Sunday 24 November 2013

BirdBoxPiCam 2014; #3 Camera Modification

The RaspberryPi camera board is a great accessory, but the lens does not give a wide enough viewing angle for use in BirdBoxPiCam 2014.

So this is how I modified the camera assembly to fit an M12 board lens.

The first step is to remove the existing lens from the Pi camera without breaking something.

Some people have suggested that this is easy, and can be done by gripping the lens with a pair of tweezers. Well good for them!

Not So Easy!

The lens on my PiCam was not just held in with a blob of rubber cement. It appeared to be secured by thread-lock, so I made a bit of a mess of it. But I'm not going to be using the lens again, and the important thing is not to damage anything else.

It seems to me that the important thing is to minimise stress on the assembly as much as possible. So I used a small adjustable spanner to hold the existing lens mount, while trying to turn the lens with snipe nosed pliers.

The next step was to find a suitable lens mount for a standard M12 board lens.

Supply Problems

Initially I placed an order with SourcingMap via Amazon, for a lens (that I didn't need) which came with a mount. Long-story-short; it got lost in the post somewhere between Hong Kong and Sussex, so I placed an order with Stock Optics Ltd for a lens (which I did need) and a mount. Their goods turned up within a couple of days, great! ....but they forgot to include the mount...the bit I really needed.

SourcingMap were brilliant. They had already agreed to ship a replacement when their first package turned up, by this time 6 weeks since the order was placed. But Stock Optics just seemed to have ignored my calls and emails. (edit: please see footnote)

The SourcingMap lens mount was a bit of a surprise because it is metal, not plastic. How they can supply a lens and metal mount for £2.58 is a mystery.

Attaching The Mount

In order to position the new mount centrally over the existing camera, its necessary to grind away part of the new mount. As this is a metal mount, it is especially important not to allow the mount to touch the board components.

I temporarily attached the new mount using a couple of pieces of insulated wire (the cores of a network cable). This allowed me to fit a lens and play around with the camera.

Once happy, I applied a couple of blobs of hot-melt glue, which I hope will be enough to keep the mount attached to the board.

Checking For Leaks

My handy work grinding away with the Dremel had left small gaps at the base of the mount. So I fitted a lens cap and turned the system on to check for light leaks.

Light entering the lens mount can clearly be seen on the attached monitor

Sure enough, I had a problem, so I attached a few pieces of black tape around the mount base. This fixed the problem, but I'll probably need to apply some stronger adhesive to ensure this tape does not peel off when the system is in use.

A better approach might have been to attached the tape to the board before gluing the mount in place. The tape would then have been trapped like a gasket.

27th Nov: Stock Optics have subsequently apologised for the delay and communication breakdown, and I now have one of their plastic lens mounts.

These are available in different sizes; quoted hole spacing (actually this is the pitch) 18, 20 or 22mm. Mine is a 20mm and the square part of the base is 17 x 17mm. The Sourcingmap one is 15 x 15mm.

The holes on the camera board are about 21mm pitch, so if you wanted to try to fix with screws, I'd suggest the 20mm pitch is the closest option, then carefully try to enlarge the holes on the mount.

This plastic mount may be easier to work with, and there is no risk of shorting anything on your camera board.

There is a big difference between cost (relatively small in both cases) and delivery time:-
Sourcingmap: free with a £2.56 lens, normal lead time up to 4 weeks.
Stock Optics: £4.44 (inc VAT), normal lead time 3 working days.

1 comment:

  1. Hey there Captain Bodgit. I had the same issue as you with Raspberry Pi Lens mounts having the spacing of 21mm. However I have managed to get a supply that are in good condition. Please feel free to link to my blog post if anyone wants them.