In order to solve the problem of the short working distance of the microscope objective in a large aperture, this paper designs a 50× microscope objective with a numerical aperture of 0.75 and a long working distance of 6.2 mm. The objective achieves flat-field and apochromatic for the wavelength range from 436 to 656 nm and maintains high focusing quality in both femtosecond laser (770-790 nm) and YAG laser (1059-1069 nm) ranges. The performance evaluations of the objective show that the resolution reaches 2200 lp/mm, and the modulation transfer function (MTF) indicates that the image quality is close to the diffraction limit within the working ranges. The tolerance analysis reveals that the design meets the requirements for mass production. This paper provides a solution for semiconductor defect detection by combining high resolution with a large working distance.

Optical glass selection is an important research object in optical design, which is an important way to aberration correction. However, these methods to our knowledge either do not correct aberration well or consume too much time. To efficiently solve the apochromatic problems in optical design, this paper presents what we believe to be a novel automatic optimization method for discontinuous optical glass based on auto glass selection (AGS). The method first calculates several aberrations related to glass materials in the optical system to select candidate optical glasses, which include longitudinal aberration, lateral chromatic aberration, and Petzval sum. It then skillfully explores the candidate optical glass list for the optimization of discontinuous glass. Using a flat-field apochromatic microscope and a wide-angle lens as examples, this method demonstrates its superiority in aberration correction and efficiency, can be automated optimization, requires relatively less computational effort, and achieves fast and stable convergence of results.

In this paper, we present a method based on the conjugate image principle and micro-nano optics to detect tilt aberrations of a phased fiber laser array system. A co-aperture optics system was adapted to detect the tilt aberrations of a seven-element phased fiber laser array system simultaneously. A Kepler telescope was designed to construct the conjugate relation between the exit pupil of a fiber optic laser array system and a microlens array and also to match the size of the seven beams and the microlens array. The apochromatic theory was used to meet the multispectral (1064 ± 0.3 nm, 1030 ± 0.3 nm, and 633 ± 0.2 nm) detection needs. A far-field detection unit was also designed to evaluate beam quality. When the actual beam was offset by 1 pixel, the beam tilt was about 0.7 µrad. The maximum detection error of the seven-element system was about 7 µrad. It could not only directly detect the beam's tilt angle but also maintained detection accuracy while reducing the algorithm complexity.

A theoretical analysis of an afocal compensator of the secondary longitudinal chromatic aberration is provided. Such a compensator is able to compensate for chromatic aberration of an achromatic optical system and make an apochromatic correction of the system. The parameters of the proposed chromatic aberration compensator are described and the principle is presented in examples.

This work proposes an optimization algorithm in optical design based on the concepts of ergodic and stochastic processes in statistical mechanics. In mixed-variable optimization problems, pseudo-random number and discrete-to-continuous variable conversion dramatically increase the speed at which the system solves for the optimal solution. Pseudo-random numbers are mainly applied in two important steps in the optimization algorithm: determining the combination of glasses involved and the order in which the successive glass parameters are replaced by real glasses. After two series of stochastic processes, the merit function value decreases rapidly along the steepest descent path, and thus the optical system approaches the optimal solution within a very short duration of time. By using the method proposed in this paper, a plan apochromatic objective with a long working distance was optimized, and finally, a high-quality optical system was obtained.

The investigation of deep-sea microorganisms holds immense significance and value in advancing the fields of life sciences, biotechnology, and environmental conservation. However, the current lack of specialized underwater objectives specifically designed for in situ studies of deep-sea microorganisms hampers progress in this area. To address this limitation, we present the design of a multi-band Raman tweezer objective tailored for deep-sea environments. The objective is integrated into a high-pressure chamber capable of withstanding depths up to 1.5 km, enabling in situ microscopic imaging, optical tweezer capture, and Raman detection of deep-sea microorganisms. Through meticulous structural optimization, meticulous material selection, and thorough mechanical analysis of the underwater optical window, the objective exhibits remarkable attributes such as multi-band functionality, extended working distance, and high numerical aperture. Our design yields image quality near the diffraction limit, successfully achieving flat-field and apochromatic performance in each respective wavelength bands. Moreover, the tolerance analysis demonstrates that the full-field root mean square (RMS) wave aberration approaches λ/14, effectively meeting the demands of manufacturing and practical applications. This objective lens constitutes a vital tool for the in situ exploration of deep-sea microorganisms.

It is important to determine the ideal combination of housing materials, groups of refractive materials, and their optical powers for athermalizing achromatic and apochromatic optical systems. This study proposes a combined design approach that utilizes three or more glass types to resolve thermal aberrations and defocus achromatic and apochromatic optical systems. It selects a suitable glass type using a 3D glass chart and calculates the optical power analytically. Furthermore, a temperature-insensitive optical system with a 450-750 nm band based on refractive materials (CDGM Glass Co., Ltd.) is designed, with the modular transfer function value of the center field of view decreasing by less than 0.024 in the temperature range of -40[∘] C to +80[∘] C and the secondary spectrum aberration decreasing by over three times and being maintained within 0.08 mm.

Planar super-oscillatory lens (SOL), a far-field subwavelength-focusing diffractive device, holds great potential for achieving sub-diffraction-limit imaging at multiple wavelengths. However, conventional SOL devices suffer from a numerical-aperture-related intrinsic tradeoff among the depth of focus (DoF), chromatic dispersion and focusing spot size. Here, we apply a multi-objective genetic algorithm (GA) optimization approach to design an apochromatic binary-phase SOL having a prolonged DoF, customized working distance (WD), minimized main-lobe size, and suppressed side-lobe intensity. Experimental implementation demonstrates simultaneous focusing of blue, green and red light beams into an optical needle of ~0.5λ in diameter and DOF > 10λ at WD = 428 μm. By integrating this SOL device with a commercial fluorescence microscope, we perform, for the first time, three-dimensional super-resolution multicolor fluorescence imaging of the "unseen" fine structures of neurons. The present study provides not only a practical route to far-field multicolor super-resolution imaging but also a viable approach for constructing imaging systems avoiding complex sample positioning and unfavorable photobleaching.

Achromatic doublets are combinations of two individual lenses designed to focus different wavelengths of light in the same position. Apochromatic optics are improved versions of the achromatic schemes which extend the wavelength range significantly. Both achromatic and apochromatic optics are well-established for visible light. However, X-ray achromatic lenses did not exist until very recently, and X-ray apochromatic lenses have never been experimentally demonstrated. Here, we create an X-ray apochromatic lens system using an appropriate combination of a Fresnel zone plate and a diverging compound refractive lens with a tuned separation distance. The energy-dependent performance of this apochromat was characterized at photon energies between 6.5 and 13.0 keV by ptychographic reconstruction of the focal spot and scanning transmission X-ray microscopy of a resolution test sample. The apochromat delivered a reconstructed focal spot size of 940 × 740 nm[2]. The apochromatic combination shows a four-fold improvement in the chromatic aberration correction range compared to an achromatic doublet configuration. Thus, apochromatic X-ray optics have the potential to increase the focal spot intensity for a wide variety of X-ray applications.

Achromatic focusing systems for hard X-rays are examined which consist of a refractive lens paired with a diffractive lens. Compared with previous analyses, we take into account the behaviour of thick refractive lenses, such as compound refractive lenses and waveguide gradient index refractive lenses, in which both the focal length and the position of the principal planes vary with wavelength. Achromatic systems formed by the combination of such a thick refractive lens with a multilayer Laue lens are found that can operate at a focusing resolution of about 3 nm, over a relative bandwidth of about 1%. With the appropriate distance between the refractive and diffractive lenses, apochromatic systems can also be found, which operate over relative bandwidth greater than 10%. These systems can be used to focus short pulses without distorting them in time by more than several attoseconds. Such systems are suitable for high-flux scanning microscopy and for creating high intensities from attosecond X-ray pulses.

Three-dimensional (3D) direct laser writing is a powerful technology to create nano- and microscopic optical devices. While the design freedom of this technology offers the possibility to reduce different monochromatic aberrations, reducing chromatic aberrations is often neglected. In this Letter, we successfully demonstrate the combination of refractive and diffractive surfaces to create a refractive/diffractive achromat and show, to the best of our knowledge, the first refractive/diffractive apochromat by using DOEs and simultaneously combining two different photoresists, namely IP-S and IP-n162. These combinations drastically reduce chromatic aberrations in 3D printed micro-optics for the visible wavelength range. The optical properties, as well as the substantial reduction of chromatic aberrations, are characterized, and we outline the benefits of 3D direct laser written achromats and apochromats for micro-optics.

We present the development of a dual-mode imaging platform that combines optical microscopy with magnetic resonance microscopy. Our microscope is designed to operate inside a 9.4T small animal scanner with the option to use a 72mm bore animal RF coil or different integrated linear micro coils. With a design that minimizes the magnetic distortions near the sample, we achieved a field inhomogeneity of 19 ppb RMS. We further integrated a waveguide in the optical layout for the electromagnetic shielding of the camera, which minimizes the noise increase in the MR and optical images below practical relevance. The optical layout uses an adaptive lens for focusing, 2 × 2 modular combinations of objectives with 0.6mm to 2.3mm field of view and 4 configurable RGBW illumination channels and achieves a plano-apochromatic optical aberration correction with 0.6μm to 2.3μm resolution. We present the design, implementation and characterization of the prototype including the general optical and MR-compatible design strategies, a knife-edge optical characterization and different concurrent imaging demonstrations.

A novel technique is developed to improve the resolution of two-photon direct laser writing lithography. Thanks to the high collimation enabled by extraordinary εNZ (near-zero) metamaterial features, ultrathin dielectric hyper-resolute nanostructures are within reach. With respect to the standard direct laser writing approach, a size reduction of 89% and 50%, in height and width respectively, is achieved with the height of the structures adjustable between 5 and 50 nm. The retrieved 2D fabrication parameters are exploited for realizing extremely thin all-dielectric metalenses tailored through deep machine learning codes. The hyper-resolution achieved in the writing process enables the fabrication of a highly detailed dielectric 3D bas-relief (with full height of 500 nm) of Da Vinci's "Lady with an Ermine". The proof-of-concept results show intriguing cues for the current and trendsetting research scenario in anti-counterfeiting applications and ultracompact photonics, paving the way for the realization of all-dielectric and apochromatic ultrathin imaging systems.

We develop a multimodal imaging platform, combining depth-resolved scattering contrast from spectral-domain optical coherence tomography (SD-OCT) with complementary, non-contact absorption contrast using photoacoustic remote sensing (PARS) microscopy. The system provides a widefield OCT mode using a telecentric scan lens, and a high-resolution, dual-contrast mode using a 0.26 numerical aperture apochromatic objective. An interlaced acquisition approach is used to achieve simultaneous, co-registered imaging. The SD-OCT modality provides a 9.7 µm axial resolution. Comprehensive in vivo imaging of a nude mouse ear is demonstrated, with the SD-OCT scattering intensity revealing dermal morphology, and PARS microscopy providing a map of microvasculature.