JP6225040B2 - Wide angle lens - Google Patents

Description

  The present invention relates to a wide-angle lens mounted on a surveillance camera or the like.

  Since lenses for surveillance cameras are capable of electronically correcting captured images, in general, with a small number of components prioritizing wide angle and low cost over optically correcting distortion. Designed. The lens for surveillance cameras is, for example, a bright pan-focus lens with an open F value of less than 2 in order to compensate for the lack of sensitivity of the sensor, or a focus that depends on temperature changes to ensure durability in outdoor use. In order to suppress the change in position, it may be a glass lens.

  Surveillance cameras are capable of processing high-pixel image data as digitalization proceeds with the spread of digital communication infrastructure such as the Internet and LAN (Local Area Network). Therefore, in order to expand the monitoring range and to obtain detailed information within the monitoring range, the lenses for surveillance cameras are compatible with the Hi-Vision standard (for example, megapixel compatible) from the conventional VGA (Video Graphics Array) standard. Is spreading. However, when a lens for a surveillance camera that supports megapixels is configured with a small number of lenses, it is difficult to correct longitudinal chromatic aberration. In order to improve this kind of optical performance, it is conceivable to design a lens for a surveillance camera supporting megapixels with an aspheric glass lens. However, designing a megapixel-compatible surveillance camera lens with an aspheric glass lens increases initial investment when production is low. For megapixel-compatible lenses for surveillance cameras, it is difficult to introduce an aspheric glass lens to reduce initial investment, and a design that adds the number of spherical lenses must be selected. For these reasons, most of the lenses for surveillance cameras that support megapixels have six or more lenses.

  A specific configuration of the surveillance camera lens is described in Patent Document 1, for example. The lens for surveillance cameras described in Patent Document 1 is composed of four glass lenses in order to achieve miniaturization.

Japanese Patent Laid-Open No. 5-264895

  Glass lenses are expensive to manufacture when aspherical, even when mass-produced. Therefore, the aspherical glass mold lens is adopted as the lens for the surveillance camera only in some high-end products and some mass-produced products, and the spherical glass lens is adopted otherwise. Also in Patent Document 1, a spherical glass lens is employed.

  In the surveillance camera lens described in Patent Document 1, chromatic aberration is corrected by arranging two lenses (third lens and fourth lens) having different dispersions side by side. However, this configuration has a problem that the amount of light loss due to surface reflection increases because the number of lens surfaces increases compared to a cemented lens in which two lenses are cemented. Further, as the curvature of the facing surfaces increases, the amount of coma aberration and the amount of image plane tilt due to surface decentering increase and the sensitivity of aberration generation due to lens spacing error increases. Therefore, it may be difficult to correct lateral chromatic aberration and axial chromatic aberration at the same time.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wide-angle lens in which improvement in optical performance is achieved with a small number of components while ensuring manufacturability.

  The wide-angle lens of the embodiment of the present invention has a half angle of view exceeding 30 °, and in order from the object side, a negative lens group having one or two negative lenses, a positive glass lens, and a positive resin lens And a positive cemented lens in which a negative resin lens is cemented. The cemented surface of the cemented lens is an aspheric surface whose sag amount becomes smaller from the optical axis toward the periphery as compared with the paraxial spherical surface defined by the paraxial radius of curvature of the cemented surface.

  The image side surface of the cemented lens may be an aspheric surface in which the sag amount changes in the positive direction as it goes from the optical axis toward the periphery as compared with the paraxial spherical surface defined by the paraxial radius of curvature of the image side surface.

In the wide-angle lens of the present embodiment, when the Abbe number of the positive resin lens is defined as ν _pp and the Abbe number of the negative resin lens is defined as ν _np , the following formula ν _pp −ν _np > 28
It is good also as composition which satisfies.

In the wide-angle lens of this embodiment, the temperature change coefficient of the refractive index of the positive resin lens is defined as a _pp (unit: 1 / ° C.), and the temperature change coefficient of the refractive index of the negative resin lens is defined as _anp (unit: 1 / ° C.), the following formula | a _pp −a _np | <0.00004
It is good also as composition which satisfies.

In the wide-angle lens of the present embodiment, when the temperature change coefficient of the refractive index of a positive glass lens is defined as a _pg (unit: 1 / ° C.), the following expression | a _pg | <0.00001
It is good also as composition which satisfies.

The wide-angle lens of this embodiment defines the paraxial incident light height on each surface with the paraxial incident light height from an object at infinity as 1, and the power of the positive glass lens is φ (unit: 1 / mm). When the height of paraxial incident light on the object side surface of the positive glass lens is defined as H, the following formula 0.63 <φ × H <1.60
It is good also as composition which satisfies.

When the negative lens group is formed of a resin lens, for example, the following formula 0.63 <φ × H <1.30
Is satisfied.

When the negative lens group is composed of a glass lens, for example, the following formula 0.80 <φ × H <1.60
Is satisfied.

In the wide-angle lens of this embodiment, the height from the optical axis is defined as h (unit: mm), the radius of curvature on the optical axis of the aspheric surface is defined as r (unit: mm), and the coordinates on the aspheric surface are defined. When the sag amount, which is the distance between the point and the tangential plane on the optical axis of the aspherical surface, is defined as X (h), the cemented surface of the cemented lens has the following expression | X (h) | <| (H ² /r)/(1+SQRT(1−(1−0.8×(h/r) ² )) |
It is good also as composition which satisfies.

For example, when the effective light beam radius is defined as h _MAX (unit: mm) and the aspherical slope at the effective light beam radius h _MAX is defined as dX (h _MAX ) / dh, the cemented surface of the cemented lens is expressed by the following formula. 0.5 <| dX (h _MAX ) / dh | <1.30
It is good also as composition which satisfies.

Cemented surface of the cemented lens, for example, in the case where the second order derivative in the sag amount X (h) is defined as ^{d 2 X (h) / dh} 2, the following equation ^{d 2 X (h) / dh} 2 ≠ 0
(However, 0 <h <h _MAX )
It is good also as composition which satisfies.

The wide-angle lens of the present embodiment has a configuration in which the negative lens group has a single lens configuration and the diaphragm is arranged on the image side of the positive glass lens, and the Abbe number of the negative lens of the negative lens group is defined as ν _n When the Abbe number of the positive glass lens is defined as ν _p , the following expression 0 ≦ ν _n −ν _p <18
It is good also as composition which satisfies.

In the wide-angle lens of this embodiment, when the negative lens group is formed of a resin lens, the focal length of the wide-angle lens is defined as f (unit: mm), and the curvature radius of the object side surface of the cemented lens is r ′ (unit: mm), the following formula 0.50 <f / r ′ <1.33
It is good also as composition which satisfies.

In the wide-angle lens of this embodiment, when the negative lens group is formed of a glass lens, the focal length of the wide-angle lens is defined as f (unit: mm), and the curvature radius of the object side surface of the cemented lens is r ′ (unit: mm), the following formula −0.28 <f / r ′ <0.63
It is good also as composition which satisfies.

  According to this embodiment, a wide-angle lens is provided in which improvement in optical performance is achieved with a small number of components while ensuring ease of manufacture.

It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of embodiment (Example 1) of this invention. FIG. 6 is a diagram illustrating various aberrations of the wide-angle lens according to the first embodiment of the present invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 2 of this invention. It is various aberrational figures of the wide angle lens of Example 2 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 3 of this invention. It is various aberrational figures of the wide angle lens of Example 3 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 4 of this invention. It is various aberrational figures of the wide angle lens of Example 4 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 5 of this invention. FIG. 9 is various aberration diagrams of the wide-angle lens according to Example 5 of the present invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 6 of this invention. It is various aberrational figures of the wide angle lens of Example 6 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 7 of this invention. FIG. 11 is various aberration diagrams of the wide-angle lens according to Example 7 of the present invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 8 of this invention. It is various aberrational figures of the wide angle lens of Example 8 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 9 of this invention. It is various aberrational figures of the wide angle lens of Example 9 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 10 of this invention. It is various aberrational figures of the wide angle lens of Example 10 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 11 of this invention. It is various aberrational figures of the wide angle lens of Example 11 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 12 of this invention. It is various aberrational figures of the wide angle lens of Example 12 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 13 of this invention. It is various aberrational figures of the wide angle lens of Example 13 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 14 of this invention. It is various aberrational figures of the wide angle lens of Example 14 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 15 of this invention. It is various aberrational figures of the wide angle lens of Example 15 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 16 of this invention. It is various aberrational figures of the wide angle lens of Example 16 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 17 of this invention. It is various aberrational figures of the wide angle lens of Example 17 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 18 of this invention. It is various aberrational figures of the wide angle lens of Example 18 of this invention. It is a lens arrangement | positioning figure which shows the structure of the wide angle lens of Example 19 of this invention. FIG. 20 is a diagram illustrating various aberrations of the wide-angle lens according to Example 19 of the present invention.

  Hereinafter, a wide-angle lens according to an embodiment of the present invention will be described with reference to the drawings. In the following, a wide-angle lens mounted on a high-pixel type surveillance camera will be described as an embodiment of the present invention. Note that a wide-angle lens mounted on another device that is required to be downsized and reduced in price as in the surveillance camera is also within the scope of the present invention. An example of another device on which a wide-angle lens is mounted is an in-vehicle camera.

  The wide-angle lens of this embodiment is for a surveillance camera of 1 to 2 megapixels, for example, and the half angle of view exceeds 30 °. For example, in the case of 2 megapixels, the number of pixels increases by about 6 times and 2.5 times higher resolution than in the case of VGA, which has been the mainstream until now.

  In general, a wide-angle surveillance camera is equipped with a wide-angle retrofocus lens in which a negative lens is disposed on the object side of the diaphragm and a positive lens group is disposed on the rear stage of the diaphragm. In this type of retrofocus lens, the chromatic aberration of magnification is canceled out in balance with the rear group while being suppressed by using a low dispersion material for the most negative lens on the object side. On the other hand, in order to suppress the longitudinal chromatic aberration, it is basically necessary to use a low dispersion material for the positive lens and a high dispersion material for the negative lens to leave positive power so that the longitudinal chromatic aberration is corrected. is there. However, as described above, a low-dispersion material is used for the negative lens closest to the object in order to correct lateral chromatic aberration. Therefore, in consideration of correction of axial chromatic aberration, an optical lens with a small number of components is 2 megapixels or the like. It was difficult to correspond to the high pixel type.

  Therefore, in general, the wide-angle lens of the present embodiment includes, in order from the object side, a negative lens group having one or two negative lenses, a positive glass lens disposed in the vicinity of the stop, and a pair of positive and negative resin lenses. A cemented lens in which aspheric surfaces are cemented is disposed. With this configuration, the wide-angle lens according to the present embodiment is compatible with a high pixel type such as 2 megapixels while having a small number of components.

  FIG. 1 is a lens arrangement diagram showing a configuration of a wide-angle lens 10 according to an embodiment of the present invention. Here, the lens arrangement diagram of Example 1 (described later) of the present invention is used. In each layout diagram of the wide-angle lens 10 including FIG. 1, the left side in the drawing is the object side, and the right side in the drawing is the image side (the image sensor side mounted on the surveillance camera).

  As shown in FIG. 1, the wide-angle lens 10 of this embodiment includes at least a negative lens L1, a positive lens L2, a diaphragm S, and a cemented lens L3 in order from the object side. Each optical lens constituting the wide-angle lens 10 has a rotationally symmetric shape around the optical axis AX of the wide-angle lens 10. In the above description, “having at least (omitted)” is because there may be a configuration example in which another optical element is added within the scope of the technical idea of the present invention. For example, a configuration example in which a parallel plate, an ND filter, a low-pass filter, an IR cut filter, or the like that does not substantially contribute to aberration correction is added to the wide-angle lens according to the present invention, and the configuration and effect of the wide-angle lens according to the present invention. A configuration example in which another optical element is added while maintaining is assumed.

In the present embodiment, the negative lens group has a single lens configuration of the negative lens L1, but in another embodiment, it may have a dual lens configuration including a negative lens L1 ′. The negative lens L1 and the negative lens L1 ′ have the following variations.
・ Aspherical glass lens ・ Spherical glass lens ・ Aspherical resin lens ・ Spherical resin lens Here, the lens required for the negative lens group is one factor that determines whether the negative lens group is composed of a glass lens or a resin lens. Surface hardness is considered. When the required lens surface hardness is high, the negative lens group is composed of, for example, a glass lens. In a camera including a lens dome or the like, generally, since the required lens surface hardness is low, the negative lens group may be formed of a resin lens. In addition, by making the lens surface of the negative lens group an aspherical surface, distortion can be suppressed.

The positive lens L2 has the following variations.
・ Aspherical glass lens ・ Spherical glass lens

  When the positive lens L2 is an aspheric glass lens, it is advantageous to suppress the occurrence of aberration due to decentering during assembly. Further, as will be described later, the cemented lens L3 is a resin lens. In general, the power of the resin lens decreases due to linear expansion when the temperature rises, and the power also decreases due to a decrease in refractive index, and the change in back focus and field curvature due to astigmatism tend to change. The back focus change is not a substantial problem in a system having an AF function. However, when a field curvature occurs in a wide-angle lens having a large distortion aberration, a problem is pointed out that the resolving power at the peripheral portion where the object-side resolving power is originally low further decreases. Therefore, it is desirable to suppress the occurrence of field curvature as much as possible regardless of the presence or absence of the AF function. In this embodiment, the positive lens L2 is formed of a glass material having a low linear expansion coefficient, thereby contributing to suppression of field curvature.

  The arrangement pattern of the diaphragm S includes a pattern arranged adjacent to the positive lens L2 and closer to the object side than the positive lens L2, and a pattern arranged adjacent to the positive lens L2 and closer to the image side than the positive lens L2. .

  The cemented lens L3 is obtained by cementing a pair of positive and negative resin lenses having different dispersions, has a positive power as a whole, and has a cemented surface that is aspherical. In the cemented lens L3, for example, the object side lens is a positive lens and the image side lens is a negative lens. Further, the object side lens may be a negative lens and the image side lens may be a positive lens.

  As described above, the wide-angle lens 10 of this embodiment includes the cemented lens L3 in which a pair of positive and negative lenses is cemented. More specifically, in the cemented lens L3, a pair of positive and negative lenses are cemented with an adhesive having a refractive index close to that of the lens material. An error in the distance between the surfaces to be joined can be suppressed to a variation in the thickness of the adhesive layer. Therefore, the eccentricity in the direction perpendicular to the optical axis does not substantially occur between the pair of positive and negative lenses. Moreover, even if it is a structure arrange | positioned from the object side in order of negative positive, total reflection does not occur in a joint surface.

  On the other hand, in the case of a configuration that does not include a cemented lens, since a light beam is emitted into the air between a pair of positive and negative lenses, a difference in refractive index (a difference in refractive index between the lens and air) between each facing lens surface. It is necessary to consider the fact that a large aberration is generated due to the large size, the axial chromatic aberration must be canceled, and the like. For this reason, an allowable manufacturing error for a pair of positive and negative lenses must be set strictly. Further, in the configuration in which the object side is arranged in the negative order, total reflection may occur due to off-axis light.

The cemented surface of the cemented lens L3 is an aspheric surface, and the sag amount X (h) becomes smaller toward the periphery from the optical axis AX than the paraxial spherical surface defined by the paraxial radius of curvature of the cemented surface. The sag amount X (h) is the distance between the coordinate point on the aspheric surface and the tangent plane on the optical axis of the aspheric surface. The sag amount X (h) defines the height from the optical axis AX as h (unit: mm), the radius of curvature on the optical axis AX of the aspheric surface as r (unit: mm), and the cone coefficient. defined as kappa, when the aspherical coefficient is defined as a _n, represented by the following equation.
X (h) = (h ² / r) / (1 + SQRT (1− (1 + κ) × (h / r) ² )) + ΣA _n × h ⁿ

  When a lens system with positive power as a whole is designed with a small number of spherical lenses, the divergence surface, which has a function of correcting chromatic aberration, generally has a strong curvature, so that chromatic aberration is excessively corrected from the optical axis toward the periphery. The Thereby, chromatic aberration of spherical aberration occurs. In order to suppress this type of chromatic aberration, spherical aberration on the short wavelength side where the refractive index difference between the pair of positive and negative lenses increases tends to be excessively corrected. In order to avoid such a problem, the cemented surface of the cemented lens L3 is an aspheric surface whose power becomes weaker from the optical axis toward the periphery.

  The pair of positive and negative lenses forming the cemented lens L3 is a resin lens manufactured by injection molding. Each of the pair of positive and negative resin lenses is molded by injecting molten resin into a cavity defined by a mold in which the shape from the optical surface to the collar portion is integrally processed. The pair of positive and negative resin lenses formed in this way are joined with a very small amount of eccentricity. According to this embodiment, an aspherical surface having an excellent chromatic aberration correction function can be joined easily and at low cost with high accuracy compared to a case where a pair of positive and negative lenses is made of glass.

  Since the cemented lens L3 is a resin lens having a lower refractive index than glass, the Petzval sum that determines the basic characteristics of field curvature is likely to swing in the positive direction. Therefore, the cemented lens L3 has an aspherical surface in a direction in which the image side surface exceeds the astigmatic difference, and a function of bringing the image surface close to flat is added. Specifically, the image side surface of the cemented lens L3 increases as the sag amount X (h) moves from the optical axis AX toward the periphery as compared with the paraxial spherical surface defined by the paraxial radius of curvature of the image side surface of the cemented lens L3. It has a surface shape that changes in direction. Note that the sign of the sag amount X (h) is negative on the object side and positive on the image side. Furthermore, the object side surface of the cemented lens L3 is also aspherical, so that the field curvature can be adjusted for each angle of view.

For example, when the Abbe number of a positive resin lens is defined as ν _pp and the Abbe number of a negative resin lens is defined as ν _np , the cemented lens L3 has the following formula (1).
ν _pp −ν _np > 28 (1)
Is satisfied.

  In the present embodiment, since a configuration that suppresses the occurrence of chromatic aberration of magnification by using a low-dispersion material for the negative lens L1 (and L1 ') is employed, it is necessary to correct axial chromatic aberration with the cemented lens L3. For this reason, it is desirable to select a material having a large Abbe number difference for the pair of positive and negative resin lenses forming the cemented lens L3 so that the conditional expression (1) is satisfied. However, since the high-dispersion resin lens material has a higher refractive index than the low-dispersion resin lens material, a difference in refractive index always occurs on the cemented surface of the cemented lens L3. For this reason, there is a possibility that monochromatic aberration may occur at the same time that axial chromatic aberration is corrected. In the present embodiment, the object side surface of the cemented lens L3 is aspherical in order to suppress this type of monochromatic aberration. If conditional expression (1) is not satisfied (if the Abbe number difference is small), the inclination of the surface around the lens becomes too large to correct chromatic aberration, and the injection molding shape of the negative resin lens is unstable. This is disadvantageous for bonding with a positive resin lens.

  As the resin material used for the cemented lens L3, for example, a material such as a polycarbonate type or a polyester type having a refractive index of around 1.6 and an Abbe number of 20 is conceivable. A cycloolefin polymer, a cyclic olefin copolymer, etc. can be considered as a resin material having a low dispersion and a relatively high refractive index so that the difference in refractive index from such a high dispersion material does not increase. By combining the former and the latter materials, the Abbe number difference is increased and the refractive index difference is reduced, which is further advantageous by correcting axial chromatic aberration and suppressing monochromatic aberration. For example, when the cemented lens L3 is a cemented lens of a resin lens and an ultra-low dispersion glass mold lens, the Abbe number difference can be increased, and good aberration correction can be obtained. However, since the difference in coefficient of linear expansion between the resin lens and the glass lens is large, there is a possibility that the bonding of the bonding surface may be peeled off when the temperature changes. Therefore, it is unsuitable for application to surveillance cameras and vehicle-mounted cameras with severe temperature environments. For these reasons, it is desirable to join resin lenses together as in this embodiment.

For the cemented lens L3, for example, the temperature change coefficient of the refractive index of the positive resin lens is defined as a _pp (unit: 1 / ° C.), and the temperature change coefficient of the refractive index of the negative resin lens is defined as _anp (unit: 1). / ° C), the following formula (2)
| A _pp −a _np | <0.00004 (2)
Is satisfied.

  In the case of a resin lens, the linear expansion of the lens due to a temperature change, and the focus position change and aberration change due to a refractive index change become problems. When AF (Auto Focus) is possible, the shift of the focus position can be practically canceled. However, it is desirable to suppress the shift of the focus position around the screen due to the change in astigmatism at the design stage. In the cemented lens L3, the positive resin lens has an action of changing the peripheral image plane in the under direction, and the negative resin lens has an action of changing the peripheral image plane in the over direction. For example, when the temperature rises, the lens swells, so the curvature of the lens surface becomes loose and the density decreases. Since the curvature of the lens surface is reduced and the density of the resin lens is lowered, the refractive index is lowered. Therefore, in any of the positive and negative pair of resin lenses, the function as a lens is substantially weakened. When the linear expansion coefficients of a pair of positive and negative resin lenses are equal, a lens with a higher original refractive index tends to have a larger amount of change in refractive index due to a temperature change. In the present embodiment, a negative resin lens material having a high dispersion and a high refractive index has a higher temperature change coefficient of the refractive index. For this reason, when the temperature rises, the action of the joint surface is weakened, the back focus is reduced, and the curvature of field changes in the under direction.

  In order to avoid the above problem, it is necessary to design the cemented lens L3 in consideration of the occurrence of aberration due to refraction at the front and rear surfaces of the cemented lens L3 and the cancellation of the refractive index change in the negative lens L1 and the positive lens L2. . However, if the difference in temperature change coefficient between the pair of positive and negative resin lenses becomes large, the power balance of the pair of positive and negative resin lenses must be biased to balance the change in curvature of field and the change in back focus. . As the temperature change coefficient of the refractive index of the negative lens of the cemented lens L3 is negatively increased, the power of the positive lens of the cemented lens L3 increases. In this case, it is difficult to secure the edge of the positive lens of the cemented lens L3, and the shape is difficult to produce. It becomes. On the other hand, the negative lens power of the cemented lens L3 increases as the temperature change coefficient of the refractive index of the positive lens of the cemented lens L3 increases negatively. However, in this case, since the positive power of the entire cemented lens L3 is reduced, the incident angle of the off-axis principal ray on the image plane is increased and the light use efficiency is lowered or the back focus is shortened. Occurs. Therefore, it is desirable to combine resin lenses having a small difference in temperature change coefficient so that the conditional expression (2) is satisfied.

For example, when the temperature change coefficient of the refractive index is defined as a _pg (unit: 1 / ° C.), the positive lens L2 has the following formula (3):
| A _pg | <0.00001 (3)
Is satisfied.

  By satisfying the conditional expression (3), the contribution of the positive lens L2 to the performance change of the wide-angle lens 10 at the time of temperature change is suppressed to, for example, about 1/10 of the entire performance change.

For example, the positive lens L2 defines the height of the paraxial incident light beam on each surface with the paraxial incident light height from an object at infinity as 1, and defines the power of the positive lens L2 as φ (unit: 1 / mm). When the paraxial incident light height on the object side surface of the positive lens L2 is defined as H, the following equation (4)
0.63 <φ × H <1.60 (4)
Is satisfied.

Further, when the negative lens L1 (and L1 ′) is a resin lens, the positive lens L2 is expressed by the following formula (5).
0.63 <φ × H <1.30 (5)
May be further satisfied.

Further, when the negative lens L1 (and L1 ′) is a glass lens, the positive lens L2 is expressed by the following formula (6).
0.80 <φ × H <1.60 (6)
May be further satisfied.

  Conditional expressions (4) to (6) stipulate that the positive lens L2 whose incident ray height is increased by the action of the negative lens L1 (and L1 ') bears almost the entire power. When the negative lens L1 (and L1 ') is a resin lens, it is desirable that the positive lens L2 has a power close to 1 so that the conditional expression (5) is satisfied. When the negative lens L1 (and L1 ') is a glass lens, it is desirable to satisfy the conditional expression (6) because the influence of the temperature change is suppressed as the power of the positive lens L2 increases.

  If the lower limit of each of the conditional expressions (4) to (6) is not reached, it is necessary to increase the power of the positive resin lens forming the cemented lens L3 in order to compensate for the power shortage of the positive lens L2. For this reason, the negative resin lens forming the cemented lens L3 is a meniscus lens having a convex surface in contact with air, but the curvature radius of the cemented surface is small because it is necessary to correct chromatic aberration with a convex lens having large dispersion. As a result, the pair of positive and negative resin lenses forming the cemented lens L3 are difficult to be injection molded together. For these reasons, it is not desirable to fall below the respective lower limits of conditional expressions (4) to (6).

  If the upper limit of each of the conditional expressions (4) to (6) is exceeded, the back focus is reduced in the shrinking direction and the flange back length is extended due to the temperature rise. Therefore, a space must be provided for adjusting the focus. . In addition, in the configuration in which the AF operation is not performed, the back focus shift and the field curvature change appear in the same direction, so that it is difficult to allow the focus shift at the periphery of the screen. For these reasons, it is not desirable to exceed the upper limits of conditional expressions (4) to (6).

In the present embodiment, the cemented surface of the cemented lens L3 has a sag amount X (h) within the effective light beam diameter and the following formula (7).
| X (h) | <| (h ² /r)/(1+SQRT(1−(1−0.8)×(h/r) ² )) | (7)
Meet. In Expression (7), r represents the paraxial radius of curvature of the cemented surface of the cemented lens L3.

  Conditional expression (7) stipulates that the cemented surface of the cemented lens L3 has a smaller amount of sag than the spheroid with κ = −0.8 within the effective beam diameter (having the same paraxial radius of curvature as the cemented surface). To do.

  A low dispersion material is used for the negative lens L1 (and L1 ') in order to suppress the occurrence of lateral chromatic aberration. Therefore, axial chromatic aberration cannot be corrected by the negative lens L1 (and L1 ') and the positive lens L2. In order to correct axial chromatic aberration with the cemented lens L3, it is necessary to have a strong color correction surface. If the strong color correction surface is made as a spherical surface having a curvature radius necessary for correcting axial chromatic aberration as it is, the effective radius does not become larger than the curvature radius, so that the lens cannot be brightened. In this embodiment, when the cemented surface is a spherical surface, the chromatic aberration of the spherical aberration is excessively corrected at the peripheral portion, so that the sag amount X (h) is compared with a paraxial spherical surface having the same paraxial radius of curvature. It is aspherical so as to decrease from the optical axis AX toward the periphery. By satisfying the conditional expression (7), the sag amount is made smaller than the spheroid of κ = −0.8 within the effective light beam diameter as the degree of aspherical surface, thereby reducing the aperture while correcting the axial chromatic aberration. Can be avoided. The wide-angle lens 10 becomes a lens brighter than, for example, F2.8 by satisfying conditional expression (7).

For example, when the effective light beam radius is defined as h _MAX (unit: mm) and the aspherical slope at the effective light beam radius h _MAX is defined as dX (h _MAX ) / dh, the cemented surface of the cemented lens L3 is as follows. Formula (8)
0.5 <| dX (h _MAX ) / dh | <1.30 (8)
Is satisfied.

  When the lower limit of conditional expression (8) is not reached, since the inclination of the cemented surface of the cemented lens L3 is small and there is little deterioration in optical performance due to decentering, the technical significance of cementing a pair of positive and negative resin lenses is substantially lost. When the upper limit of conditional expression (8) is exceeded, since the inclination of the joint surface is too large, the shape measurement accuracy and molding accuracy are likely to be insufficient at the periphery of the lens, and a weld line is generated in the concave lens. Difficulty is likely to occur. Therefore, it is desirable to satisfy conditional expression (8).

For example, when the second-order differential value of the sag amount X (h) is defined as d ² X (h) / dh ² , the cemented surface of the cemented lens L3 is expressed by the following formula (9).
d ² X (h) / dh ² ≠ 0 (9)
(However, here 0 <h <h _MAX )
Is satisfied.

  For example, consider the case where spherical surfaces are joined together. In this case, the lens surfaces (concave surface and convex surface) of each other do not enter a stable position regardless of the inclination, and therefore slide through the thin adhesive layer. Therefore, the operator can adjust the bonding state of the bonding surface while observing the state of the non-bonding surface through transmitted light or reflected light. On the other hand, when aspherical surfaces are joined together, each lens surface (concave and convex) has a local area where the second-order differential value is zero, and is stable at the position where the two points contact, Sliding may be worse. In other words, each lens surface (concave surface and convex surface) avoids the design of a region where the second-order differential value is zero (that is, it is designed so that the inclination of the aspherical surface always changes), for example, regular Even if the contact is made with any inclination other than the position, the position is not stabilized and it becomes easy to slide. Thereby, it becomes easy to avoid the problem that the aspheric surfaces are joined at a wrong position. For these reasons, it is desirable to satisfy the conditional expression (9).

In the wide-angle lens 10, for example, when the negative lens group has a single lens configuration of the negative lens L1 and the diaphragm S is arranged on the image side of the positive lens L2, the Abbe number of the negative lens L1 is defined as ν _n. When the Abbe number of the positive lens L2 is defined as ν _p , the following equation (10)
0 ≦ ν _n −ν _p <18 (10)
Is satisfied.

  In order to suppress the occurrence of lateral chromatic aberration, it is desirable to use a low-dispersion material for the negative lens L1 and a slightly high-dispersion material for the positive lens L2 so that the conditional expression (10) is satisfied. On the other hand, when a low-dispersion material is used for the positive lens L2 to correct the longitudinal chromatic aberration (below the lower limit of the conditional expression (8)), the positive lens L2 cancels out the occurrence of lateral chromatic aberration in the negative lens L1. Therefore, it is necessary to cancel the lateral chromatic aberration by increasing the distance between the aperture stop S and the cemented lens L3. In this case, the overall length of the lens is increased, the outer diameter is increased, and the back focus length is decreased. If a highly dispersed material is used for the positive lens L2 (exceeding the upper limit of conditional expression (8)), the bending radius of the cemented surface of the cemented lens L3 becomes too small, and injection molding becomes difficult.

For example, when the negative lens L1 (and L1 ′) is formed of a resin lens, the wide-angle lens 10 defines the focal length (focal length of the entire system) of the wide-angle lens 10 as f (unit: mm), and is a cemented lens. When the curvature radius of the object side surface of L3 is defined as r ′ (unit: mm), the following equation (11)
0.50 <f / r ′ <1.33 (11)
Is satisfied.

  Conditional expression (11) is a conditional expression defined on the assumption that the AF function is not provided. In order to cancel the change in the back focus caused by the negative lens L1 (and L1 ') when the temperature changes, it is desirable that the object side surface of the cemented lens L3 is a convex surface so that the conditional expression (11) is satisfied. However, if the lower limit of conditional expression (11) is not reached, the back focus becomes too short when the temperature rises, so the AF function becomes essential. If the object side surface of the cemented lens L3 is a strong convex surface so as to exceed the upper limit of the conditional expression (11), the image side surface of the cemented lens L3 is designed to be a concave surface because it is necessary to appropriately set the back focus change accompanying the temperature change. Is done. However, since the exit pupil is too much on the image side in such a power balance, it is difficult to satisfy the pupil condition of the image sensor, and the light amount loss increases.

For example, when the negative lens L1 (and L1 ′) is formed of a glass lens, the wide-angle lens 10 has the following formula (12):
−0.28 <f / r ′ <0.63 (12)
Is satisfied.

  It is desirable that the object side surface of the cemented lens L3 be designed from a loose convex shape to a loose concave shape so that the conditional expression (12) is satisfied in order to avoid an excessive change in back focus accompanying a temperature change.

  Next, 19 specific numerical examples of the wide-angle lens 10 described so far will be described. In each embodiment, the cover glass of the image sensor is assumed to have a refractive index of 1.51680, an Abbe number (d line) of 64.20, and a thickness of 0.250 (unit: mm).

  As described above, the configuration of the wide-angle lens 10 according to the first embodiment of the present invention is as illustrated in FIG. In Example 1, the negative lens group includes a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side.

Table 1 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 1. The numbers NO shown in Table 1 (surface data and aspheric surface data) correspond to the surface code rn (n is a natural number) and the aperture code sn in FIG. “*” Attached to the number NO in Table 1 (surface data) indicates that the surface corresponding to the number NO is an aspherical surface. In Table 1 (surface data), R (unit: mm) is the radius of curvature of each surface of the optical member, D (unit: mm) is the optical member thickness or optical member interval on the optical axis AX, N (D) Is the refractive index of the d-line (wavelength 588 nm), ν (D) is the Abbe number of the d-line, α (unit: 1 / K) is the linear expansion coefficient, and dN / dT (unit: 1 / ° C.) is the refractive index. The temperature change coefficient of the rate, h _MAX (unit: mm) represents the effective luminous flux radius, respectively. The notation E in Table 1 (surface data and aspheric surface data) represents a power in which 10 is a radix and the number on the right of E is an exponent.

  2A to 2E are various aberration diagrams of the wide-angle lens 10 of the first embodiment. Specifically, FIG. 2A shows the spherical aberration and axial chromatic aberration at the d-line (588 nm), g-line (436 nm), C-line (656 nm), F-line (486 nm), and e-line (546 nm). Show. FIG. 2B shows chromatic aberration of magnification at d-line, g-line, C-line, F-line, and e-line. FIG. 2C shows astigmatism (S: sagittal component, M: meridional component). FIG. 2 (d) shows distortion. 2A to 2C, the vertical axis represents the image height, and the horizontal axis represents the aberration amount. In FIG. 2D, the vertical axis represents the image height, and the horizontal axis represents the distortion. FIG. 2E is a lateral aberration diagram of the d line at each image height of the wide-angle lens 10 of the first embodiment. 2E, the vertical axis represents the amount of lateral aberration, and the horizontal axis represents the entrance pupil coordinates. In each drawing of FIG. 2E, the left side of the horizontal axis indicates the lower light beam, and the right side indicates the upper light beam. In addition, the description about the table | surface and each drawing of the present Example 1 is applied also to the table | surface and each drawing which are shown by each subsequent example.

  FIG. 3 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the second embodiment of the present invention. In Example 2, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. 4A to 4E are graphs showing various aberrations (spherical aberration, longitudinal chromatic aberration, lateral chromatic aberration, astigmatism, distortion, and lateral aberration) of the wide-angle lens 10 according to the second embodiment. Table 2 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 2.

  FIG. 5 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the third embodiment of the present invention. In Example 3, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. 6A to 6E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the third embodiment. Table 3 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of the third embodiment.

  FIG. 7 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the fourth embodiment of the present invention. In Example 4, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. FIGS. 8A to 8E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the fourth embodiment. Table 4 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of the fourth embodiment.

  FIG. 9 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the fifth embodiment of the present invention. In Example 5, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. 10A to 10E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion, and lateral aberration) of the wide-angle lens 10 of the fifth embodiment. Table 5 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 5.

  FIG. 11 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the sixth embodiment of the present invention. In Example 6, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 12A to 12E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the sixth embodiment. Table 6 shows specific numerical configurations (surface data, aspherical data, various data) of the wide-angle lens 10 of the sixth embodiment.

  FIG. 13 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the seventh embodiment of the present invention. In the seventh embodiment, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 14A to 14E are diagrams showing various aberrations (spherical aberration, longitudinal chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the seventh embodiment. Table 7 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 7.

  FIG. 15 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the eighth embodiment of the present invention. In the eighth embodiment, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 16A to 16E are graphs showing various aberrations (spherical aberration, longitudinal chromatic aberration, lateral chromatic aberration, astigmatism, distortion, and lateral aberration) of the wide-angle lens 10 according to the eighth embodiment. Table 8 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 8.

  FIG. 17 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the ninth embodiment of the present invention. In the ninth embodiment, the negative lens group includes a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 18A to 18E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion, and lateral aberration) of the wide-angle lens 10 of the ninth embodiment. Table 9 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 9.

  FIG. 19 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the tenth embodiment of the present invention. In Example 10, the negative lens group is composed of a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 20A to 20E are graphs showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the tenth embodiment. Table 10 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 10.

  FIG. 21 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the eleventh embodiment of the present invention. In Example 11, the negative lens group is composed of a glass negative lens L1. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. 22A to 22E are graphs showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of Example 11. FIG. Table 11 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 11.

  FIG. 23 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the twelfth embodiment of the present invention. In the twelfth embodiment, the negative lens group includes a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 24A to 24E are graphs showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the twelfth embodiment. Table 12 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 12.

  FIG. 25 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the thirteenth embodiment of the present invention. In the thirteenth embodiment, the negative lens group includes a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 26A to 26E are graphs showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 according to the thirteenth embodiment. Table 13 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 13.

  FIG. 27 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the fourteenth embodiment of the present invention. In Example 14, the negative lens group includes a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 28A to 28E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of Example 14. FIG. Table 14 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 14.

  FIG. 29 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the fifteenth embodiment of the present invention. In Example 15, the negative lens group includes a glass negative lens L1. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 30A to 30E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of the fifteenth embodiment. Table 15 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 15.

  FIG. 31 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the sixteenth embodiment of the present invention. In Example 16, the negative lens group includes a resin negative lens L1. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. 32A to 32E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of Example 16. FIG. Table 16 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 16.

  FIG. 33 is a lens arrangement diagram illustrating the configuration of the wide-angle lens 10 according to the seventeenth embodiment of the present invention. In Example 17, the negative lens group includes resin negative lenses L1 and L1 '. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. FIGS. 34A to 34E are graphs showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of Example 17. FIGS. Table 17 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 17.

  FIG. 35 is a lens layout diagram showing the configuration of the wide-angle lens 10 according to Example 18 of the present invention. In Example 18, the negative lens group includes a glass negative lens L1 and a resin negative lens L1 '. The cemented lens L3 has a configuration in which a positive lens and a negative lens are arranged from the object side. 36A to 36E are diagrams showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of Example 18. Table 18 shows the specific numerical configuration (surface data, aspherical data, various data) of the wide-angle lens 10 of Example 18.

  FIG. 37 is a lens layout diagram showing the configuration of the wide-angle lens 10 according to Example 19 of the present invention. In the nineteenth embodiment, the negative lens unit includes resin negative lenses L1 and L1 '. The cemented lens L3 has a configuration in which a negative lens and a positive lens are arranged from the object side. 38A to 38E are graphs showing various aberrations (spherical aberration, axial chromatic aberration, lateral chromatic aberration, astigmatism, distortion aberration, lateral aberration) of the wide-angle lens 10 of Example 19. Table 19 shows specific numerical configurations (surface data, aspheric surface data, various data) of the wide-angle lens 10 of Example 19.

(Numerical verification of each example)
Table 20 is a list of values calculated when each of the conditional expressions (1) to (12) is applied in Examples 1 to 19. In Table 20, the right side and the left side of conditional expression (7) and conditional expression (9) are numerical values for height h _MAX (= effective light beam radius) for convenience. It should be noted that that the conditional expressions (7) and (9) are satisfied at each height h from the optical axis AX is obtained from the aspheric data in the tables of Examples 1 to 19 (however, only Example 11 is Conditional expression (9) is not satisfied at a certain high h.)

  As can be seen from the tables of Examples and Table 20, the wide-angle lens 10 of Example 1 satisfies the conditional expressions (1) to (4), (6) to (10), and (12). The wide-angle lens 10 of Example 2 satisfies the conditional expressions (1) to (5), (7), (9), and (11). The wide-angle lens 10 of Examples 3 to 5 satisfies the conditional expressions (1) to (5), (7) to (9), and (11). The wide-angle lens 10 of Examples 6 to 8 satisfies the conditional expressions (1) to (5) and (7) to (10). The wide-angle lens 10 of Examples 9 and 10 satisfies the conditional expressions (1) to (4) and (6) to (10) and (12). The wide-angle lens 10 of Example 11 satisfies the conditional expressions (1) to (4), (6) to (8), (10), and (12). The wide-angle lens 10 of Examples 12 to 15 satisfies the conditional expressions (1) to (4) and (6) to (10) and (12). The wide-angle lens 10 of Examples 16, 17, and 19 satisfies the conditional expressions (1) to (5) and (7) to (9). The wide-angle lens 10 of Example 18 satisfies the conditional expressions (1) to (4) and (6) to (9). In each Example 1-19, the effect by satisfy | filling each conditional expression is show | played.

  The above is the description of the exemplary embodiments of the present invention. Embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical idea of the present invention. For example, the embodiment of the present application also includes contents appropriately combined with examples and the like clearly shown in the specification or obvious examples.

L1, L1 ′ Negative lens L2 Positive lens L3 Joint lens 10 Wide angle lens

Claims (13)

A wide-angle lens with a half angle of view exceeding 30 °,
From the object side,
Negative lens ,
Positive glass lens,
A positive cemented lens in which a positive resin lens and a negative resin lens are cemented,
Have
An aperture is disposed on the image side of the positive glass lens,
The cemented surface of the cemented lens is
Ri aspheric der to sag compared with paraxial spherical surface defined by the paraxial radius of curvature of the cemented surface becomes smaller as toward the periphery from the optical axis,
When the Abbe number of the negative lens is defined as ν _n and the Abbe number of the positive glass lens is defined as ν _p ,
0 ≦ ν _n −ν _p <18
Meet ,
Wide angle lens. The image side surface of the cemented lens is
Compared to a paraxial spherical surface defined by the paraxial radius of curvature of the image side surface, the sag amount is an aspherical surface that changes in the positive direction toward the periphery from the optical axis.
The wide-angle lens according to claim 1. When the Abbe number of the positive resin lens is defined as ν _pp and the Abbe number of the negative resin lens is defined as ν _np , the following formula ν _pp −ν _np > 28
Meet,
The wide-angle lens according to claim 1 or 2. The positive refractive index of the resin lens temperature change coefficient a _{pp (Unit:} 1 / ° C.) and defining, a temperature change coefficient of the refractive index of the negative resin lens a _{np (Unit:} 1 / ° C.) and definition In this case, the following formula | a _pp −a _np | <0.00004
Meet,
The wide-angle lens according to any one of claims 1 to 3. When the temperature change coefficient of the refractive index of the positive glass lens is defined as a _pg (unit: 1 / ° C.), the following expression | a _pg | <0.00001
Meet,
The wide-angle lens according to any one of claims 1 to 4. The height of the paraxial incident light on each surface is defined with the height of the paraxial incident light from an object at infinity as 1, the power of the positive glass lens is defined as φ (unit: 1 / mm), and the positive glass When the height of the paraxial incident light beam on the object side surface of the lens is defined as H, the following expression 0.63 <φ × H <1.60
Meet,
The wide-angle lens according to any one of claims 1 to 5. When the negative lens is formed of a resin lens, the following formula 0.63 <φ × H <1.30
Meet,
The wide-angle lens according to claim 6. When the negative lens is composed of a glass lens, the following formula 0.80 <φ × H <1.60
Meet,
The wide-angle lens according to claim 6. The height from the optical axis is defined as h (unit: mm), the radius of curvature on the optical axis of the aspheric surface is defined as r (unit: mm), the coordinate point on the aspheric surface and the optical axis of the aspheric surface When the sag amount, which is the distance from the tangent plane at X, is defined as X (h), the joint surface is within the effective beam diameter, and the following expression | X (h) | <| (h ² / r) / (1 + SQRT (1- (1-0.8) × (h / r) ² )) |
Meet,
The wide-angle lens according to any one of claims 1 to 8. When the effective beam radius is defined as h _MAX (unit: mm) and the aspherical slope at the effective beam radius h _MAX is defined as dX (h _MAX ) / dh,
The joint surface has the following formula: 0.5 <| dX (h _MAX ) / dh | <1.30
Meet,
The wide-angle lens according to claim 9. When the second-order differential value of the sag amount X (h) is defined as d ² X (h) / dh ² ,
The joint surface has the following formula: d ² X (h) / dh ² ≠ 0
(However, 0 <h <h _MAX )
Meet,
The wide-angle lens according to claim 10. When the negative lens is a resin lens, the focal length of the wide-angle lens is defined as f (unit: mm), and the radius of curvature of the object side surface of the cemented lens is defined as r ′ (unit: mm) And the following formula 0.50 <f / r ′ <1.33
Meet,
The wide-angle lens according to any one of claims 1 to 7, and 9 to 11 . When the negative lens is composed of a glass lens, the focal length of the wide-angle lens is defined as f (unit: mm), and the radius of curvature of the object side surface of the cemented lens is defined as r ′ (unit: mm) And the following formula −0.28 <f / r ′ <0.63
Meet,
The wide-angle lens according to any one of claims 1 to 6 and claims 8 to 11 .

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