Abstract: A beam splitting optical system for an automatic focusing apparatus includes a telescopic system having an objective optical system and a viewing optical system, a beam splitter which splits object-carrying light transmitted through the objective optical system from the telescopic optical system by a splitter surface, and a focus detection optical system having a pair of light receivers which receive beams of the object-carrying light split by the splitter surface. The focus detection optical system is arranged so that beams of the object-carrying light to be respectively received by the light receiver are incident upon the splitter surface of the beam splitter at different incident angles. The transmittance and reflectance of the splitter surface of the beam splitter is not uniform in distribution and changes depending on the incident angle of the object-carrying light incident thereupon.

Abstract: A light interception structure for an automatic focus detection surveying instrument that includes a telescopic optical system having an objective optical system and an ocular optical system. A beam splitting optical element splits object light transmitted through the objective optical system of the telescopic optical system and includes a splitting surface. A focus detection device has a light receiving device for receiving light split by the beam splitting optical element. One surface of the beam splitting optical element is provided with an anti-reflection treatment. The one surface is a surface upon which external light entering the telescopic optical system through the ocular optical system is first incident after passing through or being reflected by the beam splitting surface of the beam splitting optical element.

Abstract: A beam splitting optical system for an automatic focusing apparatus includes a telescopic system having an objective optical system and a viewing optical system, a beam splitter which splits object-carrying light transmitted through the objective optical system of the telescopic optical system by a splitter surface, and a focus detection optical system having a pair of light receivers which receive beams of the object-carrying light split by the splitter surface. The focus detection optical system is arranged so that beams of the object-carrying light to be respectively received by the light receivers are incident upon the splitter surface of the beam splitter at different incident angles. An optical element is provided in a light path of at least the larger quantity of beams of the object-carrying light, among those to be received by the pair of light receivers so as to reduce the quantity of light to be transmitted therethrough.

Abstract: An electronic distance meter includes a sighting telescope having an objective lens for sighting an object; a reflection member positioned behind the objective lens; an optical distance meter which includes a light-transmitting optical system for transmitting a measuring light via the reflection member and the objective lens, and a light-receiving optical system for receiving light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member; a beam-diameter varying device, provided in association with the light-transmitting optical system, for varying a beam diameter of the measuring light; and a controller which varies the beam diameter via the beam-diameter varying device in accordance with a distance from the object to the electronic distance meter.

Abstract: A surveying instrument includes a sighting telescope for sighting an object; an optical distance meter which includes a light-transmitting optical system for transmitting a measuring light toward the object via the sighting telescope, a light-receiving optical system for receiving light reflected by the object, and a light-receiving element which receives the measuring light reflected by the object and received by the light-receiving optical system; and a light shield mask positioned on an optical axis between the eyepiece and the light-receiving element to cut off incoming rays from the eyepiece.

Abstract: A surveying instrument includes a sighting telescope having an objective lens and an eyepiece; a Porro-prism erecting system; a semitransparent surface formed on a reflection surface of the Porro-prism erecting system; a beam splitting prism adhered to the semitransparent surface; and a focus detecting device which detects a focus state from a correlation between a pair of images respectively formed by two light bundles which are respectively passed through two different pupil areas of the objective lens and passed through two separate areas on the semitransparent surface. An area of a surface of the beam splitting prism which is adhered to the semitransparent surface is smaller than an effective area of the reflection surface of the Porro-prism erecting system. The semitransparent surface and the beam splitting prism are positioned so that the two light bundles are incident on the semitransparent surface at the same incident angle.

Abstract: A magnetic incremental encoder includes a plurality of detection devices which are provided on an outer periphery of a rotational member at a predetermined phase difference, wherein each of the detection devices outputs signals which vary periodically in accordance with the rotational angle of the rotational member upon rotation thereof; wherein the plurality of detection devices are provided in sets of two detection devices on the outer periphery of the rotational member, wherein a phase difference between one of the sets of two detection devices and an adjacent another of the sets of two detection devices is determined according to the following formula:

Abstract: A beam splitting optical system for an automatic focusing apparatus includes a telescopic system having an objective optical system and a viewing optical system, a beam splitter which splits object-carrying light transmitted through the objective optical system from the telescopic optical system via a splitter surface, and a focus detection optical system having a pair of light receivers which receive object-carrying light beams split by the splitter surface. The focus detection optical system is arranged so that the object-carrying light beams to be received by the light receivers are incident upon the splitter surface of the beam splitter at different incident angles. The splitter surface is coated with a thin metal coating.

Abstract: A light interception structure for an automatic focus detection surveying instrument includes a telescopic optical system having an objective optical system and an ocular optical system, a beam splitting optical element which splits object light transmitted through the objective optical system from the telescopic optical system, and a focus detector having a light receiver which receives the object light split by the beam splitting optical element. One surface of the beam splitting optical element upon which external light entering the telescopic optical system through the ocular optical system is first made incident after the external light passes through or is reflected by a beam splitting surface of the beam splitting optical element is subject to an anti-reflection treatment.

Abstract: A surveying instrument includes a sighting for sighting an object; a beam-splitting optical system positioned between an objective lens and an eyepiece, and having a wavelength selection mirror which reflects light with specific wavelengths while allowing light having wavelengths other than the specific wavelengths to pass therethrough; an optical distance meter which includes a light-transmitting optical system for transmitting measuring light toward the object, and a light-receiving optical system for receiving light reflected by the object; and a phase-difference detection type focus detecting device which detects a focus state from a correlation between a pair of images respectively formed by two light bundles which are passed through two different pupil areas on the objective lens and the wavelength selection mirror. The two different pupil areas are positioned so that the two light bundles are incident on the wavelength selection mirror at the same incident angle.

Abstract: A surveying instrument includes a distance-measuring optical system having an objective lens via which a distance from the surveying instrument to an object is measured; and an optical distance meter which includes a reflection member positioned behind the objective lens, a light-transmitting optical system for transmitting a measuring light toward the object via the reflection member and the objective lens, and a light-receiving optical system for receiving a portion of the measuring light which is reflected by the object, subsequently passed through the objective lens, and not interrupted by the reflection member. The light-receiving optical system includes a plurality of light-guiding optical systems, so that the measuring light which is reflected by the object is selectively incident on an end of one of the plurality of light-guiding optical systems in accordance with the distance from the surveying instrument to the object.

Abstract: An electronic distance meter includes a sighting telescope having an objective lens for sighting an object; a reflection member positioned behind the objective lens; an optical distance meter which includes a light-transmitting optical system for transmitting a measuring light via the reflection member and the objective lens, and a light-receiving optical system for receiving a portion of the measuring light which is reflected by the object, passed through the objective lens and not obstructed by the reflection member; a focus detecting device which detects a focus state from a correlation between a pair of images respectively formed by two light bundles which are respectively passed through two different pupil areas on the objective lens; and at least one optical element, positioned outside the two different pupil areas, to deflect the portion of the measuring light toward an optical axis of the light-receiving optical system.

Abstract: A surveying instrument having a sighting optical system and a phase-difference detection type focus detection device which detects a focus state of the sighting optical system from a correlation between a pair of images respectively formed by two light bundles which are respectively passed through two different pupil areas on an objective lens of the sighting optical system, the phase-difference detection type focus detection device includes a pair of line sensors, a condenser lens group for condensing the two light bundles which are respectively passed through the two different pupil areas, and a pair of separator lens groups for forming two images of the two light bundles which are passed through the condenser lens group on the pair of line sensors, respectively. The condenser lens group includes more than one sub lens group.

Abstract: A reflector is used with an electric distance meter, for measuring a distance of two positions. The reflector includes a reflecting member which reflects an incident light in parallel to the direction of incidence, and a selective transmission member provided to a light-incident surface of the reflecting member. The selective transmission member allows infrared ray to pass, while the selective transmission member prevents visible light from passing.

Abstract: An incremental rotary encoder outputs two sine wave signals having a phase difference of 90 degrees when the incremental rotary encoder is in operation, the incremental rotary encoder including a binary coding circuit which codes each of the two sine wave signals into a binary signal, a voltage detector which detects the voltage of one of the two sine wave signals at the moment of variation in a signal level of the binary signal, and a controller which includes a calculator which takes an even number of voltage values from each of the two sine wave signals to take an average of the even number of voltage values for each of the two sine wave signals.

Abstract: A surveying instrument includes an optical distance meter which has a light-transmitting optical system and a light-receiving optical system, the light-receiving optical system including a light-receiving element; a first wavelength selection filter and a second wavelength selection filter for allowing only light within a first wavelength range to pass therethrough, to be thereafter incident on the light-receiving element, wherein the first wavelength selection filter allows light with a wavelength equal to or greater than a first specific wavelength to pass therethrough, and a second wavelength selection filter allows light with a wavelength equal to or shorter than a second specific wavelength, which is longer than the first specific wavelength, to pass therethrough; and an angle adjusting device for adjusting an angle of inclination of the first and second wavelength selection filter with respect to an optical path thereof.

Abstract: An autofocus distance-measuring optical system includes a sighting telescope having an objective lens for sighting an object; an optical distance meter which includes a light-transmitting optical system for transmitting a measuring light via the, and a light-receiving optical system for receiving light reflected by the object; a focus detecting device for detecting a focus state of the sighting telescope; and a controller for controlling the sighting telescope to automatically focus on the object in accordance with the focus state detected by the focus detecting device. The focus detecting device is a phase-difference detection type which detects an in-focus state from a pair of images respectively formed by two light bundles which are passed through two different pupil areas. The two different pupil areas are positioned so as not to interfere with any optical elements of the optical distance meter.

Abstract: A surveying instrument is provided with a sighting telescope, an auto-focusing system, a switch and a correction system for correcting a focusing state. The correction system controls the auto-focusing system, in response to an operation of the switch, to change a focusing state of the image of the sighting telescope from a first state to a second state. The first state is a state where an object whose object distance is a first distance is focused on, and the second state is a state where an object whose object distance is a second distance is focused on, wherein the second distance is substantially a half of the first distance.

Abstract: Disclosed is a focusing lens position detection apparatus provided in an auto-focus surveying instrument that includes a telescopic optical system having a focusing lens which moves along an optical axis, a beam splitter which splits object light transmitted through the focusing lens to produce light split from the telescopic optical system, and a focus detector which receives the split light from the beam splitter. The focusing lens position detection apparatus includes: an indicia member provided on the focusing lens, which is located outside the light path of the telescopic optical system; and a light path changing member provided between the beam splitter and the focus detector, which is movable between a first position in which the split beam from the beam splitter can be received by the focus detector and a second position; wherein the light from the indicia member can be received by the focus detector.

Abstract: A handgrip mounting structure in an electric device comprises a main body and a handgrip to be mounted on the main body. The handgrip includes a holding portion, to be held by an operator, having a predetermined length, and mounting portions to be mounted on the main body. The mounting portions are provided at each end of the holding portion. The handgrip has a thermal expansion ratio in the longitudinal direction of the holding portion that is different from that of the main body. At least one of the mounting portions of the holding portion is mounted to the main body so that a shaft member, provided on one of the mounting portions and the main body, is inserted into a through hole formed on the other of the main body and the one of the mounting portions.