JP2003060844A - Reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reader equipped with a back light whose power consumption can be reduced. SOLUTION: The emitting angle of maximum luminance in the distributed light of a back light 50 arranged on the rear side of a photosensor part for optically reading a fingerprint by transmitting light made incident from the rear side, reflecting the light on the tip of a finger touching the front side and receiving this reflected light by a double gate transistor 10a is made oblique to the direction perpendicular to the front of the back light 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reading a subject, and more particularly to a reading device for reading a fingerprint.

[0002]

2. Description of the Related Art Conventionally, a fingerprint reading device has been known as a two-dimensional image reading device for reading a fingerprint by fine irregularities on the fingertip of a subject. This fingerprint reading device includes a photo sensor device having a photo sensor unit for reading a fingerprint of a fingertip and a driver circuit unit arranged near the photo sensor unit and supplying a drive signal for driving the photo sensor unit. There is. In this fingerprint reading device, when reading the fingerprint of the fingertip, the fingertip is brought into contact with the photosensor portion, and the unevenness of the skin forming the fingerprint is optically recognized by the photosensor portion so that the fingerprint can be read. There is.

By the way, in recent years, a photosensor portion for reading a fingerprint has been developed with improved light transmittance. When a photo sensor unit having such light transmissivity is applied to a fingerprint reading device, a backlight is provided on the back surface of the photo sensor unit, and light is emitted to the photo sensor unit by the backlight, and the photo sensor unit The fingerprint can be read by recognizing the light that is transmitted and hits the fingertip and reflected. Such photosensors include one that reads light that is incident on the fingertip surface from a direction normal to the fingertip surface (small incident angle) and that is reflected by the convex portion of the finger, or a prism that uses a prism to measure the total reflection critical angle. There is one that reads the light (incident angle is large) that is incident and reflected by the concave portion of the finger.

As the structure of the above-mentioned backlight, a light source such as a cold cathode fluorescent tube or an LED (Light Emitting Diode) is arranged at the end of a light guide plate having a reflection plate on the bottom side, and the light emitted from the light guide plate is diverged. A side-light type that illuminates the fingertip with can be considered.

[0005]

However, a general backlight, which is also applied to a liquid crystal display device, is applied to the fingertip surface by irradiating the fingertip surface with light from the normal direction (small incident angle). When applied to a photo sensor that reads the light reflected by the convex portion, the light diffuses to some extent, and the amount of light incident at the angle at which the optimum sensitivity of the photo sensor can be obtained is small, and highly accurate sensing as a sensor is possible. However, there is a problem in that the power consumption of the backlight increases if the illuminance of the backlight is increased to increase the overall brightness of light. The object of the present invention is to
An object of the present invention is to provide a reading device equipped with a backlight that can perform sensing more efficiently.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 reflects incident light on an object (for example, a finger) which is in contact with the surface as shown in FIG. Then, the reflected light is received by the light receiving element, and the brightness differs depending on the sensor unit (for example, the photo sensor unit 10) that optically reads the subject based on the amount of light received by the light receiving unit and the emission angle. A backlight (for example, the backlight unit 50) that emits light whose emission angle at the maximum brightness of light is within the allowable incident angle range of the sensitivity of the sensor unit.

According to the first aspect of the invention, the brightness of the backlight is changed according to the emission angle, and the emission angle at which the maximum brightness is obtained is set within the allowable incident angle range of the sensitivity of the sensor section. Can be sensed efficiently with low power consumption.

According to a second aspect of the present invention, in the reading apparatus according to the first aspect, the maximum brightness of the backlight is at least twice the minimum brightness of the backlight at a predetermined emission angle. It is characterized by By setting the maximum brightness to be twice or more the minimum brightness in this way, the light is condensed in the allowable incident angle range of the sensitivity of the sensor portion, and thus the subject can be efficiently read.

Further, as in the invention described in claim 4, the sensor part is applied such that the maximum range of the sensor sensitivity is a light incident angle of 30 ° to 55 ° and a light incident angle of −30 ° to −55 °. You may. It has been relatively difficult to set the brightness of the emitted light to the front of the sensor to the maximum for an LED or a fluorescent tube that is not directly under the sensor as the light source of the backlight, but such a sensor is applied. Therefore, the light incident angle is 30 ° to 55 ° or the light incident angle is −30 ° to −55.
Since it suffices that the light is incident on the sensor unit in the range of 0 °, it is possible to easily set a backlight that emits oblique light having the maximum brightness in the above range with a relatively simple structure.

According to a fifth aspect of the present invention, the backlight is a light source, a bottom light guide plate, a light diffusion plate provided above the bottom light guide plate and having a large number of prism portions on the light emission side, and You may make it have a diffusion sheet. With such a configuration, for example, the brightness distribution as shown in FIG. 11 can be obtained, and the emission angle of the light with the maximum brightness that is 5 times or more than the minimum brightness is within the maximum range of the sensor sensitivity of the sensor unit. Since it can be set to, reading with low power consumption is possible.

The fourteenth aspect of the present invention includes the first to thirteenth aspects.
In the reading device described in any one of the above items, the sensor unit 10 has a double gate type transistor 10a.

The double gate type transistor can be set so as to exhibit maximum sensitivity when the direction of incident light is deviated from the direction perpendicular to the incident surface.

Therefore, according to the invention of claim 14,
Since the range of the incident light in the maximum sensor sensitivity region of the sensor unit can be set in the oblique direction other than the front, the backlight can be easily set.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a fingerprint reading apparatus of the present invention will be described below with reference to the drawings.

<First Embodiment> As shown in FIG.
The fingerprint reading device A is a device for optically reading a raised convex portion at a fingertip that defines a fingerprint and a linear concave portion arranged between the convex portions, and is a fingertip holding portion that holds the fingertip at a predetermined position. B, and a photo sensor device C that reads the fingerprint of the fingertip
It has and. FIG. 2 is a sectional view taken along line XX of FIG.

The fingertip holding portion B is a member opaque to the excitation light that excites the sensor of the photosensor device C and the semiconductor layers of the drivers 11 to 13 which will be described later and which is shaped so as to fit the fingertip. Therefore, the photo sensor device C is attached so as to be placed on the surface thereof. In the fingertip holding portion B, an ellipse-shaped opening 1 having an opening size as large as that of the fingertip is formed at a portion where the fingertip is in contact. Then, the fingertip holding portion B is arranged and attached on the photosensor device C so that a photosensor portion of the photosensor device C, which will be described later, is arranged in the opened portion of the opening portion 1. The fingertip holder B is made of a conductive material and is grounded via the wiring 2 continuous from the fingertip holder B. Therefore, even when the subject touches the fingertip holding portion B with the fingertip, it is possible to prevent malfunction and damage of the photosensor device C due to static electricity charged on the fingertip.

As shown in FIGS. 1 and 2, the photosensor device C includes a photosensor portion 10 provided on a transparent insulating substrate 20 for optically reading a fingerprint and a fingertip holding portion B.
It has various driver circuit parts (top gate driver 11, bottom gate driver 12, drain driver 13), which are arranged below, and which supplies drive signals for driving the photosensor part 10, and a backlight part 50.

As shown in FIG. 1, the photosensor portion 10 is arranged in an exposed state in the opening portion of the opening portion 1 of the fingertip holding portion B described above. Further, as shown in FIG. 1, the photo sensor unit 10 includes a plurality of double gate transistors 10a (hereinafter, referred to as DG) arranged in a matrix.
-TFT 10a). Since the opaque fingertip holder B is arranged above the top gate driver 11, the bottom gate driver 12, and the drain driver 13, ultraviolet light emitted from above and light in the wavelength band that excites the transistor of each driver are protected. Since the included external light is prevented from directly entering the drivers 11 to 13, it is possible to prevent malfunction of the transistors of the drivers 11 to 13 due to the excitation light and deterioration due to ultraviolet rays.

As shown in FIGS. 3 and 4, each DG-TF
T10a is a bottom gate electrode 21, a bottom gate insulating film 22, a semiconductor layer 23, a block insulating film 24a,
24b, impurity layers 25a, 25b and 26, source electrodes 27a and 27b, a drain electrode 28, a top gate insulating film 29, a top gate electrode 30, and a protective insulating film 31.

The bottom gate electrode 21 is formed on the insulating substrate 20.
Formed on. The insulating substrate 20 has a property of transmitting visible light and also having an insulating property. By covering the bottom gate electrode 21 and the insulating substrate 20,
The bottom gate insulating film 22 is provided on the bottom gate electrode 21 and the insulating substrate 20. Bottom gate electrode 2
The semiconductor layer 23 is provided on the bottom gate insulating film 22 so as to face No. 1. The semiconductor layer 23 is made of amorphous silicon, polysilicon, or the like, and when visible light enters the semiconductor layer 23, electrons-holes are generated in the semiconductor layer 23.

A block insulating film 24 is formed on the semiconductor layer 23.
a and 24b are arranged in parallel so as to be separated from each other. The impurity layer 25a is provided at one end of the semiconductor layer 23 in the channel length direction, and the impurity layer 25b is provided at the other end. Block insulating film 24a and block insulating film 24b
And the impurity layer 26 is provided on the center of the semiconductor layer 23.
It is separated from a and 25b. Then, the impurity layers 25a,
The semiconductor layer 23 is configured to be covered with 25b, 26 and the block insulating films 24a, 24b. In plan view, a part of the impurity layer 25a overlaps a part of the block insulating film 24a, and the impurity layer 25b overlaps a part of the block insulating film 24b. In addition, the impurity layer 25
a, 25b, and 26 are made of amorphous silicon doped with n-type impurity ions.

A source electrode 27a is provided on the impurity layer 25a, a source electrode 27b is provided on the impurity layer 25b, and a drain electrode 28 is provided on the impurity layer 26. In plan view, the source electrode 27a overlaps part of the block insulating film 24a, the source electrode 27b overlaps part of the block insulating film 24b, and the drain electrode 28 forms the block insulating films 24a and 24b.
It overlaps the upper part. In addition, the source electrodes 27a, 2
7b and the drain electrode 28 are separated from each other. The top gate insulating film 29 is formed so as to cover the bottom gate insulating film 22, the block insulating films 24a and 24b, the source electrodes 27a and 27b, and the drain electrode 28. A top gate electrode 30 is provided on the top gate insulating film 29 so as to face the semiconductor layer 23. A protective insulating film 31 is provided on the top gate insulating film 29 and the top gate electrode 30.

The DG-TFT 10a described above has a structure in which the following first and second double gate type photosensors are arranged in parallel on the insulating substrate 20. That is, the first double-gate type photosensor includes a semiconductor layer 23, a block insulating film 24a, a source electrode 27a, a drain electrode 28, a top gate insulating film 29, and a top gate electrode 30, and a photocarrier storage portion, and a semiconductor. The semiconductor layer 23 includes a layer 23, a source electrode 27a, a drain electrode 28, a bottom gate insulating film 22 and a bottom gate electrode 21.
Function as the light generation region of the photocarrier storage portion and the channel region of the MOS transistor. On the other hand, the second double-gate type photo sensor includes the semiconductor layer 23, the block insulating film 24a, the source electrode 27b, and the drain electrode 2.
8. Top gate insulating film 29 and top gate electrode 30
And a MOS transistor composed of a semiconductor layer 23, a source electrode 27b, a drain electrode 28, a bottom gate insulating film 22, and a bottom gate electrode 21. It functions as the light generation region of the carrier storage portion and the channel region of the MOS transistor.

In the DG-TFT 10a, as shown in FIGS. 1 and 3, the top gate electrode 30 is a top gate line (hereinafter referred to as TGL) and the bottom gate electrode 21 is a bottom gate line (hereinafter referred to as BGL). In addition, the drain electrode 28 is a drain line (hereinafter, D
Source electrodes 27a and 27b are connected to a ground line (hereinafter referred to as GL), which is grounded.

In FIGS. 1 to 4, the protective insulating film 31 provided on the block insulating films 24a and 24b, the top gate insulating film 29, and the top gate electrode 30 is made of a transparent insulating film such as silicon nitride. In addition, the top gate electrode 30 and the TGL are made of a transparent conductive material such as ITO (Indium-Tin-Oxide), and both show a high transmittance for visible light. On the other hand, the source electrodes 27a and 27b, the drain electrode 28, the bottom gate electrode 21, and the BGL are made of a material selected from chromium, a chromium alloy, aluminum, an aluminum alloy, or the like that blocks transmission of visible light.
The protective insulating film 31 is exposed from the opening 1 of the fingertip support portion B shown in FIG. 1 and becomes a place where the convex portion of the fingertip comes into contact.
In addition, below the insulating substrate 20, the DG-TFT 10a is provided.
A backlight 50 (described later) that irradiates the photosensor unit 10 with light in the wavelength range that is excited by the light source is disposed.

The photo sensor unit 10 described above has a matrix of DG-Ts in and around the opening 1 of the fingertip holder B.
The FT 10a is in a placed state. Then, when the charged fingertip is brought into contact with and held by the fingertip holding portion B during fingerprint collation, the controller 14 which will be discharged via the fingertip, and will also change voltage or current due to the capacitance of the finger, which will be described later.
Is detected, and the light source 52 is emitted for the photo sense, that is, the fingerprint reading process, the control signal Tcnt is sent to the top gate driver 11, the control signal Bcnt is sent to the bottom gate driver 12, and the control signal Dcnt is sent to the drain driver 13. Send. The controller 14 reads the electric displacement due to the capacitor peculiar to the finger and reads the control signal Tcnt,
In addition to being able to output the control signal Bcnt and the control signal Dcnt, the electrical displacement when the subject of the capacitor other than the finger other than the finger comes into contact is read and it is verified that the subject is not the finger. Control signal Tcnt, control signal Bcnt,
It is possible not to output the control signal Dcnt.

Here, as shown in FIG. 1, the top gate driver 11 is a shift register which is connected to the TGL of the photosensor section 10 and sequentially and selectively outputs a drive signal to each TGL. Depending on the output control signal group Tcnt, the reset voltage (+25 [V]) or the carrier storage voltage (-15) is appropriately applied to the plurality of TGLs.
[V]) is applied. The bottom gate driver 12 is a shift register that is connected to the BGL of the photo sensor unit 10 and sequentially and selectively outputs a drive signal to each BGL. The bottom gate driver 12 is a plurality of BGLs according to the control signal group Bcnt output from the controller 14. In addition, a channel forming voltage (+10 [V]) or a channel non-forming voltage (± 0
[V]) is applied. Drain driver 13
Is connected to the DL of the photo sensor unit 10 and applies the reference voltage (+10 [V]) to all the DLs according to the control signal group Dcnt output from the controller 14,
Precharge the charge. Then, the drain driver 13 has a DL voltage that varies in accordance with the amount of incident light in each double gate transistor 10a or a source of each DG-TFT 10a in a predetermined period after precharge.
The drain current flowing between the drains is detected and output to the controller 14 as a data signal DATA.

The controller 14 controls the control signal group Tcn.
Top gate driver 1 by t and Bcnt respectively
1, the bottom gate driver 12 is controlled so that both drivers output signals of a predetermined level for each row at a predetermined timing. As a result, each row of the photo sensor unit 10 is sequentially brought into the reset state, the photo sense state, and the read state. The controller 14 also causes the drain driver 13 to read the potential change of DL by the control signal group Dcnt, and sequentially captures it as the data signal DATA.

Next, the photo sense will be described in detail. The DG-TFT 10 which constitutes the photo sensor section 10.
a is the voltage applied to the top gate electrode 30 is +2
When the voltage applied to the bottom gate electrode 21 is ± 0 [V] at 5 [V], the top gate insulating film 29 made of silicon nitride and disposed between the top gate electrode 30 and the semiconductor layer 23. The holes accumulated in the semiconductor layer 23 and the semiconductor layer 23 are discharged, and a reset state is set. DG-TFT
10a is a source electrode 27a, 27b and a drain electrode 2
8 is ± 0 [V], the voltage applied to the top gate electrode 30 is -15 [V], and the voltage applied to the bottom gate electrode 21 is ± 0 [V]. Holes of the hole-electron pairs generated by the incidence of light are accumulated in the semiconductor layer 23 and the top gate insulating film 29, resulting in a photosense state. The amount of holes accumulated during this predetermined period depends on the amount of light.

In the photo-sensing state, the backlight 50 irradiates the DG-TFT 10a with light. However, the bottom gate electrode 21 located below the semiconductor layer 23 of the DG-TFT 10a shields light from the DG-TFT 10a. Does not generate enough carriers. At this time, D
When the fingertip is placed on the protective insulating film 31 above the G-TFT 10a, the light reflected by the protective insulating film 31 or the like is not much incident on the semiconductor layer 23 which is directly below the concave portion of the fingertip along the fingerprint pattern.

As described above, the incident amount of light is small and a sufficient amount of holes are not accumulated in the semiconductor layer 23, the voltage applied to the top gate electrode 30 is -15 [V], and the bottom gate electrode is When the voltage applied to +10 [V] is applied, the depletion layer spreads in the semiconductor layer due to the electric field of the top gate electrode 30, the n-channel is pinched off, and the semiconductor layer 23 has a high resistance. On the other hand, in the photosensing state, the light reflected by the protective insulating film 31 is incident on the semiconductor layer 23 of the DG-TFT 10a which is directly below the convex portion of the fingertip, and a sufficient amount of holes are generated in the semiconductor layer. When such a voltage is applied to the top gate electrode 30, the accumulated holes are attracted to and retained by the top gate electrode 30, so that the charges of the holes are accumulated in the top gate electrode 30. Since the electric field is relaxed, the n-channel is formed on the bottom gate electrode 21 side of the semiconductor layer 23, and the semiconductor layer 23 has a low resistance. The difference in the resistance value of the semiconductor layer 23 in these read states appears as a change in the DL potential.

With respect to the above-mentioned photosense, the driving principle of the DG-TFT 10a constituting the photosensor section 10 will be described with reference to the schematic diagrams of FIGS.

Since the channel formation region of the semiconductor layer 23 of the DG-TFT 10a is generated under the block insulating films 24a and 24b between the impurity layers 25a and 26 and between the impurity layers 25b and 26, the channel length is the block insulating film 24a. , 2
4b is equal to the length in the channel length direction. Therefore, as shown in FIG. 5A, the bottom gate electrode 21 (BG) is formed.
When the voltage applied to the gate electrode is ± 0 [V], the voltage applied to the top gate electrode 30 (TG) is +2.
Even if the voltage is 5 [V], the source / drain electrodes 27a, 2
In the semiconductor layer 23 immediately below 7b and 28, the source, not the voltage applied to the top gate electrode 30 (TG),
Since the applied voltage to the drain electrodes 27a, 27b, 28 is more strongly influenced, the n-channel continuous in the channel length direction is not formed in the semiconductor layer 23.
Even if a voltage of +10 [V] is applied to (D), no current flows between the drain electrode 28 (D) and the source electrodes 27a and 27b (S). Further, in this state, as will be described later, the holes accumulated in the semiconductor layer 23 and the block insulating films 24a and 24b immediately above the channel regions of the semiconductor layer 23 are repelled by the voltage of the top gate electrode 30 (TG) having the same polarity. , Is ejected. Hereinafter, this state is referred to as a reset state.

As shown in FIG. 5B, the voltage applied to the top gate electrode 30 (TG) is -15 [V], and the voltage applied to the bottom gate electrode 21 (BG) is ±. When it is 0 [V], the n-channel is not formed in the semiconductor layer 23, and +10 is formed in the drain electrode 28 (D).
Even if the voltage of [V] is applied, the drain electrode 28 (D)
No current flows between the source electrode 27a and the source electrode 27b (S).

As described above, the drain electrode 28 (D) and the source electrodes 27a and 27b are provided between both ends of the channel region of the semiconductor layer 23 and the top gate electrode 30 (TG), respectively.
Since (S) is arranged, both ends of the channel region are
Drain electrode 28 (D) and source electrodes 27a, 27b
The top gate electrode 3 is affected by the electric field with (S).
A continuous channel cannot be formed with an electric field of 0 (TG) only. Therefore, the bottom gate electrode 21 (B
When the voltage applied to G) is ± 0 [V], a channel is not formed in the semiconductor layer 23 regardless of the voltage applied to the top gate electrode 30 (TG). Absent.

As shown in FIG. 5C, the voltage applied to the top gate electrode 30 (TG) is +25 [V], and the voltage applied to the bottom gate electrode 21 (BG) is +10 ( V), an n channel is formed on the bottom gate electrode (BG) 21 side of the semiconductor layer 23. As a result, the resistance of the semiconductor layer 23 is lowered, and when a voltage of +10 [V] is applied to the drain electrode 28, a current flows between the drain electrode 28 (D) and the source electrodes 27a and 27b (S).

As shown in FIG. 5D, as will be described later, a sufficient amount of holes are not accumulated in the semiconductor layer 23, and the voltage applied to the top gate electrode 30 (TG) is -15.
When it is [V], even if the voltage applied to the bottom gate electrode 21 (BG) is +10 [V], the semiconductor layer 2
3, the depletion layer spreads inside, the n-channel is pinched off, and the semiconductor layer 23 has a high resistance. Therefore, even if a voltage of +10 [V] is applied to the drain electrode 28, the drain electrode 28 (D) and the source electrodes 27a, 27b (S)
No current flows between and. Hereinafter, this state is referred to as a first read state.

Hole-electron pairs are generated in the semiconductor layer 23 in accordance with the amount of incident excitation light. At this time, as shown in FIG. 5E, the voltage applied to the top gate electrode 30 (TG) is −15 [V], and the bottom gate electrode 2
When the voltage applied to 1 (BG) is ± 0 [V], positive holes in the electron-hole pair are the semiconductor layer 23 and the block insulating film 2 immediately above the channel region of the semiconductor layer 23.
It is stored in 4a and 24b. Hereinafter, this state up to the reset state described above and the read state described later is referred to as a photosense state. Note that, in this way, the semiconductor layer 23 is responsive to the electric field of the top gate electrode 30 (TG).
The holes accumulated therein are not ejected from the semiconductor layer 23 until the reset state is reached.

As shown in FIG. 5 (f), the voltage applied to the top gate electrode 30 (TG) is -15 [V], and the voltage applied to the bottom gate electrode 21 (BG) is +10. Even at (V), when holes are accumulated in the semiconductor layer 23, the accumulated holes are attracted to and retained by the top gate electrode 30 (TG) to which a negative voltage is applied. And the top gate electrode 30 (TG)
Acts to reduce the influence of the negative voltage applied to the semiconductor layer 23. Therefore, the n-channel is formed on the bottom gate electrode 21 (BG) side of the semiconductor layer 23, the resistance of the semiconductor layer 23 is reduced, and the drain electrode 28 is +10.
When the voltage of (V) is supplied, the drain electrode 28 (D)
A current flows between the source electrode 27a and the source electrode 27b (S). Hereinafter, this state is referred to as a second read state.

Here, the driver circuit section including the top gate driver 11, the bottom gate driver 12, and the drain driver 13 has a plurality of TFTs (Thin
Film Transistor). Each TFT is composed of an n-channel MOS type field effect transistor, silicon nitride is used for the gate insulating film, and amorphous silicon is used for the semiconductor layer. Each of the above TFTs is D
It is manufactured in the same manufacturing process as the G-TFT 10a, and has substantially the same structure as the DG-TFT 10a.

Specifically, the DG-TFT 10 shown in FIG.
Explaining with reference to the sectional structure of a, the driver circuit section described above includes a transistor group 34 in which the top gate electrode 30 is not stacked. The transistors of the transistor group 34 have basically the same basic structure, but are designed to have different sizes and shapes depending on their functions, as will be described later. A fingertip holding portion B is provided so as to cover the transistor group 34 provided in the driver circuit portion.

Here, the top gate driver 1 described above is used.
1 and the bottom gate driver 12 (see FIG. 1) will be described in detail. The top gate driver 11
The bottom gate driver 12 is one to which the shift register shown in FIG. 6 is applied. The number of rows (TGL, BGL) of the DG-TFT 10a arranged in the photo sensor unit 10
6), the top gate driver 11 and the bottom gate driver 12 have n stages RS (1) to RS (n) that output gate signals and a stage RS (n) as shown in FIG. ) Etc. dummy stage RS (n + 1) for controlling
And a dummy stage RS (n + 2). In addition,
The shift register shown in FIG. 6 shows a configuration when n is an even number of 2 or more. The stage RS (1) is the first stage, the stage RS (2) is the second stage, ..., The stage RS (n) is the nth stage, the stage RS (n + 1) is the n + 1th stage, and the stage RS (n + 2).
Indicates the n + 2nd stage.

The start signal Dst from the controller 14 is input to the first stage RS (1). When the shift register shown in FIG. 6 is the top gate driver 11, the high level of the start signal Dst is +25 [V] and the low level of the start signal Dst is -15 [V].
Is. On the other hand, when the shift register shown in FIG. 6 is the bottom gate driver 12, the high level of the start signal Dst is +10 [V] and the low level of the start signal Dst is -15 [V].

The second and subsequent stages RS (2) to RS
In (n), each preceding stage RS (1) to stage RS (n-
The output signals OUT (1) to OUT (n-1) from 1) are input as input signals. When the shift register shown in FIG. 6 is the top gate driver 11, the output signal OUT (1) to the output signal OUT (n) of each stage corresponds to 1.
It is output to the TGL of the nth row. On the other hand, when the shift register shown in FIG. 6 is the bottom gate driver 12, the output signals OUT (1) to OUT (n) of the respective stages are:
It is output to the corresponding BGL of the 1st to nth rows.

Further, the stages RS other than the stage RS (n + 2)
(1) to the stage RS (n + 1) include the succeeding stage RSs.
(2) to output signal OUT (2) from the stage RS (n + 2)
~ OUT (n + 2) is input as a reset signal.
The reset signal Dent from the controller 14 is input to the stage RS (n + 2). When the shift register shown in FIG. 6 is the top gate driver 11, the high level of the reset signal Dent is +25 [V] and the low level of the reset signal Dent is −15 [V]. On the other hand, when the shift register shown in FIG. 6 is the bottom gate driver 12, the high level of the reset signal Dent is +10 [V] and the low level of the reset signal Dent is −15 [V].

A reference voltage Vss is applied from the controller 14 to each stage RS (k) (k is an arbitrary integer of 1 to n + 2). When the shift register shown in FIG. 6 is the top gate driver 11, the level of the reference voltage Vss is -1.
It is 5 [V]. On the other hand, when the shift register shown in FIG. 6 is the bottom gate driver 12, the level of the reference voltage Vss is ± 0 [V]. Also, in each stage RS (k),
A constant voltage Vdd is applied from the controller 14. Figure 6
When the shift register shown in (1) is the top gate driver 11, the level of the constant voltage Vdd is +25 [V].
On the other hand, when the shift register shown in FIG. 6 is the bottom gate driver 12, the level of the constant voltage Vdd is +10.
[V].

The clock signal CK1 from the controller 14 is input to the odd-numbered stages RS (k). Also,
The clock signal CK2 is input to the even-numbered stages RS (k). The clock signals CK1 and CK2 are alternately set to a high level for each time slot for a predetermined period of time slots in which the output signal of the shift register is shifted. That is, when the clock signal CK1 is at the high level for a predetermined period of one time slot,
During the time slot, the clock signal CK2 is at low level, during the next time slot, the clock signal CK1 is at low level and the clock signal CK2 is at high level for a predetermined period.

When the shift register shown in FIG. 6 is the top gate driver 11, clock signals CK1 and CK2 are used.
Is +25 [V] for high level and -15 for low level
[V]. On the other hand, when the shift register shown in FIG. 6 is the bottom gate driver 12, the high level is +10.
[V], the low level is ± 0 [V].

Then, as shown in FIG. 6, each stage RS (k) of the above-mentioned shift register constituting the top gate driver 11 and the bottom gate driver 12 has, as a basic configuration, six TFTs 41 to 41 which are the transistor group 34.
It is equipped with 46. Each of the TFTs 41 to 46 is an n-channel MOS type field effect transistor,
Silicon nitride is used for the gate insulating film, and amorphous silicon is used for the semiconductor layer.

As shown in FIGS. 6 and 7, the first stage R
The start signal Dst is input to the gate electrode and the drain electrode of S (1). The gate electrode and the drain electrode of the TFT 41 of each stage RS (k) other than the first stage RS (1) are connected to the source electrode of the TFT 45 of the preceding stage RS (k−1), and the source electrode of the TFT 41 is the TFT 4
4 gate electrode, TFT 42 drain electrode and TFT
It is connected to the gate electrode of 43. The source electrode of the TFT 41 of each stage RS (k), the gate electrode of the TFT 44, T
The wiring connected to the drain electrode of the FT 42 and the gate electrode of the TFT 43 includes the TFT 41 related to this wiring itself.
The parasitic capacitances of ~ 44 and the wiring itself form a capacitance Ca (k) for accumulating charges.

The drain electrode of the TFT 43 is the TFT 46.
Connected to the source electrode of and the gate electrode of the TFT 45,
The reference voltage Vss is applied to the source electrode of the TFT 42 and the source electrode of the TFT 43. And TFT4
A constant voltage Vdd is applied to the gate electrode and drain electrode of No. 6. Further, the clock signal CK1 is input to the drain electrode of the odd-numbered TFT 44, and the even-numbered TF
The clock signal CK2 is input to the drain electrode of T44. The source electrode of the TFT 44 in each stage is the TFT 4
5, the reference voltage Vss is applied to the source electrode of the TFT 45. The output signal OUT (k + 1) from the next stage is applied to the gate electrode of the TFT 42.
Has been entered.

Next, the T provided in each stage RS (k)
The functions of the FTs 41 to 46 will be described. Whether the output signal OUT (k-1) from the preceding stage RS (k-1) is input to the gate electrode and the drain electrode of the TFT 41 (in this case, k is 2 to n + 2), or the start signal is input from the controller 14. Dst is input (in this case, k is 1). Output signal OUT (k-1) or start signal Ds
When t becomes high level, the TFT 41 is turned on, current flows from the drain electrode to the source electrode, and T
The FT 41 outputs a high level output signal OUT (k-1) or a start signal Dst to the source electrode. Here, when the TFT 42 is in the off state, the high-level output signal OUT (k-1) or the start signal Dst output from the source electrode of the TFT 41 is output.
Thus, the capacity Ca (k) is accumulated. On the other hand, when the output signal OUT (k-1) or the start signal Dst becomes low level, the TFT 41 is turned off and no current flows through the drain electrode to the source electrode of the TFT 41.

A constant voltage Vdd is applied to the gate electrode and drain electrode of the TFT 46. This gives T
The FT 46 is always in an ON state, a current flows through the drain electrode to the source electrode of the TFT 46, and the TFT 46 outputs a signal of a substantially constant voltage Vdd level to the source electrode. The TFT 46 has a function as a load that divides the constant voltage Vdd.

The TFT 43 is turned off when electric charge is not stored in the capacitor Ca (k), and the capacitor Cb is generated by the constant voltage Vdd level signal output from the TFT 46.
(K) is accumulated. On the other hand, the TFT 43
Is turned on when electric charge is accumulated in the capacitor Ca (k), and a current flows from the drain electrode to the source electrode of the TFT 43, so that the TFT 43 has a capacity Cb (k).
It is designed to discharge the charge accumulated in the.

The TFT 45 is turned off when no charge is stored in the capacitor Cb (k), and the capacitor Cb (k) is turned off.
It is turned on when electric charges are accumulated in. TFT
The capacitor 44 is turned on when electric charges are accumulated in the capacitor Ca (k), and is turned off when electric charges are not accumulated in the capacitor Ca (k). Therefore, when the TFT 45 is in the off state, the TFT 44 is in the on state, and the TFT 4
The TFT 44 is turned off when 5 is turned on.

The reference voltage V is applied to the source electrode of the TFT 45.
ss is applied. TFT 45 turned on
Is a reference voltage Vss level (low level) signal from the drain electrode to the output signal OUT of the stage RS (k).
(K) is output. The TFT 45 in the off state sets the level of the signal output from the source electrode of the TFT 44 to the output signal OUT of the stage RS (k).
(K) is output.

The clock signal CK1 or CK2 is input to the drain electrode of the TFT 44. When the TFT 44 is off, the TFT 44 blocks the output of the clock signal CK1 or CK2 input to the drain electrode. When the TFT 44 is in the ON state, the TFT 44 outputs the low level clock signal CK.
1 or CK2 is output to the source electrode. Here, when the TFT 44 is in the ON state, T
Since the FT 45 is in the off state, the low-level clock signal CK1 or CK2 is the output signal O of the stage RS (k).
It is output as UT (k).

On the other hand, when the high-level clock signal CK1 or CK2 is input to the drain electrode when the TFT 44 is in the ON state, the parasitic capacitance composed of the gate electrode and the source electrode and the gate insulating film between them is charged. Is accumulated. That is, the potential of the capacitance Ca (k) rises due to the bootstrap effect, and the capacitance Ca (k)
The source-drain current of the TFT 44 is saturated when the potential of the gate voltage reaches the gate saturation voltage. As a result, the TFT 44 in the ON state outputs a signal having substantially the same potential as the high-level clock signal CK1 or CK2 to the source electrode. Where TFT
When 44 is in the ON state, the TFT 45 is in the OFF state, so the high-level clock signal CK1 or CK
2 is output as the output signal OUT (k) of the stage RS (k).

The gate electrode of the TFT 42 is connected to the next stage RS.
(K + 1) (where k is 1 to n + 1) output signal O
UT (k + 1) is input. The TFT 42 is turned on when the output signal OUT (k + 1) input to the gate electrode is at high level, and discharges the electric charge accumulated in the capacitor Ca (k).

The TFT 4 of the dummy stage RS (n + 2)
In 2, the reset signal Dend is input from the controller 14 to the gate electrode of the TFT 42, but the third output signal OUT (3) in the next scan may be used instead.

Next, the above-mentioned top gate driver 11
The operation of the bottom gate driver 12 will be described with reference to FIG. In the figure, one T period is one selection period. Note that the top gate driver 11 and the bottom gate driver 12 are substantially different in the signal input timing and the level of the reference voltage Vss, and only the output signal output timing and the level are different accordingly. Regarding the driver 12, only the part different from the top gate driver 11 will be described.

As shown in FIG. 8, at timing T0, the high-level (+25 [V]) start signal Dst is generated.
Is input to the first stage RS (1) from the controller 14. The start signal Dst remains high level for a predetermined period until the timing T1 when one horizontal period ends.

At timing T0, the TFT 41 is turned on, and the high-level input signal (start signal Dst) input to the drain electrode of the TFT 41 is output from the source electrode. Since the TFT 42 is in the off state, the high level input signal output from the source electrode of the TFT 41 causes the charge to be accumulated in the capacitor Ca (1). By accumulating charges in the capacitor Ca (1),
The potential of the capacitor Ca (1) rises and the TFTs 43 and 44 are turned on. Then, the TFT 4 in the ON state during the period when the high-level start signal Dst is input.
The low-level (-15 [V]) clock signal CK1 is input to the drain electrode of No. 4, and this low-level clock signal CK1 is the output signal OUT (1) of the stage RS (1).
Is output as.

After timing T0 and before timing T1,
The start signal Dst becomes low level, and the TFT 43,
44 is turned off. In this case, the capacity Ca
The electric charge is accumulated in (1). When the TFT 44 is turned off, a signal of a constant voltage Vdd level (+25 [V]) is output to the source electrode of the TFT 46, and the electric charge is accumulated in the capacitor Cb (1). The charge is accumulated in the capacitor Cb (1) to turn on the TFT 45, which causes the reference voltage Vss level (−15).
[V]) is the output signal OUT of the stage RS (1).
It is output as (1).

Next, at the timing T1, the clock signal CK
1 becomes high level (+25 [V]). Then TF
The parasitic capacitance formed by the gate electrode and the source electrode of T44 and the gate insulating film between them is charged up. That is, the capacitance Ca (1) is charged up,
When the potential of the capacitor Ca (1) reaches the gate saturation voltage due to the bootstrap effect, the current flowing between the drain electrode and the source electrode of the TFT 44 is saturated. As a result, the output signal OUT output from the stage RS (1) is output.
(1) is +25 having substantially the same potential as the clock signal CK1.
[V], which is at a high level. Note that, while the clock signal CK1 is at the high level, the capacitance Ca (1) is charged by the parasitic capacitance of the TFT 44 being charged up.
Also reaches a potential of approximately +45 [V].

Next, after the timing T1 and before the timing T2, the clock signal CK1 is at a low level (-15
[V]). As a result, the level of the output signal OUT (1) also becomes approximately -15 [V]. Further, the electric charge charged to the parasitic capacitance of the TFT 44 is released, and the capacitance Ca
The potential of (1) decreases.

The high level output signal OUT (1) output from the first stage RS (1) during the predetermined period from timing T1 to T2 is the second stage RS (2).
Is input to the gate electrode and the drain electrode of the TFT 41. As a result, as in the case where the high-level start signal Dst is input to the first stage RS (1), charges are accumulated in the capacitor Ca (2) of the second stage RS (2). During a part of the timing T1 to T2, in the second stage RS (2), the TFT 44 is in the ON state, TF
T45 is turned off. Then, during the period when the high-level input signal (output signal OUT (1)) is input,
A low level (-
15 [V]) of the clock signal CK2 is input, and the low-level clock signal CK2 is output as the output signal OUT (2) of the stage RS (2).

Next, at the timing T2, the clock signal CK2 becomes high level (+25 [V]). Then, the parasitic capacitance formed by the gate electrode and the source electrode of the TFT 44 of the stage RS (2) and the gate insulating film between them is charged up. That is, when the capacitance Ca (2) is charged up and the potential of the capacitance Ca (2) reaches the gate saturation voltage due to the bootstrap effect, TF
The current flowing between the drain electrode and the source electrode of T44 is saturated. As a result, the output signal OUT (2) output from the stage RS (2) becomes +25 [V], which is substantially the same potential as the clock signal CK2, and is at a high level. It should be noted that while the clock signal CK2 is at the high level, T
As the parasitic capacitance of the FT 44 is charged up, the potential of the capacitance Ca (2) also reaches approximately +45 [V].

Further, after the timing T2 and before the timing T3, the high-level output signal OUT (2) is input to the gate electrode of the TFT 42 of the first stage RS (1). As a result, the potential of the capacitor Ca (1) of the stage RS (1) becomes the reference voltage Vss.

Next, after the timing T2 and before the timing T3, the clock signal CK2 is at a low level (-15
[V]). As a result, the level of the output signal OUT (2) also becomes approximately -15 [V]. Further, the electric charge charged to the parasitic capacitance of the TFT 44 is released, and the capacitance Ca
The potential of (2) decreases.

In the same manner, the output signal OUT (1) of each stage is output within one scanning period Q until the next timing T1.
~ OUT (n) sequentially becomes high level. That is, the stage where the high-level output signal is output is sequentially shifted to the next stage. High level output signal O
UT (1) to OUT (n) do not decrease even if they are shifted to the next stage. Then, after one scanning period Q, the start signal Dst becomes a high level again, and the subsequent stages RS
The above operation is repeated in (1) to the stage RS (n).

In the final stage RS (n) of the TGL, even after the high level output signal OUT (n) is output to the dummy RS (n + 1) of the next stage, the potential of the capacitor Ca (n) is high level. It remains. When the high-level output signal OUT (n) is output to the next stage RS (n + 1), the output signal OUT (n +) of the dummy stage RS (n + 1) is output.
Due to 1), the TFT 42 of the final stage RS (n) is turned on, and the potential of the capacitor Ca (n) becomes the reference voltage Vss. Similarly, the output signal OUT of the dummy stage RS (n + 2)
By (n + 2), the TFT 4 of the dummy stage RS (n + 1)
2 is turned on, and the potential of the capacitor Ca (n + 1) becomes the reference voltage Vss. Then, by inputting the high-level reset signal Dent to the TFT 42 of the dummy stage RS (n + 2), the potential of the dummy stage RS (n + 2) becomes
The reference voltage Vss changes from the high level.

The operation of the bottom gate driver 12 is almost the same as that of the top gate driver 11, but the clock signal CK input from the controller 14 is used.
Since the high level of 1 and CK2 is +10 [V], the output signal ou of each stage RS (k) (k is 1 to n in this case)
The high level of t (k) is approximately +10 [V], and the level of the capacitance Ca (k) at this time is approximately +18 [V]. Clock signal CK1, of the bottom gate driver 12
The period in which CK2 is at high level is shorter than the period in which the clock signals CK1 and CK2 of the top gate driver 11 are at high level.

The top gate driver 11 and the bottom gate driver 12 to which the above shift register is applied.
Is a control signal group Tcnt, Bc from the controller 14.
According to nt, TGL and BGL are sequentially selected and a predetermined voltage is applied. This control signal group Tcnt, B
The clock signals CK1 and CK2, the start signal Dst, the reset signal Dend, and the constant voltage Vdd are added to cnt.
And the reference voltage Vss.

FIG. 9 shows distribution data of the light sensitivity of the above-mentioned photosensor section 10. In FIG. 9, the horizontal axis represents the angle of light incident on the photosensor unit 10, and the direction perpendicular to the incident surface of the photosensor unit 10 is 0 °. Since the photo sensor unit 10 is formed in a substantially left-right symmetric shape as shown in FIG. 3, it has the same sensitivity characteristic symmetrical with respect to the vertical axis of the graph even at an angle in the minus direction. . In addition, the vertical axis represents the electric charge accumulated according to the angle of the light incident on the photo sensor unit 10, and here, the electric charge amount (white voltage) accumulated when the photo sensor unit 10 is incident from the vertical direction of 0 ° is shown. It is set to 2V. The higher the value on the vertical axis, the higher the sensitivity. That is, the maximum region of the sensor sensitivity of the photosensor unit 10 having the above-described configuration is the light incident angle of 30 ° to 55 ° and the light incident angle of −30 ° to −55 °, and the allowable incident angle of the sensor sensitivity of the photosensor unit 10 is about −. It is between 75 ° and about 75 °,
Light incident obliquely has a higher sensor sensitivity than light incident in the vertical direction.

Here, FIG. 10 shows an example of a detailed structure of the backlight 50 provided below the insulating substrate 20 shown in FIGS. 2 and 4. Backlight 5 shown in FIG.
Reference numeral 0 denotes a light guide system unit 51 having a planar bottom diffusion light guide plate 511 and an LED (Light-Emitting Diode) arranged around the light guide plate 511 of the light guide system unit 51, a hot cathode discharge tube, or a cold cathode. The light source unit 52 includes a straight tube type L-shaped fluorescent tube and a L-shaped fluorescent tube. In the present embodiment, the light source unit 52 is an LED, and the light guide plate 511 is configured to emit light in the wavelength range excited by the DG-TFT 10 a according to the controller 14.

The light guide system section 51 shown in FIG. 10 has a bottom diffusion light guide plate (light guide body) 511 which receives the light from the light source section 52 from one side surface 511a, diffuses the light inside, and emits the light. A reflection plate 512 that covers the bottom surface 511c of the light plate 511;
The surface (light emitting surface) 511b of the bottom diffusion light guide plate 511 is covered, and the surface 511b of the bottom diffusion light guide plate 511 is covered.
The light distribution emitted from the light guide plate 511 in the direction deviated from the vertical direction of the upper surface 511b with respect to the surface 511b of the light guide plate 511,
A light diffusion plate 513 and a light diffusion plate 513 for emitting the emission light so that the emission angle of the maximum brightness of the light distribution of the backlight 50 is displaced from the direction perpendicular to the front surface of the backlight 50.
And a diffusion sheet 514 arranged so as to cover the surface of the. The diffusion light guide plate 511 is not limited to the reflection plate 512 covering the bottom surface 511c, but is not shown in the figure.
It is in a state of being covered with a reflecting member except for the side surface and the upper surface on which the light source unit 52 is arranged. Diffusion sheet 514
The surface of is arranged in parallel with the surface of the photosensor unit 10.

The bottom diffusion light guide plate 511 is made of a transparent resin such as acrylic. In the bottom surface diffusion light guide plate 511 of this embodiment, a process for diffusing light, for example, white diffusion dots are printed on the bottom surface. Then, the light of the light source unit 52, which is incident on the one end surface 511a facing the light source unit 52, is configured to diffuse inside. Reflector 51
Reference numeral 2 is for preventing the light incident on the inside of the light guide plate 511 from leaking and has specular reflection.

The diffuser plate (indicated by a prism sheet in FIG. 10) 513 is a well-known one which is basically transparent and has many fine irregularities on its surface. In addition, the diffusion plate 51
3 has a large number of prism portions 5 in which, for example, a large number of peak surfaces and valley surfaces having a triangular cross section are continuously arranged on the light emission side.
15 is formed. Then, in such a diffusion plate 513, it is known that light transmitted at various angles is refracted to increase the component of light traveling forward. The diffuser plate 513 has a large number of fine irregularities on its surface, and changes the angle of light to be transmitted depending on the angle of the surface of each irregularity, the incident angle of light, and the difference in the refractive index at the interface. The diffused light is reflected. The diffusion plate 513 of this embodiment is
A plurality of stepped triangular protrusions are provided on the upper surface in a state of being arranged in parallel between two opposing side edges. The diffusing plate 513 is installed on the light guide plate 511 so that the prism portion 515 on the upper surface of the diffusing plate 513 extends from the end surface 511a on which light is incident from the light source section 52 to the end surface 511d facing the end surface 511a. Has been done. That is, the prism portion 515 is arranged so as to extend in parallel to the propagation direction of the light incident from the light source portion 52 to the bottom diffusion light guide plate 511.

As the diffusing plate 513 of this example, for example, Light Up 100PBU, Light Up 100S, Light Up 100SX, Light Up 100MX-A, Light Up 100TL, Light Up 100SH, etc. manufactured by KIMOTO Co., Ltd. And the brightness enhancement film (BEFIII) manufactured by Sumitomo 3M Limited.
90 / 50T, BEFIII 90 / 50M, etc.). In addition, you may use the other diffuser plate. Further, the diffusion sheet 514 is a well-known one,
In addition to making the reflective dots inconspicuous, it has the function of increasing the front brightness of the backlight 50 by collecting light in the front direction.

In the structure of the backlight 50, the light source section 52, for example, an LED is driven to emit light, and the light from the light source section 52 is diffused and guided by the light guide system 51 of the light guide system section 51.
1, the maximum brightness of the light distribution of the backlight 50 is at the front of the backlight 50, here the diffusion sheet 51.
4 is an oblique direction with respect to the normal direction of the exit surface (the normal direction to the entrance surface of the photosensor unit 10), specifically, −1 when the normal direction of the front surface of the backlight 50 is 0 °.
It is in the range of 0 ° to −70 °.

FIG. 11 shows the brightness distribution of the backlight 50 of the present embodiment. In FIG. 11, when the brightness enhancement film (BEFIII90) manufactured by Sumitomo 3M Co., Ltd. is used, the vertical direction of the front surface of the backlight 50 is 0 °.
Shows the distribution of the light distribution, and the positive value of the emission angle increases as the emission angle of the light from the diffusion sheet 514 is inclined toward the light source unit 52 side with the perpendicular line of 0 ° as an axis. It is defined that the absolute value of the negative angle increases as it inclines to the opposite side. The vertical axis represents the brightness per unit area. As shown in FIG. 11, the emission angle of the maximum luminance of the light distribution of the backlight 50 according to the present embodiment is determined by the backlight 5
When the normal direction of the exit surface of the front surface of 0 (the normal direction to the incident surface of the photosensor unit 10) is 0 °, the direction inclined by 45 ° or more with respect to the normal direction, that is, the direction near −50 ° Has become.

Next, the operation of the fingerprint reading device A when reading the fingerprint of the subject will be described. First, the subject
As shown in FIG. 1, the fingertip is brought into contact with the fingertip holding portion B so that the fingertip fits the fingertip holding portion B. When the fingertip comes into contact with the fingertip holder B, the controller 14 detects the voltage or current displaced by the fingertip holder B due to the addition of the finger capacitor. Then, the controller 14
Control signal groups Tcnt, B to start photosense
Top gate driver 1 for cnt and Dcnt respectively
1, bottom gate driver 12, drain driver 13
And a light emission signal to the light source unit 52. In response to this, the light from the light source unit 52 is condensed at a predetermined angle by the diffusion plate 513 and emitted from the surface of the diffusion sheet 514 toward the photosensor unit 10, and the top gate driver 11, the bottom gate driver 12, The drain driver 13 is used for each DG-TF of the photo sensor unit 10.
An appropriate signal is output to T10a to perform photo sensing for each row.

Photosensing will be described with reference to FIG. 1. Irradiation light emitted from the light guiding system section 51 is not directly incident on the semiconductor layer 23 by the bottom gate electrode 21 and is protected. It proceeds toward the insulating film 31. The convex portion of the fingertip is in contact with the protective insulating film 31,
Irradiation light emitted from the backlight 50 and hitting the fingertip is diffusely reflected, and the DG-TFT 10a arranged immediately below the convex portion.
Incident on the semiconductor layer 23, and electron-hole pairs are generated in the semiconductor layer 23 according to the amount of light. On the other hand, since the concave portion of the fingertip is not in contact with the protective insulating film 31, diffuse reflection does not occur,
Light enough to generate sufficient carriers is not incident on the semiconductor layer 23 of the DG-TFT 10a immediately below it.

The DG-TFT 10a is composed of the generated electrons.
The holes of the hole pairs are accumulated in the semiconductor layer 23 and the top gate insulating film 29 by the carrier accumulation voltage (-15 [V]) applied to the top gate electrode 30, and the charges due to the holes are carriers. Reduces the effect of accumulated voltage.
After a certain period of time, the potential of the bottom gate electrode 21 changes from the channel non-formation voltage (0 [V]) to the channel formation voltage (+).
10 [V]), the larger the amount of accumulated holes, in other words, the larger the amount of incident light, DG−.
The drain current value increases in the TFT 10a, and the displacement of the DL potential also increases. Then, the drain driver 13
Reads the DL potential row by row and outputs the data signal DATA.
Is output to the controller 14, and as a result, the fingerprint pattern of the subject is read.

In the above-described operation of reading the fingerprint pattern, the DG-TF provided in the photo sensor unit 10
About concrete operation of T10a, FIG.
This will be described with reference to the schematic diagram shown in (i). In the following description, the 1T period has the same length as the 1T selection period shown in FIG. Further, in order to simplify the description, the D
Only the first three rows of the G-TFT 10a will be considered.

First, 1T from timing T1 to T2
12A, the top gate driver 11 applies +25 [V] to the TGLs of the first row and −15 to the TGLs of the second and third rows (all other rows) during the period.
[V] is applied. That is, the top gate driver 1
The high level output signal is output from the first stage RS (1), and the low level output signal is output from the stages RS (2) and RS (3). On the other hand, the bottom gate driver 12
0 [V] is applied to all BGLs. That is, low-level output signals are output from the stages RS (1) to RS (3) of the bottom gate driver 12. During this period, the DG-TFT 10a in the first row is in the reset state (see FIG.
(See (a)), and the DG-TFT 10a in the second and third rows.
Indicates that the read state in the previous vertical period has been completed (state not affecting photosense).

Next, 1T from timing T2 to T3
12B, the high-level output signal changes to the stage RS of the top gate driver 11 during the period of
Shifting to (2), the top gate driver 11 applies +25 [V] to the TGL of the second row and-to the other TGL.
Apply 15 [V]. On the other hand, bottom gate driver 1
2 applies 0 [V] to all BGLs. During this period, the DG-TFT 10a in the first row is in the photosense state (see FIG. 5E), and the DG-TFT in the second row is in the photosense state.
10a is in a reset state (see FIG. 5A), and the DG-TFT 10a in the third row is in a state in which the reading state in the previous vertical period has been completed (state that does not affect photosense).

Next, 1T from timing T3 to T4
12C, the high-level output signal changes to the stage RS of the top gate driver 11 during the period
Shifting to (3), the top gate driver 4 applies +25 [V] to the TGL in the third row and -1 to the other TGLs.
5 [V] is applied. On the other hand, the bottom gate driver 12
Applies 0 [V] to all BGLs. During this period, the DG-TFTs 10a in the first and second rows are in the photo-sensing state (see FIG. 5E), and the DG-TFs in the third row are DG-TF.
T10a is in the reset state (see FIG. 5 (a)).

Next, in the period of 0.5T from the timing T4 to T4.5, as shown in FIG.
The top gate driver 11 is -15 for all TGLs.
[V] is applied. On the other hand, the bottom gate driver 12
Applies 0 [V] to all BGLs. Further, the drain driver 13 applies +10 [V] to all DLs. During this period, all rows of DG-TFTs
10a becomes the photo sense state (see FIG. 5 (e)).

Next, in the period of 0.5T from timing T4.5 to T5, as shown in FIG.
The top gate driver 11 is -15 for all TGLs.
[V] is applied. On the other hand, the bottom gate driver 5
+10 [V] is applied to the BGL in the first row, and 0 [V] is applied to the other BGL. That is, the high level output signal is output from the stage RS (1) of the bottom gate driver 12, and the low level output signal is output from the stages RS (2) and RS (3). During this period, the first line DG-T
The FT 10a is in the first or second read state (see FIG. 5).
(See (d) or (f)), and DG-T in the second and third lines
The FT 10a remains in the photosense state (see FIG. 5E).

Here, in the DG-TFT 10a in the first row, when the semiconductor layer 23 is irradiated with sufficient light during the period from the timing T2 to the timing T4.5 in the photosensing state, the second reading state is obtained. (See FIG. 5 (f)) and an n-channel is formed in the semiconductor layer 23.
The charge on the corresponding DL is discharged. on the other hand,
If the semiconductor layer 23 is not sufficiently irradiated with light during the period from the timing T2 to T4.5, the n-channel in the semiconductor layer 23 is pinched off in the first read state (see FIG. 5D). Therefore, the charges on the corresponding DL are not discharged. The drain driver 13 reads the potential on each DL in the period from timing T4.5 to timing T5, converts it into the data signal DATA, and outputs D in the first row.
The data is supplied to the controller 14 as data detected by the G-TFT 10a.

Next, in the period of 0.5T from the timing T5 to T5.5, as shown in FIG.
The top gate driver 11 is -15 for all TGLs.
[V] is applied. On the other hand, the bottom gate driver 12
Applies 0 [V] to all BGLs. Further, the drain driver 13 applies +10 [V] to all DLs. During this period, the DG-TFT 10 in the first row is
a has finished reading, and the DG in the second and third rows
-TFT 10a is in a photo sense state (see FIG. 5 (e))
Becomes In addition, between the timing T5 and T5.5,
The high level output signal of the stage RS (1) of the bottom gate driver 12 is input to the stage RS (2).
Since the clock signal CK2 input to (2) is not at the high level, the BGL of the second row is applied to 0 [V].

Next, in the period of 0.5T from timing T5.5 to timing T6, as shown in FIG.
The top gate driver 11 is -15 for all TGLs.
[V] is applied. On the other hand, the high-level output signal shifts to the stage RS (2) of the bottom gate driver 12, and the bottom gate driver 12 adds +10 to the second row BGL.
[V] is applied, and 0 [V] is applied to the other BGL. During this period, the DG-TFT 10a in the first row is in a state where the reading is completed, and the DG-TFT 10a in the second row is
Becomes the first or second read state (see FIG. 5D or 5F), and the DG-TFT 10a in the third row becomes the photosense state (see FIG. 5E).

Here, in the DG-TFT 10a in the second row, when the semiconductor layer 23 is irradiated with sufficient light during the period from the timing T3 to T5.5 in the photosensing state, the second reading is performed. In this state (see FIG. 5F), an n channel is formed in the semiconductor layer 23,
The charge on the corresponding DL is discharged. on the other hand,
If the semiconductor layer 23 is not sufficiently irradiated with light during the period from timing T3 to timing T5.5, the n-channel in the semiconductor layer 23 is pinched off in the first read state (see FIG. 5D). Therefore, the charges on the corresponding DL are not discharged. The drain driver 13 reads the potential on each DL in the period from timing T5.5 to timing T6, converts it into the data signal DATA, and outputs D in the second row.
The data is supplied to the controller 14 as data detected by the G-TFT 10a.

Next, in the period of 0.5T from the timing T6 to T6.5, as shown in FIG.
The top gate driver 11 is -15 for all TGLs.
[V] is applied. On the other hand, the bottom gate driver 12
Applies 0 [V] to all BGLs. Further, the drain driver 13 applies +10 [V] to all DLs. During this period, the first and second rows of DG-TFT
10a is in a state where reading has been completed, and DG in the third row
-TFT 10a is in a photo sense state (see FIG. 5 (e))
Becomes

Next, in the period of 0.5T from the timing T6.5 to T7, as shown in FIG.
The top gate driver 11 is -15 for all TGLs.
[V] is applied. On the other hand, the high-level output signal shifts to the stage RS (3) of the bottom gate driver 12, and the bottom gate driver 12 adds +10 to the third row BGL.
[V] is applied, and 0 [V] is applied to the other BGL. During this period, the DG-TFTs 10a in the first and second rows are in a state of having finished reading, and the DG-TFT1 in the third row
0a is the first or second read state (see FIG. 5D or 5F).

Here, in the double-gate transistor 7 in the third row, the timing T when it is in the photo-sensing state.
When the semiconductor layer 23 is irradiated with sufficient light in the period from 4 to T6.5, the second read state (see FIG. 5F) is established and an n-channel is formed in the semiconductor layer 23. Therefore, the charge on the corresponding DL is discharged.
On the other hand, if the semiconductor layer 23 is not sufficiently irradiated with light in the period from the timing T4 to T6.5, the first read state (see FIG. 5D) results and n in the semiconductor layer 23 is reached.
Since the channel is pinched off, the charge on the corresponding DL is not discharged. Drain driver 13
Reads the potential on each DL in the period from timing T6.5 to timing T7, converts it into a data signal DATA, and supplies it to the controller 14 as data detected by the DG-TFT 10a in the third row.

In this way, the controller 14 performs a predetermined process on the data signal DATA supplied from the drain driver 13 for each row, so that the fingerprint pattern of the fingertip of the subject can be read.

Here, the incident angle of the photosensor unit 10 is set to 0 ° in the direction of the normal of the emission surface of the backlight 50, that is, the normal direction of the incident surface of the photosensor unit 10 in accordance with the definition of the emission angle of FIG. The photosensor unit 10 is defined such that the negative absolute value of the incident angle increases as the axis is inclined toward the light source unit 52 side, and the positive absolute value of the incident angle is increased as the axis is inclined toward the side opposite to the light source unit 52. The maximum sensor sensitivity area of
As is clear from the description in FIG. 9, the photo sensor unit 10
Light incident angle of 30 ° to 55 ° (corresponding to light emitting angle of 30 ° to 55 ° on the diffusion sheet 514), and light incident angle of −30 ° to −55 ° on the photosensor unit 10 (on the diffusion sheet 514). It corresponds to the light emission angle of -30 ° to -55 °).
Since the backlight 50 of the fingerprint reader A according to the present embodiment can collect light so that the emission angle of maximum brightness is within this range, that is, compared with the backlight emitted from the vertical direction, that is, The sensor sensitivity is higher than in the case where light is incident from the back surface of the photo sensor unit 10 in the direction perpendicular to the back surface. The maximum brightness in the maximum sensor sensitivity region is preferably twice or more, more preferably three times or more, and further preferably five times or more as high as the brightness at the lowest angle. Since the backlight 50 of the fingerprint reading device A according to the present embodiment focuses the light so that the maximum brightness is provided within the range of this angle, in the fingerprint reading device A, the backlight 50 of the light source unit 52 is provided. Light can be more efficiently emitted from the light guide system unit 51 with reduced power consumption, and the emitted light allows the photosensor unit 10 to emit light.
The fingerprint can be read in the maximum sensitivity area, that is, in the area where stable reading is possible.

As described above, according to the fingerprint reader A,
The emission angle of the maximum brightness of the light of the backlight 50 that irradiates the photo sensor unit 10 with light is set to a range of the allowable incident angle of about −75 °.
Approximately 75 ° (Allowable emission angle of the diffusion sheet 514 is approximately −75
The angle of incidence of light at the photosensor unit 10 is 30 ° to 30 °, which is the maximum sensor sensitivity region.
Although the power consumption of the light source unit is reduced by setting the angle within the range of 55 °, −30 ° to −55 °, if the luminance is sufficiently large within the allowable incident angle range, the sensing can be performed efficiently.

Here, as shown in FIG. 13, as the structure of the backlight 500, two diffusion plates 513 are extended above the bottom diffusion light guide plate 511 above the reflection plate 512 so that the prism portions 515 extend from each other. Arrange so that the directions are orthogonal.
Then, in the backlight 500, as shown in FIG. 14, the emission angle of the maximum brightness comes closer to the vertical direction. Figure 1
4 is a graph showing the luminance distribution of the backlight 500 when using a brightness enhancement film (BEFIII90) manufactured by Sumitomo 3M Co., Ltd. as the two diffusion plates 513, the angle in the direction perpendicular to the light emitting surface is 0. When the angle is set to °, light is condensed in the vicinity of -22 °, the emission angle of maximum brightness is in the vicinity of -22 °, and the power consumption of the backlight can be suppressed by condensing the light within the range of the allowable incident angle. . However, in the backlight 500, the number of the diffusion plates 513 is increased as compared with the backlight 50, so that the cost is increased and the light absorption of the diffusion plates 513 lowers the brightness as a whole.

Further, in the fingerprint reading apparatus A having the above-described structure, the backlight is arranged so that the photo sensor unit 10 arranged above the backlight is tilted in an oblique direction with respect to the vertical line in front of the backlight. Any configuration may be used as long as it is configured to emit light having an emission angle of maximum brightness. Hereinafter, modified examples of the configuration of the backlight included in the fingerprint reading device A will be described with reference to FIGS. In the description of the backlight as a modified example, when the same member as the above-mentioned member constituting the backlight 50 is used, the same reference numeral and the same name are given and the description thereof will be omitted.

<Modification 1> FIG. 15 shows a structure of a backlight as a modification of the backlight 50 included in the fingerprint reading device A having the above-described structure. In the backlight 50A shown in FIG. 15, in the configuration of the light source unit 52 and the light guide system unit 51, the diffusion plate 513 is the upper surface 51 of the diffusion light guide plate 511.
1B and the light guide system part 51A provided closely. The extending direction of the prism portion 515 of the diffusion plate 513 is arranged in the same direction as the prism portion 515 of the diffusion plate 513 in the light guide system unit 51 described above. That is, in the light guide system unit 51A, the diffusion plate 513 is arranged in close contact with the bottom diffusion light guide plate 511 without forming an air layer. The diffusion plate 513 and the bottom diffusion light guide plate 511 may be bonded to each other with an adhesive material or the like. At this time, the adhesive is the bottom diffusion light guide plate 51.
If one having a refractive index close to that of the base material of the diffusion plate 513 or the diffusion plate 513 is used, attenuation of light due to diffused reflection inside can be suppressed, and a more preferable effect can be obtained.

<Modification 2> FIG. 16 shows a structure of a backlight as a modification 2 of the backlight 50 included in the fingerprint reading device A having the above-described structure. A light guide system unit 51B shown in FIG. 16 is a diffusion light guide plate (light guide body) in which light from the light source unit 52 is incident from one end surface 511f adjacent to the light source unit (LED) 52 and diffuses inside to emit the light. ) 511B and a reflector 512 that covers the bottom surface 511c of the diffused light guide plate 511B,
And a diffusion sheet 514 arranged so as to cover the upper surface 511g of the diffusion light guide plate 511B. The diffused light guide plate 511B is not covered with the reflector 512 which covers the bottom surface 511c with the reflector 512, but is covered with the reflector except the side surface and the upper surface where the light source unit 52 is arranged. Has become.

The surface 511g of the diffusing light guide plate 511B is formed in a prism shape having a large number of fine uneven portions, and the convex portions extend from the end surface 511f on which light is incident from the light source unit 52 to the end surface 511h facing the end surface 511f. Is formed. That is, from the light source unit 52 to the diffusion light guide plate 51.
A convex portion forming a prism is arranged so as to extend in parallel to the propagation direction of light incident on 1B, and the light emitted from the upper surface 511g is displaced from the surface 511g in the direction perpendicular to the surface 511g. And the emission angle of the maximum brightness is the surface of the backlight 50B (here, the diffusion sheet 514
The surface of the) is to be displaced from the perpendicular. In this way, since the prism portion is directly formed on the surface of the diffusion light guide plate 511B, the light transmissivity is improved as compared with the configuration in which the both are separated.

<Modification 3> FIG. 17 shows a structure of a backlight as a modification 3 of the backlight 50 included in the fingerprint reading device A having the above-described structure. In the backlight 50C shown in FIG. 17, in the configuration of the backlight 50, the diffusion plate 5 having a large number of prism portions 515 having a triangular cross section on the surface thereof.
Instead of No. 13, the second diffusion plate 513C is provided with a large number of prism portions (Sumitomo Chemical Lumithrough) 516 having a substantially semicircular cross section on the surface. That is, in the light guide system unit 50C in which the second diffusion plate 513C is arranged on the upper surface of the diffusion light guide plate 511, a large number of prism portions 516 are arranged in parallel with the propagation direction of the light incident from the light source unit 52 to the bottom diffusion light guide plate 511. The backlight 5 is arranged so as to extend.
The light emitted from the 0D surface is collected in a direction deviated from the direction perpendicular to the surface to the backlight 50D.
The emission angle of the maximum brightness of the light distribution is shifted from the vertical line of the surface of the backlight 50D (here, the surface of the diffusion sheet 514). In addition, the light of the light source unit 52 is the second diffusion plate 5 including the prism portion 516 having a semicircular step surface.
By transmitting 13D, the light emitted from the front surface of the backlight 50D is made uniform in the plane. That is, the emission angle of the maximum brightness of the light distribution is inclined, and substantially uniform light can be emitted to the photo sensor unit 10.

In FIG. 17, a large number of stepped semicircular prism portions 516 are formed on the second diffusion light guide plate 511C, but the invention is not limited to this, and the surface shape of the bottom diffusion light guide plate 511 is You may form in a substantially semicircular shape with the same cross section. If the surface of the bottom surface diffusion light guide plate 511 is formed in the shape of a prism having a substantially semicircular cross section in this manner, the same effects as those described above can be obtained, and, of course, compared with the above,
The light transmittance can be improved and the thickness can be further reduced.

<Modification 4> Backlight 5 shown in FIG.
The configuration of 0D includes a light source unit 52 including an LED and a light source unit 5
And a light guide system unit 51D that irradiates the photosensor unit 10 side with two lights.

The light guide system portion 51D is formed in a substantially flat shape, and the bottom prism light guide plate 511D having a bottom surface portion on which a large number of prism portions 517 are formed while light from the light source portion 52 is incident from the one end surface 511j, Bottom prism light guide plate 5
A reflection plate 512 that covers the bottom surface 511k of 11D, a light diffusion plate 513 that is arranged so as to cover the surface 511b that is the light emission surface of the bottom prism light guide plate 511D, and a light diffusion plate 513.
And a diffusion sheet 514 that covers the above from above.

The bottom prism light guide plate 511D is molded from a transparent resin, and when the light of the light source section 52 that has entered from one end surface reaches the bottom section, it is scattered by the prism section 517 of the bottom section and is reflected on the surface 511b. It is configured to emit light from a certain light emitting surface. The large number of prism parts 517 are formed on the bottom surface of the substantially horizontal bottom prism light guide plate 511D, and the cutout parts 5 extend in a direction intersecting the direction of light incident from the light source part 52.
A large number of 17a are formed in parallel at a predetermined interval.

Backlight 50D formed in this way
As shown in FIG. 19, the maximum luminance emission angle of the light distribution is 0 ° to − when the direction of the normal of the emission surface of the backlight (the direction of the normal to the incident surface of the photosensor unit 10) is 0 °.
The direction of the angle range is 40 °. According to the backlight 50D configured as described above, the backlight 5 described above is used.
Compared with 0, since the bottom surface prism light guide plate 511D is used instead of the bottom surface diffusion type light guide plate 511, the bottom surface is not diffused, light loss inside the light guide plate is small, and light in a wide angle region is highly efficient. Can be emitted from the light emitting surface. Since the light efficiency is improved in this way, it is possible to realize a fingerprint reading device with further reduced power consumption. In addition, in the light guide system unit 51D of FIG.
Instead of the above, a second diffusion plate 513C including a large number of prism portions 516 having a substantially semicircular cross section shown in FIG. 17 may be applied.

<Modification 5> FIG. 20 shows the structure of a backlight as a modification 5 of the backlight 50 included in the fingerprint reading device A having the above-described structure. The configuration of the backlight 50E shown in FIG. 20 includes a light source section 52 formed of an LED and a light guide system section 51E for irradiating the photosensor section 10 side (not shown) with light from the light source section 52. The light guide system unit 51E has a configuration in which the diffusion plate 513 is omitted from the configuration of the light guide system unit 51D of the backlight 50D of Modification 4 described above (see FIG. 18).
The same reflector 512 and diffusion sheet 5 used in
The bottom prism light guide plate 511D is disposed between the bottom surface 14 and the base plate 14.

FIG. 21 shows the brightness distribution when the direction of the normal to the exit surface of the backlight 50E (the direction of the normal to the incident surface of the photosensor section 10) is 0 °. That is, according to the backlight 50E, the emission angle of the maximum brightness of the light distribution on the front surface of the backlight 50E is in a direction inclined with respect to the vertical direction of the front surface and is 45 ° (or −45 °) from the vertical direction. The tilted direction is −70 °, and is −70 °. In this way, the backlight 5 in which the direction of the emission angle of the maximum light distribution is −70 °
Even when the photosensor unit 10 arranged above the backlight 50E is illuminated by using 0E, the photosensor unit 10 can be kept in the same sensitivity as in the front light distribution.

<Modification 6> The bottom prism light guide plate 511D used in the backlight 50E as Modification 5 described above.
22 is made of transparent resin. However, as shown in FIG. 22, the light guide plate disposed between the reflection plate 512 and the diffusion sheet 514 is a substance having a refractive index different from that of the main material of the light guide plate. Bottom prism light guide plate 51 containing a diffusing material, which is made of a mixed material of the above and is configured to diffuse light by the difference in the refractive index.
It may be eight. The backlight 50F shown in FIG.
The light source unit 52 and the light from the light source unit 52 are connected to the photo sensor unit 1.
A bottom prism light guide plate 518 with a diffusing material, which is provided in the light guide system part 51F and is mixed with a main material of the light guide plate 518 and a filler material having a different refractive index. is doing.

Here, the main raw material 518a of the light guide plate 518 is used.
Is an acrylic resin having a refractive index n = 1.49, and a filler material (diffusing material) 518b is a resin bead 518b having a refractive index n = 1.42. A bottom prism light guide plate 518 containing a diffusing material is formed by mixing the resin beads 518b with acrylic 518a. This resin bead 51
By 8b, when the light propagates in the bottom prism light guide plate 518 containing the diffusing material, the light is diffused. Note that, as the resin beads 518b, silicon, epoxy resin, or the like can be given. In addition, the bottom prism light guide plate 518 containing the diffusing material is used.
The difference in the refractive index between the main raw material and the filler material (diffusing material) constituting the is preferably 0.03 to 0.4.

<Modification 7> Backlight 5 shown in FIG.
The 0G includes a light source unit 52 and a light guide system unit 51G. The light guide system unit 51G has a reflection plate 512 and one end face 519a facing the light source unit 52, and the one end face 519a.
The wedge-shaped light guide plate 519 on which the light from the light source unit 52 enters is provided, and the diffusion sheet 514 arranged so as to cover the upper surface of the wedge-shaped light guide plate 519. The wedge-shaped light guide plate 519 has a surface 519b serving as a light emitting surface that is substantially horizontal, a bottom surface 519c that is inclined with respect to the surface 519b, and is formed in a substantially triangular cross-section so that it gradually becomes thinner from the light source 52 side. There is.

Further, the bottom surface portion of the wedge-shaped light guide plate 519 is provided with a large number of prism portions 520 formed by forming notches 519d extending parallel to the bottom surface 519c and parallel to the one end surface 519a. , These prism parts 5
One surface (one side) of 20 functions as a reflector. The light propagated in the wedge-shaped light guide plate 519 is diffused by the prism portions 520. The reflector 512 is
It is arranged along the inclined bottom surface 519c and reflects the light emitted outward from the bottom surface 519c of the wedge-shaped light guide plate 519.

In the light guide system section 51G, the light source section 5
Since the light guide plate 519 having a function of causing the light incident from the light source 2 to be emitted from the surface 519b, which is a light emitting surface, has a wedge shape, the light from the light source unit 52 is concentrated and the light emitting surface 51 is concentrated.
It can be emitted from 9b. Therefore, the emission efficiency can be increased more than that of a flat light guide plate having the same shape in a plan view, and thus, the light guide plate having a flat shape is used to allow the photo sensor unit 10 above to emit light necessary for reading a fingerprint. It is possible to weaken the light of the light source section and obtain the same light output amount as that of the flat light guide plate as compared with the backlight configured to emit the above amount. Therefore, low power consumption of the light source unit can be realized. In addition, the light guide system unit 51G of FIG.
Then, resin beads 518b made of a filler material having a different refractive index from the main material of the light guide plate 519 of FIG. 22 may be mixed in the wedge-shaped light guide plate 519.

<Modification 8> FIG. 24 shows a backlight 50H as a modification 8. Backlight 5 shown in FIG.
The 0H includes a light source unit 52 and a light guide system unit 51H that emits light from the light source unit 52 to an upper photo sensor unit. In the light guide system unit 51H, the light guide plate disposed between the reflection plate 512H and the diffusion sheet 514 which are arranged opposite to each other has a substantially triangular cross section which gradually becomes narrower in the direction away from the one end face 521a on the light source unit side. And the bottom surface 521b
Is a curved bottom light guide plate 521. The surface of the bottom curved light guide plate 521, that is, the light emitting surface is a horizontal plane. The reflection plate 512H is curved in a shape along the bottom surface 521b of the curved bottom light guide plate 521 and has an arc-shaped cross section.

The degree of curvature of the bottom surface 521b of the bottom curved light guide plate 521 is such that the angle difference with respect to the top surface 521c, which is the light emitting surface, is large on the side closer to the light source. That is, as shown in FIG. 25, on the bottom surface 521b, the light L1 reflected by the light source side portion having a large angle with respect to the surface 521c is the surface 521 of the bottom curved light guide plate 521.
The light L2 emitted from the light source side of c and reflected by the bottom surface portion having a small angle with respect to the surface 521c is emitted from the portion of the surface 521 away from the light source unit 52. With this configuration, the front surface 521c which is the light emitting surface of the bottom curved light guide plate 521 is formed.
The light emitted from the surface has an emission angle of maximum brightness at the surface 52.
Although it is a direction inclined with respect to the perpendicular line of 1c, the uniformity within the image is improved. In the light guide system 51H of FIG. 24, resin beads 518b made of a filler material having a different refractive index from the main material of the light guide plate 519 of FIG. 22 may be mixed in the bottom curved light guide plate 521.

<Modification 9> Backlight 5 shown in FIG.
0I includes a light source unit 52 and a light guide system unit 51I,
In this light guide system unit 51I, a staircase-shaped light guide plate 522, through which light from the light source unit 52 enters from one side surface 522a, is arranged between the reflection plate 512 and the diffusion sheet 514. The step-shaped light guide plate 522 has a rectangular shape in a plan view,
The upper surface to be the light emitting surface 522b is formed in a step shape.

That is, the upper surface 522 of the stepwise light guide plate 522.
b has a plurality of step surfaces 523 having different heights, and a step surface 524 connecting the step surfaces 523, and the height of the cross section 523 becomes lower as the distance from the light source unit 52 side increases.
Further, each step surface 523 is formed parallel to the bottom surface 522c,
The step surface 524 is formed so as to be orthogonal to the bottom surface 522c, and all the corners of the joint between the step surface 523 and the step surface 524 are arranged in the same plane.

The staircase-shaped light guide plate 522 is installed so that its corners are located on a horizontal plane, and thus the bottom surface 522c is arranged so as to be inclined so as to rise in the direction away from the light source 52 side. The reflector 512 is arranged along the inclined bottom surface 522c so as to cover the bottom surface 522c. In this backlight 50I, as shown in FIG. 27, the light of the light source unit 52 that is incident from the one end surface 522a side of the staircase light guide plate 522 has upper and lower interfaces (bottom surface, step surface, etc.) inside the staircase light guide plate 522. ), High-efficiency total reflection is repeated (see arrow L3 in the figure), and the light emitting surface, especially the step surface 52
From the light source 4, the light is emitted to the photo sensor unit 10 side above the backlight. On such a light emitting surface, the number of highly efficient vertical emission increases. As a result, the emission efficiency in the staircase light guide plate 522 is increased, and even if the light output from the light source unit 52 is reduced, the photosensor unit can emit the necessary light to the photosensor unit. That is, the power consumption of the light source unit 52 can be reduced.

In the fingerprint reader A having the backlight of each of the above-described modifications 1 to 9, the same operation as that of the fingerprint reader A having the backlights 50 and 500 described above can be obtained. Photo sensor unit 10
The light efficiency can be improved and the power consumption can be reduced while concentrating the light and maintaining the sensor sensitivity.

The above-mentioned reading device is attached to an information terminal such as a mobile phone or a personal computer in order to restrict access to unregistered persons, and is also placed at a door or entrance to prevent intrusion of persons who are not registered in advance. It can be applied to personal authentication devices for.

[0127]

According to the present invention, the luminance of the backlight is changed according to the emission angle, and the emission angle that maximizes the luminance is set within the allowable incident angle range of the sensitivity of the sensor unit. Sensing can be performed efficiently with power consumption.

Further, the sensor section is a double gate type TFT.
If an image sensor is provided, the subject can be read with maximum sensitivity for oblique light, and the angle of the emitted light of the backlight light source can be easily set, so that it is not necessary to make the entire surface emit brighter light. Low power consumption can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a photo sensor device of a fingerprint reading device according to the present embodiment.

FIG. 2 is a sectional view showing an XX section in FIG.

FIG. 3 is a plan view showing a specific mode of a double gate transistor of a photo sensor unit provided in the fingerprint reading device.

FIG. 4 is a diagram showing a specific mode of the double gate transistor and is a cross-sectional view showing a ZZ cross section in FIG. 3;

FIG. 5 is a schematic diagram for explaining a driving principle of a double gate transistor which constitutes the photo sensor unit.

FIG. 6 is a diagram showing an overall configuration of a top gate driver or a bottom gate driver which constitutes the driver circuit unit.

FIG. 7 is a diagram showing a circuit configuration of each stage of the top gate driver or the bottom gate driver.

FIG. 8 is a timing chart showing an operation of the top gate driver or the bottom gate driver.

FIG. 9 is a diagram illustrating data of light sensitivity of the photo sensor unit 10.

FIG. 10 is a perspective view showing a configuration of a backlight of the fingerprint reading device according to the present embodiment.

11 is a diagram showing a distribution of brightness of light emitted by the backlight shown in FIG.

FIG. 12 is a schematic diagram for explaining a fingerprint reading operation of a subject in the fingerprint reading device.

FIG. 13 is a perspective view showing a configuration of a backlight configured by using two diffusion plates each having a large number of prisms on the surface.

14 is a diagram showing a light distribution curve of light emitted by the backlight of FIG.

FIG. 15 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

FIG. 16 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

FIG. 17 is a diagram showing a modified example of the configuration of the backlight included in the fingerprint reading device.

FIG. 18 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

19 is a diagram showing a light distribution curve of light emitted from the backlight shown in FIG.

FIG. 20 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

FIG. 21 is a diagram showing a light distribution curve of light emitted by the backlight shown in FIG. 20.

FIG. 22 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

FIG. 23 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

FIG. 24 is a diagram showing a modification of the configuration of the backlight included in the fingerprint reading device.

25 is a diagram showing a light reflection state in the curved bottom light guide plate included in the backlight of FIG. 24.

FIG. 26 is a diagram showing a modified example of the configuration of the backlight included in the fingerprint reading device.

FIG. 27 is a cross-sectional view of a stepwise light guide plate included in the backlight shown in FIG.

[Explanation of symbols]

A Fingerprint reader (reader) B Fingertip holder C Photo sensor device 10 Photo sensor part (sensor part) 10a Double gate transistor 50, 50A, 50B, 50C, 50D, 50E, 50
F, 50G, 50H, 50I Backlight (backlight part) 51, 51A, 51B, 51C, 51D, 51E, 51
F, 51G, 51H, 51I Light guide system part 52 Light source part 511 Bottom diffusion light guide plate (light guide) 511a One side surface 511b Light emission surface 511B Diffuse light guide plate (light guide) 511C Diffuse light guide plate (light guide) 511D Bottom prism light guide plate (light guide) 512H Reflecting plates 513, 513C, 513D Diffusing plates 515, 516, 517 Prism section 518 Bottom prism light guide plate (light guide) 518a Main raw material 518b Resin beads (mixed material) 519 Wedge-shaped light guide plate (Light guide) 520 Prism 521 Bottom curved light guide plate (light guide) 522 Stepwise light guide plate (light guide) 522b Top surface

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F065 AA02 AA49 AA56 BB05 CC16                       DD01 DD05 FF42 FF63 GG03                       GG07 HH02 HH12 HH15 JJ03                       JJ18 JJ26 LL01 LL12 QQ03                       QQ12 QQ31 QQ47 UU07                 5B047 AA01 AA25 BB02 BC12 BC14                       CA19 CB04 CB05                 5C024 AX03 DX04 EX47 GX04                 5C051 AA01 DB28 DC07

Claims (14)

[Claims] 1. A sensor unit that reflects incident light on a subject in contact with a surface thereof, causes the light receiving element to receive the reflected light, and optically reads the subject based on the amount of light received by the light receiving element, A reading device, comprising: a backlight that emits light having an emission angle at maximum luminance that varies depending on the emission angle within the allowable incident angle range of the sensitivity of the sensor unit. 2. The reading device according to claim 1, wherein the maximum brightness of the backlight is at least twice the minimum brightness of the backlight at a predetermined emission angle. 3. The allowable incident angle range of the sensitivity of the sensor unit is about −75 ° to about 75 °.
Or the reading device described in 2. 4. The maximum range of the sensor sensitivity of the sensor unit is a light incident angle of 30 ° to 55 ° and a light incident angle of −30 ° to.
The reading device according to claim 1, wherein the reading device has an angle of −55 °. 5. The backlight is a light source, a bottom light guide plate,
The reading according to any one of claims 1 to 4, further comprising: a light diffusion plate provided above the bottom light guide plate and having a large number of prism portions on a light emission side, and a diffusion sheet. apparatus. 6. The reading device according to claim 5, wherein each of the plurality of prism portions included in the light diffusion plate has a substantially semicircular cross section. 7. The bottom prism light guide plate is a bottom prism light guide plate having a notch on the bottom surface.
Or the reading device according to item 6. 8. The backlight according to claim 1, further comprising a light source, a light guide plate having a plurality of prisms on a light emitting side, and a diffusion sheet. Reader. 9. The reading device according to claim 1, wherein the backlight includes a light source, a bottom prism light guide plate having a cutout portion on a bottom surface, and a diffusion sheet. 10. The reader according to claim 9, wherein the bottom prism light guide plate is formed by mixing a main material of the bottom prism light guide plate and a filler material having a different refractive index. 11. The reading device according to claim 9, wherein the bottom prism light guide plate is a wedge-shaped light guide plate. 12. The reading device according to claim 9, wherein the bottom surface of the light guide is a curved surface. 13. The backlight according to claim 1, further comprising a light source, a light guide plate having a light emitting surface formed in a stepped shape, and a diffusion sheet. Reader. 14. The reading device according to claim 1, wherein the sensor unit has a double gate type transistor.