Imaging lens system

Abstract

An imaging lens system includes a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, a sixth lens having a positive refractive power, a seventh lens having a negative refractive power, and a stop disposed on an image side of one of the first lens through the sixth lens, wherein the first lens through the seventh lens are sequentially disposed in order from an object side, wherein the imaging lens system has a total of seven lenses having refractive power, wherein one or more of the second lens through the seventh lens disposed on the image side of the stop each has a positive refractive power and a negative refractive index temperature coefficient, and wherein |f4| < 2 x f, where f is a focal length of the optical imaging system and f4 is a focal length of the fourth lens.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2019-0111393, filed with the Korean Intellectual Property Office on September 9, 2019, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0003] The following description relates to an imaging lens system that can achieve constant optical performance independent of changes in ambient temperature. Background Technology

[0004] Small surveillance cameras are configured to acquire image information from the monitored area. For example, a small surveillance camera can be mounted on the front and rear bumpers of a vehicle and can provide the acquired images to the driver.

[0005] Because early models of small surveillance cameras were configured to image obstacles near vehicles, they had relatively low resolution, which could vary depending on temperature ranges from -40°C to 80°C. More recently, there has been a demand for surveillance cameras with high resolution and the ability to maintain constant optical properties under harsh temperature conditions, in order to enable autonomous driving in vehicles. Summary of the Invention

[0006] The summary portion of this invention is intended to provide a brief overview of the chosen inventive concepts, which will be further described in the detailed description portion below. This summary portion is not intended to identify key or essential features of the claimed subject matter, nor to help determine the scope of the claimed subject matter.

[0007] An imaging lens system that achieves constant optical properties independent of ambient temperature.

[0008] In one general aspect, the imaging lens system includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially from the object side; and an aperture stop disposed on the image side of one of the first to sixth lenses, wherein one or more of the second to seventh lenses disposed on the image side of the aperture stop each have a positive refractive power and a negative temperature coefficient of refractive index.

[0009] The aperture can be positioned between the third lens and the fourth lens.

[0010] The fourth or sixth lens may have positive refractive power.

[0011] The fourth or sixth lens may have a negative temperature coefficient of refractive index.

[0012] The refractive index temperature coefficient of the fourth lens or the sixth lens can be greater than -10 x 10 -6 / °C and less than -0.5 x 10 -6 / °C.

[0013] The second lens can have a concave object side surface.

[0014] The sixth lens can have a convex image side surface.

[0015] The seventh lens can have a negative refractive power.

[0016] The seventh lens can have a concave object side surface.

[0017] In another general aspect, an imaging lens system includes: a first lens group disposed on an object side of a stop; and a second lens group disposed between the stop and an image plane. A sum DTnT of refractive index temperature coefficients of lenses included in the first lens group and lenses included in the second lens group is -3.5 [10 -6 / °C] or more and 3.5 [10 -6 / °C] or less.

[0018] The sum DTnF of refractive index temperature coefficients of the lenses included in the first lens group can be 5.0 [10 -6 / °C] or more and 15 [10 -6 / °C] or less.

[0019] The sum DTnR of refractive index temperature coefficients of the lenses included in the second lens group can be -20 [10 -6 / °C] or more and -8.0 [10 -6 / °C] or less.

[0020] The sum DTnF of refractive index temperature coefficients of the lenses included in the first lens group and the sum DTnR of refractive index temperature coefficients of the lenses included in the second lens group can satisfy 0.8 ≤ |DTnF / DTnR| ≤ 1.2.

[0021] Among the lenses included in the first lens group, a lens nearest to the stop can have a positive refractive power.

[0022] Among the lenses included in the second lens group, a lens nearest to the stop can have a positive refractive power.

[0023] Among the lenses included in the second lens group, a lens nearest to the image plane can have a negative refractive power.

[0024] In another general aspect, an imaging lens system includes: a stop; a first lens group disposed on an object side of the stop and including two or more lenses, the two or more lenses of the first lens group each having a positive refractive index temperature coefficient; and a second lens group disposed between an image side of the stop and an image sensor and including two or more lenses, the two or more lenses of the second lens group each having a negative refractive index temperature coefficient.

[0025] The first lens group can include three lenses, and the second lens group can include four lenses.

[0026] The lens of the second lens group disposed closest to the stop can have a positive refractive index temperature coefficient.

[0027] At least two of the lenses of the first lens group can each have a negative refractive power, and at least two of the lenses of the second lens group can each have a negative refractive power.

[0028] Other features and aspects will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 FIG. 1 is a diagram illustrating a first example of an imaging lens system.

[0030] Figure 2 FIG. 2 shows aberration curves of the imaging lens system illustrated in FIG. 1. Figure 1

[0031] FIG. 3 shows MTF curves of the imaging lens system illustrated in FIG. 1. Figure 3 Figure 1 FIG. 4 shows a curve representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 1 as a function of temperature.

[0032] Figure 4 Figure 1 FIG. 5 is a diagram illustrating a second example of an imaging lens system.

[0033] Figure 5 FIG. 6 shows aberration curves of the imaging lens system illustrated in FIG. 5.

[0034] Figure 6 FIG. 7 shows MTF curves of the imaging lens system illustrated in FIG. 5. Figure 5

[0035] FIG. 8 shows a curve representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 5 as a function of temperature. Figure 7 Figure 5 FIG. 9 shows a curve representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 5 as a function of temperature.

[0036] Figure 8 Figure 5 FIG. 10 shows a curve representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 5 as a function of temperature. ​​​​

[0037] Figure 9 is a diagram illustrating a third example of an imaging lens system.

[0038] Figure 10 illustrated in FIG. 11. Figure 9 aberration curves of the imaging lens system illustrated in FIG. 11.

[0039] Figure 11 illustrated in FIG. 11. Figure 9 MTF curves of the imaging lens system illustrated in FIG. 11.

[0040] Figure 12 illustrated in FIG. 11. Figure 9 curves representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 11 according to a temperature change.

[0041] Figure 13 is a diagram illustrating a fourth example of an imaging lens system.

[0042] Figure 14 illustrated in FIG. 12. Figure 13 aberration curves of the imaging lens system illustrated in FIG. 12.

[0043] Figure 15 illustrated in FIG. 12. Figure 13 MTF curves of the imaging lens system illustrated in FIG. 12.

[0044] Figure 16 illustrated in FIG. 12. Figure 13 curves representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 12 according to a temperature change.

[0045] Figure 17 is a diagram illustrating a fifth example of an imaging lens system.

[0046] Figure 18 illustrated in FIG. 13. Figure 17 aberration curves of the imaging lens system illustrated in FIG. 13.

[0047] Figure 19 illustrated in FIG. 13. Figure 17 MTF curves of the imaging lens system illustrated in FIG. 13.

[0048] Figure 20 illustrated in FIG. 13. Figure 17 curves representing a back focal length (BFL) of the imaging lens system illustrated in FIG. 13 according to a temperature change.

[0049] Figure 21 is a diagram illustrating a sixth example of an imaging lens system.

[0050] Figure 22 illustrated in FIG. 14. Figure 21 aberration curves of the imaging lens system illustrated in FIG. 14.

[0051] Figure 23 It shows Figure 21 The MTF curve of the imaging lens system shown is shown.

[0052] Figure 24 It shows the representation Figure 21 The curves showing the back focal length (BFL) of the imaging lens system as a function of temperature are shown.

[0053] Throughout the accompanying drawings and detailed embodiments, the same reference numerals refer to the same elements. For purposes of clarity, illustration, and convenience, the drawings may not be drawn to scale, and the relative dimensions, scale, and depiction of elements in the drawings may be exaggerated. Detailed Implementation

[0054] The following detailed embodiments are provided to help readers gain a comprehensive understanding of the methods, apparatus, and / or systems described in this application. However, various changes, modifications, and equivalents to the methods, apparatus, and / or systems described in this application will be readily apparent to those skilled in the art. The order of operations described in this application is merely illustrative, and is not limited to the order set forth herein, except for operations that must occur in a specific order, and can be varied, as will be apparent to those skilled in the art. Furthermore, for clarity and conciseness, descriptions of functions and structures well-known to those skilled in the art may be omitted.

[0055] The features described in this application may be implemented in various forms and should not be construed as being limited to the examples described herein. Rather, the examples described herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0056] It should be noted that in this application, the use of the word "may" with respect to examples or implementations, for example, with respect to what an example or implementation may include or implement, means that there exists at least one example or implementation that includes or implements such features, and that all examples and implementations are not limited thereto.

[0057] Throughout this specification, when an element such as a layer, region, or substrate is described as being "on," "connected to," or "attached to" another element, the element may be directly "on," directly "connected to," or directly "attached to" the other element, or there may be one or more other elements between the element and the other element. Conversely, when an element is described as being "directly on," "directly connected to," or "directly attached to" another element, there may be no other elements between the element and the other element.

[0058] As used in this application, the words "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or variations thereof, do not have a limiting meaning and are used in their open-ended sense to encompass the items listed thereafter and any additional items.

[0059] Although the terms "first," "second," and "third" can be used herein to describe various elements, components, regions, layers, or sections, these elements, components, regions, layers, or sections should not be limited by these terms. Rather, these terms are used only to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section mentioned in one example can also be called a second element, component, region, layer, or section in another example without departing from the teachings of the examples described in this application.

[0060] Spatially relative terms such as "on", "upper", "lower", "above", "below", and "below" can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms can be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "upper" relative to other elements or features would then be oriented "below" or "lower" relative to the other elements or features. Accordingly, the expression "above" encompasses both "above" and "below" orientations in view of the device's spatial orientation. The device can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0061] The terminology used in this application is for the purpose of describing various examples only and is not intended to be limiting of the disclosure. The use of the singular herein includes the plural unless the context clearly dictates otherwise. The use of the term "a" or "an" herein does not exclude a plurality, and "comprises" or "comprising" does not exclude the presence of other elements or steps. Furthermore, unless otherwise noted, the use of the term "includes" or "including" in this specification shall not be considered limiting.

[0062] Variations can be made in the shape of the elements shown in the figures due to manufacturing techniques and / or tolerances. Therefore, the examples described in this application are not limited to the specific shapes of the elements shown in the figures, but include deviations in shapes that occur due to manufacturing techniques and / or tolerances.

[0063] The features of the examples described in this application can be combined in various ways. In addition, although examples described in this application have a variety of configurations, other configurations are possible in accordance with the disclosure of this application.

[0064] In an example, the first lens refers to a lens nearest to an object, and the seventh lens refers to a lens nearest to an imaging surface (or an image sensor). In an example, a radius of curvature, a thickness, a distance from an object side surface of the first lens to the imaging surface (TTL), a half of a diagonal length of the imaging surface (IMG HT), and a focal length are expressed in millimeters (mm).

[0065] The thickness of the lens, the interval between the lenses, and the TTL refer to a distance of the lens taken in an optical axis direction. Also, in the description of the shape of the lens, the configuration in which one surface is convex indicates that a paraxial region of the surface is convex, and the configuration in which one surface is concave indicates that a paraxial region of the surface is concave. Thus, even when one surface of the lens is described as convex, an edge of the lens can be concave. Similarly, even when one surface of the lens is described as concave, an edge of the lens can be convex.

[0066] The imaging lens system includes seven lenses. For example, the imaging lens system can include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens disposed in order from an object side. The first lens to the seventh lens can be disposed to have a certain interval between each of the adjacent lenses. For example, an image side surface and an object side surface of the adjacent lenses can not be in contact with each other in a paraxial region. Thus, even when the image side surface of the lens on one side and the object side surface of the lens on the other side are shown as being in contact with each other in the drawing, the image side surface and the object side surface are not in contact with each other between the two lenses.

[0067] The first lens has a refractive power. For example, the first lens has a negative refractive power. One face of the first lens can be convex. For example, an object side surface of the first lens can be convex.

[0068] The first lens includes a spherical surface. For example, both faces of the first lens can be spherical. The first lens can be manufactured using a material having high light transmittance and excellent machinability. For example, the first lens can be manufactured using a glass or a plastic material. The first lens has a high refractive index. For example, the refractive index of the first lens can be 1.7 or more. As another example, the refractive index of the first lens can be 1.7 or more and 1.8 or less.

[0069] The second lens has a refractive power. For example, the second lens can have a negative refractive power. One face of the second lens can be concave. For example, an object side surface or an image side surface of the second lens can be concave.

[0070] The second lens can include a spherical surface. For example, both surfaces of the second lens can be spherical. The second lens can be manufactured using a material having high light transmittance and excellent processability. For example, the second lens can be manufactured using a glass or plastic material. The second lens can have a refractive index greater than that of the first lens. For example, the refractive index of the second lens can be 1.8 or more. As another example, the refractive index of the second lens can be 1.8 or more and less than 2.0.

[0071] The third lens can have a refractive power. For example, the third lens can have a positive refractive power. One surface of the third lens can be convex. For example, the object side surface of the third lens can be convex.

[0072] The third lens can include a spherical surface. For example, both surfaces of the third lens can be spherical. The third lens can be manufactured using a material having high light transmittance and excellent processability. For example, the third lens can be manufactured using a glass or plastic material. The third lens can have a refractive index similar to that of the second lens. For example, the refractive index of the third lens can be 1.8 or more. As another example, the refractive index of the third lens can be 1.8 or more and less than 2.0.

[0073] The fourth lens can have a refractive power. For example, the fourth lens can have a positive refractive power. One surface of the fourth lens can be convex. For example, the object side surface of the fourth lens can be convex.

[0074] The fourth lens can include an aspherical surface. For example, both surfaces of the fourth lens can be aspherical. The fourth lens can be manufactured using a material having high light transmittance and excellent processability. For example, the fourth lens can be manufactured using a glass or plastic material. Among the first to seventh lenses, the fourth lens can have the lowest refractive index. As an example, the refractive index of the fourth lens can be less than 1.6. As another example, the refractive index of the fourth lens can be 1.2 or more and less than 1.6.

[0075] The fifth lens can have a refractive power. The fifth lens can have a negative refractive power. One surface of the fifth lens can be concave. For example, the object side surface of the fifth lens can be concave.

[0076] The fifth lens can include a spherical surface. For example, both surfaces of the fifth lens can be spherical. The fifth lens can be manufactured using a material having high light transmittance and excellent processability. For example, the fifth lens can be manufactured using a glass or plastic material. The fifth lens can have a refractive index similar to that of the third lens. For example, the refractive index of the fifth lens can be 1.8 or more. As another example, the refractive index of the fifth lens can be 1.8 or more and less than 2.0.

[0077] The sixth lens can have a refractive power. For example, the sixth lens can have a positive refractive power. One surface of the sixth lens can be convex. For example, the image-side surface of the sixth lens can be convex.

[0078] The sixth lens can include a spherical surface. For example, both surfaces of the sixth lens can be spherical. The sixth lens can be manufactured using a material having high light transmittance and excellent machinability. For example, the sixth lens can be manufactured using a glass or plastic material. The sixth lens can have a refractive index similar to that of the fourth lens. For example, the refractive index of the sixth lens can be 1.5 or more and less than 1.7.

[0079] The seventh lens can have a refractive power. For example, the seventh lens can have a negative refractive power. At least one surface of the seventh lens can be concave. For example, the object-side surface of the seventh lens can be concave.

[0080] The seventh lens can include an aspherical surface. For example, both surfaces of the seventh lens can be aspherical. The seventh lens can be manufactured using a material having high light transmittance and excellent machinability. For example, the seventh lens can be manufactured using a glass or plastic material. The seventh lens can have a refractive index similar to that of the first lens. For example, the refractive index of the seventh lens can be 1.7 or more. As another example, the refractive index of the seventh lens can be 1.7 or more and less than 1.9.

[0081] The fourth lens and the seventh lens can include an aspherical surface as described above. The aspherical surface of the fourth lens and the seventh lens can be represented by Equation 1 below.

[0082] Equation 1:

[0083]

[0084] In Equation 1, "c" is the reciprocal of the radius of curvature of the corresponding lens, "k" is a conic constant, "r" is the distance from a certain point on the aspherical surface of the lens to the optical axis, "A", "B", "C", and "D" are aspherical constants, and "Z" (or SAG) is the distance from a certain point on the aspherical surface of the lens to the vertex of the aspherical surface, which is taken in the direction of the optical axis.

[0085] The imaging lens system can include a filter, an image sensor, and a stop. The imaging lens system can further include a protection glass.

[0086] A filter can be disposed between the seventh lens and the image sensor. The filter can block light having a specific wavelength. For example, the filter can block light having an infrared wavelength. The image sensor can form an imaging surface. A stop can be configured to adjust the amount of light incident to the lens. For example, the stop can be disposed between the third lens and the fourth lens. A protective glass can be disposed between the filter and the image sensor, and can prevent contamination and damage of the image sensor caused by foreign matter.

[0087] Each of the first to seventh lenses can have a specific refractive index temperature coefficient (DTn -6 / ℃). The refractive index temperature coefficients (DTn) of the lenses can be distinguished from each other by a stop disposed between the lenses. As an example, most of the lenses disposed on the object side of the stop (first lens group) can have a positive refractive index temperature coefficient, and most of the lenses disposed between the stop and the imaging surface (second lens group) can have a negative refractive index temperature coefficient. However, not all of the lenses included in the second lens group can have a negative refractive index temperature coefficient. As an example, among the lenses included in the second lens group, the lens disposed closest to the imaging surface can have a positive refractive index temperature coefficient.

[0088] Among the lenses included in the second lens group, the lens having a positive refractive power can have a negative refractive index temperature coefficient. For example, the fourth lens or the sixth lens included in the second lens group can have a positive refractive power, and can have a negative refractive index temperature coefficient.

[0089] The lenses included in each of the lens groups can have a specific refractive power at a specific position. As an example, among the lenses included in the first lens group, the lens closest to the stop can have a positive refractive power. As another example, among the lenses included in the second lens group, the lens closest to the stop can have a positive refractive power. As another example, among the lenses included in the second lens group, the lens closest to the imaging surface can have a negative refractive power.

[0090] The lenses included in the imaging lens system can satisfy one or more of the following conditional equations regarding the refractive index temperature coefficient (hereinafter, referred to as "DTn").

[0091] Conditional Equation 1: -3.5 ≤ DTnT ≤ 3.5 [10 -6 / ℃]

[0092] Conditional Equation 2: 5.0 ≤ DTnF ≤ 15 [10 -6 / ℃]

[0093] Conditional Equation 3: -20 ≤ DTnR ≤ -8.0 [10 -6 / ℃]

[0094] Condition Equation 4: 0.8 ≤ |DTnF / DTnR| ≤ 1.2 [10 -6 / °C

[0095] In the condition equations 1 to 4, "DTnT" is the sum of DTn of lenses included in the imaging lens system, "DTnF" is the sum of DTn of lenses (first lens group) disposed on the object side of the stop, and "DTnR" is the sum of DTn of lenses (second lens group) disposed between the stop and the imaging plane.

[0096] The DTn of the lenses included in the second lens group can have a certain range. As an example, the refractive index temperature coefficient of the fourth lens (DTn4) or the refractive index temperature coefficient of the sixth lens (DTn6) can be greater than -10 x 10 -6 / °C and less than -0.5 x 10 -6 / °C.

[0097] The lenses included in the imaging lens system can have a certain thermal expansion constant (10 -6 / °C). For example, the thermal expansion constant (CTE) of the first lens to the seventh lens can be 2.0 [10 -6 / °C] or more and 20 [10 -6 / °C] or less. At least one of the lenses included in the imaging lens system can have a thermal expansion constant different from that of the other lenses. As an example, the thermal expansion constant of the sixth lens (CTE6) can be greater than the thermal expansion constants of the other lenses (CTE1, CTE2, CTE3, CTE4, CTE5, and CTE7). As another example, the thermal expansion constant of the seventh lens (CTE7) can be less than the thermal expansion constant of the sixth lens (CTE6).

[0098] The difference between the thermal expansion constant of the sixth lens (CTE6) and the thermal expansion constant of the seventh lens (CTE7) (CTE6-CTE7) can be 1.0 [10 -6 / °C] or more and 5.0 [10 -6 / °C] or less.

[0099] Each of the lenses included in the imaging lens system can have a focal length temperature coefficient (VT) that varies according to temperature. The focal length temperature coefficient (VT) of each of the lenses can be obtained by the following equation.

[0100] VTi = (DTni / (Ndi-1) - CTEi) -1

[0101] In the equation, "VTi" is a focal length temperature coefficient of the i-th lens, "DTni" is a refractive index temperature coefficient of the i-th lens, "Ndi" is a refractive index of the i-th lens, and "CTEi" is a thermal expansion constant of the i-th lens.

[0102] The focal length temperature coefficient obtained by the above equation can satisfy the following conditional equation.

[0103] Conditional equation 5: VT5 < VT4

[0104] Conditional equation 6: |1 / (f5 x VT5)| < |1 / (f4 x VT4)|

[0105] Conditional equation 7: 1 / (f4 x VT4) + 1 / (f6 x VT6) < -2 / (f5 x VT5)

[0106] In the conditional equations 5 to 7, "f4" is a focal length of the fourth lens, "f5" is a focal length of the fifth lens, "f6" is a focal length of the sixth lens, "VT4" is a focal length temperature coefficient of the fourth lens, "VT5" is a focal length temperature coefficient of the fifth lens, and "VT6" is a focal length temperature coefficient of the sixth lens.

[0107] Each of the lenses included in the imaging lens system can have a negative focal length temperature coefficient. The negative focal length temperature coefficient can be represented by the following conditional equation.

[0108] Conditional equation 8: VTi < 0

[0109] In the imaging lens system, the focal length temperature coefficients of the lenses disposed with a stop therebetween can satisfy the following conditional equation.

[0110] Conditional equation 9: 100 < VTS1 - VTS2 < 400[10 -6 / °C]

[0111] In the conditional equation 9, "VTS1" is a focal length temperature coefficient of a lens disposed on an image side closest to the stop, and "VTS2" is a focal length temperature coefficient of a lens disposed on an object side closest to the stop.

[0112] In the imaging lens system, the focal length temperature coefficients of the lenses adjacent to the imaging surface can satisfy the following conditional equation.

[0113] Conditional equation 10: 300 < VTM2 - VTM1 < 900[10 -6 / °C]

[0114] In the imaging lens system, the difference in the focal length temperature coefficients between the lenses adjacent to the imaging surface can be greater than the difference in the focal length temperature coefficients between the lenses adjacent to the object. This configuration can be represented by the following conditional equation.

[0115] Conditional Equation 11: 0 < (VTO1-VTO2) / (VTM1-VTM2) < 1.0

[0116] In Conditional Equations 10 and 11, "VTO1" is a focal length temperature coefficient of a lens disposed closest to an object, "VTO2" is a focal length temperature coefficient of a lens disposed second closest to an object, "VTM1" is a focal length temperature coefficient of a lens of a second closest image-forming surface, and "VTM2" is a focal length temperature coefficient of a lens of a closest image-forming surface.

[0117] The imaging lens system can satisfy one of the following conditional equations.

[0118] Conditional Equation 12: 30 < V4-V5

[0119] Conditional Equation 13: |f4| < 2xf

[0120] Conditional Equation 14: |f5| < 2xf

[0121] In Conditional Equations 12 to 14, "V4" is an Abbe number of the fourth lens, "V5" is an Abbe number of the fifth lens, and "f" is a focal length of the imaging lens system.

[0122] In the following description, the imaging lens system will be described according to one or more examples.

[0123] Reference will be made to Figure 1 A first example of the imaging lens system will be described.

[0124] The imaging lens system 100 can include a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170.

[0125] The first lens 110 can have a negative refractive power, and can have a convex object side surface and a concave image side surface. The second lens 120 can have a negative refractive power, and can have a concave object side surface and a convex image side surface. The third lens 130 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The fourth lens 140 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The fifth lens 150 can have a negative refractive power, and can have a concave object side surface and a concave image side surface. The sixth lens 160 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The seventh lens 170 can have a negative refractive power, and can have a concave object side surface and a convex image side surface.

[0126] The imaging lens system 100 can further include a filter 182, a protective glass 184, an image sensor 190, and a stop ST. The filter 182 and the protective glass 184 can be disposed between the seventh lens 170 and the image sensor 190. The stop ST can be disposed between the third lens 130 and the fourth lens 140.

[0127] Figure 2 and Figure 3 Aberration characteristics and MTF characteristics of the imaging lens system 100 are shown. Figure 4 The amount of change in back focal length (ΔBFL: μm) of the imaging lens system 100 according to temperature is shown. As shown in FIG. 12, the amount of change in back focal length of the imaging lens system 100 is 2.2 μm and 2.6 μm at -40℃ or less and at 80℃ or more, respectively, but is 1.5 μm or less in the range of -20℃ to 60℃. Figure 4

[0128] Table 1 and Table 2 list lens characteristics and aspherical surface values of the imaging lens system 100.

[0129] Table 1

[0130]

[0131]

[0132] Table 2

[0133] Surface Number K A B C D 8 -7.7205E-01 5.2940E-06 3.4185E-08 - - 9 -3.4660E+00 2.7021E-05 -3.4495E-08 - - 14 - -7.9572E-05 -2.2783E-07 -9.8448E-10 1.3392E-11 15 - -7.5011E-05 -3.6238E-07 1.9905E-09 5.4521E-13

[0134] A second example of an imaging lens system will be described with reference to Figure 5 A second example of an imaging lens system will be described with reference to

[0135] The imaging lens system 200 can include a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens 260, and a seventh lens 270.

[0136] The first lens 210 can have a negative refractive power, and can have a convex object side surface and a concave image side surface. The second lens 220 can have a negative refractive power, and can have a concave object side surface and a convex image side surface. The third lens 230 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The fourth lens 240 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The fifth lens 250 can have a negative refractive power, and can have a concave object side surface and a concave image side surface. The sixth lens 260 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The seventh lens 270 can have a negative refractive power, and can have a concave object side surface and a convex image side surface.

[0137] ​The imaging lens system 200 may further include a filter 282, a protective glass 284, an image sensor 290, and an aperture ST. The filter 282 and the protective glass 284 may be disposed between the seventh lens 270 and the image sensor 290. The aperture ST may be disposed between the third lens 230 and the fourth lens 240.

[0138] Figure 6 and Figure 7 The aberration characteristics and MTF characteristics of the imaging lens system 200 are shown. Figure 8 The variation of the back focal length of the imaging lens system 200 with temperature (ΔBFL: μm) is shown. For example... Figure 8 As shown, the variation in back focal length of the imaging lens system 200 is expected to be approximately 2.2 μm at -40°C or less and 2.8 μm at 80°C or greater. However, using a lens characteristic (ΔLENS BACK) in which the focal length can vary with temperature, the substantial variation (DEFOCUS) of the back focal length of the imaging lens system 200 is reduced to ±0.5 μm even in the range of -40°C to 80°C.

[0139] Tables 3 and 4 list the lens characteristics and aspherical surface values ​​of the imaging lens system 200.

[0140] Table 3

[0141] Surface Number Label Radius of Curvature Thickness / Interval Refractive Index Abbe Number DTn CTE VT 1 First Lens 62.561 2.518 1.773 49.62 3.60 8.00 -301.8 2 13.565 9.077 3 Second Lens -27.214 5.900 1.835 42.72 3.80 8.00 -284.2 4 -42.497 15.027 5 Third Lens 61.159 4.691 1.804 46.50 3.70 8.00 -292.8 6 -61.159 7.788 7 Stop Infinity 4.000 8 Fourth Lens 19.140 6.496 1.497 81.56 -6.80 8.00 -46.4 9 -35.374 3.858 10 Fifth Lens -96.821 2.550 1.808 22.76 -3.70 8.00 -79.5 11 18.101 4.458 12 Sixth Lens 26.191 7.327 1.593 68.62 -7.00 11.10 -43.7 13 -29.622 8.772 14 Seventh Lens -42.943 3.050 1.756 45.59 4.90 8.00 -658.8 15 -120.000 0.500 16 Filter Infinity 1.100 1.517 64.17 17 Infinity 0.500 18 Protective Glass Infinity 1.100 1.517 64.17 19 Infinity 3.388 20 Image Side Surface Infinity 0.000

[0142] Table 4

[0143] Surface Number K A B C D 8 -7.72E-01 5.01E-06 3.53E-08 - - 9 -3.47E+00 2.80E-05 -3.40E-08 - - 14 - -8.19E-05 -1.97E-07 -7.33E-10 1.23E-11 15 - -8.14E-05 -3.05E-07 1.95E-09 4.71E-13

[0144] Reference Figure 9 A third example describing an imaging lens system.

[0145] The imaging lens system 300 may include a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, a sixth lens 360, and a seventh lens 370.

[0146] The first lens 310 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. The second lens 320 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. The third lens 330 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fourth lens 340 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fifth lens 350 may have negative refractive power and may have a concave object-side surface and a concave image-side surface. The sixth lens 360 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The seventh lens 370 may have negative refractive power and may have a concave object-side surface and a convex image-side surface.

[0147] The imaging lens system 300 may further include a filter 382, ​​a protective glass 384, an image sensor 390, and an aperture ST. The filter 382 and the protective glass 384 may be disposed between the seventh lens 370 and the image sensor 390. The aperture ST may be disposed between the third lens 330 and the fourth lens 340.

[0148] Figure 10 and Figure 11 The aberration characteristics and MTF characteristics of the imaging lens system 300 are shown. Figure 12 The variation of the back focal length of the imaging lens system 300 with temperature (ΔBFL: μm) is shown. Figure 12 As shown, the variation in back focal length of the imaging lens system 300 is expected to be approximately 1.0 μm at -40°C or less and 4.6 μm at 80°C or greater. However, by using a lens characteristic (ΔLENS BACK) in which the focal length can vary with temperature, even within the range of -40°C to 80°C, the substantial variation (DEFOCUS) of the back focal length of the imaging lens system 300 is reduced to ±2.0 μm.

[0149] Tables 5 and 6 list the lens characteristics and aspherical surface values ​​of the imaging lens system 300.

[0150] Table 5

[0151]

[0152]

[0153] Table 6

[0154] Surface Number K A B C D 8 -7.72E-01 3.51E-06 4.83E-08 - - 9 -3.47E+00 2.82E-05 -1.04E-08 - - 14 - 1.33E-05 -4.56E-07 2.63E-10 -4.37E-12 15 - 1.04E-05 -6.41E-07 1.66E-10 2.85E-12

[0155] Reference Figure 13 The fourth example describes an imaging lens system.

[0156] The imaging lens system 400 may include a first lens 410, a second lens 420, a third lens 430, a fourth lens 440, a fifth lens 450, a sixth lens 460, and a seventh lens 470.

[0157] The first lens 410 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. The second lens 420 may have negative refractive power and may have a concave object-side surface and a convex image-side surface. The third lens 430 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fourth lens 440 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fifth lens 450 may have negative refractive power and may have a concave object-side surface and a concave image-side surface. The sixth lens 460 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The seventh lens 470 may have negative refractive power and may have a concave object-side surface and a convex image-side surface.

[0158] The imaging lens system 400 may further include a filter 482, a protective glass 484, an image sensor 490, and an aperture ST. The filter 482 and the protective glass 484 may be disposed between the seventh lens 470 and the image sensor 490. The aperture ST may be disposed between the third lens 430 and the fourth lens 440.

[0159] Figure 14 and Figure 15 The aberration characteristics and MTF characteristics of the imaging lens system 400 are shown. Figure 16 The variation of the back focal length of the imaging lens system 400 with respect to temperature (ΔBFL: μm) is shown. For example... Figure 16 As shown, the variation in back focal length of the imaging lens system 400 is approximately -6.0 μm at -40°C or less and 12 μm at 80°C or greater. However, using a lens characteristic (ΔLENS BACK) in which the focal length can vary with temperature, the substantial variation (DEFOCUS) of the back focal length of the imaging lens system 400 is reduced to 3.0 μm even in the range of -40°C to 80°C.

[0160] Tables 7 and 8 list the lens characteristics and aspherical surface values ​​of the imaging lens system 400.

[0161] Table 7

[0162]

[0163]

[0164] Table 8

[0165] Surface Number K A B C D 8 -7.72E-01 4.69E-06 2.63E-08 - - 9 -3.47E+00 1.96E-05 -2.34E-08 - - 14 - -5.35E-05 -3.29E-07 -9.15E-10 -4.88E-12 15 - -3.68E-05 -3.84E-07 3.62E-10 1.79E-12

[0166] Reference Figure 17 The fifth example describing an imaging lens system.

[0167] The imaging lens system 500 may include a first lens 510, a second lens 520, a third lens 530, a fourth lens 540, a fifth lens 550, a sixth lens 560, and a seventh lens 570.

[0168] The first lens 510 may have negative refractive power and may have a convex object-side surface and a concave image-side surface. The second lens 520 may have negative refractive power and may have a concave object-side surface and a convex image-side surface. The third lens 530 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fourth lens 540 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The fifth lens 550 may have negative refractive power and may have a concave object-side surface and a concave image-side surface. The sixth lens 560 may have positive refractive power and may have a convex object-side surface and a convex image-side surface. The seventh lens 570 may have negative refractive power and may have a concave object-side surface and a convex image-side surface.

[0169] The imaging lens system 500 may further include a filter 582, a protective glass 584, an image sensor 590, and an aperture ST. The filter 582 and the protective glass 584 may be disposed between the seventh lens 570 and the image sensor 590. The aperture ST may be disposed between the third lens 530 and the fourth lens 540.

[0170] Figure 18 and Figure 19 The aberration characteristics and MTF characteristics of the imaging lens system 500 are shown. Figure 20 The variation of the back focal length of the imaging lens system 500 with temperature (ΔBFL: μm) is shown. Figure 20 As shown, the variation in back focal length of the imaging lens system 500 is expected to be approximately -4.0 μm at -20°C or less and 10 μm at 80°C or greater. However, using a lens characteristic (ΔLENS BACK) in which the focal length can vary with temperature, the substantial variation (DEFOCUS) of the back focal length of the imaging lens system 500 is reduced to 2.5 μm even in the range of -20°C to 80°C.

[0171] Tables 9 and 10 list the lens characteristics and aspherical surface values ​​of the imaging lens system 500.

[0172] Table 9

[0173] Surface Number Label Radius of Curvature Thickness / Interval Refractive Index Abbe Number DTn CTE VT 1 First Lens 73.449 2.590 1.773 49.62 3.60 8.00 -301.8 2 13.367 9.679 1.000 0.00 3 Second Lens -21.099 6.296 1.835 42.72 3.80 8.00 -284.2 4 -27.339 12.933 1.000 0.00 5 Third Lens 70.821 4.826 1.835 42.72 3.80 8.00 -284.2 6 -70.821 5.420 1.000 0.00 7 Stop Infinity 5.435 1.000 0.00 8 Fourth Lens 19.439 6.942 1.497 81.56 -6.80 8.00 -46.4 9 -30.510 2.682 1.000 0.00 10 Fifth Lens -94.519 2.500 1.808 22.76 -3.70 8.00 -79.5 11 21.323 2.469 1.000 0.00 12 Sixth Lens 25.687 6.178 1.593 68.62 -7.00 11.10 -43.7 13 -62.987 9.450 1.000 0.00 14 Seventh Lens -72.856 6.000 1.770 49.35 3.80 7.40 -401.9 15 -120.000 0.500 1.000 0.00 16 Filter Infinity 1.100 1.517 64.17 17 Infinity 0.500 1.000 0.00 18 Protective Glass Infinity 1.100 1.517 64.17 19 Infinity 3.389 1.000 0.00 20 Image Side Surface Infinity 0.000 1.000 0.00

[0174] Table 10

[0175]

[0176]

[0177] A sixth example of an imaging lens system will be described with reference to Figure 21

[0178] The imaging lens system 600 can include a first lens 610, a second lens 620, a third lens 630, a fourth lens 640, a fifth lens 650, a sixth lens 660, and a seventh lens 670.

[0179] The first lens 610 can have a negative refractive power, and can have a convex object side surface and a concave image side surface. The second lens 620 can have a negative refractive power, and can have a concave object side surface and a convex image side surface. The third lens 630 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The fourth lens 640 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The fifth lens 650 can have a negative refractive power, and can have a concave object side surface and a concave image side surface. The sixth lens 660 can have a positive refractive power, and can have a convex object side surface and a convex image side surface. The seventh lens 670 can have a negative refractive power, and can have a concave object side surface and a convex image side surface.

[0180] The imaging lens system 600 can further include a filter 682, a protective glass 684, an image sensor 690, and a stop ST. The filter 682 and the protective glass 684 can be disposed between the seventh lens 670 and the image sensor 690. The stop ST can be disposed between the third lens 630 and the fourth lens 640.

[0181] Figure 22 and Figure 23 Aberration characteristics and MTF characteristics of the imaging lens system 600 are shown. Figure 24 A variation amount (ΔBFL: μm) of a back focal length of the imaging lens system 600 according to temperature is shown. As shown in Table 11, the variation amount of the back focal length of the imaging lens system 600 is expected to be about -4.0 μm at -20°C or less and about 10 μm at 80°C or more, respectively. However, using the lens characteristics (ΔLENS BACK) in which the focal length can vary according to temperature, the substantial variation amount (DEFOCUS) of the back focal length of the imaging lens system 600 is reduced to 2.5 μm even in the range of -20°C to 80°C. Figure 24

[0182] Table 11 and Table 12 list the lens characteristics and aspheric surface values of the imaging lens system 600.

[0183] Table 11

[0184]

[0185] ​​

[0186] Table 12

[0187] Surface Number K A B C D 8 -7.72E-01 4.99E-08 6.95E-09 - - 9 -3.47E+00 2.45E-05 -5.69E-08 - - 14 - -9.06E-05 -2.41E-07 1.27E-09 8.58E-12 15 - -4.84E-05 -3.36E-07 2.69E-09 -4.94E-12

[0188] The imaging lens system in the example can have the following optical properties. For example, the total track length TTL of the imaging lens system can be in a range of 60 mm to 100 mm, the focal length f can be in a range of 12.0 mm to 16.0 mm, the focal length f1 of the first lens can be in a range of -18 mm or less, the focal length f2 of the second lens can be in a range of -20 mm or less, the focal length f3 of the third lens can be in a range of 30 mm to 50 mm, the focal length f4 of the fourth lens can be in a range of 17 mm to 30 mm, the focal length f5 of the fifth lens can be in a range of -30 mm to -10 mm, the focal length f6 of the sixth lens can be in a range of 15 mm to 40 mm, and the focal length f7 of the seventh lens can be in a range of -20 mm or less.

[0189] Table 13 lists the optical properties of the imaging lens system according to the first example to the sixth example.

[0190] Table 13

[0191]

[0192]

[0193] Table 14 lists the values of the conditional equations of the imaging lens system according to the first example to the sixth example.

[0194] Table 14

[0195] Equation First Example Second Example Third Example Fourth Example Fifth Example Sixth Example DTnT -1.500 -1.500 -1.500 -2.500 -2.500 1.500 DTnF 11.100 11.100 11.100 11.200 11.200 11.200 DTnR -12.600 -12.600 -12.600 -13.700 -13.700 -9.700 |DTnF / DTnR| 0.8810 0.8810 0.8810 0.8175 0.8175 1.1546 CTE6-CTE7 3.1000 3.1000 3.1000 3.7000 3.7000 1.4000 1 / (f4 x VT4) -0.0008 -0.0008 -0.0008 -0.0008 -0.0009 -0.0011 1 / (f5 x VT5) 0.0007 0.0007 0.0006 0.0006 0.0006 0.0006 1 / (f6 x VT6) -0.0009 -0.0009 -0.0009 -0.0007 -0.0007 -0.0007 VT4-VT3 246.4 246.4 246.4 237.8 237.8 242.8 VT6-VT7 615.1 615.1 615.1 358.2 358.2 824.1 |(VT1-VT2) / (VT6-VT7)| 0.0286 0.0286 0.0286 0.0491 0.0491 0.0147 V4-V5 58.80 58.80 58.80 58.80 58.80 48.92

[0196] According to the foregoing examples, an imaging lens system that can achieve constant optical properties at high ambient temperatures or low ambient temperatures can be provided.

[0197] While the present disclosure includes specific examples, it will be apparent to one of ordinary skill in the art, having the benefit of this disclosure, that various changes in form and detail can be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described in this application should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects in each example should be considered as being applicable to similar features or aspects in other examples. Suitable results can be achieved if the described techniques are performed in a different order, and / or if the described systems, architectures, devices, or circuits are combined or substituted with other components or their equivalents. Therefore, the scope of the present disclosure should not be deemed limited to the specific examples described herein, but should be understood to include any and all variations that are within the scope of the appended claims and their equivalents.

Claims

1. An imaging lens system comprising: a first lens group disposed on an object side of a stop; and a second lens group disposed between the stop and an image plane, wherein the first lens group includes a total of three lenses having refractive power, and the second lens group includes a total of four lenses having refractive power, wherein a sum DTnT of a temperature coefficient of refractive index of a lens included in the first lens group and a temperature coefficient of refractive index of a lens included in the second lens group is -3.5 [10 -6 / °C] or more and 3.5 [10 -6 / °C] or less, wherein the first lens group includes, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, and the second lens group includes, in order from the object side, a fourth lens having positive refractive power, a fifth lens having negative refractive power and a concave object side surface, a sixth lens having positive refractive power, and a seventh lens having negative refractive power, and wherein the imaging lens system has a total of seven lenses having refractive power. a sum DTnF of the refractive index temperature coefficients of the lenses included in the first lens group and a sum DTnR of the refractive index temperature coefficients of the lenses included in the second lens group satisfy 0.8 ≤ |DTnF / DTnR| ≤ 1.

2.

2. The imaging lens system of claim 1, wherein, The sum DTnF of the temperature coefficients of refractive indices of the lenses included in the first lens group is 5.0 [10 -6 / °C] or more and 15 [10 -6 / °C] or less.

3. The imaging lens system of claim 1, wherein, The sum DTnR of the refractive index temperature coefficients of the lenses included in the second lens group is -20 [10 -6 / °C] or more and -8.0 [10 -6 / °C] or less.

4. The imaging lens system of claim 1, wherein, The second lens has a convex image side surface.

5. The imaging lens system of claim 1, wherein, The third lens has a convex image side surface.

6. The imaging lens system of claim 1, wherein, The fourth lens has a convex image side surface.

7. The imaging lens system of claim 1, wherein, ​

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