Abstract: A keratometer includes illuminating optics centered along a common measurement axis in alignment with a patient's cornea and with area detection means of the keratometer. A conical reflector is positioned with its apex facing a source of collimated light, such that light incident upon the conical reflector is divided into rays expanding radially outward from the measurement axis. A frusto-conical reflector surrounds the conical reflector to receive the radially expanding rays and redirect them along the measurement axis as an annulus of light large enough to pass around the area detector to a mire ring occluder and refractor which pass a refined converging annulus of light to the cornea.

Abstract: An apparatus for adjusting a viewing angle of a microscope is disclosed. In a preferred embodiment thereof, a bent eyepiece tube includes a prism on a first optical axis thereof for redirecting an object image to a second optical axis of the tube on which a magnifying eyepiece is aligned. The eyepiece tube is mounted on the microscope for rotation about the first optical axis by a collar, and a spring plunger carried by the tube is biased for respective engagement with a pair of opposing recesses in the collar to releasably secure the eyepiece tube in predetermined rotational positions corresponding to a pair of different viewing angles.

Abstract: An air pulse generator for a non-contact tonometer comprises a bi-directional linear motor drivably connected to a compression mechanism and responsive to an applanation signal for reducing unnecessary air pulse energy delivered to an eye. Upon receiving the applanation signal from an applanation detector, a motor controller reverses current flow in the coil of the motor to create a reverse electromagnetic force to stop generation of the air pulse. In a first embodiment, the linear motor includes a moving permanent magnet armature for reversibly driving the compression mechanism, while in a second embodiment, the linear motor includes a moving coil for reversibly driving the compression mechanism.

Abstract: A non-contact tonometer includes a fixation axis intersecting the corneal vertex, and a fluid axis angularly displaced from the fixation axis to form a non-zero angle therewith. A nozzle is axially aligned along the fluid axis for discharging a fluid pulse along the fluid axis to the corneal surface of the eye. In a preferred embodiment, the fixation and fluid axes reside in the same vertical plane, with the fluid axis below the fixation axis approaching the eye. Alignment and applanation detection optics are arranged coplanar with the fluid axis.

Abstract: A microscope lens guide system is disclosed wherein a plurality of lens carriers are magnetically biased to guide rods to ensure rectilinear motion of lenses held by the carriers along an optical axis of the microscope. In a first embodiment, each lens carrier includes a first portion having a passage for slidably receiving a guide rod and a second portion having a magnet for biasing the second portion for engagement with another guide rod formed of magnetic material. In a second embodiment, additional magnets are provided to bias the passage for engagement with the guide rod received by the passage.

Abstract: A glare tester suitable for use with conventional subjective refractors for testing visual acuity is disclosed. The tester may be fitted to new refractors or retrofitted to existing refractors. The preferred tester is a plastic annular ring with a plurality of LEDs mounted in recesses to direct light toward the test axis and a surface to reflect the LED light toward the patient's eye. A coating on the ring surface opposite the patient's eye improves the LED efficiency.

Abstract: A bearing for supporting a load for axial and rotational motion relative to a shaft is disclosed as including an outer shell having a cylindrical inner wall supporting a plurality of circumferentially spaced arcuate bearing pads for engaging the shaft. Each bearing pad includes a pair of elastically deformable lateral tip portions arranged for interference fit with the shaft to exert a static preload on the shaft, and a mid portion intermediate the lateral tip portions arranged for clearance fit with the shaft. A plurality of lubricant channels communicate with the shaft through gaps between the separate bearing pads.

Abstract: A lensmeter accessory is disclosed for supporting and positioning a corneal contact lens in a light path of a lensmeter. The accessory comprises a generally planer body with a tapered slot therein having a slot wall defining a recessed groove for receiving and removably holding a contact lens. The accessory may be placed on an adjustable lens platform of a lensmeter to position the contact lens in the lensmeter light path.

Abstract: An alignment override control for effecting automatic vertical alignment of a test axis of an ophthalmic instrument with the center of an eye is disclosed. The test axis is associated with optical alignment means of the instrument vertically movable by an elevation motor controlled by a motor drive. A joystick and a pair of directional switches are connected to the motor drive for manual positioning of the test axis. When the eye comes within a field of view defined by the optical means, the override control disconnects the switches and automatically signals the elevation motor to effect automatic alignment using signal information originating from the optical means.

Abstract: A Global Positioning System (GPS) commercial receiver including a digital processor disposed to utilize the energy of both the L1 and L2 GPS satellite signals in order to derive an estimate of an unknown security code used to modulate the signals. In processing the signal energy from the received L1 and L2 signals in accordance with statistical Maximum A Posteriori (MAP) estimation theory, the received L1 signal is correlated with a locally generated replica of the P-code, and passed through a bandpass filter having a bandwidth approximating the bandwidth of the unknown modulation code. The received L2 signal is similarly correlated and filtered, and the decorrelated signals are then latched in such a way as to account for the differential ionospheric refraction of the L1 and L2 signals. The bandlimited L2 signal is used to produce quadrature error signals related to phase difference between the L2 signal and a locally generated L2 replica.

Abstract: An apparatus and method for aligning the optical elements of a microscope are disclosed wherein a fixture is provided for locating and mounting a plurality of mirrors for reflecting an object image along an optical path to an adjacent eyepiece connected to the fixture by an eyepiece holder. The eyepiece holder includes an outer sleeve attachable to the fixture, an inner sleeve transversely movable within the outer sleeve for slidably receiving the eyepiece, and positioning means comprising a plurality of angularly spaced screws extending through the outer sleeve for engaging the inner sleeve, whereby the eyepiece may be aligned on the optical path by selectively adjusting the screws.

Abstract: Microscopes having plastic components such as knobs, covers and eyepiece rings are rendered antistatic by using static charge dissipating plastic materials instead of conventional plastics. Such antistatic microscopes are especially useful in the manufacture and inspection of semi-conductors which are easily damaged by exposure to static charges.

Abstract: An improved tonometer is disclosed having a pachymetric device means for measuring a patient's corneal thickness to allow for correction of the intraocular pressure measurement where the corneal thickness measurement deviates from a calibration mean corneal thickness. In a preferred embodiment, a single light source is pulsed just prior to intraocular pressure measurement to illuminate a central corneal section, and a pair of lateral light detector arrays are arranged to obliquely image the corneal section and generate signals which may be processed by a CPU to produce a corneal thickness measurement. If the corneal thickness measurement deviates from the calibration mean corneal thickness, the CPU calculates a thickness-corrected intraocular pressure measurement. The intraocular pressure measurement, corneal thickness measurement, and/or corrected intraocular pressure measurement may then be reported by a suitable display.

Abstract: The disclosure relates to a joystick for positioning a test axis of an ophthalmic instrument relative to an eye of a patient. In a preferred embodiment, the joystick includes an actuator extending therefrom and arranged to alternately engage a pair of motor control switches incident to slight rotation of the joystick in opposite directions, thereby activating a motor drive to raise and lower the test axis.

Abstract: A polar or vector display provides an operator of an optical instrument with a symbolic instruction regarding the direction and amount of motion required to center an optical element on a chosen path.

Abstract: A device for testing visual contrast sensitivity is disclosed whereby the contrast between a vectographically polarized test symbol and a reference background may be continuously varied by changing the direction of polarization of a polarization analyzer situated along the test axis. The invention is practiced by providing a chart projector or a conventional refractor with a rotatable analyzer.

Abstract: An apparatus and method for creating an aligned subassembly of optically critical components of a temperature compensated, hand-held refractometer prior to installing the subassembly in a refractometer housing is disclosed. The preferred embodiment is a plastic subassembly frame with a critical angle prism reference surface, a temperature responsive member fulcrum, a compensating prism mount, an objective lens mount, and a reticle mount.