Image analysis – Applications – Personnel identification
Reexamination Certificate
2000-01-20
2003-04-22
Ahmed, Samir (Department: 2623)
Image analysis
Applications
Personnel identification
C250S556000
Reexamination Certificate
active
06553134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading apparatus which is capable of reading a fingerprint and the like.
2. Description of the Related Art
As the development of a networked society, the integration of portable equipments and a radio network has been progressed, and the necessity of a security function such as personal identification has also been increased in portable equipments, which need to be downsized. As personal identification, identification by living body information such as a fingerprint has received attention, because a portable equipment which adopts this identification cannot be easily abused by another person, and living body information can never be lost unlike a key and an IC card. As a method of reading a fingerprint, a method using an optical system such as a prism is dominating.
FIGS. 9A
,
9
B are views showing a fingerprint reading apparatus which uses a prism. In
FIG. 9A
, among a top face
1
a
and side faces
1
b
,
1
c
of a prism
1
, a finger is rested on the top face
1
a
and irradiated with light via the side face
1
b
, and light reflected on the top face
1
a
and coming out through the side face
1
c
is picked up by a CCD (charge-coupled device) camera
2
. In
FIG. 9B
, the CCD camera
2
, which is positioned on the side of a light source, picks up light scattered on the top face
1
a
and coming out through the side face
1
b.
Further, Japanese Unexamined Patent Publication JP-A 9-186312 (1997) discloses a liquid crystal display device in which a photoreceptor device is imbedded. This device has a condenser lens for condensing light onto the photoreceptor device, thereby imaging a face of a person who is away from a display screen.
Since the fingerprint reading apparatus shown by
FIGS. 9A
,
9
B uses a prism, it is impossible to decrease the thickness of the apparatus and difficult to downsize the apparatus, and since the liquid crystal display device disclosed in JP-A 9-186312 has a condenser lens, it is also difficult to downsize the device.
SUMMARY OF THE INVENTION
An object of the invention is to provide a small-size image reading apparatus which shows an excellent accuracy in image reading, by a different means from the prior arts.
The invention provides an image reading apparatus comprising:
a panel including a pair of light-transmitting substrates and a plurality of photoreceptor devices which are two-dimensionally arranged and interposed between the pair of substrates, an edge of one of the pair of light-transmitting substrates being provided with a slope; and
a light source opposed to the slope of the light-transmitting substrate,
wherein an object in contact with a surface of the panel is irradiated with light transmitted within the panel, and the light returned from the object is received by the photoreceptor devices, whereby an image of the object is read.
According to the invention, light from the light source is let in through the slope of the light-transmitting substrate, and the light is transmitted by reflection on the surface of the panel, whereby a direction in which the light is transmitted within the panel can be restricted.
In other words, light from the light source enters through the slope opposed to the light source, so that light from a direction of reaching the slope at a relatively small incident angle enters in the light-transmitting substrate, whereas light from a direction of reaching the slope at a relatively large incident angle is reflected by the slope and does not enter in the light-transmitting substrate. As a result, a direction in which light travels in the panel can be restricted. Moreover, among light beams reaching the surface of the panel, a light beam reaching at an angle equal to or more than a critical angle is totally reflected. On the other hand, as for light beams reaching at an angle less than the critical angle, some of the light beams are reflected and travel in the panel again, whereas the rest go out of the panel. By reflected on the surface of the panel again and again, the light beams travelling in a direction of reaching at an incident angle less than the critical angle are screened out. As a result, a direction in which light travels in the panel can be restricted still more.
Thus, an image of an object in contact with the surface of the panel is read by using light travelling in a restricted specific direction, so that the accuracy in image reading can be increased. Moreover, since a direction in which light travels can be restricted only by forming a slope at an edge of the light-transmitting substrate and opposing a light source to the slope, another optical system such as a condenser or a spectroscope is not needed, and a downsized apparatus can be produced.
Further, the invention provides an image reading apparatus comprising:
a panel including a pair of light transmitting substrates, a plurality of photoreceptor devices which are two-dimensionally arranged and a liquid crystal layer having a variable transmittance, the plurality of photoreceptor devices and the liquid crystal layer constituting photoreceptive pixels and being interposed between the pair of substrates, an edge of one of the pair of light-transmitting substrates being provided with a slope; and
a light source for launching light into the panel,
wherein an object in contact with a surface of the panel is irradiated with light transmitted within the panel, and the light returned from the object is received by the photoreceptor devices, whereby an image of the object is read.
According to the invention, a direction in which light travels within the panel can be restricted in the same manner as mentioned before, so that the accuracy in image reading can be increased. Moreover, the panel is provided with a liquid crystal layer, and thereby a transmittance can be changed for each photoreceptive, so that a direction in which light travels within the panel can be restricted still more, and the accuracy in image reading can be increased. In addition, by controlling a transmittance of the liquid crystal layer for each photoreceptive pixel, it is also possible to use the panel for display.
Still further, the image reading apparatus of the invention further comprises liquid crystal controlling means for carrying out control of allowing light to pass through a portion of the liquid crystal layer, the portion of the liquid crystal layer being located on an optical path extending from the slope of the light-transmitting substrate to a photoreceptor device.
According to the invention, light travelling in a direction restricted in a manner as described before passes through a restricted optical path and reaches a photoreceptor device. Since a portion of the liquid crystal layer which is located on the optical path leading to the photoreceptor device is controlled so that light passes therethrough, light which passes through another path would not be received, the occurrence of noise can be prevented, and the accuracy in image reading can be increased still more.
Still further, the image reading apparatus of the invention further comprises data extracting means for extracting photoreceptive data of a photoreceptor device located on an optical path which extends from the slope of the light-transmitting substrate and passes through a portion of the liquid crystal layer through which light has passed, from among photoreceptive data of all the photoreceptor devices.
According to the invention, light which has passed through a portion of the liquid crystal layer travels through a restricted optical path and reaches a photoreceptor device. In the invention, firstly, photoreceptive data are derived from all the photoreceptor devices including a specific photoreceptor device located on the restricted optical path. Since photoreceptive data of the specific photoreceptor device associated with the portion of the liquid crystal layer through which light has passed is extracted from among all the photoreceptive data, photoreceptive data on light which has passed in another pa
Amano Masashi
Harada Kouichi
Hinoue Sadahiko
Satoh Masaharu
Ahmed Samir
Bali Vikkram
Birch & Stewart Kolasch & Birch, LLP
Sharp Kabushiki Kaisha
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