Electrically tunable phase gratings are able to steer an incoming light beam without employing movable parts. Here, we present the design and implementation of a 2D beam steering device by cascading two orthogonal 1D liquid crystal (LC) based phase gratings, each having an array of 72 rectangular individually controlled pixels and driven by a custom 12-bit Pulse-Width Modulation (PWM) electrical driver. High-resolution structures in glass wafers coated with transparent Indium-Tin Oxide (ITO) have been prepared using Direct Laser Writing (DLW) techniques. With DLW, a high number of pixels can easily be drawn with an interpixel space of less than 3 μm, leading to devices with a high fill factor. The active area of the cascaded device is 1.1 × 1.1 mm2. We present a 72 × 72 point efficiency map corresponding to a maximum diagonal steering angle of 1.65°. Special attention has been paid to make the device compatible with space application by avoiding electronics in the active area.

Optical beam steering (BS) has multiple applications in fields like target seeking and tracking, optical tweezers, billboard displays and many others. In this work, a two-dimensional beam deflector based on blaze gratings is presented. Phase-only 1D blaze gratings have been prepared using maskless Direct Laser Writing (DLW) resulting in high-resolution structures in indium-tin oxide (ITO) coated glass wafers. The device is composed of two identical 1D liquid crystal (LC) cells cascaded orthogonally back-to-back, with a resultant active area of 1.1 × 1.1 mm2. The 1D cells have been prepared with 144 pixels each with a 7.5 µm pitch. The total 288 pixels are driven by a custom made 12-bit Pulse Width Modulation (PWM) electronic driver, allowing for an arbitrarily high resolution. The system performance is documented, and the efficiency of the system has been tested. A maximum diagonal steering angle of ± 3.42° was achieved.

Lenticular array products have experienced a growing interest in the last

Reconfigurable diffractive lenses manufactured in liquid crystal are presented. The lenses show an unprecedented performance in terms of active diameter and focal distance range when compared to any other transparent adaptive lens. The lenses are characterized by an active area free of electronic components, with a fill factor of 98% which combined with a low operating voltage (<10Vrms), open for applications ranging from eye contact lenses to space applications. The addressing of the liquid crystal is done exclusively from the periphery of the device. The lenses are based on tunable spiral diffractive lenses (SDL) for which the focal length may be changed by changing the topological charge, i.e. twist of the spiral in the lens. The twist in the resulting wavefront is eliminated by cascading two spiral plates with opposite twists emulating a conventional diffractive lens. The presented lenses have a tuning range from -2 to +2 diopters and an active diameter of 25mm.

In the previous chapter, we have browsed upon the optics of photographic cameras, focusing on the specific features of digital cameras and their sensors. We have also compared the camera performance with eye, including grayscale, sensitivity, dynamic range, field of view and many others. Eyes are far superior to cameras in several aspects, those favored by evolution, while cameras prevail in other aspects not so relevant for vision. Yet digital cameras are still quite similar to analog film-based cameras in all issues related to optics. In this part we will concentrate on the most distinctive element of modern digital cameras, the optoelectronic sensor. We will study the fundamentals of optoelectronic light to electric signal conversion, the different families of sensors and detection modes, their advantages and flaws. Finally we will show the current trends in sensors and explain the reasons why manufacturers have chosen them.