For the past several days, I have received parts for constructing my touchscreen prototype which is based on Frustrated Total Internal Reflection (FTIR).
Today I will cover how the lens of the Philips webcam can be dismounted and replaced by one without an infrared (IR) blocking filter.
Most consumer webcams contain an IR filter which will prevent IR light coming through. This is done to prevent image distortion. However in our case we want to capture the IR light. On some webcams it’s possible to remove the IR filter (which is behind the lens and often has a red colour). With our current webcam from Philips this isn’t possible. Therefor a new camera lens has been ordered on eBay.
It was called “4.3MM 4.3 MM CCTV Camera board Lens IR DVR NEW”
Some specifications of the new camera lens:
- Glass Lens
- Focal length: 4.3 mm
- Aperture F/1.8
- Image format 1/3 inch
- Angel of view 68°
- Mount M12 x P0.5
- Size 14.75mm (L) x 14mm (D)
- A screwdriver or a swiss knife
- A steady hand
- Some patience
Step 1: Turn it
Because we don’t want to take the whole camera apart, we will start by removing the lens adjuster (normally used to focus manually).
First turn the lens adjuster counter clockwise untill it won’t go any further. If you feel like it’s being stuck, try a bit harder untill you have something similar as the image below:
Step 2: Removing the lens adjuster.
Now there should be enough space to put a screwdriver in the gap.
You should now be able to take the lens adjuster off. You could do it nice and gently, but in my case I broke a few parts of it :D. Not something to worry about though.
You can cleary see the CCD sensor:
Step 3: Mount the new lens.
Finally you should be able to mount the new lens. This might be tricky if you got large fingers. You might want to use the lens adjuster as a tool to mount it.
Some extra images
The old (left) and the new (right) lens:
The IR filter on the old lens:
The next blog entry will be about how to polish the acrylic plate.