Title: Projector executing keystone correction
Abstract: An automatic keystone correction which enables even an inexperienced user to easily obtain an image corrected using the keystone distortion during a tilted projection. The projector detects varying of its elevation angle by using an elevation detecting module. When the angle stops varying, the projector determines that the elevation adjustment by the user ends, and executes auto keystone correction of the input image according to the elevation angle.
Patent Number: 6,974,217 Issued on 12/13/2005 to Kimura, et al.
| Inventors:
|
Kimura; Keishi (Matsumoto, JP);
Koyama; Takaaki (Matsumoto, JP)
|
| Assignee:
|
Seiko Epson Corporation (Tokyo, JP)
|
| Appl. No.:
|
465879 |
| Filed:
|
June 20, 2003 |
Foreign Application Priority Data
| Mar 20, 2002[JP] | 2002-79313 |
| Jun 20, 2002[JP] | 2002-180265 |
| Jun 05, 2003[JP] | 2003-160374 |
| Current U.S. Class: |
353/69; 353/70 |
| Intern'l Class: |
G03B 021/00; G03B 021/14 |
| Field of Search: |
348/745,806
353/69,70,121
|
References Cited [Referenced By]
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| 5355187 | Oct., 1994 | Ogino et al.
| |
| 5537168 | Jul., 1996 | Kitagishi et al.
| |
| 5788355 | Aug., 1998 | Na.
| |
| 6362573 | Mar., 2002 | Helbing et al.
| |
| 6481855 | Nov., 2002 | Oehler.
| |
| 6520647 | Feb., 2003 | Raskar.
| |
| 6686973 | Feb., 2004 | Su.
| |
| 2003/0068094 | Apr., 2003 | Kimura et al.
| |
| 2004/0036844 | Feb., 2004 | Wood et al.
| |
| Foreign Patent Documents |
| A 7-270748 | Oct., 1995 | JP.
| |
| A 8-9306 | Jan., 1996 | JP.
| |
| A 10-1115/33 | Apr., 1998 | JP.
| |
| 11-282438 | Oct., 1999 | JP.
| |
| 2000/-196978 | Jul., 2000 | JP.
| |
| 2000/-241874 | Aug., 2000 | JP.
| |
| A 2001-69433 | Mar., 2001 | JP.
| |
| 2001/-186538 | Jul., 2001 | JP.
| |
| 2001/-339671 | Dec., 2001 | JP.
| |
| A 2002-112148 | Apr., 2002 | JP.
| |
| 2002/-268142 | Sep., 2002 | JP.
| |
Primary Examiner: Nguyen; Judy
Assistant Examiner: Sever; Andrew
Attorney, Agent or Firm: Oliff & Berridge, PLC
Parent Case Text
This is a Continuation-In-Part of application Ser. No. 10/386,534 filed Mar.
13, 2003.
Claims
1. A projector performing a keystone correction of a projected image during a
tilted projection, comprising:
a trigger determination module configured to determine a predetermined trigger
state included in normal procedure to project an image except for an instruction
to perform a keystone correction;
an elevation detecting module configured to detect an elevation angle of the
projector; and
a keystone correction module configured to perform a keystone correction based
on the elevation angle in response to the trigger state;
a light source lamp; and
an light-on detecting module configured to detect a light-on state of the light
source lamp, the trigger state including the light-on state.
2. The projector in accordance with claim 1, wherein the elevation angle is input
into the keystone correction module after a predetermined time has passed.
3. A method for correcting keystone distortion of a projected image during a
tilted projection of a projector, comprising:
determining a predetermined trigger state included in normal procedure to project
an image except for an instruction to perform a keystone correction;
detecting an elevation angle of the projector; and
performing a keystone correction based on the elevation angle in response to
the trigger state; and
detecting a light-on state of a light source lamp of the projector, the trigger
state including the light-on state.
4. The method in accordance with claim 3, wherein the elevation angle is input
after a predetermined time has passed.
5. A method for controlling a projector, which includes an optical unit that
modulates a light flux illuminated from a light source according to image data
so as to form an optical image and performs an extended projection of the optical
image, and an elevation adjustment mechanism to adjust the tilted state of the
optical unit, comprising:
an adjust-completion-determining-step determining a completion of an operation
for the elevation adjustment mechanism;
a tilted state measuring step measuring a tilted state of the optical unit in
response to a determination of the completion of the operation; and
a projection correction step executing a distortion correction of the optical
image according to a measured tilted state; and
a time measuring step measuring an elapsed time from the start of an adjustment
by the elevation adjustment mechanism, the correction is executed in a case where
the elapsed time exceeds a predetermined threshold in the projection correction
step.
6. A computer program to control a projector, the computer program stored in
a computer readable recording medium, the projector including an optical unit that
modulates a light flux illuminated from a light source according to an image data
so as to form an optical image and performs an extended projection of the optical
image, and an elevation adjustment mechanism to adjust a tilted state of the optical
unit, the computer program, comprising:
an adjust-completion-determining-code determining completion of an operation
for the elevation adjustment mechanism;
a tilted state measuring code measuring the tilted state of the optical unit
in response to a determination of the completion of the operation;
a projection correction code executing a distortion correction of the optical
image according to the measured tilted state; and
a time measuring code measuring an elapsed time from a start of an adjustment
by the elevation adjustment mechanism, the projection correction code executing
the correction in a case where the elapsed time exceeds a predetermined threshold.
7. A projector performing a keystone correction of a projected image during a
tilted projection, comprising:
a trigger determination module configured to determine a predetermined trigger
state included in normal procedure to project an image except for an instruction
to perform a keystone correction;
an elevation detecting module configured to detect an elevation angle of the
projector;
a keystone correction module configured to perform a keystone correction based
on the elevation angle in response to the trigger state; and
an elevation adjustment mechanism configured to adjust the elevation angle of
the projector, the trigger state including an operation of the elevation adjustment
mechanism,
the elevation angle being inputted into the keystone correction module after
a predetermined time has passed.
8. A projector performing a keystone correction of a projected image during a
tilted projection, comprising:
a trigger determination module configured to determine a predetermined trigger
state included in normal procedure to project an image except for an instruction
to perform a keystone correction;
an elevation detecting module configured to detect an elevation angle of the
projector; and
a keystone correction module configured to perform a keystone correction based
on the elevation angle in response to the trigger state, the trigger state including
a variation of the elevation angle of the projector,
the elevation angle being inputted into the keystone correction module after
a predetermined time has passed.
9. A method for correcting keystone distortion of a projected image during a
tilted projection of a projector, comprising:
determining a predetermined trigger state included in normal procedure to project
an image except for an instruction to perform a keystone correction;
detecting an elevation angle of the projector; and
performing a keystone correction based on the elevation angle in response to
the trigger state, the trigger state including an operation of an elevation adjustment
mechanism, which is equipped with the projector to adjust the elevation angle,
the elevation angle being inputted after a predetermined time has passed.
10. A method for correcting keystone distortion of a projected image during a
tilted projection of a projector, comprising:
determining a predetermined trigger state included in normal procedure to project
an image except for an instruction to perform a keystone correction;
detecting an elevation angle of the projector; and
performing a keystone correction based on the elevation angle in response to
the trigger state, the trigger state including a variation of the elevation angle,
the elevation angle being inputted after a predetermined time has passed.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a projector which performs a keystone correction of
an image during tilted projection.
2. Description of Related Art
Projectors project images onto screens. In some cases, projectors are
set at a low position and project images onto screens that are set at a relatively
higher position, which is called "tilted projections". During the tilted projections,
images projected on the screens are distorted to trapezoidal shapes from rectangular
shapes due to an elevation angle in the tilted projection. Such a distortion is
called "a keystone distortion".
Related art projectors may include a special button and menu to correct the
keystone distortion. A user can adjust the keystone distortion manually with this
button and menu. Some related art projectors automatically detect the elevation
angle and correct the keystone distortion in response to an instruction from the user.
SUMMARY OF THE INVENTION
However, for inexperienced users, it is hard to recognize the function of
causing the projector to perform the auto keystone correction. Moreover, even if
the user knows the function, it often takes the user a long time to understand
actual operations for the correction when the type of the projector is unfamiliar
for the user.
This invention addresses or solves the above-mentioned problem by providing
a technique to make a projector execute an auto keystone correction easily, even
when an inexperienced user operates it.
This invention provides a projector that performs a keystone correction of a
projected image during a tilted projection. The projector includes a trigger determination
module, an elevation detecting module, and a keystone correction module. The trigger
determination module determines a predetermined trigger state that is included
in normal procedure to project an image except for an instruction to perform a
keystone correction. The elevation detecting module detects an elevation angle
of the projector. The keystone correction module performs a keystone correction
based on the elevation angle in response to the trigger state. For instance, an
angle sensor or a G-sensor is applicable for the detection of the elevation angle.
The projector of this invention can automatically execute the keystone correction.
Because the trigger state is not a specified operation to instruct the correction
but one of states included in the normal procedure, any user can cause the projector
to perform the correction without any knowledge about the correction. As a result
of this, for example, a presentation with the projector can be started with no
loss of time.
Various modifications may be made to the trigger state. As a first exemplary
embodiment, the projector further includes an operation determination module that
is configured to determine a user operation which is required to projecting an
image. The trigger state may include the user operation.
The user operation may include an operation for a power supply. In this case,
the keystone correction can be executed in response to the power supply.
When the projector includes an elevation adjustment mechanism, such as stay
adjusters, configured to adjust the elevation angle of the projector, the user
operation may include an operation of the elevation adjustment mechanism. In this
case, the keystone correction can be executed in response to the elevation angle adjustment.
Additionally, the user operation may include various operations, such
as focus adjustment, zooming, connecting an image source, and switching to another
image source. The image source may include various apparatus, such as DVD players,
personal computers, and VCRs, which can be the input source of the image to be
projected by the projector. As is mentioned above, the user operation may include
various operations required for the user to project images with the projector.
As a second exemplary embodiment, the projector of this invention may further
include a light source lamp and an light-on detecting module that is configured
to detect a light-on state of the light source lamp. In this case, the trigger
state may include the light-on state.
In the second exemplary embodiment, the keystone correction can be executed in
response to the light-on of the light source lamp. The accuracy of keystone correction
may be affected by noises due to the high voltage of the light source lamp. Therefore,
it is preferable to execute the correction after the light source lamp lights and
a predetermined time passes.
As a third exemplary embodiment, the trigger state may include a variation of
the elevation angle. In this embodiment, the keystone correction can be executed
when the elevation angle of the projector is changed without any specified operation
for the correction. In the third embodiment, the trigger state may include a state
that the elevation angle stops varying.
In this case, for example, the state can be detected when a varying rate of the
elevation angle decreases below a predetermined value after exceeding over the
value once. This detection can reduce a measurement error of the elevation angle
due to environmental factors, such as thermal drift of the sensor, thereby stabilizing
the correction.
As a fourth exemplary embodiment, the projector of this invention may include
an optical unit that modulates light flux illuminated from a light source according
to image data so as to form an optical image and performs an extended projection
of the optical image, and an elevation adjustment mechanism configured to adjust
the tilted state of the optical unit. This invention determines completion of an
operation for the elevation adjustment mechanism and measures a tilted state of
the optical unit in response to the completion. Thus, the completion of the operation
can be a trigger for executing the correction which makes it possible to execute
the distortion correction after setting the projector without delay. The distortion
correction includes the keystone correction.
In the fourth exemplary embodiment, the projector may perform a function of a
forced distortion correction that is executed in response to a specified user operation
regardless of operations to the elevation adjustment mechanism, in addition to
the automatic distortion correction described above. The forced distortion correction
enables the user to instruct re-execution of the distortion correction in a case
where the automatic distortion correction is not appropriately executed. The forced
distortion correction may be instructed in various ways including the following:
by a switch for the specified purpose and by specified operations to a power supply
switch or focus ring.
The distortion correction can be executed in various manners including the following:
1) calculating a distortion correction value of the optical image according to
the tilted state and executing the distortion correction based on the distortion
correction value; and 2) executing the distortion correction directly using the
tilted state instead of converting it into the distortion correction value.
In the fourth exemplary embodiment, the distortion correction may be executed
in a case where an elapsed time from the start of the adjustment by the elevation
adjustment mechanism exceeds a predetermined threshold. The elapsed time can be
measured by using a timer that starts measuring time in response to the start of
the adjustment of adjusting the elevation adjustment mechanism. The elapsed time
is rather short in a case where the user erroneously operates the elevation adjustment
mechanism, so this exemplary embodiment reduces or prevents unintended distortion
correction in response to such erroneous operations. The threshold may also be
arbitrarily set. For example, it can be set based on a required time to make a
significant change of the tilted state of the projector by operating the elevation
adjustment mechanism.
In the fourth exemplary embodiment where the elevation adjustment mechanism is
power-driven, the adjust-completion-determining-module may determine the completion
of the operation in a case where power-driving of the elevation adjustment mechanism
is stopped. Various actuators, such as a stepping motor, can be applicable as the
power source to drive the elevation adjustment mechanism. In one example where
the elevation adjustment mechanism includes a variable length stay configured to
stay the projector and an adjust switch configured to control the extending and
contracting of the stay, the adjust-completion-determining-module may determine
the completion of the operation in a case where the adjust switch is turned off.
In another example where the elevation adjustment mechanism includes a plurality
of stay mechanisms configured to stay the projector and individually extend and
contract, the adjust-completion-determining-module may determine the completion
of the operation in either a case where all operations for the plurality of the
stay mechanisms are completed or a case where a part of the operations is completed.
The former case reduces or prevents unintended distortion corrections when only
a part of the operations is completed.
In one example of the former case where the projector includes a package installing
an optical unit therein, a plurality of stays extending from the package and a
plurality of stay adjusting switches to control extending and contracting of the
stays may determine the completion of the operation in a case where all of the
stay adjusting switches turns off.
In the fourth exemplary embodiment, the tilted state may be measured in various
ways. For example, a gyro sensor to measure the tilted angle or an G-sensor to
measure acceleration are applicable. In the latter case, for example, the G-sensor,
which is mounted on a board horizontally fixed in the projector, can determine
the tilted angle by measuring the component of the gravity varying according to
the tilted angle. To ensure the accuracy of the measurement, these sensors are
preferably mounted on a rear half of the projector to the opposite side of a supporting
point for tilting the projector, that is, the distance between the sensor and the
supporting point is larger than the distance between the sensor and the opposite
side. Instead of using these sensors, the tilted state may be calculated according
to the state of the elevation adjustment mechanism. For example, in the elevation
adjustment mechanism using the stays, the tilted angle can be calculated according
to the extended length of the stays.
The application of the present invention is not restricted to the projector.
There are, however, many other diverse applications, such as a method for correcting
keystone distortion of a projected image during a tilted projection of a projector,
a computer program that causes a computer to perform the keystone correction, and
a computer readable recording medium in which the computer program is recorded,
for example. Typical examples of the recording medium include: flexible disks,
CD-ROMs, magnet-optic discs, IC cards, ROM cartridges, punched cards, prints with
barcodes or other codes printed thereon, internal storage devices (memories such
as a RAM and a ROM, for example) and external storage devices of the computer,
and a variety of other computer readable media, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic that shows the general construction of the projector used
for the following various exemplary embodiments;
FIG. 2 is a schematic that shows the relationship between the projected image
on the screen SC and the image formed on the LC light valve 17;
FIG. 3 is a schematic that shows the principle of detecting the elevation angle
of the projector 10;
FIG. 4 is a flowchart of an auto keystone correction process in the projector 10;
FIG. 5 is a graph showing varying the elevation angle of the projector 10; and
FIG. 6 is a flowchart of an auto keystone correction process of a second exemplary embodiment.
FIG. 7 is a top, front perspective view of the projector 1000 of the
fourth exemplary embodiment;
FIG. 8 is a bottom, rear perspective view of the projector 1000;
FIG. 9 is a perspective view of the projector 1000 with the upper case
100 removed;
FIG. 10 is a perspective view of the projector 1000 with the shield and
the control boards removed;
FIG. 11 is a schematic of the optical unit 400 of the projector 1000;
FIG. 12 is a perspective view of the optical device 440 of the projector 1000;
FIG. 13 is an exploded perspective view of the optical unit 400 of the
projector 1000;
FIG. 14 is a schematic that shows the function blocks of the control unit 700
of the projector 1000;
FIG. 15 is a flowchart of a keystone correction process in the projector 1000;
FIG. 16 is a schematic that shows the way to calculate a correction value of
the optical image formed by the projector 1000;
FIG. 17 is a flowchart of a keystone correction process of an exemplary modification
in the projector 1000;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Exemplary embodiments of the present invention are discussed below in the
following sequence:
- A. First Exemplary Embodiment
- (A1) General Construction of Projector
- (A2) Auto Keystone Correction Process
- B. Second Exemplary Embodiment
- C. Exemplary Modifications
- D. Third Exemplary Embodiment
- (D1) General Construction of Projector
- (D2) Detailed Construction of Optical Unit
- (D3) General Construction of Control Unit
- (D4) Keystone Correction
- (D5) Effects of Third Exemplary Embodiment
- (D6) Exemplary Modification of Third Exemplary Embodiment
- (D7) Other Exemplary Modifications of Third Exemplary Embodiment
A. First Exemplary Embodiment
(A1) General Construction of Projector
FIG. 1 is a schematic that shows the general construction of the projector used
for the following first and second exemplary embodiments. The projector
10
includes an image data input module
11, an elevation detecting module
13,
a keystone correction module
14, a manual adjusting module
15, a
light source
16, a LC (Liquid Crystal) light valve
17, and a projection
lens unit
18.
The image data input module
11 inputs image data from various image output
devices. FIG. 1 shows a DVD player
22 as an example of an image output device.
The image output devices may include VCRs and personal computers, for example.
Moreover, the image data may be delivered via a network.
The elevation detecting module
13 detects the elevation angle of the projector
10 by using G-sensor
21. The principle as to how to detect the elevation
angle is described later. The detected elevation angle is transmitted to the keystone
correction module
14.
The keystone correction module
14, provided by using a micro-computer
with CPU and memories, executes a keystone correction to the image data that is
transmitted from the image data input module
11. In this case, the degree
of the correction is adjusted according to the elevation angle that is transmitted
from the elevation detecting module
13. Moreover, the keystone correction
module
14 can perform the correction according to a correction instruction
by the user, which is transmitted from the manual adjusting module
15.
The manual adjusting module
15 includes a power supply switch, and a button
which allows the user to manually adjust the degree of the keystone correction.
The projector
10 is able not only to correct the image by the keystone correction
module
14 automatically, but also to perform a manual correction. Accordingly,
the user can make a fine adjustment to the image, for instance, after the automatic
correction by the keystone correction module
14. The manual adjusting module
15 may be installed in the projector
10, and may also be a remote
controller using infrared rays etc.
The light source
16 includes a light source lamp, and a polarization converting
device which converts the light from the light source lamp into linear polarized light.
The image that is corrected by the keystone correction module
14 is formed
on the LC light valve
17. The image that is transmitted from the image data
input module
11 can be directly formed thereon when such a correction is
not required.
The LC light valve
17 is illuminated by the light from the light source
16, and the image formed thereon is projected onto the screen SC through
the lenses included in the projection lens unit
18.
The projection lens unit
18 includes a zooming module
20 to scale
the projected image, and a focusing module
19 to adjust foci according to
the distance between the projector and the screen.
FIG. 2 is a schematic that shows the relationship between the projected image
on the screen SC and the image formed on the LC light valve
17. The grid
shows the image in FIG.
2. When a tilted projection is performed, the image
30 formed on the LC light valve
17 is projected as the image
31
on the screen SC with the trapezoidal shape. To correct such a trapezoid distortion
or a keystone distortion, the keystone correction module
14 corrects the
image
30 like image
32 according to the elevation angle of the projector
10, and sets a surrounding blank (hatching part in FIG. 2) to the black
area. This correction eliminates the distortion from the projected image
33
on the screen SC during the tilted projection.
FIG. 3 is a schematic that shows the principle of detecting the elevation angle
of the projector
10. FIG. 3 shows right side views of the projector
10,
the level floor H on which the projector
10 is placed, and the screen SC.
The level floor H is assumed to be horizontal. G-sensor
21 is installed
to detect the elevation angle of the projector
10 in this embodiment, as
mentioned above. MAS1370P of Mitsubishi Electric Corporation may be used as the
G-sensor
21, for example. G-sensor
21 is mounted in the projector
10 and detects the acceleration in the direction of the left side (rear
side of the projector
10) on the chain line shown in the upper part of FIG.
3. When the projector
10 is horizontally set on the level floor H
and no gravity works along the chain line, the acceleration output from the G-sensor
21 equals zero.
The lower part of FIG. 3 shows the projector
10 set diagonally by adjusting
the height of the length of the stay B. Projecting images on the screen SC in such
a state is called "a tilted projection". When the elevation angle is assumed to
be Ac, the acceleration element along the chain line equals "g×sin(Ae)" as
shown in FIG.
3. G-sensor
21 outputs the voltage corresponding to
the acceleration element. In above-mentioned MAS1370P, the voltage of about 17
mV per the elevation angle of 1 degree (acceleration 0.167 m/s
2 (=9.8
m/s
2×0.017)) is output. Therefore, when the elevation angle is
10 degrees, the output of the sensor becomes about 170 mV (=10×17 mV), for
instance. The elevation detecting module
13 can detect the elevation angle
of the projector
10 based on the voltage output from the G-sensor
21
like this.
Other various detection devices and methods are applicable to detect the elevation
angle, and the invention is not restricted to the G-sensor used in this exemplary
embodiment. For instance, the elevation angle can be calculated based on the length
of the stay, and also detected with an angle sensor which uses a pendulum.
(A2) Auto Keystone Correction Process
FIG. 4 is a flowchart of an auto keystone correction process in the projector
10. This process is performed by the keystone correction module
14
and using the elevation detecting module
13. First, the keystone correction
module
14 detects the variation of the elevation angle by using the elevation
detecting module
13 (step S
110). The variation suggests that the
user starts setting of the projector
10 for a tilted projection.
FIG. 5 is a graph showing varying the elevation angle of the projector
10.
The abscissa axis shows the time passage, and the coordinate axis shows the elevation
angle. The elevation angle grows after the time "0" when the user turns on the
power supply of the projector and the time "t" when the adjustment of the elevation
angle of the projector begins. When the adjustment is ended at the time "t
2",
the elevation angle achieves a constant value. The chain line, labelled in FIG.
5 as "Actual", shows this series of variations of the elevation angle.
On the other hand, the dotted line, labelled in FIG. 5 as "Thermal Drift", shows
an increase in detected angle by thermal drift of the G-sensor
21. The temperature
rises up to about 75° C. in the projector with the time passage due to the
heat of the strong light source lamp. Therefore, the output value of the G-sensor
may increase by the influence of the heat like the dotted line of shown in FIG.
5, even when the elevation angle of the projector is actually
0. For instance,
the output error rises up to 2 degrees when the temperature is 75° C., in
above-mentioned MAS1370P.
This thermal drift causes the detected angle by the elevation detecting module
13 to rise like a solid line labelled in FIG. 5 as "Detected", which is
summation of the thermal drift and the actual angle.
The thermal drift increases gradually for a few minutes, while the adjustment
of the elevation angle by the user lasts a few seconds. Accordingly, in this exemplary
embodiment, when the time differentiation of the detected angle exceeds a prescribed
value, the keystone correction module
14 determines that as the start varying
of the elevation angle, so as to clearly distinguish the adjustment by the user
from the thermal drift.
Specifically, the start of the variation of the elevation angle can
be determined under the following condition: the elevation detecting module
13
detecting the elevation angle using the G-sensor
21 every 0.7 seconds, and
the difference between last detected angle and the angles detected eight times
in the past being three degrees or more. This condition performs an acute detection
of the start varying of the elevation angle, even when the thermal drift occurs
up to two degrees.
Referring back to FIG. 4, when no variation of the angle is detected at
step S
10, the keystone correction module
14 keeps observing the angle
variation by looping this step. In this way, the keystone correction module
14
can detect whether the tilted projection is applied or not by the user at anytime
while the projector
10 works.
Next, the keystone correction module
14 detects whether the detected
angle varies less than three degrees compared with the past detected angle (step
S
11). The process proceeds to the next step, when the variation is less
than three, and it can be assumed that the user has stopped installing the projector
10. Otherwise, the keystone correction module
14 keeps observing
the end of the installation by looping this step.
The keystone correction module
14 inputs the elevation angle from the
elevation detecting module
13 (step S
12), and executes the keystone
correction of the image according to the elevation angle (step S
13) when
the completion of the installation is detected, based on the two above-mentioned
steps. Thus, the projector
10 can automatically execute the keystone correction
of the image due to the tilted projection without a specified operation by the user.
The image may be corrected in real time simultaneously with the elevation angle
adjustment by the user, after varying of the angle is detected, while the distortion
is corrected after the installation ends in the above-mentioned process. This allows
the user to view the corrected image with no delay during the elevation angle adjustment.
B. Second Exemplary Embodiment
The trigger of auto keystone correction is not restricted to the variation of
the elevation angle applied in the exemplary embodiment. FIG. 6 is a flowchart
of an auto keystone correction process of the second exemplary embodiment.
First, the keystone correction module
14 detects the light source lamp
in the light source
16 lighting (step S
20). This detection can be
executed by detecting voltage being applied to the power supply line to the light
source lamp, for instance. Moreover, a photo-sensor mounted in an arbitrary location
that is illuminated by the light source lamp can be used to detect the lighting.
In the latter case where a photo-sensor is used the lighting should be detected
when the brightness of the light source lamp reaches a prescribed brightness.
The keystone correction module
14 keeps observing the light source lamp
by looping this step, in the case where no lighting is detected at step S
20.
The keystone correction module
14 inputs the elevation angle from the elevation
detecting module
13 (step S
21), and executes keystone correction
based on this angle, when the lighting is detected (step S
22). According
to this process, keystone correction can be executed in response to a trigger of
the lighting of the light source lamp.
It is preferable to input the elevation angle in above-mentioned step S
21
after the predetermined time has passed since the lighting was detected at step
S
20. That is because the noise due to the high voltage, generated by lighting
the light source lamp, affects the accuracy of the G-sensor
21.
The trigger is not restricted to the lighting applied in the second exemplary
embodiment, and instead various triggers can be used, such as the elevation angle
adjustment using the stay, and turning on the power supply, for example. In the
latter case, the above-mentioned step S
20 that is can be omitted. The operation
of the focusing module
19 or the zooming module
20 that is installed
in projection lens unit
18 can also be used as the trigger. Keystone distortion
is affected by projection distance or projected area, and it is preferable that
the amount of the adjustment of the focusing module
19 or the zooming module
20 is reflected in the correction at step S
22, thereby executing
the correction according to the projection distance and the projected area.
C. Exemplary Modifications
Various modifications can be made to the above first and second exemplary
embodiments. Even if the user horizontally sets up projector
10, the elevation
detecting module
13 occasionally detects a constant angle. This is an inevitable
problem that is caused by the difference of the quality in the manufacturing process
of the G-sensor
21 and secular change of sensitivity. Therefore, the elevation
detecting module
13 may store the constant angle in advance in the memory
in the projector, and determine the angle by subtracting the constant angle from
the detected angle. This detection can achieve more accurate correction. The constant
angle may be stored in the factory, and also by users after shipping. The manual
adjusting module
15 or some specified menus can be used by the user to store
the constant angle.
The keystone correction at step S
13 or step S
22 may be prohibited
when the elevation angle that is input at step S
21 or step S
12 is
negative, while the keystone correction executes at every elevation angle in the
above-mentioned embodiments. That is because, in that case, the projector is assumed
to hang from a ceiling in an upset state by a user who is highly skilled in operating
the projector and for whom a manual adjustment button would be more intuitive and
easy to understand.
The keystone correction may also be prohibited when right-left reversing projection
of the projector is applied, because the user is assumed to be highly skilled.
Moreover, the keystone correction may also be prohibited when the initial
detected angle input by the keystone correction module
14 at step S
13
and step S
22 is very small (for instance, range of +4 degree and -4 degree).
That is because such an angle is possibly a detection error due to secular change
of the G-sensor
21 or thermal drift and the projector is possibly set in
a horizontal state at the end of the installation.
Additionally, during the distortion correction at step S
22 in
step S
13, the amount of the correction or the elevation angle that is input
by the keystone correction module
14 may be projected onto the screen SC.
This could inform the user of a standard of the elevation angle when the user sets
up the projector afterwards. Moreover, it is preferable to inform the user by a
beep sound or same other alerting method when the automatic distortion correction
function works.
D. Third Exemplary Embodiment
(D1) General Construction of Projector
FIG. 7 is a top, front perspective view of the projector
1000. Hereinafter
each direction, such as upper, lower, left, right, front, rear, is used to explain
the construction of the apparatus. The projector
1000 includes an exterior
package or a chassis that is produced by injection molding of synthetic resins
in the shape like a rectangular box. Major parts of the projector
1000 are
built in the exterior package. The exterior package is assembled by combining the
upper package
100 and the lower package
200. By way of example, the
left side surfaces
105,
205 of the upper package
100 and the
lower package
200 are combined together with other surfaces of the exterior
package to define a continuous left side of the exterior package.
Speaker perforations
120 for phonetic output and an operation panel
110 are installed in a front area of the top surface
103 of the upper
package
100. Pressing each function button of the operation panel
110
causes a control signal corresponding to the function to be transmitted to internal
control boards. The function may include the following: cooling control to cool
down the projector
1000; changing the settings to protect images; controlling
the volume of the phonetic output; and switching over input sources of image data.
An interface panel
500 is installed facing to an opening
301 in
the left side surface
105. The interface panel
500 mounts connectors
511,
521 to connect peripheral devices and such. These connectors
511,
521 are respectively connected to a main board and an interface
board internally installed in the exterior package.
Installed in the left side surface
205 is a stay adjusting switch
220 that adjusts the tilted state of the projector
1000. The stay
adjusting switch
220 is connected to the internal control boards and transmits
control signals thereto according to pressing/stop-pressing. The movement of projector
1000 according to the operation of the stay adjusting switch
220
is described later.
Exhaust slots
310, with a safety cover
311 attached thereto,
are respectively formed in the right portion of the front surfaces
101,
201 of the upper package
100 and the lower package
200. In
the left portion of the front surfaces
101,
201, close to the operation
panel
110, a circular opening
302 is formed. A projection lens
460
is arranged in the exterior package with one end exposed outward from the opening
302. Around the exposed portion of the projection lens
460 is mounted
a focus knob
461 to manually adjust the focus.
FIG. 8 is a bottom, rear perspective view of the projector
1000. In right
portion of rear surfaces
102,
202 of the upper package
100
and the lower package
200, a rectangular opening
303 is formed to
receive an inlet connector
304 to which electric power cable is connected.
In right middle portion of the lower package
200, a rectangular opening
330 is formed to receive a detachable lamp cover
331. A light source
lamp is mounted in the opening
330 inside the projector
1000 so as
to make it easy to change the light source lamp by detaching the lamp cover
331.
In a portion near the left rear surface of the bottom surface
204, an
air
inlet
322 to let cold air into the projector
1000 is formed in the
exterior package and an air inlet cover
321 is attached thereto. In the
air inlet cover
321, openings
320 are formed facing the air inlet
322. In the openings
320, an air filter is attached to reduce or
prevent dust from coming into the projector
1000.
A rear stay
221 is mounted in the rear middle portion of the bottom surface
204. Two front stays
222 are respectively mounted in the right and
left corner of the front portion of the bottom surface
204. The projector
1000 is supported with three supporting point, that is, the rear stay
221
and the two front stays
222.
Each front stay
222 is linked to a stepping motor. Pressing the respective
stay adjusting switch
220, as described above, causes the stepping motor
to drive the front stay
222, thereby extending and contracting the front
stay
222. The stepping motor first drives in a direction that extends the
stay during pressing the stay adjusting switch
220, and then drives in the
reverse direction to contract the stay after the length of the stay reaches a maximum
extension. The stepping motor again drives in a reverse direction to extend the
stay after the length of the stay reaches a minimum contraction. In this embodiment,
the stay adjusting switch
220 is used both to extend and contract the stay.
However, various configuration are applicable as follows: mounting respective switches
for extending and contracting the stay; and applying a switch that can accept both
instructions of extending and contracting according to operation manners, such
as a seesaw type switch and a lever.
Stopping the press of the stay adjusting switch
220 turns the switch
for the stepping motor off and makes the front stay
222 stop extending and
contracting. Respective adjustments of the front stays
222 can adjust the
tilted state and the rotated state of the projector
1000, thereby adjusting
the position of projected images. Extending the front stay
222 performs
a tilted projection in which the normal axis of the screen and the light axis of
the light flux projected from the projection lens
460 are not parallel.
According to these adjustment functions, the front stays
222 and the stay
adjusting switches
220 can be called an elevation adjustment mechanism.
In the front middle portion of the bottom surface
204, a concave portion
340 is formed to put a remote controller therein. A cover
341 slidable
in a front-to-rear direction is attached to the concave portion
340.
FIG. 9 is a perspective view of projector
1000 with the upper case
100
removed. In the exterior package, an electric power unit
600 is arranged
in a right-to-left direction along the rear surface of the exterior package.
The electric power unit
600 includes an electric power source and a lamp
driving circuit or a ballast. The electric power source supplies electric power,
which is received through the electric power cable connected to the inlet connector,
to the lamp driving circuit and the control boards. The lamp driving circuit supplies
the electric power received from the electric power source to the light source lamp.
The front surface, rear surface, and top surface of the electric power source
and the lamp driving circuit are covered with a shield
601 that is made
of metal such as aluminum. The shield
601 has functions as follows: guiding
cold air as a duct and reducing or preventing electromagnetic noise generated in
the electric power source and the lamp driving circuit from leaving.
The control boards are arranged under the metal shield
520. In this embodiment,
a main board and an interface board is arranged as the control boards. The main
board, which mounts a CPU and the connector
511, is horizontally arranged
under the shield
520. The interface board, which mounts the connector
521,
is arranged under the main board along the left surface of the exterior package.
The main board performs various controls as follows: controlling the LC panels
of the optical unit
400 according to image data that is input through the
connectors
511,
521; performing a predetermined extending process
to audio data input from a peripheral device and output it from the speaker; controlling
the revolving speed and driving time period of the cooling fan; and executing the
keystone correction for the image projected onto the screen.
A gyro sensor is mounted on the main board close to the projection lens
460,
so that the gyro sensor can detect the tilted state in the front-to-rear direction
of the projector
1000 or an elevation angle that is required for the keystone
correction. Detail illustration of the gyro sensor is omitted. The gyro sensor
may also detect a tilted state in the right-to-left direction or a roll angle.
Various sensors besides the gyro sensor are applicable to detect the elevation
angle, such as various types of angle sensors using electromagnetic effect, variation
of resistance, and light. The elevation angle may be calculated according to the
extending length of the front stay
222.
FIG. 10 is a perspective view of projector
1000 with the shield
520
and the control boards removed. As illustrated in the figure, the optical unit
400, whose plan view is approximately "L" shape, is arranged in front of
the electric power unit
600. The main board described above is arranged
so as to touch with an upper edge
482 of an upper light guide
481
of the optical unit
400.
(D2) Detailed Construction of Optical Unit
FIG. 11 is a schematic of the optical unit
400 of projector
1000.
The optical unit
400 performs an extended projection of an optical image
that is formed by modulating the light flux illuminated from the light source
411
according to image data. The optical unit
400 includes an integrator illumination
optical unit
410, a color separation optical unit
420, a relay optical
unit
430, an optical device
440 and the projection lens
460.
The integrator illumination optical unit
410 uniformly illuminates the
image generation area of three LC panels
441R,
441G,
441B
corresponding to red light, green light, and blue light, respectively. The integrator
illumination optical unit
410 includes a light source
411, a first
lens array
412, a second lens array
413, a polarization converting
device
414 and an overlay lens
415. Hereinafter the LC panels
441R,
441G,
441B maybe generically called as LC panel
441.
The light source
411 includes a light source lamp
416 as a light
emitting source and a reflector
417, collimates radial light illuminated
from the light source lamp
416 and reflected by the reflector
417,
and emits the collimated light. A high pressure hydrargyrum lamp is applied to
the light source lamp
416, but a metal halide lamp and a halogen lamp are
also applicable. A paraboloid mirror is applied to the reflector
417, but
a combination of a concave lens for collimation and an ellipsoidal mirror are also applicable.
In the first lens array
412, small lenses, which are approximately rectangular
shape in a view along the light axis, are arranged in a matrix. Each small lens
divide the light flux illuminated from the light source lamp
416 into a
plurality of partial light flux. The shape of the small lenses is approximately
analogous to that of the image generation area of the LC panel
441. Accordingly,
in a case where the aspect ratio, which is a ratio of width to height, of the LC
panel
441 is 4:3, the small lenses have the same aspect ratio.
In the second lens array
413, as well as the first lens array
412,
the small lenses are arranged in a matrix. This second lens array
413 makes
each light flux, which is illuminated from the small lens of the first lens array
412, focus and produce an image on the LC panel
441 using the overlay
lens
415.
The polarization converting device
414 is arranged between the second
lens array
413 and the overlay lens
415. The polarization converting
device
414 converts the light transmitting from the second lens array
413
into a single kind of polarizing beam. Each partial light flux converted by the
polarization converting device
414 is overlaid onto the LC panel
441
by the overlay lens
415. While LC panels usually utilize one kind of polarizing
beam, the function of the polarization converting device
414 can enhance
the effectiveness of utilization of the light illuminated from the light source
as a mixture of various kind of polarizing beams by converting them into a single
kind of polarizing beam. A polarization converting device, e.g., disclosed in JP1996-304739A1
is applicable.
The color separation optical unit
420 includes two dichroic mirrors
421,
422 and a reflecting mirror
423, and divides partial light flux,
which is illuminated from the integrator illumination optical unit
410,
into three colors of light which are red (R), green (G), and blue (B).
The dichroic mirror
421 transmits red light and green light out of the
light, which is illuminated from the integrator illumination optical unit
410,
and reflects blue light. The reflected blue light is again reflected on the reflecting
mirror
423, goes through the field lens
418 and gets to the LC panel
441B for blue color.
The dichroic mirror
422 selectively reflects green light. Accordingly,
out of the light transmitted from the dichroic mirror
421, green light is
reflected by the dichroic mirror
422, goes through the field lens
418
and gets to the LC panel
441G for green color, while red light transmits
through the dichroic mirror
422, goes through the relay optical unit
430
and the field lens
418, and gets to the LC panel
441R for red color.
The field lens
418 makes each portion of the light flux, which is illuminated
from the second lens array
413, parallel to the center axis of the light
flux or chief ray as do the field lenses
418 that are arranged in the illuminated
sides of the other LC panels
441G,
441R.
The relay optical unit
430 guides the red light to the LC panel
441R
using the incident lens
431, the relay lens
433 and the reflecting
mirrors
432,
434. The relay optical unit
430 reduces divergence
loss of the light flux transmitting from the incident lens
431 to the field
lens
418. The reason why the relay optical unit
430 is applied for
red light is that the light path of the red light is maximum and the long light
path tends to cause the divergence loss. In other modifications, the relay optical
unit
430 may be applied to colors other than the red color, such as blue color.
The optical device
440 modulates the incident light flux according to
the image data and forms a color image, and includes the following: three incident
polarizing beam plates
442 into which each color light separated by the
color separation optical unit
420 is incident; the LC panels
441R,
441G,
441B as light modulation devices that are respectively arranged
behind the incident polarizing beam plates
442; three projecting polarizing
beam plates
443 that are respectively arranged behind the LC panels
441R,
441G,
441B; and a cross dichroic prism
444 as a color integrating
optical unit.
The LC panels
441R,
441G,
441B may apply, e.g., TFT-type
which uses polysilicon TFTs as switch devices.
The incident polarizing beam plates
442 transmits the polarizing beam
only in one direction out of each color light split by the color separation optical
unit
420 and absorbs other light flux. Various types are applicable as follows:
a polarizing beam membrane attached onto a substrate of sapphire glass; and a polarizing
beam membrane attached onto the field lens
418 instead of the substrate.
The projecting polarizing beam plates
443, as well as the incident polarizing
beam plates
442, transmits the polarizing beam only in one direction transmitted
from the LC panel
441 and absorbs other light flux. The projecting polarizing
beam plate
443 may be formed by a polarizing beam membrane attached to the
cross dichroic prism
444.
The incident polarizing beam plates
442 and the projecting polarizing
beam plates
443 are arranged so that respective polarizing beam axis cross
each other at right angles.
The cross dichroic prism
444 integrates optical images, which are formed
by modulating respective color lights illuminated from the projecting polarizing
beam plates
443, into a color image. In the cross dichroic prism
444,
dielectric multi-layer membranes respectively reflect red light and blue light
and are arranged in approximately an "X" shape along surfaces of four right angle
prisms in order to integrate three colors of light.
FIG. 12 is a perspective view of the optical device
440 of the projector
1000. The LC panel
441, the projecting polarizing beam plates
443
and the cross dichroic prism
444 described above are combined into a unit
called an optical device
440.
In the optical device
440, a fixing plate
447, which is made of
synthetic resin, is fixed onto the top surface of the cross dichroic prism
444.
Four arms
447A, in which circular holes
447B are formed, are extended
from the fixing plate
447.
In the incident surface of the cross dichroic prism
444, metallic support
plates
446 are attached to support the projecting polarizing beam plates
443. In the incident surface of each support plate
446, four pins
445 are attached, which are made of transparent plastic and support the
LC panels
441R,
441G,
441B. Between each support plate
446
and the LC panel <
