Section 11: Cameras
targets illumination microscopy filters imaging lenses imaging resource guide 148 +44 (0)1904 788600 • EDMUND OPTICS® cameras
Digital Camera Interfaces
Digital cameras are available with a variety of interface options that
are often dependent on an application’s requirements. Some formats,
such as the two USB varieties, can greatly simplify the setup process by
supplying video output and power via a single interface. Other formats
may require an additional power supply but provide advantages such as
higher data transfer rates, which a ects the frames per second a camera
is capable of outputting, or support for a greater number of simultaneous
devices. Table 1 compares the di erent digital camera interfaces.
DIGITAL INTERFACE COMPARISON
NOTE: images not
drawn to scale
USB (Universal Serial Bus)
USB-C (USB Type C), nalized by the USB Implementers Forum
in August 2014, is the connection type designed for the future, featuring
single and dual band speeds of 10 and 20 Gb/s respectively. In addition
to fast data transfer speeds, cable reversibility, and reduced connector
size, USB-C uses 128b/132b encoding to improve data transfer e -
ciency. USB-C is also able to deliver up to 100 W of power at 20 V and
5 A and enables Dual-Role-Data port functionality for bidirectional power
and data transfer. The current limitations of USB-C are cable length.
At a maximum of 1 to 2 m in cable length, e orts have been made to create
high- delity repeaters and extenders for longer distance applications.
USB 3.0 is a popular interface due to its ubiquity among computers.
It is high speed and convenient; maximum attainable speed depends
upon the number of USB peripheral components, as the transfer
rate of the bus is xed at 5 Gb/s. In USB 3 Vision, camera control
registers are based on the EMVA GenICam standard. The USB 3.0
standard does not match that of the computer standard of backwards
compatibility, but some USB 3.0 cameras are backward compatible
making them run at the slower speed of USB 2.0.
USB 2.0 features the plug-and play bene ts of USB 3.0, however
it is much slower than USB 3.0 with data transmission rates of
480 Mb/s. Cables are readily available anywhere computer components
are sold for both USB 2.0 and 3.0.
GigE (GigE Vision Standard)
GigE is based on the gigabit ethernet internet protocol and uses standard
Cat 5e and Cat 6 cables for a high-speed camera interface. Standard
ethernet hardware such as switches, hubs, and repeaters can be
used for multiple cameras, although overall bandwidth must be taken
into consideration whenever non peer-to-peer (direct camera to card)
connections are used. In GigE Vision, camera control registers are
based on the EMVA GenICam standard. Optional on some cameras,
Link Aggregation (LAG) uses multiple ethernet ports in parallel to increase
data transfer rates. Also supported by some cameras, the network
Precision Time Protocol (PTP) can be used to synchronize the
clocks of multiple cameras connected on the same network, allowing
for a xed delay relationship between their associated exposures.
For more information on cameras go to
Camera Link® is a high speed serial interface standard developed
explicitly for machine vision applications. A Camera Link® capture
card is required for usage, and power must be supplied separately to
the camera. Special cabling is required because, in addition to lowvoltage
di erential pair (LVDP) signal lines, separate asynchronous
serial communication channels are provided to retain full bandwidth
for data transmission. The single-cable base con guration allows 255
MB/s transfer dedicated for video. Dual outputs (full con guration) allow
for separate camera parameter send/receive lines to free up more
data transfer space (680 MB/s) in extreme high-speed applications.
FireWire (IEEE 1394.b/IIDC DCAM Standard)
FireWire, aka IEEE 1394.b, is an isochronous camera interface due to
the widespread availability of FireWire ports on computers. FireWire.b
allows for the connection of multiple cameras and provides power
through the FireWire cable. Hot-swap/hot-plugging is not recommended,
as the connector’s design may cause power pin shorting to signal
pins, potentially damaging the port or the device. FireWire.a is an older,
slower version of FireWire and is not used often anymore.
Image processing typically involves the use of computers, which means a
digital interface is necessary when using analog cameras. Capture boards
allow users to output analog camera signals into a computer for analysis;
for analog signals (NTSC, YC, PAL, CCIR), the capture board contains an
analog-to-digital converter (ADC) to digitize the signal for further image
processing. Users can then capture images and save them for future manipulation
and printing. Basic capturing software is included with capture
boards, allowing users to save, open, and view images.
The term capture board also refers to cards that are necessary to acquire
and interpret the data from digital camera interfaces, but are not
based on standard computer connectors.
Table 1: Comparison of Popular Digital Camera Interfaces.
USB-C USB 3.0 USB 2.0 GigE (PoE) Camera Link® FireWire 1394.b
Data Transfer Rate: up to 10 and 20 Gb/s 5 Gb/s 480 Mb/s 1000 Mb/s up to 3,6 Gb/s 800 Mb/s
Max Cable Length: 2 m, Gen 1 1 m (Gen 2) 3 m (recommended) 5 m 100 m 10 m 100 m (with GOF cable)
# Devices: up to 127 up to 127 up to 127 unlimited 1 up to 63
Connector: USB USB USB RJ45 / Cat5e or 6 26 pin 9 pin-9 pin
Capture Board: Optional Optional Optional Not Required Required Optional
External Power: Optional Optional Optional Reguired (Optional with PoE) Required Optional
See pages 64-69 for TECHSPEC® HP Series Fixed Focal Length Lenses