As part of a larger project (a portable Raspberry PI computer), this is an adapter to provide a macro/closeup lens for the camera module, allowing closer focus to about 18cm.

Although this is designed for this particular computer/case, the idea can easily be adapted for others.

Step 1: Parts List

Materials:

Pine Wood 44mm x 150 mm x 12 mm
Polymorph plastic and hot water
SLR/Compact Camera Lens, or other Convex/Magnifying lens
Paints (Primer, Undercoat and Matt Black Spray)
Spray Clear Cellulose Lacquer
PVA Glue
Pins (2)

Tools:

Forstener Drill set
Saw
X-acto knife
Hammer and pin punch

Step 2: Main Hole Location

The lens needs to be a convex (magnifying) lens style, otherwise it won't work.

Test the lens you are planning to use to make sure it provides a decent closeup image. Of a few old lenses I tried, some focused far too close -- about 5cm. About 18cm matches the "macro" setting on my digital camera, so I used this one.

As this is designed to mount onto a flat/square surface, I held a piece of wood flush to the side and top of the main computer case, and marked the centre line of where the camera's window would be, to get a centre mark.

Step 3: Step Drill

I've no idea what lens mount this lens is -- it came from a scrap compact camera I disassembled long ago. To make a matching mount, I measured off the various diameters and depths, and drilled a series of different size holes into the wood with a Forstener bit set. The lens sits in the wood and doesn't protrude out of the back of the wood, so it won't scratch the main case.

Clamp the wood down on a drill press, because after the first hole you will lose the centre mark! Use a piece of backing wood behind the main hole, so you don't drill into the drill's table.

I drilled the smallest hole first (22mm) right through. Then stepped up to a 28mm, 32mm, and 35mm bit with increasingly shallow holes, hence the steps. The depths were measured off the features of the lens.

Blow away the dust and test fit the lens. It should be able to drop in without too much movement. If not, repeat some of the drill steps.

Only when it fits flat to the wood, unclamp the wood and sand any rough bits.

Step 4: Smooth It Out

To get a smoother surface that correctly fits the lens, I used some polymorph plastic. Heated in hot water, and rolled into a thin sausage shape, it can be curled round the hole and then quickly smoothed into place with a finger. Press it well into the wood, then screw in the lens as far as possible. Let it cool and set.

Afterwards, you can remove the lens, and trim any excess/squeeze out with a sharp blade, and sand it smooth.

Step 5: Stops

I added a couple of positioning stops from offcuts of the same pine piece. One is a simple small right angle corner hook, this holds the lens to the top corner of the case. The second is a right-angle flat tab that stops it twisting, and this rests against the side of the case.

The top stop is pinned and glued on, the side tabs are just glued.

Set the pins below the surface with a hammer and punch.

Step 6: Painting and Finishing

Once the glue is dry, you can sand, prime, undercoat and paint it.

I painted it black and clear-coated it to match the woodwork of the computer case.

Step 7: Done!

Here's a quick test with a credit-card sized target.

The full field of view of the Raspberry Pi Camera (at 2592x1944 pixels), yields a useful close-focus centre image of about 1220x950 pixels, or more if you like round pictures!