CN206147657U - Thin Optical Fingerprint Sensor - Google Patents

Abstract

The utility model provides a slim optical fingerprint sensor, include: a housing; the optical prism is arranged in the shell and comprises a collecting surface arranged at the top, a bottom surface corresponding to the collecting surface and positioned at the bottom of the optical prism, a mirror surface arranged at one end of the optical prism and an output surface arranged at the other end of the optical prism; the flexible circuit board is arranged on the shell; the light source is arranged on the flexible circuit board and corresponds to the bottom surface of the optical prism; the image sensing unit is arranged on the flexible circuit board and corresponds to the output surface of the optical prism; the light emitted by the light source enters the optical prism through the bottom surface and is reflected by the finger print placed on the collecting surface to form an image light beam, and the image light beam enters the image sensing unit through the output surface after being reflected by the mirror surface, so that the thickness of the optical prism can be reduced, the optical prism is suitable for various fingerprint collecting areas, and the resolution of the fingerprint image is increased.

Description

Thin Optical Fingerprint Sensor

technical field

The utility model relates to a thin optical fingerprint sensor, in particular to a thin optical fingerprint sensor which can be used for fingerprint collection and identification.

Background technique

According to, the general existing optical fingerprint image capture device can usually be composed of a prism, a convex lens, an image sensor and a light source, wherein the prism is arranged in an inverted triangle, the convex lens corresponds to the first side of the prism, and the image sensor The light source corresponds to the convex lens, and the light source corresponds to the second side of the prism.

When in use, the operator places the fingerprint on the third side of the prism, at this time the light source is irradiated by the second side of the prism at the same time, and the light is reflected by the fingerprint image to the first side of the prism, Then the light enters the convex lens and then focuses on the image sensor, so as to collect and identify fingerprints.

However, in the above-mentioned known optical fingerprint image capture device, the volume of the prism is usually limited by the shape and cannot be reduced, so that it cannot be effectively applied to the current miniaturized electronic devices.

In order to solve the lack of existing optical fingerprint image capture devices, there are related patents such as the People's Republic of China Invention Patent Publication No. CN101034437A "Fingerprint Collection Method and High-Definition Thin Fingerprint Collector", which solves the problem of the small collection area of the prior art. , The problem of poor clarity, the method is to cut a slope on the side of the prism, the light source is set near the slope, the light emitted from the light source passes through the side of the prism and irradiates the bottom surface of the prism, and the fingerprints on the bottom surface of the prism are reflected by the prism reflected and projected onto the photodetector. The photoelectric detector is arranged on one side of the straight waist of the prism, the oblique waist of the prism is equipped with a reflective mirror, the outside of the lens is equipped with a reflective mirror arranged obliquely, and the photoelectric detector is above the reflective mirror. It is characterized in that the light source is arranged on the side of the prism On the other hand, it has the advantages of large fingerprint reflection surface, large collection area and high definition.

Although the above-mentioned patent case is to make the light enter the prism, and then output it to the photodetector in the form of reflection, so as to shorten the single optical path by using the reflected optical path, and then reduce the volume of the fingerprint collection device. However, this method can improve The lack of existing optical fingerprint image capture devices, but these existing fingerprint image capture devices still cannot meet the current increasingly thin electronic products. Therefore, the above-mentioned various existing products are still in practical use. There are deficiencies.

In view of this, the inventors of the present application devoted themselves to research and developed a thin optical fingerprint sensor, which can further reduce the thickness of the prism in order to improve the above-mentioned deficiencies in the prior art.

Utility model content

The main purpose of the utility model is to set the light source on the bottom surface of the optical prism, let the operator place the fingerprint on the collection surface, make the light source of the light-emitting element input and irradiate on the fingerprint from the bottom surface of the prism, and use the mirror surface of the optical prism to irradiate the fingerprint. The light is reflected, and then the output surface is used as the output after the light reflection, so that the image sensing unit receives the light and forms a fingerprint image, so as to achieve the effect of reducing the volume of the optical fingerprint sensor and increasing the resolution of the fingerprint image.

In order to achieve the above-mentioned purpose, the preferred embodiment of the thin optical fingerprint sensor of the present invention includes: a housing; The collection surface corresponds to the bottom surface at the bottom of the optical prism, a mirror surface arranged at one end of the optical prism, and an output surface arranged at the other end of the optical prism; a flexible circuit board, the housing is arranged on the flexible circuit board ; a light source, located on the flexible circuit board, and the light source corresponds to the bottom surface of the optical prism; and an image sensing unit, located on the flexible circuit board, corresponding to the output surface of the optical prism, wherein The light emitted by the light source enters the optical prism through the bottom surface, and is reflected by the fingerprint placed on the collection surface to form an image beam, and the image beam is reflected by the mirror surface and enters the image sensing unit through the output surface .

In the above-mentioned embodiment, the casing is provided with a containing portion for containing the optical prism, and the bottom of the containing portion is provided with a plurality of through holes.

In the above embodiment, there is a first included angle between the mirror surface and the collecting surface of the optical prism, a second included angle between the mirror surface and the bottom surface, and a third included angle between the output surface and the collecting surface. angle, and there is a fourth included angle between the output surface and the bottom surface.

In the above-mentioned embodiment, the first included angle of the optical prism is 75-85 degrees, the second included angle is 95-105 degrees, and the third included angle and the fourth included angle are 90 degrees.

In the above-mentioned embodiments, the optical prism is made of transparent materials such as glass, plastic, quartz or crystal.

In the above-mentioned embodiments, a light source, at least one resistor and an image sensing unit are arranged on the flexible circuit board.

In the above embodiments, the light source includes a plurality of LED light-emitting elements, which are respectively disposed in the through holes of the housing.

In the above-mentioned embodiments, the LED light-emitting elements are configured as multiple rows of light-emitting elements in such a way that the light refraction angle of the optical prism is within the range of the critical angle.

In the above-mentioned embodiment, the image sensing unit includes a lens, which is arranged on the output surface corresponding to the optical prism; a reflector, which is arranged on the inner surface of the front slope of the housing; and a mirror which is arranged below the reflector. Image sensing receiver.

Description of drawings

Fig. 1 is the three-dimensional appearance schematic diagram of the utility model;

Fig. 2 is an exploded schematic diagram of a three-dimensional element of the utility model;

Fig. 3 is a schematic diagram of the light path when the utility model is in use;

Fig. 4 is the schematic diagram of the prism of the present utility model;

FIG. 5A is a reference diagram for explaining the principle;

Fig. 5B is a schematic diagram of known light source irradiation;

Fig. 5C is a schematic diagram of light source irradiation of the present invention.

reference sign

1: shell

11: Housing

12: Through hole

2: Optical prism

21: Acquisition surface

211: Fingerprint placement area

22: bottom surface

23: mirror surface

24: output surface

201: first angle

202: second included angle

203: third angle

204: Fourth angle

3: Flexible printed circuit board

4: light source

5: Resistor

6: Image sensing unit

61: lens

62: mirror

621: inclination

63: Image sensing receiver

a: left endpoint

b: right endpoint

A1: First incident ray

B1: first reflection line

A2: Second incident ray

B2: second reflection line

N1: Refractive index of the first medium

N2: Refractive index of the second medium

α ₁ : the incident angle of the first medium

α ₂ : Refraction angle of the second medium

A: Fingerprint collection surface width

B: dark background surface width

d: Prism thickness

detailed description

In order to fully understand the purpose, features and effects of the utility model, the utility model will be described in detail as follows through the following specific embodiments and accompanying drawings.

Please refer to Fig. 1, Fig. 2, Fig. 3 and Fig. 4, which are respectively the three-dimensional appearance schematic diagram of the present invention, the three-dimensional component decomposition schematic diagram of the present utility model, the light path schematic diagram of the present utility model and the prism schematic diagram of the present utility model. As shown in the figure: the utility model is a thin optical fingerprint sensor, which includes a housing 1, an optical prism 2, a flexible circuit board 3, a light source 4, a resistor 5 and an image sensing unit 6 .

As shown in Figure 2, the housing 1 of the preferred embodiment of the utility model has a housing portion 11, the housing portion 11 is in a concave shape, and can accommodate the optical prism 2, and the bottom surface of the housing portion 11 is provided with six The through hole 12 is used to penetrate the light source 4 composed of six LED light-emitting elements. The six light sources 4 are arranged on the flexible circuit board 3. These light sources 4 correspond to the bottom surface 22 of the optical prism 2. The flexible circuit board 3 It is arranged on the bottom of the casing 1 , and the casing 1 is installed on the flexible circuit board 3 so that the six light sources 4 are located in each through hole 12 . In this embodiment, the light source 4 includes 2 rows of LED light-emitting elements, and each row of light-emitting elements has three LED light-emitting elements; a plurality of resistors 5 are arranged on the flexible circuit board 3 as a power control for adjusting each LED light-emitting element circuit. The image sensing unit 6 is arranged on the other side of the flexible circuit board 3 relative to the light source 4, and it includes a lens 61 arranged in front of the output surface 24 corresponding to the optical prism 2; a reflector 62 arranged in the casing 1 the inner surface of the front slope; and an image sensing receiver 63 located below the reflector 62.

Please refer to FIG. 3 at the same time. When in use, the light emitted by the light source 4 enters the prism through the bottom surface 22 of the optical prism 2, and forms an image beam after being reflected by the finger fingerprint placed on the collection surface 21, and the image beam is then transmitted by the optical prism. After being reflected by the mirror surface 23 of the prism 2 , it enters the image sensing unit 6 through the output surface 24 .

Please refer to Fig. 3 and Fig. 4, the optical prism 2 comprises a collection surface 21 with a fingerprint placement area 211 located at the top, a bottom surface 22 corresponding to the collection surface 21 and positioned at the bottom of the optical prism 2, and a bottom surface 22 located at the bottom of the optical prism 2. A mirror surface 23 at one end, and an output surface 24 located at the other end of the optical prism 2, and a first angle 201 between the mirror surface 23 and the collecting surface 21, and a second angle between the mirror surface 23 and the bottom surface 22 Angle 202 , there is a third included angle 203 between the output surface 24 and the collection surface 21 , and a fourth included angle 204 between the output surface 24 and the bottom surface 22 . When the optical prism 2 is placed in the accommodating portion 11, the light source 4 faces the bottom surface 22 of the optical prism 2, and the light emitted by the light source 4 enters the optical prism 2 from the bottom surface 22 and irradiates onto the fingerprint placement area 211 placed on the collection surface 21. Fingerprint (not shown), through the concave and convex lines of the fingerprint, the light emitted by the light source 4 forms the first incident ray A1 of the left end point a of the fingerprint placement area 211 and the second incident ray A2 of the right end point b, and then passes through the mirror surface 23 After reflection, they become the first reflection ray B1 and the second reflection ray B2. The light rays B1 and B2 leave the optical prism 2 from the output surface 24, and after being converged by the lens 61, they are reflected by the mirror 62 to the image sensing receiver 63 and pass through the mirror 62. The setting of the image sensing unit 6 can reduce the volume of the image sensing unit 6 and increase the image resolution; in this embodiment, the inclination angle 621 of the mirror 62 is 20-40 degrees, and the image sensing receiver 63 is a CMOS.

As shown in Figure 4, the first angle 201 of the optical prism 2 is an acute angle, the second angle 202 is an obtuse angle, the third angle 203 and the fourth angle 204 are an appropriate angle, so that the light emitted by the light source 4 with the light path described above. Preferably, in this embodiment, the first included angle 201 is 75-85 degrees, the second included angle 202 is 95-105 degrees, the third included angle 203 and the fourth included angle 204 are both 90 degrees; the optical prism 2 is made of transparent materials such as glass, plastics, quartz or crystal.

Please refer to FIG. 5A , FIG. 5B , and FIG. 5C , which are respectively a reference diagram for explaining the principle, a schematic diagram of illumination by a known light source, and a schematic diagram of illumination by a light source of the present invention. As shown in Figure 5A, when light is obliquely incident from one medium to another, the angle of the light changes, which is related to the refractive index of the medium. As shown in the figure, draw a vertical normal line on the interface between the first medium and the second medium, and the angle of the light will produce total reflection based on a certain numerical limit for the normal line. Wherein N1 is the refractive index of the first medium, N2 is the refractive index of the second medium, α ₁ is the incident angle of the first medium, α ₂ is the refraction angle of the second medium, in the present embodiment, the first medium is air When N1=1, the medium of N2 can be a transparent material such as glass, plastic, quartz or crystal, and its refractive index is about N2=1.5. Substitute into the equations for the angles of incidence and angles of refraction for the two different media:

N1Sinα1=N2Sinα2;

When N1=1, α ₁ =90° and N2=1.5 are substituted into the above formula, α ₂ =42° is obtained. When α ₂ exceeds 42° from 0°, α ₁ exceeds 90°, and total reflection occurs in the second medium. At this time, α ₂ =42° is the critical angle, that is to say, through the optical prism 2 Only when α ₂ =0°˜α ₂ =42° does the refracted light exit the prism and become the light required by the fingerprint collection area 211 .

As shown in FIG. 5B , the known illumination method of the light source is to cut a slope on the side of the prism, and the light source is arranged at the irradiation opening formed by the slope. The principle of dark background fingerprint collection of this product is to use LED to irradiate in the direction of 42 degrees between the fingerprint collection surface and its vertical line, so when the light passes through the fingerprint collection surface, a black dark background surface is formed. The texture of the finger print contact produces a reflection phenomenon, forming a white fingerprint texture on a black background. If you want to irradiate light at 42 degrees from both sides of the prism to the fingerprint collection surface, you need to make the thickness d of the prism more than half of the width A of the fingerprint collection surface, that is, d>A/2, and the thickness d of the prism is greater than the fingerprint collection surface. One-half of the face width A.

As shown in Figure 5C, the irradiation method of the present invention is to arrange two rows of LED light sources 4 on the bottom surface of the optical prism 2, and form an irradiation range of 42 degrees on both sides to the fingerprint collection surface and its vertical line. Through this irradiation method, The thickness d of the optical prism 2 can be made to be only a quarter of the width A of the fingerprint collection surface, ie d=1/4A.

Please refer to Fig. 2, two rows of 6 LED light sources in the present invention only irradiate their respective effective ranges, that is, the 1/6 area of the fingerprint collection surface A; Light can be transmitted out of the prism to form a dark background surface B. As shown in Figure 5C, through the light source configuration of the present invention, each LED light source irradiates 42° from both sides of the prism to the fingerprint collection surface, so that the light refraction angle of the optical prism is within the range of the critical angle for total reflection. Just can make the width A of fingerprint collection surface reach four times of prism thickness d, so the utility model can make prism thickness d smaller than the width A of fingerprint collection surface, and reach the effect of thinning fingerprint collector.

The thin optical fingerprint sensor of the utility model has a larger fingerprint collection area than the prior art, and can make the thickness of the prism smaller than the width of the fingerprint collection surface, so it can be applied to an effective fingerprint collection area of 6*6 mm to 60 * All fingerprint collection devices between 60 millimeters (mm) can reduce the thickness of optical prisms, are suitable for various fingerprint collection areas, and have the effect of increasing the resolution of fingerprint images. It is undoubtedly of practical value and indeed has a patent application. The required elements of novelty, creativity and industrial applicability shall be filed in accordance with the law for a utility model patent application.

But what is described above is only a preferred embodiment of the utility model, and all equal design changes made according to the claims of the utility model should be covered by the technical scope of the utility model.

Claims (10)

1. a kind of thin optical fingerprint sensor, it is characterised in that described thin optical fingerprint sensor includes：

One housing；

One optical prism, in the housing, the optical prism include one located at top collection face, one with collection face The corresponding and bottom surface positioned at optical prism bottom, one are located at the minute surface and of optical prism one end located at the optical prism other end Output face；

One flexible circuit board, the housing is on the flexible circuit board；

One light source, on the flexible circuit board, and the light source is corresponding to the bottom surface of the optical prism；

One resistor, on the flexible circuit board；And

One image sensing unit, corresponding to the output face of the optical prism, wherein the light that the light source sends is via described The bottom surface of optical prism enters the optical prism, and forms an image by being positioned over after the reflection of the finger print in the collection face Light beam, described image light beam enters described image sensing unit via the output face again by the mirror-reflection.

2. thin optical fingerprint sensor according to claim 1, it is characterised in that the housing is provided with a receiving portion, For housing the optical prism, the bottom of described accommodation section is provided with multiple through holes.

3. thin optical fingerprint sensor according to claim 1, it is characterised in that the minute surface of the optical prism with adopt Between collection face have one first angle, between the minute surface and bottom surface have one second angle, the output face with collection face it Between have one the 3rd angle, and between the output face and bottom surface have one the 4th angle.

4. thin optical fingerprint sensor according to claim 3, it is characterised in that the first angle of the optical prism For 75～85 degree, second angle is 95～105 degree, and the 3rd angle and the 4th angle are 90 degree.

5. thin optical fingerprint sensor according to claim 1, it is characterised in that the optical prism is glass, modeling Glue, quartz or crystal transparent material are made.

6. thin optical fingerprint sensor according to claim 1, it is characterised in that the flexible circuit board is provided with Light source, at least a resistor and an image sensing unit.

7. thin optical fingerprint sensor according to claim 1, it is characterised in that the light source includes multiple LED and sends out Optical element, in being respectively arranged at the through hole of the housing.

8. thin optical fingerprint sensor according to claim 7, it is characterised in that the plurality of LED light-emitting component is matched somebody with somebody Multiple rows of light-emitting component is set to, its mode for arranging is the light refraction angle for making the optical prism in the range of critical angle.

9. thin optical fingerprint sensor according to claim 1, it is characterised in that described image sensing unit includes Lens, located at the output face of the correspondence optical prism；One speculum, located at the inner face on the front inclined-plane of the housing；And The one image sensing receiver below the speculum.

10. thin optical fingerprint sensor according to claim 9, it is characterised in that the angle at the inclination angle of the speculum Spend for 20～40 degree.