Optical projection apparatus

Abstract: Described is an optical projection apparatus comprising, in this order, a radiation source (30), a liquid crystal display panel (33) and a projection lens (35). By arranging the axis of a projection lens portion (21) at an angle of substantially 90° with the axis (L) of the remaining portion (29a), a compact apparatus is obtained, the projection axis of which can easily be setted, by rotating the projection lens portion around an axis is parallel to the remainder portion axis.

Description: The present invention relates to an optical projection apparatus comprising, in this order, a light source, a liquid crystal display panel and a projection lens for projecting an image generated by said panel onto a projection screen. Such apparatus is widely known, see for example JP-A-04-306 629 and figure 1 shows an example of such apparatus. In a rectangular housing 1 are provided from the rear end to the front end, and along a projection axis 14 a lamp 6, a filter 5, a converging lens 4, a liquid crystal display panel 3 and a projection lens 2. The housing 1 is provided with air inlet holes 7 and 8 for inhaling coolant ambient air and with a fan 9 for exhausting this air. The directions of the air streams are indicated by arrows 12. The projector housing is placed so as to have an inclination with respect to a surface 10 such as a table or the like by means of a stand 11 drawn by a dot line. Details of the stand 11 are not shown, but the upper end of the stand 11 is shifted in upward and downward direction, indicated by an arrow 13, by hand adjustment, which is a well-known technology. It is remarked that in US-A 4,735,499, a film projector is disclosed comprising a first holder and a second holder. Each of the holders has an optical axis, the two optical axes extending perpendicularly to each other. The second holder comprises an illumination system, while the first holder houses a projection lens and a mirror to reflect light coming from the illumination system towards the lens. A film holder is fixed to the second holder which is rotatable around its own optical axis, so that the orientation of a frame to be projected can be varied. In this way it may be possible to realize a compact construction, but the setting of the projection axis inclination would be as complicated as in a conventional projection apparatus. Other similar film projectors are disclosed in EP-A-0 313 395. It is difficult to make the conventional projector compact due to its construction. Furthermore a complicated angle adjustment mechanism for adjusting the inclination of the body is required in order to project an image onto a screen. The purpose of the present invention is to solve these problems and to provide a compact projection apparatus as defined in Claim 1. In this projection apparatus the light path is folded so that the length of the apparatus is decreased, and the projection axis inclination can be set easily by manually rotating the first holder. This apparatus may be further characterized in that the first holder comprises a reflector arranged at an angle of substantially 45° with the first optical axis and the second optical axis. By the 45° reflector folding of the light path is achieved in the most simple way. A preferred embodiment of the apparatus according to the present invention is characterized in that the first holder is fixed to the second holder and in that the latter is rotatably arranged in a stationary case which is fixed to the support. As the second holder rotates with the first holder, the orientation of the liquid crystal display panel with respect to the projection lens is kept constant. A constructively preferred embodiment of the apparatus is characterized in that the second holder is provided with bearings supported in the stationary case and in that an elastic member is provided between an end portion of the second holder and the end of a neighbouring bearing. An embodiment of the projection apparatus wherein the liquid crystal display panel is arranged in a supporting member, may be further characterized in that said member is provided on its surface with a plurality of radially arranged fins which surround the liquid crystal display panel. The invention will now be described more in detail by referring to the accompanying drawings, in which Figure 1 shows a conventional projection apparatus, Figure 2 shows a view of the apparatus according to the invention, Figure 3 shows an embodiment of this apparatus in cross-section, Figure 4 illustrates how cooling is performed in this apparatus, and Figure 5 shows a liquid crystal panel supporting member for use in this apparatus. In figure 2 numeral 21 denotes the first holder which is arranged rotatably and comprises a projection lens 22. Numeral 23 denotes a tubular case which comprises other members of the optical projection system. The axis L of case 23 coincides with the rotation axis of holder 21. The case 23 may have a speaker part 24 at its end remote from the first holder 21. Numeral 25 denotes a support for the case 23. The support 25 may incorporate terminals of an electronic system, an electronic circuit, a fan, an adjustment member and the like. Numeral 26 denotes a coupling member which couples the first holder 21 rotatably to the case 23. This projection apparatus can be very compact. Figure 3 shows, in cross-section an embodiment of the projection apparatus in which the holder 21 of figure 2 forms a part 29b of an L-shaped holder 29, which has a second tubular holder part 29a. In the latter a lamp 30, a filter 31, a converging lens 32 and a liquid crystal display panel 33 are accommodated. In the holder 29b a reflector 34 is arranged which reflects the optical axis L of the beam emanating from the holder 29a over 90° so that it coincides with the axis of the projection lens 35. The tubular holder 29a is inserted between bearings 27 and 28 which are fitted in and fixed to the outer case 23 shown in figure 2. The holder 29 is fixed to the bearing 28 by means of a washer 36 and a ring shaped plate spring 37 between the rear end portion 29c of the holder and the rear side of bearing 28. The coupling part 26 comprises a similar spring construction which enables the holder 21 to be rotated by hand with respect to the outer case 23. Although the design of the apparatus may be such that only the holder 21 with the projection lens 35 and the reflector 34 is rotated to set the projection axis angle, it is preferred that the whole optical system, except the radiation source 30, is rotatable. The display panel 33 may also be accommodated in the holder 21. In order to ensure that in the case of a rotatable display panel this panel is efficiently cooled at any angle position of the panel, according to the invention special cooling means are provided as illustrated in figures 4 and 5. Figure 4 shows the cooling principle and figure 5 a perspective view of a heat radiating supporting member D for the display panel. In these figures A denotes a part containing the projection lens, the reflecting mirror and the like therein, B denotes a fan provided in the support member 25, C denotes another fan provided at the other end of the projector for example together with the speaker part 24 and D denotes a liquid-crystal-display-panel heat radiation supporting member arranged upwardly of the fan B. The supporting member carries the liquid crystal panel 33 therein and has a plurality of tapered fins d at its surface as clearly shown in Figure 5. Numeral 29 denotes a tube or the like and is integrally rotatable with A and D. E denotes an outer case containing the tubular holder 29a, the holder 21 and the like therein. With the above-described construction, a cooling operation according to the invention is as follows. The open air 40 is inhaled by the fan B and then reaches the liquid-crystal-display-panel supporting member D arranged upwardly, whereby the liquid crystal panel of which temperature is rising is cooled. Then the open air flows in a direction indicated by arrows so as to cool the other internal members, and finally is exhausted (43) by means of the fan C. The liquid-crystal-display-panel supporting member D is rotatable over any desired angle as described before, and a plurality of tapered fins d are arranged radially with respect to the liquid crystal device panel 33 such that the cool air reaches the liquid crystal panel 33 efficiently at any angle about which the liquid-crystal-panel-radiation member D rotates. An explanation on the operation of the liquid crystal display projector is omitted since it is well-known. The above-described embodiments are only examples and various embodiments can be adopted within the scope of the invention without deviating from the invention. According to the invention as described above, a compact projector having a good operationability can be obtained. In such a projector, a complicated projection axis angle adjustment mechanism needed in the conventional projector can be omitted, whereby a considerable cost reduction can be obtained. Since the projector is compact, it can easily be carried to any place. Especially, if the compact projector is used in a car or in a plane in which space is very limited, projection can easily be performed by using a ceiling, wall or the like as a screen since the projection lens holding part is rotatable. Furthermore, according to the invention, cooling of the liquid crystal device panel can be performed efficiently only by providing a plurality of fins arranged radially on the panel supporting member in compliance with the rotation construction according to the invention, without having a complicated construction like before.

Claims: An optical projection apparatus comprising in this order, a light source (30), a liquid crystal display panel (33) and a projection lens (35) of a projection optical system (31,32,35) for projecting an image generated by said panel (33) onto a projection screen, the apparatus further comprising a first holder (21), for holding the projection lens (35) having a first optical axis, characterized by a second, tubular, holder (29a) for holding the light source (30), and other components (31,32) of the projection optical system, the liquid crystal display parcel (33) being accomodated in the first or in the second holder, the other components (31,32) of the projection optical system having a second optical axis (L), the first optical axis being substantially perpendicular to the second optical axis (L), a support (25) having a flat base for the second, tubular holder, the second, tubular holder being horizontally supported with respect to the flat base, and the first holder (21) being rotatable around an axis parallel to the second optical axis (L). An optical projection apparatus as claimed in Claim 1, characterized in that the first holder (21) comprises a reflector (34) arranged at an angle of substantially 45° with the first optical axis and the second optical axis (L). An optical projection apparatus as claimed in Claim 1 or 2, characterized in that the first holder (21) is fixed to the second holder (29a) and in that the latter is rotatably arranged in a stationary case (23) which is fixed to the support (25). An optical projection apparatus as claimed in Claim 3, characterized in that the second holder (29a) is provided with bearings (27, 28) supported in the stationary case (23) and in that an elastic member (37) is provided between an end portion (29c) of the second holder (29a) and the end of a neighbouring bearing (28). An optical projection apparatus as claimed in Claim 1, 2, 3 or 4, characterized in that the liquid crystal display panel (33) is rotatable with the first holder (21). An optical projection apparatus as claimed in Claim 5, having a supporting member (D) for the liquid crystal display panel (33), characterized in that said member (D) is provided on its surface with a plurality of radially arranged fins (d) which surround the panel (33).

Inventors: YAMAMOTO MITSUO, YAMAMOTO, MITSUO
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 1993
Main classification: G03B21
IPC codes: G03B21, H04N9