KR20100119522A - Method and apparatus for detecting defects in glass sheet - Google Patents

Abstract

PURPOSE: A device and a method for detecting defects in a glass sheet are provided to effectively test a small-size glass and to reduce costs of output consumption. CONSTITUTION: A device for detecting defects in a glass sheet comprises a light source(10), a screen(14), and a light member. The light source emits a light beam. The light beam is projected on the top of the screen. The light member is located between the light source and the screen and blocks the light beam projected on the screen.

Description

Apparatus and method for detecting defects in a glass sheet {METHOD AND APPARATUS FOR DETECTING DEFECTS IN GLASS SHEET}

This application claims the priority of 12/433215 for "Apparatus and Method for Detecting Defects in Glass Sheets," filed April 30, 2009. The present invention generally relates to detecting defects of a plate transparent material such as, for example, a plate glass sheet, using light. More particularly, the present invention relates to a method and apparatus for providing a uniform illuminance distribution for the detection of defects in planar transparent materials such as, for example, planar glass sheets.

Recent technological advances in liquid crystal display (LCD) technology have led to more stringent requirements regarding the quality of glass substrates for LCD panels. Abnormalities of glass substrates, such as surface discontinuities, cords and streaks, or optical inhomogeneities in the bulk of the substrate, are among the factors contributing to the "Mura" defects in LCDs. “Is a Japanese word for blotches and has been adopted in the LCD industry for visual panel imperfections that appear in low contrast or non-uniform brightness regions. Substrate surface non-flatness introduces variations in LCD cell gaps and bulk heterogeneity. This results in refractive distortion of the light wave front and consequent mura defects Surface discontinuity usually arises from inclusions embedded in glass, which can be made of solid or gaseous materials. Striae-type defects such as leaks occur mainly due to the lack of homogeneity of the molten raw material. In turn, the streaks and cords are commonly manifested as surface projections or typically depressions extending along the glass drawing direction, while the streak defects usually appear as single stripes, while the cord defects are in millimeter range distance. It consists of a plurality of separate lines: The stripe effect associated with changes in optical path length (OPL) in excess of 10 nm in bulk optical glass is generally not negligible. It is becoming more rigorous with progress and approaching the rigorous demand for bulk optical glass at a tolerant level.

Substrate inspection is important to prevent defective substrates from being introduced into expensive panel fabrication processes and to provide feedback to the control system of the glass forming process. Historically, tests have been performed by a coroner using a shadowgraph method. See, for example, US Pat. No. 4,182,575 to Clark et al. And US Pat. No. 6,433,353 to Okugawa. Later, various automated methods were implemented to improve the continuity and reliability of the inspection. See, for example, US Application 2004/174519 (Gahagan), WO 2006/108137 (Zoeller), and US Publication 2008/0204741 (Hill). Manual inspection is still widely used in the production of LCD substrates due to the low equipment costs of high sensitivity, simplicity and shading.

The shading method used to inspect flat glass for the presence of defects causes light from a point-type light source such as, for example, a short arc discharge lamp to project through a glass sample onto a white screen. Steps. Without the sample, the illumination pattern on the screen consists of a bright area. When a glass sample is placed in the light beam between the light source and the screen, streaks or substrate defects change the luminous intensity of the transmitted light, thereby changing the distribution of illuminance on the screen. Variations in illuminance on the screen formed by defects in the glass can be visually observed or captured by a charge-coupled device (CCD) camera. When light passes through or is reflected from the glass sheet, the wavefront is distorted by the defect. The term "lensing effect" is sometimes used to describe such small disturbances caused by the inhomogeneity of the medium. The “focusing” portion of such a disturbance causes an increase in illuminance at the corresponding portion of the screen, and the “defocusing” portion of the disorder causes a decrease in the illuminance at the corresponding portion of the screen.

Another method of inspecting surface irregularities (see, eg, US Pat. No. 6,433,353, Okugawa) includes projecting a reflection from the glass sheet on the screen. By selection of the appropriate polarization and angle of incidence, contributions from one of the sheet surfaces can be minimized, thus enabling inspection of a single sheet surface primarily.

Using a light source with a small size is essential to achieving high spatial resolution for inspection for small-size, point-type defects and small-width, streaks, eg, codes or streaks. Realistically inconsistent white light is generally used, but some diffraction effects can be observed based on partial spatial coherence of the light source from small-size (point-type) sources over long distances. Light emitted from a source of size R _s at the point of glass separated by the distance L _Coh

Where L _Coh = 0.16Rλ / R _s , (1)

-Will have a spatial coherence of 88% (see M. Born and E. Wolf, Principles of optics, Cambridge University Press, 1999, Chapter X, Section 4.2), where R is from source to glass Distance, and λ is the average light wavelength. Spatial coherence is important if the magnitude ω of the surface perturbations satisfies:

(2)

(2)

Diffraction based on spatial coherence can disperse the sharpness of the shadows on the surface, or in some cases amplify the intensity modulation at the surface.

In illuminating only streaks in glass, a linear-type light source can be used. The light source should extend in a direction parallel to the stripe direction. It will increase the contrast of the stripes in this direction and spread the sharpness of other types of defects.

The illuminance distribution generated by the point light source and projected onto the screen is perceived as non-uniform by the inspector due to variations in the angles of incidence and distance between the light source and the screen. For a consistent interpretation of the test results, the luminance distribution of the light emitted by the light source must be altered so that the brightness (detected by local illuminance) over the detection area of the screen is perceived as uniform by the inspector. This is particularly important when inspecting glass panels for LCD manufacturing, where large size glass panels must meet stringent standards. Providing proper brightness distribution is an issue with the increasing size of glass substrates required for the LCD industry. Shading proportional to the glass size may also be impossible or impractical to simply scale up the composition. In addition to the increase in space required for such inspection and screen size, the lamp output must be increased in proportion to the increase in glass size. Larger output lamps may have a more effective size of the arc. With increasing lamp output, arc illuminance tends to be less stable, because increasing the size of the discharge plasma can cause the development of transient or spatial instability. The instability will manifest as brightness fluctuations and spatial brightness non-uniformity on the screen, thus making the inspection inconsistent. The life of bulbs generally decreases with power. In addition, safety measures for the human eye will be required to operate the lamp by an inspector placed near the high power light source.

Several aspects of the invention are disclosed herein. It should be understood that this aspect may or may not overlap with the other. Thus, some of one aspect may fall into the category of another aspect and vice versa.

Each aspect is described by embodiments, which in turn may include one or more specific embodiments. It should be understood that this aspect may or may not overlap with the other. Thus, some embodiments or portions of certain embodiments thereof may or may not be included within the scope of other embodiments, or specific embodiments thereof, and vice versa.

One technical challenge that needs to be addressed is how to provide a uniform illuminance distribution from the light source onto the screen for constant inspection over a large area of the glass sheet. Another technical challenge to be solved is the uniform illuminance distribution on the screen from the light source for large-scale glass sheets of different sizes using the same or similar devices to make a uniform inspection over all areas of different glass sheets of different sizes in different manufacturing facilities. How can you provide?

In a first aspect, an apparatus for detecting a defect in a transparent material is provided. The apparatus is adapted to intercept a light source that emits a light beam, a screen on which the light source is projected, and a light beam positioned between the light source and the screen and projected onto the screen. It includes an optical element. The light member is configured to change the luminous intensity of at least a portion of the light beam and to create a substantially uniform illuminance distribution on the screen.

In a second aspect, a method for detecting a defect in a transparent material is provided. The method includes projecting a light beam from a light source through a transparent material onto a screen. The method includes blocking, at a location between the light source and the screen, the light beam with a light member configured to change the luminous intensity of at least a portion of the light beam from the light source and produce a substantially uniform illuminance distribution on the screen. It further includes. The method further includes observing or recording the illuminance distribution on the screen.

One or more aspects of the present invention may have one or more of the following advantages.

Light members according to one or more aspects of the present invention that produce a uniform brightness distribution from a point light source enable inspection of large-sized transparent materials, for example glass sheet materials. The light member essentially decouples the screen illuminance distribution in the detection area of the screen from the distance between the light source and the screen. Because of this separation, different glass sizes can be inspected with the same apparatus while achieving the same inspection conditions. As a result, the consistency of the inspection process is improved over a wide range of glass areas from one measurement to another, from one size of glass sheet to another, from one manufacturing facility to another. The improvement is achieved without changing the optical magnification, the distance from the light source to the screen, or the brightness of the light source (eg, without changing the output of the light source). As a result, smaller laboratories can be used even if the size of the glass being inspected is increased. As a result, a relatively low power light source, which is effective for inspecting smaller glass sizes, can be used to inspect larger glass in smaller laboratories. Less powerful lamps tend to have longer lifetimes, which allows cost savings in lamp, maintenance and power consumption when inspecting relatively large sheets of glass.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious to those skilled in the art from the description, or may be practiced by practicing the invention as set forth in the disclosed description and claims as well as the accompanying drawings. It will be easily recognized.

The foregoing general description and the following detailed description are merely exemplary of the invention and should be understood to provide an overview or overview for understanding the nature and characteristics of the invention as claimed.

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification.
1 is a schematic diagram of shading, which is a traditional glass inspection apparatus.
2 is a schematic diagram of a glass inspection apparatus having a variable transmission optical filter.
3 is a cross-sectional schematic diagram of a variable transmission optical filter.
4 is a schematic diagram of a variable transmission optical filter in the filter plane.
5 is a float showing the transmission distribution of an exemplary variable transmission light filter.
FIG. 6 is a plot of the general angular distribution of luminous intensity at the cd of a 150 W xenon lamp (NewPort Corporation, Part number 6253).
7 is a schematic view of a glass inspection apparatus having a refractive light member having an aspherical surface.
8A is a calculated profile of the refractive light element.
8B is a schematic representation of a cross section of a refractive light member having the calculated profile of FIG. 8A.
9A is a plot of numerical ray tracing analysis results for illuminance (arbitrary units) versus location on the screen without the refractive light member of FIG. 8B.
9B is a plot of numerical ray tracing analysis results for illuminance (arbitrary units) versus location on the screen with the refracting light member of FIG. 8B.
9C is a plot of numerical ray tracing analysis results for illuminance (arbitrary units) versus location on the screen with the refractive light member of FIG. 8B defocused at 1 mm.

Considering the arrangement shown in FIG. 1, for example a light source 10, such as a point light source, and a screen 14 are arranged along the optical axis 16. In the conventional device used in FIG. 1, the optical axis 16 is in some cases perpendicular to the screen 14 and passes through the center of the light source 10. Also disposed on the optical axis 16 is a flat transparent material, for example flat glass 12, to be inspected. If the light source 10 can be considered to be Lembertian, then the illuminance at one point on the screen 14 (ie the incident illuminance at the surface per unit area) will be given as follows:

(3)

(3)

Where Iv is the luminosity, α is the angle between the optical axis 16 and the direction of the (light) ray 18 emitted by the light source 10, and S is the point source 10 Is the distance between the screens 14). The dependence of the light transmission through the glass sheet examined at the angle of incidence was not taken into account in equation (3). This may be valid if the angle of incidence does not exceed 35 degrees and the light from the light source 10 is not polarized. If necessary, a more accurate representation can be extracted by introducing a transmission coefficient that depends on the angle of incidence. From equation (3), the roughness is maximized at the center of the screen 14 (ie at the optical axis 16) and reduced towards the corner of the screen 14 according to Cos ³ a . Aspects of the present invention discuss how to make the ideal illuminance distribution on the screen 14 uniform as recognized by the inspector. The term “ideal illuminance distribution” assumes that the flat glass 12 has no detectable defects or that a glass sheet (or transparent material) is positioned between the light source 10 and the screen 14. It is used to describe the illuminance distribution on the screen when not. Therefore, the ideal illuminance distribution should be uniform to achieve consistent inspection of all quality areas.

Among the factors disclosed herein contribute to the perceived non-uniformity in the illuminance distribution:

(i) Variations of the distance to the screen (from the light source) and the angle of incidence on the screen described by equation (3).

(ii) Angular luminous intensity distribution of the light source. For example, referring to FIG. 6, this shows the dependence of the brightness on the vertical angle with respect to the short arc Xe light source. Angular dependence of the light intensity may be a result of the influence of the shape of the electrode on the discharge plasma. In the example shown in FIG. 6, the cathode is the lower electrode and the light intensity is about 5-10% greater in the downward direction.

(iii) the angle of incidence on the glass sheet, for example as disclosed in Fresnel refraction formulae (M. Born and E. Wolf, Principles of optics, Cambridge University Press, 1999 Chapter I, Section 1.5.2) Variation of light transmission (or reflection) of glass (or transparent material) due to differences in.

(iv) the position of the inspector relative to the screen. The brightness of point P on the screen captured by the human eye or CCD camera is determined by the total luminous flux received by the detector. The detected luminous flux is proportional to the flux incident at point P, the screen reflectivity of the light received from the incident direction and reflected in the viewing direction, and the distance from the point to the detector.

Only some of the above mentioned elements may be important in certain cases. For example, a spot light meter, such as a photographic spot light meter, measures the dispersion of screen brightness and takes all factors into account by mapping the required filter transmission dispersion to obtain a constant screen brightness. It is possible.

2 shows an inspection apparatus 20 comprising a light source 22, a variable transmission optical filter 24, and a screen 26 positioned along the optical axis 28. In the convention used herein, the optical axis 28 is a line perpendicular to the screen 26 and passes through the center of the light source 22. The flat transparent material to be inspected, for example flat glass 30, is located along the optical axis 28, more specifically between the variable transmission light filter 24 and the screen 26. The normal to the material 30 to be inspected is generally not perpendicular to the optical axis 28. The light beam 32 is projected from the light source 22 to the screen 26 through the variable transmission light filter 24 and the flat glass 30. In some embodiments, the light source 22 may be a point light source. The light source 22 may be, for example, a short-arc discharge lamp. The operating wavelength of the light source 22 is selected in the transmission range through the flat glass 22 and is visible by the coroner in the case of manual inspection. If the image formed on the screen 26 is obtained by the camera, the light should be detected by the camera medium. For example, the operating wavelength of light source 22 can range from 400 nm to 750 nm. If a person is to be used as an examiner, UV and IR wavelengths, which may be harmful to human eye, should be blocked by filter 24 or a separate filter. In other embodiments, light source 22 may be a linear light source.

The variable transmission light filter 24 changes the intensity distribution of the light beam 32 within the cone 33 defined by the maximum working light beam angle α _max , which is the screen 26 within the cone 33. It is essentially uniform in all points on the plane. For light rays outside of the cone 33, there may be a decrease in illuminance according to equation (3), or such light rays may be blocked by an optical filter 24 or other suitable aperture. The light cone 33, which is modified by the filter 24, passes through the flat glass 30 to the screen 26. Any distortion to the illuminance distribution observed on the screen 26 may be an indication of a defect in the plate glass 30. Observations can be made by human inspectors. Alternatively, or in addition to a human inspector, the device may include a camera to capture an image of the screen 26. The apparatus may further comprise a process for processing the image captured by the camera 41 to determine if there is a defect in the flat glass 30. The processing may include comparing the captured image based on the presence of the flat glass 30 between the light source 22 and the screen 26 and the baseline image without the flat glass 30.

Referring to FIG. 3, the variable transmission light filter 24 includes an input side 35 for receiving the light beam and an output side 37 for outputting the light beam. The variable transmission optical filter 24 includes a substrate layer 36 on the input surface 35. In certain embodiments, the substrate layer 36 has an essentially uniform light transmittance. In certain embodiments, the substrate layer 36 may be made of a transparent material, for example a glass material, for example fused silica. One of the faces of the substrate 36, preferably the output face 37 of the variable transmission optical filter 24 comprises a filter layer 34. In certain instances, the filter layer 34 may be sandwiched between two substrates. In certain embodiments, the filter 34 has variable light transmission. The light transmission at one point on the filter is the ratio of the intensity of light exiting the filter at that point to the intensity of light entering the filter at that point. The spatial variation in the light transmission of the filter layer 34, for example represented by equation (4) below, is used to adjust the respective intensity distributions of the light cones exiting the filter 24. The variable transmissive layer 34 is formed on the substrate layer 36 by any known method. The variable transmission optical filter 24 may be circular, for example, as shown in FIG. 4, or may have another shape. In certain embodiments, the variable transmission is achieved by spatial variation of light absorption or spatial variation of light reflection, or both. For example, thin variable thickness layers of metals such as silver, aluminum or other metals or alloys may be used. In certain embodiments, the material of filter layer 34 and substrate layer 36 is selected to withstand thermal stresses due to high temperatures and thermal expansion when exposed to high intensity light beams 32 (FIG. 2).

In some embodiments, an anti-reflection (AR) coating 38 is formed on one or both sides of the permeable filter 24. In addition to increasing the transmission of light through the filter, the non-reflective layer 38 will also protect the filter layer 34 from exposure to oxygen and ozone in the ambient air. In some cases, for example, if the filter layer 34 is made of an oxidizable material, such as a metal or metal alloy, the exposure may cause undesirable oxidation of the filter layer 34. The increase in overall light transmission due to the AR coating can result in a lower power demand on the light source and a lower temperature for the filter in operation. AR coatings also reduce undesirable multiple reflections from the filter surface. Multiple reflections form additional virtual light sources that increase the effective size of the light source. A protective layer (not shown in FIG. 3), for example transparent glass, resin or polymer, is provided to the AR coating 38 or from chemical reactions with the environment or from mechanical damage such as friction, scratching and chipping. It can be provided directly on the filter layer to protect the filter layer 34.

In some cases, the substrate material for the filter may absorb or reflect undesirable spectral portions of the light source radiation, such as UV (ultraviolet) or IR (infrared). In other embodiments, one or more light coating additional layers may be applied to the filter surface to block undesirable spectral portions of radiation, such as UV or IR.

In some embodiments, a small grain structure of filter layer 34 may be tolerated. The size and other attributes for suitable granularity depend on the resolution conditions and geometrical layout of the inspection equipment. In certain embodiments, the maximum particle diameter is 2 mm or less, preferably 1 mm or less. The maximum quotable particle structure should be determined such that the particle structure does not form a roughness non-uniformity of visibility on the screen.

With reference to FIG. 2, the variation in light transmission can be expressed as a dependency of the local value of the transmission coefficient T at that point on the filter on the appropriate coordinates of the particular point. If only the variation of the distance from the light source 22 to the screen 26 and the angle of incidence on the screen 26 are to be taken into account, the variable transmission optical filter 24 has a distance ρ from the point C at the filter face (see FIG. 4). It will have a permeability distribution T (ρ) defined as a function, which is given by the following equation (4):

, (4)

, (4)

Where T ₀ is the transmission coefficient of the substrate layer 36, d is the distance from the light source 22 to the position of the variable transmission optical filter 24, ρ _max is the maximum beam radius in the filter plane (filter plane 25 ) And ρ), which is given by:

, (5)

, (5)

Α _max in equation (5) is the maximum working beam angle defined by the angle of the cone 33 providing a uniform illuminance distribution. Desirably, the distance from the light source 22 to the variable transmission light filter 24 cannot be made too small because of the heat radiated from the light source 22. If the actual working distances d and α _max between the light source 22 and the variable transmission light filter 24 are determined, then equation (5) will define ρ _max . From equation (4) as follows, the permeability is at the center of the filter (where α = 0 and ρ = 0), from ToCos ³ α _max , at the outer periphery of the filter (where α = α _max and ρ = ρ _max ) or In the vicinity, it increases to T ₀ . In other words, the transmission T of light through the optical filter 24 is 100% of T ₀ at the maximum working beam angle α _max and decreases as it approaches the center of the filter at α = 0. The example in FIG. 5 shows the transmittance distribution of the variable transmission optical filter when T ₀ = 85%, d = 70.8 mm, and α _max = 27 degrees. Using this parameter, ρ _max is approximately 36 mm. The filter permeability coefficient T was plotted against the beam radius position ρ at the filter plane.

In the general case, for example, if multiple elements from the list are to be considered, the transmission distribution is not axially symmetrical as in the above example. If the theoretical analysis is not practical, the following process may be employed. Light from light source 22 is projected onto screen 26 without filters through high quality glass samples. Using a spot exposure meter positioned where the inspector should be located, the distribution of screen brightness is determined by measuring the brightness at multiple points on the screen. When measuring brightness from enough points of the screen, the brightness distribution, i.e. brightness versus position on the screen, will be interpolated with an appropriate function, for example polynomial interpolation. Point P ₀ of the minimum brightness I ₀ are located and mapped to a point on the filter surface which the light P ₀ passes through illuminating. The other point at which the brightness was measured is mapped to a corresponding point of P _i , i = {0, N} in the filter plane, where N is the number of points. The total transmission coefficient T _i (substrate and filter layer) at the point on the filter face corresponding to P _i is determined as follows:

, (6)

, (6)

Where T ₀ is the substrate transmission and I ₀ is the brightness at point P _i . The distribution of transmission coefficients will then be interpolated by a suitable method, for example polynomial interpolation. If a filter made in the process defined above is placed between the light source and the screen, the brightness of the screen will be essentially uniform.

In another embodiment, as disclosed in FIG. 7, a refractive optical element 40 is used to redistribute the light emitted from the point light source 22 to achieve the desired illuminance distribution at the screen face 26. do. The refractive light member 40 has at least one aspherical surface, as described below. In this embodiment, instead of blocking the excess light in bright areas to provide uniform illuminance on the screen, the light beams are dark areas in the bright areas on the screen. The direction is changed by refraction.

The following teaches how to obtain the formation of the refractive light member (or lens). In FIG. 7, it is assumed that the first surface 42 (facing the light source 22) of the refractive light member 40 is a concave spherical shape. The center of the sphere coincides with the light source position 22. The second convex surface 44 (facing away from the light source 22) is defined by the function r (α) , where r is the distance from the center of the first surface sphere in the angle α direction. The light beam at angle α will reach the screen at a distance from the next given optical axis.

, (7)

, (7)

가 제2 표면에 대한 법선과 상기 광축 사이의 각도라면, Snell의 굴절 법칙이 다음과 같이 표현될 수 있을 것이며,Where φ is the angle of the light beam after exiting the lens. if

If is an angle between the normal to the second surface and the optical axis, then Snell's law of refraction could be expressed as

, (8)

, (8)

Where n is the refractive index of the lens material. The tangent angle of the normal to the surface can be expressed as follows.

(9)

(9)

When formula (8) and formula (9) are combined,

(10)이 된다.

(10).

First order differential equation 10 may be used to determine the shape of aspherical surface 44. The dependence of the substrate transmission coefficient on the angle of refraction was not taken into account because all angles are only within a few degrees from the normal. Total transmittance can be considered constant. The solution of equation (10) can be expressed as follows.

(11)

(11)

For a given dependency ρ (α) , the function φ (α) can be found from equation (7).

(12)

(12)

If a ray with the maximum exiting angle α _max is required to leave the lens in the same direction, then,

; (13)

; (13)

Equations (11) and (13) thus define an aspherical profile 44 in polar coordinates.

FIG. 8A shows the calculated profile for the refractive light member 40 having the structure shown in FIG. 8B (or FIG. 7). In the plot shown in FIG. 8A, the horizontal axis R is the distance from the optical axis 28 to the point at the surfaces 42, 44 of the lens 40, and the vertical axis Z is the focal plane at that point in FIG. 7. , 45). In other words, the plot in FIG. 8A shows the sag profile of the refractive light member 40 in FIG. 8B. Profile 50 in FIG. 8A corresponds to first spherical surface 42 in FIG. 8B. Profile 52 in FIG. 8A corresponds to second surface 44, which is an aspherical surface in FIG. 8B. Profile 54 (shown for illustrative purposes only and does not represent the actual physical surface) corresponds to a sphere with a 87-mm radius. The difference between aspherical profile 52 and 87-mm spherical profile 54 is about 2 mm. 9A, 9B and 9C show the results of numerical ray tracing analysis to explain the performance of an aspherical light member (40 in FIG. 8B). In this float, the horizontal axis is the radial position h of point Q on the screen, and the vertical axis is the relative illuminance calculated at point Q. 9A shows the illuminance distribution (arbitrary unit) on the screen without the refracting light member. 9B shows a uniform illuminance distribution (arbitrary unit) with refractive light member. 9C shows the result of lens tolerance analysis. The plot in FIG. 9C shows 90% uniformity when the uniformed (refractive light) member is 1mm out of focus, ie 1mm out of its designed position along the optical axis. Numerical simulations show that the 1mm decentration (moving in the direction perpendicular to the optical axis) and the finite size of the light source (1mm) provide a significant degree of nonuniformity over the screen area similar to that shown in FIG. 9C. Positioning the refractive light member with accuracy better than 1 mm can be easily achieved.

Referring to FIG. 7, in some cases, for example, the surface or surfaces 42 and 44 facing the light source 22 may be aspheric to simplify the manufacture of the light member. The equation for the surface profile can be obtained in a similar manner as described above.

The light member configured to change the light intensity distribution of the light beam from the light source to produce a uniform illuminance distribution has been described above. The light member, for example the variable transmission light filter 24 or the refractive light member 40 as described above, is made with inspection equipment designed to detect defects in a flat transparent material, for example an LCD glass substrate. May be included. Such defects may be surface abnormalities such as cords, streaks, surface discontinuities or other types of defects. In such a device, the light member receives a light beam from a light source, for example a point light source or a linear light source, to produce a uniform illuminance distribution on the screen surface. If the light modulated by the light member passes through the transparent material before reaching the screen, the distortion of the illuminance distribution on the screen surface provides an indication of the defect of the transparent material. Such distortion can be visually observed by a human driver or captured by a camera for further automated processing. If the illuminance distribution of the light beam projected onto the screen is uniform and constant over the quality region of the sample being examined, an operator who is one measurement to another measurement, human or machine, may be able to determine the test results from one measurement to another. A more consistent interpretation will be possible.

The present specification includes the following non-limiting aspects and / or embodiments:

C1. A light source emitting a light beam;

A screen onto which the light beam is projected; And

A light member positioned between the light source and the screen to intercept a light beam projected onto the screen, the light member altering the intensity of at least a portion of the light beam and being substantially uniform on the screen. Apparatus for detecting defects in transparent materials, configured to produce a roughness distribution.

C2. In C1, the light member comprises a variable light transmission filter having a transmission profile defined as K / (d ² + ρ ² ) ^3/2 , where ρ is the variable transmission light filter Is a radius measured from a center to a given point on the variable transmission light filter, and d and K are constants, wherein the variable transmission light filter is formed on a substrate layer having a substantially uniform optical transmission, 10. An apparatus comprising a filter layer having variable optical transmission.

C3. The device of C1 or C2, wherein the variable transmission light filter further comprises an anti-reflection layer formed on at least one of the filter layer and the substrate layer.

C4. In C2 or C3, the constant K is defined as K = T ₀ (d ² + ρ _max ² ) ^3/2 , wherein T ₀ is the transmittance of the substrate layer, ρ _max is the variable transmission optical filter The maximum value of a predetermined ρ that changes the luminous intensity, and d is the distance between the variable transmission light filter and the light source.

C5. The device of any of C1-C4, wherein the light member is a reflective light member having one or more aspherical surfaces.

C6. The device of any of C1-C5, wherein the light source is selected from the group consisting of point-type light sources and linear-type light sources.

C7. Projecting a light beam from the light source through the transparent material onto the screen and illuminating the screen; And

Blocking, at a location between the light source and the screen, the light beam with a light member configured to change the luminous intensity of at least a portion of the light beam from the light source and produce a substantially uniform illuminance distribution on the screen; And

Observing or recording the illuminance distribution on the screen.

C8. The method of C7, wherein the optical member is a variable transmission optical fiber.

C9. The method of C7, wherein the light member is a reflective light member having at least one aspherical surface.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope and spirit of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Reference numerals in the drawings have the following meanings:
10: light source; 12: flat glass or flat transparent material; 14: screen; 16; Optical axis; 18: ray; 20: LCD glass inspection device; 22: light source; 24: variable transmission optical filter; 25: filter face; 26: screen; 28: optical axis; 30: flat glass; 32: light beam; 33: cone; 34: filter layer; 35: input surface; 36: substrate layer; 37: output surface; 38: non-reflective layer; 40: refractive light member; 41: camera; 42: first aspherical surface; 43: processor; 44: second aspherical surface; 45: focal plane; 50: first aspherical profile; 52 second aspherical profile; 54: spherical profile.

Claims (9)

A light source emitting a light beam;
A screen onto which the light beam is projected; And
A light member positioned between the light source and the screen to intercept a light beam projected onto the screen, the light member altering the intensity of at least a portion of the light beam and being substantially uniform on the screen. And to produce a roughness distribution. The method of claim 1, wherein the light member comprises a variable light transmission filter having a transmission profile defined as K / (d ² + ρ ² ) ^3/2 , wherein ρ is the variable transmission light The radius measured from the center of the filter to a given point on the variable transmission light filter, d and K are constants, wherein the variable transmission light filter has a variable light transmission formed on a substrate layer having a substantially uniform light transmission And a filter layer. The device of claim 2, wherein the variable transmission light filter further comprises an anti-reflection layer formed on at least one of the filter layer and the substrate layer. The method according to claim 2 or 3, wherein the constant K is defined as K = T ₀ (d ² + ρ _max ² ) ^3/2 , T ₀ is the transmittance of the substrate layer, ρ _max is the light transmittance of the variable transmission optical filter Is a maximum value of a predetermined p to change d, and d is a distance between the variable transmission light filter and a light source. The device of claim 1, wherein the light member is a reflective light member having at least one aspherical surface. The apparatus of claim 1 wherein the light source is selected from the group consisting of point-type light sources and linear light sources. Projecting a light beam from the light source through the transparent material onto the screen and illuminating the screen; And
Blocking, at a location between the light source and the screen, the light beam with a light member configured to change the luminous intensity of at least a portion of the light beam from the light source and produce a substantially uniform illuminance distribution on the screen; And
Observing or recording the illuminance distribution on the screen. 8. The method of claim 7, wherein the optical member is a variable transmission optical fiber. The method of claim 7, wherein the light member is a reflective light member having at least one aspherical surface.

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