Acoustic touchscreen constructed directly on a cathode ray tube

Details Acoustic touchscreen constructed directly on a cathode ray tube Acoustic touchscreen constructed directly on a cathode ray tube

1999-03-26

2001-05-01

Hjerpe, Richard A. (Department: 2774)

Computer graphics processing and selective visual display system

Display peripheral interface input device

Touch panel

C345S173000

Reexamination Certificate

active

06225985

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an acoustic touchscreen constructed directly on a cathode ray tube, and methods therefor.
2. Description of Related Art
An acoustic touchscreen has a touch-sensitive area on which the occurrence and location of a touch is sensed via the touch's effect on the transmission of acoustic waves thereacross. A common type of acoustic touchscreen employs Rayleigh waves (a term which, as used herein, subsumes quasi-Rayleigh waves). Illustrative disclosures relating to Rayleigh wave touchscreens include Adler, U.S. Pat. No. 4,642,423 (1987); U.S. Pat. No. 4,645,870 (1987); U.S. Pat. No. 4,700,176 (1987); U.S. Pat. No. 4,746,914 (1988) (hereinafter “Adler '914”); U.S. Pat. No. 4,791,416 (1988); and Re 33,151 (1990); Adler et al., U.S. Pat. No. 4,825,212 (1989); U.S. Pat. No. 4,859,996 (1989); and U.S. Pat. No. 4,880,665 (1989); Brenner et al., U.S. Pat. No. 4,644,100 (1987); Davis-Cannon et al., U.S. Pat. No. 5,739,479 (1998); and Kent, U.S. Pat. No. 5,708,461 (1998) and U.S. Pat. No. 5,854,450 (1998). Acoustic touchscreens employing other types of acoustic waves such as Lamb or shear waves, or combinations of different types acoustic waves (including combinations involving Rayleigh waves) are also known, illustrative disclosures including Kent, U.S. Pat. No. 5,591,945 (1997) and U.S. Pat. No. 5,854,450 (1998); Knowles, U.S. Pat. No. 5,072,427 (1991); U.S. Pat. No. 5,162,618 (1992); U.S. Pat. No. 5,177,327 (1993); U.S. Pat. No. 5,243,148 (1993); U.S. Pat. No. 5,329,070 (1994); and U.S. Pat. No. 5,573,077; and Knowles et al., U.S. Pat. No. 5,260,521 (1993). The documents cited in this paragraph are incorporated herein by reference.
FIG. 1
illustrates the operation of a typical acoustic touchscreen
1
, having an active, or touch-sensitive area
2
. A first transmitting transducer
3
a
is positioned outside of touch-sensitive area
2
, acoustically coupled to the surface of touchscreen
1
, and sends an acoustic signal in the form of an acoustic wave
11
a
traveling parallel to the top edge of touchscreen
1
and generally in the plane of touchscreen
1
. Aligned in the transmission path of acoustic wave
11
a
is a linear array of partially acoustically reflective elements
4
a
, each of which partially reflects (by approximately 90°) and partially transmits the acoustic signals, creating a plurality of acoustic waves (exemplarily
5
a
,
5
b
, and
5
c
) traveling vertically (parallel to the Y-axis) across touch-sensitive area
2
. (The spacing of reflective elements
4
a
is variable to compensate for the attenuation of the acoustic signals with increasing distance from first transmitter
3
a
.) Acoustic waves
5
a
,
5
b
, and
5
c
, upon reaching the lower edge of touchscreen
1
, are again reflected by approximately 90° (arrow
11
b
) by another linear array of similarly partially acoustically reflective elements
4
b
towards a first receiving transducer
6
a
, where they are detected and converted to electrical signals for data processing. Along the left and right edges of touchscreen
1
are located a similar arrangement. A second transmitting transducer
3
b
generates an acoustic wave
12
a
along the left edge, and a linear array of partially acoustically reflective elements
4
c
creates therefrom a plurality of acoustic waves (exemplarily
7
a
,
7
b
, and
7
c
) traveling horizontally (parallel to the X-axis) across touch-sensitive area
2
. Acoustic waves
7
a
,
7
b
, and
7
c
are redirected (arrow
12
b
) by yet another linear array of partially acoustically reflective elements
4
d
towards receiving transducer
6
b
, where they are also detected and converted to electrical signals.
If touch-sensitive area
2
is touched at position
8
by an object such as a finger or a stylus, some of the energy of the acoustic waves
5
b
and
7
a
is absorbed by the touching object. The resulting attenuation is detected by receiving transducers
6
a
and
6
b
as a perturbation in the acoustic signal. Analysis of the data with the aid of a microprocessor (not shown) allows determination of the coordinates of position
8
.
Those skilled in the art will appreciate that it is not essential to have two sets of transmitting/receiving transducers to make a touchscreen. The device of
FIG. 1
, without one set of transducers, will still function as a touchscreen, detecting the occurrence of a touch and providing limited location information (one of the coordinates). Or, a touchscreen can be designed with only two transducers by using a common transmit/receive transducer scheme, as disclosed in Adler '914 (FIG. 8).
In normal usage a housing
9
, typically made of molded polymer, is associated with touchscreen
1
. Housing
9
contains a bezel
10
that overlays touchscreen
1
, concealing the transmitting and receiving transducers, the reflective elements, and other components, but exposing touch-sensitive area
2
. This arrangement protects the concealed components from contamination and/or damage, presents a more aesthetically pleasing appearance, and defines the touch-sensitive area for the user.
A touchscreen may comprise a separate faceplate (typically made of glass, but other hard substrates may be used) overlaid on a display panel such as a cathode ray tube (CRT), a liquid crystal display (LCD), plasma, electroluminescent, or other type of display. Alternatively it has been proposed to construct a touchscreen directly on the glass surface of a CRT, so that the CRT surface is the touch-sensitive surface, Adler '914 discloses such a construction. A direct-on-CRT touchscreen construction is desirable because it eliminates a piece of glass or other material between the viewer and the CRT, increasing the perceived display brightness. Also, there are economic advantages in dispensing with the overlay glass and not having to modify CRT chassis to make room for the overlay glass.
FIG. 2
a
shows a conventional CRT
15
on which a touchscreen may be constructed. CRT
15
comprises two glass sections, a rear tapering section referred to as a funnel
28
and, in front thereof, a panel
27
. In turn, panel
27
includes a substantially rectangular frontal region
16
on which an image is displayed and which, if a touchscreen is installed, also serves as touch-sensitive area
2
. Ancillary features include mounting ears
18
for attaching the housing (not shown) and a protective steel implosion band
23
.
Frontal region
16
typically is not truly flat, but curved to an extent varying from CRT to CRT, with the more expensive CRT's tending to be less curved. But, for general purposes and also for the purposes of this invention, frontal region
16
may be considered to be substantially planar and defining a plane. Panel
27
further has, outside of the viewing area (and the touch-sensitive area, if a touchscreen has been installed) and below frontal region
16
, a shoulder region
17
where the glass curves down and away from the plane of frontal region
16
. Shoulder region
17
includes corner regions
26
having complex non-Euclidean topography, at the confluences of the corners of frontal region
16
and shoulder region
17
. The degree of curvature of CRT
15
's glass surface in shoulder region
17
(including corner regions
26
) may be quite high, compared to that of frontal region
16
. The radius of curvature of frontal region
16
may be on the order of 50 centimeters or more, while shoulder region
17
may have much smaller radii of curvature, on the order of a few centimeters. Thus, transition
29
from frontal region
16
to shoulder region
17
may be defined as occurring where there is a sharp discontinuity (decrease) in the radius of curvature of the glass surface. If frontal region
16
is treated as being substantially planar, the plane perpendicular to the axis of the CRT and intersecting this discontinuity may be considered to be its plane.
In building a direct-on-CRT touchscreen, the touchscreen manufacturer normally does not manufacture the CRT itself. Rather, the

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