JPH05303052A - Forming method for annular light and detecting method for internal defect of glass - Google Patents

Abstract

PURPOSE:To enhance the utilization efficiency of an irradiation light, and to improve the detection sensitivity by converting parallel rays to an annular light by using one piece or more of conical optical elements, and radiating the obtained light as an excitation light to an examinee. CONSTITUTION:Parallel rays B from a light source transmit through two pieces of conical optical elements (conical axially symmetric prisms) 1, 2 in which its optical axis A-A' becomes a symmetry axis of a cone, and thereafter, become light of an annular cross section being vertical to the optical axis A-A'. As for the incident parallel rays B from the light source, ultraviolet rays are used, and a transparency glass examinee having fluorescence is irradiated with annular ultraviolet rays centering around its inspection object position X0. The radiated annular ultraviolet rays generate annular fluorescence as an excitation light in the examinee. An area surrounded by this annular fluorescence is irradiated with the fluorescence and used for detecting a defect. In such a manner, the parallel rays can be converted to the annular light without a loss caused by light-shielding. Accordingly, a defect detecting inspection can be executed by bright illumination and with high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming annular light and a method for detecting internal defects in glass.

[0002]

2. Description of the Related Art As a method for detecting an internal defect of a glass inspection object that emits fluorescence upon irradiation with ultraviolet rays, the glass inspection object is irradiated with ultraviolet light and the fluorescence generated inside the inspection object is used as an illumination light source. Therefore, a method of detecting an internal defect of glass has been proposed (Japanese Patent Application No. 3-19).
No. 5847). In this method, an annular ultraviolet light is irradiated to surround the inspection position of the glass inspected object, thereby generating an annular fluorescence around the inspection position of the glass inspected object, and the fluorescence is particularly used as an illumination light source. It is preferable to inspect the inspection position. In this case, a method of providing a circular light shield plate on the optical axis is conceivable as a means for obtaining the irradiated ultraviolet light having an annular intensity distribution on a plane perpendicular to the optical axis from the irradiated ultraviolet light.

[0003]

In the method using the above-mentioned light shielding plate, since the central portion of the luminous flux of the irradiation ultraviolet light is shielded, the utilization efficiency of the irradiation light is lowered and sufficient detection sensitivity cannot be obtained. Since normally irradiated ultraviolet light has the maximum intensity on the optical axis,
This decrease in detection sensitivity is remarkable. On the other hand, there has been a problem that a high output irradiation ultraviolet light source is required to increase the detection sensitivity.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and irradiates a translucent glass inspected object having fluorescence with excitation light, whereby the inspected object is exposed. In the method of detecting an internal defect of the glass inspection object by using internally generated fluorescence as an illumination light source, the excitation light is one or more in which the parallel light is parallel light having an optical axis of the conical light as an axis of symmetry of a cone. It is intended to provide a method of detecting defects inside a glass, which is excitation light obtained by converting a cross section perpendicular to the optical axis into an annular shape by using a conical optical element. In particular, ultraviolet light can be used as the excitation light.

Further, according to the present invention, the parallel light is generated by using one or more conical optical elements in which the optical axis of the parallel light is the axis of symmetry of the cone, and the cross section perpendicular to the optical axis is annular. To provide a method of forming light having an annular cross section. Especially when the parallel light is ultraviolet light,
Ultraviolet light having an annular cross section obtained by the conversion can be used as excitation light to irradiate a translucent glass test object, and the resulting fluorescence of the annular cross section can be used for detecting internal defects of glass.

An embodiment of the defect detection method of the present invention is shown in FIG. AA ′ is the optical axis of the irradiation ultraviolet light B as excitation light, and the irradiation ultraviolet light B is parallel light obtained by a gas discharge tube and a parabolic mirror or a condenser lens, or TE.
A light source that oscillates in the M ₀₀ mode, for example, collimated light using an argon ion laser or the like as a light source can be used. These are all ultraviolet rays having the maximum intensity distribution on the optical axis AA ', and the intensity distribution on the incident virtual plane YY' of FIG. 1 by the TEM ₀₀ mode gas laser is as shown in FIG. It exhibits a Gaussian distribution. The excitation light source in the defect detection method of the present invention is not particularly limited, but the above-mentioned ones are easily available and the object of the present invention can be achieved.

The ultraviolet ray B from the light source is the optical axis A- of B.
After passing through the two conical optical elements having A ′ as the axis of symmetry of the cone, the cross section perpendicular to the optical axis becomes circular ultraviolet light. That is, the ultraviolet light is a virtual X- that is perpendicular to the optical axis in FIG.
An annular cross section is shown on the X ′ plane. FIG. 3 shows the intensity distribution at this time. By irradiating the inspected object having fluorescence with the ultraviolet light of such an annular cross section, it is possible to generate fluorescence of the annular cross section in the inspected object.

A method of forming light or a light flux having an annular cross section according to the present invention and its result will be described with reference to FIGS. X
₀ is the inspection target position of the inspection object. The optical element 1 has an apex on the optical axis and is composed of a polishing surface composed of a conical surface having the optical axis of parallel light from a light source as the axis of symmetry of a cone and a plane perpendicular to the optical axis ( A conical axisymmetric prism), and the parallel light B incident from the left side in the figure is refracted by the optical element 1 in an axially symmetrical manner. Further, the incident light B refracted by the optical element (conical axisymmetric prism) 2 having a conical shape having an apex on the optical axis and sharing the axis of symmetry with the optical axis, is the inspection target position X ₀ of the inspection object. The light becomes an annular light centered at or an annular light surrounding X ₀ . If ultraviolet light is selected as the incident parallel light from the light source, the object to be inspected can be irradiated with annular ultraviolet light. The fluorescence generated at that time also exhibits an annular shape surrounding X ₀ .

The arrangement relationship between the vertices of the optical elements 1 and 2 and the light from the light source is not limited to the arrangement shown in FIG. Further, the optical elements 1 and 2 may not have a simple conical shape as shown in FIG. 1, but may have an axial symmetry in which two cones have their bottom surfaces integrated face-to-face, but the one shown in FIG. 1 has a simple shape. It is easy to make.

The optical element 2 may be replaced by a general convex lens when the position of the object to be inspected is limited. Further, by changing the distance between the optical elements 1 and 2, the diameter of the ring centered at X ₀ changes. Therefore, the distance may be determined so that a desired annular diameter can be obtained.

In the present invention, the ultraviolet light having a circular cross-sectional shape perpendicular to the optical axis, which is irradiated to the translucent glass inspection object having fluorescence, is an annular fluorescence in the inspection object as excitation light. Generate. The area surrounded by the annular fluorescent light is efficiently irradiated with the fluorescent light and is used for defect detection. This annular fluorescence can be used for scanning the inspection target part, but the method of the present invention wastefully reduces the amount of light even when using a light source with the same output, as compared with the method of using a circular light shield plate on the optical axis. Since it does not, bright and efficient defect detection inspection can be performed as illumination.

FIG. 4 is an intensity distribution of light in an annular cross section when a circular light shield plate is used on the optical axis, and the vertical axis (intensity) is the same as that in FIGS. 2 and 3 on the same scale. .. Figure 4
In contrast, in the case of FIG. 3 according to the present invention, the intensity is high and the integrated value is remarkably large.

The area surrounded by the annular fluorescence is formed by the annular fluorescence generated by irradiating the glass test object which emits the fluorescence by the ultraviolet light with the annular ultraviolet light obtained by the method of the present invention. Illuminates brighter than with conventional methods. By scanning the irradiated ultraviolet light, the inspection object can be scanned with the fluorescence for inspection.

The internal defect detection method of the present invention is not necessarily limited to glass, but can be applied to a translucent inspection object made of a material that emits fluorescence inside the inspection object by excitation light. Further, as is apparent from the above description, the method of forming light having an annular cross section of the present invention does not limit parallel light to ultraviolet light. According to the method of the present invention, in general, parallel light is generated by using one or more conical optical elements in which the optical axis of the parallel light is the axis of symmetry of the cone, and the cross section perpendicular to the optical axis is annular. Can be converted to.

[0015]

EXAMPLE In FIG. 1, one side of synthetic quartz glass has an apex angle of 1
5mm thickness with 50 degree conical surface and other surface optically polished to flat surface
Two optical elements having a cone height and a diameter of 30 mm (bottom diameter of the cone) are arranged at a distance of 96 mm so as to share the axis of symmetry of the cone.
By irradiating the ultraviolet parallel light of mm with the optical axis overlapping the symmetry axis, irradiation light having an annular intensity distribution with an inner diameter of 15 mm and an outer diameter of 25 mm was obtained.

[0016]

According to the present invention, it is possible to convert parallel light into light having a circular sectional shape perpendicular to the optical axis without loss due to light shielding. Further, by using ultraviolet light as parallel light for irradiating an object to be inspected made of a material in which fluorescence is generated by using ultraviolet light as excitation light, the surface and the inside of the object to be inspected are ultraviolet rays having the annular cross section according to the method of the present invention. Can be irradiated with. Since the fluorescent light generated at this time also has an annular shape,
Since the area surrounded by the ring is efficiently illuminated by the fluorescence, it is possible to detect minute defects or indistinct defects that cannot be detected by the conventional technique when inspecting internal defects of the object to be inspected. The property is improved. Further, since a light source having a smaller output than that of the prior art can be used, the cost of the inspection device can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is a graph of an example of intensity distribution of parallel light from a light source, which is perpendicular to an optical axis before being incident on an optical element.

FIG. 3 is a graph showing an example of the intensity distribution of light having a ring-shaped cross section perpendicular to the optical axis after passing through two optical elements.

FIG. 4 is a graph showing an example of intensity distribution of irradiation light in the related art.

[Explanation of symbols]

1, 2: Conical optical element X ₀ : Inspection target location

Claims (5)

[Claims] 1. Converting parallel light into light having a toroidal cross section perpendicular to the optical axis by using one or more conical optical elements having the optical axis of the parallel light as the symmetry axis of the cone. A method of forming light having an annular cross-section. 2. The method of forming light having an annular cross section according to claim 1, wherein the parallel light is ultraviolet light. 3. An internal defect of the glass inspected object is detected by irradiating a translucent glass inspected object having fluorescence with excitation light and using fluorescence generated inside the inspected object as an illumination light source. In the method described above, the excitation light is converted into an annular cross section perpendicular to the optical axis by using one or more conical optical elements in which the parallel light has an optical axis of the parallel light as a symmetry axis of a cone. A method for detecting internal defects in glass, characterized in that 4. The method for detecting internal defects in glass according to claim 3, wherein the excitation light is ultraviolet light. 5. The method for detecting internal defects in glass according to claim 4, wherein the ultraviolet light source is a laser light source that oscillates in a TEM ₀₀ mode.