U.S. patent number 3,777,135 [Application Number 05/270,750] was granted by the patent office on 1973-12-04 for illumination system.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to James D. Rees.
United States Patent |
3,777,135 |
Rees |
December 4, 1973 |
ILLUMINATION SYSTEM
Abstract
An illumination system having four lamps arranged orthogonally
around a subject to be illuminated with each lamp positioned
outside the corresponding adjacent edge of the subject. A reflector
system having a cylindrical surface and a plurality of flat
reflectors are associated with each of the lamps for directing
light rays to the subject from the adjacent edge thereof to the
edge opposite thereto.
Inventors: |
Rees; James D. (Pittsford,
NY) |
Assignee: |
Xerox Corporation (Rochester,
NY)
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Family
ID: |
23032643 |
Appl.
No.: |
05/270,750 |
Filed: |
July 11, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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157754 |
Jun 28, 1971 |
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813201 |
Apr 3, 1969 |
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Current U.S.
Class: |
362/225;
355/70 |
Current CPC
Class: |
F21V
7/09 (20130101); G03B 27/542 (20130101) |
Current International
Class: |
F21V
7/09 (20060101); F21V 7/00 (20060101); G03B
27/54 (20060101); F21v 007/00 (); G03b
027/54 () |
Field of
Search: |
;240/41.1,41.3,41.35,103
;355/67,68,69,70 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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64,022 |
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Oct 1912 |
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CH |
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605,609 |
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Feb 1926 |
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FR |
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201,755 |
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Mar 1939 |
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DD |
|
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Sheer; Richard M.
Parent Case Text
This is a continuation of application Ser. No. 157,754, filed June
28, 1971, which, in turn, is a continuation of application Ser. No.
813,201, filed Apr. 3, 1969, both now abandoned.
Claims
What is claimed is:
1. An illumination system for illuminating a planar object defined
by a plurality of boundaries including
a plurality of illumination devices, one being arranged generally
in parallel with one of at least two opposing boundaries of the
object, and another of the devices being arranged generally in
parallel with the other of the opposing boundaries,
each of said devices having an elongated light source and a
reflecting surface of concave configuration disposed parallel to
and adjacent the respective light source to reflect light rays from
its respective light source and directly project the rays upon the
object,
each of said devices having a reflecting surface of planar
configuration for its respective light source and disposed parallel
to and adjacent said light source to recieve some of the light rays
emanating directly from its respective light source and to direct
these rays upon the object,
each of said illumination devices having its light source and
reflecting surfaces disposed relative to one another for directing
light rays respectively from one of the opposing boundaries to the
other with an intensity that varies decreasingly from the former to
the latter.
2. An illumination system for illuminating a planar object defined
by a plurality of boundaries including
a plurality of illumination devices, one being arranged generally
in parallel with one of at least two opposing boundaries of the
object, and another of the devices being arranged generally in
parallel with the other of the opposing boundaries,
each of said devices having an elongated light source and
reflecting surface of concave configuration disposed parallel to
and adjacent the respective light source to reflect light rays from
its respective light source and directly project the rays upon the
object,
each of said devices having a reflecting surface of planar
configuration for its respective light source and disposed parallel
to and adjacent said light source to receive some of the light rays
emanating directly from its respective light source and to direct
these rays upon the object,
each of the illumination devices having its light source and
reflecting surfaces disposed relative to one another for directing
light rays respectively from one of the opposing boundaries to the
other with an intensity that varies decreasingly from the former to
the latter, said variation in intensity from one of the devices
being substantially equal to the variation in intensity of another
of the devices.
3. The illumination system of claim 1 for planar objects having a
rectangular shape and the illumination system comprising four light
sources, one parallel to each of the boundaries of the object, and
said reflecting surfaces for each of the light sources.
4. The illumination system of claim 1 wherein each light source and
its associated concave reflecting surface are positioned outside of
the corresponding boundary of the object.
5. The illumination system of claim 2 wherein each of said devices
having a second reflecting surface of planar configuration disposed
parallel to and adjacent each of said light sources to recive some
of the light rays from its respective light source and to direct
these rays upon the object.
6. The illumination system of claim 5 wherein each of said devices
having a third reflecting surface of planar configuration disposed
parallel to and adjacent each of said light sources to receive
still other light rays from its respective light source and to
direct these rays upon the object.
7. The illumination system in claim 5 wherein said planar
reflecting surfaces are at angles less than 180.degree. relative to
one another.
8. In a utilization device wherein an object is arranged to be
illuminated from one boundary to another boundary thereof, an
illumination device comprising an elongated light source disposed
to project light rays directly upon the object, an element having
reflective surface of concave configuration disposed parallel to
and adjacent the light source for receiving light rays therefrom
and reflecting the same directly upon the object, an element having
a reflecting surface of planar configuration extending along said
concave surface and disposed parallel to and adjacent said light
source to receive some of the light rays directly from said source
and to reflect the same directly upon the object, said light source
and reflecting surfaces disposed for directing light rays
respectively from said one boundary of the object to said another
boundary with an intensity that varies decreasingly from the former
to the latter.
9. In a utilization device wherein an object is arranged to be
illuminated from one boundary to another thereof, an illumination
device comprising an elongated light source disposed to project
light rays directly upon the object, an element having a reflective
surface of concave configuration disposed parallel to and adjacent
the light source for receiving light rays therefrom and reflecting
the same directly upon the object, an element having a plurality of
reflecting surfaces of planar configuration extending along with
said concave surface with each planar surface disposed parallel to
and adjacent said light source to receive some of the light rays
directly from said source and to reflect the same directly upon the
object in superimposed relation to the other rays directed to the
object, said light source and reflecting surfaces disposed for
directing light rays respectively from said boundary of the object
to said another boundary with an intensity that varies decreasingly
from the former to the latter.
10. In a projection apparatus for illuminating a planar object
having at least two opposed sides and directing light rays
emanating therefrom through a lens system and onto an image plane,
the combination including
a plurality of illumination devices, one being disposed adjacent
one of the sides of the object and another device disposed adjacent
the other side, each of the devices having an elongated light
source arranged generally parallel to the respective sides of the
object, each of said light sources projecting light rays therefrom
directly upon the object,
each of said devices having an element formed with a reflecting
surface of right cylindrical configuration disposed parallel to and
adjacent each of said light sources and reflecting light rays
reaching said first surface from said source and directing the same
upon the object in superimposed relation to the rays reaching the
object directly from said source,
said element having a reflecting surface of planar configuration
extending along each cylindrical surface to receive some of the
light rays directly from each source and to reflect the same
directly upon the object,
each of said devices having its light source and reflecting
surfaces disposed relative to one another for directing light rays
respectively from one of the opposed sides to the other with an
intensity that varies decreasingly from the former to the
latter.
11. In a projection apparatus for illuminating a planar object
having at least two opposed sides and directing light rays
emanating therefrom through a lens system and onto an image plane,
the combination including
a plurality of illumination devices, one being disposed adjacent
one of the sides of the object and another device disposed adjacent
the other side, each of the devices having an elongated light
source arrnged generally parallel to the respective sides of the
object, each of said light sources projecting light rays therefrom
directly upon the object,
each of said devices having an element formed with a reflecting
surface of right cylindrical configuration disposed parallel to and
adjacent each of said light sources and reflecting light rays
reaching said first surface from said source and directing the same
upon the object in superimposed relation to the rays reaching the
object directly from said source,
said element having a reflecting surface of planar configuration
extending along each cylindrical surface to receive some of the
light rays directly from each source and to reflect the same
directly upon the object,
each of said devices having its light source and reflecting
surfaces disposed relative to one another for directing light rays
respectively from one of the opposed sides to the other with an
intensity that varies decreasingly from the former to the latter,
said variation in intensity from one of the devices being
substantially equal to the variation in intensity of another of the
devices.
12. In a utilization device wherein a planar object is arranged to
be illuminated and the light rays therefrom projected onto an image
plane, an illumination system comprising at least two opposed
elongated illumination devices each having a light source and
reflecting means arranged along the object such that each of at
least two opposite boundaries of the object has one of said
illuminating devices adjacent thereto, each of said light sources
having its longitudinal axis disposed outside the boundary of the
object adjacent thereto and arranged to direct light rays from that
light source directly upon the object, across the same and to an
opposite boundary thereof at angles less than 90.degree. relative
to the plane of the object and with an intensity that varies
decreasingly from said adjacent boundary to said opposite boundary,
each of said reflecting means including a reflecting surface of
planar configuration, each of said reflecting means together with
its associated planar reflecting surface being arranged relative to
its corresponding light source for reflecting light rays from that
source and to direct these rays between said adjacent boundary and
said opposite boundary with an intensity that varies decreasingly
from the former to the latter, said variations in intensities from
each of said illumination devices being substantially equal whereby
the resultant illumination irradiance at the image plane is
substantially homogeneous.
13. In a utilization device wherein a planar object is arranged to
be illuminated and the light rays therefrom projected onto an image
plane, an illumination system comprising at least two opposed
elongated illumination devices each having a light source and a
reflecting means arranged along the object such that each of at
least two opposite boundaries of the object has one of said
illumination devices adjacent thereto, each of said reflecting
means including a reflecting surface of planar configuration, each
of said illumination devices having its longitudinal axis disposed
outside the boundary of the object adjacent thereto and arranged
for producing light rays which project upon the object with an
intensity that varies decreasingly from said adjacent boundary to
said opposite boundary, said variation in intensity of one of said
illumination devices being substantially equal and from an opposite
directional orientation relative to the variation of intensity of
the other illumination device whereby the resultant irradiance
illumination at the image plane is substantially homogeneous.
Description
This invention relates to illumination systems, and particularly,
to improvements in the arrangement of lamps and associated
reflectors relative to a subject to be illuminated. The
illumination system arranged in accordance with the present
invention is particularly adapted for use with optical systems for
illuminating originals to be reproduced in automatic
copiers/duplicators that are adapted for high speed operation and
capable of having its sequence timing varied thereby permitting
variable speeds of output.
As is well known in recent years, the steadily increasing size of
various industries has required an enormous increase in the amount
of paper work that must be accomplished, maintained, and made
available for wide interplant or department circulation. In the
present day commercial automatic copier/reproduction machines,
which are adapted to produce copies of between 5 and 60 8 .times.
11 inch sheets of copy per minute, the photo-receptor device is in
the form of a drum which rotates in timed unison relative to a
plurality of processing stations. The limiting feature in these
present day machines is the use of the xerographic drum which
seriously limits the positioning and action of each of the
processing devices and, in particular, the requirement of
presenting a flowing image upon the xerographic drum as a document
is being scanned.
The mechanism which accomplishes the scan of a fixed document in
the drum type copier/duplicator generally involves a slidable
carriage for supporting illumination lamps in addition to drive
mechanisms, levers, pulleys, switches, etc. for accomplishing
scanning of the document. As the demands for faster copying or
duplicating has come about, these conventional machines generally
have been modified in their respective drive systems and electrical
circuits in order to accomplish a faster scan for the scanning
mechanisms already in the machine. The result of these
modifications is to propel the structures that go to make up the
scanning mechanisms at very great speeds and, as will be apparent,
will place undue burden upon the structural supports of the machine
and the scanning mechanism.
As a solution for overcoming the multitude of disadvantages for
high speed copying, the latest machine concept for copiers utilizes
flash exposure of a document and the arrangement of a moving
photoconductor material in a flat condition at the instant of
exposure. However, in order to overcome the loss of exposure time
that these copiers usually demand the intensity of the illumination
lamps, in order to accomplish adequate imaging, must be extremely
high requiring specially designed lamps and overly large power
sources.
It is therefore the principal object of this invention to improve
illumination systems for effecting maximum capability of the lamps
utilized therein, which system is capable for general copying
applications and for making high speed copies in variable time
sequences.
Another object of this invention is to improve illumination systems
for flat objects wherein dark spots and light spots are
substantially eliminated.
Another object of this invention is to improve illumination systems
whereby light rays produced thereby when directed upon an object
being illuminated is such as to effect homogeneous illumination at
an image plane.
Another object of this invention is to improve illumination systems
employing elongated lamps by arranging the same so as to achieve
uniform illumination at maximum intensity and with a minimum of
power requirements.
These and other objects of this invention are obtained by means of
the orthogonal arrangement of a plurality of elongated light
sources or lamps which are positioned outside the outer edges of a
flat object being illuminated. The light rays from each of the
lamps are directed on the adjacent edge of the object and extend
across the object to the remote edge thereof thereby overlapping
the light rays from the other lamps. In conjunction with each lamp
there is provided a semi-cylindrical reflector and planar
reflectors arranged edge to edge at different angles relative to
each other and in position adjacent one edge of the
semi-cylindrical reflector for directing different light rays
therefrom for optimizing the projection of the light rays from each
lamp to the object.
For a better understanding of the invention as well as other
objects and further features thereof, reference is had to the
following detailed description of the invention to be read in
conjunction with the accompanying drawings, wherein:
FIG. 1 is a schematic sectional view of a typical reproduction
machine showing the various electrostatic processing stations;
FIG. 2 is an isometric schematic view of a portion of the lamp
assembly of an illumination system arranged in accordance with the
present invention;
FIG. 3 is a partial top view of a portion of the lamp assembly and
document platen; and
FIG. 4 is a sectional view of one side of the lamp assembly.
For a general understanding of the illustrated copier/reproduction
machine, in which the invention may be incorporated, reference is
had to FIG. 1 in which the various system components for the
machine are schematically illustrated. As in all electrostatic
systems such as a xerographic machine of the type illustrated, a
light image of a document to be reproduced is projected onto the
sensitized surface of a xerographic plate to form an electrostatic
latent image thereon. Thereafter, the latent image is developed to
form xerographic powder image, corresponding to the latent image on
the plate surface. The powder image is then electrostatically
transferred to a support surface to which it may be fused by a
fushing device whereby the powder image is caused permanently to
adhere to the support surface.
In the illustrated machine, an original D to be copied is placed
upon a transparent support platen P fixedly arranged in an
illumination lamp assembly 10 arranged at the left end of the
machine as viewed in FIG. 1. While upon the platen, an illumination
system, to be described herein, flashes light rays upon the
original thereby producing image rays corresponding to the
informational areas on the original. The image rays, indicated by
lines 11 are projected by means of an optical system for exposing
the photosensitive surface of a xerographic plate at the exposure
station A, the plate being in the form of a flexible
photoconductive belt 12 arranged on a belt assembly generally
indicated by the reference numeral 13.
The photoconductive belt assembly 13 is slidably mounted upon a
support bracket secured to the frame of the machine and is adapted
to drive the selenium belt 12 in the direction of the arrow as
shown in FIG. 1 at a constant rate. During this movement of the
belt, the light imaging rays of an original are flashed upon the
xerographic surface of the belt. The belt surface that intercepts
the light rays comprises a layer of photoconductive material such
as selenium on a conductive backing that is sensitized prior to
exposure by means of a suitable charging corona generator
device.
The flash exposure of the belt surface to the light image
discharges the photoconductive layer in the areas struck by light,
whereby there remains on the belt a latent electrostatic image in
image configuration corresponding to the light image projected from
the original on the supporting platen. As the belt surface
continues its movement, the electrostatic image passes through a
developing station B in which there is positioned a developer
assembly generally indicated by the reference numeral 14 and where
the belt is maintained in a flat condition. The developer assembly
14 comprises a vertical conveying mechanism which carries
developing material to the upper part of the belt assembly 13
whereat the material is dispensed and directed to cascade down over
the upwardly moving inclined selenium belt 12 in order to provide
development of the electrostatic image. As the developing material
is cascaded over the xerographic plate, toner particles in the
development material are deposited on the belt surface to form
powder images.
The developed electrostatic image is transported by the belt to a
transfer station C whereat a sheet of copy paper is moved at a
speed approximately in synchronism with the moving belt in order to
accomplish transfer of the developed image. There is provided at
this station a sheet transport mechanism generally indicated at 16
adapted to transport sheets of paper from a paper handling
mechanism generally indicated by the reference numberal 18 to the
developed powder image on the belt at the station C. The transfer
of the developed image from the selenium belt surface to sheet
material is effected by means of a suitable corona transfer device
that is located within the sheet transport mechanism to the point
of contact between the sheet and selenium belt as the sheet passes
the transfer station C.
After the sheet is stripped from the belt 12 it is conveyed into a
fuser assembly generally indicated by the reference numeral 20
wherein the developed and transferred xerographic powder image on
the sheet material is permanently affixed thereto. After fusing the
finished copy is discharged from the apparatus at a suitable point
for collection externally of the apparatus.
Suitable drive means may be arranged to drive the selenium belt 12
in conjunction with timed flash exposure of an original to be
copied to effect conveying and cascade of toner material, to
separate and feed sheets of paper and to transport the same across
the transfer station C and to convey the sheet of paper through the
fuser assembly in timed sequence to produce copies of the
original.
It is believed that the foregoing description is sufficient for the
purposes of this application to show the general operation of an
electrostatic copier using an illumina-tion system constructed in
accordance with the invention. For further details concerning the
specific construction of the electrostatic copier, reference is
made to U.S. Pat. No. 3,661,452, issued May 9, 1972 in the name of
Hewes et al.
The illumination system of the present invention is illustrated in
detail in FIGS. 2-4 and is designed for irradiating the diffusely
reflecting original D such that the image of the original produced
by a lens has irradiance uniformity to a maximum of .+-.5 percent.
This uniform image irradiance is obtained by the use of four linear
light sources L.sub.1, L.sub.2, L.sub.3 and L.sub.4 and their
associated reflectors R.sub.1, R.sub.2, R.sub.3 and R.sub.4
arranged orthogonally relative to the original. The arrangement is
such as to compensate for the relative illumination functions of
the lens, for example, the illumination falloff due to vignetting
of the optical aperture for the system and to the cosine to the
fourth power law.
Each of the four linear light sources, which may be in the form of
a xenon flash lamp or other gaseous discharge tube having a small
diameter, is provided with a semi-cylindrical reflector and at
least one plano reflector. The radio-metric equations for the
reflectors are utilized to project reflected light from a platen
supporting an original onto an image plane where the irradiated
image has nearly uniform irradiance.
As shown in FIGS. 2 and 3, the lamps L.sub.1, L.sub.2, L.sub.3 and
L.sub.4 are arranged along the sides of a rectangle somewhat larger
than the rectangle defined by the original D. The inner edges of
the reflectors R.sub.1, R.sub.2, R.sub.3 and R.sub.4 being parallel
to the respective lamps are also arranged as the sides of a
rectangle having its inner edges spaced slightly outwardly from the
edges which define the original. With this arrangement, the light
rays which emanate from each of the lamps, are directed toward the
original, to impinge thereon at various angles other than directly
or at 90.degree.. This arrangement, then, eliminates direct
perpendicular impingement of the light rays upon the document
thereby preventing excessively high intensity illumination of the
edges of the document if such were extended over the light
sources.
In order to provide homogeneous illumination wherein there will be
a minimum amount of variation in the image irradiance from an
original and, to increase the amount of light that can be directed
toward the original D to near perfect efficiency, the illumination
system is provided with a semi-cylindrical shape reflective surface
in combination with at least one plano reflective surface for each
of the linear lamps. These reflective surfaces are designed to
direct light upon the original being illuminated and are so
arranged that the impinging rays of one lamp and its corresponding
reflective surfaces overlap with the impinging rays of the opposing
lamp and its corresponding reflective surfaces. These reflected
rays coupled with the rays emanating directly from each of the
lamps upon the original and result in a more uniform, homogeneous
illumination of the photoconductive surface.
Each of the reflectors, and for simplicity the reflector R.sub.1
will be the only one described in detail, comprises a first
reflector surface R.sub.a having the form of a right circular
cylinder with the axis of the surface of revolution parallel to and
offset relative the axis of the linear lamp L.sub.1 by an amount
approximately equal to the radius of the lamp. The reflector
surfaces R.sub.a, one for each of the reflectors in the
illumination system, define the inner limits of the four assembled
reflectors. When assembled, the surfaces define an opening through
which the light rays emanating from an illuminated original are
directed therethrough to a projection lens for the document
illumination system. Light rays, as illustrated in FIG. 4 by lines
A.sub.1 and A.sub.2 emanate from the lamp L.sub.1 and from the cone
A.sub.3 of light directly in back of the lamp and reflected by the
surface R.sub.a through the lamp. The lines A.sub.1 and A.sub.2
extend to the adjacent and furthermost edges, respectively, of the
document D and define the outer limits of the light reaching the
document from lamp L.sub.1 and cone A.sub.3. In addition, with the
axis of the lamp L.sub.1 being located adjacent the axis of the
cylindrical surface R.sub.a, light is also reflected from this
surface and directed upon the original.
Joined along the outer edge of the reflector surface R.sub.a is a
second reflector surface R.sub.b in the form of an elongated plane
surface having its inner longitudinal edge connected to the edge of
the surface R.sub.a and arranged to redirect some of the light rays
from the lamp L.sub.1 between the lines B.sub.1 and B.sub.2 that
extend to the adjacent and furthermost edges, respectively of the
document. The light falling upon the surface R.sub.b that is
redirected upon the document would otherwise be lost for
illumination purposes if this surface was not provided. The ray
B.sub.2 may be made to fall very near to the ray A.sub.2 in order
to minimize the light that may be lost at the juncture of the
surfaces R.sub.a and R.sub.b. The line B.sub.2 and its originating
direct light line that extends between the lamp and the surface has
been illustrated relative to a point away from the R.sub.a -R.sub.b
junction point for clarity reasons. The only light that is lost by
operation of the surfaces R.sub.a, R.sub.b would be at this
junction and then only for a very narrow cone of light rays, too
small to be illustrated.
In order to enhance the illumination uniformity by the illumination
system at the image plane, which for the machine of FIG. 1 is the
same as the exposure station A, a second elongated plano reflective
surface R.sub.c is provided and has one of its longitudinal edges
joined to the outer longitudinal edge of the plano surface R.sub.b.
The surface R.sub. c redirects still more of the light emanating
from the lamp L.sub.1 that would be otherwise lost, along light
rays extending away from the document and the other surfaces
R.sub.a, R.sub.b. The plane of the surface R.sub.c is at an angle
relative to the plane of the surface R.sub.b such that the light
rays falling thereon from the lamp L.sub.1 and from the cone
C.sub.3 immediately behind the lamp from the surface R.sub.c is
reflected and directed along the light lines C.sub.1 and C.sub.2.
These lines define the limits of the light reaching the document
from the surface R.sub.c. As was the case for the R.sub.a -R.sub.b
junction, the light line C.sub.2 is illustrated in FIG. 4 slightly
away from the R.sub.b -R.sub.c junction in order to permit better
visualization. In actual practice, the line C.sub.2 would be
effectively closer to the R.sub.b -R.sub.c junction thereby
minimizing light losses due to this reflector junction.
Additional effeciency is possible with the illumination system by
the provision of a third elongated plano reflective surface R.sub.d
having its inner longitudinal edge connected to the outer edge of
the surface R.sub.c and at an angle relative thereto for
redirecting additional light from the lamp L.sub.1 upon the
document. The surface R.sub.d is arranged so as to redirect light
reaching the same from the lamp and from the cone D.sub.3
immediately behind the lamp from the surface R.sub.d upon the
document between light lines D.sub.1 and D.sub.2. These lines
define the limits of the light reaching the document from the
reflective surface R.sub.d. As in the previous cases, the line
D.sub.2 has been shown slightly displaced relative to the R.sub.c
-R.sub.d junction in order to permit better illustration thereof.
The angles between the planes of the surfaces R.sub.b, R.sub.c and
R.sub.d are less than 180 degrees relative to one another.
In actual practice, there is negligible light losses from the
linear junction R.sub.a - R.sub.b, R.sub.b -R.sub.c, R.sub.c
-R.sub.d of the reflective surfaces. The cones A.sub.3, B.sub.3,
C.sub.3 and D.sub.3 having been drawn in FIG. 4 to correspond with
their respective light lines reaching the document being
illuminated. As shown, there are appreciable gaps between the cones
signifying light losses in the gaps. Actually, with light lines
impinging upon points closer to the above referred to junctions,
the cone angles would be larger and the gaps therebetween smaller
and negligible. The dimension for the width of each of the surfaces
R.sub.b, R.sub.c and R.sub.2 is chosen so that the portions of the
surfaces nearest the edges will effect reflection to the edges of
the document,no more, no less. In this manner, there is a minimum
of loss of light directed upon the reflecting surfaces.
From an analysis of FIG. 2, in conjunction with the description
above, it will be seen that each lamp L.sub.1, L.sub.2, L.sub.3 and
L.sub.4 generates seven images, some real and some virtual, which
serves as light sources. Again, using lamp L.sub.1 as typical of
the operation of the other lamps in the illumination system, the
seven images are disposed approximately in the portions illustrated
in FIG. 2. With the lamp L.sub.1 being slightly displaced relative
to the longitudinal axis of the cylindrical reflector R.sub.a, the
first read image thereof is illustrated at L.sub.1.sup.1 being
produced by the internal reflection of the reflective surface
R.sub.a. Both the lamp L.sub.1 and its image L.sub.1.sup.1, serving
as light sources for the reflector R.sub.b in turn generate the
virtual images L.sub.1.sup.a and L.sub.1.sup.1a respectively. By
reflecting from the reflective surface R.sub.c, the lamp L.sub.1
and its image L.sub.1.sup.1 also effect the virtual images at
L.sub.1.sup.b and L.sub.1.sup.1b. Similarly, the reflective
surface, R.sub.d will effect the virtual images L.sub.1.sup.c and
L.sub.1.sup.1c from the lamp L.sub.1 and its image L.sub.1.sup.1,
respectively. Each of the seven images will serve as light sources
for illuminating the document D, thereby optimizing the efficiency
of the illumination system.
From the foregoing it will be apparent that the reflecting surfaces
R.sub.a, R.sub.b, R.sub.c and R.sub.d serve to reflect the light
rays emanating from the lamp L.sub.1 upon the original D between
both extreme edges thereof in overlapping fashion. This means the
light reflected from the surface R.sub.a will be directed upon the
document starting from line ray A.sub.1 coincident with the
adjacent edges of the original, and sweeping across the document to
the other edge thereof terminating in the line ray A.sub.2. Light
reflected from the plano reflectors R.sub.b, R.sub.c and R.sub.d
are directed upon the document between the line rays B.sub.1,
B.sub.2 ; C.sub.1, C.sub.2 ; and D.sub.1, D.sub.2 respectively.
Similarly, as viewed in FIGS. 2 and 3, the reflector R.sub.2 serves
to reflect light from the lamp L.sub.2 upon the original D. The
light rays so reflected overlap those reflected from the reflecting
surfaces of the reflector R.sub.1. In similar fashion, light is
directed from the reflectors R.sub.3 and R.sub.4 by reflection from
the lamps L.sub.3 and L.sub.4 respectively, upon the original in
overlapping ray-trace arrangement.
The effect then, of the use of four orthogonally arranged lamps
arranged beyond the edges of an original being illuminated, and
especially with the provision of the reflecting surfaces for each
of the lamps and the relative positions thereof, an original is
illuminated in such a manner that the object irradiance is
cos..sup.-.sup.4 or otherwise circularly symetrical for the center
point of the surface of the original. It will be apparent from this
arrangement of reflecting surfaces that the illumination assembly
10 makes effective use of a large part of the light flux emitted
from the light sources except for those areas wherein reflection
losses are behind the lamps themselves. It will be appreciated from
the foregoing that the arrangement of the lamps provides cos.
.sup.-.sup.4 illumination. By incorporating the illustrated plano
reflectors R.sub.b, R.sub.c and R.sub.d with each of the lamps, the
resultant illumination profile for an object being illuminated is
changed to be symmetrical. It will also be appreciated that the
optimum illumination is available for an arrangement of light
sources and reflectors which, in themselves, are of simple design,
involving little manufacturing skill and expense and may be the
result of relatively calculations. Each of the reflectors are made
up of one cylindrical surface and one or more plane surfaces rather
than some complex surfaces, such as ellipses, spirals, or
combinations.
Each of the lamps L.sub.1, L.sub.2, L.sub.3 and L.sub.4 is
connected to a suitable source electrical circuit for energizing
these lamps. For the particular reproduction machine illustrated in
FIG. 2, the particular electrical circuit for energizing the lamps
should be in the form of a flashing circuit which will energize the
lamps for short periods of time, such as, for example, 100
microseconds. In this particular use, this short period of time
will be suitable for flash exposing the original D upon a
photoreceptor surface such, for example, as the selenium belt
12.
The image forming light rays emanating from the original D during
illumination thereof are directed to a suitable projection lens
system 30. Details of the lens system and mirrors 32 therefor and
the housings for containing and supporting the illumination system
as well as the lens system are not necessary for understanding the
present invention. Further details of such matters may be derived
from the U.S. Pat. application Ser. No. 731,960, filed May 24, 1968
in the name of Starkweather et al., the application being assigned
to same assignee as the present application.
The illumination system is adapted to present light image
representation of an original document upon the selenium belt 12
sequentially in timed relation to the movement of the belt which in
the particular xerographic reproduction apparatus illustrated,
continuously moves during the xerographic processing stations. The
light image of the original being reproduced, is directed out of a
housing for the illumination system and through a suitable
rectangular opening on the side of the machine adjacent the
selenium belt 12. The housing may serve as a light shield for the
selenium belt in order to present extraneous light from impinging
upon a belt during use of the apparatus.
While the invention has been described with reference to the
structures disclosed herein, it is not to be confined to the
details set forth and this application is intended to cover such
modifications or changes as may come within the purpose of the
improvements of the following claims.
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