Illumination – Light modifier – Reflector
Utility Patent
1998-06-22
2001-01-02
Sember, Thomas M. (Department: 2875)
Illumination
Light modifier
Reflector
C362S244000, C362S245000, C362S268000
Utility Patent
active
06168296
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a lighting unit for reading marks which makes it possible to read a mark carved on a specular finished surface of a base such as a silicon wafer or a glass base.
Generally a silicon wafer or a glass base as a raw material of an integrated circuit has a specular finished surface. On the surface of the wafer or base carved is an identification mark consisting of a series of characters such as a manufacturing number or a specification number. The base or wafer is to be classified for its use according to the identification mark carved on the surface thereof. However, it is very hard to read and identify the identification mark just by a visual observation since the identification mark is carved by means of laser etching or photo etching. Conventionally an area-illuminating lighting unit or a ring-shaped lighting unit is used to illuminate the identification mark or the surrounding area of the identification mark and then the light reflected in the identification mark is read by means of a TV camera or a visual observation.
However, it sometimes happens that a series of characters as an identification mark is failed to be read accurately due to deterioration of the surface of the base or depending on a kind of the base. If an identification mark consists of a long series of characters, the center portion of the identification mark is difficult to be read. In such a case the identification mark is likely to be misread.
In order to solve the above-mentioned problems, the inventor has devoted himself to conducting various experiments and reached a following solution. If two light sources are arranged separately, rays of light emitted from each of the light sources are made parallel and then they are irradiated on a mark, it is possible to read a mark accurately by means of light reflection into the mark. Then the inventor finally accomplished the lighting unit for reading marks in accordance with this invention. It is an object of the present invention to provide a lighting unit for reading marks which can read a mark carved on a base accurately with a simple arrangement.
SUMMARY OF THE INVENTION
In order to accomplish the above-mentioned object the invention is characterized by the following structure. The lighting unit for reading marks in accordance with the invention makes it possible to read a mark carved on a surface of a base having a surface of specular finished, and characterized by that comprising two light sources and a light parallel means which makes rays of light emitted from each of the light sources parallel or generally parallel respectively and that each of the rays of light emitted from the two light sources are made parallel respectively by the light parallel means and irradiated on two areas of the base wherein the two areas face each other across the mark carved on the base.
In order to obtain an effective light source for reading a mark with a simple arrangement it is preferable that an illuminating surface of an illuminant is provided with a single slit which divides the illuminating surface into two illuminating areas and that each of the illuminating areas serves as the light source.
In accordance with the invention, the following functions and effects are achieved.
Since the lighting unit for reading marks in accordance with the invention comprises two light sources and a light parallel means which makes rays of light emitted from each of the light sources parallel or generally parallel respectively and each of the rays of light emitted from the two light sources are made parallel respectively by the light parallel means and irradiated on two area of the base wherein the two areas face each other across the mark carved on the base, the mark can be read easily and accurately with a simple arrangement of the lighting unit without using a complicated appliance such as a computer or conducting a complicated treatment. In addition, since the rays of light are made parallel by means of a light parallel means, a distance between the light source and the base can be set short, thereby to downsize the lighting unit.
Further, if the lighting unit for reading marks has such an arrangement that an illuminating surface of an illuminant is provided with a single slit which divides the illuminating surface into two illuminating areas and each of the illuminating areas serves as the light source, it is possible to obtain an effective light source for reading a mark with a simple arrangement.
REFERENCES:
patent: 5737112 (1998-04-01), Wilt et al.
patent: 5954424 (1999-09-01), Anderson et al.
Banner & Witcoff , Ltd.
CCS Co., Ltd.
Sember Thomas M.
Ward John Anthony
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