A wide-band, large relative aperture, low-distortion ultraviolet focusing optical system and lens

Abstract

The present invention discloses a wide-band, large relative aperture, low-distortion ultraviolet focusing optical system and lens, belonging to the field of optical imaging technology. The system comprises: a concave-convex lens (1), a first biconcave lens (2), a first biconvex lens (3), a second biconvex lens (4), a second biconcave lens (5), a third biconvex lens (6), a plano-concave lens (7), a filter (8), and a focal plane (9) arranged in sequence; the optical centers of the lenses are located on the same straight line; light passes through the concave-convex lens (1), the first biconcave lens (2), the first biconvex lens (3), the second biconvex lens (4), the second biconcave lens (5), the third biconvex lens (6), and the plano-concave lens (7) in sequence, and then reaches the focal plane (9) through the filter (8). The present invention has a wide-band ultraviolet imaging function, and can solve the problems of the existing ultraviolet imaging optical system, such as narrow working band, large imaging distortion, small relative aperture, or failure to achieve athermalization.

Description

Technical Field

[0001] The invention belongs to the technical field of optical imaging, and in particular relates to a wide-band, large-relative-aperture, low-distortion ultraviolet focusing optical system and a lens. Background Art

[0002] Ultraviolet optical systems play an important role in many application fields, including scientific research, industrial detection and medical diagnosis.

[0003] There are some UV imaging optical systems disclosed in literature. For example, a document entitled "Design of a "solar-blind" UV optical system for missile approach warning" published in the journal "Infrared and Laser Engineering" Volume 43, Issue 9 in 2014 reported a UV imaging optical system. The focal length of the optical system is 50mm, the working band is 240nm~280nm, the F number is 4, and the UV optical system for missile approach warning is realized by combining spherical, aspherical, and diffraction elements. A document entitled "Design of a medium-long focal length transmission solar-blind UV optical system" published in the journal "Optical Instruments" Volume 39, Issue 2 in 2017 reported a UV imaging optical system. The focal length of the optical system is 160mm, the working band is 240nm~280nm, the F number is 3.5, the distortion is better than 3%, the total length is 154mm, and 6 spherical lenses are used to realize a UV optical system with MTF>0.8@20lp / mm. In 2018, a document entitled "Design of Optical System for Large Relative Aperture Ultraviolet Imager" published in the journal "Chinese Optics" Vol. 11, No. 2 reported a large-aperture ultraviolet optical system for corona detection. The optical system has a focal length of 100mm, an operating band of 240nm~280nm, and a clear aperture of 50mm, which can realize a large-aperture ultraviolet optical system with a resolution of 20lp / mm within a 10° field of view. In 2020, a document entitled "Athermal Design of Deep Ultraviolet Optical System with a Wide Temperature Range" published in the journal "Acta Optica Sinica" Vol. 40, No. 17 reported a UV athermalized optical system. The optical system has a focal length of 110mm, an operating band of 230nm~270nm, and an F number of 3.5. The method of adding DOE to the structure realizes an ultraviolet optical system with MTF>0.65@18.5lp / mm suitable for -60~+100℃ environment. A paper titled "Design of a large-aperture transmissive UV optical system based on a solar-blind UV image intensifier" published in the journal Infrared Technology, Vol. 43, No. 2, 2021, reported a large-aperture UV optical system. The optical system has a focal length of 21.22 mm, an operating band of 240 nm to 280 nm, an F number of 2.5, and uses 5 spherical mirrors to achieve a transmissive UV optical system with a total length of 50.74 mm and MTF>0.6@401p / mm.

[0004] All of the above have realized ultraviolet imaging optical systems, but the applicable working band is relatively narrow.

[0005] In 2021, a document entitled "Design of Ultraviolet Broad Spectrum Large Relative Aperture Optical System" published in the journal "Applied Optics" Volume 42, Issue 5 reported a wide-band ultraviolet imaging optical system. The optical system has a focal length of 100mm, an operating band of 240nm~360nm, an F number of 2.5, a distortion better than 2%, a total length of 150mm, and uses 8 spherical lenses to achieve a wide-spectrum ultraviolet large relative aperture optical system with a transfer function of >0.4@50lp / mm. In 2022, a document entitled "Design of Ultraviolet Optical System Based on Flame Detection" published in the journal "Optical Technology" Volume 48, Issue 6 reported a large-aperture ultraviolet optical system. The optical system has a focal length of 100mm, an operating band of 240nm~390nm, an F number of 2.5, a distortion better than 0.5%, and uses 10 spherical mirrors (including a set of cemented mirrors) to achieve an ultraviolet optical system with MTF>0.5@50lp / mm.

[0006] All of the above have achieved ultraviolet imaging optical systems, but the distortion or resolution can still be improved or the number of lenses may be reduced.

[0007] Patent CN113504627 B discloses a compact ultraviolet optical system with large field of view and small F number made of the same material. The system has an operating band of 250nm~270nm, a central field of view F number of 0.97, an edge field of view F number of 0.93, a focal length of 7.77mm, and a field of view angle of 130°. The system uses 8 spherical quartz material lenses to achieve a large field of view and small F number ultraviolet optical system. Patent CN112162388 B discloses a solar-blind ultraviolet optical system with large relative aperture and large field of view. The system has an operating band of 250nm~280nm, an F number of 1.3, and a field of view angle of 115°. The system uses 7 pieces of glass and a filter group containing no less than 1 aspherical surface to achieve a large relative aperture and large field of view ultraviolet energy detection optical system. Patent CN210572981U discloses a large-field solar-blind ultraviolet optical system, which has an operating wavelength of 240nm~280nm, an F number of 2, a focal length of 9mm, a field of view of 120°, and a distortion better than 50%. The system uses 7 lenses to achieve a large-field solar-blind ultraviolet optical system. Patent CN211826686U discloses an ultra-wide-angle solar-blind ultraviolet optical system, which uses a structure of two filter groups consisting of 10 lenses and 6 filters to achieve an ultra-wide-angle solar-blind ultraviolet optical system with an operating wavelength of 240nm~280nm, a focal length of 7.3mm, an F number of 2.4, a distortion better than 40%, and a field of view of 210°.

[0008] All of the above have realized ultraviolet optical systems, but there are problems such as narrow working band or large system distortion. Summary of the invention

[0009] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0010] To this end, the purpose of the present invention is to provide a wide-band, large relative aperture, low-distortion ultraviolet focusing optical system and lens, which have ultraviolet imaging function under a wide band and can solve the problems of existing ultraviolet imaging optical systems such as narrow working band, large imaging distortion, small relative aperture, or failure to achieve athermalization.

[0011] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0012] The embodiment of the present invention provides a wide-band, large relative aperture, low-distortion ultraviolet focusing optical system, the system comprising: a concave-convex lens 1, a first biconcave lens 2, a first biconvex lens 3, a second biconvex lens 4, a second biconcave lens 5, a third biconvex lens 6, a plano-concave lens 7, a filter 8, and a focal plane 9, which are arranged in sequence from the object side to the image side along the optical axis;

[0013] The optical centers of the concave-convex lens 1, the first biconcave lens 2, the first biconvex lens 3, the second biconvex lens 4, the second biconcave lens 5, the third biconvex lens 6 and the plano-concave lens 7 are located on the same straight line;

[0014] The light passes through the concave-convex lens 1, the first biconcave lens 2, the first biconvex lens 3, the second biconvex lens 4, the second biconcave lens 5, the third biconvex lens 6 and the plano-concave lens 7 in sequence, and then passes through the filter 8 to reach the focal plane 9.

[0015] In addition, the wide-band, large relative aperture, low-distortion ultraviolet focusing optical system according to the present invention may also have the following additional technical features:

[0016] In some embodiments, the meniscus lens 1 has positive power; the concave surface is meniscus-shaped, and the concave surface faces the image side;

[0017] The optical power of the meniscus lens 1 is: 0.012<absolute value of optical power<0.015.

[0018] In some embodiments, the first biconcave lens 2 has a negative optical power, and its optical power is: 0.04<absolute value of optical power<0.05;

[0019] The second biconcave lens 5 has negative optical power, and its optical power is: 0.06<absolute value of optical power<0.08.

[0020] In some embodiments, the first biconvex lens 3, the second biconvex lens 4 and the third biconvex lens 6 all have positive optical power;

[0021] The optical power of the first biconvex lens 3 is: 0.043<absolute value of optical power<0.046;

[0022] The optical power of the second biconvex lens 4 is: 0.04<absolute value of optical power<0.05;

[0023] The optical power of the third biconvex lens 6 is: 0.04<absolute value of optical power<0.048.

[0024] In some embodiments, a stop is disposed on the front surface of the first biconvex lens 3 .

[0025] In some embodiments, the plano-concave lens 7 has a negative optical power, and its optical power is: 0.028<absolute value of optical power<0.033.

[0026] In some embodiments, the filter 8 is an ultraviolet filter, and its filtering band is between 280nm-400nm.

[0027] In some of the embodiments, the diagonal length of the focal plane 9 is 17.4 mm.

[0028] In some embodiments, the materials of the concave-convex lens 1, the first biconvex lens 3, the second biconvex lens 4 and the third biconvex lens 6 are all single crystal calcium fluoride materials;

[0029] The first biconcave lens 2 , the second biconcave lens 5 , the plano-concave lens 7 and the filter 8 are made of quartz material.

[0030] An embodiment of the present invention further provides a wide-band, large relative aperture, low-distortion ultraviolet focusing optical lens, comprising the wide-band, large relative aperture, low-distortion ultraviolet focusing optical system as described in any one of the above.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] In the embodiment of the present invention, the wide-band, large relative aperture, low-distortion ultraviolet focusing optical system provided has good imaging performance and realizes an ultraviolet focusing optical system with an F number of 2.5 using only two common materials. The image plane position of the system is adjustable in high and low temperature environments, meeting the use requirements of the system for clear imaging in high and low temperature environments.

[0033] In the embodiment of the present invention, the wide-band, large relative aperture, low-distortion ultraviolet focusing optical system provided meets the characteristics of wide-band range, large relative aperture, and extremely low distortion compared with other optical systems with similar usage scenarios;

[0034] In the embodiment of the present invention, the wide-band, large relative aperture, low-distortion ultraviolet focusing optical system provided has a simple and compact structure, and all lenses are spherical lenses, which is easy to process and has a relatively low cost;

[0035] In the embodiment of the present invention, a wide-band, large relative aperture, low-distortion ultraviolet focusing optical system is provided, and the working band can be widened from 280-400nm to 220-400nm, and the image quality corresponding to the widened working band is good.

[0036] The wide-band large relative aperture low-distortion ultraviolet focusing optical lens of the present invention includes the wide-band large relative aperture low-distortion ultraviolet focusing optical system, and thus has at least all the features and advantages of the wide-band large relative aperture low-distortion ultraviolet focusing optical system, which will not be described in detail here. Additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A structural diagram of an optical system disclosed in one embodiment of the present invention;

[0038] Figure 2 A modulation transfer function of an optical system disclosed in one embodiment of the present invention;

[0039] Figure 3 A modulation transfer function of an optical system disclosed in one embodiment of the present invention with a broadened working band of 220-400 nm;

[0040] Figure 4 A distortion curve of an optical system disclosed in one embodiment of the present invention.

[0041] Description of reference numerals:

[0042] 1- meniscus lens, 2- first biconcave lens, 3- first biconvex lens, 4- second biconvex lens, 5- second biconcave lens, 6- third biconvex lens, 7- plano-concave lens, 8- filter, 9- focal plane. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0045] See also Figure 1 As shown, in some embodiments of the present invention, a wide-band large relative aperture low-distortion ultraviolet focusing optical system is provided, comprising a concave-convex lens 1, a first biconcave lens 2, a first biconvex lens 3, a second biconvex lens 4, a second biconcave lens 5, a third biconvex lens 6, a plano-concave lens 7, a filter 8 and a focal plane 9 arranged in sequence from the object side to the image side along the optical axis. The light path is from left to right, passing through the concave-convex lens 1, the first biconcave lens 2, the first biconvex lens 3, the second biconvex lens 4, the second biconcave lens 5, the third biconvex lens 6, the plano-concave lens 7, and finally reaching the focal plane 9 through the filter 8.

[0046] In some embodiments of the present invention, the optical centers of the concave-convex lens 1, the first biconcave lens 2, the first biconvex lens 3, the second biconvex lens 4, the second biconcave lens 5, the third biconvex lens 6, and the plano-concave lens 7 are all located on the same straight line.

[0047] The meniscus lens 1 has positive optical power; it is made of single crystal calcium fluoride material, the concave surface is meniscus-shaped, the concave surface faces the image side, and the optical power is: 0.012<absolute value of optical power<0.015.

[0048] The first biconcave lens 2 has negative optical power; it is made of quartz material, and the optical power is: 0.04<absolute value of optical power<0.05.

[0049] The first biconvex lens 3 and the second biconvex lens 4 both have positive optical power; both lenses are made of single crystal calcium fluoride material; the optical power of the first biconvex lens 3 is: 0.043 < optical power absolute value < 0.046; the optical power of the second biconvex lens 4 is: 0.04 < optical power absolute value < 0.05. The front surface of the first biconvex lens 3 is provided with an aperture.

[0050] The second biconcave lens 5 has negative optical power; it is made of quartz material, and the optical power is: 0.06<absolute value of optical power<0.08.

[0051] The third biconvex lens 6 has positive optical power; it is made of single crystal calcium fluoride material, and the optical power is: 0.04<absolute value of optical power<0.048.

[0052] The plano-concave lens 7 has a negative optical power; it is made of quartz material, and the optical power is: 0.028<absolute value of optical power<0.033.

[0053] In some embodiments of the present invention, the filter 8 is an ultraviolet filter made of quartz material, also called a quartz filter, and its filtering band is between 280nm-400nm.

[0054] In some embodiments of the present invention, the diagonal length of the focal plane 9 is 17.4 mm.

[0055] The lens of the present invention adopts 7 lenses and 1 filter, all of which are spherical structures.

[0056] In the present invention, the entire lens uses only two materials (single crystal calcium fluoride material and quartz material), achieving an optical lens design with a focal length of 42.4mm, an F number of 2.5, and a distortion better than 0.01%. All fields of view achieve a transfer function index of more than 0.68 at a spatial frequency of 90lp / mm.

[0057]

[0058] In Table 1, the surface numbers 1 and 2 correspond to the front and back surfaces of the concave-convex lens 1, 3 and 4 correspond to the front and back surfaces of the first biconcave lens 2, and so on... 13 and 14 correspond to the front and back surfaces of the plano-concave lens 7, and 15 and 16 correspond to the front and back surfaces of the filter 8. Such a parameter combination is a parameter combination with better performance after continuous optimization of the initial system structure built for the system indicators to be achieved. Through this combination, an optical system with ultraviolet wide band (280-400nm), large relative aperture (1 / 2.5) and low distortion (0.01%) performance is achieved.

[0059] The light transmittance of most optical materials decreases as the wavelength decreases. Therefore, there are few optical lens materials that can be used in the ultraviolet spectrum. Available materials include calcium fluoride, magnesium fluoride, quartz, etc., and only calcium fluoride and fused quartz are commonly used. Due to the short-wave characteristics of the ultraviolet spectrum, fused quartz alone will bring large chromatic aberration to the system; and calcium fluoride alone will show strong intrinsic birefringence, which seriously affects the resolution of the system. Therefore, fused quartz and calcium fluoride are selected as the raw materials of the ultraviolet optical system.

[0060] According to the actual application scenarios of engineering projects, the system working band, relative aperture and other parameters are determined, and the parameter combination that can achieve better imaging performance (higher MTF value, lower distortion, etc.) is obtained through continuous optimization of material combination and optical power distribution;

[0061] Athermalization refers to the use of some means to compensate for the temperature effect of the optical system, keeping the image plane from displacement or producing very small displacement, thereby meeting the application requirements of the optical system for clear imaging in high and low temperature environments; the present invention compensates for the image plane defocus under high and low temperature conditions by adjusting the focus of the system, thereby enabling the system to maintain clear imaging under high and low temperature conditions.

[0062] The modulation transfer function (MTF) of an optical system refers to the function of how the modulation changes with the spatial frequency. It is a recognized lens performance metric, that is, a quantitative method for comprehensively evaluating the resolution and contrast of a lens. The imaging process can be seen as the process of transferring information from the object to the image through the imaging lens. The higher the MTF, the less information loss.

[0063] Figure 2 is the modulation transfer function of the optical system in this embodiment (280-400nm band).

[0064] Figure 3 This is the modulation transfer function after the band is further widened from 280-400nm to 220-400nm on the basis of this embodiment. This transfer function is slightly lower than the transfer function of the 280-400nm band, but is still greater than 0.6@90lp / mm in the full field of view, indicating that good imaging quality can still be maintained within this band. This shows that this embodiment has the possibility of further expansion on the application parameters of the original system.

[0065] Figure 4 : is an imaging distortion diagram of the system shown in the embodiment. It can be seen from the curve in the figure that the distortion in the entire field of view is better than 0.01%, corresponding to the low distortion characteristics of the present invention.

[0066] Parts not described in detail in the present invention may refer to the prior art or are well known to those skilled in the art, and the present invention is not limited thereto and will not be described in detail here.

[0067] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A wide-band, large relative aperture, low-distortion ultraviolet focusing optical system, characterized in that: The system comprises: a concave-convex lens (1), a first biconcave lens (2), a first biconvex lens (3), a second biconvex lens (4), a second biconcave lens (5), a third biconvex lens (6), a plano-concave lens (7), a filter (8) and a focal plane (9) which are arranged in sequence from the object side to the image side along the optical axis; The optical centers of the concave-convex lens (1), the first biconcave lens (2), the first biconvex lens (3), the second biconvex lens (4), the second biconcave lens (5), the third biconvex lens (6) and the plano-concave lens (7) are located on the same straight line; The light passes through the concave-convex lens (1), the first biconcave lens (2), the first biconvex lens (3), the second biconvex lens (4), the second biconcave lens (5), the third biconvex lens (6) and the plano-concave lens (7) in sequence, and then passes through the filter (8) to reach the focal plane (9); The meniscus lens (1) has positive focal power; the concave surface is meniscus-shaped and faces the image side; The optical power of the meniscus lens (1) is: 0.012<absolute value of optical power<0.015; The first biconcave lens (2) has a negative optical power, and its optical power is: 0.04<absolute value of optical power<0.05; The second biconcave lens (5) has a negative optical power, and its optical power is: 0.06<absolute value of optical power<0.08; The first biconvex lens (3), the second biconvex lens (4) and the third biconvex lens (6) all have positive optical power; The optical power of the first biconvex lens (3) is: 0.043<absolute value of optical power<0.046; The optical power of the second biconvex lens (4) is: 0.04<absolute value of optical power<0.05; The optical power of the third biconvex lens (6) is: 0.04<absolute value of optical power<0.048; The plano-concave lens (7) has a negative optical power, and its optical power is: 0.028<absolute value of optical power<0.033; The working wavelength band of the optical system is 220-400nm, and the distortion is better than 0.01%.

2. The wide-band, large relative aperture, low-distortion ultraviolet focusing optical system according to claim 1, characterized in that: The front surface of the first biconvex lens (3) is provided with an aperture.

3. The wide-band, large relative aperture, low-distortion ultraviolet focusing optical system according to claim 1, characterized in that: The filter (8) is an ultraviolet filter, and its filtering band is between 280nm and 400nm.

4. The wide-band, large relative aperture, low-distortion ultraviolet focusing optical system according to claim 1, characterized in that: The diagonal length of the focal plane (9) is 17.4 mm.

5. The wide-band, large relative aperture, low-distortion ultraviolet focusing optical system according to claim 1, characterized in that: The materials of the concave-convex lens (1), the first biconvex lens (3), the second biconvex lens (4) and the third biconvex lens (6) are all single crystal calcium fluoride materials; The first biconcave lens (2), the second biconcave lens (5), the plano-concave lens (7) and the filter (8) are made of quartz material.

6. A wide-band, large relative aperture, low-distortion ultraviolet focusing optical lens, characterized in that: It comprises the wide-band, large relative aperture, low-distortion ultraviolet focusing optical system as claimed in any one of claims 1 to 5.

Images