Note: Descriptions are shown in the official language in which they were submitted.
~045600
The invention relates to illuminators particularly,
-- though not exclusively, for use in copying machines.
At the present time there are a great number of
applications where an illuminator is required which is safe
to operate and is capable of providing a high intensity of
illumination per unit volume. Further, in copying machines,
for example, there is usually a requirement for an illuminator
which is capable of providing illumination of substantially
uniform intensity over a wide area. At the present time
fluorescent lamps are commonly used in copying machines.
Proposals and some current modern machines use
quartz-halogen lamps or illuminators of the type illustrated,
for example, in U. S. Patent No. 3,211,938 in which a coiled
element extends the length of quartz envelope containing
15 --~ ~--~ gaseous iodine. As is described in the mentioned patent, the
lamp generates a great amount of heat as well as light, and
causes, in its described configuration, difficulties of
dissipating the heat and of the effect of heat on a mounted
; reflector, for example. Generally, whereas a quartz-halogen
lamp of the type mentioned provides a high degree of illumina-
j:
tion compared with a similar sized fluorescent lamp, it has
certain drawbacks including difficulty of heat dissipation.
~ Such guartz-halogen lamps are also less robust mechanically
i and in copying machines in particular, the lamp is often
required to stand up to high levels of acceleration and
deceleration of scanning mechanisms. A difficulty of satis-
factorily mounting the filament is also experienced while
r~taining uniform illumination output along the length of the
lamp throughout the required lifetime of the lamp.
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lC)45600
It is an object of an aspect of the present invention
to provide an improved illuminator suitable for use in copying
machines.
In accordance with one aspect of the present
invention there is provided an illuminator including: an
elongated tubular envelope having a reflective surface extending
along its length, said reflective surface defining a clear
transparent aperture along said tubular envelope, a separable
lamp disposed at each end of said tubular envelope to direct
radiant energy to the interior thereof, said lamps each including
a source of radiant energy and a concave reflective surface
disposed adjacent to said source of radiant energy on the side
: thereof opposite to said tubular envelope, said tubular envelope
constituting an integrating cavity into which radiant energy is
directed from said sources of radiant energy and said concave
reflective surfaces, and from which said energy is emitted
through said transparent aperture.
In accordance with another aspect of the present
invention there is provided an illuminator for a photocopying
apparatus, including: an elongated tubular envelope having a
reflective surface extending along its length, said reflective
surface defining a clear transparent aperture along said tubular
envelope, a separable lamp disposed at each end of said tubular
envelope to direct radiant energy to the interior thereof, said
lamps each including a source of radiant energy and a concave
reflective surface disposed adjacent to said source of radiant
energy on the side thereof opposite to said tubular envelope,
said tubular envelope constituting an integrating cavity into
which radiant energy is directed from said sources of radiant
energy ~nd said concave reflective surfaces, and from which
said energy is emitted through said transparent aperture.
~n illuminator acco~din~ to the inventi~n will now
f~,
~45600
be described by way of example with reference to the accom-
panying drawing in which:
Figure 1 shows schematically in section the
illumination device; and
Figure 2 shows view A-A of Figure 1.
Referring to the drawings, an elongated tubular
envelope 10 is provided on its internal surface with diffuse
reflective material 11 extending over the internal surface.
The envelope 10 substends an arc of 315 about its longi-
tudinal axis (see Figure 2 where angle B = 45) to provide anarrow window 12 extending along the length of the envelope
10 through which light can pass. Window 12 is shown as a
clear, open aperture for ease of illustration. Of course,
window 12 might also be defined by a clear portion in a
closed 360 ring of the envelope. At each end of the
envelope 10, there is provided a quartz-halogen lamp 13 and
14, as sold under the trade mark "Atlas" type No. A1231 being
rated at 12 volts and 100 watts. The lamps 13 and 14 are
- releasably attached by means not shown to the envelope 10.
The lamps 13 and 14 have respective concave reflective
f~
5600
surfaces 13B and 14B, behind the filaments 13A and 14A, which
direct light generally along the axis of the envelope 10.
In use, light radiates through the window 12 from
the filaments 13A and 14A either directly or after single or
multiple reflection within the envelope 10.
The lamps 13 and 14 are preferably matched where the
illuminator is for use in electrostatographic copying machines
especially those machines incorporating liquid development.
This ensures a high intensity and substantially uniform intensity
of illumination output along the length of the window 12. In
practiceO the lamps are tested as supplied and matched in pairs
for equal or near equal output.
In the illuminator described, a substantial amount
of heat is liberated by the lamps and a convection cooling system
is provided in a copying machine application to dissipate the
heat generated. Compared to quartz-halogen lamps in which the
active part, that is the filament, extends along the length of
the illuminator, the cooling system necessitated by the lamp
disclosed herein is much simplified. This is because it is
relatively easier to provide cooling air ducts, for example,
at either end of the illuninator than along the whole length.
In the embodiment, the lamps 13 and 14 are releasably
attached to the envelope 10. This facilitates the attachment
and replacement of the lamps in the event of lamp failure. It
will be appreciated, however, that the illuninator can be formed
as an integral unit with the lamps 13 and 14 permanently or more
permanently attached than described.
Preferably the reflective material comprises a high
diffuse reflectance material such as, for example,
1~4S6~0
available under the trademark EASTMAN white reflective paint
no. ~080.
In other embodiments, the envelope 10 itself is
formed of reflective material, or is transparent and has a
reflective layer on its outer surface instead of its inner
surface. The envelope may be formed such that the window is
defined by the part of the envelope, its inner or outer
surface, not coated with reflective material. Further, it
is within the scope of this invention to provide further
layers for absorbing unwanted visible and invisible light
rays, such as in techniques commonly used in optical filter
technology.
The window 12 may also be formed by a slot removed
from the surface of the envelope 10 (as actually shown in the
drawing) or otherwise. Generally, as a requirement for a
sealed atmosphere, manufacturing the envelope 10 is much
easier than the manufacture of the comparable envelopes of
fluorescent and enveloped quartz-halogen lamps which are
totally enclosed tubes. In one embodiment, for example,
; 20 comparatively cheap plastic materials have been used to form
the envelope 10.
In matching illumination intensity output of lamps
and illumination sensing properties of image forming surfaces,
a technique of varying the optical path between them in some
~l 25 way is often used. It will be apparent that such can be
readily and integrally incorporated in this invention. For
example, window 12 can be shaped to provide such adjustment
ar~ compensation as might be required. However, one aspect
of the present invention is that it enables an illuminator
having the possibility of maximum intensity of illumination
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~045600
at its ends, so less compansation is usually required in
practice. Fall-off of illumination at the ends of extended
filament quartz-halogen lamps and fluorescent lamps is one
difficulty of using such lamps particularly for some copying
machine applications.
We prefer to use as illumination sources the
quartz-halogen lamps of the type shown because they provide
; a high output per unit volume. However, an illuminator
according to the invention can be formed with other types of
souece, such as vacuum filament lamps or xenon flash tubes.
But, in each case due regard is given to the spectral output
of the chosen lamps in relation to the spectral response of
the associated image receiving component.
For general purpose copying machines, a satisfac-
tory illuminator can be provided in which the arc subtended
by the window is in the range of a few degrees up to around
65. We prefer an arc of about 4S for use with an electro-
statographic copying machine incorporating liquid development.
In one embodiment of the invention we provide an illuminator
-in which the arc subtended by the window is about 1 or 2.
Such an illuminator is useful in a punched-card reader, for
example, which requires preferably a well-defined linear
; illuminating device.
While a particular embodiment of the invention has
been described above, it will be appreciated that various
modifications may be made by one skilled in the art without
departing from the scope of the invention as defined in the
appended claims.
