Angular aperture

About: Angular aperture is a research topic. Over the lifetime, 1771 publications have been published within this topic receiving 27257 citations.

Uv-capable dry lens for microscopes

Abstract: An UV-capable dry objective for microscopes in which aperture aberration is corrected, at the same time, both for the visible spectrum and for a selected UV-wavelength. The objective comprises two lens groups separated by an air gap which is varied in size by relative movement between the two lens groups. The size of the air gap is adjusted to correct aperture aberration for the selected UV-wavelength. The objective is designed so that the mathematical sign is the same for both (i) the corrections required as the illumination moves toward the longer-wave portion of the visible spectrum, and (ii) for the corrections required as the illumination moves toward the shorter-wave portion of the UV-spectrum. The objective has an aperture of at least 0.7 and a magnification of more than 60×.

Effect of Numerical Aperture of Microscope Objectives on Film‐Thickness Determinations

Abstract: The use of high‐power magnification with large numerical aperture (N.A.) objectives in determining the thickness of transparent films requires a thickness correction due to the effective angle of incidence not being perpendicular to the substrate. The effective angle of incidence is dependent upon both the numerical aperture of the objective and the aperture diaphragm of the microscope. Under extreme conditions the uncorrected measured thickness can be as much as 10% smaller than the actual thickness. The error can be kept to less than 3% or 4% with reasonably high N.A. objectives by reducing the aperture diaphragm of the microscope. In many cases, the correction can be neglected depending on the precision required.

Standard lens system having a large aperture ratio

Abstract: A standard lens system composed, in order from the object side, of a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power: the first lens unit being composed of at least one positive meniscus lens component which has a convex surface on the object side, and at least one doublet which consists of a positive meniscus lens component and a negative lens component; the second lens unit being composed of at least one cemented doublet which consists of a negative lens element and a positive lens element, and a positive lens component; and the third lens unit being composed of at least one positive lens component and a negative lens component or at least one negative lens component.

IR fast low light level lens system

Abstract: A compound lens for use in a low light level system operating in the near-infrared region. The lens system includes a high light-gathering ability requiring both a large aperture and good transmissivity over the wavelengths of interest. A wide field of view (e.g., 50°) without excessive chromatic and geometric aberrations that generally accompanies systems with a large aperture is provided. Space is provided in the lens system for a variable iris and variable density spot subassembly. Desired optical quantities are obtained through the use of zinc selenide as the material for an aspheric lens. The use of this diamond-turnable infrared material as a field lens yields exceptional performance for a fast (e.g., F/1.25) lens with a wide field of view.

Imaging lens and imaging apparatus using the same

Abstract: An imaging lens formed of 4 lenses, in which a negative first lens having a meniscus shape with a convex surface on the object side, a biconvex positive second lens, a negative third lens having a concave surface on the image side, and a positive fourth lens having a convex surface on the object side, arranged in order from the object side, and the imaging lens satisfies conditional expressions (1): L12/f<0.82; (2): 2.3