Long-wave ultra-wide-angle athermalization lens

Abstract

The utility model relates to the technical field of infrared lenses, and discloses a long-wave ultra-wide-angle athermalization lens, which comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from an object side to an image side, the first lens and the second lens are negative lenses, the third lens, the fourth lens and the fifth lens are positive lenses, the second lens, the fourth lens and the fifth lens are all made of chalcogenide glass through the arrangement of a negative-negative-positive-positive-positive structure, the refractive index change is small during temperature fluctuation, the thermal expansion coefficient is close to that of the lens barrel, and the thermal expansion coefficient of the second lens, the fourth lens and the fifth lens is close to that of the lens barrel. In addition, the total focal power of the negative lens is-0.0966, the total focal power of the positive lens is + 0.116, when the temperature changes, the direction of the focus displacement of the negative lens group is opposite to that of the focus displacement of the positive lens group, displacement offset is achieved through the focal power matching, and therefore the effect of reducing the pressure deformation between the lens and the lens barrel is achieved. Therefore, the problems of focus offset, aberration, image quality influence and the like caused by temperature difference are avoided.

Description

Technical Field

[0001] This utility model relates to the field of infrared lens technology, specifically to a long-wave ultra-wide-angle non-thermalized lens. Background Technology

[0002] Infrared thermal imaging lenses, based on passive infrared night vision technology, collect the infrared radiation energy of objects on a thermal imager to generate real-time images, converting invisible thermal radiation into clear images visible to the human eye. In recent years, long-wavelength infrared uncooled optical lenses have been widely used in both military and civilian fields due to their lower cost and excellent performance. In the civilian security sector, the demand for ultra-wide field-of-view and short-range, large-area observation is particularly prominent. Ultra-wide-angle infrared thermal imaging lenses can meet this market demand.

[0003] When long-wavelength thermal imaging lenses experience temperature changes, the focal length changes due to factors such as thermal expansion and contraction of the lens and barrel materials, and changes in the lens's refractive index. This leads to severe aberrations and defocusing, resulting in a decline in image quality. To address the negative impact of temperature on infrared optical systems, this design utilizes IG6, a chalcogenide material, to ensure reliable imaging within a certain range of commonly used temperatures. Utility Model Content

[0004] The purpose of this invention is to provide a long-wave ultra-wide-angle non-thermalized lens to solve the above-mentioned technical problems.

[0005] This utility model provides the following technical solution:

[0006] The long-wave ultra-wide-angle athermalized lens includes: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side;

[0007] The first and second lenses are negative lenses, the third, fourth and fifth lenses are positive lenses, the first, second and third lenses are convex surfaces facing the object side, the fourth lens is convex surfaces facing both the object side and the image side, and the fifth lens is convex surfaces facing the image side.

[0008] The second, fourth, and fifth lenses are made of chalcogenide glass, while the first and third lenses are made of germanium.

[0009] As a preferred embodiment of the above technical solution, the second lens, the fourth lens, and the fifth lens are made of chalcogenide material IG6.

[0010] As a preferred embodiment of the above technical solution, the object-side surfaces of the first lens, the second lens, and the third lens are aspherical, the object-side surface of the fourth lens has a diffraction structure, and the image-side surface of the fifth lens is aspherical.

[0011] As a preferred embodiment of the above technical solution, the optical power of the first lens is -0.094, the optical power of the second lens is -0.0026, the optical power of the third lens is 0.017, the optical power of the fourth lens is 0.062, and the optical power of the fifth lens is 0.037.

[0012] Compared with the prior art, the beneficial effects of this utility model are:

[0013] In this invention, by setting a negative-negative-positive-positive-positive structure, the second, fourth, and fifth lenses are all made of chalcogenide glass, which has a small change in refractive index when the temperature fluctuates and is similar to the coefficient of thermal expansion of the lens barrel. Therefore, the pressure deformation between the lens and the lens barrel is reduced. In addition, the total optical power of the negative lens is -0.0966, while the total optical power of the positive lens is +0.116. When the temperature changes, the focal displacement of the negative lens group is opposite to that of the positive lens group. The displacement is canceled out by the optical power ratio, thereby avoiding problems such as focal shift, aberration, and image quality effects caused by temperature differences. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the optical path of the long-wave ultra-wide-angle athermalized lens of this utility model;

[0015] Figure 2 This is the 20°C transfer function diagram of the present invention;

[0016] Figure 3 This is the -40°C transfer function diagram of the present invention;

[0017] Figure 4 This is the 80°C transfer function diagram of the present invention.

[0018] In the diagram: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Protective window; 7. Image plane. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] like Figure 1As shown, this utility model provides a technical solution: a long-wave ultra-wide-angle non-thermalized lens. The thermalized lens includes a negative lens group and a positive lens group arranged sequentially. The negative lens group is arranged in sequence according to the optical path as a first lens 1 and a second lens 2. The positive lens group is arranged in sequence according to the optical path as a third lens 3, a fourth lens 4, and a fifth lens 5. The lens also includes a protective window 6 and an image plane 7. During operation, the lens receives and converges the infrared radiation of the target. The converged infrared radiation passes through the protective window 6 and forms an image on the image plane 7. Through the thermal difference design of the lens material, it is ensured that after focusing, when the ambient temperature changes within the range of -40℃ to 80℃, the lens does not produce focal plane drift and the infrared imaging quality remains stable.

[0021] Furthermore, such as Figure 1 As shown, the first lens 1, the second lens 2, and the third lens 3 are all meniscus lenses with their convex surfaces facing the object side and aspherical surfaces on their front surfaces. The materials used for the first lens 1, the second lens 2, and the third lens 3 are germanium, chalcogenide material IG6, and germanium, respectively. The remaining two sets of positive lenses are the fourth lens 4 and the fifth lens 5. The fourth lens 4 is a biconvex positive lens with a diffraction surface on its front surface and is made of chalcogenide material IG6. The fifth lens 5 is a meniscus positive lens with its convex surface facing the image side and aspherical surfaces on its front surface and is made of chalcogenide material IG6.

[0022] Optical structural parameters:

[0023]

[0024] Among them, the technical indicators are:

[0025] F number: 1.2

[0026] Horizontal field of view: 155°, circular field of view: 206°

[0027] Operating wavelength: 8-12μm

[0028] When the temperature changes, the refractive index of traditional infrared material germanium will change significantly, resulting in focus shift and aberration. However, the second lens 2, the fourth lens 4, and the fifth lens 5, which are made of chalcogenide material IG6, have a low temperature coefficient of refractive index (dn / dT) and their refractive index changes only slightly when the temperature fluctuates. Therefore, the problem of focus drift is suppressed from an optical perspective. As a result, the imaging position of the second lens 2, the fourth lens 4, and the fifth lens 5 remains basically stable when the temperature changes from -40℃ to 80℃.

[0029] From the perspective of this optical structure design, by setting up negative and positive lens groups, when the temperature rises, the focal length of the negative lens group becomes longer (i.e., the focal point moves backward), while the focal length of the positive lens group becomes shorter (i.e., the focal point moves forward). The total optical power of the negative lens group is -0.0966, while the total optical power of the positive lens group is +0.116. The focal displacement directions of the two lens groups are opposite, and the displacement is canceled out by the optical power matching design.

[0030] The coefficient of thermal expansion (CTE) of the chalcogenide material IG6 is close to that of the lens barrel material (an aluminum alloy). The matching between the lens material and the lens barrel material reduces the pressure deformation between the lens and the lens barrel caused by temperature changes, avoiding problems such as mechanical displacement or surface distortion of the lens. This reduces the impact of temperature fluctuations on image quality. Therefore, lenses made with the above materials can effectively avoid problems such as focus shift, aberrations and image quality issues caused by temperature differences between -40℃ and 80℃.

[0031] Figure 2-4 The following graphs show the lens transfer function curves for operating ambient temperatures of 20℃, -40℃, and 80℃. The graphs show that the lens transfer function is greater than 0.2 at 301p / mm when the ambient temperature changes from -40℃ to 80℃, indicating stable image quality and good thermal compensation effect.

[0032] In this embodiment, the lens temperature range is -40 degrees Celsius to 80 degrees Celsius. Temperature compensation within this temperature range is reliable, and the image is clear without the need for focusing. Furthermore, the optical system consists of 5 lenses, resulting in a smaller size and weight, and lower cost.

[0033] The above embodiments are only used to illustrate the technical solution of this utility model, and are not intended to limit it.

Claims

1. Long-wave, ultra-wide-angle athermalized lens, characterized in that, include: The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged sequentially from the object side to the image side; The first and second lenses are negative lenses, the third, fourth and fifth lenses are positive lenses, the first, second and third lenses are convex surfaces facing the object side, the fourth lens is convex surfaces facing both the object side and the image side, and the fifth lens is convex surfaces facing the image side. The second, fourth, and fifth lenses are made of chalcogenide glass, while the first and third lenses are made of germanium.

2. The long-wave, ultra-wide-angle athermalized lens according to claim 1, characterized in that: The second lens, the fourth lens, and the fifth lens are made of chalcogenide material IG6.

3. The long-wave, ultra-wide-angle athermalized lens of claim 1, wherein: The object-side surfaces of the first, second, and third lenses are aspherical, the object-side surface of the fourth lens has a diffraction structure, and the image-side surface of the fifth lens is aspherical.

4. The long-wave, ultra-wide-angle athermalized lens according to claim 3, characterized in that: The first lens has an optical power of -0.094, the second lens has an optical power of -0.0026, the third lens has an optical power of 0.017, the fourth lens has an optical power of 0.062, and the fifth lens has an optical power of 0.

037.

5. The long-wave, ultra-wide-angle athermalized lens of claim 1, wherein: The long-wave ultra-wide-angle athermalized lens also includes a protective window and an image plane.

Images