KR100366723B1 - Lighting apparatus for iris recognition system - Google Patents

Abstract

The present invention relates to an infrared LED module used as an illumination device of an optical imager for extracting an iris image from an iris recognition system. In particular, the present invention utilizes the multi-wavelength characteristics of an LED chip inside an infrared LED module. The present invention relates to an illumination device of an iris recognition system for capturing an iris at a constant brightness, and includes a plurality of LED chips having different wavelengths in one infrared LED module, and the same wavelength among the plurality of LED chips. LED chips are to provide an illumination device for an iris recognition system, characterized in that configured to be symmetrical with each other.

Description

Lighting device of iris recognition system {LIGHTING APPARATUS FOR IRIS RECOGNITION SYSTEM}

The present invention relates to an infrared LED module used as an illumination device of an optical imager for extracting an iris image from an iris recognition system. In particular, the present invention utilizes the multi-wavelength characteristics of an LED chip inside an infrared LED module. The present invention relates to an illumination device of an iris recognition system for photographing an iris with a constant brightness.

Recently, biological features have been used for user identification in automated access systems and commerce systems using the Internet.

Biological features such as fingerprints, voices, retinas, and irises may exist, but iris recognition systems that differ from person to person, with low risk of imitation, and do not change well over a lifetime are attracting attention as important technologies for user identification.

Iris recognition refers to a system for identifying an individual by using the features of the iris and comparing the iris feature pattern captured by the video camera with image processing technology and comparing it with his or her own iris data.

Figure 1 is a block diagram of a general iris recognition system, as shown in this, a distance measuring sensor for measuring the distance to the user using an infrared sensor (1), and informs the user whether the system is active and recognized External indicator (3), an illumination device (4) for adjusting the illuminance when taking iris images irrespective of the surrounding brightness, an optical window (5) for positioning the user's eyes, and the optical window A cold mirror 6 for passing infrared rays through and blocking visible light, a camera 7 for photographing an iris image of the user transmitted through the cold mirror, and a frame grabber for processing the photographed iris image ( 8) and determining whether the user is within the operating range by receiving the distance measurement value measured by the distance measuring sensor 1, automatically recognizing the iris and adjusting the light intensity And an optical imager driver 2 for controlling the operation of the external indicator 3 and the illumination device 4 by the control of the control device. Looking at the operation of such a general iris recognition device as follows.

When the user approaches the iris recognition system, the distance measuring sensor 1 measures the distance to the user and transmits it to the control device 9. The control device 9 determines whether the received distance measurement value is within the operating range.

If the determination result is within the operating range, a control signal is output to the optical imager driver 10 to prepare for iris image extraction.

The optical imager driver 2 sends an active signal to the external indicator 3 to inform the user that the system has been activated.

After the user approaches the optical imager and places the eye on the optical axis of the camera 7 through the optical window 5, the cold mirror 6 passes infrared rays and blocks visible light. In addition, the cold mirror displays a portion where the iris should be located so that the user can easily check whether or not his eyes are positioned on the optical axis of the camera 7.

After that, the controller 9 drives the camera 7 to control the iris image.

When the iris image photographed by the camera 7 is provided to the frame grabber 8, the frame grabber 8 processes the signal to be provided for the image analysis and provides it to the controller 9. The control device 9 receiving the processed signal informs the user whether the recognition is made through the external indicator 3 through the optical imager driver 2.

In the general iris recognition device, a halogen lamp is generally used as the lighting device 4 that can greatly affect the recognition rate.

The halogen lamp includes visible light and infrared rays in various wavelength bands so that the characteristics of each wavelength band may appear in a user's eyes when iris is recognized. Therefore, the distinction between the iris and the pupil and between the iris and the white has the advantage that it is easy to extract the pattern of only the iris part.However, when the optical imager is observed for a long time, the user may feel rejection due to the visible light. And there is a heat generation problem. A typical optical imager uses a fixed focus camera, so the distance between the user and the optical imager is fixed. Therefore, the intensity of light can be made constant by making the amount of electric current which flows through a lighting apparatus constant. However, when the distance between the user and the optical imager changes, that is, the optical imager system using the auto zoom camera is used within a certain range without limiting the user's use distance. In order to provide convenience to the user, it is necessary to change the output of the lighting device so that the iris image can be captured at a constant brightness.

Another conventional optical imager of the iris recognition device uses a single-wavelength infrared LED array as an illumination device, and is placed on the left and right of the iris camera. This method can obtain high power by using infrared LED with long wavelength, but short wavelength can affect only the part responding to the wavelength band, which may cause difficulty in extracting the pattern only for the iris part.

It can be a factor in the performance of the system.

In order to solve the problems of the prior art, an object of the present invention is to construct an illumination device having a wide band of wavelength bands such as a halogen lamp in an iris recognition device. Another object of the present invention is to clarify the control method in the iris recognition system to improve the performance of the iris recognition system.

In order to achieve the above object, the present invention provides a lighting device of an iris recognition system, comprising a plurality of LED chips having different wavelengths in one infrared LED module, and having the same wavelength among the plurality of LED chips. The LED chips are to provide a lighting device for the iris recognition system, characterized in that configured to be symmetrical to each other.

The LED chips of the present invention are divided into two or more parts, each of which is connected to a power source in parallel, and another feature of the LED chips in each part is connected in series.

In still another aspect of the present invention, an iris recognition system includes a distance measuring sensor for measuring a distance to a user, a controller for calculating and outputting a current amount for each distance according to the measured distance value, and according to an output of the controller. It comprises an LED driver for supplying the LED drive current, and a plurality of LED chips having different wavelengths, and a multi-wavelength infrared LED for irradiating light by receiving the drive current of the LED driver. It is to provide a lighting device for the iris recognition system. The control unit may control to increase or decrease the LED driving current according to the brightness of the photographed iris image.

1 is a schematic diagram of a general iris recognition system

2 is an iris image photographed using a halogen lamp

3 is the brightness deviation for each part when using a halogen lamp

Figure 4 is a connection structure between the chip (chip) inside the infrared LED of the present invention

5 is another embodiment of the infrared LED of the present invention.

6 is a block diagram showing an infrared LED control of the present invention.

==== Explanation of symbols for the main parts of the drawings ====

100: camera 200: distance measuring sensor

300: infrared LED 400: control unit

500: Infrared LED Driver

Hereinafter, a preferred embodiment of the present invention will be described in detail.

2 is a view illustrating an iris image photographed using a halogen lamp. Referring to the multi-wavelength characteristic of an infrared LED for an iris recognition system to help understand the present invention, the following description will be made.

1-1) Wavelength Characteristics of Halogen Lamps

In order to analyze the characteristics of halogen lamps having a wide wavelength band such as visible light and infrared light, average values of brightness of specific parts of whites, irises and pupils were obtained for images photographed using halogen lamps as shown in FIG. 2.

In Table 1, S_L and I_L represent the white and iris of the left part, P represents the pupil, and S_R and I_R represent the specific part of the white and iris of the right part. In the photographed image, each pixel Pixel has a value of 255 at the brightest and 0 at the darkest. The average value of the pixels inside the rectangle shown in FIG. 2 is obtained to represent the brightness of the portion.

Figure 3 shows this graphically, the deviation rate indicates the degree of brightness deviation between the white and iris and the iris and the pupil with respect to the brightness deviation of the white and the pupil. The degree is clearly distinguished. It is assumed that the closer the deviation rate is to 0.5, the clearer the distinction between the iris and the white and the iris and pupil.

Deviation Rate (S_L) = (Average Value (S_L)-Average Value (I_L)) / (Average Value (S_L)-Average Value (P))

Deviation Rate (I_L) = (Average Value (I_L)-Average Value (P)) / (Average Value (S_L)-Average Value (P))

1-2) Wavelength Characteristics

Iris images were taken using infrared LEDs with wavelengths of 750 nm, 790 nm, and 880 nm. The average values of the brightnesses were calculated for the five specific parts as shown in FIG. [Table 2] below shows the deviation rate after taking the iris image for each wavelength and then the average of the deviation rate.

As shown in Table 2, the shorter the wavelength becomes, the clearer the distinction between the iris and the white is. The longer the wavelength becomes, the clearer the distinction is between the iris and the pupil. However, the distinction between the white and the iris may become unclear. In addition, as the wavelength is shorter and closer to the visible light region, the user may feel rejection due to the influence of the visible light.

In an embodiment of the present invention, after dividing a plurality of LED chips having wavelengths of 750 nm, 790 nm, and 880 nm into two parts in one infrared LED module, each part is in parallel, and the LED chips in the part are in series. Infrared LED module was connected. Of course, each of the wavelengths can be replaced by any number of LED chips of other wavelengths that can maximize the effect of the present invention.

Figure 4 shows the inter-chip connection structure inside the infrared LED of the present invention. In the present invention as shown in Figure 4 the number of LED chips (Chip) to maintain sufficient brightness even in the maximum operating area to shoot the iris image at a constant brightness within the operating range of the optical imager (Optical Imager) for the iris recognition system Is determined. The number of LED chips by wavelength is determined so that the output of LED chips by each wavelength is similar so that the characteristics of any one wavelength band do not appear remarkably. This is because they are different. The division of LED chips into several parts is affected by the power used in the system.Reducing the number of parts allows control with a small amount of current, but requires a higher voltage. However, the maximum current must be increased. In addition, the wavelength-specific LED chips (chips) are positioned in consideration of symmetry so as not to be biased to either side of the infrared LED module.

4 shows a multi-wavelength infrared LED module composed of four 750nm LED chips, two 790nm LED chips, and two 880nm LED chips, and the interconnection structure between the internal chips is symmetrical. It is supposed to have a structure.

In another embodiment of the present invention, the number of LED chips for each wavelength may be changed by modifying the multi-wavelength infrared LED module, and the position may be changed as shown in FIG. 5-1.

In addition, the present invention may be configured by dividing the LED chip (Chip) into three parts as shown in Figure 5-2. The three parts are connected in parallel to the power supply and the LED chips in each part are configured to be connected in series.

Looking at the characteristics of the multi-wavelength infrared LED of the present invention configured as described above are as follows.

[Table 3] is a iris image is taken by applying the present invention and the average value of the brightness is calculated for the five specific parts as shown in Figure 2 and the deviation rate is calculated, the deviation rate after taking the iris image for a number of users The average of the deviation rates is obtained.

As shown in [Table 3], the multi-wavelength infrared LED module of the present invention has a deviation ratio approaching 0.5, and thus the iris has a characteristic of being clearly distinguished from other parts around it.

In this regard, in one infrared LED module, an LED chip having a wavelength band other than the above-mentioned wavelength may be added or replaced with an LED chip having a different wavelength band.

When the present invention configured as described above will be described the operation controlled in the iris recognition system as follows.

In order to capture the iris image with a constant brightness within the optical imager's optical imager's operating range, the current is applied experimentally to the infrared LED module for each distance. However, there is a big difference in the brightness of the iris image taken according to the output deviation of the multi-wavelength infrared LED module, the user's gaze angle, and the face, particularly the position of the eye. By reducing this difference, the amount of current flowing through the infrared LED module is adjusted to capture the iris at a constant brightness. 6 is a block diagram showing a procedure for controlling the brightness of the multi-wavelength infrared LED of the present invention and has a feedback control structure.

In order to maintain a constant brightness around the user's eyes, the distance is first measured by the distance sensor 200, and the controller notifies the infrared LED driver 500 by referring to the current amount reference value for each distance. The infrared LED driver supplies the required current to the infrared LED so that the infrared LED 300 irradiates light. Once the user's eyes are bright, the iris image is taken using the camera 100. The controller 400 analyzes the image to calculate the degree of brightness and determines whether this value is within the allowed range. If the degree of brightness has a small value out of the allowable range, it becomes dark, so it informs the infrared LED driver 500 to increase the current flowing through the infrared LED. On the contrary, if the average value of the brightness has a large value out of the allowable range, it becomes bright, so the infrared LED driver 500 is informed to reduce the current flowing through the infrared LED. Then, the above operation is continued until the average value of the brightness falls within the allowable range or the iris recognition is completed, so that the iris image can be captured with a constant brightness.

As described above, the present invention, by using a multi-wavelength infrared LED to obtain a characteristic that can be clearly distinguished between the iris and the surroundings, such as a halogen lamp, to the optical imager (Optical Imager) and the user Regardless of distance, the iris image can be captured at a constant brightness within the operating area, thereby increasing the recognition performance of the iris recognition system.

Claims (7)

In the illumination device of the iris recognition system, a plurality of LED chips having different wavelengths are provided in one infrared LED module, and the LED chips having the same wavelength among the plurality of LED chips are configured to be symmetric with each other. Lighting device for iris recognition system. The illumination device for an iris recognition system according to claim 1, wherein the wavelength of the LED chip is 750 nm, 790 nm, or 880 nm. The illumination device for an iris recognition system according to claim 1, wherein the LED chips are divided into two or more parts, each of which is connected in power and the LED chips in each part are connected in series. An iris recognition system comprising: a distance measuring sensor for measuring a distance to a user, a controller for calculating and outputting a current amount for each distance according to the measured distance value, and an LED for supplying an LED driving current according to the output of the controller. An iris recognition system comprising a driver and a plurality of LED chips having different wavelengths and including a multi-wavelength infrared LED for irradiating light by receiving a driving current of the LED driver. Device. The illumination device for an iris recognition system according to claim 5, wherein the controller controls the LED driving current to increase or decrease according to the brightness of the photographed iris image. The illumination device for an iris recognition system according to claim 5, wherein the multi-wavelength infrared LED is configured such that LED chips having the same wavelength are arranged symmetrically. 7. The lighting device for an iris recognition system according to claim 6, wherein the two parts are divided into two parts, each of which is connected in parallel and the LED chips in each part are connected in series.