Abstract: In an objective lens assembly for an optical instrument comprising inner and outer tube members with outer and inner engaged helicoidal screws, respectively, the normal trapezoidal-section main ridge of the helicoidal screw of the outer tube member is modified to provide one or more wall surfaces that reflect stray light from the object side of the objective lens assembly to prevent such light from reaching the image side of the assembly. The wall surface or surfaces are provided by one or more sub-ridges or grooves at the top of the trapezoidal-section main ridge. Bottom portions between successive elements of the main ridge may be angulated to prevent stray light reflected therefrom from reaching the image end of the assembly.

Abstract: Range measuring device for a camera measures the distances to objects respectively present in a central area of the photographing field and in plural areas including those surrounding the central area, then produces an outdoor signal indicating that the photographing is conducted outdoors or an indoor signal indicating that the photographing is conducted indoors, discriminates whether the object in the central area is the main object to be focused from the measured distance of the central area, and, if the distance in the central area is included in a reference distance range, determines the photographing distance based at least on the measured distance of the central area. The reference distance range is selected to be larger when the outdoor signal is produced than the case when the indoor signal is produced.

Abstract: Variable focus camera includes primary and secondary lens systems, in which only the primary lens system is used for wide angle shots while the combination of the primary with the secondary lens system is used for telephoto shots.The variable focus camera can exactly and positively control the focus change region, the automatic focusing region and other regions.

Abstract: A camera containing at least one first battery and at least one second battery therein includes first means supplied with an electric power by the at least one first battery, thereby becoming operable, second means supplied with an electric power by the at least one second battery, thereby controlling the operation of the first means, and third means operated to render the at least one second battery removable from the camera, the power supply from the at least one second battery to the second means being impeded by the third means being operated, the third means impeding the power supply from the at least one first battery to the first means prior to the impediment of the power supply from the at least one second battery to the second means, in response to the operation of the third means.

Abstract: A view finder unit removably mounted on a single lens reflex camera body to enable the in-focus state of a picture-taking lens to be observed, the camera body having an opening portion provided to direct an imaging light beam projected by the picture-taking lens to the outside of the camera body, includes a housing removably mounted on the camera body and having an opening portion for directing the imaging light beam into the housing, said opening portion being coincident with the opening portion of the camera body, an optical system disposed in the housing to enable a first image formed by the imaging light beam to be observed through the opening portion of the housing, imaging means disposed in the housing for forming a second image substantially equivalent to the first image, in-focus detecting means including photoelectric detecting means disposed in the housing adjacent to the focal plane of the imaging means and producing an electrical signal representing the state of the second image in the focal plane

Abstract: An interchangeable finder device of a single lens reflex camera has a finder optical system in which a focusing screen, a pentaprism and an eyepiece are fixed in a predetermined positional relation, a casing containing the optical system therein, and a mounting-dismounting device provided on the casing to mount the casing to the camera body. The finder device further has a sliding mechanism for supporting the finder optical system slidably in a direction perpendicular to the focus surface of the focusing screen relative to the mounting-dismounting mechanism so that the finder optical system can move in said perpendicular direction independently of the mounting-dismounting device when the casing is mounted to the camera body by means of the mounting-dismounting device.

Abstract: In a camera which has a through-hole formed in a portion of a wall forming a chamber for containing therein a magazine of roll film wound around a spool shaft which faces the end surface of the spool shaft and to which is mountable an electric film rewind device having a drive shaft inserted into the chamber through the through-hole and coupled to the spool shaft and wherein a light-intercepting ring having a contact surface bearing against the end surface of the spool shaft and biased axially of the spool shaft toward the interior of the chamber is slidably fitted in the through-hole, the light-intercepting ring has on said contact surface an annular ridge projected axially of the spool shaft. The ridge is provided at a location which is adjacent to and along the end surface during the contact thereof with the end surface.