JP2001204049A - Display device evaluation method and evaluation device - Google Patents

Abstract

(57) [Summary] A method and an evaluation device for objectively and numerically evaluating the moving image quality of a display device are provided. A moving image displayed on a display device to be evaluated is captured as a time-series still image by a CCD, the time-series still image is taken into a controller, and the time-series still image is moved in a moving direction of the moving image. The images are superimposed while synchronizing with each other, and synthesized, and the luminance information and the cross-section plot form of the synthesized image are evaluated by numerical values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating a display device, and more particularly to a method and an apparatus for evaluating a moving image display characteristic of a display device.

[0002]

2. Description of the Related Art In recent years, LCDs and PDPs have been used as display devices.
With the widespread use of such devices, it has become clear that the moving image display characteristics of these display devices are different from those of conventional display devices using CRTs. This is because the conventional CRT is an impulse-type display device, whereas the LCD or PDP is a hold-type display device.

[0003] The moving image display characteristics of such impulse type display devices and hold type display devices and methods of evaluating the moving image display characteristics are described in, for example, IEICE Technical Report, EID96-4, p.
See p.19-26 (1996-06). According to this method, there is a method in which the moving image display characteristics are evaluated by a sensory test based on human subjective judgment, and the moving image display characteristics are evaluated in five stages.

[0004]

However, in the evaluation using the human sensory test described above, only five-level evaluation is possible, so that a delicate evaluation or an objective evaluation cannot be performed, and numerical values for improving the quality of a moving image cannot be obtained. Goals could not be determined. In addition, strict maintenance of the measurement environment and the need to collect a large number of subjects required a lot of cost and time.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a moving image display characteristic evaluation method and an evaluation apparatus which can be easily managed by numerical targets.

[0006]

In order to achieve the above object, according to the present invention, a moving image displayed on a display device to be evaluated is photographed as a time-series still image, and the plurality of photographed time-series still images are taken. The moving image perceived by the human eye is reproduced by superimposing and synthesizing the images while shifting the images, and moving image display is performed using information on the synthesized image, for example, information on the luminance distribution of the synthesized image and the shape of the cross-sectional luminance profile. Quantify physical quantities for evaluating characteristics.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In one embodiment, a moving picture display characteristic evaluation apparatus according to the present invention takes in a photographing element (CCD) having a shutter function capable of performing a random trigger operation and an image photographed by the photographing element (CCD). An image processing controller that superimposes a plurality of captured images while displacing the images and performs image processing on a synthesized image, and a display control signal of a display device to be measured that displays an image for evaluating moving image quality, and receives an image capturing element ( And a trigger output circuit that outputs a trigger output to a trigger input of a CCD (CCD). The moving image displayed on the display device to be evaluated is photographed by the photographing element, and superimposed while being shifted by the image processing controller. The combined image and its cross-sectional plot form are configured to be evaluation values.

According to the present invention, there is no need to rigorously maintain a measurement environment or to gather a large number of subjects, so that the cost and time for measurement are short, and a high level of five or more evaluations based on sensory evaluation. Numerical evaluation with high accuracy and high objectivity becomes possible.

Hereinafter, the moving image display characteristic device of the present embodiment will be described more specifically.

FIG. 1 is a block diagram of an apparatus for evaluating moving image display characteristics according to the present embodiment. The moving image display characteristic evaluation device includes a moving image signal generation circuit 100, a CCD 120, and a controller 200.

A moving image signal generating circuit 100 supplies an image signal of a moving image for measurement and a control signal to a display device 110 to be measured, and a photographing trigger generating circuit 1 in the circuit.
At 04, a shooting trigger in synchronization with the measurement timing is generated and supplied to the CCD 120.

The CCD 120 captures the whole or a part of the display area of the display device 110 displaying a moving image by the supplied capture trigger, and sequentially transfers the captured image data to the controller 200.

The controller 200 is realized by, for example, executing a program corresponding to a process described below in a well-known computer system having a CPU, a memory, and input / output means.

In the controller 200, first, the CCD 12
The image data transferred from 0 is stored as a time-series still image (time-series still image storage block 210). Here, each rectangular area 2101 exemplifies one still image. The still image to be acquired does not need to be an image shown in the entire display area of the display device, and is displayed in a partial area of the display area as long as at least a part of the moving image is displayed. The image may be a processed image.

Next, a series of stored time-series still images are synthesized while being spatially shifted so as to be synchronized with the moving direction and the moving amount of the moving image, and a synthesized image 2201 is created (time-series still image shifting synthesis). Block 220). Synthetic image 2201
Is obtained by adding the pixel values of the corresponding region of each still image along the arrow 2102 corresponding to the moving speed of the moving image shown in the figure. Details will be described later with specific examples.

The synthesized image obtained in this manner is generated so that a human looks at the moving image while following the moving image and is substantially equal to the recognized image. In the present embodiment, a numerical value as a moving image display characteristic is analyzed and obtained from the cross-sectional profile and luminance information of the composite image (numerical analysis block 230).

FIG. 2 is a block diagram of the moving picture signal generating circuit 100 for explaining the details. In the moving image signal generation circuit 100, the dot clock frequency and resolution are set according to the resolution and frequency characteristics of the display device 110 to be measured, and the dot clock and horizontal synchronization are set by the dot clock generation circuit 101 and the control signal generation circuit 102. , And generates a vertical synchronizing signal. Next, using these control signals, a moving image signal for measurement is converted into a moving image signal generation circuit 103.
Generated by

In this embodiment, three patterns of horizontal scrolling at a constant speed are prepared as moving images for measurement.
This is shown in FIG.

The pattern (1) is a vertical bar solid-filled with a constant fill gradation in the background gradation. The bar scrolls in the horizontal direction with respect to the background gradation, and when reaching one short portion, scrolling is restarted from the other end.
In FIG. 3, the background gradation is white and the fill gradation is black, but the background gradation, the fill gradation, the bar width, the scroll moving speed, and the like can be changed as measurement image parameters. In particular, the moving speed is an important parameter, and in the present embodiment, the number of moving pixels per rewriting cycle (pp
f: Pixel Per Frame).

Next, in the pattern (2), the painted portion of the pattern (1) changes continuously in a one-cycle wave (isolated wave). In FIG. 3, the background gradation is white and the center of the wave is black. The background gradation, wave phase, width, scroll speed, and the like can be similarly changed.

Finally, the pattern (3) corresponds to the pattern (2)
The wave of one cycle becomes continuous and the background disappears.

Note that the pattern used in the present invention is not limited to the above-mentioned pattern, and the shape, luminance, color, gradation, moving direction, moving speed, etc. of the pattern are determined according to the display characteristics to be evaluated. May be set.

In the evaluation apparatus of the present embodiment, any one of the three types of patterns described above is displayed as a moving image (scroll). Watching the display while following the scroll. In this case, an image recognized by a human is an image obtained as a result of time-integrating luminance while moving (shifting the location) in accordance with scrolling.

That is, in order to reproduce the image perceived by the human eyes, the image displayed on the display device may be continuously photographed and synthesized while shifting in the scroll direction. At this time, the shooting cycle (sampling cycle) is at least 1/1 of one rewriting cycle (one frame).
2 is necessary (Nyquist frequency), and considering that the time resolution of the human eye is about 1/300 seconds, it is preferable that the time resolution is about 3 ms or less. In the present embodiment, one frame of display is 16.6 ms (60 Hz), so it is desirable to divide one frame into six or more at equal intervals and shoot.

By the way, a CCD camera having a photographing frequency of 360 Hz or more is required for performing continuous photographing six times or more in the same frame. Since such a high-speed CCD camera has a limited number of pixels, the present embodiment detects a frame in which the display pattern returns to the same place when a scrolling moving image is displayed as shown in FIG. And
Six or more shots were taken on different frames displaying the same image while changing the timing.

The trigger necessary for photographing as described above is generated from the photographing trigger generating circuit 104. FIG. 4 shows a block diagram of the photographing trigger generating circuit 104.

In the photographing trigger generation circuit 104,
The 1 / n frame counter 131, the dot clock counter 132, and the comparator 135 output 1 / n timing in the case of shooting n times in one frame. The dot clock counter 132 is a counter that counts dot clocks for one frame period. The output value of the dot clock counter 132 is 1 / n frame counter 1
When the value matches the output value of the comparator 31, the output of the comparator 135 becomes positive. The 1 / n frame counter 131 has 1 internally.
A value obtained by dividing the number of dot clocks of a frame by 1 / n is held, and the output value is counted up by that value each time one image is taken, so that continuous timing in the frame can be always output.

Next, the scroll measurement position counter 133
And scroll current position counter 134, comparator 13
At 6, it is detected whether or not the scroll position of the moving image scroll display has returned to the original position. The scroll current position counter 134 counts the current scroll position by adding the scroll movement amount for each vertical synchronization. On the other hand, the scroll measurement position counter 133 starts scrolling and holds the scroll position at the time of the first shooting, and the output of the comparator 136 becomes positive when the outputs of the two coincide with each other.

When both outputs of the two comparators become positive, the output of the AND circuit 137 becomes positive,
A shooting output trigger is output. When the 1 / n frame counter 131 counts up n times and moves up, the scroll measurement position counter 133 counts up by the number of pixels corresponding to the moving speed, and indicates the next scroll measurement position. The continuity of shooting is also maintained.

In this manner, the photographing trigger output circuit 10
4 has different timings depending on the moving speed and the number of divisions n in the frame.
D120 uses a CCD camera that can be shuttered by an external random trigger, and performs accurate shuttering by an external trigger.

As a CCD photographing method, a progressive scan CCD for photographing the entire screen at once is used.
Is used. As described above, the exposure time (shutter time) is about 1/300 of the time resolution of the human eye.
Since it is seconds, it is desirable that the exposure time be 1/300 seconds or less. In the present embodiment, the exposure time is 1/500 seconds.

Next, the processing in the controller 200 will be described in detail. In the following description, an example in which a liquid crystal display device is used as the display device 110 to be measured and measurement is performed using the moving image signal generation circuit 100 and the CCD 120 will be described. The moving image display is a solid black pattern (1) on a white background. When the pattern (1) is displayed without scrolling (still image display),
FIG. 5 shows an image captured by the CD 120. The width of the bar of this pattern (1) is 32 pixels.

This pattern (1) is moved at a moving speed of 8ppf.
The display area when scrolling with (pixel per frame) is C
FIG. 6 shows one of the still images continuously shot by the CD 120. In the present controller 200, the still images as described above are acquired in time series, and the time-series still image storage block 210
To save.

In the still picture shown in FIG. 6, halftones are displayed on the left and right of the bar of the pattern (1) due to the delay of the voltage-luminance response of the liquid crystal. In this example, the pattern is scrolling from right to left, so the right halftone area of the solid black pattern should gradually change to white, and the left halftone area should gradually change to black. is there.

In this embodiment, the number of photographing divisions n within a frame is n = 16, and a total of 32 (two frames) time-series still images are photographed, including this FIG. As described above, the number of divisions within a frame is desirably 6 or more. However, since it is desirable that the number of movements is twice or more of the movement amount from the viewpoint of accuracy, n = 16.

When this time-series still image is continuously observed, it can be seen that the black solid pattern moves from right to left while changing the halftone. In this case, the nth and n + 16th still images have the same halftone pattern,
Only the location differs by the movement amount of one frame. In this example, since the uniform movement amount is 8 ppf, the position is moved by 8 pixels on the display device to be measured. The human eye follows this movement, and the point of gaze always shifts. Therefore, by synthesizing each image while shifting it in the scroll direction according to the time timing within the frame for each still image of the time-series still image, Therefore, it is possible to reproduce an image perceived by human eyes.

That is, as shown in this example, with a movement amount of 8ppf,
When the number of divisions in a frame is 16, a still image at a timing of 2/16 is shifted by one pixel, a still image at a timing of 8/16 is shifted by four pixels, and a still image at a timing of 14/16 is shifted by 7 pixels.
That is, it is necessary to shift the pixels and combine them. FIG. 7 shows an image synthesized in this manner. In the controller 200 of the present embodiment, the above-described synthesizing process is performed by the time-series still image shift synthesizing block 220.

The delay in response speed and blurring caused by the hold-type display device are added to the synthesized image in FIG. 7, and the image to be viewed as a still image similar to that in FIG. 5 is considerably blurred by scrolling. Actually, even by visual observation, it is observed almost the same. This is the deterioration of the display characteristics of the moving image display (moving image display characteristics). It is known that such deterioration varies depending on the moving speed, and the higher the moving speed, the greater the deterioration. In the present embodiment, in order to numerically evaluate such deterioration of the moving image display characteristics, the luminance information of the composite image and the cross-sectional luminance profile are analyzed by the numerical analysis block 230 of the controller 200.
Digitize.

FIG. 8 shows a cross-sectional luminance profile of a composite image when the above pattern (1) is scrolled at scrolling speeds of 1, 2, 4, and 8 ppf. It can be seen that as the moving speed increases, the halftone region expands and the blur increases. By analyzing this cross-sectional brightness profile, the moving image display characteristics can be digitized.

First, the ratio between the white luminance level and the black luminance level of this sectional luminance profile is compared with the contrast ratio of a still image to obtain a dynamic contrast ratio.
CR) can be quantified. This is shown in FIG. FIG.
According to the graph, as the moving speed increases, Dynamic-
It was observed that the CR went down. This means that the faster the moving speed of the moving image, the lower the contrast value of the display.

Further, the size and half-value width of the left and right halftone areas of the sectional luminance profile can be digitized. These are shown in FIG. FIG. 10 shows the relationship between the half-width of the cross-sectional luminance profile of the pattern (1) and the width of the halftone area appearing before and after the pattern (1), and the moving speed.
Note that the pixel number parameter on the vertical axis of the graph is the CCD 12
0 represents the width on the imaging screen, and corresponds to the number of pixels on the display screen. From this graph, the size of the left and right halftone areas increases in proportion to the moving speed,
It is shown that the blur is larger. Also, it was observed that the half width became smaller as the moving speed increased.

In the present embodiment, the pattern (1) is used as an example of the moving image display pattern. However, the same evaluation can be performed when the pattern (2) or the pattern (3) is used. In particular, the pattern (2) and the pattern (3) have a stricter value of Dynamic-CR, and the pattern approaches a real image such as a natural image, so that the pattern (2) and the pattern (3) are suitable for evaluation of Dynamic-CR characteristics.

In the present embodiment, the photographing trigger generating circuit 104 is formed in the moving image signal generating circuit 100. However, when a general-purpose image signal source is used as the moving image signal generating circuit, the photographing trigger generating circuit 104 is used. The generation circuit 104 may be provided between the image signal source and the display device to be measured, and data such as the moving amount of the moving image may be input.

Furthermore, the digitization of the dynamic image display characteristics such as Dynamic-CR, halftone width and half width in the present embodiment is merely an example, and evaluation items that can appear due to the dynamic image display characteristics of the display device, for example, moving image Other parameters set for detecting blur, color change, and the like in the boundary area can be quantified in the same manner as described above.

As described above, in this embodiment, since the image perceived by human eyes can be reproduced by using the moving image signal generation circuit, the CCD, and the controller, the measurement is performed in order to perform a sensory test. Since there is no need to strictly maintain the environment or to collect many subjects, the cost and time for measurement are short.
Since a numerical evaluation equal to or higher than the graded evaluation is possible, it is possible to provide a method and an apparatus for evaluating a moving image display characteristic which can be easily managed by numerical targets and can be evaluated with high accuracy.

[0046]

By introducing the present invention as a means for evaluating the moving image display characteristics of the display device, it is not necessary to rigorously prepare a measurement environment for sensory tests and to collect a large number of subjects. In addition, the cost and time for measurement are short, and numerical evaluation of five or more levels by sensory evaluation is possible, so that management by numerical targets becomes easy.

[Brief description of the drawings]

FIG. 1 is a block diagram of a moving image display performance evaluation device for a display device according to an embodiment of the present invention.

FIG. 2 is a moving image signal generation circuit 1 in the embodiment of FIG.
00 is a block diagram.

FIG. 3 is an explanatory diagram for explaining a moving image pattern for measurement in the embodiment of FIG. 1;

FIG. 4 is a block diagram of a shooting trigger generation circuit in the embodiment of FIG. 1;

FIG. 5 is an explanatory diagram showing a still image captured by the evaluation device of the embodiment of FIG. 1;

FIG. 6 is an explanatory diagram showing an example of a moving image continuously photographed by the evaluation device of the embodiment in FIG. 1;

FIG. 7 is an explanatory diagram showing an image synthesized by shifting moving images continuously shot by the evaluation apparatus of the embodiment of FIG. 1;

8 is a graph showing a cross-sectional luminance profile of a composite image in the evaluation device of the embodiment shown in FIG.

9 is a graph showing one example (Dynamic CR) of the result of evaluating moving image display characteristics in the evaluation device of the embodiment of FIG. 1;

FIG. 10 is a graph showing an example (halftone width, half width) of a moving image display characteristic evaluation result in the evaluation device of the embodiment of FIG. 1;

[Explanation of symbols]

Reference numeral 100: moving image signal generating circuit, 101: dot clock generating circuit, 102: control signal generating circuit, 103: moving image signal generating circuit, 104: photographing trigger generating circuit, 110
... Display device to be measured, 120 ... CCD, 131 ... 1 /
n frame counter, 132 dot clock counter, 133 scroll measurement position counter, 134 current scroll position counter, 135 comparator, 13
6 comparator, 137 AND circuit, 200 controller, 210 time-series still image storage block, 220
... Time-series still image shifting synthesis block, 230...

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Makoto Tsumura 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. 5B057 BA02 BA11 CA08 CA12 CA16 CB08 CB12 CB16 CC01 CE08 CE11 DA20 DB02 DB09 DC22 5C061 BB07 CC07 5C082 AA11 AA27 BA20 BA27 BA41 CA55 CA72 CA81 CB05 CB08 EA20 MM05 MM10

Claims (13)

[Claims] 1. A method for evaluating a moving image display characteristic of a display device for displaying a moving image, comprising: capturing a moving image displayed on a display device to be measured as a time-series still image; Time-series still images are superimposed and synthesized while being spatially shifted, and using the information of the synthesized image, a physical quantity corresponding to the moving image display characteristic to be evaluated is quantified and evaluated. Evaluation method of video display characteristics. 2. An apparatus for evaluating a moving image display characteristic of a display device that displays a moving image, comprising: an imaging unit that captures a moving image of the display device to be evaluated; and a still image captured by the imaging unit. Image processing means for capturing the time-series still images, superimposing the plurality of captured time-series still images while spatially shifting them, and performing image processing on the synthesized image, wherein the image processing means A moving image display characteristic evaluation device, characterized in that a physical quantity corresponding to the evaluation target moving image display characteristic is quantified and evaluated using image information. 3. The evaluation device according to claim 2, wherein the image processing device sets at least one of a luminance distribution and a cross-sectional luminance profile of the synthesized image as a physical quantity corresponding to the moving image display characteristic to be evaluated. An apparatus for evaluating moving image display characteristics, characterized in that it is converted into a numerical value. 4. The evaluation device according to claim 2, wherein the display device to be evaluated displays a moving image that is moving as a moving image quality evaluation image, and displays the captured time-series image. An apparatus for evaluating moving image display characteristics, wherein a shift amount when combining images while shifting is equal to an amount corresponding to the moving speed in the captured image. 5. The evaluation device according to claim 4, wherein the moving image displayed by the display device to be evaluated displays a certain luminance for a certain width in the moving direction. An evaluation device for characteristic moving image display characteristics. 6. The evaluation device according to claim 4, wherein the moving image displayed by the display device to be evaluated is an isolated single-period wave within a certain width in the moving direction. An apparatus for evaluating moving image display characteristics, comprising a region having a luminance distribution that changes in shape, and displaying a constant luminance in other regions located before and after the region. 7. The evaluation device according to claim 4, wherein the moving image displayed by the display device to be evaluated has a constant period in a moving direction and changes into a continuous wave shape. An evaluation device for a moving image display characteristic, characterized by having a luminance distribution as follows. 8. An evaluation device according to claim 2, wherein a display control signal of said display device to be evaluated displaying a moving image quality evaluation image is input, and a photographing timing of said image pickup means is set. An apparatus for evaluating a moving image display characteristic, further comprising a trigger output circuit for outputting a trigger signal for determination. 9. The evaluation device according to claim 8, wherein the timing of capturing the time-series still image or the timing of outputting a trigger signal of the trigger output circuit is synchronized with a one-screen rewriting cycle of the display device to be evaluated. A moving image display characteristic evaluation device, wherein the timing is such that the photographed still images are equally spaced for an integral time of one rewriting cycle. 10. The evaluation device according to claim 9, wherein the integer value dividing the one rewrite cycle is a numerical value such that a time equal to an integer of the one rewrite cycle is 3 ms or less. An apparatus for evaluating moving image display characteristics, characterized in that: 11. The evaluation device according to claim 9, wherein the integer value dividing the one rewrite cycle is a moving amount (pixel number) per one rewrite cycle of a moving image displayed by the display device to be evaluated. A) a moving image display characteristic evaluation device characterized in that the value is at least twice the value of 12. The evaluation apparatus according to claim 2, wherein one of a photographing time of each of the time-series still images and an exposure time of the photographing unit is 3 ms or less. Of moving image characteristics. 13. An apparatus for reproducing a moving image displayed on a display device perceived by human eyes, wherein said imaging means captures a moving image displayed on said display device to be evaluated. Reproduces a moving image perceived by the human eye by capturing multiple still images captured by the imaging means in time series and superimposing and combining the captured multiple time-series still images while spatially shifting A moving image reproducing apparatus, comprising: