JPH11149552A - Reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a whole device at the time of reading fingerprint or the like. SOLUTION: A second-dimensional photo-sensor 12 is provided with a transmissive part, and even when a facial light source 11, second-dimensional photo- sensor 12, and projection and recession detecting optical element 13 are horizontally arranged in a row in this order, fingerprint or the like can be read. Also, the projection and recession detecting optical element 13 is constituted by thickening plural optical fibers and attaching a light absorbing sheet 17 on a prescribed outer peripheral face so that this device itself can be provided with a function for turning lights outgoing from the facial light source 11 at random into almost parallel lights. Then, almost parallel lights are fully reflected on the parts corresponding to the recessed parts of the fingerprint of a finger 31 brought into contact with an inclined face 13a of the projection and recession detecting optical element 13, and those reflected light are absorbed by the light absorbing sheet 17. On the other hand, almost parallel lights are scattered on the parts corresponding to the projecting parts of the fingerprint of the finger 31, and one part of the scattered lights are returned to the second-dimensional photo-sensor 12 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading device for reading an object to be read having minute concave and convex portions such as a fingerprint.

[0002]

2. Description of the Related Art Conventionally, as a reading apparatus for reading an object to be read having minute concave and convex portions such as a fingerprint, as shown in FIG. Is provided on the rear side of the right-angle prism 2, that is, on the right side in FIG. 6, the image forming optical system 3 and the CCD sensor 4 are provided. In this case, the right angle prism 2
Are arranged such that the lower surface 2a is a horizontal surface, the right side surface 2b is a vertical surface, and the inclined surface 2c is an inclined surface inclined at 45 ° with respect to the horizontal surface.

In this reading apparatus, when the finger 5 is not in contact with the inclined surface 2c of the right-angle prism 2, the light emitted from the upper surface of the surface light source 1 is reflected by the right-angle prism 2 as shown by an arrow in FIG. The incident light is totally reflected by the inclined surface 2c, and the reflected light is
Is emitted from the right side surface 2b of the imaging optical system 3
And is incident on the CCD sensor 4.
Therefore, in this case, all of the light totally reflected by the inclined surface 2c is incident on the CCD sensor 4, and white display is performed. On the other hand, when the finger 5 is in contact with the inclined surface 2c of the right-angle prism 2, total reflection occurs at a portion corresponding to the concave portion (downline) of the fingerprint of the finger 5 contacted with the inclined surface 2c. The light is absorbed by the portions corresponding to the convex portions (ridges) of the fingerprint of the finger 5, thereby obtaining an image in which the brightness of the finger 5 is optically enhanced in accordance with the unevenness of the fingerprint of the finger 5, and the fingerprint of the finger 5 is read. Will be.

[0004]

However, in such a conventional reading apparatus, since the CCD sensor 4 has a light shielding structure, the surface light source 1 is provided below the right-angle prism 2 and is provided on the right side of the right-angle prism 2. Since the CCD sensor 4 is provided, the size of the entire apparatus in the vertical direction becomes large, and an image forming optical system is provided between the right-angle prism 2 and the CCD sensor 4 because light is emitted from the surface light source 1 at random. 3, the size of the entire apparatus in the left-right direction is also increased, and therefore, there is a problem that the entire apparatus is increased in size. An object of the present invention is to reduce the size of the entire device.

[0005]

According to the first aspect of the present invention,
A reading device that reads an object to be read having a concave portion and a convex portion, a light source, a photosensor in which a plurality of sensor units are formed on a light-transmitting base layer that transmits light from the light source, an input / output surface, and An unevenness detecting optical element having an inclined surface inclined with respect to the incident / exit surface, wherein light is scattered corresponding to the convex portion of the object to be read in contact with the inclined surface, and the light is scattered from the incident / exit surface side. The light is incident on the sensor section of the photo sensor. According to the first aspect of the present invention, since a photosensor having a light-transmitting base layer is used,
Even if the light source, the photo sensor, and the unevenness detecting optical element are arranged in a line in this order, the object to be read that contacts the inclined surface of the unevenness detecting optical element can be read, and therefore, is orthogonal to the arrangement direction of each component. The size in the direction can be reduced, and thus the entire device can be reduced in size.
According to a fourth aspect of the present invention, the unevenness detecting optical element has a function of converting incident light into substantially parallel light. According to the fourth aspect of the present invention, since an unevenness detecting optical element having a function of converting incident light into substantially parallel light is used, even if light is randomly emitted from the light source, this light is substantially emitted. The light can be collimated, so that the conventional imaging optical system is not required, and thus the entire apparatus can be further miniaturized.

[0006]

FIG. 1 is a schematic sectional view of a main part of a reading apparatus according to an embodiment of the present invention.
Although this reading device can read an object to be read having minute concave and convex portions, the following embodiment will be described as a fingerprint reading device for reading a fingerprint. This fingerprint reader has a structure in which a two-dimensional photosensor 12 is provided on the left side of a vertically arranged surface light source 11, and an unevenness detecting optical element 13 is provided on the left side of the two-dimensional photosensor 12. The surface light source 11 includes an edge light type backlight used in an electroluminescence panel or a liquid crystal display device. In the case of an edge light type backlight, not shown, typically, a reflecting plate is provided on the right side of a vertically arranged light guide plate, and a light emitting diode or the like is provided near a predetermined end surface of the light guide plate. One point light source is provided, and this point light source is covered with a reflection sheet.

Next, the structure of the unevenness detecting optical element 13 will be described together with its manufacturing method. First, as shown in FIG. 2A, a rectangular parallelepiped optical fiber block 14 is prepared. The optical fiber block 14 is formed by densely joining a plurality of optical fibers (linear light guide members) 15 each having a core covered with a clad. As an example of the method of forming the optical fiber block 14, as an example, a plurality of optical fibers 15 are bundled into a rod shape, and a plurality of the optical fiber rods are densely housed in a mold.
There is a method of forming a rectangular parallelepiped optical fiber block 14 by heating under pressure. Then, when the optical fiber block 14 thus formed is cut into a trapezoidal side surface as shown by a dashed line in FIG. 2A, the cut surface of the optical fiber 15 has an inclination angle of 45 °. By cutting as described above, two side-trapezoidal unevenness detecting optical element forming bodies 16 shown in FIG. 2B are obtained. Next, the cut surface of the unevenness detecting optical element forming body 16 is polished.
Next, as shown in FIG.
A black light absorbing sheet (light absorbing layer) 17 is attached to the outer peripheral surface of the optical fiber 15 except for both end surfaces. Thereby, the unevenness detecting optical element 13 is obtained. In the unevenness detecting optical element 13 thus obtained, the cut and polished surface has an inclined surface 13a.
And the opposite surface is the incident / exit surface 13b. In this case, the inclination angle θ of the inclined surface 13a with respect to the horizontal plane (see FIG. 2B) is 45 °, but is 45 °.
The following may be sufficient. However, if the inclination angle θ is too small, the size of the unevenness detecting optical element 13 in the left-right direction increases, so it is not preferable to make the inclination angle too small.

Next, regarding the two-dimensional photo sensor 12,
This will be described with reference to FIG. The two-dimensional photo sensor 12
A plurality of sensor units 20 are arranged in a matrix, and include a transparent substrate (light-transmitting base layer) 21 made of acrylic resin, glass, or the like. On the left surface of the transparent substrate 21, a bottom gate electrode 22 made of a light-shielding electrode such as chromium or aluminum is provided for each sensor unit 20, and a bottom gate insulating film made of silicon nitride is formed on the entire left surface. Film 23 is provided. On the left surface of the bottom gate insulating film 23, the bottom gate electrode 22
Is provided with a semiconductor layer 24 made of amorphous silicon. On both left sides of the semiconductor layer 24, n ⁺ silicon layers 25 are provided. A source electrode 26 and a drain electrode 27 made of a light-shielding electrode such as chromium or aluminum are provided on the left surface of the n ⁺ silicon layers 25 and the left surface of the bottom gate insulating film 23 in the vicinity thereof, and silicon nitride is formed on the entire left surface. A top gate insulating film (light-transmitting insulating film) 28 made of is provided. On the left surface of the top gate insulating film 28, a portion corresponding to the semiconductor layer 24 is provided with a top gate electrode 29 made of a transparent electrode (transparent electrode) such as ITO, and the entire left surface is an overcoat film made of silicon nitride. (Transparent insulating film)
30 are provided. In the two-dimensional photosensor 12, when light is randomly incident from the right side, the light is transmitted to the bottom gate electrode 2 made of a light-shielding electrode.
2. While transmitting through a transmission portion other than the source electrode 26 and the drain electrode 27, the bottom gate electrode 2
2 prevents light from being directly incident on the semiconductor layer 24.

[0009] In this fingerprint reading apparatus, when the finger 31 is not contacted to the inclined surface 13a of the concave-convex detecting optical element 13, as indicated by an arrow, for example sign A _1, A _2, A ₃ in FIG. 1, Light randomly emitted from the left surface of the surface light source 11 passes through the transmitting portion of the two-dimensional photosensor 12, and the transmitted light is incident on the input / output surface 13 b of the unevenness detecting optical element 13. This incident light travels in the core of the optical fiber 15 of the unevenness detecting optical element 13 while repeating total reflection. That is, the light randomly emitted from the left surface of the surface light source 11 travels in the core of the optical fiber 15 of the unevenness detecting optical element 13 while repeating the total reflection, and becomes substantially parallel light. The substantially parallel light is totally reflected by the inclined surface 13 a of the unevenness detecting optical element 13, and the reflected light passes through the optical fiber 15 in the radial direction and is absorbed by the light absorbing sheet 17. Therefore, in this case, there is no light returning to the two-dimensional photosensor 12 side, and black display is performed.

On the other hand, the inclined surface 13 of the unevenness detecting optical element 13
When the finger 31 is in contact with the finger 31a, total reflection occurs at a portion corresponding to the concave portion of the fingerprint of the finger 31 contacted with the inclined surface 13a, and light is emitted at a portion corresponding to the convex portion of the fingerprint of the finger 31. Scattered. That is, in the portion corresponding to the concave portion of the fingerprint of the finger 31 in contact with the inclined surface 13a, as indicated by the arrows in example sign A ₂ in FIG. 1, it is totally reflected by the inclined surface 13a on the light-absorbing sheet 17 absorbent Is done. On the other hand, in the portion corresponding to the convex portion of the fingerprint of the finger 31 in contact with the inclined surface 13a, as shown by the example of sign B _1, B ₂ arrows in FIG. 1, it is scattered by the inclined surface 13a. A part of the scattered light is, for example, as shown by arrows C ₁ and C ₂ in FIG.
5 repeats in the core in the opposite direction while repeating total reflection, and exits from the entrance / exit surface 13b. Referring to FIG. 3, the outgoing light passes through the top gate electrode 29 made of a transparent electrode of the two-dimensional photosensor 12 and enters the incident surface between the source electrode 26 and the drain electrode 27 of the semiconductor layer 24 on the right side thereof. More incident. And as I will explain later,
When the amount of light incident on the semiconductor layer 24 is equal to or greater than a preset amount of light (threshold), the light detection state of the sensor unit 20 is set to the bright state. The light detection state by 20 is a dark state. As a result, an image in which light and dark are emphasized optically according to the unevenness of the fingerprint of the finger 31 is obtained, and the fingerprint of the finger 31 is read.

As described above, in this fingerprint reader, since the two-dimensional photosensor 12 having a light transmitting portion is used, the surface light source 11, the two-dimensional photosensor 12, and the unevenness detecting optical element 13 are arranged in this order. It can be provided in a line in the left-right direction, and therefore, the size of the entire device in the vertical direction can be reduced. The unevenness detecting optical element 13
Since a plurality of optical fibers 15 are densely packed, that is, an optical fiber having a function of converting incident light into substantially parallel light, even if light is randomly emitted from the surface light source 11, this light is substantially parallel. Light, and thus an imaging optical system as in the related art becomes unnecessary. As a result, the entire device can be reduced in size.

Here, the operation of the two-dimensional photosensor 12 will be described. In one sensor section 20 of the two-dimensional photosensor 12, a bottom gate electrode (BG) 22, a semiconductor layer 24, a source electrode (S) 26, and a drain electrode (D)
27 and the like constitute a bottom gate transistor, and the top gate electrode (TG) 29, the semiconductor layer 24, the source electrode (S) 26, the drain electrode (D) 27 and the like constitute a top gate transistor. That is, the sensor unit 20 is configured by a photoelectric conversion transistor in which a bottom gate electrode (BG) 22 and a top gate electrode (TG) 29 are arranged below and above the semiconductor layer 24, respectively. The equivalent circuit of FIG. Can be shown as follows.

First, in a state where a positive voltage (for example, +5 V) is applied between the source electrode (S) and the drain electrode (D), a positive voltage (for example, +10 V) is applied to the bottom gate electrode (BG). Then, a channel is formed in the semiconductor layer 24, and the drain current _IDS flows. In this state,
Bottom gate electrode (BG) on top gate electrode (TG)
When a negative voltage (for example, −20 V) at a level that extinguishes the channel due to the electric field is applied, the top gate electrode (T
The electric field from G) acts in a direction that hinders channel formation due to the electric field of the bottom gate electrode (BG), and the channel is pinched off. At this time, when the semiconductor layer 24 is irradiated with light from the top gate electrode (TG) side, an electron-hole pair is induced on the top gate electrode (TG) side of the semiconductor layer 24. The electron-hole pairs are accumulated in the channel region of the semiconductor layer 24 and cancel the electric field of the top gate electrode (TG). Therefore, a channel is formed in the semiconductor layer 24, and the drain current _IDS flows. This drain current I
_DS changes according to the amount of light incident on the semiconductor layer 24.

As described above, the two-dimensional photo sensor 12
In this case, the electric field from the top gate electrode (TG) acts in a direction to hinder the channel formation due to the electric field of the bottom gate electrode (BG) and pinches off the channel. _DS can be made extremely small, for example, about 10 ^-14 A. For this reason, the difference between the drain currents I _DS flowing when light is incident and when light is not incident can be made sufficiently large. As a result, as described above, when the amount of light incident on the semiconductor layer 24 is equal to or more than a predetermined amount of light (threshold), a large drain current _IDS flows, and the light detection state by the sensor unit 20 is changed. Is set to a bright state, and when it is less than that, a small drain current _IDS flows, and the light detection state by the sensor unit 20 can be set to a dark state. As a result, an image in which light and dark are emphasized optically according to the unevenness of the fingerprint of the finger 31 is obtained, and the fingerprint of the finger 31 is read.

By the way, in the two-dimensional photosensor 12, one sensor unit 20 can have both a sensor function and a selection transistor function. Next, these functions will be briefly described (for details, see JP-A-6-1325).
No. 60). When a positive voltage (+10 V) is applied to the bottom gate electrode (BG) and the top gate electrode (TG) is set to, for example, 0 V, holes are generated from trap levels between the semiconductor layer 24 and the top gate insulating film 19. To be refreshed, that is, reset. That is, when used continuously, the semiconductor layer 2
The trap level between the gate insulating film 4 and the top gate insulating film 19 is filled with holes generated by light irradiation and holes injected from the drain electrode (D). And the drain current I _DS increases when no light is incident. Therefore, the top gate electrode (TG)
Is set to 0 V, and the holes are discharged to reset.

When a positive voltage is not applied to the bottom gate electrode (BG), no channel is formed in the bottom transistor, and even if light is incident, the drain current I _DS does not flow and the non-selection is not performed. State. That is, by controlling the voltage applied to the bottom gate electrode (BG), the selected state and the non-selected state can be controlled. In addition, when 0 V is applied to the top gate electrode (TG) in the non-selected state, similarly to the above, reset is performed by discharging holes from the trap level between the semiconductor layer 24 and the top gate insulating film 19. it can.

As a result, as shown in FIG. 5, for example, the sense state and the reset state can be controlled by controlling the top gate voltage _VTG to 0V and -20V. Further, the bottom gate voltage V _{BG is set} to 0V and + 10V.
Thus, the selected state and the non-selected state can be controlled. That is, the top gate voltage V _TG
In addition, by controlling the bottom gate voltage V _BG , one sensor unit 20 of the two-dimensional photo sensor 12 can have both a function as a photo sensor and a function as a selection transistor.

In FIG. 1, the surface light source 11, the two-dimensional photo sensor 12, and the unevenness detecting optical element 13 are arranged at predetermined intervals, but they may be arranged closely. Also, in FIG.
1. The two-dimensional photosensor 12 and the surface light source 11 are arranged on the right side of FIG. 3. The unevenness detecting optical element 13 shown in FIG. Alternatively, the surface light source 11 may be provided. In the above embodiment, the unevenness detecting optical element 1
Although the description has been given of the case where the main part 3 is constituted by a plurality of optical fibers 15 closely contacted with each other, the present invention is not limited to this. It is also possible to employ a structure obtained by alternately laminating layer materials having different ratios, that is, a structure obtained by laminating (closely contacting) a plurality of plate-shaped light guide members. further,
In the above embodiment, the present invention is applied to the two-dimensional photo sensor 12
The case where the present invention is applied to a reading device having
The present invention is not limited to this, and can be applied to a reading device including a one-dimensional photosensor.

[0019]

As described above, according to the first aspect of the present invention, since the photosensor having the translucent base layer is used, the light source, the photosensor and the unevenness detecting optical element are arranged in this order. The components can be arranged in a line, so that the size of each component in the direction orthogonal to the arrangement direction can be reduced, and thus the entire device can be reduced in size. According to the fourth aspect of the present invention,
Since an unevenness detecting optical element having a function of converting incident light into substantially parallel light is used, even when light is randomly emitted from a light source, this light can be converted into substantially parallel light. Eliminates the need for conventional imaging optics,
Therefore, the whole apparatus can be further miniaturized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of a reading apparatus according to an embodiment of the present invention.

FIGS. 2A and 2B are perspective views showing an example of a method for manufacturing the unevenness detecting optical element shown in FIG.

FIG. 3 is a sectional view of a part of the two-dimensional photosensor shown in FIG. 1;

FIG. 4 is an equivalent circuit diagram of the sensor unit shown in FIG.

5A to 5D are diagrams illustrating voltages applied to the respective electrodes of the sensor unit illustrated in FIG. 4 and changes in the states thereof.

FIG. 6 is a schematic cross-sectional view of an example of a conventional reading device.

[Explanation of symbols]

 11 surface light source 12 two-dimensional photo sensor 13 unevenness detecting optical element

Claims (6)

[Claims] 1. A reading device for reading an object to be read having a concave portion and a convex portion, comprising: a light source; and a photosensor having a plurality of sensor portions formed on a light-transmitting base layer that transmits light from the light source. And an irregularity detecting optical element having an incident / exit surface and an inclined surface inclined with respect to the incident / exit surface, wherein light is scattered corresponding to the convex portion of the object to be read contacting the inclined surface. A reading device, wherein the light enters a sensor unit of the photosensor from an emission surface side. 2. The reading device according to claim 1, wherein the photosensor comprises a two-dimensional photosensor in which a sensor unit is two-dimensionally arranged. 3. The method according to claim 1, wherein
In each of the sensor units of the photosensor, a first gate electrode made of a material having a light-shielding property is arranged on the light source side, and a second gate electrode made of a material having a light-transmitting property is provided on the unevenness detecting optical element side.
A reading device comprising a photoelectric conversion transistor in which a gate electrode is arranged. 4. The reading device according to claim 1, wherein the unevenness detecting optical element has a function of converting incident light into substantially parallel light. 5. The reading apparatus according to claim 4, wherein the unevenness detecting optical element comprises a plurality of linear or plate-shaped light guide members which are closely attached. 6. The reading device according to claim 5, wherein a light absorbing layer is provided on an outer peripheral surface of the unevenness detecting optical element except for both end surfaces of the light guide member.