Abstract: An interchangeable lens assembly includes a plurality of lens-side claw portions configured to be engaged with a plurality of camera-side claw portions, and a lock pin groove portion into which a lock pin is inserted, a lens barrel, and a lens mount fixing member. When ?1 is an angle formed by a line passing through a fifth lens-side end and an optical axis, and a line passing through a center of the lock pin groove portion and the optical axis, and ?2 is an angle formed by a line passing through a fourth lens-side end and the optical axis, and a line that passes through the center of the lock pin groove portion and the optical axis, ?1 and ?2 satisfy a predetermined conditional expression.

Abstract: The present invention concerns a method for producing acrylic acid which involves subjecting an acrylic acid-containing aqueous solution obtained by catalytic vapor phase oxidation of propylene and/or acrolein to evaporation whereby an acrylic acid-containing vapor is obtained; and subjecting the acrylic acid-containing vapor to azeotropic dehydration. The present invention offers a number of advantages including a reduce amount of polymer that may adhere to the surface of an azeotropic dehydration column, a low-blowing separation column or an in a high-boiling separation column in a plant for producing acrylic acid. Consequently, the production plant can be operated for a long time without stopping operations.