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CN-121978820-A - Compact double-view-field long-wave infrared lens

CN121978820ACN 121978820 ACN121978820 ACN 121978820ACN-121978820-A

Abstract

The invention discloses a compact double-view-field long-wave infrared lens which sequentially comprises a first lens, a second lens, a lens, an optical total length (TTL) and a lens, wherein the first lens is provided with positive diopter, the object side is provided with a convex surface, the image side is provided with a concave surface, the second lens is provided with negative diopter, the object side is provided with a concave surface, the image side is provided with a concave surface, the maximum outer diameter of the lens is not more than 59mm, the optical total length (TTL) is less than 85.1mm, the structural size of the whole lens is only phi 68 mm by 79mm, the requirements of equipment integration and miniaturization are greatly met, and the system has good imaging quality in two focal sections of 22mm (short focal) and 62mm (long focal) and is close to a diffraction emitter.

Inventors

  • WU YUTING
  • XU JINLONG
  • ZHANG JUNGUANG

Assignees

  • 厦门力鼎光电股份有限公司

Dates

Publication Date
20260505
Application Date
20260228

Claims (8)

  1. 1. The compact double-view-field long-wave infrared lens is characterized by sequentially comprising the following components from an object side to an image side along an optical axis: a first lens element with positive refractive power having a convex object-side surface and a concave image-side surface; a second lens element with negative refractive power having a concave object-side surface and a concave image-side surface; The third lens is provided with positive diopter, the object side surface is a convex surface, and the image side surface is a concave surface; a fourth lens element with positive refractive power having a convex object-side surface and a concave image-side surface; a diaphragm positioned between the third lens and the fourth lens; the second lens is the only motion component in the system, and moves along the optical axis in the switching process of the field of view of the system so as to realize the zoom function and the back focus compensation function; the object side surface or the image side surface of the first lens is provided with a binary diffraction surface which is used for correcting higher-order aberration and optimizing the image quality of a long focal length section; At least one surface of the first lens, the second lens, the third lens and the fourth lens is an aspheric surface.
  2. 2. The compact dual-field long-wave infrared lens as set forth in claim 1, wherein the lens has a system focal length of 22mm in a short focal state and a system focal length of 62mm in a long focal state, and wherein the lens has an F-number of less than 1.1 in the long focal state.
  3. 3. The compact dual-field long-wave infrared lens as set forth in claim 1, wherein a thickness interval between said first lens and said second lens is defined as d12, and a thickness interval between said second lens and said third lens is defined as d23; In the tele state, d12 is 32.2mm and d23 is 3.6mm; in the short focus state, d12 is 11.6mm and d23 is 24.2mm; The total movement amount of the second lens at the time of switching the long and short focuses is 20.6mm.
  4. 4. The compact dual-field long-wave infrared lens as set forth in claim 1, wherein an optical back focal length of said lens is defined as BFL, a focal length of said lens is defined as f, and an image plane half-diagonal length of said lens is defined as y; In the tele state, the relation is satisfied that BFL/f=0.22 and y/f=0.16; in the short focus state, the relation BFL/f=0.62 and y/f=0.45 is satisfied.
  5. 5. The compact dual-field long-wave infrared lens as set forth in claim 1, wherein the focal length of the second lens is f2, and the relationship f2<0 is satisfied.
  6. 6. The dual-view long-wave infrared lens as set forth in claim 1, wherein the maximum outer diameter of the lens is not more than 59mm, the total optical length is less than 85.1mm, and the optical back focal length is greater than 13.6mm.
  7. 7. The dual-view long-wave infrared lens assembly of claim 1, wherein the refractive indices of said first, second, third and fourth lenses are 2.78, and wherein each lens surface comprises an aspheric surface and a diffractive surface.
  8. 8. The dual-view long-wave infrared lens as set forth in claim 1, wherein said lens is adapted to a non-refrigerated detector having a resolution of 640X 512 and a pixel spacing of 12. Mu.m.

Description

Compact double-view-field long-wave infrared lens Technical Field The invention relates to a compact double-view-field long-wave infrared lens, and belongs to the field of lenses. Background The dual-view long-wave infrared lens is an extremely valuable optical technology, and has the core advantage of being capable of realizing the view conversion from 'longitudinal global' to 'visual autumn milli' in a very short time (through electric or manual switching). The technology greatly improves the adaptability and the operation efficiency of the infrared detection equipment by balancing the contradiction of 'wide view field' and 'high resolution' in single equipment, and effectively solves the limitation of a single focal length lens in application. At present, the long-wave infrared lens has great application potential in the fields of military reconnaissance, security monitoring, industrial detection, fire rescue, automatic driving and the like. However, with the complexity of application scenarios, the prior art is faced with challenges of firstly miniaturization, how to realize dual-field switching in a limited space, secondly imaging sharpness, especially maintaining image quality close to diffraction limit under different focal lengths, and finally balance of zoom ratio and structural complexity while pursuing higher performance. Therefore, developing a dual-field long-wave infrared lens with compact structure, excellent imaging and strong environmental adaptability is an important point of industry. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a compact double-view-field long-wave infrared lens so as to solve the problem. In order to achieve the above purpose, the invention is realized by the following technical scheme that the compact double-view-field long-wave infrared lens sequentially comprises, from an object side to an image side along an optical axis: a first lens element with positive refractive power having a convex object-side surface and a concave image-side surface; a second lens element with negative refractive power having a concave object-side surface and a concave image-side surface; The third lens is provided with positive diopter, the object side surface is a convex surface, and the image side surface is a concave surface; a fourth lens element with positive refractive power having a convex object-side surface and a concave image-side surface; a diaphragm positioned between the third lens and the fourth lens; the second lens is the only motion component in the system, and moves along the optical axis in the switching process of the field of view of the system so as to realize the zoom function and the back focus compensation function; the object side surface or the image side surface of the first lens is provided with a binary diffraction surface which is used for correcting higher-order aberration and optimizing the image quality of a long focal length section; At least one surface of the first lens, the second lens, the third lens and the fourth lens is an aspheric surface. Preferably, the lens has a system focal length of 22mm in a short focal state and a system focal length of 62mm in a long focal state, and the lens has an F number of less than 1.1 in the long focal state. Preferably, a thickness interval between the first lens and the second lens is defined as d12, and a thickness interval between the second lens and the third lens is defined as d23; In the tele state, d12 is 32.2mm and d23 is 3.6mm; in the short focus state, d12 is 11.6mm and d23 is 24.2mm; The total movement amount of the second lens at the time of switching the long and short focuses is 20.6mm. Preferably, the optical back focal length of the lens is defined as BFL, the focal length is defined as f, and the half diagonal line length of the image plane is defined as y; In the tele state, the relation is satisfied that BFL/f=0.22 and y/f=0.16; in the short focus state, the relation BFL/f=0.62 and y/f=0.45 is satisfied. Preferably, the focal length of the second lens is f2, and the relation f2<0 is satisfied. Preferably, the maximum outer diameter of the lens is not more than 59mm, the total optical length is less than 85.1mm, and the optical back focus is more than 13.6mm. Preferably, the refractive index of each of the first lens, the second lens, the third lens and the fourth lens is 2.78, and each lens surface of the lens comprises an aspheric surface and a diffraction surface. Preferably, the lens is adapted to a non-refrigerated detector with 640×512 resolution and 12 μm pixel pitch. Advantageous effects The invention only adopts four optical lenses, the maximum outer diameter of the lenses is not more than 59mm, the total optical length (TTL) is less than 85.1mm, the whole structure size is only phi 68 mm 79mm, the requirements of equipment integration and miniaturization are greatly met, the system has good imaging quality in two focal length sect