Microfilm viewer/printer projection system

A microfilm viewer/printer projection system particularly adapted for full plane plain paper copying has a first, a second and a third mirror which selectively project a document image from a horizontal object plane to a vertical viewing plane or a horizontal exposure plane. In the view mode, the first and second mirrors reflect the document image to a screen which defines the viewing plane. An AC motor movement drives the first and second mirrors to a print mode, in which the second mirror is parked in a parking zone which is enveloped by the projection path from the object plane to the exposure plane, which is defined by a belt type photoreceptor. In the print mode, the first mirror reflects the entire document image to the third mirror, which is a black mirror, and the third mirror reflects the entire document image to the photoreceptor, to expose the photoreceptor to the entire document image simultaneously.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a microfilm viewer/printer, and more particularly 
to a full plane exposure image projection system for a plain paper 
microfilm viewer/printer. 
2. Discussion of the Prior Art 
Microfilm is a well-known medium for storing and/or distributing large 
volumes of documents. Microfilm viewers are necessary for a user to read 
the documents stored on microfilm and microfilm printers are necessary to 
make a paper copy of a document stored on the microfilm. Consequently, 
machines performing both functions, commonly referred to as microfilm 
viewer/printers, are commercially available and widespread. 
In microfilm viewer/printers, it has typically been the case that in a view 
mode of the machine, the machine user could observe an image of the 
document recorded on the microfilm at a viewing screen. In a print mode, 
the projection system inside the viewer/printer directs the image to a 
xerographic copying engine inside the viewer/printer which makes a paper 
copy of the image, typically by a scanning process. 
In the scanning process, the image of the document is projected to the 
copying engine in sections by scanning consecutive portions of the 
document being reproduced. The scanning speed in such a device must be 
synchronized with the rate at which a receptor surface of the copying 
engine is moving. The mechanism for performing the scanning operation adds 
a level of complexity not necessary in full plane exposure systems. Also, 
the overall size of the microfilm viewer/printer is larger in order to 
house the scanning mechanism. 
A major difference between microfilm viewer/printers and copy machines is 
that the object being copied on a copy machine is usually copied at a 
ratio of no more than 2 to 1 as compared with copies made from microfilm 
that are copied at a ratio of from about 12:1 up to about 72:1. This 
difference makes scanning an object on a copy machine relatively non 
critical whereas the scanning of an object on a microfilm viewer/printer 
requires extremely smooth movement of the scanning device. Otherwise, the 
image being scanned will be blurred. The critical nature of the scanning 
mechanism on a microfilm viewer/printer results in this mechanism being 
more complex and more costly than the scanning mechanism of a copy 
machine. 
It has become accepted in the industry to provide a carrier for the 
microfilm which can be moved to position the image of the desired document 
of the microfilm on the viewing screen. It has also become generally 
preferred to use a plain paper copying engine, rather than a treated paper 
type engine. With the plain paper engine, separate sheets of ordinary 
paper, usually of a standard size, for example 8.5 .times. 11 inch letter 
size, are placed in a stack in a paper cassette. The copying engine feeds 
sheets from the cassette as required to make copies and when the copies 
are made, the engine issues them to the exterior of the machine. 
Microfilm viewer/printers utilizing full plane exposure are known, but a 
major problem with such prior viewer/ printers has been their size, which 
in large part has been required by their projection systems. Since the 
viewer/ printers are typically kept on a desk or countertop, it is 
important that their "footprint" on the countertop be as small as 
possible. The cost of such machines has also in part been determined by 
the complexities of the projection systems and the mechanisms associated 
with the projection systems. 
SUMMARY OF THE INVENTION 
The invention provides a microfilm viewer/printer for reproducing an image 
of a document recorded on microfilm onto a receptor sheet which overcomes 
the above problems. Means defining an object plane are provided for 
holding the microfilm bearing a microimage of the document to be 
reproduced. Means are also provided defining a viewing plane from which a 
user can view a projected image of the document. A photoreceptor defines a 
substantially horizontal exposure plane, and projection means are operable 
by the user to selectively project an image of the document from the 
object plane to either the viewing plane or to the exposure plane. By 
providing a horizontal exposure plane, a paper cassette can be positioned 
so as to feed sheets from the cassette through the machine from side to 
side. 
In a preferred form, the photoreceptor is sized and shaped to be 
simultaneously exposed to a projected image of substantially the entire 
document. Therefore, the photoreceptor surface in the exposure plane is at 
least as large as the document image projected at the exposure plane, 
which would typically be substantially the same size as the receptor 
sheet. In a preferred form of the photoreceptor, the photoreceptor is 
provided as a belt of photoconductive material, which is at least twice as 
long as the corresponding dimension of an entire document image projected 
to the exposure plane. 
In a preferred form, the projection means includes the same number of 
mirrors along a projection path from the object plane to the viewing plane 
as the number of mirrors along a projection path from the object plane to 
the exposure plane. First and second mirrors are moveable from view 
positions to exposure positions. In the view positions, the first mirror 
reflects a document image from the object plane to the second mirror, and 
the second mirror reflects the image to the viewing screen. In the 
exposure positions, the second mirror is parked out of the projection path 
and the first mirror is repositioned to reflect the image to a third 
mirror which reflects the image to the exposure plane at the 
photoreceptor. 
In an especially useful form, the exposure position of the second mirror 
positions the second mirror in a parking zone which is rearward of a 
projection path from the object plane to the first mirror, below the 
projection path from the first mirror to the third mirror, and forwardly 
of the projection path from the third mirror to the exposure plane. Thus, 
the second mirror is enveloped by the projection path from the object 
plane to the exposure plane, thereby avoiding moving the mirror 
considerably further which would be the case if it were moved to one side 
or the other of the projection path. 
In another aspect, the first and second mirrors are connected to move in 
unison between the view and exposure positions and are driven by an 
alternating current motor movement. The motor is nondirectional, so that 
an on signal will cause it start in either direction so as to move the 
first and second mirrors between the view and exposure positions by simply 
turning the motor on.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1-3 are exterior views of a viewer/printer 10 incorporating the 
invention. The viewer/printer 10 has a housing 12 which at its front has a 
screen 14 in a generally vertical viewing plane, a control panel 16 and a 
microfilm carrier 18. The microfilm viewer/printer 10 is placed on a desk 
or countertop with a user sitting in front of and facing the machine to 
operate the carrier 18 and control panel 16 so as to view a document 
recorded on the microfilm on the screen 14 or to print the document. 
In viewing a document on the screen 14, the view mode is selected on the 
control panel 16 and the carrier 18 is moved so as to place the document 
desired to be viewed over a relatively small image area which gets 
projected to the viewing screen 14. Referring to FIGS. 4-7, an object 
plane 22 is defined between two flat glass plates 24 and 25, which are 
carried by the carrier 18. A microfilm sheet held in the object plane 22 
between the glass plates 24 and 25 is moved in any direction in the object 
plane 22 to position the document desired to be viewed in the image area 
of the object plane. The document desired is then projected to either the 
viewing screen 14 for viewing by the user or to an electrophotographic 
copying engine 30 housed in the rear portion of the viewer/printer 10. 
While in the preferred embodiment a carrier 18 for microfilm sheets is 
employed, it should be understood that the principles of the invention 
could also be applied to other forms of microfilm, for example, roll type 
microfilm. 
Any suitable electro-photographic copying engine 30 may be employed in 
practicing the invention. However, to fully realize the advantages 
afforded by the invention, the copying engine should be a plain paper type 
copying engine capable of "full plane" exposure. A "plain paper" type 
copying engine has a photoreceptor which is a reusable photoconductor 
element that is charged and exposed to a projected document image to 
produce a latent electrostatic image on the photoreceptor. The latent 
electrostatic image formed on the photoreceptor by exposing it to the 
document image is subsequently developed using fine developer particles 
which in turn are transferred to a sheet of paper and fused to the paper 
to make the copy. In the embodiment illustrated, a belt type photoreceptor 
34 is employed by the electrophotographic copying engine 30 and presents 
an upwardly facing surface in a horizontal exposure plane 35. Further 
details of an electro-photographic copying engine 30 usable in practicing 
the present invention are described in copending, commonly owned U.S. 
patent application Ser. No. 07/627,678 filed Dec. 14, 1990 entitled 
"Electrostatic Image Developer Dispenser" and in co-pending, commonly 
owned U.S. patent application Ser. No. 07/682,2782 filed on the same day 
as the present application and entitled "Electro-photographic Copying 
Process", the disclosures of which patent applications are hereby 
incorporated by reference. 
What is meant by "full plane" exposure is that a microimage of an entire 
document positioned within the image area 20, is projected and 
simultaneously exposed to the copying engine. That is, the entire image of 
which a copy is desired to be made is simultaneously exposed to the 
photoreceptor. This is in contrast to many prior art microfilm 
viewer/printers in which the copying engine was serially exposed to 
portions of the entire document by a scanning process, to produce a copy 
of the entire document 
Still referring to FIGS. 1-3, for the print mode of the viewer/printer 10, 
it is desirable to provide the sheets of paper on which copies are to be 
made in a paper cassette tray 32 which is inserted on the right side of 
the viewer/printer 10. Individual sheets typically of a standard size 
(e.g., 8.5 .times. 11 inches) are stacked in the paper tray 32 and are fed 
by suitable means from the stack to the copying engine 30 for document 
images to be transferred to them Completed copies exit the machine 10 
through a slot (not shown) provided on the left side of the machine as 
viewed in FIGS. 1 and 2. Further details about the paper path through the 
machine 10 are described in the co-pending, commonly owned U.S. patent 
application Ser. No. 07/682,782, filed on the same day as this 
application, and entitled "Electro-photographic Copying Process", referred 
to above. Thus, in "full plane exposure" plain paper development, a 
photoreceptor such as the photoreceptor 34 is exposed simultaneously by 
the projection system to the entire image which ultimately is copied onto 
a sheet from the paper cassette Hence, the surface of the photoreceptor 34 
in the exposure plane 35 is at least as large as the paper held in the 
paper cassette, in order to fully utilize the area of each sheet. 
The viewer/printer 10 has a projection system which allows selectively 
projecting a document image from the object plane 22 to either the viewing 
plane defined by the screen 14 or to the exposure plane 35 defined by the 
photoreceptor 34. The projection system for the viewer/printer 10 includes 
a light source 36 provided in a drawer 38 which mounts a bulb and 
reflector unit 40, a heat filter 41, a right angle reflector 42, and a 
Fresnel lens 43. The light source 36 provided by the drawer 38 results in 
a vertical upwardly directed converging beam of light passing through the 
object plane 22 in the image area 20 thereof 
A focusing lens 46 is provided directly above the image area of the object 
plane to focus the image in the image area 20 at the object plane 22 at a 
certain distance away from the object plane 22. In the preferred 
embodiment, this distance is approximately 33 inches. This distance is 
substantially the same regardless of whether the document image from the 
object plane 22 is being projected to the viewing plane at the viewing 
screen 14 or to the exposure plane 35 at the photoreceptor 34 surface. 
That being the case, the projected document image at the viewing plane or 
at the exposure plane is in focus and projected to approximately the same 
level of magnification. It is also possible to provide different lenses 46 
to produce different levels of magnification at the same object to image 
distance. 
FIGS. 4 and 5 illustrate the projection system of the viewer/printer 10 in 
the view mode. For ease of description, it is helpful to imagine that a 
microfilm is held by the carrier 18 in the object plane 22 (between the 
glass plates 24 and 25) with a document image on the microfilm in the 
image area. Typically, the original document of which the image on the 
microfilm is a copy is a standard size. For example, a common size for 
originals is the standard 11 inch high by 14 inch wide computer document, 
hereinafter referred to as a "comdoc". Other sizes are of course also 
possible. However, for ease of description, let it be assumed that a 
comdoc microimage on the microfilm is positioned using the carrier 18 in 
the image area 20 so that its image is projected to the viewing plane 
defined by the screen 14. In this regard, preferably corner markers 48 are 
printed or otherwise provided on the screen 14 so as to identify the 
boundaries of the image to be copied properly within the image area 20. 
Note that a comdoc, which in full size is 11 inches high by 14 inches 
wide, can be reduced in size to an image which is 8 1/2 inches high by 11 
inches wide to fit the ordinary and commonly available 8 1/2 by 11 inch 
size of copier paper. In other words, the proportion of the height to 
width dimension of computer sized documents is the same as the proportion 
of the width to height dimensions of letter size documents. Thus, the 
corner markers 48 can conveniently define an area which is 8.5 inches high 
by 11 inches wide so that the image of an entire comdoc can be projected 
to the viewing plane within the boundaries of the marks 48. 
Referring to FIG. 4, ray 50 represents the top border (as viewed on the 
viewing screen 14) of a document positioned within the corner markers 48, 
ray 51 represents the bottom border of the document and ray 52 represents 
a central ray of the document In FIG. 5, ray 53 represents the left border 
or edge of a document positioned within the corner markers 48, ray 54 
represents the right border of the document and ray 52 is, as stated 
above, the central ray. Thus, rays 50-54 represent the projection of a 
rectangular or square document which is positioned at the viewing plane of 
the screen 14 within the corner markers 48. The rays 50-54 emanate from 
the image area 20 identically regardless of whether the projection system 
is in the view mode as shown in FIGS. 4 and 5 or whether it is in the 
print mode shown in FIGS. 6 and 7. 
In the view mode, a first mirror 60 and second mirror 62 are in the 
positions shown in FIGS. 4 and 5. The first and second mirrors 60 and 62 
are preferably high quality optical mirrors having a reflectivity of 
approximately 90% or greater. Substantially all of the light impinging 
upon these mirrors is reflected. 
As shown in FIG. 4, rays 50-52 are reflected by the first mirror 60 to form 
rays 50A, 51A and 52A, respectively, which are directed toward the second 
mirror 62. The second mirror 62 in turn reflects rays 50A-52A to form rays 
50B, 51B and 52B, respectively, which impinge upon the viewing screen 14 
at the viewing plane. Since the viewing screen 14 is made of or coated 
with a light filtering material, a human eye at the front of the screen 14 
can detect the image projected onto the screen 14 from the rear. 
Referring to FIG. 5, the rays represented by lines 53 and 54 are reflected 
by the first mirror 60 into rays 53AL and 54AL at the lower edge of the 
image and into rays 53AU and 54AU at the upper edge of the image. Rays 
53AL, 54AL, 53AU and 54AU are reflected by the second mirror 62 
respectively into rays 53BL, 54BL, 53BU and 54BU, which are directed 
toward the corners of the screen 14 to focus at the viewing plane defined 
by the screen 14. 
In the print mode shown in FIGS. 6 and 7, the first mirror 60 and the 
second mirror 62 are in the positions shown in FIGS. 6 and 7. Referring to 
FIG. 6, the rays 50-52 are reflected by the first mirror 60 into rays 
50A', 51A' and 52A', respectively, toward a third mirror 64. Third mirror 
64 reflects rays 50A', 51A' and 52A' to form rays 50B', 51B' and 52B', 
which are directed toward the photoreceptor 34 to focus at the exposure 
plane 35. 
Referring to FIG. 7, the rays 53 and 54, which represent the left and right 
edges of a document in the image area 20 of the object plane 22, are 
reflected by the first mirror 60 into rays 53AL' and 54AL', which 
represent respectively the left and right lower corners of the document, 
and into rays 53AU' and 54AU', which represent respectively the left and 
right upper corners of the document. The rays 53AU' and 53AL' are 
reflected by the third mirror 64 into rays represented by line 53B', which 
represents the left edge of the document, and rays 54AL' and 54AU' are 
reflected by the third mirror 64 into rays represented by line 54B', which 
represents the right edge of the document. 
In the print mode, the second mirror 62 is not used in the projection path 
between the object plane and the exposure plane. Rather, the second mirror 
62 is parked in a parking zone defined by ray 50, ray 51A', and ray 50B'. 
To ensure that the second mirror 62 does not reflect diverging light and 
thereby interfere with the projection path between the object plane 22 and 
the exposure plane 35 in the print mode, an L-shaped shading device 66 is 
utilized at the base of the mirror 62 which places the central portion of 
the mirror 62 in a shadow so that diverging rays between the object plane 
and the first mirror 60 are not reflected by the second mirror 62. It 
should also be understood that suitable blinds or other shading devices 
should be employed at the edges of the mirror 62 to prevent ambient light 
entering the viewer/printer 10 through the screen 14 from reaching the 
photoreceptor 34. 
In the preferred embodiment, the mirror 64 has a low reflectivity and may 
be referred to as a "black mirror". The mirror 64 in the preferred 
embodiment is simply a plate of optical quality glass with a flat black 
coating on its rear side. The reason for providing the mirror 64 as having 
low reflectivity is to avoid providing an excessive intensity of light at 
the exposure plane 35 which may overexpose the photoreceptor 34. 
The fore and aft dimension of the photoreceptor 34 shown in FIG. 6, which 
corresponds to the height-wise dimension of the image projected onto the 
screen 14, is substantially equal to the height of the borders defined by 
the corner marks 48. Correspondingly, the lateral dimension of the 
photoreceptor 34 from side to side as best shown in FIG. 5 is 
substantially equal to the lateral dimension on the screen 14 from side to 
side defined by the corner marks 48. Thus, a document positioned within 
the corner marks 48 on the screen 14 during the view mode will be 
projected in substantially the same dimensions at the surface of the 
photoreceptor 34 in the exposure plane 35 during the print mode. 
During viewing at the screen 14, the light source 36 is continuously lit. 
During the print mode however, the light source 36 is lit for a certain 
period of time sufficient to expose the photoreceptor 34. The period of 
time may be adjusted with an appropriate slide control 70 as shown in 
FIGS. 1 and 2. The period of illumination is thereby adjusted to produce 
the best quality copy. 
The mirrors 60 and 62 are moved in unison by the mechanism illustrated in 
FIGS. 8, 10 and 11. The first mirror 60 is hinged on pins 72 of mounts 74 
which are secured to the top of the housing 12. The mirror 60 is 
adhesively secured to a mounting plate 76 having ears 78 which pivotally 
fit over the pins 72. Adjustable stop screws 80 and 82 bear against the 
housing 12 in the extreme positions of the mirror 60 and are adjustable so 
as to adjust the angle of the mirror in its view and exposure positions 
(the view position being shown in FIG. 4 and the exposure position being 
shown in FIG. 6). The pivot axis provided by the ears 78 and pins 72 is 
positioned so as to provide a slight gravity bias of the mirror 60 into 
the print position shown in FIG. 6. 
An elastic strap 84 connects the upper edge of the mounting plate 76 for 
the first mirror 60 to the upper edge of mounting plate 86 for the second 
mirror 62. The second mirror 62 is adhesively or otherwise secured to the 
mounting plate 86 and the mounting plate 86 has ears 88 at its upper side 
edges. A rod 90 is journaled in the ears 88 by suitable lubricious plastic 
bushings (not shown). The rod 90 bears a gear 92 at each end which is 
axially sandwiched between two locking collars 94 and 95 at the left end 
as viewed in FIG. 8 and is trapped at the right end by a locking collar 95 
on the inside and an electric motor 96 on the outside. Each gear 92 meshes 
with a rack 100 formed in an L-shaped bracket 102 which is fastened to the 
top of the housing 12. The motor 96 also carries a pair of grooved rollers 
104 which are diagonally opposed and ride in slots 106 of the right hand 
L-shaped bracket 102 as viewed in FIG. 8. The rollers 104 prevent the 
motor 96 from rotating relative to the bracket 102. The brackets 102 are 
identical, and the slots 106 in the left hand bracket 102 shown in FIG. 8 
are not used. One end of the slots 106 (i.e. the rear end as shown in FIG. 
10) can be made enlarged so as to facilitate assembly of the rollers 104 
in the slots 106. 
The electric motor 96 is an AC synchronous motor which is provided with no 
internal stops. As such, the motor is non-directional and will start in 
either direction at random. If rotation in one direction is prevented, the 
motor will start in the other direction. 
The motor shaft, which extends from the left end of the motor as viewed in 
FIG. 8, is provided with a flat or other suitable means to drivingly 
engage the rod 90 and therefore the gears 92 held at the ends of the rod. 
As such, the gears 92 are driven by the motor 92 to walk along their 
corresponding racks 100. When at the rearward end of the rack, i.e., in 
the view position of the mirrors 60 and 62, if the print mode is selected 
at the control panel 16, an on signal is latched on and provided to the 
motor 96. If the motor 96 attempts to move the mirror 62 further 
rearwardly, it will be prevented since the motor is already at the 
rearward end of the rack 100. The motor will therefore start in the other 
direction to move the upper end of the mirror 62 forwardly along the rack 
100. In doing so, the lower end of the mirror 62 slides on lubricious 
plastic wear pads 108 (see FIGS. 4 and 6) and on knob 110 until the 
position shown in FIG. 6 is reached by the mirror 62. In this position, 
slack has been provided in the elastic strap 84 so that the mirror 60 is 
gravity biased to the position shown in FIG. 6. Also note that the knob 
110 is preferably mounted on a screw 112 so that turning the knob 110 will 
adjust the fore and aft position of the lower end of the mirror 62 so as 
to properly adjust its position relative to the projection path from the 
object plane 22 to the exposure plane 35 in the print mode. 
At the forward end of travel in moving from the view position to the 
exposure position of the mirrors 60 and 62, the collar 95 actuates 
position switch 114 which turns power to the motor 96 off. The balance of 
forces and friction in the mechanism is sufficient to hold the mirrors 60 
and 62 in this position. After exposure, the mirrors 60 and 62 return to 
the view position. In the view position of the mirrors 60 and 62, position 
switch 116 is actuated by collar 95 which turns off power to the electric 
motor 96. A spring mounted roller 118 may be provided at each side edge of 
the mirror 62 (See FIG. 4) to engage in the lower slots 106 at the 
corresponding side when the front of the mirror 62 is rotated upwardly, 
thereby holding the mirror 62 in the upward position so as to facilitate 
access to the rearward compartment of the housing 12 through the front of 
the machine 10. 
As best shown in FIGS. 6, 7, and 9, the photoreceptor 34 used in the 
preferred embodiment is a belt type photoreceptor in which a belt made of 
a photoconductor material suitable for plain paper electro-photographic 
image transfer processes is rotatably mounted by end rollers 120 and 122 
which are journaled on a frame 124. The roller 120 is mounted on sliding 
pins 126 which are spring biased by springs 128 so as to hold the 
photoreceptor belt 34 in tension. A third roller 130 is spring biased 
downwardly as viewed in FIG. 9 so as to maintain a certain spacing between 
the surface of the photoreceptor 34 and the developer dispenser, as more 
fully described in U.S. patent application Ser. No. 07/627,678, referred 
to above. The roller 122 is driven by a gear at its end (not shown) which 
meshes with a gear of the developer dispenser unit described in 
application Ser. No. 07/627,678 to drive the photoreceptor 34 rotatively. 
Therefore, since the surface of the photoreceptor 34 in the exposure 
plane, i.e. its top surface, is at least as large as the image of the 
entire document projected at that surface, the actual entire 
circumferential length of the photoreceptor 34 is at least twice that 
size. Since in the preferred embodiment, the dimensions of a document 
image at the exposure plane from side to side are approximately 11 inches, 
i.e., the height of standard letter size paper, the total circumferential 
length of the photoreceptor belt is more than 22 inches. In the preferred 
embodiment, the entire circumferential length of the photoreceptor belt 34 
is approximately 26 1/4 inches and its fore and aft dimension is 
approximately 8 9/16 inches.