CN113805307B

CN113805307B - Five-piece infrared single-focus lens group

Info

Publication number: CN113805307B
Application number: CN202010532911.4A
Authority: CN
Inventors: 黄靖昀
Original assignee: Xinju Technology Co ltd
Current assignee: Xinju Technology Co ltd
Priority date: 2020-06-12
Filing date: 2020-06-12
Publication date: 2022-09-02
Anticipated expiration: 2040-06-12
Also published as: CN113805307A

Abstract

The invention discloses a five-piece infrared monofocal 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 refractive power; a third lens element with refractive power; a fourth lens element with positive refractive power; and a fifth lens element with negative refractive power; the distance on the optical axis from the object-side surface of the first lens element to the imaging plane is TL, the overall focal length of the five-piece infrared monofocal lens group is f, the distance on the optical axis from the image-side surface of the fifth lens element to the imaging plane is BFL, half of the imaging height of the five-piece infrared monofocal lens group captured on the imaging plane is IMH, and the following conditions are satisfied: 3< TL xf/(BFL × IMH) <7. Therefore, the invention provides a five-piece infrared single-focus lens set with wide viewing angle, high resolution capability, short lens length and small distortion.

Description

Five-piece infrared single-focus lens group

Technical Field

The present invention relates to a five-piece lens assembly, and more particularly to a miniaturized five-piece infrared single-focus lens assembly applied to an electronic product.

Background

Nowadays, digital graphics technology is continuously innovated and changed, especially digital carriers of digital cameras and mobile phones are all miniaturized, so that photosensitive components such as CCDs or CMOSs are also required to be more miniaturized, and in addition to being applied to the field of photography, infrared focusing lenses are also widely applied to the field of infrared receiving and sensing of game machines in recent years, and in order to make the range of the game machines for sensing users wider, the current lens group for receiving infrared wavelengths mostly adopts a wide-angle lens group with a larger drawing angle as a main stream.

In which, the applicant has also previously proposed a plurality of lens sets related to infrared wavelength reception, and only the current game machine is based on a 3D game with more stereoscopic, real and realistic sensation, so that the current or previous lens sets of the applicant have been required to be detected by a 2D plane game, so that the depth sensing effect of the 3D game 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.

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 five-piece infrared single-focus lens set, and more particularly, to a four-piece infrared single-wavelength lens set with improved view angle, high resolution, short lens length, and small distortion.

To achieve the above object, the present invention provides a five-piece infrared monofocal lens assembly, which comprises an aperture stop and an optical assembly consisting of five lens elements, in order from an object side to an image side: the aperture; the first lens element with positive refractive power has an object-side surface being convex in a paraxial region thereof, and at least one of the object-side surface and the image-side surface thereof being aspheric; the second lens element with refractive power has at least one of an object-side surface and an image-side surface thereof being aspheric; the third lens element with refractive power has at least one of an object-side surface and an image-side surface thereof being aspheric; the fourth lens element with positive refractive power has an object-side surface being concave at a paraxial region thereof and an image-side surface being convex at a paraxial region thereof, and at least one of the object-side surface and the image-side surface of the fourth lens element is aspheric; the fifth lens element with negative refractive power has a convex object-side surface in a paraxial region thereof, a concave image-side surface in a paraxial region thereof, and at least one of the object-side surface and the image-side surface thereof is aspheric;

the distance on the optical axis from the object-side surface of the first lens element to the imaging plane is TL, the overall focal length of the five-piece infrared monofocal lens group is f, the distance on the optical axis from the image-side surface of the fifth lens element to the imaging plane is BFL, half of the imaging height of the five-piece infrared monofocal lens group captured on the imaging plane is IMH, and the following conditions are satisfied: 3< TL xf/(BFL IMH) <7.

Preferably, the overall focal length of the five-piece infrared monofocal lens group is f, the focal length of the first lens element is f1, and the following conditions are satisfied: 0.23< f/f1< 1.04. Therefore, the refractive power of the first lens is maintained in a proper range, the field angle (FOV) of the five-piece infrared single-focus lens group is maintained at a proper angle, and the assembly sensitivity of the first lens is reduced.

Preferably, the overall focal length of the five-piece infrared monofocal lens group is f, and 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: 0.20< f/f234< 1.83. Therefore, light rays with wider visual angles can be incident on the five-piece infrared single-focus lens group, so that the peripheral illumination is improved and the visual angle is enlarged.

Preferably, 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: 0.23< f1/f234< 5.85. Therefore, the five-piece infrared single-focus lens group has a large picture angle, and the resolution capability is obviously improved.

Preferably, a combined focal length of the first lens, the second lens and the third lens is f123, and a combined focal length of the first lens, the second lens, the third lens and the fourth lens is f1234, and the following conditions are satisfied: 0.8< f123/f1234< 2.4. This achieves an ideal resolving power.

Preferably, the overall focal length of the five-piece infrared monofocal lens group is f, and the combined focal length of the first lens element, the second lens element, the third lens element and the fourth lens element is f1234, and the following conditions are satisfied: 0.65< f/f1234< 1.72. Therefore, light with a wider visual angle can be incident on the five-piece infrared single-focus lens group, so that the peripheral illumination is improved and the visual angle is enlarged.

Preferably, a combined focal length of the third lens and the fourth lens is f34, and a combined focal length of the second lens, the third lens and the fourth lens is f234, and the following conditions are satisfied: 0.34< f34/f234< 1.40. Thus, ideal resolution capability is achieved.

Preferably, wherein the focal length of the first lens is f1, the radius of curvature of the object-side surface of the first lens is R1, and the following condition is satisfied: 1.1< f1/R1< 6.8. Thereby, the regulation of incident light rays is facilitated, especially for incident light rays with large viewing angles.

Preferably, a radius of curvature of the image-side surface of the third lens element is R6, a radius of curvature of the object-side surface of the third lens element is R5, and the following condition is satisfied: 0.16< R5/R6< 2.14. Therefore, the image bending can be corrected, and the imaging quality is improved.

Preferably, a radius of curvature of the object-side surface of the fifth lens element is R9, a radius of curvature of the image-side surface of the fifth lens element is R10, and the following condition is satisfied: 0.95< R9/R10< 7.61. Therefore, the thickness change from the near-optical axis position to the off-axis position of the fifth lens can be relieved, and the situation of poor molding caused by overlarge thickness difference at the off-axis position can be relieved.

Preferably, a focal length of the third lens element is f3, a radius of curvature of an object-side surface of the third lens element is R5, a radius of curvature of an image-side surface of the third lens element is R6, and the following conditions are satisfied: -0.2 mm ^-1 <f3/(R5×R6)<21.1 mm ^-1 . This improves lens formability.

Preferably, an axial distance between the object-side surface of the first lens element and the image plane is TL, an axial thickness of the second lens element is CT2, an axial thickness of the third lens element is CT3, and an axial thickness of the fourth lens element is CT4, and the following conditions are satisfied: 2.3< TL/(CT2+ CT3+ CT4) < 6.2. Therefore, the five-piece infrared single-focus lens group is beneficial to maintaining the miniaturization of the five-piece infrared single-focus lens group and can be loaded on light and thin electronic products.

Preferably, a distance between the object-side surface of the first lens element and the image plane on the optical axis is TL, a total focal length of the five-piece infrared monofocal lens group is f, and the following conditions are satisfied: 1.0< TL/f < 2.0. This is advantageous in obtaining a wide field angle (field angle) and in maintaining the size reduction of the five-piece infrared single-focus lens group, and the five-piece infrared single-focus lens group can be mounted on a thin and light electronic product.

Preferably, an axial distance between the image-side surface of the fifth lens element and the image plane is BFL, an axial distance between the object-side surface of the first lens element and the image plane is TL, and the following conditions are satisfied: 0.18< BFL/TL < 0.35. Thus, a suitable after-coke can be obtained.

Preferably, a distance between the object-side surface of the first lens element and the image plane is TL, a half of an imaging height of the five-piece infrared monofocal lens group on the image plane is IMH, and the following conditions are satisfied: 1.4< TL/IMH < 2.4. Therefore, the balance can be obtained between the reduction of the volume of the five-piece infrared single-focus lens group and the increase of the area of an imaging surface.

Preferably, the total focal length of the five-piece infrared monofocal lens group is f, the radius of curvature of the object-side surface of the fifth lens element is R9, and the radius of curvature of the image-side surface of the fifth lens element is R10, and the following conditions are satisfied: 0.48 mm < (f x R10)/R9<3.77 mm. Therefore, the image bending can be corrected, and the imaging quality is improved.

Drawings

Fig. 1A is a schematic view of a five-piece infrared monofocal lens set according to a first embodiment of the invention.

Fig. 1B is a graph illustrating the curvature of field and distortion aberration of the five-piece infrared single-focus lens assembly according to the first embodiment in order from left to right.

Fig. 2A is a schematic view of a five-piece infrared monofocal lens set according to a second embodiment of the present invention.

Fig. 2B is a graph of field curvature and distortion aberration curves of the five-piece infrared single-focus lens assembly of the second embodiment in order from left to right.

Fig. 3A is a schematic view of a five-piece infrared single-focal lens assembly according to a third embodiment of the present invention.

Fig. 3B is a graph illustrating the curvature of field and distortion aberration of the five-piece infrared single-focus lens assembly according to the third embodiment.

Fig. 4A is a schematic view of a five-piece infrared monofocal lens set according to a fourth embodiment of the present invention.

Fig. 4B is a graph of field curvature and distortion aberration curves of the five-piece infrared single-focus lens assembly of the fourth embodiment in order from left to right.

Fig. 5A is a schematic view of a five-piece infrared monofocal lens set according to a fifth embodiment of the present invention.

Fig. 5B is a graph of the field curvature and distortion difference curves of the five-piece infrared single-focus lens assembly of the fifth embodiment in order from left to right.

Fig. 6A is a schematic view of a five-piece infrared monofocal lens assembly according to a sixth embodiment of the invention.

FIG. 6B is a graph showing the curvature of field and distortion aberration of the five-piece infrared single-focal-point lens assembly according to the sixth embodiment in order from left to right.

Fig. 7A is a schematic view of a five-piece infrared monofocal lens set according to a seventh embodiment of the invention.

Fig. 7B is a graph sequentially showing the curvature of field and distortion aberration curves of the five-piece infrared single-focus lens assembly of the seventh embodiment from left to right.

Fig. 8A is a schematic view of a five-piece infrared monofocal lens assembly according to an eighth embodiment of the present invention.

Fig. 8B is a graph sequentially showing the curvature of field and distortion aberration curves of the five-piece infrared single-focus lens assembly according to the eighth embodiment from left to right.

Description of the symbols in the drawings:

100. 200, 300, 400, 500, 600, 700, 800: aperture of light

110. 210, 310, 410, 510, 610, 710, 810: first lens

111. 211, 311, 411, 511, 611, 711, 811: object side surface

112. 212, 312, 412, 512, 612, 712, 812: surface of image side

120. 220, 320, 420, 520, 620, 720, 820: second lens

121. 221, 321, 421, 521, 621, 721, 821: object side surface

122. 222, 322, 422, 522, 622, 722, 822: surface of image side

130. 230, 330, 430, 530, 630, 730, 830: third lens

131. 231, 331, 431, 531, 631, 731, 831: object side surface

132. 232, 332, 432, 532, 632, 732, 832: surface of image side

140. 240, 340, 440, 540, 640, 740, 840: fourth lens

141. 241, 341, 441, 541, 641, 741, 841: object side surface

142. 242, 342, 442, 542, 642, 742, 842: surface of image side

150. 250, 350, 450, 550, 650, 750, 850: fifth lens element

151. 251, 351, 451, 551, 651, 751, 851: object side surface

152. 252, 352, 452, 552, 652, 752, 852: surface of image side

160. 260, 360, 470, 570, 670, 770, 870: infrared band-pass assembly

180. 280, 380, 480, 580, 680, 780, 880: image plane

190. 290, 390, 490, 590, 690, 790, 890: optical axis

f: focal length of five-piece infrared single-focus lens group

Fno: aperture value of five-piece infrared single-focus lens group

FOV: maximum field angle in five-piece infrared single-focus lens group

f 1: focal length f3 of first lens: focal length f5 of third lens: focal length of the fifth lens

f 234: the combined focal length of the second lens, 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 34: the combined focal length of the third lens and the fourth lens

f 1234: the combined focal length of the first lens, the second lens, the third lens and the fourth lens

R1: radius of curvature of first lens object side surface R5: radius of curvature of object-side surface of third lens

R6: radius of curvature R9 of the image-side surface of the third lens: radius of curvature of object-side surface of fifth lens

R10: radius of curvature CT2 of the image-side surface of the fifth lens element: thickness of the second lens on the optical axis

CT 3: thickness CT4 of the third lens on the optical axis: thickness of the fourth lens on the optical axis

TL: distance between the object side surface of the first lens element and the image plane on the optical axis

IMH: half of the imaging height of the five-piece infrared single-focus lens group on the imaging surface

BFL: the distance between the image side surface of the fifth lens element and the image plane on the optical axis

Detailed Description

The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

First embodiment

Referring to fig. 1A and fig. 1B, fig. 1A is a schematic diagram of a five-piece infrared single-focus lens assembly according to a first embodiment of the invention, and fig. 1B is a graph of image plane curvature and distortion aberration of the five-piece infrared single-focus lens assembly of the first embodiment in order from left to right. In fig. 1A, the five-piece infrared monofocal 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, a fifth lens element 150, an infrared bandpass element 170, and an image plane 180, wherein five lens elements have refractive power. The diaphragm 100 is disposed between the subject and the first lens 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 convex 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 negative 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 the second lens element 120 is made of plastic material and both the object-side surface 121 and the image-side surface 122 are aspheric.

The third lens element 130 with positive refractive power has an object-side surface 131 being convex in a paraxial region 190 thereof and an image-side surface 132 being concave in the paraxial region 190 thereof, wherein the third lens element 130 is made of plastic material, 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 concave at a paraxial region 190 and an image-side surface 142 being convex at a paraxial region 190, and both the object-side surface 141 and the image-side surface 142 are aspheric.

The fifth lens element 150 with negative refractive power has an object-side surface 151 being convex in a paraxial region 190 and an image-side surface 152 being concave in a paraxial region 190, wherein the object-side surface 151 and the image-side surface 152 are aspheric and the object-side surface 151 and the image-side surface 152 have at least one inflection point.

The infrared band pass assembly 170 is made of glass, and is disposed between the fifth lens element 150 and the image plane 180 without affecting the focal length of the five-piece infrared single-focus 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 a 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 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, F, G … … is a higher order aspheric coefficient.

In the five-piece infrared single-focus lens group of the first embodiment, the focal length of the five-piece infrared single-focus lens group is f, the aperture value (f-number) of the five-piece infrared single-focus lens group is Fno, and the maximum field angle (view angle) in the five-piece infrared single-focus lens group is FOV, and the values thereof are as follows: f ═ 3.29 (millimeters); fno 1.35; and FOV 79.5 (degrees).

In the first embodiment of the present five-piece infrared monofocal lens group, a distance between the object-side surface 111 of the first lens element 110 and the image plane 180 on the optical axis 190 is TL, a total focal length of the five-piece infrared monofocal lens group is f, a distance between the image-side surface 152 of the fifth lens element 150 and the image plane 180 on the optical axis 190 is BFL, a half of an imaging height of the five-piece infrared monofocal lens group on the image plane 180 is IMH, and the following conditions are satisfied: TL × f/(BFL × IMH) ═ 4.18.

In the five-piece infrared monofocal lens group of the first embodiment, the overall focal length of the five-piece infrared monofocal lens group is f, the focal length of the first lens element 110 is f1, and the following conditions are satisfied: f/f1 is 0.65.

In the first embodiment of the five-piece infrared single-focus lens assembly, the total focal length of the five-piece infrared single-focus lens assembly is f, 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: f/f234 is 0.44.

In the first embodiment of the five-piece infrared monofocal lens group, 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 0.68.

In the first embodiment of the five-piece infrared monofocal lens group, a combined focal length of the first lens element 110, the second lens element 120 and the third lens element 130 is f123, and a combined focal length of the first lens element 110, the second lens element 120, the third lens element 130 and the fourth lens element 140 is f1234, and the following conditions are satisfied: f123/f1234 equals 1.36.

In the first embodiment of the five-piece infrared monofocal lens group, the overall focal length of the five-piece infrared monofocal lens group is f, and the combined focal length of the first lens element 110, the second lens element 120, the third lens element 130 and the fourth lens element 140 is f1234, and the following conditions are satisfied: f/f1234 is 0.82.

In the first embodiment of the five-piece infrared monofocal lens group, a combined focal length of the third lens element 130 and the fourth lens element 140 is f34, and a 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: f34/f234 equals 0.79.

In the first embodiment of the five-piece infrared monofocal lens group, the focal length of the first lens element 110 is f1, the radius of curvature of the object-side surface 111 of the first lens element 110 is R1, and the following conditions are satisfied: f1/R1 equals 1.41.

In the first embodiment of the present five-piece infrared monofocal lens group, the radius of curvature of the object-side surface 131 of the third lens element 130 is R5, the radius of curvature of the image-side surface 132 of the third lens element 130 is R6, and the following conditions are satisfied: R5/R6 is 0.63.

In the first embodiment of the five-piece infrared monofocal lens group, the radius of curvature of the object-side surface 151 of the fifth lens element 150 is R9, the radius of curvature of the image-side surface 152 of the fifth lens element 150 is R10, and the following conditions are satisfied: R9/R10 ═ 1.24.

In the first embodiment of the five-piece infrared monofocal lens group, the focal length of the third lens element 130 is f3, the radius of curvature of the object-side surface 131 of the third lens element 130 is R5, and the radius of curvature of the image-side surface 132 of the third lens element 130 is R6, wherein the following conditions are satisfied: f3/(R5 × R6) 0.48 mm ^-1 。

In the first embodiment of the five-piece infrared monofocal lens group, a distance TL from the object-side surface 111 of the first lens element 110 to the image plane 180 along the optical axis 190 is equal to TL, a thickness CT2 of the second lens element 120 along the optical axis 190 is equal to CT3 of the third lens element 130 along the optical axis 190, and a thickness CT4 of the fourth lens element 140 along the optical axis 190 satisfy the following conditions: TL/(CT2+ CT3+ CT4) is 3.63.

In the first embodiment of the present five-piece infrared single-focal lens assembly, a distance TL from the object-side surface 111 of the first lens element 110 to the image plane 180 on the optical axis 190 is equal to f, and the following conditions are satisfied: TL/f is 1.62.

In the first embodiment of the present invention, a distance between the image-side surface 152 of the fifth lens element 150 and the image plane 180 along the optical axis 190 is BFL, a distance between the object-side surface 111 of the first lens element 110 and the image plane 180 along the optical axis 190 is TL, and the following conditions are satisfied: BFL/TL is 0.29.

In the first embodiment of the present five-piece infrared single-focal lens assembly, a distance TL from the object-side surface 111 of the first lens element 110 to the image plane 180 on the optical axis 190 is equal to TL, a half of an imaging height of the five-piece infrared single-focal lens assembly on the image plane 180 is IMH, and the following conditions are satisfied: TL/IMH ═ 1.96.

In the first embodiment of the present five-piece infrared monofocal lens group, the overall focal length of the five-piece infrared monofocal lens group is f, the radius of curvature of the object-side surface 151 of the fifth lens element 150 is R9, the radius of curvature of the image-side surface 152 of the fifth lens element 150 is R10, and the following conditions are satisfied: (f × R10)/R9 ═ 2.66 mm.

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 radius of curvature, the thickness and the focal length are in mm, and the surfaces 0-15 sequentially represent the surfaces from the object side to the image side, and include the test surface (i.e., surface 1). 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, G … denotes a higher-order aspheric coefficient. 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, wherein fig. 2A is a schematic diagram of a five-piece infrared single-focus lens assembly according to a second embodiment of the invention, and fig. 2B is a graph of curvature of field and distortion aberration of the five-piece infrared single-focus lens assembly of the second embodiment in order from left to right. In fig. 2A, the five-piece infrared monofocal 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, a fifth lens element 250, an infrared bandpass element 270, and an image plane 280, wherein five of the five-piece infrared monofocal lens assembly has refractive power. The diaphragm 200 is disposed between the subject and the first lens 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 convex at a paraxial region 290, and the object-side surface 211 and the image-side surface 212 of the first lens element are aspheric.

The second lens element 220 with negative refractive power has an object-side surface 221 being concave at a paraxial region 290 thereof and an image-side surface 222 being concave at a paraxial region 290 thereof, and the object-side surface 221 and the image-side surface 222 are aspheric.

The third lens element 230 with positive refractive power has an object-side surface 231 being convex at a paraxial region 290 and an image-side surface 232 being concave at a paraxial region 290, and both 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 concave at a paraxial region 290 thereof and an image-side surface 242 being convex at a paraxial region 290 thereof, and the object-side surface 241 and the image-side surface 242 are aspheric.

The fifth lens element 250 with negative refractive power has an object-side surface 251 being convex at a paraxial region 290 and an image-side surface 252 being concave at a paraxial region 290, wherein the object-side surface 251 and the image-side surface 252 are aspheric and the object-side surface 251 and the image-side surface 252 have at least one inflection point.

The infrared band pass assembly 270 is made of glass, and is disposed between the fifth lens element 250 and the image plane 280 without affecting the focal length of the five-piece infrared single focal 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 3B, wherein fig. 3A is a schematic diagram illustrating a five-piece infrared single-focus lens assembly according to a third embodiment of the invention, and fig. 3B is a graph of image plane bending and distortion aberration curves of the five-piece infrared single-focus lens assembly of the third embodiment in order from left to right. In fig. 3A, the five-piece infrared monofocal lens assembly includes an aperture stop 300 and an optical assembly including, 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, a fifth lens element 350, an infrared bandpass element 370 and an image plane 380, wherein five of the five-piece infrared monofocal lens assembly has refractive power. The diaphragm 300 is disposed between the subject and the first lens 310.

The first lens element 310 with positive refractive power has an object-side surface 311 being convex at a paraxial region 390, an image-side surface 312 being concave at a paraxial region 390, and both the object-side surface 311 and the image-side surface 312 being aspheric.

The second lens element 320 with positive refractive power has an object-side surface 321 being concave at a paraxial region 390, and an image-side surface 322 being convex at a paraxial region 390, wherein the object-side surface 321 and the image-side surface 322 are aspheric.

The third lens element 330 with positive refractive power has an object-side surface 331 being convex at a paraxial region 390, an image-side surface 332 being concave at a paraxial region 390, and both the object-side surface 331 and the image-side surface 332 being aspheric.

The fourth lens element 340 with positive refractive power has an object-side surface 341 being concave at a paraxial region 390, an image-side surface 342 being convex at a paraxial region 390, and both the object-side surface 341 and the image-side surface 342 being aspheric.

The fifth lens element 350 with negative refractive power has an object-side surface 351 being convex at a paraxial region 390, an image-side surface 352 being concave at a paraxial region 390, the object-side surface 351 and the image-side surface 352 being aspheric, and the object-side surface 351 and the image-side surface 352 both have at least one inflection point.

The infrared bandpass element 370 is made of glass and disposed between the fifth lens element 350 and the image plane 380 without affecting the focal length of the five-piece infrared single-focus 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, wherein fig. 4A is a schematic diagram of a five-piece infrared single-focus lens assembly according to a fourth embodiment of the invention, and fig. 4B is a graph of curvature of field and distortion aberration of the five-piece infrared single-focus lens assembly of the fourth embodiment in order from left to right. In fig. 4A, the five-piece infrared monofocal lens assembly includes an aperture stop 400 and an optical group comprising, 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, a fifth lens element 450, an infrared bandpass element 470 and an image plane 480, wherein five lens elements have refractive power. The diaphragm 400 is disposed between the subject and the first lens 410.

The first lens element 410 with positive refractive power has an object-side surface 411 being convex at a position close to an optical axis 490, an image-side surface 412 being concave at the position close to the optical axis 490, and both the object-side surface 411 and the image-side surface 412 being aspheric.

The second lens element 420 with negative refractive power has an object-side surface 421 being concave at a position close to the optical axis 490, an image-side surface 422 being concave at a position close to the optical axis 490, and both the object-side surface 421 and the image-side surface 422 being aspheric.

The third lens element 430 with positive refractive power has an object-side surface 431 being convex at a paraxial region 490 thereof and an image-side surface 432 being concave 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 concave at a paraxial region 490 thereof and an image-side surface 442 being convex at the paraxial region 490 thereof, wherein the fourth lens element 440 is made of plastic material and both the object-side surface 441 and the image-side surface 442 are aspheric.

The fifth lens element 450 with negative refractive power has an object-side surface 451 being convex at a paraxial region 490 thereof and an image-side surface 452 being concave at a paraxial region 490 thereof, wherein the object-side surface 451 and the image-side surface 452 are aspheric, and the object-side surface 451 and the image-side surface 452 both have at least one inflection point.

The infrared band pass element 470 is made of glass and disposed between the fifth lens element 450 and the image plane 480 without affecting the focal length of the five-piece infrared single-focus 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 illustrating a five-piece infrared single-focus lens assembly according to a fifth embodiment of the invention, and fig. 5B is a graph illustrating curvature of field and distortion aberration curves of the five-piece infrared single-focus lens assembly of the fifth embodiment from left to right. In fig. 5A, the five-piece infrared monofocal lens assembly includes an aperture stop 500 and an optical group comprising, 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, a fifth lens element 550, an infrared bandpass element 570 and an image plane 580, wherein five lens elements in the five-piece infrared monofocal lens assembly have refractive power. The diaphragm 500 is disposed between the subject and the first lens 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 convex 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 negative 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 positive refractive power has an object-side surface 531 being convex at a paraxial region 590 and an image-side surface 532 being concave at a paraxial region 590, and both 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 concave in a paraxial region 590, an image-side surface 542 being convex in a paraxial region 590, and both the object-side surface 541 and the image-side surface 542 being aspheric.

The fifth lens element 550 with negative refractive power has an object-side surface 551 being convex in a paraxial region 590, an image-side surface 552 being concave in a paraxial region 590, the object-side surface 551 and the image-side surface 552 being aspheric, and the object-side surface 551 and the image-side surface 552 both have at least one inflection point.

The infrared band pass element 570 is made of glass and disposed between the fifth lens element 550 and the image plane 580 without affecting the focal length of the five-piece infrared single-focus 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, wherein fig. 6A is a schematic diagram illustrating a five-piece infrared single-focus lens assembly according to a sixth embodiment of the invention, and fig. 6B is a graph of field curvature and distortion aberration of the five-piece infrared single-focus lens assembly of the sixth embodiment in order from left to right. In fig. 6A, the five-piece infrared monofocal 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, a fifth lens element 650, an infrared bandpass element 670 and an image plane 680, wherein five lens elements have refractive power. The diaphragm 600 is disposed between the subject and the first lens 610.

The first lens element 610 with positive refractive power has an object-side surface 611 being convex in a paraxial region 690 thereof and an image-side surface 612 being concave in a paraxial region 690 thereof, and 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 convex in a paraxial region 690 thereof, an image-side surface 622 being concave in a paraxial region 690 thereof, and both the object-side surface 621 and the image-side surface 622 being aspheric.

The third lens element 630 with negative refractive power has an object-side surface 631 being convex in a paraxial region 690 and an image-side surface 632 being concave in a paraxial region 690, wherein the object-side surface 631 and the image-side surface 632 are aspheric.

The fourth lens element 640 with positive refractive power has an object-side surface 641 being concave in a paraxial region 690 thereof, an image-side surface 642 being convex in a paraxial region 690 thereof, and the object-side surface 641 and the image-side surface 642 being aspheric.

The fifth lens element 650 with negative refractive power has an object-side surface 651 being convex at a paraxial region 690 and an image-side surface 652 being concave at a paraxial region 690, wherein the object-side surface 651 and the image-side surface 652 are aspheric, and the object-side surface 651 and the image-side surface 652 both have at least one inflection point.

The infrared band pass element 670 is made of glass material, and is disposed between the fifth lens element 650 and the image plane 680 without affecting the focal length of the five-piece infrared single-focus 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:

seventh embodiment

Referring to fig. 7A and 7B, fig. 7A is a schematic diagram illustrating a five-piece infrared single-focus lens assembly according to a seventh embodiment of the invention, and fig. 7B is a graph sequentially showing a curvature of field and a skew aberration curve of the five-piece infrared single-focus lens assembly of the seventh embodiment from left to right. In fig. 7A, the five-piece infrared monofocal lens assembly includes an aperture stop 700 and an optical assembly including, in order from an object side to an image side, a first lens element 710, a second lens element 720, a third lens element 730, a fourth lens element 740, a fifth lens element 750, an infrared bandpass element 770 and an image plane 780, wherein five of the five-piece infrared monofocal lens assembly has refractive power. The aperture stop 700 is disposed between the subject and the first lens 710.

The first lens element 710 with positive refractive power has an object-side surface 711 being convex at a paraxial region 790, an image-side surface 712 being concave at a paraxial region 790, and both the object-side surface 711 and the image-side surface 712 being aspheric.

The second lens element 720 with positive refractive power has an object-side surface 721 being convex at a paraxial region 790, an image-side surface 722 being concave at a paraxial region 790, and both the object-side surface 721 and the image-side surface 722 are aspheric.

The third lens element 730 with positive refractive power has an object-side surface 731 being convex in a paraxial region 790, an image-side surface 732 being concave in a paraxial region 790, and both the object-side surface 731 and the image-side surface 732 being aspheric.

The fourth lens element 740 with positive refractive power is made of plastic material, and has an object-side surface 741 being concave at a paraxial region 790, and an image-side surface 742 being convex at a paraxial region 790, wherein the object-side surface 741 and the image-side surface 742 are aspheric.

The fifth lens element 750 with negative refractive power is made of plastic material, and has an object-side surface 751 which is convex at a paraxial region 790, an image-side surface 752 which is concave at a paraxial region 790, wherein the object-side surface 751 and the image-side surface 752 are aspheric, and the object-side surface 751 and the image-side surface 752 both have at least one inflection point.

The infrared band pass element 770 is made of glass and disposed between the fifth lens element 750 and the image plane 780 without affecting the focal length of the five-piece infrared single-focus lens assembly.

Further, the following Table 13 and Table 14 are referred to.

In the seventh 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 the coordination tables 13 and 14:

eighth embodiment

Referring to fig. 8A and 8B, wherein fig. 8A is a schematic diagram illustrating a five-piece infrared single-focus lens assembly according to an eighth embodiment of the invention, and fig. 8B is a graph illustrating an image plane curvature and a distortion tolerance of the five-piece infrared single-focus lens assembly of the eighth embodiment in order from left to right. In fig. 8A, the five-piece infrared monofocal lens assembly includes an aperture stop 800 and an optical assembly including, in order from an object side to an image side, a first lens element 810, a second lens element 820, a third lens element 830, a fourth lens element 840, a fifth lens element 850, an infrared bandpass element 870 and an image plane 880, wherein five of the five-piece infrared monofocal lens assembly has refractive power. The aperture 800 is disposed between the subject and the first lens 810.

The first lens element 810 with positive refractive power has an object-side surface 811 being convex at a paraxial region 890 thereof and an image-side surface 812 being concave at a paraxial region 890 thereof, wherein the object-side surface 811 and the image-side surface 812 are aspheric.

The second lens element 820 with positive refractive power has an object-side surface 821 being concave in a paraxial region 890 thereof and an image-side surface 822 being convex in a paraxial region 890 thereof, wherein the object-side surface 821 and the image-side surface 822 are aspheric.

The third lens element 830 with positive refractive power has an object-side surface 831 being concave in a paraxial region 890 thereof and an image-side surface 832 being convex in a paraxial region 890 thereof, wherein the object-side surface 831 and the image-side surface 832 are aspheric.

The fourth lens element 840 with positive refractive power has an object-side surface 841 being concave at a paraxial region 890 thereof and an image-side surface 842 being convex at a paraxial region 890 thereof, wherein the object-side surface 841 and the image-side surface 842 are aspheric.

The fifth lens element 850 with negative refractive power has an object-side surface 851 being convex in a position near the optical axis 890, an image-side surface 852 being concave in a position near the optical axis 890, wherein the object-side surface 851 and the image-side surface 852 are aspheric, and the object-side surface 851 and the image-side surface 852 both have at least one inflection point.

The infrared band pass assembly 870 is made of glass and disposed between the fifth lens element 850 and the image plane 880, and does not affect the focal length of the five-piece infrared single-focus lens assembly.

Further, the following table 15 and table 16 are referred to.

In the eighth 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 the coordination table 15 and the table 16:

in the five-piece infrared single-focus 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 five-piece infrared single-focus lens group can be increased. In addition, the object side surface and the image side surface of the lens in the five-piece infrared monofocal 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 aberration, and the number of the used lenses is further reduced, so that the total length of the five-piece infrared monofocal lens group can be effectively reduced.

In the five-piece infrared monofocal lens group provided by the invention, regarding the lens with refractive power, if the lens surface is a convex surface and the position of the convex surface is not defined, the lens surface is a convex surface at a 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 five-piece infrared single-focus 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 in many aspects.

Claims

1. A five-piece infrared monofocal lens assembly, comprising an aperture stop and an optical assembly consisting of five lens elements, in order from an object side to an image side:

the aperture;

the first lens element with positive refractive power has an object-side surface being convex in a paraxial region thereof, and at least one of the object-side surface and the image-side surface thereof being aspheric;

the second lens element with refractive power has at least one of an object-side surface and an image-side surface thereof being aspheric;

the third lens element with refractive power has at least one of an object-side surface and an image-side surface thereof being aspheric;

the fourth lens element with positive refractive power has an object-side surface being concave at a paraxial region thereof and an image-side surface being convex at a paraxial region thereof, and at least one of the object-side surface and the image-side surface of the fourth lens element is aspheric; and

a fifth lens element with negative refractive power having a convex object-side surface and a concave image-side surface, wherein at least one of the object-side surface and the image-side surface of the fifth lens element is aspheric, and the at least one of the object-side surface and the image-side surface of the fifth lens element has at least one inflection point;

wherein an axial distance between the object-side surface of the first lens element and the image plane is TL, a total focal length of the five-piece infrared monofocal lens group is f, an axial distance between the image-side surface of the fifth lens element and the image plane is BFL, a half of an imaging height of the five-piece infrared monofocal lens group captured by the image plane is IMH, a radius of curvature of the object-side surface of the fifth lens element is R9, a radius of curvature of the image-side surface of the fifth lens element is R10, and the following conditions are satisfied:

3< TL xf/(BFL XMIH) <7 and 1.20 < R9/R10< 1.29, or 3< TL xf/(BFL XMIH) <7 and 6.34 < R9/R10< 7.61.

2. The set of five-piece infrared monofocal lens of claim 1, wherein the overall focal length of the set of five-piece infrared monofocal lens is f, and the focal length of the first lens element is f1, wherein the following conditions are satisfied: 0.23< f/f1< 1.04.

3. The five-piece infrared monofocal lens group of claim 1, wherein the overall focal length of the five-piece infrared monofocal lens group is f, and 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: 0.20< f/f234< 1.83.

4. The set of five-piece infrared monofocal lens according to claim 1, wherein the first lens element has a focal length f1, and the combined focal length of the second, third and fourth lens elements is f234, and the following conditions are satisfied: 0.23< f1/f234< 5.85.

5. The set of five-piece infrared monofocal lenses according to claim 1, wherein the first lens element, the second lens element and the third lens element have a combined focal length f123, and the first lens element, the second lens element, the third lens element and the fourth lens element have a combined focal length f1234, wherein the following conditions are satisfied: 0.8< f123/f1234< 2.4.

6. The five-piece infrared monofocal lens group of claim 1, wherein the total focal length of the five-piece infrared monofocal lens group is f, the combined focal length of the first lens, the second lens, the third lens and the fourth lens is f1234, and the following conditions are satisfied: 0.65< f/f1234< 1.72.

7. The set of five-piece infrared monofocal lens of claim 1, wherein the combined focal length of the third lens element and the fourth lens element is f34, and 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: 0.34< f34/f234< 1.40.

8. The set of five-piece infrared monofocal lens of claim 1, wherein the first lens element has a focal length of f1, and the object-side surface of the first lens element has a radius of curvature of R1, wherein the following conditions are satisfied: 1.1< f1/R1< 6.8.

9. The five-piece infrared monofocal lens group of claim 1, wherein the radius of curvature of the image-side surface of the third lens element is R6, the radius of curvature of the object-side surface of the third lens element is R5, and the following conditions are satisfied: 0.16< R5/R6< 2.14.

10. The five-piece infrared monofocal lens group of claim 1, wherein the third lens element has a focal length of f3, a radius of curvature of its object-side surface is R5, and a radius of curvature of its image-side surface is R6, wherein the following conditions are satisfied: -0.2 mm ^-1 <f3/(R5×R6)<21.1 mm ^-1 。

11. The five-piece infrared monofocal lens assembly of claim 1, wherein the distance along the optical axis from the object-side surface of the first lens element to the image plane is TL, the thickness along the optical axis of the second lens element is CT2, the thickness along the optical axis of the third lens element is CT3, and the thickness along the optical axis of the fourth lens element is CT4, and wherein the following conditions are satisfied: 2.3< TL/(CT2+ CT3+ CT4) < 6.2.

12. The five-piece infrared monofocal lens assembly of claim 1, wherein the distance from the object-side surface of the first lens element to the image plane is TL, the overall focal length of the five-piece infrared monofocal lens assembly is f, and the following conditions are satisfied: 1.0< TL/f < 2.0.

13. The five-piece infrared monofocal lens assembly of claim 1, wherein an axial distance BFL between the image-side surface of the fifth lens element and the image plane, an axial distance TL between the object-side surface of the first lens element and the image plane satisfy the following condition: 0.18< BFL/TL < 0.35.

14. The five-piece infrared monofocal lens assembly of claim 1, wherein the distance from the object-side surface of the first lens element to the image plane is TL, and half of the height of the image captured by the image plane of the five-piece infrared monofocal lens assembly is IMH, and satisfies the following condition: 1.4< TL/IMH < 2.4.

15. The set of five-piece infrared monofocal lens of claim 1, wherein the overall focal length of the set of five-piece infrared monofocal lens is f, the radius of curvature of the object-side surface of the fifth lens element is R9, the radius of curvature of the image-side surface of the fifth lens element is R10, and the following conditions are satisfied: 0.48 mm < (f x R10)/R9<3.77 mm.