Description:FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

1. TITLE OF THE INVENTION: “A POLARIZATION GATING METHOD FOR AN OPTICAL FINGERPRINT SCANNER”
2. APPLICANTS:

(A) NAME : MANTRA SOFTECH (INDIA) PRIVATE LIMITED
(B) NATIONALITY : INDIAN
(C) ADDRESS : B-203 SHAPATH HEXA, OPP. GUJARAT HIGH COURT, S. G. HIGHWAY,
SOLA, AHMEDABAD 380 060

PROVISIONAL
The following specification describes the invention. þ COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Field of invention
The present invention relates to an optical biometric fingerprint scanner, specifically involve a spectral biometric fingerprint imaging via differential polarized gating based spectroscopy that uses information and concept of imaging with telescopic lens configuration for detection of external and internal surface of the finger and provides the liveness detection using illumination source.
Background of invention
The optical biometric fingerprint scanner provides a high contrast image of the finger surface topology which has ridges and valleys shaped characteristically different for each individual. The identification can be done by matching a unique set of features like islands, pores, crossovers, ridge endings, bifurcations etc. Biometric systems are normally thought to provide advanced level of accuracy, be more robust to sampling and environmental conditions, and are difficult to do fraud or spoof. Biometric systems combine multiple Scanners such as a camera for facial imaging, a Scanner for iris detection, and/or a Scanner for fingerprint capture.
The optical biometric fingerprint scanners illuminating a skin area of an individual and receiving light scattered from the skin area under multi spectral conditions in visible along with NIR range, the light scattered from tissue beneath a surface of the skin. A plurality of biometric modalities is derived from the received light. For example, in one embodiment, the skin area comprises a palm of the hand and at least one fingertip of the hand. In some instances, the skin area is illuminated and the scattered light is received while the skin area is in at least partial contact with a platen.
The combined fingerprint modality may be analyzed in different embodiment to perform a number of different kinds of biometric function. For example, it may be analyzed to determine an identity of an individual or to verify the identity of the individual. It may be analyzed to verify that the hand is living tissue. In other instances, it is analyzed to estimate a demographic or anthropomorphic characteristic of the individual.
The technique used by optical biometric fingerprint scanner is called frustrated total internal reflection (FTIR). The light travelling in a glass medium when incident on the air-glass interface gets reflected into the glass if the angle of incidence is greater than the critical angle. This phenomenon is called total internal reflection. When a finger is placed on the glass plate, the light sees a denser refractive index from ridges of the finger than air, therefore transmits into the ridges then, reflecting. Since the light is frustrated in this way by the ridges of the finger thus called FTIR. The light will be reflected into the glass from the valley regions of the finger since the light see air in the space created between consecutive ridges and valleys, pores. Therefore there is a bright valley and darker ridge regions when the light is captured by an imaging system that is coming from the air-glass interface. Optical arrangement used in this invention used to detect the variation of the optical interface in dark field illumination.
The implementation of the FTIR technique is done using a prism as the glass base for placing the finger, different LED light source (9) with spectral illumination in NIR range illuminate the finger and an imaging system having a CMOS at the image plane to capture the fingerprint. In the very near infrared spectral regions (600–1000) nm, hemoglobin, collagen, melanin, bilirubin, and structural aspects of the skin layers can be detected. There are many ways to implement each one of the three components. Specific NIR bandwidth is chosen so that the light penetration and reflection will be higher leading to higher contrast between the ridges and valleys.
Subsurface polarization imaging is an advanced setup to view the finger surface with liveness detection incorporated by optical elements to choose polarization states using illumination source and detect particular polarized back scattering light. Furthermore, most of the related studies have shown, using polarization gating to reject surface glare for internal deep tissue, or to selectively detect photons from superficial layers.
Depth-selective measurements are crucial to differentiate single and low-order scattering originating in the superficial tissue from the multiple scattered lights in internal surface of finger. Polarization gating, as a depth-selective technique, has been used to selectively probe the structures of internal sub surface based on the fact that multiple scattering depolarizes light. The sensitivity of the scattered light to near-surface structures can be increased by rejecting the depolarized diffusive light from the deeper internal surface structure. The interest to polarization gating as a means to study/image the morphology of superficial tissue in general and to detect the liveliness in the user finger compared to other depth-resolved techniques, polarization gating is simple and inexpensive.
The patent application number KR201601178524 discloses a single state polarization filter for fingerprint recognition. It uses direct imaging using polarization filters making it difficult to produce high end resolution and contrast in contamination environment.
Hence, it is needed to invent optical imaging system that uses multi-spectral with differential polarization gating using telescopic lenses to capture spectroscopic information of a fingerprint.
Object of Invention
The main object of present invention is to provide optical fingerprint Scanner with a polarization gating method.
Yet another object of the present invention is to provide multi-spectral biometric imaging system having differential polarization gating technique that uses telescopic lenses to capture spectroscopic information of a fingerprint.
Further object of the present invention is to provide moisture discriminating optics with two-finger fingerprint scanner along with rolled fingers optical module having high performance and spoof free detection.
Another object of the present invention is to facilitate detection of external and internal surface of the finger and provide the livenesss detection by polarization based gating techniques using illumination source.
Another object of the present invention is to provide high contrast and high resolution images that are able to capture high-end fingerprint images even with dirt, moisture and other contaminations caused by the environment.
Another object of the present invention is to provide difference between co and cross linear/circular/elliptically polarization and simultaneous external and internal finger print imaging using circular\elliptical polarization in image formation and known as differential polarized gating techniques.
These and other objects will be apparent based on the disclosure herein.
Summary of invention
The invention describes an optical fingerprint scanner utilizing differential polarization gating for liveness detection. It employs a telecentric telescopic lens configuration with two optical paths to capture high-resolution fingerprint images. The system includes components such as an illumination source, platen, prism, polarizing beam splitter (PBS), polarizers, image Scanners, photo detectors, and computational units. The fingerprint scanner enhances image contrast and resolution by differentiating between reflected polarized light and scattered depolarized light from the finger’s surface. Differential polarization gating is achieved by subtracting orthogonal polarization images, enabling effective reconstruction of the fingerprint while reducing the impact of scattering. This method simplifies data analysis compared to multispectral imaging while improving spoof resistance. The approach provides reliable liveness detection by leveraging polarization-based gating to detect genuine skin properties, making it a robust tool for biometric authentication. The Optical fingerprint Scanner module using polarization gating method provides multiple benefits to the end users which are described in the following pages of specification.
Brief description of drawings
Fig. 1 illustrates an optical path of the present invention for simultaneous external and internal finger print imaging using differential polarization gating technique.
Fig. 2 illustrates a model when linear polarized light is reflected from the outer surface of the fingerprint and finger internal sub surface due to internal scattering and reflection.
Fig. 3 illustrates an optical path of the present invention for simultaneous external and internal finger print imaging using circular/elliptical or differential polarization gating.
Fig. 4 illustrates a model when circular/elliptical polarized light is reflected from the outer surface of the fingerprint and finger internal sub surface due to internal scattering and reflection.
Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.
Detailed Description of Invention
Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the accompany drawings. The invention is capable of other embodiment, as depicted in different figures as described above and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.
It is to be also understood that the term "comprises" and grammatical equivalents thereof are used herein to mean that other components, ingredients, steps, etc. are optionally present. For example, an article "comprising" (or "which comprises") components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also contain one or more other components.
The present invention relates to optical fingerprint scanner (20) (Not shown in fig.) for differential polarization gating livenesss detection feature provided in the conventional optical fingerprint scanner. The present invention provides the less data analysis as compare to multi spectral imaging and provides a better spoof.
As shown in Fig. 1, it illustrates an optical fingerprint scanner comprising of a optical path (12) to capture the fingerprint of the internal surface (6), light source (9) which is adapted to emit a broad NIR wavelength band which can be a array of LED, a laser diode or a incandescent lamp, array of light should not be a planer means it can have a taper surface or non uniform surface to uniformly illuminate the platen area (1). The light source (9) LED could be controlled by turning the drive currents ON and OFF. If an incandescent lamp is used than a switch is used in form of spatial light modulator.
Further, Fig. 1 describes a prism (18) being placed at a distance to the light source (9) and having a platen surface (1) whereon a user finger is placed. The Scanner position and image lenses (10) have to be selected at a particular position so that direct reflection from the illumination source in to lenses can be minimized. A mirror surface(2) from which optical path (12A) reflect which is from internal surface of finger & optical path (11A) which is from external surface of a finger is getting reflected and pass through a non platen surface(4) on another side of the first prism (18),a lens (8) located in line between the light source (9) and the first prism (18), a polarizer (7) is kept in between lens (8) and prism (18) to get the linearly polarized light optical path (11), linear polarized light reflected from internal surface second optical path (12A) of finger gets unpolarized while light reflected from external optical path (11A) at the surface of the finger and remained in the same polarization state.
Both polarized light first optical path (11A) from external surface of finger(6A) and un-polarized second optical path light (12A) from internal surface finger(6) passing through the non platen surface (4) and directed towards telecentric telescopic imaging lens (10) which contain a front lens group (10A), an aperture stop (10C) and back lens group (10B). After passing through the telecentric telescopic imaging lens (10) both polarized light first optical path (11A) and un-polarized light second optical path (12A) fall on a polarized beam splitter PBS (13) where un-polarized light get split in to its S & P component. P component get passed through PBS (13) while S component get reflected, polarized light having P component also Pass through PBS (13) and formed an image on a two dimensional photo detector Scanner (15) through another optical path (11B) from finger surface (6A) & optical path (12B) from internal finger surface (6). “S” component is an optical path (12C), which got reflected from PBS (13) and forms an image on an image Scanner (14).
The photo diode may be based on a silicon detector element or other detector materials which is sensitive to such wavelength emitted by illumination source. Further, the electronically processed output data of the two dimensional photo detector array (15) gives the fingerprint data for the external surface of the finger (6A) or palm print data. The image Scanner (14) provides the internal surface finger.
The light which passes through skin and tissue is having different optical properties based on the different wavelength presented in broadband illumination source. The tissue inside the finger have different optical variation in terms of scattering and absorbance depends on different tissue include melanin, water content, carotene, biliruben and glucose.
The optical path as shown in Figure 1 describes the method according to the present invention. The Figure 1 describes the differential polarization gating based surface imaging of the finger (5). The light emitted from broadband light source(9) is passed through the lens(8) which uniformly distribute the light passing through a polarizer(7) where light get polarized in one direction. The finger (5) of a user is placed on the platen surface (1) of the prism (18). Further, the polarized optical path (11) passed through the prism (18) captures the internal surface (6) of a finger (5). Furthermore, the spatial micro profile depth variation during scattering or reflectance variations of the internal surface (6) produces irradiance variations in the image produced on image Scanner (14). Image signal obtained by image Scanner (14) reflects the spatial micro profile depth or reflectance properties of the pres-selected internal surface (6) of the finger (5).
Polarized light gets reflected from the finger external surface (6A) and maintain the same polarization same as an incoming light. Some of polarized light will penetrate through the finger surface and get reflected, absorbed and scattered inside the finger. The polarized light which did not penetrate enough and having low order scattering and reflection is able to maintain the same polarization as incoming polarized light (11). Polarized light optical paths (11) which penetrate deeper in internal finger (6) have multiple scattering due to tissue and deform from the original polarization state and become depolarized light. Light reflected from finger external surface (6A) and scattered off and those who maintain polarization within the tissue inside the internal surface(6) can be capture at two dimensional photo detector (15) to form FTIR images and internal surface tissue images. For instance, the tissue images used to verify liveness inside a tissue while FTIR image is used to verify for identity.
A planer polarizer (7) at the illumination source side, plane polarized beam spillter PBS (13) at the imaging detector side. The PBS (13) is situated at a particular position where it is formed as co planer polarizer with respect to two dimensional photo detectors (15) and cross plane polarizer with respect to image Scanner (14). When, a plane polarizer (7) at illumination side and PBS (13) at image Scanner (14) side is having a collinear polarizer formation, the image getting formed on two dimensional photo detector (15) is having the low order scattering which is same polarization state as compared to illumination side polarizer (7), surface reflected polarization from the finger surface (6A) and multiple scattered photons which is having a component as same as illumination side polarizer(7) formed a image on two dimensional photo detector (15). Another embodiment, when plane polarizer (7) and PBS (13) at image Scanner (14) side is having a cross- linear polarizer formation, the image getting formed for cross- linear polarizer at image Scanner (14) is having the multi-scattered photons from the deeper internal surface from the finger. However, the image formed at two dimensional photo detectors (15) with co-linear polarized is finger external surface image and having the higher surface reflection which will reduce the artifacts of a finger.
Figure 2 illustrates a linearly polarized (201), the tissue concentrations is always a fraction of the light that has been directly back scattered by the medium in a single, or at least relatively low scattering events in figure 2 maintain polarization (202) . In addition, there is a portion that has been multiple scattered and contribute equally to each detected polarization state. At a high scatter concentration there are a high proportion of photons that have been multiply scattered and get depolarized (203) and return to the detector and contribute equally to each polarization state, which is resulting a relatively low degree of polarization. As a low concentrated tissue in finger, it does not contribute to detected signal at the image Scanner (14) side. This causes in the degree of polarization until the reflected light from internal surface tissue dominated and degree of polarization is close to unity.
In polarization gating, a polarized light illuminates a particular site on the surface of a finger, and the returned elastic scattering signal is split into two components with polarization's parallel (co-polarized signal I||) and perpendicular (cross-polarized signal I⊥) to that of the incident light, respectively. The co-polarized signal is generated by both low order scattering (primarily from scatters located close to the surface) and multiple scattering (primarily from scatters located deeper into the medium).
Furthermore, the cross polarized signal is predominantly generated by the multiply scattered photons from the deeper layers of the medium. Because multiple scattering depolarizes scattered light, the sensitivity to the low-order scattering component can be increased by subtracting off the depolarized multiple scattering signals. This can be achieved by subtracting I⊥ from I||. The resulting signal ΔI= I||− I⊥ is referred to as the differential polarization signal and predominately determined by the single and low-order scattering in the superficial layer of the scattering medium.
Figure 3 illustrates an embodiment, a prism (318) being placed at a distance to the light source (309) and having a platen surface (301) whereon a user finger (305) is placed. The Scanner position and image lenses(310) have to be selected particular position so that direct reflection from the illumination source in to lenses can be minimize and circularly/elliptical light enters from prism bottom non-platen surface(303) in to prism platen surface (301) to finger(305) through circularly/elliptically polarized optical path(311). A mirror surface(302) from which second optical path(312A) which is from internal surface of finger & first optical path(311A) which is from outer surface of a finger is getting reflected and pass through a non platen surface(304) on another side of the prism(318), a illumination lens(308) located in line between the light source and the prism(318), a polarization state generator(322) includes a polarizer(307) and Quarter wave plate(319) is kept in between illumination lens(308) and prism(318) to get the circularly/elliptically polarized light path(311),circularly polarized light reflected from internal surface(306) of finger gets un-polarized while light reflected at the external surface(306A) of the finger reversed in the circular\elliptical polarization state.
Both polarized light first optical path (311A) from external surface of finger (306A) and unpolarized light second optical path (312A) which originate from optical path (312) from internal surface finger (306) after hitting mirror surface (302) passing through the prism non-platen surface (304) and directed towards telecentric telescopic imaging lens (310) which contain a front lens group (310A), an aperture stop (310C) and back lens group (310B). After passing through the telecentric telescopic imaging lens (310) both circularly polarized light first optical path (311A) and un-polarized light second optical path (312A) pass through the polarized state analyzer (321) includes a component of Quarter wave plate (320) and polarized beam splitter PBS (313). Circular polarized light first optical path(311A) get reversed and when again it pass through the quarter wave plate(320) at polarized state analyzer(321), the reversed circular polarized light first optical path(311A) get change it polarization state perpendicular to the initial polarization state.
Furthermore, the polarization direction of the external finger surface reflection, which passes the quarter wave plate (320), is rotated by 90 degree with respect to the incident polarization direction. This will process reflected light partially pass through circularly polarizer (320) and block the back reflection to pass through PBS (313). Polarized light having S component due to reversal of polarization state also reflected through PBS (313) and formed an image on an image Scanner (314) through another optical path (312C) from internal finger surface (306). While another second optical Path(311B) from external finger surface(306A) and p component of internal finger tissue follow optical path(312B) which got pass from PBS(313) formed a image on a two- dimensional photo diode array(315) and with the help of computational unit\computer(317) which is connected with cables(316) give a differential polarized image.
Figure 4 illustrates, three types of photons emerging from the scattering medium during circular/elliptical polarized light is incident on the finger internal surface as shown in finger 4. The first are those that are directly back scattered by the medium. These obtain a flip in circular polarized light (402) i.e. from right handed polarization light to left handed polarization light as they undergo a reflection from the front surface of the finger and analyzed, contribute to the cross polar component. The second type emerges from the scattering medium via a series of forward scattering events and maintains its original polarization state. When analyzed at the detector these contribute to the co polar polarization component (403). The third type of photon has been depolarized by many scattering events and contributes equally to both polarization states. It should be noted that the depolarized component (404) is different for circular and linear as it takes more scattering events to depolarize circular and easy to detect the livenesss in a finger, thus hard to spoof.
The four raw component images consisted of the linearly and circularly co-polarized (Co) and cross-polarized (Cross) images post-normalization. When linearly/circularly/elliptical polarized light is incident on the finger, measurements are made of the Co and Cross polarized components to record the degree of polarization of the emerging light. When linear/circular/elliptical polarized light is incident on the medium the amount of clockwise and anticlockwise light is recorded to obtain the degree of polarization. The pixel values for the components were straightforward representation of illumination ranging from 0 to 255. The linear polarization differential imaging is defined as:
Linear polarization differential imaging: (Ico - Icross)
The degree of polarization is defined by:
Degree of polarization: (Ico - Icross)/(Ico + Icross)
Where, Ico is the intensity of light maintaining the original polarization, Icross is the intensity of light emitting in the reversed polarization state i.e. cross linear polarization or circular/elliptical polarization.
The invention has been explained in relation to specific embodiment. It is inferred that the foregoing description is only illustrative of the present invention and it is not intended that the invention be limited or restrictive thereto. Many other specific embodiments of the present invention will be apparent to one skilled in the art from the foregoing disclosure.
All substitution, alterations and modification of the present invention which come within the scope of the following claims are to which the present invention is readily susceptible without departing from the invention. The scope of the invention should therefore be determined not with reference to the above description but should be determined with reference to appended claims along with full scope of equivalents to which such claims are entitled.

List of Reference Numerals
1 A Platen Surface
2 A Mirror Surface
3 A Bottom Non Platen Surface
301 A Platen Surface
302 A Mirror Surface
303 Bottom Non Platen Surface
304 A Non Platen Surface
305 Finger
306 Internal Surface
306a External Surface
307 A Polarizer
308 Illumination Lens
309 Light Source
310 Image Lenses
310a A Front Lens Group
310b Back Lens Group
310c Aperture Stop
311 Circularly\Elliptically Polarized Light Path
311a First Optical Path
311b Another optical path towards two- dimensional photo diode array
312 Optical Path Inside Finger
312a Second Optical Path
312b Optical Path towards Image Scanner
312c Second Optical Path towards Image Scanner
313 Polarized Beam Splitter PBS
314 Image Scanner
315 Two- Dimensional Photo Diode Array
316 Cables
317 Computational Unit
318 Prism
319 Quarter Wave Plate
320 Quarter Wave Plate
321 Polarized State Analyzer
322 Polarization State Generator
4 Focus Lens
5 Finger
6 Internal Surface Finger
6a External Surface of Finger
7 Planer Polarizer
8 Illumination Lens
9 Illumination Source
10 The Object Space Telecentric Imaging Lens
10a Front Lens Group
10b Back Lens Group
10c Aperture Stop
11 Polarized Light Optical Path
11a First Optical Path
11b Second Optical Path
12 Optical Path
12a Un-Polarized Light Optical Path
12b Un-Polarized Light Second Optical Path
12c S Component Optical Path
13 Polarized Beam Splitter (PBS)
14 Image Scanner
15 Two-Dimensional Photo Detector
16 Cable
17 Computer
18 Telecentric Telescopic Imaging Lens
20 Fingerprint Scanner
, Claims:We Claim:
1. A differential polarization gating method for optical fingerprint scanning, comprising;
illuminating a platen surface (1) with an IR spectral band of 600-1000 nm range produced by an illumination source (9) positioned below a planar polarizer (7) preceded by an illumination lens (8);
directing polarized light (11) into the prism (18), where the polarized light (11) interacts with a user's finger (5) placed on the platen surface (1);
reflecting light from both the external surface (6a) and internal surface (6) of the finger (5),
wherein the light reflected from the external surface (6a) retains polarization and travels on a polarized light first optical path (11a), while the light from the internal surface (6) is depolarized and travels on an un-polarized light first optical path (12a) getting through a mirror surface (2) of the prism (18);
capturing the polarized light of first optical path (11a) from the external surface (6) and the unpolarized light of second optical path (12a) from the internal surface (6a) using a telecentric telescopic imaging lens (10);
splitting the unpolarized captured light into S and P components by a polarizing beam splitter (13), directing the polarized light of first optical path (11a) along with “P” component of the un-polarized light of the second optical path (12a) towards two-dimensional photo detector (15) via “P” component optical path (12b) to obtain fingerprint data, while directing the “S” component of the un-polarized light of the second optical path (12a) towards an image Scanner (14) via S component optical path (12c) to obtain internal surface (6);
analyzing combined biometric information from the captured images through a computation unit (17) based on the varying scattering and absorbance properties of the user’s finger (5) to perform the biometric function.
2. The method as claimed in claim 1, wherein at least a partial contact of the user’s finger (5) with a platen surface (1) is necessary to capture the images of the outer surface of finger (6a) and internal surface of finger (6) by the image Scanner (14) and two-dimensional photo detector (15).
3. The method as claimed in claim 1, wherein the illumination source (9) is configured with a planar or non-planar surface for uniform illumination of the platen surface (1) and the illumination source (9) is an array of LEDs, a laser diode, an incandescent lamp or combinations thereof.
4. A optical fingerprint scanner with a polarized gating method, comprising;
an illumination source (9) emits light that passes through an illumination lens (8) and a planer polarizer (7) illuminates a user’s finger (5) placed on a platen surface (1);
a prism (18) consisting of a non-platen surface (3) opposite to the platen surface (1) on which the user’s finger (5) is placed, a mirror surface (2) adjacent to the non-platen surface (3) with a specific angle to reflect light towards focus lens surface (4);
a telecentric telescopic imaging lens (10) consisting of a front lens group (10a), a back lens group (10b) and an aperture stop (10c) configured to collect and guide the said light towards a polarized beam splitter (PBS) (13);
characterized in that, the telecentric telescopic imaging lens (10) collects light being reflected from the mirror surface(2), including light reflected from both finger internal surface (6) and finger external surface (6A) follows the optical path towards the polarized beam splitter (PBS) (13) configured to direct the polarized light of first optical path (11a) along with “P” component of the un-polarized light of the second optical path (12a) towards two-dimensional photo detector (15) via “P” component optical path (12b) obtains fingerprint data, while directing the “S” component of the un-polarized light of the second optical path (12a) towards the image Scanner (14) via S component optical path (12c) to obtain internal surface (6) data,
5. The optical fingerprint scanner (20) as claimed in claim 4, wherein a quarter wave plate (319) to be placed above a planer polarizer (7) to get the circularly/elliptically polarized light and component of quarter wave plate (320) to be placed before a polarized beam splitter PBS (13) to reverse a circular/elliptically polarized light and changes it’s polarization state perpendicular to a initial polarization state.
6. The optical fingerprint scanner (20) as claimed in claim 4, wherein a prism (18) with a specific angle of mirror surface (2) to differentiate the ridges and valleys in a fingerprint and guide the illumination light from the finger (5) towards the imaging Scanner (14) and the two-dimensional photo detector (15).
7. The optical fingerprint scanner (20) as claimed in claim 4, wherein an image signal obtained from one of the image Scanner (14) reflects a spatial micro profile depth or reflectance properties of the preselected internal surface of the finger (5).
8. The optical fingerprint scanner (20) as claimed in claim 4, wherein the image Scanner (14) capture images that differentiate between co-linear and cross-linear polarization states to extract combined image information and yield spectroscopic information using a computation unit (17).
9. The optical fingerprint scanner (20) as claimed in claim 4, wherein a direct subtraction of the polarization states performed to obtain absorption information from the polarization-maintaining light, determining the liveness of a finger (5).

Dated this on 17th February, 2025