JPH11150744A - Instrument for measuring jitter amount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the jitter amount of a CRT with high accuracy. SOLUTION: A CCD camera 11 detects a luminance emitted from a phosphor, a synchronizing signal delay section 25 delays a horizontal synchronizing signal little by little to shift an electron beam by a very small distance in an arrangement direction of the phosphors on a display screen of a CRT 16 based on a control signal from a CPU 23 obtain a calibration constant denoting cross reference between a delay of the horizontal synchronizing signal and a moving distance of the electron beam based on the luminance emitted from the phosphors obtained every movement. A delay of the synchronizing signal when a beam movement distance is 1/4 of the phosphor interval is obtained by using the calibration constant, and the electron beam is moved by a prescribed distance in the arrangement direction of the phosphors on the display screen of the CRT 16 by delaying the synchronizing signal by each delay amount. Then the CPU 23 calculates a luminance gravity coordinate of the electron beam every movement to calculate dispersion in the luminance gravity coordinate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jitter amount measuring device for measuring a jitter amount of a cathode ray tube.

[0002]

2. Description of the Related Art In recent years, a cathode ray tube (hereinafter, referred to as "CRT") for displaying an image by deflecting an electron beam to horizontally and vertically scan a phosphor surface has been used for information processing devices such as television devices. It is used as a display unit of various devices such as a measuring device, and high image quality is required for any of the devices.

One of the characteristics indicating the image quality of a CRT is a jitter amount. The CRT is configured such that an electron beam emitted from an electron gun is deflected by receiving a magnetic field from a deflecting unit and irradiates a desired position on a CRT tube surface.
When trying to irradiate the same location on the surface of the T tube with the electron beam, the electron beam may vary spatially due to the influence of an electric circuit in the CRT, an external magnetic field, or the like. This spatial variation of the electron beam is called jitter.

Conventionally, the measurement of the jitter amount has been generally performed by visual observation based on the dot pitch of a CRT or the like. For example, JIS Z 8513 states that, for a display having only a continuous luminance distribution of pixels, jitter may be measured using a measuring microscope with a magnification of 20 or more. The cursor or the comparator reticle is aligned with both ends of the character or the center of gravity of the test object or the edge deflection. "

[0005]

However, in the case of measurement by visual observation, there is a possibility that variation may occur due to individual differences of the measurers and the like, so it is desired to measure the jitter amount objectively. In addition, it is preferable that the measurement of the jitter amount can be performed accurately without being affected by the instrumental difference of the CRT.

[0006] The present invention has been made in view of the above,
It is an object of the present invention to provide a jitter amount measuring apparatus capable of objectively measuring a jitter amount of a CRT by obtaining luminance centroid coordinates of a phosphor that emits light by irradiation with an electron beam.

Another object of the present invention is to provide a jitter amount measuring apparatus capable of measuring a jitter amount of a CRT with high accuracy without being affected by an instrumental difference of the CRT.

[0008]

According to the first aspect of the present invention, a CR
Brightness measurement control means for measuring the emission brightness when the phosphors arranged on the display surface of the T emit light by irradiation of the electron beam; and performing the measurement of the emission brightness a plurality of times. A luminance centroid calculating means for calculating a luminance centroid coordinate of the electron beam based on the luminance beam; and a jitter amount calculating means for calculating a variation as the jitter amount of the CRT from the luminance centroid coordinate calculated for each measurement. It is characterized by:

According to this structure, the measurement of the emission luminance when the phosphor arranged on the display surface of the CRT emits light by the irradiation of the electron beam is performed a plurality of times, and the electron beam is measured based on the emission luminance for each measurement. Are calculated from the luminance barycentric coordinates calculated for each measurement.
By obtaining the jitter amount of T, the jitter amount is quantified and objectively obtained.

According to a second aspect of the present invention, in the jitter amount measuring apparatus according to the first aspect, the luminance measurement control means includes:
An optical detection unit that is disposed opposite to the display surface of the CRT and detects the emission luminance of the phosphor at a plurality of detection positions; and a synchronization signal for displaying an image on the CRT is shifted by a predetermined amount. Beam movement control means for moving the display position of the electron beam on the display surface of the CRT by a predetermined distance in the direction in which the phosphors are arranged, wherein the luminance center-of-gravity calculation means uses the optical detection means at each of the display positions. The detection of the light emission luminance is performed a plurality of times, and the luminance centroid coordinate of the electron beam is calculated based on the detection result of the light emission luminance for each detection. It is characterized in that the variation is obtained as the jitter amount of the CRT from the calculated luminance barycenter coordinates.

According to this configuration, the synchronization signal for displaying an image on the CRT is shifted by a predetermined amount, so that C
On the display surface of the RT, the display position of the electron beam moves by a predetermined distance in the arrangement direction of the phosphor, and at each display position,
The light emission luminance of the phosphor is detected a plurality of times by the optical detection means opposed to the display surface of the CRT, and the luminance centroid coordinates of the electron beam are calculated based on the detection result for each detection.

Then, the variation is obtained as the amount of jitter of the CRT from the luminance barycentric coordinates of the electron beam calculated for each detection, whereby the luminance barycentric coordinates based on the positional relationship between the display position of the electron beam and the phosphor are obtained. The influence is reduced, and the luminance barycentric coordinates are accurately calculated.
The jitter amount of the RT can be determined with high accuracy.

The predetermined distance for moving the display position of the electron beam may be smaller than the distance between the phosphors arranged on the display surface of the CRT.

According to a third aspect of the present invention, in the jitter amount measuring apparatus of the second aspect, a calibration constant for obtaining a calibration constant representing a relationship between a shift amount of the synchronization signal and a moving distance of a display position of the electron beam. Calculating means, wherein the beam movement control means shifts the synchronization signal by a shift amount when the movement distance of the display position of the electron beam becomes the predetermined distance by using the calibration constant. Features.

According to this configuration, the shift when the moving distance of the display position of the electron beam becomes a predetermined distance is determined by using the calibration constant indicating the relationship between the amount of shift of the synchronization signal and the moving distance of the display position of the electron beam. By shifting the synchronization signal by an amount, the display position of the electron beam moves by a predetermined distance in the arrangement direction of the phosphor on the display surface of the CRT.

By using the calibration constant, the movement of a predetermined distance is accurately performed, whereby the coordinates of the luminance center of gravity of the electron beam are accurately calculated regardless of the positional relationship between the display position of the electron beam and the phosphor. Accordingly, variations in the coordinates of the luminance centroid are calculated with high accuracy, whereby the amount of jitter of the CRT is obtained with high accuracy.

According to a fourth aspect of the present invention, in the jitter amount measuring apparatus according to the third aspect, the calibration constant calculating means includes:
By shifting the synchronization signal by a small amount,
The display position of the electron beam is moved on the display surface of the RT by a small distance in the arrangement direction of the phosphors, and the emission luminance is measured at each movement of the small distance, and the calibration is performed based on the measurement result. It is characterized by obtaining a constant.

According to this configuration, the display position of the electron beam on the display surface of the CRT is moved by a very small distance in the direction in which the phosphors are arranged by shifting the synchronization signal by a very small amount. Is performed, and the calibration constant is obtained based on the measurement result, so that the calibration constant is accurately obtained regardless of the CRT instrumental difference. As a result, the variation of the coordinates of the luminance center of gravity is accurately calculated, and the jitter amount of the CRT is accurately obtained.

According to a fifth aspect of the present invention, in the jitter amount measuring apparatus according to the third aspect, the arrangement direction of the phosphors is
In the horizontal direction, the synchronization signal is a horizontal synchronization signal, and the calibration constant calculation means calculates the calibration constant based on the horizontal dimension of the CRT, the frequency of the horizontal synchronization signal, and the horizontal resolution of the CRT. It is characterized by what you want.

According to this configuration, since the horizontal size of the CRT, the frequency of the horizontal synchronization signal and the horizontal resolution of the CRT are known, the displacement of the horizontal synchronization signal and the display position of the electron beam are based on these. Is obtained, the calibration constant is easily obtained without moving the display position of the electron beam.

According to a sixth aspect of the present invention, in the jitter amount measuring apparatus according to the third aspect, the arrangement direction of the phosphors is
In the vertical direction, the synchronization signal is a vertical synchronization signal, and the calibration constant calculation means calculates the calibration constant based on the vertical dimension of the CRT, the frequency of the vertical synchronization signal, and the vertical resolution of the CRT. It is characterized by what you want.

According to this configuration, since the vertical dimension of the CRT, the frequency of the vertical synchronizing signal and the vertical resolution of the CRT are known, the displacement of the vertical synchronizing signal and the display position of the electron beam are based on these. Is obtained, the calibration constant is easily obtained without moving the display position of the electron beam.

[0023]

FIG. 2 is an overall configuration diagram of an embodiment of a CRT inspection apparatus to which the jitter amount measuring apparatus according to the present invention is applied, and FIG. 3 is a view showing an imaging surface 31 of the CCD camera 11. This CRT inspection apparatus has a CC
The CRT 1 to be measured includes a D camera 11, a general-purpose signal generator 12, a main body 13, an external monitor 14, and a personal computer (hereinafter referred to as a "PC") 15.
6 to measure the amount of jitter and the like. Main body 13
Is electrically connected to a CCD camera 11, a general-purpose signal generator 12, an external monitor 14, a personal computer 15, and a CRT 16, and the general-purpose signal generator 12 is electrically connected to the CRT 16.

The CCD camera 11 captures an image of the display screen of the CRT 16 in a state where the lens barrel 11a formed of a soft synthetic resin or the like formed at the tip is in close contact with the tube surface of the CRT 16, and constitutes optical detection means. doing.

The CCD camera 11 is a single-panel 1 / 2-inch black-and-white image sensor in which photoelectric conversion elements (hereinafter, referred to as "pixels") such as CCDs are arranged in a two-dimensional matrix. As shown in FIG.
It has 768 pixels (1 pixel = 8.4 μm) and 242 pixels (1 pixel = 19.6 μm) in the vertical (V) direction.

The general-purpose signal generator 12 generates a horizontal synchronizing signal and a vertical synchronizing signal for causing the CRT 16 to display an image, and outputs an arbitrary measurement pattern such as a dot pattern or a cross hatch at a desired position on the CRT 16. It generates a video signal to be displayed.

The main body 13 performs image processing on a video signal picked up by the CCD camera 11 and controls the general-purpose signal generator 12, and its configuration will be described later.
The external monitor 14 displays an image captured by the CCD camera 11. The personal computer 15 controls the operation of the main body 13.

The CRT 16 as a measurement object used in the present embodiment is a so-called aperture grill type in which the phosphor arrangement on the display surface has a vertical stripe pattern, but the present invention is not limited to this type. Also, the sweep method of the CRT is not particularly limited.

FIG. 1 is a block diagram showing the structure of the main body 13. The main unit 13 includes an A / D conversion unit 21, a measurement data storage unit 22, a CPU 23, a vertical synchronization signal detection unit 24, a synchronization signal delay unit 25, and I / F units 26, 27, 28.

The A / D converter 21 converts an analog video signal from the CCD camera 11 into a digital value. For example, the A / D converter 21 converts the analog video signal from the CCD camera 11 into a digital signal of 10 bits in accordance with the level of the video signal. Convert to The measurement data storage unit 22 includes a RAM or the like, and stores measurement data such as a video signal converted into a digital value. The measurement data storage unit 22 has 768 × 242 pixels, which is the number of pixels of the CCD camera 11.
At least a capacity capable of storing bit data is provided, and the measurement data is stored at an address corresponding to the pixel arrangement position.

The I / F section 26 receives a vertical synchronizing signal, a horizontal synchronizing signal, and a video signal generated by the general-purpose signal generator 12, and outputs the vertical and horizontal synchronizing signals to the vertical synchronizing signal detecting section 2.
4 and a synchronization signal delay unit 25, and a video signal to the CRT 16.

The I / F section 28 receives a video signal from the CCD camera 11 and transmits the video signal to the A / D conversion section 21 and the external monitor 14.

The CPU 23 controls the operation of each unit in the main body 13, and also controls the general-purpose signal generator 12 via the I / F 27.
In addition to controlling the vertical synchronizing signal, the horizontal synchronizing signal, and the video signal generation, the control for taking necessary data communication and timing between the personal computer 15 and the CCD camera 11 is performed.

The vertical synchronizing signal detecting section 24 detects a vertical synchronizing signal input from the general-purpose signal generator 12 via the I / F section 26 and the synchronizing signal delay section 25, and sends it to the CPU 23.

The synchronizing signal delay unit 25 includes the general-purpose signal generator 1
2 delays the vertical synchronization signal and the horizontal synchronization signal input via the I / F unit 26 individually.
Each delay amount is set by a control signal from the CPU 23. The synchronizing signal delay unit 25 transmits a vertical and horizontal synchronizing signal to the CRT 16 to cause the CRT 16 to sweep.

The CPU 23 constitutes beam movement control means, measurement control means, luminance center of gravity calculation means, jitter amount calculation means, and calibration constant calculation means. Further, the synchronization signal delay unit 25 constitutes a beam movement control unit and a measurement control unit.

The measurement of the amount of jitter in the present embodiment is performed after performing the first calibration and the second calibration. The first calibration is for correcting the variation in the luminous efficiency of the phosphor, that is, the luminance unevenness of the phosphor. In the second calibration, the delay time (shift amount) of the horizontal synchronization signal, that is, the relationship between the horizontal movement time and the movement distance of the display position of the electron beam (hereinafter, simply referred to as the “movement distance of the electron beam”). Is a calibration constant representing the following.

First, referring to FIGS. 1, 3 to 5,
The first calibration operation by the CPU 23 will be described with reference to FIG. FIG. 4A is a diagram showing an electron beam intensity during horizontal sweep, FIG. 4B is a diagram showing a captured image of the CCD camera 11 in a state where the CRT 16 is fully lit in a single color, and FIG.
FIG. 5B is a diagram showing the luminance centroid of the image shown in FIG. 4B by a + sign, FIG. 5B is a diagram showing the emission luminance of the phosphor in the horizontal direction, and FIG. 6 is a flowchart showing the operation procedure of the first calibration. It is.

First, referring to FIGS. 4A and 4B, the CCD
The received light data in the camera 11 will be described. FIG.
In (b), only six aperture grill type phosphors 32 of a predetermined width can be seen at a predetermined interval d in the imaging surface 31 of the CCD camera, and the black portion indicates the horizontal sweep line position (four are visible). The shaded area indicates the valley of the horizontal sweep line,
The white portion indicates an area that does not emit light because a phosphor of another color is applied.

As shown in FIG. 4A, the electron beam during the horizontal sweep has a high intensity at the center of the beam, and a valley is generated between adjacent horizontal beams. Therefore, the luminance is high at the position of the horizontal sweep line, which is the black portion, and low at the valley of the horizontal sweep line, which is the hatched portion. As described above, if the intensity of the emitted electron beam differs depending on the position on the surface of the phosphor 32, it is not possible to know the uneven brightness of the phosphor 32 itself.

Therefore, in the first calibration, the electron beam is moved in the vertical direction by a very small pitch such that the intensity of the electron beam applied to each position of the phosphor 32 can be regarded as being equal, and obtained at each movement. The processing of holding the maximum value of the measured data is performed.

In FIG. 6, first, with the CCD camera 11 opposed to a predetermined position of the CRT 16, the general-purpose signal generator 12 turns on the CRT 16 in a single color (#).
2). Monochromatic full lighting refers to sweeping irradiation of an electron beam of a constant level from the electron gun over the entire area of the CRT display surface. Instead of full-color lighting, a required area specially prepared for measurement may be lit as a detection range of the CCD camera 11.

Next, the light from the phosphor that emits light by the operation of the CCD camera 11 is applied to each pixel (768 × 2) of the image pickup surface 31.
42 pixels), and the received light data from each pixel is A
After the / D conversion, it is stored in the measurement data storage unit 22 (# 4).

Subsequently, each time the electron beam is moved in step # 8, the magnitude of the measurement data stored in the measurement data storage unit 22 and the light reception data received this time is determined by the CCD.
The comparison is made for all the pixels of the camera 11, and the larger data is updated and stored in the measurement data storage unit 22 as the measurement data (# 6). In the first measurement, the measurement data stored in the measurement data storage unit 22 has been reset to 0, and the first received light data is stored as it is as the measurement data.

Subsequently, the vertical movement of the electron beam is performed by sequentially delaying the vertical synchronization signal by a minute pitch (for example, 2 μsec in this embodiment) by the synchronization signal delay unit 25 (# 8).

Next, it is determined whether or not the vertical movement of the electron beam by the delay operation has been performed a predetermined number of times (for example, 15 times in the present embodiment) (# 10), and until it is repeated the predetermined number of times (NO in # 10). ), The measurement and the maximum value hold processing of the measurement data are executed for each movement (# 4 to # 4).
# 8) This covers the valley between the horizontal sweep lines.

As a result, when the vertical movement of the electron beam is completed (YES in # 10), the phosphor surface has been irradiated with the electron beam of the same intensity, so that the maximum value of the received light data at each pixel is obtained. Can be grasped as a difference in luminous efficiency of the phosphor 32, that is, luminance unevenness of the phosphor 32.

When the vertical movement of the electron beam is completed (# 1)
If 0 (YES), the luminance centroid coordinates (H, V) are calculated using the measurement data stored in the measurement data storage unit 22 (# 12).

For the calculation of the luminance center-of-gravity coordinates, measurement data equal to or greater than a preset threshold value (for example, 30% of the peak value in the stored measurement data in this embodiment) is used.
The accuracy is improved by removing the measurement data with the level difference more than necessary.

Assuming that an address corresponding to each pixel in the measurement data storage unit 22 is H and the measurement data stored at this address is L (H),

[0051]

[Mathematical formula-see original document] H coordinate of luminance center of gravity = ΣHL (H) / ΣL (H). On the other hand, the V coordinate of the luminance centroid has a constant pitch ΔV
(In the present embodiment, for example, 40 μm).

Therefore, as shown in FIG. 5A, the coordinates of the luminance center of gravity (H, V) are the positions marked with +, and FIG.
In (a), there are 60 pieces.

Next, 2 including each luminance barycenter coordinate (H, V)
× 5 sum of the measured data of pixels _{Sum 1 (1) ~Sum 1 (} 60) is obtained (# 14), so that each sum _{Sum 1 (1) ~Sum 1 (} 60) becomes the same value, luminance An unevenness correction coefficient is calculated (# 1
6).

For example, with reference to the luminance barycentric coordinates (H, V) corresponding to the sum Sum ₁ (1), the luminance unevenness correction coefficient of the luminance centroid coordinates (H, V) corresponding to each sum Sum ₁ (N) K (N) is

[0055]

K (N) = Sum ₁ (1) / Sum ₁ (N) Here, N is an integer of 1 to 60.

As described above, by using the sum of the measurement data of 2 × 5 pixels including the luminance gravity center coordinates (H, V) instead of the luminance gravity center coordinates (H, V) itself, the influence of noise and the like can be reduced. It is removed to improve the measurement accuracy.

Next, a second calibration operation, that is, an operation for obtaining a calibration constant α representing the relationship between the horizontal movement time and the electron beam movement distance will be described with reference to FIGS.

FIG. 7A shows dots D1, D on the CRT 16.
FIG. 3B is a diagram showing a captured image of the CCD camera 11 in a state where 2 is displayed, and FIG. 4B is a diagram showing the light emission luminance of the phosphor in the horizontal direction. FIG. 8 is a diagram for explaining the relationship between the horizontal movement distance and the movement time of a dot, together with the emission luminance. FIG. 9 is a flowchart showing the second calibration operation.

The CRT 16 used in this embodiment is
Is an aperture grill type, it is sufficient to take into account only the moving time in the horizontal direction, which is the arrangement direction of the phosphors, and the moving distance of the electron beam.

First, the general-purpose signal generator 12 prints dots D1, D on the CRT 16 within the detection range of the CCD camera 11.
2 is displayed (# 20). The display of the dots D1 and D2 may be controllable so that they can be displayed on the left and right in accordance with the detection range of the CCD camera 11, or the dot display position is specified in advance, and the CCD is adjusted in accordance with the position.
The camera 11 may be arranged at the time of calculating the luminance center of gravity.

In this state, the CCD camera 11 operates,
The light from the phosphor portion that is illuminated by the electron beam is received, and the received light data from each pixel is A / D converted and then stored in the measurement data storage unit 22 (# 2).
2). At this time, data obtained by multiplying the received light data of the digital value by the correction coefficient obtained by the first calibration in FIG. 6 is stored in the measurement data storage unit 22 as measurement data.

Next, the dot D1 is examined by using the measurement data corresponding to the left half of the imaging surface 31. That is, the total sum ₂ of the measurement data of 2 × 5 pixels including the luminance center-of-gravity coordinates (H, V) belonging to the left half is obtained, and the phosphor 32 having the maximum total amount (FIG. 7A )) Is specified (# 24).

That is, the shape of the electron beam intensity on the left side has a mountain shape as shown in FIG. 7B, and the light emission intensity of the phosphor near the top becomes maximum.

Next, the sums Sum ₃ included in the phosphors 32 indicated by the circles are summed, and a predetermined threshold value (in the present embodiment, for example, 50% of the peak sum amount) %), The H coordinates of the luminance centroids having the total amount equal to or more than the sum are summed up, and the total value is further divided by the number of luminance centroids to calculate the average centroid coordinates Ave ₁ (# 26).

Next, similarly, the dot D2 is examined using the measurement data corresponding to the right half of the imaging surface 31. That is, 2 × 5 including each luminance barycentric coordinate (H, V) belonging to the right half
Each sum Sum ₄ is determined of the measured data of pixels, a phosphor 32 with a maximum total amount (indicated by △ mark in FIG. 7 (a)) is identified from among the (# 28).

That is, the shape of the electron beam intensity on the right side has a mountain shape as shown in FIG. 7B, and the light emission intensity of the phosphor near the top becomes maximum.

[0067] Then, 50 with each sum Sum ₅ is total contained in the phosphor 32 in the △ mark, among the luminance center, of taking into account the accuracy predetermined threshold (in this embodiment for example the peak total amount %), The H coordinates of the luminance centroids having the total amount equal to or more than the sum are calculated, and the total value is further divided by the number of luminance centroids to calculate the average centroid coordinates Ave ₂ (# 30).

Next, the horizontal movement of the electron beam is performed by delaying the horizontal synchronization signal by a minute pitch (for example, 1 nsec in this embodiment) by the synchronization signal delay unit 25 (# 32).

Next, light from the phosphor portion is received,
After the receiving data from each pixel is converted A / D, is stored in the measurement data storage unit 22 (# 34), followed by the total of the sum Sum ₃ contained in the phosphor of the ○ mark is calculated (# 3
6), the sum of the sum Sum ₅ is calculated to be contained in the phosphor of the △ mark (# 38). At this time, in # 34, data obtained by multiplying the received light data of the digital value by the correction coefficient obtained by the first calibration in FIG. 6 is stored in the measurement data storage unit 22 as measurement data.

Next, it is determined whether or not a preset end determination condition of the horizontal movement of the electron beam is satisfied (#
40) until the end determination condition is satisfied (N in # 40)
O), measurement and total processing are executed every horizontal movement (#)
32 to # 38). The termination determination condition will be described later.

Next, when the horizontal movement of the predetermined electron beam is completed (YES in # 40), the average luminance centroids Ave ₁ and Ave ₂
, The distance L between the phosphor marked with ○ and the phosphor marked with Δ
(μm)

[0072]

L = 8.4 × (Ave ₂ −Ave ₁ ) / M (# 42)

Here, M is the optical magnification of the CCD camera 11 and is detected by the main body 13. The optical magnification M may be stored in the main unit 13 in advance.

Next, a horizontal movement time T corresponding to the distance L is calculated (# 44). The calculation of the movement time T will be described with reference to FIG. In the drawing, solid lines B1 and B2 indicate left and right electron beams respectively corresponding to dots D1 and D2 (FIG. 7) before horizontal movement, and broken lines B1 ′ and B2 ′ indicate dots D1 and D2 at the end of horizontal movement (FIG. 7). The left and right electron beams respectively corresponding to () are shown.

Regarding the dot D1 on the left side (FIG. 7), the sum of the respective sums Sum ₃ contained in the phosphors marked with a circle every horizontal movement is calculated, and this total value is included in the phosphor marked with a circle before the horizontal movement. determining whether the lowered to the preset movement end level for the sum of the sum sum ₃ which, the travel time when lowered to the movement end level and T1.

[0076] On the other hand, with regard to the right of the dot D2 (FIG. 7), we obtain the sum of the sum Sum ₅ contained in the phosphor of the △ mark every horizontal movement phosphor of the total value is the horizontal movement before △ mark determining whether the lowered to the preset movement end level for the sum of the sum sum ₅ contained, the movement time when lowered to the movement end level and T2.

Therefore, in step # 40, it is determined whether or not both of the respective sums have decreased to a preset movement end level, and if this judgment condition is satisfied, the horizontal movement of the electron beam is ended. Will be.

Note that this movement end level is the sum of the respective sums Sum ₃ included in the phosphors marked with a circle before the horizontal movement, or the sum of the sums Sum ₅ included in the phosphors marked with a triangle before the horizontal movement. Is set to a fixed value, for example, about 50%.

In FIG. 8, a time TT indicates a time between two dots D1 and D2 by the general-purpose signal generator 12. For example, the CRT 16 is displayed in the VGA mode (dot clock frequency = 25.175 MHz), and the dots D1 and D2 are displayed.
Is 8 dots, the time TT (μsec) is

[0080]

TT = 8 / 25.175 Therefore, the horizontal movement time corresponding to the distance L between the phosphor marked with a circle and the phosphor marked with a triangle, that is, the time T between the dots D1 and D2 is:

[0081]

## EQU5 ## T = TT + T1-T2.

Subsequent to # 44, the calibration constant α representing the relationship between the horizontal movement time and the electron beam movement distance is

[0083]

## EQU6 ## It is obtained by α = L / T (# 46).

Next, the measurement of the amount of jitter will be described with reference to FIGS. Fig. 10 shows the CCD when measuring the amount of jitter.
FIG. 11 is a view showing an image captured by the camera 11, FIG. 11 is a view showing a result of simulating an error amount of a luminance barycentric coordinate of an electron beam with respect to a positional relationship between a phosphor and an electron beam, and FIG. 12 is a view using the simulation result of FIG. FIG. 13 is a diagram showing a result of simulating a jitter amount with respect to a positional relationship between a phosphor and an electron beam. FIG. 13 shows a result of simulating a jitter amount measurement when the electron beam is moved three times by の of the phosphor interval. FIG.

In the present invention, the amount of jitter is set to twice the standard deviation σ of the variation in the coordinates of the luminance center of gravity of the electron beam.
Therefore, when measuring the amount of jitter, as shown in FIG. 10, the electron beam is applied to the imaging surface 3 of the CCD camera on the CRT tube surface.
One dot D0 is displayed on one, and the light emitting phosphor 32
Based on the luminance of, the luminance barycentric coordinates of the electron beam are calculated.

At this time, since the electron beam is observed only by the light emission of the phosphor 32, there is little measurement data that can be used for calculating the luminance barycentric coordinates. Thus, a simulation was performed on how the error amount of the luminance barycentric coordinate of the electron beam calculated from the emitting phosphor changes with respect to the positional relationship between the phosphor and the electron beam. The result is shown in FIG.

The simulation shown in FIG. 11 is based on the assumption that the electron beam profile is a normal distribution, the beam size at 5% light quantity is 500 μm, the CRT is an aperture grill type, and the distance between the phosphors is 240 μm.
Fix the phosphor under the condition that the phosphor emits light only in the area where the electron beam and the phosphor overlap, and move the electron beam from the position where the center of the phosphor and the position of the maximum brightness of the electron beam match. , At a fine pitch of 45 ° above the horizontal direction.

As described above, by fixing the phosphor and moving the electron beam, the positional relationship between the electron beam and the phosphor, that is, the light emission degree of the phosphor is changed.

As shown in FIG. 11, in particular, periodicity depending on the positional relationship with the phosphor is observed in the calculation error amount of the luminance barycentric coordinate regarding the horizontal component indicated by the + mark in the figure, and the error amount is large. It has become. This indicates that it is difficult to accurately determine the luminance center-of-gravity coordinates based on the emission luminance of the phosphor.

Based on the simulation results shown in FIG. 11, it is assumed that a jitter of 20 μm exists in the same direction as the moving direction of the electron beam, and how the amount of the jitter changes with the change in the positional relationship between the phosphor and the electron beam. We simulated the change. FIG. 12 shows the result.

As shown in FIG. 12, the jitter of the horizontal component is reduced by 14 with respect to the change in the positional relationship between the phosphor and the electron beam.
It changes from μm to 28 μm. This indicates that when the amount of jitter is measured using the luminance barycentric coordinates of the electron beam, the error becomes extremely large.

On the other hand, by utilizing the periodicity of the calculation error amount of the luminance barycentric coordinate depending on the positional relationship between the electron beam and the phosphor shown in FIG. 11, the error amount can be reduced. Conceivable. That is, by moving the electron beam by a distance that is 1/2 or smaller than the distance between the phosphors, and calculating the luminance centroid coordinates for each movement,
The positive error amount and the negative error amount of the luminance barycentric coordinates are mutually canceled.

As an example, the electron beam is moved three times by の of the phosphor interval, the luminance barycentric coordinates of the electron beam are calculated a predetermined number of times for each movement, and the jitter amount is calculated after the movement is completed. FIG. 13 shows the result of the simulation.

As shown in FIG. 13, even if the positional relationship between the phosphor and the electron beam changes, the change in the jitter amount is 19.5 μm.
220.7 μm, which is significantly reduced as compared with FIG.

Therefore, in the present invention, in measuring the amount of jitter, the amount of jitter can be accurately measured by moving the electron beam.

Next, referring to FIGS. 1 and 10, FIG.
The operation of measuring the amount of jitter will be described with reference to FIG. FIG. 14 is a flowchart showing the procedure of measuring the amount of jitter.

The measurement of the amount of jitter is performed following the first and second calibration operations.
One dot D0 (FIG. 10) is displayed at T16 (# 60).

The CCD camera 11 is held so as to be able to observe the same portion of the CRT 16 following the first and second calibration operations. Further, the dot D0 is controlled so as to be displayed preferably at substantially the center of the detection range of the CCD camera 11, or at least at a position where a chip does not occur even by a horizontal movement of an electron beam described later. I have.

In this state, the CCD camera 11 is operated, and
Light from the phosphor portion that is emitted by the irradiation of the electron beam is received by each pixel of the CCD camera 11, and the received light data from each pixel is A / D converted and then stored in the measurement data storage unit 22. (# 62).

Next, the coordinates of the luminance center of gravity are calculated from the measured data (# 64). The luminance gravity center coordinates are calculated in the (H, V) coordinate system. In calculating the luminance centroid coordinates, measurement data having a preset threshold value (for example, 5% of the peak value in the measurement data) or more is used, and noise level data is excluded.

Here, the address of the measurement data storage section 22 corresponding to each pixel of the CCD camera 11 is (H, V),
When the measurement data of the address (H, V) is L (H, V),
The H coordinate K _H of the luminance center of gravity is

[0102]

K _H = ΣH · L (H, V) / ΣL (H, V), and the V coordinate K _V of the luminance center of gravity is

[0103]

K _V = ΣV · L (H, V) / ΣL (H, V)

Subsequently, a predetermined number of times (for example, in this embodiment,
It is determined whether or not the measurement has been performed only 30 times (# 6).
6) Until a predetermined number of times are performed (NO in # 66), # 62
To 64 are repeatedly performed, and a predetermined number of luminance centroid coordinates (K _H ,
K _V ) is calculated.

When a predetermined number of measurements are completed (Y in # 66)
ES), the average at this position is calculated by the following equations 9 and 10 (# 68).

[0106]

[Equation 9] AVE _H = ΣK _Hi / n

[0107]

AVE _V = ΣK _Vi / n where AVE _H is the average H coordinate, AVE _V is the average V coordinate, K _Hi
Is the H coordinate of the luminance centroid in the i-th measurement, K _Vi is the V coordinate of the luminance centroid in the i-th measurement, and n is the number of measurements.

Next, the amount of delay of the horizontal synchronizing signal is calculated using the calibration constant α so that the moving distance of the electron beam becomes exactly a predetermined distance (for example, 1/4 of the phosphor interval in this embodiment).
That is, the travel time is obtained (# 70).

Subsequently, the electron beam moves a predetermined distance in the horizontal direction by delaying the horizontal synchronizing signal generated by the general-purpose signal generator 12 by the synchronizing signal delay unit 25 by the obtained moving time (# 72). .

Next, it is determined whether the horizontal movement of the electron beam has been performed a predetermined number of times (for example, three times in this embodiment) (# 74), and until the horizontal movement of the electron beam is performed a predetermined number of times (# 7).
No. 4), # 62 to # 72 are repeated.

On the other hand, if the movement of the electron beam has been performed a predetermined number of times (YES in # 74), the variation of the coordinates of the luminance barycenter is obtained.
(σ _H , σ _V ) is calculated (# 76), and this variation (σ _H , σ _V ) is calculated.
_V ) is the amount of jitter to be obtained.

In this embodiment, the total number of measurements, ie, #
The number of times of calculation of the luminance barycentric coordinates in 64 is basically based on twice the number of vertical frequencies (Hz) of the video signal input to the CRT 16. For example, if the vertical frequency is 60Hz,
120 measurements will be performed.

Since the number of movements of the electron beam in # 70 is basically three times, the measurement of # 62 is performed at four positions of the first to fourth display positions (first to fourth measurement positions). Number of measurements at each measurement position, ie, # 6
The predetermined number of times in 6 is 30 if the vertical frequency is 60 Hz.

For example, if the total number of measurements (the number of times of calculation of the luminance barycentric coordinates in # 64) is m and the number of electron beam movements is three, that is, the display position of the electron beam to be measured is four, the luminance centroid coordinates , That is, the amount of jitter (σ _H , σ _V )

[0115]

Σ _H = 2 · √ [{Σ (K _H1i −AVE _H1 ) ² + Σ (K _H2i −AVE _H1 −M _H ) ²
+ Σ (K _H3i −AVE _H1 −2M _H ) ² + Σ (K _H4i −AVE _H1 −3M _H ) ² } /
(m−1)] σ _V = 2 · √ [{Σ (K _V1i −AVE _V1 ) ² + Σ (K _V2i −AVE _V1 −M _V ) ²
+ Σ (K _V3i −AVE _V1 −2M _V ) ² + Σ (K _V4i −AVE _V1 −3M _V ) ² } /
(m−1)].

Here, (K _H1i , K _V1i ) to (K _H4i , K _V4i ) are measurement data of each component at the first to fourth measurement positions and n times of measurement, and (AVE _H1 , AVE _V1 ) are The average of each component at the first measurement position. M _H is the amount of movement in the horizontal direction, M _V is the amount of movement in the vertical direction, and M _V = 0 when not moving in the vertical direction.

The predetermined number of measurements at each measurement position, the predetermined number of electron beam movements, and the total number of measurements are not limited to the above.

In the above equation (11), (AVE _H1 −M _H ,
The average value of the luminance center coordinates in the second measuring position in place of the _{AVE V1 -M V) (AVE H2} , the _{AVE V2), (AVE H1 -2M} H, AVE V1 -2M V)
Instead of the average value (A
VE _H3 , AVE _V3 ) is replaced with (AVE _H1 −3M _H , AVE _V1 −3M _V ), and the average value (AVE _H4 , AVE
_V4 ) may be used respectively.

As described above, according to the present embodiment, the display position of the electron beam is moved a predetermined number of times by a predetermined number of times.
By obtaining the luminance barycentric coordinates for each movement, the luminance barycentric coordinates can be obtained with high accuracy regardless of the positional relationship between the display position of the electron beam and the phosphor, whereby the jitter amount can be obtained with high accuracy.

In particular, by moving the display position of the electron beam by (n-1) times 1 / n of the phosphor interval and measuring at n display positions, the display position of the electron beam and the phosphor can be compared. The influence of the positional relationship can be eliminated.

Further, since the luminance when the phosphor is irradiated and emitted by passing through the aperture grill (or shadow mask) while oscillating the electron beam is directly measured to calculate the luminance centroid coordinates, the measurement accuracy is improved. And a result with good correlation with visual observation is obtained.

Also, since the amount of jitter is obtained by displaying one dot on the display surface of the CRT 16, the amount of jitter at each position can be measured on the display surface of the CRT 16.
The performance related to the amount of jitter of the CRT 16 can be grasped quantitatively.

Since the measurement can be performed without moving the lens barrel 11a of the CCD camera 11, the operability as a measuring device is good, and the jitter amount can be measured in a very short time.

The CRT inspection apparatus shown in FIG.
In the case of having a function of measuring the focusing state of the electron beam at T16, that is, the function of measuring the focus performance, the jitter performance is measured accurately to remove the influence of the jitter performance from the focus performance greatly affected by the jitter performance. As a result, the focus performance of the CRT 16 can be accurately evaluated.

The present invention is not limited to the above-described embodiment, but can adopt the following modifications (1) to (4).

(1) The calibration constant α may be obtained as follows instead of the second calibration operation. That is, FIG.
, The horizontal dimension S _H of the display surface of the CRT 16 to be measured, the horizontal resolution, that is, the number of dots R _H
And the frequency F _H of the horizontal synchronizing signal can be input from the input keyboard of the personal computer 15, and the input data is
Transmit to PU23.

Further, the CPU 23 calculates the horizontal dot distance D _H (mm) and the horizontal dot time T _H (sec) as follows:

[0128]

D _H = S _H / R _H T _H = 1 / F _H , and the calibration constant α is calculated from:

[0129]

## EQU13 ## The function is obtained by α = D _H / T _H.

According to this embodiment, the calibration constant α can be easily obtained. It should be noted that instead of inputting each data relating to the CRT 16 through the personal computer 15,
May be configured to allow input.

(2) In the above embodiment, since the CRT 16 to be measured is of the aperture grill type,
Assuming that only the horizontal component of the luminance barycentric coordinate is affected by the positional relationship with the phosphor, the electron beam is finely moved only in the horizontal direction and the amount of jitter is accurately obtained, but the present invention is not limited to this. The jitter amount may be obtained by slightly moving in the vertical direction.

The movement of the electron beam may be performed individually in the horizontal and vertical directions, or may be performed simultaneously by moving the electron beam in an oblique direction.

(3) In the above embodiment, the CRT 16 to be measured is of the aperture grill type, but is not limited to this, and may be of the dot matrix type.

In this case, since the vertical component as well as the horizontal component of the luminance barycentric coordinate is affected by the positional relationship between the electron beam and the phosphor, the electron beam is moved in the vertical direction in the second calibration operation. May be moved slightly to obtain a calibration constant representing the relationship between the vertical movement time and the electron beam movement distance.

The movement of the electron beam may be performed individually in the horizontal and vertical directions, or may be performed simultaneously by moving the electron beam in an oblique direction.

(4) In the modifications (2) and (3), the electron beam is slightly moved in the vertical direction, and the calibration constant representing the relationship between the vertical movement time and the electron beam movement distance is obtained. Alternatively, the calibration constant may be obtained in the same manner as in the above-described modification (1).

That is, in FIG. 1, the vertical dimension S _V of the display surface of the CRT 16 to be measured, the vertical resolution, ie, the number of dots R _V, and the frequency F _V of the vertical synchronizing signal are input to the input keyboard of the personal computer 15. And the input data is transmitted to the CPU 23.

[0138] In addition, CPU 23 is vertical dot distance D _V (mm) of and vertical dot time T _V (sec),

[0139]

D _V = S _V / R _V T _V = 1 / F _V , from which the vertical calibration constant α _V is

[0140]

## EQU15 ## A function is obtained by α _V = D _V / T _V.

According to this embodiment, the vertical calibration constant α
_V can be easily obtained. Note that instead of inputting the data relating to the CRT 16 using the personal computer 15, the main body 13 may be configured to allow input.

(5) In the above embodiment, the second calibration operation for obtaining the calibration constant representing the relationship between the horizontal movement time and the electron beam movement distance is performed, and the calibration constant is used in # 70 in FIG. The moving time is obtained, and the display position of the electron beam is accurately moved in the horizontal direction by a predetermined distance by delaying by the moving time obtained in # 72. Instead of this, the calibration constant is not obtained. Alternatively, it may be moved as a predetermined distance by a distance shorter than the distance between the phosphors arranged on the display surface of the CRT.

Also in this case, the influence of the positional relationship between the display position of the electron beam and the phosphor is reduced, and the variation of the luminance barycenter coordinate, that is, the jitter amount can be obtained relatively accurately.

[0144]

As described above, according to the first aspect of the present invention, the emission luminance when the phosphors arranged on the display surface of the CRT emit light by the irradiation of the electron beam is measured a plurality of times. The luminance centroid coordinates of the electron beam are calculated based on the emission luminance for each measurement, and the variation is calculated as the jitter amount of the CRT from the luminance centroid coordinates calculated for each measurement. Can be obtained objectively.

According to the second aspect of the present invention, the display position of the electron beam on the display surface of the CRT is determined in the direction in which the phosphors are arranged by shifting the synchronization signal for displaying an image on the CRT by a predetermined amount. The display is moved by a distance, and at each display position, the light emission luminance of the phosphor is detected a plurality of times by optical detection means disposed opposite to the display surface of the CRT, and the luminance center of the electron beam is determined based on the detection result for each detection. By calculating the coordinates and determining the variation as the amount of jitter of the CRT, the influence on the luminance barycentric coordinates due to the positional relationship between the display position of the electron beam and the phosphor can be reduced. Well calculated, C
The jitter amount of the RT can be obtained with high accuracy.

According to the third aspect of the present invention, a calibration constant representing the relationship between the shift amount of the synchronization signal and the moving distance of the display position of the electron beam is obtained, and the display position of the electron beam is determined using the calibration constant. By moving the phosphor on the display surface of the CRT in the arrangement direction of the phosphors by a predetermined distance accurately, it is possible to accurately calculate the luminance centroid coordinates of the electron beam regardless of the positional relationship between the display position of the electron beam and the phosphor. . Therefore, it is possible to accurately calculate the variation in the coordinates of the luminance barycenter, and thereby to accurately obtain the amount of jitter of the CRT.

According to the fourth aspect of the invention, the display position of the electron beam on the display surface of the CRT is moved by a very small distance in the direction in which the phosphors are arranged by shifting the synchronization signal by a very small amount. The measurement of the emission luminance is performed every movement, and the calibration constant is obtained based on the measurement result, so that the calibration constant can be accurately obtained regardless of the CRT instrument difference.

According to the fifth aspect of the present invention, since the horizontal dimension of the CRT, the frequency of the horizontal synchronizing signal, and the horizontal resolution of the CRT are known, the displacement of the horizontal synchronizing signal and the By obtaining the calibration constant indicating the relationship between the display position of the electron beam and the moving distance, the calibration constant can be easily obtained without moving the display position of the electron beam.

According to the invention of claim 6, since the vertical dimension of the CRT, the frequency of the vertical synchronizing signal and the vertical resolution of the CRT are known, the displacement of the vertical synchronizing signal and the vertical By obtaining the calibration constant indicating the relationship between the display position of the electron beam and the moving distance, the calibration constant can be easily obtained without moving the display position of the electron beam.

[Brief description of the drawings]

FIG. 1 shows a C to which a jitter amount measuring apparatus according to the present invention is applied.
It is a block diagram showing composition of a main part of one embodiment of an RT inspection device.

FIG. 2 is an overall configuration diagram of the embodiment.

FIG. 3 is a diagram illustrating an imaging surface of a CCD camera.

4A is a diagram showing an electron beam intensity during horizontal sweep, and FIG. 4B is a diagram showing a captured image of a CCD camera in a state where a CRT is fully lit in a single color.

FIG. 5 (a) shows the luminance centroid of the image shown in FIG. 4 (b) as +
FIG. 3B is a diagram showing the emission luminance of the phosphor in the horizontal direction.

FIG. 6 is a flowchart illustrating an operation procedure of a first calibration.

FIG. 7A is a diagram illustrating an image captured by a CCD camera in a state where dots D1 and D2 are displayed on a CRT, and FIG. 7B is a diagram illustrating light emission luminance of a phosphor in a horizontal direction.

FIG. 8 is a diagram for explaining a relationship between a horizontal movement distance and a movement time of a dot together with light emission luminance.

FIG. 9 is a flowchart showing a second calibration operation.

FIG. 10 is a diagram showing an image captured by a CCD camera when measuring a jitter amount.

FIG. 11 is a diagram illustrating a result of simulating an error amount of a luminance barycentric coordinate of an electron beam with respect to a positional relationship between a phosphor and an electron beam.

12 is a diagram showing a result of simulating a jitter amount with respect to a positional relationship between a phosphor and an electron beam using the simulation result of FIG. 11;

FIG. 13 is a diagram showing a result of a simulation of jitter amount measurement when the electron beam is moved three times by の of the phosphor interval.

FIG. 14 is a flowchart illustrating a procedure of measuring a jitter amount.

[Explanation of symbols]

 Reference Signs List 11 CCD camera 12 General-purpose signal generator 13 Main unit 14 External monitor 15 Personal computer 16 CRT 21 A / D conversion unit 22 Measurement data storage unit 23 CPU 24 Vertical synchronization signal detection unit 25 Synchronization signal delay unit 26, 27, 28 I / F Part 31 imaging surface 32 phosphor

Claims (6)

[Claims] 1. A luminance measurement control means for measuring a light emission luminance when a phosphor arranged on a display surface of a CRT emits light by irradiating an electron beam, and the light emission luminance is measured a plurality of times. A luminance centroid calculating means for calculating a luminance centroid coordinate of the electron beam based on the light emission luminance; and a jitter amount calculation for calculating a variation as the jitter amount of the CRT from the luminance centroid coordinates calculated for each measurement. And a jitter amount measuring device. 2. The jitter amount measuring apparatus according to claim 1, wherein the luminance measurement control means is disposed opposite to a display surface of the CRT, and optically detects the light emission luminance of the phosphor at a plurality of detection positions. Means for moving the display position of the electron beam on the display surface of the CRT by a predetermined distance in the arrangement direction of the phosphors by shifting a synchronization signal for displaying an image on the CRT by a predetermined amount. The luminance center-of-gravity calculation means causes the optical detection means to perform the detection of the light emission luminance a plurality of times at each of the display positions, and performs the detection based on the detection result of the light emission luminance for each detection. The jitter amount calculating means calculates the luminance barycentric coordinates of the electron beam. Jitter amount measuring apparatus, characterized in that to determine the amount of jitter. 3. The jitter amount measuring apparatus according to claim 2, further comprising: a calibration constant calculating unit that determines a calibration constant representing a relationship between a shift amount of the synchronization signal and a moving distance of a display position of the electron beam. The movement control means shifts the synchronization signal by a shift amount when the movement distance of the display position of the electron beam becomes the predetermined distance by using the calibration constant. . 4. The jitter amount measuring apparatus according to claim 3, wherein the calibration constant calculating means shifts the synchronization signal by a minute amount.
The display position of the electron beam is moved on the display surface of the RT by a small distance in the arrangement direction of the phosphors, and the emission luminance is measured at each movement of the small distance, and the calibration is performed based on the measurement result. A jitter amount measuring device for obtaining a constant. 5. The jitter amount measuring apparatus according to claim 3, wherein the arrangement direction of the phosphors is a horizontal direction, the synchronization signal is a horizontal synchronization signal, and the calibration constant calculating means is a horizontal direction of the CRT. A jitter amount measuring device for obtaining the calibration constant based on the size of the horizontal synchronization signal and the horizontal resolution of the CRT. 6. The jitter amount measuring apparatus according to claim 3, wherein the arrangement direction of the phosphors is a vertical direction, the synchronization signal is a vertical synchronization signal, and the calibration constant calculating means is a vertical direction of the CRT. A jitter measuring device for obtaining the calibration constant based on the size of the vertical synchronization signal, the frequency of the vertical synchronization signal, and the vertical resolution of the CRT.