Low refractive power inner focus lens unit and optical system thereof

Abstract

The present disclosure relates to an inner focus lens unit combined with an imaging lens, the inner focus lens unit comprising at least one positive lens group and at least one negative lens group, the imaging lens can be used as an individual lens, the inner focus lens unit provides a focusing function by moving the negative lens group toward the imaging surface when focusing from infinity to a minimum object distance (MOD) to focus on a closer object distance and vice versa, and the inner focus lens unit is disposed within a flange back between the imaging lens and an image sensor surface. The good optical performance of the imaging lens is not substantially affected by disposing the inner focus lens unit within the flange back between the imaging lens and the image sensor surface.

Description

[Technical field]

[0001] This disclosure relates to optical systems, and more particularly, to focusing systems for cameras. [Background technology]

[0002] There are several types of focusing methods that are commonly known and used to focus lenses. Among these methods, two main methods are commonly known to focus telephoto lenses. One of the two methods is the "full extension" type, which moves the entire lens group to focus. In this method, the total length of the lens (TTL) changes. The other method is the "inner focus" type, which moves one or more lens groups inside the lens system to focus without changing the TTL. The "full extension" type is generally used in mobile devices such as mobile phones and tablets due to the advantages of simple structure and good productivity, while the inner focus system is often used in still cameras or video cameras due to the advantages of fixed TTL. On the other hand, the inner focus system requires a more complex mechanical and optical structure, since some of the optical components must be moved inside the lens system, etc. Therefore, mass production becomes more difficult due to the need for more precise manufacturing techniques, as product accuracy increases the impact of optical performance.

[0003] Therefore, there has always been a need for inner focus lenses to be used in mobile devices such as mobile phones and tablets due to the advantages of fixed TTL. However, the introduction of inner focus lenses on mobile devices has been hesitant due to the complexity of assembly and construction.

[0004] In the "full extension" type, since the entire optical components are moved, focusing does not affect the optical performance much, which facilitates mass production. However, these methods are not favorable for miniaturization, especially for telephoto lenses, which generally have a longer stroke of the entire optical components and require a longer focal length compared to wide-angle lenses, because their TTL changes. The focus stroke is correlated with its focal length, and a telephoto lens must extend the lens with a longer focus stroke to focus from infinity (INF) to the minimum object distance (MOD). Therefore, applying the "full extension" type to a small camera for a mobile device is not favorable, especially for a telephoto lens. In addition, the "full extension" type has another problem in that the amount of extension becomes very large when focusing on a subject at a nearby point. In addition, the entire lens system including the focusing device needs to be assembled and inspected, which imposes a problem on mass production.

[0005] For example, the refractive power of the inner focus type lens disclosed in the prior art is too high, and the manufacturing error sensitivity cannot be reduced to improve mass productivity, resulting in a focus stroke that is too long.

[0006] In the case of the "full extension" optical system having an integrated structure disclosed in the prior art, the optical system has better mass productivity, but the TTL changes during focusing, which makes miniaturization difficult, and this is a big problem, especially when focusing on a subject at a nearby point, because the TTL expansion amount is large.

[0007] Therefore, there is a need for an inner focus system for telephoto lenses used in small cameras for mobile devices such as cell phones and tablets, which requires a simple structure and high productivity. There is also a need for an inner focus system with a short MOD, which is difficult to achieve in a compact size with a conventional "full extension" type focus mechanism when used in a mobile device.

[0008] The present invention alleviates and / or eliminates the above mentioned disadvantages. Summary of the Invention [Problem to be solved by the invention]

[0009] The main objective of the focus system of the present disclosure is to provide a low refractive power inner focus lens unit and its optical system to provide fixed TTL, short MOD and high productivity. [Means for solving the problem]

[0010] The low refractive power inner focus lens unit, also called the focus lens unit, according to the present disclosure has a very low refractive power as an entire optical unit and comprises at least one positive lens group and at least one negative lens group, the negative lens group being configured to move toward the imaging surface when focusing from INF to MOD and vice versa. In some cases, the at least one positive lens group of the focus lens unit may also be configured to move toward the object side to compensate for possible aberration disturbances during focusing. It is envisioned that the low refractive power inner focus lens unit according to the present disclosure can be used with an imaging lens, which is the main lens unit of an optical system. The inner focus function is provided to the optical system by inserting the low refractive power inner focus lens unit according to the present disclosure within the flange back between the main imaging lens and the image sensor surface to provide the imaging lens with a focus function while retaining the optical performance of the main imaging lens.

[0011] According to one aspect of the present low refractive power inner focus lens unit, when the magnification of the negative lens group of the focus lens unit, which is configured to move during focusing, is β, the following relationship is satisfied: (i) 0.5≦|1-β 2 |≦3.5, more preferably 0.7≦|1-β 2 |≦3.0

[0012] Satisfying these conditions (i) keeps the amount of focusing stroke small enough to make the optical system compact and prevents the error sensitivity of moving the focus lens unit from becoming too large, which is a disadvantage in manufacturing and mass production.

[0013] According to one aspect of the present low refractive power inner focus lens unit, when the half diagonal length of an image sensor of an optical system used with the present focus lens unit is IMH and the focal length of the focus lens unit is Ff, the following relationship is satisfied. (ii) |Ff| / IMH≧10, more preferably |Ff| / IMH≧17

[0014] Satisfying these conditions (ii) prevents the refractive power of the focusing unit from being unnecessarily large with respect to the sensor size, which would make it unsuitable for miniaturization and would cause reduced sensitivity to manufacturing errors and reduced manufacturability due to its impact on the performance of the main imaging lens.

[0015] According to one aspect of the present low refractive power inner focus lens unit, when the focal length of the combined main imaging lens is Fmain and the focal length of this focus lens unit is Ff, the following relationship is satisfied. (iii) Fmain / Ff ≦0.55, more preferably Fmain / Ff ≦0.4

[0016] Satisfying these conditions (iii) avoids the degradation of manufacturability and mass production that would result from excessively strengthening the refractive power of the focus lens unit and reducing the versatility of this optical system due to a significant change in the performance of the main imaging lens when the focus lens unit is combined with the main imaging lens.

[0017] According to one aspect of the present low refractive power inner focus lens unit, when the maximum optical effective diameter of the lens in the focus lens unit is φmax, and the distance between the opposing lens surfaces between different lens groups of the focus lens unit approaching each other at the INF lens position is Dmin, the following relationship is satisfied. (iv) Dmin / φmax < 0.2, more preferably Dmin / φmax < 0.1

[0018] By satisfying these conditions (iv), the influence of the focus lens unit on the main imaging lens is maintained small enough to maintain the optical performance of the main imaging lens.

[0019] According to one aspect of the present low refractive power inner focus lens unit, the opposing lens surfaces between different lens groups of the focus lens unit approaching each other at the INF lens position have substantially corresponding surface shapes. When the surface shape (SAG amount) of the object-side surface of the opposing lens surfaces is Sob(h) defined by the lens diameter height h, and the surface shape (SAG amount) of the image-side surface of the opposing lens surfaces is Sim(h), they satisfy the following relationship. (v) 0.5 < abs[Sob(h) / Sim(h)] < 2.0, more preferably 0.5 < abs[Sob(h) / Sim(h)] < 1.8, even more preferably 0.6 < abs[Sob(h) / Sim(h)] < 1.7

[0020] According to one aspect of the present low refractive power inner focus lens unit, the radius of the object-side surface of the above-mentioned opposing surface is Rob, and the radius of the image-side surface of the above-mentioned opposing surface is Rim, and they satisfy the following relationship. (vi) 0.5 < Rob / Rim < 2.0

[0021] By satisfying conditions (v) and (vi), the surface shapes of the above-mentioned opposing surfaces are not so different from each other as to approximate them as a single lens unit having low aberration when the two surfaces approach, thus avoiding the difficulty of maintaining the optical specifications of the main imaging lens.

[0022] According to a second aspect, a low refractive power inner focus lens system is provided. The low refractive power inner focus lens system includes the low refractive power inner focus lens unit of the present disclosure and a main imaging lens. Since the low refractive power inner focus lens unit provides a focus function for the main imaging lens, the lens elements of the main imaging lens are fixed without a focusing unit. Furthermore, in the lens performance inspection process, various inspections can be performed using only the main imaging lens apart from the focus lens unit, facilitating manufacturing. Meanwhile, by focusing with this focus lens unit, it is possible to avoid changing the TTL to increase the overall length of the lens. It is possible to adopt an inner focus method in which the overall length does not change and the MOD is short. Furthermore, since the focus lens unit according to the present invention has a very low refractive power, it can have a very small effect on the optical performance of the main imaging lens. Therefore, this can maintain the manufacturing error sensitivity at a very low level, enabling the realization of high manufacturability and mass production.

[0023] According to a third aspect, there is provided a camera comprising a low refractive power inner focus lens system and an image sensor. The low refractive power inner focus lens system is configured to input light used to carry image data to the image sensor, and the image sensor is configured to convert the image into digital image data.

[0024] According to a fourth aspect, a terminal is provided. The terminal, such as a mobile phone and a tablet, comprises at least one camera provided in the third aspect and a graphics processing unit (GPU). The GPU is connected to the camera. The camera is configured to acquire image data and input the image data to the GPU, and the GPU is configured to process the image data received from the camera.

[0025] The present disclosure will now be presented in more detail from the following description, taken in conjunction with the accompanying drawings, which show, for purposes of illustration only, preferred embodiments according to the present disclosure.

[0026] The present disclosure can be better understood from the following detailed description of non-limiting embodiments thereof and by studying the accompanying drawings, in which: [Brief description of the drawings]

[0027] [Figure 1-1] FIG. 2 is a cross-sectional view of an optical lens system according to a first embodiment of the present disclosure in an INF lens position. [Figure 1-2] FIG. 2 is a cross-sectional view of an optical lens system according to a first embodiment of the present disclosure in a MOD lens position. [Figure 1-3] 4A and 4B are diagrams illustrating a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to the first embodiment of the present disclosure. [Figure 1-4] 5A and 5B are diagrams illustrating a comparison of astigmatism aberration between the main imaging lens of the present disclosure according to the first embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 1-5] 5A to 5C are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the first embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 2-1] FIG. 2 is a cross-sectional view of an optical lens system according to a second embodiment of the present disclosure at an infinity lens position. [Figure 2-2] FIG. 13 is a cross-sectional view of an optical lens system according to a second embodiment of the present disclosure in a MOD lens position. [Figure 2-3] FIG. 11 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a second embodiment of the present disclosure. [Figure 2-4] 13A and 13B are diagrams illustrating a comparison of astigmatism aberration between the main imaging lens of the present disclosure according to the second embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 2-5]13A and 13B are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the second embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 3-1] FIG. 13 is a cross-sectional view of an optical lens system according to a third embodiment of the present disclosure at an infinity lens position. [Figure 3-2] FIG. 13 is a cross-sectional view of an optical lens system according to a third embodiment of the present disclosure in the MOD lens position. [Figure 3-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a third embodiment of the present disclosure. [Diagram 3-4] 13A and 13B are diagrams illustrating a comparison of astigmatism aberration between the main imaging lens of the present disclosure according to the third embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 3-5] 13A and 13B are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the third embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 4-1] FIG. 13 is a cross-sectional view of an optical lens system according to a fourth embodiment of the present disclosure at an infinity lens position. [Figure 4-2] FIG. 13 is a cross-sectional view of an optical lens system according to a fourth embodiment of the present disclosure in the MOD lens position. [Figure 4-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a fourth embodiment of the present disclosure. [Figure 4-4] 13A and 13B are diagrams illustrating a comparison of astigmatism aberration between the main imaging lens of the present disclosure according to the fourth embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 4-5] 13A and 13B are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the fourth embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 5-1] FIG. 13 is a cross-sectional view of an optical lens system according to a fifth embodiment of the present disclosure at an infinity lens position. [Figure 5-2]FIG. 13 is a cross-sectional view of an optical lens system according to a fifth embodiment of the present disclosure in the MOD lens position. [Figure 5-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a fifth embodiment of the present disclosure. [Figure 5-4] 13A and 13B are diagrams illustrating a comparison of astigmatism aberration between a main imaging lens of the present disclosure according to a fifth embodiment and a combination of a main imaging lens and a focus lens unit. [Figure 5-5] 13A and 13B are diagrams illustrating a comparison of distortion between a main imaging lens of the present disclosure according to a fifth embodiment and a combination of a main imaging lens and a focus lens unit. [Figure 6-1] FIG. 13 is a cross-sectional view of an optical lens system according to a sixth embodiment of the present disclosure at an infinity lens position. [Figure 6-2] FIG. 13 is a cross-sectional view of an optical lens system according to a sixth embodiment of the present disclosure in the MOD lens position. [Figure 6-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a sixth embodiment of the present disclosure. [Figure 6-4] FIG. 13 is a diagram showing a comparison of astigmatism aberration between the main imaging lens of the present disclosure and a combination of the main imaging lens and a focus lens unit according to the sixth embodiment. [Figure 6-5] 13A to 13C are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the sixth embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 7-1] FIG. 13 is a cross-sectional view of an optical lens system according to a seventh embodiment of the present disclosure at an infinity lens position. [Figure 7-2] FIG. 13 is a cross-sectional view of an optical lens system according to a seventh embodiment of the present disclosure in the MOD lens position. [Figure 7-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a seventh embodiment of the present disclosure. [Figure 7-4]FIG. 13 is a diagram showing a comparison of astigmatism aberration between the main imaging lens of the present disclosure and a combination of the main imaging lens and a focus lens unit according to the seventh embodiment. [Figure 7-5] 13A to 13C are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the seventh embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 8-1] FIG. 13 is a cross-sectional view of an optical lens system according to an eighth embodiment of the present disclosure at an infinity lens position. [Figure 8-2] FIG. 13 is a cross-sectional view of an optical lens system according to an eighth embodiment of the present disclosure in the MOD lens position. [Figure 8-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to an eighth embodiment of the present disclosure. [Figure 8-4] FIG. 23 is a diagram showing a comparison of astigmatism aberration between the main imaging lens of the present disclosure and a combination of the main imaging lens and a focus lens unit according to the eighth embodiment. [Figure 8-5] 13A to 13C are diagrams illustrating a comparison of distortion between the main imaging lens of the present disclosure according to the eighth embodiment and a combination of the main imaging lens and a focus lens unit. [Figure 9-1] FIG. 13 is a cross-sectional view of an optical lens system according to a ninth embodiment of the present disclosure at an infinity lens position. [Figure 9-2] FIG. 13 is a cross-sectional view of an optical lens system according to a ninth embodiment of the present disclosure in the MOD lens position. [Figure 9-3] FIG. 13 is a diagram showing a comparison of spherical aberration of a main imaging lens and a combination of a main imaging lens and a focus lens unit according to a ninth embodiment of the present disclosure. [Figure 9-4] FIG. 13 is a diagram showing a comparison of astigmatism aberration between the main imaging lens of the present disclosure and a combination of the main imaging lens and a focus lens unit according to the ninth embodiment. [Figure 9-5] 13A and 13B are diagrams illustrating a comparison of distortion between a main imaging lens of the present disclosure according to a ninth embodiment and a combination of a main imaging lens and a focus lens unit. [Figure 10]FIG. 1 illustrates an implementation of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The following embodiments of the low refractive power inner focus lens system of the present disclosure are described with reference to figures and optical data. This lens system can be applied to small cameras for mobile devices such as mobile phones and tablets. In addition, the present optical system includes a main imaging lens and a focus lens unit. The following embodiments are described as a combination of the main imaging lens, which has good optical performance by itself, and the focus lens unit of the present disclosure. However, the focusing unit can be used with various common main imaging lenses, because the focusing unit has a very low refractive power and does not affect the optical performance of the main imaging lens when the focusing unit is inserted into the flange back between the main imaging lens and the image sensor surface to provide the main imaging lens with a focus function.

[0029] Therefore, the main lens unit and the focus lens unit can be inspected separately to improve productivity. The low refractive power inner focus lens system makes it easier for academic designers to select or design the main imaging lens.

[0030] The low refractive power inner focus lens system also achieves a short minimum object distance (MOD) and a fixed layer track length (TTL), features that are particularly suitable for telephoto lenses used in small cameras for mobile devices such as cell phones and tablets.

[0031] First embodiment FIG. 1-1 shows a cross-sectional view of an optical lens system according to a first embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, and ML4, and the focus lens unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is made up of FL1, and the second negative lens group is made up of FL2 and FL3.

[0032] 1-2 shows a cross-sectional view of an optical lens system according to a first embodiment of the present disclosure in the MOD lens position, where opposing lens surfaces between FL1 and FL2 have substantially corresponding surface shapes.

[0033] 1-1 and 1-2 show that only the lens elements FL2 and FL3 of the focus lens unit are moved together toward the image side to focus on a closer object distance and toward the object side to focus on a farther object distance, so the focus mechanism can be designed more easily.

[0034] Table 1-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and clear diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the first embodiment. The term "stop" refers to the iris surface.

[0035] [Table 1]

[0036] Table 1-2 shows the aspheric coefficients of the optical surfaces of the low refractive inner focus lens system, where the numbers 2, 4, ..., 10 represent higher order aspheric coefficients. The equation of the aspheric profile is expressed as follows:

number

[0037] 1-3 show a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the first embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0038] 1-4 show a comparison of the astigmatism of the main imaging lens of the present disclosure according to the first embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0039] 1-5 show a comparison of distortion of the main imaging lens of the present disclosure according to the first embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by the addition of the focus lens unit.

[0040] Second embodiment FIG. 2-1 shows a cross-sectional view of an optical lens system according to a second embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, ML4, and ML5, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is composed of FL1 and FL2, and the second negative lens group is composed of FL3.

[0041] FIG. 2-2 shows a cross-sectional view of an optical lens system according to a second embodiment of the present disclosure in the MOD lens position. Opposing lens surfaces between FL2 and FL3 have substantially corresponding surface shapes.

[0042] 2-1 and 2-2 show that only the lens element FL3 of the focus lens unit is moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0043] Table 2-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the second embodiment.

[0044] [Table 3]

[0045] Table 2-2 shows the aspheric coefficients of the optical surfaces of the low refractive inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0046] [Table 4]

[0047] 2-3 show a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the second embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0048] 2-4 show a comparison of the astigmatism of the main imaging lens of the present disclosure according to the second embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0049] 2-5 show a comparison of distortion of the main imaging lens of the present disclosure according to the second embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by the addition of the focus lens unit.

[0050] Third embodiment 3-1 shows a cross-sectional view of an optical lens system according to a third embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, ML4, and ML5, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is composed of FL1 and FL2, and the second negative lens group is composed of FL3.

[0051] 3-2 shows a cross-sectional view of an optical lens system according to a third embodiment of the present disclosure in the MOD lens position. The opposing lens surfaces between FL2 and FL3 have substantially corresponding surface shapes.

[0052] 3-1 and 3-2 show that only the lens element FL3 of the focus lens unit is moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0053] Table 3-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the third embodiment.

[0054] [Table 5]

[0055] Table 3-2 shows the aspheric coefficients of the optical surfaces of the low deflection inner focus system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0056] [Table 6]

[0057] 3-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the third embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0058] 3-4 show a comparison of astigmatism of the main imaging lens of the present disclosure according to the third embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0059] 3-5 show a comparison of distortion of the main imaging lens of the present disclosure and the combination of the main imaging lens and the focus lens unit according to the third embodiment. The comparison shows that the distortion of the main imaging lens alone is hardly affected by the addition of the focus lens unit.

[0060] Fourth embodiment 4-1 shows a cross-sectional view of an optical lens system according to a fourth embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, and ML4, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is composed of FL1 and FL2, and the second negative lens group is composed of FL3.

[0061] 4-2 shows a cross-sectional view of an optical lens system according to a fourth embodiment of the present disclosure in the MOD lens position. The opposing lens surfaces between FL2 and FL3 have substantially corresponding surface shapes.

[0062] 4-1 and 4-2 show that only the lens element FL3 of the focus lens unit is moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0063] Table 4-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the fourth embodiment.

[0064] [Table 7]

[0065] Table 4-2 shows the aspheric coefficients of the optical surfaces of the low refractive power inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0066] [Table 8]

[0067] 4-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the fourth embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0068] 4-4 shows a comparison of astigmatism of the main imaging lens of the present disclosure according to the fourth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0069] 4-5 show a comparison of distortion of the main imaging lens of the present disclosure according to the fourth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by the addition of the focus lens unit.

[0070] Fifth embodiment FIG. 5-1 shows a cross-sectional view of an optical lens system according to a fifth embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, and ML4, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is made up of FL1, the second negative lens group is made up of FL2 and FL3, and the third positive lens group is made up of FL3.

[0071] 5-2 shows a cross-sectional view of an optical lens system according to a fifth embodiment of the present disclosure in the MOD lens position. Opposing lens surfaces between FL1 and FL2 have substantially corresponding surface shapes.

[0072] 5-1 and 5-2 show that only the lens element FL2 of the focus lens unit is moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0073] Table 5-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the fifth embodiment.

[0074] [Table 9]

[0075] Table 5-2 shows the aspheric coefficients of the optical surfaces of the low refractive power inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0076] [Table 10]

[0077] 5-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the fifth embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0078] FIG. 5-4 shows a comparison of astigmatism of the main imaging lens of the present disclosure according to the fifth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0079] FIG. 5-5 shows a comparison of distortion of the main imaging lens of the present disclosure according to the fifth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0080] Sixth embodiment FIG. 6-1 shows a cross-sectional view of an optical lens system according to a sixth embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, and ML4, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is composed of FL1, and the second negative lens group is composed of FL2 and FL3.

[0081] 6-2 shows a cross-sectional view of an optical lens system according to a sixth embodiment of the present disclosure in the MOD lens position. Opposing lens surfaces between FL1 and FL2 have substantially corresponding surface shapes.

[0082] 6-1 and 6-2 show that only the lens elements FL2 and FL3 of the focus lens unit are moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0083] Table 6-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the sixth embodiment.

[0084] [Table 11]

[0085] Table 6-2 shows the aspheric coefficients of the optical surfaces of the low refractive power inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0086] [Table 12]

[0087] FIG. 6-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the sixth embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0088] FIG. 6-4 shows a comparison of astigmatism of the main imaging lens of the present disclosure according to the sixth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0089] FIG. 6-5 shows a comparison of distortion of the main imaging lens of the present disclosure according to the sixth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0090] Seventh embodiment FIG. 7-1 shows a cross-sectional view of an optical lens system according to a seventh embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, ML4, and ML5, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is made up of FL1, the second negative lens group is made up of FL2 and FL3, and the third negative lens group is made up of FL3.

[0091] 7-2 shows a cross-sectional view of an optical lens system according to a seventh embodiment of the present disclosure in the MOD lens position. Opposing lens surfaces between FL1 and FL2 have substantially corresponding surface shapes.

[0092] 7-1 and 7-2 show that only the lens element FL1 of the focus lens unit is moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0093] Table 7-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the seventh embodiment of the low refractive power inner focus lens system.

[0094] [Table 13]

[0095] Table 7-2 shows the aspheric coefficients of the optical surfaces of the low refractive power inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0096] [Table 14]

[0097] FIG. 7-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the seventh embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0098] FIG. 7-4 shows a comparison of astigmatism of the main imaging lens of the present disclosure according to the seventh embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0099] FIG. 7-5 shows a comparison of distortion of the main imaging lens of the present disclosure according to the seventh embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0100] Eighth embodiment FIG. 8-1 shows a cross-sectional view of an optical lens system according to an eighth embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, ML4, and ML5, and the focusing unit includes lens elements FL1, FL2, and FL3. In the focus lens unit of this embodiment, the first positive lens group is composed of FL1 and FL2, and the second negative lens group is composed of FL3.

[0101] 8-2 shows a cross-sectional view of an optical lens system according to an eighth embodiment of the present disclosure in the MOD lens position. The opposing lens surfaces between FL2 and FL3 have substantially corresponding surface shapes.

[0102] 8-1 and 8-2 show that only the lens element FL2 of the focus lens unit is moved toward the image side to focus on a shorter focal length and toward the object side to focus on an infinity focal length, so the focus mechanism can be designed more easily.

[0103] Table 8-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the low refractive power inner focus lens system of the eighth embodiment.

[0104] [Table 15]

[0105] Table 8-2 lists the aspheric coefficients of the optical surfaces of the low refractive power inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0106] [Table 16]

[0107] FIG. 8-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the eighth embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0108] FIG. 8-4 shows a comparison of the astigmatism of the main imaging lens of the present disclosure according to the eighth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0109] FIG. 8-5 shows a comparison of distortion of the main imaging lens of the present disclosure according to the eighth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is almost unaffected by adding the focus lens unit.

[0110] Ninth embodiment FIG. 9-1 shows a cross-sectional view of an optical lens system according to a ninth embodiment of the present disclosure at an infinity lens position. The main imaging lens includes lens elements ML1, ML2, ML3, and ML4, and the focusing unit includes lens elements FL1, FL2, FL3, and FL4. In the focus lens unit of this embodiment, the first positive lens group is made up of FL1, the second negative lens group is made up of FL2 and FL3, the third positive lens group is made up of FL3, and the fourth negative lens group is made up of FL4.

[0111] 9-2 shows a cross-sectional view of an optical lens system according to a ninth embodiment of the present disclosure in the MOD lens position. The opposing lens surfaces between FL1 and FL2 have substantially corresponding surface shapes, and the opposing lens surfaces between FL3 and FL4 have substantially corresponding surface shapes.

[0112] 9-1 and 9-2 show that only the lens elements FL2 and FL3 of the focus lens unit are moved in opposite directions to focus to a shorter focal length or an infinity focal length, so the focus mechanism can be designed more easily.

[0113] Table 9-1 shows the radius of curvature (r) and thickness or spacing (d) of each of the optical surfaces, as well as the refractive index (N), Abbe number (v), and effective diameter (φ) of each of the lens elements of the ninth embodiment of the low refractive power inner focus lens system.

[0114] [Table 17]

[0115] Table 9-2 lists the aspheric coefficients of the optical surfaces of the low refractive power inner focus lens system, with the numbers 2, 4, ..., 10 representing higher order aspheric coefficients.

[0116] [Table 18]

[0117] FIG. 9-3 shows a comparison of spherical aberration of the main imaging lens and the combination of the main imaging lens and the focus lens unit according to the ninth embodiment of the present disclosure. The comparison shows that the aberration of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0118] FIG. 9-4 shows a comparison of the astigmatism of the main imaging lens of the present disclosure according to the ninth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the astigmatism of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0119] FIG. 9-5 shows a comparison of distortion of the main imaging lens of the present disclosure according to the ninth embodiment and the combination of the main imaging lens and the focus lens unit. The comparison shows that the distortion of the main imaging lens alone is hardly affected by adding the focus lens unit.

[0120] As shown in the optical data, the low refractive power inner focus lens system according to the present disclosure is arranged with a main imaging lens and a focusing unit, which can be inspected independently of each other. Only one lens or a pair of lenses of the focus lens unit is moved to focus the lens system without changing the TTL, so that the focus mechanism can be greatly simplified. In addition, the focus lens unit does not affect the performance of the main imaging lens. In other words, the focus lens unit can provide focus adjustment function for various main imaging lenses without degradation of the image quality of the main imaging lens. The low refractive power inner focus lens unit, also called the focus lens unit, described in the present invention has a very low refractive power and comprises at least one positive lens group and at least one negative lens group, and the negative lens group moves toward the imaging plane to focus on closer object distances when focusing from infinity to MOD, and vice versa. The above-mentioned advantages are achieved when the following relationship is satisfied: (i): 0.5≦|1-β 2 |≦3.5 where β is the magnification of the negative lens group of the focus lens unit, (ii): |Ff| / IMH≧10 Here, Ff is the focal length of the focus lens unit, and IMH is the half diagonal length of the image sensor. (iii):| Fmain / Ff |≦0.55 Here, Fmain is the focal length of the combined main imaging lens. (iv): Dmin / φmax<0.2 Here, Dmin is the distance between opposing lens surfaces between different lens groups in the focus lens unit, which are close to each other at the INF lens position, and φmax is the maximum optical effective diameter of the lenses in the focus lens unit. (v):0.5 <abs[Sob(h) / Sim(h)]<2.0 Here, opposing lens surfaces between different lens groups of the focus lens unit, which approach each other at the INF lens position, have substantially corresponding surface shapes, Sob(h) is the surface shape (SAG amount) of the object-side surface of the opposing lens surfaces defined by the lens diameter height h, and Sim(h) is the surface shape (SAG amount) of the image-plane side of the opposing surfaces. (vi): 0.5 <Rob / Rim<2.0 Here, Rob is the radius of the object-side surface of the aforementioned opposing lens surface, and Rim is the radius of the image-side surface of the aforementioned opposing lens surface.

[0121] Condition (i) keeps the amount of focus stroke small enough to miniaturize the optical system and avoids the error sensitivity of moving the focus lens unit becoming too large, which is disadvantageous in manufacturing and mass production. From this perspective, the following ranges are more preferable. (i)-2:0.7≦|1-β 2 |≦3.0

[0122] Condition (ii) avoids a situation in which the refractive power of the focusing unit becomes unnecessarily large with respect to the sensor size, which makes it unsuitable for miniaturization and causes a decrease in sensitivity to manufacturing errors and a decrease in mass productivity due to the effect on the performance of the main imaging lens. From this perspective, the following ranges are more preferable. (ii)-2:Preferably,|Ff| / IMH≧17

[0123] Condition (iii) avoids a decrease in manufacturability and mass production caused by excessively strengthening the refractive power of the focus lens unit and reducing the versatility of this optical system due to a significant change in the performance of the main imaging lens when the focus lens unit is combined with the main imaging lens. From this viewpoint, the following ranges are more preferable. (iii)-2:| Fmain / Ff |≦0.4

[0124] The condition (iv) maintains the effect of the focus lens unit on the main imaging lens small enough to maintain the optical performance of the main imaging lens. From this viewpoint, the following range is more preferable. (iv)-2:Dmin / φmax<0.1

[0125] Condition (v) maintains the situation where the opposing lens surfaces are sufficiently close to each other. Condition (v) maintains the situation where the opposing lens surfaces are sufficiently close to each other. When the opposing lens surfaces between the different lens groups of the focus lens unit approaching each other in the INF lens position are too different from each other to approximate them as a single lens unit with low aberration when the two surfaces approach, it becomes difficult to maintain the optical performance of the main imaging lens. From this point of view, the following ranges are more preferable. (v)-2:0.5 <abs[Sob(h) / Sim(h)]<1.8、もしくは (v)-3:0.6 <abs[Sob(h) / Sim(h)]<1.7

[0126] In the low refractive power inner focus lens unit of the present invention, the main imaging lens does not need to have a focus optical function, which allows for compact design and inexpensive mass production. Furthermore, in the lens performance inspection process, various inspections can be performed using only the main lens, apart from the focus lens unit, which facilitates manufacturing. Meanwhile, by focusing with this focus lens unit, it is possible to avoid changing the TTL to increase the overall length of the lens. It is possible to adopt an inner focus method in which the overall length does not change and the MOD is short. Furthermore, since the focus lens unit according to the present invention has a very low refractive power, it can have a very small effect on the optical performance of the main imaging lens. Therefore, this can maintain the manufacturing error sensitivity at a very low level, which allows the realization of high manufacturability and mass production.

[0127] Further, a camera is provided. The camera of the present disclosure includes the low-refractive inner focus lens system of the present disclosure and an image sensor. The low-refractive inner focus lens system is configured to input light used to project an image onto the image sensor, and the image sensor is configured to convert the image into digital image data. The camera has a fixed TTL, which is preferable for implementation in a mobile device.

[0128] 10 shows a terminal 1000 disclosed in the present disclosure. The terminal 1000 includes the camera 100 provided in the above implementation form and a graphics processing unit (GPU) 200. The camera 100 is configured to convert an image into digital image data through the low-refractive inner focus lens system of the present disclosure and input the digital image data to the GPU 200, and the GPU 200 is configured to process the image data received from the camera.

[0129] In Fig. 10, the terminal 1000 includes two cameras 100. However, the terminal may include a single camera or two or more cameras, which may be connected to at least one GPU 200. The camera 100 can be applied as a high-resolution mobile device camera, such as a mobile phone camera, due to its high image quality, fixed TTL, and high productivity.

[0130] Those skilled in the art will appreciate that it is difficult to have high manufacturability in mass-produced inner focus lens systems with fixed TTL. The present disclosure meets these dual requirements by satisfying the above-mentioned relationships.

[0131] In this disclosure, the use of "low refractive power" refers to the relationship | Fmain / Ff |≦0.55, where Ff is the focal length of the inner focus lens unit, and Fmain is the focal length of the combined main imaging lens.

[0132] The lens system according to the present disclosure may be particularly applicable to mobile phone cameras, but may also be applied to cameras in any mobile device, such as tablet devices and wearable devices.

[0133] Although preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will recognize that various modifications, additions, and substitutions can be made without departing from the scope and spirit of the present disclosure, as set forth in the appended claims. [Explanation of symbols]

[0134] 100 Cameras 200 Graphics Processing Units (GPU) 1000 devices

Claims

1. A low refractive power inner focus lens unit combined with an imaging lens and an image sensor, comprising: at least one positive lens group and at least one negative lens group; The imaging lens can be used as an individual lens, and the low refractive power inner focus lens unit provides a focusing function by moving the negative lens group toward an imaging surface when focusing from infinity to a minimum object distance (MOD) to focus on closer object distances, and vice versa, and is disposed within a flange back between the imaging lens and a surface of the image sensor; the opposing lens surfaces between different lens groups of the low refractive power inner focus lens unit have substantially corresponding surface shapes; 0.5<abs[Sob(h) / Sim(h)]<2.0 The relationship is fulfilled, A low refractive power inner focus lens unit, wherein Sob(h) is the surface shape of the object side surface of the opposing lens surface defined by the lens diameter height h, and Sim(h) is the surface shape of the image plane side of the opposing lens surface.

2. ０．５≦｜１－β ２ ｜≦３．５ The relationship is fulfilled, 2. The low refractive power inner focus lens unit according to claim 1, wherein β is the magnification of the negative lens group of the low refractive power inner focus lens unit.

3. |Ff| / IMH≧10 The relationship is fulfilled, 3. The low refractive power inner focus lens unit of claim 1, wherein Ff is the focal length of the low refractive power inner focus lens unit and IMH is the half diagonal length of the image sensor.

4. |Fmain / Ff|≦0.55 The relationship is fulfilled, 4. The low refractive power inner focus lens unit according to claim 1, wherein Ff is a focal length of the low refractive power inner focus lens unit, and Fmain is the focal length of the imaging lens combined therewith.

5. Dmin / φmax<0.2 The relationship is fulfilled, 5. The low refractive power inner focus lens unit according to claim 1, wherein Dmin is the distance between opposing lens surfaces between different lens groups of the low refractive power inner focus lens unit at the INF lens position, and φmax is the maximum optical effective diameter of the low refractive power inner focus lens unit.

6. 0.5<Rob / Rim<2.0 The relationship is fulfilled, 6. The low refractive power inner focus lens unit of claim 1, wherein the radius of the surface on the object side of the opposing lens surfaces is Rob and the radius of the surface on the image side of the opposing lens surfaces is Rim.

7. 1. A low refractive power inner focus lens system, comprising: A main imaging lens; A low refractive power inner focus lens unit; Equipped with The main imaging lens can be used as an individual lens unit, and the low refractive power inner focus lens unit comprises at least one positive lens group and at least one negative lens group, the low refractive power inner focus lens unit provides the main imaging lens with a focusing function by moving the negative lens group towards an imaging surface to focus on short distance objects when focusing from infinity to a short focal length, and vice versa, and is within a flange back between the main imaging lens and a surface of an image sensor; the opposing lens surfaces between different lens groups of the low refractive power inner focus lens unit have substantially corresponding surface shapes; 0.5<abs[Sob(h) / Sim(h)]<2.0 The relationship is fulfilled, A low refractive power inner focus lens system, wherein Sob(h) is the surface shape of the object side surface of the opposing lens surface defined by the lens diameter height h, and Sim(h) is the surface shape of the image plane side of the opposing lens surface.

8. ０．５≦｜１－β ２ ｜≦３．５ The relationship is fulfilled, 8. The low refractive power inner focus lens system according to claim 7, wherein β is the magnification of the negative lens group of the low refractive power inner focus lens unit.

9. |Ff| / IMH≧10 The relationship is fulfilled, 9. The low refractive power inner focus lens system of claim 7, wherein Ff is the focal length of the low refractive power inner focus lens unit and IMH is the half diagonal length of the image sensor.

10. |Fmain / Ff|≦0.55 The relationship is fulfilled, 10. The low refractive power inner focus lens system according to claim 7, wherein Ff is the focal length of the low refractive power inner focus lens unit and Fmain is the focal length of the combined main imaging lens.

11. Dmin / φmax<0.2 The relationship is fulfilled, 11. The low refractive power inner focus lens system according to claim 7, wherein Dmin is the distance between opposing lens surfaces between different lens groups of the low refractive power inner focus lens unit at the INF lens position, and φmax is the maximum optical effective diameter of the low refractive power inner focus lens unit.

12. 0.5<Rob / Rim<2.0 The relationship is fulfilled, 12. The low refractive power inner focus lens system of claim 7, wherein the radius of the surface on the object side of the opposing lens surface is Rob and the radius of the surface on the image side of the opposing lens surface is Rim.

13. A camera, A low refractive power inner focus lens system according to any one of claims 7 to 12, An image sensor; Equipped with A camera, wherein the low refractive power inner focus lens system is configured to project an image onto the image sensor, the image sensor being configured to convert the image into digital image data.

14. A terminal, A camera comprising at least one camera according to claim 13 and a graphics processing unit (GPU), The GPU is coupled to the at least one camera for receiving and processing the digital image data.

Images