Optical imaging system

Abstract

The present invention provides an optical imaging system, comprising a first lens having positive refractive power, a concave object surface and a convex image surface. The optical imaging system also comprises a second lens having positive refractive power, a convex object surface and a concave image surface. The optical imaging system also comprises a third lens, a fourth lens and a fifth lens. The first lens to the fifth lens are sequentially arranged from the object side to the image side.

Description

[0001] This application is a divisional application of the invention patent application "Optical Imaging System" with application date of May 22, 2017 and application number 202110060391.6. Technical Field

[0002] The following description relates to an optical imaging system. Background Art

[0003] Typically, a camera module is installed in a mobile communication terminal, a computer, a vehicle, a camera, a mobile device, or a tablet computer, and enables an image of a surrounding environment to be captured.

[0004] According to the slimming trend of mobile communication terminals, camera modules have been required to have a small size and high image quality.

[0005] Furthermore, a camera module for a vehicle is also required to have a small size and high image quality in order to prevent a driver's field of view from being obstructed or to negatively affect the appearance of the vehicle.

[0006] For example, the camera used in the rearview mirror of a vehicle should be able to capture clear images during vehicle operation to ensure the field of view of the rear view, so it needs to have high image quality and a lens system with a wide field of view to capture a wide image.

[0007] In addition, it is required that cameras used in vehicles can clearly capture images of objects even at night when illumination is low. Therefore, a lens system having a small size and capturing images in both the visible light region and the near infrared region in the visible spectrum is desired. Summary of the invention

[0008] This Summary is provided to introduce selected concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0009] According to an embodiment, an optical imaging system is provided, comprising: a first lens, which may have positive refractive power, a concave object-side surface, and a convex image-side surface; a second lens, which may have positive refractive power, a convex object-side surface, and a concave image-side surface; a third lens; a fourth lens; and a fifth lens, wherein the first lens to the fifth lens are sequentially arranged from the object side to the image side.

[0010] The object-side surface and the image-side surface of the first lens and the second lens and the object-side surface and the image-side surface of the fourth lens may be spherical, and the object-side surface and the image-side surface of the third lens and the fifth lens may be aspherical.

[0011] The first lens to the fifth lens may be formed of glass.

[0012] The third lens may have a negative refractive power, a concave object-side surface, and a concave image-side surface.

[0013] The fourth lens may have a positive refractive power, a concave object-side surface, and a convex image-side surface.

[0014] The fifth lens may have a positive refractive power, a convex object-side surface, and a concave image-side surface.

[0015] -6.5 < {(1 / f) × (IMG HT / tanθ) - 1} × 100 < -1.0 may be satisfied, where f may be the total focal length of the optical imaging system, IMG HT may be half of the diagonal length of the imaging surface of the image sensor, and θ may be half of the field of view (FOV) of the optical imaging system.

[0016] TTL / (2IMG HT) < 2.0 may be satisfied, where TTL may be the distance on the optical axis from the object-side surface of the first lens to the imaging surface of the image sensor, and IMG HT may be half of the diagonal length of the imaging surface of the image sensor.

[0017] -60 < R1 / f < 0 may be satisfied, where R1 may be the radius of curvature of the object-side surface of the first lens, and f may be the total focal length of the optical imaging system.

[0018] -10 < R2 / f < 0 may be satisfied, where R2 may be the radius of curvature of the image-side surface of the first lens, and f may be the total focal length of the optical imaging system.

[0019] 0.2 < f / f1 < 0.6 may be satisfied, where f may be the total focal length of the optical imaging system, and f1 may be the focal length of the first lens.

[0020] -2.5 < f / f3 < -1.5 may be satisfied, where f may be the total focal length of the optical imaging system, and f3 may be the focal length of the third lens.

[0021] 5 < (T1 + T2) / T3 < 12 may be satisfied, where T1 may be the thickness of the first lens, T2 may be the thickness of the second lens, and T3 may be the thickness of the third lens.

[0022] 0 ≤ |N1 - N2| < 0.2 may be satisfied, where N1 may be the refractive index of the first lens, and N2 may be the refractive index of the second lens.

[0023] It can satisfy 0.92 < f / IMG HT < 1.85, where f can be the total focal length of the optical imaging system, and IMG HT can be half of the diagonal length of the imaging surface of the image sensor.

[0024] The total focal length f of the optical imaging system can be 5.5 mm, the constant (F number) representing the brightness of the optical imaging system can be less than 2.0, and the field of view angle of the optical imaging system can be 58.03°.

[0025] The total focal length f of the optical imaging system can be 5.44 mm or less, the constant (F number) representing the brightness of the optical imaging system can be less than 2.0, and the field of view angle of the optical imaging system can be 58.64°.

[0026] According to another embodiment, there is provided an optical imaging system, which includes: a first lens that can have a positive refractive power, a concave object-side surface, and a convex image-side surface; a second lens that can have a positive refractive power; a third lens that can have a negative refractive power; a fourth lens that can have a positive refractive power; and a fifth lens that can have a positive refractive power, wherein the first lens to the fifth lens can be sequentially arranged from the object side to the image side, the third lens can be formed of glass, and the object-side surface and the image-side surface of the third lens can be aspherical.

[0027] The object-side surface of the third lens and the fourth lens can be concave, the object-side surface of the second lens and the fifth lens can be convex, the image-side surface of the second lens, the third lens, and the fifth lens can be concave, and the image-side surface of the fourth lens can be convex.

[0028] The object-side surface and the image-side surface of the first lens, the second lens, and the fourth lens can be spherical, and at least one of the object-side surface and the image-side surface of the fifth lens can be aspherical.

[0029] Through the following specific embodiments, drawings, and claims, other features and aspects will be obvious. Description of the Drawings

[0030] Through the following description of the embodiments in conjunction with the drawings, these and / or other aspects will become obvious and easier to understand. In the drawings:

[0031] Figure 1 is a diagram showing an optical imaging system according to the first embodiment;

[0032] Figure 2 shows Figure 1 a graph of a curve representing the aberration characteristics of the optical imaging system shown in;

[0033] Figure 3 Yes means Figure 1 A table of various characteristics of the lenses of the optical imaging system shown in;

[0034] Figure 4 It is shown Figure 1 A table of various aspheric coefficients of the lenses of the optical imaging system shown in ;

[0035] Figure 5 is a diagram showing an optical imaging system according to a second embodiment;

[0036] Figure 6 Shown Figure 5 A graph of aberration characteristics of the optical imaging system shown in FIG.

[0037] Figure 7 Yes means Figure 5 A table of various characteristics of the lenses of the optical imaging system shown in;

[0038] Figure 8 Yes means Figure 5 A table of various aspheric coefficients of the lenses of the optical imaging system shown in .

[0039] Throughout the drawings and detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative sizes and depictions of the elements in these drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0040] The following specific embodiments are provided to help the reader gain a comprehensive understanding of the methods, devices and / or systems described herein. However, various permutations, modifications and equivalents of the methods, devices and / or systems described herein will be apparent to those of ordinary skill in the art. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein, but changes may be made that will be apparent to those of ordinary skill in the art, except for operations that must occur in a particular order. In addition, descriptions of functions and configurations known to those of ordinary skill in the art may be omitted for clarity and brevity.

[0041] In all drawings and detailed descriptions, the same reference numerals refer to the same elements. The drawings may not be drawn to scale, and the relative sizes, proportions, and depictions of the elements in the drawings may be exaggerated for clarity, illustration, and convenience.

[0042] The features described herein may be implemented in different forms and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete and will convey the full scope of this disclosure to those of ordinary skill in the art.

[0043] It will be apparent that, although the terms "first," "second," "third," etc., may be used herein to describe various members, components, regions, layers, and / or portions, these members, components, regions, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one member, component, region, layer, and / or portion from another member, component, region, layer, and / or portion. Thus, the first member, component, region layer, and / or portion discussed below may be referred to as a second member, component, region layer, and / or portion without departing from the teachings of the embodiments.

[0044] In the following, various embodiments will be described with reference to the schematic diagrams. In the accompanying drawings, for example, due to manufacturing techniques and / or tolerances, variations in the shapes shown may be expected. Therefore, the embodiments should not be interpreted as being limited to the specific shapes of the regions shown herein, for example, including changes in shapes caused by manufacturing. The following embodiments may also be formed by one or a combination thereof.

[0045] According to an embodiment, the first lens is the lens closest to the object or subject from which the image is captured. The fifth lens is the lens closest to the image sensor or closest to the imaging plane.

[0046] In addition, the first surface of each lens refers to its surface closest to the object side (or object side surface), and the second surface of each lens refers to its surface closest to the image side (or image side surface). In addition, all values ​​such as the radius of curvature and thickness of the lens, half the diagonal length of the imaging surface of the image sensor (IMG HT) are expressed in millimeters (mm), and the field of view (FOV) of the optical imaging system is expressed in degrees.

[0047] Furthermore, with respect to the shape of the lens, these shapes are expressed relative to the optical axis of the lens. That the surface of the lens is convex means that the optical axis portion of the corresponding surface is convex, and that the surface of the lens is concave means that the optical axis portion of the corresponding surface is concave. Therefore, in a configuration in which one surface of the lens is described as being convex, an edge portion of the one surface of the lens may be concave. Similarly, in a configuration in which one surface of the lens is described as being concave, an edge portion of the one surface of the lens may be convex. In other words, the paraxial region of the lens may be convex, while the rest of the lens outside the paraxial region may be convex, concave, or flat. Furthermore, the paraxial region of the lens may be concave, while the rest of the lens outside the paraxial region may be convex, concave, or flat. The paraxial region refers to a very narrow area near the optical axis.

[0048] According to the embodiments, an optical imaging system is described that can enhance the aberration improvement effect, achieve a high level of resolution, capture images even in a low illumination environment, have a wide field of view, and suppress resolution deviation even under wide temperature changes.

[0049] An optical imaging system according to various embodiments may include five lenses.

[0050] Furthermore, in an embodiment, the thickness and the radius of curvature of a lens are measured based on the optical axis of the corresponding lens.

[0051] For example, the optical imaging system according to the embodiment may include a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially arranged from the object side. However, those skilled in the art will appreciate that the number of lenses in the optical system may be changed, for example, between two lenses and five lenses, when achieving the various results and effects described below.

[0052] However, the optical imaging system according to the embodiment is not limited to including only five lenses, but may also include other components if necessary. For example, the optical imaging system may also include an image sensor that converts an image of an object incident on the image sensor into an electrical signal. The image sensor is configured to capture an image of an object in a near-infrared region as well as a visible light region. In addition, the optical imaging system also includes an aperture to control the amount of light. For example, the aperture is disposed between the second lens and the third lens.

[0053] In the optical imaging system according to the embodiment, the first to fifth lenses may be formed of glass, plastic, or polyurethane material.

[0054] In addition, in the optical imaging system according to the embodiment, some of the first to fifth lenses may be spherical lenses, and other lenses of the first to fifth lenses may be aspherical lenses. In other embodiments, all of the first to fifth lenses may be spherical lenses, or all of the first to fifth lenses may be aspherical lenses.

[0055] As an example, the first surfaces and the second surfaces of the first lens, the second lens, and the fourth lens may be spherical, and the third lens and the fifth lens may have at least one aspherical surface, respectively.

[0056] The aspherical surfaces of the third lens and the fifth lens may be expressed by the following Equation 1:

[0057] [Equation 1]

[0058]

[0059] In the example, c represents the curvature of the lens (the inverse of the radius of curvature), K represents the cone constant, and Y is the distance from a point on the aspheric surface of the lens to the optical axis in a direction perpendicular to the optical axis. In addition, constants A to D are aspheric coefficients. In addition, Z is the distance between a point on the aspheric surface of the lens at a distance Y from the optical axis and a tangent plane, wherein the tangent plane intersects with the vertex of the aspheric surface of the lens.

[0060] The optical imaging system including the first lens to the fifth lens may have positive refractive power, positive refractive power, negative refractive power, positive refractive power, positive refractive power sequentially from the object side toward the image side. However, although each lens is described as having a specific refractive power, at least one of the lenses may use a different refractive power to achieve a desired result.

[0061] The optical imaging system according to various embodiments satisfies the following conditional expression:

[0062] [Conditional Expression 1] -6.5<{(1 / f)×(IMG HT / tanθ)-1}×100<-1.0

[0063] [Conditional expression 2]TTL / (2IMG HT)<2.0

[0064] [Conditional expression 3] -60 <R1 / f<0

[0065] [Conditional expression 4]-10 <R2 / f<0

[0066] [Conditional expression 5] 0.2 <f / f1<0.6

[0067] [Conditional expression 6]-2.5 <f / f3<-1.5

[0068] [Conditional expression 7] 0.92 <f / IMG HT<1.85

[0069] [Conditional Expression 8] 5<(T1+T2) / T3<12

[0070] [Conditional Expression 9] 0≤|N1-N2|<0.2.

[0071] In the example, f is the total focal length of the optical imaging system, IMG HT is half of the diagonal length of the imaging plane of the image sensor, θ is half of the field of view (FOV) of the optical imaging system, TTL is the distance on the optical axis from the object surface of the first lens to the imaging plane of the image sensor, R1 is the radius of curvature of the object surface of the first lens, R2 is the radius of curvature of the image surface of the first lens, f1 is the focal length of the first lens, f3 is the focal length of the third lens, T1 is the thickness of the first lens, T2 is the thickness of the second lens, T3 is the thickness of the third lens, N1 is the refractive index of the first lens, and N2 is the refractive index of the second lens.

[0072] Furthermore, the thickness of a lens refers to its thickness in the paraxial region or on the optical axis of the lens.

[0073] Next, first to fifth lenses forming the optical imaging system according to various embodiments will be described.

[0074] The first lens has positive refractive power. In addition, the first lens is in a meniscus shape with a convex image-side surface. For example, the first surface (object-side surface) of the first lens is concave in the paraxial region, and the second surface (image-side surface) of the first lens is convex in the paraxial region.

[0075] Both surfaces of the first lens may be spherical.

[0076] The second lens has positive refractive power. In addition, the second lens is in a meniscus shape with a convex object surface. For example, the first surface (object surface) of the second lens is convex in the paraxial region, and the second surface (image surface) of the second lens is concave in the paraxial region.

[0077] Both surfaces of the second lens may be spherical.

[0078] The third lens has negative refractive power. In addition, two surfaces of the third lens are concave surfaces. In detail, the first surface and the second surface (object-side surface and image-side surface) of the third lens are concave in the paraxial region.

[0079] At least one of the first surface and the second surface of the third lens may be aspherical. For example, both surfaces of the third lens are aspherical.

[0080] The fourth lens has positive refractive power. In addition, the fourth lens is in a meniscus shape with a convex image surface. In detail, the first surface of the fourth lens is concave in the paraxial region, and the second surface of the fourth lens is convex in the paraxial region.

[0081] Both surfaces of the fourth lens may be spherical.

[0082] The fifth lens has positive refractive power. In addition, the fifth lens may be in a meniscus shape with a convex object-side surface. For example, the first surface (object-side surface) of the fifth lens is convex in the paraxial region, and the second surface (image-side surface) of the fifth lens is concave in the paraxial region.

[0083] At least one of the first surface and the second surface of the fifth lens may be aspherical. For example, both surfaces of the fifth lens are aspherical.

[0084] In the optical imaging system constructed as described above, a plurality of lenses perform an aberration correction function to enhance the aberration improvement performance.

[0085] In addition, the optical imaging system may have an F number (a constant representing the brightness of the optical imaging system) of 2 or less, thereby clearly capturing an image of an object even in a low-illuminance environment.

[0086] Furthermore, according to the embodiment, the optical imaging system described above clearly captures an image of an object in both the visible light region and the near infrared region of the visible spectrum.

[0087] Furthermore, since a spherical lens is used in the optical imaging system according to the embodiment, the cost required for manufacturing the optical imaging system can be reduced.

[0088] Furthermore, in the optical imaging system according to the embodiment, all of the lenses may be formed of glass having a relatively low coefficient of thermal expansion (CTE), so that a predetermined level of resolution may be ensured even in a temperature range of -40° C. to 80° C. Therefore, the optical imaging system according to the exemplary embodiment may achieve a high level of resolution even in an environment where a wide range of temperature variations exists.

[0089] Will refer to Figures 1 to 4 An optical imaging system according to a first embodiment is described.

[0090] The optical imaging system according to the first embodiment includes an optical system having a first lens 110 , a second lens 120 , a third lens 130 , a fourth lens 140 , and a fifth lens 150 , and may further include a stop ST and an image sensor 160 .

[0091] Figure 3 Various properties of the lenses (radius of curvature, thickness or distance between lenses, refractive index and Abbe number) are shown in .

[0092] In addition, the total focal length f of the optical imaging system according to the first embodiment is 5.5 mm, the F number (a constant representing the brightness of the optical imaging system) of the optical imaging system is 1.93, and the field angle of the optical imaging system is 58.03°.

[0093] In the first embodiment, the first lens 110 has positive refractive power, a first surface of the first lens 110 is concave in the paraxial region, and a second surface of the first lens 110 is convex in the paraxial region.

[0094] The second lens 120 has positive refractive power, a first surface of the second lens 120 is convex in the paraxial region, and a second surface of the second lens 120 is concave in the paraxial region.

[0095] The third lens 130 has negative refractive power, and the first surface and the second surface of the third lens 130 are concave in the paraxial region.

[0096] The fourth lens 140 has positive refractive power, a first surface of the fourth lens 140 is concave in the paraxial region, and a second surface of the fourth lens 140 is convex in the paraxial region.

[0097] The fifth lens 150 has positive refractive power, a first surface of the fifth lens 150 is convex in the paraxial region, and a second surface of the fifth lens 150 is concave in the paraxial region.

[0098] In addition, each surface of the third lens 130 and the fifth lens 150 has the following Figure 4 For example, the first and second surfaces of the third lens 130 and the fifth lens 150 are aspherical, and the first and second surfaces of the first lens 110, the second lens 120, and the fourth lens 140 are spherical.

[0099] In addition, all of the first to fifth lenses 110 to 150 are formed of glass.

[0100] In addition, the stop ST is provided between the second lens 120 and the third lens 130 .

[0101] In addition, the optical imaging system constructed as described above has the following features: Figure 2 Aberration characteristics shown.

[0102] Will refer to Figures 5 to 8 An optical imaging system according to a second exemplary embodiment of the present disclosure is described.

[0103] The optical imaging system according to the second embodiment includes an optical system having a first lens 210 , a second lens 220 , a third lens 230 , a fourth lens 240 , and a fifth lens 250 , and further includes a stop ST and an image sensor 260 .

[0104] Figure 7 Various properties of the lenses (radius of curvature, thickness or distance between lenses, refractive index and Abbe number) are shown in .

[0105] In addition, the total focal length f of the optical imaging system according to the second embodiment is 5.44 mm, the F number (a constant representing the brightness of the optical imaging system) of the optical imaging system is 1.88, and the field angle of the optical imaging system is 58.64°. Although the total focal length f of the optical imaging system in the second embodiment is 5.44 mm, in other embodiments, the total focal length f of the optical imaging system may be less than 5.44 mm, the F number (a constant representing the brightness of the optical imaging system) of the optical imaging system may be less than 2.0, and the field angle of the optical imaging system may be 58.64°.

[0106] In the second embodiment, the first lens 210 has positive refractive power, the first surface of the first lens 210 is concave in the paraxial region, and the second surface of the first lens 210 is convex in the paraxial region.

[0107] The second lens 220 has positive refractive power, a first surface of the second lens 220 is convex in the paraxial region, and a second surface of the second lens 220 is concave in the paraxial region.

[0108] The third lens 230 has negative refractive power, and the first surface and the second surface of the third lens 230 are concave in the paraxial region.

[0109] The fourth lens 240 has positive refractive power, a first surface of the fourth lens 240 is concave in the paraxial region, and a second surface of the fourth lens 240 is convex in the paraxial region.

[0110] The fifth lens 250 has positive refractive power, a first surface of the fifth lens 250 is convex in the paraxial region, and a second surface of the fifth lens 250 is concave in the paraxial region.

[0111] In addition, each surface of the third lens 230 and the fifth lens 250 has the following Figure 8 For example, the first and second surfaces of the third lens 230 and the fifth lens 250 are aspherical, and the first and second surfaces of the first lens 210, the second lens 220, and the fourth lens 240 are spherical.

[0112] In addition, all of the first to fifth lenses 210 to 250 are formed of glass.

[0113] In addition, the stop ST is provided between the second lens 220 and the third lens 230 .

[0114] In addition, the optical imaging system constructed as described above has the following features: Figure 6 Aberration characteristics shown.

[0115] As described above, in the optical imaging system according to the various embodiments described, the aberration improvement effect can be enhanced, a high level of resolution can be achieved, images can be captured even in a low illumination environment, the field of view is wide, and the resolution deviation can be suppressed even under wide temperature changes.

[0116] Although the present disclosure includes specific examples, it will be apparent to those of ordinary skill in the art that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein will be understood to be merely descriptive and not for limiting purposes. The description of features or aspects in each example will be understood to be applicable to similar features or aspects in other examples. Suitable results may be obtained if the described techniques are performed in a different order, and / or if the components in the described systems, architectures, devices, or circuits are combined in different ways and / or replaced or supplemented by other components or their equivalents. Therefore, the scope of the present disclosure is not limited by specific embodiments, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents will be understood to be included in the present disclosure.

Claims

1. An optical imaging system, include: The first lens has a positive refractive power, a concave object-side surface and a convex image-side surface; The second lens has positive refractive power, a convex object-side surface and a concave image-side surface; a third lens having negative refractive power, a concave object-side surface and a concave image-side surface; a fourth lens element having positive refractive power, a concave object-side surface and a convex image-side surface; and The fifth lens has positive refractive power, a convex object-side surface and a concave image-side surface. The optical imaging system has a total of five lenses with refractive power, and the first lens to the fifth lens are arranged sequentially from the object side to the image side. Wherein, 0.92 < f / IMG HT < 1.85 is satisfied, wherein f is the total focal length of the optical imaging system, IMG HT is half of the diagonal length of the imaging surface of the image sensor, and Among them, the first lens to the fifth lens are formed of glass, the object surface and the image surface of the first lens, the second lens and the fourth lens are spherical, and the object surface and the image surface of the third lens and the fifth lens are aspherical.

2. The optical imaging system according to claim 1, in, Satisfies TTL / (2IMG HT)<2.0, where TTL is the distance on the optical axis from the object surface of the first lens to the imaging surface of the image sensor.

3. The optical imaging system according to claim 1, in, Satisfies 0 ≤ |N1-N2| < 0.2, wherein N1 is the refractive index of the first lens, and N2 is the refractive index of the second lens.

4. The optical imaging system according to claim 1, in, Satisfies -60<R1 / f<0, where R1 is the radius of curvature of the object-side surface of the first lens.

5. The optical imaging system according to claim 1, in, Satisfies -10<R2 / f<0, where R2 is the radius of curvature of the image-side surface of the first lens.

6. The optical imaging system according to claim 1, in, 0.2 < f / f1 < 0.6 is satisfied, where f1 is the focal length of the first lens.

7. The optical imaging system according to claim 1, in, Satisfies -2.5 < f / f3 < -1.5, where f3 is the focal length of the third lens.

8. The optical imaging system according to claim 1, in, Satisfies 5<(T1+T2) / T3<12, wherein T1 is the thickness of the first lens, T2 is the thickness of the second lens, and T3 is the thickness of the third lens.

Images