Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-04-27
2004-07-20
Shalwala, Bipin (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
Reexamination Certificate
active
06765550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to apparatus providing for private viewing of information displayed on the LCD screen of a notebook or laptop computer, and, more particularly, to a filtering device extending in front of an LCD screen, having an active mode in which a limitation is placed on the viewing angle through which data on the screen can be read and an inactive mode, in which the screen can be viewed normally.
2. Background Art
Laptop or notebook computers are often used in crowded, public places such as airplanes for writing personal or otherwise confidential information. Under such circumstances, there is generally a concern the a nearby person, such as the person in the next airplane seat, may be reading sensitive material. This concern keeps many people from using a laptop computer in many instances when its use would be particularly convenient. If the computer is used in this way, sensitive data may be stolen.
Privacy can be provided during the use of a laptop computer by restricting the viewing angle through which the screen may be viewed, so that only the person sitting directly in front of the screen can read the data written on it. This angle can be limited by holding a privacy screen across the front of the computer display screen, so that the display screen can only be viewed through the privacy screen.
FIG. 1
is a fragmentary cross-sectional view of a first type of privacy screen
10
placed in front of a computer display screen
12
. The privacy screen
10
includes a number of partitions
14
separated by transparent light channels
16
. The partitions
14
limit the angle at which light is transmitted through the privacy screen
10
to the angle indicated by the reference numeral
18
. When a portion of the screen is viewed from outside this angle, it appears to be dark. If the partitions
14
extend only vertically, the angle of view is limited from side to side, so that a person sitting next the person using the computer is prevented from reading the data on the screen. If the partitions
14
extend horizontally, as well as vertically, the angle of view is also limited vertically, so that a person standing behind the person sitting and using the computer is also prevented from reading the data on the screen. An example of a privacy screen having closely-spaced partitions or louvers is sold by the 3M Company as a PF14.1 Notebook Privacy Filter.
The partitions may be small louvers, ridges, or other shapes. A number of examples from the patent literature describe ways of making and using films including such shapes. For example, U.S. Pat. No. 4,766,023 describes a louvered plastic film that can be more easily handled and installed by coating at least one surface with a solvent-free monomer composition and exposing the coating to ultraviolet radiation to polymerize the coating. U.S. Pat. No. 4,764,410 describes such a film in which the coating is polymerized to an adhesive state, preferably forming a pressure-sensitive adhesive. U.S. Pat. No. 4,812,702 describes a privacy screen using a pair of films with small louvers, placed against one another so that the image from a color CRT must pass through both the films. The louvers of each of the films are tilted in opposite directions at angles from the vertical, substantially reducing any visual Moire patterns resulting from an interaction between the pixels on the CRT screen and the louvers. U.S. Pat. No. 5,528,319 describes a privacy filter having two or more aligned and spaced-apart grids, each of which includes a array of strips blocking light transmission. U.S. Pat. No. 5,993,940 describes a composite including a polymeric film having a first generally planar major surface and an opposite second major surface defined by a multiplicity of elongate parallel contiguous ridge portions, each of which has a generally triangular cross section. The film can provide visual transmission between its first major surface and its second major surface, while coatings along obscured portions of the second major surface prevent viewing of visual images through the film.
The patents referenced above do not describe a means for selectively providing the effect of the louvers or partitions. Such means for selectively providing is particularly desirable in the application of a method for achieving privacy in the use of a notebook computer, since such a device is typically used both in public places, such as airplanes and waiting rooms, requiring such privacy, and in more private places, where there is no need for such privacy. In such more private places, a failure to cancel the effect of the louvers or partitions means that the notebook computer is unnecessarily difficult to use, first because the privacy film covering the screen of the computer absorbs a significant portion of the light used to form the image visible on the screen, and second because it is often more difficult to use a computer when the screen has a narrow angle of view. In particular, what is needed is a convenient way to move a louvered privacy filter into place in front of the LCD screen of a notebook computer for use in a situation requiring privacy, and to move the louvered privacy filter out of place to be stored within the notebook computer for use in a situation not requiring privacy.
One method for varying the angle through which an LCD screen may be viewed is described in U.S. Pat. No. 6,211,930, which describes variable viewing angle LCD systems for use in automatic teller machines where, during parts of a transaction, it is desirable that information on the screen can be read only by the person using the machine and standing directly in front of the screen. The system includes conventional elements for backlighting a transmission type LCD screen, with such conventional backlighting elements including a reflector, a light source, and an optional brightness enhancer. A collimator and a variable diffuser are interposed between these conventional backlighting elements and the LCD screen. The collimator consists of a pair of louver films through which light passes only in essentially straight lines. The variable diffuser, which can be switched between a transparent state and a scattering state by the application of an electric field, may be a polymer dispersed liquid crystal cell or reverse mode polymer stabilized collisteric texture cell. When the variable diffuser is in its transparent state, the light passing through the LCD screen remains collimated, so that the screen is only visible over a narrow viewing angle. When the variable diffuser is set to scatter the collimated light, light passes through the LCD screen at a range of angles, so a large angle of viewing is made available.
What is needed is a method for varying the angle of view without requiring the illumination for wide angles to be first collimated and then scattered. The process of collimating absorbs much of the illumination, in the form of light not passing through the louvers in essentially straight lines. Then, for wide angle viewing, the light is scattered by the diffuser, lowering the peak level of illumination at a viewing angle perpendicular to the screen.
FIG. 2
is a fragmentary cross-sectional view of a second type of privacy screen
20
placed in front of a liquid crystal display (LCD) screen
22
. This privacy screen
20
is a polarizing film, which takes advantage of the fact that the light output of the LCD
22
, is strongly polarized. The LCD screen
22
is of a conventional type, including a light source
26
, such as a flourescent light; a diffuser
27
, which directs light from the light source in the outward direction of arrow
28
; an inner polarizing filter
30
; a liquid crystal panel
32
including liquid crystal material
34
, extending between a pair of glass plates
36
; and an outer polarizing filter
38
. Light emitted by the light source
26
is polarized by the inner polarizing filter in a first direction, forming a plane polarized area of illumination passing through the liquid crystal panel
32
and throug
Janick Jan Michael
Locker Howard Jeffrey
Resnick Russell Alan
Davidge Ronald V.
Dharia Prabodh
International Business Machines - Corporation
Munoz-Bustamante Carlos
Shalwala Bipin
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