JP2023018819A - Sensor module and biometric authentication device - Google Patents

Abstract

To provide a sensor module and a biometric authentication device capable of suppressing crosstalk at low cost and in a simple manner.SOLUTION: The present invention solves the above problem by providing a sensor module, which includes an imaging device having a light source, a plurality of pixels arranged in two-dimensional directions, and a transmission part that transmits light from the light source, and an optical film that guides the light transmitted through the transmission part to a sensing object and guides reflected light from the sensing object to the pixels. The optical film has a flexible substrate having a first surface and a second surface facing the first surface, and a plurality of crazes penetrating from the first surface to the second surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to sensor modules and biometric authentication devices.

2. Description of the Related Art In high-precision sensing such as biometric authentication, the pixel size of an imaging device is becoming finer. As the pixel size of the imaging device is reduced, the probability of crosstalk occurring increases. Crosstalk means that light incident on a certain pixel leaks out and enters another pixel. The occurrence of crosstalk causes a problem of a decrease in the signal-to-noise ratio of the image sensor.

Patent Document 1 describes a sensor that suppresses crosstalk by blocking light with porous glass placed on an imaging element. However, the sensor described in Patent Literature 1 uses glass as a material for the porous glass, and is therefore expensive. Moreover, since making glass porous requires a number of steps, it is not easy to manufacture the sensor described in Patent Document 1.

WO2015/005959

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sensor module and a biometrics authentication system capable of suppressing crosstalk in a simple and inexpensive manner.

A first invention is an imaging device having a light source, a plurality of pixels arranged in a two-dimensional direction, and a transmission section that transmits light from the light source, and the light transmitted through the transmission section is a sensing target. and an optical film that guides light reflected from the sensing object to the pixels, the optical film being flexible and having a first surface and a second surface facing the first surface. A sensor module comprising a substrate and a plurality of crazes penetrating from the first surface to the second surface.

A second invention is the sensor module according to the first invention, wherein the transmittance of light from the light source of the flexible base material is 5% or less.

A third invention is the sensor module according to the first invention or the second invention, wherein the ratio of the height of the craze to the width of the opening of the craze is 11 or more and 20 or less.

A fourth invention is the sensor module according to any one of the first invention to the third invention, wherein the occupation ratio of the craze to the optical film is 25% or more and 70% or less.

A fifth invention is the sensor module according to any one of the first invention to the fourth invention, wherein the flexible base material is made of resin.

A sixth invention is the sensor module according to any one of the first invention to the fifth invention, wherein the flexible base material has a thickness of 2 μm or more and 75 μm or less.

A seventh invention is the sensor module according to any one of the first invention to the sixth invention, comprising two or more layers of the optical film.

An eighth invention is a biometrics authentication system comprising the sensor module according to any one of the first invention to the seventh invention.

As described above, according to the present invention, it is possible to provide a sensor module and a biometric authentication device capable of suppressing crosstalk at low cost and in a simple manner.

FIG. 1 is a diagram showing the configuration of the sensor module 1. As shown in FIG. FIG. 2 is a diagram showing the configuration of the imaging element 3. As shown in FIG. FIG. 3 is a diagram showing the structure of the optical film 4. As shown in FIG. FIG. 4 is a diagram showing the configuration of the craze 42. As shown in FIG. FIG. 5 is a diagram showing a method of forming the craze 42 using the blade 5. FIG. FIG. 6 is a diagram showing a sensing method by the sensor module 1. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated with reference to drawings. In the drawings attached to this specification, the scale, dimensional ratios, etc. are changed and exaggerated from those of the real thing for ease of illustration and understanding.

Also, as used herein, terms specifying shapes and geometric conditions and degrees thereof, such as "parallel", "perpendicular", "identical", length and angle values, etc., are not strictly defined. It is interpreted to include the extent to which similar functions can be expected without being bound by the meaning.

Here, the term "craze" in this specification and the like may be generally written as "craze", but both have the same meaning. A "craze" in this specification and the like refers to a substantially linear crack or fissure formed in a substrate. When fibrils, which will be described later, remain between the walls of cracks or fissures generally formed in a film, are defined as narrowly defined crazes, and when this narrowly defined craze is expanded and fibrils do not remain, they are distinguished from cracks. However, the term “craze” in this specification and the like is a concept that includes both narrowly defined crazes and cracks.

The sensor module 1 is a module that detects an object to be sensed. The sensor module 1 can be used, for example, as a biometric authentication device such as a fingerprint authentication device. FIG. 1 is a diagram showing the configuration of the sensor module 1. As shown in FIG. The sensor module 1 may have, for example, a rectangular parallelepiped shape, with a length of 15 mm or more and 200 mm or less, a width of 15 mm or more and 150 mm or less, and a thickness of 0.3 mm or more and 3 mm or less. A sensor module 1 includes a light source 2 , an imaging device 3 and an optical film 4 .

The light source 2 is a member that emits light 20 . The light source 2 may be, for example, a surface light source, a linear light source, a point light source, or the like. Also, the light 20 from the light source 2 may be visible light, infrared light, or the like. If the light 20 from the light source 2 is visible light, it can also be used as the screen light of the electronic equipment on which the sensor module 1 is mounted. When the light 20 from the light source 2 is infrared light, it is possible to suppress the obstruction of the screen light of the electronic equipment in which the sensor module 1 is mounted and the obstruction of the user's view of the electronic equipment.

In the sensor module 1, the position of the light source 2 may be, for example, the bottom layer of the sensor module 1, part or all of the outer circumference of the sensor module 1, or the like. FIG. 1 illustrates the case where the light source 2 is positioned at the bottom layer of the sensor module 1 .

The imaging element 3 is a member that converts the light received by the light receiving surface into an electric signal and outputs the electric signal. The imaging device 3 may be, for example, a CCD, CMOS, or the like. A CCD is also called a Charge Coupled Device. CMOS is also called Complementary Metal Oxide Semiconductor. FIG. 2 is a diagram showing the configuration of the imaging element 3. As shown in FIG. FIG. 2A is a plan view of the imaging element 3. FIG. FIG. 2(b) is a cross-sectional view of the imaging device 3 taken along the line AA in FIG. 2(a). The imaging element 3 has a plurality of pixels 31 arranged two-dimensionally, and a transmission portion 32 that transmits the light 20 from the light source 2 .

The pixel 31 is a member capable of detecting the intensity of incident light. A plurality of pixels 31 are arranged two-dimensionally on the light-receiving surface side of the image sensor 3 . FIG. 2 illustrates a case in which a plurality of pixels 31 are arranged in the horizontal direction and the vertical direction. The pixel 31 may have, for example, a rectangular shape with a length of 2 μm or more and 100 μm or less and a width of 2 μm or more and 100 μm or less. The pixels 31 may be, for example, a photosensor array typified by CMOS and thin film transistors. The material of the pixels 31 may be inorganic or organic.

The transmission portion 32 is a portion that transmits the light 20 from the light source 2 . The transmissive portion 32 is, for example, a portion where the transparent substrate 30 is exposed on the upper surface of the imaging device 3, as shown in FIG. 2(b). The transparent substrate 30 may be any material as long as it transmits the light 20 from the light source 2, such as glass, quartz, polycarbonate, or the like. The transparent substrate 30 may have, for example, a rectangular parallelepiped shape, with a length of 15 mm or more and 200 mm or less, a width of 15 mm or more and 150 mm or less, and a thickness of 0.02 mm or more and 3 mm or less.

As shown in FIG. 2, a light blocking plate 33 may be positioned between the pixels 31 and the transparent substrate 30 . The light shielding plate 33 may be any material as long as it does not transmit the light 20 from the light source 2. For example, it may be a blackened film made of a metal oxide made of a metal such as chromium, copper, iron, molybdenum, or cobalt. By providing the light shielding plate 33, it is possible to prevent the light 20 from the light source 2 from entering the pixels 31 without passing through the sensing target.

Although not shown in FIG. 2, the pixel 31 may be connected to one end of a switch. The switch may be connected to the signal read wiring and the switch wiring. One end of the pixel 31 may be connected to a bias application wiring.

The optical film 4 is a member that defines an optical path and suppresses crosstalk between pixels 31 . The optical film 4 guides the light 20 transmitted through the transmissive portion 32 to the sensing target, and guides the reflected light from the sensing target to the pixels 31 . A sensing method by the sensor module 1 will be described later.

The optical film 4 has a flexible substrate 41 having a first surface and a second surface facing the first surface, and a plurality of crazes 42 penetrating from the first surface to the second surface. FIG. 3 is a diagram showing the structure of the optical film 4. As shown in FIG. FIG. 3(a) is a plan view of the optical film 4. FIG. FIG. 3(b) is a cross-sectional view of the optical film 4 taken along the line BB in FIG. 3(a).

The flexible base material 41 is a member that forms the optical film 4 . The flexible base material 41 may be sheet-like. The opposing surfaces of the flexible substrate 41 may be the first surface and the second surface, respectively. The thickness of the flexible base material 41 may be 2 μm or more and 75 μm or less, preferably 12 μm or more and 50 μm or less. When the thickness of the flexible base material 41 is 2 μm or more, the optical film 4 having sufficient strength can be obtained. Since the thickness of the flexible base material 41 is 75 μm or less, the craze 42 can penetrate the flexible base material 41 .

The transmittance of the light 20 from the light source 2 of the flexible base material 41 may be 5% or less, preferably 1% or less. Since the transmittance of the light 20 from the light source 2 of the flexible base material 41 is 5% or less, leakage of the light 20 from the craze 42 can be suppressed, so crosstalk between the pixels 31 can be suppressed. Since the transmittance of the light 20 from the light source 2 of the flexible base material 41 is 1% or less, leakage of the light 20 from the craze 42 can be strongly suppressed, so crosstalk between the pixels 31 can be strongly suppressed. can be suppressed.

The flexible base material 41 may be made of resin. Since the flexible base material 41 is made of a resin and has flexibility, the crazes 42 can be easily formed. The resin may be, for example, a crystalline or amorphous thermoplastic synthetic resin, a thermosetting synthetic resin, or the like.

The crystalline thermoplastic synthetic resin may be, for example, polyolefins such as polyethylene and polypropylene, mixtures of polyethylene and polypropylene, polyamides, polyesters such as polyethylene terephthalate, polyvinylidene fluoride, and the like.

Examples of amorphous thermoplastic synthetic resins include polystyrene, styrene-based resins such as styrene acrylonitrile and acrylonitrile-butadiene-styrene copolymer, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, polycarbonate, and the like. good too.

Thermosetting synthetic resins may be, for example, epoxy resins, acrylic epoxy resins, polyol isocyanate urethane resins, phenol resins, melamine resins, and the like.

The synthetic resin may contain an appropriate additive or the like. The additive may be, for example, titanium oxide, calcium carbonate, and the like.

The craze 42 is a hole penetrating from the first surface to the second surface of the flexible base material 41 . FIG. 4 is a diagram showing the configuration of the craze 42. As shown in FIG. The craze 42 may be composed only of the hollow portion 43 as shown in FIG. 4(a), or may be a mixture of the hollow portion 43 and the fiber portion 44 as shown in FIG. 4(b). . The cavity 43 is a minute space also called a void. The fiber portion 44 is a fine fiber bundle also called fibril.

The craze 42 can be formed, for example, by pressing the surface of the flexible base material 41 against the blade 5 and applying tension while bending the flexible base material 41 to pull it. FIG. 5 shows a method of forming the craze 42 used for the blade 5. FIG. The blade 5 is formed with a straight blade, and may be a plate-like member such as metal. The surface of the flexible base material 41 is pressed against the blade 5, and the flexible base material 41 is pulled in the first direction D1. Thereby, the crazes 42 are repeatedly formed along the first direction D<b>1 of the flexible base material 41 .

In forming the craze 42 , the angle at which the blade 5 contacts the flexible substrate 41 may be appropriately adjusted to an angle at which a desired craze is formed. In FIG. 5, the angle θ between the blade 5 and the first direction D1 may be 10° or more and 60° or less, preferably 20° or more and 40° or less.

The tension of the flexible base material 41 when the flexible base material 41 is pressed against the blade 5 may be appropriately adjusted so as to form desired crazes. The tension may be 100 N/m or more and 1000 N/m or less, preferably 300 N/m or more and 800 N/m or less.

Fillers may also be used in forming the craze 42 . The filler may be, for example, carbon black, black filler of metal oxides made of metals such as chromium, copper, iron, molybdenum, and cobalt, and the like. The size and density of the obtained fibrils can be controlled by the particle size distribution and amount of the filler used.

The craze 42 has different widths depending on the thickness and material of the flexible base material 41, the width of the blade 5, the magnitude of tension, and the like. w shown in FIG. 4 is the width of the craze 42 . The width of the craze 42 may be, for example, 50 nm or more and 10 μm or less. When the width of the craze 42 is 50 nm or more, it is possible to suppress the disappearance of the craze 42 even after the optical film 4 is heated. When the width of the craze 42 is 10 μm or less, streaks caused by the craze 42 are less visible. The width of the craze 42 can be calculated by observing the cross section of the optical film 4 with a scanning electron microscope and measuring the width of one craze 42 .

The ratio of the height of the craze 42 to the width of the opening of the craze 42 may be 11 or more and 20 or less. w 0 shown in FIG. 4 is the width of the opening of the craze 42 . h shown in FIG. 4 is the height of the craze 42 . By setting the ratio of the height of the craze 42 to the width of the opening of the craze 42 to be 11 or more, crosstalk between the pixels 31 can be suppressed, and a signal-to-noise ratio necessary for sensing can be ensured. By setting the ratio of the height of the craze 42 to the width of the opening of the craze 42 to be 20 or less, the shape of the craze 42 penetrating the flexible base material 41 can be maintained, and a decrease in yield can be suppressed.

The occupation ratio of the craze 42 to the optical film 4 may be 25% or more and 70% or less, preferably 40% or more and 50% or less. When the craze 42 occupies 25% or more of the optical film 4, the accuracy of sensing can be ensured. When the craze 42 occupies 40% or more of the optical film 4, higher sensing accuracy can be ensured. When the occupation rate of the craze 42 with respect to the optical film 4 is 70% or less, it is possible to suppress damage to the optical film 4 due to an external stimulus. When the occupation ratio of the craze 42 to the optical film 4 is 50% or less, it is possible to strongly suppress the optical film 4 from being damaged by an external stimulus.

The optical film 4 may have a single layer structure, or may have two or more layers. Since the optical film 4 has two or more layers, crosstalk between the pixels 31 can be further suppressed, so that the signal-to-noise ratio of the imaging device 3 can be improved. In addition, even if the flexible base material 41 is made of a material in which the ratio of the height of the craze 42 to the width of the opening of the craze 42 cannot be 11 or more with a single layer, the signal of the imaging device 3 can be obtained by using two or more layers. Noise ratio can be improved. By improving the signal-to-noise ratio of the imaging device 3, a clearer image with sharper edges can be obtained.

As described above, the flexible base material 41 that forms the base of the optical film 4 is less expensive than glass. Moreover, the craze 42 can be easily formed with a small number of forming steps. Therefore, according to the present invention, the optical film 4 can be produced easily and at low cost, so that the sensor module 1 capable of suppressing crosstalk can be provided easily and at low cost. Furthermore, a biometrics authentication system having the sensor module 1 can be provided.

A sensing method by the sensor module 1 will be described. FIG. 6 is a diagram showing a sensing method by the sensor module 1. FIG. FIG. 6 illustrates an example in which the finger 7 is used as the sensing object. In the case of contact-type sensing as shown in FIG. 6, a protective layer 6 may be provided on the optical film 4 . Since the sensor module 1 includes the protective layer 6, deterioration of the optical film 4 can be suppressed.

In FIG. 6, the light 20 emitted from the light source 2 passes through the transparent substrate 30 and the craze 42 and obliquely irradiates the finger 7 in contact with the protective layer 6 . Light 20 reflected at the interface between finger 7 and protective layer 6 reaches pixel 31 via craze 42 different from the incident light path, as shown in FIG. Thereby, the fingerprint of the finger 7 can be sensed.

1 sensor module 2 light source 20 light 3 imaging element 30 transparent substrate 31 pixel 32 transmission part 33 light shielding plate 4 optical film 41 flexible base material 42 craze 43 hollow part 44 fiber part 5 blade 6 protective layer 7 finger

Claims (8)

a light source;
an imaging device having a plurality of pixels arranged in a two-dimensional direction and a transmission section that transmits light from the light source;
an optical film that guides light transmitted through the transmission part to a sensing target and guides reflected light from the sensing target to the pixel;
The optical film has a flexible substrate having a first surface and a second surface facing the first surface, and a plurality of crazes penetrating from the first surface to the second surface.
sensor module. The transmittance of light from the light source of the flexible base is 5% or less.
The sensor module according to claim 1. The ratio of the height of the craze to the width of the opening of the craze is 11 or more and 20 or less.
The sensor module according to claim 1 or 2. The occupation ratio of the craze to the optical film is 25% or more and 70% or less.
The sensor module according to any one of claims 1 to 3. The flexible base material is made of resin,
The sensor module according to any one of claims 1 to 4. The flexible substrate has a thickness of 2 μm or more and 75 μm or less.
The sensor module according to any one of claims 1 to 5. Two or more layers of the optical film,
7. The sensor module according to any one of claims 1-6. A sensor module comprising the sensor module according to any one of claims 1 to 7,
Biometric device.

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