JPH063586A - Optical recording lens - Google Patents

Abstract

PURPOSE:To secure a working distance, to excellently compensate aberrations including the curvature of field, and to make the lens relatively light in weight by composing the lens with four lens groups, i.e., negative, positive, positive, and positive lens groups which are arrayed in order from a front side. CONSTITUTION:The lens is constituted by arraying a 1st lens group being a negative meniscus lens having a concave surface on a parallel luminous flux side, i.e., the front side, a 2nd positive lens group, a 3rd positive lens group having a convex surface on the front side, and a 4th lens group being a positive meniscus lens having a convex surface on the front side in order from the front side, and meets the requirements shown by inequalities. Here, (f) is the focal length of a whole system, f1 the composite focal length of the 1st lens group, f12 the composite focal length of the 1st and 2nd lens groups, d4 the on-axis interval between the 2nd lens group and 3rd lens group, r1, r3, and r5 the radii of curvature of the front-side surfaces of the 1st, 2nd, and 3rd lens groups, and r4 the radius of curvature of the rear surface of the 2nd lens group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording lens suitable for an optical system of a system for recording information on an optical information recording medium such as a magneto-optical disk or a magneto-optical tape or reproducing the recorded information. .

[0002]

2. Description of the Related Art Conventionally, there have been many designs of optical recording lenses, and in recent years, a lens having a double-sided aspherical surface has been used. Further, as a lens type having a relatively large image circle, there are those disclosed in JP-A-52-104244, JP-A-61-173215 and JP-A-61-289314.

[0003]

However, an ordinary optical recording lens represented by the above-mentioned single lens having aspherical surfaces on both sides is designed on the assumption that it is used with a single light beam, and the Outer aberration correction is not considered important because it is considered to be a margin for lens tilt and light beam tilt, so off-axis performance is poor, and in particular field curvature can be canceled by the autofocus mechanism even if this occurs, so I did not target it.

In order to increase the speed of recording / reproducing, a multi-beam method which enables parallel recording or parallel reading by a plurality of light beams is effective. However, in an optical system for multi-beam, if the lens has a field curvature, the focal position of each beam varies, so that a lens having good off-axis performance including the field curvature is required.

In particular, in a system in which an objective lens for converging a light beam on a recording surface is fixedly provided on a moving optical head, and a movable lens for focusing and tracking is provided outside the optical head, the movable lens receives light. The number of lens elements such as a lens to be incident or a lens for collimating the light emitted from the movable lens to a parallel light is increased, and thus the field curvature of the lens element that is undercorrected is accumulated and the field curvature is increased. There is a tendency.

Therefore, when the multi-beam method is adopted, it is necessary to reduce the field curvature as much as possible to the other lenses including the movable lens.

Further, the lens of the type having a relatively large image circle disclosed in the above-mentioned publication is considered to be designed for a tracking system using a mirror, and is designed in consideration of astigmatic difference and field curvature. Has become
Out-of-axis performance is better than ordinary optical recording lenses,
It has the following drawbacks.

The lens disclosed in Japanese Unexamined Patent Publication No. 52-104244 has a problem that the radius of curvature of the first surface on the incident side of parallel light is small and the fluctuation of aberration due to manufacturing error is large.
The lens disclosed in Japanese Patent No. 61-289314 has a problem that astigmatism cannot be sufficiently corrected because the incident light to the third lens is divergent light in order to increase the NA.

When used as a movable lens,
The lens itself must be lightweight and have a large working distance due to the placement of the lens actuator. In order to secure the working distance, it is necessary to increase the height of incidence of the marginal ray on the final lens.

However, in the lens disclosed in Japanese Unexamined Patent Publication No. 61-173215, the total lens length reaches 6 times the focal length, and the lens diameter in the middle portion becomes more than twice the effective light beam diameter, so that the movable portion The lens used for is too heavy.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and ensures a working distance, satisfactorily corrects aberrations including field curvature, and is relatively lightweight. It is an object to provide an optical recording lens.

[0012]

In order to achieve the above-mentioned object, an optical recording lens according to the present invention is a negative meniscus lens having a concave surface toward the front side in order from the front side with the parallel light flux side as the front side. 1 lens group, a positive second lens group, a positive third lens group having a convex surface facing the front side, and a fourth lens group that is a positive meniscus lens having a convex surface facing the front side are arranged and arranged. It is characterized by satisfying the following conditions.

[0013]

[Expression 1] -1.00 <r1 / f <-0.75 (1) -0.45 <f / f1 <-0.12 (2) 0.20 <f / f12 <0.41 (3) 0.30 <d4 / f <1.20 (4) 0.33 < r5 / f12 <0.75 (5) -1.20 <(r3 + r4) / (r3-r4) <0.20 (6) where f is the focal length of the entire system, f1 is the combined focal length of the first lens group, and f12 is The composite focal length from the first lens group to the second lens group, d4 is the distance between the second lens group and the third lens group on the optical axis, r1 is the radius of curvature of the front surface of the first lens group, and r3
Is the radius of curvature of the front side surface of the second lens group, r4 is the radius of curvature of the rear side surface of the second lens group, and r5 is the radius of curvature of the front side surface of the third lens group.

[0014]

Embodiments of the present invention will be described below.

The optical recording lens according to the present invention can be used both for the purpose of collecting parallel light and for the purpose of converting divergent light emitted from a point light source into parallel light. The side having a farther conjugate point, that is, the side on which parallel light enters and exits is defined as the front side, and the side on which condensed light exits or divergent light enters is defined as the rear side. In the following description, the operation will be described on the assumption that a parallel light beam is incident.

The lens of the embodiment has negative, positive, positive,
It is composed of four lens groups arranged in positive order, and satisfies the above-mentioned conditional expressions (1)-(6).

Expression (1) defines the degree of divergence of the light beam on the incident side surface of the first lens group, and by satisfying this condition, spherical aberration of the entire system can be corrected well. If the value is below the lower limit, the negative power of the concave surface on the incident side becomes weak, so that the spherical aberration is insufficiently corrected and the total lens length cannot be shortened. If the upper limit is exceeded, spherical aberration will be overcorrected, and the amount of spherical aberration generated by the convex surface of the other lens group must be increased to cancel it. Will be greatly deteriorated.

Equation (2) defines the degree of divergence of the light flux after it has exited the first lens group, that is, the height of incidence of the marginal ray on the second lens group. By satisfying this condition, a long back focus can be secured and the first
The spherical aberration correction effect of the lens group can be secured.
When the value is below the lower limit, the negative power of the first lens group becomes excessive, and similarly to the case where the value is below the lower limit of the expression (1), the sensitivity of performance deterioration to the manufacturing error becomes high. If the upper limit is exceeded, the negative power of the first lens group becomes too small, and it becomes difficult to secure the back focus.

The expressions (3) and (4) are conditions for limiting the height of the marginal ray incident on the third lens, and the expression (3) is the degree of focusing of the light flux after the second lens group exits, (4) Expression) defines the distance between the second lens group and the third lens group. By satisfying both conditions, the incident height of the marginal ray on the third lens group becomes appropriate, and by simultaneously satisfying the expression (5) that defines the radius of curvature of the entrance side surface of the third lens group, the third lens group It becomes possible to correct the astigmatic difference on the incident side surface of.

When the value goes below the lower limit of the expression (3), the degree of focusing of the light beam incident on the third lens group is weak, and the incident height of the marginal ray cannot be made sufficiently low. If the upper limit is exceeded, the degree of focusing becomes strong. Therefore, in order to make the incident height of the marginal ray on the third lens group an appropriate value, the distance d4 between the second and third lens groups must be reduced. I don't get. However, in this case, the height of the paraxial chief ray does not increase, and astigmatism cannot be sufficiently corrected.

When the value goes below the lower limit of the expression (4), the distance between the second and third lens groups becomes small, and the height of the paraxial chief ray does not increase as described above, so that astigmatism is sufficiently corrected. Can not. If the upper limit is exceeded, the total lens length increases, the lens weight increases, and aberrations are overcorrected.

If the lower limit of the equation (5) is exceeded, the effect of correcting astigmatism becomes too small, and if the upper limit is exceeded, the third
Since the power of the entrance side surface of the lens group becomes too small, the power distribution to the exit side surface becomes large in order to maintain the power of the third lens group, and it becomes difficult to correct coma aberration.

Equation (6) defines the shape balance of both surfaces of the second lens group. By satisfying this condition, it is possible to suppress the occurrence of spherical aberration in the second lens group to be small and to reduce the sensitivity of occurrence of aberration to manufacturing errors on both surfaces. When the value goes below the lower limit of the equation (6), the power that the incident side surface must bear becomes excessive, and when it exceeds the upper limit, the power that the exit side surface must bear becomes excessive, and in any case, the sensitivity of aberration occurrence to the manufacturing error becomes high. At the same time, under spherical aberration occurs. In order to correct this spherical aberration, it is necessary to make the shape of the first lens group an extreme meniscus shape in which the power of each surface is large, and the aberration generation sensitivity of the first lens group must be high. .

The lens of the embodiment has the following conditional expression:
(7) (8) is satisfied.

[0025]

N3> 1.60 (7) n4> 1.75 (8) where n3 is the refractive index of the lens forming the third lens group, and n4 is the refractive index of the lens forming the fourth lens group.

Equations (7) and (8) define the glass materials of the positive third and fourth lens groups. In order to correct the field curvature, it is desirable that the positive lens has a high refractive index, and if it falls below the lower limit of each formula, the field curvature becomes large and the image performance especially in the peripheral area deteriorates. I can't secure a circle. Since the third lens group has a great influence on chromatic aberration, its refractive index is a slightly low value as shown in equation (7) in consideration of the balance between field curvature and chromatic aberration correction. on the other hand,
The refractive index of the fourth lens group needs to be high as shown in equation (8) in order to balance the correction of spherical aberration and coma due to the shape of the fourth lens group.

When each lens group is constructed as a positive and negative cemented lens in order to correct chromatic aberration, it is desirable to select a negative lens that also satisfies the conditional expressions (7) and (8). If the negative lens has a refractive index lower than that of the positive lens, under spherical aberration occurs, and it becomes impossible to correct spherical aberration of the entire system by only the negative first lens group. For the correction of chromatic aberration, it is desirable to use a high-dispersion glass material also for the negative lens, but there is no high-dispersion glass material with a low refractive index, so a glass material with a high refractive index is selected. There is a need.

A semiconductor laser is promising as a light source of the multi-beam system, but since the oscillation wavelength of the semiconductor laser changes with an output change and a focus shift occurs, in a recordable system using the semiconductor laser, its influence is affected. To prevent this, it is necessary to suppress the axial chromatic aberration to a sufficiently small value.

When all the groups of the four-group lens according to the present invention are composed of a single lens, since the negative first lens group is a meniscus lens and its power is not sufficiently large, a high dispersion material is used for the first lens group. However, even if a low dispersion material is used for the positive second to fourth lens groups, axial chromatic aberration cannot be sufficiently corrected as shown in Examples 1 and 2.

In order to correct the axial chromatic aberration, it is conceivable to configure either of the lens groups as a positive / negative cemented lens. In that case, it is desirable that the lens groups having a high incident height of marginal rays be cemented together, and when the axial chromatic aberration correction in the near infrared region is performed by the four-group lens system according to the present invention, the first, second, Sufficient aberration correction can be achieved by cementing any one of the three groups of the third lens to have a chromatic aberration correcting action.

When the first lens group is cemented, it is a cemented lens composed of a negative lens and a positive lens with a concave surface facing the front side from the front side, and is set so as to satisfy the following conditions.

[0032]

[Equation 3] νdp / νdm> 1.7 (9) 2.00 <rC / f <3.50 (10) However, in the following equation, νdp is the Abbe number of the positive lens of the cemented lens group, and νdm is the negative of the cemented lens group. The Abbe number of the lens, rC, is the radius of curvature of the bonding surface.

When the second lens group is cemented, it is a cemented lens of a negative meniscus lens having a convex surface facing the front side and a positive lens, and is set so as to satisfy the following conditions.

[0034]

[Equation 4] νdp / νdm> 1.6 (11) 0.45 <rC / f <0.72 (12)

Alternatively, the second lens group is a cemented lens in which a positive lens and a negative lens each having a convex surface directed from the front side to the front side are cemented, and the following conditions are set.

[0036]

[Equation 5] νdp / νdm> 1.6 (13) -0.94 <rC / f <-0.62 (14)

When the third lens group is cemented,
It is a cemented lens of a negative lens and a positive lens with a convex surface facing the front side from the front side, and is set so as to satisfy the following conditions.

[0038]

[Equation 6] νdp / νdm> 1.8 (15) 0.43 <rC / f <0.77 (16)

Alternatively, the third lens group is a cemented lens composed of a positive lens and a negative lens whose convex surface faces the front side from the front side, and is set so as to satisfy the following conditions.

[0040]

[Equation 7] νdp / νdm> 1.8 (17) -0.96 <rC / f <-0.66 (18)

The expressions (9), (11), (13), (15), and (17) define the ratio of the Abbe numbers of the positive and negative lenses, and when the ratio is below the lower limit, the difference in dispersion between the positive and negative lenses is small. Therefore, the chromatic aberration cannot be sufficiently corrected unless the radius of curvature of the bonding surface is made small, but when the radius of curvature of the bonding surface is small, a bright lens having a large NA cannot be constructed. Although the incident height of the marginal ray varies depending on each lens group, in order to correct the chromatic aberration in the third lens group having a low incident height, as shown by the equations (15) and (16), the other lenses can be corrected. It is necessary to make the Abbe number ratio larger than in the case of correcting chromatic aberration by a group.

The equations (10), (12), (14), (16) and (18) define the radius of curvature of the bonding surface, and the radius of curvature becomes small beyond the limit on the side where the absolute value of the numerical value is small. In this case, it becomes difficult to secure the edge of the lens, and the rate of change of spherical aberration with respect to the wavelength change becomes excessive. If the absolute value of the numerical value exceeds the limit on the large side, chromatic aberration cannot be sufficiently corrected.

When the refractive index of the positive lens of the cemented lens group is higher than that of the negative lens, spherical aberration occurs when rC that allows sufficient color correction is selected, and the refractive index of the negative lens is increased. When it is high, the field curvature cannot be corrected sufficiently, so it is desirable to combine glass materials having a small difference in refractive index that satisfy the following conditional expression.

[0044]

[Equation 8] -0.25 <np-nn <0.05 where np is the refractive index of the positive lens of the cemented lens, nn
Is the refractive index of the negative lens of the cemented lens.

[0045]

[Embodiment 1] FIG. 1 shows Embodiment 1 of the present invention. The specific numerical structure is shown in Table 1. In the table,
The surface numbers are shown in order from the front side where the parallel light flux enters or exits, NA is the numerical aperture, f is the focal length at the wavelength of 780 nm, ω is the half angle of view, fB is the back focus, r is the radius of curvature, and d is Lens thickness or air gap, nd is d-line (588n
m), ν is the Abbe number, and n780 is the refractive index at a wavelength of 780 nm.

FIG. 2 shows spherical aberration SA, sine condition SC, wavelength 750.
It shows chromatic aberration, astigmatism (S: sagittal, M: meridional), and distortion that are indicated by spherical aberration at nm, 780 nm, and 810 nm.

[0047]

[Table 1]

[0048]

Second Embodiment FIG. 3 shows a second embodiment of the present invention. The specific numerical structure is shown in Table 2. During actual use, it functions as a collimator lens that emits a light beam from a semiconductor laser as a divergent light source arranged on the rear side as a parallel light beam. The laser protective glass is represented by the ninth surface and the tenth surface. FIG. 4 shows various aberrations of the lens of this example.

[0049]

[Table 2]

[0050]

[Third Embodiment] FIG. 5 shows a third embodiment of the present invention. The specific numerical structure is shown in Table 3. Figure 6
The various aberrations of the lens of this example are shown.

[0051]

[Table 3]

[0052]

Fourth Embodiment FIG. 7 shows a fourth embodiment of the present invention. The specific numerical structure is shown in Table 4. Figure 8
The various aberrations of the lens of this example are shown.

[0053]

[Table 4]

[0054]

[Fifth Embodiment] FIG. 9 shows a fifth embodiment of the present invention. The specific numerical structure is shown in Table 5. Figure 10
Shows various aberrations of the lens of this example.

[0055]

[Table 5]

[0056]

Sixth Embodiment FIG. 11 shows a sixth embodiment of the present invention. The specific numerical structure is shown in Table 6. Figure 12
Shows various aberrations of the lens of this example.

[0057]

[Table 6]

[0058]

Seventh Embodiment FIG. 13 shows a seventh embodiment of the present invention. The specific numerical structure is shown in Table 7. At the time of actual use, it functions as an objective lens that focuses the parallel light flux incident from the front side onto the optical disc that is a recording medium. First
The protective layer of the optical disk is represented by the tenth surface and the eleventh surface. FIG. 14 shows various aberrations of the lens of this example.

[0059]

[Table 7]

[0060]

[Eighth Embodiment] FIG. 15 shows an eighth embodiment of the present invention. The specific numerical structure is shown in Table 8. 10th
The protective layer of the optical disk is represented by the surface and the eleventh surface. FIG. 16 shows various aberrations of the lens of this example.

[0061]

[Table 8]

[0062]

[Ninth Embodiment] FIG. 17 shows a ninth embodiment of the present invention. The specific numerical structure is shown in Table 9. Figure 18
Shows various aberrations of the lens of this example.

[0063]

[Table 9]

Table 10 below shows the correspondence between the above-mentioned conditional expressions and the respective embodiments. Regarding the condition (7) that defines the refractive index of the third lens group, Examples 6-9 in which the third lens group is composed of a cemented lens are shown for both positive and negative lenses. Further, the conditional expressions (9) to (18) that define the configuration of the cemented lens group are not applied to Examples 1 and 2 in which each group is composed of a single lens.

[0065]

[Table 10] Example 1 2 3 4 5 6 7 8 9 Article (1) -0.840 -0.932 -0.825 -0.886 -0.863 -0.771 -0.772 -0.864 -0.771 (2) -0.163 -0.136 -0.138 -0.161- 0.154 -0.279 -0.390 -0.158 -0.379 (3) 0.304 0.270 0.338 0.326 0.326 0.336 0.248 0.294 0.330 (4) 0.719 1.142 0.923 0.800 0.815 0.360 0.391 0.353 0.733 Formula (5) 0.566 0.320 0.524 0.518 0.502 0.601 0.428 0.597 0.571 (6) -0.490 -1.011 -0.562 -0.744 -0.629 -0.707 -0.093 -1.638 0.104 (7) 1.792 1.792 1.745 1.762 1.745 1.785 1.785 1.824 1.611 1.611 1.611 1.611 1.731 (8) 1.868 1.868 1.868 1.868 1.868 1.868 1.868 1.868 1.868 (9) (11) ) (13) (15) (17) 1.08 1.79 2.09 2.49 2.49 2.66 2.52 (10) (12) (14) (16) (18) 2.517 0.580 -0.790 0.530 0.624 0.629 -0.777

[0066]

As described above, according to the present invention, a wide image circle lens required as a lens such as a collimating lens, a condensing lens, a focusing lens, a tracking lens, etc., which constitutes a multi-beam recording / reproducing lens system is provided. Can be configured. Further, axial chromatic aberration can be corrected by using the first lens group, the second lens group, or the third lens group as a cemented lens.

[Brief description of drawings]

FIG. 1 is a lens diagram of an optical recording lens according to a first example.

FIG. 2 is a diagram of various types of aberration of the optical recording lens according to the first example.

FIG. 3 is a lens diagram of an optical recording lens according to a second example.

FIG. 4 is a diagram of various types of aberration of the optical recording lens according to the second example.

FIG. 5 is a lens diagram of an optical recording lens according to a third example.

FIG. 6 is a diagram of various types of aberration of the optical recording lens according to the third example.

FIG. 7 is a lens diagram of an optical recording lens according to a fourth example.

FIG. 8 is a diagram of various types of aberration of the optical recording lens according to the fourth example.

FIG. 9 is a lens diagram of an optical recording lens according to a fifth example.

FIG. 10 is a diagram of various types of aberration of the optical recording lens according to the fifth example.

FIG. 11 is a lens diagram of an optical recording lens according to a sixth example.

FIG. 12 is a diagram of various types of aberration of the optical recording lens according to the sixth example.

FIG. 13 is a lens diagram of an optical recording lens according to a seventh example.

FIG. 14 is a diagram of various types of aberration of the optical recording lens according to the seventh example.

FIG. 15 is a lens diagram of an optical recording lens according to an eighth example.

FIG. 16 is a diagram of various types of aberration of the optical recording lens according to the eighth example.

FIG. 17 is a lens diagram of an optical recording lens according to a ninth example.

FIG. 18 is a diagram of various types of aberration of the optical recording lens according to the ninth example.

Claims (7)

[Claims] 1. An optical recording lens having a function of condensing an incident parallel light beam, wherein a parallel light beam side is a front side, and a first lens group is a negative meniscus lens having a concave surface facing the front side in order from the front side, A positive second lens group, a positive third lens group having a convex surface facing the front side, and a fourth positive meniscus lens having a convex surface facing the front side.
An optical recording lens, which is configured by arranging a lens group and satisfies the following conditions. -1.00 <r1 / f <-0.75 (1) -0.45 <f / f1 <-0.12 (2) 0.20 <f / f12 <0.41 (3) 0.30 <d4 / f <1.20 (4) 0.33 <r5 / f12 < 0.75 (5) -1.20 <(r3 + r4) / (r3-r4) <0.20 (6) where f is the focal length of the entire system, f1 is the combined focal length of the first lens group, and f12 is the first lens group. To the second lens group, d4 is the distance between the second lens group and the third lens group on the optical axis, r1 is the radius of curvature of the front surface of the first lens group, and r3 is the curvature of the front surface of the second lens group Radius, r4 is the radius of curvature of the rear surface of the second lens group, and r5 is the radius of curvature of the front surface of the third lens group. 2. The optical recording lens according to claim 1, wherein the following condition is satisfied. n3> 1.60 (7) n4> 1.75 (8) where n3 is the refractive index of the lens forming the third lens group, and n4 is the refractive index of the lens forming the fourth lens group. 3. The first lens group is composed of, in order from the front side, a negative first lens having a concave surface facing the front side and a positive second lens bonded to the first lens, and The second lens group is composed of a biconvex positive single lens,
The third lens group is composed of a positive single lens having a convex surface facing the front side, and the fourth lens group is composed of a positive meniscus single lens having a convex surface facing the front side. The optical recording lens according to claim 1, wherein the optical recording lens is configured and satisfies the following conditions. νdp / νdm> 1.7 (9) 2.00 <rC / f <3.50 (10) where νdp is the Abbe number of the positive lens of the first lens group, νdm is the Abbe number of the negative lens of the first lens group, and rC is the first lens It is the radius of curvature of the bonding surface of the group. 4. The first lens group is a negative meniscus single lens with a concave surface facing the front side, and the second lens group is
A second lens having a negative meniscus having a convex surface facing the front side and a positive third lens are cemented together, and the third lens group is a positive single lens having a convex surface facing the front side. The lens group for optical recording according to claim 1, wherein the lens group is a positive meniscus single lens having a convex surface facing the front side, is composed of 5 elements in 4 groups as a whole, and satisfies the following conditions. νdp / νdm> 1.6 (11) 0.45 <rC / f <0.72 (12) where νdp is the Abbe number of the positive lens of the second lens group, νdm is the Abbe number of the negative lens of the second lens group, and rC is the second lens It is the radius of curvature of the bonding surface of the group. 5. The first lens group is a negative meniscus single lens with a concave surface facing the front side, and the second lens group is
A positive second lens having a convex surface facing the front side and a negative third lens are cemented together, and the third lens group is a positive single lens having a convex surface facing the front side, and the fourth lens group 2. The optical recording lens according to claim 1, wherein is a positive meniscus single lens with a convex surface facing the front side, is composed of 5 elements in 4 groups as a whole, and satisfies the following conditions. νdp / νdm> 1.6 (13) -0.94 <rC / f <-0.62 (14) where νdp is the Abbe number of the positive lens of the second lens group, νdm is the Abbe number of the negative lens of the second lens group, and rC is the It is the radius of curvature of the cemented surface of the two lens groups. 6. The first lens group is composed of a negative meniscus single lens with a concave surface facing the front side, and the second lens group is composed of a biconvex positive single lens, and the third lens group is composed of
The lens group is configured by laminating a negative third lens having a convex surface facing the front side and a positive fourth lens, and the fourth lens group is configured by a positive meniscus single lens having a convex surface facing the front side. The lens for optical recording according to claim 1, characterized in that it is composed of 5 elements in 4 groups as a whole and satisfies the following conditions. νdp / νdm> 1.8 (15) 0.43 <rC / f <0.77 (16) where νdp is the Abbe number of the positive lens of the third lens group, νdm is the Abbe number of the negative lens of the third lens group, and rC is the third lens It is the radius of curvature of the bonding surface of the group. 7. The first lens group comprises a negative meniscus single lens having a concave surface facing the front side, and the second lens group comprises a biconvex positive single lens.
The lens group is configured by laminating a positive third lens having a convex surface facing the front side and a negative fourth lens, and the fourth lens group is configured by a positive meniscus single lens having a convex surface facing the front side. The optical recording lens according to claim 1, characterized in that it is composed of 5 elements in 4 groups as a whole and satisfies the following condition. νdp / νdm> 1.8 (17) -0.96 <rC / f <-0.66 (18) where νdp is the Abbe number of the positive lens of the third lens group, νdm is the Abbe number of the negative lens of the third lens group, and rC is the It is the radius of curvature of the cemented surface of the three lens groups.