Considerations When Choosing A Smart Camera

Smart cameras are the most effective means of rapidly
implementing simple machine-vision systems due to their reliability,
cost effectiveness and easy to integration. As a self-contained unit,
Smart cameras can be used for embedded single unit applications
or networked to industrial manufacturing systems.

Below is a breakdown of the basic components of a smart camera
and some important considerations when choosing a camera for
your application.

Basic smart camera architecture:1

What are the parts and specific considerations?

Sensor

An image sensor is an integrated circuit that converts a visual
image into an electrical signal. There are several different
components to consider when selecting a sensor to fit the given
application. The basic parameters for smart camera sensors are
type, resolution, pixel size, frame rate, and shutter types

Type: two types of sensors commonly used in machine vision:
charge-coupled device (CCD) and complementary metal-oxide-
semiconductor (CMOS). Both sensors capture light using pixels to
digitize the information.

CMOS imagers offer superior integration, power dissipation and system size at the expense of
image quality (particularly in low light) and flexibility. They are the technology of choice for
high-volume, space constrained applications where image quality requirements are low. This
makes them a natural fit for security cameras, PC videoconferencing, wireless handheld devices,
bar-code scanners, fax machines, consumer scanners, toys, biometrics and some automotive in
vehicle uses.

1
http://www.scribd.com/doc/15844869/Smart-Cameras-and-Embedded-SystemsReport-by-rajat

CCDs offer superior image quality and flexibility at the expense of system size. They remain the
most suitable technology for high-end imaging applications, such as digital photography,
broadcast television, high-performance industrial imaging, and most scientific and medical
applications. Furthermore, flexibility means users can achieve greater system differentiation with
CCDs than with CMOS imagers.

Resolution: This refers to the number of pixels in the sensor region.
Resolution and zoom ability grows in direct proportion to the number
of pixels in the sensor. However, higher resolution images require
more processing power and large data lines. So when evaluating
resolution needs it is important to correctly determine the necessary
level of clarity to complete the application.

Pixel size: Overall pixel size affects the sensors light sensitivity. The
larger the pixel the more sensitive to light it will be. However other
factors contribute to this equation, including ambient light, projected
light and of course what is being imaged.

Frame rate: This refers the amount of frames that can be captures in a
given second. A standard rule is that the greater the resolution the
lower the frame rate, however, it is also a function of the size of the
image. Smart cameras have a frame rate advantage because the
onboard processor can predetermine fields of interest and only
capture a small part of each image.

Shutter types: There are two ways in which the sensor is exposed to
light: global and rolling. Rolling exposes each line of the sensor
successively over time, which is an overall simpler method and ends
up significantly less expensive. But the rolling method can distort
objects moving at high speed and is therefore unsuitable for some
applications. Global shutters expose the pixels all at once, taking a
complete shot of the field of view. Although ideal for high speed
applications, Global shutters are inherently more expensive and
sometimes require larger processing power to manage the large
amount of data.

Processor

The heart of any smart camera system is the digital signal processor
(DSP), and the storage hardware. The DSP processes images by
executing algorithmic programs designed to interpret digital image

code. Storage hardware is the primary and secondary memory,
such as RAM or Flash, used to run CPU programs, or to record and
store images for future use. DSPs are quite complex but there are
two main considerations for selection, processing capabilities and
manufacturer. The higher the processing power, the more
expensive the device will typically be. When deciding on
manufacturers look at reviews and overall market presence
because the chips durability and the reliability depend solely on the
manufacture. The more established companies will be able to
provide more support and guidance when using their products.

Interface

I/O capabilities connect cameras to external devices transmitting
encoded images to a computer for analysis, or delivering
instructions to reactive equipment. Smart camera I/O capabilities
are expanding and now include Ethernet (GigE), USB 2.0, Bluetooth,
Wi-Fi, and GPRS.

Ethernet: Most common I/O solution can handle large amounts of
data, but can be expensive and is not compatible with all
computers.

USB2.0: Simple and easy to use solution that is universally compatible
and inexpensive. Although many vendors do not see USB2.0 as
capable enough, many machine builders looking for inexpensive yet
high performance cameras are turning to USB2.0 to solve their price
performance dilemma.

Blue tooth, Wifi and GPRS: All of the non wired solutions are practical for
remote location application and represent a new field of smart
camera capabilities. But they are limited to low bandwidth
applications and are often very expensive to produce.

Software

While some camera vendors support just one operating system, a
number have chosen to support one or more operating systems in

their products. The reason for such multiple operating system
support is clear. Doing so allows these camera vendors to rapidly
port existing PC-based software to their products. At the same time,
developers of lower-cost open sourced systems can take
advantage of the number of free software packages and
development tools currently available.

In this manner, companies can offer their cameras with a range of
application software while reducing the developer’s time to market.
Third-party software developers can also add their own functionality
to the cameras, offering unique products that serve specific
markets.

Of course, with added programming complexity comes the need to
offer the integrator a set of easy-to-configure machine-vision tools
that require little or no programming expertise.

Summary:

Smart cameras represent the cutting edge of imaging technologies and new advancement
in every part of the camera system will lead to only better and faster machines. The
single most important element of the smart camera is the vendor who will be responsible
for helping you choose the best camera, provide support and additional information
regarding the capabilities of the specific application.

Considerations When Choosing A Smart Camera

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