Relay Lens Research Articles

Fourier-transform ring laser

A Fourier-transform ring laser has been designed and toleranced to produce a good-quality beam from a solid-state laser. Extremely high volumetric utilization of the gain distribution is accomplished by injecting a super-Gaussian-shaped beam profile of uniform phase and nearly uniform intensity into the ring resonator. This beam fills most of the rod and is reproduced at the rod center in both intensity and phase by an exact Fourier-transform relay lens scheme. The laser is shown to be most stable when the diameter of the super-Gaussian beam is equal to diameter of the eigenmode for the optical system. It is shown to be most reliable when the relay system has a magnification such that the beam expands from its initial eigenmode size to fill the rod on its final pass.

Correction of chromatic aberrations in GRIN endoscopes

A gradient-index (GRIN) endoscope can be constructed by substituting for the usual objective and relay sections suitable cylindrical index-distribution rod lenses. Currently available GRIN lenses exhibit large amounts of chromatic aberration. Axial color arises mostly from the relay lens, while lateral color is due to the objective lens. A negative lens cemented to a shortened GRIN relay lens can simultaneously correct axial and lateral chromatic aberrations with commercially available components. This correction system reduces the requirements for mechanical centration better than do color correctors that are incorporated into the ocular design. Monochromatic aberrations are also considered.

Thick meniscus field correctors

Thick meniscus lenses with almost equal curvatures are routinely used for the correction of spherical aberration in optical systems. The use of such quasi-concentric menisci (QCM) for correction of field curvature and astigmatism is less well known. Three limiting forms of QCM can be identified, namely, equal curvatures, true concentric, and zero deviation, and each exhibits radically different field aberrations. A doublet lens has field curvature and astigmatism; the former can be removed by adding a strong negative lens at the image plane, but the latter is uncorrected. Use of a QCM, however, corrects both aberrations, moreover, without causing the chief rays to diverge as the conventional field flattener does. Indeed the chief rays may be made to converge so that the QCM can be used as a field-correcting field lens, and we illustrate its use in a periscopic vehicle sight comprising an objective lens, relay stage, and eyepiece. Even in cases in which a measure of field curvature and astigmatism correction is possible, for example, when a double Gauss-type relay lens is used, the QCM results in smaller high-order aberrations and lower ray heights through the system.

Ionic and atomic absorption in stable spark discharges

Transient ionic and atomic emission-absorption measurements on a train of positionally-stable copper spark discharges are described. The measurements are made as a function of discharge current duration at constant amplitude and rise time. Spatial observation zones are isolated in the spark gap with a set of masks and a relay lens to estimate the movement of electrode vapor. Absorption measurements required custom circuitry for a pulsed hollow-cathode backlight and synchronously gated dual-channel boxcar integrator. Results indicated that electrode vapor moves primarily along the interelectrode axis in response to current duration, with substantial ionization remaining in the post-discharge period. Neutral atoms remain in the gap for long times after current cessation.

A multi-slit spectrograph and H? Doppler system

A multiple entrance slit spectrograph was built for time-lapse photography of the spectra of flares and other transient solar phenomena. This spectrograph employs narrow-band filters to limit the wavelength range of the spectrograph to several angstroms centered at Hα or other spectral lines. The passband of the filter, and the dispersion of the spectrograph determine the number of parallel slits through which light may be passed to achieve multiple adjacent spectral displays. By using a 7 A filter, a dispersion of 10.8 A mm−1, and 35 mm film, adjacent Hα spectra are imaged from 30 parallel slits. A system of mirrors and relay lenses transfers the slitjaw image to the same film plane as the spectral image. A 2 frame camera is used to simultaneously record both images on adjacent frames. Filtering of the reference spatial image to 1.0 A allows the observer to see the position of the slits relative to the Hα centerline structure and to match the brightness of the spatial image to the spectral display. A polarizing beamsplitter, prior to the slits, provides a prefiltered second solar image to a narrow band Hα Doppler filter for simultaneous photography in the wings of the Hα line. The multislit monochromatic spectrograph and Hα Doppler system constitute a flexible instrument in which components may be substituted to achieve different passbands width, image scales, dispersions and corresponding numbers and spacings of adjacent spectra at a selected wavelength.

High-Quality Laser Color Television Display

Special features of a new 523-line scanned laser display system are described. These include: (1) the addition of beam wobbling to the polygonal mirror scanning system to allow improvement of the horizontal resolution by a factor of 3.6; (2) a relay lens between the horizontal and vertical deflectors, to minimize deflector aperture requirements; (3) an auxiliary deflection system to compensate for raster irregularity; and (4) an automatic optical black-level control system. The resulting horizontal and vertical resolutions are 500 and 370 TV lines, respectively, and raster uniformity is excellent. Horizontal jitter is less than 0.02 μs and vertical jitter is unnoticeable. The primary colors used and their sources are: 632.8 nm (He–Ne laser), 514.5 nm (argon ion laser) and 476.5 nm (argon ion laser). Low screen brightness is the biggest remaining problem.

High Resolution Portable Holocamera

The design, construction, and testing of a portable hologram microscope are described. The instrument is based on a small, reliable, pulsed ruby laser to avoid the degrading effects of vibration; the instrument weighs 7.9 kg and measures 30.5 cm x 33 cm x 15.5 cm. A magnifying relay lens is used in a design such that resolution is limited by the effects of speckle. These effects can be reduced by incoherent superposition of images from the four independent holograms of each object that are automatically recorded. Resolution is 3-4 microm, field of view is 4.5 mm, and depth of field is 4 mm. Results of measurements on resolution, image quality, image intensity fluctuations, and image signal-to-noise ratio are presented.

A Professional through-the-Lens CdS Exposure Control System with Optical Data Input for Motion-Picture Cameras

A need for a precise TTL exposure measurement accompanied the development of color reversal film. This new exposure system does not electrically introduce film speed and exposure time data into the meter circuit, but instead the data input is achieved by two unique, counter-rotating precision neutral density discs which maintain the illumination level on the photoresistor at a defined reference value. This method allows the photoresistor to work at a predetermined operating point irrespective of exposure data settings and object illumination. A measuring field of about 30% of the filmed area was determined advantageous for the 16mm film. The light to be measured is diverted by a beamsplitter in the viewfinder's light path, where a relay lens projects the light onto the photoresistor. A galvanometer indicates the illumination level on the film. The reduced light during camera operation is electrically compensated by switching bridge-resistors. The power supply for the exposure meter is stabilized and derived from the camera battery. Illumination of the indicator scale is attained through a light collecting prism. This exposure system sets new standards in measuring accuracy with a wide variety of interchangeable lenses.

Optical Systems for Use at Low Light Levels

The development of image intensifier tubes and their application in instruments for operation under low light-level conditions created the need for optics which require specific properties. Recognition of the problems involved when combining a lens with a tube results in general requirements for the lens, some of which are different from those in standard lens design. Refined basic lens configurations and new systems have been introduced in this field, e.g. refractive and catadioptric lenses. Some examples of their performance are shown. In addition relay lenses having an extremely high speed have been realized for applications mainly for x-ray image intensifier systems. Single-tube instruments with a bi-ocular eyepiece are shown to have many advantages over the double-tube binocular.

Analysis and Correction of Secondary Color in Optical Systems

A technique of chromatic image analysis for optical systems has been developed. The advantages of the technique in giving the lens designer an understanding of the significant inherent sources of secondary color in a particular design are demonstrated. Methods of reducing the secondary color through optimization of glass choice and the actual lens configuration are shown in the application of the analysis to the design of a highly corrected, finite conjugate relay lens.

An All-Electronic Field-Sequential Closed-Circuit Color Television System

An inexpensive closed-circuit color television system which has a simple construction and good color rendering properties has been developed. It is a field-sequential system which uses only one vidicon and has no mechanical rotating parts. Three color images are simultaneously projected onto the vidicon surface; the electron beam of the vidicon scans these images on the vidicon target and field-sequential signals are obtained. A triad relay lens system has been developed and adapted for color separation. A unique method is used for generating the vertical sweep waveform for the camera tube. The final resolution obtained in the experimental set was about 280 TV lines.

Cascade Image Intensifiers for Astronomical Spectroscopy.

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Cascade Image Intensifiers for Astronomical Spectroscopy. Ford, W. Kent, Jr. Abstract A cascaded image intensifier suitable for use in astronomical spectroscopy has been developed at the Electron Tube Division of RCA for the Carnegie Image Tube Committee. This tube gives a substantial gain in speed over ordinary photographic techniques, it can be used for long exposures, and it is simple and reliable in operation compared with other intensifying devices. We now have two samples of these experimental tubes with both good cathodes and low background. The resolution at the phosphor screen, measured visually, is 40 line pairs per mm, and is uniform over the 38-mm diameter field. With our present relay or transfer lens the resolution is limited to 25 to 30 line pairs per mm on IIa-O plates. The gain in exposure time over baked I Ia-O plates is 30 and 40 in the sense that with the image intensifying system plates are obtained in 10 and ~2' min, respectively that are equal in density to 300-min exposures directly on the IIa-0 plates. The gain in the rate of recording information is determined by the efficiency of the photocathode, by the resolution of the system, by the statistical processes involved in the electron multiplication, and by the granularity of the recorded image. An increase in the electron multiplication would increase the rate of blackening but not the information rate. Spectrograms that demonstrate a useful gain of 10 over direct plates have been obtained with these tubes on the DTM spectrograph ~t Lowell Observatory. Dispersions of 90 and 22 A/mm are available at the photocathode with 3 and 12-in. focal length cameras. The development of these tubes was supported by grants from the National Science Foundation. Publication: The Astronomical Journal Pub Date: October 1964 DOI: 10.1086/109312 Bibcode: 1964AJ.....69..541F full text sources ADS |

An Improved ƒ/10 Sweeping-Image Camera

A rotating-mirror sweeping-image camera with mirror distortion corrector, faster writing speed, and apochromatic relay lens has resolving power greater than that of earlier models. An adjustable cylinder lens corrects astigmatism from mirror surface distortion. The mirror, rotating up to 2000 rps, gives a maximum writing speed of 13 mm/μsec for about 10 μsec. The ƒ/10 lens gives static resolution of 36 lines/mm on film. Time resolution is estimated at about 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> sec.