1. Technical Field
The present invention relates to a wide-angle imaging device. Specifically, the present invention relates to a wide-angle imaging device that can widely photograph an image through an optical system.
2. Related Art
Nowadays, in a monitoring camera or an image sensor, there is an increasing need to photograph a wider range (wider angle) using one imaging device. Conventionally, the following solutions are proposed to the need.
A first method is one in which the wide range can be photographed using a fish-eye lens. However, for the wide-angle imaging device provided with the fish-eye lens, because an image is largely distorted in a surrounding portion, a complicated correction needs to be performed using a microcomputer or a computer through image processing, and the microcomputer or the computer needs to have a high processing capability. For the use of the fish-eye lens, resolution of the image deteriorates because the surrounding image is reduced. Therefore, a higher-density imaging element needs to be used to increase cost of the wide-angle imaging device.
A second method is one in which an optical path is folded using a mirror to guide light beams from right and left visual fields to the imaging element. For example, Patent Document 1 discloses this type of wide-angle imaging device (panoramic imaging device). However, in a wide-angle imaging device 11 with such a configuration, when a direction inclined small with respect to a front of an imaging element 12 is photographed, a length A in a front-back direction of a mirror 13 increases due to spread of an angle of view, and an installation space of the mirror 13 increases, as illustrated in
A third method is one in which the wide range is photographed by rotating the wide-angle imaging device. However, in the third method, cables used for a power supply and input and output of a signal need to be also rotated because the imaging element that is of an electronic device is rotated. There is a risk of disconnecting the cable or a connection portion of the cable, and therefore durability and reliability of the wide-angle imaging device deteriorate.
Patent Document 1: Japanese Unexamined Patent Publication No. 2009-232278
One or more embodiments of the present invention provides a low-cost, high-reliability wide-angle imaging device in which the thickness in the front-back direction can be decreased using a refractive optical system.
According to one or more embodiments of the present invention, a wide-angle imaging device configured to photograph a range wider than an angle of view of an imaging element, the wide-angle imaging device includes: the imaging element configured to photograph an image; a visual field switching optical system including one or two or more optical elements, the optical element including a refractive type prism that refracts light incident from a visual field in a direction inclined with respect to an optical axis direction to collect the light to the imaging element; and an optical system driving mechanism configured to move the optical element of the visual field switching optical system.
In the wide-angle imaging device of one or more embodiments of the present invention, the optical element of the visual field switching optical system is moved and switched to be able to sequentially form the images of different visual field directions on the imaging element, so that the wide-range image can be photographed without enlarging the imaging element. The refractive type prism, which refracts the light incident from the visual field in a direction inclined with respect to the optical axis direction to collect the light to the imaging element, is used as the visual field switching optical system. Therefore, even in the case that the image is photographed in the direction inclined relatively small with respect to the optical axis direction, the thickness in the front-back direction of the visual field switching optical system hardly increases, and the compact wide-angle imaging device can be made.
In the wide-angle imaging device according to one or more embodiments of the present invention, for example, in the case that the visual field direction is switched while the visual field switching optical system includes two or more optical elements, the optical system driving mechanism may move the visual field switching optical system to selectively locate one of the optical elements of the visual field switching optical system on the optical axis. In the wide-angle imaging device according to one or more embodiments of the present invention, with all the optical elements of the visual field switching optical system located in positions shifted from the optical axis, the image of the optical axis direction may be photographed with no use of the optical element, or the image of the oblique direction may be photographed using the optical element.
In the wide-angle imaging device according to one or more embodiments of the present invention, the optical system driving mechanism may move each optical element by rotating the visual field switching optical system such that the optical element passes over the optical axis, or the optical system driving mechanism may move each optical element by linearly moving the visual field switching optical system such that the optical element passes over the optical axis.
In the wide-angle imaging device according to one or more embodiments of the present invention, the visual field switching optical system may include a reflective type prism or a mirror as the optical element, the reflective type prism or the mirror reflecting the light incident from the visual field in the direction inclined with respect to the optical axis direction to collect the light to the imaging element, and light incident from a visual field in a relatively small inclination direction with respect to the optical axis may be collected to the imaging element by the refractive type prism, and light incident from a visual field in a relatively large inclination direction with respect to the optical axis may be collected to the imaging element by the reflective type prism or the mirror. Accordingly, the wider-range image can be photographed.
In the wide-angle imaging device according to one or more embodiments of the present invention, a plurality of prisms in the optical elements constituting the visual field switching optical system may integrally be formed. In this case, the refractive type prisms may integrally be formed. In the case that the visual field switching optical system includes the reflective type prism, the refractive type prism and the reflective type prism may integrally be formed, or the reflective type prisms may integrally be formed.
As used herein, the prism means a transparent substance that refracts a traveling direction of the light entering a transparent medium. Particularly, the prism is called a refractive type prism in the case that the light is incident on the transparent medium and refracted at an interface with another transparent medium having a different refractive index. The prism is called a reflective type prism in the case that the light is incident on the transparent medium and reflected by the interface with another transparent medium having a different refractive index or by a surface processed into a mirror (for example, an evaporated film) formed on or in the transparent medium.
In the wide-angle imaging device according to one or more embodiments of the present invention, a vertical length may be longer than a horizontal length in a pixel region of the imaging element. Accordingly, the angle of view can be widened in a longitudinal direction (vertical direction) of the imaging element.
In the wide-angle imaging device according to one or more embodiments of the present invention, a surface on the imaging element side may be constructed with a concave curve in the refractive type prism. In the wide-angle imaging device according to one or more embodiments of the present invention, a surface on a photographing object side may be constructed with a convex curve in the refractive type prism. Accordingly, the distortion of the photographed image can be decreased.
In the wide-angle imaging device according to one or more embodiments of the present invention, an unnecessary portion of each of the optical elements may be removed with only a portion constituting an optical path of a light beam necessary for photographing being left, and the optical elements in which the unnecessary portions are removed may overlap each other when the optical elements are viewed from the side surface side with respect to an array direction of the optical elements with the optical elements in which the unnecessary portions are removed being adjacent to each other. Accordingly, the optical elements are arranged so as to come close to each other, so that the size of the visual field switching optical system can be reduced.
In the wide-angle imaging device according to one or more embodiments of the present invention, the optical elements may be arrayed in line when viewed in the optical axis direction, and the optical elements may be arranged such that visual field directions of the light beams incident on the imaging element through the optical elements are in alternate and opposite directions across the array direction of the optical elements. In the arrangement, because the optical paths of the optical elements adjacent to each other do not interfere with each other, the optical elements can be arranged while a distance between the optical elements is shortened, and the size of the wide-angle imaging device can further be reduced.
In the wide-angle imaging device according to one or more embodiments of the present invention, images of respective visual field directions may be arrayed and displayed on a monitor. Accordingly, entire circumstances are easily recognized because the images of respective directions, which are photographed while time is shifted, are displayed side by side.
According to one or more embodiments of the present invention, a wide-angle imaging device configured to photograph a range wider than an angle of view of an imaging element, the wide-angle imaging device includes: the imaging element configured to photograph an image; and two or more optical elements including refractive type prisms that refract light beams incident from visual fields in different directions inclined with respect to an optical axis direction to collect the light beams to the imaging element. At this point, the light beams, from respective visual field directions, passing through the optical elements are collected to different regions of the imaging element.
In the wide-angle imaging device of one or more embodiments of the present invention, the images of different visual field directions are formed on the imaging element at once by two or more optical elements, so that the wide-range image can be photographed. The refractive type prism, which refracts the light incident from the visual field in the direction inclined with respect to the optical axis direction to collect the light to the imaging element, is used as the visual field switching optical system. Therefore, even in the case that the image is photographed in the direction inclined relatively small with respect to the optical axis direction, the thickness in the front-back direction of the visual field switching optical system hardly increases, and the wide-angle imaging device can be downsized.
According to one or more embodiments of the present invention, a wide-angle imaging device configured to photograph a range wider than an angle of view of an imaging element, the wide-angle imaging device includes: the imaging element configured to photograph an image; and one or two or more optical elements including a refractive type prism that refracts light incident from a visual field in a direction inclined with respect to an optical axis direction to collect the light to the imaging element. At this point, light in the optical axis direction that does not pass through the optical element is collected to a region different from a region to which the light, from the visual field direction, passing through the optical element is collected in the imaging element.
In the wide-angle imaging device of one or more embodiments of the present invention, the images of different visual field directions are formed on the imaging element at once by one or two or more optical elements with no use of other optical elements, so that the wide-range image can be photographed. The refractive type prism, which refracts the light incident from the visual field in the direction inclined with respect to the optical axis direction to collect the light to the imaging element, is used as the visual field switching optical system. Therefore, even in the case that the image is photographed in the direction inclined relatively small with respect to the optical axis direction, the thickness in the front-back direction of the visual field switching optical system hardly increases, and the wide-angle imaging device can be downsized.
The wide-angle imaging device according to one or more embodiments of the present invention may further include a reflective type prism or a mirror that reflects the light incident from the visual field in the direction inclined with respect to the optical axis direction to collect the light to a partial region of the imaging element. At this point, light incident from a visual field in a relatively small inclination direction with respect to the optical axis is collected to the imaging element by the refractive type prism, and light incident from a visual field in a relatively large inclination direction with respect to the optical axis is collected to the imaging element by the reflective type prism or the mirror. Accordingly, the wider-range image can be photographed.
In the wide-angle imaging device according to one or more embodiments of the present invention, distortion correction processing may be performed on images of different visual field directions, the images being photographed with the imaging element, and image processing may be performed on the images. Accordingly, the image processing is performed after the distortion correction processing is performed on the image, so that a load of the image processing can be reduced.
In the wide-angle imaging device having the reflective type prism or the mirror according to one or more embodiments of the present invention, distortion correction processing may be performed on images of different visual field directions, the images being photographed with the imaging element, reverse correction processing may be performed on images of light which is reflected by the reflective type prism or the mirror and collected to the imaging element, and image processing may be performed on the images. Accordingly, the distortion correction processing is performed on the image, and the image processing is performed after the reverse correction processing is performed on the image of light which is reflected by the reflective type prism or the mirror and collected to the imaging element, so that the load of the image processing can be reduced. Orientations of the images can be aligned when the images are displayed on a monitor.
The wide-angle imaging device according to one or more embodiments of the present invention can be incorporated in an electronic instrument. Examples of the electronic instrument in which the wide-angle imaging device is incorporated include an image sensor, a human body detection sensor, a face detection sensor, a car-mounted sensor, and other sensors. The wide-angle imaging device can also be incorporated in large-size electronic instruments such as an air conditioner and other home appliances.
One or more embodiments of the present invention may be combined, and many variations can be made thereto.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various changes can be made without departing from the scope of the present invention. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention.
As illustrated in
As illustrated in
The visual field switching optical system 23 includes the refractive type of first prism 24 and the refractive type of second prism 25. The first prism 24 is fixed to a top surface of a table 29 using an adhesive agent. The second prism 25 is fixed to the top surface of the first prism 24 using the adhesive agent. The first prism 24 and the second prism 25 have an identical shape, and are arranged so as to be symmetrical with respect to a vertical surface that is parallel to an optical axis of the lens 27 and includes the optical axis of the lens 27.
As illustrated in
The visual field switching optical system 23 is vertically moved by the optical system driving mechanism 28 as shown in
In the optical system driving mechanism 28, when the motor 34 rotates the cam 36, the cam 36 pushes up the cam abutment plate 32 against the elastic force of the spring 33, and the slide shaft 30 is vertically moved between a top dead center and a bottom dead center. As a result, the optical system driving mechanism 28 vertically moves the first prism 24 and the second prism 25.
Additionally, the image of a certain visual field direction can be photographed by the whole imaging element 26 by switching the prisms, so that an increase in size of the imaging element 26 is prevented to make the wide-angle imaging device 21 compact compared with the case that a pixel region (imaging region) of the imaging element is divided to photograph the images of respective visual field directions at once. In other words, the definition of the image can be improved compared to the imaging element having the identical size.
As a modification of the first embodiment, using one prism, that is, one of the prisms 24 and 25 for example, the state in which the prism is located in front of the camera and the state in which the prism is not located in front of the camera may be switched to monitor the visual field in front of the camera and one of the visual fields in the right and left oblique directions. In contrast, three or more prisms can be used as the optical element to photograph the images of different visual field directions. Alternatively, combination with a reflective type prism and a mirror (to be described later) may be employed as the optical element.
In the case that a plurality of prisms are used, the prisms may integrally be formed. For example,
In the first embodiment, the prisms having the identical two-dimensional shape are symmetrically arranged. However, the visual field switching optical system 23 is not limited to the optical system of the first embodiment. For example, as illustrated in
An optical system driving mechanism 28 of the wide-angle imaging device 51 includes a guide rail 52, a slider 53 that moves along the guide rail 52, and a driver 54 that moves the slider 53. The guide rail 52 includes two rail grooves 55 that extend in the vertical direction. An opening 59 is provided between the rail grooves 55 of the guide rail 52, and the front surface of the camera 22 is exposed at the opening 59.
The slider 53 includes projections 56 that are fitted in the rail grooves 55 of the guide rail 52 on both side surfaces. The projections 56 of the slider 53 are slidably fitted in the rail grooves 55 of the guide rail 52, and the slider 53 is vertically slidable along the rail grooves 55. The slider 53 substantially has a frame shape. The refractive type first prism 24, the refractive type second prism 25, a reflective type third prism 57, and a reflective type fourth prism 58, which are of the optical element, are held inside the slider 53. In the prisms 57 and 58, a metal evaporated film is formed on the surface of the prisms 57 and 58 or in the prisms 57 and 58 to provide a mirror surface (57a and 58a). The reflective type prisms 57 and 58 may totally reflect the light at an interface (surface) with air, or a mirror such as a metal mirror may be used instead of the reflective type prisms 57 and 58.
A female screw is formed on an inner surface of a substantial U-shape female screw unit 61, and a fixing unit 60 of the female screw unit 61 is screwed on the side surface of the slider 53. On the other hand, an attaching unit 62 extends from a lateral side of the guide rail 52, and the driver 54 is fixed to the attaching unit 62. In the driver 54, a motor 64 (for example, a pulse step motor and a servo motor) is fixed to a top surface of a screw shaft supporting plate 63. A lower end of a screw shaft 65 is pivoted on the bottom surface of the screw shaft supporting plate 63, and an upper end of the screw shaft 65 is coupled to the motor 64. When the slider 53 is attached to the guide rail 52, the female screw of the female screw unit 61 is pressed against the screw shaft 65 to engage the screw shaft 65. The camera 22 is mounted on a circuit board 66.
When the motor 64 normally or reversely rotates the screw shaft 65, the female screw unit 61 engaged with the screw shaft 65 travels along an axial direction of the screw shaft 65, thereby vertically moving the slider 53.
As illustrated in
As illustrated in
In
The optical system driving mechanism 28 of the second embodiment can also be used in the case that two or three prisms or mirrors are moved, or in the case that five or more prisms or mirrors are moved.
The visual field switching optical system 23, that is, the visual field switching optical system 23 of the second embodiment for example, can be downsized as follows.
The light beam L indicated in the third prism 57 and fourth prism 58 of
Similarly, the light beam L indicated in the first prism 24 and second prism 25 of
In the arrangement of
As illustrated in
The third embodiment can be applied to the case of three or more prisms.
Although not illustrated, the optical system driving mechanism 28 of the fourth embodiment can have a structure in which the optical system driving mechanism 28 of the second embodiment is laid.
(Image Processing)
An image processor 94 used in a wide-angle imaging device 92 will be described below with reference to
(Prism)
Prisms having various shapes can be used as the first and second prisms 24 and 25 used in each embodiment.
In the prisms 24 and 25 (the prisms of the first embodiment) of
In Table 1, a numerical value indicated in a field of the refracted light (rearward-inclined surface) expresses the angle formed by each of the light beams L1, L2, and L3 incident on the prisms 24 and 25 from the rearward-inclined surface 42 with respect to the optical axis C. In Table 1, a numerical value indicated in a field of the refracted light (forward-inclined surface) expresses the angle formed by each of the light beams L1, L2, and L3 output to the outside of the prism from the forward-inclined surface 43 with respect to the optical axis C. In Table 1, a numerical value indicated in a field of an bending angle expresses a change in direction of each of the light beams L1, L2, and L3 passing through the prisms 24 and 25 (that is, a change in light beam direction between each of the light beams L1, L2, and L3 before the incidence on the rearward-inclined surface 42 and each of the light beams L1, L2, and L3 after the output from the forward-inclined surface 43).
In the prisms 24 and 25 of
Table 3 illustrates behaviors of light beams L1, L2, and L3 incident on the lens 27 at angles of +25°, 0°, and −25° with respect to the optical axis C of the lens 27 when the inclined surface 39 has the inclination of α=30° with respect to the back surface 38 and the refractive index of 1.5 in the prisms 24 and 25 of
In Table 3, the numerical values indicated in the fields of the refracted light (rearward-inclined surface), the refracted light (forward-inclined surface), and the bending angle are identical to those in Table 1. The numerical value indicated in the field of the tangential angle expresses an angle formed between a tangent of the curved surface 40 at a point at which each of the light beams L1, L2, and L3 passes through the curved surface 40 and the direction orthogonal to the optical axis C.
In the prisms 24 and 25 constructed only with the flat surfaces as illustrated in
In the prisms 24 and 25 of
The refractive type prism is described above, and the same holds true for the reflective type prism. That is, the reflective type prism can be formed by adjusting the inclination angle of the surface on the front surface side based on the prisms in
In Table 4, the numerical value indicated in the field of the refracted light (back surface) expresses the angle formed by the light beam L2 incident on the prisms 57 and 58 from the back surface 48 with respect to the optical axis C. In Table 4, the numerical value indicated in the field of the reflected light (first inclined surface) expresses the angle formed by the light beam L2 reflected from the first inclined surface 49 with respect to the optical axis C. In Table 4, the numerical value indicated in the field of the refracted light (second inclined surface) expresses the angle formed by the light beam L2 reflected from the second inclined surface 50 with respect to the optical axis C. In Table 4, the numerical value indicated in the field of the bending angle expresses the change in direction of the light beam L2 passing through the prisms 57 and 58 (that is, the change in light beam direction between the light beam L2 before the incidence on the back surface 48 and the light beam L2 after the output from the second inclined surface 50). Although the numerical values are not indicated in Table 4 for the light beams L1 and L3, the numerical values for the light beams
L1 and L3 can easily be obtained by calculation. However, because the change in light beam direction during the transmission of the light through the back surface 48 or the second inclined surface 50 is smaller than the change in light beam direction caused by the reflection of the light from the first inclined surface 49, the bending angles of the light beams L1 and L3 have a value of about ±23.5° with respect to the bending angle of the light beam L2.
A plurality of prisms may integrally be formed in the case that a plurality of prisms are used. For example,
(Arrangement of Imaging Element)
The arrangement of the imaging element 26 of each embodiment will be described below. Generally, the vertical length differs from the horizontal length in the pixel region of the imaging element. For example, the pixel region of the imaging element has an aspect ratio of 9:16 or 3:4. As illustrated in
(Applications)
The wide-angle imaging device of one or more embodiments of the present invention can be incorporated in an electronic instrument. Examples of the electronic instrument in which the wide-angle imaging device is incorporated include an image sensor, a human body detection sensor, a face detection sensor, a car-mounted sensor, and other sensors. The wide-angle imaging device can also be incorporated in large-size electronic instruments such as an air conditioner and other home appliances.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
Number | Date | Country | Kind |
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2013-036905 | Feb 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2014/050410 | 1/14/2014 | WO | 00 |