Apochromat

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

Microscope objective lens

Abstract: PROBLEM TO BE SOLVED: To realize a high-magnification apochromat microscope objective lens constituted of the comparatively small number of lenses and obtained by sufficiently correcting chromatic coma aberration at the peripheral part of an image SOLUTION: A front group provided with positive refractive power is constituted by including a 1st meniscus lens which is provided with the positive refractive power and whose concave surface is made to face an object side, a 2nd meniscus lens which is provided with the positive refractive power and whose concave surface is made to face the object side, a 3rd lens provided with the positive refractive power, a 4th biconcave lens provided with negative refractive power and a 5th biconvex lens provided with the positive refractive power A rear group provided with the negative refractive power is constituted of at least two positive lenses and at least two negative lenses When the focal distance of a whole system is defined as (f), the focal distance of the 4th lens in the front group is defined as (f4 ), the focal distance of the rear group is defined as (fii ), the average value of the Abbe's numbers of the positive lenses in the rear group is defined as νp and the average value of the Abbe's numbers of the negative lenses in the rear group is defined as νn , the conditions of (1) 3<|f4 /f|<8, (2) 2<|fii /f|<5 and (3) νp /νn are satisfied

Continuous Measurement of Particle Depth in a Microchannel Using Chromatic Aberration

Abstract: Detecting the z-position of moving objects in an embedded microchannel is an important but highly challenging problem in the MEMS field. The present study proposes a new depth measurement system based on the chromatic aberration effect under a dark-field illumination scheme. The microchannel is illuminated by dispersed white light and the light scattered from the moving objects is captured by a low numerical aperture (N.A.) objective lens. Due to chromatic aberration effect, sample in various positions will scatter different wavelengths. The depth of each moving object is then determined by inspecting the intensity ratio of the scattered spectral components with wavelengths of 450 nm (blue light) and 670 nm (red light), respectively. Experimental results show that the proposed system enables the object depth to be measured over a range of ±15 μm while using acrylic lens for light aberration. Alternatively, the developed system is capable to discriminate the depth change of 2 μm micro-beads when a higher Abbe number material of BK7 lens is used for light aberration. The depth measurements are obtained without the need for a delicate optical system or scanning process with the developed system. The use of UV-Vis-NIR spectrometer enables this system to analyze the depths of the samples in flow velocity 500 μm/sec. The proposed system provides a straightforward yet highly effective means of determining the depth of moving objects in microfluidic channels in a continuous manner.

Correction to “Filtering Chromatic Aberration for Wide Acceptance Angle Electrostatic Lenses II—Experimental Evaluation and Software-Based Imaging Energy Analyzer”

Abstract: Here, the experimental results of the method of filtering the effect of chromatic aberration for wide acceptance angle electrostatic lens-based system are described. This method can eliminate the effect of chromatic aberration from the images of a measured spectral image sequence by determining and removing the effect of higher and lower kinetic energy electrons on each different energy image, which leads to significant improvement of image and spectral quality. The method is based on the numerical solution of a large system of linear equations and equivalent with a multivariate strongly nonlinear deconvolution method. A matrix whose elements describe the strongly nonlinear chromatic aberration-related transmission function of the lens system acts on the vector of the ordered pixels of the distortion free spectral image sequence, and produces the vector of the ordered pixels of the measured spectral image sequence. Since the method can be applied not only on 2D real- and $k$ -space diffraction images, but also along a third dimension of the image sequence that is along the optical or in the 3D parameter space, the energy axis, it functions as a software-based imaging energy analyzer (SBIEA). It can also be applied in cases of light or other type of optics for different optical aberrations and distortions. In case of electron optics, the SBIEA method makes possible the spectral imaging without the application of any other energy filter. It is notable that this method also eliminates the disturbing background significantly in the present investigated case of reflection electron energy loss spectra. It eliminates the instrumental effects and makes possible to measure the real physical processes better.

Color-selective geometric phase lens for apochromatic lens system

Abstract: Thin lenses have potentially much lower weight and volume than traditional refractive lenses, and therefore enable compelling solutions in augmented-/virtual-/mixed-reality (AR/VR/MR) headsets. The geometric-phase lens (GPL), formed either with liquid crystals (LCs) or metasurfaces, is emerging as a leading technology because of its ability to implement arbitrary aspherical phase profiles and its potential for low loss and minimal ghosting. However, a strong chromatic dispersion is inherent to each singlet. One prior method to overcome this employs a stack of multiple achromatic GPLs acting on all colors simultaneously with color filters and other waveplates to achieve an apochromatic lens system. Another concept in the prior art is to use multiple color-selective GPLs (CS-GPLs) wherein each diffracts only a single color while transmitting the others. In this work, we report on a family of color-selective GPLs with highly chromatic efficiency spectra, made using multi-twist LC coatings. In both theory and experiment, we show the diffraction efficiency of red, green, and blue lenses is high (< 91%) while the complementary colors of each coating are almost fully transmitted undiffracted. The CS-GPLs is a promising optical element to provide a new route to mitigate the chromatic abberation in the AR/VR/MR lens system.