Optical system, imaging apparatus, system, and moving apparatus

Abstract

To provide an optical system having high optical performance in spite of a large aperture.SOLUTION: The optical system includes, in order from the object side to the image side, first and second meniscus lenses that are disposed apart from each other, the first meniscus lens includes a first transmissive-reflective surface that is convex toward the object side, the second meniscus lens includes a second transmissive-reflective surface that is convex toward the object side, and light from the object side passes through the first transmissive-reflective surface, is reflected by the second transmissive-reflective surface toward the object side, is reflected by the first transmissive-reflective surface toward the image side, and passes through the second transmissive-reflective surface toward the image side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical system. [Background technology]

[0002] In recent years, optical systems have been proposed that use a reflecting surface to control the angle of incidence of light rays onto an imaging element. Patent Document 1 discloses a configuration that uses a transflective surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-80411 [Patent Document 2] International Publication No. 2023 / 136167 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration of Patent Document 1, the refractive power of the transmission-reflection lens is large, so if the diameter is increased, it becomes difficult to correct aberrations.

[0005] An object of the present invention is to provide an optical system that has a large aperture and high optical performance. [Means for solving the problem]

[0006] An optical system according to one aspect of the present invention comprises first and second meniscus lenses arranged at a distance from an object side to an image side, the first meniscus lens including a first transmission-reflection surface convex toward the object side, and the second meniscus lens including a second transmission-reflection surface convex toward the object side, wherein light from the object side passes through the first transmission-reflection surface, is reflected toward the object side by the second transmission-reflection surface, is reflected toward the image side by the first transmission-reflection surface, and passes through the second transmission-reflection surface toward the image side. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical system that has a large aperture and high optical performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram illustrating an optical path of an optical system. [Figure 2] FIG. 1 is a cross-sectional view of an optical system according to a first embodiment. [Figure 3] FIG. 2 is an MTF diagram of the optical system of Example 1. [Figure 4] FIG. 10 is a cross-sectional view of an optical system according to a second embodiment. [Figure 5] FIG. 10 is an MTF diagram of the optical system of Example 2. [Figure 6] FIG. 10 is a cross-sectional view of an optical system according to a third embodiment. [Figure 7] FIG. 10 is an MTF diagram of the optical system of Example 3. [Figure 8] FIG. 10 is a cross-sectional view of an optical system according to a fourth embodiment. [Figure 9] FIG. 10 is an MTF diagram of the optical system of Example 4. [Figure 10] FIG. 1 is a schematic diagram of a main part of an imaging device. [Figure 11] 1 is a functional block diagram of an in-vehicle system according to an embodiment; [Figure 12] 1 is a schematic view of a main part of a vehicle according to an embodiment; [Figure 13] 4 is a flowchart illustrating an example of the operation of the in-vehicle system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted.

[0010] The optical system of each embodiment can be used in imaging devices such as smartphone imaging cameras having an imaging element that photoelectrically converts an image formed by the optical system, distance detection cameras, fixed-lens cameras, disposable film cameras, vehicle-mounted cameras, etc. The optical system of each embodiment can also be used in video cameras, digital still cameras, and interchangeable lenses for interchangeable-lens cameras.

[0011] The optical system in each embodiment has a first transmissive-reflective surface and a second transmissive-reflective surface arranged in this order from the object side to the image side. Furthermore, a linear polarizer and an element (a retarder) for imparting a phase difference to incident light may be arranged on the object side of the first transmissive-reflective surface, in this order from the object side to the image side. Furthermore, a retarder may be arranged between the first transmissive-reflective surface and the second transmissive-reflective surface. Light from the object side passes through the first transmissive-reflective surface, is reflected by the second transmissive-reflective surface toward the object side, is reflected by the first transmissive-reflective surface toward the image side, and passes through the second transmissive-reflective surface toward the image plane. Examples of retarders that can be used include a wave plate (phase plate) such as a quarter-wave plate (QWP) or a 45° optical rotator (such as a Faraday rotator). In each embodiment, a QWP is used as the retarder.

[0012] Here, the first and second transmission-reflection surfaces do not necessarily have to have a transmittance of 50% and a reflectance of 50%. The ratio of transmittance to reflectance for randomly polarized light is preferably in the range of 1:3 to 3:1. Randomly polarized light is light with Stokes parameters S0 = 1, S1 = S2 = S3 = 0. The first and second transmission-reflection surfaces may also absorb light.

[0013] For example, a birefringent polymer film or a liquid crystal alignment layer can be used as a QWP. A stack of such polymer films or liquid crystal alignment layers can also be used as a QWP. By appropriately stacking these, a phase difference close to one-quarter of the wavelength can be obtained over a wide wavelength range. In addition to the above, inorganic wave plates from Dexerials Corporation can also be used as QWPs.

[0014] The QWP can be arranged by bonding, for example, to a first transmissive-reflective surface or a second transmissive-reflective surface. Alternatively, the QWP can be arranged separately from these transmissive-reflective surfaces. For example, the film itself can be inserted into the optical path, or a film bonded to a glass plate can be inserted into the optical path. Alternatively, lenses can be formed or bonded to one or both sides of the QWP. For example, lenses can be molded on one or both sides of an inorganic waveplate using wafer-level optics technology as a substrate.

[0015] Next, the characteristic configuration of the optical system of each embodiment will be described.

[0016] Each embodiment of the optical system includes first and second meniscus lenses spaced apart from each other from the object side to the image side. The first meniscus lens includes a first transmissive-reflective surface convex toward the object side. The second meniscus lens includes a second transmissive-reflective surface convex toward the object side. Off-axis light rays traveling from the object side to the image side pass through the first transmissive-reflective surface, then reflect off the second transmissive-reflective surface, and then pass through the second transmissive-reflective surface, resulting in light rays with relatively good telecentricity. Because the first and second transmissive-reflective surfaces have a convex shape toward the object side, off-axis light rays traveling from the object side to the image side move in a direction perpendicular to the optical axis from the transmission point of the first transmissive-reflective surface to the transmission point of the second transmissive-reflective surface. Therefore, the transmission point of the second transmissive-reflective surface and the image position can be positioned approximately at the same position in a direction perpendicular to the optical axis. In other words, telecentric light rays can be obtained. A meniscus lens is a lens having one lens surface that is convex and the other lens surface that is concave. It is preferable that no lens is disposed between the first meniscus lens and the second meniscus lens. Furthermore, it is preferable that the first and second meniscus lenses each include a first and second transmissive-reflective surface on the image side.

[0017] The light ray passes through the first transmissive-reflective surface, is reflected by the second transmissive-reflective surface, and returns to the first transmissive-reflective surface, but the light path between them goes back and forth, which has the effect of bending the light ray. The length of the light ray that would normally be needed is folded, and the overall length of the lens can be shortened.

[0018] Because the first and second transflective surfaces have a reflective structure, no chromatic aberration occurs, and the positive and negative Petzval sums can be controlled with a large refractive power, making it possible to obtain good imaging performance with a small number of lenses and a large aperture.

[0019] Next, the configurations that are preferably satisfied in the optical systems of the respective embodiments will be described.

[0020] One of the first and second transflective surfaces is preferably a surface that separates incident light into reflected light and transmitted light according to its polarization state. Specifically, as described below, it is preferable to use a polarization-selective transflective element as one of the first and second transflective surfaces. Examples of polarization-selective transflective elements include those manufactured by Asahi Kasei Corporation under the trade name "WGF" and 3M Company under the trade name "IQPE." Alternatively, the polarization-selective transflective element may be an optical element created by forming a grid on the lens reflective surface during lens molding and then depositing, printing, or lithographically depositing a metal or dielectric material thereon. The other polarization-selective transflective element may be a half mirror, a cholesteric liquid crystal, a holographic optical element, or the like. When a half mirror is used, the amount of randomly polarized light incident from the object side is reduced to 12.5% ​​or less by the time it reaches the image plane. Using a cholesteric liquid crystal or a holographic optical element can approximately double the amount of light on the image plane compared to using a half mirror.

[0021] In order for the first transmissive-reflective surface to converge a large light beam, it needs to have a positive refractive power. Furthermore, in order to correct the spherical aberration and curvature of field that occur due to the positive refractive power, the second transmissive-reflective surface needs to have a negative refractive power. In this way, the positive and negative refractive powers of the reflecting surfaces allow for correction of spherical aberration and curvature of field, while the first and second transmissive-reflective surfaces can correct curvature of field.

[0022] The optical system of each embodiment is preferably rotationally symmetric about the optical axis.

[0023] In the optical systems of the respective embodiments, it is preferable that the refractive power of the first meniscus lens provided with the first transmissive-reflective surface and the second meniscus lens provided with the second transmissive-reflective surface be smaller than the refractive power of the optical system as a whole. If the refractive power of each meniscus lens is large, unnecessary aberrations such as chromatic aberrations will occur in each lens group. Since it is preferable that the aspherical lens effect is large during the round trip of the optical path, it is preferable that the refractive power of each meniscus lens during transmission be as small as possible.

[0024] Next, conditions that the optical system of each embodiment should preferably satisfy will be described. The optical system of each embodiment should preferably satisfy one or more of the following conditional expressions (1) to (5).

[0025] 0.00<|f / f1|≦0.47 (1) 0.00<|f / f2|≦0.56 (2) 1.11≦|R1 / f|≦3.47 (3) 1.00≦|R2 / f|≦3.46 (4) 0.29≦L1 / f≦1.13 (5) where f is the focal length of the optical system. f1 is the focal length of the first meniscus lens. f2 is the focal length of the second meniscus lens. R1 is the radius of curvature of the first transflective surface. R2 is the radius of curvature of the second transflective surface. L1 is the distance on the optical axis between the first and second meniscus lenses (the distance (air distance) on the optical axis from the image-side lens surface of the first meniscus lens to the object-side lens surface of the second meniscus lens).

[0026] If the upper limit of conditional expression (1) is exceeded, the refractive power of the first meniscus lens becomes large, which is undesirable as it significantly increases the amount of axial chromatic aberration that occurs.

[0027] If the upper limit of conditional expression (2) is exceeded, the refractive power of the second meniscus lens becomes large, which is undesirable as it significantly increases the amount of chromatic aberration of magnification.

[0028] If the lower limit of conditional expression (3) is exceeded, the positive refractive power of the first meniscus lens becomes too large, causing large spherical aberrations to occur on the underside and becoming unable to be fully corrected, which is undesirable.If the upper limit of conditional expression (3) is exceeded, the positive refractive power of the first meniscus lens becomes too small, causing spherical aberrations to occur on the overside, which is undesirable.

[0029] If the lower limit of conditional expression (4) is not reached, the negative refractive power of the second meniscus lens becomes too large, which undesirably causes large negative spherical aberration that cannot be fully corrected, whereas if the upper limit of conditional expression (4) is reached, the negative refractive power of the second meniscus lens becomes too small, which undesirably causes insufficient correction of spherical aberration and curvature of field.

[0030] If the lower limit of conditional expression (5) is exceeded, the distance on the optical axis between the first and second transmissive-reflective surfaces becomes too narrow, forcing light rays to move in a direction perpendicular to the optical axis within this narrow distance, making it difficult to ensure telecentricity when passing through the second transmissive-reflective surface. Ensuring telecentricity requires strengthening the shape of the convex surface facing the object side, which undesirably results in an unnecessary air gap between the second transmissive-reflective surface and the image point, resulting in increased size. If the upper limit of conditional expression (5) is exceeded, the distance on the optical axis between the first and second transmissive-reflective surfaces becomes too wide, making it difficult to arrange lenses capable of correcting aberrations, making aberration correction difficult and undesirable.

[0031] It is more preferable that the numerical ranges of the following conditional expressions (1) to (5) be the numerical ranges of the following conditional expressions (1a) to (5a).

[0032] 0.00<|f / f1|≦0.44 (1a) 0.00<|f / f2|≦0.52 (2a) 1.29≦|R1 / f|≦3.22 (3a) 1.16≦|R2 / f|≦3.21 (4a) 0.34≦L1 / f≦1.05 (5a) It is more preferable that the numerical ranges of the following conditional expressions (1) to (5) be the numerical ranges of the following conditional expressions (1b) to (5b).

[0033] 0.00<|f / f1|≦0.40 (1b) 0.00<|f / f2|≦0.48 (2b) 1.47≦|R1 / f|≦2.97 (3b) 1.33≦|R2 / f|≦2.97 (4b) 0.39≦L1 / f≦0.97 (5b) The various values ​​for each example are summarized in Table 1.

[0034] [Table 1]

[0035] [Polarized configuration] A configuration using polarized light will be described with reference to Fig. 1. The optical system of each embodiment has, arranged in order from the object side to the image side, a linear polarizer POL, a quarter-wave plate QWP, a first transmission-reflection surface HM, a quarter-wave plate QWP, and a second transmission-reflection surface PBS.

[0036] Light from the object side becomes linearly polarized after passing through the linear polarizer POL, and becomes circularly polarized after passing through the quarter-wave plate QWP. The circularly polarized light becomes linearly polarized after passing through the first transflective surface HM and the quarter-wave plate QWP, and is reflected as linearly polarized light by the polarized reflection action of the second transflective surface PBS. The light beam is converted to circularly polarized light after passing through the quarter-wave plate QWP, and reflected by the first transflective surface HM. When it passes through the quarter-wave plate QWP, it is converted to linearly polarized light with an orthogonal polarization direction, and passes through the second transflective surface PBS before being directed to the image sensor IM.

[0037] The optical systems of the respective examples will be described below. [Example]

[0038] FIG. 2 is a cross-sectional view of the optical system 101 of this embodiment. The optical system 101 includes, arranged in order from the object side to the image side, a polarizing element F11, a fully open aperture S1, a first meniscus lens L11, an element F12, and a second meniscus lens L12. The polarizing element F11 serves both as a linear polarizer POL and a quarter-wave plate QWP. Separate elements may be provided for each function of the linear polarizer POL and the quarter-wave plate QWP. The first meniscus lens L11 is provided with a first transmissive-reflective surface L11R2. The element F12 functions as a quarter-wave plate QWP. The second meniscus lens L12 is provided with a second transmissive-reflective surface L12R2. An element F13, which functions as a wavelength-selective filter and a polarizing element, and a cover glass CG1 are arranged on the object side of the image sensor IM1. Tables 2 and 3 show the numerical data of this embodiment.

[0039] [Table 2]

[0040] Aspheric shape data is shown in Table 3. The aspheric shape is expressed by the following equation, where Z is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and Ai (i = 2, 4, 6, 8, ...) are the aspheric coefficients of each order.

[0041]

number

[0042] [Table 3]

[0043] 3 is an MTF diagram of the optical system 101. A sufficiently high MTF value is obtained at 83 lp / mm, which is half the Nyquist frequency of the 3.0 μm pitch sensor. [Example]

[0044] FIG. 4 is a cross-sectional view of the optical system 102 of this embodiment. The optical system 102 includes, arranged in order from the object side to the image side, a positive lens L21, a polarizing element F21, a fully open aperture stop S2, a first meniscus lens L22, an element F22, and a second meniscus lens L23. The polarizing element F21 functions as both a linear polarizer POL and a quarter-wave plate QWP. The first meniscus lens L22 is provided with a first transmissive-reflective surface L22R2. The element F22 functions as a quarter-wave plate QWP. The second meniscus lens L23 is provided with a second transmissive-reflective surface L23R2. An element F23, which functions as a wavelength-selective filter or a polarizing element, and a cover glass CG2 are arranged on the object side of the image sensor IM2. Tables 4 and 5 show the numerical data of this embodiment.

[0045] [Table 4]

[0046] [Table 5]

[0047] 5 is an MTF diagram of the optical system 102. A sufficiently high MTF value is obtained at 83 lp / mm, which is half the Nyquist frequency of the 3.0 μm pitch sensor. [Example]

[0048] FIG. 6 is a cross-sectional view of the optical system 103 of this embodiment. The optical system 103 includes, arranged in order from the object side to the image side, a negative lens L31, a polarizing element F31, a fully open aperture stop S3, a first meniscus lens L32, an element F32, and a second meniscus lens L33. The polarizing element F31 functions as both a linear polarizer POL and a quarter-wave plate QWP. The first meniscus lens L32 is provided with a first transmissive-reflective surface L32R2. The element F32 functions as a quarter-wave plate QWP. The second meniscus lens L33 is provided with a second transmissive-reflective surface L33R2. An element F33 having functions such as a wavelength-selective filter and a polarizing element, and a cover glass CG3 are arranged on the object side of the image sensor IM3. Tables 6 and 7 show the numerical data of this embodiment.

[0049] [Table 6]

[0050] [Table 7]

[0051] 7 is an MTF diagram of the optical system 103. A sufficiently high MTF value is obtained at 83 lp / mm, which is half the Nyquist frequency of the 3.0 μm pitch sensor. [Example]

[0052] FIG. 8 is a cross-sectional view of the optical system 104 of this embodiment. The optical system 104 includes, arranged in order from the object side to the image side, a polarizing element F41, a fully open aperture stop S4, a first meniscus lens L41, an element F42, a second meniscus lens L42, and a positive lens L43. The polarizing element F41 functions as both a linear polarizer POL and a quarter-wave plate QWP. The first meniscus lens L41 is provided with a first transmissive-reflective surface L41R2. The element F42 functions as a quarter-wave plate QWP. The second meniscus lens L42 is provided with a second transmissive-reflective surface L42R2. An element F43 having functions such as a wavelength-selective filter and a polarizing element, and a cover glass CG4 are arranged on the object side of the image sensor IM4. Tables 8 and 9 show the numerical data of this embodiment.

[0053] [Table 8]

[0054] [Table 9]

[0055] 9 is an MTF diagram of the optical system 103. A sufficiently high MTF value is obtained at 83 lp / mm, which is half the Nyquist frequency of the 3.0 μm pitch sensor. [Imaging device] An imaging device 70 using any of the optical systems of the embodiments as an imaging optical system will be described. Fig. 10 is a schematic diagram of the main parts of the imaging device 70. The imaging device 70 has an imaging optical system 71 of any of the embodiments, a light receiving element 72 that photoelectrically converts an image of an object formed by the imaging optical system 71, and a camera body (housing) 73 that holds the light receiving element 72. The imaging optical system 71 is held by a lens barrel (holding member) and connected to the camera body 73. A display unit 74 that displays an image acquired by the light receiving element 72 may be connected to the camera body 73. The light receiving element 72 can be an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor.

[0056] When the imaging device 70 is used as a focus detection device, for example, an imaging element (image plane phase difference sensor) having pixels that can split a light beam from an object into two and perform photoelectric conversion can be used as the light receiving element 72. When the object is on the front focal plane of the imaging optical system 71, no positional shift occurs between the images corresponding to the two split light beams on the image plane of the imaging optical system 71. However, when the object is located at a position other than the front focal plane of the imaging optical system 71, a positional shift occurs between the images. In this case, the positional shift between the images corresponds to the amount of displacement from the front focal plane of the object, so the distance to the object can be measured by obtaining the amount and direction of the positional shift between the images using the image plane phase difference sensor.

[0057] The imaging optical system 71 and the camera body 73 may be configured to be detachable from each other. That is, the imaging optical system 71 and the lens barrel may be configured as an interchangeable lens (lens device). The optical system of each embodiment is not limited to imaging devices such as digital still cameras, silver halide film cameras, video cameras, vehicle-mounted cameras, and surveillance cameras, but can also be applied to various optical devices such as telescopes, binoculars, projectors (projection devices), and digital copiers. [In-vehicle system] FIG. 11 is a configuration diagram of an in-vehicle camera 10 according to this embodiment and an in-vehicle system (driving assistance device) 600 equipped with the same. The in-vehicle system 600 is held by a movable body (mobile device) such as an automobile (vehicle, mobile device), and is a system for assisting the driving (piloting) of the vehicle based on image information of the surroundings of the vehicle acquired by the in-vehicle camera 10. FIG. 12 is a schematic diagram of a vehicle 700 as a mobile device equipped with the in-vehicle system 600. While FIG. 12 shows a case where the imaging range 50 of the in-vehicle camera 10 is set in front of the vehicle 700, the imaging range 50 may also be set behind or to the side of the vehicle 700, etc.

[0058] 11, the in-vehicle system 600 includes an in-vehicle camera 10, a vehicle information acquisition device 20, a control device (controller, ECU: Electronic Control Unit) 30, and a warning device (warning unit) 40. The in-vehicle camera 10 also includes an imaging unit 1, an image processing unit 2, a parallax calculation unit 3, a distance acquisition unit (acquisition unit) 4, and a collision determination unit 5. The image processing unit 2, the parallax calculation unit 3, the distance acquisition unit 4, and the collision determination unit 5 constitute a processing unit. The imaging unit 1 includes any one of the optical systems of the respective embodiments and an imaging element.

[0059] 13 is a flowchart showing an example of the operation of the in-vehicle system 600 according to this embodiment. The operation of the in-vehicle system 600 will be described below with reference to this flowchart.

[0060] First, in step S1, the imaging unit 1 captures images of objects (subjects) such as obstacles and pedestrians around the vehicle, and acquires a plurality of image data (parallax image data).

[0061] In step S2, vehicle information is acquired by the vehicle information acquisition device 20. The vehicle information includes the vehicle speed, yaw rate, steering angle, and the like.

[0062] In step S3, the image processing unit 2 performs image processing on the multiple image data acquired by the imaging unit 1. Specifically, image feature analysis is performed to analyze feature quantities such as the amount and direction of edges in the image data, density values, etc. Here, the image feature analysis may be performed on each of the multiple image data, or may be performed on only some of the multiple image data.

[0063] In step S4, disparity (image shift) information between the multiple image data acquired by the imaging unit 1 is calculated by the disparity calculation unit 3. As a method for calculating disparity information, known methods such as the SSDA method and the area correlation method can be used, and therefore a description thereof will be omitted in this embodiment. Note that steps S2, S3, and S4 may be performed in the above order, or may be processed in parallel with each other.

[0064] In step S5, distance information about the object captured by the imaging unit 1 is acquired (calculated) by the distance acquisition unit 4. The distance information can be calculated based on the parallax information calculated by the parallax calculation unit 3 and the internal and external parameters of the imaging unit 1. Note that the distance information here refers to information about the relative position of the object, such as the distance from the object, the amount of defocus, and the amount of image shift, and may directly represent the distance value of the object in the image, or may indirectly represent information corresponding to the distance value.

[0065] Then, in step S6, the collision determination unit 5 determines whether the distance to the object is within a preset distance range using the vehicle information acquired by the vehicle information acquisition device 20 and the distance information calculated by the distance acquisition unit 4. This makes it possible to determine whether an object exists within a set distance around the vehicle and to determine the possibility of a collision between the vehicle and the object. If an object exists within the set distance, the collision determination unit 5 determines that there is a "possibility of collision" (step S7), and if there is no object within the set distance, it determines that there is "no possibility of collision" (step S8).

[0066] Next, if the collision determination unit 5 determines that there is a "possibility of collision," it notifies (transmits) the determination result to the control device 30 and the warning device 40. At this time, the control device 30 controls the vehicle based on the determination result of the collision determination unit 5 (step S6), and the warning device 40 issues a warning to the vehicle user (driver, passengers) based on the determination result of the collision determination unit 5 (step S7). The notification of the determination result may be sent to at least one of the control device 30 and the warning device 40.

[0067] The control device 30 can control the movement of the vehicle by outputting control signals to the drive units (engine, motor, etc.) of the vehicle. For example, it performs control such as applying the brakes on the vehicle, releasing the accelerator, turning the steering wheel, and generating control signals to generate braking forces on each wheel to suppress the output of the engine or motor. In addition, the warning device 40 warns the user by, for example, issuing a warning sound (alarm), displaying warning information on the screen of a car navigation system or the like, or vibrating the seat belt or steering wheel.

[0068] As described above, the in-vehicle system 600 according to this embodiment can effectively detect an object through the above-described processing, thereby making it possible to avoid a collision between the vehicle and the object. In particular, by applying any of the optical systems of the respective examples to the in-vehicle system 600, it becomes possible to detect an object and determine a collision over a wide angle of view while miniaturizing the entire in-vehicle camera 10 and increasing the degree of freedom in placement.

[0069] The vehicle-mounted camera 10 may be configured to include only one imaging unit 1 with an imaging surface phase difference sensor, or may be a stereo camera with two imaging units 1. In this case, even if an imaging surface phase difference sensor is not used, image data may be simultaneously acquired by each of the two synchronized imaging units 1, and the two image data may be used. However, if the difference in imaging time between the two imaging units 1 is known, the two imaging units 1 do not need to be synchronized.

[0070] Furthermore, various embodiments are possible for calculating the distance information. As an example, a case will be described in which a split-pupil image sensor having a plurality of pixels regularly arranged in a two-dimensional array is used as the image sensor of the image capturing unit 1. In the split-pupil image sensor, each pixel is composed of a microlens and a plurality of photoelectric conversion units, and can receive a pair of light beams passing through different regions in the pupil of the optical system and output a pair of image data from each photoelectric conversion unit.

[0071] Then, the image shift amount for each region is calculated by a correlation calculation between the paired image data, and image shift map data representing the distribution of the image shift amount is calculated by the distance acquisition unit 4. Alternatively, the distance acquisition unit 4 may further convert the image shift amount into a defocus amount to generate defocus map data representing the distribution of the defocus amount (distribution on a two-dimensional plane of the captured image). Furthermore, the distance acquisition unit 4 may acquire distance map data of the distance to the object converted from the defocus amount.

[0072] Furthermore, the in-vehicle system 600 and the vehicle 700 may be provided with a notification device (notification unit) for notifying the manufacturer of the in-vehicle system or the distributor (dealer) of the mobile device, etc., if the vehicle 700 collides with an obstacle. For example, the notification device may be one that transmits information (collision information) related to the collision between the vehicle 700 and an obstacle to a preset external notification destination by e-mail or the like.

[0073] In this way, by adopting a configuration in which the notification device automatically notifies collision information, it is possible to promptly take measures such as inspection and repair after a collision occurs. The destination of the collision information may be an insurance company, a medical institution, the police, or any other party set by the user. Furthermore, the notification device may be configured to notify the destination not only of collision information but also of malfunction information of each part and information on consumption of consumables. The detection of the presence or absence of a collision may be performed using distance information acquired based on the output from the above-mentioned imaging unit 1, or may be performed by another detection unit (sensor).

[0074] In this embodiment, the in-vehicle system 600 is applied to driving assistance (collision damage reduction), but the application is not limited to this. The in-vehicle system 600 may also be applied to cruise control (including an all-speed tracking function) or autonomous driving. The in-vehicle system 600 is not limited to vehicles such as automobiles, but can be applied to moving bodies such as ships, aircraft, and industrial robots. The in-vehicle system 600 is not limited to moving bodies, but can be applied to various devices that use object recognition, such as intelligent transport systems (ITS).

[0075] The disclosure of each embodiment includes the following configuration. (Configuration 1) a first meniscus lens and a second meniscus lens arranged in this order from the object side to the image side, the first meniscus lens and the second meniscus lens arranged in this order from the object side to the image side, the the first meniscus lens includes a first transmission-reflection surface that is convex toward an object side, the second meniscus lens includes a second transmissive-reflective surface that is convex toward an object side, an optical system in which light from the object side passes through the first transmissive-reflective surface, is reflected by the second transmissive-reflective surface toward the object side, is reflected by the first transmissive-reflective surface toward the image side, and passes through the second transmissive-reflective surface toward the image side. (Configuration 2) When the focal length of the first meniscus lens is f1 and the focal length of the optical system is f, 0.00<|f / f1|≦0.47 The optical system according to configuration 1, characterized in that the following condition is satisfied: (Configuration 3) When the focal length of the second meniscus lens is f2 and the focal length of the optical system is f, 0.00<|f / f2|≦0.56 3. The optical system according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 4) When the radius of curvature of the first transmissive-reflective surface is R1 and the focal length of the optical system is f, 1.11≦|R1 / f|≦3.47 4. The optical system according to any one of the configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) When the radius of curvature of the second transmissive-reflective surface is R2 and the focal length of the optical system is f, 0.00≦|R2 / f|≦3.46 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) When the distance between the first and second meniscus lenses on the optical axis is L1 and the focal length of the optical system is f, 0.29≦L1 / f≦1.13 6. The optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) 7. The optical system according to any one of configurations 1 to 6, wherein no lens is disposed between the first and second meniscus lenses. (Configuration 8) 8. The optical system according to any one of configurations 1 to 7, wherein the first and second meniscus lenses include the first and second transmissive-reflective surfaces on the image side, respectively. (Configuration 9) 9. An imaging device comprising: the optical system according to any one of configurations 1 to 8; and an imaging element that images an object via the optical system. (Configuration 10) the imaging device according to configuration 9; The system further comprises a determination unit that determines a possibility of a collision between the mobile device and the object based on distance information of the object acquired by the imaging device. (Configuration 11) The system according to configuration 10, further comprising a control device that outputs a control signal to generate a braking force in a drive unit of the mobile device when it is determined that there is a possibility of a collision between the mobile device and the object. (Configuration 12) 12. The system according to configuration 10 or 11, further comprising a warning device that warns a user of the mobile device when it is determined that there is a possibility of a collision between the mobile device and the object. (Configuration 13) 13. The system according to any one of configurations 10 to 12, further comprising a notification device that notifies an outside party of information relating to a collision between the mobile device and the object. (Configuration 14) A moving device having the imaging device according to configuration 9, capable of holding and moving the imaging device. (Configuration 15) The moving device according to configuration 14, further comprising a determination unit that determines the possibility of a collision with the object based on distance information of the object obtained by the imaging device. (Configuration 16) 16. The moving device according to configuration 15, further comprising a control unit that outputs a control signal for controlling movement when it is determined that there is a possibility of collision with the object. (Configuration 17) 17. The mobile device according to configuration 15 or 16, further comprising a warning unit that issues a warning to a user of the mobile device when it is determined that there is a possibility of a collision with the object. (Configuration 18) 18. The moving device according to any one of configurations 14 to 17, further comprising a notification unit that notifies an outside party of information relating to the collision with the object.

[0076] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0077] L11R2, L22R2, L32R2, L41R2 First transflective surface L12R2, L23R2, L33R2, L42R2 Second transflective surface L11, L22, L32, L41 First meniscus lens L12, L23, L33, L42 Second meniscus lens

Claims

1. The optical system has first and second meniscus lenses spaced apart from each other in order from the object side to the image side, the first meniscus lens includes a first transmission-reflection surface that is convex toward an object side, the second meniscus lens includes a second transmissive-reflective surface that is convex toward the object side, an optical system in which light from an object side is transmitted through the first transmitting-reflecting surface, reflected by the second transmitting-reflecting surface toward the object side, reflected by the first transmitting-reflecting surface toward the image side, and transmitted through the second transmitting-reflecting surface toward the image side.

2. When the focal length of the first meniscus lens is f1 and the focal length of the optical system is f, 0.00<|f / f1|≦0.47 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. When the focal length of the second meniscus lens is f2 and the focal length of the optical system is f, 0.00<|f / f2|≦0.56 3. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the radius of curvature of the first transmissive-reflective surface is R1 and the focal length of the optical system is f, 1.11≦|R1 / f|≦3.47 3. The optical system according to claim 1, wherein the following condition is satisfied:

5. When the radius of curvature of the second transmissive-reflective surface is R2 and the focal length of the optical system is f, 0.00≦|R2 / f|≦3.46 3. The optical system according to claim 1, wherein the following condition is satisfied:

6. When the distance between the first and second meniscus lenses on the optical axis is L1 and the focal length of the optical system is f, 0.29≦L1 / f≦1.13 3. The optical system according to claim 1, wherein the following condition is satisfied:

7. 3. The optical system according to claim 1, wherein no lens is disposed between the first and second meniscus lenses.

8. 3. The optical system according to claim 1, wherein the first and second meniscus lenses include the first and second transmissive / reflective surfaces on the image side, respectively.

9. 3. An imaging apparatus comprising: the optical system according to claim 1; and an imaging element for imaging an object via the optical system.

10. The imaging device according to claim 9 ; The system further comprises a determination unit that determines a possibility of a collision between the mobile device and the object based on distance information of the object acquired by the imaging device.

11. The system according to claim 10, further comprising a control device that outputs a control signal to generate a braking force in a drive unit of the mobile device when it is determined that there is a possibility of a collision between the mobile device and the object.

12. 11. The system according to claim 10, further comprising a warning device that warns a user of the mobile device when it is determined that there is a possibility of a collision between the mobile device and the object.

13. The system according to claim 10, further comprising a notification device that notifies an external device of information regarding a collision between the mobile device and the object.

14. A moving device comprising the imaging device according to claim 9, and capable of holding and moving the imaging device.

15. The moving device according to claim 14, further comprising a determination unit that determines a possibility of collision with the object based on distance information of the object obtained by the imaging device.

16. 16. The moving device according to claim 15, further comprising a control unit that outputs a control signal for controlling movement when it is determined that there is a possibility of collision with the object.

17. 16. The mobile device according to claim 15, further comprising a warning unit that issues a warning to a user of the mobile device when it is determined that there is a possibility of a collision with the object.

18. The mobile device according to claim 14, further comprising a notification unit that notifies an external device of information regarding the collision with the object.

Images