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 convex critical point off-axis. The fourth lens has positive refractive power. 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 field of view.

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 simultaneously meet the requirements of large aperture, miniaturization and wide viewing angle.

[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 object side surface of the first lens is concave at the near optical axis, and the object side surface of the first lens has at least one convex critical point at the off-axis. The fourth lens has positive refractive power. The total number of lenses in the lens system is four. The distance from the object side surface of the first lens to the imaging surface on the optical axis is TL, the focal length of the lens system is f, the thickness of the second lens on the optical axis is CT2, the thickness of the third lens on the optical axis is CT3, the radius of curvature of the object side surface of the fourth lens is R7, the radius of curvature of the image side surface of the fourth lens is R8, and the entrance pupil diameter of the lens system is EPD, which satisfies the following conditions:

[0007] 4.85 < TL / f < 15.0;

[0008] 0.10 < CT2 / CT3 < 0.95;

[0009] (R7+R8) / (R7-R8) < 0.35; and

[0010] 1.25 < f / EPD < 2.50.

[0011] The present invention further provides a lens system, including four lenses. The four lenses are, in sequence from the object side to the image side, the first lens, the second lens, the third lens, and the 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 near the optical axis, and the object-side surface of the first lens has at least one convex critical point at the off-axis position. The fourth lens has a positive refractive power. The total number of lenses in the lens system is four. The distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, the focal length of the lens system is f, the Abbe number of the fourth lens is Vd4, the radius of curvature of the object-side surface of the fourth lens is R7, and the radius of curvature of the image-side surface of the fourth lens is R8, which satisfy the following conditions:

[0012] 4.85 < TL / f < 15.0;

[0013] 10.0 < Vd4 < 38.0; and

[0014] -3.50 < (R7 + R8) / (R7 - R8) < 0.85.

[0015] When TL / f satisfies the above conditions, the total length and the viewing angle can be effectively balanced to meet the specification requirements.

[0016] When CT2 / CT3 satisfies the above conditions, the thickness ratio of the second lens and the third lens can be adjusted to balance the system space allocation, improve the qualified rate and quality, and at the same time strengthen the system control ability of the third lens.

[0017] When (R7 + R8) / (R7 - R8) satisfies the above conditions, the control ability of the object-side end of the fourth lens can be strengthened, and the imaging quality can be corrected by using the image-side end.

[0018] When f / EPD satisfies the above conditions, the light entrance aperture of the lens can be adjusted, the light input amount of the lens system can be controlled, and thus the image brightness can be improved.

[0019] When Vd4 satisfies the above conditions, the light deflection ability of the fourth lens can be improved to effectively shorten the total length of the lens system.

[0020] The above description of the content of the present invention and the following description of the embodiments are used to demonstrate and explain the spirit and principle of the present invention, and provide a further explanation of the scope of protection of the patent application rights of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shows a schematic diagram of an identification module and a tablet according to the first embodiment of the present invention.

[0022] Figure 2 Shows Figure 1 a schematic diagram of the identification module of

[0023] Figure 3 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the first embodiment.

[0024] Figure 4 A schematic diagram of the identification module and the tablet according to a second embodiment of the present invention is shown.

[0025] Figure 5 It shows Figure 4 A schematic diagram of the identification module.

[0026] Figure 6 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the second embodiment.

[0027] Figure 7 A schematic diagram of an identification module and a tablet according to a third embodiment of the present invention is shown.

[0028] Figure 8 It shows Figure 7 A schematic diagram of the identification module.

[0029] Figure 9 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the third embodiment.

[0030] Figure 10 A schematic diagram of the identification module and the tablet according to a fourth embodiment of the present invention is shown.

[0031] Figure 11 It shows Figure 10 A schematic diagram of the identification module.

[0032] Figure 12 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the fourth embodiment.

[0033] Figure 13 A schematic diagram of the identification module and the tablet according to the fifth embodiment of the present invention is shown.

[0034] Figure 14 It shows Figure 13 A schematic diagram of the identification module.

[0035] Figure 15 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the fifth embodiment.

[0036] Figure 16 A schematic diagram of the identification module and the tablet according to the sixth embodiment of the present invention is shown.

[0037] Figure 17 It shows Figure 16 A schematic diagram of the identification module.

[0038] Figure 18 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the sixth embodiment.

[0039] Figure 19 A schematic diagram of the identification module and the tablet according to the seventh embodiment of the present invention is shown.

[0040] Figure 20 It shows Figure 19 A schematic diagram of the identification module.

[0041] Figure 21 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the seventh embodiment.

[0042] Figure 22 A schematic diagram of the identification module and the tablet according to the eighth embodiment of the present invention is shown.

[0043] Figure 23 It shows Figure 22 A schematic diagram of the identification module.

[0044] Figure 24 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the eighth embodiment.

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

[0046] Figure 26 It shows Figure 25 A diagram illustrating an electronic device for fingerprint recognition.

[0047] Figure 27 A schematic diagram of an electronic device for fingerprint recognition according to a tenth embodiment of the present invention is shown.

[0048] Figure 28 A perspective view of one side of an electronic device according to the eleventh embodiment of the present invention is shown.

[0049] Figure 29 It shows Figure 28 A three-dimensional view of the other side of the electronic device.

[0050] Figure 30 A schematic diagram of parameters Y12, Yc11, Yc41, Yc42, and the inflection point and critical point of the first and fourth lenses according to the first embodiment of the present invention is shown.

[0051] Figure 31 A schematic diagram of the second lens and parameters SAG21 and SAG22 according to the first embodiment of the present invention is shown.

[0052] In the attached figures, the following labels are used:

[0053] 20a, 20b, 20c: Electronic devices

[0054] 10a, 21c, 22c, 23c, 24c: Image capturing devices

[0055] 25c: Display device

[0056] 30a, 30b: Identification Module

[0057] 50a, 50b: Flat plate

[0058] S: Light source

[0059] P: Inversion point

[0060] C: Critical point

[0061] 100, 200, 300, 400, 500, 600, 700, 800: Aperture

[0062] 110, 210, 310, 410, 510, 610, 710, 810: First lens

[0063] 111, 211, 311, 411, 511, 611, 711, 811: Object-side surface

[0064] 112, 212, 312, 412, 512, 612, 712, 812: Image side surface

[0065] 120, 220, 320, 420, 520, 620, 720, 820: Second lens

[0066] 121, 221, 321, 421, 521, 621, 721, 821: Object-side surface

[0067] 122, 222, 322, 422, 522, 622, 722, 822: Image side surface

[0068] 130, 230, 330, 430, 530, 630, 730, 830: Third lens

[0069] 131, 231, 331, 431, 531, 631, 731, 831: Object-side surface

[0070] 132, 232, 332, 432, 532, 632, 732, 832: Image side surface

[0071] 140, 240, 340, 440, 540, 640, 740, 840: Fourth lens

[0072] 141, 241, 341, 441, 541, 641, 741, 841: Object-side surface

[0073] 142, 242, 342, 442, 542, 642, 742, 842: Image side surface

[0074] 150, 250, 350, 450, 550, 650, 750, 850: Filter elements

[0075] 160, 260, 360, 460, 560, 660, 760, 860: Imaging plane

[0076] 170, 270, 370, 470, 570, 670, 770, 870: Electronic photosensitive element

[0077] 180, 280, 380, 480, 580, 680, 780, 880: Flat panel

[0078] SAG21: The displacement parallel to the optical axis from the point where the object-side surface of the second lens intersects the optical axis to the position of the maximum effective radius of the object-side surface of the second lens.

[0079] SAG22: The displacement parallel to the optical axis from the point where the image-side surface of the second lens intersects the optical axis to the position of the maximum effective radius of the image-side surface of the second lens.

[0080] Y12: Maximum effective radius of the image-side surface of the first lens

[0081] Yc11: The perpendicular distance between the critical point of the object-side surface of the first lens and the optical axis.

[0082] Yc41: The perpendicular distance between the critical point of the object-side surface of the fourth lens and the optical axis.

[0083] Yc42: The perpendicular distance between the critical point of the image-side surface of the fourth lens and the optical axis. Detailed Implementation

[0084] The following detailed description of the features and advantages of the present invention in the embodiments is sufficient to enable any person skilled in the art to understand the technical content of the present invention and implement it accordingly. Based on the disclosure in this specification, the scope of protection of the claims, and the accompanying drawings, any person skilled in the art can easily understand the related objects and advantages of the present invention. The following embodiments further illustrate the points of the present invention in detail, but are not intended to limit the scope of the present invention in any way.

[0085] The electronic device includes a recognition module and a flat panel. The recognition module includes a lens system and an electronic photosensitive element. The lens system includes 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 electronic photosensitive element is disposed on the imaging surface of the lens system. The flat panel is disposed in the object-side direction of the recognition module.

[0086] The first lens may have negative refractive power; this helps to expand the field of view of the lens system, thereby increasing the image judgment range. The object-side surface of the first lens may be concave near the optical axis; this facilitates the formation of a retro-focus system, thereby expanding the sensing range of the lens system. The object-side surface of the first lens may have at least one convex critical point off-axis; this effectively controls the incident angle between the off-axis ray and the lens to avoid total internal reflection, and also controls the spatial proportion occupied by the first lens, thereby reducing the overall volume. At least one of the object-side surface and the image-side surface of the first lens has at least one inflection point; this effectively controls the size of the first lens while receiving light with a wide viewing angle, thereby avoiding an excessively large volume at the object-side end of the lens system. Please refer to... Figure 30 This figure shows a schematic diagram of the convex critical point C and the inflection point P of the first lens object-side surface 111 according to the first embodiment of the present invention.

[0087] The image-side surface of the third lens can be concave near the optical axis; this helps to shorten the back focal length, thereby controlling the overall length of the lens system. The image-side surface of the third lens can have at least one convex critical point off-axis; this allows for balancing the surface shape of the image-side surface of the third lens to correct off-axis aberrations and achieve miniaturization requirements.

[0088] The fourth lens has positive refractive power; thereby, it provides the main converging power of the lens system, controlling the lens size and facilitating the configuration of a refocusing system. The object-side surface of the fourth lens may be convex near the optical axis; this effectively distributes the curvature of the fourth lens, allowing it to provide the main converging power of the lens system. The object-side surface of the fourth lens may have at least one concave critical point off-axis; this ensures that peripheral light rays enter the fourth lens at a gentler angle of incidence, correcting image curvature. The image-side surface of the fourth lens may be convex near the optical axis; this effectively controls the angle at which light rays enter the sensor, preventing vignetting in the peripheral image. The image-side surface of the fourth lens may transition from convex to concave and then back to convex from near the optical axis to off-axis; this effectively corrects off-axis aberrations and contributes to lens miniaturization. At least one of the object-side surface and the image-side surface of the fourth lens may have at least one inflection point; thereby, the back focal length of the lens system can be effectively shortened, thus controlling the overall optical length. Please refer to...Figure 30 This figure shows a schematic diagram of the critical point C and the inflection point P of the fourth lens 140 in the first embodiment of the present invention. Figure 30 The critical points and partial inflection points of the object-side surface of the first lens, the object-side surface of the fourth lens, and the image-side surface of the fourth lens are shown as exemplary illustrations. However, the remaining object-side surfaces or image-side surfaces of the lenses may also have critical points or inflection points.

[0089] The distance from the object-side surface of the first lens to 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. Thereby, the total length and the viewing angle can be effectively balanced to meet the specification requirements. Among them, the following condition can also be satisfied: 5.50 < TL / f < 12.0.

[0090] The Abbe number of the fourth lens is Vd4, which can satisfy the following condition: 10.0 < Vd4 < 38.0. Thereby, the light deflection ability of the fourth lens can be improved to effectively shorten the total length of the lens system. Among them, the following condition can also be satisfied: 13.0 < Vd4 < 30.0. In the present invention, 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 wavelength of helium d line (587.6 nm), NF is the refractive index of the single lens measured at the wavelength of hydrogen F line (486.1 nm), and NC is the refractive index of the single lens measured at the wavelength of hydrogen C line (656.3 nm).

[0091] The radius of curvature of the object-side surface of the fourth lens is R7, and the radius of curvature of the image-side surface of the fourth lens is R8, which satisfies the following condition: -3.50 < (R7 + R8) / (R7 - R8) < 0.85. Thereby, the control ability of the object-side end of the fourth lens can be strengthened, and the imaging quality can be corrected by the image-side end. Among them, the following condition can also be satisfied: -1.80 < (R7 + R8) / (R7 - R8) < 0.50. Among them, the following condition can also be satisfied: (R7 + R8) / (R7 - R8) < 0.35. Among them, the following condition can also be satisfied: -50.0 < (R7 + R8) / (R7 - R8) < 0.25.

[0092] 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. Thereby, the thickness ratio of the second lens and the third lens can be adjusted to balance the system space distribution, improve the qualification rate and quality, and at the same time strengthen the system control ability of the third lens. Among them, the following condition can also be satisfied: 0.20 < CT2 / CT3 < 0.65. Among them, the following condition can also be satisfied: 0.40 < CT2 / CT3 < 0.63.

[0093] 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 conditions: 1.25 < f / EPD < 2.50. Thereby, the light entrance aperture of the lens can be adjusted, the light input amount of the lens system can be controlled, and thus the image brightness can be improved. Among them, the following conditions can also be satisfied: 1.0 < f / EPD < 2.05. Among them, the following conditions can also be satisfied: 1.0 < f / EPD < 2.0. Among them, the following conditions can also be satisfied: 1.20 < f / EPD < 1.80.

[0094] The focal length of the lens system is f, and the focal length of the second lens is f2, which can satisfy the following conditions: -0.15 < f / f2 < 0.15. Thereby, using the second lens as a correction lens, the spherical aberration and coma generated by the first lens can be effectively corrected, and the image quality of the off-axis field can be improved. Among them, the following conditions can also be satisfied: -0.10 < f / f2 < 0.10.

[0095] The minimum Abbe number among all the lenses of the lens system is Vdmin, which can satisfy the following conditions: 13.0 < Vdmin < 21.0. Thereby, the light path control ability of the lens can be improved, the design freedom can be increased, and more stringent specification requirements can be met.

[0096] The maximum effective radius of the image-side surface of the first lens is Y12, and the radius of curvature of the image-side surface of the first lens is R2, which can satisfy the following conditions: 1.02 < Y12 / R2 < 4.50. Thereby, the lens size of the first lens can be effectively controlled to simultaneously meet the requirements of a large viewing angle and a small volume of the lens. Among them, the following conditions can also be satisfied: 1.02 < Y12 / R2 < 2.50. Please refer to Figure 30 , this figure shows a schematic diagram of the parameter Y12 in the first embodiment of the present invention.

[0097] The perpendicular distance between the critical point on 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 at the off-axis position that satisfies the following conditions: 0.50 < Yc11 / f < 5.0. Thereby, the off-axis aberration correction ability of the lens system can be improved, the total length can be effectively compressed, and the requirements of miniaturization and a large viewing angle can be met simultaneously. Among them, the following conditions can also be satisfied: 0.80 < Yc11 / f < 3.0. Please refer to Figure 30 , this figure shows a schematic diagram of the parameter Yc11 in the first embodiment of the present invention.

[0098] The maximum imaging height of the lens system is ImgH (i.e., half of the total length of the diagonal of the effective sensing area of the electronic photosensitive element), and the focal length of the lens system is f, which can meet the following conditions: 2.0 < ImgH / f < 8.0. Thereby, the lens system can provide a better field angle for applications in different fields. Among them, the following conditions can also be met: 2.3 < ImgH / f < 4.0.

[0099] Half of the maximum viewing angle in the lens system is HFOV, and the aperture value (F-number) of the lens system is Fno, which can meet the following conditions: 1.50 < tan(HFOV) / Fno. Thereby, under the requirement of a large viewing angle, the light reception amount can be increased. Among them, the following conditions can also be met: 1.70 < tan(HFOV) / Fno < 5.50.

[0100] The lens system disclosed in the present invention further includes an aperture, and the aperture can be disposed between the second lens and the third lens. Thereby, the aperture position can be controlled to balance the viewing angle and the total length, which helps to meet the requirements of a wide viewing angle and miniaturization.

[0101] The distance from the aperture to the image side surface of the fourth lens on the optical axis is SD, and the distance from the object side surface of the first lens to the image side surface of the fourth lens on the optical axis is TD, which can meet the following conditions: 0.40 < SD / TD < 0.95. Thereby, the position of the aperture in the lens system can be balanced to control the viewing angle and the total length.

[0102] The distance from the object side surface of the first lens to the imaging surface on the optical axis is TL, and the maximum imaging height of the lens system is ImgH, which can meet the following conditions: 2.0 < TL / ImgH < 3.50. Thereby, while the lens system pursues miniaturization, it can maintain a sufficient light reception area to maintain sufficient brightness of the image. Among them, the following conditions can also be met: 2.0 < TL / ImgH < 3.0. Among them, the following conditions can also be met: 2.30 < TL / ImgH < 3.0.

[0103] 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 meet the following conditions: -12.0 < R1 / f < 0. Thereby, the first lens can have sufficient light divergence ability to facilitate the formation of an optical system with a wide viewing field. Among them, the following conditions can also be met: -8.0 < R1 / f < -2.0.

[0104] The displacement parallel to the optical axis from the intersection point of the object-side surface of the second lens on the optical axis to the maximum effective radius position of the object-side surface of the second lens is SAG21, and the displacement parallel to the optical axis from the intersection point of the image-side surface of the second lens on the optical axis to the maximum effective radius position of the image-side surface of the second lens is SAG22. The focal length of the lens system is f, and the following conditions can be satisfied: 0 ≤ (|SAG21| + |SAG22|) / f < 0.50. Thereby, it can effectively avoid the excessive change of the second lens surface shape and affect the peripheral image quality. Among them, the following conditions 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 invention, where the displacement value is positive in the image-side direction and negative in the object-side direction.

[0105] In the lens system disclosed in the present invention, the Abbe number of at least one lens with positive refractive power can be less than 30.0. Thereby, it can improve the light deflection ability in the lens system, which is beneficial to reducing the volume to meet the miniaturization requirement. Among them, the Abbe number of at least one lens with positive refractive power in the lens system can also be less than 28.0.

[0106] 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. At least one lens in the lens system can satisfy the following conditions: Vdi / Ni < 13.5, where i = 1, 2, 3 or 4. Thereby, it can improve the light deflection ability of the lens to facilitate achieving better specification design and imaging quality. Among them, at least one lens in the lens system can also satisfy the following conditions: Vdi / Ni < 12.0, where i = 1, 2, 3 or 4.

[0107] 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 can be satisfied: 1.0 [mm] < TL < 3.0 [mm]. Thereby, it can effectively control the total length to meet the miniaturization requirement.

[0108] In the lens system disclosed in the present invention, the thickness of the third lens on the optical axis can be the largest among the thicknesses of each single lens in the lens system on the optical axis. Thereby, it can balance the refractive power configuration of the lens system.

[0109] The perpendicular distance between the critical point on the image side surface of the fourth lens and the optical axis is Yc42, the focal length of the lens system is f, and the image side surface of the fourth lens may have at least one critical point off the axis that satisfies the following condition: 0.20 < Yc42 / f < 2.0. Thereby, the image curvature and the overall compressed length can be corrected, and the Petzval Surface of the lens system can be made flatter. Please refer to Figure 30 , which shows a schematic diagram of the parameter Yc42 in the first embodiment of the present invention.

[0110] The perpendicular distance between the critical point on the object side surface of the fourth lens and the optical axis is Yc41, the focal length of the lens system is f, and the object side surface of the fourth lens may have at least one critical point off the axis that satisfies the following condition: 0.30 < Yc41 / f < 2.0. Thereby, it is beneficial to reduce the back focal length of the lens system, and thus reduce the overall volume of the lens. Please refer to Figure 30 , which shows a schematic diagram of the parameter Yc41 in the first embodiment of the present invention.

[0111] In the electronic device disclosed in the present invention, the spacing distance of the first lens on the optical axis in the lens system of the flat plate and the identification module can be less than 1.50 millimeters (mm). Thereby, the thickness of the electronic device can be effectively controlled to meet the more lightweight and thin usage requirements.

[0112] The lens system disclosed in the present invention can be applied to infrared rays, visible light or single wavelength light, but the present invention is not limited thereto.

[0113] Each technical feature in the above-mentioned lens system of the present invention can be combined and configured to achieve the corresponding effects.

[0114] In the lens system disclosed in the present invention, 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 external environmental temperature change on imaging can be reduced, and the glass lens can be made by techniques such as grinding or molding. If the lens material is plastic, the production cost can be effectively reduced. In addition, a spherical or aspherical surface (ASP) can be provided on the lens surface. Among them, the spherical lens can reduce the manufacturing difficulty, and if an aspherical surface is provided on the lens surface, more control variables can be obtained thereby to eliminate aberration, reduce the number of lenses, and effectively reduce the overall length of the lens system of the present invention. Further, the aspherical surface can be made by methods such as plastic injection molding or molded glass lenses.

[0115] In the lens system disclosed in the present invention, if the lens surface is aspherical, it means that all or a part of the optically effective area of the lens surface is aspherical.

[0116] In the lens system disclosed in this invention, additives can be selectively added to any (or more) lens materials to alter the lens's transmittance for specific wavelengths of light, thereby reducing stray light and color shift. For example, the additives may filter out light in the 600 nm to 800 nm wavelength range to help reduce excess red or infrared light; or they may filter out light in the 350 nm to 450 nm wavelength range to reduce excess blue or ultraviolet light. Therefore, the additives can prevent specific wavelengths of light from interfering with imaging. Furthermore, the additives can be uniformly mixed into plastic and manufactured into lenses using injection molding technology.

[0117] In the lens system disclosed in this invention, 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 in its region, 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.

[0118] Unless otherwise defined, the parameter values ​​(such as refractive index, focal length, etc.) of the lens system, identification module, and electronic device described in this invention can be determined according to the operating wavelength of the system.

[0119] In the lens system disclosed in this invention, the inflection point of the lens surface refers to the boundary point where the curvature of the lens surface changes from positive to negative. The critical point of the lens surface refers to the point of tangency on the tangent line between a plane perpendicular to the optical axis and the lens surface, and the critical point is not located on the optical axis.

[0120] In the lens system disclosed in this invention, the imaging surface of the lens system can be a plane or a curved surface with any curvature, depending on the corresponding electronic photosensitive element, especially a curved surface with the concave surface facing the object side.

[0121] In the lens system disclosed in this invention, one or more imaging correction elements (such as planar elements) can be selectively disposed between the lens closest to the imaging plane and the imaging plane to achieve the effect of correcting image curvature, etc. The optical properties of the imaging correction element, such as curvature, thickness, refractive index, position, and surface type (convex or concave, spherical or aspherical, diffractive surface, and Fresnel surface, etc.), can be adjusted according to the requirements of the recognition module or imaging device. Generally, a preferred configuration of the imaging correction element is to place a thin plano-concave element with a concave surface in the object-side direction close to the imaging plane.

[0122] In the lens system disclosed in this invention, at least one aperture stop may be provided, which may be located before the first lens, between the lenses, or after the last lens. The aperture stop may be of the type such as a glare stop or a field stop, and may be used to reduce stray light and help improve image quality.

[0123] In the lens system disclosed in this invention, the aperture can be configured as a front aperture or a central aperture. A front aperture means the aperture is positioned between the subject and the first lens, while a central aperture means the aperture is positioned between the first lens and the imaging plane. A front aperture allows for a longer distance between the exit pupil and the imaging plane, resulting in a telecentric effect and increasing the efficiency of image reception by the CCD or CMOS sensor. A central aperture helps to expand the field of view of the lens system.

[0124] This invention may appropriately incorporate a variable aperture element, which can be a mechanical component or a light-regulating element, and whose aperture size and shape can be controlled electrically or by electrical signals. The mechanical component may include movable parts such as a blade assembly or a shielding plate; the light-regulating element may include a filter element, an electrochromic material, a liquid crystal layer, or other shielding material. This variable aperture element can enhance image adjustment capabilities by controlling the amount of light entering the image or the exposure time. Furthermore, this variable aperture element can also be the aperture of this invention, allowing image quality, such as depth of field or exposure speed, to be adjusted by changing the aperture value.

[0125] Based on the above implementation methods, specific embodiments are presented below and described in detail with reference to the accompanying drawings.

[0126] <First Embodiment>

[0127] Please refer to Figures 1 to 3 ,in Figure 1 A schematic diagram of an identification module and a tablet according to a first embodiment of the present invention is shown. Figure 2 It shows Figure 1 A schematic diagram of the identification module, and Figure 3 From left to right, the graphs show the spherical aberration, astigmatism, and distortion curves of the first embodiment. Figure 1 and Figure 2 As can be seen, the recognition module includes a lens system (unlabeled) and an electronic photosensitive element 170. The lens system, from the object side to the image side, sequentially includes a first lens 110, a second lens 120, an aperture 100, a third lens 130, a fourth lens 140, a filter element 150, and an imaging surface 160. The electronic photosensitive element 170 is disposed on the imaging surface 160. The lens system comprises four lenses (110, 120, 130, and 140), and there are no other interposed lenses between the lenses.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] The equations for the aspherical surfaces of the above lenses are expressed as follows:

[0135]

[0136] 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.

[0137] Y: The perpendicular distance between a point on the aspherical curve and the optical axis;

[0138] R: Radius of curvature;

[0139] k: cone coefficient; and

[0140] Ai: The i-th order aspherical coefficient.

[0141] 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.

[0142] The Abbe number of the fourth lens 140 is Vd4, which satisfies the following condition: Vd4 = 19.4.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] Please refer to Table 1 and Table 2 below.

[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] 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.

[0180]

[0181] <Third Embodiment>

[0182] 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 8As 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] Please refer to Table 5 and Table 6 below.

[0190]

[0191]

[0192]

[0193] 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.

[0194]

[0195] <Fourth Embodiment>

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] Please refer to Tables 7 and 8 below.

[0204]

[0205]

[0206]

[0207] 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.

[0208]

[0209] <Fifth Embodiment>

[0210] 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 14 As 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] Please refer to Tables 9 and 10 below.

[0218]

[0219]

[0220]

[0221] 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.

[0222]

[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] 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.

[0236]

[0237] <Seventh Embodiment>

[0238] 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 20 As 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] 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.

[0245] Please refer to Tables 13 and 14 below.

[0246]

[0247]

[0248]

[0249] 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.

[0250]

[0251] <Eighth Embodiment>

[0252] 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 24From 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.

[0253] 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.

[0254] 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.

[0255] 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.

[0256] 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.

[0257] 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.

[0258] 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.

[0259] Please refer to Tables 15 and 16 below.

[0260]

[0261]

[0262] 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.

[0263]

[0264] <Ninth Embodiment>

[0265] 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.

[0266] 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.

[0267] 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.

[0268] <Tenth Embodiment>

[0269] Please refer to Figure 27This 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.

[0270] 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.

[0271] 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.

[0272] <Eleventh Embodiment>

[0273] 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.

[0274] 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.

[0275] 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.

[0276] 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.

[0277] 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.

[0278] 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 on-axis position, the first lens object side surface has at least one convex critical point at the off-axis position, and the fourth lens has a positive refractive power; wherein the total number of lenses in the lens system is four, the distance from the first lens object side surface to an image plane on the optical axis is TL, the focal length of the lens system is f, the thickness of the second lens on the optical axis is CT2, the thickness of the third lens on the optical axis is CT3, the radius of curvature of the fourth lens object side surface is R7, the radius of curvature of the fourth lens image side surface is R8, the entrance pupil diameter of the lens system is EPD, and the following conditions are satisfied: 4.85 < TL / f < 15.0; 0.10 < CT2 / CT3 < 0.95; (R7+R8) / (R7-R8) < 0.35; and 1.25 < f / EPD < 2.

50.

2. The lens system of claim 1, wherein The fourth lens object side surface has at least one concave critical point at the off-axis position.

3. The lens system of claim 1, wherein, The focal length of the lens system is f, the focal length of the second lens is f2, and the following condition is satisfied: -0.15 < f / f2 < 0.

15.

4. The lens system of claim 1, wherein, The distance from the first lens object side surface to the image plane on the optical axis is TL, the focal length of the lens system is f, the thickness of the second lens on the optical axis is CT2, the thickness of the third lens on the optical axis is CT3, the radius of curvature of the fourth lens object side surface is R7, the radius of curvature of the fourth lens image side surface is R8, the Abbe number of the fourth lens is Vd4, and the following conditions are satisfied: 7.37 ≤ TL / f ≤ 8.04; 0.40 < CT2 / CT3 < 0.63; -32.17 ≤ (R7+R8) / (R7-R8) < 0.25; and 17.0 ≤ Vd4 ≤ 27.

7.

5. The lens system of claim 1, wherein, The perpendicular distance between the critical point of the first lens object side surface and the optical axis is Yc11, the focal length of the lens system is f, and the following condition is satisfied: 0.50 < Yc11 / f < 5.

0.

6. The lens system of claim 1, wherein, The maximum image height of the lens system is ImgH, the focal length of the lens system is f, and the following condition is satisfied: 2.0 < ImgH / f < 8.

0.

7. The lens system of claim 1, wherein, Half of the maximum viewing angle of the lens system is HFOV, the F number of the lens system is Fno, and the following condition is satisfied: 1.50 < tan(HFOV) / Fno.

8. The lens system of claim 1, wherein, Further comprising a stop disposed between the second lens and the third lens, wherein the distance from the stop to the fourth lens image side surface on the optical axis is SD, the distance from the first lens object side surface to the fourth lens image side surface on the optical axis is TD, the focal length of the lens system is f, the entrance pupil diameter of the lens system is EPD, and the following conditions are satisfied: 0.40 < SD / TD < 0.95; and 1.60 < f / EPD < 2.

05.

9. The lens system of claim 1, wherein, The first lens has a first lens object-side surface and a first lens image-side surface, the first lens object-side surface has a radius of curvature R1, the lens system has a focal length f, and the following conditions are satisfied: -12.0 < R1 / f < 0.

10. The lens system of claim 1, wherein, The first lens has a first lens object-side surface and a first lens image-side surface, the first lens object-side surface has a radius of curvature R1, the lens system has a focal length f, and the following conditions are satisfied: 0 < (|SAG21| + |SAG22|) / f < 0.

50.

11. The lens system of claim 1, wherein, The first lens has an Abbe number Vd1, the second lens has an Abbe number Vd2, the third lens has an Abbe number Vd3, the fourth lens has an Abbe number Vd4, the ith lens has an Abbe number Vdi, the first lens has a refractive index N1, the second lens has a refractive index N2, the third lens has a refractive index N3, the fourth lens has a refractive index N4, and the ith lens has a refractive index 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.

12. A lens system characterized by comprising: The lens system includes four lenses arranged in order from an object side to an image side as a first lens, a second lens, a third lens, and a fourth lens, and the four lenses respectively have an object-side surface facing the object side and an image-side surface facing the image side; wherein the first lens has negative refractive power, the first lens object-side surface is concave at a near optical axis, the first lens object-side surface has at least one convex critical point at an off-axis position, and the fourth lens has positive refractive power; wherein the total number of lenses in the lens system is four, the distance from the first lens object-side surface to an imaging surface on the optical axis is TL, the focal length of the lens system is f, the Abbe number of the fourth lens is Vd4, 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, and the following conditions are satisfied: 4.85 < TL / f < 15.0; 10.0 < Vd4 < 38.0; and -3.50 < (R7+R8) / (R7-R8) < 0.

85.

13. The lens system of claim 12, wherein, The lens system has a focal length f, and the second lens has a focal length f2, and the following condition is satisfied: -0.15 < f / f2 < 0.

15.

14. The lens system of claim 12, wherein, The first lens has a first lens object-side surface and a first lens image-side surface, the first lens object-side surface has a radius of curvature R1, the lens system has a focal length f, and the following conditions are satisfied: 5.50 < TL / f < 12.0; 13.0 < Vd4 < 30.0; -3.50 < (R7+R8) / (R7-R8) < 0.25; and -3.50 < (R7+R8) / (R7-R8) < 0.

25. 1.25 < f / EPD < 2.

05.

15. The lens system of claim 12, wherein, The perpendicular distance between the critical point of the object side surface of the first lens and the optical axis is Ycll, the focal length of the lens system is f, and the object side surface of the first lens has at least one critical point at an off-axis position satisfying the following condition: 0.80 < Ycll / f < 3.

0.

16. The lens system of claim 12, wherein, The maximum image height of the lens system is ImgH, the focal length of the lens system is f, and the following condition is satisfied: 2.3 < ImgH / f < 4.

0.

17. The lens system of claim 12, wherein, Half of the maximum view angle in the lens system is HFOV, the aperture value of the lens system is Fno, and the following condition is satisfied: 1.50 < tan(HFOV) / Fno ≤ 2.

19.

18. The lens system of claim 12, wherein, Further comprising an aperture disposed between the second lens and the third lens, wherein the distance from the aperture to the image side surface of the fourth lens on the optical axis is SD, the distance from the object side surface of the first lens to the image side surface of the fourth lens on the optical axis is TD, the focal length of the lens system is f, and the entrance pupil diameter of the lens system is EPD, and the following conditions are satisfied: 0.40 < SD / TD < 0.95; and 1.0 < f / EPD < 2.

05.

19. The lens system of claim 12, wherein, The thickness of the second lens on the optical axis is CT2, the thickness of the third lens on the optical axis is CT3, and the following condition is satisfied: 0.20 < CT2 / CT3 < 0.

65.

20. The lens system of claim 12, wherein, The radius of curvature of the object side surface of the first lens is Rl, the focal length of the lens system is f, and the following condition is satisfied: -12.0 < Rl / f < 0.

21. The lens system of claim 12, wherein, The displacement amount of the intersection point of the object side surface of the second lens on the optical axis to the position of the maximum effective radius of the object side surface of the second lens parallel to the optical axis is SAG21, the displacement amount of the intersection point of the image side surface of the second lens on the optical axis to the position of the maximum effective radius of the image side surface of the second lens parallel to the optical axis is SAG22, the focal length of the lens system is f, and the following condition is satisfied: 0 ≤ (|SAG21| + |SAG22|) / f < 0.

35.

22. The lens system of claim 12, wherein, The Abbe number of the first lens is Vdl, 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 Nl, 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.

23. The lens system of claim 22, wherein, The Abbe number of the first lens is Vdl, 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 Nl, 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 < 12.0, where i = 1, 2, 3, or 4.

24. The lens system of claim 12, wherein, The perpendicular distance between the critical point of the fourth lens image-side surface and the optical axis is Yc42, the focal length of the lens system is f, and the fourth lens image-side surface has at least one critical point at an off-axis position satisfying the following condition: 0.20 < Yc42 / f < 2.0.

Images