Optical: systems and elements – Glare or unwanted light reduction
Reexamination Certificate
1999-12-17
2001-08-07
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Glare or unwanted light reduction
C359S603000, C359S604000, C359S608000, C359S609000, C359S610000
Reexamination Certificate
active
06270223
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an electro-optical filtering device and more particularly, to a glare-protection device.
BACKGROUND OF THE INVENTION
A filter device is used as a glare-protection device, for example, in protective welders' masks, welders' helmets or welders' goggles. Such a device comprises a light-protection filter with at least one active optical filter element, an electronic device for controlling the at least one active optical filter element, a light sensor working together with the electronic device, an electric power supply, in particular a solar cell, for the electronic device and the at least one active filter element.
Glare-protection devices of this type are known, for example from WO 96/10767 and EP-A-0 678 288. Usually they contain a liquid crystal cell (LC cell) as the active filter element, which more or less blocks the penetration of light as soon as the light sensor is acted upon by light past a preset intensity threshold. Such filter devices have many uses, a typical example is the use as windows for protective welders' masks, welders' helmets or welders' goggles.
The filter devices described in the mentioned publications are designed as so-called “monoblocs”, i.e. they physically consist of a single component containing all functional elements of the filter device. Here, the functional elements have been encapsulated in a thin plate and in this way are protected from the effects of the surroundings. Because of the design as a thin, plate-shaped monobloc, the physical compatibility with the common passive light-protection filters (dark glasses) is achieved, so that the filter device can be directly exchanged against such passive light-protection filters. By means of this it is possible to retrofit glare-protection devices equipped with passive light-protection filters in a simple way by means of the more effective and more advantageous active electro-optical filter devices.
However, designing the filter in the form of a monobloc has the important economical disadvantage, also doubtful for reasons of protecting the environment, that the filter device as a whole must always be replaced, even if only one of its functional elements fails. Because of the encapsulated structure, a repair of the functional elements is as good as impossible.
SUMMARY OF THE INVENTION
This disadvantage is now intended to be overcome by a first aspect of the present invention, and the efficiency and multiplicity of use of an active electro-optical filter device of the type in accordance with the species is to be improved.
With an exemplary embodiment in accordance therewith, the filter component and the control component are embodied as physically separate components, which can be mechanically and electrically separated from each other, or respectively combined with each other to form a single unit, and to this end they are provided with mutually cooperating mechanical and electric components.
The filter component containing the light-protection filter, and the control component containing the electronics, the light sensor and the electrical power supply, are each preferably designed as encapsulated plates having a constant thickness of 1 to 5 mm for example. The filter component and the control component can also be of different thickness.
In accordance with this first basic concept of the invention, the filter device is therefore divided into two (or several) separate components, which are releasably connected with each other. Because of this division, in case of the loss of a functional element it is necessary to only replace the respective component. Furthermore, the division in accordance with the invention into control and filter components permits an increased constructive flexibility since, for example, the same control component can be employed together with different filter components. This results in considerable practical and economic advantages, both in use as well as in production.
The conventional filter devices described in the publications mentioned at the outset consist of active and passive filter elements with optical polarizers, which offer sufficient protection against ultraviolet, visible and infrared radiation and whose embodiment in the normal case includes a window designed in accordance with current production standards, such as EN 379 (90×35 mm) and EN 166 (96×25 mm). These windows are usually not sufficiently matched in the homogeneity of their light distribution to the right and the left eye to human visual perceptions, in particular if they use certain optically anisotropic technologies, or if they have been installed in an awkward position in a glare-protection cassette and protective welding mask. Besides a protection against optical radiation, protective devices should provide physiologically unhampered vision. Physiologically unhampered vision makes spatial vision easier, therefore assuring a sufficient feeling of balance, and provides protection from approaching objects. Interfering situations in the immediate area can be better detected by the user and therefore make his own actions easier.
When used as glare-protection devices, electro-optical filtering devices must be designed in such a way that the filtering devices interfere as little as possible with the effects of chronological and local actions on the eyes. This can only be assured if the geometric dimensions of the filter and its physical properties only affect and limit the information in a defined manner.
It is important for interference-free stereoscopic vision, or respectively the perception of spatial depth, and therefore for the orientation in space, that both eyes perceive the same brightness of the same object, along with a sufficient size of the field of vision. In this case the entire field of vision must not be homogeneously weakened by the same amount. It is only necessary to offer the same strength of illumination of the same object in the same viewing direction of the left and right eye.
A further important aspect of the present invention is to overcome these difficulties and to improve a glare-protection device of the type of the species designed as a mask, helmet or goggles in such a way that, in its employment in his work, it provides the user with a visual perception with the least physiological interference in all viewing directions possible through the filtering element, which therefore better meets basic requirements relating to safety, as well as improved spatial vision and therefore also an undisturbed feeling of balance and recognition of approaching objects.
In accordance with a further aspect of the invention, the dependence on the viewing angle of the light transmitted by the active optical filtering element is compensated by means of optically active or passive phase retardation elements (so-called retarders) in order to obtain a more homogeneous intensity distribution with less dependence on the viewing angle. The glare-protection device is equipped with a field of vision which is matched to the natural visual perception. With the glare-protection device in accordance with the invention, the combination of these two measures, i.e. the homogenization of the light distribution to both eyes with every shape and size of the filtering device by means of the employment of active and/or passive optical retarders, and the increase of the lateral field of vision of the filtering device, contributes to meeting the requirement for improved visual perception under extreme light conditions, for example in connection with electric welding.
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patent: 4130903 (1978-12-01), van den Berg et al.
patent: 4155122 (1979-05-01), Budmiger
patent: 5510609 (1996-04-01), Ackermann
patent: 5930047 (1999-07-01), Gunz et al.
patent: 6096212 (2000-08-01), Quick et al.
patent: 25 50 559 (1977-09-01), None
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patent: 0 678 288A2 (1996-10-01), None
patent: 2 122 366A (1984-01-01), None
patent: 96/10767 (1996-04-01), None
patent: 97/15255 (1997-05-01), None
Del Bon Franco
Keller Leo
Syré Phillip
Burns Doane Swecker & Mathis L.L.P.
Optrel AG
Sikder Mohammad
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