The Hardware:

The cheap camera to use and improve the putting fitting data is the Playstation Eye (PlayStation Eye).

This small camera has some great specifications. Not only is the used image sensor sensitive to IR but it also has a resolution of 640x480 with a maximum frame rate of 75fps! When using it at a resolution of 320x240 (the same resolution as the TOMI ) it will even do 187fps. The TOMI can only do 30fps, more then 6 times less frames per second then this rather cheap camera!

The Drivers:

As this camera is intended to be used together with a Sony PlayStation normally no drivers are available for the Windows platform. However Alex Popovich did some fantastic hacking and developed driver for the Windows platform. Those drivers can be downloaded from his website : Code Laboratories These driver will allow any Windows developers to start using this camera in his software. This is why I could use it for the PutPi software as well.

The Lens

Because the image sensor is sensitive to InfaRed Sony used a lens with a IR blocking filter to prevent it from overexposing. The TOMI marker unit is using IR Leds. Without any modifications to the camera lens the IR markers would be visible but rather dim.

Below the same image but now using a lens without any IR filter.

As you can see those IR markers are much more "visible" making it easier for any software to find them and measure their position.

Removing the IR Filter

Removing the IR filter used to be rather easy. See this tutorial PS3Eye Disassembly & IR Filter However Sony has released a new version of the camera and in this new version a new lens configuration is to be found. Removing the IR filter from this lens configuration is not longer possible!

In order to make a camera that can easily see those IR markers it's necessarily to replace the original lens with a new one. Use the above mentioned tutorial to disassemble the camera and to remove the lens configuration. This will be your end result:

Assembling a new Lens configuration

Using the internet it's now time to find a new lens holder, that the plastic holder that connects the lens to the board., and a new lens without any IR filter. The lens holder should have the correct dimensions (M12 x 0.5 , 18mm screw distance) and the lens itself should fit in the holder. I did al that work for you and this is what I found on internet:

Ebay : 5 lens holders M12 x 0.5 (18mm screw distance)
Price? US $3.31(!)

Ebay: M12 x 0.5 Mount 75 Degree View Angle 4.2mm IR Mega Lens F1.8
Price? US $8.85

And if you need a link for the camera, at this moment Amazon is the cheapest : Amazon : PlayStation Eye
Price? US $10.62

So for a total of US $22.78 you will end up with this InfraRed 75fps 640x480 camera.

Ready?

No, not yet. The original lens used by Sony was very good and it's a shame we could not remove the IR filter anymore. The new lens has no IR filter but is of lesser quality. Cheap lenses like this will distort the images:


This "barrel" distortion is not something we can use when trying to measure the markers position as precisely as possible. Luckily we can use software to correct this radial distortion. In a next blog entry I will explain how to remove this distortion using calibration software and provide the software to do this.

to be continued....