*4.4.2. Retina*

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

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.

Retinal scanning of the eye is a relatively problematic process that cannot be easily imitated. To cheat such a sensor, it would be necessary to use a spoofed eye with the same characteristics as a live eye, which is a very complicated and nearly impossible to replicate (the use of medical ophthalmologic eye phantoms should be taken into account). There is not much information about the liveness test on the retina, but it could again take advantage of medical information, for example, that the non-living retina has a different color. Light refraction of

Since the eye is a very sensitive organ, an invasive method cannot be used for this reason. There is a similar liveness test as for the iris; however, this testing can be used to cheat the system when the right eye is replaced by a false (spoofed) eye after a successful test life. For this reason, it is more appropriate to test liveness with another method. The first test is to test the color of the yellow spot. It is done during the use of the scanned eye. It is only with the

Another option is to test liveness using eye movements. The same principle is used in medicine when examining the eye background. The medical doctor needs to see the whole retina and not just the part seen from a direct view. Therefore, the device is equipped with a deliberate point that the patient watches to slightly retract the eye, allowing the doctor to monitor almost the entire retina. This principle can also be used to test for liveness. The device is equipped with a similar observation point and moves it several times. In each relocation, it performs scans of the retina and compares the position of the blind or the yellow spot. If it is

• *ANSI INCITS 379–2004: Information Technology: Iris Image Interchange Format* [29]. Describes the format for exchanging iris image information. This includes the definition of attributes,

• *ISO/IEC 19794–6: 2011: Information Technology—Biometric Data Interchange Formats—Part 6: Iris Image Data* [29, 30]. Specifies two alternative formats for data representation. The first one is based on direct storage in an uncompressed format, the other requires some prepro-

cessing; however, the data are compact and only carry the iris information.

from a pink retina back into the camera.

the retina or blood flow in blood vessels may also be tested.

in another place after each scan, it is a living eye.

data and sample logging, and compliance criteria.

**4.4. Related standards**

*4.4.1. Iris*

dead person that the yellow spot becomes yellow, until then it is reddish.

*4.3.2. Retina*

30 Machine Learning and Biometrics

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 Ophthalmic Instrument Standards.
