CN220913425U

CN220913425U - Optical system and optical lens working in far infrared band

Info

Publication number: CN220913425U
Application number: CN202322657537.2U
Authority: CN
Inventors: 赵小波; 赵梓良; 郝成龙; 谭凤泽; 朱健
Original assignee: Shenzhen Metalenx Technology Co Ltd
Current assignee: Shenzhen Metalenx Technology Co Ltd
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2024-05-07
Anticipated expiration: 2033-09-28

Abstract

The application provides an optical system and an optical lens working in a far infrared band, which sequentially comprise, along an optical axis from an object side to an image side: a first chalcogenide refractive lens, a superlens, a second chalcogenide refractive lens; the first chalcogenide refractive lens and the second chalcogenide refractive lens are positive lenses; the super lens comprises a substrate and a super structure unit, wherein a micro-nano structure is arranged in the super structure unit; the optical system satisfies the following conditions in units of 1/mm: n (|C ₁|+|C₂ |) is more than or equal to 0.25 and less than or equal to 2.01; wherein, when n is the refractive index of the first chalcogenide refractive lens, C ₁ is the curvature of the front surface of the first chalcogenide refractive lens, and C ₂ is the curvature of the rear surface of the first chalcogenide refractive lens; when n is the refractive index of the second chalcogenide refractive lens, C ₁ is the curvature of the front surface of the second chalcogenide refractive lens, and C ₂ is the curvature of the rear surface of the second chalcogenide refractive lens. The optical system provided by the application can simultaneously meet the requirements of the optical system on good imaging quality, small volume, sufficient athermal performance and high lens processability.

Description

Optical system and optical lens working in far infrared band

Technical Field

The application relates to the field of lenses, in particular to an optical system and an optical lens working in a far infrared band.

Background

The optical system working in the far infrared band can be well adapted to working environments such as rain, night, fog and the like, so that the optical system is widely applied to the fields of vehicle-mounted, security and the like. The optical system operating in the far infrared band provided in the related art has difficulty in simultaneously satisfying the requirements of the optical system for good imaging quality, small volume, sufficient athermalization and high lens processability.

Disclosure of utility model

An objective of the present application is to provide an optical system and an optical lens operating in the far infrared band, which are capable of satisfying the requirements of the optical system for good imaging quality, small volume, sufficient athermalization and high lens processability.

According to an aspect of an embodiment of the present application, an optical system operating in a far infrared band is disclosed, comprising, in order from an object side of the optical system to an image side of the optical system along an optical axis of the optical system: a first chalcogenide refractive lens, a superlens, a second chalcogenide refractive lens; the first chalcogenide refractive lens and the second chalcogenide refractive lens are both positive lenses; the super lens comprises a substrate and a super structure unit, wherein a micro-nano structure is arranged in the super structure unit; the optical system satisfies the following conditions in units of 1/mm:

0.25≤n*(|C₁|+|C₂|)≤2.01

Wherein, when n is the refractive index of the first chalcogenide refractive lens, C ₁ is the curvature of the front surface of the first chalcogenide refractive lens toward the object side, and C ₂ is the curvature of the rear surface of the first chalcogenide refractive lens toward the image side; when n is the refractive index of the second chalcogenide refractive lens, C ₁ is the curvature of the front surface of the second chalcogenide refractive lens toward the object side, and C ₂ is the curvature of the rear surface of the second chalcogenide refractive lens toward the image side.

In an exemplary embodiment of the present application, the optical system provided by the present application further satisfies the following condition in units of femtosecond fs:

and GD is the group delay of the micro-nano structure, and V is the Abbe number of the first chalcogenide refractive lens or the Abbe number of the second chalcogenide refractive lens.

In an exemplary embodiment of the present application, the first chalcogenide refractive lens and the second chalcogenide refractive lens are spherical lenses; the optical system provided by the application also satisfies the following conditions in rad/mm ²:

Wherein M is the maximum value of the absolute value of the slope of the phase provided by the superlens, f ₁ is the effective focal length of the first chalcogenide refractive lens, and f ₂ is the effective focal length of the second chalcogenide refractive lens.

In an exemplary embodiment of the present application, the optical system provided by the present application further satisfies the following condition:

Wherein h ₂ is the optical effective caliber of the second chalcogenide refractive lens, and BFL is the back focal length of the optical system.

In an exemplary embodiment of the application, the micro-nano structure is a positive micro-nano structure or a negative micro-nano structure.

In an exemplary embodiment of the application, the superlens comprises at least one layer of the superstructural units.

In an exemplary embodiment of the application, the optical system is provided with a diaphragm adjacent to the superlens; the diaphragm is arranged on the surface of the superlens, or the diaphragm and the superlens are arranged at intervals.

In an exemplary embodiment of the present application, the front surface of the first chalcogenide refractive lens is convex, and the rear surface of the first chalcogenide refractive lens is concave; the front surface of the second chalcogenide refractive lens is concave, and the rear surface of the second chalcogenide refractive lens is convex.

According to an aspect of an embodiment of the present application, there is disclosed an optical lens operating in a far infrared band, the optical lens including: a lens barrel; the pressing ring, the first spacing ring, the second spacing ring and the optical system provided by any embodiment are arranged in the lens barrel;

The clamping ring abuts against the front surface of the first chalcogenide refractive lens; the first space ring abuts against the front surface of the super lens facing the object side; the second spacer abuts against the front surface of the second chalcogenide refractive lens.

In an exemplary embodiment of the present application, the optical lens further includes: window glass, imaging detector set on the image surface of the optical system; the window glass is arranged between the second chalcogenide refractive lens and the imaging detector.

In the optical system provided by the embodiment of the application, along the optical axis of the optical system, from the object side of the optical system to the image side of the optical system, the optical system sequentially comprises: a first chalcogenide refractive lens, a superlens and a second chalcogenide refractive lens. The optical system provided by the application can have good imaging quality through the common matching of the first chalcogenide refractive lens, the superlens and the second chalcogenide refractive lens. In addition, the thickness of the superlens is far smaller than that of the traditional lens, so that compared with an optical system at least using three traditional lenses in the related art, the optical system provided by the application has greatly reduced volume. Further, the optical system provided by the application meets the following conditions: n (|C ₁|+|C₂ |) is more than or equal to 0.25 and less than or equal to 2.01; wherein, when n is the refractive index of the first chalcogenide refractive lens, C ₁ is the curvature of the front surface of the first chalcogenide refractive lens toward the object side, and C ₂ is the curvature of the rear surface of the first chalcogenide refractive lens toward the image side; when n is the refractive index of the second chalcogenide refractive lens, C ₁ is the curvature of the front surface of the second chalcogenide refractive lens toward the object side, and C ₂ is the curvature of the rear surface of the second chalcogenide refractive lens toward the image side. By the constraint of the condition, the optical system is fully subjected to athermalization, and meanwhile, the good processability of the refractive lens is ensured, and the refractive lens can fully focus light rays, so that the optical system can have good imaging quality. In summary, the optical system provided by the application simultaneously meets the requirements of the optical system on good imaging quality, small volume, sufficient heat difference elimination and high lens processability.

Other features and advantages of the application will be apparent from the following detailed description, or may be learned by the practice of the application.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.

Drawings

The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

Fig. 1 shows an architectural layout for an optical system operating in the far infrared band in an embodiment of the present application.

Fig. 2 shows an architecture layout of an optical lens operating in the far infrared band in an embodiment of the present application.

Fig. 3 shows a layout diagram of an optical system operating in the far infrared band in one embodiment of the present application.

Fig. 4 shows a graph of MTF as a function of field of view for an optical system in an ambient environment in one embodiment of the application.

Fig. 5 shows a graph of MTF versus field of view for an optical system in an environment of-40 c in one embodiment of the application.

Fig. 6 shows a graph of MTF versus field of view for an optical system in an 80 ℃ environment in one embodiment of the application.

Fig. 7 shows a field curvature diagram of an optical system in one embodiment of the application.

Fig. 8 shows a distortion diagram of an optical system in one embodiment of the application.

Fig. 9 shows an architectural layout for an optical system operating in the far infrared band in an embodiment of the present application.

Fig. 10 shows a graph of MTF as a function of field of view for an optical system in an ambient environment in one embodiment of the application.

FIG. 11 shows a graph of MTF versus field of view for an optical system in an environment of-40 ℃ in one embodiment of the present application.

Fig. 12 shows a graph of MTF versus field of view for an optical system in an 80 ℃ environment in one embodiment of the application.

Fig. 13 shows a field curvature of an optical system in an embodiment of the application.

Fig. 14 shows a distortion diagram of an optical system in one embodiment of the application.

Fig. 15 shows an architectural layout for an optical system operating in the far infrared band in an embodiment of the present application.

Fig. 16 shows a graph of MTF as a function of field of view for an optical system in an ambient environment in one embodiment of the application.

Fig. 17 shows a graph of MTF versus field of view for an optical system in an environment of-40 ℃ in one embodiment of the application.

Fig. 18 shows a graph of MTF versus field of view for an optical system in an 80 ℃ environment in one embodiment of the application.

Fig. 19 shows a field curvature diagram of an optical system in one embodiment of the application.

Fig. 20 shows a distortion diagram of an optical system in one embodiment of the application.

Fig. 21 shows an architectural layout for an optical system operating in the far infrared band in an embodiment of the present application.

Fig. 22 shows a graph of MTF as a function of field of view for an optical system in an ambient environment in one embodiment of the application.

FIG. 23 shows a graph of MTF versus field of view for an optical system in an embodiment of the present application at-40 ℃.

Fig. 24 shows a graph of MTF versus field of view for an optical system in an 80 ℃ environment in one embodiment of the application.

Fig. 25 shows a field profile of an optical system in one embodiment of the application.

Fig. 26 shows a distortion diagram of an optical system in one embodiment of the application.

Fig. 27 shows an architectural layout for an optical system operating in the far infrared band in an embodiment of the present application.

Fig. 28 shows a graph of MTF as a function of field of view for an optical system in an ambient environment in one embodiment of the application.

Fig. 29 shows a graph of MTF versus field of view for an optical system in an environment of-40 ℃ in one embodiment of the application.

Fig. 30 shows a graph of MTF versus field of view for an optical system in an 80 ℃ environment in one embodiment of the application.

Fig. 31 shows a field curvature diagram of an optical system in one embodiment of the application.

Fig. 32 shows a distortion diagram of an optical system in one embodiment of the application.

FIG. 33 shows an architectural layout for an optical system operating in the far infrared band in an embodiment of the present application.

Fig. 34 shows a graph of MTF as a function of field of view for an optical system in an ambient environment in one embodiment of the application.

Fig. 35 shows a graph of MTF versus field of view for an optical system in an embodiment of the present application at-40 c.

Fig. 36 shows a graph of MTF versus field of view for an optical system in an 80 ℃ environment in one embodiment of the application.

Fig. 37 shows a field curvature diagram of an optical system in one embodiment of the application.

Fig. 38 shows a distortion diagram of an optical system in one embodiment of the application.

Reference numerals:

1-a first chalcogenide refractive lens; 2-superlens; 3-a second chalcogenide refractive lens; 4-window glass; 5-image plane; 6-lens barrel; 7-pressing rings; 8-a first spacer ring; 9-a second spacer ring.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments may be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The drawings are merely schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. In the following description, numerous specific details are provided to give a thorough understanding of example embodiments of the application. One skilled in the relevant art will recognize, however, that the application may be practiced without one or more of the specific details, or with other modules, components, etc. In other instances, well-known structures, methods, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the application.

In order to overcome the above-mentioned drawbacks of the related art, the present application provides an optical system and an optical lens operating in the far-infrared band, which can simultaneously satisfy the requirements of the optical system for good imaging quality, small volume, sufficient heat-eliminating difference, and high lens processability.

Fig. 1 shows a layout of an optical system operating in the far infrared band according to the present application. The left-to-right direction in fig. 1 is a direction from the object side of the optical system to the image side of the optical system. Referring to fig. 1, the optical system provided by the present application sequentially includes, along an optical axis of the optical system from an object side of the optical system to an image side of the optical system: a first chalcogenide refractive lens 1, a superlens 2, and a second chalcogenide refractive lens 3.

Wherein, the first chalcogenide refractive lens 1 and the second chalcogenide refractive lens 3 are both positive lenses. The superlens 2 includes a substrate, and a superstructural unit provided on a front surface of the substrate toward the object side and/or on a rear surface of the substrate toward the image side. The vertex and/or center of the super-structure unit is provided with a micro-nano structure. The filling material between the micro-nano structures is air or other material transparent in the working band.

In the optical system provided by the application, the first chalcogenide refractive lens 1 is mainly used for correcting primary spherical aberration in the system, and the second chalcogenide refractive lens 3 is mainly used for collecting light. In addition, the second catadioptric lens 3 generates a high-order spherical aberration and chromatic aberration in the process of collecting light. The superlens 2 is mainly used for correcting the advanced spherical aberration and chromatic aberration introduced by the second chalcogenide refractive lens 3, and off-axis aberration which is difficult to correct by the first chalcogenide refractive lens 1 and the second chalcogenide refractive lens 3; the off-axis aberration in the present application mainly includes coma, distortion and off-axis spherical aberration.

Thus, by the co-combination of the first chalcogenide refractive lens 1, the superlens 2 and the second chalcogenide refractive lens 3, the optical system provided by the application can have good imaging quality. Also, since the thickness of the superlens 2 is much smaller than that of the conventional lens, the volume of the optical system provided by the present application is greatly reduced compared to an optical system using at least three conventional lenses in the related art.

Further, since the first chalcogenide glass material and the second chalcogenide glass material are both chalcogenide glass materials, and the refractive index temperature coefficient of the chalcogenide glass material is lower than that of other materials, the use of the chalcogenide glass material can contribute to the heat difference elimination of the optical system. Further, the optical system provided by the application satisfies the following conditions in units of 1/mm:

0.25≤n*(|C₁|+|C₂|)≤2.01

Wherein, when n is the refractive index of the first chalcogenide refractive lens 1, C ₁ is the curvature of the front surface of the first chalcogenide refractive lens 1 toward the object side, and C ₂ is the curvature of the rear surface of the first chalcogenide refractive lens 1 toward the image side; when n is the refractive index of the second chalcogenide refractive lens 3, C ₁ is the curvature of the front surface of the second chalcogenide refractive lens 3 toward the object side, and C ₂ is the curvature of the rear surface of the second chalcogenide refractive lens 3 toward the image side. n is a dimensionless parameter; units of C ₁ and C ₂ are 1/mm.

In detail, the condition consisting of n, |c ₁ | and |c ₂ | is combined to constrain the first and second chalcogenide lenses 1 and 3. By setting the lower limit value of this condition to 0.25, the curvature of the refractive lens (including the first chalcogenide refractive lens 1 and the second chalcogenide refractive lens 3) is prevented from being excessively small, so that the refractive lens can provide sufficient optical power even if the refractive index of the refractive lens is small, thereby enabling the refractive lens to sufficiently focus light, and thus enabling the optical system to have good imaging quality.

The larger the refractive index of the refractive lens, the larger the duty ratio of the refractive lens acting in the optical system, and the larger the influence of the temperature change on the optical system. The larger the curvature of the refractive lens, the more susceptible it is to temperature changes, and thus the greater the influence it has on the optical system. Therefore, by setting the upper limit value of this condition to 2.01, the refractive index of the refractive lens is prevented from being excessively large, and at the same time, the curvature of the refractive lens is prevented from being excessively large, and further, the refractive lens is prevented from being inferior in performance under the condition of high temperature or low temperature, thereby sufficiently completing the athermalization of the optical system, and at the same time, the refractive lens is also ensured to have good workability.

Therefore, the optical system provided by the application fully eliminates the heat difference of the optical system by the constraint of the conditions consisting of n, |C ₁ | and|C ₂ |, ensures that the refractive lens has good processability, and can fully focus light, so that the optical system has good imaging quality.

In summary, the optical system provided by the application reduces the volume while having good imaging quality, fully completes the heat elimination difference, and ensures that the refractive lens has good processability; thus, the requirements of the optical system for good imaging quality, small volume, sufficient heat removal difference and high lens processability are simultaneously met.

Preferably, in one embodiment, the optical system provided by the present application satisfies the following conditions in units of 1/mm:

0.36≤n*(|C₁|+|C₂|)≤1.06

In one embodiment, the front surface of the first chalcogenide refractive lens 1 is convex, and the rear surface of the first chalcogenide refractive lens 1 is concave; the front surface of the second chalcogenide refractive lens 3 is concave, and the rear surface of the second chalcogenide refractive lens 3 is convex. In the present embodiment, the first chalcogenide refractive lens 1 has a crescent shape facing the object side as a whole, and the second chalcogenide refractive lens 3 has a crescent shape facing the image side as a whole.

In an embodiment, the optical system provided by the present application further satisfies the following condition in units of femtosecond fs:

wherein GD (GroupDelay) is the group time delay of the micro-nano structure, and V is the Abbe number of the first chalcogenide refractive lens 1 or the Abbe number of the second chalcogenide refractive lens 3. GD is given in femtoseconds, V is a dimensionless parameter.

In detail, can be adoptedDescribing the phase/>, provided by the micro-nano structure at radial position r at angular frequency ω, in the superlens 2Pair/>After the taylor expansion is performed, the obtained first-order expansion term is the group delay GD. It should be noted that the same micro-nano structure generally provides different phases for different wavelengths, so that a certain phase difference exists between phases provided by the same micro-nano structure for different wavelengths; if the group delay GD of the micro-nano structure at a certain position is larger, it is indicated that the phase difference of the phase provided by the micro-nano structure at the position for different wavelengths is larger, so that the group delay GD can be regarded as the dispersion coefficient of the micro-nano structure, and can be used for describing the dispersion introduced by the micro-nano structure.

It should be noted that, the dispersion introduced by the micro-nano structure in the superlens 2 is negative dispersion, that is, the longer the wavelength of the light, the larger the deflection angle of the light. This is in contrast to conventional refractive lenses. The dispersion introduced by conventional refractive lenses is positive, i.e., the longer the wavelength of the light, the smaller the angle of deflection of the light. Also, the positive dispersion introduced by a conventional refractive lens can be described by the Abbe number: the larger the Abbe number is, the smaller the positive dispersion introduced by the corresponding refractive lens is; conversely, the smaller the Abbe number, the larger the positive dispersion introduced by the corresponding refractive lens. Therefore, by combining the group delay GD corresponding to the micro-nano structure and the Abbe number V corresponding to the refractive lens, negative chromatic dispersion introduced by the superlens 2 and positive chromatic dispersion introduced by the refractive lens can be balanced, and chromatic aberration correction is realized.

Then, by setting the lower limit of the condition constituted by GD and V together to 5.31, it is possible to prevent the refractive lenses (including the first chalcogenide refractive lens 1 and the second chalcogenide refractive lens 3) from introducing excessive positive dispersion; by configuring the upper limit of this condition to 17.90, the superlens 2 can be prevented from introducing excessive negative dispersion. Thus, under the constraint of this condition, the negative dispersion introduced by the superlens 2 and the positive dispersion introduced by the refractive lens compensate each other and balance, thereby sufficiently correcting chromatic aberration of the optical system.

Preferably, in an embodiment, the optical system provided by the present application satisfies the following condition in units of femtosecond fs:

In one embodiment, since the combination performance of the aspherical lens is better than that of the spherical lens, in this example, the first chalcogenide refractive lens 1 and the second chalcogenide refractive lens 3 are both aspherical lenses, thereby providing a more excellent basis for the optical system to have good imaging quality.

In one embodiment, the first chalcogenide lens 1 and the second chalcogenide lens 3 are spherical lenses for cost reduction. In this case, in order to ensure that the optical system still has good imaging quality, the optical system provided by the present embodiment also satisfies the following conditions in rad/mm ²:

Where M is the maximum value of the absolute value of the slope of the phase provided by the superlens 2, f ₁ is the effective focal length of the first chalcogenide refractive lens 1, and f ₂ is the effective focal length of the second chalcogenide refractive lens 3. M is in rad/mm, and f ₁ and f ₂ are in mm.

In detail, M may be used to characterize the optical power provided by the superlens 2 to the system in the off-axis field of view: the larger M is, the larger the focal power provided by the super lens 2 in the off-axis visual field for the system is, and the larger the light deflection capability of the super lens 2 in the off-axis visual field is; conversely, a smaller M indicates a smaller optical power provided by the superlens 2 to the system in the off-axis field, and a smaller light deflection capability of the superlens 2 in the off-axis field.

Thus, in the present embodiment, by setting the lower limit of the condition constituted by M, f ₁ and f ₂ together to 0.48, it is ensured that the superlens 2 has a sufficient light ray deflection capability in the off-axis field, and further it is possible to sufficiently correct off-axis aberrations, particularly coma, distortion and off-axis spherical aberration, which are difficult to be corrected by the first and second chalcogenide lenses 1 and 3, which are spherical lenses; by configuring the upper limit of this condition to be 1.34, the superlens 2 is prevented from having excessive light-deflecting power in the off-axis field, thereby preventing the superlens 2 from introducing excessive chromatic aberration.

Preferably, in one embodiment, the optical system provided by the present application satisfies the following conditions in rad/mm ²:

in one embodiment, the optical system provided by the present application satisfies the following conditions:

Wherein h ₂ is the optical effective aperture of the second chalcogenide refractive lens 3, and BFL (Back Focal Length) is the back focal length of the optical system. h ₂ is the same unit as BFL (e.g., in mm).

In this embodiment, the condition consisting of h ₂ and BFL together can be used to characterize the light refractive power of the second chalcogenide refractive lens 3 in the optical system. The larger the value of the condition is, the stronger the light refraction capability corresponding to the second chalcogenide refractive lens 3 is, the faster the light is converged, the smaller the system volume is, but the larger the chromatic aberration introduced by the second chalcogenide refractive lens 3 is at the same time; conversely, the smaller the value of the condition, the weaker the light refractive power corresponding to the second chalcogenide refractive lens 3, the slower the light converging, the larger the system volume, but at the same time, the smaller the chromatic aberration introduced by the second chalcogenide refractive lens 3.

Thus, by configuring the lower limit of the condition to be 0.54, the system is prevented from becoming excessively large; by configuring the upper limit of this condition to 1.52, the second chalcogenide refractive lens 3 is prevented from introducing excessive chromatic aberration.

Preferably, in an embodiment, the optical system provided by the present application satisfies the following conditions:

In an embodiment, the micro-nano structure is a positive micro-nano structure or a negative micro-nano structure. When the superlens 2 is assembled with other structural members, the negative micro-nano structure is less susceptible to damage than the positive micro-nano structure.

In order to further improve the transmittance of the superlens in the far infrared band, in this embodiment, the substrate side of the superlens having the micro-nano structure may be covered with a side antireflection film. Specifically, when the micro-nano structure is a positive micro-nano structure, the antireflection film covers the upper part of the area where the micro-nano structure is arranged on the surface of one side of the substrate; when the micro-nano structure is a negative micro-nano structure, the anti-reflection film is covered above the area of the surface of one side of the substrate, where the micro-nano structure is not arranged.

In an embodiment, the superlens 2 comprises at least one layer of superstructural units.

In this embodiment, the superlens 2 may include one layer of superstructural units or may include multiple layers of superstructural units. The superlens 2 of the multilayer superstructure unit has a higher degree of freedom in modulating light than the superlens 2 of one layer superstructure unit.

In an embodiment, the optical system is provided with a stop adjacent to the superlens 2; the diaphragm is arranged on the surface of the superlens 2 or the diaphragm is arranged at intervals with the superlens 2.

In this embodiment, the optical system is provided with a diaphragm to control the light entering amount of the optical system. The diaphragm is adjacent to the superlens 2; specifically, the diaphragm may be disposed on a front surface of the base of the superlens 2 facing the object side, or may be disposed on a rear surface of the base of the superlens 2 facing the image side, or may be disposed at a distance from the superlens 2, between which no other optical element is disposed, but other non-optical elements (for example, a spacer for maintaining a distance therebetween) may be disposed.

Fig. 2 shows a layout of an optical lens operating in the far infrared band according to the present application. Referring to fig. 2, the present application also provides an optical lens operating in a far infrared band, the optical lens comprising: a lens barrel 6; the optical system (the first chalcogenide refractive lens 1, the superlens 2, and the second chalcogenide refractive lens 3) provided in any of the above embodiments, the pressing ring 7, the first spacer ring 8, the second spacer ring 9, and the lens barrel are provided.

In the optical lens, the pressing ring 7 is abutted against the front surface of the first chalcogenide refractive lens facing the object side, the first spacer ring 8 is abutted against the front surface of the superlens facing the object side, and the second spacer ring 9 is abutted against the front surface of the second chalcogenide refractive lens facing the object side.

In an embodiment, the optical lens provided by the present application further includes: window glass 4, imaging detector set on image plane 5. The window glass 4 is arranged between the second chalcogenide refractive lens 3 and the imaging detector to protect the second chalcogenide refractive lens 3 and the imaging detector.

TABLE 1 target demand for various system parameters of optical system

System parameters	Data
		Optical total length (TTL)	≤20mm
Visual field (2 omega)	≥31°
		F number	≤1.05
MTF	≥0.2
		Operating band	8～12μm

Table 1 shows the target requirements for various system parameters for the optical system to be provided in one embodiment. Specifically, in one embodiment, the optical system target to be provided operates in the far infrared band, i.e., 8-12 μm band; an optical Total length TTL (Total TRACK LENGTH) target of less than or equal to 20mm; the field of view target is greater than or equal to 31 °; the F number target is less than or equal to 1.05. In this embodiment, the MTF target requirements for each spatial frequency in the full field range are: greater than or equal to 0.2. Wherein MTF (Modulation Transfer Function), also called modulation transfer function, is an important index for describing the imaging quality of the optical system. The closer the MTF value is to the diffraction limit, the better the imaging quality.

Targeting the target requirements shown in table 1, the present application illustratively provides 6 optical systems in 6 embodiments that meet the target requirements shown in table 1. Next, the 6 optical systems provided by the present application will be described in detail.

Example 1

Fig. 3 shows a layout structure diagram of the optical system operating in the far infrared band provided in embodiment 1. Referring to fig. 3, the optical system provided in this embodiment includes, in order from an object side to an image side along an optical axis: a first chalcogenide refractive lens, a diaphragm, a superlens, and a second chalcogenide refractive lens; wherein, the diaphragm is arranged on the front surface of the superlens. On the basis of the optical system, a window glass can be further arranged, and the window glass is arranged between the second chalcogenide refractive glass and the image plane.

TABLE 2 System parameters of the optical System provided in example 1

System parameters	Data
		Optical total length (TTL)	13.75mm
Visual field (2 omega)	31.1°
		F number	1.0
Effective focal length	7.05mm
		Operating band	8～12μm

As can be seen from table 2, the optical system provided in this embodiment works in the 8-12 μm band, and has an optical total length of 13.75mm, which fully satisfies the requirement of the optical system for miniaturization; the view field is 31.1 degrees, so that the requirement of an optical system on the view field is fully met; the F number is 1.0, and the requirement of the optical system on the light inlet quantity is fully met.

In the direction from the object side to the image side, the surfaces included from the first chalcogenide lens to the image plane in this embodiment are labeled, and the parameters of the surfaces are summarized to obtain table 3 shown below.

TABLE 3 parameters from the first chalcogenide lens to the surfaces included in the image plane in example 1

Surface serial number	Surface type	Radius of curvature	Thickness of (L)	Material
					1	Object plane	Infinite number of cases	Infinite number of cases	-
2	Spherical surface	5.41mm	1.11mm	IRG204
					3	Spherical surface	5.06mm	1.03mm	-
4	Diaphragm	Infinite number of cases	0.375mm	Silicon
					5	Super surface	Infinite number of cases	1.81mm	-
6	Even aspherical surface	-33.42mm	4.00mm	IRG204
					7	Even aspherical surface	-10.09mm	4.80mm	-
8	Spherical surface	Infinite number of cases	0.5mm	Silicon
					9	Spherical surface	Infinite number of cases	0.13mm	-
10	Image plane	Infinite number of cases	-	-

Wherein table 1 is an object plane (which is not shown in fig. 3) which is located to the left of the first chalcogenide refractive lens. The surface 2 is the front surface of the first chalcogenide refractive lens. The surface 3 is the rear surface of the first chalcogenide refractive lens. The surface 4 is the front surface of the superlens substrate, and since the aperture is provided on the front surface of the superlens in this embodiment, the surface type of the surface 4 is denoted as aperture. The surface 5 is the rear surface of the superlens, and since the micro-nano structure is provided on the rear surface of the superlens in this embodiment, the surface type of the surface 5 is referred to as a supersurface. The surface 6 is the front surface of the second chalcogenide refractive lens. The surface 7 is the rear surface of the second chalcogenide refractive lens. The surface 8 is the front surface of the window glass facing the object side. The surface 9 is the rear surface of the window glass facing the image side. The surface 10 is an image plane.

As can be seen from table 3, the radius of curvature of the surface 1 is infinite (i.e. it is planar), the distance between it and the surface 2 is variable, and the material between it and the surface 2 is air. Surface 2 is a sphere with a radius of curvature of 5.41mm, the distance between the surface and surface 3 is 1.11mm, and the material between the surface and surface 3 is IRG204 chalcogenide glass. The surface 3 is a sphere with a radius of curvature of 5.06mm, the distance between the surface and the surface 4 is 1.03mm, and the material between the surface and the surface 4 is air. The surface 4 is planar with a distance of 0.375mm from the surface 5 and the material from the surface 5 is silicon, including but not limited to intrinsic silicon, optical silicon, crystalline silicon, amorphous silicon, extrinsic silicon. The surface 5 is planar and has a distance of 1.81mm from the surface 6 and the material from the surface 6 is air. Surface 6 is an even aspherical surface with a radius of curvature of-33.42 mm, the distance between the surface and surface 7 is 4.00mm, and the material between the surface and surface 7 is IRG204 chalcogenide glass. Surface 7 is an even aspherical surface with a radius of curvature of-10.09 mm, the distance between the surface and surface 8 is 4.80mm, and the material between the surface and surface 8 is air. The surface 8 is planar with a distance of 0.5mm from the surface 9 and the material from the surface 9 is silicon, including but not limited to intrinsic silicon, optical silicon, crystalline silicon, amorphous silicon, extrinsic silicon. The surface is planar and is spaced from the surface 10 by 0.13mm and the material from the surface 10 is air.

FIG. 4 is a graph showing MTF versus field of view for the optical system provided in example 1 under ambient conditions; in general, the normal temperature environment refers to an environment of 25 ℃. Fig. 5 shows a graph of MTF versus field of view for the optical system provided in example 1 at-40 ℃. Fig. 6 shows a graph of MTF versus field of view for the optical system provided in example 1 at 80 ℃.

In any of the figures 4 to 6, the horizontal axis represents the field of view in degrees on the Y-axis; the vertical axis represents the MTF value; and, T represents a meridian direction curve, and S represents a sagittal direction curve. Specifically, meridian curve T1 and sagittal curve S1 correspond to a spatial frequency of 5.00 cycles per millimeter (cyc/mm); meridian T2 corresponds to a spatial frequency of 10.00cyc/mm with sagittal S2; meridian T3 corresponds to a spatial frequency of 15.00cyc/mm with sagittal S3; meridian T4 corresponds to a spatial frequency of 20.00cyc/mm with sagittal S4; meridian T5 corresponds to a spatial frequency of 40.00cyc/mm with sagittal S5; the meridian curve T6 corresponds to a spatial frequency of 42.00cyc/mm with the sagittal curve S6.

As can be seen from fig. 4, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.2 all the time in a normal temperature environment, thereby demonstrating that the optical system has excellent imaging quality in a normal temperature environment. As can be seen from fig. 5, the optical system provided in this embodiment has an MTF of each spatial frequency within the full field of view of greater than 0.2 all the time in an environment of-40 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of-40 ℃. As can be seen from fig. 5, the optical system provided in this embodiment has an MTF of each spatial frequency substantially always greater than 0.2 in the full field of view at 80 ℃, thereby demonstrating that the optical system has good imaging quality at 80 ℃.

As can be seen from a combination of fig. 4 to 6, the optical system provided in this embodiment can always maintain good imaging quality in the temperature range of-40 ℃ to 80 ℃, thereby explaining that the optical system sufficiently realizes the athermalization.

Fig. 7 shows a field diagram of the optical system provided in embodiment 1. The horizontal axis of fig. 7 represents the distance deviation between the actual focal point of the optics and the image plane in millimeters; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 7, T represents a meridian direction curve, and S represents a sagittal direction curve; specifically, meridian T ₈ and sagittal S ₈ correspond to 8 μm operating wavelength; meridian T ₁₀ corresponds to a 10 μm operating wavelength with sagittal S ₁₀; the meridian T ₁₂ corresponds to the 12 μm operating wavelength with the sagittal S ₁₂.

As can be seen from fig. 7, in this embodiment, the curvature of field for each wavelength in the 8-12 μm band is smaller than 0.05 mm, thereby indicating that the curvature of field of the optical system is small.

Fig. 8 shows a distortion chart of the optical system provided in embodiment 1. The horizontal axis of fig. 8 represents the degree of distortion of the image in percent; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 8, three curves of a distortion curve corresponding to a wavelength of 8 μm, a distortion curve corresponding to a wavelength of 10 μm, and a distortion curve corresponding to a wavelength of 12 μm are actually shown, except that the three curves are almost completely overlapped.

As can be seen from fig. 8, in this embodiment, the distortion for each wavelength in the 8 to 12 μm band is less than 2.0%, thus indicating that the distortion of the optical system is small.

Example 2

Fig. 9 shows a layout structure diagram of an optical system operating in the far infrared band provided in embodiment 2. Referring to fig. 9, the optical system provided in this embodiment includes, in order from an object side to an image side along an optical axis: a first chalcogenide refractive lens, a diaphragm, a superlens, and a second chalcogenide refractive lens; wherein, the diaphragm is arranged between the first chalcogenide refractive lens and the superlens. On the basis of the optical system, a window glass can be further arranged, and the window glass is arranged between the second chalcogenide refractive glass and the image plane.

TABLE 4 System parameters of the optical System provided in example 2

System parameters	Data
		Optical total length (TTL)	11.82mm
Visual field (2 omega)	31°
		F number	1.0
Effective focal length	7.02mm
		Operating band	8～12μm

As can be seen from table 4, the optical system provided in this embodiment works in the 8-12 μm band, and has an optical total length of 11.82mm, which fully satisfies the requirement of the optical system for miniaturization; the view field is 31 degrees, so that the requirement of an optical system on the view field is fully met; the F number is 1.0, and the requirement of the optical system on the light inlet quantity is fully met.

In the direction from the object side to the image side, the surfaces included from the first chalcogenide lens to the image plane in this embodiment are labeled, and the parameters of the surfaces are summarized to obtain table 5 shown below.

TABLE 5 parameters from the first chalcogenide lens to the surfaces included in the image plane in example 2

Surface serial number	Surface type	Radius of curvature	Thickness of (L)	Material
					1	Object plane	Infinite number of cases	Infinite number of cases	-
2	Spherical surface	5.34mm	1.48mm	IRG204
					3	Spherical surface	5.12mm	0.98mm	-
4	Diaphragm	Infinite number of cases	0.29mm	-
					5	Spherical surface	Infinite number of cases	0.375mm	Silicon
6	Super surface	Infinite number of cases	1.34mm	-
					7	Spherical surface	-14.38mm	2.67mm	IRG204
8	Spherical surface	-8.19mm	4.70mm	-
					9	Image plane	Infinite number of cases	-	-

See the explanation for table 3 and the details of table 5 will not be repeated here.

Fig. 10 shows a graph of MTF versus field of view for the optical system provided in example 2 under an ambient temperature environment. Fig. 11 shows a graph of MTF versus field of view for the optical system provided in example 2 at-40 ℃. Fig. 12 shows a graph of MTF versus field of view for the optical system provided in example 2 at 80 ℃.

In any of fig. 10-12, the horizontal axis represents the field of view on the Y-axis in degrees; the vertical axis represents the MTF value. Meridian T1 corresponds to a spatial frequency of 5.00cyc/mm with sagittal S1; meridian T2 corresponds to a spatial frequency of 10.00cyc/mm with sagittal S2; meridian T3 corresponds to a spatial frequency of 15.00cyc/mm with sagittal S3; meridian T4 corresponds to a spatial frequency of 20.00cyc/mm with sagittal S4; meridian T5 corresponds to a spatial frequency of 40.00cyc/mm with sagittal S5; the meridian curve T6 corresponds to a spatial frequency of 42.00cyc/mm with the sagittal curve S6.

As can be seen from fig. 10, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.32 all the time in a normal temperature environment, thereby demonstrating that the optical system has excellent imaging quality in a normal temperature environment. As can be seen from fig. 11, the optical system provided in this embodiment has an MTF of each spatial frequency within the full field of view of greater than 0.28 all the time in an environment of-40 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of-40 ℃. As can be seen from fig. 12, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.34 all the time in an environment of 80 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of 80 ℃.

As can be seen from a combination of fig. 10 to 12, the optical system provided in this embodiment can always maintain excellent imaging quality in the temperature range of-40 to 80 ℃, thereby demonstrating that the optical system sufficiently realizes the athermalization.

Fig. 13 shows a field profile of the optical system provided in example 2. The horizontal axis of fig. 13 represents the distance deviation between the actual focal point of the optics and the image plane in millimeters; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 13, meridian T ₈ and sagittal S ₈ correspond to 8 μm operating wavelength; meridian T ₁₀ corresponds to a 10 μm operating wavelength with sagittal S ₁₀; the meridian T ₁₂ corresponds to the 12 μm operating wavelength with the sagittal S ₁₂.

As can be seen from fig. 13, in this embodiment, the curvature of field for each wavelength in the 8-12 μm band is smaller than 0.02 mm, thus indicating that the curvature of field of the optical system is small.

Fig. 14 shows a distortion chart of the optical system provided in embodiment 2. The horizontal axis of fig. 14 represents the degree of distortion of the image in percent; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 14, three curves of a distortion curve corresponding to a wavelength of 8 μm, a distortion curve corresponding to a wavelength of 10 μm, and a distortion curve corresponding to a wavelength of 12 μm are actually shown, except that the three curves overlap almost completely.

As can be seen from fig. 14, in this embodiment, the distortion for each wavelength in the 8 to 12 μm band is less than 1.0%, thus indicating that the distortion of the optical system is small.

Example 3

Fig. 15 shows a layout structure diagram of an optical system operating in the far infrared band provided in embodiment 3. Referring to fig. 15, the optical system provided in this embodiment includes, in order from an object side to an image side along an optical axis: a first chalcogenide refractive lens, a superlens, a diaphragm, and a second chalcogenide refractive lens; the diaphragm is arranged on the rear surface of the superlens, and the micro-nano structure is also arranged on the rear surface of the superlens. On the basis of the optical system, a window glass can be further arranged, and the window glass is arranged between the second chalcogenide refractive glass and the image plane.

TABLE 6 System parameters of the optical System provided in example 3

System parameters	Data
		Optical total length (TTL)	10.92mm
Visual field (2 omega)	34°
		F number	1.0
Effective focal length	6.87mm
		Operating band	8～12μm

As can be seen from table 6, the optical system provided in this embodiment works in the 8-12 μm band, and has an optical total length of 10.92mm, which fully satisfies the requirement of the optical system for miniaturization; the view field is 34 degrees, so that the requirement of an optical system on the view field is fully met; the F number is 1.0, and the requirement of the optical system on the light inlet quantity is fully met.

In the direction from the object side to the image side, the surfaces included from the first chalcogenide lens to the image plane in this embodiment are labeled, and the parameters of the surfaces are summarized to obtain table 7 shown below.

TABLE 7 parameters from the first chalcogenide lens to the surfaces included in the image plane in example 3

Surface serial number	Surface type	Radius of curvature	Thickness of (L)	Material
					1	Object plane	Infinite number of cases	Infinite number of cases	-
2	Spherical surface	5.85mm	2.63mm	IRG206
					3	Spherical surface	5.33mm	1.29mm	-
4	Spherical surface	Infinite number of cases	0.375mm	Silicon
					5	Super surface (diaphragm)	Infinite number of cases	1.18mm	-
6	Spherical surface	-12.12mm	1.68mm	IRG206
					7	Spherical surface	-7.09mm	3.12mm	-
8	Spherical surface	Infinite number of cases	0.5mm	Silicon
					9	Spherical surface	Infinite number of cases	0.13mm	-
10	Image plane	Infinite number of cases	-	-

See the explanation for table 3, and the details of table 7 will not be repeated here.

Fig. 16 shows a graph of MTF versus field of view for the optical system provided in example 3 under an ambient temperature environment. Fig. 17 shows a graph of MTF versus field of view for the optical system provided in example 3 at-40 ℃. Fig. 18 shows a graph of MTF versus field of view for the optical system provided in example 3 at 80 ℃.

In any of fig. 16-18, the horizontal axis represents the field of view on the Y-axis in degrees; the vertical axis represents the MTF value. Meridian T1 corresponds to a spatial frequency of 5.00cyc/mm with sagittal S1; meridian T2 corresponds to a spatial frequency of 10.00cyc/mm with sagittal S2; meridian T3 corresponds to a spatial frequency of 15.00cyc/mm with sagittal S3; meridian T4 corresponds to a spatial frequency of 20.00cyc/mm with sagittal S4; meridian T5 corresponds to a spatial frequency of 40.00cyc/mm with sagittal S5; the meridian curve T6 corresponds to a spatial frequency of 42.00cyc/mm with the sagittal curve S6.

As can be seen from fig. 16, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.3 all the time in a normal temperature environment, thereby demonstrating that the optical system has excellent imaging quality in a normal temperature environment. As can be seen from fig. 17, the optical system provided in this embodiment has an MTF of each spatial frequency within the full field of view of greater than 0.25 all the time in an environment of-40 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of-40 ℃. As can be seen from fig. 18, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.3 all the time in an environment of 80 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of 80 ℃.

As can be seen from a combination of fig. 16 to 18, the optical system provided in this embodiment can always maintain excellent imaging quality in the temperature range of-40 to 80 ℃, thereby demonstrating that the optical system sufficiently realizes the athermalization.

Fig. 19 shows a field profile of the optical system provided in embodiment 3. The horizontal axis of fig. 19 represents the distance deviation between the actual focal point of the optics and the image plane in millimeters; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 19, meridian T ₈ and sagittal S ₈ correspond to 8 μm operating wavelength; meridian T ₁₀ corresponds to a 10 μm operating wavelength with sagittal S ₁₀; the meridian T ₁₂ corresponds to the 12 μm operating wavelength with the sagittal S ₁₂.

As can be seen from fig. 19, in this embodiment, the curvature of field for each wavelength in the 8-12 μm band is smaller than 0.09 mm, thereby indicating that the curvature of field of the optical system is small.

Fig. 20 shows a distortion chart of the optical system provided in embodiment 3. The horizontal axis of fig. 20 represents the degree of distortion of the image in percent; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 20, three curves of a distortion curve corresponding to a wavelength of 8 μm, a distortion curve corresponding to a wavelength of 10 μm, and a distortion curve corresponding to a wavelength of 12 μm are actually shown, except that the three curves are almost completely overlapped.

As can be seen from fig. 20, in this embodiment, the distortion for each wavelength in the 8 to 12 μm band is less than 1.2%, thus indicating that the distortion of the optical system is small.

Example 4

Fig. 21 shows a layout structure diagram of an optical system operating in the far infrared band provided in embodiment 4. Referring to fig. 21, the optical system provided in this embodiment includes, in order from an object side to an image side along an optical axis: a first chalcogenide refractive lens, a superlens, a diaphragm, and a second chalcogenide refractive lens; the diaphragm is arranged on the rear surface of the superlens, and the micro-nano structure is also arranged on the rear surface of the superlens. On the basis of the optical system, a window glass can be further arranged, and the window glass is arranged between the second chalcogenide refractive glass and the image plane.

TABLE 8 System parameters of the optical System provided in example 4

System parameters	Data
		Optical total length (TTL)	11.32mm
Visual field (2 omega)	34°
		F number	1.0
Effective focal length	6.89mm
		Operating band	8～12μm

As can be seen from table 8, the optical system provided in this embodiment works in the 8-12 μm band, and has an optical total length of 11.32mm, which fully satisfies the requirement of the optical system for miniaturization; the view field is 34 degrees, so that the requirement of an optical system on the view field is fully met; the F number is 1.0, and the requirement of the optical system on the light inlet quantity is fully met.

In the direction from the object side to the image side, the surfaces included from the first chalcogenide lens to the image plane in this embodiment are labeled, and the parameters of the surfaces are summarized to obtain table 9 shown below.

TABLE 9 parameters from the first chalcogenide lens to the surfaces included in the image plane in example 4

Surface serial number	Surface type	Radius of curvature	Thickness of (L)	Material
					1	Object plane	Infinite number of cases	Infinite number of cases	-
2	Spherical surface	5.57mm	1.89mm	IRG206
					3	Spherical surface	5.12mm	1.25mm	-
4	Spherical surface	Infinite number of cases	0.375mm	Silicon
					5	Super surface (diaphragm)	Infinite number of cases	1.80mm	-
6	Spherical surface	-19.66mm	1.68mm	IRG206
					7	Spherical surface	-8.32mm	3.69mm	-
8	Spherical surface	Infinite number of cases	0.50mm	Silicon
					9	Spherical surface	Infinite number of cases	0.13mm	-
10	Image plane	Infinite number of cases	-	-

See the explanation for table 3 and the details of table 9 will not be repeated here.

Fig. 22 shows a graph of MTF versus field of view for the optical system provided in example 4 under an ambient temperature environment. Fig. 23 shows a graph of MTF versus field of view for the optical system provided in example 4 at-40 ℃. Fig. 24 shows a graph of MTF versus field of view for the optical system provided in example 4 at 80 ℃.

In any of fig. 22-24, the horizontal axis represents the field of view on the Y-axis in degrees; the vertical axis represents the MTF value. Meridian T1 corresponds to a spatial frequency of 5.00cyc/mm with sagittal S1; meridian T2 corresponds to a spatial frequency of 10.00cyc/mm with sagittal S2; meridian T3 corresponds to a spatial frequency of 15.00cyc/mm with sagittal S3; meridian T4 corresponds to a spatial frequency of 20.00cyc/mm with sagittal S4; meridian T5 corresponds to a spatial frequency of 40.00cyc/mm with sagittal S5; the meridian curve T6 corresponds to a spatial frequency of 42.00cyc/mm with the sagittal curve S6.

As can be seen from fig. 22, the optical system provided in this embodiment has an MTF of each spatial frequency substantially always greater than 0.19 in the full field of view under the normal temperature environment, thereby indicating that the optical system has good imaging quality under the normal temperature environment. As can be seen from fig. 23, the optical system provided in this embodiment has an MTF of each spatial frequency substantially always greater than 0.15 in a full field of view at-40 ℃, thereby demonstrating that the optical system has good imaging quality at-40 ℃. As can be seen from fig. 24, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.2 all the time in an environment of 80 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of 80 ℃.

As can be seen from a combination of fig. 22 to 24, the optical system provided in this embodiment can always maintain good imaging quality in the temperature range of-40 to 80 ℃, thereby demonstrating that the optical system sufficiently realizes the athermalization.

Fig. 25 shows a field profile of the optical system provided in embodiment 4. The horizontal axis of fig. 25 represents the distance deviation between the actual focal point of the optics and the image plane in millimeters; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 25, meridian T ₈ and sagittal S ₈ correspond to 8 μm operating wavelength; meridian T ₁₀ corresponds to a 10 μm operating wavelength with sagittal S ₁₀; the meridian T ₁₂ corresponds to the 12 μm operating wavelength with the sagittal S ₁₂.

As can be seen from fig. 25, in this embodiment, the curvature of field for each wavelength in the 8-12 μm band is smaller than 0.08 mm, thereby indicating that the curvature of field of the optical system is small.

Fig. 26 shows a distortion chart of the optical system provided in embodiment 4. The horizontal axis of fig. 26 represents the degree of distortion of the image in percent; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 26, three curves of a distortion curve corresponding to a wavelength of 8 μm, a distortion curve corresponding to a wavelength of 10 μm, and a distortion curve corresponding to a wavelength of 12 μm are actually shown, except that the three curves overlap almost completely.

As can be seen from fig. 26, in this embodiment, the distortion for each wavelength in the 8 to 12 μm band is less than 0.8%, thus indicating that the distortion of the optical system is small.

Example 5

Fig. 27 shows a layout structure diagram of an optical system operating in the far infrared band provided in embodiment 5. Referring to fig. 27, the optical system provided in this embodiment includes, in order from an object side to an image side along an optical axis: a first chalcogenide refractive lens, a superlens, a diaphragm, and a second chalcogenide refractive lens; wherein, the diaphragm is arranged on the rear surface of the superlens. On the basis of the optical system, a window glass can be further arranged, and the window glass is arranged between the second chalcogenide refractive glass and the image plane.

TABLE 10 System parameters of the optical System provided in example 5

System parameters	Data
		Optical total length (TTL)	11.70mm
Visual field (2 omega)	34°
		F number	0.99
Effective focal length	6.98mm
		Operating band	8～12μm

As can be seen from table 10, the optical system provided in this embodiment works in the 8-12 μm band, and has an optical total length of 11.70mm, which fully satisfies the requirement of the optical system for miniaturization; the view field is 34 degrees, so that the requirement of an optical system on the view field is fully met; the F number is 0.99, and the requirement of the optical system on the light inlet quantity is fully met.

In the direction from the object side to the image side, the surfaces included from the first chalcogenide lens to the image plane in this embodiment are labeled, and the parameters of the surfaces are summarized to obtain table 11 as shown below.

TABLE 11 parameters from the first chalcogenide lens to the surfaces included in the image plane in example 5

Surface serial number	Surface type	Radius of curvature	Thickness of (L)	Material
					1	Object plane	Infinite number of cases	Infinite number of cases	-
2	Spherical surface	6.07mm	2.99mm	IRG206
					3	Spherical surface	5.33mm	0.94mm	-
4	Spherical surface	Infinite number of cases	0.375mm	Silicon
					5	Super surface (diaphragm)	Infinite number of cases	0.89mm	-
6	Spherical surface	-13.07mm	2.60mm	IRG206
					7	Spherical surface	-7.40mm	3.28mm	-
8	Spherical surface	Infinite number of cases	0.50mm	Silicon
					9	Spherical surface	Infinite number of cases	0.13mm	-
10	Image plane	Infinite number of cases	-	-

See the explanation for table 3, and the details of table 11 will not be repeated here.

Fig. 28 shows a graph of MTF versus field of view for the optical system provided in example 5 under an ambient temperature environment. Fig. 29 shows a graph of MTF versus field of view for the optical system provided in example 5 at-40 ℃. Fig. 30 shows a graph of MTF versus field of view for the optical system provided in example 5 at 80 ℃.

In any of the figures 28-30, the horizontal axis represents the field of view on the Y-axis in degrees; the vertical axis represents the MTF value. Meridian T1 corresponds to a spatial frequency of 5.00cyc/mm with sagittal S1; meridian T2 corresponds to a spatial frequency of 10.00cyc/mm with sagittal S2; meridian T3 corresponds to a spatial frequency of 15.00cyc/mm with sagittal S3; meridian T4 corresponds to a spatial frequency of 20.00cyc/mm with sagittal S4; meridian T5 corresponds to a spatial frequency of 40.00cyc/mm with sagittal S5; the meridian curve T6 corresponds to a spatial frequency of 42.00cyc/mm with the sagittal curve S6.

As can be seen from fig. 28, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.2 all the time in a normal temperature environment, thereby demonstrating that the optical system has excellent imaging quality in a normal temperature environment. As can be seen from fig. 29, the optical system provided in this embodiment has an MTF of each spatial frequency substantially always greater than 0.18 in the full field of view at-40 ℃, thereby demonstrating that the optical system has good imaging quality at-40 ℃. As can be seen from fig. 30, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.23 all the time in an environment of 80 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of 80 ℃.

As can be seen from fig. 28 to 30, the optical system provided in this embodiment can always maintain good imaging quality in the temperature range of-40 to 80 ℃, thereby demonstrating that the optical system sufficiently realizes the athermalization.

Fig. 31 shows a field profile of the optical system provided in example 5. The horizontal axis of fig. 31 represents the distance deviation between the actual focal point of the optics and the image plane in millimeters; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 31, meridian T ₈ and sagittal S ₈ correspond to 8 μm operating wavelength; meridian T ₁₀ corresponds to a 10 μm operating wavelength with sagittal S ₁₀; the meridian T ₁₂ corresponds to the 12 μm operating wavelength with the sagittal S ₁₂.

As can be seen from fig. 31, in this embodiment, the curvature of field for each wavelength in the 8-12 μm band is less than 0.04 mm, thereby indicating that the curvature of field of the optical system is small.

Fig. 32 shows a distortion chart of the optical system provided in embodiment 5. The horizontal axis of fig. 32 represents the degree of distortion of the image in percent; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 32, three curves of a distortion curve corresponding to a wavelength of 8 μm, a distortion curve corresponding to a wavelength of 10 μm, and a distortion curve corresponding to a wavelength of 12 μm are actually shown, except that the three curves overlap almost completely.

As can be seen from fig. 32, in this embodiment, the distortion for each wavelength in the 8 to 12 μm band is less than 0.45%, thus indicating that the distortion of the optical system is small.

Example 6

Fig. 33 shows a layout structure diagram of an optical system operating in the far infrared band provided in embodiment 6. Referring to fig. 33, the optical system provided in this embodiment includes, in order from an object side to an image side along an optical axis: a first chalcogenide refractive lens, a superlens, a diaphragm, and a second chalcogenide refractive lens; the diaphragm is arranged on the rear surface of the superlens, and the micro-nano structure is also arranged on the rear surface of the superlens. On the basis of the optical system, a window glass can be further arranged, and the window glass is arranged between the second chalcogenide refractive glass and the image plane.

TABLE 12 System parameters of the optical System provided in example 6

System parameters	Data
		Optical total length (TTL)	11.43mm
Visual field (2 omega)	30.9°
		F number	1.0
Effective focal length	6.90mm
		Operating band	8～12μm

As can be seen from table 12, the optical system provided in this embodiment works in the 8-12 μm band, and has an optical total length of 11.43mm, which fully satisfies the requirement of the optical system for miniaturization; the visual field is 30.9 degrees, so that the requirement of an optical system on the visual field is fully met; the F number is 1.0, and the requirement of the optical system on the light inlet quantity is fully met.

In the direction from the object side to the image side, the surfaces included from the first chalcogenide lens to the image plane in this embodiment are labeled, and the parameters of the surfaces are summarized to obtain table 13 as shown below.

TABLE 13 parameters from the first chalcogenide lens to the surfaces included in the image plane in example 6

Surface serial number	Surface type	Radius of curvature	Thickness of (L)	Material
					1	Object plane	Infinite number of cases	Infinite number of cases	-
2	Spherical surface	5.65mm	2.10mm	IRG206
					3	Spherical surface	5.45mm	1.58mm	-
4	Spherical surface	Infinite number of cases	0.375mm	Silicon
					5	Super surface (diaphragm)	Infinite number of cases	1.09mm	-
6	Spherical surface	-13.20mm	2.20mm	IRG206
					7	Spherical surface	-7.94mm	3.28mm	-
8	Spherical surface	Infinite number of cases	0.70mm	Silicon
					9	Spherical surface	Infinite number of cases	0.10mm	-
10	Image plane	Infinite number of cases	-	-

See the explanation for table 3 and the details of table 13 will not be repeated here.

Fig. 34 shows a graph of MTF versus field of view for the optical system provided in example 6 under an ambient temperature environment. Fig. 35 shows a graph of MTF versus field of view for the optical system provided in example 6 at-40 ℃. Fig. 36 shows a graph of MTF versus field of view for the optical system provided in example 6 at 80 ℃.

34-36, The horizontal axis represents the field of view on the Y-axis in degrees; the vertical axis represents the MTF value. Meridian T1 corresponds to a spatial frequency of 5.00cyc/mm with sagittal S1; meridian T2 corresponds to a spatial frequency of 10.00cyc/mm with sagittal S2; meridian T3 corresponds to a spatial frequency of 15.00cyc/mm with sagittal S3; meridian T4 corresponds to a spatial frequency of 20.00cyc/mm with sagittal S4; meridian T5 corresponds to a spatial frequency of 40.00cyc/mm with sagittal S5; the meridian curve T6 corresponds to a spatial frequency of 42.00cyc/mm with the sagittal curve S6.

As can be seen from fig. 34, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.25 all the time in a normal temperature environment, thereby demonstrating that the optical system has excellent imaging quality in a normal temperature environment. As can be seen from fig. 35, the optical system provided in this embodiment has an MTF of each spatial frequency within the full field of view of greater than 0.23 all the time in an environment of-40 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of-40 ℃. As can be seen from fig. 36, the optical system provided in this embodiment has an MTF of each spatial frequency in the full field of view of greater than 0.27 all the time in an environment of 80 ℃, thereby demonstrating that the optical system has excellent imaging quality in an environment of 80 ℃.

As can be seen from a combination of fig. 34 to 36, the optical system provided in this embodiment can always maintain excellent imaging quality in the temperature range of-40 to 80 ℃, thereby demonstrating that the optical system sufficiently realizes the athermalization.

Fig. 37 shows a field profile of the optical system provided in example 6. The horizontal axis of fig. 37 represents the distance deviation between the actual focal point of the optics and the image plane in millimeters; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. In fig. 37, meridian T ₈ and sagittal S ₈ correspond to 8 μm operating wavelength; meridian T ₁₀ corresponds to a10 μm operating wavelength with sagittal S ₁₀; the meridian T ₁₂ corresponds to the 12 μm operating wavelength with the sagittal S ₁₂. The meridian curve T ₈ overlaps almost completely with the meridian curve T ₁₂ at the maximum field of view.

As can be seen from fig. 37, in the present embodiment, the curvature of field for each wavelength in the 8-12 μm band is smaller than 0.06 mm, thereby indicating that the curvature of field of the optical system is small.

Fig. 38 shows a distortion chart of the optical system provided in embodiment 6. The horizontal axis of fig. 38 represents the degree of distortion of the image in percent; the vertical axis represents the field of view in degrees along the positive direction of the Y-axis. Fig. 38 shows a distortion curve i corresponding to a wavelength of 8 μm, a distortion curve ii corresponding to a wavelength of 10 μm, and a distortion curve iii corresponding to a wavelength of 12 μm.

As can be seen from fig. 38, in this embodiment, the distortion for each wavelength in the 8 to 12 μm band is less than 0.09%, thus indicating that the distortion of the optical system is small.

The parameters of the optical system provided in the above 6 embodiments were summarized to obtain table 14 shown below. The table 14 is mainly used for illustrating various conditions satisfied by the optical system provided by the present application, and all conditions are experimentally verified and supported.

Since n represents the refractive index of the first chalcogenide refractive lens or the refractive index of the second chalcogenide refractive lens, n in each embodiment in table 14 has two values; specifically, in the same embodiment, the former value represents the refractive index of the first chalcogenide refractive lens, and the latter value represents the refractive index of the second chalcogenide refractive lens. Similarly, details of |c ₁|、|C₂ |, V, and n (|c ₁|+|C₂ |) will not be described in detail.

It should be further noted that, since one superlens includes a plurality of micro-nano structures, and group delays of different micro-nano structures are generally different, for each micro-nano structure of the superlens in each embodiment, the group delay GD is not enumerated by discrete specific values, so the group delay GD is represented by a range of values in the following table; for the same reason, the following table is given in numerical rangesThis condition is expressed.

TABLE 14 parameters of the optical systems provided by the various embodiments

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Other embodiments of the utility model will be apparent to those skilled in the art from consideration of the specification and practice of the utility model disclosed herein. This utility model is intended to cover any variations, uses, or adaptations of the utility model following, in general, the principles of the utility model and including such departures from the present disclosure as come within known or customary practice within the art to which the utility model pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the utility model being indicated by the following claims.

Claims

1. An optical system operating in the far infrared band, characterized by comprising, in order from an object side of the optical system to an image side of the optical system, along an optical axis of the optical system: a first chalcogenide refractive lens, a superlens, a second chalcogenide refractive lens; the first chalcogenide refractive lens and the second chalcogenide refractive lens are both positive lenses; the super lens comprises a substrate and a super structure unit, wherein a micro-nano structure is arranged in the super structure unit; the optical system satisfies the following conditions in units of 1/mm:

0.25≤n*(|C₁|+|C₂|)≤2.01

2. The optical system of claim 1, wherein the optical system further satisfies the following conditions in units of femtoseconds fs:

3. The optical system of claim 1, wherein the first and second chalcogenide refractive lenses are spherical lenses; the optical system also satisfies the following conditions in rad/mm ²:

4. The optical system of claim 1, wherein the optical system further satisfies the following condition:

5. The optical system of claim 1, wherein the micro-nano structure is a positive micro-nano structure or a negative micro-nano structure.

6. The optical system of claim 1, wherein the superlens comprises at least one layer of the superstructural units.

7. The optical system of claim 1, wherein the optical system is provided with a stop adjacent to the superlens; the diaphragm is arranged on the surface of the superlens, or the diaphragm and the superlens are arranged at intervals.

8. The optical system of claim 1, wherein the front surface of the first chalcogenide refractive lens is convex and the back surface of the first chalcogenide refractive lens is concave; the front surface of the second chalcogenide refractive lens is concave, and the rear surface of the second chalcogenide refractive lens is convex.

9. An optical lens operating in the far infrared band, the optical lens comprising: a lens barrel; a pressing ring, a first spacer, a second spacer, and the optical system according to any one of claims 1 to 8, which are provided inside the lens barrel;

10. The optical lens of claim 9, further comprising: window glass, imaging detector set on the image surface of the optical system; the window glass is arranged between the second chalcogenide refractive lens and the imaging detector.