WO2001048545A1

WO2001048545A1 - Improved lcd with filters adapted for a slide projector

Info

Publication number: WO2001048545A1
Application number: PCT/AU2000/001574
Authority: WO
Inventors: Kevin James Soper; Philip Brendan Banks
Original assignee: Digislide International Pty Ltd
Priority date: 1999-12-24
Filing date: 2000-12-21
Publication date: 2001-07-05
Also published as: AUPQ488299A0

Abstract

An apparatus for use with a slide projector (10) or other light source so as to project an image onto a surface, the apparatus including a liquid crystal display (LCD) screen (18) and generally three filters that are positioned in between the LCD and the light source, the three filters being in a sandwich type arrangement and consisting of a polarising filter (24), an ultraviolet filter (22) and an infrared filter (20). The filters are either attached to the LCD (18) or are mounted in a housing together with the LCD (18). The infrared filter (20) is nearest the lamp, the polarising filter (24) is nearest the LCD (18) with the ultraviolet filter (22) being located there in between.

Description

IMPROVED LCD WITH FILTERS ADAPTED FOR A SLIDE PROJECTOR

This invention is directed to improvements and/or modifications to LCD's and apparatus using the same to produce a projected image. In particular the present invention enables the use of LCD's in conventional slide projectors or light sources with similar lamps.

BACKGROUND OF THE INVENTION

Since the advent of television, home entertainment has become an integral and focused part of everyday life. For that reason, numerous improvements to television, video and audio systems have been commonplace during the last several decades.

One of the most common sought-after improvements is to increase the size of the image whilst sill maintaining good resolution. Until the advent of large screen televisions large images were only available in commercial arenas such as cinemas where reel-to-reel films are used to project an image onto a screen. For the domestic or professional market however, whether it be television or video, the only known way to produce a large image is by simply using a bigger television screen. The difficulty with large television screens is that they are inherently expensive, are relatively complex and thus expensive to repair, and by their large size are not very mobile or portable.

Although it has been attempted to produce a large image by projecting light through a LCD (Liquid Crystal Display), the larger the area of the image the greater then intensity of light required to pass through the LCD. One such source of light is the conventional slide projector. However, the intensity of the various bands of the electromagnetic spectrum of lamps used in a slide projector leads to operational failure of a LCD within a very short period of time. It has been long suspected that heat is a major cause of these failures. Heat shields have thus been proposed to protect the LCD's.

However, it has been a discovery by the applicant that failure in LCD's is caused by several distinct parts of the electromagnetic spectrum as opposed to simply heat from the lamp and that heat shields in solus will not achieve long term operation of the LCD. In addition, it has been a further discovery by the applicant that the shielding of the LCD can be accomplished using layers of suitable material whose thickness is sufficiently small to still allow the LCD to be used in a conventional slide projector. It is therefore an object of the present invention to provide an improved LCD in combination with suitable filters or shielding which overcomes at least some of the abovementioned problems or provides the public with a useful alternative, and which can be used in a conventional slide projector.

SUMMARY OF THE INVENTION

Therefore in one form of the invention there is proposed an apparatus for use with a slide projector said apparatus including: a liquid crystal display screen, said liquid crystal display screen being of a shape and size to locate in an operative position in a slide projector to enable illumination through said liquid crystal display screen for projection onto another surface through the use of an electromagnetic lamp; and at least one filter disposed between the LCD and said lamp.

In preference filter is mounted integrally on the LCD panel.

Preferably the filter is adapted to affect at least three different properties of electro-magnetic radiation including the ultra-violet range, infra red range and polarising of said radiation.

Advantageously there are three filters disposed between the LCD and the lamp wherein: said first filter is adapted to polarise said electromagnetic radiation; said second filter is adapted to substantially filter the ultra-violet portion of electromagnetic radiation from the lamp; and said third filter is adapted to substantially filter the infra-red portion of electromagnetic radiation from the lamp

Preferably the three filters are arranged in a sandwich type arrangement wherein the said first filter is located nearest the liquid crystal display, said second filter is located adjacent the first filter and said third filter is located adjacent said second filter and nearest the lamp.

Preferably the first filter is attached to the surface of the liquid crystal display, said second filter is placed on top of the first filter and said third filter is placed on top of the second filter.

Preferably the apparatus is of a size to be inserted into a slide holder of the slide projector.

Preferably the polarising filter is chosen to match the polarisation of the liquid crystal display. Preferably the liquid crystal display and filters are housed in a housing, said housing adapted to lock in place said liquid crystal display and filters.

In preference the housing includes two shells defining a cavity therein between for housing said liquid crystal display and said filters and that are adapted to be held together in a snap- lock arrangement.

In a further form of the invention there is proposed an adaptor for use with a slide projector including: a controlled transparency liquid crystal display panel, and a supporting perimeter frame which frame has a shape, width and perimeter dimensions such that the frame will locate in an operative position in the slide projector and hold the panel for illuminating projection there through from such a projector; said liquid crystal display further including a plurality of filters positioned between the LCD and said lamp.

In a still further form of the invention there is proposed an adaptor for use with a light emitting apparatus: said adaptor including a controlled transparency liquid crystal display panel; a plurality of filters disposed between the LCD and said light emitting apparatus, there being at least one of each of an ultra-violet, infra-red, and a polarising filter.

In a yet further form of the invention there is proposed a method of enlarging an image using a slide projector including adapting a liquid crystal display for insertion into said slide projector by placing on said liquid crystal display at least three filters to construct an assembly, the filters being arranged on top of the liquid crystal display in the order of a polarising filter, ultra violet filter and an infra red filter, wherein in operation the assembly is inserted into the slide projector so that the infra red filter faces a slide projector lamp.

Other objects and advantages of the present invention will become apparent in view of the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings, Figure 1 is a perspective view of a LCD (Liquid Crystal Display) in accordance with the present invention when used with a slide projector.

Figure 2 is a side view of a first embodiment of a LCD according to the present invention;

Figure 3 is an exploded side view of the LCD of Fig 2;

Figure 4 is a perspective view of the LCD of Figs 2 and 3 when mounted in a housing; and

Figure 5 illustrates in an exploded perspective view a second embodiment of a LCD according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

Thus there is shown in Figure 1 a slide projector 10 that is commonly used to show slides (not shown) by inserting a slide 12 into the projector via an aperture (not shown) and into a position where an internal light (not shown) projects a light through the slide contained within aperture and through lens 14 to be displayed on some surface such as a screen. The lens 14 is generally adjustable in focus so as to project a clear image onto the screen depending on the distance from the slide projector to the screen.

Slide projectors are usually constructed either to take individual slides, or are adapted to accommodate a slide holder that may take a number of slides. Slide holders may further be of a linear construction or a carousel 16 as shown in Figure 1. In both cases the slide holder is adapted to change slides automatically without the necessity to manually change the slides.

It has been discovered by the applicant that using a conventional LCD in a typical slide projector will cause irreversible damage to the LCD under the influence of damaging ultraviolet and infrared radiation. The use of heat shields alone will not completely eliminate the damage to the LCD because ultra violet rays degrade the LCD and the epoxy plug that holds the liquid crystal in place, causing leakage and degradation which could lead to the destruction of the LCD panel in :ime.

As shown in Figures 2 and 3 the) present invention overcomes the problems of using a conventional LCD 18 in a slide projector. Up to three filters are provided being an polarising filter 24, an ultraviolet filter 22, and a heat/infra red filter 20. For convenience the filters are mounted integrally on the LCD panel although it is to be understood that this is a preferred not an essential feature.

The polarising filter 24 is mounted on the LCD side facing the lamp within the slide projector. Disposed on top of the polarising filter is the ultra-violet filet. The heat/infra red filter must be located as far as is practicable form the LCD. In manufacture, the three filters may be sequentially placed on the LCD. Alternatively, they may be adhered to each other to provide for a laminated construction and then mounted on the LCD. The mounting may be achieved using suitable mechanical brackets or fasteners such as retaining clips.

Furthermore, in a preferred embodiment there is a preferred order in the placement of filters.

Of course, it is important that the filters that block heat or other potentially damaging parts of the spectrum be located as far from the panel as practicable to ensure no damage to the LCD. It is also necessary to use polarisers on the other side of the LCD. That depends very much on the particular structure of the LCD which can be bought as an off-the shelf product. It is also to be understood that the polarisation must be linear so that the image that is projected is of the highest quality definition.

The use of thin filters allows the LCD device to be constructed of a size able to be inserted into a conventional slide projector enabling an image to be formed whilst protecting the LCD. As shown in Figures 4 and 5 where the filters do not need to be mounted integrally on the LCD but may form a separate laminate construction 26 that is locked into place adjacent the LCD in a housing 28 made up of two shells 30 and 32 that engage the LCD panel and the laminate filter construction. The construction housing 30 and 32 may have ventilation holes/slots to allow circulation of air between the LCD panel and the filters thus further protecting the LCD. An aperture 34 allows electrical signals and power to be fed to the LCD via cable 36.

The shells 30 and 32 may be correspondingly shaped and designed that one is slightly smaller than the other and frictionally engage each other. Alternatively, the housings may have appropriate lugs and recesses and may be joined together in a snap-lock type of arrangement.

The LCD 18 can be used to display either television or video or any other computer or digital image, with the slide projector simply projecting and thereby greatly enlarging whatever image is being shown by the LCD. Ergo, one obtains an image whose size may be greater than that available by conventional television receivers and whose resolution is dependant only on the total number of pixel's contained within the LCD panel and supported by RGB/video-composite converter and the ultimate size of the image is fully controllable by the user.

Thus one can see that the present invention allows the use of a modified LCD by a conventional slide projector, which is protected from irreversible damage by the slide projector lamp.

Many other improvements may be made to the apparatus and still falling within the scope of the invention. Different filters and optical components may be used to improve or change the quality or colour of the image. It may also be possible to provide a liquid crystal display screen slide that may incorporate two individual screens, and allows one to display two simultaneous images. This though may be controlled by the signals that are fed into the liquid crystal display screen slide and may not require any change in the construction of the liquid crystal display screen slide.

The present invention relates to light that finally reaches the LCD panel to generally be visible light whose wavelength is around 415 to 780 nanometres. We want to ensure that the wavelength will not go beyond 780 nanometres since infra red light will produce unwanted temperature rises that may damage the liquid crystal in the panel or the image projected.

Similarly we want to ensure that the wavelength will not go below 415 nanometres because ultra violet light will produce irreversible changes in the display panel and its characteristics.

This is achieved by placing integrally mounted filters between the LCD and the light source as necessary depending on the characteristics of the light source. No one has previously been aware that ultra violet light can damage the LCD.

Preferentially the lighting intensity should not exceed 1 ,000,000 lux and the panel surface temperature should not exceed 42 degrees Celsius at lower resolution and 55 degrees Celsius in the higher resolution panels, through the use of integrally mounted filters. Further, the use of an integrally mounted polarising filter, generally a linear polariser (neutral grey) enables the image to be clearly displayed. Depending on the specific panel used, there may be different embodiments as different LCD's have different crystal alignments. Accordingly some LCD panels will require tilting a complementary angle to the polarisation of the liquid crystal, of 45 degrees (or less) to obtain the appropriate polarisation results, whilst in other panels, the polarising filter may need to be aligned at angles of 180 degrees or a range in-between.

Although not shown, it may therefore be envisaged that the polarising filter may be so constructed that it may be rotatable with respect to the liquid crystal display. This may be achieved by either being able to rotate just the polarising filter or alternatively, be able to rotate the three filters with respect to the liquid crystal display. The housing could therefore be so constructed to accommodate for this rotation, and which could be controlled by an external lever or other mechanism. Further, where different types of polarisers may be required, it is envisaged that the polarising filter may be replaceable with different types of polarisers.

The present invention therefore teaches that an integrally mounted filter, aligned in such a way as governed by the alignment of crystals, coupled with the integrally mounted infra read and ultra violet filters will make unnecessary various conductivity devices, heat dissipation, air spaces, air inlet holes, and additional air circulation fans and other requirements that is taught in the prior art.

It is further to be understood that whereas reference has been made to the use of the liquid crystal display and filter assembly in a slide projector, the assembly could very well be used in dedicated equipment wherein the assembly is constructed to be integral with a lamp. The advantage of the present invention is that it provides for protection of the liquid crystal display without the use of complex optical and heat dissipation engines.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

Claims

1. An apparatus for use with a slide projector said apparatus including: a liquid crystal display screen, said liquid crystal display screen being of a shape and size to locate in an operative position in a slide projector to enable illumination through said liquid crystal display screen for projection onto another surface through the use of an electromagnetic lamp; and at least one filter disposed between the LCD and said lamp.

2. An apparatus as in claim 1 wherein said at least one filter is mounted integrally on the LCD panel.

3. An apparatus as in claim 1 wherein said filter is adapted to affect at least three different properties of electro-magnetic radiation including the ultra-violet range, infra red range and polarising of said radiation.

4. An apparatus as in either one of claims 1 or 2 including three filters disposed between the LCD and the lamp wherein: said first filter is adapted to polarise said electromagnetic radiation; said second filter is adapted to substantially filter the ultra-violet portion of electromagnetic radiation from the lamp; and said third filter is adapted to substantially filter the infra-red portion of electromagnetic radiation from the lamp

5. An apparatus as in claim 4 wherein the three filters are arranged in a sandwich type arrangement wherein the said first filter is located nearest the liquid crystal display, said second filter is located adjacent the first filter and said third filter is located adjacent said second filter and nearest the lamp.

6. An apparatus as in any either one of claim 4 or claim 5 wherein said first filter is attached to the surface of the liquid crystal display, said second filter is placed on top of the first filter and said third filter is placed on top of the second filter.

7. An apparatus as in any one of the above claims wherein the apparatus is of a size to be inserted into a slide holder of the slide projector.

8. An apparatus as in any one claims 4 to 8 wherein said polarising filter is chosen to match the polarisation of the liquid crystal display.

9. An apparatus as in any one of claims 4 to 8 wherein said liquid crystal display and filters are housed in a housing, said housing adapted to lock in place said liquid crystal display and filters.

10. An apparatus as in clam 9 wherein said housing includes two shells defining a cavity therein between for housing said liquid crystal display and said filters and that are adapted to be held together in a snap-lock arrangement.

11. An adaptor for use with a slide projector including: a controlled transparency liquid crystal display panel, and a supporting perimeter frame which frame has a shape, width and perimeter dimensions such that the frame will locate in an operative position in the slide projector and hold the panel for illuminating projection there through from such a projector; said liquid crystal display further including a plurality of filters positioned between the LCD and said lamp.

12. An adaptor for use with a light emitting apparatus: said adaptor including a controlled transparency liquid crystal display panel; a plurality of filters disposed between the LCD and said light emitting apparatus, there being at least one of each of an ultra-violet, infra-red, and a polarising filter.

13. A method of enlarging an image using a slide projector including adapting a liquid crystal display for insertion into said slide projector by placing on said liquid crystal display at least three filters to construct an assembly, the filters being arranged on top of the liquid crystal display in the order of a polarising filter, ultra violet filter and an infra red filter, wherein in operation the assembly is inserted into the slide projector so that the infra red filter faces a slide projector lamp.

Dated this 21st day of December 2000

Digislide International Pty Ltd By their Patent Attorneys LESICAR PERRIN