Imaging lens, iris imaging module and iris identification device
Technical field
The present invention relates to field of biological recognition, particularly relates to a kind of imaging lens, iris imaging module and iris recognition
Device.
Background technology
Iris recognition belongs to field of biological recognition, is a kind of biological identification technology based on iris, and the technology passes through
Iris texture information less than 10mm regions is handled and carrys out certification user identity, iris recognition and other biological identification technology
Compared to the distinguishing feature such as uniqueness and stability, turn into current most accurate identification technology.And the reality of iris recognition technology
Existing difficult point is the iris image for how collecting clear high quality, therefore the optical system for gathering iris image is known as iris
The key of other device.
Existing iris capturing optical system can be divided into:Varifocal optical system and focus optical system, wherein zoom light
System bulk is big, complicated, cost is high, assembly difficulty is big, such as:Four constituent elements are employed in patent CN200810071474.X
Mechanical compensation zoom lens, it is made up of more than ten lens;It is simple to focus optical system structure, low cost, device is convenient, such as:Day
Iris identification equipment in this patent JP2004-167046, it gathers camera lens and is made up of two panels lens and filter plate, but the system
Image quality is poor, has larger spherical aberration and an other aberrations, and the free degree of optical design is smaller;U.S. patent Nos
20090161069A1, improved for the optical texture in above-mentioned patent, change filter plate into rotational symmetric aspheric mirror,
That is three-chip type system, image quality is preferably improved, but uses aspherical mirror, improve manufacturing cost, therefore, image quality
Good, the optical system that focuses simple in construction and low cost turns into the emphasis studied at present.
The content of the invention
The present invention provides a kind of good imaging quality, imaging lens simple in construction and low cost, iris imaging module with
And iris identification device.
In order to solve the above technical problems, present invention offer technical scheme is as follows:
A kind of imaging lens, include successively from front to back along light incident direction:
First lens, first lens are the meniscus with positive light coke, and its preceding surface is convex surface, and rear surface is
Concave surface;
Second lens, second lens are the meniscus with negative power, and its preceding surface is convex surface, and rear surface is
Concave surface;
3rd lens, the 3rd lens are the meniscus with positive light coke, and its preceding surface is convex surface, and rear surface is
Concave surface.
A kind of iris imaging module, including above-mentioned imaging lens and the image sensing positioned at the imaging lens rear
Device, described image sensor are CCD or cmos sensor.
A kind of iris identification device, including above-mentioned iris imaging module and the hardware that is connected with the iris imaging module
Circuit.
The invention has the advantages that:
Compared with prior art, imaging lens of the invention are made up of three lens, especially suitable for closely gathering list
Mesh iris image, and miniaturization portable harvester can be made;It has higher image quality near infrared band,
Distort small;Three lens are spherical lens, and without non-spherical lens, and three lens are meniscus, simple in construction,
It is easy to assembly, low cost.
Brief description of the drawings
Fig. 1 is the structural representation of the imaging lens of the present invention;
Fig. 2 is the structural representation of the imaging lens embodiment one of the present invention;
Fig. 3 is the optical performance curve figure of imaging lens shown in Fig. 2, wherein:3A is the distortion curve figure of embodiment one;3B
For the curvature of field curve map of embodiment one;3C is the relative illumination curve map of embodiment one;3D is the encircled energy of embodiment one
Curve map;3E is the MTF performance diagrams of embodiment one;
Fig. 4 is the structural representation of the imaging lens embodiment two of the present invention;
Fig. 5 is the optical performance curve figure of imaging lens shown in Fig. 4, wherein:5A is the distortion curve figure of embodiment two;5B
For the curvature of field curve map of embodiment two;5C is the relative illumination curve map of embodiment two;5D is the encircled energy of embodiment two
Curve map;5E is the MTF performance diagrams of embodiment two.
Embodiment
To make the technical problem to be solved in the present invention, technical scheme and advantage clearer, below in conjunction with accompanying drawing and tool
Body embodiment is described in detail.
On the one hand, the present invention provides a kind of imaging lens, as shown in figure 1, being wrapped successively from front to back along light incident direction
Include:
First lens 1, the first lens 1 are the meniscus with positive light coke, and its preceding surface 11 is convex surface, rear surface 12
For concave surface;
Second lens 2, the second lens 2 are the meniscus with negative power, and its preceding surface 21 is convex surface, rear surface 22
For concave surface;
3rd lens 3, the 3rd lens 3 are the meniscus with positive light coke, and its preceding surface 31 is convex surface, rear surface 32
For concave surface;The preceding surface of above-mentioned each lens refers to the face that infrared light is injected, and rear surface refers to the face that infrared light projects, similarly hereinafter.
Compared with prior art, imaging lens of the invention are made up of three lens, especially suitable for closely gathering list
Mesh iris image, and miniaturization portable harvester can be made;It has higher image quality near infrared band,
Distort small;Three lens are spherical lens, and without non-spherical lens, and three lens are meniscus, simple in construction,
It is easy to assembly, low cost.
As a modification of the present invention, the focal length of each lens can meet:- 1.5f≤f2≤- 1.2f, 1.5f≤f3
≤ 2.0f, 0.5≤f1/f3≤0.7, wherein, f is the total focal length of the imaging lens, and f1 is the focal length of the first lens 1, and f2 is
The focal length of second lens 2, f3 are the focal length of the 3rd lens 3.
When the focal length of each lens meets above-mentioned relation, there is higher image quality near infrared band, almost without
Distortion.
Further, 12mm≤f1≤22.4mm, -24mm≤f2≤- 19.2mm, 24mm≤f3≤32mm.
Another as the present invention improves, and the material of the first lens 1, the second lens 2 and the 3rd lens 3 meets:1.50
≤ nd≤1.75,30≤vd≤65, wherein, nd is the refractive index of lens material, and vd is the abbe number of lens material.Using upper
Preferable image quality can be accessed by stating the material of refractive index and abbe number, and and can saves material cost.
Preferably, it is provided with as shown in Figure 2 and Figure 4 between the front end of the first lens 1 or the first lens 1 and the second lens 2
For controlling the diaphragm 4 of near infrared light percent of pass.Diaphragm can adjust the power of the near-infrared light beam passed through, different illumination rings
Different diaphragms can be selected under border.
Furthermore, it is possible to visible ray can be reflected and through the filter coating of near infrared light by being coated with the preceding surface 11 of the first lens 1
(such as near infrared band narrow-band-filter film);Filter coating can avoid interference of the visible ray to imaging lens, meanwhile, reflection it is visible
Light can see the eyes image of itself using family from imaging lens, facilitate user to adjust self-position, play the work of positioning
With.
Or imaging lens also include that visible ray can be reflected and through the optically flat filter 5 of near infrared light, optically flat filter
5 can avoid interference of the visible ray to imaging lens, and optically flat filter may be disposed at the front end or rear end of whole imaging lens,
As shown in Figure 2.
At the same time it can also on the lens 2 of rear surface 12 and second of the first lens 1 and the preceding surface of the 3rd lens 3 and
Surface is coated with the near infrared band anti-reflection film that can strengthen near infrared light transmitance afterwards.Anti-reflection film can strengthen the saturating of near infrared light
Rate is crossed, more visible iris image can be obtained with less transmission power.
In the present invention, the wave band of above-mentioned near infrared light is 700-900nm.The near infrared light of the wave band can collect higher
The iris image of quality.
To be further cost-effective, the material of the first lens 1, the second lens 2 and the 3rd lens 3 can be glass.
With two specific embodiments, the present invention will be further elaborated below:
Embodiment one:
The present embodiment is a kind of imaging lens for being used for closely monocular iris recognition, as shown in Fig. 2 by three lens
Group, optically flat filter 5 form, and the rear of imaging lens is provided with imaging sensor 6, is followed successively by along light incident direction:Plane
Optical filter 5;The first lens 1 with positive light coke, it is meniscus, and preceding surface 11 is convex surface, and rear surface 12 is concave surface;Tool
There are the second lens 2 of negative power, it is meniscus, and preceding surface 21 is convex surface, and rear surface 22 is concave surface;With positive light coke
The 3rd lens 3, it is meniscus, and preceding surface 31 is convex surface, and rear surface 32 is concave surface;Three lens and optically flat filter
It is glass material;Imaging surface is imaging sensor face, and it is CCD or cmos sensor.
The imaging lens imaging wavelength of the present embodiment is near infrared band 700-900nm, is coated with optically flat filter 5 near red
Wave section narrow-band-filter film, play a part of filtering out visible light-transmissive near infrared light, the preceding surface and rear surface of each lens
Near infrared band anti-reflection film is coated with, strengthens the transmitance of near infrared band light.
When imaging lens collocation less than the million or VGA imaging sensors of the present invention, iris imaging module is formed, for adopting
When collecting monocular iris image, (13-18cm) clearly iris image can be photographed at closer distance, the imaging lens are specifically tied
Structure parameter refers to table one, including the surface type of lens face, radius of curvature, lens thickness, refractive index, abbe number etc..This reality
The focal length of lens parameter for applying csr optical system is:Total focal length f=16mm, the first focal length of lens f1=16.7mm, the second lens are burnt
Away from f2=-20.5mm, the 3rd focal length of lens f3=25mm.
Table one:The concrete structure parameter of embodiment one of the imaging lens of the present invention
Fig. 3 is the optical performance curve figure of imaging lens of the embodiment of the present invention, and Fig. 3 A show the distortion curve of the present embodiment
Scheme (%), in the range of full filed, distortion aberration is in the range of 0.51%;Fig. 3 B show the curvature of field curve map of the present embodiment
(mm), in the range of full filed, the curvature of field aberration of meridian plane and each light of sagittal surface is respectively less than 0.18mm;Fig. 3 C show this implementation
The relative illumination curve map of example, in the range of full filed, relative illumination is all higher than 95% so that the overall brightness of shooting image is equal
It is even, it is good without dark angle, uniformity;Fig. 3 D show the encircled energy curve map of the present embodiment, and energy has been totally absorbed in 50 μm of models
In enclosing, there is higher encircled energy;Fig. 3 E show the MTF characteristic curves of the present embodiment, find out from curve in full filed model
In enclosing, mtf value is all higher than 0.5 at spatial frequency 65lp/mm.The present invention is real it can be seen from above optical indicatrix figure
Applying an imaging lens has higher image quality.
Embodiment two:
The present embodiment is a kind of imaging lens for monocular iris recognition, as shown in figure 4, by three lens groups and light
Door screen 4 forms, and imaging lens rear is provided with imaging sensor 6, is followed successively by along light incident direction:First with positive light coke
Lens 1, it is meniscus, and preceding surface 11 is convex surface, and rear surface 12 is concave surface;The second lens 2 with negative power, it is
Meniscus, preceding surface 21 are convex surface, and rear surface 22 is concave surface;The 3rd lens 3 with positive light coke, it is meniscus,
Preceding surface 31 is convex surface, and rear surface 32 is concave surface;For diaphragm 4 between the first lens 1 and the second lens 2, three lens are glass
Glass material;Imaging surface is imaging sensor face, and it is CCD or cmos sensor.
The imaging lens imaging wavelength of the present embodiment is near infrared band 700-900nm, and the preceding surface 11 of the first lens 1 is plated
Near infrared band narrow-band-filter film, plays and filters out the effect of visible light-transmissive near infrared light, and remaining lens face is coated near infrared band
Anti-reflection film, strengthen the transmitance of near infrared band light.
When imaging lens collocation less than the million or VGA imaging sensors of the present invention, iris imaging module is formed, for adopting
Collect monocular iris image when, can at closer distance (13-18cm) shooting clear iris image, the imaging lens concrete structure
Parameter refers to table two, including the surface type of lens face, radius of curvature, lens thickness, refractive index, abbe number etc..This implementation
The focal length of lens parameter of csr optical system is:Total focal length f=16mm, the first focal length of lens f1=16.21mm, second focal length of lens
F2=-23.35mm, the 3rd focal length of lens f3=27.24mm.
Table two:The concrete structure parameter of embodiment two of the imaging lens of the present invention
Fig. 5 is the optical performance curve figure of imaging lens of the embodiment of the present invention, and Fig. 5 A show the distortion curve of the present embodiment
Scheme (%), in the range of full filed, distortion aberration is in the range of 0.4%;Fig. 5 B show the curvature of field curve map of the present embodiment
(mm), in the range of full filed, the curvature of field aberration of meridian plane and each light of sagittal surface is respectively less than 0.15mm;Fig. 5 C show this implementation
The relative illumination curve map of example, in the range of full filed, relative illumination is all higher than 95% so that the overall brightness of shooting image is equal
It is even, it is good without dark angle, uniformity;Fig. 5 D show the encircled energy curve map of the present embodiment, and energy has been totally absorbed in 50 μm of models
In enclosing, there is higher encircled energy;Fig. 5 E show the MTF characteristic curves of the present embodiment, find out from curve in full filed model
In enclosing, mtf value is all higher than 0.5 at spatial frequency 65lp/mm.The present invention is real it can be seen from above optical indicatrix figure
Applying an imaging lens has higher image quality.
On the other hand, the present invention provides a kind of iris imaging module, as shown in Figure 2 and Figure 4, including above-mentioned imaging lens with
And the imaging sensor 6 positioned at the imaging lens rear, the imaging sensor 6 are CCD or cmos sensor.The iris of the present invention
Imaging modules have higher image quality near infrared band, distort small;Simple in construction, easy to assembly, low cost is especially suitable
For closely monocular iris capturing, and miniaturization portable harvester can be made.
Another further aspect, the present invention provide a kind of iris identification device, wrap state iris imaging module and with the iris into
The hardware circuit connected as module.The iris identification device of the present invention has higher image quality near infrared band, distorts
It is small;Simple in construction, easy to assembly, low cost, be particularly suitable for use in closely monocular iris capturing, and can make miniaturization just
Prompt formula harvester.
Described above is the preferred embodiment of the present invention, it is noted that for those skilled in the art
For, on the premise of principle of the present invention is not departed from, some improvements and modifications can also be made, these improvements and modifications
It should be regarded as protection scope of the present invention.