CN118244483B - Optical system, camera module and electronic equipment - Google Patents

Abstract

The application discloses an optical system, a camera module and electronic equipment. Wherein the optical system includes: a lens assembly for imaging; the reflection assembly is arranged on the object side or the image side of the lens assembly and is used for changing the direction of light rays entering or exiting the lens assembly; and the optical sheet is arranged on the optical path of the optical system and comprises a first optical surface and a second optical surface which are opposite, 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 equipment

Technical Field

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

Background

With the popularization and development of smart phones, mobile phone photographing has become one of the indispensable functions in people's daily life. In order to meet the higher requirements of users on photographing effects, manufacturers are continuously improving the imaging system of mobile phones, wherein periscope type tele lenses are one of the most interesting in recent years. The periscope type long-focus lens is based on the principle that an original straight light path is bent by 90 degrees by using a reflecting mirror or a prism, so that the thickness of the lens is converted into a length, and a longer focal length is realized, so that the mobile phone can have stronger optical zoom capability under the condition that the thickness of the mobile phone is not increased.

A tele lens generally tends to exhibit astigmatism due to its longer focal length, because an increase in the focal length of the optical system means that the light travels longer in the optical system, increasing the chance of light deflection, resulting in more severe astigmatism.

Disclosure of Invention

An object of the present application is to provide an optical system that is advantageous for improving the imaging quality of periscope type camera modules.

Another object of the present application is to provide an optical system with less astigmatism.

Another object of the present application is to provide an image capturing module and an electronic apparatus including the optical system.

To achieve the above object, the present application provides an optical system comprising:

a lens assembly for imaging;

The reflection assembly is arranged on the object side or the image side of the lens assembly and used for changing the direction of light rays entering or exiting the lens assembly; and

The optical sheet is arranged on the optical path of the optical system and comprises a first optical surface and a second optical surface which are opposite, 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.

In some embodiments, the lens assembly includes a diaphragm and a lens group disposed on an image side of the diaphragm, and the optical sheet is disposed on an object side of the diaphragm.

In some embodiments, the optical sheet is disposed adjacent to the reflective assembly.

In some embodiments, the curvature of the first optical surface in the first direction is zero, the curvature radius of the first optical surface in the second direction is R ₂,|R₂ | and the value is 1000 mm-10000 mm, and the first direction is orthogonal to the second direction.

In some embodiments, the ratio of R ₂ to the effective focal length of the optical system is 0.0012-0.03.

In some embodiments, the lens assembly includes a first lens closest to the object side, the first lens being a convex lens, a ratio of R ₂ to a radius of curvature of the object side or the image side of the first lens being 10:1-50:1.

In some embodiments, the first optical surface includes a first curved surface close to the optical axis and a second curved surface far away from the optical axis, the second curved surface is located at two sides of the first curved surface far away from the optical axis, curvatures of the first curved surface and the second curved surface in a first direction are both zero, a curvature radius of the first curved surface in a second direction is R ₂₁, and curvature radii of the second curved surface in the second direction are R ₂₂,R₂₁≠R₂₂,|R₂₁ | and |r ₂₂ | which take values of 1000mm to 10000mm respectively.

In some embodiments, R ₂₁ and R ₂₂ are both positive values, and R ₂₁＜R₂₂.

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

In some embodiments, the first optical surface has a curvature k ₁ in a first direction, a curvature k ₂,k₁≠k₂ in a second direction, and neither k ₁、k₂ is zero, the first direction being orthogonal to the second direction.

In some embodiments, k ₁ is the same sign as k ₂.

In other embodiments, one of k ₁ and k ₂ is positive and the other is negative.

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 are curved in the same direction and degree of curvature.

In some embodiments, the second optical surface is a plane, and a ratio of a center thickness to an edge thickness of the optical sheet is 0.8-1.25.

In some embodiments, the optical sheet includes a substrate and a curved portion formed on the substrate by a micro-imprinting process, a surface of the substrate remote from the curved portion forming the second optical surface, and a surface of the curved portion remote from the substrate forming the first optical surface.

In some embodiments, the optical sheet includes an optical region and a structural region located outside the optical region, the structural region extending outwardly from at least two sides of the optical region.

In some embodiments, the reflective assembly includes a prism and a prism carrier, and the optical sheet is attached to the prism surface through the structural area.

In some embodiments, the optical sheet is disposed on an optical sheet mounting structure, and the structural region of the optical sheet and the optical sheet mounting structure are connected by a plurality of low stress connection structures, so that there is a space for deformation or displacement in a direction perpendicular to the optical axis when the optical sheet is held at the optical sheet mounting structure.

In some embodiments, the low stress connection structure is a spring plate, one end of the spring plate is connected with the structural region of the optical sheet, the other end of the spring plate is connected with the optical sheet mounting structure, and the plurality of spring plates are symmetrically distributed on the periphery of the structural region of the optical sheet.

In some embodiments, the low stress connection structure is foam filled between the structural region of the optical sheet and the optical sheet mounting structure, and the plurality of foam are symmetrically distributed on the peripheral side of the structural region of the optical sheet.

The application also provides an image pickup module, which comprises the optical system and a photosensitive chip, wherein the photosensitive component is positioned at the image side of the lens component.

The application also provides electronic equipment comprising the camera module.

Further advantageous effects of the application will be further explained in the detailed description.

Drawings

Fig. 1 is a schematic diagram of astigmatism generation in a conventional optical system.

Fig. 2A illustrates the effect of a change in the angle of the reflecting surface on imaging when the reflecting surface is on the object side of the lens.

Fig. 2B illustrates the effect of the change in the angle of the reflecting surface on imaging when the reflecting surface is on the image side of the lens.

Fig. 3A is a design optical path of a lens and its corresponding design defocus curve.

Fig. 3B is a diagram illustrating an optical path and a corresponding defocus curve when the lens in the lens of fig. 3A is decentered.

FIG. 4 is a schematic diagram of an embodiment of an optical system of the present application.

Fig. 5 is a schematic view of another embodiment of the optical system of the present application.

Fig. 6 is a schematic view of a first embodiment of the optical sheet of the present application.

Fig. 7 is a schematic view of a second embodiment of the optical sheet of the present application.

Fig. 8 is a schematic view of a third embodiment of the optical sheet of the present application.

Fig. 9 is a schematic view of a fourth embodiment of the optical sheet of the present application.

Fig. 10 is a schematic view of a fifth embodiment of the optical sheet of the present application.

Fig. 11 is a schematic view of a sixth embodiment of the optical sheet of the present application.

Fig. 12 is a schematic view of an embodiment of an optical sheet of the present application prepared by an embossing process.

FIG. 13 is a schematic view of an embodiment of the optical area and the structural area of the optical sheet of the present application.

FIG. 14 is a schematic view of another embodiment of the optical area and the structural area of the optical sheet of the present application.

Fig. 15 is a schematic view of an embodiment of an image capturing module according to the present application.

Fig. 16 is a schematic cross-sectional view of fig. 15.

Fig. 17 is a schematic diagram of another embodiment of an image capturing module according to the present application.

Fig. 18 is a schematic view of an embodiment of the optical sheet and the optical sheet mounting structure of the present application.

Fig. 19 is a schematic view of an embodiment of the optical sheet mounting structure of the present application.

Fig. 20 is a schematic view of an embodiment of an optical sheet, an optical sheet mounting structure, and a low stress connection structure of the present application.

Fig. 21 is a schematic view of another embodiment of the optical sheet, the optical sheet mounting structure, and the low stress connection structure of the present application.

Detailed Description

The present application will be further described with reference to the following specific embodiments, and it should be noted that, on the premise of no conflict, new embodiments may be formed by any combination of the embodiments or technical features described below.

In the description of the present application, it should be noted that, for the azimuth words such as terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the azimuth and positional relationships are based on the azimuth or positional relationships shown in the drawings, it is merely for convenience of describing the present application and simplifying the description, and it is not to be construed as limiting the specific scope of protection of the present application that the device or element referred to must have a specific azimuth configuration and operation.

It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.

The terms "comprises" and "comprising," along with any variations thereof, in the description and claims, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In the present application, the curvature of a curved surface in a certain direction means the curvature of a curve extending in the certain direction, and the curvature of a curve means the rotation rate of a tangential angle to a certain point with respect to the arc length, indicating the degree to which the curve deviates from a straight line. The larger the curvature, the greater the degree of curvature of the curve, and the curvature is the inverse of the radius of curvature.

In the present application, astigmatism is defined as: as shown in fig. 1, after a light ray emitted from an off-axis point light source P passes through the lens L, the meridian focus S ₁ and the sagittal focus T ₁ are not located at the same position, i.e. the light beam cannot be focused on a point, the imaging is unclear, and astigmatism is generated. It should be noted that, in fig. 1, P is a light emitting point, the optical axis is denoted by Q, the light emitting point P is not located on the optical axis Q, Φ represents an included angle between a central axis of a light ray of the light emitting point P and the optical axis Q, a blue line represents a meridian direction light ray, a red light ray represents a sagittal direction light ray, a blue light incident in a meridian direction emitted by the light emitting point P is imaged at a point S ₁ after being imaged by a lens, a red light incident in a sagittal direction is imaged at a point T ₁, and an astigmatic difference is between T ₁ and Q ₁. One point of the image axis is denoted by Q ₁, Q ₁ forms an angle with S ₁ and T ₁, respectively, and the angle error affects the sharpness.

The inventor deeply analyzes the cause of serious astigmatism of the existing periscope type camera module, and considers the following influence factors.

1. Influence of prism or mirror surface accuracy

The periscope type camera module is provided with the prism/reflector, the surface of the prism/reflector is difficult to be absolutely smooth, the accuracy of the incident surface, the reflecting surface and the emergent surface of the periscope type camera module can directly influence the consistency of light rays in the refraction and reflection processes, and the periscope type camera module can lead to that meridian focus and sagittal focus are not on the same point, so that astigmatism is generated, and the definition of images is influenced. To illustrate the effect of prism/mirror surface type accuracy on light propagation and imaging, fig. 2A and 2B illustrate in a simplified manner the effect of a change in the angle of the reflecting surface on imaging, as will be appreciated by those skilled in the art, when there is a localized protrusion or depression in the surface of the prism/mirror, the corresponding localized change in the angle of the reflecting surface occurs.

Fig. 2A illustrates that the reflecting surface F is located at the object side of the lens J, wherein the dashed line shows the reflecting surface F after the angle change θ of the reflecting surface F, the reflected light, and the imaging position, and the reflecting surface F changes angle to shift the imaging position on the photosensitive chip under the condition that the position of the object W is unchanged, the angle change θ of the nodding direction of the reflecting surface F changes to 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.

Fig. 2B illustrates that the reflecting surface F is located at the image side of the lens J, wherein the dashed line shows the reflecting surface, the reflected light and the image surface after the angle change θ of the reflecting surface F, the angle change of the reflecting surface F causes the deflection (tilt) of the imaging surface X of the lens, the deflection angle is 2θ, the angle change ratio is 1:2, and in addition, the angle change θ of the nodding direction of the reflecting surface F, the angle change of the light ray is 2θ, and the angle change ratio is 1:2.

Whether the reflecting surface is positioned on the object side or the image side of the lens, when the angle of the reflecting surface is changed, the angle of light rays is changed, so that astigmatism is generated, and imaging is finally affected. Therefore, in the optical system of the periscope type imaging module, astigmatism is easily generated due to the influence of the surface type precision of the prism/reflector, and imaging quality is easily affected.

2. Influence of decentration or tilting of lenses in lens assemblies

Decentration or tilting may occur during assembly of the lens due to the accuracy of assembly, and such assembly errors may also affect imaging quality. Fig. 3A and 3B illustrate, in a simplified manner, the change of the defocus curves before and after decentering of a lens, wherein fig. 3A is a designed optical path of the lens and a designed defocus curve corresponding thereto, and fig. 3B is an optical path of the lens and a defocus curve corresponding thereto after decentering of the lens, and it can be seen from the change of the defocus curves that astigmatism is also easily caused by decentering of the lens.

3. Influence of the assembly process

The lens or prism in the camera module is generally assembled by dispensing, but the dispensing and the subsequent baking can cause stress to the optical element, thereby affecting the surface shape of the optical element, and further causing the astigmatism problem of the whole optical system according to the analysis of the 1 st point.

Based on the above analysis, the inventor of the present application proposes an optical system 10 suitable for a periscope type camera module to alleviate the problem of serious astigmatism of the existing periscope type camera module.

The optical system 10 of the present application includes 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 disposed on an object side or an image side of the lens assembly 100, and is used for changing a direction of light entering or exiting the lens assembly 100; the optical sheet 300 is disposed on the optical path of the optical system 10. There are various arrangements of the lens assembly 100, the reflection assembly 200 and the optical sheet 300, for example: sequentially arranged in the order of the optical sheet 300, the reflection assembly 200, and the lens assembly 100; or sequentially arranged in the order of the optical sheet 300, the lens assembly 100, and the reflection assembly 200; or sequentially arranged in the order of the reflection assembly 200, the optical sheet 300, and the lens assembly 100; or sequentially arranged in the order of the reflection assembly 200, the lens assembly 100, and the optical sheet 300; or sequentially arranged in the order of the lens assembly 100, the reflection assembly 200, and the optical sheet 300; or sequentially arranged in the order of the lens assembly 100, the optical sheet 300, and the reflection assembly 200.

The optical sheet 300 includes a first optical surface 301 and a second optical surface 302 opposite to each other, the first optical surface 301 is a curved surface, the second optical surface 302 is a plane or a curved surface, and curvatures of the first optical surface 301 in two orthogonal directions are different, so that field curvature compensation amounts of the optical sheet 300 in the two orthogonal directions are different. The field curvature compensation amount refers to an amount of adjustment or change of the optical system to reduce or eliminate field curvature aberration, and the "the field curvature compensation amount of the optical sheet 300 is different in two orthogonal directions" in the present application may be understood as that the compensation amount of the optical sheet 300 for the noon focus displacement and the compensation amount for the radian focus displacement are different.

In other words, the curvature of the first optical surface 301 in the first direction is k ₁, and the curvature in the second direction is k ₂,k₁ different from k ₂, and the first direction is orthogonal to the second direction. It should be noted that the first optical surface 301 may be a light incident surface or a light emergent surface, and correspondingly, the second optical surface 302 may be a light emergent surface or a light incident surface.

The present application adds an optical sheet 300 to the optical system 10, which can be used to compensate for the astigmatism caused by the addition of the reflective assembly 200. Specifically, the present application mainly uses the optical sheet 300 to implement the compensation of the sagittal and/or meridional view field, and referring to the astigmatic diagram shown in fig. 1, the optical sheet 300 of the present application is disposed on the object side of the lens L, so that the view field in the rear side is pulled forward, i.e. the sagittal focal point is moved forward, or the view field in the front side is pulled backward, i.e. the meridional focal point is moved backward. The curvatures k ₁ and k ₂ of the first optical surface 301 of the optical sheet 300 are selected in consideration of the degree of deviation of the meridian direction and the sagittal direction in the whole optical system, so that the meridian focus and the sagittal focus which are originally far away are close to each other, thereby reducing astigmatism and improving imaging quality. In other words, the difference in curvature of the first optical surface 301 in two orthogonal directions enables the optical sheet 300 to change the focus of the field of view in one direction to be close to the focus of the field of view in the other direction, thereby solving the astigmatism problem.

In addition, since astigmatism mainly occurs in a field of view away from the optical axis, several fields of view away from the optical axis are generally selected for testing when testing the compensation effect of the optical sheet 300. It should be noted 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, a specific field of view can be expressed by the ratio of the edge to the center, for example, 0.8 field of view is the distance of the edge to the center with the ratio of 0.8, a range is defined near 0.8 field of view, for example, 0.75-0.85, an annular area is defined, and in this annular area, all can be considered as 0.8 field of view.

In some embodiments, the optical sheet is disposed adjacent to the reflection assembly, and the light is adapted to be incident on the reflection assembly after passing through the optical sheet, or the light exiting 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, and the light diffusion is prevented from being more serious after the optical path is prolonged. The more severe the light diffusion, the more the optical sheet having a larger curvature or a thicker thickness is required to compensate for astigmatism, and thus, the more the astigmatism is compensated in advance, the more the light and thin optical sheet 300 is facilitated.

In some embodiments, the reflective element 200 and the optical sheet 300 are disposed on the image side (not shown in the drawings) of the lens assembly 100, that is, the light is first converged by the lens assembly 100 and then the light path is changed by the reflective element 200, and the optical sheet 300 may be disposed on the light incident side of the reflective element 200 or on the light emergent side of the reflective element 200.

In other embodiments, as shown in fig. 4 or 5, the reflection assembly 200 and the optical sheet 300 are disposed on the object side of the lens assembly 100. Since decentering or tilting of the lenses in the lens assembly 100 may also cause astigmatism, the appropriate first optical surface of the optical sheet 300 may be designed to compensate for this astigmatism, considering that the longer the optical path, the more severe the light diffusion in the meridian and sagittal directions in the optical system, and if a certain degree of compensation is performed before the light diffusion, the optical sheet 300 can better achieve the compensation with a smaller curvature or a thinner thickness. Therefore, disposing the reflection assembly 200 and the optical sheet 300 at the object side of the lens assembly 100 is advantageous in achieving light and slim 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 at the light-emitting side of the reflection assembly 200. For the same reason, the optical sheet 300 is disposed on the light incident side of the reflection assembly 200 to further facilitate the light and thin reduction of the optical sheet 300.

It should be noted that the lens assembly 100 includes a diaphragm 110 and a lens group 120 disposed on an image side of the diaphragm 110, the diaphragm 110 can affect a field of view of the lens assembly 100, and in practice, the influence of astigmatism can be reduced by adjusting a position of the diaphragm 110.

In some preferred embodiments, the optical sheet 300 is disposed on the object side of the aperture 110. In an optical system, a diaphragm is a very important concept that determines resolution and imaging quality of the optical system, and is generally an optical element having a small aperture, which functions to limit the amount of light passing through the optical system, thereby controlling the definition of imaging. The optical sheet 300 is disposed on the object side of the aperture 110, and can perform astigmatism compensation with an amplifying effect.

Specifically, in the optical system, all the optical apertures are imaged into the object space of the first optical aperture, the optical aperture conjugated by the optical aperture "image" with the smallest aperture angle of the object point on the axis is the aperture diaphragm, and if the optical element on the front side of the aperture diaphragm is changed, the effect of compensating the "image" is more obvious when compensating the astigmatism due to the conjugated relation with the "image". It should be noted that the conjugate relation means that the modification on the optical surface affects the image in a conjugate manner, and has a magnifying effect.

In the above embodiment, the optical sheet 300 compensates for both the central field of view and the full field of view. Generally, in an optical system, a central field of view refers to an area with best imaging quality, because light rays are almost incident along an optical axis, aberration is small, a full field of view refers to an entire imaging area including an edge area outside the central field of view, and at an edge of the full field of view, light rays are incident at a larger angle and are more susceptible to various optical aberrations, resulting in degradation of imaging quality.

The effective aperture corresponding to light refers to aperture of a diaphragm corresponding to light that can contribute to imaging in a specific view field region. Analyzing from the angle of the corresponding caliber of the effective light, wherein the caliber of the effective light is similar to the diameter of the entrance pupil of the system in the central view field, because the light almost propagates along 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 of the incident angle of the light, and as the position of the light moves backward, the aperture corresponding to the effective light may further decrease. Therefore, in the preferred embodiment of the present application, the optical sheet 300 is disposed on the object side of the diaphragm 110, so that the effective apertures of the central field of view and the full field of view are close, which makes the light incidence conditions of the central field of view and the edge field of view similar, so that consistency of imaging quality is maintained to some extent, that is, the optical sheet 300 compensates both the central field of view and the full field of view in the above embodiment.

The lens closest to the object side of the lens group 120 is a first lens 121, and in order to better collect the light, a convex lens is preferably used for the first lens 121. When the optical sheet 300 is disposed near the first lens 121, the radius of curvature of the optical sheet 300 should be designed in consideration of the radius of curvature of the first lens 121, and the relationship therebetween will be further described later.

In addition, the radius of curvature of the optical sheet 300 should be designed in consideration of the focal length of the entire optical system 10, the relationship between which will be further described later.

Preferably, the focal lengths of the optical system 10 of the present application in the sagittal and meridional directions differ by no more than 5%.

The following embodiments of the optical sheet 300 are provided as examples, and are not exhaustive of the structures of the optical sheet 300, and any rearrangement of technical features within the scope of the inventive concept is within the scope of the present application.

[ Optical sheet example 1]

As shown in fig. 6, the optical sheet 300A includes a first optical surface 301A and a second optical surface 302A.

The second optical surface 302A is a planar surface. The second optical surface 302A may be used as an attachment reference surface, for example, the optical sheet 300A is attached to the prism surface of the reflection assembly 200 or attached to the optical sheet mounting structure 400, and the planar attached bondable surface is larger than the curved surface and has higher bonding strength; in addition, the second optical surface 302A is a plane surface, which is also advantageous for height measurement of the optical sheet 300A by the height measuring device, thereby improving assembly accuracy of the optical sheet 300A.

The curvature k ₁ of the first optical surface 301A in the first direction is zero, the curvature k ₂ of the first optical surface 301A in the second direction is equal to R ₂,R₂=1/k₂,R₂, and the curvature radius is 1000mm to 10000mm. That is, the optical sheet 300A mainly provides compensation over the second-direction field of view, bringing the focus of the second-direction field of view closer to the focus of the first-direction field of view.

Further, the ratio of the center thickness to the edge thickness of the optical sheet 300A is 1 to 1.25, i.e., the center thick edge is thin. The center thickness and the edge thickness of the optical sheet 300A determine the surface accuracy thereof, and controlling the ratio of the center thickness to the edge thickness to 1 to 1.25 is beneficial to ensuring that the surface of the optical sheet 300A is close to the design value, so as to ensure that the surface of the optical sheet 300A can achieve the purpose of reducing aberration.

It should be noted that the thickness of the optical sheet 300A is unchanged in the first direction, and only the thickness is changed in the second direction.

Preferably, the ratio of R ₂ to the effective focal length of the optical system 10 is 0.0012-0.03. 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 in general, the Effective Focal Length (EFL) of the periscope type camera module is 12-30 mm, and in the case of a large size limitation of the camera module, in order to achieve the diffraction limit of the optical design, the performance of the limit condition needs to be considered, so that the application considers that in the case of the effective focal length of 12-30 mm, R ₂ of the first optical surface 301A corresponds to two end values of the effective focal length in the case of 1000-10000 mm, thereby obtaining the range of 0.0012-0.03.

Further, the ratio of the radius of curvature of the object side or the image side of the first lens element 121 to the R ₂ is 10:1-50:1. The longer the focal length of the optical lens at the same image height, the longer the optical path that the light beam travels, and the greater the possibility of deflection of the light beam emitted from the off-axis point light source after passing through the optical element, so that the radii of curvature of the object side and the image side of the first lens element 121 of the lens assembly 100 determine the approximate extent of diffusion of the light beam into the entire lens assembly 100, and when the reflective assembly 200 and the optical sheet 300 are located on the object side of the lens assembly 100, the radii of curvature of the optical sheet 300A and the first lens element 121 have a critical influence on the imaging quality of the entire optical system.

[ Optical sheet example 2]

As shown in fig. 7, the optical sheet 300B includes a first optical surface 301B and a second optical surface 302B.

The curvature k ₁ of the first optical surface 301B in the first direction is zero, the curvature k ₂ of the first optical surface 301B in the second direction, and the curvature radius R ₂,R₂=1/k₂,R₂ is 1000mm to 10000mm. That is, the optical sheet 300B mainly provides compensation over the field of view in the second direction, bringing the focal point of the field of view in the second direction closer to the focal point of the field of view in the first direction.

The second optical surface 302B is a curved surface, but the second optical surface 302B is not used for realizing astigmatism compensation, and the thickness of the optical sheet 300B is thin, and the distance between the second optical surface 302B and the first optical surface 301B is substantially the same, or the bending degree in the bending direction is the same between the first optical surface 301B and the second optical surface 302B, as shown in fig. 7.

Preferably, the ratio of R ₂ to the effective focal length of the optical system 10 is 0.0012-0.03.

Preferably, the ratio of the radius of curvature of R ₂ to the object-side or image-side of the first lens 121 is 10:1-50:1.

[ Optical sheet example 3]

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 planar surface.

The curvature k ₁ of the first optical surface 301C in the first direction is zero, and the curvature radius R ₂,R₂ of the first optical surface 301C in the second direction is-10000 mm to-1000 mm. That is, the optical sheet 300C mainly provides compensation over the second-direction field of view, bringing the focus of the second-direction field of view closer to the focus of the first-direction field of view.

Further, the ratio of the center thickness to the edge thickness of the optical sheet 300C is 0.8 to 1, i.e., the center thin edge thickness. It should be noted that the thickness of the optical sheet 300C is unchanged in the first direction, and only the thickness is changed in the second direction.

Preferably, the ratio of the i R ₂ to the effective focal length of the optical system 10 is 0.0012 to 0.03.

Preferably, the ratio of R ₂ to the radius of curvature of the object side or image side of the first lens 121 is 10:1-50:1.

[ Optical sheet example 4]

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 planar surface.

The first optical surface 301D includes a first curved surface 3011D close to the optical axis and a second curved surface 3012D distant from the optical axis, and the second curved surface 3012D is located on both sides of the first curved surface 3011D distant from the optical axis. The curvatures of the first curved surface 3011D and the second curved surface 3012D in the first direction are 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, the radius of curvature of the second curved surface 3012D in the second direction is R ₂₂,R₂₁≠R₂₂, specifically, R ₂₁ is positive, R ₂₂ is negative, and values of |r ₂₁ | and |r ₂₂ | are 1000 mm-10000 mm respectively. That is, the bending directions of the first curved surface 3011 and the second curved surface 3012 are different, and the inflection point exists on the first optical surface 301D, which can be applied to partition compensation in some special cases.

The application of the zonal compensation capability of the optical sheet 300 to periscopic camera modules, especially in macro situations, can achieve unexpected results. In an optical system with a long focal length, the function of optical path turning is generally realized by adopting a turning optical path element, the imaging position on a chip is offset due to the angle change between the turning optical path element and a design position, so that the turning optical path element and a photosensitive chip are required to be actively calibrated, the calibration can realize the alignment of the central axis of emergent light rays of a prism and the central axis of the photosensitive chip, thus preventing the problem of periscope type shooting, and the lens, the lens and the photosensitive chip are aligned, and then the central axis position can be considered to be corresponding, but the lens of the periscope type camera module is limited by adopting a straight-edge design, the height direction of the lens is made into a straight edge, the optical area occupied ratio of the lens can be improved, but the shrinkage stress of the straight edge lens in injection molding is obviously uneven due to the asymmetric relation, and the curved surface at the off-axis position of the lens is easier to cause local deformation, so that the optical lens 300 can be better compensated by adopting a sectional curved surface.

In some special cases, local deformation of the lens occurs, the lens surface shape change of the area may cause unexpected aberration of the optical system, and the inventor finds that, because the straight edge lens leaves less structural area outside the optical area in the height direction, the optical area is easier to deform, and in this case, the optical system is easier to generate two-side aberration and the like, in order to adapt to the special case, the stress concentration area of the straight edge lens can be improved through the optical sheet 300, for example, a first curved surface 3011D and at least one inflection point are arranged on one side of the optical sheet 300D, the second curved surface 3012D is connected to the first curved surface 3011D through the inflection point, in this way, the second curved surface 3012D is designed to be different from the curvature direction of the first curved surface 3011D, the inflection point refers to a junction point of positive and negative change of the surface of the optical sheet 300D, and by the design of the inflection point, the optical sheet can compensate for aberration at the paraxial position and utilize aberration at the far axis 3012D.

[ Optical sheet example 5]

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 planar surface.

The first optical surface 301E includes a first curved surface 3011E close to the optical axis and a second curved surface 3012E distant from the optical axis, and the second curved surface 3012E is located on both sides of the first curved surface 3011E distant from the optical axis. The curvatures of the first curved surface 3011E and the second curved surface 3012E in the first direction are zero or the radius of curvature is infinite, the radius of curvature of the first curved surface 3011E in the second direction is R ₂₁, the radius of curvature of the second curved surface 3012E in the second direction is R ₂₂,R₂₁≠R₂₂, and specifically, values of 0 < R ₂₁＜R₂₂,R₂₁ and R ₂₂ are 1000 mm-10000 mm respectively. I.e. the surface profile of the first optical surface 301E at the off-axis has a stronger compensation effect.

The optical sheet 300E also has the capability of zone compensation.

[ Optical sheet example 6 ]

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.

The first optical surface 301F is hyperbolic, having a curvature k ₁ in the first direction, a curvature k ₂,k₁≠k₂ in the second direction, and neither k ₁、k₂ is zero, specifically, k ₂ is positive and k ₁ is negative. Preferably, the value of R ₁=1/k₁,R₂=1/k₂,R₁ is-10000 mm to-1000 mm, and the value of R ₂ is 1000mm to 10000mm.

In optical design, hyperboloids may provide more design freedom than single-curved surfaces, thereby more effectively compensating for astigmatism and other optical distortions. The first optical surface 301F is designed to be hyperbolic, and may better cope with some special situations (for example, when the prism adopts a reflective lens, extra aberration may be introduced, or if the straight edges at two ends of the lens in the height direction become larger, the aberration between paraxial rays and off-axis rays may be excessively large, or the plane mirror may cause aberration problems of an optical system if the plane mirror is improperly attached or deformed), if the single curved surface is adopted for compensation or correction, the first optical surface 301 may need to have a larger curvature, which may increase difficulty in manufacturing and molding, and the curved surface may be excessively curved, which may cause the surface type accuracy of the optical sheet 300 to be reduced, thereby introducing new optical aberration.

The advantage of using hyperboloid for astigmatism compensation is represented by: (1) By using curved surfaces in two directions and compensating for the curved surfaces respectively, the overlarge curvature of a single curved surface can be avoided; (2) The curved surface in each direction can have opposite curvature, so that the compensation effect can be balanced, and meanwhile, the smaller curvature is kept, thereby being convenient for manufacturing and controlling the precision; (3) This method is advantageous in ensuring the surface accuracy of the optical sheet 300F and reducing the optical aberration caused by the optical sheet 300F itself.

In general, the optical astigmatism in the image capturing module is represented in the micrometer scale, and in order to compensate for the optical astigmatism, the optical sheet 300 needs to be compensated in the micrometer scale, which has a high requirement on the molding accuracy of the optical sheet, and molding the optical sheet 300 by using the embossing technique can be considered. In a preferred embodiment, the optical sheet 300 is molded using a micro-embossing technique, and it is necessary to ensure embossing accuracy of the optical sheet 300 to ensure that the compensation capability of the optical sheet 300 is controllable, and in particular, to ensure molding accuracy of the first optical surface 301 and the second optical surface 302.

A specific description is provided below with respect to the preparation of one embodiment of the optical sheet 300. As shown in fig. 12, the optical sheet 300 includes a substrate 310 and a curved surface portion 320, wherein the curved surface portion 320 is formed on the substrate 310 through a micro imprinting process. The surface of the substrate 310 away from the curved surface portion 320 forms the second optical surface 302, and the surface of the curved surface portion 320 away from the substrate 310 forms the first optical surface 301.

The optical sheet 300 of the present application can ensure that the difference between the oa sagittal height in the x direction and the ob sagittal height in the y direction of the planar accuracy is within 5 μm.

Preferably, the thickness of the substrate 310 is 0.21mm to 0.6mm. The thickness of the substrate 310 may cause plate offset, and the curvature of field due to the thickness of the substrate 310 may be compensated for by optical design. The absolute value of 0.8 field curvature of the lens assembly 100 of the present application is ∈gtoreq (thickness of the substrate 310/100), and the refractive index of the optical sheet 300 is generally close to that of the lens assembly 100, so that the resulting plate offset is approximately 0.01mm, resulting in a change in field curvature of 1 μm.

After the optical sheet 300 is molded, its mounting may also affect the area accuracy, thereby affecting the compensation effect.

The optical sheet 300 includes an optical region 3001 (an area within a broken line in fig. 13 and 14), and a structural region 3002 (an area outside the broken line in fig. 13 and 14) outside the optical region 3001, the optical region 3001 being for realizing an astigmatism compensation function, the structural region 3002 being for realizing mounting of the optical sheet 300. The structure area 3002 may be disposed around the entire circumference of the optical area 3001, or may be disposed only partially outside the optical area 3001.

The structured zone 3002 extends outwardly from at least two sides of the optical zone 3001. In the embodiment shown in fig. 13, the structured region 3002 of the optical sheet 300G extends outwardly from opposite sides of the optical region 3001. In the embodiment shown in fig. 14, the structured region 3002 of the optical sheet 300H extends outwardly from three sides adjacent to the optical region 3001.

In some embodiments, the optical sheet 300 is attached to the prism 201 of the reflective assembly 200. As in the embodiment shown in fig. 15 and 16, the second optical surface 302 of the optical sheet 300 is a plane, and the second optical surface 302 is attached to the surface of the prism 201, which is advantageous in simplifying the structure and reducing the overall size of the optical system. The optical sheet 300 and the prism 201 may be bonded by glue, that is, the structural region 3002 of the optical sheet 300 and the structural region of the prism 201 are bonded using glue.

In other embodiments, the optical sheet 300 is disposed 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 structural region 3002 of the optical sheet 300 is connected to the optical sheet mounting structure 400.

In the embodiment shown in fig. 18, the structural region 3002 of the optical sheet 300 is bonded to the optical sheet mounting structure 400A.

In other embodiments, the structural region 3002 of the optical sheet 300 is connected with the optical sheet mounting structure 400 by a clamping groove, and in particular, the structural region 3002 of the optical sheet 300H extends outwardly from three sides adjacent to the optical region 3001, and the optical sheet mounting structure 400B includes three mounting grooves 401 opposite to the structural region 3002 in each direction, as shown in fig. 19, the structural region 3002 of the optical sheet 300 being adapted to be inserted into the three mounting grooves 401. By providing the mounting groove 401, glue bonding can be replaced.

In other embodiments, the structural region 3002 of the optical sheet 300 is connected to the optical sheet mounting structure 400 by a plurality of low stress connection structures, such that there is room for deformation or displacement in a direction perpendicular to the optical axis of the optical sheet 300 when the optical sheet 300 is held at the optical sheet mounting structure 400. In other words, the low stress connection structure may ensure that the optical sheet 300 is not displaced in the direction along the optical axis, but allows the optical sheet 300 to be deformed or displaced toward the circumferential side to prevent the surface type accuracy of the first and second optical surfaces thereof from being greatly affected when the optical sheet 300 is subjected to a stress change. It is worth mentioning that the stress variation of the optical sheet 300 may be caused by various factors, such as temperature variation, etc. The optical sheet 300 and the optical sheet mounting structure 400 are connected through the low-stress connection structure, so that the surface deformation caused by the influence of stress on the optical sheet 300 can be effectively reduced, the surface type precision is ensured, the compensation effect is realized, and the low-stress connection structure has great significance for mass production of the optical system.

In the embodiment shown in fig. 20, the low stress connection structure is implemented as a foam 500a, and the foam 500a is filled between the structural region 3002 of the optical sheet 300 and the optical sheet mounting structure 400.

In the embodiment shown in fig. 21, the low stress connection structure is implemented as a spring 500b, and one end of the spring 500b is connected to the structure area 3002 of the optical sheet 300 and the other end is connected to the optical sheet mounting structure 400.

Further, the plurality of low stress connection structures are symmetrically at the peripheral sides of the structure region 3002 of the optical sheet 300, respectively.

In some embodiments, the reflective assembly 200 includes a prism 201 and a prism carrier 202, where the prism 201 is disposed on the prism carrier 202, as shown in fig. 15 or 17. The optical sheet mounting structure 400 and the prism carrier 202 are integrated or separated, which is advantageous in simplifying the mounting process.

The present application further provides an image capturing module 1, as shown in fig. 15 or 17, where the image capturing module 1 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.

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

The foregoing has outlined the basic principles, features, and advantages of the present application. It will be understood by those skilled in the art that the present application is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present application, and various changes and modifications may be made therein without departing from the spirit and scope of the application, which is defined by the appended claims. The scope of the application is defined by the appended claims and equivalents thereof.

Claims (17)

1. An optical system, comprising:

a lens assembly for imaging;

The reflection assembly is arranged on the object side or the image side of the lens assembly and is used for changing the direction of light rays entering or exiting the lens assembly; and

The optical sheet is arranged on the optical path of the optical system and comprises a first optical surface and a second optical surface which are opposite, wherein 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;

The curvature of the first optical surface in the first direction is zero, the curvature radius of the first optical surface in the second direction is R ₂,|R₂ | and the value is 1000 mm-10000 mm, and the first direction is orthogonal to the second direction;

The ratio of R ₂ 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 diaphragm and a lens group disposed on an image side of the diaphragm, the optical sheet being located on an object side of the diaphragm.

3. The optical system of claim 1, wherein the optical sheet is disposed adjacent to the reflective assembly.

4. 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, a ratio of R ₂ to a radius of curvature of the first lens object side or image side being 10:1-50:1.

5. 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 far away from the optical axis, the second curved surface is located at two sides of the first curved surface far away from the optical axis, curvatures of the first curved surface and the second curved surface in a first direction are both zero, a radius of curvature of the first curved surface in a second direction is R ₂₁, and a radius of curvature of the second curved surface in the second direction is R ₂₂,R₂₁≠R₂₂,|R₂₁ | and |r ₂₂ | respectively take values of 1000 mm-10000 mm.

6. The optical system of claim 5, wherein R ₂₁ and R ₂₂ are both positive values, and R ₂₁＜R₂₂; or one of R ₂₁ and R ₂₂ is positive and the other is negative.

7. The optical system of claim 1, wherein the first optical surface has a curvature of k ₁ in a first direction, a curvature of k ₂,k₁≠k₂ in a second direction, and neither of k ₁、k₂ is zero, the first direction being orthogonal to the second direction,

Wherein k ₁ is the same symbol as k ₂; or one of k ₁ and k ₂ is positive and the other is negative.

8. The optical system of any one of claims 1-7, wherein the first optical surface and the second optical surface are curved surfaces, and wherein the first optical surface and the second optical surface have the same bending direction and bending degree.

9. The optical system of any one of claims 1-7, wherein the second optical surface is a planar surface, and the ratio of the center thickness to the edge thickness of the optical sheet is 0.8-1.25.

10. The optical system of any one of claims 1-7, wherein the optical sheet comprises a substrate and a curved surface portion formed on the substrate by a micro-embossing process, a surface of the substrate remote from the curved surface portion forming the second optical surface, and a surface of the curved surface portion remote from the substrate forming the first optical surface.

11. The optical system of any of claims 1-7, wherein the optical sheet comprises an optical zone and a structural zone outside the optical zone, the structural zone extending outwardly from at least two sides of the optical zone.

12. The optical system of claim 11, wherein the reflective assembly comprises a prism and a prism carrier, the optical sheet being attached to the prism surface by the structured zone.

13. The optical system of claim 11, wherein the optical sheet is disposed on an optical sheet mounting structure, and the structural region of the optical sheet is connected to the optical sheet mounting structure by a plurality of low stress connection structures, so that there is a space for deformation or displacement in a direction perpendicular to the optical axis when the optical sheet is held at the optical sheet mounting structure.

14. The optical system of claim 13, wherein the low stress connection structure is a spring plate, one end of the spring plate is connected to the structural region of the optical sheet, the other end of the spring plate is connected to the optical sheet mounting structure, and the plurality of spring plates are symmetrically distributed on the periphery of the structural region of the optical sheet.

15. The optical system of claim 13, wherein the low stress connection structure is foam filled between the structural region of the optical sheet and the optical sheet mounting structure, and a plurality of the foam are symmetrically distributed on a peripheral side of the structural region of the optical sheet.

16. An imaging module comprising the optical system of any one of claims 1-15 and a photosensitive assembly, the photosensitive assembly being located on an image side of the lens assembly.

17. An electronic device comprising the camera module of claim 16.