Method of making microfiche laminate having apertures with doublet lenses

A microfiche structure consisting of a laminate of an opaque, apertured web sandwiched between two transparent sheets. The transparent material partially extends into each aperture to thereby define, for each aperture, an optical doublet. The laminate may be continuously formed by compression, as by rolls.

This invention relates to a microfiche and to its method of manufacture. 
In my U.S. Pat. No. 3,864,034, entitled, "MICROFICHE AND READER," (herein 
incorporated by reference) there is disclosed a microfiche construction, 
there termed a lensfiche, defined by a transparent member coated on one 
surface with a photographic emulsion and having on its other surface an 
array of integral lenses. The term lensette has been applied to such 
lenses because of their small size. The inter-lensette space, i.e., the 
space between the lenses on the non-emulsion side of the transparent 
member, is opaque. While such a lensette, such as illustrated at FIGS. 5, 
6 and 7 of this patent is satisfactory, I have now evolved a new lensfiche 
construction and have also evolved a novel method of manufacture. 
According to the practice of this invention, a lensfiche is formed wherein 
each integral lensette, of the type shown in my above U. S. Patent, is 
replaced by dual lenses, often termed doublet lenses, i.e., an optical 
doublet. Each such doublet is positioned generally medially of the 
lensfiche. The doublets are thus more or less equally spaced from both 
sides of the transparent member which carries them and which carries the 
photographic emulsion. By the use of this construction certain 
simplicities and certain economies in manufacture such as tolerance 
control may be realized. Thus, in addition to embossing or impressing a 
transparent plastic sheet with a die having the appropriate recesses to 
form the integral lensettes, I may also press transparent plastic sheets 
onto both sides of an apertured and opaque member, with resulting partial 
flow of the plastic through the apertures which thus define the optical 
doublet for each aperture. The same general technique may be employed to 
make a lensette of the type similar to that shown in my above U. S. 
Patent, namely, a microfiche of the type having integral lenses on one 
surface and a photographic emulsion on the other surface.

Referring now to FIG. 1 of the drawings, the numeral 10 denotes generally a 
microfiche, also termed a lensfiche because the lenses are integral with 
the body of the fiche. The lensfiche is identical in general structure and 
form to that shown in my noted U. S. Patent. The numeral 10 denotes 
generally the lensfiche and includes an opaque web 12 such as may be 
fashioned from aluminum provided on both surfaces with a plurality of 
generally semispherical recesses 14 regularly spaced to define an array 
over the web. The recesses 14 are pairwise vertically aligned. Apertures 
16 connect the bottoms of recesses 14. The web 12 may be termed a 
reticulate grid. The remaining top and bottom surfaces of the grid or web 
12 are denoted by the numeral 18. The numerals 20 and 22 denoted curved, 
convex portions which extend toward each other and into the apertures 16. 
The numerals 26 and 28 denoted plastic or other transparent material 
sheets with the lower sheet 26 provided with a photographic emulsion 30. 
Curved portions 20 are an integral part of sheet 28, while curved portions 
22 are an integral part of sheet 26. The sheets may be of 
poly(methylmethacrylate). The diameter of the apertures 16 is denoted by 
D.sub.1 and their rectangular spacing over the area of the microfiche 
denoted by D.sub.0. A portion of a viewing screen, also formed of a 
transparent plastic, is denoted by the numeral 32 and is provided at its 
lower portion with an opaque coating 24 and regularly spaced apertures 
such as 36. Opaque septa 60, only one of which is illustrated, preclude 
optical cross-talk in both the taking and in the viewing process. A source 
of illumination schematically denoted by the numeral 40 is positioned 
beneath the lensfiche 10. The general arrangement of elements, namely, the 
lensfiche, the viewing screen, and a source of illumination, is entirely 
analogous to that illustrated in my noted U. S. Patent, and accordingly 
the complete assembly is not illustrated. Further, their use as either a 
camera or as a projector are also entirely analogous. 
In operation, again as described in my noted U. S. Patent, microimages 
within the fixed or developed photographic emulsion 30 are projected by 
means of illumination sources 40 through those apertures 16 corresponding 
to a single micro scene, here along an axis denoted by the numeral 39. 
Light passing parallel to the indicated optic axis at 39 is refracted at 
the lower convex surface 22 and also at the upper convex surface 20 and 
passes through opening 36 to the viewing screen. Alternatively, when 
employed as a camera, the reverse operation takes place, with the 
photographic emulsion area beneath and corresponding to each doublet lens 
pair 20, 22, being activated. After each macro scene is either projected 
or photographed, the lensfiche 10 is indexed for the next operation. 
The lower sheet 26 may be of the same or of a different index of refraction 
relative to that of the upper sheet 28. While the grid or web 12 has been 
described as being of metal, it will be apparent that other opaque members 
may be employed. It will further be apparent that the parameters t.sub.1 
and t.sub.2 may be varied, as well as the radii R.sub.1 and R.sub.2. 
Referring now to FIG. 2 of the drawings, another modification is 
illustrated which is identical in construction and in operation to the 
modification shown at FIG. 1, except that the web or grid member, now 
denoted by the numeral 120, is flat on both sides, i.e., there are no 
semispherical depressions 14 of the radii R.sub.1 and R.sub.2. 
As in the previously-described embodiment an optical doublet is defined by 
the curved portion 20 associated with the upper plastic sheet 28 and the 
curved portion 22 integral with the lower plastic sheet 26. The 
construction and operation is otherwise the same as in the embodiment of 
FIG. 1. 
Referring now to FIG. 3 of the drawings, still another modification is 
illustrated, which is similar to the embodiment of FIG. 2, except that the 
apertures 16 extend between chamfered portions of radii R.sub.1 and 
R.sub.2 defined by striking out associated areas above and below the 
apertures of the indicated radii of curvature. The chamfered portions 
define concavities contiguous to their associated apertures 16. The web or 
grid is denoted in this embodiment by the numeral 122. The construction 
and operation is otherwise the same as in the embodiment of FIG. 1. 
Referring now to FIG. 6 of the drawings, a method of manufacture of any of 
the lensfiches of FIGS. 1-3 (and FIGS. 5 and 6, to be later described) is 
illustrated. The numeral 50 denotes a first or upper roll of plastic or 
other transparent material which unwinds in the indicated direction to 
yield a web or sheet of indefinite lengths denoted by the numeral 52. The 
numeral 54 denotes a central drum or roll unwinding in the indicated 
direction to yield an indeterminate length web 56, the latter formed of 
apertured metal or other opaque substance. The numeral 58 denotes a lower 
drum or roll of plastic or other transparent material unwinding to yield a 
web 60 of indeterminate length. The mumerals 62, 64, and 66 schematically 
denote radiant or other heating elements which transfer heat to the 
indicated adjacent webs. Rollers 68 and 70 may be employed to adjust the 
tension in the webs 52 and 60. Rollers 72 and 74 serve to press the webs 
52 and 60 together, on top of and on bottom of, respectively, the 
intermediate grid or web 56. The resultant laminate is denoted by the 
numeral 76 and is wound on drum 78. Later, the drum 78 may be unwound and 
cut into the desired lengths. As indicated by the exploded view of portion 
67, the reader will immediately understand that the upper web 52 defines 
the upper transparent plastic mass or sheet 28 of any of the lensfiches of 
FIGS. 1-5 while the lower web 60 defines the lower plastic mass or sheet 
26. The intermediate web 56 defines the web or grid 12, 120, or 122. Upon 
heating by the indicated heating elements, the plastic material becomes 
more readily deformable and flowable. By proper adjustment of the 
temperature and the tension in the webs and the pressure at the nip of 
rolls 72 and 74, the reader will readily understand that plastic is 
partially forced into the apertures 16 to thereby define curved, convex 
portions 20 and 22. These latter portions define optical doublets. Thus, 
referring to FIG. 1, the surface 20 in combination with the upper planar 
surface 29 of plastic mass 28 defines a first plano-convex lens while 
lower curved portion 22 in combination with its associated flat portion of 
plastic mass 26 adjacent emulsion 30 defines a second plano-convex lens. 
The openings 16 may be etched on the web 12 in the case of a metal. In the 
case of aluminum for example such techniques are well known. For the 
embodiment of FIG. 1, the aluminum sheet may be passed through embossing 
rolls (not illustrated) to generate the depressions 14 having radii of 
curvature R.sub.1 and R.sub.2. It will also be apparent that instead of 
forming the convex portions 20 and 22 of any of the embodiments by the 
means described above, such convex portions may be preformed or 
pre-embossed on the webs 52 and 60, with the structure shown at FIG. 6 
employed merely to assembly or laminate them with the intermediate and 
metallic grid portion. 
Should the diameter D.sub.1 of the aperture 16 shrink to a valve 
approximately 2 t.sub.1 lambda, where lambda is, for example, 5500 A, the 
system of any of the embodiments of FIGS. 1-6 would then define a pinhole 
lensfiche such as described in my copending application Ser. No. 474,795, 
entitled, "PINHOLE MICROFICHE CAMERA", filed May 30, 1974, here 
incorporated by reference. 
The reader will recognize that the apertures 16 define an aperture stop 
positioned midway between the two curved surfaces. Aperture stops are 
well-known in optics. The illustrated midthickness location is by far the 
best position or location for such a stop. The position of the aperture 
stop midway of the curved surfaces 20 and 22 displays the additional 
advantage of providing a degree of symmetry between the two halves of the 
optical system. Such an advantage is well known in the theory of the 
Stanhope magnifier, and, the combination of the curved surfaces 20, 22 in 
their position relative to the aperture 16 may be regarded as a minature 
Stanhope magnifier. 
By selecting the radii of curvature R.sub.1, R.sub.2 properly, chromatic 
aberration may be corrected as follows. Let B stand for a blue wavelength 
and let R stand for a read wavelength. Then the focal length of the 
lensettes for the blue light if given by: 
##EQU1## 
For the read wavelength the new focal length becomes 
##EQU2## 
In order to correct for the difference in focal lengths due to the index of 
refraction variation of the plastic, the two focal lengths are equated, 
i.e., 
##EQU3## 
The above expression yields a unique relationship between R.sub.1 and 
R.sub.2 knowing n.sub.1B , N.sub.1R , N.sub.2B , N.sub.2R 
##EQU4## 
and thereby the doublet lenslet is corrected for chromatic aberrations. 
While in general, the temperature of webs 52 and 60 are the same, the radii 
of curvature of surfaces 20 and 22 may be varied by having the temperature 
of webs 52 and 60 different. For example, different temperature will 
necessarily partially define the flow rate and hence the amount of plastic 
entering into the apertures 16 and thus the convexity or curvature of 
surfaces 20 and 22. Preferably, in order that the co-efficient of thermal 
expansion of the web 12 be the same as that of sheets 26 and 28, aluminum 
may be employed as the web and a polyester as the plastic. It will also be 
apparent that the photographic emulsion 30 may be applied to the web 60 at 
FIG. 4 at any point in the process, preferably after passing the nip of 
rolls 72 and 74. Alternatively, the emulsion may be applied after the 
laminate is unwound from roll 78. 
Referring now to FIG. 4 of the drawings, an embodiment is illustrated 
similar to that of FIG. 2, except that each optical doublet is adapted to 
accommodate only a single color to thereby permit the use of black and 
white emulsion for the taking and for the projection of color macro 
scenes. The use of black and white emulsion for the photographing and for 
the projection of color macro scenes is described in my U.S. Pat. No. 
3,824,609 , dated July 16, 1974, the teachings of which are hereby 
incorporated by references. The apertures 162, 164, 166 are of different 
diameters. The apertures of one sub-set have the diameter of aperture 162, 
the second sub-set apertures have the diameter of aperture 164, the third 
sub-set apertures have the diameter of aperture 166 (the three sub-sets 
defining the entire set of apertures.) As shown in that patent, each 
lensette of each triad of lensettes accommodates so to speak a single 
primary color such as blue or red or green. If all light of these three 
wavelengths is to be focused an equal distance from the lensettes, i.e., 
focus on the photographic emulsion, some method must be envolved which 
will compensate for the fact that these different wavelengths undergo 
different amounts of refraction. Otherwise, they would focus at different 
distances from the lensettes. In order to accomplish this I make different 
the radii of curvature for each optical doublet (in each color triad). 
Reference now to FIG. 4 will make plain this construction. If light of the 
three primary colors red, green, and blue is incident on the top of the 
lensfiche at FIG. 4, then in association with color filters such as shown 
in my U.S. Pat. No. 3,824,609, these wavelengths will all be focused on 
emulsion 30 if their associated optical doublets are properly configured. 
Such a condition is realized if the following is met: 
##EQU5## 
This condition may be met if the equation if rewritten in the following 
form, wherein the subscript 1 refers to the top radii 20 and wherein 
subscript 2 refers to the bottom radii 22. 
##EQU6## 
For the simple symmetric case of 
##EQU7## 
These last equations uniquely determine the realtionship between R.sub.1B , 
R.sub.1G and R.sub.1R knowing n(.lambda..sub.B), n(.lambda..sub.G) and 
n(.lambda..sub.R). Since in general n(.lambda..sub.B) &gt; n(.lambda..sub.B) 
&gt; n(.lambda..sub.R), R.sub.1B must be greater than R.sub.1G which in turn 
is greater than R.sub.1R , i.e., R.sub.1B &gt; R.sub.1G &gt; R.sub.1R . 
FIG. 4 has shown, for convenience, the elements of a triad of lensettes as 
positioned in a single row. This need not always be the case, as may be 
seen by reference to FIG. 1 of my 3,824,609 U.S. Pat. No. While three 
sub-sets define the "color" microfiche of FIG. 4, the number of sub-sets 
may be two (for two colors) or four (for four colors), or, in general, N. 
The above description has treated the case wherein the convex portions 20 
and 22 are either preformed and sandwiched to the central opaque and 
apertured web, or alternatively, these convex portions have been formed 
during the lamination process by plastic flow of the transparent material 
partially into the web apertures 16. In this latter method of 
construction, it may be convenient for the purpose of more accurately 
controlling the operation to place a relatively thin plastic sheet over 
both sides of the apertured web. Such a sheet is of a thickness, for 
example, of 1/2 mil and is applied to the web prior to the lamination. 
Such a sheet functions as a cushioning agent. This is illustrated at FIG. 
5 of the drawings. 
Referring now to FIG. 7 of the drawings, the numeral 82 schematically 
indicates a fan for directing ambient or refrigerated air, depending upon 
conditions of operation, onto the web 56. The reader will understand that 
fan 82 may be constructed so as to direct cooling air on either or both 
sides of web 56. 
Referring now to FIG. 8 of the drawings, similar apparatus 84 and 86 is 
arranged to direct ambient or conditioned air parallel to web 56, as 
opposed to the arrangement of FIG. 7 wherein such air is directed normal 
to the web. Fans 84 and 86 of FIG. 8 thus modify the temperatures of both 
sides of web 56 as well as the inner surfaces of the transparent sheet 
elements 26 and 28. 
The purpose of fans 82, 84, 86 is to so control the temperature of the 
sheets 26 and 28 as well as that of opaque web 56 so as to preclude the 
bonding together of the facing, convex tips of the lenses. For example, by 
reference now to FIG. 1 of the drawings, the aparatus of FIGS. 7 and 8 is 
intended to preclude the bonding together of convex lens portions 20 of 
sheet 28 and lens portions 22 of sheet 26. By cooling the heated webs 52, 
60 just prior to bonding them to the opaque sheet, such inadvertent 
touching of the facing convex lenses of the sheets is precluded. Thus, if 
the convex portions of the lenses are too hot they could fuse and join to 
thereby forbid the formation of the desired optical element. As set forth 
at FIG. 7 of the drawings, such cooling may be carried out on the opaque 
webs such that the surfaces only of the plastic sheets are chilled, but 
that the flow action is relatively unimpeded. Another method of shown at 
FIG. 8 of the drawings wherein a blast or current of cold air is directed 
to the elements just prior to joining them. Again, since only the contact 
surfaces of the transparent sheets is affected, the pressure flow will not 
be impeded and the doublet lensettes accordingly formed. Clearly, the 
cooling rate of the four surfaces involved will depend upon the velocity 
of these surfaces and the exact nature of the plastic sheets and opaque 
web. In addition, the volume flow and temperature differential of the 
coolant air and concerned surfaces will influence the overall cooling 
rate. In view of this, experimentation of a routine nature will quickly 
identify the proper flow rate and speeds of the surfaces which will yield 
the desired surface cooling, without impairing the bulk flow of plastic 
desired.