Corrector Lens Research Articles

Skylab ultraviolet stellar astronomy experiment S019

An objective-prism stellar spectrograph of 15-cm aperture was flown on all three Skylab missions. The wavelength region from 1300 A to 5000 A was covered by a special optical system containing a combination of reflecting telescope optics, a CaF(2) objective prism, and an achromatized field corrector lens system of CaF(2) and LiF. Observations of 188 star fields, each covering 4.0 degrees 5.0 degrees , were conducted at the Skylab antisolar airlock with the aid of an articulated mirror system (AMS) which allowed acquisition within 30 degrees degrees 360 degrees band of the sky.

FOCAL PREDICTIONS FOR SPECTROGRAPHS EMPLOYING A MAKSUTOV CAMERA

ABSTRACT An analysis has been made of a spectrograph with a Maksutov camera. Because of chromatic aberration in the corrector lens, the focus and plate tilt are sensitive to dispersion and wavelength. Simple approximate formulae for calculating collimator focus and plate tilt are found and numerical results, applicable to a particular commercial spectrograph, are presented. The choice of field flattener lens is discussed. Key words: spectrographs - instrumentation - optics

High resolution imaging properties of the stem

The effect of the finite size of the atom on the resolution of the STEM is investigated. When the probe size becomes comparable to the size of the atom, the quality of the image depends on the scattering properties of the atom as well as the distribution of electrons in the probe. A technique for calculating the image of a single atom is developed by expanding the scattering amplitude. This allows the image of an atom or its spatial frequency to be expanded into various components. The specific case of dark field contrast formed with elastically scattered electrons is considered. The coefficients of the components are evaluated for carbon and thorium using complex scattering amplitudes derived from relativistic Hartree-Fock-Slater wavefunctions. The coefficients are evaluated for a 100 keV microscope using an immersion type objective lens whose aperture is limited to 12 mrad by primary spherical aberration and a 100 keV microscope using the same objective lens in conjunction with a corrector lens for spherical aberration. Secondary spherical aberration limits the objective aperture of the corrected microscope to 30 mrad.

Performance of Schmidt and Field-corrected Telescopes

Wynne (1) has recently defended the approach to systems-design of field-imaging telescopes by correction of a configuration initially stigmatic only paraxially, as opposed to the approach of preferring a Schmidt or other configuration inherently suited to wide-field operation, as advocated by the present author (2). Wynne asserts that my discussion somewhat underestimates the performance of current field-corrected systems. This is of course now perfectly true, and is so in large measure because of the valuable contributions that Wynne has himself made to the design of corrector lenses during the past few years.

Quadrupole-Octopole and Foil Lens Corrector Systems

The theorem due to Scherzer which states, in essence, that a conventional axially symmetric, magnetic or electrostatic lens can never be free from third order spherical aberration is well known. Attempts to circumvent this limitation have been carried out over the past thirty years with little result, but meanwhile the ill effects have been minimized by using magnetic lenses of very short focal length.The most studied alternative is the use of doubly symmetric strong focusing lenses. The first order imaging is performed with three or more quadrupoles, and the third order aberrations corrected with three octopoles. The design by Deltrap for example has no first order effect other than to invert the image, and has a third order spherical aberration coefficient which exactly cancels out that of the magnetic objective lens with which it us used. To avoid chromatic aberration this magnetic objective lens must have a very short focal length (2 mm for 100 kv operation with a resolution of 1 Å), and the overall system then has so much coma that the field of view is limited to 50 Å diameter.

New telescope at Palomar

The first major addition to Mount Palomar since the 200‐inch telescope was completed in 1948 is a 60‐inch telescope, which was dedicated in October. A Raytheon 703 computer controls operation and acquires data. An unusual optical system of six mirrors and a corrector lens enables the telescope to combine the maneuverability advantages of a short tube (154 inches) and the higher magnifications possible with a long focal length of 1800 inches (at the coudé focus) or 525 inches (at the Cassegrain focus). The telescope, built largely in the Cal Tech shops, cost more than $1 million; funds came from NSF, the family of the late Oscar G. Mayer, NASA, Cal Tech and the Carnegie Institution.

Effects of Elastic Distortion of Rotating Mirrors on Time Resolution in Smear Cameras*

The basic relations for the rotating mirror smear camera are reviewed and expressions are obtained for the maximum time resolution obtainable in systems uncorrected for the elastic distortion of the mirror surface. Instrumentation for the measurement of the surface distortion at high speed is described and data are reported for rotating rectangular parallelepipeds as a function of size and width-to-thickness ratio. The central sections of the mirrors deform cylindrically, the power varying nearly with the square of the peripheral speed. The distortion effects can be almost completely compensated by the introduction of negative astigmatism into the system. An auxiliary optical system is described which aids in the adjustment of the corrector lens to obtain optimum resolution. A corrected system in current use has a time resolution of 10−8 sec with relative aperture f6.

High-Speed Wide-Range Fluorite Spectrograph*

A plane-grating spectrograph using a movable calcium fluoride camera corrector lens has been designed and constructed. It can be used to cover a wavelength range from about 12 000 A to 1500 A. The dispersion is approximately 58 A/mm, in the first order. The camera focal ratio of f/2 gives the instrument a speed such that for relatively weak sources, the exposure times have been reduced from several weeks to a number of hours.

A New Reflecting Spectrograph Camera

The camera which has been developed consists of a spherical mirror and a corrector lens with spherical surfaces. The equivalent focal length is about 900 mm and the relative aperture is f/4. The design is based on the theory by Argentieri and becomes a camera of the nonconcentric type. The useful range of the camera is from 2500 A to 12 000 A. Some details of the construction and results obtained are shown.

Optical Problems at the Palomar Observatory

The great flexibility of the 200-inch mirror required the development of new and elaborate support systems to maintain the figure in all orientations. New methods had, therefore, to be devised for testing the mirror in the telescope while on these supports. The final figuring was done on the mountain on the basis of these tests.To increase the effectiveness of the instrument, corrector lenses were designed by Ross greatly to enlarge the field of the main mirror. Likewise the method of evaporating a reflecting coat of aluminum was developed by Strong to replace the old silvering procedures. Several new optical designs were introduced in the spectrographs to make optimum use of the light collected. These included the use of (1) a composite of four “blazed” gratings to permit a collimator aperture of 12 inches; (2) Schmidt cameras with half-strength corrector plate placed practically in contact with the grating, the light passing through the plate twice (this eliminates many vignetting problems and permits higher speeds and larger fields); and (3) a combination of a quartz aplanatic sphere with a Schmidt camera for the shortest focal-length camera to obtain a much higher speed (F/D = 0.7) than would otherwise have been possible.

Field Correctors for Parabolic Mirrors

Optical systems to correct the oblique aberrations of large parabolic mirrors in astronomical telescopes are discussed. The earlier work of F. E. Ross on doublet lens correctors in the converging beam is extended, and the residual first order spherical aberration is shown to depend only on the power of the corrector, its elimination requiring an impracticably large power; these results are independent of the arrangement and the optical constants of the components, and are unaffected by aspherizing the lens surfaces. Correction by two aspheric plates is shown to lead to systems of relatively great length, with consequent heavy vignetting. Finally, systems are discussed consisting of a doublet lens with one aspheric plate or secondary mirror; such a secondary mirror may be used to correct field curvature, giving corrector lenses which are afocal and therefore free from secondary spectrum, and the departure of the secondary mirror from the spherical form may be made zero by a suitable choice of the other variables. Details are given of the calculated performance of four three-component systems.

Correcting Lenses for Refractors

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Correcting Lenses for Refractors Ross, Frank E. Abstract A short history is given of the use of zero-power correcting lenses with visually corrected refracting telescopes. The object of the corrector is to change the refractor over into a photographically corrected telescope, in order that it may be better adapted for spectrum photography. An analysis and reconstruction of the optical design of the 40-inch lens of the Yerkes Observatory is presented, furnishing data useful for the proper design of the corrector lens. The design and data on the corrector lens are given, and a comparison of its performance with that of the older corrector lens, showing gain in speed. The general theory of corrector lenses of this type is presented in some detail; in particular, it is shown that there is a large outstanding optical aberration, chromatic magnification, which cannot be eliminated, but is capable of material reduction by proper design. The effect of flexure of the telescope tube is considered, and found to be negligible. It is pointed out that the most serious outstanding defect of the corrector lens is secondary axial-color aberration. The question of reducing this by suitable choice of glass is discussed, and it is shown that little can be expected in this direction Publication: The Astrophysical Journal Pub Date: October 1932 DOI: 10.1086/143413 Bibcode: 1932ApJ....76..184R full text sources ADS |