JP2009047511A - Waveform-measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveform-measuring device capable of increasing the number of gradations, even for a liquid crystal monitor having few input bits. <P>SOLUTION: This device has improvements on waveform-measuring device added for converting a waveform to be measured into digital data, compressing the digital data, and displaying a waveform on a liquid crystal monitor. The device is provided with a display processing part for performing waveform display by making the luminance change, by time-sharing waveform display of one screen portion with a frame unit, corresponding to the frequency of duplication of digital data after compression in each pixel of the liquid crystal monitor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a waveform measuring apparatus in which an AD converter converts a waveform to be measured into digital data, compresses the converted digital data, and displays the waveform on a liquid crystal monitor. Specifically, the present invention relates to a liquid crystal monitor with a small number of input bits. However, the present invention relates to a waveform measuring apparatus capable of increasing the number of gradations.

  The waveform measuring apparatus has changed from an analog system to a digital system, and the display unit of the waveform measuring apparatus has also changed from a CRT (Cathode Ray Tube) to an LCD (Liquid Crystal Display).

  The digital waveform measuring apparatus acquires digital data of several thousand to several tens of thousands of points (time axis direction) with a single waveform acquisition by increasing the capacity of the acquisition memory and improving the resolution of the AD converter. The resolution in the vertical axis direction is also more than a dozen bits.

  On the other hand, the number of pixels of the LCD used in the waveform measuring apparatus is smaller than the number of data on the horizontal axis (time axis) and the resolution on the vertical axis (particularly in the horizontal axis direction). Therefore, the digital data is compressed and displayed in accordance with the number of pixels on the vertical axis and the horizontal axis. Accordingly, a plurality of digital data are displayed in an overlapping manner on one pixel of the LCD, and the number of overlapping frequencies is different for each pixel.

  Further, the conventional CRT has afterimage characteristics, and a repeatedly generated waveform portion is displayed brighter than a waveform portion having a small number of occurrences. On the other hand, since a digital LCD has no afterimage characteristics, a waveform portion having a high overlap frequency and a waveform portion having a low overlap frequency are displayed with the same brightness.

  Therefore, the CRT is simulated using the gradation range of the LCD, and the brightness of the LCD is changed in accordance with the frequency of overlapping / occurrence of waveforms (for example, see Patent Documents 1 and 2). Some display is performed by changing the color according to the overlap frequency (see, for example, Patent Document 3).

JP-A-7-128371 Japanese Patent No. 3084729 JP 2006-300573 A

  FIG. 9 is a display example of a conventional waveform measuring apparatus, in which a waveform on which pulsed noise is superimposed is measured. A waveform portion (sine wave-shaped waveform portion) having a high overlap frequency on the pixel is bright, and a pulse-like noise portion having a low occurrence frequency and a low overlap frequency on the pixel has a low brightness.

  In the field related to broadcasting, a frequency sweep signal of a sine wave is measured. In this case, it is very important to discriminate group delay characteristics, phase distortion, amplitude clips, and the like from the LCD display screen. However, these phenomena to be observed have a low luminance on the LCD because the frequency of overlap in each pixel is low when each axis is displayed with compression.

  In the case of waveform measurement devices, the LCD screen of the display unit is small and the number of digital input bits to the LCD is for TV LCDs, PC LCDs, and high-definition monitors because priority is given to reducing the size and cost of the entire device. It is remarkably small compared with LCD etc.

  Specifically, the LCD screen of the waveform measuring apparatus has a screen size of about 6.4 inches, 8.4 inches, and 10.4 inches, while television LCDs have several tens of inches. In addition, the number of input bits to the LCD of the waveform measuring apparatus is about 5 bits, and some LCDs for televisions exceed 10 bits.

  In order to simplify the description, it is assumed that the digital input bit number of the LCD for the waveform measuring apparatus is 2 bits. When the number of input bits is 2, there are four types (2 ^ 2 = 4) of luminance information for each pixel of the LCD (640 × 480 pixels if VGA). Therefore, when the overlap frequency at each pixel is converted into the luminance information of the LCD, the data of each pixel is divided into four areas according to the overlap frequency number (hereinafter abbreviated as the frequency number).

  For example, the frequency number 0 to i times per unit time is the minimum frequency area (LCD input bit value “00”), the frequency number (i + 1) to j times frequency small and medium area (input bit value “01”), The frequency number (j + 1) to k times are divided into frequency medium and large regions (input bit value “10”), and the frequency number (k + 1) times or more are divided into frequency maximum regions (input bit value “11”). The data of the minimum frequency area is displayed with the minimum luminance on the LCD, and the data of the maximum frequency area is displayed with the maximum luminance. Of course, 0 <i <j <k.

  However, the gradation characteristic of a general LCD is adjusted to the same gamma 2.2 as that of a CRT monitor. Here, FIG. 10 is a diagram showing the gradation characteristics (gamma 2.2 and gamma 1) of the LCD, where the horizontal axis is the input signal (bit value) to the LCD and the vertical axis is the output (luminance) of the LCD. It is.

  FIG. 11 is a diagram showing a display example of the LCD when the number of input bits of the LCD is 2 bits. FIG. 11A is a display example of gamma 2.2, and FIG. Is a display example of gamma 1.

  As shown in FIG. 10, when the number of input bits is 2, the number of gradations of the LCD is 4, and the bit value “00” (corresponding to input 0 [%]) is the output brightness 0 on the LCD. The bit value “01” (corresponding to the input 33.3 [%]) is an output luminance of less than 10 [%]. For this reason, with gamma 2.2, it is difficult to discriminate the luminance difference between the bit values “00” and “01” on the LCD (see FIG. 11), and the waveform portion most desired to be observed as shown in FIG. There is a problem that data of a certain noise part (data of occurrence frequency is small and medium), group delay characteristics, phase distortion, etc. are overlooked.

  Accordingly, an object of the present invention is to realize a waveform measuring apparatus capable of increasing the number of gradations even in a liquid crystal monitor having a small number of input bits.

The invention described in claim 1
A waveform measuring device that converts a waveform to be measured into digital data, compresses the digital data, and displays the waveform on a liquid crystal monitor,
A display processing unit is provided that displays a waveform for one screen by changing the luminance in a time-divided manner in units of frames in accordance with the frequency of overlap of compressed digital data in each pixel of the liquid crystal monitor. It is a feature.
The invention according to claim 2 is the invention according to claim 1,
The display processing unit is characterized in that the luminance of each pixel of the liquid crystal monitor is changed within one cycle including a plurality of frames.
The invention according to claim 3 is the invention according to claim 2,
The display processor
A frequency-luminance conversion means for converting the number of overlapping frequencies of each pixel into luminance information;
In accordance with the luminance information of the frequency-luminance conversion means, there is provided time division means for time-dividing one cycle in units of frames and changing the luminance of each pixel to display the waveform on the liquid crystal monitor. To do.
The invention according to claim 4 is the invention according to claim 3,
The time division means is characterized by performing pseudo gamma adjustment.
The invention according to claim 5 is the invention according to claim 3 or 4,
A time-division pattern memory for storing a correspondence relationship between the luminance information and the time-division pattern in the one cycle;
The time division means changes the luminance based on the correspondence relationship of the time division pattern memory.

The present invention has the following effects.
Since the display processing unit displays the waveform display for one screen in a time-sharing manner in units of frames, it is recognized with different luminance due to the integration effect when a human visually observes. Thereby, even in a small liquid crystal monitor with a small number of input bits, the number of gradations (gradation range) can be expanded due to visual effects, and frequency information can be displayed finely, and the amount of display information increases. Therefore, at least the overlapping frequency number on the pixel of the liquid crystal monitor does not miss the waveform portion that needs to be observed.

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 1 is a block diagram showing a first embodiment of the present invention.
In FIG. 1, an input unit 10 receives a waveform to be measured, converts it into digital data, and outputs it. The acquisition memory 20 stores digital data from the input unit 10. The frequency memory 21 stores data related to frequency.

  The display processing unit 30 includes a frequency-luminance conversion unit 31 and a time division unit 32, and reads digital data from the acquisition memory 20, inputs / outputs data to / from the frequency memory 21, and generates image data for display.

  The display memory 40 stores image data of the display processing unit 30. The display unit 50 includes an LCD driver 51 and an LCD 52 and displays the image data in the display memory 40 in accordance with instructions from the display processing unit 30. The LCD driver 51 receives a bit value (digital input bit for the LCD 52) from the time division unit 32 of the table processing unit 30, and displays it on the LCD 52 with a luminance corresponding to the bit value. The LCD 52 is provided on the front surface of the apparatus.

  The operation of such an apparatus will be described. Here, FIG. 2 is a diagram showing an example of the operation of the display screen of the frequency memory 21, frequency-luminance conversion means 31, time division means 32, and LCD 52 of the apparatus shown in FIG.

  The input unit 10 adjusts the amplitude of the input waveform to be measured, converts it to digital data with an AD converter (not shown), and stores digital data of a predetermined length in the acquisition memory 20.

  After the digital data having a predetermined length is acquired, that is, after the storage in the memory 20 is completed, the display processing unit 30 reads the digital data in the memory 20. In general, the number of digital data (several thousand to several tens of thousands) and the resolution of amplitude (ten bits) are significantly larger than the number of pixels of the LCD 52 (for example, 640 × 480 pixels (dots) for VGA).

  Therefore, the compression means (not shown) of the display processing unit 30 compresses the digital data in each of the horizontal axis direction and the vertical axis direction. At this time, a compression unit (not shown) performs compression by associating frequency information indicating how many points of compressed digital data overlap each pixel of the LCD 52 with the address of the pixel.

  Then, the frequency-luminance conversion unit 31 sorts the frequency number data (referred to as frequency data) of each pixel obtained by the compression unit by the frequency number, and stores the frequency data in the frequency memory 21 in the sort order. The total number of frequency data is the number of pixels of the LCD 52 (640 × 480 in the case of VGA).

  Then, the frequency-luminance conversion means 31 converts the frequency data associated with the address of each pixel of the LCD 52 into luminance information. Specifically, when the number of digital input bits to the LCD 52 is 2, the display memory 40 is divided into four basic data areas as luminance areas. That is, a region with the highest frequency, a region with a medium frequency, a region with a medium frequency, and a region with a minimum frequency.

  Then, the conversion means 31 adds N regions in each of the region with the highest frequency, the region with the middle frequency, and the region with the middle frequency. In FIG. 2, the description will be made assuming that N = 2. Here, L (1) to L (10) are set in order from the highest frequency region.

  The conversion means 31 stores the frequency data in each of the areas L (1) to L (10) of the display memory 40, and each of the areas L (1) to L (10) including the frequency number of the frequency data. ).

For example,
Store frequency data of 900 or more in the area L (1),
Store frequency data in the range of the frequency number 800 to 899 in the area L (2),
Store frequency data in the range of the frequency number 700 to 799 in the area L (3),
The frequency data in the range of the frequency number 600 to 699 is stored in the area L (4),
In the area L (5), frequency data in the frequency range of 500 to 599 is stored,
Store frequency data in the range of frequency numbers 400 to 499 in the area L (6),
Store frequency data in the range of frequency numbers 300 to 399 in the area L (7),
Store frequency data in the range of frequency numbers 200 to 299 in area L (8),
Store frequency data in the range of frequency numbers 100 to 199 in the area L (9),
Frequency data in the range of frequency numbers 0 to 99 is stored in the area L (10).

  The numerical range of each of the areas L (1) to L (10) may be set in advance. In addition, the numerical range of each of the above areas is an example, and the range can be divided by the number of digital data stored in the acquisition memory 20, the resolution of the AD converter, the frequency data of the frequency number to be emphasized, and the like. Well, the numerical ranges do not have to be equal.

  As a result, the display memory 40 stores image data having luminance information of each pixel on the LCD 52 (information on which region L (1) to L10 the frequency data belongs to).

  Then, the time division means 32 reads the image data from the display memory 40 every cycle, and from this image data, the video signal for each frame (bit values “11”, “10” indicating the luminance of each pixel of the LCD 52, “01”, “00”) are generated and output to the LCD driver 51. As a result, the LCD driver 51 displays the waveform of each pixel of the LCD 52 with the luminance corresponding to the bit value.

  Here, one cycle is the number of frames of “basic data area” + “number of additional data areas N”. In FIG. 2, two additional data areas exist in one basic data area. A set of 3 (1 + N (= 2)) frames is one cycle. Further, the frame frequency of the LCD 52 is normally 60 [Hz] as in the case of the CRT monitor (of course, there are frame frequencies other than 60 [Hz] depending on the standard), so one cycle is 50 [ms]. Therefore, the image data is read from the display memory 40 every cycle, and the waveform display is performed by the image data for one screen read as a set of three frames.

  Specifically, when the time division unit 32 displays the pixels of the frequency data belonging to the region L (1), the bit value “11” that outputs the maximum luminance is output for all the first to third frames in one cycle. To do. In the case of the region L (2), the first frame and the second frame output the bit value “11”, the third frame outputs the bit value “00” having the minimum luminance, and in the case of the region L (3), the first frame The bit value “11”, the second frame, and the third frame output the bit value “00”.

  That is, the time division means 32 time-divides one cycle into 1 to 3 frames in each of the areas L (1) to L (10) and outputs them in the order of the following bit values.

The order of bit values “11”, “11”, “11” in the region L (1).
The order of bit values “11”, “11”, “00” in the area L (2).
The order of bit values “11”, “00”, “00” in the area L (3).
The order of bit values “10”, “10”, “10” in the region L (4).
The order of bit values “10”, “10”, “00” in the region L (5).
The order of bit values “10”, “00”, “00” in the region L (6).
The order of bit values “01”, “01”, “01” in the region L (7).
The order of bit values “01”, “01”, “00” in the area L (8).
The order of bit values “01”, “00”, “00” in the area L (9).
The order of bit values “00”, “00”, “00” in the area L (10).

  Here, FIG. 3 is a diagram showing a display example of the LCD 52 of the apparatus shown in FIG. FIG. 3A is a display example of the conventional waveform measuring apparatus, and FIG. 3B is a display example of the apparatus shown in FIG.

  As described above, the time division unit 32 time-divides one cycle to change the bit value for each frame (that is, the frame frequency) to change the luminance of each pixel of the LCD 52. (Luminance change) is earlier than the time during which the human eye can identify. Accordingly, when the display screen of the LCD 52 is viewed with human eyes, it is captured as a gradation change of 2 ^ x · (1 + N) −N due to the integration effect of the eyes. Here, x is the number of digital input bits of the LCD, and N is the number of additional data. In the case of the apparatus shown in FIG. 2, since the number of digital input bits = 2 bits and the number of additional data N = 2, it is displayed in 10 gradations. As a result, even with the LCD 52 having a small number of input bits, the gradation range can be expanded, and a waveform portion (noise portion, group delay characteristic, phase distortion, etc.) that requires observation with little overlap frequency on the pixel. But you won't miss it.

[Second Embodiment]
FIG. 4 is a block diagram showing a second embodiment of the present invention. Here, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 4, a time division pattern memory 22 is newly provided. The time division pattern memory 22 stores the time division pattern and the correspondence relationship of the time division pattern with respect to each of the regions L (1) to L (10), and is read by the time division means 32.

  A case where N = 2 (one cycle is divided into three frames in time) will be described in detail with reference to FIG. The time division pattern memory 22 is preliminarily inputted with a time division pattern of bit values of each frame in one cycle (see FIG. 5A).

For example, the following pattern is stored.
The order of bit values “11”, “11”, “11” of the time division of the pattern P (1).
The order of bit values “11”, “11”, “00” of the time division of the pattern P (2).
The order of bit values “11”, “00”, “00” of the time division of the pattern P (3).
The order of bit values “10”, “10”, “10” of the time division of the pattern P (4).
The order of bit values “10”, “10”, “00” of the time division of the pattern P (5).
The order of bit values “10”, “00”, “00” of the time division of the pattern P (6).
The order of bit values “01”, “01”, “01” of the time division of the pattern P (7).
The order of bit values “01”, “01”, “00” of the time division of the pattern P (8).
The order of bit values “01”, “00”, “00” of the time division of the pattern P (9).
The order of bit values “00”, “00”, “00” of the time division of the pattern P (10).

  A plurality of correspondence relationships between each of the regions L (1) to L (10) and the time division patterns P (1) to P (10) are stored. For example, when displaying with gamma 2.2, displaying with gamma 1 adjusted by pseudo-gamma, highlighting a pixel with a small frequency number, etc. (see FIG. 5B).

The operation of such an apparatus will be described.
Since the operation until the frequency-luminance conversion means 31 allocates frequency data to each of the regions L (1) to L (10) and converts the frequency data into luminance information is the same, the description thereof is omitted.

  Then, the time division means 32 sends the patterns P (1) to P (10) assigned to the patterns P (1) to P (10) and the regions L (1) to L (10) from the time division pattern memory 22. ) Is read out. The kind of display is set in advance.

  Further, the time division means 32 reads the image data from the display memory 40 every cycle, and the read image data is read out based on the correspondence relationship of the time division pattern memory 22 and the patterns P (1) to P (10). A video signal for each frame (bit values “11”, “10”, “01”, “00” indicating the luminance of each pixel of the LCD 52) is generated and output to the LCD driver 51. As a result, the LCD driver 51 displays the waveform of each pixel of the LCD 52 with the luminance corresponding to the bit value.

  Here, FIG. 6 is a diagram showing another display example of the LCD 52 of the apparatus shown in FIG. 6A shows a display example of gamma 2.2, FIG. 6B shows a display example when the gamma is adjusted to gamma 1, and FIG. 6C shows a waveform with a low frequency as the maximum luminance. It is a display example in which pseudo-gamma adjustment is performed so as to be reversed.

  FIG. 7 is a diagram showing the gradation characteristics (pseudo gamma 1 adjustment, inverted display) of the LCD 52, where the horizontal axis is the input signal (bit value) to the LCD and the vertical axis is the output (luminance) of the LCD. is there.

  For example, as shown in FIG. 6B, when the gamma is corrected from gamma 2.2 to gamma 1 (pseudo gamma adjustment) and displayed, the same effect as changing the gamma value is obtained, and the frequency number is intermediate. The halftone of the part is emphasized, and it is possible to visualize the image information that was sinking in black.

  In addition, when the correction display is reversed and displayed as shown in FIG. 6C, even in the waveform portion where the frequency number in the pixel is small and the gamma 2.2 is darkly displayed on the LCD 52, the waveform having the low frequency number is displayed. By displaying the portion brighter on the contrary, even a waveform portion having a small frequency number is displayed with the maximum luminance and a phenomenon that is easily overlooked is highlighted as image information. Note that the one with the lowest frequency (for example, 0 times) is displayed with the lowest luminance.

  In this way, the correspondence between the respective areas L (1) to L (10) and the respective patterns P (1) to P (10) that provide the desired pseudo gamma correction is stored in the time division pattern memory 22, Based on this correspondence, the time division means 32 displays the waveform on the LCD 52. Thereby, it is possible to emphasize and display a waveform portion that is easily overlooked.

The present invention is not limited to this, and may be as shown below.
(A) In the apparatus shown in FIG. 4, the time-division pattern memory 22 is used and the time-division unit 32 performs the pseudo-gamma adjustment. The pseudo gamma adjustment may be performed by correcting from gamma 2.2 to gamma 1.

  An example of time division conversion from gamma 2, 2 to gamma 1 is shown in FIG. As shown in FIG. 8, the time division means 32 shifts the data to the maximum luminance side in the allocation of the regions L (1) to L (10) to the patterns P (1) to P (10), and after the shift Pseudo gamma adjustment to gamma 1 may be performed by shifting the data again to the minimum luminance side.

(B) The time division means 32 has shown a configuration in which one cycle is displayed in three frames (when N = 2), but the waveform acquisition of the input unit 10 and the display processing of the display processing unit 30 are 50 [ms]. ], The cycle may be a multiple of (1 + N). For example, when 9 frames are used as one cycle instead of 3 frames, time division may be performed by 1 to 3 frames, 4 to 6 frames, and 7 to 9 frames. For example, in the case of the luminance data in the region L (2) in the apparatus shown in FIG. Is output to the LCD driver 51.

(C) The portion corresponding to the additional data regions L (2) and L (3) of L (1) of the basic data region with the maximum frequency is set to “00” in the second frame and the third frame. The bit value “10” in the lower basic data area L (4) may be set.

For example,
The order of bit values “11”, “11”, “11” in the region L (1)
The order of bit values “11”, “11”, “10” in the region L (2)
The order of bit values “11”, “10”, “10” in region L (3)
The order of bit values “10”, “10”, and “10” in the region L (4) may be used. The double brackets are the parts where the bit values are changed.

  Similarly, the bit values of the additional data areas L (5) and L (6) of the medium data size of the basic data area L (4) are not “00”, but are one of the basic data areas L (7). The bit value may be set to “01”.

(D) The portion corresponding to the additional data areas L (3) and L (6) is “00” in the second frame and the third frame, but is combined with a bit value other than “00” as described below. May be.
For example,
The order of bit values “11”, “10”, “00” in the region L (3),
The order of bit values “11”, “10”, “01” in the region L (3)
The order of bit values “10”, “01”, and “00” in the region L (6) may be used.

(E) The additional data areas L (2), L (5), and L (8) have a configuration in which the bit value is “00” in the third frame in one cycle, but the bit value “00” is Any number of frames may be displayed as long as it is displayed once in one cycle. Similarly, the additional data areas L (3), L (6), and L (9) have a configuration in which the bit value is “00” in the second and third frames in one cycle. The value “00” may be displayed twice in one cycle, and may be any number of frames.

(F) Although the configuration in which the number of input bits for the LCD 52 is two bits is shown, any number of bits may be used.
(G) Although the number of additional data is set to N = 2, it may be 1 or 3 or more.
(H) Although the LCD 52 has been described as a VGA, any number of pixels may be used.
(I) A display example in which the pseudo gamma correction is set to gamma 1 and a display example in which the pseudo gamma correction is performed are shown. However, any pseudo gamma correction may be performed.

It is the block diagram which showed the 1st Example of this invention. It is the block diagram which showed the apparatus shown in FIG. 1 in detail. It is the figure which showed the example of a display of a display part. It is the block diagram which showed the 2nd Example of this invention. It is the figure which showed the example of data of the time division pattern memory. It is the figure which showed the other example of a display of a display part. It is the figure which showed the gradation characteristic of the apparatus shown in FIG. It is the block diagram which showed the 3rd Example of this invention. It is the figure which showed the example of a display of the waveform measurement result in the conventional waveform measuring apparatus. It is the figure which showed the gradation characteristic in the conventional waveform measuring apparatus. It is the figure which showed the example of a display in the conventional waveform measuring apparatus.

Explanation of symbols

22 Time-division pattern memory 30 Display processing unit 31 Frequency-luminance conversion means 32 Time-division means 52 LCD (liquid crystal monitor)

Claims (5)

A waveform measuring device that converts a waveform to be measured into digital data, compresses the digital data, and displays the waveform on a liquid crystal monitor,
A display processing unit is provided that displays a waveform for one screen by changing the luminance in a time-divided manner in units of frames in accordance with the frequency of overlap of compressed digital data in each pixel of the liquid crystal monitor. A characteristic waveform measurement device.   2. The waveform measuring apparatus according to claim 1, wherein the display processing unit changes the luminance of each pixel of the liquid crystal monitor within one cycle of a set of a plurality of frames. The display processor
A frequency-luminance conversion means for converting the number of overlapping frequencies of each pixel into luminance information;
In accordance with the luminance information of the frequency-luminance conversion means, there is provided time division means for time-dividing one cycle in units of frames and changing the luminance of each pixel to display the waveform on the liquid crystal monitor. The waveform measuring apparatus according to claim 2.   4. The waveform measuring apparatus according to claim 3, wherein the time division means performs pseudo gamma adjustment. A time-division pattern memory for storing a correspondence relationship between the luminance information and the time-division pattern in the one cycle;
5. The waveform measuring apparatus according to claim 3, wherein the time division means changes the luminance based on the correspondence relationship of the time division pattern memory.