Parallel scanning system

Apparatus for scanning microimages containing graphic information which iudes a film provided with a matrix of microimage spaces, at least some of the spaces being occupied by microimages, and a light source for illuminating the microimages to generate light images of the graphic information contained on the microimages. The apparatus further includes light sensing devices for generating analog signals which represent the graphic information contained upon the microimages and missing image sensors for generating a signal which signifies that a given microimage space of the matrix is not occupied by a microimage.

BACKGROUND OF THE INVENTION 
The invention disclosed and claimed herein pertains to apparatus for 
scanning graphic information contained upon light transmissive plates, 
such as microimages, to provide electrical signals which represent or 
encode the information. More particularly, the invention pertains to 
apparatus for parallel scanning, or for simultaneously scanning all of the 
microimages included in a row of a matrix of microimage spaces. Even more 
particularly, the invention pertains to scanning apparatus of the above 
type which is provided with means for sensing that a given space of the 
matrix is not occupied by a microimage. 
It is presently well known to store the graphic information contained upon 
a page of a document by copying the information upon a microimage, or 
light transmissive plate which is greatly reduced in size from the page. 
It is also well known to position the microimages of a given document or 
related documents upon a single sheet of film, or microfiche, which has a 
standard size and a standard array of spaces for each microimage. A common 
microfiche format is that of the National Micrographic Association (NMA), 
which prescribes microfiche of six inches by four inches, each sheet 
provided with a 14.times.7 matrix array of spaces for microimages, and 
some or all the spaces being occupied by microimages. 
To transmit information contained upon microfiche to a remote location in a 
manner which avoids physical transfer of the microfiche, various systems 
have been developed for successively scanning sheets of microfiche 
containing the required information. The output of such a system is a 
series of electrical signals in which the information is encoded and which 
is readily communicable to the remote location. However, such scanning 
systems as are presently available generally are unable to simultaneously 
scan more than one microimage at a given time or to simultaneously scan 
all points across the entire width of the microimage. Rather, most 
presently available systems must sweep a light source across the width of 
a microimage, sensing light intensity at different points or pixels 
(picture elements) at different times during the sweep with a light 
sensitive device. 
In addition, a microfiche of the above type, having a given number of 
microfiche spaces, may contain fewer microimages than the number of 
spaces. If a scanning apparatus was not provided with a means for sensing 
unoccupied or blank spaces, all parts of a blank space would be scanned 
and converted to electrical signals. Because such signals would represent 
no graphic information, their transmission to a remote location is 
unnecessary. Their elimination would result in lower cost for a 
transmission link to the location. 
SUMMARY OF THE INVENTION 
The present invention provides apparatus for scanning graphic information 
contained upon light transmissive plates, and includes immovable light 
sensing means for responding to received light images by generating a 
plurality of analog signals which represent the graphic information upon 
each of the light transmissive plates. The invention further includes an 
immovable light source for projecting light toward the sensing means and a 
transport means for passing the light transmissive plates between the 
light source and the light sensing means. Preferably, the transport means 
comprises film upon which the light transmissive plates are selectively 
arrayed, and roller means for providing motion to the film. It is 
anticipated that an embodiment of the invention may be usefully employed 
to scan light transmissive plates containing any sort of graphic 
information, such as lines of printed characters, photographic images or 
pictorial images. 
In a preferred embodiment of the invention, a film may be employed which 
comprises a plurality of microfiche which are successively joined along 
the length of the film, each microfiche having a matrix array of 
microimage spaces, some or all of the spaces being occupied by 
microimages. The light sensing means comprises a number of charge coupled 
devices (CCD's) which is equal to the number of microimage spaces in a 
matrix row. The CCD's are selectively spaced apart in a linear array so 
that each of the microimages in a given matrix row simultaneously passes 
between the light source and a different CCD. Each CCD simultaneously 
scans each of the pixels in a line across the width of a microimage and 
couples the graphic information contained therein to a scanning processor, 
in the form of a set of analog signals. The scanning processor provides a 
digital output in which the graphic information contained upon respective 
light transmissive plates is encoded and suitably addressed. 
To achieve data compression in the digital output of the scanning 
processor, in applications where the invention is to be used to scan 
microfiche or other arrays of light transmissive plates in which some of 
the spaces for light transmissive plates may not be occupied, the 
invention is further provided with missing image sensor means. The missing 
image sensor is coupled to the scanning processor, and is positioned to 
sense the absence of a light transmissive plate in the space provided 
therefor before the space is scanned by a CCD. Whenever the sensor detects 
an unoccupied space in a matrix array, a signal characteristic thereof is 
coupled to the scanning processor. In response, the scanning processor 
inserts a code into its output which identifies the unoccupied space, and 
which is a much shorter digital transmission than the transmission 
required to encode each pixel of every line of the microimage. 
OBJECTS OF THE INVENTION 
An object of the present invention is to reduce the mechanical complexity 
of a system for scanning graphic information contained upon light 
transmissive plates. 
Another object is to provide an improved system for scanning graphic 
information contained upon light transmissive plates which are positioned 
in successive matrix arrays, such as microimages contained upon 
microfiche. 
Another object is to provide an apparatus for increasing the rate at which 
graphic information contained upon microimages or other light transmissive 
plates may may be scanned. 
Another object is to provide improved apparatus for simultaneously scanning 
graphic information contained upon each of a plurality of light 
transmissive plates. 
Another object is to provide an apparatus for simultaneously scanning each 
of the pixels of a scan line of a light transmissive plate containing 
graphic information. 
Another object is to eliminate acceleration and deceleration of moving 
parts in an apparatus for scanning graphic information contained upon a 
succession of light transmissive plates. 
Another object is to provide an apparatus for scanning a continuous input 
of microimages, such as microimages contained upon microfiche. 
Another object is to provide an apparatus for scanning microimages 
contained upon a plurality of microfiche sheets, which prevents loss or 
mixing of individual sheets. 
Another object of the invention is to provide apparatus for scanning 
microfiche containing an array of microimage spaces, some of the spaces 
being occupied by microimages and other spaces not so occupied, wherein 
the apparatus provides means for indicating unoccupied spaces. 
These and other objects of the invention will become more readily apparent 
from the ensuing specification when taken together with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, there are shown CCD's 10 immovably positioned in a 
linear array, each CCD 10 comprising a linear array of resolution or light 
responsive elements, and there is also shown a light source 12 immovably 
positioned to project light of constant intensity toward each of the 
elements of CCD's 10. Light source 12 comprises an incandescent source of 
selected intensity, and each CCD 10 comprises a 1728 element Fairchild 
CCD. As is well known in the art, when a CCD receives a light image, each 
light responsive element stores an amount of charge which is proportional 
to the intensity of the portion of the image impinging thereupon. The CCD 
is then clocked, and signals proportional to the respective stored charges 
are serially shifted out of the CCD. If the intensity of the impinging 
light is an analog quantity, the shifted signals are also analog, that is, 
they may have any value within a range of values. Scanning controller 14, 
which controls the operation of each CCD 10 and includes a clock, 
typically 10 MH.sub.z, is coupled to each CCD 10 to provide the required 
clock pulses therefor. 
A film 16 is joined to both a supply roller 18 and a take-up roller 20, and 
is positioned between pinch drive rollers 22 and 24, which are rotated by 
a mechanical drive 26 to move film 16. It is clear that the intensity of 
light impinging upon a CCD 10 varies with the transmittance of the 
particular portion of film passing between the CCD and light source 12. 
Film 16 is formed of material of sufficient flexibility to be wrapped 
around rollers 18 and 20, and includes a number of light transmissive 
plates, which contain graphic information and are arrayed in a matrix, or 
a plurality of matrices of rows and columns. For example, film 16 may 
contain or be comprised of a plurality of standard National Micrographic 
Association microfiche 28, which are positioned one after another along 
the length of film 16, and each of which includes a 14.times.7 matrix of 
microimage spaces or positions, some or all of the spaces being occupied 
by microimages 30. Microimages 30 may comprise, for example, light 
transmissive microimages of pages containing printed or written 
information. All portions of film 16 not included within the boundaries of 
a microimage are of selected uniform transmittance. 
Rollers 18, 20, and 22 and 24 are respectively oriented to move film 16 in 
a direction orthogonal to a plane which includes light source 12 and CCD's 
10. Each matrix of microimage spaces is oriented upon film 16 so that the 
columns thereof are parallel to the direction of motion of film 16, and so 
that the rows thereof are parallel to the linear array of CCD's 10. The 
number of CCD's 10 in the linear array is equal to the number of spaces in 
each matrix row, and one CCD 10 corresponds to each matrix column. That 
is, CCD's 10 are selectively spaced apart so that microimages 30 in 
different columns of a matrix pass betwwen light source 12 and different 
CCD's 10. 
Given the structure shown in FIG. 1, all of the microimages 30 in a given 
matrix row simultaneously pass between light source 12 and a different CCD 
10, so that all of the microimages in the row are simultaneously scanned. 
The time period required for a microimage 30 to pass between a CCD 10 and 
light source 12 comprises a number of scan intervals, and during each scan 
interval a CCD receives an image of the graphic information contained 
within, or scans, one of a plurality of scan lines. Each scan line 
comprises a very narrow segment of a microimage 30, one dimension of a 
scan line being parallel to and equal to a horizontal edge of a 
microimage, and the second dimension of the scan line being parallel to a 
vertical edge of the microimage, and being very small in comparison to the 
first dimension. 
Referring further to FIG. 1, there is shown a focusing lens 32 immovably 
positioned between film 16 and each of the CCD's 10, each lens 32 provided 
to focus a scan line 34 of a microimage upon the light responsive elements 
of a CCD 10 at the beginning of each scan interval. The intensity of the 
portion of the focused light which impinges upon a given element is 
directly related to the transmittance of, and therefore to the graphic 
information included within, a very small partition of scan line 34, or 
pixel, which corresponds to the element. Consequently, the element stores 
an amount of charge which defines or represents the graphic information 
included within the pixel. The charges respectively stored by each of the 
1728 elements of the CCD 10 is response to the focused scan line together 
define or represent all of the graphic information included within scan 
line 34. 
After each element of a scanning CCD has stored its respective charge, but 
before the conclusion of the scan interval, a clock signal coupled to the 
CCD from scanning controller 14 serially shifts 1728 analog signals into 
scanning processor 36, each analog signal being functionally related to 
one of the stored charges, and the analog signals together representing 
the graphic information included within scan line 34. During the same scan 
interval, 1728 analog signals from each of the other CCDs of the linear 
array are also shifted into scanning processor 36, the conclusion of the 
scan interval coinciding with the beginning of the next following scan 
interval. 
Scanning processor 36 comprises a device which receives the analog signals 
from each CCD 10, and responds thereto by providing a digital output in 
which all the information contained in received analog signals is 
represented or encoded. In a simple embodiment, scanning processor 36 may 
comprise conventional analog to digital conversion circuitry. In a more 
complicated embodiment, scanning processor 36 may include circuitry for 
generating a digital output in which the information contained in the 
analog signals is encoded and suitably addressed, scanning processor 36 
making use of standard coding or data compression techniques to minimize 
the amount of digital output required to communicate a given amount of 
scanned graphic information. 
It will be readily apparent that the time width of a scan interval, during 
which a CCD 10 receives a scan line image and shifts out 1728 analog 
signals, depends on the frequency of the clock 14 contained in scanning 
controller 14. It will be further apparent that each successive scan line 
must be focused upon a CCD precisely at the beginning of a scan interval. 
Otherwise, the analog signals generated by a scanning CCD will either 
represent only part of the graphic informaton contained in a scan line, or 
else will represent interference between the graphic information in 
adjacent scan lines. To achieve the required precision, rollers 22 and 24 
are rotated in such manner that film 16 moves at a constant speed, which 
may be determined by dividing the aforementioned second dimension of a 
scan line by the time width of a scan interval. To assure that film speed 
is retained at the selected constant value within very close limits, speed 
monitor 38 is coupled to scanning controller 14 such that the measured 
film speed is compared to the reference clocked speed. The constantly 
adjusted speed controlling signals are input to drive mechanism 26 to 
control speed of rotation of rollers 22 and 24, and thereby to control 
film speed. Monitor 38 may comprise a device conventionally known as an 
optical shaft encoder, which is mechanically coupled to the drive 
mechanism 26, and through the scanning controller 14 is coupled 
electrically to drive mechanism 26 in a conventionally known manner so 
that the speed of rotation of roller 24 is phase lock looped to the 
scanning rate, that is, to the number of scan intervals per unit time. 
Referring once more to FIG. 1, there are shown missing image sensors 40 
comprising a linear array of CCD's, photodiodes, or similar photoelectric 
sensors, one sensor 40 corresponding to each matrix column, and there is 
further shown a light source 42 positioned to project light toward missing 
image sensors 40. The sensor 40 corresponding to a matrix column is 
positioned with respect to the CCD 10 corresponding to the same column so 
that each microimage space in the column passes between the CCD 10 and 
light source 12 a selected time after passing between the missing image 
sensor 40 and light source 42. 
As unoccupied microimage space 44 passes between light source 42 and a 
sensor 40, a number of sets of analog signals are successively generated 
thereby, all of the signals having an equal value determined by the 
aforementioned uniform transmittance of film 16. All of the signals 
generated by the sensor 40 are coupled to missing image circuitry in 
scanning processor 36, and together comprise a signal pattern which 
signifies that a microimage is missing from the space. Missing image 
circuitry comprises any conventional circuitry which is capable of 
recognizing the above pattern signifying an unoccupied microimage space, 
and which is further capable of subsequently responding to the pattern, 
when the unoccupied space is passing between light source 12 and a CCD 10. 
The missing image circuitry causes all of the analog signals from a CCD 10 
scanning the unoccupied space to be ignored, and further causes a brief 
digital code, representing the unoccupied space, to be inserted into the 
digital output of scanning processor 36. 
Referring to FIG. 2, there are shown microfiche 28A and 28B each comprising 
a 14.times.7 matrix of microimage spaces. FIG. 2 shows each of the 
microimage spaces of microfiche 28A to be occupied by a microimage 30, and 
further shows some of the microimage spaces of microfiche 28B to be 
occupied by microimages, and other of the spaces thereof to be unoccupied. 
Referring further to FIG. 2, there is shown a bar code 46 preceding each 
microfiche on film 16 to specifically identify the microfiche. Each bar 
code is scanned by CCD's 10, and information represented thereby is 
included in the digital output of scanning processor 36. 
Referring to FIG. 3, there are shown light responsive elements 48 
comprising a CCD 10, each element receiving the image of a corresponding 
pixel 50, or partition of a scan line 34, as hereinbefore described. For 
example, FIG. 3 shows element 48a, corresponding to pixel 50a, receiving a 
small part of an image of a character "X" contained by microimage 30. 
If a microimage 30 comprises a microimage of a page of printed characters, 
the microimage 30 is very usefully oriented on film 16 so that lines of 
characters are parallel to CCD 10. By so orienting the microimages, 
scanning processor 36 will readily detect a scan line which includes only 
a space between character lines, since each of the signals from the CCD 
will be equal and at their maximum value. To enhance data compression, 
scanning processor 36 may be further provided with circuitry which is 
sensitive to a pattern of signals characteristic of a space between 
characters, which responds thereto by inserting a brief code into the 
digital output of scanning processor 36, which represents the scanned 
blank space in abbreviated form. 
While the aforementioned embodiment of the invention employs a system of 
film and rollers to continuously move a plurality of microfiche between 
light source 12 and CCDs 10, it is anticipated that other embodiments of 
the invention may employ other means for continuously passing sheets of 
microfiche therebetween, including sheets of microfiche which are 
separated from one another. 
While the aforementioned embodiment discloses a system for sensing light 
images generated by passing light through plates containing graphic 
information, it is anticipated that in other embodiments of the invention, 
light images may be sensed which are generated by reflecting light from 
plates containing graphic information. 
Obviously, many other modifications and variations of the present invention 
are possible in the light of the above teachings, and, it is therefore 
understood that within the scope of the disclosed inventive concept, the 
invention may be practiced otherwise than specifically described.