Biological object detection apparatus

An apparatus for detecting and identifying a biological object. A transparent plate has a first surface onto which a light beam is projected and a second surface onto which a biological object to be detected and identified is placed. The light beam projected toward the first plate surface is transmitted through the plate and toward the object on the second surface, from which the light beam is reflected and retransmitted through the plate toward and through the first surface thereof and received and detected by an optical detector. The detection of a biological object is confirmed by comparing the change of the wavelength characteristics of the reflected and detected light beam in a predetermined time sequence according to the object being first placed upon and then pressed upon the second surface of the transparent plate with respective, known such characteristics thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS 
U.S. Patent application Ser. No. 07/370,768 of Masayuki KATO et al. 
entitled "UNEVEN-SURFACE DATA DETECTION APATUS" filed June 23, 1989 and 
U.S. Patent application Ser. No. 07/408,090 of Masayuki KATO et al. 
entitled "BIOLOGICAL DETECTING SYSTEM AND FINGERPRINT COLLATING SYSTEM 
EMPLOYING SAME" filed Sept. 14, 1989, each thereof assigned to the common 
assignee of the present application, Fujitsu Limited, as shown by the 
assignment records of the United States Patent and Trademark Office, are 
related to the invention of the present, new U.S. patent application. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an apparatus for detecting a biological 
object. The apparatus according to the invention is used for a personal 
identification system in which a person is identified by identifying a 
fingerprint of the person. 
In a personal identification system using fingerprint identification, a 
fingerprint sensor is provided for reading a fingerprint, as a picture 
image, of a person, and a processing device for generating reference data 
from the picture signal read by the fingerprint sensor, registering the 
generated reference data, and comparing the picture signal read by the 
fingerprint with the reference data to identify whether or not the 
fingerprint belongs to an authorized person. In such a personal 
identification system, the fingerprint sensor must read the fingerprint 
picture image clearly and correctly without distortion. 
In general, in a fingerprint sensor, a detection light is irradiated at a 
preselected angle onto the ridge line portions and the groove line 
portions of the fingerprint pressed against a light conducting plate (a 
transparent plate), through this transparent plate. According to Snell's 
law, only light reflected from the ridge line portions of fingerprint is 
transmitted by the full reflection inside thereof through the transparent 
plate to reach a light receiving element and produce a fingerprint picture 
electrical signal. The light reflected from the groove line portions of 
fingerprint is not transmitted by such a full reflection, and thus such an 
electrical signal is not produced. 
In such a fingerprint sensor, a fraudulent operation of the fingerprint 
identification system having such a biological object detection means, 
with criminal intention, can be carried out by using a replica of a human 
finger, made of rubber or plaster, and therefore, protection from 
fraudulent use of the personal identification system by a false 
identification of a fingerprint by the fingerprint sensor was required. 
A number of attempts have been made to provide such protection against a 
fraudulent operation of the fingerprint sensor. For example, a pulsating 
electrical signal corresponding to the pulsation of the blood flow in the 
human finger is derived from a light receiver receiving light irradiated 
from a light emitter and transmitted through the finger to identify the 
fingerprint thereof. 
In another example, an electric current corresponding to the skin 
resistance of a human finger is measured by an electrical circuit formed 
by a pair of electrically conductive electrodes against which the human 
finger is pressed. In a further example, a change with time of the degree 
of contact between the surface of the human fingerpad (the palm side of a 
human fingertip) and the surface of the transparent plate for the 
fingerprint detection, which is affected by perspiration from the surface 
of the human fingerpad, is detected by an electrical signal output from 
the light receiver. Nevertheless, these attempts at protection against 
fraudulent operation were not successful, because a considerable length of 
time is required for the detection or a very precise detection cannot be 
obtained, and thus practical use of the above attempts was not adequate. 
A prior art fingerprint sensor having a biological object discriminating 
means has been proposed, in which the nature of the skin of a living human 
fingerpad, i.e., that the spectral reflectance of the skin of a living 
human fingerpad to which a pressure is applied is different from that of a 
non-living object such as a replica finger, is utilized. 
The color of the skin of a finger not under pressure is usually reddish, 
but becomes whitish when a pressure is applied to the skin of the finger 
by, for example, pressing the fingerpad against a plate. It has been 
acknowledged that the spectral reflectance of the light in the red 
spectral range, i.e., the light wavelength of approx. 640 to 770 nm, does 
not show a substantial difference between the pressed state and the not 
pressed state, and the spectral reflectance of the light in the blue and 
green spectral range, i.e., the light wavelength of approx. 400 to 600 nm, 
in the not pressed state is much less than in the pressed state. 
Accordingly, by measuring the spectral reflectance in the blue and green 
spectral range of the surface of an object in question, it is possible to 
detect whether or not this object is a biological object. 
In this prior art biological object detection means there is provided a 
finger nipping member constituted by a pair of nip elements for nipping 
the tip of a finger therebetween, and a spring bridging these nip elements 
for developing a force to cause these nip elements to be biased toward 
each other. Each nip element is provided with a light emitting element for 
emitting a light having a spectral wavelength range including the blue or 
green range, and a light sensing element for responding to a light having 
the spectral wavelength range of blue or green. 
Namely, when a fingertip is forced into the gap between these nip elements 
against the force of the spring thereof, the gap between these nip element 
is enlarged and thus pressure is applied to the sides of the fingertip by 
the action of the spring. As the pressure applied to the sides of the 
fingertip increases, the color of the skin of the finger changes from 
reddish to whitish, to thus change the spectral reflectance, and 
accordingly, the value of the light having the spectral wavelength of the 
blue and green ranges detected by the light sensing element is increased. 
Therefore, the biological object detection is carried out by using the 
result of the detection of the reflected blue or green range light by the 
light sensing element. 
Nevertheless, a fraudulent operation of the fingerprint identification 
system having such a biological object detection means can be carried out 
by lo using a first replica of a finger for counterfeiting a human 
fingerprint and the spectral reflectance characteristic of human finger 
skin in the pressed state and a second replica of a finger for 
counterfeiting the spectral reflectance characteristic of human finger 
skin in the not-pressed state. The fraudulent operation is carried out by, 
first forcing the first replica of a finger covered by the second replica 
of a finger into the space between the above-described nip elements to 
imitate the human finger in the not-pressed state, and second, taking the 
second replica of a finger out of the first replica of a finger to imitate 
the human finger in the pressed state. Accordingly, protection of the 
personal identification system by fingerprint identification against such 
fraudulent operation of the fingerprint sensor is urgently required. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an improved apparatus for 
detecting a biological object based on changes in a color of the surface 
of a biological object due to a pressure applied to the biological object 
by a biological object discrimination means, using the light reflection on 
the fingerprint surface of a finger to prevent a fraudulent operation of a 
fingerprint sensor and enhance the security and reliability of the 
biological object detecting apparatus. 
According to the invention, there is provided an apparatus for detecting a 
biological object based on changes in a color of a surface of a biological 
object du to a pressure applied to the biological object when the 
biological object is pressed onto a transparent plate, the apparatus 
comprising: a transparent plate, onto which an object to be detected is 
placed, for allowing the passage of projected light and reflected light 
used for an optical detection; a light source located under the 
transparent plate for projecting a light beam used for a biological object 
detection toward a portion of the surface of the placed object toward 
which a light beam for detecting a characteristic pattern of the surface 
of the placed object is directed; and a light detection unit located below 
the transparent plate for receiving the light projected from the light 
source and subsequently reflected by the..surface of the object 
alternatively when placed on or pressed onto the transparent plate and 
detecting the corresponding characteristics of the reflected received 
light. The detection of whether or not the detected object is a biological 
object is based on the detection of the characteristic of the reflection 
rate of the received light by the light detection unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Before describing the preferred embodiments of the present invention, prior 
art apparatuses for detecting a biological object associated with a 
personal identification system in which a person is identified by 
identifying a fingerprint of the person are described with reference to 
FIG. 1 to FIG. 5. 
The principle of the detection of a biological object used in a prior art 
is illustrated in FIG. 1 and FIG. 2. In FIG. 1, a human finger is 
illustrated as a cross-section with the upper nail side and the lower 
fingerprint side. The color of the skin of a human finger not under 
pressure, as shown in the left of FIG. 1, is usually reddish, but becomes 
whitish when a pressure is applied to the skin of the finger by, for 
example, pressing the finger to a plate as shown in the right of FIG. 1. 
It has been acknowledged that the spectral reflectance of the light in the 
red spectral range, i.e., the light wavelength of approx. 640 to 770 nm, 
does not show a substantive difference between the pressed state and the 
not-pressed state, but the spectral reflectance of the light in blue and 
green spectral range, i.e., the light wavelength of approx. 400 to 600 nm 
in the not-pressed state is much smaller than in the pressed state as 
shown in FIG. 2. Therefore, by measuring the spectral reflectance in the 
blue and green spectral range of the surface of an object in question, it 
is possible to detect whether or not this object is a biological object. 
A prior art apparatus for detecting a biological object is shown in FIG. 3 
and FIG. 4. FIG. 3 is a top view and FIG. 4 is an elevation view. As shown 
in FIG. 3, a finger nipping member is constituted by a pair of nip 
elements 81, 82 for nipping the tip of a finger 1 therebetween and a 
spring 83 bridging these nip elements 81, 82 for biasing these nip 
elements 81, 82 toward each other. The nip elements 81, 82, contain light 
emitting elements 811, 821, and light sensing elements 812, 822. Each of 
the light emitting elements 811, 821 emits light including the blue or 
green light wavelength, and each of the light sensing elements 812, 822 is 
sensitive to the light having the blue or green light wavelength. Each of 
the light emitting elements 811, 821 may be a light emitting element which 
emits the white light. 
When a fingertip is forced into the gap between the nip elements 81 and 82, 
the gap between the nip elements 81 and 82 is enlarged and a pressure is 
applied to the sides of the fingertip by the action of the spring 83. As 
the pressure applied to the sides of the finger tip increases, the color 
of the skin of the finger changes from reddish to whitish, to thereby 
change the spectral reflectance thereof, and accordingly, the value of the 
light having the spectral wavelength of the blue and green ranges detected 
by the light sensing elements 812, 822 is increased. Accordingly, the 
biological object detection is carried out by using the result of the 
detection of the reflected blue or green range light by the light sensing 
elements 812, 822. This prior art apparatus, however, cannot prevent a 
fraudulent operation of the fingerprint identification system by sing 
replicas of a finger. The apparatus of this type for detecting a 
biological object is disclosed, for example, in Japanese Unexamined Patent 
Publication (Kokai) No. 61-221883 corresponding to U.S. Pat. No. 
4,728,186. 
Another prior art apparatus for detecting a biological object is shown in 
FIG. 5. As shown in FIG. 5, the apparatus is constituted by a light 
conducting plate (a transparent plate) 2, a green light emitting element 
33 for biological object detection, a light sensor element 59 for 
biological object detection, a laser emitting element 34, a hologram 
element 43, for fingerprint detection, and a light sensor element 44 for 
fingerprint detection. In the apparatus, the green light having a spectral 
wavelength of approx. 450 to 570 ns, emitted from the green light emitting 
element 33, is reflected at the surface of the finger 1 pressed against 
the surface 21 of the plate 2, and the reflection light is transmitted 
through the plate 2 in accordance with the principle of a full reflection 
filtering, to the light sensor element 59. Based on the difference of the 
reflectance of the skin of the fingerpad in the state in which the flow 
rate of blood is low and in the state in which the flow rate of blood is 
high, due to the pulsation of the blood flow in the human finger, it is 
possible to detect the biological object from the reflected light detected 
by the light sensor element 59. After the detection of the biological 
object, the fingerprint detection is carried out by using the laser 
emitting element 34, a hologram element 43, and the light sensor element 
44. 
Nevertheless, this prior art apparatus is not successful because a 
considerable length of time is required for the detection. The apparatus 
of this type is disclosed, for example, in Japanese Unexamined Patent 
Publication (Kokai) No. 62-74173. 
((Embodiment of FIG. 6)) 
An apparatus for detecting a biological object according to an embodiment 
of the present invention is shown in FIG. 6. The apparatus of FIG. 6 is 
provided with a transparent plate 2 able to conduct light and having an 
inspection surface 21 on which a finger 1 to be identified is placed, a 
light emitting element 31 for biological object detection, a light 
emitting element 32 for fingerprint picture image detection, an optical 
lens 41, a light sensing element 42 for fingerprint picture image 
detection, an optical lens 500, light sensing elements 501 and 502, and a 
detection unit 6 having a level detection circuit 61, a comparator circuit 
62, and an AND circuit 63. The optical lens 500, the light sensing 
elements 501 and 502, and the signal processing unit 6 are used 
specifically for the biological object detection. 
It is possible to incorporate the light emitting element 31 for biological 
object detection and the light emitting element 32 for fingerprint picture 
image detection into a single light emitting element. 
The light sensing element 501 responds to the light of the red spectral 
wavelength range of approx. 640 to 770 nm, to generate a signal S(R) which 
corresponds to this light of the red spectral wavelength range. The light 
sensing element 502 responds to the light of the spectral wavelength range 
shorter than that of the red spectral wavelength, such as the green 
spectral wavelength range of approx. 490 to 550 nm, the blue spectral 
wavelength range of approx. 430 to 490 nm, or a combination of these green 
and blue spectral wavelength ranges, to generate a signal S(GB) which 
corresponds to this light of the green, blue, or green-blue combination 
spectral wavelength range. 
In the level detection circuit 61, which is constituted by an analog 
comparator such as a window comparator, the signal S(R) is compared with a 
predetermined reference value V.sub.1, and when the signal S(R) is greater 
than the reference value V.sub.1, an instruction signal S.sub.1 is 
produced. The instruction signal S.sub.1 represents the detection of the 
contact of a finger 1 with the glass plate 2. The value of V.sub.1 is 
selected as a value slightly smaller than the level of the reflected light 
based on the reflectance of the skin of a human finger in the red spectral 
wavelength range, in both the pressed state and the not-pressed state, 
In the comparator circuit 62, the signal S(R) is compared with the signal 
S(GB) - S(GB)" becomes smaller as a result of the pressed state, than the 
value of "S(R) - S(GB)" as was produced in the not-pressed state, the 
signal S.sub.2, which represents a color change of an object under 
detection, is produced. 
In the AND circuit 63, when both signals S.sub.1 and S.sub.2 are received, 
a biological object determination signal S.sub.3 is produced, and the 
produced signal S.sub.3 is supplied to a fingerprint picture image 
processing device (not shown) to allow, or enable registration and 
comparison operations of ,the fingerprint picture image to be carried out. 
The operation of the apparatus of FIG. 6 will be described. First, a person 
to be identified places, i.e., gently presses, a finger 1 against the 
inspection surface 21 of the plate 2. In this state, the color of the skin 
of the finger 1 is reddish, which corresponds to the curve shown by a 
solid line in FIG. 2. The reflected light from the skin of the fingerpad 
contains a high red light value and a low blue or green light value. The 
signals S(R) and S(GB) generated in the light sensor elements 501 and 502 
correspond to the values shown by the solid line of FIG. 2. Since the 
condition S.sub.R &gt;V.sub.1 is satisfied, the level detection circuit 61 
produces the signal S.sub.1, which indicates that the finger 1 is touching 
the inspection surface 21 of the plate 2. Note, as the finger is still 
only gently placed, the difference "S(R) - S(GB)" is the value for the 
not-pressed state and thus the signal S.sub.2 is not produced in the 
comparison circuit 64 in this state. 
Next, the person to be identified firmly presses the finger 1 against the 
inspection surface 21 of the plate 2. Accordingly, the color of the skin 
of the finger 1 becomes whitish, which corresponds to the curve shown by a 
broken line in FIG. 2. The reflected light from the skin of the fingerpad 
now contains high red, as well as high blue, and green light values; 
accordingly, the difference "S(R) - S(GB)" becomes smaller for the pressed 
state than the difference "S(R) - S(GB)" in the not pressed state, and the 
signal S.sub.2 is produced by the comparator circuit 62. Upon receiving 
the signal S.sub.1 from the level detection circuit 61 and the signal 
S.sub.2 from the comparison circuit 62, the AND gate 63 produces the 
signal S.sub.3, which indicates that the finger 1 on the plate 2 is a 
biological object, whereby the biological object detection of the finger 
under detection is carried out. 
In the apparatus of FIG. 6, since the light for the biological object 
detection is irradiated onto the inspection surface 21 of the plate 2 
against which the fingerprint of the finger 1 is pressed, and the 
biological object detection is carried out based on the reflected light 
from the skin of the fingerpad, a fraudulent operation of the fingerprint 
sensor having a biological object detection means by using first and 
second replicas of a finger, which was successful in the hereinbefore 
described prior art apparatus, cannot succeed in the apparatus of FIG. 6. 
This is because, first the formation of a counterfeit fingerprint on the 
second replica of finger is required, and second, the reading of the 
fingerprint picture images becomes impossible due to the removal of the 
second replica of a finger from the first replica of a finger and thus a 
fingerprint identification operation per se becomes impossible. 
Therefore the biological object detection as carried out by the apparatus 
of FIG. 6, prevents the fraudulent operation of the fingerprint sensor 
with criminal intent. 
In the fingerprint picture image detection by the apparatus of FIG. 6, it 
is possible to use either a prism system or a holographic system. 
((Embodiment of FIG. 7)) 
An apparatus according to another embodiment of the present invention is 
shown in FIG. 7. The apparatus of FIG. 7 is provided with a light switch 
unit 7 constituted by a light source element 71 and a light receiving 
element 72, a lens 510, light sensor elements 511, 512, and 513 having a 
red filter, blue filter, and green filter, respectively, and a detection 
circuit 6. 
The light switch unit 7 produces a finger presence signal S.sub.4 from the 
light receiving element 72 when a finger is placed on the inspection 
surface 21 of the plate 2, in either the not-pressed state 1 or in the 
pressed state 1'. In operation, the finger is first in the not pressed 
state 1, and subsequently, in the pressed state 1'. 
In the detection circuit 6, the red light signal S.sub.R, the blue light 
signal S.sub.B, and the green light signal S.sub.G from the light sensor 
elements 511, 512, and 513 are compared when the operation of the 
detection circuit 6 is enabled by the finger presence signal S.sub.4 from 
the light switch unit 7. When the relative level relationships between the 
signals S.sub.R, S.sub.B, and S.sub.G satisfy in time succession the 
respective characteristics for both the not-pressed finger and the pressed 
finger shown in FIG. 2, the biological object detection signal S.sub.5 is 
output by the detection unit 6. 
Namely, if the object in question is a human finger as a biological object, 
the relationship is first S.sub.R &gt;S.sub.B =S.sub.G, and subsequently, 
becomes S.sub.R .apprxeq.S.sub.B .apprxeq.S.sub.G. If the object in 
question is a replica of a finger, the above relationship cannot be 
established. 
The fingerprint picture image detection is carried out in the same manner 
as shown in FIG. 6, and thus the description thereof is abbreviated with 
regard to FIG. 7. 
((Embodiment of FIG. 8)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 8. The apparatus of FIG. 8 is provided with a light 
emitting element 31 for biological object detection, slit plates 521 and 
522, a prism 523, a line sensor 524, and a detection circuit 6. 
The reflected light from the skin of the fingerpad is led to the prism 523 
through the slits of the slit plates 521 and 522, and light beams 
spectrally separated by the prism 523 are led to the line sensor 524. The 
line sensor 524 produces the signals S.sub.R, S.sub.B, and S.sub.G, which 
correspond to the red, blue, and green lights, respectively. The 
operations of the light switch unit 7 and the detection unit 6 are 
substantially the same as in the apparatus of FIG. 7, and thus description 
of the fingerprint picture image detection is abbreviated with regard to 
FIG. 8. 
((Embodiment of FIGS. 9A and 9B, combined as shown in FIG. 9)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 9 (i.e., 9A and 9B, combined as shown in a light emitting 
element 3 such as a laser light source for both a biological object 
detection and fingerprint picture image detection, a lens 531, a filter 
532, a light sensing element 533, a detection unit 6, a lens 41, a light 
sensing element 42, and a personal identification unit 43. 
The light emitting element 3 is selected to emit a white light or a light 
having the green light wavelength at the center thereof, and the light 
sensor element 533 is selected to be sensitive to a light having the green 
light wavelength at the center thereof. 
The detection unit 6 is constituted by a comparator circuit 64, a one shot 
multivibrator circuit 65, a comparator circuit 66, and an AND circuit 67. 
The personal identification unit 43 (FIG. 9B) comprises a picture 
receiving portion 431, a picture storage circuit 432, a binary value 
forming circuit 433, a fine line formation circuit 434, a characteristic 
extraction circuit 435, an adjacent pattern planting circuit 436, an angle 
and crosspoint inspection circuit 437, and an operation control circuit 
438. The personal identification unit 43 may be constructed, for example, 
as a 16 bit personal computer. 
The comparator circuit 66 uses a predetermined first reference level, and 
the comparator circuit 64 uses a predetermined second reference level, in 
evaluating the characteristic of the output of the light sensor element 
533 of FIG. 9A, as shown in FIG. 10. In the sensed light output 
characteristic as shown in FIG. 10, in the first period during which the 
finger is not present ("NO FINGER"), the output is at a high level; next 
in the second period during which the finger is/placed on the plate in the 
not-pressed state ("FINGER NOT PRESSED), the output is at a low level; and 
further, in the third period during which the finger is placed on the 
plate in the pressed state ("FINGER PRESSED), the output is at an 
intermediate level. The first reference level is selected to be between 
the high "no finger" level and the intermediate "pressed finger" level, 
and the second reference level is selected to be between the intermediate 
"pressed finger" level and the low finger "not-pressed" level. 
When the comparator circuits 64 and 66 detect that the sensor output has 
changed from the "no finger" level to the "not-pressed finger" level, and 
subsequently, changed from the "not-pressed finger" level to the "pressed 
finger" level, the one shot multivibrator circuit 65 (FIG. 9A) generates a 
HIGH level signal which is supplied to the AND circuit 67. The output 
signal of the comparator 66, which represents the contact of the finger 1 
with the glass plate 2, is also supplied to the AND circuit 67. The AND 
circuit 67 produces the output signal as the biological object detection 
signal to be supplied to the personal identification unit 43 of FIG. 9B 
when both the signal from the one shot multivibrator circuit 65 and the 
signal from the comparator circuit 66 are supplied to the AND circuit 67, 
i.e., when a genuine biological object is in contact with the plate 2. 
This operation of the AND circuit 67 cannot be carried out by a fraudulent 
operation of the fingerprint sensor in which the object under detection is 
removed from the inspection surface 21 of the plate 2 and replaced by a 
replica of a finger. 
In the personal identification unit 43 (FIG. 9B), the picture receiving 
portion 431 receives the signal from the light sensing element 42, whereby 
the light transmitted through the plate 2 and the lens 41 is converted to 
an electric signal. In the picture storage circuit 432, the picture data 
from the picture receiving portion 431 is analog-to-digital converted and 
the converted data is stored therein. Data exchanges are carried out 
between the picture storage circuit 432 and the binary value forming 
circuit 433. In the binary value forming circuit 433, the binary value 
data of the picture data is formed, and in the fine line formation circuit 
434, the formation of ridge lines and groove lines is carried out from the 
binary digital data. In the characteristic (points) extraction circuit 
435, the characteristic points are extracted from the picture in the fine 
line form, and in the angle and crosspoint inspection circuit 437, angles 
and crosspoints between the lines connecting the branching points or the 
end points in the characteristic points are extracted. In the adjacent 
pattern planting circuit 436, a pattern of the binary form adjacent to an 
end point is separated, based on the output of the angle and crosspoint 
inspection circuit 437, and the separated pattern is planted adjacent to 
bridges or interruptions. In the operation control circuit 438, a 
registration of a personal fingerprint and a comparison of the registered 
personal fingerprint with the picture input data for fingerprint 
identification are carried out when the detection of the biological object 
is confirmed by the receipt of the biological object detection signal from 
the biological object detection unit 6. The data of the picture processing 
described above is supplied from the picture storage circuit 432 or the 
operation control circuit 438 to a CRT display or the like (not shown) for 
monitoring. In the processing of the picture, the formations of windows by 
a ten-key or a mouse, and procedures for searching for characteristic 
points or branching points are carried out. A fraudulent operation of the 
fingerprint sensor by using a replica of a finger may be displayed on a 
display device. 
As shown in FIG. 10, while the finger is not in contact with the plate 2, 
the level of the light sensor output is at a high level. At the time 
immediately after the finger is brought into contact with the plate 2, 
there is a high blood flow rate through the vein of the finger and the 
color of the skin of the finger is reddish, and thus the reflectance of 
the surface of the fingerpad is low. Accordingly, the level of the light 
sensor output becomes low. After the finger is pressed onto the plate 2, 
the blood flow rate through the vein of the finger is lowered and the 
color of the skin of the finger becomes whitish, and thus the reflectance 
of the surface of the fingerpad is increased. Accordingly, the level of 
the light sensor reaches an intermediate level. 
There is little difference in the reflectance of the surface of the human 
fingerpad in the high blood flow state and the low blood flow state, for 
the red spectral wavelength range of light, but there is a great 
difference in the green spectral wavelength range of light. This is 
considered to be based on the effect of hemoglobins in the blood. 
In the apparatus of FIG. 9, the detection of the biological object is 
carried out by checking the change with time of the light sensor output 
from the time at which the finger comes into contact with the plate to the 
time at which the finger is pressed on the plate, based on the 
above-described nature of the reflectance of the skin of the human 
fingerpad. 
In the apparatus of FIG. 9, when a replica of a finger made of, for 
example, silicon plastic, is applied to the plate 2, the change of the 
reflectance does not occur, and thus the light sensor output is changed 
from a high level directly to an intermediate level without going through 
the low level. Therefore, by checking by the biological object detection 
circuit 6 whether or not the light sensor output has changed through a 
high level-low level-intermediate level route, it is possible to 
discriminate a human finger as a biological object from a replica of a 
finger. Therefore, a fraudulent operation of the fingerprint sensor by 
first applying a human fingerpad onto the plate 2, and subsequently 
inserting a replica of finger made of a thin membrane between the human 
finger and the plate 2 cannot be successful. 
In the apparatus of FIG. 9, it is possible to emit the light from the light 
emitting element directly from the light sensor element 533 in an upward 
direction. Also, in the biological object detection unit 6 in the 
apparatus of FIG. 9, it is possible to limit the time of the effectiveness 
of the biological object detection signal, and accordingly, to dispense 
with the comparator circuit 66. 
((Embodiment of FIG. 11)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 11. The apparatus of FIG. 11 is provided with a prism 200 
having an inspection surface 201, a light emitting element 3, a lens 541, 
a filter 542, and light sensor elements 543 and 42'. The output of the 
light sensor element 543 is supplied to the biological object detection 
unit, and the output of the light sensor element 42' is supplied to the 
personal identification unit. The operation of the apparatus of FIG. 11 is 
similar to that of the apparatus of FIG. 9. 
((Embodiment of FIG. 12)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 12. The apparatus of FIG. 12 is provided with a 
transparent plate 2 having an upper surface 21 as the inspection surface, 
a lower surface 22, and a mirror 23, a diaphragm 451, a spherical surface 
lens 452, a light sensor element 453 for fingerprint picture image 
detection, a light emitting element 351, a semitransparent mirror 352, a 
light conducting transparent member 354, mirrors 355 and 356, a light 
collecting lens 551, a filter 552, and a light sensor element 553. Each 
end of the light conducting transparent member 354 is cut to form an 
oblique surface on which a reflection coating is deposited to form the 
mirrors 355 and 356. 
The light emitting element 351 emits a light including green light of a 
wavelength of approx. 500 to 550 nm, and the filter 551 allows only light 
of the green range to pass therethrough. 
In the operation of the apparatus of FIG. 12, the change of the value of 
the green light detected by the light sensor element 553 in a sequence 
from the time before the contact of the finger with the plate 2 through 
the coming of the fingerpad into contact with the plate 2, to the pressing 
of the fingerpad onto the plate 2, is measured. 
If this change of the value of the green light shows the characteristic of 
the change in the green light range shown in FIG. 2, the object on the 
inspection surface of the plate 2 can be determined to be a human finger 
as a biological object. If not, the object on the inspection surface of 
the plate 2 cannot be determined to be a biological object. 
In the apparatus of FIG. 12, the light emitting element 351, the 
semitransparent mirror 352, the light collecting lens 551, the filter 552, 
and the light sensor element 553 are located above the level of the lower 
surface 22 of the plate 2, and the light conducting transparent member 354 
having the mirrors 355 and 356 is located below the level of the lower 
surface 22 of the plate 2. Therefore, the distance between the lower 
surface 22 of the plate 2 and the lower surface 354C of the transparent 
member 354 can be made as thin as, for example, approx. 5 mm. 
In the most preferable arrangement all of the light emitting element 351, 
the semitransparent mirror 352, the light collecting lens 551, the filter 
552, and the light sensor element 553 are included within the thickness of 
the plate 2. Such an arrangement effectively realizes a fingerprint sensor 
apparatus having a small thickness. 
((Embodiment of FIG. 13)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 13. The apparatus of FIG. 13 is provided with a 
transparent plate 2 having an upper surface 21 as the inspection surface, 
a lower surface 22, and a mirror 23, a diaphragm 451, a spherical surface 
lens 452, a light sensor element 453 for fingerprint picture image 
detection, a light emitting element 351, a light collecting lens 352, a 
light conducting transparent member 357, reflection type holograms 358 and 
359 having a wavelength selection characteristic, and a light sensor 
element 553. 
In the operation of the apparatus of FIG. 13, the change of value of the 
green light detected by the light sensor element 553 in a sequence from 
the time before the contact of the finger with the plate 2 through the 
coming of the fingerpad into contact with the plate 2 to the pressing of 
the fingerpad onto the plate 2 is measured. 
In the apparatus of FIG. 13, the hologram 358 has a wavelength selection 
characteristic allowing only the green light range to be reflected toward 
the upper surface of the transparent member 357. The reflected light is 
fully reflected at the upper surface of the transparent member 357 toward 
the hologram 359, at which the fully reflected light is reflected upward 
toward the fingerpad on the plate 2. The reflected light from the surface 
of the fingerpad is reflected at the hologram 359, fully reflected at the 
upper surface of the transparent member 357, reflected at the hologram 
358, and is detected by the light sensor element 553. 
The determination of whether or not the object on the inspection surface of 
the plate 2 is a human finger as a biological object, based on the 
detection by the light sensor element 553 in the apparatus of FIG. 13, is 
similar to that in the apparatus of FIG. 12. 
In the apparatus of FIG. 13, the distance between the lower surface 22 of 
the plate 2 and the lower surface 357C of the transparent member 357 can 
be made as thin as, for example, approx. 2 to 3 mm. 
((Embodiment of FIG. 14)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 14. The apparatus of FIG. 14 is provided with a light 
emitting element 351 for emitting a light including light in the green 
light range, a first optical fiber 356, a light expansion lens 357 for 
expanding the light, a light collecting lens 551, a second optical fiber 
554, a filter 552 for passing light of only the green light range, and a 
light sensor element 553. 
The determination of whether or not the object on the inspection surface of 
the plate 2 is a human finger as a biological object, based on the 
detection by the light sensor element 553 in the apparatus of FIG. 14, is 
similar to that in the apparatus of FIG. 12. 
In the apparatus of FIG. 14, the distance between the lower surface 22 of 
the plate 2 and the lower end of the second optical fiber 554 can be made 
as thin as, for example, approx. 5 mm. 
((Embodiment of FIG. 15)) 
An apparatus according to still another embodiment of the present invention 
is shown in FIG. 15. The apparatus of FIG. 15 is provided with a light 
emitting element 351, a semitransparent mirror 352, a light conducting 
transparent plate 354, mirrors 355 and 356, a light collecting lens 551, a 
filter 552, a light sensor element 553, and a light switch unit 7 having a 
light source element 71 and a light receiving element 72, 
In the apparatus of FIG. 15, the presence of the object on the plate 2 is 
detected by using a light transmitted from the light source element 71 to 
the light receiving element 72. 
Instead of the light guiding structure using a light conducting transparent 
member with mirrors, it is possible to use a light guiding structure using 
a light conducting transparent member with holograms as shown in FIG. 13 
or a light guiding structure using optical fibers as shown in FIG. 14. 
Also, instead of locating the light guiding structure directly below the 
glass plate as shown in FIGS. 12, 13, 14 and 15, it is possible to cut a 
side of the plate 2 to form an oblique surface and locate the light 
guiding structure directly below this oblique surface. 
((Embodiment of FIG. 16)) 
An apparatus according to a further embodiment of the present invention is 
shown in FIG. 16. The apparatus of FIG. 16 is provided with a transparent 
plate 2 having an upper surface 21 as the inspection surface, a lower 
surface 22, a mirror 23, a diaphragm 451, a spherical surface lens 452, a 
light sensor element 81 such as a color charge-coupled device (color CCD) 
having a red detection element, a blue detection element, and a green 
detection element for detecting both a fingerprint picture image and a 
change of color of the skin of the fingerpad, an RGB separation circuit 
82, a biological object detection unit 83 having a color shift correction 
circuit 831, and a color discrimination circuit 832, and a personal 
identification unit 84 having a fingerprint picture image receiving 
circuit 841 and a fingerprint comparison circuit 842. In the apparatus of 
FIG. 16, the light wavelength selection means is incorporated with the 
fingerprint picture image detecting element. 
The red, blue, and green fingerprint signals S(R), S(B), and S(G) from the 
RGB separation circuit 82 are supplied to the color shift correction 
circuit 831 and the color shift corrected fingerprint signals generated in 
the color shift correction circuit 831 are supplied to the color 
discrimination circuit 832, which functions as the biological object 
detection circuit for outputting a biological object confirmation signal. 
In the color discrimination circuit 832, a change of color of fingerprint 
picture image between the fingerprint picture image at the moment of 
contact of an object to be identified with the plate 2 and the fingerprint 
picture image after the pressing of the object onto the plate 2 is 
detected, and it is determined whether or not the object is a biological 
object. The phenomena whereby the color of the ridge line of the 
fingerprint is reddish when a fingerpad comes into contact with the glass 
plate 2 and the color of the ridge line of the fingerprint becomes whitish 
color after the fingerpad is pressed onto the plate 2, is utilized in this 
detection. The biological object confirmation signal from the color 
discrimination circuit 832 is supplied to the fingerprint comparison 
circuit 842 in the personal identification unit 84 to enable the operation 
of the fingerprint comparison circuit 842. 
One of the red, blue, and green fingerprint signals S(R), S(B), and S(G) 
from the RGB separation circuit 82, for example, the red fingerprint 
signal S(R), is supplied to the fingerprint picture image receiving 
circuit 841 in the personal identification unit 84. The fingerprint 
picture image signal from the fingerprint picture image receiving circuit 
841 is supplied to the fingerprint comparison circuit 842. In the 
fingerprint comparison circuit 842, the identification of the supplied 
fingerprint picture image is carried out based on the result of comparison 
.