JP2017156713A - Image capturing device and projection device - Google Patents

Image capturing device and projection device Download PDF

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Publication number
JP2017156713A
JP2017156713A JP2016042685A JP2016042685A JP2017156713A JP 2017156713 A JP2017156713 A JP 2017156713A JP 2016042685 A JP2016042685 A JP 2016042685A JP 2016042685 A JP2016042685 A JP 2016042685A JP 2017156713 A JP2017156713 A JP 2017156713A
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Japan
Prior art keywords
surface
aperture stop
imaging
optical
front group
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JP2016042685A
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Japanese (ja)
Inventor
鈴木 雅之
Masayuki Suzuki
雅之 鈴木
石原 圭一郎
Keiichiro Ishihara
圭一郎 石原
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キヤノン株式会社
Canon Inc
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60RVEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R11/00Arrangements for holding or mounting articles, not otherwise provided for
    • B60R11/04Mounting of cameras operative during drive; Arrangement of controls thereof relative to the vehicle
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B62LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62DMOTOR VEHICLES; TRAILERS
    • B62D1/00Steering controls, i.e. means for initiating a change of direction of the vehicle
    • B62D1/02Steering controls, i.e. means for initiating a change of direction of the vehicle vehicle-mounted
    • B62D1/04Hand wheels
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/18Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B17/00Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08Catadioptric systems
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/74Projection arrangements for image reproduction, e.g. using eidophor

Abstract

PROBLEM TO BE SOLVED: To provide a compact, wide-angle image capturing device and projection device.SOLUTION: An image capturing device 1000 comprises an image sensor 200 for capturing object images, and an optical system 100 for imaging an object on an image capturing surface IMG of the image sensor 200, where the optical system 100 comprises a front group G1, aperture stop STO, and rear group G2 in order from the object side, the front group G1 having a refractive surface 1a that is concave toward the object side, and the rear group having a concave reflective surface 3b. An opening of the aperture stop STO is at a distance from the image sensor 200 in a direction perpendicular to an optical axis A of the front group G1, and is offset toward a side opposite to the image sensor 200 with respect to the optical axis A.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus and a projection apparatus, and is suitable for an imaging apparatus such as a digital still camera, a digital video camera, a mobile phone camera, a surveillance camera, a wearable camera, a medical camera, and a projection apparatus such as a projector. It is.

  In recent years, there has been a demand for an imaging device and a projection device that have a high resolution and a small size over a wide angle of view.

  Patent Document 1 describes an imaging device including a spherical lens. With this spherical lens, it is possible to satisfactorily correct axial aberrations such as spherical aberration and axial chromatic aberration while suppressing the occurrence of off-axis aberrations such as coma, astigmatism, and lateral chromatic aberration. A high-resolution optical system can be realized over the angle of view.

  Patent Document 2 describes a catadioptric optical system in which a plurality of refracting surfaces, a reflective aperture stop, and a reflecting surface are integrated with each other through a medium, thereby improving aberrations. A small optical system that can be corrected can be realized.

JP 2013-210549 A JP 2004-361777 A

  However, since the imaging surface formed by the spherical lens described in Patent Document 1 is spherical, when this spherical lens is provided in an imaging apparatus or projection apparatus, a spherical imaging element or display element, or one end is spherical. And the light guide means etc. whose other end is a plane are needed. As a result, the entire apparatus becomes complicated and large, and the cost increases.

  In the optical system described in Patent Document 2, the aperture stop and the image plane are close to each other, and unnecessary light that is not shielded by the aperture stop may reach the image plane. Keratinization is difficult.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus and a projection apparatus that are small and have a wide angle of view.

  In order to achieve the above object, an imaging apparatus according to an aspect of the present invention is an imaging apparatus that includes an imaging element that images an object and an optical system that forms an image of the object on an imaging surface of the imaging element. The optical system has a front group, an aperture stop, and a rear group in order from the object side, the front group includes a refractive surface that is convex toward the object side, and the rear group has a concave shape. An aperture portion of the aperture stop including a reflective surface is separated from the image sensor in a direction perpendicular to the optical axis of the front group, and is eccentric to the opposite side of the image sensor with respect to the optical axis. It is characterized by that.

  According to the present invention, it is possible to provide an imaging device and a projection device that are small and have a wide angle of view.

1 is a schematic diagram of a main part of an imaging apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram of a main part of an imaging apparatus according to Comparative Example 1. FIG. 6 is a schematic diagram of a main part of an imaging apparatus according to Comparative Example 2. The figure which shows the example of the aperture stop which the opening part decentered. The figure which shows the modification of the imaging device which concerns on embodiment. 1 is a schematic diagram of a main part of an imaging apparatus according to Embodiment 1 of the present invention. FIG. 3 is a lateral aberration diagram of the optical system according to Example 1 of the present invention. FIG. 6 is a schematic diagram of a main part of an imaging apparatus according to Embodiment 2 of the present invention. FIG. 6 is a lateral aberration diagram of the optical system according to Example 2 of the present invention. FIG. 9 is a schematic diagram of a main part of an imaging apparatus according to a third embodiment of the present invention. FIG. 6 is a lateral aberration diagram of the optical system according to Example 3 of the present invention. FIG. 6 is a diagram illustrating a modification of the imaging apparatus according to the first embodiment. The functional block diagram of the vehicle-mounted camera system which concerns on embodiment of this invention. The principal part schematic of the vehicle which concerns on embodiment of this invention. The flowchart which shows the operation example of the vehicle-mounted camera system which concerns on embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Each drawing may be drawn on a different scale for convenience. Moreover, in each drawing, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  FIG. 1 is a main part schematic diagram in a YZ section including an optical axis A of an imaging apparatus 1000 according to an embodiment of the present invention. The imaging apparatus 1000 includes an imaging element 200 that images an object (not shown), and an optical system 100 as an imaging optical system that forms an image on an imaging surface IMG of the imaging element 200. As the imaging element 200, a solid-state imaging element (photoelectric conversion element) having a planar imaging surface such as a CCD sensor or a CMOS sensor can be employed.

  The optical system 100 includes an aperture stop STO for limiting the beam width, a front group G1 that is an optical element group disposed on the object side of the aperture stop STO, and an optical element group disposed on the image side of the aperture stop STO. And rear group G2. In the present embodiment, the front group G1 is a refractive optical system composed of the optical element L1 and the optical element L2, and the rear group G2 is a catadioptric optical system composed of the optical element L3. The aperture stop STO is provided on the joint surface between the front group G1 and the rear group G2. In FIG. 1, the opening of the aperture stop STO is indicated by a dotted line, and the light shielding portion is omitted.

  In the present embodiment, the optical element L1 is a lens including a refractive surface 1a that is convex toward the object side (toward incident light), and the optical element L3 is a reflective surface 3b that is concave toward incident light. Is a catadioptric lens. With this configuration, the optical system 100 can image an object on the planar imaging surface IMG while satisfactorily correcting various aberrations. Therefore, in the imaging apparatus 1000, a spherical imaging element or light guiding unit is provided. There is no need to provide it, and the entire apparatus can be downsized.

  As shown in FIG. 1, the aperture of the aperture stop STO is separated from the image sensor 200 in the direction perpendicular to the optical axis A (Y direction), and with respect to the optical axis A of the front group G1. It is eccentric to the opposite side to the image sensor 200. However, the optical axis A is an axis that passes through the center (surface vertex) of each optical surface that contributes to image formation in the front group G1. That is, the aperture stop STO according to the present embodiment is arranged so that the center of the opening does not exist on the optical axis A. As shown in FIG. 1, when the imaging device 200 is disposed on the same side (−Z side) as the aperture stop STO with respect to the reflecting surface 3b, the aperture stop must be decentered unless the opening of the aperture stop STO is decentered. This is because the STO and the image sensor 200 are close to each other.

  By decentering the opening of the aperture stop STO in the direction away from the image sensor 200, the opening of the aperture stop STO and the image sensor 200 can be sufficiently separated. Thereby, it is possible to suppress interference between the light rays around the opening and the imaging element 200 and unnecessary light that is not shielded by the light shielding part of the aperture stop STO from reaching the imaging surface IMG. Therefore, it is not necessary to increase (darken) the F value or reduce the size of the imaging surface IMG, so that it is possible to realize a wide angle of view of the imaging apparatus 1000.

  FIG. 2 is a main part schematic diagram of an imaging apparatus according to Comparative Example 1. The imaging apparatus according to Comparative Example 1 replaces the rear group G2 of the optical system 100 according to the present embodiment with a refractive optical system having a symmetric configuration with the front group G1, and replaces the imaging element 200 according to the present embodiment with a spherical shape. It is replaced with an image sensor having an imaging surface. As shown in FIG. 2, since the imaging device according to Comparative Example 1 does not include a concave reflecting surface, the imaging surface of the optical system is curved to be spherical. For this reason, an imaging element having a curved imaging surface IMG is required, and the entire apparatus is increased in size.

  FIG. 3 is a main part schematic diagram of an imaging apparatus according to Comparative Example 2. The imaging apparatus according to Comparative Example 2 has the same configuration as that of the imaging apparatus 1000 according to the present embodiment, except that the opening of the aperture stop STO is not decentered. As shown in FIG. 3, in the imaging device according to Comparative Example 2, the aperture of the aperture stop STO and the imaging surface IMG are close to each other, so that interference between the light rays around the aperture and the imaging element can be avoided. It is difficult to realize a wide angle of view while reducing the F value.

  In order to decenter the aperture of the aperture stop STO, it is not limited to physically moving the light shielding portion of the aperture stop STO, but only by shifting the center (center of gravity) of the aperture from the optical axis A of the front group G1. Good. For example, if a desired F value can be ensured, as shown in FIG. 4, the opening of the aperture stop STO may be decentered by shielding a part of the opening. As shown in FIG. 4, with respect to the aperture stop STO in which the center of the opening is on the optical axis A, a light shielding member OBS is provided on a part (upper part) of the opening, so that the center of gravity of the opening is the optical axis. It moves downward from A and becomes point B.

  As shown in FIG. 1, in the imaging apparatus 1000 according to the present embodiment, the angle of view is set so that the light beam is obliquely incident on each optical surface of the optical system 100 in the YZ section, and the optical axis A is Only the light beam incident on the optical system 100 from the side opposite to the imaging element 200 is used. Therefore, as shown in FIG. 5, the front group G1 may have a configuration in which portions other than the effective portion through which the effective luminous flux passes are omitted (cut).

  In the optical system 100 according to the present embodiment, the front group G1 is composed of two optical elements, and the rear group G2 is composed of one optical element, but the number of optical elements constituting each group is as follows. It is not limited to this. For example, the rear group G2 may be composed of one or more refractive optical elements (such as lenses) and one reflective optical element (such as a mirror).

  Further, the optical system 100 may be applied to a projection apparatus as a projection optical system. In this case, a display surface of a display element such as a liquid crystal panel (spatial modulator) is disposed at the position of the imaging surface IMG. However, when the optical system 100 is applied to a projection apparatus, the object side and the image side are reversed, the front group G1 is the rear group, the rear group G2 is the front group, and the optical path is reversed. That is, it is possible to adopt a configuration in which an image displayed on the display surface of the display element is projected (imaged) onto a projection surface such as a screen by an optical system.

[Example 1]
Hereinafter, the imaging apparatus according to the first embodiment of the present invention will be described in detail.

  FIG. 6 is a schematic diagram of a main part in a YZ section including the optical axis A of the imaging apparatus 1100 according to the present embodiment. For the optical system 110 according to this example, the focal length of the entire system is f = 29.13 mm, the angle of view in the ZX cross section is θx = 54 ° (θx = −27 ° to + 27 °), and the YZ cross section is The angle of view is θy = 35 ° (θy = + 8 ° to + 43 °), and the F value is F = 2.0.

  In the optical system 110, the front group G <b> 1 is a refractive optical system including four lenses of the first optical element 1, the second optical element 2, the third optical element 3, and the fourth optical element 4. The second surface 1 b of the first optical element 1 and the first surface 2 a of the second optical element 2, the second surface 2 b of the second optical element 2, the first surface 3 a of the third optical element 3, and the third optical element 3 The second surface 3b and the first surface 4a of the fourth optical element 4 are joined to each other. The front group G1 is a coaxial system with respect to the optical axis A.

  In the optical system 110 according to the present embodiment, the rear group G2 is a catadioptric optical system composed of three lenses: a fifth optical element 5, a sixth optical element 6, and a seventh optical element 7. . The second surface 5b of the fifth optical element 5 and the first surface 6a of the sixth optical element 6, the second surface 6b of the sixth optical element 6, and the first surface 7a of the seventh optical element 7 are joined together. ing. The aperture stop STO is provided at the joint surface between the front group G1 and the rear group G2, and the opening is eccentric to the opposite side of the imaging surface IMG with respect to the optical axis A of the front group G1. .

  In the present embodiment, the fifth optical element 5 includes three optical surfaces, that is, a first surface 5a, a second surface 5b, and a third surface 5c, and the first surface 5a and the third surface 5c are mutually connected. Have different shapes. The seventh optical element 7 is a catadioptric lens, and its second surface 7b is a concave reflecting surface. That is, in the rear group G2, since the optical path is folded back by the reflecting surface 7b, the light flux passes through each joint surface twice. The reflective surface 7b can be formed by providing a reflective film such as a metal film or a dielectric multilayer film on the optical surface.

  As shown in FIG. 6, a light beam from an object (not shown) enters the front group G1 from the convex first surface 1a toward the object side of the first optical element 1, and the first optical element 1, the first optical element 1, The light passes through the second optical element 2, the third optical element 3, and the fourth optical element 4 in order, and enters the aperture stop STO. At this time, since a part of the light beam is shielded by the light shielding portion of the aperture stop STO, the light beam width is limited.

  The light beam that has passed through the aperture of the aperture stop STO has the first surface 5a of the fifth optical element 5, the first surface 6a and the second surface 6b of the sixth optical element 6, and the first surface 7a of the seventh optical element 7. Are sequentially reflected and reflected by the second surface 7b of the seventh optical element 7. Then, the light beam reflected by the second surface 7b of the seventh optical element 7 sequentially passes through the first surface 7a of the seventh optical element 7, the second surface 6b of the sixth optical element 6, and the first surface 6a. , Emitted from the third surface 5c of the fifth optical element 5, and condensed on the planar imaging surface IMG.

  As described above, according to the optical system 110 according to the present example, various aberrations are excellent due to the front group G1 including the convex refracting surface 1a and the rear group G2 including the concave reflecting surface 7b toward the object side. The object can be imaged on the imaging surface IMG having a planar shape. Thereby, size reduction of the imaging device 1100 can be realized. Further, by widening the opening of the aperture stop STO to the side opposite to the imaging surface IMG with respect to the optical axis A, it is possible to realize a wide angle of view of the imaging device 1100.

Here, the distance in the optical axis direction between the optical surface closest to the object in the front group G1 and the aperture stop STO in the optical axis direction is L1 (mm), and the distance in the optical axis direction between the aperture stop STO and the imaging surface IMG is L2 (mm). ), It is desirable to satisfy the following conditional expression (1). However, L1> 0 and L2 ≧ 0.
L2 / L1 <0.3 (1)

If the upper limit of conditional expression (1) is exceeded, the optical surface closest to the object will be too close to the aperture stop STO, making it difficult to correct aberrations. Furthermore, it is more preferable that the following conditional expression (1 ′) is satisfied. In this embodiment, the distance between the refractive surface 1a and the aperture stop STO is L1 = 45.149 mm, and the distance between the aperture stop STO and the imaging surface IMG is L2 = 0.004 mm, and L2 / L1 = 0.0001. Therefore, the conditional expressions (1) and (1 ′) are satisfied.
L2 / L1 <0.1 (1 ′)

In addition, it is desirable that the refractive surface convex toward the object side of the front group G1 has a shape (point-symmetric shape) in which the distance to the aperture stop STO and the radius of curvature are substantially equal. Specifically, when the radius of curvature of the refractive surface is Rl (mm) and the distance between the refractive surface and the aperture stop STO is Ll (mm), it is desirable that the following conditional expression (2) is satisfied. However, unless otherwise specified, “interval” indicates “interval on the optical axis A”.
0.7 ≦ | Rl | /Ll≦1.5 (2)

  By satisfying conditional expression (2), off-axis aberrations can be favorably corrected even with a simple and compact configuration. If the range of the conditional expression (2) is not satisfied, the amount of off-axis aberration increases, and there is a possibility that good optical characteristics cannot be obtained. This will be described below.

  In general, when designing an optical system, coma, astigmatism, curvature of field, distortion, and lateral chromatic aberration, as well as off-axis aberrations such as spherical aberration and axial chromatic aberration, Correction is required. However, when a normal axisymmetric refracting surface is used, off-axis aberrations are greatly generated at the peripheral angle of view (off-axis), and the optical performance on the optical axis (on-axis) is the highest. As a result, the optical performance at the peripheral angle of view deteriorates.

  On the other hand, since the point-symmetric refracting surface has substantially the same shape from the optical axis to the peripheral angle of view, it is possible to suppress the occurrence of off-axis aberrations and to suppress the deterioration of the optical performance at the peripheral angle of view. Therefore, by adopting a point-symmetric refracting surface, the aberration to be corrected can be limited to spherical aberration, axial chromatic aberration, Petzval image surface, etc. It becomes possible to correct.

  In this embodiment, since the first surface 1a of the first optical element 1 satisfies the conditional expression (2), a small optical system having a high resolution over a wide angle of view is realized while reducing the F value. be able to. At this time, the image forming surface of the front group G1 is curved due to the point-symmetric refracting surface, but by providing the concave reflecting surface 7b in the rear group G2 as in this embodiment, A planar image plane IMG can be formed.

  In the front group G1, a plurality of refracting surfaces that satisfy the conditional expression (2) may be provided. Even in that case, the effect of the present invention can be obtained by configuring so that at least one of the plurality of refractive surfaces in the front group G1 satisfies the conditional expression (2). However, in order to satisfactorily correct off-axis aberrations, as in this embodiment, a refracting surface further away from the aperture stop STO, or a refracting surface having a large refractive index difference from the adjacent medium, that is, the most object side. It is desirable that the refractive surface has a point-symmetric shape.

Furthermore, it is more preferable that the following conditional expression (2 ′) is satisfied. In this example, since | Rl | /Ll=0.947 is satisfied for the first surface 1a of the first optical element 1, the conditional expressions (2) and (2 ′) are satisfied.
0.8 ≦ | Rl | /Ll≦1.3 (2 ′)

Further, regarding the concave reflecting surface of the rear group G2, when the radius of curvature is Rm (mm) and the distance from the aperture stop STO is Lm (mm), the following conditional expression (3) is satisfied. desirable.
2 ≦ | Rm | / Lm ≦ 7 (3)

  By satisfying conditional expression (3), it is possible to favorably correct field curvature while avoiding interference between the imaging surface IMG and the optical path. If the upper limit of conditional expression (3) is exceeded, there is a possibility that the amount of field curvature will increase. If the lower limit of conditional expression (3) is not reached, there is a possibility that the imaging surface IMG will interfere with the optical path. When the rear group G2 has a plurality of reflecting surfaces, it is desirable that the reflecting surface with the highest power satisfies the conditional expression (3).

Furthermore, it is more preferable that the following conditional expression (3 ′) is satisfied. In this example, since | Rm | /Lm=4.520 is satisfied for the second surface 7b of the seventh optical element 7, the conditional expressions (3) and (3 ′) are satisfied.
2.5 ≦ | Rm | / Lm ≦ 5 (3 ′)

If the front group G1 has a plurality of refractive surfaces, the absolute value of the radius of curvature of the refractive surface closest to the object is R1A, and the absolute value of the radius of curvature of the refractive surface closest to the aperture stop STO is R1B. When, it is desirable to satisfy the following conditional expression (4).
0 ≦ R1A / R1B <4 (4)

  By satisfying conditional expression (4), it is possible to reduce the aberration that occurs due to the eccentricity of the opening of the aperture stop STO. If the range of the conditional expression (4) is not satisfied, the occurrence of asymmetric aberration increases as the opening of the aperture stop STO increases, which may make it difficult to correct the aberration.

Furthermore, it is more preferable that the following conditional expression (4 ′) is satisfied. In the present embodiment, in the front group G1, the radius of curvature of the refractive surface 1a closest to the object side is 42.75 mm, the radius of curvature of the refractive surfaces 3b and 4a closest to the aperture stop STO is 13.94 mm, and R1A / R1B = Therefore, conditional expressions (4) and (4 ′) are satisfied.
0 ≦ R1A / R1B <3.5 (4 ′)

  In the present embodiment, the first surface 1a of the first optical element 1 and the second surface 7b of the seventh optical element 7 are aspherical surfaces. However, each of the aspheric surfaces in this embodiment has a rotationally symmetric shape with the optical axis A as the center, and is expressed by the following aspheric expression.

  Here, z is the sag amount (mm) of the aspherical shape in the optical axis direction, c is the curvature (1 / mm) on the optical axis A, K is the conical coefficient, and h is the radial distance from the optical axis A ( mm), A, B, C,... are aspherical coefficients of the fourth, sixth, eighth,. In this aspherical formula, the first term indicates the sag amount of the base spherical surface, and the radius of curvature of the base spherical surface is R = 1 / c. The second and subsequent terms indicate the sag amount of the aspherical component provided on the base spherical surface.

  Tables 1 to 4 show the configuration of the optical system 110 according to the present example.

  In Tables 1 to 4, the optical surfaces and the aperture stop STO that are bonded to each other are shown as the same surface. In Table 1, r is the paraxial radius of curvature (mm) of the relevant surface, d is the surface spacing (mm) from the relevant surface to the next surface, and Nd is the d-line of the medium between the relevant surface and the next surface ( The refractive index for a wavelength of 587.56 nm), νd is the Abbe number for the d-line of the medium between the corresponding surface and the next surface. Tables 2 and 3 show the aspheric coefficients of the refractive surface 1a (surface number 1) and the reflecting surface 7b (surface number 9), respectively.

  Table 4 shows eccentric data of the aperture stop STO (surface number 5) and the optical surface 5a (surface number 6). In Table 4, X is the amount of eccentricity in the X direction perpendicular to the paper surface in FIG. 1, Y is the amount of eccentricity in the Y direction perpendicular to the optical axis A in the paper surface in FIG. 1 (upward in FIG. 1 is positive), Z indicates the amount of eccentricity in the optical axis direction (Z direction), respectively. In this embodiment, both the aperture stop STO and the optical surface 5a are decentered in parallel (shift decentered), but not decentered in rotation (tilt decenter). The unit of each eccentricity is mm.

  Note that “normal decentering” in Tables 1 and 4 indicates that when the corresponding surface is decentered, the optical surface on the image side is also decentered while being fixed to the axis of the corresponding surface. Specifically, in this embodiment, the opening of the aperture stop STO is decentered by -1.3098 mm in the Y direction. The optical surface 5a immediately after the eccentric opening is decentered by +1.3098 mm in the Y direction. That is, Table 4 shows that only the aperture stop STO is decentered with respect to the optical axis A, and other optical surfaces are not decentered with respect to the optical axis A.

  FIG. 7 is an aberration diagram of the optical system 110 according to the present example. In FIG. 7, the lateral aberration regarding the light of each wavelength of 656.2700 nm (C line), 587.5600 nm (d line), 486.1300 nm (F line), 435.8350 nm (g line) is shown. In FIG. 7, the YZ cross section (meridional surface) shows aberration for the angle of view θy = + 8 ° to + 43 °, and the ZX cross section (sagittal surface) shows aberration for the angle of view θx = 0 °. As is apparent from FIG. 7, various aberrations are corrected satisfactorily.

[Example 2]
Hereinafter, an imaging apparatus according to Example 2 of the present invention will be described in detail.

  FIG. 8 is a schematic diagram of a main part in a YZ cross section including the optical axis A of the imaging apparatus 1200 according to the present embodiment. For the optical system 120 according to this example, the focal length of the entire system is f = 29.08 mm, the angle of view in the ZX cross section is θx = 54 ° (θx = −27 ° to + 27 °), and the YZ cross section is The angle of view is θy = 38 ° (θy = + 10 ° to + 48 °), and the F value is F = 2.0.

In the imaging apparatus 1200 according to the present embodiment, compared to the imaging apparatus 1100 according to the first embodiment, the front group G1 in the optical system 120 is more concentric in order to ensure optical performance at a wider angle of view. It is configured. Specifically, in the front group G1, the optical system 120 has the following conditions when the maximum value is RMAX and the minimum value is RMIN among the absolute values of the radius of curvature of the refractive surface convex toward the object side. It is comprised so that Formula (5) may be satisfied.
1 ≦ RMAX / RMIN <10 (5)

Satisfying conditional expression (5) makes it possible to obtain good optical performance over a wide angle of view. If the conditional expression (5) is not within the range, off-axis aberrations such as coma and astigmatism may be increased. Furthermore, it is more preferable that the following conditional expression (5 ′) is satisfied. In this embodiment, RMAX = 42.47 mm, RMIN = 15.29 mm, and RMAX / RMIN = 2.78, which satisfies the conditional expressions (5) and (5 ′).
1 ≦ RMAX / RMIN <5 (5 ′)

  In this embodiment, L1 = 49.383 mm, L2 = 0.004 mm, and L2 / L1 = 0.0001, which satisfies the conditional expressions (1) and (1 ′). Further, since | Rl | /Ll=0.947 is satisfied for the refracting surface 1a, conditional expressions (2) and (2 ′) are satisfied, and | Rm | /Lm=4.520 is satisfied for the reflecting surface 7b. (3) and (3 ′) are satisfied. Furthermore, since R1A = 42.47 mm and R1B = 15.29 mm and R1A / R1B = 2.78, the conditional expressions (4) and (4 ′) are satisfied.

  Tables 5 to 9 show the configuration of the optical system 120 according to the present example.

  As shown in Table 5, in this example, all the centers of curvature of the refracting surfaces of the front group G1 exist on the aperture stop STO side with respect to each refracting surface. That is, all the refractive surfaces of the front group G1 are convex toward the object side. The first surface 1a (surface number 1) of the first optical element 1, the second surface 7b (surface number 9) of the seventh optical element 7, and the third surface 5c (surface number 12) of the fifth optical element 5, These three optical surfaces are aspherical, and the other optical surfaces are spherical or flat. Further, as shown in Table 9, similarly to the first embodiment, only the aperture stop STO (surface number 5) is eccentric with respect to the optical axis A in this embodiment.

  FIG. 9 is an aberration diagram of the optical system 120 according to the present example, and corresponds to FIG. In FIG. 9, the YZ cross section (meridional surface) shows the aberration for the angle of view θy = + 10 ° to + 48 °, and the ZX cross section (sagittal surface) shows the aberration for the angle of view θx = 0 °. As is apparent from FIG. 9, various aberrations are corrected satisfactorily.

[Example 3]
Hereinafter, an imaging apparatus according to Embodiment 3 of the present invention will be described in detail.

  FIG. 10 is a schematic diagram of a main part in a YZ section including the optical axis A of the imaging apparatus 1300 according to the present embodiment. Regarding the optical system 130 according to the present embodiment, the focal length of the entire system is f = 0.799 mm, the angle of view in the ZX cross section is θx = 72 ° (θx = −36 ° to + 36 °), and the YZ cross section is The angle of view is θy = 40 ° (θy = + 18 ° to + 58 °), and the F value is F = 1.8.

  Unlike the first and second embodiments, an imaging apparatus 1300 according to the present embodiment includes an optical system 130 that includes two lenses, a first optical element 1 and a second optical element 2, and the first optical element. Each of the first and second optical elements 2 is shared by the front group G1 and the rear group G2.

  The first optical element 1 is a lens having two optical surfaces, a first surface 1a and a second surface 1b, and the second optical element 2 includes a first surface 2a, a second surface 2b, and a third surface 2c. A lens having three optical surfaces. The second surface 1b of the first optical element 1 and the first surface 2a of the second optical element 2 are joined to each other. The second surface 2b of the second optical element 2 is a reflecting surface, and an aperture stop STO is provided there. That is, the aperture of the aperture stop STO according to the present embodiment is a reflecting surface, and is decentered to the opposite side of the imaging surface IMG with respect to the optical axis A of the front group G1 as in the other embodiments. .

  Further, with respect to the first surface 1a of the first optical element 1, the lower part is a convex refracting surface (refractive part) toward the object side, and the upper part is a concave reflecting surface (reflective part). The reflection portion of the first surface 1a of the first optical element 1 is configured to further reflect the light beam reflected by the opening portion of the aperture stop STO. That is, since the light beam incident on the optical system 130 is reflected a total of two times at the aperture of the aperture stop STO and the first surface 1a of the first optical element 1, the second surface 1b and the second surface 1b of the first optical element 1 are reflected. The joint surface with the first surface 2a of the optical element 2 passes three times. The second surface 2b and the third surface 2c of the second optical element 2 have different shapes.

  As shown in FIG. 10, a light beam from an object (not shown) enters the front group G <b> 1 from the refracting portion of the first surface 1 a of the first optical element 1 and passes through the second surface 1 b of the first optical element 1. Thus, the light is reflected by the aperture stop STO provided on the second surface 2b of the second optical element 2. The light beam reflected by the opening of the aperture stop STO again passes through the second surface 1b of the first optical element 1 and is reflected by the reflecting portion of the first surface 1a of the first optical element 1. The light beam reflected by the reflecting portion of the first surface 1 a of the first optical element 1 further passes through the second surface 1 b of the first optical element 1 and is emitted from the third surface 2 c of the second optical element 2. Thus, the light is condensed on a planar imaging surface IMG.

  In this embodiment, L1 = 1.179 mm, L2 = 0.86 mm, and L2 / L1 = 0.073, which satisfies the conditional expressions (1) and (1 ′). Further, since the reflecting portion of the first surface 1a of the first optical element 1 is | Rm | /Lm=3.679, the conditional expressions (3) and (3 ′) are satisfied.

  Tables 10 to 17 show the configuration of the optical system 130 according to the present example.

  In Table 10, surface number 1 is the first surface 1a (refractive part) of the first optical element 1, and surface numbers 2, 7, and 9 are the second surface 1b of the first optical element 1 and the first surface of the second optical element 2. Surface 2a and surface numbers 3 to 6 indicate the second surface 2b and the aperture stop STO of the second optical element 2, respectively. Specifically, the surface number 3 is a refractive surface component of the second surface 2b as the front group G1, the surface number 4 is an aperture stop STO, and the surface number 5 is set to eliminate the influence of the eccentricity of the aperture stop STO. The surface component of the second surface 2b and the surface number 6 indicate the reflecting surface component of the second surface 2b, respectively. The surface number 8 is the first surface 1a (reflecting part) of the first optical element 1, the surface number 10 is the third surface 2c of the second optical element 2, and the surface number 11 is a virtual surface that coincides with the image surface. Show.

  The first surface 1a (surface numbers 1, 8) of the first optical element 1 and the third surface 2c (surface number 10) of the second optical element 2 are aspherical surfaces, and the other optical surfaces are spherical surfaces or flat surfaces. It is. The second surface 2b (surface number 6) of the second optical element 2 and the third surface 2c (surface number 10) of the second optical element 2 are diffractive surfaces having diffractive characteristics. Tables 14 and 15 show the results. However, each diffractive surface gives a rotationally symmetric phase change around the surface vertex, and is expressed by the following polynomial.

  “Return to designated surface” in Tables 10 and 17 indicates that the coordinates of the corresponding surface are decentered so as to return to the coordinates of the designated surface. Specifically, in this embodiment, the opening of the aperture stop STO is decentered by −0.2735 mm in the Y direction. Then, the surface component of surface number 5 is decentered with respect to the eccentric opening so that the coordinate system thereof matches the surface component of surface number 3. That is, Tables 16 and 17 indicate that the coordinates of each optical surface on the image side of the aperture stop STO are not affected by the eccentricity of the aperture stop STO.

  In Table 16, α, β, and γ indicate rotation angles (deg) when the X, Y, and Z axes are the rotation axes. As shown in Table 16, the surface component of surface number 11 is rotated by 0.5808 ° within the paper surface in FIG. 10, thereby suppressing the influence of field curvature. That is, the image plane (imaging plane IMG) is also rotated by 0.5808 ° in association with the plane component of plane number 11.

  FIG. 11 is an aberration diagram of the optical system 130 according to the present example, and corresponds to FIG. In FIG. 11, the YZ cross section (meridional surface) shows the aberration for the angle of view θy = + 18 ° to + 58 °, and the ZX cross section (sagittal surface) shows the aberration for the angle of view θx = 0 °. As is apparent from FIG. 11, various aberrations are corrected satisfactorily.

[Modification]
The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes can be made within the scope of the gist.

  For example, the reflective surface according to each of the embodiments described above is a back surface reflective surface formed by providing a reflective film on the surface of the lens, but is not limited thereto, and instead of the back surface reflective surface, it is different from the lens. An optical element (such as a mirror) having a surface reflecting surface may be provided. FIG. 12 is a modified example in which a reflective optical element (mirror) MR having a surface reflective surface MRa is provided in place of the second surface 7b of the seventh optical element 7 as a reflective surface in the imaging apparatus 1100 according to the first embodiment. Show. In the configuration of FIG. 12, the light beam that has passed through the aperture stop STO is transmitted without being reflected by the surface 7b, and is reflected by the reflecting surface MRa of the mirror MR. In the configuration of the modified example, the required surface accuracy of the reflecting surface is reduced as compared with the configuration according to the first embodiment.

  In each embodiment, all the optical elements are bonded to each other. However, if necessary, a configuration may be adopted in which the optical elements are arranged with air separated from each other. The optical system in each embodiment can be applied to the projection apparatus as it is. In that case, as described above, the object side (reduction side) and the image side (enlargement side) in the imaging apparatus are reversed and the optical path is reversed, the front group G1 is the rear group, and the rear G2 is the front group. The incident surface of each optical element is the exit surface, and the exit surface is the entrance surface. Also in this case, it is desirable to satisfy each conditional expression in each embodiment, as in the case where the optical system is applied to the imaging apparatus.

[In-vehicle camera system]
FIG. 13 is a configuration diagram of an in-vehicle camera 610 according to this embodiment and an in-vehicle camera system (driving support device) 600 including the same. The in-vehicle camera system 600 is an apparatus that is installed in a vehicle such as an automobile and supports driving of the vehicle based on image information around the vehicle acquired by the in-vehicle camera 610. FIG. 14 is a schematic diagram of a vehicle 700 including an in-vehicle camera system 600. Although FIG. 14 shows a case where the imaging range 650 of the in-vehicle camera 610 is set in front of the vehicle 700, the imaging range 650 may be set behind the vehicle 700.

  As shown in FIG. 13, the in-vehicle camera system 600 includes an in-vehicle camera 610, a vehicle information acquisition device 620, a control device (ECU: electronic control unit) 630, and an alarm device 640. The in-vehicle camera 610 includes an imaging unit 601, an image processing unit 602, a parallax calculation unit 603, a distance calculation unit 604, and a collision determination unit 605. The imaging unit 601 includes an optical system according to any of the above-described embodiments and an imaging surface phase difference sensor. Note that the imaging surface phase difference sensor according to the present embodiment corresponds to, for example, the imaging element 200 included in the imaging apparatus 1000 according to the embodiment illustrated in FIG.

  FIG. 15 is a flowchart showing an operation example of the in-vehicle camera system 600 according to the present embodiment. Hereinafter, the operation of the in-vehicle camera system 600 will be described with reference to this flowchart.

  First, in step S <b> 1, an object (subject) around the vehicle is imaged using the imaging unit 601 to obtain a plurality of image data (parallax image data).

  In step S2, vehicle information is acquired from the vehicle information acquisition device 620. The vehicle information is information including a vehicle speed, a yaw rate, a steering angle, and the like of the vehicle.

  In step S <b> 3, the image processing unit 602 performs image processing on the plurality of image data acquired by the imaging unit 601. Specifically, image feature analysis is performed to analyze feature amounts such as the amount and direction of edges and density values in image data. Here, the image feature analysis may be performed on each of the plurality of image data, or may be performed on only a part of the plurality of image data.

  In step S <b> 4, parallax (image shift) information between a plurality of pieces of image data acquired by the imaging unit 601 is calculated by the parallax calculation unit 603. As a method for calculating the parallax information, a known method such as the SSDA method or the area correlation method can be used, and thus the description thereof is omitted in the present embodiment. Steps S2, S3, and S4 may be processed in the above order or may be performed in parallel with each other.

  In step S <b> 5, the distance calculation unit 604 calculates distance information to the object imaged by the imaging unit 601. The distance information can be calculated based on the parallax information calculated by the parallax calculation unit 603 and the internal and external parameters of the imaging unit 601. Here, the distance information is information on the relative position with respect to the object such as the distance to the object, the defocus amount, and the image shift amount, and the distance value of the object in the image is directly determined. The information corresponding to the distance value may be indirectly expressed.

  In step S <b> 6, the collision determination unit 605 determines whether the distance information calculated by the distance calculation unit 604 is included within a preset set distance range. Thereby, it can be determined whether or not an obstacle exists within a set distance around the vehicle, and the possibility of collision between the vehicle and the obstacle can be determined. The collision determination unit 605 determines that there is a possibility of collision when an obstacle exists within the set distance (step S7), and determines that there is no possibility of collision when there is no obstacle within the set distance (step S8). ).

  Next, when the collision determination unit 605 determines that there is a possibility of collision (step S7), the collision determination unit 605 notifies the control device 630 and the alarm device 640 of the determination result. At this time, control device 630 controls the vehicle based on the determination result in collision determination unit 605, and alarm device 640 issues an alarm based on the determination result in collision determination unit 605.

  For example, the control device 630 performs control such as braking the vehicle, returning the accelerator, and generating a control signal for generating a braking force on each wheel to suppress the output of the engine and the motor. Further, the alarm device 640 warns the user (driver) of the vehicle, such as sounding an alarm such as a sound, displaying alarm information on a screen of a car navigation system, or giving vibration to the seat belt or the steering. I do.

  As described above, according to the vehicle-mounted camera system 600 according to the present embodiment, the obstacle can be effectively detected by the above processing, and the collision between the vehicle and the obstacle can be avoided. In particular, by applying the optical system according to each embodiment described above to the in-vehicle camera system 600, the entire in-vehicle camera 610 can be downsized to increase the degree of freedom of arrangement, and obstacle detection and collision determination can be performed over a wide angle of view. It becomes possible to do.

  Here, in the present embodiment, the configuration in which the in-vehicle camera 610 includes only one imaging unit 601 having an imaging surface phase difference sensor has been described. However, the present invention is not limited to this, and the in-vehicle camera 610 is a stereo camera including two imaging units. May be adopted. In this case, even if an imaging surface phase difference sensor is not used, image data is simultaneously acquired by each of the two synchronized imaging units, and the same processing as described above is performed by using the two image data. be able to. However, if the difference in imaging time between the two imaging units is known, the two imaging units need not be synchronized.

  Various embodiments are conceivable for calculating the distance information. As an example, a case where a pupil division type imaging device having a plurality of pixel units regularly arranged in a two-dimensional array is adopted as the imaging device included in the imaging unit 601 will be described. In the pupil division type imaging device, one pixel unit is composed of a microlens and a plurality of photoelectric conversion units, receives a pair of light beams passing through different regions in the pupil of the optical system, and forms a pair of image data. It can output from each photoelectric conversion part.

  Then, the image shift amount of each region is calculated by the correlation calculation between the paired image data, and the image shift map data representing the distribution of the image shift amount is calculated by the distance calculation unit 604. Alternatively, the distance calculation unit 604 may further convert the image shift amount into a defocus amount, and generate defocus map data representing the distribution of the defocus amount (distribution on the two-dimensional plane of the captured image). Further, the distance calculation unit 604 may acquire distance map data of the distance to the target object converted from the defocus amount.

  As described above, the vertical angle of view of the optical system according to each embodiment is set only on one side with respect to the optical axis A. Therefore, when the optical system according to each embodiment is applied to the in-vehicle camera 610 and the in-vehicle camera 610 is installed in the vehicle, the optical axis A of the optical system is disposed so as not to be parallel to the horizontal direction. Is desirable. For example, when the optical system 100 according to the embodiment shown in FIG. 1 is employed, the optical axis A is tilted upward with respect to the horizontal direction (Z direction), and the center of the vertical angle of view is arranged so as to approach the horizontal direction. That's fine. Alternatively, the optical system 100 may be arranged so that the optical axis A is inclined downward with respect to the horizontal direction after the optical system 100 is rotated 180 ° around the X axis (upside down). Thereby, the imaging range of the vehicle-mounted camera 610 can be set appropriately.

  However, as described above, in the optical system, the optical performance on the axis is the highest, and the optical performance at the peripheral angle of view is decreased. It is more preferable to arrange so as to pass near the upper part. For example, when it is necessary to pay attention to a sign or obstacle on the road by the in-vehicle camera 610, the optical performance is improved at an angle of view below the ground (on the ground side) with respect to the horizontal direction (on the sky side). It is preferable. At this time, when the optical system 100 according to the first embodiment is employed, the optical system 100 is once turned upside down as described above, and then the optical axis A is tilted downward with respect to the horizontal direction so as to be in the vicinity of the optical axis A. May be arranged so that the angle of view is directed downward.

  In the present embodiment, the in-vehicle camera system 600 is applied to driving assistance (collision damage reduction). However, the present invention is not limited to this, and the in-vehicle camera system 600 is used for cruise control (including an all-vehicle speed tracking function) or automatic driving. You may apply. The in-vehicle camera system 600 can be applied not only to the vehicle such as the own vehicle but also to a moving body (moving device) such as a ship, an aircraft, or an industrial robot. Further, the present invention can be applied not only to the in-vehicle camera 610 according to the present embodiment and the moving body but also to devices that widely use object recognition such as an intelligent road traffic system (ITS).

DESCRIPTION OF SYMBOLS 1a Refractive surface 3b Reflective surface 100 Optical system 200 Imaging element 1000 Imaging device G1 Front group G2 Rear group IMG Imaging surface STO Aperture stop

Claims (14)

  1. An imaging device comprising: an imaging device that images an object; and an optical system that forms an image of the object on an imaging surface of the imaging device,
    The optical system has a front group, an aperture stop, and a rear group in order from the object side,
    The front group includes a refractive surface convex toward the object side,
    The rear group includes a concave reflecting surface,
    The aperture of the aperture stop is spaced apart from the image sensor in a direction perpendicular to the optical axis of the front group, and is eccentric to the side opposite to the image sensor relative to the optical axis. Imaging device.
  2. When the radius of curvature of the refractive surface is Rl (mm) and the distance between the refractive surface and the aperture stop is Ll (mm),
    0.7 ≦ | Rl | /Ll≦1.5
    The imaging apparatus according to claim 1, wherein the following condition is satisfied.
  3. When the radius of curvature of the reflecting surface is Rm (mm) and the distance between the aperture stop and the reflecting surface is Lm (mm),
    2 ≦ | Rm | / Lm ≦ 7
    The imaging apparatus according to claim 1, wherein the following condition is satisfied.
  4. In the front group, when the absolute value of the radius of curvature of the refractive surface closest to the object is R1A, and the absolute value of the radius of curvature of the refractive surface closest to the aperture stop is R1B,
    0 ≦ R1A / R1B <4
    The imaging apparatus according to claim 1, wherein the following condition is satisfied.
  5. Among the absolute values of the radius of curvature of the refracting surface convex toward the object side in the front group, when the maximum value is RMAX and the minimum value is RMIN,
    1 ≦ RMAX / RMIN <10
    The imaging apparatus according to claim 1, wherein the following condition is satisfied.
  6.   The imaging apparatus according to claim 1, wherein all of the refractive surfaces of the front group are convex toward the object side.
  7.   The imaging apparatus according to claim 1, wherein the front group is a coaxial system.
  8.   The imaging apparatus according to claim 1, wherein the imaging surface is a flat surface.
  9.   The imaging apparatus according to claim 1, wherein the front group and the rear group are joined to each other via the aperture stop.
  10.   An imaging apparatus that acquires image data of an object, and a distance calculation unit that acquires distance information to the object based on the image data, the imaging apparatus according to any one of claims 1 to 9. An in-vehicle camera system, characterized by being an imaging device.
  11.   The in-vehicle camera system according to claim 10, further comprising a collision determination unit that determines a possibility of collision between the host vehicle and the object based on the distance information.
  12.   The control device according to claim 11, further comprising: a control device that outputs a control signal for generating a braking force for each wheel of the host vehicle when it is determined that there is a possibility of collision between the host vehicle and the object. The on-vehicle camera system described.
  13.   The vehicle-mounted vehicle according to claim 11 or 12, further comprising an alarm device that issues an alarm to a driver of the host vehicle when it is determined that there is a possibility of collision between the host vehicle and the object. Camera system.
  14. A projection device comprising: a display element that displays an image; and an optical system that forms an image on a display surface of the display element,
    The optical system has a front group, an aperture stop, and a rear group in order from the object side,
    The front group includes a concave reflecting surface;
    The rear group includes a refractive surface convex toward the image side,
    The aperture of the aperture stop is spaced apart from the display element in a direction perpendicular to the optical axis of the rear group, and is eccentric to the opposite side of the display element with respect to the optical axis. Projection device.
JP2016042685A 2016-03-04 2016-03-04 Image capturing device and projection device Pending JP2017156713A (en)

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JP2000019402A (en) * 1998-07-01 2000-01-21 Olympus Optical Co Ltd Image-formation optical system
JP2000019407A (en) * 1998-07-06 2000-01-21 Olympus Optical Co Ltd Image-formation optical system
JP2002122784A (en) * 2000-08-08 2002-04-26 Olympus Optical Co Ltd Optical device
JP2004361777A (en) * 2003-06-06 2004-12-24 Nikon Corp Solid type catadioptric optical system
JP4029154B2 (en) * 2003-06-17 2008-01-09 株式会社ニコン Projector
US7038846B2 (en) * 2003-11-24 2006-05-02 Electronic Scripting Products, Inc. Solid catadioptric lens with a single viewpoint
JP4855076B2 (en) * 2006-01-04 2012-01-18 オリンパス株式会社 Optical system
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