Small, Lightweight Connectors Enable Today’s Powerful Optical Electronics
The latest generation of high-tech digital cameras has been sized down for small, lightweight military, medical, and surveillance equipment. High-speed miniature interconnect products make it possible to capture and send images in even the most rigorous operating conditions.
High-speed cameras, machine learning, and robotics are changing the world for interconnects that support data services to and from the optical lens. Key designs are often selected from older, standard micro- and nano-sized connectors, but these almost always need physical and electrical adjustments to serve the newer camera products. For instance, as image resolution and frame rates increase, the older copper connector wiring must be adapted to handle high-speed digital transmission. When dual cable is used, the designer must choose either parallel coax or differential pair data transmission. When two lines are used, electron propagation rates must be carefully matched to ensure both the positive and negative sides of the signal arrive at the camera processing board at the same time.
Reserve component sailors assigned to Explosive Ordnance Disposal Operational Support Unit (EODOSU) 7 use a man-transportable robot system equipped with advanced optical technology, the “Talon” Mark 2, to approach a suspected bomb maker’s building during a mobility exercise at the Naval Air Weapons Station in China Lake, California, in March 2012. (Image courtesy of the U.S. Navy.)
In addition to better lens development in advanced optical equipment, the photon capture process is faster and the output rate of charge-coupled devices (CCD) and complementary metal-oxide-semiconductor (CMOS) chips is increasing. Parallel chip receivers are also extending image capture breadth and resolution. As a result, processing speeds are rapidly increasing from 60 frames per second to up to 300 frames per second. This is driving digital signal data rates from the older 5Gb/s to above 10Gb/s. To handle higher speeds, new cable and connector designs are required to manage signal integrity during image transfer. In addition, infrared spectrum scanning and mixed light frequency monitoring support use of hyperspectral imaging. This optical technology is used for military surveillance, agricultural management, and even food analysis. We also see high-resolution imaging used for facial recognition security scanning in airports. These multispectral imaging systems actually capture cube-like structures of many wavelength frequency bands of image data that must be processed after collection and, as such, will push the limits of high-speed Ethernet processing systems, as well as the interconnect technologies that serve them.
Scaled-Down Interconnects Enable Small Cameras
Since more and more optical applications are being used in mobile or environmentally rigorous applications, we again see the need for small, rugged, and lightweight interconnect solutions. Standard connectors that have been designed to be small, lightweight, and meet specifications such as MIL-DTL-83513 for micro-size connectors and MIL-DTL-32139 for nano-size connectors use small pin-to-socket elements that carry the specified current flows and maintain constant signal integrity during operation. To do this, the pin-to-socket systems are often made of highly tempered beryllium copper springs or flex elements that are then carefully nickel-plated and subsequently coated with gold. The spring strength must remain consistent throughout temperature cycling and rugged daily use, and the plating on the key elements must retain very low contact resistance throughout the life of the instrument. In many cases, micro- or nano-sized coaxial cable is used to match signals from camera to camera, as well as to isolate the image signal from cyber intrusion.
Micro-sized cameras are used in endoscopes, eyeglasses, and miniature drones that fly in swarms. Portable surveillance equipment employs imaging data from visual, infrared, or multi-spectral LiDAR scanners. Surveillance planes and satellites constantly survey and register images of critical areas from afar. These cameras must be small and lightweight, and rugged enough to withstand the shock and vibrations that occur during use or in the crash landings drones typically experience. Miniature surveillance cameras must also increase their resolution and run faster frame rates, and many now include a wide field of view to capture images below. Data processing and storage and remote image transfer systems are often included within the camera package as well. At present, standard surveillance camera systems are still widely used throughout public spaces, but customized equipment is increasingly coming into favor.
Some of the smallest cameras are custom designed for the medical field. These include optical probes and image sensors, such as tracheoesophageal scopes, catheters, and endoscopes. The connectors utilize nano-sized beryllium copper spring-loaded pins to ensure constant contact during the diagnostic process and wiring especially designed for strength and flexibility. The wires are insulated in Teflon jacketing and run as small as 32–36AWG. Medical scopes must also survive thousands of connection and disconnection cycles. Due to these rigorous performance demands, connector assembly is done in clean rooms and high-level quality inspections are enacted to ensure reliability. Micro-medical connectors also use materials that resist bacteria growth and endure serializing or autoclave sterilization between uses.
Nano-sized connectors used inside data packs for covert surveillance equipment need cable to route data throughout the module. Nano-sized cameras offer stealthy performance for mounted viewing and can be employed in portable systems. Micro-sized data devices now require ultra-miniature connectors such as the polarized nanominiature format. Surface-mount receptacles fit with the size and height of other active components on the PCB. The nano interconnecting pin-to-socket method maintains signal integrity during active pursuit situations in rugged environments and is easy to plug in and disconnect. Board designers can also specify the number of pin elements needed to keep size and weight to a minimum.
Rugged Interconnects Endure Harsh Environments
When even more severe and covert environments are expected, design engineers can select a customized version of the well-established MIL-DTL-32135 nano-D connector. Nano-D connectors offer the extreme strength of a metal connector at a minimal size and weight and are used throughout military personal packs, on UAVs, and in aircraft weapon systems due to their proven reliability and ease of use.
Covert and military systems are often used in the dark. In these applications, connectors cannot reflect light and must be easily to operate. Features including special black plating and thumb indents are often designed into these types of connectors so users can mate and disconnect them in total darkness without being detected. Special covert designs often vary in wire count but must always be as small as possible. Quick-turn solid modeling systems are used to rapidly adjust existing high-reliability nano-D connectors that have the exact pin counts needed.
Interconnections for airborne cameras face their own special challenges. Standard demands include the need for quick and easy connector mating and unmating, especially for systems that are recording data in onboard storage modules. As high-resolution capabilities and frame rates increase, the amount of digital data streaming off the camera to the storage unit increases exponentially. Cables may have to exceed 5Gb/s to keep up. At a minimum, one might consider using FireWire cable (IEEE 1394) equipped with a drain to tame both speed and potential noise during signal transmission. Aircraft are also simultaneously operating under high vibration that can add electrical noise to the inline cable if it’s not designed correctly. Final landing on many imaging-based drones is rough, so connectors must remain intact and survive what’s often referred to as intentional crash landings. Aerospace electronics systems must be small and lightweight to fit into drone and helicopter-type systems, and one advantage of lightweight components is that, when designed correctly, they withstand much higher shocks due to the fact that continued force is reduced with less weight. Ground-based remote military surveillance systems require similar specifications to military airborne cameras.
Quick-Turn Custom Connectors Within Reach
The choice between specifying standard connectors versus custom designed ones is often a question of time and cost. Today, however, tailored variations of high-reliability customized standards can be made quickly and at a much lower cost than in the past. Most standard connector models are in residence in solid modeling software at the connector supplier’s factory, which means that a system designer can work with the connector supplier to adapt and even resize such connectors for new camera and surveillance systems with little effort. The solid works systems send data to 3-D modeling or CNC machines to build up the first article product, which can then be placed into the new unit to ensure form and fit within a very short timeframe. The key is using the same pin-to-socket mating elements as those used within the high-reliability connectors that are currently available.
Application-specific interconnections for cameras are increasingly required as size and weight goes down while data link speeds go up. Image designers can work directly with connector designers to quickly design reliable solutions for new instruments, and they can have assurance that these components will survive the many rigors of surveillance systems today.
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