JP2011090235A - Achromatic lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an achromatic lens which is thin and has high chromatic aberration correction capability. <P>SOLUTION: The achromatic lens has at least a first base material L11; a second base material L12 cemented with the first base material L11; a third base material L13 cemented with the second base material L12 on an opposite side to the base material L11; and a fourth transparent base material L14, cemented with the third base material L13 on an opposite side to the second base material L12. The second base material L12 is a positive lens, and the third base material L13 is a negative lens. The first base material L11 and the second base material L12 are different in the refractive index with respect to at least one wavelength, the second base material L12 and the third base material L13 are different in the Abbe number, and the third base material L13 and the fourth base material L14 are different in the refractive index with respect to at least one wavelength. The second base material L12 and the third base material L13 are energy-curable resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an achromatic lens capable of suppressing chromatic aberration generated when used at a plurality of wavelengths.

  A lens is well known as an optical element that forms an image by refracting incident light and collecting or spreading the light. Optical glass and various resins are used for the optical material used for this lens, but since these optical materials have characteristics that the refractive index differs depending on the wavelength, the deviation of the condensing position between the wavelengths during condensing, that is, Chromatic aberration occurs.

  In Patent Document 1, it is proposed to correct chromatic aberration by arranging an ultraviolet curable resin between glass substrates. Patent Document 2 proposes that chromatic aberration correction using a diffractive surface is effectively performed by using a diffractive optical element.

JP 2006-349947 A Japanese Patent No. 3717555

  However, Patent Document 1 proposes that an ultraviolet ray curable resin is disposed between glass substrates to correct chromatic aberration. However, in Patent Document 1, the bonded optical element becomes thick, and there is a problem that it is difficult to make the optical element thin especially when the outer diameter is reduced. This is due to the fact that in manufacturing a glass lens with a reduced outer diameter, a certain amount of required inner wall thickness and edge thickness must be secured. This problem is also inherent in the case of using not only a glass lens but also a resin lens by injection molding.

  Patent Document 2 proposes that chromatic aberration correction is effectively performed by employing an optical material that satisfies a predetermined condition for the diffractive optical element. However, in Patent Document 2, since the lens is made of glass or resin by injection molding, the thickness of the entire optical element is increased as in Patent Document 1. Since the chromatic aberration correction surface is limited to one surface, it is difficult to perform effective aberration correction.

  The present invention has been made paying attention to the problems of the above-mentioned problems, and proposes an optical element capable of effectively correcting chromatic aberration within a limited thickness.

  In order to solve the above-described problems, the achromatic lens of the present invention is any one of the following.

The first configuration of the achromatic lens of the present invention includes a transparent first base material, a transparent second base material joined to the first base material, and the second base material sandwiched between the first base material and the second base material. And a transparent third substrate bonded to the opposite side of the first substrate and a transparent third substrate bonded to the opposite side of the second substrate across the third substrate. 4 base materials, the second base material is a positive lens, the third base material is a negative lens, and the first base material and the second base material are , The refractive index for at least one wavelength is different, the second base material and the third base material have different Abbe numbers, and the third base material and the fourth base material are at least one wavelength. The second base material is an energy curable resin, and the third base material is an energy curable resin. It is intended.

The second configuration of the achromatic lens of the present invention is characterized in that the following conditional expression (1) is satisfied in the first configuration.
0.008 <| 1 / νp−1 / νn | <0.035 (1)
here,
νp is the Abbe number of the second base material,
νn is the Abbe number of the third substrate,
It is.

The third configuration of the achromatic lens of the present invention is characterized in that, in the first or second configuration, the following conditional expression (2) is satisfied.
0.05 [mm] <(d2 + d3) <1.00 [mm] (2)
here,
d2 is the thickness of the second base material;
d3 is the inner thickness of the third substrate,
It is.

  According to a fourth configuration of the achromatic lens of the present invention, in any one of the first to third configurations, an interface between the second base material and the third base material forms a relief pattern. It is a diffractive optical surface.

The fifth configuration of the achromatic lens according to the present invention is characterized in that, in the fourth configuration, the following conditional expressions (3) and (4) are satisfied.
n1 (λ)> n2 (λ) (3)
((n1 (λ2) −n2 (λ2)) / (n1 (λ1) −n2 (λ1)))
-(N1 (λ2) -1) / (n1 (λ1) -1)> 0 (4)
here,
n1 (λ) is the refractive index of the second substrate,
n2 (λ) is the refractive index of the third substrate,
However,
λ1 <λ <λ2, and
λ1 and λ2 are arbitrary light wavelengths.

  According to a sixth configuration of the achromatic lens of the present invention, in any one of the first to fifth configurations, the energy curable resin used for the second base material or the third base material is light. It is a curable resin.

  A seventh configuration of the achromatic lens according to the present invention is the same as any one of the first to sixth configurations, the interface between the first base material and the second base material, or the third base material. And at least one of the interfaces of the fourth base material is provided with a light shielding portion.

  According to an eighth configuration of the achromatic lens of the present invention, in any one of the first to seventh configurations, at least one of the first base material and the fourth base material is configured by a plane parallel plate. It is characterized by being.

The ninth configuration of the achromatic lens according to the present invention is characterized in that, in any one of the first to eighth configurations, the following conditional expression (5) is satisfied.
κ1, κ4 <0.1 [%] (5)
here,
κ1 is the water absorption rate of the first substrate,
κ4 is the water absorption rate of the fourth substrate,
It is.

  According to the present invention, it is possible to provide a thin achromatic lens having high chromatic aberration correction capability.

Sectional drawing which developed the achromatic lens of Example 1 of this invention and took along the optical axis. FIG. 6 is a diagram for explaining a manufacturing process of the achromatic lens according to the first embodiment of the present invention. FIG. 6 is a diagram for explaining a manufacturing process of the achromatic lens according to the first embodiment of the present invention. Sectional drawing which developed the achromatic lens of Example 2 of this invention, and took it along the optical axis. Sectional drawing which developed the achromatic lens of Example 3 of this invention, and took it along the optical axis. Sectional drawing which developed the achromatic lens of Example 4 of this invention, and took it along the optical axis. Sectional drawing which developed the achromatic lens of Example 5 of this invention, and took it along the optical axis. Sectional drawing which developed the achromatic lens of Example 6 of this invention, and took it along the optical axis. Sectional drawing which developed the achromatic lens of Example 7 of this invention, and took it along the optical axis.

  The configuration of the first achromatic lens of the present embodiment includes a transparent first base material, a transparent second base material joined to the first base material, and a second base material sandwiched therebetween. A transparent third substrate bonded to the opposite side of the first substrate, and a transparent fourth substrate bonded to the opposite side of the second substrate across the third substrate; The second substrate is a positive lens, the third substrate is a negative lens, and the first substrate and the second substrate have a refractive index with respect to at least one wavelength. In contrast, the second substrate and the third substrate have different Abbe numbers, the third substrate and the fourth substrate have different refractive indices for at least one wavelength, and the second substrate has It is an energy curable resin, and the third base material is an energy curable resin.

  Below, the reason and effect | action which employ | adopt the 1st structure of this achromatic lens are demonstrated.

  According to the first configuration of the achromatic lens, it is possible to effectively correct chromatic aberration mainly at the interface between the second base material and the third base material. It is also possible to correct various aberrations at the interface between the first base material and the second base material, and at the interface between the third base material and the fourth base material. Therefore, the performance of the entire optical system incorporating this achromatic lens can be improved.

  Further, since the second base material and the third base material are made of energy curable resin, the edge thickness of the second base material constituting the positive lens, and the third lens constituting the negative lens Since the inner thickness of the base material can be formed extremely thin, the entire achromatic lens can be reduced in thickness. Such a thin achromatic lens is particularly convenient when applied to an imaging optical system for photographing a small area.

The configuration of the second achromatic lens of the present embodiment is characterized in that the following conditional expression (1) is satisfied.
0.008 <| 1 / νp−1 / νn | <0.035 (1)
here,
νp is the Abbe number of the second substrate,
νn is the Abbe number of the third substrate,
It is.

  Below, the reason and effect | action which employ | adopt the 2nd structure of this achromatic lens are demonstrated. If the lower limit of conditional expression (1) is not reached, it is necessary to increase the radius of curvature of the joint surface in order to obtain the effect of correcting chromatic aberration. For this reason, it is difficult to reduce the thickness of the achromatic lens. Further, when the value exceeds the upper limit value, a change in performance due to variations in the surface accuracy of the joint surface becomes large, which is not preferable.

The configuration of the third achromatic lens of the present embodiment is characterized in that the following conditional expression (2) is satisfied.
0.05 [mm] <(d2 + d3) <1.00 [mm] (2)
here,
d2 is the thickness of the second base material,
d3 is the thickness of the third base material,
It is.

  Below, the reason and effect | action which employ | adopts the 3rd structure of this achromatic lens are demonstrated. When the lower limit value of conditional expression (2) is not reached, it is difficult to secure the respective powers of the second base material and the third base material, so that a sufficient chromatic aberration correction effect cannot be obtained. Further, when the upper limit value of the conditional expression (2) is exceeded, the achromatic lens becomes thick, so that the merit of using the energy curable resin is diminished.

  Further, the configuration of the fourth achromatic lens of the present embodiment is characterized in that it is a diffractive optical surface formed with a relief pattern.

  Below, the reason and effect | action which employ | adopts the 4th structure of this achromatic lens are demonstrated. The diffractive optical surface forming the relief pattern has a value of −3.45 when converted to the Abbe number. Therefore, chromatic aberration can be corrected more favorably by using a diffractive optical surface. In addition to the use of the diffractive optical surface, for example, by setting the refractive indexes of the first base material and the fourth base material to appropriate values, it is possible to improve chromatic aberration correction in a wider wavelength range. It becomes possible.

The configuration of the fifth achromatic lens of the present embodiment is characterized in that the following conditional expressions (3) and (4) are satisfied.
n1 (λ)> n2 (λ) (3)
((n1 (λ2) −n2 (λ2)) / (n1 (λ1) −n2 (λ1)))
-(N1 (λ2) -1) / (n1 (λ1) -1)> 0 (4)
here,
n1 (λ) is the refractive index of the second substrate,
n2 (λ) is the refractive index of the third substrate,
However,
λ1 <λ <λ2, and
λ1 and λ2 are arbitrary light wavelengths,
It is.

Below, the reason and effect | action which employ | adopts the 5th structure of this achromatic lens are demonstrated. When the conditional expressions (3) and (4) are satisfied, the wavelength dependence of the diffraction efficiency on the diffractive optical surface can be reduced. As a result, it is possible to effectively prevent the occurrence of uneven color and the occurrence of flare due to unnecessary order light. For the derivation of this conditional expression, refer to Patent Document 2 (Japanese Patent No. 3717555).

Moreover, it is preferable that the following conditional expressions are satisfied.
T ² > 4πλd / {n1 (λ) + n2 (λ)}
here,
d is the groove depth of the relief pattern,
T is the pitch of the periodic structure of the relief pattern,
However,
λ1 <λ <λ2,
It is.

  The configuration of the sixth achromatic lens of the present embodiment is characterized in that the energy curable resin used for the second substrate or the third substrate is a photocurable resin.

  Below, the reason and effect | action which employ | adopt the 6th structure of this achromatic lens are demonstrated. As described above, it is preferable to use an energy curable resin for the second base material or the third base material. Further, it is preferable to use a photocurable resin as the energy curable resin. Thus, by making a base material into a photocurable resin, light can be irradiated through a transparent base material, and resin can be hardened. Thereby, the first base material and the second base material can be stably molded, and as a result, high aberration correction performance can be exhibited. In addition, when compared with a thermosetting resin that is one of energy curable resins, it is possible to suppress adverse effects due to thermal expansion, so that the first base material and the second base material can be stably molded. it can. Therefore, the aberration correction capability is not deteriorated also from this aspect.

  In addition, the seventh achromatic lens of the present embodiment is configured to shield light from at least one of the interface between the first substrate and the second substrate, or the interface between the third substrate and the fourth substrate. It is characterized by providing a section.

  Below, the reason and effect | action which employ | adopts the 7th structure of this achromatic lens are demonstrated. In the seventh configuration, a light blocking portion for reducing unnecessary light (flare light) is provided at an appropriate interface. By providing the light shielding portion in this manner, unnecessary light can be reduced, and the contrast of the achromatic lens can be significantly improved. In addition, even if the light-shielding part is provided as another member pinched | interposed between the base materials, it may be provided by printing on a base material. In addition, the shape of the light shielding portion can be an arbitrary shape according to the form of unnecessary light.

  In addition, the configuration of the eighth achromatic lens of the present embodiment is characterized in that at least one of the first base material and the fourth base material is formed of a plane parallel plate.

  Below, the reason and effect | action which employ | adopts the 8th structure of this achromatic lens are demonstrated. According to this configuration, it is not necessary to perform the centering process on the first base material or the fourth base material. As a result, a thin plane parallel plate can be used as it is, and the manufacturing process can be simplified. Further, since chromatic aberration correction can be mainly performed at the interface between the second base material and the third base material, it is easy to combine with other optical devices that correct the condensing effect and the aberration of the reference wavelength.

Further, the ninth achromatic lens structure of the present embodiment is characterized in that the following conditional expression (5) is satisfied.
κ1, κ4 <0.1 [%] (5)
here,
κ1 is the water absorption rate of the first substrate,
κ4 is the water absorption rate of the fourth substrate,
It is.

  Below, the reason and effect | action which employ | adopts the 9th structure of this achromatic lens are demonstrated. When the conditional expression (5) is satisfied, the aberration fluctuation accompanying the change in humidity can be suppressed even when the energy-curable resin having a high water absorption rate is used for the second base material or the third base material. That is, since the water absorption rate of the first base material and the fourth base material is low, the influence of humidity can be prevented from reaching the second base material and the third base material. In addition, with respect to the first base material and the fourth base material itself, it is possible to suppress fluctuations in aberrations accompanying changes in humidity.

  If the upper limit value of conditional expression (5) is exceeded, the shape of the first to fourth substrates changes according to the change in humidity, resulting in aberration fluctuations.

  The achromatic lens according to this embodiment will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view taken along the optical axis of the outline of the achromatic lens in Example 1 of the present invention. In the achromatic lens shown in this figure, a first base material L11, a second base material L12, a third base material L13, and a fourth base material L14 are arranged in order from the A side to the B side. It is configured. Moreover, each base material L11-L14 forms five interfaces of r11-r15 in order toward the B side from the A side. It is arbitrary whether the A side is the object side and the B side is the emission side, or the A side is the emission side and the B side is the object side.

  The first base material L11 is a plano-concave lens having a concave surface facing the A side and a flat surface facing the B side, that is, the adjacent second base material L12 side, and a glass base material is adopted as the material thereof. ing.

  The second base material L12 is a plano-convex lens having a flat surface facing the A side, that is, the adjacent first base material L11 side, and a convex surface facing the B side, that is, the adjacent third base material L13. Therefore, an epoxy-based photocurable resin is adopted as the base material.

  The third base material L13 is a plano-concave lens having a concave surface facing the A side, that is, the adjacent second base material L12 side, and a flat surface facing the B side, that is, the adjacent fourth base material L14. Therefore, an epoxy-based photocurable resin is adopted as the base material.

  The fourth base material L14 is a plano-convex lens having a flat surface facing the A side, that is, the adjacent third base material L13 side, and a convex surface facing the B side, and a glass base material is adopted as the base material. is doing.

Thus, in Example 1, the convex surface of the second base material L12 and the concave surface of the third base material L13 were combined, and an energy curable resin such as a photocurable resin was used for these two base materials. Thus, it is possible to effectively correct chromatic aberration in a thin space. In addition, since the first base material L11 and the fourth base material L14 can select materials having a relatively wide refractive index, various aberrations at the reference wavelength can be effectively corrected. Note that chromatic aberration can also be corrected at the interface r12 between the first base material L11 and the second base material L12 and the interface r14 between the third base material L13 and the fourth base material L14. In Example 1, the corresponding value of conditional expression (1) is 0.011, and the corresponding value of κ1 and κ4 is almost zero. The second base material L12 and the third base material L13 are energy curable resins such as a photo-curing resin, and the first base material L11 and the fourth base material L14 are glass base materials or injection molding. If it is a resin base material by, it will not specifically limit.

  Numerical data of Example 1 is shown below. In the numerical data, nd is the refractive index of the d-line of each substrate (optical medium), and νd is the Abbe number of each substrate. According to this numerical data, the Abbe number of the second base material L12 and the third base material satisfies the conditional expression (1) (corresponding value is 0.011), and has sufficient chromatic aberration correction capability. Yes.

Example 1
Base material number nd νd
L11 1.717 30
L12 1.514 58
L13 1.573 35
L14 1.65 59.

  2 and 3 are diagrams showing an embodiment of the manufacturing process of the achromatic lens in Example 1. FIG. In this embodiment, achromatic lenses are manufactured in the order of (1) to (6). In the step (1), the first mold K1 is fitted into the first base material L11. At that time, the surface of the first base L11 facing the first mold K1 is an interface r12 formed between the first base L11 and the second base L12 in the completed achromatic lens. It is formed in the same shape. Further, the surface of the first mold K1 facing the first base material L11 is the same as the interface r13 formed between the second base material L12 and the third base material L13 in the completed achromatic lens. It is formed to have a shape or substantially the same shape. By causing the first mold K1 having such a shape to face the first base material L11, a gap is formed between the two.

  In the step (2), an epoxy-based photocurable resin is injected into the formed gap from an appropriate injection port (not shown) provided in the first mold K1, and is formed of a transparent glass substrate. In addition, ultraviolet light is irradiated from the first base material L11 side, and the photocurable resin filled in the gap is cured on the first base material L11. In this embodiment, the photocurable resin is injected from the injection port provided in the first mold K1, but before the first base material L11 is fitted into the first mold K1, the photocurable mold is used. It is good also as filling with resin. In this way, the step of removing burrs formed at the injection port of the first mold K1 becomes unnecessary.

  (3) is the figure which showed the state hardened | cured at the process of (2). An interface r12 is formed between the first base material L11 and the second base material L12. Further, the surface on which the second base L12 faces the first first mold K1 has the same shape as the interface r13 in the completed achromatic lens, depending on the shape of the first mold K1, or It is formed to have substantially the same shape. Further, by polishing the exposed surface of the second base material L12, it is possible to improve the accuracy of the interface r13.

  In this way, by forming the second base material L12 with a photocurable resin, it is possible to form the rim portion (the peripheral end portion indicated by E in the drawing) of the second base material L12 extremely thin. Thus, the thickness of the entire achromatic lens can be suppressed. Further, when the exposed surface of the second base material L12 is polished, the second base material L12 can be polished in a state where the first base material L11 is supported, so that the rim portion is processed thinly. It becomes possible.

  In the step (4), the fourth base material is spaced apart from the second base material L12 by a predetermined distance with respect to the set of the first base material L11 and the second base material L12 formed in (3). Install L14. The installation is performed using a second mold K2 that surrounds each substrate. At that time, the surface of the fourth base material L14 facing the second base material L12 is formed in the same shape as the interface r14 in the completed achromatic lens. The gap formed between the second base material L12 and the fourth base material L14 has the same shape as the third base material L13.

  In the step (5), an epoxy-based photocurable resin is injected into the formed gap from an appropriate injection port (not shown) provided in the second mold K2, and is formed of a transparent glass substrate. In addition, ultraviolet light is irradiated from the first base material L11 side, and the photocurable resin filled in the gap is cured on the second base material L12 and the fourth base material L14. Here, instead of injecting the photocurable resin from the injection port of the second mold K2, the photocurable resin is filled in advance between the second base material L12 and the fourth base material L14. Also good. Further, in this step, since the fourth base material L14 also uses a transparent glass base material, the ultraviolet light irradiation is performed from the third base material L14 side, or from the first base material L11 side, the third base material L14 side. It is good also as performing from both the base-material L14 side. When ultraviolet light is irradiated from both, the curing time can be shortened.

  (6) is the figure which showed the completed achromatic lens. (4) In the process of (5), by using a photocurable resin for the third base material L13 and curing it in a state sandwiched between the second base material L12 and the fourth base material L14, It is possible to form a very thin inner portion (thickness in the vicinity of the optical axis indicated by T in the drawing) of the third base material L13.

  As described above, in the manufacturing process of the achromatic lens according to the present embodiment, the overall thickness is obtained by combining the convex surface of the second base material constituting the positive lens and the concave surface of the third base material constituting the negative lens. Can be suppressed. Moreover, the edge part E of the 2nd base material L12 and the middle part T of the 3rd base material L13 by using photocurable resin for the 2nd base material L12 and the 3rd base material L13, It becomes possible to form very thinly compared with the case where each forms independently. Further, since only one mold (first mold K1) is sufficient to form an interface for the mold, the manufacturing process can be simplified.

  In addition, the manufacturing process of the achromatic lens of this embodiment shows an example, and the selection of the material as the energy curable resin can be appropriately performed. Moreover, also about the order of a process, after hardening and forming the 3rd base material L13, it is good also as hardening and forming the 2nd base material L12.

  FIG. 4 is a cross-sectional view taken along the optical axis of the outline of the achromatic lens in Example 2 of the present invention. In the achromatic lens shown in this figure, a first base material L21, a second base material L22, a third base material L23, and a fourth base material L24 are arranged in order from the A side to the B side. It is configured. Moreover, each base material L21-L24 forms five interfaces of r21-r25 in order toward B side from A side. It is arbitrary whether the A side is the object side and the B side is the emission side, or the A side is the emission side and the B side is the object side.

  The first base material L21 is a plano-convex lens having a convex surface directed to the A side and a flat surface directed to the B side, that is, the adjacent second base material L22 side, and a cycloolefin polymer is adopted as the material thereof. ing.

  The second base material L22 is a plano-convex lens having a flat surface facing the A side, that is, the adjacent first base material L21 side, and a convex surface facing the B side, that is, the adjacent third base material L23. Therefore, an epoxy-based cured resin is adopted as the base material.

  The third base material L23 is a plano-concave lens having a concave surface facing the A side, that is, the adjacent second base material L22 side, and a flat surface facing the B side, that is, the adjacent fourth base material L24 side. Therefore, an epoxy-based cured resin is adopted as the base material.

  The fourth base material L24 is a plano-convex lens having a flat surface facing the A side, that is, the adjacent third base material L23 side, and a convex surface facing the B side, and a cycloolefin polymer is adopted as the base material. is doing.

  With this configuration, chromatic aberration can be effectively corrected in a thin space with L22 and L23, and a sufficient light condensing function can be provided with L21 and L24. Particularly in this configuration, since all the base materials are made of a resin material, there is an effect of reducing the weight.

  Numerical data of Example 2 is shown below. In the numerical data, nd is the refractive index of the d-line of each substrate (optical medium), and νd is the Abbe number of each substrate. According to this numerical data, the Abbe number of the second base material L12 and the third base material satisfies the conditional expression (1) (corresponding value is 0.011), and has sufficient chromatic aberration correction capability. Yes. Further, the corresponding values of the water absorption rates κ1 and κ4 of the first base material L21 and the fourth base material L41 are 0.01 or less, and the second base material L22 and the third base material L23 are removed from moisture. Sufficient protection is possible.

Example 2
Base material number nd νd
L21 1.53 56
L22 1.514 58
L23 1.573 35
L24 1.53 56.

  FIG. 5 is a cross-sectional view taken along the optical axis of the outline of the achromatic lens in Example 3 of the present invention. The third embodiment is a modification of the second embodiment. In the second embodiment, the interface r32 between the first base material L31 and the second base material L32 has a shape with a convex surface facing the A side. This is different in that the interface r34 between the third base material L33 and the fourth base material L34 has a convex surface facing the B side.

  As described above, the interface r32 between the first base material L31 and the second base material L32 and the interface r34 between the third base material L33 and the fourth base material L34 may be appropriately curved. According to such a configuration of the achromatic lens, it is possible to increase the degree of freedom in correcting various aberrations.

  FIG. 6 is a cross-sectional view taken along the optical axis by developing the outline of the achromatic lens of Example 4 of the present invention. In Example 4, the shape is the same as that of Example 2, but the interface r43 between the second base material L42 and the third base material L43 is a diffractive optical surface formed by forming a relief pattern. Is different.

In addition, as the material of the second base material L42 and the third base material L43, an acrylic cured resin having the following numerical values is used. n1 to n4 are refractive indexes at wavelengths (unit: [nm]) shown in parentheses, and νd is an Abbe number. Assuming an imaging optical system using an infrared cut filter under visible light, these values are as follows: λ1 is 404.66 [nm] and λ2 is 656.27 [nm]
((n1 (λ2) −n2 (λ2)) / (n1 (λ1) −n2 (λ1))) − (n1 (λ2) −1) / (n1 (
λ1) -1) = 0.327
Thus, conditional expression (4) is satisfied, and it is possible to effectively correct chromatic aberration in the photographing optical system.

Example 4
Substrate number n1 (404.66) n2 (486.13) n3 (587.56) n4 (656.27) νd
L42 1.63977 1.626 1.60999 1.6038 27
L43 1.66194 1.65086 1.63762 1.63222 27
.

  In Example 4, the material of the second base material L42 and the third base material L43 is not limited to the acrylic curable resin, and may be an energy curable resin that satisfies the conditional expression (4). . The first base material L41 and the fourth base material L43 may be made of a glass base material or a resin lens by injection molding.

  FIG. 7 is a cross-sectional view taken along the optical axis of the outline of the achromatic lens in Example 5 of the present invention. In the achromatic lens shown in this figure, a first base material L51, a second base material L52, a third base material L53, and a fourth base material L54 are arranged in order from the A side to the B side. It is configured. Moreover, each base material L51-L54 forms five interfaces r51-r55 in order toward the B side from the A side. It is arbitrary whether the A side is the object side and the B side is the emission side, or the A side is the emission side and the B side is the object side.

  The first base material L51 is a parallel flat plate having a planar shape on both the A side and the B side and a thickness of 0.4 [mm], and a glass base material is adopted as the material thereof. .

  The second base material L52 is a plano-convex lens having a flat surface facing the A side, that is, the adjacent first base material L51 side, and a convex surface facing the B side, that is, the adjacent third base material L53 side. Therefore, an epoxy-based cured resin is adopted as the base material. The medium thickness (distance between the interfaces r52 and r53 on the optical axis) is 0.3 [mm], and the radius of curvature at the interface r53 is 8 [mm].

  The third base material L53 is a plano-concave lens having a concave surface facing the A side, that is, the adjacent second base material L52 side, and a flat surface facing the B side, that is, the adjacent fourth base material L54 side. Therefore, an epoxy-based cured resin is adopted as the base material. The medium thickness (distance between the interfaces r53 and r54 on the optical axis) is 0.1 [mm], and the radius of curvature at the interface r53 is 8 [mm].

  The fourth base material L54 is a plane parallel plate having a planar shape on both the A side and the B side and a thickness of 0.4 [mm], and a glass base material is adopted as the material thereof. .

  With such a configuration, the total thickness of the achromatic lens can be formed as extremely thin as 1.2 [mm]. The effective diameter of the achromatic lens is 4 [mm]. In the fifth embodiment, since the first base material L51 and the fourth base material L54 are parallel flat plates, the centering process for each base material can be simplified and thinned. In addition, the second base material L52 and the third base material L53 are made of a photo-curing resin, so that the thickness of the medium thickness and the edge thickness can be reduced, and the thickness of the entire achromatic lens can be suppressed. .

  Further, the materials of the first base material L51 and the second base material L52, and the third base material L53 and the fourth base material L54 have different Abbe numbers. As a result, it is possible to correct chromatic aberration also at the interfaces r52 and r54.

  Numerical data of Example 5 is shown below. In the numerical data, nd is the refractive index of the d-line of each substrate (optical medium), and νd is the Abbe number of each substrate. Note that the material, thickness, and radius of curvature are not limited to the numerical values of the present embodiment, and can be selected corresponding to the optical system to be used as appropriate.

Example 5
Base material number nd νd
L51 1.516 64
L52 1.514 58
L53 1.573 35
L54 1.516 64.

  FIG. 8 is a cross-sectional view taken along the optical axis by developing the outline of the achromatic lens of Example 6 of the present invention. In Example 6, the shape is the same as that of Example 5, but the interface r63 between the second base material L62 and the third base material L63 is a diffractive optical surface formed by forming a relief pattern. Is different.

In addition, as the material of the second base material L62 and the third base material L63, an acrylic curable resin having the following numerical values is used. n1 to n4 are refractive indexes at wavelengths (unit: [nm]) shown in parentheses, and νd is an Abbe number. Assuming an imaging optical system using an infrared cut filter under visible light, these values are as follows: λ1 is 404.66 [nm] and λ2 is 656.27 [nm]
((n1 (λ2) −n2 (λ2)) / (n1 (λ1) −n2 (λ1))) − (n1 (λ2) −1) / (n1 (
λ1) -1) = 0.327
Thus, conditional expression (4) is satisfied, and it is possible to effectively correct chromatic aberration in the photographing optical system.

Example 6
Substrate number n1 (404.66) n2 (486.13) n3 (587.56) n4 (656.27) νd
L62 1.63977 1.626 1.60999 1.6038 27
L63 1.66194 1.65086 1.63762 1.63222 27
.

  The interface between the second base material L62 and the third base material L63 is a diffractive optical surface, but macroscopically has a shape with a radius of curvature of 40 [mm]. The thickness of the second substrate L62 having a convex surface on the B side (distance between the interfaces r62 and r63 on the optical axis) is 0.1 [mm], and the thickness of the third substrate L63 (optical axis). The distance between the upper interfaces r63 and r64) is 0.05 [mm]. The first base material L61 and the second base material L62 are glass base materials having a refractive index nd of 1.516 and an Abbe number νd of 64, and each thickness is 0.4 [mm]. It is. Therefore, the total thickness of the achromatic lens is 0.95 [mm]. The effective diameter of this achromatic lens is 4 [mm].

  FIG. 9 is a cross-sectional view taken along the optical axis by developing an outline of the achromatic lens in Example 7 of the present invention. The achromatic lens shown in this figure is the same as the achromatic lens having the configuration of Example 5 described in FIG. 7 except that a zeroth base material L70 is added to the A side and a fifth base material L75 is added to the B side. It has become.

  The 0th base material L70 is a plano-convex lens having a convex surface facing the A side and a flat surface facing the B side, that is, the adjacent first base material L70 side, and the material thereof is an epoxy photocurable resin. Is adopted.

  The fifth base material L75 is a plano-convex lens having a convex surface facing the B side and a flat surface facing the A side, that is, the adjacent fourth base material L74 side, and is made of an epoxy-based photocurable resin. Is adopted.

  Numerical data of Example 7 is shown below. In the numerical data, nd is the refractive index of the d-line of each substrate (optical medium), and νd is the Abbe number of each substrate.

Example 7
Base material number nd νd
L70 1.514 58
L71 1.516 64
L72 1.51458 58
L73 1.573 35
L74 1.516 64
L75 1.514 58.

  Thus, on the optical element surface formed of the first to fourth base materials, the thickness of the 0th base material and the fifth base material made of an energy curable resin were not greatly changed. It is also possible to form an achromatic lens that enhances the light condensing action and the aberration correction power.

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention. Is.

L70: 0th base material L * 1 in the seventh embodiment ... 1st base material L * 2 ... 2nd base material L * 3 ... 3rd base material L * 4 ... 4th base material ( (The asterisk * attached to each substrate corresponds to the number in the example)
L75: fifth base material r70 in the seventh embodiment ... 0th surface r * 1 ... first surface r * 2 ... second surface r * 3 ... third surface r * 4 ... third surface in the seventh embodiment 4th surface r * 5 ... 5th surface (asterisk * attached to each surface number corresponds to the number of the example)
r76 ... sixth surface K1 in the seventh embodiment ... first mold K2 ... second mold

Claims (9)

A transparent first substrate;
A transparent second substrate joined to the first substrate;
A transparent third substrate bonded to the opposite side of the first substrate across the second substrate;
A transparent fourth base material that is bonded to the opposite side of the second base material with the third base material sandwiched therebetween,
The second substrate is a positive lens;
The third substrate is a negative lens;
The first substrate and the second substrate have different refractive indexes for at least one wavelength,
The second base material and the third base material have different Abbe numbers,
The third substrate and the fourth substrate have different refractive indices for at least one wavelength,
The second base material is an energy curable resin,
The achromatic lens, wherein the third base material is an energy curable resin. The achromatic lens according to claim 1, wherein the following conditional expression (1) is satisfied.
0.008 <| 1 / νp−1 / νn | <0.035 (1)
here,
νp is the Abbe number of the second base material,
νn is the Abbe number of the third substrate,
It is. The achromatic lens according to claim 1, wherein the following conditional expression (2) is satisfied.
0.05 [mm] <(d2 + d3) <1.00 [mm] (2)
here,
d2 is the thickness of the second base material;
d3 is the inner thickness of the third substrate,
It is. The color according to any one of claims 1 to 3, wherein an interface between the second base material and the third base material is a diffractive optical surface formed with a relief pattern. Eraser lens. The achromatic lens according to claim 4, wherein the following conditional expressions (3) and (4) are satisfied.
n1 (λ)> n2 (λ) (3)
((n1 (λ2) −n2 (λ2)) / (n1 (λ1) −n2 (λ1)))
-(N1 (λ2) -1) / (n1 (λ1) -1)> 0 (4)
here,
n1 (λ) is the refractive index of the second substrate,
n2 (λ) is the refractive index of the third substrate,
However,
λ1 <λ <λ2, and
λ1 and λ2 are arbitrary light wavelengths,
It is. The color according to any one of claims 1 to 5, wherein the energy curable resin used for the second substrate or the third substrate is a photocurable resin. Eraser lens. 2. A light-shielding portion is provided on at least one of an interface between the first base material and the second base material, or an interface between the third base material and the fourth base material. The achromatic lens according to any one of claims 6 to 6. 8. The achromatic lens according to claim 1, wherein at least one of the first base material and the fourth base material is configured by a plane-parallel plate. The achromatic lens according to any one of claims 1 to 8, wherein the following conditional expression (5) is satisfied.
κ1, κ4 <0.1 [%] (5)
here,
κ1 is the water absorption rate of the first substrate,
κ4 is the water absorption rate of the fourth substrate,
It is.

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