CN1061767C - Digital multi-purpose disk, video digital optical disk compatible double-lens optical probe - Google Patents

Abstract

The present invention relates to a structural design of an optical head of a DVD player, which belongs to the technical field of optical disc design. The present invention comprises a semiconductor laser, a reading / writing light path composed of a polarized light spectroscope and a 1/4 wave plate, and a light signal receiving and converting unit composed of a polarized light spectroscope, a collecting mirror and a photoelectric receiver, wherein the reading / writing light path also comprises a DVD reading objective, a VDC reading objective, and a light path switching mechanism for switching the light path, and the DVD reading objective and the VDC reading objective are arranged on a dual-shaft torquer. The present invention has the advantages of simple structure, convenient realization, and high utilization rate of light energy.

Description

Digital Versatile Disk, Video Digital Disc Compatible Dual Lens Optical Head

The invention belongs to the technical field of optical disc drive design, in particular to the structural design of the optical head of the DVD player.

Digital Versatile Disc-DVD (Digital Versatile Disc-DVD) technology is the next-generation multimedia technology that is currently being developed, and it will become the mainstream product in the future multimedia market. However, in the current situation where Video Compact Disc (VCD) occupies the mainstream of the market, DVD is required to be compatible with VCD. In order to do this, the optical head must first be improved. At present, some international companies such as MB Video, Mitsubishi, Sony, Philips and Thomson have proposed some improvement schemes. The commonly used schemes are as follows:

(1) Install two sets of optical heads in the player, one for DVD and the other for VCD. This scheme is a simple combination of two sets of independent optical systems of DVD and VCD in a DVD player, which is easy to realize, but increases the volume and mechanism of the player.

(2) Install two objective lenses on a torquer. This scheme is proposed by Mitsubishi on the basis of its original technology. It realizes switching of the objective lens through the rotation of the torquer (it uses this rotation to Tracking). The disadvantage of this scheme is that the torque device has a large inertial force and its dynamic characteristics are not good.

(3) Using holographic optical elements to realize single-lens dual-focal length, this solution has high requirements on the processing technology of the lens, and it is difficult to realize, and the light energy utilization rate of this solution is not high.

(4) Use the liquid crystal panel as a diaphragm to change the numerical aperture, thereby realizing the change of the focal length. This solution also has the problem of low utilization rate of light energy.

The purpose of the present invention is to overcome the deficiencies of the prior art, and design an optical head compatible with VCD and DVD, which has the advantages of simple structure, easy realization and high utilization rate of light energy.

A DVD and VCD compatible dual-lens optical head designed by the present invention includes a semiconductor laser and a read/write optical path composed of a condenser lens, a diffraction grating, a polarized beam splitter, and a 1/4 wave plate, and a polarized beam splitter and a condenser 1. An optical signal receiving conversion unit composed of a photoelectric receiver, characterized in that the read/write optical path also includes a DVD disk readout objective lens and a VDC disk readout objective lens installed together on a biaxial torque device and the optical path is carried out Switched optical path switching mechanism.

The present invention is characterized in that two objective lenses with different numerical apertures (NA _DVD = 0.62, NA _VCD = 0.38) are installed on the same frame and biaxial torquer, the front working distance of the objective lens differs by 0.60mm, and The two disks of DVD and VCD are parfocal respectively, and the switching of the optical path is realized by the beam switching mechanism. The schematic diagram of the optical path of the optical head is shown in Figure 1, including a semiconductor laser 1 and a condenser lens 2 arranged in alignment with the beam emitted by the laser, a diffraction grating 3, a polarizing beam splitter 4, a 1/4 wavelength plate 5, and an optical path switching mechanism 9. The DVD objective lens 6, the VCD objective lens 8, the condenser lens collimated with the reflected light beam of the polarization beam splitter 4, and the photoelectric receiver installed together.

As can be seen from Figure 1, the difference between this optical path principle and the optical reading mechanism of a general DVD or VCD machine lies in the optical path switching mechanism and the double objective lens structure in the figure. They are the core part of realizing compatibility between DVD and VCD in this scheme. When the disc 7 is a DVD disc, the light beam switching mechanism switches the beam to the objective lens 6 with NA=0.62, and the front working distance of the objective lens is set to 1, which can be used to read the information of the DVD disc. When the disc is a VCD disc, the light beam is switched to the objective lens 8 with NA=0.38. The front working distance of the objective lens is 1+0.6 mm, which can be used to read the information of the VCD disc. The objective lens 6 and the objective lens 8 are fixed on the same mirror frame and a biaxial torquer, and they can be controlled by the torquer to move in two directions at the same time, so as to realize focusing and track tracking.

The beam switching mechanism of the present invention has two schemes: mechanical and photoelectric.

The first is the translation mirror method:

In this solution, the beam switching mechanism is a mirror with a driving device, as shown in Figure 2. It switches the light beam by moving the mirror. When the objective lens with NA=0.62 is used, the reflector is located at position 1, and the light passes through the reflector and reaches the DVD reading objective lens 6; when the objective lens with NA=0.38 is used, the reflector is shifted by about 6mm and is located at position 2. At this time, the light reaches the VCD readout objective lens 8 through the reflector, and the position 1 and position 2 can be positioned by a positioning card.

The second is optical polarization spectroscopy:

The principle of this scheme is to determine the switching of the light beam according to the polarization direction of the light, as shown in Figure 3.

In this scheme, the readout objective lens is selected by controlling the 1/2-full-wave variable wavelength plate 12 . This 1/2-full-wave variable wavelength plate is an electro-optic material (such as liquid crystal material), which can be controlled to switch between 1/2-wave plate or full-wave plate by changing the electric field. The beam switching mechanism used in this solution is composed of a polarizing beam splitter 91 and a reflector 92 .

The laser light emitted from the semiconductor laser 1 is shaped, collimated, and polarized to form linearly polarized light. After the linearly polarized light passes through the 1/4 wave plate 5, the polarization direction is rotated by 45 degrees and enters the 1/2-full wave variable wavelength. slice 12. When the disc 7 is a DVD disc, the 1/2-full-wave variable wavelength plate 12 is set as a 1/2 wave plate through an electric field, and the polarization direction of the linearly polarized light will rotate 90 degrees after passing through the 1/2 wave plate , and the polarizing beamsplitter 91 will reflect this kind of linearly polarized light, so that the DVD disc reading objective lens 6 is effective; when the disc 7 is a VCD disc, the 1/2-full wave variable wavelength plate 12 is set to Full-wave plate, now linearly polarized light passes through this full-wave plate, and the polarization direction remains unchanged. The polarized beam splitter 91 will transmit this polarized light, and it will enter the reflector 92, thereby making the VCD disk readout objective lens 8 effective. This is a complete electro-optic control scheme without adding other mechanical structures in the optical path.

The invention realizes the use of a set of optical path system to be applicable to the optical head of VCD disk and DVD disk at the same time, and the structure is simple, which can be realized by using the original single VCD or DVD optical head with a little modification, so that the utilization rate of light energy can be improved. Greatly improve.

Brief description of the drawings:

Fig. 1 is the overall structural schematic diagram of the present invention.

FIG. 2 is a schematic diagram of a mechanical or beam switching mechanism of the present invention.

Fig. 3 is a schematic diagram of the photoelectric or beam switching mechanism of the beam of the present invention.

Fig. 4 is a structural schematic diagram of an embodiment of the present invention.

Fig. 5 is a schematic structural diagram of a biaxial torque device according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of the structure of the double lens in this embodiment.

The present invention designs an embodiment of a DVD and VCD compatible dual-lens optical head, the structure of which is shown in Figures 4-6. In conjunction with accompanying drawing, describe in detail as follows:

Fig. 4 is the overall structure of this embodiment. The entire light path is divided into two parts: one is a fixed part and the other is a moving part. The fixed part consists of a semiconductor laser 1 with a wavelength of 635nm or 650nm, a condenser lens 2, a diffraction grating 3, a polarizing beam splitter 4, a 1/4 wavelength plate 5, a condenser lens 10 and a photoelectric receiver 11. These devices are installed in a box fixed on the DVD rack. When installing the device, semiconductor laser 1, condenser mirror 2, diffraction grating 3, polarizing beam splitter 4, 1/4 wavelength plate 5 with common optical axis, condenser mirror 10 and photoelectric receiver are required. The optical axis of 11 should be perpendicular to the above-mentioned optical axis. The semiconductor laser 1 should be placed at the focal point of the condenser 2 to ensure that the light coming out from the condenser 2 is parallel light. The fixed part stands still. The moving part is composed of reflector 9, objective lens 6 and objective lens 8 and their biaxial torquer. The reflector should be installed at 45 degrees to the optical axis to ensure that the incident light and outgoing light are perpendicular. The optical axes of the objective lens 6 and the objective lens 8 should be parallel, and their optical axes should be perpendicular to the optical axis where the 1/4 wavelength plate 5 is located. The reflector 9 in the moving part can translate a distance of about 6 mm along the incident light direction to ensure the switching of the light beam between the objective lens 6 and the objective lens 8, and the movement of the reflector 9 can be realized by an electromagnetic device. A coil is installed on the reflector 9, and a magnetic material is installed in the moving part, and the movement of the reflector 9 is positioned by the magnetic material and the guide groove to ensure accuracy. The moving part is installed on the guide rail, and it will move along the guide rail in the disk radial direction during addressing. The fixed part and the moving part are connected by parallel light.

The structures of the objective lens 6 and the objective lens 8 and their biaxial torquer in this embodiment are shown in FIG. 5 and FIG. 6 . The biaxial torquer consists of a DVD objective lens, a VCD objective lens, a mirror frame, a tracking coil 51 , a focusing coil 52 , a magnetic material 53 , a cantilever 54 and a support 55 . The focusing coil is wound on the frame along the horizontal direction, and the axis of the focusing coil is perpendicular to the magnetic field direction of the magnetic material; the tracking coil is wound and pasted on the side of the frame, and its axis is parallel to the magnetic field direction of the magnetic material. When the focus coil of the biaxial torquer is energized, it will move up and down under the action of the magnetic field, so that the information plane of the disc is always located on the focal plane of the readout objective lens. When the tracking coil is energized, it will move forward and backward under the action of the magnetic field (as shown by the arrow in the figure), so that the focus of the readout beam is always located in the information track of the disk. Because the DVD objective lens and the VCD objective lens are in focus, a dual-axis torque device can be used to realize the focusing and tracking control of the two objective lenses.

In addition, the objective lens 6 and the objective lens 8 in this embodiment can be integrally manufactured by opening a mold, thereby forming a combined objective lens fixed in the same frame 61 , the appearance of the combined objective lens is shown in FIG. 6 . The two objective lenses 6 and 8 in the figure are designed for lasers with a wavelength of 635nm or 650nm. The main difference between the two objective lenses is that the numerical aperture is different, one is 0.62, and the other is 0.38. The numerical aperture is different. It is achieved by changing the radius of curvature of the lens and the lens aperture. These two objective lenses are respectively used for reading out DVD discs and VCD discs. Since the composite objective lens is manufactured as a whole, it is more convenient and simple to install on the biaxial torque device, and because the weight is reduced, the dynamic characteristics of the entire biaxial torque device will be better.

Claims (5)

1. a DVD, VCD compatible double-lens optical probe, comprise semiconductor laser and the read/write light path that constitutes by condenser, diffraction grating, polarized light beam splitter, quarter wave plate, the light signal that is made of polarized light beam splitter, condenser photelectric receiver receives converting unit, it is characterized in that also comprising in the said read/write light path that the DVD dish that is installed in together on the twin shaft torquer is read object lens and VDC coils object lens of reading and the light path switching mechanism that this light path is switched.

2. as the said a kind of DVD of claim 1, VCD compatible double-lens optical probe, it is characterized in that said light path switching mechanism is made of a drive unit and reflecting prism mounted thereto, this drive unit is provided with the locator card that makes reflecting prism aim at said two object lens respectively.

3. as the double-lens optical probe of the said a kind of DVD of claim 1, VCD compatibility, it is characterized in that said light path switching mechanism is by being arranged on the variable wavelength sheet in the read/write light path and being formed with polarization spectroscope that is arranged on said two object lens correspondence positions and catoptron.

4. as the said a kind of DVD of claim 1, VCD compatible double-lens optical probe, it is characterized in that said light path switching mechanism by installation, the calutron and the reflecting prism that connect firmly are together formed.

5. as claim 1,2,3 or 4 said a kind of DVD, VCD compatible double-lens optical probe, it is characterized in that said twin shaft torquer is made up of tracking coil, focusing coil and the cantilever, the support that are arranged on the magnetic material.

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