FR3113430A1 - Image acquisition system - Google Patents

Abstract

Image acquisition system The present description relates to an image acquisition system (11) comprising: a single sensor (31) with organic photodetectors, at least a first light source (17) adapted to emit only a first radiation (19) in the red and/or near infrared, and a processing unit; And in which : the sensor and the first source are carried by a single chassis (23), the sensor is suitable for capturing images, the processing unit is configured to extract information relating to the veins and the fingerprint of a finger (15) from said images, and the first light source is adapted to emit the first radiation in a direction opposite the chassis. Figure for abstract: Fig. 2

Description

Image acquisition system

The present description relates generally to image acquisition systems and, more particularly, to systems for acquiring fingerprints, for example, on mobile telephones.

Fingerprint acquisition systems are used in many fields in order, for example, to secure devices, secure buildings, control access or control the identities of individuals.

While the data, information and access protected by fingerprint sensors are increasing, fingerprint acquisition systems are the target of numerous frauds.

The most common frauds are the photocopying of fingers or fingerprints or the reconstruction of fingers or fingerprints in resin, silicone or gelatin.

There is a need to improve and secure fingerprint acquisition systems.

One embodiment overcomes all or part of the drawbacks of known fingerprint acquisition systems.

One embodiment provides an image acquisition system comprising:
a single sensor with organic photodetectors,
at least one first light source suitable for emitting only first radiation in the red and/or near infrared, and
a processing unit; And
in which :
the sensor and the first source are carried by a single frame,
the sensor is suitable for capturing images,
the processing unit is configured to extract from said images information relating to the veins and to the fingerprint of a finger, and
the first light source is adapted to emit the first radiation in a direction opposite to the frame.

According to one embodiment, the first radiation comprises only wavelengths comprised in the band from 600 nm to 1100 nm, preferably between 630 nm to 940 nm.

According to one embodiment, the system comprises a first polarizer, the first radiation coming from the first light source then passes through the first polarizer before reaching the sensor.

According to one embodiment, the first polarizer covers the first light source on the side opposite the chassis.

According to one embodiment, the first light source comprises one or more light-emitting diodes.

According to one embodiment, each photodetector delimits a pixel, each pixel being substantially square, the length of the sides of each pixel preferably being of the order of 50 μm.

According to one embodiment, the system comprises, in order:
the chassis;
the sensor;
an optical filter;
a second light source; And
a protective layer.

According to one embodiment, the second light source is adapted to emit a second radiation in the visible.

According to one embodiment, the optical filter is an angular filter.

According to one embodiment, the system comprises a second polarizer covering the sensor on the side of the sensor opposite the chassis.

According to one embodiment, the second polarizer is located:
between the optical filter and the second light source; Or
between the optical filter and the sensor.

According to one embodiment, the second polarizer is formed on a substrate.

According to one embodiment, the first polarizer and the second polarizer are linear polarizers.

According to one embodiment:
the first polarizer performs a polarization in a first direction; And
the second polarizer comprises a first part carrying out a polarization in the first direction and a second part carrying out a polarization in a second direction, perpendicular to the first direction.

According to one embodiment, the pixels of the sensor are surmounted by the first parts or the second parts with an alternation, so that two pixels surmounted by a first part are separated by one to nineteen pixels, preferably nine pixels, surmounted by a second party.

According to one embodiment, the first part of the second polarizer has an area equal to at least the area of four pixels.

According to one embodiment, the repetition pitch of the first parts is equal to the dimension of three to twenty pixels, preferably ten pixels.

According to one embodiment, the sensor is separated from the first light source by one or more walls opaque to the first radiation.

According to one embodiment, the first source is covered with an angular filter.

According to one embodiment, the sensor picks up first rays, originating from the first radiation, polarized according to the first direction by the first polarizer then according to the second direction by the second polarizer and second rays, originating from the first radiation, polarized according to the first direction by the first polarizer then in the first direction by the second polarizer.

These characteristics and advantages, as well as others, will be set out in detail in the following description of particular embodiments given on a non-limiting basis in relation to the attached figures, among which:

FIG. 1 represents by a partial and schematic block diagram an example of an image acquisition system;

FIG. 2 represents, by a partial and schematic sectional view, an embodiment of an image acquisition device;

FIG. 3 represents, by a block diagram, an example of implementation of an image acquisition method;

FIG. 4 represents, by a partial and schematic sectional view, another embodiment of an image acquisition device;

FIG. 5 represents, by a partial and schematic sectional view, part of the image acquisition device represented in FIG. 2;

FIG. 6 represents, by a partial and schematic top view, an embodiment of the part of the image acquisition device represented in FIG. 5;

FIG. 7 represents, by a partial and schematic top view, another embodiment of the part of the image acquisition device represented in FIG. 5;

FIG. 8 represents, by a block diagram, another example of implementation of an image acquisition method;

FIG. 9 represents, by a partial and schematic sectional view, a structure provided with a polarizer;

FIG. 10 represents, by a partial and schematic sectional view, yet another embodiment of an image acquisition device; And

FIG. 11 represents, by a partial and schematic sectional view, yet another embodiment of an image acquisition device.

The same elements have been designated by the same references in the different figures. In particular, the structural and/or functional elements common to the various embodiments may have the same references and may have identical structural, dimensional and material properties.

For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed. In particular, the realization of the image acquisition system and its components has been detailed only briefly, the embodiments and the modes of implementation described being compatible with the usual realizations of image acquisition systems. known pictures.

Unless otherwise specified, when reference is made to two elements connected together, this means directly connected without intermediate elements other than conductors, and when reference is made to two elements connected (in English "coupled") between them, this means that these two elements can be connected or be linked through one or more other elements.

In the following description, when referring to absolute position qualifiers, such as "front", "rear", "up", "down", "left", "right", etc., or relative, such as the terms "above", "below", "upper", "lower", etc., or to qualifiers of orientation, such as the terms "horizontal", "vertical", etc., it reference is made unless otherwise specified to the orientation of the figures.

In the rest of the description, unless otherwise specified, a layer or a film is said to be opaque to radiation when the transmittance of the radiation through the layer or the film is less than 10%. In the rest of the description, a layer or a film is said to be transparent to radiation when the transmittance of the radiation through the layer or the film is greater than 10%, preferably greater than 50%. According to one embodiment, for the same optical system, all the elements of the optical system which are opaque to radiation have a transmittance which is less than half, preferably less than a fifth, more preferably less than a tenth, of the transmittance the weakest of the elements of the optical system transparent to said radiation. In the remainder of the description, the term "useful radiation" is used to refer to the electromagnetic radiation passing through the optical system in operation.

In the remainder of the description, the term “optical element of micrometric size” is used to refer to an optical element formed on one face of a support whose maximum dimension, measured parallel to said face, is greater than 1 μm and less than 1 mm.

Embodiments of optical systems will now be described for optical systems comprising a matrix of optical elements of micrometric size in the case where each optical element of micrometric size corresponds to a lens of micrometric size, or microlens, composed of two diopters . However, it is clear that these embodiments can also be implemented with other types of optical elements of micrometric size, each optical element of micrometric size being able to correspond, for example, to a Fresnel lens of micrometric size, to a micron-sized gradient index lens or to a micron-sized diffraction grating.

In the rest of the description, visible light is called electromagnetic radiation whose wavelength is between 400 nm and 700 nm, and, in this range, red light is electromagnetic radiation whose wavelength is between 600 nm and nm and 700 nm. Infrared radiation is electromagnetic radiation with a wavelength between 700 nm and 1 mm. In infrared radiation, a distinction is made in particular between near infrared radiation, the wavelength of which is between 700 nm and 1.1 μm.

For the purposes of the present description, the refractive index of a medium is defined as being the refractive index of the material constituting the medium for the range of wavelengths of the useful radiation picked up by the image sensor. The refractive index is considered to be substantially constant over the range of wavelengths of the useful radiation, for example equal to the average of the refractive index over the range of wavelengths of the useful radiation picked up by the sensor of pictures.

Unless specified otherwise, the expressions “about”, “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably within 5%.

Unless specified otherwise, the expressions “all the elements”, “all the elements”, “each element”, mean between 95% and 100% of the elements.

Unless otherwise specified, the expression "it comprises only the elements" means that it comprises, at least 90% of the elements, preferably that it comprises at least 95% of the elements.

FIG. 1 represents by a block diagram, partial and schematic, an example of an image acquisition system.

The image acquisition system, illustrated in figure 1, comprises:
an image acquisition device 1 (DEVICE); And
a processing unit 2 (PU).

Processing unit 2 preferably comprises signal processing means provided by device 1, not shown in FIG. 1. Processing unit 2 comprises, for example, a microprocessor.

The device 1 and the processing unit 2 are preferably connected by a link 3. The device 1 and the processing unit 2 are, for example, integrated in the same circuit .

FIG. 2 represents, by a partial and schematic sectional view, an embodiment of a device 11.

More particularly, FIG. 2 illustrates an embodiment of device 1 illustrated in FIG. 1. Device 11 can, for example, be coupled to a processing unit and be integrated into the image acquisition system as described in relation to Figure 1. The device 11 is, for example, part of a mobile phone.

The device 11 illustrated in FIG. 2 comprises:
an optical sensor 13;
at least a first light source 17; And
a frame 23 (Mid frame).

The optical sensor 13 is suitable for capturing images. Images captured by the optical sensor 13 are extracted from the information relating to the veins and to the fingerprint of a finger 15 located above the upper face of the device 11. The extraction of this information is carried out by the unit of treatment illustrated in figure 1.

The first source 17 and the optical sensor 13 are carried by the frame 23. Preferably, the lower faces (in the orientation of FIG. 2) of the first source 17 and of the optical sensor 13 are on the frame 23 and in contact with frame 23.

The first light source 17 is adapted to emit only a first red and/or infrared radiation 19 . The first source 17 emits the radiation 19 mainly in a direction opposite to the frame 23. In other words, according to the embodiment illustrated in FIG. 2, the first source 17 emits the radiation 19 mainly in the direction of a screen 21. The screen 21 is preferably located on the side of the upper face of the optical sensor 13 (in the orientation of FIG. 2) and comprises a lower face substantially parallel to the upper face of the frame 23. According to the embodiment of Figure 2, the device 11 comprises several first light sources 17 located around the optical sensor 13. Each first source 17 is composed of one or more light-emitting diodes (LED, Light-Emitting Diode).

The radiation 19 corresponds to light radiation in the red and/or the infrared, that is to say radiation the set of wavelengths of which it is composed is between 600 nm and 1700 nm. More preferably, the radiation 19 corresponds to light radiation, the set of wavelengths of which it is composed is between 600 nm and 1100 nm, and is even more preferably between 630 nm and 940 nm.

According to the embodiment illustrated in FIG. 2, device 11 comprises a succession of superimposed layers of different natures. The device 11 comprises, from top to bottom, in the orientation of the figure:
a layer 25, preferably a protective glass (Cover glass);
the screen 21, composed of a panel of one or more organic light-emitting diodes (OLED, Organic Light-Emitting Diode) (OLED panel), or a liquid crystal display or LCD (Liquid Crystal Display). The screen 21 constitutes a second light source adapted to emit only a second radiation 27 in the visible;
the optical sensor 13 composed of:
- An optical filter 29, preferably an angular filter (Angular filter); And
- An image sensor 31 (Image sensor);
frame 23;
a battery 33 (Battery); And
a rear shell 35 (Back cover).

In the present description, the embodiments of the devices and other stacks of FIGS. 2, 4 to 7 and 10 to 11 are represented in space according to a direct orthogonal XYZ frame, the Y axis of the XYZ frame being orthogonal to the face top of the image sensor 31.

The radiation 27 corresponds to light radiation in the visible, that is to say radiation of which at least one of the wavelengths which compose it is between 400 nm and 800 nm. Preferably, the radiation 27 corresponds to light radiation of which at least one of the wavelengths which compose it is between 400 nm and 650 nm. More preferentially, the radiation 27 corresponds to radiation whose set of wavelengths which compose it is between 400 nm and 700 nm, and is, even more preferentially, between 460 nm and 600 nm.

Layer 25 is, for example, tempered glass. Layer 25 preferably has a thickness between 25 μm and 2 mm, preferably between 600 μm and 1.5 mm.

According to the embodiment illustrated in FIG. 2, layer 25 is partially transparent, preferably transparent, to radiation 19 and 27. Thus, layer 25 is, in a preferred embodiment, transparent to wavelengths between 400 nm and 1700 nm. More preferably, layer 25 is transparent to wavelengths between 400 nm and 1100 nm.

According to one embodiment, the screen 21 is composed of a single OLED. The OLED panel can, depending on the application, be pixelated or not. The OLED panel preferably rests on a substrate. For example, the screen 21 has a thickness of between 200 μm and 400 μm.

According to one embodiment, the device 11 does not include a layer 25. The screen 21 is therefore, for example, oriented so that the substrate, on which the OLED panel rests, faces the finger 15. The substrate is thus used as a protective layer.

The frame 23 is preferably made of plastic or a metallic material and has, for example, a thickness of between 1 mm and 4 mm. By way of example, in the case of a telephone application, preferably an intelligent telephone (smartphone), electronic components of the telephone are transferred to the frame 23.

The rear shell 35 is preferably made of plastic, glass or a metallic material and has, for example, a thickness of between 200 μm and 2 mm.

The angular filter 29 is adapted to filter the incident radiation according to the incidence of the radiation with respect to the Y axis.

The angular filter 29 is more particularly adapted so that the image sensor 31 only receives the rays whose respective incidences relative to the Y axis are less than a maximum incidence of less than 45°, preferably less than 30°, more preferably less than 10°, even more preferably less than 4°. The angular filter 29 is adapted to block the rays of the incident radiation whose respective incidences with respect to the Y axis are greater than the maximum incidence.

The image sensor 31 is a sensor with photodetectors or organic photodiodes (OPD, Organic Photodiode). The photodiodes are, for example, integrated on a substrate with CMOS transistors (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor) or a substrate with thin film transistors (TFT or Thin-Film Transistor). The photodiodes of the image sensor 31 comprise, for example, a mixture of organic semiconductor polymers such as poly(3-hexylthiophene) or poly(3-hexylthiophene-2,5-diyl), known under the name P3HT, mixed with methyl [6,6]-phenyl-C61-butanoate (N-type semiconductor), known under the name PCBM. The photodiodes of the image sensor 31 comprise, for example, small molecules, that is to say molecules having molar masses of less than 500 g/mol, preferably less than 200 g/mol. The photodiodes can be inorganic photodiodes, for example, made from amorphous silicon or crystalline silicon. By way of example, the photodiodes are composed of quantum boxes (quantum dots).

The substrate is, for example, made of silicon, preferably monocrystalline silicon. The channel, source and drain regions of TFT transistors are for example made of amorphous silicon (a-Si or amorphous Silicon), indium, gallium, zinc and oxide (IGZO Indium Gallium Zinc Oxide) or low temperature polycrystalline silicon ( LTPS or Low Temperature Polycrystalline Silicon).

The image sensor 31 is preferably sensitive to the wavelengths of the radiations 19 and 27.

The optical sensor 13 further comprises, from top to bottom, in the orientation of Figure 2:
the angular filter 29;
the image sensor 31;
a shielding layer 37, preferably a copper layer (Copper sheet) having a thickness of between 25 μm and 200 μm;
a layer 39 of heat dissipation (Heat dissipation sheet), for example, in graphite having a thickness of between 25 μm and 200 μm; And
a layer 41 of shock absorption (Cushion), for example, made of a polymer foam having a thickness of between 25 μm and 200 μm.

Layers 37, 39 and 41 of optical sensor 13 are optional layers.

Adhesive layers making it possible to fix all or part of the aforementioned layers together may be present.

According to the embodiment illustrated in FIG. 2, the optical sensor 13 comprises:
an adhesive layer 43 between the image sensor 31 and the shielding layer 37;
an adhesive layer 45 (Adhesive) between the shock absorption layer 41 and the frame 23; And
an adhesive layer 47 (OCA), for example optically partially transparent, preferably optically transparent and non-diffusing (Optically Clear Adhesive, OCA), between the angular filter 29 and the image sensor 31.

Within the meaning of the present description, a layer is considered to be "non-scattering" if the rays of a beam passing through it emerge in a scattering cone having a half angle (at the top of the cone) less than approximately 3.5 degrees.

Layers 43, 45 and 47 are, for example, made from acrylic components. They preferably each have a thickness of between 12.5 μm and 50 μm, for example, of the order of 25 μm.

According to the embodiment illustrated in FIG. 2, device 11 comprises an optional adhesive layer 49, optically partially transparent, for example transparent, and non-diffusing (OCA), located between layer 25 and screen 21. Layer 49 is , preferably, partially transparent, for example transparent, and non-scattering for the wavelengths of the radiations 19 and 27. The layer 49 is, for example partially transparent, for example, transparent for the wavelengths comprised between 400 nm and 1700 nm, and preferably between 400 nm and 1100 nm.

According to the embodiment illustrated in FIG. 2, the screen 21, the layer 25, the layer 49, the chassis 23 and the rear shell 35 are called outer layers and all have substantially the same area (in the XZ plane).

In the device 11 represented in FIG. 2, the optical sensor 13 and the layers which compose it have an area (in the XZ plane) equal to or less than that of the external layers, that is to say the layer 25, the layer 49, the screen 21, the frame 23 and the rear shell 35. Preferably, the optical sensor 13 has an area (in the XZ plane) less than that of the external layers.

For example, the optical sensor 13 is centered on the upper face of the frame 23.

According to the embodiment of FIG. 2, the device 11 comprises peripheral stacks 51 arranged on each side of the optical sensor 13. The peripheral stacks 51 extend vertically (along the Y axis) from the lower face of the screen 21 towards frame 23.

The peripheral stacks 51 extend horizontally (along the Z axis) from the peripheral end of the device 11 to a limit close to the optical sensor 13, so as to leave a space 61 between the optical sensor 13 and the peripheral stacks 51. The space 61 is extended, preferably, by a space 63 located between the upper face of the optical sensor 13 and the screen 21. The spaces 61 and 63 are, for example, filled with air, a vacuum partial or resin.

The space 63 is, for example, filled with a partially transparent material, preferably transparent, to the radiations 19 and 27. The material filling the space 63 has a lower refractive index of at least 0.1, of preferably at least 0.15, relative to the refractive index of the material of the optical sensor 13.

For example, the material of optical sensor 13 has a refractive index between 1.5 and 1.6. The space 63 is for example a layer of air, a layer of resin or a layer of low refractive index adhesive, having a refractive index of the order of 1.34 to 1.45.

In the remainder of the description, the term "low" refractive index means a refractive index of less than 1.5, and "high" refractive index means a refractive index greater than or equal to 1.5. The low refractive index resin and the low refractive index adhesive are for example colored and thus allow wavelength filtering.

The peripheral stacks 51 have, for example, a function of supporting the screen 21 on the frame 23.

The peripheral stacks 51 preferably comprise layers similar, by their functions, to the layers making up the optical sensor 13.

The peripheral stacks 51 thus comprise:
an adhesive layer 59 (Adhesive), similar to the adhesive layer 43, having a thickness of between 25 μm and 200 μm;
a shielding layer 53 (Copper sheet), optional and similar to shielding layer 37, having a thickness of between 25 μm and 200 μm;
a heat dissipation sheet 55, optional and similar to layer 39, having a thickness of between 25 μm and 200 μm; And
a shock absorption layer 57 (Cushion), optional and similar to layer 41, having a thickness of between 25 μm and 200 μm.

The adhesive layer 59 is, according to the embodiment illustrated in FIG. 2, on the lower face of the screen 21 and in contact with the lower face of the screen 21.

Furthermore, according to the embodiment illustrated in FIG. 2, the device 11 comprises housings 65 (Housing) located on the upper face of the frame 23. The housings 65 can be aligned with the stacks 51 and have an area (in the plane XZ) similar to the area of the stacks 51 or a different area from the area of the stacks 51. The housings 65 facilitate, for example, the assembly of the screen 21 on the frame 23 and in particular the positioning of the optical sensor 13.

Contrary to what is represented in FIG. 2, each stack 51 is preferably in contact with the underlying housing 65.

The chassis 23 comprises, for example, a printed circuit board, not shown in FIG. 2, on the face opposite to that on which the image sensor 31 is arranged (lower face of the chassis 23 in FIG. 2).

FIG. 3 represents, by a block diagram, an example of implementation of an image acquisition method.

More particularly, FIG. 3 illustrates, by a block diagram, the implementation of a method for acquiring images of the finger 15 (FIG. 2) for the extraction of information concerning the veins and the fingerprints of the finger 15.

This process is broken down into two streams. A first stream relates to the acquisition of images by the image sensor 31. A second stream relates to the processing carried out on the images taken. The first flow is preceded by a step 66 (Finger on display) of placing the finger 15 on the surface of the protective layer or pane 25 (FIG. 2).

According to the mode of implementation illustrated in FIG. 3, the first and the second stream comprise a first phase of acquisition and processing of images intended for fingerprint recognition followed by a second phase of acquisition and image processing for vein recognition.

The first phase of the first stream begins with a step 67 of switching on the "visible" source 21 (Visible source ON). Step 67 is followed by a step 68 of acquisition (Image 1 acquisition) and storage of a first image.

The second phase of the first stream includes the switching on of the "infrared" source 17 (step 71, IR Source ON).

Step 71 is followed by:
a step 72 of switching off the source 21 (Visible source OFF) and a step 73 of acquiring and storing a second image (Image 2 acquisition); Or
a step 77 of acquiring and storing a third image (Image 2' acquisition).

The first phase of the second stream includes a step 69 of processing the first image acquired (Image 1 processing), in order to extract therefrom an image of the fingerprints 70 (Fingerprint feature).

During the second phase, if the acquired image was acquired in step 73 (source 21 off), the image is processed, during a step 74 (Image 2 processing), in order to extract a Veins feature 75 (Veins feature).

Otherwise, if the image acquired during the second phase was acquired in step 77 (source 21 on), the image is processed, during a step 78 (Image 2' processing) in order to extract an image from which the first image is subtracted to obtain an image of veins 79 (Veins feature).

Flows and phases can be nested in various ways.

For example, the two phases of the first flow are executed before executing the two phases of the second flow.

According to another example, the first phases of the first and second streams are executed before the execution of the second phases of the first and second streams.

Furthermore, the order of the phases can be reversed in one of the fluxes or in the other.

FIG. 4 represents, by a partial and schematic sectional view, another embodiment of a device 81.

More particularly, in FIG. 4, device 81 is similar to device 11 illustrated in FIG. 2 except that it comprises two polarizers.

The device 81 comprises:
at least a first polarizer 83; And
a second polarizer 85.

Each first polarizer 83 preferably covers a single first source 17. For example, each source 17 is covered, along the Y axis, by a first polarizer 83. The radiation 19 from the first source 17 thus preferably crosses , the first polarizer 83 before reaching the finger 15.

The number of first polarizers 83 is preferably equal to the number of first sources 17, so that each first source 17 is associated with a single first polarizer 83 and each first polarizer 83 is associated with a single first source 17.

According to the embodiment of FIG. 4, each first polarizer 83 has an area (in the XZ plane) equal to or greater than the area of the source 17 with which it is associated.

According to the embodiment illustrated in FIG. 4, the second polarizer 85 is located on the upper face of the angular filter 29, in contact with the upper face of the angular filter 29, and has an area (in the XZ plane) similar to the area of the angular filter 29.

Alternatively, the second polarizer 85 is located between the angular filter 29 and the image sensor 31.

According to the embodiment illustrated in FIG. 4, the first polarizer(s) 83 and the second polarizer 85 are rectilinear, or in other words linear.

According to the embodiment illustrated in FIG. 4, the first polarizer(s) 83 polarize in a first direction, which will be referred to below as the horizontal direction.

According to the embodiment illustrated in FIG. 4, the second polarizer 85 is composed of:
one or more first parts which polarize in a second direction, perpendicular to the first direction, which will be referred to below as the vertical direction; And
one or more second parts which polarize in the horizontal direction.

The arrangement of the first and second parts of the second polarizer 85 is illustrated in Figures 5 and 6.

FIG. 5 represents, by a partial and schematic sectional view, part of the image acquisition device 81 represented in FIG. 4.

More particularly, FIG. 5 illustrates a stack 87 of the image sensor 31, of the layer 47, of the angular filter 29, of the second polarizer 85 and of the screen 21.

According to the embodiment illustrated in FIG. 5, the angular filter 29 comprises, from top to bottom:
a layer 89 comprising an array of microlenses 91 covered by a filling layer 93;
a substrate 95 on which the microlenses 91 are formed; And
a matrix comprising walls 97 opaque, at least partially, to radiation 19 and 27 (FIG. 4) and openings 99, the openings 99 being filled by the material of the layer 47.

The substrate 95 can be made of a transparent polymer which does not absorb at least the wavelengths considered, here in the visible and infrared range. This polymer may in particular be poly(ethylene terephthalate) PET, poly(methyl methacrylate) PMMA, cyclic olefin polymer (COP), polyimide (PI) or polycarbonate (PC). The thickness of the substrate 95 can, for example, vary between 1 μm and 100 μm, preferably between 10 μm and 100 μm. The substrate 95 can correspond to a colored filter, to a polarizer, to a half-wave plate or to a quarter-wave plate.

Lenses 91 can be made of silica, PMMA, positive photoresist, PET, poly(ethylene naphthalate) (PEN), COP, polydimethylsiloxane (PDMS)/silicone, epoxy resin, or resin. acrylate. The lenses 91 can be formed by flowing blocks of a photoresist. The lenses 91 can further be formed by molding on a layer of PET, PEN, COP, PDMS/silicone, epoxy resin or acrylate resin. The lenses 91 are converging lenses each having a focal distance f between 1 μm and 100 μm, preferably between 1 μm and 70 μm. According to one embodiment, all the lenses 91 are substantially identical.

According to the present embodiment, the lenses 91 and the substrate 95 are preferably made of transparent or partially transparent materials, that is to say transparent in a part of the spectrum considered for the targeted domain, for example the imaging, over the wavelength range corresponding to the wavelengths used in the exposure.

According to one embodiment, the layer 93 is a layer which matches the shape of the lenses 91. The layer 93 can be obtained from an optically transparent adhesive (Optically Clear Adhesive - OCA), in particular a liquid optically transparent adhesive, or a material with a low refractive index, or an epoxy/acrylate glue, or a film of a gas or a gas mixture, for example air.

The openings 99 are, for example, filled with air, with a partial vacuum or with a material that is at least partially transparent in the visible and infrared domains.

The optical axes of the lenses 91 are preferably directed along the Y axis.

Each aperture 99 is preferably associated with a single lens 91. The optical axes of the lenses 91 are preferably centered with the centers of the apertures 99. The diameter of the lenses 91 is preferably greater than the maximum size of the section (perpendicular to the optical axis of the lenses 91) of the openings 99.

According to the embodiment illustrated in FIG. 5, the image sensor 31 comprises photodetectors 103 delimiting pixels 105. The term pixel is used throughout the description to define a part of the image sensor 31 comprising a single photodetector 103. The denomination pixel can be applied to the scale of the image sensor 31 but also to the scale of the stack 87. At the scale of the stack 87, a pixel is the set of layers , constituting said stack, plumb with the pixel of the image sensor 31. Throughout this description, the term pixel, unless otherwise specified, refers to a pixel on the scale of the stack 87.

Each photodetector 103 is preferably associated with at least four apertures 99 (and four lenses 91). Preferably, each photodetector 103 is associated with exactly four apertures 99.

In the example of FIG. 5, a pixel 105 corresponds to each part of the stack 87 comprising, among other things, a photodetector 103 surmounted by four openings 99, themselves surmounted by four lenses 91. Each pixel 105 has, from preferably, a substantially square shape seen in a direction perpendicular to the upper face of the image sensor 31. For example, the area of each pixel corresponds to a square whose dimension on one side is between 32 μm and 100 μm, preferably between 50.8 μm and 80 μm. The area of a pixel is, more preferably, equal to a square of approximately 50.8 μm by 50.8 μm.

Each pixel 105 can be associated with a number of lenses 91 different from four, depending on the diameter of the lenses 91, their network arrangement and the dimensions of the pixels 105.

In the example of FIG. 5, a pixel 105 comprises a photodetector 103 surmounted by four openings 99. In practice, the angular filter 29 comprising the openings 99 can be rolled onto the image sensor 31 without prior alignment of the angular filter 29 on the image sensor 31. Certain lenses 91 and apertures 99 can then be located, in the orientation of the stack, that is to say along the Y direction, straddling two photodetectors 103.

According to the embodiment illustrated in FIG. 5, the stack 87 comprises the second polarizer 85 on the upper face of the optical filter 29, more precisely on the upper face of the layer 93.

FIG. 6 represents, by a partial and schematic top view, an embodiment of the part of the image acquisition device represented in FIG. 5.

More particularly, FIG. 6 illustrates an embodiment of the arrangement of the first parts 107 and second parts 109 of the second polarizer 85 (FIG. 5).

According to the embodiment illustrated in FIG. 6, each first part 107 and each second part 109 of the second polarizer 85 has a substantially square shape in the view of FIG. 6. For example, the area of each first part 107 and each second part 109 of the second polarizer 85 is equal to the area of a pixel 105 (FIG. 5), ie, for example, a square of approximately 50.8 μm by 50.8 μm.

According to the embodiment illustrated in FIG. 6, the first parts 107 and second parts 109 of the polarizer 85 are formed on the surface of the angular filter 29 (FIG. 5) so that one out of two pixel 105 is covered by a first part 107 and one pixel 105 out of two, different from the previous ones, is covered by a second part 109. Each part 107 and each part 109 is aligned with a pixel 105 and a photodetector 103. For each square grouping of four pixels 105, two of the pixels 105 are covered by first parts 107 and two of the pixels 105, different from the preceding pixels 105, are, for example, covered by second parts 109.

As a variant, the repetition pitch of the first parts 107 can be greater than one pixel. The repetition pitch of the first parts 107 can be between two pixels 105 and twenty pixels 105, preferably between five pixels 105 and fifteen pixels 105, and more preferably equal to about ten pixels 105. In other words, the number of first parts 107 is then different and, for example, less than the number of second parts 109. The first parts 107 can be arranged so that, for example, within a set of eight pixels (two columns of pixels by four lines of pixels), two first parts 107 are formed on the surface of the angular filter 29 so as to cover two pixels of the same column. The first parts 107 can be arranged so that, for example, within a set of eight pixels (two columns of pixels by four rows of pixels), two first parts 107 are formed on the surface of the angular filter 29 in such a way to cover two pixels, not adjacent, located within two different columns. In other words, a square repeat pattern of four pixels is repeated on two consecutive rows offset by one pixel. In these two embodiments, the repetition pitch of the first parts 107 is two pixels, however these embodiments are easily adaptable for a repetition pitch of the first parts 107 greater than two pixels.

According to one mode of implementation, the second polarizer 85 is, for example, formed by successive deposits of the first parts 107 and the second parts 109 on the surface of the angular filter 29.

As a variant, for each square grouping of four pixels, only one pixel 105 is covered by a first part, the other three pixels being covered by second parts 109.

FIG. 7 represents, by a partial and schematic top view, another embodiment of the part of the image acquisition device represented in FIG. 5.

More particularly, FIG. 7 illustrates another embodiment of the arrangement of the first parts 107 and second parts 109 of the second polarizer 85 (FIG. 5).

Preferably, the first parts 107 and second parts 109 of the second polarizer 85 are formed arbitrarily on the surface of the angular filter 29 (FIG. 5).

In Figure 7, each first part 107 of the second polarizer 85 has a larger area (in the XZ plane) than the area of each first part 107 of the second polarizer 85 shown in Figure 6.

According to the embodiment illustrated in FIG. 7, each first part 107 of the second polarizer 85 is formed on the upper face of the angular filter 29 without prior alignment of the latter with the photodetectors 103 or the underlying lenses 91.

According to the embodiment illustrated in FIG. 7, each first part 107 has a substantially square shape in the view of FIG. 7. Preferably, each first part 107 has an area (in contact with layer 93, FIG. 5) making it possible to completely cover, on the upper face of the angular filter 29, at least one pixel 105 (or a photodetector 103) and this regardless of its location on the upper face of the angular filter 29. Thus, the area of each first part 107 is at least equal to the area of four pixels 105. Preferably, the area of each first part 107 is between the area of four pixels 105 and the area of six pixels 105. For example, the area of each first part 107 is equal to the area of four pixels 105. The upper face of the optical filter 29, not covered by the first parts 107, is covered by second parts 109. The relative positions between the pixels 105 and the p first and second parts 107, 109 not being known, a calibration step can be provided to determine the positions of the pixels covered by the first parts 107, for example by illuminating the image acquisition device with radiation polarized by example horizontally so that only the pixels covered by second parts will pick up radiation.

According to one mode of implementation, the second polarizer 85 is, for example, formed by successive deposits of the first parts 107 and the second parts 109 on the surface of the angular filter 29.

According to one embodiment, the repetition pitch of the first parts 107 is between a distance corresponding to the dimension of three pixels and a distance corresponding to the dimension of twenty pixels. Preferably, the repetition pitch is between a distance corresponding to the dimension of eight pixels and a distance corresponding to the dimension of fifteen pixels. More preferably, the repetition pitch of the first parts 107 is equal to a distance corresponding to the dimension of ten pixels. The distribution of the first parts 107 is aligned, that is to say that the repetition is done in rows and columns, or shifted, that is to say that the distribution is shifted by one or more pixels by one row to the next or from one column to the next.

According to one embodiment, not shown, the second polarizer 85 is located between the angular filter 29 and the image sensor 31, more precisely, between the layer 47 and the image sensor 31 (FIG. 5).

An advantage of the embodiments and modes of implementation described previously in relation to FIGS. 4 to 7 is that they make it possible to simultaneously take an image under the horizontally polarized radiation 19 then, after reflection on the finger 5, horizontally ( that is to say an image under the radiation 19 having crossed two aligned polarizers) and an image under the radiation 19 polarized horizontally then, after reflection on the finger 15, vertically (that is to say an image under the radiation 19 having passed through two crossed polarizers).

FIG. 8 represents, by a block diagram, another example of implementation of an image acquisition method.

More particularly, FIG. 8 illustrates a method allowing the acquisition of images and the processing thereof in the case of a device comprising the source 17.

This process is broken down into two streams. A first stream relates to the acquisition of images by the image sensor 31. A second stream relates to the processing carried out on the acquired images.

According to the mode of implementation illustrated in FIG. 8, the first flow begins with a step 123 of positioning the finger 15 on the upper face of the layer 25 (Finger on display). Step 123 is followed by a step 125 in which the position of the finger 15 is detected (Detecting finger position) and localized on the layer 25. The detection of the position of the finger 15 can be carried out by a detection element included in the image acquisition device or by an element internal to the image sensor 31, for example one of its electrodes.

The first stream comprises, in a subsequent step 127, the switching on of the source 17 (IR source ON).

Step 127 is followed by a step 129 of acquiring an image, of dividing this image into two distinct images depending on whether the pixels are associated with a first part 107 or a second part 109 of the second polarizer 85, and storage of these images (Image acquisition).

The first image is the image which is associated with the photodetectors 105 (FIG. 5) surmounted by a first part 107 of the second polarizer 85. Thus, before reaching the photodetector 105, the radiation 19 is polarized by the first polarizer 83 in horizontal (H) then, after reflection on the finger 15, is polarized by the first part 107 of the second polarizer 85 in vertical (V), before reaching the image sensor 31.

The second image is the image associated with the photodetectors 105 (FIG. 5) surmounted by a second part 109 of the second polarizer 85. Thus, before reaching the photodetector 105, the radiation 19 is polarized by the first polarizer 83 horizontally (H ) then, after reflection on the finger 15, is polarized by the second part 109 of the second polarizer 85 in horizontal (H), before reaching the image sensor 31.

The second stream comprises two phases respectively dedicated to the separate processing of the two images and to the processing of the combination of the two images.

The first phase of the second flow comprises the processing of the first acquired image (output HV of block 129) in order to extract therefrom, in a step 131, an image comprising volume information on the finger 15 (Volume information (veins)). Volume information is called information which required the penetration of light into the volume of the finger 15 in order to be acquired. The information concerning the veins, for example their number, their shape or their arrangement within the finger, is, for example, volume information.

The first phase of the second stream further includes the processing of the second acquired image (output HH of block 129) in order to extract therefrom, in a step 133, an image comprising surface and volume information on the finger 15 (Surface and volume information).

The second phase of the second flow comprises a step 135 during which the information coming from the first image and the information coming from the second image are processed together in order to extract only surface information (Surface information (fingerprint)). This may include the determination of a third image corresponding to the difference, possibly weighted, between the second image and the first image. We call surface information, the information which required the reflection of light on the surface of the finger to be acquired. The information concerning the fingerprints is, for example, areal information. This is for example an image of the grooves and ridges of fingerprints.

FIG. 9 represents, by a partial and schematic sectional view, a structure 111 equipped with a polarizer 85.

More particularly, FIG. 9 illustrates an embodiment of a structure 111 in which the second polarizer 85 has been formed on the surface of a support or substrate 113.

Preferably, the second polarizer 85 illustrated in Figure 9 is identical to the second polarizer 85 illustrated in Figure 5. The second polarizer 85 in Figure 9 is however formed on the support 113, unlike Figure 5 where the polarizer 85 is formed on the angular filter 29. This advantageously makes it possible to produce the second polarizer 85 separately from the other elements of the stack 87.

The support 113 can be made of a transparent polymer which does not absorb, at least, the wavelengths considered, here in the visible and infrared range. This polymer may in particular be poly(ethylene terephthalate) (PET), poly(methyl methacrylate) (PMMA), cyclic olefin polymer (COP), polyimide (PI) or polycarbonate (PC). Substrate 113 is preferably PET. The thickness of the substrate 113 can vary from 1 μm to 100 μm, preferably from 10 μm to 50 μm. The support 113 can correspond to a colored filter, to a half-wave plate or to a quarter-wave plate.

The arrangement of the first parts 107 and the second parts 109 of the second polarizer 85 illustrated in figure 9 is similar to the arrangement of the parts 107 and 109 of the second polarizer 85 illustrated in figure 7.

According to one embodiment, the structure 111 is mounted in the stack 87 of FIG. 5, in place of the second polarizer 85, above the angular filter 29.

According to one embodiment, the structure 111 is mounted in the stack 87 of FIG. 5, replacing the second polarizer 85, between the filter 29 and the image sensor 31, more precisely, between the layer 47 and the sensor of images 31.

As a variant, the polarizer 85 is formed under the substrate 113. When the transfer of the structure 111, the lower face of the polarizer 85 is then in contact with the upper face of the angular filter 29 or in contact with the upper face of the sensor of images 31 depending on whether the structure 111 is positioned on the angular filter 15 or between the angular filter 29 and the image sensor 31.

FIG. 10 represents, by a partial and schematic sectional view, yet another embodiment of an image acquisition device.

More particularly, FIG. 10 illustrates a device 115 similar to device 81 illustrated in FIG. 4 except that it comprises one or more walls 117 that are opaque to radiation 19, around optical sensor 13.

According to one embodiment, the wall 117 covers all the side edges of the optical sensor 13 extending from the frame 23 until it is flush with the upper face of the angular filter 29.

According to one embodiment, each first source 17 is separated from the optical sensor 13 by a wall 117. There are thus as many walls 117 as there are sources 17. Each wall 117 extends from the frame 23 to the upper face of the angular filter 29 over a width (in direction X in figure 10) equal to or greater than the width (in direction X in figure 10) of source 17.

An advantage of the embodiment illustrated in FIG. 10 is that the radiation 19 coming from the first source 17 is perceived by the optical sensor 13 only if it is reflected on the finger 15. The optical sensor 13 is therefore not disturbed by the 19 non-reflected or direct radiation.

FIG. 11 represents, by a partial and schematic sectional view, yet another embodiment of an image acquisition device.

More particularly, FIG. 11 illustrates an image acquisition device 119 similar to device 81 illustrated in FIG. 4 except that it comprises an angular filter 121 between each source 17 and its associated first polarizer 83.

According to one embodiment, the device 119 comprises a number of angular filters 121 equal to the number of sources 17 and first polarizers 83.

Each angular filter 121 is preferably composed of a matrix of radiation-opaque walls 19 and apertures surmounted by an array of lenses (not shown). Each angular filter has for example an area (in the XZ plane) similar to the area of the first polarizer 83 with which it is associated.

As a variant, each filter 121 is positioned on the upper face of the first polarizer 83 with which it is associated.

An advantage of the embodiment illustrated in FIG. 11 is that the radiation 19 issuing from the first source 17 is, at the output of the angular filter 121, substantially collimated.

An advantage of the embodiments and modes of implementation described is that they make it possible to considerably reduce the possibilities of fraud on fingerprint sensors.

Yet another advantage of the embodiments and modes of implementation described is that they make it possible to reduce manufacturing costs since a single sensor is used to capture the visible radiation and the infrared radiation.

Various embodiments and variants have been described. The person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to the person skilled in the art. In particular, the embodiments and implementations described can be combined. The embodiments described are not limited to the examples of dimensions and materials mentioned above.

Finally, the practical implementation of the embodiments and variants described is within the abilities of those skilled in the art based on the functional indications given above.

Claims (21)

Image acquisition system (11; 81; 115; 119) comprising:
a single sensor (31) with organic photodetectors (103),
at least one first light source (17) capable of emitting only first radiation (19) in the red and/or near infrared, and
a processing unit (2); And
in which :
the sensor and the first source are carried by a single frame (23),
the sensor is suitable for capturing images,
the processing unit is configured to extract from said images information relating to the veins and to the fingerprint of a finger (15), and
the first light source is adapted to emit the first radiation in a direction opposite to the frame. A system according to claim 1, wherein the first radiation (19) comprises only wavelengths in the band 600nm to 1100nm, preferably between 630nm to 940nm. System according to Claim 1 or 2, comprising a first polariser (83) and in which the first radiation (19) originating from the first light source (17) passes through the first polariser (83) before reaching the sensor (31). A system according to claim 3, wherein the first polarizer (83) covers the first light source (17) on the side opposite the frame (23). A system according to any of claims 1 to 4, wherein the first light source (17) comprises light emitting diode(s). System according to any one of Claims 1 to 5, in which each photodetector (103) delimits a pixel (105), each pixel being substantially square, the length of the sides of each pixel being, preferably, of the order of 50 µm. A system according to any of claims 1 to 6, comprising, in order:
the frame (23);
the sensor (31);
an optical filter (29);
a second light source (21); And
a protective layer (25). A system according to claim 7, wherein the second light source (21) can be selected from an organic light emitting diode and a liquid crystal display. System according to claim 7 or 8, in which the second light source (21) is adapted to emit a second radiation (27) in the visible. A system according to any of claims 7 to 9, wherein the optical filter (29) is an angle filter. A system according to any of claims 1 to 10, comprising a second polarizer (85) covering the sensor (31) on the side of the sensor opposite the frame (23). A system according to claim 11 when appended to any one of claims 7 to 10, wherein the second polarizer (85) is located:
between the optical filter (29) and the second light source (21); Or
between the optical filter (29) and the sensor (31). A system according to claim 11 or 12, wherein the second polarizer (85) is formed on a substrate (113). A system according to claim 3 and any of claims 11 to 13, wherein the first polarizer (83) and the second polarizer (85) are linear polarizers. A system according to claim 3 and any of claims 11 to 14, wherein:
the first polarizer (83) carries out a polarization in a first direction (H); And
the second polarizer (85) comprises a first part (107) carrying out a polarization in the first direction (H) and a second part (109) carrying out a polarization in a second direction (V), perpendicular to the first direction. A system according to claim 3, claim 6 and any one of claims 11 to 15, in which the pixels of the sensor are overlaid by the first parts or the second parts with an alternation, so that two pixels overlaid by a first part (107) are separated by one to nineteen pixels, preferably nine pixels, surmounted by a second part. A system according to any of claims 11 to 15 when appended to claim 6, wherein the first portion (107) of the second polarizer (85) has an area equal to at least the area of four pixels (105). A system according to claim 17, wherein the repetition pitch of the first parts is equal to the size of three to twenty pixels, preferably ten pixels. System according to any one of Claims 1 to 18, in which the sensor (31) is separated from the first light source (17) by one or more walls (117) opaque to the first radiation (19). System according to any one of claims 1 to 19, in which the first source (17) is covered with an angular filter (121). System according to Claim 3 or 4 and any one of Claims 11 to 20, in which the sensor (31) picks up first rays, originating from the first radiation (19), polarized in the first direction by the first polarizer (83) then in the second direction (HV) by the second polarizer (85) and second rays, coming from the first radiation, polarized in the first direction by the first polarizer (83) then in the first direction (HH) by the second polarizer ( 85).