Optical system and imaging apparatus including the same

Abstract

To provide an optical system capable of suppressing the occurrence of ghost light while maintaining excellent imaging performance.SOLUTION: An optical system (100) comprises a front group (G101), an aperture stop (STO), and a rear group (G102) having positive refractive power. The front group includes a first lens (L101) having negative refractive power, a second lens (L102) having negative refractive power, and a third lens (L103). The third lens is a plano-convex lens, a plano-concave lens, or a meniscus lens. When the focal length of the optical system is f, a half angle of view is θ, a projective characteristic representing a relationship between the half angle of view θ and an image height y is y(θ), a maximum half angle of view is θmax, and curvature radii of the object side surface and the image side surface of the third lens are RG3R1 and RG3R2 respectively, conditional expressions 1.0<f×sin(θmax) / y(θmax)≤1.9, -0.57≤f / RG3R1<0.00, and -0.47≤f / RG3R2<0.00 are satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical system, and is suitable for imaging devices such as digital still cameras, digital video cameras, in-vehicle cameras, mobile phone cameras, surveillance cameras, wearable cameras, medical cameras, and the like.

Background Art

[0002] Patent Document 1 discloses a wide-angle optical system for an in-vehicle camera. Patent Document 2 discloses an optical system in which the object side surface of the second lens has a convex shape and has an inflection point in the radial cross section in order to combine the characteristics of a telephoto lens and a wide-angle lens.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the optical system disclosed in Patent Document 1, means for reducing ghosts caused by unnecessary light (ghost light) reflected on each lens surface reaching the imaging element is not considered. In the optical system disclosed in Patent Document 2, since the radius of curvature of the object side surface of the third lens is relatively large, the astigmatism difference is large and good imaging performance cannot be obtained.

[0005] An object of the present invention is to provide an optical system capable of suppressing the generation of ghost light while maintaining good imaging performance.

Means for Solving the Problems

[0006] As one aspect of the present invention, an optical system is composed of a front group, an aperture stop, and a rear group with positive refractive power, which are arranged in order from the object side to the image side. The front group has a first lens with negative refractive power, a second lens with negative refractive power, and a third lens, which are arranged in order from the object side to the image side. The third lens is a plano-convex lens with a flat object side and a convex image side, a plano-concave lens with a concave object side and a flat image side, or a meniscus lens with a concave object side and a convex image side. Let the focal length of the optical system be f, the semi-field angle of the optical system be θ, the projection characteristic representing the relationship between the semi-field angle θ and the image height y be y(θ), and the maximum semi-field angle of the optical system be θ max , the radius of curvature of the object side surface of the third lens be R G3R1 , and the radius of curvature of the image side surface of the third lens be R G3R2 . When this is the case, 1.0 < f×sin(θ max ) / y(θ max ) ≤ 1.9 -0.57 ≤ f / R G3R1 < 0.00 -0.47 ≤ f / R G3R2 < 0.00 The conditional expression is satisfied.

[0007] Other objects and features of the present invention will be described in the following examples.

Effects of the Invention

[0008] According to the present invention, it is possible to provide an optical system that can suppress the generation of ghost light while maintaining good imaging performance.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, desirable 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 one for convenience. Also, in each drawing, the same members are given the same reference numerals, and duplicate explanations are omitted.

[0011] FIG. 1 is a cross-sectional view including the optical axis OA of the optical system 100 in the present embodiment. In FIG. 1, the left side is the object side (front side), and the right side is the image side (rear side). The optical system 100 of the present embodiment is an imaging optical system used for an imaging device. The imaging surface of the imaging element is arranged at the position of the image plane IMG. The IRCF arranged on the object side of the image plane IMG is an infrared light cut filter, and the CG is a cover glass. These optical elements do not contribute to the imaging of the optical system 100. Note that the optical system 100 of the present embodiment may be used as a projection optical system in a projection device such as a projector. In this case, the display surface of a display element such as a liquid crystal panel is arranged at the position of the image plane IMG.

[0012] Next, the characteristics of the optical system 100 in the present embodiment will be described. The optical system 100 in the present embodiment is composed of a front group G101 with a positive refractive power, an aperture stop STO, and a rear group G102 with a positive refractive power, which are arranged in order from the object side to the image side. Here, it is considered that the infrared light cut filter IRCF and the cover glass CG are not included in the optical system 100.

[0013] The front group G101 includes a first lens L101 with negative refractive power, a second lens L102 with negative refractive power, a third lens L103, and a fourth lens L104 with positive refractive power, which are arranged in order from the object side to the image side. The third lens L103 may be any one of a plano-convex lens with a flat object side and a convex image side, a plano-concave lens with a concave object side and a flat image side, or a meniscus lens with a concave object side and a convex image side.

[0014] The rear group G102 includes a fifth lens L105 with positive refractive power, a sixth lens L106 with negative refractive power, and a seventh lens L107 with positive refractive power arranged closest to the image side, which are arranged in order from the object side to the image side. The fifth lens L105 and the sixth lens L106 are cemented lenses joined to each other. Here, the lens refers to an optical element having refractive power, and optical elements such as parallel plate glass without refractive power are not included.

[0015] In the optical system 100 of the present embodiment, both the front group G101 and the rear group G102 have positive refractive power, and by configuring the front group G101 as described above, the overall length of the optical system 100 is shortened while achieving a wide angle of view. Also, by configuring the rear group G102 as described above, it is possible to satisfactorily correct the field curvature and longitudinal chromatic aberration that occur due to the wide angle of view of the optical system 100.

[0016] In the present embodiment, let the focal length of the optical system (entire system) be f, the half angle of view of the optical system be θ [deg.], the projection characteristic representing the relationship between the half angle of view θ and the image height y be y(θ), and the maximum half angle of view of the optical system be θ max When this is the case, the following conditional expression (1) is satisfied.

[0017] 1.0 < f × sin(θ max ) / y(θ max ) ≤ 1.9 (1) Although details will be described later, by configuring the optical system so as to satisfy the conditional expression (1), it is possible to increase the resolution of the subject image at the angle of view near the optical axis OA while having a wide angle of view.

[0018] Preferably, the numerical range of conditional expression (1) is set as in the following conditional expression (1a): More preferably, the numerical range of conditional expression (1) is set as in the following conditional expression (1b):

[0019] 1.0 <f×sin(θ max ) / y(θ max )≦1.7 (1a) 1.0 <f×sin(θ max ) / y(θ max )≦1.4 (1b) Moreover, it is preferable that the optical system in this embodiment satisfies the following conditional expression (2).

[0020] 0.65 <y(θ max / 2) / y(θ max )<0.85 (2) Condition (2) satisfies the maximum half angle of view θ max Image height y(θ max ) and maximum half angle of view θ max Half the angle of view θ max Image height y(θ max / 2). By satisfying conditional expression (2), it is possible to improve the resolution of subject images in the angle of view near the optical axis OA while maintaining a wide angle of view.

[0021] More preferably, the numerical range of conditional formula (2) is set as in the following conditional formula (2a): Even more preferably, the numerical range of conditional formula (2) is set as in the following conditional formula (2b):

[0022] 0.65 <y(θ max / 2) / y(θ max )<0.83 (2a) 0.65 <y(θ max / 2) / y(θ max )<0.81 (2b) Here, the radius of curvature of the object side surface of the third lens L103 is R G3R1 , the radius of curvature of the image side surface of the third lens L103 is R G3R2、The sign of the radius of curvature of the surface convex on the object side is defined as positive. At this time, the optical system of this embodiment satisfies both of the following conditional expressions (3) and (4).

[0023] -0.57 ≦ f / R G3R1 <0.00 (3) -0.47 ≦ f / R G3R2 <0.00 (4) Although details will be described later, by determining the radius of curvature of the object-side surface of the third lens L103 so as to satisfy the conditional expression (3), it is possible to reduce the light intensity of ghost light that is reflected from the object-side surface of the third lens L103 and the image-side surface of the second lens L102 and reaches the image plane IMG. Further, by determining the radius of curvature of the object-side surface of the third lens L103 so as to satisfy the conditional expression (4), it is possible to reduce the astigmatism difference.

[0024] Preferably, the numerical ranges of the conditional expressions (3) and (4) are set as the following conditional expressions (3a) and (4a), respectively.

[0025] -0.57 ≦ f / R G3R1 ≦ -0.10 (3a) -0.42 ≦ f / R G3R2 <0.00 (4a) More preferably, the numerical ranges of the conditional expressions (3) and (4) are set as the following conditional expressions (3b) and (4b), respectively.

[0026] -0.57 ≦ f / R G3R1 ≦ -0.10 (3b) -0.37 ≦ f / R G3R2 <0.00 (4b) The optical system according to this embodiment can achieve the effects of the present invention as long as it satisfies at least the above-described configuration. For example, the front group G101 may have a configuration having lenses other than the first lens L101 to the fourth lens L104 (a configuration having five or more lenses). However, in order to miniaturize the optical system (the entire system), it is preferable that the front group G101 is composed of four lenses. Regarding the third lens L103, since the absolute value of the power (refractive power) is small as described later, whether to have a positive refractive power or a negative refractive power can be determined according to the specifications of each optical system.

[0027] In addition, in an imaging device such as an in-vehicle camera described later, not only a wide angle of view but also an increase in the imaging magnification in the vicinity of the optical axis (central region) is required. For example, when the imaging device is disposed at the rear of a moving device (vehicle), an image corresponding to the central region, which is the main attention region, is enlarged and displayed on an electronic rearview mirror, and an entire image including regions other than the central region (peripheral regions) is displayed on an in-vehicle display. Therefore, it is preferable to make the imaging magnification (focal length) of the optical system different between the central region and other regions.

[0028] Therefore, the object side surface of the second lens L102 is preferably an aspherical surface. According to this configuration, among the light fluxes from the first lens L101, light rays from the peripheral portion in the radial direction can be greatly refracted toward the optical axis OA by the object side surface of the second lens L102. Thereby, it becomes easy to make the imaging magnification different between the central region and the peripheral region of the optical system. At this time, the object side surface of the second lens L102 is preferably an aspherical surface having an inflection point in a cross section including the optical axis OA. Thereby, while reducing the number of lenses constituting the optical system, it is possible to easily achieve a wide angle of view and an increase in the imaging magnification in the central region.

[0029] In the optical system according to this embodiment, it is preferable that the third lens L103 has a negative power. Further, it is preferable to satisfy the following conditional expression (5).

[0030] 1.0≦(R G3R2 +RG3R1 ) / (R G3R2 -R G3R1 )≦5.1 (5) More preferably, the numerical range of conditional expression (5) is set as the following conditional expression (5a). Even more preferably, the numerical range of conditional expression (5) is set as the following conditional expression (5b).

[0031] 1.0≦(R G3R2 +R G3R1 ) / (R G3R2 -R G3R1 )≦4.1 (5a) 1.0≦(R G3R2 +R G3R1 ) / (R G3R2 -R G3R1 )≦3.1 (5b) Also, in this embodiment, when the focal length of the third lens L103 is f G3 , it is preferable to satisfy the following conditional expression (6).

[0032] -11<f G3 / f<0 (6) More preferably, the numerical range of conditional expression (6) is set as the following conditional expression (6a). Even more preferably, the numerical range of conditional expression (6) is set as the following conditional expression (6b).

[0033] -10<f G3 / f<-1 (6a) -9<f G3 / f<-2 (6b) Also, in order to improve the imaging performance of the optical system, it is preferable to arrange an auxiliary diaphragm between the third lens L103 and the fourth lens L104, that is, the front group G101 has an auxiliary diaphragm arranged between the third lens L103 and the fourth lens L104. Any auxiliary diaphragm may be used as long as it blocks or reduces the light incident outside the effective diameter of the auxiliary diaphragm among the light beams emitted from the third lens L103. Specifically, a light-shielding sheet or plate having a circular opening, a mechanical diaphragm (aperture diaphragm), etc. can be considered.

[0034] In addition, in an imaging device such as an in-vehicle camera described later, in order to prevent the lens from being damaged by a stone or the like hitting the first lens L101 which is the frontmost surface of the optical system, it is preferable that the center thickness (thickness on the optical axis) of the first lens L101 is thick to a certain extent. Specifically, the thickness on the optical axis of the first lens L101 is d G1 , the effective radius of the first lens L101 is y effG1 When, it is preferable to satisfy the following conditional expression (7).

[0035] 0.16 < d G1 / y effG1 (7) More preferably, the numerical range of the conditional expression (7) is set as the following conditional expression (7a). Even more preferably, the numerical range of the conditional expression (7) is set as the following conditional expression (7b).

[0036] 0.18 < d G1 / y effG1 (7a) 0.20 < d G1 / y effG1 (7b) Hereinafter, the detailed configuration of the optical system in each embodiment will be described.

Example

[0037] FIG. 1 is a cross-sectional view including the optical axis OA of the optical system 100 in the first embodiment. The optical system 100 is composed of a first lens L101, a second lens L102, a third lens L103, a fourth lens L104, an aperture stop STO, a fifth lens L105, a sixth lens L106, and a seventh lens L107 arranged in order from the object side to the image side. The front group G101 has the first lens L101, the second lens L102, the third lens L103, and the fourth lens L104. The rear group G102 has the fifth lens L105, the sixth lens L106, and the seventh lens L107.

[0038] FIG. 2 shows the aspherical shape of the object side surface of the second lens L102 in this embodiment. In FIG. 2, the horizontal axis represents the position in the radial direction in the cross section including the optical axis OA of the object side surface of the second lens L102, and the vertical axis represents the curvature [1 / mm] of the object side surface of the second lens L102. That is, FIG. 2 shows a graph plotting the curvature for each position of the object side surface of the second lens L102. Note that the numerical values on the horizontal axis indicate the distance (normalized distance) from the optical axis OA to each position within the effective radius of the object side surface of the second lens L102 when normalized such that the distance from the optical axis OA to the position of the effective radius (maximum effective radius) is 1.

[0039] The object side surface of the second lens L102 is preferably an aspherical surface such that the graph representing the curvature with respect to the distance from the optical axis OA shown in FIG. 2 has a plurality of extreme values. As shown in FIG. 2, the graph in this embodiment has a first extreme value (maximum value) and a second extreme value (minimum value). Thereby, the difference in imaging magnification between the central region and the peripheral region of the optical system can be made prominent. Specifically, since the imaging magnification of the central region can be made larger with respect to the peripheral region, the visibility of the image for the user of the imaging device can be improved.

[0040] Also, on the optical axis OA, it is preferable that the first lens L101 and the second lens L102 are meniscus lenses (negative meniscus lenses) convex toward the object side, and the object side surface of the third lens L103 is concave toward the object side. Also, on the optical axis OA, it is preferable that the fourth lens L104 is a biconvex lens. By adopting such a configuration, the incident angle of each ray with respect to the rear group G102 can be reduced, and changes in optical performance due to arrangement errors (manufacturing errors) of each lens can be suppressed.

[0041] As described above, since the optical performance can be improved by using the second lens L102 as an aspherical lens, it is preferable that each lens is a lens made of a resin material (resin lens). Here, the resin material refers to a material mainly composed of resin (plastic), and includes not only those made of only resin but also those containing a small amount of substances other than resin (impurities). By configuring each lens with a resin material, the molding of the aspherical surface can be facilitated compared to the case of using a glass material, and the manufacturing cost can be reduced.

[0042] However, compared with a glass lens made of a general glass material, the temperature coefficient of the refractive index of a resin lens is large. Therefore, when only the second lens L102 having a strong negative power is a resin lens, it may not be possible to completely cancel out the focus shift caused by temperature changes in each lens. Therefore, in order to suppress the focus shift caused by temperature changes, it is desirable that the third lens L103 is also a resin lens.

[0043] FIG. 3 is an optical path diagram of ghost light in which light incident on the optical system 100 of the present embodiment at an angle of 45° is reflected by the object side surface of the third lens L103 and the image side surface of the second lens L102 and reaches the image plane IMG. FIG. 27 is an optical path diagram of ghost light as a comparative example.

[0044] FIG. 4 is the light intensity distribution at the image plane IMG in the present embodiment. FIG. 28 is the light intensity distribution at the image plane IMG as a comparative example. As can be seen by comparing FIG. 28 and FIG. 4, by determining the radius of curvature of the object side surface of the third lens L103 so as to satisfy the conditional expression (3), the light intensity of the ghost light at the image plane IMG can be sufficiently reduced.

[0045] FIG. 5 is a longitudinal aberration diagram of the optical system 100 of this embodiment. The longitudinal aberration diagram of FIG. 4 shows spherical aberration, field curvature (astigmatism), and distortion in order from the left. In the longitudinal aberration diagram of FIG. 4, the aberrations related to 656.3 nm (C line), 587.6 nm (d line), 486.1 nm (F line), and 435.8 nm (g line) are shown by different lines respectively. This is the same in the subsequent embodiments. As can be seen from FIG. 5, the astigmatic difference is sufficiently reduced.

[0046] Numerical Example 1 shows specific numerical values of the optical system 100 of this embodiment. Table 1 shows the numerical values of each conditional expression. The auxiliary diaphragms in this embodiment are the 7th surface and the 11th surface. The 11th surface is also the object side surface of the 5th lens L105. The auxiliary diaphragm of the 11th surface has the role of defining the effective radius of the object side surface of the 5th lens L105. The optical system 100 of this embodiment satisfies the conditional expressions (1) to (7).

[0047] With the above configuration, the optical system 100 of this embodiment can reduce the influence of ghost light while maintaining good imaging performance.

Embodiment

[0048] FIG. 6 is a cross-sectional view including the optical axis OA of the optical system 200 in this embodiment. The optical system 200 is composed of a 1st lens L201, a 2nd lens L202, a 3rd lens L203, a 4th lens L204, an aperture stop STO, a 5th lens L205, a 6th lens L206, and a 7th lens L207 arranged in order from the object side to the image side. The front group G201 has the 1st lens L201, the 2nd lens L202, the 3rd lens L203, and the 4th lens L204. The rear group G202 has the 5th lens L205, the 6th lens L206, and the 7th lens L207.

[0049] FIG. 7 shows the aspherical shape of the object side surface of the 2nd lens L202 in this embodiment. As shown in FIG. 7, the graph in this embodiment has a 1st extreme value (maximum value) and a 2nd extreme value (minimum value).

[0050] FIG. 8 is an optical path diagram of ghost light in which light incident on the optical system 200 of this embodiment at an angle of 45° is reflected by the object side surface of the third lens L203 and the image side surface of the second lens L202 and reaches the image plane IMG.

[0051] FIG. 9 is the light intensity distribution at the image plane IMG in this embodiment. As can be seen by comparing FIG. 28 and FIG. 9, by determining the radius of curvature of the object side surface of the third lens L203 so as to satisfy the conditional expression (3), the light intensity of the ghost light at the image plane IMG can be sufficiently reduced.

[0052] FIG. 10 is a longitudinal aberration diagram of the optical system 200 of this embodiment. As can be seen from FIG. 10, the astigmatic difference is sufficiently reduced.

[0053] Numerical Example 2 shows specific numerical values of the optical system 200 of this embodiment. Table 1 shows the numerical values of each conditional expression. The auxiliary aperture in this embodiment is the seventh surface. The optical system 200 of this embodiment satisfies the conditional expressions (1) to (7).

[0054] With the above configuration, the optical system 200 of this embodiment can reduce the influence of ghost light while maintaining good imaging performance.

Embodiment

[0055] FIG. 11 is a cross-sectional view including the optical axis OA of the optical system 300 in this embodiment. The optical system 300 is composed of a first lens L301, a second lens L302, a third lens L303, a fourth lens L304, an aperture stop STO, a fifth lens L305, a sixth lens L306, and a seventh lens L307, which are arranged in order from the object side to the image side. The front group G301 includes the first lens L301, the second lens L302, the third lens L303, and the fourth lens L304. The rear group G302 includes the fifth lens L305, the sixth lens L306, and the seventh lens L307.

[0056] FIG. 12 shows the aspherical shape of the object side surface of the second lens L302 in this embodiment. As shown in FIG. 12, the graph in this embodiment has a first extreme value (maximum value) and a second extreme value (minimum value).

[0057] FIG. 13 is an optical path diagram of ghost light in which light incident on the optical system 300 of this embodiment at an angle of 45° is reflected by the object side surface of the third lens L303 and the image side surface of the second lens L302 and reaches the image plane IMG.

[0058] FIG. 14 shows the light intensity distribution at the image plane IMG in this embodiment. As can be seen by comparing FIG. 28 and FIG. 14, by determining the radius of curvature of the object side surface of the third lens L303 so as to satisfy the conditional expression (3), the light intensity of the ghost light at the image plane IMG can be sufficiently reduced.

[0059] FIG. 15 is a longitudinal aberration diagram of the optical system 300 of this embodiment. As can be seen from FIG. 15, the astigmatic difference is sufficiently reduced.

[0060] Numerical Example 3 shows specific numerical values of the optical system 300 of this embodiment. Table 1 shows the numerical values of each conditional expression. The auxiliary diaphragms in this embodiment are the seventh surface and the eleventh surface. The eleventh surface is also the object side surface of the fifth lens L305. The auxiliary diaphragm of the eleventh surface serves to define the effective radius of the object side surface of the fifth lens L305. The optical system 300 of this embodiment satisfies the conditional expressions (1) to (7).

[0061] With the above configuration, the optical system 300 of this embodiment can reduce the influence of ghost light while maintaining good imaging performance.

Embodiment

[0062] FIG. 16 is a cross-sectional view including the optical axis OA of the optical system in the present embodiment. The optical system 400 is composed of a first lens L401, a second lens L402, a third lens L403, a fourth lens L404, an aperture stop STO, a fifth lens L405, a sixth lens L406, and a seventh lens L407, which are arranged in order from the object side to the image side. The front group G401 has the first lens L401, the second lens L402, the third lens L403, and the fourth lens L404. The rear group G402 has the fifth lens L405, the sixth lens L406, and the seventh lens L407.

[0063] FIG. 17 shows the aspherical shape of the object side surface of the second lens L402 in the present embodiment. As shown in FIG. 17, the graph in the present embodiment has a first extreme value (maximum value) and a second extreme value (minimum value).

[0064] FIG. 18 is an optical path diagram of ghost light in which light incident on the optical system 400 of the present embodiment at an angle of 45° is reflected by the object side surface of the third lens L403 and the image side surface of the second lens L402 and reaches the image plane IMG.

[0065] FIG. 19 is the light intensity distribution at the image plane IMG in the present embodiment. As can be seen by comparing FIG. 28 and FIG. 19, by determining the radius of curvature of the object side surface of the third lens L403 so as to satisfy the conditional expression (3), the light intensity of the ghost light at the image plane IMG can be sufficiently reduced.

[0066] FIG. 20 is a longitudinal aberration diagram of the optical system 400 of the present embodiment. As can be seen from FIG. 20, the astigmatism difference is sufficiently reduced.

[0067] Numerical Example 4 shows specific numerical values of the optical system 400 of the present embodiment. Table 1 shows the numerical values of each conditional expression. The auxiliary stops in the present embodiment are the 7th surface and the 11th surface. The 11th surface is also the object side surface of the fifth lens L405. The auxiliary stop of the 11th surface serves to define the effective radius of the object side surface of the fifth lens L405. The optical system 400 of the present embodiment satisfies the conditional expressions (1) to (7).

[0068] With the above configuration, the optical system 400 of this embodiment can reduce the influence of ghost light while maintaining good imaging performance.

[0069] Numerical Examples 1 to 5 corresponding to Examples 1 to 5 are shown below. In each numerical example, the surface number is the order of each optical surface when counted from the object surface. r [mm] represents the radius of curvature of the i-th optical surface, and d [mm] represents the distance (distance on the optical axis) between the i-th optical surface and the (i + 1)-th optical surface. n d is the refractive index for the d-line of the medium between the i-th surface and the (i + 1)-th surface, and ν d represents the Abbe number based on the d-line of the medium. Note that the Abbe number ν d is defined by the following formula (8) when the refractive indices for the F-line, d-line, and C-line are n F , n d , n C respectively. ν d =(n d -1) / (n F -n C ) (8) For aspherical surfaces, an asterisk (*) symbol is attached after the surface number. Also, "E±P" in each numerical value means "×10 ±P ". The shape of each aspherical surface is represented by the following formula when the displacement amount from the vertex of the surface in the optical axis direction is z, the height from the optical axis OA in the direction perpendicular to the optical axis direction is h, the curvature (reciprocal of the radius of curvature r) is c, the conic coefficient is k, and the aspherical coefficients are A, B, C, D, E, F, G, H, I···.

[0070]

Number

[0071] Note that the optical system in each numerical example is a single - focus optical system with a constant focal length (no zooming) and is configured not to perform focusing. That is, the distance between each lens constituting the optical system is always fixed. This can avoid fluctuations in optical performance due to the movement of each lens. However, if necessary, the optical system may be configured to perform at least one of zooming and focusing, and for this purpose, the distance between each lens may be configured to change.

[0072] [Numerical Example 1] Surface data Surface number r d n d ν d y 1 31.50 2.00 1.703 52.4 7.16 2 11.57 0.20 4.73 3* 4.72 1.91 1.583 59.5 4.12 4* 2.11 2.34 2.43 5 -8.21 1.00 1.518 58.9 2.17 6 ∞ 1.02 1.94 7 ∞ 0.00 1.65 8 9.65 1.91 1.693 50.8 1.61 9 -7.77 0.20 1.53 10(STO) ∞ 1.78 1.46 11 9.53 3.77 1.595 67.7 1.70 12 -3.51 0.60 1.847 23.8 2.34 13 -9.76 2.25 2.68 14* 9.93 3.63 1.583 59.5 3.73 15* 131.94 0.63 4.17 16 ∞ 0.40 1.56 56.0 4.06 17 ∞ 0.41 4.03 18 ∞ 0.50 1.507 63.0 3.98 19 ∞ 0.44 3.94 20 ∞ 0.00 3.90 Surface numbers 3 4 14 15 K -3.344E+00 -9.029E-01 -6.353E+00 -1.000E+01 A 4.307E-03 7.273E-03 1.753E-03 1.162E-02 B -3.984E-04 1.167E-03 -5.067E-04 -2.825E-03 C -4.790E-05 -2.262E-03 4.900E-05 2.684E-04 D 8.900E-06 8.540E-04 -1.200E-06 -1.300E-05 E -6.000E-07 -1.549E-04 -1.000E-07 3.000E-07 F 0.000E+00 1.380E-05 0.000E+00 0.000E+00 G 0.000E+00 -5.000E-07 0.000E+00 0.000E+00 H 0.000E+00 0.000E+00 0.000E+00 0.000E+00 I 0.000E+00 0.000E+00 0.000E+00 0.000E+00 [Numerical Example 2] Surface data Surface number r d n d ν d y 1 18.03 1.50 1.703 52.4 6.19 2 7.79 0.88 4.08 3* 4.24 1.42 1.583 59.5 3.07 4* 1.54 1.64 1.70 5 -7.75 1.09 1.516 64.1 1.54 6 -19.45 0.20 1.33 7 ∞ 0.20 1.25 8 7.92 2.44 1.571 53.0 1.26 9 -4.04 0.23 1.21 10(STO) ∞ 1.21 1.13 11 6.22 2.76 1.595 67.7 1.82 12 -2.84 1.00 1.847 23.8 2.04 13 -11.40 0.85 2.43 14* 14.43 2.30 1.583 59.5 2.76 15* -19.28 0.81 3.03 16 ∞ 0.40 1.560 56.0 2.90 17 ∞ 0.54 2.88 18 ∞ 0.40 1.507 63.0 2.83 19 ∞ 0.15 2.81 20 ∞ 0.00 2.80 Plane numbers 3 4 14 15 K -9.810E-01 -5.569E-01 1.017E+01 8.579E+00 A 5.509E-03 5.102E-03 3.598E-03 1.793E-02 B -2.341E-03 3.624E-02 -2.653E-03 -7.402E-03 C 4.717E-04 -8.428E-02 4.411E-04 1.015E-03 D -1.731E-04 1.052E-01 -3.770E-05 -6.710E-05 E 3.350E-05 -8.485E-02 1.400E-06 1.800E-06 F -3.000E-06 4.262E-02 0.000E+00 0.000E+00 G 1.000E-07 -1.277E-02 0.000E+00 0.000E+00 H 0.000E+00 2.088E-03 0.000E+00 0.000E+00 I 0.000E+00 -1.433E-04 0.000E+00 0.000E+00 [Numerical Example 3] Surface data Surface number r d n d ν d y 1 32.73 2.00 1.703 52.4 7.31 2 11.74 0.20 4.85 3* 4.72 2.04 1.583 59.5 4.25 4* 2.10 2.39 2.49 5 -9.65 1.00 1.518 58.9 2.22 6 ∞ 1.11 1.98 7 ∞ 0.00 1.64 8 9.68 1.83 1.693 50.8 1.60 9 -8.14 0.20 1.51 10(STO) ∞ 1.84 1.43 11 10.33 3.77 1.595 67.7 1.75 12 -3.51 0.60 1.847 23.8 2.39 13 -9.37 2.46 2.75 14* 8.15 3.05 1.583 59.5 3.99 15* 36.91 0.76 4.23 16 ∞ 0.40 1.560 56.0 4.11 17 ∞ 0.41 4.08 18 ∞ 0.50 1.507 63.0 4.02 19 ∞ 0.44 3.97 20 ∞ 0.00 3.91 Surface numbers 3 4 14 15 K -5.204E+00 -9.213E-01 -1.680E+00 -2.424E-02 A 6.534E-03 8.326E-03 2.579E-03 1.453E-02 B -6.258E-04 2.445E-04 -8.349E-04 -3.612E-03 C -2.830E-05 -1.795E-03 1.168E-04 4.065E-04 D 7.300E-06 6.727E-04 -9.200E-06 -2.570E-05 E -5.000E-07 -1.153E-04 4.000E-07 9.000E-07 F 0.000E+00 9.600E-06 0.000E+00 0.000E+00 G 0.000E+00 -3.000E-07 0.000E+00 0.000E+00 H 0.000E+00 0.000E+00 0.000E+00 0.000E+00 I 0.000E+00 0.000E+00 0.000E+00 0.000E+00 [Numerical Example 4] Surface Data Surface Number r d n d ν d y 1 24.58 2.00 1.703 52.4 6.27 2 12.49 0.53 4.58 3* 4.70 1.71 1.583 59.5 3.78 4* 1.93 2.58 2.35 5 -9.99 2.56 1.516 64.1 2.09 6 -31.40 0.24 1.74 7 ∞ 0.00 1.68 8 10.14 1.33 1.571 53.0 1.65 9 -6.46 0.20 1.55 10(STO) ∞ 1.97 1.44 11 9.45 3.49 1.595 67.7 2.00 12 -3.59 0.60 1.847 23.8 2.39 13 -9.49 2.24 2.68 14* 13.97 3.21 1.583 59.5 3.32 15* -53.98 0.60 3.68 16 ∞ 0.40 1.560 56.0 3.60 17 ∞ 0.41 3.58 18 ∞ 0.50 1.507 63.0 3.55 19 ∞ 0.44 3.52 20 ∞ 0.00 3.49 Surface numbers 3 4 14 15 K -1.725E+00 -6.459E-01 4.786E+00 1.225E+00 A 3.967E-03 9.029E-03 1.811E-03 1.750E-02 B -8.968E-04 -3.458E-03 -1.088E-03 -4.574E-03 C 5.270E-05 -3.614E-04 1.817E-04 5.902E-04 D -2.800E-06 3.358E-04 -1.840E-05 -4.960E-05 E 2.000E-07 -8.610E-05 1.000E-06 2.600E-06 F 0.000E+00 1.030E-05 0.000E+00 -1.000E-07 G 0.000E+00 -5.000E-07 0.000E+00 0.000E+00 H 0.000E+00 0.000E+00 0.000E+00 0.000E+00 I 0.000E+00 0.000E+00 0.000E+00 0.000E+00

[0073]

Table 1

[0074] [Imaging device] FIG. 21 is a schematic diagram of the main part of the imaging device 20 according to an embodiment of the present invention. The imaging device 20 in this embodiment includes the optical system (imaging optical system) 100 in the above-described embodiment, an imaging element (light receiving element) 21 that photoelectrically converts an image of an object formed by the optical system 100, and an imaging unit (camera body) 22 that holds the imaging element 21. The optical system 100 is held by a lens barrel (holding member) and is connected to the imaging unit 22. A display unit 28 that displays an image acquired by the imaging element 21 may be connected to the imaging unit 22. As the imaging element 21, an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor can be used.

[0075] When the imaging device 20 is used as a distance measuring device, for example, an imaging surface phase difference sensor having pixels capable of splitting a light beam from an object into two and performing photoelectric conversion can be adopted as the imaging element 21. When the subject is on the front focal plane of the optical system 100, there is no displacement in the images corresponding to the two split light beams on the image plane of the optical system 100. However, when the subject is at a position other than the front focal plane of the optical system 100, displacement occurs in each image. At this time, since the displacement of each image corresponds to the amount of displacement from the front focal plane of the subject, the distance to the subject can be measured by using the imaging surface phase difference sensor to acquire the amount and direction of displacement of each image.

[0076] Note that the optical system 100 and the imaging unit 22 may be configured to be detachable from each other. That is, the optical system 100 and the lens barrel may be configured as an interchangeable lens (lens device). Further, the optical system in the above-described embodiment is not limited to imaging devices such as digital still cameras, silver halide film cameras, video cameras, in-vehicle cameras, and surveillance cameras, and can be applied to various optical devices such as telescopes, binoculars, projectors (projection devices), and digital copiers. [In-vehicle system] FIG. 22(A) is a schematic diagram of the mobile device 10 and the imaging device 20 (in-vehicle camera) held by it in an embodiment of the present invention. In FIG. 22(A), the case where the mobile device 10 is an automobile (vehicle) is shown. The mobile device 10 includes an in-vehicle system (driving support device) (not shown) for assisting the user 40 (such as a driver or a passenger) of the mobile device 10 using the image acquired by the imaging device 20. In this embodiment, the case where the imaging device 20 is installed so as to image the rear of the mobile device 10 is shown, but the imaging device 20 may be installed so as to image the front or side of the mobile device 10. Further, two or more imaging devices 20 may be installed at two or more locations of the mobile device 10.

[0077] The imaging device 20 has the optical system 100 and the imaging unit 22 in any of the above-described embodiments. The optical system 100 is an optical system (variable angle-of-view lens) having different imaging magnifications for the first angle of view (first field of view) 30 and the second angle of view (second field of view) 31 larger than the first angle of view 30. The imaging surface (light-receiving surface) of the imaging element 21 includes a first region for imaging an object included in the first angle of view 30 and a second region for imaging an object included in the second angle of view 31. At this time, the number of pixels per unit angle of view in the first region is larger than the number of pixels per unit angle of view in the second region excluding the first region. In other words, the resolution in the first angle of view (first region) of the imaging device 20 is higher than the resolution in the second angle of view (second region).

[0078] Hereinafter, the optical characteristics of the optical system 100 will be described in detail. The left diagram in FIG. 22(B) shows the image height y [mm] at each half angle of view θ [deg.] on the imaging surface of the imaging element 21 in a contour line. The right diagram in FIG. 22(B) shows, in a graph, the relationship (projection characteristics of the optical system 100) between each half angle of view θ and the image height y in the first quadrant of the left diagram.

[0079] As shown in FIG. 22(B), the optical system 100 is configured such that the projection characteristics y(θ) are different for an angle of view less than a predetermined half angle θa and an angle of view greater than or equal to the half angle θa. Therefore, the increase amount (resolution) of the image height y with respect to the half angle θ per unit also differs for each angle of view. The local resolution of the optical system 100 is represented by the differential value dy(θ) / dθ with respect to the half angle θ of the projection characteristics y(θ). In the left diagram of FIG. 22(B), it shows that the higher the resolution, the larger the interval between the contour lines of the image height y for each half angle θ. Also, in the right diagram of FIG. 22(B), it shows that the higher the resolution, the larger the slope of the graph of the projection characteristics y(θ).

[0080] In the left diagram of FIG. 22(B), the first region 20a, which is the central region, corresponds to an angle of view less than the half angle θa, and the second region 20b, which is the peripheral region, corresponds to an angle of view greater than or equal to the half angle θa. The angle of view less than the half angle θa corresponds to the first angle of view 30 in FIG. 22(A), and the combined angle of view of the angle of view less than the half angle θa and the angle of view greater than or equal to the half angle θa corresponds to the second angle of view 31 in FIG. 22(A). As described above, the first region 20a is a region of high resolution and low distortion, and the second region 20b is a region of low resolution and high distortion. The half angle θa is preferably 13.5° or more and 31.5° or less, and more desirably 14.4° or more and 22.5° or less.

[0081] Also, the optical system 100 is configured such that the projection characteristics y(θ) in the first region 20a are different from f×θ (equidistant projection method), and are also different from the projection characteristics in the second region 20b. At this time, it is desirable that the projection characteristics y(θ) of the optical system 100 satisfy the conditional expression (1).

[0082] By satisfying conditional expression (1) and reducing the resolution in the second region 20b, it is possible to achieve a wide-angle conversion of the optical system 100. Furthermore, in the first region 20a, the resolution can be made higher than that of the central region of a general fisheye lens that adopts the orthographic projection method (y(θ) = f×sinθ). If it is below the lower limit of conditional expression (1), compared with the orthographic projection fisheye lens, the resolution in the first region 20a becomes low, or the maximum image height becomes large, leading to an increase in the size of the optical system, which is not preferable. If it exceeds the upper limit of conditional expression (1), the resolution in the first region 20a becomes too high, making it difficult to achieve a wide-angle equivalent to that of the orthographic projection fisheye lens, or it becomes impossible to maintain good optical performance, which is not preferable. Also, it is more desirable for the optical system 100 to satisfy conditional expression (2).

[0083] As described above, since the distortion is small and the resolution is high in the first region 20a, a high-definition image can be obtained compared with the second region 20b. Therefore, good visibility can be obtained by setting the first region 20a (the first angle of view 30) as the area of interest for the user 40. For example, when the imaging device 20 is arranged at the rear part of the moving device 10 as shown in Fig. 22(A), by displaying the image corresponding to the first angle of view 30 on the electronic rearview mirror, a natural sense of perspective can be obtained when the user 40 gazes at a vehicle behind. On the other hand, for the second region 20b (the second angle of view 31), it corresponds to a wide angle including the first angle of view 30. Therefore, for example, when the moving device 10 is traveling in reverse, by displaying the image corresponding to the second angle of view 31 on the in-vehicle display, driving support for the user 40 can be provided.

[0084] FIG. 23 is a functional block diagram for explaining a configuration example of the in-vehicle system 2 in the present embodiment. The in-vehicle system 2 is a system for displaying an image obtained by an imaging device 20 installed behind the moving device 10 to the user 40. The in-vehicle system 2 includes an imaging device 20, a processing device 220, and a display device (display unit) 230. The imaging device 20 has the optical system 100 and the imaging element 21 as described above. The imaging element 21 includes an imaging element such as a CCD sensor or a CMOS sensor, generates imaging data by photoelectrically converting the optical image formed by the optical system 100, and outputs it to the processing device 220.

[0085] The processing device 220 includes an image processing unit 221, a rear vehicle distance detection unit 222, a display angle determination unit 223, a reverse gear detection unit 224, a user setting change unit 225, and a display angle change unit 226. The processing device 220 is a computer such as a CPU (Central Processing Unit) microcomputer, for example, and functions as a control unit that controls the operations of each component based on a computer program. At least one component in the processing device 220 may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or a PLA (Programmable Logic Array).

[0086] The image processing unit 221 generates image data by performing image processing such as WDR (Wide Dynamic Range) correction, gamma correction, LUT (Look Up Table) processing, and distortion correction on the imaging data acquired from the imaging element 21. Note that the distortion correction is performed on at least the imaging data corresponding to the second region 20b. As a result, when the image is displayed on the display device 230, it becomes easier for the user 40 to visually recognize it, and the detection rate of the rear vehicle in the rear vehicle distance detection unit 222 is improved. Note that the distortion correction may not be performed on the imaging data corresponding to the first region 201a. The image processing unit 221 outputs the image data generated by executing the above-described image processing to the rear vehicle distance detection unit 222 and the display angle change unit 226.

[0087] The rear vehicle distance detection unit 222 uses the image data output from the image processing unit 221 to obtain information on the distance to a rear vehicle included in the image data corresponding to a range that does not include the first viewing angle 30 in the second viewing angle 31. The rear vehicle distance detection unit 222 corresponds to the distance information calculation unit 25 described above. For example, the rear vehicle distance detection unit 222 can detect a rear vehicle based on the image data corresponding to the second region 20b in the image data, and calculate the distance to the host vehicle from changes in the position and size of the detected rear vehicle. The rear vehicle distance detection unit 222 outputs the calculated distance information to the display viewing angle determination unit 223.

[0088] Furthermore, the rear vehicle distance detection unit 222 may determine the vehicle type of the rear vehicle based on data regarding feature information such as the shape and color for each vehicle type, which is output as a result of machine learning (deep learning) based on images of a large number of vehicles. At this time, the rear vehicle distance detection unit 222 may output information regarding the vehicle type of the rear vehicle to the display viewing angle determination unit 223. The reverse gear detection unit 224 detects whether the transmission of the moving device 10 (host vehicle) is in the reverse gear, and outputs the detection result to the display viewing angle determination unit 223.

[0089] The display angle determination unit 223 determines whether to set the viewing angle (display viewing angle) of the image to be displayed on the display device 230 to the first viewing angle 30 or the second viewing angle 31 based on the output from at least one of the rear vehicle distance detection unit 222 or the reverse gear detection unit 224. Then, the display viewing angle determination unit 223 outputs to the display viewing angle change unit 226 according to the determination result. For example, when the value of the distance in the distance information is equal to or less than a certain threshold value (for example, 3 m), the display viewing angle determination unit 223 can determine to set the display viewing angle to the second viewing angle 31, and when it is greater than the threshold value, it can determine to set the display viewing angle to the first viewing angle 30. Alternatively, when the display viewing angle determination unit 223 receives a notification from the reverse gear detection unit 224 that the transmission of the moving device 10 has entered the reverse gear, it can determine to set the display viewing angle to the second viewing angle 31. Also, when the transmission of the moving device 10 has not entered the reverse gear, the display viewing angle determination unit 223 can determine to set the display viewing angle to the first viewing angle 30.

[0090] Furthermore, when the transmission of the moving device 10 has entered the reverse gear, the display viewing angle determination unit 223 can determine to set the display viewing angle to the second viewing angle 31 regardless of the result of the rear vehicle distance detection unit 222. Also, when the transmission of the moving device 10 has not entered the reverse gear, the display viewing angle determination unit 223 can determine to determine the display viewing angle according to the detection result of the rear vehicle distance detection unit 222. Note that the display viewing angle determination unit 223 may change the determination criterion for viewing angle change according to the vehicle type of the moving device 10 by receiving vehicle type information from the rear vehicle distance detection unit 222. For example, when the moving device 10 is a large vehicle such as a truck, since the braking distance is longer than that of a normal vehicle, it is desirable to set the aforementioned threshold value longer than that of a normal vehicle (for example, 10 m).

[0091] The user setting change unit 225 is for allowing the user 40 to change the determination criterion for whether to change the display viewing angle to the second viewing angle 31 by the display viewing angle determination unit 223. The determination criterion set (changed) by the user 40 is input from the user setting change unit 225 to the display viewing angle determination unit 223.

[0092] The display angle change unit 226 generates a display image to be displayed on the display device 230 according to the determination result in the display angle determination unit 223. For example, when it is determined that the first display angle is 30°, the display angle change unit 226 cuts out a rectangular included angle image (the first image) from the image data corresponding to the first display angle 30° and outputs it to the display device 230. Also, when there is a rear vehicle that satisfies a predetermined condition in the image data corresponding to the second display angle 31°, the display angle change unit 226 outputs an image (the second image) including the rear vehicle to the display device 230. Note that the second image may include an image corresponding to the first region 20a. The display angle change unit 226 functions as a display control unit that performs display control to switch between a first display state in which the display device 230 displays the first image and a second display state in which the display device 230 displays the second image.

[0093] The cutting out of the image by the display angle change unit 226 is executed by storing the image data output from the image processing unit 221 in a storage unit (memory) such as a RAM and then reading out the image to be cut out therefrom. Note that the region corresponding to the first image in the image data is a rectangular region at the first display angle 30° corresponding to the first region 20a. Also, the region corresponding to the second image in the image data is a rectangular region including the rear vehicle at the second display angle 31° corresponding to the second region 20b.

[0094] The display device 230 has a display unit such as a liquid crystal display or an organic EL, and displays the display image output from the display angle change unit 226. For example, the display device 230 has a first display unit as an electronic rearview mirror disposed above the windshield (front glass) of the mobile device 10, and a second display unit as an operation panel (monitor) disposed below the windshield of the mobile device 10. According to this configuration, the first image and the second image generated from the above-described image data can be respectively displayed on the first display unit and the second display unit. The first display unit may be configured to be usable as a mirror when not used as a display, for example, by including a half mirror or the like. The second display unit may also serve as a display of a navigation system or an audio system, for example.

[0095] FIG. 24 shows the configuration of an imaging device (in-vehicle camera) 20 using the optical system of each of the above-described embodiments as an imaging optical system and an in-vehicle system (driving support device) 600 including the same. The in-vehicle system 600 is a system held by a movable body (mobile device) such as an automobile (vehicle) and assisting the driving (operation) of the vehicle based on the image information around the vehicle acquired by the imaging device 20.

[0096] FIG. 25 shows a vehicle 700 as a mobile device including the in-vehicle system 600. In FIG. 25, a case where the imaging range 70 of the imaging device 20 is set in front of the vehicle 700 is shown, but the imaging range 70 may be set behind or on the side of the vehicle 700. As shown in FIG. 25, the in-vehicle system 600 includes an imaging device 20, a vehicle information acquisition device 27, a control device (control unit, ECU: electronic control unit) 50, and a warning device (warning unit) 60. The imaging device 20 includes an imaging unit 22, an image processing unit 23, a parallax calculation unit 24, a distance information calculation unit 25, and a collision determination unit 26. The image processing unit 23, the parallax calculation unit 24, the distance information calculation unit 25, and the collision determination unit 26 constitute a processing unit. The imaging unit 22 has the optical system and the imaging element of each of the above-described embodiments.

[0097] The flowchart of FIG. 26 shows an operation example of the in-vehicle system 600. In step S1, the imaging unit 22 is used to image objects (subjects) such as obstacles and pedestrians around the vehicle, and a plurality of image data (parallax image data) are acquired.

[0098] In step S2, vehicle information is acquired by the vehicle information acquisition device 27. The vehicle information includes information such as the vehicle speed, yaw rate, and steering angle of the vehicle.

[0099] In step S3, image processing is performed on the plurality of image data acquired by the imaging unit 22 by the image processing unit 23. Specifically, image feature analysis is performed to analyze feature amounts such as the amount and direction of edges and density values in the 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.

[0100] In step S4, the parallax (image displacement) information between the plurality of image data acquired by the imaging unit 22 is calculated by the parallax calculation unit 24. As a method for calculating the parallax information, known methods such as the SSDA method and the area correlation method can be used, so the description is omitted here. Note that steps S2, S3, and S4 may be performed in the above order, or may be processed in parallel with each other.

[0101] In step S5, the distance information between the object imaged by the imaging unit 22 is acquired (calculated) by the distance information calculation unit 25. The distance information can be calculated based on the parallax information calculated by the parallax calculation unit 24 and the internal and external parameters of the imaging unit 22. Here, the distance information refers to information regarding the relative position of the object, such as the distance to the object, the defocus amount, and the image displacement amount, and may directly represent the distance value of the object in the image or may indirectly represent information corresponding to the distance value.

[0102] Then, in step S6, the collision determination unit 26 determines whether or not the distance to the object is within a preset distance range using the vehicle information acquired by the vehicle information acquisition device 27 and the distance information calculated by the distance information calculation unit 25. Thereby, it can be determined whether or not an object exists within the preset distance around the vehicle, and the possibility of collision between the vehicle and the object can be determined. When an object exists within the preset distance, in step S7, the collision determination unit 26 determines that "there is a possibility of collision". When no object exists within the preset distance, in step S8, the collision determination unit 26 determines that "there is no possibility of collision".

[0103] Next, when the collision determination unit 26 determines that "there is a possibility of collision", it notifies (transmits) the determination result to the control device 50 and the warning device 60. At this time, in step S7, the control device 50 controls the vehicle based on the determination result of the collision determination unit 26. Also in step S7, the warning device 60 warns the user (driver, passenger) of the vehicle based on the determination result of the collision determination unit 26. Note that the notification of the determination result may be made to at least one of the control device 50 and the warning device 60.

[0104] The control device 50 can control the movement of the vehicle by outputting a control signal to the drive unit (engine, motor, etc.) of the vehicle. For example, control such as applying brakes to the vehicle, returning the accelerator, turning the steering wheel, generating a braking force on each wheel, and suppressing the output of the engine or motor by generating a control signal is performed. Also, the warning device 60 warns the user, for example, by emitting a warning sound (alarm), displaying warning information on the screen of a car navigation system, or vibrating the seat belt or steering wheel.

[0105] According to the in-vehicle system 600 described above, by the above processing, it is possible to effectively detect an object and avoid a collision between the vehicle and the object. In particular, by applying the optical systems of the above-described respective embodiments to the in-vehicle system 600, while miniaturizing the entire imaging device 20 and increasing the degree of freedom of arrangement, it becomes possible to detect an object and perform collision determination over a wide angle of view.

[0106] Regarding the calculation of distance information, various methods can be adopted. As an example, in the case where a pupil division type imaging element having a plurality of pixel portions regularly arranged in a two-dimensional array is adopted as the imaging element of the imaging element 21, it will be described. In a pupil division type imaging element, one pixel portion is composed of a microlens and a plurality of photoelectric conversion portions, receives a pair of light beams passing through different regions in the pupil of the optical system, and can output paired image data from each photoelectric conversion portion.

[0107] Then, the amount of image displacement of each region is calculated by performing a correlation operation between the paired image data, and the image displacement map data representing the distribution of the amount of image displacement is calculated by the distance information calculation unit 25. Alternatively, the distance information calculation unit 25 may further convert the amount of image displacement 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 information calculation unit 25 may acquire distance map data of the distance to the object converted from the defocus amount.

[0108] Further, the in-vehicle system 600 and the mobile device 700 may include a notification device (notification unit) for notifying the manufacturer of the in-vehicle system (manufacturer), the dealer of the mobile device (dealer), etc. in the event that the mobile device 700 collides with an obstacle. For example, as the notification device, one that transmits information regarding the collision between the mobile device 700 and the obstacle (collision information) to a preset external notification destination by e-mail or the like can be adopted.

[0109] By adopting such a configuration that the collision information is automatically notified by the notification device, it is possible to promptly take measures such as inspection and repair after a collision occurs. Note that the notification destination of the collision information may be an insurance company, a medical institution, the police, etc., or any arbitrary one set by the user. Also, not limited to the collision information, the notification device may be configured to notify the notification destination of the failure information of each part and the consumption information of consumables. Regarding the detection of the presence or absence of a collision, it may be performed using the distance information acquired based on the output from the imaging unit 22 described above, or may be performed by another detection unit (sensor).

[0110] Although the application of the in-vehicle system 600 to driving support (collision damage reduction) has been described, it is not limited to this, and the in-vehicle system 600 may be applied to cruise control (including the full vehicle speed following function) or automatic driving, etc. Also, the in-vehicle system 600 is not limited to vehicles such as automobiles, and can be applied to moving bodies such as ships, airplanes, and industrial robots, for example. Further, not limited to moving bodies, it can be applied to various devices that utilize object recognition such as the intelligent transport system (ITS). [Modification Example] As described above, the desirable embodiments and examples of the present invention have been explained, but the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist thereof.

[0111] For example, the optical systems in the above-described respective embodiments are assumed to be used in the visible range and are configured to perform good aberration correction over the entire visible range, but the wavelength range for performing aberration correction may be changed as necessary. For example, each optical system may be configured to perform aberration correction only in a specific wavelength range in the visible range, or may be configured to perform aberration correction in the wavelength range of the infrared region outside the visible range.

[0112] In the in-vehicle system 600 described above, a distance measuring device as described above may be adopted as the imaging device 20. At this time, the in-vehicle system 600 may include a determination unit that determines the possibility of collision with the object based on the distance information to the object acquired by the imaging device 20. Further, a stereo camera including a plurality of imaging units 22 may be adopted as the imaging device 20. In this case, even without using an imaging surface phase difference sensor, image data can be simultaneously acquired by each of the synchronized imaging elements, and the same processing as described above can be performed by using the two image data. However, if the difference in imaging time by each imaging element is known, it is not necessary to synchronize each imaging element.

[0113] The disclosure of each embodiment includes the following configurations and methods. (Configuration 1) An optical system composed of a front group, an aperture stop, and a rear group with a positive refractive power, arranged in order from the object side to the image side, The front group has a first lens with a negative refractive power, a second lens with a negative refractive power, and a third lens, arranged in order from the object side to the image side, The third lens is a plano-convex lens with a flat object side surface and a convex image side surface, a plano-concave lens with a concave object side surface and a flat image side surface, or a meniscus lens with a concave object side surface and a convex image side surface, Let the focal length of the optical system be f, the semi-field angle of the optical system be θ, the projection characteristic representing the relationship between the semi-field angle θ and the image height y be y(θ), and the maximum semi-field angle of the optical system be θ max Let the radius of curvature of the object side surface of the third lens be R G3R1 Let the radius of curvature of the image side surface of the third lens be R G3R2 When this is the case, 1.0 < f × sin(θ max ) / y(θ max ) ≤ 1.9 -0.57 ≤ f / R G3R1 < 0.00 -0.47 ≤ f / R G3R2 < 0.00 An optical system characterized by satisfying the conditional expression. (Configuration 2) 0.65 < y(θmax / 2) / y(θ max ) < 0.85 The optical system according to Configuration 1, characterized by satisfying the conditional expression (Configuration 3) The optical system according to Configuration 1 or 2, characterized in that the object side surface of the second lens has an inflection point in a cross-section including the optical axis. (Configuration 4) The optical system according to any one of Configurations 1 to 3, characterized in that the third lens has a negative refractive power. (Configuration 5) 1.0 ≦ (R G3R2 +R G3R1 ) / (R G3R2 -R G3R1 ) ≦ 5.1 The optical system according to Configuration 4, characterized by satisfying the conditional expression (Configuration 6) When the focal length of the third lens is f G3 then, -11 < f G3 / f < 0 The optical system according to Configuration 4 or 5, characterized by satisfying the conditional expression (Configuration 7) The optical system according to any one of Configurations 1 to 6, characterized in that the front group further has a fourth lens with a positive refractive power arranged on the image side of the third lens. (Configuration 8) The optical system according to Configuration 7, characterized in that the front group further has an auxiliary diaphragm arranged between the third lens and the fourth lens. (Configuration 9) The optical system according to any one of Configurations 1 to 8, characterized in that the rear group has, in order from the object side to the image side, a fifth lens with a positive refractive power, a sixth lens with a negative refractive power, and a seventh lens with a positive refractive power. (Configuration 10) The optical system according to Configuration 9, characterized in that the front group is composed of four lenses and the rear group is composed of three lenses. (Configuration 11) The optical system according to Configuration 9 or 10, wherein the fifth lens and the sixth lens are joined lenses joined to each other. (Configuration 12) When the thickness of the first lens on the optical axis is d G1 and the effective radius of the first lens is y effG1 then 0.16 < d G1 / y effG1 The optical system according to any one of Configurations 1 to 11, which satisfies the conditional expression. (Configuration 13) The optical system according to any one of Configurations 1 to 12, wherein the object side surface of the second lens is an aspherical surface. (Configuration 14) The optical system according to Configuration 13, wherein the aspherical surface has an inflection point in a cross section including the optical axis. (Configuration 15) The optical system according to Configuration 13 or 14, wherein a graph representing the curvature with respect to the radial position in a cross section including the optical axis of the aspherical surface has a first extreme value and a second extreme value. (Configuration 16) An imaging device comprising the optical system according to any one of Configurations 1 to 15 and an imaging element that images an object through the optical system. (Configuration 17) An in-vehicle system comprising the imaging device according to Configuration 16 and a display device that displays an image obtained based on the output of the imaging device. (Configuration 18) The in-vehicle system according to Configuration 17, wherein the display device has a first display unit that displays a first image corresponding to a first viewing angle and a second display unit that displays a second image corresponding to a second viewing angle including the first viewing angle among the images. (Configuration 19) A mobile device comprising the imaging device according to Configuration 16 and being movable while holding the imaging device. (Configuration 20) A distance measuring device comprising the imaging device according to Configuration 16 and a distance information calculation unit that calculates distance information based on an image signal from the imaging element. (Configuration 21) A moving device having the distance measuring device according to Configuration 20 and being movable while holding the imaging device.

Explanation of Signs

[0114] 100 Optical system G101 Front group G102 Rear group L101 First lens L102 Second lens L103 Third lens STO Aperture stop

Claims

1. An optical system composed of a front group, an aperture stop, and a rear group with positive refractive power, arranged in order from the object side to the image side, The front group has a first lens with negative refractive power, a second lens with negative refractive power, and a third lens, arranged in order from the object side to the image side, The third lens is a plano-convex lens with a flat object side and a convex image side, a plano-concave lens with a concave object side and a flat image side, or a meniscus lens with a concave object side and a convex image side, Let the focal length of the optical system be f, the semi-field angle of the optical system be θ, the projection characteristic representing the relationship between the semi-field angle θ and the image height y be y(θ), the maximum semi-field angle of the optical system be θ ｍａｘ , the radius of curvature of the object side surface of the third lens be R Ｇ３Ｒ１ , the radius of curvature of the image side surface of the third lens be R Ｇ３Ｒ２ When doing so, 1.0 < f × sin(θ ｍａｘ ) / y(θ ｍａｘ ) ≤ 1.9 -0.57 ≤ f / R Ｇ３Ｒ１ < 0.00 -0.47 ≤ f / R Ｇ３Ｒ２ < 0.00 An optical system characterized by satisfying the conditional expressions.

2. 0.65 < y(θ ｍａｘ / 2) / y(θ ｍａｘ ) < 0.85 The optical system according to Claim 1, characterized by satisfying the conditional expressions.

3. The optical system according to Claim 1, characterized in that the object side surface of the second lens has an inflection point in a cross-section including the optical axis.

4. The optical system according to Claim 1, characterized in that the third lens has negative refractive power.

5. 1.0 ≤ (R Ｇ３Ｒ２ + R Ｇ３Ｒ１ ) / (R Ｇ３Ｒ２ - R Ｇ３Ｒ１ ) ≤ 5.1 The optical system according to claim 4, characterized in that it satisfies the following conditional expression.

6. When the focal length of the third lens is f Ｇ３ then -11 < f Ｇ３ / f < 0 The optical system according to claim 4, characterized in that it satisfies the following conditional expression.

7. The front group further has a fourth lens with a positive refractive power disposed on the image side of the third lens, the optical system according to claim 1.

8. The front group further has an auxiliary diaphragm disposed between the third lens and the fourth lens, the optical system according to claim 7.

9. The rear group has, in order from the object side to the image side, a fifth lens with a positive refractive power, a sixth lens with a negative refractive power, and a seventh lens with a positive refractive power, the optical system according to any one of claims 1 to 8.

10. The front group is composed of four lenses, and the rear group is composed of three lenses, the optical system according to claim 9.

11. The fifth lens and the sixth lens are cemented lenses cemented to each other, the optical system according to claim 9.

12. When the thickness of the first lens on the optical axis is d Ｇ１ and the effective radius of the first lens is y ｅｆｆＧ１ then 0.16 < d Ｇ１ / y ｅｆｆＧ１ The optical system according to any one of claims 1 to 8, characterized in that it satisfies the following conditional expression.

13. The object side surface of the second lens is an aspherical surface, the optical system according to any one of claims 1 to 8.

14. The aspherical surface has an inflection point in a cross section including the optical axis, and the optical system according to claim 13 is characterized in that.

15. The graph representing the curvature with respect to the position in the radial direction in the cross section including the optical axis of the aspherical surface has a first extreme value and a second extreme value, and the optical system according to claim 13 is characterized in that.

16. An imaging device comprising the optical system according to any one of claims 1 to 8 and an imaging element that images an object through the optical system.

17. An in-vehicle system comprising the imaging device according to claim 16 and a display device that displays an image obtained based on the output of the imaging device.

18. The display device has a first display unit that displays a first image corresponding to a first angle of view among the images, and a second display unit that displays a second image corresponding to a second angle of view including the first angle of view, and the in-vehicle system according to claim 17 is characterized in that.

19. A moving device comprising the imaging device according to claim 16 and being movable while holding the imaging device.

20. A distance measuring device comprising the imaging device according to claim 16 and a distance information calculation unit that calculates distance information based on an image signal from the imaging element.

21. A moving device having the distance measuring device according to claim 20 and being movable while holding the imaging device.

Images