Abstract: An optical apparatus includes a viewer for viewing an object therethrough, a light receiving device for receiving a reflected light beam from an eyeball of an observer looking into the viewer, and a device for obtaining at least one optical constant of the eyeball from the electrical signal of the light receiving device, effecting correction during the calculation of the direction of the visual axis by the use of the optical constant, and producing a signal indicative of the direction of the visual axis.

Abstract: An overlay with indicia is sandwiched between a pair of flat plates to form an assembly which is adapted to be mounted in the exposure window of a film cassette housing. The assembly locates the overlay out of any physical contact with film units in the cassette.

Abstract: A film winding device for a camera is provided in which a drive motor is housed in a film winding spool, and an output shaft of the drive motor projects from the film winding spool. A reduction mechanism is provided between the output shaft and the film winding spool to rotate the film winding spool and to thus wind film thereon. The reduction mechanism comprises a parent gear rotating with the output shaft, a planet gear provided at a position offset from the center of the parent gear, a stationary gear fixed to a camera body, and a rotational gear connected to the film winding device. The stationary gear and the rotational gear are coaxial with the parent gear and mesh with the planet gear. The rotational gear rotates relative to the stationary gear, so that the planet gear is rotated at a rotational speed dependent on the difference between the number of teeth of the stationary gear and the number of teeth of the rotational gear.