JP6708026B2 - Imaging optical system, imaging device, and compound-eye imaging device - Google Patents

Description

The present invention relates to an image pickup optical system, an image pickup apparatus, and a compound eye image pickup apparatus.

Recently, an imaging optical system for imaging an object to be imaged is not limited to a silver halide camera, but is also used for so-called digital cameras, personal digital assistants, video cameras, stereo cameras, and various optical sensors. This type is known.
As one type of these various types of imaging optical systems, a "retro focus type imaging optical system" is known as being suitable for a relatively wide-angle single-focus lens (for example, Patent Documents 1 to 4).

An object of the present invention is to realize a novel retrofocus type imaging optical system.

The image pickup optical system according to the present invention comprises a negative first lens group, an aperture stop, and a positive second lens group arranged in order from the object side to the image side, and the first lens group is an image from the object side. A first lens, a second lens, a third lens, and a fourth lens in this order toward the side, the first lens is a positive meniscus lens having a convex surface facing the object side, and the second lens is a negative lens. The third lens is a negative lens, the fourth lens is a positive lens, and the second lens group has, in order from the object side to the image side, a cemented lens of a negative lens and a positive lens, and a positive lens. And the surface closest to the object side is concave toward the object side, the focal length of the entire system is f, and the air gap on the optical axis between the third lens and the fourth lens of the first lens group is L34L. An air gap on the optical axis through the aperture stop between the image side surface of the fourth lens of the first lens group and the object side surface of the cemented lens of the second lens group: SL is a conditional expression.
(1) 5.00 <f/L34L <50.00
(2) 2.00 <f/SL <15.00
To be satisfied.

According to the present invention, a new retrofocus type imaging optical system can be realized.

FIG. 3 is an optical layout diagram showing Numerical Example 1 of the imaging optical system. It is an optical layout diagram showing Numerical example 2 of the imaging optical system. FIG. 9 is an optical layout diagram showing Numerical Example 3 of the imaging optical system. FIG. 9 is an optical layout diagram showing Numerical Example 4 of the imaging optical system. FIG. 9 is an optical layout diagram showing Numerical Example 5 of the imaging optical system. FIG. 6 is an aberration curve diagram for an object at infinity in the imaging optical system of Numerical Example 1. FIG. 9 is an aberration curve diagram for an object at infinity in the imaging optical system of Numerical Example 2. FIG. 9 is an aberration curve diagram for an object at infinity in the imaging optical system of Numerical Example 3. FIG. 11 is an aberration curve diagram for an object at infinity in the imaging optical system of Numerical Example 4. FIG. 16 is an aberration curve diagram for an object at infinity in the imaging optical system of Numerical Example 5. It is a figure for explaining one embodiment of an imaging device. It is a figure for demonstrating the system structure of the imaging device of FIG. It is a figure for explaining one embodiment of a compound eye imaging device.

As described above, the image pickup optical system according to the present invention includes, in order from the object side to the image side, the negative first lens group, the aperture stop, and the positive second lens group.
The first lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in order from the object side to the image side.
The first lens is a positive meniscus lens having a convex surface directed toward the object side, the second lens is a negative lens, the third lens is a negative lens, and the fourth lens is a positive lens. The first lens group includes these positive, negative and negative lenses.・It consists of four positive lenses.
The second lens group, "a negative lens and a cemented lens of a positive lens" in order from the object side to the image side, have a positive lens, and the surface on the most object side Ru concave der the object side. The second lens group can be composed of only the "cemented lens and the positive lens", but can further include one or more other lenses on the image side of the positive lens.
In such a configuration, the focal length of the entire system: f, “air distance on the optical axis between the third lens and the fourth lens on the optical axis: L34L” of the first lens group, “image of the fourth lens of the first lens group” The air gap on the optical axis through the aperture diaphragm between the side surface and the object side surface of the cemented lens of the second lens group (the surface closest to the object side of the second lens group): SL” is a conditional expression.
(1) 5.00 <f/L34L <50.00
(2) 2.00 <f/SL <15.00
To be satisfied.

As described above, the image pickup optical system of the present invention is a “retro focus type” in which the negative first lens group is arranged on the object side and the positive second lens group is arranged on the image side. With this configuration, it is possible to "suppress the angle of incidence of off-axis light on the image plane, which tends to increase as the angle of view increases.
Inside the first lens group, there is a “positive (first lens), negative (second lens and third lens), positive (fourth lens) power arrangement” in order from the object side to the image side.
The first lens group has "a negative power as a whole", the second lens group has a "positive power as a whole", and the positive power of the first lens is combined with the second and third lenses. Due to the negative power, the positive power of the fourth lens, and the "positive power of the entire 2 lens group", a triplet type refracting power (power arrangement of positive/negative/positive) is formed, and various aberrations such as chromatic aberration The difficulty of correction of is reduced.

Further, by making the power of the first lens group located closer to the object side of the aperture stop to be negative as a whole, it is possible to capture a light beam having a wide field angle with a relatively small size.

By setting the first lens arranged closest to the object side of the first lens group to be a “positive meniscus lens having a convex surface facing the object side”, “spherical aberration that tends to increase particularly when the imaging optical system has a large aperture” It is easy to correct.
By dividing the negative power in the first lens group into “two lenses of the second lens and the third lens”, it is not necessary to give “strong curvature” to each surface of these two negative lenses, This makes it possible to improve productivity and suppress performance deterioration due to manufacturing errors and assembly eccentricity.

In the second lens group, in the “near the aperture stop” where the luminous flux of each angle of view is thick, the lens element closest to the object side is “a cemented lens of a negative lens and a positive lens”, so that the axial chromatic aberration is mainly reduced. The correction is easy.
The cemented lens closest to the object side in the second lens group is composed of “a negative lens and a positive lens in this order” from the object side toward the image side, and includes a positive lens of the cemented lens and a positive lens following the image side. At the same time, the control of the exit pupil distance is facilitated.
In this way, if the cemented lens is composed of "a negative lens and a positive lens in this order" from the object side to the image side, the "incident angle and exit angle on the cemented lens surface" of the light ray on the image side with respect to the aperture stop can be further improved. It is easy to adopt a configuration that keeps it small, and it is easy to suppress the sensitivity of performance deterioration due to manufacturing errors.

Conditional expression (1) defines the optimum range of “the air distance between the third lens and the fourth lens in the first lens group with respect to the focal length of the entire system”.
The negative third lens and the positive fourth lens in the first lens group are parts that mainly "exchange" spherical aberration largely and contribute to the aberration correction balance of the entire imaging optical system.
If the parameter: f/L34L is less than the lower limit value of the conditional expression (1), the distance between the third lens and the fourth lens becomes too large, which is advantageous for suppressing the manufacturing error sensitivity, but directly affects the total optical length. In addition, the height of the ray after the fourth lens increases, the size in the lens radial direction increases, and the total optical length increases, which makes it difficult to make the imaging optical system compact.
If the parameter: f/L34L exceeds the upper limit of conditional expression (1), the ray tilt angle between the second surface of the third lens and the first surface of the fourth lens increases, and the manufacturing error sensitivity increases. However, it may be difficult to manufacture an individual that satisfies the desired performance.

Conditional expression (2) defines the optimum range of “air distance before and after diaphragm: SL” with respect to the focal length of the entire system.
If the parameter: f/SL falls below the lower limit of conditional expression (2), the air gap SL between the first lens group and the second lens group becomes too large, and in addition to directly increasing the optical total length, The ray height in the first lens group increases, and the radial size of the first lens group tends to increase.
If the parameter: f/SL exceeds the upper limit of conditional expression (2), the negative refracting power of the first lens group becomes relatively large, and the manufacturing error sensitivity for the second lens group may increase.
According to the above-described configuration of the photographing optical system of the present invention, it is possible to obtain a great effect on aberration correction, and as shown in specific numerical examples described later, a wide field of view with a half angle of view of about 29 degrees. It is possible to secure good image performance while maintaining a low distortion while maintaining a small size with a corner and a large aperture of about F2 or less.

The parameter of conditional expression (1): f/L34L, the parameter of conditional expression (2): f/SL is more preferably the following conditional expression instead of conditional expressions (1) and (2).
(1A) 5.50 <f/L34L <30.00
(2A) 3.00 <f/SL <10.00
Is good to satisfy.

The imaging optical system of the present invention, together with the arrangement, have preferred to satisfy one or more arbitrary in the following condition.
(4) 0.01 <|f/f1| <0.50
(5) 0.10 <f/AL <0.50
(6) 0.000 <|f/f2F| <0.500.

The meanings of the symbols in the parameters in these conditional expressions are as follows .
“F1” is the focal length (<0) of the first lens group.
“AL” is the total optical length (the distance from the object side surface of the first lens to the image plane on the optical axis).
“F2F” is a composite focal length of the “objective side cemented lens of the negative lens and the positive lens” of the second lens group.

Conditional expression (4) defines a preferable range of the focal length: f1 of the first lens group with respect to the focal length: f of the entire system.
By setting the parameter of conditional expression (4): |f/f1| within the range of conditional expression (4), the chromatic aberration correction capability is reduced due to the reduction of the refracting power, and the "positive/negative refraction" in the first lens group is decreased. It is possible to effectively avoid the increase in the sensitivity of performance deterioration to the manufacturing error due to the “increased force difference”.
Further, it is possible to effectively avoid an increase in sensitivity of performance deterioration due to a manufacturing error due to “increase in difference in refractive power” between the first lens group and the second lens group and an increase in size of the entire optical system.
The parameter of conditional expression (4): |f/f1| is more preferably conditional expression (4A) 0.01 <|f/f1| <0.30 instead of conditional expression (4).
Is good to satisfy.

Conditional expression (5) defines a preferable range of the optical total length: AL with respect to the focal length: f of the entire system. By setting the parameter of conditional expression (5): f/AL within the range of conditional expression (5), it becomes possible to reduce the difficulty level of distortion aberration correction, and effectively avoid the increase in size of the entire optical system. ..
Parameter of conditional expression (5): f/AL is more preferably conditional expression (5A) instead of conditional expression (5) 0.15 <f/AL <0.40
Is good to satisfy.
Conditional expression (6) defines a preferable range of the combined focal length: f2F of the “composite lens of the negative lens and the positive lens” arranged on the most object side of the second lens group.
By setting the parameter of conditional expression (6): |f/f2F| within the range of conditional expression (6), the refractive power of the above-mentioned “junction lens”, the exit pupil position adjusting function, and the “first lens group” can be set. It becomes possible to satisfactorily balance the spherical aberration correction capability and the chromatic aberration correction capability exhibited by pairing with the negative lens.

The parameter of conditional expression (6): |f/f2F| is more preferably the following conditional expression (6A) 0.000 <|f/f2F| <0.400 instead of conditional expression (6).
Is good to satisfy.
Furthermore, it is preferable that the third lens in the first lens group be a “negative meniscus lens having a convex surface facing the object side”. The third lens has a strong "mainly spherical aberration correction function" in the first lens group, and by making this third lens a meniscus shape with a convex surface facing the object side, increase in manufacturing error sensitivity is suppressed. At the same time, the aberration correction capability can be improved.
The imaging optical system of the present invention, as described above, the most object-side surface of the second lens group (the object-side surface of the negative lens of the cemented lens of a negative lens and a positive lens) is a "concave on the object side" .. By making the most object-side surface of the second lens group concave to the object side, the second lens group faces the respective second surfaces of the positive meniscus first lens and the negative meniscus third lens in the first lens group. concave to form, it tends to increase with the wide angle, balancing the worse easy distortion in biased retrofocus power balance, and facilitate lowering the difficulty level of distortion correction.

The second lens group is composed of a positive second F lens group as a whole and a positive second R lens group as a whole, and the second F lens group has “at least one negative lens and one positive lens”. It is preferable that the second R lens group includes “at least one positive lens”.
As described above, since the 2nd F lens group “has at least one negative lens and one positive lens”, these lenses are paired with the “negative third lens and positive fourth lens” in the first lens group. Therefore, it is possible to improve the chromatic aberration correction capability.
In addition, by including "one or more positive lenses" in the second R lens group, "a function of adjusting the exit pupil position" can be added, and it becomes easy to suppress the incident angle of the image forming light beam on the image plane.
In order to improve resistance to environmental changes and changes over time, it is preferable that all lenses are made of glass spherical lenses, and the image pickup optical system of the present invention has the following characteristics. The lens may be a spherical lens made of glass.

By adopting a glass lens that has a smaller coefficient of thermal expansion than the optical resin material and a small change in optical characteristics due to environmental changes for all lenses, it is possible to configure an optical system with excellent resistance to environmental changes and aging. Also, by using a spherical lens that can be inexpensively selected for polishing with a relatively small residual internal stress, it is possible to further suppress changes in optical characteristics due to environmental changes.

Furthermore, it is preferable that the second lens and the third lens in the first lens group are “negative meniscus lenses having a convex surface facing the object side”. By making these second and third lenses “meniscus shape with the convex surface facing the object side”, it becomes possible to better correct spherical aberration that increases with an increase in aperture.
The most image side surface of the first lens group is preferably “concave to the image side”.
By making the air lens formed by the most image side surface of the first lens group and the most object side surface of the second lens group "biconvex shape" and forming "concave surfaces facing each other across the aperture stop", It becomes possible to balance the distortion aberration, which tends to increase with the widening of the angle, and the retrofocus type in which the refractive power balance is biased, which is more likely to deteriorate, and to reduce the difficulty level of the distortion aberration correction.

The main function of the second R lens group is to secure the exit pupil distance. In order to reduce the size of the entire image pickup optical system, it is necessary to have a configuration that is as simple as possible, and it is desirable that the number of positive lenses is approximately two or less.

It is preferable that the negative lens and the positive lens forming the cemented lens located closest to the object in the second lens group are made of materials that satisfy the following conditional expressions.

1.75 <N21 <2.20, 15 <ν21 <35
1.65 <N22 <2.20, 35 <ν22 <55
"N21" is the refractive index of the material of the negative lens that constitutes the cemented lens, "ν21" is the Abbe number of the material of the negative lens, "N22" is the refractive index of the material of the positive lens that constitutes the cemented lens, and "ν22" Represents the Abbe number of the positive lens. By selecting such a glass type, it becomes possible to easily correct chromatic aberration favorably while balancing the Petzval sum.

The fourth lens in the first lens group is preferably made of a material that satisfies the following conditional expression.
1.75 <N14 <2.20
“N14” represents the refractive index of the material of the fourth lens. By selecting such a glass type, it becomes easy to configure the fourth lens as a positive meniscus lens, and mainly it becomes easy to favorably correct spherical aberration and distortion.

1 to 5 show five embodiments of the image pickup optical system.
The embodiments of these five examples correspond to Numerical Examples 1 to 5 described later in this order.
The imaging optical system shown in FIG. 4 is a “reference example”, and the corresponding Numerical Example 4 is also a reference example. However, since it is considered that there is no fear of confusion, the embodiments and numerical values in this specification will be described. Described as Example 4.
1 to 5, the left side of the figures is the "object side" and the right side is the "image side".
In order to avoid complexity, common reference numerals are used in FIGS. 1 to 5.
In these figures, reference numeral 1G indicates a "first lens group", reference numeral 2G indicates a "second lens group", and reference numeral S indicates an "aperture stop". The symbol Im indicates the "image plane".
Each of the imaging optical systems of the embodiments shown in FIGS. 1 to 5 is supposed to “capture an image formed by an imaging device”, and in FIGS. 1 to 5, “cover glass of imaging device and infrared cutoff” is used. "Various filters such as filters" are shown as one transparent flat plate F equivalent to these. The transparent flat plate F has a “parallel flat plate shape”, and the light receiving surface of the image pickup element matches the image plane Im.

1 to 5, reference numeral 2FG indicates a "second F lens group", and reference numeral 2RG indicates a "second R lens group".
Further, in FIGS. 1 to 5, reference numerals L1 to L8 denote lenses. Hereinafter, these lenses L1 to L8 are referred to as the first lens L1 to the eighth lens L8 in order from the object side.

As shown in these figures, the first lens group 1G includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.
The first lens L1 is a positive meniscus lens having a convex surface facing the object side, the second lens L2 and the third lens L3 are all negative lenses, and the fourth lens L4 is a positive lens.
The second lens L2 and the third lens L3 are both “negative meniscus lenses having a convex surface facing the object side”. In addition, the image side surface of the fourth lens L4, which is the “most image-side surface” of the first lens group 1G, is “concave on the image side”.

The second lens group 2G is composed of three lenses, that is, the fifth lens L5 to the seventh lens L7 in the embodiment shown in FIGS. 1 and 2, and in the embodiment shown in FIGS. It is composed of four lenses, that is, a fifth lens L5 to an eighth lens L8.

The second F lens group 2FG is a cemented lens of a fifth lens L5, which is a negative lens having a concave surface facing the object side, and a sixth lens L6, which is a positive lens, and has a positive power.
The second R lens group 2RG is composed only of the lens L7 which is a positive lens in the embodiments of FIGS. 1 and 2, and in the embodiments of FIGS. 3 to 5, both the lenses L7 and L8 which are positive lenses. It is composed of two sheets.
In any of the embodiments, the second lens group 2G includes a positive 2F lens group 2FG as a whole and a positive 2R lens group 2RG as a whole, and the 2F lens group 2FG includes “at least one lens. Negative lens (lens L5) and one positive lens (lens L6)", and the second R lens group 2RG includes "at least one positive lens (lens L7, lens L8)".

Prior to describing specific examples, an “imaging device” and a “compound eye imaging device” using the imaging optical system of the present invention will be described.
As shown in FIG. 12, the system configuration of the image pickup apparatus shown in FIG. 11 includes a taking lens 1 as an “imaging optical system” and a light receiving element 13 as an “imaging element”, and an imaging target formed by the taking lens 1 Is configured to be picked up by the light receiving element 13.
The output from the light receiving element 13 is processed by the signal processing device 14 under the control of the central processing unit 11 and converted into digital information.
The image converted into digital information is displayed on the liquid crystal monitor 7, stored in the semiconductor memory 15, or provided to the outside by the communication card 16 or the like. As a simpler configuration of the “imaging device”, there may be mentioned one configured by “a portion excluding the communication function”.
As the taking lens 1, it is possible to use the image pickup optical system according to any one of claims 1 to 7 , specifically, any one of the “imaging lenses” of Numerical Examples 1 to 3 and 5 described later. it can.
The “image being taken” can be displayed on the liquid crystal monitor 7, or the image recorded in the semiconductor memory 15 can be displayed.
FIG. 11A shows the front part of the image pickup apparatus. In the illustrated state (when carried), the taking lens 1 which is the image pickup optical system is in the “collapsed state”, and the power switch 6 (see FIG. When the power is turned on by the operation of )), the lens barrel is extended from the housing 5. The photographic lens 1 that is extended is "in focus at infinity".

When the shutter button 4 shown in FIG. 11A is "half-pressed" with the image pickup device facing the image pickup target, focusing is performed on the image pickup target, and when the shutter button 4 is further pushed, image pickup is performed, and then the above processing is performed. Is done.
When an image recorded in the semiconductor memory 15 is displayed on the liquid crystal monitor 7 or transmitted to the outside using the communication card 16 or the like, the operation button 8 is operated. The semiconductor memory 15 and the communication card 16 are used by inserting them into the dedicated or general-purpose slot 9.
As shown in FIG. 11A, when the taking lens 1 is in the “collapsed state”, the lens groups 1G and 2G of the taking optical system 1 do not necessarily have to be aligned on the optical axis. For example, if the second lens group 2G is retracted from the optical axis and is configured to be “stored in parallel with the first lens group 1G”, the imaging device can be made even thinner.
In the image forming lenses of Numerical Examples 1 to 5, the first lens group 1G has a larger "group thickness" than the second lens group 2G, and thus it is better to retract the first lens group G1 from the optical axis. It is possible to greatly contribute to "thinning".

Next, an example of an embodiment of the “compound eye imaging device” will be described with reference to FIG.
This compound-eye image pickup device is a “vehicle-mounted stereo camera”, and as shown in FIG. 13A, is mounted on the vehicle 100 to form a “device control system”.
The device control system has an imaging unit 102, an analysis unit 103, a control unit 104, and a display unit 105.
The image pickup unit 102 is provided in the vicinity of the rearview mirror of the windshield 106 of the vehicle 100, and picks up, for example, an “image of the traveling direction or the like” of the vehicle 100. Various data including image data obtained by the imaging operation of the imaging unit 102 is supplied to the analysis unit 103.
The analysis unit 103 analyzes a recognition target object such as a road surface on which the vehicle 100 is traveling, a vehicle ahead, a pedestrian, an obstacle, or the like, based on various data supplied from the imaging unit 102. The control unit 104 issues a warning or the like to the driver of the vehicle 100 via the display unit 105 based on the analysis result of the analysis unit 103.
The control unit 104 can also perform traveling support such as control of various in-vehicle devices, steering control of the vehicle 100, or brake control based on the analysis result.

FIG. 13B is a schematic block diagram of the imaging unit 102 and the analysis unit 103. As shown in this figure, the imaging unit 102 is a “stereo camera” including two imaging units 110A and 110B. The two imaging units 110A and 110B have the same configuration.
Specifically, the image pickup section 110A has an image pickup optical system 111A, an image pickup element 112A having a two-dimensional light receiving section, and a controller 113A for driving the image pickup element 112A. Similarly, the image pickup section 110B has an image pickup optical system 111B, an image pickup element 112B having a two-dimensional light receiving section, and a controller 113B for driving the image pickup element 112B.
As the image pickup optical systems 111A and 111B, the image pickup optical system according to any one of claims 1 to 7 , specifically, the image pickup optical system according to any one of Numerical Examples 1 to 3 and 5 described later is used. be able to.
The analysis unit 103 is an example of an object recognition device, has an FPGA (Field-Programmable Gate Array) 114, a RAM (Random Access Memory) 115, a ROM (Read Only Memory) 116, a CPU 117, and further has a serial IF 118, It has a data IF 119.

The FPGA 114 to the data IF 119 are connected to each other via the data bus line 210 of the analysis unit 103.
The imaging unit 102 and the analysis unit 103 are connected to each other via the data bus line 210 and the serial bus line 200.
The RAM 115 stores parallax image data and the like generated based on the luminance image data supplied from the imaging unit 102. The ROM 116 stores “various programs such as an object detection program including an operation system and a parallax image generation program”.
Further, the FPGA 114 operates according to the "parallax image generation program" included in the object detection program. The FPGA 114 sets one of the picked-up images picked up by the image pickup units 110A and 110B as a reference image and the other as a comparison image.
Then, the FPGA 114 calculates the amount of positional deviation between the corresponding image portion on the reference image and the corresponding image portion on the comparison image corresponding to the same point in the imaging area as the parallax value (parallax image data) of the corresponding image portion. ..

The CPU 117 operates based on the operation system stored in the ROM 116, and performs “overall imaging control” of the imaging units 110A and 110B. The CPU 117 also loads the object detection program from the ROM 116 and executes various processes using the parallax image data written in the RAM 115.
Specifically, the CPU 117 acquires CAN (Controller Area Network) information such as vehicle speed, acceleration, steering angle, yaw rate, etc., obtained from each sensor provided in the vehicle 100 via the data IF 119, based on the object detection program. With reference to, a recognition process of a recognition target object such as a road surface, a guardrail, a vehicle, a human being, parallax calculation, calculation of a distance to the recognition target object, and the like are performed.

The CPU 117 supplies the processing result to the control unit 104 in FIG. 13A via the serial IF 118 or the data IF 119. The control unit 104 is an example of a control device and performs, for example, brake control, vehicle speed control, steering wheel control, and the like based on the data that is the processing result. The control unit 104 also displays a warning on the display unit 105 based on the data that is the processing result. As a result, driving assistance for the driver of the vehicle 100 can be provided.

"Numerical example"
Five specific numerical examples of the image pickup optical system of the present invention will be given below.
The meanings of the symbols in the numerical examples are as follows.

f: focal length of the entire system
Fno: F number
ω: Half angle of view (unit: degree)
Y': Maximum image height
R: radius of curvature
D: Face spacing
Nd: Refractive index at d-line
νd: Abbe number
BF: Back focus
The glass type described in the numerical examples is "Ohara's optical glass type name".
"Surface number" is the number of the surface (including the surface of the aperture stop) counted from the object side.
Further, in FIG. 1 etc., what is shown as the transparent flat plate F is described as “various filters etc.” in each numerical example.

The unit of the "quantity having the dimension of length" is "mm" unless otherwise specified.

"Numerical Example 1"
Numerical Example 1 corresponds to the imaging optical system shown in FIG.
f=5.40, Fno=1.91, ω=29.43
Surface number RD Nd νd Glass type
1 10.34900 1.74 1.77250 49.60 S-LAH66(OHARA)
2 42.56200 0.11
3 8.80000 0.81 1.51633 64.14 S-BSL7(OHARA)
4 3.58 200 0.97
5 12.00000 0.80 1.51633 64.14 S-BSL7(OHARA)
6 2.74500 0.89
7 4.46000 2.35 1.85026 32.27 S-LAH71(OHARA)
8 12.68100 0.49
9 (aperture stop) 0.33
10 -8.11900 0.90 1.84666 23.78 S-TIH53(OHARA)
11 4.04600 2.46 1.69350 53.20 S-LAL13(OHARA)
12 -4.73400 0.15
13 12.41500 1.64 1.85150 40.78 S-LAH89(OHARA)
14 -12.41500 5.35
18 ∞ 0.4 1.51633 64.14 Various filters, etc.
19 ∞ BF.

"Parameter value of conditional expression"
The parameter values of each conditional expression are as follows.
(1) 6.07
(2) 6.5 9
(4) 0.06
(5) 0.28
(6) 0.213.
"Numerical Example 2"
Numerical Example 2 corresponds to the imaging optical system shown in FIG.
f=5.41, Fno=1.91, ω=29.37
Surface number RD Nd νd Glass type
1 11.16100 1.66 1.85150 40.78 S-LAH89(OHARA)
2 45.52700 0.12
3 8.30000 0.70 1.51633 4.14 S-BSL7(OHARA)
4 3.50000 1.11
5 19.43600 0.72 1.51633 64.14 S-BSL7(OHARA)
6 2.91300 0.45
7 4.44800 2.16 1.85150 40.78 S-LAH89(OHARA)
8 16.00000 0.45
9 (aperture stop) 0.73
10 -7.13100 1.20 1.85478 24.80 S-NBH56(OHARA)
11 4.75600 2.42 1.71300 53.87 S-LAL8(OHARA)
12 -4.75600 0.15
13 12.67300 1.64 1.85150 40.78 S-LAH89(OHARA)
14 -12.67 300 5.40
18 ∞ 0.4 1.51633 64.14 Various filters, etc.
19 ∞ BF.

"Parameter value of conditional expression"
The parameter values of each conditional expression are as follows.
(1) 12.01
(2) 4.5 8
(4) 0.06
(5) 0.28
(6) 0.221.

"Numerical Example 3"
Numerical Example 3 corresponds to the imaging optical system shown in FIG.
f=5.40, Fno=1.90, ω=29.35
Surface number RD Nd νd Glass type
1 9.01700 1.57 1.77250 49.60 S-LAH66(OHARA)
2 44.64000 0.23
3 12.96700 0.70 1.51633 64.14 S-BSL7(OHARA)
4 2.82700 0.95
5 11.26100 0.70 1.51633 64.14 S-BSL7(OHARA)
6 3.28800 0.46
7 4.47600 2.82 1.85026 32.27 S-LAH71(OHARA)
8 15.47000 0.26
9 (aperture stop) 0.35
10 -7.74000 0.70 1.84666 23.78 S-TIH53(OHARA)
11 4.51600 2.57 1.73400 51.47 S-LAL59(OHARA)
12 -5.12 100 0.15
13 26.08400 1.35 1.85150 40.78 S-LAH89(OHARA)
14 -11.74 700 0.10
15 29.88700 1.05 1.61800 63.33 S-PHM52(OHARA)
16 -53.09300 5.00
17 ∞ 0.4 1.51633 64.14 Various filters, etc.
18 ∞ BF.

"Parameter value of conditional expression"
The parameter values of each conditional expression are as follows.
(1) 11.75
(2) 8.8 6
(4) 0.09
(5) 0.28
(6) 0.225.

"Numerical Example 4"
Numerical Example 4 corresponds to the image pickup optical system shown in FIG. As described above, this example is a "reference example".
f=5.40, Fno=1.91, ω=29.34
Surface number RD Nd νd Glass type
1 9.42800 1.46 1.83481 42.72 S-LAH55V(OHARA)
2 98.67700 0.15
3 29.06600 0.75 1.51633 64.14 S-BSL7(OHARA)
4 2.59600 0.90
5 11.07300 0.75 1.51633 64.14 S-BSL7(OHARA)
6 3.96900 0.24
7 4.14100 1.63 1.85150 40.78 S-LAH89(OHARA)
8 176.63500 0.21
9 (aperture stop) 0.73
10 -6.23100 0.82 1.84666 23.78 S-TIH53(OHARA)
11 5.31700 1.84 1.60300 65.44 S-PHM53(OHARA)
12 -4.10900 0.15
13 46.21900 1.28 1.85026 32.27 S-LAH71(OHARA)
14 -9.77300 0.10
13 10.18300 0.99 1.80400 46.58 S-LAH65V(OHARA)
14 17.10600 4.40
15 ∞ 0.4 1.51633 64.14 Various filters, etc.
16 ∞ BF.

"Parameter value of conditional expression"
The parameter values of each conditional expression are as follows.
(1) 22.52
(2) 5.7 5
(4) 0.23
(5) 0.32
(6) 0.004.

"Numerical Example 5"
Numerical Example 5 corresponds to the imaging optical system shown in FIG.
f=5.40, Fno=1.91, ω=29.33
Surface number RD Nd νd Glass type
1 9.98100 1.49 1.77250 49.60 S-LAH66(OHARA)
2 63.48400 0.15
3 10.70800 0.75 1.51633 64.14 S-BSL7(OHARA)
4 2.48 600 0.95
5 7.30900 0.75 1.51633 64.14 S-BSL7(OHARA)
6 3.67 300 0.27
7 4.07700 1.80 1.85026 32.27 S-LAH71(OHARA)
8 8.97700 0.30
9 (aperture stop) 0.54
10 -6.03700 0.75 1.85478 24.80 S-NBH56(OHARA)
11 4.94700 1.81 1.73400 51.47 S-LAL59(OHARA)
12 -4.41700 0.15
13 22.61500 1.27 1.85150 40.78 S-LAH89(OHARA)
14 -13.05900 0.10
15 -162.82400 1.15 1.61800 63.33 S-PHM52(OHARA)
16 -12.00600 4.95
17 ∞ 0.4 1.51633 64.14 Various filters, etc.
18 ∞ BF.

"Parameter value of conditional expression"
The parameter values of each conditional expression are as follows.
(1) 20.02
(2) 6.4 3
(4) 0.10
(5) 0.30
(6) 0.196.

FIG. 6 shows an aberration curve diagram of an object at infinity of the imaging optical system of Numerical Example 1.
FIG. 7 shows an aberration curve diagram of an object at infinity of the imaging optical system of Numerical Example 2.
FIG. 8 shows an aberration curve diagram of an object at infinity of the imaging optical system of Numerical Example 3.
FIG. 9 shows an aberration curve diagram of an object at infinity of the imaging optical system of Numerical Example 4.
FIG. 10 shows an aberration curve diagram of an object at infinity of the imaging optical system of Numerical Example 5.
In the astigmatism, the solid line represents sagittal and the broken line represents meridional. “D” is an aberration curve diagram for the d line and “g” is for the g line.
As shown in the aberration curve diagrams, all of the imaging optical systems of Numerical Examples 1 to 5 have a small distortion and a high performance, a wide angle of view of about 58 degrees, and a large F number of about 2. It is a caliber, and is composed of about 7 to 8 "only polished spherical surfaces" and has good performance.

Although the embodiment of the “stereo camera using the image pickup optical system” has been described above with reference to FIG. 13, the distortion aberration is one of the major factors that deteriorate the ranging accuracy of the stereo camera. .. Therefore, it is preferable that the distortion of the image pickup optical system used for the stereo camera be “optically or electronically corrected”.
The amount of distortion aberration that is electronically corrected affects the circuit capacity and calculation ability in the stereo camera board, and is reflected in the camera size and cost. Further, when the stereo camera is mounted on a vehicle, it is necessary to secure an oncoming lane, a sidewalk, etc. within the angle of view in addition to the traveling lane of the own vehicle.
In order to measure a distance to a distant vehicle and to identify and recognize an object, a certain degree of high performance is required as the image quality of the camera.

Taking these into consideration, the maximum amount of distortion that is allowed for electronic correction is required to be “less than ±2%”, and in terms of wide angle, the total angle of view is about 58 degrees. .. Further, in terms of image quality, it is required to have a resolution corresponding to at least an “SXGA size image sensor”, have less chromatic aberration, and be less likely to cause a color difference due to image height.

Further, in order to improve the recognition in a low-luminance scene such as during twilight or at dawn, it is desirable that the diameter is about F2 or less.

The image pickup optical systems of the specific numerical examples 1 to 5 listed above have a distortion of 2% or less, a wide angle of view of about 58 degrees in total angle of view, and a large aperture of about 2 in F number. Meets the requirements for the imaging optical system of a stereo camera.

Although the embodiment of the stereo camera device using two image pickup optical systems of the present invention has been described above as an example of the “compound eye image pickup device”, the compound eye image pickup device of the present invention has “three image pickup optical systems”. The above-mentioned configuration" can also be used.

As described above, according to the present invention, it is possible to realize a novel imaging optical system, imaging device, and compound-eye imaging device.

[1]
A negative first lens group (1G), an aperture stop (S), and a positive second lens group (2G) are arranged in this order from the object side to the image side, and the first lens group (1G) is A first lens (L1), a second lens (L2), a third lens (L3), and a fourth lens (L4) are arranged in this order from the object side to the image side. The first lens (L1) Is a positive meniscus lens having a convex surface facing the object side, the second lens (L2) is a negative lens, the third lens (L3) is a negative lens, and the fourth lens (L4) is a positive lens. The lens group (2G) has, in order from the object side to the image side, a cemented lens of a negative lens (L5) and a positive lens (L6) and a positive lens (L7), and the surface closest to the object side is the object. Is concave on the side, the focal length of the entire system is f, the air distance between the third lens and the fourth lens of the first lens group on the optical axis is L34L, and the fourth lens of the first lens group is the fourth. An air gap on the optical axis through the aperture stop between the image side surface of the lens and the object side surface of the cemented lens of the second lens group: SL is a conditional expression.
(1) 5.00 <f/L34L <50.00
(2) 2.00 <f/SL <15.00
An imaging optical system that satisfies the conditions ( Numerical Examples 1 to 3 and 5).

[2]
The imaging optical system according to [1], wherein the third lens (L3) in the first lens group (1G) is a negative meniscus lens having a convex surface facing the object side ( Numerical Example 1 ~ 3, 5).

[3]
The imaging optical system according to [1] or [2] , wherein the focal length of the entire system is f, and the focal length of the first lens group is f1, the conditional expression (4) 0.01 <|f/f1| <0.50
An imaging optical system that satisfies the conditions ( Numerical Examples 1 to 5 ).

[4]
The imaging optical system according to any one of [1] to [3] , wherein the focal length of the entire system is f and the optical axis from the object side surface of the first lens to the image surface in the infinity in-focus state Distance: AL is conditional expression (5) 0.10 <f/AL <0.50
An imaging optical system that satisfies the conditions ( Numerical Examples 1 to 3 and 5).

[5]
The imaging optical system according to any one of [1] to [4] , wherein the second lens group (2G) is a positive second F lens group (2FG) as a whole, and a positive second 2R lens as a whole. Lens group (2RG
), the second F lens group (2FG) includes at least one negative lens (L5) and one positive lens (L6), and the second R lens group (2RG) includes at least one negative lens (L5). An imaging optical system ( Numerical Examples 1 to 5 ) including a positive lens (L7, L8).

[6]
The imaging optical system according to any one of [1] to [5] , wherein the focal length of the entire system is f, the negative lens (L5) closest to the object in the second lens group (2G), and the positive lens. Synthetic focus of cemented lens with (L6): f2F is expressed by the conditional expression (6) 0.000 <|f/f2F| <0.500
An imaging optical system that satisfies the conditions ( Numerical Examples 1 to 3 and 5).

[7]
The imaging optical system according to any one of [1] to [6] , wherein all the lenses (L1 to L7, L1 to L8) are spherical lenses made of glass (Numerical Examples 1 to 1). 3, 5 ).

[8]
An image pickup apparatus having the image pickup optical system according to any one of [1] to [7] (FIGS. 11 and 12 ).

[9]
[8] The imaging device according to any one of [1] to [7], which has a function of converting a captured image by the imaging optical system into digital information (FIGS. 11 and 12 ).

[10]
A compound eye image pickup apparatus having two or more image pickup optical systems according to any one of [1] to [7] and having a function of converting each image pickup image by the two or more image pickup optical systems into digital information (FIG. 13). ).

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described specific embodiments, and unless otherwise specified in the above description, the invention described in the claims. Various modifications and changes can be made within the scope of the above.
For example, the imaging optical system of the present invention can be used as a “projection optical system used in a projection optical system” with the “image side” in the above description as the object side and the “object side” as the image side.

Further, the image pickup optical system of the present invention can be used as an image pickup optical system for a digital camera, a portable information terminal device, a video camera or a silver halide camera, and can also be used as an image pickup optical system for various optical sensors. Is.

The effects described in the embodiments of the present invention are merely enumerations of suitable effects resulting from the invention, and the effects according to the invention are not limited to "the effects described in the embodiments".

1G 1st lens group
2G 2nd lens group
2FG 2nd lens group
2RG 2R lens group
S aperture stop
F Various filters and image sensor covers, etc.
D spectrum d line
G spectrum g line

Japanese Patent Laid-Open No. 11-052228 JP, 2012-220741, A Patent No. 4667269 Japanese Patent No. 4004587

Claims (10)

A negative first lens group, an aperture stop, and a positive second lens group are arranged in order from the object side to the image side,
The first lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in this order from the object side to the image side, and the first lens has a positive surface with a convex surface facing the object side. A meniscus lens, the second lens is a negative lens, the third lens is a negative lens, and the fourth lens is a positive lens,
The second lens group has, in order from the object side to the image side, a cemented lens of a negative lens and a positive lens, a positive lens, and a surface closest to the object side is concave toward the object side.
Focal length of the entire system: f, air distance on the optical axis between the third lens and the fourth lens of the first lens group: L34L, the image side surface of the fourth lens of the first lens group, and the An air gap on the optical axis through the aperture stop between the object side surface of the cemented lens of the two lens groups: SL is a conditional expression
(1) 5.00 <f/L34L <50.00
(2) 2.00 <f/SL <15.00
Imaging system that satisfies the requirements. The imaging optical system according to claim 1, wherein
An imaging optical system in which the third lens in the first lens group is a negative meniscus lens having a convex surface facing the object side. The imaging optical system according to claim 1 or 2, wherein
The focal length of the entire system: f, the focal length of the first lens group: f1 is a conditional expression
(4) 0.01 <|f/f1| <0.50
Imaging system that satisfies the requirements. The imaging optical system according to any one of claims 1 to 3, wherein:
The focal length of the entire system: f, the distance on the optical axis from the object side surface of the first lens to the image plane in the in-focus state at infinity: AL is a conditional expression
(5) 0.10 <f/AL <0.50
Imaging system that satisfies the requirements. The imaging optical system according to any one of claims 1 to 4,
The second lens group comprises a positive second F lens group as a whole and a positive second R lens group as a whole, and the second F lens group includes at least one negative lens and one positive lens. The second R lens group is an image pickup optical system including at least one positive lens . The imaging optical system according to any one of claims 1 to 5, wherein:
The focal length of the entire system is f, and the combined focus of the cemented lens of the negative lens and the positive lens closest to the object side of the second lens group is f2F, which is a conditional expression.
(6) 0.000 <|f/f2F| <0.500
Imaging system that satisfies the requirements. The imaging optical system according to any one of claims 1 to 6, wherein:
An imaging optical system in which all lenses are spherical lenses made of glass. An image pickup apparatus having the image pickup optical system according to claim 1. The imaging device according to claim 8, wherein
An imaging device having a function of converting a captured image by the imaging optical system according to any one of claims 1 to 7 into digital information. A compound eye image pickup apparatus having two or more of the image pickup optical systems according to any one of claims 1 to 7, and having a function of converting each image picked up by the two or more image pickup optical systems into digital information.

Images