WO2021120056A1

WO2021120056A1 - Fisheye lens system, camera module and electronic apparatus

Info

Publication number: WO2021120056A1
Application number: PCT/CN2019/126322
Authority: WO
Inventors: Makoto Fujimoto
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-06-24
Also published as: CN114830006A; CN114830006B

Abstract

A fisheye lens system comprising, sequentially from an object side to an image side, a first lens group having a first negative meniscus lens which is convex to the object side, a second negative meniscus lens which is convex to the object side, a third meniscus lens which is convex to the image side, and a fourth positive lens, a second lens group comprising more than one lenses, and an aperture stop on either side of any lens, wherein a center thickness of the third meniscus lens is less than an edge thickness of the third meniscus lens, wherein the first lens group has at least one aspherical surface, and the second lens group has at least one aspherical surface.

Description

FISHEYE LENS SYSTEM, CAMERA MODULE AND ELECTRONIC APPARATUS

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a fisheye lens system, particularly a fisheye lens having an angle of view of 160° or more, a camera module and an electronic apparatus.

Description of the Related Art

The first practical use of the fisheye lens was in the 1920s for use in meteorology to study cloud formation. Since then, fisheye lenses have been used for a variety of purposes.

Mass-produced fisheye lenses for photography first appeared in the early 1960s. For the popular 35mm film format, a typical focal length of fisheye lenses is between 8mm and 10mm for circular images, and 15 mm to 16 mm for full-frame images. An F-number of fisheye lenses is generally between F 2.8 and F 3.5 since it is difficult to design fisheye lenses faster than F 2.0.

In a circular fisheye lens, the image circle is inscribed in the film or sensor area.

In a full-frame fisheye lens, the image circle is circumscribed around the film or sensor area.

Further, different fisheye lenses distort images differently, and the manner of distortion is referred to as their projection function. Basically, projection functions of fisheye lenses are stereographic, equidistant, equisolid angle, and orthographic projections.

A common projection method of a fisheye lens is equidistant projection. It is mostly used in meteorology such as in ephemeris measurement and cloudiness measurement.

Fisheye lenses have been used in automobiles. Initially, a fisheye lens was used for a car back-camera. As an F-number of fisheye lenses is generally between F2.8 and F3.5 as mentioned above, F 2.8 was fast enough for a car back-camera since a car is equipped with a reverse light.

In recent years, however, fisheye lenses in automobiles are also used for other purposes, such as dash cam, driver status monitor (DSM) , advanced driver-assistance system (ADAS) , Self-Driving, etc. Fisheye lenses faster than F2.8 are required for these purposes in darker environments without assisting light.

SUMMARY OF THE INVENTION

The embodiments of the present invention is to provide a fish eye lens system (an optical lens system) , a camera module and an electronic apparatus for imaging a high quality image with a fast F-number of around F 1.6. The fast fish eye lens system can be applied to any of automobile cameras, smartphone cameras, security cameras, and standard cameras. Fisheye lenses with a fast F-number of around F 1.6 can be applied to more various field where an ordinal fisheye lens, i.e. with a fast F-number of up to F 2.8, was not fast enough. For example, the present fisheye lens system can be used for dash cam, driver status monitor (DSM) , advanced driver-assistance system (ADAS) , Self-Driving, etc, to provide a wide, clear, and bright view monitoring without an additional lighting such a reverse light. For smartphone cameras, the requirements for a wide and bright lens keep increasing. The present fisheye lens system can provide smartphone cameras with a wide and high-quality image with minimum ISO which creates noise. The present fisheye lens system can be also used for a fisheye lens camera based surveillance system for the same reason. The present fisheye lens can be used for longer time in a surveillance system before using lighting system or an infrared camera.

According to a first aspect of the present invention, a fish eye lens system is comprised of, sequentially from an object side to an image side, a first lens group having first and second negative meniscus lenses both convex to the object side, a third meniscus lens which is convex to the image side, and a fourth positive lens, and a second lens group comprising more than one lenses, and an aperture stop on either side of any lens.

The center thickness of the third meniscus lens is less than the edge thickness of the third meniscus lens.

According to a first aspect of the present invention, the ratio of the edge thickness of the third meniscus lens to the center thickness of the third meniscus lens is in range of 1.03 to 1.3, preferably in range of 1.05 to 1.25.

The first lens group has at least one aspherical surface, and the second lens group has at least one aspherical surface

The first and the second negative meniscus lenses have at least one spherical surface such that they have very small spherical aberration and coma aberration.

According to a first aspect of the present invention, the z factor of the third meniscus lens is preferably in the following range.

i) 0 < z factor < 0.15

The z factor indicates the ability of a lens to automatically center itself between bell clamps.

The z factor is given as below:

If a lens is biconvex or biconcave,

ii) z factor = 0.5 × | (B1/R1 + B2/R2) |

If lens is meniscus,

iii) z factor = 0.5 ×| (B1/R1 -B2/R2) |

where B1 and B2 are the semi-diameters of the clear aperture of the lens. R1 and R2 are the curvature radius of the first and second surfaces (i.e. the front and back surfaces) of the lens.

The spherical aberration and coma aberration will be larger when the z factor is larger than 0.15.

The third meniscus lens has very small spherical aberration and coma aberration, which is very effective to keep astigmatism at a low level. Furthermore, the third meniscus lens makes the height of marginal ray higher for enabling lenses to correct spherical aberration.

According to a first aspect of the present invention, the fisheye lens system satisfies the following condition:

iv)

where

is the power of the whole fisheye lens system, and

is the power of the first lens group.

v)

where

is the power of the whole fisheye lens system, and

is the power of the third negative meniscus lens.

The first lens group has very small positive power

so that the decenter tolerance and tilt tolerance of the first lens group should be large enough.

The third lens has very small negative power

so that the decenter tolerance and tilt tolerance are large enough.

According to a first aspect of the present invention, the second lens group includes three lenses.

According to a first aspect of the present invention, the second lens group includes two lens sub-groups.

By satisfying the above-mentioned conditions, the fisheye lens system according to the present the invention can have an F-number of the lens faster than F 1.8.

A fisheye lens system with F-number of the lens faster than F 1.8 can be advantageously applied to various camera systems without an additional lighting.

According to a first aspect of the present invention, the fisheye lens system is used for an automobile

According to a first aspect of the present invention, the fisheye lens system is applied to at least one of automobile cameras, smartphone cameras, or security cameras.

According to a second aspect, the invention relates to a fisheye lens camera based imaging (surveillance) system. The system comprises: at least one fisheye lens camera including the fisheye lens system according to any preceding implementation of the first aspect or the first aspect as such; and a controller configured to transform a fisheye lens image into an output image. That is, the fisheye lens system is applied to imaging (surveillance) system comprising, at least one fisheye lens cameras and a controller configured to transform a fisheye lens image into an output image.

According to a third aspect, the invention relates to a camera module. The camera module comprises: the fisheye lens system according to any preceding implementation of the first aspect or the first aspect as such; an image sensor configured to capture an input image; one or more image processors; and a non-transitory computer-readable storage medium storing instructions that when executed cause the one or more image processors to generate an output image. That is, the fisheye lens system is applied to a camera module comprising an image sensor configured to capture an input image, one or more image processors, and a non-transitory computer-readable storage medium storing instructions that when executed cause the one or more image processors to generate an output image. The camera module may be applied to any electronic apparatus.

According to a fourth aspect, the invention relates to an electronic apparatus. The electronic apparatus comprises: the camera module according to any preceding implementation of the third aspect or the third aspect as such; a display unit; and a control unit that controls the camera module and the display unit. That is, the present camera module is applied to an electronic apparatus comprising a display unit and a control unit that controls the camera module and the display unit. The electronic apparatus may be, such as dash cam, driver status monitor (DSM) , advanced driver-assistance system (ADAS) , and Self-Driving for an automobile, a smart phone (mobile phone) , a security camera system, and etc.

The present invention will be presented in further detail from the following descriptions with the accompanying drawings, which show, for purpose of illustration only, the preferred embodiments in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood from the following detailed description of non-limiting embodiments thereof, and from examining the accompanying drawings, in which:

FIG. 1 shows a cross-sectional illustration of a fisheye lens in a prior art.

FIG. 2 shows a bar chart for spherical aberration coefficients of the fisheye lens shown in FIG. 1.

FIG. 3 shows a bar chart for coma aberration coefficients of the fisheye lens shown in FIG. 1.

FIG. 4 shows a bar chart for astigmatism aberration coefficients of the fisheye lens shown in FIG. 1.

FIG. 5 shows a cross-sectional illustration of a fisheye lens in an embodiment.

FIG. 6 shows a bar chart for spherical aberration coefficients of the fisheye lens as shown in FIG. 5 in the embodiment.

FIG. 7 a bar chart for coma aberration coefficients of the fisheye lens as shown in FIG. 5 in the embodiment.

FIG. 8 shows a bar chart for astigmatism aberration coefficients of the fisheye lens as shown in FIG. 5 in the embodiment.

FIG. 9 shows a graph of spherical aberration of the fisheye lens as shown in FIG. 5 in the embodiment.

FIG. 10 shows a graph of field curvature of the fisheye lens as shown in FIG. 5 in the embodiment.

FIG. 11 shows a graph of distortion of the fisheye lens as shown in FIG. 5 in the embodiment.

FIG. 12 shows a cross-sectional illustration of a fisheye lens in another embodiment.

FIG. 13 shows a graph of spherical aberration of the fisheye lens as shown in FIG. 12 in the embodiment.

FIG. 14 shows a graph of field curvature of the fisheye lens as shown in FIG. 12 in the embodiment.

FIG. 15 shows a graph of distortion of the fisheye lens as shown in FIG. 12 in the embodiment.

FIG. 16 shows a cross-sectional illustration of a fisheye lens in another embodiment.

FIG. 17 shows a graph of spherical aberration of the fisheye lens as shown in FIG. 16 in the embodiment.

FIG. 18 shows a graph of field curvature of the fisheye lens as shown in FIG. 16 in the embodiment.

FIG. 19 shows a graph of distortion of the fisheye lens as shown in FIG. 16 in the embodiment.

FIG. 20 shows an example architecture of a camera module.

FIG. 21 is a block diagram of the electronic apparatus according to the present embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a cross-sectional illustration of a fisheye lens system in a prior art, comprising, sequentially from an object side to an image side, the first lens group G1, an aperture stop S, the second lens group G2, and a filter F.

The first lens group G1 is constructed of, sequentially from the object side to the image side, a first negative meniscus lens L1 which is convex to the object side, a second negative meniscus lens L2 which is convex to the object side, and a third cemented convex lens L3 consisting of two lenses L3 ₁ and L3 ₂.

The center thickness of the third lens L3 is thicker than the edge thickness since the third lens L3 is a positive lens.

The second lens group G2 is constructed of, sequentially from the object side, a fourth cemented positive meniscus lens L4 consisting of two lenses L4 ₁ and L4 ₂ and a fifth cemented positive lens L5 consisting of two lenses L5 ₁ and L5 ₂.

Please note that the fisheye lens system in a prior art has F number of F 2.8 and an angle of view of 200°.

FIG. 2 shows a bar chart for spherical aberration coefficients of the fisheye lens system in a prior art shown in FIG. 1.

FIG. 3 shows a bar chart for coma aberration coefficients of the fisheye lens system in a prior art shown in FIG. 1.

FIG. 4 shows a bar chart for astigmatism aberration coefficients of the fisheye lens system in a prior art shown in FIG. 1.

The bar charts of FIG. 2 to 4 are calculated by Zemax ^TM in the case that the total focal length is normalized to 1. Welford, Aberrations of Optical Systems was used as a reference for the derivation of the Seidel aberration coefficients.

First Embodiment

FIG. 5 shows a cross-sectional illustration of a seven-piece fisheye lens system in the first embodiment, comprising, sequentially from an object side to an image side, the first lens group G1, the second lens group G2 and a filter F.

The first lens group G1 is constructed of, sequentially from the object side to the image side, a first negative meniscus lens L1 which is convex to the object side, a second negative meniscus lens L2 which is convex to the object side, a third negative meniscus lens L3 which is convex to the image side, and a fourth positive lens L4.

The second negative meniscus lens L2 is aspheric on both sides.

The center thickness TL3 of the third negative meniscus lens L3 is less than the edge thickness EL3 of the third negative meniscus lens L3.

The second lens group G2 is constructed of, sequentially from the object side, a fifth positive lens L5, an aperture stop S, a sixth cemented negative lens L6 consisting of a positive lens L6 ₁ and a negative lens L6 ₂, and a seventh positive lens L7.

The seventh positive lens L7 is aspheric on both sides.

FIG. 6 shows a bar chart for spherical aberration coefficients of the fisheye lens system in the first embodiment.

FIG. 7 shows a bar chart for coma aberration coefficients of the fisheye lens system in the first embodiment.

FIG. 8 shows a bar chart for astigmatism aberration coefficients of each lens element of the fisheye lens system in the first embodiment.

The bar charts of FIG. 6 to 8 are calculated by Zemax ^TM in the case that the total focal length is normalized to 1. Welford, Aberrations of Optical Systems was used as a reference for the derivation of the Seidel aberration coefficients.

Referring to the bar charts of FIG. 6 and 7, and 8, it should be noted that the first lens group G1 has very small spherical and astigmatism aberration compared to those of the prior art.

It should be also noted that the third negative meniscus lens has very small spherical aberration and coma aberration. So, it’s very effective to control especially astigmatism aberration.

It should be also noted that the fourth positive lens has some spherical aberration, small coma aberration and astigmatism aberration. The positive spherical aberration cancels with the spherical aberration of the second lens group. So, it’s very effective to control spherical aberration.

It should be also noted that the spherical aberration is mainly canceled with the fifth positive lens L5 and the sixth cemented negative lens L6 and that the astigmatism aberration is mainly canceled with the fifth positive lens L5 and the seventh positive lens L7.

The graphs of FIG. 9, FIG. 10, and FIG. 11 show spherical aberration, field curvature, and distortion respectively. Regarding distortion, the ideal image height is calculated to be equidistant.

The z factor of the third negative meniscus lens L3 and other key factors are as below,

Z factor = 0.05

TL3 = 3.77

EL3 = 4.14

EL3/TL3 = 1.10

where

is the power of the whole lens system,

is the power of the first lens group, and

is the power of the third negative meniscus lens L3.

Therefore, the first embodiment satisfies the conditions i) , ii) , and iii) .

Table 1-1 shows the specification of each lens element of the fisheye lens system in the first embodiment.

Table 1-1

f=1.904

2ω=200°

Fno=1.8

Table 1-2 shows the conic constant of the aspherical surfaces of lenses L2 and L7.

Table 1-2

	L2 Front	L2 Back	L7 Front	L7 Back
Conic Constant	-2.41E+00	-8.06E-01	-9.06E-01	-3.42E+01
4th Order Coefficient	-2.12E-03	-1.22E-02	-1.10E-03	-2.92E-03
6th Order Coefficient	7.50E-05	2.67E-04	1.33E-04	3.98E-04
8th Order Coefficient	-8.17E-07	-2.55E-05	-3.46E-06	-1.10E-05

The fisheye lens system according to the first embodiment achieved an F-number of F 1.8 and an angle of view of 200°.

Second Embodiment

FIG. 12 shows a cross-sectional illustration of a seven-piece fisheye lens system in the second embodiment, comprising, sequentially from an object side to an image side, the first lens group G1, the second lens group G2 and a filter F.

The first lens group G1 is constructed of, sequentially from the object side, a first negative meniscus lens L1 which is convex to the object side, a second negative meniscus lens L2 which is convex to the object side, a third negative meniscus lens L3 which is convex to the image side, and a fourth positive lens L4.

The second negative meniscus lens L2 is aspheric on both sides.

The second lens group G2 is constructed of, sequentially from the object side, a fifth positive lens L5, an aperture stop S, a sixth cemented negative lens L6 consisting of a positive lens L6 ₁ and a negative lens L6 ₂, a seventh positive lens L7.

The seventh positive lens L7 is aspheric on both sides.

The graphs of FIG. 13 FIG. 14, and FIG. 15 show spherical aberration, field curvature, and distortion respectively. Regarding distortion, the ideal image height is calculated to be equidistant.

Z factor = 0.04

TL3 = 3.66

EL3 = 4.03

EL3/TL3 = 1.10

where

is the power of the whole lens system,

is the power of the first lens group, and

is the power of the third negative meniscus lens L3.

Therefore, the second embodiment satisfies the conditions i) , ii) , and iii) .

Table 2-1 shows the specification of each lens element of the fisheye lens system in the second embodiment.

Table 2-1

f=1.904

2ω=200°

Fno=1.6

Table 2-2 shows the conic constant of the aspherical surfaces of lenses L2 and L7.

Table 2-2

	L2 Front	L2 Back	L7 Front	L7 Back
Conic Constant	-2.22E+00	-8.18E-01	-1.01E+00	-3.15E+01
4th Order Coefficient	-2.25E-03	-1.24E-02	-1.08E-03	-3.16E-03
6th Order Coefficient	7.60E-05	2.73E-04	1.54E-04	4.37E-04
8th Order Coefficient	-8.15E-07	-2.42E-05	-4.41E-06	-1.28E-05

The fisheye lens system according to the second embodiment achieved an F-number of F 1.6 and an angle of view of 200°.

Third Embodiment

FIG. 16 shows a cross-sectional illustration of a seven-piece fisheye lens system in the third embodiment, comprising, sequentially from an object side to an image side, the first lens group G1, the second lens group G2 and a filter F.

The first lens group G1 is constructed of, sequentially from the object side, a first negative meniscus lens L1 which is convex to the object side, a second negative meniscus lens L2 which is convex to the object side, a third meniscus lens L3 which is convex to the image side, and a fourth positive lens L4.

The first negative meniscus lens L1 is spherical on both sides and made of glass.

The second negative meniscus lens L2 is aspheric on both sides and made of plastic.

The third meniscus L3 is aspheric on both sides and made of plastic. The center thickness TL3 of the third meniscus lens L3 is less than the edge thickness EL3 of the third meniscus lens L3.

The fourth positive lens L4 is aspheric on both sides and made of plastic.

The second lens group G2 is constructed of, sequentially from the object side, a fifth positive lens L5, an aperture stop S, a sixth negative lens L6, and a seventh positive lens L7.

The fifth positive lens L5 is spherical on both sides and made of glass.

The sixth negative lens L6 is aspheric on both sides and made of plastic.

The seventh positive lens L7 is aspheric on both sides and made of plastic.

The fisheye lens system in the third embodiment uses plastic aspheric lenses and glass spherical lenses for reducing the cost since glass aspheric lenses are very expensive.

Glass spherical lenses give the third embodiment good environmental characteristics.

The graphs of FIG. 17 FIG. 18, and FIG. 19 show spherical aberration, field curvature, and distortion respectively. Regarding distortion, the ideal image height is calculated to be equidistant.

Key factors are as below. Since the third meniscus lens L3 is aspheric on both sides, there is no z factor.

TL3 = 3.46

EL3 = 4.12

EL3/TL3 = 1.19

where

is the power of the whole lens system,

is the power of the first lens group, and

is the power of the third negative meniscus lens L3.

Therefore, the third embodiment satisfies the conditions 2) , and 3) . There is no z factor as mentioned above.

Table 3-1 shows the specification of each lens element of the fisheye lens system in the third embodiment.

Table 3-1

f=1.904

2ω=200°

Fno=1.6

Table 3-2 shows conic constant of the aspherical surfaces of lenses L2, L3, L4, L6, and L7.

Table 3-2

The fisheye lens system according to the third embodiment achieved an F-number of F 1.6 and an angle of view of 200°.

Example Camera Configuration

FIG. 20 is a block diagram illustrating a fisheye lens camera (camera module) 10, according to one embodiment. In the illustrated embodiment, the fisheye lens camera 10 may comprise an imaging unit 20 comprising a fisheye lens system 22, an image sensor 24, and an image processor 26. The fisheye lens camera 10 may additionally or optionally include a system controller 30 (e.g., a microcontroller or microprocessor) that may control the operation and functionality of the fisheye lens camera 10 and system memory 40 that may be configured to store executable computer instructions that, when executed by the system controller 30 and/or the image processors 26, may perform the camera functionalities. The fisheye lens camera 10 may additionally or optionally include Sensors 50, audio system 60, I/O interface 70 and control display 80. In some embodiments, a fisheye lens camera 10 may optionally include multiple imaging units 20 to capture fields of view in different fields of view or for different functions. One of the multiple imaging units 20 may have a lens system (not shown) other than the fisheye lens system.

The fisheye lens system 22 can focus light entering the fisheye lens to the image sensor 24 which captures images and/or video frames.

The image sensor 24 may capture high-definition images or video having a resolution of, for example, 720p, 1080p, 4k, or higher. For video, the image sensor 24 may capture video at frame rates of, for example, 30 frames per second, 60 frames per second, or higher. The image processor 26 may perform one or more image processing functions of the captured images or video. For example, the image processor 26 may perform a Bayer transformation, demosaicing, noise reduction, image sharpening, image stabilization, rolling shutter artifact reduction, color space conversion, compression, or other in-camera processing functions. Processed images and video may be temporarily or persistently stored to system memory 40 and/or to a non-volatile storage, which may be in the form of internal storage or an external memory card.

An input/output (I/O) interface 70 may transmit and receive data from various external devices. For example, the I/O interface 70 may facilitate the receiving or transmitting video or audio information through an I/O port. Examples of I/O ports or interfaces may include USB ports, HDMI ports, Ethernet ports, audioports, and the like. Furthermore, embodiments of the I/O interface 70 may include wireless ports that can accommodate wireless connections. Examples of wireless ports include Bluetooth, Wireless USB, Near Field Communication (NFC) , and the like. The I/O interface 70 may also include an interface to synchronize the fisheye lens camera 10 with other cameras or with other external devices, such as automobile cameras, smartphone cameras, security cameras, and standard cameras..

A control/display subsystem 80 may include various control and display components associated with operation of the fisheye lens camera 10 including, for example, LED lights, a display, buttons, microphones, speakers, and the like. The audio system 60 may include, for example, one or more microphones and one or more audio processors to capture and process audio data correlated with video capture. In one embodiment, the audio system 60 may include a microphone array having two or microphones arranged to obtain directional audio signals.

Sensors 50 may capture various metadata concurrently with, or separately from, video or image capture. For example, the sensors 50 may capture time-stamped location information based on a global positioning system (GPS) sensor, and/or an altimeter. Other sensors 50 may be used to detect and capture orientation of the fisheye lens camera 10 including, for example, an orientation sensor, an accelerometer, a gyroscope, or a magnetometer. Sensor data captured from the various sensors 50 may be processed to generate other types of metadata. For example, sensor data from the accelerometer may be used to generate motion metadata, comprising velocity and/or acceleration vectors representative of motion of the fisheye lens camera 10. Furthermore, sensor data from the may be used to generate orientation metadata describing the orientation of the fisheye lens camera 10. Sensor data from the GPS sensor provides GPS coordinates identifying the location of the fisheye lens camera 10, and the altimeter measures the altitude of the fisheye lens camera 10. In one embodiment, the sensors 50 may be rigidly coupled to the fisheye lens camera 10 such that any motion, orientation or change in location experienced by the fisheye lens camera 10 may also be experienced by the sensors 50. The sensors 50 furthermore may associates a time stamp representing when the data was captured by each sensor. In one embodiment, the sensors 50 may automatically begin collecting sensor metadata when the fisheye lens camera 10 begins recording a video or captures an image.

FIG. 21 is a block diagram of an electronic apparatus 100 according to the present embodiment. As an example in the present embodiment, the electronic apparatus 100 is a device, such as dash cam, driver status monitor (DSM) , advanced driver-assistance system (ADAS) , and Self-Driving for an automobile, a smart phone, a security camera system, and etc. The electronic apparatus 100 may have a housing (not shown) .

The electronic apparatus 100 includes a fisheye lens camera 110, a display unit 140, a wireless communication unit 150, an user interface 120 and a control unit 130. Any of the fisheye lens camera 110, the display unit 140, the wireless communication unit 150 and the user interface 120 do not need to be included in the electronic apparatus 100.

The fisheye lens camera 110 images an object. The fisheye lens camera 110 may be mounted in the housing, such that an optical axis of the fisheye lens camera 110 is parallel to a thickness direction of the thin housing. The fisheye lens camera 110 may generate image data and supply it to at least one of the display section 101, the wireless communication unit 150 and a storage section (not shown) .

The display unit 140 displays the image data. The display unit 140 may display character data and operational buttons that are manipulated by a user.

The wireless communication unit 150 may transmits and receives information using wireless communication such as wireless telecommunication network, wireless LAN (Local Area Network) , Bluetooth, or infrared communication. As an example, the wireless communication unit 150 may transmit the image data to another electronic apparatus.

The user interface 120 receives manipulation input from the user. The user interface 120 may be formed integrally with the display unit 140.

The control unit 130 may perform overall control of the electronic apparatus 100. For example, the control unit 130 controls imaging by the fisheye lens camera 110.

The above-described embodiments of the present invention provide the faster fisheye lens system having F-number of F 1.8 or faster than F 1.8 and an angle of view of around 200° while a conventional fisheye lens system has F-number of around F 2.8.

Therefore, the fisheye lens system according to the present invention can be used for not only automobiles but various applications even in an environment where enough light cannot be supplied.

Although preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

A fisheye lens system comprising, sequentially from an object side to an image side:

a first lens group comprising,

a first negative meniscus lens element which is convex to the object side,

a second negative meniscus lens element which is convex to the object side,

a third meniscus lens element which is convex to the image side, and

a fourth positive lens element,

a second lens group comprising more than one lenses element, and

an aperture stop on either side of any lens element,

wherein a center thickness of the third meniscus lens element is less than an edge thickness of the third meniscus lens element,

wherein the first lens group has at least one aspherical surface, and the second lens group has at least one aspherical surface.
The fisheye lens system according to claim 1, wherein the ratio of the edge thickness of the third meniscus lens element to the center thickness of the third meniscus lens element is in range of 1.03 to 1.3.
The fisheye lens system according to claim 1 or 2, wherein the ratio of the edge thickness of the third meniscus lens element to the center thickness of the third meniscus lens element is in range of 1.05 to 1.25.
The fisheye lens system according to any one of the proceeding claims, wherein a z factor of the third meniscus lens element is preferably in the following range:

i) 0 < z factor < 0.15;

where the z factor for the third meniscus lens element is as follows:

if the third meniscus lens element is biconvex or biconcave,

ii) z factor = 0.5 × | (B1/R1 + B2/R2) |

if the third meniscus lens element is meniscus,

iii) z factor = 0.5 ×| (B1/R1 -B2/R2) |

where B1 and B2 are the semi-diameters of the clear aperture of the third meniscus lens element, and R1 and R2 are the curvature radius of the front and back surfaces of the third meniscus lens element.
The fisheye lens system according to any one of the preceding claims, wherein the fisheye lens system satisfies the following condition:

iv)
where
is the power of the whole fisheye lens system,
is the power of the first lens group.
The fisheye lens system according to any one of the proceeding claims, wherein the fisheye lens system satisfies the following condition:

v)
where
is the power of the whole fisheye lens system,
is the power of the third meniscus lens element.
The fisheye lens system according to one of the proceeding claims, wherein the second lens group is comprised of three lens elements.
The fisheye lens system according to any one of the proceeding claims, wherein the second lens group includes two lens sub-groups.
The fisheye lens system according to any one of the proceeding claims, wherein the fisheye lens system is used for an automobile.
The fisheye lens system according to any one of claims 1 to 8, wherein the fisheye lens system is applied to at least one of automobile cameras, smartphone cameras, or security cameras.
A fisheye lens camera based imaging system comprising,

at least one fisheye lens camera including the fisheye lens system of any one of claims 1-10; and

a controller configured to transform a fisheye lens image into an output image.
A camera module comprising:

the fisheye lens system of any one of claims 1-10; and

an image sensor configured to capture an input image;

one or more image processors; and

a non-transitory computer-readable storage medium storing instructions that when executed cause the one or more image processors to generate an output image.
An electronic apparatus comprising:

the camera module of claim 12;

a display unit; and

a control unit that controls the camera module and the display unit.