JP2007273044A - Optical head and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical head and optical disk device capable of thinning an optical disk device for recording a visible image on a label face of the optical disk which can record visible images on the label face. <P>SOLUTION: By providing liquid crystal elements making variable a focus distance which drives when recording a visible image in a label recording area on an optical path between a semiconductor laser of the optical head and an objective lens, a movable range of an objective lens actuator is suppressed narrower and the optical disk device can eventually be thinned. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical head and an optical disc apparatus for recording an image on an optical disc that forms an image on a label surface with laser light.

  As is well known, in recent years, optical discs such as CDs and DVDs have become widespread as information recording media. The CD includes a reproduction-only CD-ROM, a recordable CD-R, a rewritable CD-RW, and the like. As the DVD, a reproduction-only DVD-ROM, a recordable DVD-R, and a rewritable DVD- There are RAM, DVD-RW, and the like. A recordable optical disk, that is, a recordable or rewritable optical disk has an information recording layer, and the recording capacity of the information recording layer is, for example, about 700 MB for a CD-R and 4.7 GB for a DVD-R (single layer) or the like. Degree.

  On the label surface opposite to the surface on the information recording layer side of the recordable optical disc, characters or logos indicating the type of the optical disc or the like are silk-printed, for example. Inkjet printers or optical disks having a label surface on which characters and pictures can be recorded by hand are also popular.

  Recently, an optical disc called light Scribe (registered trademark) capable of recording a visible image such as a picture or a character on a label surface using a laser beam has begun to spread. When a visible image is recorded on the label surface using laser light, it is mounted on a rotary table that rotates the optical disk of the optical disk apparatus so that the label surface faces the optical head. That is, the direction of the mounting surface of the optical disk is opposite between the time of recording information on the optical disk and the time of recording a visible image on the label surface.

  FIG. 6 is a diagram showing a difference in position of the objective lens when information is recorded / reproduced with respect to a CD (CD-ROM, CD-R, CD-RW, etc.) and when a visible image is recorded on the label surface. . The optical disk 2 in FIG. 6 is a CD. The objective lens 9 and the λ / 4 plate 8 are moved together in the focusing direction by the objective lens actuator 12. In the recording / reproducing on the information recording layer, the laser beam is condensed so as to be focused on the information recording layer, and when a visible image is recorded on the label surface, it is condensed so as to be focused on the label surface. The CD has a substrate thickness of 1.2 mm, which indicates that the position of the objective lens is different by about 1.2 mm when information is recorded on the information recording layer 28 and when a visible image is recorded on the label surface.

  FIG. 7 shows the difference in the position of the objective lens when recording and reproducing information on a DVD (DVD-ROM, DVD-R, DVD-RAM, DVD-RW, etc.) and when recording a visible image on the label surface. It is a figure. The DVD has a structure in which two 0.6 mm-thick substrates are bonded together, and an information recording layer is provided at a position of about 0.6 mm from the substrate surface on the objective lens side. It shows that the position of the objective lens is different by about 0.6 mm when recording information on the information recording layer 28 and when recording a visible image on the label surface.

  For an optical disk device that does not have a function of recording a visible image on the label surface, an operation neutral point may be set at 0.6 to 1.2 mm from the substrate surface. The operation range at the time of recording information includes a mechanical error, optical disk mounting variation, deformation due to warping of the mounting substrate, optical disk substrate thickness variation, and the like. On the other hand, when a visible image is recorded on the label surface, the objective lens has to be moved in the direction of the 0.6 mm objective lens side, and the movement range of the objective lens becomes very large. For this reason, it is difficult to reduce the height of the optical head, which has been an obstacle to realizing a thin optical disk drive.

On the other hand, as described above, the distance from the substrate surface to the information recording layer is different by 0.6 mm between the CD and the DVD, and the substrate thickness through which the laser beam passes is different. Although Fresnel type hologram lenses are used for such discs having different thicknesses, there is a problem in that light utilization efficiency is poor. In addition, there is a method of switching two objective lenses having different focal lengths between CD and DVD. However, there is a problem that it is difficult to reduce the thickness by a switching mechanism or the like. Optical heads corresponding to both optical disks have been devised. (See Patent Document 1).
Japanese Patent Laid-Open No. 10-188332

  An optical disc apparatus that records a visible image on an optical disc that can record a visible image using a laser beam on a label surface is desired to be thin when mounted on, for example, a notebook computer. Accordingly, it is desired to reduce the thickness of the optical head. An optical head that records a visible image on the label surface has a large operating range of the objective lens, and it is difficult to reduce the thickness of the optical head.

  The present invention has been made to solve the above-described problems, and provides an optical head and an optical disc apparatus capable of reducing the thickness of an optical disc apparatus that records a visible image on a label surface of an optical disc capable of recording a visible image on a label surface. With the goal.

  In order to achieve the above object, the optical head of the present invention records a visible image on the label recording area of an optical disc having a label recording area capable of recording a visible image on the label surface side, and records it on the information recording layer of the optical disc. An optical head for recording / reproducing information with respect to the optical head, condensing the laser beam emitted from the semiconductor laser toward the optical disc and receiving the return laser beam reflected from the optical disc, the semiconductor laser, And a liquid crystal element which is provided on an optical path between the objective lenses and which can change a focal length when a visible image is recorded in the label recording area of the optical disc.

  The optical disc apparatus of the present invention records a visible image on the label recording area of an optical disc having a label recording area capable of recording a visible image on the label surface side, and records and reproduces information on the information recording layer of the optical disc. An optical head having an objective lens actuator, a drive control unit for controlling driving of the objective lens actuator, a reproduction processing unit for reproducing a signal output from the optical head, and a recording A recording processing unit that modulates data and outputs the laser control signal as a laser control signal to the optical head. The optical head condenses laser light emitted from a semiconductor laser toward the optical disc, and from the optical disc. An objective lens that receives the reflected return laser beam and an optical path between the semiconductor laser and the objective lens. , And having a liquid crystal element to the focal length variable when recording a visible image on the label recording area of the optical disc.

  According to the present invention, the movable range of the objective lens actuator provided in the optical disk apparatus that records a visible image on the label surface can be suppressed to be small, and the optical disk apparatus can be reduced in thickness.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration example of the optical disc apparatus 1. The optical disc apparatus 1 includes an optical head 3, an actuator drive control unit 13, a reproduction processing unit 16, and a recording processing unit 19.

  The optical head 3 irradiates the optical disc 2 with laser light for information recording and reproduction, converts the reflected light from the optical disc 2 into an electrical signal, and outputs it as a reproduction signal. As a semiconductor laser 4, a collimating lens 5, a PBS (polarizing beam splitter) 6, a liquid crystal element 7, a λ / 4 plate 8, an objective lens 9, a condenser lens 10, and a photodetector 11.

  The optical head 3 includes an objective lens actuator 12 on which the objective lens 9 and the λ / 4 plate 8 are mounted. The objective lens actuator 12 controls the objective lens 9 and the λ / 4 plate 8. The actuator drive control unit 13 includes a focus error and tracking error signal generation circuit 14 and a focus and tracking control circuit 15.

  Control signals generated by these circuits included in the actuator drive control unit 13 are output to the objective lens actuator 12 to control the position of the objective lens 9. Specifically, focus control for controlling the separation distance between the objective lens 9 and the recording surface of the optical disc 2 so that the focal point of the laser beam is accurately positioned on the recording surface of the optical disc 2, and the center of a desired track of the optical disc 2 Servo-controlled tracking control for finely adjusting the radial position of the optical disc so that the focal point of the laser beam is located at the same time. The liquid crystal control circuit 23 controls the voltage applied to the liquid crystal element 7 in order to make the focal length variable when recording an image on the label surface.

  The reproduction processing unit 16 performs reproduction processing on the signal output from the optical head 3 and includes a signal processing circuit 17 and a demodulation circuit 18. The recording processing unit 19 mainly records information on the optical disc 2, and includes a modulation circuit 22, a recording / reproducing control unit 21, and a laser control circuit 20.

  The operation of the information recording / reproducing apparatus 1 configured as described above will be described. First, the operation of recording information on the optical disc 2 will be described. The modulation circuit 22 of the recording processing unit 19 modulates recording information (data symbols) provided from a host, for example, a personal computer main body into a channel bit sequence based on a predetermined modulation method. A channel bit sequence corresponding to the recording information is input to the recording / reproducing control unit 21.

  The recording / reproduction control unit 21 receives a recording / reproduction instruction (in this case, a recording instruction) from the host. The recording / reproducing control unit 21 outputs a control signal to the actuator drive control unit 13 and drives the objective lens actuator 12 so that the light beam is appropriately condensed at a target recording position. Further, the recording / reproducing control unit 21 supplies the channel bit sequence to the laser control circuit 20. The laser control circuit 20 converts the channel bit series into a laser driving waveform, and drives the semiconductor laser 4 in a pulse manner. As a result, the semiconductor laser 4 generates a recording light beam corresponding to a desired bit sequence.

  The recording light beam generated by the semiconductor laser 4 is converted into parallel light by the collimating lens 5, enters the PBS 6, and passes therethrough. The light beam that has passed through the PBS 6 passes through the liquid crystal element 7 and the λ / 4 plate 8 and is focused on the recording surface of the optical disc 2 by the objective lens 9. The condensed light beam for recording is maintained in a state where the best light beam spot is obtained on the recording surface of the optical disc 2 by focus control and tracking control by the actuator drive control 13 and the objective lens actuator 12.

  Next, the reproduction of information from the optical disc 2 by the information recording / reproducing apparatus 1 will be described. The recording / playback control unit 21 receives a recording / playback instruction (in this case, a playback instruction) from the host. The recording / reproduction control unit 21 outputs a reproduction control signal to the laser control circuit 20 in accordance with a reproduction instruction from the host.

  The laser control circuit 20 drives the semiconductor laser 4 based on the reproduction control signal to generate a reproduction light beam. The reproduction light beam generated by the semiconductor laser 4 is converted into parallel light by the collimator lens 5, and enters and passes through the PBS 6. The light beam that has passed through the PBS 6 passes through the liquid crystal element 7 and the λ / 4 plate 8 and is focused on the recording surface of the optical disc 2 by the objective lens 9.

  The condensed light beam for reproduction is maintained in a state where the best light beam spot is obtained on the recording surface of the optical disc 2 by the focus control and tracking control by the actuator drive control 13 and the objective lens actuator 12. The reproducing light beam irradiated on the optical disk 2 is reflected by the reflective film or the reflective recording film in the recording surface. The reflected light passes through the objective lens 9 in the reverse direction to become parallel light again, passes through the λ / 4 plate 8, and is reflected by the PBS 6 having a polarization perpendicular to the incident light.

  The light beam reflected by the PBS 6 becomes convergent light by the condenser lens 10 and enters the photodetector 11. The photodetector 11 is composed of, for example, a quadrant photodetector. The light beam incident on the photodetector 11 is photoelectrically converted into an electric signal and amplified. The amplified signal is equalized in the signal processing circuit 17 of the reproduction processing unit 16, binarized, and sent to the demodulation circuit 18. The demodulation circuit 18 performs a demodulation operation corresponding to a predetermined modulation method and outputs reproduction data.

  On the other hand, part of the electrical signal output from the photodetector 11 is input to the actuator drive control 13, and the focus error and tracking error signal generation circuit 14 generates a focus error signal and a tracking error signal. The focus and tracking control circuit 15 controls the objective lens actuator 12 based on the focus error signal, controls the focus of the beam spot, controls the objective lens actuator 12 based on the tracking error signal, and controls the tracking of the beam spot.

  As described above, the objective lens actuator 12 controls the position and posture angle of the objective lens 9 mounted on the objective lens actuator 12 based on the control signal from the actuator drive control unit 13, and the position of the beam spot with respect to the optical disc 2. Is maintained to be optimal.

  FIG. 2 is a diagram showing the structure of an optical disc having a label recording area 24 capable of recording a visible image on the label surface side. The optical disc 2 is an information recording type disc, and has an information recording surface on one side of the disc substrate and a label surface on the other side. FIG. 2A is a diagram of the optical disc 2 as viewed from the label surface.

  On the label surface side of the disk 2, a label recording area 24 is formed concentrically with the outer diameter of the disk 2. The label recording area 24 is an area where printing is possible using laser light emitted from the semiconductor laser 4 of the optical disc apparatus 1. There is a clamp area 25 on the inner peripheral side of the label recording area 24. There is a hole 26 in the center of the disk 2 for mounting the disk 2 on the optical disk apparatus 1.

  FIG. 2B is a cross-sectional view of the disk 2. An information recording layer 28 is formed on the optical disk substrate 27, a protective film 29 is formed thereon so as to cover the information recording layer 28, and a label recording layer 30 is formed thereon. By focusing the CD laser on the information recording layer 28, information can be recorded and reproduced.

  Next, recording of a visible image on the label surface will be described. First, the optical disk 2 is attached to a table of a disk rotation motor (not shown) with the label surface facing the objective lens. Thereafter, the optical disk 2 is rotated by a disk rotation motor (not shown). Thereafter, the optical head 3 is moved in the radial direction of the optical disc 2. For example, the optical head 3 is moved from the center of the optical disc 2 to a certain radial position in order to focus the laser beam at a position where the formation of an image in the label recording area 24 of the optical disc 2 is started. At this time, the laser beam is not yet emitted from the semiconductor laser 4.

  Next, a voltage is applied to the liquid crystal element 7 to focus the laser beam of the optical head 3 on the label surface. The label recording layer 30 is discolored by condensing the laser light from the semiconductor laser 4 on the label recording layer 30 with the liquid crystal element 7 and the objective lens 9 while the optical disk 2 is rotated. Focusing on the label recording layer 30 is maintained by driving the objective lens actuator 12. When the light is condensed on the label recording layer 30 by the lens effect by the liquid crystal element 7, the moving range of the objective lens 9 in the focus direction can be suppressed to a small range.

  By flashing the semiconductor laser 4 in accordance with the rotation of the optical disc 2, dots (locations where the label recording layer 30 has been changed to spots) are formed in the circumferential direction of the label surface of the optical disc 2. This is because an image is formed as a set of dots. In addition, if a dot continues, it will become a line (line). The condensing part of the optical head 3 is moved in the radial direction of the optical disk 2 to create dots in the circumferential direction of the optical disk 2. When the optical head 3 is moved, the semiconductor laser 4 is turned off or turned on as necessary.

  As described above, an image can be formed on the label surface by focusing the laser beam on the label recording layer 30 of the optical disc 2 and changing the color.

  FIG. 3 is a cross-sectional view of the liquid crystal element 7. A liquid crystal layer 33 containing liquid crystal molecules is disposed between the glass substrates 31 and 32. Transparent electrodes 34 and 35 for applying an electric field to the liquid crystal are formed on the inner surfaces (surfaces on the liquid crystal layer 33 side) of the glass substrates 31 and 32. The liquid crystal element 7 is an element that changes the optical path length of the laser light by changing the refractive index of the laser light transmitted through the liquid crystal layer 32. The glass substrates 31 and 32 have a thickness of about 0.5 mm, and the liquid crystal layer 32 has a thickness of several μm to several tens of μm (micrometer). The total thickness of the liquid crystal element 7 is about 1 mm. The external shape is a square of several millimeters square or a rectangle close to it, or a circle with almost the same area. The glass substrates 31 and 32 may constitute a Fresnel lens.

  FIG. 4 is a diagram showing a division pattern 36 of the transparent electrodes 34 and 35 of the liquid crystal element 7. At least one of the transparent electrodes 34 and 35 has a pattern divided into a plurality of concentric circular rings. The liquid crystal element 7 functions as a liquid crystal lens, and by applying an electric charge for each pattern divided into an annular shape, the laser light that has passed through the PBS 6 is preliminarily focused and delivered to the objective lens. When no charge is applied, the laser beam is transmitted without being narrowed.

  FIG. 5 is a diagram showing the lens action of the liquid crystal element 7. Since the liquid crystal element 7 acts as a liquid crystal lens, the focal length is adjusted, and a predetermined amount is reduced before the laser light is delivered to the objective lens 9, the objective lens 9 is a lens compared to when the liquid crystal element 7 has no lens action. The travel distance can be reduced. Therefore, even when the laser beam is focused on the label recording layer 29 on the label surface, the moving distance of the objective lens can be reduced.

  As described above, when the light is condensed on the label recording layer 30 by the lens effect of the liquid crystal element 7, the moving range of the objective lens 9 in the focus direction can be suppressed to a small range. Therefore, the objective lens actuator can be made smaller, and accordingly, the optical head can be made thinner.

The block diagram which shows the Example of the optical disk device by this invention. The figure which shows the optical disk which has a label recording area which can record a visible image on the label surface side. Sectional drawing of a liquid crystal element. The figure which shows the division | segmentation pattern of the transparent electrode of a liquid crystal element. The figure which shows the lens effect | action of a liquid crystal element. The figure which showed the difference of the position of the objective lens when recording / reproducing information with respect to CD, and recording a visible image on a label surface. The figure which showed the difference of the position of the objective lens when recording / reproducing information with respect to DVD, and recording a visible image on a label surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Optical disk 3 Optical head 4 Semiconductor laser 6 PBS
7 Liquid Crystal Element 9 Objective Lens 11 Photodetector 12 Objective Lens Actuator 13 Actuator Drive Control Unit 16 Playback Processing Unit 19 Recording Processing Unit 23 Liquid Crystal Control Circuit 24 Label Recording Area 27 Optical Disc Substrate 28 Information Recording Layer 29 Protective Layer 30 Label Recording Layer 31 , 32 Glass substrate 33 Liquid crystal layer 34, 35 Transparent electrode

Claims (2)

An optical head for recording a visible image on the label recording area of an optical disc having a label recording area capable of recording a visible image on the label surface side, and recording and reproducing information on an information recording layer of the optical disc,
An objective lens for condensing the laser beam emitted from the semiconductor laser toward the optical disc and receiving the return laser beam reflected from the optical disc;
An optical head, comprising: a liquid crystal element which is provided on an optical path between the semiconductor laser and the objective lens and has a variable focal length when a visible image is recorded in the label recording area of the optical disc. An optical disc apparatus for recording a visible image on the label recording area of an optical disc having a label recording area capable of recording a visible image on a label surface side, and recording / reproducing information on / from an information recording layer of the optical disc,
An optical head comprising an objective lens actuator;
A drive controller for controlling the drive of the objective lens actuator;
A reproduction processing unit for reproducing the signal output from the optical head;
A recording processing unit that modulates recording data and outputs the data to the optical head as a laser control signal;
The optical head condenses the laser beam emitted from the semiconductor laser toward the optical disc, and receives an objective lens that receives the return laser beam reflected from the optical disc;
An optical disc apparatus comprising: a liquid crystal element which is provided on an optical path between the semiconductor laser and the objective lens and has a variable focal length when a visible image is recorded in the label recording area of the optical disc.

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