CN220305552U - Heavy caliber secondary imaging system - Google Patents
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- CN220305552U CN220305552U CN202322001076.3U CN202322001076U CN220305552U CN 220305552 U CN220305552 U CN 220305552U CN 202322001076 U CN202322001076 U CN 202322001076U CN 220305552 U CN220305552 U CN 220305552U
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Abstract
The disclosure provides a large-caliber secondary imaging system, and relates to the technical field of super-surface imaging. The system includes a diaphragm and a plurality of optical elements disposed in an optical path of incident light; the plurality of optical elements are refractive lenses and superlenses, and include a first optical element, a second optical element, a third optical element, and a fourth optical element that are sequentially arranged along an optical path; the plurality of optical elements are configured to: enabling the incident light to be focused and imaged a first time after passing through the second optical element and focused and imaged a second time after passing through the fourth optical element. The system can realize passive temperature compensation and simultaneously reduce the number of lenses, so that the F number is smaller, and the advantages of thinness, simplicity and low cost of the superlens also greatly reduce the volume of the system.
Description
Technical Field
The present disclosure relates to the field of superlens imaging technology, and in particular, to a large-caliber secondary imaging system.
Background
The secondary imaging system generally uses a plurality of traditional lenses, however, the traditional lenses have larger temperature drift influence, so that the performance of the imaging system using the traditional lenses is unstable, and the imaging quality of the system is low.
Temperature drift effect is solved through temperature compensation in the prior art, so that stability and imaging quality of the system are improved. Such as a secondary imaging passive temperature compensating optical system provided in the western patent (CN 113448067B). Although the problem of temperature drift is solved, the number of the traditional lenses is too large, especially 6 aspherical lenses are used, and the F number of the system is large, so that the system is unfavorable for a large-caliber secondary imaging system.
Disclosure of Invention
In order to solve the problems in the prior art, embodiments of the present disclosure provide a large-caliber secondary imaging system. The system includes a diaphragm and a plurality of optical elements disposed in an optical path of incident light;
the plurality of optical elements are refractive lenses and superlenses, and include a first optical element, a second optical element, a third optical element, and a fourth optical element disposed in order along the optical path;
the plurality of optical elements are configured to: enabling the incident light to be focused and imaged a first time after passing through the second optical element and focused and imaged a second time after passing through the fourth optical element.
Optionally, the large-caliber secondary imaging system satisfies:
wherein L is 1 A distance between the first imaging location and the second imaging location; f is the equivalent focal length of the large-caliber secondary imaging system.
Optionally, the refractive lens is an aspherical mirror, the aspherical mirror is one of a first optical element, a second optical element, a third optical element and a fourth optical element, and the rest is a superlens.
Optionally, at least one diaphragm aperture is provided at the location of the first imaging.
Optionally, the large-caliber secondary imaging system satisfies:
wherein T is a1 Is the change value of refractive index of the aspherical mirror at the unit temperature of d light of reference light at the ambient temperature of +20 ℃ to +40 ℃, T a1 Is 10E-6/. Degree.C; n (N) a1 Is the refractive index of the aspherical mirror.
Optionally, the large-caliber secondary imaging system further satisfies:
wherein T is a1 The refractive index of the reference light is a change value of the refractive index of the aspherical mirror at the ambient temperature of +20 ℃ to +40 ℃ under the unit temperature of d light; n (N) a1 Is the refractive index of the aspherical mirror.
Optionally, the diaphragm is disposed on the front surface or the rear surface of the first optical element; wherein,
the large-caliber secondary imaging system also meets the following conditions:
wherein D is 1 Is the effective diameter of the first optical element; d is the entrance pupil diameter of the large-caliber secondary imaging system.
Optionally, the large-caliber secondary imaging system further satisfies:
wherein f a1 Is the focal length of the aspherical mirror; f is the equivalent focal length of the large-caliber secondary imaging system.
Optionally, the optical power of the superlens in the plurality of optical elements is greater than the system optical power, and comprises a first superlens (3), a second superlens (4) and a third superlens (5) arranged in sequence along the optical path; wherein,
the large-caliber secondary imaging system also meets the following conditions:
wherein f m1 A focal length of the first superlens; f (f) m2 A focal length of the second superlens; f (f) m3 A focal length of the third superlens; f is the equivalent focal length of the large-caliber secondary imaging system.
Optionally, the large-caliber secondary imaging system further satisfies:
f is the equivalent focal length of the large-caliber secondary imaging system; d is the entrance pupil diameter of the large-caliber secondary imaging system.
The technical scheme in the disclosure has the beneficial effects that:
the large-caliber secondary imaging system provided by the disclosure only uses 3 superlenses and 1 aspheric mirror, wherein the superlenses have the characteristics of small temperature drift and high stability when the temperature changes, the temperature compensation of the secondary imaging system can be realized, the temperature drift influence of the system is solved, the imaging quality of the system is ensured, the stability of the system in the temperature change is ensured, the imaging of the system is free from ghost shadow, and the cost is reduced.
In addition, compared with the prior art, the present disclosure not only uses a smaller number of lenses, but also its F-number can be reduced to 1.8, so that the aperture of the secondary imaging system can be larger. The superlens has the characteristics of simple manufacturing process, low cost and light weight, thereby reducing the whole volume of the system and conforming to the development trend of miniaturization.
Drawings
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure.
FIG. 1 is a schematic diagram of a large caliber secondary imaging system according to an embodiment;
FIG. 2 is a graph of MTF (modulation transfer function) data analysis for a large caliber secondary imaging system provided in example one at an ambient temperature of +20℃;
FIG. 3 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example one at an ambient temperature of-40 ℃;
FIG. 4 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example one at an ambient temperature of +85℃;
FIG. 5 is a schematic diagram of the composition of a large caliber secondary imaging system provided in example two;
FIG. 6 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example two at an ambient temperature of +20℃;
FIG. 7 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example two at an ambient temperature of-40 ℃;
FIG. 8 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example two at an ambient temperature of +85℃;
FIG. 9 is a schematic diagram of the composition of a large caliber secondary imaging system provided in example three;
FIG. 10 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example three at an ambient temperature of +20℃;
FIG. 11 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example three at an ambient temperature of-40 ℃;
FIG. 12 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example three at an ambient temperature of +85℃;
FIG. 13 is a schematic diagram of the composition of a large caliber secondary imaging system provided in example four;
FIG. 14 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example four at an ambient temperature of +20℃;
FIG. 15 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example four at an ambient temperature of-40 ℃;
fig. 16 is a graph of MTF data analysis for a large caliber secondary imaging system provided in example four at an ambient temperature of +85℃.
Reference numerals in the drawings denote:
1: a diaphragm; 2: an aspherical mirror; 3: a first superlens; 4: a second superlens; 5: and a third superlens.
Detailed Description
The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout. Also, in the drawings, the thickness, ratio, and size of the parts are exaggerated for clarity of illustration.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, "a," "an," "the," and "at least one" are not meant to limit the amount, but are intended to include both the singular and the plural. For example, unless the context clearly indicates otherwise, the meaning of "a component" is the same as "at least one component". The "at least one" should not be construed as limited to the number "one". "or" means "and/or". The term "and/or" includes any and all combinations of one or more of the associated listed items.
Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms as defined in commonly used dictionaries should be interpreted as having the same meaning as the relevant art context and are not interpreted in an idealized or overly formal sense unless expressly so defined herein.
The meaning of "comprising" or "including" indicates a property, quantity, step, operation, component, element, or combination thereof, but does not preclude other properties, quantities, steps, operations, components, elements, or combinations thereof.
Embodiments are described herein with reference to cross-sectional illustrations that are idealized embodiments. Thus, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region shown or described as being flat may typically have rough and/or nonlinear features. Also, the acute angles shown may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.
Hereinafter, exemplary embodiments according to the present disclosure will be described with reference to the accompanying drawings.
The embodiment of the disclosure provides a large-caliber secondary imaging system based on a super lens, which comprises: a diaphragm (1) and a plurality of optical elements arranged on the optical path of the incident light;
the plurality of optical elements are refractive lenses and superlenses, and include a first optical element, a second optical element, a third optical element, and a fourth optical element that are sequentially arranged along an optical path;
the plurality of optical elements are configured to: enabling the incident light to be focused and imaged a first time after passing through the second optical element and focused and imaged a second time after passing through the fourth optical element.
Further, the relationship between the distance between the position of the first imaging and the position of the second imaging and the equivalent focal length of the system satisfies:
wherein L is 1 A distance between the first imaging location and the second imaging location; f is the equivalent focal length of the large caliber imaging system.
According to the above embodiment, equation 1 represents the power distribution of the optical elements before and after the first imaging position, that is, the power distribution of the second optical element and the third optical element. The upper limit of equation 1 is to ensure that the optical power of the front optical element (second optical element) is not excessively large, and the temperature compensation effect thereof is not excessively large, thereby degrading the sensitivity of the second optical element; the lower limit of equation 1 is to prevent the optical power of the rear optical element (third optical element) from being excessively large, and to prevent the temperature compensation effect from being excessively large, thereby degrading the sensitivity of the third optical element.
According to the embodiment, at least one very small diaphragm hole can be arranged at the first imaging position, and the diaphragm hole can intercept a plurality of parasitic lights so as to achieve the effect of extremely low influence of ghosts in imaging, and further improve imaging quality.
According to the above embodiment, the four optical elements may be the first superlens 3, the second superlens 4, the third superlens, and the aspherical mirror 5, respectively, and in the embodiment of the present application, the order of the four optical elements is not limited.
Further, the first optical element may be an aspherical mirror 2, the second optical element may be a first superlens 3, the third optical element may be a second superlens 4, and the fourth optical element may be a third superlens 5; alternatively, the first optical element may be the first superlens 3, the second optical element may be the aspherical mirror 2, the third optical element may be the second superlens 4, and the fourth optical element may be the third superlens 5; alternatively, the first optical element may be the first superlens 3, the second optical element may be the second superlens 4, the third optical element may be the aspherical mirror 2, and the fourth optical element may be the third superlens 5.
Further, the temperature compensation performance that the aspherical mirror 2 can provide satisfies the relation:
wherein T is a1 The refractive index change value of the aspherical mirror 2 at the unit temperature of d light, which is the helium yellow line with the wavelength of 587.56nm, is the reference light at the ambient temperature of +20 ℃ to +40 ℃, T a1 Is 10E-6/. Degree.C; n (N) a1 Is the refractive index of the aspherical mirror 2.
Further, when the aspherical mirror 2 can provide temperature compensation performance satisfying the relation:
wherein T is a1 The refractive index change value of the aspherical mirror 2 at a unit temperature of d light, which is helium with a wavelength of 587.56nm, is the reference light at an ambient temperature of +20 ℃ to +40 DEG CYellow lines; n (N) a1 Is the refractive index of the aspherical mirror 2. At this time, the temperature compensation performance of the aspherical mirror 2 is optimal.
According to the formula (2) and the formula (3), the aspherical mirror 2 is used for providing main temperature compensation performance, and the upper limit and the lower limit in the formula (2) are used for ensuring that reasonable temperature compensation glass is selected and used, so that passive temperature compensation can be effectively regulated and controlled.
Further, to determine the position of the diaphragm 1, it is necessary that the entrance pupil diameter and the effective diameter of the first optical element satisfy the relation:
wherein D is 1 Is the effective diameter of the first optical element; d is the entrance pupil diameter of the large-caliber secondary imaging system.
The diaphragm 1 may be disposed on the front surface or the rear surface of the first optical element, and according to formula 1, the upper limit thereof is to ensure that the diaphragm 1 is located behind the rear surface of the first optical element, and the lower limit thereof is to ensure that the diaphragm 1 is located in front of the front surface of the first optical element, i.e., the upper and lower limits together ensure that the mechanical caliber of the system can be minimized.
Further, the focal length of the aspherical mirror 2 and the system equivalent focal length satisfy the relation:
wherein f a1 Is the focal length of the aspherical mirror 2; f is the equivalent focal length of the large-caliber secondary imaging system.
As can be seen from the above formula (6), the aspherical mirror 2 mainly plays a role of receiving light in the system. The upper limit is to ensure that the aspherical mirror has a certain optical power to finish the light adjustment within the length of the system, and the lower limit is to avoid that the aspherical mirror 2 provides a larger optical power, i.e. the larger the optical power of the aspherical mirror 2 is, the higher the assembly sensitivity is.
Further, the first superlens 3, the second superlens 4 and the third superlens 5 satisfy the relation with the equivalent focal length of the system:
wherein f m1 Is the focal length of the first superlens 3; f (f) m2 A focal length of the second superlens 4; f (f) m3 A focal length of the third superlens 5; f is the equivalent focal length of the large-caliber secondary imaging system.
From the above formulas (7), (8) and (9), it is clear that the superlens provides a far greater optical power in the system than the system, with the effect being mainly compensation of axial aberrations. The upper limit is to ensure that the superlens has a certain focal power to finish the light ray adjustment within the length of the system, and the lower limit is to avoid that the superlens provides larger focal power, and the larger the focal power of the superlens is, the larger spherical aberration is brought to the system.
Further, the equivalent focal length and the entrance pupil diameter of the system satisfy the relation:
f is the equivalent focal length of the large-caliber secondary imaging system; d is the entrance pupil diameter of the large-caliber secondary imaging system.
As can be seen from the formula (10), the current system belongs to a large aperture optical system, namely, the aperture use requirements of F1.8-F2.2 can be satisfied.
In the embodiment of the present disclosure, it is preferable that the phase distribution of the superlens satisfies the following formula:
according to the above embodiment, it is preferable that the aspherical mirror 2 has a surface shape of an even aspherical surface whose surface vector parallel to the z axis satisfies:
wherein c is the curvature of the center point of the aspherical mirror 2; r is the curvature radius of the center point of the aspherical mirror 2; k is a quadric constant; A. b, C, D, E, F, G, H, J are respectively corresponding higher order coefficients.
In the embodiment of the disclosure, the system is subjected to temperature compensation by using 3 superlenses and 1 aspheric mirror, so that the system is less influenced by temperature drift when the temperature changes, the imaging quality of the system is improved, and a plurality of parasitic lights are intercepted by arranging the diaphragm holes at the first imaging position, so that the effect of extremely low influence of imaging ghost images is achieved. Meanwhile, the system integrally adopts fewer lenses, and the F number of the system is smaller, so that the caliber of the secondary imaging system provided by the disclosure is larger, namely the large-caliber secondary imaging system has the characteristics of small size and light weight.
An example will be provided below to detail one type of large caliber secondary imaging system provided by the present disclosure.
Example 1
In the first embodiment provided in the present application, as shown in fig. 1, along the optical path of the incident light, a diaphragm 1, an aspherical mirror 2, a first superlens 3, a second superlens 4, and a third superlens 5 are sequentially disposed, where O in fig. 1 represents the optical axis, and I represents the image plane. The system parameters are shown in Table 1-1:
table 1-1 system parameters of embodiment one
| Parameters (parameters) | Data |
| System volume (TTL) | 75mm |
| Visual field (2 omega) | 2.84° |
| F number | 1.8 |
| Equivalent focal length | 90mm |
| Operating band | Near infrared light (1060 nm-1070 nm) |
According to the first embodiment, the data of each surface of the lens are shown in tables 1-2:
tables 1-2 surface data for lenses of example one
| Surface serial number | Surface type | Radius (mm) | Thickness (mm) | Material |
| 1 | Diaphragm | Infinite number of cases | -6 | — |
| 2 | Even aspherical surface | 24 | 21.3 | 1.59,68.3 |
| 3 | Even aspherical surface | -204.9 | 23.5 | — |
| 4 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 5 | Spherical surface | Infinite number of cases | 5.4 | — |
| 6 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 7 | Spherical surface | Infinite number of cases | 5.16 | — |
| 8 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 9 | Spherical surface | Infinite number of cases | 17.47 | — |
According to the first embodiment, the respective order coefficients of the aspherical mirror are shown in tables 1 to 3:
tables 1-3 the aspherical mirror order coefficients of embodiment one
| Surface serial number | K | A | B | C | D | E | F | G |
| 2 | -0.603 | 2.4387E-07 | -4.6702E-11 | 0 | 0 | 0 | 0 | 0 |
| 3 | -281 | 8.0E-07 | -1.7E-11 | 0 | 0 | 0 | 0 | 0 |
According to example 1 above, the performance output of the system is shown in fig. 2-4. Fig. 2 to 4 are graphs showing data analysis of MTF (modulation transfer function) of the large-caliber secondary imaging system provided in this embodiment at ambient temperatures of +20 ℃, -40 ℃ and +85 ℃, respectively. As shown in fig. 2, the MTF at 30 line pairs per millimeter is higher than 0.88 for half field angles between 0 ° -1.42 °. As shown in fig. 3, the MTF at 30 line pairs per millimeter is higher than 0.58 at half field angles of 0 ° -1.42 °. As shown in fig. 4, the MTF at 30 line pairs per millimeter is higher than 0.70 at half field angles of 0 ° -1.42 °. Fig. 2 to fig. 4 show that the MTF of the large-caliber secondary imaging system provided by the embodiment is greater than 0.5 at different environmental temperatures, and the large-caliber secondary imaging system can be well matched with the chip.
Example 2
In the second embodiment provided in the present application, as shown in fig. 5, along the optical path of the incident light, a diaphragm 1, a first superlens 3, an aspherical mirror 2, a second superlens 4, and a third superlens 5 are sequentially disposed, where O in fig. 5 represents the optical axis, and I represents the image plane. The system parameters are shown in Table 2-1.
Table 2-1 System parameters of embodiment two
| Parameters (parameters) | Data |
| System volume (TTL) | 75mm |
| Visual field (2 omega) | 2.84° |
| F number | 1.8 |
| Equivalent focal length | 90mm |
| Operating band | Near infrared light (1060 nm-1070 nm) |
According to the second embodiment, the data of each surface of the lens are shown in Table 2-2:
table 2-2 lens surface data for embodiment two
According to the second embodiment, the respective order coefficients of the aspherical mirror are shown in tables 2 to 3:
tables 2-3 aspherical mirror order coefficients for embodiment two
| Surface serial number | K | A | B | C | D | E | F | G |
| 4 | 1.124 | -1.17E-07 | 5.1E-08 | 0 | 0 | 0 | 0 | 0 |
| 5 | 5.64 | -2.8E-06 | 3.2E-07 | 0 | 0 | 0 | 0 | 0 |
The performance output of the system according to example 2 above is shown in fig. 6-8. Fig. 6 to 8 are graphs showing data analysis of MTF (modulation transfer function) of the large-caliber secondary imaging system provided in this embodiment at ambient temperatures of +20 ℃, -40 ℃ and +85 ℃, respectively. As shown in fig. 6, the MTF at 30 line pairs per millimeter is higher than 0.87 for half field angles of 0 ° -1.42 °. As shown in fig. 7, the MTF at 30 line pairs per millimeter is higher than 0.86 for half field angles of 0 ° -1.42 °. As shown in fig. 8, the MTF at 30 line pairs per millimeter is higher than 0.88 for half field angles between 0 ° -1.42 °. Fig. 6 to 8 show that the MTF curves of the large-caliber secondary imaging system provided by the embodiment are close to the diffraction limit under different fields at different environmental temperatures, and have good resolution.
Example 3
In the third embodiment provided in the present application, as shown in fig. 9, along the optical path of the incident light, the diaphragm 1, the first superlens 3, the second superlens 4, the aspherical mirror 2, and the third superlens 5 are sequentially disposed. In fig. 9, O represents an optical axis, and I represents an image plane. The system parameters are shown in Table 3-1.
TABLE 3-1 System parameters for example III
| Parameters (parameters) | Data |
| System volume (TTL) | 75mm |
| Visual field (2 omega) | 2.84° |
| F number | 1.8 |
| Equivalent focal length | 89mm |
| Operating band | Near infrared light (1060 nm-1070 nm) |
According to the third embodiment, the data of each surface of the lens are shown in Table 3-2:
table 3-2 lens surface data for example three
| Surface serial number | Surface type | Radius (mm) | Thickness (mm) | Material |
| 1 | Diaphragm | Infinite number of cases | 0 | — |
| 2 | Spherical surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 3 | Super surface | Infinite number of cases | 36.2 | — |
| 4 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 5 | Spherical surface | Infinite number of cases | 8.8 | — |
| 6 | Even aspherical surface | 82 | 3 | 1.54，55.7 |
| 7 | Even aspherical surface | -10.8 | 0.1 | — |
| 8 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 9 | Spherical surface | Infinite number of cases | 24.7 | — |
According to the third embodiment, the respective order coefficients of the aspherical mirror are shown in tables 3 to 3:
table 3-3 aspherical mirror order coefficients of embodiment three
| Surface serial number | K | A | B | C | D | E | F | G |
| 6 | 51 | -2.25E-04 | -6.8E-07 | 0 | 0 | 0 | 0 | 0 |
| 7 | 0.57 | 2.30E-04 | -1.6E-06 | 0 | 0 | 0 | 0 | 0 |
According to example 3 above, the performance outputs of the system are shown in fig. 10-12. Fig. 10 to 12 are graphs showing MTF (modulation transfer function) data analysis of the large-caliber secondary imaging system provided in this embodiment at ambient temperatures of +20 ℃, -40 ℃ and +85 ℃, respectively. As shown in fig. 10, the MTF at 30 line pairs per millimeter is higher than 0.82 at half field angles of 0 ° -1.42 °. As shown in fig. 11, the MTF at 30 line pairs per millimeter is higher than 0.82 at half field angles of 0 ° -1.42 °. As shown in fig. 12, the MTF at 30 line pairs per millimeter is higher than 0.73 at half field angles of 0 ° -1.42 °. Fig. 10 to 12 show that the MTF curves of the large-caliber secondary imaging system provided by the embodiment are close to the diffraction limit under different fields at different environmental temperatures, and have good resolution.
Example 4
In the fourth embodiment provided in the present application, as shown in fig. 13, the diaphragm 1, the first superlens 3, the second superlens 4, the third superlens 5, and the aspherical mirror 2 are sequentially disposed along the optical path of the incident light. In fig. 13, O represents an optical axis, and I represents an image plane. The system parameters are shown in Table 4-1.
Table 4-1 System parameters of embodiment IV
| Parameters (parameters) | Data |
| System volume (TTL) | 75mm |
| Visual field (2 omega) | 2.84° |
| F number | 1.8 |
| Equivalent focal length | 89mm |
| Operating band | Near infrared light (1060 nm-1070 nm) |
According to the fourth embodiment, the data of each surface are shown in Table 4-2:
table 4-2 lens surface data for example four
| Surface serial number | Surface type | Radius (mm) | Thickness (mm) | Material |
| 1 | Diaphragm | Infinite number of cases | 0 | — |
| 2 | Spherical surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 3 | Super surface | Infinite number of cases | 35.8 | — |
| 4 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 5 | Spherical surface | Infinite number of cases | 10.8 | — |
| 6 | Super surface | Infinite number of cases | 0.73 | 1.46，67.8 |
| 7 | Spherical surface | Infinite number of cases | 0.1 | — |
| 8 | Even aspherical surface | 20.6 | 2.2 | 1.54，55.7 |
| 9 | Even aspherical surface | -34.6 | 23.9 | — |
According to the fourth embodiment, the aspherical coefficients of each order are shown in tables 4 to 3:
table 4-3 aspherical coefficients of embodiment four
| Surface serial number | K | A | B | C | D | E | F | G |
| 8 | -0.06 | 1.8E-04 | -3.61E-07 | 0 | 0 | 0 | 0 | 0 |
| 9 | -36.5 | 1.85E-04 | -2.77E-06 | 0 | 0 | 0 | 0 | 0 |
According to the above example 4, the performance outputs of the system are shown in fig. 14 to 16 as graphs of MTF (modulation transfer function) data analysis of the large-caliber secondary imaging system provided in the present embodiment at the ambient temperatures of +20 ℃, -40 ℃ and +85 ℃, respectively. As shown in fig. 14, the MTF at 30 line pairs per millimeter is higher than 0.86 for half field angles of 0 ° -1.42 °. As shown in fig. 15, the MTF at 30 line pairs per millimeter is higher than 0.83 at half field angles of 0 ° -1.42 °. As shown in fig. 16, the MTF at 30 line pairs per millimeter is higher than 0.77 at half field angles of 0 ° -1.42 °. Fig. 14 to 16 show that the MTF curves of the large-caliber secondary imaging system provided by the embodiment are close to the diffraction limit under different fields at different environmental temperatures, and have good resolution.
The following table is a summary table of four examples provided by the present disclosure, as shown in table 5.
Table 5 conditional summary of four examples
Embodiments of the present disclosure also provide a supersurface comprising a superlens. The superlens consists of a substrate and a nano structure arranged on the substrate. In the embodiment of the disclosure, the nanostructure is an all-dielectric structural unit, has high transmittance in the visible light band, and the nanostructure optionally comprises: one or more of silicon nitride, titanium oxide, gallium nitride, gallium phosphide, and hydrogenated amorphous silicon. The nanostructures may be polarization dependent structures, such as nanofins and nanoellipsoids, which impart a geometric phase to incident light; the nanostructures may also be polarization independent structures, such as nano-cylinders and nano-square columns, which impart a propagation phase to the incident light.
In the above embodiments, the nanostructures are periodically arranged and form a super-structure unit, which is a close-packed pattern, such as square, hexagonal, or fan, and each period contains a set of nanostructures, and the vertices and/or centers of the super-structure unit may be provided with nanostructures, for example.
It should be noted that the superlens provided by the embodiments of the present disclosure may be processed by a semiconductor process, and has the advantages of light weight, thin thickness, simple structure and process, low cost, high mass production uniformity, and the like.
In summary, the large-caliber secondary imaging system provided by the embodiment of the disclosure uses 3 superlenses and 1 aspheric mirror to realize temperature compensation on the system, and the superlenses have the advantages of small temperature drift and high stability when the temperature changes, so that the system provided by the disclosure does not need excessive temperature compensation regulation and control, and the imaging quality of the system and the performance of the system when the temperature changes are ensured to be stable enough.
In addition, compared with the prior art, the system provided by the disclosure can realize temperature compensation by using only 4 lenses, and meanwhile, the superlens can provide spherical aberration for compensating phase to eliminate residual phase difference and fringe field of view so as to realize better imaging effect.
Because the superlens has the advantages of light weight, simplicity and low cost, the whole system has the advantages of small weight, small volume, simple manufacturing process and low cost.
While the embodiments of the present disclosure have been described in detail, the scope of the embodiments of the present disclosure is not limited thereto, and any changes or substitutions can be easily made by those skilled in the art within the scope of the embodiments of the present disclosure, which are intended to be covered by the embodiments of the present disclosure. Therefore, the protection scope of the embodiments of the present disclosure shall be subject to the protection scope of the claims.
Claims (10)
1. A large-caliber secondary imaging system is characterized by comprising a diaphragm (1) and a plurality of optical elements, wherein the diaphragm is arranged on the light path of incident light;
the plurality of optical elements are refractive lenses and superlenses, and include a first optical element, a second optical element, a third optical element, and a fourth optical element disposed in order along the optical path;
the plurality of optical elements are configured to: the incident light is allowed to be focused and imaged a first time after passing through the second optical element and focused and imaged a second time after passing through the fourth optical element.
2. The heavy caliber secondary imaging system of claim 1, wherein the heavy caliber secondary imaging system satisfies:
wherein L is 1 A distance between the first imaging location and the second imaging location; f is the equivalent focal length of the large-caliber secondary imaging system.
3. The large caliber secondary imaging system according to claim 1, wherein the refractive lens is an aspherical mirror (2), the aspherical mirror (2) is one of the first, second, third and fourth optical elements, and the rest is the superlens.
4. The large caliber secondary imaging system of claim 1 wherein at least one diaphragm aperture is provided at the location of the first imaging.
5. A heavy caliber secondary imaging system according to claim 3, wherein the heavy caliber secondary imaging system satisfies:
wherein T is a1 An ambient temperature of +20 ℃ to +40 ℃ for the aspherical mirror (2)The time reference light is the change value of refractive index at unit temperature of d light, T a1 Is 10E-6/. Degree.C; n (N) a1 Is the refractive index of the aspherical mirror (2).
6. The heavy caliber secondary imaging system of claim 5, wherein the heavy caliber secondary imaging system satisfies:
wherein T is a1 The refractive index change value of the aspherical mirror (2) at the unit temperature of d light is the reference light at the ambient temperature of +20 ℃ to +40 ℃; n (N) a1 Is the refractive index of the aspherical mirror (2).
7. The large caliber secondary imaging system according to claim 1, wherein the diaphragm (1) is provided to a front surface or a rear surface of the first optical element; wherein,
the large-caliber secondary imaging system also meets the following conditions:
wherein D is 1 An effective diameter for the first optical element; d is the entrance pupil diameter of the large-caliber secondary imaging system.
8. The large caliber secondary imaging system of claim 3, further satisfying:
wherein f a1 Is the focal length of the aspherical mirror (2); f is the equivalent focal length of the large-caliber secondary imaging system.
9. The large caliber secondary imaging system according to claim 1, wherein the optical power of the superlens in the plurality of optical elements is larger than the system optical power, and includes a first superlens (3), a second superlens (4), and a third superlens (5) disposed in this order along the optical path; wherein,
the large-caliber secondary imaging system also meets the following conditions:
wherein f m1 Is the focal length of the first superlens (3); f (f) m2 Is the focal length of the second superlens (4); f (f) m3 Is the focal length of the third superlens (5); f is the equivalent focal length of the large-caliber secondary imaging system.
10. The heavy caliber secondary imaging system of claim 7, further satisfying:
f is the equivalent focal length of the large-caliber secondary imaging system; d is the entrance pupil diameter of the large-caliber secondary imaging system.
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