Machine Vision Interface Comparison and Evolution

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Oct 17, 2013 (4 years and 26 days ago)

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Machine Vision Interface

Comparison and Evolution


June 27, 2012







Revised:
6/27/2012

©
2012 Point Grey Research Inc.

2

Machine Vision Interface Comparison and Evolution

In today’s thriving machine vision industry, there is a number of competing interface standards.
Each standard arose with the goal to
out
-
perform the previous one and address more complex
system requirements. In order to understand how each interface compares, it is important to
know the evolution of their development. This paper analyzes the merits of four of the most
popular imaging i
nterfaces and describes how they accelerated the growth of the machine
vision industry.


FireWire (IEEE1394b)

Gigabit Ethernet

USB 3.0

Camera Link

Bandwidth

80 MB/s

125 MB/s

440

MB/s

680

MB/s (Full)

Cable length

4.5

m

100

m

3

m

10

m

CPU usage

Low

Medium

Low

Medium

Consumer

Acceptance

Declining

Excellent

Excellent

Low

Difficulty of System
Integration

Medium

Low

Low

High

Power Delivery

45 W

15.4

W
1

4.5 W

None

Multiple cameras

Excellent

Good

Excellent

Fair

System Cost (Single
Camera)

Medium

Medium

Low

High

Vision Standard

IIDC DCAM

GigE Vision

USB
3

Vision

Camera Link

Table
1
:

Interface Comparison

Bandwidth

defines t
he
average maximum
data

transfer

the interface can
sustain
.

Cable length

identifies the length of the interface cable connecting the camera to the host computer

Consumer acceptance

r
ates how ubiquitous an interface is.
Excellent consumer acceptance indicates
there are new customers in the marketplace transitioning to this tec
hnology, compared to declining
where customers are slowly moving away from this technology to something else.

Difficulty of integration

aims to evaluate
engineering effort required to implement a machine vision
system on the selected interface.

Power de
livery

specifies the amount of

power that can be delivered over the interface cable itself.

Multiple cameras

Identifies
how well the interface supports multiple camera system requirements such
as synchronized triggering and bandwidth management.

System co
st

indicates the cost for the system based on the cost of camera peripherals needed to
implement a single camera system. This does not include the cost of the camera.

Vision standard

is the corresponding interface standard that supports the interface.




1

Based on

IEEE 802.3a
f
-
200
3 PoE standard


Revised:
6/27/2012

©
2012 Point Grey Research Inc.

3

Interface timeline


This timeline below illustrates important milestones in the development of the various machine
vision standards. IIDC and Camera Link are two of the older standards and differ greatly from
each other. GigE Vision and USB3 Vision are mo
re recent standards and have more
commonality between them.


Figure
1
:

Machine Vision Standard Timeline


Choosing the right interface

By
understanding

how each interface standard came about and its role in the machine vision industry,
users can have a better overall perspective when comparing these interfaces and deciding which to use
for their application. With the broad range of requirements addressed

by machine vision systems, there
is no single interface that can address them all. Each interface has its own unique strength that makes it
more effective and efficient for certain kinds of applications.



Revised:
6/27/2012

©
2012 Point Grey Research Inc.

4

FireWire (IEEE1394)









Created in 1995 by the 1394 Trade Association to promote
FireWire products, the IIDC DCAM standard was one of the first
viable digital interface standards to be available.

This continunes
to be the case as
F
irewire cameras remain popular.

Although IIDC wa
s not created by the machine vision industry, it
has been widely adopted by the industry for its common protocol
interface. The IIDC specification provides a global register map
for all FireWire cameras to follow, allowing third
-
party
applications to becom
e camera vendor agnostic. System
integrators can switch between camera models and camera
vendors with minimal impact to their application as long as the
cameras support IIDC.

FireWire is also highly effective for multi
-
camera systems. It
provides the abil
ity to daisy chain cameras and create multi
-
camera systems without the use of hubs. FireWire cameras use a
peer
-
to
-
peer communication protocol and provide the ability to
synchronize trigger broadcast with other cameras on the same
bus. In terms of bandwid
th allocation, FireWire uses isochronous
transfer which allocates and guarantees bandwidth for each
device on the same bus. For these reasons and because it is
proven reliable in a wide variety of applications, FireWire
continues to be popular interface.


Figure 2: IEEE1394 interface
logo




Point Grey
Grasshopper Express

FireWire Camera


Revised:
6/27/2012

©
2012 Point Grey Research Inc.

5

Camera Link








As machine vision applications became more demanding, there was a
need for an interface, and corresponding standard, capable of
supporting more machine vision specific features and much higher
bandwidths. Led by the

A
utomated Imaging Association (AIA)
,
members of the machine vision community worked together to design
the Camera Link interface. Camera Link supports Direct Memory Access
which reduces the load on the CPU when capturing images. This

creates more CPU cycles dedicated to other things such as post
processing of images. Camera Link also separate control signals with
video signals, providing low latency triggering and data delivery.

Camera Link supports up to 680 MB/s of data transfer. T
he high
bandwidth allows higher resolution sensors, higher frame rate and high
bit depth images. The tradeoff for higher bandwidth is cost. Compared
to other interfaces, system costs are higher due to frame grabber and
a
power supply is

needed for every c
amera in the system. However,
having a frame grabber in the system does off
-
load some of the
processing done by the CPU. Frame grabbers can also buffer images,
with some high
-
end frame grabbers even offering some hardware
image processing capabilities.

De
spite low consumer acceptance and higher system cost, Camera Link
is widely used for applications requiring real time processing and high
bandwidth.




Figure
3
: Camera Link Interface
Logo






Point Grey Gazelle Camera Link Camera


Revised:
6/27/2012

©
2012 Point Grey Research Inc.

6

Gigabit Ethernet (GigE)





With the wide spread deployment of
Gigabit Ethernet on PC and
laptops, it became a strong contender as a viable machine vision

interface. In 2006, members of AIA
came together to develop the first
GigE Vision standard. A challenge the members wanted to address is
the limitation of camera r
egister mapping. With that, the Generic
Interface for Cameras (GenICam) was born. GenICam was designed to
promote interoperability both within an interface and across
interfaces. This implementation has certain advantages over FireWire’s
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vendors’ ability to define features. GigE Vision uses GenICam's XML
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cable lengths. Compared to FireWire’s maximum single cable length
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there’s no limit on how many cameras can operate on the same
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Figure
2
: GigE Vision Standard
Logo




















Point Grey F
lea3 GigE Camera


Revised:
6/27/2012

©
2012 Point Grey Research Inc.

7

Universal Serial Bus (USB

3.0
)




The development of the USB 3.0 interface was originally driven by the
consumer need for a PC based interface with higher bandwidths. The
USB 3.0 interface came to market in 2009 with support for up to 440
MB/s of bandwidth;
10 times faster than US
B 2.0 and 5 times faster
than FireWire
-
B.

Adoption of the interface increased by mid
-
2012. Support from major
vendors such as Intel, AMD, Microsoft, Apple and the Linux community
are
under development
.
At the current rate of deployment
, every
new
PC
manu
factured in 2015
will support USB 3.0. With adoption of this
magnitude, vendors can build applications and deploy them on almost
any PC without the need of additional hardware.


Pricing for
peripherals that are required, such as cables and hubs, will benef
it
from a highly competitive

consumer oriented marketplace.

In terms of machine vision, USB 3.0 offers a number of attractive
features in addition to the high bandwidth. USB 3.0 supports Direct
Memory Access which allows the data to be written directly to

memory
reducing CPU processing load. USB 3.0 is capable of delivering up to 4.5
W
atts

of pow
er over a single USB 3.0 cable. Multiple camera systems
can be deployed using
USB 3.0 hubs.


In 2011, the AIA decided to
implement

the
USB3 Vision

standard
.
Simi
larly to

GigE Vision,
USB3 Vision
follows

the
same robust
framework using the GenICam programming interface and XML
description files. With this commonality between the two standards,
system integrators will be able to easily learn one after working with
the other. With its high bandwidth, ease of use, and low cost, USB 3.0
is ideal for a wide variety applications both within machine vision and
in the consumer world.



Figure
3
: USB3 Vision Standard
Logo



Point Grey

Flea3 USB 3.0 Camera


Revised:
6/27/2012

©
2012 Point Grey Research Inc.

8

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Distributors

Japan

ViewPLUS Inc.

www.viewplus.co.jp

Korea

Cylod Co. Ltd.

www.cylod.com

China

LUSTER LightVision Tech. Co., Ltd

www.lusterlighttech.com

Singapore, Malaysia, &
Thailand

Voltrium Systems Pte Ltd.

www.voltrium.com.sg

Taiwan

Apo Star Co., Ltd.

www.apostar.com.tw

United Kingdom

ClearView Imaging Ltd.

Tel:

+44 (0) 845 606 0457

Fax:

+44 (0) 845 606 0458

www.clearviewimaging.co.uk