GB2306266A

GB2306266A - LCD projector with uniform cooling of the LCD

Info

Publication number: GB2306266A
Application number: GB9621034A
Authority: GB
Inventors: Peter Hein Grunwald
Original assignee: GRUNWALD PROJEKTOREN AG
Current assignee: GRUNWALD PROJEKTOREN AG
Priority date: 1995-10-13
Filing date: 1996-10-09
Publication date: 1997-04-30
Also published as: DE19538141A1; GB9621034D0

Description

2306266 1 LCID PROJECTOR The invention relates to a liquid crystal display

(LCID) projector, comprising a housing, which is closed at the top by a glass plate, and is provided with air intake openings and air discharge openings. The housing accommodates a light source, a Fresnel lens and an LCID as well as electronic components and equipment for operating the LCID, and an objective. The glass plate, the Fresnel lens and the LCID are installed approximately parallel to one another in the housing and enclosing between them air spaces which are cooled by an air flow generated by a blower.

Such LCID projectors exist in various forms of construction. They all have the drawback of a relatively low luminous intensity of the projected image. This is in the nature of the LCID: the liquid crystals of the LCID, which are formed into orderly arrangements under the action of electric fields generated by electrodes, are disrupted by heat. For this reason, the temperature of an LCID in the LCID projector should not exceed specific values. An LCD however absorbs considerable quantities of light when illuminated, with less than 10% of the irradiated light quantity passing through the LCD and being usable for projection. Extremely intense light sources are therefore employed to increase the brightness of the projected image and, at the same time, an attempt is made to cool the LCID as much as possible in order to keep the temperature of the LCID below the upper limit temperature in spite of the high luminous intensities. Such a procedure does achieve successful results, but soon encounters the phenomenon that the image quality becomes uneven. Blurred patches form in the projected image.

The invention proceeds from the finding that the phenomenon is a result of insufficiently uniform cooling, in that at the points which appear blurred the permissible temperature limit has already been exceeded.

The invention avoids the drawbacks of prior art. The object of the invention is to achieve intensive and uniform cooling of the LCID using simple means.

2 The invention is such that the blower is a tangential blower of the width of the assembly comprising the Fresnei lens, the LCID and the glass plate, that the blower is disposed laterally of this assembly and blows cooling air through the two air spaces enclosed by the components of the assembly, and that disposed at the opposite side of the assembly is a further tangential blower which extracts air at least from the air space between the Fresnei lens and the LCID.

The object may however alternatively be achieved in a kinematically reversed manner, in an arrangement wherein the blower is a tangential blower of the width of the assembly comprising the Fresnel lens, the LCID and the glass plate, that the blower is disposed laterally of the assembly and sucks cooling air through the two air spaces enclosed by the components of the assembly, and that disposed at the opposite side of the assembly is a further tangential blower which blows an air flow into the air space between the Fresnei lens and the LCID.

The effect thereby achieved is that a totally uniform air flow is moved through the air space between the LCO and the Fresnel lens and achieves the uniform cooling of the LCID. In the process, the rough surface of the Fresnel lens gives rise to a whirling effect, which causes eddies of cooler air situated at the bottom of the air flow to move in an upward direction and thereby intensifies cooling, although the eddies move in a continuous parallel flow which quickly conveys the heated cooling air out of the air space between the LCID and the Fresnei lens and draws fresh cooling air in its wake.

For intensive cooling it is advantageous if air-directing plates are disposed between the assembly comprising the Fresnel lens, the LCID and the glass plate, and the blowers.

As it is particularly important to cool the LCID at the light incidence side, the possibility exists of allowing one of the two blowers to act only upon the air space between the Fresnel lens and the LCID, while the other blower acts also upon the air space between the LCID and the glass plate. In this case it is advantageous if a partition wall is disposed to extend between the LCID and the wall of the housing at the side of the LCID remote from the blower disposed at the input side, with air 3 discharge holes disposed in the housing wall on either side of the partition wall, the output-side blower being disposed below the partition wall between the LCID and the wall of the housing.

Embodiments of the invention will now be described in detail, with reference to the accompanying drawings, in which:

Figure 1 is a side view of the projector in its operating position; Figure 2 is a side view of the projector in its transport or inoperative position, seen in section through the projector housing; Figure 3 is a section through the assembly comprising a Fresnel lens, an LCID and a glass plate, the two tangential blowers of the assembly acting upon the two spaces between the components and discharging the outlet air in a lateral direction; Figure 4 is a section through the assembly comprising the Fresnel lens, the LCID and the glass plate, the two tangential blowers of the assembly acting upon the two spaces between the components and discharging the outlet air in an upward direction; and Figure 5 is a section through the assembly comprising the Fresnel lens, the LCID and the glass plate, one of the two tangential blowers acting upon the two spaces between the components, while the other acts only upon the space between the LCID and the Fresnel lens.

Referring now to the drawings, the projector comprises a housing 1, which is closed at the top by a glass plate 2 Below the glass plate 2 is mounted an LCID 8 and, below the LCD, a Fresnel lens 9. A bracket 3 which is pivotally fastened to the housing 1 carries a mirror 4 intermediate its length, and has an objective 5 at its end. Situated within the housing 1 are a light source 6 and an inclined mirror 7.

The light source 6 preferably comprises an elongate metal-vapour lamp 10, a reflector 11 and a condenser 12. A partition wall 13, which has an opening into which the condenser 12 is inserted, closes off the light source 2 from the rest of the interior of the housing 1. A tangential blower 14 disposed above the metal-vapour lamp 10 draws in cooling air through air intake slots 15 in the base of the housing 1, through the area enclosing the light source 6 and into the blower 14. The 4 blower 14 then blows the heated cooling air out through air discharge slots 16.

The LCID 8 is cooled by means of a second tangential blower 17, which draws in cooling air through air intake slots 18 and directs it past electronic equipment, the power supply unit 19, a computer 20 and an interface 21 and then via air-directing plates 22 into the air space 23 between the Fresnel lens 9 and the LCID 8 and into the air space 24 between the LCID 8 and the glass plate 2.

From these two air spaces 23 and 24, in the embodiment of Figure 3, air is extracted via further air-directing plates 25 through a third tangential blower 26 and discharged through air discharge slots 27 in the wall of the housing 1 into the open air.

In the embodiment shown in Figure 4, the cooling air is discharged in an upward direction through an air discharge grille 30.

In the embodiment shown in Figure 5, a partition wall 28 is arranged as an extension of the LCID 8, the partition wall 28 extending horizontally to the sidewall of the housing 1. Above this partition wall 28, air discharge slots 29 are situated in the sidewall of the housing 1. The third tangential blower 26 extracts heated cooling air exclusively from the space 23 between Fresnei lens 9 and LCD 8.

The air-directing plates 22, 25 are installed, as a rule, in an inclined manner in order to direct the cooling air towards specific points where cooling is required to an increased extent. The tangential blowers 17 and 26 may be disposed at the same height or at different heights above the base of the housing 1 of the projector, and the outlet air may be discharged from the housing 1 of the projector either in a horizontal direction or with a downward or upward direction component.

Claims

1. An LCID projector, comprising a housing, which is closed at the top by a glass plate and is provided with air intake openings and air discharge openings and accommodates a light source, a Fresnel lens and an LCID as well as electronic components and equipment for operating the LCID, and further comprising an objective, wherein the glass plate, the Fresnel lens and the LCID are installed approximately parallel to one another in the housing so as to enclose between them air spaces which are cooled by an air flow generated by a first blower, wherein the first blower is a tangential blower (17) of the width of the assembly comprising the Fresnel lens (9), the LC1) (8) and the glass plate (2), the first blower (17) being disposed laterally of the assembly (9, 8, 2) to blow cooling air through the two air spaces (23, 24) enclosed by the assembly (9, 8, 2), and a second tangential blower (26) being disposed at the opposite side of the assembly (9, 8, 2) to extract air at least from the air space (23) between the Fresnel lens (9) and the LCID (8).

2. An LCID projector, comprising a housing, which is closed at the top by a glass plate and is provided with air intake openings and air discharge openings and accommodating a light source, Fresnel lens and an LCID as well as electronic components and equipment for operating the LCID, and further comprising an objective, wherein the glass plate, the Fresnel lens and the LCID are installed approximately parallel to one another in the housing so as to enclose between them air spaces which are cooled by an air flow generated by a first blower, wherein the first blower is a tangential blower (17) of the width of the assembly comprising the Fresnel lens (9), the LCID (8) and the glass plate (2), the first blower (17) being disposed laterally of the assembly (9, 8, 2) to suck cooling air through the two air spaces (23, 24) enclosed by the assembly (9, 8, 2), and a second tangential blower (26) is disposed at the opposite side of the assembly (9, 8, 2), to blow an air flow into the air space (23) between the Fresnei lens (9) and the LCID (8).

6

3. An LCID projector according to claim 1 or 2, wherein air-directing plates (22, 25) are disposed between the respective first and second blowers (17, 26) and the assembly comprising the Fresnei lens (9), the LCID (8) and the glass plate (2).

4. An LCID projector according to claim 1, wherein a partition wall (28) is disposed between the LCID (8) and the sidewall of the housing (1) at the side of the LCID (8) remote from the first blower (17), and air discharge holes (16, 27) are formed in the housing sidewall on either side of the partffion wall (28), the second blower (26) being disposed below the partition wail (28) between the LCD (8) and the sidewall of the housing (1).

5. An LCD projector substantially as herein described, with reference to Figures 1 and 2, Figure 3, Figure 4, or Figure 5 of the accompanying drawings.