| 摘要 |
PURPOSE:To prevent the variation of condensation characteristic of a spherical lens by moving the lens by a bimetal in accordance with movement of the focus position of the lens due to thermal expansion. CONSTITUTION:Disk-shaped bimetals 12 and 13 are provided for the purpose of moving a spherical lens 14 in accordance with the variation of temperature. When the temperature rises around the aspherical lens 14, the lens 14 is gradually expanded by this rise of temperature to displace the focus position, and simultaneously, bimetals 12 and 13 are deformed also, and the lens 14 held between inside parts as maximally mobile parts of bimetals 12 and 13 is slided in a housing 11 in accordance with displacement of inside parts of bimetals 12 and 13. Consequently, displacement of the focus position of the lens 14 due to the rise of temperature is compensated with slide of the lens 14. The movement range of mobile parts of bimetals 12 and 13 corresponds to that of the focus position of the lens 14 due to the variation of temperature. |
