KR100421008B1 - Method of making multi-beams and an optical pickup apparatus employing it - Google Patents

Abstract

Disclosed are a method for forming multiple lights using a dual beam splitter or sawtooth grating that is easy to manufacture, and an optical pickup apparatus employing the same.

This disclosed multiple light formation method comprises the steps of reflecting light from a light source through a first reflective layer having a first reflective surface having a first reflectance to produce a first beam and transmitting the remaining light; Reflecting the transmitted light through a second reflecting surface having a second reflectance; Transmitting the reflected light through the first reflection surface to generate a second beam, and reflecting the remaining light; And splitting the reflected light into a plurality of beams by transmission or reflection through the second reflection surface and the first reflection surface.

In addition, the disclosed optical pickup apparatus includes a light source, an optical path converter for converting a path of light emitted from the light source, an objective lens for focusing the light incident from the optical path converter on an optical disk, and a photodetector for receiving light reflected from the optical disk. In the optical pickup device comprising a sawtooth grating for making the light incident from the light source into a plurality of multiple light.

The dual beam splitter or sawtooth grating has an advantage of easy manufacturing and low manufacturing cost.

Description

Method for making multi-beams and an optical pickup apparatus employing it

The present invention relates to a method for forming multiple light using a dual beam splitter or sawtooth grating easy to manufacture and an optical pickup device employing the same.

An optical pickup apparatus is an apparatus that records by recording light onto a recording surface of a recording medium such as an optical disc, or reproduces information recorded on the recording medium. In general, the optical pickup device, as shown in FIG. 1, has passed through a light source 10, an optical path converter 15 for converting a path of light emitted from the light source 10, and the optical path converter 15. An objective lens 45 for focusing light onto the optical disc 50 and a photodetector 60 reflected from the optical disc 50 to receive light through the objective lens 45 and the optical path converter 15. It is configured to include. In addition, the collimating lens 40, which makes the light passed through the optical path converter 15 in parallel, and the light reflected by the optical disk 50 and returned, pass through the coma aberration generated through the optical path converter 15. A condenser lens 55 may be further provided to remove and converge the photodetector 60. Reference numeral 35 denotes a reflection mirror.

In the optical pickup device as described above, the light reflected from the optical disk 50 is returned by the photodetector 60 to be converted into video / audio signals and electrical signals of tracking servos and focusing servos and recorded on the optical disks. Read the information. However, in recent years, a faster playback speed is required, and efforts have been made to increase the rotational speed of an optical disc in accordance with such a demand. However, due to the mechanical limitation of the rotational speed of the step motor for rotating the optical disk, there is no choice but to limit the high speed response force. As another method, a method of increasing the reproduction speed has been developed by making light from a light source into multiple lights so that a plurality of tracks formed on a recording surface of an optical disc can be simultaneously reproduced.

As a method of forming multiple lights in the related art, a method of making light emitted from the light source 10 into multiple lights using the hologram 13 as shown in FIGS. 1 and 2 has been proposed. The hologram 13 divides incident light into 0th order light, ± 1st order light, ± 2nd order light. Here, the interval between the multiple lights and the light intensity are adjusted by adjusting the depth w and the pitch p of the unevenness 13a formed on the incident surface of the hologram 13. However, the hologram is difficult to manufacture and the manufacturing cost is expensive.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for forming a multi-beam using a dual beam splitter or sawtooth grating easy to manufacture and an optical pickup device employing the same.

1 is a schematic layout view of a general optical pickup device.

2 is a view showing a hologram device for forming a conventional multiple light.

3 and 4 are diagrams illustrating a dual beam splitter used in a multiple light forming method according to an embodiment of the present invention.

5 is a diagram illustrating grating used in a multiple light forming method according to another exemplary embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

10 ... light source 15 ... optical converter

40,155 ... collimating lens 45 ... Objective lens

50 ... optical disk 60 ... photodetector

100,100 '... double beam splitter 105a, 120a ... first reflecting surface

105,120 ... 1st reflective layer 110a, 120b ... 2nd reflective surface

150 ... Serrated grating R1 ... First reflectance

R2 ... Second reflectance

In order to achieve the above object, in the multiple light forming method according to the present invention, the light from the light source is reflected through a first reflecting layer having a first reflecting surface having a first reflectance, thereby generating a first beam, and transmitting the remaining light. Making a step; Reflecting the transmitted light through a second reflecting surface having a second reflectance; Transmitting the reflected light through the first reflection surface to generate a second beam, and reflecting the remaining light; And splitting the reflected light into a plurality of beams by transmission or reflection through the second reflection surface and the first reflection surface.

In addition, the first reflectance is characterized in that less than 0.5.

In addition, the second reflectance is characterized in that greater than 0.5.

In addition, the second reflection surface is characterized in that the total reflection surface.

The method may further include adjusting an interval between the plurality of multiple lights by adjusting at least one of a thickness and a refractive index of the first reflective layer.

In order to achieve the above object, an optical pickup apparatus according to the present invention includes a light source, an optical path converter for converting a path of light emitted from the light source, an objective lens for focusing light incident from the optical path converter on an optical disc, and reflected from the optical disc. An optical pickup apparatus comprising a photodetector for receiving light, comprising: a first reflecting surface reflecting incident light at a first reflectance on a light path between the light source and an optical path converter and transmitting the remaining light; And a dual beam splitter having a second reflecting surface for reflecting light incident therefrom and transmitted at a second reflectance.

The photodetector may be configured as a plurality of photodetectors so that the plurality of multiple lights may be reflected from the optical disk to be received, respectively.

In order to achieve the above object, an optical pickup apparatus according to the present invention includes a light source, an optical path converter for converting a path of light emitted from the light source, an objective lens for focusing light incident from the optical path converter on an optical disc, and reflected from the optical disc. An optical pickup apparatus including a photodetector in which light is received, characterized in that it comprises a sawtooth grating for making the light incident from the light source into a plurality of multiple lights.

Hereinafter, a method for forming multiple light according to the present invention and an optical pickup apparatus employing the same will be described in detail with reference to the accompanying drawings.

Here, in the optical pickup device illustrated in FIG. 1, other elements except for the hologram 13 may be equally used in the present invention.

In the multiple light forming method according to the present invention, referring to FIG. 3, the first reflective layer 105 having the first reflecting surface 105a having the first reflectance R1 as the light S incident from the light source 10 is formed. Partially reflecting through and partially transmitting the light; and partially reflecting and partially transmitting the transmitted light through the second reflecting layer 110 having the second reflecting surface 110a having the second reflectance R2. It includes;

When the light amount of the light emitted from the light source 10 is S, when the light from the light source 10 is incident on the first reflection surface 105a, the light of S * R1 is reflected and the first light (I) Will be emitted. And the remaining S * (1-R1) is transmitted through the second reflection surface (110a). Then, light of S (1-R1) R2 is reflected from the second reflecting surface 110a to the first reflecting surface 105a. As much as (1-R1) of the reflected light of S (1-R1) R2, that is, S (1-R1) ² R2 is transmitted through the first reflecting surface 105a and the second light (II) Will be emitted.

In addition, light as much as R1 of the light of S (1-R1) R2, that is, light of S (1-R1) R2 * R1 is reflected from the first reflecting surface 105a and thus the second reflecting surface 110a. Headed to. The light is partially reflected by the second reflecting surface 110a and transmitted through the first reflecting surface 105a to be emitted as the third light III. As this process continues, the light from the light source 10 is split into multiple lights and directed to the optical disc 50 via the collimating lens 40 and the objective lens 45. S1, S2, and S3, respectively, the amount of light of the first light (I), the second light (II) and the third light (III) according to the first reflectance (R1) and the second reflectance (R2) is as follows. The same relation holds.

When the first reflectance R1 of the first reflecting surface 105a is 0.5, for example, and the second reflectance R2 of the second reflecting surface 110a is 0.5, for example, the first light ( The light quantity ratio of I, 2nd light (II), and 3rd light (III) is as follows. Here, the light quantity is expressed as a percentage. The light S from the light source 10 reflects 50% of the light from the first reflecting surface 105a, and transmits the remaining 50% of the light toward the second reflecting surface 110a. In addition, 25% of light is reflected from the second reflecting surface 110a to the first reflecting surface 105a. Subsequently, 12.5% of the light, which is half of the light, passes through the first reflection surface 105a and is emitted as the second light II.

The first reflectance R1 is 0.5 or less and the second reflectance R2 to increase and uniformly distribute the amounts of light of the first light I, the second light II and the third light III. It is good to set it as 0.5 or more. More preferably, it is preferable to totally reflect the second reflecting surface 110a.

In addition, as shown in FIG. 4, the first reflection surface 120a having the first reflectance R1 is coated on one surface of the first reflection layer 120, and the second half having the second reflection factor R2 on the other surface. The slope 120b may be coated. Here, light is divided by using the second reflection surface 120b as a total reflection surface.

On the other hand, when the interval between multiple lights such as the first light (I), the second light (II), the third light (III), and the like is d, this interval d can be adjusted according to the track pitch of the optical disc. The distance d between the multiple lights may be controlled by the thickness t of the first reflection layers 105 and 120 and the refractive index n of the first reflection layers 105 and 120. The process is expressed as a formula as follows. Here, the angle of incidence from the light source 10 to the first reflective surfaces 105a and 120a is referred to as θ1, and the incident angle to the second reflective surfaces 110a and 120b is referred to as θ2. θ3 represents a transmission angle to the second reflection layer 110. In addition, a distance between the neighboring normals of the first reflecting surfaces 105a and 120a and the second reflecting surfaces 110a and 120b is referred to as a. At this time, θ1 = 45 °.

First, the following relation holds according to Snell's law.

In the above equation, the relationship of a = t * tanθ ₂ is used, and the following conditional expression can be obtained by substituting the relationship of Equation 2 into Equation 3 above.

According to Equation 4, the distance d between the multiple lights I, II and III may be adjusted by adjusting the refractive index n and the thickness t of the first reflection layers 105 and 120. .

Next, an optical pickup apparatus employing the multiple light forming method as described above will be described. Here, elements having the same function and the same structure as those in the optical pickup apparatus shown in Fig. 1 use the same reference numerals.

An optical pickup apparatus according to the present invention includes a light source 10, an optical path converter 15 for converting a path of light S emitted from the light source 10, and an optical disk (10) to receive light incident from the optical path converter 15. An objective lens 45 for focusing at 50, and a photodetector 60 for receiving the light reflected from the optical disk 50, and as shown in FIGS. 3 and 4, the light source 10 and the optical path converter. A first reflecting surface 105a reflecting incident light at a first reflectance R1 and transmitting the remaining light on the optical path between the first and second reflecting surfaces 105a and 120a Dual beam splitters 100 and 100 ′ having second reflecting surfaces 110a and 120b reflecting incident light at a second reflectance R2.

The collimating lens 40 may further include a collimating lens 40 that makes the multiple lights (I) (II) (III) formed by the dual beam splitters 100 and 100 'into parallel lights. In addition, a plurality of photodetectors corresponding to each of the plurality of light (I) (II) (III) may be provided to receive and detect the light reflected from the optical disk 50, respectively.

As another example, as shown in FIG. 5, the sawtooth grating 150 may be used to form multiple light I ′ (II ′) (III ′) (IV ′) (V ′). In addition, the collimating lens 155 is provided to make the multiple light formed by the sawtooth grating 150 into parallel light. Here, the distance d 'between the multiple lights may be adjusted by adjusting the depth m and the distance n of the sawtooth unevenness 150a. The serrated grating 150 has an advantage that it is easy to manufacture compared to the hologram.

The multiple beam forming method according to the present invention and the dual beam splitter or the sawtooth grating used in the optical pickup apparatus employing the same are easy to manufacture, low in manufacturing cost, and easy to adjust the spacing between the multiple lights. You can get a signal.

Claims (12)

Reflecting light from the light source through a first reflective layer having a first reflective surface having a first reflectance to produce a first beam, and transmitting the remaining light; Reflecting light transmitted through the first reflective layer through a second reflective surface having a second reflectance; Transmitting the light reflected from the second reflecting surface through the first reflecting surface to generate a second beam, and reflecting the remaining light; And reflecting or transmitting the light reflected from the first reflection surface through the second reflection surface and the first reflection surface to form a plurality of beams. The method of claim 1, wherein said first reflectance is less than 0.5. The method of claim 2, And said second reflectance is greater than 0.5. The method according to claim 1 or 2, And said second reflecting surface is a total reflecting surface. The method of claim 1, And adjusting an interval between the plurality of multiple lights by adjusting at least one of a thickness and a refractive index of the first reflective layer. An optical pickup apparatus comprising a light source, an optical path converter for converting a path of light emitted from the light source, an objective lens for focusing light incident from the optical path converter on an optical disk, and a photodetector for receiving light reflected from the optical disk. A first reflection surface that reflects incident light at a first reflectance on the optical path between the light source and the optical path transducer, and transmits the remaining light; and a first reflection surface that reflects light transmitted through the first reflection surface at a second reflectance And a dual beam splitter having a second reflecting surface facing a slope. The optical pickup apparatus of claim 6, wherein the first reflectance is less than 0.5. The method of claim 7, wherein And said second reflectance is greater than 0.5. The method according to claim 6 or 7, And said second reflecting surface is a total reflecting surface. The method of claim 6, And a collimating lens for making the plurality of multiple lights formed by the first reflecting surface and the second reflecting surface into parallel light. The method according to claim 6 or 10, wherein the photodetector, And a plurality of photodetectors so that the plurality of multiple lights can be reflected from the optical disk and received respectively. An optical pickup apparatus comprising a light source, an optical path converter for converting a path of light emitted from the light source, an objective lens for focusing light incident from the optical path converter on an optical disk, and a photodetector for receiving light reflected from the optical disk. And multiplexed light focused on the optical disk, including a sawtooth grating that makes the light incident from the light source into a plurality of multiplexed lights.