[0001] It has previously been determined that a reliable method of checking the identification
of an individual is to measure the dimensions of a human hand and particularly the
lengths of the various fingers. For instance, when it is desired to know whether an
individual who presents a credit card is the proper holder of the credit card, one
can compare the lengths of the fingers with stored data to determine with a high degree
of accuracy whether the person presenting the card is the one to whom the card was
issued.
[0002] The advantages of such identification systems are fully set forth in U.S. patents
3,576,538 and 3,648,240 both of which relate to identification systems based on the
lengths of fingers. The former patent employed mechanical probes to determine finger
lengths and it was found that this was objectionable by many people. The second patent
was an improvement thereon in that one merely held his hand over a flat surface having
a plurality of light pick up means imbedded within the surface; a light was placed
over the identification plate so that one could scan the light pick up points and
determine the finger lengths. This apparatus had the disadvantage of being affected
by the length of the fingernails. Thus, when fingernails grew or were cut, an authorized
person's identity would fail to be verified by the machine. Also, the only biometric
information sensed by the previous inventions was the location of the fingertips and
webbing between fingers. With this limited amount of information, "false accept" and
"false reject" error rates were on the order of 2%-5%.
[0003] Also, because of the methods of the previous inventions, it was relatively simple
to produce an artificial hand from a simple cardboard cutout. This made the previous
inventions unsuitable for use in high security areas.
[0004] In accordance with the present invention, an improved apparatus of the finger or
hand identification type is provided wherein the entire apparatus is included within
a member on which a hand can be placed. In accordance with a preferred embodiment,
a flat plate which occupies little counter space and which has a relatively low power
consumption is employed. Further, all significant optical features along the length
of the finger and the webbing between fingers can be measured and some or all used
in the determination of valid identity. Also because of the optical geometry of the
measuring device, the measurement is free from artifact due to fingernails.
[0005] Likewise, the system is very difficult to defeat with an artificial hand since to
do so would require the adequate replication of the many features which are measured.
[0006] Accordingly, it is an object of the present invention to provide an identification
apparatus of the type wherein one determines the characteristics of one or more fingers
which does not require an overhead light source and which measures a plurality of
characteristics of the hand or fingers.
[0007] Other objects and features of the invention will be brought out in the balance of
the specification.
[0008] In order that the present invention may more readily be understood the following
description is given, merely by way of example, with reference to the accompanying
drawings, in which:-
Fig. 1 is a perspective view of an apparatus embodying the present invention.
Fig. 2 is a plan view of the apparatus.
Fig. 3 is a diagrammatic view illustrating the scanning action which is employed in
accordance with the present invention.
Fig. 4 is a exploded view of an apparatus suitable for carrying out the present invention.
Fig. 5 is a plan view of the apparatus with the hand plate removed.
Fig. 6 is an enlarged section on the line 6-6 of Fig. 5.
Fig. 7 is an enlarged perspective view, partly in section, illustrating the motion
of the scanning elements.
Fig. 8 is a simplified schematic diagram of the logic circuitry.
Fig. 9 is an enlarged partial view of a finger being scanned and the response curve.
Fig. 10 is an enlarged partial view showing an alternate scheme for illuminating a
finger
Fig. 11 is a typical voltage response curve by a finger scan.
Fig. 12 is another scan curve.
Fig. 13 is still another scan curve.
Fig. 14 is another scan curve.
Fig. 15 is a first derivative curve, i.e. dV of dt the curve of Fig. 14.
Fig. 16 is a second derivative (d2v) of the same (dt ) curve.
[0009] Referring now to the drawings by reference characters, there is shown an identification
system which includes a hand plate 10 mounted on a base 12. A card reader 14 is connected
by a suitable cable 16 to the identification device. The hand plate 10 has a plurality
of slots therein and, in the embodiment illus
- trated, has slots for four fingers designated 18, 20, 22 and 24 which are splayed
as in a normal hand. In addition, two slots are provided designated 26 and 28, the
purpose of which is to identify the crotch positions between the fingers placed between
slots on 18 and 20 as well as between slots 22 and 24, respectively. The hand plate
also has a locating pin 30 to insure that one places the hand in the proper position
on the identification device. Normally, the hand plate is hollowed around each of
the finger slots as is shown at 32; ordinarily the crotch slots are not so hollowed.
This hollowing of the finger slots makes it simpler to place the hand in the proper
position and also secures better contact between the finger and the hand plate.
[0010] In accordance with a preferred embodiment of the present invention, both the light
source and the light sensing device are incorporated in a cell located under the hand
plate 10. The cells move up and down on the finger slots and the crotch slots to measure
the desired characteristics of the fingers. One of the cells is shown enlarged in
Fig. 7. The cell is generally designated 34 and has a round body portion 36 with opposed
flat sides 38. The flat sides 38 form a sliding fit in one of the longitudinal slots.
The cell also has flat sides 39 at right angles to the flat sides 38 which fit into
a transverse slot as at 20B in figures 6 and 7. Each of the cells contains a light
source such as a LED 40 and a photoelectric pick up cell 42. Thus each of the units
34 is self contained with its light source and pick up so that if there is light colored
object, such as a finger in the slot, light will be reflected back from the light
source to the pick up cell 42.
[0011] As can best be seen in Fig. 3, the path of travel of the cells 34 is up and down
the path of the extended fingers. Since the fingers are spread out in a normal hand
it is necessary that the path of the cells have both a longitudinal and a transverse
component.
[0012] The method of achieving the combination of the longitudinal and the transverse travel
will now be described. Mounted under the hand plate 10 is a longitudinal guide plate
44 which has a plurality of slots therein corresponding to the slots in the hand plate.
Thus slot 18A in the longitudinal guide plate corresponds to slot 18 in the hand plate
and so on.
[0013] Mounted under the longitudinal guide plate is the movable transverse guide plate
46 which is mounted for longitudinal movement on the rods 48 and 50. This plate has
a series of short slots corresponding with the slots in the longitudinal guide plate
except that these slots are at right angles to the slots in the longitudinal guide
plate. Thus, slot 18B is lo cated at a right angle to slot 18A and so on. In addition,
plate 46 has a transverse slot 52 extending for almost the complete width of the plate.
[0014] .Mounted under the transverse drive plate 46 is a motor 54 with a gear box 56 mounted
thereon with an output shaft 58. Shaft 58 is coupled to a crank arm 60 provided with
a roller 62 which fits into slot 52. The motion imparted can best be appreciated with
reference to Fig's. 3 and 5. As shaft 58 revolves, the drive plate 46 moves up and
down on rods 48 and 50 in the direction shown by the double arrow 64. This will cause
cells 34 to move in a transverse direction and at the same time in a longitudinal
direction; the interaction of the two sets of slots produces a vector upon each of
the cells so that as the shaft 58 makes one revolution, each of the cells will follow
an angling path up and down one of the finger slots.
[0015] It is preferred that the device work on infrared light to reduce the effect of ambient
light on the operation. Accordingly, the strips 66 which are transparent to infrared
light and opaque to visible light would normally be placed under each of the slots
of the hand plate 10.
[0016] The drive plate 46 also carries a transparent grid blade 68 which has a series of
dark lines 70 thereon. The grid plate 68 passes between the arms 71 and 72 of an optical
sensor which can be of substantially the same structure as the device 34 so that as
the grid 68 passes over the pick up.72, a series of pulses will be produced to serve
as a clock to indicate the position of the drive plate.
[0017] Optically significant features are determined by a measurement of optical reflectance
along the finger. Such features include: the position of maximum reflectance points,
minimum reflectance points, and points half-way in reflectance between maximum and
minimum points. The position of the maximum, minimum and midpoints of the spacial
lst, 2nd, 3rd---Nth derivatives of the reflectance signal can serve as reference points.
[0018] Since fingers differ in albedo it is preferable not to look for some absolute value
of reflectivity but it is better to employ a circuit which has a floating reference
point and which adjusts for differences in the reflectivity of fingers. Strangely
enough, it has been found that the refectivity reaches a peak near the tip of the
finger where the tip of the finger is not in contact with the plate. Advantage is
taken of this in one practical embodiment of the invention and the cut off point is
the 50% fall off in light pick up after the circuit reaches a peak value. This is
illustrated in Fig. 9 where the sensor 34 is shown moving along a finger 75. The amount
of light pick up is shown on the curve below. It will be seen that there as the sensor
moves along the finger, various peaks in reflectivity such as those designated 77A,
77B and 77C are noted. Just as the pick up reaches a point just short of the fingertip
a peak 79 is reached. Now as the sensor moves farther out, the light pick up gradually
falls off and the half value point 81 can be employed as a trigger. Similarly, the
position of the crotch can be.measured, and in one embodiment of the invention, identification
is made based solely on the length of the fingers as determined by the position of
the tip and crotch. However, in other embodiments, other features such as the points
77A-C can be measured and compared with stored data as is described later.
[0019] Figs. 11, 12, 13 and 14 show scans of typical fingers. It will be seen that the maximum
value of reflected light does not reach a sharp peak so that the maximum value is
not a suitable reference point. However by measuring the minimum reflectance point
as well as the maximum and taking a value half-way between these points, one obtains
a valid and reproducible reference point.
[0020] Another method of securing significant measurements is illustrated in Figs. 14, 15
and l6. In Fig. 15 the first derivative (dV) of the curve of Fig. 14 is plot-(dt)
ted so that one obtains a plurality of peaks such as those designated 43A, 43B and
43C which can be compared with stored data. One can now take the second derivative
(d
2V) of this curve, as is shown in Fig. 16, and (dt ) obtain a series of flip-flops
from a positive to a negative value at the cross-over points 45A, 45B...45X which
are easy to detect. Higher derivations provide even more sharply defined points. Thus,
by taking the first, second or higher derivatives of the response curves, one can
convert subtle, almost imperceptible changes into sharply defined points.
[0021] In Fig. 8 there is shown a highly simplified diagram of the detection system and
it will be seen that the light falling on the sensors 42A, 42B, 42C, 42D,
42
E and 42F (representing four fingers and two crotches of a hand) is fed to an analog
signal multiplexer 83 whose inputs are connected to each of the photo detector circuits;
this signal is fed to an analog to digital converter 84 connected to the output of
the analog multiplexer, and then to a microprocessor 85 which controls the multiplexer
and receives the output of the analog to digital converter. A grid clock 87 develops
a position signal which is fed to the microprocessor 85. A magnetic card reader 14
which is connected to the microprocessor stores and provides the reference hand geometry
data. In this manner, one or more characteristics such as the length of the finger
are determined and is compared with data included on the card, or supplied from a
separate source.
[0022] Normally it is preferred that the light source and photosensor be mounted as a unit
in a cell which scans a portion of the hand. However, it is also possible to use a
fixed light source as is shown in Fig. 10. Here a fixed light source 95 is employed
which illuminates the end and a portion of the under surface of a finger and the moving
cell 97 contains only the photosensor.
[0023] It will be obvious to those skilled in the art that many variations can be made in
the exact structure shown without departing from the spirit of this invention. For
instance, instead of the flat plate illustrated, the sensor could be enclosed in a
cylindrical or round object which the subject would grasp.
1. Personnel identification apparatus comprising:
a. means having a surface for supporting a hand,
b. slot means in said surface whereby a finger can cover at least a portion of said
slot means,
c. a light source illuminating at least a portion of the under surface of a finger,
d. a light detecting means movable under said slot means,
e. means to determine the amount of reflected light from said light source and,
f. electronic means to determine a desired characteristic of a finger based on said
reflected light and to compare the same with stored data.
2. The apparatus of claim 1 wherein said surface is planar.
3. The apparatus of claim 1 having a plurality of slots corresponding with a plurality
of fingers.
4. The apparatus of claim 2 having additionally a slot between finger slots to determine
the position of the crotch between fingers.
5. The apparatus of claim 2 wherein said slots extend at an acute angle to each other,
approximating the normal spread of fingers on a hand.
6. The apparatus of claim 1 having a holder movable beneath said slot means, said
holder having a light source and a light detecting means therein.
7. Apparatus according to claim 1 having a plurality of slots, said slots being set
at an acute angle to each other, and holder means corresponding to said slots, each
holder means including a light source and a light detecting means and means for moving
said holders along the undersides of said slots.
8. Apparatus in accordance with claim 1 having a fixed light source directed toward
the finger.
9. The apparatus of claim 1 wherein said electronic means includes a plurality of
photodetector circuits and means for determining maximum reflectance points, minimum
reflectance points and half-way points and comparing at least one of said points with
stored data.
10. The apparatus of claim 1 including means to derive the first, second or higher
derivatives from said reflectance points and means to compare significant points on
one or more derivatives with stored data.
11. The apparatus of claim 1 wherein said electronic means comprises the following:
a. a plurality of photodetector means,
b. an analog signal multiplexer having inputs connected to each of said photodetector
means,
c. an analog to digital converter connected to the output of said analog signal multiplexer,
d. a microprocessor which controls the multiplexer and receives the output of the
analog to digital converter,
e. a grid clock connected to said microprocessor, said grid clock indicating the position
of said photodetector means, and
_f. means to compare stored data with data generated by said photodetector means.
12. The apparatus of claim 10 having in addition a magnetic card reader to receive
stored data from a magnetic card.
13. The method of identification which includes illuminating at least a portion of
the under surface of at least one finger and scanning the reflected light from said
finger for optically significant features and comparing the results of said scanning
with stored data.
14. The method of claim 12 wherein the maximum reflectance from the finger is determined
as well as the minimum reflectance and the value half-way between the maximum and
minimum is taken as a reference point.
15. The method of claim 12 wherein singular points of a derivative of the reflectance
are taken as reference points.