Apochromat

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

Correction of secondary spectrum with intrinsic chromatic aberration

Abstract: An achromatic lens system may consists of several cemented or separated groups of orown and flint glasses. If there is a value of chromatic aberration in each group, and a certain relationship between the positive or negative sign of chromatic aberration and the selection of glasses, the secondary spectrum of the whole lens system can be reduced to any small value. According to this principle, two complicated triplets with secondary spectrum corrected, are given as an example. Their focal lengths are 1.5m, F numbers are 7, and field angles are 15° and 18° respectively.It is entirely common glasses used in one of the lens.

Three-band apochromatic ultraviolet optical system

Abstract: The invention discloses a three-band apochromatic ultraviolet optical system. The system successively consists of a front lens set G1, a relay lens set G2, a diaphragm front mirror set G3, a diaphragm, a diaphragm rear mirror set G4 and rear mirror set G5 from object space to image space. The system is compact in structure and suitable for scenes such as criminal investigation site searching and photo taking; three-band achromatism of 250-400 nm, 450-660 nm and 700-900 nm can be realized, so that imaging can be more intelligible and sharper; the system has a large aperture, can be used for ultraviolet, visible light and near infrared, and integrates long distance target searching and macro shooting and evidence collecting, so that the excellent quality of imaging can be realized; close-shot distances can be greatly compressed by 100 mm, so that shot images can obtain more detail characteristics; and through the using of quartz and calcium fluoride spherical glass, easy processing can be achieved, and the transmittance in a band range of 250-900 nm is greater than 90%.

Spherical and Chromatic Aberration Correction using Aperture Lens —Computer Simulation—

Abstract: The electron trajectories from a Pierce-type electron gun are calculated. The aperture lens which is formed by an anode hole acts as a concave lens and produces negative-sign spherical and chromatic aberrations. The negative-sign focal length which is calculated by the trajectories coincides with the value calculated by the formula derived by Davisson and Calbick 60 years ago. For an electrode of practical size, the negative-sign spherical and chromatic aberration coefficients are on the order of 100 to 102 m and of 10-3 to 10-1 m, respectively. It is shown that when the electron beam from this type of electron gun is focused by a magnetic lens, most of the spherical aberration is compensated. These aperture lenses are expected to improve the characteristics of the charged particle beam systems.

Influence of spherical aberration and astigmatism on the imaging of extended objects using a holographic lens

Abstract: Investigations on the imaging of extended objects by a holographic lens in the presence of third-order spherical aberration and astigmatism have been carried out. Light intensity distribution in the aberration spot observed at the Gaussian plane has been evaluated numerically, using a ray-tracing procedure, for different amounts of astigmatism and for a fixed value of spherical aberration. The images of extended coherent and incoherent edges as well as bar objects have been computed and the results have been compared with that for the aberration-free case. All the results are illustrated in graphical form.