JPH07296733A - Measurement method for focus state of electron beam and adjustment method for image display device - Google Patents

Abstract

PURPOSE:To provide an adjustment method for accurately performing adjustment of focus, which has been indirectly performed conventionally by the image display device having stripe R, G and B phosphors, by directly finding out the density function of an electron beam. CONSTITUTION:One beam emission region is subjected to beam scanning by changing deflecting voltage so that emission quantities in two points under conditions of deflecting voltage (a) when the emission quantity reaches the peak or the beam center comes to the center of a phosphor 1, and a deflecting voltage (b) when the beam center found by deflecting voltage difference between the peaks comes on the phosphor boundary are measured. Respective emission quantities are in areas of the shaped portion 3 in a graph so that parameters of a beam density function on respective phosphors are found thereby. Unevenness of the parameters is uniformalized in the emission area so that the image display device can be adjusted in the optimum focus state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a television receiver,
The present invention relates to a method of adjusting a focus state and the like of a flat panel cathode ray tube used as an image display device such as a computer display.

[0002]

2. Description of the Related Art The present applicant has already filed Japanese Patent Application Laid-Open No.
The flat-plate cathode ray tube described in Japanese Patent Laid-Open No. 130453 is proposed. The internal electrode configuration diagram of the flat panel cathode ray tube shown in FIG. 6 is described in the above publication.

This cathode ray tube comprises a linear cathode 51 as an electron beam emission source, a back electrode 52 facing the linear cathode 51 on the side opposite to the image display surface, and a linear cathode on the image display surface side.
Electron beam extraction electrode 53, electron beam modulation electrode 54, vertical focusing electrode 55, horizontal focusing electrode 56, horizontal deflecting electrodes 57a and 57b, and vertical deflecting electrodes 58a and 5 which are placed in order with 51 sandwiched therebetween.
8b and a screen 59 coated with phosphor, which are housed in a flat vacuum glass container (a face plate 61 and a back plate 62 form a part thereof).

The linear cathodes 51 are stretched horizontally, and a plurality of such linear cathodes are arranged at appropriate intervals in the vertical direction (L in the description, only four are shown in FIG. 6). There is.

The sheet-shaped electron beam extracted from the linear cathode 51 passes through the through hole of the electron beam extraction electrode 53 and is divided into M thin beams, and the beam modulation electrode 54
Head to. The beam modulating electrode 54 is horizontally divided into M pieces, and the passing amount of each of the divided electron beams can be independently and simultaneously controlled (only nine pieces are shown in FIG. 6). .

The vertical focusing electrode 55 and the horizontal focusing electrode 56 serve to focus the beam vertically or horizontally, respectively.

The horizontal deflection electrode is provided with two electrodes 57 from the both sides in the horizontal direction for each of the electron beams divided in the horizontal direction.
A pair of electrodes formed so as to be sandwiched between a and 57b
The beam is deflected in the horizontal direction by the potential difference applied between 57a and 57b.

The vertical deflection electrodes are two electrodes 58a and 5a which form a pair of all beams for one scanning line from both sides in the vertical direction.
It is formed so as to be sandwiched by 8b, and the beam is deflected in the vertical direction by the potential difference applied between the two electrodes.

The focused, modulated, and deflected electron beams are accelerated by the high voltage applied to the screen 59 and impinge on the phosphor on the screen 59 to emit light. Each phosphor stripe has one electron beam modulation electrode 54.
For example, two pairs of RGB (two triplets) correspond to one through hole.

Next, regarding the method of applying the beam deflection potential in this conventional example, the number of display scanning lines is 480 in the NTSC system.
Taking the case of a book as an example, a waveform is shown in FIG. 7 for description.
The horizontal deflection is performed by the staircase-shaped deflection waveforms h1 and h2 shown in the figure. If the deflection width is two triplets of RGB, the deflection waveforms h1 and h2 are synchronized with the horizontal synchronizing signal H.D to generate H / 6. It is a step-like waveform in which the voltage rises or falls every cycle. Therefore, the electron beam is R / 6 for each H / 6 period.
It stands still on each of the G and B phosphors.

On the other hand, the vertical deflection is performed by using the stepwise deflection waveforms v1 and v2. The period for extracting the beam from each cathode is (240 / L) H, and each beam is drawn in the vertical direction.
(240 / L) -stage deflection (L = 40 in the figure is assumed to be 240/40 = 6-stage deflection), and 240 rasters are drawn by total 240 stages in one vertical scanning period (1 field) on the entire screen. .
In the next field, the voltage value of the vertical deflection waveform is shifted so that the beam will land during the raster drawn in the previous field, and interlaced scanning is performed.

The horizontal deflection and the vertical deflection are performed as described above, and one image display section 10 is formed by 12 vertical and 6 horizontal spots which are emitted by one electron beam, and this image display section is displayed on the screen 9. By arranging regularly,
Obtain one display image.

In the above image display device, it is desirable that the focus diameter (φH) of the beam be as uniform as possible when the beam is deflected in the horizontal direction within the one-beam emission region. The change characteristic of the focus diameter is generally as shown in FIG. 5 with the deflection middle point voltage VHC (horizontal focus voltage) for driving the horizontal deflection electrode as a parameter.
Therefore, the horizontal focus voltage is adjusted so as to approach the state of VHC2. A means for automatically performing this adjustment was devised, and is filed as Japanese Patent Application No. 04-311749.

According to this method, the change in the light emission amount with respect to the horizontal deflection amount of the beam is obtained by detecting the light emission amount while continuously changing the horizontal deflection electrode voltage, and the maximum value, the minimum value, or the maximum value thereof is obtained. It is possible to set the voltage that optimizes the focus state by measuring the value or the half value width of the minimum value as the information indicating the beam focusing state at a plurality of horizontal focus voltages.

[0015]

As described above, in the conventional example, the change of the light emission amount with respect to the horizontal deflection amount of the beam is obtained,
The maximum value or the minimum value, or the half-value width of the maximum value or the minimum value is adopted as the information indicating the focused state of the beam.

However, since the amount of emitted light is proportional to the sum of the beams that strike the phosphor, when the width of the phosphor is wide,
The change in the light emission amount is smaller than the change in the focus state,
For measurement error and variation of each point on the image display device,
It was difficult to accurately obtain the change in the focus state.

In view of the above problems, the present invention provides a measuring method capable of accurately detecting a change in focus state, and a method of adjusting an image display device based on the information.

[0018]

In order to solve the above problems, the electron beam focus state measuring method of the present invention uses the deflecting means to detect the focus state of the beam so that the center of the electron beam is the light emitting means. The deflection state of hitting the center of each section formed separately, and the deflection state such that the center of the beam hits the boundary of each section, the amount of light emitted from each light emitting means is detected by the light detecting means, The focus state can be quantitatively measured by calculating the density function of the electron beam with respect to the position on the light emitting means using the ratio of the detected light emission amounts.

Further, the adjusting method of the image display device of the present invention is
The horizontal focus voltage is set in a plurality of steps, the focus state is measured by using the electron beam focus state measuring method according to claim 1, and a horizontal focus voltage that gives an optimum focus state is obtained to determine the image display device. It adjusts automatically.

[0020]

In the present invention, since the density function of the electron beam itself with respect to the position on the light emitting means can be obtained by the above means, accurate information on the focused state of the electron beam can be obtained regardless of the width of the phosphor. In addition, it is possible to accurately obtain a change in the focus state due to a measurement error or a variation in each point on the image display device.

[0021]

【Example】

(Embodiment 1) An embodiment of the electron beam focus state measuring method of the present invention will be described with reference to the drawings. First, FIG. 1 shows the relationship between the phosphor that is emitting light and the electron beam.

The electron beam density distribution normally has a normal distribution curve as shown in FIG. The focus state of the electron beam at an arbitrary deflection position can be evaluated by obtaining the standard deviation of this normal distribution. Here, the focus diameter is considered as the value of this standard deviation. Of course, the focus diameter may be defined as the 50% point with respect to the peak value, which is easily calculated from this standard deviation. The amount of light emitted at this time is the sum of the beam densities in the range where the electron beam strikes the phosphor, as shown by the shaded area in FIG.
It corresponds to the density distribution curve of the electron beam integrated over the width of the phosphor.

On the other hand, FIG. 2 is an enlarged view of the fluorescent screen at an arbitrary point on the screen. It is assumed that the phosphor has R, G, and B colors periodically formed at the same pitch.
In a normal image display, the beam is scanned in a range from R1 to B2 (one-beam emission region) in six steps to emit light. To find the focus diameter at each phosphor position,
First, the beam is moved in steps (which may be continuous) much smaller than the above-described deflection interval of 6 steps, and the emission of the R, G, B phosphors at that time is detected. A video camera (both color and monochrome possible), a photodiode, etc. are suitable as the detection means.

As means for moving the beam, it is sufficient to change the deflection voltage applied to the horizontal deflection electrode. For example, if the deflection waveforms h1 and h2 are created by D / A converting digital data, that data is used. Can be forcibly rewritten from outside.

When the beam is moved by this method, it is assumed that the beam moves in the order of phosphor B → R1 → G1 → ... → B2 → R, and the emission output waveform shown in the lower part of FIG. 2 is obtained. Although shown separately for R, G, and B, this is an example of output signals of each color when picked up by a color camera. The horizontal axis represents the deflection voltage and the vertical axis represents the light emission output.

From this result, first, the deflection voltage at the peak, that is, the deflection voltage when the beam is landed on the center of the phosphor, is obtained for each of two points for each color (FIG. 2a,
a '). Next, since the actual pitch between the phosphors and the width of the phosphors are known, the deflection voltage is determined so that the center of the beam is on the boundary between the phosphors and the black stripes (FIGS. 2b, b ′, c). , C '). The relationship between the phosphor and the electron beam at these points is shown in FIG.

In FIG. 3, assuming that the width of the phosphor is 2w and the center of the beam is the origin of the horizontal axis, the brightness when the beam is landed at the center of the phosphor is from -w to + w of the beam density function. Equal to the integrated one (Fig. 3
(a) The shaded area). On the other hand, the brightness when the beam lands on the boundary between the phosphor and the black stripe is equal to the integral of the density function of the beam from 0 to + 2w (hatched portion in FIG. 3 (b)). When the respective luminances already measured are Lmax and Lhf, and the ratio R = Lhf / Lmax of these is calculated,

[0028]

[Equation 1]

The standard deviation of the density function of the beam, that is, the focus diameter can be obtained from the equation shown in FIG.

It goes without saying that these series of calculations can be completely automated using a computer or the like.

By the measuring method described above, it is possible to accurately detect the change in the focus state.

(Embodiment 2) Next, another embodiment of the present invention will be described.

In order to adjust the image display device to the optimum focus state, it is desirable that the focus diameters of the phosphors R1 and B2 in FIG. 2 are as uniform as possible. Therefore, assuming that the focus diameters at _{R1 to B2} are φH _R1 to φH _{B2 at} any position on the screen, as an example of the definition of the focus evaluation formula,

[0034]

[Equation 2]

When is minimum, the focus state can be optimum. Of course, it is not limited to this calculation formula.

The evaluation value calculated by this evaluation formula changes according to the setting of the focus voltage. FIG. 6 shows an example of changes in the evaluation value with respect to the focus voltage. According to this, the evaluation value is obtained in the form of a quadratic curve with respect to the focus voltage. Therefore, the focus voltage giving the minimum value can be calculated by measuring at least three focus voltages and obtaining the evaluation value, so that the image display device can be adjusted to the optimum focus state.

In order to obtain the optimum focus state over the entire screen, the above measurement may be performed at a plurality of points on the screen, and the evaluation values obtained at each point may be averaged and used.

Needless to say, like the first embodiment, the series of adjustment operations can be carried out completely automatically using a computer or the like.

In addition, in these adjustment operations, it is specified that the landing pitch adjustment operations described in Japanese Patent Application No. 04-311749 can be performed at the same time.

Further, as described in Japanese Patent Application No. 04-311749, even if the deflection voltage is sequentially changed with respect to the time axis when obtaining the light emission amount with respect to the deflection voltage, one step in the vertical scanning is performed. The adjustment can be executed even if the deflection voltage is changed every time.

[0041]

By implementing the present invention, a change in the focus state can be detected regardless of the width of the phosphor, and the focus state of the image display device can be adjusted with high accuracy, resulting in efficient image display. Enables production of equipment.

[Brief description of drawings]

1A and 1B are views showing the relationship between a phosphor and an electron beam in an embodiment of the present invention.

2 (a), (b), (c), (d) an enlarged view of a phosphor screen and a characteristic diagram showing the amount of emitted light in the same embodiment.

3A and 3B are diagrams showing a deflection state for obtaining a focus diameter in the same embodiment.

FIG. 4 is a diagram showing a characteristic of a focus voltage vs. an evaluation value in the example.

FIG. 5 is a diagram showing a characteristic of a focus diameter φH with respect to a deflection voltage.

FIG. 6 is an exploded perspective view showing an electrode structure of the image display device.

7A to 7J are diagrams showing drive waveforms of each electrode in a conventional image display device.

[Explanation of symbols]

 1 Phosphor 2 Black stripe 3 Diagonal area

Claims (2)

[Claims] 1. A means for generating a plurality of electron beams, a means for deflecting an electron beam, a means for focusing an electron beam, and a light emitting means which is separately formed into a plurality of sections which emit light when the electron beam strikes. In an image display device including: a deflection state in which the center of the electron beam hits the center of each of the separately formed sections of the light emitting means using the deflecting means, and the center of the electron beam is on the boundary of each section. And a deflection state corresponding to the above, the light emission amount on the light emitting means in each of these states is detected by the light detecting means, and the density of the electron beam with respect to the position on the light emitting means is used by using the ratio of the detected light emission amounts. A method of measuring a focus state of an electron beam, which comprises calculating a function to measure a focus state. 2. An electron beam focusing means driving voltage or current is set in a plurality of steps, the focusing state of the electron beam is measured, and a focusing means driving voltage or focusing means driving current of the electron beam that gives an optimum focusing state is set. A method for adjusting an image display device, which is characterized by: