In-vehicle camera system

Abstract

To provide an on-vehicle camera device capable of focusing on a wide range from a near view to a distant view as an imaging object.SOLUTION: An on-vehicle camera device 1 includes an imaging lens 2 having a predetermined focal length, a far-near lens 4 arranged to overlap the imaging lens 2 and having different focal lengths set for each of a plurality of partial areas, and an image sensor 3 having a sensor surface 3A that detects light incident through the imaging lens 2 and a far-near lens 4, and the sensor surface 3A is inclined with respect to a plane perpendicular to the optical axis of the imaging lens 2.SELECTED DRAWING: Figure 3

Description

【Technical Field】 【0001】 The present invention relates to an in-vehicle camera device mounted on a vehicle for imaging the surroundings. 【Background Art】 【0002】 Generally, cameras for imaging the rear or front of a vehicle, such as electronic mirrors and drive recorders, have a single focus, and the distance between the lens and the sensor is adjusted to a fixed focal length suitable for the application, such as 2 m or 4 m, so as to perform focus adjustment as uniform as possible. 【0003】 However, in the conventional adjustment, when attached to an actual vehicle, if the focus is set on a nearby subject, the image of a distant subject will become blurred, and conversely, if the focus is set on a distant subject, the image of a nearby subject will become blurred, resulting in so-called out-of-focus. 【0004】 As cameras for electronic mirrors and drive recorders mounted on vehicles, it is desirable to be able to display clear images both far and near. 【0005】 As a prior art that enables focusing from a short distance to a long distance, an in-vehicle camera device in which the inclination and relative position of a lens and an image sensor are set is known (see, for example, Patent Document 1). 【Prior Art Documents】 【Patent Documents】 【0006】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2001-285701 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0007】 By the way, in the in-vehicle camera device disclosed in Patent Document 1 mentioned above, the tilt of the imaging lens and the tilt of the image sensor are set so that the entire road surface to be imaged can be focused from near to far. However, when the target of imaging is a wide range from the road surface at very close range to the distant scenery, as in the case of cameras in electronic mirrors and dashcams, there is a problem that it is not possible to focus on the entire range. 【0008】 This invention was created in view of these points, and its purpose is to provide an in-vehicle camera device that can focus on a wide range of subjects, from near to far. [Means for solving the problem] 【0009】 To solve the above-mentioned problems, the in-vehicle camera device of the present invention comprises an imaging lens having a predetermined focal length, a distance lens positioned on top of the imaging lens and having different focal lengths set for each of a plurality of sub-regions, and an image sensor having a sensor surface for detecting light incident through the imaging lens and the distance lens, the sensor surface being inclined with respect to a plane perpendicular to the optical axis of the imaging lens. 【0010】 By using both near and far lenses and tilting the sensor surface of the image sensor, the overall focal length of the lens can be changed according to the imaging angle, making it possible to focus on a wide range of subjects, from near to far. 【0011】 Furthermore, by stacking a distance lens on top of the aforementioned imaging lens, the overall focal length can be set to be longer for distant objects and shorter for close objects. It is being done By using these settings, it is possible to obtain clear images of both distant and near objects. 【0012】 Furthermore, it is desirable that the aforementioned distance lens has different refractive indices in each of its multiple sub-regions. Also, the aforementioned distance lens has a longer focal length in the sub-region where light is incident from the distant view through the imaging lens, and a shorter focal length in the sub-region where light is incident from the near view through the imaging lens. It is set. By using such distance lenses, it becomes possible to set the overall focal length of the lens for each imaging area. 【0013】 Furthermore, it is desirable that the sensor surface described above has a long distance between the region where light is incident from the distant view through the imaging lens and the imaging lens, and a short distance between the region where light is incident from the near view through the imaging lens and the imaging lens. By tilting the sensor surface in this way, it becomes possible to obtain a high resolution that could not be adjusted by using only distance lenses. [Brief explanation of the drawing] 【0014】 [Figure 1] This figure shows the mounting state of an in-vehicle camera device according to one embodiment. [Figure 2] This diagram shows the correspondence between the imaging range and display range of an in-vehicle camera device. [Figure 3] This diagram shows the configuration of the in-vehicle camera device according to this embodiment. [Modes for carrying out the invention] 【0015】 Hereinafter, an in-vehicle camera device according to one embodiment to which the present invention is applied will be described with reference to the drawings. This embodiment of the in-vehicle camera device is for realizing an electronic mirror by, for example, capturing images of the area behind the vehicle and displaying the resulting images on a display device inside the vehicle. 【0016】 Figure 1 shows the mounting configuration of an in-vehicle camera device according to one embodiment. As shown in Figure 1, the in-vehicle camera device 1 of this embodiment is installed on the upper rear of the vehicle, and its imaging range extends from the road surface 2m away from the rear end of the vehicle to the distant view behind it. A, B, and C in Figure 1 are divisions of this imaging range, from the closest to the furthest point. A represents the relatively close range of 2 to 5m from the vehicle, B represents the slightly more distant range of 5 to 10m from the vehicle, and C represents the farther range of 10m or more from the vehicle. 【0017】 FIG. 2 is a diagram showing the correspondence between the imaging range and the display range of the in-vehicle camera device 1. The display device 10 shown in FIG. 2 is obtained by replacing the mirror surface of a conventional rearview mirror with a liquid crystal device or the like, and can display an image depicting a subject behind the vehicle imaged by the in-vehicle camera device 1. a, b, and c included in FIG. 2 indicate display areas corresponding to the imaging ranges A, B, and C of the in-vehicle camera device 1. In a conventional in-vehicle camera device using a single-focus lens, it was not possible to focus (bring into focus) on all three imaging ranges A, B, and C with greatly different distances, so it was not possible to display a clear image in focus in all of the display areas a, b, and c. This point is improved in the in-vehicle camera device 1 of the present embodiment. 【0018】 FIG. 3 is a diagram showing the configuration of the in-vehicle camera device 1 of the present embodiment. FIG. 3 shows an arrangement mainly focusing on the relationship between the lens and the image sensor. As shown in FIG. 3, the in-vehicle lens device 1 of the present embodiment includes an imaging lens 2, an image sensor 3, and a zoom lens 4. 【0019】 The imaging lens 2 is composed of a combination of a plurality of lenses and is a single-focus lens having a predetermined focal length as a whole. In FIG. 3, the principal point of the imaging lens 2 is indicated by p. 【0020】 The image sensor 3 detects light (video) incident through the imaging lens 2, and a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like can be used. 【0021】 The zoom lens 4 is disposed overlapping the imaging lens 2, and different focal lengths (different refractive indices) are set for each of a plurality of partial regions. For example, the zoom lens 4 is disposed between the principal point p of the imaging lens 2 and the sensor surface 3A of the image sensor 3. 【0022】 The overall focal length obtained by stacking the zoom lens 4 on the imaging lens 2 is longer for a distant view and shorter for a close view. Specifically, the focal length increases in the order of the imaging ranges A, B, and C shown in FIG. 2. 【0023】 In this embodiment, in order to set different focal lengths for each of the imaging ranges A, B, and C (FIG. 1) in this way, when the zoom lens 4 is divided into three parts, upper, middle, and lower parts along the vertical direction, the focal length of the lower part is made long corresponding to the imaging range C, the focal length of the upper part is made short corresponding to the imaging range A, and the focal length of the middle part is set to an intermediate value corresponding to the imaging range B. 【0024】 Incidentally, since the distances from the in-vehicle camera device 1 to each of the above-described three imaging ranges A, B, and C are significantly different, it is not easy to align the focal positions corresponding to each part on the sensor surface 3A of the image sensor 3 only by adjusting the focal lengths (refractive indices) of each part of the zoom lens 4. Therefore, in this embodiment, a measure is taken to incline the sensor surface 3A with respect to the surface 2A perpendicular to the optical axis of the imaging lens 2 to bring it closer to each focal position. Specifically, the angle of the sensor surface 3A is set such that the distance between the imaging lens 2 and the opposing sensor surface 3A is longer at the lower part of the sensor surface 3A and shorter at the upper part. 【0025】 In practice, as shown in Figure 3, a resolution test chart conforming to ISO 12233, for example, is placed at three positions La, Lb, and Lc, which represent the imaging ranges A, B, and C shown in Figure 1, respectively, to adjust the MTF (Modulation Transfer Function) and set the angle of the image sensor 3. Specifically, when this resolution test chart is divided vertically into three parts: the upper chart H1, the central chart H2, and the lower chart H3, the upper chart H1 is placed at position Lc, which represents imaging range C; the central chart H2 is placed at position Lb, which represents imaging range B; and the lower chart H3 is placed at position La, which represents imaging range A. The angle of the image sensor 3 is then adjusted to maximize the resolution when imaging each area. Note that the tilt of the imaging lens 2 and the distance lens 4 also affects the resolution, so the tilt of these lenses may also be adjusted along with the angle of the image sensor 3 to improve the resolution. 【0026】 Thus, in the in-vehicle camera device 1 of this embodiment, by using a near and far lens 4 and tilting the sensor surface 3A of the image sensor 3, the focal length of the entire lens can be changed according to the imaging angle, making it possible to focus on a wide range of subjects, from near to far. 【0027】 Furthermore, by stacking the distance lens 4 on top of the imaging lens 2, the overall focal length of the lens is set to be longer for distant objects and shorter for close objects, thus enabling the acquisition of clear images for both distant and close objects. 【0028】 Furthermore, the distance lens 4 has different refractive indices in each of its multiple sub-regions. The focal length of the sub-region where light is incident from the distant view through the imaging lens 2 is set to be longer, and the focal length of the sub-region where light is incident from the near view through the imaging lens 2 is set to be shorter. This makes it possible to set the overall focal length of the lens for each imaging range. 【0029】 Furthermore, by tilting the sensor surface 3A of the image sensor 3 such that the distance between the region where light is incident from the distant view through the imaging lens 2 and the imaging lens 2 is long, and the distance between the region where light is incident from the near view through the imaging lens 2 and the imaging lens 2 is short, it becomes possible to obtain a high resolution that could not be adjusted by using only the distance lens 4. 【0030】 It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the gist of the invention. For example, although the above-described embodiment described the application of the present invention to an electronic mirror used as a rearview mirror, the present invention may also be applied to electronic mirrors used as left and right door mirrors or to an in-vehicle camera device that images an area including the road surface in front of the vehicle. Specifically, for example, in the case of a right-side door mirror, the upper left of the imaging range behind the vehicle is the range that images the furthest view (requiring a long focal length), and the lower right and lower parts are the range that images the closest view (requiring a short focal length). Therefore, the refractive index (focal length) of each part of the near and far lenses and the inclination of the sensor surface 3A of the image sensor 3 should be set so that these focal lengths can be achieved within the imaging range. [Explanation of Symbols] 【0031】 1. In-vehicle camera system 2 imaging lenses 3 Image Sensors 3A Sensor surface 4. Progressive lenses

Claims

[Claim 1] An imaging lens having a predetermined focal length, A distance lens is positioned in superimposed on the aforementioned imaging lens, with each of the multiple sub-regions having a different focal length. An image sensor having a sensor surface for detecting light incident through the imaging lens and the near / far lens, wherein the sensor surface is inclined with respect to a plane perpendicular to the optical axis of the imaging lens, The system is equipped with such a configuration, and by superimposing the distance lens on the imaging lens, the overall focal length is set to be longer for distant objects and shorter for close objects. The aforementioned telephoto lens is characterized in that the focal length of the partial region into which light is incident from a distant view through the imaging lens is long, and the focal length of the partial region into which light is incident from a close view through the imaging lens is short. [Claim 2] The vehicle-mounted camera device according to claim 1, characterized in that the near and far lenses have different refractive indices in each of the plurality of subregions. [Claim 3] The in-vehicle camera device according to claim 1 or 2, characterized in that the sensor surface has a long distance between the region into which light is incident from a distant view through the imaging lens and the imaging lens, and a short distance between the region into which light is incident from a close view through the imaging lens and the imaging lens.

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