TWI709782B - 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, a stop, a second lens element with a refractive power, a third lens element with a positive refractive power, a fourth lens element with a negative refractive power, a focal length of the first lens element and the second lens element combined is f12, a focal length of the third lens element and the fourth lens element combined is f34, and they satisfy the relation: 0.2< f12/f34 <1.4. Such a system has a wide field of view, large stop, short length and less distortion.

Description

Four-piece infrared single wavelength lens group

The present invention relates to a lens group, and particularly refers to a miniaturized four-piece infrared single-wavelength lens group applied to electronic products.

Nowadays, digital imaging technology continues to innovate and change. In particular, digital carriers such as digital cameras and mobile phones are developing towards miniaturization, and photosensitive elements such as CCD or CMOS are also required to be miniaturized. In infrared focusing lens applications, in addition to using 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 game consoles have a wider range of sensing users, the current lens groups that receive infrared wavelengths mostly have larger angles. The wide-angle lens group is the mainstream.

Among them, the applicant previously proposed a number of lens sets related to infrared wavelength reception, but the current game machine is mainly based on 3D games that are more three-dimensional, real and realistic. Therefore, the current or the applicant’s previous lens sets are all based on 2D flat game detection is a demand, so that it cannot meet the depth sensing function that 3D games focus on.

Furthermore, for the infrared receiver and sensor lens set dedicated to game consoles, plastic lenses are used in pursuit of low cost. The poor light transmittance of the material is one of the key factors affecting the lack of depth detection accuracy of game consoles. Second, plastic lenses are easy to The ambient temperature is too hot or too cold, so that the focal length of the lens group changes and accurate focus detection is impossible. As mentioned above, the current lens group receiving infrared wavelengths cannot meet the two major technical issues of accurate sensing of depth and distance in 3D games.

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

The purpose of the present invention is to provide a four-piece infrared single-wavelength lens group, especially a four-piece infrared single-wavelength lens group with improved angle of view, large aperture, short lens length, and small distortion.

In order to achieve the foregoing objective, a four-piece infrared single-wavelength lens group provided by the present invention includes an aperture and an optical group composed of four lenses, from the object side to the image side, in order: a first lens , With positive refractive power, the object side surface of the first lens is convex near the optical axis, the image side surface of the first lens is concave near the optical axis, and the object side surface and the image side surface of the first lens are at least one The surface is aspherical; an aperture; a second lens with refractive power, at least one of the object side surface and the image side surface of the second lens is aspherical; a third lens with positive refractive power, the third lens The object side surface of the third lens is concave near the optical axis, the image side surface of the third lens is convex near the optical axis, and at least one of the object side surface and the image side surface of the third lens is aspherical; a fourth lens, It has negative refractive power, the object side surface of the fourth lens is convex near the optical axis, the image side surface of the fourth lens is concave near the optical axis, and at least one of the object side surface and the image side surface of the fourth lens It is an aspheric surface; wherein the composite focal length of the first lens and the second lens is f12, and the composite focal length of the third lens and the fourth lens is f34, and the following conditions are met: 0.2<f12/f34<1.2.

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 met: -0.3<f1/f2<1.6. In this way, the refractive power configuration of the first lens and the second lens is more suitable, which can help to obtain a wide angle of view (field of view) and reduce excessive increase in system aberrations.

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: -8.6<f2/f3<2.7. In this way, the peripheral resolution and illuminance 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<-0.2. In this way, the refractive power configuration of the system can be effectively balanced, and the sensitivity can be reduced to improve the 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: 1.6<f1/f3<3.5. 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: -2.5<f2/f4<7. In this way, the distribution of the positive refractive power of the system is more appropriate, which is beneficial to correct the aberration of the system 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: 1.8<f1/f23<4. In this way, when f1/f23 meets the above conditions, the four-piece infrared single-wavelength lens group can obtain a wide angle of view (field of view) while significantly improving its resolution.

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

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 the following conditions are met: 0.6<f/TL <0.9. Thereby, it can be beneficial to maintain the miniaturization and long focus of the four-piece infrared single-wavelength lens group to be mounted on thin and light electronic products.

Preferably, the curvature radius of the object side surface of the third lens is R5, and the curvature radius of the image side surface of the third lens is R6, and the following conditions are satisfied: 1.5<R5/R6<5.2. Thereby, the spherical aberration and astigmatism of the four-piece infrared single-wavelength projection lens group are effectively reduced.

Preferably, the curvature radius of the object side surface of the fourth lens is R7, and the curvature radius of the image side surface of the fourth lens is R8, and the following conditions are satisfied: 1.3<R7/R8<5.0. Thereby, the spherical aberration and astigmatism of the four-piece infrared single-wavelength projection lens group are effectively reduced.

Preferably, the thickness of the first lens on the optical axis is CT1, and the thickness of the second lens on the optical axis is CT2, and the following conditions are met: 0.7<CT1/CT2<1.5. In this way, the first lens and the second lens have an appropriate thickness, which makes injection molding easier.

Preferably, the thickness of the third lens on the optical axis is CT3, and the thickness of the fourth lens on the optical axis is CT4, and the following conditions are satisfied: 0.5<CT3/CT4<1.3. Thereby, when the aforementioned conditions are satisfied, it contributes to the moldability and homogeneity of the lens.

100, 200, 300, 400, 500, 600, 700: aperture

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

111, 211, 311, 411, 511, 611, 711: Object side surface

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

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

121, 221, 321, 421, 521, 621, 721: Object side surface

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

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

131, 231, 331, 431, 531, 631, 731: Object side surface

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

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

141, 241, 341, 441, 541, 641, 741: Object side surface

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

170, 270, 370, 470, 570, 670, 770: infrared bandpass components

180, 280, 380, 480, 580, 680, 780: imaging surface

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

f: The focal length of the four-piece infrared single-wavelength lens group

Fno: The aperture value of the four-piece infrared single-wavelength lens group

FOV: The maximum field of view in the four-piece infrared single-wavelength lens group

f1: focal length of the first lens

f2: the 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

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

R5: Curvature radius of the object side surface of the third lens

R6: The curvature radius of the image side surface of the third lens

R7: The curvature radius of the object side surface of the fourth lens

R8: The radius of curvature of the image side surface of the fourth lens

CT1: The thickness of the first lens on the optical axis

CT2: The thickness of the second lens on the optical axis

CT3: The thickness of the third lens on the optical axis

CT4: The thickness of the fourth lens 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 graph showing the curvature of field and the distortion of the four-piece infrared single-wavelength lens set in the first embodiment from left to right.

2A is a schematic diagram of a four-piece infrared single-wavelength lens group according to the second embodiment of the present invention.

Fig. 2B is a graph showing the curvature of field and the distortion of the four-piece infrared single-wavelength lens group in the second embodiment from left to right.

Fig. 3A is a schematic diagram of a four-piece infrared single-wavelength lens group according to the third embodiment of the present invention.

Fig. 3B is a graph of field curvature and distortion reduction curves of the four-piece infrared single-wavelength lens group in 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 the fourth embodiment of the present invention.

FIG. 4B is a graph showing the curvature of field and the distortion of the four-piece infrared single-wavelength lens group in the fourth embodiment from left to right.

Fig. 5A is 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 graph showing the curvature of field and the distortion of the four-piece infrared single-wavelength lens group of the fifth embodiment in order from left to right.

Fig. 6A is a schematic diagram of a four-piece infrared single-wavelength lens group according to the sixth embodiment of the present invention.

Fig. 6B is a graph showing the curvature of field and the distortion of the four-piece infrared single-wavelength lens group in the sixth embodiment from left to right.

Fig. 7A is a schematic diagram of a four-piece infrared single-wavelength lens group according to a seventh embodiment of the present invention.

Fig. 7B is a graph showing the curvature of field and the distortion of the four-piece infrared single-wavelength lens group in the seventh embodiment from left to right.

<First embodiment>

Please refer to FIGS. 1A and 1B, where FIG. 1A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a first embodiment of the present invention, and FIG. 1B shows the four-piece infrared lens of the first embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 1A that the four-piece infrared single-wavelength lens group includes an aperture 100 and an optical group. The optical group includes a first lens 110, a second lens 120, and a third lens 130 from the object side to the image side. The fourth lens 140, the infrared bandpass element 170, and the imaging surface 180, wherein there are four lenses having refractive power in the four-piece infrared single-wavelength lens group. The aperture 100 is arranged between the first lens 110 and the second lens 120.

The first lens 110 has a positive refractive power and is made of plastic. Its object side surface 111 is convex near the optical axis 190, and its 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 aspherical.

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

The third lens 130 has a positive refractive power and is made of plastic. Its object side surface 131 is concave near the optical axis 190, and its image side surface 132 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. Its object side surface 141 is convex near the optical axis 190, and its image side surface 142 is concave near the optical axis 190. The object side surface 141 and the image side The surface 142 is aspherical, and the object side surface 141 and the image side surface 142 both have at least one inflection point.

The infrared bandpass element 170 is made of glass, which is arranged between the fourth lens 140 and the imaging surface 180 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

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

Where z is the position value referenced by the apex of the surface at a height h along the optical axis 190; c is the curvature of the lens surface close to the optical axis 190, and is the reciprocal of the radius of curvature (R) (c=1/R) , R is the radius of curvature of the lens surface close to the optical axis 190, h is the vertical distance between the lens surface and the optical axis 190, k is the conic constant, and A, B, C, D, E, F, G,... … Are high-order aspheric coefficients.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the four-piece infrared single-wavelength lens group is f, the aperture value (f-number) of the four-piece infrared single-wavelength lens group is Fno, and the four-piece infrared single-wavelength lens group is Fno. The maximum field of view (angle of view) in the infrared single-wavelength lens group is FOV, and its value is as follows: f=3.40 (mm); Fno=1.45; and FOV=78.00 (degree).

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 met: f1/f2=1.29.

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 met: f2/f3=2.60.

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=-0.91.

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=3.35.

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 met: f2/f4=-2.37.

In the four-piece infrared single-wavelength lens group of the first embodiment, the focal length of the first lens 110 is f1, the combined focal length of the second lens 120 and the third lens 130 is f23, and the following conditions are met: f1/f23= 3.80.

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, and the focal length of the fourth lens 140 is f4, and the following conditions are met: f23/f4= -0.80.

In the four-piece infrared single-wavelength lens group of the first embodiment, the composite focal length of the first lens 110 and the second lens 120 is f12, and the composite focal length of the third lens 130 and the fourth lens 140 is f34, and meets the following requirements Condition: f12/f34=0.43.

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 distance between the object side surface 111 of the first lens 110 and the imaging surface 180 on the optical axis 190 The distance is TL and meets the following conditions: f/TL=0.69.

In the four-piece infrared single-wavelength lens group of the first embodiment, the object-side surface 131 of the third lens 130 has a curvature radius of R5, and the image-side surface 132 of the third lens 130 has a curvature radius of R6, and meets the following conditions: R5/R6=2.70.

In the four-piece infrared single-wavelength lens group of the first embodiment, the object side surface 141 of the fourth lens 140 has a curvature radius of R7, and the image side surface 142 of the fourth lens 140 has a curvature radius of R8, and meets the following conditions: R7/R8=2.66.

In the four-piece infrared single-wavelength lens group of the first embodiment, the thickness of the first lens 110 on the optical axis 190 is CT1, and the thickness of the second lens 120 on the optical axis 190 is CT2, and the following conditions are met: CT1/CT2=0.78.

In the four-piece infrared single-wavelength lens set of the first embodiment, the thickness of the third lens 130 on the optical axis 190 is CT3, and the thickness of the fourth lens 140 on the optical axis 190 is CT4, and the following conditions are met: CT3/CT4=0.78.

Refer to Table 1 and Table 2 below for cooperation.

Table 1 shows the detailed structure data of the first embodiment in FIG. 1A, in which the unit of the radius of curvature, the thickness and the focal length is mm, and the surface 0-12 indicates the surface from the object side to the image side in sequence. Table 2 is the aspheric surface data in the first embodiment, where k represents the conical surface coefficient in the aspheric curve equation, and A, B, C, D, E, F, G, ... are high-order aspheric surface coefficients. In addition, the following embodiment tables correspond to the schematic diagrams and aberration curve diagrams of the respective embodiments, and the definitions of the data in the tables are the same as the definitions of Table 1 and Table 2 of the first embodiment, and will not be repeated here.

<Second Embodiment>

Please refer to Figures 2A and 2B, in which Figure 2A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a second embodiment of the present invention, and Figure 2B shows the four-piece infrared lens of the second embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 2A that the four-piece infrared single-wavelength lens group includes an aperture 200 and an optical group. The optical group includes a first lens 210, a second lens 220, a third lens 230, and an optical group from the object side to the image side. The fourth lens 240, the infrared bandpass element 270, and the imaging surface 280, wherein there are four lenses with refractive power in the four-piece infrared single-wavelength lens group. The aperture 200 is arranged between the first lens 210 and the second lens 220.

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

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

The third lens 230 has a positive refractive power and is made of plastic. Its object side surface 231 is concave near the optical axis 290, and its image side surface 232 is convex near the optical axis 290, and 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. Its object side surface 241 is convex near the optical axis 290, and its image side surface 242 is concave near the optical axis 290, and the object side surface 241 and the image side The surface 242 is aspherical, and the object side surface 241 and the image side surface 242 both have at least one inflection point.

The infrared band-pass element 270 is made of glass, which is arranged between the fourth lens 240 and the imaging surface 280 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 3 and Table 4 below for cooperation.

In the second embodiment, the curve equation of the aspheric surface is expressed as in 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 FIGS. 3A and 3B, where FIG. 3A shows a schematic diagram of a four-piece infrared single-wavelength lens set according to a third embodiment of the present invention, and FIG. 3B shows the four-piece infrared lens of the third embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 3A that the four-piece infrared single-wavelength lens group includes an aperture 300 and an optical group. The optical group includes a first lens 310, a second lens 320, a third lens 330, and an optical group from the object side to the image side. The fourth lens 340, the infrared bandpass element 370, and the imaging surface 380, wherein there are four lenses with refractive power in the four-piece infrared single-wavelength lens group. The aperture 300 is arranged between the first lens 310 and the second lens 320.

The first lens 310 has positive refractive power and is made of plastic. Its 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 object side surface 311 and the image side The surfaces 312 are all aspherical.

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

The third lens 330 has positive refractive power and is made of plastic. Its object side surface 331 is concave near the optical axis 390, and its image side surface 332 is convex near the optical axis 390. 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. Its 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 surface 342 is aspherical, and the object side surface 341 and the image side surface 342 both have at least one inflection point.

The infrared bandpass element 370 is made of glass, which is arranged between the fourth lens 340 and the imaging surface 380 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 5 and Table 6 below for cooperation.

In the third embodiment, the curve equation of the aspheric surface is expressed as in 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 FIGS. 4A and 4B, where FIG. 4A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a fourth embodiment of the present invention, and FIG. 4B shows the four-piece infrared lens in the fourth embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 4A that the four-piece infrared single-wavelength lens group includes an aperture 400 and an optical group. The optical group includes a first lens 410, a second lens 420, and a third lens 430, from the object side to the image side. The fourth lens 440, the infrared bandpass element 470, and the imaging surface 480, wherein the four-piece infrared single-wavelength lens group has four lenses with refractive power. The aperture 400 is arranged between the first lens 410 and the second lens 420.

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

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

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

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

The infrared bandpass element 470 is made of glass, which is arranged between the fourth lens 440 and the imaging surface 480 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 7 and Table 8 below for cooperation.

In the fourth embodiment, the curve equation of the aspheric surface is expressed as in 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.

In conjunction with Table 7 and Table 8, the following data can be calculated:

<Fifth Embodiment>

Please refer to FIGS. 5A and 5B, where FIG. 5A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a fifth embodiment of the present invention, and FIG. 5B shows the four-piece infrared lens in the fifth embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 5A that the four-piece infrared single-wavelength lens group includes an aperture 500 and an optical group. The optical group includes a first lens 510, a second lens 520, and a third lens 530 from the object side to the image side. The fourth lens 540, the infrared bandpass element 570, and the imaging surface 580, wherein the four-piece infrared single-wavelength lens group has four lenses with refractive power. The aperture 500 is arranged in front of the first lens 510.

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

The second lens 520 has positive refractive power and is made of plastic material. Its object side surface 521 is convex near the optical axis 590, and its image side surface 522 is concave near the optical axis 590, and the object side surface 521 and the image side The surfaces 522 are all aspherical.

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

The fourth lens 540 has a negative refractive power and is made of plastic. Its object side surface 541 is convex near the optical axis 590, and its image side surface 542 is concave near the optical axis 590. The object side surface 541 and the image side The surface 542 is aspherical, and the object side surface 541 and the image side surface 542 both have at least one inflection point.

The infrared band-pass element 570 is made of glass, which is arranged between the fourth lens 540 and the imaging surface 580 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 9 and Table 10 below for cooperation.

In the fifth embodiment, the aspherical curve equation is expressed as in 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.

In conjunction with Table 9 and Table 10, the following data can be calculated:

<Sixth Embodiment>

Please refer to FIGS. 6A and 6B, in which FIG. 6A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a sixth embodiment of the present invention, and FIG. 6B shows the four-piece infrared lens of the sixth embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 6A that the four-piece infrared single-wavelength lens group includes an aperture 600 and an optical group. The optical group includes a first lens 610, a second lens 620, and a third lens 630 from the object side to the image side. The fourth lens 640, the infrared bandpass element 670, and the imaging surface 680, wherein there are four lenses with refractive power in the four-piece infrared single-wavelength lens group. The aperture 600 is arranged in front of the first lens 610.

The first lens 610 has positive refractive power and is made of plastic. Its object-side surface 611 is convex near the optical axis 690, and its image-side surface 612 is concave near the optical axis 690, and the object-side surface 611 and the image side The surfaces 612 are all aspherical.

The second lens 620 has positive refractive power and is made of plastic. Its object side surface 621 is convex near the optical axis 690, and its image side surface 622 is concave near the optical axis 690. The object side surface 621 and the image side The surfaces 622 are all aspherical.

The third lens 630 has positive refractive power and is made of plastic. Its object side surface 631 is concave near the optical axis 690, and its image side surface 632 is convex near the optical axis 690. The object side surface 631 and the image side The surfaces 632 are all aspherical.

The fourth lens 640 has a negative refractive power and is made of plastic. Its object-side surface 641 is convex near the optical axis 690, and its image-side surface 642 is concave near the optical axis 690, and the object-side surface 641 and the image side The surface 642 is aspherical, and the object side surface 641 and the image side surface 642 both have at least one inflection point.

The infrared bandpass element 670 is made of glass, which is arranged between the fourth lens 640 and the imaging surface 680 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 11 and Table 12 below for cooperation.

In the sixth embodiment, the curve equation of the aspheric surface is expressed as in 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 11 and Table 12, the following data can be calculated:

<Seventh Embodiment>

Please refer to FIGS. 7A and 7B, in which FIG. 7A shows a schematic diagram of a four-piece infrared single-wavelength lens group according to a seventh embodiment of the present invention, and FIG. 7B shows the four-piece infrared lens of the seventh embodiment in order from left to right. Curve of field curvature and distortion of single-wavelength lens group. It can be seen from FIG. 7A that the four-piece infrared single-wavelength lens group includes an aperture 700 and an optical group. The optical group includes a first lens 710, a second lens 720, and a third lens 730, from the object side to the image side. The fourth lens 740, the infrared band-pass element 770, and the imaging surface 780, wherein the four-piece infrared single-wavelength lens group has four lenses with refractive power. The aperture 700 is arranged between the first lens 710 and the second lens 720.

The first lens 710 has positive refractive power and is made of plastic. Its object side surface 711 is convex near the optical axis 790, and its image side surface 712 is concave near the optical axis 790. The object side surface 711 and the image side The surfaces 712 are all aspherical.

The second lens 720 has negative refractive power and is made of plastic. Its object-side surface 721 is concave near the optical axis 790, and its image-side surface 722 is convex near the optical axis 790, and the object-side surface 721 and the image side are convex. The surfaces 722 are all aspherical.

The third lens 730 has positive refractive power and is made of plastic. Its object side surface 731 is concave near the optical axis 790, and its image side surface 732 is convex near the optical axis 790. The object side surface 731 and the image side The surfaces 732 are all aspherical.

The fourth lens 740 has a negative refractive power and is made of plastic. Its object side surface 741 is convex near the optical axis 790, and its image side surface 742 is concave near the optical axis 790, and the object side surface 741 and the image side The surface 742 is aspherical, and the object side surface 741 and the image side surface 742 both have at least one inflection point.

The infrared bandpass element 770 is made of glass, which is arranged between the fourth lens 740 and the imaging surface 780 and does not affect the focal length of the four-piece infrared single-wavelength lens group.

Refer to Table 13 and Table 14 below for cooperation.

In the seventh embodiment, the aspherical curve equation is expressed as in 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 13 and Table 14, the following data can be calculated:

In the four-piece infrared single-wavelength lens group provided by the present invention, the lens material can be plastic or glass. When the lens material is plastic, the production cost can be effectively reduced. In addition, when the lens material is glass, a four-piece infrared lens can be added. The degree of freedom for 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-element infrared single-wavelength lens group can be aspherical, and the aspherical surface can be easily made into a shape other than the spherical surface to obtain more control variables to reduce aberrations, and then The number of lenses used is reduced, so 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 set provided by the present invention, for a lens with 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 applied to a mobile focusing optical system 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 many ways , Digital cameras, mobile devices, digital tablets or car photography and other electronic imaging systems.

To sum up, the above-mentioned embodiments and drawings are only preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention, that is, all equal changes and modifications made in accordance with the scope of the patent application of the present invention are all It should fall within the scope of the invention patent.

100: aperture

110: first lens

111: Object side surface

112: Image side surface

120: second lens

121: Object side surface

122: image side surface

130: third lens

131: Object side surface

132: Image side surface

140: fourth lens

141: Object side surface

142: Image side surface

170: infrared bandpass element

180: imaging surface

190: optical axis

Claims (12)

A four-element infrared single-wavelength lens group, including an aperture and an optical group composed of four lenses, from the object side to the image side in sequence: a first lens with positive refractive power, the first lens The object-side surface is convex near the optical axis, the image-side surface of the first lens is concave near the optical axis, and at least one of the object-side surface and the image-side surface of the first lens is aspherical; an aperture; a second A lens having refractive power, at least one of the object side surface and the image side surface of the second lens is aspherical; a third lens having positive refractive power, the object side surface of the third lens is concave near the optical axis, The image-side surface of the third lens is convex near the optical axis, and at least one of the object-side surface and the image-side surface of the third lens is aspherical; a fourth lens has a negative refractive power. The side surface is convex near the optical axis, the image side surface of the fourth lens is concave near the optical axis, and at least one of the object side surface and the image side surface of the fourth lens is aspherical; wherein the first lens and the second lens The composite focal length of the two lenses is f12, the composite focal length of the third lens and the fourth lens is f34, and meets the following conditions: 0.2<f12/f34<1.2; wherein the focal length of the first lens is f1, and the focal length of the second lens The focal length is f2, and the following conditions are met: 1.29≦f1/f2<1.6. 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 met: -8.6<f2/f3<2.7. 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 met: -1.0<f3/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 focal length of the third lens is f3, and the following conditions are satisfied: 1.6<f1/f3<3.5. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the second lens is f2, the focal length of the fourth lens is f4, and the following conditions are met: -2.5<f2/f4<7. The four-piece infrared single-wavelength lens group according to claim 1, wherein the focal length of the first lens is f1, the combined focal length of the second lens and the third lens is f23, and the following conditions are met: 1.8<f1/f23 <4. 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 met: -1.0<f23/ f4<-0.2. 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 meet the following conditions: 0.6<f/TL<0.9. The four-piece infrared single-wavelength lens group according to claim 1, wherein the object side surface of the third lens has a curvature radius of R5, and the image side surface of the third lens has a curvature radius of R6, and the following conditions are met: 1.5< R5/R6<5.2. The four-piece infrared single-wavelength lens group according to claim 1, wherein the curvature radius of the object side surface of the fourth lens is R7, and the curvature radius of the image side surface of the fourth lens is R8, and the following conditions are met: 1.3< R7/R8<5.0. The four-piece infrared single-wavelength lens group according to claim 1, wherein the thickness of the first lens on the optical axis is CT1, and the thickness of the second lens on the optical axis is CT2, and the following conditions are met: 0.7< CT1/CT2<1.5. The four-piece infrared single-wavelength lens group according to claim 1, wherein the thickness of the third lens on the optical axis is CT3, and the thickness of the fourth lens on the optical axis is CT4, and the following conditions are met: 0.5< CT3/CT4<1.3.

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