Lightweight Optics Research Articles

Wide field of view large aperture meta-doublet eyepiece

Wide field of view and light weight optics are critical for advanced eyewear, with applications in augmented/virtual reality and night vision. Conventional refractive lenses are often stacked to correct aberrations at a wide field of view, leading to limited performance and increased size and weight. In particular, simultaneously achieving a wide field of view and large aperture for light collection is desirable but challenging to realize in a compact form-factor. Here, we demonstrate a wide field of view (greater than 60∘) meta-optic doublet eyepiece with an entrance aperture of 2.1 cm. At the design wavelength of 633 nm, the meta-optic doublet achieves comparable performance to a refractive lens-based eyepiece system. This meta-doublet eyepiece illustrates the potential for meta-optics to play an important role in the development of high-quality monochrome near-eye displays and night vision systems.

Review of: "This field becomes Especially, nanoelectronic lithography has great potential to set new standards for making miniature, low-cost, and light-weight optics that can be used in many fields of applications."

Review of: "This field becomes Especially, nanoelectronic lithography has great potential to set new standards for making miniature, low-cost, and light-weight optics that can be used in many fields of applications."

Review of: "This field becomes Especially, nanoelectronic lithography has great potential to set new standards for making miniature, low-cost, and light-weight optics that can be used in many fields of applications"

Review of: "This field becomes Especially, nanoelectronic lithography has great potential to set new standards for making miniature, low-cost, and light-weight optics that can be used in many fields of applications"

Review of: "This field becomes Especially, nanoelectronic lithography has great potential to set new standards for making miniature, low-cost, and light-weight optics that can be used in many fields of applications."

Review of: "This field becomes Especially, nanoelectronic lithography has great potential to set new standards for making miniature, low-cost, and light-weight optics that can be used in many fields of applications."

Hybrid achromatic microlenses with high numerical apertures and focusing efficiencies across the visible

Compact visible wavelength achromats are essential for miniaturized and lightweight optics. However, fabrication of such achromats has proved to be exceptionally challenging. Here, using subsurface 3D printing inside mesoporous hosts we densely integrate aligned refractive and diffractive elements, forming thin high performance hybrid achromatic imaging micro-optics. Focusing efficiencies of 51–70% are achieved for 15μm thick, 90μm diameter, 0.3 numerical aperture microlenses. Chromatic focal length errors of less than 3% allow these microlenses to form high-quality images under broadband illumination (400–700 nm). Numerical apertures upwards of 0.47 are also achieved at the cost of some focusing efficiency, demonstrating the flexibility of this approach. Furthermore, larger area images are reconstructed from an array of hybrid achromatic microlenses, laying the groundwork for achromatic light-field imagers and displays. The presented approach precisely combines optical components within 3D space to achieve thin lens systems with high focusing efficiencies, high numerical apertures, and low chromatic focusing errors, providing a pathway towards achromatic micro-optical systems.

The simulation of thermal deformation on lightweight optics with thick coatings

Lightweight optics utilized in high-power laser system can dissipate heat better and reduce system weight. Dielectric films can be designed for laser pulse modulation, high reflect rate and wide bandwidth. However, the deformation caused by coating residual stress will be large due to the large thickness of dielectric films and low stiffness of lightweight mirror, which brings a large bending deformation with the temperature variation. The traditional surface compensation technology is double-sided coating, but it is not suitable for lightweight mirrors. In this study, we construct a finite shell-element model to estimate the surface shape error caused by dielectric film coating residual stress on a lightweight mirror for surface pre-processing. Thermal deformation and bimetal effect deformation are also simulated.

Stress-induced deformation of the coating on large lightweight freeform optics.

Large aperture, lightweight optics are frequently utilized in modern optical systems. However, despite the use of advanced techniques for developing their materials, fabrication, and mechanical structure, the coatings placed on the substrates induce slight lattice mismatches and increase the thin film stress on polished surfaces. This significantly distorts nano-accuracy optical surfaces, especially on lightweight freeform surfaces. In this study, we construct a finite element model (FEM) and a ray tracing model to estimate the impact of the stress-induced deformation of the coating on a 1.5m class lightweight silicon carbine (SiC) mirror with a freeform surface. Our simulation results are within 10% deviation from the experimental results, and the deformation texture map matches these results as well. We discuss several possible strategies to overcome stress-induced deformation, including fabrication pre-compensation, lightweight structure redesign, and an inverse print-through effect.

Broadband High-Reflection Dielectric PVD Coating with Low Stress and High Adhesion on PMMA

Polymethyl methacrylate (PMMA) is an attractive optical plastic that is widely used in augmented reality, virtual reality devices, display, wearable devices, portable optical equipment, and lightweight optics. Thin film prepared by physical vapor deposition (PVD) is the primary choice of coating on PMMA. However, it faces problems with coating adhesion and stress. In this paper, we analyze the problems existing in the current PMMA high-reflection (HR) coating in detail and propose a way to effectively solve issues with bonding force and stress. Based on the current research background, the bonding force was enhanced by introducing a special hard coating as the connection layer between the dielectric film and the substrate. After comparing the stresses of different coating materials and material combinations, the optimal combination of Nb2O5 and SiO2 was determined, and the requirements were successfully prepared. An HR coating that satisfies requirements, with low stress and excellent environmental adaptability, was successfully prepared. Based on this, a broadband HR coating from 750 to 1550 nm was formed on the surface of PMMA by adjusting the partial pressure of oxygen.

Fast positioning for X-ray scanning microscopy by a combined motion of sample and beam-defining optics.

Scanning X-ray microscopy such as X-ray ptychography requires accurate and fast positioning of samples in the X-ray beam. Sample stages often have a high mobile mass as they may carry additional mechanics or mirrors for position measurements. The high mobile mass of a piezo stage can introduce vibrations in the setup that will lead to imaging quality deterioration. Sample stages also require a large travel range which results in a slow positioning step response and thus high positioning overhead. Moving lightweight X-ray optics, such as focusing Fresnel zone plates, instead of the sample can improve the situation but it may lead to undesired variations in the illumination probe which may result in reconstruction artifacts. This paper presents a combined approach in which a slow sample stage mechanism covers the long distance range for a large field of view, and a light-weight optics scanner with a small travel range creates a superimposed motion to achieve a fast step response. The step response in the ptychographic tomography instrument used was thereby improved by an order of magnitude, allowing for efficient measurement without loss of imaging quality.

Influence of ply misalignment on form error in the manufacturing of CFRP mirrors

We describe our study conducted within the framework of the design of composite mirrors for use in future generation astronomical telescopes. The work is also relevant to applications requiring lightweight optics and other unidirectional-ply fibre-composite-polymer constructs that require improved accuracy of form. Misalignment of layers (plies) in a composite laminate gives an astigmatic type deformation of the surface after cure. The influence of ply misalignment on surface form has been investigated via a series of finite element analyses. Thirty-two different layup sequences have been investigated: the angular increment between each ply, the number of plies and the number of sequence repeats were varied. Samples with random alignment errors have been simulated in order to compare the robustness of these different layup sequences toward ply misalignment; some design recommendations have been made. The finite element modelling method and results are presented here.

Sputter deposition of PZT piezoelectric films on thin glass substrates for adjustable x-ray optics

Piezoelectric PbZr(0.52)Ti(0.48)O(3) (PZT) thin films deposited on thin glass substrates have been proposed for adjustable optics in future x-ray telescopes. The light weight of these x-ray optics enables large collecting areas, while the capability to correct mirror figure errors with the PZT thin film will allow much higher imaging resolution than possible with conventional lightweight optics. However, the low strain temperature and flexible nature of the thin glass complicate the use of chemical-solution deposition due to warping of the substrate at typical crystallization temperatures for the PZT. RF magnetron sputtering enabled preparation of PZT films with thicknesses up to 3 μm on Schott D263 glass substrates with much less deformation. X-ray diffraction analysis indicated that the films crystallized with the perovskite phase and showed no indication of secondary phases. Films with 1 cm(2) electrodes exhibited relative permittivity values near 1100 and loss tangents below 0.05. In addition, the remanent polarization was 26 μC/cm(2) with coercive fields of 33 kV/cm. The transverse piezoelectric coefficient was as high as -6.1±0.6 C/m(2). To assess influence functions for the x-ray optics application, the piezoelectrically induced deflection of individual cells was measured and compared with finite-element-analysis calculations. The good agreement between the results suggests that actuation of PZT thin films can control mirror figure errors to a precision of about 5 nm, allowing sub-arcsecond imaging.

Reactive atom plasma (RAP) figuring machine for meter class optical surfaces

A new surface figuring machine called Helios 1200 is presented in this paper. It is designed for the figuring of meter sized optical surfaces with form accuracy correction capability better than 20 nm rms within a reduced number of iterations. Unlike other large figuring facilities using energy beams, Helios 1200 operates a plasma torch at atmospheric pressure, offers a high material removal rate, and a relatively low running cost. This facility is ideal to process large optical components, lightweight optics, silicon based and difficult to machine materials, aspheric, and free form surfaces. Also, the surfaces processed by the reactive atom plasma (RAP) are easy to fine polish through hand conventional sub-aperture polishing techniques. These unique combined features lead to a new capability for the fabrication of optical components opening up novel design possibilities for optical engineers. The key technical features of this large RAP machine are fast figuring capabilities, non-contact material removal tool, the use of a near Gaussian footprint energy beam, and a proven tool path strategy for the management of the heat transfer. Helios 1200 complies with the European machine safety standard and can be used with different types of reactive gases using either fluorine or chlorine compounds. In this paper, first the need for large optical component is discussed. Then, the RAP facility is described: radio frequency R.F generator, plasma torch, and 3 axis computer numerically controlled motion system. Both the machine design and the performance of the RAP tool is assessed under specific production conditions and in the context of meter class mirror and lens fabrication.

The imaging performance of the SRC on Mars Express

The Mars Express spacecraft carries the pushbroom scanner high-resolution stereo camera (HRSC) and its added imaging subsystem super resolution channel (SRC). The SRC is equipped with its own optical system and a 1024×1024 framing sensor. SRC produces snapshots with 2.3 m ground pixel size from the nominal spacecraft pericenter height of 250 km, which are typically embedded in the central part of the large HRSC scenes. The salient features of the SRC are its light-weight optics, a reliable CCD detector, and high-speed read-out electronics. The quality and effective visibility of details in the SRC images unfortunately falls short of what has been expected. In cases where thermal balance cannot be reached, artifacts, such as blurring and “ghost features” are observed in the images. In addition, images show large numbers of blemish pixels and are plagued by electronic noise. As a consequence, we have developed various image improving algorithms, which are discussed in this paper. While results are encouraging, further studies of image restoration by dedicated processing appear worthwhile. The SRC has obtained more than 6940 images at the time of writing (1 September 2007), which often show fascinating details in surface morphology. SRC images are highly useful for a variety of applications in planetary geology, for studies of the Mars atmosphere, and for astrometric observations of the Martian satellites. This paper will give a full account of the design philosophy, technical concept, calibration, operation, integration with HRSC, and performance, as well as science accomplishments of the SRC.

X-ray Vision

We are fabricating optics for the hard-x-ray region using electroless nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently stable and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics (nickel has a relatively high density of 8.9 g/cu cm), and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength nickel alloys that permit very thin shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these and other hard-x-ray optics will be reviewed.

Development of Micro-Optics Using Total Internal Reflection for an Optical Tracking Sensor

A compact and lightweight optics that can be used as an optical tracking sensor for a large capacity floppy disk drive (FDD) is proposed. The developed micro-optics is featured with three points in construction. One is the total internal reflection (TIR) in the substrate which requires no coating material. Another is a refraction-type aperture which eliminates the unnecessary light. The last is a Fresnel lens with a blazed relief structure which realizes high diffraction efficiency. The optics is made of plastic molding that is suitable for mass production. The aperture and Fresnel lens patterns on the molding die can be easily fabricated by machining.

Progress in very lightweight optics using graphite fiber composite materials

We report progress in the fabrication of very low areal density (,5 kg/m 2 ) optical mirrors using space-flight-qualified graphite-fiber- reinforced cyanate ester composite materials. Previous attempts have been thwarted by fiber print-through at the surface. We find that the problem can be successfully overcome if the composite is processed to leave a very thin layer of resin at the surface. Results thus far include replicas with surface microroughness ,1 nm rms, midfrequency ripples ,3 nm rms, areal density 2 kg/m 2 at 42-cm aperture, and freedom from print-through after vacuum drying and ion milling. The process is being extended to the fabrication of very lightweight meter-class optics for space UV astronomy applications, x-ray optics, and other ground- and space-based applications. © 1998 Society of Photo-Optical Instrumentation Engi- neers. (S0091-3286(98)04002-1)

The Edison international space observatory and the future of infrared space astronomy

Edison is a 1.7 m long-lived radiatively/mechanically-cooled space observatory proposed to operate over λ ∼ 3 – 100 + μ m using a suite of imaging and spectroscopic instruments. Thanks to innovative use of radiative cooling and very lightweight optics, the total size and mass of the baseline Edison spacecraft is only modestly larger than that of ESA's ISO mission. Thermal models indicate that the optical system will cool radiatively to about 20 K, while mechanical refrigerators now in advanced laboratory development will be used to cool the detectors to temperatures below 2 K. Continuing design work on this project indicates that these cryo-coolers may in fact be used to lower the entire optical system to temperatures as low as 5 K or below. This would achieve the advantages of purely cryogenic space observatories, while avoiding their limitations. Therefore, within a few years, mixed radiative/mechanical systems may replace cryogenic systems for most cooling applications in space. As this is being written, Edison is under consideration by the European Space Agency as a candidate for a ‘Cornerstone’ mission as part of the “Horizon 2000 Plus” process. As such, it is the only candidate for a future infrared space observatory after about 2005.

High-throughput optics for X-ray astronomy (*)(**)

High-throughput X-ray optics are required for future X-ray astronomy missions. These optics are composed of a large number of nested confocal mirrors with very thin thickness in order to reduce the losses due to the obstruction of the mirrors wall and to keep the weight within acceptable values. The replica technique by electroforming the mirrors from mandrels provides a cost-effective solution for the manufacture of these X-ray optical systems. In the paper is reported the application of the electroforming process for the fabrication of the X-ray imaging concentrators for the SAX project and for the JET-X X-ray telescope. Moreover some considerations are given concerning a possible use of more elaborated electroforming processes for manufacturing light-weight large-aperture X-ray optics.

Infrared Technology: Advances 1975-84, Challenges 1985-94

Some of the major accomplishments of infrared technology in the decade 1975-84 are reviewed. The trend most influential on technology was development of sensors for use in space. Advances in technology to make these accomplishments possible include evolution of (1) longer-wavelength detectors, (2) techniques to make large lightweight and adaptive optics, (3) mosaic focal plane arrays using CCDs, and (4) staring sensors. Likely major challenges for the next decade are strategic defense from space, global resource management, and understanding of ecology and astronomy preparatory to space colonization. Technology changes to support these challenges are estimated.