An optical system or front end for adding an optical depth information to a two-dimensional image, wherein the optical system includes an array of optical lenses arranged in front of the two-dimensional image. The retaining strap is attached to the sole, and the decorative pieces are releasably attached to the retaining strap, thereby allowing a wearer to remove and replace the decorative pieces in an interchangeable manner. This makes it possible to perform stable focusing control on each recording plane of a multi-layer optical disk with high density by using an objecting lens having a large NA after spherical aberration has been corrected properly. In the joint rubber, there is formed in advance a fissure hole, to be penetrated by a hollow needle provided in the main body of the liquid discharge recording apparatus and having fissures in not less than three directions from the crossing center of the fissures, in a plane perpendicular to the direction of depth of the hole portion.