U.S. patent number 3,815,094 [Application Number 05/098,259] was granted by the patent office on 1974-06-04 for electron beam type computer output on microfilm printer.
This patent grant is currently assigned to Micro-Bit Corporation. Invention is credited to Donald O. Smith.
United States Patent |
3,815,094 |
Smith |
June 4, 1974 |
ELECTRON BEAM TYPE COMPUTER OUTPUT ON MICROFILM PRINTER
Abstract
An electron beam type computer output on microfilm printer
employing an electron beam writing apparatus having an evacuated
housing closed by a Lenard window fabricated from a differentially
etched bulk supporting member through which the electron beam is
directed for permitting egress out of the evacuated housing into a
higher pressure ambient atmosphere surrounding the housing with a
minimum of beam scattering while maintaining the integrity of the
evacuated space within the housing. The thin window portion
consists of a material different than the bulk supporting member
and not susceptible to the etchant employed to form the window in
the supporting bulky member and may be formed by chemical reaction
with the bulk supporting member from the class of materials
consisting of Si--SiO.sub.2 ; Al--Al.sub.2 O.sub.3 ; Ta--TaO;
Ti--TiO; Si--SiC; Si--SiN; Al.sub.2 O.sub.3 on Si; and the like.
The thin SiO.sub.2, Al.sub.2 O.sub.3, TaO, TiO, etc window layer
preferably first is formed to a desired thickness on the surface of
a bulk supporting member by chemical reaction with the thin
elongated window then being etched in the bulk supporting member by
an etchant which does not react on the thin window layer. The
electron beam type computer output on microfilm printer further
includes an electron sensitive microfilm recording medium and
transport means supporting the microfilm recording medium
immediately adjacent the thin window portion of the electron beam
recording apparatus. Printer control circuit means are coupled to
the electron beam writing apparatus and the transport means for
controlling the operation thereof. A character generator supplied
from a buffer memory unit and controlled by the printer control
circuit controls deflection and beam blanking of the electron beam
recording apparatus. Use of the buffer memory allows the E-Beam COM
printer to be easily interfaced with any computer system as a
standard plug compatible peripheral equipment.
Inventors: |
Smith; Donald O. (Lexington,
MA) |
Assignee: |
Micro-Bit Corporation
(Burlington, MA)
|
Family
ID: |
22268435 |
Appl.
No.: |
05/098,259 |
Filed: |
December 15, 1970 |
Current U.S.
Class: |
347/121;
347/900 |
Current CPC
Class: |
G06K
15/1233 (20130101); H01J 37/3023 (20130101); H01J
33/04 (20130101); Y10S 347/90 (20130101) |
Current International
Class: |
H01J
37/302 (20060101); H01J 33/00 (20060101); H01J
33/04 (20060101); G06K 15/12 (20060101); H01J
37/30 (20060101); H01j 037/22 () |
Field of
Search: |
;340/172.5,173,173.2,173TP ;95/4.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Henon; Paul J.
Assistant Examiner: Woods; Paul R.
Attorney, Agent or Firm: Helzer; Charles W.
Claims
What is claimed is:
1. In an electron beam apparatus of the type including a source of
electrons disposed within an evacuated housing and means for
directing the electrons in the form of a beam toward one of the
walls of the housing, the improvement comprising a Lenard window
fabricated from a differentially etched bulk supporting member
secured to the wall of the evacuated housing and having an
extremely thin window portion through which the electron beam is
directed for permitting egress of the electron beam of the
evacuated housing into a higher pressure space surrounding the
housing with a minimum of beam scattering while maintaining the
integrity of the evacuated space within the housing, said thin
window portion consisting of a material different than the bulk
supporting member and not susceptible to be etchant employed to
form the window in the supporting bulk member.
2. thin electron beam apparatus according to claim 1, wherein the
think window portion is formed by chemical reaction with the bulk
supporting member and the differentially etched bulk supporting
member and thin window portion are from the class of materials
consisting essentially of silicon-silicon dioxide (Si--SiO.sub.2);
aluminum-aluminum oxide (Al--Al.sub.2 O.sub.3); tantalum-tantalum
oxide (Ta--TaO); titanium-titanium oxide (Ti--TiO); silicon-silicon
nitride (Si--SiN); silicon-silicon carbide (Si--SiC)
silicon-aluminum oxide (Si--Al.sub.2 O.sub.3).
3. An electron beam apparatus according to claim 1, wherein the
differentially etched bulk supporting member has a thin conductive
layer formed over at least a part of the surface of bulk supporting
member exposed to the electron beam and extending over at least
part of the thin window portion whereby build-up of a substantial
charge on the window can be minimized.
4. An electron beam apparatus according to claim 1, wherein the
electron beam apparatus is of the type including deflecting means
for deflecting the electron beam along at least one axis of
movement and said window portion comprises an elongated thin slit
having its long axis extending in the direction of deflection of
the electron beam.
5. An electron beam apparatus according to claim 1, wherein said
window portion comprises an elongated thin slit having a width
which is more narrow than the largest dimension of the cross
section of an elongated electron beam produced by the electron beam
apparatus.
6. An electron beam apparatus to claim 1, wherein the
differentially etched bulk supporting member is silicon and the
thin window portion is comprised by a thin layer of silicon dioxide
previously formed to a desired thickness on the surface of the bulk
supporting silicon member by controlled chemical reaction prior to
etching the window therein and wherein the thin slit window portion
as a width on the order of 5-75 microns and a thickness on the
order of 500-2,000 angstrom units.
7. An electron beam apparatus according to claim 4, wherein the
electron beam apparatus further includes additional micro
deflecting means for deflecting the electron beam along two
transverse axes of movement with respect to a character wide thin
slit window portion for writing a line of alphanumeric characters,
and beam blanking means for blanking the electron beam at
appropriate points along the line of characters to provide for
separation and formatting of the written characters.
8. An electron beam apparatus according to claim 4, wherein an
array of characters masks having openings there in forming
alphanumeric characters are arranged along the longitudinal
dimension of the elongated thin slit window portion and the
deflecting means serves to deflect the electron beam to a selected
character on one of the character masks, and the electron beam
apparatus further includes micro deflection means disposed
intermediate the array of character masks and the first mentioned
deflecting means for focusing and deflecting a desired alphanumeric
character-shaped electron beam produced by passage of the electron
beam through a selected character opening on one of the character
masks to cause the same to be directed through the thin window
portion and a desired point along its length.
9. An electron beam apparatus according to claim 4, wherein an
extremely fine slit window portion is provided having a width on
the order of the diameter of the electron beam whereby partial
character recording can be achieved during each scan of the
electron beam across the longitudinal direction of the window
portion accompanied with appropriate beam blanking at selected
points along the path of travel thereof to provide character
spacing and formatting and repetitive scans of the electron beam
are required for complete character recording.
10. An electron beam apparatus according to claim 9, wherein the
differentially etched bulk supporting member is silicon and the
thin window portion is comprised by a thin layer of silicon dioxide
previously formed on the surface of the bulk supporting silicon
member prior to etching the window therein and the elongated thin
slit window portion has a longitudinal dimension on the order of
the length of a line of recorded characters and a thin width
portion on the order of 5 microns with the thickness of the window
portion being on the order of 500-2,000 angstrom units.
11. An electron beam apparatus according to claim 9, further
including means for blanking the beam of electrons at appropriate
points along the path of travel thereof during the scanning of the
beam in the longitudinal direction of the thin slit window
portion.
12. An electron beam apparatus according to claim 11, wherein said
electron beam blanking means comprises means for producing suitable
on-off blanking signals supplied to the control grid of the
electron beam apparatus.
13. An electron beam apparatus according to claim 11, wherein said
electron beam blanking means comprises deflecting means for
deflecting the electron beam transversely to the longitudinal axis
of the elongated thin slit window portion so that the sides of the
supporting bulk member intercept and blank the beam at points where
beam blanking is desired.
14. An electron beam COM printer system including an electron beam
apparatus of the type set forth in claim 1, an electron sensitive
microfilm recording medium, transport means for supporting the
microfilm recording medium immediately adjacent the thin window
portion of the electron beam recording apparatus for recording data
thereon, printer control circuit means coupled to said electron
beam writing apparatus and the transport means for controlling the
operation thereof, and character generator circuit means controlled
by the printer control circuit means and coupled to the electron
beam writing apparatus for controlling the operation thereof in
conjunction with the printer control circuit means, said printer
control circuit means and said character generator circuit means
being controlled from the output of a computer system with which
the COM printer is used as a print-out device.
15. An electron beam COM printer system according to claim 14,
further including buffer memory means intercoupled with the printer
control circuit means and the character generator means for
receiving a predetermined number of lines of data to be printed
from a computer system central processing unit plus control data
for directing operation of the printer control circuit means, said
buffer memory means serving to store temporarily the predetermined
number of lines of data while each line of data is being printed
out by the COM printer thereby freeing the computer system central
processing unit for further operations during printing of the
stored lines of data.
16. An electron beam COM printer system according to claim 15,
wherein the electron beam recording apparatus is of the type
including deflecting means for deflecting the electron beam along
at least one axis of movement and the window portion comprises an
elongated thin slit having its long axis extending in the direction
of deflection of the electron beam, said transport means operates
to move the microfilm recording medium in a direction transverse to
the longitudinal axis of the elongated thin slit window whereby
successive lines of data can be recorded raster fashion, said
printer control circuit means is coupled to and controls operation
of the deflecting means to cause tracing of the electron beam along
the longitudinal dimension of the elongated thin slit window
portion, and the character generator circuit means controls beam
blanking and character formatting.
17. An electron beam COM printer system according to claim 16,
wherein the differentially etched bulk supporting member is silicon
and the thin window portion is comprised by a thin layer of silicon
dioxide previously formed on the surface of the bulk supporting
silicon member by chemical reaction prior to etching the window
therein and wherein the thin slit window portion has a length on
the order of one line of recorded alphanumeric characters on
microfilm, a width on the order of 75 microns and a thickness on
the order of 1,000-5,000 angstrom units.
18. An electron beam COM printer system according to claim 17,
further including means enclosing the Lenard window portion of the
electron beam apparatus and the microfilm disposed immediately
adjacent the Lenard window portion in an enclosed space maintained
at a reduced pressure relative to the surrounding ambient
atmosphere.
19. An electron beam COM printer system according to claim 16,
wherein said window portion comprises an elongated thin slit having
its longest dimension approximating the length of a line of
microfilm recorded alphanumeric characters and having the thin
dimension thereof approximating the height of an individual
alphanumeric character recorded on microfilm, and wherein the
electron beam recording apparatus further includes additional micro
deflecting means for deflecting the electron beam along two
transverse axes of movement with respect to the character wide
elongated thin slit window portion for writing a line of
alphanumeric characters, and beam blanking means for blanking the
electron beam at appropriate points along the line of characters to
provide for separation and formatting of the written line of
characters, said character generator circuit means controlling
operation of both said additional micro deflecting means and said
beam blanking means.
20. An electron beam COM printer system according to claim 19,
wherein the differentially etched bulk supporting member is silicon
and the thin window portion is comprised by a thin layer of silicon
dioxide previously formed on the surface of the bulk supporting
member by chemical reaction prior to etching the window therein and
wherein the thin slit window portion has a width on the order of 75
microns and a thickness on the order of 1,000-5,000 angstom
units.
21. An electron beam COM printer system according to claim 16,
wherein an array of character masks having openings therein forming
alphanumeric characters are arranged along the longitudinal axis of
the elongated thin slit window portion and the deflecting means
serves to deflect the electron beam to a selected character on one
of the character masks, and said electron beam recording apparatus
further including micro deflection means disposed intermediate the
array of character masks and the first mentioned deflecting means
for focusing and deflecting a desired alphanumeric character-shaped
electron beam produced by passage of the electron beam through a
selected character opening on one of the character masks to cause
the same to be directed through the thin window portion at a
desired point along its length and thereby record an electron image
of the selected character at a desired point on the microfilm
recording medium disposed under the thin window portion.
22. An electron beam COM printer system according to claim 16,
wherein an extremely fine elongated slit window portion is provided
having a width on the order of the diameter of the electron beam
and means are provided for repetitively scanning the electron beam
in the direction of the longitudinal axis of the elongated window
portion together with means for blanking the beam of electrons at
appropriate points along the path of travel thereof whereby partial
character recording is achieved during each scan of the electron
beam, and the transport means moves the microfilm recording medium
transverse to the longitudinal dimension of the elongated fine slit
window portion intermediate each scan whereby during successive
scans of the electron beam raster recording of lines of complete
alphanumeric characters is achieved by the accumulation of partial
character recordings accomplished during each respective scan of
the electronic beam.
23. An electron beam COM printer system according to claim 22
wherein the thin window portion is formed by chemical reaction with
the bulk supporting member and the differentially etched bulk
supporting member and thin window portion of the electron beam
recording apparatus are from the class of materials consisting
essentially of silicon-silicon dioxide (Si--SiO.sub.2);
aluminum-aluminum oxide (Al--Al.sub.2 O.sub.3); tantalum-tantalum
oxide (Ta--TaO); titanium-titanium oxide (Ti--TiO); silicon-silicon
nitride (Si--SiN); and silicon-silicon carbide (Si-SiC);
silicon-aluminium oxide (Si--Al.sub.2 O.sub.3).
24. An electron beam COM printer system according to claim 22
wherein the differentially etched bulk supporting member comprising
a part of the electron beam recording apparatus is silicon and the
thin window portion thereof is comprised by a thin layer of silicon
dioxide previously formed to a desired thickness on the surface of
the bulk supporting silicon member by chemical reaction prior to
etching the window therein and the elongated thin slit window
portion has a longitudinal dimension on the order of the length of
a line of recorded characters and a width on the order of 5 microns
with the thickness of the window portion being on the order of
500-2,000 angstrom units.
25. An electron beam COM printer system according to claim 24,
wherein the means for blanking the beam of electrons at appropriate
points during each individual scan thereof comprises on-off
blanking signals supplied to the control grid of the electron beam
recording apparatus from the character generator circuit means.
26. An electron beam COM printer system according to claim 24,
wherein the means for blanking the beam of electrons at appropriate
points during each individual scan thereof comprises deflecting
means for deflecting the electron beam transversely to the
longitudinal axis of the elongated thin slit window portion so that
the sides of the supporting bulk member intercept and blank the
beam at points where beam blanking is desired.
27. An electron beam COM printer system including in combination an
electron beam recording apparatus comprising an evacuated housing
having a source of electrons disposed therein and controlled by a
control grid, means for directing the electrons in a beam toward
one end of the housing, a Lenard window secured to the housing
against which the electrons are directed, said Lenard window being
fabricated from a differentially etched bulk supporting member
secured to the wall of the evacuated housing and having an
extremely thin window portion in the form of an elongated thin slit
through which the electron beam is directed to permit egress of the
electron beam out of the evacuated housing, said elongated slit
thin window portion consisting of a material formed on but
different than the bulk supporting member and not susceptible to
the etchant employed to form the window in the bulk supporting
member, deflecting means for deflecting the electron beam along the
longitudinal axis of the elongated thin slit window portion, an
electron sensitive microfilm tape recording medium, tape transport
means for disposing the microfilm tape recording medium immediately
adjacent the elongated slit window portion of the electron beam
recording apparatus and for transporting the tape past the window
portion in a direction transverse to the longitudinal axis of the
elongated thin slit window portion, developing means for developing
electron images recorded on the microfilm tape recording medium,
printer control circuit means coupled to the deflecting means for
said electron beam recording apparatus, to said tape transport
means and to said developing means for controlling the operation
thereof, and character generator circuit means controlled by the
printer control circuit means and coupled to the control grid for
the electron source of the electron beam recording apparatus for
controlling operation of the electron beam recording apparatus in
conjunction with the printer control circuit means whereby the
electron beam is caused repetitively to scan along the longitudinal
axis of the elongated thin slit window portion and is blanked at
appropriate points in accordance with characters to be recorded,
said printer control circuit means and said character generator
circuit means being controlled from the output of an electronic
computer system with which the COM printer is used as a print-out
device.
28. An electron beam COM printer system according to claim 27,
wherein the differentially etched bulk supporting member and thin
window portion are from the class of materials consisting
essentially of silicon-silicon dioxide (Si--SiO.sub.2);
aluminum-aluminum oxide (Al--Al.sub.2 O.sub.3); tantalum-tantalum
oxide (Ta--TaO); and titanium-titanium oxide (Ti--TiO);
silicon-silicon nitride (Si--SiN); silicon-silicon carbide
(Si--SiC); and silicon-aluminium oxide (Si--Al.sub.2 O.sub.3).
29. An electron beam COM printer system according to claim 27,
wherein an extremely fine slit window portion is provided having a
width on the order of the diameter of the electron beam whereby
partial character recording is achieved during each scanning of the
electron beam across the longitudinal direction of the window
portion accompanied with appropriate beam blanking at selected
points along the path of travel thereof to provide character
spacing and formatting, and the transport means moves the microfilm
recording medium transverse to the longitudinal dimension of the
elongated thin slit window portion intermediate each scan whereby
during successive scans of the electron beam raster recording of
lines of complete alphanumeric characters is achieved by the
accumulation of partial character recordings accomplished during
each respective scan of the electron beam.
30. An electron beam COM printer system according to claim 27,
further including buffer memory means intercoupled with the printer
control circuit means and the character generator means for
receiving a predetermined number of lines of data to be printed
from a computer system central processing unit plus control
instructions for directing operations of the printer control
circuit means, said buffer memory means serving to store
temporarily the predetermined number of lines of data plus control
instructions while it is being printed out by the COM printer
device thereby freeing the computer system central processing unit
for further operations during printing of the stored lines of
data.
31. An electron beam COM printer system according to claim 30,
wherein each character recorded on the microfilm tape recording
medium is comprised of a matrix of horizontal coextending and
vertical transversely placed dots measured with respect to the
longitudinal axis of the elongated thin slit window and with the
equivalent of a predetermined number of dot spacings between
characters in each line and between each line of characters, the
placement of a dot in the formation of a character in a line of
characters and the spacing thereof with respect to other dots
comprising the character and line of characters being controlled by
appropriate manipulation of the beam deflection means and beam
blanking means of the electron beam recording apparatus.
32. An electron beam COM printer system according to claim 31,
wherein the printer control circuit means comprises dot clock pulse
and control circuit means coupled to and responsive to the buffer
memory means for generating the basic dot clock pulse signal,
horizontal dot position-in-a-character counter means responsive to
the dot clock pulse and control circuit means, horizontal
characters-in-a-line counter means responsive to the horizontal dot
position-in-a-character counter means and coupled to and
controlling a ramp generator means for driving the deflection means
for deflecting the electron beam horizontally along the
longitudinal axis of the elongated thin slit window portion, means
for coupling the output from said characters-in-a-line counter
means back to the input of the dot clock pulse and control circuit
means for inhibiting operation of said dot clock pulse and control
circuit means during the retrace portion of the beam deflection
means, vertical line-in-a-page counter means coupled to the output
from said characters-in-a-line counter means and controlling said
tape transport and developing means,
vertical-dot-position-in-a-character counter means responsive to
the output from the characters-in-a-line counter means, said
character generator means comprising a read only memory matrix
responsive to the buffer memory means and the output of the
vertical-dot-position-in-a-character counter means and digital
multiplexing circuit means supplied with said dot clock pulses and
controlled by read only memory matrix for controlling the grid
driving amplifier supplying the control grid of the electron beam
recording apparatus for intensifying the electron beam at points
where dots are to be recorded.
33. An electron beam COM printer system according to claim 32,
wherein an extremely fine elongated slit window portion is provided
having a width on the order of the diameter of the electron beam
whereby partial character recording is achieved during each
individual scan and recording of a complete character is
accomplished by a series of successive scans of the electron beam
across the longitudinal axis of the elongated thin slit window
portion accompanied with appropriate intensification of the
electron beam at selected points as determined by the read only
memory along the path of travel of the electron beam to provide dot
spacing and formatting of the characters being printed.
34. An electron beam COM printer system according to claim 33,
wherein the differentially etched bulk supporting member is silicon
and the thin window portion is comprised by a thin layer of silicon
dioxide previously formed to a desired thickness on the surface of
the bulk supporting silicon member by chemical reaction prior to
etching the window therein and the elongated thin slit window
portion has a longitudinal dimension corresponding to the length of
a line of 132 recorded alphanumeric characters plus appropriate
spacing between characters and a width on the order of 5 microns
with the thickness of the window portion being on the order of
500-2,000 angstrom units.
35. An electron beam COM printer system including in combination an
electron beam recording apparatus comprising an evacuated housing
having a source of electrons disposed therein and controlled by a
control grid, means for directing the electrons in a beam toward
one end of the housing, a target window secured to the housing
against which the electrons are directed, said target window being
capable of emanating radiation exterior of said housing through an
extremely thin window portion in the form of an elongated thin slit
through which radiation is directed to permit egress out of the
evacuated housing, said target windows comprising a bulk supporting
portion having a window etched therein and secured to said housing
and said thin window portion being formed from a material different
from the bulk supporting portion and not susceptible to the etchant
employed to form the window in the bulk supporting portion,
deflecting means for deflecting the electron beam along the
longitudinal axis of the elongated thin slit target window, a
microfilm tape recording medium, tape transport means for disposing
the microfilm tape recording medium immediately adjacent the
elongated slit target window of the electron beam recording
apparatus and for transporting the tape past the window in a
direction transverse to the longitudinal axis of the elongated thin
slit target window developing means for developing images recorded
on the microfilm tape recording medium, printer control circuit
means coupled to the deflecting means for said electron beam
recording apparatus, to said tape transport means and to said
developing means for controlling the operation thereof, and
character generator circuit means controlled by the printer control
circuit means and coupled to the control grid for the electron
source of the electron beam recording appartus for controlling
operation of the electron beam recording apparatus in conjunction
with the printer control circuit means whereby the electron beam is
caused repetitively to scan along the longitudinal axis of the
elongated thin slit target window and is blanked at appropriate
points in accordance with characters to be recorded, said printer
control circuit means and said character generator circuit means
being controlled from the output of an electronic computer system
with which the COM printer is used as a print-out device.
36. An electron beam COM printer system according to claim 35,
further including buffer memory means intercoupled with the printer
control circuit means and the character generator means for
receiving a predetermined number of lines of data to be printed
from a computer system central processing unit plus control
instructions for directing operation of the printer control circuit
means, said buffer memory means serving to store temporarily the
predetermined number of lines of data while it is being printed out
by the COM printer device thereby freeing the computer system
central processing unit for further operations during printing of
the stored lines of data.
37. An electron beam COM printer system according to claim 36,
wherein each character recorded on the microfilm tape recording
medium is comprised of a matrix of horizontal dots coextensive with
the longitudinal axis of the elongated thin slit window and
vertical dots disposed transverse to the longitudinal axis of the
elongated thin slit window with the equivalent of a predetermined
number of dot spacings between characters and each line of
characters, the placement of a dot in the formation of a character
in a line of characters and the spacing thereof with respect to
other dots comprising the character and line of characters being
controlled by appropriate manipulation of the beam deflection means
and beam blanking means for the electron beam recording
apparatus.
38. An electron beam COM printer system according to claim 37,
wherein the printer control circuit means comprises dot clock pulse
and control circuit means coupled to and responsive to the buffer
memory means for generating the basic dot clock pulse signal,
horizontal dot position-in-a-character counter means responsive to
the dot clock pulse and control circuit means, horizontal
characters-in-a-line counter means responsive to the horizontal dot
position-in-a-character counter means and coupled to and
controlling a ramp generator means for driving the deflection means
for deflecting the electron beam horizontally along the
longitudinal axis of the elongated thin slit target window, means
for coupling the output from said characters-in-a-line counter
means back to the input of the dot clock pulse and control circuit
means for inhibiting operation of said dot clock pulse and control
circuit means during the retrace portion of the beam deflection
means, vertical line-in-a-page counter means coupled to the output
from said characters-in-a-line counter means and controlling said
tape transport and developing means, vertical
dot-position-in-a-character counter means responsive to the output
from the characters-in-a-line counter means, said character
generator means comprising a read only memory matrix responsive to
the buffer memory means and the output of the vertical dot
position-in-a-character counter means, and digital multiplexing
circuit means supplied with said dot clock pulses and controlled by
said read only memory matrix for controlling the grid driving
amplifier supplying the control grid of the electron beam recording
apparatus for intensifying the electron beam at points where dots
are to be recorded.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a new and improved electron beam type of
computer output on microfilm printer.
More particularly, the invention relates to a computer output
printer of the type which records data to be printed-out from a
computer system on a microfilm recording medium and which employs
an electron beam recording apparatus having a novel Lenard window
which allows the electron beam to be brought out into ambient
atmospheric conditions for direct recording of electron images on
the microfilm without undue scattering of the beam and while
maintaining the integrity of the evacuated electron beam
source.
2. Prior Art Situation
The end product of most computer systems traditionally has been
hard copy print-outs which are usually in human readable form.
These hard copy print-outs traditionally have been obtained from
impact line printers such as drum printers, chain printers and
oscillating bar printers. In all of these devices, the printing
technique employed involves an "on-the-fly" approach in which high
print speeds are achieved by extremely rapid hammer action against
continuously moving type elements. The print cycle is the time
required to load a buffer storage servicing the printer, decode its
contents, print one line including hammer action and recoil, and
space the paper. In this process, all characters move past the
print hammers, the character to be printed is selected by decoding,
and a fast action hammer, controlled by an actuator, presses the
paper against the type slugs at the exact moment the required
character is in correct position. The limiting factors on printing
speed with impact type printers, tend to be mechanical in nature
and are associated with paper handling and paper motion. Hence,
current impact printers approach the upper limit of the fastest
printing speed of which impact type printers inherently are capable
and this is on the order of 2,000 alphanumeric character lines per
minute.
Computer systems generally consist of three basic components: input
devices for entering data into the system, a processing unit for
processing the data, and output devices for recording the process
results. The throughput of a computer system is governed by the
slowest component. In most computer system applications, the
processing unit and the input device transfer rates are
sufficiently fast so that the output device of the system is the
limiting factor in the overall system speed.
Output devices can consist of card punches, paper tape punches,
magnetic tape unit, or line printers. All of these units can accept
information transmitted from the processing unit and record the
information as directed by the programmed instructions. However,
only the line printer has the capability of rendering the
information human readable. The other type of output devices
require separate "off line" stations to transcribe the data to
human readable form. Such stations are expensive and perform only a
single function; hence, most "off line" stations have been replaced
by small computing stations comprising buffer storage and
peripheral control units. The buffer storage unit is placed between
the input-output devices and the processing unit and data is
transferred on command from the processing unit to the buffer
storage, and then from the buffer storage to the printer. The time
required for transfer of data between the processing unit and the
buffer storage is only a fraction of the time that otherwise would
be required to transfer the data directly from the processing unit
to the printer. Hence, the line printer can be directed to record
the contents of the buffer storage while the processing unit is
free to continue with the processing for the next data
manipulation.
The prime prerequisites for a good printer are a high transfer rate
or speed expressed as lines per minute and print quality. As stated
above, impact printers using some kind of mechanically driven type
bar currently are used extensively where human readable print-out
is required. Because impact printers require mechaincal movement
and are therefore speed limited, non-impact printers which require
no mechanical movement to achieve print-out have come into wide
spread use. Since speed is the major consideration as discussed
above, non-impact printers have become quite popular.
Non-impact printers usually employ techniques such as photographic,
xerograpic and cathode-ray tube methods where the final copy
normally is in the form of microfilm or specially treated paper.
Where a hard copy is required, the microfilm image normally is
transferred to specially treated paper. This is a maor disadvantage
of known non-impact printers in that the specially treated paper is
expensive and often of unknown consistency. In addition, the known
non-impact printers are incapable of producing more than one copy
of the print-out. However, non-impact printers offer the potential
of extremely high printing speeds at comparatively low costs. It is
this high speed - low cost factor that has caused a recent spin of
activity in computer-output to microfilm printing.
Recently, computer-output microfilmers (COM) have come into
widespread use becaue of their high speed - low cost factor and due
to the fact that they convert machine readable data directly to
eye-legible information on microfilm through the medium of an
appropriate microfilm reader. These COM printers constitute a new
class of peripheral output devices for use with computer
systems.
The COM printing process can be briefly summarized as follows:
1. The COM printer sends a signal to the central processing unit of
the computer system when it is ready to print. Alternatively, the
COM printer could be used with a magnetic tape unit to print out
results previously recorded on a magnetic tape. However, for the
purposes of the present discussion, it will be assumed that the COM
printer is on line and printing results supplied thereto directly
from the central processing unit of the computer. The information
transmitted by the processing unit contains instructions
interspersed with the data concerning procesures for frame advance,
retrieval code, forms projections and the like.
2. The output data to be printed out is fed into a character
generator where it is converted into deflection voltages for
controlling an electron beam for a cathode ray tube (CRT), a
photo-diode matrix or the like.
3. The controlled electron beam is used to construct the desired
character on the face of a CRT or directly onto a film.
4. The image if not written directly into the microfilm recording
medium, is displayed on the fluorescent face of a CRT and
photographed.
5. The microfilm subsequently is developed and distributed for
copying, printing or viewing in a microfilm reader.
In general, the most interesting aspect of COM has been the
revelation to the electronic data processing industry that
microfilm can be the heart of a sophisticated information storage
and retrieval system that can be and is used on day-to-day active
records, rather than dead storage. In addition, COM is the first
practical device that can produce original data at a lower price
than it could be produced on paper.
The two basic techniques employed by known COM printer systems are
optics and electron beams. Most of the known systems use an
electron beam in a CRT to produce a light image that then is
focused on the microfilm. Currently, there are approximately 24
commercially available COM printer systems of this general type.
Another known COM printer system writes directly into the microfilm
with an electron beam while yet another employs fiber optic devices
responsive to a photo-diode matrix to achieve recording on the
microfilm. At least one of these devices operates like a standard
plug compatible peripheral equipment for use with known computer
systems.
In the past, microfilm information sotrage systems were limited by
their incapacity to record information on film at high speed and
their inability to easily restructure, reorganize and update
information. COM has given to microfilm these abilities. However,
with respect to existing COM printer systems, these known systems
all have certain deficiencies in one respect or another. Those
systems employing CRT's for converting the data to light images
that then are focused on the microfilm produce poor quality images
due to low resolution, insufficient intensity and the like. While
one known electron beam COM printer system which records directly
on microfilm with electron images, overcomes certain of these
problems, because of its nature and design to bring the electron
beam directly to the microfilm recording medium, it is difficult
and costly to maintain. This is due to the fact that the microfilm
is brought into the electron beam recording space through seals
which also of necessity lowers the evacuation of the space. This in
turn results in the burning out of cathode sources for the electron
beam because of the poor vacuum in which they operate. Others of
the devices are incapable of producing good quality images because
of limited intensity or limited resolution.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to
provide a new and improved electron beam type computer output on
microfilm printer (hereinafter referred to as an EBCOM printer) and
electron beam recording apparatus having high speed printing
capabilities together with good resolution and high intensity to
provide good quality microfilm prints, and which possesses long
cathode life for its electron beam source.
Another object of the invention is to provide an EBCOM printer
having the above characteristics which is adapted for use with a
wide variety of character formation techinques and is usable with a
large number of different microfilm recording mediums both as to
composition (i.e., wet silver, dry silver, etc.) and form (i.e.,
tape, card, drum, disk, etc.).
A further object of the invention is the provision of an EBCOM
printer employing a new recording techinque involving the partial
recording of a character with each individual scan of a recording
electron beam while mechanically moving the microfilm recording
medium transversely to the direction of the scanning electron beam
to accomplish raster recording of characters in a line after a
series of repetitive scans.
A still further object of the invention is the provision of an
EBCOM printer as set forth above which in actuality comprises a
combined controller-EBCOM printer having a buffer memory that
allows it to be easily interfaced with any known computer system as
a standard, plug-in compatible peripheral equipment and having a
print-out speed on the order of 10,000 to 25,000 lines per minute
so that it places little or no constraints on the high speed
processing capability of a computer system with which it is used as
a printout device.
In practicing the invention, the EBCOM printer system is provided
employing an electron beam apparaus having a source of electrons
disposed within an evacuated housing together with means for
directing the electrons in the form of a beam toward one of the
walls of the housing. A Lenard window fabricated from a
differentially etched bulk supporting member is secured to the wall
of the evacuated housing and has an extremely thin window portion
through which the electron beam is directed for permitting egress
of the electron beam out of the evacuated housing into higher
pressure ambient conditions surrounding the housing with a minimum
of beam scattering while maintaining the integrity of the evacuated
space within the housing. The thin window portion consists of a
material different than the bulk supporting member and is not
susceptible to the etchant employed to form the window in the
supporting bulk member. Preferably, the thin window ortion is
formed by chemical reaction with the bulk supporting member. It
should be noted at this point in the description that the terms
"thin window portion" and "window" are considered to be synonymous
while the bulk supporting member forms the window frame. The bulk
supporting member and thin window portion maybe from the class of
materials comprising Si--SiO.sub.2, A1--A1.sub.2 O.sub.3, Ta--TaO,
T1--TiO, Si--SiC, Si--SiN, A1.sub.2 O.sub.3 on Si and the like. In
a preferred embodiment of the invention, the differentially etched
bulk supporting member is silicon (Si) and the thin window portion
is comprised by a thin layer of silicon dioxide (SiO.sub.2)
previously formed to a desired thickness on the surface of the bulk
supporting silicon member by chemical reaction prior to etching the
window therein.
The electron beam apparatus is of the type including deflecting
means for deflecting the electron beam along at least one axis of
movement and the this window portion comprises an elongated thin
slit having its long axis extending in the direction of deflection
of the electron beam. The EBCOM printer system is further comprised
by transport means for supporting a microfilm recording medium
immediately adjacent the elongated thin slit window portion and is
designed to move the microfilm recording medium in a direction
transverse to the longitudinal axis of the elongated thin slit
window. A printer control circuit is coupled to and controls the
electron beam apparatus and the transport means together with a
character generator which also is coupled to the electron beam
apparatus. The arrangement is such that the electron beam is caused
to repetitively scan along the longitudinal axis of the elongated
thin slit window while the character generator blanks the beam at
appropriate points to provide character formatting and spacing. If
desired, X-Y deflection of the electron beam can be provided
whereby an entire character is written out as the electron beam is
scanned across the width of the microfilm recording tape.
In a preferred form of an EBCOM printer constructed in accordance
with the invention, each character recorded on the microfilm tape
recording medium is comprised of a matrix of horizontal
co-extending and vertical transversely placed dots measured with
respect to the longitudinal axis of the elongated tin slit window
and with the equivalent of a predetermined number of dot spacings
between characters in each line and between each line of
characters. Placement of a dot in the formation of a character in a
line of characters and the spacing thereof with respect to other
dots comprising each character and line of characters is controlled
by appropriate manipulation of the beam deflection means and the
beam blanking means of the electron beam recording apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and many of the attendant advantages of
this invention will be appreciated more readily as the same becomes
better understood by reference to the following detailed
description, when considered in connection with the accompanying
drawings, wherein like parts in each of the several figures are
identified by the same reference character, and wherein:
FIG. 1 is an overall functional block diagram of a EBCOM printer
system constructed in accordance with the invention;
FIGS. 1A and 1B are partial cross-sectional views of novel Lenard
window constructions used with the EBCOM printer system of FIG. 1,
and constructed in accordance with the invention;
FIG. 2 is a schematic functional diagram of one form of electron
beam recording apparatus constructed in accordance with the
teachings of the present invention and usable in the EB COM printer
system of FIG. 1;
FIG. 3 is a functional schematic diagram of still a different form
of E-beam recording apparatus constructed in accordance with the
invention and usable with the EB COM printer system of FIG. 1;
FIG. 3A illustrates a character mask employed in the embodiment of
the invention shown in FIG. 3; and
FIGS. 4A and 4B are functional block diagrams of still a different
form of EB COM printer system constructed in accordance with the
invention and providing a novel recording technique employing
partial character recording during each individual scan of an
electron beam writing apparatus employing the novel Lenard window
structure of the invention as depicted in FIG. 4C.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
1. Electron Beam Recording Apparatus
FIG. 1 is a functional block diagram of a new and improved EB COM
printer constructed in accordance with the invention. The heart of
the EB COM printer is comprised by an electron beam recording
apparatus 10 contained within an evacuated housing indicated by the
dotted lines 11 and including an electron beam source comprised by
the cathode 12, control grid 13, and anode 14, maintained at
suitable potentials supplied thereto from a power supply 15.
Electrons produced by sources 12-14 are formed in the shape of a
beam indicated by 16, by a suitable focusing lens arrangement 17,
and directed towards a wall of the evacuated housing 11.
The wall of evacuated housing 11 against which the electron beam 16
is directed has a new and improved Lenard window structure shown
generally at 18 secured thereto. FIG. 1A of the drawings is an
enlarged cross-sectional view of the Lenard window structure 18 and
illustrates its construction in greater detail. The Lenard window
structure is fabricated from a differentially etched bulk
supporting member 19, which may be formed from one of the class of
materials comprising silicon (Si), aluminum (Al), tantalum (Ta) and
titanium (Ti). The differentially etched bulk supporting member 19,
is secured to the wall of the evacuated housing 11 in a vacuum
tight manner, and includes a window area or opening 21 etched
therein over which an extremely thin window portion 22 extends. The
window portion 22 is formed from the class of materials comprising
silicon dioxide (SiO.sub.2), aluminum oxide (Al.sub.2 O.sub.3),
Tantalum oxide (TaO), titanium oxide (TiO) silicon nitride (SiN),
silicon carbide (SiC) or the like porperly mated to the
characteristics of the particular material used to form the bulk
supporting member 19. The electron beam 16, is directed against and
through the thin window portion 22, for permitting egress of the
electron beam out of the evacuated housing 11 into a higher
pressure ambient space surrounding the housing. Because of the
particular nature and construction of the novel Lenard window
structure 18, this is achieved with a minimum of electron beam
scattering while at the same time maintaining the integrity of the
evacuated space within the housing 11. As a consequence of this
arrangement, the electron beam may be used to directly record
electron images on a microfilm recording medium shown at 23 without
substantial impairment of the degree of vacuum of the evacuated
space within housing 11. This in turn results in greatly extended
cathode life for the electron beam sources 12-14.
From a consideration of the materials listed in the above
description of the construction of Lenard window 18, it will be
appreciated that the thin window portion 22 consists of a material
different than the bulk supporting member 19 which serves as a
frame for holding the window portion 22 and defines the window
opening 21 through which the electron beam passes in order to
impinge upon and pass through the thin window portion 22 without
undue scattering or attenuation. A further desirable characteristic
of the material of the thin window portion 22, is that it can be
previously formed on the thick bulk supporting member 19 to a
predetermined thickness preferably through an appropriate chemical
reaction process involving the surface of the bulk supporting
member so as to result in a material which is not susceptible to an
etchant employed to form the window area 21 in the bulk supporting
member 19. For this purpose, it is desirable that the
differentially etched bulk supporting member 19 and thin window
portion 22, be from the class of materials comprising
silicon-silicon dioxide (Si--SiO.sub.2); aluminum-aluminum oxide
(Al--Al.sub.2 O.sub.3); tantalum-tantalum oxide (Ta-TaO);
titanium-titanium oxide (Ti--TiO); Si---SiN; Si--SiC; Al.sub.2
O.sub.3 or Si; or the like. While any of these materials may be
suitable the preferred construction is for the differentially
etched bulk supporting member to be comprised of silicon and the
thin window portion 22 be comprised of a thin layer of silicon
dioxide (SiO.sub.2) previously formed to a desired thickness of the
surface of the bulk supporting silicon member 19 by chemical
reaction prior to the etching of the window area 21 in the bulk
supporting member 19. For a more detailed description of suitable
SiO.sub.2 layer growing techniques and subsequent selective etching
to form thin SiO.sub.2 windows that could be employed in the manner
taught by the instant invention, reference is made to an article
entitled "Film Stripping Techniques for Making Thin Silicon Window"
by E. Tannenbaum, of the Bell Telephone Laboratories, Inc.,
appearing in the Journal of Applied Physics -- Vol 31, pg. 940
(1960) and to an article entitled "Gas Permeation Study and
Imperfection Detection of Thermally Grown and Deposited Thin
Silicon Dioxide Films" by S. W. Ing, R. E. Morrison and J. E.
Sandor of the Semiconductor Products Department, General Electric
Company, Syracuse, N.Y., reported in the Journal of the Electro
Chemical Society, Mar. 1962, pg. 221 through 226. Still other
suitable microcircuit techniques suitable for use with the present
invention are reported in unclassified Report No. AD603715 entitled
"Integrated Silicon Device Technology," Vol. III -- Photo Engraving
by J. J. Wortman et al., prepared by the Research Triangle
Institute of Durham, N.C., dated January 1964 and available through
the Defense Documentation Center of the Defense Supply Agency of
the U.S. Government.
From a consideration of the above-noted references, it will be
appreciated that the production of the Lenard window structure 18
can be achieved with well known and established micro-circuit
masking and etching techniques employed in the semiconductor
industry. It should be noted that only the window area 21, is
required to be etched to form the thin window portion 22 of
SiO.sub.2 leaving the rest of the wafer as a bulk supporting
chamber that can be used as a sturdy mounting or window frame for
securing the window to the evacuated housing 11. The thinness of
the window portion 22 is subject to excellent control during the
SiO.sub.2 layer growing operation by controlling the extent of
thermal oxidation, etc so as to produce an SiO.sub.2 layer on the
order of 1 micron or less down to the order of 500 angstrom units
in thickness. The etchant used to form the window area 21, which
may be hot chlorine, then will not attack the underlying thin
window portion 22 of SiO.sub.2. Thus, it will be seen that control
of the thickness of the resulting window portion 22 is separately
performed in one operation and the subsequent etching operation
need not be the subject of fine control to result in a desired
thickness window layer 22 since the etchant used in forming the
window area 21 through the bulk supporting member 19, does not
attack the window portion 22, that is, it is differential in its
action. The other materials listed above are also known to possess
differential etching characteristics and can be employed in a
similar manner to form suitable Lenard window structures for use in
practicing the invention.
Where silicon or other similar semiconductor materials are used as
the bulk supporting member 19, it may be desirable to include a
thin conducting layer shown as phantom at 19A to keep the Lenard
window structure at substantial ground or other potential. This is
particularly required if the sides of the bulk supporting member
defining the thin window area are to be used for blanking part of a
fan-shaped beam that is deflected along the longitudinal axis of
the window, and with respect to which the sides of the window
intercept and blank part of the beam as will be described more
fully hereinafter. The conductive coating 19A may extend completely
over the back or electron source side of the supporting member 19
including the thin window portion 22. If desired this conductive
layer could be formed of chromium by vaporization to a thickness on
the order of 3,000-10,000 angstrom thick, and could have an even
smaller window area shown at 21A etched therein by a suitable
etchant which does not attack the underlying layer of SiO.sub.2 or
other similar material from which the window portion 22 is formed.
Alternatively, the conductive layer 19A could be made sufficiently
thin so that it does not unduly attenuate or scatter the electron
beam and could cover the entire back surface of the thin window
portion 22.
Another considerable advantage to the Lenard window constructed in
the above described manner from a monocrystaline supporting member
such as silicon, is provided by the uniformly straight lines and
sloping sides that are characteristic of the window aperture or
opening 21 and that are formed during the etching operation due to
the planes of the monocrystaline body. As a consequence, extremely
fine, straight uniformly shaped window openings can be fabricated
in accordance with this technique which are particularly
advantageous for use with electron optic recording systems of the
type herein disclosed.
FIG. 1B is a partial cross-sectional view of an alternative form of
Lenard window constructed in accordance with the invention. In FIG.
1B the thin window portion 22a is recessed a few microns (on the
order of 2-10 microns) below the surface of the supporting bulk
member of silicon 19. By constructing the Lenard window in this
manner, the thin target window portion 22 can be protected from
abrasion and damage from the microfilm recording medium 23 which is
allowed to contact and ride along the lower surface of the
supporting bulk member 19 in order to minimize the space between
the microfilm 23 and target window portion 22. In fabricating the
structure of FIG. 1B, the lower recession is first introduced by
suitably etching for only a short period of time the bottom surface
of the supporting bulk member 19. Thereafter the entire bottom
surface is oxidized to form a layer of SiO.sub.2 of about
1,000-5,000 angstrom units thick but may be even as low as 500
angstrom units in thickness. A thin layer of long wearing, low
friction conductive material such as chromium (Cr) then is
deposited by evaporation, sputtering, etc over the layer of
SiO.sub.2 to a thickness of about 3,000-10,000 angstrom units
thick. The function of this layer 19B is to provide a good wearing
interface between the Lenard window structure and the recording
microfilm tape 23 and also to act as a lubricating or low friction
surface for engaging the microfilm.
An extremely fine exit opening shown at 21B maybe provided in the
protective layer 19B by etching this layer through to the
underlying SiO.sub.2 thin window layer 22 with an etchant that does
not attack the SiO.sub.2 layer 22. This opening could be made on
the order of 1-5 microns wide, and can act as a limiting
one-dimensional aperture fo the electron beam 16. This very thin
exit aperture 21B can be etched in the layer 19B with equal or
better precision and with greater ease than if one tried to form
the narrow recession in the supporting bulk member of silicon 19
with equal precision. The thin slit 21B thus obtained can then act
as the limiting one-dimensional aperture for the electron beam
thereby allowing for greater recording resolution. Furthermore, it
is not too difficult to produce an electron beam having a pinched I
shape beam and align the beam so that the center of the pinched I
is focussed on the thin window portion 22. In this manner an
extremely fine electron beam spot of comparatively high intensity
can be obtained for providing high resolution recordings on the
microfilm recording medium 23.
An alternative method for forming the Lenard target window
structure shown in FIG. 1B would be first to apply an overlaying
film such as 19 of chromium completely over the bottom surface of
the supporting bulk member of silicon 19 which previously has been
oxidized to a thickness of the order of two microns. Then a thin
recession is etched in the overlaying layer 19B and through the
underlying oxidized layer to expose the surface of the supporting
bulk member of silicon. At this point the structure is re-oxidized
to form a new SiO.sub.2 layer to the desired thickness for the thin
window portion 22. Subsequently, the back or upper side of the bulk
supporting member of silicon is differentially etched through to
the last mentioned SiO.sub.2 layer and the conductive layer 19A
then formed in the manner shown. The conductive layer 19A should be
sufficiently thin so that it does not attenuate or scatter the
electron beam 16. If desired, an opening such as that shown at 21A
in FIG. 1A could be formed in the conductive layer 19A of the
structure shown in FIG. 1B.
It is desirable that the thickness of the window portion 22, be
maintained as thin as possible to minimize both beam attenuation
due to the window and scattering effects of the window on the beam.
Accordingly, it is desirable that the window portion 22 have a
thickness on the order of 500 to 2,000 angstrom units and possibly
even less if the window area 21 can be made sufficiently thin. The
transmittance of SiO.sub.2 is excellent for a thickness even as
high as 2,000 angstrom units for a 10 kilovolt electron beam. Of
course for a 20 kilovolt beam or some higher value than 10
kilovolts, the transmittance would be that much better. However a
more serious problem exists due to the scattering of the beam by
the window portion. A rough value estimated from the published
literature indicates that a 10 kilovolt electron beam is scattered
on the order of 18.degree. when transmitted through a 2,000
angstrom unit thick SiO.sub.2 film. This can be translated into
meaning that a beam spot size on the order of 3 to 5 microns
impinging on the SiO.sub.2 Lenard window, would be double that size
due to scattering at a distance of about 11 microns away from the
window. Again, of course, a higher energy beam such as a 20
kilovolt beam would experience much less scattering. In either
event, however, there is little or no problem to control the
spacing between the microfilm recording medium 23 and the SiO.sub.2
window 22 so as not to exceed 10 to 15 microns. With a spacing on
this order, the transmittance of the electron beam through the air
presents no problem whatsoever since the representative figure
obtained from the literature indicates that a 10 kv beam loses
about 10 percent of its energy after travelling a distance of 300
microns in air. To avoid even this kind of a loss, it would be
possible to include the portion of the microfilm recording medium
23 on which the electron beam impinges in a partially evacuated
space or enclosure indicated by the dotted lines 25 which can be
evacuated by a vacuum pump 26, an d allow the microfilm recording
medium in the form of a tape to be brought into the space through
suitable sealed openings indicated at 27 and 28. The provision of
the partially evacuated space within housing 25 would also tend to
alleviate somewhat the stresses on the thin SiO.sub.2 Lenard window
portion 22 in comparison to the stresses that would be obtained if
the beam were brought directly out into ambient atmospheric
conditions. This would be particularly advantageous for those
applications where it is desired to have a quite wide target window
portion 22. Alternatively, the window structure of FIG. 1B could be
employed to minimize spacing between film 23 and the target window
22.
With respect to the microfilm recording medium 23, any known
microfilm recording material can be employed which is electron
sensitive. For example, the conventional silver halide photographic
film composition requiring wet development processes could be
employed. A dry silver recording microfilm employing thermal
processing for development purposes is preferred, however, because
of the relative simplicity and speed with which dry silver can be
heated and developed. It is also possible to use diazo, vesicular
and Kalvar R film recording mediums, or for that matter any other
known high resolution recording film which is electron sensitive.
For the purpose of the instant disclosure, it will be assumed
however that a dry silver, diazo or vesicular recording film is
employed using thermal processing. The form of the recording
microfilm medium 23 is unimportant and may comprise tape, cards,
drums, disk or any other known structural arrangement whereby
unexposed areas of the recording medium sequentially may be brought
under the electron beam 16 emanating from the Lenard window portion
22. In the instant disclosure, the microfilm recording medium 23 is
in the form of a tape transported between a take-up spool 31 and a
play-out spool 32, driven by suitable drive motors and clutch
arrangements controlled by a motor controller in the conventional
manner. It is preferred that the take-up and drive spool have at
least two forward speeds, one for recording and the other for fast
advance to a desired area on the tape as well as a reverse,
although the latter capability is not required. The take-up and
play-out of the mocrofilm tape 23 may be either continuous at a
desired recording speed related to the number of lines per minute
to be recorded, or it may be stepped in nature through the use of
suitable stepping motors. However, if the microfilm 23 is to be
moved and stopped between each sweep of the electron beam (as
described hereinafter), printing speed will probably be reduced by
about 1,500 lines per minute which may be unacceptable depending
upon the type of recording technique employed. If such a stepping
motor arrangement is used, however, the printer should be capable
of buffering several lines of data to be printed in order not to
place a constraint on the computer system read-out.
2. Character Genration and Beam Deflection
The alphanumeric characters to be recorded on the mocrofilm tape
23, can be generated in a number of different ways. There are three
commonly employed techniques now being used in known COM printers.
These employ a shaped beam, a dot matrix and a stroke. Other known
techniques not so widely used include generation of symbols by a
programmed control of the electron beam deflection, the use of
Lissajous techniques, dot generation, line generation and the
television type raster technique. Generation of characters is most
generally done by the application of a computer-originated signal
to a character generator module which decodes the signal and
cooperates with a printer controller to control operation of the
deflection and blanking circuit of a CRT. By such arrangements, the
electron beam is moved to a proper location and then intensified to
cause a visual output to be generated.
The following list of known character generation techniques is not
considered to be exhaustive but is merely set forth as explanatory
of a number of known character generation techniques usable with
the present invention by appropriate design of the printer
controller and character generator circuitry.
FIXED STROKE GENERATOR
With this technique the electron beam is caused to follow a
predetermined path composed of a number of strokes. The beam is
gated on and off at appropriate points in the predetermined path to
generate the desired character. The system electronics required to
practice this technique is relatively simple and inexpensive,
however, it generates rather poor characters and is quite limited
with respect to its use for lower case letters. If the number of
strokes in the predetermined path is increased in order to improve
the quality of the characters, the cost of the circuitry increases
as does the time required to trace each character pattern.
PROGRAMMED STROKE GENERATOR
With this technique, each stroke of the electron beam is
characterized by 7 bits of data. Three bits control the X component
of the stroke, 3 bits control the Y component and one bit controls
the blanking. Of the 3 bits for each component, one controls the
sign and two control the amplitude. Thus, each stroke describes a
motion of the beam. Several strokes are connected to form
characters. This method is capable of generating quite good
characters, but at least 16 strokes or 112 bits of space are
required in the character generator memory for each character to be
recorded. Hence, the electronic circuitry required to implement
this technique becomes elaborate and somewhat expensive.
SIMPLE DOT MATRIX
In this technique, the electron beam scans a raster either
horizontal or vertical covering an area of the recording medium
where a character is to be formed. The character is generated by
gating the electron beam (i.e. intensifying it) at the appropriate
points in the matrix where dots are to be formed. A 5 .times. 7
matrix is the minimum required and a 7 .times. 9 matrix would be
preferred for good quality character recording. Again, as the
number of dots is increased, cost and trace time likewise is
increased.
MOVABLE DOT MATRIX
This method is similar to the dot matrix but allows more freedom in
the dot location. In addition to blanking information, position
information is supplied for each dot to be recorded. The scan of
the electron beam then no longer is a simple raster. The technique
is more expensive but generates quite good quality characters and
requires little scan time. For dry-process film recording mediums,
the use of this technique may be advantageous.
MONOSCOPE OR SHAPED BEAM
A monoscope is a tube which contains a character mask. A coarse
deflection system mask deflects the electron beam to the desired
character and a fine deflection system scans the character. By
passing the electron beam through the mask having various symbols
and characters cut into it, the electron beam is "shaped" into a
desired symbol. The beam is then deflected to a desired position by
normal deflection techniques. The computer requirements for such a
system are simply positional information stored in memory for each
symbol. Data is the form of a symbol code and XY position are
required. A limit of 64 symbols requiring a character mask
containing 8 .times. 8 array of characters can be used with each
character being identified by a 6 bit 3 bits for the X position and
3 bits for the Y position) signal.
3. Printer-Controller Control Circuitry
Suitable printer-controller control circuitry for operating the
electron beam recording apparatus in accordance with any of the
above-listed as well as other known techniques, is shown generally
in block diagram form to the left of the evacuated housing. The
control circuitry is comprised by a printer control logic module 41
supplied from a buffer memory 42 which may comprise a MOS dynamic
shift register having a storage capacity on the order of 150 words
with each word comprising 9 bits. The buffer memory 42 is supplied
with output data from a computer system central processing unit
which data is to be printed out by the EBCOM printer. For this
purpose, the memory 42 will be supplied an edited line of data plus
a few control characters from the computer. The control characters
will operate through the control logic module 41 to advance the
microfilm tape 23 through the medium of the film advance control
subcircuit 43, project and print forms through the medium of a form
selector and projector 44 under the control of a forms projection
control subcircuit 45; develop the recorded images on the microfilm
tape 23 by a heat source or other suitable development system 46
under the control of a heat control subcircuit 47 together with
controlling the performance of other necessary functions under the
central control of the control logic module 41. The output from the
buffer memory 42 is supplied to the control logic module 41 through
a parity checker and control decode section 48. The output from the
buffer memory 42 also is supplied to a character generator module
49 that may comprise a MOS read only memory or core read only
memory having a capacity on the order of 10,000 bits such as the
TMS 2400 integrated read-only memory circuit chip manufactured and
sold by the Texas Instrument Co. The character generator 49 also is
under the control of the control logic module 41 which serves to
clock appropriate character forming signals out of the character
generator 49 for supply to the electron beam recording apparatus
11. Control logic module 41 therefore serves as a central control
employing a relatively simple set of logic elements for developing
the necessary clocks and control signals to be used as command
signals for the various components of the E COM printer system and
also for communicating with the computer system central processing
unit to inform it when additional lines of data are to be supplied,
detection of errors, etc.
Depending upon the particular character formation techniques
employed, the printer-controller control circuitry would be
structured appropriately to implement the desired technique. For
the purpose of the present disclosure, it will be assumed that the
EB COM printer system shown in FIG. 1 will record a line of full
characters across the width of the microfilm recording type 23 one
line at a time for each scan of the electron beam. Hence, it will
be necessary that the target window portion 22 by sufficiently wide
to accommodate the height of a character. In FIG. 1 it is assumed
that the longitudinal dimension of tape 23 extends between the
spools 31 and 32 and the width of the tape extends into the plane
of the paper. Accordingly, it will be appreciated that as shown in
FIG. 1, the viewer is looking at a cross sectional view of the
target window portion 22 and that this target window portion will
be in the form of an elongated thin slit extending into the plane
of the paper.
With the electron beam recording apparatus structured in the manner
described in the preceding paragraph, the apparatus would be
designed to include deflecting means shown generally at 20 for
deflecting the electron beam along at least the longitudinal axis
of the elongated thin slit target window 22. Further, since the
target window is sufficiently wide to accommodate the height of a
character, additional means shown in FIG. 1 as comprising a micro
deflection system 51 are provided for deflecting the beam 16 along
XY axes to cause it to trace out the character patterns to be
recorded. This coupled with appropriate blanking (enhancement) of
the electron beam by the application of suitable control signals to
the control grid 13, will result in the formation of electron
images on the surfaces of the microfilm recording type 23 in
accordance with the characters desired to be recorded. For this
purpose fine X and Y control voltages are supplied to the micro
deflection system 51 from a fine X and Y deflection control voltage
subcircuit 52 that in turn is controlled from the character
generator 49. For certain of the techniques it would be possible to
control the fine deflection control circuit 52 directly from the
control logic module 41 depending of course upon the writing
technique employed. For either arrangement, the control logic
module 41 supplies the required slow trace, fast retrace (reset)
deflection signals required to cause the electron beam 16 to be
scanned back and forth across the entire length of the elongated
thin slit target window portion 22. These voltages are supplied
through a course deflection control subcircuit 53 to the course
deflection means 20 which may comprise electro-magnetic deflection
coils. It is of course possible to employ eleectrostatic deflection
plates in place of the electro-magnetic coils illustrated in FIG.
1. Beam blanking (enhancement) control signals are supplied to the
control grid 13 of the electron beam recording apparatus from a
suitable CRT gate driver control subcircuit 54 that in turn is
supplied from the character generator circuit 49. For a more
detailed description of suitable circuitry for the construction of
the CRT gate driver, deflection circuits, stepping motor control,
digital-analog conversion circuitry, buffer memories and the like,
reference is made to a number of issued United States patents and
publications relating to the electron beam recording art such as
U.S. Pat. No. 3,195,112 -- W. C. Hughes, et al., issued July 13,
1965; U.S. Pat. No. 3,167,747 -- W. C. Hughes, et al., issued Jan.
26, 1965; and U.S. Pat. No. 3,121,216 -- J. D. Wolf, et al., issued
Feb. 11, 1964. All of these patents include detailed descriptions
of the construction and interconnection of a number of elemental
subcircuits illustrated in block diagram form in the present
disclosure and readily could be utilized by one skilled in the art
to fabricate an EBCOM printer system according to the present
invention.
FIG. 2 is a schematic, sectional view of an electron beam recording
apparatus suitable for use with the EB COM printer system of FIG. 1
where it is desired to perform character writing in accordance with
the movable dot matrix technique described briefly above. For this
purpose, the electron beam recording apparatus 11 shown
diagramatically in FIG. 2 includes all of the elements listed in
connection with the electron beam recording apparatus 11 of FIG. 1.
In FIG. 2 however the electron beam recording apparatus is shown in
a different plane so that in effect the viewer is looking at a
cross sectional view of the microfilm recording medium 23. Thus, it
will be appreciated that the view shown in FIG. 2 has been rotated
substantially 90.degree. with respect to the view shown in FIG. 1.
Also in FIG. 2 the construction of the micro-deflection system 51
has been illustrated in greater detail.
The micro-deflection system 51 is comprised by a linear array of 22
micro-deflection lenslets which are arranged along the longitudinal
axis of the elongated Lenard target window portion 22. The
construction of the micro-deflection lenslets has been described in
detail in a number of published articles, and hence has not been
illustrated in constructional detail. Briefly, however, the
micro-deflection lenslets (sometimes referred to in the art as
fly's eye lenslets) are fabricated from a serial array of planar
members 51A, 51B, 51C and 51D. These planar members are stacked
pancake fashion tranverse to the path of the electron beam 16 and
have appropriate openings or apertures therein through which the
electron beam 16 passes. The plate 51A comprises an aperture plate
having a potential of about -15 kilo volts applied thereto and
through which the electron beam 16 is sequentially scanned by means
of appropriate deflection signals supplied to the course deflection
coil 20A and 20B. In this manner, the electron beam 16 can be
caused sequentially to scan across each of the 22 micro deflection
lenslets which in turn extend across the length of the elongated
thin target window 22 and the width of the microfilm recording tape
23. The plate 51B also has a potential of about -15 kilo volts
supplied to it and serves as an accelerating micro deflection lens
for accelerating the electron beam past the two micro deflecting
plates 51C having the fine horizontal or Y deflecting control
signals supplied thereto from the control subcircuit 52 in FIG. 1.
Within the area of view of each micro-deflection lenslet, the
electron beam can be deflected along the longitudinal axis of the
elongated thin target window 22 to some 6 character sites spaced
along the width of the microfilm recording tape 23. In conjunction
with the horizontal or fine Y placement of electron beam 16, the
fine vertical or X control potentials are supplied to the plate 51D
for deflecting the electron beam vertically (transverse to the
longitudinal axis of the elongated thin window 22) to provide dot
placement in the character formation technique envisioned.
Concurrently with deflection of the beam in accordance with the
character position controlling signals supplied to the respective X
and Y micro deflecting lenslets formed on plates 51C and 51D, beam
blanking (enhancement) is accomplished by provision of suitable
control signals to the control grid 13 from the gate driver control
subcircuit 54 in FIG. 1 that in turn is supplied from the character
generator circuit 49. It is anticipated that with such a structure
the appropriate energizing potentials would be supplied to the
aperture plate 51A and accelerating plate 51B from the power supply
circuit 15 with the cathode 12 being maintained at a potential of
-20 kilo volts and anode 14 maintained at a potential of about -15
kilo volts corresponding to the potential of the plates 51A and
51B. The conductive film 19A or 19B of the Lenard window is
grounded to prevent build up of charge on this element. This should
provide an electron beam having a current density of about 50
amperes per square centimeter formed into a focused beam of about 5
microns spot diamter by the coarse and fine focussing lens
assemblies 17 and 51B. A more detailed description of a suitable
electron beam write-read apparatus employing a microdeflection lens
assembly and similar to that shown at (11) in FIG. 1, is set forth
in U.S. Pat. No. 3,710,352 -- Smith, et al., issued Jan. 9, 1973,
the disclosure of which is hereby incorporated by reference.
In operation it will be appreciated that as the electron beam 16 is
caused to scan say from left to right across the width of the
microfilm recording tape 23 by coarse deflection lens 20A and 20B,
it will proceed sequentially along the serially arrayed micro
deflection lenslets 51. Each individual micro deflection lenslet 51
will in turn cause the beam to be deflected horizontally across the
width of the tape corresponding to six character sites. Since there
are 22 lenslets this will allow 132 characters to be recorded in a
line across the width of the microfilm recording tape 23. Within
each of the micro deflection lenslets, the X deflection voltage
will cause the focused electron beam 16 to be deflected in the
vertical X (transverse to the longitudinal axis of elongated thin
slit window 22) direction by an amount corresponding to the height
of the characters to be recorded so as to scan or write out in
conjunction with appropriate beam blanking (enhancement) the
characters to be formed at each of the six character sites within
the field of operation of each lenslet. Upon completion of a
recorded line of characters the transport mechanism causes the
microfilm recorded tape to move a distance corresponding to the
spacing of each line of characters during the intervals that the
electron beam 16 is retraced back to its starting point to initiate
a new writing cycle.
FIG. 3 is a diagramatic view of a different form of an electron
beam writing apparatus 10 structured to provide character
generation in accordance with a modified monoscope technique as
outlined briefly above. With the arrangement shown in FIG. 3 an
array of four character generator and micro deflection and focusing
lens structures 51' are arranged linearly across the width of the
microfilm tape 23 in the manner shown. Each of the character
generator micro deflection structures 51' includes a character mask
(shown in FIG. 3A of the drawings) having an 8.times.8 array of
alphanumeric characters formed therein. Coarse selection of one of
the structures 51' is achieved by appropriate energization of the
coarse deflection coils 20A and fine selection of desired character
within the array of characters formed on the character mask
disposed within the selected structure 51' is achieved through
appropriate energization of fine deflection means comprised by a
fine Y deflection coil 20B and a fine X deflection coil 20C. The
structures 51' also include appropriate focusing lens arrangements
for focusing the resultant character shaped electron beam and
directing it through the associated character position deflector
micro structure 51 arranged immediately below the character
generator structure 51'. The fine deflectors in micro structure 51'
are designed to deflect the electron beam to anyone of 33 different
character site locations along the width of the microfilm tape 23
within its view in accordance with fine horizontal or Y position
control signals supplied thereto. If desired in place of the
character mask arrangement used in conjunction with fine deflection
control signals supplied to the deflection coils 20B and 20C, the
micro deflection structure 51' could be provided with transversely
disposed X and Y deflection plates, and character generation could
be performed by these deflecting plates under the character
generator control using for example a raster scan with appropriate
beam blanking (enhancement) to form a dot matrix. With such an
arrangement, character positioning of the beam would be done with
the last set 51 of deflection electrodes each of which would access
33 character positions. The actual number of micro deflection
structures required with such an arrangment would depend upon the
ease of manufacturing and spot size requirements. With a fan shaped
beam and at the cost of an extra character generator memory, it
would be possible to generate more than one character at different
positions on the line simultaneously, thus achieving a greater
printing speed. Such modifications would require greater beam
current from the cathode however and might impair cathode life. To
overcome this problem it is feasible to provide an electron beam
recording apparatus having a replaceable cathode. For example the
electron source and relatively inexpensive electrostatic focusing
electrodes could be fabricated within a removeable envelope or
housing including a Lenard window and would be arranged to slip
within a second housing containing the more expensive and
micro-deflection electromagnetic lens assemblies. For a detailed
description of comparable electron beam recording devices employing
character masks, reference is made to U.S. Pat. No. 3,382,392 --
Corpew, issued May 7, 1968 and U.S. Pat. No. 3,299,418 -- Treseder,
issued Jan. 17, 1967.
From the preceding description of FIGS. 1-3 of the drawings, it
will be appreciated that the invention makes available a novel EB
COM printer system capable of high speed, high resolution and high
intensity printing on microfilm at ambient pressure. In addition,
the printer includes the ability to print out graphics and forms by
reason the inclusion of the buffer memory and the forms projection
system. The EB COM printer comprises a combined printer-controller
that can be easily interfaced with any known computer system and
because of its high printing speed on the order of between 10,000
lines per minute to 25,000 lines per minute it places little or no
constraints on the through-put of the computer system. Because of
these characteristics, the EB COM printer can be used as an on-line
COM printer device operable as a standard plug-in compatible
peripheral equipment for use with computer systems. It makes
available a new and improved electron beam apparatus having a
Lenard window fabricated from a differentially etched bulk
supporting member of silicon and silicon dioxide or the like with
the Lenard window portion having a thickness on the order of
500-5,000 angstrom units thick. If desired the electron beam
apparatus can include both electrostatic and electromagnetic
deflection lens structure with a removable electron source whereby
the source can be replaced after a number of hours of use without
requiring the complete electron beam recording apparatus be
replaced or rebuilt. By appropriate fabrication of the Lenard
window, the size of the window can be used for blanking the
electron beam by the use of appropriate beam blanking deflection
potentials provided to the deflection lens of the structure. The
microfilm recording medium used with the EB COM printer may
comprise wet silver requiring a wet developing process, dry silver,
diazo, vesicular calvar or some other dry recording medium and/or
technique using thermal processing for development. The recording
medium may be in the form of a tape, card, drum, disk, or any other
form presently known in the art for transporting the recording
medium past the Lenard window portion of the electron beam
recording apparatus.
4. High Speed Multiple Scan/Character EB COM Printer System
FIG. 4A and 4B comprise a functional block diagram of a new and
improved high speed multiple scan per character EB COM printer
system made available by the invention. This system differs from
the previously described EB COM systems in that it employs a very
fine elongated thin slit SiO.sub.2 Lenard window along which the
electron beam is traced repetitively for a predetermined number of
scans. Each individual scan of the electron beam is used in
conjunction with suitable beam blanking (enhancement) and results
in the recording of a partial character at each character site
along a line of characters. Concurrently with the microfilm tape
wide scanning and partial character recording, the microfilm tape
is moved transversely to the longitudinal axis of the elongated
thin slit window so that repetitive scanning of the electron beam
for a predetermined number of scans results in the raster recording
of a line of complete characters across the width of the tape. For
recording in this manner, a continuous speed tape drive is desired
whose speed of movement is related to the scanning frequency of the
electron beam as will be described more fully hereinafter.
In the embodiment of the invention shown in FIG. 4B the electron
beam recording apparatus 10 is somewhat different in construction
from that employed in previously described embodiments. The
electron beam recording apparatus 10 shown in FIG. 4B is comprised
by an evacuated housing 11 having an electron source shown
generally at 12-14 including a cathode, control grid and anode
which are not shown individually. The electron source 12-14 is
mounted at one end of the evacuated housing 11 and a Lenard target
window shown at 18 is mounted at the other for permitting egress of
the electron beam 16 out of the evacuated housing 11 and onto the
recording microfilm tape 23. The lenard target window 18 is
fabricated in the manner previously described in connection with
FIG. 1A of the drawing and hence will not again be described in
detail. There is one difference however, in the construction of the
Lenard target window which is important to note. Because of the
capability of forming very fine straight cuts or openings defining
the target window using well known micro circuit etching techniques
on a crystalline semiconductor body such as silicons the target
window 18 employed in the electron beam apparatus in FIG. 4 is made
to be a very fine thin slit whose width is on the order of the
diameter of the electron beam 16 produced by the electron beam
recording apparatus. This slit may be as small as 5 microns in
width and conceivably could extend to as much as a ten or 50 micron
wide slit or larger, but preferably is as small as possible to
provide good resolution. The length of the target window is of
course determined by the length of line of characters to be
recorded and should be sufficiently long to accommodate a scanning
trace of the electron beam sufficiently wide to record 132
alphanumeric characters in a line.
Similar to FIG. 1, FIG. 4 illustrates the electron beam apparatus
arranged in a manner such that its electron beam is scanned back
and forth along an axis extending into the plane of the paper. The
microfilm tape take up and play out spools are arranged to
transport the microfilm tape 23 in a direction transverse to the
longitudinal axis of the elongated thin slit window 18. The
electrons produced by the source 12-14 are accelerated through an
apertured anode plate 61 and directed through a spray aperture
plate 62 mounted on one end of a four fold electrostatic deflector
element 63. The spray aperture 62 operates as a beam defining
aperture to limit the beam current and also serves to shape the
electrons in the form of a pencil-like beam. The four fold
electrostatic deflecting plates 63 then operate to deflect or
displace the beam so as to align it along a central axis extending
between the source 12-14 and the Lenard target window 18. The beam
of electrons then is directed through an electrostatic focusing
lens arrangement 17 and through a second beam defining aperture 64
which may be adjustable if desired, and thence through a second
focusing lens structure 65. The first focusing lens 17, the second
aperture 64 and the second focusing lens 65, which may be either
electro magnetic or electrostatic in nature, are included in the
electron beam recording apparatus to provide further shaping of the
electron beam so as to result in an extremely fine pencil-like
electron beam writing probe having a diameter on the order of 5
microns. This finely shaped electron beam then travels through an
electromagnetic deflecting lens 66 for deflecting the electron beam
across the longitudinal axis of the elongated thin slit Lenard
target window 18 in the manner described above.
FIG. 4C of the drawings is a diagrammatic sketch illustrating how
the multiple scan characters are built up or recorded on the
surface of the microfilm tape 23 as a result of the partial
character recording achieved during each individual scan of the
electron writing probe accompanied by appropriate beam blanking
(enhancement). In FIG. 4C the arrows associated with the numerals
10 and 7 extend in the direction of the longitudinal axis of the
microfilm recording tape (and hence in the direction of movement
thereof) and the arrows associated with the numerals 5 and 8 extend
in a direction across the width of microfilm tape 23. Each line of
characters to be recorded is transmitted in the form of pulsed,
coded, digital electric signals to a character generator to be
described herein after which converts the signals to appropriate
beam blanking (enhancement) signals that are supplied to the
control grid of the electron beam recording apparatus 11. Placement
of a dot at a particular point along the width of the microfilm
recording tape 23 will of course be determined by this signal in
conjunction with the deflection potentials supplied to the
deflecting lens arrangement 66. As illustrated in FIG. 4C a line of
characters is printed by splitting each character in the line into
a matrix of 5 .times. 7 dots with the equivalent of a three dot
spacing being interposed between each character in a line and the
equivalent of three dot spacing being interposed between each line
of characters in a frame. It is presumed that the now generally
accepted format of 66 lines in a frame and 132 characters per line
is used in carrying out the recording process. The technique is in
no way restricted to this specific format however and it is cited
only as exemplary of one mode in which the novel EB COM system of
FIG. 4 can be operated. From a consideration of FIG. 4C it will be
appreciated therefor that some ten horizontal scans of the electron
beam is required in order to complete the recording of a complete
line of characters including appropriate line spacing and seven of
these scans will be productive in producing the character to be
recorded in a particular character site along the width of the
microfilm tape 23. Similarly, only five vertically placed dots are
required to construct the character for each horizontally placed
character site along the axis of scan of the electron beam. Which
dots in the five by seven dot matrix are blanked and which are
enhanced to result in the production of a dot recording on the
surface of the microfilm tape 23, is determined by the character
control signal supplied to the control grid of source 12-14.
Accordingly, at any given point along the microfilm tape 23 the
electron beam 16 will be scanned across its width and appropriately
blanked or enhanced to produce a partial character dot pattern
which when accumulated over a predetermined number of 10 scans
measured from the initiation of a new line of characters recording
cycle, results in a recording such as the BB shown in FIG. 4C.
Suitable control circuitry for controlling operation of the
electron beam writing apparatus 10 in the above briefly described
manner is illustrated in FIG. 4A. This control circuitry is
comprised basically by a printer-controller 41, a character
generator 49 and buffer memory means 42. The heart of the
printer-controller 41 is comprised by a dot clock and control
circuit 71 that sets up the timing sequence with which the electron
beam will be blanked. The output from the dot clock and control
circuit 71 is supplied to a modulo-8 horizontal dot
position-in-a-character counter 72 which determines which dots in a
character extending in the horizontal (co-extending with the
longitudinal axis of elongated thin slit target window 18)
direction are to be printed. Modulo-eight dot counter 72 supplies
its output over a conductor 73 to the input to a modulo-132
horizontal characters-in-a-line counter 74 whose output in turn
controls a ramp generator 75 supplying a horizontal coil driver
amplifier 76 that in turn supplies deflection potentials to the
deflecting lens arrangement 66. The ramp generator 75 develops a
substantially linear saw tooth wave-shaped excitation potential
that is amplified in the horizontal coil driver amplifier 76 and
serves to deflect the finely focused electron beam probe width-wise
across the microfilm recording tape 23 in a continuous linear
manner. At the end of a line of 132 characters represented by 8
.times. 132 dot clock pulses from the dot clock and control circuit
71, the ramp generator 75 produces a retrace potential that causes
the electron beam deflecting lens 66 quickly to retrace the beam
back to its initial starting point while being blanked by an
appropriate potential supplied to its control grid. During this
retrace portion, intermediate each line scan of the recording
electron beam, a retrace, inhibit potential is supplied back over a
conductor 77 to inhibit operation of the dot clock and control
circuit 71. This retrace inhibit potential is supplied from the
output of the modulo 132 characters-in-a-line counter 74 whose
output is also supplied to a modulo 66 lines-in-a-frame counter 78
whose output in turn is supplied over a conductor 79 to control the
operation of a page and film advance and develop control circuit 81
controlling operation of the take up and pay out spools 31 and 32
through a motor driver control circuit 82. The page and film
advance and develop control 81 also controls operation of a heat
source 83 which serves to develop the electron image written on the
microfilm tape 23 during earlier writing cycles.
The dot clock and control circuit 71 is in turn controlled from the
output of a buffer control circuit 85 contained within the buffer
memory means 42 and which further controls operation of a three
line buffer memory 86. Additionally, the buffer control 85
communicates via line 87 with the central processing unit 88 of a
computer system with which the EB COM printer is used as a print
out device. The computer system normally will include a working
memory such as the core memory 89 under the control of the central
processing unit. The central processing unit 88 on request from the
buffer control 85 will operate to transfer from the core memory 89
one page or frame of 66 lines of character into a disc memory unit
91 comprising a part of the overall EB COM printer system memory 42
which further includes the three line buffer memory unit 86. The
buffer control on direction from the central processing unit
indicating that the disc memory 91 is full will initiate read out
of the disc memory 91 three lines at a time into the three line
buffer memory 86. The three line buffer memory 86 may comprise a
conventional MOS dynamic counter using integrated circuit multi
vibrator units, or it may comprise a memory tube such as the
Lithicon or other similar small memory means Similarly, the disc
memory 91 could be replaced with a small ferrite core memory, a MOS
dynamic counter memory, a Lithicon memory, or the like. The disc
memory 91 serves as an interface between the three line buffer
memory 86 of the EB COM printer system and the central processing
unit of the computer system with which the EB COM printer system is
being used.
The three line buffer memory 86 stores three lines of characters
and transmits them serially one line at a time over conductor 92 to
a MOS read only memory 93 that comprises a part of a character
generator 49 and may comprise a TMS 2400 integrated read-only
memory circuit chip manufactured and sold by Texas Instruments Co.
Read out of each line of characters stored in the buffer 86 into
the read only memory 93 is under the control of buffer control 85.
In order to inform the buffer control 85 of the completion of one
scanning line by the electron recording beam, the output of the
modulo 132 characters-in-a-line counter 74 is supplied over
conductor 94 and 95 to a control input of the buffer control 85.
The output characters-in-a-line counter 74 also is supplied to the
input of a modulo - 10 vertical dot position-in-a character counter
96 that supplies its output over line 97 to the read only memory
93. The output from the vertical dot position-in-a character
counter 96 in conjunction with the character indicating signals
supplied from buffer 96 and the horizontal in-a-character count
signal supplied from counter 72 over a conductor 98 to a digital
multiplexer 99 connected to the output of read only memory unit 93,
operates to establish which dot in any given character matrix
corresponding to a desired character site across the width of the
microfilm tape is to be intensified, and hence recorded on the
microfilm tape. The resultant is an intensifying control signal
supplied at the output of the five position digital electronic
multiplexer switch 99, and is supplied through a grid driver 101 to
the control grid of the electron beam controlling apparatus 10. For
a more detailed description of suitable component subcircuits
usable in the above-described EBCOM printer system, reference is
made to the above-cited U.S. Pat. Nos. 3,195,112; 3,167,747;
3,121,216; and to such text books as The Source Book of Electronic
Circuits published by the McGraw-Hill Co., John Markus, Ed.,
Copyrighted 1968, Library of Congress Catalog Card Number 67-15037.
Any of the known subcircuits described in these prior art reference
texts and patents, or their integrated circuit counterparts,
readily could be employed by one skilled in the art to fabricate
the above-briefly-described EBCOM printer system in the light of
the present disclosure.
Having described the construction of the multiple scan/character EB
COM printer system shown in FIGS. 4A and 4B, its operation is as
follows. Information to be printed which is being transferred out
of the core memory 89, or alternatively is being generated by the
central processing unit 88, is transferred to the disc memory 91
and stored. The disc memory is capable of storing at least one
complete page or frame of 66 lines of characters with each line
containing a maximum of 132 characters. When a full page or frame
has been generated and stored in disc memory 91, the central
processing unit signals the buffer control 85 that it is ready to
print. Upon sensing that the three line buffer memory unit 86 is
full, the buffer control 85 initiates operation of the dot clock
and control circuit 71 and printing commences. Upon one line in
buffer memory 86 becoming empty the buffer control signals the
central processing unit 88 to transfer another line of data which
it will do at the next available moment before the disc memory has
been emptied. Thus it will be seen that the printing operation is
performed on a "line of characters" basis.
Upon the dot clock and control circuit 71 being turned on by buffer
control 85, a line of characters to be printed is transmitted to
read only memory 93 out of the buffer memory 86 through line 92.
Concurrently turn on of the dot clock and control will initiate
operation of the ramp generator 75 which will start to sweep the
electron beam horizontally across the width of the microfilm tape
23. As the electron beam scans across the width of the microfilm
tape in a line, the read only memory 93 in conjunction with the
digital multiplexer 99 which is under the control of modulo 8
horizontal position-in-a-character dot counter, and the modulo-10
vertical dot position-in-a-character counter 96, determines which
dots are to be intensified and hence recorded on the microfilm tape
23. As stated previously the line of characters are printed by
splitting each character in a line into a matrix of five by seven
dots with the equivalent of three dot spacing between characters
and between each line of characters. To complete a line of
characters, 10 scans of the electron beam across the width of tape
23 is required with only selected ones of a five by seven dot
matrix within the 132 character positions contained within a line
of characters being generated to form the desired character on a
given character recording site. During this process the modulo-8
horizontal dot position-in-a-character counter 72 keeps track of
the horizontal position of the beam in any given charcter site
along the line of characters being recorded while the modulo 10
vertical dot position-in-a-character counter keeps track of the
particular scan line being scanned of the ten scan lines required
to form a line of characters. As the electron beam is being scanned
across the full width of the microfilm tape 23, the modulo 132
character-in-a-line counter 74 keeps track of which particular
character is being partially printed during any particular portion
of a scan of the electron beam.
Once the printing of a line of characters is completed, this fact
will be signaled to the buffer control 85 by the characters in a
line counter 74 which will then operate to read into the read only
memory 93 another line of characters to be printed out.
Concurrently the central processing unit 88 will be signaled that
the printer system is ready to receive another line of data to be
printed. This process is repeated until a complete page or frame of
66 lines of characters is printed. The number of character lines
printed in a frame is controlled by modulo 66 character lines
counter 78 which signals the page and film advance and develop
control circuitry 88 when a frame is completed. It should be noted
that while the instant system is described as including
substantially simultaneous development of the recorded electron
image following printing of the image in the above described
manner, it is entirely feasible for the electron image to be stored
on the microfilm and developed subsequently at a more convenient
time and under less strenuous conditions. Additionally, while in
the system of FIG. 4, beam blanking (enhancement) is employed to
achieve dot recording, it is entirely feasible to include an
additional deflecting signal for deflecting the recording electron
beam probe to one side of the other of the Lenard window so as to
achieve beam blanking by interception of the beam by the sides of
the Lenard window structures as described earlier with respect to
FIG. 1A of the drawings.
With the multiple scan per character EB COM printer system shown in
FIGS. 4A and 4B and employing an electron beam spot size of 5
micron diameter, it would be possible to write characters in the
above-identified fashion having a height of 75 microns, a width of
50 microns and with a spacing of 30 microns between characters and
between character lines. With such a system employing 10 scans per
character to write a character, a complete line of characters could
be traced out in 24,000 microseconds corresponding to 240
microseconds for a one line scan of 132 partial characters or an
average of 18 microseconds per character. With a system having the
above constraints, the frequency of writing each character would be
f/character = 1/1.8 .times. 10.sup.-.sup.6 = 550 kilohertz and the
frequency per line would f/line of characters = 1/2.40 .times.
10.sup.-.sup.4 = 4 kilohertz. At these writing rates, the microfilm
tape take-up and pay-out spools can be driven by continuous drive
motors whose speed of advance during a recording operation would be
correlated to the inhibit period provided at the end of each line
scan of the recording electron beam so that the tape advances a
distance on the order of 10 microns during this interval before
again initiating a write cycle on the part of the dot clock and
control circuit 71. It should be noted however that the systems
specifications listed above are only exemplary and can be varied
widely to meet the needs of any particular installation. For
example the recording beam spot diameter can be varied from the 5
microns indicated up to a 75 micron diameter spot to provide a
required amount of energy to accomplish high speed recordings
having good resolution and high intensity. Other variation and
modifications to meet the requirements of different high speed
printer installations will be suggested to those skilled in the
art.
From the foregoing description, it will be appreciated that the
invention provides a new and improved EB COM printer system and
electron beam recording apparatus therefor having high speed
printing capabilities together with good resolution and high
intensity to provide good quality microfilm prints. The electron
beam recording apparatus possesses long cathode life for its
electron beam source due to the novel construction of a Lenard
window structure. The EB COM printer system can be adapted for use
with a wide variety of character formation techniques using a large
number of microfilm recording mediums having different compositions
such as wet silver, dry silver, diazo, Kalvar, etc and having
widely different forms such as tape, card, drum, disc, etc. The
invention also makes available to the art a novel recording
technique employing partial electron beam recording with each
individual scan of the recording electron beam while moving the
record medium transversely to the direction of scan of the electron
beam to accomplish raster recording of characters in a line over a
predetermined number of scans. The EB COM printer system
incorporating the above characteristics actually comprises a
combined controller-EB COM printer having a buffer memory that
allows it to be easily interfaced with any known computer system as
a standard, plug compatible peripheral equipment having print-out
speeds on the order of 10,000 to 25,000 lines per minute and even
higher so that it places little or no constraints on the high speed
processing capabilities of the computer system with which it is
used.
While the electron beam recording apparatus described herein has
been disclosed as primarily intended for use in an EB COM printer
system, it is believed obvious to those skilled in the art that the
novel electron beam apparatus can find application in a wide
variety of uses wherein it is desired to impart the energy of an
electron beam to a medium exteriorily of an evacuated space. Such
applications as electron beam analog recording on microfilm and
television picture recording are believed to be logical uses for
the new and improved electron beam apparatus made available by this
invention. Accordingly it will be seen that the novel electron beam
apparatus can be used in a wide variety of applications in addition
to those detailed above.
Having described several embodiments of a new and improved electron
beam type computer output on microfilm printer and electron beam
apparatus therefor, constructed in accordance with the invention,
it is believed obvious that other modifications and variations of
the invention are possible in the light of the above teachings. It
is therefor to be understood that changes may be made in the
particular embodiments of the invention described which are within
the full intended scope of the invention as defined by the appended
claims.
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