Abstract: An electro-optical measuring system in a photogrammetric comparator or stereocompiler comprises a visible light transparent phase grating which is carried upon a surface of the photo support plate of the device. The grating is formed as a composite layer of .lambda./4 films of at least two dielectric materials of different refractive index which are deposited on the support in such a manner as to yield parallel bands in which the two film materials are in alternating sequence from band to band. As a result of this structure which ensures a constant physical and optical thickness with respect to transmitted imaging light over the whole granting pattern, image-degrading diffraction of the transmitted visible light is avoided, yet the grating pattern provides interfering diffraction in reflection which may be utilized in a precise displacement measuring system.

Abstract: Means for conjointly mounting center members of dissimilar metals for stable concentric rotation about a theodolite spindle comprises a plurality of radially-extending guide grooves on one of the members disposed regularly about the axis of the spindle, and a like plurality of support elements affixed to another of the center members and similarly disposed about the spindle axis to seat respectively in the guide grooves. The support elements being thus limited by the guide grooves to precise radial movement, any dissimilar thermal expansions of the center members result in relative movement between them which is concentric with the spindle axis.

Abstract: A low-profile theodolite leveling means comprises a tribrach assembly including three separate platforms of which the second is mounted upon the first by means of a pair of pivot elements which establish a first fixed axis of tilt of the second platform, and the third is similarly mounted on the second by means of a pair of pivots which likewise establish a second fixed axis of tilt, orthogonal to the first axis, for the third platform. Located in use between a tripod head and the base of a theodolite geodetic instrument, the tribrach assembly provides means for tilting the theodolite instrument with respect to independent planes defined by the orthogonally disposed axes of tilt and respective adjustment screw members.

Abstract: Means for centering a reticle on the optical axis of a telescope comprises, within the telescope body, a split collar tapped to accommodate two pairs of diametrically opposed adjustment screws which bear upon rectilinear surfaces of a centrally located reticle mount. The arrangement provides a dust-proof seal for the telescope interior and ensures against stresses tending toward reticle misalignment.

Abstract: The surveying system comprises a theodolite which provides digital data from electro-optical horizontal and vertical circle reading components and includes a level sensor which generates digital data relative to the attitude of the vertical axis of the instrument. Additional means are included for presetting instrument correction and scaling factors which together with angle and level data are processed by an on-board microcomputer to yield accurate digital displays of horizontal and vertical angles. Provision is also made for the input of digital slope range data from an electronic distance measuring instrument to be displayed directly or processed with horizontal and vertical angle data by the microcomputer to provide vector coordinates of the observed target. In response to operator selection from parameter and vector functions the control program cycles the processing of relevant data in order to provide a repeatedly updated display of any desired function.

Abstract: Azimuth and elevation adjustments in a geodetic instrument are provided by systems which include coaxial locking and two-speed adjustment control knobs. In each such system, the control knobs are accessible at both the front and rear of the instrument to facilitate operation in either of the forward- or back-sighting mode.

Abstract: The surveying system comprises a theodolite which provides digital data from electro-optical horizontal and vertical circle reading components and includes a level sensor which generates digital data relative to the attitude of the vertical axis of the instrument. Additional means are included for presetting instrument correction and scaling factors which together with angle and level data are processed by an on-board microcomputer to yield accurate digital displays of horizontal and vertical angles. Provision is also made for the input of digital slope range data from an electronic distance measuring instrument to be displayed directly or processed with horizontal and vertical angle data by the microcomputer to provide vector coordinates of the observed target. In response to operator selection from parameter and vector functions the control program cycles the processing of relevant data in order to provide a repeatedly updated display of any desired function.

Abstract: Focusing mechanism for a telescope utilized in geodetic instruments and the like comprises a pair of manually accessible ring members mounted coaxially of the line of sight axis at the eyepiece end of the telescope. Rapid image acquisition is effected by means of a first of the rings which is associated with a multiple lead screw element while fine focusing is obtained by means of the second ring member which operates a single screw thread drive for the draw tube focusing lens assembly.

Abstract: A photopolymerizable composition useful in photo-imaging processes comprises an ethylenically unsaturated polymerizable compound and a photoinitiator comprising a combination of a photoreducible dye and an alkanolamine. The composition is substantially insensitive to visible light when in an acidic pH condition, yet may be made highly sensitive to visible light upon adjustment to a condition of alkaline pH. Imaging materials may be repeatedly sensitized and desensitized by pH adjustment and multiple-spaced exposures made prior to final washoff development processing.

Abstract: Fine adjustment of a surveying instrument telescope reference spirit level is effected by rotating the bubble vial of the level about an axis which is slightly angularly displaced from the longitudinal axis of the vial.

Abstract: Sheet material useful in the preparation of draftsmen's and engineers' plans and drawings comprises a base support, preferably of a stable polyester film, bearing a translucent pencil- and ink-receptive coating comprising finely-divided silica pigment dispersed throughout a binder matrix which is essentially a cross-polymerized reaction product of a mixture of a relatively low molecular weight acrylic or methacrylic ester vinyl monomer, a drying oil acrylate, and a blend of polyene and polythiol radiation curable polymers. The coating composition is substantially devoid of volatile solvent vehicle, yet is readily set to a functional drafting surface by exposure to actinic radiation, such as ultraviolet light.

Abstract: Means for producing a counter reset pulse at the precise zero datum in an electro-optical measuring device comprises a sub-assembly including a light source, a patterned reticle, and a pair of photosensors, and a cooperating imaging reflector element. Each of the sub-assembly and reflector element are respectively mounted on the separate portions of the measuring device between which relative movement is effected during the measuring operation. Light from the source illuminates a pair of parallel transparent slots in the reticle pattern and is imaged back upon a second pair of transparent windows in the same reticle by the reflector element and is incident upon a pair of photosensors, each of which is associated with one of the windows. Equal illumination of each of the photosensors establishes the precise zero datum in the device and associated electronics provides a counter resetting pulse at that position.

Abstract: Telescope elevation controls in a geodetic instrument include coaxially mounted control knobs which respectively effect positive clamping of a lever arm member to the telescope axle, and fine adjustment drive of telescope elevation. Kinematic bearing means are also provided along with telescope plumb line adjustment means capable of effecting true vertical telescope axle adjustment.