You might want to Google =E2=80=9CCMUCAM=E2=80=9D. It is a low-cost =
computer vision sensor that can, among other functions, track a colored =
object in its field of view and report its X-Y coordinates. The =
resolution may be too low for your application, but it is open source =
and a starting point.
Les
From: Geoff=20
Sent: Tuesday, March 26, 2013 3:56 AM
To: psnlist@.................
Cc: Charles R Patton=20
Subject: Re: Seismic Sensors
I like the idea of using a WEBcam or something to look at the red dot
then use a custom program to read the video and turn the graphic data
into rectangular coordinates of a standard four quadrant graph
with the point resting in the center of the graph
But to do this in near real time may not be possible for myself to do.
The max rate will be like 30Hz to 60Hz which is a video frame rate.
Video is usually encoded and needs to be uncompressed.
Uncompressing video takes lots of time to do so like a
series of BMP captures at whatever rate would be the thing to do.
You would take screenies at like 30 per second in a modulo fashion
then save all after an alarm and the series of like
108000 BMP images would be decoded into a series of (X,Y) coordinates ??
The concept as seen From a layman's point of view.
A mass on end of a bent over spring wire might do for a vertical sensor =
?
Regards,
geoff
On 3/8/2013 3:05 PM, Charles R Patton wrote:
I would use a shorter projection distance so the dot is on a smaller =
surface -- perhaps 10" square. Or even smaller -- you'll get the idea =
in a moment. I'd make this surface a back projection screen such as in =
the old microfilm readers. Frosty Mylar sheet or some similar. Mainly =
rear projection so I wouldn't have to get into correcting for angular =
skew, but that would be your choice if you want to do slightly more =
image processing. Next I'd take a standard USB webcam and view the =
image of the dot projected on the film. Run this through any one of =
several free image processing libraries (depends a bit whether you're =
using Windows or Linux) or write a simple custom program to extract the =
pixel position of the dot. Typical low resolution webcams give the =
position to 640x480. Actually if you use image processing, this can be =
interpolated due to the 8 bit quantization of the dot in the image and =
that it will typically spread over several pixels. Your frame update =
rate will be around 30 times a second. The size of the image is not the =
resolution limit, the webcam is. So you can also get higher resolution =
webcams. In any case, the projected image size is not very critical =
unless you make it too small. The point here being that it can easily =
be made to be a table top size. =20
Regards,
Charles R. Patton
On 3/8/2013 5:47 AM, Geoff wrote:
Scholars and Gentle-peoples,=20
Here is a Video created by myself which shows=20
what i want to measure=20
http://youtu.be/w-6r9o7Mds8=20
Can someone tell me how they might=20
actually, or Do now, measure in real time,=20
the (x,y) coordinate of this moving Laser spot ?=20
Youtube says my video is blocked in some countries,=20
Don't know why, or where it is blocked.=20
Most likely because I used FM general radio broadcast=20
for the Audio part of the video.=20
This station damages the audio before it is transmitted=20
so i do not understand why it makes any difference anywhere.=20
Any Comments ?=20
Regards,=20
geoff=20
__________________________________________________________=20
Public Seismic Network Mailing List (PSNLIST)=20
To leave this list email PSNLIST-REQUEST@.............. with the =
body of the message (first line only): unsubscribe=20
See http://www.seismicnet.com/maillist.html for more information.=20
--=20
*************
It is by the Entropy, That I set my mind in Motion.
Entropy is the seeking of equilibrium.
You might want to Google =E2=80=9CCMUCAM=E2=80=9D. It is a =
low-cost computer vision=20
sensor that can, among other functions, track a colored object in its =
field of=20
view and report its X-Y coordinates. The resolution may be too low =
for=20
your application, but it is open source and a starting point.
I like the idea of using a WEBcam or =
something to=20
look at the red dot then use a custom program to read the video and =
turn the=20
graphic data into rectangular coordinates of a standard four quadrant =
graph with the point resting in the center of the graph But to do =
this in=20
near real time may not be possible for myself to do. The max rate =
will be=20
like 30Hz to 60Hz which is a video frame rate. Video is usually =
encoded=20
and needs to be uncompressed. Uncompressing video takes lots of time =
to do so=20
like a series of BMP captures at whatever rate would be the thing to=20
do. You would take screenies at like 30 per second in a modulo=20
fashion then save all after an alarm and the series of like 108000 =
BMP=20
images would be decoded into a series of (X,Y) coordinates ??
The =
concept=20
as seen From a layman's point of view.
A mass on end of a bent =
over=20
spring wire might do for a vertical sensor=20
?
Regards, geoff
On 3/8/2013 3:05 =
PM,=20
Charles R Patton wrote:
I would use a shorter projection distance so the dot is on a smaller =
surface=20
-- perhaps 10" square. Or even smaller -- you'll get the =
idea in a=20
moment. I'd make this surface a back projection screen such as =
in the=20
old microfilm readers. Frosty Mylar sheet or some similar. =
Mainly=20
rear projection so I wouldn't have to get into correcting for angular =
skew,=20
but that would be your choice if you want to do slightly more image=20
processing. Next I'd take a standard USB webcam and view the =
image of=20
the dot projected on the film. Run this through any one of =
several free=20
image processing libraries (depends a bit whether you're using Windows =
or=20
Linux) or write a simple custom program to extract the pixel position =
of the=20
dot. Typical low resolution webcams give the position to=20
640x480. Actually if you use image processing, this can be =
interpolated=20
due to the 8 bit quantization of the dot in the image and that it will =
typically spread over several pixels. Your frame update rate =
will be=20
around 30 times a second. The size of the image is not the =
resolution=20
limit, the webcam is. So you can also get higher resolution=20
webcams. In any case, the projected image size is not very =
critical=20
unless you make it too small. The point here being that it can =
easily be=20
made to be a table top size. Regards, Charles R.=20
Patton
On 3/8/2013 5:47 AM, Geoff wrote:
Scholars and Gentle-peoples,
Here is a Video =
created by=20
myself which shows what i want to measure
http://youtu.be/w-6r9o7Mds8
Can =
someone=20
tell me how they might actually, or Do now, measure in real =
time,=20
the (x,y) coordinate of this moving Laser spot ?
Youtube =
says my=20
video is blocked in some countries, Don't know why, or where it =
is=20
blocked. Most likely because I used FM general radio broadcast =
for=20
the Audio part of the video. This station damages the audio =
before it is=20
transmitted so i do not understand why it makes any difference =
anywhere.=20
To =
leave this=20
list email PSNLIST-REQUEST@.............. with the =
body of=20
the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html =
for more=20
information.
--=20
*************
It is by the Entropy, That I set my mind in Motion.
Entropy is the seeking of equilibrium.
It is by the Entropy that, I set my mind in =
motion.