CN1291395C - Optical reading/writing system - Google Patents

Abstract

An optical reading/writing system includes a first optical transceiver unit, a second optical transceiver unit, a collimating lens, an objective lens and a composite prism. The first optical transceiver unit has a first light source for emitting a first incident beam of a first wavelength, and the second optical transceiver unit has a second light source for emitting a second incident beam of a second wavelength. greater than the first wavelength. Both the collimator lens and the objective lens have optical parameters corresponding to the first wavelength. The composite prism is arranged between the first and second optical transceiver units and the collimating lens, and has a first part and a second part, the first and second parts are oppositely arranged, and the first part has a light incident surface and at least two reflectors The second part has a light emitting surface and at least two reflecting surfaces. The light-incident surface and the light-exit surface are arranged facing the first and second incident light beams and the collimating lens respectively, and the first and second incident light beams are reflected by the plurality of reflective surfaces and then exit facing the collimating lens.

Description

Optical read/write system

【Technical field】

The invention relates to an optical disc recording/reproducing system, in particular to a high-density optical reading/writing system compatible with optical discs of different specifications.

【Background technique】

The optical read/write system used in the recording/reproducing device mainly utilizes a series of optical components to focus the laser light of a specific wavelength emitted by the laser into a spot and focus it on the optical disc to realize the read/write operation on the optical disc. With the continuous evolution of optical disc specifications from CD, DVD to HD-DVD, the information tracks of optical discs are made more and more compact, which requires the smaller the light spot for reading/writing information on optical discs. The size of the spot is related to the wavelength of the laser and the numerical aperture (NA) of the objective lens. The size of the spot is proportional to the wavelength of the laser and inversely proportional to the numerical aperture (NA) of the objective lens. In this way, the evolution of optical disc specifications to high density leads to the continuous reduction of the wavelength of the laser light and the continuous increase of the numerical aperture (NA) of the objective lens. The changes of wavelength and numerical aperture (NA) with disc specifications are shown in the table below: Disc Specifications cd DVD HD-DVD wavelength 780nm 650nm 405nm Numerical aperture (NA) 0.45 0.6 0.65 or 0.8

Due to the different optical parameters of different optical disc specifications, the compatibility problem of each specification becomes prominent. To read/write information on an optical disc of a specific specification, it is necessary to use an optical component that meets the specification of the optical disc, otherwise, it will cause the possibility of misreading/writing. However, it is obviously not wise to design a corresponding optical read/write system for each specification in order to realize the read/write operation to a variety of optical discs in a set of optical read/write devices. The excessive volume of the device makes the optical system complicated and increases the cost. In existing optical read/write devices, such as hybrid HD-DVD and DVD optical read/write devices, it has a HD-DVD laser and a DVD laser, respectively emitting blue light with a wavelength of about 405nm and red light with a wavelength of 650nm, and After entering the respective diffractive elements, they pass through the shared optical components such as the beam splitting prism, collimating lens, mirror and objective lens, and then converge to the optical disc for reading/writing information. This optical read/write device can reduce its volume to a certain extent by sharing some optical components. Since the collimating lens can only converge the light beam emitted from its focal plane into parallel light, that is, the optical path distance between the laser and the collimating lens is a fixed value. In existing optical read/write devices, the laser is arranged on the focal plane of the collimator lens in order to satisfy the condition that the optical path distance is a fixed value. However, the spatial distance between the laser and the collimator lens is just an important factor affecting the volume of the optical read/write device. Although the number of optical components in the existing optical read/write device has been reduced, the distance between the laser and the collimator lens has not been shortened. The spatial distance, so its reduction in the size of the optical read/write device is limited.

【Content of invention】

The technical problem to be solved by the present invention is to provide an optical reading/writing system used in recording/reproducing devices of different optical disc specifications, which can reduce the volume of the optical reading/writing device.

The invention provides an optical reading/writing system, which includes a first optical transceiver unit, a second optical transceiver unit, a collimating lens, an objective lens and a composite prism. The first optical transceiver unit has a first light source for emitting a first incident beam of a first wavelength, and the second optical transceiver unit has a second light source for emitting a second incident beam of a second wavelength. greater than the first wavelength. Both the collimator lens and the objective lens have optical parameters corresponding to the first wavelength. The composite prism is arranged between the first and second optical transceiver units and the collimating lens, and has a first part and a second part, the first and second parts are oppositely arranged, and the first part has a light incident surface and at least two reflectors The second part has a light emitting surface and at least two reflecting surfaces. The light-incident surface and the light-exit surface are arranged facing the first and second incident light beams and the collimating lens respectively, and the first and second incident light beams are reflected by the plurality of reflective surfaces and then exit facing the collimating lens.

Compared with the prior art, in the optical read/write system of the present invention, the optical paths of the first and second incident light beams share some optical components, thereby reducing the number of optical components required by the optical read/write system, and at the same time, the shared prism The unit and the composite prism shorten the space distance between the first and second optical transceiver units and the collimating lens while ensuring that the total optical path of the optical path remains unchanged, so that the device using the optical read/write system can be effectively reduced volume.

【Description of drawings】

Fig. 1 is a schematic diagram of the optical read/write system of the present invention.

FIG. 2 is a top view of a prism unit of the optical read/write system of FIG. 1 .

Fig. 3 is a front view of the composite prism of the optical read/write system of Fig. 1 .

FIG. 4 is a top view of the wavelength selective plate of the optical read/write system of FIG. 1. FIG.

Fig. 5 is a cross-sectional view of the wavelength selection sheet of Fig. 4 taken along line V-V.

【Detailed ways】

Please refer to FIG. 1 , which is a schematic diagram of an optical read/write system 100 of the present invention. The optical reading/writing system 100 of the present invention is suitable for recording/reproducing devices of different optical disc specifications. This embodiment takes an optical reading/writing system suitable for HD-DVD recording/reproducing devices as an example. Optical read/write system 100 comprises a first optical transceiver unit 11, a second optical transceiver unit 12, a first diffraction element 21, a second diffraction element 22, a prism unit 3, a composite prism 4, a collimator Lens 5 , a mirror 6 , a wavelength selection plate 7 and an objective lens 8 .

The first and second optical transceiver units 11 and 12 are arranged in parallel and juxtaposed. The first optical transceiver unit 11 has a first light source (not marked) and a first detector (not marked). The first light source emits a first incident light beam, and the first incident light beam has a first wavelength. The first detector detects the first reflected light beam returning from the optical disc. The second optical transceiver unit 12 includes a second light source (not marked) and a second detector (not marked). The second light source emits a second incident beam having a second wavelength. The second detector detects the second reflected light beam returning from the optical disc. In this embodiment, the first and second wavelengths are blue light with a wavelength of 405 nm for readable/writable HD-DVD standard discs and red light with a wavelength of 650 nm for readable/writable DVD standard discs.

The first diffractive element 21 and the second diffractive element 22 are arranged facing the first and second light sources of the first and second optical transceiving units 11 and 12 respectively.

Please refer to FIG. 2 , which is a top view of the prism unit 3 of the optical read/write system 100 of the present invention. The prism unit 3 includes a first prism 31 , a second prism 32 , and a third prism 33 , and the first and second prisms 31 and 32 are located on the same side of the third prism 33 . The first, second and third prisms 31, 32 and 33 are all quadrangular prism structures. The first prism 31 has a parallelogram cross section, that is, the first light incident surface 310 of the first prism 31 is parallel to the first light output surface 311 , and the two first reflective surfaces 312 and 313 are parallel to each other. The first reflective surface 312 forms an included angle of 45 degrees with the first light incident surface 310 . The second prism 32 has a second light incident surface 320 and a second light exit surface 321. The second light exit surface 321 has an aspherical structure to correct the spherical aberration generated by the DVD optical path. The third light incident surface 330 of the third prism 33 is parallel to the third light exit surface 331, one end of the third prism 33 has a third reflective surface 332 at an angle of 45 degrees with the third light incident surface, and the other end has a third reflection surface 332 with the third light incident surface. The three reflection surfaces 332 are parallel to the optical path conversion interface 333, which has different reflection or transmission functions for incident light of different wavelengths.

Please refer to FIG. 3 , which is a front view of the compound prism 4 of the present invention. The composite prism 4 includes first and second parts 41 and 42 . The first part 41 and the second part 42 are prisms made of the same material. The first portion 41 has a quadrangular cross-section and includes a fourth incident surface 410 , a fourth reflective surface 411 , a fifth reflective surface 412 , and a missing edge 413 . The second portion 42 also has a quadrangular cross-section, which includes a fourth light-emitting surface 420 , a sixth reflective surface 421 , a seventh reflective surface 422 , and a missing edge 423 . The fourth light incident surface 410 is parallel to the fourth light exit surface 420 . The first and second parts 41, 42 are combined with the fourth reflective surface 411 and the sixth reflective surface 421, and the fourth reflective surface 411 and the sixth reflective surface 421 are only coated with reflective film in their partial areas respectively, so as to make the incident Beams incident on coated areas are reflected and beams incident on uncoated areas are transmitted. The missing edges 413 and 423 are formed by cutting off a part of the material at a corner of the first and second parts 41 and 42 in order to save material, and the cut part is limited to not affect the internal optical transmission of the composite prism 4 . The composite prism 4 is arranged between the first and second optical transceiver units 11 and 12 and the collimator lens 5 , and is arranged in the common optical path of the first and second incident light beams. The basic parameters of the compound prism 4 are: a=4mm, b=4.828mm, =45 degrees, θ=112.5 degrees, β=67.5 degrees.

The collimating lens 5 is disposed facing the fourth light-emitting surface 420 of the composite prism 4 . The collimating lens 5 is designed for the first incident light beam with a shorter wavelength adopted by the HD-DVD standard, and it can convert the first incident light beam with the first wavelength into a parallel light beam, and the DVD standard shown in this embodiment A second incident light beam of a second wavelength is employed and converted into approximately parallel light.

The objective lens 8 is set facing the optical disk, has an aspherical structure, and is also designed for the wavelength and numerical aperture (NA) adopted by the HD-DVD standard.

Please refer to Figure 4 and Figure 5 at the same time. The wavelength selection plate 7 is located between the objective lens 8 and the reflector 6. The wavelength selection plate 7 has an inner circle area A and an outer circle area B. The inner circle area A can allow light beams with a shorter first wavelength and a longer second wavelength. Passing, the outer ring region B only allows light beams of the shorter first wavelength to pass through.

Please refer to FIG. 1 again. When reading/writing an HD-DVD disc, the first incident beam of the first light source of the first optical transceiver unit 11 passes through the first diffractive element 21 and passes through the first incident surface 310 of the first prism 31. incident, and two reflections occur on the first reflective surfaces 312 and 313. Since the first reflective surfaces 312 and 313 are parallel to each other, the outgoing direction of the first incident light beam emitted from the first light emitting surface 311 is consistent with the incident direction of the first incident light beam incident from the first light incident surface 310 . The emitted first incident light beam enters the optical path conversion interface 333 from the third incident surface 330 of the third prism 33 . Since the optical path conversion interface 333 is designed to transmit the first incident light beam of the first wavelength and reflect the second incident light beam of the second wavelength, the first incident light beam is transmitted through the optical path conversion interface 333 and then emerges from the third light output surface 331 .

The first incident light beam emitted from the third prism 33 enters the fourth reflective surface 411 through the fourth incident surface 410 of the compound mirror 4 . Since the fourth reflective surface 411 is partially coated with a reflective film, the first incident light beam incident on the fourth reflective surface 411 is reflected for the first time. The first incident light beam after the first reflection is second reflected by the fifth reflective surface 412 coated with a reflective film, and then reaches the junction of the fourth reflective surface 411 and the sixth reflective surface 421 . At this time, since the fourth reflective surface 411 and the sixth reflective surface 421 are only partially coated with a reflective film, the first incident light beam reflected for the second time will not be blocked. Therefore, the first incident light beam is transmitted from the region of the fourth reflective surface 411 not coated with a reflective film to the fourth light-emitting surface 420 .

According to the principle of total reflection of light, when light is transmitted from an optically dense medium to an optically sparse medium, if the incident angle is greater than or equal to the critical angle C of total reflection, the incident light will be totally reflected at the interface of the two media without being transmitted out of the optically dense medium , On the contrary, if the incident angle is less than the critical angle C of total reflection, the incident light will be transmitted out of the optically dense medium and into the optically sparse medium. Therefore, the first incident light beam is totally reflected on the fourth light emitting surface 420 (that is, the third reflection). The critical angle C of total reflection can be calculated according to the formula C=arcsin(l/n), where n is the refractive index of the optically dense medium. The optically dense medium of this embodiment is a compound prism, and its refractive index is n. According to the above formula and the incident angle I of the first incident light beam transmitted from the fourth reflection surface 411 to the fourth light exit surface 420 is greater than the total reflection angle C, Therefore, the first incident light beam can be totally reflected on the fourth light output surface 420 and not transmitted out. The totally reflected first incident light beam is reflected for the fourth time on the seventh reflective surface 422 coated with a reflective film, and then reflected for the fifth time on the sixth reflective surface 421 . The first incident light beam reflected for the fifth time on the sixth reflection surface 421 is incident on the fourth light exit surface 420 again, and since the incident angle is smaller than the total reflection angle C at this time, the first incident light beam incident on the fourth light exit surface 420 again can be Emit from the fourth light-emitting surface 420 to the collimator lens 5 .

The first incident light beam emitted from the fourth light output surface 420 is collimated into a parallel light beam by the collimator lens 5 designed for the first incident light beam with the first wavelength. Reflected by the reflector 6 to the wavelength selective plate 7 . The wavelength selection sheet 7 has an inner circle area A and an outer ring area B, the inner circle area A can allow light beams with a shorter first wavelength and a longer second wavelength to pass through, and the outer ring area B only allows the shorter first wavelength beam of light passes through. The first incident light beam reflected by the mirror 6 passes through the wavelength selective plate 7 and is converged into a light spot by the objective lens 8 for reading/writing information from an HD-DVD disc (not shown). The first reflected light beam reflected from the surface of the optical disk returns through the objective lens 7, and its returning light path is substantially the same as the incident light path. The difference is that the first reflected beam is refracted by the first diffractive element 21 after passing through the first diffractive element 21, and the refracted first reflected beam is projected onto the first detector (not shown) on the first optical transceiver unit 11 , the first detector converts the optical signal into an electrical signal and outputs it to a related circuit.

Since the optical parameters of various optical components included in the optical path of the first incident light beam and the first reflected light beam are designed according to the HD-DVD standard, there will be no aberration caused by the collimating lens and the objective lens. At the same time, the prism unit 3 and the compound prism 4 shorten the spatial distance between the optical transceiver unit 11 and the collimator lens 5 while ensuring that the total optical path of the optical path remains constant, thereby effectively reducing the optical read/write system 100 using the optical read/write system 100. volume of the device.

When reading/writing a DVD disc, the second incident light beam emitted by the second light source of the second optical transceiver unit 12 passes through the second diffractive element 22 and enters from the second light incident surface 320 of the second prism 32, and is incident with an aspheric surface. The second light emitting surface 321 of the structure converges for the first time. The second incident light beam after the first convergence is incident from the third incident surface 330 of the third prism 33 , and is reflected to the optical path conversion interface 333 by the third reflecting surface 332 of the third prism 33 . The optical path conversion interface 333 has selectivity, it transmits the first incident light beam with the first wavelength (eg 405nm), and reflects the second incident light beam with the second wavelength (eg 650nm). Meanwhile, since the third reflective surface 332 is parallel to the optical path conversion interface 333 , the direction of the second reflected light beam exiting from the third light emitting surface 331 is consistent with the direction of incident from the third light incident surface 330 after two reflections.

The second incident light beam after the first convergence and exiting from the third prism 33 passes through the compound prism 4 in the same optical path as the first incident light beam, and then enters the collimator lens 5 . Since the optical parameters of the collimator lens 5 are designed for the first incident light beam with a shorter wavelength (first wavelength), it can only converge the second incident light beam into an approximately parallel light beam for the second time. The approximately parallel second incident light beam is reflected to the wavelength selection plate 7 through the reflector 6. Since the inner circle area A of the wavelength selection plate 7 allows incident light beams with shorter wavelengths and longer wavelengths (second wavelengths) to pass through, the outer ring area B only allows the incident beam of shorter wavelength (first wavelength) to pass through. Therefore, the second incident light beam can only pass through the inner circle area A, while the outer peripheral part of the second incident light beam is blocked by the outer circle area B and cannot pass through. The second incident light beam passing through the inner circle area A satisfies the smaller numerical aperture of the DVD specification, and it is incident on the objective lens 8 and converged by the objective lens 8 for the third time to form a light spot for reading/writing information from the DVD disc. The second reflected light beam reflected from the surface of the DVD disc returns through the objective lens 8, and its return light path is substantially the same as the incident light path. The difference is that the second reflected beam is refracted by the second diffractive element 21 after passing through the second diffractive element 21, and the refracted second reflected beam is projected onto the second detector (not shown) on the second optical transceiver unit 12 , the second detector converts the optical signal into an electrical signal and outputs it to a relevant circuit.

Although the optical parameters of the shared part of the optical components in the optical path of the second incident light beam and the first incident light beam are all designed with reference to the HD-DVD specification, the second incident light beam is converged three times through the second prism 32, the collimating lens 5 and the objective lens 8, and The wavelength selection plate 7 is used to make the second incident light beam meet the numerical aperture of the DVD standard, so that the aberration caused by the mismatch between the collimating lens and the objective lens can be effectively eliminated. Simultaneously, utilize prism unit 3 and compound prism 4 to shorten the spatial distance between optical transceiver unit 11 and collimator lens 5 under the condition that the total optical path of the optical path is guaranteed to be constant, and then effectively reduce the use of the optical read/write The volume of the device of the system 100.

Claims (10)

1. optical read/write system, it comprises one first smooth Transmit-Receive Unit, one second smooth Transmit-Receive Unit, collimation lens, object lens and a composite prism, this first smooth Transmit-Receive Unit has first light source in order to first incident beam that sends first wavelength; This second smooth Transmit-Receive Unit has a secondary light source in order to second incident beam that sends second wavelength, and this second wavelength is greater than first wavelength; This collimation lens and object lens all have and the corresponding optical parametric of first wavelength; This composite prism has a first, one second portion, this is first years old, second portion is oppositely arranged, first has quadrangular section, it comprises one the 4th incidence surface, one the 4th reflecting surface and one the 5th reflecting surface, this second portion has quadrangular section, it comprises one the 4th exiting surface, one the 6th reflecting surface and one the 7th reflecting surface, the 4th incidence surface of first is parallel with the 4th exiting surface of second portion, first and second portion combine with the 6th reflecting surface of second portion by the 4th reflecting surface of first, the 4th reflecting surface, the 6th reflecting surface only is coated with reflectance coating in its subregion respectively, with so that be incident to the beam reflection of coating film area, and make and be incident to the not light beam transmission of coating film area, it is characterized in that: described composite prism is located at first, between the second smooth Transmit-Receive Unit and the collimation lens, and this incidence surface and exiting surface are respectively over against first, second incident beam and collimation lens setting, first, second incident beam reflects the back over against the collimation lens outgoing at described a plurality of reflectings surface; This optical read/write system further comprises a prism unit, this prism unit comprises one second prism, this second prism is arranged between the second smooth Transmit-Receive Unit and the composite prism, this second prism has one second incidence surface and one second exiting surface, this second exiting surface is a non-spherical structure, and this second prism is used to transmit second incident beam.

2. optical read/write according to claim 1 system, it is characterized in that: the 4th incidence surface of this first and the 4th reflecting surface are in angle of 45 degrees, and become 112.5 degree angles with the 5th reflecting surface, first, second incident beam reflects at the 4th reflecting surface after the 4th incidence surface incident, and the light beam after the reflection reflection takes place and export second portion at the 5th reflecting surface.

3. optical read/write according to claim 1 system, it is characterized in that: the 6th reflecting surface of this second portion and the 4th exiting surface are in angle of 45 degrees, and become 67.5 degree angles with the 7th reflecting surface, first, second incident beam is transmitted through the 4th exiting surface and total reflection takes place, and the light beam after the total reflection successively exports collimation lens in the 7th, the 6th reflecting surface reflection back to from the 4th exiting surface.

4. optical read/write according to claim 1 system, it is characterized in that: the 4th incidence surface is parallel to the 4th exiting surface so that first, second incident beam from the direction of the 4th incidence surface incident with identical from the direction of the 4th exiting surface outgoing.

5. optical read/write according to claim 2 system, it is characterized in that: the 5th reflecting surface is coated with reflectance coating.

6. optical read/write according to claim 3 system, it is characterized in that: the 7th reflecting surface is coated with reflectance coating.

7. optical read/write according to claim 1 system, it is characterized in that: this prism unit further comprises one first prism and a prism, first prism is arranged in the light path of first incident beam, prism is arranged in the common light path of first, second incident beam, this first prism transmits first incident beam, and exporting it to prism, this prism will be exported by same position from first, second incident beam of different light paths.

8. optical read/write according to claim 7 system is characterized in that: the prism of this prism unit further comprises one for the first incident beam transmission and for the light path translation interface of second incident beam reflection.

9. optical read/write according to claim 1 system, it is characterized in that: these object lens have non-spherical structure.

10. optical read/write according to claim 1 system is characterized in that: sheet is selected in a wavelength is set near the object lens place by this optical read/write system.

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