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United States Patent 
[li] 4,322,163  Mar. 30, 1982
 FINGER IDENTIFICATION
 Inventor: Michael Schiller, Riverdale, N.Y.
 Assignee: Fingermatrix Inc., North White Plains, N.Y.
 Appl. No.: 207,639
 Filed: Nov. 17,1980
Related U.S. Application Data
 Continuation-in-part of Ser. No. 42,605, May 25, 1979, abandoned, and a continuation-in-part of Ser. No. 891,497, Mar. 20, 1978, abandoned, which is a continuation-in-part of Ser. No. 844,580, Oct. 25, 1977, abandoned, said Ser. No. 42,605, is a continuation-inpart of Ser. No. 844,719, Oct. 25, 1977, abandoned.
 Int. C1.3 G06K 9/00; G06K 9/20
 U.S. CI 356/71
 Field of Search 356/71, 371, 394, 446,
356/448; 350/146.3 E; 250/566
 References Cited
U.S. PATENT DOCUMENTS
3,443,098 5/1969 Lewis 350/485
3,627,991 12/1971 Beall et al 356/71
3,865,488 2/1975 Del Rio 356/71
4,120,585 10/1978 DePalma et al 356/71
Primary Examiner—William H. Punter
Attorney, Agent, or Firm—McAulay, Fields, Fisher,
Goldstein & Nissen
A finger pressed against a platen provides a fingerprint object which is scanned by an interrogating beam of collimated light in the form of a slit and that is linearly displaced across the platen. As the slit-beam scans across the back surface of the platen, the reflected light beam is modulated. The modulated beam is imaged onto a linear array of photodiodes to provide a series of output signals indicative of modulation information. The outputs of the diodes are serially interrogated at each of successive scan positions to provide a set of signals containing fingerprint information. The platen has a transparent glass base. A layer of transparent, compressible, resilient epoxy is on the back of the glass base. The epoxy layer has a flat back surface. A thin silver reflecting layer on the back surface of the epoxy provides a flat mirrored surface to reflect the light beam. A further epoxy layer on top of the silver provides mechanical filtering. A lacquer layer at the back protects the platen from wear. When a finger is applied to the back surface, the ridges of the finger distort the underlying layers sufficiently so that the reflected light at the ridge zones is scattered while the reflected light at the valley zones is collimated. This difference in scatter is transformed by an imaging lens to a difference in intensity at the diode array.
12 Claims, 9 Drawing Figures
U.S. Patent Mar. 30, 1982 Sheet 1 of 2 4,322,163
U.S. Patent Mar. 30, 1982 Sheet 2 of 2 4,322,163
REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of the fol- 5 lowing applications: (a) now abandoned co-pending application Ser. No. 042,605 entitled "Fingerprint Processing Method and Apparatus", filed May 25, 1979 which patent application is in turn a continuation-inpart of now abandoned application Ser. No. 844,719 10 having the same title and filed Oct. 25, 1977; and (b) now abandoned co-pending application Ser. No. 891,497 entitled "Finger Identification" filed Mar. 20, 1978, which patent application is in turn a continuationin-part of now abandoned application Ser. No. 844,580 15 entitled "Fingerprint Processing Apparatus" filed Oct. 25, 1977.
BACKGROUND OF THE INVENTION
This invention relates generally to a finger identifica- 20 tion and finger image processing apparatus. More particularly it relates to apparatus and method for encoding finger image information into machine readable language with apparatus that is simple, inexpensive and reliable. 25
There are a number of systems that have been proposed for the processing of identification information based on the unique configuration of ridges and valleys in an individual's finger. When such information is taken from an ink impression of an individual's finger it 30 is normally called a fingerprint. The more sophisticated techniques that employ optical techniques tend to provide a more refined, discriminate and accurate identification image; which image applicant has frequently called a fingerpress in order to distinguish it from the 35 more primitive ink fingerprint. However, since both are based on the same unique ridge and valley finger characteristics, it should be understood that the term fingerprint is used by applicant generically while the term fingerpress is used to refer to the actual configuration of 40 the ridges and valleys of the finger when pressed against a surface or to the fairly precise image of such that can be obtained by using certain optical systems. In these optical systems, the finger of the subject individual is placed against the back of a transparent platen and the 45 normally flat finger image on the back surface of the platen is imaged through the front of the platen and projected onto a receiving or processing equipment. This receiving equipment may take the form of a screen, of a camera or of an array of photocells. 50
For example U.S. Pat. No. 3,138,059 discloses such a system. As described in the '0.59 patent, the finger is pressed against a transparent platen and a light beam is projected against the platen. Light is reflected from the finger to a recorder in the form of a camera. U.S. Pat. 55 No. 4,053,228, issued on Oct. 11, 1977 discloses a holographic identification system the disclosure of which is incorporated herein by reference. As described in the '228 patent, a collimated, coherent light beam is projected against the front surface of a transparent platen. 60 The light is reflected from the back surface of the platen, against which surface the subject's finger is pressed. The reflected light beam is modulated with the finger image and is correlated against a hologram of the same fingerpress to provide identification. 65
However, systems of this type suffer from a number of disadvantages, formost among which is a high degree of inaccuracy. That is, mismatching can easily occur
between the hologram and the image. Mismatching error is reduced by employing accurate alignment procedures but this solution increases the cost and complexity of the system. Aside from the question of alignment apparatus, such systems are extremely expensive as they require beam splitters, devices to change direction of the light beams, focusing lenses, devices to effect the necessary correlations, etc. Additionally, these systems are difficult to maintain and service because of the number of elements comprising the systems and the fact that even the slightest vibration can knock a lens or a mirror out of position.
Accordingly, it is a major purpose of this invention to provide a technique for processing a fingerprint or finger image in a fashion that is simple and unambiguous, that avoids undue messiness, provides a high degree of reliability in operation and that can be implemented in equipment which is relatively trouble free and that requires a minimum of maintenance.
It is a further object of this invention to provide all of the above mentioned objects in a system that provides an accurate and unambiguous finger image or fingerprint image which in turn is susceptible to being encoded into machine readable signals.
In the holographic systems, stringent requirements are placed on the platen. The surfaces of the platen must be completely flat to minimize inaccuracies introduced into the reflected light beam. In general, where a lot of light is lost and where the contrast between the ridges and valleys in the image is low, the platen must be an expensive precision unit.
In addition, build up of finger oil introduces inaccuracies into the system. Often, a latent image is fixed to the platen by the finger oil residue on the platen. The operator must maintain the platen clean by wiping it after each use. However, even if the platen is clean, these systems are sensitive to either too much or too little oil from the finger. Either case may produce erroneous results. Other problems occur when the platen is cold and a warm finger is placed against it. This fogs the platen. While a platen may be preheated to eliminate this problem, such a solution is impractical.
Accordingly, a further object of this invention is to provide a highly accurate and reliable finger identification and processing apparatus that includes a relatively inexpensive platen.
Another object of the invention is to provide a finger receiving platen, for such an apparatus, that is insensitive to the amount of oil on a finger.
A further object of the invention is to provide optical fingerprint processing apparatus with greatly enhanced optical contrast between the valley zones and the ridge zones of the finger image.
In brief, a laser provides an interrogating light beam which is shaped by two cylindrical lenses into a slitbeam of light. This beam is collimated and scanned across a finger placed against a platen. The finger is pressed against the back surface of the platen and provides a fingerprint object that is constituted by a series of ridges and valleys. The beam is directed towards the front surface of the platen, at a slight angle to normal, and passes through the transparent substrate of the platen to be reflected from the fingerprint object as a modulated beam. The platen may have a deformable resilient layer that conforms to the pattern of ridges and