JPH05145954A - Chart for measuring horizontal resolution and horizontal resolution measuring system using this chart - Google Patents

Abstract

PURPOSE:To more exactly measure horizontal resolution or the like by forming the density distribution of a vertical stripe in a horizontal scan direction to be a sine wave shaped density change. CONSTITUTION:A vertical stripe chart 14 is arranged with a prescribed pitch and thickness in the horizontal direction while arranging vertical stripes 14A-14N at every respective measuring frequencies. The vertical stripes 14A-14N are formed so that the density distribution of the own vertical stripe in the horizontal scan direction can be the density change in the shape of the sine wave. When the chart 14 is turned into such density distribution, the curve of density distribution in the horizontal scan direction is turned into the distribution curve in the shape of the sine wave. The chart 14 is completed by applying such density distribution to the vertical stripes expressing the respective frequencies and an area following to them. Therefore, when a chart 10 for measuring horizontal resolution is used, an image pickup output corresponding to all the vertical stripes 14 is turned to be a sine wave signal. Thus, the various characteristics of a television camera to be measured at respective measuring frequencies can exactly be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal resolution measuring chart suitable for horizontal resolution measurement of a television camera (in-station television camera) used in a broadcasting station and the like, and a horizontal resolution measurement using the same. Regarding the system.

[0002]

2. Description of the Related Art For television cameras used in broadcasting stations and the like, various measuring systems have been developed in order to measure various characteristics of the cameras. One of the most popular measurement items of camera characteristics is horizontal resolution. This is because how much the horizontal resolution is is the most basic criterion for judging the quality of the TV camera.

In the case of measuring the horizontal resolution and the frequency characteristic in the horizontal direction, conventionally, a horizontal resolution measurement chart, commonly known as IN MEGA CY, as shown in FIG.
A standardized chart 10 called CLECHART) is often used.

As shown in FIG. 9, the horizontal resolution measuring chart 10 is provided with a rectangular image frame 12 having a predetermined size which is controlled by a wedge-shaped marker 11.
The inside of is a gray area having a density of 50 to 60% of the white level as a background area. A vertical stripe chart 14 is printed at the center of the background area 13.

The vertical stripe chart 14 is formed by printing a plurality of vertical stripe patterns each having a plurality of vertical stripe patterns having a pitch and a thickness (line width of vertical stripes) corresponding to the horizontal resolution to be measured, as shown in FIG. Vertical stripes are black and white stripes. Vertical stripes 14A-14
N (N = 9 in this example) marked below (0.
Numerical values (5, 1.0, 1.5, etc.) indicate the horizontal frequency when the chart is imaged. The horizontal frequency of 0.5 MHz is a reference frequency when measuring the horizontal resolution.

Since the vertical stripe chart 14 thus printed is imaged and its horizontal resolution is measured, the black-and-white pitch of the vertical stripe chart 14 is set with reference to the image frame 12 and the vertical stripes are set. The chart 14 is printed by using a highly accurate printing technique so that the width and pitch of the chart 14 are as designed. From the interpretation result (direct reading) of the vertical stripe chart 14, the horizontal resolution of the television camera used and the frequency characteristic in the horizontal direction are obtained.

FIG. 10 shows an example of a horizontal resolution measuring system 20 using the horizontal resolution measuring chart 10. In the figure, the TV camera 21 to be measured and the horizontal resolution measuring chart 10 are faced to each other with a predetermined distance therebetween,
The horizontal resolution measuring chart 10 is imaged with the lens system 22 adjusted so that the image frame 12 has a predetermined size. The optical image of the horizontal resolution measurement chart 10 is converted into an image pickup signal by an image pickup device 23 such as an image pickup tube or a CCD, and is supplied to a signal processing circuit 25 via an amplifier 24 to be subjected to γ correction, emphasis correction, contour correction and the like. After that, a video signal is output from the terminal 26.

This video signal is supplied to an encoder 27 constituting a camera control unit to generate a predetermined video signal (primary color signal or composite signal). The video signal obtained at the terminal 26 is further supplied to a waveform monitor 28 using an oscilloscope or the like, and the horizontal resolution and the like are measured while observing (direct reading) the waveform projected on this.

In measuring the horizontal resolution, first, an iris (not shown) provided in the lens system 22 is adjusted so that the amplitude of the reference horizontal frequency of 0.5 MHz is 100%, and the linear processing is performed. As described above, various processing systems such as γ correction and contour correction are disconnected. In this state, the amplitude of each chart, the collapsed state of the line width, and the like are measured, and the measurement items such as the horizontal resolution of the TV camera 21 used are comprehensively determined.

[0010]

By the way, since the horizontal resolution measurement chart 10 described above uses black and white binary vertical stripes, a change point at which white changes to black and a change point at which black changes to white. All the points are steep. Therefore, the imaging waveform (waveform on one horizontal scanning line) corresponding to each of the vertical stripes 14A to 14N obtained when imaging the horizontal resolution measurement chart 10 should be a square wave as shown in FIG.

However, since it is a square wave, a harmonic component is generated, and this harmonic component is output after being distorted by the nonlinear processing system such as the amplifier 24.
It is observed as a waveform including ringing as shown in. In the waveform shown in FIG. 12, the model number of the TV camera is HK
327, the model number of the lens is P20X14ESB-2V, and the iris is 7.
8 is a waveform when a green signal is monitored. 13 shows a ringing state at a horizontal frequency of 0.5 MHz, and FIG. 14 shows a ringing state at a horizontal frequency of 1.0 MHz.

Since ringing occurs in each measurement frequency region as described above, it is extremely difficult to directly read the horizontal resolution accurately from the waveform monitor 28, and the ringing causes a reference horizontal of 0.5 MHz. It is difficult to match the frequency amplitude to the specified amplitude, and it is the actual situation that usually depends on the intuition of the measurer for many years. Therefore, it is difficult to set the reference amplitude quickly and accurately, and if the amplitude of the reference horizontal frequency cannot be set correctly, the measurement error with respect to other horizontal frequencies also becomes large.

Further, even when observing the entire frequency characteristic, the ringing waveform and the like interfere and cannot be accurately observed. Furthermore, even if an attempt is made to enhance a specific frequency, the enhancement process performed on the specific frequency actually affects other frequency regions. As is clear from FIG. 15, it is clear that the enhancement effect is exerted on other frequency regions even though the enhancement is performed in the vicinity of 3 to 4 MHz, and the enhancement effect cannot be accurately grasped.

Therefore, the present invention solves the conventional problems as described above, and proposes a measurement chart and a measurement system therefor capable of measuring the horizontal resolution more accurately.

[0015]

In order to solve the above problems, a horizontal resolution measuring chart according to the present invention is composed of vertical stripes arranged at a predetermined pitch in the horizontal scanning direction,
The density distribution of the vertical stripes themselves in the horizontal scanning direction is formed so as to have a sinusoidal density change.

In the horizontal resolution measuring system according to the present invention, a horizontal resolution measuring chart in which a plurality of vertical stripes are arranged at a predetermined pitch in the horizontal scanning direction so that the density distribution in the horizontal scanning direction has a sine wave shape is displayed on a television. The horizontal resolution of the television camera can be directly read by capturing an image with a camera and monitoring the waveform of the captured output.

[0017]

In FIG. 2, since the density distribution of the vertical stripes themselves in the horizontal scanning direction is formed to have a sinusoidal density change, the waveform diagram obtained when the chart 10 is imaged is as shown in FIG. Since it becomes a sine wave signal, even when the vertical stripes 14A to 14N are imaged, harmonics of the frequency components do not occur. Therefore, the horizontal resolution measuring system 10 using this has the frequency characteristic as shown in FIG. 5, and the amplitude value (peak value) of 0.5 MHz which is the reference frequency can be correctly set to 100%. Therefore, the horizontal resolution can be read directly, the amplitude characteristic at other frequencies can be accurately measured, and the frequency characteristic can be accurately obtained.

Even when an enhancement characteristic is applied to a specific frequency region, the enhancement characteristic is given only to that frequency region, so that it is possible to correctly know how effective it is.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A horizontal resolution measuring chart according to the present invention and an example of a horizontal resolution measuring system using the horizontal resolution measuring chart will be described in detail with reference to the drawings when applied to a measuring system for a commercial television camera. ..

FIG. 1 shows a measuring chart 10 according to the present invention.
FIG. 2 shows an example of this by tracing the main part thereof as faithfully as possible. As shown in FIG. 2, the measurement chart 10 according to the present invention is also provided with the reference image frame 12, and the background region 13 is formed inside the image frame 12 with a gray level density of 50 to 60%. Figure 9
Is the same as. A vertical stripe chart 14 is formed by printing at approximately the center of the image frame 12. The vertical stripe chart 14 has vertical stripes 14A to 14N (in this example, N for each measurement frequency).
= 9) is controlled, and is arrayed with a predetermined pitch and thickness (line width of vertical stripes) in the horizontal scanning direction. In the figure, nine vertical stripes 14A to 14N having different pitches and line widths are formed by printing so that nine horizontal frequencies (the maximum frequency is 6 MHz) can be measured as in the conventional case.

The vertical stripes 14A to 14N are formed so that the density distribution of the vertical stripe itself in the horizontal scanning direction has a sinusoidal density change. The details will be described with reference to FIG. 3A. One vertical stripe 16 has a maximum density at its center x, decreases sinusoidally from the center point x toward points a and b, and has a minimum density at point b. The density further increases sinusoidally after passing the point b toward the point c, and is maintained at this density from the point where the density reaches 50 to 60% of the white level. The concentration distribution in the opposite direction from the center point x is exactly the same as the points a, b, and c. Therefore, the density distribution is controlled so that the point a'has the same density as the point a, the point b'has the same density as the point b, and the point c'has the same density as the point c.

When the vertical stripe chart 14 has such a density distribution, the density distribution curve in the horizontal scanning direction becomes a sinusoidal distribution curve as shown in FIG. 3B. Whether or not the density distribution curve is a sinusoidal curve correctly depends on the printing accuracy of the vertical stripe chart 14. Since there is an extremely advanced printing technology with high precision and high reproducibility that can control the printing accuracy to the micron order, the target density distribution curve can be realized relatively easily by using this printing technology.

By applying such a density distribution to both the vertical stripes representing the respective frequencies and the area subsequent thereto, the vertical stripe chart 14 of FIGS. 1 and 2 is completed. Therefore, when the horizontal resolution measuring chart 10 shown in FIG. 1 is used, the imaging output corresponding to all the vertical stripes 14A to 14N is output as a sine wave signal as shown in FIG.

When the horizontal resolution measuring chart 10 is composed of the vertical stripe chart 14 having a sinusoidal concentration distribution, its frequency is a single sinusoidal signal, so that the horizontal resolution measuring chart 10 is actually imaged. The monitor signal sometimes obtained is as shown in FIG.

As is clear from the above description, the harmonic components of the frequency components to be measured are scarcely included, so that no overshoot occurs in each monitor signal as shown in FIG. More specifically, looking at the results of the 0.5 MHz waveform monitor shown in FIG. 6 and the results of the 1,0 MHz waveform monitor shown in FIG.
It can be seen more clearly that each vertical stripe chart 14 is composed of only a single frequency component and has no ringing.

As a result, the amplitude of the reference horizontal frequency of 0.5 MHz can be adjusted easily and quickly to the specified amplitude value, whereby the amplitude characteristics, frequency characteristics, horizontal resolution, etc. at each measurement frequency can be adjusted. Various characteristics of the TV camera under measurement 21 can be accurately measured. Even when the frequency characteristics at that time are observed by enhancing only a specific frequency region, the enhancement effect does not spread to other frequency bands, so as shown in FIG. It is possible to grasp extremely accurately whether or not there is a problem. FIG. 8 shows a case where the enhancement process is performed on the same frequency band as in FIG.

These various characteristics are measured by using the measuring system 20 itself shown in FIG. 10. As the horizontal resolution measuring chart 10, the horizontal resolution measuring chart of FIG. 1 is used. Then, the waveform monitor 28 observes the frequency characteristic, the amplitude characteristic at each specific frequency, the horizontal resolution, and the like. Since the configuration of the measurement system 20 is the same as that of the case of FIG. 10, its detailed description is omitted.

[0028]

As described above, the horizontal resolution measuring chart according to the present invention is composed of vertical stripes arranged at a predetermined pitch in the horizontal scanning direction, and the density distribution of the vertical stripes itself in the horizontal scanning direction is sinusoidal. It is characterized in that it is formed so as to have a change in concentration.

According to this, since the image pickup output obtained when the image is picked up is only a single horizontal frequency component, ringing does not occur unlike the conventional case. Therefore, in the case of the present invention in which a horizontal resolution measurement system is constructed using such a special horizontal resolution measurement chart, the amplitude of the reference horizontal frequency can be easily and quickly adjusted to the specified amplitude value, and therefore each measurement It is possible to accurately measure various characteristics of the TV camera under test, such as amplitude characteristics at frequency, frequency characteristics, and horizontal resolution.

Even when the frequency characteristics at that time are observed by enhancing only a specific frequency region, the enhancement effect does not spread to other frequency bands, and therefore, to what frequency and to what extent the enhancement is applied. It has the feature that it is possible to grasp whether or not it is extremely accurate.

[Brief description of drawings]

FIG. 1 is a diagram (photograph represented by shading) showing an example of a horizontal resolution measuring chart according to the present invention.

FIG. 2 is a view similar to FIG. 1, showing an example of a horizontal resolution measurement chart according to the present invention.

FIG. 3 is a diagram showing a partially enlarged view of a chart and a concentration distribution curve at that time.

FIG. 4 is a horizontal frequency waveform chart obtained from a horizontal resolution measurement chart.

FIG. 5 is a diagram showing an example of an actual waveform monitor.

FIG. 6 is an enlarged waveform diagram of 0.5 MHz.

FIG. 7 is an enlarged waveform diagram of 1.0 MHz.

FIG. 8 is a diagram of a waveform monitor of enhancement characteristics.

FIG. 9 is a diagram of a horizontal resolution measurement chart that has been conventionally used.

FIG. 10 is a system diagram showing an example of a camera characteristic measuring system.

FIG. 11 is an output waveform diagram according to a conventional horizontal resolution measurement chart.

FIG. 12 is a diagram of a waveform monitor showing frequency characteristics.

FIG. 13 is an enlarged waveform diagram of 0.5 MHz.

FIG. 14 is an enlarged waveform diagram of 1.0 MHz.

FIG. 15 is a waveform monitor diagram of enhancement characteristics.

[Explanation of symbols]

 10 Horizontal Resolution Measurement Chart 12 Image Frame 13 Background Area 14 Vertical Stripe Chart 14A to 14N Vertical Stripe 20 Measurement System 21 Television Camera for Measurement 28 Waveform Monitor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaichi Saji 14-2 Nibancho, Chiyoda-ku, Tokyo NTV Broadcasting Network Co., Ltd.

Claims (3)

[Claims] 1. The vertical stripes are arranged in the horizontal scanning direction at a predetermined pitch, and the vertical stripes themselves have a density distribution in a sinusoidal density distribution in the horizontal scanning direction. Chart for measuring horizontal resolution. 2. The horizontal resolution measuring chart according to claim 1, wherein the vertical stripes are arranged in correspondence with a horizontal resolution to be measured. 3. A television camera is used to image a horizontal resolution measurement chart in which a plurality of vertical stripes are arranged at a predetermined pitch in the horizontal scanning direction so that the density distribution in the horizontal scanning direction is sinusoidal, and the imaging is performed. A horizontal resolution measuring system using a horizontal resolution measuring chart, characterized in that the horizontal resolution of the television camera can be directly read by monitoring the output waveform.