Sensor module and biometric authentication device

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

[Technical field]

[0001] The present invention relates to a sensor module and a biometric authentication device. [Background technology]

[0002] In high-precision sensing, such as biometric authentication, the pixel size of image sensors is becoming smaller. As the pixel size of image sensors decreases, the probability of crosstalk occurring increases. Crosstalk occurs when light incident on a pixel leaks out and enters another pixel. Crosstalk causes a problem of a decrease in the signal-to-noise ratio of image sensors.

[0003] 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 Document 1 is expensive because it uses glass as the material for the porous glass. In addition, since making glass porous requires many steps, it is not easy to manufacture the sensor described in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 005959 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a sensor module and a biometric authentication device that can suppress crosstalk easily and at low cost. [Means for solving the problem]

[0006] A first invention is a sensor module comprising: an imaging element having a light source, a plurality of pixels arranged in a two-dimensional direction, and a transmissive portion that transmits light from the light source; and an optical film that guides the light that has passed through the transmissive portion to an object to be sensed and guides reflected light from the object to the pixels, wherein the optical film has a flexible substrate having a first surface and a second surface opposite to the first surface, and a plurality of crazes that penetrate from the first surface to the second surface.

[0007] A second invention is the sensor module according to the first invention, wherein the flexible base material has a transmittance of 5% or less for light from the light source.

[0008] A third invention is the sensor module according to the first or second invention, wherein a ratio of the height of the crazes to the width of the opening of the crazes is 11 or more and 20 or less.

[0009] A fourth invention is the sensor module according to any one of the first to third inventions, wherein an occupancy rate of the crazes in the optical film is 25% or more and 70% or less.

[0010] A fifth invention is the sensor module according to any one of the first to fourth inventions, wherein the flexible base material is made of resin.

[0011] A sixth invention is the sensor module according to any one of the first to fifth inventions, wherein the flexible base material has a thickness of 2 μm or more and 75 μm or less.

[0012] A seventh invention is a sensor module according to any one of the first to sixth inventions, comprising two or more layers of the optical film.

[0013] An eighth invention is a biometric authentication device including the sensor module according to any one of the first to seventh inventions. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to provide a sensor module and a biometric authentication device that can suppress crosstalk easily and at low cost. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing the configuration of a sensor module 1. As shown in FIG. [Diagram 2] FIG. 2 is a diagram showing the configuration of the imaging element 3. As shown in FIG. [Diagram 3] FIG. 3 is a diagram showing the structure of the optical film 4. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing the configuration of the crazes 42. As shown in FIG. [Diagram 5] FIG. 5 is a diagram showing a method of forming crazes 42 using a blade 5. As shown in FIG. [Figure 6] FIG. 6 is a diagram showing a sensing method using the sensor module 1. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to this specification, the scale and dimensional ratios are changed and exaggerated from those of the actual objects for ease of illustration and understanding.

[0017] In addition, terms used in this specification that specify shapes and geometric conditions and their degrees, such as "parallel," "orthogonal," "same," length and angle values, etc., are not limited to their strict meanings and are interpreted to include the extent to which similar functions can be expected.

[0018] Here, the term "craze" in this specification is sometimes also written as "craze", but both are synonymous. In this specification, "craze" refers to a substantially linear crack or fissure formed in a substrate. In general, a craze in the narrow sense refers to a crack or fissure formed in a film with fibrils remaining between the walls, as described below, and a craze in the narrow sense that has expanded and no fibrils remain may be distinguished from a crack, but "craze" in this specification is a concept that includes both crazes in the narrow sense and cracks.

[0019] The sensor module 1 is a module that detects a sensing target. 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 a configuration of the sensor module 1. The sensor module 1 may have, for example, a rectangular parallelepiped shape with a length of 15 mm to 200 mm, a width of 15 mm to 150 mm, and a thickness of 0.3 mm to 3 mm. The sensor module 1 includes a light source 2, an imaging element 3, and an optical film 4.

[0020] The light source 2 is a member that emits light 20. The light source 2 may be, for example, a surface light source, a line light source, a point light source, or the like. The light 20 from the light source 2 may be visible light, infrared light, or the like. When the light 20 from the light source 2 is visible light, it can also be used as a screen light for an electronic device that includes the sensor module 1. When the light 20 from the light source 2 is infrared light, it can suppress the obstruction of the screen light of the electronic device that includes the sensor module 1, as well as the obstruction of the field of vision of the user of the electronic device.

[0021] In the sensor module 1, the position of the light source 2 may be, for example, the bottom layer of the sensor module 1, a part or the entire periphery of the sensor module 1, etc. Fig. 1 illustrates the case where the light source 2 is located in the bottom layer of the sensor module 1.

[0022] The imaging element 3 is a member that converts light received on a light receiving surface into an electric signal and outputs it. The imaging element 3 may be, for example, a CCD, a CMOS, or the like. A CCD is also called a Charge Coupled Device. A CMOS is also called a Complementary Metal Oxide Semiconductor. FIG. 2 is a diagram showing the configuration of the imaging element 3. FIG. 2(a) is a plan view of the imaging element 3. FIG. 2(b) is a cross-sectional view of the imaging element 3 taken along line AA in FIG. 2(a). The imaging element 3 has a plurality of pixels 31 arranged in a two-dimensional direction and a transmission portion 32 that transmits light 20 from the light source 2.

[0023] The pixel 31 is a member capable of detecting the intensity of incident light. A plurality of pixels 31 are arranged in a two-dimensional direction on the surface of the light receiving surface side of the imaging element 3. FIG. 2 illustrates a case where a plurality of pixels 31 are arranged in the left-right direction and the up-down direction. The pixel 31 may be, for example, rectangular, with a length of 2 μm to 100 μm and a width of 2 μm to 100 μm. The pixel 31 may be, for example, an optical sensor array represented by a CMOS or a thin film transistor. The material of the pixel 31 may be either inorganic or organic.

[0024] The transmitting portion 32 is a portion that transmits the light 20 from the light source 2. For example, as shown in FIG. 2(b), the transmitting portion 32 is a portion where the transparent substrate 30 is exposed on the upper surface of the imaging element 3. The transparent substrate 30 may be made of any material that transmits the light 20 from the light source 2, and may be, for example, glass, quartz, polycarbonate, or the like. The transparent substrate 30 may have, for example, a rectangular parallelepiped shape with a length of 15 mm to 200 mm, a width of 15 mm to 150 mm, and a thickness of 0.02 mm to 3 mm.

[0025] 2, a light shielding plate 33 may be located between the pixel 31 and the transparent substrate 30. The light shielding plate 33 may be made of any material that does not transmit the light 20 from the light source 2, and may be, for example, a blackened film made of a metal oxide 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 pixel 31 without passing through the sensing object.

[0026] Although not shown in Fig. 2, the pixel 31 may be connected to one end of a switch. The switch may be connected to a signal readout wiring and a switch wiring. One end of the pixel 31 may be connected to a bias application wiring.

[0027] The optical film 4 is a member that defines an optical path and suppresses crosstalk between the pixels 31. The optical film 4 guides the light 20 that has passed through the transmissive portion 32 to the sensing object, and guides the reflected light from the sensing object to the pixels 31. A sensing method using the sensor module 1 will be described later.

[0028] The optical film 4 has a flexible substrate 41 having a first surface and a second surface opposite to 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 configuration of the optical film 4. Fig. 3(a) is a plan view of the optical film 4. Fig. 3(b) is a cross-sectional view of the optical film 4 taken along line BB in Fig. 3(a).

[0029] The flexible substrate 41 is a base material for the optical film 4. The flexible substrate 41 may be in the form of a sheet. The opposing surfaces of the flexible substrate 41 may be the first surface and the second surface, respectively. The thickness of the flexible substrate 41 may be 2 μm or more and 75 μm or less, and preferably 12 μm or more and 50 μm or less. When the thickness of the flexible substrate 41 is 2 μm or more, an optical film 4 having sufficient strength can be obtained. When the thickness of the flexible substrate 41 is 75 μm or less, the crazes 42 can penetrate the flexible substrate 41.

[0030] The transmittance of the flexible substrate 41 for the light 20 from the light source 2 may be 5% or less, and preferably 1% or less. When the transmittance of the flexible substrate 41 for the light 20 from the light source 2 is 5% or less, leakage of the light 20 from the crazes 42 can be suppressed, and crosstalk between the pixels 31 can be suppressed. When the transmittance of the flexible substrate 41 for the light 20 from the light source 2 is 1% or less, leakage of the light 20 from the crazes 42 can be strongly suppressed, and crosstalk between the pixels 31 can be strongly suppressed.

[0031] The flexible base material 41 may be made of a resin. Since the flexible base material 41 is made of a resin, it has flexibility and can easily form the crazes 42. The resin may be, for example, a crystalline or amorphous thermoplastic synthetic resin, a thermosetting synthetic resin, or the like.

[0032] The crystalline thermoplastic synthetic resin may be, for example, a polyolefin such as polyethylene or polypropylene, a mixture of polyethylene and polypropylene, a polyester such as polyamide or polyethylene terephthalate, or polyvinylidene fluoride.

[0033] The amorphous thermoplastic synthetic resin may be, for example, a styrene-based resin such as polystyrene, styrene-acrylonitrile, or acrylonitrile-butadiene-styrene copolymer, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, polycarbonate, or the like.

[0034] The thermosetting synthetic resin may be, for example, an epoxy resin, an acrylic epoxy resin, a polyol isocyanate urethane resin, a phenol resin, a melamine resin, or the like.

[0035] The synthetic resin may contain appropriate additives, etc. The additives may be, for example, titanium oxide, calcium carbonate, etc.

[0036] The crazes 42 are holes penetrating from the first surface to the second surface of the flexible substrate 41. FIG. 4 is a diagram showing the configuration of the crazes 42. The crazes 42 may have only hollow portions 43 as shown in FIG. 4(a), or may have hollow portions 43 and fibrous portions 44 mixed therein as shown in FIG. 4(b). The hollow portions 43 are minute gaps also called voids. The fibrous portions 44 are minute fiber bundles also called fibrils.

[0037] The crazes 42 can be formed, for example, by pressing the surface of the flexible substrate 41 against the blade 5, and pulling the flexible substrate 41 while bending it and applying tension. FIG. 5 is a diagram showing a method of forming the crazes 42 using the blade 5. The blade 5 has a linear edge formed thereon, and may be, for example, a plate-like member made of metal or the like. The surface of the flexible substrate 41 is pressed against the blade 5, and the flexible substrate 41 is pulled in the first direction D1. As a result, the crazes 42 are repeatedly formed along the first direction D1 of the flexible substrate 41.

[0038] In forming the crazes 42, the angle at which the blade 5 contacts the flexible substrate 41 may be appropriately adjusted to an angle at which desired crazes are 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, and preferably 20° or more and 40° or less.

[0039] The tension of the flexible substrate 41 when it 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, and preferably 300 N / m or more and 800 N / m or less.

[0040] A filler may be used in forming the crazes 42. The filler may be, for example, carbon black or a black filler of a metal oxide made of a metal such as chromium, copper, iron, molybdenum, or cobalt. The size and density of the obtained fibrils can be controlled by the particle size distribution and the amount of the filler used.

[0041] The width of the crazes 42 varies depending on the thickness and material of the flexible substrate 41, the width of the blade 5, the magnitude of tension, and the like. The width w shown in FIG. 4 is the width of the crazes 42. The width of the crazes 42 may be, for example, 50 nm or more and 10 μm or less. When the width of the crazes 42 is 50 nm or more, it is possible to prevent the crazes 42 from disappearing even after heat is applied to the optical film 4. When the width of the crazes 42 is 10 μm or less, streaks caused by the crazes 42 become less visible. The width of the crazes 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.

[0042] The ratio of the height of the crazes 42 to the width of the openings of the crazes 42 may be 11 or more and 20 or less. w0 shown in FIG. 4 is the width of the openings of the crazes 42. h shown in FIG. 4 is the height of the crazes 42. When the ratio of the height of the crazes 42 to the width of the openings of the crazes 42 is 11 or more, crosstalk between the pixels 31 can be suppressed, and the signal-to-noise ratio required for sensing can be ensured. When the ratio of the height of the crazes 42 to the width of the openings of the crazes 42 is 20 or less, the shape of the crazes 42 penetrating the flexible substrate 41 can be maintained, and a decrease in yield can be suppressed.

[0043] The occupancy rate of the crazes 42 in the optical film 4 may be 25% or more and 70% or less, preferably 40% or more and 50% or less. When the occupancy rate of the crazes 42 in the optical film 4 is 25% or more, sensing accuracy can be ensured. When the occupancy rate of the crazes 42 in the optical film 4 is 40% or more, higher sensing accuracy can be ensured. When the occupancy rate of the crazes 42 in the optical film 4 is 70% or less, damage to the optical film 4 due to external stimuli can be suppressed. When the occupancy rate of the crazes 42 in the optical film 4 is 50% or less, damage to the optical film 4 due to external stimuli can be strongly suppressed.

[0044] The optical film 4 may be a single layer or may be a two or more layer structure. By using the optical film 4 with two or more layers, crosstalk between the pixels 31 can be further suppressed, and the signal-to-noise ratio of the imaging element 3 can be improved. Even if the flexible substrate 41 is made of a material that does not allow the ratio of the height of the crazes 42 to the width of the opening of the crazes 42 to be 11 or more in a single layer, the signal-to-noise ratio of the imaging element 3 can be improved by using two or more layers. By improving the signal-to-noise ratio of the imaging element 3, it is possible to obtain an image with sharper edges and clearer images.

[0045] As described above, the flexible substrate 41 on which the optical film 4 is made is less expensive than glass. Furthermore, the crazes 42 can be easily formed with fewer steps. Therefore, according to the present invention, the optical film 4 can be easily produced at low cost, and therefore the sensor module 1 capable of suppressing crosstalk can be easily provided at low cost. Furthermore, a biometric authentication device including the sensor module 1 can be provided.

[0046] A sensing method using the sensor module 1 will now be described. FIG. 6 is a diagram showing the sensing method using the sensor module 1. FIG. 6 illustrates an example in which a finger 7 is used as a sensing target. In the case of contact-type sensing as shown in FIG. 6, a protective layer 6 may be provided on the optical film 4. By providing the sensor module 1 with the protective layer 6, deterioration of the optical film 4 can be suppressed.

[0047] In Fig. 6, light 20 emitted from a light source 2 passes through a transparent substrate 30 and crazes 42 and irradiates a finger 7 placed on a protective layer 6 from an oblique direction. The light 20 reflected at the interface between the finger 7 and the protective layer 6 passes through crazes 42, which are different from the incident light path, as shown in Fig. 6, and reaches a pixel 31. This allows sensing of the fingerprint of the finger 7. [Explanation of symbols]

[0048] 1 Sensor module 2 light source 20 light 3. Image sensor 30 Transparent Substrate 31 pixels 32 Transparent part 33 Shading plate 4. Optical Film 41 Flexible base material 42 Craze 43 Cavity 44 Textile Department 5 Blades 6 Protective layer 7 fingers

Claims

1. A light source; an imaging element having a plurality of pixels arranged in a two-dimensional direction and a transmission portion that transmits light from the light source; an optical film that guides the light transmitted through the transmission portion to a sensing object and guides the reflected light from the sensing object to the pixel; The optical film has a flexible substrate having a first surface and a second surface opposite to the first surface, and a plurality of crazes extending from the first surface to the second surface. Sensor module.

2. The transmittance of the flexible substrate for light from the light source is 5% or less. The sensor module according to claim 1 .

3. 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 .

4. The occupancy rate of the crazes in the optical film is 25% or more and 70% or less. The sensor module according to claim 1 .

5. The flexible substrate is made of a resin. The sensor module according to claim 1 .

6. The thickness of the flexible substrate is 2 μm or more and 75 μm or less. The sensor module according to claim 1 .

7. The optical film has two or more layers. The sensor module according to claim 1 .

8. A sensor module according to any one of claims 1 to 7, Biometric authentication device.

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