JP2012078674A - Omnidirectional camera and omnidirectional lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an omnidirectional camera and an omnidirectional lens, improving resolution which might be easily inhomogeneous among each field angle of an display image.SOLUTION: The omnidirectional camera comprises: a lens prism 10 which has an entrance surface 11 having a side face formed peripherally where light enter from all directions in a 360 degree radius, a convex reflection surface 12 where a reflection layer 13 for reflecting the entering light is formed, and an emission surface 15 for emitting the light reflected by the reflection layer 13; an optical systems 30, 40 and 51 for guiding the light emitted from the lens prism 10 to a prescribed direction; and an imaging element 55 for acquiring a photographic image by receiving the light guided by the optical systems 30, 40 and 51. Each of the entrance surface 11 and the reflection surface 12 forms an aspherical typed toroidal surface while the emission surface 15 forms an aspherical typed concave surface.

Description

  The present invention relates to an omnidirectional camera capable of imaging omnidirectional (360 degrees) and an omnidirectional lens used therefor.

  An example of a conventional omnidirectional camera is disclosed in Patent Document 1. The omnidirectional camera disclosed in Patent Document 1 includes a reflecting mirror formed with a predetermined curved surface, and an optical lens that collects reflected light from the reflecting mirror on an imaging unit. Further, as a conventional omnidirectional camera, for example, there is one disclosed in Patent Document 2. An omnidirectional camera disclosed in Patent Document 2 includes a regular polygonal pyramid reflecting mirror formed by arranging triangular plane mirrors, an imaging unit disposed on the top side of the reflecting mirror, and the imaging unit and the reflecting mirror. And a rotating means for rotating together.

JP 2002-290807 A JP 2010-45555 A

  In such a conventional omnidirectional camera, the peripheral portion thereof expands and contracts in the radial direction and extends in the circumferential direction as compared with the central portion of the captured image. Therefore, when the captured image is converted into a display image (panoramic image), There has been a problem that the resolution at the angle of view tends to be uneven.

  The present invention has been made in view of the above problems, and provides an omnidirectional camera with improved resolution that is likely to be nonuniform at each angle of view of a display image, and an omnidirectional lens used in the omnidirectional lens. Objective.

  In order to solve the above problems, an omnidirectional camera according to the present invention comprises a side surface formed in a circumferential shape, a light incident surface on which light is incident from a direction of 360 degrees around, and a reflection that reflects the incident light. A lens having a light reflecting surface that is a convex surface on which a layer is formed, a light emitting surface that emits light reflected by the reflecting layer, an optical system that guides the light emitted from the lens in a predetermined direction, and An image sensor that receives light guided to the optical system and obtains a captured image, wherein the light reflecting surface forms an aspherical toroidal surface, and the light emitting surface has an aspherical concave surface. It is characterized by forming. Here, the optical system includes all optical elements for guiding light emitted from the lens to the image sensor. The term “lens” includes all lenses such as a lens prism that allow light to enter from all directions and emit light in a predetermined direction.

  Moreover, in order to solve the said subject, the omnidirectional lens which concerns on this invention comprises the side surface formed in the periphery shape, the light-incidence surface which injects light from the direction of 360 degrees of periphery, and the said incident light is reflected A light reflecting surface that is a convex surface on which a reflecting layer is formed, and a light emitting surface that emits light reflected by the reflecting layer, the light reflecting surface forming an aspherical toroidal surface, and the light The exit surface is characterized by forming an aspherical concave surface.

  ADVANTAGE OF THE INVENTION According to this invention, the omnidirectional camera and omnidirectional lens which improved the resolution which was easy to become non-uniform | heterogenous at each angle of view of a display image can be provided.

The block diagram of the omnidirectional camera which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the shape of the lens prism which concerns on embodiment of this invention, (a) is sectional drawing of a lens prism, (b) is a graph showing the outer surface shape of the lens prism. FIG. 2 shows an image diagram of an image obtained by an omnidirectional camera according to an embodiment of the present invention, where (a) is an image diagram of an image formed on an image sensor, and (b) is obtained by image conversion of the obtained captured image. FIG.

  Hereinafter, an omnidirectional camera according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an omnidirectional camera according to an embodiment of the present invention.

  As shown in FIG. 1, the omnidirectional camera 1 according to the present embodiment includes a lens prism 10 that reflects incident light L by a reflecting layer 13 and emits the light L to the outside, and a lens barrel 20 connected to the lens prism 10. It has. In addition, the lens barrel 20 houses a relay lens 30, an actual aperture 40, and an imaging unit 50.

  The lens prism 10 is formed, for example, by injection-molding an optical resin that is a medium higher than air, and the lens prism 10 is rotated when the outline of the lens prism 10 shown in FIG. It is formed in a shape having a locus as an outer peripheral surface. The lens prism 10 is preferably made of an optical resin having a refractive index of 1.6 or more for light with a wavelength of 587.56 mm and an Abbe number of 30 or less for light with the same wavelength. The side surface of the lens prism 10 is incident surface 11 on which the light L is incident, and the upper surface is a reflective surface 12 that reflects the incident light L (a reflective layer 13 is formed on the reflective surface 12 by depositing aluminum. And the lower surface is set to an emission surface 15 that emits the light L reflected by the reflection layer 13 to the outside.

  2A and 2B are explanatory diagrams for explaining the shape of the lens prism 10, wherein FIG. 2A is a cross-sectional view of the lens prism 10, and FIG. 2B is a graph showing the outer surface shape of the lens prism 10. FIG. In FIG. 2B, for convenience, a curve representing the incident surface 11 is represented as a curve A, a curve representing the reflecting surface 12 is represented as a curve B, and a curve representing the exit surface 15 is represented as a curve C. In addition, the origins corresponding to the curves A, B, and C are denoted as origins A ′, B ′, and C ′ by adding “′” to A, B, and C, respectively. As shown in FIG. 2B, the origins A ′, B ′, and C ′ are located at different locations, and the curves A, B, and C are respectively corresponding to the origins A ′, B ′, and C. It is illustrated with reference to '.

  A curve A is a curve representing the incident surface 11, and as shown in FIG. 2B, when a zy coordinate is defined with the origin A ′ as a reference, it is defined by the following formula 1. Incidentally, the origin A ′ is located at a position shifted by 10.5 mm to the left in the figure from the central axis 2 (optical axis) of the lens prism 10 and at a position shifted by 19.5 mm from the origin C ′ to the upper side in the figure. Yes. Further, the curve A is assumed to be a curve (curve indicated by a solid line in the figure) within a predetermined range among the curves represented by the expression 1.

  Here, CUY (1 / mm) is a curvature at the origin A ′ (CUY = 1 / r (curvature radius (mm))), k is a conic coefficient, A is a fourth-order aspheric coefficient, and B is a sixth-order aspheric surface. Table 1 shows the values of these parameters of the curve A.

  The incident surface 11 can be represented by a locus obtained by rotating the curve A shown in FIG. In FIG. 2B, a curve that is symmetrical with the curve A about the central axis 2 of the lens prism 10 is also shown. The incident surface 11 in which the curve A is set as an outline forms an aspheric type toroidal surface.

  A curve B is a curve representing the reflecting surface 12, and as shown in FIG. 2B, when the zy coordinates are defined with the origin B ′ as a reference, the curve B is defined by the above equation 1 as in the case of the curve A. . Note that the origin B ′ is located at a position shifted by 15.0 mm from the central axis 2 (optical axis) of the lens prism 10 and at a position shifted by 40.5 mm from the origin C ′ to the upper side in the drawing. Further, the curve B is assumed to be a curve (curve indicated by a solid line in the figure) within a predetermined range among the curves represented by Expression 1.

  Table 1 shows the values of the parameters of the curve B. Similar to the incident surface 11, the reflecting surface 12 can be represented by a locus obtained by rotating the curve B around the central axis 2. FIG. 2B also shows a curve that is symmetrical with the curve B about the central axis 2 of the lens prism 10. The reflecting surface 12 having the curved line B set as an outline forms an aspheric type toroidal surface.

  As described above, the reflective surface 12 formed in this manner is formed by depositing aluminum to form the reflective layer 13, and the light L incident from the incident surface 11 is reflected by the reflective layer 13 and is emitted to the output surface 15. Lead. As shown in FIGS. 2A and 2B, the reflecting surface 12 is a convex surface formed by an aggregate of curves extending radially upward from the top, and columnar light shielding from the top downward. A portion 14 is formed. The light shielding portion 14 is formed by injecting a black paint into a hole formed in the top of the lens prism 10. Since the light shielding portion 14 is formed on the lens prism 10, the light L incident on the lens prism 10 and the light L incident on the lens prism 10 and reflected by the reflective layer 13 pass through the central axis 2 or the vicinity thereof. Can be suppressed. Thereby, it is possible to suppress the incident light L from being reflected a plurality of times within the lens prism 10 and generating stray light depending on the reflection angle.

  The incident surface 11 and the reflecting surface 12 formed in this way have a circular shape cut by a plane orthogonal to the central axis 2. Therefore, the lens prism 10 can enter the light L from 360 ° around the omnidirectional camera 1 and can reflect the light L entered from 360 ° around the reflection surface 12 to the exit surface 15. it can. Further, since the light shielding portion 14 is provided at the apex of the reflecting surface 12 and in the vicinity thereof, instead of the reflecting layer 13, it is possible to prevent the imaging unit 50 from being reflected in the reflecting layer 13.

  A curve C is a curve representing the emission surface 15 and is defined by the following equation 2 when the zy coordinates are defined with the origin C ′ as a reference, as shown in FIG. The origin C ′ is located on the central axis 2 (optical axis) of the lens prism 10. Further, the curve C is assumed to be a curve (curve indicated by a solid line in the figure) within a predetermined range among the curves that can be expressed by Expression 2.

  Here, CUY (1 / mm) is a curvature at the origin C ′ (CUY = 1 / r (curvature radius (mm))), k is a conic coefficient, A is a fourth-order aspheric coefficient, and B is a sixth-order aspheric surface. The coefficient, C, is an 8th-order aspheric coefficient, and the values of these parameters for curve C are shown in Table 1.

  The exit surface 15 can be represented by a locus rotated around the central axis 2 on the curve C shown in FIG. As described above, the emission surface 15 with the curve C set as the outer shape constitutes a concave aspherical surface having negative power. The emission surface 15 thus formed emits the light L reflected by the reflection surface 12 and guides it to the relay lens 30 accommodated in the lens barrel 20.

  In addition, the output surface 15 is set so that the lens prism 10 has a negative power together with the reflection surface 12. Therefore, the image formed by the lens prism 10 is a virtual image, and this virtual image exists behind the reflecting surface 12 (upward in the figure) with curvature of field.

  As shown in FIG. 1, the relay lens 30 is disposed immediately below the lens prism 10 and has a function of guiding a virtual image created by the lens prism 10 to the real diaphragm 40. The relay lens 30 includes a first convex lens 31 and a first concave lens 32, and the relay lens 30 as a whole has a positive power. The focal length of the relay lens 30 is set to be substantially the same as the distance from the principal point of the relay lens 30 to the virtual image created by the lens prism 10. Thus, by installing the relay lens 30, a clear image can be captured and the image height can be controlled.

  The actual diaphragm 40 is provided between the relay lens 30 and the imaging unit 50, and limits the amount of light L that is guided to the relay lens 30 and incident on the imaging unit 50. The actual diaphragm 40 may be disposed inside the imaging unit 50.

  The imaging means 50 includes an imaging lens 51 formed by bonding a second convex lens 52 and a second concave lens 53, and an imaging element 55 that receives the light L condensed on the imaging lens 51. . The second convex lens 52 and the second concave lens 53 are made of optical glass having different properties. Thereby, chromatic aberration caused by the imaging lens 51 can be corrected.

  The imaging lens 51 causes the light L that has passed through the actual diaphragm 40 to enter, and guides the incident light L to the imaging element 55.

  The imaging element 55 is configured by arranging a plurality of photoelectric conversion elements (not shown) in a matrix on a substrate (not shown). The plurality of light conversion elements receive the light L condensed by the imaging lens 51 and convert the intensity of the received light L into an electric signal. The imaging element 55 can be configured by a known image sensor such as a CMOS image sensor or a CCD image sensor, for example.

  FIG. 3 shows an image diagram of an image obtained by the omnidirectional camera according to the embodiment of the present invention. (A) is an image diagram of an image formed on the image sensor, and (b) is a conversion of the obtained captured image. The image figure of the display image (panoramic image) obtained by doing in this way is shown.

  As shown in FIG. 3A, an image 56 formed by various optical elements constituting the omnidirectional camera 1 (FIG. 1) is circular. The circumferential direction of the circular image 56 corresponds to the horizontal direction of the omnidirectional camera 1 (FIG. 1), and the radial direction of the image 56 corresponds to the vertical direction of the omnidirectional camera 1 (FIG. 1). The image 56 formed on the imaging element 55 is acquired as a captured image by converting the intensity of the light into an electric signal by photoelectric conversion elements (not shown) arranged in a matrix.

  3A and 3B, an image 56 (FIG. 3A) formed on the image sensor 55 and a display image 57 obtained by converting the captured image 56 (FIG. 3B). ) Is shown. That is, the display image 57 shown in FIG. 3B is an image obtained by capturing the image 56 ′ of the upper right sector (center angle 90 degrees) in FIG. Therefore, an image in the range of 90 degrees around the horizontal direction of the omnidirectional camera 1 (FIG. 1) is shown on the display image 57.

  As shown in FIG. 3, for convenience, the image 56 and the display image 57 are each divided into 16 regions. A region a1 of the image 56 and a region a1 ′ of the display image 57 are corresponding regions before and after image conversion. Also, in other areas, each area of the image 56 corresponds to an area of the display image 57 with a symbol “′”. Note that, as described above, FIG. 3 is an image diagram, and each region that divides the image 56 is not related to the arrangement mode of the photoelectric conversion elements (not shown) constituting the imaging element 55.

  As shown in FIG. 3A, the omnidirectional camera 1 (FIG. 1) according to the present embodiment has a degree to which the image 56 formed on the image sensor 55 contracts in the radial direction as the image 56 is separated from the center in the radial direction. The light is concentrated so as to increase. That is, the image formed in the region a1 is formed in a state in which the image formed in the region a2 is contracted in the radial direction as compared with the image formed in the region a2. Further, the image formed in the region a2 is formed in a state of being contracted in the radial direction as compared with the image formed in the region a3. Furthermore, the image formed in the region a3 is formed in a state in which the image formed in the region a4 is contracted in the radial direction compared to the image formed in the region a4. The same applies to images formed in other regions.

  Further, as shown in FIG. 3A, the omnidirectional camera 1 (FIG. 1) according to the present embodiment has an image 56 formed on the image sensor 55 that is constant in the circumferential direction regardless of its angular position. It is condensed so as to have a degree of expansion and contraction. Therefore, the degree that the image 56 formed on the image sensor 55 extends in the circumferential direction increases as the distance from the center in the radial direction increases. That is, the image formed in the region a1 is formed in a state extending in the circumferential direction than the image formed in the region a2. Further, the image formed in the region a2 is formed in a state extending in the circumferential direction than the image formed in the region a3. Further, the image formed in the region a3 is formed in a state extending in the circumferential direction from the image formed in the region a4. The same applies to images formed in other regions.

  The image 56 formed on the image sensor 55 is converted into an electric signal by photoelectric conversion elements (not shown) arranged in a matrix, and a captured image is acquired. As described above, the captured image is acquired in a state of being expanded or contracted in the circumferential direction or the radial direction. Therefore, in order to convert the captured image into the display image 57, it is necessary to perform correction according to the degree of expansion / contraction of the captured image.

  This correction will be described. In a circular captured image, correction is performed such that an image located at a position distant from the center in the radial direction is expanded in the radial direction, and an image closer to the center is corrected in the circumferential direction. An image of such correction is represented by an arrow shown on the right side of FIG. As shown in the figure, correction is made so that the image in the upper direction (position farther from the center of the captured image) extends in the vertical direction (radial direction), and the image in the lower position (located near the center of the captured image). The correction is made so as to extend greatly in the left-right direction (circumferential direction). By performing such correction, it is possible to obtain a display image 57 of 90 degrees around the omnidirectional camera 1 (FIG. 1) with distortion corrected as shown in FIG.

  In the above, the case where the image 56 ′ of the upper right sector (center angle 90 degrees) in FIG. 3A is converted into the display image 57 has been described, but the image of the other sector is similarly displayed in the display image 57. Convert. Thereby, each display image which imaged 90 degree | times surrounding the omnidirectional camera 1 (FIG. 1) can be obtained, and the display image (panoramic image) which imaged 360 degree | times by combining these can be obtained. .

  By using the omnidirectional camera 1 according to the above-described embodiment, the following effects can be obtained.

  As described above, since the reflective layer 13 is not formed at the apex of the reflective surface 12 and in the vicinity thereof, the imaging unit 50 does not appear in the reflective layer 13. Therefore, an image of the image sensor 55 that is not necessary as a captured image is not formed on the image sensor 55. As a result, an image around the omnidirectional camera 1 can be formed at the center of the image sensor 55, and the image sensor 55 can be used effectively.

  Further, the reflecting surface 12 and the emitting surface 15 of the lens prism 10 are formed as described above (in this embodiment, the incident surface 11, the reflecting surface 12, the reflecting layer 13, and the emitting surface 15 are formed as described above. By adopting the shape, the image 56 formed on the image sensor 55 can be formed so that the degree of contraction in the radial direction increases as the distance from the center in the radial direction increases. As a result, correction for stretching in the radial direction and / or circumferential direction is performed relatively evenly in the captured image. Thereby, it is possible to improve the resolution that tends to be nonuniform at each angle of view of the display image 57.

  Moreover, stray light due to the light L incident on the omnidirectional camera 1 can be suppressed by forming the light shielding portion 14 downward from the top of the reflecting surface 12. Thereby, a high-quality display image 57 can be obtained.

DESCRIPTION OF SYMBOLS 1 Omnidirectional camera 2 Center axis 10 Lens prism 11 Incident surface 12 Reflective surface 13 Reflective layer 14 Light-shielding part 15 Outgoing surface 20 Lens tube 30 Relay lens 31 First convex lens 32 First concave lens 40 Actual aperture 50 Imaging means 51 Imaging lens 52 Second convex lens 53 Second concave lens 55 Image sensor 56 Image 57 Display image

Claims (9)

A light incident surface that forms a side surface formed in a circumferential shape and receives light from a 360-degree direction, a light reflection surface that is a convex surface on which a reflection layer that reflects the incident light is formed, and the reflection layer A lens having a light exit surface for emitting the light reflected by
An optical system for guiding light emitted from the lens in a predetermined direction;
An image sensor that receives light guided to the optical system and obtains a captured image, and
An omnidirectional camera, wherein the light reflecting surface forms an aspherical toroidal surface, and the light emitting surface forms an aspherical concave surface.   The omnidirectional camera according to claim 1, wherein the light incident surface forms an aspheric type toroidal surface.   3. The omnidirectional camera according to claim 1, wherein the reflective layer is not formed in a predetermined range centered on an apex of the light reflecting surface. 4.   4. The omnidirectional camera according to claim 1, wherein a columnar light-shielding portion is formed from an apex of the light reflecting surface toward the light emitting surface. 5.   5. The omnidirectional camera according to claim 1, wherein the light shielding portion is formed by filling a hole formed from the apex with a black paint. 6.   The lens is made of an optical resin having a refractive index with respect to light with a wavelength of 587.56 nm of 1.6 or more and an Abbe number with respect to light with the wavelength of 30 or less. The omnidirectional camera according to any one of 1 to 5. The optical system includes a relay lens formed by combining a convex lens and a concave lens, and an imaging lens, and an actual diaphragm that limits the amount of light passing therethrough,
The omnidirectional camera according to claim 1, wherein the real diaphragm is disposed between the relay lens and the imaging lens.   The omnidirectional camera according to claim 1, wherein each of the relay lens and the imaging lens has a positive power. A light incident surface that forms a side surface formed in a circumferential shape and receives light from a 360-degree direction, a light reflection surface that is a convex surface on which a reflection layer that reflects the incident light is formed, and the reflection layer A light exit surface for emitting the light reflected by
An omnidirectional lens, wherein the light reflecting surface forms an aspherical toroidal surface, and the light emitting surface forms an aspherical concave surface.

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