Abstract: The present invention relates to a coating film comprising: a polyester film and at least one coating layer formed by coating a coating solution containing a polyer (A) comprising a copolymer of oxazoline group-containing monomer, (meth)acrylonitrile and styrene, having an equivalent weight of oxazoline group of less than 300 g/equivalent, and drying and stretching thereof.

Abstract: A two-group lens is comprised of a first lens and a second lens. The first lens is driven in an optical-axis direction by a magnetic circuit including a variable-distance use coil. As the first lens is driven, the second lens is also driven in an opposite direction to the first lens by a magnetic circuit including a mass-body driving coil, where the center-of-gravity position of movable part of an objective lens driver is kept at a generally constant position. The variable-distance use coil is disposed with the same gap as the mass-body driving coil. Thus, the distance between the first lens and the second lens can be held constant with a simple structure, without involving any complex structure, so that an accurate tracking can be achieved.