1. Field of Invention
The present invention relates to a projector including optical modulation devices for modulating a plurality of colored light beams in accordance with image data, a prism for combining the modulated luminous fluxes modulated by the optical modulation devices, and a projection lens for enlarging and projecting the light beams combined by the prism.
2. Description of Related Art
Hitherto, projectors have been used which include three optical modulation devices for modulating a plurality of colored light beams in accordance with image data, a crossed dichroic prism for combining the light beams modulated by the three optical modulation devices, and a projection lens for enlarging and projecting the light beams combined by the prism.
The projectors are widely used for multimedia presentations at public meetings, such as conferences, academic meetings, and exhibitions. The projector is brought to the conference room, as needed, and is moved to another place after the use. Therefore, a progessive reduction in size of the projectors has occurred.
Recently, projectors have been reduced in size and have been provided with a structure in which three optical modulation devices are fixed to the side faces of a crossed dichroic prism via a fixing member, so as to simplify the structure. Hereinafter, the structure is called a xe2x80x9cPOPxe2x80x9d structure (panel on prism structure).
In the POP structure, optical modulation devices supported by supporting frames are fixed by soldering or via an adhesive to the faces of a prism at a predetermined distance from the faces of the prism.
In the POP structure, gaps are likely to be produced in the fixed parts because the optical modulation devices and the prism are fixed to each other at a predetermined distance from each other. In this case, other than the light beams emitted by the prism, the projection lens receives light beams leaking toward the projection lens from the gaps between the prism and the optical modulation devices. There is a problem in that the quality of images projected on a screen deteriorates when leakage from the light beams is applied to the projection lens.
Accordingly, an object of the present invention is to provide a projector in which the quality of projected images does not deteriorate when the size of the projector is reduced.
According to the present invention, a projector comprises a plurality of optical modulation devices for modulating a plurality of colored light beams in accordance with image data; a prism for combining the light beams modulated by the optical modulation devices; and a projection lens for enlarging and projecting the light beams combined by the prism. The plurality of optical modulation devices are mounted on the prism at side faces thereof at a predetermined distance from the side faces of the prism. A light shielding member is provided for shielding light which leaks from gaps between the optical modulation devices and the side faces of the prism toward the projection lens side.
According to the present invention, the light shielding member shields leakage light from the gaps between the optical modulation device and the prism toward the projection lens side, whereby only the luminous fluxes emitted by the prism are applied to the projection lens. Therefore, the quality of projected images does not deteriorate when reducing the size.
The projector preferably further comprises an outer casing for receiving the optical modulation devices, the prism, and the projection lens; an air inlet formed in the external face of the outer casing, for introducing air from the outside to the inside of the outer casing as cooling air; and a cooling fan for introducing the cooling air through the air inlet and cooling the optical modulation devices. The light shielding member may be provided with a flow-regulating part for introducing the cooling air from the cooling fan toward the optical modulation devices.
With this arrangement, cooling air from the cooling fan can be applied easily in large volume to the optical modulation devices which are not heat resistant, by guiding the cooling air by the flow-regulating part, thereby cooling the optical modulation devices effectively.
The plurality of optical modulation devices are preferably three optical-modulation devices for modulating red, green, and blue colored luminous fluxes, respectively. The flow-regulating part is preferably disposed in the vicinity of the optical modulation device for modulating the blue colored luminous flux.
The blue luminous flux contains large energy. Therefore, a modulation device for modulating the blue luminous flux is likely to heat up excessively. By disposing the flow-regulating part in the vicinity of the optical modulation device for modulating the blue luminous flux, the cooling air from the cooling fan guided by the flow-regulating part can be applied in large volume to the optical modulation device for modulating the blue luminous flux, thereby suppressing rapid rise in the temperature of the optical modulation device, whereby the cooling efficiency of the optical modulation devices can be further improved.
The light shielding member is preferably provided with an opening for leading therethrough light beams emitted from the prism and a positioning part for determining the relative position between the opening and a light emission surface of the prism. When an opening is formed in the light shielding member through which the light beams are to be emitted by the prism, and the opening is not disposed at a predetermined position, there is a risk of deteriorating the quality of projected images by cutting away a part of the luminous flux emitted by the prism. In contrasts, such a problem can be avoided when the light shielding member is provided with a positioning part. The positioning part is configured with a first positioning section which comes into contact with the upper or lower face of the prism and a second positioning section which comes into contact with side faces of the prism, whereby the horizontal and vertical position of the opening of the light shielding member can be determined easily, thereby facilitating the operation of mounting the light shielding member.
The light shielding member is preferably made of a metal, and is preferably provided with a temperature-determining unit for determining the temperature of the optical modulation devices. Since the light shielding member made of a metal is thermally conductive, the temperature-determining unit can determine the temperature close to the actual temperature of the optical modulation devices. Therefore, the temperature of the optical modulation devices can be determined with high accuracy compared with a case in which the temperature of cooling air in the vicinity of the optical modulation devices is determined, whereby the temperature rise in the optical modulation devices can be suppressed easily and positively.
The temperature-determining unit is preferably formed so as to output determined signals to a control board for controlling the cooling fan. By the temperature-determining unit thus formed, when the temperature of the light shielding member is high, that is, when the temperature of the optical modulation devices is determined to be higher than a given temperature, the revolution of the cooling fan can be controlled to increase so as to rapidly cool the optical modulation devices. When the temperature of the light shielding member is low, that is, when the temperature of the optical modulation devices is determined to be lower than a given temperature, the revolution of the cooling fan can be controlled to decrease so as to gradually cool the optical modulation devices.
The light shielding member is preferably provided with a cut-and-raised tab formed by cutting and raising a part of the light shielding member.
With this arrangement, the light shielding member can be easily mounted on and removed from the prism by moving the light shielding member by holding the cut-and-raised tab. The operator can more easily mount and remove the light shielding member on and from the prism without touching the incident surfaces and the light emission surface of the prism.
The opening is preferably formed in a shielding part disposed in contact with the light emission surface of the prism, the shielding part is preferably fixed to the light emission surface of the prism, and the positioning part is preferably fixed to a surface of the prism other than the light emission surface thereof. The shielding part is preferably bonded to the light emission surface of the prism along edges of the opening. Double-sided tapes, liquid adhesive, or the like may be used as an adhesive.
With this arrangement, the operation of mounting the shielding member on the prism can be simplified. By using double-sided tapes, the bonding operation can be made simple, and since it is not necessary to be concerned about leakage or the like of an adhesive, the operation of mounting the light shielding member on the prism can be made more simple.
An antireflection film for suppressing reflection of light beams is preferably provided at at least one section of the light shielding member. When the light shielding member is provided with an antireflection film, a risk can be avoided, in which light beams shielded by the light shielding member are reflected thereby and are applied to optical elements, such as the projection lens, thereby affecting the images.
The projector preferably further comprises an optical-component casing for receiving optical components. The prism may be mounted in the optical-component casing via a prism-supporting member for supporting the prism, and the light shielding member may be disposed between the prism and the optical-component casing so as to cover the lower part of the side faces of the prism on which the optical modulation device is mounted.
With this arrangement, leakage light from the lower part of the prism can be shielded, whereby only the luminous fluxes emitted by the prism are applied to the projection lens. Therefore, the quality of projected images does not deteriorate when the size is reduced.