Horology: time measuring systems or devices – Displays or display device details – Optical
Reexamination Certificate
2000-03-03
2003-02-11
Miska, Vit (Department: 2841)
Horology: time measuring systems or devices
Displays or display device details
Optical
C368S084000, C349S096000, C349S097000, C349S113000, C359S487030, C359S490020, C359S506000
Reexamination Certificate
active
06519209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device for displaying characters, numbers, patterns, etc. The present invention also relates to electronic watches, such as a wristwatch, a stopwatch, etc., incorporating the display device. Particularly, the present invention relates to a display device, such as a liquid-crystal display element, which displays information by selecting between a state which varies the polarization axis of a linearly polarized light component transmitted therethrough and a state which does not vary the polarization axis.
2. Description of Related Art
Electronic watches are the most common display devices which make use of outdoor external light to present a display. In one of the known electronic watches, a first polarizer, a polarization axis varying optical element (polarization axis varying means), such as a liquid-crystal display element, which selects between a state for varying the polarization axis of a linearly polarized light component transmitted therethrough and a state for not varying the polarization axis of the linearly polarized light component, a second polarizer, and a reflector, are laminated in that order. The liquid-crystal display element employs TN (Twisted Nematic) liquid crystal, STN (Super-Twisted Nematic) liquid crystal, or ECB (Electrically Controlled Birefringence) liquid crystal, for example.
In the electronic watch (the display device) thus constructed, each of the first and second polarizers transmits a linearly polarized light component, of an incident light ray, in alignment with its polarization axis, while absorbing a linearly polarized light component aligned in its absorption axis perpendicular to the polarization axis. Therefore, when an external light ray enters the first polarizer, only a linearly polarized light component having the polarization axis in a first direction is incident on the polarization axis varying optical element. Out of a linearly polarized light component transmitted through an area of the polarization axis varying optical element which varies the polarization axis and a linearly polarized light component transmitted through an area of the polarization axis varying optical system which does not vary the polarization axis, one of the linearly polarized light components is absorbed by the second polarizer while the other of the linearly polarized light components is transmitted through the second polarizer and reaches the reflector. Only a light ray reflected from the reflector, namely, a light ray which is transmitted through one of the area of the polarization axis varying optical element which varies the polarization axis and the area of the polarization axis varying optical element which does not vary the polarization axis, is transmitted through the polarization axis varying optical element and the first polarizer, and based on this light ray, time is visibly recognized.
In the conventional electronic watch, out of the linearly polarized light component transmitted through the area of the polarization axis varying optical element which varies the polarization axis and the linearly polarized light component transmitted through the area of the polarization axis varying optical element which does not vary the polarization axis, only one of the linearly polarized light components is reflected from the reflector, and is then transmitted through the polarization axis varying optical element and the polarizer, and then contributes to the displaying. On the other hand, the light ray transmitted through the other area is absorbed through the second polarizer, and contributes nothing to the displaying.
The conventional electronic watch thus suffers a problem that a segment portion or a background portion becomes a dark display. The legibility and brightness of the display are greatly affected by the light quantity of linearly polarized light component transmitted through the polarizers. For the same reason in the conventional electronic watch, it is difficult to present both the segment portion and the background portion in a mirror-like image, a matte image or a color display.
Also in the conventional electronic watch, a linearly polarized light component, which is supposed to be transmitted through the polarizers, is absorbed by the polarizer and contributes nothing to the displaying, because the orientation of the polarization axis is deflected from the polarization axis of the polarizer.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the above problems, and two principal objects are set as follows. A first object of the present invention is to provide a display device and an electronic watch employing the display device, which presents a high legibility and gives a reflective display made up of combinations of a diversity of textures and tones, by making use of external light and by outputting toward the user a linearly polarized light component, regardless of whether it is transmitted through the area for varying the polarization axis or the area for not varying the polarization axis.
A second object of the present invention is to provide a display device and an electronic watch employing the display device, which increases the quantity of light contributing to displaying and presents a bright display by transmitting a linearly polarized light component, even with its polarization axis deflected, through the polarizing splitter means, of linearly polarized light components, transmitted through polarizing splitter means and in order to contribute to displaying.
The present invention has been developed in view of the above background, and to achieve the first object, the following display device is provided. The display device includes first polarizing splitter means (first polarization separator) which transmits a linearly polarized light component, of an incident light ray, aligned in a first direction, while not transmitting a linearly polarized light component aligned perpendicular thereto, polarization axis varying means (polarization changing element) which selects one of a first state which varies the polarization axis of an incident linearly polarized light component when the incident linearly polarized light component is transmitted therethrough and a second state which does not vary the polarization axis when the incident linearly polarized light component is transmitted therethrough, second polarizing splitter means (second polarization separator) which transmits a linearly polarized light component, of an incident light ray, aligned in a second direction, while specularly reflecting a linearly polarized light component aligned in a third direction perpendicular to the second direction, and specular reflective means (reflecting element) which specularly reflects a linearly polarized light component, transmitted through the second polarizing splitter means, toward the second polarizing splitter means, wherein the first polarizing splitter means, the polarization axis varying means, the second polarizing splitter means, and specular reflective means are arranged in that order, and wherein the display device displays predetermined information using a first returning light ray which is specularly reflected from the specular reflective means, and transmitted through the second polarizing splitter means, the polarization axis varying means, and the first polarizing splitter means, and a second light ray which is specularly reflected from the second polarizing splitter means, and transmitted through the polarization axis varying means and the first polarizing splitter means, out of light rays which come in on the first polarizing splitter means from the side of the first polarizing splitter means diametrically opposite to the polarization axis varying means.
The specular reflective means may be a total reflection optical element for reflecting the total of or most of the linearly polarized light component incident thereon.
The total reflection optical element may be a total reflection mirror for reflecting th
Arikawa Yasuo
Matsui Tsuyoshi
Goodwin Jeanne-Marguerite
Miska Vit
Seiko Epson Corporation
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