Optical: systems and elements – Mirror – With support
Reexamination Certificate
2000-12-11
2003-04-08
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Mirror
With support
C359S884000, C359S584000
Reexamination Certificate
active
06543903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reflecting mirror for use in a display device by which an image to be displayed is enlarged and reflected on a mirror and thereby is projected on a screen, such as that of a rear projection television, and the invention relates to a rear projection display making use thereof.
2. Description of Prior Art
Conventionally, in a reflecting mirror for a rear projection display, a reflecting film of aluminum is formed by an evaporation method or a sputtering method. Also, a glass substrate which is produced by a float process is normally used.
However, on a surface of such glass substrate formed by a float process, minute irregularities which are referred to as microcorrugations (around 0.1 &mgr;m-0.16 &mgr;m on the measurement condition that the cut-off value is 0.8 mm to 8 mm) occur parallel to the transfer direction of the float process in the course of the production. Such irregularities inevitably occur on a surface of the glass substrate due to the production process of the glass substrate.
Therefore, in a case of using a reflecting mirror which is obtained by forming a reflecting film on a surface of such glass substrate for a rear projection display, parallel light which is incident on a reflecting mirror
100
is reflected by a reflection surface
101
which has irregularities, so as to be deviated from being parallel, as shown in FIG.
4
. As a result, a pattern of light and shade occurs in an image projected on a screen
102
due to the spatial difference in light intensity, thereby presenting a cause of remarkable deterioration in image quality.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a reflecting mirror, wherein any pattern of light and shade in an image projected on a screen that may be due to the spatial difference in light intensity is not present, thereby enabling an improvement in image quality, and a rear projection display making use thereof.
According to one aspect of the present invention, there is provided a reflecting mirror for use in a rear projection display and so on, comprising a glass substrate at least one surface of which is polished to have a predetermined surface waviness, and a reflecting film which is formed on the polished surface of the glass substrate.
According to another aspect of the present invention, in the reflecting mirror mentioned above, the glass substrate is produced by a float process to have minute irregularities of 0.1 &mgr;m or less on the measurement condition that the cut-off value is 0.8 mm to 8 mm.
According to still another aspect of the present invention, in the reflecting mirror mentioned above, the predetermined surface waviness is 0.05 &mgr;m or less on the measurement condition that the cut-off value is 0.8 mm to 8 mm.
According to still another aspect of the present invention, in the reflecting mirror mentioned above, the reflecting film is obtained by film-forming in the order of aluminum (Al), magnesium fluoride (MgF
2
) and titanium dioxide (TiO
2
). Formed by this method, it is possible that the reflecting mirror has a reflectance of 94%, while a reflecting mirror formed only of aluminum has a lesser reflectance of 88-90%.
According to still another aspect of the present invention, there is provided a rear projection display, comprising the reflecting mirror mentioned above, an optical unit, and a screen.
REFERENCES:
patent: 4072541 (1978-02-01), Meulenberg, Jr. et al.
patent: 4456336 (1984-06-01), Chung et al.
patent: 4928301 (1990-05-01), Amoot
patent: 5447208 (1995-09-01), Lund et al.
patent: 5549212 (1996-08-01), Kanoh et al.
patent: 5929954 (1999-07-01), Negishi et al.
“Surface Roughness-Definitions and Designation,”Japanese Industrial StandardUIS B 0601 (1994).
Akimoto Toshio
Nishikawa Hiroshi
Merchant & Gould P.C.
Nippon Sheet Glass Co. Ltd.
Sikder Mohammad
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