JPH09139960A - Equipment and method for spatial frequency characteristic measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately measure the spatial frequency characteristic without any expert skill by providing a means applying a measurement image signal to a display device to be measured while a phase of a horizontal synchronizing signal and/or a vertical synchronizing signal is being changed slightly. SOLUTION: A spatial frequency characteristic measurement equipment 10 uses a signal generator 20 to generate a measurement signal S1 and to give the signal S1 to a display device 30 to be measured, on which a measurement image is displayed. The image is picked up by a CCD camera 40 and obtained luminance information is fed to a computer 70 via an image processing circuit 50. The equipment 10 varies a phase of a horizontal synchronizing signal of the signal S1 fed from the generator 20 to the display device 30 slightly to inch an image in the horizontal direction. The luminance information at a highest luminance level is extracted and an accurate luminance distribution is measured. Furthermore, a difference between a maximum luminance level and a minimum luminance level is measured while varying a frequency of the signal S1 to obtain a spatial frequency characteristic plotting.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. TECHNICAL FIELD OF THE INVENTION Conventional Technology (FIG. 10) Problem to be Solved by the Invention (FIG. 11) Means for Solving the Problem Embodiments of the Invention (FIGS. 1 to 9)

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial frequency characteristic measuring device and a spatial frequency characteristic measuring method, and is particularly suitable for use in measuring the spatial frequency characteristic of a television receiver having a color selection mechanism. .

[0003]

2. Description of the Related Art Generally, in an image display device such as a television receiver, the resolution and sharpness of the picture tube are evaluated by measuring the spatial frequency characteristic of the surface of the picture tube. This spatial frequency characteristic is obtained from the distribution of the luminance on the surface of the picture tube and the difference in the luminance level between the brightest part and the darkest part, and to what extent the resolution changes when the frequency of the image displayed on the screen is changed. It also serves as an evaluation criterion indicating whether or not an image with high sharpness can be displayed.

Conventionally, as a method of measuring such a spatial frequency characteristic, there is a method of displaying an image for measurement such as a resolution chart on a display to be measured and visually measuring the image. For example, the limit position where the line displayed in the resolution chart is clearly visible is visually determined, and the number of resolutions corresponding to this position is read to measure. In addition, the measurement image signal is input to the display under measurement to display a measurement image of a predetermined pattern, the pattern image is captured by, for example, a CCD (Charge Coupled Device) camera, and the brightness amplitude is measured. There are also methods.

[0005]

However, in the above-mentioned method of measuring by visual observation, there is a problem that skill is required for the measurement because the measurement accuracy easily varies among individuals.
Also, because this measurement method depends on the sense of the measurer,
There is always a problem when an error occurs in the measurement result when the measurement is repeated.

Further, in the case of the method of photometrically measuring the luminance amplitude of the measurement image displayed on the display under measurement, the original luminance information cannot be obtained by the color selection mechanism in the display under measurement, and the accurate spatial frequency characteristic is obtained. There are some problems when it is difficult to measure.

This point will be specifically described with reference to FIG. In FIG. 10, reference numeral 1 denotes an electron gun of an image display device of the trinitron system, which emits electron beams L1, L2, and L3 for emitting respective colors of R, G, and B. The emitted electron beams L1, L2, and L3 are respectively applied to the R, G, and B three-color phosphors 21, 22 and 23 arranged on the phosphor screen 2 formed on the tube surface. Each of the phosphors 21, 22 and 23 emits light by the electron beam L1, L2 or L3 thus irradiated. In front of the fluorescent screen 2, an aperture grill 3 is provided as a color selection mechanism, which is a vertical slit formed in stripes. The electron beams L1, L2 and L3 are applied to the phosphor screen 2 through the aperture grill 3 to
Only the target phosphor is irradiated. In this way, by irradiating only the target phosphor with the electron beam through the aperture grill 3, it is possible to display an image with clear color development.

However, as shown in FIG. 11, the aperture grill 3 shields the irradiated electron beam within a predetermined range so that only the target phosphor is irradiated with the electron beam. For example, when it is desired to irradiate only the fluorescent body 22 with the electron beam L2, only the fluorescent body 22 is irradiated by blocking the beam of the portion irradiated to the fluorescent bodies 21 and 23 with the slit portion. Therefore, the electron beam L
The blocked portion of the second light flux is cut, and the original beam shape and beam intensity cannot be obtained. As described above, since the electron beam emitted to the tube surface is cut by the color selection mechanism including the aperture grill in the picture tube, it is difficult to obtain an accurate measurement value based on the original brightness.

The present invention has been made in consideration of the above points, and proposes a spatial frequency measuring apparatus and a spatial frequency measuring method that can easily measure the spatial frequency characteristic regardless of skill and can measure the spatial frequency characteristic more accurately. Is what you are trying to do.

[0010]

In order to solve the above problems, the present invention provides a measurement image signal supply for supplying a measurement image signal to a display under measurement while slightly changing a horizontal synchronization signal and / or a vertical synchronization signal. A means is provided.

The influence of the color selection mechanism can be avoided by slightly changing the horizontal synchronizing signal and / or the vertical synchronizing signal to slightly move the electron beam emitted in the display under test horizontally and / or vertically. The measurement image can be displayed at the beam position. Thereby, the influence of the color selection mechanism can be avoided and the luminance information can be collected accurately.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, reference numeral 10 indicates a spatial frequency characteristic measuring apparatus as a whole, which supplies a predetermined measurement signal to a display under test of a trinitron system to display a measurement image, and based on the luminance information of this image. To measure the spatial frequency characteristics. At this time, luminance information is accurately obtained by slightly changing the horizontal synchronizing signal of the supplied measurement signal, whereby the spatial frequency characteristic can be accurately measured.

The spatial frequency characteristic measuring device 10 supplies the measuring signal S1 generated by the signal generator 20 to the display 30 to be measured, and displays an image based on the measuring signal S1 on the tube surface of the display 30 to be measured. . The image displayed in this manner has a striped pattern in which the R (red) portion, the G (green) portion, or the B (blue) portion is displayed, and the light and dark changes continuously and periodically. The tube surface display of the measured display 30 shown in FIG. 2 shows a case in which the G (green) portion is displayed, and it gradually becomes dark with the brightest portion as the apex, and the darkest portion as the end of the cycle, and then again. The brightest part is displayed. The image thus displayed is picked up by the CCD camera 40 and input to the image processing circuit 50 as a camera output signal S3. An image monitor 60 is connected to the image processing circuit 50, and the focus of the CCD camera 40 is adjusted while watching the image displayed on the image monitor 60 by the image signal S4 sent from the image processing circuit 50. It is becoming like this.

Further, the signal generator 20 sends a control signal S2 so that the CCD (Charge Coupled Device)
The shutter speed and the like of the camera 40 are set. For example,
If double exposure occurs in the captured image because the shutter speed of the CCD camera 40 and the frequency of the image displayed on the measured display 30 are different, the exposure time setting is adjusted. If the black level differs due to the type of display, adjust the pedestal level. Further, if the red level cannot be accurately measured due to an infrared cut filter provided in the CCD camera 40, the red level gain is adjusted.

The image processing circuit 50 converts the input image from the camera output signal S3 into a digital format and temporarily stores it, and then sends it to the computer device 70 as image data S5. The computer device 70 obtains a brightness distribution curve based on the input image data S5.
Based on this curve, the brightness level difference between the brightest part and the darkest part is obtained while changing the frequency of the image signal for measurement, and the obtained measurement result is displayed on the display monitor 80. Specifically, the computer device 70 forms an image signal S6 by graphing the obtained measurement result, and supplies the image signal S6 to the display monitor 80 to display an image. In this way, the user can easily confirm the spatial frequency characteristic of the display 30 to be measured by graphically displaying the result obtained by the measurement on the display monitor 80.

Further, the signal generator 20 and the image processing circuit 50.
An optical fiber cable (not shown) is connected between the image processing circuit 50 and the computer device 70, and an AT bus (not shown) is connected between the image processing circuit 50 and the computer device 70. The computer device 70 has a program for measurement, and controls the image processing circuit 50 via the AT bus and the signal generator 20 sequentially via the AT bus, the image processing circuit 50, and the optical fiber cable. In fact, the signal generator 20
The image processing circuit 50 and the image processing circuit 50 execute respective measuring operations according to the program data S7 supplied from the computer device 70.

Next, an internal circuit block of the signal generator 20 is shown. In FIG. 3, reference numeral 20 denotes a signal generator as a whole, which supplies a measurement signal S1 to the display under test 30 and sends a control signal S2 to the CCD camera 40 (FIG. 1). Further, these measuring operations are executed by the program data S7 supplied from the computer device 70 (FIG. 1).

The signal generator 20 is an optical fiber cable (not shown) connected to the image processing circuit 50 (FIG. 1).
The program data S7 supplied from the computer device 70 via the optical signal interface 201 is input to the control unit 202 via the optical signal interface 201. The control unit 202 stores the program data S7 and executes the measurement work according to the procedure shown in the program data S7. The control unit 202 uses the digital interface 2
The control signal S10 is sent to the setting unit 204 via 03. The setting unit 204 sets signals to be sent as the measurement signal S1 and the control signal S2 based on the control signal S10. The digital interface 203 distributes and supplies the control signal S10 to each setting unit of the setting unit 204 according to the command content.

Dot consisting of a dot clock setting unit
The clock generation unit 205 sets and generates the frequency of the dot clock S11 serving as the reference signal by the supplied control signal S10. Dot / clock generation unit 205
Supplies the generated dot clock signal S11 to the synchronization signal generation unit 206. The sync signal generator 206 forms a vertical sync signal S12, a horizontal sync signal S13, and a blanking signal S14 based on the dot / clock signal S11 and the control signal S10. The synchronization signal generation unit 206
The formed vertical synchronizing signal S12 is output as it is, and the horizontal synchronizing signal S13 is sent to the horizontal synchronizing shift unit 207. In addition, the synchronization signal generator 206 detects the vertical synchronization signal S
12, horizontal synchronizing signal S13 and blanking signal S14
Is supplied to the counter 208. Horizontal sync shift unit 207
Changes the phase of the horizontal synchronizing signal S13 based on the control signal S10 and outputs it. Thereby, the image position displayed on the measured display 30 (FIG. 1) can be moved in the horizontal direction.

The counter 208 receives the input vertical synchronizing signal S12, horizontal synchronizing signal S13 and blanking signal S.
Based on 14 and the control signal S10, the timing signal S15 for setting the image display interval is formed. The generated timing signal S15 is a video digital / analog converter 209 (hereinafter referred to as video D / A.
(Referred to as converter 209). Video / D /
The A / converter 209 forms and outputs an R signal S16, a G signal S17, and a B signal S18 based on the control signal S10 and the timing signal S15.

In practice, the vertical synchronizing signal S12, the horizontal synchronizing signal S13, the R signal S16, and the G signal S thus formed are
17 and the B signal S18 are combined as a measurement signal S1 and sent to the display under test 30 (FIG. 1).
Further, the camera control section 210 forms and outputs a control signal S2 for setting the shutter speed, gain and pedestal level of the CCD camera 40 based on the control signal S10. As a result, the CCD camera 40 (FIG. 1) can execute the image pickup of the display image based on a certain reference regardless of the type of display.

Next, FIG. 4 shows the structure of the internal block of the image processing circuit 50. In FIG. 4, reference numeral 50 denotes an image processing circuit as a whole, which temporarily stores a camera output signal S3 supplied from the CCD camera 40 and sends it as image data S5 to the computer device 70 via an AT bus (not shown). To do. Further, an image signal S4 is formed based on the camera output signal S3 and sent to the image monitor 60, and C
The image captured by the CD camera 40 is displayed. Furthermore, these measuring operations are performed by the computer device 70 from the AT.
It is executed by the program data S7 supplied via a bus (not shown) (FIG. 1).

The image processing circuit 50 includes a computer device 7.
The program data S7 supplied from 0 is controlled by the control unit 502 via the AT bus and the optical signal interface 501.
To enter. The controller 502 stores the program data S7 and executes the measurement work according to the procedure shown in the program data S7. The program data S7 thus supplied is also given to the signal generator 20 (FIG. 1) via the optical signal interface 501 and the optical fiber cable (not shown).

The image processing circuit 50 includes the CCD camera 4
The camera output signal S3 supplied from 0 (FIG. 1) is temporarily stored in the internal frame memory. The R signal S20, the G signal S21, and the B signal S22 input to the image processing circuit 50.
The camera output signal S3 consists of an analog digital
Converter 503 (hereinafter referred to as A / D converter 50
3)) to a digital image signal S23, and then a frame selector 505 via a bus 504.
To TRUE / COLOR / R via bus 506
It is sent to the AMDAC 507 and the frame memory 508. The frame selector 505 is the frame memory 50.
9 or 510 is selected to supply the digital image signal S23. In this way, the CCD camera 40 is stored in the frame memory 508 and the frame memory 509 or 510.
The image information captured in (FIG. 1) is stored.

The image information thus stored in each frame memory is selectively read by the control signal S24 sent from the control unit 502 via the processor bus 511, and the optical signal interface 50 is output as the image data S5.
1 and an AT bus (not shown) sequentially to the computer device 70 (FIG. 1).

TRUE / COLOR / RAMDAC50
7 forms an image signal S4, which is an image similar to that stored in each frame memory, based on the image signal S3 imaged by the CCD camera 40 (FIG. 1) and converted into a digital signal, and the image monitor 60 ( 1). TRUE
The COLOR RAMDAC 507 is based on the supplied digital image signal S23, and outputs an R signal S25 and a G signal S.
26 and B signal S27. In addition, the synchronization signal generator 512 includes a vertical synchronization signal S28 and a horizontal synchronization signal S29.
To form The R signal S25, the G signal S26, the B signal S27, the vertical synchronization signal S28, and the horizontal synchronization signal S29 formed in this way are displayed on the image monitor 60 as an image signal S4.
(Fig. 1). As a result, the image captured by the CCD camera 40 is displayed on the image monitor 60.

In the above structure, the spatial frequency characteristic measuring apparatus 10 supplies the measurement signal S1 generated by the signal generator 20 to the display under test 30 to display the measurement image. Further, this image is captured by the CCD camera 40, and the obtained luminance information is supplied to the computer device 70 via the image processing circuit 50. The spatial frequency characteristic measuring device 10 minutely changes the phase of the horizontal synchronizing signal of the measuring signal S1 supplied from the signal generator 20 to the display 30 to be measured, thereby slightly moving the measuring image in the horizontal direction. . As a result, it is possible to extract the luminance information at the position where the luminance level is the highest, and it is possible to measure the accurate luminance distribution. Further, the spatial frequency characteristic curve can be obtained by measuring the brightness level difference between the maximum brightness level and the minimum brightness level of the brightness information thus obtained while changing the frequency of the measurement signal S1.

That is, conventionally, when the measurement signal is supplied to the display under measurement to display the measurement image, the electron beam L1, L2 or L3 is scraped by the aperture grill 3 in the display under measurement. (Figure 10),
It was difficult to obtain the brightness distribution curve with accurate brightness without obtaining the original beam shape. For example, as shown in FIG. 5, it can be seen that the influence of the aperture grill 3 is hardly seen in P1, but the electron beam is largely shaved by the aperture grill 3 in P2.

Spatial frequency characteristic measuring apparatus 10 of this embodiment
The horizontal synchronization shift unit 207 converts the horizontal synchronization signal S13 of the measurement signal S1 generated by the signal generator 20 as described above.
The electron beam is slightly moved in the horizontal direction by making a slight change. As a result, as shown in FIG. 6, the measurement can be performed at a point where the influence of the aperture grill 3 can be avoided, for example, a point at which the brightness level has the highest value, and the original brightness distribution curve can be obtained. Here, the vertical axis represents the brightness level, A represents the maximum brightness level, and B represents the minimum brightness level.
-B indicates the sharpness.

Further, as shown in FIGS. 7 and 8, the dot
Comparing the case where the frequency of the clock is high and the case where the frequency of the clock is low, the difference between the maximum brightness level and the minimum brightness level is larger by C when the frequency is low than when the frequency is high. From this, a quantified spatial frequency characteristic can be obtained by measuring the difference AB between the maximum luminance level and the minimum luminance level while changing the frequency of the dot clock.

FIG. 9 is a graph showing the spatial frequency characteristics thus obtained. In this figure, the horizontal axis represents the frequency of dots and clocks, and the vertical axis represents the difference in brightness level between the brightest part and the darkest part, which represents the resolution and sharpness, and is digitized by photoelectric conversion (A / D value). ) Is shown. As shown in this figure, the sharpness decreases as the frequency increases. Thus, it is found that the position where the slope of the curve is substantially parallel to the horizontal axis is the display limit of the display that is the measurement target, and the frequency indicating that position is the limit value of the frequency that can be used in this display.

According to the above configuration, the horizontal synchronization of the measurement signal S1 is slightly changed to slightly move the electron beam emitted from the electron gun 1 in the measured display 30 in the horizontal direction, so that It is possible to accurately measure the brightness information while avoiding the lack of the brightness information due to the color selection mechanism including the grill 3. Thus, it is possible to realize the spatial frequency characteristic measuring apparatus 10 and the spatial frequency characteristic measuring method that can perform the measurement easily regardless of skill and can measure the spatial frequency characteristic more accurately.

In the above embodiment, the case where the present invention is applied to the spatial frequency characteristic measuring device 10 for measuring the spatial frequency characteristic of the image display device of the trinitron system has been described, but the present invention is not limited to this, and color selection is not limited to this. Any image display device having a mechanism can be applied. For example, the present invention can be applied to an image display device using a circular shadow mask such as the delta dot system as a color selection mechanism. In this case, the electron beam may be scraped not only in the horizontal direction but also in the vertical direction. In a spatial frequency characteristic measuring device for measuring such an image display device, a signal generator to which a vertical synchronizing shift section is added is provided. By making it possible to shift both the horizontal synchronizing signal and the vertical synchronizing signal in this way, the electron beam emitted from the electron gun can be moved in the horizontal and vertical directions within the display under test. Thus, the present invention can be applied to an image display device using any type of color selection mechanism.

Further, in the above embodiment, the signal generator 20 and the image processing device 50 which mutually input and output signals by the optical signal are described, but the present invention is not limited to this.
You may use the signal generator and image processing apparatus which input / output a signal mutually by a normal electric signal.

[0036]

As described above, according to the present invention, by providing the measuring image signal supplying means for supplying the measuring image signal to the display under measurement while slightly changing the horizontal synchronizing signal and / or the vertical synchronizing signal. Therefore, it is possible to collect the luminance information accurately while avoiding the influence of the color selection mechanism. As a result, it is possible to realize a spatial frequency characteristic measuring device and a spatial frequency characteristic measuring method that can perform the measurement easily regardless of skill and can measure the spatial frequency characteristic more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a spatial frequency characteristic measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a measurement image displayed on a display under measurement.

FIG. 3 is a block diagram showing an internal configuration of a signal generator.

FIG. 4 is a block diagram showing an internal configuration of an image processing circuit.

FIG. 5 is a chart showing a luminance distribution curve measured when information is lost due to the electron beam being cut.

FIG. 6 is a chart showing an original luminance distribution curve that is not affected by a color selection mechanism.

FIG. 7 is a chart showing a luminance distribution curve when a dot clock frequency is high.

FIG. 8 is a chart showing a luminance distribution curve when the frequency of the dot clock is low.

FIG. 9 is a chart showing an example of spatial frequency characteristics.

FIG. 10 is a perspective view showing the principle of image display in the Trinitron format.

FIG. 11 is a schematic diagram provided for explaining blocking of an electron beam by a color selection mechanism.

[Explanation of symbols]

1 ... Electron gun, 2 ... Fluorescent screen, 3 ... Aperture grill, 10 ... Spatial frequency characteristic measuring device, 20 ... Signal generator, 21, 22, 23 ... Phosphor, 30 ... Measured Display, 40 ... CCD camera, 50 ... Image processing circuit, 60 ... Image monitor, 70 ... Computer device, 80 ... Display monitor, 201, 501 ... Optical signal interface, 202, 502 ... Control unit , 203 ...
… Digital interface, 204… Setting section,
205 ... Dot / Clock generator, 206, 512 ...
... Synchronization signal generation unit, 207 ... Horizontal synchronization shift unit, 20
8 ... Counter, 209 ... Video D / A converter, 210 ... Camera control unit, 503 ... A / D converter, 504, 506 ... Bus, 505 ... Frame ...
Selector, 507 ... TRUE, COLOR, RAMD
AC, 508, 509, 510 ... Frame memory.

Claims (3)

[Claims] 1. A spatial frequency characteristic measuring device for displaying a measuring image by supplying a measuring image signal to the measuring display and obtaining luminance information from the measuring image to obtain a spatial frequency characteristic of the measuring display. In, while generating the measurement image signal, the measurement image signal supply means for transmitting while slightly changing the phase of the horizontal synchronization signal and / or the vertical synchronization signal of the measurement image signal, and the measurement image signal. An image pickup means for picking up the measurement image displayed on the display under measurement by supplying the image information, and luminance information of the measurement image obtained from the measurement image picked up by the image pickup means. Image processing means for obtaining the spatial frequency characteristic of the display to be measured based on the luminance information . 2. The image information processing means, while changing the frequency of the measuring image signal by the measuring image signal supplying means, calculates the difference in luminance level between the brightest part and the darkest part of the measuring image. The spatial frequency characteristic measuring apparatus according to claim 1, wherein the spatial frequency characteristic of the measured display is obtained by measuring. 3. A spatial frequency characteristic measuring method for displaying a measuring image by supplying a measuring image signal to the measuring display and obtaining luminance information from the measuring image to obtain a spatial frequency characteristic of the measuring display. , The measurement image signal is generated and transmitted while slightly changing the phase of the horizontal synchronization signal and / or the vertical synchronization signal of the measurement image signal, and is displayed on the display under measurement by supplying the measurement image signal. A space characterized by capturing the measured image obtained, obtaining the luminance information of the measured image from the captured measuring image, and determining the spatial frequency characteristic of the display under measurement based on the obtained luminance information. Frequency characteristic measurement method.