Thanks to their portability, connectivity, and their image performance – which is constantly improving – smartphone cameras (SPCs) have been people’s loyal companions for quite a while now. In the past few years, multicamera systems have become well and truly established, alongside 3D acquisition systems such as time-of-flight (ToF) sensors. This article looks at the evolution and status of SPC imaging technology. After a brief assessment of the SPC market and supply chain, the camera system and optical image formation is described in more detail. Subsequently, the basic requirements and physical limitations of smartphone imaging are examined, and the optical design of state-of-the-art multicameras is reviewed alongside their optical technology and manufacturing process. The evolution of complementary metal oxide semiconductor (CMOS) image sensors and basic image processing is then briefly summarized. Advanced functions such as a zoom, shallow depth-of-field portrait mode, high dynamic range (HDR), and fast focusing are enabled by computational imaging. Optical image stabilization has greatly improved image performance, enabled as it is by built-in sensors such as a gyroscope and accelerometer. Finally, SPCs’ connection interface with telescopes, microscopes, and other auxiliary optical systems is reviewed.

At present, compact camera modules are included in many mobile electronic devices such as mobile phones, personal digital assistants or tablet computers. They have various uses, from snapshots of everyday situations to capturing barcodes for product information. This paper presents an overview of the key design challenges and some typical solutions. A lens design for a mobile phone camera is compared to a downscaled 35 mm format lens to demonstrate the main differences in optical design. Particular attention is given to scaling effects.

Zusammenfassung Smartphonekameras stellen wegen ihrer Kompaktheit hohe Anforderungen an Optik und Bildsensoren. Dies erfordert neue technologische Lösungen. Teil 1 dieser Serie aus zwei Folgen stellt die Optik vor. Dabei gibt die flache Bauweise von Smartphones den Kameraabmessungen enge Grenzen vor. Sie erlaubt Brennweiten von nur wenigen Millimetern, auch die Sensoren müssen entsprechend klein sein. Um trotzdem gute Abbildungsleistungen zu erzielen, werden die kleinen Objektive möglichst lichtstark ausgelegt. Bei der kleinen Bauform erhält man eine große Tiefenschärfe. Die kompakte Bauweise erfordert ausschließlich asphärische Linsen. Diese werden so in Kunststoff inklusive Fassungen gefertigt, dass die Objektive durch Aufeinanderstapeln herstellbar sind. Kurze Telebrennweiten lassen sich durch eine Periskopbauweise mit im Smartphonegehäuse quer liegendem Objektiv realisieren. Heutige Smartphones besitzen in der Regel mehrere Kameras mit unterschiedlichen Festbrennweiten vom Weitwinkel‐ bis in den Telebereich. Eine Software kombiniert diese zu optisch‐elektronischen Hybridzooms.

This paper presents lithographic performance results obtained from the newest member of ASML's TWINSCAN TM platform-based step & scan systems, the TWINSCAN TM XT:1400. The system has been designed to meet the semiconductor industry's aggressive requirements on CD control, overlay and productivity at and below the 65 nm node. This dual stage 193 nm lithographic system combines the worlds highest NA, with excellent overlay and CD control at high throughput on both 200 and 300 mm wafers and is intended for use in volume production environments. Advances in stage technology have enabled further extension of stage scan speeds and an associated increase in tool productivity. However, maximizing the number of yielding die per day also requires stringent overlay and Critical Dimension (CD) control. Tight CD control at improved resolution is supported by the Starlith TM 1400 projection lens and the extended sigma capabilities of the new AERIAL TM -E illumination system. Focus control is improved in line with the stringent requirements posed by low-k 1 imaging applications, taking full advantage of the unique dual-stage TWINSCAN TM system architecture.

There is a surprising lack of clarity about the exact quantity that a lithographic source map should specify. Under the plausible interpretation that input source maps should tabulate radiance, one will find with standard imaging codes that simulated wafer plane source intensities appear to violate the brightness theorem. The apparent deviation (a cosine factor in the illumination pupil) represents one of many obliquity/inclination factors involved in propagation through the imaging system whose interpretation in the literature is often somewhat obscure, but which have become numerically significant in today's hyper-NA OPC applications. We show that the seeming brightness distortion in the illumination pupil arises because the customary direction-cosine gridding of this aperture yields non-uniform solid-angle subtense in the source pixels. Once the appropriate solid angle factor is included, each entry in the source map becomes proportional to the total |E|^2 that the associated pixel produces on the mask. This quantitative definition of lithographic source distributions is consistent with the plane-wave spectrum approach adopted by litho simulators, in that these simulators essentially propagate |E|^2 along the interfering diffraction orders from the mask input to the resist film. It can be shown using either the rigorous Franz formulation of vector diffraction theory, or an angular spectrum approach, that such an |E|^2 plane-wave weighting will provide the standard inclination factor if the source elements are incoherent and the mask model is accurate. This inclination factor is usually derived from a classical Rayleigh-Sommerfeld diffraction integral, and we show that the nominally discrepant inclination factors used by the various diffraction integrals of this class can all be made to yield the same result as the Franz formula when rigorous mask simulation is employed, and further that these cosine factors have a simple geometrical interpretation. On this basis one can then obtain for the lens as a whole the standard mask-to-wafer obliquity factor used by litho simulators. This obliquity factor is shown to express the brightness invariance theorem, making the simulator's output consistent with the brightness theorem if the source map tabulates the product of radiance and pixel solid angle, as our source definition specifies. We show by experiment that dose-to-clear data can be modeled more accurately when the correct obliquity factor is used.