Abstract: The invention provides a projector having a light source, a display device to modulate light emitted from the light source, a lens device to project light emitted from the light source and modulated by the display device, wherein the lens device comprises a diaphragm mechanism, an image signal intensity detector to detect image signals input into the display device and to evaluate an intensity of the signals, a diaphragm mechanism drive control to drive the diaphragm mechanism so as to reduce the size of an aperture of the diaphragm mechanism when the image signal intensity detector ascertains that the intensity of the image signal is lower than a given level, and an image signal controller to increase the intensity of the image signal when the image signal intensity detector ascertains that the intensity of the image signal is lower than a given level.

Abstract: The invention provides a projector having a light source, a display device to modulate light emitted from the light source, a lens device to project light emitted from said light source via said display device, wherein said lens device has a diaphragm mechanism formed having an aperture, an ambient light illuminance detector to measure illuminance of ambient light, a projected image illuminance detector to measure illuminance of an image projected on the screen, an illuminance comparator to compare an illuminance detected by said ambient light illuminance detector and an illuminance detected by said projected image illuminance detector, and a diaphragm mechanism/image signal controler to control an intensity of image signals input into the display device and to control a size of an opening of the aperture of the diaphragm mechanism in accordance with a result of comparison by the illuminance comparator.

Abstract: The invention provides a lens device and projector in which light passing through liquid crystal panels is projected on a screen using the lens device. The lens device includes a diaphragm mechanism. A telecentric optical system for the display device is provided between the diaphragm mechanism and the liquid crystal panels. An aperture of the diaphragm mechanism is positioned at a location where primary rays that are emitted from the liquid crystal panels parallel to an optical axis intersect with the optical axis. Contrast characteristics of the liquid crystal panels vary depending on angles and directions of incidence of rays of light. The aperture of the diaphragm mechanism is formed in a substantially triangular shape in accordance with the shape of the contrast characteristics.

Abstract: To ensure both telecentricity and a sufficiently high contrast, and to facilitate the improvement of performance characteristics of a projector that uses liquid crystal panels.

Abstract: A projection display apparatus including an optical system having a lens for projecting a light emitted from a light source onto a screen and a cooler having an exhaust fan for cooling the light source is disclosed. The projection display apparatus includes a light receiver for receiving a light reflected from the screen, a first controller for controlling a quantity of the light emitted from the light source in accordance with an intensity of the light received by the light receiver, a heat sensor for sensing a heat given off from the light source, and a second controller for controlling a volume of air exhausted by the exhaust fan per unit time in accordance with a quantity of the heat sensed by the heat sensor.

Abstract: A projecter having a lamp, a lamp box containing the lamp, an outlet fan for discharging air from the lamp box, an optical system member which receives a light beam from the lamp and outputs an image light, an optical system box containing the optical system member, and an inlet fan for blowing outside air into the optical system box. The projector also has a first ventilating duct that directs the outside air blown in by the inlet fan into the lamp box.

Abstract: A light source apparatus has a luminescent tube, a reflecting mirror, a securing member and bonding material as a holding member disposed to block a part of a small opening of the reflecting mirror and holding the luminescent tube in the reflecting mirror, a transparent protection plate for blocking the large opening of the reflecting mirror, a ventilator for sucking air inside the reflecting mirror through the small opening and sending out the air through an outlet, and a housing for combining the reflecting mirror and the ventilator; and the reflecting mirror includes an air inlet disposed closer to the large opening than a center position of the luminescent tube.

Abstract: A video projector includes a cabinet having a scren mounting opening, a projector unit housed within the cabinet, and a generally rectangular composite projection screen secured to the cabinet to cover the screen mounting opening and a picture is projected from the projector unit onto the screen. The composite screen includes a laminar structure of a Fresnel lens plate and a lenticular lens plate. The lenticular lens plate has a height smaller than the height of the Fresnel lens plate and an upper edge connected by adhesive tape with an upper edge of the Fresnel lens plate such than a lower edge of the lenticular lens plate opposite to the upper edge is offset in an upward direction relative to a lower edge of the Fresnel lens plate to provide a margin extending along the width of the composite screen for accommodating the expansion of the lenticular lens plate.