TW201935073A - Four-piece infrared single wavelength lens system - Google Patents

Abstract

A four-piece infrared single wavelength lens system includes, in order from the object side to the image side: a first lens element with a positive refractive power having an object-side surface being convex near an optical axis and an image-side surface being concave near the optical axis, a stop, a second lens element with a refractive power, a third lens element with a positive refractive power having an object-side surface being concave near the optical axis and an image-side surface being convex near the optical axis, a fourth lens element with a negative refractive power having an object-side surface being convex near the optical axis and an image-side surface being concave near the optical axis. Such arrangements can provide a four-piece infrared single wavelength lens system which has a wide field of view, high resolution, short length and less distortion.

Description

Four-piece infrared single-wavelength lens group

The invention relates to a lens group, in particular to a miniaturized four-piece infrared single-wavelength lens group applied to electronic products.

Today's digital imaging technology is constantly innovating and changing. Especially in digital cameras such as digital cameras and mobile phones, miniaturization is developing, and photosensitive elements such as CCD or CMOS are also required to be miniaturized. In the application of infrared focusing lenses, in addition to the application In the field of photography, in recent years, it has also been widely used in the field of infrared receiving and sensing of game consoles. In order to make the range of users of the game console more broad, the current lens groups that receive infrared wavelengths are mostly larger in angle. The wide-angle lens group is mainstream.

Among them, the applicant also previously proposed a number of lens sets related to infrared wavelength reception. However, the current game consoles are mainly 3D games that are more three-dimensional, realistic and realistic. Therefore, the current or applicant's previous lens groups are based on The 2D plane game detection is an appeal, so that it cannot meet the depth sensing effect that 3D games focus on.

Moreover, the infrared receiving and sensing lens group dedicated to game consoles uses plastic lenses for the pursuit of low cost. One of the key factors that affects the lack of precision in depth detection of game consoles is the poor material transmission. The ambient temperature is too hot or too cold, so that the focal length of the lens group changes to prevent accurate focus detection. As mentioned above, the current infrared lens group cannot meet the two major technical issues of accurate sensing of depth distances in 3D games.

In view of this, how to provide an accurate depth distance detection and reception, and prevent the focal length change of the lens group from affecting the depth detection effect, has become a technical bottleneck that the infrared wavelength receiving lens group is currently desperate to overcome.

The object of the present invention is to provide a four-piece infrared single-wavelength lens group, in particular to a four-piece infrared single-wavelength lens group with enhanced picture angle, high resolution, short lens length, and small distortion.

The reason is that, in order to achieve the foregoing object, a four-piece infrared single-wavelength lens group according to the present invention includes, in order from the object side to the image side: a first lens having a positive refractive power, and an object-side surface thereof is near-light The axis is convex, the image side surface is near the optical axis is concave, at least one of the object side surface and the image side surface is aspherical; an aperture; a second lens has a refractive power, and the object side surface and the image side At least one of the surfaces is aspherical; a third lens has a positive refractive power, and its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis, and its object-side surface and image-side surface are at least one The surface is aspherical; a fourth lens has a negative refractive power, and its object-side surface is convex near the optical axis, its image-side surface is concave near the optical axis, and at least one of its object-side surface and the image-side surface is non- Sphere.

Preferably, the focal length of the first lens is f1, and the focal length of the second lens is f2, and the following conditions are satisfied: -1.0 <f1 / f2 <1.0. Therefore, the configuration of the refractive power of the first lens and the second lens is more appropriate, which can help to obtain a wide picture angle (field of view angle) and reduce excessive increase of system aberration.

Preferably, the focal length of the second lens is f2, and the focal length of the third lens is f3, and the following conditions are satisfied: -10.4 <f2 / f3 <13.8. In this way, the peripheral resolution and illumination of the system can be improved.

Preferably, the focal length of the third lens is f3, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -1.0 <f3 / f4 <-0.1. This can effectively balance the system's flexing force configuration, help reduce sensitivity and improve manufacturing yield.

Preferably, the focal length of the first lens is f1, and the focal length of the third lens is f3, and the following conditions are satisfied: 1.4 <f1 / f3 <3.0. Thereby, the positive refractive power of the first lens is effectively distributed, and the sensitivity of the four-piece infrared single-wavelength lens group is reduced.

Preferably, the focal length of the first lens is f1, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -2.1 <f1 / f4 <-0.5. Thereby, the positive refractive power of the first lens is effectively distributed, and the sensitivity of the four-piece infrared single-wavelength lens group is reduced.

Preferably, the focal length of the second lens is f2, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -9.0 <f2 / f4 <7.1. Therefore, the system's positive inflection force distribution is more appropriate, which is beneficial to correct the system aberrations and improve the imaging quality of the system.

Preferably, the focal length of the first lens is f1, and the combined focal length of the second lens and the third lens is f23, and the following conditions are satisfied: 1.2 <f1 / f23 <3.1. Therefore, when f1 / f23 satisfies the above conditions, the four-piece infrared single-wavelength lens group can obtain a wide angle of view (field of view), and its resolution can be significantly improved.

Preferably, 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: 0.48 <f12 / f34 <2.23. Thereby, it can be beneficial to obtain a wide picture angle (field of view angle) and effectively correct image plane curvature.

Preferably, the focal length of the second lens is f2, and the combined focal length of the third lens and the fourth lens is f34, and the following conditions are satisfied: -5.3 <f2 / f34 <6.7. Thereby, it can be beneficial to obtain a wide picture angle (field of view angle) and effectively correct image plane curvature.

Preferably, a combined focal length of the second lens and the third lens is f23, a focal length of the fourth lens is f4, and the following conditions are satisfied: -1.0 <f23 / f4 <-0.2. Thereby, it can be beneficial to obtain a wide picture angle (field of view angle) and effectively correct image plane curvature.

Preferably, the focal length of the first lens is f1, and the combined focal length of the second lens, the third lens, and the fourth lens is f234, and the following conditions are satisfied: 0.7 <f1 / f234 <1.8. Thereby, it can be beneficial to obtain a wide picture angle (field of view angle) and effectively correct image plane curvature.

Preferably, the combined focal length of the first lens, the second lens, and the third lens is f123, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -1.0 <f123 / f4 <-0.15. Thereby, it can be beneficial to obtain a wide picture angle (field of view angle) and effectively correct image plane curvature.

Preferably, the refractive index of the fourth lens is N4, the dispersion coefficient of the fourth lens is V4, and the following conditions are satisfied: 1.61 <N4; V4 <25. This is beneficial to the transmittance of the overall four-piece infrared single-wavelength lens group and reduces the absorption rate of the single-wavelength infrared group by the lens group.

Preferably, the overall focal length of the four-piece infrared single-wavelength lens group is f, and the distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, and satisfies the following conditions: 0.4 <f / TL <0.85. This can help maintain the miniaturization and long focus of the four-piece infrared single-wavelength lens group for mounting on thin and light electronic products.

Regarding the technology, means, and other effects adopted by the present invention to achieve the foregoing objectives, five preferred feasible embodiments are described in detail below with reference to the drawings.

<First Embodiment>

Please refer to FIG. 1A and FIG. 1B. FIG. 1A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to the first embodiment of the present invention. FIG. Single-wavelength lens group image plane curve and distortion aberration curve. It can be known from FIG. 1A that the four-piece infrared single-wavelength lens group includes an aperture 100 and an optical group, and the optical group sequentially includes the first lens 110, the second lens 120, the third lens 130, The fourth lens 140, the infrared filtering filter 170, and the imaging surface 180. Among the four-piece infrared single-wavelength lens group, there are four lenses with refractive power. The aperture 100 is disposed between the image-side surface 112 of the first lens 110 and the object-side surface 121 of the second lens 120.

The first lens 110 has a positive refractive power and is made of plastic. The object-side surface 111 is convex near the optical axis 190, the image-side surface 112 is concave near the optical axis 190, and the object-side surface 111 and the image side The surfaces 112 are all aspheric.

The second lens 120 has a positive refractive power and is made of plastic. The object-side surface 121 thereof is concave near the optical axis 190, the image-side surface 122 thereof is convex near the optical axis 190, and the object-side surface 121 and the image side The surfaces 122 are all aspheric.

The third lens 130 has a positive refractive power and is made of plastic. The object-side surface 131 of the third lens 130 is concave near the optical axis 190, the image-side surface 132 of the third lens 130 is convex near the optical axis 190, and the object-side surface 131 and the image side The surfaces 132 are all aspherical.

The fourth lens 140 has a negative refractive power and is made of plastic. The object-side surface 141 is convex near the optical axis 190, the image-side surface 142 is concave near the optical axis 190, and the object-side surface 141 and the image side The surfaces 142 are all aspheric, and at least one of the object-side surface 141 and the image-side surface 142 has at least one inflection point.

The infrared filter 170 is made of glass and is disposed between the fourth lens 140 and the imaging surface 180 without affecting the focal length of the four-piece infrared single-wavelength lens group.

The aspheric curve equations of the above lenses are expressed as follows:

Where z is the position value with the surface apex as the reference at the height h along the direction of the optical axis 190; c is the curvature of the lens surface near the optical axis 190, and is the inverse of the radius of curvature (R) (c = 1 / R) , R is the curvature radius of the lens surface close to the optical axis 190, h is the vertical distance of the lens surface from the optical axis 190, k is the conic constant, and A, B, C, D, E, G, ... are Higher-order aspheric coefficient.

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, and the aperture value (f-number) of the four-piece infrared single-wavelength lens group is Fno. The maximum field of view (picture angle) in the infrared single-wavelength lens group is FOV, and the values are as follows: f = 2.52 (mm); Fno = 1.94; and FOV = 91.4 (degrees).

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f1, and the focal length of the second lens 120 is f2, and the following conditions are satisfied: f1 / f2 = 0.31.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the second lens 120 is f2, and the focal length of the third lens 130 is f3, and the following conditions are satisfied: f2 / f3 = 7.88.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the third lens 130 is f3, and the focal length of the fourth lens 140 is f4, and the following conditions are satisfied: f3 / f4 = -0.69.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f1, and the focal length of the third lens 130 is f3, and the following conditions are satisfied: f1 / f3 = 2.47.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f1, and the focal length of the fourth lens 140 is f4, and the following conditions are satisfied: f1 / f4 = -1.69.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the second lens 120 is f2, and the focal length of the fourth lens 140 is f4, and the following conditions are satisfied: f2 / f4 = -5.40.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f1, and the combined focal length of the second lens 120 and the third lens 130 is f23, and satisfies the following conditions: f1 / f23 = 2.68.

In the four-piece infrared single-wavelength lens group of the first embodiment, the combined focal length of the first lens 110 and the second lens 120 is f12, and the combined focal distance of the third lens 130 and the fourth lens 140 is f34, and satisfies the following Conditions: f12 / f34 = 0.89.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f2, and the combined focal length of the third lens 130 and the fourth lens 140 is f34, and satisfies the following conditions: f2 / f34 = 3.45.

In the four-piece infrared single-wavelength lens group of the first embodiment, the combined focal length of the second lens 120 and the third lens 130 is f23, the focal length of the fourth lens 140 is f4, and the following conditions are satisfied: f23 / f4 = -0.63.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f1, and the combined focal length of the second lens 120, the third lens 130, and the fourth lens 140 is f234, and satisfies the following conditions : F1 / f234 = 1.39.

In the four-piece infrared single-wavelength lens group of the first embodiment, the combined focal length of the first lens 110, the second lens 120, and the third lens 130 is f123, the focal length of the fourth lens 140 is f4, and the following conditions are satisfied: : F123 / f4 = -0.66.

In the four-piece infrared single-wavelength lens group of the first embodiment, the overall focal length of the four-piece infrared single-wavelength lens group is f, and the object-side surface 111 to the imaging surface 180 of the first lens 110 are on the optical axis 190. The distance is TL and the following conditions are satisfied: f / TL = 0.61.

Refer to Tables 1 and 2 below for further cooperation.

Table 1 is the detailed structural data of the first embodiment of FIG. 1A, where the units of the radius of curvature, thickness, and focal length are mm, and the surface 0-13 shows the surface from the object side to the image side in order. Table 2 is the aspherical data in the first embodiment, where k represents the cone coefficient in the aspheric curve equation, and A, B, C, D, E, F, G, H, ... are high-order aspheric coefficients. In addition, the tables of the following embodiments are schematic diagrams and aberration curves corresponding to the embodiments. The definitions of the data in the tables are the same as the definitions of Tables 1 and 2 of the first embodiment, and will not be repeated here.

<Second Embodiment>

Please refer to FIG. 2A and FIG. 2B. FIG. 2A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a second embodiment of the present invention. FIG. 2B is a four-piece infrared of the second embodiment in order from left to right. Single-wavelength lens group image plane curve and distortion aberration curve. As can be seen from FIG. 2A, the four-piece infrared single-wavelength lens group includes an aperture 200 and an optical group, and the optical group sequentially includes a first lens 210, a second lens 220, a third lens 230, The fourth lens 240, the infrared filter 270, and the imaging surface 280. Among the four-piece infrared single-wavelength lens group, four lenses have refractive power. The aperture 200 is disposed between the image-side surface 212 of the first lens 210 and the object-side surface 221 of the second lens 220.

The first lens 210 has a positive refractive power and is made of plastic. The object-side surface 211 is convex near the optical axis 290, the image-side surface 212 is concave near the optical axis 290, and the object-side surface 211 and the image side The surfaces 212 are all aspheric.

The second lens 220 has a positive refractive power and is made of plastic. The object-side surface 221 of the second lens 220 is concave near the optical axis 290, and its image-side surface 222 is convex near the optical axis 290. The surfaces 222 are all aspheric.

The third lens 230 has a positive refractive power and is made of plastic. The object-side surface 231 of the third lens 230 is concave near the optical axis 290, and the image-side surface 232 of the third lens 230 is convex near the optical axis 290. The object-side surface 231 and the image side The surfaces 232 are all aspherical.

The fourth lens 240 has a negative refractive power and is made of plastic. The object-side surface 241 is convex near the optical axis 290, and its image-side surface 242 is concave near the optical axis 290. The object-side surface 241 and the image side The surfaces 242 are all aspheric, and at least one of the object-side surface 241 and the image-side surface 242 has at least one inflection point.

The infrared filter 270 is made of glass and is disposed between the fourth lens 240 and the imaging surface 280 without affecting the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 3 and Table 4 below for further cooperation.

In the second embodiment, the aspherical curve equation is expressed as the first embodiment. In addition, the definitions of the parameters in the following table are the same as those in the first embodiment, and will not be repeated here.

With Table 3 and Table 4, the following data can be calculated:

<Third Embodiment>

Please refer to FIG. 3A and FIG. 3B, wherein FIG. 3A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a third embodiment of the present invention, and FIG. Single-wavelength lens group image plane curve and distortion aberration curve. It can be seen from FIG. 3A that the four-piece infrared single-wavelength lens group includes an aperture 300 and an optical group, and the optical group sequentially includes a first lens 310, a second lens 320, a third lens 330, The fourth lens 340, the infrared filtering filter 370, and the imaging surface 380. Among the four-piece infrared single-wavelength lens group, there are four lenses having refractive power. The aperture 300 is disposed between the image-side surface 312 of the first lens 310 and the object-side surface 321 of the second lens 320.

The first lens 310 has a positive refractive power and is made of plastic. The object-side surface 311 is convex near the optical axis 390, and its image-side surface 312 is concave near the optical axis 390. The surfaces 312 are all aspheric.

The second lens 320 has a positive refractive power and is made of plastic. The object-side surface 321 is concave at the near optical axis 390, the image-side surface 322 is convex at the near-optical axis 390, and the object-side surface 321 and the image side The surfaces 322 are all aspheric.

The third lens 330 has a positive refractive power and is made of plastic. The object-side surface 331 is concave near the optical axis 390, the image-side surface 332 is convex near the optical axis 390, and the object-side surface 331 and the image side The surfaces 332 are all aspherical.

The fourth lens 340 has a negative refractive power and is made of plastic. The object-side surface 341 is convex near the optical axis 390, and its image-side surface 342 is concave near the optical axis 390. The object-side surface 341 and the image side The surfaces 342 are all aspheric, and at least one of the object-side surface 341 and the image-side surface 342 has at least one inflection point.

The infrared filter 370 is made of glass and is disposed between the fourth lens 340 and the imaging surface 380 without affecting the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 5 and Table 6 below for further cooperation.

In the third embodiment, the aspherical curve equation is expressed as the first embodiment. In addition, the definitions of the parameters in the following table are the same as those in the first embodiment, and will not be repeated here.

With Table 5 and Table 6, the following data can be calculated:

<Fourth embodiment>

Please refer to FIG. 4A and FIG. 4B. FIG. 4A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a fourth embodiment of the present invention. FIG. Single-wavelength lens group image plane curve and distortion aberration curve. It can be seen from FIG. 4A that the four-piece infrared single-wavelength lens group includes an aperture 400 and an optical group, and the optical group sequentially includes a first lens 410, a second lens 420, a third lens 430, The fourth lens 440, the infrared filtering filter 470, and the imaging surface 480. Among the four-piece infrared single-wavelength lens group, four lenses have refractive power. The aperture 400 is disposed between the image-side surface 412 of the first lens 410 and the object-side surface 421 of the second lens 420.

The first lens 410 has a positive refractive power and is made of plastic. The object-side surface 411 is convex near the optical axis 490, the image-side surface 412 is concave near the optical axis 490, and the object-side surface 411 and the image side The surfaces 412 are all aspherical.

The second lens 420 has a negative refractive power and is made of plastic. The object-side surface 421 is convex near the optical axis 490, the image-side surface 422 is concave near the optical axis 490, and the object-side surface 421 and the image side The surfaces 422 are all aspherical.

The third lens 430 has a positive refractive power and is made of plastic. The object-side surface 431 is concave near the optical axis 490, the image-side surface 432 is convex near the optical axis 490, and the object-side surface 431 and the image side The surfaces 432 are all aspheric.

The fourth lens 440 has a negative refractive power and is made of plastic. The object-side surface 441 is convex near the optical axis 490, the image-side surface 442 is concave near the optical axis 490, and the object-side surface 441 and the image side The surface 442 is an aspheric surface, and at least one surface of the object-side surface 441 and the image-side surface 442 has at least one inflection point.

The infrared filter 470 is made of glass and is disposed between the fourth lens 440 and the imaging surface 480 without affecting the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 7 and Table 8 below for further cooperation.

In the fourth embodiment, the curve equation of the aspherical surface is expressed as the first embodiment. In addition, the definitions of the parameters in the following table are the same as those in the first embodiment, and will not be repeated here.

With Table 7 and Table 8, the following data can be calculated:

<Fifth Embodiment>

Please refer to FIG. 5A and FIG. 5B. FIG. 5A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a fifth embodiment of the present invention. FIG. 5B is a four-piece infrared of the fifth embodiment in order from left to right. Single-wavelength lens group image plane curve and distortion aberration curve. It can be seen from FIG. 5A that the four-piece infrared single-wavelength lens group includes an aperture 500 and an optical group, and the optical group sequentially includes a first lens 510, a second lens 520, a third lens 530, The fourth lens 540, the infrared filter 570, and the imaging surface 580. Among the four-piece infrared single-wavelength lens group, there are four lenses having refractive power. The aperture 500 is disposed between the image-side surface 512 of the first lens 510 and the object-side surface 521 of the second lens 520.

The first lens 510 has a positive refractive power and is made of plastic. The object-side surface 511 is convex near the optical axis 590, the image-side surface 512 is concave near the optical axis 590, and the object-side surface 511 and the image side The surfaces 512 are all aspheric.

The second lens 520 has a negative refractive power and is made of plastic. The object-side surface 521 thereof is concave near the optical axis 590, and the image-side surface 522 thereof is concave near the optical axis 590. The object-side surface 521 and the image side The surfaces 522 are all aspherical.

The third lens 530 has a positive refractive power and is made of plastic. The object-side surface 531 of the third lens 530 is concave near the optical axis 590, the image-side surface 532 of the third lens 530 is convex near the optical axis 590, and the object-side surface 531 and the image side The surfaces 532 are all aspherical.

The fourth lens 540 has a negative refractive power and is made of plastic. The object-side surface 541 is convex near the optical axis 590, the image-side surface 542 is concave near the optical axis 590, and the object-side surface 541 and the image side The surfaces 542 are all aspheric, and at least one surface of the object-side surface 541 and the image-side surface 542 has at least one inflection point.

The infrared filter 570 is made of glass and is disposed between the fourth lens 540 and the imaging surface 580 without affecting the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 9 and Table 10 below for further cooperation.

In addition, the definitions of the parameters in the following table are the same as those in the first embodiment, and will not be repeated here.

With Table 9 and Table 10, the following data can be calculated:

In the four-piece infrared single-wavelength lens group provided by the present 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. When the material of the lens is glass, the four-piece infrared single lens can be added. The degree of freedom in the configuration of the refractive power of the wavelength lens group. In addition, the object-side surface and image-side surface of the lens in the four-piece infrared single-wavelength lens group can be aspheric, and the aspheric surface can be easily made into a shape other than a spherical surface, and more control variables are obtained to reduce aberrations and further By reducing the number of lenses used, the total length of the four-piece infrared single-wavelength lens group of the present invention can be effectively reduced.

In the four-piece infrared single-wavelength lens group provided by the present invention, in the case of a lens having a refractive power, if the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at the near optical axis. ; If the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at the near optical axis.

The four-piece infrared single-wavelength lens set provided by the present invention can be more applied to the optical system of mobile focusing according to requirements, and has the characteristics of excellent aberration correction and good imaging quality, and can be applied to 3D (three-dimensional) image capture in various aspects. , Electronic cameras such as digital cameras, mobile devices, digital tablets, or car photography.

In summary, the above-mentioned embodiments and drawings are only preferred embodiments of the present invention. When the scope of implementation of the present invention cannot be limited by this, that is, all equal changes and modifications made in accordance with the scope of the patent application of the present invention, It should be within the scope of the invention patent.

100, 200, 300, 400, 500‧‧‧ aperture

110, 210, 310, 410, 510‧‧‧ first lens

111, 211, 311, 411, 511‧‧‧ object-side surface

112, 212, 312, 412, 512‧‧‧ image side surface

120, 220, 320, 420, 520‧‧‧ second lens

121, 221, 321, 421, 521‧‧‧ object-side surface

122, 222, 322, 422, 522‧‧‧ image side surface

130, 230, 330, 430, 530‧‧‧ Third lens

131, 231, 331, 431, 531‧‧‧ object-side surface

132, 232, 332, 432, 532‧‧‧ image side surface

140, 240, 340, 440, 540‧‧‧ Fourth lens

141, 241, 341, 441, 541‧‧‧ object-side surface

142, 242, 342, 442, 542‧‧‧ image side surface

170, 270, 370, 470, 570‧‧‧ infrared filter

180, 280, 380, 480, 580‧‧‧ imaging surface

190, 290, 390, 490, 590‧‧‧ Optical axis

f‧‧‧Focal length of four-piece infrared single-wavelength lens group

Aperture value of Fno‧‧‧ four-piece infrared single-wavelength lens group

Maximum field of view in FOV‧‧‧ four-piece infrared single-wavelength lens group

f1‧‧‧ focal length of the first lens

f2‧‧‧ focal length of the second lens

f3‧‧‧ focal length of the third lens

f4‧‧‧ focal length of the fourth lens

f12‧‧‧The combined focal length of the first lens and the second lens

f23‧‧‧The combined focal length of the second lens and the third lens

f34‧‧‧The combined focal length of the third lens and the fourth lens

f123‧‧‧The combined focal length of the first lens, the second lens and the third lens

TL‧‧‧The distance from the object-side surface of the first lens to the imaging plane on the optical axis

FIG. 1A is a schematic diagram of a four-piece infrared single-wavelength lens group according to the first embodiment of the present invention. FIG. 1B is a curve diagram of the curvature and distortion of the image plane of the four-piece infrared single-wavelength lens group of the first embodiment in order from left to right. FIG. 2A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a second embodiment of the present invention. FIG. 2B is a curve diagram of the curvature and distortion of the image plane of the four-piece infrared single-wavelength lens group of the second embodiment in order from left to right. 3A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a third embodiment of the present invention. FIG. 3B is a curve diagram of the curvature and distortion of the image plane of the four-piece infrared single-wavelength lens group of the third embodiment in order from left to right. 4A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a fourth embodiment of the present invention. FIG. 4B is a curve diagram of the curvature and distortion of the image plane of the four-piece infrared single-wavelength lens group of the fourth embodiment in order from left to right. 5A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a fifth embodiment of the present invention. 5B is a curve diagram of the curvature and distortion of the image plane of the four-piece infrared single-wavelength lens group of the fifth embodiment in order from left to right.

Claims (15)

A four-piece infrared single-wavelength lens group includes, in order from the object side to the image side, a first lens having a positive refractive power, the object side surface near the optical axis is convex, and the image side surface near the optical axis is Concave surface, at least one of the object-side surface and the image-side surface is aspherical; an aperture; a second lens having a refractive power, and at least one of the object-side surface and the image-side surface is aspherical; a third lens having Positive refractive power, the object side surface is concave near the optical axis, the image side surface is convex near the optical axis, and at least one of the object side surface and the image side surface is aspherical; a fourth lens has a negative refractive power The object-side surface is convex near the optical axis, the image-side surface is concave near the optical axis, and at least one of the object-side surface and the image-side surface is aspherical. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the first lens is f1 and the focal length of the second lens is f2, and the following conditions are satisfied: -1.0 <f1 / f2 <1.0. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the second lens is f2, and the focal length of the third lens is f3, and the following conditions are satisfied: -10.4 <f2 / f3 <13.8. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the third lens is f3, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -1.0 <f3 / f4 <-0.1. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the first lens is f1, and the focal length of the third lens is f3, and the following conditions are satisfied: 1.4 <f1 / f3 <3.0. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the first lens is f1, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -2.1 <f1 / f4 <-0.5. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the second lens is f2, and the focal length of the fourth lens is f4, and the following conditions are satisfied: -9.0 <f2 / f4 <7.1. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the first lens is f1, and the combined focal length of the second lens and the third lens is f23, and the following conditions are satisfied: 1.2 <f1 / f23 <3.1. The four-piece infrared single-wavelength lens group according to claim 1, wherein the combined focal length of the first lens and the second lens is f12, the combined focal distance of the third lens and the fourth lens is f34, and the following conditions are satisfied: 0.48 <f12 / f34 <2.23. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the second lens is f2, and the combined focal length of the third lens and the fourth lens is f34, and the following conditions are satisfied: -5.3 <f2 / f34 <6.7. The four-piece infrared single-wavelength lens group according to claim 1, wherein the combined 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: -1.0 <f23 / f4 <-0.2. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the first lens is f1, and the combined focal length of the second lens, the third lens, and the fourth lens is f234, and the following conditions are satisfied: 0.7 <F1 / f234 <1.8. The four-piece infrared single-wavelength lens group according to 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:- 1.0 <f123 / f4 <-0.15. The four-piece infrared single-wavelength lens group according to claim 1, wherein the refractive index of the fourth lens is N4, the dispersion coefficient of the fourth lens is V4, and the following conditions are satisfied: 1.61 <N4; V4 <25. The four-piece infrared single-wavelength lens group according to claim 1, wherein the overall focal length of the four-piece infrared single-wavelength lens group is f, and the distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL and satisfy the following conditions: 0.4 <f / TL <0.85.