Optics: image projectors – Lens support – Lens position adjustable
Reexamination Certificate
2001-10-23
2002-11-26
Dowling, William (Department: 2851)
Optics: image projectors
Lens support
Lens position adjustable
C353S098000
Reexamination Certificate
active
06485147
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a projection system capable of automatic focus adjustment. In particular, the invention relates to a projection system that automatically adjusts the projection focus by an evaluation function applied in projective image analysis.
2. Description of the Related Art
Traditionally, projection systems have relied on the user's visual assessment to adjust the focus of the projected image.
FIG. 1
shows a schematic diagram of the automatic focal adjustment device of a typical LCD projection system. In a Japan Patent Laying Open Hei No. 11-119185, as shown in
FIG. 1
, three LCD display devices
1400
r,
1400
g
and
1400
b
respectively produce red, green and blue images through a cross prism
4000
to form a color image. The color image passes through a semitransparent reflective device
3000
to form images on the screen s through a projective lens
1000
. The image on the screen s is reflected on an optical receiving device
500
through the semitransparent reflective device
3000
. Further, a signal generation device
1600
, a control device
9000
, an operation device
8000
and a focus adjustment/control device
6000
are used to analyze and compare each image on the focal position of the projective lens
1000
. However, as such, a semitransparent reflective device is required, which increases the distance from the projective lens
1000
to the three LCD display devices. As a result, the rear focal length of a projective lens and design difficulty for the projective lens are increased concurrently.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a projection system that automatically adjusts the focus of an optical projection device by an evaluation function applied in projective image analysis. The projective system includes a total reflection element, an image reader, an analysis system and a server device. The image reader reads the projective image guided by the optical projection device and the total reflection element and outputs a read signal. The analysis system analyzes the read image by an evaluation function and determines the clearest image on the projective plane so as to output an adjustment signal. The server device automatically performs the focal adjustment to the optical projection device based on the adjustment signal.
The invention has the advantage that the projective system can automatically adjust the focus of the optical projection device in any projective distance to produce the clearest image.
The invention is characterized in that the analysis system uses a modulation transfer function (MTF) analysis to have the clearest projective image.
REFERENCES:
patent: 3813155 (1974-05-01), Szymber et al.
patent: 5400093 (1995-03-01), Timmers
patent: 5479225 (1995-12-01), Kuga
patent: 5537168 (1996-07-01), Kitagishi et al.
patent: 11-119185 (1999-04-01), None
Benq Corporation
Dowling William
Ladas & Parry
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