JPS6341483B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a pattern measuring device that measures the dimensions of a pattern that is repeatedly arranged substantially regularly.

[Technical background of the invention and its problems]

``Conventionally, as a device for measuring the dimensions of a pattern, there was one that used a lens to image the pattern to be measured, focused the image on an image sensor such as a CCD, photoelectrically converted it, and measured the electrical signal. Measurement cannot be performed unless an image of the measurement pattern is accurately formed on an image sensor, and an automatic focusing mechanism is required.Automatic focusing mechanisms are generally complex and lead to higher quality devices. Furthermore, when measuring a pattern on a three-dimensional curved surface, it takes time to focus, making it difficult to increase the measurement speed.Also, in such measurements, each point is measured point by point, so In the case where the temperature is irregularly disturbed, it is necessary to perform measurements at multiple points and find the average value.Therefore, in this case, there were many problems such as additional time required.

In addition, a pattern measuring device (specially designed) that irradiates a pattern to be measured with a laser beam, performs Fourier transform on the transmitted light or reflected light using a lens, and measures the pattern width based on the intensity of a specific frequency component of the Fourier transformed pattern. (1973-27321). This device had many advantages, such as no need for focusing on the pattern to be measured, and the average value of all patterns included within the beam diameter of the irradiated laser light could be immediately determined. However, when measuring optically inhomogeneous diffusers such as ground glass or patterns printed on opaque materials such as paper, the S/N ratio is low when determining the Fourier transform pattern, making measurement impossible. Ta.

Furthermore, if the object to be measured is limited to the measurement of a black stripe (registered trademark of Tokyo Shibaura Electric Co., Ltd.) pattern on a colored Braum tube face plate,
A narrowly focused laser beam is scanned over a black stripe, and a detector detects the intensity of the transmitted light.
There are also devices that measure the time width of the signal. (Nonaka,
Others, Journal of the Television Society 34 No. 2 pp.141-146
(1980)) This device had the disadvantage that it was difficult to focus the laser beam sufficiently narrowly relative to the black stripe width, and errors were likely to occur when detecting the pattern width from the electrical signal. Another drawback is that in order to focus the laser beam uniformly on the pattern to be measured, the center of scanning the laser beam must be precisely set at the center of curvature of the curved surface of the face plate of the color cathode ray tube. moreover,
This device also measures one point at a time, so when measuring irregular patterns that occur near the edges of straight stripes, which are the basic pattern of black stripe patterns, it is possible to measure by averaging after measuring multiple points. It took a lot of time to measure just one spot. As described above, this device also had many problems.

[Purpose of the invention]

This invention was made in order to eliminate the above-mentioned drawbacks, and it does not require focusing and can directly measure the average pattern size of the measurement area at high speed. Even patterns printed on non-uniform media or opaque objects,
It is an object of the present invention to provide a pattern measuring device that can perform measurements at high speed and with high precision.

[Summary of the invention]

In this invention, a reference pattern is irradiated with a light beam. Furthermore, the pattern to be measured is irradiated with light that passes through this reference pattern and carries the reference pattern information. Next, a photoelectric conversion element placed behind the pattern to be measured converts the amount of light that has passed through the reference pattern and the pattern to be measured into an electrical signal. At this time, only the angle of the light incident on the reference pattern is changed using a galvanometer mirror, a lens, or the like. Then, the shadow of the reference pattern moves on the pattern to be measured. Therefore, an electric signal obtained by photoelectrically converting the amount of light that has passed through the reference pattern and the pattern to be measured becomes a signal representing a correlation function between the shadow of the reference pattern and the pattern to be measured.

Therefore, if the dimensions of this reference pattern are known and the shape of the pattern to be measured is unknown, it is possible to determine the dimensions of the pattern to be measured from the maximum and minimum values of this electrical signal. In other words, by calculating in advance the correlation function between the shadow of this known reference pattern and the measured pattern of each dimension, and comparing this value with the measurement results, it is possible to determine the size of the measured object. becomes.

〔Effect of the invention〕

In the present invention, the size is determined by the correlation between the shadow of the reference pattern and the pattern to be measured. Furthermore, in a system where the distance between the reference pattern and the pattern to be measured is kept substantially constant, this correlation is uniquely determined. Therefore, in a system where the distance between the reference pattern and the pattern to be measured is kept constant and all or part of the transmitted light is photoelectrically converted by the detector, the position of the illumination system and the position of the detector Measurements can be made with almost no influence. That is, measurement without the need for focusing becomes possible. For example, even if the pattern is on a three-dimensional curved surface, such as the black stripe pattern patterned on the inner surface of the face plate of a color cathode ray tube, it is best to choose a pattern that keeps the reference pattern at a constant distance from the curved surface. , measurements can be made without any focusing.

Next, the correlation signal calculates the average value of all patterns within the illuminated area, so even if there are irregular disturbances at the edge of the pattern, for example, the average value of the exact pattern within the illuminated area Dimensions can be measured.

Furthermore, even if the pattern to be measured is patterned on an opaque object such as a diffuser plate or paper, and the transmitted light is diffused, the present invention can measure the maximum and minimum amounts of transmitted light between the reference pattern and the pattern to be measured. Since it is determined only by the ratio of values, it is possible to measure without being influenced in any way. As described above, the present invention makes it possible to construct an extremely practical measuring device that has many advantages.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a pattern of bracket stripes formed on the inner surface of the face plate of a color cathode ray tube is measured.

First, the black stripe will be briefly explained in order to better understand this embodiment. The basic structure of a normal color television is a mask with a large number of pores (called apertures), that is, a shadow mask, and three-color phosphorescent surfaces formed corresponding to the individual apertures. Color selection is performed depending on the incident angle of each of the three electron beams incident on the aperture. In this embodiment, a slot mask having vertical rectangular holes is used as the shadow mask.

Such a shadow mask is attached to the face plate that becomes the screen of the color cathode ray tube that is the object to be measured. The inner surface of the faceplate is provided with phosphor strips, with a black light absorber or black stripe between each phosphor.
At this time, if the widths of the phosphor strips are not equal, the color balance will be disrupted.

As shown in FIG. 1, a pattern measuring device for a face plate, which is a pattern to be measured, uses a laser beam 11 that emits a laser beam that is coherent light, and a beam diameter of the laser beam from this laser light source 11. Collimating lenses 12a and 12b that once expand and converge again, and a galvano mirror 13 that changes the traveling direction of the laser light from these collimating lenses 12a and 12b.
and a lens 14 whose front focal position is the position where the laser beam from the galvanometer mirror 13 converges.
, a shadow mask 15 as a reference pattern onto which the parallel beam from the lens 14 is irradiated, a face plate 16 of a color cathode ray tube to which this shadow mask 15 is integrally attached, and a moving device 1 for moving this face plate 16.
7, a detector 18 that receives transmitted light from the face plate 16 and converts it into an electrical signal, and an amplifier 19 that amplifies the electrical signal from the detector 18.
An A-D converter 20 that converts an analog signal from this amplifier 19 into a digital signal, and an A-D converter 20 that converts an analog signal from this amplifier 19 into a digital signal
A signal processing device 21 that performs processing to be described later on the digital signal from the converter 20, and this signal processing device 2.
1, and a drive circuit 23 that is controlled by a signal processing device 21 to drive the galvanometer mirror 13 and change the reflection angle of the laser beam.

In this device, the inner surface of the face plate 16 is irradiated with a bundle of parallel rays only through the apertures of the shadow mask 15. That is, the shadow mask 15 is placed on the inner surface of the face plate 16.
A shadow picture of is projected.

This situation will be explained together with the principle of this invention.

The laser beam emitted from the laser light source 11 passes through the collimating lenses 12a and 12b, the galvano mirror 13, and the lens 14, and the mirror surface of the galvano mirror 13 substantially forms an image on the shadow mask 15, which is a reference pattern. However, it is not necessary to have a strict imaging relationship. The parallel beam from the lens 14 passes through a shadow mask 15 and is incident on a face plate 16 on which a black stripe is formed. At this time, the light passing through the face plate 16 is converted into an electrical signal. This electrical signal is a correlation signal between the shadow pattern of the shadow mask 15 and the black stripe.

When the galvanometer mirror 13 is vibrated in this state, the angle of incidence of the parallel beam onto the shadow mask 15 changes. Then, the correlation signal also changes, and from this change the dimension of the black stripe, which is the pattern to be measured, is measured.

Further, a detailed explanation will be given using FIG. 2. A parallel beam bundle 31 having a diameter D=2 to 3φ is incident on a shadow mask 15 having an aperture pitch, that is, a slot center spacing p=750 μm. The center spacing of the phosphor strips L=250 μm. For convenience of explanation, parallel line bundle 31
is a shadow mask 15 and a face plate 1
It is assumed that the incident angle is perpendicular to 6.

At this time, the parallel line bundle 31 is
Only the light beam 33 passing through the slot enters the inner surface of the face plate 16. Of the incident destinations,
The light irradiated onto the black stripe 32 does not pass through the face plate 16. Only the light irradiated onto the phosphor strips provided between the black stripes 32 passes through the face plate 16 and reaches the detector 1.
Reach 8. Further, the inner surface of the face plate 16 is provided with a rough diffusion surface 16a. The diffusion surface 16a is provided so that the inside cannot be seen through the surface of the face plate 16. It is preferable that the inside cannot be seen by the viewer, and furthermore, the coloring state becomes preferable due to the diffusion of light. Further, by utilizing the rough surface of the diffusion surface 16a, the slurry and the like are not easily peeled off. Because of the presence of such a diffusing surface 16a, measurement cannot be performed using coherent light using Fourier diffraction. As can be seen from the overall description, this invention is characterized in that it does not use Fourier diffraction but uses a correlation function between two patterns.

Further, as will be described later, in this embodiment, since the ratio of the maximum value and the minimum value of the amount of transmitted light is determined, the measurement can be performed without being influenced by the presence of the diffusing surface 16a.

Now, to qualitatively explain the change in the amount of transmitted light, when the luminous flux 33 avoids the black stripe 32,
Minimum. Conversely, it is at a maximum when the light flux 33 is incident on the phosphor strips.

Furthermore, it should be noted that, as shown in FIG. 2, one parallel thin bundle 31 irradiates a plurality of slots in the shadow mask 15 and a plurality of black stripes 32 on the inner surface of the face plate 16. It is. That is, individual black stripes 3
The average value will be measured for a plurality of black stripes 12 instead of two.

Keeping the above points in mind, we will conduct a more analytical discussion. Now, the shadow of the shadow mask 15, that is, the Fresnel diffraction pattern of the shadow mask 15, is f
(x) and the pattern of the black stripe 32 is g(x) (indicating the distribution of the area through which light passes), then the amount of light I(τ) that passes through the face plate 16 and reaches the detector 18 is: I(τ)=∫ ^a _-a f(x-τ)g(x)dx...(1). However, a=D/2 (D is the diameter of the parallel beam bundle 31 incident on the shadow mask 15 as described above), and τ is the diameter of the parallel beam bundle 31 incident on the shadow mask 15 from the perpendicular direction as shown in FIG. This is the distance traveled between the projection pattern of the beam 31 onto the inner surface of the face plate 16 and the projection pattern of the parallel beam 33 incident on the shadow mask 15 at an angle of θ from the perpendicular direction.

Here, τ is as follows, where q is the distance between the shadow mask 15 and the inner surface of the face plate 16. τ=q tan θ (2). For the following discussion, Shadow Mask 1
5, normalize I(τ) by I(o), the amount of light when the parallel ray bundle 31 is incident from the normal direction, and let this function be φ(τ), then φ(τ)= I(τ)/I(o)...(3). Furthermore, since the beam diameter D of the parallel beam bundle is sufficiently larger than the pitch p of the slot of the shadow mask 15, φ(τ)=∫ ^p/2 / _-p/2 f(x-τ)g(x)dx/∫ ^p
/2 / _-p/2 f(x)g(x)dx...(4). φ(τ) may be a ratio of light amounts or a ratio of output signals from the detector 18. Also, this φ
(τ) does not depend on the beam size (diameter) of the illumination light.

Next, as mentioned above, the black stripe 32
g(x) representing the pattern has a period of one third of the opening pitch p of the shadow mask 15, and
It is a binary function of 0 and 1. On the other hand, f(x)
is a Fresnel diffraction pattern, as mentioned above. If we keep the above in mind and actually calculate equation (4), we will get the results shown in Figure 3.

It is clear that qualitatively the output from the detector 18 depends on the width of the black stripe 32. For example, as shown in FIG. 4, when the black stripe 32 on the inner surface of the face plate 16 is located at the center of the parallel beam 33 that has passed through the slot of the shadow mask 15, the output from the detector 18 is at a minimum. Conversely, as shown in FIG. 5, when the center of the parallel beam bundle 33 is located in an area where the black stripe 32 is not coated and the phosphor is coated, the output from the detector 18 is at its maximum. Become. That is, the maximum and minimum values of the output of the detector 18 are determined by the center position of the black stripe 32 and
It can be inferred from a simple qualitative discussion that this is influenced by the spacing of the black stripes 32.

We will treat this quantitatively. It has been found that although the Fresnel diffraction pattern of the shadow mask 15 on the inner surface of the face plate 16 is analytically very complex, it can be approximated very well by trigonometric functions. For example, as shown in FIG. 6, when the value of q mentioned above is set appropriately, a waveform shown by a solid line 61 is obtained. When this waveform is approximated by the dotted line 62 shown in FIG. 6, there is little error in this example.

Therefore, the Fresnel diffraction pattern f(x) and a trigonometric function, for example, 1+cos ax, are approximated. Furthermore, when we calculate equation (4) when the positional relationship is as described above, and actually calculate the ratio between the maximum value and the minimum value, we get Rαa/π・sinπ/2・B/αa+αa−B/ 2/α
a/2・sinπ/2・p/3-B/αa+p/3-B/2
...(5) becomes. However, a is the aperture size of the shadow mask 15, and α is a coefficient when the Fresnel diffraction pattern is approximated by a trigonometric function. When q was around 10 mm, α=0.76 showed the best agreement with the calculation using the Fresnel diffraction pattern. This trigonometric function can also be considered as a first-order component of the Fresnel diffraction pattern.

Normally, before measuring the black stripe pattern 32, the inspection of the shadow mask 15 has been completed and the entrance size a of the shadow mask 15 is known. Therefore, in equation (5),
α, a, and p are known.

Therefore, when B is taken as an independent variable and R is illustrated, it becomes as shown in FIG. 7. This diagram contains more useful information. That is, when R, which is the ratio of the maximum value and minimum value of φ(τ), is determined, the width B of the black stripe 32 can be determined using FIG.

The above is the basic aspect of this embodiment. Furthermore, when the galvanometer mirror 13 shown in FIG. 1 is slightly rotated, the angle of incidence of the parallel beam onto the shadow mask 15 changes, as shown in FIG. The parallel line bundle 33 moves. Along with this, the diffraction pattern of the shadow mask 15 also moves. Then, the amount of light reaching the detector 18 also changes, and as shown in FIG.
The output waveform of will also change.

The first three sets of maximum and minimum values then give the width of the black stripe 32, which contains the red, green and blue phosphor strips. For example, point 7
From the ratio of the value I 1 at point ₁ and the value I ₂ at point 72, the width of the black stripe 32 corresponding to red is the value at point 73.
The width of the black stripe 32 corresponding to green is calculated from the ratio of I ₃ to the value I ₄ at point 74, and the width of the black stripe 32 corresponding to blue is calculated from the ratio of the value I ₅ at point 75 to the value I ₆ at point 76. The width of each stripe 32 is determined. here,
Which black stripe 32 corresponds to can be determined when forming the phosphor stripes and the black stripe 32 on the inner surface of the face plate 16.

Furthermore, the amount of movement τ of the diffraction pattern of the shadow mask 15 is expressed by the incident angle θ of the parallel ray bundle onto the shadow mask 15 according to equation (2). Therefore, φ(τ) shown in FIG. 3 is expressed as θ, and φ
(θ).

Since it is expressed as φ(θ) in this way, as will be described later, by specifying the angle of the galvano mirror 13 using the signal processing device 21 and the drive circuit 23, it is possible to determine which black stripe 32 the measured amount corresponds to. I can see what is going on.

The measurement principle in this embodiment has been explained above, and next, the configuration for realizing this will be explained in detail. As shown in FIG. 1, the light from the face plate 16 is transmitted to a detector 18, an amplifier 19,
The signal is input to the signal processing device 21 as a digital signal via the D converter 20.

The signal processing device 21 is basically a CPU (Central
processing unit) and ROM (Read only memory)
It consists of The functions of the CPU are to detect the maximum and minimum values each time a signal is input from the A-D converter 20, and to detect the maximum and minimum values through the drive circuit 23 each time the detection of the maximum and minimum values is completed. The function of changing the angle of the galvano mirror 13, the function of changing the angle of the galvano mirror 13 via the drive circuit 23 every time the detection of the maximum value and minimum value is completed, and the function of changing the angle of the galvano mirror 13 through the drive circuit 23.
After reaching one-third of the aperture pitch p of No. 5, the ratio of the maximum value and minimum value in this section is calculated, and the ROM address is specified using this ratio.
It has a function of extracting data stored at a designated address in this ROM and sending it to the display device 22, and a function of controlling the mobile device 17.

Here, the ROM contains R-B shown in FIG.
The curve is memorized. However, as described above, address specification is performed by the ratio R between the maximum value and the minimum value.

Furthermore, when the angle of the galvano mirror 13 is known, the angle of incidence of the parallel beam onto the shadow mask 15 is specified. Then, as described above, it is possible to know which black stripe 32 corresponds to.

The moving device 17 moves the face plate 16 to which the shadow mask 15 is attached,
Change the measurement position. Normally, it is not necessary to measure the entire inner surface of the face plate 16;
Around 10 points is sufficient. This moving device 17 also only needs to have the ability to set a similar number of positions.

Therefore, by controlling the moving device 17 and the drive circuit 23 by the CPU, the display device 22
In addition to the information on the width of the black stripe 32, the measurement position and the type of the black stripe 32 can be given and displayed.

Furthermore, since this embodiment uses laser light, the amount of light that enters the detector 18 is large, making it resistant to external light. Furthermore, in order to operate stably against external light, a dye filter or an interference filter that allows only laser light to pass may be used in front of the detector 18 in FIG. 1. In Figure 1,
Similar measurements can be made using an incoherent light source such as a white light bulb instead of the laser light source 11.

Furthermore, the light beams incident on the shadow mask 15 do not have to be completely parallel.

[Other embodiments of the invention]

FIG. 8 shows another embodiment of the present invention. The embodiment is basically the same as the embodiment shown in FIG. 1, but in this embodiment, the object to be measured remains fixed on the same cathode ray tube face plate, and This made measurement possible. That is, a deflecting galvano mirror 13a is arranged near the center of curvature of the curved surface of the cathode ray tube face plate, and this galvano mirror 13a is further rotated by a motor 81 to enable two-dimensional scanning. 23a is a drive circuit that controls the galvanometer mirror 13a and the motor 81 using signals from the signal processing device 21. Next, for light detection, light is collected onto the detector 18 using a condenser 82 such as a Fresnel lens. At this time, since there is a possibility that external light is also collected, the interference filter 83 is used to receive only the laser light. By scanning the laser beam with the galvanometer mirror 13a in this manner, it is possible to measure the entire surface of the object while keeping it fixed. The other operations are similar to the embodiment shown in FIG.

[Other embodiments of the invention]

FIG. 9 shows another embodiment of the present invention. This embodiment is also essentially the same as the embodiment shown in FIG.
The difference is that multiple light sources are used as a means to change the direction of light incident on the shadow mask. That is, as a light source, for example, an LED or a semiconductor laser is used as the light source 91, 9 as shown in FIG.
The direction of light incident on the shadow mask is changed by arranging 2 and 93 and causing them to emit light using a switching drive circuit 94 that switches and drives each of them. By doing so, it becomes possible to perform measurements at extremely high speed. The rest is exactly the same as the embodiment shown in FIG. If the light emitting elements are arranged not one-dimensionally but as shown in FIG. 10, it becomes possible to measure the aperture diameter of the black matrix instead of the black stripe. Note that using a large number of light sources instead of three allows for more stable measurement with respect to the relative angular deviation between the light source and the shadow mask. Alternatively, the measurement may be performed by moving the light source in FIG. Furthermore, instead of moving the light source, an optical fiber can be used, and measurement can be made in the same way by moving the optical fiber.

In the above embodiments, the width of a black stripe patterned on the inner surface of a color cathode ray tube was measured as an example of the object to be measured, but the present invention is not limited to this. For example, when measuring a pattern printed on a ceramic substrate, if a reference pattern is prepared, it becomes possible to perform the same measurement as in this embodiment. It is also possible to measure the pitch of black stripes.

Further, since the present invention requires a superimposed signal of the reference pattern and the pattern to be measured, it is natural that not only the light passing through the pattern to be measured but also the reflected light may be used. As described above, it is natural that any modifications are included in the present invention as long as they do not depart from the spirit of the invention.

[Brief explanation of the drawing]

FIGS. 1 to 7 show one embodiment, FIG. 1 is a diagram showing the overall configuration, and FIGS. 2 to 7 are diagrams for explaining the measurement principle in this embodiment. , FIG. 8 to FIG. 10 are diagrams showing other embodiments. 11... Laser light source, 13... Galvanometer mirror, 14... Lens, 15... Shadow mask,
16... Face plate, 18... Detector, 2
1...Signal processing device.

Claims (1)

[Claims] 1. In an apparatus for measuring the dimensions of a pattern to be measured of an object to be measured, in which a reference pattern is provided at a predetermined distance above the pattern to be measured, a light source that irradiates light to the reference and the pattern to be measured; an optical section that changes the incident angle of the light irradiated onto the pattern; a photodetection section that converts the amount of light that has passed through the pattern to be measured via the reference pattern into an electrical signal; A pattern measuring device comprising: a signal processing section that calculates dimensions of the pattern to be measured using maximum and minimum values of electrical signals.