All-quartz large-aperture solar-blind ultraviolet wide-angle optical system

Abstract

This invention discloses an all-quartz large-aperture solar-blind ultraviolet wide-angle optical system, comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side. The first lens is a meniscus spherical lens with negative optical power and its convex surface curved towards the object side. The second lens is a biconcave spherical lens with negative optical power. The third lens is a biconvex spherical lens with positive optical power. The fourth lens is a biconvex aspherical lens with positive optical power and its aspherical surface located on the object side. The fifth lens is a biconvex aspherical lens with positive optical power and its aspherical surface located on the object side. All five lenses are made of quartz. The optical system has an aperture of F#1.4, which is much larger than that of typical ultraviolet optical systems, providing sufficient energy and high optical responsivity. It requires fewer lenses, resulting in high optical transmittance, and its lens manufacturing is simple and cost-effective. The total field of view reaches 112°.

Description

Technical Field

[0001] This invention relates to an all-quartz large-aperture solar-blind ultraviolet wide-angle optical system, belonging to the technical field of ultraviolet optical systems. Background Technology

[0002] Because sunlight in the "solar-blind" ultraviolet band (220-300nm) is absorbed by ozone in the atmosphere, the solar radiation in this band reaching the ground and even low-altitude areas is almost zero. Using this band to image and detect targets can avoid interference from the largest natural light—sunlight, which is beneficial for target detection.

[0003] Due to wavelength limitations, the lens materials available for ultraviolet optical systems are mainly limited to a few types, such as quartz, calcium fluoride, barium fluoride, and magnesium fluoride, all of which have a refractive index of less than 1.45. The low refractive index makes aberration correction difficult, and it is difficult to achieve a light-transmitting aperture greater than F#2.0. Apart from quartz, the other ultraviolet optical materials are expensive and difficult to process.

[0004] In response, this invention provides an all-quartz solar-blind ultraviolet wide-angle optical system with a full field of view of 112 degrees and an optical aperture of F#1.4. It features sufficient energy, a large field of view, a small number of lenses, and low cost, and can be used in multiple fields such as high-voltage arc detection and high-heat exhaust flame detection of aircraft. Summary of the Invention

[0005] This invention provides an all-quartz large-aperture solar-blind ultraviolet wide-angle optical system. Utilizing 5 quartz lenses, it achieves a full field of view of 112 degrees, an optical aperture of F#1.4, excellent image quality, a full field of view relative illumination greater than 97%, a field curvature of less than 0.05 mm, and a full field of view distortion of less than 50%.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A large-aperture, all-quartz, solar-blind, ultraviolet wide-angle optical system includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side.

[0008] The first lens is a meniscus spherical lens with negative optical power and a convex surface bent towards the object side;

[0009] The second lens is a biconcave spherical lens with negative optical power;

[0010] The third lens is a biconvex spherical lens with positive optical power;

[0011] The fourth lens is a biconvex aspherical lens with positive optical power and the aspherical surface located on the object side;

[0012] The fifth lens is a biconvex aspherical lens with positive optical power and the aspherical surface located on the object side;

[0013] The first, second, third, fourth, and fifth lenses are all made of quartz.

[0014] The above-mentioned all-quartz large-aperture solar-blind ultraviolet wide-angle optical system operates in the wavelength range of 240nm to 365nm, has a field of view of 112°, and an optical aperture of F#1.4.

[0015] An aperture stop is provided between the third and fourth lenses mentioned above.

[0016] The principle of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention is as follows: From the object side to the image side, the first, second, and third lenses form the front group of the optical system to compress the wide-angle field of view; the aperture stop of the entire optical system is located between the third and fourth lenses; the fourth and fifth lenses form the rear group of the entire optical system, focusing the light from the front group to form an image. At the same time, aspherical surfaces are introduced on the surface of the fourth and fifth lenses to correct various aberrations of the large-aperture, large-field ultraviolet optical system, including spherical aberration and coma. The aspherical surfaces also have good shape and are easy to process.

[0017] To ensure image quality, the focal lengths of the first lens are f1, the second lens is f2, the third lens is f3, the fourth lens is f4, and the fifth lens is f5. The focal length of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system is F, satisfying the following relationship:

[0018] -6.5F<f1<-3.5F; -3.5F<f2<-2.5F; 6.5F<f3<7.5F; 5F<f4<6F; 4F<f5<5F.

[0019] To further improve imaging quality, from the object side to the image side, the two sides of the first lens are the first object side and the first image side, the two sides of the second lens are the second object side and the second image side, the two sides of the third lens are the third object side and the third image side, the two sides of the fourth lens are the fourth object side and the fourth image side, and the two sides of the fifth lens are the fifth object side and the fifth image side.

[0020] The radius of curvature of the side surface of the first object is 257.0050±0.0030mm, and the radius of curvature of the side surface of the first image is 31.1500±0.0030mm.

[0021] The radius of curvature of the second object's side surface is -54.6200±0.0030mm, and the radius of curvature of the second image's side surface is 37.9600±0.0030mm;

[0022] The radius of curvature of the third object's side surface is 101.0000±0.0030mm, and the radius of curvature of the third image's side surface is -99.0000±0.0030mm;

[0023] The radius of curvature of the fourth object's side surface is 68.2370±0.0030mm, and the radius of curvature of the fourth image's side surface is -80.4100±0.0030mm.

[0024] The radius of curvature of the fifth object's side surface is 61.2395±0.0030mm, and the radius of curvature of the fifth image's side surface is -65.6600±0.0030mm.

[0025] Both the fourth and fifth object sides mentioned above are aspherical.

[0026] To further ensure image quality, the center thickness of the first lens is 4.97±0.03 mm, the second lens is 3.48±0.03 mm, the third lens is 8.17±0.03 mm, the fourth lens is 13.58±0.03 mm, and the fifth lens is 14.33±0.03 mm. The center-to-center spacing between the first and second lenses is 23.75±0.03 mm, between the second and third lenses is 25.82±0.03 mm, between the third and fourth lenses is 17.66±0.03 mm, and between the fourth and fifth lenses is 19.67±0.03 mm.

[0027] Any techniques not mentioned in this invention are based on existing technologies.

[0028] The present invention has the following beneficial effects:

[0029] 1. The light transmission aperture of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention is F#1.4, which is much larger than that of general ultraviolet optical systems, with sufficient energy and high optical responsivity.

[0030] 2. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention consists of 5 all-quartz lenses. The number of lenses is small, the optical transmittance is high, and the lens processing is simple and low-cost.

[0031] 3. The present invention is a full quartz large aperture solar blind ultraviolet wide-angle optical system with a full field of view of 112°, which is large. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the principle of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention;

[0034] Figure 3This is a transfer function curve of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention;

[0035] Figure 4 This is a full-field relative illumination diagram of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of the present invention;

[0036] Figure 5 The field curvature and distortion diagrams are shown for the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system of this invention. Detailed Implementation

[0037] To better understand the present invention, the following embodiments further illustrate its content, but the content of the present invention is not limited to the following embodiments. The accompanying drawings are for reference and illustration only and are not intended to limit the present invention.

[0038] Example 1

[0039] like Figure 1-2 As shown, an all-quartz large-aperture solar-blind ultraviolet wide-angle optical system includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5 arranged sequentially from the object side to the image side. The first lens L1, second lens L2, and third lens L3 form the front group of the optical system, compressing the wide-angle field of view. The aperture stop of the entire optical system is located between the third lens L3 and the fourth lens L4. The fourth lens L4 and the fifth lens L5 form the rear group of the entire optical system, focusing the light rays from the front group to form an image.

[0040] Let the focal lengths of the first to fifth lenses be f1, f2, f3, f4, and f5, respectively, and the focal length of the optical system be F. Each lens has the following characteristics:

[0041] The first lens L1 is a meniscus spherical lens with negative optical power and its convex surface curved towards the object side, with a power of -6.5F < f1 < -3.5F; the second lens L2 is a biconcave spherical lens with negative optical power, with a power of -3.5F < f2 < -2.5F; the third lens L3 is a biconvex spherical lens with positive optical power, with a power of 6.5F < f3 < 7.5F; the fourth lens L4 is a biconvex aspherical lens with positive optical power and its aspherical surface located on the object side, with a power of 5F < f4 < 6F; the fifth lens L5 is a biconvex aspherical lens with positive optical power and its aspherical surface located on the object side, with a power of 4F < f5 < 5F.

[0042] In this example, f1 is -75.45mm, f2 is -45.47mm, f3 is 105.74mm, f4 is 79.2mm, and f5 is 68.67mm.

[0043] Table 1 shows the technical specifications of the optical system in this embodiment, Table 2 shows the specific optical parameters of the optical system in this embodiment, and Table 3 shows the aspherical coefficients specifically used in the optical system described in this embodiment.

[0044] Table 1 Technical Specifications of the Optical System

[0045]

[0046] Table 2 Specific optical parameters of the optical system:

[0047]

[0048] In Table 2, radius of curvature refers to the radius of curvature of each lens surface, thickness or spacing refers to the lens thickness or the center-to-center spacing between adjacent lens surfaces, material refers to the material used in the lens, and air refers to the medium between the two lenses being air. The two sides of the first lens L1 are the first object-side surface S1 and the first image-side surface S2, the two sides of the second lens L2 are the second object-side surface S3 and the second image-side surface S4, the two sides of the third lens L3 are the third object-side surface S5 and the third image-side surface S6, the two sides of the fourth lens L4 are the fourth object-side surface S7 and the fourth image-side surface S8, and the two sides of the fifth lens L5 are the fifth object-side surface S9 and the fifth image-side surface S10.

[0049] Table 3 shows the aspheric coefficients used in specific embodiments.

[0050]

[0051] The aspherical equations used for each surface in Table 3 are as follows:

[0052]

[0053] The meanings of each quantity are as follows:

[0054] ZA: The lens sagitta along the optical axis of the aspherical surface;

[0055] R: Radius of curvature at the intersection of the surface and the optical axis OO';

[0056] Y: Half-aperture of the lens perpendicular to the optical axis;

[0057] k: Conic coefficient;

[0058] A, B, C, and D aspheric coefficients;

[0059] Figure 3 The transfer function curves of the above optical system are shown in the figure. It can be seen from the figure that the transfer function of this system is better than 0.6 in the central field of view of 90 lp / mm and better than 0.3 at the edge, indicating excellent image quality. Figure 4The figure shows the relative illumination curve of the entire field of view of the above optical system. It can be seen from the figure that the relative illumination of the entire field of view of this system is greater than 97%, and the energy distribution of the image plane is uniform. Figure 5 The above optical system has field curvature and distortion diagrams. As can be seen from the diagrams, the field curvature of this system is less than 0.05 mm, and the distortion across the entire field of view is less than 40%.

Claims

1. A large-aperture, all-quartz, solar-blind, ultraviolet wide-angle optical system, characterized in that: It consists of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side; The first lens is a meniscus spherical lens with negative optical power and a convex surface bent towards the object side; The second lens is a biconcave spherical lens with negative optical power; The third lens is a biconvex spherical lens with positive optical power; The fourth lens is a biconvex aspherical lens with positive optical power and the aspherical surface located on the object side; The fifth lens is a biconvex aspherical lens with positive optical power and the aspherical surface located on the object side; The first lens, second lens, third lens, fourth lens and fifth lens are all made of quartz. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system has a field of view of 112° and an optical aperture of F#1.

4.

2. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1, characterized in that: The operating wavelength is 240nm~365nm.

3. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1 or 2, characterized in that: An aperture stop is provided between the third and fourth lenses.

4. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1 or 2, characterized in that: The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system is F, satisfying the following relationships: -6.5F < f1 < -3.5F; -3.5F < f2 < -2.5F; 6.5F < f3 < 7.5F.

5. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1 or 2, characterized in that: The focal length of the fourth lens is f4, the focal length of the fifth lens is f5, and the focal length of the all-quartz large-aperture solar-blind ultraviolet wide-angle optical system is F, satisfying the following relationship: 5F < f4 < 6F; 4F < f5 < 5F.

6. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1 or 2, characterized in that: From the object side to the image side, the two sides of the first lens are the first object side and the first image side, the two sides of the second lens are the second object side and the second image side, the two sides of the third lens are the third object side and the third image side, the two sides of the fourth lens are the fourth object side and the fourth image side, and the two sides of the fifth lens are the fifth object side and the fifth image side. The radius of curvature of the side surface of the first object is 257.0050±0.0030mm, and the radius of curvature of the side surface of the first image is 31.1500±0.0030mm. The radius of curvature of the second object's side surface is -54.6200±0.0030mm, and the radius of curvature of the second image's side surface is 37.9600±0.0030mm; The radius of curvature of the third object's side surface is 101.0000±0.0030mm, and the radius of curvature of the third image's side surface is -99.0000±0.0030mm; The radius of curvature of the fourth object's side surface is 68.2370±0.0030mm, and the radius of curvature of the fourth image's side surface is -80.4100±0.0030mm. The radius of curvature of the fifth object's side surface is 61.2395±0.0030mm, and the radius of curvature of the fifth image's side surface is -65.6600±0.0030mm.

7. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 6, characterized in that: Both the fourth and fifth object sides are aspherical.

8. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1 or 2, characterized in that: The center thickness of the first lens is 4.97±0.03mm, the center thickness of the second lens is 3.48±0.03mm, the center thickness of the third lens is 8.17±0.03mm, the center thickness of the fourth lens is 13.58±0.03mm, and the center thickness of the fifth lens is 14.33±0.03mm.

9. The all-quartz large-aperture solar-blind ultraviolet wide-angle optical system as described in claim 1 or 2, characterized in that: The center-to-center distance between the first and second lenses is 23.75±0.03mm, the center-to-center distance between the second and third lenses is 25.82±0.03mm, the center-to-center distance between the third and fourth lenses is 17.66±0.03mm, and the center-to-center distance between the fourth and fifth lenses is 19.67±0.03mm.

Images