The CMUcam1 Vision Sensor
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The CMUcam1 Vision Sensor
Frequently Asked Questions
General Questions / Technical Questions
Traditionally fast computers are needed to capture and process camera images. It is also necessary to write the software to perform this processing. Because of this it is difficult to use vision as a sensor in simple systems. The CMUcam vision system uses a fast low cost microcontroller to handle all of the high speed processing of the camera data and contains software to perform simple vision tasks. Because the user can choose to output only low bandwidth high level information from the vision system, like the red object is at position X-Y, it is possible for a simple processor like a PIC microcontroller to read this data and direct a small robot in tasks like chasing a colored ball. The CMUcam vision system makes it possible to ignore the complexity of camera interfacing and use vision just like any other sensor (i.e. sonar) often used in robotic systems. How much would it
cost to build a complete CMUcam?
The CMOS camera board costs
$60. The CMUcam PCB board costs about $10. The cost of the
components to stuff
the board at unit cost is about $30. The total cost of a single
vision system is about $100.
You can now purchase the CMUcam from Acroname, Seattle Robotics, and Lextronic.
What is CMUcam's
frame rate?
The fastest frame rate is 16.7 frames per second. This means CMUcam
can tell you the position of an object about 17 times per second.
Using the serial software protocol you can slow this down if desired.
What baud rates does the CMUcam
support?
As of the latest version of the firmware (v1.12) the CMUcam can communicate
at baud rates of 9600, 19200, 38400 or 115200. The baud rate is selected
via jumper settings on the board.
How do I upgrade my CMUcam firmware?
If you are currently using firmware v1.11 there is no reason to upgrade unless you need support for the lower baud rates. Version 1.11 supports 38400 and 115200 baud. Version 1.12 supports those baud rates and
adds support for 9600 and 19200 baud. To upgrade your firmware you will need to reprogram the flash memory in your processor chip. The easiest way to upgrade is to purchase a new processor with the new code flashed into it. To do this contact the company you purchased your CMUcam from.
If you have a programmer (which are expensive) you can download the current version from our Downloads page and re-flash the processor yourself.
Does CMUcam work
outside?
CMUcam works outside but not in direct sunshine. The CMOS camera
we are using does not have a high-quality IR filter, and so sunlight saturates
the red pixels and the image becomes, essentially, monochrome in direct
sunlight. (It is possible to add an external filter to improve outdoor
operation.) We have a short write up in
Publications that shows you how illumination
conditions affect CMUcam.
Can I write custom
code for CMUcam?
Certainly. To do this, ask us for the firmware source code, order
yourself a C programming environment for the Ubicom (Scenix) chip and go
for it. When we send you the firmware source code we will also send
you a summary of how the code is structured and information about the programming
environment we use.
How much power does
CMUcam consume?
The complete system consumes about 200 milliamperes.
What is the camera's
field of view?
This depends on the lens that you fit to the CMOS camera. If you
order the CMOS camera as it is sold standard, you will end up with about
a 25 degree field of view, which is relatively narrow. You can custom-order
wider angle lenses when you order your CMOS camera, however.
What processor does CMUcam use?
Our image processing code resides on a microcontroller chip from Ubicom
running at 75 MHz, the SX28AC.
(Note that the company that manufactures this chip recently changed their
name from Scenix to Ubicom.) This chip reads all the pixels from
the CMOS camera via a parallel interface and does all the processing in
real time. It then communicates the results to your microcontroller
or computer via a serial port interface.
What CMOS camera does CMUcam use?
We use a CMOS camera which utilizes the
Omnivision
OV6620
CMOS camera on a chip. We use a model number C3088 CMOS camera board
which is available from
Amazon
Electronics on which is mounted the sensor, a connector and a
lens.
Does CMUcam work
with other CMOS cameras?
No. Currently the hardware and software system have been designed
to work specifically with the Omnivision OV6620 CMOS camera. The
system would need to be completely redesigned to work with another camera.
Are you developing
more powerful versions of this vision sensor?
Yes. We are currently working on a system which uses the Ubicom
SX52
processor. This processor runs 33% faster than the processor we are
currently using and has almost twice as much RAM and twice as much flash
program ROM. With this processor we should be able to achieve a higher
frame rate and include more functionality in the system. We chose
not to use this processor in the initial system because it is only available
in a harder to work with surface mount package.
Is there some place I can find answers to additional questions I have?
Yes.
We have some info about more Technical Questions on this page.
Also, Acroname hosts a
forum about the CMUcam
where people can post questions regarding the CMUcam or other vision related topics.
Where can I find out more about computer vision in general?
CMUcam performs the simple computer vision task it was designed to perform
in a small,
inexpensive package. However, the general computer vision problem of trying
to recognize arbitrary objects under arbitrary conditions
is still a very active research topic and very far from being anywhere near a solved problem.
If you want to learn more about computer vision,
you might want to try these links:
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Technical Questions