JPH08162023A - Inspection device for picture tube panel inner surface and method for setting objective distance of image pick-up camera - Google Patents

Abstract

PURPOSE: To accurately and quantitatively inspect the precision of a stripe position on a panel inner surface by processing images of black stripes and fluorescent stripes through a process of irradiating the inner surface of a picture tube panel with an ultraviolet ray and irradiating the outer surface with a visible light. CONSTITUTION: A visible light irradiates the outer surface of a picture tube panel 5, a carbon stripe CS image transmitted through the panel 5 is taken into an image pick-up camera 7 and digitized by an image processing unit 3, and then image operation is performed by a control unit 4 and the positional precision of the CS image is inspected. The fluorescent stripes PS are made to emit the light by radiating an ultraviolet ray emitted from an ultraviolet lamp 6 to the inner surface of the panel 5, taken into the camera 7 through a spectral filter 11, and input into the image processing unit 3 and the control unit 4, and the positional precision of the PS image is inspected. The image data output from the image processing unit 3 is projectively operated into the stripe forming direction, and the concentration value data is extracted and differential-processed in the stripe intersecting direction, and the concentration value changing data is extracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the inner surface of a picture tube panel for inspecting the positional accuracy of black stripes and phosphor stripes formed on the inner surface of the picture tube panel, and an image capturing camera suitable for use therein. The present invention relates to a method of setting an object distance.

[0002]

2. Description of the Related Art A phosphor screen of a picture tube panel has black stripes, that is, carbon stripes formed at a predetermined pitch on the inner surface of the panel, and then red, green, and blue phosphor stripes in white spaces between the carbon stripes. Is created by forming. In such a picture tube panel, the red, green, and blue phosphor stripes are simultaneously caused to emit light by irradiation with an electron beam, so that the entire panel appears as a white screen. However, if there are variations in the width of each stripe or in the relative positions of the black stripes and the phosphor stripes, whitening is not performed uniformly over the entire panel, and local color unevenness occurs, which results in the quality of the color picture tube. The characteristics, especially white uniformity (white uniformity) are deteriorated. Therefore, in the process of manufacturing the picture tube panel, in order to guarantee the above-mentioned white uniformity, the stripe position accuracy on the inner surface of the panel, such as the width of each stripe and the relative position of the black stripe and the phosphor stripe, is inspected, and the picture tube panel alone. We carry out quality control in.

Initially, the mainstream of this type of inspection method was a visual inspection using a microscope. However, this takes a long time for measurement, and artificial variations in inspection accuracy and the like occur, which is sufficient. There was a problem that the measurement accuracy could not be obtained. Therefore, recently, an apparatus for automatically inspecting the stripe position accuracy on the inner surface of the picture tube panel has also been proposed. For example, by irradiating the picture tube panel with visible light or ultraviolet rays, a stripe image of carbon stripes or phosphor stripes of each color is captured by an image capturing camera, and suitable for density data obtained from the stripe image. There is a method in which a threshold value is set to detect the stripe edge position.

[0004]

However, in the conventional cases, the cathode ray tube panel with the carbon stripes and the cathode ray tube panel with the phosphor stripes were inspected by different devices, so that the devices were inspected. There were variations in inspection accuracy. In addition, when irradiating the picture tube panel with visible light or ultraviolet rays, there is a difference in the amount of irradiation light between the central part and the corners of the panel due to the positional deviation from the light source, and the irradiation level of ultraviolet rays becomes uneven. However, there is a problem in that the measurement data greatly varies depending on the setting condition of the threshold value, and the stripe position accuracy cannot be quantitatively inspected over the entire panel.

The present invention has been made to solve the above problems, and mainly provides an inspection apparatus for the inner surface of a picture tube panel, which can inspect the stripe position accuracy of the inner surface of the panel accurately and quantitatively. To aim.

[0006]

The present invention has been made to achieve the above object, and is an apparatus for inspecting the positional accuracy of a black stripe and a phosphor stripe formed on the inner surface of a picture tube panel. , A visible light lamp that irradiates the outer surface of the picture tube panel with visible light, an ultraviolet lamp that irradiates the inner surface of the picture tube panel with ultraviolet light, and a stripe image of a black stripe that has passed through the picture tube panel by visible light irradiation, and An image capturing camera that captures a stripe image of a phosphor stripe emitted by ultraviolet irradiation, an image processing unit that performs predetermined image processing on the stripe image captured by the image capturing camera, and outputs image data, and an image processing unit The image data output from the computer is projected in the stripe formation direction to extract density value data, and the extracted data is also extracted. The density value change data is extracted by differentiating the frequency value data in the stripe orthogonal direction orthogonal to the stripe forming direction, and the position in the stripe orthogonal direction corresponding to the peak value of the density value change data obtained by this is the stripe edge position. And a control unit for inspecting the stripe position accuracy of the panel inner surface based on the edge position detection data.

[0007]

In the apparatus for inspecting the inner surface of the picture tube panel according to the present invention, the image of the black stripe due to the visible light irradiation of the visible light lamp and the image of the phosphor stripe due to the ultraviolet irradiation are both obtained by the same image capturing camera. It is captured. Further, the stripe image captured by the image capturing camera is output from the image processing unit to the control unit as image data. In the control unit, the image data output from the image processing unit is subjected to projection calculation in the stripe formation direction, and then differentiated in the stripe orthogonal direction orthogonal thereto, and the stripe orthogonality corresponding to the peak value of the density value change data obtained by this is processed. The position in the direction is detected as the stripe edge position. Then, the stripe position accuracy on the inner surface of the panel is inspected based on the detection result.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1A and 1B are views for explaining an embodiment of an inspection apparatus for an inner surface of a picture tube panel according to the present invention, in which FIG. 1A is a schematic view of a mechanical mechanism portion thereof, and FIG. 1B is a functional block diagram thereof. There is. First, as shown in FIG. 1B, the inspection apparatus of the present embodiment is mainly mechanical, such as a measurement system including an optical system and a camera and its drive system, and further a panel support system and a power supply system. A mechanical mechanism unit 1 made up of components, a mechanical controller 2 that controls the operation of the mechanical mechanism unit 1, and an image processing unit 3 that performs predetermined image processing on a stripe image obtained via a measurement system of the mechanical mechanism unit 1. And a control unit 4 which controls the stripe position accuracy by an image calculation process described later while controlling the above.

The measuring system of the mechanical mechanism 1 is shown in FIG.
As shown in (a), a visible light lamp (not shown) that irradiates the outer surface of the picture tube panel 5 with visible light, an ultraviolet lamp 6 that irradiates the inner surface of the picture tube panel 5 with ultraviolet rays, and an inner surface of the picture tube panel 5. And an image capturing camera 7 for capturing the strap image of the carbon stripe CS and the phosphor stripe PS formed on the black stripe CS. An objective lens 8 is provided at the tip of the image capturing camera 7,
The objective lens 8 is attached to the tip of a lens barrel 9.
Further, a UV dichroic mirror, a spectral filter 11 and a CCD image pickup device 12 are incorporated on the axis of the lens barrel 9, and a stripe image taken through the objective lens 8 is formed on the CCD image pickup device 12, and from there. The video signal is output to the image processing unit 3. Further, a shutter 13 is provided between the ultraviolet lamp 6 and the UV dichroic mirror, and the shielding function of the shutter 11 interrupts the irradiation of ultraviolet rays on the inner surface of the panel. Incidentally, the "UV dichroic mirror" is a multilayer film vapor deposition mirror that reflects UV (ultraviolet rays) and transmits visible light.

By the way, when a color camera is adopted as the image capturing camera 7, only the spectral filter provided for the color camera can be used, that is, the spectral filter to be used is limited, so that the light is emitted at the level of the limit of visible light. Red,
In order to accurately capture the blue stripe image, it must be expensive and specially made. Therefore, in order to further increase the resolution, three CCDs corresponding to red, blue, and green are used.
It is conceivable to employ a so-called three-plate CCD camera composed of sensors, but in this case sufficient measurement accuracy cannot be obtained due to the relative positional deviation between the CCD sensors. From this point of view, in the case of the present embodiment, a monochrome camera is adopted as the image capturing camera 7, and red, blue,
A high-precision spectral filter 11 corresponding to each green color is installed, and a spectral filter 1 is provided by a filter switching mechanism (not shown).
By sliding 1 in the direction orthogonal to the axis of the optical system, a stripe image of each color can be obtained through the same optical system. Further, even when the image of the carbon stripe CS is obtained, the stripe image can be passed through (blank) by the switching mechanism of the spectral filter 11.

The structure of the fluorescent screen formed on the inner surface of the picture tube panel 5 will be briefly described. First, as shown in FIG. 2, black carbon stripes CS are formed on the inner surface of the picture tube panel 5 at predetermined pitch intervals. Since only the carbon stripes CS are not filled between the stripes, the stripes are in a blank state. From this state, the phosphor slurry of each color is embedded in the white portion in the order of, for example, red (R), green (G) and blue (B), and the phosphor slurry of three colors is dried and exposed respectively. The stripes CS are regularly formed. At this time, there are variations in the stripe widths, or the centers between the carbon stripes CS, that is, the centers of the white portions (shown by the one-dot chain line in the figure) and the phosphor stripes PS.
If there is a positional deviation relative to the center of the panel (shown by the chain double-dashed line in the figure), the panel characteristics (white uniformity) as described earlier
Will be deteriorated.

Therefore, in the inspection apparatus of this embodiment, the stripe position accuracy of the inner surface of the panel is inspected according to the following procedure. First, in setting the objective distance of the image capturing camera 7 with respect to the inner surface of the panel (object surface) (distance between the lens system of the image capturing camera 7 and the object surface), an autofocus algorithm based on the extreme value prediction method was adopted. Generally, the contrast value of an image with clear black and white such as a stripe structure changes as shown in FIG. 3 with respect to the object distance (distance of the camera system from the object plane). At this time, the objective distance Z0 corresponding to the extreme value of the contrast becomes the just focus distance of the camera system. However, since the change in the contrast value becomes extremely small in the vicinity of this just focus, the normal autofocus algorithm, that is, the constant step In the method of continuously detecting the contrast value in the width and detecting the inflection point (extreme value) of the contrast value, the convergence speed is slow, and an erroneous aberration may occur, resulting in poor focus.

On the other hand, in the autofocus algorithm of this embodiment, while changing the objective distance of the camera system with respect to the inner surface of the panel by the operation of the camera drive system (not shown),
Objective distances Z1, Z2, Z with arbitrary step distances
The contrast values T1, T2 and T3 corresponding to 3 are discontinuously detected. Further, using the following formula 1, a two-dimensional curve showing the correlation between the contrast values T1, T2, T3 and the corresponding object distances Z1, Z2, Z3 (see FIG. 3).
The contrast curve inside) is approximated.

[Equation 1] In the equation (1), T is a contrast value, Z is an object distance, A, B, and C are unconstant.
B and C are the correlation between the contrast value and the object distance (Z
1, T1), (Z2, T2), and (Z3, T3) are all satisfied.

At this time, since the contrast curve at the just focus distance shows a maximum value, the object distance Z corresponding to the peak value of the previously approximated two-dimensional curve is obtained by using the following equation (2).

[Equation 2] Since the objective distance Z thus obtained becomes the just focus distance Z0 of the camera system with respect to the subject surface, the image capturing camera 7 is set to the objective distance Z0. As a result, the convergence speed of the camera system and the measurement accuracy for the object surface can be significantly improved.

Next, a procedure for actually inspecting the stripe position accuracy will be described. FIG. 4 is a measurement flowchart in the case where the picture tube panel 5 after the phosphor stripe is formed is an inspection target, and this mainly shows the operation flow of the mechanical mechanism section 1. First, in step S1, the image capturing camera 7 is focused on the carbon stripe CS on the inner surface of the panel by the autofocus algorithm. At this time, both the visible light lamp and the ultraviolet lamp 6 (not shown) are in a lit state, but since the shutter 13 is closed, the irradiation of ultraviolet rays on the inner surface of the panel is blocked.

Next, in step S2, the image capturing camera 7 captures the carbon stripe image transmitted through the picture tube panel 5 by irradiating the outer surface of the panel with visible light, and when that is completed, the visible light lamp is turned off (step S2). S3). At this time, the carbon stripe image captured by the image capturing camera 7 is transferred to the image processing unit 3 as a video signal, and predetermined image processing (for example, A / D conversion) is performed there.
And digitized, and the digitized image data is output to the control unit 4. Further, the control unit 4 subjects the received image data to image calculation processing, which will be described later, to inspect the positional accuracy of the carbon stripes.

When the image capture of the carbon fiber CS is completed, the shutter 13 is opened subsequently,
The ultraviolet rays emitted from the ultraviolet lamp 6 are refracted by the UV dichroic mirror and applied to the inner surface of the panel, and the phosphor stripes PS of the respective colors formed there are emitted (step S4). Next, the spectral filter 11 is passed through the filter switching mechanism from the blank (blank) state to green (G).
(Step S5). Here, when capturing the image of the phosphor stripe, the objective distance is finely adjusted in order to correct the slight chromatic aberration remaining in the optical system in order to make the just focus state of the camera system for each color stripe uniform ( Step S6). This is because the wavelength of the light to be measured extends over the entire visible light, but at the present time, there is no optical system in which the chromatic aberration is completely 0 (zero) over the entire visible light. The chromatic aberration correction distance may be experimentally determined in advance, and it is not necessary to change the correction distance each time measurement is performed. After the fine adjustment of the objective distance is completed in this way, the green (G) is passed through the spectral filter 11.
The image of the phosphor stripe of is captured by the image capturing camera 7 (step S7). The subsequent image processing and the like are the same as in the case of the carbon stripe.

Thereafter, as in the case of the green (G) phosphor stripe, the image capturing of the blue (B) phosphor stripe is performed in steps S8 to S10, and the red (R) phosphor is used in steps S11 to S13. The stripe image is captured.
After that, when the image capturing of the phosphor stripes of each color is completed, the spectral filter 1 is again operated by the filter switching mechanism.
1 switches to the blank (blank) state (step S
14) Then, after the shutter 13 is closed (step S15), a visible light lamp (not shown) on the outer surface side of the panel.
Lights up (step S16). When a series of stripe images are thus captured, the picture tube panel 5 to be inspected is replaced, and the next measurement is started again in the same procedure as above.

Here, the image calculation processing by the control unit 4 will be described. First, the control unit 4 performs a projection operation on the image data output from the image processing unit 3 in the vertical direction, that is, the stripe forming direction Y (see FIG. 5), and the image is captured from the stripe image captured by the image capturing camera 7. The density value data shown in 5 (b) is extracted. The projection calculation formula at this time is shown in Formula 3.

(Equation 3) In Equation 3, P (i) is the projection calculation result of the i-th line, F (i, j) is the density value data at the j-th coordinate position on the i-line, S and E are the start point of the processing range and The coordinates of the end points are shown.

Further, the control unit 4 differentiates the density value data extracted by the projection calculation processing in the horizontal direction, that is, the stripe orthogonal direction X orthogonal to the stripe forming direction Y. Since the differential processing for the digital image is executed by replacing it with the differential processing, the first partial differential D (*) in the horizontal direction X
Is defined by the following equation (4).

[Equation 4] That is, if the density value of the projection data increases, its differential value becomes (+), and conversely, if it decreases, the differential value becomes (-). Furthermore, the greater the degree of increase or decrease, the greater the absolute value of the differential value. Therefore, the density value change data in the image data of the stripe image is extracted by using the above equation (4).

FIG. 5C shows the extraction result of the density value change data obtained by the above equation (4). As shown, the carbon stripe CS to the phosphor stripe PS
The density value change greatly changes in the (+) direction at the boundary part changing to, and conversely, the density value change changes greatly in the (-direction) at the boundary part changing from the phosphor stripe PS to the carbon stripe CS. There is. Here, in order to inspect each stripe position accuracy of the carbon stripe CS and the phosphor stripe PS, it is necessary to detect each stripe edge position. In the density value change data shown in FIG. 5C, the position indicating the stripe edge is (+)
Direction and the maximum density change point in the (-) direction, that is, the peak position of the density value change data.

Therefore, in the present embodiment, the density value change curve shown in FIG. 5C is given by the following calculation formulas (Equation 5 and Equation 6) in the (+) direction and the (-) direction. The threshold values Dif were set respectively.

(Equation 5)

(Equation 6) In Expressions 5 and 6, Difmax is the maximum value of the differential data, and Difmin is the minimum value of the differential data. At that time, the distance between the obtained stripe edges, that is, the stripe width is basically 40 to the stripe formation pitch / 3.
Since it falls within the range of 70%, there is a high possibility of a measurement error if it deviates from this range, and it is necessary to optimize the threshold setting with the correction value. At this time, since there is a difference in the degree of change in density between the panel having only the carbon stripe and the panel having the phosphor stripe, different correction values are adopted. By the way, in this embodiment, 0.95 is adopted as the correction value in the case of only the carbon stripe, and 1.10 is adopted in the case of the phosphor stripe.

Further, from the points Ee (i) and Ee (i + 1) at which the set threshold value Dif and the density value change curve intersect, the stripe edge position E (j) on the left side in the figure, and Ee (i
+2) and Ee (i + 3) are used to detect the stripe edge position E (j) on the right side of the figure using the following formulas (Equation 7 and Equation 8).

(Equation 7)

(Equation 8) In the equations 7 and 8, the symbol K indicates the coordinate position in the lateral direction, that is, the stripe orthogonal direction X, and D (K) indicates the first partial differential value at the K coordinate position. The stripe edge position data calculated by the equations (7) and (8) can obtain almost the same result even if there is some variation in the setting of the threshold value, and thus has an advantage that it is not easily influenced by the threshold value.

When inputting image data, the stripe image captured by the monochrome CCD image pickup device 12 is converted by the image processing unit 3 into 512 × 480 pixels (a total of 256 levels of density values 0 to 255). . In the case of a phosphor stripe, the brightness of each color sensed by the CCD image pickup device 12 is different due to the difference in the intensity of ultraviolet light transmitted through the lens system, the spectral transmittance of the spectral filter 11, etc. Then, the images are continuously captured, and the added image data is processed.

By the way, when measuring a panel with a phosphor stripe, it is assumed that the edge position may not be detected correctly depending on the coating state. This is because the density value data (projection calculation data) of the stripe image becomes a peculiar state due to the gaps and pinholes in the phosphor stripe, the edge state, the difference in film thickness, etc. This is due to the occurrence of irregularity, inappropriate setting of the threshold value, and erroneous recognition of an extreme density change portion as a stripe edge. FIG. 6 specifically illustrates such a problem. Figure 6
As shown in FIG. 6A, if there are gaps or pinholes in the phosphor stripe, or if there is something with a poor edge state, the spots where the gaps or pinholes are generated are shown in FIG.
As shown in (b), a local sudden change appears in the change in the density value obtained by the projection calculation process, and the change in the density is smaller in the place where the edge state is poor than in the other edge parts. . Therefore, as shown in FIG. 6C, when a stripe edge position is detected by setting a threshold value in the density value change data obtained by the differentiating process, it is possible to determine the location of the gap or pinhole as the stripe edge position. In addition to being erroneously recognized, the degree of change becomes smaller than the threshold value at a location where the edge state is poor, and edge detection becomes impossible.

From these considerations, in the present embodiment, the image flattening process is performed as described below for the purpose of coping with fine fluctuations and discontinuities in the density values that locally occur such as gaps and pinholes. did. Specifically, the average value of a total of three data before and after the data array to be measured is given to the central data as shown in the following Expression 9.

[Equation 9] This image smoothing process was performed once when differentiating the density value data by the projection calculation, and similarly three times in the projection calculation in the case of the panel with the phosphor stripe. As a result, local changes in the density value due to gaps and pinholes in the phosphor stripe are leveled and the threshold setting is optimized, so that the above-described edge detection error (erroneous recognition of edge position, etc.) By doing so, the stripe edge position can be detected more accurately.

By detecting the stripe edge position in this manner, in the case of a panel having only carbon stripes, the position shown in FIG.
As shown in (a), stripe width CW, each color R, G,
The outline width U between the stripes corresponding to B, the center-to-center distances K1 and H2, and the formation pitch P thereof are obtained as measurement data. Also in the case of a panel with a phosphor stripe, as shown in FIG. 7B, in addition to the measured data of the carbon stripe, the stripe widths RW, GW, BW of the respective colors R, G, B and the white Matching amount of each color stripe with respect to the central position of the removed portion (deviation amount between the CS central position and the PS central position) ΔR, ΔG, ΔB,
Furthermore, the edge intervals R-G, G- between the color stripes
B, BR, etc. are obtained as measurement data. Therefore, the control unit 4 determines the stripe position on the inner surface of the panel for the prescribed items based on the measurement data thus obtained, for example, the variation of each stripe width, the stripe formation pitch, and the overlapping degree of the phosphor stripes. The accuracy will be inspected.

[0028]

As described above, according to the present invention,
In the case of a picture tube panel with a black stripe only, and a picture tube panel with a phosphor stripe, both of which can be measured using the same measurement system (including optical system and camera system) In this case, the positional accuracy of the black stripe and the phosphor stripe can be simultaneously and automatically measured at multiple points. In addition, the image data output from the image processing unit is projected in the stripe forming direction to extract density value data, and then differential processing is further performed in the stripe orthogonal direction to extract density value change data, and the peak value is calculated. Since the stripe edge position is detected at the corresponding position in the orthogonal direction to the stripe, the detection accuracy of the stripe edge position is significantly improved, and the measurement data is affected by the difference in the irradiation light amount at each part of the panel as in the past. The stripe position accuracy can be quantitatively inspected over the entire surface of the panel. As a result, the reliability of the picture tube panel in terms of quality control is improved, and the characteristics of the picture tube panel, especially the whiteness uniformity, are fed back by feeding back the inspection results from the inspection apparatus to the stripe forming device as correction data. It is possible to significantly improve.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of an inspection apparatus for an inner surface of a picture tube panel according to the present invention.

FIG. 2 is an enlarged view of an essential part for explaining the structure of the fluorescent screen of the picture tube panel.

FIG. 3 is a correlation diagram between a contrast value and an object distance.

FIG. 4 is a flowchart showing an operation procedure of the inspection device.

FIG. 5 is a diagram illustrating an image calculation processing result in a control unit.

FIG. 6 is a diagram illustrating a cause of occurrence of an edge position detection error.

FIG. 7 is a diagram illustrating measurement data obtained by edge position detection.

[Explanation of symbols] 3 image processing unit 4 control unit 5 picture tube panel 6 ultraviolet lamp 7 image capturing camera

Claims (3)

[Claims] 1. A device for inspecting the positional accuracy of a black stripe and a phosphor stripe formed on the inner surface of a picture tube panel, the visible light lamp irradiating the outer surface of the picture tube panel with visible light, and the image receiving device. An ultraviolet lamp for irradiating the inner surface of the tube panel with ultraviolet rays, and a stripe image of the black stripes transmitted through the picture tube panel by the visible light irradiation, and a stripe image of the phosphor stripes emitted by the ultraviolet irradiation. An image capturing camera, an image processing unit that performs predetermined image processing on a stripe image captured by the image capturing camera and outputs image data, and image data output from the image processing unit in a stripe forming direction. Projection calculation is performed to extract density value data and the extracted density value data is The density value change data is extracted by differentiating in the stripe orthogonal direction orthogonal to the forming direction, and the position in the stripe orthogonal direction corresponding to the peak value of the density value change data obtained by this is detected as the stripe edge position. And a control unit for inspecting the stripe position accuracy of the panel inner surface based on the edge position detection data, and a picture tube panel inner surface inspecting device. 2. The inspection apparatus for the inner surface of a picture tube panel, wherein the control section performs an image smoothing process in the projection calculation or the differentiation process. 3. A method for setting an object distance of an image capturing camera with respect to a subject surface, wherein the object distance with respect to the subject surface is changed while changing the objective distance with an arbitrary step distance. A plurality of contrast values are detected, and then a two-dimensional curve showing the correlation between the detected plurality of contrast values and the object distance is approximated, and the peak value of the two-dimensional curve is obtained, and the peak value is calculated. A method for setting an object distance of an image capturing camera, characterized in that the image capturing camera is set to an object distance corresponding to.