CN211528806U - Fixed focus lens - Google Patents

Abstract

The embodiment of the utility model discloses tight shot is disclosed. The fixed-focus lens comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, a diaphragm, a fifth lens with negative focal power, a sixth lens with positive focal power, a seventh lens with positive focal power and an eighth lens with positive focal power or negative focal power, which are sequentially arranged from an object side to an image side along an optical axis; the first lens, the third lens, the fifth lens and the sixth lens are all spherical lenses, and the fifth lens and the sixth lens form a cemented lens; the second lens, the fourth lens, the seventh lens and the eighth lens are all aspheric lenses. The embodiment of the utility model provides a tight shot has the characteristics of super large light flux, is particularly suitable for the control demand under the complex condition, can reach the big light ring of F0.8 ~ 1.2, supports the image plane of 1/1.8 inch, and the field angle scope can reach 90 ~ 130.

Description

Fixed focus lens

Technical Field

The embodiment of the utility model provides a relate to the camera lens technique, especially relate to a tight shot.

Background

With the improvement of safety consciousness of people, higher-level requirements are also made on security, and the monitoring lens is born immediately. Compared with the zoom lens, the fixed-focus lens is simple in design and manufacture, and the shot moving object has clear and stable images and fine and smooth pictures, so that the fixed-focus lens occupies an important position in the security monitoring industry.

At present, image sensor manufacturers have already provided 1/1.8 inch large-image-plane low-illumination image sensors with better light receiving capability. However, the lens in the prior art capable of meeting the requirement has the problems of an aperture virtual mark, an overlarge volume, a low yield, only supporting 2 million pixels at most and the like, so that a 1/1.8 inch ultra-low illumination lens with a small volume, a high cost performance and a large aperture range is very necessary.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a fixed focus camera lens, this fixed focus camera lens have the characteristics of super large light flux, are particularly suitable for the control demand under the complex condition, can reach the big light ring of F0.8 ~ 1.2, support the image plane of 1/1.8 inch, and the field angle scope can reach 90 ~ 130.

The embodiment of the utility model provides a fixed focus camera lens, include along the optical axis from the object space to the first lens of the negative focal power, the second lens of negative focal power, the third lens of positive focal power, the fourth lens of negative focal power, the diaphragm of negative focal power, the fifth lens of negative focal power, the sixth lens of positive focal power, the seventh lens of positive focal power and the eighth lens of positive focal power or negative focal power that arrange in proper order;

the first lens, the third lens, the fifth lens and the sixth lens are all spherical lenses, and the fifth lens and the sixth lens form a cemented lens; the second lens, the fourth lens, the seventh lens, and the eighth lens are all aspheric lenses.

Optionally, the focal lengths of the first lens to the seventh lens and the focal length of the fixed-focus lens satisfy:

1.5<|f1/f|<3.5；

3.2<|f2/f|<5.6；

0.8<|f12/f|<2.2；

1.0<|f3/f|<2.3；

6.0<|f4/f|<8.5；

0.7<|f5/f|<2.0；

0.7<|f6/f|<2.0；

|f56/f|>10；

2.0<|f7/f|<4.0；

wherein f1, f2, f3, f4, f5, f6, and f7 denote focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens, respectively, f12 denotes a combined focal length of the first lens and the second lens, f56 denotes a combined focal length of the fifth lens and the sixth lens, and f denotes a focal length of the prime lens.

Optionally, abbe numbers of the second lens and the seventh lens are both greater than 50.

Optionally, the refractive index of the third lens is greater than 1.8, the refractive index of the fourth lens is greater than 1.6, and the refractive index of the fifth lens is greater than 1.8.

Optionally, the first lens is a meniscus lens, the second lens is a meniscus lens, the third lens is a biconvex lens, the fourth lens is a meniscus lens, the fifth lens is a biconcave lens, the sixth lens is a biconvex lens, and the seventh lens is a biconvex lens.

Optionally, the first lens is a convex-concave lens, a convex surface of the first lens faces one side of an object space, the second lens is a convex-concave lens, a convex surface of the second lens faces one side of the object space, the fourth lens is a convex-concave lens, and a convex surface of the fourth lens faces one side of an image space.

Optionally, the first lens, the third lens, the fifth lens and the sixth lens are all glass spherical lenses; the second lens, the fourth lens, the seventh lens and the eighth lens are all plastic aspheric lenses.

Optionally, the fixed-focus lens satisfies the following conditions: 4.0< TTL/f < 7.0;

wherein TTL represents the optical total length of the fixed-focus lens, and f represents the focal length of the fixed-focus lens.

The embodiment of the utility model provides a fixed focus camera lens, include along the optical axis from the object space to the image space first lens of negative focal power, the second lens of negative focal power, the third lens of positive focal power, the fourth lens of negative focal power, the diaphragm, the fifth lens of negative focal power, the sixth lens of positive focal power, the seventh lens of positive focal power and the eighth lens of positive focal power or negative focal power that arrange in proper order; the first lens, the third lens, the fifth lens and the sixth lens are all spherical lenses, and the fifth lens and the sixth lens form a cemented lens; the second lens, the fourth lens, the seventh lens and the eighth lens are all aspheric lenses. The first lens and the second lens with negative focal power have the function of collecting light rays for the large-field-of-view optical system, and the second lens can correct the size of distortion while collecting the light rays; the spherical aberration of the system is corrected while the optical path is turned by the third lens with positive focal power; the fourth lens with negative focal power is more beneficial to correcting the off-axis field aberration; the fifth lens and the sixth lens are set to be in a negative and positive focal power double-cemented lens form, so that the correction of system chromatic aberration is facilitated; meanwhile, the third lens, the fourth lens, the fifth lens and the sixth lens form a Gaussian structure which is symmetrical about the diaphragm, so that the off-axis aberration of the system can be corrected more favorably; by arranging the seventh lens with positive focal power, the field curvature and astigmatism of the system can be corrected, the direction of light can be changed, and the inclination angle of the principal light of the system can be effectively reduced; the focal power of the eighth lens can be positive or negative and is used for correcting residual aberration of light after passing through the seven front lenses; through the matching of the spherical lens and the aspheric lens, the large-light-transmission fixed-focus lens suitable for monitoring requirements under complex conditions is realized, a large aperture of F0.8-1.2 can be achieved, a 1/1.8-inch image surface is supported, and the field angle range can reach 90-130 degrees.

Drawings

Fig. 1 is a schematic structural diagram of a fixed focus lens provided in an embodiment of the present invention;

fig. 2 is a schematic view of a spherical aberration of a fixed focus lens provided in an embodiment of the present invention;

fig. 3 is a field curvature schematic diagram of a fixed focus lens provided in an embodiment of the present invention;

fig. 4 is a schematic diagram illustrating distortion of a fixed-focus lens according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the embodiments of the present invention are described in terms of the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element. The terms "first," "second," and the like, are used for descriptive purposes only and not for purposes of limitation, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Fig. 1 is a schematic structural diagram of a fixed focus lens according to an embodiment of the present invention. Referring to fig. 1, a fixed focus lens provided in an embodiment of the present invention includes a first lens 10 with negative refractive power, a second lens 20 with negative refractive power, a third lens 30 with positive refractive power, a fourth lens 40 with negative refractive power, a diaphragm 90, a fifth lens 50 with negative refractive power, a sixth lens 60 with positive refractive power, a seventh lens 70 with positive refractive power, and an eighth lens 80 with positive refractive power or negative refractive power, which are sequentially arranged from an object side to an image side along an optical axis; the first lens 10, the third lens 30, the fifth lens 50 and the sixth lens 60 are all spherical lenses, and the fifth lens 50 and the sixth lens 60 form a cemented lens; the second lens 20, the fourth lens 40, the seventh lens 70, and the eighth lens 80 are all aspheric lenses.

Therein, it is understood that the optical power is equal to the difference between the image-side and object-side convergence, which characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal power is, the stronger the bending ability to the light ray is, and the smaller the absolute value of the focal power is, the weaker the bending ability to the light ray is. When the focal power is positive, the refraction of the light is convergent; when the focal power is negative, the refraction of the light is divergent. The optical power can be suitable for representing a certain refractive surface of a lens (namely, a surface of the lens), can be suitable for representing a certain lens, and can also be suitable for representing a system (namely a lens group) formed by a plurality of lenses together. In this embodiment, each lens may be fixed in a lens barrel (not shown in fig. 1), and the lens may have a large light flux amount by reasonably distributing the focal power of the lens, optionally, the total optical length TTL of the fixed focus lens provided in this embodiment satisfies 28mm ≦ TTL ≦ 32mm, the aperture F may reach 0.8 to 1.2, and support an image plane of 1/1.8 inch, and the FOV range of the field angle may reach 90 ° to 130 °. In an embodiment of the present invention, the focal length F of the fixed focus lens is 5.2mm, the aperture F is 1.08, the field angle can reach 112 °, and the imaging module can match 1/1.8 inch, which has the advantages of large light transmission and high resolution.

According to the technical scheme of the embodiment, the first lens and the second lens with negative focal power are arranged, so that the effect of collecting light rays for the large-field optical system is achieved, and the distortion can be corrected while the second lens collects the light rays; the spherical aberration of the system is corrected while the optical path is turned by the third lens with positive focal power; the fourth lens with negative focal power is more beneficial to correcting the off-axis field aberration; the fifth lens and the sixth lens are set to be in a negative and positive focal power double-cemented lens form, so that the correction of system chromatic aberration is facilitated; meanwhile, the third lens, the fourth lens, the fifth lens and the sixth lens form a Gaussian structure which is symmetrical about the diaphragm, so that the off-axis aberration of the system can be corrected more favorably; by arranging the seventh lens with positive focal power, the field curvature and astigmatism of the system can be corrected, the direction of light can be changed, and the inclination angle of the principal light of the system can be effectively reduced; the focal power of the eighth lens can be positive or negative and is used for correcting residual aberration of light after passing through the seven front lenses; through the matching of the spherical lens and the aspheric lens, the large-light-transmission fixed-focus lens suitable for monitoring requirements under complex conditions is realized, the large aperture of F0.8-1.2 can be achieved, a 1/1.8-inch image surface is supported, and the field angle range can reach 90-130 degrees.

On the basis of the above technical solution, optionally, the focal lengths of the first lens 10 to the seventh lens 70 and the focal length of the fixed-focus lens satisfy:

1.5<|f1/f|<3.5；

3.2<|f2/f|<5.6；

0.8<|f12/f|<2.2；

1.0<|f3/f|<2.3；

6.0<|f4/f|<8.5；

0.7<|f5/f|<2.0；

0.7<|f6/f|<2.0；

|f56/f|>10；

2.0<|f7/f|<4.0；

where f1, f2, f3, f4, f5, f6, and f7 denote focal lengths of the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, the sixth lens 60, and the seventh lens 70, respectively, f12 denotes a combined focal length of the first lens 10 and the second lens 20, f56 denotes a combined focal length of the fifth lens 50 and the sixth lens 60, and f denotes a focal length of the prime lens.

The focal length relationship of the first lens 10 to the seventh lens 70 is set, so that the fixed focus lens meets the performance requirement of definition while meeting the large light flux. The focal power of the eighth lens 80 is not limited, and the focal length range is not limited, and the eighth lens 80 is used for correcting residual aberration of the first seven lenses, and is designed according to actual imaging conditions in specific implementation.

Optionally, the first lens element 10 is a meniscus lens element, the second lens element 20 is a meniscus lens element, the third lens element 30 is a biconvex lens element, the fourth lens element 40 is a meniscus lens element, the fifth lens element 50 is a biconcave lens element, the sixth lens element 60 is a biconvex lens element, and the seventh lens element 70 is a biconvex lens element.

Optionally, the first lens element 10 is a convex-concave lens, the convex surface of which faces the object side, the second lens element 20 is a convex-concave lens, the convex surface of which faces the object side, and the fourth lens element 40 is a convex-concave lens, the convex surface of which faces the image side.

Optionally, the abbe numbers of the second lens 20 and the seventh lens 70 are both greater than 50.

Optionally, the refractive index of the third lens 30 is greater than 1.8, the refractive index of the fourth lens 40 is greater than 1.6, and the refractive index of the fifth lens 50 is greater than 1.8.

In one embodiment, the first lens 10 is a meniscus lens with convex-concave negative power, and the convex surface faces the object side, so as to collect light and increase the field angle; the second lens 20 is a meniscus lens with convex-concave negative focal power, the concave surface faces the image side, and the distortion can be corrected while light is collected; the third lens 30 adopts a positive focal power lens with high refractive index (>1.8), and corrects the spherical aberration of the system while turning the optical path; the fourth lens 40 adopts a meniscus lens with concave-convex negative focal power, which is more beneficial to the correction of off-axis field aberration; the fifth lens 50 and the sixth lens 60 adopt a negative and positive focal power double-cemented lens form, which is beneficial to the correction of system chromatic aberration; meanwhile, the third lens 30, the fourth lens 40, the fifth lens 50 and the sixth lens 60 form a Gaussian structure which is symmetrical about the diaphragm 90, so that the correction of off-axis aberration of the system is facilitated; the seventh lens 70 adopts a biconvex positive focal power lens, which is beneficial to correcting the curvature of field and astigmatism of the system, and can change the direction of light rays and effectively reduce the size of the inclination angle CRA of the chief rays of the system; the eighth lens 80 mainly corrects residual aberration of light passing through the seven front lenses, and the focal power can be positive or negative, and can be designed according to actual conditions in specific implementation. In this example, the parameters such as the refractive index and abbe number of the lens were values of the d-line (587.6 nm).

Optionally, the first lens 10, the third lens 30, the fifth lens 50, and the sixth lens 60 are all glass spherical lenses; the second lens 20, the fourth lens 40, the seventh lens 70, and the eighth lens 80 are all plastic aspherical lenses.

The prime lens that this embodiment provided adopts four glass lens, four plastic lens's glass to mould mixed structure design, through reasonable material collocation, wherein glass spherical lens processes easily, and plastic aspherical lens has good aberration correction ability, has controlled the cost effectively when guaranteeing optical system performance. The maximum supporting target surface reaches 1/1.8 inch, the maximum supporting aperture reaches F0.8, the maximum field angle can reach 130 degrees, and the imaging requirements under various application scenes are met.

Optionally, the surface type of the aspheric lens satisfies the formula:

wherein z represents a rise in a distance from a vertex of the aspherical surface when the aspherical surface is at a position having a height y in the optical axis direction,

r represents a curvature radius of the center of the surface profile, k represents a conic coefficient, and A, B, C, D, E, F and G represent high-order aspherical coefficients, respectively.

Exemplarily, table 1 shows a design value of a focal length parameter of a fixed-focus lens provided by an embodiment of the present invention:

TABLE 1 focal length parameters of prime lenses

f1＝-12.6	|f1/f|＝2.4
		f2＝-21.56	|f2/f|＝4.2
f12＝-6.8	|f12/f|＝1.3
		f3＝7.9	|f3/f|＝1.5
f4＝-40.4	|f4/f|＝7.79
		f5＝-5.7	|f5/f|＝1.1
f6＝6.2	|f6/f|＝1.2
		f56＝109.4	|f56/f|＝21.1
f7＝14.5	|f7/f|＝2.8

Where f1 denotes a focal length of the first lens 10, f2 denotes a focal length of the second lens 20, f12 denotes a combined focal length of the first lens 10 and the second lens 20, f3 denotes a focal length of the third lens 30, f4 denotes a focal length of the fourth lens 40, f5 denotes a focal length of the fifth lens 50, f6 denotes a focal length of the sixth lens 60, f56 denotes a combined focal length of the fifth lens 50 and the sixth lens 60, f7 denotes a focal length of the seventh lens 70, and f denotes a focal length of the fixed focus lens. The focal length of the fixed focus lens is 5.2mm, the aperture F is 1.08, the field angle FOV is 112 °, and the total optical system length TTL is 29.9 mm.

Table 2 shows a design value of the fixed-focus lens provided in the embodiment of the present invention:

TABLE 2 design value of prime lens

The surface numbers in table 2 are numbered in accordance with the surface order of the respective lenses, where "S1" denotes the front surface (surface on the object side) of the first lens 10, "S2" denotes the rear surface (surface on the image side) of the first lens 10, and so on, where "S11" is the cemented surface of the fifth lens 50 and the sixth lens 60; "S17" and "S18" denote the front surface and the rear surface of the lens protective glass, respectively. The curvature radius represents the bending degree of the lens surface, a positive value represents that the surface is bent to the image surface side, a negative value represents that the surface is bent to the object surface side, wherein 'PL' represents that the surface is a plane, and the curvature radius is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the deflection capability of the material between the current surface and the next surface to light, the blank space represents that the current position is air, and the refractive index is 1; the abbe number represents the dispersion characteristic of the material between the current surface and the next surface to light, and the blank space represents that the current position is air; the K value represents the magnitude of the best fitting conic coefficient for the aspheric surface.

Table 3 shows the aspheric surface parameters in this embodiment:

TABLE 3 design value of aspheric surface coefficient in fixed focus lens

wherein-2.43E-03 indicates that the coefficient A with the surface number S3 is-2.43 × 10^-3。

Fig. 2 is shown as the embodiment of the utility model provides a spherical aberration schematic diagram of tight shot, fig. 3 is shown to be the utility model provides a field curvature schematic diagram of tight shot, fig. 4 is shown to be the utility model provides a distortion schematic diagram of tight shot, wherein known by fig. 2 ~ 4, the tight shot that this embodiment provides has good imaging ability.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims (8)

1. A fixed focus lens is characterized by comprising a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, a diaphragm, a fifth lens with negative focal power, a sixth lens with positive focal power, a seventh lens with positive focal power and an eighth lens with positive focal power or negative focal power, which are sequentially arranged from an object side to an image side along an optical axis;

the first lens, the third lens, the fifth lens and the sixth lens are all spherical lenses, and the fifth lens and the sixth lens form a cemented lens; the second lens, the fourth lens, the seventh lens, and the eighth lens are all aspheric lenses.

2. The prime lens according to claim 1, wherein the focal lengths of the first to seventh lenses and the focal length of the prime lens satisfy:

1.5<|f1/f|<3.5；

3.2<|f2/f|<5.6；

0.8<|f12/f|<2.2；

1.0<|f3/f|<2.3；

6.0<|f4/f|<8.5；

0.7<|f5/f|<2.0；

0.7<|f6/f|<2.0；

|f56/f|>10；

2.0<|f7/f|<4.0；

wherein f1, f2, f3, f4, f5, f6, and f7 denote focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens, respectively, f12 denotes a combined focal length of the first lens and the second lens, f56 denotes a combined focal length of the fifth lens and the sixth lens, and f denotes a focal length of the prime lens.

3. The prime lens according to claim 1, wherein the abbe numbers of the second lens and the seventh lens are both greater than 50.

4. The prime lens according to claim 1, wherein the refractive index of the third lens is greater than 1.8, the refractive index of the fourth lens is greater than 1.6, and the refractive index of the fifth lens is greater than 1.8.

5. The prime lens according to claim 1, wherein the first lens is a meniscus lens, the second lens is a meniscus lens, the third lens is a double convex lens, the fourth lens is a meniscus lens, the fifth lens is a double concave lens, the sixth lens is a double convex lens, and the seventh lens is a double convex lens.

6. The prime lens according to claim 5, wherein the first lens is a convex-concave lens with a convex surface facing the object side, the second lens is a convex-concave lens with a convex surface facing the object side, and the fourth lens is a convex-concave lens with a convex surface facing the image side.

7. The prime lens according to claim 1, wherein the first lens, the third lens, the fifth lens and the sixth lens are all glass spherical lenses; the second lens, the fourth lens, the seventh lens and the eighth lens are all plastic aspheric lenses.

8. The prime lens according to claim 1, wherein the prime lens satisfies:

4.0<TTL/f<7.0；

wherein TTL represents the optical total length of the fixed-focus lens, and f represents the focal length of the fixed-focus lens.

Images