KR19980060318A - Optical pickup device with light intensity control - Google Patents

Abstract

The present invention relates to an optical pickup apparatus having a light intensity control function capable of accurately accessing an optical disc by maintaining a constant intensity of a light beam generated from a light source.

An optical pickup apparatus according to the present invention includes a light source for generating a light beam to be irradiated to an optical disk, a first photodetector for detecting the intensity of the light beam generated from the light source, and an optical disk arranged side by side on the same plane as the first photodetector. And a second photodetector for detecting the light beam reflected by the light source, separating a part of the light beam from the light source toward the optical disk and the other part toward the first photodetector, and transferring the light beam reflected by the optical disk to the second detector. And an adaptive beam splitter and a controller for controlling the light source in accordance with the output signal of the first photodetector.

By such a configuration, the optical pickup apparatus according to the present invention can simplify the volume and configuration.

Description

Optical pickup device with light intensity control

1 is a diagram schematically showing the structure of a conventional optical pickup apparatus having a light intensity control function.

2 is a diagram schematically showing the structure of an optical pickup apparatus having a light intensity control function according to an embodiment of the present invention.

FIG. 3 shows the photodetector in detail in FIG.

Explanation of symbols for the main parts of the drawings

10,30 light source 12,32 objective lens

14,16,34: photodetector 18: beam splitter

20: partial mirror 22, 36C: λ / 4 plate

24,40: collimating lens 26,28,42: sensor lens

29 control unit 36 adaptive beam splitter

36A: Selective Reflective Surface 36B: Hexahedral Prism

36D: λ / 4 plate with total reflection surface 38: right angle prism

44: A-D converter 46: optical controller

48: support plate 50,52: light receiving element

The present invention relates to an optical pickup apparatus for optically accessing an optical disc, and more particularly, to an optical pickup apparatus having a light intensity control function capable of accurately accessing an optical disc by maintaining a constant intensity of the light beam.

A conventional optical pickup apparatus accesses an optical disc by irradiating a light beam onto the information recording surface of the optical disc. Accordingly, the optical pickup apparatus must maintain the intensity of the light beam traveling from the recording and player light source toward the information recording surface of the optical disk. In addition, the optical pickup device must irradiate a relatively light beam at the time of reproduction so as to change the material structure of the information recording surface of the optical disk during recording, and must generate a light beam of constant intensity. To this end, the optical pickup apparatus detects the intensity of the light beam generated by the light source using a separate photodetector for detecting the intensity of the light beam, and controls the light source by using an electrical signal from the photodetector.

However, the photodetector separately installed to detect the intensity of the light beam acted as a factor to increase the volume of the optical pickup device and to complicate the configuration of the optical pickup device. The problem of the conventional optical pickup apparatus will be described in detail with reference to FIG. 1.

Referring to FIG. 1, a conventional optical pickup apparatus includes a light source 10 generating a light beam to be irradiated onto an optical disc D, and focusing the light beam from the light source 10 in the form of a spot on the surface of the optical disc D. The objective lens 12, the first photodetector 14 for converting the light beam reflected by the optical disk D into an electrical signal, and the second photodetector for detecting the intensity of the light beam generated by the light source 10. (16) is provided. In addition, the conventional optical pickup device includes a beam splitter 18 and a partial mirror 20 arranged side by side between the light source 10 and the second photodetector 16, and between the partial mirror 20 and the objective lens 12. It is further provided with a λ / 4 plate 22 located.

The light beam generated by the light source 10 is either a vertical linearly polarized beam (i.e., TE wave, also referred to as S-wave) or a horizontal linearly polarized beam (i.e., TM wave, also referred to as P-wave), which flows in a short or long axis direction with respect to an ellipse. The process proceeds toward the partial mirror 20 via the splitter 18 and the collimation lens 24. In the partial mirror 20, most of the light beams from the collimation lens 24 (for example, about 70%) travel through the λ / 4 plate 22 and the objective lens 12 toward the optical disk D. And the rest (eg, about 30%) is passed through the second sensor lens 28 toward the second photodetector 16. The partial mirror 20 reflects the light beam reflected by the optical disk D via the objective lens 12 and the λ / 4 plate 22 to travel through the collimator lens 24 toward the beam splitter 18. . At this time, the light beam traveling through the collimating lens 24 toward the beam splitter 18 has a polarization characteristic different from that of the light beam generated by the light source 10. For example, when the light beam generated by the light source 10 is a vertical linearly polarized beam (ie, S wave), the light beam traveling through the collimation lens 24 toward the beam splitter 18 is a horizontal linearly polarized beam (ie, P wave). On the contrary, when the light beam generated from the light source 10 is a horizontal linearly polarized beam (that is, P wave), the light beam traveling through the collimation lens 24 toward the beam splitter 18 becomes a vertical linearly polarized beam (ie, S). Par). The beam splitter 18 selectively reflects the light beam in accordance with the polarization characteristic of the light beam, thereby passing the light beam from the light source 10 toward the collimation lens 24, and the light beam from the collimation lens 24 passes through the first sensor lens 26. B) to be directed toward the first photodetector 14.

Meanwhile, the second photodetector 16 receives a light beam incident from the light source 10 via the beam splitter 18, the collimating lens 24, the partial mirror 20, and the second sensor lens 28 to the amount of light. The signal is converted into an electrical signal having a corresponding voltage level, and the electrical signal is supplied to the controller 29. The controller 29 determines the intensity of the light beam generated by the light source 10 according to the voltage level of the electrical signal from the second photodetector 16 and accordingly results in the voltage of the driving signal supplied to the light source 10. Adjust As a result, the light beam generated from the light source 10 maintains a constant intensity.

As such, the conventional optical pickup apparatus must use another sensor lens for focusing the light beam by installing a separate photodetector to detect the intensity of the light beam generated from the light source. For this reason, the conventional optical pickup device has a disadvantage that the configuration is complicated as well as the butch.

Accordingly, an object of the present invention is to provide an optical pickup apparatus having three control functions of a light beam that can simplify the volume and configuration.

In order to achieve the above object, the optical pickup apparatus according to the present invention is a light source for generating a light beam to be irradiated on the optical disk, a first photodetector for detecting the intensity of the light beam generated from the light source, the same plane as the first photodetector A second photodetector for detecting a light beam reflected by the optical disk arranged side by side on the optical beam, and separating the part of the light beam from the light source toward the optical disk and the other part toward the first photodetector, as well as the light beam reflected by the optical disk Optical path separating means for transmitting the light toward the second detector, and control means for controlling the light source according to the output signal of the first photodetector.

Other objects and advantages of the present invention in addition to the above objects will become apparent from the following description of the preferred embodiments with reference to the accompanying drawings.

Hereinafter, with reference to Figures 2 and 3 attached to a preferred embodiment of the present invention will be described in detail.

2 shows an adaptive beam splitter 36 positioned between the light source 30, the objective lens 32, and the photodetector 34, and a right angle positioned between the objective lens 32 and the adaptive beam splitter 36. An optical pickup apparatus according to an embodiment of the present invention having a prism 38 is shown. The light source 32 is installed to generate light beams having two polarization characteristics. That is, the light beam generated by the light source 30 includes a vertical linearly polarized beam (that is, S wave) flowing in the axial direction with respect to the ellipse and a horizontal linearly polarized beam (P wave) flowing in the major axis direction with respect to the ellipse. The objective lens 32 focuses the light beam incident from the light source 30 via the adaptive beam splitter 36 and the right angle prism 38 on the surface of the optical disc D in the form of a spot.

The photodetector 34 detects the intensity of the light beam generated in the light source by the light amount of the light beam from the light source 30 via the adaptive beam splitter 36, and the information contained in the servo control state and the optical disk D is stored. Detect the reflected light beam. To this end, the photodetector 34 includes a first light receiving element 50 and a second light receiving element 52 provided at regular intervals on the support plate 48 as shown in FIG. 3. The first light receiving element is converted by the optical disk (D) to convert the light beam incident through the objective lens 32, the right angle prism 38 and the adaptive beam splitter 36 into an electrical signal. The electrical signal generated by the first light receiving element 50 includes three high frequency signals and is used for controlling the tracking and focus of the light beam. In addition, the information contained in the optical disk D is loaded on the electrical signal generated by the first light receiving element 50. To this end, the first light receiving element 50 is composed of three light receiving element pieces divided into three parts. On the other hand, the second light receiving element 52 converts the light beam from the light source 30 via the adaptive beam splitter 36 into an electrical signal. The electrical signal generated by the second light receiving element 52 represents the intensity of the light beam generated by the light source 30.

In addition, the adaptive beam splitter 36 selectively reflects an incident light beam according to the polarization characteristic of the light beam, thereby detecting a part of the light beam (for example, a vertical linearly polarized beam S wave) from the light source 30. Reflects toward the second light-receiving element 52 and the rest of the light beam (e.g., horizontal linearly polarized beam (P wave)) is a right-angle prism 38 Pass it toward). In addition, the adaptive beam splitter 36 is reflected by the optical disk D and enters the light beam incident through the objective lens 32 and the right angle prism 38 toward the first light receiving element 50 of the photodetector 34. Reflect. To this end, the adaptive beam splitter 36 has a hexahedral prism 36B having a selective reflective surface 36A in the diagonal direction and λ / 4 attached to the side wall of the hexahedral prism 38B located on the right angle prism 38 side. [Lambda] / 4 having a plate 36C and a total reflection surface attached to the side of the hexahedral prism 38B on the side opposite to the photodetector 34 with respect to the optical axis extending from the light source 30 toward the right prism 38 36D is provided.

The selective reflection surface 36A is formed of a PBS coating film to selectively reflect the polarization characteristics of the incident light beam. In detail, the selective reflecting surface 36A reflects the perpendicular linearly polarized beam (i.e., S-wave) of the light beams from the light source 30 at right angles to the λ / 4 plate 36D having a total reflection surface and from the light source 30. The horizontal linearly polarized beam (P wave) of the light beams is passed toward the λ / 4 plate 36C. In addition, the selective reflection surface 36A reflects the perpendicular linearly polarized beam S wave from the λ / 4 plate 36C at right angles to travel toward the first light receiving element 50 of the photodetector 34. In addition, the selective reflection surface 36A passes the vertical linearly polarized beam S wave from the lambda / 4 plate 36D having a total reflection surface toward the photodetector 34.

Then, the λ / 4 plate 36C changes the horizontal linearly polarized beam from the selective reflecting surface 36A into a right-turning circularly polarized beam and sends the converted right-turning circularly polarized beam toward the right angle prism 38. The right-turn circularly polarized light beam sent out from the λ / 4 plate 36C reaches the optical disk D via the right-angle prism 38 and the objective lens 32. When the right rotating circularly polarized beam reaching the optical disk D is reflected by the optical disk D, the left rotating circularly polarized beam is changed. This left rotating circularly polarized beam travels to the λ / 4 plate 36C via the objective lens 32 and the right angle prism 38. In addition, the lambda / 4 plate 36C converts the left rotating circularly polarized beam from the right angle prism 38 into a vertical linearly polarized beam.

Further, the lambda / 4 plate 36D having a total reflection surface is formed of a mirror coating film to totally reflect the vertical linearly polarized beam from the selective reflection surface 36A at a constant angle with respect to the incident path. To this end, the λ / 4 plate 36D having a total reflection surface is formed to be inclined at a constant angle θ with respect to the optical path leading from the light source 30 to the right angle prism 38. Accordingly, the vertical linearly polarized beam reflected by the λ / 4 plate 36D having a total reflection surface passes toward the second light receiving element 52 located on the left side on the photodetector 34 via the selective reflection surface. As a result, the λ / 4 plate 36D having a total reflection surface passes through the path of the light beam passing through the λ / 4 plate 36C and the selective reflection surface from the right angle prism 38 and the selective reflection surface 36A from the light source 30. It functions to separate the path of the vertical linearly polarized beam by a certain angle (θ) or more.

Next, the optical pickup device includes a collimating lens 40 positioned between the light source 30 and the adaptive beam splitter 36, and a sensor lens 42 positioned between the adaptive beam splitter 36 and the photodetector 34. And an analog-digital (AD) converter 44 and an optical controller 46 connected in series between the second light receiving element 52 of the photodetector 34 and the light source 30. It is provided with. The collimation lens 40 minimizes the leakage of the light beam by paralleling the light beam traveling in a form diverging from the light source 32 toward the adaptive beam splitter 36. The sensor lens 42 focuses the light beams traveling from the adaptive beam splitter 36 toward the first and second light receiving elements 50 and 52 of the photodetector 34 to prevent leakage of the reflected light beam. As a result, the collimating lens 40 and the sensor lens 42 may be said to be responsible for maintaining the optical sensitivity of the optical pickup device to a predetermined level or more.

The A-D converter 44 converts the electrical signal for the intensity of the light beam from the second light receiving element 52 into the form of a digital signal. Then, the optical controller 46 compares the voltage level of the output signal of the A-D converter 44 with the reference voltage level and generates an optical drive signal that is increased or decreased by a voltage corresponding to the difference. This light driving signal is supplied to the light source 30 to maintain the intensity of the light beam generated in the light source 30 constant.

As described above, the optical pickup device according to the present invention is a light detecting element for detecting the light amount of the light beam generated from the light source by separating the path of the light beam by a beam splitter and a light detection element for detecting the light amount of the light beam reflected from the optical disk Can be integrated. Accordingly, the optical pickup device according to the present invention can not only reduce the number of optical elements but also simplify the configuration. Furthermore, the optical pickup apparatus according to the present invention provides an advantage that can shorten the manufacturing process.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

A light source for generating a light beam to be irradiated to the optical disk, a first light detector for detecting the intensity of the light beam generated by the light source, and a light beam arranged parallel to the first light detector and reflected by the optical disk And a second photodetector for detecting a signal, separating a part of the light beam from the light source toward the optical disk and a part of the light beam toward the first photo detector, and transferring the light beam reflected by the optical disk to the second detector. And an optical path separating means and a control means for controlling the light source in accordance with an output signal of the first photodetector. The hexahedron according to claim 1, wherein the optical path separating means comprises: a first reflecting surface formed in a diagonal direction on a prism of the hexahedron and selectively transmitting and reflecting according to polarization characteristics, and the hexahedron to match the optical path from the light source to the optical disk; [Lambda] having a polarization transducer attached to the side wall of the prism and a total reflection surface attached to the side of the hexahedral prism 38B on the side opposite to the photodetectors with respect to the optical axis from the light source to the optical disk to totally reflect the light beam. An optical pickup device having a light intensity control function, characterized by having four plates. The optical beam of claim 2, wherein the light beams generated by the light source include vertical and horizontal linearly polarized beams, and the first reflection surface transmits the horizontal linearly polarized beams and selectively reflects the vertical linearly polarized beams according to the incident direction. Optical pickup device having a light intensity control function, characterized in that. The optical pickup apparatus of claim 3, wherein the first reflecting surface is formed of a PBS coating film. The optical pickup apparatus of claim 2, wherein the λ / 4 plate having the total reflection surface is inclined to form a predetermined angle with an optical axis from the light source to the optical disk. The collimating lens according to claim 1, further comprising: a collimating lens positioned between the light source and the light path separating means and allowing a light beam incident from the light source to the light path separating means to travel in parallel; And a sensor lens for focusing the light beams incident toward the first and second photodetectors.