Reflecting Microscope Objective Research Articles

Off-axis reflective microscope objective with a centimeter scale field of view and micron resolution.

Microscope objectives with wide field-of-view (FOV) and high resolution are urgently needed for the frontier research in life sciences. However, traditional transmission microscope objectives typically have a narrow FOV and severe chromatic aberration. A new off-axis reflective microscope objective with a centimeter scale FOV and micron resolution is proposed in this paper. This objective, with its simple structure, can operate over a wide wavelength range. A design method for a wide FOV optical system is presented, which can eliminate the obstruction of the rays and control the intermediate image plane. Using this method, we design a novel off-axis four-mirror microscope objective with a FOV of 10 mm × 1.5 mm and a numerical aperture of 0.33.

Multi-field cosine condition in the design of wide-field freeform microscope objectives.

To break through the limitations of the classical sine condition, a multi-field cosine condition (MCC) is proposed in this paper. Building on this condition, a design method for wide field-of-view (FOV) freeform aplanatic systems is also proposed. This design method ensures that the optical system meets the MCC by correcting the mapping relationships of rays that originate from different apertures on both the object and image sides of the optical system. Using this method, we have successfully designed a chromatic-aberration-free and unobstructed freeform off-axis reflective microscope objective that is characterized by a wide FOV, an extensive spectral working range, and an extended working distance. The objective, which comprises only three freeform mirrors, has a numerical aperture (NA) of 0.4, magnification of 20×, an FOV of 2mm × 2 mm, and an extended working distance of up to 60 mm. The objective demonstrates imaging quality close to the diffraction limit across the visible band to the short-wave infrared band (0.4-3 µm). When compared with a transmission-type wide-field microscope objective with identical NA and magnification properties, the reflective microscope objective nearly triples the FOV.

Application of a reflective microscope objective for multiphoton microscopy.

Reflective objectives (ROs) mitigate chromatic aberration across a broad wavelength range. Yet, a systematic performance characterisation of ROs has not been done. In this paper, we compare the performance of a 0.5 numerical-aperture (NA) reflective objective (RO) with a 0.55 NA standard glass objective (SO), using two-photon fluorescence (TPF) and second-harmonic generation (SHG). For experiments spanning ∼1 octave in the visible and NIR wavelengths, the SO leads to defocusing errors of 25-40% for TPF images of subdiffraction fluorescent beads and 10-12% for SHG images of collagen fibres. The corresponding error for the RO is ∼4% for both imaging modalities. This work emphasises the potential utility of ROs for multimodal multiphoton microscopy applications.

45.5X Infinity Corrected Schwarzschild Microscope Objective Lens Design

In this article, the design of a 45.5X (numerical aperture (NA) =0.5) infinity corrected, or infinite conjugate, Schwarzschild reflective microscope objective lens is discussed. Fast Fourier transform modulation transfer function (FFT MTF= 568.4 lines/mm at 50% contrast for the on-axis field-of-view), root-mean-square wavefront error (RMS WFE= 0.024 waves at 700 nm), point spread function (PSF, Strehl ratio= 0.972), encircled energy (0.88 µm spot radius at 80% fraction of enclosed energy), optical path difference (OPD=-0.644 waves) and Seidel coefficients calculated with Zemax® are provided to show that the design is diffraction-limited and aberration-free. Furthermore, formulas expressing the relationship between the parameters of the two spherical mirrors and the Schwarzschild objective lens focal length are given. In addition, tolerance and sensitivity analysis for the Schwarzschild objective lens, two spherical mirrors indicate that tilting the concave mirror (or secondary mirror) has a higher impact on the modulation transfer function values than tilts introduced by the convex mirror (or primary mirror). Finally, the performed tolerance and sensitivity analysis on the lens design suggests that decentering any of the mirrors by the same distance has the same effect on the modulation transfer function values.

Extended transient-grating self-referenced spectral interferometry for sub-100 nJ femtosecond pulse characterization

A geometry of transient-grating self-referenced spectral interferometry (TG-SRSI) is proposed for weak femtosecond pulse characterization. By using a reflective microscope objective (RMO), we build a compact, robust, and easy to adjust device with a higher sensitivity to pulse energy in comparison to all previous SRSI methods. A 65 nJ/∼40 fs/1 kHz pulse at 800 nm is successfully characterized, which speaks to the capability of our device to characterize a weak pulse. It is expected to extend the TG-SRSI method to the characterization of femtosecond pulses from oscillators in the near future.

Common path Fourier domain optical coherence tomography based on multiple reflections within the sample arm

We present a common path Fourier domain optical coherence tomography (FDOCT) setup where the reference signal arises from multiple reflections within the sample arm. Two configurations are demonstrated. The first is based on a reflective microscope objective while the second is based on a normal (refractive) microscope objective. The second configuration is effectively a Mireau interferometer. We present a sensitivity analysis of these setups and images of in vivo skin. Advantages of both common path arrangements include: 1) the reference surface is not close to the sample surface while keeping the optical path lengths matched (so the additional interferometer is not needed) and 2) the user can independently control reference and sample arm power. Additionally, the configuration using the refractive objective ensures that the coherence gate and focus gate always match. A disadvantage is that the reference arm power in certain circumstances is not optimal (i.e. close to saturating the CCD). However, this issue can be removed by a light source of sufficient output power. We believe the idea is scalable and therefore of interest to endoscopy applications.

Fourier transform infrared transmission microspectroscopy of photonic crystal structures

The detailed microscopic characterization of photonic crystal (PC) structures is challenging due to their small sizes. Generally, only the gross macroscopic behavior can be determined. This leaves in question the performance at the basic structure level. The single-incident-angle plane-wave transmittances of one-dimensional photonic crystal (PC) structures are extracted from multiple-incident-angle, focused-beam measurements. In the experimental apparatus, an infrared beam is focused by a reflecting microscope objective to produce an incident beam. This beam can be modeled as multiple, variable-intensity plane waves incident on the PC structure. The transmittance of the structure in response to a multiple-incident-angle composite beam is measured. The composite beam measurement is repeated at various incident angle orientations with respect to the sample normal so that, at each angular orientation, the included set of single-angle plane-wave components is unique. A set of measurements recorded over a range of angular orientations results in an underspecified matrix algebra problem. Regularization techniques can be applied to the problem to extract the single-angle plane-wave response of the structure from the composite measurements. Experimental results show very good agreement between the measured and theoretical single-angle plane-wave transmittances.

Sensitive light-scattering detection–magnetophoretic acceleration mass analysis of single microparticles in an atmosphere

Optically detected magnetophoretic acceleration mass analysis of an individual micro-particle in an atmosphere has been remarkably improved in sensitivity by using a reflective microscope objective, by which forward scattered light from a particle could be effectively collected. From the light-scattering simulation, the detection limit for the radius of a micro-particle was estimated to be smaller than 0.4μm, and about 60 times intensity enhancement was observed for a polystyrene particle with a radius of 2.8μm. For both paramagnetic and diamagnetic micro-particles, the mass magnetic susceptibility and the relaxation time could be determined without knowing any parameters of the particles. From the relaxation time, the mass of a particle was obtained if the radius or the density of the particle was known. For a test sample silica particles were used to adsorb paramagnetic dysprosium(III), the surface concentration of dysprosium(III) on a single particle could be successfully determined by use of this method.

Fast microtomography using high energy synchrotron radiation

At the High Energy Beamline ID15A at the European Synchrotron Radiation Facility we have developed a fast three-dimensional x-ray microtomography system, which acquires a complete dataset in typically less than 10s. This unprecedented speed is achieved by combining a high efficiency phosphor screen, a reflecting microscope objective and a fast charge coupled device detector with the very intense high-energy white beam radiation provided by a wiggler source. The achieved spatial resolution is 2μm. The available x-ray energy spectrum spans from 20to250keV and can therefore be used for low and high Z materials. The spectrum can be modified by inserting different filters into the x-ray beam in order to optimize the signal-to-noise ratio and to avoid beam-hardening artifacts. Different phosphors with different energy sensitivity can be used. The very high speed allows in situ studies of systems evolving on the time scale of a few seconds or minutes. Three examples are given on sintering of metallic powders, solidification of binary alloys and liquid front propagation in granular materials.

Compact high-aperture optical setup for excitation of dynamic gratings by ultrashort light pulses

A stable and compact experimental setup for excitation and investigation of large-wave-vector dynamic gratings by ultrashort light pulses is proposed. Its essential parts are an optical transmission diffraction grating and a large-aperture reflecting microscope objective. Varying the demagnification allows one to change the period of the dynamic grating that is created. The working principle and performance are demonstrated by measurement of the dephasing times of TO phonon–polaritons in GaP. The lower limits of the applicable pump pulse duration are analyzed by ray-tracing calculation.

Analysis of trace level peptides using capillary electrophoresis with UV laser-induced fluorescence

In order to measure trace level peptides (< 1 μM) in exceedingly small sample sizes (< 100 pl) from neuronal or subneuronal samples, sophisticated separation and detection methods are required. Novel instrumentation is described that employs UV laser excitation of fluorescamine labeled peptides for fluorescence detection in capillary electrophoresis. Small injections of standard analyte mixtures or biological samples are efficiently separated on the basis of their electrophoretic mobilities in an electric field applied across the capillary. For sensitive detection, we use the 354 nm line from a helium-cadmium laser for excitation, a reflecting microscope objective for fluorescence collection, and a photomultiplier tube for photon counting. A large excess of fluorescamine derivatizes amino acids and peptides down to concentrations of 10 nM with a previously unreported but manageable fluorescence background resulting from reagent hydrolysis and impurities. This detection method gives a linear working range of four orders of magnitude and a limit of detection for labeled Aplysia californica egg-laying hormone of 2.3 × 10 −9 M. Finally, assays of individual Aplysia c. neurons produce electropherograms unique to the identified neuron type and peaks corresponding to peptide standards.

The Scanning Photoelectron Microscope : A Novel Tool in Surface Science

Photoelectron microscopes using electron optics had been built long before. Until recently these microscopes were not widely used in surface science due to unsufficient vacuum conditions as well as weak image intensifying devices. In this paper we will present a new approach to photoelectron microscopy, the Scanning Photoelectron Microscope (SPM).Photoelectron emission will occur as soon as the photon energy is higher than the work function on the illuminated area. Since work functions never exceed 6.5 eV, ultraviolet (UV) light with λ ≥ 190 nm will be appropriate. This kind of radiation is a very gentle probe, even for sensitive adlayers.The experimental setup is shown schematicaly in Fig. 1. A UV light optics outside the ultra high vacuum (UHV) system focusses the actual 30 W Deuterium discharge lamp through a grid monochromator onto a small aperture (50 to 400 microns). The aperture hole is projected with a reflecting microscope objective (Schwarzschild type) onto the surface of the sample yielding a lateral resolution of about 3 microns.

Fourier emission infrared microspectrophotometer for surface analysis—I. Application to lubrication problems

A Beckman-RIIC FS-720 far-infrared interferometer was converted into an emission microspectrophotometer for surface analysis. To cover the mid-infrared as well as the far-infrared the Mylar beamsplitter was made replaceable by a germanium-coated salt plate, and the Moiré fringe counting system used to locate the moveable Michelson mirror was improved to read 0.5 μm of mirror displacement. Digital electronics and a dedicated minicomputer were installed for data collection and processing. The most critical element for the recording of weak emission spectra from small areas was, however, a reflecting microscope objective and phase-locked signal detection with simultaneous referencing to a blackbody source. An application of the technique to lubrication problems is shown.

Non-dispersive atomic fluorescence spectrometry with a carbon filament atom reservoir

The non-dispersive atomic fluorescence spectrometric determination of Bi, Cd, Hg, Te, Tl and Zn on a carbon filament atom reservoir with electrodeless discharge lamp sources and reflecting microscope objective lenses is described. The non-dispersive system shows distinct advantages for an element such as tellurium whose principal fluorescence lines fall within the useful range of the solar-blind photomultiplier detector, and marginal advantages for mercury, cadmium and zinc where only one line is within the detector range. It is inferior for bismuth, thallium and lead where lines lie at the extremes of the useful detector range. The technique was applied successfully to the determination of cadmium (0.012%) in a copper-base alloy.

A New Reflecting Microscope Objective with Two Concentric Spherical Mirrors

A New Reflecting Microscope Objective with Two Concentric Spherical Mirrors

Improved Ultraviolet Microbeam Apparatus

An ultraviolet microbeam apparatus utilizing the principle of incident illumination has been developed for the irradiation of small parts of living cells or other microscopic objects. A reflecting microscope objective is used simultaneously in a visible light viewing-aiming system and in a bombardment system to focus a spot of ultraviolet light (as small as one micron in diameter) onto part of an experimental preparation. Provision is made in the apparatus for auxiliary phase contrast viewing and for monitoring of the energy in the microbeam. Details of construction and alignment are given and the distribution of intensities in the microbeam is discussed.

Reflecting Objective for Microspectroscopy*

Interest in the low-temperature ultraviolet absorption spectra of biological materials has led to the design and construction of a reflecting microscope objective in which the conventional, two-element system is modified by the addition of a reflecting correction plate. The system has high aperture, low central obstruction, long working distance, and zero chromatic aberration. The correction plate simplifies certain problems in construction and eliminates the need for figuring surfaces with deep curvatures.