Optical imaging system, image taking device, time-of-flight depth camera and optical recognition device

Abstract

The application relates to an optical imaging system, an image capturing device, a time-of-flight depth camera and an optical recognition device. The optical imaging system is used for infrared light imaging and sequentially comprises, along an optical axis from an object side to an image side, a lens with a positive focal length, wherein a near-axis region of an object side surface of the lens is convex, an image side surface is flat, and the object side surface of the lens is aspheric; and a glass substrate which is glued to the image side surface of the lens. The optical imaging system can be applied to infrared band imaging by reasonably adjusting the focal length, surface type and effective focal length of the lens, and a clear, bright and high-resolution image containing depth information of an object can be obtained. The optical imaging system can be fixed by only using one lens to abut against the glass substrate, so that the total length of the optical imaging system can be significantly reduced, the lens is miniaturized, and batch production is facilitated.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to an optical imaging system, an image acquisition device, a time-of-flight depth camera, and an optical recognition device. Background Technology

[0002] In recent years, with the rapid development of portable electronic devices such as smartphones, the camera devices mounted on them have become increasingly diverse, including dual cameras, triple cameras, telephoto lenses, wide-angle lenses, and optical lenses that support 3D imaging technology.

[0003] Traditional mobile phone lenses typically use 3D structured light for 3D imaging. However, 3D structured light camera modules are complex, bulky, and expensive, making them unsuitable for mass production.

[0004] Time-of-Flight (TOF) technology is a 3D imaging technology that has been applied to mobile phone cameras in the last year or two. It works by emitting continuous pulses of infrared light of a specific wavelength towards a target object, and then using a specific sensor to receive the light signal transmitted back from the object. By calculating the round-trip time or phase difference of the light rays, it obtains the depth information of the target object. Lenses using TOF technology can be used for facial recognition on mobile phones, autonomous driving in automobiles, human-computer interfaces and games, industrial machine vision and measurement, and security monitoring, among other applications.

[0005] Compared to mature 3D structured light, TOF technology has the advantage of a longer range. In addition, TOF modules have low complexity and small space occupation, which can assist the main camera to achieve better depth-of-field shooting effects. Therefore, it has gradually gained favor among mobile phone manufacturers. Summary of the Invention

[0006] Therefore, it is necessary to provide an optical imaging system based on TOF technology that is easy to mass-produce, addressing the issues of complex and bulky 3D structured light technology modules.

[0007] An optical imaging system for infrared imaging, comprising, in sequence along the optical axis from the object side to the image side:

[0008] A lens with positive optical power, wherein the paraxial region of the object-side surface of the lens is convex, the image-side surface is planar, and the object-side surface of the lens is aspherical; and,

[0009] A glass substrate, wherein the glass substrate is bonded to the image side of the lens.

[0010] The aforementioned optical imaging system, by reasonably adjusting the lens's power, shape, and effective focal length, can be applied to infrared imaging and capture clear, bright images with good resolution containing depth information of the subject. Furthermore, this optical imaging system can be mounted on a glass substrate using only a single lens, which facilitates fixation of the system and significantly reduces its overall length, achieving lens miniaturization. In addition, the lens of this optical imaging system uses a one-piece imprinting process, which is simple to manufacture and lower in cost compared to multi-element TOF lenses, making it more suitable for mass production.

[0011] In one embodiment, an aperture stop is also included, which is disposed on the object side or image side of the optical imaging system.

[0012] By setting an aperture stop, the size of the light beam incident on the optical imaging system can be better controlled.

[0013] In one embodiment, the optical imaging system satisfies the following relationship:

[0014] 20° < FOV < 40°; where FOV is the field of view of the optical imaging system.

[0015] By controlling the field of view of the optical imaging system to satisfy the above relationship, it is beneficial for the optical imaging system to obtain a wider range of scene image information.

[0016] In one embodiment, the optical imaging system satisfies the following relationship: 1 ≤ FNO ≤ 1.8; where FNO is the aperture number of the optical imaging system.

[0017] By controlling the aperture number of the optical imaging system to satisfy the above relationship, the optical imaging system can have a larger entrance pupil diameter, thereby increasing the amount of light passing through, which is beneficial to improving the brightness of the image, enhancing its low-light shooting capability, and obtaining excellent shooting performance.

[0018] In one embodiment, the optical imaging system satisfies the following relationship: TTL < 1.2 mm; where TTL is the distance on the optical axis from the object side of the lens to the imaging surface of the optical imaging system.

[0019] By controlling the distance on the optical axis from the object side of the lens to the imaging surface of the optical imaging system to satisfy the above relationship, it is beneficial to shorten the overall length of the optical imaging system and achieve miniaturization, thereby making it easier to adapt the optical imaging system to ultra-thin portable electronic devices such as mobile phones and tablets.

[0020] In one embodiment, the optical imaging system satisfies the following relationship:

[0021] 2 < CT1 / ET1 < 5.5; where CT1 is the thickness of the lens on the optical axis and ET1 is the thickness of the lens at its maximum effective aperture.

[0022] By controlling the thickness of the lens along the optical axis to satisfy the above relationship with the thickness at the maximum effective aperture of the lens, it is possible to ensure that the lens has a uniform thickness ratio, which is beneficial to the processing and shaping of the lens.

[0023] In one embodiment, the optical imaging system satisfies the following relationship:

[0024] 0.5 < R1 / f < 0.51; where R1 is the radius of curvature of the object side of the lens at the optical axis, and f is the effective focal length of the optical imaging system.

[0025] By controlling the radius of curvature of the lens side at the optical axis to satisfy the above relationship with the effective focal length of the optical imaging system, the shape of the lens side can be reasonably configured, which is beneficial to adjust the lens power so that the light rays converge to form an image and ensure good imaging resolution of the optical imaging system.

[0026] An image-capturing device includes an optical imaging system as described above; and a photosensitive element located on the image side of the optical imaging system.

[0027] The aforementioned imaging device utilizes the aforementioned optical imaging system to image the infrared light emitted or reflected by the subject, thereby obtaining a bright, wide-viewing-angle, and high-resolution image. At the same time, the imaging device is also characterized by its miniaturization and simple assembly, making it easy to adapt to devices with size constraints, such as ultra-thin portable electronic devices.

[0028] This application also provides a time-of-flight depth camera.

[0029] A time-of-flight depth camera includes a light emitting device for projecting light onto a target; and an image acquisition device as described above for receiving the light projected by the light emitting device reflected by the target to acquire a depth image of the target.

[0030] The aforementioned time-of-flight depth camera, by using the image acquisition device described above to receive the light emitted by the light emitting device reflected by the target object, can capture bright and clear depth images of the target object. It is also beneficial for measuring the depth data in the image, so as to blur the objects in the image to different degrees and improve the shooting effect of the camera.

[0031] This application also provides an optical recognition device.

[0032] An optical recognition device includes a glass screen and an image acquisition device as described in the above embodiments, wherein the glass screen is located on the object side of the optical imaging system.

[0033] The aforementioned optical recognition device has a wide viewing angle and a large aperture, which is conducive to fully acquiring detailed depth information of the target object and improving the recognition response speed. At the same time, it also has the structural characteristics of being thin and small in size, which is conducive to being adapted to terminal devices such as mobile phones and tablets for fingerprint recognition and facial recognition. Attached Figure Description

[0034] Figure 1 A schematic diagram of the optical imaging system of Embodiment 1 of this application is shown;

[0035] Figures 2A to 2C The figures shown are the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical imaging system in Example 1.

[0036] Figure 3 A schematic diagram of the optical imaging system of Embodiment 2 of this application is shown;

[0037] Figures 4A to 4C The figures shown are the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical imaging system in Example 2.

[0038] Figure 5 A schematic diagram of the optical imaging system of Embodiment 3 of this application is shown;

[0039] Figures 6A to 6C The figures shown are the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical imaging system in Example 3.

[0040] Figure 7 A schematic diagram of the optical imaging system of Embodiment 4 of this application is shown;

[0041] Figures 8A to 8C The figures shown are the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical imaging system in Example 4.

[0042] Figure 9 A schematic diagram of the optical imaging system of Embodiment 5 of this application is shown;

[0043] Figures 10A to 10C The figures shown are the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical imaging system in Example 5.

[0044] Figure 11 A schematic diagram of the structure of the optical recognition device according to an embodiment of this application is shown. Detailed Implementation

[0045] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0046] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "upper," "lower," "front," "rear," "circumferential," and similar expressions used herein are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0047] For ease of illustration, the shapes of spherical or aspherical surfaces shown in the accompanying drawings are illustrated by way of example. That is, the shapes of spherical or aspherical surfaces are not limited to those shown in the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not drawn strictly to scale.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0049] Traditional Time-of-Flight (TOF) lenses typically employ multi-element lens groups to ensure image quality. However, the use of multi-element lens groups results in higher costs and a longer overall length, making it difficult to meet the growing trend of ultra-thin electronic devices.

[0050] The shortcomings of the above solutions are the result of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the inventors in the embodiments of this application below should be considered as contributions made by the inventors to this application.

[0051] The features, principles and other aspects of this application will be described in detail below.

[0052] Please refer to the following: Figure 1 , Figure 3 , Figure 5 , Figure 7 and Figure 9 This application provides an optical imaging system suitable for infrared imaging, which features both a large aperture and an ultra-thin design. Specifically, the optical imaging system includes, along the optical axis from the object side to the image side, a lens with optical power and a glass substrate cemented to the lens, with the imaging surface of the optical imaging system located on the image side of the glass substrate.

[0053] This lens has positive optical power to converge light into an image. The paraxial region of the object-side surface of the lens is convex, which facilitates the adjustment of the lens's optical power. Setting the object-side surface as an aspherical surface can effectively correct aberrations and improve the imaging resolution of the optical imaging system. The image-side surface of the lens is flat, which is beneficial for lens processing and shaping, and also makes it easier to support the lens on a glass substrate.

[0054] The glass substrate is used to support the lens, which facilitates the fixation of the optical imaging system so that it can be adapted to different portable electronic devices.

[0055] When the aforementioned optical imaging system is used for imaging, infrared light emitted or reflected by the object enters the optical imaging system from the object side, passes through the lens and glass substrate, and finally converges onto the imaging surface.

[0056] The aforementioned optical imaging system, by reasonably adjusting the optical power, surface shape, and effective focal length of the lens, can be applied to infrared imaging and capture clear, bright images with good resolution containing depth information of the subject. At the same time, the aforementioned optical imaging system can be supported on a glass substrate using only one lens, which not only facilitates the fixation of the optical imaging system but also significantly reduces the overall length of the optical imaging system, achieving lens miniaturization. In addition, the object side of the lens can be prepared by an imprinting process, and its image side is flat, which is beneficial for mass production.

[0057] In an exemplary embodiment, the optical imaging system also includes an aperture stop to better control the size of the incident beam. Specifically, the aperture stop includes an aperture stop and a field stop, and can be located on the object side or image side of the optical imaging system. Preferably, the aperture stop is an aperture stop. The aperture stop can be located on the surface of the lens (e.g., the object side and the image side) and interact with the lens. For example, an aperture stop can be formed on the surface of the lens by coating the surface with a light-blocking coating; or the surface of the lens can be fixed by a clamping member, the clamping member structure located on the surface of which can limit the width of the on-axis object point imaging beam, thereby forming an aperture stop on the surface of the lens.

[0058] In an exemplary embodiment, both the object-side and image-side surfaces of the lens are coated with infrared anti-reflection films. By providing infrared anti-reflection films, the wavelength of light incident on the imaging surface of the optical imaging system can be selected. For example, it can increase the transmittance of infrared light emitted by the TOF transmitter reflected from the subject, thereby ensuring that the optical imaging system can meet the application requirements of TOF technology. In other embodiments, an infrared bandpass filter can also be provided between the glass substrate and the imaging surface of the optical imaging system to achieve the same wavelength selection effect; this application does not limit this.

[0059] In an exemplary embodiment, the optical imaging system satisfies the following relationship: 20° < FOV < 40°; where FOV is the field of view of the optical imaging system. Specifically, FOV is the diagonal field of view of the effective pixel area on the imaging surface of the optical imaging system. FOV can be 22°, 24°, 26°, 30°, 32°, 34°, 36°, or 38°. By controlling the field of view of the optical imaging system to satisfy the above relationship, it is beneficial for the optical imaging system to acquire a wider range of scene image information, enhancing its wide-angle shooting capability. When FOV is less than or equal to 20°, it is impossible to fully acquire information about the subject, resulting in poor shooting effects; while when FOV is greater than or equal to 40°, it can easily cause difficulties in configuring the lens power and adjusting the surface shape.

[0060] In an exemplary embodiment, the optical imaging system satisfies the following relationship: 1 ≤ FNO ≤ 1.8; where FNO is the aperture number of the optical imaging system. FNO can be 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8. Furthermore, 1 ≤ FNO ≤ 1.4. By controlling the aperture number of the optical imaging system to satisfy the above relationship, the optical imaging system can have a larger aperture, which is beneficial for improving image brightness, enhancing its low-light shooting capabilities, and obtaining excellent shooting performance. However, when FNO is less than 1, it easily leads to an excessively large effective light-transmitting aperture of the lens, which is not conducive to lens assembly and surface shape adjustment; while when FNO is greater than 1.8, it is impossible to achieve the effect of improving image brightness and improving shooting performance.

[0061] In an exemplary embodiment, the optical imaging system satisfies the following relationship: TTL < 1.2 mm; where TTL is the distance on the optical axis from the object-side surface of the lens to the imaging surface of the optical imaging system. TTL can be 0.6 mm, 0.7 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.1 mm, 1.15 mm, or 1.18 mm. Satisfying this relationship helps to shorten the overall length of the optical imaging system, achieving miniaturization and facilitating its adaptation to ultra-thin portable electronic devices such as mobile phones and tablets. However, when TTL is greater than or equal to 1.2 mm, the overall length of the optical imaging system becomes too long, which is detrimental to miniaturization.

[0062] In an exemplary embodiment, the optical imaging system satisfies the following relationship: 2 < CT1 / ET1 < 5.5; where CT1 is the thickness of the lens along the optical axis, and ET1 is the thickness at the maximum effective aperture of the lens. CT1 / ET1 can be 2.1, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.2, 4.5, 4.8, 5.1, 5.4, or 5.45. Under the condition of satisfying the above relationship, the lens can be guaranteed to have a uniform thickness ratio, which is beneficial to the lens processing and forming. However, when CT1 / ET1 is less than or equal to 2 or greater than or equal to 5.5, the thickness variation of the lens will be too large, which is not conducive to the lens processing and forming, and thus easily reduces the lens production yield.

[0063] In an exemplary embodiment, the optical imaging system satisfies the following relationship: 0.5 < R1 / f < 0.51; where R1 is the radius of curvature of the object-side surface of the lens at the optical axis, and f is the effective focal length of the optical imaging system. R1 / f can be 0.501, 0.502, 0.503, 0.504, 0.505, 0.506, 0.507, 0.508, or 0.509. Under the condition of satisfying the above relationship, the shape of the object-side surface of the lens can be reasonably configured, which is beneficial for adjusting the optical power of the lens to converge light and ensure good imaging resolution of the optical imaging system. However, when R1 / f is less than or equal to 0.5 or greater than or equal to 0.51, it is not conducive to adjusting the shape of the object-side surface of the lens, and good optical performance of the optical imaging system cannot be guaranteed.

[0064] In an exemplary embodiment, the lens in the optical imaging system can be made of glass or plastic. Plastic lenses can reduce the weight of the optical imaging system and lower production costs, while glass lenses can give the optical imaging system better temperature resistance and excellent optical performance.

[0065] In an exemplary embodiment, the optical imaging system further includes a protective glass for protecting a photosensitive element, wherein the photosensitive element is located on the imaging surface of the optical imaging system. Further, the imaging surface can be the photosensitive surface of the photosensitive element.

[0066] The optical imaging system described above utilizes a single lens bonded to a glass substrate, significantly reducing the overall length of the system. Simultaneously, the lens can be fixed to the glass substrate, allowing the system to be adapted to various portable electronic devices. Furthermore, by rationally allocating the lens's focal length, power, shape, and thickness, the system can be miniaturized while still possessing a large aperture (FNO can be 1.0), a wide field of view, and high resolution, thus better meeting the infrared imaging application requirements of ultra-thin electronic devices such as mobile phones and tablets.

[0067] However, those skilled in the art should understand that, without departing from the technical solutions claimed in this application, the number of lenses constituting the optical imaging system can be changed to obtain the various results and advantages described in this specification.

[0068] Specific embodiments of the optical imaging system applicable to the above-described embodiments are further described below with reference to the accompanying drawings. In the following embodiments, if the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. Here, the paraxial region refers to the region near the optical axis. The surface of each lens closest to the object is called the object-side surface, and the surface of each lens closest to the imaging plane is called the image-side surface.

[0069] Example 1

[0070] The following is for reference Figures 1 to 2C The optical imaging system of Embodiment 1 of this application is described.

[0071] Figure 1 A schematic diagram of the optical imaging system of Embodiment 1 is shown. Figure 1 As shown, the optical imaging system includes, in sequence from the object side to the image side along the optical axis, a lens L1, a glass substrate L2 cemented to the lens L1, and an imaging surface S5.

[0072] Lens L1 has positive optical power. Its object-side surface S1 is aspherical, and its image-side surface S2 is planar. The object-side surface S1 is convex at the optical axis and convex at the circumference.

[0073] Setting the object side S1 as an aspherical surface helps to solve the problem of field distortion and enables the lens to achieve excellent optical imaging effect in a smaller, thinner and flatter case, thereby enabling the optical imaging system to have miniaturization characteristics.

[0074] Lens L1 is made of plastic, which reduces the weight of the optical imaging system and lowers production costs. An aperture stop STO is also provided on the image side of the glass substrate L2 to further improve the image quality of the optical imaging system.

[0075] The object-side surface S1 of lens L1 is coated with an infrared anti-reflection film to enhance the transmittance of infrared light. Infrared light from object OBJ passes through surfaces S1-S4 sequentially and is finally imaged on the imaging surface S5.

[0076] Table 1 shows the surface type, radius of curvature, thickness, material, refractive index, Abbe number (i.e., dispersion coefficient), and effective focal length of the lens in the optical imaging system of Example 1. The units for radius of curvature, thickness, and effective focal length are millimeters (mm). The surface of the lens closest to the object is called the object-side surface, and the surface closest to the imaging plane is called the image-side surface. Furthermore, taking lens L1 as an example, the first value in the "thickness" parameter column of lens L1 is the thickness of the lens along the optical axis, and the second value is the distance along the optical axis from the image-side surface of this lens to the object-side surface of the next lens in the image-side direction. The reference wavelength in Table 1 is 850 nm.

[0077] Table 1

[0078]

[0079]

[0080] The aspherical surface shape in a lens is defined by the following formula:

[0081]

[0082] Where x is the distance vector from the vertex of the aspherical surface at a height h along the optical axis; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1); k is the conic coefficient; Ai is the i-th order coefficient of the aspherical surface. Table 2 below gives the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for the aspherical lens S1 in Example 1.

[0083] Table 2

[0084]

[0085] In this embodiment, half the diagonal length of the effective pixel area on the imaging surface S5 of the optical imaging system is 0.19 mm. Combining the data in Tables 1 and 2, it can be seen that the optical imaging system in Embodiment 1 satisfies:

[0086] FOV = 31°, where FOV is the field of view of the optical imaging system. Specifically, FOV is the diagonal field of view of the effective pixel area on the imaging surface S5 of the optical imaging system.

[0087] FNO = 1.4, where FNO is the aperture number of the optical imaging system;

[0088] TTL = 0.871 mm, where TTL is the distance on the optical axis from the object side of lens L1 to the imaging surface S5 of the optical imaging system.

[0089] CT1 / ET1=2.521, where CT1 is the thickness of lens L1 on the optical axis, and ET1 is the thickness of lens L1 at its maximum effective aperture.

[0090] R1 / f = 0.508, where R1 is the radius of curvature of the object side surface S1 of lens L1 at the optical axis, and f is the effective focal length of the optical imaging system.

[0091] Figure 2A The longitudinal spherical aberration curves of the optical imaging system of Embodiment 1 are shown, which respectively represent the deflection of the focal point of infrared light with wavelengths of 840nm, 850nm and 860nm after passing through the optical imaging system; Figure 2B The astigmatism curves of the optical imaging system of Embodiment 1 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature; Figure 2C The distortion curves of the optical imaging system of Example 1 are shown, representing the distortion rate under different image heights. According to... Figures 2A to 2C As can be seen, the optical imaging system given in Example 1 can achieve good imaging quality.

[0092] Example 2

[0093] The following is for reference Figures 3 to 4C The optical imaging system of Embodiment 2 of this application is described. In this embodiment, for the sake of brevity, descriptions similar to those in Embodiment 1 are omitted. Figure 3 A schematic diagram of the optical imaging system of Embodiment 2 is shown.

[0094] like Figure 3 As shown, the optical imaging system includes, in sequence from the object side to the image side along the optical axis, a lens L1, a glass substrate L2 cemented to the lens L1, and an imaging surface S5.

[0095] Lens L1 has positive optical power. Its object-side surface S1 is aspherical, and its image-side surface S2 is planar. The object-side surface S1 is convex at the optical axis and convex at the circumference.

[0096] Setting the object side S1 as an aspherical surface helps to solve the problem of field distortion and enables the lens to achieve excellent optical imaging effect in a smaller, thinner and flatter case, thereby enabling the optical imaging system to have miniaturization characteristics.

[0097] Lens L1 is made of plastic, which reduces the weight of the optical imaging system and lowers production costs. An aperture stop STO is also provided on the image side of the glass substrate L2 to further improve the image quality of the optical imaging system.

[0098] The object-side surface S1 of lens L1 is coated with an infrared anti-reflection film to enhance the transmittance of infrared light. Infrared light from object OBJ passes through surfaces S1-S4 sequentially and is finally imaged on the imaging surface S5.

[0099] Table 3 shows the surface type, radius of curvature, thickness, material, refractive index, Abbe number (i.e., dispersion coefficient), and effective focal length of the lens in the optical imaging system of Example 2. The units for radius of curvature, thickness, and effective focal length are millimeters (mm). The reference wavelength in Table 3 is 850 nm. Table 4 shows the higher-order coefficients applicable to the aspherical surface S1 of the lens in Example 2, where the aspherical surface shape can be defined by formula (1) given in Example 1. Table 5 shows the relevant parameter values ​​of the optical imaging system of Example 2.

[0100] Table 3

[0101]

[0102] Table 4

[0103]

[0104]

[0105] Table 5

[0106] f(mm) 0.976 ImgH(mm) 0.19 FNO 1.0 CT1 / ET1 5.429 FOV(degree) 22.4 R1 / f 0.507 TTL(mm) 1.175

[0107] Figure 4A The longitudinal spherical aberration curves of the optical imaging system of Embodiment 2 are shown, which respectively represent the deflection of the focal point of infrared light with wavelengths of 840nm, 850nm and 860nm after passing through the optical imaging system; Figure 4B The astigmatism curves of the optical imaging system of Embodiment 2 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature; Figure 4C The distortion curves of the optical imaging system of Example 2 are shown, representing the distortion rate under different image heights. According to... Figures 4A to 4C As can be seen, the optical imaging system given in Example 2 can achieve good imaging quality.

[0108] Example 3

[0109] The following is for reference Figures 5 to 6C The optical imaging system of Embodiment 3 of this application is described. In this embodiment, for the sake of brevity, parts of the description similar to those in Embodiment 1 are omitted. Figure 5 A schematic diagram of the optical imaging system of Embodiment 3 is shown.

[0110] like Figure 5 As shown, the optical imaging system includes, in sequence from the object side to the image side along the optical axis, a lens L1, a glass substrate L2 cemented to the lens L1, and an imaging surface S5.

[0111] Lens L1 has positive optical power. Its object-side surface S1 is aspherical, and its image-side surface S2 is planar. The object-side surface S1 is convex at the optical axis and convex at the circumference.

[0112] Setting the object side S1 as an aspherical surface helps to solve the problem of field distortion and enables the lens to achieve excellent optical imaging effect in a smaller, thinner and flatter case, thereby enabling the optical imaging system to have miniaturization characteristics.

[0113] Lens L1 is made of plastic, which reduces the weight of the optical imaging system and lowers production costs. An aperture stop STO is also provided on the image side of the glass substrate L2 to further improve the image quality of the optical imaging system.

[0114] The object-side surface S1 of lens L1 is coated with an infrared anti-reflection film to enhance the transmittance of infrared light. Infrared light from object OBJ passes through surfaces S1-S4 sequentially and is finally imaged on the imaging surface S5.

[0115] Table 6 shows the surface type, radius of curvature, thickness, material, refractive index, Abbe number (i.e., dispersion coefficient), and effective focal length of the lens in the optical imaging system of Example 3. The units for radius of curvature, thickness, and effective focal length are millimeters (mm). The reference wavelength in Table 6 is 850 nm. Table 7 shows the higher-order coefficients applicable to the aspherical surface S1 of the lens in Example 3, where the aspherical surface shape can be defined by formula (1) given in Example 1. Table 8 shows the relevant parameter values ​​of the optical imaging system of Example 3.

[0116] Table 6

[0117]

[0118] Table 7

[0119]

[0120]

[0121] Table 8

[0122] f(mm) 0.806 ImgH(mm) 0.19 FNO 1.2 CT1 / ET1 3.467 FOV(degree) 26.0 R1 / f 0.507 TTL(mm) 0.968

[0123] Figure 6A The longitudinal spherical aberration curves of the optical imaging system of Embodiment 3 are shown, which respectively represent the deflection of the focal point of infrared light with wavelengths of 840nm, 850nm and 860nm after passing through the optical imaging system; Figure 6B The astigmatism curves of the optical imaging system of Embodiment 3 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature; Figure 6C The distortion curves of the optical imaging system of Example 3 are shown, representing the distortion rate under different image heights. According to... Figures 6A to 6C As can be seen, the optical imaging system given in Example 3 can achieve good imaging quality.

[0124] Example 4

[0125] The following is for reference Figures 7 to 8C The optical imaging system of Embodiment 4 of this application is described. In this embodiment, for the sake of brevity, descriptions similar to those in Embodiment 1 are omitted. Figure 7 A schematic diagram of the optical imaging system of Embodiment 4 is shown.

[0126] like Figure 7 As shown, the optical imaging system includes, in sequence from the object side to the image side along the optical axis, a lens L1, a glass substrate L2 cemented to the lens L1, and an imaging surface S5.

[0127] Lens L1 has positive optical power. Its object-side surface S1 is aspherical, and its image-side surface S2 is planar. The object-side surface S1 is convex at the optical axis and convex at the circumference.

[0128] Setting the object side S1 as an aspherical surface helps to solve the problem of field distortion and enables the lens to achieve excellent optical imaging effect in a smaller, thinner and flatter case, thereby enabling the optical imaging system to have miniaturization characteristics.

[0129] Lens L1 is made of plastic, which reduces the weight of the optical imaging system and lowers production costs. An aperture stop STO is also provided on the image side of the glass substrate L2 to further improve the image quality of the optical imaging system.

[0130] The object-side surface S1 of lens L1 is coated with an infrared anti-reflection film to enhance the transmittance of infrared light. Infrared light from object OBJ passes through surfaces S1-S4 sequentially and is finally imaged on the imaging surface S5.

[0131] Table 9 shows the surface type, radius of curvature, thickness, material, refractive index, Abbe number (i.e., dispersion coefficient), and effective focal length of the lens in the optical imaging system of Example 4. The units for radius of curvature, thickness, and effective focal length are millimeters (mm). The reference wavelength in Table 9 is 850 nm. Table 10 shows the higher-order coefficients applicable to the aspherical surface S1 of the lens in Example 4, where the aspherical surface shape can be defined by formula (1) given in Example 1. Table 11 shows the relevant parameter values ​​for the optical imaging system of Example 4.

[0132] Table 9

[0133]

[0134] Table 10

[0135]

[0136]

[0137] Table 11

[0138] f(mm) 0.645 ImgH(mm) 0.19 FNO 1.6 CT1 / ET1 2.188 FOV(degree) 32.3 R1 / f 0.507 TTL(mm) 0.804

[0139] Figure 8A The longitudinal spherical aberration curves of the optical imaging system of Example 4 are shown, which respectively represent the deflection of the focal point of infrared light with wavelengths of 840nm, 850nm and 860nm after passing through the optical imaging system; Figure 8B The astigmatism curves of the optical imaging system of Embodiment 4 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature; Figure 8C The distortion curves of the optical imaging system of Example 4 are shown, representing the distortion rate under different image heights. According to... Figures 8A to 8C As can be seen, the optical imaging system given in Example 4 can achieve good imaging quality.

[0140] Example 5

[0141] The following is for reference Figures 9 to 10C The optical imaging system of Embodiment 5 of this application is described. In this embodiment, for the sake of brevity, parts of the description similar to those in Embodiment 1 are omitted. Figure 9 A schematic diagram of the optical imaging system of Embodiment 5 is shown.

[0142] like Figure 9 As shown, the optical imaging system includes, in sequence from the object side to the image side along the optical axis, a lens L1, a glass substrate L2 cemented to the lens L1, and an imaging surface S5.

[0143] Lens L1 has positive optical power. Its object-side surface S1 is aspherical, and its image-side surface S2 is planar. The object-side surface S1 is convex at the optical axis and convex at the circumference.

[0144] Setting the object side S1 as an aspherical surface helps to solve the problem of field distortion and enables the lens to achieve excellent optical imaging effect in a smaller, thinner and flatter case, thereby enabling the optical imaging system to have miniaturization characteristics.

[0145] Lens L1 is made of plastic, which reduces the weight of the optical imaging system and lowers production costs. An aperture stop STO is also provided on the image side of the glass substrate L2 to further improve the image quality of the optical imaging system.

[0146] The object-side surface S1 of lens L1 is coated with an infrared anti-reflection film to enhance the transmittance of infrared light. Infrared light from object OBJ passes through surfaces S1-S4 sequentially and is finally imaged on the imaging surface S5.

[0147] Table 12 shows the surface type, radius of curvature, thickness, material, refractive index, Abbe number (i.e., dispersion coefficient), and effective focal length of the lens in the optical imaging system of Example 5, wherein the units for radius of curvature, thickness, and effective focal length are millimeters (mm). The reference wavelength in Table 12 is 850 nm. Table 13 shows the higher-order coefficients that can be used for the aspherical surface S1 of the lens in Example 5, wherein the aspherical surface shape can be defined by formula (1) given in Example 1; Table 14 shows the relevant parameter values ​​of the optical imaging system of Example 5.

[0148] Table 12

[0149]

[0150] Table 13

[0151]

[0152]

[0153] Table 14

[0154] f(mm) 0.526 ImgH(mm) 0.19 FNO 1.8 CT1 / ET1 2.410 FOV(degree) 37.7 R1 / f 0.508 TTL(mm) 0.674

[0155] Figure 10A The longitudinal spherical aberration curves of the optical imaging system of Example 5 are shown, which respectively represent the deflection of the focal point of infrared light with wavelengths of 840nm, 850nm and 860nm after passing through the optical imaging system; Figure 10B The astigmatism curves of the optical imaging system of Embodiment 5 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature; Figure 10C The distortion curves of the optical imaging system of Example 5 are shown, representing the distortion rate under different image heights. According to... Figures 10A to 10C As can be seen, the optical imaging system given in Example 5 can achieve good imaging quality.

[0156] This application also provides an image-capturing device, including an optical imaging system as described above; and a photosensitive element disposed on the image side of the optical imaging system to receive light projected by the optical imaging system. Specifically, the photosensitive element may be a complementary metal-oxide-semiconductor (CMOS) image sensor or a charge-coupled device (CCD) image sensor.

[0157] The aforementioned imaging device utilizes the aforementioned optical imaging system to image the infrared light emitted or reflected by the subject, thereby obtaining a bright, wide-viewing-angle, and high-resolution image. At the same time, the imaging device is also characterized by its miniaturization and simple assembly, making it easy to adapt to devices with size constraints, such as ultra-thin portable electronic devices.

[0158] Specifically, the aforementioned portable electronic devices include, but are not limited to, devices configured to receive or transmit communication signals via wired connections and / or via wireless interfaces. Electronic devices configured to communicate via wireless interfaces may be referred to as “wireless communication terminals,” “wireless terminals,” or “mobile terminals.” Examples of mobile terminals include, but are not limited to, satellite or cellular phones; personal communication system (PCS) terminals that can combine cellular radiotelephones with data processing, fax, and data communication capabilities; personal digital assistants (PDAs) that may include radiotelephones, pagers, Internet / intranet access, web browsers, notebooks, calendars, and / or global positioning system (GPS) receivers; and conventional laptop and / or handheld receivers or other electronic devices that include radiotelephone transceivers.

[0159] This application also provides a time-of-flight depth camera, including a light emitting device for projecting light onto a target; and an image acquisition device as described above for receiving the light projected by the light emitting device reflected by the target to obtain a depth image of the target.

[0160] The aforementioned time-of-flight depth camera, by using the image acquisition device described above to receive the light emitted by the light emitting device reflected by the target object, can capture bright and clear depth images of the target object. It is also beneficial for measuring the depth data in the image, so as to blur the objects in the image to different degrees and improve the shooting effect of the camera.

[0161] This application also provides an optical recognition device. For example... Figure 11As shown, the optical recognition device includes a glass screen 10 and an image-capturing device as described above. The glass screen is located on the object side of the optical imaging system, and the image-capturing device includes the optical imaging system as described above and a photosensitive element 20. The imaging surface of the optical imaging system coincides with the photosensitive surface of the photosensitive element 20.

[0162] The aforementioned optical recognition device has a wide viewing angle and a large aperture, which is conducive to fully acquiring detailed depth information of the target object and improving the recognition response speed. At the same time, it also has the structural characteristics of being thin and small in size, which is conducive to being adapted to terminal devices such as mobile phones and tablets for fingerprint recognition and facial recognition.

[0163] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0164] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An optical imaging system characterized by, An optical imaging system for infrared light imaging has a lens with refractive power, comprising, in order from the object side to the image side along the optical axis: the lens has positive refractive power, the object side surface of the lens has a convex near-axis region, the image side surface is flat, and the object side surface of the lens is aspherical; and a glass substrate is bonded to the image side surface of the lens; wherein the optical imaging system satisfies the following relationships: 20° < FOV < 40°, 2 < CT1 / ET1 < 5.5; wherein FOV is the field of view of the optical imaging system, CT1 is the thickness of the lens on the optical axis, and ET1 is the thickness of the lens at the maximum effective aperture.

2. The optical imaging system of claim 1, wherein, Further comprising a diaphragm, which is arranged on the object side or the image side of the optical imaging system.

3. The optical imaging system of claim 1, wherein, The optical imaging system satisfies the following relationship: 1 ≤ FNO ≤ 1.8; wherein FNO is the aperture number of the optical imaging system.

4. The optical imaging system of claim 1, wherein, The optical imaging system satisfies the following relationship: TTL < 1.2 mm; wherein TTL is the distance from the object side surface of the lens to the imaging surface of the optical imaging system on the optical axis.

5. The optical imaging system of claim 1, wherein, The optical imaging system satisfies the following relationship: 0.5 < R1 / f < 0.51; wherein R1 is the radius of curvature of the object side surface of the lens at the optical axis, and f is the effective focal length of the optical imaging system.

6. An image pickup device, comprising: An optical imaging system as claimed in any one of claims 1-5; and a photosensitive element, which is located on the image side of the optical imaging system.

7. A time-of-flight depth camera characterized by, Comprising: a light emitting device for projecting light onto a target object; and a taking device as claimed in claim 6, which is used to receive the light projected by the light emitting device and reflected by the target object to obtain a depth image of the target object. Comprising a glass screen and a taking device as claimed in claim 6, which is located on the object side of the optical imaging system.

8. An optical recognition device, characterized by ​

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