Abstract: A wide-angle zoom lens has a first lens group having a positive refracting power and a second lens group having a negative refracting power, which are moved relative to each other along the optical axis so as to attain zooming. The first lens group is constituted in turn from the object side by a front group having a negative refracting power and a rear group having a positive refracting power. The front group has at least one negative lens. The rear group has at least two positive lenses. The zoom lens is constituted to satisfy the following conditions:0.75<.vertline.f.sub.F /f.sub.W .vertline.<4, f.sub.F <00.1<K/f.sub.W <0.40.1<L/f.sub.W <0.7wherein f.sub.F is the focal length of the front group in the first lens group, f.sub.

Abstract: In a pair of eyeglasses with filter lenses, each filter is mounted in a ring shaped in the form of a prone U whose opening is directed toward the center of the ring. The ring is contained within an outer ring connected to the eyeglasses mounting frame. A manipulating device comprising a molded member is located inside the ring in a recess formed in the periphery of the filter lens. The outer ring has a semicircular slot permitting the angular displacement of a positioning rod, which is integral with a piston slidably mounted in a recess against the action of a spring. One end of the rod is integral with a gripping member, while the other end is engageable in one of the positioning openings formed through one limb of the shaped outer ring.

Abstract: An examining device is provided which quickly and easily determines the "sidedness" of an individual's eyes. The device has a viewing port and conical opaque sidewalls which converge to a small diameter viewing port. The device is constructed so that the individual being tested can see with both eyes an object just beyond the end of the viewing port, but cannot see with both eyes an object which is relatively further away from the viewing port. A first blocking device is provided for alternatively blocking and unblocking the right eye line of sight of the person being examined. A second blocking device is provided for alternatively blocking and unblocking the left eye line of sight of the person being examined. The device is used by asking the individual being examined to look through the device to an object which is located relatively far beyond the end of the viewing port. While the device is held steady, the first blocking device is used to block the right eye line of sight.

Abstract: A simple and relatively inexpensive system has been developed for screening people both with normal vision and those with ocular and optic nerve disease using the Pulfrich stereo-illusion phenomenon. The system uses an audio/visual recording showing a ballerina moving in a pendulum fashion in front of a cone. The person to be tested uses a device which sequentially has no filters and filters of varying density whereby the patient with normal vision will see the ballerina moving back and forth in front of the cone and then rotating around the cone clockwise and counter-clockwise. The audio/visual recording may be shown to the person to be tested on a television set or a tv monitor.

Abstract: A process and apparatus for measuring an axial eye length takes the steps of projecting monochromatic coherent light of which wavelengths are variable onto an eye to be tested, causing an interference between reflected light from a retina of the eye and reference light corresponding to the retina to generate interference signals while reflected light from a cornea of the eye is interfered with reference light corresponding to the cornea to generate interference signals, mixing these interference signals to generate beat signals while varying the wavelength, and measuring an axial eye length based on the beat signals.

Abstract: An adapter is provided for enabling the use of night vision goggle having a plug-type mounting connector and a spring biased latch, with a head mounting assembly having a plate-type receiving carriage. The adapter comprises a housing having a plug-type receptacle which is configured to receive the plug-type mounting connector and a bar capable of engaging the latch. The adapter also comprises a mounting plate which is integrally formed to the hosing and configured to engage the plate-type receiving carriage. The plug-type mounting connector is secured within the plug-type receptacle by an engagement between the latch and the bar. The plug-type mounting connector is capable of selective disengagement from the plug-type receptacle by manual manipulation of the latch.

Abstract: A sunshade and sunglasses which may be interchangeably detachably attached to vision correcting eye glasses is provided. The atttachment being by means of flexigrip-catch pairs. A pair of flexigrips are integrally formed on the top of an eyeglass frame for correcting lenses and are adapted for being received by a first pair of catches that are integrally formed on the top of a frame of a pair of sunglasses which has no temples, or a second pair of catches fixedly positioned underneath a sunshade. The position of the respective first and second pairs of catches are in alignment with the position of the flexigrips. By pressing the first pair of catches onto the respective flexigrips, the sunglass lenses are pivotally attached thereon.

Abstract: An improved method for storing permanent holographic gratings in photorefractive materials for use in narrow band filters such as the H.sub.60 filter, as well as the filters themselves. The invention also provides an improved method of controlling the electric field and the nature of the photorefraction to minimize wavelength shifts and band broadening at a minimal reduction of diffraction efficiency.

Abstract: A holographic display apparatus reconstructs an image by projecting a beam of a luminous source to a holographic sheet including a plurality of holograms. The holograms are arranged so that the central axes of images recorded in the holographic sheet are directed in a same direction, in the diverging direction, or in a converging direction. Additionally, each hologram has a first focal distance f1 (mm) and a second focal distance f2 (mm) which are in a relationship such that f1.ltoreq.f2/28+50 and f1<f2.

Abstract: Reflection holograms to be viewed through the front side of a transparent and preferably flexible substrate, and which are insensitive to moisture in liquid and in vapor form, are produced by attaching a layer of holographic recording material to the back side of a transparent substrate, attaching a layer of moisture barrier resin to the back side of the recording material in sufficient thickness to render the hologram insensitive to moisture, and attaching a layer of opaque material to the back side of the moisture barrier layer. Further protection against moisture may be achieved by attaching a solvent deposited layer of transparent moisture barrier resin to the front side of the substrate and/or attaching a layer of moisture barrier sheet to the back side of the opaque layer.

Abstract: A zoom lens system comprises, in order from the object side, a negative first lens group N, a diaphragm stop A, a positive second lens group P and a blocking element B for blocking deleterious rays of light, with the first and second lens groups N and P movable for zooming, and with the diaphragm stop A moving independently of the second lens group P during zooming. The lens system satisfies the conditions 2.5<Xs/fs<3.0, 0<.DELTA.XA/fs<X2/fs, and 0.ltoreq..DELTA.XB/fs<.DELTA.X2/fs, where Xs is the distance from the diaphragm stop to the image plane at the wide-angle end, fs is the focal length of the overall system at the wide-angle end, .DELTA.XA is the range of movement of the diaphragm stop, and .DELTA.XB is the range of movement of the second lens group.

Abstract: A hologram system comprises two volume holograms on two separate substrates which are cemented together with an optical cement. The two volume holograms are manufactured with identical Bragg planes. The two volume holograms are oriented with respect to one another such that the Bragg planes are optically aligned. The result is that the two volume holograms operate as a single thicker volume hologram wherein the Bragg angle sensitivity is greatly increased.

Abstract: An intraocular length measuring instrument in which a measuring optical path is formed via an eye to be tested, and a reference optical path having a variable optical path length is formed within the instrument, light via the measuring object path and reflected by an intraocular object to be measured and light passed through the reference optical path being caused to be interfered with each other, the optical path length of the reference optical path being varied to form interference fringes, the intraocular length being found based on the reference optical path length where the interference fringes are formed, wherein the intraocular length measuring instrument further includes: a rotatable optical path length variable member for varying the optical path length of the reference optical path in accordance with an angle of rotation; and a rotary device for rotating the optical path length variable member to vary the optical path length of the reference optical path sequentially.

Abstract: An improved vision tester apparatus and method are disclosed for use in conducting optometric examinations of patients who use video display terminals (VDTs). Specifically, the tester simulates images that are displayed to the patient by a typical VDT, so as to facilitate prescribing corrective lenses that will perform well for the patient when used with an actual VDT. The tester (10) includes a flat-panel electroluminescent light source (32) for illuminating a screen (14) without hot spots. The screen includes a colored ink layer (78,80,82) and an opaque ink mask (70) for forming pixel-like light elements (24). Lensing structures (52,56,58,60) degrade the image such that each light element exhibits a generally Gaussian light amplitude curve (FIG. 5B) characteristic of a pixel of an actual VDT. A rechargeable battery (34) coupled to a inverter circuit (30) provide portable power for the EL panel to complete a compact, portable tester.

Abstract: Adjustable pairs of eyeglasses are disclosed which retain the precise adjustments during long periods of wear. Apparatus and methods are provided for so adjusting rim separation at the bridge of the frame of the eyeglasses and for so adjusting the effective length of temples between shoulders and bow of the frame.

Abstract: A beam sampler comprises a substrate made of highly transparent fused silica or zinc selenide, both capable of sustaining high power laser beams. The substrate defines an outer surface through which the light beam being sampled propagates. A sinusoidal diffracting relief is etched on this outer surface directly into the light-propagating material of the substrate. When a light beam propagates through the outer surface of the substrate, the three-dimensional diffracting relief extracts from this light beam at least one pair of low power beam samples.

Abstract: A real image mode variable magnification finder optical system has an objective lens system including a first lens unit of negative refracting power, a second lens unit of positive refracting power, and a third lens unit of negative refracting power, provided with positive refracting power as a whole; and image erecting system for erecting an image of an object; and an eyepiece system for observing the erected image, in which the first and second lens units are moved and the third lens unit is fixed to vary magnification. Thus, the finder optical system has important advantages in practical use that its overall length is reduced, aberrations are favorably corrected, and manufacturing costs are low.

Abstract: In a slit lamp microscope, changeover can be selectively made between conventional slit lamp microscopy and confocal perforated disk microscopy. In slit lamp operation, the microscope is constructed as a stereo microscope. The Nipkow perforated disk required for the confocal perforated disk microscopy is arranged in an indirect beam path. Alternatively, the Nipkow disk can be arranged on a pivotable support element and can be pivoted into the beam path in the vicinity of an intermediate image plane. For confocal perforated disk microscopy, an additional illumination device is provided that is reflected into the beam path between the Nipkow disk and the oculars. The insertion of the Nipkow disk or the switching of the beam paths takes place such that the focal plane of the objective is constant. A changeover is made from conventional slit lamp microscopy to confocal perforated disk microscopy without refocusing. A direct comparison of the images observed with the two procedures is therefore possible.

Abstract: A pair of eyeglasses includes an eyeglass frame and a lens unit mounted detachably on the eyeglass frame. The eyeglass frame includes a curved front frame with two downwardly projecting end portions, and two bows. The curved front frame has an engagement groove formed therein, and a retained portion disposed at the middle section of the curved front frame. The engagement groove has two end portions respectively extending into the front surfaces of the downwardly projecting end portions of the curved front frame. The lens unit includes two lenses and a plastic lens rim mounted securely on the lenses. The lens rim has a rib projecting upward from the upper end portion thereof so as to engage the engagement groove. The rib has two lugs projecting respectively and outwardly from two ends thereof and being inserted into the end portions of the engagement groove. A hook is fixed on the lens rim and has a retaining space formed therein so as to retain the retained portion of the curved front frame.

Abstract: An improved zoom lens system includes at least three lens groups which are arranged, in order from the object side, as a first lens group having a positive focal length, a second lens group having a positive focal length and a third lens group having a negative focal length. When zooming is carried out from the wide angle to the telephoto end, the first, second and third lens group are all moved towards the object so that the distance between the first and second lens groups increases whereas the distance between the second and third lens groups decreases. The first lens group has a first lens element with a concave lens surface on the side the closest to object while satisfying specific conditions.