Optical system and imaging apparatus

Abstract

To provide an optical system which is capable of capturing images in both a visible light region and a near-infrared light region with a wide angle of view and maintains optical characteristics resistant to changes caused by ambient temperature variations, and an imaging apparatus equipped with the optical system.SOLUTION: An optical system 4 comprises, in order along an optical axis P from an object B side toward an image plane S side: a front lens group FL having negative refractive power, a stop 90 in which an aperture is formed, and a rear lens group RL having positive refractive power and including apochromatic lenses or achromatic lenses (apochromatic lenses) 40, 50, 60. The total number of lenses included in the front lens group FL and the rear lens group RL is seven. An effective radius r1 of a first lens 10 is 3.75 mm or less. A distance along the optical axis P from a vertex 11 of the first lens 10 to the image plane S is 16 mm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical system and an imaging device.

Background Art

[0002] In recent years, in order to improve the safety and comfort of automobiles, there has been an increasing demand for a driver monitoring system (DMS) that monitors the driver's state (such as signs of decreased attention or drowsiness) and an occupant monitoring system (OMS) that monitors the state of the entire passenger compartment. Conventionally, in such systems, an optical system in which all lenses are composed of glass lenses has been used in consideration of resistance to ambient temperature changes (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when all lenses are configured with glass lenses in this way, there is a problem that the entire optical system becomes large. Further, in such an optical system, it is required to be able to take pictures with a wide angle of view in both the visible light region and the near-infrared light region.

[0005] The present invention has been made in view of such problems of the prior art, and an object thereof is to provide an optical system that has a wide angle of view and can take pictures in both the visible light region and the near-infrared light region, and whose optical characteristics hardly change with respect to ambient temperature changes, and an imaging device including such an optical system.

Means for Solving the Problems

[0006] According to the first aspect of the present invention, there is provided an optical system that can capture images in both the visible light region and the near-infrared light region while having a wide angle of view, and whose optical characteristics are less likely to change with respect to ambient temperature changes. This optical system includes a front lens group having a negative refractive power and including a first lens, an aperture with an opening formed therein, and a rear lens group including an apochromatic lens or an achromatic lens and having a positive refractive power, which are arranged in order from the object side toward the image plane side along the optical axis. The total number of lenses included in the front lens group and the lenses included in the rear lens group is seven. The effective radius r1 of the first lens is 3.75 mm or less. The distance TTL along the optical axis from the vertex of the first lens to the image plane is 16 mm or less.

[0007] According to the second aspect of the present invention, there is provided an imaging device including the above-described optical system and an imaging element disposed on the image plane.

Effects of the Invention

[0008] According to the present invention, an optical system can be obtained that can capture images in both the visible light region and the near-infrared light region while having a wide angle of view, and whose optical characteristics are less likely to change with respect to ambient temperature changes.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the optical system and the imaging device according to the present invention will be described in detail with reference to FIGS. 1 and 2. In FIGS. 1 and 2, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. Also, in FIGS. 1 and 2, the scales and dimensions of each component may be exaggerated or some components may be omitted. In the following description, unless otherwise specified, terms such as "first" and "second" are used only to distinguish components from each other and do not represent a specific order or sequence.

[0011] FIG. 1 is a schematic diagram showing the configuration of an imaging device 1 according to a first embodiment of the present invention. As shown in FIG. 1, the imaging device 1 includes a casing 2, a base plate 3, an optical system 4 housed between the casing 2 and the base plate 3, and an imaging element 5 disposed on the base plate 3. The imaging element 5 is disposed on the image plane S of the optical system 4. In this specification, the object (subject) B side along the optical axis P is defined as "front", and the image plane S side is defined as "rear".

[0012] The optical system 4 includes a front lens group FL having a negative refractive power, a rear lens group RL having a positive refractive power, a diaphragm 90 disposed between the front lens group FL and the rear lens group RL, and a sensor protection glass 82 disposed between the rear lens group RL and the imaging element 5. An aperture is formed in the diaphragm 90. The front lens group FL in the present embodiment is composed of a first lens 10 having a negative refractive power and a second lens 20 having a positive refractive power, and the rear lens group RL is composed of a third lens 30 having a positive refractive power, a fourth lens 40 having a positive refractive power, a fifth lens 50 having a negative refractive power, a sixth lens 60 having a positive refractive power, and a seventh lens 70 having a positive refractive power. Thus, the optical system 4 of the present embodiment is composed of seven lenses. The first lens 10, the second lens 20, the diaphragm 90, the third lens 30, the fourth lens 40, the fifth lens 50, the sixth lens 60, the seventh lens 70, and the sensor protection glass 82 are arranged in order from the object B side toward the image plane S side along the optical axis P.

[0013] The first lens 10 has a convex front lens surface 10F on the object B side and a concave rear lens surface 10R on the image plane S side. The first lens 10 is formed of resin (plastic), and the front lens surface 20F and the rear lens surface 20R of the second lens 20 are aspherical. If the effective radius of the first lens 10 is r1, r1 ≦ 3.75 mm ···(1) and if the distance along the optical axis P from the vertex 11 of the first lens 10 to the image plane S (the overall lens length) is TTL, TTL ≦ 16 mm ···(2) That is.

[0014] The second lens 20 has a concave front lens surface 20F on the object B side and a convex rear lens surface 20R on the image plane S side. The second lens 20 is formed of resin (plastic), and the front lens surface 20F and the rear lens surface 20R of the second lens 20 are aspherical.

[0015] The third lens 30 has a concave front lens surface 30F on the object B side and a convex rear lens surface 30R on the image plane S side. The third lens 30 is formed of glass.

[0016] The fourth lens 40 has a convex front lens surface 40F on the object B side and a convex rear lens surface 40R on the image plane S side. The fourth lens 40 is formed of glass. It is preferable that the Abbe number of the fourth lens 40 is high.

[0017] The fifth lens 50 is formed of resin (plastic), and the front lens surface 50F and the rear lens surface 50R of the fifth lens 50 are aspherical. The fifth lens 50 has a concave front lens surface 50F on the object B side and a concave rear lens surface 50R on the image plane S side.

[0018] The sixth lens 60 is formed of resin (plastic), and the front lens surface 60F and the rear lens surface 60R of the sixth lens 60 are aspherical. The sixth lens 60 has a convex front lens surface 60F on the object B side and a convex rear lens surface 60R on the image plane S side.

[0019] The seventh lens 70 is formed of resin (plastic), and the front lens surface 70F and the rear lens surface 70R of the seventh lens 70 are aspherical surfaces. The seventh lens 70 has a front lens surface 70F convex toward the object B side and a rear lens surface 70R convex toward the image plane S side.

[0020] In this embodiment, the fourth lens 40 which is a biconvex lens with a high Abbe number, the fifth lens 50 which is a biconcave lens, and the sixth lens 60 which is a biconvex lens are arranged close to each other in the optical axis direction, constituting an apochromatic lens. Chromatic aberration in the visible light region and the near-infrared light region is corrected by this apochromatic lens.

[0021] In order to enable wide-angle shooting, the distance from the vertex 11 of the first lens 10 to the aperture 90 is t1, the focal length of the first lens 10 is f1, the combined focal length of the front lens group FL is f F , the combined focal length of the rear lens group RL is f R , the combined focal length from the fourth lens 40 to the sixth lens 60 is f 456 , the combined focal length from the first lens 10 to the seventh lens 70 is f 1234567 Then, it is preferable to satisfy the following formulas (3) to (8). 1.3 < t1 / r1 < 1.5 ···(3) 4.1 < TTL / r1 < 4.4 ···(4) 1.3 < |f1 / r1| < 1.8 ···(5) 2 < |f F / f R | < 5 ···(6) 1.5mm < f 1234567 < 2.5mm ···(7) 3 < f 456 < 6 ···(8)

[0022] With the above configuration, an optical system 4 is realized which can perform shooting in both the visible light region and the near-infrared light region while having a wide angle, and whose optical characteristics hardly change with respect to ambient temperature changes.

[0023] FIG. 2 is a schematic diagram showing the configuration of the imaging device 101 in the second embodiment of the present invention. The optical system 104 in the present embodiment includes, similar to the optical system 4 in the first embodiment, a front lens group FL having a negative refractive power, a rear lens group RL having a positive refractive power, a diaphragm 90 disposed between the front lens group FL and the rear lens group RL, and two sensor protection glasses 82 and 84 disposed between the rear lens group RL and the imaging element 5.

[0024] The front lens group FL in the present embodiment is composed of a first lens 110 having a negative refractive power, a second lens 120 having a negative refractive power, and a third lens 130 having a positive refractive power. The rear lens group RL is composed of a fourth lens 140 having a positive refractive power, a fifth lens 150 having a negative refractive power, a sixth lens 160 having a positive refractive power, and a seventh lens 170 having a negative refractive power. Thus, the optical system 104 of the present embodiment is also composed of seven lenses. The first lens 110, the second lens 120, the third lens 130, the diaphragm 90, the fourth lens 140, the fifth lens 150, the sixth lens 160, the seventh lens 170, the sensor protection glass 82, and the sensor protection glass 84 are arranged in order from the object B side to the image plane S side along the optical axis P.

[0025] The first lens 110 has a front lens surface 110F convex toward the object B side and a rear lens surface 110R concave toward the image plane S side. The first lens 110 is formed of glass. If the effective radius of the first lens 110 is r1, r1 ≦ 3.75 mm ···(9) and if the distance along the optical axis P from the vertex 111 of the first lens 110 to the image plane S (the overall lens length) is TTL, TTL ≦ 16 mm ···(10) is satisfied.

[0026] The second lens 120 has a front lens surface 120F that is concave on the object B side and a rear lens surface 120R that is convex on the image plane S side. The second lens 120 is formed of resin (plastic), and the front lens surface 120F and the rear lens surface 120R of the second lens 120 are aspherical surfaces.

[0027] The third lens 130 has a front lens surface 130F that is convex on the object B side and a rear lens surface 130R that is convex on the image plane S side. The third lens 130 is formed of resin (plastic), and the front lens surface 130F and the rear lens surface 130R of the third lens 130 are aspherical surfaces.

[0028] The fourth lens 140 has a front lens surface 140F that is convex on the object B side and a rear lens surface 140R that is convex on the image plane S side. The fourth lens 140 is formed of glass. It is preferable that the Abbe number of the fourth lens 140 is high.

[0029] The fifth lens 150 is formed of resin (plastic), and the front lens surface 150F and the rear lens surface 150R of the fifth lens 150 are aspherical surfaces. The fifth lens 150 has a front lens surface 150F that is concave on the object B side and a rear lens surface 150R that is concave on the image plane S side.

[0030] The sixth lens 160 is formed of resin (plastic), and the front lens surface 160F and the rear lens surface 160R of the sixth lens 160 are aspherical surfaces. The sixth lens 160 has a front lens surface 160F that is convex on the object B side and a rear lens surface 160R that is convex on the image plane S side.

[0031] The seventh lens 170 is formed of resin (plastic), and the front lens surface 170F and the rear lens surface 170R of the seventh lens 170 are aspherical surfaces. The seventh lens 170 has a front lens surface 170F that is concave on the object B side and a rear lens surface 170R that is convex on the image plane S side.

[0032] In this embodiment, a fifth lens 150 which is a biconcave lens and a sixth lens 160 which is a biconvex lens are arranged close to each other in the optical axis direction, constituting an achromatic lens. Chromatic aberration in the visible light region and the near-infrared light region is corrected by this achromatic lens.

[0033] In order to enable wide-angle shooting, the distance from the vertex 111 of the first lens 110 to the aperture 90 is t1, the focal length of the first lens 110 is f1, the combined focal length of the front lens group FL is f F and the combined focal length of the rear lens group RL is f R and the combined focal length from the fourth lens 140 to the sixth lens 160 is f 456 and the combined focal length from the first lens 110 to the seventh lens 170 is f 1234567 Then, similar to the first embodiment, it is preferable to satisfy the following formulas (11) to (16). 1.3 < t1 / r1 < 1.5 ···(11) 4.1 < TTL / r1 < 4.4 ···(12) 1.3 < |f1 / r1| < 1.8 ···(13) 2 < |f F / f R | < 5 ···(14) 2.0mm < f 1234567 < 4.0mm ···(15) 3 < f 456 < 6 ···(16)

[0034] With the above configuration, an optical system 104 is realized which can shoot in both the visible light region and the near-infrared light region while having a wide angle, and whose optical characteristics are less likely to change with respect to ambient temperature changes.

[0035] When the lens surfaces of the lenses described above are configured as aspherical surfaces, the profile of this aspherical surface is represented by the following formula (17).

Equation

Example

[0036] As a first embodiment of the present invention, the imaging device 1 of the above-described embodiment was configured by an optical system having the following parameters, and its characteristics were analyzed. <Radius of curvature of the lens surface on the optical axis P> Front lens surface 10F of the first lens 10: 41.326 mm (aspherical surface) Rear lens surface 10R of the first lens 10: 2.490 mm (aspherical surface) Front lens surface 20F of the second lens 20: -3.738 mm (aspherical surface) Rear lens surface 20R of the second lens 20: -3.367 mm (aspherical surface) Front lens surface 30F of the third lens 30: -4.098 mm Rear lens surface 30R of the third lens 30: -3.202 mm Front lens surface 40F of the fourth lens 40: 9.203 mm Rear lens surface 40R of the fourth lens 40: -2.807 mm Front lens surface 50F of the fifth lens 50: -5.468 mm (aspherical surface) Rear lens surface 50R of the fifth lens 50: 2.898 mm (aspherical surface) Front lens surface 60F of the sixth lens 60: 3.815 mm (aspherical surface) Rear lens surface 60R of the sixth lens 60: -2.929 mm (aspherical surface) Front lens surface 70F of the seventh lens 70: 22.605 mm (aspherical surface) Rear lens surface 70R of the seventh lens 70: -84.556 mm (aspherical surface)

[0037] <Thickness or interval on the optical axis P> Thickness D1 of the first lens 10 = 0.60 mm Interval D between the first lens 10 and the second lens 2012 = 1.87 mm The thickness D2 of the second lens 20 = 2.32 mm The distance D between the second lens 20 and the aperture 90 2P = 0.19 mm The distance D between the aperture 90 and the third lens 30 P3 = 0.31 mm The thickness D3 of the third lens 30 = 1.25 mm The distance D between the third lens 30 and the fourth lens 40 34 = 0.05 mm The thickness D4 of the fourth lens 40 = 2.50 mm The distance D between the fourth lens 40 and the fifth lens 50 45 = 0.05 mm The thickness D5 of the fifth lens 50 = 0.50 mm The distance D between the fifth lens 50 and the sixth lens 60 56 = 0.05 mm The thickness D6 of the sixth lens 60 = 2.54 mm The distance D between the sixth lens 60 and the seventh lens 70 67 = 0.05 mm The thickness D7 of the seventh lens 70 = 0.90 mm The distance D between the seventh lens 70 and the sensor protection glass 82 7G = 2.00 mm The thickness D of the sensor protection glass 82 G = 0.30 mm The distance D between the sensor protection glass 82 and the image plane S GS = 0.10 mm

[0038] <Refractive index for d-line> The refractive index N of the first lens 10 d1 = 1.544 The refractive index N of the second lens 20 d2 = 1.636 The refractive index N of the third lens 30 d3 = 1.834 The refractive index N of the fourth lens 40 d4 = 1.438 The refractive index N of the fifth lens 50 d5 = 1.636 The refractive index N of the sixth lens 60 d6=1.544 Refractive index N of the 7th lens 70 d7 =1.544 Refractive index N of the sensor protection glass 82 dG =1.517

[0039] <Abbe number> Abbe number ν1 of the 1st lens 10 = 55.9 Abbe number ν2 of the 2nd lens 20 = 24.0 Abbe number ν3 of the 3rd lens 30 = 37.2 Abbe number ν4 of the 4th lens 40 = 94.5 Abbe number ν5 of the 5th lens 50 = 24.0 Abbe number ν6 of the 6th lens 60 = 55.9 Abbe number ν7 of the 7th lens 70 = 55.9 Abbe number ν of the sensor protection glass 82 G =64.2

[0040] <Focal length> Focal length f1 of the 1st lens 10 = -4.898 mm Focal length f2 of the 2nd lens 20 = 15.550 mm Focal length f3 of the 3rd lens 30 = 10.753 mm Focal length f4 of the 4th lens 40 = 5.246 mm Focal length f5 of the 5th lens 50 = -2.913 mm Focal length f6 of the 6th lens 60 = 3.514 mm Focal length f7 of the 7th lens 70 = 32.894 mm Combined focal length f of the 1st lens 10 and the 2nd lens 20 12 =-16.394 mm Combined focal length f of the 2nd lens 20 and the 3rd lens 30 23 =6.048 mm Combined focal length f of the 3rd lens 30 and the 4th lens 40 34 =3.522 mm Combined focal length f of the 4th lens 40 and the 5th lens 50 45 =-9.236 mm Combined focal length f of the 5th lens 50 and the 6th lens 60 56 =16.312 mm The combined focal length f of the 6th lens 60 and the 7th lens 70 67 = 3.264 mm The combined focal length f of the 1st lens 10, the 2nd lens 20, and the 3rd lens 30 123 = 7.223 mm The combined focal length f of the 2nd lens 20, the 3rd lens 30, and the 4th lens 40 234 = 2.681 mm The combined focal length f of the 3rd lens 30, the 4th lens 40, and the 5th lens 50 345 = 160.814 mm The combined focal length f of the 4th lens 40, the 5th lens 50, and the 6th lens 60 456 = 5.638 mm The combined focal length f of the 5th lens 50, the 6th lens 60, and the 7th lens 70 567 = 9.741 mm The combined focal length f of the 1st lens 10, the 2nd lens 20, the 3rd lens 30, and the 4th lens 40 1234 = 1.826 mm The combined focal length f of the 2nd lens 20, the 3rd lens 30, the 4th lens 40, and the 5th lens 50 2345 = 11.638 mm The combined focal length f of the 3rd lens 30, the 4th lens 40, the 5th lens 50, and the 6th lens 60 3456 = 4.269 mm The combined focal length f of the 4th lens 40, the 5th lens 50, the 6th lens 60, and the 7th lens 70 4567 = 4.938 mm The combined focal length f of the 1st lens 10, the 2nd lens 20, the 3rd lens 30, the 4th lens 40, and the 5th lens 50 12345 = -16.192 mm The combined focal length f of the 2nd lens 20, the 3rd lens 30, the 4th lens 40, the 5th lens 50, and the 6th lens 60 23456 = 3.403 mm The combined focal length f of the 3rd lens 30, the 4th lens 40, the 5th lens 50, the 6th lens 60, and the 7th lens 70 34567 = 3.976 mm The combined focal length f of the 1st lens 10, the 2nd lens 20, the 3rd lens 30, the 4th lens 40, the 5th lens 50, and the 6th lens 60 123456=2.150 mm The combined focal length f of the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, the sixth lens 60, and the seventh lens 70 234567 =3.255 mm The combined focal length f of the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, the sixth lens 60, and the seventh lens 70 1234567 =1.969 mm

[0041] <Aspherical data> The front lens surface 10F of the first lens 10: κ = 0 A4 = 6.20836×10 -3 A6 = -6.43404×10 -4 A8 = 2.86702×10 -5 A 10 =-5.78944×10 -7 A 12 =1.20978×10 -8 A 14 =-5.66942×10 -10 A 16 =0

[0042] The rear lens surface 10R of the first lens 10: κ = 0 A4 = -2.96988×10 -3 A6 = 6.52766×10 -4 A8 = -7.80959×10 -5 A 10 =2.82983×10 -5 A 12 =-2.13976×10 -5 A 14 =6.87612×10 -8 A 16 =0

[0043] Front lens surface 20F of the second lens 20: κ = 0 A4 = 6.46889×10 -7 A6 = 8.07673×10 -4 A8 = -3.73465×10 -5 A 10 = -4.19082×10 -5 A 12 = 1.55366×10 -5 A 14 = -1.27696×10 -6 A 16 = 0

[0044] Rear lens surface 20R of the second lens 20: κ = 0 A4 = 1.31329×10 -2 A6 = 3.08413×10 -3 A8 = -3.54957×10 -3 A 10 = 1.76005×10 -3 A 12 = -1.55516×10 -4 A 14 = -2.82559×10 -5 A 16 = 0

[0045] Front lens surface 50F of the fifth lens 50: κ = 0 A4 = -4.23916×10 -2 A6 = 1.50789×10 -2 A8 = -1.43392×10 -3 A 10 = -5.17936×10 -4 A 12=2.17311×10 -5 A 14 =2.70464.×10 -5 A 16 =-2.76561×10 -6

[0046] Rear lens surface 50R of the fifth lens 50: κ = 0 A4 = -4.83687×10 -2 A6 = 1.41579×10 -2 A8 = -1.77856×10 -3 A 10 =-3.69980×10 -4 A 12 =1.49987×10 -4 A 14 =-2.05887×10 -5 A 16 =1.07213×10 -6

[0047] Front lens surface 60F of the sixth lens 60: κ = 0 A4 = -8.66249×10 -3 A6 = 2.54570×10 -3 A8 = -3.23629×10 -4 A 10 =-1.09711×10 -5 A 12 =7.86042×10 -6 A 14 =-6.69702×10 -7 A 16 =9.30035×10 -9

[0048] Rear lens surface 60R of the sixth lens 60: κ = 0 A4 = -2.31210×10 -3 A6 = 2.38346×10 -3 A8 = -2.59283×10 -4 A 10 = 3.08019×10 -4 A 12 = -1.04653×10 -4 A 14 = 1.49361×10 -5 A 16 = -7.64687×10 -7

[0049] Front lens surface 70F of the seventh lens 70: κ = 0 A4 = 1.35479×10 -2 A6 = -1.40042×10 -2 A8 = 1.36049×10 -3 A 10 = 3.58827×10 -4 A 12 = -4.52771×10 -5 A 14 = -5.79851×10 -6 A 16 = 7.53818×10 -7

[0050] Rear lens surface 70R of the seventh lens 70: κ = 0 A4 = 4.87633×10 -2 A6 = -2.54136×10 -2 A8 = 4.50452×10 -3 A 10 = -2.11445×10 -4 A 12=-2.67769×10 -5 A 14 =3.34296×10 -6 A 16 =-9.44974×10 -8

[0051] <Other values> F value: 2.20 Angle of view: 160 degrees Back focus: 2.40 mm Effective radius r1 of the first lens 10: 3.6 mm

[0052] Here, consider the above formulas (1) to (8). Equation (1) The effective radius r1 of the first lens 10 = 3.6 mm and r1 ≦ 3.75 mm so it satisfies formula (1).

[0053] Equation (2) Overall lens length TTL = D1 + D 12 + D2 + D 2P + D P3 + D3 + D 34 + D4 + D 45 + D5 + D 56 + D6 + D 67 + D7 + D 7G + D G + D GS = 15.57 mm and TTL ≦ 16 mm so it satisfies formula (2).

[0054] Equation (3) The distance t1 from the vertex 11 of the first lens 10 to the aperture 90 = D1 + D 12 + D2 + D 2P = 4.98 mm and t1 / r1 = 4.98 mm / 3.6 mm = 1.38 That is. 1.3 < t1 / r1 < 1.5 Therefore, it satisfies Equation (3).

[0055] Equation (4) TTL / r1 = 15.57 mm / 3.6 mm = 4.325 and 4.1 < TTL / r1 < 4.4 Therefore, it satisfies Equation (4).

[0056] Equation (5) |f1 / r1| = |-4.898 mm / 3.6 mm| = 1.36 and 1.3 < |f1 / r1| < 1.8 Therefore, it satisfies Equation (5).

[0057] Equation (6) Since the front lens group FL is composed of the first lens 10 and the second lens 20, the combined focal length f of the front lens group FL F = f 12 = -16.394 mm is as follows. Since the rear lens group RL is composed of the third lens 30, the fourth lens 40, the fifth lens 50, the sixth lens 60, and the seventh lens 70, the combined focal length f of the rear lens group RL R = f 34567 = 3.976 mm is as follows. |f F / f R | = |-16.394 mm / 3.976 mm| = 4.12 and 2 < |f F / f R | < 5 Therefore, it satisfies Equation (6).

[0058] Equation (7) The combined focal length f from the first lens 10 to the seventh lens 70 1234567 = 1.969 mm and 1.5mm < f 1234567 < 2.5mm Since it is, Equation (7) is satisfied.

[0059] Equation (8) The combined focal length f of the fourth lens 40 to the sixth lens 60 456 = 5.638mm and 3 < f 456 < 6 Since it is, Equation (8) is satisfied.

[0060] Thus, the optical system in the first embodiment satisfies all of the above equations (1) to (8).

Embodiment

[0061] As a second embodiment of the present invention, an imaging device 101 of the above-described second embodiment was configured with an optical system having the following parameters, and its characteristics were analyzed. <Radius of curvature of the lens surface on the optical axis P> Front lens surface 110F of the first lens 110: 26.003mm Rear lens surface 110R of the first lens 110: 3.772mm Front lens surface 120F of the second lens 120: -2.273mm (aspherical surface) Rear lens surface 120R of the second lens 120: -3.076mm (aspherical surface) Front lens surface 130F of the third lens 130: -493.201mm (aspherical surface) Rear lens surface 130R of the third lens 130: -9.696mm (aspherical surface) Front lens surface 140F of the fourth lens 140: 5.154mm Rear lens surface 140R of the fourth lens 140: -2.973mm Front lens surface 150F of the fifth lens 150: 17.822mm (aspherical surface) Rear lens surface 150R of the fifth lens 150: 3.084mm (aspherical surface) Front lens surface 160F of the 6th lens 160: 4.402 mm (aspherical surface) Rear lens surface 160R of the 6th lens 160: -2.959 mm (aspherical surface) Front lens surface 170F of the 7th lens 170: -3.251 mm (aspherical surface) Rear lens surface 170R of the 7th lens 170: 25.686 mm (aspherical surface)

[0062] <Thickness or interval on the optical axis P> Thickness D1 of the 1st lens 110 = 1.00 mm Interval D between the 1st lens 110 and the 2nd lens 120 12 = 1.87 mm Thickness D2 of the 2nd lens 120 = 1.00 mm Interval D between the 2nd lens 120 and the 3rd lens 130 23 = 0.06 mm Thickness D3 of the 3rd lens 130 = 0.87 mm Interval D between the 3rd lens 130 and the aperture 90 3P = 0.28 mm Interval D between the aperture 90 and the 4th lens 140 P4 = 0.00 mm Thickness D4 of the 4th lens 140 = 2.37 mm Interval D between the 4th lens 140 and the 5th lens 150 45 = 0.05 mm Thickness D5 of the 5th lens 150 = 0.50 mm Interval D between the 5th lens 150 and the 6th lens 160 56 = 0.08 mm Thickness D6 of the 6th lens 160 = 2.52 mm Interval D between the 6th lens 160 and the 7th lens 170 67 = 1.12 mm Thickness D7 of the 7th lens 170 = 0.67 mm Interval D between the 7th lens 170 and the sensor protection glass 82 7G = 0.98 mm Thickness D of the sensor protection glass 82 G = 0.30 mm Interval D between the sensor protection glass 82 and the sensor protection glass 84GH = 0.10 mm Thickness D of the sensor protection glass 84 H = 0.40 mm Distance D between the sensor protection glass 84 and the image plane S HS = 0.10 mm

[0063] <Refractive index with respect to the d-line> Refractive index N of the first lens 110 d1 = 1.772 Refractive index N of the second lens 120 d2 = 1.544 Refractive index N of the third lens 130 d3 = 1.636 Refractive index N of the fourth lens 140 d4 = 1.439 Refractive index N of the fifth lens 150 d5 = 1.636 Refractive index N of the sixth lens 160 d6 = 1.544 Refractive index N of the seventh lens 170 d7 = 1.636 Refractive index N of the sensor protection glass 82 dG = 1.517 Refractive index N of the sensor protection glass 84 dH= 1.517

[0064] <Abbe number> Abbe number ν1 of the first lens 110 = 49.6 Abbe number ν2 of the second lens 120 = 55.9 Abbe number ν3 of the third lens 130 = 24.0 Abbe number ν4 of the fourth lens 140 = 94.7 Abbe number ν5 of the fifth lens 150 = 24.0 Abbe number ν6 of the sixth lens 160 = 55.9 Abbe number ν7 of the seventh lens 170 = 24.0 Abbe number ν of the sensor protection glass 82 G = 64.2 Abbe number ν of the sensor protection glass 84 H = 64.2

[0065] <Focal length> The focal length f1 of the first lens 110 = -5.826 mm The focal length f2 of the second lens 120 = -28.605 mm The focal length f3 of the third lens 130 = 15.553 mm The focal length f4 of the fourth lens 140 = 4.717 mm The focal length f5 of the fifth lens 150 = -5.946 mm The focal length f6 of the sixth lens 160 = 3.701 mm The focal length f7 of the seventh lens 170 = -4.500 mm The combined focal length f of the first lens 110 and the second lens 120 12 = -5.064 mm The combined focal length f of the second lens 120 and the third lens 130 23 = 24.567 mm The combined focal length f of the third lens 130 and the fourth lens 140 34 = 3.891 mm The combined focal length f of the fourth lens 140 and the fifth lens 150 45 = 12.114 mm The combined focal length f of the fifth lens 150 and the sixth lens 160 56 = 6.516 mm The combined focal length f of the sixth lens 160 and the seventh lens 170 67 = 6.144 mm The combined focal length f of the first lens 110, the second lens 120, and the third lens 130 123 = -11.661 mm The combined focal length f of the second lens 120, the third lens 130, and the fourth lens 140 234 = 3.598 mm The combined focal length f of the third lens 130, the fourth lens 140, and the fifth lens 150 345 = 6.620 mm The combined focal length f of the fourth lens 140, the fifth lens 150, and the sixth lens 160 456 = 3.769 mm The combined focal length f of the fifth lens 150, the sixth lens 160, and the seventh lens 170 567 = -21.800 mm The combined focal length f of the first lens 110, the second lens 120, the third lens 130, and the fourth lens 140 1234 = 3.242 mm The combined focal length f of the second lens 120, the third lens 130, the fourth lens 140, and the fifth lens 150 2345 = 7.116 mm The combined focal length f of the third lens 130, the fourth lens 140, the fifth lens 150, and the sixth lens 160 3456 = 3.636 mm The combined focal length f of the fourth lens 140, the fifth lens 150, the sixth lens 160, and the seventh lens 170 4567 = 4.392 mm The combined focal length f of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, and the fifth lens 150 12345 = 19.208 mm The combined focal length f of the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, and the sixth lens 160 23456 = 3.141 mm The combined focal length f of the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160, and the seventh lens 170 34567 = 3.450 mm The combined focal length f of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, and the sixth lens 160 123456 = 2.232 mm The combined focal length f of the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160, and the seventh lens 170 234567 = 3.254 mm The combined focal length f of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160, and the seventh lens 170 1234567 = 3.199 mm

[0066] <Aspherical data> The front lens surface 120F of the second lens 120: κ = 0 A4 = 1.90077×10 -2 A6 = 3.54368×10 -3 A8 = -9.88892×10 -4 A 10 = -5.07096×10 -5 A 12 = 1.62583×10 -4 A 14 = -4.40267×10 -5 A 16 = 4.43972×10 -6

[0067] Rear lens surface 120R of the second lens 120: κ = 0 A4 = 4.24664×10 -2 A6 = -1.62316×10 -2 A8 = 3.52571×10 -3 A 10 = 9.12921×10 -4 A 12 = -9.79460×10 -4 A 14 = 2.95538×10 -4 A 16 = -2.97336×10 -5

[0068] Front lens surface 130F of the third lens 130: κ = 0 A4 = 2.37222×10 -2 A6 = -1.79049×10 -2 A8 = 8.94790×10 -3 A 10 = -3.21075×10 -3 A 12 = 5.16197×10 -4 A 14=1.09057×10 -4 A 16 =-3.12811×10 -5

[0069] Rear lens surface 130R of the third lens 130: κ = 0 A4 = 2.12088×10 -3 A6 = 3.99389×10 -4 A8 = 1.31617×10 -3 A 10 =4.78926×10 -5 A 12 =-7.33099×10 -4 A 14 =4.82588×10 -4 A 16 =-9.17958×10 -5

[0070] Front lens surface 150F of the fifth lens 150: κ = 0 A4 = -2.92425×10 -2 A6 = 7.98770×10 -3 A8 = -1.73521×10 -3 A 10 =1.03705×10 -4 A 12 =1.30860×10 -4 A 14 =-5.20927×10 -5 A 16 =5.65484×10 -6

[0071] Rear lens surface 150R of the fifth lens 150: κ = 0 A4 = -2.50583×10 -2 A6 = 5.92909×10 -3 A8 = -4.90291×10 -4 A 10 = -3.19076×10 -4 A 12 = 1.33517×10 -4 A 14 = -2.46198×10 -5 A 16 = 1.72266×10 -6

[0072] Front lens surface 160F of the 6th lens 160: κ = 0 A4 = 5.94161×10 -3 A6 = -2.94351×10 -4 A8 = -2.15529×10 -4 A 10 = 1.03279×10 -5 A 12 = 7.00871×10 -6 A 14 = -6.18878×10 -7 A 16 = -2.54981×10 -8

[0073] Rear lens surface 160R of the 6th lens 160: κ = 0 A4 = 1.54152×10 -2 A6 = -2.08183×10 -3 A8 = 3.13113×10 -4 A 10 = 1.96445×10 -4 A 12 = -1.02878×10 -4 A 14=1.80089×10 -5 A 16 =-1.04211×10 -6

[0074] Front lens surface 170F of the 7th lens 170: κ = 0 A4 = -1.09578×10 -2 A6 = -8.83292×10 -4 A8 = 6.61382×10 -4 A 10 =-9.04789×10 -5 A 12 =-2.19094×10 -5 A 14 =8.03842×10 -6 A 16 =-5.75167×10 -7

[0075] Rear lens surface 170R of the 7th lens 170: κ = 0 A4 = -3.01911×10 -2 A6 = 2.92412×10 -3 A8 = -9.02140×10 -5 A 10 =-3.87262×10 -5 A 12 =8.10260×10 -6 A 14 =-5.44493×10 -7 A 16 =1.26192×10 -8

[0076] <Other values> F value: 2.20 Angle of view: 150 degrees Back focus: 1.88 mm Effective radius r1 of the first lens 110: 3.4 mm

[0077] Here, consider the above formulas (9) to (16). Equation (9) Effective radius r1 of the first lens 110 = 3.4 mm and r1 ≦ 3.75 mm Therefore, formula (9) is satisfied.

[0078] Equation (10) Total lens length TTL = D1 + D 12 + D2 + D 23 + D3 + D 3P + D P4 + D4 + D 45 + D5 + D 56 + D6 + D 67 + D7 + D 7G + D G + D GH + D H + D HS = 14.28 mm and TTL ≦ 16 mm Therefore, formula (10) is satisfied.

[0079] Equation (11) Distance t1 from the vertex 11 of the first lens 110 to the aperture 90 = D1 + D 12 + D2 + D 23 + D3 + D 3P = 5.08 and t1 / r1 = 5.08 mm / 3.4 mm = 1.49 and 1.3 < t1 / r1 < 1.5 Therefore, formula (11) is satisfied.

[0080] Equation (12) TTL / r1 = 14.68 mm / 3.4 mm = 4.318 and 4.1 < TTL / r1 < 4.4 Therefore, equation (12) is satisfied.

[0081] Equation (13) |f1 / r1| = |-5.826 mm / 3.4 mm| = 1.71 and 1.3 < |f1 / r1| < 1.8 Therefore, equation (13) is satisfied.

[0082] Equation (14) Since the front lens group FL is composed of the first lens 110, the second lens 120, and the third lens 130, the combined focal length f of the front lens group FL F = f 123 = -11.661 mm is. Since the rear lens group RL is composed of the fourth lens 140, the fifth lens 150, the sixth lens 160, and the seventh lens 170, the combined focal length f of the rear lens group RL R = f 4567 = 4.392 mm is. |f F / f R | = |-11.661 mm / 4.392 mm| = 2.66 and 2 < |f F / f R | < 5 Therefore, equation (14) is satisfied.

[0083] Equation (15) The combined focal length f from the first lens 110 to the seventh lens 170 1234567 = 3.199 mm and 2.0 mm < f 1234567 < 4.0 mm Therefore, equation (15) is satisfied.

[0084] Equation (16) The combined focal length f from the fourth lens 140 to the sixth lens 160456 = 3.769 mm and 3 < f 456 <6 Therefore, it satisfies Equation (16).

[0085] Thus, the optical system in the second embodiment satisfies all of the above Equations (9) to (16).

[0086] The optical system according to the present invention can adopt the following configuration. [Configuration 1] A front lens group including a first lens, having a negative refractive power, arranged in order from the object side to the image side along the optical axis, a diaphragm provided with an aperture, and a rear lens group including an apochromatic lens or an achromatic lens, having a positive refractive power are provided, the total number of lenses included in the front lens group and the lenses included in the rear lens group is 7, the effective radius r1 of the first lens is 3.75 mm or less, and the distance TTL along the optical axis from the vertex of the first lens to the image plane is 16 mm or less, Optical system. Optical system.

[0087] [Configuration 2] When the distance from the vertex of the first lens to the diaphragm is t1, 1.3 < t1 / r1 < 1.5 is satisfied, The optical system according to Configuration 1.

[0088] [Configuration 3] 4.1 < TTL / r1 < 4.4 is satisfied, The optical system according to Configuration 1 or 2.

[0089] [Configuration 4] When the focal length of the first lens is f1, 1.3 < |f1 / r1| < 1.8 The optical system according to any one of Configurations 1 to 3.

[0090] [Configuration 5] Let the combined focal length of the front lens group be f F and let the combined focal length of the rear lens group be f R then 2 < |f F / f R | < 5 is satisfied, The optical system according to any one of Configurations 1 to 4.

[0091] [Configuration 6] The front lens group includes the first lens, a second lens located behind the first lens and is composed of The rear lens group includes a third lens located behind the aperture, a fourth lens located behind the third lens, a fifth lens located behind the fourth lens, a sixth lens located behind the fifth lens, and a seventh lens located behind the sixth lens and is composed of The optical system according to any one of Configurations 1 to 5.

[0092] [Configuration 7] When the combined focal length of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens is f 1234567 then 1.5 mm < f 1234567 < 2.5 mm is satisfied, The optical system according to Configuration 6.

[0093] [Configuration 8] The first lens is formed of resin, includes a front lens surface convex on the object side and a rear lens surface concave on the image surface side, and has a negative refractive power. The second lens is formed of resin and includes a front lens surface that is concave on the object side and a rear lens surface that is convex on the image plane side, and has a positive refractive power. The optical system according to Configuration 6 or 7.

[0094] [Configuration 9] The fourth lens is formed of glass and includes a front lens surface that is convex on the object side and a rear lens surface that is convex on the image plane side. The fifth lens is formed of resin and includes a front lens surface that is concave on the object side and a rear lens surface that is concave on the image plane side. The sixth lens is formed of resin and includes a front lens surface that is convex on the object side and a rear lens surface that is convex on the image plane side. The fourth lens, the fifth lens, and the sixth lens constitute the apochromatic lens. The optical system according to any one of Configurations 6 to 8.

[0095] [Configuration 10] Let the combined focal length of the fourth lens, the fifth lens, and the sixth lens be f 456 Then, 3 < f 456 < 6 satisfies, The optical system according to any one of Configurations 6 to 9.

[0096] [Configuration 11] The front lens group includes the first lens, a second lens located behind the first lens, and a third lens located behind the second lens and is composed of The rear lens group includes a fourth lens located behind the aperture, a fifth lens located behind the fourth lens, a sixth lens located behind the fifth lens, and a seventh lens located behind the sixth lens and is composed of The optical system according to any one of Configurations 1 to 5.

[0097] [Configuration 12] Let the combined focal length of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens be f 1234567 Then, 2.0 mm < f 1234567 < 4.0 mm satisfying The optical system according to Configuration 11.

[0098] [Configuration 13] The first lens is formed of glass and includes a front lens surface that is convex on the object side and a rear lens surface that is concave on the image plane side, and has a negative refractive power. The second lens is formed of resin and includes a front lens surface that is concave on the object side and a rear lens surface that is convex on the image plane side, and has a positive refractive power. The optical system according to Configuration 11 or 12.

[0099] [Configuration 14] The fifth lens is formed of resin and includes a front lens surface that is concave on the object side and a rear lens surface that is concave on the image plane side. The sixth lens is formed of resin and includes a front lens surface that is convex on the object side and a rear lens surface that is convex on the image plane side. The fifth lens and the sixth lens constitute the achromatic lens. The optical system according to any one of Configurations 11 to 13.

[0100] [Configuration 15] Let the combined focal length of the fourth lens, the fifth lens, and the sixth lens be f 456 Then, 3 < f 456 < 6 satisfying The optical system according to any one of Configurations 11 to 14.

[0101] In addition, the imaging device according to the present invention can adopt the following configuration. [Configuration 16] The optical system according to any one of Configurations 1 to 15, and an imaging device including an imaging element disposed on the image plane. An imaging device comprising:

[0102] Although the preferred embodiments of the present invention have been described so far, it goes without saying that the present invention is not limited to the above-described embodiments and may be implemented in various different forms within the scope of its technical idea.

Explanation of Reference Numerals

[0103] 1,101 Imaging device 2 Casing 3 Base plate 4,104 Optical system 5 Imaging element 10,110 First lens 11,111 Vertex 20,120 Second lens 30,130 Third lens 40,140 Fourth lens 50,150 Fifth lens 60,160 Sixth lens 70,170 Seventh lens 82,84 Sensor protection glass 90 Diaphragm B Object FL Front lens group P Optical axis RL Rear lens group S Image plane

Claims

1. An optical system comprising, in order from the object side to the image plane side along the optical axis, a front lens group including a first lens and having a negative refractive power, a diaphragm provided with an aperture, a rear lens group including an apochromatic lens or an achromatic lens and having a positive refractive power, wherein the total number of lenses included in the front lens group and the rear lens group is 7, The effective radius r of the first lens 1 is 3.75 mm or less, the distance TTL along the optical axis from the vertex of the first lens to the image plane is 16 mm or less. Optical system.

2. Let the distance from the vertex of the first lens to the diaphragm be t 1 Then 1.3 < t 1 / r 1 < 1.5 Satisfying the optical system according to Claim 1.

3. 4.1 < TTL / r 1 < 4.4 Satisfying the optical system according to Claim 1.

4. Let the focal length of the first lens be f 1 Then 1.3 < |f 1 / r 1 | < 1.8 the optical system according to Claim 1.

5. Let the combined focal length of the front lens group be f F and Let the combined focal length of the rear lens group be f R Then 2 < |f F / f R | < 5 Satisfying the optical system according to Claim 1.

6. The front lens group consists of the first lens, a second lens located behind the first lens, and the rear lens group consists of a third lens located behind the diaphragm, a fourth lens located behind the third lens, a fifth lens located behind the fourth lens, a sixth lens located behind the fifth lens, a seventh lens located behind the sixth lens, and the optical system according to Claim 1.

7. Satisfying Let the combined focal length of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens be f 1234567 Then 1.5 mm < f 1234567 < 2.5 mm the optical system according to Claim 6.

8. The first lens is formed of resin and includes a front lens surface convex on the object side and a rear lens surface concave on the image plane side, and has a negative refractive power. The second lens is formed of resin and includes a front lens surface concave on the object side and a rear lens surface convex on the image plane side, and has a positive refractive power. The optical system according to Claim 6.

9. The fourth lens is formed of glass and includes a front lens surface convex on the object side and a rear lens surface convex on the image plane side. The fifth lens is formed of resin and includes a front lens surface concave on the object side and a rear lens surface concave on the image plane side. The sixth lens is formed of resin and includes a front lens surface convex on the object side and a rear lens surface convex on the image plane side. The fourth lens, the fifth lens, and the sixth lens constitute the apochromatic lens. The optical system according to Claim 6.

10. Satisfying Let the combined focal length of the fourth lens, the fifth lens, and the sixth lens be f 456 Then 3 < f 456 < 6 the optical system according to Claim 6.

11. The front lens group consists of the first lens, a second lens located behind the first lens, a third lens located behind the second lens, and the rear lens group consists of ​ A fourth lens located behind the aperture, A fifth lens located behind the fourth lens, A sixth lens located behind the fifth lens, A seventh lens located behind the sixth lens Composed of, The optical system according to claim 1.

12. Let the combined focal length of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens be f 1234567 Then, 2.0 mm < f 1234567 < 4.0 mm Satisfying, The optical system according to claim 11.

13. The first lens is formed of glass and includes a front lens surface convex on the object side and a rear lens surface concave on the image plane side, and has a negative refractive power. The second lens is formed of resin and includes a front lens surface concave on the object side and a rear lens surface convex on the image plane side, and has a negative-positive refractive power. The third lens is formed of resin and includes a front lens surface convex on the object side and a rear lens surface convex on the image plane side, and has a positive refractive power The optical system according to claim 11.

14. The fifth lens is formed of resin and includes a front lens surface concave on the object side and a rear lens surface concave on the image plane side. The sixth lens is formed of resin and includes a front lens surface convex on the object side and a rear lens surface convex on the image plane side. The fifth lens and the sixth lens constitute the achromatic lens. The optical system according to claim 11.

15. Let the combined focal length of the fourth lens, the fifth lens, and the sixth lens be f 456 Then 3 < f 456 < 6 Satisfying, The optical system according to claim 11.

16. The optical system according to any one of claims 1 to 15, An imaging device including an imaging element disposed on the image plane And an imaging device comprising.

Images