CN117270170A - Near ultraviolet athermalization optical system - Google Patents

Abstract

The invention relates to a near ultraviolet athermalization optical system, which is sequentially provided with a protection window, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, a CCD window and an image plane along the light propagation direction; the first lens is a negative meniscus lens protruding to the object space; the second lens is a positive meniscus lens protruding to the object space; the third lens is a biconcave lens; the fourth lens, the fifth lens and the sixth lens are all biconvex lenses; the seventh lens is a biconcave lens; each lens surface of (2) is spherical. The invention realizes the high resolution imaging with the full field of view of more than 0.38 at the cut-off frequency of 77 line pairs in the temperature range of-40 ℃ to 60 ℃ by selecting the optical materials with proper refractive index range and dispersion range.

Description

Near ultraviolet athermalization optical system

Technical Field

The invention belongs to the technical field of optical lens imaging, and particularly relates to a compact image space telecentric athermalization imaging optical system.

Background

The near ultraviolet 310nm-400nm wave band is widely applied to a remote sensing system, the capture of a target signal is realized, the system is often required to work in environments with changeable climates and large temperature differences, the image surface of the optical system is offset along with the change of the environmental temperature, the imaging quality is inconsistent, at the moment, the lens is required to have temperature adaptability, and even if the temperature changes, the system can always keep clear imaging. At present, some lenses for realizing near ultraviolet temperature adaptability in the market are realized by adjusting single lenses or whole groups of lenses or adjusting the positions of image planes, and the method makes the structure of the system complex and increases the cost. Therefore, it is necessary to develop and design a near ultraviolet athermalized optical system.

Disclosure of Invention

The invention aims to solve the technical problem of providing a near ultraviolet athermalization optical system, which can keep stable and clear imaging quality in the process of changing the ambient temperature, and the aim of temperature adaptability and simple structure is fulfilled without adding a focusing mechanism.

In order to solve the technical problem, the near ultraviolet athermalization optical system of the present invention sequentially sets a protection window W1, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, a CCD window W2 and an image plane I1 along the light propagation direction; the first lens L1 is a negative meniscus lens protruding to the object space; the second lens L2 is a positive meniscus lens protruding to the object space; the third lens L3 is a biconcave lens; the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all biconvex lenses; the seventh lens L7 is a biconcave lens; the surfaces of the lenses are spherical surfaces.

The focal length of the near ultraviolet athermalization optical system is 30-40 mm.

The front and back surface of the first lens L1 have a curvature radius of 16.458 mm-22.675 mm and a curvature radius of the front and back surface of the second lens L1, respectively

8.394 mm-13.455 mm, and the thickness is 2.5 mm-3 mm; the radius of curvature of the front surface and the back surface of the second lens L2 are 8.726 mm-14.685 mm and 147.632 mm-347.414 mm respectively, and the thickness is 4.4 mm-6.5 mm; the radius of curvature of the front surface and the back surface of the third lens L3 are respectively-24.117 mm to-19.940 mm and 13.917mm to 24.087mm, and the thickness is 2.5mm to 4mm; the curvature radius of the front surface and the back surface of the fourth lens L4 is 18.806 mm-35.900 mm and-17.846 mm-15.266 mm respectively, and the thickness is 6 mm-7 mm; the radius of curvature of the front surface and the rear surface of the fifth lens L5 are 33.974 mm-44.804 mm and-53.207 mm to-37.029 mm respectively, and the thickness is 4.5 mm-6 mm; the radius of curvature of the front surface and the rear surface of the sixth lens L6 are 19.055 mm-26.673 mm and-30.306 mm to-16.843 mm respectively, and the thickness is 5.7 mm-6.3 mm; the radius of curvature of the front and rear surfaces of the seventh lens L7 is-25.950 mm to-16.695 mm and 12.208mm to 12.763mm respectively, and the thickness is 5mm to 5.5mm.

The air interval between the first lens L1 and the second lens L2 is 0.57 mm-1.93 mm, the air interval between the second lens L2 and the third lens L3 is 1.36 mm-5.48 mm, the air interval between the third lens L3 and the fourth lens L4 is 0.24 mm-1.32 mm, the air interval between the fourth lens L4 and the fifth lens L5 is 0.1 mm-10.96 mm, and the air interval between the fifth lens L5 and the sixth lens L6 is 0.1 mm-0.5 mm, and the air interval between the sixth lens L6 and the seventh lens L7 is 0.95 mm-1.93 mm.

The refractive index of the first lens L1 is 1.52, and the abbe number is 58.6; the refractive index of the second lens L2 is 1.46, and the abbe number is 67.8; the refractive index of the third lens L3 is 1.52, and the abbe number is 58.6; the refractive index of the fourth lens L4 is 1.43, and the abbe number is 95.0; the refractive index of the fifth lens L5 is 1.46, and the abbe number is 67.8; the refractive index of the sixth lens L6 is 1.43, and the abbe number is 95.0; the refractive index of the seventh lens L7 is 1.52 and the abbe number is 58.6.

The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are respectively B270, quartz, B270, calcium fluoride, quartz, calcium fluoride, and B270.

And the two sides of the protection window W1 are plated with three-proofing films.

The thickness of the protection window W1 is 3mm, and the material is quartz glass.

The air interval between the protective window W1 and the first lens L1 is 3 mm-4 mm; the air interval between the seventh lens L7 and the CCD window W2 is 9.47 mm-11.17 mm.

The CCD window W2 is quartz plate glass.

The focal length range of the near ultraviolet athermalization optical system is 30-40 mm, and the near ultraviolet athermalization optical system is maximally adaptable to 2048X2048, and has a pixel size of 6.5um type detector.

The optical system is a athermalized lens, and by selecting the optical materials with proper refractive index range and dispersion range, the optical materials selected by the invention also use the Schottky B270 optical material besides the conventional quartz and calcium fluoride, the material has higher transmittance at 310nm-1040nm, high refractive index and small Abbe number, and can well realize athermalization difference, so that the system can realize full-view field >0.38 high-resolution imaging at 77 line pair cutoff frequency in the temperature range of-40 ℃ to 60 ℃.

Based on the technical scheme, the invention has the following advantages:

the optical system provided by the invention is provided with the protection window W1, and the three-proofing film is plated on the two sides of the protection window W1, so that the whole system has the shock and vibration resistance, is dustproof, waterproof and mildew-proof, and is suitable for complex and changeable environments.

The athermalization lens realizes optical passive athermalization by selecting optical materials with different refractive index ranges and dispersion ranges and mechanical materials with proper thermal expansion coefficients, clearly images at the temperature of-40 ℃ to 60 ℃, has simple and reliable structure and high assembly efficiency, and can be produced in a large scale.

All lenses of the invention adopt single lenses, and compared with double-cemented lenses, the structure of the single lenses has higher stability and is not easy to deform. All lenses are spherical, the processing and assembling technologies are mature, and the cost is low.

Drawings

The invention is described in further detail below with reference to the drawings and the detailed description.

FIG. 1 is a schematic diagram of a near-UV athermalized optical system according to the present invention.

FIGS. 2 (a), 2 (b) and 2 (c) are transfer diagrams of example 1 at a room temperature of 20 ℃, a low temperature of-40 ℃ and a high temperature of +60 ℃, respectively.

Detailed Description

The present invention will now be described in further detail with reference to the drawings and examples, it being understood that the specific examples described herein are intended to illustrate the invention only and are not intended to be limiting. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

In the description of the present invention, unless explicitly stated and limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements or interaction relationship between the two elements. The specific meaning of the above terms in the present invention can be understood in detail by those skilled in the art.

In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below", "beneath" the second feature includes the first feature being "directly under" and obliquely below "the second feature, or simply indicating that the first feature is less level than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are orientation or positional relationships based on those shown in the drawings, for convenience of description and simplicity of operation, and are not meant to indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like, are used merely for distinguishing between descriptions and not for distinguishing between them.

As shown in fig. 1, the near ultraviolet athermalization optical system of the present invention is provided with a protection window W1, a first lens L1 having negative diopter, a second lens L2 having positive diopter, a third lens L3 having negative diopter, a fourth lens L4 having positive diopter, a fifth lens L5 and a sixth lens L6, a seventh lens L7 having negative diopter, a CCD window W2 and an image plane I1. The first lens L1 is a negative meniscus lens protruding to the object space; the second lens L2 is a positive meniscus lens protruding to the object space; the third lens L3 is a biconcave lens; the fourth lens L4 is a biconvex lens; the fifth lens L5 is a biconvex lens; a sixth lens L6 biconvex lens; the seventh lens L7 is a biconcave lens. The surfaces of the lenses are spherical surfaces.

In the embodiment of the invention, the thickness of the protection window W1 is 3mm, the material is quartz glass, and the two sides of the protection window W1 are plated with three-proofing films. Plays a role of protecting a mirror for the whole system, is dustproof, waterproof and mildew-proof, and is suitable for complex and changeable environments.

In the embodiment of the present invention, the refractive index of the first lens L1 is 1.52, and the abbe number is 58.6. The refractive index of the second lens L2 is 1.46, and the Abbe number is 67.8. The refractive index of the third lens L3 is 1.52, and the abbe number is 58.6. The refractive index of the fourth lens L4 is 1.43, and the abbe number is 95.0. The refractive index of the fifth lens L5 is 1.46, and the abbe number is 67.8. The refractive index of the sixth lens L6 is 1.43 and the abbe number is 95.0. The refractive index of the seventh lens L7 is 1.52, and the abbe number is 58.6.

In the embodiment of the present invention, the CCD window W2 is a quartz plate glass.

The optical system is a athermalized lens, and by selecting the optical materials with proper refractive index range and dispersion range, the optical materials selected by the invention also apply the Schottky B270 optical material besides the conventional quartz and calcium fluoride, the material has higher transmittance at 310nm-1040nm, high refractive index and small Abbe number, and can well realize athermalization difference, so that the system can realize high-resolution imaging with full field of view larger than 0.38 at 77 line pair cutoff frequency in the temperature range of minus 40 ℃ to 60 ℃.

All lenses of the invention adopt single lenses, and compared with double-cemented lenses, the structure of the single lenses has higher stability and is not easy to deform. All lenses are spherical, the processing and assembling technologies are mature, and the cost is low.

Example 1

The parameters of each optical element in the embodiment are shown in table 1; where ti is the thickness of the ith optical element and di is the spacing between the ith optical element and the i+1th optical element.

TABLE 1

The above example 1 can achieve the following criteria:

a) Focal length: 30.0mm;

b)F/#：2.8；

c) Wave band: 310-400 nm;

d) MTF: on-axis field of view >0.5@77lp/mm, full field of view >0.38@77lp/mm;

e) And (3) adapting to the environmental temperature: -40-60 DEG C

Example 2

The parameters of each optical element in this example are shown in Table 2; where ti is the thickness of the ith optical element and di is the spacing between the ith optical element and the i+1th optical element.

TABLE 2

The above example 2 can achieve the following criteria:

a) Focal length: 32.0mm;

b)F/#：2.8；

c) Wave band: 310-400 nm;

d) MTF: on-axis field of view >0.5@77lp/mm, full field of view >0.38@77lp/mm; e) And (3) adapting to the environmental temperature: -40-60 DEG C

Example 3

The parameters of each optical element in this example are shown in Table 3; where ti is the thickness of the ith optical element and di is the spacing between the ith optical element and the i+1th optical element.

TABLE 3 Table 3

The above example 3 can achieve the following criteria:

a) Focal length: 34.0mm;

b)F/#：2.8；

c) Wave band: 310-400 nm;

d) MTF: on-axis field of view >0.5@77lp/mm, full field of view >0.38@77lp/mm;

e) And (3) adapting to the environmental temperature: -40-60 DEG C

Example 4

The parameters of each optical element in this example are shown in Table 4; where ti is the thickness of the ith optical element and di is the spacing between the ith optical element and the i+1th optical element.

TABLE 4 Table 4

The above example 4 is able to achieve the following criteria:

a) Focal length: 38.0mm;

b)F/#：2.8；

c) Wave band: 310-400 nm;

d) MTF: on-axis field of view >0.5@77lp/mm, full field of view >0.38@77lp/mm;

e) And (3) adapting to the environmental temperature: -40-60 DEG C

Example 5

The parameters of each optical element in this example are shown in Table 5; where ti is the thickness of the ith optical element and di is the spacing between the ith optical element and the i+1th optical element.

TABLE 5

The above example 5 is able to achieve the following criteria:

a) Focal length: 40.0mm;

b)F/#：2.8；

c) Wave band: 310-400 nm;

d) MTF: on-axis field of view >0.5@77lp/mm, full field of view >0.38@77lp/mm;

e) And (3) adapting to the environmental temperature: -40-60 DEG C

As shown in fig. 2a, 2b and 2c, at normal temperature of 20 ℃, the transfer function value of the central view field of the compact image-space telecentric athermalization system provided by the invention is greater than 0.5 at 77lp/mm frequency, the transfer function values of the central view field are both greater than 0.5 at-40 ℃ and 60 ℃, the transfer function values of other view fields are both greater than 0.38, and the compact image-space telecentric athermalization system has clear imaging in the full view field and full band range and good athermalization effect.

The embodiments described herein represent only a few embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the present invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention.

Claims (10)

1. The near ultraviolet athermalization optical system is characterized in that a protection window W1, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, a CCD window W2 and an image plane I1 which are on the same optical axis are sequentially arranged along the light propagation direction; the first lens L1 is a negative meniscus lens protruding to the object space; the second lens L2 is a positive meniscus lens protruding to the object space; the third lens L3 is a biconcave lens; the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all biconvex lenses; the seventh lens L7 is a biconcave lens; the surfaces of the lenses are spherical surfaces.

2. The near ultraviolet athermalized optical system according to claim 1, wherein the focal length of the system is 30-40 mm.

3. The near ultraviolet athermalized optical system according to claim 1, wherein the front and rear surfaces of said first lens L1 have radii of curvature of 16.458mm to 22.675mm and 8.394mm to 13.455mm, respectively, and a thickness of 2.5mm to 3mm; the radius of curvature of the front surface and the back surface of the second lens L2 are 8.726 mm-14.685 mm and 147.632 mm-347.414 mm respectively, and the thickness is 4.4 mm-6.5 mm; the radius of curvature of the front surface and the back surface of the third lens L3 are respectively-24.117 mm to-19.940 mm and 13.917mm to 24.087mm, and the thickness is 2.5mm to 4mm; the curvature radius of the front surface and the back surface of the fourth lens L4 is 18.806 mm-35.900 mm and-17.846 mm-15.266 mm respectively, and the thickness is 6 mm-7 mm; the radius of curvature of the front surface and the rear surface of the fifth lens L5 are 33.974 mm-44.804 mm and-53.207 mm to-37.029 mm respectively, and the thickness is 4.5 mm-6 mm; the radius of curvature of the front surface and the rear surface of the sixth lens L6 are 19.055 mm-26.673 mm and-30.306 mm to-16.843 mm respectively, and the thickness is 5.7 mm-6.3 mm; the radius of curvature of the front and rear surfaces of the seventh lens L7 is-25.950 mm to-16.695 mm and 12.208mm to 12.763mm respectively, and the thickness is 5mm to 5.5mm.

4. The near ultraviolet athermalized optical system according to claim 3, wherein the air gap between the first lens L1 and the second lens L2 is 0.57mm to 1.93mm, the air gap between the second lens L2 and the third lens L3 is 1.36mm to 5.48mm, the air gap between the third lens L3 and the fourth lens L4 is 0.24mm to 1.32mm, the air gap between the fourth lens L4 and the fifth lens L5 is 0.1mm to 10.96mm, and the air gap between the fifth lens L5 and the sixth lens L6 is 0.1mm to 0.5mm, and the air gap between the sixth lens L6 and the seventh lens L7 is 0.95mm to 1.93mm.

5. The near ultraviolet athermalized optical system according to claim 1, wherein said first lens L1 has a refractive index of 1.52 and an abbe number of 58.6; the refractive index of the second lens L2 is 1.46, and the abbe number is 67.8; the refractive index of the third lens L3 is 1.52, and the abbe number is 58.6; the refractive index of the fourth lens L4 is 1.43, and the abbe number is 95.0; the refractive index of the fifth lens L5 is 1.46, and the abbe number is 67.8; the refractive index of the sixth lens L6 is 1.43, and the abbe number is 95.0; the refractive index of the seventh lens L7 is 1.52 and the abbe number is 58.6.

6. The near ultraviolet athermalized optical system according to claim 1, wherein the materials of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are B270, quartz, B270, calcium fluoride, quartz, calcium fluoride and B270, respectively.

7. The near ultraviolet athermalized optical system according to claim 1, wherein said protective window W1 is coated with a three-proofing film on both sides.

8. The near ultraviolet athermalized optical system according to claim 1, wherein the thickness of the protective window W1 is 3mm, and the material is quartz glass.

9. The near ultraviolet athermalized optical system according to claim 1, wherein the air gap between the protective window W1 and the first lens L1 is 3 mm-4 mm; the air interval between the seventh lens L7 and the CCD window W2 is 9.47 mm-11.17 mm.

10. The near ultraviolet athermalized optical system according to claim 1, wherein said CCD window W2 is a quartz plate glass.