JP2005353250A - Optical pickup and optical disk apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup having an optical system consisting of a common collimator lens and an objective lens for multi-wavelength laser beams, in which magnification being optimum for respective wavelengths is set, and also to provide an optical disk apparatus using this optical pickup. <P>SOLUTION: By putting in and out a magnification conversion element 3 to/from an optical path between a multi-wavelength collimator lens 2 and a multi-wavelength correspondence objective lens 4 depending on the wavelengths of the laser beams, that is, in the case of the wavelength of 407 mm for BD, composite focal distance with the multi-wavelength correspondence objective lens 4 is shortened and optical magnification is enlarged by putting the magnification conversion element 3 in the optical path. In the case of the wavelength of 650 mm for DVD, optical magnification is made five times of the original one by putting the magnification conversion element 3 off the optical path. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup and an optical disc apparatus capable of recording and reproducing a plurality of types of discs such as CDs, DVDs and BDs, and more particularly to an optimum optical magnification of laser light corresponding to a disc to be recorded and reproduced.

  In recent years, CDs and DVDs for recording and reproducing video information and music information have become widespread, and compatible pickups for CDs and DVDs have also been developed (see Patent Document 1), but meet the demand for further improvement in recording density and increase in capacity. For this reason, BD (Blu-ray Disc) using laser light having a wavelength of 407 nm in the blue wavelength region has appeared.

  Accordingly, an optical disc apparatus for recording and reproducing three types of discs, CD, DVD and BD, has been developed and commercialized. In such an optical disc apparatus, laser beams having wavelengths of 780, 650, and 407 nm are used for recording and reproducing CDs, DVDs, and BDs. At this time, the optical system including the objective lens for condensing the laser beam on the disk and receiving the reflected light is simpler when the optical system is common to the above three types of laser beams. This can contribute to reduction in size and weight.

  By the way, the laser light emitted from the laser diode (LD) for three wavelengths as described above is different in wavelength from 407, 650, and 780 nm, and the divergence (radiation) angle, emission power, etc. of the laser are different. The optimum optical magnification (outgoing optical magnification) for condensing the laser light on each disk differs due to the difference in the optimal state of the intensity distribution of the light incident on the BD, and the BD is 10 to 12 times. DVD is about 5 times, CD is about 4 times. However, hereinafter, it is simply referred to as optical magnification, but it is the optical magnification of the forward path.

  FIG. 14 is a block diagram showing an optical system for determining an optical magnification when condensing laser light. Laser light emitted from the laser diode 91 is converted into substantially parallel light by the collimator lens 92, and this laser light is condensed on the disk 94 by the objective lens 93. The optical magnification β of such an optical system is NA1 where the effective numerical aperture on the disc side (objective lens 93 side) (the numerical aperture NA of the light beam that actually reaches the optical disc) is NA1, and the effective aperture on the light source side (collimator lens 92 side). When the number is NA2, β = NA1 / NA2 (1).

  Here, when the forward optical magnification (ratio between the focal length of the collimator lens 92 and the focal length of the objective lens 93) from the laser diode 91 to the signal surface of the disk 94 is optimized for one wavelength, the other wavelengths are related. Deviates from the optimum value because there is no freedom of magnification. As a result, recording / reproducing characteristics at other wavelengths are deteriorated.

In order to solve this problem, a method of changing the focal length of the collimator lens 92 or the focal length of the objective lens 93 is necessary, and the following two methods are conceivable. (1) When the LD emission points are different, if the LD emission points are independent, a coupling lens for magnification adjustment is arranged between each LD and the collimator lens 92, and the coupling lens and the collimator lens A method of adjusting the composite focal length. (2) When a separate objective lens is arranged for each wavelength, there is a method of adjusting the focal length of the objective lens by using a plurality of objective lenses by branching for each wavelength in the optical path before the objective lens.
JP-A-10-199026 (page 3-4, FIG. 1)

  However, in the method (1), when the LD emission points are arranged at substantially the same position, it is not possible to arrange a coupling lens corresponding to each wavelength because the LD and the collimator lens are also a common optical path. Is possible. In the method (2), it is impossible to reduce the size and cost by using a single objective lens.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is an optical system comprising a common collimator lens and an objective lens for multi-wavelength laser light without increasing the size and cost. It is an object of the present invention to provide an optical pickup capable of setting an optimum optical magnification for each wavelength and an optical disc apparatus using the optical pickup.

  In order to achieve the above object, the present invention provides an optical system having a collimator lens that makes incident laser light substantially parallel light, and an objective lens that makes the laser light that has become substantially parallel light incident thereon and condenses it on a recording medium. And a magnification conversion element that is inserted into and removed from the optical path between the collimator lens and the objective lens in accordance with the wavelength of the laser light.

  Further, the present invention is an optical disc apparatus for condensing laser light from an optical pickup onto a disc and receiving and reflecting data from the disc with the optical pickup to record / reproduce data, the optical pickup including an incident light A collimator lens that makes the laser light to be substantially parallel light, an objective lens that makes the laser light that has become substantially parallel light incident thereon and focuses it on a recording medium, and the collimator lens and the objective lens according to the wavelength of the laser light And a magnification conversion element that is inserted into and removed from the optical path, and an optical element moving unit that moves the magnification conversion element into and out of the optical path.

  As described above, in the present invention, when a plurality of recording media such as a BD, a DVD, and a CD are recorded and reproduced through an optical system including a common collimator lens and an objective lens, laser beams having a plurality of wavelengths are disposed between the collimator lens and the objective lens. Depending on the wavelength of the laser light, for example, when the recording medium is a BD and the laser light has a wavelength for recording / reproducing BD, the magnification converting element is inserted into the optical path. When the recording medium is a DVD and the laser beam has a wavelength for recording / reproducing the DVD, the optimum magnification for a recording medium such as a BD or DVD is obtained by removing the magnification conversion element from the optical path. Can be freely set in the optical system with a simple configuration.

According to the present invention, when a plurality of recording media such as a BD, a DVD, and a CD are recorded and reproduced through an optical system composed of a common collimator lens and an objective lens, the optical path between the collimator lens and the objective lens is obtained. By taking in and out the magnification conversion element according to the wavelength of the laser beam, the optical system consisting of a common collimator lens and objective lens for the multi-wavelength laser beam has a simple configuration with the optimum optical magnification for each wavelength. A plurality of recording media such as a BD, a DVD, and a CD can be recorded and reproduced with high quality by one optical pickup.
In addition, since the optical system only includes inexpensive parts such as a magnification conversion element, the above-described effects can be obtained without making the optical pickup small and light and expensive.

  A collimator lens is used for the purpose of freely setting the optimum optical magnification for each wavelength by an optical system consisting of a common collimator lens and objective lens for multi-wavelength laser light without making the optical pickup large and expensive. The magnification conversion element can be put in and out of the optical path between the lens and the objective lens in accordance with the wavelength of the laser beam.

  FIGS. 1A and 1B are block diagrams showing the configuration of an optical system housed in the optical pickup according to the first embodiment of the present invention. The optical system of the optical pickup includes a multi-wavelength laser diode (LD) 1, a multi-wavelength collimator lens 2, a magnification conversion element 3 that can be inserted into and removed from the optical path, a multi-wavelength objective lens 4, and disks 100 and 200. .

  Next, the operation of the present embodiment will be described. FIG. 1A shows a case where a laser beam having a wavelength of 407 nm for BD is emitted from the multi-wavelength laser diode 1, and the magnification conversion element 3 is inserted in the optical path. The laser light emitted from the multi-wavelength laser diode 1 is converted into substantially parallel light by the multi-wavelength collimator lens 2, which passes through the magnification conversion element 3 and enters the multi-wavelength objective lens 4. 4 is condensed on the BD 100. Thus, when the magnification conversion element 3 is on the optical path, the effective numerical aperture on the disk side (objective lens 93 side (see FIG. 12)) is NA3, and the effective numerical aperture on the light source side (collimator lens 92 side (see FIG. 12)). When the numerical aperture is NA4, the optical magnification is represented by β1 = NA3 / NA4 (2). Further, when the effective numerical aperture when the magnification conversion element 3 is not on the optical path is NA5 and the effective numerical aperture on the light source side (collimator lens 92 side (see FIG. 12)) is NA6, the optical magnification is β2 = NA5 / NA6 (3). At this time, the magnification K of the magnification conversion element 3 is expressed by β1 / β2. Alternatively, in the embodiment, when the light beam between the collimator lens and the objective lens is approximately parallel light, the focal length of the multi-wavelength collimator lens 2 is f2, the focal length of the multi-wavelength objective lens 4 is f1, and the optical magnification is β. The magnification K of the magnification conversion element 3 is represented by β = K · f2 / f1. When the magnification conversion element 3 is not on the optical path, the optical magnification β is represented by β = f2 / f1.

  If the magnification conversion element 3 is K> 1, the beam diameter of the incident laser beam is increased, the combined focal length with the multi-wavelength compatible lens 4 is changed, and the combined focal length is shortened. Therefore, when the magnification conversion element 3 is inserted into the optical path from the expression (2), the optical magnification β increases, for example, 12 times.

  FIG. 1B shows a case where a laser beam having a wavelength of 650 nm for DVD is emitted from the multi-wavelength laser diode 1, and the magnification conversion element 3 is removed from the optical path. Laser light emitted from the multi-wavelength laser diode 1 is converted into substantially parallel light by the multi-wavelength collimator lens 2, which is incident on the multi-wavelength objective lens 4 and is condensed on the DVD 200 by the multi-wavelength objective lens 4. . In this case, the optical magnification β is expressed by the equation (3), for example, 5 times. That is, when the magnification conversion element 3 is removed from the optical path, the optical magnification β decreases.

  Here, as the magnification conversion element 3, two groups of expander lenses as shown in FIGS. 1A and 1B, two groups of two expander lenses as shown in FIG. 2, as shown in FIG. An expander lens of 2 groups and 3 sheets can be used.

  Although not shown, the magnification conversion element 3 is also removed from the optical path as shown in FIG. 1B even when a laser beam having a wavelength of 780 nm for CD is emitted from the multi-wavelength laser diode 1. In this case, the optical magnification β is 5 times as shown in the equation (3), but the optimum optical magnification for recording / reproducing a CD is about 4 times and does not change so much, so that the recording / reproducing characteristics deteriorate. There is almost no.

  According to the present embodiment, the optical magnification β of the optical path having the multi-wavelength collimator lens 2 and the multi-wavelength objective lens 4 shared by the multi-wavelength laser beams of BD, DVD, and CD is set according to the wavelength of the laser beam. By putting the magnification conversion element 3 in and out of the optical path, it is possible to freely change the value to the optimum value for the type of disc to be recorded and reproduced, and high quality recording and reproduction can be performed regardless of the type of disc.

  Further, when a magnification conversion element 3 includes a first group two-element expander lens and a second group three-element expander lens, the chromatic aberration of the optical system when the magnification conversion element 3 is inserted in the optical path can be corrected.

  The magnification conversion element 3 is inserted into or removed from the optical path by the magnification conversion element moving mechanism 10.

  4A and 4B are block diagrams showing the configuration of the optical system housed in the optical pickup according to the second embodiment of the present invention. However, the same parts as those in the first embodiment will be described with the same reference numerals. The optical system of the optical pickup includes a multi-wavelength laser diode (LD) 1, a multi-wavelength collimator lens 2, a magnification conversion element 8 that can be inserted into and removed from the optical path, a multi-wavelength objective lens 4, and disks 100 and 200. .

  Next, the operation of the present embodiment will be described. The magnification conversion element 8 in this case is K <1, and when a laser beam having a wavelength of 407 nm for BD is emitted as shown in FIG. 4A, the magnification conversion element 8 is removed from the optical path. As shown in 4 (B), when a laser beam having a wavelength of 650 nm for DVD is emitted, the magnification conversion element 8 is inserted into the optical path.

  The optical magnification β in the case of FIG. 4A is expressed by the expression (3), and the optical magnification β in the case of FIG. 4B is expressed by the expression (2). That is, if the optical magnification β in the case of FIG. 4A is set to be 12, for example, the magnification conversion element 8 is inserted and the magnification K is smaller than 1 in the case of FIG. The magnification β is reduced to, for example, 5. Also in this case, when a laser beam having a wavelength of 780 nm for CD is emitted, the optical system of FIG. 4B is used for the same reason as in the first embodiment.

  According to the present embodiment, the magnification conversion element 8 is removed from the optical path when recording / reproducing BD, and the magnification conversion element 8 is inserted into the optical path when recording / reproducing DVD. Has the same effect.

  FIGS. 5A and 5B are block diagrams showing the configuration of the optical system housed in the optical pickup according to the third embodiment of the present invention. However, the same parts as those in the first embodiment will be described with the same reference numerals. The optical system of the optical pickup includes a multi-wavelength laser diode (LD) 1, a multi-wavelength collimator lens 2, an anamorphic magnification conversion element (single-axis magnification conversion element) 9 that can be inserted into and removed from the optical path, a multi-wavelength objective lens 4, The disc 100, 200 is included. It is assumed that the anamorphic magnification conversion element 9 in this example is composed of two prisms.

  Next, the operation of the present embodiment will be described. The magnification conversion element 9 in this case is K> 1, and when the laser beam having a wavelength of 407 nm for BD is emitted as shown in FIG. 5A, the magnification conversion element 9 is inserted into the optical path. The laser beam that has become substantially parallel light by the multi-wavelength collimator lens 2 is expanded in one direction by the magnification conversion element 9, is incident on the multi-wavelength objective lens 4, and is focused on the BD 100. At this time, since the magnification conversion element 9 is anamorphic, for example, the optical axis direction is the Z axis, the direction perpendicular to the paper surface is the Y axis, the Y axis, and the direction perpendicular to both the Z axis is the X axis. Then, only in the X-axis direction, the laser beam is enlarged, and only the optical magnification in the X-axis direction is increased.

  FIG. 5B shows a case where a laser beam having a wavelength of 650 nm (or 780 nm) for DVD is emitted from the multi-wavelength laser diode 1, and the one-side magnification conversion element 9 is removed from the optical path. Laser light emitted from the multi-wavelength laser diode 1 is converted into substantially parallel light by the multi-wavelength collimator lens 2, which is incident on the multi-wavelength objective lens 4 and is condensed on the DVD 200 by the multi-wavelength objective lens 4. . In this case, since there is no uniaxial magnification conversion element 9, the optical magnification is determined by the focal lengths of the multi-wavelength collimator lens 2 and the multi-wavelength objective lens 4, and the optical magnification is reduced.

  As in this embodiment, the optical magnification of the optical path having the multi-wavelength collimator lens 2 and the multi-wavelength objective lens 4 is obtained by inserting / removing the single-axis magnification conversion element 9 in which the luminous flux of the laser light increases only in one direction. Can be changed only with respect to one side (for example, the X-axis direction), and the optical magnification in the X-axis direction can be optimized when recording / reproducing BD or DVD. In particular, since the magnification of only one axis can be changed, the characteristics of the laser beam can be adjusted according to the direction. For example, the intensity of the laser beam on the optical disk surface can be adjusted according to the direction.

  6 (A) and 6 (B) are the one-axis magnification conversion element (K> 1) 13 that is configured by combining two concave and convex cylindrical lenses 131 and 132, and FIG. 6 (A). As shown in the figure, when a laser beam having a wavelength of 407 nm for BD is emitted, the uniaxial magnification conversion element 13 is inserted in the optical path, and a laser having a wavelength of 650 nm (or 780 nm) for DVD as shown in FIG. When light is emitted, the same effect as in the third embodiment can be obtained by removing the uniaxial magnification conversion element 13 from the optical path.

  FIGS. 7A and 7B are block diagrams showing the configuration of the optical system housed in the optical pickup according to the fourth embodiment of the present invention. However, the same parts as those in the first embodiment will be described with the same reference numerals. The optical system of the optical pickup includes a multi-wavelength laser diode (LD) 1, a multi-wavelength collimator lens 2, an anamorphic magnification conversion element (single-axis magnification conversion element) 11 that can be inserted into and removed from the optical path, a multi-wavelength objective lens 4, The disc 100, 200 is included. In this example, the anamorphic magnification conversion element 11 is composed of two prisms.

  Next, the operation of the present embodiment will be described. In this case, the uniaxial magnification conversion element 11 is one having K <1, and as shown in FIG. 7A, when a laser beam having a wavelength of 407 nm for BD is emitted, the uniaxial magnification conversion element 11 is used as an optical path. 7B, when a laser beam having a wavelength of 650 nm (or 780 nm) for DVD is emitted as shown in FIG. 7B, the uniaxial magnification conversion element 11 is inserted into the optical path.

  The optical magnification in the case of FIG. 7A is determined by the focal lengths of the multi-wavelength collimator lens 2 and the multi-wavelength objective lens 4 because the single-axis magnification conversion element 11 is not on the optical path, and FIG. In this case, since the uniaxial magnification conversion element 11 is on the optical path and the magnification K is smaller than 1, the optical magnification in the X-axis direction is smaller than that in the case of FIG.

  According to the present embodiment, the uniaxial magnification conversion element (magnification K <1) 11 is removed from the optical path when recording and reproducing BD, and the uniaxial magnification conversion element 11 is inserted into the optical path when recording and reproducing DVD. This has the same effect as the first embodiment.

  8A and 8B, a uniaxial magnification conversion element (K <1) 12 is used which is configured by combining two concave and convex cylindrical lenses, as shown in FIG. 8A. When a laser beam having a wavelength of 407 nm for BD is emitted, the single-axis magnification conversion element 12 is removed from the optical path, and a laser beam having a wavelength of 650 nm (or 780 nm) for DVD is emitted as shown in FIG. If the uniaxial magnification conversion element 12 is inserted into the optical path, the same effect as in the fourth embodiment can be obtained.

  FIG. 9 is a block diagram showing a configuration of an optical system housed in an optical pickup according to the fifth embodiment of the present invention. However, the same parts as those in the first embodiment will be described with the same reference numerals. The optical system of the optical pickup includes a two-wavelength laser diode (LD) 1-1, a one-wavelength laser diode (LD) 1-2, an optical path branching element (for example, prism) 14, a multi-wavelength collimator lens 2, and a magnification that can be inserted into and removed from the optical path. A conversion element 15, an optical path branching element 16, a mirror 17, a two-wavelength objective lens 4-1, a one-wavelength objective lens 4-2, and disks 100 and 200 are configured.

  Next, the operation of the present embodiment will be described. The two-wavelength laser diode 1-1 selectively emits laser light having a wavelength for CD, DVD, for example, and the emitted laser light passes through the optical path branching element 14 and becomes substantially parallel light by the multi-wavelength collimator lens 2. When the magnification K of the magnification conversion element 15 is greater than 1, the magnification conversion element 15 is out of the optical path, so that substantially parallel light is directly reflected by the optical path branching element 16 in the optical path. Is changed by 90 degrees, and further changed by 90 degrees by the mirror 17 to be incident on the objective lens 4-2 for two wavelengths. The two-wavelength objective lens 4-2 focuses the laser beam on the DVD disk 200.

  The one-wavelength laser diode 1-2 emits, for example, a laser beam having a wavelength for BD. The emitted laser beam is changed by 90 degrees by the optical path branching element 14, and becomes substantially parallel light by the multi-wavelength collimator lens 2. The light enters the magnification conversion element 15. Since the magnification K of the magnification conversion element 15 is larger than 1, the magnification conversion element 15 is inserted on the optical path. The magnification conversion element 15 expands the light beam of substantially parallel light and passes through the optical path branching element 16 to 1 The light enters the wavelength-corresponding objective lens 4-2. The one-wavelength objective lens 4-2 collects the laser beam on the BD disc 100.

  According to the present embodiment, also in the optical system having the two objective lenses 4-1 and 4-2 and the two laser diodes 1-1 and 1-2, the magnification conversion element 15 is taken in and out of the optical path. As a result, it is possible to set the optical magnification most suitable for recording / reproducing the disk in accordance with the wavelength emitted from the laser diodes 1-1 and 1-2. In this case, as the two laser diodes 1-1 and 1-2, in addition to the above, there are combinations of BD and DVD and CD, and BD and CD and DVD. In addition to the above, 4-1 and 4-2 also have combinations of BD and DVD and CD, and BD and CD and DVD. Depending on each combination, the magnification conversion element 15 is placed on the optical path. By taking in and out, the optimum optical magnification can be set for each combination.

  In the above-described embodiment, K> 1 is used as the magnification conversion element 15. However, when K <1 is used, the conditions for putting the magnification conversion element 15 in and out of the optical path are reversed. The operation is the same as that described in the second embodiment, for example. In general, when the optical magnification is insufficient, a magnification conversion element larger than 1 is inserted, or a magnification conversion element smaller than 1 is removed. When the optical magnification is excessive, magnification adjustment is performed by removing a magnification conversion element larger than 1 or inserting a magnification conversion element smaller than 1. As the magnification conversion element, any of the specific examples used in the first to fourth embodiments can be used.

  Here, when at least one of the objective lens and the light source is separated into two, it is possible to improve the optical magnification by adjusting the magnification with f of the collimator lens or the objective lens. However, due to mechanical restrictions such as pickup size and optical component placement, or restrictions on optical characteristics such as wavelength synthesis / separation prism or compatible objective lens, the magnification cannot be improved favorably for BD, DVD and CD. Conceivable. For example, the transmission / reflection characteristics of the wavelength synthesizing prism optical film have an incident angle dependency, and the incident angle is limited depending on the wavelength. When the incident angle to the prism is made close to parallel light, the characteristics are improved. However, in this case, for example, the focal length of the collimator lens is increased, and inconvenience that the optical magnification cannot be improved depending on the wavelength occurs. In addition, for compatible objective lenses, there are cases where the interchangeable format is limited due to restrictions on size and differential distance for thin pickups and the like, and the magnification cannot be adjusted well only by adjusting the focal length f of the two objective lenses. In some cases. Even in such a case, it is possible to improve the magnification for each of BD, DVD, and CD by using the magnification conversion principle as in this embodiment.

  According to the present embodiment, when there are two objective lenses and the optical magnification cannot be adjusted for some reason by the collimator lens or f of the objective lens, the optical magnification is recorded and reproduced on the disc using the magnification conversion element. The optimum value can be set accordingly.

  FIG. 10 is a block diagram showing a configuration of an optical system housed in an optical pickup according to the sixth embodiment of the present invention. However, the same parts as those in the fifth embodiment will be described with the same reference numerals. The optical system of the optical pickup includes a two-wavelength laser diode (LD) 1-1, a one-wavelength laser diode (LD) 1-2, an optical path branching element (for example, prism) 14, a multi-wavelength collimator lens 2, and a magnification that can be inserted into and removed from the optical path. A conversion element 15, a three-wavelength objective lens 4, and a disk 100 are included.

  In the present embodiment, as in the fifth embodiment, the laser diodes 1-1 and 1-2 use two ones corresponding to two wavelengths and one corresponding to one wavelength, but the objective lens 4 has three wavelengths. The configuration uses one corresponding objective lens. Even in such a configuration, the disk according to the wavelength emitted from the laser diodes 1-1 and 1-2 can be obtained by putting the magnification conversion element 15 in and out of the optical path under the same conditions as in the ninth embodiment. The most suitable optical magnification for recording / reproducing can be set, and the same effect as in the ninth embodiment can be obtained. In this case, the two laser diodes 1-1 and 1-2 include a combination of DVD and CD and BD, BD and DVD and CD, and BD and CD and DVD. In any case, the objective lens 4 is used for both BD, DVD and CD.

  FIG. 11 is a block diagram showing a configuration of an optical system housed in an optical pickup according to the seventh embodiment of the present invention. However, the same parts as those in the fifth embodiment will be described with the same reference numerals. The optical system of the optical pickup includes a three-wavelength laser diode (LD) 1, a multi-wavelength collimator lens 2, a magnification conversion element 15 that can be inserted into and removed from the optical path, an optical path branching element 16, a mirror 17, and a two-wavelength objective lens 4-1, 1 It has a wavelength-corresponding objective lens 4-2 and disks 100 and 200.

  In the present embodiment, as in the fifth embodiment, the objective lenses 4-1 and 4-2 use two lenses corresponding to two wavelengths and one corresponding to one wavelength, but one laser diode 1 is used. The three-wavelength compatible laser diode is used. Even in such a configuration, the disk according to the wavelength emitted from the laser diodes 1-1 and 1-2 can be obtained by putting the magnification conversion element 15 in and out of the optical path under the same conditions as in the ninth embodiment. The most suitable optical magnification for recording / reproducing can be set, and the same effect as in the ninth embodiment can be obtained. In this case, the two-wavelength objective lens 4-1 and the one-wavelength objective lens 4-2 include a combination of DVD and CD and BD, BD and DVD and CD, and BD and CD and DVD. . The laser diode 1 is used for both BD, DVD and CD in any case.

  FIG. 12 is a block diagram showing a configuration of an optical system housed in an optical pickup according to the eighth embodiment of the present invention. However, the same parts as those in the first embodiment will be described with the same reference numerals. The optical system of the optical pickup has a multi-wavelength laser diode (LD) 1, an optical path branching element (for example, a prism) 18, a multi-wavelength objective lens 4, a signal detector 19, and a disk 100, and is an optical device composed of these components. The magnification conversion element (not shown) is inserted into and removed from the path, and there are arrangement A, arrangement B, and arrangement C in the optical path where the magnification conversion element is inserted and removed. Thus, the magnification conversion element is taken in and out.

  Next, the operation of the present embodiment will be described. In the first to fourth embodiments, a magnification conversion element that can be inserted into and removed from the position of the arrangement B, that is, the optical path from the multi-wavelength objective lens 4 to the signal detector 19 is provided. In this case, the laser light that has passed through the optical path branching element 18 is adjusted in its optical magnification by the insertion / extraction of the magnification conversion element, and enters the multi-wavelength objective lens 4, and the multi-wavelength objective lens 4 condenses the laser light on the disk 100. . The reflected light from the disk 100 at that time is received by the multi-wavelength objective lens 4, the optical magnification is adjusted by inserting / removing the magnification conversion element, and the light enters the optical path branching element 18, where the optical path is changed by 90 degrees and the signal is changed. Light is received by the detector 19. Therefore, when the magnification conversion element is installed in the arrangement B, the optical magnification from the multiwavelength laser diode 1 to the disk 100 can be adjusted, and the optical magnification from the disk 100 to the signal detector 19 can be adjusted.

  Next, when a magnification conversion element that can be inserted and removed is installed at the position of arrangement C, that is, in the optical path from the optical path branching element 18 to the signal detector 19, the return light from the disk 100 passes through this optical path. To the signal detector 19 can be adjusted. Assuming that the optimum magnification from the disc 100 to the signal detector 19 is DVD / CD magnification βa and BD magnification βb, the ratio βb / βa is preferably about 2-3. This suitable magnification is determined by the restriction of the pull-in range of the focus error signal. Therefore, stable focus error signal detection and focus servo can be realized by setting a suitable magnification. However, if βb / βa deviates greatly from 2 to 3, either DVD and CD or BD narrows the focus error signal pull-in range to a suitable state, and as a result, in the extreme case Inconveniences such as the focus servo being easily removed due to disturbances occur. Therefore, in order to stabilize the focus servo, a magnification conversion element that can be inserted and removed is installed in the arrangement C, and the optical magnification up to the optical path branching element 18 and the signal detector 19 corresponding to the disk to be recorded / reproduced is a suitable value. Can be adjusted.

  Finally, when a magnification conversion element that can be inserted and removed is installed at the position of the arrangement C, that is, in the optical path from the multiwavelength laser diode 1 to the optical path branching element 18, the optical magnification from the multiwavelength laser diode 1 to the disk 100 can be adjusted. However, the optical magnification from the disk 100 to the signal detector 19 cannot be adjusted. However, when only the adjustment of the optical magnification from the multi-wavelength laser diode 1 to the disk 100 is sufficient, a magnification conversion element may be installed in the arrangement C.

  According to the present embodiment, by appropriately selecting the installation position of the magnification conversion element to be taken in and out of the optical path, it is possible to select an optical path that requires adjustment of the optical magnification, and to improve the degree of design freedom, It can correspond to optical systems with various characteristics.

  FIG. 13 is a block diagram showing the configuration of the main part of an optical disc apparatus according to the ninth embodiment of the present invention. The optical disk device accesses a disk type disk 202 such as DVD ± R / RW, CD ± R / RW, or BD by an optical pickup 204, records and reproduces data, and rotates the disk 202. A spindle motor 203 as a driving means for driving, an optical pickup 204 for reading / writing data from / to the disk 202, a feed motor 205 as a driving means for moving the optical pickup 204 in the radial direction of the disk 202, and the entire apparatus A system controller 207 that performs control, a signal processing unit 208 that performs predetermined processing such as demodulation and error correction processing based on an output signal from the preamplifier 220, a servo control unit 209 that controls the spindle motor 203 and the feed motor 205, Various output from the optical pickup 204 A pre-amplifier 220 that generates a focus error signal, a tracking error signal, an RF signal, and the like based on the above signal, an interface 211 that connects the signal processor 208 and the external computer 230, and a laser control that drives a laser light source in the optical pickup 204. An external computer 230 that receives a signal recorded on the disk 202 as a reproduction signal, modulates the data by the signal processing unit 208 and outputs it to the laser control unit 221 to drive the laser light source in the optical pickup 204. The D / A conversion of the signal from the signal processing unit 208 or the A / D converter 212 for A / D converting the signal from the audio / visual processing unit 213, and the recorded or reproduced audio / video signal Audio / visual processing unit 213 for processing And configured. Here, the optical pickup 204 houses the optical system of the first or second embodiment described above.

  For example, a feed motor 205 for moving to a predetermined recording track on the disk 202 is connected to the optical pickup 204. Control of the spindle motor 203, control of the feed motor 205, and control of the focusing direction and tracking direction of the biaxial actuator that holds the objective lens of the optical pickup 204 are the focus error signal input from the preamplifier 220 by the servo control unit 209, respectively. This is performed based on the tracking error signal. The laser control unit 221 controls the laser diodes 11 and 28 in the optical pickup 204, and variably controls the output power of the laser diodes 11 and 28 in the recording mode and the reproduction mode. The system controller 207 controls the magnification conversion element moving mechanism 10 according to the wavelength of the laser light emitted from the optical pickup 204 to control the magnification conversion element (any one described in the first to fourth embodiments). It is assumed that the magnification conversion element is controlled to be inserted into and removed from the optical path.

  According to this embodiment, since the optical pickup 204 having the optical system shown in the first to fourth embodiments is mounted, when recording / reproducing three types of discs of BD, DVD, and CD, The optical magnification can be optimized, and any disc can be recorded and reproduced with high quality.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can implement also with another various form in a concrete structure, a function, an effect | action, and an effect. For example, in the above embodiment, the wavelength of the laser beam used for recording / reproducing BD, DVD, and CD is 407, 650, and 780 nm, but practically wavelengths in the range of 400 to 415, 630 to 670, and 760 to 800 nm. Can be used for each disk, and the numerical aperture NA of the objective lens at that time is 0.80-0.90, 0.58-0.68, 0.43-0. 53. When recording / reproducing HD-DVD, the wavelength of the laser beam is 400 to 415 nm, and the numerical aperture NA of the objective lens is 0.65 to 0.75. Further, the magnification conversion element may have an n group and m lens configuration (n = 0, 1, 2,..., M = 0, 1, 2,...).

1 is a block diagram showing a configuration of an optical system housed in an optical pickup according to a first embodiment of the present invention. It is the figure which showed the detailed structural example of the magnification conversion element shown in FIG. It is the figure which showed the other detailed structural example of the magnification conversion element shown in FIG. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 2nd Embodiment of this invention. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 3rd Embodiment of this invention. It is the block diagram which showed the structure of the other optical system of the optical pick-up in 3rd Embodiment. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 4th Embodiment of this invention. It is the block diagram which showed the structure of the other optical system of the optical pick-up in 4th Embodiment. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 5th Embodiment of this invention. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 6th Embodiment of this invention. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 7th Embodiment of this invention. It is the block diagram which showed the structure of the optical system accommodated in the optical pick-up concerning the 8th Embodiment of this invention. It is the block diagram which showed the structure of the principal part of the optical disk apparatus based on the 9th Embodiment of this invention. It is the block diagram which showed the conventional optical system which determines the optical magnification at the time of condensing a laser beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multi-wavelength (3 wavelengths) laser diode, 1-1 ... 2-wavelength laser diode, 1-2 ... 1-wavelength laser diode, 2 ... Multi-wavelength collimator lens, 3, 8, 15 ... Magnification conversion element 4 ... objective lens for multiple wavelengths (3 wavelengths), 4-1 ... objective lens for 2 wavelengths, 4-2 ... objective lens for 1 wavelength, 5 ... concave lens, 6 ... convex lens, 7 ... synthesis Lenses 9, 11, 12, 13... Single axis magnification conversion element, 10... Magnification conversion element moving mechanism, 14, 16, 18 .. Optical path branch element, 17. ... optical pickup, 207 ... system controller.

Claims (11)

An optical pickup containing an optical system having a collimator lens that makes incident laser light substantially parallel light and an objective lens that makes the laser light that has become substantially parallel light incident and focused on a recording medium,
According to the wavelength of the laser light, comprising a magnification conversion element that is taken in and out of the optical path between the collimator lens and the objective lens,
An optical pickup characterized by that. A collimator lens that makes incident laser light substantially parallel light; a first objective lens that makes the laser light that has become substantially parallel light incident thereon and focused on a recording medium; and the laser light that has become substantially parallel light. An optical pickup that contains an optical system having a second objective lens that is incident and focused on a recording medium,
According to the wavelength of the laser light, comprising a magnification conversion element that is taken in and out of the optical path between the collimator lens and the first objective lens,
An optical pickup characterized by that.   When the wavelength of the laser beam is 400 to 415 nm, and when the recording medium is recorded and reproduced by the laser beam of this wavelength and the magnification of the magnification conversion element is greater than 1, the magnification conversion element is inserted into the optical path, 3. The optical pickup according to claim 1, wherein when the magnification of the magnification conversion element is smaller than 1, the magnification conversion element is removed from the optical path.   When the wavelength of the laser beam is 630 to 670 nm and the recording medium is recorded and reproduced with the laser beam having this wavelength and the magnification of the magnification conversion element is greater than 1, the magnification conversion element is removed from the optical path, 3. The optical pickup according to claim 1, wherein when the magnification of the magnification conversion element is smaller than 1, the magnification conversion element is inserted into the optical path.   When the wavelength of the laser beam is 760 to 800 nm, and the recording medium is recorded and reproduced by the laser beam having this wavelength, and the magnification of the magnification conversion element is greater than 1, the magnification conversion element is removed from the optical path, 3. The optical pickup according to claim 1, wherein when the magnification of the magnification conversion element is smaller than 1, the magnification conversion element is inserted into the optical path.   3. The optical pickup according to claim 1, wherein the magnification conversion element is a single-axis magnification conversion element that changes a laser beam only in a predetermined direction.   3. The optical pickup according to claim 1, wherein the magnification conversion element is any one of a first group two-expander lens, a second group two-expander lens, or a second group three-expander lens.   3. The optical pickup according to claim 1, wherein the laser beam is emitted from only a single multi-wavelength laser diode or from either a single-wavelength laser diode or a multi-wavelength laser diode. A laser light source that emits laser light, a collimator lens that makes the laser light substantially parallel light, an objective lens that makes the laser light that has become substantially parallel light incident and focused on a recording medium, and received by the objective lens An optical device having a signal detector that collects the return light from the recorded recording medium, a laser beam that collects light on the recording medium, and an optical branch element that branches the return light collected on the signal detector An optical pickup containing the system,
Depending on the wavelength of the laser beam, a magnification conversion element that is taken in and out of the optical path between the collimator lens and the objective lens is provided between the laser light source and the optical branching element or between the optical branching element and the multi-wavelength objective. An optical pickup, which is disposed either between a lens or between the optical branch element and the signal detector. An optical disc apparatus that focuses laser light on a disc from an optical pickup, receives light reflected from the disc by the optical pickup, and records and reproduces data.
The optical pickup includes a collimator lens that makes incident laser light substantially parallel light;
An objective lens for condensing the laser beam, which has become the substantially parallel light, on the recording medium;
A magnification conversion element that is taken in and out of the optical path between the collimator lens and the objective lens according to the wavelength of the laser light;
Optical element moving means for taking the magnification conversion element into and out of the optical path;
An optical disc apparatus comprising: 11. The optical disc apparatus according to claim 10, wherein the wavelength of the laser beam is 400 to 415 nm, 630 to 670 nm, or 760 to 800 nm.

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