Optics: image projectors – Lens support – Lens position adjustable
Reexamination Certificate
2002-04-01
2003-04-15
Dowling, William (Department: 2851)
Optics: image projectors
Lens support
Lens position adjustable
C353S100000
Reexamination Certificate
active
06547402
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a projection lens shifting mechanism of a projector apparatus for projecting a light beam from a light source such as a lamp onto a screen by way of a projection lens to make an enlarged projection of an image rendered on a display device such as a liquid crystal panel
Conventionally, a liquid crystal projector apparatus, in which a liquid crystal display panel is provided, has been employed to make an enlarged projection of an image in a personal computer display or video device. The liquid crystal projector generates a light signal of a picture by transmitting or screening the light projected from the lamp light source, in response to the image of the liquid crystal display panel.
The liquid crystal display panel is made up of liquid crystal elements arranged in a two-dimensional plane on a liquid crystal panel, and a projection lens serves the enlarged projection of the image to present a picture on a screen. The projection lens is normally equipped with a cam and screw mechanism whereby the lens-barrel can be rotated to shift a part of a plurality of lenses in the direction of the optical axis to adjust focus and zoom.
The position of the projection lens in a liquid crystal projector is typically fixed with respect to the liquid crystal panel, and the position and size of the picture projected onto the screen is therefore determined by the relative positions of the screen and projector. In order to project a picture of the proper size onto the proper position of the screen, the projector must be adjusted to the proper relative position with respect to the screen, and considerable time and effort are therefore required to position the projector.
In many liquid crystal projectors, the projection lens is shifted in advance to a fixed height above the liquid crystal panel and then secured. Thus, by projecting the light beam from the fixed height shifted upward with respect to the liquid crystal panel, a picture can be projected onto a screen at a high position to facilitate viewing regardless of the height of the stand on which the projector is set up. When it is desired to shift the position of the picture on the screen still higher, the projection direction is shifted upward by means of a height adjustment mechanism attached to the forward legs of the projector. In such a case, however, since the angle between the liquid crystal panel surface and the screen surface changes, the picture that should be projected, for example, as a square is distorted to a trapezoid. To eliminate this distortion, the inclination of the screen must be adjusted according to the inclination of the liquid crystal panel, and it was therefore necessary to provide a screen having a tilting mechanism.
To solve this problem, some high-function liquid crystal projectors are provided with a mechanism for electric-powered shifting of the projection lens by means of, for example, a motor. However, such devices necessitate a complex mechanism to enable vertical and horizontal movement while accurately holding the heavy projection lens. This requirement results in an increase in cost. The following examples have been proposed in the prior art as liquid crystal projectors provided with mechanisms for moving the projection lens.
A liquid crystal projector is disclosed in Japanese Utility Model Laid-open No. 21246/1993 (hereinbelow referred to as the first example of the prior art) in which a projection lens is supported by a pantograph mechanism constituted by four control links and in which rotating of a dial drives the pantograph mechanism to enable vertical movement of the projection lens.
A method of adjusting the alignment of a liquid crystal panel in a liquid crystal projector is disclosed in Japanese Patent Laid-open No. 107434/1993 (hereinbelow referred to as the second example of the prior art). According to this method, a liquid crystal panel holding part is constituted by a bracket secured to a base plate and a liquid crystal attachment plate secured to this bracket by means of securing screws. A jig is used for shifting the liquid crystal attachment plate with respect to the bracket, and after adjusting the position of the liquid crystal attachment plate by means of adjustment screws of the jig, the bracket and liquid crystal attachment plate are secured by the securing screws. The jig is then removed.
A projection display device in which the projection lens can be moved vertically by means of a projection-lens moving mechanism is disclosed in Japanese Patent Laid-open No. 196888/1993 (hereinbelow referred to as the third example of the prior art). This projection-lens moving mechanism is provided with a lead screw that is rotatably borne by a housing and a projection-lens holding member having a threaded hole that engages with this lead screw such that the projection-lens holding member moves up and down with rotation of this lead screw. This lead screw is provided with a knob for rotating the screw. The projection lens holding member, being accommodated inside the housing, can both hold the projection lens and translate while being guided vertically by the rotation of the lead screw. The projection lens holding member is thus movable vertically by rotating the knob.
A liquid crystal projector is disclosed in Japanese Patent Laid-open No. 249409/1993 (hereinbelow referred to as the fourth example of the prior art) in which a projection lens is installed in a projector body so as to allow horizontal and vertical movement of the projection lens by magnetic force or by leaf springs and in which the user applies force manually against the projection lens to move the projection lens.
A liquid crystal projector is disclosed in Japanese Patent Laid-open No. 138377/1997 (hereinbelow referred to as the fifth example of the prior art) in which light from a light source is collimated by a first condenser lens to a substantially parallel light beam and incident on a liquid crystal panel, this light beam is optically modulated in response to a video signal that is externally supplied to the liquid crystal panel, and the modulated light beam emitted from the liquid crystal panel is then condensed by a second condenser lens to enter a projection lens to present a picture on a screen. In this liquid crystal projector, when the position of projection on the screen is to be moved up and down, a motor provided for shifting the projection lens is activated and a link mechanism that supports the projection lens is moved in a vertical direction.
A liquid crystal projector is disclosed in Japanese Patent Laid-open No. 258565/1999 (hereinbelow referred to as the sixth example of the prior art) in which pictures from two projectors are superimposed on each other on a screen in order to brighten the picture projected on the screen. In the lens moving mechanism for shifting the position of projection on the screen, a lead screw rod is rotatably attached to the housing of the liquid crystal projector and a nut to be engaged with the lead screw is secured to the lens-barrel of the projection lens. When the lead screw rod is rotated by operating a control member provided on the side surface of the housing, the nut moves to cause the lens-barrel to move in a vertical direction. This lens moving mechanism is basically equivalent to the previously described third example of the prior art, but differs from the third example of the prior art in that the lead screw rod tilts forward. The reason for this is to compensate for change in the size of the projected picture that is brought about by a change in the distance between the liquid crystal panel and projection lens caused by the vertical movement of the projection lens.
Thus, although a number of liquid crystal projectors provided with projection lens moving mechanisms have been proposed in the prior art, the projection lens moving mechanism disclosed in the first example of the prior art has the problem of large-scale structure resulting from the use of a pantograph mechanism. The second example of the prior art is a m
Dowling William
NEC Viewtechnology Ltd.
Sughrue & Mion, PLLC
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