WO2017150486A1

WO2017150486A1 - Optical system, imaging device provided with same, and projection device

Info

Publication number: WO2017150486A1
Application number: PCT/JP2017/007616
Authority: WO
Inventors: 中野　正嗣
Original assignee: キヤノン株式会社
Priority date: 2016-03-04
Filing date: 2017-02-28
Publication date: 2017-09-08
Also published as: JP2017156712A

Abstract

An optical system 100 provided with a first group G1, an opening aperture STO, and a second group G2 in the stated order from the magnification side, wherein: the first group G1 includes a refraction surface 11 that is convex toward the magnification side; the second group G2 includes a transmissive reflection surface 31 and a concave reflection surface 32; light from the magnification side that has been transmitted through the opening aperture STO is transmitted through the transmissive reflection surface 31 and then is reflected by the reflection surface 32 and the transmissive reflection surface 31 in the stated order; and the condition of 0.7 ≤ |Rl|/Ll ≤ 1.5 is satisfied, where Rl is the radius of curvature of the refraction surface 11 (mm) and Ll is the distance between the refraction surface 11 and the opening aperture STO (mm).

Description

OPTICAL SYSTEM, IMAGING DEVICE AND PROJECTION DEVICE PROVIDED WITH SAME

The present invention relates to an optical system having a refracting surface and a reflecting surface, and, 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 Are preferred.

In recent years, as an optical system used for an imaging device or a projection device, a high resolution and small size is required over a wide angle of view.

Patent Document 1 describes an imaging device provided with a spherical lens. With this spherical lens, on-axis aberrations such as spherical aberration and axial chromatic aberration can be favorably corrected while suppressing occurrence of off-axis aberrations such as coma aberration, astigmatism and lateral chromatic aberration. It becomes possible to realize a high resolution optical system over the angle of view.

Patent Document 2 describes a catadioptric optical system in which a plurality of refracting surfaces, a reflection-type aperture stop, and a reflecting surface are integrated via a medium, thereby correcting aberrations well. It is possible to realize a compact optical system that can Further, Patent Document 3 describes an optical system having a lens with 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 by the spherical lens described in Patent Document 1 is spherical, when this spherical lens is provided in an imaging apparatus or a projection apparatus, the imaging element or display element of a spherical shape 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 enlarged, and the cost increases.

In the optical system described in Patent Document 2, the aperture stop and the image plane are in close proximity, and unnecessary light not blocked 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 correct the aberration well while reducing the F value, so it is difficult to achieve both size reduction and high resolution.

Therefore, an object of the present invention is to provide an optical system capable of realizing high resolution over a small size and a wide angle of view in an imaging device and a projection device.

An optical system as one aspect of the present invention for achieving the above object is an optical system including a first group, an aperture stop, and a second group in order from the enlargement side, and the first group is an enlargement. The second group includes a transmissive reflective surface and a concave reflective surface, and the light from the enlarged side which has passed through the aperture stop is the transmissive reflective surface. The light is reflected sequentially by the reflecting surface and the transmitting / reflecting surface, and the radius of curvature of the refracting surface is Rl (mm), and the distance between the refracting surface and the aperture stop is Ll (mm). It is characterized in that the condition of 0.7 ≦ | Rl | /Ll≦1.5 is satisfied.

BRIEF DESCRIPTION OF THE DRAWINGS The principal part schematic of the imaging device which concerns on Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The principal part schematic of the optical system which concerns on Example 1 of this invention. FIG. 2 is an aberration diagram of an optical system according to Example 1 of the present invention. The principal part schematic of the optical system which concerns on Example 2 of this invention. FIG. 7 shows aberration of an optical system according to Example 2 of the present invention. FIG. 1 is a functional block diagram of an on-vehicle camera system according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The principal part schematic of the vehicle which concerns on embodiment of this invention. 6 is a flowchart showing an operation example of the on-vehicle camera system according to the embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that each drawing may be drawn at a scale different from the actual scale for convenience. Moreover, in each drawing, the same reference numeral is given to the same member, and the overlapping description is omitted.

Example 1
FIG. 1 is a schematic view of an essential part in an YZ cross section including an optical axis A of an imaging device 1000 provided with an optical system 100 according to a first embodiment of the present invention. The imaging apparatus 1000 includes an optical system 100 as an imaging optical system, an imaging element 110 including an imaging surface (light receiving surface) disposed at a position of an image surface (reduction surface) IMG of the optical system 100, a cable 120, and a processing unit 130. Equipped with

In the image pickup apparatus 1000, the optical system 100 condenses a light flux from an unshown object present on the left side of FIG. 1 and forms an image of the object on the imaging surface IMG of the image sensor 110. The image sensor 110 photoelectrically converts the image of the subject formed by the optical system 100 and outputs an electrical signal. The processing unit 130 processes the electrical signal from the imaging element 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 schematic view of an essential part in the YZ cross section including the optical axis A of the optical system 100. FIG. The optical system 100 according to the present embodiment includes an aperture stop STO for limiting the light beam width, a first group G1 disposed on the object side (enlargement side) of the aperture stop STO, and an image side (reduction) of the aperture stop STO. And a second group G2 disposed on the side).

The first group G1 includes a first optical element L1 including a refracting surface (incident surface) 11 having a convex shape toward the object side, a second optical element L2, and an aperture stop STO for limiting the luminous flux width. Further, the second group G2 has a first optical element L1, a second optical element L2, a third optical element L3 including a concave-shaped reflecting surface 32, and a fourth optical element CG. Thus, in the present 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 contributing to image formation passes, and more specifically, three of the first surface 11, the second surface 12, and the third surface 13 It has a transparent 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 on the object side, and has a first surface 21 which is a refracting surface and a second surface 22 which is a reflecting surface. The second surface 22 of the second optical element L2 is an internal reflection surface formed of a metal film, a dielectric multilayer film, or the like. The aperture stop STO is formed of a light shielding member provided with an opening and disposed on the second surface 22 of the second optical element L2.

The third optical element L3 includes three optical surfaces: a first surface 31, which is a transmission / reflection surface, a second surface 32, which is concave toward the incident light, and a third surface 33, which 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 adopted 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 in the optical path have the same shape. As described above, by making the radius of curvature of the transmission / reflection surface and the optical surface closest to the transmission / reflection surface 31 on the light path the same, the light from the aperture stop STO is efficiently transmitted through the transmission / reflection surface. You 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 via air.

In the present embodiment, the optical axis A is an axis passing through the center (face vertex) of each optical surface having a power in the optical system 100. That is, the surface apexes of the refractive surface and the reflective surface of the optical system 100 exist on the optical axis A. Although the first surface 11 of the first optical element L1 does not intersect with the optical axis A, it cuts out part of the surface where the surface apex exists on the optical axis A (the optical axis A coincides with the central axis) Shape.

Here, the refracting surface 11 of the first group G1 according to this embodiment has a shape (point-symmetrical shape) in which the distance to the aperture stop STO and the radius of curvature are substantially equal. Specifically, when the refractive surface 11 has a radius of curvature of Rl (mm) and the distance between the refractive surface 11 and the aperture stop STO is Ll (mm), it has a shape satisfying the following conditional expression (1) is there. However, unless otherwise noted, "spacing" indicates "spacing 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 the conditional expression (1), the amount of off-axis aberration generated increases, and good optical characteristics can not be obtained. This is explained below.

In general, when designing an optical system, off-axis aberrations such as coma, astigmatism, curvature of field, distortion and lateral chromatic aberration, and on-axis aberrations such as spherical aberration and on-axis chromatic aberration are used. Correction is required. However, when a normal axisymmetric refracting surface is used, a large off-axis aberration occurs at the peripheral angle of view (off-axis), so the optical performance on the optical axis (on-axis) becomes the highest. Therefore, the optical performance at the peripheral angle of view decreases.

On the other hand, since the refracting surface having a point-symmetrical shape 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 aberration and to suppress the decrease in optical performance at the peripheral angle of view. Therefore, by adopting a point-symmetrical refracting surface, the aberration to be corrected can be limited to spherical aberration, axial chromatic aberration, Petzval image surface, etc., so that various aberrations can be made excellent even with a simple configuration. It becomes possible to correct.

Thus, by adopting the point-symmetrical refracting surface 11 satisfying the conditional expression (1), it is possible to realize a high-resolution and compact optical system over a wide angle of view while reducing the aperture value. . At this time, although the image forming surface of the first group G1 is curved due to the point-symmetrical refracting surface 11, the image of the planar shape is formed by providing the concave reflecting surface 32 in the second group G2. It becomes possible to form a face IMG. Therefore, in the imaging apparatus 1000, there is no need to provide a spherical imaging element and light guiding means, so that the overall size of the apparatus can be reduced.

In the first group G1, a plurality of refracting surfaces which satisfy the conditional expression (1) may be provided. Also in such a case, the effect of the present invention can be obtained by configuring at least one of the plurality of refractive surfaces in the first group G1 to satisfy the conditional expression (1). However, in order to correct off-axis aberration well, as in the present embodiment, the refractive surface further away from the aperture stop STO, or the refractive surface having a large difference in refractive index with the adjacent medium, ie, the most object side It is desirable to make the refracting surface point-symmetrical.

Furthermore, it is more preferable to satisfy the following conditional expression (1 '). In the present embodiment, since | R1 | /L1=1.012, the conditional expressions (1) and (1 ') are satisfied.
0.8 ≦ | Rl | /Ll≦1.3 (1 ′)

In FIG. 2, light from an object (not shown) is incident on 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 is apertured. It enters into the aperture stop STO. At this time, since a part of the light is blocked by the light blocking portion of the aperture stop STO, 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 is transmitted through the third surface 13 of the first optical element L1.

Then, the light transmitted through the first surface 31 of the third optical element L3 is reflected by the second surface 32 of the third optical element L3 and reaches the first surface 31 of the third 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 L 3, passes through the third surface 33 of the third optical element L 3, and an image plane IMG having a planar shape Form

As described above, in the third optical element L 3, 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 any position. As a result, unnecessary light that is not blocked by the light blocking portion of the aperture stop STO can be prevented from reaching the image plane IMG, so that a wide angle of view of the imaging device 1000 can be realized.

As described above, in the present 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 is provided. The light reflected by the light source is configured to satisfy the total reflection condition at the first surface 31 of the third optical element L3. According to this configuration, it is possible to suppress the loss of light quantity when light is reflected by the first surface 31 as compared with the case where the transmission / reflection film is provided on the first surface 31 of the third optical element L3.

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

As described above, in the YZ cross section, the light incident on each optical surface of the optical system 100 causes the image pickup surface of the image pickup device 110 to be the optical system 100 from the side opposite to the image pickup device 110 with respect to the optical axis A. It can be configured to receive only the light beam incident on. Thereby, the imaging element 110 can be prevented 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) be configured to be close to each other. Specifically, when the distance 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 to satisfy the following conditional expression (2). 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), it is possible to provide a concentric configuration in which light rays of each angle of view are incident at an angle close to perpendicular to the point-symmetrical refracting surface. The surface makes it easy to correct the aberration. When the value exceeds the upper limit value of the conditional expression (8), it deviates from the concentric configuration, and the effect due to the refracting surface of the point symmetric shape can not be sufficiently obtained. In the present embodiment, since Lp / f = −0.005, the conditional expression (2) is satisfied.

Further, it is preferable that the following conditional expression (3) is satisfied, where Rm (mm) is the radius of curvature and Lm (mm) is the distance between the aperture stop STO and the reflecting surface 32 of the second group G2. .
2 ≦ | Rm | / Lm ≦ 7 (3)

By making the shape of the reflective surface 32 a shape satisfying the conditional expression (3), it is possible to correct the curvature of field well while avoiding the interference between the image plane IMG and the optical path. If the upper limit value of the conditional expression (3) is exceeded, the curvature of field may be increased. If the lower limit value of the conditional expression (3) is not reached, there is a possibility that the image plane IMG may interfere with the light path. When the second group G2 has a plurality of reflecting surfaces, it is desirable that the reflecting surface with the largest power satisfy the conditional expression (3).

Furthermore, it is more preferable to satisfy the following conditional expression (3 '). In the present embodiment, since | Rm | /Lm=2.765, the conditional expressions (3) and (3 ′) are satisfied.
2.5 ≦ | Rm | /Lm≦5.7 (3 ′)

Further, in order to satisfactorily correct the on-axis aberration caused by the point-symmetrical refractive surface 11, it is desirable to provide a convex optical surface on the image side of the refractive surface 11 toward the object side. Therefore, in the present embodiment, the cemented surface (the second surface 12 and the first surface 21) of the first optical element L1 and the second optical element L2 has a convex shape toward the object side. Furthermore, in this configuration, the Abbe number for the d line of the first optical element L1 disposed on the object side is νA, and the Abbe number for the d line of the second optical element L2 disposed on the image side is BB. It is preferable to satisfy the following conditional expression (4).
A A <B B (4)

By satisfying conditional expression (4), it is possible to satisfactorily correct axial chromatic aberration generated on the refracting surface 11 of the first optical element L1 by generating axial chromatic aberration of the opposite sign. In the present embodiment, since AA = 43.7 and BB = 57.7, the conditional expression (4) is satisfied.

Further, when the refractive index to the d-line of the first optical element L1 disposed on the object side is NA, and the refractive index to the d-line of the second optical element L2 disposed 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 refracting surface 11 of the first optical element L1 by generating the spherical aberration of the opposite sign. In the present embodiment, since NA = 1.606 and NB = 1.573, the conditional expression (5) is satisfied.

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, by making the first surface 11 of the first optical element L1 an aspheric surface, correction of coma aberration generated in the astigmatic components of the second surface 32 of the third optical element L3 and other optical surfaces is corrected. It is carried out. Further, by making the second surface 32 of the third optical element L3 an aspheric surface, correction of astigmatism generated by the spherical component of this surface and other astigmatism components of the optical surface is performed.

However, each of the aspheric optical surfaces in the present embodiment has a rotationally symmetric shape about the optical axis A, and is expressed by the following aspheric expression.

Here, z is the sag amount (mm) in the optical axis direction of the aspheric shape, c is the curvature on the optical axis A (1 / mm), k is the conical coefficient, h is the radial distance from the optical axis A ( mm), A, B, C,... are aspheric coefficients of the fourth order term, the sixth order term, the eighth order term,. In the aspheric 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 amount of sag of the aspheric surface component provided on the base spherical surface.

Respective data of Numerical value example 1 corresponding to the present example are shown in Tables 1 to 3. Table 1 shows surface data of each optical surface in the optical system 100. In Table 1, r is the radius of curvature (mm), d is the surface distance (mm), nd is the refractive index for d line, and ν d is Abbe for d line Represents a number. However, the surface separation is positive when going to the image side along the optical path, and negative when going to the object side. Table 2 shows eccentricity data of the surface vertex of each optical surface. In Table 2, each of x, y and z represents coordinates based on the surface vertex of the optical surface of surface number 1, and α is around the x axis 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 the aperture value (F value) of the optical system 100.

Numerical Embodiment 1

FIG. 3 is an aberration diagram of the optical system 100 according to the present embodiment. FIG. 3 shows transverse aberration with respect to light of each wavelength of 656 nm, 587 nm, 486 nm and 435 nm at vertical angle of view of 53 °, 34 ° and 15 °. As apparent from FIG. 3, various aberrations are well corrected in the visible wavelength range (400 to 700 nm).

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

Example 2
FIG. 4 is a schematic view of an essential part in the YZ cross section including the optical axis A of the optical system 200 according to the second embodiment 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 L2 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 the third optical element L3, the fourth optical element L4, the fifth optical element L5, and the 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 is a reflection that 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 exit 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 and the first surface 21 of the second optical element L2, the second surface 22 of the second optical element L2, and the first surface 31 of the third optical element L3, and the third optical element L3 Each of the second surface 32 and the first surface 41 of the fourth optical element L4 is bonded to each other. The aperture stop STO is formed of a light shielding member provided with an opening, which is disposed on the joint surface of 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 formed of a metal film, a dielectric multilayer film, or the like ( It consists of a half mirror, a beam splitter, etc.). As a result, it is not necessary to consider the total reflection condition of the transmission / reflection surface, so it is easy to secure the angle of view and the brightness.

The first surface 11 of the first optical element L1 and the second surface 52 of the fifth optical element L5 are aspheric 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 radius of curvature, and face each other via 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 the aperture is opened. It enters into the aperture stop STO. At this time, since a part of the light is blocked by the light blocking portion of the aperture stop STO, 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. Transmit in order.

Then, 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, and is further reflected by the first surface 51 of the fifth optical element L5. The light is transmitted through the third surface 53 of the element L5 to form a planar image plane IMG. As described above, in the fifth optical element L5, the first surface 51 is made to be 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 any position.

In the present embodiment, since | Rl | /Ll=1.116, the conditional expressions (1) and (1 ′) are satisfied, and since Lp / f = 0.044, the conditional expression (2) is satisfied. Since | Rm | /Lm=5.635, conditional expressions (3) and (3 ') are satisfied. Further, in the present embodiment, for the first optical element L1 and the second optical element L2 having a cemented surface convex toward the object side, since νA = 19.3 and BB = 44.3, the conditional expression (4 The conditional expression (5) is satisfied because NA = 2.003 and NB = 1.613.

Similar to the first embodiment, data of the second numerical embodiment corresponding to the present embodiment are shown in Tables 4 to 6.

Numerical Embodiment 2

FIG. 5 is an aberration diagram of the optical system 200 according to the present example, and as in FIG. 3, light of each wavelength of 656 nm, 587 nm, 486 nm, 435 nm at vertical angle of view 53 °, 34 °, 15 ° Shows the transverse aberration of. As apparent from FIG. 5, various aberrations are well corrected in the visible wavelength range (400 to 700 nm).

As described above, according to the optical system 200 according to the present embodiment, high resolution over a wide angle of view can be realized while having a simple and compact configuration. Specifically, although the overall length is as small as 45.20 mm, the F value is as bright as Fno = 2.3, and various aberrations can be favorably corrected in a wide angle of view.

[Modification]
Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the present invention.

In each of the first and second embodiments, the concave-shaped reflective surface in the second group G2 is an internal reflective surface configured by providing a reflective film on the optical element, but the present invention is not limited to this. For example, instead of the internal reflection surface, another optical element (such as a mirror) having a surface reflection surface may be provided.

In each embodiment, an air gap is provided between the transmission / reflection surface in the second group G2 and the optical surface closest to the transmission / reflection surface in the optical path, but the invention is not limited thereto. The rate may be filled with one or more media. In the case where 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. It is also good.

In each embodiment, the optical system is applied as an imaging optical system to an imaging apparatus. However, for example, the optical system may be applied as a projection optical system to a projection apparatus. In this case, the display surface of a display element such as a liquid crystal panel (spatial modulator) is disposed at the position of the reduction plane IMG. However, when the optical system is applied to a projection apparatus, the object side and the image side are reversed and the light 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, the second group G2 is the first group G1, 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 (reduction surface) of the display element disposed on the object side is projected (imaged) on 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, as in the case where the optical system is applied to an imaging device, it is desirable to satisfy each conditional expression in each embodiment. In conditional expression (2), the entrance pupil (magnification 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.

[Vehicle camera system]
FIG. 6 is a configuration diagram of the on-vehicle camera 10 according to the present embodiment and the on-vehicle camera system (drive support device) 600 including the on-vehicle camera 10. The on-vehicle camera system 600 is a device installed in a vehicle such as a car and supporting driving of the vehicle based on the image information of the surroundings of the vehicle acquired by the on-vehicle camera 10. FIG. 7 is a schematic view of a vehicle 700 equipped with an on-board camera system 600. Although FIG. 7 shows the case where the imaging range 50 of the on-vehicle camera 10 is set to the front of the vehicle 700, the imaging range 50 may be set to the rear of the vehicle 700.

As shown in FIG. 6, the on-vehicle camera system 600 includes an on-vehicle camera 10, a vehicle information acquisition device 20, a control device (ECU: electronic control unit) 30, and an alarm device 40. The on-vehicle camera 10 further 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 the optical system according to any one of the above-described embodiments and an imaging surface phase difference sensor. 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 provided in the imaging apparatus 1000 according to the first embodiment shown in FIG.

FIG. 8 is a flowchart showing an operation example of the on-vehicle camera system 600 according to the present embodiment. Hereinafter, the operation of the on-vehicle camera system 600 will be described along the flowchart.

First, in step S1, an object (subject) around the vehicle is imaged using the imaging unit 1, and a plurality of image data (parallax image data) are acquired.

In step S2, vehicle information is acquired from the vehicle information acquisition device 20. The vehicle information is information including the vehicle speed of the vehicle, the yaw rate, the steering angle, and the like.

In step S 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 in image data, and density values. 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 image data acquired by the imaging unit 1 is calculated by the parallax calculation unit 3. A known method such as an SSDA method or an area correlation method can be used as a method of calculating disparity information, and thus the description thereof will be omitted in this embodiment. Steps S2, S3 and S4 may be processed in the order described above, or may be processed in parallel with each other.

In step S <b> 5, the distance calculation unit 4 calculates distance information to the object captured by the imaging unit 1. The distance information can be calculated based on the parallax information calculated by the parallax calculation unit 3 and the internal parameter and the external parameter of the imaging unit 1. Here, the distance information is information on the relative position to the object such as the distance to the object, the defocus amount, the image shift amount, etc., and the distance value of the object in the image is directly Or may indirectly represent information corresponding to the distance value.

Then, in step S6, the collision determination unit 5 determines whether the distance information calculated by the distance calculation unit 4 is included in the range of the preset distance set in advance. Thus, it is possible to determine whether an obstacle is present within the set distance around the vehicle and to determine the possibility of collision between the vehicle and the obstacle. The collision determination unit 5 determines that there is a collision possibility if there is an obstacle within the set distance (step S7), and determines that there is no collision possibility if there is no obstacle within the set distance (step S8) ).

Next, when the collision determination unit 5 determines that there is a collision possibility (step S7), the collision determination unit 5 notifies the control device 30 or the alarm device 40 of the determination result. At this time, the control device 30 controls the vehicle based on the determination result of the collision determination unit 5, and the alarm device 40 issues an alarm based on the determination result of the collision determination unit 5.

For example, the control device 30 performs control such as applying a brake to the vehicle, returning an accelerator, or generating a control signal for causing each wheel to generate a braking force to suppress an output of an engine or a motor. Further, the alarm device 40 sounds an alarm such as a sound to a user (driver) of the vehicle, displays alarm information on a screen of a car navigation system or the like, gives a vibration to a seat belt or steering wheel, etc. I do.

As mentioned above, according to the vehicle-mounted camera system 600 which concerns on this embodiment, an obstacle can be detected effectively by said process, and it becomes possible to avoid the collision with a vehicle and an obstacle. In particular, by applying the optical system according to each of the above-described embodiments to the on-vehicle camera system 600, the entire on-vehicle camera 10 can be miniaturized to increase the degree of freedom of arrangement while detecting obstacles with high accuracy over wide angles of view. It becomes possible to perform collision determination.

Here, in the present embodiment, the configuration in which the on-vehicle camera 10 includes only one imaging unit 1 having an imaging surface phase difference sensor has been described, but the present invention is not limited thereto. A stereo camera including two imaging units as the on-vehicle camera 10 May be adopted. In this case, even without using the imaging surface phase difference sensor, 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 between the imaging times of the two imaging units is known, it is not necessary to synchronize the two imaging units.

In addition, various embodiments can be considered for the calculation of 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 an imaging device of the imaging unit 1 will be described. In the pupil division type imaging device, one pixel unit is composed of a micro lens and a plurality of photoelectric conversion units, receives a pair of light beams passing through different areas in the pupil of the optical system, and makes a pair of image data It can be output from each photoelectric conversion unit.

Then, the image shift amount of each area is calculated by correlation calculation between the pair of image data, and the distance calculation unit 4 calculates image shift map data representing the distribution of the image shift amount. 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). In addition, the distance calculation unit 4 may acquire distance map data of the distance to the object to be converted from the defocus amount.

As described above, the vertical angle of view of the optical system according to each embodiment is set to only one side with respect to the optical axis A. Therefore, when the optical system according to each embodiment is applied to the on-vehicle camera 10 and the on-vehicle camera 10 is installed in a vehicle, the optical axis A of the optical system should be arranged 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 adopted, 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 to approach the horizontal direction. do it. Alternatively, after the optical system 100 is rotated 180 degrees (vertically reversed) around the X axis, the optical axis A may be arranged to be inclined downward with respect to the horizontal direction. 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, while the optical performance at the peripheral angle of view decreases, so that the light from the target object of interest is the axis in the optical system. It is more preferable to arrange so as to pass near the upper side. For example, when it is necessary to pay attention to a sign or an obstacle on a road by the on-vehicle camera 10, the optical performance at an angle of view below the ground (ground side) relative to the upper side (air side) with respect to the horizontal direction is enhanced. Is preferred. At this time, when the optical system 100 according to the first embodiment is adopted, the optical system 100 is temporarily turned upside down as described above, and then the optical axis A is inclined downward with respect to the horizontal direction. It may be disposed so that the angle of view of the lens faces downward.

In the present embodiment, the on-vehicle camera system 600 is applied for driving assistance (collision damage reduction), but the invention is not limited thereto. For example, the on-vehicle camera system 600 may be used for cruise control (including all vehicle speed tracking function) and automatic driving. It may apply. In addition, the on-vehicle camera system 600 can be applied not only to a vehicle such as a host vehicle but also to a mobile object (mobile device) such as a ship, an aircraft, or an industrial robot. Further, the present invention can be applied not only to the on-vehicle camera 10 and the moving body according to the present embodiment, but also to devices that widely use object recognition, such as the Intelligent Transportation System (ITS).

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the following claims are attached to disclose the scope of the present invention.

The present application claims priority based on Japanese Patent Application No. 2016-042684 filed Mar. 4, 2016, the entire contents of which are incorporated herein by reference.

11 refracting surface 31 transmitting / reflecting surface 32 reflecting surface 100 optical system G1 first group G2 second group STO aperture stop IMG image plane

Claims

An optical system comprising a first group, an aperture stop, and a second group in this order from the enlargement side,
The first group includes a refracting surface having a convex shape toward the enlargement side,
The second group includes a transmission / reflection surface and a concave reflection surface,
The light from the enlargement side, which has passed through the aperture stop, is transmitted through the transmission / reflection surface, and then reflected in order by the reflection surface and the transmission / reflection surface,
Assuming that the radius of curvature of the refracting surface is Rl (mm) and the distance between the refracting 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 distance between the aperture stop and the enlargement side pupil is Lp (mm) and the focal length of the whole system is f (mm),
−0.2 ≦ Lp / f ≦ 0.2
The optical system according to claim 1, wherein the following condition is satisfied.
Assuming that 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 or 2, wherein the following condition is satisfied.
The first group has 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.
5. The optical system according to claim 4, wherein a cemented surface of the first optical element and the second optical element is convex toward the enlargement side.
Assuming that the Abbe number for the d line of the first optical element is dA and the Abbe number for the d line of the second optical element is BB,
AA <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 or 6, wherein the following condition is satisfied.
The optical system according to any one of claims 1 to 7, wherein the light reflected by the reflection surface is totally reflected by the transmission / reflection surface.
The optical system according to any one of claims 1 to 7, wherein the transmission and reflection surface includes a transmission and reflection film.
10. The optical system according to any one of claims 1 to 9, wherein the transmission / reflection surface and the optical surface closest to the transmission / reflection surface on the optical path are opposed to each other via air. system.
The radius of curvature of the transmission / reflection surface and the radius of curvature of the optical surface closest to the transmission / reflection surface in the optical path are the same as one another. Optical system.
The optical system according to any one of claims 1 to 11, wherein the aperture of the aperture stop is a reflective surface.
An imaging device for imaging an object, and an optical system for imaging the object on an imaging surface of the imaging device, the optical system being the optical system according to any one of claims 1 to 12. An imaging device characterized by
The imaging device according to claim 13, wherein the imaging surface is a flat surface.
An imaging device for acquiring image data of an object, and a distance calculation unit for acquiring distance information to the object based on the image data, wherein the imaging device is the imaging device according to claim 13 or 14 An in-vehicle camera system characterized by
The on-vehicle camera system according to claim 15, further comprising: a collision determination unit that determines a collision possibility between the host vehicle and the object based on the distance information.
17. The control device according to claim 16, further comprising: a control device that outputs a control signal that causes each wheel of the host vehicle to generate a braking force when it is determined that there is a collision possibility between the host vehicle and the object. In-vehicle camera system as described.
18. The on-vehicle according to claim 16, further comprising: an alarm device that issues an alarm to a driver of the host vehicle when it is determined that there is a collision possibility between the host vehicle and the object. Camera system.
A display device for displaying an image, and an optical system for forming an image on a display surface of the display device, the optical system being an optical system according to any one of claims 1 to 12. Projection device.