Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
1999-04-08
2003-01-07
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S067000, C355S069000, C355S040000
Reexamination Certificate
active
06504598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an illumination device provided with a rotating panel for switching color of illumination light.
2. Description of the Related Art
Conventionally, printers have been proposed which are provided with a printing head using a light shutter that comprises, for example, a PLZT. Furthermore, printing heads have been proposed which are provided with an illumination device having a rotating panel to modulate light emitted from a light source into light of each color red (R), green (G) and blue (B) and direct the modulated light to the light shutter.
The general construction of a full color printer provided with a PLZT printing head is described below.
FIG. 10
briefly shows a partial construction of the full color printer. Part of light emitted from a halogen lamp
21
as a light source is directed to an illumination device
24
by an aluminum pipe
23
. Only a color wheel
11
is shown in the drawing as a rotating panel forming a structural element of the illumination device
24
, and other structural elements which are not illustrated include a drive source for driving the rotation of the color wheel
11
, and a housing for accommodating the color wheel
11
. Reference number
22
refers to a light-transmitting heatproof filter for blocking the heat generated by the halogen lamp
21
.
The color wheel
11
of the illumination device
24
is provided with a plurality of glass panels as transparent members sequentially arranged in a direction of rotation of the color wheel
11
. The light emitted from the halogen lamp
21
passes through the pipe
23
and is modulated sequentially to R, G, B by the respective glass panels via the rotation of the color wheel
11
. Details of the construction of the color wheel
11
and the illumination device
24
are described later.
Reference number
25
is a fiber bundle comprising a lot of plastic fibers. The light modulated by the illumination device
24
(i.e., color wheel
11
), is transmitted within the fibers to a polarizer
26
. The fiber bundle
25
has a circular cross section on the color wheel
24
side, and the fibers are arranged in a linear array on the polarizer
26
side.
Only the light oscillating in a predetermined direction is transmitted through the polarizer
26
. The light which is transmitted through the polarizer
26
further passes through an integrator
27
to suppress dispersion. A shutter array
28
is a member in which a plurality of PLZT elements as optical shutters is arranged in the form of an array, and these shutters are turned ON and OFF via the application of a voltage to the PLZT elements. The light passing through the shutter array
28
arrives at an analyzer
29
, and only the light oscillating in a predetermined direction passes through the analyzer
29
. The light passing through the analyzer
29
forms an image on a color photographic paper
31
as a recording medium via a lens
30
. A full color image is printed on the photographic paper
31
by regulating an amount of R, G, B light via the shutter array
28
.
The color wheel
11
is described below.
FIG. 11
is a top view of the color wheel
11
.
FIG. 12
is a cross section view on an A-A′ plane in FIG.
11
. Glass panels
1
r
,
1
g
and
1
b
are each 1 mm thick, and are processed such that these have a fan-like shape with an interior angle of 60°. The glass panels
1
r
,
1
g
and
1
b
are optically coated so as to modulate white light transmitted therethrough to R (
1
r
), G (
1
g
), B (
1
b
) light, respectively. That is, the glass panels
1
r
,
1
g
and
1
b
have mutually different light transmitting characteristics. The glass panels
1
r
,
1
g
and
1
b
respectively comprise a pair of elements, for a total of six elements.
A top flange
2
and a bottom flange
3
fixedly hold the glass panels
1
r
,
1
g
and
1
b
. The top flange
2
and bottom flange
3
made of aluminum both have a disk-like shape. The bottom flange
3
is provided with an opening
3
a
on its center. A wall
3
b
is formed on one side of the bottom flange
3
along a circumferential edge of the opening
3
a.
The glass panels
1
r
,
1
g
and
1
b
are locked by the top flange
2
and the bottom flange
3
as described below. The bottom flange
3
is disposed with a surface on which the wall
3
b
is formed facing upward, and the glass panels
1
r
,
1
g
and
1
b
are placed on the bottom flange
3
and abut the wall
3
b
, such that like color panels face one another across the center. Then, the top flange
2
is overlaid onto the bottom flange
3
so as to hold the glass panels
1
r
,
1
g
and
1
b
between the two flanges, and the top flange
2
is fixed to the bottom flange
3
via adhesive or screws or the like.
By the way, in the full color printer provided with the PLZT printing head of the aforesaid construction, the color wheel
11
must rotate at approximately 12000 rpm to attain a desirable printing speed. When rotating at such a high speed, however, the color wheel
11
is subject to extremely large centrifugal force which rapidly causes damage to the glass panels
1
r
,
1
g
and
1
b.
Gaps may be generated at mutual connective regions of the glass panels
1
r
,
1
g
and
1
b
of the color wheel
11
due to measurement discrepancies during manufacture. Light may disadvantageously leak from these gaps, and adversely affect printing.
Furthermore, another problem occurs when the color wheel
11
rotates.
FIG. 13
is a side section view of a conventional illumination device
24
. The color wheel
11
is accommodated in a dustproof housing
8
. A motor
10
as a drive source is provided in the opening
3
a
of the bottom flange
3
of the color wheel
11
(refer to FIG.
12
). The color wheel
11
is rotated within the housing
8
via the drive provided by the motor
10
. The light emitted from the halogen lamp
21
(refer to
FIG. 10
) enters the color wheel
11
through an entrance window (not illustrated) in the housing
8
, passes through the glass panel
1
r
(or
1
g
, or
1
b
), and is emitted from an exit window (not illustrated) in the housing
8
.
As shown in the drawing, the housing
8
has two mutually opposing surfaces parallel to the rotational plane of the color wheel
11
, i.e., a bottom surface of the housing body
8
a
and the back surface of the housing cover
8
b
. The color wheel
11
is disposed within these two surfaces so as to be closer to the housing body
8
a
. When the color wheel
11
is rotated, the area near the rotational axis and the area of the exterior circumference have different circumferential speeds, such that an airflow is generated from the center of the color wheel
11
toward the exterior side in a space (B) between the color wheel
11
and the housing body
8
a
(indicated by an arrow
12
in the drawing).
The space (B) is subject to a low air pressure condition due to this airflow
12
, which produces a force in a downward direction (indicated by an arrow
14
in the drawing) on the color wheel
11
. The rotational balance of the color wheel
11
is disrupted under the effects of this downward force, and rotational stability is lost. These effects are particularly pronounced when an air motor is used as the drive source.
OBJECTS AND SUMMARY
An object of the present invention is to eliminate the previously described disadvantages by providing an improved illumination device.
Another object of the present invention is to provide an illumination device provided with a rotating panel capable of high-speed rotation.
Still another object of the present invention is to provide an illumination device which does not leak light from a rotating panel.
Yet another object of the present invention is to provide an illumination device capable of stable rotation of a rotating panel.
These objects are attained by providing an illumination device comprising:
a rotating panel including a plurality of transparent members having different light transmitting characteristics sequentially arranged in a rotational direction of the rotating panel;
Minolta Co. , Ltd.
Nguyen Henry Hung
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