JPH04341935A - Optical information recording/reproducing device - Google Patents

Abstract

PURPOSE:To prevent disturbance to tracking control due to return light by reducing the quantity of the return light from an optical information recording medium to a laser light source by irradiating the recording medium by a laser beam in a non-focusing state at the time of tracking jump and seek. CONSTITUTION:The optical information recording medium 7 is positioned at one of two non-focusing positions A, B to hold a fucusing position between at the time of the track jump and the seek. At the position A, reflected light from the medium 7 becomes diffused light through an objective lens 6, and a part of it is vignetted by a diaphragm 22, and after passing through a beam splitter 4 and a diffration grating 3, it is vignetted again by the diaphragm 21, and the return light to reach the laser light source 1 is reduced. Besides, at the time of the position B, it becomes convergent light, and it is less vignetted, but it forms a focus at the point D at this side of the light emitting point of the light source 1, and a light spot becomes blurred at the light emitting point, and consequently, the quantity of the return light can be made small. Then, at the fucusing position, a focus error signal is zero, and it has a positive or a negative value at the positions A, B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording/reproducing device, and more particularly, to an optical information recording medium having a tracking track and an information recording track, an optical information recording medium is irradiated with a laser beam to record information while being guided by the tracking track. The present invention relates to a device that performs playback.

0002

[Prior Art] Conventionally, when track jump or seek is required when recording and reproducing information on an optical information recording medium such as an optical card, the number of track crossings is counted based on a tracking error signal, and the number of track crossings is counted based on a tracking error signal. The head is moved in a direction perpendicular to the track so that a light spot is irradiated to the desired track position. The tracking error signal and focus error signal used at this time are detected by, for example, the edge mirror method (Japanese Patent Application No. 1-282167).

FIG. 3 shows the configuration of an optical device used in this edge mirror method. In this device, diffused light emitted from a laser diode 1 is converted into parallel light by a collimator lens 2, passes through a diffraction grating 3, a beam splitter 4, an optical path changing mirror 5, and an objective lens 6 onto an optical information recording medium 7. Connect light spots. The objective lens 6 is provided with a focusing direction driving coil L1 and a tracking direction driving coil L2.

[0004] The way to connect the light spots is as shown in FIG.
It differs between a focused state and an out-of-focus state, and the out-of-focus state also differs depending on whether the objective lens 6 and the optical information recording medium 7 are far or close. In the focused state, the light beam reflected from the optical information recording medium 7 in FIG. 3 returns along the same path as the incident light as parallel light. Next, when out of focus, when the objective lens 6 approaches the optical information recording medium 7, it becomes diffused light, and when it moves away, it becomes convergent light, and this light passes through the beam splitter 4 and becomes convergent light at the collimator lens 8. Half of the luminous flux is reflected by the edge mirror 9, and the remaining half of the luminous flux travels straight.

[0005] This linearly traveling light beam is divided into two parts by a detector 10 and a subtracter 12 to generate a focus error signal (D1 - D2).
Take it out as When in focus, D1 - D2 = 0,
When the objective lens 6 and the optical information recording medium 7 are close, D1-
D2 >0, and when it is far, D1 - D2 <0.

Tracking detection is performed by a three-beam method as shown in FIG. 5(a). Diffraction grating 3 in Figure 3
Due to the diffraction phenomenon, the parallel light is split into three beams, 0th-order diffracted light and ±1st-order diffracted light, which are focused and irradiated onto the optical information recording medium 7 as three spots via the beam splitter 4 and the objective lens 6. The 0th-order diffracted light is used for focus control, and the ±1st-order diffracted light is turned into a convergent light by a collimator lens 8 as a tracking light flux, and furthermore, an edge mirror 9
The semicircular light beam passing through becomes S2, and the semicircular spot reflected by the edge mirror 9 becomes S1, both of which are fed to the differential amplifier 13 and the difference is taken out and used as a tracking error signal. FIG. 5(b) shows this tracking error signal. Tracking control is performed so that this tracking error signal becomes zero.

[0007] Here, the optical information recording medium 7 has a structure as shown in FIG. 6, for example, and an appearance as shown in FIG.
In addition, as shown in FIG. 6(b), the surface hardened layer 71 in the cross section taken along the line A-A in FIG.
It has a laminated structure of a cover glass made of a polycarbonate layer 72 of about 595 mm, a silver salt-based information recording layer 73, and an acrylic layer 74 as a card base material.

[0008] Depending on the manufacturing method, some optical cards may have irregular steps at the interface between the tracking track and the data track. When tracking control is performed on such an optical card, the tracking error signal fluctuates unstablely as shown in FIGS. 7(a) and 7(b) due to the influence of the return light to the laser diode. Then, when seek control is performed, the tracking error signal that should be as shown in Figure 8(a) becomes a tracking error signal with undulations as shown in Figure 8(c), and the tracking error signal as shown in Figure 8(b).
The track position signal that should be as shown in FIG. 10 becomes an inaccurate track position signal with a part missing, as shown in FIG. 3(d). Since tracking control is performed while counting this track position signal, if the track position signal is inaccurate, tracking control will be performed incorrectly.

One way to solve this problem is to use a beam splitter to completely isolate the light emitting part of the laser and the reflected light from the recording/reproducing medium, that is, to completely isolate the transmitted light from the beam splitter to the light source. may be set to 0%.

[0010] This will be described in more detail. As shown in FIG. 9, the laser beam is vertically polarized, is converted into parallel light by the collimator lens 2, and enters the beam splitter 4. This incident light is transmitted 100% and reflected light is 0%. Next, the polarization plane of the light flux transmitted through the quarter-wave plate 20 becomes circularly polarized light in the counterclockwise direction, and a light spot is focused and irradiated onto the optical information recording medium 7 via the objective lens 6. The reflected light from the optical information recording medium 7 rotates in the opposite direction to the traveling direction, that is, becomes circularly polarized clockwise in the figure, and the light beam after passing through the quarter-wave plate 20 enters the optical information recording medium 7. 90 against light
The horizontally polarized light is rotated by .degree., and at the beam splitter 4, it becomes 100% reflected light and 0% transmitted light, making it possible to realize an ideal optical system without returning light.

[0011]

[Problems to be Solved by the Invention] This optical system cannot be used in the optical information recording medium that is the object of the present invention. This is because the birefringence of the cover glass of the optical information recording medium is too large, and this birefringence prevents the polarizing beam splitter 4 from operating properly.

Therefore, an optical system as shown in FIG. 10 is currently used. This device has an appropriately selected ratio of transmitted light and reflected light at the beam splitter 4, and requires a high-output laser and a high-transmittance beam splitter. In practice, the laser output is 40 mW, and the ratio of transmitted light and reflected light at beam splitter 4 is 80%.
and 20%.

The problem here is that 80% of the light returns to the light source as return light from the beam splitter 4, and it is important to keep the amount of this return light to a minimum.

The present invention has been made in consideration of the above points, and it is an object of the present invention to provide an optical information recording/reproducing apparatus that can accurately detect a tracking error signal.

[0015]

[Means for Solving the Problems] In order to achieve this object, the present invention irradiates a laser beam onto an optical information recording medium having a tracking track and an information recording track to provide information while guiding by the tracking track. In an optical information recording and reproducing device for recording and reproducing information, the device includes a signal output means for generating a signal when the device performs a track jump and seek operation, and a signal output means for generating a signal when the device performs a track jump and seek operation, and a laser beam directed to the optical information recording medium when the signal from this means is applied. The present invention provides an optical information recording/reproducing apparatus characterized by comprising: a control means for bringing the irradiation of the light into an out-of-focus state.

[0016]

[Operation] The signal output means generates a signal during track jump and seek in the optical information recording and reproducing apparatus. This signal is
As a result of the application to the control means, the laser beam irradiation becomes out of focus, so the amount of reflected light from the optical information recording medium is reduced, and the amount of light returned to the laser light source is also reduced.

[0017]

Effects of the Invention As described above, in the present invention, since the laser beam is irradiated in an unfocused state during track jump and seek, the amount of light returned from the optical information recording medium to the laser light source during track jump and seek can be reduced. By reducing the amount of light, it is possible to prevent disturbance to tracking control caused by the returned light.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1(a) and 1(b) show the configuration of an optical system used in the present invention and a focus error signal obtained by this configuration in order to illustrate the basic idea of the present invention. The optical system shown in FIG. 2A has the same structure except that the collimator lens 2 and the objective lens 6 have apertures 21 and 22, respectively.

In FIG. 3A, during track jump and seek, the optical information recording medium 7 shown by the broken line is positioned at one of two out-of-focus positions A and B sandwiching the in-focus position. Position A is a position where the objective lens 6 is close to the optical information recording medium 7, and position B is a position where the objective lens 6 is far from the optical information recording medium 7. At the near position shown in FIG. 2(a), the reflected light from the optical information recording medium 7 becomes diffused light after passing through the objective lens 6, and a part of it is kicked off by the aperture 22 of the objective lens 6, and then the beam splitter 4 and After passing through the diffraction grating 3, the returned light is kicked off by the diaphragm 21, so that the amount of returned light reaching the laser light source is considerably reduced. Also,
When the objective lens 6 and the optical information recording medium 7 are far apart, the light becomes convergent, and in this case, there is little kicking, but the light is focused at point D, which is in front of the light emitting point of the laser light source 1, so there is a light spot at the light emitting point. The image becomes blurred, and as a result, the amount of returned light can be reduced.

FIG. 2B shows the waveform of the focus error signal. At the in-focus position, the focus error signal is zero, and at the out-of-focus position B or A, the focus error signal is either positive or negative. have value.

FIG. 2 shows a circuit according to an embodiment of the present invention. In this circuit, operational amplifiers A1 to A
3 constitutes a focus control circuit that controls the current of the focus direction drive coil L1 provided in the objective lens 6 in FIG. The circuit configuration is such that the signals are superimposed and given.

The operational amplifier A1 is supplied with a focus error signal from an input terminal IN1 via a resistor R1, and is also supplied with a reference signal from an input terminal IN2 via a voltage dividing circuit made up of resistors R2 and R3. And resistance R
4 as a feedback element and operates as a comparator, the operational amplifier A1 compares these two and extracts the difference, and the resistor R5
is applied to operational amplifier A2 via. The operational amplifier A2 has a series circuit of a capacitor C1 and a resistor R7 as a feedback element, and a resistor R8 inserted in parallel with this series circuit, and operates as an integrating circuit. The integrating circuit is provided considering that the focus direction driving coil L1 has a resonance point, and emphasizes low frequencies below the resonance point to efficiently feed power.

The output of this integrating circuit is sent to an operational amplifier A3 via a differentiating circuit consisting of a series circuit of a resistor R9 and a capacitor C2, and a resistor R10 inserted in parallel to this series circuit.
given to. This differentiating circuit advances the signal phase in advance as a countermeasure against the delay in operation of the focus direction drive coil L1.

The operational amplifier A3 supplies a drive current to a series circuit consisting of a focus direction drive coil L1 and a resistor R12. And this drive current is resistor R
11 to the operational amplifier A3.

The switch SW is closed when a defocus command signal is applied to the input terminal DEF, and the operational amplifier A is closed.
A voltage signal to be superimposed on the difference signal applied to the second input terminal is applied from a voltage source Er via a resistor R6. When the defocus command signal is not applied to the input terminal DEF, the switch SW is open and only the difference signal is applied to the input terminal of the operational amplifier A2, resulting in a normal focusing control operation.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an optical system used in the present invention and a focus error signal obtained by this configuration.

FIG. 2 is a diagram showing a circuit according to an embodiment of the present invention.

FIG. 3 is a diagram showing the configuration of an optical device used in a conventional edge mirror method.

FIG. 4 is a diagram showing how to connect light spots using the edge mirror method.

FIG. 5 is an explanatory diagram of a three-beam method for tracking control.

FIG. 6 is a diagram showing the structure of an optical information recording medium.

FIG. 7 is a diagram showing a state where the tracking error signal due to the return light to the laser becomes unstable.

FIG. 8 is a diagram showing a state in which a tracking error signal and a track position signal due to return light to a laser have become unstable.

FIG. 9 is a diagram showing the configuration of a conventional return light isolation type optical system.

FIG. 10 is a diagram showing the configuration of a conventional optical system for reducing returned light.

[Explanation of symbols]

1 Laser diode 2, 8 Collimator lens 3 Diffraction grating 4 Beam splitter 5 Mirror 6 Objective lens 7 Optical information recording medium 9 Edge mirror 10, 11 Photodetector 12 Subtractor 21, 22 Aperture 71 Surface hardening layer 72 Polycarbonate layer 73 Information recording layer 74 Acrylic base material A1, A2, A3 Operational amplifier DEF Defocus command signal input terminal L1 Focus direction drive coil L2 Tracking direction drive coil SW Switch

Claims (2)

[Claims] 1. An optical information recording and reproducing apparatus that records and reproduces information while guiding the optical information recording medium by the tracking track by irradiating a laser beam onto an optical information recording medium having a tracking track and an information recording track. The apparatus includes a signal output means for generating a signal when the apparatus performs a track jump and a seek operation, and a control means for bringing the irradiation of laser light onto the optical information recording medium into an out-of-focus state when the signal from the means is given. An optical information recording/reproducing device characterized by: 2. The optical information recording and reproducing apparatus according to claim 1, wherein the out-of-focus state is predetermined, and the control means selects the predetermined state.