Compact optical imaging system and lens module

Abstract

The invention discloses a compact optical imaging system and a lens module, the compact optical imaging system comprises a lens group arranged between an object side and an image side, a light-transmitting optical compensation layer is arranged on a light path between the lens group and the image side, the lens group comprises n lenses which are sequentially arranged from the object side to the image side, the n lens and the optical compensation layer have positive diopter and negative diopter respectively, the optical compensation layer is suitable for compensating and adjusting light rays emitted to the image side by the lens group, elements such as a photosensitive chip on the image side are sealed and protected by adding the additional optical compensation layer, and meanwhile, the optical compensation layer is used as a part of optical optimization design, so that the optical efficiency is improved. The aspheric characteristic of the optical compensation layer is utilized to optimize the propagation path of light, so that the total height of the optical imaging system is reduced while the optical imaging quality is ensured.

Description

Technical Field

[0001] The present application relates to the field of optical imaging technology, and in particular to a compact optical imaging system and a lens module. Background Art

[0002] With the increasing popularity and development of mobile phone photography, users are increasingly demanding higher performance from the hardware of their phone lenses. This presents a challenge for the continued development of mobile phone lenses: to improve image quality, the number of lenses within the lens module needs to be increased. However, this results in a more complex and thicker lens module, which protrudes excessively from the phone's back cover, affecting its aesthetics. Therefore, to simplify and thin the lens module design while maintaining image quality, current solutions include the use of high-refractive-index materials, aspheric lenses, and optical design optimization technologies. By combining these methods and designs, a balance is achieved between image quality and design requirements.

[0003] However, existing lens modules have the following defects: the current lens module design, especially the lens module design with a high lens count, has optimized the performance and size to near the extreme through optimization solutions such as high refractive index materials and adding aspheric lenses, and there is relatively little room for further improvement. Summary of the Invention

[0004] One object of the present application is to provide a compact optical imaging system and lens module with a low overall height and small size.

[0005] To achieve the above objectives, the technical solution adopted in this application is: a compact optical imaging system, including a lens group arranged between the object side and the image side, a transparent optical compensation layer is provided on the optical path between the lens group and the image side, the lens group includes n lenses arranged in sequence from the object side to the image side, the nth lens and the optical compensation layer have positive and negative refractive powers respectively, and the optical compensation layer is suitable for compensating and adjusting the light emitted from the lens group to the image side.

[0006] In some embodiments, the dispersion coefficient of the n-th lens is V1, the dispersion coefficient of the optical compensation layer is V2, and the relationship between V1 and V2 satisfies the following formula: 20<V2-V1<60, V2 / V1>2.

[0007] In some embodiments, the parameters of the optical imaging system satisfy: 1≤TTL / ImgH≤1.2, where TTL is the distance from the object side surface of the first lens to the imaging surface of the optical imaging system at the optical axis, 6.12mm≤TTL≤6.18mm, and ImgH is half of the image height corresponding to the maximum field of view of the optical imaging system.

[0008] In some embodiments, the effective focal length f of the optical imaging system and the effective focal length f of the optical compensation layer are (n+1) The relationship between them satisfies the following formula: 4.3 <f (n+1) / f<4.5.

[0009] In some embodiments, the object side of the optical compensation layer has a curvature radius R at the optical axis. (n+1) and the thickness CT of the optical compensation layer at the optical axis (n+1) The relationship between them satisfies the following formula: <R (n+1) / CT (n+1) <310.

[0010] In some embodiments, the combined focal length f of the nth lens and the optical compensation layer is (nn+1) and the combined focal length f of the first and second lenses (12) The relationship between them satisfies the following formula: -0.65 <f (nn+1) / f (12) <0.

[0011] In some embodiments, the relationship between the optical compensation layer and the lenses in the lens group satisfies the following formula:

[0012] 1.5<(SD (n+1) -SD n ) / (SD n -SD (n-1) )<1.8

[0013] Among them, SD (n+1) SD is the maximum effective semi-aperture of the image side of the optical compensation layer. n SD is the maximum effective semi-aperture of the image side of the nth lens. (n-1) It is the maximum effective semi-aperture of the image side of the n-1 lens.

[0014] In some embodiments, the maximum effective semi-aperture SD of the image side of the optical compensation layer is (n+1) and the thickness CT of the optical compensation layer at the optical axis (n+1) The relationship between satisfies the following formula: 88≤SD (n+1) / CT (n+1) ≤101.

[0015] In some embodiments, the thickness of the optical compensation layer is less than a field curvature value of a field outside a corrected field of view of the optical imaging system.

[0016] In some embodiments, a flatness error of the optical compensation layer is smaller than a field curvature value of a field outside a correction field of view of the optical imaging system.

[0017] In some embodiments, an aperture is provided on the lens group, and the aperture is located in the front or middle of the lens group. The first lens has positive refractive power, and the object side surface of the first lens is convex at the near optical axis. The nth lens has negative refractive power, and the object side surface of the nth lens is concave at the near optical axis. The image side surface of the nth lens is concave at the near optical axis. The optical compensation layer has positive refractive power, and the object side surface of the optical compensation layer is convex at the near optical axis.

[0018] A lens module comprises a photosensitive chip and any of the above-mentioned optical imaging systems, wherein the photosensitive chip is arranged on the image side of the optical imaging system, the optical compensation layer is located between the lens group and the photosensitive chip, and the optical compensation layer is suitable for adjusting the light emitted from the lens group to the photosensitive chip. A gap is set between the optical compensation layer and the photosensitive chip, or the optical compensation layer is attached to the photosensitive chip.

[0019] In some embodiments, the upper surface of the optical compensation layer is flat, the optical compensation layer is suitable for forming by embossing using the upper surface as a base surface, and the lower surface of the optical compensation layer is suitable for directly attaching to the photosensitive chip.

[0020] In some embodiments, a color filter is provided between the optical imaging system and the photosensitive chip, the gap between the optical compensation layer and the photosensitive chip is d1, the gap between the color filter and the photosensitive chip is d2, and 0<d1<d2.

[0021] In some embodiments, the optical compensation layer is located between the color filter and the photosensitive chip, the thickness of the optical compensation layer is t1, the gap between the color filter and the photosensitive chip is d2, and 0<t1<d2.

[0022] In some embodiments, the relative tilt angle between the optical compensation layer and the photosensitive chip is smaller than the tilt value of the field of view outside the correction field of view of the optical imaging system.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The optical imaging system of the present application sets an aspherical optical compensation layer on the image plane as part of the optical imaging system design, and optimizes the propagation path of light by utilizing the optical performance obtained by the material of the optical compensation layer being different from that of the lens group, as well as the aspherical characteristics of the optical compensation layer itself, thereby breaking through the performance limitations of the lens group. While ensuring the quality of optical imaging, it can reduce the overall height of the optical imaging system and achieve a smaller size design.

[0025] 2. The lens module of the present application is equipped with an optical compensation layer between the lens group and the photosensitive chip. The optical compensation layer can provide dust-proof sealing and anti-slip protection for the photosensitive chip, thereby improving the stability of the lens. In addition, by setting the combination method between the optical compensation layer and the photosensitive chip, the lens size can be further reduced while achieving higher manufacturing precision, thereby reducing the loss of imaging accuracy caused by assembly errors between different components during the assembly process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram showing the principle of correction of spherical aberration by an optical compensation layer according to a preferred embodiment of the present application.

[0027] Figure 2 It is a layout diagram of an optical imaging system according to a preferred embodiment of the present application.

[0028] Figure 3 1 is a distortion and astigmatism curve diagram according to a preferred embodiment of the present application.

[0029] Figure 4 is a diffraction MTF curve diagram according to a preferred embodiment of the present application.

[0030] Figure 5 is a layout diagram of an optical imaging system according to another preferred embodiment of the present application.

[0031] Figure 6 is a distortion and astigmatism curve diagram according to another preferred embodiment of the present application.

[0032] Figure 7 is a diffraction MTF curve diagram according to another preferred embodiment of the present application.

[0033] Figure 8 It is a structural schematic diagram of a lens module according to a preferred embodiment of the present application.

[0034] Figure 9 This is an adjustment view of the gap setting between the optical compensation layer and the photosensitive chip according to a preferred embodiment of the present application.

[0035] Figure 10 This is an adjustment diagram of an optical compensation layer attached to a photosensitive chip according to a preferred embodiment of the present application.

[0036] Figure 11 It is a field of view orientation diagram according to a preferred embodiment of the present application.

[0037] Figure 12 This is an optical defocus curve diagram according to a preferred embodiment of the present application.

[0038] In the figure: 1. Lens group; 2. Optical compensation layer; 3. Photosensitive chip; 4. Aperture; 5. Color filter. DETAILED DESCRIPTION

[0039] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0040] In the description of this application, it should be noted that for directional words, such as the terms "center", "horizontal", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and so on, the directions and positional relationships indicated are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of this application.

[0041] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0042] The terms "comprises" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, product or apparatus.

[0043] The present application will be further described below with reference to the accompanying drawings:

[0044] like Figures 1 to 12As shown, the present application provides a compact optical imaging system, including a lens group 1 arranged between the object side and the image side, a transparent optical compensation layer 2 is provided on the optical path between the lens group 1 and the image side, the lens group 1 includes n lenses arranged in sequence from the object side to the image side (from the object side to the image side, the arrangement order is first lens, second lens...n-1th lens, nth lens), the nth lens and the optical compensation layer 2 can be combined into positive and negative lens groups through different focal lengths, thereby constituting an optical compensation lens as a whole, the nth lens and the optical compensation layer 2 have positive and negative refractive power, respectively, which can be specifically divided into two cases, namely, when the nth lens has a positive refractive power, the optical compensation layer 2 has a negative refractive power, and when the nth lens has a negative refractive power, the optical compensation layer 2 has a positive refractive power. The selection and design can be made according to the actual needs of the optical imaging system.

[0045] It is understandable that when lens group 1 forms an image, the light emitted from the nth lens will produce spherical aberration. Spherical aberration is caused by the different electromagnetic wave converging abilities of the central area and the edge area of ​​the electromagnetic lens. The far-axis electromagnetic wave is refracted much more strongly than the near-axis electromagnetic wave when passing through the lens. Therefore, the electromagnetic waves scattered by the same object point do not intersect at one point after passing through the lens, but become a diffuse circular spot on the lens phase plane. Spherical aberration is the most important factor limiting the resolving power of the lens. Due to the existence of spherical aberration, the focus on the image plane is easily affected by the spherical surface. The image plane is a relatively complex curved surface or free-form surface. This defect makes optical spherical aberration visible everywhere in the optical system.

[0046] When the object distance L of an on-axis object point is determined, the position of its image point L' is a function of the aperture angle U (or h). The difference between the position of the actual image point and the ideal image point is called spherical aberration. Spherical aberration is also called spherical aberration. The light beam emitted by the on-axis object point, after passing through the optical system, intersects the optical axis at different positions with the light rays at different angles to the optical axis. Therefore, a circular diffuse spot is formed on the image plane. This is spherical aberration, which is generally measured by the axial distance between the intersection of the actual light ray and the optical axis on the image side and the intersection of the paraxial light ray and the optical axis (i.e., the Gaussian image point).

[0047] For monochromatic light, spherical aberration is the only aberration that exists when imaging an on-axis point. When imaging an off-axis point, there are many types of aberrations, and spherical aberration is only one of them. Except for special cases, a single spherical lens cannot generally correct spherical aberration. Positive lenses produce negative spherical aberration, and negative lenses produce positive spherical aberration. For an object point at a certain position, when the aperture and focal length of the lens are kept unchanged, the size of the spherical aberration varies with the shape of the lens. Therefore, a double lens group or a double cemented lens group composed of positive and negative lenses of appropriate shapes is a structure that can eliminate spherical aberration. Keeping the focal length of the lens unchanged and changing the lens shape is like bending a soft object, so it is called the overall curvature of the lens.

[0048] like Figure 1 In the embodiment shown, the optical compensation layer 2 is suitable for compensating and adjusting the light emitted from the lens group 1 to the image side. The figure illustrates a situation in which chromatic aberration occurs in an optical imaging system. The lines in the figure can respectively represent the three colors R, G, and B. When chromatic aberration occurs, the optical compensation layer 2 can compensate for the light emitted from the lens group 1 to make the image clearer. The optical performance obtained by the optical imaging system through the combination of the optical compensation layer 2 and the lens group 1 can optimize the imaging performance of the lens group 1, break through the performance upper limit of the lens group 1 due to its own material limitations, thereby increasing the performance upper limit of the optical imaging system, and can achieve the purposes of improving the imaging effect and reducing the system size.

[0049] In some embodiments, the optical compensation layer 2 is made of a glue material with high light transmittance, which ensures light transmission while providing vibration reduction, dust prevention, and scratch resistance.

[0050] In some embodiments, the dispersion coefficient of the n-th lens is V1, the dispersion coefficient of the optical compensation layer 2 is V2, and the relationship between V1 and V2 satisfies the following formula: 20<V2-V1<60, V2 / V1>2.

[0051] In some embodiments, the lens assembly 1 is generally a cemented lens assembly, such as a double cemented lens assembly or a double separated lens assembly with a small air gap, if:

[0052]

[0053]

[0054] Where, φ represents the optical power and V represents the dispersion;

[0055] From this we can solve that if the primary chromatic aberration can be eliminated, we can get:

[0056]

[0057]

[0058] From the above formula, we can see that a doublet or doublet lens system with a certain optical power can only be achromatized by using a combination of positive and negative lenses made of two different glass pieces. To minimize the optical power of the two lenses, the difference in the Abbe constants of the two glasses should be as large as possible. Typically, a combination of optical crown and flint is used. In this application, the refractive index can be used as the boundary for differentiation. For example:

[0059] Crown glasses: small dispersion, Ve<55,

[0060] Flint glasses: large dispersion, Ve>55,

[0061] If the primary chromatic aberration of the achromatic double lens is to be zero, which is equivalent to the Abbe number V being infinite, that is, the close-contact double lens and the double-cemented lens can be equivalent to a lens with an infinite Abbe number (equivalent to the material being dispersion-free). In fact, such an equivalent glass material does not exist. In this application, the dispersion coefficient of the optical compensation layer 2 is within 60 of the dispersion coefficient of the last lens, so as to meet the requirements that the crown glass is selected from Lak material, PSK material, PK material, BK material, SK material, BaK material, TiK material and equivalent materials, and the flint glass is selected from BaF material, BaLF material, BaSF material, LLF material, KF material, KzF material, LaF material, LaSF material, LF material, SF material, TiF material, TiSF material, KzFS material and equivalent materials.

[0062] Among general materials, the material with a larger dispersion coefficient usually has a dispersion coefficient of 55 to 85, while the material with a smaller dispersion coefficient has a dispersion coefficient of 20 to 55. Generally speaking, the dispersion coefficient of the optical compensation layer 2 differs from the dispersion coefficient of the last lens by about 20 to 60, which enables the optical compensation layer 2 to meet the compensation adjustment conditions for most glasses.

[0063] In simple terms, the present application uses an optical compensation layer 2 made of a material having a significantly different dispersion coefficient from that of the lens in the lens group 1. The positive and negative lens combination formed by the optical compensation layer 2 and the nth lens can effectively eliminate chromatic aberration. In the present application, the nth lens in the lens acts as a compensation lens combination working together with the optical compensation layer 2. In order to prevent the optical focal length of the nth lens from being too large, the difference in dispersion coefficients between the two materials used to make the optical compensation layer 2 and the nth lens should be as large as possible.

[0064] In some embodiments, to ensure that the nth lens can cooperate with the optical compensation layer 2 to form a compensation lens combination, the nth lens can be made of a material such as an equivalent combination of crown glass and flint glass.

[0065] From another perspective, the dispersion coefficient of the optical compensation layer 2 in the present application is more than twice that of the dispersion coefficient of the last lens. In this case, the compensation lens combination composed of the last lens in the lens combination and the optical compensation layer 2 can allocate a larger optical focal length to the original lens to realize that both lenses are used to bear the optical focal length. As a result, when the number of lens lenses is increased, the last lens in the compensation lens combination can still have a thinner thickness, thereby reducing the overall thickness of the lens. This can also reduce the overall height of the lens to a certain extent, thereby reducing the overall height of the camera module.

[0066] In some embodiments, the parameters of the optical imaging system satisfy: 1≤TTL / ImgH≤1.2, where TTL is the distance from the object side surface of the first lens to the imaging surface of the optical imaging system at the optical axis, 6.12mm≤TTL≤6.18mm, and ImgH is half of the image height corresponding to the maximum field of view of the optical imaging system.

[0067] In some embodiments, the parameters of the optical imaging system of the present application also meet the following requirements: a large field of view greater than 80°, FNO=1, and EFL=5.4 mm.

[0068] In some embodiments, the effective focal length f of the optical imaging system and the effective focal length f of the optical compensation layer 2 are (n+1) The relationship between them satisfies the following formula: 4.3 <f (n+1) / f<4.5. When the above conditional expression is met, the optical power proportion of the optical compensation layer 2 in the system can be reasonably configured, which is beneficial for the optical compensation layer 2 to contribute appropriate positive refractive power to the entire optical imaging system, thereby facilitating shortening the size of the optical imaging system.

[0069] In some embodiments, the curvature radius R of the object side of the optical compensation layer 2 at the optical axis is (n+1) and the thickness CT of the optical compensation layer 2 at the optical axis (n+1) The relationship between them satisfies the following formula: <R (n+1) / CT (n+1) <310, when the above conditional expression is satisfied, the optical compensation layer 2 can effectively shorten the total length of the optical imaging system, thereby realizing a miniaturized design of the optical imaging system.

[0070] In some embodiments, the combined focal length f of the nth lens and the optical compensation layer 2 is (nn+1) and the combined focal length f of the first and second lenses (12) The relationship between them satisfies the following formula: -0.65 <f (nn+1) / f (12)<0, when the above conditional expression is met, the refractive power contributions of the front (first lens end) and rear (nth lens end) lenses of the optical imaging system can be reasonably configured, which is beneficial to correcting aberrations such as field curvature and distortion, thereby improving the imaging quality of the optical imaging system, and is also beneficial to shortening the overall length of the system and realizing a miniaturized design.

[0071] In some embodiments, the relationship between the optical compensation layer 2 and the lenses in the lens group 1 satisfies the following formula:

[0072] 1.5<(SD (n+1) -SD n ) / (SD n -SD (n-1) )<1.8

[0073] Among them, SD (n+1) SD is the maximum effective semi-aperture of the image side of the optical compensation layer 2. n SD is the maximum effective semi-aperture of the image side of the nth lens. (n-1) It is the maximum effective semi-aperture of the image side of the n-1 lens.

[0074] When the above conditional formula is met, the step difference between the n-1th lens, the nth lens and the optical compensation layer 2 can be reasonably configured, which is conducive to the light having a uniform and gentle turning angle in the n-1th lens, the nth lens and the optical compensation layer 2, thereby avoiding serious aberration caused by excessive light deflection angle. At the same time, it is also conducive to the effective transition of light to the imaging surface, thereby improving the relative illumination of the optical imaging system.

[0075] In some embodiments, the maximum effective semi-aperture SD of the image-side surface of the optical compensation layer 2 is (n+1) and the thickness CT of the optical compensation layer 2 at the optical axis (n+1) The relationship between satisfies the following formula: 88≤SD (n+1) / CT (n+1) ≤101. When the above conditions are met, it is beneficial for the optical compensation layer 2 to effectively transmit light to the imaging surface for imaging, thereby facilitating the expansion of the imaging surface size of the optical imaging system and shortening the total length of the optical imaging system.

[0076] In some embodiments, the thickness of the optical compensation layer 2 is less than the field curvature value of the field outside the corrected field of view of the optical imaging system (for example, the corrected field of view is 0.5, and the field outside the corrected field of view may be 0.8), indicating that the optical compensation layer 2 can at least optimize the field curvature value of the inner field of view. In addition, considering that there may be a flat plate offset phenomenon at the optical compensation layer 2, it is necessary to consider the actual ability of the optical compensation layer 2 and the trade-off between the larger factors in the lens module. Generally speaking, it is necessary to give up optimizing certain extreme optical errors in the outer field of view and give priority to ensuring the optical error of the inner field of view.

[0077] In some embodiments, the flatness error of the optical compensation layer 2 is smaller than the field curvature value of the field outside the corrected field of view of the optical imaging system (for example, the corrected field of view is 0.5, and the field outside the corrected field of view may be 0.8), indicating that the optical compensation layer 2 can at least optimize the field curvature value of the inner field of view. In addition, considering that there may be a flat plate offset phenomenon at the optical compensation layer 2, it is necessary to consider the actual capability of the optical compensation layer 2 and the trade-off between the larger factors in the lens module. Generally speaking, it is necessary to give up optimizing certain extreme optical errors in the outer field of view and give priority to ensuring the optical error of the inner field of view. The error of the optical compensation layer 2 itself needs to ensure a certain degree of accuracy.

[0078] In such Figure 1 In the illustrated embodiment, an aperture 4 is provided on the lens group 1, and the aperture 4 is located in the front or middle portion of the lens group 1. The first lens has positive refractive power, and the object side surface of the first lens is convex at the near optical axis. The nth lens has negative refractive power, and the object side surface of the nth lens is concave at the near optical axis. The image side surface of the nth lens is concave at the near optical axis. The optical compensation layer 2 has positive refractive power, and the object side surface of the optical compensation layer 2 is convex at the near optical axis.

[0079] Through the surface structure of the first lens and the nth lens and the position of the aperture 4, it can be determined that when the light passes through the aperture 4 and the lens group 1, it will be converged in the lens group 1 and then diffused, so that the optical imaging system presents a structure with a small front and a large rear. In this type of optical presentation system, when there are a large number of lenses in the lens group 1, especially in the case of a large image surface, the degree of diffusion of the light through the nth lens tends to be greater, which will make the astigmatism caused by closer light more serious. However, if a combination of positive and negative lenses can be set at the rear of the lens group 1, the negative spherical aberration of the positive lens, or the positive spherical aberration of the negative lens can be satisfied, thereby reducing the overall spherical aberration of the optical imaging system, so as to improve the imaging performance of the optical imaging system, and finally converge the light to the image surface and image more clearly.

[0080] Specifically, when the number of lenses in the lens group 1 is 7: the first lens has positive refractive power, the object side surface of the first lens is convex at the near optical axis, and the image side surface of the first lens is concave at the near optical axis, which can effectively converge the light incident on the optical imaging system, thereby helping to shorten the total length of the system and promote the realization of miniaturized design; the second lens has negative refractive power, the object side surface of the second lens is convex at the near optical axis, and the image side surface of the second lens is concave at the near optical axis, which is beneficial to balancing the spherical aberration, chromatic aberration and other aberrations generated by the first lens, thereby helping to improve the imaging quality of the system; the third lens has negative refractive power, the object side surface of the third lens is convex at the near optical axis, and the image side surface of the third lens is concave at the near optical axis, which is beneficial to correct the aberrations generated by the first lens and the second lens, and further improve the imaging quality of the system; the fourth lens has positive refractive power, the object side surface of the fourth lens is convex at the near optical axis, and the image surface of the fourth lens is convex at the near optical axis. The fifth lens has a negative refractive power, the object side surface of the fifth lens is convex at the near optical axis, and the image side surface of the fifth lens is concave at the near optical axis, which is conducive to correcting the aberrations produced by the previous four lenses; the sixth lens has a positive refractive power, the object side surface of the sixth lens is convex at the near optical axis, and the image side surface of the sixth lens is concave at the near optical axis. The convex-concave surface of the sixth lens at the near optical axis is conducive to further converging light, thereby shortening the back focal length and total length of the system; the seventh lens has a negative refractive power, the object side surface of the seventh lens is concave at the near optical axis, and the image side surface of the seventh lens is concave at the near optical axis. The concave-concave surface of the seventh lens at the near optical axis can effectively transmit light to the image side surface of the optical compensation layer 2. The image-side surface of the optical compensation layer 2 has positive refractive power, and the object-side surface of the optical compensation layer 2 is convex near the optical axis.

[0081] like Figures 2 to 4 As shown, Example 1 is specifically shown. The aspheric coefficients of the object side and image side of each lens in the optical imaging system are shown in Table 1-1 and Table 1-2.

[0082] In Table 1-1, surface number 2 represents the object side surface of the first lens, surface number 3 represents the image side surface of the first lens, and so on. Surface number 18 represents the object side surface of the optical compensation layer 2.

[0083] The surface numbers K-A20 in Table 1-2 represent the types of aspheric coefficients, where K represents the conic coefficient, A4 represents the quartic aspheric coefficient, A6 represents the sextic aspheric coefficient, A8 represents the octadecane aspheric coefficient, and so on.

[0084] Except for the object side surface of the optical compensation layer 2 with serial number 18, which has a twelve-order aspheric coefficient, the aspheric coefficients of the remaining lenses are all up to twenty-order aspheric coefficients, which is conducive to reducing the difficulty of aspheric processing of the glue surface.

[0085] In addition, the aspheric coefficient formula is as follows:

[0086]

[0087] Where z is the sag of the surface; r is the radial radius; a1 to a7 are the coefficients of the even-order terms r2 to r14 respectively; k is the cone coefficient; and c is the radius of curvature.

[0088] like Figure 2 In the illustrated embodiment, according to the 2D layout diagram of the optical imaging system, it can be seen that the aperture 4 is located in front of the lens group 1. Specifically, the aperture 4 is located at the first lens close to the object side.

[0089] like Figure 3 In the illustrated embodiment, graph ( a1 ) and graph ( b1 ) in the figure respectively represent a distortion curve graph and an astigmatism curve graph in the optical imaging system.

[0090] The distortion curve (a1) shows the distortion values ​​corresponding to different field of view angles. The horizontal axis represents the distortion value in %, and the vertical axis represents the field of view angle in degrees. As can be seen from the figure, the image deformation caused by the main beam is small, and the imaging quality of the system is excellent.

[0091] The abscissa of the astigmatism curve graph (b1) represents focus shift, and the ordinate represents the field angle, both in degrees. The solid line in the astigmatism curve graph represents sagittal field curvature, and the dashed line represents meridional field curvature. As can be seen from graph (b1), the optical system has a small field curvature. Both the field curvature and astigmatism are well corrected for each field of view, resulting in clear imaging at the center and edges of the field of view.

[0092] like Figure 4 In the embodiment shown, a diffraction MTF curve is displayed, where the horizontal axis represents the distance of the image plane offset forward and backward, and the vertical axis represents the MTF value. The curve shows that the optical imaging system has good imaging quality. At the test frequency of 140lp / mm, the astigmatism and field curvature are small (within 25μm) and the peak value is high.

[0093] like Figures 5 to 7As shown, Example 1 is specifically illustrated, and the aspheric coefficients of the object side and image side of each lens in the optical imaging system are shown in Table 2-1 and Table 2-2.

[0094] In Table 2-1, surface number 2 represents the object side surface of the first lens, surface number 3 represents the image side surface of the first lens, and so on. Surface number 18 represents the object side surface of the optical compensation layer 2.

[0095] The surface numbers K-A20 in Table 2-2 represent the types of aspheric coefficients, where K represents the conic coefficient, A4 represents the fourth-order aspheric coefficient, A6 represents the sixth-order aspheric coefficient, A8 represents the eighth-order aspheric coefficient, and so on.

[0096] Except for the object side surface of the optical compensation layer 2 with serial number 18, which has a twelve-order aspheric coefficient, the aspheric coefficients of the remaining lenses are all up to twenty-order aspheric coefficients, which is conducive to reducing the difficulty of aspheric processing of the glue surface.

[0097] like Figure 2 In the illustrated embodiment, according to the 2D layout diagram of the optical imaging system, it can be seen that the aperture 4 is located in front of the lens group 1. Specifically, the aperture 4 is located at the first lens close to the object side.

[0098] like Figure 3 In the illustrated embodiment, graph (a2) and graph (b2) in the figure respectively represent a distortion curve graph and an astigmatism curve graph in the optical imaging system.

[0099] The distortion curve (a2) shows the distortion values ​​corresponding to different field of view angles. The horizontal axis represents the distortion value in %, and the vertical axis represents the field of view angle in degrees. As can be seen from the figure, the image deformation caused by the main beam is small, and the imaging quality of the system is excellent.

[0100] The abscissa of the astigmatism curve graph (b2) represents focus shift, and the ordinate represents the field angle, both in degrees. The solid line in the astigmatism curve graph represents sagittal field curvature, and the dashed line represents meridional field curvature. As can be seen from graph (b2), the optical system has minimal field curvature, and both field curvature and astigmatism are well corrected for each field of view, resulting in clear imaging at the center and edges of the field of view.

[0101] like Figure 4In the embodiment shown, a diffraction MTF curve is displayed, where the horizontal axis represents the distance of the image plane offset forward and backward, and the vertical axis represents the MTF value. The curve shows that the optical imaging system has good imaging quality, small astigmatism and field curvature, and a high peak value.

[0102] like Figures 8 to 12 In the embodiment shown, the present application provides a lens module, including a photosensitive chip 3 and an optical imaging system of any of the above embodiments, the photosensitive chip 3 is arranged on the image side of the optical imaging system, the optical compensation layer 2 is located between the lens group 1 and the photosensitive chip 3, the optical compensation layer 2 is suitable for adjusting the light emitted from the lens group 1 to the photosensitive chip 3, a gap is set between the optical compensation layer 2 and the photosensitive chip 3, or the optical compensation layer 2 is attached to the photosensitive chip 3.

[0103] In some embodiments, a color filter 5 is arranged between the optical imaging system and the photosensitive chip 3, the gap between the optical compensation layer 2 and the photosensitive chip 3 is d1, and the gap between the color filter 5 and the photosensitive chip 3 is d2, 0<d1<d2, indicating that the optical compensation layer 2 and the photosensitive chip 3 of the present application are relatively tightly attached, reducing the error caused by the assembly of the color filter 5.

[0104] In some embodiments, the optical compensation layer 2 is located between the color filter 5 and the photosensitive chip 3, the thickness of the optical compensation layer 2 is t1, and the gap between the color filter 5 and the photosensitive chip 3 is d2, 0<t1<d2, indicating that the optical compensation layer 2 is a more sophisticated element than the color filter 5, which allows the optical compensation layer 2 to be assembled between the photosensitive chip 3 and the color filter 5.

[0105] like Figure 9 In the embodiment shown, a scheme for setting the gap between the optical compensation layer 2 and the photosensitive chip 3 is demonstrated. When chromatic aberration occurs in the optical imaging system and the optical compensation layer 2 is used to compensate for the light emitted by the lens group 1, attention must be paid to the gaps between the optical compensation layer 2 and the lens group 1 and between the optical compensation layer 2 and the photosensitive chip 3. Incorrectness in the gaps between the optical compensation layer 2 and the lens group 1 and the photosensitive chip 3 will affect the compensation effect, making it impossible to achieve optimal imaging quality. Therefore, there are two variables. When designing, producing and assembling the lens, the accuracy of the two variables must be considered at the same time to ensure the imaging effect. When the overall light performance of the lens needs to be adjusted, it is only necessary to adjust the gap between the optical compensation layer 2 and the lens group 1.

[0106] In some embodiments, the optical compensation layer 2 is positioned and fixed by a lens holder of the lens module.

[0107] like Figure 10In the embodiment shown, a solution for attaching the optical compensation layer 2 to the photosensitive chip 3 is demonstrated. In this solution, the optical compensation layer 2 is directly attached to the imaging surface of the photosensitive chip 3, and the two are in direct contact. At this time, the variable affecting the optical compensation effect of the optical compensation layer 2 is mainly the gap between the optical compensation layer 2 and the lens group 1. The reduction in the number of variables can greatly reduce the requirements for lens design, production and assembly.

[0108] When the optical compensation layer 2 is arranged close to the photosensitive chip 3, the back focus part of the optical compensation layer 2 serves as the light emitting end, and the photosensitive chip 3 can be considered to have a certain optical length with the optical compensation layer 2, so that the photosensitive chip 3 can use the light emitted after the optical compensation layer 2 is in close contact as the receiving end. When they are in close contact, there is basically no assembly tolerance between the optical compensation layer 2 and the photosensitive chip 3, so that the light emitted by the optical compensation layer 2 will not have optical defects such as spherical aberration, coma, etc. caused by optical path tolerance due to the gap error with the photosensitive chip 3.

[0109] Since the optical compensation layer 2 and the photosensitive chip 3 are in close contact, the angle change of light is generally large, which can produce high-order aberrations. On the contrary, it is difficult to produce corresponding high-order aberrations if it is split into a single lens. Since the primary aberration mainly acts on the paraxial area, and the higher-order aberration has little effect on the paraxial area, but has a great effect on the edge aperture, they act on different aperture bands. The combination of multiple primary aberrations basically cannot replace one higher-order aberration, and it is difficult to replace each other. Therefore, the high-order aberration effect obtained by the close contact between the optical compensation layer 2 and the photosensitive chip 3 is difficult to be replaced by other designs.

[0110] In some embodiments, the bonding surface between the optical compensation layer 2 and the photosensitive chip 3 is a plane. Since the aberration has high precision requirements (possibly μm level), compared with the scheme of segmented assembly with a gap between the optical compensation layer 2 and the photosensitive chip 3, it can reduce the inaccuracy of aberration compensation caused by the relative height error between the optical compensation layer 2 and the photosensitive chip 3 due to assembly, thereby further reducing the aberration.

[0111] like Figure 8 In the embodiment shown, the upper surface of the optical compensation layer 2 is a plane. The optical compensation layer 2 can be formed by embossing and then transferred to the photosensitive chip 3, so that the two can be more closely combined. It can also achieve higher manufacturing accuracy, avoid the loss of accuracy caused by errors between different components during the assembly process, and achieve a more compact design and reduce the size of the lens.

[0112] Since the thickness of the optical compensation layer 2 affects the relative thickness of the photosensitive chip 3 and the color filter 5, and if the optical compensation layer 2 is too far away from the photosensitive chip 3, there will be a problem of spherical focus offset. The optical compensation layer 2 of the present application can be directly attached to the chip, utilizing the space between the IR film and the chip. At the same time, the optical compensation layer 2 also plays a role in deflecting light. After the light is deflected, it can be directly received by the photosensitive chip 3, thereby preventing the problem of light offset again due to the optical path. Compared with the previous optical design, this can shorten the optical path to a certain extent, reducing the phenomenon of light offset again due to the additional increase in the optical path after compensation.

[0113] During stamping, the upper surface of the optical compensation layer 2 can be used as a base surface, and the base surface can be used as a basic surface to improve the processing yield. The stamping method can improve the molding accuracy. Since the aberration has high precision requirements (possibly μm level), compared with the scheme of segmented assembly with a gap between the optical compensation layer 2 and the photosensitive chip 3, the stamping method can reduce the inaccuracy of aberration compensation caused by the relative height error between the optical compensation layer 2 and the photosensitive chip 3 due to assembly, thereby further reducing the aberration.

[0114] After the embossed optical compensation layer 2 is transferred to the photosensitive chip 3, the optical compensation layer 2 and the photosensitive chip 3 can be regarded as an integrated component and calibrated with the lens group 1 of the lens module, thereby reducing the number of components that need to be adjusted for compensation. This method will achieve better optical performance than directly adjusting the three-component structure of the photosensitive chip 3, the optical compensation layer 2, and the lens group 1.

[0115] Another advantage of using embossing is that after the optical compensation layer 2 is embossed, the optical compensation layer 2 can be bonded to the photosensitive chip 3 by setting some adhesive structures on the surface, such as setting an adhesive layer on the periphery of the optical compensation layer 2, and forming a whole. In addition, the optical compensation layer 2 can also use a material with a certain flexibility, such as soft plastic, so that the optical compensation layer 2 can be attached to the photosensitive chip 3 through the adhesive layer, so that the optical compensation layer 2 can have a certain flexible contact with the photosensitive chip 3, so that the optical compensation layer 2 can be set in a manner that is relatively close to the photosensitive chip 3. In this case, because the height required and occupied by the adhesive layer during curing deformation is relatively low, the relative distance between the optical compensation layer 2 and the photosensitive chip 3 can be defaulted to 0.

[0116] In addition, in essence, since the incident angle of the upper edge light between the optical compensation layer 2 and the photosensitive chip 3 is much larger than that of the lower edge light, the nonlinearity of the refraction law means that, in this case, the upper edge light is refracted downward more than the angle it should be deflected by linearly predicting. Therefore, the upper edge light can reduce the positive coma of the light (the comet head is facing the optical axis), which means that the optical compensation layer 2 can also be used to correct the aberration of the asymmetric light of the oblique light beam. Such a situation also exists in the close-contact double lens of the present application (referring to the solution in which the optical compensation layer 2 is closely attached to the photosensitive chip 3). This solution of transferring and attaching the optical compensation layer 2 after printing has the advantage of inherent high assembly precision. Therefore, the solution of using a close-contact double lens can also improve the coma correction capability in optical aberrations.

[0117] like Figure 11 In the embodiment shown, the gap between the optical compensation layer 2 and the photosensitive chip 3 is smaller than the standard tolerance value of the optical imaging system in a specific area (for example, considering the upper left, upper right, lower right, and lower left areas of the captured image) within the correction field of view (which can be a test area specified by the customer, such as 0.3, 0.5, 0.7, 0.8 fields of view, etc.), in the first direction (S direction) and the second direction (T direction), thereby ensuring that the optical compensation value of the optical compensation layer 2 can at least meet the aberration analysis of the specific field of view, such as the effects of field curvature and astigmatism.

[0118] like Figure 12 In the embodiment shown, the gap between the optical compensation layer 2 and the photosensitive chip 3 can also be understood as being smaller than the difference between the optical defocus curves of the optical imaging system in the first direction and the second direction in a specific area within the correction field of view, that is, the difference between the optical defocus curves within the range indicated by the horizontal arrow, thereby ensuring that the optical compensation value of the optical compensation layer 2 can at least meet the aberration analysis of the specific field of view, such as the effects of field curvature and astigmatism.

[0119] In some embodiments, the relative tilt angle between the optical compensation layer 2 and the photosensitive chip 3 is smaller than the tilt value of the field of view outside the corrected field of view of the optical imaging system, indicating that the optical compensation layer 2 can at least optimize the tilt value of the inner field of view. Because if the tilt of the optical compensation layer 2 is too large, it may be impossible to compensate for the inner and outer field values ​​together.

[0120] The above 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. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A compact optical imaging system, characterized in that: The invention comprises a lens group arranged between an object side and an image side, wherein a light-transmitting optical compensation layer is provided on the optical path between the lens group and the image side, the lens group comprises n lenses arranged in sequence from the object side to the image side, the nth lens and the optical compensation layer respectively having a positive refractive power and a negative refractive power, and the optical compensation layer is suitable for compensating and adjusting the light emitted from the lens group toward the image side.

2. The compact optical imaging system according to claim 1, wherein: The dispersion coefficient of the n-th lens is V1, the dispersion coefficient of the optical compensation layer is V2, and the relationship between V1 and V2 satisfies the following formula: 20<V2-V1<60, V2 / V1>2.

3. The compact optical imaging system according to claim 1, wherein: The parameters of the optical imaging system satisfy: 1≤TTL / ImgH≤1.2, where TTL is the distance from the object side surface of the first lens to the imaging surface of the optical imaging system at the optical axis, 6.12mm≤TTL≤6.18mm, and ImgH is half of the image height corresponding to the maximum field of view of the optical imaging system.

4. The compact optical imaging system according to claim 1, wherein: The effective focal length f of the optical imaging system and the effective focal length f of the optical compensation layer (n+1) The relationship between them satisfies the following formula: 4.3 <f (n+1) / f<4.

5.

5. The compact optical imaging system according to claim 1, wherein: The curvature radius R of the object side of the optical compensation layer at the optical axis (n+1) and the thickness CT of the optical compensation layer at the optical axis (n+1) The relationship between them satisfies the following formula: <R (n+1) / CT (n+1) <310.

6. The compact optical imaging system according to claim 1, wherein: The combined focal length f of the nth lens and the optical compensation layer (nn+1) and the combined focal length f of the first and second lenses (12) The relationship between them satisfies the following formula: -0.65 <f (nn+1) / f (12) <0.

7. The compact optical imaging system according to claim 1, wherein: The relationship between the optical compensation layer and the lenses in the lens group satisfies the following formula: 1.5<(SD (n+1) -SD n ) / (SD n -SD (n-1) )<1.8 Among them, SD (n+1) SD is the maximum effective semi-aperture of the image side of the optical compensation layer. n is the maximum effective semi-aperture of the image side of the nth lens, SD (n-1) It is the maximum effective semi-aperture of the image side of the n-1 lens.

8. The compact optical imaging system according to claim 1, wherein: The maximum effective semi-aperture SD of the image side of the optical compensation layer (n+1) and the thickness CT of the optical compensation layer at the optical axis (n+1) The relationship between satisfies the following formula: 88≤SD (n+1) / CT (n+1) ≤101.

9. The compact optical imaging system according to claim 1, wherein: The thickness of the optical compensation layer is smaller than the field curvature value of the field outside the correction field of view of the optical imaging system.

10. The compact optical imaging system according to claim 1, wherein: The flatness error of the optical compensation layer is smaller than the field curvature value of the field outside the correction field of view of the optical imaging system.

11. The compact optical imaging system according to claim 1, wherein: The lens group is provided with an aperture, which is located at the front or middle part of the lens group. The first lens has positive refractive power, and the object side surface of the first lens is convex at the near optical axis. The nth lens has negative refractive power, and the object side surface of the nth lens is concave at the near optical axis. The image side surface of the nth lens is concave at the near optical axis. The optical compensation layer has positive refractive power, and the object side surface of the optical compensation layer is convex at the near optical axis.

12. A lens module, characterized in that: The optical imaging system comprises a photosensitive chip and any one of claims 1 to 11, wherein the photosensitive chip is arranged on the image side of the optical imaging system, the optical compensation layer is located between the lens group and the photosensitive chip, the optical compensation layer is suitable for adjusting the light emitted from the lens group to the photosensitive chip, a gap is set between the optical compensation layer and the photosensitive chip, or the optical compensation layer is attached to the photosensitive chip.

13. The lens module according to claim 12, wherein: The upper surface of the optical compensation layer is a plane, and the optical compensation layer is suitable for being formed by embossing using the upper surface as a base surface, and the lower surface of the optical compensation layer is suitable for being directly attached to the photosensitive chip.

14. The lens module according to claim 12, wherein: A color filter is provided between the optical imaging system and the photosensitive chip. The gap between the optical compensation layer and the photosensitive chip is d1, and the gap between the color filter and the photosensitive chip is d2, where 0<d1<d2.

15. The lens module according to claim 14, wherein: The optical compensation layer is located between the color filter and the photosensitive chip. The thickness of the optical compensation layer is t1. The gap between the color filter and the photosensitive chip is d2, and 0<t1<d2.

16. The lens module according to claim 12, wherein: The relative tilt angle between the optical compensation layer and the photosensitive chip is smaller than the tilt value of the field of view outside the correction field of view of the optical imaging system.

Images