Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Reexamination Certificate
1999-03-23
2001-05-01
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
C356S239800
Reexamination Certificate
active
06226080
ABSTRACT:
BACKGROUND OF THE INVENTION
1.Field of the Invention
The present invention relates to a method for detecting a defect of a transparent body and a method for producing a transparent body. In particular, the present invention relates to a method for detecting a defect of a transparent body, which is preferably used to detect the defect such as the bubble, the foreign matter, and the surface scratch existing, for example, in an acrylic plate, as well as the bend, the waviness, and the warpage of the acrylic plate itself. The present invention also relates to a method for producing a transparent body, in which an obtained result of detection of the defect is sent in a feedback manner to a production line for the transparent body to make changes to the production of the transparent body.
2. Description of the Related Art
Those hitherto known as the display include, for example, cathode ray tubes (CRT) and liquid crystal display apparatuses.
The material, which is often used for an optical guide plate of such a display, is glass or a transparent material, because it is necessary to totally reflect, within the optical guide plate, the light introduced from a light source.
When the optical guide plate is composed of glass, the following problems occur. That is, the weight of the optical guide plate is large when the display surface has a large size. Further, the price of glass is expensive.
In order to solve the problems as described above, an acrylic plate is also used as a material for the optical guide plate.
However, as shown in
FIG. 15
, when an optical guide plate is produced by using an acrylic plate
200
, a scratch
202
tends to be formed on its surface. Further, for example, a bubble
204
and a foreign matter
206
sometimes appear in the acrylic plate
200
. Furthermore, the flatness is occasionally lost due to any bend or waviness of the acrylic plate
200
itself.
Because of the circumstances as described above, an inspection is made whether any defect as described above is present or absent by means of visual observation effected by human eyes, during the inspection step for the products of the acrylic plates
200
. However, such a process is not necessarily efficient.
On the other hand, a technique for inspecting defect of a transparent body has been disclosed in which a light beam originating from a light source is radiated onto a plate member to inspect the plate member for its defect or the like (see, for example, Japanese Laid-Open Patent Publication No. 58-158920). An apparatus for inspecting the defect described in this document is operated as follows for the foreign matter and the scratch on the surface. That is, the light beam originating from the light source regulated by a slit in the radiation direction is radiated in parallel to a transparent body such as a glass mask for photolithography (in parallel to a principal surface of the transparent body), and scattered light concerning the foreign matter and the scratch on the surface is received by using a light-receiving unit so that the inspection is made for the presence or absence of the foreign matter and the surface scratch directed to the mask aperture.
However, in the case of the conventional apparatus for inspecting the defect, it is required to radiate the parallel light beam onto the plate member, and hence it is necessary to newly provide any optical system for producing the parallel light beam from the light supplied, for example, from a point light source. Therefore, it is feared that the system may be complicated. Further, a problem arises in that the positional control to radiate the parallel light beam onto the entire transparent body is difficult to implement.
When the parallel light beam is used, the following inconvenience arises. That is, it is impossible to detect any foreign matter or the like adhering to the surface of the plate member if the slit is located on the side surface of the plate member. When the surface of the foreign matter existing in the plate member is a mirror surface, the reflected light of the parallel light beam is not transmitted to the side of the principal surface depending on the position and the angle thereof. The reflected light is transmitted toward the side surface of the transparent body, and it cannot be detected by the light-receiving unit which is installed over the principal surface of the transparent body.
As understood from the principle of detection, the conventional technique described above makes it possible to detect a surface scratch and the foreign matter existing at the inside of the transparent body. However, the conventional technique fails to detect, for example, the bend and the waviness of the transparent body itself.
Further, in the conventional technique, the parallel light beam is introduced via a slit into a measurement space in which the transparent body is installed. For this reason, in order to perform the detection of the bubble, the foreign matter and the like existing in the transparent body and the detection of the scratch existing on the surface, it is necessary to move the slit in the thickness direction of the transparent body. Therefore, it is impossible to simultaneously perform the two detection processes described above. When the transparent body has a large thickness, a new problem arises in that the detection requires a lot of time and labor.
SUMMARY OF THE INVENTION
The present invention has been made taking the foregoing problems into consideration, an object of which is to provide a method for detecting a defect of a transparent body, which makes it possible to quantitatively and accurately detect, for example, a surface scratch, a bubble, and foreign matter in the transparent body, which are the defect of the transparent body.
Another object of the present invention is to provide a method for detecting a defect of a transparent body, which makes it possible to quantitatively and accurately detect, for example, the bend and the waviness of the transparent body itself.
Still another object of the present invention is to provide a method for detecting a defect of a transparent body, which makes it possible to perform a detection of a surface scratch of the transparent body, a bubble, foreign matter or the like in the transparent body simultaneously with the detection of the defect such as the bend and the waviness of the transparent body itself by using an identical optical system.
Still another object of the present invention is to provide a method for producing a transparent body, which makes it possible to produce the transparent body having fewer defects and having a high quality by sending, in a feedback manner to a production line for the transparent body, a result of the detection of defect obtained by the method for detecting defects of the transparent body to be achieved as described above.
The present invention lies in a method for detecting a defect of a transparent body, comprising the step of introducing a light beam predominantly including non-parallel rays which are not parallel to a principal surface of the transparent body, through at least one side surface which is formed substantially perpendicularly to the principal surface of the transparent body to detect the defect of the transparent body. The transparent body includes, for example, an acrylic plate to be used as an optical guide plate for the optical application such as the display.
Explanation will now be made for the optical path obtained when the light beam predominantly including the nonparallel rays is introduced into the transparent body, and for the principle of detection of the defect of the transparent body.
With reference to
FIG. 1
, when a light beam is transmitted from the transparent body
10
having a large refractive index (absolute refractive index) into the air
12
having a small refractive index, if the angle of incidence &thgr;
r
is gradually increased, the angle of refraction &thgr;
r
is increased corresponding thereto. However, when the angle of refraction &thgr;
r
arrives at 90°, the light beam is not transmitted (see
Nanataki Tsutomu
Ohwada Iwao
Sato Kei
Takeuchi Yukihisa
Burr & Brown
NGK Insulators Ltd.
Pham Hoa Q.
LandOfFree
Method for detecting defect of transparent body, method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for detecting defect of transparent body, method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for detecting defect of transparent body, method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2538008