Showing papers on "Apochromat published in 2000"

Apochromatic optical correlation.

Abstract: Optical correlation, or matched filtering, can now be applied more widely than before, because the light is now allowed to be totally incoherent, spatially and spectrally. Two such correlators were demonstrated recently. Their state of chromatic correction can be called achromatic, since the scaling error has two zero crossings within the visible range of wavelengths. We present a new apochromatic correlator, in which the scaling error has three zero crossings. The maximum error and the rms error are reduced by a factor of 5. Our apochromatic correlator is composed of two highly dispersive heavy flint lenses that are in contact with two diffractive lenses and two chromatic corrected refractive lenses. The uncommon combination of flint dispersion and diffractive dispersion enabled us to achieve apochromatic correction of the scaling factor of the correlator.

Microscope connected to image processor for simultaneous monitoring of photographed object on projector

Abstract: A spherical aberration lens adjusts spherical aberration of a digital-camera lens (90) and the chromatic aberration lens adjusts the chromatic aberration of light output by lens barrel. An enlargement lens increases the size of the image more than that viewed through objective lens (30) which is then fed to computer.

A study of first- and third-order chromatic aberrations for electrostatic round lenses

Abstract: In this paper the first- and third-order chromatic aberrations of electrostatic round lenses have been studied based on the electron optical-canonical aberration theory. The present work uses the Hamiltonian function expansion method to derive all analytical expressions of the first- and third-order chromatic aberration coefficients instead of the generalized integration transformation method. Its advantage is that it is much simpler. An application to bi-potential immersion lens has been illustrated. It is hoped that this work would be helpful for investigating high-order electron optical aberrations in rotationally symmetric lenses, including geometric aberrations.

Stability of the spherical aberration up to the fifth order in cemented doublets

Abstract: A theoretical method is proposed to calculate variations in the spherical aberration up to fifth order in cemented doublets when some of the parameters that specify the system are modified. This method permits the evaluation of the stability of the spherical aberration with variations in the refractive indices and Abbe numbers of the glasses and radii of the lenses. Using this procedure we have verified that the so-called tangent doublets have a higher stability than those which are not of a tangent type.

Null lens design for small aspherical surface with large NA

Abstract: To test the small aspherical mold surface with large NA, we develop a kind of null lens system which is made up of four thin lenses, the first two thin lenses form a system with small NA which is mainly used to produce positive spherical aberration; the other two thin lens form a large NA system which offers negative spherical aberration; the latter together with that of the front two elements meets the null testing need. The wavefront variation of testing system due to the manufacture & test & assembly and adjustments error is analyzed, by this analyses, we know that we are capable of measuring the aspherical surface to the accuracy of 0.05λ, it is enough to satisfy the testing of mold surface of compact disc object lenses.

IODC 1998 Lens Design Problem Revisited: A Strategy for Simplifying Glass Choices in an Apochromatic Design

Abstract: A glass-choice strategy, based on separately designing an achromatic lens before progressing to an apochromatic lens, simplified my approach to solving the International Optical Design Conference (IODC) 1998 lens design problem. The glasses that are needed to make the lens apochromatic are combined into triplet correctors with two ''buried'' surfaces. By applying this strategy, I reached successful solutions that used only six glasses--three glasses for the achromatic design and three additional glasses for the apochromatic design.

Wide-field aberration corrector for spherical primary mirrors

Abstract: The cost of astrographs with pupil diameters greater than 1 or 2 meters can be somewhat reduced if the primary mirror is made spherical and the aberration corrected at or near the prime focus, thus avoiding the classical Schmidt or Maksutov full pupil diameter refractive components. Such a corrector solution is presented here for large spherical primaries with speeds up to f/4. This is based on the KiwiStar principle presented here in 1997, in which a large spherical-concentric catoptric is combined by pupil transfer with a smaller spherical-concentric catadioptic to give well-corrected wide-field images of high speed and broad passband. The designs studied at the time were limited to those with entrance pupils 8 pixels of 5μm dimension. An extended design with an 8m diameter primary is also shown, that may be scalable to ~30m. To achieve this performance, the strictly concentric format of the original KiwiStar design has been relaxed, thus providing extra degrees of freedom to compensate the large pupil aberrations introduced by the spherical aberration of the primary. Nevertheless, the new design still has only one relatively small and weak aspheric surface to provide zonal correction, all other surfaces being spherical.

Simple system of aberration correction for very large spherical primary mirrors

Abstract: Several large telescopes are now being proposed that would benefit from the cost reduction due to the use of spherical primary mirror. However, structural cost constraints require compact formats that tend to impose very high speeds, e.g. f/1.5, which renders difficult the correction of the resulting very large spherical aberration. A technique is described here in which a spherical concentric Cassegrain-like primary-secondary combination is followed by a simple catadioptric focal modifier. The spherical primary is 9m diameter, f/1.5, and the final focus is f/5 with a sub-arcsecond resolution over a 5 arcminute angular field for a passband of 480-850nm. Primary- secondary separation is only 11m and central obscuration is only 11% of pupil area. The two relatively small corrector components provide the functions of concentric meniscus and zonal corrector plate and are made from the same single glass- BK7 is the example given, but silica or any other preferred glass is possible. The relatively small zonal corrector is the only aspheric surface in the entire system. A related system is described elsewhere in which a 30 arcminute angular field can be achieved with a similar resolution, but with more complex glass requirements. However, supply of such exotic glasses may be difficult in large diameters, and the system presented here may find a place in some specialized applications.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.