Projector that automatically adjusts the projection parameters

Details Projector that automatically adjusts the projection parameters Projector that automatically adjusts the projection parameters

1999-06-24

2002-07-23

Dowling, William (Department: 2851)

Optics: image projectors

Miscellaneous

C353S101000, C348S745000

Reexamination Certificate

active

06422704

ABSTRACT:

This application is based on Application Ser. Nos. H10-180130, H10-198485 and H10-198486 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projector that automatically adjusts projection parameters such as zoom ratio, focus, and convergence.
2. Description of Related Art
In the field of projectors, one example of a technology that automatically adjusts projection parameters such as convergence and focus is disclosed in U.S. Pat. No. 5,231,481. In this technology, a photographic device, such as a video camera, photographs an image that a projector projects onto a screen to obtain image data. An information processing apparatus such as a microcomputer then analyzes this image data to detect adjustment errors in the projection parameters and performs suitable corrections to the settings of the projector. The following describes the operation of this technology when automatically adjusting the focus of the projection lens.
FIG. 1
is a block diagram showing the construction of the projector
900
in this related art. As shown in
FIG. 1
, the projector
900
includes a projection lens
901
, dichroic mirrors
902
,
903
,
906
, and
907
, mirrors
904
and
905
, light valves
908
,
909
, and
910
, a light source
911
, an A/D convertor
915
, a microcomputer
916
, a test pattern generating circuit
929
, and a projection lens focus adjusting mechanism
933
. The image that this projector
900
projects onto the screen
980
is photographed by the video camera
990
. The image photographed by the video camera
990
is subjected to A/D (analog to digital) conversion by the A/D convertor
915
and is then inputted into the microcomputer
916
as image data.
The microcomputer
916
analyzes the inputted image data and, based on the results of this analysis, controls the projection lens focus adjusting mechanism
933
to have the focus of the projection lens
901
adjusted. Note that while the optical paths from each of the light valves
908
,
909
, and
910
to the projection lens
901
appear to have different lengths in the example illustrated in
FIG. 1
, such paths can be easily adjusted using conventional technologies, such as through the use of additional lenses (not illustrated). As described in the embodiments of the invention, this problem can also be addressed by changing the positioning of the dichroic mirrors or other components.
As described above, the projector
900
of the above technology requires the further use of a video camera
990
to photograph the image projected onto the screen
980
. This leads to the problems of a rise in the cost of the technology and of the user having to perform the difficult task of correctly orienting the video camera
990
toward the screen
980
.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a projector that can automatically adjust the projection parameters with a simple operation while suppressing the cost of the overall equipment.
This primary object can be realized by a projector that projects images onto a screen by passing light from a light source through a light valve and a projection lens, the projector comprising: reflected light detecting means for detecting light that has been reflected off the screen and back through the light valve; and projection parameter adjusting means for adjusting a projection parameter based on a detection result of the reflected light detecting means.
With the stated construction, light reflected back off a screen is detected and used to adjust the projection parameters, so that there is no need to use expensive equipment, such as a video camera, for photographing an image projected onto the screen. Adjustments to the positioning of the video camera or other such additional equipment are also unnecessary, thereby making automatic adjustment possible with a simple operation.


REFERENCES:
patent: 5276523 (1994-01-01), Kurematsu et al.
patent: 5400093 (1995-03-01), Timmers
patent: 5479225 (1995-12-01), Kuga
patent: 5197014 (1993-08-01), None

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