JPH07168543A - Resolution measuring device for display - Google Patents

Abstract

PURPOSE:To correctly obtain the resolution of a display. CONSTITUTION:This device is provided with a detector 5 detecting the optical output on the screen of a display 1 and a CPU 7, a RAM 8 and a ROM 9 calculation a difference between an optical output detection result on the screen of the display 1 based on a gray signal input from the detector 5 and an optical output detection result of the display 1 from the detector 5 based on an input in which a sine wave signal is superposed on the gray signal and obtaining frequency characteristics of the display 1 by obtaining amplitude response characteristics at sine wave frequencies based on the plural calculated results at the time of changing sine wave phases and by obtaining amplitude response characteristics at the time of changing sine wave frequencies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display resolution measuring apparatus.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the resolution of a display, the methods shown in FIGS. 1 and 2 have been used (hereinafter referred to as method 1 and method 2).

(1) Method 1 (FIG. 1) A sine wave reproduced on the screen of the display 1 when a sine wave is input from the signal generator 2 to the display 1 including a signal processing circuit for displaying an image. It measures how the detected value of the image output by the wave (amplitude of the sine wave) changes with the frequency. In order to detect the light from the display screen, the detector 3 in which a slit having a minute value is combined with the photoelectric converter is used, and only the output of a minute portion on the display is detected. The detection output is
It is input to the signal processing unit 4. As described above, this method focuses on only one point on the screen for measurement. The signal generator 2 outputs a signal obtained by multiplexing a sine wave on a gray signal. By changing the phase of the sine wave, the signal processing unit 4 measures the maximum-minimum value of the output of the detector 3 and obtains the frequency characteristic.

(2) Method 2 (FIG. 2) When an impulse is input from the signal generator 2 to the display 1, the optical output reproduced on the screen of the display 1 is detected by the detector 5 and the signal is processed. The frequency characteristic is obtained by performing Fourier transform in the unit 4. A one-dimensional line sensor is used as the detector 5 in order to detect the shape of the impulse on the screen. The signal generator 2 outputs an impulse signal, and the signal processing unit 4 Fourier transforms the output of the detector 5.

[0005]

There is a shadow mask in a CRT and a pixel structure in a liquid crystal on the display screen. Since method 1 measures only a minute portion on the screen, the effect of this structure cannot be measured.

Method 2 is a measurement by impulse.
This method 2 cannot fully measure the overall characteristics including the electric circuit, such as the effect of aperture correction, due to the gamma characteristics of the display. Therefore, it is possible to use a sine wave instead of an impulse, but the following problems remain.

(1) Amplitude Detection FIG. 3 shows the detector output when a sine wave signal is input to the display. FIG. 3A shows a sinusoidal signal to the display. Due to the pixel structure of the display, the detector output is as shown in FIG. 3 (b).
It takes some ingenuity to ask for ... Here, if there is a defect in the pixel, the detector output lacks the dotted line part a as shown in (c) of FIG. I will end up. further,
Due to shading on the display and the detector, the amplitude at the edge of the detector may be smaller than that at the center.

(2) Signal and Phase of Display Pixel Structure Since the detected amplitude differs depending on the relationship between the input sine wave and the phase of the display pixel structure, usually the maximum and minimum amplitude values for various phases, The average value is used to represent the resolution. Measures are necessary to measure the amplitude for many phase relationships.

An object of the present invention is to provide a display resolution measuring apparatus which solves the above problems.

[0010]

In order to achieve the above object, the present invention provides a detecting means for detecting the light output on the screen of a display, and a light on the screen of the display based on a gray signal input from the detecting means. A first calculating means for calculating a difference between an output detection result and an optical output detection result on the screen of the display based on an input obtained by superimposing a sine wave signal on a gray signal; and a step of changing the phase of the sine wave. And a second calculation means for obtaining an amplitude response characteristic at the frequency of the sine wave based on a plurality of calculation results obtained from the first calculation means.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 4 shows an embodiment of the present invention. As shown in FIG. 4, reference numeral 5 is a detector composed of a one-dimensional line sensor, and the measurement surface is brought into contact with the screen of the display 1 to detect the light output. The output signal (analog signal) from the detector 5 is converted into digital data by the A / D converter 6 and stored in the RAM (random access memory) 8. Reference numeral 7 denotes a CPU (central processing unit), which executes a measurement procedure described later according to a program in a ROM (read only memory) 9. The RAM 8 also has a work area for the CPU 7. Reference numeral 10 is a printer, and 11 is a CRT, which records (prints out) and displays the measurement result by the CPU 7 and information necessary for the measurement. Signal generator 2
Outputs a gray signal and a sine wave signal. The measurement procedure is shown below.

(1): The gray signal of FIG. 5A is displayed on the display. The output of the detector 5 is as shown in FIG. 7B, and the horizontal axis represents the position of the line sensor in the line direction. Further, the output ((d) of FIG. 6) from which the high frequency component of this (each detection data) is removed is calculated.

(2): The sine wave signal is multiplexed on the gray signal and the sine wave of FIG. 3 (a) is displayed on the display.
The detector output is shown in FIG.

(3): The difference between (1) and (2) is calculated.
The result is as shown in FIG.

(4): From FIG. 5C, the maximum value Max. And the minimum value Min.
(Depending on the frequency of the sine wave and the number of pixels of the detector, the detector detects a sine wave of several to several tens of cycles at a time, so the maximum value and the minimum value are calculated).

(5): Max. Obtained in (c) of FIG. ，
Min. Is divided by (d) in FIG. 6 to obtain (e) in FIG. This means correcting the shading that occurs in the display and detector. The amplitude p (difference between the adjacent maximum value and minimum value) is calculated from the maximum value and the minimum value in each cycle of the sine wave thus obtained.

(6): The phase of the sine wave is changed (for example, 8 times at intervals of 45 degrees), the processes of (2) to (5) are repeated, and the average, maximum value and minimum value of the amplitude of the detected data are calculated. calculate.

(7): The frequency of the sine wave is changed (for example, every 1 MHz from 1 MHz to 30 MHz), and (2) to
The frequency characteristic is obtained by repeating (6) and is printed out by, for example, a printer.

According to this method, even if there is a pixel defect, the difference between the gray signal and the sine wave signal is taken as shown in FIG. That is, FIG. 7A shows the detection data when the gray signal is displayed, and the amplitude of the pixel defect portion is small. (B) of the figure is detection data at the time of sine wave display, and the amplitude of the pixel defect portion is small as in (a). It is understood that (c) in the figure is the calculation result of the difference between (a) and (b), and the data of the pixel defect portion is not detected as a peak.

As a detector, a television camera can be used instead of the one-dimensional line camera. By adding the camera outputs horizontally or vertically,
(B) and (b) of FIG. 5 are obtained, the frequency characteristic can be measured by the same method as described above.

[0022]

As described above, according to the present invention, the resolution of the display can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a conventional measuring apparatus.

FIG. 2 is a diagram showing another example of a conventional measuring apparatus.

FIG. 3 is a diagram showing a detector output example when a sine wave is input.

FIG. 4 is a block diagram of an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a signal (data) accompanying detection according to the same embodiment.

FIG. 6 is a diagram showing another example of signals (data) accompanying detection according to the embodiment.

FIG. 7 is a diagram showing still another example of signals (data) accompanying detection according to the embodiment.

[Explanation of symbols]

 1 Display 2 Signal Generator 5 Detector 6 A / D Converter 7 CPU 8 RAM 9 ROM

Claims (2)

[Claims] 1. A detection means for detecting a light output on a screen of a display, and a light output detection result on the screen of the display based on a gray signal input from the detection means and a sine wave signal superimposed on the gray signal. Calculating a difference between a light output detection result on the screen of the display based on an input;
And a second calculating means for calculating the amplitude response characteristic at the frequency of the sine wave based on a plurality of calculation results obtained from the first calculating means when the phase of the sine wave is changed.
And a resolution measuring device for a display. 2. The display resolution measuring apparatus according to claim 1, wherein the second calculating unit obtains the frequency characteristic of the display by changing the frequency of the sine wave.