Lens system

Abstract

This invention discloses a lens system comprising four lenses, which are sequentially arranged from the object side to the image side as a first lens, a second lens, a third lens, and a fourth lens. Each of the four lenses has an object-side surface facing the object side and an image-side surface facing the image side. The object-side surface of the first lens is concave near the optical axis and has at least one inflection point. The second lens has positive refractive power, and its object-side surface is concave near the optical axis. The lens system comprises a total of four lenses. Under certain conditions, the lens system can simultaneously meet the requirements of a large aperture, miniaturization, and a wide viewing angle.

Description

[0001] This application is a divisional application of the original application with the filing date of December 11, 2019, the original application number of 201911265650.8, and the original application title of Lens system and electronic device. TECHNICAL FIELD

[0002] The present application relates to a lens system, in particular, to a lens system suitable for an electronic device. BACKGROUND

[0003] With the advancement of semiconductor process technology, the performance of electronic photosensitive elements has been improved, and the pixel size can be made smaller. Therefore, optical lenses with high imaging quality are indispensable.

[0004] With the rapid development of technology, electronic devices equipped with optical lenses are more widely used, and the requirements for optical lenses are more diverse. Since the existing optical lenses are not easy to balance the demands of imaging quality, sensitivity, aperture size, volume, or viewing angle, the present application provides an optical lens to meet the needs. SUMMARY

[0005] The present application provides a lens system. The lens system includes four lenses. When certain conditions are met, the lens system provided by the present application can meet the requirements of large aperture, miniaturization and wide viewing angle at the same time.

[0006] The present application provides a lens system, including four lenses. The four lenses are sequentially arranged from the object side to the image side as the first lens, the second lens, the third lens and the fourth lens. The four lenses each have an object side surface facing the object side direction and an image side surface facing the image side direction. The first lens has a negative refractive power, the first lens object side surface is concave at the near optical axis, and the first lens object side surface has at least one inflection point. The second lens has a positive refractive power, and the second lens object side surface is concave at the near optical axis. The total number of lenses in the lens system is four, and the lens system further includes an aperture arranged between the second lens and the third lens. The minimum Abbe number of all lenses in the lens system is Vdmin, the curvature radius of the first lens object side surface is R1, the focal length of the lens system is f, and the entrance pupil diameter of the lens system is EPD, which satisfies the following conditions:

[0007] 13.0 < Vdmin < 21.0;

[0008] -12.0 < R1 / f < 0; and

[0009] 1.25 < f / EPD < 2.50.

[0010] The present application also provides a lens system, which includes four lenses. The four lenses are sequentially arranged from an object side to an image side as a first lens, a second lens, a third lens and a fourth lens. The four lenses respectively have an object side surface facing the object side direction and an image side surface facing the image side direction. The object side surface of the first lens is concave at a vicinity of an optical axis, and the object side surface of the first lens has at least one inflection point. The second lens has a positive refractive power, and the object side surface of the second lens is concave at the vicinity of the optical axis. The total number of lenses in the lens system is four. The thickness of the second lens on the optical axis is greater than the thickness of the fourth lens on the optical axis. The minimum Abbe number of all the lenses in the lens system is Vdmin, the radius of curvature of the object side surface of the first lens is R1, the focal length of the lens system is f, the entrance pupil diameter of the lens system is EPD, and the distance from the object side surface of the first lens to the image plane on the optical axis is TL, which satisfy the following conditions:

[0011] 13.0 < Vdmin < 21.0;

[0012] -12.0 < R1 / f < 0;

[0013] 1.25 < f / EPD < 2.50; and

[0014] 4.85 < TL / f < 15.0.

[0015] When Vdmin satisfies the above conditions, the light path control capability of the lens can be improved, the design freedom is increased, and more stringent specification requirements can be met.

[0016] When R1 / f satisfies the above conditions, the first lens can have sufficient light divergence capability, which is beneficial to form a wide field of view optical system.

[0017] When f / EPD satisfies the above conditions, the lens entrance pupil can be adjusted, the amount of light entering the lens system is controlled, and the image brightness is improved.

[0018] When TL / f satisfies the above conditions, the total length and the viewing angle can be effectively balanced to meet the specification requirements.

[0019] The above description of the present application and the following description of the embodiments are used to demonstrate and explain the spirit and principles of the present application, and provide further explanation of the scope of protection of the patent claims of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A schematic diagram of an identification module and a tablet according to a first embodiment of the present application is shown.

[0021] Figure 2 A schematic diagram of an identification module of Figure 1 is shown.

[0022] Figure 3From left to right sequentially are the spherical aberration, astigmatism and distortion curves of the first embodiment.

[0023] Figure 4 A schematic diagram of the recognition module and the flat plate according to the second embodiment of the present application is shown.

[0024] Figure 5 A schematic diagram of the recognition module according to the second embodiment is shown. Figure 4

[0025] Figure 6 From left to right sequentially are the spherical aberration, astigmatism and distortion curves of the second embodiment.

[0026] Figure 7 A schematic diagram of the recognition module and the flat plate according to the third embodiment of the present application is shown.

[0027] Figure 8 A schematic diagram of the recognition module according to the third embodiment is shown. Figure 7

[0028] Figure 9 From left to right sequentially are the spherical aberration, astigmatism and distortion curves of the third embodiment.

[0029] Figure 10 A schematic diagram of the recognition module and the flat plate according to the fourth embodiment of the present application is shown.

[0030] Figure 11 A schematic diagram of the recognition module according to the fourth embodiment is shown. Figure 10

[0031] Figure 12 From left to right sequentially are the spherical aberration, astigmatism and distortion curves of the fourth embodiment.

[0032] Figure 13 A schematic diagram of the recognition module and the flat plate according to the fifth embodiment of the present application is shown.

[0033] Figure 14 A schematic diagram of the recognition module according to the fifth embodiment is shown. Figure 13

[0034] Figure 15 From left to right sequentially are the spherical aberration, astigmatism and distortion curves of the fifth embodiment.

[0035] Figure 16 A schematic diagram of the recognition module and the flat plate according to the sixth embodiment of the present application is shown.

[0036] Figure 17 A schematic diagram of the recognition module according to the sixth embodiment is shown. Figure 16

[0037] Figure 18 From left to right sequentially are the spherical aberration, astigmatism and distortion curves of the sixth embodiment.​​​​​

[0038] Figure 19 A schematic diagram of a recognition module and a flat plate according to a seventh embodiment of the present application is shown.

[0039] Figure 20 A schematic diagram of a recognition module according to the seventh embodiment is shown. Figure 19

[0040] Figure 21 From left to right in order are a spherical aberration, an astigmatism and a distortion curve diagram of the seventh embodiment.

[0041] Figure 22 A schematic diagram of a recognition module and a flat plate according to an eighth embodiment of the present application is shown.

[0042] Figure 23 A schematic diagram of a recognition module according to the eighth embodiment is shown. Figure 22

[0043] Figure 24 From left to right in order are a spherical aberration, an astigmatism and a distortion curve diagram of the eighth embodiment.

[0044] Figure 25 A schematic diagram of an electronic device according to a ninth embodiment of the present application is shown.

[0045] Figure 26 A schematic diagram of an electronic device according to the ninth embodiment recognizing a fingerprint is shown. Figure 25

[0046] A schematic diagram of an electronic device according to a tenth embodiment recognizing a fingerprint is shown. Figure 27

[0047] A perspective view of one side of an electronic device according to an eleventh embodiment of the present application is shown. Figure 28

[0048] A perspective view of the other side of the electronic device according to the eleventh embodiment is shown. Figure 29 Figure 28 A schematic diagram of parameters Y12, Yc11, Yc41, Yc42 and inflection points and critical points of the first lens and the fourth lens in the first embodiment of the present application is shown.

[0049] Figure 30 A schematic diagram of the second lens and parameters SAG21 and SAG22 in the first embodiment of the present application is shown.

[0050] Figure 31 BRIEF DESCRIPTION OF THE DRAWINGS

[0051] 20a, 20b, 20c: electronic device

[0052] 20a, 20b, 20c: electronic device

[0053] ​​​10a, 21c, 22c, 23c, 24c: image capturing device

[0054] 25c: display device

[0055] 30a, 30b: recognition module

[0056] 50a, 50b: flat plate

[0057] S: light source

[0058] P: inflection point

[0059] C: critical point

[0060] 100, 200, 300, 400, 500, 600, 700, 800: stop

[0061] 110, 210, 310, 410, 510, 610, 710, 810: first lens

[0062] 111, 211, 311, 411, 511, 611, 711, 811: object-side surface

[0063] 112, 212, 312, 412, 512, 612, 712, 812: image-side surface

[0064] 120, 220, 320, 420, 520, 620, 720, 820: second lens

[0065] 121, 221, 321, 421, 521, 621, 721, 821: object-side surface

[0066] 122, 222, 322, 422, 522, 622, 722, 822: image-side surface

[0067] 130, 230, 330, 430, 530, 630, 730, 830: third lens

[0068] 131, 231, 331, 431, 531, 631, 731, 831: object-side surface

[0069] 132, 232, 332, 432, 532, 632, 732, 832: image-side surface

[0070] 140, 240, 340, 440, 540, 640, 740, 840: fourth lens

[0071] 141, 241, 341, 441, 541, 641, 741, 841: object-side surface

[0072] 142, 242, 342, 442, 542, 642, 742, 842: image side surface

[0073] 150, 250, 350, 450, 550, 650, 750, 850: light filtering element

[0074] 160, 260, 360, 460, 560, 660, 760, 860: imaging surface

[0075] 170, 270, 370, 470, 570, 670, 770, 870: electron photosensitive element

[0076] 180, 280, 380, 480, 580, 680, 780, 880: flat plate

[0077] SAG21: displacement amount of the intersection of the second lens object side surface on the optical axis to the position of the maximum effective radius of the second lens object side surface parallel to the optical axis

[0078] SAG22: displacement amount of the intersection of the second lens image side surface on the optical axis to the position of the maximum effective radius of the second lens image side surface parallel to the optical axis

[0079] Y12: maximum effective radius of the first lens image side surface

[0080] Yc11: perpendicular distance between the critical point of the first lens object side surface and the optical axis

[0081] Yc41: perpendicular distance between the critical point of the fourth lens object side surface and the optical axis

[0082] Yc42: perpendicular distance between the critical point of the fourth lens image side surface and the optical axis DETAILED DESCRIPTION

[0083] The detailed features and advantages of the present application are described in detail in the embodiments below, which are sufficient for any person skilled in the art to understand the technical content of the present application and to implement it, and any person skilled in the art can easily understand the purposes and advantages related to the present application according to the content disclosed in the present specification, the scope of claims, and the drawings. The following examples further illustrate the points of the present application, but do not limit the scope of the present application in any way.

[0084] The electronic device includes an identification module and a flat plate. The identification module includes a lens system and an electronic photosensitive element. The lens system includes four lenses. The four lenses are sequentially arranged from an object side to an image side as a first lens, a second lens, a third lens, and a fourth lens. The four lenses each have an object side surface facing the object side and an image side surface facing the image side. The electronic photosensitive element is disposed on an imaging surface of the lens system. The flat plate is disposed in the object side direction of the identification module.

[0085] The first lens can have a negative refractive power. Thus, the field angle of the lens system can be enlarged to increase the image judgment range. The object side surface of the first lens can be concave at the vicinity of the optical axis. Thus, a retro-focus system can be formed to enlarge the sensing range of the lens system. The object side surface of the first lens can have at least one convex critical point at the off-axis position. Thus, the incident angle between the off-axis light and the lens can be effectively controlled to avoid total reflection, and the space proportion occupied by the first lens can be controlled to reduce the overall volume. At least one of the object side surface of the first lens and the image side surface of the first lens has at least one inflection point. Thus, the volume of the first lens can be effectively controlled while receiving light with a large viewing angle to avoid the volume of the lens system being too large at the object side end. Please refer to Figure 30 This figure shows the convex critical point C and the inflection point P of the object side surface 111 of the first lens in the first embodiment of the present application.

[0086] The image side surface of the third lens can be concave at the vicinity of the optical axis. Thus, the back focal length can be shortened to control the overall length of the lens system. The image side surface of the third lens can have at least one convex critical point at the off-axis position. Thus, the surface shape of the image side surface of the third lens can be balanced to correct the off-axis aberration to meet the miniaturization requirement.

[0087] The fourth lens has a positive refractive power. Thus, the main converging ability of the lens system can be provided to control the lens volume and facilitate the formation of a retro-focus system configuration. The object side surface of the fourth lens can be convex at the vicinity of the optical axis. Thus, the curvature distribution of the fourth lens can be effectively distributed to enable the fourth lens to provide the main converging ability of the lens system. The object side surface of the fourth lens can have at least one concave critical point at the off-axis position. Thus, the peripheral light can be ensured to be incident on the fourth lens at a relatively gentle incident angle to correct the image curvature. The image side surface of the fourth lens can be convex at the vicinity of the optical axis. Thus, the angle of light incident on the photosensitive element can be effectively controlled to avoid the peripheral image dark angle. The image side surface of the fourth lens can change from convex to concave and then to convex from the vicinity of the optical axis to the off-axis position. Thus, the off-axis aberration can be effectively corrected, and the lens volume can be miniaturized. At least one of the object side surface of the fourth lens and the image side surface of the fourth lens has at least one inflection point. Thus, the back focal length of the lens system can be effectively shortened to control the overall optical length. Please refer toFigure 30 This figure shows the schematic diagram of the critical point C and the inflection point P of the fourth lens 140 according to the first embodiment of the present application. Figure 30 The critical points and the partial inflection points of the first lens object-side surface, the fourth lens object-side surface and the fourth lens image-side surface are shown as an example for illustration, but the rest of the lens object-side surfaces or image-side surfaces can also have critical points or inflection points.

[0088] The distance between the first lens object-side surface and the imaging plane on the optical axis is TL, and the focal length of the lens system is f, which satisfies the following condition: 4.85 < TL / f < 15.0. In this way, the total length and the viewing angle can be effectively balanced to meet the specification requirements. In addition, the following condition can also be satisfied: 5.50 < TL / f < 12.0.

[0089] The Abbe number of the fourth lens is Vd4, which can satisfy the following condition: 10.0 < Vd4 < 38.0. In this way, the light deflection capability of the fourth lens can be improved to effectively shorten the total length of the lens system. In addition, the following condition can also be satisfied: 13.0 < Vd4 < 30.0. In the present application, the Abbe number Vd of a single lens can be calculated by the following formula: Vd = (Nd-1) / (NF-NC), where Nd is the refractive index of the single lens measured at the helium d line wavelength (587.6 nm), NF is the refractive index of the single lens measured at the hydrogen F line wavelength (486.1 nm), and NC is the refractive index of the single lens measured at the hydrogen C line wavelength (656.3 nm).

[0090] The radius of curvature of the fourth lens object-side surface is R7, and the radius of curvature of the fourth lens image-side surface is R8, which satisfy the following condition: -3.50 < (R7+R8) / (R7-R8) < 0.85. In this way, the control capability of the object-side end of the fourth lens can be strengthened, and the image-side end is used to correct the imaging quality. In addition, the following condition can also be satisfied: -1.80 < (R7+R8) / (R7-R8) < 0.50. In addition, the following condition can also be satisfied: (R7+R8) / (R7-R8) < 0.35. In addition, the following condition can also be satisfied: -50.0 < (R7+R8) / (R7-R8) < 0.25.

[0091] The thickness of the second lens on the optical axis is CT2, and the thickness of the third lens on the optical axis is CT3, which can satisfy the following condition: 0.10 < CT2 / CT3 < 0.95. In this way, the thickness ratio of the second lens and the third lens can be adjusted to balance the system space distribution, improve the yield and quality, and strengthen the system control capability of the third lens. In addition, the following condition can also be satisfied: 0.20 < CT2 / CT3 < 0.65. In addition, the following condition can also be satisfied: 0.40 < CT2 / CT3 < 0.63.

[0092] The focal length of the lens system is f, and the entrance pupil diameter of the lens system is EPD, which can satisfy the following condition: 1.25 < f / EPD < 2.50. In this way, the lens entrance pupil diameter can be adjusted, the light amount of the lens system is controlled, and the image brightness is improved. Wherein, the following condition can also be satisfied: 1.0 < f / EPD < 2.05. Wherein, the following condition can also be satisfied: 1.0 < f / EPD < 2.0. Wherein, the following condition can also be satisfied: 1.20 < f / EPD < 1.80.

[0093] The focal length of the lens system is f, and the focal length of the second lens is f2, which can satisfy the following condition: -0.15 < f / f2 < 0.15. In this way, the second lens is used as a correction lens, which can effectively correct the spherical aberration and coma generated by the first lens, and improve the image quality of the off-axis field. Wherein, the following condition can also be satisfied: -0.10 < f / f2 < 0.10.

[0094] The minimum Abbe number of all lenses in the lens system is Vdmin, which can satisfy the following condition: 13.0 < Vdmin < 21.0. In this way, the light path control ability of the lens is improved, the design freedom is increased, and more stringent specification requirements are met.

[0095] The maximum effective radius of the image side surface of the first lens is Y12, and the curvature radius of the image side surface of the first lens is R2, which can satisfy the following condition: 1.02 < Y12 / R2 < 4.50. In this way, the size of the first lens can be effectively controlled to meet the requirements of large viewing angle and small volume of the lens. Wherein, the following condition can also be satisfied: 1.02 < Y12 / R2 < 2.50. Please refer to Figure 30 This figure shows the schematic diagram of the parameter Y12 in the first embodiment of the application.

[0096] The vertical distance between the critical point of the object side surface of the first lens and the optical axis is Yc11, the focal length of the lens system is f, and the object side surface of the first lens can have at least one critical point satisfying the following condition: 0.50 < Yc11 / f < 5.0. In this way, the off-axis aberration correction ability of the lens system is improved, and the total length is effectively compressed, while meeting the requirements of miniaturization and large viewing angle. Wherein, the following condition can also be satisfied: 0.80 < Yc11 / f < 3.0. Please refer to Figure 30 This figure shows the schematic diagram of the parameter Yc11 in the first embodiment of the application.

[0097] The maximum imaging height of the lens system is ImgH (i.e. half of the diagonal length of the effective sensing area of the electronic photosensitive element), and the focal length of the lens system is f, which can satisfy the following condition: 2.0 < ImgH / f < 8.0. In this way, the lens system can provide a better field of view angle for application in different fields. In addition, the following condition can also be satisfied: 2.3 < ImgH / f < 4.0.

[0098] Half of the maximum view angle of the lens system is HFOV, and the F-number of the lens system is Fno, which can satisfy the following condition: 1.50 < tan(HFOV) / Fno. In this way, the amount of light received can be increased under the demand of a large view angle. In addition, the following condition can also be satisfied: 1.70 < tan(HFOV) / Fno < 5.50.

[0099] The lens system disclosed in the present application also includes an aperture, and the aperture can be arranged between the second lens and the third lens. In this way, the position of the aperture can be controlled to balance the view angle and the total length, which helps to achieve the requirements of a wide view angle and miniaturization.

[0100] The distance between the aperture and the image side surface of the fourth lens on the optical axis is SD, and the distance between the object side surface of the first lens and the image side surface of the fourth lens on the optical axis is TD, which can satisfy the following condition: 0.40 < SD / TD < 0.95. In this way, the position of the aperture in the lens system can be balanced to control the view angle and the total length.

[0101] The distance between the object side surface of the first lens and the imaging surface on the optical axis is TL, and the maximum imaging height of the lens system is ImgH, which can satisfy the following condition: 2.0 < TL / ImgH < 3.50. In this way, the lens system can maintain sufficient light receiving area while pursuing miniaturization, so as to maintain sufficient brightness of the image. In addition, the following condition can also be satisfied: 2.0 < TL / ImgH < 3.0. In addition, the following condition can also be satisfied: 2.30 < TL / ImgH < 3.0.

[0102] The radius of curvature of the object side surface of the first lens is R1, and the focal length of the lens system is f, which can satisfy the following condition: -12.0 < R1 / f < 0. In this way, the first lens can have sufficient light divergence capability to facilitate the formation of a wide field of view optical system. In addition, the following condition can also be satisfied: -8.0 < R1 / f < -2.0.

[0103] The displacement of the intersection of the second lens object-side surface on the optical axis to the position of the maximum effective radius of the second lens object-side surface parallel to the optical axis is SAG21, the displacement of the intersection of the second lens image-side surface on the optical axis to the position of the maximum effective radius of the second lens image-side surface parallel to the optical axis is SAG22, and the focal length of the lens system is f, which can satisfy the following condition: 0≤(|SAG21|+|SAG22|) / f<0.50. In this way, the second lens surface shape change can be effectively avoided to affect the peripheral image quality. In addition, the following condition can also be satisfied: 0≤(|SAG21|+|SAG22|) / f<0.35. Please refer to Figure 31 This figure shows a schematic diagram of the second lens 120 and the parameters SAG21 and SAG22 in the first embodiment of the present application, wherein the displacement value is positive in the image side direction and negative in the object side direction.

[0104] In the lens system disclosed in the present application, the Abbe number of at least one lens with positive refractive power is less than 30.0. In this way, the light deflection capability of the lens system can be improved, which is beneficial to reduce the volume to meet the miniaturization requirement. In addition, the Abbe number of at least one lens with positive refractive power in the lens system can be less than 28.0.

[0105] The Abbe number of the first lens is Vd1, the Abbe number of the second lens is Vd2, the Abbe number of the third lens is Vd3, the Abbe number of the fourth lens is Vd4, the Abbe number of the ith lens is Vdi, the refractive index of the first lens is N1, the refractive index of the second lens is N2, the refractive index of the third lens is N3, the refractive index of the fourth lens is N4, and the refractive index of the ith lens is Ni. In the lens system, at least one lens can satisfy the following condition: Vdi / Ni<13.5, wherein i=1, 2, 3 or 4. In this way, the light deflection capability of the lens can be improved to facilitate better specification design and imaging quality. In addition, at least one lens in the lens system can satisfy the following condition: Vdi / Ni<12.0, wherein i=1, 2, 3 or 4.

[0106] The distance from the first lens object-side surface to the imaging surface on the optical axis is TL, which can satisfy the following condition: 1.0[mm]<TL<3.0[mm]. In this way, the total length can be effectively controlled to meet the miniaturization requirement.

[0107] In the lens system disclosed in the present application, the thickness of the third lens on the optical axis can be the largest among the thicknesses of each single lens on the optical axis in the lens system. In this way, the refractive power configuration of the lens system can be balanced.

[0108] The vertical distance between the critical point of the image-side surface of the fourth lens and the optical axis is Yc42, and the focal length of the lens system is f. The image-side surface of the fourth lens can have at least one critical point at an off-axis position satisfying the following condition: 0.20 < Yc42 / f < 2.0. In this way, the image curvature and the total length can be corrected, and the Petzval surface of the lens system can be made more flat. Please refer to Figure 30 This figure shows the schematic diagram of the parameter Yc42 in the first embodiment of the present application.

[0109] The vertical distance between the critical point of the object-side surface of the fourth lens and the optical axis is Yc41, and the focal length of the lens system is f. The object-side surface of the fourth lens can have at least one critical point at an off-axis position satisfying the following condition: 0.30 < Yc41 / f < 2.0. In this way, the back focal length of the lens system can be reduced, and the overall size of the lens can be reduced. Please refer to Figure 30 This figure shows the schematic diagram of the parameter Yc41 in the first embodiment of the present application.

[0110] In the electronic device disclosed in the present application, the interval distance of the first lens on the optical axis in the lens system of the flat plate and the recognition module can be less than 1.50 millimeters (mm). In this way, the thickness of the electronic device can be effectively controlled to meet the demand for lighter and thinner use.

[0111] The lens system disclosed in the present application can be applied to infrared rays, visible light, or single-wavelength light, but the present application is not limited thereto.

[0112] The technical features of the lens system of the present application described above can be combined to achieve the corresponding effects.

[0113] In the lens system disclosed in the present application, the material of the lens can be glass or plastic. If the material of the lens is glass, the degree of freedom of the refractive power configuration of the lens system can be increased, and the influence of the change in the external environment temperature on imaging can be reduced. The glass lens can be made by grinding or molding technology. If the material of the lens is plastic, the production cost can be effectively reduced. In addition, a spherical surface or an aspherical surface (ASP) can be provided on the lens surface. The spherical lens can reduce the manufacturing difficulty. If an aspherical surface is provided on the lens surface, more control variables can be obtained to reduce aberration, reduce the number of lenses, and effectively reduce the total length of the lens system of the present application. Further, the aspherical surface can be made by plastic injection molding or molded glass lens.

[0114] In the lens system disclosed in the present application, if the lens surface is an aspherical surface, it means that all or part of the optical effective area of the lens surface is an aspherical surface.

[0115] The lens system of the present application can selectively add additives to any of the above lens materials to change the transmittance of the lens to specific wavelength bands of light, thereby reducing stray light and color cast. For example, the additives can filter out 600-800 nm wavelength bands of light to help reduce excess red or infrared light, or can filter out 350-450 nm wavelength bands of light to reduce excess blue or ultraviolet light, so that the additives can avoid interference with imaging caused by specific wavelength bands of light. In addition, the additives can be uniformly mixed in the plastic and made into lenses by injection molding technology.

[0116] In the lens system of the present application, if the lens surface is convex and the position of the convex surface is not defined, it means that the convex surface can be located near the optical axis of the lens surface. If the lens surface is concave and the position of the concave surface is not defined, it means that the concave surface can be located near the optical axis of the lens surface. If the refractive power or focal length of the lens is not defined, it means that the refractive power or focal length of the lens can be the refractive power or focal length of the lens near the optical axis.

[0117] The values of the parameters (such as refractive index, focal length, etc.) of the lens system, recognition module and electronic device of the present application are not specifically defined, and can be determined according to the operating wavelength of the system.

[0118] In the lens system of the present application, the inflection point of the lens surface refers to the junction point where the curvature of the lens surface changes in sign. The critical point of the lens surface refers to the tangent point on the tangent line that is tangent to the lens surface at a plane perpendicular to the optical axis, and the critical point is not located on the optical axis.

[0119] In the lens system of the present application, the imaging surface of the lens system can be a plane or a curved surface with any curvature, especially a concave surface facing the object side, depending on the corresponding electronic photosensitive element.

[0120] In the lens system of the present application, one or more imaging correction elements (flat field elements, etc.) can be selectively arranged between the lens closest to the imaging surface and the imaging surface to achieve the effect of correcting the image (such as image curvature). The optical properties of the imaging correction elements, such as curvature, thickness, refractive index, position, surface type (convex or concave, spherical or aspherical, diffractive surface and Fresnel surface, etc.), can be adjusted according to the needs of the recognition module or image capturing device. In general, the preferred imaging correction element configuration is to set a thin flat concave element with a concave surface facing the object side near the imaging surface.

[0121] In the lens system of the present application, at least one diaphragm can be arranged, which can be located before the first lens, between the lenses or after the last lens. The diaphragm can be a glare stop or a field stop, etc., which can be used to reduce stray light and improve image quality.

[0122] In the lens system of the present application, the aperture can be a front aperture or a middle aperture. The front aperture means that the aperture is arranged between the object and the first lens, and the middle aperture means that the aperture is arranged between the first lens and the imaging surface. If the aperture is a front aperture, the exit pupil and the imaging surface can have a long distance, which can have a telecentric effect and increase the efficiency of the CCD or CMOS image receiving element. If the aperture is a middle aperture, it can help to expand the field of view of the lens system.

[0123] The present application can appropriately arrange a variable aperture element, which can be a mechanical member or a light control element, and the size and shape of the aperture can be controlled by electricity or electrical signals. The mechanical member can include movable members such as a blade group and a shielding plate, and the light control element can include a shielding material such as a filter element, an electrochromic material and a liquid crystal layer. The variable aperture element can strengthen the image adjustment capability by controlling the light amount or exposure time of the image. In addition, the variable aperture element can also be the aperture of the present application, which can adjust the image quality such as the depth of field or the exposure speed by changing the aperture value.

[0124] According to the above-mentioned embodiments, the following specific examples are proposed in detail with reference to the accompanying drawings.

[0125] <First embodiment>

[0126] Please refer to Figures 1 to 3 , wherein Figure 1 a schematic diagram of the recognition module and the flat plate according to the first embodiment of the present application is shown, Figure 2 a schematic diagram of the recognition module of Figure 1 is shown, and Figure 3 the ball aberration, the astigmatism and the distortion curves of the first embodiment are shown from left to right. As can be seen from Figure 1 and Figure 2 , the recognition module includes a lens system (not labeled separately) and an electronic photosensitive element 170. The lens system includes, in order from the object side to the image side, a first lens 110, a second lens 120, an aperture 100, a third lens 130, a fourth lens 140, a filter 150 and an imaging surface 160. The electronic photosensitive element 170 is arranged on the imaging surface 160. The lens system includes four lenses (110, 120, 130, 140), and there is no other lens inserted between the lenses.

[0127] The first lens 110 has negative refractive power and is made of plastic. Its object-side surface 111 is concave near the optical axis, and its image-side surface 112 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 111 has at least one inflection point, its image-side surface 112 has at least one inflection point, and its object-side surface 111 has at least one convex critical point off-axis.

[0128] The second lens 120 has positive refractive power and is made of plastic. Its object-side surface 121 is convex near the optical axis, and its image-side surface 122 is concave near the optical axis. Both of its surfaces are aspherical.

[0129] The third lens 130 has positive refractive power and is made of plastic. Its object-side surface 131 is convex near the optical axis, and its image-side surface 132 is convex near the optical axis. Both of its surfaces are aspherical.

[0130] The fourth lens 140 has positive refractive power and is made of plastic. Its object-side surface 141 is convex near the optical axis, and its image-side surface 142 is convex near the optical axis. Both surfaces are aspherical. Its object-side surface 141 has at least one inflection point, and its image-side surface 142 has at least one inflection point. Its object-side surface 141 has at least one concave critical point off-axis, and its image-side surface 142 has at least one critical point off-axis. Furthermore, its image-side surface 142 changes from convex to concave and then back to convex from near the optical axis to off-axis.

[0131] The filter element 150 is made of glass and is positioned between the fourth lens 140 and the imaging surface 160, without affecting the focal length of the lens system.

[0132] The plate 180 is made of glass. It is positioned on the object side of the recognition module and is 1.000 mm away from the first lens 110 on the optical axis. This does not affect the focal length of the lens system.

[0133] The equations for the aspherical surfaces of the above lenses are expressed as follows:

[0134]

[0135] X: The distance between a point on the aspherical surface at a distance Y from the optical axis and the tangent plane at the intersection point of the aspherical surface and the optical axis.

[0136] Y: The perpendicular distance between a point on the aspherical curve and the optical axis;

[0137] R: Radius of curvature;

[0138] k: cone coefficient; and

[0139] Ai: The i-th order aspherical coefficient.

[0140] In the lens system of the first embodiment, the focal length of the lens system is f, the aperture value of the lens system is Fno, and half of the maximum field of view of the lens system is HFOV, with the following values: f = 0.37 mm, Fno = 1.63, HFOV = 73.3 degrees.

[0141] The Abbe number of the fourth lens 140 is Vd4, which satisfies the following condition: Vd4 = 19.4.

[0142] The minimum Abbe number among all lenses in the lens system is Vdmin, which satisfies the following condition: Vdmin = 19.4. In this embodiment, among the four lenses (110, 120, 130, 140) in the lens system, the Abbe number of the fourth lens 140 is less than the Abbe numbers of the other lenses, therefore Vdmin is equal to the Abbe number of the fourth lens 140.

[0143] The Abbe number of the first lens 110 is Vd1, and the refractive index of the first lens 110 is N1, which satisfies the following condition: Vd1 / N1 = 36.18.

[0144] The Abbe number of the second lens 120 is Vd2, and the refractive index of the second lens 120 is N2, which satisfies the following condition: Vd2 / N2=23.79.

[0145] The Abbe number of the third lens 130 is Vd3, and the refractive index of the third lens 130 is N3, which satisfies the following condition: Vd3 / N3 = 36.18.

[0146] The Abbe number of the fourth lens 140 is Vd4, and the refractive index of the fourth lens 140 is N4, which satisfies the following condition: Vd4 / N4=11.53.

[0147] The thickness of the second lens 120 on the optical axis is CT2, and the thickness of the third lens 130 on the optical axis is CT3, which satisfies the following condition: CT2 / CT3=0.50.

[0148] The radius of curvature of the object-side surface 111 of the first lens is R1, and the focal length of the lens system is f, which satisfies the following condition: R1 / f = -6.00.

[0149] The radius of curvature of the object-side surface 141 of the fourth lens is R7, and the radius of curvature of the image-side surface 142 of the fourth lens is R8, which satisfies the following condition: (R7+R8) / (R7-R8)=-0.45.

[0150] The focal length of the lens system is f, and the focal length of the second lens 120 is f2, which satisfies the following condition: f / f2=0.002.

[0151] The distance on the optical axis from the object-side surface 111 of the first lens to the imaging surface 160 is TL, which satisfies the following condition: TL = 2.81 mm.

[0152] The distance from aperture 100 to the image-side surface 142 of the fourth lens on the optical axis is SD, and the distance from the object-side surface 111 of the first lens to the image-side surface 142 of the fourth lens on the optical axis is TD, which satisfies the following condition: SD / TD = 0.45.

[0153] The maximum imaging height of the lens system is ImgH, and the focal length of the lens system is f, which satisfies the following condition: ImgH / f=2.71.

[0154] The distance on the optical axis from the object-side surface 111 of the first lens to the imaging surface 160 is TL, and the maximum imaging height of the lens system is ImgH, which satisfies the following condition: TL / ImgH=2.81.

[0155] The distance on the optical axis from the object-side surface 111 of the first lens to the imaging plane 160 is TL, and the focal length of the lens system is f, which satisfies the following condition: TL / f = 7.60.

[0156] The focal length of the lens system is f, and the entrance pupil diameter of the lens system is EPD, which satisfies the following condition: f / EPD = 1.63.

[0157] The maximum effective radius of the image-side surface 112 of the first lens is Y12, and the radius of curvature of the image-side surface 112 of the first lens is R2, which satisfies the following condition: Y12 / R2=1.45.

[0158] Half of the maximum field of view in the lens system is HFOV, and the aperture value of the lens system is Fno, which satisfies the following condition: tan(HFOV) / Fno=2.04.

[0159] The displacement of the point where the object-side surface 121 of the second lens intersects the optical axis to the position of the maximum effective radius of the object-side surface 121 of the second lens parallel to the optical axis is SAG21. The displacement of the point where the image-side surface 122 of the second lens intersects the optical axis to the position of the maximum effective radius of the image-side surface 122 of the second lens parallel to the optical axis is SAG22. The focal length of the lens system is f, which satisfies the following condition: (|SAG21|+|SAG22|) / f=0.23.

[0160] The vertical distance between the critical point of the object-side surface 111 of the first lens and the optical axis is Yc11, and the focal length of the lens system is f, which satisfies the following condition: Yc11 / f=1.93.

[0161] The perpendicular distance between the critical point of the object-side surface 141 of the fourth lens and the optical axis is Yc41, and the focal length of the lens system is f, which satisfies the following condition: Yc41 / f=1.33.

[0162] The perpendicular distance between the critical point of the image-side surface 142 of the fourth lens and the optical axis is Yc42, and the focal length of the lens system is f, which satisfies the following conditions: Yc42 / f = 0.75 and 1.40.

[0163] Please refer to Table 1 and Table 2 below.

[0164]

[0165]

[0166]

[0167] Table 1 is... Figure 1 The first embodiment provides detailed structural data, where the units for radius of curvature, thickness, and focal length are millimeters (mm), and surfaces 0 to 14 sequentially represent surfaces from the object side to the image side. Table 2 shows the aspherical data in the first embodiment, where k is the cone coefficient in the aspherical curve equation, and A4 to A18 represent the 4th to 18th order aspherical coefficients of each surface. Furthermore, the tables for the following embodiments are corresponding schematic diagrams and aberration curves for each embodiment. The definitions of the data in the tables are the same as those in Tables 1 and 2 of the first embodiment, and will not be repeated here.

[0168] <Second Embodiment>

[0169] Please refer to Figures 4 to 6 ,in Figure 4 A schematic diagram of an identification module and a tablet according to a second embodiment of the present invention is shown. Figure 5 It shows Figure 4 A schematic diagram of the identification module, and Figure 6 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the second embodiment. Figure 4 and Figure 5 As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 270. The lens system, from the object side to the image side, sequentially includes a first lens 210, a second lens 220, an aperture 200, a third lens 230, a fourth lens 240, a filter element 250, and an imaging plane 260. The electronic photosensitive element 270 is disposed on the imaging plane 260. The lens system comprises four lenses (210, 220, 230, and 240), and there are no other interposed lenses between the lenses.

[0170] The first lens 210 has negative refractive power and is made of plastic. Its object-side surface 211 is concave near the optical axis, and its image-side surface 212 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 211 has at least one inflection point, its image-side surface 212 has at least one inflection point, and its object-side surface 211 has at least one convex critical point off-axis.

[0171] The second lens 220 has negative refractive power and is made of plastic. Its object-side surface 221 is convex near the optical axis, and its image-side surface 222 is concave near the optical axis. Both of its surfaces are aspherical.

[0172] The third lens 230 has positive refractive power and is made of plastic. Its object-side surface 231 is convex near the optical axis, and its image-side surface 232 is convex near the optical axis. Both of its surfaces are aspherical.

[0173] The fourth lens 240 has positive refractive power and is made of plastic. Its object-side surface 241 is convex near the optical axis, and its image-side surface 242 is convex near the optical axis. Both surfaces are aspherical. Its object-side surface 241 has at least one inflection point, and its image-side surface 242 has at least one inflection point. Its object-side surface 241 has at least one concave critical point off-axis, and its image-side surface 242 changes from convex to concave and then back to convex from near the optical axis to off-axis.

[0174] The filter element 250 is made of glass and is positioned between the fourth lens 240 and the imaging surface 260, without affecting the focal length of the lens system.

[0175] The plate 280 is made of glass. It is positioned on the object side of the recognition module and is 1.000 mm away from the first lens 210 on the optical axis. This does not affect the focal length of the lens system.

[0176] Please refer to Table 3 and Table 4 below.

[0177]

[0178]

[0179]

[0180] In the second embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0181]

[0182]

[0183] <Third Embodiment>

[0184] Please refer to Figures 7 to 9 ,in Figure 7 A schematic diagram of an identification module and a tablet according to a third embodiment of the present invention is shown. Figure 8 It shows Figure 7 A schematic diagram of the identification module, and Figure 9 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the third embodiment. Figure 7 and Figure 8 As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 370. The lens system, from the object side to the image side, sequentially includes a first lens 310, a second lens 320, an aperture 300, a third lens 330, a fourth lens 340, a filter element 350, and an imaging surface 360. The electronic photosensitive element 370 is disposed on the imaging surface 360. The lens system comprises four lenses (310, 320, 330, and 340), and there are no other interposed lenses between the lenses.

[0185] The first lens 310 has negative refractive power and is made of plastic. Its object-side surface 311 is concave near the optical axis, and its image-side surface 312 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 311 has at least one inflection point, its image-side surface 312 has at least one inflection point, and its object-side surface 311 has at least one convex critical point off-axis.

[0186] The second lens 320 has positive refractive power and is made of plastic. Its object-side surface 321 is concave near the optical axis, and its image-side surface 322 is convex near the optical axis. Both of its surfaces are aspherical.

[0187] The third lens 330 has positive refractive power and is made of plastic. Its object-side surface 331 is convex near the optical axis, and its image-side surface 332 is convex near the optical axis. Both of its surfaces are aspherical.

[0188] The fourth lens 340 has positive refractive power and is made of plastic. Its object-side surface 341 is convex near the optical axis, and its image-side surface 342 is convex near the optical axis. Both surfaces are aspherical. Its object-side surface 341 has at least one inflection point, and its image-side surface 342 has at least one inflection point. Its object-side surface 341 has at least one concave critical point off-axis, and its image-side surface 342 has at least one critical point off-axis. Furthermore, its image-side surface 342 changes from convex to concave and then back to convex from near the optical axis to off-axis.

[0189] The filter element 350 is made of glass and is positioned between the fourth lens 340 and the imaging surface 360, without affecting the focal length of the lens system.

[0190] The plate 380 is made of glass. It is positioned on the object side of the recognition module and is 1.000 mm away from the first lens 310 on the optical axis. This does not affect the focal length of the lens system.

[0191] Please refer to Table 5 and Table 6 below.

[0192]

[0193]

[0194]

[0195] In the third embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0196]

[0197] <Fourth Embodiment>

[0198] Please refer to Figures 10 to 12 ,in Figure 10 A schematic diagram of an identification module and a tablet according to a fourth embodiment of the present invention is shown. Figure 11 It shows Figure 10 A schematic diagram of the identification module, and Figure 12 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the fourth embodiment. Figure 10 and Figure 11 As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 470. The lens system, from the object side to the image side, sequentially includes a first lens 410, a second lens 420, an aperture 400, a third lens 430, a fourth lens 440, a filter element 450, and an imaging plane 460. The electronic photosensitive element 470 is disposed on the imaging plane 460. The lens system comprises four lenses (410, 420, 430, and 440), and there are no other interposed lenses between the lenses.

[0199] The first lens 410 has negative refractive power and is made of plastic. Its object-side surface 411 is concave near the optical axis, and its image-side surface 412 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 411 has at least one inflection point, its image-side surface 412 has at least one inflection point, and its object-side surface 411 has at least one convex critical point off-axis.

[0200] The second lens 420 has positive refractive power and is made of plastic. Its object-side surface 421 is convex near the optical axis, and its image-side surface 422 is concave near the optical axis. Both of its surfaces are aspherical.

[0201] The third lens 430 has negative refractive power and is made of plastic. Its object-side surface 431 is convex near the optical axis, and its image-side surface 432 is concave near the optical axis. Both surfaces are aspherical, and its image-side surface 432 has at least one convex critical point off-axis.

[0202] The fourth lens 440 has positive refractive power and is made of plastic. Its object-side surface 441 is convex near the optical axis, and its image-side surface 442 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 441 has at least one inflection point, its image-side surface 442 has at least one inflection point, its object-side surface 441 has at least one concave critical point off-axis, and its image-side surface 442 has at least one critical point off-axis.

[0203] The filter element 450 is made of glass and is positioned between the fourth lens 440 and the imaging surface 460, without affecting the focal length of the lens system.

[0204] The plate 480 is made of glass. It is positioned on the object side of the recognition module and is 1.000 mm away from the first lens 410 on the optical axis. This does not affect the focal length of the lens system.

[0205] Please refer to Tables 7 and 8 below.

[0206]

[0207]

[0208]

[0209] In the fourth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0210]

[0211] <Fifth Embodiment>

[0212] Please refer to Figures 13 to 15 ,in Figure 13 A schematic diagram of an identification module and a tablet according to a fifth embodiment of the present invention is shown. Figure 14 It shows Figure 13 A schematic diagram of the identification module, and Figure 15 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the fifth embodiment. Figure 13 and Figure 14As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 570. The lens system, from the object side to the image side, sequentially includes a first lens 510, a second lens 520, an aperture 500, a third lens 530, a fourth lens 540, a filter element 550, and an imaging surface 560. The electronic photosensitive element 570 is disposed on the imaging surface 560. The lens system comprises four lenses (510, 520, 530, and 540), and there are no other interposed lenses between the lenses.

[0213] The first lens 510 has negative refractive power and is made of plastic. Its object-side surface 511 is concave near the optical axis, and its image-side surface 512 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 511 has at least one inflection point, its image-side surface 512 has at least one inflection point, and its object-side surface 511 has at least one convex critical point off-axis.

[0214] The second lens 520 has positive refractive power and is made of plastic. Its object-side surface 521 is convex near the optical axis, and its image-side surface 522 is convex near the optical axis. Both of its surfaces are aspherical.

[0215] The third lens 530 has negative refractive power and is made of plastic. Its object-side surface 531 is convex near the optical axis, and its image-side surface 532 is concave near the optical axis. Both surfaces are aspherical, and its image-side surface 532 has at least one convex critical point off-axis.

[0216] The fourth lens 540 has positive refractive power and is made of plastic. Its object-side surface 541 is convex near the optical axis, and its image-side surface 542 is convex near the optical axis. Both surfaces are aspherical. Its object-side surface 541 has at least one inflection point, and its image-side surface 542 has at least one inflection point. Its object-side surface 541 has at least one concave critical point off-axis, and its image-side surface 542 has at least one critical point off-axis. Furthermore, its image-side surface 542 changes from convex to concave and then back to convex from near the optical axis to off-axis.

[0217] The filter element 550 is made of glass and is positioned between the fourth lens 540 and the imaging surface 560, without affecting the focal length of the lens system.

[0218] The plate 580 is made of glass. It is positioned on the object side of the recognition module and is 1.050 mm away from the first lens 510 on the optical axis. This does not affect the focal length of the lens system.

[0219] Please refer to Tables 9 and 10 below.

[0220]

[0221]

[0222] In the fifth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0223]

[0224] <Sixth Embodiment>

[0225] Please refer to Figures 16 to 18 ,in Figure 16 A schematic diagram of an identification module and a tablet according to a sixth embodiment of the present invention is shown. Figure 17 It shows Figure 16 A schematic diagram of the identification module, and Figure 18 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the sixth embodiment. Figure 16 and Figure 17 As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 670. The lens system, from the object side to the image side, sequentially includes a first lens 610, a second lens 620, an aperture 600, a third lens 630, a fourth lens 640, a filter element 650, and an imaging surface 660. The electronic photosensitive element 670 is disposed on the imaging surface 660. The lens system comprises four lenses (610, 620, 630, and 640), and there are no other interposed lenses between the lenses.

[0226] The first lens 610 has negative refractive power and is made of plastic. Its object-side surface 611 is concave near the optical axis, and its image-side surface 612 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 611 has at least one inflection point, its image-side surface 612 has at least one inflection point, and its object-side surface 611 has at least one convex critical point off-axis.

[0227] The second lens 620 has positive refractive power and is made of plastic. Its object-side surface 621 is convex near the optical axis, and its image-side surface 622 is convex near the optical axis. Both of its surfaces are aspherical.

[0228] The third lens 630 has negative refractive power and is made of plastic. Its object-side surface 631 is convex near the optical axis, and its image-side surface 632 is concave near the optical axis. Both surfaces are aspherical, and its image-side surface 632 has at least one convex critical point off-axis.

[0229] The fourth lens 640 has positive refractive power and is made of plastic. Its object-side surface 641 is convex near the optical axis, and its image-side surface 642 is convex near the optical axis. Both surfaces are aspherical. Its object-side surface 641 has at least one inflection point, and its image-side surface 642 has at least one inflection point. Its object-side surface 641 has at least one concave critical point off-axis, and its image-side surface 642 has at least one critical point off-axis. Furthermore, its image-side surface 642 changes from convex to concave and then back to convex from near the optical axis to off-axis.

[0230] The filter element 650 is made of glass and is positioned between the fourth lens 640 and the imaging surface 660, without affecting the focal length of the lens system.

[0231] The plate 680 is made of glass. It is positioned on the object side of the recognition module and is 1.050 mm away from the first lens 610 on the optical axis. This does not affect the focal length of the lens system.

[0232] Please refer to Table 11 and Table 12 below.

[0233]

[0234]

[0235]

[0236] In the sixth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0237]

[0238] <Seventh Embodiment>

[0239] Please refer to Figures 19 to 21 ,in Figure 19 A schematic diagram of an identification module and a tablet according to a seventh embodiment of the present invention is shown. Figure 20 It shows Figure 19 A schematic diagram of the identification module, and Figure 21 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the seventh embodiment. Figure 19 and Figure 20As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 770. The lens system, from the object side to the image side, sequentially includes a first lens 710, a second lens 720, an aperture 700, a third lens 730, a fourth lens 740, a filter element 750, and an imaging surface 760. The electronic photosensitive element 770 is disposed on the imaging surface 760. The lens system comprises four lenses (710, 720, 730, and 740), and there are no other interposed lenses between the lenses.

[0240] The first lens 710 has negative refractive power and is made of plastic. Its object-side surface 711 is concave near the optical axis, and its image-side surface 712 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 711 has at least one inflection point, its image-side surface 712 has at least one inflection point, and its object-side surface 711 has at least one convex critical point off-axis.

[0241] The second lens 720 has negative refractive power and is made of plastic. Its object-side surface 721 is convex near the optical axis, and its image-side surface 722 is concave near the optical axis. Both of its surfaces are aspherical.

[0242] The third lens 730 has positive refractive power and is made of plastic. Its object-side surface 731 is convex near the optical axis, and its image-side surface 732 is concave near the optical axis. Both surfaces are aspherical, and its image-side surface 732 has at least one convex critical point off-axis.

[0243] The fourth lens 740 has positive refractive power and is made of plastic. Its object-side surface 741 is convex near the optical axis, and its image-side surface 742 is convex near the optical axis. Both surfaces are aspherical. Its object-side surface 741 has at least one inflection point, and its image-side surface 742 has at least one inflection point. Its object-side surface 741 has at least one concave critical point off-axis, and its image-side surface 742 has at least one critical point off-axis. Furthermore, its image-side surface 742 changes from convex to concave and then back to convex from near the optical axis to off-axis.

[0244] The filter element 750 is made of glass and is positioned between the fourth lens 740 and the imaging surface 760, without affecting the focal length of the lens system.

[0245] The plate 780 is made of glass. It is positioned on the object side of the recognition module and is 1.000 mm away from the first lens 710 on the optical axis. This does not affect the focal length of the lens system.

[0246] Please refer to Tables 13 and 14 below.

[0247]

[0248]

[0249]

[0250] In the seventh embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0251]

[0252]

[0253] <Eighth Embodiment>

[0254] Please refer to Figures 22 to 24 ,in Figure 22 A schematic diagram of the identification module and the tablet according to the eighth embodiment of the present invention is shown. Figure 23 It shows Figure 22 A schematic diagram of the identification module, and Figure 24 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the eighth embodiment. Figure 22 and Figure 23 As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 870. The lens system, from the object side to the image side, sequentially includes a first lens 810, a second lens 820, an aperture 800, a third lens 830, a fourth lens 840, a filter element 850, and an imaging surface 860. The electronic photosensitive element 870 is disposed on the imaging surface 860. The lens system comprises four lenses (810, 820, 830, and 840), and there are no other interposed lenses between the lenses.

[0255] The first lens 810 has negative refractive power and is made of plastic. Its object-side surface 811 is concave near the optical axis, and its image-side surface 812 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 811 has at least one inflection point, its image-side surface 812 has at least one inflection point, and its object-side surface 811 has at least one convex critical point off-axis.

[0256] The second lens 820 has positive refractive power and is made of plastic. Its object-side surface 821 is concave near the optical axis, and its image-side surface 822 is convex near the optical axis. Both of its surfaces are aspherical.

[0257] The third lens 830 has positive refractive power and is made of plastic. Its object-side surface 831 is convex near the optical axis, and its image-side surface 832 is convex near the optical axis. Both of its surfaces are aspherical.

[0258] The fourth lens 840 has positive refractive power and is made of plastic. Its object-side surface 841 is convex near the optical axis, and its image-side surface 842 is concave near the optical axis. Both surfaces are aspherical. Its object-side surface 841 has at least one inflection point, its image-side surface 842 has at least one inflection point, its object-side surface 841 has at least one concave critical point off-axis, and its image-side surface 842 has at least one critical point off-axis.

[0259] The filter element 850 is made of glass and is positioned between the fourth lens 840 and the imaging surface 860, without affecting the focal length of the lens system.

[0260] The plate 880 is made of glass. It is positioned on the object side of the recognition module and is 1.039 mm away from the first lens 810 on the optical axis. This does not affect the focal length of the lens system.

[0261] Please refer to Tables 15 and 16 below.

[0262]

[0263]

[0264]

[0265] In the eighth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in the table below are the same as in the above embodiments and will not be repeated here.

[0266]

[0267] <Ninth Embodiment>

[0268] Please refer to Figure 25 and Figure 26 ,in Figure 25 A schematic diagram of an electronic device according to a ninth embodiment of the present invention is shown, and Figure 26 It shows Figure 25 A diagram illustrating an electronic device for fingerprint recognition.

[0269] In this embodiment, the electronic device 20a is a smartphone with biometric identification functionality. The electronic device 20a includes an image capturing device 10a, an identification module 30a, and a tablet 50a. The image capturing device 10a serves as the front-facing camera of the electronic device 20a to provide a selfie function, and includes the lens system and electronic photosensitive element of this invention. The identification module 30a has fingerprint identification functionality and includes the lens system and electronic photosensitive element of the first embodiment described above, but is not limited thereto; other lens systems of other embodiments can also be used. In this embodiment, both the image capturing device 10a and the identification module 30a include the lens system of this invention, but are not limited thereto. For example, only one of the image capturing device 10a and the identification module 30a may include the lens system of this invention.

[0270] The tablet 50a is positioned on the object side of the recognition module 30a. It is a module with display functionality, provides protection, and reduces the need for additional components. Furthermore, the tablet 50a can be a light-transmitting tablet, allowing light to pass through and enter the lens system within the recognition module 30a beneath the screen, enabling more applications. The tablet 50a can also have a touchscreen function, eliminating the need for additional input devices and making operation more intuitive. Additionally, the tablet 50a can have a light-emitting function, which may be, for example but not limited to, an organic light-emitting diode (OLED) or an active-matrix organic light-emitting diode (AMOLED). This allows the tablet 50a to act as a light source to illuminate the subject, eliminating the need for an additional light source.

[0271] <Tenth Embodiment>

[0272] Please refer to Figure 27 This diagram illustrates a fingerprint recognition process using an electronic device according to a tenth embodiment of the present invention. In this embodiment, the electronic device 20b is a smartphone with biometric recognition capabilities. The electronic device 20b includes a recognition module 30b, a light source S, and a tablet 50b. The recognition module 30b has fingerprint recognition functionality and includes the lens system and electronic photosensitive element described in the first embodiment above, but is not limited thereto; other lens systems may also be used in the present invention. The tablet 50b is disposed on the object side of the recognition module 30b and is, for example, a light-transmitting glass substrate. The light source S is disposed on one side of the lens system to illuminate the object, allowing light from the object to pass through the tablet 50b and enter the lens system in the recognition module 30b. In this embodiment, the recognition module 30b is the recognition module described in the first embodiment above, but is not limited thereto.

[0273] The above embodiments use a display module or glass substrate as an example of a flat panel, but the present invention is not limited thereto. In other embodiments, the flat panel may be, for example, a light filter.

[0274] The identification module of this invention is applicable to fingerprint recognition under touch screens and features excellent aberration correction and good imaging quality, but its application is not limited to fingerprint recognition. For example, the identification module can also be applied to various biometric identification methods such as iris recognition and face recognition.

[0275] <Eleventh Embodiment>

[0276] Please refer to Figure 28 and Figure 29 ,in Figure 28 A perspective view of one side of an electronic device according to the eleventh embodiment of the present invention is shown, and Figure 29 It shows Figure 28 A three-dimensional view of the other side of the electronic device.

[0277] In this embodiment, the electronic device 20c is a smartphone. The electronic device 20c includes image capturing devices 21c, 22c, 23c, and 24c, and a display device 25c. Image capturing device 21c includes the lens system and electronic photosensitive element disclosed in the first embodiment, but is not limited thereto; other lens systems may also be used in this invention.

[0278] Image capturing devices 22c, 23c, and 24c in this embodiment have different viewing angles. Specifically, image capturing device 22c is a telephoto image capturing device, image capturing device 23c is a wide-angle image capturing device, and image capturing device 24c is an ultra-wide-angle image capturing device. Therefore, electronic device 20c can provide different magnifications to achieve optical zoom shooting effects and can increase the application range of electronic device 20c to adapt to various usage needs.

[0279] In this embodiment, the image capturing device 22c, the image capturing device 23c and the image capturing device 24c are disposed on one side of the electronic device 20c, while the image capturing device 21c and the display device 25c are disposed on the other side of the electronic device 20c. The image capturing device 21c can be used as a front-facing camera to provide a selfie function, but the present invention is not limited thereto.

[0280] The lens system of this invention can be applied to various electronic devices, and its application areas include imaging needs such as image capture and recognition functions. For example, the lens system can be used in a variety of electronic devices such as biometrics, 3D image capture, digital cameras, mobile devices, tablet computers, smart TVs, network monitoring equipment, dashcams, reversing cameras, multi-lens devices, motion-sensing game consoles, and wearable devices. The above-mentioned electronic devices are merely illustrative examples of practical applications of this invention and are not intended to limit the scope of application of the lens system of this invention.

[0281] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the appended claims.

Claims

1. A lens system characterized by comprising: The lens system includes four lenses, which are sequentially a first lens, a second lens, a third lens, and a fourth lens from an object side to an image side, and each of the four lenses has an object side surface facing the object side direction and an image side surface facing the image side direction; wherein the first lens has a negative refractive power, the first lens object side surface is concave at the vicinity of the optical axis, the first lens object side surface has at least one inflection point, the second lens has a positive refractive power, the second lens object side surface is concave at the vicinity of the optical axis, and the fourth lens has a positive refractive power; wherein the lens system has a total of four lenses and further includes an aperture disposed between the second lens and the third lens, the lens system has a minimum Abbe number Vdmin among all the lenses, the first lens object side surface has a radius of curvature R1, the lens system has a focal length f, the lens system has an entrance pupil diameter EPD, and the following conditions are satisfied: 13.0 < Vdmin < 21.0; -12.0 < R1 / f < 0; and 1.25 < f / EPD < 2.

50.

2. The lens system of claim 1, wherein The third lens has a positive refractive power, the third lens object side surface is convex at the vicinity of the optical axis, and the third lens image side surface is convex at the vicinity of the optical axis.

3. The lens system of claim 1, wherein, The fourth lens image side surface is concave at the vicinity of the optical axis.

4. The lens system of claim 1, wherein, The lens system has a minimum Abbe number Vdmin among all the lenses, and the following condition is satisfied: 13.0 < Vdmin ≤ 19.

4.

5. The lens system of claim 1, wherein, The fourth lens has an Abbe number Vd4, and the following condition is satisfied: 10.0 < Vd4 < 38.

0.

6. The lens system of claim 5, wherein, The fourth lens has an Abbe number Vd4, and the following condition is satisfied: 13.0 < Vd4 < 30.

0.

7. The lens system of claim 1, wherein, The lens system has a minimum Abbe number Vdmin among all the lenses, the first lens object side surface has a radius of curvature R1, the lens system has a focal length f, the lens system has an entrance pupil diameter EPD, and the first lens object side surface to an imaging surface has a distance on the optical axis TL, and the following conditions are satisfied: 17.0 ≤ Vdmin ≤ 19.4; -11.05 ≤ R1 / f ≤ -5.99; 1.72 ≤ f / EPD < 2.05; and 7.63 ≤ TL / f ≤ 8.

04.

8. The lens system of claim 7, wherein, The first lens object side surface has a perpendicular distance Yc11 between a critical point and the optical axis, the lens system has a focal length f, and the first lens object side surface has at least one critical point off-axis, and the following condition is satisfied: 0.80 < Yc11 / f < 3.

0.

9. The lens system of claim 1, wherein, The first lens object side surface has a radius of curvature R1, the lens system has a focal length f, and the following condition is satisfied: -8.0 < R1 / f < -2.

0.

10. The lens system of claim 1, wherein, The first lens object side surface has a radius of curvature R1, the lens system has a focal length f, and the following condition is satisfied: -5.99 ≤ R1 / f < 0.

11. The lens system of claim 1, wherein, The fourth lens object side surface has a radius of curvature R7, the fourth lens image side surface has a radius of curvature R8, and the following conditions are satisfied: -1.80 < (R7+R8) / (R7-R8) < 0.

50.

12. The lens system of claim 1, wherein, The distance on the optical axis from the first lens object side surface to an imaging surface is TL, which satisfies the following condition: 1.0 millimeter < TL < 3.0 millimeters; wherein the Abbe number of the first lens is Vd1, the Abbe number of the second lens is Vd2, the Abbe number of the third lens is Vd3, the Abbe number of the fourth lens is Vd4, the Abbe number of the i-th lens is Vdi, the refractive index of the first lens is N1, the refractive index of the second lens is N2, the refractive index of the third lens is N3, the refractive index of the fourth lens is N4, the refractive index of the i-th lens is Ni, and at least one lens in the lens system satisfies the following condition: Vdi / Ni < 13.5, where i = 1, 2, 3, or 4.

13. A lens system characterized by comprising: The lens system includes four lenses, which are sequentially the first lens, the second lens, the third lens, and the fourth lens from the object side to the image side, and the four lenses respectively have an object side surface facing the object side direction and an image side surface facing the image side direction; wherein the first lens has negative refractive power, the first lens object side surface is concave at the vicinity of the optical axis, the first lens object side surface has at least one inflection point, the second lens has positive refractive power, the second lens object side surface is concave at the vicinity of the optical axis, and the fourth lens has positive refractive power; wherein the total number of lenses in the lens system is four, the thickness of the second lens on the optical axis is greater than the thickness of the fourth lens on the optical axis, the minimum Abbe number of all the lenses in the lens system is Vdmin, the radius of curvature of the first lens object side surface is R1, the focal length of the lens system is f, the entrance pupil diameter of the lens system is EPD, the distance on the optical axis from the first lens object side surface to an imaging surface is TL, which satisfies the following conditions: 13.0 < Vdmin < 21.0; -12.0 < R1 / f < 0; 1.25 < f / EPD < 2.50; and 4.85 < TL / f < 15.

0.

14. The lens system of claim 13, wherein, The first lens image side surface is concave at the vicinity of the optical axis, and the second lens image side surface is convex at the vicinity of the optical axis.

15. The lens system of claim 13, wherein, The first lens object side surface has at least one convex critical point at the off-axis position.

16. The lens system of claim 13, wherein, The distance on the optical axis from the first lens object side surface to the imaging surface is TL, and the focal length of the lens system is f, which satisfies the following condition: 5.50 < TL / f < 12.

0.

17. The lens system of claim 16, wherein, The distance on the optical axis from the first lens object side surface to the imaging surface is TL, and the focal length of the lens system is f, which satisfies the following condition: 5.50 < TL / f ≤ 8.

04.

18. The lens system of claim 13, wherein, The radius of curvature of the fourth lens object side surface is R7, and the radius of curvature of the fourth lens image side surface is R8, which satisfy the following condition: -50.0 < (R7+R8) / (R7-R8) < 0.

25.

19. The lens system of claim 13, wherein, A displacement of the intersection of the second lens object-side surface on the optical axis to a position of the maximum effective radius of the second lens object-side surface parallel to the optical axis is SAG21, a displacement of the intersection of the second lens image-side surface on the optical axis to a position of the maximum effective radius of the second lens image-side surface parallel to the optical axis is SAG22, and a focal length of the lens system is f, which satisfy the following condition: 0 ≤ (|SAG21| + |SAG22|) / f < 0.

50.

20. The lens system of claim 19, wherein, A displacement of the intersection of the second lens object-side surface on the optical axis to a position of the maximum effective radius of the second lens object-side surface parallel to the optical axis is SAG21, a displacement of the intersection of the second lens image-side surface on the optical axis to a position of the maximum effective radius of the second lens image-side surface parallel to the optical axis is SAG22, and a focal length of the lens system is f, which satisfy the following condition: 0 ≤ (|SAG21| + |SAG22|) / f < 0.

35.

21. The lens system of claim 13, wherein, An Abbe number of the first lens is Vd1, an Abbe number of the second lens is Vd2, an Abbe number of the third lens is Vd3, an Abbe number of the fourth lens is Vd4, an Abbe number of the i-th lens is Vdi, a refractive index of the first lens is N1, a refractive index of the second lens is N2, a refractive index of the third lens is N3, a refractive index of the fourth lens is N4, and a refractive index of the i-th lens is Ni, and at least one lens in the lens system satisfies the following condition: 9.97 ≤ Vdi / Ni < 13.5, where i = 1, 2, 3, or 4.

22. The lens system of claim 21, wherein, An Abbe number of the first lens is Vd1, an Abbe number of the second lens is Vd2, an Abbe number of the third lens is Vd3, an Abbe number of the fourth lens is Vd4, an Abbe number of the i-th lens is Vdi, a refractive index of the first lens is N1, a refractive index of the second lens is N2, a refractive index of the third lens is N3, a refractive index of the fourth lens is N4, and a refractive index of the i-th lens is Ni, and at least one lens in the lens system satisfies the following condition: 9.97 ≤ Vdi / Ni < 12.0, where i = 1, 2, 3, or 4.

23. The lens system of claim 13, wherein, A focal length of the lens system is f, an entrance pupil diameter of the lens system is EPD, an Abbe number of the fourth lens is Vd4, and a minimum value of the Abbe number among all the lenses of the lens system is Vdmin, which satisfy the following conditions: 1.25 < f / EPD < 2.05; 17.0 ≤ Vd4 < 30.0; and 17.0 ≤ Vdmin < 21.0.

Images