Poll: Would you be interested in an inexpensive Wide-Angle lens for the Axis Webcam?

[Greg McKaskle]

A wide angle lens would be nice, for ~ $30.

Man, the Axis 206 has the narrowest FoV I've ever seen, save a pinhole in a wall.

-Nick

The URL I posted contains wide angle and narrow/tele ones too. The second tab gives a table of specifications for the various lenses. Note that the 4mm lens has a viewing angle of ~70 deg. I never tried to make an accurate measure of the Axis, and instead relied on tables like this along with field of view calculators such as http://www.123securityproducts.com/calculator.html.

Anyway, note that the wider the viewing angle the higher the Distortion. Even with the Axis 4mm lens, the vertical lines are curving out or becoming barrels. The wider you go, the stronger this effect. Processing an image looking at size and shapes gets trickier unless you correct for the distortion -- taking more processing and introducing new artifacts due to resampling.

This isn't the same thing as this poll, but I'd be curious if/when teams buy alternative lenses to see comparative photos compared to the stock lens. This will in the long run save lots of team money and lead to better naive choices. It'd be a great little white paper, but may be better done as a collaborative wiki or collective forum post.

A strong cautionary note.
The axis sensor doesn't contain an IR blocking filter. Instead, the filter is expected to be built into the lens. This is cool in case you want to change the lens and do some rudimentary IR imaging. Not so cool if you neglect to use a lens with an IR filter somewhere around 650nm or so, and then notice that your contrast and color saturation are lousy -- I speak from experience. And in the end it is pretty much a waste of money. I have heard of teams that were able to transfer the IR filter from one lens to another, but I question whether this is a good use of time over ordering what you need in the first place. Note that on the page I posted, only two lenses contain the filter. So in fact, while this table is useful for comparison, I no longer recommend purchasing the lenses here unless someone comes up with an easy process for the IR cutoff.

Greg McKaskle

[PhilBot]

Originally Posted by Greg McKaskle

Anyway, note that the wider the viewing angle the higher the Distortion.

Greg McKaskle

I wonder if anyone has considered making a spherical imaging sensor.....

Hmmmm. Off to patent search.

Phil.

[Greg McKaskle]

Funny you mention that. I think most RoboCup teams that are allowed use the camera pointed up towards a mirrored surface, hyperbolic is really common I think, so as to have coverage of the entire field. I spoke with a professor who built a cheapy version using a mirrored light bulb and a different transform, and they were able to use robot motion as a stereo-optical substitute with pretty good results.

RoboCup has very standard lines on the field and markings on the robots to make it a bit easier for vision, but it would be a cool system even if you only had a few items to reference for orientation.

Greg McKaskle

[dlavery]

Originally Posted by PhilBot

I wonder if anyone has considered making a spherical imaging sensor.....

Hmmmm. Off to patent search.

Spherical reflective camera systems (both monocular and stereo) are fairly common. Several groups (including NASA, Carnegie-Mellon, Stanford, and MIT) did a lot of early development of the technology more than 15 years ago. Here is one example of a commercialized system from back in 1997.

-dave



.

[Ed Law]

I know this is an old thread. The URL posted http://www.edmundoptics.com/onlineca...productID=2196 now links to a product page that has lots of lens with different FL and with IR filter. However these lens are threaded for M12 X 0.5. How do I attach them since the Axis M1011 has no threads? Is there another source I can get a lens I can replace the original lens with? How do I replace it?

Originally Posted by Greg McKaskle

The URL I posted contains wide angle and narrow/tele ones too. The second tab gives a table of specifications for the various lenses. Note that the 4mm lens has a viewing angle of ~70 deg. I never tried to make an accurate measure of the Axis, and instead relied on tables like this along with field of view calculators such as http://www.123securityproducts.com/calculator.html.

Anyway, note that the wider the viewing angle the higher the Distortion. Even with the Axis 4mm lens, the vertical lines are curving out or becoming barrels. The wider you go, the stronger this effect. Processing an image looking at size and shapes gets trickier unless you correct for the distortion -- taking more processing and introducing new artifacts due to resampling.

This isn't the same thing as this poll, but I'd be curious if/when teams buy alternative lenses to see comparative photos compared to the stock lens. This will in the long run save lots of team money and lead to better naive choices. It'd be a great little white paper, but may be better done as a collaborative wiki or collective forum post.

A strong cautionary note.
The axis sensor doesn't contain an IR blocking filter. Instead, the filter is expected to be built into the lens. This is cool in case you want to change the lens and do some rudimentary IR imaging. Not so cool if you neglect to use a lens with an IR filter somewhere around 650nm or so, and then notice that your contrast and color saturation are lousy -- I speak from experience. And in the end it is pretty much a waste of money. I have heard of teams that were able to transfer the IR filter from one lens to another, but I question whether this is a good use of time over ordering what you need in the first place. Note that on the page I posted, only two lenses contain the filter. So in fact, while this table is useful for comparison, I no longer recommend purchasing the lenses here unless someone comes up with an easy process for the IR cutoff.

Greg McKaskle

[Greg McKaskle]

That was written when the 206 was still being produced.

Since you asked, I removed the bezel from an M1011, and it looks to me like it uses the same thread pitch, but it has dabs of glue to hold the focus constant. They clearly don't expect lens upgrades because the glue was hard and didn't remove easily. I was able to extract the lens, but from the Edmunds site, couldn't determine which would be compatible.

I'll try to ask some camera/lens folks about compatible lenses.

Greg McKaskle