CN216901111U - Large-relative-aperture large-target-surface long-wave infrared athermalization lens - Google Patents
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- CN216901111U CN216901111U CN202123256454.XU CN202123256454U CN216901111U CN 216901111 U CN216901111 U CN 216901111U CN 202123256454 U CN202123256454 U CN 202123256454U CN 216901111 U CN216901111 U CN 216901111U
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- 230000003287 optical effect Effects 0.000 claims abstract description 47
- 239000000463 material Substances 0.000 claims description 10
- 239000005387 chalcogenide glass Substances 0.000 claims description 7
- 229910052732 germanium Inorganic materials 0.000 claims description 5
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 3
- 238000003384 imaging method Methods 0.000 abstract description 7
- 230000004907 flux Effects 0.000 abstract description 2
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- 150000003839 salts Chemical class 0.000 abstract description 2
- 239000004576 sand Substances 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 5
- 230000004075 alteration Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 229910021385 hard carbon Inorganic materials 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
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Abstract
The invention discloses a long-wave infrared athermalization lens with a large relative aperture and a large target surface, which comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object space to an image space along an optical axis; the first lens is a negative focal power lens, the second lens is a positive focal power lens, the third lens is a negative focal power lens, and the fourth lens is a positive focal power lens; from the object space to the image space along the optical axis, two surfaces of the first lens are sequentially aspheric and spherical, two surfaces of the second lens are sequentially aspheric and spherical, two surfaces of the third lens are sequentially diffractive and aspheric, and two surfaces of the fourth lens are sequentially spherical and aspheric. The invention adopts optical compensation, and the imaging of the lens is clear, reliable and stable within the temperature range of-80 ℃ to 100 ℃; the relative aperture of the lens optical system is large, and the optical light flux is large; meanwhile, the designed image plane of the lens is large, and the lens can be used for a non-refrigeration detector 1024x768(17 um); the lens can be used in severe environments such as sand blown by wind, salt fog and the like.
Description
Technical Field
The invention relates to a large-relative-aperture large-target-surface long-wave infrared athermalization lens, in particular to an athermalization lens for a large-target-surface image plane, and belongs to the field of long-wave infrared band optical athermalization.
Background
In recent years, infrared uncooled detectors tend to be mature more and more, and infrared lenses are also widely applied to the fields of monitoring, security protection, military and the like. The infrared lens is under different ambient temperatures, because of the difference in temperature, the lens out of focus can all be caused to the change of curvature, thickness, the refracting index and the lens-barrel of lens. In order to eliminate the influence of temperature variation, a athermal design is required, and the athermal design usually adopts different optical materials to perform optical compensation (temperature difference), or adopts a design with a mechanical material and an optical material having a reverse variation trend to perform optical-mechanical compensation.
The target surface of the athermal lens disclosed at present is small in size and small in relative aperture (F number is large), along with the development of an uncooled detector, the movement of the detector tends to be large in target surface and high in pixel, and the infrared lens is required to be designed to be large in target surface size and large in relative aperture. However, it is known that the larger the image plane size, the larger the large relative aperture (the smaller the F #), and the greater the difficulty in designing the optical system.
Disclosure of Invention
The invention provides a long-wave infrared athermalization-free lens with large relative aperture and large target surface, which adopts optical compensation, and the imaging of the lens is clear, reliable and stable within the temperature range of-80-100 ℃; the defects of small size of a target surface of an athermal lens, small relative aperture (large F/# number) and the like in the prior art are overcome.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a long-wave infrared athermalization lens with a large relative aperture and a large target surface comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object side to an image side along an optical axis; the first lens is a negative focal power lens, the second lens is a positive focal power lens, the third lens is a negative focal power lens, and the fourth lens is a positive focal power lens; the optical axis is from an object space to an image space, two surfaces of the first lens are a first object side surface and a first image side surface in sequence, two surfaces of the second lens are a second object side surface and a second image side surface in sequence, two surfaces of the third lens are a third object side surface and a third image side surface in sequence, and two surfaces of the fourth lens are a fourth object side surface and a fourth image side surface in sequence, wherein the first object side surface is an aspheric surface, the first image side surface is a spherical surface, the second object side surface is an aspheric surface, the second image side surface is a spherical surface, the third object side surface is a diffraction surface, the third image side surface is an aspheric surface, the fourth object side surface is a spherical surface, and the fourth image side surface is an aspheric surface.
The long-wave infrared athermalization lens with the large relative aperture and the large target surface corrects high-level aberration by using aspheric and binary DOE (optical element analysis) technologies, positive thermal difference generated by the first lens and the third lens and negative thermal difference generated by the second lens and the fourth lens are compensated by eliminating thermal difference, and the lens imaging is clear, reliable and stable within the temperature range of-80-100 ℃.
In order to further improve the effect of eliminating the thermal difference, the first lens, the third lens and the fourth lens are made of single-crystal germanium materials, and whether a hard carbon film is plated or not can be selected according to application; the second lens adopts chalcogenide glass material with low photo-thermal coefficient.
In order to further improve the imaging effect, the curvature radius of the first object side surface is 80.42 +/-0.02 mm, and the curvature radius of the first image side surface is 65.00 +/-0.02 mm; the radius of curvature of the second image side surface is 62.10 +/-0.02 mm, and the radius of curvature of the second image side surface is-1640.00 +/-0.02 mm; the radius of curvature of the third object side surface is 29.06 +/-0.02 mm, and the radius of curvature of the third image side surface is 21.47 +/-0.02 mm; the radius of curvature of the fourth object-side surface is-74.01 + -0.02 mm, and the radius of curvature of the fourth image-side surface is-51.29 + -0.02 mm.
In order to further take the stability and the effect of imaging into consideration, the central thickness of the first lens is 3.20 +/-0.05 mm, the central thickness of the second lens is 6.50 +/-0.05 mm, the central thickness of the third lens is 9.00 +/-0.05 mm, and the central thickness of the fourth lens is 6.00 +/-0.05 mm. The center interval between the first lens and the second lens is 16.84 + -0.02 mm, the center interval between the second lens and the third lens is 0.80 + -0.02 mm, and the center interval between the third lens and the fourth lens is 5.35 + -0.02 mm.
In order to further ensure the imaging effect, the outer diameter of the first lens is 35-37 mm, the outer diameter of the second lens is 37 +/-0.05 mm, the outer diameter of the third lens is 25.2-35.6 mm, and the outer diameter of the fourth lens is 25-26.4 mm.
The aspheric surface equation adopted by each aspheric surface is as follows:
wherein Z (Y) is a lens run-out of the aspherical surface in the optical axis direction; r is the radius of curvature of the lens; y is a half aperture of the lens perpendicular to the optical axis direction; k is the conic coefficient; A. b, C, D, E are aspheric coefficients.
The expression adopted by the diffraction surface is as follows:
wherein,
is the phase of the diffraction plane; y is a half aperture of the lens perpendicular to the optical axis direction; a1 and A2 are diffraction plane phase coefficients.
The long-wave infrared athermalization lens with large relative aperture and large target surface has a focal length of 25mm, an F number of 1.0, a working wavelength band of 8-12um, and is suitable for infrared movement with pixels of 1024x768 and pixel size of 17 um.
The prior art is referred to in the art for techniques not mentioned in the present invention.
The large-relative-aperture large-target-surface long-wave infrared athermalization lens adopts optical compensation, and the imaging of the lens is clear, reliable and stable within the temperature range of-80-100 ℃; the relative aperture of the lens optical system is large (F number is 1.0 and is small), and the optical light flux is large; meanwhile, the image plane designed by the lens is large, the lens can be used for a non-refrigeration detector 1024x768(17um), the diagonal size is 21.8mm, and compared with a large target surface detector (1280x1024@12um detector) released by the current detector manufacturer, the diagonal size of the target surface designed by the lens is obviously large; furthermore, the first lens is made of a single crystal germanium material, a hard carbon film is easier to plate than chalcogenide glass, the surface of the first lens cannot be scratched, and the lens can be used in severe environments such as sand wind, salt fog and the like.
Drawings
FIG. 1 is an optical schematic diagram of a large relative aperture large target surface long-wave infrared athermalization lens of an embodiment;
FIG. 2 is a graph of MTF for a particular embodiment at 20 ℃ ambient temperature;
FIG. 3 is a graph of MTF for a specific embodiment at ambient temperature-80 deg.C;
FIG. 4 is a graph of MTF at 100 deg.C of ambient temperature for a specific embodiment;
FIG. 5 is a spot diagram of the exemplary embodiment at 20 deg.C ambient temperature;
FIG. 6 is a graph of light spots at ambient temperature-80 ℃ for the specific embodiment;
FIG. 7 is a graph of light spots for an embodiment at an ambient temperature of 100 ℃;
FIG. 8 is a graph of field curvature versus distortion for an embodiment at an ambient temperature of 20 ℃;
FIG. 9 is a graph of field curvature and distortion at ambient temperature-80 ℃ for the example embodiment;
FIG. 10 is a graph of field curvature and distortion at ambient temperature 100 ℃ for a specific embodiment.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.
As shown in fig. 1, the optical system of the long-wave infrared athermalization lens with large relative aperture and large target surface is sequentially arranged from an object side to an image side along an optical axis: a first lens L1 having negative power, a system stop ST, a second lens L2 having positive power, a third lens L3 having negative power, a fourth lens L4 having positive power, a detector window W, and an image plane S. The infrared detector is suitable for 8-12um infrared band, 25mm focal length, 1.0F number, 1024x768 detector pixels and 17um pixel size.
In the infrared athermal lens optical system, the first lens L1, the third lens L3 and the fourth lens L4 are made of germanium materials, and the germanium materials have high refractive index, are more favorable for aberration correction and are easier to be plated with hard carbon films; the second lens uses chalcogenide glass, the refractive index of the chalcogenide glass is relatively small along with the coefficient of change dn/dT of the temperature, and the chalcogenide glass can achieve a good athermalization effect when used in an infrared athermal optical system. In the aspect of production and processing, the chalcogenide glass can be polished and turned, and can also be subjected to high-precision die pressing, so that the cost can be reduced during batch production, and great advantages are achieved.
The infrared athermal lens optical system is matched with a detector, the image plane specification is 1024x768, the pixel is 17um, and the image plane size is larger, so that the system aperture diaphragm is arranged between the first lens and the second lens.
Fig. 2 to 4 are graphs of optical transfer functions of the athermal lens optical system at ambient temperatures of +20 ℃, -80 ℃, and +100 ℃ respectively, which can determine the resolution of the optical system, and it can be known from the graphs that the optical transfer function of the long-wave infrared athermal lens is close to the diffraction limit, which is sufficient to meet the practical requirements. Fig. 5 to 7 are spot diagrams of the athermalized lens optical system in different fields of view at ambient temperatures of +20 ℃, -80 ℃ and +100 ℃, respectively, the focused spot of the system is close to the airy-fleshed spot, and the practical requirement is met for a pixel size of 17 um. Fig. 8 to 10 are graphs of field curvature and distortion of the athermal lens optical system at ambient temperature of +20 ℃, -80 ℃, +100 ℃, respectively, and the field curvature and distortion of the system are well controlled.
The optical system parameters of the present embodiment are shown in table 1, table 2 and table 3.
Table 1 is a parameter table of optical elements
In table 1, the first lens element has first object-side surface S1 and first image-side surface S2 on both surfaces thereof, the second lens element has second object-side surface S4 and second image-side surface S5 on both surfaces thereof, the third lens element has third object-side surface S6 and third image-side surface S7 on both surfaces thereof, and the fourth lens element has fourth object-side surface S8 and fourth image-side surface S9 on both surfaces thereof.
Aspheric equation used in Table 1
The meaning of each quantity in the equation is as follows:
z (Y) is a lens run-out of the aspherical surface in the optical axis direction;
r is the radius of curvature of the lens;
y is a half aperture of the lens in a direction perpendicular to the optical axis;
k is the conic coefficient;
A. b, C, D, E are aspherical coefficients, see table 2 for specific data.
Table 2 shows aspherical coefficients of examples
| Aspherical surface | K | A | B | C | D | E |
| S1 | 0 | -2.223E-06 | 1.755E-09 | -2.658E-13 | ||
| S4 | 0 | 4.7005E-06 | 5.6192E-09 | -6.1E-11 | 7.6835E-14 | |
| S6 | 0 | -3.283E-07 | 2.05E-08 | -2.683E-11 | 5.7523 | |
| S7 | ||||||
| 0 | 1.0602E-05 | -1.725E-07 | 7.3824E-10 | -2.77E-12 | 2.1833E-14 | |
| S9 | 0 | 6.5295E-06 | -1.06E-08 | 4.0118E-10 | -2.607E-12 |
Table 3 shows the diffraction surface coefficients of the examples
| Diffraction surface | Diffraction orders | Center wavelength | A1 | A2 |
| S6 | 17.8 | 10um | -52.3822 | 3.4179 |
The expression adopted by the above diffraction planes is:
the meanings of the amounts in the expression are as follows:
y is a half aperture of the lens perpendicular to the optical axis direction;
a1 and A2 are diffraction plane phase coefficients.
Fig. 2 to 4 are graphs of optical transfer functions of the athermal lens optical system at ambient temperature of +20 ℃, -80 ℃, and +100 ℃ respectively, which represent resolving power of the optical system with temperature change. Fig. 5 to 7 are speckle patterns of the athermalized lens optical system in different fields of view at ambient temperatures of +20 ℃, -80 ℃, and +100 ℃. Fig. 8 to 10 are graphs of field curvature and distortion of the athermal lens optical system at ambient temperature of +20 ℃, -80 ℃, and +100 ℃. It can be seen from the figure that the aberration of each environmental temperature is well corrected, the MTF performance is good, the diffuse spot is close to the Elegano spot, and the distortion is less than 2%.
Claims (9)
1. The utility model provides a big target surface long wave infrared athermalization camera lens of big relative aperture which characterized in that: the lens comprises a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence from an object side to an image side along an optical axis; the first lens is a negative focal power lens, the second lens is a positive focal power lens, the third lens is a negative focal power lens, and the fourth lens is a positive focal power lens; from an object space to an image space along an optical axis, two surfaces of a first lens are a first object side surface and a first image side surface in sequence, two surfaces of a second lens are a second object side surface and a second image side surface in sequence, two surfaces of a third lens are a third object side surface and a third image side surface in sequence, and two surfaces of a fourth lens are a fourth object side surface and a fourth image side surface in sequence, wherein the first object side surface is an aspheric surface, the first image side surface is a spherical surface, the second object side surface is an aspheric surface, the second image side surface is a spherical surface, the third object side surface is a diffraction surface, the third image side surface is an aspheric surface, the fourth object side surface is a spherical surface, and the fourth image side surface is an aspheric surface.
2. The large relative aperture large target surface long wave infrared athermalization lens of claim 1, wherein: the first lens, the third lens and the fourth lens are made of single crystal germanium materials; the second lens is made of chalcogenide glass material.
3. The large relative aperture large target surface long wave infrared athermalization lens of claim 1 or 2, wherein: the curvature radius of the first object side surface is 80.42 +/-0.02 mm, and the curvature radius of the first image side surface is 65.00 +/-0.02 mm; the radius of curvature of the second image side surface is 62.10 +/-0.02 mm, and the radius of curvature of the second image side surface is-1640.00 +/-0.02 mm; the radius of curvature of the third object side surface is 29.06 +/-0.02 mm, and the radius of curvature of the third image side surface is 21.47 +/-0.02 mm; the radius of curvature of the fourth object side is-74.01 + -0.02 mm, and the radius of curvature of the fourth image side is-51.29 + -0.02 mm.
4. The large relative aperture large target surface long wave infrared athermalization lens of claim 1 or 2, wherein: the center thickness of the first lens is 3.20 +/-0.05 mm, the center thickness of the second lens is 6.50 +/-0.05 mm, the center thickness of the third lens is 9.00 +/-0.05 mm, and the center thickness of the fourth lens is 6.00 +/-0.05 mm.
5. The large relative aperture large target surface long wave infrared athermalization lens of claim 1 or 2, wherein: the center interval between the first lens and the second lens is 16.84 + -0.02 mm, the center interval between the second lens and the third lens is 0.80 + -0.02 mm, and the center interval between the third lens and the fourth lens is 5.35 + -0.02 mm.
6. The large relative aperture large target surface long wave infrared athermalization lens of claim 1 or 2, wherein: the outer diameter of the first lens is 35-37 mm, the outer diameter of the second lens is 37 +/-0.05 mm, the outer diameter of the third lens is 25.2-35.6 mm, and the outer diameter of the fourth lens is 25-26.4 mm.
7. The large relative aperture large target surface long wave infrared athermalization lens of claim 1 or 2, wherein: the aspherical equation used was:
wherein Z (Y) is a lens run-out of the aspherical surface in the optical axis direction; r is the radius of curvature of the lens; y is a half aperture of the lens perpendicular to the optical axis direction; k is the conic coefficient; A. b, C, D, E are aspheric coefficients.
8. The large-relative-aperture large-target-surface longwave infrared athermalization lens of claim 1 or 2, wherein: the expression adopted by the diffraction surface is:
wherein,
is the phase of the diffraction plane; y is a half aperture of the lens perpendicular to the optical axis direction; a1 and A2 are diffraction plane phase coefficients.
9. The large relative aperture large target surface long wave infrared athermalization lens of claim 1 or 2, wherein: the focal length is 25mm, the F number of the athermal lens is 1.0, the working wavelength band is 8-12um, and the athermal lens is suitable for an infrared movement with pixels of 1024x768 and pixel size of 17 um.
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| CN202123256454.XU CN216901111U (en) | 2021-12-23 | 2021-12-23 | Large-relative-aperture large-target-surface long-wave infrared athermalization lens |
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| CN202123256454.XU CN216901111U (en) | 2021-12-23 | 2021-12-23 | Large-relative-aperture large-target-surface long-wave infrared athermalization lens |
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