Abstract:
An apparatus can include a digitizer configured to digitize input data into a plurality of digitized signals, a rasterizer configured to generate a plurality of raster images from the plurality of digitized signals, the rasterizer including a subtractor configured to decrement a pixel intensity counter, a processor configured to manipulate the raster images based on the pixel intensity counter, and a display device configured to display the raster images.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to test and measurement apparatuses, such as oscilloscopes. In particular, oscilloscopes capable of displaying digitized waveforms with a modified persistence decay algorithm are described. 
       BACKGROUND 
       [0002]    Known oscilloscopes are not entirely satisfactory for the range of applications in which they are employed. For example, existing oscilloscopes are incapable of displaying anomalous or infrequent waveforms with sufficient intensity and for a sufficient period of time, thus denying the ability of a user to adequately view the waveforms before they dissipate from being displayed. In addition, conventional oscilloscopes having modifiable persistence decay algorithms fail to allow an anomalous waveform to be displayed for a predetermined period of time as defined by the user. 
         [0003]    Examples of references relevant to addressing these problems can be found in the following U.S. patent references: U.S. Pat. Nos. 4,504,827; 5,283,596; and 6,333,732. However, each of these references suffers from one or more of the following disadvantages: anomalous waveforms decay away too quickly and aren&#39;t displayed in a discernible manner for the user to perceive them. 
         [0004]    One example of how existing oscilloscopes display waveforms can be seen in  FIGS. 1A and 1B . In  FIG. 1A , a waveform that occurs frequently  102  and a waveform that is significantly different from the frequently-occurring waveform  104  are shown in a very early stage of rasterization. Specifically, the pixel intensities  106  and  107  of pixels of both waveforms,  103  and  105  respectively, are illustrated as having low or minimum intensity upon initial rasterization. It should be noted that the pixel “blocks”  103  and  105  represent a single pixel along each waveform  102  and  104 , and each waveform actually contains many pixels represented on the screen by a 32-bit value. 
         [0005]    Turning attention to  FIG. 1B , at some point in time after initial rasterization occurs, a frequently-occurring waveform  102  will be drawn with pixels  103  that have much greater intensity as evidenced by the maximum value  106  stored in the pixel intensity counter. In contrast, a waveform  104  that is significantly different from the frequently-occurring waveform  102  will be dimly lit as its pixel intensity value  107  will be at a minimum value because of the rarity in which that waveform is rasterized and then displayed. 
         [0006]    Conventional oscilloscopes as described above do not allow a waveform  104  that is significantly different from a frequently-occurring waveform  102  to appear with more intensity and longer duration. Indeed, the “rare” waveform  104  of  FIG. 1B  will appear dim in comparison to waveform  102  and have a faster decay rate. This faster decay rate prevents a user from being able to view the “rare” waveform  104  for longer periods of time. 
         [0007]    As the reader can appreciate, there exists a need for oscilloscopes that improve upon and advance the design of known oscilloscopes. Examples of new and useful oscilloscopes relevant to the needs existing in the field are discussed below. 
       SUMMARY 
       [0008]    An embodiment of the disclosed technology includes an oscilloscope for displaying a waveform including a digitizer to digitize input data into a plurality of digitized signals, a rasterizer configured to generate a plurality of raster images from the digitized signals, the rasterizer further having a subtractor configured to decrement a pixel intensity counter, a processor configured to manipulate the raster images based on the pixel intensity counter, and a display device configured to display the raster images. 
         [0009]    Another embodiment of the disclosed technology includes a method of displaying a waveform in an oscilloscope. The method includes acquiring input data corresponding to the waveform, decrementing each of a plurality of pixel intensity based on a first rate of decay, and displaying the waveform based on the plurality of pixel intensity counters. 
         [0010]    Yet another embodiment of the disclosed technology includes a method of displaying multiple waveforms in an oscilloscope. The method includes acquiring input data corresponding to a first waveform and a second waveform, where the first waveform is a frequently-occurring waveform and the second waveform is significantly different from the first waveform, decrementing each of a plurality of pixel intensity counters based on a first rate of decay corresponding to the first waveform or a second rate of decay corresponding to the second waveform, and displaying the first and second waveforms based at least in part on values of the plurality of the pixel intensity counters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1A  is a diagram illustrating prior art waveforms where both waveforms have the same pixel intensity. 
           [0012]      FIG. 1B  is a diagram illustrating prior art waveforms where one waveform has brighter pixel intensity than the other waveform. 
           [0013]      FIG. 2A  is a signal diagram of a first example of a plurality of waveforms being displayed on an oscilloscope and having the same pixel intensity. 
           [0014]      FIG. 2B  is a signal diagram of the plurality of waveforms being displayed on the oscilloscope and having different pixel intensities. 
           [0015]      FIG. 3  is a block diagram of an oscilloscope for displaying the waveforms shown in  FIGS. 2A and 2B . 
           [0016]      FIG. 4  is a block diagram of a first embodiment of a rasterizer of the oscilloscope shown in  FIG. 3 . 
           [0017]      FIG. 5  is a block diagram of a second embodiment of a rasterizer of the oscilloscope shown in  FIG. 3 . 
           [0018]      FIG. 6  is flowchart of a method of displaying a plurality of waveforms according to an embodiment of the disclosed technology. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The disclosed oscilloscopes will become better understood through review of the following detailed description in conjunction with the figures. The detailed description and figures provide examples of the various inventions described herein. Those skilled in the art will understand that the disclosed examples may be varied, modified, and altered without departing from the scope of the inventions described herein. Many variations are contemplated for different applications and design considerations; however, for the sake of brevity, each and every contemplated variation is not individually described in the following detailed description. 
         [0020]    Throughout the following detailed description, examples of various oscilloscopes are provided. Related features in the examples may be identical, similar, or dissimilar in different examples. For the sake of brevity, related features will not be redundantly explained in each example. Instead, the use of related feature names will cue the reader that the feature with a related feature name may be similar to the related feature in an example explained previously. Features specific to a given example will be described in that particular example. The reader should understand that a given feature need not be the same or similar to the specific portrayal of a related feature in any given figure or example. 
         [0021]    With reference to  FIG. 3 , a first example of an oscilloscope  300  will now be described. Oscilloscope  300  includes a digitizer  302 , a memory  304 , a rasterizer  306 , a processor  312  and a display device  314 . Rasterizer  306  further includes a subtractor unit  310 . Oscilloscope  300  functions to display less frequently occurring waveforms with increased brightness and persistence by modifying the persistence decay algorithm. Additionally, oscilloscope  300  can be used to modify the decay rates of multiple waveforms as selected by a user. 
         [0022]    With continuing reference to  FIG. 3 , digitizer  302  acquires input data and transforms that data into a digital representation. For example, digitizer  302  may include a successive approximation analog-to-digital converter (ADC) operating in a real-time sampling mode, sampling as often as possible. Alternatively, digitizer  302  may include a direct conversion ADC operating in an equivalent-time sampling mode, sampling at a determined time period after a triggering event. 
         [0023]    Memory  304  is shown in  FIG. 3  as being located between digitizer  302  and rasterizer  306 ; however, such memory storage is not required. For example, digitizer  302  may send digitized signals directly to rasterizer  306  rather than through memory  304 . 
         [0024]    Processor  312  may communicate directly or indirectly with rasterizer  306 . For example, a data bus (not shown) may link processor  312  and rasterizer  306 . In addition, processor  312  may communicate with rasterizer  306  through a common memory (not shown). However, common memory may be memory  304  itself or another memory separate from memory  304 . 
         [0025]    During general operation, the digitized signal is rasterized in rasterizer  306  into a raster image (not shown) to be displayed as a two dimensional (m×n) array of pixels on display  314 . A raster image (not shown) is formed of multiple pixels (not shown). Each pixel may be arranged in an m×n array of rows and columns. For example, a rasterizer plane (not shown) is typically 512×1024 bytes, where each pixel is made up of a total of 32-bits, 6-bits for pixel information and a 26-bit counter. 
         [0026]    Rasterizer  306  further includes a subtractor  310  that is used to decrement the 26-bit counters of each pixel in the raster plane for “rare” waveforms. Generally speaking, the 26-bit pixel intensity counter will start at a count of 2 N−1  and incrementally subtract away from that initial value based on the frequency of the pixel hit. For example, a “rare” waveform normally receives less pixel hits than a frequently-occurring waveform that receives more pixel hits. However, “rare” events, or waveforms significantly differing from frequently-occurring waveforms would have greater pixel intensity values than frequently-occurring waveforms, thus increasing their pixel brightness and allowing the “rare” waveform to stay on display  314  longer due to the extra time it would take to decrement away from such a large 2 N−1  number. 
         [0027]    Conversely, frequently-occurring waveforms would have much lower pixel intensity values and would decay away from their respective 2 N−1  counters at a much faster rate, thus causing them to be dimly lit when compared to a “rare” waveform. 
         [0028]    Additionally, rasterizer  306  is able to modify the persistence decay algorithm in order to apply different decay rates to the displayed waveforms. Rasterizer  306  records the minimum pixel count and the maximum pixel count in the entire rasterizer image. Then, when the pixel intensity counts are converted to the digitized display signal, these counts are copied and decayed so that the rasterization process can continue in parallel with the on-going conversion of the display intensities. 
         [0029]    Rasterizer  306  further employs a decay process that uses a range from the minimum count (non-zero) to the maximum count and divides this range into a set of contiguous sub-ranges and applies a different decay algorithm to the pixel counts in each sub-range. Thus, rasterizer  306  may apply different persistence decay algorithms to large and small pixel intensity counts. 
         [0030]    Turning attention to  FIGS. 2A and 2B , these figures illustrate two data inputs that have been digitized by digitizer  302 , rasterized by rasterizer  306 , and displayed on display device  314 .  FIG. 2A  specifically illustrates that a frequently-occurring waveform  202  and a waveform  204  differing significantly from waveform  202 , or a “rare” waveform are at maximum intensity because their pixel intensity counters,  206  and  207  respectively, have an initial maximum pixel intensity value. Thus, all pixels of waveforms  202  and  204  are brightest at this initial stage. As mentioned earlier, the reader can appreciate that pixels  203  and  205  represent but one of thousands of pixels in each of waveforms  202  and  204 . 
         [0031]      FIG. 2B  illustrates the two waveforms of  FIG. 2A  after some time has elapsed. Frequently-occurring waveform  202  would have a minimum pixel intensity value  206  for each of its pixels  203 . However, “rare” waveform  204  would have a maximum pixel intensity value  207  for each of its pixels  205 , making the waveform brighter on display device  314 . Further, the persistence decay algorithm would be modified so that the decay rate of waveform  204  would be longer than waveform  202 , thus displaying waveform  204  for a longer period of time. 
         [0032]    Turning attention to  FIG. 4 , a second example of an oscilloscope  400  will now be described. Oscilloscope  400  includes many similar or identical features to oscilloscope  300 . Thus, for the sake of brevity, each feature of oscilloscope  400  will not be redundantly explained. Rather, key distinctions between oscilloscope  400  and oscilloscope  300  will be described in detail and the reader should reference the discussion above for features substantially similar between the two oscilloscopes. 
         [0033]    As can be seen in  FIG. 4 , oscilloscope  400  includes a digitizer  402  (not shown), a memory  404  (not shown), a rasterizer  406 , a processor  412  (not shown), and a display device  414  (not shown). In this example, oscilloscope  400  further includes an adder  408  and a switching module  412 , both of which are located internally to rasterizer  406 , whereas rasterizer  306  of oscilloscope  300  did not include either of those elements. 
         [0034]    Adder  408  functions to operate the same as adders of conventional oscilloscopes. The pixel intensity counter of adder  408  will have an initial value of zero and will increment by a fixed value for each acquisition that falls within that pixel location. Switching module  412  functions to allow oscilloscope  400  to employ either adder  408  or subtractor  410 . 
         [0035]    Turning attention to  FIG. 5 , a third example of an oscilloscope  500  will now be described. Oscilloscope  500  includes many similar or identical features to oscilloscope  400 . Thus, for the sake of brevity, each feature of oscilloscope  400  will not be redundantly explained. Rather, key distinctions between oscilloscope  500  and oscilloscope  400  will be described in detail and the reader should reference the discussion above for features substantially similar between the two oscilloscopes. 
         [0036]    As can be seen in  FIG. 5 , oscilloscope  500  includes a digitizer  502  (not shown), a memory  504  (not shown), a rasterizer  506 , a processor  512  (not shown), and a display device  514  (not shown). In this example, oscilloscope  500  further includes a register  513 , whereas rasterizer  406  of oscilloscope  400  did not include this element. Register  513  functions to store pixel intensity values of the rasterized images. 
         [0037]    Turning attention to  FIG. 6 , a method  600  of displaying a waveform will now be described. Method  600  includes acquiring input data corresponding to a waveform  602 , setting each pixel intensity counter to an initial value  604 , decrementing the pixel intensity counters based on a decay rate  606 , and displaying the waveforms based on the pixel intensity counters  608 . 
         [0038]    With continuing reference to  FIG. 6 , block  602  illustrates the step of acquiring an input signal that is digitized for later use by the rasterizer. Additionally, the digitized input may be stored into a memory for later manipulation by the rasterizer or processor. 
         [0039]    Next, block  604  illustrates the step of setting each pixel intensity counter to an initial value of 2 N−1 . This initial value is set when pixel information pertaining to the waveforms is acquired. In this example, and as previously described above, the initial pixel intensity values for the frequently-occurring waveform  202  and the “rare” waveform  204  (see  FIG. 2A ) will be at a maximum value. However, after a brief period of time, the pixel intensity value for frequently-occurring waveform  202  will be a minimum value and “rare” waveform  204  will be at a maximum value (see  FIG. 2B ). 
         [0040]    In block  606 , the step of decrementing the pixel intensity counters is illustrated. The pixel intensity counter of the “rare” waveform  204  (see  FIG. 2B ) will have an initial maximum value of 2 N−1 . For each subsequent pixel that is acquired in this waveform, the 26-bit counter will be decremented at a much slower decay rate than frequently-occurring waveform  202 . This slower decay rate will allow the “rare” waveform  204  to remain displayed for a longer period of time than frequently-occurring waveform  202 . Once the counter has decremented down to zero, it will automatically reset back to the maximum value of 2 N−1  value when the next pixel for the waveform has been acquired and the decrementing process begins again. 
         [0041]    Regarding the frequently-occurring waveform  202 , its 26-bit counter will also decrement after each pixel acquisition; however, the decay rate will be much greater. In other words, these waveforms will decay away very rapidly making their pixels much less prominent than the pixels for the “rare” waveform  204 . 
         [0042]    Additionally or alternatively, both frequently-occurring waveform  202  and “rare” waveform  204  may be set to several different rates of decay. For example, as previously mentioned above, the decay rate for “rare” waveforms will be lower so that these waveforms are displayed for longer periods of time before decaying away from view. In contrast, the decay rate for frequently-occurring waveforms  202  will typically be much greater than the decay rate for “rare” waveforms as the goal is to make the “rare” waveforms  204  more prominent by causing the frequently-occurring waveforms  202  to decay very rapidly. 
         [0043]    Still referring to  FIG. 6 , block  608  illustrates the step of displaying the frequently-occurring waveform  202  and the “rare” waveform  204  on a display device. This is generally done once rasterizer  306  has rasterized the image and it is ready to be drawn. 
         [0044]    The disclosure above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in a particular form, the specific embodiments disclosed and illustrated above are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed above and inherent to those skilled in the art pertaining to such inventions. Where the disclosure or subsequently filed claims recite “a” element, “a first” element, or any such equivalent term, the disclosure or claims should be understood to incorporate one or more such elements, neither requiring nor excluding two or more such elements. 
         [0045]    Applicant reserves the right to submit claims directed to combinations and subcombinations of the disclosed inventions that are believed to be novel and non-obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of those claims or presentation of new claims in the present application or in a related application. Such amended or new claims, whether they are directed to the same invention or a different invention and whether they are different, broader, narrower or equal in scope to the original claims, are to be considered within the subject matter of the inventions described herein.