LIGHT EMITTING DEVICE

A light emitting device includes: a light source; a fixing part on which the light source is mounted; and a rotary light emitting part rotatably supported by the fixing part around a rotational axis Ax and provided such that a light axis of the light source is aligned with the rotational axis. The rotary light emitting part includes: a rod-shaped light guide having an incidence surface from which light from the light source enters and an exit surface from which the light guided inside exits, the rod-shaped light guide being arranged along the rotational axis Ax; a half mirror that changes a direction of light emitted from the exit surface of the rod-shaped light guide; and a light guide plate that receives light from the half mirror and emits light accordingly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device.

2. Description of the Related Art

Light emitting devices capable of rotating a light emitting body provided with a light source such as an LED are known (see, for example, patent document 1).

In the light emitting devices as mentioned above, there are cases where it is difficult to rotate the light emitting body as desired due to the electrical connection (cable, etc.) to the light source. For example, if the light emitting body is rotated continuously, the cables may be twisted, which may not only prevent desired rotation of the light emitting body but also result in disconnection in the cables.

SUMMARY OF THE INVENTION

In this background, a purpose thereof is to provide a light emitting device capable of rotating a light emitting body as desired.

A light emitting device according to an embodiment of the present invention comprises: a light source; a fixing part on which the light source is mounted; and a rotary light emitting part rotatably supported by the fixing part around a rotational axis and provided such that a light axis of the light source is aligned with the rotational axis. The rotary light emitting part includes: a rod-shaped light guide having an incidence surface from which light from the light source enters and an exit surface from which the light guided inside exits, the rod-shaped light guide being arranged along the rotational axis; a light direction changing element that changes a direction of light emitted from the exit surface of the rod-shaped light guide; and a light emitting body that receives light from the light direction changing element and emits light accordingly.

A cross section of the rod-shaped light guide may be shaped in a regular polygon. The regular polygon may be a regular triangle, regular tetragon, or regular hexagon.

The exit surface of the rod-shaped light guide may include a frost finished part.

The light direction changing element may include a half mirror that transmits a portion of the light emitted from the exit surface of the rod-shaped light guide and reflects another portion of the light emitted from the exit surface of the rod-shaped light guide toward the light emitting body.

Optional combinations of the aforementioned constituting elements, and implementations of the invention in the form of methods, apparatuses, and systems may also be practiced as additional modes of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a perspective cross-sectional view of an important part of a light emitting device10according to an embodiment of the present invention.FIG. 2is an exploded perspective cross-sectional view of an important part of the light emitting device10according to the embodiment of the present invention.FIG. 3is a lateral cross-sectional view of an important part of the light emitting device10according to the embodiment of the present invention.FIG. 4is a schematic cross-sectional view of an important part of the light emitting device10according to the embodiment of the present invention.FIG. 5is an exploded perspective view of an important part of the light emitting device10according to the embodiment of the present invention.

The light emitting device10according to the embodiment includes a fixing part11and a rotary light emitting part12rotatably supported by the fixing part11around a rotational axis Ax.

A description will first be given of the rotary light emitting part12. The rotary light emitting part12is a substantially T-shaped component and includes a hollow cylindrical shaft part13and a light emitting part housing14fixed to one end of the shaft part13. The light emitting part housing14is a housing that extends in the direction perpendicular to the central axis of the shaft part13. The rotary light emitting part12is supported by the fixing part11so as to be rotatable such that the central axis of the shaft part13is the rotational axis Ax.

A rod-shaped light guide15is provided inside the hollow cylindrical shaft part13. The rod-shaped light guide15has an incidence surface15afrom which light from a light source enters and an exit surface15bfrom which the light guided inside is emitted. The rod-shaped light guide15is arranged along the rotational axis Ax.

The light emitting part housing14is comprised of a body16and a cover17that covers the body16. The body16and the cover17form an interior space21. An end of the shaft part13is fixed to the center of the under surface of the body16. A hole16ais provided at the center of the under surface of the body16so that the interior space21of the light emitting part housing14and the interior of the shaft part13communicate. The hole16aallows the exit surface15bof the rod-shaped light guide15provided inside the shaft part13to be exposed in the interior space21of the light emitting part housing14.

Four magnets23used to mount the rotary light emitting part12to the fixing part11and two rotation prevention pins24are provided at the center of the under surface of the body16. The four magnets are fixed to the center of the under surface of the body16by a flange22. The flange22is formed with four holes for accommodating the four magnets23. The rotation prevention pins24project from the under surface of the body16. The flange22is formed with through holes22bin which the rotation prevention pins24extend through.

A half mirror18and two light guide plates19, i.e., light emitting bodies, are provided in the interior space21of the light emitting part housing14.

The half mirror18is provided at the center of the interior space21so as to face the exit surface15bof the rod-shaped light guide15. The half mirror18functions as a light direction changing element that changes the direction of the light emitted from the exit surface15bof the rod-shaped light guide15. The half mirror18transmits a portion of the light from the exit surface15bof the rod-shaped light guide15and reflects another portion toward the light guide plate19. In this embodiment, the half mirror18transmits a portion of the light from the exit surface15bof the rod-shaped light guide15in the direction of the rotational axis Ax and reflects another portion in the direction perpendicular to the rotational axis Ax. The half mirror18has two reflecting surfaces that reflect portions of the light from the exit surface15bof the rod-shaped light guide15in mutually opposite directions.

The two light guide plates19are arranged to extend in mutually opposite directions from the neighborhood of the center of the light emitting part housing14. The light guide plate19receives the light from the half mirror18via the incidence surface19a, guides the light inside, and emits the light from an exit surface19bprovided along a direction of extension. The light emitted from the exit surface19bof the light guide plate19is transmitted through the cover17and radiated outside.

In the light emitting device10according to the embodiment, the light transmitted through the half mirror18and the light emitted from the light guide plate19are radiated outside from the cover17. If a mere mirror is provided in place of the half mirror18, the central portion of the rotary light emitting part12will be darker. By using the half mirror18as in this embodiment, the uniformity of brightness of illumination light is improved. The inner surface or outer surface of the cover17may be processed to scatter light in order to further improve the uniformity of brightness of illumination light. In addition to or in place of that, a light scattering member may be provided in the neighborhood of the inner surface of the cover17.

A description will now be given of the fixing part11. The fixing part11includes a base member30and a light source31mounted on the base member30. The light source31is comprised of an LED32and a reflecting mirror33and is configured to emit light in a predetermined light axis direction. The LED32is provided such that the exit surface thereof is perpendicular to the light axis. The reflecting mirror33is configured to surround the LED32and reflects the light emitted from the LED32in the horizontal direction in a direction parallel to the light axis. The reflecting mirror33may have a reflecting surface shaped in a paraboloid of revolution. When the rotary light emitting part12is fitted to the fixing part11, the light axis of the light source31is aligned with the rotational axis Ax of the rotary light emitting part12.

The fixing part11further includes a hollow cylindrical rotary member34for supporting the rotary light emitting part12above the light source31. The shaft part13of the rotary light emitting part12is inserted in the rotary member34. The rotary member34is supported on the base member30by support members40and41so as to be rotatable around the rotational axis Ax. Bearings42and43are provided between the rotary member34and the support members40and41.

Rotation prevention holes34bare formed on an end face34aof the rotary member34toward the rotary light emitting part. Four magnets34care provided on the end face34aof the rotary member34. When the shaft part13of the rotary light emitting part12is fully inserted into the rotary member34, the rotation prevention pins24of the rotary light emitting part12are inserted into the rotation prevention holes34bformed on the end face34aof the rotary member34and the magnets23provided in the flange22of the rotary light emitting part12and the magnets34cprovided on the end face34aof the rotary member34are attracted by a magnetic force, fixing the rotary light emitting part12to the rotary member34.

While the rotary light emitting part12is being rotated, a large load is applied in the direction of rotation. For this reason, the rotation prevention pins24of the rotary light emitting part12are inserted into the rotation prevention holes34bon the end face34aof the rotary member34. However, the flange22of the rotary light emitting part and the end face34aof the rotary member34are merely placed in a contact so that noise or play may be created, and the durability will be lowered when the assembly repeatedly undergoes abrupt changes in the direction of rotation or speed. This is addressed in the light emitting device10according to the embodiment by sandwiching a thin rubber washer25between the end face34aof the rotary member34and the flange2of the rotary light emitting part12. The rubber washer25converts the attractive force of the magnets23and the magnets34cinto a large frictional force in the direction of rotation. The rotational load is supported in substance by the large frictional force. Further, the impact caused by the abrupt change in the rotation is absorbed by the rubber washer25so that noise can be prevented, and the life of the device can be extended. Still further, the rubber washer25also plays the role of preventing water from entering the fixing part11and protecting electronic components such as the LED32.

The fixing part11further includes a rotary mechanism for rotating the rotary member34into which the rotary light emitting part12is inserted. The rotary mechanism includes a first pulley35fitted to the rotary member34, a motor36provided on the base member30, a second pulley37fitted to a shaft36aof the motor36, a belt38joining the first pulley35and the second pulley37, and an encoder39for detecting the rotational position of the rotary member34.

As the second pulley37fitted to the shaft36aof the motor36is rotated, the belt38causes the first pulley35to rotate, causing the rotary member34and the rotary light emitting part12to be rotated around the rotational axis Ax. Thus, according to the embodiment, the rotary member34and the rotary light emitting part12are rotated without arranging the shaft36aof the motor36coaxially with the rotational axis Ax, by using the first pulley35, the second pulley37, and the belt38. This makes it easy to provide the light source31on the rotational axis Ax.

Rotation of the motor36is controlled by a control unit (not shown). For control, rotational position information on the rotary member34detected by the encoder39is used. The control unit may control light emission from the LED32.

A description will be given of the operation of the light emitting device10configured as described above. The light from the light source31enters the rod-shaped light guide15via the incidence surface15a. The light guided inside the rod-shaped light guide15is emitted from the exit surface15b. A portion of the light emitted from the exit surface15bis transmitted through the half mirror18and another portion is reflected by the half mirror18before entering the light guide plate19via the incidence surface19a. The light guided inside the light guide plate19is emitted from the exit surface19b. The light emitted from the exit surface19bof the light guide plate19and the light transmitted through the half mirror18are transmitted through the cover17and radiated outside.

In the light emitting device10according to the embodiment, the light source31is fixed to the fixing part11. Meanwhile, the rotary light emitting part12is rotatably supported by the fixing part11around the rotational axis Ax. No electric connection by, for example, a cable exists between the light source31and the rotary light emitting part12. It is therefore possible to continuously rotate the rotary light emitting part12as desired without minding, for example, twisting of cables.

Since no electronic components are provided in the rotary light emitting part12itself, galvanic corrosion is prevented even when the rotary light emitting part12is installed in a place that could be hit by the rain. If the device is installed outdoors, frequent maintenance is expected. In the light emitting device10according to the embodiment, the rotary light emitting part12and the fixing part11are merely fixed by the magnetic force so that it is easy to remove the rotary light emitting part12from the fixing part11. Accordingly, the light emitting device10is excellent in maintainability.

It will now be assumed that the an integrated RGB type LED is used as the LED32in the light emitting device10. In an integrated RGB type LED, chips of the R, G, and B colors are arranged on a plane. Therefore, the positions of light emission of the RGB colors in the LED will be displaced from each other. If the light of the RGB colors with the displaced light emission positions is guided as it is in the rod-shaped light guide15, the light of the RGB colors may be radiated from the exit surface15bby maintaining the displacement, with the result that the appearance may become poor.

To prevent this situation, it is desired that the cross section of the rod-shaped light guide15be shaped in a regular polygon such as a regular triangle, regular tetragon, and regular hexagon. By shaping the cross section of the rod-shaped light guide15in a regular polygon, the light guided in the rod-shaped light guide15is uniformized according to a principle similar to that of a kaleidoscope. Accordingly, the displacement in between the RBG light is mitigated. Conversely, if the cross section of the rod-shaped light guide15is circular, the displacement in between the light on the incidence surface15ais likely to be directly guided in the rod-shaped light guide15.

FIG. 6shows how light is emitted from the exit surface15bin the rod-shaped light guide15having a circular cross section.FIG. 7shows how light is emitted from the exit surface15bin the rod-shaped light guide15having a square cross section.FIGS. 6 and 7show photos taken by causing the light from the light source using an integrated RGB type LED to be incident on the incidence surface of the rod-shaped light guide15and imaging the exit surface15bof the rod-shaped light guide15.

FIG. 6shows an image of the LED near the center of the exit surface15b, revealing that there a displacement in between the RGB light in the case of a circular cross section of the rod-shaped light guide15. Meanwhile,FIG. 7does not show an image of the LED, revealing that the RGB colors are averaged in the case of a square cross section of the rod-shaped light guide15.

The exit surface15bof the rod-shaped light guide15may be provided with a frost finished part in order to further average the displacement in between the RGB light. As described above, the displacement in between the RGB light can be averaged to a certain degree merely by shaping the cross section of the rod-shaped light guide15in a square. By providing a frost finished part in the exit surface15bin addition to shaping the cross section of the rod-shaped light guide15in a square to further average the light emitted from the exit surface15b, it is possible to create high-quality light in which the displacement between the emitted colors is further improved. Improvement in the displacement between the emitted colors is particularly important in an embodiment like the embodiment described above in which the light emitting body is rotated, for the purpose of representing high-quality of mixture of colors and beautiful light and dark contrast capable of meeting requirements for full-fledged decorative illumination.

For example, the two light guide plates19are provided to extend in mutually opposite directions in the embodiment described above. The embodiment is non-limiting as to the number and arrangement of the light guide plates19. For example, five light guide plates may be arranged in a star array.

In the embodiment described above, the half mirror18is used as a light direction changing element. Alternatively, a prism may be provided in place of the half mirror18.