Infinite far infrared target generator and optical system

Abstract

The invention discloses an infinite far infrared target generator and an optical system. The infrared target generator comprises a reflective bowl, an infrared light source, a lighting lens group, a target and a collimating lens group which are sequentially arranged on the same optical axis, the infrared light source is arranged at the focus of the reflective bowl, and emitted infrared light is reflected into parallel light by the reflective bowl and enters the illumination lens group; the illumination lens group comprises a front illumination lens group and a rear illumination lens group, and parallel infrared light is converged at an image space focus of the front illumination lens group, enters the rear illumination lens group and is converted into parallel light to irradiate a target; a target is arranged at the focus of the collimating lens group, and infrared light passing through the target is converted into parallel light by the collimating lens group. According to the invention, infinite imaging of the infrared target is realized in the optical path sharing the optical axis, and the structure of the infrared target generator is simplified.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared optical systems, and in particular to an infinite infrared target generator and an optical system. Background Art

[0002] Infinite infrared target generators are crucial for infrared testing. They are required for image quality testing of infrared lenses and thermal imagers. Existing infinite infrared target generators often use a blackbody and off-axis reflective system, which has drawbacks such as high cost, bulk, and low energy. Summary of the Invention

[0003] The main purpose of the present invention is to provide an infinite infrared target generator and an optical system, reduce the volume of the infinite infrared target generator, simplify the structure of the infinite infrared target generator, and reduce the cost of the infinite infrared target generator.

[0004] The technical solution adopted by the present invention is: an infinite infrared target generator, comprising a reflective bowl, an infrared light source, an illumination lens group, a target and a collimating lens group arranged in sequence along the optical axis in the direction of incident light; wherein,

[0005] The infrared light source is located at the focus of the reflective bowl, and the infrared light emitted is reflected by the reflective bowl as parallel light and enters the illumination lens group;

[0006] The illumination lens group includes a front illumination lens group and a rear illumination lens group. The image focus of the front illumination lens group coincides with the object focus of the rear illumination lens group. Parallel infrared light converges at the image focus of the front illumination lens group and enters the rear illumination lens group to be converted into parallel light to illuminate the target.

[0007] The target is set at the focus of the collimating lens group, and the infrared light passing through the target is converted into parallel light by the collimating lens group.

[0008] According to the above technical solution, the front lighting lens group includes a first lighting lens, and the rear lighting lens group includes a second lighting lens and a third lighting lens.

[0009] According to the above technical solution, the first illumination lens is a meniscus lens with a convex surface facing the image side; the second illumination lens is a meniscus lens with a concave surface facing the image side; the third illumination lens is a meniscus lens with a convex surface facing the image side; and the image is an image of the target at infinity.

[0010] According to the above technical solution, the targets include a cross target, a pinhole target, a double-slit target, and a four-rod target, and the material is zinc selenide.

[0011] According to the above technical solution, the collimating lens group includes a first collimating lens and a second collimating lens.

[0012] According to the above technical solution, the first collimating lens and the second collimating lens are meniscus lenses with convex surfaces facing the image side; the image is the image formed by the infrared target generator.

[0013] According to the above technical solution, the convex surface of the third illumination lens is aspherical.

[0014] According to the above technical solution, the convex surface of the first collimating lens is an aspherical diffraction surface.

[0015] According to the above technical solution, the first illumination lens, the second illumination lens, the third illumination lens and the first collimating lens are made of germanium, and the second collimating lens is made of zinc selenide.

[0016] Another aspect of the present invention provides an optical system comprising the above-mentioned infinite infrared target generator.

[0017] The present invention provides an infinite infrared target generator and optical system, which positions the target at the focal point of a collimating lens group, achieving infinite imaging of the infrared target within a coaxial transmission light path. The illumination lens group of the present invention is configured so that the image-side focus of the front illumination lens group coincides with the object-side focus of the rear illumination lens group. Based on the Köhler illumination principle, this ensures uniform infrared light illumination of the target. Compared to existing off-axis reflective infrared target generators, the coaxial transmission infinite infrared target generator of the present invention has a simpler structure and lower construction costs.

[0018] Furthermore, the convex surface of the third illumination lens and the convex surface of the first collimating lens of the present invention are aspherical surfaces, and the light refraction path is optimized by changing the surface shape of the lens, which is beneficial to reducing aberrations.

[0019] Furthermore, the convex surface of the first collimating lens of the present invention adopts a diffraction surface to modulate the propagation of infrared light, which is beneficial to reducing aberrations.

[0020] Furthermore, the materials of the illumination lens and the collimating lens of the present invention are germanium and zinc selenide, which improves the transmittance of the infinite infrared target generator to the infrared band.

[0021] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 1 is a schematic structural diagram of an infinite infrared target generator according to an embodiment of the present invention;

[0024] Figure 2 is an MTF diagram of an optical system according to an embodiment of the present invention;

[0025] Figure 3 is a spot diagram of an optical system according to an embodiment of the present invention;

[0026] Figure 4 This is a simulation diagram of the illumination uniformity of an image formed by the optical system according to an embodiment of the present invention at a distance of 3 meters.

[0027] Reference numerals: 1. infrared light source; 2. reflective bowl; 3. first illumination lens; 4. second illumination lens; 5. third illumination lens; 6. target; 7. first collimating lens; 8. second collimating lens; 9. first image plane. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic illustrations of the basic concept of the present invention. Therefore, the drawings only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0030] In the present invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like are used to indicate positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present application and to simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used solely for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0031] Example 1

[0032] This embodiment provides an infinite infrared target generator, the structure of which is as follows: Figure 1As shown, the infrared light source 1, reflector 2, illumination lens group, collimating lens group, and target 6 are composed. Target 6 is located between the illumination lens group and the collimating lens group and is located at the focus of the collimating lens group. After the infrared light source 1, reflector 2, illumination lens group, collimating lens group, and target 6 are assembled to form a stable optical path.

[0033] The illumination lens assembly comprises multiple illumination lenses arranged along a common optical axis. Infrared light source 1 is positioned at the focal point of reflector 2, so that a portion of the infrared light emitted by infrared light source 1 is reflected by reflector 2 and incident as parallel light on first illumination lens 3, thereby enhancing the uniformity of the light emitted by infrared light source 1. The collimating lens assembly comprises multiple collimating lenses arranged along a common optical axis.

[0034] When constructing the optical path, the infrared light source 1, the lens centers of the plurality of illumination lenses, the center of the target 6 and the lens centers of the plurality of collimating lenses are sequentially arranged collinearly.

[0035] The illumination lens group includes a front illumination lens group and a rear illumination lens group, and the image-side focus of the front illumination lens group coincides with the object-side focus of the rear illumination lens group. The front illumination lens group includes a first illumination lens 3, and the rear illumination lens group includes a second illumination lens 4 and a third illumination lens 5. After the assembly is completed, the infrared light emitted by the infrared light source 1 is reflected by the reflective bowl 2 and enters the first illumination lens 3 as parallel light, converging at the focal point where the first illumination lens 3 and the illumination lens group coincide. Then, after passing through multiple illumination lenses, it becomes parallel light and illuminates the target 6. The infrared light passing through the target 6 is collimated by multiple collimating lenses and formed into an image at infinity.

[0036] Furthermore, the number of illumination lenses is three, namely, a first illumination lens 3, a second illumination lens 4, and a third illumination lens 5, which are sequentially arranged along the incident direction of the optical axis light. In this embodiment, the curvature radius of each illumination lens is set.

[0037] Among them, the first illumination lens 3 is a meniscus lens with a convex surface facing the image side, with the radius of curvature of the convex surface set to 114.29 and the radius of curvature of the concave surface set to 32.182. The second illumination lens 4 is a meniscus lens with a concave surface facing the image side, with the radius of curvature of the convex surface set to 95.72 and the radius of curvature of the concave surface set to 57.81. The third illumination lens 5 is a meniscus lens with a convex surface facing the image side, with an aspheric convex surface. The use of an aspheric surface can reduce aberrations by changing the refraction path of infrared light. The radius of curvature of the convex surface of the third illumination lens 5 is set to 125.89 and the radius of curvature of the concave surface is set to 42.27. The above image is the image of the target 6 at infinity.

[0038] Furthermore, target 6 can be a cross target, a pinhole target, a double-slit target, or a four-bar target, made of zinc selenide with a thickness of 0.5 mm.

[0039] Furthermore, the number of the collimating lenses is two, including a first collimating lens 7 and a second collimating lens 8 arranged in sequence along the incident direction of the optical axis light. In this embodiment, the curvature radius of each collimating lens is set.

[0040] The first collimating lens 7 is a meniscus lens with a convex surface facing the image side, with the convex surface having a radius of curvature of 96.797 and the concave surface having a radius of curvature of 88.92. The second collimating lens 8 is a meniscus lens with a convex surface facing the image side, with the convex surface having a radius of curvature of 254.7 and the concave surface having a radius of curvature of 145.88. The convex surface of the first collimating lens 7 is an aspherical diffraction surface on a germanium substrate, which modulates the infrared light to further reduce aberrations. The above image is an image of the target 6 at infinity.

[0041] Furthermore, the first lighting lens 3, the second lighting lens 4, the third lighting lens 5 and the first collimating lens 7 are made of germanium, and the second collimating lens 8 is made of zinc selenide. By selecting zinc selenide and germanium to match the materials of each lens, the transmittance of infrared light is improved.

[0042] Furthermore, the radius of the reflective bowl 2 is set to 40 mm.

[0043] Preferably, the infrared light source 1 in this embodiment is an infrared filament.

[0044] The device spacing is set based on the above-mentioned optical device parameters. In this embodiment, the distance between the infrared light source 1 and the surface of the convex surface of the first illumination lens is set to 23.71±0.04 mm, the distance between the surface of the convex surface of the first illumination lens 3 and the surface of the convex surface of the second illumination lens 4 is set to 53.92±0.04 mm, the distance between the surface of the convex surface of the second illumination lens 4 and the surface of the convex surface of the third illumination lens 5 is set to 6.25±0.04 mm, the distance between the surface of the convex surface of the third illumination lens 5 and the target 6 is set to 50 mm, the distance between the target 6 and the first collimating lens 7 is set to 136.07±0.02 mm, and the distance between the surface of the convex surface of the first collimating lens 7 and the surface of the convex surface of the second collimating lens 8 is set to 44.52±0.03 mm.

[0045] According to the above optical device parameters and device spacing, the distance between the infrared light source 1 and the second collimating lens 8 of the infinite infrared target generator of this embodiment is fixed at 336.97 mm, achieving structural simplification and volume compression. The focal length is 300 mm, the aperture stop is 50 mm, the numerical aperture is 0.25, and the band covers 8 to 14 μm.

[0046] Example 2

[0047] This embodiment provides an optical system, the structure of which is as follows Figure 1As shown, it includes the infinite infrared target generator described in Example 1, the first image plane 9 and the second image plane.

[0048] The first image plane 9 is located at the focal plane where the front and rear illumination lens groups overlap, and is 35.74 mm away from the convex surface of the first illumination lens 3. The second image plane is the plane where the image of the target 6 formed at infinity by the collimating lens group is located.

[0049] The optical system in this embodiment was tested.

[0050] First, a preliminary test is conducted on the imaging quality of the optical system in this embodiment to obtain the DIFFLIMT (diffraction limit) curve of the optical system. The results are as follows: Figure 2 shown.

[0051] The horizontal axis is the spatial frequency, with the unit of cy / mm (cycles per millimeter), and the vertical axis is the transfer function, which is a unitless normalized dimension. The DIFF LIMT curve represents the highest transfer function that the optical system can theoretically achieve. It can be seen from the curve that the transfer functions of each field of view of the collimating optical system have reached the theoretical value, indicating that the optical system has good imaging quality.

[0052] Further testing of the imaging quality of the optical system in this embodiment, obtaining the point diagram of the optical system, the results are as follows: Figure 3 shown.

[0053] Figure 3 The left side of the middle is the linear field size in millimeters, and the right side is the geometric root mean square spot diagram and geometric full spot diagram size of the corresponding field of view. The circle outside the spot diagram represents the diffraction-limited theoretical spot diagram size. Figure 3 It can be seen that the sizes of the geometric RMS (root mean square) spot diagram and the geometric full spot diagram are both smaller than the diffraction-limited theoretical spot diagram size, indicating that the imaging quality of the optical system has reached the diffraction limit and has good imaging quality.

[0054] The simulation test of the illumination uniformity of the optical system in this embodiment at a distance of 3 meters shows the following results: Figure 4 shown.

[0055] Figure 4 The left side of the middle is the illumination of the simulated light spot 3 meters away from the collimation system. The horizontal and vertical coordinates are both distances, in millimeters, indicating the illumination of the simulated light spot within a certain range. The right side of the figure represents the illumination size, in W / mm (watts per square millimeter). Figure 4 It can be seen that the optical system has uniform illumination within a certain range of 3 meters away from the light emission.

[0056] In summary, the present invention provides an infinite infrared target generator and an optical system, which improves the energy of the emitted infrared light while simplifying the structure of the infrared target generator, effectively compressing the volume of the infrared target generator, and reducing the construction cost of the infrared target generator.

[0057] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0058] The size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0059] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. An infinite infrared target generator, characterized in that: It comprises a reflective bowl (2), an infrared light source (1), an illumination lens group, a target (6) and a collimating lens group which are arranged in sequence on the same optical axis; wherein, The infrared light source (1) is arranged at the focus of the reflective bowl (2); the infrared light reflected by the reflective bowl (2) is converted into parallel light and enters the illumination lens group; The illumination lens group comprises a front illumination lens group and a rear illumination lens group, wherein the image side focus of the front illumination lens group coincides with the object side focus of the rear illumination lens group; parallel infrared light entering the illumination lens group converges at the image side focus of the front illumination lens group, and then enters the rear illumination lens group and is converted into parallel light to illuminate the target (6); The target (6) is located at the focus of the collimating lens group; the infrared light passing through the target (6) is converted into parallel light by the collimating lens group.

2. The infinite infrared target generator according to claim 1, characterized in that: The front lighting lens group includes a first lighting lens (3), and the rear lighting lens group includes a second lighting lens (4) and a third lighting lens (5).

3. The infinite infrared target generator according to claim 2, characterized in that: The first lighting lens (3) is a meniscus lens with a convex surface facing the image side; the second lighting lens (4) is a meniscus lens with a concave surface facing the image side; and the third lighting lens (5) is a meniscus lens with a convex surface facing the image side. The image is an image of the target (6) at infinity.

4. The infinite infrared target generator according to claim 3, characterized in that: The convex surface of the third illumination lens (5) is an aspherical surface.

5. The infinite infrared target generator according to claim 1, characterized in that: The targets (6) include cross targets, pinhole targets, double-slit targets, and four-bar targets, and are made of zinc selenide.

6. The infinite infrared target generator according to claim 1, characterized in that: The collimating lens group comprises a first collimating lens (7) and a second collimating lens (8).

7. The infinite infrared target generator according to claim 6, characterized in that: The first collimating lens (7) and the second collimating lens (8) are meniscus lenses with convex surfaces facing the image side; The image is an image of the target (6) at infinity.

8. The infinite infrared target generator according to claim 7, characterized in that: The convex surface of the first collimating lens (7) is an aspherical diffraction surface.

9. The infinite infrared target generator according to claim 1, characterized in that: The materials of the illumination lens and the collimating lens include germanium and zinc selenide.

10. An optical system, characterized in that: The invention comprises the infinite infrared target generator described in any one of claims 1 to 9.

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