This invention relates to a solar ray collecting device.
It has been previously proposed that various solar ray collecting devices be used in which the solar rays focused by a lense or the like are guided into an optical conductor cable and transmitted onto an optional desired place for the purpose of illumination or for other uses. One of the main solar ray collecting devices is the one in which a plurality of Fresnel lenses of approximately 40 cm in diameter (for example 7, 19, or 37 Fresnel lenses of the same diameter) are used for collecting solar rays on the light-receiving edge surface of an optical conductor cable of about 1 cm in diameter. It is then mounted at the focus of the Fresnel lenses and the solar rays focused by the Fresnel lenses are guided into the optical conductor cable and transmitted to the optional desired place through it. Another type of solar ray collecting device is one in which a large number of lenses, of less than about 4 cm in diameter, (for example 2,000 lenses of the same diameter) are used for collecting solar rays on the light-receiving edge of an optical fiber having a diameter of about 0.1 to 0.2 mm. These are precisely positioned at the focus of each lense, and the solar rays focused by each lense are then guided into them. The focal length of the lense is about 40 cm in the case of the former device while its focal length is about 4 cm or less in the case of the latter. Consequently the value of the latter is that it makes it possible to create a very thin solar ray collecting device. On the contrary there exist drawbacks in that the focus position of the lense needs to coincide precisely with the light-receiving edge surface, and as a result the lense and its supporting member tend to expand due to the extreme heat. This is especially true if the device is used in a desert, in space, or in a tropical area where the ambient temperature varies to a great extent. As a result the positional relationship between the focus position of the lense and the light-receiving edge surface of the optical fiber largely deviates from its predetermined relationship, and consequently the lense and its supporting member are apt to be destroyed by the extreme heat.