JP2006017830A - Optical system and optical head device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system which can sufficiently correct aberration induced by wavelength variation. <P>SOLUTION: The optical system 10 is temperature-compensated such that a lens holder 40 holding a lens group for collimation and a light source 30 or a light receiving part are supported by one supporting member 20 and changes in a synthesized focal length of a lens group due to changes in the refractive index and linear expansion of each lens by temperature change are controlled to be equal to the changes in the linear expansion of the supporting member in a direction of the optical axis caused by the temperature change. The lens group for collimation is composed of a front group FG having positive refractive power and a rear group having positive refractive power, wherein the front group consists of a first lens L1 which is a convex lens and a second lens L2 which is a concave lens, and the rear group consists of a third lens L3 which is a convex lens and a fourth lens L4 which is a concave lens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel optical system and optical head device. More specifically, the present invention relates to a technique for preventing performance deterioration due to temperature change in an optical system and an optical head device including a collimating lens group and a light source or a light receiving unit.

  In response to market demand for high-density, large-capacity optical disks, optical disk systems using blue-violet LDs (laser diodes) centered around 405 nm and high numerical aperture objective lenses with a numerical aperture (NA) of 0.85 It has been put into practical use in recent years. This optical disc system is required to have higher component accuracy and higher assembly accuracy than conventional optical disc systems using infrared LDs and red LDs.

  On the other hand, in recent years, there has been a strong demand for miniaturization of optical disc apparatuses, and since the miniaturization has been achieved, the heat dissipation has deteriorated and the internal temperature has risen. In addition, the blue-violet LD has a higher driving voltage than the conventional infrared LD and red LD, and it is necessary to drive at a high speed for higher density, so that the heat generated by the driving IC is larger than the conventional temperature. It is a factor to raise.

  An LD is mainly used as a light source used in an optical disk device. In general, the oscillation wavelength of an LD varies depending on temperature. In particular, in the blue-violet LD assumed in the present invention, the oscillation wavelength shifts to the long wavelength side by about 0.06 to 0.08 nm with a temperature increase of 1 ° C. Further, in the optical disc, the optical output of the LD differs between signal reproduction and recording, but at this time, the oscillation wavelength is shifted to the long wavelength side by several nm. For this reason, in an optical system of an optical disc system, it is essential to correct aberrations (chromatic aberrations) caused by wavelength fluctuations, including during temperature compensation.

  Patent Document 1 shows an optical system that is temperature-compensated.

JP 2003-177295 A

  However, it cannot be said that the invention disclosed in Patent Document 1 sufficiently corrects the aberration caused by the above-described wavelength fluctuation. When the practical wavelength fluctuation range is about ± 7 nm, it is desirable that the fluctuation of the focal position is about 0.5 μm at the maximum. However, even in the embodiment according to the invention disclosed in Patent Document 1, the fluctuation is the smallest. It is 1.9 μm, and it is difficult to say that it is sufficiently practical when using a blue-violet LD.

  Therefore, an object of the present invention is to provide an optical system in which aberrations caused by wavelength fluctuations are sufficiently corrected.

  In the optical system of the present invention, in order to solve the above-described problem, the lens holder that holds the collimating lens group and the light source or the light receiving unit are supported by the same support member, and the support member that is generated due to a temperature change is provided. The temperature is compensated so that the change in refractive index of each lens due to temperature change and the change in the combined focal length of the lens group due to change in linear expansion are equal to the change in linear expansion in the optical axis direction. The group includes a front group having a positive refractive power and a rear group having a positive refractive power. The front group includes a first lens that is a convex lens and a second lens that is a concave lens, and the rear group is a convex lens. It is composed of three lenses and a fourth lens which is a concave lens.

  In order to solve the above-described problems, the optical head device of the present invention includes a light source or a light receiving unit and a collimating lens group for reading or recording a signal on a recording medium, and the collimating lens group. The lens holder and the light source or light receiving unit are supported by the same support member, and the refractive index of each lens due to the temperature change with respect to the linear expansion change in the optical axis direction of the support member caused by the temperature change Temperature compensation is performed so that the amount of change in the combined focal length of the lens group due to change and linear expansion change is equal, and the collimating lens group has a positive refractive power and a rear group having positive refractive power. The front group is composed of a first lens that is a convex lens and a second lens that is a concave lens, and the rear group is composed of a third lens that is a convex lens and a fourth lens that is a concave lens. To have.

  Therefore, in the present invention, the linear expansion change in the optical axis direction of the support member caused by the temperature change is almost due to the change in the refractive index of each lens due to the temperature change and the change in the combined focal length of the lens group due to the linear expansion change. In addition, the focal length variation accompanying the wavelength variation due to the temperature change is suppressed to a practical range, and aberrations, in particular, chromatic aberration is effectively corrected.

  In the optical system of the present invention, the lens holder holding the collimating lens group and the light source or the light receiving unit are supported by the same support member, and the amount of linear expansion change in the optical axis direction of the support member caused by temperature change is reduced. On the other hand, in a temperature-compensated optical system in which the change in the refractive index of each lens due to temperature change and the change in the combined focal length of the lens group due to linear expansion change are equal, the collimating lens group has a positive refractive power. The front group includes a first lens that is a convex lens and a second lens that is a concave lens, and the rear group is a third lens that is a convex lens and a concave lens. It is composed of four lenses.

  In addition, the optical head device of the present invention includes a light source or a light receiving unit and a collimating lens group, and a lens holder holding the collimating lens group and the light source or light receiving in order to read or record a signal on the recording medium. Are supported by the same support member, and the change in refractive index of each lens due to temperature change and the change in lens expansion due to change in linear expansion with respect to the change in linear expansion in the optical axis direction of the support member caused by temperature change. In an optical head device that is temperature-compensated so that the amount of change in the combined focal length is equal, the collimating lens group is composed of a front group having a positive refractive power and a rear group having a positive refractive power. The first lens is a convex lens and the second lens is a concave lens, and the rear group is a third lens that is a convex lens and a fourth lens that is a concave lens. To.

  Therefore, in the present invention, the linear expansion change in the optical axis direction of the support member caused by the temperature change is almost due to the change in the refractive index of each lens due to the temperature change and the change in the combined focal length of the lens group due to the linear expansion change. In addition, the focal length variation accompanying the wavelength variation due to the temperature change is suppressed to a practical range, and aberrations, in particular, chromatic aberration is effectively corrected.

In the invention described in claims 2 and 12, the temperature change rate of the refractive index in the convex lens is dN (convex) / dT, and the temperature change rate of the refractive index in the concave lens is dN (concave) / dT. Since the conditional expression (1) dN (convex) / dT <1.2 × 10 ⁻⁶ / ° C. and (2) dN (concave) / dT> 5.7 × 10 ⁻⁶ / ° C. is satisfied, the focal point due to the temperature variation of the entire lens Good temperature compensation can be performed by making the variation amount of the distance substantially coincide with the expansion / contraction amount due to the temperature variation of the support member.

  In the invention described in claim 3, claim 4, claim 13, and claim 14, the temperature change rate of the refractive index in the support member is defined as dN (base) / dT, and conditional expression (3) 0.253 < Since (dN (concave) / dT-dN (convex) / dT) / (dN (base) / dT) <0.367 is satisfied, the amount of focal length variation due to temperature variation of the entire lens is expanded or contracted due to temperature variation of the support member. Good temperature compensation can be performed in general with the amount.

  In the invention described in claim 5, claim 6, claim 15 and claim 16, the Abbe number of the concave lens at the d-line is νdn, the Abbe number of the convex lens at the d-line is νdp, and the d of each lens The conditional expression (4) 0.54 <νdn / νdp <0.79 is satisfied where the Abbe number ratio in the line is νdn / νdp, so that the chromatic aberration is corrected well.

  In the invention described in claim 7, claim 8, claim 17 and claim 18, the Abbe number in the d-line of the concave lens in the front group is νdfn, the Abbe number in the d-line of the convex lens in the front group is νdfp, Conditional expression (5) νdfn / νdfp <νdrn / νdrp is satisfied, where νdrn is the Abbe number of the rear group concave lens at the d-line and νdrp is the Abbe number of the rear lens group convex lens. Is made well.

  In the invention described in claim 9, claim 10, claim 19 and claim 20, the focal length of the front group is f (front) and the focal length of the rear group is f (rear). 6) Since 0.24 <f (rear) / f (front) <0.49 is satisfied, the chromatic aberration is corrected well and the necessary focal length is secured.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a configuration of an optical system 10 according to the present invention.

  The optical system 10 includes a light source 30 supported by a support member 20 and a collimator lens 50 supported by the support member 20 via a lens holder 40.

  The collimator lens 50 emits divergent light emitted from the light source 30 as parallel light, and is composed of two groups of a front group FG located on the emission side and a rear group RG located on the incident side. . The front group FG is composed of a cemented lens of a first lens L1 of a biconvex lens positioned in order from the output (parallel light) side and a second lens L2 of a negative meniscus lens having a concave surface facing the output side, and the rear group RG is output. It is composed of a cemented lens composed of a third lens L3 of a biconvex lens positioned in order from the side and a fourth lens L4 of a negative meniscus lens having a concave surface facing the exit side.

  Here, a laser diode (LD) is used as the light source 30, and the front surface of the laser diode 32 disposed in the package 31 is covered with a cover glass 33.

  The collimator lens 50 is held by the lens holder 40 as described above, and the light source 30 and the collimator lens 50 are arranged so that the emitted light from the collimator lens 50 becomes parallel light in accordance with the radiation angle of the light source 30. The lens holder 40 and the light source 30 are fixed to the support member 20.

  Due to the temperature change, the support member 20 and the lens holder 40 expand and contract according to their respective linear expansion coefficients. For this reason, the distance between the collimator lens 50 and the light source 30 also expands and contracts by a length determined by the linear expansion coefficient of the support member 20 and the lens holder 40 and the amount of change in temperature.

  On the other hand, each lens L1, L2, L3, L4 expands and contracts according to the respective linear expansion coefficient due to temperature change, and the refractive index also changes according to the temperature change rate specific to the glass material. For this reason, the focal length of the collimator lens 50 changes according to the temperature change rate, the linear expansion coefficient, and the temperature change rate of the refractive index. In the present invention, the change in the distance between the collimator lens 50 and the light source 30 due to the expansion and contraction of the support member 20 and the lens holder 40 and the change in the focal length due to the expansion and contraction of the lens and the change in the refractive index almost coincide with each other. Designed.

  In the present invention, a glass material having a large refractive index temperature change rate is used for the concave lenses L2 and L4, and a glass material having a low refractive index temperature change rate or a negative temperature change rate glass material is used for the convex lenses L1 and L3. The temperature compensation is performed by making the amount of change in the focal length due to the temperature variation substantially equal to the amount of expansion / contraction due to the temperature variation of the support member. Therefore, assuming that the temperature change rate of the refractive index in the convex lenses L1 and L3 is dN (convex) / dT and the temperature change rate of the refractive index in the concave lenses L2 and L4 is dN (concave) / dT, the following conditional expression (1) And it is desirable to satisfy (2).

(1) dN (convex) / dT <1.2 × 10 ⁻⁶ / ° C
(2) dN (concave) / dT> 5.7 × 10 ⁻⁶ / ° C
In the conditional expression (1), when dN (convex) / dT exceeds 1.2 × 10 −6 / ° C., the fluctuation amount of the focal length of the entire collimator lens 50 becomes small, and in the conditional expression (2), dN ( If (concave) / dT is less than 5.7 × 10 ⁻⁶ / ° C., the amount of variation in the focal length of the entire collimator lens 50 becomes large, and in either case, sufficient temperature compensation cannot be performed.

  Further, it is desirable that the following conditional expression (3) is satisfied, where dN (base) / dT is the temperature change rate of the refractive index in the support member 20.

(3) 0.253 <(dN (concave) / dT-dN (convex) / dT) / (dN (base) / dT) <0.367
When the upper limit of conditional expression (3) is exceeded, the amount of fluctuation of the focal length of the entire collimator lens 50 becomes larger than the amount of expansion / contraction of the support member 20. The amount of expansion / contraction becomes smaller than that, and in either case, sufficient temperature compensation cannot be performed.

  By satisfying the above conditional expressions (1), (2), and (3), the difference between the change in the distance between the collimator lens 50 and the light source 30 and the change in the focal length of the lens is 4 μm at a temperature difference of 50 ° C. The following can be suppressed.

  In the present invention, the chromatic aberration caused by the wavelength variation of the light source 30 based on the temperature change is corrected by a cemented lens made of glass materials having different Abbe numbers. That is, a glass material having a large Abbe number is used for the first and third lenses L1 and L3 made of the convex lens, and a glass material having a small Abbe number is used for the second and fourth lenses L2 and L4 made of a concave lens. ing.

  In the present invention, the Abbe number at the d-line of the concave lens is νdn, the Abbe number at the d-line of the convex lens is νdp, and the ratio of the Abbe number at the d-line of each lens is νdn / νdp. It is desirable to satisfy (4).

(4) 0.54 <νdn / νdp <0.79
If the upper limit of conditional expression (4) is exceeded, the chromatic aberration will be undercorrected, and if it falls below the lower limit, the correction of chromatic aberration will be excessive and the variation in focal length will increase.

  Further, in order to optimally share the correction of chromatic aberration and spherical aberration, the Abbe number at the d-line of the front group concave lens is νdfn, the Abbe number at the d-line of the front group convex lens is νdfp, and the Abbe number at the d-line of the rear group concave lens is It is desirable that the following conditional expression (5) is satisfied, where νdrn is the number and νdrp is the Abbe number in the d-line of the rear group convex lens.

(5) νdfn / νdfp <νdrn / νdrp
That is, a large difference in Abbe number between the positive lens and the negative lens in the front group is used to mainly share the correction of chromatic aberration in the front group, and the correction of the spherical aberration in the rear group. Therefore, if νdfn / νdfp ≧ νdrn / νdrp, the correction of chromatic aberration is insufficient and the variation in focal length becomes large, or the correction of chromatic aberration is excessive, and the correction of spherical aberration is relatively insufficient, thereby deteriorating the wavefront aberration. .

  Further, in order to appropriately correct the chromatic aberration while ensuring the necessary focal length, in order to appropriately distribute the refractive power of the front group and the rear group, the focal length of the front group FG is f (front), and the rear group It is desirable to satisfy the following conditional expression (6), where the focal length of RG is f (rear).

(6) 0.24 <f (rear) / f (front) <0.49
That is, the front group FG is mainly assigned correction of chromatic aberration, so that the refractive power is reduced, and the rear group RG is increased in refractive power to ensure the focal length. If the upper limit of conditional expression (6) is exceeded, the chromatic aberration will be undercorrected, and if it falls below the lower limit, the necessary focal length cannot be secured.

  According to the present invention as described above, it is possible to satisfactorily correct the focal length variation caused by the wavelength variation of the light source 30, so that parallel light can be stably emitted.

  In the above description, the example in which the present invention is applied to the light source unit has been described. However, the present invention can be applied to the light receiving unit by disposing the light receiving element at the position where the light source 30 in FIG. 1 is disposed.

  FIG. 2 schematically shows only a main part of the configuration of the embodiment in which the present invention is applied to the optical head device 60.

  The recording medium 70 is, for example, an optical disk, and is configured to be able to read or record an optical signal. The recording medium 70 is applied to the recording surface 71 of the recording medium 70 through an objective lens 61 provided in the optical head device 60. Irradiation of spot light is performed. Although not shown, the objective lens 61 is driven and controlled in the focusing direction and the tracking direction by a driving device (biaxial actuator) that supports the objective lens 61.

  The optical head device 60 includes a light source, a light receiving unit, and a lens system. The light emitted from the laser diode 62 (light source) is converted into parallel light by the lens 63, travels toward the objective lens 61 through the beam splitter 64, the λ / 4 wavelength plate, and the like, and is spotted by the objective lens 61 as the spot light. The recording surface 71 is irradiated. The return light reflected by the recording surface 71 of the recording medium 70 follows the path opposite to the forward path through the objective lens 61, is reflected by the beam splitter 64, and is received by the light receiving element 66 through the lens 65.

  The light source 62 and the lens 63, and the light receiving element 66 and the lens 65 are respectively attached to the same support member, and the present invention is applied to these portions. Although FIG. 1 shows an example in which the light source 30 and the collimator lens 50 are supported by the same support member 20, the light receiving unit can be supported by the support member 20 instead of the light source 30.

  Tables 1 to 5 show five numerical examples in which specific numerical values are applied to each lens of the optical system of the present invention. In each table, “si” is the surface number of the i-th surface from the parallel light side, “r” is the radius of curvature of the si surface, “d” is the surface spacing between the si surface and the si + 1 surface, and “n ( 408 nm) "is the refractive index at a wavelength of 408 nm of the glass material whose si surface is a parallel light side surface, and" nd "is the refractive index at the d-line (597.6 nm) of the glass material whose si surface is a parallel light side surface, “νd” is the Abbe number in the d-line of the glass material whose si surface is the parallel light side surface, “dN / dT” is the temperature change rate of the refractive index in the d-line of the glass material whose si surface is the parallel light side surface, “ “α” is a linear expansion coefficient of the glass material in which the si surface forms a parallel light side surface. “F” is a focal length at a wavelength of 408 nm, and s7 and s8 are both surfaces of the cover glass 33 of the light source 30.

  Table 6 shows parameters of νdfn / νdfp, νdrn / νdrp, νdfn / νdfp−νdrn / νdrp, f (rear), f (front), and f (rear) / f (front) in the above numerical examples.

Table 7 shows dN (convex) / dT (10 ⁻⁶ / ° C.), dN (concave) / dT (10 ⁻⁶ / ° C.), (dN (concave) / dT−dN (convex)) in each numerical example. Indicates the parameters of / dT) / (dN (base) / dT). Here, the support member 20 is assumed to be a magnesium alloy, and is shown as dN (base) / dT = 260 × 10 −7 / ° C. Further, an epoxy resin was used for the lens holder 40, and its linear expansion coefficient was set to 100 × 10 −7 / ° C.

  FIG. 3 shows a numerical example 1, FIG. 4 shows a numerical example 2, FIG. 5 shows a numerical example 3, FIG. 6 shows a numerical example 4, and FIG. The deviation of the focal length from the ideal state due to the wavelength was shown.

  As can be seen from FIGS. 3 to 7, in each of the above numerical examples, the variation of the focal length in the range of ± 7 nm with respect to the design center wavelength (408 nm) is suppressed to 0.5 μm or less. The difference between the change in the distance between the collimator lens and the light source and the change in the focal length of the lens is suppressed to 4 μm or less at a temperature difference of 50 ° C.

  It should be noted that the shapes, structures, and numerical values of the respective parts shown in the above-described embodiments and numerical examples are merely examples of the implementation performed in carrying out the present invention, and the present invention is thereby limited. This technical scope should not be interpreted in a limited way.

  Since the chromatic aberration caused by the shift of the collimated light from the parallel light due to the wavelength fluctuation caused by the temperature change is corrected well, a signal with good quality can be obtained. Therefore, it is suitable for application to an optical head device using a light source that is expected to have a wavelength variation due to a temperature change.

It is a schematic block diagram which shows embodiment of the optical system of this invention. It is a figure which shows the outline of an optical head apparatus. It is a graph which shows the shift | offset | difference from the ideal state of the focal distance by the wavelength in 20 degreeC and 70 degreeC in Numerical Example 1. FIG. It is a graph which shows the shift | offset | difference from the ideal state of the focal distance by the wavelength in 20 degreeC and 70 degreeC in Numerical Example 2. FIG. It is a graph which shows the shift | offset | difference from the ideal state of the focal distance by the wavelength in 20 degreeC and 70 degreeC in Numerical Example 3. FIG. It is a graph which shows the shift | offset | difference from the ideal state of the focal distance by the wavelength in 20 degreeC and 70 degreeC in Numerical Example 4. FIG. It is a graph which shows the shift | offset | difference from the ideal state of the focal distance by the wavelength in 20 degreeC and 70 degreeC in Numerical Example 5. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Optical system, 20 ... Support member, 30 ... Light source, 40 ... Lens holder, 50 ... Collimator lens (collimating lens group), FG ... Front group, RG ... Rear group, L1 ... First lens, L2 ... First 2 lenses, L3 ... 3rd lens, L4 ... 4th lens

Claims (20)

The lens holder holding the collimating lens group and the light source or light receiving unit are supported by the same support member, and the change in temperature with respect to the linear expansion change in the optical axis direction of the support member caused by the temperature change In the optical system temperature-compensated so that the change in the combined focal length of the lens group due to the refractive index change and linear expansion change of each lens becomes equal,
The collimating lens group is composed of a front group having a positive refractive power and a rear group having a positive refractive power. The front group is composed of a first lens that is a convex lens and a second lens that is a concave lens. An optical system comprising a third lens that is a convex lens and a fourth lens that is a concave lens. The following conditional expressions (1) and (2) are satisfied, where dN (convex) / dT is the temperature change rate of the refractive index in the convex lens and dN (concave) / dT is the temperature change rate of the refractive index in the concave lens. The optical system according to claim 1.
(1) dN (convex) / dT <1.2 × 10 ⁻⁶ / ° C
(2) dN (concave) / dT> 5.7 × 10 ⁻⁶ / ° C 2. The optical system according to claim 1, wherein the following conditional expression (3) is satisfied, where dN (base) / dT is a temperature change rate of the refractive index of the support member.
(3) 0.253 <(dN (concave) / dT-dN (convex) / dT) / (dN (base) / dT) <0.367 The optical system according to claim 2, wherein the following conditional expression (3) is satisfied, where dN (base) / dT is a temperature change rate of the refractive index of the support member.
(3) 0.253 <(dN (concave) / dT-dN (convex) / dT) / (dN (base) / dT) <0.367 The following conditional expression (4) is satisfied, where the Abbe number at the d-line of the concave lens is νdn, the Abbe number at the d-line of the convex lens is νdp, and the ratio of the Abbe numbers at the d-line of each lens is νdn / νdp. The optical system according to claim 1.
(4) 0.54 <νdn / νdp <0.79 The following conditional expression (4) is satisfied, where the Abbe number at the d-line of the concave lens is νdn, the Abbe number at the d-line of the convex lens is νdp, and the ratio of the Abbe numbers at the d-line of each lens is νdn / νdp. The optical system according to claim 2.
(4) 0.54 <νdn / νdp <0.79 The Abbe number at the d-line of the front group concave lens is νdfn, the Abbe number at the d-line of the front group convex lens is νdfp, the Abbe number at the d-line of the rear group concave lens is νdrn, and the Abbe number at the d-line of the rear group convex lens is The optical system according to claim 1, wherein the following conditional expression (5) is satisfied as νdrp.
(5) νdfn / νdfp <νdrn / νdrp The Abbe number at the d-line of the front group concave lens is νdfn, the Abbe number at the d-line of the front group convex lens is νdfp, the Abbe number at the d-line of the rear group concave lens is νdrn, and the Abbe number at the d-line of the rear group convex lens is The optical system according to claim 2, wherein the following conditional expression (5) is satisfied as νdrp.
(5) νdfn / νdfp <νdrn / νdrp 2. The optical system according to claim 1, wherein the following conditional expression (6) is satisfied, where f (front) is the focal length of the front group and f (rear) is the focal length of the rear group.
(6) 0.24 <f (rear) / f (front) <0.49 The optical system according to claim 2, wherein the following conditional expression (6) is satisfied, where f (front) is the focal length of the front group and f (rear) is the focal length of the rear group.
(6) 0.24 <f (rear) / f (front) <0.49 In order to read or record a signal on a recording medium, a light source or light receiving unit and a collimating lens group are provided, and the lens holder holding the collimating lens group and the light source or light receiving unit are supported by the same support member. The change in the refractive index of each lens due to the temperature change and the change in the combined focal length of the lens group due to the linear expansion change are equal to the change in the linear expansion of the support member caused by the temperature change. In the temperature-compensated optical head device,
The collimating lens group is composed of a front group having a positive refractive power and a rear group having a positive refractive power. The front group is composed of a first lens that is a convex lens and a second lens that is a concave lens. An optical head device comprising a third lens that is a convex lens and a fourth lens that is a concave lens. The following conditional expressions (1) and (2) are satisfied, where dN (convex) / dT is the temperature change rate of the refractive index in the convex lens and dN (concave) / dT is the temperature change rate of the refractive index in the concave lens. The optical head device according to claim 11.
(1) dN (convex) / dT <1.2 × 10 ⁻⁶ / ° C
(2) dN (concave) / dT> 5.7 × 10 ⁻⁶ / ° C 12. The optical head device according to claim 11, wherein the following conditional expression (3) is satisfied, where dN (base) / dT is a temperature change rate of the refractive index of the support member.
(3) 0.253 <(dN (concave) / dT-dN (convex) / dT) / (dN (base) / dT) <0.367 13. The optical head device according to claim 12, wherein the following conditional expression (3) is satisfied, where dN (base) / dT is a temperature change rate of the refractive index of the support member.
(3) 0.253 <(dN (concave) / dT-dN (convex) / dT) / (dN (base) / dT) <0.367 The following conditional expression (4) is satisfied, where the Abbe number at the d-line of the concave lens is νdn, the Abbe number at the d-line of the convex lens is νdp, and the ratio of the Abbe numbers at the d-line of each lens is νdn / νdp. The optical head device according to claim 11.
(4) 0.54 <νdn / νdp <0.79 The following conditional expression (4) is satisfied, where the Abbe number at the d-line of the concave lens is νdn, the Abbe number at the d-line of the convex lens is νdp, and the ratio of the Abbe numbers at the d-line of each lens is νdn / νdp. The optical head device according to claim 12.
(4) 0.54 <νdn / νdp <0.79 The Abbe number at the d-line of the front group concave lens is νdfn, the Abbe number at the d-line of the front group convex lens is νdfp, the Abbe number at the d-line of the rear group concave lens is νdrn, and the Abbe number at the d-line of the rear group convex lens is The optical head device according to claim 11, wherein the following conditional expression (5) is satisfied as νdrp.
(5) νdfn / νdfp <νdrn / νdrp The Abbe number at the d-line of the front group concave lens is νdfn, the Abbe number at the d-line of the front lens group is νdfp, the Abbe number at the d-line of the rear lens group is νdrn, and the Abbe number at the d-line of the rear lens group is The optical head device according to claim 12, wherein the following conditional expression (5) is satisfied as νdrp.
(5) νdfn / νdfp <νdrn / νdrp 12. The optical head device according to claim 11, wherein the following conditional expression (6) is satisfied, where f (front) is the focal length of the front group and f (rear) is the focal length of the rear group.
(6) 0.24 <f (rear) / f (front) <0.49 13. The optical head device according to claim 12, wherein the following conditional expression (6) is satisfied, where f (front) is the focal length of the front group and f (rear) is the focal length of the rear group.
(6) 0.24 <f (rear) / f (front) <0.49

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