JP2017156712A - Optical system, and imaging device and projection device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system that can achieve size reduction and high resolution across a wide angle of view in an imaging device and a projection device.SOLUTION: There is provided an optical system 100 comprising, in order from an enlargement side, a first group G1, an aperture stop STO, and a second group G2, where the first group G1 includes a refractive surface 11 in a convex shape toward the enlargement side; the second group G2 includes a transmission reflection surface 31 and a concave reflection surface 32; light from the enlargement side passed through the aperture stop STO transmits through the transmission reflection surface 31 and then sequentially reflected on the reflection surface 32 and transmission reflection surface 31; when the radius of curvature of the refractive surface 11 is Rl (mm) and the interval between the refractive surface 11 and aperture stop STO is Ll (mm), the condition 0.7≤|Rl|/Ll≤1.5 is satisfied.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical system having a refracting surface and a reflecting surface, for example, an imaging device such as a digital still camera, a digital video camera, a mobile phone camera, a surveillance camera, a wearable camera, a medical camera, or a projection device such as a projector. It is suitable for.

  In recent years, an optical system used in an imaging apparatus or a projection apparatus has been required to 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 through a medium, thereby correcting aberrations satisfactorily. This makes it possible to realize a compact optical system that can be used. Patent Document 3 describes an optical system having a lens having a convex surface facing the object side and a catadioptric lens having a concave internal reflection surface, thereby realizing a wide angle of view. be able to.

JP 2013-210549 A JP 2004-361777 A JP 2009-300994 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. Therefore, 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. Is difficult. Further, in the optical system described in Patent Document 3, it is difficult to satisfactorily correct aberrations while reducing the F value, and it is difficult to achieve both miniaturization and high resolution.

  Accordingly, an object of the present invention is to provide an optical system capable of realizing downsizing and high resolution over a wide angle of view in an imaging apparatus and a projection apparatus.

  In order to achieve the above object, an optical system according to one aspect of the present invention is an optical system including a first group, an aperture stop, and a second group in order from the magnification side. The second group includes a transmissive reflecting surface and a concave reflecting surface, and light from the enlarged side that has passed through the aperture stop is transmitted through the transmissive reflecting surface. Are reflected in order by the reflection surface and the transmission reflection surface, 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). The condition of 0.7 ≦ | Rl | /Ll≦1.5 is satisfied.

  ADVANTAGE OF THE INVENTION According to this invention, the optical system which can implement | achieve size reduction and high resolution over a wide angle of view can be provided in an imaging device or a projection device.

1 is a schematic diagram of a main part of an imaging apparatus according to Embodiment 1 of the present invention. 1 is a schematic diagram of a main part of an optical system according to Example 1 of the present invention. FIG. 6 is an 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 optical system according to Example 2 of the present invention. FIG. 6 is an aberration diagram of the optical system according to Example 2 of the present invention. 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 of this invention.

  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.

[Example 1]
FIG. 1 is a schematic diagram of a main part in a YZ section including an optical axis A of an imaging apparatus 1000 including an optical system 100 according to Embodiment 1 of the present invention. The imaging apparatus 1000 includes an optical system 100 as an imaging optical system, an imaging device 110 including an imaging surface (light receiving surface) disposed at a position of an image plane (reduction surface) IMG of the optical system 100, a cable 120, and a processing unit 130. Is provided.

  In the imaging apparatus 1000, the optical system 100 collects a light beam from a subject (not shown) on the left side in FIG. 1 and forms an image of the subject on the imaging surface IMG of the imaging device 110. The image sensor 110 photoelectrically converts an object image formed by the optical system 100 and outputs an electrical signal. The processing unit 130 processes an electrical signal from the image sensor 110 transmitted via the cable 120, and acquires image data of the subject. As the imaging device 110, a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor can be employed.

  FIG. 2 is a main part schematic diagram in the YZ section including the optical axis A of the optical system 100. The optical system 100 according to the present embodiment includes an aperture stop STO for limiting the beam width, a first group G1 disposed on the object side (enlargement side) with respect to the aperture stop STO, and an image side (reduction) with respect to the aperture stop STO. 2nd group G2 arrange | positioned at the side).

  The first group G1 includes a first optical element L1 including a refracting surface (incident surface) 11 that is convex toward the object side, a second optical element L2, and an aperture stop STO that limits the beam width. The second group G2 includes a first optical element L1, a second optical element L2, a third optical element L3 including a concave reflecting surface 32, and a fourth optical element CG. Thus, in this embodiment, a part of the first optical element L1 and the second optical element L2 are shared by the first group G1 and the second group G2.

  The first optical element L1 is a lens having three optical surfaces through which an effective light beam that contributes to image formation passes. Specifically, the first optical element L1 has three surfaces: a first surface 11, a second surface 12, and a third surface 13. It has a transmission surface. In the first optical element L1, the first surface 11 and the second surface 12 are the first group G1, and the second surface 12 and the third surface 13 are the second group G2. The second optical element L2 is a meniscus lens having a convex surface facing the object side, and includes a first surface 21 that is a refractive surface and a second surface 22 that is a reflective surface. The second surface 22 of the second optical element L2 is an internal reflection surface formed by a metal film, a dielectric multilayer film, or the like. The aperture stop STO is formed of a light shielding member provided on the second surface 22 of the second optical element L2 and provided with an opening.

  The third optical element L3 is a reflection that includes three optical surfaces: a first surface 31 that is a transmission / reflection surface, a second surface 32 that is concave toward incident light, and a third surface 33 that is an emission surface. It is a refractive lens. In the third optical element L3, the first surface 31 is a transmission / reflection surface, the second surface 32 is an internal reflection surface formed of a metal film, a dielectric multilayer film, or the like, and the third surface 33 is a transmission surface. . The fourth optical element CG is an optical filter such as an IR cut filter. However, if necessary, a lens or the like may be employed as the fourth optical element CG.

  The transmission / reflection surface 31 of the third optical element L3 and the third surface 13 of the first optical element L1 closest to the transmission / reflection surface 31 on the optical path have the same shape. In this way, by making the transmissive reflection surface and the optical surface closest to the transmissive reflection surface 31 on the optical path have the same curvature radius, light from the aperture stop STO efficiently transmits the transmissive reflection surface. Will be able to. In the present embodiment, the third surface 13 of the first optical element L1 and the transmission / reflection surface 31 of the third optical element L3 face each other through air.

  In this embodiment, the optical axis A is an axis passing through the center (surface vertex) of each optical surface having power in the optical system 100. That is, the surface vertices of the refracting surface and the reflecting surface of the optical system 100 exist on the optical axis A. The first surface 11 of the first optical element L1 does not intersect the optical axis A, but a part of the surface where the surface vertex exists on the optical axis A (the optical axis A coincides with the central axis) is cut out. Shape.

Here, the refractive surface 11 included in the first group G1 according to the present embodiment has a shape (point-symmetric shape) in which the distance to the aperture stop STO and the radius of curvature are substantially equal. Specifically, the refracting surface 11 has a shape satisfying the following conditional expression (1) when the radius of curvature is Rl (mm) and the distance between the refracting surface 11 and the aperture stop STO is Ll (mm). is there. However, unless otherwise specified, “interval” indicates “interval on the optical axis A”.
0.7 ≦ | Rl | /Ll≦1.5 (1)

  By satisfying conditional expression (1), off-axis aberrations can be favorably corrected even with a simple and compact configuration. Outside the range of conditional expression (1), the amount of off-axis aberration increases, and 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.

  As described above, by adopting the point-symmetrical refracting surface 11 that satisfies the conditional expression (1), it is possible to realize a small optical system with a high resolution over a wide angle of view while reducing the aperture value. . At this time, the imaging surface of the first group G1 is curved due to the refracting surface 11 having a point-symmetric shape, but by providing the concave reflecting surface 32 in the second group G2, a planar image is obtained. It becomes possible to form the surface IMG. Therefore, since it is not necessary to provide a spherical imaging element or light guiding unit in the imaging apparatus 1000, the entire apparatus can be reduced in size.

  In the first group G1, a plurality of refractive surfaces that satisfy the conditional expression (1) 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 refracting surfaces in the first group G1 satisfies the conditional expression (1). 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 (1 ′) is satisfied. In this embodiment, | Rl | /Ll=1.010, which satisfies the conditional expressions (1) and (1 ′).
0.8 ≦ | Rl | /Ll≦1.3 (1 ′)

  In FIG. 2, light from an object (not shown) enters the first group G1 from the first surface 11 of the first optical element L1, passes through the first optical element L1 and the second optical element L2 in order, and opens. The light enters the stop STO. At this time, part of the light is blocked by the light blocking portion of the aperture stop STO, so that the beam width is limited. The light reflected by the aperture of the aperture stop STO, that is, the second surface 22 of the second optical element L2, passes again through the first surface 21 of the second optical element L2 and the second surface of the first optical element L1, The light passes through the third surface 13 of the first optical element L1.

  And the light which permeate | transmitted the 1st surface 31 of the 3rd optical element L3 is reflected by the 2nd surface 32 of the 3rd optical element L3, and reaches | attains the 1st surface 31 of the 3rd optical element L3 again. At this time, light incident at an incident angle larger than the critical angle is totally reflected on the first surface 31 of the third optical element L3, passes through the third surface 33 of the third optical element L3, and has a planar image surface IMG. Form.

  As described above, in the third optical element L3, the first surface 31 is a transmission / reflection surface, and the light reflected by the second surface 32 is further reflected by the first surface 31, thereby separating from the aperture stop STO. The image plane IMG can be formed at the predetermined position. Accordingly, it is possible to suppress unnecessary light that has not been blocked by the light blocking portion of the aperture stop STO from reaching the image plane IMG, and thus it is possible to realize a wide angle of view of the imaging apparatus 1000.

  As described above, in this embodiment, an air layer is provided between the third surface 13 of the first optical element L1 and the first surface 31 of the third optical element L3, and the second surface 32 of the third optical element L3. The light reflected by the first optical element L3 is configured to satisfy the total reflection condition on the first surface 31 of the third optical element L3. According to this configuration, it is possible to suppress a loss of light amount when light is reflected by the first surface 31 as compared with a case where a transmission / reflection film is provided on the first surface 31 of the third optical element L3.

  In this embodiment, the angle of view (horizontal angle of view) in the ZX section (first section) is ± 27 (deg), and the angle of view (vertical angle of view) in the YZ section (second section) is 15 to 53. (Deg). That is, the horizontal field angle is set symmetrically on both sides of the optical axis A, while the vertical field angle is set only on one side (+ side) with respect to the optical axis A.

  In this manner, in the YZ cross section, the light beam is obliquely incident on each optical surface of the optical system 100 so that the imaging surface of the imaging device 110 is viewed from the side opposite to the imaging device 110 with respect to the optical axis A. It can be configured to receive only the light beam incident on the. Thereby, it is possible to prevent the image sensor 110 from interfering with each optical element and each optical path.

In the optical system 100, it is desirable that the aperture stop STO and the entrance pupil (enlargement side pupil) are close to each other. Specifically, when the interval between the aperture stop STO and the entrance pupil is Lp (mm) and the focal length of the entire system is f (mm), it is preferable that the following conditional expression (2) is satisfied. However, the focal length is positive when the optical system has positive power and negative when the optical system has negative power.
−0.2 ≦ Lp / f ≦ 0.2 (2)

  By satisfying conditional expression (2), a light beam having each angle of view is incident on the refracting surface having a point-symmetrical shape at an angle close to the normal angle. The aberration can be easily corrected by the surface. When the upper limit value of conditional expression (8) is exceeded, the concentric structure is left, and the effect of the point-symmetric refracting surface cannot be obtained sufficiently. In this example, since Lp / f = −0.005, conditional expression (2) is satisfied.

Further, regarding the reflective surface 32 of the second group G2, it is desirable that the following conditional expression (3) is satisfied when the radius of curvature is Rm (mm) and the distance from the aperture stop STO is Lm (mm). .
2 ≦ | Rm | / Lm ≦ 7 (3)

  By making the shape of the reflecting surface 32 satisfy the conditional expression (3), it is possible to favorably correct the curvature of field while avoiding the interference between the image 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 image plane IMG will interfere with the optical path. In addition, when the 2nd group G2 has two or more reflective surfaces, it is desirable that the reflective surface with the largest power satisfy | fills conditional expression (3).

Furthermore, it is more preferable that the following conditional expression (3 ′) is satisfied. In this embodiment, | Rm | /Lm=2.765, which satisfies the conditional expressions (3) and (3 ′).
2.5 ≦ | Rm | /Lm≦5.7 (3 ′)

In order to satisfactorily correct the axial aberration caused by the point-symmetric refracting surface 11, it is desirable to provide a convex optical surface closer to the object side on the image side than the refracting surface 11. Therefore, in this embodiment, the joint surfaces (second surface 12 and first surface 21) between the first optical element L1 and the second optical element L2 are convex toward the object side. Furthermore, in this configuration, when the Abbe number with respect to the d-line of the first optical element L1 disposed on the object side is νA and the Abbe number with respect to the d-line of the second optical element L2 disposed on the image side is νB. It is preferable that the following conditional expression (4) is satisfied.
νA <νB (4)

  By satisfying the conditional expression (4), the axial chromatic aberration generated on the refractive surface 11 of the first optical element L1 can be favorably corrected by generating the axial chromatic aberration having the opposite sign. In this example, since νA = 43.7 and νB = 57.7, conditional expression (4) is satisfied.

Further, when the refractive index with respect to the d-line of the first optical element L1 arranged on the object side is NA and the refractive index with respect to the d-line of the second optical element L2 arranged on the image side is NB, the following conditional expression It is preferable to satisfy (5).
NA> NB (5)

  By satisfying the conditional expression (5), it is possible to satisfactorily correct the spherical aberration generated on the refractive surface 11 of the first optical element L1 by generating the spherical aberration having the opposite sign. In this embodiment, NA = 1.606 and NB = 1.573, which satisfies the conditional expression (5).

  In the optical system 100, each of the first surface 11 of the first optical element L1, the second surface 22 of the second optical element L2, and the second surface 32 of the third optical element L3 is aspheric. In the present embodiment, the first surface 11 of the first optical element L1 is aspherical, thereby correcting coma generated by the astigmatic component of the second surface 32 of the third optical element L3 and other optical surfaces. It is carried out. Further, by making the second surface 32 of the third optical element L3 an aspherical surface, astigmatism generated by the spherical component of this surface and the astigmatic components of other optical surfaces is corrected.

  However, each of the aspherical optical surfaces in this embodiment has a rotationally symmetric shape with the optical axis A as the center, and is expressed by the following aspherical expression.

  Here, z is the sag amount (mm) of the aspherical surface 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.

  Each data of Numerical Example 1 corresponding to the present example is shown in Tables 1-3. Table 1 shows surface data of each optical surface in the optical system 100. In Table 1, r is a radius of curvature (mm), d is a surface interval (mm), nd is a refractive index with respect to the d line, and νd is an Abbe with respect to the d line. Number. However, the surface interval is positive when going to the image side along the optical path and negative when going to the object side. Table 2 shows the eccentricity data of the surface vertices of each optical surface. In Table 2, each of x, y, and z represents coordinates based on the surface vertices of the optical surface of surface number 1, and α is around the x axis. , Β represents rotation about the y axis, and γ represents rotation about the z axis. Table 3 shows various data of the imaging apparatus 1000. In Table 3, Fno represents an aperture value (F value) of the optical system 100.

  [Numerical Example 1]

  FIG. 3 is an aberration diagram of the optical system 100 according to the present example. FIG. 3 shows lateral aberrations relating to light of each wavelength of 656 nm, 587 nm, 486 nm, and 435 nm at vertical angles of view of 53 °, 34 °, and 15 °. As is apparent from FIG. 3, various aberrations are favorably corrected in the visible wavelength region (400 to 700 nm).

  As described above, according to the optical system 100 according to the present embodiment, it is possible to achieve high resolution over a wide angle of view while having a simple and small configuration. Specifically, although the overall length is a small configuration of 36.59 mm, the F value is bright as Fno = 2.3, and various aberrations can be corrected satisfactorily at a wide angle of view.

[Example 2]
FIG. 4 is a schematic diagram of a main part in the YZ section including the optical axis A of the optical system 200 according to Example 2 of the present invention.

  In the optical system 200, the first group G1 includes a first optical element L1 and a second optical element L2 in order from the object side. The first optical element L1 is a meniscus lens having a convex surface facing the object side, and has a first surface 11 and a second surface 12. The second optical element L <b> 2 is a plano-convex lens and has a first surface 21 and a second surface 22.

  In the optical system 200, the second group G2 includes a third optical element L3, a fourth optical element L4, a fifth optical element L5, and a sixth optical element CG. The third optical element L3 is a plano-convex lens and has a first surface 31 and a second surface 32. The fourth optical element L4 has a concave first surface 41 and a planar second surface 42 toward the object side.

  The fifth optical element L5 includes three optical surfaces: a first surface 51 that is a transmission / reflection surface, a second surface 52 that is concave toward the image side, and a third surface 53 that is an emission surface. It is a refractive lens. In the fifth optical element L5, the first surface 51 is a transmission / reflection surface, the second surface 52 is an internal reflection surface formed of a metal film, a dielectric multilayer film, or the like, and the third surface 53 is a transmission surface. . The sixth optical element CG is an optical filter such as an IR cut filter.

  The second surface 12 of the first optical element L1, the first surface 21 of the second optical element L2, the second surface 22 of the second optical element L2, the first surface 31 of the third optical element L3, and the third optical element L3. The second surface 32 and the first surface 41 of the fourth optical element L4 are joined to each other. The aperture stop STO is composed of a light shielding member provided with an opening, which is disposed on the joint surface between the second optical element L2 and the third optical element L3.

  Unlike the transmission / reflection surface 31 of the second group G2 according to the first embodiment, the transmission / reflection surface 51 of the second group G2 according to the present embodiment is a transmission / reflection film (such as a metal film or a dielectric multilayer film). Half mirror and beam splitter). As a result, it is not necessary to consider the total reflection condition of the transmissive reflection surface, so that the angle of view and the brightness can be easily ensured.

  The first surface 11 of the first optical element L1 and the second surface 52 of the fifth optical element L5 are aspherical surfaces. Further, the fourth surface 42 of the fourth optical element L4 and the first surface 51 of the fifth optical element L5 have the same curvature radius, and face each other through air.

  In FIG. 4, light from an object (not shown) enters the first group G1 from the first surface 11 of the first optical element L1, passes through the first optical element L1 and the second optical element L2 in order, and opens. The light enters the stop STO. At this time, part of the light is blocked by the light blocking portion of the aperture stop STO, so that the beam width is limited. The light that has passed through the aperture of the aperture stop STO, that is, the first surface 31 of the third optical element L3, passes through the second surface 32 of the third optical element and the first surface 41 and the second surface 42 of the fourth optical element L4. Transparent in order.

  The light transmitted through the first surface 51 of the fifth optical element L5 is reflected by the second surface 52 of the fifth optical element L5, further reflected by the first surface 51 of the fifth optical element L5, and the fifth optical element. The third surface 53 of the element L5 is transmitted to form a planar image surface IMG. In this way, in the fifth optical element L5, the first surface 51 is used as a transmission / reflection surface, and the light reflected by the second surface 52 is further reflected by the first surface 51, thereby separating from the aperture stop STO. The image plane IMG can be formed at the predetermined position.

  In this example, | Rl | /Ll=1.116 is satisfied, thereby satisfying conditional expressions (1) and (1 ′), and Lp / f = 0.044 is satisfied, which satisfies conditional expression (2). Since | Rm | /Lm=5.635, the conditional expressions (3) and (3 ′) are satisfied. Further, in this example, for the first optical element L1 and the second optical element L2 having a convex joint surface toward the object side, since νA = 19.3 and νB = 44.3, the conditional expression (4 ), NA = 2.003, and NB = 1.613, which satisfies the conditional expression (5).

  Similarly to Example 1, Tables 4 to 6 show data of Numerical Example 2 corresponding to the present Example.

  [Numerical Example 2]

  FIG. 5 is an aberration diagram of the optical system 200 according to the present example. Similarly to FIG. 3, light having wavelengths of 656 nm, 587 nm, 486 nm, and 435 nm at vertical angles of view of 53 °, 34 °, and 15 ° are illustrated. The lateral aberration is shown. As is apparent from FIG. 5, various aberrations are favorably corrected in the visible wavelength region (400 to 700 nm).

  As described above, according to the optical system 200 according to the present embodiment, it is possible to realize high resolution over a wide angle of view while having a simple and small configuration. Specifically, the F-number is as bright as Fno = 2.3, and the various aberrations can be favorably corrected at a wide angle of view, although the total length is 45.20 mm.

[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.

  In each of Examples 1 and 2, the concave reflecting surface in the second group G2 is an internal reflecting surface configured by providing a reflecting film on the optical element, but is not limited thereto. For example, another optical element (such as a mirror) having a surface reflection surface may be provided instead of the internal reflection surface.

  In each embodiment, a gap is provided between the transmission / reflection surface in the second group G2 and the optical surface closest to the transmission / reflection surface on the optical path, but the invention is not limited to this, and the gap is refracted. The medium may be filled with a rate of 1 or more. When a transmission / reflection film is provided on the transmission / reflection surface of the second group of catadioptric lenses, the transmission / reflection surface of the second group G2 and the optical surface closest to the transmission / reflection surface on the optical path are joined. Also good.

  In each embodiment, the case where the optical system is applied to the imaging apparatus as the imaging optical system has been described. However, for example, the optical system may be applied to the projection apparatus as the 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 reduction surface IMG. However, when the optical system is applied to a projection apparatus, the object side and the image side are reversed and the optical path is reversed. Therefore, the reduction side is the object side, the enlargement side is the image side, the first group G1 is the second group G2, and the second group G2 is the first group G1, and the entrance surface of each optical element is the exit surface, and the exit surface is the entrance surface. Become.

  That is, a configuration in which an image displayed on the display surface (reduced surface) of the display element disposed on the object side is projected (imaged) onto a projection surface (enlarged surface) such as a screen disposed on the image side by the optical system. Can be taken. 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. Regarding conditional expression (2), the entrance pupil (enlargement side pupil) of the aperture stop in the imaging optical system corresponds to the exit pupil (reduction side pupil) of the aperture stop in the projection optical system.

[In-vehicle camera system]
FIG. 6 is a configuration diagram of the in-vehicle camera 10 according to the present embodiment and the 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 10. FIG. 7 is a schematic diagram of a vehicle 700 including an in-vehicle camera system 600. Although FIG. 7 shows a case where the imaging range 50 of the in-vehicle camera 10 is set in front of the vehicle 700, the imaging range 50 may be set behind the vehicle 700.

  As shown in FIG. 6, the in-vehicle camera system 600 includes an in-vehicle camera 10, a vehicle information acquisition device 20, a control device (ECU: electronic control unit) 30, and an alarm device 40. The in-vehicle camera 10 includes an imaging unit 1, an image processing unit 2, a parallax calculation unit 3, a distance calculation unit 4, and a collision determination unit 5. The imaging unit 1 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 and the image processing unit 2 according to the present embodiment correspond to, for example, the imaging element 110 and the processing unit 130 included in the imaging apparatus 1000 according to Example 1 illustrated in FIG.

  FIG. 8 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 S1, a target object (subject) around the vehicle is imaged using the imaging unit 1, and a plurality of image data (parallax image data) is acquired.

  In step S <b> 2, vehicle information is acquired from the vehicle information acquisition device 20. 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 2 performs image processing on a plurality of image data acquired by the imaging unit 1. 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, the parallax calculation unit 3 calculates parallax (image shift) information between a plurality of pieces of image data acquired by the imaging unit 1. 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, distance information to the object imaged by the imaging unit 1 is calculated by the distance calculation unit 4. The distance information can be calculated based on the parallax information calculated by the parallax calculation unit 3 and the internal and external parameters of the imaging unit 1. 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 5 determines whether or not the distance information calculated by the distance calculation unit 4 is included in a preset 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 5 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 5 determines that there is a possibility of collision (step S7), the collision determination unit 5 notifies the control device 30 and the alarm device 40 of the determination result. At this time, the control device 30 controls the vehicle based on the determination result in the collision determination unit 5, and the alarm device 40 issues an alarm based on the determination result in the collision determination unit 5.

  For example, the control device 30 performs control such as braking the vehicle, returning the accelerator, and generating a control signal for generating a braking force for each wheel to suppress the output of the engine and the motor. Further, the alarm device 40 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 of the embodiments described above to the in-vehicle camera system 600, it is possible to detect obstacles with high accuracy over a wide angle of view while reducing the size of the entire in-vehicle camera 10 and increasing the degree of freedom of arrangement. It becomes possible to perform collision determination.

  Here, in the present embodiment, the configuration in which the in-vehicle camera 10 includes only one imaging unit 1 having the imaging surface phase difference sensor has been described. However, the present invention is not limited thereto, and the in-vehicle camera 10 includes 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 will be described in which 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 of the imaging unit 1. 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 4. Alternatively, the distance calculation unit 4 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 4 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 10 and the in-vehicle camera 10 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 first embodiment shown in FIG. 2 is employed, the optical axis A is inclined 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. do it. 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 10 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 an obstacle on the road by the in-vehicle camera 10, the optical performance at the angle of view below (the ground side) from the upper side (the sky side) with respect to the horizontal direction is improved. 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 vehicle-mounted camera 10 and the moving body according to the present embodiment but also to devices that widely use object recognition, such as an intelligent road traffic system (ITS).

DESCRIPTION OF SYMBOLS 11 Refractive surface 31 Transmitting / reflecting surface 32 Reflecting surface 100 Optical system G1 1st group G2 2nd group STO Aperture stop IMG Image surface

Claims (19)

In order from the enlargement side, an optical system comprising a first group, an aperture stop, and a second group,
The first group includes a refracting surface convex toward the enlargement side,
The second group includes a transmission reflection surface and a concave reflection surface,
The light from the enlarged side that has passed through the aperture stop is reflected by the reflection surface and the transmission reflection surface in order after passing through the transmission reflection surface,
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
An optical system characterized by satisfying the following conditions. When the interval between the aperture stop and the enlargement-side pupil is Lp (mm) and the focal length of the entire system is f (mm),
−0.2 ≦ Lp / f ≦ 0.2
The optical system according to claim 1, wherein the following condition is satisfied. 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 optical system according to claim 1, wherein the following condition is satisfied.   The first group includes a first optical element and a second optical element arranged in order from the enlargement side, and the first optical element and the second optical element are bonded to each other. The optical system according to any one of 1 to 3.   The optical system according to claim 4, wherein a joining surface of the first optical element and the second optical element is convex toward the enlargement side. When the Abbe number of the first optical element with respect to the d-line is νA, and the Abbe number of the second optical element with respect to the d-line is νB,
νA <νB
The optical system according to claim 5, wherein the following condition is satisfied. When the refractive index for the d-line of the first optical element is NA and the refractive index for the d-line of the second optical element is NB,
NA> NB
The optical system according to claim 5, wherein the following condition is satisfied.   The optical system according to claim 1, wherein the light reflected by the reflection surface is totally reflected by the transmission reflection surface.   The optical system according to claim 1, wherein the transmission / reflection surface includes a transmission / reflection film.   10. The optical device according to claim 1, wherein the transmissive reflection surface and the optical surface closest to the transmissive reflection surface on an optical path are opposed to each other through air. system.   The radius of curvature of the transmissive reflecting surface and the radius of curvature of the optical surface closest to the transmissive reflecting surface on the optical path are the same as each other. Optical system.   The optical system according to claim 1, wherein the aperture of the aperture stop is a reflecting surface.   An image pickup device that picks up an image of an object, and an optical system that forms an image of the object on an image pickup surface of the image pickup device, wherein the optical system is the optical system according to any one of claims 1 to 12. An imaging apparatus characterized by the above.   The imaging apparatus according to claim 13, wherein the imaging surface is a flat surface.   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, wherein the imaging apparatus is the imaging apparatus according to claim 13 or 14. In-vehicle camera system characterized by the above.   The in-vehicle camera system according to claim 15, further comprising a collision determination unit that determines a possibility of collision between the host vehicle and the object based on the distance information.   The apparatus according to claim 16, 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.   The in-vehicle device according to claim 16 or 17, 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 a collision between the host vehicle and the object. Camera system.   A display element that displays an image and an optical system that forms an image on a display surface of the display element, wherein the optical system is the optical system according to any one of claims 1 to 12. Projection device.

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