Illumination – Light source and modifier – Including selected wavelength modifier
Reexamination Certificate
2000-06-27
2003-04-29
O'Shea, Sandra (Department: 2875)
Illumination
Light source and modifier
Including selected wavelength modifier
C362S280000, C362S282000, C362S317000, C362S322000, C362S324000, C359S889000, C359S890000, C359S891000, C359S892000
Reexamination Certificate
active
06554454
ABSTRACT:
The application is based on application No. JP 11-181094 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an improved filter, illumination device and illumination method, and as a specific application thereof, to a filter, illumination device and illumination method that are suitable for an optical print head used in a color printer, for example.
2. Description of the Related Art
As a solid scanning type optical recording device, a PLZT optical shutter array is known. A PLZT optical shutter array is formed of PLZT ceramic having a superior electrooptical effect, and through appropriate selection of the operating voltage, high-speed control of whether incident light passes through or is blocked by the array may be performed irrespective of the wavelength of the incident light. Moreover, because a PLZT optical shutter array can optically record information in a very small area, it may be used in an optical print head. It is especially effective in an optical print head for a color printer that uses color-photosensitive silver halide paper as the recording medium.
There are various methods employed by the color printer optical print head using this PLZT optical shutter array (hereinafter ‘PLZT color print head’). In one method, a single PLZT optical shutter array is used, and the color of the incident light that strikes the PLZT optical shutter array is sequentially alternated according to a timing sequence.
FIG. 6
shows the basic construction of a PLZT color print head using this method, which offers high performance.
First, the construction of the PLZT color print head shown in
FIG. 6
will be explained. The PLZT color print head shown in
FIG. 6
comprises a halogen lamp
1
, which works as a light source, a heat filter
2
, a color filter constructed as a color wheel
3
, an integrator
4
that makes the intensity of the light uniform, an optical fiber light guide
5
that guides the light and converts the light leaving the light exit outlet into a linear beam, and an optical shutter unit comprising a polarizer
6
, a PLZT optical shutter array
7
, an analyzer
8
and a rod lens array
9
. The integrator
4
is located at a position at which it can receive the light emitted from the halogen lamp
1
, and the heat filter
2
and the color filter comprising light-permeable optical filters are located between the integrator
4
and the halogen lamp
1
. The color filter comprises a round color wheel
3
, in which color filters that respectively allow blue (B), green (G) and red (R) light to pass through are located in an area having a fan configuration that includes straight lines radiating outward from the center of the wheel and representing the radius of the circle. The light inlet
4
a
of the integrator
4
has a size and position that allow it to receive only light that passes through one of the multiple areas into which the color wheel
3
is divided. The light that passes through the B, G and R color filters that sequentially alternate according to a timing sequence through the rotation of the color wheel
3
strikes the integrator
4
.
The operation of the PLZT color print head shown in
FIG. 6
will now be explained. The white light emitted from the halogen lamp
1
comprising the light source (rated voltage=24V, rated power=250 W) first passes through the heat filter
2
. Light that is harmful to the color development of the color-photosensitive silver halide paper (i.e., UV light and infrared light) is screened out from this white light by means of this heat filter
2
. The white light that passes through the heat filter
2
then passes through the color wheel
3
that rotates in one direction at a high fixed speed (12,000 rpm or higher).
FIG. 7
shows the positions of the filters in the color wheel
3
as seen from the side of the heat filter
2
. The color wheel
3
is divided into six segments. In the color wheel
3
are color filters
3
B,
3
G and
3
R, which allow only blue (B), green (G) and red (R) light to pass through, respectively, and there are two filters of each type. The filters are positioned in a concyclic fashion (in other words, each filter has a fan configuration), with each filter located opposite its matching filter around the circumference of the round color wheel
3
. Because the central angle &thgr; formed by each color filter
3
B,
3
G and
3
R is 60°, when the color wheel
3
rotates, the color filters
3
B,
3
G and
3
R that allow the light from the halogen lamp
1
to pass through alternate in a prescribed time sequence, and as a result, light of a single color is emitted from the color wheel
3
according to an alternating time-based sequence (i.e., B→G→R→B, etc.).
The light inlet
4
a
of the integrator
4
is positioned relative to the center of the color wheel
3
in the manner shown by the solid lines in
FIG. 7
, and appears to move around the circumference of the color wheel as the color wheel rotates. (In fact, the light inlet
4
a
is fixed and the filter rotates, and as described above, the light striking the light inlet
4
a
is sequentially alternated according to a timing sequence.) The light that strikes the light inlet
4
a
at the time that the light inlet
4
a
is positioned such that it extends onto the next filter (or the component that serves as a border) cannot be used to expose the recording medium. Therefore, only the light that passes through the filter within the range of the central angle &agr; (the range that excludes the area within the central angle &thgr; where the color wheel is switching from one filter to another) in
FIG. 7
is used as light to perform actual exposure.
The light that exits the color wheel
3
enters the integrator
4
from the square light inlet
4
a
, and by passing through the integrator
4
, is converted to uniform illumination light. The light passing through the integrator
4
strikes the optical fiber light guide
5
. This optical fiber light guide
5
comprises multiple plastic optical fibers that are bound such that together they comprise a cylindrical configuration at the light inlet end, whereas the light outlets are aligned in a linear fashion. Therefore, the light striking the optical fiber light guide
5
is converted into straight-line illumination light having a high level of brightness at the light exit outlet. The light converted into straight-line illumination light illuminates the PLZT optical shutter array
7
after passing through the polarizer
6
. After being modulated by the PLZT optical shutter array
7
and passing through the analyzer
8
and rod lens array
9
(such as the SELFOC lens manufactured by Nihon Panel Glass Co., Ltd.), it reaches a recording medium not shown in the drawing, such as color-photosensitive silver halide paper.
The PLZT optical shutter array
7
has an array construction in which approximately 60 &mgr;m optical modulation elements are aligned at a 400 dpi pitch. The PLZT optical shutter array
7
selectively allows the light to pass through or be blocked on a pixel-by-pixel basis through electrical drive control in response to the color of the incident light, based on exposed image information. Therefore, the light of each color that is modulated by the PLZT optical shutter array
7
is made to strike the recording medium by the rod lens array
9
in accordance with a timing sequence, thereby exposing the recording medium. At the same time, the recording medium moves in the secondary scanning direction Y (the direction perpendicular to the shutter array line direction X) relative to the PLZT color print head. In this way, a two-dimensional color image is recorded on the recording medium.
The PLZT color print head can print images at a print speed of one inch per second. However, to make it compatible with faster printers, the print speed of the print head must be increased. In order to do this, the alternating of the exposure colors must be speeded up by increasing the speed of rotation of
Minolta Co. , Ltd.
O'Shea Sandra
Sidley Austin Brown & Wood LLP
Zeade Bertrand
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