Abstract:
A display for an instrument includes a graphical display and a tabular display. On the graphical display is shown a plurality of traces. The tabular display lists, for each of at least a portion of the traces, a center point of interest to a user. Upon the user selecting a first center point for a first trace, the graphical display shows just the first trace. A horizontal span of the graphical display is adjusted to equal a preselected zoom span.

Description:
BACKGROUND 
     The present invention pertains to display of signals and pertains particularly to a waveform zoom feature within an instrument having a table driven graphical display. 
     Signal analysis systems, such as optical spectrum analyzers, multi-wavelength meters and oscilloscopes, generally allow display of one or more waveforms, each waveform representing a signal or signal portion. Some signal analysis systems allow both a tabular display and a graphical display of multiple waveforms. 
     It is often desirable to zoom in on particularly areas of interest in a single waveform within a graphical display of multiple waveforms. For example, within a spectral analysis system, to graphically view the center wavelength of a particular waveform of interest, a user first manually enters the center wavelength. The center wavelength can be obtained, for example, from a value listed in a tabular display. The user can then manually adjust the graph wavelength span until the desired view is achieved. 
     Alternatively, to graphically view the center wavelength of a particular waveform of interest, a marker search function can be used to position a marker on the signal of interest. If available, the user can then utilize a “Marker-&gt;Center” function. After the “Marker-&gt;Center” function is used, the user can manually adjust the graph wavelength span until the desired view is achieved. 
     The above-described methods to graphically view the center wavelength of a particular waveform of interest both require the user to perform several manual adjustments in order to achieve the desired graphical view of the desired waveform. In order to restore the original multi-waveform view, the user then has to perform several more manual adjustments. 
     The situation is the same for other types of instruments that provide both a graphical view of a raw measurement trace along with some number of numerical parameters derived from the raw measurement trace. If the user is interested in zooming in on just the portion of the trace used to calculate a particular numerical parameter, the graphical limits must be adjusted manually. 
     SUMMARY OF THE INVENTION 
     In accordance with the preferred embodiment of the present invention, a display for an instrument includes a graphical display and a tabular display. On the graphical display is shown a plurality of traces. The tabular display lists, for each of at least a portion of the traces, a center point of interest to a user. Upon the user selecting a first center point for a first trace, the graphical display shows just the first trace. A horizontal span of the graphical display is adjusted to equal a preselected zoom span. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a flowchart that describes operation of a waveform zoom feature within an instrument having a table driven graphical display in accordance with a preferred embodiment of the present invention. 
     FIG. 2 shows a display of multiple traces within a table driven graphical display. 
     FIG. 3 illustrates a waveform zoom feature within an instrument having a table driven graphical display in accordance with a preferred embodiment of the present invention. 
     FIG. 4 also illustrates a waveform zoom feature within an instrument having a table driven graphical display in accordance with a preferred embodiment of the present invention. 
     FIG. 5 illustrates return to a display of multiple traces within a table driven graphical display. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a flowchart that describes operation of a waveform zoom feature within an instrument having a table driven graphical display. The instrument is, for example, an optical spectrum analysis instrument, such as a multi-wavelength meter (MWM) or optical spectrum analyzer (OSA) used to characterize a signal made up of one or more laser lines. Alternatively, the instrument can be another instrument used for signal analysis, such as an oscilloscope. 
     A user of a MWM or an OSA is usually interested in several pieces of information. For example, the user typically wants to know what is the center wavelength and peak power of a detected laser line. The user also may want to know what is the qualitative spectral characteristics of individual laser lines. 
     In the preferred embodiment, a tabular display is used to list all of the detected peaks by their center wavelength and peak power level. A graphical display is used to display the function of power versus wavelength for the measurable spectrum. By adjusting start wavelength and stop wavelength or center wavelength and wavelength span, a user can manually “zoom” the graphical display to get a more detailed view of a selected laser line. 
     The preferred embodiment of the present invention, allows the user to automatically zoom the graphical display to any waveform of interest by simply selecting a center wavelength cell for the waveform in the tabular display. 
     In block  11  of the flowchart shown in FIG. 1, a center wavelength is selected. This is illustrated by FIG.  2 . FIG. 2 shows a display  20  of an instrument. The display includes a graphic display  21  and a tabular display  22 . Multiple traces are shown within graphic display  21 . Each trace is a waveform representing, for example, a laser line within an optical transmission system. A scroll bar  23  can be used to scroll tabular display  21 . 
     Within tabular display  22 , a first column indicates a channel number for a single trace (waveform). A second column indicates a center wavelength for the waveform. A third column indicates peak power for the waveform. A forth column includes a bar that graphically represents power. A scroll bar  24  is used to scroll tabular display  22 . 
     A cursor  26  is controlled by a pointing device, such as a mouse or touchpad, to select one of the center wavelengths listed in the second column. For example a center wavelength is selected by a user placing cursor  26  over one of the center wavelengths listed in the second column of tabular display  22  and “clicking” a button on the pointing device. In FIG. 2, cursor  26  is shown selecting the center wavelength for the channel 1 wavelength. 
     In a block  12  of the flowchart shown in FIG. 1, a check is made to ascertain whether the zoom feature is active. Within the example shown in FIG. 2, the zoom feature was not active. When the zoom feature is not active, in a block  13 , the current graph start and stop wavelengths are stored. This stores the current state of graphic display  21 . Then, in a block  14  of the flowchart shown in FIG. 1, the selected waveform is displayed. The center wavelength for graphic display  21  is set to the center wavelength for the selected waveform. The wavelength span for graphic display  21  is set equal to a preselected zoom span. The selected cell in tabular display  22  is also highlighted. 
     This is illustrated by FIG.  3 . In FIG. 3, the waveform for channel 1 is selected. The center wavelength for graphic display  21  is set to 1553.3 nanometers (nm) which is approximately the center wavelength for the waveform for channel 1. The wavelength span for graphic display  21  is set equal to 0.6 nm which is the preselected zoom span. The selected cell in tabular display  22  is also highlighted. 
     As shown in FIG. 1, after completing the zoom display of the waveform, in a block  17 , the zoom display routine is completed. 
     If in block  12  of the flowchart shown in FIG. 1, the check determines that the zoom feature is active, in a block  15 , a check is made to determine whether the row in which the selected center wavelength cell resides is the current zoom row. If not, block  14  is performed for the selected center wavelength cell. 
     This is illustrated in the transition from the state of display  20  shown in FIG. 3 to the state of display  20  shown in FIG.  4 . From the state of display  20  shown in FIG. 3, the user uses cursor  26  to select the center wavelength for the channel 4 waveform. Since the zoom feature was active and the center wavelength for the channel 4 waveform is represented in a different row that the center wavelength for the channel 1 waveform, block  14  of FIG. 1 has been executed for the channel 4 wavelength. 
     Specifically, in FIG. 4, the waveform for channel 4 is selected. The center wavelength for graphic display  21  is set to 1556.9 nm, which is approximately the center wavelength for the waveform for channel 4. The wavelength span for graphic display  21  is set equal to 0.6 nm, which is the preselected zoom span. The selected cell in tabular display  22  is also highlighted. 
     If in block  15  of the flowchart shown in FIG. 1, the check determines the row in which the selected center wavelength cell resides is the current zoom row, in a block  16  the previously stored graph start and stop wavelengths are restored. This is illustrated in the transition from the state of display  20  shown in FIG. 4 to the state of display  20  shown in FIG.  5 . From the state of display  20  shown in FIG. 4, the user uses cursor  26  to again select the center wavelength for the channel 4 waveform. Since the zoom feature was active and the center wavelength for the channel 4 waveform was reselected, block  16  of FIG. 1 has been executed. This is illustrated in FIG. 5 by the restoration of the start and stop wavelengths resulting in the restoration of the wavelength span and center of graphical display  21 . Also, all the waveforms are now displayed in graphical display  21  and no cell in tabular display  22  is highlighted. 
     As illustrated above, the preferred embodiment of the present invention allows a user to view an entire spectrum, and, with a single action, zoom in to see the detailed spectral characteristics of any and all waveforms of interest. When this detailed viewing of an individual waveform is completed, with another single action the user can return the graphical displays to the previous “pre-zoom” limits, typically a display of the entire measurement spectrum. 
     The present invention allows for greatly improved ability for the user of an instrument to quickly retrieve both qualitative and quantitative information. The present invention is applicable to any measurement instrument that displays both a graphical representation of the raw measurement data and some number of numerical parameters calculated from features in the raw measurement data. For example, in an alternative embodiment of the present invention, an oscilloscope can display both the raw time-domain trace of an electrical signal along with a measured rise time parameter for a detected rising-edge in the signal. The user may wish to zoom-in on just the portion of the trace used to calculate the rise time parameter. Implementing the present invention in this scenario allows, for example, the oscilloscope to make the rise time display text “active” and the user to click on this text to zoom-in on that portion of the trace. 
     Embodiments of the present invention allow an unprecedented level of ease-of-use in correlating between quantitative and qualitative information in measurement instruments. Many manual operations can be replaced with a single selection, allowing the user to focus on interpretation of the information presented by the graphical display and not on the instrument-centric operations required to format the graphical data appropriately for viewing. 
     The foregoing discussion discloses and describes merely exemplary methods and embodiments of the present invention. As will be understood by those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.