Illumination – Light source and modifier – Including reflector
Reexamination Certificate
1999-10-20
2002-11-19
Quach-Lee, Y. My (Department: 2875)
Illumination
Light source and modifier
Including reflector
C362S346000, C362S804000
Reexamination Certificate
active
06481872
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an illumination unit and, more particularly, to an astral lamp used in dental and other medical treatments.
An illumination unit used in dental and other medical treatments is designed to avoid generation of a shadow in the illumination area, and is accordingly usually called an astral lamp. As shown in
FIG. 26
, an astral lamp of this type has a heat-resistant-glass reflecting mirror, in this case, a parabolic mirror
52
of revolution, an arm
59
, a protection cover
57
, a light source light-shielding cylinder
58
, and a light source
51
. The parabolic mirror
52
has a plurality of segments
53
made of flat mirrors. The arm
59
supports the parabolic mirror
52
. The light source
51
is comprised of a linear halogen lamp or other linear light source, and will be referred to as a linear light source hereinafter. Generally, the linear light source
51
is arranged in front of the focal point of the parabolic mirror
52
.
The parabolic mirror
52
of revolution is formed into a concave mirror along a concave paraboloid of revolution formed by rotating a predetermined parabola about its vertex as the center. The parabolic mirror
52
reflects light emitted by the linear light source
51
toward the linear light source
51
to form a light path
55
. The light path
55
condenses light toward a predetermined illumination area
56
remote from the linear light source
51
, thereby irradiating only the specific portion, i.e., morbid portion of a patient. Even if the linear light source
51
, the doctor's hand, or other light-shielding object enters the light path
55
to partially block light, the light path
55
must be able to ensure a high shadowless degree and illumination uniformity. A “shadowless degree” is a degree with which, even if a light-shielding object enters a light path having a predetermined illumination area, a shadow image is not formed in the illumination area. An “illumination uniformity” is a degree with which the reflected light beam is diffused uniformly and theoretically within the illumination area.
The size of the illumination area
56
of the light path
55
is determined by the position of the linear light source
51
. More specifically, when the linear light source
51
is arranged at the focal position of the parabolic mirror
52
, the light beam reflected by the parabolic mirror
52
forms parallel light substantially parallel to the axis of rotation of the paraboloid of revolution, i.e., the optical axis of the parabolic mirror
52
, so that the size of the illumination area
56
becomes substantially equal to or larger than the opening area of the parabolic mirror
52
. When the linear light source
51
is arranged behind the focal position, the reflected light beam is diffused, and the size of the illumination area
56
becomes larger than the opening area of the parabolic mirror
52
. Inversely, when the linear light source
51
is arranged in front of the focal position, the reflected light beam is condensed, and the size of the illumination area
56
becomes smaller than the opening area of the parabolic mirror
52
.
Usually, when an astral lamp is used for dental treatment, the linear light source
51
is arranged in front of the focal point to reduce the light path
55
toward a desired illumination area
56
smaller than the parabolic mirror
52
.
As the reflecting mirror of such an astral lamp, various types are conventionally proposed, and among them, prior arts disclosed in Japanese Utility Model Publication Nos. 61-25123 and 60-31695, Japanese Utility Model Laid-Open No. 3-88215, and the like are known.
In a reflecting mirror for an astral lamp described in Japanese Utility Model Publication No. 61-25123 (to be referred to as prior art 1 hereinafter), as shown in
FIG. 27
, in order to obtain a high shadowless degree and illumination uniformity, a large number of segments
53
formed of rectangular flat mirrors are formed on the fundamental paraboloid of a parabolic mirror
52
of revolution divisionally in the direction of the major axis of the parabolic mirror
52
of revolution. Each rectangular flat mirror segment
53
has a long side coinciding with the minor axis of the fundamental paraboloid. The short width of each segment is set to a value corresponding to the major-axis width of the light path formed by the astral lamp.
In a reflecting mirror for an astral lamp described in Japanese Utility Model Publication No. 60-31695 (to be referred to as prior art 2 hereinafter), in order to similarly obtain a high shadowless degree and illumination uniformity, a large number of segments formed of flat mirrors are formed on the fundamental paraboloid of a parabolic mirror of revolution divisionally in the main direction (major-axis direction) and the subdirection (minor-axis direction) of the parabolic mirror of revolution. The long and short widths of each segment are set to values respectively corresponding to the major- and minor-axis widths of the light path. In other words, each segment is formed into such a size that it can diffuse the reflected light beam to reach the illumination area of the light path.
In an astral lamp described in Japanese Utility Model Laid-Open No. 3-88215 (to be referred to as prior art 3 hereinafter), in order to diverge the light in the subdirection and main direction, a large number of convex reflecting surfaces are aligned on the inner surface of a parabolic mirror of revolution or elliptic mirror of revolution in the main direction and subdirection. The vertical width (short width) of each convex reflecting surface is set smaller than the horizontal width (long width) thereof.
As another conventional unit, an astral lamp for dental treatment disclosed in Japanese Patent Laid-Open No. 2-65856 (to be referred to as prior art 4 hereinafter) is known. According to this prior art 4, the reflecting mirror is constituted by a curved surface portion corresponding to an operation field and having a function of condensing light to increase the luminous intensity, and a curved surface portion corresponding to a peripheral part of the operation field and having a function of dispersing light to lower the luminous intensity. The curved surface portion having the condensing function is formed of a spherical surface, a paraboloid, an ellipsoid of revolution, or the like. The curved surface portion having the light dispersing function is formed of a spherical surface having a radius larger than that of the curved surface portion having the condensing function.
Any one of the conventional prior arts 1 to 4 is still insufficient to obtain a high shadowless degree and illumination uniformity.
In prior art 1, as shown in
FIG. 28
, a fundamental paraboloid
54
that forms the inner surface of the parabolic mirror
52
is a paraboloid of revolution having a constant focal point, e.g., a focal length Fa. A plurality of segments
53
formed of flat mirrors are formed on the fundamental paraboloid
54
divisionally in the main direction of the fundamental paraboloid
54
. Each segment
53
forms a paraboloid identical to the fundamental paraboloid
54
in the direction of the long side.
Light reflected by any point of the parabolic mirror
52
must form an illumination area, even at a position far from the parabolic mirror
52
, to have a desired width smaller than the sub-direction width of the parabolic mirror
52
, and condense the reflected light toward the illumination area at high precision. However, since each segment
53
is formed along one fundamental paraboloid
54
in its long-side direction, these two requirements cannot be satisfied.
In
FIG. 28
, the segment
53
is formed by using the fundamental paraboloid
54
that enables light reflected by any point of the parabolic mirror
52
to have a desired width in the subdirection within the illumination area far from the parabolic mirror
52
. When, however, compared to an illumination area
56
c
formed by reflected light
55
c
reflected at an arbitrary point P
3
on the segment
53
which
Hayashi Yasuo
Seki Toshihiko
Blakely & Sokoloff, Taylor & Zafman
Koito Industries Ltd.
Quach-Lee Y. My
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