JP4590510B2 - Optical information recording apparatus and optical information reproducing apparatus - Google Patents

Description

  The present invention relates to an optical information recording apparatus and an optical information reproducing apparatus using holography, and in particular, an optical information recording apparatus and an optical information reproducing apparatus having a servo mechanism for accessing a predetermined recording position or reproducing position of a recording medium. About.

  Conventionally, holographic recording in which information is recorded on a recording medium using holography is generally performed by superimposing information light carrying image information constituting recording light and recording reference light inside the recording medium. This is done by writing the interference pattern generated at that time on the recording medium. At the time of reproducing recorded information, image information is reproduced by diffracting the interference pattern by irradiating the recording medium with reproduction reference light (see Patent Documents 1 and 2).

  In recent years, volume holography, particularly digital volume holography, has been developed and attracted attention for practical use for ultra-high density optical recording. Volume holography is a method of writing interference patterns in three dimensions by actively utilizing the thickness direction of the recording medium. Increasing the thickness increases the diffraction efficiency and increases the recording capacity using multiple recording. There is a feature that can be planned. Digital volume holography is a computer-oriented holographic recording method that uses a recording medium and a recording method similar to those of volume holography, but restricts image information to be recorded to a binarized digital pattern. In this digital volume holography, for example, image information such as an analog picture is once digitized, developed into two-dimensional digital pattern information, and recorded as image information. At the time of reproduction, the digital pattern information is read and decoded so that the original image information is restored and displayed. As a result, even if the S / N ratio (signal to noise ratio) is somewhat poor at the time of reproduction, the original information is reproduced very faithfully by performing differential detection or encoding binary data and performing error correction. It becomes possible.

  By the way, as a holographic recording method, a disc-shaped recording medium is adopted as in a CD (Compact Disc), a DVD (Digital Versatile Disc), etc., and information is recorded on the recording medium and information is reproduced from the recording medium. A method of using an optical pickup device including an optical system for performing the above is prominent.

  An optical pickup device in a conventional optical information recording / reproducing apparatus includes: a light source that emits a light beam; and an information light generating unit that generates information light carrying information by spatially modulating the light beam emitted from the light source. Recording reference light generating means for generating recording reference light using the light beam emitted from the light source, reproduction reference light generating means for generating reproduction reference light using the light beam emitted from the light source, and recording Information light and recording reference light are irradiated onto the hologram recording layer so that information is recorded on the hologram recording layer of the medium by an interference pattern due to interference between the information light and the recording reference light. Recording / reproducing optical system for collecting reproducing light generated from the hologram recording layer by irradiating the hologram recording layer with reference light for reproduction, and the recording / reproducing optical system Had a detecting means for detecting the reproduction light collected by (Patent Documents 1 and 2).

JP 11-311938 A (refer to claim 17) JP-A-2004-362750

  The conventional optical information recording / reproducing apparatus described in Patent Document 1 described above performs slide servo by moving the entire optical pickup apparatus in the radial direction of the recording medium in order to record or reproduce at a predetermined recording position or reproducing position. I was going. However, since the optical pickup device includes a light source, information light generation means, recording reference light generation means, reproduction reference light generation means, recording / reproduction optical system, and detection means, the volume is large and heavy. For this reason, the driving means for driving the optical pickup device has been enlarged, and as a result, the optical information recording / reproducing apparatus has also been enlarged.

  Further, the conventional optical information recording / reproducing apparatus has a heavy optical pickup device and exerts inertia, so that the optical pickup device cannot access the recording medium at a high speed, and the transfer rate is lowered.

  2. Description of the Related Art Conventionally, in a CD drive or DVD drive that is an optical information recording / reproducing apparatus that does not use holography, the objective lens is separated from the light source side in order to reduce the volume of the moving part and reduce the weight. It was moved according to the irradiation position. This is possible in a CD drive or DVD drive because it is sufficient if the optical system can transmit only the intensity (energy) of light.

  However, an optical system for holographic recording / reproduction is one in which information light spatially modulated by an objective lens and recording reference light are irradiated onto a recording medium, and interference is recorded in a hologram recording layer of the recording medium for recording. On the entrance pupil plane of the objective lens, it is necessary to image at least information light spatially modulated by a spatial light modulator (information expression means). Further, at the time of reproduction, it is necessary to finally form an image on the exit pupil plane of the objective lens of the reproduction light generated from the hologram recording layer of the recording medium by the reproduction reference light on the detection means.

  For this reason, as shown in FIG. 8A, a pair of relay lenses 103 and 105 having the same focal length are provided, and an image displayed on the display surface 101a of the spatial light modulator (information expression means) 101 is converted into an objective lens 109. The image is formed on the entrance pupil surface 109a. That is, as the 4f optical system, the first relay lens 103 is disposed at a position away from the spatial light modulator (information representation means) 101 by the focal length f1, and the focal length f1 is 2 from the first relay lens 103. The second relay lens 105 is disposed at a position separated by twice, and the objective lens 109 is disposed such that the entrance pupil plane 109a is located at a position separated from the second relay lens 105 by a focal length f1. Further, at the time of reproduction, an image reproduced on the exit pupil plane of the objective lens is similarly formed on the incident surface of the detection means by the 4f optical system. In FIG. 8, the recording medium 111 shows a cross section in the radial direction, and the rotation center of the recording medium 111 exists on the right side in FIG. The mirror 107 is bent so that the direction of the optical axis is perpendicular to the recording medium 111.

  In such holographic recording / reproduction, when the objective lens is separated and moved as conventionally used in CD drives and DVD drives that do not use holography, the position of the entrance pupil plane of the objective lens also moves. The distance between the objective lens and the second relay lens also changes.

  FIG. 8B is a diagram showing an optical system required when the position of the spatial light modulator (information expression means) 101 is fixed and the objective lens 109 is separated and moved. As shown in FIG. 8B, when the position of the spatial light modulator 101 is fixed and the position of the objective lens 109 is moved to the inner peripheral side (right side in FIG. 8) of the recording medium 111, the spatial light modulator The display surface 101a of 101 and the entrance pupil surface 109a of the objective lens 109 need to have a conjugate relationship. Therefore, a pair of relay lenses 103 ′ and 105 ′ having a focal length f 2 different from the pair of relay lenses 103 and 105 in FIG.

  In response to such a problem, the applicant of the present application in Japanese Patent Application No. 2004-235105, as shown in FIG. 9, a pair of reflectors 113a and 113b whose reflecting surfaces are orthogonal between a pair of relay lenses 103 and 105. The optical information is provided with the first moving unit 115 in which the objective lens 109 and the second relay lens 105 on the objective lens side are arranged, and the second moving unit 117 in which the pair of reflectors 113a and 113b are arranged. A recording and playback device was proposed. According to this configuration, the objective lens 109 can be moved without changing the distance from the first relay lens 103 to the second relay lens 105. That is, when the objective lens 109 is moved by the distance L, the first moving unit 115 on which the objective lens 109 is arranged is moved by the distance L. Further, when the second moving unit 117 is moved in the same direction by a half distance L / 2, the distance from the first moving unit 115 to the second moving unit 117 approaches the distance L / 2, The distance between the moving unit 117 and the first relay lens 105 is increased by a distance L / 2. As a result, the distance from the first relay lens 103 to the second relay lens 105 does not change, and the image displayed on the spatial light modulator 101 can be formed on the entrance pupil plane 109 a of the objective lens 109.

  However, since the distance from the recording medium 111 to the objective lens 109 changes due to the undulation of the surface of the recording medium 111 and vibration during recording and reproduction, the objective lens 109 is further moved in the optical axis direction (for example, the direction of the arrow 119 in FIG. 9). ) To adjust the focus (hereinafter referred to as “focus servo”). In the configuration of FIG. 9, when the objective lens 109 is moved in the direction of the arrow 119 by the distance x, the entrance pupil plane 109a of the objective lens 109 is also moved by the distance x in the optical axis direction (direction of the arrow 120 in FIG. 9). Thus, the image displayed on the spatial light modulator 101 cannot be formed on the entrance pupil plane 109a.

  Further, since the vibration also occurs in the direction parallel to the surface of the recording medium at the time of recording / reproducing, a positional deviation occurs. Further, when recording and reproducing by rotating the disk-shaped recording medium 111, if the center of the disk and the center of rotation are shifted, the track position is shifted in the radial direction. In order to correct these misalignments, it is preferable to make the moving portion as small and light as possible when performing fine positioning in a direction parallel to the surface of the recording medium (hereinafter referred to as “tracking servo”).

  In view of the above points, the present invention reduces the moving part of the optical pickup device so that the recording medium can be accessed at a high speed, thereby improving the transfer rate and downsizing the driving means. It is an object to reduce the size of a recording apparatus and an optical information reproducing apparatus.

  In order to achieve the above-described object, an optical information recording apparatus of the present invention includes a light source, a spatial light modulator that generates information light by carrying information from the light from the light source, and reference light from the light from the light source. A reference light generating means for generating, an objective lens for irradiating the recording medium with the information light and the reference light, a pair of relay lenses arranged between the spatial light modulator and the objective lens, and the pair of pairs A pair of reflectors having orthogonal reflecting surfaces disposed between the relay lenses, and a deflecting unit that directs the direction of the optical axis disposed between the pair of relay lenses and the objective lens toward the objective lens. A first moving unit in which the objective lens and the deflecting unit are arranged, a second moving unit in which a relay lens on the objective lens side of the pair of relay lenses is arranged, and the pair of reflectors. Placed Characterized by comprising a third moving unit.

  Furthermore, in the optical information recording apparatus, the first moving unit is disposed in the second moving unit, and the first moving unit is independently movable in addition to the movement by the second moving unit. It is preferable that

  The optical information recording apparatus further includes a control unit that controls movement of the first to third moving units, and the control unit has a constant optical path length from the spatial light modulator to the objective lens. It is preferable to control the first to third moving parts.

  Furthermore, in the optical information recording apparatus, it is preferable that the objective lens is further movable in the optical axis direction independently of the polarizing means.

  The optical information reproducing apparatus of the present invention includes a light source, reference light generating means for generating reference light from the light from the light source, and irradiating the recording medium with the reference light, and reproducing light generated from the recording medium An incident objective lens, detection means for detecting the reproduction light, a pair of relay lenses arranged between the objective lens and the detection means, and a reflecting surface arranged between the pair of relay lenses A pair of orthogonal reflectors, and a deflecting unit that directs the direction of the optical axis disposed between the pair of relay lenses and the objective lens toward the objective lens, and the objective lens and the deflecting unit are disposed A first moving unit, a second moving unit in which a relay lens on the objective lens side of the pair of relay lenses is disposed, and a third moving unit in which the pair of reflectors are disposed. Characterized by To.

  Furthermore, in the optical information reproducing apparatus, the first moving unit is disposed in the second moving unit, and the first moving unit is independently movable in addition to the movement by the second moving unit. It is preferable that

  The optical information reproducing apparatus further includes a control unit that controls movement of the first to third moving units, and the control unit has a constant optical path length from the spatial light modulator to the detection unit. It is preferable to control the first to third moving parts.

  Furthermore, in the optical information reproducing apparatus, it is preferable that the objective lens is further movable in the optical axis direction independently of the polarizing means.

  In the optical information recording apparatus of the present invention, the relative positional relationship between the objective lenses can be changed while keeping the distance between the pair of relay lenses constant. By moving the moving part, slide servo can be performed to a predetermined irradiation position of the recording medium. In addition, since the first moving unit in which the objective lens and the polarization unit are arranged is provided, the moving unit can be further reduced in weight and can be positioned more accurately and at a high speed even with a minute displacement. And since the moving part of an optical pick-up apparatus becomes light, a drive means can be reduced in size and an optical information recording apparatus can also be reduced in size. Furthermore, since the moving part of the optical pickup device becomes light, the recording medium can be accessed at high speed, and the transfer rate can be improved. Even if only the objective lens is moved and focus servo is performed, the image displayed on the spatial light modulator can be formed on the entrance pupil plane of the objective lens, and the reliability can be improved.

  Further, in the optical information reproducing apparatus of the present invention, the relative positional relationship of the objective lens can be changed while keeping the distance between the pair of relay lenses constant, and the first to th By moving the third moving unit, slide servo can be performed to a predetermined irradiation position of the recording medium. In addition, since the first moving unit in which the objective lens and the polarization unit are arranged is provided, the moving unit can be further reduced in weight and can be positioned more accurately and at a high speed even with a minute displacement. And since the moving part of an optical pick-up apparatus becomes light, a drive means can be reduced in size and an optical information reproducing | regenerating apparatus can also be reduced in size. Furthermore, since the moving part of the optical pickup device becomes light, the recording medium can be accessed at high speed, and the transfer rate can be improved. Even if only the objective lens is moved and focus servo is performed, the image of the reproduced light reproduced on the exit pupil plane of the objective lens can be formed on the detection means, and the reliability can be improved. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, an overall configuration of the optical information recording / reproducing apparatus 1 according to the present embodiment will be described with reference to FIG. The optical information recording / reproducing apparatus 1 includes an attachment portion 61 to which a recording medium 51 is attached, a pickup 2, a pickup driving unit 62, and a control unit 63.

  The recording medium 51 has a hologram recording layer for recording a hologram. In the case of using a disk-shaped recording medium as the recording medium 51 and performing recording and reproduction while rotating, a disk drive mechanism used in a CD drive or a DVD drive can be used. It is preferable because compatibility with a drive or a DVD drive can be easily provided. In this case, the optical information recording / reproducing apparatus 1 is provided with a recording medium driving unit 64 that drives the attachment unit 61 to rotate the recording medium 51, and the control unit maintains the rotation speed of the recording medium 51 at a predetermined value. 63 controls the recording medium driving means 64.

  The recording medium 51 is not limited to a disk shape, and the recording medium 51 does not have to be rotated or moved during recording and reproduction. For example, the present invention can be applied even when the pickup is moved after the card-shaped recording medium 51 is held at a predetermined position.

  In addition, it is preferable that information for positioning is recorded on the recording medium 51 in advance and a feedback mechanism is used for positioning of the pickup 2 because more accurate positioning can be performed. The point that information for positioning is recorded in advance on the recording medium 51 is described in detail in Patent Document 1.

  The pickup 2 records information by irradiating the recording medium 51 with information light and recording reference light, and irradiates the recording medium 51 with reproduction reference light, detects the reproduction light, and performs recording. Information recorded on the medium 1 is reproduced. The pickup 2 includes a first moving unit 2a, a second moving unit 2b, and a third moving unit 2c, and the objective lens can be moved to a recording position or a reproduction position of the recording medium 51.

  The objective lens 23 and the deflecting means 21 are arranged in the first moving unit 2a, the relay lens 19 on the objective lens side is arranged in the second moving unit 2b, and the third moving unit 2c. A pair of reflectors 15 and 17 are arranged. The other part of the pickup 2 may be fixed to the optical information recording / reproducing apparatus or may be movable. For example, a multi-stage positioning mechanism that first performs a general positioning of the pickup 2 at a recording position or a reproducing position (hereinafter referred to as “slide servo”) and then performs precise positioning (for example, tracking servo or focus servo). By adopting the slide servo, the entire pickup 2 may be moved to an approximate position, and then the first to third moving parts 2a to 2c may be used for precise positioning.

  Information reproduced from the recording medium 51 by the pickup 2 is sent to the control means 63 and decoded by the signal processing function of the control means 63. When the pickup 2 is provided with a function for reading the information for positioning the recording medium 51, the positioning information read from the recording medium 51 by the pickup 2 is sent to the control means 63, and the control means 63. The position shift is detected by this detection function and fed back to the positioning of the irradiation position by the pickup driving means 62 or the pickup 2.

  The pickup driving means 62 may have means for moving the first to third moving portions 2a to 2c independently, or may be partially shared. As will be described later, since the second moving unit 2b and the third moving unit 2c have the same moving axis, a part of the pickup driving means 62 can be shared. For example, the same transport rail can be used. It is preferable to make the parts common because it is effective in reducing the size and weight, and the manufacturing cost can be reduced. As the pickup driving means 62, for example, a linear motor can be used.

  The control means 63 has a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), and the CPU executes a program stored in the ROM using the RAM as a work area. By doing so, the function of the control means 63 is implement | achieved. The control unit 63 controls the pickup driving unit 62 to control the movement of the first to third moving units 2 a to 2 c of the pickup 2. Further, the information to be recorded is encoded by the signal processing function, sent to the spatial light modulator of the pickup 2, and the information is recorded on the recording medium 51 by the pickup 2. Further, as described above, the control means 63 has a function of decoding information reproduced at the time of reproduction, and may further have a function of detecting a positional deviation from the positioning information.

  FIG. 2 is a schematic plan view of the pickup 2 of the optical information recording / reproducing apparatus according to the present invention. FIGS. 3 to 6 are views showing a state in which the irradiation position is moved in the pickup 2 of FIG. is there. The pickup 2 of the present invention includes a light source 3 for recording and reproduction, a collimator lens 5, a first polarizing beam splitter 7, a spatial light modulator 9, a second polarizing beam splitter 11, a first relay lens 13, and a pair. Reflectors 15 and 17, second relay lens 19, deflecting means 21, objective lens 23, and detecting means 25.

  Further, the pickup 2 includes a first moving unit 2a in which the objective lens 23 and the deflecting unit 21 are arranged, a second moving unit 2b in which the second relay lens 19 is arranged, and a pair of reflectors 15 and 17. Is provided with a third moving part 2c. The first to third moving units 2a to 2c may be provided with not only the above components but also necessary components as appropriate. For example, a focus servo actuator 27, which will be described later, may be disposed in the first moving unit 2a, or a quarter-wave plate may be disposed in the second moving unit 2b. In the third moving part 2c, an opening (aperture) for removing high-order diffracted light is arranged at the focal point f between the pair of reflectors 15 and 17 so as to be movable in accordance with the movement of the focal point f. Good.

  2 to 6, the light source 3, the collimator lens 5, the first polarization beam splitter 7, the spatial light modulator 9, the second polarization beam splitter 11, the first relay lens 13, and the detection means 25 are arranged. The portion 2d is fixed without moving in position, but this is for ease of explanation, and as described above, it may be a moving portion or a fixed portion.

  The recording medium 51 includes a first substrate 52, a reflective layer 53, a hologram recording layer 54, and a second substrate 55. Furthermore, it is preferable to record information for positioning on the recording medium 51 in advance, and to employ a feedback mechanism for positioning the irradiation position, because more accurate positioning can be performed. For example, pits may be formed as positioning information on the surface of the reflective layer 53, and positioning information may be recorded in advance. When light having a wavelength different from that for recording or reproduction is used as the light for reading the positioning information, the light for recording or reproduction is used separately from the reflection layer for the light for reading the positioning information for forming the pits. A wavelength selective reflection layer for reflection may be provided. For example, if a wavelength selective reflection layer that reflects light for recording or reproduction and transmits light for reading positioning information is formed between the reflective layer 53 and the hologram recording layer 54, the positioning is superimposed on the recording / reproduction area. Information can be recorded.

  The recording / reproducing light source 3 generates a coherent linearly polarized light beam, and for example, a semiconductor laser can be used. As the recording / reproducing light source 3, a shorter wavelength is advantageous in order to perform high-density recording, and it is preferable to employ a blue laser or a green laser.

  The collimator lens 5 makes the divergent beam from the recording / reproducing light source 3 substantially parallel. The first polarization beam splitter 7 has a semi-reflective surface that reflects or transmits linearly polarized light (for example, P-polarized light) and transmits or reflects linearly polarized light (for example, S-polarized light) perpendicular to the polarized light. In FIG. 2, the first polarization beam splitter 7 reflects the light beam generated from the recording / reproducing light source 3 toward the spatial light modulator 9, and the polarization direction is rotated 90 degrees by the spatial light modulator 9. Transmits the information light and the recording reference light.

  The spatial light modulator 9 has a large number of pixels arranged in a grid and uses a transmissive or reflective spatial light modulator that can modulate the phase or / and intensity of the emitted light for each pixel. can do. As the spatial light modulator 9, a DMD (digital micromirror device) or a matrix type liquid crystal element can be used. The DMD can modulate the intensity by changing the reflection direction of incident light for each pixel, and spatially modulate the phase by changing the reflection position of the incident light for each pixel. The liquid crystal element can spatially modulate the intensity and phase of incident light by controlling the alignment state of the liquid crystal for each pixel. For example, the phase of the light can be spatially modulated by setting the phase of the emitted light for each pixel to one of two values that differ from each other by π radians. The spatial light modulator further rotates the polarization direction of the outgoing light by 90 ° with respect to the polarization direction of the incident light.

  Then, information light carrying the two-dimensional digital pattern information can be generated by spatially modulating the light from the light source 3 with the two-dimensional digital pattern information displayed on the display surface of the spatial light modulator 9. it can.

  In FIG. 2, the spatial light modulator 9 also functions as reference light generating means for generating reference light for recording during recording and reference light for reproduction during reproduction from the light of the light source. As shown in FIG. 2, when information light and reference light are formed by one spatial light modulator, two regions are provided in the spatial light modulator, information light is formed in one region, and the other region is formed. In this case, reference light may be formed.

  The reference light generation means can be provided separately from the spatial light modulator 9. For example, the light from the light source 3 may be divided, information light may be generated by the spatial light modulator 9 with one light, and the other light may be used as reference light. In this case, the optical system that propagates the other light including the optical element that divides the light from the light source 3 becomes the reference light generating means. Further, another spatial light modulator may be provided in the optical system that propagates the other light to spatially modulate the reference light. In this case, since the two-dimensional digital pattern information of the reference light needs to be imaged on the entrance pupil plane of the objective lens 23 as with the information light, the spatial light modulator that generates the information light and the reference light are generated. The spatial light modulator has a conjugate relationship and is propagated by a pair of relay lenses.

  The second polarization beam splitter 11 transmits the reference light for reproduction during reproduction, and reflects the reproduction light generated from the recording medium 51 by the reference light toward the detection means 25.

  The first and second relay lenses 13 and 19 are disposed between the spatial light modulator 9 and the objective lens 23, and an image displayed on the spatial light modulator 9 is an entrance pupil plane 23 a of the objective lens 23. Are arranged so as to form an image. That is, the distance 31 from the spatial light modulator 9 to the first relay lens 13 becomes the focal length f1 of the first relay lens 13, and the distance 34 from the second relay lens 19 to the entrance pupil plane 23a of the objective lens 23. Is the focal length f2 of the second relay lens 19, and the distances 32 and 33 between the first and second relay lenses 13 and 19 are the focal length f1 of the first relay lens 13 and the focal point of the second relay lens 19. They are arranged so as to be the sum of the distances f2.

  In FIG. 2, the first and second relay lenses 13 and 19 are arranged between the objective lens 23 and the detection means 25, and are generated from the hologram recording layer 54 of the recording medium 51 by the reproduction reference light. The reproduced light is arranged so that the image on the exit pupil plane 23a of the objective lens 23 is formed again as a real image. That is, the distance 34 from the exit pupil plane 23a of the objective lens 23 to the second relay lens 19 is the focal length f2, and the distance 35 from the first relay lens 13 to the detection means 25 is the focal length f1, The distances 32 and 33 between the second relay lenses 13 and 19 are arranged to be the sum of the focal length f1 and the focal length f2.

  The arrangement of the pair of relay lenses 13 and 19 is changed by appropriately arranging other optical elements. For example, if a magnifying lens is arranged between the first relay lens 13 and the detection means 25, the distance from the first relay lens 13 to the entrance pupil plane of the magnifying lens is arranged to be the focal length f1. .

  The pair of reflectors 15 and 17 are disposed between the pair of relay lenses 13 and 19, and are disposed so that the reflecting surfaces of both of them are orthogonal to each other. The information light and the reference light are reflected in a U shape by the pair of reflectors 15 and 17, and the light is propagated between the pair of relay lenses 13 and 19 arranged in parallel. That is, the first reflector 15 reflects the light from the first relay lens 13 toward the second reflector 17, and the second reflector 17 reflects the light from the first reflector 15. Reflected toward the second relay lens 19. The reflectors 15 and 17 are not particularly limited as long as the traveling direction of light can be changed, and a mirror, a prism, or the like can be used.

  The polarization means 21 reflects the light from the second relay lens 19 toward the objective lens 23. The polarizing means 21 is not particularly limited as long as the traveling direction of light can be changed, and a mirror, a prism, or the like can be used. As shown in FIG. 2, when the light traveling direction is directed to the recording medium 55 by the polarizing means 21, the first direction is the same as the moving direction of the second and third moving units 2b, 2c (lateral direction). By moving the moving unit 2a, the irradiation position of the objective lens 23 can be moved in parallel with the surface of the recording medium 51, and tracking servo can be performed. Further, even if the objective lens 23 is moved in the vertical direction of the drawing in order to perform focus servo, the moving direction is the same as the moving direction of the second and third moving parts 2b and 2c by the polarizing means 21. (Horizontal direction) can be changed. For this reason, the displacement of the objective lens 23 caused by the focus servo can be corrected by the first to third moving units 2a to 2c, which is preferable.

  The objective lens 23 irradiates the recording medium 51 with information light and reference light imaged on the entrance pupil plane 23a during recording, and causes the hologram recording layer 34 to interfere and record, and also during reproduction. The reference light imaged on the entrance pupil plane 23a is irradiated onto the recording medium 51, and the reproduction light generated from the recording medium 51 is incident thereon to form an image on the exit pupil plane 23a. Since the reference light and the reproduction light have different incident surfaces on the objective lens 23, the entrance pupil plane 23a of the objective lens 23 for the reference light and the exit pupil plane 23a of the objective lens 23 for the reproduction light are at the same position.

  Further, a focus servo actuator 27 may be provided for performing focus servo by moving the objective lens 23 in the optical axis direction (vertical direction in FIG. 2).

  The detection means 25 has a large number of pixels arranged in a lattice pattern, and can detect the intensity of light received for each pixel. As the photodetector 25, a CCD solid-state image sensor or a MOS solid-state image sensor can be used. Further, as the photodetector 25, a smart optical sensor in which a MOS type solid-state imaging device and a signal processing circuit are integrated on one chip (for example, a document “O plus E, September 1996, No. 202, Nos. 93 to 93). (See page 99). Since this smart optical sensor has a high transfer rate and a high-speed calculation function, it is possible to perform high-speed reproduction by using this smart optical sensor, for example, reproduction at a transfer rate on the order of G (giga) bits / second. Can be performed.

  Further, the pickup 2 is provided with a quarter wave plate (not shown). The quarter-wave plate is a phase plate that changes the optical path difference of polarized light that vibrates in directions perpendicular to each other by a quarter wavelength. The P-polarized light is changed to circularly polarized light by the quarter-wave plate, and further, when this circularly-polarized light passes through the quarter-wave plate, it is changed to S-polarized light. With this quarter-wave plate, the reproduction reference light and reproduction light during reproduction can be separated by the second polarization beam splitter 11. The quarter-wave plate may be disposed between the second polarizing beam splitter 11 and the recording medium 55. For example, the quarter-wave plate is disposed in the first moving unit 2a or the second moving unit 2b. Alternatively, it may be fixed to another part in the pickup 2.

  At least the objective lens 23 and the polarization means 21 are disposed in the first moving unit 2a, and the first moving unit 2a is movable in parallel with the surface of the recording medium 51. Since the first moving unit 2a is lighter and smaller than the first moving unit 115 of FIG. 9, the first moving unit 2a is caused by waviness or eccentricity of the recording medium 51 or vibration of the apparatus during recording and reproduction. It is suitable for positioning following a slight displacement.

  As far as slide servo is concerned, the first moving part 2a and the second moving part 2b move in the same way, so that the first moving part 2a is arranged on the second moving part 2b as shown in FIG. May be. In this case, in addition to the movement by the second moving unit 2b, the first moving unit 2a is independently movable in parallel with the surface of the recording medium 51. When the first moving unit 2a is arranged in the second moving unit 2b, the rough slide servo control may be performed on the second moving unit 2b and the third moving unit 2c. Since it is only necessary to perform fine positioning control for the minute displacement with respect to the moving portion 2a, the control circuit can be simplified. Since the slide servo itself may be performed by the entire pickup 2 or the slide servo and precise positioning may be performed at the same time, the configuration is limited to a configuration in which the first moving unit 2a is disposed on the second moving unit 2b. It is not something.

  The second moving unit 2 b is provided with the second relay lens 19 and is movable in parallel with the surface of the recording medium 51. As described above, the first moving unit 2a may be disposed in the second moving unit 2b. The second moving unit 2b is controlled in cooperation with the third moving unit 2c so that the distances 32 and 33 between the pair of relay lenses 13 and 19 are always constant. Furthermore, even if the second moving unit 2b moves the first moving unit 2a to perform positioning following a slight displacement, the entrance pupil plane 23a of the objective lens 23 and the second relay lens 19 are moved. Is controlled so that the distance 34 between is constant. In addition, even if the objective lens 23 is moved in the optical axis direction by the focus servo actuator 27, the entrance pupil plane 23 a of the objective lens 23, the second relay lens 19, and the third moving unit 2 c cooperate with each other. The distance 34 between the two is preferably controlled so as to be always constant.

  At least a pair of reflectors 15 and 17 are disposed in the third moving unit 2 c and can be moved in parallel with the surface of the recording medium 51. The third moving unit 2c is controlled so that the distances 32 and 33 between the pair of relay lenses 13 and 19 are always constant in cooperation with the second moving unit 2b.

  Next, the recording operation of the optical information recording / reproducing apparatus 1 shown in FIGS. 1 and 2 will be described. The light emitted from the light source 3 is converted into parallel light by the collimator lens 5, and the parallel light is reflected toward the spatial light modulator 9 by the first polarization beam splitter 7. The parallel light becomes information light and recording reference light by the two-dimensional digital pattern information expressed in the spatial light modulator 9. The information light and the recording reference light are propagated by the pair of relay lenses 13 and 19 so that the two-dimensional digital pattern information expressed by the spatial light modulator 9 is imaged on the entrance pupil plane 23a of the objective lens 23. . In the middle, the light is reflected by the pair of reflectors 15 and 17, further reflected by the mirror 21 toward the objective lens 23, and passes through a quarter-wave plate (not shown). Then, the recording medium 51 is irradiated by the objective lens 23, and an interference pattern of information light and recording reference light is recorded on the hologram recording layer 54 of the recording medium 51.

  Further, the operation during reproduction of the optical information recording / reproducing apparatus 1 shown in FIGS. 1 and 2 will be described. The light emitted from the light source 3 is converted into parallel light by the collimator lens 5, and the parallel light is reflected toward the spatial light modulator 9 by the first polarization beam splitter 7. Reproduction reference light is generated by the two-dimensional digital pattern information expressed in the spatial light modulator 9. The reproduction reference light passes through the polarization beam splitter 11 and forms a two-dimensional digital pattern information expressed by the spatial light modulator 9 on the entrance pupil plane 23a of the objective lens 23 by the pair of relay lenses 13 and 19. Propagated to be. In the middle, the light is reflected by the pair of reflectors 15 and 17, further reflected by the mirror 21 toward the objective lens 23, and passes through a quarter-wave plate (not shown). Then, the recording medium 51 is irradiated by the objective lens 23 and interferes with the interference pattern recorded on the hologram recording layer 54 of the recording medium 51 to generate reproduction light.

  The reproduction light and the reproduction reference light are reflected by the reflection layer 53 of the recording medium 51 and are emitted from the recording medium 51 toward the objective lens 23. Then, the reproduction light and the reproduction reference light are reproduced by the objective lens 23 so that the two-dimensional digital pattern information of the reproduction light is reproduced on the surface of the exit pupil 23a and imaged on the detection means 25 by the pair of relay lenses 13 and 19. Is propagated to. In the middle, it passes through the quarter-wave plate 19, is reflected by the mirror 21 toward the pair of relay lenses 13 and 19, is reflected by the pair of reflectors 15 and 17, and is reflected by the polarization beam splitter 11. Then, the detection means 25 detects the two-dimensional digital pattern information of the reproduction light and reproduces the information.

  A case where the irradiation position is changed in the recording / reproducing apparatus 1 will be described with reference to FIGS. FIG. 3 shows a case in which slide servo is performed by moving the irradiation position of the objective lens 28 from the position X to the position Y in FIG. 4 to 6 show the case where the tracking servo ΔT, the focus servo ΔF, and both are performed at the position Y. FIG. 3 to 6, only the optical axis is shown as the optical path of the light beam.

  As shown in FIG. 3, in order to focus the objective lens 23 on the position Y, the pickup driving means 62 moves the first moving portion 2a and the second moving portion 2b by a distance L and the pickup driving means 62. The third moving part 2c is moved by the distance L / 2 in the same direction (right direction in the drawing). For this reason, the irradiation position on the recording medium 51 can be changed without changing the distance between the first relay lens 13 and the second relay lens 19. In FIG. 3, the positions of the components in FIG. 2 are indicated by dotted lines.

  That is, when the second moving unit 2b moves by a distance L and the third moving unit 2c moves by a distance L / 2 in the right direction in the drawing, the distance from the second relay lens 19 to the second reflector 17 is increased. The distance approaches L / 2, and the focal point of the second relay lens 19 moves from the position f in FIG. 2 by the distance L / 2 to a position f ′. On the other hand, since the third moving unit 2c has moved by the distance L / 2, the distance from the first relay lens 13 to the first reflector 15 is increased by L / 2, and the focus of the first relay lens 13 is increased. Is moved from the position f in FIG. 2 by a distance L / 2 to become a position f ′. Eventually, the distance from the second relay lens 19 to the second reflector 17 approaches L / 2, and the distance from the first relay lens 13 to the first reflector 15 moves L / 2 away, so that the subtraction is zero. The distance from the relay lens 13 to the second relay lens 19 does not change. In FIG. 3, since the relative positional relationship between the first moving unit 2a and the second moving unit 2b is not changed, the distance from the second relay lens 19 to the entrance pupil plane 23a of the objective lens 23 is not changed. The distance 34 does not change.

  The same applies when moving in the opposite direction. If the first moving unit 2a has moved by a distance L in the left direction of the drawing, the distance between the first moving unit 2a and the second moving unit 2b is increased by the distance L, but the second moving unit 2b is Since the distance L / 2 moves in the same direction, the distance between the second moving part 2b and the first moving part 2a is shortened by the distance L / 2, and the distance between the second moving part 2b and the fixed part 2c is the distance. L / 2 shorter. Eventually, the distance from the first moving part 2a to the fixed part 2c via the second moving part 2b does not change.

  As described above, since the distance between the pair of relay lenses 13 and 19 does not change even if the position is changed by performing slide servo as shown in FIG. 3, the two-dimensional digital pattern displayed on the spatial light modulator 9 is not changed. Information can be formed on the entrance pupil plane 23 a of the objective lens 23, and an image of the reproduced light reproduced on the exit pupil plane 23 a of the objective lens 23 can be formed on the detection means 25.

  In addition, as shown in FIG. 3, it is preferable in terms of the simplification of the configuration and the transfer rate to fix the portion 2d in which other members of the pickup 2 are gathered. However, it is not limited to the configuration in which the portion d is fixed. Even if the part 2d is a moving part, the moving distance of the first and second moving parts 2a, 2b is x, the moving distance of the third moving part 2c is y, and the moving distance of the part 2d is If it is controlled so that x−2y + z = 0 (when the moving direction is reverse, the sign of the moving distance is reversed), the distance between the first relay lens and the second relay lens is The relative positional relationship can be changed while keeping constant.

  In FIG. 4, in order to correct a minute positional deviation ΔT in a direction parallel to the surface of the recording medium at the position Y, the first moving unit 2 a is moved leftward in the drawing by the distance ΔT by the pickup driving means 62 and tracking is performed. Servo was performed. Then, since the distance 34 between the second relay lens 19 and the entrance pupil plane 23a of the objective lens 23 is moved away by the distance ΔT, the second moving part 2b is moved by the distance ΔT in the same direction, and the second relay lens. 19 and the distance 34 from the objective lens 23 to the entrance pupil surface 23a is set to a predetermined distance, and the third moving unit 2c is moved by a distance ΔT / 2, so that the first relay lens 13 and the second relay lens 19 are moved. It is preferable to perform control to keep the distance to the constant. However, if the distance ΔT is short and the imaging accuracy on the entrance pupil plane 23a is within an allowable range, the second and third moving units 2b and 2c need not be moved.

  For example, when recording / reproducing while rotating the disk-shaped recording medium 51, the displacement due to the deviation between the center of the disk and the center of rotation is periodic, and its frequency is low, so tracking is relatively easy. On the other hand, the displacement caused by the vibration of the apparatus is sudden and has a high frequency. For this reason, with respect to the displacement having a low frequency, the second and third moving units 2b and 2c are moved, and the distance from the spatial light modulator 9 to the entrance pupil plane 23a of the objective lens 23 is made constant. Recording and reproduction may be performed, and for a high frequency displacement, the light and small first moving unit 2a may be moved to follow the displacement. Further, as will be described below, the distance ΔT may be canceled by the displacement ΔF caused by the focus servo, and it is preferable to control the distance ΔT to be within an allowable range throughout the servo operation including the slide servo. 4 to 6, the position of each component in FIG. 3 is indicated by a dotted line.

  In FIG. 5, in order to correct the focus shift ΔF due to unevenness or deflection of the recording medium 51, the focus servo actuator 27 moves the objective lens 23 by a distance ΔF in the upward direction in the drawing to perform focus servo. Then, in accordance with the movement of the objective lens 23, the entrance pupil plane 23a moves upward in the drawing by a distance ΔF from the position 23a 'in FIG. For this reason, since the distance 34 between the second relay lens 19 and the entrance pupil plane 23a of the objective lens 23 approaches the distance ΔF, the second relay unit 2b is moved rightward in the drawing by the distance ΔF, and the second relay The distance 34 between the lens 19 and the entrance pupil surface 23a of the objective lens 23 is set to a predetermined distance, and the third moving unit 2c is moved by the distance ΔF / 2, so that the first relay lens 13 and the second relay lens are moved. It is preferable to perform control to keep the distance up to 19 constant. Also in the focus servo, if the distance ΔF is short and the imaging accuracy on the entrance pupil plane 23a is within an allowable range, the second and third moving units 2b and 2c need not be moved.

  In FIG. 6, both tracking servo and focus servo are performed. The distance 34 between the second relay lens 19 and the entrance pupil surface 23a of the objective lens 23 is moved away by the distance ΔT by the tracking servo, but by the focus servo. It approaches by a distance ΔF. In FIG. 6, since ΔT> ΔF, the distance 34 eventually changes by the difference (ΔT−ΔF). Therefore, the second moving unit 2b is moved to the left in the drawing by a distance (ΔT−ΔF) to set the distance 34 between the second relay lens 19 and the entrance pupil plane 23a of the objective lens 23 to a predetermined distance, and It is preferable that the third moving unit 2c is moved to the left in the drawing by a distance (ΔT−ΔF) / 2 to perform control to make the distance from the first relay lens 13 to the second relay lens 19 constant. As shown in FIG. 6, when the displacement ΔT by the tracking servo and the displacement ΔF by the focus servo are in the opposite directions, the difference is small, so that it is easy to correct only by the movement of the first moving unit 2a. If the imaging accuracy on the entrance pupil plane 23a is within an allowable range, the second and third moving units 2b and 2c need not be moved.

  If the direction of movement is more generalized and included in the displacement as a sign, for example, the movement toward the recording medium 51 along the optical axis is positive, the movement in the reverse direction is negative, the displacement by the tracking servo is ΔT, and the focus servo Is ΔF, the total displacement of the entrance pupil plane 23a of the objective lens 23 when tracking servo and focus servo are performed is ΔT + ΔF. Then, correction may be performed by moving the second and third moving units 2b and 2c so that the imaging accuracy is within the allowable range on the entrance pupil plane 23a moved by ΔT + ΔF.

  As described above, even when the irradiation position is changed by performing tracking servo or focus servo as shown in FIGS. 4 to 6, the distances 32 and 33 between the pair of relay lenses 13 and 19 and the second relay lens 19 are changed. Since the distance 34 from the entrance pupil plane of the objective lens 23 to the exit pupil plane 23a can be made constant, the two-dimensional digital pattern information displayed on the spatial light modulator 9 is displayed on the entrance pupil plane 23a of the objective lens 23. An image of the reproduction light reproduced on the exit pupil plane 23 a of the objective lens 23 can be formed on the detection means 25.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed. For example, an optical information recording device can be obtained by using only the portion used during recording of the optical information recording / reproducing device in the above embodiment, and an optical information reproducing device can be obtained by using only the portion used during reproduction.

Schematic configuration diagram of an optical information recording / reproducing apparatus of the present invention Schematic plan view of a pickup of an optical information recording / reproducing apparatus according to the present invention The figure which shows the state which moved the irradiation position in the pickup of FIG. The figure which shows the state which performed the tracking servo in the pickup of FIG. The figure which shows the state which performed the focus servo in the pickup of FIG. The figure which shows the state which performed tracking servo and focus servo in the pickup of FIG. Schematic plan view of another embodiment of the pickup of the optical information recording / reproducing apparatus according to the present invention (A) And (B) is a figure explaining the subject of this invention Schematic configuration diagram of an optical information recording / reproducing apparatus having first and second moving units

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical information recording / reproducing apparatus 2 Pickup 2a 1st moving part 2b 2nd moving part 2c 3rd moving part 3 Light source 9 Spatial light modulator 13, 19 Relay lens 15, 17 Reflector 25 Deflection means 23 Objective lens 25 Detection means 51 Recording medium

Claims (8)

A light source;
A spatial light modulator for generating information light by supporting information in the light from the light source;
Reference light generating means for generating reference light from light from the light source;
An objective lens that irradiates a recording medium with the information light and the reference light;
A pair of relay lenses disposed between the spatial light modulator and the objective lens;
A pair of reflectors, the reflecting surfaces of which are arranged between the pair of relay lenses are orthogonal;
Deflection means for directing the direction of the optical axis disposed between the pair of relay lenses and the objective lens toward the objective lens;
A first moving part in which the objective lens and the deflecting means are arranged;
A second moving unit in which a relay lens on the objective lens side of the pair of relay lenses is disposed;
An optical information recording apparatus comprising: a third moving unit on which the pair of reflectors are disposed.   The first moving unit is disposed in the second moving unit, and the first moving unit is independently movable in addition to the movement by the second moving unit. The optical information recording apparatus according to claim 1. Control means for controlling movement of the first to third moving parts;
The control means controls the first to third moving units so that an image displayed on the spatial light modulator is formed on an entrance pupil plane of the objective lens. Or the optical information recording device of 2.   4. The optical information recording apparatus according to claim 1, wherein the objective lens is further movable in an optical axis direction independently of the polarization unit. 5. A light source;
Reference light generating means for generating reference light from light from the light source;
An objective lens that irradiates the recording medium with the reference light and is incident with reproduction light generated from the recording medium;
Detecting means for detecting the reproduction light;
A pair of relay lenses disposed between the objective lens and the detection means;
A pair of reflectors, the reflecting surfaces of which are arranged between the pair of relay lenses are orthogonal;
Deflection means for directing the direction of the optical axis disposed between the pair of relay lenses and the objective lens toward the objective lens;
A first moving part in which the objective lens and the deflecting means are arranged;
A second moving unit in which a relay lens on the objective lens side of the pair of relay lenses is disposed;
An optical information reproducing apparatus comprising: a third moving unit on which the pair of reflectors are disposed.   The first moving unit is disposed in the second moving unit, and the first moving unit is independently movable in addition to the movement by the second moving unit. The optical information reproducing apparatus according to claim 5. Control means for controlling movement of the first to third moving parts;
The control unit controls the first to third moving units so that an image of the reproduction light reproduced on an exit pupil plane of the objective lens is formed on the detection unit. Item 7. The optical information reproducing apparatus according to Item 5 or 6. The optical information reproducing apparatus according to claim 5, wherein the objective lens is further movable in the optical axis direction independently of the polarization unit.

Images