Abstract: An optical system for recording or reproducing of information to or from an optical information recording medium, includes a light source, a coupling lens for converting a diverging light emergent from the light source to a converging light, and an objective lens for further converging the converted converging light and for focusing on an information recording surface of the optical information recording medium. A lateral magnification M.sub.c of the coupling lens on an image side for a light source side and a numerical aperture NA.sub.o on the light source side of the coupling lens satisfy the following expressions respectively, -7.0.ltoreq.M.sub.c .ltoreq.-0.5 and 0.06.ltoreq.NA.sub.o .ltoreq.0.21.

Abstract: An optical system for recording or reproducing of information to or from an optical information recording medium, includes: a light source; a coupling lens for converting a diverging light emergent from the light source to a converging light; and an objective lens for further converging the converted converging light and for focusing on an information recording surface of the optical information recording medium. A lateral magnification of the objective lens in which a wavefront aberration within a Marechal criterion is minimum, satisfies the following conditional expression,O<M<1where M represents the lateral magnification of the objective lens.

Abstract: A single-use camera which includes: a film winding knob, capable of rotating in the winding direction, for winding a film so as to feed the film frame by frame; a reversion-preventing member, having an engagement with the film winding knob, for preventing the film winding knob from rotating in the opposite direction to the winding direction; a releasing member for releasing the engagement of the reversion-preventing member with the film winding knob when the film is wound by the film winding knob so that the noise, generated from the reversion-preventing member, is prevented.

Abstract: A single-use camera which is loaded with a film cartridge, having a light-shielding cover on a film gate, when the single-use camera is assembled. The camera includes: the film cartridge for accommodating a photographic film; a film-winding knob, capable of rotating, for winding the photographic film; a film detection member for detecting the photographic film at a position outside the film cartridge in the camera; and a mechanism for moving the light-shielding cover to a closed position where the light-shielding cover closes the film gate when the film detection member detects absence of the photographic film at the position.

Abstract: A photographic film is previously wound around a spool in a scroll chamber to be ready for photographing. The film is wound by one frame when a film winding knob is operated. After all the frames have been exposed, it is wound back to a film magazine in a film magazine chamber. The film magazine in which the film has been wound, is taken out from the film magazine chamber when a rear cover is folded at a groove portion provided on the rear cover after at least one of the three engaging hook portions between the rear cover and the film unit body has been disengaged.