U.S. patent application number 09/730470 was filed with the patent office on 2001-08-23 for image projection system.
Invention is credited to Fujita, Manabu, Higurashi, Masaki, Kobayashi, Susumu, Komiya, Yasuhiro, Kosaka, Fujio, Kubota, Akihiro.
Application Number | 20010015793 09/730470 |
Document ID | / |
Family ID | 18410541 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015793 |
Kind Code |
A1 |
Fujita, Manabu ; et
al. |
August 23, 2001 |
Image projection system
Abstract
An image projection system includes projection means for
projecting an image on a transmission type screen from a rear
surface side of the screen, standard image information generating
means for generating standard image information of a standard
image, image capturing means for capturing an image on the rear
surface of the screen from an inside of a casing in which the
projection means is housed, the image capturing means capturing the
standard image projected onto the screen from the projection means,
which receives the standard image information from the standard
image information generating means, removing means for removing
influences of external light from the standard image projected from
the projection means onto the screen, correction value computing
means for computing a correction value on the basis of image
information of the standard image from which the influences of the
external light are removed by the removing means, correction value
storage means for storing the correction value information obtained
by the correction value computing means, and correction means for
correcting image information from a picture signal source by using
the correction value information stored in the correction value
storage means, and supplying the corrected image information to the
projection means.
Inventors: |
Fujita, Manabu; (Hino-shi,
JP) ; Komiya, Yasuhiro; (Hino-shi, JP) ;
Higurashi, Masaki; (Hino-shi, JP) ; Kosaka,
Fujio; (Hino-shi, JP) ; Kubota, Akihiro;
(Kokubunji-shi, JP) ; Kobayashi, Susumu;
(Sayama-shi, JP) |
Correspondence
Address: |
STRAUB & POKOTYLO
1 BETHANY ROAD, SUITE 83
BUILDING 6
HAZLET
NJ
07730
US
|
Family ID: |
18410541 |
Appl. No.: |
09/730470 |
Filed: |
December 5, 2000 |
Current U.S.
Class: |
353/74 ;
348/E9.027; 353/122 |
Current CPC
Class: |
H04N 9/3185 20130101;
G03B 21/00 20130101 |
Class at
Publication: |
353/74 ;
353/122 |
International
Class: |
G03B 021/22; G03B
021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 1999 |
JP |
11-350443 |
Claims
What is claimed is:
1. An image projection system comprising: projection means for
projecting an image on a transmission type screen from a rear
surface side of the screen; standard image information generating
means for generating standard image information of a standard
image; image capturing means for capturing an image on the rear
surface of the screen from an inside of a casing in which said
projection means is housed, said image capturing means capturing
the standard image projected onto the screen from said projection
means, which receives the standard image information from said
standard image information generating means; removing means for
removing influences of external light from the standard image
projected from said projection means onto the screen; correction
value computing means for computing a correction value on the basis
of image information of the standard image from which the
influences of the external light are removed by said removing
means; correction value storage means for storing the correction
value information obtained by said correction value computing
means; and correction means for correcting image information from a
picture signal source by using the correction value information
stored in said correction value storage means, and supplying the
corrected image information to said projection means.
2. A system according to claim 1, wherein said removing means has a
function of blocking the external light that reaches said image
capturing means through the screen.
3. A system according to claim 1, wherein said removing means has a
computing function of removing the influences of the external light
on the basis of image information obtained by capturing an image on
the screen by using said image capturing means while the standard
image is projected from said projection means onto the screen and
image information obtained by capturing an image on the screen by
using said image capturing means while the standard image is not
projected from said projection means onto the screen.
4. A system according to claim 1, further comprising means for
storing information based on image information obtained by
capturing an image on the screen from the rear surface side of the
screen while the standard image is projected from said projection
means onto the screen and image information obtained by capturing
an image on the screen from the front surface side of the screen
while the standard image is projected from said projection means
onto the screen.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 11-350443,
filed Dec. 9, 1999, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an image projection system
and, more particularly, to a calibration technique therefor.
[0003] A back projection type display apparatus has been available,
which uses a transmission type screen and projects an image from
the opposite surface side (rear surface side) to the observation
surface side (front surface side) onto the screen by using a
projector. As an advanced form of this system, a high-resolution
back projection type large-screen display apparatus is also
available, which projects a plurality of images from a plurality of
projectors onto a screen to display them as one image.
[0004] In this back projection type large-screen display apparatus,
since a plurality of projected images are joined into one image,
the following measures must be taken.
[0005] First, this apparatus requires measures to correct
distortion of each projected image. For this purpose, there have
been provided a method of adjusting the angle of each projector to
prevent each projected image from being distorted, and a method of
giving an original image distortion that cancels out distortion of
each projected image. Either of the methods requires means for
detecting information about distortion of each projected image. For
this purpose, a method using a digital camera and a method using a
sensor placed on the screen have been proposed.
[0006] Second, this apparatus requires measures to perform
correction associated with joining of projected images. For this
purpose, a technique of smoothly joining images by overlapping
adjacent images each other has been proposed. This technique,
however, requires a means for detecting information about
overlapping areas. For this purpose, a method of extracting a
correction value from an image captured by a digital camera has
been proposed.
[0007] Third, this apparatus requires measures to perform color
correction of each projected image. For this purpose, a method has
been proposed, in which a standard image is projected from a
projector onto a screen, the overall projected standard image is
captured by a digital camera, a correction value is extracted from
the captured standard image, and color correction is performed by
using this correction value.
[0008] Correction value acquiring operation (adjustment processing)
for performing the above series of correcting operations will be
referred to as calibration. This calibration is performed when the
image projection system is influenced by age-based change as well
as system installation.
[0009] The conventional image projection system is, however,
designed to execute calibration while placing the digital camera on
the front surface side of the screen. For this reason, in executing
calibration, a user must adjust the installation position, angle,
focus, and the like of the digital camera, imposing a heavy load on
the user in adjustment.
[0010] The digital camera may be fixed in advance on the rear
surface side of the screen to reduce the load of adjustment on the
user in executing calibration. In this arrangement, however, an
image on the screen is captured in a direction different from the
direction (front surface side) in which the user sees the image
projected on the screen, and hence it is difficult to perform
appropriate adjustment.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention has been made to solve the above
problems, and has as its object to provide a back projection type
image projection system which allows appropriate adjustment when
the digital camera used for calibration is installed on the rear
surface side of the screen.
[0012] According to the present invention, there is provided an
image projection system comprising projection means for projecting
an image on a transmission type screen from a rear surface side of
the screen, standard image information generating means for
generating standard image information of a standard image, image
capturing means for capturing an image on the rear surface of the
screen from an inside of a casing in which the projection means is
housed, the image capturing means capturing the standard image
projected onto the screen from the projection means, which receives
the standard image information from the standard image information
generating means, removing means for removing influences of
external light from the standard image projected from the
projection means onto the screen, correction value computing means
for computing a correction value on the basis of image information
of the standard image from which the influences of the external
light are removed by the removing means, correction value storage
means for storing the correction value information obtained by the
correction value computing means, and correction means for
correcting image information from a picture signal source by using
the correction value information stored in the correction value
storage means, and supplying the corrected image information to the
projection means.
[0013] In the above image projection system, the removing means may
have a function of blocking the external light that reaches the
image capturing means through the screen.
[0014] In the above image projection system, the removing means may
have a computing function of removing the influences of the
external light on the basis of image information obtained by
capturing an image on the screen by using the image capturing means
while the standard image is projected from the projection means
onto the screen and image information obtained by capturing an
image on the screen by using the image capturing means while the
standard image is not projected from the projection means onto the
screen.
[0015] The above image projection system may further comprise means
for storing information based on image information obtained by
capturing an image on the screen from the rear surface side of the
screen while the standard image is projected from the projection
means onto the screen and image information obtained by capturing
an image on the screen from the front surface side of the screen
while the standard image is projected from the projection means
onto the screen.
[0016] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0017] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0018] FIG. 1 is a view showing an example of the basic arrangement
of an image projection system according to the first embodiment of
the present invention;
[0019] FIG. 2 is a view showing an example of the basic arrangement
of an image projection system according to the second embodiment of
the present invention;
[0020] FIG. 3 is a view showing the functional arrangement of the
image projection system according to the second embodiment of the
present invention;
[0021] FIG. 4 is a flow chart showing the operation of the
arrangement in FIG. 3; and
[0022] FIG. 5 is a view showing an example of the basic arrangement
of an image projection system according to the third embodiment of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Embodiments of the present invention will be described below
with reference to the views of the accompanying drawing.
[0024] [First Embodiment]
[0025] (Arrangement of Apparatus)
[0026] FIG. 1 is a view showing an example of the basic arrangement
of an image projection system according to the first embodiment.
This image projection system is a back projection type image
projection system designed to project images from a plurality of
projectors from the rear surface side of a transmission type screen
onto the screen to display the images as one image. Similar image
projection systems are assumed in other embodiments unless
otherwise specified.
[0027] Projectors 102 are mounted in a casing 101 of a display
section 100. Although only one projector is shown in FIG. 1, a
plurality of projectors are arranged in practice. An image emerging
from this projector 102 is projected on a transmission type screen
105 via mirrors 103 and 104. A digital camera 106 is fixed at a
predetermined position in the casing 101 so as to capture an image
on the rear surface of the screen 105 from the inside of the casing
101.
[0028] The display section 100 has a shielding sheet
(light-shielding sheet) 107 that can cover the entire surface of
the screen 105. With this shielding sheet 107, external light
entering from the front surface side of the screen 105 into the
casing can be blocked. Since the shielding sheet 107 can be taken
up by a take-up roller 108, the sheet can cover the entire surface
of the screen 105, as needed. Since external light is blocked by
the casing 101 except for a portion where the screen 105 is
disposed, the influences of external light on the digital camera
106 can be removed by fully closing the shielding sheet 107. Note
that an openable shielding door may be used in place of the
shielding sheet to block external light. In addition, the shielding
sheet or door may be used for the protection of the screen or an
ornamental purpose while the display section is not used.
[0029] The output terminal of the digital camera 106 is connected
to a processing section 120 and can transmit the image data of a
captured image to the processing section 120 by a general serial
communication interface such as IEEE1394 or RS232C.
[0030] The image data output from the digital camera 106 is input
to a correction value computing circuit 121 of the processing
section 120 through the above serial communication interface. A
standard image generating circuit 122 is connected to this
correction value computing circuit 121. The correction value
computing circuit 121 performs predetermined correction value
computation processing on the basis of the image data from the
digital camera 106 and standard image data from the standard image
generating circuit 122. In performing adjustment processing
(calibration), the shielding sheet 107 is fully closed, and a
standard image is projected from the projector 102 onto the screen
105. A correction value corresponding to the difference between the
image data of the standard image captured by the digital camera
106, from which the influences of external light are removed, and
the standard image data from the standard image generating circuit
122 is obtained by the correction value computation processing.
[0031] A correction value table 123 is connected to the correction
value computing circuit 121. The correction value data obtained by
the correction value computing circuit 121 is stored in the
correction value table 123. This correction value table 123 can be
formed by using a rewritable non-volatile memory such as an
EEPROM.
[0032] A correction circuit 124 is connected to the correction
value table 123. A picture (moving picture) signal (picture data)
is input to the correction circuit 124, which corrects the picture
signal by using the correction value data stored in the correction
value table 123.
[0033] The picture signal output from the correction circuit 124 is
input to the projector 102 through a switch 140. If the switch 140
is placed on the standard image generating circuit 122 side, the
standard image data from the standard image generating circuit 122
is input to the projector 102.
[0034] (Operation)
[0035] The operation of this embodiment will be described next.
[0036] In adjustment processing (calibration), the switch 140 is
switched to the standard image generating circuit 122 side. In
addition, the shielding sheet 107 is pulled out from the take-up
roller 108 to cover the entire surface of the screen 105 to prevent
any external light from entering the casing 101.
[0037] Subsequently, a standard image is projected from the
projector 102 onto the screen 105, and the standard image projected
on the screen 105 is captured by the digital camera 106. The image
data of the captured standard image is transmitted to the
correction value computing circuit 121. The correction value
computing circuit 121 calculates a correction value from the image
data of the standard image sent from the digital camera 106, from
which the influences of external light are removed, and the
standard image data from the standard image generating circuit 122.
The obtained correction value data is stored in the correction
value table 123. The switch 140 is switched to the correction
circuit 124 side to terminate the adjustment processing.
[0038] When a picture (moving picture) is to be actually projected
on the screen, the shielding sheet 107 is taken up by the take-up
roller 108 to allow a user to see the picture from the front
surface side of the screen 105. In this state, a picture signal is
input to the correction circuit 124. The input picture signal is
corrected by using the correction value data stored in the
correction value table 123. An image based on the corrected picture
signal is then projected from the projector 102 onto the screen
105.
[0039] As described above, in this embodiment, since the influences
of external light are removed by using the shielding member such as
the shielding sheet, when a digital camera for capturing a standard
image is placed on the rear surface side of the screen to capture a
standard image, appropriate correction data can be obtained, and
appropriate adjustment can be performed.
[0040] [Second Embodiment]
[0041] (Arrangement of Apparatus)
[0042] FIG. 2 is a view showing an example of the basic arrangement
of an image projection system according to the second embodiment.
Note that the same reference numerals as in FIG. 1 denote the same
parts in FIG. 2.
[0043] The basic arrangement of a display section 100 is the same
as that of the first embodiment shown in FIG. 1. In the first
embodiment, however, the influences of external light are
mechanically removed by using the shielding sheet. In the second
embodiment, the influences of external light are removed by
processing in a processing section 120. For this purpose, a
projector 102 is turned on/off by a power switch 109 to perform
adjustment processing.
[0044] More specifically, the power switch 109 is turned off to
prohibit the projector 102 from projecting any image onto a screen
105 (while setting the light amount of the projector 102 to zero),
and the screen 105 is image-captured by a digital camera 106.
Alternatively, the power switch 109 is turned on to make the
projector 102 project a standard image onto the screen 105, and the
screen 105 is image-captured by the digital camera 106. Note that a
relay or the like can be used as the power switch 109, which can be
electrically controlled.
[0045] With regard to the processing section 120 and a switch 140
as well, the basic arrangement of a correction value computing
circuit 121, standard image generating circuit 122, correction
value table 123, and correction circuit 124 is the same as that in
the first embodiment shown in FIG. 1. In the second embodiment,
however, the influences of external light are removed by processing
in the processing section 120, and hence the processing section 120
includes a bank switching circuit 125, frame memory 126, and
external light removing circuit 127.
[0046] Image data output from the digital camera 106 is input to
the bank switching circuit 125. The bank switching circuit 125
switches the storage locations of the frame memory 126 with respect
to two image data output from the digital camera 106 in accordance
with the ON and OFF states of the power switch 109. The frame
memory 126 is connected to the external light removing circuit 127.
The external light removing circuit 127 performs a computation for
removing the influences of external light by using the two image
data stored in the frame memory 126.
[0047] (Operation)
[0048] The operation of this embodiment will be described next.
[0049] In adjustment processing (calibration), first of all, the
power switch 109 is turned off to set the light amount of the
projector 102 to zero and prohibit the projector 102 from
projecting any image onto the screen 105. In this state, the screen
105 is image-captured by the digital camera 106 from the rear
surface side. The image data of the captured image is stored in one
of the banks of the frame memory 126 through the bank switching
circuit 125. In this manner, image data in which only external
light components are influenced can be obtained.
[0050] The power switch 109 is then turned on to supply standard
image data from the standard image generating circuit 122 to the
projector 102 through the switch 140 and project a standard image
from the projector 102 onto the screen 105. In this state, the
screen 105 is image-captured by the digital camera 106 from the
rear surface side. The image data of the captured standard image is
stored in the other bank of the frame memory 126 through the bank
switching circuit 125. In this manner, the image data of the
standard image in which external light components are influenced
can be obtained.
[0051] Subsequently, the external light removing circuit 127
performs arithmetic processing by using the two image data stored
in the two banks of the frame memory 126 to obtain the image data
of a standard image from which the influences of external light
components are removed. Both the two image data stored in the two
banks of the frame memory 126 contain external light components.
For this reason, by using arithmetic processing using the two image
data, the image data of a standard image from which the influences
of external light components are removed can be obtained.
[0052] The image data of the standard image obtained by the
external light removing circuit 127, from which the influences of
external light are removed, is sent to the correction value
computing circuit 121. The correction value computing circuit 121
calculates a correction value from the image data of the standard
image from the external light removing circuit 127, from which the
influences of external light are removed, and the standard image
data from the standard image generating circuit 122. The obtained
correction value data is stored in the correction value table 123.
In addition, the switch 140 is switched to the correction circuit
124 side to terminate the adjustment processing.
[0053] When a picture is to be actually projected onto the screen,
a picture signal is input to the correction circuit 124. The input
picture signal is corrected by using the correction value data
stored in the correction value table 123, and an image based on the
corrected picture signal is projected from the projector 102 onto
the screen 105.
[0054] In the above case, in adjustment processing, the power
switch 109 is turned on and off, and the screen 105 is
image-captured once in each of the ON and OFF states. However, the
screen 105 may be image-captured a plurality of number of times in
each of the ON and OFF states, and weighted mean processing may be
performed to improve the precision.
[0055] As described above, in this embodiment, since the influences
of external light are removed by the external light removing
circuit, when a standard image is to be captured by arranging a
digital camera for standard image capturing operation on the rear
surface side of the screen, appropriate correction data can be
acquired, and appropriate adjustment can be performed.
[0056] (Functional Arrangement and Flow Chart)
[0057] FIG. 3 is a view showing the functional arrangement of the
image projection system according to the second embodiment. FIG. 4
is a flow chart showing the operation of the arrangement in FIG. 3.
A description will be made with reference to FIGS. 3 and 4.
[0058] In adjustment processing, a light source switch section 201
is turned off to set the light amount of an image projection
section 202 to zero to prohibit the image projection section 202
from projecting any image onto a transmission type display section
203 (step S11). Subsequently, the transmission type display section
203 is image-captured by an image capturing section 204 from the
rear surface side (step S12). The image data of the captured image
is stored in a first storage section 206 through a storage area
switching section 205 (step S13).
[0059] A signal switching section 207 is then switched to the
standard image generating section 208 side (step S14). The light
source switch section 201 is turned on to cause the light source of
the image projection section 202 to emit light, thereby projecting
a standard image on the transmission type display section 203 (step
S15). The transmission type display section 203 is then
image-captured by the image capturing section 204 from the rear
surface side (step S16). The image data of the captured image is
stored in a second storage section 209 (step S17).
[0060] A computation for removing the influences of external light
is performed by an external light removing section 210 using the
image data stored in the first storage section 206 and second
storage section 209, and the computation result is transferred onto
a correction value computing section 21:L (step S18).
[0061] Subsequently, the correction value computing section 211
calculate a correction value from the image data of the standard
image from the external light removing section 210, from which the
influences of external light are removed, and the standard image
data from the standard image generating section 208. The obtained
correction value is stored in a correction value storage section
212 (step S19).
[0062] Lastly, the signal switching section 207 is switched to the
correcting section 213 side (step S20). With this operation, when a
picture is to be actually projected on the transmission type
display section 203, a signal from a picture signal source 214 is
corrected by the correcting section 213, and an image based on the
corrected picture signal is projected from the image projection
section 202 onto the transmission type display section 203.
[0063] [Third Embodiment]
[0064] (Arrangement of Apparatus)
[0065] FIG. 5 is a view showing an example of the basic arrangement
of an image projection system according to the third embodiment. In
addition to the arrangement of the second embodiment in FIG. 2, the
third embodiment includes new constituent elements. The same
reference numerals as in FIG. 2 denote the same parts as in FIG.
5.
[0066] The basic arrangements of a display section 100, processing
section 120, and switch 140 are the same as those in the second
embodiment shown in FIG. 2. In the third embodiment, the processing
section 120 incorporates a flash memory 128 as a non-volatile
memory.
[0067] The flash memory 128 is used to correct the difference
between an image seen from the rear surface side of a screen 105
and an image seen from the front surface side (observation surface
side). When an image is projected from a projector 102 onto the
screen 105, the image seen from the rear surface side of the screen
105 differ in image characteristics from the image seen from the
front surface side. For this reason, prior to shipment, correction
data is generated and stored in the flash memory 128 in
advance.
[0068] An inspection unit 160 generates correction data and writes
it in the flash memory 128. This inspection unit 160 is comprised
of frame memories 161 and 162, difference data generating circuit
163, and flash memory writer 164.
[0069] The frame memory 161 stores the image data obtained by
capturing a standard image from the rear surface side of the screen
105 using the digital camera 106. The frame memory 162 stores the
image data obtained by capturing a standard image from the front
surface side of the screen 105 using a digital camera 170. The
difference data generating circuit 163 is connected to the frame
memories 161 and 162. The difference data generating circuit 163
computes the difference between the image data stored in the frame
memories 161 and 162. The flash memory writer 164 is connected to
the difference data generating circuit 163. The flash memory writer
164 writes the difference data obtained by the difference data
generating circuit 163 in the flash memory 128.
[0070] (Operation)
[0071] The operation of this embodiment will be described next.
[0072] At the time of shipment, correction data (difference data)
is written in the flash memory 128. First of all, a standard image
is projected from the projector 102 onto the screen 105 in a place
with no influences of external light, e.g., a dark room, and
standard images are captured by the digital cameras 106 and 170
from the rear surface side and front surface side of the screen
105, respectively. The obtained standard image data are
respectively stored in the frame memories 161 and 162.
Subsequently, the difference data generating circuit 163 generates
difference data from these standard image data, and the flash
memory writer 164 writes the difference data in the flash memory
128. The flash memory 128 in which the difference data is written
is mounted in the processing section 120.
[0073] The basic operation of the factory-shipped image projection
system is the same as that in the second embodiment. Note, however,
that since difference data is stored in the flash memory 128, the
difference data stored in the flash memory 128 is also referred to
when the external light removing circuit 127 performs arithmetic
processing in adjustment processing.
[0074] In the above case, the flash memory writer 164 in the
inspection unit 160 writes difference data in the flash memory 128.
However, the processing section 120 may have the function of
writing data in the flash memory 128. In this case, the difference
data obtained by the inspection unit 160 is transmitted to the
processing section 120 and written in the flash memory 128 mounted
in the processing section 120.
[0075] As described above, according to this embodiment, standard
images are captured from the rear surface side and front surface
side of the screen, and the difference data between the respective
standard images is stored in the flash memory in advance. This
makes it possible to correct the difference in image
characteristics between the images on the rear and front surface
sides and perform more appropriate adjustment.
[0076] As described above, according to the present invention, when
the image capturing means for capturing a standard image is placed
on the rear surface side of the screen to capture a standard image,
appropriate correction data can be obtained by removing the
influences of external light. Hence, appropriate adjustment can be
made.
[0077] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *