Showing papers on "Apochromat published in 1980"

Influence Of Alignment Errors Of A Telescope System On Its Aberration Field

Abstract: It is shown that, for each field-dependent aberration type, the effect of tilts and decentrations is to produce a more complicated field dependence and local orientation of the aberration without otherwise changing its character. Particular attention is given to astigmatism.

Longitudinal spherical aberration of modern ophthalmic lenses and its effect on visual acuity.

Abstract: The longitudinal spherical aberration of those soft and hard contact lenses that have spherical surfaces is substantially larger than that of spectacle lenses. By applying at least one ellipsoidal surface, this type of aberration can be greatly reduced, and good conformity of the posterior surface to the cornea can be simultaneously attained. Theoretical and experimental studies were made of the effect of spherical aberration of ophthalmic lenses on visual acuity. The visual acuity measurements were made with specially designed spectacle lenses using four-position Landolt C's as test targets. The probabilistic nature of the visual resolution was considered in evaluating the results. It was found that excessive spherical aberration of ophthalmic lenses reduces visual acuity, particularly at low levels of illuminance.

Chromatic aberration of the Selfoc lens as an imaging system

Abstract: An estimating function is proposed to evaluate the chromatic aberration of a gradient-index rod lens. By suitable design a marked reduction of chromatic aberration was obtained using the Selfoc lens as an imaging system.

Color-corrected Fresnel lens for solar concentration.

Abstract: A new linear convex Fresnel lens with its groove side down is described. The design philosophy is similar to that of the highly concentrating two-focal Fresnel lens but includes a correction for chromatic aberration. A solar-concentration ratio as high as 80 is achieved. For wide-acceptance angles, the concentration nears the theoretical maximum.

Design of gradient-index spherical lenses for optical pickup systems.

Abstract: Aberration of large numerical-aperture gradient-index lenses for optical pickup systems can be corrected with spherical surfaces whose curvatures are chosen corresponding to the measured values of the fourth- and sixth-order refractive-index coefficients.

Wide Angle Lens Systems

Abstract: Characteristics of wide angle (fish-eye) optical systems having fields of view greater than 100 degrees are discussed. Design problems such as pupil aberration and glass selection are discussed. A table of lens characteristics for lenses of 140 to 190 degree fields is presented comparing image heights, lens diameters, focal length, etc. It is demonstrated that such lenses generally obey an image height relationship of y = .015F0 (0 is in degrees)

Systematics Of Photographic Lens Types

Abstract: Classification of photographic lens types has been undertaken in several ways of which the historical approach and the approach by Kingslake are the most important ones. A new classification is proposed which is based on the method of the Petzvalsum (P) correction. It is shown that the correction of P is the pivotal problem in photographic lens design and that all lenstypes can be considered as a consequence thereof. Most aberrations originate in the process of correcting P and their reduction can best be undertaken as an effort to improve the method of P correction. Fifth order field curvature is often characteristic of the method of P correction and is for most lenses the performance-limiting aberration. This classification is useful in understanding a lensform, as a guide to improve the aberration correction, and as a method to find new lensforms.

Single element spherical surfaced optics insensitive to wavelength and temperature

Abstract: These thick elements are all corrected for third order spherical aberration and they are also corrected for spherochromatism (i.e. chromatic variation of spherical aberration) or longitudinal color or both. Most are preferably made of materials of low index of refraction less than 1.55, such as BK-7 or fused silica. Most elements corrected for third order spherical and spherochromatism exhibit longitudinal color, but this poses no problem when they are used with a single wavelength laser. Such systems can be used to focus a laser beam to provide a very fast f number diffraction-limited point source, or used in optical testing, experiments, and the like. The designs are characterized by an extremely low sensitivity of performance to wavelength changes and thus to uniform temperature changes (thermal soaks). A temperature change of several hundred degrees centigrade--from cryogenic temperatures up to near the melting point of the optics, has essentially no effect on the predicted performance. Since the systems have no aspheric surfaces, they are substantially less expensive than fast f number parabolic mirrors, which would also provide point sources. The systems are also less alignment sensitive than parabolas of the same f number. Several systems have low fifth order spherical aberration which can be fully corrected if divided into two elements. Other systems useful in interferometric testing with lasers are described. Some employ multiple passes through a single optical element. These may be corrected for third spherical aberration, longitudinal color, and spherochromatism. Such an element with an index of 1.71 is described.

Three-lens apochromatic infrared objective - has germanium, arsenic tri:sulphide, and chalogenide glass lens

Abstract: The infra-red objective is for the 8-12 micrometre wavelength range. It comprises three lenses (R1,2, R3,4, R5,6) of which one (R1,2) is germanium, one (R5,6) is arsenic trisulphide, and one (R3,4) is chalcogenide glass such as is known under trade names 19 1173 (Texas instruments) or Amtir 1 (Amorphous Materials Inc.). Dimensional details are specified for two examples of objectives with focal length 250. The lens has less chromatic aberration than prior art lenses.