CN219552750U - Fixed focus lens - Google Patents

Abstract

The utility model discloses a fixed focus lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object plane to an image plane along an optical axis; the first lens is a negative focal power lens, the second lens is a positive focal power lens, the third lens is a negative focal power lens, the fourth lens is a positive focal power lens, the fifth lens is a positive focal power lens, and the sixth lens is a negative focal power lens; the focal power of the first lens is phi 1, the focal power of the second lens is phi 2, the focal power of the third lens is phi 3, the focal power of the fourth lens is phi 4, the focal power of the fifth lens is phi 5, the focal power of the sixth lens is phi 6, and the focal power of the fixed lens is phi, wherein: -0.82< Φ1/Φ < -0.71;0.59< phi 2/phi <0.78; -0.05-0.15 (Φ3+Φ4)/Φ; the ratio of (phi 5+ phi 6)/phi is more than or equal to 0.38 and less than or equal to 0.46. The technical scheme of the embodiment of the utility model can meet the requirements of high image quality, large aperture, small distortion and high stability of the lens.

Description

Fixed focus lens

Technical Field

The utility model relates to the technical field of optical devices, in particular to a fixed-focus lens.

Background

With the improvement of national security consciousness, the security lens industry rapidly develops, and how to provide a security lens with high image quality, large aperture, small distortion, high cost performance and high stability becomes a problem to be solved by research personnel.

Disclosure of Invention

The utility model provides a fixed-focus lens which meets the requirements of high image quality, large aperture, small distortion and high stability.

The fixed focus lens provided by the utility model comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object plane to an image plane along an optical axis;

the first lens is a negative focal power lens, the second lens is a positive focal power lens, the third lens is a negative focal power lens, the fourth lens is a positive focal power lens, the fifth lens is a positive focal power lens, and the sixth lens is a negative focal power lens;

the focal power of the first lens is phi 1, the focal power of the second lens is phi 2, the focal power of the third lens is phi 3, the focal power of the fourth lens is phi 4, the focal power of the fifth lens is phi 5, the focal power of the sixth lens is phi 6, and the focal power of the fixed lens is phi, wherein:

-0.82<Φ1/Φ<-0.71；

0.59<Φ2/Φ<0.78；

-0.05≤(Φ3+Φ4)/Φ≤0.15；

0.38≤(Φ5+Φ6)/Φ≤0.46。

optionally, the first lens, the second lens, the third lens, the fifth lens and the sixth lens are all plastic aspheric lenses, and the fourth lens is a glass spherical lens.

Optionally, a surface of the lens adjacent to the object plane is an object plane surface, and a surface of the lens adjacent to the image plane is an image plane surface;

the object side surface of the first lens is convex towards the object plane, and the image side surface of the first lens is concave towards the image plane;

the object side surface of the second lens is concave towards the object plane, and the image side surface of the second lens is convex towards the image plane;

the object side surface of the third lens is sunken towards the object plane, and the image side surface of the third lens is sunken towards the image plane;

the object side surface of the fourth lens is convex towards the object plane, and the image side surface of the fourth lens is convex towards the image plane;

the object side surface of the fifth lens protrudes towards the object plane, and the image side surface of the fifth lens protrudes towards the image plane;

the object side surface of the sixth lens is concave towards the object plane, and the image side surface of the fourth lens is convex towards the image plane.

Optionally, the fixed focus lens further comprises a diaphragm;

the diaphragm is positioned in the optical path between the fourth lens and the fifth lens.

Optionally, the abbe number of the fourth lens is Vd4; wherein: 63< Vd4<96.

Optionally, the distance from the center of the optical axis of the image side of the sixth lens element to the image plane is BFL, and the distance from the center of the optical axis of the object side of the first lens element to the image plane is TTL, wherein:

0.25<BFL/TTL<0.30。

optionally, the F-number of the fixed focus lens is F, wherein F is less than or equal to 1.6.

According to the fixed focus lens provided by the embodiment of the utility model, through using six lenses and reasonably configuring the focal power of each lens, the fixed focus lens has the advantages of high image quality, large aperture, small distortion and high stability, and can be maximally matched with a 1/2.5' sensor chip, so that the use requirement of a security monitoring general sensor chip is met.

It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the utility model or to delineate the scope of the utility model. Other features of the present utility model will become apparent from the description that follows.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a fixed focus lens according to a first embodiment of the present utility model;

fig. 2 is a spherical aberration diagram of a fixed focus lens according to a first embodiment of the present utility model;

fig. 3 is a field curvature distortion diagram of a fixed focus lens according to a first embodiment of the present utility model;

fig. 4 is a schematic structural diagram of a fixed-focus lens according to a second embodiment of the present utility model;

fig. 5 is a spherical aberration diagram of a fixed focus lens according to a second embodiment of the present utility model;

fig. 6 is a field curvature distortion diagram of a fixed focus lens according to a second embodiment of the present utility model;

fig. 7 is a schematic structural diagram of a fixed focus lens according to a third embodiment of the present utility model;

fig. 8 is a spherical aberration diagram of a fixed focus lens according to a third embodiment of the present utility model;

fig. 9 is a field curvature distortion diagram of a fixed focus lens according to a third embodiment of the present utility model;

fig. 10 is a schematic structural diagram of a fixed focus lens according to a fourth embodiment of the present utility model;

FIG. 11 is a spherical aberration diagram of a fixed focus lens according to a fourth embodiment of the present utility model;

fig. 12 is a field curvature distortion diagram of a fixed focus lens according to a fourth embodiment of the present utility model.

Detailed Description

In order that those skilled in the art will better understand the present utility model, a technical solution in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present utility model, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present utility model without making any inventive effort, shall fall within the scope of the present utility model.

Example 1

Fig. 1 is a schematic structural diagram of a fixed-focus lens according to a first embodiment of the present utility model, as shown in fig. 1, the fixed-focus lens according to the first embodiment of the present utility model includes a first lens element 110, a second lens element 120, a third lens element 130, a fourth lens element 140, a fifth lens element 150, and a sixth lens element 160, which are sequentially arranged along an optical axis from an object plane to an image plane; the first lens 110 is a negative power lens, the second lens 120 is a positive power lens, the third lens 130 is a negative power lens, the fourth lens 140 is a positive power lens, the fifth lens 150 is a positive power lens, and the sixth lens 160 is a negative power lens; the optical power of the first lens 110 is Φ1, the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed focus lens is Φ, wherein:

-0.82<Φ1/Φ<-0.71；

0.59<Φ2/Φ<0.78；

-0.05≤(Φ3+Φ4)/Φ≤0.15；

0.38≤(Φ5+Φ6)/Φ≤0.46。

specifically, the optical power is equal to the difference between the convergence of the image side beam and the convergence of the object side beam, which characterizes the ability of the optical system to deflect light. The greater the absolute value of the optical power, the greater the ability to bend the light, the smaller the absolute value of the optical power, and the weaker the ability to bend the light. When the focal power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light is divergent. The optical power may be suitable for characterizing a refractive surface of a lens (i.e. a surface of a lens), for characterizing a lens, or for characterizing a system of lenses together (i.e. a lens group). In the fixed focus lens provided in the present embodiment, each lens can be fixed in one barrel (not shown in fig. 1).

In this embodiment, by setting the first lens 110 as a negative focal power lens and setting its focal power Φ1 to satisfy the above range, the object-side light can be smoothly received into the imaging system, so that the light enters the second lens 120 at a smaller incident angle, and the duty ratio of the higher-order aberration is reduced; by setting the second lens 120 as a positive power lens and setting its power Φ2 to satisfy the above range, the light can be further contracted at a gentle off angle, so that the imaging system has a more relaxed tolerance sensitivity; by setting the third lens 130 as a negative focal power lens and the fourth lens 140 as a positive focal power lens, and setting the focal powers phi 3 and phi 4 of the third lens and the fourth lens to satisfy the above range, the positive and negative focal powers of the optical system can be reasonably distributed, which is beneficial to correcting the aberration of the system; by setting the fifth lens 150 as a positive power lens and the sixth lens 160 as a negative power lens, and setting the powers Φ5 and Φ6 of the two to satisfy the above range, the positive and negative powers of the optical system can be reasonably distributed, which is beneficial to correcting the aberration of the system. The focal power of the whole fixed focus lens is distributed according to a certain proportion, so that the uniformity of the incident angles of the front lens and the rear lens can be ensured, the sensitivity of the lenses is reduced, the stability of the lens is improved, the imaging quality is improved, and the realization of a large aperture is facilitated. In the embodiment, F is less than or equal to 1.6.

In summary, the fixed focus lens provided by the embodiment of the utility model has the advantages of high image quality, large aperture, small distortion and high stability by using six lenses and reasonably configuring the focal power of each lens, and can be maximally matched with a 1/2.5' sensor chip, thereby meeting the use requirement of a security monitoring general sensor chip.

On the basis of the above embodiment, optionally, the first lens 110, the second lens 120, the third lens 130, the fifth lens 150 and the sixth lens 160 are all plastic aspherical lenses, and the fourth lens 140 is a glass spherical lens.

In particular, an aspherical lens is characterized by a continuously varying curvature from the center of the lens to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center of the lens to the periphery of the lens, an aspherical lens has a better radius of curvature characteristic, and has advantages of improving distortion aberration and improving astigmatic aberration. After the aspheric lens is adopted, aberration generated during imaging can be eliminated as much as possible, and therefore the imaging quality of the lens is improved. The spherical lens is characterized in that the constant curvature is arranged from the center of the lens to the periphery of the lens, and the lens is ensured to be arranged in a simple mode.

Further, the material of the plastic aspheric lens may be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. The lens made of glass is small in thermal expansion coefficient and good in stability, when the ambient temperature used by the fixed-focus lens is changed greatly, the focal length of the fixed-focus lens is kept stable, the cost of the lens made of plastic is far lower than that of the lens made of glass, and the lens made of plastic is favorable for reducing the overall cost of the fixed-focus lens.

In this embodiment, a mode of mixing and matching glass lenses and plastic lenses is adopted, and by setting the first lens 110, the second lens 120, the third lens 130, the fifth lens 150 and the sixth lens 160 to be plastic aspheric lenses, and the fourth lens 140 to be glass spherical lenses, on one hand, the cost of the focusing lens can be effectively controlled, the processing technology of the aspheric lenses is reduced, and meanwhile, as the materials of the lenses have mutual compensation, the focusing lens can be ensured to be normally used under high and low temperature environments, and no virtual focus at-40-80 ℃ is realized.

Defining the surface of the lens adjacent to the object plane as an object space surface, and defining the surface of the lens adjacent to the image plane as an image space surface; as shown in fig. 1, optionally, an object-side surface of the first lens 110 is convex toward the object plane, and an image-side surface of the first lens 110 is concave toward the image plane; the object side surface of the second lens 120 is concave towards the object plane, and the image side surface of the second lens 120 is convex towards the image plane; the object side surface of the third lens 130 is concave towards the object plane, and the image side surface of the third lens 130 is concave towards the image plane; the object side surface of the fourth lens 140 protrudes towards the object plane, and the image side surface of the fourth lens 140 protrudes towards the image plane; the object side surface of the fifth lens 150 protrudes toward the object plane, and the image side surface of the fifth lens 150 protrudes toward the image plane; the object-side surface of the sixth lens 160 is concave toward the object plane, and the image-side surface of the fourth lens 160 is convex toward the image plane. Through the face type that rationally sets up each lens, when guaranteeing that the focal power of each lens satisfies the focal power requirement in the above-mentioned embodiment, still can guarantee whole fixed focus camera lens compact structure, fixed focus camera lens integrated level is high.

As shown in fig. 1, optionally, the fixed focus lens further includes a diaphragm 170; the diaphragm 170 is located in the optical path between the fourth lens 140 and the fifth lens 150. The propagation direction of the light beam can be adjusted by arranging the diaphragm, which is beneficial to further improving the imaging quality.

As shown in fig. 1, optionally, the fixed focus lens may further include an optical filter 180, where the optical filter 180 is located in the optical path between the sixth lens 160 and the image plane, so that infrared light can be filtered during the daytime, and the imaging effect is improved.

Alternatively, the abbe number of the fourth lens 140 is Vd4; wherein: 63< Vd4<96. Specifically, the abbe number is an index for indicating the dispersion ability of the transparent medium, and the more serious the medium dispersion, the smaller the abbe number; conversely, the more slightly the dispersion of the medium, the greater the Abbe number. By setting the fourth lens to select a high Abbe number glass material with Abbe number between 63 and 96, good chromatic aberration can be ensured, and high-definition image quality can be obtained.

Based on the above embodiment, the distance from the center of the optical axis of the image side of the sixth lens element 160 to the image plane is BFL, which can be understood as the back focal length of the fixed focus lens element, and the distance from the center of the optical axis of the object side of the first lens element 110 to the image plane is TTL, which can be understood as the total optical length of the fixed focus lens element, and optionally, the back focal length BFL and the total optical length TTL of the fixed focus lens element satisfy: 0.25< BFL/TTL <0.30. Thus, a sufficient installation space of the imaging sensor and the optical filter 180 can be ensured.

As a possible embodiment, the following describes the optical physical parameters such as the surface type, radius of curvature, thickness, refractive index, abbe number, half caliber, and the like of each lens in the fixed focus lens.

In table 1, the surface numbers are numbered according to the surface order of the respective lenses, for example, the surface number "S1" represents the object-side surface of the first lens element 110, the surface number "S2" represents the image-side surface of the first lens element 110, and so on; "STO" represents the stop of the fixed focus lens; the curvature radius represents the bending degree of the surface of the lens, a positive value represents that the surface is bent to one side of the object plane, the circle center is close to the image plane, a negative value represents that the surface is bent to one side of the image plane, the circle center is close to the object plane, INF represents the plane, and the curvature radius of the plane is infinity; thickness represents the center axial distance from the current surface to the next surface; refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, space represents the current position as air, and refractive index is 1; the Abbe number (Vd) represents the dispersive properties of the material to light between the current surface and the next surface, and the space represents the current position as air.

Table 1 design values of optical physical parameters of fixed focus lens

On the basis of the above embodiment, the aspherical surfaces of the above aspherical lenses (i.e., the first lens 110, the second lens 120, the third lens 130, the fifth lens 150, and the sixth lens 160) satisfy:

wherein Z represents the axial sagittal height of the aspheric surface in the Z direction; r represents the distance from the point on the aspherical surface to the optical axis; c represents the curvature of the fitting sphere, and is the inverse of the curvature radius in value; k represents a fitting cone coefficient; A. b, C, D, E, F, G are the 4 th, 6 th, 8 th, 10 th, 12 th, 14 th and 16 th order coefficients of the aspherical polynomial, respectively.

The data in the aspherical surface of an aspherical lens is described below in connection with table 2 in one possible embodiment.

Table 2 parameter design values for each surface of aspherical lens in fixed focus lens

Wherein, -6.644148E-03 represents a coefficient A of-6.644148 x 10 with a face number S1 ^-3 And so on.

The optical system of the embodiment achieves the following technical indexes: the focal length was 5.587mm and f-number was 1.6. By adopting the scheme, the fixed focus lens has the advantages of high image quality, large aperture, small distortion, low cost and high stability, and meets the use requirement of the security monitoring general sensor chip.

Further, fig. 2 is a spherical aberration diagram of a fixed focus lens according to an embodiment of the present utility model, wherein in fig. 2, a vertical direction represents normalization of a pupil plane of 0 field, 0 represents a pupil center, and a vertical direction vertex represents a pupil vertex; the horizontal direction is spherical aberration of different wavelengths (different linear curves in fig. 2 represent different wavelengths imaged by the system) in millimeters (mm). As shown in FIG. 2, the spherical aberration of the fixed focus lens provided by the first embodiment of the utility model is controlled within (-0.01 mm, +0.02 mm) at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm), and the different wavelength curves are relatively concentrated, which indicates that the spherical aberration of the fixed focus lens at each wavelength is better controlled, and can meet the requirements of wide spectrum application.

Fig. 3 is a field curvature distortion chart of a fixed focus lens according to an embodiment of the present utility model, as shown in fig. 3, in a left coordinate system, a horizontal coordinate represents a field curvature, and a unit is millimeters (mm); the vertical coordinates represent the normalized image height without units; as can be seen from fig. 3, the fixed focus lens provided in this embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height without units; as can be seen from fig. 3, the distortion of the fixed focus lens provided in this embodiment is well corrected, and the imaging distortion is less than 50%.

Example two

Fig. 4 is a schematic structural diagram of a fixed-focus lens according to a second embodiment of the present utility model, as shown in fig. 4, the fixed-focus lens according to the second embodiment of the present utility model includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160, which are sequentially arranged from an object plane to an image plane along an optical axis; the first lens 110 is a negative power lens, the second lens 120 is a positive power lens, the third lens 130 is a negative power lens, the fourth lens 140 is a positive power lens, the fifth lens 150 is a positive power lens, and the sixth lens 160 is a negative power lens; the optical power of the first lens 110 is Φ1, the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed focus lens is Φ, wherein:

-0.82<Φ1/Φ<-0.71；

0.59<Φ2/Φ<0.78；

-0.05≤(Φ3+Φ4)/Φ≤0.15；

0.38≤(Φ5+Φ6)/Φ≤0.46。

the material, the surface, the abbe number, and other optical physical parameter ranges of each lens are the same as those of the first embodiment, and are not described herein.

Table 3 details specific setting parameters of each lens in the fixed focus lens provided in the second embodiment of the present utility model in another possible implementation manner, where the fixed focus lens in table 3 corresponds to the fixed focus lens shown in fig. 4.

Table 3 design values of optical physical parameters of fixed focus lens

In table 3, the surface numbers are numbered according to the surface order of the respective lenses, for example, the surface number "S1" represents the object-side surface of the first lens element 110, the surface number "S2" represents the image-side surface of the first lens element 110, and so on; "STO" represents the stop of the fixed focus lens; the curvature radius represents the bending degree of the surface of the lens, a positive value represents that the surface is bent to one side of the object plane, the circle center is close to the image plane, a negative value represents that the surface is bent to one side of the image plane, the circle center is close to the object plane, INF represents the plane, and the curvature radius of the plane is infinity; thickness represents the center axial distance from the current surface to the next surface; refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, space represents the current position as air, and refractive index is 1; the Abbe number (Vd) represents the dispersive properties of the material to light between the current surface and the next surface, and the space represents the current position as air.

The data in the aspherical surface of an aspherical lens is described below in connection with table 4 in one possible embodiment.

Table 4 parameter design values for each surface of aspherical lens in fixed focus lens

Wherein, -6.758286E-03 shows that the coefficient A with the surface number S1 is-6.758886 x 10 ^-3 And so on.

The optical system of the embodiment achieves the following technical indexes: the focal length was 5.686mm and f-number was 1.6. By adopting the scheme, the fixed focus lens has the advantages of high image quality, large aperture, small distortion, low cost and high stability, and meets the use requirement of the security monitoring general sensor chip.

Further, fig. 5 is a spherical aberration diagram of a fixed focus lens according to a second embodiment of the present utility model, where in fig. 5, a vertical direction represents normalization of a pupil plane of 0 field, 0 represents a pupil center, and a vertical direction vertex represents a pupil vertex; the horizontal direction is spherical aberration of different wavelengths (different linear curves in fig. 5 represent different wavelengths imaged by the system) in millimeters (mm). As shown in FIG. 5, the spherical aberration of the fixed focus lens provided by the second embodiment of the utility model is controlled within (-0.01 mm, +0.03 mm) at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm), and the different wavelength curves are relatively concentrated, which indicates that the spherical aberration of the fixed focus lens at each wavelength is better controlled, and can meet the requirements of wide spectrum application.

Fig. 6 is a field curvature distortion diagram of a fixed focus lens according to a second embodiment of the present utility model, as shown in fig. 6, in a left coordinate system, a horizontal coordinate represents a field curvature, and a unit is millimeters (mm); the vertical coordinates represent the normalized image height without units; as can be seen from fig. 6, the fixed focus lens provided in this embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height without units; as can be seen from fig. 6, the distortion of the fixed focus lens provided in this embodiment is well corrected, and the imaging distortion is less than 50%.

Example III

Fig. 7 is a schematic structural diagram of a fixed-focus lens according to a third embodiment of the present utility model, as shown in fig. 7, the fixed-focus lens according to the third embodiment of the present utility model includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160, which are sequentially arranged from an object plane to an image plane along an optical axis; the first lens 110 is a negative power lens, the second lens 120 is a positive power lens, the third lens 130 is a negative power lens, the fourth lens 140 is a positive power lens, the fifth lens 150 is a positive power lens, and the sixth lens 160 is a negative power lens; the optical power of the first lens 110 is Φ1, the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed focus lens is Φ, wherein:

-0.82<Φ1/Φ<-0.71；

0.59<Φ2/Φ<0.78；

-0.05≤(Φ3+Φ4)/Φ≤0.15；

0.38≤(Φ5+Φ6)/Φ≤0.46。

the material, the surface, the abbe number, and other optical physical parameter ranges of each lens are the same as those of the first embodiment, and are not described herein.

Table 5 details the specific setting parameters of each lens in the fixed focus lens provided in the third embodiment of the present utility model in another possible implementation manner, where the fixed focus lens in table 5 corresponds to the fixed focus lens shown in fig. 7.

Table 5 design values of optical physical parameters of fixed focus lens

In table 5, the surface numbers are numbered according to the surface order of the respective lenses, for example, the surface number "S1" represents the object-side surface of the first lens element 110, the surface number "S2" represents the image-side surface of the first lens element 110, and so on; "STO" represents the stop of the fixed focus lens; the curvature radius represents the bending degree of the surface of the lens, a positive value represents that the surface is bent to one side of the object plane, the circle center is close to the image plane, a negative value represents that the surface is bent to one side of the image plane, the circle center is close to the object plane, INF represents the plane, and the curvature radius of the plane is infinity; thickness represents the center axial distance from the current surface to the next surface; refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, space represents the current position as air, and refractive index is 1; the Abbe number (Vd) represents the dispersive properties of the material to light between the current surface and the next surface, and the space represents the current position as air.

Table 6 parameter design values for each surface of aspherical lens in fixed focus lens

As described in table 6 above, the data in the aspherical surface of the aspherical lens in this example is described in one possible embodiment. In Table 6, -6.644084E-03 shows that the coefficient A with the surface number S1 is-6.644084 x 10 ^-3 And so on.

The optical system of the embodiment achieves the following technical indexes: the focal length was 5.711mm and f-number was 1.6. By adopting the scheme, the fixed focus lens has the advantages of high image quality, large aperture, small distortion, low cost and high stability, and meets the use requirement of the security monitoring general sensor chip.

Further, fig. 8 is a spherical aberration diagram of a fixed focus lens according to a third embodiment of the present utility model, where in fig. 8, a vertical direction represents normalization of a pupil plane of 0 field, 0 represents a pupil center, and a vertical direction vertex represents a pupil vertex; the horizontal direction is spherical aberration of different wavelengths (different linear curves in fig. 8 represent different wavelengths imaged by the system) in millimeters (mm). As shown in FIG. 8, the spherical aberration of the fixed focus lens provided in the third embodiment of the utility model is controlled within (-0.01 mm, +0.03 mm) at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm), and the different wavelength curves are relatively concentrated, which indicates that the spherical aberration of the fixed focus lens at each wavelength is better controlled, and can meet the requirements of wide spectrum application.

Fig. 9 is a field curvature distortion diagram of a fixed focus lens according to a third embodiment of the present utility model, as shown in fig. 9, in a left coordinate system, a horizontal coordinate represents a field curvature, and a unit is millimeters (mm); the vertical coordinates represent the normalized image height without units; as can be seen from fig. 9, the fixed focus lens provided in this embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height without units; as can be seen from fig. 9, the distortion of the fixed focus lens provided in this embodiment is well corrected, and the imaging distortion is less than 50%.

Example IV

Fig. 10 is a schematic structural diagram of a fixed-focus lens according to a fourth embodiment of the present utility model, as shown in fig. 10, the fixed-focus lens according to the fourth embodiment of the present utility model includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160, which are sequentially arranged from an object plane to an image plane along an optical axis; the first lens 110 is a negative power lens, the second lens 120 is a positive power lens, the third lens 130 is a negative power lens, the fourth lens 140 is a positive power lens, the fifth lens 150 is a positive power lens, and the sixth lens 160 is a negative power lens; the optical power of the first lens 110 is Φ1, the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed focus lens is Φ, wherein:

-0.82<Φ1/Φ<-0.71；0.59<Φ2/Φ<0.78；

-0.05≤(Φ3+Φ4)/Φ≤0.15；0.38≤(Φ5+Φ6)/Φ≤0.46。

the material, the surface, the abbe number, and other optical physical parameter ranges of each lens are the same as those of the first embodiment, and are not described herein.

TABLE 7 design values of optical physical parameters of fixed focus lens

Table 8 parameter design values for each surface of aspherical lens in fixed focus lens

As shown in table 7, the specific setting parameters of each lens in the fixed focus lens provided in the fourth embodiment of the present utility model are described in detail in another possible implementation manner, and the fixed focus lens in table 7 corresponds to the fixed focus lens shown in fig. 10.

In table 7, the surface numbers are numbered according to the surface order of the respective lenses, for example, the surface number "S1" represents the object-side surface of the first lens element 110, the surface number "S2" represents the image-side surface of the first lens element 110, and so on; "STO" represents the stop of the fixed focus lens; the curvature radius represents the bending degree of the surface of the lens, a positive value represents that the surface is bent to one side of the object plane, the circle center is close to the image plane, a negative value represents that the surface is bent to one side of the image plane, the circle center is close to the object plane, INF represents the plane, and the curvature radius of the plane is infinity; thickness represents the center axial distance from the current surface to the next surface; refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, space represents the current position as air, and refractive index is 1; the Abbe number (Vd) represents the dispersive properties of the material to light between the current surface and the next surface, and the space represents the current position as air.

As described in table 8 above, the data in the aspherical surface of the aspherical lens in this example is described in one possible embodiment. In Table 8, -6.885901E-03 shows that the coefficient A with the surface number S1 is-6.885901 x 10 ^-3 And so on.

The optical system of the embodiment achieves the following technical indexes: the focal length was 5.610mm and f-number was 1.6. By adopting the scheme, the fixed focus lens has the advantages of high image quality, large aperture, small distortion, low cost and high stability, and meets the use requirement of the security monitoring general sensor chip.

Further, fig. 11 is a spherical aberration diagram of a fixed focus lens according to a fourth embodiment of the present utility model, in fig. 11, a vertical direction represents normalization of a pupil plane of 0 field, 0 represents a pupil center, and a vertical direction vertex represents a pupil vertex; the horizontal direction is spherical aberration of different wavelengths (different linear curves in fig. 11 represent different wavelengths imaged by the system) in millimeters (mm). As shown in FIG. 11, the spherical aberration of the fixed focus lens provided in the fourth embodiment of the utility model is controlled within (-0.01 mm, +0.03 mm) at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm), and the different wavelength curves are relatively concentrated, which indicates that the spherical aberration of the fixed focus lens at each wavelength is better controlled, and can meet the requirements of wide spectrum application.

Fig. 12 is a field curvature distortion diagram of a fixed focus lens according to a fourth embodiment of the present utility model, where, as shown in fig. 12, in a left coordinate system, a horizontal coordinate represents a field curvature, and a unit is millimeters (mm); the vertical coordinates represent the normalized image height without units; as can be seen from fig. 12, the fixed focus lens provided in this embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height without units; as can be seen from fig. 12, the distortion of the fixed focus lens provided in this embodiment is well corrected, and the imaging distortion is less than 50%.

The above embodiments do not limit the scope of the present utility model. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included in the scope of the present utility model.

Claims (7)

1. The fixed focus lens is characterized by comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object plane to an image plane along an optical axis;

the first lens is a negative focal power lens, the second lens is a positive focal power lens, the third lens is a negative focal power lens, the fourth lens is a positive focal power lens, the fifth lens is a positive focal power lens, and the sixth lens is a negative focal power lens;

the focal power of the first lens is phi 1, the focal power of the second lens is phi 2, the focal power of the third lens is phi 3, the focal power of the fourth lens is phi 4, the focal power of the fifth lens is phi 5, the focal power of the sixth lens is phi 6, and the focal power of the fixed lens is phi, wherein:

-0.82<Φ1/Φ<-0.71；

0.59<Φ2/Φ<0.78；

-0.05≤(Φ3+Φ4)/Φ≤0.15；

0.38≤(Φ5+Φ6)/Φ≤0.46。

2. the fixed focus lens of claim 1, wherein the first lens, the second lens, the third lens, the fifth lens, and the sixth lens are all plastic aspheric lenses, and the fourth lens is a glass spherical lens.

3. The fixed focus lens of claim 1, wherein a surface of the lens adjacent to the object plane side is an object side surface, and a surface of the lens adjacent to the image plane side is an image side surface;

the object side surface of the first lens is convex towards the object plane, and the image side surface of the first lens is concave towards the image plane;

the object side surface of the second lens is concave towards the object plane, and the image side surface of the second lens is convex towards the image plane;

the object side surface of the third lens is sunken towards the object plane, and the image side surface of the third lens is sunken towards the image plane;

the object side surface of the fourth lens is convex towards the object plane, and the image side surface of the fourth lens is convex towards the image plane;

the object side surface of the fifth lens is convex towards the object plane, and the image side surface of the fifth lens is convex towards the image plane;

the object side surface of the sixth lens is concave towards the object plane, and the image side surface of the fourth lens is convex towards the image plane.

4. The fixed focus lens of claim 1, further comprising a stop;

the diaphragm is located in the optical path between the fourth lens and the fifth lens.

5. The fixed focus lens of claim 1, wherein the fourth lens has an abbe number Vd4; wherein: 63< Vd4<96.

6. The fixed focus lens of claim 1, wherein a distance from an optical axis center of an image side of the sixth lens element to an image plane is BFL, and a distance from an optical axis center of an object side of the first lens element to the image plane is TTL, wherein:

0.25<BFL/TTL<0.30。

7. the fixed focus lens of claim 1, wherein the F-number of the fixed focus lens is F, wherein F is less than or equal to 1.6.