JP4881589B2 - Displacement / tilt correction device - Google Patents

Description

  The present invention relates to a displacement / tilt correction apparatus that can simultaneously detect and correct the displacement and tilt of the focal position of laser light emitted from a light source of an optical pickup.

  2. Description of the Related Art Conventionally, various types of displacement correction apparatuses having an optical pickup including a light source and an objective lens and a displacement detection control apparatus including a displacement sensor and a control unit have been proposed. These displacement correction apparatuses are used for information recording / reproducing apparatuses for information recording media such as CD (Compact Disc) and DVD (Digital Versatile Disc). That is, the laser beam is irradiated from the light source of the optical pickup onto an information recording surface or the like (hereinafter referred to as “target object”) of the information recording medium, passes through the objective lens, and converges the laser beam to detect the target object. The object is focused, and a light spot is formed to record or reproduce information.

  At this time, if the position of the light spot (the focal position of the laser light emitted from the light source of the light spot) is displaced and displaced, accurate information recording / reproduction cannot be performed.

  In order to prevent this, the displacement correction device is provided with a displacement detection control device. This displacement detection control device has a displacement sensor and a control unit, and outputs a signal obtained from the control unit to the optical pickup based on the result of the displacement sensor. That is, the displacement is detected by a displacement sensor, a signal of the detection result is sent to the control unit, and a signal for correcting the displacement is created by the control unit so that a light spot is formed at an accurate position. It is the device which outputs to.

  As a displacement correction device having such an optical pickup and a displacement detection control device, conventionally, for example, as disclosed in Patent Document 1, a signal generated by a control unit of the displacement detection control device is output to the light source of the optical pickup. However, there has been proposed a technique that adjusts the tilt of the light source to adjust the tilt of the optical axis of the laser beam and correct the displacement.

  However, such a displacement correction device sets an initial value of the optical axis in the controller of the displacement detection control device in advance, and a signal for correcting the displacement based on the set value and the result obtained by the displacement sensor. Was produced and output to the light source of the optical pickup to correct the displacement, so that a minute displacement could not be detected. In addition, since the light source itself of the optical pickup is heavy, there is a problem that the response speed is slow and the displacement cannot be corrected at high speed.

  Therefore, for example, as shown in Patent Document 2 and as shown in FIG. 4, the optical pickup 20a includes at least a light source 21a, an objective lens 22a, and an actuator 23a that supports and controls the objective lens 22a to detect displacement. Displacement for correcting displacement by sending a signal detected by the displacement sensor 31a of the control device 30a to the control unit 32a, outputting the signal generated by the control unit 32a to the actuator 23a of the optical pickup 20a, and controlling the actuator 23a. A correction device 10a has been proposed.

  That is, the displacement correction device 10a detects the position of the light spot 11a that is irradiated from the light source 21a of the optical pickup 20a, passes through the objective lens 22a, and is converged, by the displacement sensor 31a of the displacement detection control device 30a. Then, this result is sent to the control unit 32a, a signal for correcting the displacement is generated by the control unit 32a, and the signal is output to the actuator 23a of the optical pickup 20a. The actuator 23a is controlled to adjust the inclination of the objective lens 22a. Thus, the focal position is adjusted and the displacement is corrected.

  Conventionally, as shown in Patent Document 3, for example, there are various tilt correction apparatuses including an optical pickup including a light source and an objective lens, and a tilt detection control apparatus including a tilt sensor, a light emitting element, and a control unit. Are proposed and used in an information recording / reproducing apparatus or the like in the same manner as the displacement correction apparatus described above. That is, similarly to the displacement correction apparatus, a laser beam is irradiated from the light source of the optical pickup onto the information recording surface (hereinafter referred to as “target object”) of the information recording medium, and the laser beam passes through the objective lens. The information is recorded and reproduced by forming a light spot on the object to be detected.

  At this time, if the optical axis of the laser beam and the object to be detected do not intersect perpendicularly and tilt occurs, accurate information recording / reproduction cannot be performed.

  In order to prevent this, the tilt correction control device is provided with a tilt detection control device. This tilt detection control device has a tilt sensor, a light emitting element, and a control unit, and outputs a signal obtained from the control unit to the optical pickup based on the result of the tilt sensor.

  That is, as shown in FIG. 5, the tilt correction device 10b reflects the laser beam irradiated from the light emitting element 34b reaching the object to be detected and reflecting it, and the reflected light is condensed on the light receiving surface of the light receiving element. Tilt is detected by forming a reflected light spot and detecting the reflected light spot with the tilt sensor 32b. Next, this detection result signal is sent to the control unit, and a signal for correcting the tilt is set so that the optical axis of the laser beam and the object to be detected intersect perpendicularly (so that the tilt becomes zero). It is a device that is created by the control unit and output to the optical pickup to correct the tilt.

However, such a displacement correction device 10a and tilt correction device 10b can correct displacement and tilt at high speed. However, in recent years, since the recording density of information recording media has increased, it is required to detect more minute displacements or tilts at the same time and correct them with high accuracy.
Japanese Utility Model Publication No. 60-127630 JP-A-11-144280 Japanese Patent Laid-Open No. 10-74331

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a displacement / tilt correction device capable of detecting displacement and tilt simultaneously and correcting the displacement and tilt with high accuracy. Is to provide.

The above object of the present invention is to provide an optical pickup comprising at least a light source, an objective lens having a peripheral surface formed in a planar shape and provided with a spherical surface and a flat surface, and an actuator for supporting the objective lens, and the light source. A displacement sensor for detecting a displacement of a focal position of the laser beam irradiated and focused through the spherical portion of the objective lens, and the laser beam emitted from the light emitting element is reflected by the plane portion of the objective lens A tilt sensor that receives the reflected light and detects a tilt that is a relative tilt between the optical axis of the laser light emitted from the light source of the optical pickup and the object to be measured; and the displacement sensor; wherein optimizing the displacement and the tilt of the signals obtained simultaneously by a tilt sensor, it outputs the optimized signal to the actuator of the optical pickup And at least a displacement / tilt detection control device comprising a control unit, and based on the optimized signal output from the control unit, the actuator is controlled to adjust the tilt of the objective lens, This is achieved by providing a displacement / tilt correction device that simultaneously corrects the displacement of the focal position and the tilt.

  According to another aspect of the present invention, there is provided a displacement / tilt correction device characterized in that the displacement sensor comprises a sensor for detecting xy coordinates and a sensor for detecting xz coordinates. Effectively achieved.

  According to the displacement / tilt correction device according to the present invention, the objective lens of the optical pickup is provided with the spherical surface portion and the flat surface portion, and is irradiated from the light source of the optical pickup by the displacement sensor of the displacement / tilt detection control device. The displacement of the focal position of the laser beam focused through the spherical surface is detected, and the tilted sensor reflects the laser beam emitted from the light emitting element on the flat surface of the objective lens and receives this reflected light. The tilt is detected, the two signals obtained by the displacement sensor and the tilt sensor are optimized by the control unit, the optimized signal is output to the optical pickup, the actuator is controlled, and the objective lens By adjusting the tilt, the displacement and tilt can be corrected, so that the correction accuracy can be improved even with a small size.

  Hereinafter, a displacement / tilt correction apparatus according to the present invention will be described in detail with reference to the drawings. It should be noted that the displacement / tilt correction apparatus according to the present invention is not limited to the following embodiments, and it is needless to say that the configuration can be changed as appropriate without departing from the scope of the claims.

  A displacement / tilt correction device (hereinafter referred to as “the present displacement / tilt correction device”) 10 according to the present invention is configured by including at least an optical pickup 20 and a displacement / tilt detection control device 30. For example, it is used in an information recording / reproducing apparatus that records information on an information recording medium such as a CD, an MD (Mini Disc), a DVD, or reproduces the recorded information.

  The optical pickup 20 accurately reads information from an information recording medium that is an object to be detected or records information on the information recording medium. In the present embodiment, as shown in FIG. The objective lens 22, the actuator 23, the diffraction grating 24, the polarizing plate 25, the polarizing beam splitter 26, the rising mirror 27, the collimator lens 28, and the quarter wavelength plate 29 are configured.

  The light source 21 emits laser light that irradiates an object to be measured. For example, various known light sources such as a laser diode (LD) and an LED can be used.

  As shown in the schematic sectional view of the objective lens 22 in FIG. 2, the objective lens 22 used in the present invention is formed so that the peripheral edge of the objective lens 22 is planar, and the objective lens 22 has a spherical portion 221 and a planar portion. 222. That is, the central portion of the objective lens 22 is formed in a spherical shape to provide a spherical portion 221, and the peripheral portion is formed in a flat shape to provide a flat portion 222.

  The actuator 23 supports the objective lens 22 and adjusts the tilt of the objective lens 22 based on a signal output from the displacement / tilt detection control device 30. As shown in FIG. 1, for example, a permanent magnet 231 and a coil are used. 232 (for example, a focus coil, a tracking coil, etc.), and various known ones such as one that adjusts the inclination of the objective lens 22 in proportion to the amount of current supplied can be used.

  The diffraction grating 24 is for diffracting the laser light emitted from the light source 21 to obtain a spectrum, but can be omitted if a light source 21 having a single wavelength is used. The polarizing plate 25 converts laser light into linear light, and the polarization beam splitter 26 separates laser light by polarization components. In this embodiment, a prism type is used. Various types such as a flat plate type may be used. The rising mirror 27 changes the optical path of the laser light emitted from the light source 21, but may be omitted depending on the configuration of the displacement / tilt correction apparatus 10 or may be provided in plural. The collimator lens 28 is for irradiating from the light source 21 and converting laser light into parallel light. Further, the ¼ wavelength plate 29 is for making the laser light emitted from the light source 21 circularly polarized, but is changed to a ½ wavelength plate or the like depending on the purpose and configuration of the displacement / tilt correction device 10. Alternatively, the quarter wave plate can be omitted.

  In addition, various known members such as a cylindrical lens can be provided in accordance with the purpose of the displacement / tilt correction device 10.

  First, the optical pickup 20 emits laser light from a light source 21 and makes the laser light enter a diffraction grating 24, a polarizing plate 25, and a polarizing beam splitter 26 in order. Next, after the laser beam emitted from the polarization beam splitter 26 is reflected by the rising mirror 27 to change the optical path, the laser beam is incident on the collimator lens 28 and converted into parallel light. Thereafter, the laser beam converted into the parallel beam is incident on the spherical surface portion 221 of the objective lens 22 and is focused and focused to form the light spot 11.

  The displacement / tilt detection control device 30 is a device that detects displacement and tilt and outputs a signal for correcting displacement and tilt to the actuator 23 of the optical pickup 20, and as shown in FIG. The tilt sensor 32 and the control unit 33 are provided at least.

  The displacement sensor 31 detects the position of the focal point of the laser beam irradiated from the light source 21 of the optical pickup 20 and focused after passing through the spherical surface portion 221 of the objective lens 22, that is, the position of the light spot 11. A displacement of the position (hereinafter simply referred to as “displacement”) is detected. As shown in FIG. 3, a displacement sensor 311A for detecting the xy coordinate of the light spot 11 and the xz coordinate of the light spot 11 are detected. It is comprised by the displacement sensor 311B. In addition, as such a displacement sensor 31, various well-known things, such as a CCD (Charge Coupled Devices) camera, can be used, for example.

  In addition, since these displacement sensors 311 are movable, the xy coordinates of each light spot 11 of each beam of, for example, 780 nm, 650 nm, and 410 nm decomposed when the light source 21 of the optical pickup 20 passes through the diffraction grating 24 are used. The xz coordinate can be detected by the displacement sensor 311A and the displacement sensor 311B. That is, it is possible to detect the xy coordinates and the xz coordinates of each of the three-wavelength light spots 11 with two of the displacement sensors 311A and 311B without providing six sensors. Therefore, the displacement / tilt correction apparatus 10 can detect and correct even a slight displacement, and can be manufactured at low cost.

  As shown in FIG. 1, the tilt sensor 32 reflects the laser light emitted from the light emitting element 34 provided above the objective lens 22 of the optical pickup 20 by the plane portion 222 of the objective lens 22, and this reflected light. It is a sensor that detects tilt by receiving light.

  That is, the laser light emitted from the light emitting element 34 of the displacement / tilt detection control device 30 reaches the flat portion 222 of the objective lens 22 of the optical pickup 20 and is reflected, and this reflected light is collected on the light receiving surface of the light receiving element. The reflected light spot is formed by light, and the reflected light spot is detected by the tilt sensor 32, whereby the optical axis of the laser light emitted from the light source 21 of the optical pickup 20 and the object to be measured are relative to each other. Tilt, which is a tilt, can be detected.

  For such a tilt sensor, for example, a semiconductor position detector (PSD) or the like can be used, and for the light emitting element 34, for example, various known light sources such as LEDs or LDs can be used.

  In the present embodiment, the light emitting element 34 is disposed above the objective lens 22, but is arranged so as to irradiate the laser beam toward the flat surface portion 222 of the objective lens 22 and reflect it by the flat surface portion 222. If provided, it may be provided below the objective lens 22. Further, the light emitting element 34 is not limited to being disposed on the right side of the objective lens 22 and may be disposed on the left side.

  In the displacement / tilt correction device 30, the signals obtained by the displacement sensor 31 and the tilt sensor 32 are transmitted to the control unit 33 to be optimized and output to the objective lens 22 of the optical pickup 20. That is, the respective signals based on the respective results detected by the displacement sensor 31 and the tilt sensor 32 are sent to the control unit 33, and the signals are optimized so that the displacement disappears and the tilt approaches zero, that is, the accurate position The optical axis of the laser beam is a signal to be corrected so as to form a light spot 11, and is irradiated from the light source 21 of the optical pickup 20, passes through the spherical surface portion 221 of the objective lens 22, and is focused. The control unit 33 generates a signal that is substantially perpendicular to. The signal optimized by the control unit 33 is output to the actuator 23 of the optical pickup 20.

  As described above, the displacement / tilt correction device 10 is controlled by the displacement / tilt detection control device 30, optimized, and controlled by the actuator 23 based on the signal output to the actuator 23 of the optical pickup 20. By adjusting the tilt of the lens 22, displacement and tilt are corrected. Accordingly, since the displacement / tilt correction apparatus can detect and correct the displacement and tilt at the same time, the correction accuracy can be improved.

  In addition, since the displacement sensor 31 includes the displacement sensor 311A that detects the xy coordinates of the light spot 11 and the displacement sensor 311B that detects the xz coordinates, even a minute displacement can be detected. The correction accuracy of the displacement / tilt correction device 10 can be further improved.

  In addition, since the objective lens 22 of the optical pickup 20 is provided with the spherical surface portion 221 and the flat surface portion 222, the displacement / tilt correction device 10 can be reduced in size and installed in a place where it could not be incorporated so far. be able to.

  The displacement / tilt correction device according to the present invention is not limited to use in an information reproducing / recording device for an optical disc such as a CD and a DVD as described above. In addition, for example, a mounting inspection of optical components such as a mirror, a lens, and a prism, It can be used by connecting to various known small image processing apparatuses such as a CDT monitor and an LCD monitor.

1 is a schematic view of a displacement / tilt correction apparatus according to the present invention. It is an expanded sectional view of the objective lens used by this invention. FIG. 3 is a schematic layout diagram of a displacement sensor of the displacement / tilt detection control apparatus according to the present invention. It is the schematic of the conventional displacement correction apparatus. It is this schematic of the conventional tilt correction apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Displacement / tilt correction apparatus 10a Displacement correction apparatus 10b Tilt correction apparatus 11, 11a Optical spot 20, 20a Optical pickup 21, 21a Light source 22, 22a Objective lens 221 Spherical surface part 222 Planar part 23, 23a Actuator 231 Permanent magnet 232 Coil 24 Diffraction Grating 25 Polarizing plate 26 Polarizing beam splitter 27 Rising mirror 28 Collimator lens 29 1/4 wavelength plate 30 Displacement / tilt detection control device 30a Displacement detection control device 31, 31a Displacement sensor 311A Displacement sensor 311B for detecting xy coordinates Detecting displacement sensors 32, 32b Tilt sensors 33, 33a Control units 34, 34b Light emitting element

Claims (2)

An optical pickup comprising at least a light source, an objective lens having a peripheral portion formed in a planar shape and provided with a spherical portion and a flat portion, and an actuator that supports the objective lens; and
A displacement sensor for detecting a displacement of a focal position of laser light irradiated from the light source and focused through the spherical surface portion of the objective lens, and a laser beam emitted from a light emitting element for the flat portion of the objective lens A tilt sensor that receives the reflected light and detects a tilt that is a relative tilt between the optical axis of the laser light emitted from the light source of the optical pickup and the measurement target; and the displacement A displacement / tilt detection control device comprising at least a control unit that optimizes the displacement and tilt signals obtained simultaneously by the sensor and the tilt sensor and outputs the optimized signals to the actuator of the optical pickup. Comprising at least
Based on the optimized signal output from the control unit, the actuator is controlled to adjust the tilt of the objective lens to simultaneously correct the displacement of the focal position and the tilt. -Tilt correction device.   The displacement / tilt correction apparatus according to claim 1, wherein the displacement sensor includes a sensor that detects an xy coordinate and a sensor that detects an xz coordinate.

Images