**4.3. Anti-spoofing**

#### *4.3.1. Iris*

*4.1.2. Retina*

28 Machine Learning and Biometrics

some users.

**4.2. Reliability**

*4.2.1. Iris*

tion method.

the two patterns).

information.

*4.2.2. Retina*

the eye.

the test.

In the case of the retina, the acceptance rate is low. Many people are afraid of using this technology. They are convinced that a laser will be used that could harm their eye. However, these concerns are totally unnecessary because a laser is never used in this case. Another problem is the retinal image retrieval procedure itself. This is tedious, which can be uncomfortable for

For the retina, a direct user interaction is also required (to be close to the device (centimeter distance) and focus on the fixation points). At least with the current methods, there must be a

When scanning the image of an iris, it is possible to obtain insufficient eye information due to ambient light, eyelids being too closed, and so on. However, this is a fairly reliable identifica-

The accuracy of the comparison of the two iris patterns is represented by the so-called Hamming distance, that is, the number of bits in which the comparison of two different iris patterns differs. It is reported that for the probability of an incorrect comparison of 1:26,000,000, the Hamming distance is 0.32 (i.e., only about one-third of the identical bits of

**Figure 21** shows the distribution of Hamming's distance when comparing the high number of irises [26]. The graph is a binomial distribution with a probability of 0.5. It also follows from the graph that it is highly unlikely that two different irises differ in less than one-third of the

Regarding retinal scanning, its reliability is high. However, there are conditions where it is not possible to obtain a sufficiently good image of the retina. In particular, it is bad illumination—the user has a heavily closed pupil when scanning due to the large amount of light. Another problem occurs with the abovementioned diseases or other dysfunctions of

Recognition by the retina is not very widespread, perhaps because there are not really many objective tests of this method. In 1991, the international company *Sandia National Laboratory* tested EyeDentify Inc. on several hundred volunteers. The result was a zero false accept rate and false reject rate less than 1% [27]. However, at that time, the testing of biometric systems was in its early stages, so we cannot be sure of the objectivity of

relatively large cooperation by the user. Acceptance is therefore low.

There are several possibilities on how to test the liveness (anti-spoofing) of the iris. The most common is the iris reaction to a change in light when the pupil diminishes with more intense lighting. This reflex is subconscious, and responses are usually within the range of 250–400 ms. The pupil stretches and expands even under a constant illumination, and this periodic phenomenon is called the *hippus* [28].

Another way of anti-spoofing can be eye movement, or blinking by the command of a scanning device.

Spectrographic properties of tissues, fats, and blood are used by more advanced devices. Blood reflects infrared radiation very well, as well as the iris pigment melanin. This phenomenon is called the *coaxial back retina reflection*, also called "red eyes," when the light is reflected from a pink retina back into the camera.

*4.4.2. Retina*

*4.5.1. Iris*

among several others.

bases, secret organizations, and so on.

**Figure 22.** Panasonic BM-ET200; EyeLock Nano; Iritech.

*4.5.2. Retina*

Ophthalmic Instrument Standards.

**4.5. Commercial applications and devices**

recognition to control immigrants from neighboring countries.

There are no biometric standards available for recognizing the retina; however, basically, these are images of the bloodstream as well as hand vein recognition, that is, comparable standards could be taken into account. Just only medical standards for retina scanning are available, for example, ISO 10943:2011—Ophthalmic Instruments—Indirect Ophthalmoscopes or ISO/TR 20824:2007—Ophthalmic Instruments—Background for Light Hazard Specification in

Recognition of Eye Characteristics

31

http://dx.doi.org/10.5772/intechopen.76026

There are many examples of practical applications. The most common systems are in the United Arab Emirates, where they are located in airports and seaports (about 3.8 million comparisons daily). Another example is the system at Schiphol Airport in the Netherlands, which is used by people with high-frequency flights. Another example is an application in Tokyo. Condominium employees use this system to enter, while at the same time a lift is called to take them to their office. In Afghanistan, the UNHC (*United Nations High Commission*) uses iris

Available devices capable of human iris identification also exist in a relatively large amount. **Figure 22** shows the *Panasonic BM-ET200*, *EyeLock Nano,* and *Iritech* scanners. Other manufacturers are *Iris ID Systems* and *iCAM TD100*, *IrisGuard Inc.*, *Iritech Inc.*, *AOptix Technologies,*

The use of retinal recognition is appropriate in areas with high security requirements such as nuclear development, arms development, as well as manufacturing, government and military

Purkyne's reflection from the surface of the cornea and the lens can also be used to test the liveness of the eye. When a suitable light source illuminates the surface of the eye, reflective images are produced that are reflected from the front and back surfaces of the cornea and the lens.
