Apochromat

About: Apochromat is a research topic. Over the lifetime, 642 publications have been published within this topic receiving 7934 citations.

Field curvature aberration

Abstract: This paper provides an overview of field curvature aberration correction. It is known that for sharp imaging on a flat surface the Petzval sum must be zero or nearly so. However, current lenses for mobile phones depart from this principle to some extent. We provide an insightful discussion about some mechanisms for the correction of field curvature aberration.

The effect of broadband illumination on the imaging characteristics of a birefringent lens suffering from primary spherical aberration

Abstract: This report forms a part of the systematic investigation on the imaging behaviour of an optical system consisting of a lens made of a uniaxial birefringent crystal sandwiched between two linear polarizers into which primary spherical aberration is introduced. The optic axis of the birefringent crystal is perpendicular to the lens axis. The proposed system is illuminated with a polychromatic beam of light, the spectral profile of which is considered to be uniform for all wavelengths. The axial irradiance distribution function and the intensity point spread function are used as the image assessment parameters. Some specific cases are computed and illustrated graphically. The study reveals that if the variation of the birefringent parameters of the device with wavelength is less, a larger bandwidth may be used without considerably deviating from the imaging characteristics under strictly monochromatic illumination suffering from similar primary spherical aberration.

Focusing camera used for adjusting co-focusing of astronomical telescope system and focusing method thereof

Abstract: The invention provides a focusing camera used for adjusting co-focusing of an astronomical telescope system and a focusing method thereof, belongs to the technical field of optical measurement, and solves the problems in the prior art that co-focusing of a terminal instrument and a front end telescope is unavailable and the observation precision is relatively poor. The focusing camera comprises a casing. A lens barrel and a lens chamber are installed on the front end of the casing. An outer thread of the lens chamber is in threaded connection with an inner thread on the lens barrel. The lens barrel is internally provided with a first apochromatic lens and a second apochromatic lens. The focusing method comprises the steps of: adjusting the focal length of the camera so as to enable a slit of a spectrometer to be clearly image in the focusing camera; adjusting the position of an aperture plate until the aperture plate is clearly imaged in the focusing camera; adjusting the position of an imaging system until the aperture plate is clearly imaged in the imaging system; and adjusting the position of the astronomical telescope until an observed object is clearly imaged in the imaging system. The focusing camera can be applied to focal plane object side detection and adjustment of the optical telescope telescope and a non-imaging terminal instrument, and a defocused image difference of the optical system is controlled within [lambda]/4.

Apochromatic telephoto lens

Abstract: PURPOSE:To obtain a high-contrast telephoto lens at low cost by correcting chromatic aberration by constituting the front group as one group of three combined elements including double flint glass. CONSTITUTION:The 1st group lens is composed of three combined lenses made of two pieces of double flint glass and another glass showing small dispersion, correcting chromatic aberration. Then, various aberration should be corrected excellently by the constitution of the front group in addition to the chromatic aberration. For this purpose, the rear group is constituted adequately while the aperture ratio is relatively small and the angle of view is also small, and this lens is applied with the internal focusing system. Here, if the focal length of the entire system at the infinite object distance is (f), the F number F, the focal length of the 1st group lens f1, and the sum of center thicknesses of the positive and negative lenses of a lens group movable for the internal focusing of the rear part (t), equations I and II are satisfied to correct various aberration excellently.