Optics: image projectors – Lamp control
Reexamination Certificate
2003-05-27
2004-10-19
Dowling, William C. (Department: 2851)
Optics: image projectors
Lamp control
C315S169300
Reexamination Certificate
active
06805448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a projection type display apparatus that comprises light source units comprising cooling means and light emitting units that include light emitting layers comprising organic EL (electroluminescence) elements, wherein the light emitted from the light emitting units is guided to liquid crystal panels, and the images displayed on the liquid crystal panels are enlarged and projected by a lens or lenses.
The present invention also concerns cooling control technology for cooling the light emitting units that employ light emitting layers made up of organic EL (electroluminescence) elements and that are used in various fields. More particularly, the present invention pertains to a light source apparatus formed by adding temperature detection means or elapsed time measuring means to light source units comprising light emitting units and cooling means, and to a method and apparatus for controlling a light source apparatus that controls the cooling means by the temperature detection means or elapsed time measuring means in the light source apparatus.
2. Description of the Related Art
In recent years, with the amazing advances being made in semiconductor technology, various electronic display devices other than CRT displays are being developed and turned into marketable products. One of these which is drawing much attention is the projection display apparatus, a technology that is advantageous in terms of lower power consumption and lighter weight.
One type of such a projection display apparatus that is known is the liquid crystal projector wherewith images on a liquid crystal panel are enlarged and projected by a projection lens onto a reflective or transmissive screen and thus displayed. One example of such a liquid crystal projector is diagrammed in FIG.
31
.
The liquid crystal projector diagrammed in
FIG. 31
comprises a light source lamp unit
202
inside a cabinet. Electrical discharge lamps such as metal halide lamps, or halogen lamps, are used in the light source lamp unit
202
. The light emitted from this light source lamp unit
202
is guided via a mirror
203
to dichroic mirrors
204
and
205
, whereby it is separated into red light, green light, and blue light. Of the three color components into which the light is separated, the red light passes by way of a mirror
206
to a red displaying liquid crystal panel
209
, the green light is led directly to a green displaying liquid crystal panel
210
, and the blue light is led by way of mirrors
207
and
208
to a blue displaying liquid crystal panel
211
.
The images displayed on the three liquid crystal panels
209
through
211
, respectively, are illuminated by their respective colors, and this light is combined by a dichroic prism
212
. The combined light is enlarged by a projection lens
213
and projected, in enlarged form, on a reflecting screen (not shown), for example.
With a liquid crystal projector in which a light source lamp unit
202
such as this is used, however, the light emitted from the metal halide lamp or halogen lamp must be radiated with good parallelism onto the liquid crystal panel. For this purpose, as diagrammed in
FIG. 31
, it is necessary to provide the light source lamp unit
202
with a reflector
202
A having a rather large aperture. This constitutes a serious problem in that it makes it difficult to meet the demand for lighter weights and smaller sizes in the overall projector.
As is depicted in
FIG. 31
, moreover, it is preferable that the lamp in the light source be cooled. The larger the capacity of the lamp, in fact, the higher must the cooling capability of the cooling fan be.
In the case of a so-called triple liquid crystal projector, moreover, in which three separate liquid crystal panels are provided for the red, green, and blue colors, as described in the foregoing, a light dividing optical system is necessary to take the light emitted from the single-lamp light source and divide it into the colors on the three liquid crystal panels. This makes it even more difficult to achieve the desired reduction in weight and size.
A first example of the related art is now discussed. In recent years, in an effort to break out of this dilemma, the use of organic EL elements as the light emitting unit has been proposed. This reflects the fact that many reports have been made of light of high brightness being emitted by EL elements using an organic thin film for the light emitting layer. These light emitting units are thin planar light sources in which are formed an electric-field light-emission (electroluminescence=EL) layer consisting of an organic thin film. Compared to inorganic EL elements, organic EL elements can operate at low voltage and provide high brightness. Thus they are believed to be well suited for use in enlarging-projection type projection display apparatuses, and much research is being focused on the practical implementation of such devices.
An example of a triple liquid crystal projector in which such organic EL elements are used as the light source unit is diagrammed in
FIGS. 32 and 33
. In the liquid crystal projector depicted in these drawings, light source units
224
,
225
, and
226
, in which are used organic EL elements that emit red, green, and blue light, respectively, are positioned, respectively, behind and in close proximity to three liquid crystal panels
221
,
222
, and
223
, which display red, green, and blue colors. Item
227
is a dichroic prism, and
228
is a projection lens. An example of this type of projection display apparatus is disclosed in laid-open patent application (Tokkai) S51-119243 [1976] (gazette).
Even with such a triple liquid crystal projector such as this however, in which organic EL elements are used as the light source unit, the organic EL elements produce heat when they are driven, and thus require cooling.
A second example of the related art is now discussed. One possible means of forcibly cooling such organic EL elements as these is to employ electrical cooling elements that utilize the peltier effect.
Nevertheless, in the liquid crystal projector of the first example of the related art depicted in
FIGS. 32 and 33
and described above, a planar light emitting unit in which organic EL elements are used is employed, thus making it possible to achieve smaller sizes and lighter weights, but some unresolved problems remain, as noted below. These problems present obstacles which prevent this technology from being practically implemented.
In the first place, even though these are called organic EL elements, they produce heat when they are driven, and this emission of heat causes the light emitting performance to gradually deteriorate, shortening the useful life of the elements.
Furthermore, if the light emission performance of a light source unit in which organic EL elements are used has fallen below allowable limits, then one would like to be able to replace only the light source unit. In a color-displaying triple liquid crystal projector, in particular, light source units are provided for each of the three liquid crystal panels, no the number thereof in high. A deterioration in the performance of one or two of the light source units destroys the color balance of the displays on the screen, so the effects thereof are great. In such cases, it would be economical to be able to simply replace only those light source units which have reached the limit of their useful life. Previously, however, no structure has been proposed for such light source units which would make them independent and easily replaceable. This has obliged repair personnel to go to the great trouble of changing out light source units on boards on which they are mounted.
When making such replacements, it is very important not only to insure the electrical connection with the light source unit after replacement, but also to insure that it has been restored to the prescribed optical position. If the orientation or position of the replaced light source unit is off, the way
Kamakura Hiroshi
Miyashita Satoru
Shimoda Tatsuya
Yokoyama Osamu
Dowling William C.
Seiko Epson Corporation
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