1. Field of the Invention
The present invention relates to a projector for projecting an image onto a screen, and more particularly, to a projector having an improved structure for cooling an optical system thereof.
2. Description of the Related Art
A projector is a device generally including a light source and an optical system projecting and enlarging an image onto a screen, and is divided into two types, a CRT (Cathode Ray Tube) type and an LCD (Liquid Crystal Display) type.
The CRT-type projector (hereinafter referred to as a “CRT projector”) comprises a CRT assembly projecting an image beam, a mirror reflecting the projected beam, and a screen on which the reflected beam is displayed as a picture.
The LCD-type projector (hereinafter referred to as an “LCD projector”) comprises an LCD instead of the CRT assembly, wherein the image beam is adjusted in gradation by a liquid crystal and then projected and enlarged.
Such an LCD-type projector is divided into a single panel type and a triple panel type according to the number of LCD panels, and is advantageously brighter and lighter than the CRT projector.
Hereinafter, the triple-type LCD projector will be exemplarily described.
Generally, a high-power lamp is used to enhance brightness of a picture projected from the projector, and therefore a relatively large amount of heat is generated inside the projector. This heat may cause components inside the optical system to be heated and damaged. Accordingly, to manage temperature inside the projector, a forced convection cooling method using a cooling fan is employed.
As shown in FIGS. 1 and 2, a structure cooling an optical system 120 of a conventional projector comprises a duct 160 including an inlet 166 through which cool air flows in. The cooling structure also includes a plurality of outlets 167 opening toward an optical synthesizing part 130 including panels 131, 132 and 133 and target optical components 140 respectively. The cooling structure further comprises a cooling fan 150 placed inside the duct 160 that forcefully blows the cool air convectively.
The optical system 120 of the conventional projector operates as follows.
The cooling fan 150 forcefully blows the cool air, flowing in through the inlet 166 of the duct 160, to the outlets 167 and toward places where the heat is generated in the optical system 120, thereby cooling the optical system 120.
For example, some of the places where the heat is generated in the optical system 120, include the optical synthesizing part 130 including a blue panel 131, a green panel 132 and a red panel 133, and the optical components 140 including a flyeye-lens 141.
However, color signals respectively transmitted to the blue panel 131, the green panel 132 and the red panel 133 vary in wavelength, so that respective frequencies and energies thereof are different from each other. For example, the blue panel 131 which processes a blue component of the image beam receives a color signals having the shortest wavelength and the highest frequency among the color signals, and therefore, the blue panel 131 generates maximum heat as compared with other panels.
Generally, the optical system 120 is cooled with reference to a temperature of the blue panel 131 which has the highest temperature among other panels, so that the red panel 133 and the flyeye-lens 141 which have a relatively low temperature are overcooled, thereby wasting available energy.
Further, when the optical system 120 is cooled with reference to the place having a relatively high temperature, the cooling fan 150 is driven fast so as to speed up air flow, thereby causing noise due to the rotation of the cooling fan 150 and the air flow.