Optical system, camera module, and electronic device

Abstract

The present application discloses an optical system, a camera module, and an electronic device. The optical system comprises: a lens assembly for imaging; a reflection assembly arranged on the object side or image side of the lens assembly and used for changing the direction of light entering or exiting from the lens assembly; and an optical sheet arranged on a light path of the optical system, wherein the optical sheet comprises a first optical surface and a second optical surface which are opposite to each other, the first optical surface is a curved surface, the second optical surface is a plane or a curved surface, and the curvatures of the first optical surface in two orthogonal directions are different, so that the field curvature compensation amounts of the optical sheet in the two orthogonal directions are different.

Description

Optical system, camera module and electronic device TECHNICAL FIELD

[0001] The present application relates to the technical field of camera modules, and in particular to an optical system, a camera module and an electronic device. BACKGROUND

[0002] With the popularity and development of smart phones, mobile phone photography has become one of the indispensable functions in people's daily life. In order to meet the higher requirements of users for the shooting effect, manufacturers are constantly improving the image system of mobile phones. In recent years, the periscopic long-focus lens has been the most concerned. The principle of the periscopic long-focus lens is to use a mirror or a prism to bend the original straight light path by 90 degrees, thereby converting the thickness of the lens into length, realizing a longer focal length, and enabling the mobile phone to have stronger optical zoom capability without increasing the thickness of the mobile phone.

[0003] Due to its long focal length, the long-focus lens is usually prone to astigmatism. Because the focal length of the optical system increases, the propagation distance of the light in the optical system is longer, increasing the opportunity for light deflection, thereby causing more serious astigmatism. SUMMARY

[0004] One purpose of the present application is to provide an optical system that is beneficial to improving the imaging quality of a periscopic camera module.

[0005] Another purpose of the present application is to provide an optical system with less astigmatism.

[0006] Another purpose of the present application is to provide a camera module and an electronic device comprising the aforementioned optical system.

[0007] To achieve the above purposes, the present application provides an optical system, comprising:

[0008] a lens assembly for imaging;

[0009] a reflection assembly arranged on the object side or the image side of the lens assembly for changing the direction of light entering or exiting the lens assembly; and

[0010] an optical sheet arranged on the optical path of the optical system, the optical sheet comprising opposite first and second optical surfaces, the first optical surface being a curved surface, and the second optical surface being a flat surface or a curved surface, the curvatures of the first optical surface in two orthogonal directions being different, so that the field curvature compensation amounts of the optical sheet in the two orthogonal directions are different.

[0011] In some embodiments, the lens assembly comprises a stop and a lens group arranged on the image side of the stop, and the optical sheet is located on the object side of the stop.

[0012] In some embodiments, the optical sheet is disposed adjacent to the reflection assembly.

[0013] In some embodiments, the first optical surface has a curvature of zero in a first direction and a curvature radius of R2 in a second direction, |R2| being in a range from 1000 mm to 10000 mm, the first direction being orthogonal to the second direction.

[0014] In some embodiments, a ratio of |R2| to an effective focal length of the optical system is in a range from 0.0012 to 0.03.

[0015] In some embodiments, the lens assembly includes a first lens closest to an object side, the first lens being a convex lens, a ratio of |R2| to a curvature radius of the object side or an image side of the first lens being in a range from 10:1 to 50:1.

[0016] In some embodiments, the first optical surface includes a first curved surface close to an optical axis and a second curved surface away from the optical axis, the second curved surface being located on both sides of the first curved surface away from the optical axis, the first curved surface and the second curved surface both having a curvature of zero in the first direction, the first curved surface having a curvature radius of R 21 in the second direction, the second curved surface having a curvature radius of R 22 in the second direction, R 21 ≠ R 22 , |R 21 | and |R 22 | being in a range from 1000 mm to 10000 mm, respectively.

[0017] In some embodiments, R 21 and R 22 are both positive, and R 21 < R 22 .

[0018] In other embodiments, one of R 21 and R 22 is positive, and the other is negative.

[0019] In some embodiments, the first optical surface has a curvature of k1 in the first direction and a curvature of k2 in the second direction, k1 ≠ k2, and k1 and k2 are both non-zero, the first direction being orthogonal to the second direction.

[0020] In some embodiments, k1 and k2 have the same sign.

[0021] In other embodiments, one of k1 and k2 is positive, and the other is negative.

[0022] In some embodiments, the first optical surface and the second optical surface are both curved surfaces, and the first optical surface and the second optical surface have the same bending direction and the same bending degree.

[0023] In some embodiments, the second optical surface is a flat surface, and the ratio of the center thickness to the edge thickness of the optical sheet is 0.8-1.25.

[0024] In some embodiments, the optical sheet comprises a substrate and a curved surface part, the curved surface part is formed on the substrate by a micro-imprinting process, the surface of the substrate away from the curved surface part forms the second optical surface, and the surface of the curved surface part away from the substrate forms the first optical surface.

[0025] In some embodiments, the optical sheet comprises an optical area and a structure area outside the optical area, and the structure area extends outward from at least two sides of the optical area.

[0026] In some embodiments, the reflection assembly comprises a prism and a prism carrier, and the optical sheet is attached to the surface of the prism through the structure area.

[0027] In some embodiments, the optical sheet is arranged on an optical sheet mounting structure, and the structure area of the optical sheet and the optical sheet mounting structure are connected through a plurality of low-stress connecting structures, so that the optical sheet has a space for deformation or displacement in a direction perpendicular to the optical axis when the optical sheet is held on the optical sheet mounting structure.

[0028] In some embodiments, the low-stress connecting structure is a spring, one end of the spring is connected to the structure area of the optical sheet, the other end of the spring is connected to the optical sheet mounting structure, and a plurality of springs are symmetrically distributed on the periphery of the structure area of the optical sheet.

[0029] In some embodiments, the low-stress connecting structure is a foam, the foam is filled between the structure area of the optical sheet and the optical sheet mounting structure, and a plurality of foams are symmetrically distributed on the periphery of the structure area of the optical sheet.

[0030] The present application also provides a camera module comprising the optical system and a photosensitive chip, and the photosensitive chip is located on the image side of the lens assembly.

[0031] The present application also provides an electronic device comprising the camera module.

[0032] Other benefits of the present application will be further described in the specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS

[0033] FIG. 1 is a schematic diagram of astigmatism generated in a conventional optical system;

[0034] Figure 2A illustrates the effect of the change of the angle of the reflecting surface on the imaging when the reflecting surface is located on the object side of the lens;

[0035] Figure 2B illustrates the effect of the change of the angle of the reflecting surface on the imaging when the reflecting surface is located on the image side of the lens;

[0036] Figure 3A is a schematic diagram of the design optical path and the corresponding design defocus curve of a lens;

[0037] Figure 3B is a schematic diagram of the optical path and the corresponding defocus curve of the lens of Figure 3A when the lens is decentered;

[0038] Figure 4 is a schematic diagram of an embodiment of the optical system of the present application;

[0039] Figure 5 is a schematic diagram of another embodiment of the optical system of the present application;

[0040] Figure 6 is a schematic diagram of a first embodiment of the optical sheet of the present application;

[0041] Figure 7 is a schematic diagram of a second embodiment of the optical sheet of the present application;

[0042] Figure 8 is a schematic diagram of a third embodiment of the optical sheet of the present application;

[0043] Figure 9 is a schematic diagram of a fourth embodiment of the optical sheet of the present application;

[0044] Figure 10 is a schematic diagram of a fifth embodiment of the optical sheet of the present application;

[0045] Figure 11 is a schematic diagram of a sixth embodiment of the optical sheet of the present application;

[0046] Figure 12 is a schematic diagram of an embodiment of the optical sheet of the present application prepared by the embossing process;

[0047] Figure 13 is a schematic diagram of an embodiment of the optical region and the structural region of the optical sheet of the present application;

[0048] Figure 14 is a schematic diagram of another embodiment of the optical region and the structural region of the optical sheet of the present application;

[0049] Figure 15 is a schematic diagram of an embodiment of the camera module of the present application;

[0050] Figure 16 is a schematic diagram of the cross section of Figure 15;

[0051] Figure 17 is a schematic diagram of another embodiment of the camera module of the present application;

[0052] Figure 18 is a schematic diagram of an embodiment of the optical sheet and the optical sheet mounting structure of the present application;

[0053] Figure 19 is a schematic diagram of an embodiment of the optical sheet mounting structure of the present application;

[0054] FIG. 20 is a schematic view of one embodiment of an optical sheet, an optical sheet mounting structure, and a low-stress connection structure of the present application;

[0055] FIG. 21 is a schematic view of another embodiment of an optical sheet, an optical sheet mounting structure, and a low-stress connection structure of the present application; DETAILED DESCRIPTION

[0056] Hereinafter, the present application will be further described in conjunction with specific embodiments, and it should be noted that the following described embodiments or technical features can be combined with each other in any manner to form new embodiments, without conflict.

[0057] In the description of the present application, it should be noted that for orientation words, such as the terms "center", "transverse", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation and positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the specific protection scope of the present application.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0059] The terms "include" and "have" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to such processes, methods, products or devices.

[0060] In the present application, the curvature of a curved surface in a certain direction refers to the curvature of a curve extending in that direction, and the curvature of a curve is the turning rate of the tangent direction angle to the arc length for a certain point, indicating the degree of deviation of the curve from a straight line. The greater the curvature, the greater the degree of bending of the curve, and the reciprocal of the curvature is the curvature radius.

[0061] In this application, astigmatism is defined as: as shown in Figure 1, the light emitted by an off-axis point light source P passes through the lens L, the meridional focal point S1 and the sagittal focal point T1 are not in the same position, that is, the light beam cannot be focused on a point, the image is not clear, and astigmatism is produced. It is worth mentioning that in Figure 1, P is a light emitting point, the optical axis is represented by Q, the light emitting point P is not located on the optical axis Q, φ represents the angle between the central axis of the light emitted by the light emitting point P and the optical axis Q, the blue line represents the meridional direction light, and the red light represents the sagittal direction light. The blue meridional direction incident light emitted by the light emitting point P is imaged on the S1 point after imaging through the lens, while the red sagittal direction incident light is imaged on the T1 point, and the astigmatism difference between T1 and Q1 is the astigmatism difference. The optical axis point on the image side is represented by Q1, Q1 and S1 and T1 have an angle, and the angle error will affect the clarity.

[0062] The inventor has analyzed the reasons for the serious astigmatism of the existing periscopic camera module and believes that there are the following influencing factors.

[0063] 1. Influence of prism or mirror surface type precision

[0064] A prism / reflector is introduced in the periscopic camera module, and it is difficult to make the surface of the prism / reflector absolutely flat. The precision of the incident surface, the reflecting surface and the exit surface will directly affect the consistency of the light in the refraction and reflection process, which may cause the meridional focal point and the sagittal focal point not to be at the same point, thereby producing astigmatism and affecting the clarity of the image. In order to illustrate the influence of the prism / reflector surface type precision on the light propagation and imaging, Figures 2A and 2B schematically show the influence of the change of the reflecting surface angle on the imaging in a simplified manner. Those skilled in the art can understand that when there is a local protrusion or depression on the surface of the prism / reflector, it is equivalent to the angle of the local reflecting surface changing.

[0065] Figure 2A schematically shows that the reflecting surface F is located on the object side of the lens J, and the dashed line shows the reflecting surface, the reflected light and the imaging position after the reflecting surface F angle changes by θ. In the case where the object W position remains unchanged, the reflecting surface F changes in angle, causing the imaging position on the photosensitive chip to shift. The angle of the reflecting surface F changes by θ in the nodding direction, the angle of the light changes by 2θ, the angle change ratio is 1:2, and the lens imaging surface X does not change with the angle change of the reflecting surface F.

[0066] Figure 2B schematically shows that the reflecting surface F is located on the image side of the lens J, and the dashed line shows the reflecting surface, the reflected light and the image surface after the reflecting surface F angle changes by θ. The reflecting surface F changes in angle, causing the lens imaging surface X to tilt, with a tilt angle of 2θ, and the angle change ratio is 1:2. In addition, the angle of the reflecting surface F changes by θ in the nodding direction, the angle of the light changes by 2θ, and the angle change ratio is 1:2.

[0067] No matter the reflection surface is located on the object side or the image side of the lens, when the angle of the reflection surface changes, the angle of the light changes, resulting in astigmatism, which ultimately affects imaging. Therefore, in the optical system of the periscope camera module, affected by the surface accuracy of the prism / mirror, astigmatism is easily generated, affecting the imaging quality.

[0068] 2. The impact of the eccentricity or tilt of the lens in the lens assembly

[0069] During the lens assembly process, eccentricity or tilt may occur due to assembly accuracy, and such assembly errors also affect the imaging quality. FIGS. 3A and 3B schematically show the change of the defocus curve of the lens of a certain lens before and after eccentricity, wherein FIG. 3A is the design light path of the lens and the corresponding design defocus curve, and FIG. 3B is the light path of the lens after the lens eccentricity and the corresponding defocus curve. As can be seen from the change of the defocus curve, the lens eccentricity also easily leads to the generation of astigmatism.

[0070] 3. The impact of the assembly process

[0071] The lens or prism in the camera module is generally assembled by dispensing, but dispensing and subsequent baking can cause stress to the optical element, thereby affecting the surface of the optical element, and then according to the analysis of the first point, this also causes the astigmatism problem of the entire optical system.

[0072] Based on the above analysis, the inventors of the present application propose an optical system 10 suitable for a periscope camera module to alleviate the problem of serious astigmatism of the existing periscope camera module.

[0073] The optical system 10 of the present application comprises a lens assembly 100, a reflection assembly 200, and an optical sheet 300; wherein the lens assembly 100 is used for imaging; the reflection assembly 200 is arranged on the object side or the image side of the lens assembly 100, and is used for changing the direction of the light entering or exiting the lens assembly 100; the optical sheet 300 is arranged on the light path of the optical system 10. The lens assembly 100, the reflection assembly 200, and the optical sheet 300 have various arrangement modes, for example: arranged in the order of the optical sheet 300, the reflection assembly 200, and the lens assembly 100; or arranged in the order of the optical sheet 300, the lens assembly 100, and the reflection assembly 200; or arranged in the order of the reflection assembly 200, the optical sheet 300, and the lens assembly 100; or arranged in the order of the reflection assembly 200, the lens assembly 100, and the optical sheet 300; or arranged in the order of the lens assembly 100, the reflection assembly 200, and the optical sheet 300; or arranged in the order of the lens assembly 100, the optical sheet 300, and the reflection assembly 200.

[0074] The optical sheet 300 comprises opposite first and second optical surfaces 301 and 302, the first optical surface 301 is a curved surface, and the second optical surface 302 is a flat surface or a curved surface, the first optical surface 301 has different curvatures in two orthogonal directions, so that the field curvature compensation of the optical sheet 300 in the two orthogonal directions is different. The field curvature compensation refers to the adjustment or change of the optical system to reduce or eliminate the field curvature aberration, and the field curvature compensation of the optical sheet 300 in the two orthogonal directions in the present application can also be understood as the compensation of the meridional focal shift and the compensation of the sagittal focal shift.

[0075] In other words, the first optical surface 301 has a curvature k1 in the first direction and a curvature k2 in the second direction, k1 is different from k2, and the first direction is orthogonal to the second direction. It is worth mentioning that the first optical surface 301 can be an entrance surface or an exit surface, and correspondingly, the second optical surface 302 can be an exit surface or an entrance surface.

[0076] The present application adds the optical sheet 300 in the optical system 10, which can be used to compensate for the astigmatism problem caused by the increase of the reflection assembly 200. Specifically, the present application mainly uses the optical sheet 300 to realize the compensation of the field of view in the sagittal direction and / or the meridional direction. Referring to the astigmatism diagram shown in FIG. 1, the optical sheet 300 of the present application can be arranged on the object side of the lens L, so as to pull the field of view on the rear side forward, that is, to move the sagittal focal point forward, or to pull the field of view on the front side backward, that is, to move the meridional focal point backward. The selection of the curvatures k1 and k2 of the first optical surface 301 of the optical sheet 300 needs to consider the deviation degree of the meridional direction and the sagittal direction in the whole optical system, so that the originally far apart meridional focal point and the sagittal focal point are close to each other, thereby reducing the astigmatism and improving the imaging quality. In other words, the difference in curvature of the first optical surface 301 in the two orthogonal directions enables the optical sheet 300 to change the focal point of a certain direction field of view to be close to the focal point of another direction field of view, thereby solving the astigmatism problem.

[0077] In addition, since the astigmatism mainly occurs in the field of view far from the optical axis, when testing the compensation effect of the optical sheet 300, several fields of view far from the optical axis are generally selected for testing. It is worth mentioning that in the optical system, the field of view of the lens refers to the range of the image area that the lens can capture, and a certain specific field of view can be expressed by the proportion of the edge to the center, for example, 0.8 field of view is the distance with an edge-to-center proportion of 0.8, and a range is defined near the 0.8 field of view, for example, 0.75-0.85, which defines a ring-shaped region, and within this ring-shaped region, it can be considered as 0.8 field of view. In the present application, a specific field of view position can be used as a test field of view, for example, the upper left, upper right, lower right and lower left corners, and as long as the compensation of the astigmatism of the four specific fields of view is within the qualified value, the overall test requirement can be met.

[0078] In some embodiments, the optical sheet is disposed adjacent to the reflection assembly, and light is adapted to be incident on the reflection assembly after passing through the optical sheet, or light emitted from the reflection assembly is adapted to be incident on the optical sheet. The optical sheet 300 is disposed adjacent to the reflection assembly 200, so that the light diffused by the surface of the reflection assembly 200 can be compensated in time to avoid the light diffused more seriously after the optical path is lengthened. The more serious the light diffusion, the more the optical sheet with greater curvature or greater thickness is needed to compensate for astigmatism, and therefore, the earlier the astigmatism is compensated, the more conducive to the thinness of the optical sheet 300.

[0079] In some embodiments, the reflection assembly 200 and the optical sheet 300 are both disposed on the image side (not shown in the figure) of the lens assembly 100, that is, the light passes through the lens assembly 100 to converge first, and then changes the optical path through the reflection assembly 200, and the optical sheet 300 can be disposed on the light entrance side of the reflection assembly 200 or on the light exit side of the reflection assembly 200.

[0080] In other embodiments, as shown in FIG. 4 or 5, the reflection assembly 200 and the optical sheet 300 are both disposed on the object side of the lens assembly 100. Since the decentration or tilt of the lens in the lens assembly 100 also causes astigmatism, the optical sheet 300 can be designed with a suitable first optical surface to compensate for this astigmatism. Considering that in an optical system, the longer the optical path, the more serious the light diffusion in the meridional direction and the sagittal direction, if a certain degree of compensation can be made before the light diffusion, the optical sheet 300 can better achieve compensation with smaller curvature or thinner thickness. Therefore, disposing the reflection assembly 200 and the optical sheet 300 on the object side of the lens assembly 100 is conducive to the thinness of the optical sheet 300. In the embodiment shown in FIG. 4, the optical sheet 300 is disposed on the light entrance side of the reflection assembly 200. In the embodiment shown in FIG. 5, the optical sheet 300 is disposed on the light exit side of the reflection assembly 200. For the same reason, disposing the optical sheet 300 on the light entrance side of the reflection assembly 200 is more conducive to the thinness of the optical sheet 300.

[0081] It is worth mentioning that the lens assembly 100 includes a diaphragm 110 and a lens group 120 disposed on the image side of the diaphragm 110, and the diaphragm 110 can affect the field of view of the lens assembly 100, and in practice, the influence of astigmatism can also be reduced by adjusting the position of the diaphragm 110.

[0082] In some preferred embodiments, the optical sheet 300 is disposed on the object side of the stop 110. In an optical system, the stop is a very important concept, which determines the resolution and imaging quality of the optical system. The stop is usually an optical element with a small aperture, which limits the amount of light passing through the optical system, thereby controlling the clarity of the image. By disposing the optical sheet 300 on the object side of the stop 110, the astigmatism compensation can be performed with a magnification effect.

[0083] Specifically, in an optical system, all the light holes are imaged into the object space of the first light hole. The light hole with the smallest on-axis object point angular aperture is the aperture stop. For the optical element on the front side of the aperture stop, if the optical element is changed, the compensation effect on the image is more obvious due to the conjugate relationship. It is worth mentioning that the conjugate relationship means that the change on the optical surface can affect the image in a conjugate manner, which has a magnification effect.

[0084] In the above embodiments, the optical sheet 300 compensates for both the central field of view and the full field of view. Generally, in an optical system, the central field of view refers to the area with the best imaging quality, because the light almost enters along the optical axis, and the aberration is small. The full field of view refers to the entire imaging area, including the edge area outside the central field of view. At the edge of the full field of view, the light enters at a larger angle, and is more easily affected by various optical aberrations, resulting in a decrease in imaging quality.

[0085] The effective light corresponding aperture refers to the aperture corresponding to the light that can contribute to imaging in a specific field of view area. From the perspective of the effective light corresponding aperture, in the central field of view, the aperture corresponding to the effective light is similar to the entrance pupil diameter of the system, because the light almost propagates in a straight line. At the edge of the full field of view, the aperture corresponding to the effective light may decrease due to the increase in the light incidence angle, and the aperture corresponding to the effective light will further decrease as the light position moves further. Therefore, in the preferred embodiments of the present application, the optical sheet 300 is disposed on the object side of the stop 110, which can make the effective light corresponding apertures of the central field of view and the full field of view close, which makes the light incidence conditions of the central field of view and the edge field of view similar, thereby maintaining the consistency of the imaging quality to some extent. That is, in the above embodiments, the optical sheet 300 compensates for both the central field of view and the full field of view.

[0086] The first lens 121 closest to the object side of the lens group 120 is preferably a convex lens to better achieve optical convergence. When the optical sheet 300 is disposed near the first lens 121, the curvature radius of the optical sheet 300 should be designed considering the curvature radius of the first lens 121, and the relationship between the two will be further described below.

[0087] In addition, the curvature radius of the optical sheet 300 should also be designed in consideration of the focal length of the entire optical system 10, and the relationship between the two will be further described below.

[0088] Preferably, the optical system 10 of the present application has a focal length difference in the sagittal direction and the meridional direction of no more than 5%.

[0089] The following provides several specific embodiments of the optical sheet 300, each of which is only an exemplary listing and is not an exhaustive listing of the structure of the optical sheet 300, and any recombination of technical features within the scope of the inventive concept of the present application is within the protection scope of the present application.

[0090]

Optical sheet embodiment 1

[0091] As shown in FIG. 6, the optical sheet 300A includes a first optical surface 301A and a second optical surface 302A.

[0092] The second optical surface 302A is a plane. The second optical surface 302A can serve as an attachment reference surface, for example, attaching the optical sheet 300A to the prism surface of the reflection assembly 200 or attaching the optical sheet 300A to the optical sheet mounting structure 400. The plane attachment has a larger bondable surface and higher bonding strength than the curved surface. In addition, the second optical surface 302A being a plane is also conducive to height measurement of the optical sheet 300A by a height measuring device, thereby facilitating improvement of the assembly precision of the optical sheet 300A.

[0093] The curvature k1 of the first optical surface 301A in the first direction is zero, the curvature of the first optical surface 301A in the second direction is k2, the curvature radius is R2, R2 = 1 / k2, and R2 is 1000mm-10000mm. That is, the optical sheet 300A mainly provides compensation in the second direction of view, so that the focal point of the second direction of view is closer to the focal point of the first direction of view.

[0094] Further, the ratio of the center thickness to the edge thickness of the optical sheet 300A is 1-1.25, that is, the center thickness is thicker than the edge thickness. The center thickness and the edge thickness of the optical sheet 300A determine the surface accuracy thereof. Controlling the ratio of the center thickness to the edge thickness to be 1-1.25 is conducive to ensuring that the surface of the optical sheet 300A is close to the design value, thereby ensuring that the surface of the optical sheet 300A can achieve the purpose of reducing aberration. In addition, under the condition of satisfying the ratio of the center thickness to the edge thickness, the optical sheet 300A can be processed at a lower molding thickness, so that the optical sheet 300A is suitable to be placed at various positions of the camera module, while not increasing the size of the camera module.

[0095] It is worth mentioning that the thickness of the optical sheet 300A in the first direction does not change, and only the thickness changes in the second direction.

[0096] Preferably, the ratio of R2 to the effective focal length of the optical system 10 is 0.0012-0.03. The size of the radius of curvature of the first optical surface 301A needs to be designed in combination with the focal length of the optical system, and generally, the effective focal length (EFL) of the periscopic camera module is 12-30 mm, in the case of a larger size limit of the camera module, in order to realize the diffraction limit of the optical design, the performance of the limit case needs to be considered, therefore, the present application considers the case that the R2 of the first optical surface 301A is 1000-10000 mm corresponding to the two end values of the effective focal length in the case of 12-30 mm effective focal length, so as to obtain the range of 0.0012-0.03 above.

[0097] Further, the ratio of R2 to the radius of curvature of the object side surface or the image side surface of the first lens 121 is 10:1-50:1. In the case of the same image height, the longer the focal length of the optical lens, the longer the light rays pass through the optical path, and the greater the possibility of deflection of the light rays emitted by the off-axis point source after passing through the optical element, therefore, the radius of curvature of the object side surface and the image side surface of the first lens 121 of the lens assembly 100 determines the approximate diffusion degree of the light rays entering the entire lens assembly 100, when the reflection assembly 200 and the optical sheet 300 are located on the object side of the lens assembly 100, the radius of curvature of the optical sheet 300A and the first lens 121 has a crucial influence on the imaging quality of the entire optical system.

[0098]

Optical sheet embodiment 2

[0099] As shown in FIG. 7, the optical sheet 300B includes a first optical surface 301B and a second optical surface 302B.

[0100] The curvature k1 of the first optical surface 301B in the first direction is zero, and the curvature of the first optical surface 301B in the second direction is k2, the radius of curvature of which is R2, R2=1 / k2, R2 is 1000-10000 mm. That is, the optical sheet 300B mainly provides compensation on the field of view in the second direction, so that the focal point of the field of view in the second direction is close to the focal point of the field of view in the first direction.

[0101] The second optical surface 302B is a curved surface, but the second optical surface 302B is not used to realize astigmatism compensation, the thickness of the optical sheet 300B is relatively thin, the distance between the second optical surface 302B and the first optical surface 301B is basically the same, or in other words, the bending degree of the bending direction of the first optical surface 301B and the second optical surface 302B is the same, as shown in FIG. 7.

[0102] Preferably, the ratio of R2 to the effective focal length of the optical system 10 is 0.0012-0.03.

[0103] Preferably, the ratio of |R2| to the radius of curvature of the object side surface or the image side surface of the first lens 121 is 10:1 to 50:1.

[0104] [Optical sheet embodiment 3]

[0105] As shown in FIG. 8, the optical sheet 300C includes a first optical surface 301C and a second optical surface 302C. The second optical surface 302C is a plane.

[0106] The first optical surface 301C has a curvature k1 of zero in the first direction, and a radius of curvature R2 in the second direction, R2 being -10000 mm to -1000 mm. That is, the optical sheet 300C mainly provides compensation on the field of view in the second direction, so that the focal point of the field of view in the second direction is closer to the focal point of the field of view in the first direction.

[0107] Further, the ratio of the central thickness to the edge thickness of the optical sheet 300C is 0.8 to 1, that is, the central thickness is thinner than the edge thickness. It is worth mentioning that the thickness of the optical sheet 300C in the first direction does not change, and the thickness change only occurs in the second direction.

[0108] Preferably, the ratio of |R2| to the effective focal length of the optical system 10 is 0.0012 to 0.03.

[0109] Preferably, the ratio of |R2| to the radius of curvature of the object side surface or the image side surface of the first lens 121 is 10:1 to 50:1.

[0110] [Optical sheet embodiment 4]

[0111] As shown in FIG. 9, the optical sheet 300D includes a first optical surface 301D and a second optical surface 302D. The second optical surface 302D is a plane.

[0112] The first optical surface 301D includes a first curved surface 3011D close to the optical axis and a second curved surface 3012D away from the optical axis, and the second curved surface 3012D is located on both sides of the first curved surface 3011D away from the optical axis. The curvatures of the first curved surface 3011D and the second curved surface 3012D in the first direction are both zero or the radius of curvature is infinite, the radius of curvature of the first curved surface 3011D in the second direction is R 21 , and the radius of curvature of the second curved surface 3012D in the second direction is R 22 , R 21 ≠ R 22 , specifically, R 21 is positive, R 22 is negative, |R 21 | and |R 22| The value is 1000mm-10000mm. That is, the bending directions of the first curved surface 3011 and the second curved surface 3012 are different, and there is a reverse point on the first optical surface 301D, which can be applied to the compensation of the subarea in some special cases.

[0113] The subarea compensation capability of the optical sheet 300 can be applied to the periscopic camera module, especially in the macro situation, and unexpected effects can be achieved. In a long focal length optical system, a turning light path element is generally used to achieve the function of light path turning. The angle change of the turning light path element with the design position will cause the imaging position on the chip to shift, so generally the turning light path element and the photosensitive chip need to be actively calibrated. This calibration can align the central axis of the prism exit light with the central axis of the photosensitive chip, thereby preventing problems in periscopic shooting. Due to this limitation, after the prism, lens, and photosensitive chip are aligned, the central axis positions of the three can be considered to correspond, but due to the straight edge design of the periscopic camera module lens, the height direction of the lens is made into a straight edge, which can improve the optical area ratio of the lens. However, due to the non-symmetrical relationship of the shrinkage stress during injection molding, the stress causes the curved surface at the off-axis of the lens to be more prone to local deformation, so the segmented curved surface of the optical sheet 300 in the present application can better compensate.

[0114] In some special cases, the lens appears local deformation, and the change of the lens surface in this area may cause the aberration of the optical system to appear unexpected situations. The inventor found that because the straight edge lens has less structure outside the optical area in the height direction, the optical area, especially the height direction, is more prone to lens deformation. In this case, it is also more likely to cause the optical system to have two-side direction aberration. In order to adapt to this special situation, the stress concentration area of the straight edge lens can be improved by the optical sheet 300, for example, the first curved surface 3011D and at least one reverse point are arranged on one side of the optical sheet 300D, and the second curved surface 3012D is connected to the first curved surface 3011D through the reverse point. In this way, the second curved surface 3012D is designed to have a different curvature direction from the first curved surface 3011D. The reverse point refers to the junction point of the positive and negative changes of the surface curvature of the optical sheet 300D. Through the design of the reverse point, the optical sheet can compensate for the aberration near the axis, and the second curved surface 3012D can compensate for the aberration far from the axis.

[0115]

Optical sheet embodiment 5

[0116] As shown in FIG. 10, the optical sheet 300E includes a first optical surface 301E and a second optical surface 302E. The second optical surface 302E is a plane.

[0117] The first optical surface 301E includes a first curved surface 3011E close to the optical axis and a second curved surface 3012E away from the optical axis, and the second curved surface 3012E is located on both sides of the first curved surface 3011E away from the optical axis. The curvatures of the first curved surface 3011E and the second curved surface 3012E in the first direction are both zero or the curvature radii are infinite, the curvature radius of the first curved surface 3011E in the second direction is R 21 , the curvature radius of the second curved surface 3012E in the second direction is R 22 , R 21 ≠ R 22 , and specifically, 0 < R 21 < R 22 , R 21 , and R 22 are respectively 1000mm-10000mm. That is, the surface type of the first optical surface 301E away from the optical axis has a stronger compensation effect.

[0118] The optical sheet 300E also has the ability of compensation by partition.

[0119]

Optical sheet embodiment 6

[0120] As shown in FIG. 11, the optical sheet 300F includes a first optical surface 301F and a second optical surface 302F. The second optical surface 302F is a plane.

[0121] The first optical surface 301F is a hyperboloid, and the curvatures in the first direction and the second direction are k1 and k2 respectively, k1≠k2, and both k1 and k2 are not zero, and specifically, k2 is positive and k1 is negative. Preferably, R1=1 / k1 and R2=1 / k2, R1 is-10000mm--1000mm, and R2 is 1000mm-10000mm.

[0122] In optical design, a hyperboloid can provide more design freedom than a single curved surface, thereby more effectively compensating for astigmatism and other optical distortions. The first optical surface 301F is designed as a hyperboloid, which can also better cope with some special situations (for example, when a prism adopts a reflective lens, additional aberrations may be introduced; or if the straight edges at both ends of the height direction of the lens are enlarged, the aberrations between the on-axis light and the off-axis light may be too large; or if the plane mirror is not properly attached or deformed, it may also cause aberration problems of the optical system), and if a single curved surface is used for compensation or correction, the first optical surface 301 may need to have a larger curvature, which will increase the difficulty of manufacturing and forming, and too curved surface may cause the surface precision of the optical sheet 300 to decrease, thereby introducing new optical aberrations.

[0123] The advantages of using a double curved surface to compensate for the optical aberration include: (1) by using a curved surface in two directions and compensating for the optical aberration in each direction, the curvature of a single curved surface can be avoided; (2) the curved surface in each direction can have opposite curvatures, which can balance the compensation effect while maintaining a small curvature, facilitating manufacturing and control accuracy; and (3) this method is conducive to ensuring the surface accuracy of the optical sheet 300F and reducing optical aberration caused by the optical sheet 300F itself.

[0124] Generally, the numerical value of the optical aberration in the camera module is in the order of microns. In order to compensate for the optical aberration, the optical sheet 300 needs to be compensated at the micron level, which has a high requirement for the forming accuracy of the optical sheet. The imprinting technology can be considered to form the optical sheet 300. In a preferred embodiment, the optical sheet 300 is formed by using the micron imprinting technology to ensure the imprinting accuracy of the optical sheet 300 to ensure that the compensation capability of the optical sheet 300 is controllable, and in particular, the forming accuracy of the first optical surface 301 and the second optical surface 302 needs to be ensured.

[0125] The following provides a specific description of the preparation of an embodiment of the optical sheet 300. As shown in FIG. 12, the optical sheet 300 includes a substrate 310 and a curved portion 320, and the curved portion 320 is formed on the substrate 310 by a micron imprinting process. The surface of the substrate 310 away from the curved portion 320 forms the second optical surface 302, and the surface of the curved portion 320 away from the substrate 310 forms the first optical surface 301.

[0126] The optical sheet 300 of the present application can ensure that the difference between the oa vector height in the x direction and the ob vector height in the y direction of the surface accuracy is within 5 μm.

[0127] Preferably, the thickness of the substrate 310 is 0.21 mm to 0.6 mm. The thickness of the substrate 310 can cause a flat plate offset phenomenon, and the field curvature caused by the thickness of the substrate 310 can be supplemented by optical design. The absolute value of the 0.8 field curvature of the lens assembly 100 of the present application is ≥ (the thickness of the substrate 310 / 100), and the refractive index of the general optical sheet 300 is close to the lens assembly 100, thereby causing a flat plate offset of about 0.01 mm, which causes a change of 1 μm field curvature.

[0128] After the optical sheet 300 is formed, its installation can also affect the surface accuracy and thus affect the compensation effect.

[0129] The optical sheet 300 includes an optical area 3001 (an area within the dotted line in FIGS. 13 and 14) for realizing the function of astigmatism compensation and a structure area 3002 (an area outside the dotted line in FIGS. 13 and 14) for realizing the mounting of the optical sheet 300. The structure area 3002 can be provided around the entire periphery of the optical area 3001 or can be provided only on a part of the periphery of the optical area 3001.

[0130] The structure area 3002 extends outward from at least two sides of the optical area 3001. In the embodiment shown in FIG. 13, the structure area 3002 of the optical sheet 300G extends outward from opposite sides of the optical area 3001. In the embodiment shown in FIG. 14, the structure area 3002 of the optical sheet 300H extends outward from three sides adjacent to the optical area 3001.

[0131] In some embodiments, the optical sheet 300 is attached to the prism 201 of the reflection assembly 200. In the embodiments shown in FIGS. 15 and 16, the second optical surface 302 of the optical sheet 300 is a flat surface, and the second optical surface 302 is attached to the surface of the prism 201. This embodiment is advantageous in simplifying the structure and reducing the overall size of the optical system. The optical sheet 300 and the prism 201 can be attached by using an adhesive, i.e., the structure area 3002 of the optical sheet 300 and the structure area of the prism 201 are attached by using an adhesive.

[0132] In other embodiments, the optical sheet 300 is provided on an optical sheet mounting structure 400, and the optical sheet 300 is positioned by the optical sheet mounting structure 400, as shown in FIG. 17. Specifically, the structure area 3002 of the optical sheet 300 is connected to the optical sheet mounting structure 400.

[0133] In the embodiment shown in FIG. 18, the structure area 3002 of the optical sheet 300 is attached to the optical sheet mounting structure 400A.

[0134] In other embodiments, the structure area 3002 of the optical sheet 300 is connected to the optical sheet mounting structure 400 by a card slot. Specifically, the structure area 3002 of the optical sheet 300H extends outward from three sides adjacent to the optical area 3001, and the optical sheet mounting structure 400B includes three mounting slots 401 opposite to the structure area 3002 in each direction, as shown in FIG. 19. The structure area 3002 of the optical sheet 300 is adapted to be inserted into the three mounting slots 401. By providing the mounting slots 401, the adhesive attachment can be replaced.

[0135] In some embodiments, the low-stress connecting structure is implemented as a foam 500a, which is filled between the structure area 3002 of the optical sheet 300 and the optical sheet mounting structure 400.

[0136] In the embodiment shown in FIG. 20, the low-stress connecting structure is implemented as a foam 500a, which is filled between the structure area 3002 of the optical sheet 300 and the optical sheet mounting structure 400.

[0137] In the embodiment shown in FIG. 21, the low-stress connecting structure is implemented as a spring 500b, one end of which is connected to the structure area 3002 of the optical sheet 300, and the other end of which is connected to the optical sheet mounting structure 400.

[0138] Further, the plurality of low-stress connecting structures are symmetrically arranged at the periphery of the structure area 3002 of the optical sheet 300.

[0139] In some embodiments, the reflection assembly 200 includes a prism 201 and a prism carrier 202, and the prism 201 is arranged on the prism carrier 202, as shown in FIG. 15 or 17. The aforementioned optical sheet mounting structure 400 and the prism carrier 202 are in an integrated structure or a split structure, and the two are arranged in an integrated structure, which has the advantage of simplifying the installation process.

[0140] The present application also provides a camera module 1, as shown in FIG. 15 or 17, which includes an optical system 10 and a photosensitive assembly 20, and the photosensitive assembly 20 is located on the image side of the lens assembly 100.

[0141] The present application also provides an electronic device including the camera module 1, and the electronic device can be, but is not limited to, a mobile phone, a tablet computer, a notebook computer, a smart watch, and the like.

[0142] The foregoing describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments, and the above-described embodiments and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. An optical system characterized by, The application relates to an optical system, comprising: a lens assembly for imaging; a reflecting assembly arranged on the object side or image side of the lens assembly for changing the direction of light entering or exiting the lens assembly; and an optical sheet arranged on the optical path of the optical system, the optical sheet comprising opposite first and second optical surfaces, the first optical surface being a curved surface, and the second optical surface being a flat surface or a curved surface, the curvature of the first optical surface in two orthogonal directions being different, so that the field curvature compensation of the optical sheet in the two orthogonal directions is different. The lens assembly comprises a diaphragm and a lens group arranged on the image side of the diaphragm, and the optical sheet is arranged on the object side of the diaphragm. The optical sheet is arranged adjacent to the reflecting assembly. The curvature of the first optical surface in a first direction is zero, and the curvature radius of the first optical surface in a second direction is R2, |R2| being 1000mm-10000mm, and the first direction is orthogonal to the second direction. The ratio of |R2| to the effective focal length of the optical system is 0.0012-0.

03.

2. The optical system of claim 1, wherein The lens assembly comprises a first lens closest to the object side, the first lens being a convex lens, and the ratio of |R2| to the curvature radius of the object side surface or image side surface of the first lens is 10:1-50:

1.

3. The optical system of claim 1, wherein The curvature of the first optical surface in a first direction is k1, and the curvature in a second direction is k2, k1≠k2, and k1 and k2 are both not zero, the first direction being orthogonal to the second direction, 4. The optical system of claim 1, wherein wherein the signs of k1 and k2 are the same; or one of k1 and k2 is positive, and the other is negative.

5. The optical system of claim 4, wherein, The first optical surface and the second optical surface are both curved surfaces, and the bending direction and bending degree of the first optical surface and the second optical surface are the same.

6. The optical system of claim 4, wherein The second optical surface is a flat surface, and the ratio of the central thickness to the edge thickness of the optical sheet is 0.8-1.

25.

7. The optical system of claim 1, wherein The first optical surface comprises a first curved surface close to the optical axis and a second curved surface away from the optical axis, the second curved surface is located on both sides of the first curved surface away from the optical axis, the curvatures of the first curved surface and the second curved surface in the first direction are both zero, the radius of curvature of the first curved surface in the second direction is R 21 , the radius of curvature of the second curved surface in the second direction is R 22 , R 21 ≠ R 22 , |R 21 | and |R 22 | are respectively 1000mm-10000mm.

8. The optical system of claim 7, wherein, R 21 R 22 R 21 R 22 R 21 R 22 R 9. The optical system of claim 1, wherein, The optical sheet comprises a substrate and a curved surface part, the curved surface part being formed on the substrate by a micro-imprinting process, the surface of the substrate far from the curved surface part forming the second optical surface, and the surface of the curved surface part far from the substrate forming the first optical surface. The optical sheet comprises an optical area and a structure area outside the optical area, the structure area extending outward from at least two sides of the optical area.

10. The optical system according to any one of claims 1 to 9, characterized in that The reflecting assembly comprises a prism and a prism bearing seat, and the optical sheet is attached to the surface of the prism through the structure area.

11. The optical system according to any one of claims 1 to 9, characterized in that The optical sheet is arranged on an optical sheet mounting structure, and the structure area of the optical sheet and the optical sheet mounting structure are connected through a plurality of low-stress connecting structures, so that the optical sheet has a space for deformation or displacement in the direction perpendicular to the optical axis when the optical sheet is kept at the optical sheet mounting structure.

12. The optical system according to any one of claims 1 to 9, characterized in that The low-stress connecting structure is a spring, one end of the spring is connected with the structure area of the optical sheet, the other end is connected with the optical sheet mounting structure, and a plurality of the springs are symmetrically distributed on the circumferential side of the structure area of the optical sheet.

13. The optical system according to any one of claims 1 to 9, wherein The low-stress connecting structure is foam, the foam is filled between the structure area of the optical sheet and the optical sheet mounting structure, and a plurality of the foams are symmetrically distributed on the circumferential side of the structure area of the optical sheet.

14. The optical system of claim 13, wherein, ​ 15. The optical system of claim 13, wherein, ​ 16. The optical system of claim 15, wherein, ​ 17. The optical system of claim 15, wherein, ​ 18. A camera module comprising the optical system of any one of claims 1-17 and a photosensitive component, the photosensitive component being located on an image side of the lens assembly.

19. An electronic device comprising the camera module of claim 18.

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