FINGERPRINT RECOGNITION SENSOR

• US 20170351901A1
• Filed: 12/28/2016
• Published: 12/07/2017
• Est. Priority Date: 06/07/2016
• Status: Active Grant

• Current Assignee: Silicon Display Technology
• Original Assignee: Silicon Display Technology
• Inventors: KIM, Jaemin, Kim, Kijoong, YU, Jin Hyeong, PARK, Young Man, Kim, Yeon Hwa, HUR, Ji Ho
• Granted Patent: US 10,127,430 B2
• Time in Patent Office: Days
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger
• CPC Class Codes: G06V 40/1365 Matching; Classification

Abstract

Disclosed is a fingerprint recognition sensor including: a backlight unit including a base layer positioned on one surface of a substrate and including a transparent material and a light source irradiating light to the inside of the base layer on one side of the base layer, in which light in which an incident angle on a surface facing the substrate is larger than a critical angle is transmitted toward the substrate; a cover layer spaced apart from the substrate and facing the other surface of the substrate; multiple sensor pixels defined by multiple scan lines and multiple data readout lines on the other surface of the substrate and positioned between the substrate and the cover layer; and multiple photo sensors positioned in the respective sensor pixels and sensing light transmitted on the base layer toward the substrate and total-reflected on a surface contacting a fingerprint of a user on the cover layer.

Claims

1. A fingerprint recognition sensor comprising:

a backlight unit including a base layer positioned on one surface of a substrate and including a transparent material, and a light source irradiating light to the inside of the base layer on one side of the base layer, in which light of which an incident angle on a surface facing the substrate is larger than a critical angle in the light irradiated from the light source is transmitted toward the substrate;

a cover layer spaced apart from the substrate and facing the other surface of the substrate;

multiple sensor pixels defined by multiple scan lines and multiple data readout lines on the other surface of the substrate and positioned between the substrate and the cover layer; and

multiple photo sensors positioned in the respective sensor pixels and sensing the light transmitted from the base layer toward the substrate and total-reflected on a surface contacting a fingerprint of a user on the cover layer.

2. The fingerprint recognition sensor of claim 1, wherein:

the base layer is formed to be larger than the substrate, and

the base layer includes a light transmission unit overlapped with the substrate, and a light guide unit not overlapped with the substrate and positioned between the light source and the light transmission unit, and

in the light guide unit, light of which an angle between the light and a normal of the interface between the light guide unit and the external material is larger than the critical angle in the light irradiated from the light source is guided to the light transmission unit.

3. The fingerprint recognition sensor of claim 1, wherein:

the backlight unit further includes a light direction switching member positioned on the front surface of the light source, and

the light direction switching member deflects light irradiated from the light source so that the incident angle on the surface facing the substrate in the base layer is larger than the critical angle.

4. The fingerprint recognition sensor of claim 3, wherein:

the light direction switching member includes a lens, a prism, or a mirror.

5. The fingerprint recognition sensor of claim 2, wherein:

the base layer includes a first surface facing the substrate and a second surface which is an opposite surface to the first surface, and

at least a part of the second surface has a shape to be inclined toward the first surface while being distant from the light source.

6. The fingerprint recognition sensor of claim 5, wherein:

the second surface of the base layer includes two or more protrusions having a shape to be inclined toward the first surface while being distant from the light source.

7. The fingerprint recognition sensor of claim 2, wherein:

the base layer includes a first surface facing the substrate and a second surface which is an opposite surface to the first surface, and

at least a part of the second surface has a shape to be inclined to be distant from the first surface while being distant from the light source.

8. The fingerprint recognition sensor of claim 2, wherein:

the base layer includes a first surface facing the substrate and a second surface which is an opposite surface to the first surface, and

at least a part of the first surface of the light guide unit has a shape to be inclined to be distant from the second surface while being distant from the light source.

9. The fingerprint recognition sensor of claim 1, wherein:

a refractive index of the cover layer is larger than 1.0 and equal to or less than 2.0.

10. The fingerprint recognition sensor of claim 9, wherein:

the critical angle is equal to or more than 30° and

less than 90°

.

11. The fingerprint recognition sensor of claim 1, further comprising:

a first optical adhesive layer positioned between the photo sensor and the cover layer, including the transparent material, and having a refractive index which is the same as the refractive index of the cover layer.

12. The fingerprint recognition sensor of claim 11, further comprising:

a second optical adhesive layer positioned between the substrate and the base layer, including the transparent material, and having the same refractive index with the substrate.

13. The fingerprint recognition sensor of claim 1, further comprising:

multiple thin film transistors connected to the multiple scan lines and the multiple data readout lines, and transmitting a current signal depending on resistance variation of each photo sensor to the multiple data readout lines,

wherein each photo sensor includes a first electrode formed by extending the drain electrode of the thin film transistor, a semiconductor layer positioned on the first electrode, and a second electrode including the transparent material and positioned on the semiconductor layer, and

wherein the first electrode and the second electrode form a capacitor.

14. The fingerprint recognition sensor of claim 13, further comprising:

a scan line driver driving the multiple scan lines; and

a readout controller supplying the current signal of each photo sensor to a readout driver through the data readout lines.

15. The fingerprint recognition sensor of claim 13, wherein:

the thin film transistor has one structure of a co-planar structure, a staggered structure, an inverted co-planar structure, and an inverted staggered structure.

16. The fingerprint recognition sensor of claim 13, wherein:

a channel layer of the thin film transistor includes a low-temperature polycrystalline silicon(LTPS), an amorphous silicon(a-Si), or an oxide.

17. The fingerprint recognition sensor of claim 13, wherein:

a semiconductor layer of the photo sensor includes an amorphous silicon(a-Si), an organic material, or a quantum dot.

18. A fingerprint recognition sensor comprising:

a backlight unit including a base layer and a light source irradiating light to the inside of the base layer on one side of the base layer;

a cover layer spaced apart from the base layer and facing the base layer;

multiple sensor pixels defined by multiple scan lines and multiple data readout lines on the base layer and positioned between the base layer and the cover layer; and

multiple photo sensors positioned in the respective sensor pixels and sensing light transmitted from the base layer toward the cover layer and total-reflected on a surface contacting a fingerprint of a user on the cover layer,

wherein light of which an incident angle on a surface facing the cover layer in the base layer is larger than a critical angle in the light irradiated from the light source is transmitted toward the cover layer.