Imaging lens, recognition device, and information processing device

Abstract

The invention provides a bright, high-performance and small-sized imaging lens capable of recognizing a wide-angle field angle of a face, a recognition device, and an information processing device. An imaging lens (100) includes: first to fourth lenses (L1 to L4) arranged in order from an object side; and an aperture stop (S) disposed closest to the object side. The first lens (L1) is a positive meniscus lens having a convex surface facing the object side, the second lens (L2) is a negative lens having an inflection point on at least one surface, the third lens (L3) is a positive lens having a convex surface facing the image surface side and having an inflection point at the periphery of the lens on the surface of the object side, and the fourth lens (L4) is a negative lens having a concave surface on the image surface side and having an inflection point at the periphery. The paraxial radius of curvature (R) of the lens surface closest to the image surface side in the entire optical system is the smallest.

Description

Technical Field

[0001] This disclosure relates to imaging lenses, recognition devices, and information processing devices. Background Technology

[0002] In recent years, the demand for information security has surged in society to prevent data leakage from information terminals. As a countermeasure for users, passwords have become more complex to prevent information leakage from information terminals or to restrict their use. However, in previous information security measures, making passwords more complex made them difficult for users to use, so fingerprint recognition or near-infrared facial recognition devices were also used for security enhancements.

[0003] Furthermore, in order to establish a higher level of recognition than motion sensing, these near-infrared devices are also being made more pixelated.

[0004] Furthermore, in recent years, laptops have been equipped with facial recognition devices. Therefore, miniaturization with portability in mind has been implemented in these recognition devices. The market demands recognition devices that not only provide facial authentication for login but also incorporate motion sensing and other functions. Technologies that combine high-performance imaging lenses with miniaturization are known (see, for example, Patent Documents 1 and 2).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-018162;

[0006] Patent Document 2: Japanese Patent Application Publication No. 2016-139093.

[0007] In addition, in recent years, as infrared cameras, cameras have emerged that can capture near-infrared bands with main wavelengths of 850nm and 940nm, as well as cameras that can capture monochromatic (visible light) wavelengths of 450nm in addition to the near-infrared band.

[0008] However, in the imaging lenses of the aforementioned Patent Documents 1 and 2, when applied to recognition devices, the field of view is small, resulting in an image of a person's face (facial area) that is too small on the image sensor. This makes it difficult for the recognition device to identify a human face, thus hindering its use in recognition devices. Therefore, there is a need for an imaging lens that not only meets the optical performance requirements of the near-infrared band but also the wavelength band of visible light, is smaller than conventional infrared imaging lenses, and has a bright, high-performance imaging lens with an appropriate field of view that enables the recognition device to recognize faces. Summary of the Invention

[0009] This disclosure was made in view of the above circumstances, and its purpose is to provide a shooting lens, recognition device, and information processing device that are capable of recognizing faces with an appropriate field of view, and are bright, high-performance, and compact.

[0010] To solve the above-mentioned problems and achieve the objective, the imaging lens of the first embodiment of this disclosure includes: a first lens to a fourth lens, arranged sequentially from the object side; and an aperture stop, arranged closest to the object side. The first lens is a positive meniscus lens with its convex surface facing the object side, the second lens is a negative lens with an inflection point on at least one side, the third lens is a positive lens with its convex surface facing the image plane side and an inflection point on the object side surface at the lens periphery, and the fourth lens is a negative lens with a concave surface on the image plane side and an inflection point at the periphery. In the overall optical system, the paraxial radius of curvature R of the lens surface closest to the image plane side is the smallest. When the focal length of the fourth lens is set to f4 and the focal length of the overall optical system is set to f, condition (1) is satisfied:

[0011] 0.8 < |f4 / f| < 1.0 …(1).

[0012] In addition, the identification device of the second aspect of this disclosure includes the above-described imaging lens and a single imaging element that receives the image formed by the imaging lens and generates an imaging signal.

[0013] Furthermore, the information processing apparatus of the third aspect of this disclosure includes the aforementioned identification device.

[0014] According to this disclosure, it achieves the effect of enabling the recognition device to recognize a wide field of view, and has a bright, high-performance, and small imaging lens. Attached Figure Description

[0015] Figure 1 This is a diagram showing the lens structure of the imaging lens according to Embodiment 1 of this disclosure.

[0016] Figure 2A This is an aberration diagram of the imaging lens according to Embodiment 1 of this disclosure.

[0017] Figure 2B It is the MTF of the imaging lens of Embodiment 1 of this disclosure.

[0018] Figure 2C It is the distortion grid of the imaging lens of Embodiment 1 of this disclosure.

[0019] Figure 3 This is a diagram showing the lens structure of the imaging lens according to Embodiment 2 of this disclosure.

[0020] Figure 4A This is an aberration diagram of the imaging lens according to Embodiment 2 of this disclosure.

[0021] Figure 4B It is the MTF of the imaging lens of Embodiment 2 of this disclosure.

[0022] Figure 4CIt is the distortion grid of the imaging lens in Embodiment 2 of this disclosure.

[0023] Figure 5 This is a diagram showing the lens structure of the imaging lens according to Embodiment 3 of this disclosure.

[0024] Figure 6A This is an aberration diagram of the imaging lens according to Embodiment 3 of this disclosure.

[0025] Figure 6B It is the MTF of the imaging lens of Embodiment 3 of this disclosure.

[0026] Figure 6C It is the distortion grid of the imaging lens in Embodiment 3 of this disclosure.

[0027] Figure 7 This is a diagram showing the lens structure of the imaging lens according to Embodiment 4 of this disclosure.

[0028] Figure 8A This is an aberration diagram of the imaging lens according to Embodiment 4 of this disclosure.

[0029] Figure 8B It is the MTF of the imaging lens of Embodiment 4 of this disclosure.

[0030] Figure 8C It is the distortion grid of the imaging lens in Embodiment 4 of this disclosure.

[0031] Figure 9 This is an example of the reflectivity characteristics of the coating corresponding to the near-infrared region on the lens surface of each of the first to fourth lenses of the imaging lenses in embodiments 1 to 4 of this disclosure.

[0032] Figure 10 This is a diagram showing a simplified structure of an information processing device equipped with an identification device having an imaging lens according to various embodiments of the present disclosure.

[0033] Figure 11 It means Figure 10 A simplified diagram of the identification device.

[0034] Figure 12 This is a block diagram illustrating the functional structure of an information processing device equipped with an identification device having an imaging lens according to various embodiments of the present disclosure.

[0035] Figure 13 This is a diagram showing the size of a face displayed on the screen when the field of view of the camera lens is 80 degrees or more.

[0036] Figure 14 This is a diagram showing the size of a face displayed on the screen when the field of view of the camera lens is less than 80 degrees.

[0037] Explanation of reference numerals in the attached figures

[0038] 30…Information processing device; 31…Identification device; 100…Picture lens; L1…First lens; L2…Second lens; L3…Third lens; L4…Fourth lens; S…Aperture stop; CG…Glass cover. Detailed Implementation

[0039] The imaging lens, imaging device, and information processing device of this disclosure will now be described with reference to the accompanying drawings. Furthermore, this disclosure is not limited by the embodiments described below. Additionally, the figures referred to in the following description are only schematic representations of shapes, sizes, and positional relationships to the extent that the content of this disclosure can be understood. That is, this disclosure is not limited to the shapes, sizes, and positional relationships illustrated in the figures. Furthermore, the same reference numerals are used for the same parts, and detailed descriptions are omitted.

[0040] [Implementation Method]

[0041] Figure 1 , Figure 3 , Figure 5 as well as Figure 7 These are cross-sectional views showing the lens structure of the imaging lenses in embodiments 1 to 4. In each cross-sectional view, the left side is the object side (front), and the right side is the image side (rear).

[0042] Each embodiment of the imaging lens 100 includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from the object side to the image side. Furthermore, the imaging lens 100 includes an aperture stop S disposed closer to the object side than the first lens L1.

[0043] In addition, Figure 1 , Figure 3 , Figure 5 as well as Figure 7 In the diagram, additional reference numerals 1 to 9 are used to denote the surfaces of any of the first lens L1 to the fourth lens L4 and the aperture stop S. Hereinafter, these surfaces will be referred to as surfaces 1 to 9 sequentially from the object side towards the image side. Surface 1 is the surface of the aperture stop S. Furthermore, in... Figure 1 , Figure 3 , Figure 5 as well as Figure 7 In the accompanying drawings, reference numeral CG denotes an infrared parallel plate equivalent to a component consisting of a glass cover for a single imaging element and at least one of various filters. The incident side of the infrared parallel plate CG is referred to as surface 10, and the image side is referred to as surface 11.

[0044] The imaging lens 100 is configured with an aperture stop, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4, starting from the side closest to the object. The imaging lens 100 has a lens structure in which the first lens L1 is a positive lens, the second lens L2 is a negative lens with negative optical power, the third lens L3 is a positive lens, and the fourth lens is a negative lens, with positive and negative lenses arranged sequentially. With this structure, correction of spherical aberration and coma becomes easier, and good telecentrism can also be achieved on the image side.

[0045] The first lens L1 is a positive lens with its convex surface facing the object side; it can also be a meniscus lens or a biconvex lens. As in the embodiments described later, the material of the first lens L1 can be either plastic or glass.

[0046] The second lens L2 is constructed using a negative lens that has an inflection point on at least one side and a relatively small deviation, but it may also have inflection points on both sides. Here, the inflection point on one side refers to the region encompassing 60% to 80% of the aperture of the second lens L2 relative to side 4 or side 5, from the optical axis toward the outer edge.

[0047] The third lens L3 is a positive lens with a convex surface facing the image plane and an inflection point on the object side of the lens peripheral portion. The inflection point of the lens peripheral portion refers to the region encompassing 80% to 90% of the aperture of the third lens L3 relative to the surface 7, extending from the optical axis toward the outer edge.

[0048] The fourth lens L4 is constructed using a negative lens that is concave on the image plane side and has an inflection point in the peripheral region. The inflection point in the peripheral region refers to the area encompassing 60% to 80% of the aperture of the fourth lens L4 relative to the surface 8 from the optical axis toward the outer edge.

[0049] Although the first lens L1 can be aspherical or spherical, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical lenses, each possessing the characteristics of an aspherical shape. Furthermore, by making the second lens L2, the third lens L3, and the fourth lens L4 have inflection points, aberrations can be highly corrected to achieve a thinner thickness (overall length) in the light direction of the imaging lens 100.

[0050] In addition, regarding the lens material, as shown in the embodiments, optical plastic materials or glass materials are used.

[0051] Figures 2A-2C , Figures 4A-4C , Figures 6A-6C as well as Figures 8A-8CThese are the longitudinal aberration diagram, MTF, and distortion grid of the imaging lens 100 in embodiments 1 to 4. In the spherical aberration diagram, the spherical aberration amounts for the d-line (yellow: wavelength 587.6 nm), g-line (blue: wavelength 435.8 nm), C-line (red: 653.3 nm), and near-infrared 1940 (940 nm) are shown respectively. In the astigmatism diagram, the solid line S represents the astigmatism amount on the sagittal image plane, and the dashed line T represents the astigmatism amount on the tangential image plane. Furthermore, in the distortion aberration diagram, only the distortion aberration amount for the d-line is shown. Angle (deg) represents the half field of view (°). Regarding the distortion grid, the thin line represents the paraxial FOV (ideal) grid, and the thick line represents the actual FOV (real) grid. In addition, in the MTF, at frequencies of 1 / 4Ny and 1 / 2Ny, a 5-dot dashed line represents the MTF of the sagittal image plane at 1 / 4Ny, a thick dashed line represents the MTF of the tangential image plane at 1 / 4Ny, a 3-dot dashed line represents the MTF of the sagittal image plane at 1 / 2Ny, and a thin dashed line represents the MTF of the tangential image plane at 1 / 2Ny.

[0052] Next, the conditions of the imaging lens 100 in each embodiment will be explained.

[0053] When the focal length of the first lens L1 is set to f1, the focal length of the fourth lens L4 is set to f4, and the focal length of the entire optical system is set to f, the imaging lens 100 of each embodiment satisfies the following condition (1).

[0054] 0.8 < |f4 / f| < 1.0…(1)

[0055] Condition (1) is a conditional expression related to the overall focal length of the shooting lens 100 and the optical power of the fourth lens L4.

[0056] When |f4 / f| is below the lower limit of condition (1), the overall focal length tends to shorten, which is advantageous for a wider angle of view. However, astigmatism tends to become excessive, and distortion aberration also tends to increase, making it difficult to achieve the desired performance. On the other hand, when |f4 / f| is above the upper limit of condition (1), there is a trend to improve spherical aberration and astigmatism. However, since the field of view tends to narrow, the performance desired by the present invention cannot be achieved, so it is not preferred. Therefore, by satisfying condition (1), the imaging lens 100 can achieve a balance between short profile (low height) and high performance. That is, when condition (1) is not satisfied, when the imaging lens 100 is disposed in the bezel of the display panel of a laptop computer or the like, it cannot be housed in the space of the thick portion of the bezel or the space housing the display panel, the imaging lens 100 protrudes from the surface of the bezel, or the thickness of the bezel or the display panel increases. As a result, if condition (1) is not met, and the imaging lens 100 is disposed on the frame and the display panel, the thickness of the display panel and the frame increases, thereby compromising portability and aesthetics.

[0057] Condition (2) is related to the refractive index of the lens. When the refractive index of the material of the first lens relative to the d-line is set to N1, the refractive index of the material of the second lens relative to the d-line is set to N2, the refractive index of the material of the third lens relative to the d-line is set to N3, and the refractive index of the material of the fourth lens relative to the d-line is set to N4, condition (2) is satisfied.

[0058] N1≈N3∩N2≈N4∩N1<N2…(2)

[0059] The imaging lens 100 in each embodiment has a lens structure in which the first lens L1 is positive, the second lens L2 is negative, the third lens L3 is positive, and the fourth lens L4 is negative, starting from the object side. Furthermore, the first lens L1 (as a positive lens) and the third lens L3 (as a negative lens) have the same refractive index (N1) and the third lens L3 have the same refractive index (N3), and the second lens L2 (as a negative lens) and the fourth lens L4 (as a negative lens) have the same refractive index (N2) and the fourth lens L4 (N4). By making N2 greater than N1, chromatic aberration can be reduced.

[0060] If condition (2) is not met, the chromatic aberration becomes insufficiently corrected and is therefore not preferred.

[0061] Furthermore, when the refractive index of the material of the first lens L1 relative to the d line is set to N1, the imaging lens 100 of each embodiment satisfies condition (3).

[0062] 1.49 < N1 < 1.55…(3)

[0063] When the refractive index N1 is below the lower limit of condition (3), the optical performance is further improved, but the cost increases, so it is not preferred. In addition, when the refractive index N1 is above the upper limit of condition (3), the optical performance affects chromatic aberration, so it is not preferred. Therefore, by making the imaging lens 100 satisfy condition (3), a balance between cost and chromatic aberration is achieved, and a bright, high-performance and small (compact) imaging lens 100 can be realized.

[0064] Furthermore, when the refractive index of the material of the fourth lens L4 relative to the d line is set to N4, the imaging lens 100 of each embodiment satisfies condition (4).

[0065] 1.63 < N4 < 1.67…(4)

[0066] When the refractive index N4 is below the lower limit of condition (4), or above the upper limit of condition (4), the balance of chromatic aberration is broken. Considering the balance between cost and chromatic aberration, a bright, high-performance and compact shooting lens 100 can be achieved by satisfying condition (4).

[0067] Furthermore, when the paraxial radius of curvature on the imaging side of the first lens is set to R2 and the paraxial radius of curvature on the object side of the second lens is set to R3, the imaging lens 100 of each embodiment satisfies condition (5).

[0068] 0.9 < R2 / R3 < 1.2…(5)

[0069] When condition (5) is below the lower limit, the astigmatism increases and tends to tilt towards the negative side, so it is not preferred. Conversely, when condition (5) is above the upper limit, the astigmatism also increases and tends to tilt towards the positive side, so it is not preferred. Considering astigmatism, by satisfying condition (5), a high-performance imaging lens 100 can be achieved.

[0070] In addition, when the optical length is set to TTL and the image height is set to IH, the imaging lens 100 of each embodiment satisfies condition (6).

[0071] 0.85<TTL / 2*IH<0.95…(6)

[0072] Below the lower limit of condition (6), compared with the image height, the overall optical length tends to decrease, which is beneficial for miniaturization, but the aberrations worsen, resulting in insufficient aberration correction, so it is not preferred. In addition, above the upper limit of condition (6), although the aberrations are improved, the overall length increases, so it is not preferred.

[0073] Furthermore, when the half field of view is set to ω, the imaging lens 100 of each embodiment satisfies condition (7).

[0074] 29°<ω<40°…(7)

[0075] Condition (7) is the field of view of the imaging lens 100 in each embodiment, and it is the condition that determines the appropriate field of view by the imaging lens 100. In view of the face recognition function of the infrared camera, if the lower limit of condition (7) is below, a telephoto lens is shown, which is not suitable as the field of view of the imaging lens 100. In addition, if the upper limit is above, it becomes a wide-angle lens, so it is difficult to recognize a person's face, and therefore it is not preferred.

[0076] Furthermore, when the focal length of the entire optical system (shooting lens 100) is set to f and the total length of the optical system (long side direction of shooting lens 100) is set to OAL, the shooting lens 100 of each embodiment satisfies condition (11).

[0077] 0.60 < f / OAL < 0.90…(11)

[0078] Condition (11) is the condition for achieving a balance between the focal length f and the total length OAL of the entire optical system. In the imaging lens 100 of each embodiment, when f / OAL is below the lower limit of condition (11), a further wide-angle can be achieved, but there is a trend towards an increased front spherical diameter, which raises concerns about a larger size. On the other hand, when f / OAL is above the upper limit of condition (11), the total length of the optical system becomes smaller, but it is difficult to achieve a wide field of view. The imaging lens 100 that satisfies condition (11) can achieve both miniaturization and a wide field of view.

[0079] Furthermore, when the total length of the optical system is set to OAL and the effective optical diameter of the lens (first lens L1) located closest to the object is set to EfD1, the imaging lens 100 of each embodiment satisfies condition (12).

[0080] 2.2 < OAL / EfD1 < 3.2…(12)

[0081] Condition (12) is the condition for achieving a balance between the total length of the lens and the front spherical diameter of the lens (first lens L1). When OAL / EfD1 is below the lower limit of condition (12), the optical system can be miniaturized (shortened in the optical axis direction), but it is difficult to achieve a wide field of view. When OAL / EfD1 is above the upper limit of condition (12), the performance of the optical system is improved, but it is difficult to achieve miniaturization (shortened in the optical axis direction). By satisfying condition (12), the imaging lens 100 can achieve both miniaturization (shortened in the optical axis direction) and high performance.

[0082] In addition, when the exit pupil position is set to EXP and the image height is set to IH, the imaging lens of each embodiment satisfies condition (13).

[0083] -1.3<EXP / IH<-0.90…(13)

[0084] Condition (13) is the condition that optimizes the angle of incidence of light toward the image plane. When EXP / IH is below the lower limit of condition (13), the angle of incidence of light tends to decrease, but it is difficult to shorten the overall length of the optical system to achieve miniaturization. On the other hand, when EXP / IH is above the upper limit of condition (13), the angle of incidence of light tends to increase. Therefore, by satisfying condition (13), the imaging lens 100 can be miniaturized.

[0085] Furthermore, when the focal length of the first lens L1 is set to f1 and the focal length of the second lens L2 is set to f2, the imaging lenses of each embodiment satisfy condition (14).

[0086] 0.30 < |f1 / f2| < 0.55…(14)

[0087] Condition (14) is related to the balance of the focal lengths of the first lens L1 and the second lens L2. When |f1 / f2| is below the lower limit of condition (14), the lens power of f2 is weaker than that of f1, so spherical aberration and distortion aberration are easily insufficiently corrected, making it difficult to achieve high performance. On the other hand, when |f1 / f2| is above the upper limit of condition (14), astigmatism is easily increased, which is not preferable. Therefore, the imaging lens 100 can achieve high performance by satisfying condition (14).

[0088] Furthermore, when the focal length of the first lens L1 is set to f1 and the focal length of the third lens L3 is set to f3, the imaging lens 100 of each embodiment satisfies condition (15).

[0089] 1.0 < f1 / f3 < 3.3…(15)

[0090] Condition (15) is a conditional expression related to the positive optical power of the first lens L1 and the positive optical power of the third lens L3. When f1 / f3 is below the lower limit of condition (15), astigmatism tends to be too small, and distortion aberration and coma aberration are also generated relatively large, making it difficult to achieve the desired performance. On the other hand, when f1 / f3 is above the upper limit of condition (15), spherical aberration tends to be too large, thus breaking the balance with astigmatism and making it difficult to achieve the desired performance.

[0091] Furthermore, when the focal length of the third lens L3 is set to f3 and the focal length of the fourth lens L4 is set to f4, the imaging lens 100 of each embodiment satisfies condition (16).

[0092] 0.6 < |f3 / f4| < 1.1…(16)

[0093] Condition (16) is a conditional expression related to the optical power of the third lens L3 and the fourth lens L4. When f3 / f4 is below the lower limit of condition (16), astigmatism tends to be excessive, and distortion aberration also tends to increase, making it difficult to achieve the desired performance. On the other hand, when f3 / f4 is above the upper limit of condition (16), the overall focal length increases, and the field of view tends to be angled, thus tending to improve astigmatism and distortion aberration. However, since spherical aberration tends to increase, it is difficult to achieve the desired performance. Therefore, by satisfying condition (16), the imaging lens 100 can achieve a balance between miniaturization (low height) and high performance.

[0094] Furthermore, the first lens L1 to the fourth lens L4 of the imaging lens 100 in each embodiment each have a near-infrared region corresponding coating (layer coating) covering the lens surface. This near-infrared region corresponding coating transmits light in the 450-940nm frequency band, and the reflectivity of at least the near-infrared region 850nm-940nm frequency band is less than 2%.

[0095] Figure 9 This describes the reflectivity characteristics of an example of the coating corresponding to the near-infrared region on the lens surface of each of the first lens L1 to the fourth lens L4 of the imaging lens 100 in embodiments 1 to 4. Figure 9 In the diagram, the horizontal axis represents the wavelength band, and the vertical axis represents reflectivity. Figure 9 In the diagram, curve K1 represents the reflectivity characteristics of a typical multi-coating system, while curve K2 represents the reflectivity characteristics of the coating in the near-infrared region (or the multi-coating system in the near-infrared region).

[0096] On the lens surfaces of the first lens L1 to the fourth lens L4 of the imaging lens 100, a coating (or layering) is applied to the lens surface. Figure 9 The near-infrared region corresponding coating (solid line) is shown as curve K1. By covering (coating or layering) such a near-infrared region corresponding coating on the lens, it is possible to realize an imaging lens that also corresponds to near-infrared light, and an imaging device equipped with such an imaging lens. Furthermore, the near-infrared region corresponding coating is applied and formed onto the lens surfaces of each of the first lens L1 to the fourth lens L4 using known techniques. Alternatively, a thin sheet of the near-infrared region corresponding coating can be adhered to the lens surfaces of each of the first lens L1 to the fourth lens L4.

[0097] The imaging lens 100 of the present disclosure has a four-element structure, and the lens surface has eight surfaces. The transmittance of the imaging lens 100 is also an important factor for both the imaging device and the recognition device.

[0098] Here, if we simply calculate the transmittance of the four-element imaging lens 100 in embodiments 1-4 of this disclosure at 940nm near-infrared light, then in the case of a four-element structure, since there are eight reflective surfaces, it becomes (1 - reflectance) to the power of 8. Therefore, if the reflectance at 940nm is 33%, then the coverage (coating) is sufficient. Figure 9 The transmittance at 940 nm shown by curve K1 in the general case of multiple coatings (dashed line) is 940 nm transmittance = (1 - 0.33)^8 = 4.1%, so it is not preferred.

[0099] On the other hand, such as Figure 9 As shown in curve K2, when the transmittance at 940 nm for the multi-coated near-infrared region (curve K2) was also calculated in the same way, with a reflectance of 2% at 940 nm (refer to line H1), the transmittance at 940 nm = (1 - 0.02)^8 = 85.1%, which can achieve good transmittance and is suitable as the imaging lens 100 of the imaging device capable of near-infrared imaging.

[0100] Therefore, in each of embodiments 1 to 4, the imaging lens 100 covers the first lens L1 to the fourth lens L4 with multiple coatings corresponding to the near-infrared region, transmitting light in the 450-940nm frequency band, and the reflectivity of at least the near-infrared region 850nm-940nm frequency band is less than 2%. Figure 9 As shown in curve K2, in the near-infrared region corresponding to multiple coatings, the reflectivity in the visible light region of 450–650 nm is also low. However, if the sensor characteristics (image sensor characteristics) of the near-infrared imaging device are also considered, the reflectivity in the visible light region can also be above 2%.

[0101] In addition, the glass covers described in embodiments 1 to 4 are also covered (coated). Figure 9 Such infrared radiation with a reflectivity of less than 2% in the 850-940nm band corresponds to multiple coatings and is suitable for near-infrared imaging devices.

[0102] [Filming device]

[0103] Next, an embodiment of an information processing device (PC) that uses the imaging lens 100 of each embodiment as an identification device for an imaging optical system will be described.

[0104] Figure 10This is a diagram showing a simplified structure of an information processing device equipped with an identification device having an imaging lens 100 according to various embodiments. Figure 11 It means Figure 10 A simplified diagram of the identification device. Figure 12 This is a block diagram illustrating the functional structure of an information processing device that includes an identification device with imaging lenses in various embodiments.

[0105] Figures 10-12 The information processing device 30 shown includes at least an identification device 31, a signal processing unit 32, an image processing unit 33, a control unit 34, a display unit 35, a storage unit 36, a communication unit 37, an input unit 38, a sound input / output unit 39, and an imaging device 40.

[0106] Under the control of the control unit 34, the identification device 31 generates an image signal by capturing images of a predetermined field of view, and outputs the image signal to the signal processing unit 32. The identification device 31, as... Figure 11 As shown, it includes at least a cover 311, a shooting lens 100 according to each embodiment, and a single shooting element 312. The identification device 31 is disposed on the front side of the information processing device 30. Specifically, the identification device 31 is disposed in a position parallel to the shooting device 40.

[0107] Cover 311 is constructed using a glass cover or the like, which serves as a component for preventing dirt and dust from entering the lens 100.

[0108] The single-unit imaging element 312 receives the image of the subject object imaged by the imaging lens 100 and generates an imaging signal by photoelectric conversion. The single-unit imaging element 312 is constructed using a CCD sensor, CMOS sensor, or the like. Preferably, the single-unit imaging element 312 is formed by arranging effective pixels of 8 megapixels or more, i.e., 4K or higher (3840×2160 or higher), in a two-dimensional matrix.

[0109] Under the control of the control unit 34, the signal processing unit 32 performs A / D conversion and other processing on the shooting signal input from the single imaging element 312, converting it into a digital shooting signal and outputting it to the image processing unit 33. For example, the signal processing unit 32 is configured using a DSP (Digital Signal Processor). Furthermore, under the control of the control unit 34, the signal processing unit 32 performs A / D conversion and other processing on the shooting signal input from the imaging device 40, converting it into a digital shooting signal and outputting it to the image processing unit 33.

[0110] Under the control of the control unit 34, the image processing unit 33 performs prescribed image processing on the digital capture signal input from the signal processing unit 32 and outputs it to the display unit 35 or the storage unit 36. For example, the image processing unit 33 may be configured using a GPU (Graphics Processing Unit). Here, the prescribed image processing includes shadow correction, white balance adjustment, image center cropping, and noise reduction.

[0111] The control unit 34 controls each component constituting the information processing device 30. The control unit 34 includes a processor and a memory. The processor is constructed using a CPU, FPGA (Field-Programmable Gate Array), or the like. The memory is constructed using RAM (Random Access Memory), ROM (Read Only Memory), or the like. The control unit 34 performs known pattern matching on the feature information representing the user's facial features stored in the storage unit 36 ​​and the captured signal from the recognition device 31 input via the image processing unit 33, and performs facial recognition processing on the user.

[0112] Under the control of the control unit 34, the display unit 35 displays video footage captured by the image processing unit 33, captured images, still images corresponding to image signals stored in the storage unit 36, and various information related to the information processing device 30. The display unit 35 also includes a display panel 351 for displaying images and a bezel 352 surrounding the display panel. The imaging device 40 is disposed on the bezel 352. Specifically, when using the information processing device 30, the imaging device 40 is disposed on the bezel 352 facing the object, opposite to the user. The thickness of the bezel 352 is approximately 5.0 mm. While this thickness is considered in the requirements for the imaging lens, the imaging lens of the present invention is suitable for this thickness.

[0113] Storage unit 36 ​​stores various information related to information processing device 30, programs executed by information processing device 30, and shooting signals (RAW data, JPEG data) captured by shooting device 40. Storage unit 36 ​​is composed of flash memory, SSD (Solid State Drive), HDD (Hard Disk Drive), and memory cards.

[0114] Under the control of the control unit 34, the communication unit 37 transmits the captured signal from the imaging device 40 to the outside via the network according to the prescribed communication standards, and receives various information input from the outside. The communication unit 37 uses communication standards such as those based on 3GPP (registered trademark), 4G, LTE, 5G, WiMAX, and Wi-Fi (registered trademark) as defined by IEEE.

[0115] The input unit 38 accepts user input and outputs operation information corresponding to the accepted operation to the control unit 34. For example, the input unit 38 may be constructed using a touch panel, keyboard, mouse, etc.

[0116] Under the control of the control unit 34, the sound input / output unit 39 receives external sound input, converts it into a sound signal, and outputs it to the storage unit 36 ​​or the communication unit 37. Additionally, under the control of the control unit 34, the sound input / output unit 39 converts sound signals input from the storage unit 36 ​​or the communication unit 37 and outputs them to the outside. The sound input / output unit 39 is constructed using a microphone and a speaker, among other things.

[0117] Under the control of the control unit 34, the imaging device 40 generates an imaging signal by imaging a predetermined field of view and outputs the imaging signal to the signal processing unit 32. The imaging device 40 is disposed on the front side of the information processing device 30. Specifically, the imaging device 40 is disposed at a position where the user can photograph the information processing device 30. Of course, the placement of the imaging device 40 can be appropriately changed according to the shape, size, and usage of the information processing device 30.

[0118] The information processing device 30 configured in this way can use the recognition device 31 with the imaging lens 100 to perform facial recognition and other tasks with external devices at a high image quality of 360,000 pixels or more, and can also conduct communication based on Web communication via the Internet.

[0119] Here, a comparison is made between the field of view of the imaging lens 100 used in the recognition device 31 and that of imaging lenses exceeding 80°.

[0120] Figure 13 This is a schematic diagram showing the size of the face displayed on the image P1 captured by the recognition device 1 when the field of view of the imaging lens used by the recognition device 31 exceeds 80 degrees. Figure 14 This is a schematic diagram showing the size of the face displayed on the image P1 captured by the recognition device 31 when the field of view of the imaging lens 100 of the recognition device 31 is less than 80 degrees. Furthermore, in Figure 14 In this context, the field of view of the imaging lens 100 is assumed to be approximately 60 degrees.

[0121] like Figure 13As shown in image P1, when the field of view of the imaging lens used by the recognition device 31 exceeds 80 degrees, the field of view 501 of the imaging lens is too wide, resulting in the human face 500 being imaged on the image sensor becoming smaller. As a result, the human face 500 (facial area) is too small, making it difficult for the recognition device 31, which uses an imaging lens with a field of view exceeding 90 degrees, to recognize the human face.

[0122] In contrast, such as Figure 14 As shown in image P1, with the field of view of the imaging lens 100 used by the recognition device 31 being approximately 60 degrees, the human face 500 imaged on the image sensor becomes larger. As a result, the recognition device 31 using the imaging lens 100 can easily recognize the human face. That is, since the human face 500 occupies a large area of ​​image P1, the control unit 34 can perform pattern matching with respect to the human face 500 with high accuracy.

[0123] Furthermore, while a PC has been described as an example of an information processing device 30 in this embodiment, the identification device 31 can be applied to, for example, a camera device such as a tablet terminal or a mobile phone. Of course, the identification device 31 can also be applied to a webcam or similar device capable of communicating with a PC via wired or wireless means.

[0124] According to the embodiments described above, a wide field of view, bright, high-performance and compact information processing device can be achieved.

[0125] Furthermore, according to the implementation method, a field of view of 60 to 80 degrees (with a half field of view ω of approximately 30 to 40°) can be achieved using four lenses.

[0126] Furthermore, according to Embodiment 3, since the shooting lens 100 can achieve a wide field of view, has a small F-number, and is a high-performance and compact shooting lens, it can cope with shooting in various environments such as dark environments and achieve high-speed shooting in the case of video shooting.

[0127] Furthermore, according to the implementation method, since the imaging lens is capable of achieving a wide field of view, is bright, has high performance, and is small, the matching between the incident angle in the light-receiving element of the single imaging element and the light incident on the light-receiving surface can be improved on the image side.

[0128] Furthermore, according to the embodiment, since a bright, high-performance, and small imaging lens with a half field of view of approximately 30° can be formed by three lenses, it can be used, for example, as a single-focus lens for mobile phones such as smartphones and PCs, and thus can meet the performance requirements for recognizing human faces.

[0129] Furthermore, according to the embodiment, since a bright, high-performance, and compact imaging lens with a half-field of view of approximately 30° can be formed by three lenses, the overall length of the imaging lens 100 along the optical axis can be shortened, and the lens diameter can also be reduced, thus achieving miniaturization. Therefore, the refractive power of the miniaturized lens is reduced, and the effects of manufacturing and assembly errors can be minimized. As a result, productivity can be improved, and production costs can be reduced.

[0130] Furthermore, various inventions can be formed by appropriately combining the multiple constituent elements disclosed in the information processing apparatus of the embodiments of this disclosure. For example, several constituent elements may be deleted from all the constituent elements described in the information processing apparatus of the embodiments of this disclosure described above. Also, the constituent elements described in the information processing apparatus of the embodiments of this disclosure described above may be appropriately combined.

[0131] Furthermore, in the information processing apparatus of the embodiments of this disclosure, the term "section" can be replaced with "unit," "circuit," or the like. For example, the control section can be replaced with a control unit or a control circuit.

[0132] Furthermore, the program executed by the information processing apparatus of the present disclosure is recorded in an installable or executable format as file data on a computer-readable recording medium such as a CD-ROM, floppy disk (FD), CD-R, DVD (Digital Versatile Disk), USB medium, or flash memory and provided thereon.

[0133] Furthermore, the program executed by the information processing apparatus of the present disclosure can also be configured to be stored on a computer connected to a network such as the Internet, and provided by downloading it via the network.

[0134]

Example

[0135] Hereinafter, embodiments 1 to 4 of the imaging lens 100 corresponding to embodiments 1 to 4 are shown.

[0136] The symbols in each embodiment have the following meanings.

[0137] f: Focal length of the entire lens system

[0138] fl: Focal length of each lens

[0139] FNo.: Numerical aperture (F number)

[0140] R: Radius of curvature of the surface

[0141] D: Surface spacing

[0142] Nd: Refractive index for d-lines

[0143] Vd: Abbe number for line d

[0144] SD: Effective radius

[0145] With the depth along the optical axis set as X, the height from the optical axis set as H, the periaxial radius of curvature set as R, the conic constant set as k, and the higher-order aspheric coefficients set as CN (N = 4 or more even numbers), the aspheric coefficients are used to represent the aspheric surface by the well-known formula (20).

[0146] X=(H 2 / R) / [1+{1-k(H / r) 2} 1 / 2 ]+Σ N＝4:even CNH N …(20)

[0147] Where, Σ N≥4:even It refers to the sum of even numbers where N is 4 or higher.

[0148] [Example 1]

[0149] f=1.4mm, FNo.=2.0, ω=40°

[0150] The data for Example 1 are shown in Table 1.

[0151] [Table 1]

[0152]

[0153] The data for aspherical surfaces are shown below.

[0154] [Table 2]

[0155] In the above description of aspherical surfaces, for example, "-1.7965.E-03" means "-1.7965 * 10⁻⁶". -3 The same applies to the other embodiments described below.

[0156] The values ​​of the parameters for each condition are as follows. In addition, EP: entrance pupil position is also recorded in Table 3.

[0157] [Table 3]

[0158] Item Value f 1.39 Fno 2.00 TTL 2.12 IH 1.18 EfD1 0.70 ω 40.18 EP 0.00 EXP -1.46 f1 2.72 f2 -5.60 f3 0.86 f4 -1.20 N1 1.54 N2 1.67 N3 1.54 N4 1.63 R1 0.895 R2 2.132 R3 2.123 R4 1.276 R5 -13.303 R6 -0.447 R7 0.710 R8 0.329

[0159] In this table, in addition to the conditional expressions (1) to (8), (11) to (16) are also recorded as references.

[0160] [Table 4]

[0161]

[0162] In addition, each embodiment uses aspherical surfaces in the first lens L1 to the fourth lens L4 to effectively correct aberrations.

[0163] Aberration maps, MTF, and distortion grids related to Embodiment 1 above are as follows: Figures 2A-2C As shown in the figures, the performance is good.

[0164] [Example 2]

[0165] f=1.6mm, FNo.=2.0, ω=36.1°

[0166] The data for Example 2 are shown in Table 5.

[0167] [Table 5]

[0168]

[0169] The data for aspherical surfaces are shown below.

[0170] [Table 6]

[0171] The values ​​of the parameters for each condition are as follows.

[0172] [Table 7]

[0173] Item Value f 1.59 Fno 2.00 TTL 2.11 IH 1.18 EfD1 0.80 ω 36.14 EP 0.00 EXP -1.29 f1 2.03 f2 -4.32 f3 1.16 f4 -1.43 N1 1.54 N2 1.63 N3 1.54 N4 1.63 R1 0.819 R2 2.974 R3 2.670 R4 1.288 R5 -3.527 R6 -0.547 R7 1.061 R8 0.452

[0174] [Table 8]

[0175]

[0176] These aberration maps, MTF, and distorted rasters, such as Figures 4A-4C As shown in the figures, the performance is good.

[0177] [Example 3]

[0178] f=1.8mm, FNo.=2.0, ω=32°

[0179] The data for Example 3 are shown in Table 9.

[0180] [Table 9]

[0181]

[0182] The data for aspherical surfaces are shown below.

[0183] [Table 10]

[0184] The values ​​of the parameters for each condition are as follows.

[0185] [Table 11]

[0186] Item Value f 1.80 Fno 2.00 TTL 2.12 IH 1.18 EfD1 0.90 ω 32.12 EP 0.00 EXP -1.22 f1 1.90 f2 -5.59 f3 1.63 f4 -1.63 N1 1.54 N2 1.63 N3 1.54 N4 1.63 R1 0.780 R2 2.923 R3 2.874 R4 1.520 R5 -1.748 R6 -0.616 R7 1.222 R8 0.521

[0187] [Table 12]

[0188]

[0189] These aberration maps, MTF, and distorted rasters, such as Figures 6A-6C As shown in the figures, the performance is good.

[0190] [Example 4]

[0191] f=1.8mm, FNo.=2.0, ω=30°

[0192] The data for Example 4 are shown in Table 13.

[0193] [Table 13]

[0194]

[0195] The data for aspherical surfaces are shown below.

[0196] [Table 14]

[0197] The values ​​of the parameters for each condition are as follows.

[0198] [Table 15]

[0199] Item Value f 1.80 Fno 2.00 TTL 2.11 IH 1.17 EfD1 0.90 ω 30.11 EP 0.00 EXP -1.22 f1 1.90 f2 -5.54 f3 1.63 f4 -1.63 N1 1.54 N2 1.63 N3 1.54 N4 1.63 R1 0.780 R2 2.923 R3 2.872 R4 1.511 R5 -1.760 R6 -0.616 R7 1.221 R8 0.520

[0200] [Table 16]

[0201]

[0202] These aberration maps, MTF, and distorted rasters, such as Figures 8A-8C As shown in the aberration diagrams, the performance is good.

[0203] The above are examples 1-4. Figures 2A-2C , Figures 4A-4C , Figures 6A-6C as well as Figures 8A-8C As shown, the imaging lens 100 disclosed herein is bright, high-performance, and miniaturized (shortened relative to the optical axis direction), and the half field of view is approximately 30 to 40° achieved by four lenses. Furthermore, it is clearly suitable as an imaging device, especially for laptop PCs.

[0204] The above description of several embodiments of this application is based on the accompanying drawings. However, these embodiments are illustrative and can be implemented in various modifications and variations based on the knowledge of those skilled in the art, with reference to the manner described in the disclosure of this invention.

Claims

1. A photographing lens comprising: first to fourth lenses disposed in order from an object side; and an aperture stop disposed closest to the object side, the first lens being a positive meniscus lens with a convex surface toward the object side, the second lens being a negative lens having at least one inflection point on a single surface, the third lens being a positive lens with a convex surface toward an image side and an inflection point on a surface on the object side in a lens peripheral portion, the fourth lens being a negative lens with a concave surface on the image side and an inflection point in a peripheral portion, and having a minimum paraxial radius of curvature R of a lens surface closest to the image side in an overall optical system, wherein, when a focal length of the fourth lens is set as f4 and a focal length of the overall optical system is set as f, a condition (1) is satisfied, that is: 0.8 < |f4 / f| < 1.0 … (1).

2. The photographing lens according to claim 1, wherein infrared-ray corresponding coatings are applied to surfaces of the first to third lenses, the infrared-ray corresponding coatings transmit light in a frequency band of 450 to 940 nm, and have a reflectance of 2% or less in at least a near-infrared region of 850 to 940 nm.

3. The photographing lens according to claim 1, wherein when a refractive index of d-line of a material of the first lens is set as N1, a refractive index of d-line of a material of the second lens is set as N2, a refractive index of d-line of a material of the third lens is set as N3, and a refractive index of d-line of a material of the fourth lens is set as N4, a condition (2) is satisfied, that is: N1≈N3∩N2≈N4∩N1<N2… (2).

4. The photographing lens according to claim 1, wherein when a refractive index of d-line of a material of the first lens is set as N1, a condition (3) is satisfied, that is: 1.49＜N1＜1.55…(3)。 5. The photographing lens according to claim 1, wherein when a refractive index of d-line of a material of the fourth lens is set as N4, a condition (4) is satisfied, that is: 1.63＜N4＜1.67…(4)。 6. The photographing lens according to claim 1, wherein when a paraxial radius of curvature of the image side of the first lens is set as R2 and a paraxial radius of curvature of the object side of the second lens is set as R3, a condition (5) is satisfied, that is: 0.9 < R2 / R3 < 1.2 … (5).

7. The photographing lens according to claim 1, wherein when an optical total length is set as TTL and an image height is set as IH, a condition (6) is satisfied, that is: 0.85 < TTL / 2*IH < 0.95 … (6).

8. The photographing lens according to claim 1, wherein when a field angle is set as ω, a condition (7) is satisfied, that is: 29 < ω < 40 … (7).

9. A photographing apparatus comprising: the photographing lens according to claim 1; and a single photographing element that receives an image formed by the photographing lens and generates a photographing signal.

10. An information processing apparatus comprising: the photographing apparatus according to claim 9; and a display portion that displays an image corresponding to the photographing signal generated by the photographing apparatus.

11. The information processing apparatus according to claim 10, wherein the display portion comprises: A display panel displays an image; and A frame portion is disposed around the display panel. The photographing device is disposed in the frame portion.

Images