Optical: systems and elements – Lens – With light limiting or controlling means
Reexamination Certificate
2002-10-10
2004-04-20
Spector, David N. (Department: 2873)
Optical: systems and elements
Lens
With light limiting or controlling means
C359S739000
Reexamination Certificate
active
06724546
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light converging optical system in which rays of light planned to be incident on a reflecting optical-spatial modulator element are converged for the purpose of forming an image from the converged rays. Also, the present invention relates to an image displaying apparatus in which rays of light converged in the light converging optical system are incident on the reflecting optical-spatial modulator element to modulate the rays of light and to display an image reproduced from the modulated light. Also, the present invention relates to a projection image displaying apparatus, such as a digital light processing (DLP™) projector, in which a large number of micro-minors disposed in a reflecting optical-spatial modulator element in a two-dimensional matrix are respectively switched from an “on” state (or an “off” state) to an “off” state (or the “on” state) to modulate rays of light incident on the reflecting optical-spatial modulator element and to display an image reproduced from the modulated light.
2. Description of Related Art
A digital micro-mirror device (DMD™, hereinafter, simply called DMD) is, for example, used for an image displaying apparatus having a projection type screen. The DMD is formed of a reflection type semiconductor device and functions as a reflection type optical-spatial modulator element. An optical signal is intensity-modulated in the DMD by spatially changing the intensity of the light signal according to digital image information. The DMD used for the image displaying apparatus differs from a transmission type liquid crystal which receives light on a rear surface from a light converging optical system and outputs an intensity-modulated optical signal from a front plane to a projection type optical system. In the DMD used for the image displaying apparatus, a light converging optical system and a projection type optical system are disposed on a side of a reflecting surface of the DMD to form a reflecting optical system. On the reflecting surface of the DMD, a large number of micro-mirrors respectively having a size of 16 square &mgr; m are disposed in a two-dimensional matrix shape at pitches (or intervals) of 17 &mgr;m. The number of micro-mirrors is equal to the number of pixels forming an image plane of a screen and is larger than hundreds of thousands. Each micro-mirror corresponds to one pixel. Therefore, when light radiated from a lamp light source is received as an optical signal on the reflecting surface of the DMD through a converging lens, the intensity of each optical signal is changed in the corresponding micro-mirror according to digital image information to obtain an intensity-modulated optical signal. The intensity-modulated optical signal is output from the reflecting surface of the DMD as an image information signal according to a time on-off control.
FIG. 37
is a partially enlarged schematic view of a reflecting surface of the DMD.
FIG. 38
is an explanatory view of an operation of an inclination control performed for a micro-mirror.
In FIG.
37
and
FIG. 38
,
101
indicates a reflecting surface of the DMD.
102
indicates each of a plurality of square shaped micro mirrors disposed on the reflecting surface
101
of the DMD. Ar denotes a rotation axis of each micro-mirror. The inclination of the micro mirror
102
on the rotation axis Ar is controlled. The rotation axis Ar is placed on one diagonal line of the micro mirror
102
. When a principal ray of a light flux is incident on the micro mirror
102
, an incident direction of the principal ray projected on the reflecting surface
101
is parallel to the other diagonal line of the micro mirror
102
also, the incident direction of the principal ray is set to make an angle of 20 degrees to a normal n0 of the reflecting surface
101
.
A binary control of on-off is performed for each micro-mirror
102
according to a control voltage based on digital image information stored in a memory, and the micro-mirror
102
is inclined on the rotation axis Ar. The inclination angle of each micro-mirror
102
is set to +10 degrees or −10 degrees, and a reflection direction of a light flux incident on the micro-mirror
102
is changed from a direction corresponding to an “on” state (or “off” state) to a direction corresponding to an “off” state (or “on” state). An operation of the inclination control performed for each micro-mirror
102
will be described below.
In
FIG. 38
, the reflecting surface
101
of the micro mirrors
102
is placed on the plane of horizontal.
102
a
indicates one micro-mirror inclined by an inclination angle of +10 degrees to the reflecting surface
101
. That is, the micro-mirror
102
a
is set to an “on” state.
102
b
indicates a micro-mirror inclined by an inclination angle of −10 degrees to the reflecting surface
101
. That is, the micro-mirror
102
a
is set to an “off” state. Therefore, each micro-mirror
102
make an angle of +10 degrees or −10 degrees to the reflecting surface
101
as the micro-mirror
102
a
or
102
b
. The micro-mirrors
102
a
and
102
b
are inclined on the rotation axis Ar. In this embodiment, the inclination on the rotation axis Ar in the clockwise direction is indicated by a positive inclination angle, and the inclination on the rotation axis Ar in the counterclockwise direction is indicated by a negative inclination angle.
103
indicates an incident principal ray of a converged incident light flux. The incident principal ray
103
radiated from a light converging optical system (not shown) is incident on the micro-mirror
102
a
or
102
b
.
104
a
indicates an outgoing principal ray of an outgoing light flux. The incident principal ray
103
reflected on the micro-mirror
102
a
goes out from the micro-mirror
102
a
as the outgoing principal ray
104
a
.
104
b
indicates an outgoing principal ray of another outgoing light flux. The incident principal ray
103
reflected on the micro-mirror
102
b
goes out from the micro-mirror
102
b
as the outgoing principal ray
104
b
.
105
indicates a screen.
105
a
indicates each of a plurality of pixels of the screen
105
. The outgoing principal ray
104
a
reflected on the micro-mirror
102
a
is received in one pixel
105
a
of the screen
105
.
106
indicates a projection lens of a projecting optical system. The projection lens
106
is placed between the reflecting surface
101
of the DMD and the screen
105
, and the outgoing principal ray
104
a
transmitted through the projection lens
106
is projected on one pixel
105
a
of the screen
5
.
The incident principal ray
103
makes an angle of 20 degrees to the normal n0 of the reflecting surface
101
and is incident on the micro-mirror
102
a
or the micro-mirror
102
b
. In cases where it is intended to project light on one pixel
105
a
of the screen
105
, the inclination angle of one micro-mirror
102
corresponding to the pixel
105
a
is controlled to +10 degrees according to a control voltage. In this case, the incident principal ray
103
makes an angle of 10 degrees to a normal nA of the micro-mirror
102
a
and is incident on the micro-mirror
102
a
. Therefore, the incident principal ray
103
is reflected toward the direction of the normal n0 of the reflecting surface
101
as the outgoing principal ray
104
a
according to the law of reflection, the outgoing principal ray
104
a
passes through the projection lens
106
, the outgoing principal ray
104
a
is received in the pixel
105
a
of the screen
5
, and the pixel
105
a
is brightened (or set to “on” state).
In contrast, in cases where it is intended not to project light on one pixel
105
a
of the screen
105
, the inclination angle of one micro-mirror
102
corresponding to the pixel
105
a
is controlled to −10 degrees according to another control voltage. In this case, the incident principal ray
103
makes an angle of 30 degrees to a normal nB of the micro-mirror
102
b
and is incident on the micro-mirror
102
b
. Therefor
Goto Yoshiyuki
Kawano Hiroyuki
Nishimae Jun-ichi
Okamoto Tatsuki
Sasagawa Tomohiro
Mitsubishi Denki & Kabushiki Kaisha
Spector David N.
LandOfFree
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