Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-06-25
2002-04-30
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C345S440000, C324S12100R
Reexamination Certificate
active
06380939
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to user controls for an oscilloscope, and in particular to control of horizontal display modes in an oscilloscope.
BACKGROUND OF THE INVENTION
Earlier analog oscilloscopes included a trigger circuit which analyzed an acquired input signal for a user selected event, e.g. a negative-going or positive-going transition at a user selected voltage level, and in a specified channel if the oscilloscope was a multichannel oscilloscope. When the trigger event occurred, a waveform representing the acquired input signal occurring from that point forward in time was displayed on the display screen of the oscilloscope. The trigger point was displayed as the leftmost point in the displayed waveform. The timing of the displayed waveform was controlled by the user, and could be changed. As the timing changed, the time (horizontal) magnification of the waveform also changed. The change was made relative to the trigger point, which remained fixed at the leftmost point of the displayed waveform.
FIG. 1
is a combined waveform and oscilloscope display diagram illustrating the trigger and horizontal magnification characteristics of an analog oscilloscope. In
FIG. 1
, a waveform
10
represents e.g. the voltage of an acquired input signal supplied to the oscilloscope via an oscilloscope probe. A user has set the trigger to the illustrated trigger point
12
in a known manner. A first display
11
is a waveform display on the display screen of the oscilloscope in which the time base is set to display the waveform
10
from the trigger point
12
to the point
14
. A second display
13
is a waveform display on the display screen of the oscilloscope in which the trigger point is the same as that in the first display
11
, but the time base has been adjusted to display the waveform
10
from the trigger point
12
to the point
16
.
It is apparent from
FIG. 1
that the trigger point
12
is displayed in the waveform display, regardless of the setting of the time base, and that the trigger point
12
is always displayed as the leftmost point of the waveform display. Furthermore, it is apparent that the displayed waveform is magnified from the trigger point
12
on. That is, the trigger point is co-located with the magnification point. Consequently, the waveform display may be magnified horizontally to any desired degree without losing the display of the trigger point
12
.
As digital oscilloscopes were developed, it became possible to display portions of the waveform occurring before the trigger point, as well as after. The trigger could be set by a user in the same manner as in analog oscilloscopes. However, instead of displaying the trigger point as the leftmost point in the displayed waveform. The trigger point could be displayed at any point in the displayed waveform. Also as with analog oscilloscopes, the timing of the displayed waveform was controlled by the user, and could be changed, thus changing the time (horizontal) magnification of the waveform. Again, as with analog oscilloscopes, the change was made relative to the trigger point, but in digital oscilloscopes, the trigger point was not constrained to be the leftmost point in the displayed waveform.
FIG. 2
is a combined waveform and oscilloscope display diagram illustrating the trigger and horizontal magnification characteristics of a digital oscilloscope. In
FIG. 2
, again a waveform
10
represents e.g. the voltage of an input signal supplied to an oscilloscope via an oscilloscope probe. A user has set the trigger to the illustrated trigger point
12
′ in a known manner. This trigger point
12
′ is different than that set in
FIG. 1
, however. A first display
21
is a waveform display on the display screen of the oscilloscope in which the time base is set to display the waveform
10
from the point
22
to the point
24
, and includes the trigger point
12
′ within the displayed waveform. A second display
23
is a waveform display on the display screen of the oscilloscope in which the trigger point
12
′ is displayed in the same position as that in the first display
21
, but the time base has been adjusted to display the waveform
10
from the point
26
to the point
28
.
It is apparent from
FIG. 2
that, as in
FIG. 1
, the trigger point
12
′ is displayed in the waveform display, regardless of the setting of the time base. However, in
FIG. 2
, the trigger point
12
′ is displayed within the waveform display, not at the leftmost edge, as in FIG.
1
. It is also apparent that, as in
FIG. 1
, the magnified signal in display
23
is magnified about the location of the trigger point
12
′. Thus, the trigger point is co-located with the magnification point. That is, the trigger point remains in the same place in the waveform display, while the displayed waveform expands or contracts around that point as the time base is changed by the user. Consequently, the waveform display may still be magnified horizontally to any desired degree without losing the display of the trigger point.
Other digital oscilloscopes used a different technique for triggering the waveform display, termed a viewport technique. In such a digital oscilloscope, the displayed waveform is displaced by some user controlled amount of time from the trigger point. This display is termed a viewport. The displayed waveform in the viewport does not, necessarily, contain the trigger point. The magnification of the displayed waveform takes place within the viewport and the displayed waveform expands and contracts around a magnification point, which may be any point on the display screen, such as the leftmost point of the viewport. In a preferred embodiment, however, the magnification point is the center point of the display screen.
FIG. 3
is a combined waveform and oscilloscope display diagram illustrating the trigger and horizontal magnification characteristics of a digital oscilloscope. In
FIG. 3
, again a waveform
10
represents e.g. the voltage of an input signal supplied to an oscilloscope via an oscilloscope probe. A user has set the trigger to the illustrated trigger point
12
in a known manner. This trigger point
12
is the same that set in FIG.
1
. In
FIG. 3
, a user has set a time displacement to point
32
of the input signal. This is a point after the trigger point, and is referred to as a positive time displacement. It is also possible for a user to specify a negative time displacement to a point before the trigger point. A first display
31
is a waveform display on the display screen of the oscilloscope in which the time base is set to display the waveform
10
starting from the time displacement point
32
to the point
34
. The center point of the display screen corresponds to point
35
of the waveform
10
. A second display
33
is a waveform display on the display screen of the oscilloscope in which the time base has been adjusted to display the waveform
10
from the point
36
to the point
38
. The center point of the display screen continues to correspond to point
35
of the waveform
10
. The point
35
, thus, is the magnification point.
It is apparent from
FIG. 3
that the trigger point
12
is not necessarily displayed in the waveform display, depending upon the settings of the time displacement and the time base. Also, in
FIG. 3
, the magnified signal in display
33
is magnified about the center point of the waveform display. Thus, in
FIG. 3
, the trigger point
12
is not co-located with the magnification point
35
. Instead, the displayed waveform expands or contracts around the magnification point
35
, which corresponds to the display screen center point, as the time base is changed by the user.
One skilled in the art will understand that more sophisticated triggering techniques exist. For example, there may be what is termed a main trigger, which analyzes an acquired input signal for a user specified main trigger event, and a secondary, or delayed trigger. These operate in the following manner: after the main trigger detects the main tr
Dobyns Kenneth P.
Maguire David P.
Caracappa David N.
Hjerpe Richard
Lenihan Thomas F.
Nguyen Kimnhung
Tektronix Inc.
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