objective lens changes, resulting in a focal shift of the light beam on the optical disk. Normally, when such a focus shift occurs, it is detected optically and the objective lens is moved accordingly to maintain a constant distance between the optical disc and the objective lens. Control means are provided.

As a typical example, for example, JP-A-50-1045
39 or Japanese Patent Laid-Open No. 54-4105 are known.

In both of these methods, changes in the distance between the optical disk and the objective lens are recognized as changes in the shape of the reflected beam on the light-receiving surface of the photodetector, and the objective lens is moved based on the detection signal. This is a focus control method.

Recently, high-density optical disk devices have been developed that can play back information immediately after it is recorded.The optical disks used as recording media for these devices have high sensitivity and high sensitivity so that they can record with low energy or at high speed. In the direction of the development of optical disks, efforts have been made not only to increase the sensitivity of the recording film, but also to make it difficult for the energy concentrated in the recording film to dissipate.

In such highly sensitive optical discs, even if the energy of the reproduction beam is low, if the beam continues to irradiate the same position on the optical disc, the irradiation energy will become large, so the recording film will be gradually deformed. It may cause deterioration and destruction. In particular, in an optical disk device, recording or playback is started by external control, and when it is finished, it goes into a standby state at the next designated trench. You will have to wait. Therefore, the same position in the radial direction of the optical disk continues to be scanned with the reproduction beam light. This standby state is random depending on the usage state of the device, but generally it can be considered as [standby time] recording and playback time.

Therefore, in order to solve the above problem, it is conceivable to reduce the energy of the reproduction beam light to a value of 1, which is enough to cause no problem, but in this case, it is preferable to avoid instability of laser oscillation or deterioration of S/N of signal output. do not have. Also, during standby, it is possible to turn off the focus control means and the laser beam, but when commanding recording or playback, the laser output is stabilized, the optimum focus position is searched, the control loop is closed, and the stabilization is performed before recording. Otherwise, playback must be performed, which takes a lot of time.

(Object of the Invention) The present invention has been made in view of the above circumstances, and its object is to provide an optical disc device that can prevent the recording film of an optical disc from being deformed, deteriorated, or destroyed during recording or playback standby. It is about providing.

(Summary of the Invention) The optical disc device of the present invention forcibly shifts the focus of the beam light from the optical disc when the focus control means enters the recording or playback standby state in the operating state. - The recording film of the optical disc is protected by making the energy density sufficiently lower than that during recording or reproduction.

(Embodiment of the Invention) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an optical disk, on the front surface (lower surface in the figure) of which recording tracks are formed in advance in the form of a spiral (or concentric circle) array of pre-pits. 2 is a motor that rotationally drives this optical disc 1;
is an optical head for recording and reproduction, which is linearly moved in the radial direction of the optical disk 10 by a linear motor mechanism (not shown).

The optical head 3 includes a semiconductor laser oscillator 4, a collimator lens 5, a polarizing beam slitter 6, a λ/4 plate 7, an objective lens 8, and a drive coil that moves the objective lens 8 in a direction perpendicular to the surface of the optical disk 1. 9. Cylindrical lens 10. It is composed of a condenser lens 1, a 4-part light receiver 12, and the like. That is, the laser oscillator 4 is driven and controlled by a drive circuit 13, and its output beam power is switched between two beam powers: a reproduction beam and a recording beam with higher energy. .

Thus, the beam light from the Rade oscillator 4 is collimated by the collimator lens 5, and the beam splitter 6 and λ
/4 plate 7 to the objective lens 8, where approximately 1μ
The light is focused onto the optical disk 1 to a diameter of about mφ. Then, the reflected light from the optical disk 1 is reflected by an objective lens 8, λ/
4 plates 7, beam fritter 6, cylindrical lens 1
The light passes through the 0° angle and the condensing lens 11, is imaged on the light receiving surface of the light receiver 12, and is photoelectrically converted. The light receiver 12 includes, for example, four light receiving elements 12 arranged in a square shape, as shown in FIG. + 122 112
3+124, and the reflected light is focused approximately at the center of the square.

The output signals IL and e of the light receiving elements 121 and 123 constituting the light receiver 12 are respectively supplied to a summing amplifier 141,
Further, each of the output signals s and d of the light receiving elements 122 and 124 is supplied to a summing amplifier 142, respectively. Further, the offset signal e from the focus adjustment signal generation circuit 15 is supplied to the summing amplifier 142 via the analog switch 16. The analog switch 16 is controlled on and off by a control signal. As shown in FIG. 3, the control signal is, for example, a signal that is at the "0# level" during recording or reproduction, and is at the "1" level during other standby states, and is output from a main control section (not shown). Therefore, the summing amplifiers 141, 14 . The respective outputs of are supplied to a differential amplifier 17, and the outputs of the differential amplifiers 17 and are supplied to a drive circuit 18. The differential amplifier 17 is a summing amplifier "l r 1
42 output signals are compared, and a signal corresponding to the difference between both signals is output. Further, the drive circuit 18 includes a differential amplifier 17
The drive coil 9 is controlled according to the output signal of the drive coil 9.

Note that FIG. 4 shows the light receiver 12 and the summing amplifier 141.
+142 indicates a circuit of the focus adjustment signal generation circuit 15.

Next, the operation in the above configuration will be explained. First, when recording information, the optical head 3 is positioned, for example, at the outermost circumference of the optical disk 1, the laser oscillator 4 outputs a reproduction beam light, and the objective lens 8 directs it to the outermost circumference of the optical disk 1. Focus on the track. At this time, the optical disc 1 rotates at a predetermined speed, so that the reproduction beam light starts tracking from the outermost periphery of the recording track. Thus, the light reflected by the reproduction beam on the optical disk 1 is guided to the light receiver 12 and focused on its light receiving surface.

At this time, the incident turn of the reflected light formed on the light receiving surface of the light receiver 12 is determined by the action of the astigmatism optical system formed by the combination of the cylindrical lens 10 and the condensing lens 11.
3 depending on the distance between the optical disk 1 and the objective lens 8.
Form different shapes. That is, when the beam light is correctly focused on the recording track on the optical disk 1 and there is no defocus, the incident pattern of the reflected light formed on the light receiving surface of the light receiver 12 has a minimum incidence pattern as shown in FIG. Circular shape of area/mother turn P! becomes. However, if, for example, the optical disc 1 moves away from the objective lens 8 and a defocus occurs, the above-mentioned incident pattern becomes a deformed pattern P2 extending in the vertical direction as shown in FIG. When the lens moves in a direction approaching , and a defocus occurs, the incident pattern becomes a deformation/mother turn P3 extending in the horizontal direction, as shown in FIG. The light receiver 12 performs photoelectric conversion according to the incident and main turn of the reflected light, and outputs the output signal a.
= d summing amplifier 14. ．． 74. supply to. The summing amplifier 141 adds and amplifies signals a and C, and the summing amplifier 142 adds and amplifies signals S and d, and outputs signals (a+e) and (b+a), respectively. In this case, analog switch 16 is in an off state, so offset signal e is not provided to summing amplifier 142. Thus, the summing amplifiers 141, 14 . Each output signal is supplied to a differential amplifier 10-17, and the differential amplifier 17 outputs a signal corresponding to the difference between the two signals. In other words, if there is no defocus, the incident pattern of the reflected light will be a circular/flat turn P1 (
a+c)=(b+d), so the output of the differential amplifier 17 becomes zero potential. However, if a focus shift occurs and the incident flat turn becomes a deformed turn P2, then (a+c
)<(b+d), so the output of the differential amplifier 17 becomes a positive potential, and in the case of modified pattern P3, (a+
c)) (b+d), so the output of the differential amplifier 17 becomes a negative potential. The output signal of the differential amplifier 17 becomes a focus control signal and is supplied to the drive circuit 18. Drive circuit 18
drives the drive coil 9 according to the output signal of the differential amplifier 17 and controls the position of the objective lens 8 so that the beam light is always accurately focused on the recording track on the optical disk 1. Control takes place. In this way, each output signal a of the light receiver 12.

Optimal focus control is performed by driving the drive coil 9 so that (-+c)-(b-+-a) becomes zero from b, e, and d. As a result, optical disc 1
The positional relationship between the lens and the objective lens 8 is in a focused state as shown in FIG. 5(,).

However, now, when the recording information pulse is supplied to the drive circuit 13 at a predetermined timing, the drive circuit 13 switches the output beam light of the laser oscillator 4 to the recording beam light only during the period of the pulse, thereby controlling the gap between the pre-pits. Then, focus control is performed by a force operation corresponding to the above-mentioned pulse as in the above-mentioned recording. In this case, only the reproduction beam light is continuously output from the Rade oscillator 4.

For example, when recording information, when recording of certain information is completed, the optical head 3 enters a standby state at 1 when the next recording command is given, and the optical head 3 remains positioned at the position where the recording was completed. Therefore, the same position in the radial direction of the optical disc 1 continues to be scanned with the reproduction beam light that is being outputted at this time. However, at this time, when the lens is in standby mode, the control signal goes from 'O# to P1# level, the analog switch 16 is turned on, and the offset signal e from the focus adjustment signal generation circuit 15 is sent to the summing amplifier 142. supplied to The summing amplifier 14□ is (
b+a, +e) is performed and amplified, and the output thereof is supplied to the differential amplifier 17. As a result, the focus control loop shown in FIG. 1 performs focus control such that (a+e)-(b+a+e) becomes zero. As a result, the positional relationship between the optical disc 1 and the objective lens 8 is changed, for example, in FIG.
), resulting in an out-of-focus state that deviates from the in-focus point by several microns (μm). In this manner, when the focus control loop enters the standby state while in the operating state, the focus of the reproduction beam light is forcibly shifted from the optical disk 1.

As a result, the energy density on the recording film of the optical disc 1 is approximately 1/10 of the focused spot (-2 of the 1 mm spot diameter).
(inversely proportional to the power of Therefore, even if the same position on the optical disc 1 is continuously irradiated with the reproduction beam, the recording film of the optical disc 1 can be reliably prevented from being deformed, deteriorated, or destroyed.

In this standby state, when the next recording command is given,
When the control signal changes from the "1" level to the °0" level, the analog switch 16 is turned off and the supply of the offset signal e is prohibited, so that the objective lens 8 is instantly adjusted to the in-focus position.

Note that since similar operations are performed during information reproduction, the recording film of the optical disc 1 is protected in the same manner as during recording.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to provide an optical disc device that can prevent the recording film or the recording film of an optical disc from being deformed, degraded, or destroyed during a reproduction standby state.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is an overall configuration diagram, Fig. 2 is a diagram showing the structure of a 4-split light receiver and an example of an incident light pattern thereon, and Fig. 3 is a control signal. FIG. 4 is a diagram showing an example of a waveform diagram, FIG. 4 is a diagram showing the essential circuits of FIG. 1, and FIGS. 14-5 are diagrams for explaining the positional relationship between the optical disk and the objective lens. DESCRIPTION OF SYMBOLS 1... Optical disk, 3... Optical head, 4... Semiconductor laser oscillator, 8... Objective lens, 9... Drive coil, 12... 4-split light receiver, 14. ．． 142...
- Summing amplifier, 15... Focus adjustment signal generation circuit, 16
...Analog switch, 17...Differential amplifier, 18
...Drive circuit. Applicant's agent Patent attorney Takehiko Suzue 15- Figure 2 Figure 5 (C)

Claims (1)

[Claims] In an optical disk device that records or reproduces multiple information by irradiating a rotating optical disk with a beam of light, the optical disk device has a focus control means for controlling the focus of the beam of light on the optical disk. 1. An optical disk device comprising: a focus adjustment means for forcibly shifting the focus of the beam light from above the optical disk when the focus control means enters a recording or reproduction standby state in an operating state.