JP2007141301A - Optical information recording / reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify processing relating to a control signal and an information signal even when adopting a configuration in which an optical pickup part is separated into a fixed part and a movable part, and further suitable for a finite conjugate system. To provide.
An optical information recording / reproducing apparatus is an optical information recording / reproducing apparatus for recording or reproducing information with respect to an optical disc. The optical information recording / reproducing device is configured to collect a light source and a laser beam emitted from the light source in the vicinity of a recording surface of the optical disc. A first movable part having a lens, which is movable in parallel along the radial direction of the optical disk, and a light receiving element for receiving a laser beam reflected by the optical disk and transmitted through the objective lens. And a second movable part that is movable in the same direction as the first movable part while maintaining the above distance.
[Selection] Figure 4

Description

  The present invention relates to an optical information recording / reproducing apparatus for recording / reproducing information on / from an optical disc.

  The optical information recording / reproducing apparatus condenses laser light in the vicinity of the recording surface of the optical disk placed on the turntable. Then, the reflected light from the recording surface is received by the light receiving element, thereby generating a control signal and an information signal. The control signal is used for each control of tracking and focusing. In the text, the term “optical information recording / reproducing apparatus” includes all of the information recording apparatus, the reproducing apparatus, and the recording and reproducing apparatus.

  In recent years, with an increase in density and rotation speed of an optical disk, it is desired that an optical pickup unit such as an objective lens that guides laser light to the optical disk is controlled and driven more accurately and at high speed. Therefore, the present applicant has proposed a configuration in which the optical pickup unit is separated into a movable unit mainly including an objective lens and a fixed unit including other light receiving units and the like as in Patent Document 1 below.

JP 2004-146042 A

  According to the configuration exemplified in Patent Document 1, a light source and a light receiving element are disposed in the fixed portion, and an objective lens is disposed in the movable portion. The fixed part is fixed to the frame in the optical information recording / reproducing apparatus, and the movable part is provided to be movable along the radial direction of the optical disc (that is, the tracking direction). In this way, by disposing the members constituting the optical pickup portion separately into the fixed portion and the movable portion, the weight of the movable portion is reduced, and the objective lens can be moved at high speed and accurately.

  An optical disc that can be used in a conventional optical information recording / reproducing apparatus including the configuration described in Patent Document 1 has a recording surface sandwiched between a protective layer and a label layer. Light emitted from the objective lens is condensed and reflected near the recording surface via the protective layer and guided to the light receiving element. At that time, part of the light reflected by the protective layer also enters the light receiving element as stray light. The stray light may adversely affect highly accurate information reproduction and tracking control. For this reason, in the conventional optical information light reproducing apparatus, each signal generated by the light receiving element is subjected to a predetermined offset process to maintain a good S / N ratio.

  However, in the case of the configuration described in the above-mentioned patent document, the distance between the fixed portion and the movable portion (more precisely, the optical path length) is variable. For this reason, the spread of stray light incident on the light receiving element is not uniform, and it is necessary to perform an offset process according to the optical path length between the fixed part and the movable part, resulting in complicated signal processing. .

  Further, for example, laser light emitted from the light source may be incident on the optical axis of the objective lens with an inclination due to an assembly error or the like. In this case, optical characteristics such as aberration change according to the change in the optical path length between the fixed part and the movable part, and the generated signal level changes. Therefore, an appropriate correction process according to the change in the optical path length is required.

  Furthermore, in recent years, a configuration in which the number of members is reduced for the purpose of cost reduction or the like is proposed. For example, there is a so-called finite conjugate optical information recording / reproducing apparatus that omits a collimating lens disposed in the subsequent stage of the light source. When such a configuration is adopted, non-parallel light enters the objective lens. Therefore, the aperture efficiency may change according to the change in the optical path length between the fixed part and the movable part.

  Therefore, in view of the above circumstances, the present invention simplifies the processing related to control signals and information signals even when adopting a configuration in which the optical pickup unit is separated into a fixed unit and a movable unit, and further to a finite conjugate system. An object of the present invention is to provide a suitable optical information recording / reproducing apparatus.

  In order to solve the above problem, an optical information recording / reproducing apparatus according to claim 1 is an optical information recording / reproducing apparatus for recording or reproducing information on an optical disc, wherein the optical source emits a light source and laser light emitted from the light source. An objective lens for condensing near the recording surface, a light receiving element for receiving laser light reflected by the optical disc and transmitted through the objective lens, and an optical path length holding means for keeping the optical path length between the objective lens and the light receiving element constant It is characterized by having.

  According to the optical information recording / reproducing apparatus of the first aspect, with respect to the tracking direction, the light receiving element moves following the movement of the objective lens so as to be always located at a predetermined distance from the objective lens. Therefore, the influence of stray light from the optical disk protective layer on signal generation is substantially constant regardless of the position of the objective lens. Therefore, the process for maintaining a high S / N ratio of the control signal and the information signal becomes very simple.

  Specifically, according to the optical information recording / reproducing apparatus according to claim 2, the optical path length holding means includes the first movable part provided with the objective lens and movable in parallel along the radial direction of the optical disc, and the light receiving unit. An element is provided, and the first movable part has a second movable part that is movable in the same direction as the first movable part while maintaining a predetermined distance.

  According to the optical information recording / reproducing apparatus of the third aspect, the light source can be disposed inside the second movable part. As a result, even when a finite conjugate system is adopted, the aperture efficiency does not change, and high-precision recording or reproduction of information is always achieved. Even when parallel light is used, it is possible to effectively avoid fluctuations in the S / N ratio of the signal due to oblique incidence of the parallel light on the objective lens due to assembly errors or the like.

  According to the optical information recording / reproducing apparatus of the fourth aspect, the first movable unit based on the distance measurement unit that measures the distance between the first movable unit and the second movable unit, and the measurement result by the range measurement unit. And control means for driving and controlling the first movable portion and the second movable portion so that the distance between the first movable portion and the second movable portion is a predetermined distance.

  According to the optical information recording / reproducing apparatus of the fifth aspect, the first movable part further includes a deflecting member that guides the laser light emitted from the light source to the objective lens. Thereby, optical axis alignment with an objective lens and a deflection | deviation member becomes easy.

  According to the optical information recording / reproducing apparatus of the sixth aspect, the optical information recording / reproducing apparatus can further include a collimating lens for converting the laser light emitted from the light source into parallel light.

  As described above, according to the present invention, when the objective lens and at least the light receiving element are arranged in different movable parts and are configured to always move at a constant interval, high-speed and accurate tracking control is possible. At the same time, a highly accurate signal can be generated and detected with simple signal processing.

  FIG. 1 is a perspective view showing a configuration of an optical information recording / reproducing apparatus 100 according to an embodiment of the present invention. The optical information recording / reproducing apparatus 100 includes a pickup unit 50 and a spindle motor 90. For convenience of explanation, in FIG. 1, the optical disk 200 placed on the spindle motor 90 is shown in a transparent manner to clearly show each member disposed under the table. In actual equipment,

  The pickup unit 50 includes a first optical unit 10 having an objective lens 13 and the like, and a second optical unit 20 having a light source 21 and the like which will be described in detail later. The pickup unit 50 includes two rails 30 that are parallel to each other, motors 31 and 32, and screws 33 and 34 that are parallel to each other. Each rail 30 extends from the spindle motor 90 in the radial direction of the optical disc 200, that is, in the tracking direction. The screws 33 and 34 extend from the motors 31 and 32 in the tracking direction and are configured to be rotatable. The first optical unit 10 has a guide portion 10A. The guide portion 10A has a threaded hollow portion. A screw 33 is screwed into the hollow portion. The second optical unit 20 also has a guide portion 20 </ b> A having a hollow portion that is threaded and screwed into the screw 34. Each of the optical units 10 and 20 advances and retreats along each rail 30 as the screw rotates about the axis as the motors 31 and 32 are driven.

  FIG. 2 is a perspective view showing a configuration of the second optical unit 20 according to the embodiment of the present invention. The light source unit 20 includes a laser diode 21, a collimator lens 22, a first anamorphic prism 23, a second anamorphic prism 24, a mirror 25, a right angle prism 26, a Wollaston prism 27, and a condenser lens 28. And a composite sensor 29.

  The laser diode 21 is a semiconductor laser that emits divergent laser light having an elliptical cross section. In the present embodiment, the oscillation wavelength of the laser light is set near 400 nm. The divergent laser light emitted from the laser diode 21 enters the collimator lens 22.

  The collimator lens 22 converts the divergent laser light emitted from the laser diode 21 into a parallel light beam. The converted parallel light flux is guided to the first anamorphic prism 23.

  The first anamorphic prism 23 and the second anamorphic prism 24 shape the parallel light beam emitted from the collimator lens 22 into a parallel light beam having a substantially circular cross-sectional shape. Then, the shaped parallel light beam enters the mirror 25. Further, a part of the parallel light beam emitted from the collimator lens 22 to the first anamorphic prism 23 is deflected by 90 degrees by the half mirror 23a and is incident on a laser power monitor sensor (not shown). The laser power monitor sensor is arranged to detect the output power of the laser light emitted from the laser diode 21.

  The laser power monitor sensor outputs a current corresponding to the intensity of the received light. By feeding back the output of the laser power monitor sensor to a laser power control circuit (not shown), the output of the laser diode 21 is servo-controlled and stabilized.

  The mirror 25 deflects the parallel light beam emitted from the second anamorphic prism 24 by about 90 degrees. The deflected laser light is emitted from the second optical unit 20 and enters the lens group 11 of the first optical unit 10.

  FIG. 3 is a cross-sectional view of the first optical unit 10 according to the embodiment of the present invention. The first optical unit 10 includes a lens group 11, a right-angle prism 12, an objective lens 13, and a biaxial actuator 14.

  The lens group 11 is designed to satisfactorily correct spherical aberration, chromatic aberration, and the like. The laser light that has passed through the lens group 11 is raised at a substantially right angle by the right-angle prism 12 and enters the objective lens 13.

  The objective lens 13 has an NA suitable for recording or reproducing information with respect to the optical disc 200 placed on the spindle motor 90. The laser light transmitted through the objective lens 13 is incident on the optical disc 200 placed on the spindle motor 90. The optical disc 200 is set on the spindle motor 90 and is rotated about the rotation shaft 90a by the spindle motor 90. The laser beam is condensed in the vicinity of the recording surface 200b through the protective layer 200a of the optical disc 200 in a rotating state.

  The objective lens 13 is fixed to the biaxial actuator 14. The biaxial actuator 14 makes the objective lens 13 perpendicular to the direction of the arrow F (focus direction) parallel to the optical axis of the objective lens 13 and the optical axis of the objective lens 13 according to the detection result of the composite sensor 29 described later. It is moved slightly in the direction of arrow T (tracking direction).

  The laser light reflected by the recording surface of the optical disc 200 enters the second optical unit 20 as return light via the first optical unit 10. Then, the return light is guided by the second anamorphic prism 24 after the optical path is bent 90 degrees by the mirror 25. Then, the return light is bent 90 degrees by a half mirror 23 a provided between the first anamorphic prism 23 and the second anamorphic prism 24, and enters the right-angle prism 26 and the Wollaston prism 27. .

  The Wollaston prism 27 is a polarizing prism. In the embodiment of the present invention, the return light incident through the right-angle prism 26 is separated into three light beams having different polarization directions. The three separated light beams enter the composite sensor 29 via the condenser lens 28.

  The composite sensor 29 includes a servo light receiving element and a data light receiving element (not shown). These light receiving elements are arranged along the three light beams separated by the Wollaston prism 27. Two of the three light fluxes are received by the data light receiving element and are processed as information on the optical disc 200.

  The remaining one of the light beams separated by the Wollaston prism 27 is received by the servo light receiving element. The output of the light receiving element for servo is subjected to arithmetic processing by an arithmetic unit (not shown) and detected as a focus error signal and a tracking error signal. Based on each error signal, the biaxial actuator 14 is driven, and minute adjustments regarding the position of the objective lens 13 such as tracking are performed.

  As information is recorded on or reproduced from the optical disc 200, the first optical unit 10 and the second optical unit 20 move in the tracking direction. FIG. 4 is a block diagram showing an optical path length holding unit relating to drive control of the optical units 10 and 20.

  The controller 70 shown in FIG. 4 performs not only drive control of the optical units 10 and 20 but also control of the entire optical information recording / reproducing apparatus 100. The controller 70 rotates the screw 32 via the motor 31 based on the signal from the composite sensor 29. As a result, the first optical unit 10 moves along the rail 30.

  The second optical unit 20 has a distance measuring sensor 35. Examples of the distance measuring sensor 35 include a configuration in which a light emitting diode and PSD are combined, for example, “GP2Y0D340K” manufactured by Sharp Corporation. The distance measuring sensor 35 constantly measures the distance L between the first optical unit 10 and the second optical unit 20 by, for example, projecting and receiving light in the tracking direction with respect to the first optical unit 10.

The distance measuring sensor 35 transmits the distance measurement result to the controller 70 as a displacement signal. In the controller 70, a reference level of the displacement signal, that is, a displacement signal level obtained when the distance between the first optical unit 10 and the second optical unit 20 is a distance L _ref suitable for recording or reproducing information. Is entered. The controller 70 drives and controls the motor 32 so that the level of the received displacement signal matches the reference level. As a result, the second optical unit 20 moves along the rail 30.

  As described above, drive control is performed so that a constant distance is always maintained between the two optical units, so that between the composite sensor 29 and the objective lens 13, and in this embodiment, between the light source 21 and the objective lens 13. The optical path length is always constant. Therefore, even if the first optical unit 10 (more precisely, the objective lens 13) moves between the inner periphery and the outer periphery of the optical disc 200, the level of each signal generated by the composite sensor changes or S The / N ratio does not decrease. In other words, according to the optical information recording / reproducing apparatus 100 of the present embodiment, it is possible to easily perform processing related to the control signal and the information signal while moving the objective lens accurately with the light flux.

  Further, when the finite conjugate system is employed instead of the optical system that converts the laser light from the light source 21 into a parallel light beam by the collimator lens 22 as in the optical information recording / reproducing apparatus 100 of the present embodiment, each optical unit 10, Since the optical path length between 20 does not change, the inconvenience that the aperture efficiency changes can be effectively eliminated.

  The above is the embodiment of the present invention. The present invention is not limited to these embodiments and can be modified in various ranges.

  For example, in the above embodiment, the optical information recording / reproducing apparatus 100 has been described as having a configuration in which the light source 21 is disposed in the second optical unit 20, but the present invention is not limited to this, and the light source 21 is not limited to the apparatus 100. It may be configured to be arranged and fixed in its own frame. However, in this case, a configuration using laser light converted into a parallel light beam by a collimating lens is preferable.

  Moreover, in the said embodiment, although each optical unit is moved by rotating a screw, the electromagnetic induction type using a coil etc. may be sufficient.

It is a perspective view which shows the structure of the optical information recording / reproducing apparatus of embodiment of this invention. It is a perspective view which shows the structure of the 2nd optical unit of embodiment of this invention. It is sectional drawing of the 1st optical unit vicinity of embodiment of this invention. It is a block diagram regarding drive control of each optical unit of the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st optical unit 12 Standing mirror 13 Objective lens 20 2nd optical unit 21 Light source 29 Compound sensor 31, 32 Motor 33, 34 Screw 35 Distance sensor 50 Pickup part 70 Controller

Claims (6)

An optical information recording / reproducing apparatus for recording or reproducing information with respect to an optical disc,
A light source;
An objective lens for condensing the laser light emitted from the light source near the recording surface of the optical disc;
A light receiving element that receives laser light reflected by the optical disc and transmitted through the objective lens;
An optical information recording / reproducing apparatus comprising: an optical path length holding unit configured to maintain a constant optical path length between the objective lens and the light receiving element. The optical information recording / reproducing apparatus according to claim 1.
The optical path length holding means is provided with the objective lens and is movable in parallel along the radial direction of the optical disc. The optical path length holding means is provided with the light receiving element. An optical information recording / reproducing apparatus comprising: a second movable portion that is movable in the same direction as the first movable portion while maintaining a distance of The optical information recording / reproducing apparatus according to claim 1 or 2,
An optical information recording / reproducing apparatus, wherein the light source is also disposed inside the second movable part. The optical information recording / reproducing apparatus according to claim 3 or 4,
Ranging means for measuring the distance between the first movable part and the second movable part;
Based on the measurement result by the distance measuring means, the first movable part and the second movable part are driven so that the distance between the first movable part and the second movable part becomes the predetermined distance. And an optical information recording / reproducing apparatus. The optical information recording / reproducing apparatus according to any one of claims 2 to 4,
The optical information recording / reproducing apparatus, wherein the first movable part further includes a deflecting member that guides the laser light emitted from the light source to the objective lens. The optical information recording / reproducing apparatus according to any one of claims 1 to 5,
An optical information recording / reproducing apparatus, further comprising a collimating lens for converting the laser light emitted from the light source into parallel light.

Images