Economical skin-pattern-acquisition and analysis apparatus for access control; systems controlled thereby

Surface relief of a finger etc. is read using an optical-fiber prism unit, with fiber terminations at one end to contact the surface, and at the other for light passage along fibers from the first. Light enters where NA<0.5 and fiber diameter is constant with longitudinal position. The device is in a 1.4-2 L case, with a battery or power input, converter to form a corresponding data array for verifying, digital signal processor to do the verifying, and output to indicate or implement a decision. A video controller (with custom-programmed logic circuit) operates the sensors to develop the data array; an ADC digitizes the array; memory holds an authorized-user skin-pattern template, firmware for the processor, and data used in verifying; an output register holds the decision signal--all on a control, address, and data bus. High-power, radiative elements and a fast high-impedance data reader are on a common board in an isolating layout. The prism unit is cylindrical, held by a cylindrical-section cradle and forming a novel condenser lens to support lights and couple light to the prism. The imager has a cylindrical wall, transverse face for output of a skin pattern, and angled elliptical face to contact skin. To make many optical-fiber prisms each with one transverse and one angled face, transverse and angled cuts through a fused-fiber cylinder are alternated. The verifier can be within, and respond to the analysis to control, a door handle or lock: a hand need not move from reading position to open the door.

FIELD OF THE INVENTION 
This invention relates generally to automatic acquisition of skin-patterns 
(such as fingerprints), and other relieved-surface images, for access 
control--and to systems whose access is controlled by such automatic 
fingerprint etc. acquisition. The invention relates more particularly to 
fiber-optic prism systems for such fingerprint acquisition, and to 
cooperating mechanical and electrical provisions for both enhancing the 
identity confirmation and deterring circumvention of the identity 
confirmation. 
Systems to which access is controlled in accordance with the present 
invention include personal weapons, other apparatus, facilities, financial 
services and information services. 
BACKGROUND OF THE INVENTION 
Very extensive discussion of the prior art appears in Bowker, mentioned 
above, and is earnestly commended to the attention of the reader. That 
discussion includes in particular a summary of previously known 
fingerprint techniques employing either frustrated total internal 
reflection (FTIR) or fiber-optic prisms. These topics will be only briefly 
summarized here. 
FTIR technology--In FTIR work, a so-called "critical angle" establishes key 
angular relationships between incident light and light-collection 
directions, for so-called "bright field" and "dark field" systems. As 
explained at length in Bowker, the critical angle is defined either by 
arcsin (1/n) or by arcsin (n'/n), both special cases of Snell's Law in 
which n represents the refractive index of the solid material of an 
optical block. 
The first expression applies when air is at the surface of the block; the 
second, when some other medium is juxtaposed against the block--in which 
case n' represents the refractive index of that other medium. Conventional 
FTIR fingerprint systems direct incident light to a block surface, from 
within the solid material, at an angle which is intermediate between the 
critical angles for air and for typical biological materials such as skin 
or flesh, and water. 
If no finger is present, or if a finger is present but a light ray strikes 
the surface at a groove of the fingerprint, then the light under 
consideration is all internally reflected into the block, from which it 
can be detected by a suitably positioned sensor. If instead a light ray 
strikes the surface at a ridge of a fingerprint, then part of this light 
passes through the surface and into the material of the finger where it is 
scattered diffusely--a certain fraction reemerging from the finger into 
the block, from which it, too, can be detected by a suitably positioned 
sensor. 
The two suitable positions are quite different, leading to two different 
operating modes: a "bright field" mode in which the sensor is positioned 
to capture internally reflected light at air-filled fingerprint grooves 
(creating a bright field against which fingerprint ridges appear as 
relatively dark stripes), and a "dark field" mode in which the sensor is 
positioned to avoid capturing internally reflected light (in which case 
fingerprint ridges appear as relatively bright stripes of scattered light, 
against a dark field). 
Dark-field systems, as explained at length in Bowker, are generally 
preferred for their higher contrast--ease of distinguishing ridges from 
grooves--and also from considering the ratio of signal to noise. 
Dark-field contrast is generally about unity, but bright-field contrast 
can be as low as about 1/7, with a proportionately lower signal-to-noise 
ratio. The only way to compensate in a bright-field system is to increase 
the exposure (that is, the light level or time, or their product) by about 
7.sup.2 =forty-nine times. 
As also noted in Bowker, earlier FTIR systems require a focal element such 
as a lens to image the FTIR data onto a detector array or scanning 
detector--but a lens has undesirable properties including focal distances 
ranging (for practical cases of interest) from very roughly 7 cm, with no 
magnification or reduction, to over 10 cm if magnification or reduction is 
needed. 
A lens system is also susceptible to depth of field and distortion, 
particularly severe if the lens and object plane are not reasonably 
parallel and conaxial--as is typical in bright-field devices. Such systems 
have different magnifications, and severely divergent focal positions, 
too, at top and bottom of the fingerprint image, leading to complications 
in later interpretation of the acquired image. 
Prior-art fiber prisms--Also discussed in Bowker are two prior patents 
proposing substitution of a fiber-optic prism for a clear prism, as a 
dark-field FTIR fingerprint collection block in a fingerprint reader: U.S. 
Pat. Nos. 4,785,171 and 4,932,776 of Dowling et al. Those patents appear 
to include several misunderstandings of the physical phenomena involved, 
leading to configurations that are very inefficient and marginally 
operative. 
In his first patent, Dowling retains a collection lens spaced from the 
prism face, and injects light into his system at this same output face of 
his fiber-optic prism. This configuration is very vulnerable to scattering 
of the bright incident light by contamination at the common input/output 
face. 
Dowling's '776 second patent acknowledges this problem, and teaches use of 
a fiber-optic taper, integral with the fiber prism, to match the print 
image to a relatively small CCD array. It also teaches--instead of the 
spaced-lens configuration with injection and detection at the same end of 
the fiber-optic element--attaching a CCD array directly to the end of the 
fiber taper remote from the finger, thus entirely eliminating the lens and 
associated optical gap. 
The fiber core has refractive index 1.62 and the cladding 1.48, yielding 
against air a moderately high numerical aperture NA=0.66 and critical 
angle of about 38.degree.. This choice is conventional for obtaining good 
light-gathering power, although many skilled artisans in this field would 
prefer a considerably higher numerical aperture. 
(For the majority of current applications involving fused-bundle faceplates 
or image conduits, glasses with numerical apertures of 1.0 and 0.66 are 
used. Fused-bundle materials are also available with a very few other 
numerical-aperture values such as 0.95, 0.85 and 0.35; however, 0.95 or 
0.85 faceplate material is not always available, and 0.35 is typically run 
"infrequently due to lack of demand"--see for example "Fiber Optic 
Faceplate Data", Incom, Inc., Southbridge, Mass.). 
Here Dowling sets out to apply the full capabilities of the tapered fiber 
prism to shorten the optical system, erect the image plane (supplying an 
image that is merely anamorphic but in uniform focus and free of major 
aberration), and eliminate or minimize effects of contamination and 
jarring. Unfortunately, however, Dowling's fiber prism is covered by a CCD 
at one end and a finger at the other, leaving no suitable entry point for 
illumination. 
Dowling attacks this problem with three alternative tactics: 
transillumination of the fingertip, implanting lamps in the sensor end of 
the fiber prism, and directing light into the sides of the prism. It is 
shown in Bowker that all three suffer from major defects: very evident 
ones in the case of the first two tactics, and somewhat more subtle but 
still debilitating problems in the third. 
As to the third tactic, illumination is specifically from the narrower 
sides of the taper--propagating toward the finger-contacting surface to be 
illuminated. In particular his illumination is directed into portions of 
the taper where fiber diameter is changing rapidly with respect to 
longitudinal position (i. e., the part of the taper that is actually 
tapered). 
Analysis indicates that this Dowling system will at best work very poorly, 
and most likely not at all. In particular, the efficiency of light 
injection in this manner is extremely poor, and also would require a taper 
with no absorbing material outside the individual-fiber walls (usually 
designated "extra-mural absorbing" or "EMA" material)--thereby leading to 
severe fogging of the image. 
If Dowling's apparatus has actually been made and operated, it must operate 
at the very bounds of usability--a power-hungry system working with small 
tail-end fragments of the input light that almost accidentally make their 
way to the fingerprint contact. It must have a low signal-to-noise ratio, 
due to massive diffusion of the backscattered light along the return path. 
The fiber-prism systems of Bowker--Bowker describes a solution using 
optical-fiber prism means that are crosslit. The prism means may be simply 
an optical-fiber prism, or may be a combination of such a prism with other 
elements such as an optical-fiber taper. 
Light enters the prism means in a region where the fiber diameters are 
substantially constant with respect to longitudinal position, for lighting 
the fiber terminations where a fingertip is applied. Such illumination is 
enabled by use of a fiber prism in which the numerical aperture (NA) is 
radically low--by any of several different measures. 
The NA preferably does not exceed one-half, and even more preferably does 
not exceed 0.42, and a preferred value that is available commercially is 
0.35--at least in the region where the light crosses the fibers. The 
constraint on NA is also expressed in terms of other parameters. 
In certain circumstances the prism means, at least in a region where the 
light crosses the fibers, have a numerical aperture NA that satisfies this 
maximum condition: 
EQU NA.ltoreq.2n.sub.avg (D/x.sub.F).sup.1/4, (Eq. 1) 
where 
n.sub.avg =average of core and cladding refractive indices in that region 
of the prism means; 
D=periodicity of the fiber structure in that same region; and 
x.sub.F =illumination-path distance across the prism means in that region, 
and the conventional notation (D/x.sub.F).sup.1/4 means the fourth root of 
the ratio D/x.sub.F. 
In other cases, particularly having opposed light sources to illuminate the 
fiber terminations from both sides of a square-cut-off prism, preferably 
the prism-means numerical aperture is small enough--at least where the 
light crosses the fibers--that the projected light which crosses the 
entire prism means, from each side, has at least one hundredth of the 
respective initial intensity. 
Alternatively, at least in a region where the light crosses the fibers, the 
numerical aperture satisfies a modified form of Eq. (4), 
EQU NA.ltoreq.2n.sub.avg (D/x.sub.M).sup.1/4, (Eq. 2) 
where 
x.sub.M .ident.illumination-path distance across the prism means to the 
prism midplane, in the same region. 
Forms and variants of the teachings in Bowker include both bright- and 
dark-field systems, in many different prism configurations. One aspect of 
those teachings includes illumination by means of a partial reflector at 
an end of the prism means. 
Placing fiber-prism images on a sensor--In Bowker it is also taught that a 
sensor is advantageously mounted directly to the prism means--either 
directly to a primary prism that receives the fingertip whose pattern is 
to be analyzed, or directly to a fiber-optic taper that reduces the 
fingerprint image size for use with a much smaller sensor. These two forms 
of the sensor mounting taught in Bowker represent tradeoffs of the 
relatively high cost of sensors against the relatively high cost of 
tapers. 
As pointed out in that document, the present price of even a relatively 
small detector if implemented as a conventional charge-coupled detector 
(CCD) array, is high enough to constitute the major cost element in 
apparatus according to the invention. A larger detector--the size of a 
fingerprint image--is prohibitively expensive for most applications. 
This is the motivation for considering tapers even though a taper in turn 
disadvantageously adds to the weight, size and cost of the apparatus. At 
the time of writing of Bowker, however, the CCD cost advantage in 
provision of a taper in many cases was more than offset by the incremental 
cost of the taper--even without considering the weight and size penalty. 
At that time, it was not possible to predict reliably whether eventual cost 
relief should be expected in the detector or in the taper, or in neither. 
Unfortunately at the present writing, more than a year and a half later, 
that situation has not changed. 
Accordingly for most miniaturized applications the trade-off solutions 
taught in Bowker remain uneconomical. It is still anticipated that those 
solutions will in time become practical, as the price of conventional 
crystalline-silicon CCD arrays in this size range may fall--perhaps 
partially in response to competition for usage in apparatus according to 
the present invention--or an alternative optical detector, such as for 
instance a self-scanned diode ("SSD") array or thin-film (noncrystalline) 
photosensor arrays, may become available at significantly lower cost. 
Meanwhile a practical package embodying the better-illuminated fiber-optic 
prism taught in Bowker has not appeared, heretofore. 
Self-contained print verifiers--While many fingerprint analyzers are 
available in desktop or countertop modules, no prior art teaches a 
satisfactory fingerprint reading and analyzing apparatus that is self 
contained (which, for purposes of this document, is to be understood as 
meaning at least self contained except for power source). Such apparatus 
is a necessary first step toward real-time fingerprint verification 
systems operable within either hand weapons or other tightly constrained 
volumes such as mentioned below. 
Extremely small, self-contained print verifiers present special challenges: 
extremely high optical, electronic and logical precision are required in a 
tiny but rugged system--at very low price. These challenges have not been 
adequately addressed in the art. 
Data isolation and incompatibility--A special problem of such 
self-contained systems is how to make the greatest use of data. This issue 
arises because system operations include taking original data, both from 
authorized users and candidate users. 
In either of these cases, information about the fingerprint that has been 
read by the apparatus may later be needed or desirable for other purposes. 
Such use was previously suggested in connection with anamorphism in the 
data. 
First, where a home or business has many locks, it may be desirable to take 
authorized-user data just once--using just one of the locks--and then 
electronically copy the information into all the others. Second, 
law-enforcement agencies may have a particular use for such data. 
This latter situation may arise for example when a facility has been 
entered forcibly and there is reason to believe that the intruder first 
attempted to operate the fingerprint-controlled lock. It may also arise 
when a person who has been an authorized user steals from the controlled 
facility, or commits some other crime--whether there or elsewhere. Other 
possibilities arise when an authorized user, for example a missing child, 
is not likely to have been otherwise fingerprinted. 
Data export can be a problem in particular when a system operates using 
multilevel data, or using data in a special form such as sinusoidal or 
Fourier-transform data--as is the case for instance with Thebaud's, 
mentioned previously. Exporting such data may not be useful if the 
receiving application (such as law enforcement) that could use the 
underlying information operates on data in more-conventional formats. 
Door applications--While addressed broadly to many applications of a 
fingerprint reading device, Bowker gives particular attention to the 
configurations suited for use in guarding a weapon--particularly a small 
hand weapon. Mainly because of the cost considerations discussed above, 
hand-weapon applications appear to remain for the present just slightly 
beyond the range of economic development in commercial exploitation. 
A market that is much more practical in view of the apparatus sizes that 
can be installed, and also taking into the number of now-unguarded units 
in use, is the protection of doors--and more particularly door handles. 
Although still small, a typical door handle and its associated lock have 
(at least potentially) several times greater volume for installation of 
security equipment than does a typical hand weapon. 
Accordingly it is believed that the prior art has not adequately attended 
the opportunities for optical skin-pattern readers in direct association 
with doors, door handles and doorknobs. 
Numerical aperture of tapers--In Bowker it is taught that a taper used in 
the invention should be of relatively very high NA, certainly well over 
0.5, to compensate for the intrinsic degradation in light-transmitting 
power associated with the image-reduction capabilities of a taper--and 
thereby allow transmission of enough optical energy to match the main part 
of the prism. The degradation is proportional to the square of the 
reduction; thus for example it is said that a two-times reducing taper 
should have NA.gtoreq.0.66, a three-times taper NA.gtoreq.1.05, and a 
four-times taper NA.gtoreq.1.4, in conjunction with a main-prism NA of 
0.35. 
This teaching, however, has since been recognized as partly in error. If a 
high-NA taper is employed to receive the optical image signal from a 
low-NA main prism (at least if this is done without special precautions), 
longitudinally diffusing stray light in the prism section can enter the 
taper. Such diffusing stray light arises, at the fingertip-contacting end 
face of the prism, from the excitation illumination which is reflected by 
that end face at steep angles relative to the fiber axes. 
If the main prism is short, this adverse effect is aggravated--because the 
longitudinally diffusing stray light does not have adequate longitudinal 
diffusion distance in which to escape from the system, before reaching the 
taper. Since a high-NA taper by definition has high ducting capability, 
the stray light even though angled steeply--beyond the ducting range of 
the main prism--once into the taper is all carried to the sensor. 
Such a result is undesirable because the diffusing stray light is 
uncorrelated with the signal in each fiber, and so badly fogs the image. 
The stray light can be quite bright, particularly in dark-field cases 
where it arises from the specularly reflected, unmonitored bright 
background. 
Therefore new measures are needed to accommodate the poor optical 
signal-to-noise phenomena associated with feeding a high-NA taper from a 
short, low-NA main prism. 
Applications--More generally the art has not heretofore provided an 
economical optical fingerprint reader module that is amenable to 
microminiaturization for access control in highly demanding field 
applications, particularly including common doors and door handles as well 
as personal weapons--and also encompassing access to use of portable 
computers and phones. 
Time-and-attendance systems, database access systems, public phones, phone 
credit systems, vehicles, automatic tellers and facility-entry access 
devices, although not as critical as portable personal equipment or 
self-contained door-handle systems in terms of size, time, power, 
identification certainty, etc. would also be meaningfully enhanced by 
provision of a self-contained microminiaturized reader. 
As now seen, the art has not yet provided solutions to important problems; 
and important aspects of the technology in the field of the invention are 
amenable to useful refinement. 
SUMMARY OF THE DISCLOSURE 
The present invention introduces such refinement, and corrects the failings 
of the prior art. Before offering a relatively rigorous discussion of the 
present invention, some informal orientation will be provided here. 
1. ORIENTATION 
It is to be understood that these first comments are not intended as a 
statement of the invention. They are simply in the nature of insights that 
will be helpful in recognizing the underlying character of the prior-art 
problems discussed above (such insights are considered to be a part of the 
inventive contribution associated with the present invention)--or in 
comprehending the underlying principles upon which the invention is based. 
The system described in Dowling '776 is inoperative, or marginally 
operative, for these four main reasons--discussed at considerably greater 
length in Bowker: 
(a) Light should be injected at a favorable place--Illumination should be 
injected so that it passes through the side wall immediately adjacent to 
the end-surface terminations. Light should not rely on passage ductwise 
along the fiber, but instead directly strike terminations immediately 
after passage through the side wall--with no ducting reflections. 
This principle applies whether the terminations under consideration are 
those which contact fingertips or are partial reflectors at an opposite 
end of the prism means. The Dowling '776 system departs from this 
requirement. 
(b) Light should be injected at a favorable angle--The illumination should 
first enter each fiber: 
at the proper angle for FTIR operation (or reflection, as the case may be) 
at the fiber termination; and 
at an angle to the fiber which is not favorable to direct entry of the rays 
into a ducting mode. 
Dowling's teaching of injection at "30.degree. to 45.degree. relative to 
the! major longitudinal axis" is ambiguous as to the first of these 
requirements, for he seems to state the angle outside the prism, not 
inside--and the effective incidence angle at the fingertip-contacting 
surface is hard to divine from the information he provides. He does, 
however, make plain his objective of initial ducting for injected light, 
directly contradictory to the second condition stated here. 
(c) The fiber prism should be of a favorable material--To avoid effective 
attenuation of FTIR-usable illumination, and nonuniformity of illumination 
across the field, and also associated image fogging and light loss, it is 
essential to choose fiber-prism material of suitable numerical aperture 
NA. Attenuation length for diffusion across a fiber prism varies, roughly, 
inversely with the fourth power of the NA. 
The attenuation length (2n.sub.avg /NA).sup.4 D/2 establishes the rate at 
which FTIR-usable intensity falls off with penetration depth. (Here 
n.sub.avg is the average of the core and cladding refractive indices in 
the crosslighting region of the prism, and D the periodicity of the fiber 
structure in the same region.) 
Using this very approximate relation, attenuation length can be estimated 
at very roughly 2 mm for NA=0.66, or 21 mm for NA=0.35. Ability to 
effectively crosslight a prism thus depends very strongly on selection of 
a material with suitably low numerical aperture. 
This is so, as shown in Bowker, whether light is injected from both sides 
of a prism or only one, and whether in dark- or bright-field mode. 
Effective lighting, even if from two sides, is infeasible at Dowling's 
indicated NA=0.66: only the tiniest fraction of incident energy is 
available for good FTIR operation, even halfway across the fiber prism, 
and nonuniformity amounts to a factor of about five thousand between the 
extreme values. 
Low NA, however, readily yields astonishingly high FTIR-usable intensity at 
a midplane and uniformity good within a factor of 1.4 across the full 
breadth of the prism means. Comparably excellent results arise with 
unidirectional lighting. 
In addition, at least the injection segment of the prism should be free of 
extramural-absorption material. 
(d) If a taper is used, it should be a separate element from the 
prism--Whereas the prism should have low NA to minimize attenuation, and 
should be free of EMA material, two opposite considerations apply to the 
taper. 
To constrain light within its waveguiding boundaries and minimize 
crosstalk, and also to match energy flow through the main prism, as 
mentioned earlier the taper should have high NA and should include EMA 
material. Since the prism and taper thus have diametrically conflicting 
design requirements for practice of the present invention, they are best 
fabricated as separate elements. 
In addition to the above-listed four considerations relative to Dowling, 
the present document introduces these further new developments relative to 
the teachings in Bowker: 
(e) Focal elements to relay image from prism to sensor--For the present, in 
view of the adverse economics both of sensors and of tapers, an interim 
solution is needed. Whereas one ideal would be a low-resolution CCD-like 
element, meanwhile we prefer to use a focal system--preferably two lenses, 
or two mirrors. 
None of these is fully satisfactory, but such solutions are currently 
preferred to a sensor or taper. It is contemplated that, for higher volume 
manufacture of the invention in the future, custom sensors may become 
available. 
(f) Template abstracting for storage, input to or output from 
self-contained reader--Some utilization means inherently serve a small 
number of authorized users, for example just one or two. Representative 
examples include a personal weapon, personal computer or vehicle, etc. For 
this case a correspondingly small number of templates are to be stored, 
and it may be best to store them in fully ready-to-use form--with as much 
preprocessing as possible done in advance to minimize decision-making 
time. 
Where multiple users--for example, a hundred--must be accommodated, 
however, and slight added decisional delay can be tolerated, it is 
preferable to minimize storage or data-transmission costs by placing 
templates in abstracted form such as binary or trinary form (one- or 
two-bit data). In such situations it is desirable to prefilter, smooth and 
normalize the data before such preparation for storage or transmission--to 
be certain that the level-downsampling process does not settle upon 
nonrepresentative data points. 
Similarly after data are recovered from storage, or received by 
transmission from an external source--assuming that in the actual 
verification processing the data are used in multilevel form--the data 
should be refiltered and smoothed, to eliminate spurious abrupt changes 
(high-spatial-frequency components) in the image. 
These considerations apply whether the mode of loading data into the 
apparatus is to retrieve the data from storage, or read them in from a 
remote data bank, or read them in from (for example) an identification 
card carried by the candidate user. In the latter case, the data might be 
held in a magnetic strip or two-dimensional bar code, or in other ways. 
The overall decision as to data formatting for storage (or transmission) 
depends upon the balance between urgency of decision, as for example in 
the weaponry case, and cost of storage or data transmission. In a great 
majority of present applications, transmission and storage are the 
more-limiting considerations. 
(g) Mechanical system for self-contained reader--Representative prior 
systems occupy housings well in excess of four liters. The present 
invention, however, combines extraordinarily compact optical, mechanical 
and electronic subsystems that enable overall reduction to well under two 
liters. 
In the now-preferred embodiment the total system volume, excepting only an 
external power connection when used, amounts to less than 1400 cubic 
centimeters. The optomechanical aspects of this achievement call for an 
optical bench that is unusually compact but without compromise of 
decisional accuracy--and that is well integrated with the electronics. 
In addition the optomechanical system uses a novel fiberoptic prism that is 
cylindrical, with light-transmitting input and output surfaces essentially 
at forty-five and ninety degrees to the longitudinal axis of the cylinder 
(i. e., the socalled "cylindrical axis"). These prisms are fabricated very 
economically, cut as a series of opposed units from a common optical-fiber 
cylindrical rod. 
(h) Electronic system for self-contained reader--The system uses extremely 
intensive data processing that is able to make use of essentially all the 
skin-pattern information that can be collected. This requires a very 
large, high electrical-power processor, and for most effective use of 
modern componentry this in turn requires high-power switching-type power 
supplies. 
Such a processor, and such power supplies, radiate electromagnetic 
interference copiously. Commonly such situations are approached by 
incorporating physical shielding, massive signal filtering, and placement 
of components on different boards to isolate them. 
In the present invention, however, these components must share a very small 
housing with an extremely sensitive, high-impedance detector--and with 
other components which effect data transfer from that detector into the 
processing circuits at bit-transfer rates of multiple megahertz. Such 
signal bandwidths are comparable to those of the radiated noise, 
effectively obviating the option of front-end signal filtering. 
Furthermore space and weight objectives preclude conventional shielding. 
These onerous obstacles have been overcome by an ingenious layout of all 
the components on a common surface-mount circuit board that minimizes 
their interaction and enables excellent operation without separate boards, 
shielding or filtering. The most troublesome component interactions are 
avoided by placing the components involved--the power supplies and the 
sensor--at opposite corners of the board. 
(i) Doorway access control--Although weaponry applications are exceedingly 
interesting and of course have a certain glamour, it has been observed 
that the world contains many more doors than handguns. Therefore in a 
sense the door market is much more important. 
In this regard, the present invention introduces new ways of marrying 
fingerprint-reading modules with door handles and doorknobs, so that the 
combination natural and easy--in other words, ergonomic--to use. 
2. MORE-FORMAL DISCUSSION 
Now with these preliminary observations in mind this discussion will 
proceed to a perhaps more-formal summary. The invention has several 
independent aspects or facets. 
(a) A FIRST ASPECT of the invention--In preferred embodiments of a first of 
these aspects, the present invention is apparatus for acquiring 
surface-relief data from a relieved surface such as a finger. 
The apparatus includes prism means formed from optical fibers. (A fused 
bundle of fibers is much preferred to unfused fibers, as the latter--with 
their high-index-differential boundaries between glass and air--attenuate 
crosslighting much more rapidly.) The prism means in turn include a first 
end and a second end. 
As will be seen, the phrase "prism means" is primarily used to encompass 
important embodiments of the invention in which two or more fiber-optic 
optical elements in series are included in the optical assembly. 
The first end comprises terminations of the fibers for contact with the 
relieved surface. The second end comprises opposite terminations of the 
same or corresponding fibers. 
By "corresponding fibers" here is meant fibers of a second element that may 
be in series, as mentioned just above. Such a fiber receives light from 
the fibers in the first element. 
A "corresponding fiber" typically is only very roughly aligned with any of 
the fibers in the first element, so that in practice the light from each 
fiber in the first element may pass into several fibers of the second--and 
each fiber of the second element typically receives light from several 
fibers of the first. These effects somewhat degrade image resolution, but 
can be made inconsequential by using prism materials in which the fiber 
spacing is sufficiently finer than the fingerprint ridge spacing. 
The second end of the prism means is for passage of light traveling along 
the fibers from the first end. 
Preferred apparatus according to the first aspect of the invention also 
includes means for projecting light across the fibers in a region where 
fiber diameter is substantially constant with respect to longitudinal 
position, for lighting the first-end terminations. For breadth and 
generality in discussing the invention, these means will be called the 
"light-projecting means" or simply "projecting means". 
Even though the projected light crosses the fibers and is "for 
illuminating" their first-end terminations, in some forms of the invention 
as will be seen it does not necessarily illuminate them directly or 
immediately upon fiber entry. 
A light fraction that is dependent (i. e., whose magnitude is dependent) on 
contact between the relieved surface and each illuminated first-end 
termination is ducted from that termination along its fiber. (By "its 
fiber" is meant the fiber which is terminated by the termination.) 
The present invention enables such passage of light, to and from the 
finger-contacting end of the prism means, to proceed successfully 
according to the well-known principles of FTIR introduced earlier in this 
document--despite use of fiber-optic prism means. 
In addition the apparatus includes some means for receiving--at the 
prism-means second end--each light fraction from the first end, and in 
response forming an electrical signal which is characteristic of the 
surface relief. Such means accordingly have an electrooptical character; 
here too for generality and breadth these means will be called simply the 
"electrooptical means". 
The apparatus further includes focal means for relaying each light fraction 
at the second end to the electrooptical means. The phrase "focal means" 
encompasses one or more lenses, one or more mirrors, or combinations of 
these. 
The foregoing may be a description or definition of the first aspect of the 
present invention in its broadest or most general terms. Even in such 
general or broad forms, however, as can now be seen the invention resolves 
the previously outlined problems of the prior art. 
In particular, because the light is injected in a region of the prism means 
where fiber diameter is substantially constant with longitudinal 
position--rather than in the changing-diameter region of a taper--this 
invention avoids the severe inefficiency (and at least marginal 
inoperability) of the Dowling '776 system. 
By avoiding injection into a tapered region, the present system enables 
illumination to reach crosswise, without being ducted through the fibers, 
to the fibers whose terminations are to be lighted. In fact the light can 
directly reach either (1) those terminations or (2) certain other 
terminations which reflect light directly along the fibers toward those 
finger-contacting terminations. 
This is a far more systematic, controlled, efficient optical-energy 
coupling arrangement. Furthermore, because of the selection of an 
untapered region for light injection, the light can be projected crosswise 
into the prism directly toward the optical-interaction points (or directly 
toward reflection sites whence it is in turn projected directly 
longitudinally toward the optical-interaction points). In consequence, 
essentially all the light which reaches the first-end terminations can 
satisfy FTIR requirements. 
This invention accordingly avoids the catch-as-catch-can energy usage which 
can result (as for example in Dowling '776) from illumination that is 
haphazard with respect to the relationships of frustrated total internal 
reflection. 
Use of focal elements enables enjoyment of the crosslit fiber-prism 
benefits without the cost penalty of a taper or a large CCD. 
Although the invention thus provides very significant advances relative to 
the prior art, nevertheless for greatest enjoyment of the benefits of the 
invention it is preferably practiced in conjunction with certain other 
features or characteristics which enhance its benefits. Among these are 
preferred embodiments including bright-and dark-field configurations such 
as described at very great length and in very great detail in Bowker--but 
now with focal means included. 
(b) SECOND through SIXTH ASPECTS of the invention--All of the foregoing 
summary of the invention has been presented in terms of the first main 
facet or aspect of the invention. In second through sixth such aspects, 
the invention is related to the first--but these forms of the invention, 
discussed in this section (b), are not necessarily limited to injection of 
light into a region where fiber diameter is substantially constant along 
the fibers. 
In this second aspect of the invention, however, an angled partial 
reflector intercepts light projected in through a prism input face. The 
reflector redirects that light to illuminate the fiber terminations at the 
data-input (finger contacting) face. 
In a third aspect of the invention, the numerical aperture is constrained 
to not exceed the value found from Eq. (1) or (2)--depending on whether 
illumination is projected through one side face or more than one. 
In a fourth of its facets or aspects, the invention is related to the third 
aspect--but the numerical aperture, rather than being defined by Eq. (1) 
or (2), does not exceed one-half. 
In a fifth of its facets or aspects, too, the invention is related to the 
second and third aspects--but the numerical aperture, rather than being 
defined by Eq. (1) or (2), is defined more stringently by a like equation 
but with an inserted factor of 2 in the denominator of the fourth-rooted 
function. 
In a sixth of its facets or aspects the invention is like-wise related to 
the second and third aspects, but the numerical aperture is defined more 
stringently as not exceeding 0.42. 
(c) A SEVENTH ASPECT of the invention--In a seventh aspect or facet, the 
invention is apparatus for acquiring and using surface-relief data, from a 
relieved surface such as a finger, for controlling access to facilities, 
equipment, a financial service or information. 
This apparatus includes in its entirety the first aspect of the 
invention--in other words, the above-discussed apparatus for acquiring 
surface-relief data from a relieved surface such as a finger. Here, 
however, the electrooptical means have enlarged functions. 
In this case they not only receive at the second end of the prism means the 
light fractionally directed into the fibers at the first end, and process 
the received light to determine identity of the relieved surface, but in 
addition the electrooptical means apply the determined identity to control 
access to the facilities, equipment, financial service or information. 
(d) AN EIGHTH ASPECT of the invention--In still an eighth of its major 
aspects, the invention is a secured system subject to access control based 
upon surface-relief data from a relieved surface such as a finger. 
This system includes utilization means, susceptible to misuse in the 
absence of a particular relieved surface that is related to an authorized 
user. These utilization means are a facility, an apparatus, some means for 
providing a financial service, or some means for providing information. 
In addition this system of the eighth aspect of the invention includes in 
its entirety the data-acquiring-and-using apparatus according to the 
seventh aspect of the invention, as set forth just above. Here the 
electrooptical means apply the determined identity to control access to 
the utilization means which are part of this system. 
(e) A NINTH ASPECT of the invention--Here in its preferred embodiments the 
invention is self-contained apparatus for skin-pattern verification. The 
apparatus includes a case having volume less than about two liters (one 
hundred twenty cubic inches). 
Mounted within or for access at the surface of the case are all the 
following elements; 
means for holding an electrical-energy storage device or for receiving 
electrical power from an external source, to power the apparatus; 
means for contacting a skin pattern to develop an electronic data array 
corresponding to an image of the skin pattern; 
means for generating in response a corresponding electronic data array for 
use in verification; 
means for performing a verification procedure; 
output means for indicating or effectuating, or both, a verification 
decision; 
means for formatting the data array in a compact form for use in storage, 
import or export; and 
means for converting the data array from said compact form to a different 
form for use by the verification-procedure performing means. 
(f) A TENTH ASPECT of the invention--In this regard, the invention in its 
preferred embodiments is self-contained apparatus for skin-pattern 
verification. The apparatus includes a case having volume less than about 
two liters. Mounted within or for access at the surface of the case are 
all the following elements; 
means for holding an electrical-energy storage device or for receiving 
electrical power from an external source, to power the apparatus; 
means, including an imaging unit and a sensor array disposed to receive an 
image therefrom, for contacting a skin pattern to develop an electronic 
data array corresponding to an image of the skin pattern; 
a video controller for controlling the sensor array to develop said 
electronic data array; 
an analog-to-digital converter for digitizing the electronic data array; 
a digital signal processor for performing verification procedures based 
upon the electronic data array, and for developing a decision signal based 
upon the verification procedures; 
memory means for holding an authorized-user skin-pattern template, program 
firmware for the digital signal processor, and data used in the 
verification procedures; 
an output register for holding the decision signal; 
output means for transmitting a utilization-means switching signal, based 
on the decision signal, from the apparatus for effectuation of the 
decision signal; and 
a control, address, and data bus interconnecting the video controller, 
analog-to-digital converter, video processor, memory means, and output 
register. 
(g) AN ELEVENTH ASPECT of the invention--The invention in preferred 
embodiments of its eleventh aspect is self-contained apparatus for 
skin-pattern verification. The apparatus includes a case having volume 
less than about two liters. 
Mounted within or for access at the surface of the case are all the 
following elements: 
means for holding an electrical-energy storage device or for receiving 
electrical power from an external source, to power the apparatus; 
an optical bench disposed within or forming part of, or both, the case; 
optical-fiber prism means mounted to the optical-bench bosses for 
contacting a skin pattern to develop an image thereof; 
an objective lens mounted to the optical-bench ring for relaying the 
skin-pattern image to a sensor array; 
a sensor array mounted to the optical-bench pocket for receiving said image 
and in response developing an electronic data array corresponding to the 
image; 
a surface-mount electronics board holding a digital signal-processing chip 
for analyzing the data array to verify identity corresponding to such skin 
pattern; and 
verification-decision indicating or effectuating means, or both. 
The optical bench has mounting bosses for optical-fiber prism means. The 
bench also has a mounting ring for an objective lens, and a mounting 
pocket for a sensor array. 
(h) A TWELFTH ASPECT of the invention--In preferred embodiments of this 
aspect, the invention is an optical-fiber imager for use in a skin-pattern 
analyzer. The imager includes an optical-fiber prism. 
The prism in turn has a cylindrical wall defining a longitudinal axis. It 
also has fused optical fibers parallel to the longitudinal axis, and a 
transverse face for output of a skin-pattern image from the prism. 
In addition the prism has a generally elliptical, angled face for 
contacting a skin pattern. 
(i) A THIRTEENTH ASPECT of the invention--As to this aspect of the 
invention, preferred embodiments take the form of a condenser lens for use 
with an optical-fiber prism in a skin-pattern imager. The condenser 
includes a convex, generally cylindrical-section surface of a first radius 
for receiving illumination. 
It also includes a concave, generally cylindrical-section surface of a 
second radius, smaller than the first. This concave surface is for holding 
the optical-fiber prism and for transferring illumination into the 
optical-fiber prism. 
The phrase "cylindrical-section surface" means a surface that has the form 
of a section of a cylinder. For example the concave surface preferably is 
about a half of a cylinder--i.e., a cylinder cut in half longitudinally by 
a diametral plane parallel to the longitudinal axis of the cylinder. 
The convex surface, however, preferably is less than a half cylinder. 
(j) A FOURTEENTH ASPECT of the invention--In preferred embodiments of this 
aspect, the invention is, in combination, a door handle and lock set for 
installation in a door. The door handle and lock set, considered together, 
hold a self-contained skin-pattern-verification apparatus. 
The combination includes a lock for mounting in the door, and a handle, 
interfitted with the lock, for manual operation to open the door. Wholly 
contained within the lock and handle is apparatus for acquiring 
surface-relief data from a relieved surface such as a finger. 
The apparatus includes prism means formed from optical fibers. The prism 
means have a skin-pattern contact surface exposed at the exterior of the 
lock or handle. The apparatus also includes an electrooptical sensor 
disposed for receiving an image of a skin pattern through the prism means. 
In addition the apparatus includes means for analyzing the skin-pattern 
image to verify identity based on the skin pattern. The apparatus also 
includes means, responsive to the analyzing means, for controlling 
operation of the lock or handle, or both. 
All of the foregoing operational principles and advantages of the present 
invention will be more fully appreciated upon consideration of the 
following detailed description, with reference to the appended drawings, 
of which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
1. OPTICAL CONFIGURATIONS 
(a) Bright-field systems--As shown in FIG. 1, preferred forms of the 
invention include a fiber-optic prism 110 for contact with a relieved 
surface such as a finger 11, to provide an image of its relieved surface 
(also designated 11) to electrooptical means 126, 127. 
The prism 110 includes a first end 101 for contacting the thumb 11, and 
second end 120 for transferring the image to the electrooptical means. The 
prism 110 also includes a side face 103 for receiving light, preferably 
infrared light, to illuminate the thumb 11; the width dimension of this 
side face 103 runs in and out of the FIG. 1 plane. 
For optimum operation, as suggested by FIG. 2, the width of that side face 
103 is the same as the width of the first end 101. This condition departs 
from the geometry in Dowling. If preferred, in this and the other 
embodiments described below, the side face 103 can be made wider than the 
first end 101, but the extra width serves little purpose. 
In preferred embodiments as will be seen the illumination-receiving face is 
a cylindrical wall of the prism--but its operative dimension is 
substantially independent of longitudinal position. Associated with the 
prism 110 are a light source 104, and a fiber-optic spacer element or 
other diffuser 105 to somewhat equalize the illumination at the near and 
far sides of the prism 110. In preferred embodiments, for reasons that 
will shortly appear, the spacer 105 is replaced by a condenser lens formed 
as sections of two cylindrical surfaces. 
Light rays 114 from the source 104 pass through the optional spacer 105 and 
cross varying fractions of the prism thickness, as shown, to reach the 
second end 120 of the prism. In so doing, the light must cross optical 
fibers 151, preferably fused, which make up the prism 110 and define the 
prism axis. The light 114 passes into the prism 110 at a steep angle--as 
understood from FIG. 1 a right angle--to the axis. 
Accordingly the light 114 is not ducted along the fibers 151 in reaching 
the second end 102 of the prism. In particular this light must cross 
through the side wall of each fiber to reach the termination of that fiber 
which contacts the second end 102. 
Hatching used in the drawings to represent the fibers is only illustrative, 
since the fibers are essentially microscopic. They are preferably spaced 
at a small fraction of a millimeter, though not as finely as mentioned in 
Bowker; the present coarser fibers have been found entirely adequate, and 
less costly. 
The light illuminates the fingertip--and by FTIR relations, as set forth in 
Bowker, generates an optical image that is ducted along the fibers 151 to 
the exit 120 of the prism. 
From the output face 120, field lens 121 and objective 123 carry the image 
from the end face 120 to the detector 126, which is in a housing 127. The 
field lens 121 does not reduce the image, but produces a beam 122 in which 
precompensation is present for the focal-surface-curving influence to be 
introduced by the objective 123. 
In other words, the focal surface as represented in the beam 125 from the 
objective is substantially flat, to match the flat detector surface 126. 
As a matter of ergonomics the FIG. 1 system may not offer the most 
comfortable or convenient configuration, in that no ideal position is left 
for the rest of the user's hand--that is, the knuckles of the other 
fingers, etc. Various ways of dealing with such geometrical considerations 
are shown in FIGS. 9 through 11, but here it may be noted that the thumb 
may simply be presented from the opposite direction (FIG. 2). 
Another minor drawback is that the length of the thumb, applied along the 
hypotenuse 101 of the prism, appears fore-shortened by the factor 
.sqroot.2 at the output face 120. This anamorphism is very easily 
compensated in firmware, but at the modest time penalty of an additional 
processing step. 
Anamorphism can be eliminated by fabricating the prism in the form of a 
parallelogram as shown in Bowker, but with some space penalty. Another 
approach is to insert a short EMA section 431 (FIG. 3), having the same 
numerical aperture as the prism, followed by another 45.degree. prism 432 
which has a very high numerical aperture NA. 
The fibers in the secondary prism 432 are angled at 45.degree. (other 
angles can be substituted) to the fibers 157 in the main prism, yielding 
an overall secondary-prism 432 that is narrower by the factor .sqroot.2. 
This solution corrects anamorphism while reducing the image in one 
direction, so that a smaller factor remains for the focal elements 421, 
423. 
This configuration has a drawback: coupling between the EMA section 431 and 
secondary prism 432 may be poor because the interface angles are extreme. 
Light loss may be severe. 
To avoid severe fogging of the image in such a device, it is important to 
use a secondary prism 432, 632 that is properly designed to adequately 
preserve ducting of the signal rays, particularly through the transition 
120 etc. from the primary to the secondary prism. 
This constraint calls for a fiber structure 432, 632 of relatively high 
numerical aperture--but such a structure, without precautions, will also 
accept stray light across the same interface. The EMA-material buffer 431, 
631 is important to avoid carrying stray light from the low-NA 
primary-prism fibers 151 into the secondary prism 432, 632. 
It might be supposed that a series of successively smaller prisms in series 
could step down the image to the sensor 426 without any focal relaying; 
however, because each such fore-shortening is itself anamorphic it would 
be necessary to step down separately in each direction (i. e., in the 
plane of the drawing and perpendicular to that plane). Such a geometry 
would be rather cumbersome, requiring two cascading prisms for each 
overall stepdown factor of .sqroot.2, or four such prisms for a factor of 
two. 
Another usefulness, however, of configurations such as that of FIG. 3 is to 
reduce anamorphically to a CCD 426 that is custom fabricated to a 
complementarily anamorphic pixel structure. In any of these cases the 
"prism means" 410, 610 comprise the two prisms 151, 432/632 considered 
together. 
A mechanism for cross-fiber transmission and cylindrical diffusion is not 
generally recognized, but has been set forth at length in Bowker. As there 
explained, illumination under-goes a diffusion-like spread primarily in 
one plane and angular preservation in the other. 
To approximate crosslighting penetration, it is possible to use a 
one-dimensional model that ignores the cylindrical cross-section of the 
fiber. This approximation yields transmitted flux I=I.sub.0 
exp-x.alpha.!, where .alpha.=2r/D--in which x is distance of propagation 
across the prism, r is the loss at each transition from fiber to fiber, 
the well known expression for reflection due to difference of refractive 
indices at normal incidence, r=(n.sub.core -n.sub.cladding).sup.2 
/(n.sub.core +n.sub.cladding).sup.2, and D is the periodicity of the 
optical-fiber structure in the prism. 
The above expression for the flux I is not at all exact. It does serve to 
describe the basis of the diffusion over a distance which is short in 
terms of the diffuse-transmission characteristics of the material--in 
particular, perhaps over a small range of about two attenuation lengths. 
A very generally exponential fall-off with propagation depth is expected, 
leading to an expression for required numerical aperture NA to make any 
given penetration distance x be exactly one attenuation length, 
EQU x.alpha.=1 
EQU NA=2n.sub.avg (D/2x).sup.1/4. 
To obtain this degree of penetration or better, at a distance x.sub.F along 
the illumination path needed to reach the far side of the prism, the 
condition on numerical aperture becomes instead 
EQU NA.ltoreq.2n.sub.avg (D/2x.sub.F).sup.1/4. 
Materials offering a moderately continuous selection of numerical 
apertures, particularly in a low range, are not available now; the most 
popular materials have numerical apertures NA=0.66, 0.85, 1.0 and higher. 
One material commonly on the market does have a low-NA value of 0.35, and 
this is amply low for the condition described algebraically above. 
(Numerical aperture of 0.35 is far too low for good ducting. This fact 
leads to a need for caution in configurations that require ducting.) 
Optical-fiber prism materials with numerical aperture up to about 0.5, were 
they available commercially now, would correspond to an operationally 
marginal selection of material; and materials with numerical aperture of 
0.36 to 0.42--or more generally speaking about 0.4--might be seen as 
providing an ideal tradeoff between ducting ability and amenability to 
crosslighting. Tighter ranges may be stated for prisms of specific width, 
as shown in Bowker. 
Intensity can be made to vary across the prism face smoothly (as well as 
minimally), with suitable choice of numerical aperture. Intensity varies 
abruptly (and greatly) with a poor choice. 
Other aspects of fiber-prism crosslighting that merit attention are the 
illuminating devices and their use. High-brightness light-emitting diodes 
(LEDs) appear to be best, as outlined in Bowker. 
Use of a bright-field system has some intuitive appeal, in collecting and 
analyzing the relatively intense light that internally reflects toward the 
detector at untouched portions of the prism face, producing a bright line 
on the detector corresponding to the locations of grooves in the 
thumbprint. Such a system produces a fixed upper white level. 
Unfortunately in practice the dark level, corresponding to ridges, varies 
greatly along the ridge lines--from essentially black in some spots to a 
modulation as high as seventy-five percent (of the white level). The 
contrast 
EQU (I.sub.max -I.sub.min)/(I.sub.max +I.sub.min) 
commonly ranges from about one-seventh to nearly unity. The 
undesirably-higher "dark" level in most regions of the ridge lines 
severely detracts from the overall appeal of bright-field systems. 
(b) Dark-field rectangular-prism systems--A suitable prism 210 (FIG. 4) is 
rectangular and considerably more massive than those of FIGS. 1 through 3 
(although the length need not be quite as great as shown). Of course the 
relatively greater mass in itself is a drawback for the most 
miniaturization-sensitive applications of the invention--particularly 
personal weapons, portable telephones and the like. 
In addition the illustrated auxiliary coupling prisms 205 add considerable 
undesired size and weight to the assembly. The function of these prisms is 
to avoid three problems: high reflection losses, low Lambertian (cosine 
law) flux through each side face 203 of the main prism 210, and difficult 
source-to-prism alignment. 
These adverse effects, however, can be mitigated without adding such large 
coupling prisms 205. Mitigation is attainable through substitution of a 
number of smaller prisms, side by side. While it is possible to use a 
large number of tiny molded facets similar to those of a Fresnel lens, an 
ideal number is probably small, as for example between two and five 
prisms. 
Tending to offset the drawbacks of greater mass apparent in the main prism 
210 of FIG. 45 are higher contrast and improved uniformity of illumination 
Because lighting can be applied from both sides, some evening-out of the 
illumination is possible. 
With opposed lighting the illumination from each side provides half the 
intensity at the midplane or centerline 219. In view of the binary 
character of the FTIR detection process, total midplane intensity (for the 
1/e.sup.2 case) is sufficiently close to initial intensity for marginal 
operation. Beyond that point the intensity continues to fall off 
exponentially, so that the intensity fraction which reaches the far side 
of the prism is the square of the fraction which reaches the midplane. 
Light is supplied from twice as many directions--but only half as much 
light from each direction. Consequently a derivation of numerical-aperture 
constraints for crosslighting of the FIG. 4 system proceeds to the same 
algebraic results, except for substitution of the midplane notation 
x.sub.M for the far-side notation x.sub.F. 
The main prism 210 is rectangular not only in the plane of FIG. 4 but also 
in the width dimension that runs in and out of the plane of the paper. 
Therefore, unlike the prior-art geometry, the light-entry side faces 203 
are at least as wide (not shown) as the thumb-contacting first end 201. 
Detector-size concerns mentioned above in connection with bright-field 
apparatus are even more troublesome here, due to the larger cross-section, 
by the factor .sqroot.2, of the FIG. 4 rectangular dark-field prism 
(particularly at its second end 202). They may be addressed by use of 
focal elements such as lenses 721, 723 (or mirrors). 
Unfortunately dimensions of the focal elements or stepdown modules too--and 
their resulting overall optical-train length--are larger, by at least the 
factor .sqroot.2, than the analogous bright-field elements 432, 421, 423 
and overall optical-train length of the bright-field systems. 
FIG. 4 also shows the particularly problematic stray-light rays 214b" 
derived from specular reflection 216 of the excitation illumination 214 
and diffusely propagating toward the detector--transversely to the fibers, 
through myriad reflections at the fiber interfaces. These are captured and 
absorbed by a short section, just before the second end 202, of fibers 
251' that have EMA material. 
The short EMA section 251' can be either a separately manufactured prism 
block or unitary with the main fiber block 251, as preferred. It is 
desirable that the numerical aperture of the EMA section 251' be about the 
same as the main block 251: if the EMA section 251' has higher numerical 
aperture, it will accept and transmit much or all of the stray light--thus 
defeating the purpose of the absorbing section 251'. If the numerical 
aperture of the EMA section 251' is lower than that of the main block 251, 
then some signal rays 217 will be undesirably discarded. 
As the drawings suggest, the EMA section 431 (FIG. 3), 731 (FIG. 4)need not 
be long--but again it must not have higher numerical aperture than the 
main block. Otherwise the following portions of the optical train would 
fail to serve the purpose of transmitting only the optical signal, and 
would instead transmit a large fraction of the specularly-derived stray 
light to the detector. 
(c) Dark-field partial-reflector systems--In the embodiment of FIG. 5, 
light reaching the second end 302 of the prism 310 encounters a partial 
reflector 306 that is formed on that end 302. The reflector 306 is in 
essence a half-silvered mirror, but the exact fractions of light which are 
reflected and transmitted are subject to design choice and not necessarily 
half. 
A portion of the incoming light 314 reaching the reflector 306 is 
redirected to form rays 315 ducted along the fibers 351 toward the thumb 
11. The remainder of the incoming light 314 passes through the partial 
reflector 306, and are prevented by the system geometry from reaching the 
detector 826. 
The reflected and ducted rays 15 flood essentially all the fibers 351 of 
the prism, and with relatively uniform intensity, to illuminate 
terminations of the fibers 351 at the first end 301 of the prism 310 and 
so illuminate the thumbprint or other relieved surface 11. By virtue of 
FTIR relationships, this illumination either is reflected (at thumbprint 
grooves) out of the prism as exit rays 316 or is transmitted through some 
of the fiber terminations into the relieved surface 11 (at thumbprint 
ridges). 
The relieved surface 11, and the mass of living tissue (or other material) 
within or behind that surface, is slightly translucent and acts as a 
scattering medium--diffusing and redirecting the incident light 315 in all 
directions though not uniformly. A small fraction, perhaps on the order of 
one thirtieth, of the light fraction transmitted into this medium is 
partially scattered as rays 317 back into and along the same fibers 351 
which brought the illumination 315. 
The latter, backscattered light 317 thus exists only in certain fibers that 
are in effect selected by the geometry of the thumb or other relieved 
surface 11. These rays 317, and the pattern of their occurrence in some 
fibers 351 but not others, accordingly constitute the optical data or 
information signal which is collected from the thumb etc. 11. 
Upon reaching (for the second time) the partial reflector 6, some of the 
light 317 passes through the reflector to reach the focal system 820-825 
and thereby the detector 826, 827. Most of the remaining light (not shown) 
is wasted in reflection back toward the entry face 303. 
2. DETECTION 
(a) Geometry and mechanical arrangements--As indicated in Bowker, the image 
produced by the crosslit fiber prism can be detected by using a lens to 
directly image the output face of the prism onto a self-scanned detector 
array. The present invention uses such a conventional imaging system. 
Many different combinations of element sizes and geometries of course are 
possible. We have experimented extensively with rectangular blocks cut to 
45.degree. prisms as in FIGS. 1 through 5. In that format, a 
representative successful system has input and output prism sides 103, 120 
each 16 mm long. 
Such a system may be imaged onto a CCD of dimensions 4.8 mm by 6.4 mm (with 
an 8 mm diagonal) using a field lens 121, cemented directly to the prism 
and of focal length 40 mm--and an objective 123 of focal length 8 mm. The 
objective is a compound lens having typically three to six elements. 
The object distance (overall length of the beam object segment 122), from 
prism face 120 to effective central plane 124 of the objective 123, is 
34.6 mm. The image distance (overall length of the beam image segment 
125), from the latter central plane to the sensitive surface 426 of the 
CCD, is 10.4 mm. Multiplication (actually reduction) is thus 3.33 and the 
objective representatively operates at f/1.6. 
In such a system the field lens provides no magnification, but serves 
particularly to provide a flat focal plane at the CCD and also render 
illumination more uniform there. 
We now prefer, however, an innovative cylindrical prism for bright-field 
systems such as FIGS. 1 through 3--as will be explained in greater detail 
shortly. For very economical commercial systems using such a prism, we 
currently prefer a detector of dimensions 2.4 by 3.4 mm, requiring 
stronger reduction. 
(b) Detector types--Detectors that can be used are primarily CCDs 
(charge-coupled devices), CIDs (charge-injection devices), and SSDs 
(self-scanned diodes). All of these are made in two-dimensional arrays by 
many manufacturers: Texas instruments, Fairchild. Tektronics, Kodak, 
Dalsa, Phillips, Thomson, Sony, Hitachi and so on--and in a large variety 
of sizes, and costs. 
Smaller and cheaper devices include the Texas Instruments TC211, with 192 
by 165 pixels, measuring 133/4 by 16 microns as mentioned above (for 
overall dimensions 2.64 mm square); and the TC255 with 243 by 336 pixels 
measuring 10 by 10 microns (overall 2.4 by 3.4 mm, and as mentioned above 
our current preference). These are made for mass-produced consumer items 
and cost less than $25. 
3. SIGNAL PROCESSING AND ELECTRONICS OVERVIEW 
Discussion of the sensor array leads us to the electronic and firmware 
subsystems of our invention. We therefore digress from optical details to 
an overview of those subsystems. 
A very great body of patent and other literature relates to the 
interpretation and particularly comparison of fingerprint data once 
acquired. These range from primitive visual analysis to ultramodern 
holographic correlators with neural-network sensing. Along the way are 
computerized systems that abstract, classify and compare skin-pattern 
details called minutiae. 
Also known are computerized optical correlators of somewhat greater 
sophistication, among which may perhaps be categorized the analytical 
system described in Bowker. Many of these different kinds of data-analysis 
systems, from visual analysis and minutiae analysis to nonholographic 
optical correlators including that in Bowker, suffer from inadequate 
input-image quality--and accordingly would benefit from the teachings of 
the present invention. 
Portions of the present invention are compatible with any of the analytical 
systems just mentioned; in other words, the benefits of the present 
invention will accrue in use with any of these analytical systems. The 
now-contemplated best mode of practicing the present invention, however, 
is in conjunction with a newly developed analytical system and method set 
forth in the concurrently filed patent document of Lawrence R. Thebaud, 
Ph. D., mentioned in the preceding "RELATED PATENT DOCUMENTS" section. 
Thebaud's analytical inventions are of the computerized optical-correlation 
type, but are extraordinary in many ways: they systematically take into 
account global or isomorphic dilation or compression of a print due to 
varying pressure of fingertip application to the sensor, and differential 
distortion due to uneven pressure or twisting of the fingertip; in 
addition they actually use all of the available image data, rather than 
discarding almost all of it as in all known non-holographic systems. The 
present system in conjunction with Thebaud's is commercially available 
from Biometric Identification, Incorporated of Sherman Oaks, Calif. 
The firmware resides in a circuit that is in essence a custom computer. It 
is set into operation by a microswitch 501 (FIG. 6), which in the 
preferred embodiment is actuated by fingertip pressure on the fiber-optic 
prism digital signal process 503. In other implementations, a striped vane 
or other very coarse pattern above the optical input (beyond the finger 
position) may be used to detect presence of a fingertip to be analyzed; 
however, this would require maintaining the sensor system in at least 
partly or periodically operating condition. 
Operation of the switch 501 activates a clock generator 502, which clocks a 
digital signal processor 503. The processor 503 at this point is able to 
do little more than interrogate a data bus 504 for startup instructions 
from the "boot" section of a template-and-boot EPROM 507. The EPROM 
instructs the processor 503 to load its main program and initially needed 
data from a separate read-only memory 506 into random-access memory within 
the processor 503. 
The processor complies, moving data and program into its internal RAM from 
the main ROM 506. The signal processor thereby becomes sapient to the 
extent needed for operation of the entire system through the bus 504. 
At that point the system is ready to begin actually processing new data, 
and the processor 503 via the bus 504 commands a video controller 508 to 
acquire data. The video control 508 is a custom circuit, or to put it more 
precisely a custom-programmable logic circuit, which replaces a 
conventional sensor-reading module known familiarly in the art as a "frame 
grabber". 
A conventional frame grabber would be an entire circuit board, e. g., a 
card in a personal computer. Hence a massive amount of volumetric 
compression has been obtained by development of the video control 508 
alone, and this is accordingly another important part of the invention. 
When thus actuated by the processor 503, the video control 508 takes charge 
of the front end of the system, commanding a timing generator 509 to start 
a clock driver--which in turn sequences operation of the sensor array 512. 
The latter is at present a CCD ("charge-coupled device") as shown, but as 
mentioned earlier may take any of a number of other forms for greater 
economy, convenience etc. 
As is well known, a CCD is an integrating device. The integration time of 
the CCD is settable. In the present system integration time is controlled 
in hardware. For later development stages, however, the processor 
preferably can be made to monitor contrast in the data array and 
automatically adjust the integration time so as to optimize the implicit 
image contrast thereafter--for the particular fingertip, condition of the 
prism surface, condition of the illuminators, and condition of the CCD. 
Analog data from the sensor 512 are buffered 513 and held essentially a 
frame or major frame subelement at a time in a sample-and-hold circuit 
514, from which they are available for conversion to digital form for 
processing. For convenience of understandable operation, and for 
convenience of debugging, in the present system--which is at a relatively 
low-production-volume design stage--the sample-and-hold circuit 514 
formats the CCD data as eight-bit bytes in a sixty-four-bit word. 
This may be regarded as in essence "real video" in the sense of conforming 
very generally to conventional broadcast or computer-video-display 
specifications. For higher-volume design development, however, it is 
contemplated later to use a custom chip specially programmed for more 
efficient and faster operation. 
While the video control 508 sets these data-acquisition modules into 
operation, it also synchronizes operation of an A/D converter 517 which 
reads buffered 515 analog data frame-wise or wordwise from the 
sample-and-hold circuit 514 and passes those data in digital form to the 
processor 503 via the data bus 504. Thus the start-up command launched on 
the bus 504, from the processor 503 to the video control 508, is answered 
by a very large flow of data back along the bus from the ADC 517 to the 
processor 503. 
In some applications, additional information such as a personal 
identification number of other confirming information is required, either 
before or after the candidate user's fingerprint data are obtained. If so, 
the processor may ask--audibly, as through a voice chip 505 and speaker 
505', or visually as by means of light-emitting diode indicators through 
output register 518, or an alphanumeric display 521, or by combinations of 
these--for entry of such information by the candidate user at a keypad 
522. 
For this purpose the processor 503 also activates a buffer register 523 to 
receive inputs from the keypad 522 and return them in an orderly fashion, 
also along the bus 504, to the processor. As is now commonplace for such 
processor/user dialogs, the processor advises the user--again by speaker 
505', LEDs through output register 518, or display 521--if for any reason 
the processor is unable to proceed with the information as entered. 
Otherwise the processor uses the information, as for example to select a 
particular authorized-user template from the EPROM 507, and goes on with 
the verification work--according to the program instructions and 
operational data previously read in from the memory 506--for the 
fingerprint data received. Upon completion the processor may instruct the 
sound chip 505, or LEDs, or display 521, or combinations of these 
indicators, to indicate the decision. 
Concurrently the processor, also through the same register 518, may actuate 
an internal relay 519 to provide a switch closure to an external relay 
that provides access to utilization means. In more-sophisticated systems 
as mentioned elsewhere an interactive access actuation can be substituted; 
and if desired this may be effectuated through the serial communication 
controller 524 and a conventional RS232 serial-data port 525. 
In some systems data may travel in or out of the system for other reasons. 
Templates may be fetched from a remote computer, or from an identification 
card carried by the user and inserted into a local card reader. Decisional 
signals may travel to a remote computer for logging or monitoring. For any 
of these purposes, once again the serial controller 524 and port 525 may 
provide needed links to the cooperating apparatus. 
4. DOORWAY ACCESS 
A fingerprint analyzer according to our invention is readily associated 
with locking mechanisms of a door 960 (FIG. 7) and built into an 
associated door handle 961, 962. Power connections (not illustrated) may 
link the apparatus with an outside supply or with a supply that is 
internal--e. g., batteries in the lock. 
The power is needed for illuminators 904 as well as for actuating the 
sensor 927 and verification processing system 997. In addition, in the 
case of FIG. 7 the fixed door handle 961-962 is only used to pull or push 
the door and has no part in mechanically operating the bolt 963 or its 
drive mechanism 999. 
That mechanism 999, too, accordingly must be powered--most ordinarily by 
electricity from the supply as for example in the case of a solenoid drive 
999. Since the supply must provide enough power to actuate the bolt 963, 
most ordinarily this particular embodiment will operate from external 
power rather than from internal batteries. 
Light from the illuminators 904 enters the fiber prism 910, which is also 
contacted by a thumb 11. A different finger can be used, but this 
particular type of handle is most easily operated by one hand with the 
thumb 11 at the outer top corner of the handle and other fingers curled 
about the inclined lower portion 961. 
Operation of the print analyzer and the door itself in this way is 
particularly natural, easy and instinctive. A switch or other means (not 
illustrated) are provided for initiating operation of the lights 904, 
sensor 927 and interpretation module 997. 
An image of the thumb 11 is collected by the crosslit fiber prism 910, and 
projected by a field lens 921 toward the objective 923--which focuses the 
image on the much smaller active surface of the sensor 927. The sensor 927 
responds by passing a data array to the processing system 997, generally 
in the fashion described earlier in the preceding electronics-overview 
section of this document; and if the verification is positive the 
decisional system 997 operates the mechanism 999 to withdraw the bolt 963 
from the door jamb. 
Equally ergonomic in use is a system with rotatable door handle 961', 962' 
(FIG. 8)--the shaft portion 962' of the handle being journaled 964 for 
rotation relative to the door. Here it is the mechanical rotation of the 
handle that provides the actual motive force for withdrawal of the bolt 
963. 
For example as suggested in the drawing the bolt 963 may be toothed along 
its bottom edge to form a rack. The rack engages a pinion 967 that rotates 
with the door handle shaft 962'. 
In this system the decisional module 997' may perhaps operate a smaller 
bolt or pin 965 that is withdrawn only from an associated block within the 
door. When shot, the pin 965 simply prevents operation of the door handle 
shaft 962'. 
This mechanism requires much less electrical power and so may possibly be 
suited for operation from a battery. 
One variant of the FIG. 8 rotatable configuration uses a doorknob 962" 
(FIG. 9) rather than a door handle. The prism here is off-center and its 
output image coupled by a optical-path folding mirror 932. 
If it is preferred to dispose the finger-contacting surface vertically, 
rather than at a 45.degree. angle, the prism 1010" (FIG. 10) in another 
variant of the FIG. 7 or 8 system may be coupled to the relay optics 
1021-1024 by a bent fiber-optic element ("light pipe") 1058. 
As to the optics, in still another variant of the FIG. 7 or 8 system, a 
more ideal solution is to mount the sensor 1127 (FIG. 11) directly on the 
output face of the fiber-optic prism 1110, optionally with wiring 1111' to 
carry the signal to the processor. 
5. SYSTEMS 
Our invention viewed generally may include--i. e., encompass, not only a 
print-verification system or print analyzer 96, but also an access-control 
module 97 which acts as an intermediary with utilization means 99. In 
other words, for purposes of certain of the appended claims the invention 
does not end at the case of the analyzer 96 but extends rightward in the 
drawing to include the access-control unit 97. 
Similarly for some purposes, and within the sweep of certain of the 
appended claims, the invention includes the utilization means 99. This 
simply means that the utilization means, the access-control unit 97, and 
the analyzer 96, all considered together, are part of a new and improved 
combination. 
The analyzer 96 includes a sensitive surface 91 for contact by a finger, 
thumb, toe, or other skin-pattern member 11. The sensitive surface 91 is 
part of a sensor module 92, with lights and detector powered from a supply 
95 that either is entirely internal (as with batteries) or draws power 
from an external source for conditioning within the analyzer 96. 
Signals 11' from the sensor module 92, representative of the skin-pattern 
11 image, are compared with information 21 &c. from a read-only memory 93 
(also powered from the supply 95) by a CPU 94. The CPU responds, 
particularly in case of a favorable decision, with a decisional signal 55e 
to the accesscontrol intermediary 97. 
This signal 55e is preferably not merely a unidirectional on-or-off signal 
but rather part of an interchange of signals which validates the integrity 
of the connection as well as the entity whose skin-pattern 11. The 
access-control module may typically be a switch box or heavier relay that 
provides a lower-impedance signal, or a specialized drive waveform, or 
other motive means 98 to the utilization means 99. 
The analyzer 96, through the access-control means 97, either enables 
operation of utilization means 99 if appropriate authorization is embodied 
in the received image, or maintain the utilization means 99 disabled 
otherwise. The utilization-means block 99 represents any of a wide variety 
of applications of a decisional signal 55e or access-control signal 98 
such as the present invention generates. 
One focus of the present document is upon use of the invention in, or as, a 
personal weapon; however, the invention is equally applicable to other 
apparatus, facilities, financial services and information services. The 
invention is particularly suited to field applications that are extremely 
demanding in terms of overall microminiaturization and low weight, very 
short decision time with very high certainty and reliability, and low 
power. Personal weaponry is an application which is particularly sensitive 
to several of these criteria, but close behind are other portable personal 
devices such as cellular phones and so-called "notebook" computers. 
Use of the invention to control access to public phones, automatic teller 
machines, and vehicle-usage access--even though much less critical in 
terms of weight and power--all benefit significantly from the amenability 
of the present invention to miniaturization without compromise of decision 
time, certainty, or reliability. In some uses, such as telephonic and 
in-person credit systems, the apparatus of the present invention does not 
necessarily actuate a device to automatically grant e. g. credit, but can 
instead provide a visible, audible etc. signal to a human operator who 
then actuates any necessary devices. 
Any or all of these means for utilizing the access-control signal 98 of the 
present invention are represented by the utilization means 99. 
6. PREFERRED PRISM CONFIGURATION, FABRICATION AND LIGHT COUPLING 
A cylindrical prism 530 (FIG. 13) provides several surprising advantages. 
The prism presents an elliptical face 534, the area of the hypotenuse, 
which fits the shape of a fingertip. Therefore the prism has no excess 
material--and fiberoptics prism material is costly. 
Furthermore it is fabricated directly from drawn rods 536 (FIG. 14) of 
fused fiber-optic material. To minimize material loss in fact a large 
multiplicity of prisms 530a-530d can be cut in a continuing sequence 
simply by alternating transverse cuts 531 (FIG. 14) with 45.degree.-angled 
cuts 534. 
As illustrated, the resulting successive pieces 530a-d are alternating in 
their orientation (i. e., successive units of each pair are mutually 
inverted). Each transverse cut forms a transverse face of two adjacent but 
opposed prisms, and analogously each angled cut forms an angled face of 
two adjacent but opposed prisms. 
In the preferred embodiment, prism dimensions are 15.5 mm diameter by 16 mm 
length. One side is cut at 45.degree.. The proprietary "MEGAdraw" process 
of Incom, Inc. (Southbridge, Mass.) is used. Numerical aperture is 0.35, 
fiber size less than twenty-five microns, with no EMA material. 
The cylindrical prism is, however, subject to one awkwardness in 
illumination. Whereas generally central rays 555 (FIG. 15) pass through 
the prism along fairly straight paths--as in the rectangular-prism case 
modeled earlier--rays 551, 552 near the edges or limbs of the structure 
are strongly refracted at the angled surface of the glass in those 
regions. 
These peripheral rays 551, 552 are therefore redirected inward along 
sharply inward-turned paths, leaving badly light-starved or shadowed 
regions 553. The illustration suggests that these regions may be behind 
the midline of the prism; however, in practice the exact disposition of 
these regions depends upon the illumination geometry and refractive 
indices involved. 
To provide more-uniform illumination, we have invented a special 
cylindrical condenser lens to restraighten the peripheral rays. 
A ray-trace diagram for a high-performance condenser 545-547 (FIG. 16) 
formed from hard glass shows that uniform illumination can be provided in 
a very short distance. Illumination from the light-emitting diode 541 at 
far left passes through an integral diode lens 542, and then a 
concavo-plane lens 543-544. 
The beam is tightly collimated in the dimension normal to the plane of the 
drawing, but in the drawing plane the beam from the concavo-plane lens 
543-544 diverges severely to the first cylindrical-section surface 546 of 
the condenser 545-547. That surface refracts the rays inward, making them 
almost horizontal within the condenser. 
The refractive index of the condenser rather closely matches that of the 
cladding and/or the average of cladding and cores in the cylindrical 
fused-fiber-optic prism--which is represented by the half-circle at far 
right. Moreover the second cylindrical-section surface 547 of the 
condenser closely matches the external cylindrical surface of the prism. 
Due to these matches, the extreme rays 551, 552 undergo only a very little 
bending at the condenser-prism interface 547. The criterion for judging 
goodness of illumination here is the horizontalness of the rays in the 
fiber-optic piece, particularly at top and bottom as already noted. By 
this measure, the FIG. 16 system performs very well, as can be seen. 
Angular spacing of the rays in this outer part is half as great as that of 
the rays in the center. A tilt in the rays indicates that strong shadowing 
can be expected near the edge of the prism at its widest part. 
A ray-trace diagram for a much less costly alternative condenser 545'-547' 
(FIG. 17) shows a compromise performance. Actually the axial spacings here 
are dictated by the optical bench design that set the spacings in FIG. 17; 
therefore some improvement can be obtained by optimizing for this device 
rather than accepting the design for that of FIG. 17. 
At any rate, the peripheral rays 551', 552' in this case are plainly not 
controlled as well as the corresponding rays 551, 552 in FIG. 116. 
Therefore a certain amount of shadowing 553 (FIG. 18) may be expected, as 
suggested by the conceptual view of FIG. 15. 
In this drawing, illumination is from below, and at an upward angle from 
right to left. The thin end of the prism is at right. Thus the shadowed 
regions 553 in this instance are in fact behind the midline as predicted 
from FIG. 13. 
With care this shadowing can be minimized and made essentially 
insignificant, although performance of the FIG. 16 unit is inherently 
better. This alternative condenser is made of standard acrylic 
tubing--costing some forty-three cents per foot--with as-fabricated 
polished surfaces and is simply cut out of the stock material; it can be 
made by any machine shop. 
In particular, however, care must be taken to avoid separation of the 
acrylic piece from the fiber-optic piece due to temperature expansion 
effects that might cause the rupture of a cement (e. g., epoxy) bond. If 
there is a partial rupture at the ends, where the angles exceed the 
critical angle the light will reflect at the interface--and in this case 
the outer third of the prism will not be illuminated, except by diffusion. 
The preferred embodiment uses relatively coarse fibers, which do not 
diffuse as much as the finer fibers contemplated previously. 
Stresses are smaller for a thinner cross-section at the narrow vertex 
between the two cylindrical radii. In the present configuration that neck 
is only 11/4 mm (0.05 inch) thick and so readily bends and stretches to 
accommodate differential thermal effects--as has been verified by freezer 
and oven cycling. 
The condenser in the preferred embodiment of our invention serves as the 
mounting piece for the fiber optics and the illumination device as well. 
Thus it introduces several cost savings. 
It is cemented to the prism, preferably with Norland Optical Adhesive type 
NOA 68. The condenser 545 is formed as a mounting cradle (FIGS. 19 through 
21) for the prism, with mounting holes 561 and a tapered end as 
illustrated. 
7. LAYOUT 
To adequately minimize the effects of electromagnetic interference, the 
layout of our circuit board (FIG. 22) is critical. Sensitive, extremely 
high-frequency front-end detector circuitry associated with the CCDs is at 
one corner of the board; high-radiation inductive switching power supplies 
are at an opposite corner. 
Video control (timing/frame) are at a third corner, directly opposite the 
power supplies. The moderately high-radiation digital signal processor 
(DSP) is intermediate along the edge of the board between the video 
control and the power supplies. 
The mechanical layout (FIGS. 32 through 34) of the optics, CCD and I/O 
devices is also thoroughly integrated functionally with the electronic 
system. As shown, the unusual optical bench has two legs extending 
downward, at 45.degree. to the horizontal, from the central body that 
holds the prism. 
The prism is substantially flush with the top of the case, and essentially 
spring-suspended in that condition (together with the rest of the optical 
bench) from a case mount (FIG. 34). Downward motion against the springs 
actuates the microswitch 501 (FIG. 6). 
8. ELECTRONICS 
Electronic details for all circuits appear in FIGS. 23 through 31, which 
will be self explanatory to those skilled in the art--with the exception 
of the video control 508 (FIG. 6). That unit, as previously mentioned, is 
a custom-programmed logic circuit--or programmable logic device (PLD). 
The PLD in use is known by its model or designator number C80, and is 
operated using so-called "glue" logic. Understanding its customized 
internal operation requires an operational description, which is provided 
here. The acronyms and other specialized terminology will be clear to 
those skilled in the art: 
C80 MEMORY SYSTEM 
Jun. 23, 1996. 
______________________________________ 
Ram Used GL44016 256K .times. 16 EDO, 40 nS, 8 chips 
______________________________________ 
Organization 2 .times. 256k .times. 64 
Page size 512 DRAM addresses; 4k bytes 
Refresh: 512 in 8 ms 
Transfers: Little-Endian 
______________________________________ 
Memory Control 
/RAS0,/RAS1--decode 2 banks from C80/RAS output; only enable when DRAM 
address select is active. During refresh cycle, both/RAS outputs must be 
on. Need 5 nS PLD to gate/RAS lines Need to tristate/RAS when/DACK to 
allow frame grabber to take over. 
/CAS--translated 3.3 V to 5 V only; no gating needed. Need to tristate/CAS 
when/DACK is active to allow frame grabber to take over. 
/OE--gated based on/DBEN, DDIR, DRAM address select. 
/REG.sub.-- OE--DRAM registered outputs. Gated same as/OE. 
Address Lines 12-21 go to DRAMS 
__________________________________________________________________________ 
Address Selects 
Starting 
Bank size, 
Select Line 
Description 
Address 
bytes AS2:0! 
BS1:0! 
PS3:0! 
CT2:0! 
__________________________________________________________________________ 
/EPROM0 Eprom 0, 1 10 0000 
000 00 (8 bits) 
1000 (8) 
110 
megabyte, 8 bits, (static) nonpipe, 2 
32PLCC, 80nS cyc/col 
/EPROM1 Eprom 0, 1 10 0000 
010 (256k 
00 (8 bits) 
1000 (8) 
110 
megabyte, 8 bits .times. n) nonpipe, 2 
32PLCC; 80nS cyc/col 
/DRAM 100 0000 11 (64 
2010 (4k) 
100 pipe 1 
(4meg) bits) cyc/col 
/STAT.sub.-- IN 
Status In, 8 bits; 
100h 000 01 (16 
2010 (4k) 
100 pipe 1 
take 256 locations (static) 
bits) nonpipe, 3 
cyc/col 
/CNTL.sub.-- OUT 
Control Out, 8 
100h 000 01 (16 
1000 (8) 
111 
bits; take 256 (static) 
bits) nonpipe, 3 
locations cyc/col 
/UART.sub.-- EN0 
Uart, 8 bits; take 
100h 000 00 (8 bits) 
1000 (8) 
111 
256 locations; (static) nonpipe, 3 
120nS cyc/col 
/UART.sub.-- EN1 
Uart, 8 bits; take 
100h 000 00 (8 bits) 
1000 (8) 
111 
256 locations; (static) nonpipe, 3 
120nS cyc/col 
__________________________________________________________________________ 
C80 FRAME GRABBER 
Jun. 23, 1996. 
Operation 
The frame grabber is implemented in a single PLD that includes a master 
state machine, an address counter, a DRAM address multiplexer, and a DRAM 
state machine. 
The frame grabber takes over the 'C80 bus and directly puts data into one 
DRAM byte lane; the other DRAM byte lanes are left untouched. To start a 
frame grab, the 'C80 writes to a register bit to signal that a frame 
should be grabbed on the next cycle. The master state machine immediately 
asserts/HREQ to grab the bus, and waits for/HACK to be asserted. 
After/HACK has been asserted, the master state machine continues 
performing/CAS-/RAS refresh cyles to maintain data in the DRAM until VSYNC 
is asserted. Upon VSYNC, the master state machine resets the frame grabber 
address counter to the starting address and waits for VALID to be 
asserted. While waiting, the frame grabber DRAM state machine 
performs/CAS-/RAS refresh cycles to maintain data in the DRAM. Once VALID 
has been asserted, the CCD data is valid and the state machine takes a new 
video sample every 160 nS. The address counter is incremented after each 
sample. Data acquisition continues until VALID is deasserted, 
then/CAS-/RAS refresh cycles are performed to maintain the data. When the 
next/VSYNC pulse occurs,/HREQ is deasserted and the state machine is 
stopped. 
The frame grabber state machine is synced to the CCD timing generator's 25 
MHz clock. 
One possible cycle by cycle DRAM state machine implementation is to 
assert/RAS and/WR, then change the address multiplexer, then assert/CAS, 
then deassert/CAS. This yields a very liberal DRAM cycle with a Tcac of 40 
nS, a Trac of 80 nS and a trp of 40 nS. 
The VALID signal is generated by the CCD timing generator and indicates 
when the CCD output is valid. 
The frame grabber address counter starting address is dependant on the 
system memory map which has not been determined yet. 
The timing generator may either be the TI CCD) timing generator or it may 
be part of the frame grabber PLD. Other "glue" logic may be incorporated 
into the frane grabber PLD, depending on PLC device logic and pin 
resources. 
Frame Grabber PLD Control Lines: 
/RAS0--RAS for address bank 0. Not asserted during data transfers, but 
asserted during refresh cycles. 
/RAS1--RAS output for address bank 1. Asserted during data transfers and 
during refresh cycles. 
/CAS0--/CAS output for byte lane 0. Asserted during data transfers and 
during refresh cycles. 
/CAS1 to/CAS7. /CAS outputs for byte lanes 1 through 7. Asserted only 
during refresh cycles. 
DRAMAD0..8!--Multiplexed row and column address outputs to DRAM. 
/VSYNC--active low input from video timing generator. Indicates start and 
end of frame 
VALID--active high input from video timing generator. Lndicates valid data 
from the video A/D. 
/VIDEO.sub.-- CONV--active low output to video A/D. Starts data conversion. 
/HREQ--active low output to C80. Requests bus. 
/HACQ--active low input from C80. Indicates bus has been given to the frame 
grabber. 
CLKO--50 MHz clock from C80. 
CLK25--25 MHz clock output to the video timing generator; divided by two 
from the C80. 
/DBEN--high while acquiring data--use resistor pullup on this line. 
DDIR--don't care while acquiring data--use resistor pullup on this line. 
It will be understood that the foregoing disclosure is intended to be 
merely exemplary, and not to limit the scope of the invention--which is to 
be determined by reference to the appended claims.