Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1998-12-04
2001-09-04
Metjahic, Safet (Department: 2858)
Optics: image projectors
Composite projected image
Multicolor picture
C353S034000, C349S015000, C348S766000
Reexamination Certificate
active
06283597
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a process for the projection of images on a screen by means of a light bundle. The invention is further directed to a system with an individual projector for the display of an image on a screen by means of a light bundle, wherein the system can be used especially for carrying out the process according to the invention.
b) Description of the Related Art
Image projections have already been known for a very long time. Most notable in this respect is the Latema Magica from 1569 which is often referred to as the forerunner of modem slide projectors and episcopes. Film projectors, video projectors and head-up projectors should also be mentioned in this context.
With respect to video projectors, there are at present also other projectors, aside from eidophors and picture tube projectors, which project a video image on a screen in the manner of a slide or transparency, wherein the video image is electrically adjusted on an LCD matrix. Further, projectors are currently being developed in which a light bundle is directed onto a tilting mirror array, wherein the tilting mirror array generates the image content by rapidly switching individual tilting mirrors on and off based on locally different reflections of a light bundle which is then projected through an objective onto a screen. Modern developments, e.g., according to DE 43 42 849 C2, are also directed to the display of video pictures on a screen in that a laser beam is raster-scanned on a screen similar to an electron beam in an electron beam tube. The laser beam is color-modulated and intensity-modulated for the respective image points illuminated during scanning and a video image is made visible for an observer due to the rapid scanning and the inertia of the observer's eye.
Processes for the projection of images with these projection techniques are currently used in many commercial areas. The cinema is the best known example. Further, the proceedings at spectator events, political conventions and the like large-scale events are frequently made more visible for spectators at a distance by imaging speakers or artists by means of large-format video projection.
Further, projection methods of the type mentioned above are also used in advertising, particularly at trade fairs.
However, projection of the above-mentioned type creates problems especially in daylight. The light intensity is usually not sufficient in relation to sunlight, which can also strike the screen, for delivering adequately high contrast in order to view clear, high-quality images. Usually, no image at all can be detected when bright sunlight falls on the screen. However, it would be extremely desirable to be able to use the projection techniques mentioned above also in large open-air events, outdoor concerts, ball games or the like, so that spectators at a great distance from the proceedings, for example, at a ball game, can also clearly discern details on a large screen so as to make attendance at the event more appealing to these spectators and dissuade them from the alternative of viewing the televised event.
OBJECT AND SUMMARY OF THE INVENTION
It is the primary object of the invention to increase the contrast of the image projection relative to ambient light, especially sunlight, in projections of images on a screen.
Proceeding from the prior art mentioned in the introduction, this object is met by a process in which an individual projector is provided for projecting images, wherein the light bundle used for projection is emitted from a light source in the projector whose light has at least one spectral peak in the visible wavelength range with a half-width of less than 100 nm, especially less than 30 nm, and in which the observer of the image is given eyeglasses which have a wavelength-dependent transmission function such that light in the wavelength range of at least one spectral peak or, if more than one spectral peak, in the wavelength range of at least one of these spectral peaks is transmitted by each eyeglass, and the light intensity for light with wavelengths beyond this spectral peak or spectral peaks is reduced.
A system of the type mentioned above for carrying out the process is characterized according to the invention by a light source in the projector which emits the light bundle and whose light has at least one spectral peak in the visible wavelength range with a half-width of less than 100 nm, especially less than 30 nm, and by at least one eyeglass for which a wavelength-dependent transmission function is provided such that exclusively light in the wavelength range of at least one spectral peak or, if more than one spectral peak, in the wavelength range of at least one of these spectral peaks is transmitted by the eyeglass, and the light intensity for light with wavelengths beyond this spectral peak or spectral peaks is reduced.
Accordingly, the projection is carried out with light which is emitted in a very narrow band in narrow wavelength ranges, namely, within the spectral peak. Only light generated within a wavelength range of this spectral peak is detected by the eyeglass, so that an observer seeing through this eyeglass can detect the image information in its entirety just as the observer would without the eyeglass. However, the ambient light, for example, sunlight, is attenuated overall by filtering out large wavelength regions.
In a graph in which the light intensity is plotted over wavelength, spectral peak in the present sense means a peak, a Gaussian-like distribution, a rectangular function or any curve whose half-width is appreciably less than the width of the brightness sensitivity curve or photopic response curve of the human eye, for example, in accordance with DIN 5031, which is approximately 100 nm. It is important in this respect that only a narrow wavelength range is available for the light generation and the transmission through the eyeglass because of the function shape in the intensity/wavelength graph.
The indicated haff-width of 100 nm or 30 nm of the spectral peaks has turned out to be especially advantageous as an upper limit because this also allows a proper separation of projection light and ambient light even when color display is desired. In this respect, it should be noted in particular that white light requires a mixture of at least three primary colors, so that light for displaying black-and-white images should have at least three spectral peaks. However, the invention is not limited to this. In some applications in which large-scale projection requires text in a single color, for example, in advertising events, a monochrome display with a single spectral peak would be entirely adequate. However, an upper limit of 100 nm or 30 nm half-width is also recommended in this case so that a sufficiently high contrast can still be provided relative to the ambient sunlight by taking into account the logarithmic response of the human eye.
Similar considerations also apply in laser shows, wherein the invention is also directed to these. However, in this case, the concept of the screen is understood in a very broad sense; namely, it also includes fog or the like generated by a fog machine or also a wall of water.
The eyeglasses can be installed in spectacles, for example. However, it is also possible to hand out suitable disks or sheets to the observer as eyeglasses which can then be held in front of the observer's field of view in harsh sunlight.
Unexpectedly, the object of the invention can be met through commonplace steps such as increasing the light output or other more elaborate alternatives such as a special technical design of the screen. However, the solution according to the invention is very simple. In principle, it is only necessary to separate suitable light from the light source in a spectrometric manner as in a monochromator or to replace the light source of known projectors with suitable monochromatic light sources, for example, lasers. The manufacture of usable eyeglasses also presents no substantial problems in techni
Daimler-Chrysler AG
LeRoux Etienne
Metjahic Safet
Reed Smith LLP
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