| 摘要 |
PURPOSE:To put a light emitting point into depth of a focus of a lens, irrespective of a variation of an ambient temperature, by giving a difference of thermal expansion to a lens barrel supporting member and a lens barrel member. CONSTITUTION:A lens supporting member 4 made of iron (coefficient of thermal expansion: beta1) is fixed to a substrate 9 after laser light is made to conform with an optical axis of a lens 2. A lens barrel 1 of a collimator lens is made of aluminum having a coefficient of thermal expansion (beta2) of about three times of iron, and is fixed to the lens supporting member 4 after focusing at a distance of l1 from the substrate 9. Also, a distance l2 between a fixing point A of the lens barrel to the supporting member, and the lens is about l1Xbeta1/beta2-l1/3. According to such a constitution, when an ambient temperature is varied by + or -t deg.C from the time of focusing, the lens supporting member 4 extends by +(+ or -t deg.C)Xl1Xbeta1 in the direction (y), but on the contrary, as for the lens 2 of the collimator, its lens barrel extends by -(+ or -t deg.C)Xl2Xbeta2=-(+ or -t deg.C) Xl1Xbeta1 in the laser tip direc tion. In this way, a working distance DELTAl by a temperature variation is not varied. In this regard, a distance l3 is thickness of a laser tip fitting member, and this fitting member is subjected to a temperature control, therefore, is not influenced by an environmental temperature variation. |
