CN216848318U - Small-size athermal thermal imaging optical system - Google Patents
Small-size athermal thermal imaging optical system Download PDFInfo
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- CN216848318U CN216848318U CN202220666475.4U CN202220666475U CN216848318U CN 216848318 U CN216848318 U CN 216848318U CN 202220666475 U CN202220666475 U CN 202220666475U CN 216848318 U CN216848318 U CN 216848318U
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Abstract
The utility model relates to a small-size no thermalization thermal imaging optical system belongs to no thermalization imaging optical system technical field, has solved current no thermalization optical system and has received the unable clear imaging of restriction such as illumination intensity, temperature and the complicated problem of structure. A small-sized athermal thermal imaging optical system sequentially comprises a first lens, a second lens, a third lens, a fourth lens and an infrared focal plane detector from an object space to an image space along a light incidence direction; the refractive indexes of the first lens, the second lens, the third lens and the fourth lens are all more than 2.4; the combined focal length of the optical system is f, and the focal length f1 of the first lens meets the following conditions: | f1/f | of more than or equal to 7.5 is less than or equal to 27.6; the focal length f2 of the second lens satisfies: | f2/f | is more than or equal to 0.9 and less than or equal to 1.3; the focal length f3 of the third lens satisfies: | f3/f | is more than or equal to 4.5 and less than or equal to 38.2; the focal length f4 of the fourth lens satisfies: the absolute value of f4/f is more than or equal to 2.3 and less than or equal to 7.8. The utility model discloses an optical system can adapt to the low, wide temperature range environment of illuminance, and overall structure is miniaturized.
Description
Technical Field
The utility model relates to a do not have thermalization imaging optical system technical field, especially relate to a small-size do not have thermalization thermal imaging optical system.
Background
With the continuous development of optical technology, higher requirements are put forward on the imaging quality, the working temperature and the volume miniaturization of an optical system. When the environmental temperature changes, the optical element and the mechanical element of the optical system generate thermal effect, so that the image plane of the optical system deviates, the imaging quality becomes low, and the comprehensive performance of the imaging system is finally influenced. The existing athermalized optical system has the following problems:
(1) in order to enable a thermal imaging optical system to adapt to various environments with large temperature difference, crystalline materials such as silicon, germanium, zinc sulfide, zinc selenide and the like and sulfides are adopted as lens materials of the thermal imaging optical system in the prior art, although the refractive index temperature coefficient of the materials is much larger than that of a visible light lens material, the optimal image plane is shifted due to temperature change, so that image blurring is caused, and the imaging quality is reduced.
(2) In order to improve the imaging quality of an optical system in the prior art, most of the optical systems adopt a large number of spherical lenses to correct aberrations, so that the number of required lenses is large, and the overall weight, volume and cost of the optical system are increased.
SUMMERY OF THE UTILITY MODEL
In view of the foregoing analysis, the present invention is directed to a small athermal optical imaging system, which is used to solve the problem that the conventional athermal optical system cannot be clearly imaged and has a complicated structure due to the limitation of illumination intensity and temperature.
The purpose of the utility model is mainly realized through the following technical scheme:
a small-sized athermal thermal imaging optical system sequentially comprises a first lens, a second lens, a third lens, a fourth lens and an infrared focal plane detector from an object space to an image space along a light incidence direction; the refractive indexes of the first lens, the second lens, the third lens and the fourth lens are all more than 2.4; the combined focal length of the optical system is f, and the focal length f1 of the first lens meets the following conditions: | f1/f | of more than or equal to 7.5 is less than or equal to 27.6; the focal length f2 of the second lens satisfies: | f2/f | is more than or equal to 0.9 and less than or equal to 1.3; the focal length f3 of the third lens satisfies: | f3/f | is more than or equal to 4.5 and less than or equal to 38.2; the focal length f4 of the fourth lens satisfies: the absolute value of f4/f is more than or equal to 2.3 and less than or equal to 7.8.
Furthermore, the refractive index n1 of the first lens is more than or equal to 4; the refractive index n2 of the second lens is more than or equal to 2.8; the refractive index n3 of the third lens is more than or equal to 2.4; the refractive index n4 of the fourth lens is larger than or equal to 4.
Further, the first lens is a concave-convex negative power lens; the second lens is a biconvex positive focal power lens; the third lens is a meniscus negative focal power lens; the fourth lens is a meniscus positive power lens.
Further, an aperture stop is also included.
Further, the aperture stop is disposed on an object-side surface of the second lens.
Further, a diffraction ring zone is arranged on the image side surface of the third lens.
Further, the object side surface or the image side surface of the first lens, the second lens, the third lens and the fourth lens is a spherical surface, and the other surface of the first lens, the second lens, the third lens and the fourth lens is an aspheric surface.
Further, the object side surface of the first lens, the object side surface of the second lens, the object side surface of the third lens and the image side surface of the fourth lens are set to be spherical surfaces; the image side surface of the first lens, the image side surface of the second lens, the image side surface of the third lens and the object side surface of the fourth lens are aspheric.
Further, the range of the distance d12 between the center of the image side surface of the first lens and the center of the object side surface of the second lens is 12.5 mm-13.9 mm-12 mm; the range of a distance d23 between the center of the image side surface of the second lens and the center of the object side surface of the third lens is more than or equal to 0.5mm and less than or equal to d23 and less than or equal to 3.3mm, and the range of a distance d34 between the center of the image side surface of the third lens and the center of the object side surface of the fourth lens is more than or equal to 1mm and less than or equal to d34 and less than or equal to 5.2 mm; the range of the distance BFL between the center of the image side surface of the fourth lens and the imaging surface of the infrared focal plane detector is 9.4 mm-10.5 mm.
Further, the optical system combined focal length f and the optical system clear aperture D satisfy: f/D is more than or equal to 0.9 and less than or equal to 1.1.
The utility model discloses can realize one of following beneficial effect at least:
(1) the utility model discloses a different crystal system materials and sulphide are used as thermal imaging optical system's lens material and aspheric use to equitable lens focal power distribution, collocation, make the utility model discloses use less quantity lens just can realize no matter daytime or night homoenergetic can be to the clear formation of image of heat radiation of 8-14 mu m wave band, optical system optics aberration diminishes, and the field of view scope is wide and simple structure, light in weight, with low costs.
(2) The utility model discloses a with the rational arrangement of aperture stop position setting in second lens thing side, make the utility model discloses miniaturized night vision thermal imaging optical system can receive more external thermal radiation to effectively reduce the maximum bore of each lens of camera lens optical system, alleviateed the lens quality, be favorable to simplifying the structure and realize that optical system is miniaturized.
(3) The utility model discloses processing the diffraction clitellum that the optical axis is the center pin on the lens surface, making the lens surface become the diffraction face, because the diffraction face has better correction thermal aberration and chromatic aberration characteristic, can guarantee that optical system can be in the clear formation of image of temperature range-40 ℃ -80 ℃ homoenergetic to need not to design focusing mechanism compensation optical system in addition and because of the defocusing image plane that temperature variation caused, do benefit to and realize that optical system is miniaturized.
The utility model discloses in, can also make up each other between the above-mentioned each technical scheme to realize more preferred combination scheme. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout the drawings.
Fig. 1 is an optical system diagram of a small athermal thermal imaging optical system according to the present invention;
FIG. 2 is a graph of MTF at-40 ℃ for a compact athermal thermal imaging optical system according to the present invention;
fig. 3 is a MTF graph of a small athermal thermal imaging optical system of the present invention at 20 ℃;
fig. 4 is a MTF graph of a small athermal thermal imaging optical system of the present invention at 80 ℃;
fig. 5 is a field-of-view distortion plot of a preferred embodiment of a compact athermal thermal imaging optical system according to the present invention.
Reference numerals are as follows:
100-small athermal thermal imaging optics;
0-aperture diaphragm; 1-a first lens; 2-a second lens; 3-a third lens; 4-a fourth lens; 5-infrared focal plane detector; 51-a detector protection window; 52-detector imaging plane; an X-ray axis;
s1 — the first lens object side; s2 — the first lens image side; s3 — the second lens object side; s4 — the second lens image side; s5 — third lens object side; s6-the third lens image side surface; s7-fourth lens object side; s8-the image side surface of the fifth lens; s9-protecting the side face of the window by the detector; s10-protecting the side face of the window image by the detector; s11-infrared focal plane detector imaging plane.
Detailed Description
The following detailed description of the preferred embodiments of the invention, which is to be read in connection with the accompanying drawings, forms a part of this application, and together with the embodiments of the invention, serve to explain the principles of the invention and not to limit its scope.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the term "connected" should be interpreted broadly, and may be, for example, a fixed connection, a detachable connection, or an integral connection, which may be a mechanical connection, an electrical connection, which may be a direct connection, or an indirect connection through an intermediate medium. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.
The terms "top," "bottom," "above … …," "below," and "on … …" as used throughout the description are relative positions with respect to components of the device, such as the relative positions of the top and bottom substrates inside the device. It will be appreciated that the devices are multifunctional, independent of their orientation in space.
The utility model discloses usual working face can be plane or curved surface, can incline, also can the level. For convenience of explanation, the embodiments of the present invention are placed on a horizontal plane and used on the horizontal plane, and thus "high and low" and "up and down" are defined.
The utility model discloses a specific embodiment discloses a small-size no thermalization thermal imaging optical system 100, includes first lens 1, second lens 2, third lens 3, fourth lens 4 and infrared focal plane detector 5 from the object space to the image space according to light incident direction along optical axis X in proper order.
Further, the first lens 1 is a concave-convex negative power lens; the second lens 2 is a biconvex positive focal power lens; the third lens 3 is a meniscus negative focal power lens; the fourth lens 4 is a meniscus positive power lens.
Further, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, and the optical system combined focal length is f, and the focal lengths of the four lenses and the optical system combined focal length f respectively satisfy the following formulas: | f1/f | of more than or equal to 7.5 is less than or equal to 27.6; | f2/f | is more than or equal to 0.9 and less than or equal to 1.3; | f3/f | is more than or equal to 4.5 and less than or equal to 38.2; the absolute value of f4/f is more than or equal to 2.3 and less than or equal to 7.8. This embodiment makes light gently transition in small-size no thermal imaging optical system 100 of heating through each lens focal power reasonable distribution to can reduce lens tolerance sensitivity, make it reduce the lens machining precision requirement, reduce overall cost, be favorable to lens processing and optical system assembly simultaneously.
The material used for the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 is a crystal material or chalcogenide glass having a refractive index of 2.4 or more at a wavelength of 10 μm.
Specifically, the refractive index n1 of the first lens 1 is more than or equal to 4, the refractive index n2 of the second lens 2 is more than or equal to 2.8, and the refractive index n3 of the third lens 3 is more than or equal to 2.4; the refractive index n4 of the fourth lens 4 is larger than or equal to 4. The utility model discloses only realize clear formation of image through the cooperation of above four kinds of different characteristic optical materials, simplify system architecture, weight reduction, reduce cost.
It is worth to explain that the chalcogenide glass in the utility model has smaller temperature coefficient of refractive index, thereby having important function in the thermal defocusing adjustment and chromatic aberration correction of the infrared thermal imaging optical system. Further, chalcogenide glass has a low dispersion coefficient, i.e., a large abbe number, and thus has a high achromatization ability.
Further, the small athermal thermal imaging optical system 100 further comprises an aperture stop 0, and the aperture stop 0 is disposed between the first lens 1 and the fourth lens 4.
Alternatively, the aperture stop 0 may be disposed between the first lens 1 and the second lens 2, or between the second lens 2 and the third lens 3, or between the third lens 3 and the fourth lens 4, or a surface of the object-side surface S1 of the first lens 1, or a surface of the image-side surface S2 of the first lens 1, or a surface of the object-side surface S3 of the second lens 2, or a surface of the image-side surface S4 of the second lens 2, or a surface of the object-side surface S5 of the third lens 3, or a surface of the image-side surface S6 of the third lens 3, or a surface of the object-side surface S7 of the fourth lens 4, or a surface of the image-side surface S8 of the fourth lens 4.
Preferably, the aperture stop 0 is disposed on the surface of the object-side surface S3 of the second lens 2, so that the overall aperture size of the optical system can be effectively reduced while a large luminous flux is ensured, the miniaturization of the overall optical system is facilitated, and meanwhile, a mechanical part for separately designing the aperture stop 0 is not required, so that the structure is simplified, and the assembly is easy.
Further, in the present embodiment, the object-side surface S1 of the first lens 1 is set to be spherical, and the image-side surface S2 of the first lens 1 is set to be aspherical; the object side surface S3 of the second lens 2 is arranged to be spherical, and the image side surface S4 of the second lens 2 is arranged to be aspherical; the object side surface S5 of the third lens element 3 is spherical, and the image side surface S6 of the third lens element 3 is aspherical; the object side surface S7 of the fourth lens element 4 is aspheric, and the image side surface S8 of the fourth lens element 4 is spherical.
It is worth to be noted that the optical system adopts an aspheric surface to correct aberration such as spherical aberration, coma aberration and astigmatism; compared with a spherical lens, the aspherical lens has more freedom degrees, and the capability of correcting aberration is stronger than that of the spherical lens, and if the spherical lens is to achieve the same effect, the number of lenses and the types of materials must be increased, so that the weight of the optical system is increased, the structure of the optical system is complicated, and the miniaturization of the optical system is not facilitated. However, the aspheric surface has high difficulty and cost, so the best effect is achieved by combining the spherical surface and the aspheric surface.
Further, the aspherical surface type of the aspherical lens satisfies the following expression:
in the formula, Z is the rise of the distance (Sag) from the vertex of the aspheric surface when the aspheric surface is at the position with the height of h along the X direction of the optical axis, the parameter C is the curvature corresponding to the radius of the aspheric surface, Y is a radial coordinate, and the coefficient K is a conic section coefficient; n is a multiple of 2.
Specifically, when K is less than-1, the surface-shaped curve of the lens is a hyperbolic curve, and when K is equal to-1, the surface-shaped curve of the lens is a parabola; when K is between-1 and 0, the surface curve of the lens is an ellipse, when K is equal to 0, the surface curve of the lens is a circle, and when K is more than 0, the surface curve of the lens is an oblate circle. Wherein A is2To AnRespectively representing coefficients corresponding to the radial coordinates; n is a multiple of 2.
Further, the aspherical surface type parameters of each lens surface of this example are shown in Table 1.
TABLE 1
| Number of noodles | K | A2 | A4 | A6 | | A10 |
| S2 | ||||||
| 0 | 0 | 8.231E-06 | 3.625E-08 | -1.655E-10 | 4.170 | |
| S4 | ||||||
| 0 | 0 | 6.909E-06 | -3.506E-08 | 2.310E-10 | -2.500 | |
| S6 | ||||||
| 0 | 0 | -2.545E-06 | 3.010E-07 | 8.128E-09 | -1.114 | |
| S7 | ||||||
| 0 | 0 | -2.544E-05 | -8.965E-08 | 4.285E-09 | -8.645E-11 |
The present embodiment adopts the specific combination of the spherical surface and the aspherical surface, which not only improves the imaging quality, but also effectively reduces the number of lenses, simplifies the structure of the optical system and reduces the weight, and simultaneously controls the overall cost.
Further, a diffraction ring zone, that is, a diffraction structure in the form of a ring zone, is provided on the image-side surface of the third lens 3 so that the image-side surface S6 becomes a diffraction surface. The central wavelength of the diffraction zone structure is 10 μm, the diffraction order is +1 order, and the phase distribution
The following expressions are satisfied:
where r denotes the normalized radial coordinate of the lens surface and B1, B2 are the respective order coefficients. The diffraction ring zone is a ring zone taking an optical axis X as a central axis, thermal aberration and chromatic aberration can be corrected through the diffraction surface, the optical system can be ensured to be capable of clearly imaging within the temperature range of-40 ℃ to 80 ℃, a focusing mechanism is not required to be additionally designed to compensate defocusing of an image surface of the optical system caused by temperature change, and the miniaturization of the optical system is favorably realized.
Specifically, the parameters of the diffraction zone processed on the image-side surface S6 of the third lens element 3 are shown in table 2, and table 2 shows the parameters of the diffraction surface of the image-side surface S6 of the third lens element 3.
TABLE 2
| Surface of | Number of items | r | | B2 |
| S6 | ||||
| 2 | 8 | -35.4141 | -2.8935 |
The present embodiment achieves both athermalization and achromatization functions based on the optimized results of the above optimal values of the diffraction planes. It should be noted that the diffraction surface has a negative chromatic aberration coefficient, and the refractive lens has a positive chromatic aberration coefficient (the chalcogenide glass achromatism capability is determined by the material characteristics), so the present embodiment achieves the entire achromatism effect by the mutual cancellation of the negative chromatic aberration optimized by the diffraction surface and the positive chromatic aberration formed by the special arrangement of the refractive lens.
Further, the range of the interval d12 between the center of the first lens 1 image side surface S2 and the center of the second lens 2 object side surface S3 satisfies that d12 is more than or equal to 12.5mm and less than or equal to 13.9 mm; the range of a spacing d23 between the center of the second lens 2 image-side surface S4 and the center of the third lens 3 object-side surface S5 satisfies 0.5mm ≤ d23 ≤ 3.3mm, and the range of a spacing d34 between the center of the third lens 3 image-side surface S6 and the center of the fourth lens 4 object-side surface S7 satisfies 1mm ≤ d34 ≤ 5.2 mm; the range of the distance BFL between the center of the image side surface S8 of the fourth lens 4 and the imaging surface of the infrared focal plane detector 5 meets the condition that BFL is not less than 9.4mm and not more than 10.5 mm.
Further, the curvature radius of the mirror surface S1 satisfies 460mm ≦ R1 ≦ 490 mm; the curvature radius of the mirror surface S2 satisfies that R2 is more than or equal to 135mm and is more than or equal to 168 mm; the curvature radius of the mirror surface S3 satisfies that R3 is more than or equal to 51mm and less than or equal to 58 mm; the curvature radius of the mirror surface S4 is more than or equal to-78 mm and less than or equal to R4 and less than or equal to-70 mm; the curvature radius of the mirror surface S5 satisfies that R5 is more than or equal to 12mm and less than or equal to 16 mm; the curvature radius of the mirror surface S6 satisfies 11 mm-R6-14 mm; the curvature radius of the mirror surface S7 is more than or equal to-22 mm and less than or equal to R7 and less than or equal to-18 mm; the curvature radius of the mirror surface S8 satisfies that R8 is more than or equal to-22 mm and less than or equal to-18 mm.
Further, the optical system combined focal length f and the optical system clear aperture D satisfy: f/D is more than or equal to 0.9 and less than or equal to 1.1.
Further, the infrared focal plane detector 5 includes a detector protection window 51 and a detector imaging plane 52, and the detector protection window 51 is disposed at the front end of the detector imaging plane 52, i.e. the end of the object side.
Specifically, the detector protection window 51 is used for protecting the detector, preventing the detector from being scratched due to collision and the like during the assembly of the optical system, and preventing foreign matters such as dust and the like from being adsorbed on the imaging surface; the detector imaging surface 52 is used for imaging the light rays converged on the detector imaging surface by the optical system.
Further, the utility model discloses can adapt 1024 x 768 arrays, like the infrared focal plane detector of circle interval 12 mu m.
The preferred embodiment: according to the present invention, a set of preferred combinations is implemented for each data set of the small athermalized night vision thermal imaging optical system 100, as shown in table 3 below. In table 3, the surface numbers refer to the sequential numbers of each surface of the first lens 1 from the object side to the imaging surface 52 along the optical axis. Also included in table 3 are: the profile of each surface, the radius of curvature R of each surface, the distance d from each surface to the next surface (including the thickness of the surface to the next surface or the spacing of the surface to the next surface), the refractive index at 10 μm wavelength for each piece of lens material, and the material.
TABLE 3
| Number of noodles | Surface type | R(mm) | d(mm) | Material | Refractive index |
| S1 | Spherical surface | 488.8 | 2.4 | Germanium single crystal | 4.00 |
| S2 | Aspherical surface | 160.0 | 12.8 | ||
| S3 | Spherical surface | 56.2 | 3.5 | Chalcogenide glass | 2.80 |
| S4 | Aspherical surface | -74.9 | 0.6 | ||
| S5 | Spherical surface | 15.3 | 3.2 | Germanium single crystal | 4.00 |
| S6 | Aspherical surface | 12.1 | 5.5 | ||
| S7 | Aspherical surface | -20.5 | 2.5 | Germanium single crystal | 4.00 |
| S8 | Spherical surface | -19.3 | 7.3 | ||
| S9 | Plane surface | Infinity | 1.0 | Germanium single product | 4.00 |
| S10 | Plane surface | Infinity | 2.2 | ||
| S11 | / | Infinity | 0.0 |
Further, as shown in fig. 2-4, the modulation transfer function curves (MTF) of the small athermal thermal imaging optical system 100 in the preferred embodiment are obtained by simulation calculation of optical design software at-40 ℃, 20 ℃ and 80 ℃. Each curve in the graph refers to a modulation transfer function curve of different fields of view (distinguished by image height, such as 0mm for a central field of view, and also 1.5mm, 3mm, 4.61mm, 6.14mm and 7.68mm for an edge field of view), each field of view has two directions of a meridian and a sagittal, wherein a solid line is a simulation result of the meridian direction of the different fields of view, and a dotted line is a simulation result of the sagittal direction of the different fields of view. As can be seen from the graphs of fig. 2-4, the modulation transfer function curve of the small-sized athermal thermal imaging optical system 100 of the present invention is relatively gentle and less varied in the temperature range of-40 ℃ to 80 ℃, the comprehensive image quality is good, which indicates that the optical system can clearly image in different temperature environments, and each modulation transfer function curve is close to the diffraction limit of the optical system, which is enough to satisfy the resolution requirement of the infrared focal plane detector.
Further, as shown in fig. 5, the distortion view field curve of the optical system shows that the imaging distortion of the optical system is small, the maximum distortion is less than or equal to 5%, the image distortion is small, and the imaging quality is high.
It is worth noting that the infrared focal plane detector has a common non-uniformity problem, and therefore needs to be corrected for the non-uniformity. The distance BFL between the center of the image-side surface S8 of the fourth lens 4 and the imaging surface S11 of the infrared focal plane detector is large, and a large back intercept leaves a space for installing the non-uniformity correction sheet, so that the physical size requirement of the correction shutter can be fully met.
The small athermal thermal imaging optical system 100 of the present embodiment can achieve the following performance criteria: focal length: 17 mm; relative pore diameter: 1.0; the working wavelength is as follows: 8-14 μm; field range: 40.6 ° (H). times.30.5 ° (V); optical distortion: less than or equal to 5 percent; adapting to the specification of the infrared focal plane detector 5: 1024 × 768 with an image circle diameter of 12 μm; working temperature range: -40 ℃ to 80 ℃.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the present invention.
Claims (10)
1. A small-sized athermal thermal imaging optical system is characterized by sequentially comprising a first lens (1), a second lens (2), a third lens (3), a fourth lens (4) and an infrared focal plane detector (5) from an object space to an image space along a light incidence direction;
the refractive indexes of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are all more than 2.4;
the combined focal length of the optical system is f, and the focal length f1 of the first lens (1) satisfies: absolute value of f1/f is more than or equal to 7.5 and less than or equal to 27.6; the focal length f2 of the second lens (2) satisfies: | f2/f | is more than or equal to 0.9 and less than or equal to 1.3; the focal length f3 of the third lens (3) satisfies: | f3/f | is more than or equal to 4.5 and less than or equal to 38.2; the focal length f4 of the fourth lens (4) satisfies: the absolute value of f4/f is more than or equal to 2.3 and less than or equal to 7.8.
2. The compact athermal thermal imaging optical system according to claim 1, wherein the refractive index n1 of the first lens (1) is ≧ 4; the refractive index n2 of the second lens (2) is more than or equal to 2.8; the refractive index n3 of the third lens (3) is more than or equal to 2.4; the refractive index n4 of the fourth lens (4) is more than or equal to 4.
3. The compact athermal thermal imaging optical system according to claim 1 or 2, wherein the first lens (1) is a negative meniscus power lens; the second lens (2) is a biconvex positive focal power lens; the third lens (3) is a meniscus negative focal power lens; the fourth lens (4) is a meniscus positive power lens.
4. The compact athermal thermal imaging optical system according to claim 1 or 2, further comprising an aperture stop (0).
5. The compact athermal thermal imaging optical system according to claim 4, wherein the aperture stop (0) is arranged on the object side (S3) of the second lens (2).
6. The compact athermal thermal imaging optical system according to claim 1 or 2, wherein a diffractive annular zone is provided on the image side surface (S6) of the third lens (3).
7. The compact athermal thermal imaging optical system according to any of claims 1, 2, or 5, wherein the object-side or image-side surface of the first lens (1), the second lens (2), the third lens (3), and the fourth lens (4) is spherical and the other surface is aspheric.
8. The small athermal thermal imaging optical system according to claim 7, wherein the object-side surface (S1) of the first lens (1), the object-side surface (S3) of the second lens (2), the object-side surface (S5) of the third lens (3) and the image-side surface (S8) of the fourth lens (4) are arranged as spheres; the image side surface (S2) of the first lens (1), the image side surface (S4) of the second lens (2), the image side surface (S6) of the third lens (3), and the object side surface (S7) of the fourth lens (4) are aspheric.
9. The compact athermal thermal imaging optical system according to any of claims 1, 2 or 5, wherein the separation d12 between the center of the image side surface (S2) of the first lens (1) and the center of the object side surface (S3) of the second lens (2) ranges from 12.5mm ≦ d12 ≦ 13.9 mm; the range of a distance d23 between the center of the image side surface (S4) of the second lens (2) and the center of the object side surface (S5) of the third lens (3) is more than or equal to 0.5mm and less than or equal to d23 and less than or equal to 3.3mm, and the range of a distance d34 between the center of the image side surface (S6) of the third lens (3) and the center of the object side surface (S7) of the fourth lens (4) is more than or equal to 1mm and less than or equal to d34 and less than or equal to 5.2 mm; the distance BFL between the center of the image side surface (S8) of the fourth lens (4) and the imaging surface of the infrared focal plane detector (5) is 9.4 mm-10.5 mm.
10. The compact athermal thermal imaging optical system according to claim 1 or 2, wherein the optical system combined focal length f and optical system clear aperture D satisfy: f/D is more than or equal to 0.9 and less than or equal to 1.1.
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| CN202220666475.4U CN216848318U (en) | 2022-03-25 | 2022-03-25 | Small-size athermal thermal imaging optical system |
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| CN202220666475.4U CN216848318U (en) | 2022-03-25 | 2022-03-25 | Small-size athermal thermal imaging optical system |
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