TWI583995B - Iris recognition optical system having short total length - Google Patents

Description

Short-distance iris recognition optical system

The invention provides an optical system for short-distance iris recognition, which uses a lens with two reflecting surfaces to make the focal length extremely shortened, so that it can be stably used in a mobile phone, a smart phone, a tablet computer or a notebook computer. Thinned portable electronic products to identify the user's iris.

Recently, biometrics technology that uses human body features to confirm personal identity has become more popular with the focus on access control systems and computer security systems. The range of biometric identification technology has been gradually increased from the past to fingerprint identification. Applications such as iris recognition, sound recognition or vein identification.

In particular, the iris around the pupil of the eye, even the same twins, can be distinguished into different types, and their identification characteristics are distinct, and the difference is better than fingerprint recognition, so the application example of iris recognition technology is also Gradually increase.

In order to perform iris recognition, an iris image is obtained by using an optical system, an iris code is obtained by acquiring the characteristics of the iris image data, and a process is performed to confirm whether the stored iris code matches the obtained iris code.

In addition, in order to use the software to process the iris image to obtain its characteristics correctly, such as the iris diameter of 11 ~ 12mm, the object distance is 300mm, it is ingested in the camera ( The image of the image sensor of the module usually has a portrait image of 200 pixels or more.

The smallest (1/10吋) VGA-level sensor (640*480) has a pixel size of 2.25μm, so the size of 200 pixels is 0.45mm. Compared with the iris size of 12mm, the optical system magnification is 0.0375 times. . Therefore, when the user takes an iris at a distance that does not feel very inconvenient (about 300 mm), and in order to obtain a satisfactory image, it is necessary to use a VGA level sensor to exhibit a magnification above this level as a reference.

However, as shown in the first figure, if the magnification is obtained by using a simple combination of two lenses (L1, L2) as the optical system, the focal length must be 12 mm or more. 10 VGA level sensor, and the iris is composed of 50% (0.9mm) of the unilateral side of the sensor, but the total length of the optical system (the distance from the front side of the first lens to the sensing surface) must be 10.9. Mm or so.

In terms of optical systems mounted on general security equipment, this full length should not cause major problems, but portable electronic products such as smart phones, tablets, and notebook computers that are thinner than 10 mm in overall thickness. In terms of it, it is impossible.

Even with a camera with 16 million pixels, in a normal shooting mode, such as an iris diameter of 11 to 12 mm, and an object distance of 300 mm, it is necessary to have an iris image at about 150 pixels. Therefore, it is difficult to handle with software.

Furthermore, if the magnification of the optical system is sufficiently increased, it is not difficult to obtain an iris image of 200 pixels or more, but if the magnification is increased, the focal length is enlarged, and the focal length is as If the fruit is pulled large, the total length of the optical system will also be enlarged, so that the general optical system structure cannot increase the magnification without limitation.

Moreover, it is not difficult to obtain an iris image of 200 pixels or more when photographing a user's eyes at a close distance, but this method is very inconvenient to use, and therefore the use distance (about 300 mm) of a general portable electronic product is For the benchmark, the full length of the optical system must be shortened.

Further, Patent Document 1 is a Korean Patent Publication No. 10-2008-0049022, and the second drawing is a structural diagram of an optical system for iris recognition in Patent Document 1, which is arranged in order from the object side, and includes a double convex spherical lens (2A). , double concave spherical lens (3A), visible light filter (4A), package glass (6) and image sensor (5).

However, the double convex spherical lens (2A) in Patent Document 1 has a thickness of 2.92 mm, the double concave spherical lens (3A) has a thickness of 3.00 mm, and the distance between the double concave spherical lens (3A) and the visible light filter (4A) is 2.45. Mm, the visible light filter (4A) has a thickness of 3.00 mm, and it is obvious that the entire optical system has a total length exceeding 20 mm.

Therefore, the optical system for iris recognition of the method of Patent Document 1 is not suitable for use in a small electronic product such as a smart phone.

Therefore, in view of the above-mentioned shortcomings, the inventors have collected relevant information, and through multi-party evaluation and consideration, and through years of experience in the industry, through continuous trial and modification, they have designed such devices that can be installed on mobile phones and smart phones. , tablet, notebook, etc. In the electronic product, it is possible to stably obtain an iris image under normal use conditions, and to provide an invention patent for an optical system for short-distance iris recognition which can provide a shorter total length than the conventional one.

The main object of the present invention is to provide a first lens (L1) having a positive (+) refracting power of an object itself and a second lens (L2) having a negative (-) refracting power, the object side of the first lens The second reflecting surface (S3) formed around the optical axis and the first reflecting surface (S1) formed around the second reflecting surface (S3) are included, and the image side includes a portion formed around the optical axis. a second penetration surface (S4) and a first reflection surface (S2) formed around the second penetration surface (S4), the first penetration surface (S1) being a concave curved surface or a vertical surface with respect to the optical axis .

A secondary object of the present invention is that the first reflecting surface (S2) and the second reflecting surface (S3) have a convex shape in the image side direction, and the second transmitting surface (S4) has a concave shape in the image side direction. feature.

Another object of the present invention is that the first reflecting surface (S2), the second reflecting surface (S3) and the second transmitting surface (S4) of the first lens (L1) are aspherical, and the second lens (L2) Both sides are characterized by aspherical surfaces.

Another object of the present invention is that the entire length of the optical system (the distance from the most end surface of the first lens to the sensing surface) is assumed to be T, and when the overall focal length of the optical system is assumed to be F, the conditional formula T/F<0.65 can be satisfied. It is characterized by it.

Still another object of the present invention is that the first penetration surface (S1) has a concave curved surface on the object side, and can be characterized by a condition of -100,000 mm < curvature radius (S1) < -100 mm.

An optical system for iris recognition according to the present invention, as on the first lens The two reflective surfaces are formed, so the focal length can be shortened, so it can be installed on thin and small portable electronic products such as mobile phones, smart phones, tablets or notebook computers, and portable electronic products. Users can also easily and stably obtain iris images at a distance of about 300mm.

L1‧‧‧ first lens

L2‧‧‧ second lens

S1‧‧‧ first penetration surface

S2‧‧‧ first reflecting surface

S3‧‧‧ second reflecting surface

S4‧‧‧second penetration surface

S5‧‧‧ face

S6‧‧‧ face

2A‧‧‧Double convex spherical lens

3A‧‧‧double concave spherical lens

4A‧‧‧visible light filter

5‧‧‧Image sensor

6‧‧‧Package glass

The first figure is a structural diagram of an optical system for conventional iris recognition.

The second figure is a configuration diagram of another conventional optical system for iris recognition.

The third diagram is a configuration diagram of the optical system of the first embodiment of the present invention.

The fourth figure is an optical system deviation diagram of the first embodiment of the present invention.

Fig. 5 is a configuration diagram of an optical system according to a second embodiment of the present invention.

Figure 6 is a diagram showing the deviation of the optical system of the second embodiment of the present invention.

Figure 7 is a configuration diagram of an optical system according to a third embodiment of the present invention.

The eighth figure is an optical system deviation diagram of the third embodiment of the present invention.

In order to achieve the above objects and effects, the technical means and the configuration of the present invention will be described in detail with reference to the preferred embodiments of the present invention.

Please refer to the third, fifth, and seventh figures, which are sequentially provided with a first lens (L1) having a positive (+) refracting power and a second lens (L2) having a negative (-) diopter, and A partition (not shown) is disposed between the second lens (L2) and the image sensor (5).

In particular, the first lens (L1) of the optical system in the embodiment of the present invention has a reflecting surface on the object side and the image side, respectively.

Specifically, the object side of the first lens (L1) includes a second reflecting surface (S3) formed around the optical axis and a first transmitting surface (S1) formed around the second reflecting surface (S3). The image side of the first lens (L1) includes a second penetration surface (S4) formed around the optical axis and a first reflection surface (S2) formed around the second penetration surface (S4). .

The light incident on the first penetration surface (S1) is reflected by the first reflection surface (S2) formed on the image side, and then incident on the second reflection surface (S3), and then reflected by the second reflection surface (S3). Then, after passing through the second penetration surface (S4), it is incident on the second lens (L2).

The first penetration surface (S1) preferably has a vertical shape or a concave shape with respect to the optical axis. In the conventional omnidirectional optical system or panoramic optical system, although a structure having two reflecting surface lenses has been described, the optical system is mainly wide-angle, and therefore the first penetrating surface ( S1) A convex curvature of a large curvature is formed on the object side. However, as described in the present invention, it is not appropriate to apply the first penetration surface (S1) to such an optical system in which the viewing angle is reduced for iris recognition.

That is, at a distance of about 300 mm, in order to correctly photograph the iris, it is relatively necessary to exhibit a high magnification at a narrow viewing angle, and for this reason, like the first penetration surface (S1) of the first lens (L1) of the embodiment of the present invention, Preferably, the object side direction is concave with a small curvature, and at least with respect to the optical axis, it is preferable to have a concave shape with a vertical or a small curvature.

When the first penetration surface (S1) is formed into a concave shape as described above, it is preferable to design the following conditional expression.

<Conditional formula 1>-100,000 mm<curvature radius <-100 mm

In addition, the first reflecting surface (S2) and the second reflecting surface (S3) of the first lens (L1) are respectively convex in the image side direction, and are respectively plated with a reflective substance such as aluminum or silver, or may be attached to the reflection. film. Further, the second penetration surface (S4) of the first lens (L1) is preferably concave.

According to an embodiment of the present invention, although the first lens (L1) and the second lens (L2) both use plastic lenses, the material is not limited.

According to an embodiment of the invention, the first reflecting surface (S2), the second reflecting surface (S3) and the second transmitting surface (S4) of the first lens (L1) are all aspherical, and the second lens (L2) Both sides (S5, S6) are also aspherical.

In particular, in the embodiment of the present invention, even in the iris recognition, even if a sufficient viewing angle and magnification (or focal length) are obtained, in order to be set in, for example, a mobile phone, a smart phone, or a tablet computer, a shorter full length must be specifically presented. The lens is designed to meet the above condition 1.

<Condition 2> Telephoto ratio (T/F) <0.65

T: the total length of the optical system (distance from the frontmost surface of the first lens to the sensing surface), F: the overall focal length of the optical system.

In fact, if you skip the above conditions, such as when the object distance is 300mm, the full length will become too long to be installed in thin portable small electronic products such as mobile phones, smart phones, tablets or notebook computers. on.

The following is a description of a specific embodiment of an optical system for iris recognition to which the above conditions are applied.

The third and fourth figures are the structural diagram and the deviation diagram of the optical system of the first embodiment, and the fifth and sixth figures are the structural diagram and the deviation diagram of the optical system of the second embodiment, and the seventh diagram and The eighth drawing is a configuration diagram and a deviation diagram of the optical system of the third embodiment.

The following Table 1 is the data of the radius of curvature, the thickness and the refractive index of each lens applied to the optical system for iris recognition according to the first embodiment. Table 2 is applicable to the non-optical surfaces of the optical system according to the first embodiment. Spherical data.

The following Table 3 is the data of the radius of curvature, the thickness and the refractive index of each lens applied to the optical system for iris recognition according to the second embodiment of the present invention. Table 4 is applicable to each of the optical systems according to the second embodiment. Aspherical data on the surface of the lens.

The following Table 5 is applied to the data of the radius of curvature, the thickness, and the refractive index of each lens of the optical system for iris recognition according to the third embodiment of the present invention. Table 6 is applicable to each of the optical systems according to the third embodiment. Aspherical data on the surface of the lens.

In Table 2, Table 4 and Table 6, K is a Conic constant, and A, B, C, and D are aspherical coefficients, and are applicable to the following mathematical formula 1 related to the aspherical shape.

Z is the distance from the apex of the lens to the optical axis, Y is the vertical distance of the optical axis, and c is the reciprocal of the radius of curvature (r) of the apex of the lens.

The focus distance, the full length, and the telephoto ratio (T/F) of the respective optical systems according to the first to third embodiments are as shown in the following Table 7.

Referring to Table 7, according to the optical systems for identifying irises according to the first to third embodiments of the present invention, when the object distances are 340 mm, 248 mm, and 340 mm, respectively, the focal lengths (efl) are 10.85 mm, 12.42 mm, and 10, respectively. . 81mm.

This focal length is greatly different from the existing iris identification optical system presented in the first figure, and the total length (T) of the optical system according to the example of the present invention is 3.17 mm, 3.74 mm, and 3.18 mm, respectively. It is about 1/3 or less in the prior art, so it can be known that the full length distance becomes very short.

If the iris recognition optical system has such a short full-length distance, it can be installed not only in the thinned portable electronic products such as the thinnest mobile phones, smart phones, tablets, or notebook computers that are currently on the market, but also can be installed. It is located in most portable electronic products and similar small electronic products.

The preferred embodiments of the present invention have been described above, but the present invention can achieve various types of deformations or modifications for specific applications, such as the related examples of deformation or modification described later, and the technology of the present invention included in the scope of the patent application. Within the scope of sexuality, it is of course within the scope of the invention.

L1‧‧‧ first lens

L2‧‧‧ second lens

S1‧‧‧ first penetration surface

S2‧‧‧ first reflecting surface

S3‧‧‧ second reflecting surface

S4‧‧‧second penetration surface

S5‧‧‧ face

S6‧‧‧ face

5‧‧‧Image sensor

Claims (5)

An optical system for short-distance iris recognition, wherein a first lens (L1) having positive (+) diopter and a second lens (L2) having negative (-) diopter are sequentially arranged, wherein: an object side of the first lens And including a second reflecting surface (S3) formed around the optical axis and a first transmitting surface (S1) formed around the second reflecting surface (S3), and the image side includes the optical axis as the center. a second penetration surface (S4) and a first reflection surface (S2) formed around the second penetration surface (S4); the first penetration surface (S1) is a concave curved surface or is opposite to the optical axis Vertical surface. The optical system for short-distance iris recognition according to claim 1, wherein the first reflective surface (S2) and the second reflective surface (S3) have a convex shape in an image side direction, and the second transparent surface (S4) is a concave shape in the image side direction. The optical system for short-distance iris recognition according to claim 1, wherein the first reflecting surface (S2), the second reflecting surface (S3), and the second transmitting surface (S4) of the first lens (L1) ) is an aspherical surface, and both sides of the second lens (L2) are aspherical. The optical system for short-distance iris recognition according to claim 1 or 3, wherein the total length of the optical system (distance from the front end surface of the first lens to the sensing surface) is T, and the overall focal length of the optical system is In the case of F, the conditional expression is satisfied as T/F < 0.65. The optical system for short-distance iris recognition according to claim 1, wherein the first penetration surface (S1) has a concave curved surface in the object side direction, and satisfies the conditional expression-10 0,000 mm <radius of curvature (S1) <-100 mm.