Video capture or image sensor suggestions

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I've been doing some extremely basic machine vision experiments for a
while, using STV0680-based USB cameras attached to Linux boxes.

I now want to experiment with IR-illuminated subjects, but the cheap
webcams I've been using are color cameras with IR filters.

Can someone recommend a Linux-supported USB video capture device that
accepts regular NTSC input and provides at least 320x240 @ 7.5fps? With
one of these I can use a cheapo B&W camera with good IR response.

Alternatively, I could see my way to constructing some custom optics
and lashing a bare digital image sensor directly to one of the other
pieces of hardware in the system. But in this case I would need a
recommendation for a sensor chip that is:

a) available (!!)
b) in a prototypable package (LCC is OK, but these weird packages that
have to be fused onto the board are NOT OK).

The Omnivision OV07141-C01A or -P01A might be ideal but they are
impossible to buy.


Re: Video capture or image sensor suggestions
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It strikes me that NTSC B&W at 30 fps allows about 60 uSec per
scanline, which in turn requires a-d conversion in about 200 nSec.
If you have settled the resolution required, which I doubt will
exceed 8 bits (depends on dynamic range needed) you now have a
large choice of methods.  

Don't forget delta modulation, which should be fairly useful for
video and largely limits slew rate.  The end processing may be
fairly complex, but I assume the problem is basic data capture.

In case you are not familiar with it, at the extreme each delta
modulation bit tells the destination to slew upward or downward at
some rate.  It has no dc restoration level.  Thus the digital path
for such a B&W NTSC image could be as slow as 5 Mbits/sec.
Horizontal edges would be seriously mushed.  At 7.5 fps the same
bit rate could slew at 4x the rate, or the bit rate could be cut to
1.25 Mbps.  However the NTSC conversion would require local
storage, while the 30 fps rate needs none.

Thought: you could use the horizontal sync time to delta modulate
from the rh of picture level to the lh of picture level, if you
have some other way of providing horizontal sync.  Some ingenious
coding assignments could pack the sync levels within the delta bit
stream.  This complicates things by requiring means of
synchronizing bit streams, besides the hor and ver, and the delta
itself.

--
Chuck F ( snipped-for-privacy@yahoo.com) ( snipped-for-privacy@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
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Re: Video capture or image sensor suggestions
Hi Chuck,

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Thanks for the discussion, but it's not really what I'm after... I'm
looking for a somewhat turnkey all-digital solution. Messing about with
an analog video signal is a research project beyond my time budget and
probably beyond my current ability, also.

The simplest thing to do would be to remove the IR filter from the
cameras I have, but it's not possible with the particular sensor in
these things.


Re: Video capture or image sensor suggestions
On 31 Jul, in article

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There are lots of video to USB devices about, but I doubt many have Linux
support you could try a cheap frame grabber board if you have a spare PCI
slot as people like Sensoray make one with Linux drivers

        <http://www.sensoray.com/html/611data.htm

Avoids the USB bottleneck and allows video camera direct to card in PC.
ordereable even online for $175 in one offs. Can do composite or
monochrome NTSC/PAL upto four inputs.

They also make a PC/104+ format version.

Frame rate depends on when you take the images.

If however this is a single board Linux with USB and no PCI, all bets are
off.

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Aren't the Comedia serail cameras easily available and low cost, but
serial? I have not checked but that might get you the frame rate you
require with a RS232/USB converter as well.

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The main people I use are (unfortunately) Omnivision and Sony.

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They were easily available in the UK when I last looked. If you think
Omnivision are difficult try Sony!

However have you looked at

        <http://www.micron.com/products/imaging/products/vga.html
        <http://www.st.com/stonline/products/selector/43.htm>

Others like Kodak and Mitsubishi are usually for those with much
deeper pockets.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: Video capture or image sensor suggestions
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Unfortunately I don't - this is an SBC as you surmised. The V4L pages
abounding on the net list several capture devices that are supported,
but none of them are findable - I suspect that there are many such
devices around with Linux support through a generic chipset driver, but
it's impossible to work out which device uses which chip.. :(

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I didn't know they had a serial camera. That name kept coming up in my
searches as a manufacturer of Omnivision demo boards, however I haven't
yet located a US distributor of those products. I can't actually read
most of their website but it seems as if they are wholesale only.

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I haven't been able to buy Micron's parts. ST's and Kodak's image
sensors are available at Digi-Key, so actually my first port of call
was to look at all the parts stocked there. Unfortunately they are all
color or otherwise not suitable.

I was really hoping to go the consumer peripheral route.


Re: Video capture or image sensor suggestions
On 31 Jul, in article
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They are usually sold as kits under other people's names looking for
"Serial JPEG camera" usually finds them. I know of a source in europe
who primarily is into GSM modules (serial) who have versions with ports
for these cameras.

Have a look at

        <http://www.roundsolutions.com/cmos-camera/index.htm
        <http://www.mite.cz/camerajpeg-ru/camerajpeg-ru.html
        <http://www.tdc.co.uk/camera/#itmc328 Intertec version
        <http://www.tdc.co.uk/camera/ Omnivision supplier
        <http://www.beyondlogic.org/imaging/camera1.htm
        <http://www.dpspro.com/tcs_cam2.html

or even 'IP cameras' such as
        <http://www.a3j.com.tw/network_cameras.htm

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Lots of distributors sem to think cell phone quality colour is all that is
needed for everything! I hate to think how many jobs and potential jobs
have wasted time trying to beyond this logic to what actually is
required to do the job they want.

Some machine vision jobs need high res, some need lower, some need high
end dsp, others anything all the way down to simple binary slice.

Too many years of video and computing and still I get people wanting
24bit accurate colour from SVHS recorders, recorded from a simple
board camera with lousy lens and even worse lighting.

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There may be consumer USB devices, but I have not personally seen
any with Linux support, because they are consumer devices. They may exist
but I have not seen any.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: Video capture or image sensor suggestions
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What I did (rather unintentionally) was to buy new optics for my webcams. It
turned out that the old optics had the integrated IR cut-off filter, while
the new ones had not. And voi-la, I had IR-sensitive webcams. You could do
the same thing, I suppose, but I'd rather check the datasheet of the sensor
that your cameras is currently using first to make sure that the IR cut-off
filter is not integrated into sensor itself.

Now, to buy new optics, try Fry's (if in the US) or www.optics-online.com

Regards,
Andras Tantos



Re: Video capture or image sensor suggestions

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I think I've found a 95% solution to my problem. I took a chance and
bought six cameras similar to this
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item75%36347103
from an eBay vendor ($100 total, shipped cost). VID=0x0AC8, PID=0x301B,
supported under Linux by the spca5xx driver at
<http://mxhaard.free.fr/spca5xx.html

The LEDs on the unit are actually white, not IR. There is also some
intelligence in the device to adjust the LED intensity based on light
input. It appears to be a normal color camera with a low-attenuation IR
filter.


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