JPH04329097A - Method for measuring resolution in display - Google Patents

Abstract

PURPOSE:To measure the resolution of a display such as a television set quantitatively and with reproducibility. CONSTITUTION:On a screen 2 of a display, a pattern 6 for measuring the resolution is displayed by image data from a personal computer 4. The pattern 6 for measuring the resolution is constituted of plural white and black stripe patterns 5a, 5b, 5c, 5d and 5e having the different stripe width. By a video camera 3, the pattern 6 for measuring the resolution is photographed. The special line of the scanning line of the video signal of the video camera 3 is extracted, a maximum value A and a minimum value B in the output are detected, and for example, by m=(A-B)/(A+B), a resolution index value (m) is operated. Based on the resolution index value, the identifiable minimum width stripe (then, the number of the whole screen) can be obtained and the resolution expressed by the number of the whole screen can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resolution measuring method for evaluating the resolution of a screen in a display device such as a television.

0002

2. Description of the Related Art In display devices such as televisions, the resolution of the display screen is important in evaluating the image quality, and is particularly important in projection type televisions compatible with high-definition. However, conventional resolution evaluation uses a monoscot pattern generator to display a monoscot pattern with wedge-shaped horizontal and vertical lines on the screen, and then evaluates the monoscot pattern subjectively by actually looking at the monoscot pattern. The limit of the distinguishable line density of vertical lines was judged visually.

0003

[Problems to be Solved by the Invention] As described above, when the resolution is subjectively evaluated by a person, the reproducibility of the evaluation is not sufficient. Further, it is usually not easy to correctly evaluate resolution without being influenced by the position of the monoscot pattern on the screen.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resolution measuring method that can quantitatively and reproducibly evaluate the resolution of a screen of a display device.

[0005]

[Means for Solving the Problems] The present invention, which solves the above-mentioned problems, is a resolution measuring method for evaluating the resolution of a display device, which comprises a black and white stripe pattern in which the width of one stripe is n pixels. displaying a plurality of resolution measurement patterns with different n values on the screen of a display device;
This resolution measurement pattern is applied at 2 times per pixel.
Shoot with a video camera that has a resolution that can handle dots or more, extract a specific line from the scanning line of this video camera, and calculate the maximum value A for the output of this extracted specific line.
The present invention is characterized in that it detects the maximum value A and the minimum value B, and determines the resolution based on the maximum value A and the minimum value B.

[0006] Claim 2 provides that the maximum value A and the minimum value B
The resolution index value m is obtained by substituting m=(A-B)/(A+B) into the arithmetic expression m=(A-B)/(A+B).

[0007]

[Operation] In the above configuration, the resolution measurement pattern is displayed on the screen of the display device. Each black and white stripe pattern of this pattern for resolution measurement is photographed using a video camera. A specific line of the scanning line of a video camera scanning one black and white stripe pattern is extracted, and a maximum value A and a minimum value B are detected for this extracted specific line. In this case, since the resolution of the video camera can handle two or more dots per pixel, the video camera has the ability to distinguish between black and white (distinguish stripes) even in the narrowest black and white stripe pattern. For example, the maximum value A and the minimum value B are calculated using the following formula: m=(A-B)
/(A+B) to calculate the resolution index value m. This resolution index value m is suitable as an index for quantitatively evaluating the resolution of the screen, and thus it becomes possible to measure the resolution quantitatively and with reproducibility.

[0008]

Embodiments Examples of the present invention will be described below with reference to FIGS. 1 to 9. FIG. 1 is an explanatory diagram of a resolution measuring system according to an embodiment of the present invention, in which reference numeral 1 indicates a projector of, for example, a high-definition projection television, and reference numeral 2 indicates a display screen thereof. The resolution measurement system of the present invention uses a video camera (
(preferably monochrome) 3 and a personal computer 4 are used. Further, a floppy disk 8 stores a pattern generation program for displaying on the screen a resolution measurement pattern 6 having a plurality of black and white stripe patterns 5 each having a stripe width of n pixels (picture elements) with different values of n. Use. Then, the projector 1 is connected to the personal computer 3 via the memory board 9, and the video camera 3 is connected to the personal computer 4 via the window processing circuit 10.

[0009] The number of pixels in high-definition is (1035~
1080)×1920, and correspondingly, in the embodiment, as the resolution measurement pattern 6, one line is used as the resolution measurement pattern 6, as shown in the enlarged view of FIG. 2 and the explanatory diagram of the number of pixels per stripe of FIG. A black and white stripe pattern 5a with a stripe width of 8 pixels, a black and white stripe pattern 5b with a width of 4 pixels, a black and white stripe pattern 5c with a width of 2 pixels, and a width of 1.5 pixels. Five black-and-white stripe patterns are prepared, including a corresponding black-and-white stripe pattern 5d and a black-and-white stripe pattern 5e composed of one pixel. There are even more books). The correspondence between these black and white stripe patterns and the number of lines on the entire screen is the number of pixels per stripe, n = 8.
, 4, 2, 1.5, and 1 are the number of lines on the entire screen, 13 respectively.
The numbers correspond to 5, 270, 540, 810, and 1080, respectively.

The black-and-white stripe pattern 5d in the case of n=1.5 is a black-and-white stripe pattern 5d1 in which one stripe consists of three pixels of white, white, and black;
The stripe is composed of a black and white stripe pattern 5d2 composed of three pixels of black, black, and white arranged in parallel. In addition, these two types of black and white stripe patterns 5
d1 and 5d2 can also be arranged not in parallel but in series (that is, separated into the left and right parts of FIG. 2). However, in this case, it is necessary to distinguish and detect the output of the first half and the output of the second half of one line of the video signal.

Then, the floppy disk 8 is read out by the personal computer 4, pattern data is allocated on the memory of the memory board 9, and sent to the projector 1 with a clock of 74.25 MHZ, and the pattern data for resolution measurement 6 is read out by the personal computer 4.
is displayed at a total of nine locations on the screen 2, including corners, sides, and the center. Further, the video camera 3 is
The optical system of the camera (for example, the focal length f or F value of the lens (=lens diameter D/ The focal length f) is set.

[0012] Furthermore, the video camera 3 is connected to a personal computer 4.
It is provided on a fine movement table 3a that automatically operates in conjunction with the screen 2, and is rotatable around an X axis parallel to the horizontal direction of the screen 2 and around a Y axis parallel to the vertical direction of the screen 2. It is installed at a distance three times the height H of 2. The value of three times the screen height to distance ratio is considered an appropriate viewing distance to prevent eye fatigue when viewing the screen, and is intended to match the actual viewing conditions as much as possible. is set as such.

Next, a procedure for measuring resolution using the above resolution measuring system will be explained. First, floppy disk 8
is set on the personal computer 4, and the resolution measurement pattern 6 is displayed on the screen 2 of the projector 1 at nine locations in total, including the corners, sides, and center of the screen 2, as shown in FIG. The resolution measurement pattern 6 is then photographed by the video camera 3, and a video signal output for scanning one black and white stripe pattern 5 is input to the personal computer 4 via the window processing circuit 10. When the video signal system is the NTSC system, the window processing circuit 10 processes, for example, 131±5 lines or 393 scanning lines of the video signal of the video camera 3.
One of the ±5 lines is extracted and, as shown in FIGS. 4(a), (b), and (c), only the middle part of the black and white stripe pattern is outputted by window processing. This is because the so-called shading effect lowers both end portions of the black and white stripe pattern output, resulting in a sagging output on the left and right as shown in FIG. 4(a), so only the output of the middle portion is used. 4(a) is the output waveform of one scanning line of the video signal of the video camera 4, FIG. 4(b) is the waveform for performing window processing,
FIG. 4(c) shows the output waveform of one line after window processing. In FIG. 4, the symbol S indicates a horizontal synchronization signal in the video signal of the video camera 3, and the symbol T indicates one horizontal scanning period. The above-mentioned 131±5 or 393±5 lines are scanning lines near the center of the screen of the video signal captured by the video camera 3 (that is, the first scanning line among 525 scanning lines by interlaced scanning). 13 in the center
1 line, and the center of the second scan is 393 lines).

[0014] Then, one of the black and white stripe patterns
Detect the maximum value A and minimum value B in the output of the line, and calculate the maximum value A and minimum value B using the formula m = (A-B
)/(A+B) to find the resolution index value m. This resolution index value m represents, so to speak, the magnitude of discrimination power (ease of discrimination) when identifying multiple lines, and this resolution index value m is equal to or greater than a certain value (in the measurement example described later, m ＞
1), it can be determined that the line can be identified. In this way, the resolution index value m is suitable as an index that quantitatively represents the resolution of the screen, and thus it becomes possible to measure the resolution quantitatively and with reproducibility.

Note that the resolution index value m when n=1.5
is the resolution index value m1 for the monochrome stripe pattern 5d1 in which one stripe consists of 3 pixels of white, white, and black, and the same resolution for the monochrome stripe pattern 5d2 in which 1 stripe consists of 3 pixels of black, black, and white. When the index value is m2, m=(m1 +m2
)/2. Although the resolution index value m in the case of n=1.5 is a pseudo value, it is an appropriate index value as an intermediate value between the case of n=2 and the case of n=1.

FIG. 6 shows a measurement example of the resolution index value m and its relationship with the resolution expressed in number of lines. This measurement example is when projecting onto a screen using a front projector (dashed line).
, when projecting from the rear using a rear-mounted projector (solid line), and when projecting onto a screen using a rear-mounted projector (
There are three cases (dotted chain line). In Figure 6, the number of lines on the entire screen is 1080, 720, 540, 270, and 135, and the number of pixels per stripe is n = 1.
, 1.5, 2, 4, and 8, respectively. and,
The resolution of the display device is determined based on this resolution index value m. For example, if the limit for line identification is m = 0.1 (this value itself is set based on the results of numerous tests such as visual inspection), then in the example of Figure 6, the resolution is approximately 6
00 line.

FIG. 7 shows the measured value of the resolution index value m for the entire screen. The three curved surfaces shown in the figure are each n=8 pixels (135 lines) from the top.
, n=4 pixels (270 lines), n=2 pixels (
540 lines).

When automatically measuring all nine measurement patterns 6 on the screen 2, as shown in FIG. In the illustrated example, the video camera 3 is set in the upper left corner), and the operation of changing the direction of the video camera 3 to the left and right of the screen (rotating around the Y axis) and the operation of changing the direction of the screen up and down (rotating around the X axis) ), the center point of the field of view of the video camera 3 is moved in the order indicated by the arrows, and the resolution is measured while sequentially photographing each black and white stripe pattern 5 of the resolution measurement pattern 6. It's good to do that. In addition, video camera 3 is used when shooting each pattern.
It is preferable that the center point of the visual field be located at the center of each black and white stripe pattern 5 (indicated by an x mark). The rotational operation of the video camera 3 described above is controlled by the personal computer 4 that stores an automatic measurement operation program. That is, the positions of the upper left corner and the lower left corner of the screen are preset in the personal computer 4, and the rotation angles θx and θy corresponding to the positions where the screen is equally divided vertically and horizontally are set in advance.
This is done by presetting the above-mentioned data, and operating the fine movement table 3a, which is controlled by the personal computer 4, in accordance with the preset data.

Next, an embodiment in which both horizontal resolution and vertical resolution are measured is shown in FIGS. 8 and 9. In this case, as shown in detail in FIG. 9, the resolution measurement pattern 26 includes a horizontal resolution measurement pattern 26H of vertical stripes for measuring horizontal resolution, and a horizontal stripe pattern 26H for measuring vertical resolution. The vertical resolution measurement pattern 26V is displayed as one set at, for example, nine locations on the display screen. The pattern 26H for horizontal resolution measurement is the same as that in FIG. 2 (although the number of stripes is shown in FIG. 9 as extremely small, it actually consists of many stripes), and the pattern 26V for vertical resolution measurement is the same as that in FIG. It was defeated. When measuring the horizontal resolution, the above-mentioned Figure 5
When measuring the vertical resolution, the video camera 23 is rotated 90 degrees around its lens optical axis (Z axis). The procedure for automatically measuring the nine vertical resolution measurement patterns 26V on the screen is almost the same as for the horizontal resolution. That is, the operation of setting the orientation of the video camera 23 to the diagonal position of the screen (in the illustrated example, the black-and-white stripe pattern at the left end of the vertical resolution measurement pattern 26V in the upper left) and changing the orientation of the video camera 23 to the left-right direction of the screen. The vertical resolution measuring pattern 26V is sequentially photographed by automatically changing the screen vertically and rotating the video camera 90 degrees around the optical axis to determine the resolution index value m. Measure. The arrows shown in the screen 2 of FIG. 8 indicate an example of a procedure for sequentially scanning each black and white stripe pattern of the vertical resolution measurement pattern 26V.

In the above explanation, the area of the resolution measurement pattern within the field of view of the video camera 3 was not described, but the field of view size of the video camera 3 is approximately the same size as the entire size of one resolution measurement pattern. By doing so, unnecessary output is not generated, and black and white stripe pattern output can be efficiently obtained.

It should be noted that the calculation formula for substituting the maximum value A and minimum value B of the output of the black and white stripe pattern is not limited to m=(A-B)/(A+B) in the embodiment, but for example, (A-B )/A may be employed.

Furthermore, the present invention is applicable not only to front projection type projection televisions, but also to rear projection type projection televisions, and furthermore, to direct view type displays.

[0023]

According to the present invention, a resolution measurement pattern having a plurality of black and white stripe patterns each having a stripe width of n pixels with different values of n is displayed on the screen of a display device. The resolution measurement pattern is photographed with a video camera, and the resolution is determined based on the maximum value A and minimum value B of the output of a specific scanning line of the video camera, so the screen resolution can be quantitatively evaluated. It has become possible to perform this process quickly and reproducibly. Also,
Since the measurement is done quantitatively, the evaluation is not influenced by the position of the screen. In addition, resolution can be measured quickly.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and is an explanatory diagram of a resolution measurement system.

FIG. 2 is an enlarged view of one of the resolution measurement patterns in FIG. 1;

3 is an explanatory diagram of the number of pixels per stripe of a black and white stripe pattern in the resolution measurement pattern of FIG. 2; FIG.

FIG. 4 is an explanatory diagram of the output waveform of one line in the center of the screen among the scanning lines of the video camera that captured the resolution measurement pattern and the output waveform after window processing in resolution measurement using the resolution measurement system in FIG. be.

FIG. 5 is an explanatory diagram of a method for automatically and sequentially measuring a plurality of resolution measurement patterns on a screen of a display device.

FIG. 6 is a graph showing an example of measurement of the resolution index value m by the above resolution measurement method.

FIG. 7 is a graph showing an example of measurement of the resolution index value m for the entire screen.

FIG. 8 shows another embodiment and is an explanatory diagram of a method for automatically and sequentially measuring both horizontal resolution and vertical resolution.

9 is an enlarged view of the resolution measurement pattern in FIG. 8. FIG.

[Description of symbols] 1 Projector 2 Display screen 3 Video camera 3a Fine movement table 4 Computers 5a, 5b, 5c, 5d, 5e Black and white stripe patterns 6, 26 Resolution measurement pattern 26H Horizontal resolution measurement pattern 26V Vertical resolution measurement pattern 8 Floppy disk (storing pattern generation program) 9 Memory board 10 Window processing circuit

Claims (9)

[Claims] 1. A resolution measurement method for evaluating the resolution of a display device, the resolution measurement pattern having a plurality of black and white stripe patterns each having a stripe width of n pixels with different values of n. is displayed on the screen of a display device, this resolution measurement pattern is photographed with a video camera having a resolution that can correspond to 2 dots or more per pixel, a specific line of the scanning line of this video camera is extracted, and this A method for measuring resolution in a display device, characterized in that a maximum value A and a minimum value B are detected for the output of an extracted specific line, and the resolution is determined based on the maximum value A and the minimum value B. 2. The resolution index value m is determined by substituting the maximum value A and the minimum value B into the following equation: m=(A-B)/(A+B). A method for measuring resolution in a display device. 3. The output of the resolution measurement pattern part in one line near the center of the screen of the video camera's scanning line is extracted through a window processing circuit, and the maximum value A in the output extracted through the window processing circuit is extracted. 2. The method of measuring resolution in a display device according to claim 1, further comprising detecting the minimum value B. 4. The patterns for resolution measurement in the case where the number of pixels n=1.5 are a black and white stripe pattern in which one stripe has three pixels of white, white, and black, and a pattern in which one stripe has three pixels of black, black, and white. A black and white stripe pattern of 3 pixels is provided in parallel or in series, and the resolution index value m1 of claim 2 for the white, white, black black and white stripe pattern, and the black, black, white black and white stripe pattern. 3. The resolution index value m in the case where the number of pixels n=1.5 is determined by substituting the same resolution index value m2 for the following calculation formula, m=(m1 +m2)/2. A method for measuring resolution in a display device. 5. Set the direction of the video camera at a diagonal position of the screen, and automatically change the direction of the video camera to the left and right of the screen and to change the direction of the screen up and down. 2. The method for measuring resolution in a display device according to claim 1, wherein the resolution is measured by sequentially photographing patterns for measuring resolution at locations. 6. The method for measuring resolution in a display device according to claim 1, wherein the video camera is installed at a distance three times the height of the screen of the display device and the resolution is measured. 7. The method for measuring resolution in a display device according to claim 6, wherein the size of one entire pattern for resolution measurement corresponds to the field angle size of the video camera. 8. A measurement pattern comprising a set of a horizontal resolution measurement pattern using vertical stripes for measuring horizontal resolution and a vertical resolution measurement pattern using horizontal stripes for measuring vertical resolution. 2. The method for measuring resolution in a display device according to claim 1, wherein the horizontal resolution or vertical resolution is measured by displaying the horizontal resolution measurement pattern or the vertical resolution measurement pattern on a display screen and photographing the horizontal resolution measurement pattern or the vertical resolution measurement pattern using a video camera. 9. Set the direction of the video camera at a diagonal position of the screen, change the direction of the video camera to the left and right of the screen, change the direction of the screen up and down, and rotate 90 degrees around the optical axis of the video camera. 9. The method according to claim 8, wherein the horizontal resolution measurement pattern and the vertical resolution measurement pattern are sequentially photographed at a plurality of locations on the screen to measure the horizontal resolution and the vertical resolution. A method for measuring resolution in a display device.