Folded lens system

Abstract

A folding lens system includes: a lens module comprising a plurality of lenses; an image sensor having an imaging plane; and a first reflection module disposed between the lens module and the image sensor and configured to change the path of light passing through the lens module multiple times. Light passing through the lens module undergoes three total internal reflections and two reflections by the first reflection module.

Description

[Technical Field]

[0001] [Cross-reference to related applications]

[0002] This application claims priority to Korean Patent Application No. 10-2022-0042397, filed on April 5, 2022, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

[0003] This disclosure relates to a folding lens system. [Previous Technology]

[0004] Camera modules are mainly used in portable electronic devices such as smartphones. The thickness of portable electronic devices is decreasing due to market demand, and therefore, miniaturization of camera modules may also be necessary.

[0005] In detail, in order to prevent the height of the camera module from significantly affecting the thickness of the portable electronic device, a camera module having a reflective member for changing the path of light can be proposed.

[0006] Since this type of camera module changes the path of light by means of a reflective component, it has the advantage that the total trajectory length of the camera module (the distance from the lens closest to the object to the imaging plane) does not affect the thickness of the portable electronic device.

[0007] However, in this case, there may be a problem that the total trajectory length of the camera module becomes too large in one direction.

[0008] The above information is provided as background information to help understand this disclosure. No determination or assertion is made as to whether any of the above content is suitable as prior art to this disclosure. [Summary of the Invention]

[0009] This summary is provided to introduce, in a simplified form, a series of concepts further elaborated in the embodiments below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0010] In a general case, a folding lens system includes: a lens module including a plurality of lenses; an image sensor having an imaging plane; and a first reflection module disposed between the lens module and the image sensor and configured to change the path of light passing through the lens module multiple times, wherein the light passing through the lens module undergoes three total internal reflections and two reflections by the first reflection module.

[0011] The first reflective module may include a first surface, a second surface, a third surface, a fourth surface, a fifth surface and a sixth surface. The first surface may be set to be closest to the lens module and the sixth surface may be set to be closest to the image sensor. The angle between the first surface and the second surface, the angle between the second surface and the third surface and the angle between the fourth surface and the sixth surface may be acute angles and the angle between the fifth surface and the sixth surface may be obtuse angles.

[0012] The first, second and fourth surfaces may undergo refraction or total internal reflection depending on the angle of incidence of light.

[0013] In the third and fifth surfaces, light incident on each surface can be reflected.

[0014] The second surface and the fourth surface may be arranged to face each other, and an air gap may exist between the second surface and the fourth surface.

[0015] Light passing through the lens module can be refracted when passing through the first surface and can be incident on the second surface, and the incident angle of the light incident on the second surface can be greater than the critical angle. Light totally reflected from the second surface can be incident on the third surface, and the incident angle of the light incident on the third surface can be less than the critical angle. Light reflected from the third surface can be incident on the first surface, and the incident angle of the light incident on the first surface can be greater than the critical angle. Light totally reflected from the first surface can pass through the second and fourth surfaces, can be refracted and can be incident on the fifth surface, and the incident angle of the light incident on the fifth surface can be less than the critical angle. Light reflected from the fifth surface can be incident on the fourth surface, and the incident angle of the light incident on the fourth surface can be greater than the critical angle. Light totally reflected from the fourth surface can pass through the sixth surface, can be refracted and can be incident on the image sensor.

[0016] The first reflection module may include a first prism and a second prism spaced apart from each other. Each of the first prism and the second prism may have a polygonal shape, and the first prism may have two total internal reflection surfaces and a reflection surface, and the second prism may have a total internal reflection surface and a reflection surface.

[0017] The folding lens system may further include a second reflection module, which is disposed in front of the lens module.

[0018] The folding lens system may further include a second reflection module, which is disposed between the lens module and the first reflection module.

[0019] The first reflective module may include a first surface, a second surface, a third surface, a fourth surface, a fifth surface and a sixth surface. The first surface may be positioned closest to the lens module and the fifth surface may be positioned closest to the image sensor. The angle between the first surface and the second surface, the angle between the fourth surface and the fifth surface and the angle between the fourth surface and the sixth surface may be acute angles, the angle between the first surface and the third surface may be obtuse angles, and the second surface and the fourth surface may be positioned facing each other. An air gap may exist between the second surface and the fourth surface.

[0020] Light passing through the lens module can be refracted when passing through the first surface and can be incident on the second surface, and the incident angle of the light incident on the second surface can be greater than the critical angle. Light totally reflected from the second surface can be incident on the third surface, and the incident angle of the light incident on the third surface can be less than the critical angle. Light reflected from the third surface can pass through the second and fourth surfaces, can be refracted and can be incident on the fifth surface, and the incident angle of the light incident on the fifth surface can be greater than the critical angle. Light totally reflected from the fifth surface can be incident on the sixth surface, and the incident angle of the light incident on the sixth surface can be less than the critical angle. Light reflected from the sixth surface can be incident on the fourth surface, and the incident angle of the light incident on the fourth surface can be greater than the critical angle. Light totally reflected from the fourth surface can pass through the fifth surface, can be refracted and can be incident on the image sensor.

[0021] The lens module can satisfy IMG HT / FBL < 0.7, where IMG HT is the diagonal length of the imaging plane and FBL is the distance from the vertex of the image side surface of the lens closest to the image sensor to the imaging plane.

[0022] The lens module can satisfy TTL / f < 0.75, where TTL is the distance from the vertex of the object-side surface of the lens furthest from the image sensor to the imaging plane, and f is the total focal length of the lens module.

[0023] The lens furthest from the image sensor can have a positive refractive power.

[0024] The lens module can satisfy 0 < f1 / f < 0.5, where f1 is the focal length of the lens furthest from the image sensor and f is the total focal length of the lens module.

[0025] The lens positioned at the second furthest point from the image sensor may have a negative refractive power.

[0026] The lens module can satisfy -0.7 < f2 / f < 0, where f2 is the focal length of the lens that is second farthest from the image sensor.

[0027] It can satisfy TTL / (TL+OPL) < 0.75, where TTL is the distance from the vertex of the object-side surface of the lens furthest from the image sensor to the imaging plane, TL is the distance from the vertex of the object-side surface of the lens furthest from the image sensor to the vertex of the image-side surface of the lens closest to the image sensor, and OPL is the optical path length from the image-side surface of the lens closest to the image sensor to the imaging plane.

[0028] In another general embodiment, a folding lens system includes: a lens module including a plurality of lenses; an image sensor having an imaging plane; and a first prism spaced apart from a second prism by an air gap, wherein two adjacent surfaces of one of the first or second prisms refract and reflect light respectively between the lens module and the imaging plane, the two adjacent surfaces forming an obtuse angle.

[0029] Light passing through a first or second prism, which includes the two surfaces forming an obtuse angle, may undergo one total internal reflection and one reflection, while light passing through the other of the first or second prism may undergo two total internal reflections and one reflection.

[0030] Other features and characteristics will become apparent from reading the following detailed description, drawings and claims.

Implementation Method

[0032] In the following, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, but it should be noted that the examples are not limited thereto.

[0033] The following detailed description is provided to help the reader fully understand the methods, apparatus, and / or systems described herein. However, various variations, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent after understanding this disclosure. For example, the order of operations described herein is merely an example and is not limited to the order described herein, but can be changed, as will become apparent after understanding this disclosure, except for operations that must be performed in a specific order. Furthermore, for clarity and conciseness, descriptions of features known in this art may be omitted.

[0034] The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are merely illustrative of some of the many possible ways in which the methods, apparatus and / or systems described herein may be apparent upon understanding this disclosure.

[0035] Although terms such as "first," "second," and "third" may be used herein to describe various components, parts, areas, layers, or sections, these components, parts, areas, layers, or sections are not limited by these terms. Rather, these terms are used only to distinguish individual components, parts, areas, layers, or sections. Therefore, without departing from the teaching of the examples, the first component, first part, first area, first layer, or first section mentioned in the examples described herein may also be referred to as the second component, second part, second area, second layer, or second section.

[0036] In this document, it should be noted that when the term "may" is used with respect to an instance or embodiment (e.g., with respect to what an instance or embodiment may include or what operations may be performed), it means that there exists at least one instance or embodiment that includes or performs such a feature, and all instances and embodiments are not limited thereto.

[0037] Throughout this specification, when an element such as a layer, region, or substrate is described as being "located" "on," "connected to," or "coupled to" another element, the element may be directly "located" "on," directly "connected to," or directly "coupled to" the other element, or there may be one or more other elements in between. In contrast, when an element is described as being "directly located" "on," "directly connected to," or "directly coupled to" another element, there may be no other elements in between.

[0038] The term “and / or” as used herein includes any one of the related listed items and any combination of any two or more items; similarly, “at least one of” includes any one of the related listed items and any combination of any two or more items.

[0039] For ease of explanation, spatially relative terms such as "above," "upper," "below," "lower," and similar terms may be used herein to describe the relationship between one element and another illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device during use or operation, other than those shown in the figures. For example, if the device in the figures is flipped, an element described as being "above" or "upper" relative to another element will now be described as being "below" or "lower" relative to that other element. Therefore, the term "above" encompasses both upper and lower orientations depending on the spatial orientation of the device. The device may also be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatially relative terms used herein should be interpreted accordingly.

[0040] The terminology used herein is for illustrative purposes only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the articles "a" and "the" are intended to include the plural form as well. The terms "comprises," "includes," and "has" indicate the presence of the stated features, numbers, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, components, elements, and / or combinations thereof.

[0041] Due to manufacturing techniques and / or tolerances, the shapes illustrated in the drawings may vary. Therefore, the examples described herein are not limited to the specific shapes illustrated in the drawings, but include shape variations that occur during manufacturing.

[0042] In the following lens configuration diagrams, for the purpose of illustration, the thickness, size and shape of the lenses are shown in slightly exaggerated form, and in detail, the shapes of the spherical or aspherical surfaces presented in the lens configuration diagrams are presented as examples only and are not limited thereto.

[0043] The folding lens system according to the example can be mounted on a portable electronic device. For example, the folding lens system can be a component of a camera module mounted on a portable electronic device. The portable electronic device can be, for example, a mobile communication terminal, a smartphone, or a personal computer (PC).

[0044] In the examples described herein, the first lens (or foremost lens) refers to the lens closest to the object side, while the last lens (or final lens) refers to the lens closest to the imaging plane (or image sensor).

[0045] Furthermore, in each lens, the first surface refers to the surface closer to the object side (or the object-side surface), while the second surface refers to the surface closer to the image side (or the image-side surface). Additionally, in this specification, the values ​​for the lens's radius of curvature, thickness, distance, focal length, etc., are all expressed in millimeters (mm), and the field of view (FOV) is expressed in degrees.

[0046] In addition, in the description of the shape of each lens, the convex shape of a surface means that the paraxial region of the corresponding surface is convex, while the concave shape of a surface means that the paraxial region of the corresponding surface is concave.

[0047] On the other hand, the paraxial region refers to a relatively narrow region near and including the optical axis.

[0048] The imaging plane may refer to a virtual plane on which the lens system forms a focal point. Alternatively, the imaging plane may refer to a surface on which the image sensor receives light.

[0049] One or more examples described herein provide a miniaturizable folding lens system.

[0050] Figure 1 is a schematic configuration diagram of the folding lens system according to the example, and Figure 2 is a schematic perspective view of the folding lens system according to the example.

[0051] Referring to Figures 1 and 2, the folding lens system according to the example includes a first reflection module 300, a lens module 100, a second reflection module 400, and an image sensor 600.

[0052] In addition, the folding lens system may further include an infrared cut-off filter 500 for blocking infrared light. The infrared cut-off filter 500 may be disposed between the second reflective module 400 and the image sensor 600.

[0053] The first reflection module 300 has a reflective surface for changing the path of light. For example, the first reflection module 300 may be a mirror or a prism. The first reflection module 300 is disposed in front of the lens module 100 and can change the path of light so that light incident on the first reflection module 300 is guided toward the lens module 100.

[0054] The second reflection module 400 is disposed behind the lens module 100 (for example, between the lens module 100 and the image sensor 600), and the path of light passing through the lens module 100 can be changed multiple times.

[0055] The second reflection module 400 has multiple surfaces for changing the path of light. As an example, light passing through the lens module 100 can undergo three total internal reflections and two reflections by the second reflection module 400.

[0056] For example, by changing the path of light several times through the second reflection module 400, a relatively long path of light can be formed in a relatively narrow space.

[0057] Therefore, a long focal length can be provided while miniaturizing the folding lens system.

[0058] The second reflective module 400 includes a first prism 410 and a second prism 430 spaced apart from each other, and each of the first prism 410 and the second prism 430 may have a polygonal shape.

[0059] The first prism 410 and the second prism 430 are arranged to face each other with a gap. Therefore, there is an air gap between the surfaces of the first prism 410 and the second prism 430 facing each other.

[0060] The lens module 100 includes multiple lenses. For example, the lens module 100 may include four or more lenses. For example, the lens module 100 may include five lenses.

[0061] Referring to Figures 1 and 2, the lens module 100 may include a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, and a fifth lens 150 arranged sequentially from the object side. In addition, an aperture stop may be provided between the fourth lens 140 and the fifth lens 150.

[0062] In this case, the first lens 110 has a positive refractive power, while the second lens 120 has a negative refractive power.

[0063] In an example, the lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, focal length) of each lens in the lens module 100 are shown in Table 1.

[0064] In the example shown in Figures 1 and 2, the lens module 100 is disposed between the first reflection module 300 and the second reflection module 400. For example, the first reflection module 300 is disposed in front of the lens module 100, while the second reflection module 400 is disposed behind the lens module 100.

[0065] However, the position of the lens module 100 is not limited to this, and as in the examples shown in Figures 3 and 4, the first reflection module 300 and the second reflection module 400 may also be located at the rear of the lens module 100. Table 1 shows the configuration in which the first reflection module 300 and the second reflection module 400 are located at the rear of the lens module 100.

[0066] In Table 1, the * mark on the surface number indicates that the corresponding surface is an aspherical surface.

[0067] [Table 1] Surface number Remark radius of curvature Thickness or distance Refractive index Abbe number focal length 1* First lens 7.1309 1.787 1.5349 55.7 12.6648 2* -134.8793 1.000 3 Second lens 36.1134 0.700 1.6392 23.5 -19.1519 4 9.1403 0.300 5 Third lens 8.1143 1.161 1.6608 20.4 11.5936 6 -161.9693 1.100 7* Fourth lens -11.0678 0.800 1.6392 23.5 -5.9221 8* (Aperture) 6.0059 0.285 9* Fifth lens 19.2464 1.000 1.5440 56.0 24.6716 10* -44.1533 0.500 11 First Prism infinity 3.898 1.7174 29.5 12 infinity 3.898 1.7174 29.5 13 infinity 5.513 1.7174 29.5 14 infinity 2.756 1.7174 29.5 15 infinity 0.100 16 Second prism infinity 2.756 1.7174 29.5 17 infinity 3.898 1.7174 29.5 18 infinity 2.756 1.7174 29.5 19 infinity 0.7 20 Filter infinity 0.22 1.5168 64.2 twenty one infinity 0.454 twenty two Imaging plane infinity

[0068] According to the example, the total focal length f of the lens module 100 is 30.6 mm, the distance (TTL) from the vertex of the object-side surface of the first lens 110 to the imaging plane is 16.5 mm, the distance (FBL) from the vertex of the image-side surface of the fifth lens 150 to the imaging plane is 8.37 mm, the diagonal length (IMG HT) of the imaging plane is 5.57 mm, and the Fno (F number) is 4.4.

[0069] At least one of the first lens 110 to the fifth lens 150 may be an aspherical lens. For example, the object-side surface and the image-side surface of the first lens 110, the fourth lens 140 and the fifth lens 150 are all aspherical surfaces.

[0070] The aspherical surface of each lens is represented by Equation 1.

[0071] [Equation 1]

[0072] In Equation 1, c is the curvature of the lens (the reciprocal of the radius of curvature), K is the conic constant, and Y represents the distance from any point on the aspherical surface of the lens to the optical axis. Furthermore, constants A to G and H refer to the aspherical coefficients. Additionally, Z (Sagging (SAG)) represents the distance between any point on the aspherical surface of the lens and the corresponding vertex of the aspherical surface along the optical axis.

[0073] The object-side surface and image-side surface of the first lens 110, the fourth lens 140 and the fifth lens 150 have aspherical coefficients as shown in Table 2.

[0074] [Table 2] Surface number 1 2 7 8 9 10 Conic constant (K) 7.1309E+00 -9.0000E+01 9.1158E+00 2.4552E+00 5.9018E+01 -4.4153E+01 Fourth-order coefficients (A) -4.9362E-01 -1.6709E-04 -2.7043E-03 -4.7337E-03 1.6031E-03 -9.0000E+01 Sixth-order coefficients (B) 1.1891E-04 -2.3448E-05 3.8128E-04 -2.8092E-04 -8.2411E-04 1.5605E-03 Eighth-order coefficients (C) -1.7017E-05 -5.6369E-07 7.9979E-05 1.1412E-05 -3.2407E-05 2.7941E-04 Tenth-order coefficient (D) -4.9315E-07 8.1767E-08 -9.9135E-06 3.9873E-05 2.6456E-05 -7.3063E-05 Twelfth-order coefficients (E) 1.5571E-08 3.6361E-09 2.3333E-07 -3.9568E-06 -3.2015E-06 -6.6544E-06 Fourteenth-order coefficient (F) 2.7853E-10 -6.9569E-10 0.0000E+00 0.0000E+00 4.1698E-08 1.1291E-06 Sixteenth-order coefficients (G) -3.3011E-11 1.2786E-11 0.0000E+00 0.0000E+00 9.7504E-09 -1.6256E-07 Eighteenth-order coefficient (H) -8.7682E-12 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 2.2781E-08

[0075] In another example, the lens characteristics (radius of curvature, lens thickness or distance between lenses, refractive index, Abbe number, focal length) of each lens in the lens module 100 are shown in Table 3.

[0076] [Table 3] Surface number Remark radius of curvature Thickness or distance Refractive index Abbe number focal length 1* First lens 7.3015 1.687 1.5349 55.7 13.3652 2* -393.4619 1.005 3* Second lens 41.8557 0.500 1.6392 23.5 -20.0519 4* 9.8405 0.300 5* Third lens 8.5057 1.200 1.6608 20.4 11.4277 6* -70.5921 1.215 7* Fourth lens -10.7425 0.801 1.6392 23.5 -5.8036 8* (Aperture) 5.9211 0.294 9* Fifth lens 21.3001 0.928 1.5440 56.0 20.8002 10* -23.9851 1.200 11 First Prism infinity 2.756 1.7174 29.5 12 infinity 3.898 1.7174 29.5 13 infinity 2.756 1.7174 29.5 14 infinity 0.100 15 Second prism infinity 2.756 1.7174 29.5 16 infinity 5.513 1.7174 29.5 17 infinity 3.898 1.7174 29.5 18 infinity 3.898 1.7174 29.5 19 infinity 0.5 20 Filter infinity 0.22 1.5168 64.2 twenty one infinity 0.506 twenty two Imaging plane infinity

[0077] According to another example, the total focal length f of the lens module 100 is 30.6 mm, the distance (TTL) from the vertex of the object-side surface of the first lens 110 to the imaging plane is 17.08 mm, the distance (FBL) from the vertex of the image-side surface of the fifth lens 150 to the imaging plane is 9.15 mm, the diagonal length (IMG HT) of the imaging plane is 5.57 mm, and the Fno (F number) is 4.4.

[0078] At least one of the first lens 110 to the fifth lens 150 may be an aspherical lens. For example, as shown in Table 4, the object-side surface and the image-side surface of the first lens 110 to the fifth lens 150 are both aspherical.

[0079] [Table 4] Surface number 1 2 3 4 5 Conic constant (K) -5.4878E-01 -9.0000E+01 0.0000E+00 0.0000E+00 0.0000E+00 Fourth-order coefficients (A) 8.4247E-05 -1.8073E-04 -7.0520E-06 7.4089E-06 -2.5307E-06 Sixth-order coefficients (B) -1.1888E-05 -2.4747E-05 -5.5410E-07 1.0296E-06 -9.8279E-07 Eighth-order coefficients (C) -6.7029E-07 -4.1913E-07 -3.1773E-08 5.1428E-08 -2.0475E-09 Tenth-order coefficient (D) 5.0172E-09 8.0892E-08 -1.3567E-09 1.7697E-09 7.8844E-09 Twelfth-order coefficients (E) 4.0236E-10 3.0750E-09 -2.1706E-10 1.1791E-09 -3.4100E-10 Fourteenth-order coefficient (F) 1.2333E-11 -7.0389E-10 7.1786E-12 1.5771E-10 -7.8015E-11 Sixteenth-order coefficients (G) -6.3943E-12 1.8886E-11 0.0000E+00 0.0000E+00 0.0000E+00 Surface number 6 7 8 9 10 Conic constant (K) 0.0000E+00 8.4667E+00 2.5724E+00 7.5958E+01 -9.0000E+01 Fourth-order coefficients (A) 1.0539E-06 -2.5513E-03 -4.6557E-03 2.1907E-03 1.4565E-03 Sixth-order coefficients (B) 1.1985E-06 3.9118E-04 -2.5232E-04 -7.4545E-04 9.8662E-05 Eighth-order coefficients (C) 8.8040E-09 7.8533E-05 3.1219E-05 -5.3803E-05 -5.2227E-05 Tenth-order coefficient (D) -7.2924E-09 -9.4930E-06 3.7953E-05 2.6611E-05 -4.8275E-06 Twelfth-order coefficients (E) -6.8984E-10 1.8284E-07 -4.5165E-06 -2.6356E-06 7.5540E-07 Fourteenth-order coefficient (F) -5.9647E-10 0.0000E+00 0.0000E+00 6.4315E-08 -2.5555E-07 Sixteenth-order coefficients (G) 0.0000E+00 0.0000E+00 0.0000E+00 -3.4756E-08 2.8842E-08

[0080] In this example, the first lens 110 has a positive refractive power, and both its object-side and image-side surfaces are convex. The absolute value of the radius of curvature of the object-side surface of the first lens 110 may be less than the absolute value of the radius of curvature of the image-side surface of the first lens 110. For example, when the radius of curvature of the object-side surface of the first lens 110 is R1 and the radius of curvature of the image-side surface of the first lens 110 is R2, |R2| / |R1| > 15.

[0081] The second lens 120 has a negative refractive power. The object-side surface of the second lens 120 is convex, while the image-side surface of the second lens 120 has a concave shape. The absolute value of the radius of curvature of the object-side surface of the second lens 120 can be greater than the absolute value of the radius of curvature of the image-side surface of the second lens 120. For example, when the radius of curvature of the object-side surface of the second lens 120 is R3 and the radius of curvature of the image-side surface of the second lens 120 is R4, it can satisfy |R3| / |R4|>3.

[0082] The third lens 130 has positive refractive power, and both the object-side surface and the image-side surface of the third lens 130 have convex shapes. The absolute value of the radius of curvature of the object-side surface of the third lens 130 can be smaller than the absolute value of the radius of curvature of the image-side surface of the third lens 130. For example, when the radius of curvature of the object-side surface of the third lens 130 is R5 and the radius of curvature of the image-side surface of the third lens 130 is R6, it can satisfy |R6| / |R5|>6.

[0083] The fourth lens 140 has a negative refractive power, and both the object-side surface and the image-side surface of the fourth lens 140 have concave shapes. The absolute value of the radius of curvature of the object-side surface of the fourth lens 140 can be greater than the absolute value of the radius of curvature of the image-side surface of the fourth lens 140. For example, when the radius of curvature of the object-side surface of the fourth lens 140 is R7 and the radius of curvature of the image-side surface of the fourth lens 140 is R8, it can satisfy |R7| / |R8|>1.

[0084] The fifth lens 150 has positive refractive power, and the object-side surface and the image-side surface of the fifth lens 150 each have a convex shape.

[0085] The fifth lens 150 may be the lens with the weakest refractive power among the plurality of lenses. For example, among the first lens 110 to the fifth lens 150, the absolute value of the focal length of the fifth lens 150 may be the largest.

[0086] The lens module 100 according to the example can satisfy at least one of the following conditional expressions.

[0087] [Condition 1] IMG HT / FBL < 0.7

[0088] [Condition 2] 0 < f1 / f < 0.5

[0089] [Condition 3] -0.7 < f2 / f < 0

[0090] [Condition 4] TTL / f < 0.75

[0091] [Condition 5] TTL / f < 0.59

[0092] IMG HT is the diagonal length of the imaging plane, FBL is the distance from the vertex of the image side surface of the fifth lens 150 to the imaging plane, TTL is the distance from the vertex of the object side surface of the first lens 110 to the imaging plane, f is the total focal length of the lens module 100, f1 is the focal length of the first lens 110, and f2 is the focal length of the second lens.

[0093] Figure 3 is a schematic configuration diagram of a folding lens system according to another example, and Figure 4 is a schematic perspective view of a folding lens system according to another example.

[0094] Referring to Figures 3 and 4, a folding lens system according to another embodiment includes a lens module 200, a first reflection module 300, a second reflection module 400, and an image sensor 600.

[0095] In addition, the folding lens system may further include an infrared cut-off filter 500 for blocking infrared light. The infrared cut-off filter 500 may be disposed between the second reflective module 400 and the image sensor 600.

[0096] The first reflection module 300 and the second reflection module 400 may be disposed between the lens module 200 and the image sensor 600. The first reflection module 300 may be disposed relatively closer to the lens module 200, and the second reflection module 400 may be disposed relatively closer to the image sensor 600.

[0097] The lens module 200 includes multiple lenses. For example, the lens module 200 may include four or more lenses.

[0098] Referring to Figures 3 and 4, the lens module 200 may include a first lens 210, a second lens 220, a third lens 230 and a fourth lens 240 arranged sequentially from the object side.

[0099] The first lens 210 has positive refractive power. The object-side surface of the first lens 210 is convex, and the image-side surface of the first lens 210 has a concave shape. The absolute value of the radius of curvature of the object-side surface of the first lens 210 is smaller than the absolute value of the radius of curvature of the image-side surface of the first lens 210.

[0100] The second lens 220 has a negative refractive power, and both the object-side surface and the image-side surface of the second lens 220 have concave shapes. The absolute value of the radius of curvature of the object-side surface of the second lens 220 is greater than the absolute value of the radius of curvature of the image-side surface of the second lens 220.

[0101] The third lens 230 has positive refractive power, the object side surface of the third lens 230 is convex, and the image side surface of the third lens 230 has a concave shape.

[0102] The fourth lens 240 has a positive or negative refractive power, the object side surface of the fourth lens 240 is convex, and the image side surface of the fourth lens 240 has a concave shape.

[0103] The fourth lens 240 may be the lens with the weakest refractive power among the plurality of lenses. For example, among the first lens 210 to the fourth lens 240, the absolute value of the focal length of the fourth lens 240 may be the largest.

[0104] The first reflection module 300 has a reflective surface for changing the path of light. For example, the first reflection module 300 may be a mirror or a prism. The first reflection module 300 is disposed at the rear of the lens module 200 and can change the path of light so that light passing through the lens module 200 is guided toward the second reflection module 400.

[0105] The second reflection module 400 is disposed between the first reflection module 300 and the image sensor 600, and the path of the light incident on the second reflection module 400 can be changed multiple times.

[0106] The second reflection module 400 has multiple surfaces for changing the path of light. As an example, light incident on the second reflection module 400 may undergo three total internal reflections and two reflections by the second reflection module 400.

[0107] For example, by changing the path of light several times through the second reflection module 400, a long path of light can be formed in a relatively narrow space.

[0108] Therefore, a long focal length can be provided while miniaturizing the folding lens system.

[0109] The second reflective module 400 includes a first prism 410 and a second prism 430 spaced apart from each other, and each of the first prism 410 and the second prism 430 may have a polygonal shape.

[0110] In addition, the first prism 410 and the second prism 430 are arranged to face each other with a gap. Therefore, there is an air gap between the surfaces of the first prism 410 and the second prism 430 facing each other.

[0111] Refer back to Figures 1 to 4. The folding lens system according to the example can satisfy the condition TTL / (TL+OPL) < 0.75.

[0112] TTL is the distance from the vertex of the object-side surface of the lens furthest from the image sensor 600 (e.g., the first lens 110, the first lens 210) to the imaging plane; TL is the distance from the vertex of the object-side surface of the lens furthest from the image sensor 600 (e.g., the first lens 110, the first lens 210) to the vertex of the image-side surface of the lens closest to the image sensor 600 (e.g., the fifth lens 150 or the fourth lens 240); and OPL is the optical path length from the vertex of the image-side surface of the lens closest to the image sensor 600 (e.g., the fifth lens 150 or the fourth lens 240) to the imaging plane. The optical path length can be defined as geometric distance × the refractive index of the medium.

[0113] The folding lens system according to the example can satisfy the condition CRA ≤ 15°. CRA (Chief Ray Angle) can refer to the angle between the chief ray and the optical axis on the imaging plane.

[0114] Figure 5 is a diagram showing the optical path in the second reflection module of the folding lens system according to the example.

[0115] Referring to FIG5, the second reflective module 400 includes a first surface S1, a second surface S2, a third surface S3, a fourth surface S4, a fifth surface S5, and a sixth surface S6. In this case, the first surface S1 is the surface closest to the lens module 100 and the lens module 200, while the sixth surface S6 is the surface closest to the image sensor 600.

[0116] In an example, the second reflective module 400 includes a first prism 410 and a second prism 430 spaced apart from each other, and the first prism 410 and the second prism 430 may each have a polygonal shape. The first surface S1, the second surface S2 and the third surface S3 may refer to the surface of the first prism 410, while the fourth surface S4, the fifth surface S5 and the sixth surface S6 may refer to the surface of the second prism 430.

[0117] The first prism 410 may have two total internal reflection surfaces and one reflection surface, while the second prism 430 may have one total internal reflection surface and one reflection surface.

[0118] The refractive index of the first prism 410 may be greater than 1.65, and the refractive index of the second prism 430 may be greater than 1.65. For example, the refractive index of the first prism 410 and the refractive index of the second prism 430 may be 1.7174.

[0119] The second surface S2 and the fourth surface S4 are arranged to face each other, and the second surface S2 and the fourth surface S4 are arranged to be spaced apart from each other. Therefore, an air gap may exist between the second surface S2 and the fourth surface S4.

[0120] The angle between the first surface S1 and the second surface S2, the angle between the second surface S2 and the third surface S3, and the angle between the fourth surface S4 and the sixth surface S6 are each acute angles, while the angle between the fifth surface S5 and the sixth surface S6 can be obtuse angles.

[0121] Furthermore, the angle θ1 between the optical axis and the second surface S2 can be greater than 35° and less than 55° (or greater than 125° and less than 145°). For example, the angle θ1 between the optical axis and the second surface S2 can be 45° (or 135°).

[0122] In addition, the angle θ2 between the optical axis and the fourth surface S4 can be greater than 35° and less than 55° (or greater than 125° and less than 145°). For example, the angle θ2 between the optical axis and the fourth surface S4 can be 45° (or 135°). θ2-θ1 can be greater than -5° and less than 5°.

[0123] Refraction or total internal reflection can be formed on the first surface S1, the second surface S2 and the fourth surface S4 according to the incident angle of light, and on the third surface S3 and the fifth surface S5, light incident on each surface can be reflected.

[0124] According to Snell's law, when light is refracted in two media with different refractive indices, we have ni×sinθi = nt×sinθt. In this case, there exists a situation where the angle of refraction θt becomes 90°, and the angle of incidence (θi) at this time is called the critical angle (θc).

[0125] Using Snell's law, the critical angle θc = sin^-1 (nt / ni), and when light enters at an angle of incidence greater than the critical angle θc, the light does not refract and is completely reflected to the incident medium, and this is called total internal reflection.

[0126] The path of light in the second reflection module 400 is the same as path ① to path ⑦ shown in Figure 5.

[0127] Referring to Figure 5, the light that has passed through lens module 100 and lens module 200 is refracted when it passes through the first surface S1 and is incident on the second surface S2, and the incident angle of the light incident on the second surface S2 is greater than the critical angle. Therefore, total internal reflection occurs on the second surface S2.

[0128] Light that is totally internally reflected from the second surface S2 is incident on the third surface S3, and the angle of incidence of the light incident on the third surface S3 is narrower than the critical angle. Therefore, reflection occurs on the third surface S3.

[0129] The light reflected from the third surface S3 is incident on the first surface S1 again, and the incident angle of the light incident on the first surface S1 is wider than the critical angle. Therefore, when the light reflected from the third surface S3 is incident on the first surface S1, total internal reflection occurs.

[0130] The light, which is totally internally reflected from the first surface S1, passes through the second surface S2 again and is refracted, and then passes through the fourth surface S4, which is spaced apart from the second surface S2, and is refracted again and incident on the fifth surface S5. The angle of incidence of the light incident on the fifth surface S5 is narrower than the critical angle. Therefore, reflection occurs on the fifth surface S5.

[0131] The light reflected from the fifth surface S5 is incident on the fourth surface S4 again, and the angle of incidence of the light incident on the fourth surface S4 is greater than the critical angle. Therefore, when the light reflected from the fifth surface S5 is incident on the fourth surface S4, total internal reflection occurs.

[0132] The light that is totally reflected by the fourth surface S4 passes through the sixth surface S6, is refracted and incident on the image sensor 600.

[0133] The path of light in the second reflection module 400 is summarized in Table 5 below.

[0134] [Table 5] S1 S2 S3 S1 S2 S4 S5 S4 S6 refraction Total internal reflection reflection Total internal reflection refraction refraction reflection Total internal reflection refraction

[0135] Figure 6 is a diagram showing the optical path in the second reflection module of a folding lens system according to another example.

[0136] Referring to FIG6, the second reflective module 400' has a first surface S1', a second surface S2', a third surface S3', a fourth surface S4', a fifth surface S5', and a sixth surface S6'. In this case, the first surface S1' is the surface closest to the lens module 100 and the lens module 200, while the fifth surface S5' is the surface closest to the image sensor 600.

[0137] In an example, the second reflective module 400' includes a first prism 410' and a second prism 430' spaced apart from each other, and the first prism 410' and the second prism 430' may each have a polygonal shape. The first surface S1', the second surface S2' and the third surface S3' may refer to the surface of the first prism 410', while the fourth surface S4', the fifth surface S5' and the sixth surface S6' may refer to the surface of the second prism 430'.

[0138] The first prism 410' may have a total internal reflection surface and a reflection surface, while the second prism 430' may have two total internal reflection surfaces and a reflection surface.

[0139] The second surface S2' and the fourth surface S4' are arranged to face each other, and the second surface S2' and the fourth surface S4' are arranged to be spaced apart from each other. Therefore, an air gap may exist between the second surface S2' and the fourth surface S4'.

[0140] The angle between the first surface S1' and the second surface S2', the angle between the fourth surface S4' and the fifth surface S5', and the angle between the fourth surface S4' and the sixth surface S6' are acute angles, while the angle between the first surface S1' and the third surface S3' can be an obtuse angle.

[0141] In the second surface S2', the fourth surface S4' and the fifth surface S5', refraction or total internal reflection can be formed depending on the incident angle of the light, and in the second surface S2' and the sixth surface S6', light incident on each surface can be reflected.

[0142] The path of light in the second reflection module 400' is the same as path ① to path ⑦ shown in Figure 6.

[0143] Referring to Figure 6, the light passing through the lens module 100 and the lens module 200 is refracted when it passes through the first surface S1' and is incident on the second surface S2', and the incident angle of the light incident on the second surface S2' is greater than the critical angle. Therefore, total internal reflection occurs on the second surface S2'.

[0144] Light that is totally internally reflected from the second surface S2' is incident on the third surface S3', and the angle of incidence of the light incident on the third surface S3' is narrower than the critical angle. Therefore, reflection occurs on the third surface S3'.

[0145] The light reflected from the third surface S3' passes through the second surface S2' again and is refracted, and then passes through the fourth surface S4', which is spaced apart from the second surface S2', and is refracted to be incident on the fifth surface S5'. The angle of incidence of the light incident on the fifth surface S5' is greater than the critical angle. Therefore, total internal reflection occurs on the fifth surface S5'.

[0146] Light that is totally internally reflected from the fifth surface S5' is incident on the sixth surface S6', and the angle of incidence of the light incident on the sixth surface S6' is narrower than the critical angle. Therefore, reflection occurs on the sixth surface S6'.

[0147] The light reflected from the sixth surface S6' is incident on the fourth surface S4' again, and the angle of incidence of the light incident on the fourth surface S4' is wider than the critical angle. Therefore, when the light reflected from the sixth surface S6' is incident on the fourth surface S4', total internal reflection occurs.

[0148] The light that is totally reflected from the fourth surface S4' passes through the fifth surface S5', is refracted and incident on the image sensor 600.

[0149] The path of light in the second reflection module 400' is summarized in Table 6 below.

[0150] [Table 6] S1' S2' S3' S2' S4' S5' S6' S4' S5' refraction Total internal reflection reflection refraction refraction Total internal reflection reflection Total internal reflection refraction

[0151] In summary, in the case of the folding lens system according to the example, the size of the lens system can be reduced.

[0152] Although specific examples have been shown and described above, it will be apparent upon understanding this disclosure that various changes in form and detail may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein should be considered illustrative only and not for limiting purposes. The description of features or manner in each example should be considered applicable to similar features or manner in other examples. Suitable results may also be achieved if the described technology is implemented in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in different ways and / or replaced or supplemented by other components or their equivalents. Therefore, the scope of this disclosure is not defined by the detailed description but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents should be construed as included in this disclosure. [Simplified Explanation of the Diagram]

[0031] Figure 1 is a schematic configuration diagram of a folding lens system according to an example. Figure 2 is a schematic perspective view of a folding lens system according to an example. Figure 3 is a schematic configuration diagram of a folding lens system according to another example. Figure 4 is a schematic perspective view of a folding lens system according to another example. Figure 5 is a diagram showing the optical path in the second reflection module of the folding lens system according to an example. Figure 6 is a diagram showing the optical path in the second reflection module of the folding lens system according to another example. Throughout all figures and this detailed description, the same reference numerals refer to the same elements. The figures may not be drawn to scale, and for clarity, illustrative purposes and convenience, the relative size, scale, and depiction of the elements in the figures may be exaggerated.

Claims

1. A folding lens system, comprising: A lens module includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, arranged sequentially from the object side, each having a positive refractive power; an image sensor having an imaging plane; and a first reflection module disposed between the lens module and the image sensor and configured to change the path of light passing through the lens module multiple times. The first reflection module includes a first prism and a second prism spaced apart from the first prism by an air gap. The first prism includes a first surface, a second surface, and a third surface. The second prism includes a fourth surface, a fifth surface, and a sixth surface. The second surface and the fourth surface face each other, and the air gap exists between them. The second surface and the fourth surface refract or undergo total internal reflection depending on the angle of incidence of light. The absolute value of the radius of curvature of the object-side surface of the first lens is less than the absolute value of the radius of curvature of the image-side surface of the first lens. The absolute value of the radius of curvature of the object-side surface of the second lens is greater than the absolute value of the radius of curvature of the image-side surface of the second lens. The lens module satisfies 0 < 0. f1 / f < 0.5, where f1 is the focal length of the first lens and f is the total focal length of the lens module.

2. The folding lens system as claimed in claim 1, wherein the light passing through the lens module undergoes three total internal reflections and two reflections by the first reflection module.

3. The folding lens system of claim 1, wherein the first surface is positioned closest to the lens module and the sixth surface is positioned closest to the image sensor, wherein the angle between the first surface and the second surface, the angle between the second surface and the third surface, and the angle between the fourth surface and the sixth surface are acute angles, and wherein the angle between the fifth surface and the sixth surface is an obtuse angle.

4. The folding lens system as claimed in claim 3, wherein the first surface undergoes refraction or total internal reflection depending on the angle of incidence of the light.

5. The folding lens system as claimed in claim 4, wherein light incident on each of the third and fifth surfaces is reflected.

6. The folding lens system of claim 1, wherein light passing through the lens module is refracted upon passing through the first surface and incident on the second surface, and the angle of incidence of the light incident on the second surface is greater than a critical angle; wherein light totally internally reflected from the second surface is incident on the third surface, and the angle of incidence of the light incident on the third surface is less than a critical angle; wherein light reflected from the third surface is incident on the first surface, and the angle of incidence of the light incident on the first surface is greater than a critical angle; wherein light totally internally reflected from the first surface passes through the second surface and the fourth surface, is refracted and incident on the fifth surface, and the angle of incidence of the light incident on the fifth surface is less than a critical angle; wherein light reflected from the fifth surface is incident on the fourth surface, and the angle of incidence of the light incident on the fourth surface is greater than a critical angle; and wherein light totally internally reflected from the fourth surface passes through the sixth surface, is refracted and incident on the image sensor.

7. The folding lens system of claim 1, wherein each of the first prism and the second prism has a polygonal shape, and wherein the first prism has two total internal reflection surfaces and a reflective surface, and the second prism has a total internal reflection surface and a reflective surface.

8. The folding lens system as claimed in claim 1 further includes a second reflection module disposed in front of the lens module.

9. The folding lens system as claimed in claim 1 further includes a second reflection module disposed between the lens module and the first reflection module.

10. The folding lens system of claim 1, wherein the first surface is positioned closest to the lens module and the fifth surface is positioned closest to the image sensor, wherein the angle between the first surface and the second surface, the angle between the fourth surface and the fifth surface, and the angle between the fourth surface and the sixth surface are acute angles, and wherein the angle between the first surface and the third surface is an obtuse angle.

11. The folding lens system of claim 10, wherein light passing through the lens module is refracted upon passing through the first surface and incident on the second surface, and the angle of incidence of the light incident on the second surface is greater than a critical angle; wherein light totally internally reflected from the second surface is incident on the third surface, and the angle of incidence of the light incident on the third surface is less than a critical angle; wherein light reflected from the third surface passes through the second surface and the fourth surface, is refracted and incident on the fifth surface, and the angle of incidence of the light incident on the fifth surface is greater than a critical angle; wherein light totally internally reflected from the fifth surface is incident on the sixth surface, and the angle of incidence of the light incident on the sixth surface is less than a critical angle; wherein light reflected from the sixth surface is incident on the fourth surface, and the angle of incidence of the light incident on the fourth surface is greater than a critical angle; and wherein light totally internally reflected from the fourth surface passes through the fifth surface, is refracted and incident on the image sensor.

12. The folding lens system as claimed in claim 1, wherein the second lens has a negative refractive power.

13. The folding lens system as claimed in claim 12, wherein the lens module satisfies -0.7 < f2 / f < 0, where f2 is the focal length of the second lens.

14. A folding lens system, comprising: A lens module includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side; an image sensor having an imaging plane; and a first reflection module disposed between the lens module and the image sensor and configured to change the path of light passing through the lens module multiple times. The first reflection module includes a first prism and a second prism spaced apart from the first prism by an air gap. The first prism includes a first surface, a second surface, and a third surface. The second prism includes a fourth surface, a fifth surface, and a sixth surface. The second surface and the fourth surface face each other, and the air gap exists between the second surface and the fourth surface. The second surface and the fourth surface refract or undergo total internal reflection according to the incident angle of light. The absolute value of the radius of curvature of the object-side surface of the first lens is less than the absolute value of the radius of curvature of the image-side surface of the first lens. The absolute value of the radius of curvature of the object-side surface of the second lens is greater than the absolute value of the radius of curvature of the image-side surface of the second lens. The lens module satisfies IMG HT / FBL < 0. 0.7, where IMG HT is the diagonal length of the imaging plane, and FBL is the distance from the vertex of the image-side surface of the fifth lens to the imaging plane.

15. A folding lens system, comprising: A lens module includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side; an image sensor having an imaging plane; and a first reflection module disposed between the lens module and the image sensor and configured to change the path of light passing through the lens module multiple times. The first reflection module includes a first prism and a second prism spaced apart from the first prism by an air gap. The first prism includes a first surface, a second surface, and a third surface. The second prism includes a fourth surface, a fifth surface, and a sixth surface. The second surface and the fourth surface face each other, and the air gap exists between the second surface and the fourth surface. The second surface and the fourth surface refract or undergo total internal reflection according to the incident angle of light. The absolute value of the radius of curvature of the object-side surface of the first lens is less than the absolute value of the radius of curvature of the image-side surface of the first lens. The absolute value of the radius of curvature of the object-side surface of the second lens is greater than the absolute value of the radius of curvature of the image-side surface of the second lens. The lens module satisfies TTL / f < 0. 0.75, where TTL is the distance from the vertex of the object-side surface of the first lens to the imaging plane, and f is the total focal length of the lens module.

16. A folding lens system, comprising: A lens module includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side; an image sensor having an imaging plane; and a first reflection module disposed between the lens module and the image sensor and configured to change the path of light passing through the lens module multiple times. The first reflection module includes a first prism and a second prism spaced apart from the first prism by an air gap. The first prism includes a first surface, a second surface, and a third surface. The second prism includes a fourth surface, a fifth surface, and a sixth surface. The second surface and the fourth surface face each other, and the air gap exists between the second surface and the fourth surface. The second surface and the fourth surface refract or undergo total internal reflection depending on the angle of incidence of light. The absolute value of the radius of curvature of the object-side surface of the first lens is less than the absolute value of the radius of curvature of the image-side surface of the first lens. The absolute value of the radius of curvature of the object-side surface of the second lens is greater than the absolute value of the radius of curvature of the image-side surface of the second lens, and the condition TTL / (TL+OPL) < 0.75, where TTL is the distance from the vertex of the object-side surface of the first lens to the imaging plane, TL is the distance from the vertex of the object-side surface of the first lens to the vertex of the image-side surface of the fifth lens, and OPL is the optical path length from the image-side surface of the fifth lens to the imaging plane.

Images