CN109212716B - Four-piece infrared single-wavelength lens group - Google Patents

Four-piece infrared single-wavelength lens group Download PDF

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Publication number
CN109212716B
CN109212716B CN201710546296.0A CN201710546296A CN109212716B CN 109212716 B CN109212716 B CN 109212716B CN 201710546296 A CN201710546296 A CN 201710546296A CN 109212716 B CN109212716 B CN 109212716B
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lens
focal length
image
wavelength
piece infrared
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CN109212716A (en
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赖淑姿
蔡斐欣
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Xinju Technology Co ltd
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Xinju Technology Co ltd
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/001Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/0015Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
    • G02B13/002Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
    • G02B13/004Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having four lenses
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/001Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/008Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras designed for infrared light
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/14Optical objectives specially designed for the purposes specified below for use with infra-red or ultra-violet radiation
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/18Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration

Abstract

The invention discloses a four-piece infrared single-wavelength lens group, which comprises the following components in sequence from an object side to an image side: an aperture; a first lens element with positive refractive power; a second lens element with positive refractive power; a third lens element with negative refractive power; and a fourth lens element with positive refractive power. Therefore, the present invention provides a four-piece infrared single-wavelength lens set with improved angle of view, high resolution, short lens length, and small distortion.

Description

Four-piece infrared single-wavelength lens group
Technical Field
The present invention relates to a four-piece infrared single-wavelength lens set, and more particularly to a miniaturized four-piece infrared single-wavelength lens set applied to electronic products.
Background
Nowadays, digital image technology is continuously updated and changed, especially digital carriers of digital cameras and mobile phones are all developed to be miniaturized, so that photosensitive components such as CCD or CMOS are also required to be more miniaturized, and in addition to being applied to the field of infrared focusing lens, in recent years, the infrared focusing lens is also widely used in the field of infrared receiving and sensing of game machines, and in order to make the range of the game machines for sensing users wider, the current lens group for receiving infrared wavelengths mostly uses the wide-angle lens group with larger drawing angle as the main stream.
The applicant has previously proposed sets of lenses for infrared wavelength reception, such as: taiwan application nos. 098100552 and 098125378, "SINGLE FOCUS WIDE-angle lens set SINGLE FOCUS lens WIDE-ANGLE LENS MODULE", only the current game machine is mainly 3D game with more stereo, reality and reality sense, so the current or previous lens set of the applicant all requires 2D plane game detection, so that the depth sensing effect of 3D game side weight cannot be satisfied.
Furthermore, regarding the dedicated infrared receiving and sensing lens set for game machine, in order to pursue low cost, plastic lenses are adopted, the poor light transmittance of the first material is one of the key factors that affect the depth detection precision of the game machine, and the second plastic lens is easy to overheat or overcool the ambient temperature, so that the focal length of the lens set is changed and the accurate focusing detection cannot be performed, as mentioned above, the current infrared wavelength receiving lens set cannot meet the two technical problems of the accurate sensing of the depth distance of the 3D game.
Therefore, how to provide a lens assembly capable of accurately detecting and receiving depth distances and preventing the focal length of the lens assembly from changing to affect the depth detection effect is a technical bottleneck to be overcome by the infrared wavelength receiving lens assembly.
Disclosure of Invention
The present invention provides a four-piece infrared single-wavelength lens set, and particularly relates to a four-piece infrared single-wavelength lens set with a high resolution, a short lens length, and a small distortion.
To solve the above problems, the present invention provides a four-piece infrared single-wavelength lens assembly, in order from an object side to an image side, comprising: an aperture; a first lens element with positive refractive power having an object-side surface being convex at a paraxial region and an image-side surface being concave at a paraxial region, at least one of the object-side surface and the image-side surface being aspheric; a second lens element with positive refractive power having an object-side surface being concave at a paraxial region thereof and an image-side surface being convex at a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface thereof is aspheric; a third lens element with negative refractive power having an object-side surface being concave at a paraxial region thereof and an image-side surface being convex at a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface thereof is aspheric; and a fourth lens element with positive refractive power having an object-side surface being convex at a paraxial region and an image-side surface being concave at a paraxial region, wherein at least one of the object-side surface and the image-side surface is aspheric.
Preferably, the focal length of the first lens is f1, the focal length of the second lens is f2, and the following conditions are satisfied: 0.005 < f1/f2 < 0.09. Therefore, the refractive power configuration of the first lens element and the second lens element is more suitable, which is beneficial to reducing the excessive increase of system aberration.
Preferably, the focal length of the second lens is f2, the focal length of the third lens is f3, and the following conditions are satisfied: -42 < f2/f3 < -3.2. Therefore, the refractive power configurations of the second lens element and the third lens element are balanced, which is helpful for aberration correction and sensitivity reduction.
Preferably, the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the following conditions are satisfied: -2.1 < f3/f4 < -1.3. Therefore, the total optical length of the system is effectively reduced.
Preferably, the focal length of the first lens is f1, the focal length of the third lens is f3, and the following conditions are satisfied: -0.55 < f1/f3 < -0.15. Therefore, the refractive power of the first lens element is effectively distributed, and the sensitivity of the four-piece infrared single-wavelength lens assembly is reduced.
Preferably, the focal length of the first lens is f1, the focal length of the third lens is f4, and the following conditions are satisfied: f1/f4 is more than 0.35 and less than 0.77. Therefore, the refractive power of the first lens element is effectively distributed, and the sensitivity of the four-piece infrared single-wavelength lens assembly is reduced.
Preferably, the focal length of the second lens is f2, the focal length of the fourth lens is f4, and the following conditions are satisfied: 6.0 < f2/f4 < 68.5. Therefore, the distribution of the negative refractive power of the system is more appropriate, and the aberration of the system can be corrected to improve the imaging quality of the system.
Preferably, the focal length of the first lens is f1, the combined focal length of the second lens and the third lens is f23, and the following conditions are satisfied: -0.55 < f1/f23 < -0.1. Therefore, when f1/f23 satisfies the above condition, the resolution capability of the four-piece infrared single-wavelength lens set can be significantly improved.
Preferably, a combined focal length of the first lens element and the second lens element is f12, a combined focal length of the third lens element and the fourth lens element is f34, and the following conditions are satisfied: f12/f34 is more than 0.1 and less than 0.45. Thus, the field curvature can be effectively corrected.
Preferably, the focal length of the second lens element is f2, the combined focal length of the third lens element and the fourth lens element is f34, and the following conditions are satisfied: 2.7 < f2/f34 < 30. Thus, the field curvature can be effectively corrected.
Preferably, a focal length of the second lens element and the third lens element is f23, a focal length of the fourth lens element is f4, and the following conditions are satisfied: -2.5 < f23/f4 < 1.2. Therefore, when f23/f4 satisfies the above condition, the resolution capability of the four-piece infrared single-wavelength lens set can be significantly improved.
Preferably, the focal length of the first lens element is f1, the combined focal length of the second lens element, the third lens element and the fourth lens element is f234, and the following conditions are satisfied: 0.13 < f1/f234 < 0.5. By proper configuration of the refractive power, the spherical aberration and astigmatism can be reduced.
Preferably, a focal length of the first lens element, the second lens element and the third lens element is f123, a focal length of the fourth lens element is f4, and the following conditions are satisfied: f123/f4 is more than 0.55 and less than 1.25. By proper configuration of the refractive power, the spherical aberration and astigmatism can be reduced.
Preferably, the refractive index of the fourth lens is N4, the abbe number of the fourth lens is V4, and the following conditions are satisfied: 1.61 < N4; v4 < 25. Therefore, the chromatic aberration of the four-piece infrared single-wavelength lens set is effectively reduced, and better aberration balancing capability is provided.
Preferably, the overall focal length of the four-piece infrared single-wavelength lens set is f, the distance between the object-side surface of the first lens element and the image plane on the optical axis is TL, and the following conditions are satisfied: f/TL is more than 0.5 and less than 0.9. Therefore, the four-piece infrared single-wavelength lens group can be kept miniaturized and can be carried on light and thin electronic products.
Drawings
Fig. 1A is a schematic view of a four-piece infrared single-wavelength lens set according to a first embodiment of the invention.
Fig. 1B is a graph illustrating the curvature of field and the distortion of the image plane of the four-piece infrared single-wavelength lens assembly according to the first embodiment in order from left to right.
Fig. 2A is a schematic view of a four-piece infrared single-wavelength lens set according to a second embodiment of the invention.
Fig. 2B is a graph illustrating the curvature of field and the distortion of the image plane of the four-piece infrared single-wavelength lens assembly according to the second embodiment in order from left to right.
Fig. 3A is a schematic view of a four-piece infrared single-wavelength lens set according to a third embodiment of the invention.
Fig. 3B is a graph illustrating the curvature of field and distortion aberration of the four-piece infrared single-wavelength lens assembly according to the third embodiment.
Fig. 4A is a schematic view of a four-piece infrared single-wavelength lens set according to a fourth embodiment of the invention.
Fig. 4B is a graph illustrating the curvature of field and distortion aberration of the four-piece infrared single-wavelength lens assembly according to the fourth embodiment.
Fig. 5A is a schematic view of a four-piece infrared single-wavelength lens set according to a fifth embodiment of the invention.
Fig. 5B is a graph illustrating the curvature of field and distortion of the four-piece infrared single-wavelength lens assembly of the fifth embodiment in order from left to right.
Fig. 6A is a schematic view of a four-piece infrared single-wavelength lens set according to a sixth embodiment of the invention.
FIG. 6B is a graph illustrating the curvature of field and distortion of the four-piece infrared single-wavelength lens assembly of the sixth embodiment in order from left to right.
Description of the reference numerals
100. 200, 300, 400, 500, 600: aperture
110. 210, 310, 410, 510, 610: first lens
111. 211, 311, 411, 511, 611: object side surface
112. 212, 312, 412, 512, 612: surface of image side
120. 220, 320, 420, 520, 620: second lens
121. 221, 321, 421, 521, 621: object side surface
122. 222, 322, 422, 522, 622: surface of image side
130. 230, 330, 430, 530, 630: third lens
131. 231, 331, 431, 531, 631: object side surface
132. 232, 332, 432, 532, 632: surface of image side
140. 240, 340, 440, 540, 640: fourth lens
141. 241, 341, 441, 541, 641: object side surface
142. 242, 342, 442, 542, 642: surface of image side
170. 270, 370, 470, 570, 670: infrared filtering component
180. 280, 380, 480, 580, 680: image plane
190. 290, 390, 490, 590, 690: optical axis
f: focal length of four-piece infrared single-wavelength lens group
Fno: aperture value of four-piece infrared single-wavelength lens group
FOV: maximum field angle in four-piece infrared single-wavelength lens group
f 1: focal length of the first lens
f 2: focal length of the second lens
f 3: focal length of the third lens
f 4: focal length of the fourth lens
f 12: the combined focal length of the first lens and the second lens
f 23: the combined focal length of the second lens and the third lens
f 34: the combined focal length of the third lens and the fourth lens
f 123: the combined focal length of the first lens, the second lens and the third lens
f 234: the combined focal length of the second lens, the third lens and the fourth lens
V4: abbe number of fourth lens
N4: refractive index of fourth lens
TL: distance between the object side surface of the first lens element and the image plane on the optical axis
Detailed Description
< first embodiment >
Referring to fig. 1A and fig. 1B, fig. 1A is a schematic diagram of a four-piece infrared single-wavelength lens assembly according to a first embodiment of the disclosure, and fig. 1B is a graph of image plane curvature and distortion aberration of the four-piece infrared single-wavelength lens assembly of the first embodiment in order from left to right. In fig. 1A, the four-piece infrared single-wavelength lens assembly includes an aperture stop 100 and an optical assembly, which includes, in order from an object side to an image side, a first lens element 110, a second lens element 120, a third lens element 130, a fourth lens element 140, an ir-cut filter 170, and an image plane 180, wherein the four lens elements of the four-piece infrared single-wavelength lens assembly have refractive power. The aperture stop 100 is disposed between an object-side surface 111 and an image-side surface 112 of the first lens element 110.
The first lens element 110 with positive refractive power has an object-side surface 111 being convex at a paraxial region 190 and an image-side surface 112 being concave at a paraxial region 190, and the object-side surface 111 and the image-side surface 112 are aspheric.
The second lens element 120 with positive refractive power has an object-side surface 121 being concave in a paraxial region 190 and an image-side surface 122 being convex in a paraxial region 190, and is made of plastic material, wherein the object-side surface 121 and the image-side surface 122 are aspheric.
The third lens element 130 with negative refractive power has an object-side surface 131 being concave at a paraxial region 190 and an image-side surface 132 being convex at a paraxial region 190, and the object-side surface 131 and the image-side surface 132 are aspheric.
The fourth lens element 140 with positive refractive power has an object-side surface 141 being convex at a paraxial region 190 and an image-side surface 142 being concave at a paraxial region 190, wherein the object-side surface 141 and the image-side surface 142 are aspheric, and at least one of the object-side surface 141 and the image-side surface 142 has at least one inflection point.
The ir-cut filter assembly 170 is made of glass, and is disposed between the fourth lens element 140 and the image plane 180 without affecting the focal length of the four-piece ir single-wavelength lens assembly.
The curve equation of the aspherical surface of each lens described above is as follows:
wherein z is a position value referenced to the surface vertex at a position of height h along the optical axis 190; c is a curvature of the lens surface near the optical axis 190 and is an inverse of a curvature radius (R) (c is 1/R), R is a curvature radius of the lens surface near the optical axis 190, h is a perpendicular distance of the lens surface from the optical axis 190, k is a conic coefficient (conic constant), and A, B, C, D, E, G, … … are high order aspheric coefficients.
In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the four-piece infrared single-wavelength lens group is f, the aperture value (f-number) of the four-piece infrared single-wavelength lens group is Fno, and the maximum field angle (view angle 2 ω) in the four-piece infrared single-wavelength lens group is FOV, and the values thereof are as follows: f is 2.962 (mm); fno 2.0; and FOV 78.7 (degrees).
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the first lens element 110 is f1, the focal length of the second lens element 120 is f2, and the following conditions are satisfied: f1/f2 ═ 0.009.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the second lens element 120 is f2, the focal length of the third lens element 130 is f3, and the following conditions are satisfied: f2/f 3-41.366.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the third lens element 130 is f3, the focal length of the fourth lens element 140 is f4, and the following conditions are satisfied: f3/f4 is-1.603.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the first lens element 110 is f1, the focal length of the third lens element 130 is f3, and the following conditions are satisfied: f1/f3 is-0.390.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the first lens element 110 is f1, the focal length of the fourth lens element 140 is f4, and the following conditions are satisfied: f1/f4 is 0.625.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the second lens element 120 is f2, the focal length of the fourth lens element 140 is f4, and the following conditions are satisfied: 66.328 for f2/f 4.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the first lens element 110 is f1, and the combined focal length of the second lens element 120 and the third lens element 130 is f23, and the following conditions are satisfied: f1/f23 is-0.405.
In the first embodiment of the four-piece infrared single-wavelength lens assembly, a combined focal length of the first lens element 110 and the second lens element 120 is f12, a combined focal length of the third lens element 130 and the fourth lens element 140 is f34, and the following conditions are satisfied: f12/f34 equals 0.279.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the second lens element 120 is f2, the combined focal length of the third lens element 130 and the fourth lens element 140 is f34, and the following conditions are satisfied: 28.143 for f2/f 34.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, a combined focal length of the second lens element 120 and the third lens element 130 is f23, a focal length of the fourth lens element 140 is f4, and the following conditions are satisfied: f23/f4 is-1.544.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, the focal length of the first lens element 110 is f1, and the combined focal length of the second lens element 120, the third lens element 130 and the fourth lens element 140 is f234, and the following conditions are satisfied: f1/f234 equals 0.290.
In the four-piece infrared single-wavelength lens assembly of the first embodiment, a combined focal length of the first lens element 110, the second lens element 120 and the third lens element 130 is f123, a focal length of the fourth lens element 140 is f4, and the following conditions are satisfied: f123/f4 is 1.064.
In the first embodiment of the four-piece infrared single-wavelength lens assembly, the overall focal length of the four-piece infrared single-wavelength lens assembly is f, the distance from the object-side surface 111 of the first lens element 110 to the image plane 180 on the optical axis 190 is TL, and the following conditions are satisfied: f/TL is 0.713.
Further, refer to the following Table 1 and Table 2.
Table 1 shows the detailed structural data of the first embodiment of fig. 1A, wherein the units of the radius of curvature, the thickness and the focal length are mm, and surfaces 0-13 sequentially represent the surfaces from the object side to the image side. Table 2 shows aspheric data in the first embodiment, where k denotes a cone coefficient in the aspheric curve equation, and A, B, C, D, E, F and … denote higher-order aspheric coefficients. In addition, the following tables of the embodiments correspond to the schematic diagrams of the embodiments and the field curvature and distortion aberration curves, and the definitions of the data in the tables are the same as those in tables 1 and 2 of the first embodiment, which are not repeated herein.
< second embodiment >
Referring to fig. 2A and fig. 2B, fig. 2A is a schematic diagram of a four-piece infrared single-wavelength lens assembly according to a second embodiment of the disclosure, and fig. 2B is a graph of image plane curvature and distortion aberration of the four-piece infrared single-wavelength lens assembly of the second embodiment in order from left to right. In fig. 2A, the four-piece infrared single-wavelength lens assembly includes an aperture stop 200 and an optical assembly including, in order from an object side to an image side, a first lens element 210, a second lens element 220, a third lens element 230, a fourth lens element 240, an ir-cut filter 270 and an image plane 280, wherein the four lens elements of the four-piece infrared single-wavelength lens assembly have four refractive power. The aperture stop 200 is disposed between an object-side surface 211 and an image-side surface 212 of the first lens element 210.
The first lens element 210 with positive refractive power has an object-side surface 211 being convex at a paraxial region 290 and an image-side surface 212 being concave at a paraxial region 290, and the object-side surface 211 and the image-side surface 212 are aspheric.
The second lens element 220 with positive refractive power has an object-side surface 221 being concave at a paraxial region 290 thereof and an image-side surface 222 being convex at a paraxial region 290 thereof, wherein the object-side surface 221 and the image-side surface 222 are aspheric.
The third lens element 230 with negative refractive power has an object-side surface 231 being concave at a paraxial region 290 and an image-side surface 232 being convex at a paraxial region 290, and is made of plastic material, wherein the object-side surface 231 and the image-side surface 232 are aspheric.
The fourth lens element 240 with positive refractive power has an object-side surface 241 being convex at a paraxial region 290 and an image-side surface 242 being concave at a paraxial region 290, wherein the object-side surface 241 and the image-side surface 242 are aspheric and at least one of the object-side surface 241 and the image-side surface 242 has at least one inflection point.
The ir-cut filter 270 is made of glass, and is disposed between the fourth lens element 240 and the image plane 280 without affecting the focal length of the four-piece ir single-wavelength lens assembly.
Further, the following Table 3 and Table 4 are referred to.
In the second embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.
The following data can be derived from tables 3 and 4:
< third embodiment >
Referring to fig. 3A and fig. 3B, fig. 3A is a schematic diagram of a four-piece infrared single-wavelength lens assembly according to a third embodiment of the invention, and fig. 3B is a graph illustrating an image plane curvature and a distortion tolerance of the four-piece infrared single-wavelength lens assembly of the third embodiment in order from left to right. In fig. 3A, the four-piece infrared single-wavelength lens assembly includes an aperture stop 300 and an optical assembly, which includes, in order from an object side to an image side, a first lens element 310, a second lens element 320, a third lens element 330, a fourth lens element 340, an ir-cut filter 370 and an image plane 380, wherein the four lens elements of the four-piece infrared single-wavelength lens assembly have four refractive power. The stop 300 is disposed between an object-side surface 311 and an image-side surface 312 of the first lens element 310.
The first lens element 310 with positive refractive power has an object-side surface 311 being convex at a paraxial region 390, and an image-side surface 312 being concave at a paraxial region 390, wherein the object-side surface 311 and the image-side surface 312 are aspheric.
The second lens element 320 with positive refractive power has an object-side surface 321 being concave at a paraxial region 390 thereof and an image-side surface 322 being convex at a paraxial region 390 thereof, and the object-side surface 321 and the image-side surface 322 are aspheric.
The third lens element 330 with negative refractive power has an object-side surface 331 being concave at a paraxial region 390 thereof and an image-side surface 332 being convex at a paraxial region 390 thereof, wherein the object-side surface 331 and the image-side surface 332 are aspheric.
The fourth lens element 340 with positive refractive power is made of plastic material, and has an object-side surface 341 being convex at a position close to the optical axis 390, and an image-side surface 342 being concave at a position close to the optical axis 390, wherein the object-side surface 341 and the image-side surface 342 are both aspheric, and at least one of the object-side surface 341 and the image-side surface 342 has at least one inflection point.
The ir-cut filter 370 is made of glass and disposed between the fourth lens element 340 and the image plane 380 without affecting the focal length of the four-piece ir single-wavelength lens assembly.
Further, the following Table 5 and Table 6 were referred to.
In the third embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.
The following data can be derived from tables 5 and 6:
< fourth embodiment >
Referring to fig. 4A and 4B, fig. 4A is a schematic diagram of a four-piece infrared single-wavelength lens assembly according to a fourth embodiment of the disclosure, and fig. 4B is a graph illustrating an image plane curvature and a distortion tolerance curve of the four-piece infrared single-wavelength lens assembly of the fourth embodiment from left to right. In fig. 4A, the four-piece infrared single-wavelength lens assembly includes an aperture stop 400 and an optical assembly including, in order from an object side to an image side, a first lens element 410, a second lens element 420, a third lens element 430, a fourth lens element 440, an ir-cut filter 470 and an image plane 480, wherein the four-piece infrared single-wavelength lens assembly includes four lens elements with refractive power. The aperture stop 400 is disposed between an object-side surface 411 and an image-side surface 412 of the first lens 410.
The first lens element 410 with positive refractive power has an object-side surface 411 being convex at a paraxial region 490 thereof and an image-side surface 412 being concave at a paraxial region 490 thereof, and the object-side surface 411 and the image-side surface 412 are aspheric.
The second lens element 420 with positive refractive power has an object-side surface 421 being concave at a paraxial region 490 thereof and an image-side surface 422 being convex at a paraxial region 490 thereof, wherein the object-side surface 421 and the image-side surface 422 are aspheric.
The third lens element 430 with negative refractive power has an object-side surface 431 being concave at a paraxial region 490 thereof and an image-side surface 432 being convex at a paraxial region 490 thereof, and the object-side surface 431 and the image-side surface 432 are aspheric.
The fourth lens element 440 with positive refractive power has an object-side surface 441 being convex at a paraxial region 490 thereof and an image-side surface 442 being concave at a paraxial region 490 thereof, wherein the object-side surface 441 and the image-side surface 442 are aspheric, and at least one of the object-side surface 441 and the image-side surface 442 has at least one inflection point.
The ir-cut filter 470 is made of glass and disposed between the fourth lens element 440 and the image plane 480 without affecting the focal length of the four-piece ir single-wavelength lens assembly.
Further, the following Table 7 and Table 8 are referred to.
In the fourth embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.
The following data can be derived from tables 7 and 8:
< fifth embodiment >
Referring to fig. 5A and 5B, fig. 5A is a schematic diagram of a four-piece infrared single-wavelength lens assembly according to a fifth embodiment of the invention, and fig. 5B is a graph illustrating a curvature of field and a skew aberration of the four-piece infrared single-wavelength lens assembly of the fifth embodiment in order from left to right. In fig. 5A, the four-piece infrared single-wavelength lens assembly includes an aperture stop 500 and an optical assembly, which includes, in order from an object side to an image side, a first lens element 510, a second lens element 520, a third lens element 530, a fourth lens element 540, an ir-cut filter 570 and an image plane 580, wherein the four lens elements of the four-piece infrared single-wavelength lens assembly have four refractive power. The stop 500 is disposed between an object-side surface 511 and an image-side surface 512 of the first lens element 510.
The first lens element 510 with positive refractive power has an object-side surface 511 being convex in a paraxial region 590, an image-side surface 512 being concave in a paraxial region 590, and both the object-side surface 511 and the image-side surface 512 being aspheric.
The second lens element 520 with positive refractive power has an object-side surface 521 being concave in a paraxial region 590, and an image-side surface 522 being convex in a paraxial region 590, and the object-side surface 521 and the image-side surface 522 are aspheric.
The third lens element 530 with negative refractive power has an object-side surface 531 being concave at a paraxial region 590 and an image-side surface 532 being convex at a paraxial region 590, and the object-side surface 531 and the image-side surface 532 are aspheric.
The fourth lens element 540 with positive refractive power has an object-side surface 541 being convex in a paraxial region 590 and an image-side surface 542 being concave in a paraxial region 590, the object-side surface 541 and the image-side surface 542 are aspheric, and at least one of the object-side surface 541 and the image-side surface 542 has at least one inflection point.
The ir-cut filter 570 is made of glass, and is disposed between the fourth lens element 540 and the image plane 580 without affecting the focal length of the four-piece ir single-wavelength lens assembly.
Further, the following table 9 and table 10 are referred to.
In the fifth embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.
The following data can be derived from tables 9 and 10:
< sixth embodiment >
Referring to fig. 6A and 6B, fig. 6A is a schematic diagram illustrating a four-piece infrared single-wavelength lens assembly according to a sixth embodiment of the invention, and fig. 6B is a graph illustrating a curvature of field and a skew aberration of the four-piece infrared single-wavelength lens assembly of the sixth embodiment, in order from left to right. In fig. 6A, the four-piece infrared single-wavelength lens assembly includes an aperture stop 600 and an optical assembly, which includes, in order from an object side to an image side, a first lens element 610, a second lens element 620, a third lens element 630, a fourth lens element 640, an ir-cut filter 670 and an image plane 680, wherein the four lens elements in the four-piece infrared single-wavelength lens assembly have refractive power. The aperture stop 600 is disposed between an object-side surface 611 and an image-side surface 612 of the first lens 610.
The first lens element 610 with positive refractive power has an object-side surface 611 being convex at a paraxial region 690 and an image-side surface 612 being concave at a paraxial region 690, and is made of plastic material, wherein the object-side surface 611 and the image-side surface 612 are aspheric.
The second lens element 620 with positive refractive power has an object-side surface 621 being concave in a paraxial region 690 thereof and an image-side surface 622 being convex in a paraxial region 690 thereof, and is made of plastic material, wherein the object-side surface 621 and the image-side surface 622 are aspheric.
The third lens element 630 with negative refractive power has an object-side surface 631 being concave at a paraxial region 690 and an image-side surface 632 being convex at a paraxial region 690, and the object-side surface 631 and the image-side surface 632 are aspheric.
The fourth lens element 640 with positive refractive power is made of plastic material, and has an object-side surface 641 being convex in a paraxial region 690 and an image-side surface 642 being concave in a paraxial region 690, wherein the object-side surface 641 and the image-side surface 642 are aspheric, and at least one of the object-side surface 641 and the image-side surface 642 has at least one inflection point.
The ir-cut filter 670 is made of glass and disposed between the fourth lens element 640 and the image plane 680 without affecting the focal length of the four-piece ir single-wavelength lens assembly.
Further, the following table 11 and table 12 are referred to.
In the sixth embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.
The following data can be derived from tables 11 and 12:
in the four-piece infrared single-wavelength lens group provided by the invention, the material of the lens can be plastic or glass, when the material of the lens is plastic, the production cost can be effectively reduced, and when the material of the lens is glass, the degree of freedom of the configuration of the refractive power of the four-piece infrared single-wavelength lens group can be increased. In addition, the object-side surface and the image-side surface of the lenses in the four-piece infrared single-wavelength lens group can be aspheric surfaces, the aspheric surfaces can be easily made into shapes other than spherical surfaces, more control variables are obtained for reducing the aberration, and the number of the lenses is further reduced, so that the total length of the four-piece infrared single-wavelength lens group can be effectively reduced.
In the four-piece infrared single-wavelength lens assembly provided by the invention, regarding the lens with refractive power, if the lens surface is convex and the position of the convex is not defined, the lens surface is convex at the paraxial region; if the lens surface is concave and the concave position is not defined, it means that the lens surface is concave at the paraxial region.
The four-piece infrared single-wavelength lens group provided by the invention can be applied to an optical system for moving focusing according to requirements, has the characteristics of excellent aberration correction and good imaging quality, and can be applied to electronic image systems such as 3D (three-dimensional) image acquisition, digital cameras, mobile devices, digital drawing boards or vehicle photography and the like in many aspects.
In summary, the above embodiments and drawings are only preferred embodiments of the present invention, and the scope of the present invention should not be limited thereby, that is, all equivalent changes and modifications made according to the claims of the present invention should be covered by the scope of the present invention.

Claims (14)

1. The utility model provides a four formula infrared single wavelength lens group which characterized in that: in order from an object side to an image side:
an aperture;
a first lens element with positive refractive power having an object-side surface being convex at a paraxial region and an image-side surface being concave at a paraxial region, at least one of the object-side surface and the image-side surface being aspheric;
a second lens element with positive refractive power having an object-side surface being concave at a paraxial region thereof and an image-side surface being convex at a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface thereof is aspheric;
a third lens element with negative refractive power having an object-side surface being concave at a paraxial region thereof and an image-side surface being convex at a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface thereof is aspheric; and
a fourth lens element with positive refractive power having an object-side surface being convex at a paraxial region and an image-side surface being concave at a paraxial region, at least one of the object-side surface and the image-side surface being aspheric;
the focal length of the first lens is f1, the focal length of the fourth lens is f4, and the following conditions are met: f1/f4 is more than 0.35 and less than 0.77.
2. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the first lens is f1, the focal length of the second lens is f2, and the following conditions are satisfied: 0.005 < f1/f2 < 0.09.
3. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the second lens is f2, the focal length of the third lens is f3, and the following conditions are met: -42 < f2/f3 < -3.2.
4. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the following conditions are met: -2.1 < f3/f4 < -1.3.
5. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the first lens is f1, the focal length of the third lens is f3, and the following conditions are met: -0.55 < f1/f3 < -0.15.
6. The set of four-piece infrared single-wavelength lens of claim 1, wherein the focal length of the second lens element is f2, and the focal length of the fourth lens element is f4, wherein the following conditions are satisfied: 6.0 < f2/f4 < 68.5.
7. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the first lens is f1, the combined focal length of the second lens and the third lens is f23, and the following conditions are satisfied: -0.55 < f1/f23 < -0.1.
8. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the combined focal length of the first lens and the second lens is f12, the combined focal length of the third lens and the fourth lens is f34, and the following conditions are satisfied: f12/f34 is more than 0.1 and less than 0.45.
9. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the second lens is f2, the combined focal length of the third lens and the fourth lens is f34, and the following conditions are satisfied: 2.7 < f2/f34 < 30.
10. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the second lens and the third lens is f23, the focal length of the fourth lens is f4, and the following conditions are satisfied: -2.5 < f23/f4 < 1.2.
11. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the focal length of the first lens is f1, the combined focal length of the second lens, the third lens and the fourth lens is f234, and the following conditions are satisfied: 0.13 < f1/f234 < 0.5.
12. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the combined focal length of the first lens, the second lens and the third lens is f123, the focal length of the fourth lens is f4, and the following conditions are satisfied: f123/f4 is more than 0.55 and less than 1.25.
13. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the refractive index of the fourth lens is N4, the abbe number of the fourth lens is V4, and the following conditions are met: 1.61 < N4; v4 < 25.
14. The set of four-piece infrared single wavelength lenses of claim 1, wherein: the overall focal length of the four-piece infrared single-wavelength lens group is f, the distance from the object-side surface of the first lens element to the image plane on the optical axis is TL, and the following conditions are satisfied: f/TL is more than 0.5 and less than 0.9.
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