CN1979655A - Optical read-write head - Google Patents

Abstract

The invention provides an optical read-write head with a reflection coating device, which comprises a laser diode, an optical element, a recording medium and an optical signal detector. The laser diode is a laser light source with 1-3 different wavelengths and the same linear polarization direction, and after being reflected twice by the reflection coating device, the laser diode is changed into linear polarization feedback light with 90 degrees of difference with the original linear polarization direction, so that the purpose of reducing the relative intensity noise of the laser diode caused by the feedback light of the recording medium is achieved.

Description

Optical read/write head

technical field

The invention relates to an optical pickup, in particular to an optical pickup equipped with a reflective coating device.

Background technique

Music discs (Compact Disk, CD), video discs (Video Compact Disk, VCD) and digital video discs (Digital Video Disk, DVD) have been widely used in business, family and personal life, so all related industries are committed to Research and develop more efficient reading or recording technology to improve the quality of recording media such as CD, VCD and DVD.

The optical read/write head reads or records data through a recording medium (recording). The light emitted by the laser diode (laserdiode, LD) is focused on the surface of the recording medium through the optical element set, and the optical signal detector (photo detector integrated circuit, PDIC) receives the signal or detects its reflection strength.

FIG. 1 is a schematic structural diagram of a known optical read/write head. This optical head comprises a recording medium 101, an optical signal detector 102, a laser diode 103, a polarized beam splitter (polarized beam splitter) 104, a quarter wave plate (quarter wave plate) 105, A collimator lens (collimator lens) 106 and an objective lens (objective lens) 107.

The laser light emitted by the laser diode 103 is focused on the surface of the recording medium 101 after passing through the polarization beam splitter 104 , the quarter wave plate 105 , the collimating lens 106 and the objective lens 107 . The optical read/write head utilizes the recording medium 101 to read or record data. The laser light is reflected by the surface of the recording medium 101 and guided to the optical signal detector 102 through the objective lens 107 , the collimating lens 106 , the quarter wave plate 105 and the polarization beam splitter 104 . The intensity thereof is detected by the optical signal detector 102 .

This optical read-write head uses a combination of multiple optical lenses and polarization beam splitters to reflect and guide the laser light to the recording medium 101 and the optical signal detector 102, so as to read or record data and detect signal strength the goal of.

The polarization beam splitter 104 is used to transmit and reflect laser light. Due to the factors of material selection and production quality, the price of components remains high.

The path of the emitted light and reflected light of the laser light source is from the laser diode 103 to the surface of the recording medium 101 and reflected to the optical signal detector 102 .

Since the polarization beam splitter 104 and the quarter-wave plate 105 of the optical read-write head require relatively high manufacturing technology and cumbersome manufacturing process, not only the implementation and manufacturing process is extremely complicated, but also the production cost is increased.

Contents of the invention

The invention provides an optical read-write head equipped with a reflective coating device, which mainly includes a laser diode element, an optical element, a recording medium, and an optical signal detector. The laser diode element emits 1-3 kinds of laser light with different wavelengths but the same linear polarization direction. The laser light is focused to the recording medium through the optical element group for recording and reading operations, and then reflected by the surface of the recording medium and guided to the optical signal detector through the optical element again to detect the strength of the signal.

The optical element includes a light splitting element, a reflective coating device and an objective lens. Its beam-splitting element splits one beam into three beams. The reflective coating device has the functions of reflecting and transmitting laser light, and changing the phase angle difference and linear polarization direction of the laser light with one or two or three wavelengths of wavelength 1, wavelength 2, and wavelength 3.

A coupling mirror can be added to the optical element to adjust the collimation of the laser light and increase the optical coupling effect. The coupling mirror is an optional component. The objective lens is used to focus the laser light.

The laser diode element injects the laser light with the same linear polarization direction into the reflective coating device at a polarization angle α, and converts the laser light with 1 to 3 wavelengths into circularly polarized light or elliptically polarized light. It is reflected by the surface of the recording medium, and the laser light of 1 to 3 wavelengths is converted into linearly polarized light by the reflective coating device again, and fed back to a laser diode cavity (laser diode cavity). The angle between the feedback linear polarized light and the original linear polarized light is changed to 90°. The reflective coating device can be composed of one or more reflectors, or a combination of more than one reflectors and light-transmitting lenses.

With the help of this reflective coating device, the linear polarization angle of the outgoing light and the linear polarization angle of the feedback light (feedback) are changed by 90°, so as to reduce the relative intensity noise (relative intensity noise) generated by the laser diode due to the feedback light fed back by the recording medium. Purpose.

Specifically, the present invention provides an optical read-write head, including: a laser diode element, which is a linearly polarized light source of laser light, used to emit linearly polarized light; a recording medium, which uses the laser to record or read data; an optical signal detector, which receives the signal and detects the strength of the laser signal reflected by the recording medium; and an optical element, which includes a light splitting element, a reflective coating device and an objective lens; the optical element is located at the laser Between the diode element, the recording medium and the optical signal detector, the reflective coating device reflects the linearly polarized light of the laser light source, converts the linearly polarized light into circularly polarized light or elliptically polarized light, and focuses and projects it onto the recording medium , and then guide the circularly polarized light or elliptically polarized light that is reflected back from the recording medium and passes through the reflective coating device to the optical signal detector, and the light that is reflected back from the recording medium is returned by the reflective coating device The reflected circularly polarized light or elliptically polarized light is fed back to the laser diode element.

In the above-mentioned optical read-write head, the reflective coating device transforms the phase angle difference and polarization direction of the laser light.

In the above optical read/write head, the laser diode element emits 1 to 3 kinds of laser light with different wavelengths, which are linearly polarized light with the same polarization direction.

In the above-mentioned optical read-write head, the laser light of the laser diode element passes through the reflective coating device with the linear polarization direction as an angle α and an incident angle β, and the angle α is between 10°～80° or 100°～170° °, the incident angle β is between 15° and 85°.

In the above-mentioned optical read-write head, the reflective coating device is composed of one or more reflective mirrors, or a combination of more than one reflective mirrors and light-transmitting lenses.

In the above-mentioned optical read-write head, the reflective coating device converts the linearly polarized light of laser light having one or two or three wavelengths of one to three wavelengths into the absolute value of the phase angle difference |P state phase-S state phase| =(2n+1)×90°circularly polarized light, where n=an integer of 0, 1, 2, 3....

In the above-mentioned optical read-write head, the reflective coating device converts the linearly polarized light of laser light with one or two or three wavelengths of one to three wavelengths into the absolute value of the phase angle difference |P state phase-S state phase| =(2n+1)×90°±60° elliptically polarized light, where n=0, 1, 2, 3... an integer.

In the above-mentioned optical read-write head, the optical element further includes a coupling mirror for adjusting the collimation of the laser light and increasing the light coupling effect.

In the above optical read/write head, the light splitting element is a grating.

The beneficial technical effect of the optical read-write head of the present invention is that the cost of the related reflective coating device technology is less than that of the known technology, so the production cost can be relatively reduced. Moreover, this technology effectively controls the generation of relative intensity noise of the laser diode to the feedback light, thereby improving the competitiveness of related companies.

The above and other objectives and advantages of the present invention will be described in detail below in conjunction with the following diagrams, detailed descriptions of the embodiments and the scope of the claims.

Description of drawings

Fig. 1 is a structural schematic diagram of a known optical read-write head;

Fig. 2 is the structural representation of optical head of the present invention;

Fig. 3 illustrates an embodiment of the optical read-write head of the present invention by taking the reflective coating device with two reflecting mirrors as an example;

FIG. 4 illustrates the arrangement between the linear polarization direction of the laser diode light source and the incident angle of the reflective coating device in the present invention.

Wherein, the reference signs are explained as follows:

101 Recording medium 102 Optical signal detector

103 Laser Diodes 104 Polarization Beamsplitters

105 quarter wave plate 106 collimating lens

107 objective lens 108 circular polarized light or elliptically polarized light

109 Outgoing laser linear polarization direction 110 Feedback laser linear polarization direction

201 Recording media 202 Optical signal detector

203 laser diode 203a laser diode light emitting cavity

204 optical element 204a light splitting element (grating)

204b reflective coating device 204c coupling mirror

204d objective lens 209 exit light

210 feedback light λ1-λ3 wavelength 1-wavelength 3

β incident angle α polarization angle

3041, 3042 reflector 304b reflective coating device

Detailed ways

FIG. 2 is a schematic structural diagram of the optical read-write head of the present invention. The optical read/write head includes an optical element 204 , a laser diode element 203 , a recording medium 201 and an optical signal detector 202 . The optical element 204 also includes a light splitting element 204a, a reflective coating device 204b and an objective lens 204d.

The laser diode 203 emits 1-3 kinds of linearly polarized light with different wavelengths λ ₁ -λ ₃ but with the same polarization direction. The linearly polarized light is projected on a recording medium 201 through the light splitting element 204a, the reflective coating device 204b, the coupling mirror 204c (optional), and the objective lens 204d. Then it is reflected to the objective lens 204d, the coupling mirror 204c and the reflective coating device 204b through the surface of the recording medium 201 in sequence. The light beam passing through the reflective coating device 204 b is received and detected by the optical signal detector 202 . The light beam reflected by the reflective coating device 204b is finally fed back to the laser diode light emitting cavity 203a.

The recording medium 201 records or reads data using emitted laser light. The optical signal detector 202 receives the laser light reflected by the recording medium 201 and detects the intensity of the laser signal. The light splitting element 204a, such as a grating, splits the laser beam into three beams from one beam. The objective lens 204d has a fixed focal length and focuses the laser light into one point. The coupling mirror 204c makes the laser beam into a collimated beam, which is an optional component. The reflective coating device 204b transmits a part of the laser light and reflects the other part, and has the functions of transmission and reflection.

As shown in Figure 2, when the laser diode 203 emits 1 to 3 linearly polarized lights with different wavelengths λ ₁ to λ ₃ but with the same polarization direction 109, the linearly polarized light will be polarized at the angle of polarization α (refer to Figure 4) and the angle of incidence β The linearly polarized light having one or two or three wavelengths λ ₁ -λ ₃ is converted into circularly polarized light or elliptically polarized light 108 through the reflective coating device 204 b. This circularly polarized light or elliptically polarized light 108 is still circularly polarized or elliptically polarized light 108 through the surface reflection of recording medium 201, and will have one or two or three circular polarized light of wavelength λ ₁ ～λ ₃ through reflective coating device 204b again. The polarized light or elliptically polarized light is converted into linearly polarized light 110, and fed back to the laser diode light emitting cavity 203a.

The reflective coating device 204b is composed of one or more reflectors, or a combination of more than one reflector and light-transmitting lenses, so that the linearly polarized light fed back to the laser diode light-emitting cavity 203a and the original linearly polarized light The angle change reaches 90°.

Without loss of generality, FIG. 3 illustrates an embodiment of the optical read-write head of the present invention by taking a reflective coating device with two mirrors as an example. In FIG. 3 , the reflective coating device 304b formed by the combination of mirrors 3041 and 3042 is used to change the linear polarization angles of the feedback light 210 and the outgoing light 209 by 90°.

Fig. 4 shows the arrangement between the linear polarization direction of the linearly polarized light emitted by the laser diode and the incident angle of the reflective coating device in the present invention. Referring to FIG. 4 , the linear polarization direction 109 of the linearly polarized light emitted by the laser diode is incident on the reflective coating device at a polarization angle α and the incident angle with the reflective coating device is β. In this arrangement, the phase angle difference (phase angle) between the "P" state (P state) and the "S" state (S state) of linearly polarized light with one or two or three wavelengths λ ₁ to λ ₃ is reduced by the reflective coating device. delay) is 90°±60°, that is, it is transformed into circularly polarized light (with a phase angle difference of 90°) or elliptically polarized light 108 (with a phase angle difference of 30°˜150°). The angle α of the linearly polarized light may range from 10° to 80° or from 100° to 170°. The incident angle β may range from 15° to 85°.

In FIG. 3 , the outgoing light 209 is transformed into circularly polarized light or _elliptically polarized light 108 by the two reflective mirrors 3041 and ₃₀₄₂ of the reflective coating device 304b. This circularly polarized light or elliptically polarized light 108 is reflected by the surface of the recording medium 201, and passes through the two reflection mirrors 3041 and 3042 of the reflective coating device again, so that the linearly polarized light of one or two or three wavelengths λ ₁ to λ ₃ The phase angle difference between the "P" state and the "S" state of the laser diode is 180°, that is, the linear polarization direction 110 is about 90° from the original linear polarization direction 109, and is fed back to the laser diode light-emitting cavity 203a.

Accordingly, the reflective coating device 304 b changes the linear polarization angle of the outgoing light 209 and the linear polarization angle of the feedback light 210 by 90°. Therefore, the purpose of reducing the relative intensity noise generated by the laser diode due to the feedback light 210 fed back from the recording medium 201 is achieved.

In the optical read-write head of the present invention, the cost of the relevant reflective coating device technology is less than that of the known technology, thus relatively reducing the production cost. Moreover, this technology effectively controls the generation of relative intensity noise of the laser diode to the feedback light, thereby improving the competitiveness of related operators.

However, the above descriptions are only exemplary embodiments of the present invention, and should not limit the implementation scope of the present invention. That is, all equivalent changes and modifications made according to the scope of the claims of the present invention shall fall within the scope of the present invention.

Claims (9)

1. An optical read-write head, comprising: A laser diode element, which is a linearly polarized light source of laser light, used to emit linearly polarized light; A recording medium, which utilizes the laser to record or read data; An optical signal detector, which receives the signal and detects the strength of the laser signal reflected by the recording medium; and An optical element, which includes a light splitting element, a reflective coating device and an objective lens; The optical element is located between the laser diode element, the recording medium and the optical signal detector, the reflective coating device reflects the linearly polarized light of the laser light source, converts the linearly polarized light into circularly polarized light or elliptically polarized light and Focusing and projecting onto the recording medium, and then guiding the circularly polarized light or elliptically polarized light reflected by the recording medium and penetrating the reflective coating device to the optical signal detector, and reflecting the recording medium back The circularly polarized light or elliptically polarized light reflected by the reflective coating device is fed back to the laser diode element. 2. The optical read-write head as claimed in claim 1, wherein the reflective coating device changes the phase angle difference and polarization direction of the laser light. 3 . The optical read/write head according to claim 1 , wherein the laser diode element emits 1 to 3 kinds of laser light with different wavelengths, which are linearly polarized light with the same polarization direction. 4 . 4. The optical read-write head as claimed in claim 1, wherein the laser light of the laser diode element passes through the reflective coating device with the linear polarization direction as an angle α and an incident angle β, and the angle α is between 10° ~80° or between 100°~170°, the incident angle β is between 15°~85°. 5 . The optical read-write head according to claim 1 , wherein the reflective coating device is composed of one or more reflective mirrors, or a combination of more than one reflective mirrors and a light-transmitting lens. 6. The optical read-write head as claimed in claim 1, wherein the reflective coating device converts the linearly polarized light of one or two or three lasers with 1 to 3 wavelengths into an absolute value of the phase angle difference |P-state phase-S-state phase|=(2n+1)×90°circularly polarized light, where n=an integer of 0, 1, 2, 3.... 7. The optical read-write head as claimed in claim 1, wherein the reflective coating device converts the linearly polarized light of one or two or three lasers with 1 to 3 wavelengths into an absolute value of the phase angle difference |P-state phase-S-state phase|=(2n+1)×90°±60° elliptically polarized light, where n=0, 1, 2, 3... an integer. 8. The optical read-write head as claimed in claim 1, wherein the optical element further comprises a coupling mirror for adjusting the collimation of the laser light and increasing the optical coupling effect. 9. The optical read-write head as claimed in claim 1, wherein the light splitting element is a grating.

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