Equipment for making high quality holograms

Holography is in fact a quite cheap hobby if you build most of the equipment yourself. If you believe you need acess to an advanced lab and expensive optical equipment, think again. In fact, you can build most of the equipment yourself with nothing more than ordinary tools and common materials. Of course, you will have to purchase the laser, spatial filter and some mirrors, but the rest of the equipment can be built from scap materials. Surprised? Go on reading:

If you have a small machine shop like the one below, you can build almost everything yourself except the laser and mirrors.

Before you begin: Having a drawer full of scap is very useful...

The Laser:

The above laser is of the HeNe type, and emits 15mW read laser beam. If you are lucky, you might find one in some types of large old laser printers. You may even use a common laser pointer as your light source. Even if 15mW is a very small amount of power (1% of an ordinary Christmas bulb), you should excersise care when ignited. The beam from this small laser in my lab can display a red dot on clouds far away. The laser head runs on high voltage, the start voltage is about 5000V at 7mA. This is not a toy!

The Table

You may already know that you will need to keep the optical equipment very stable during laser exposure. No equipment should be allowed to move more than 20 nanometers ( one nanometer is 1/1000000 of an millimeter, a distance of about 10 atoms!) during an ordinary exposure of say 20 seconds. This is probably the most difficult task. For this reason you can't make holograms on an ordinary table. Talking, breathing or walking around the lab during exposure will complete destroy your hologram.

You need a stable table with four or six solid legs made from ordinary Leca building blocks. On top of the Leca blocks, place some car inner tubes. On top of that, pour a large concrete slab and glue a steel plate on top. You should be able to make this table in a couple of days. The table will be a very stable work bench indeed.

Mirrors:

Buy some front surface mirrors in various sizes and mount them on solid stands made from wood.

Magnetic holders:

In order to hold all your optical equipment ( mirrors, beam splitters, diffusers etc) you will probably need about 8 magnetic holders. You can get these cheaply from good hardware stores. The image about shows various use of the holdes.

Beam splitters:

You will need at least two beam splitters. A beam splitter is a partly reflecting mirror useful for dividing the laser beam into two parts. Go for one 50/50 and one 20/70 splitter.

Film holder:

Above you can see a film holder made from ordinary concrete. This will cost you next to nothing.

The spatail filter:

You can make this yourself, but then you need to use a lathe and other types of advanced tools. Go buy one! The spatial filter cleans up the beam so that you get nice holograms. The spatial filter consists of a microscope objective and a very small disc with a pinhole.

Lenses:

You do not need these, but for serious work you will be glad you made at least one liquid filled lens.

Exposure meter:

Make a very simple one from a VOM meter and a light sensitive resistor. Nice to have, since you more easily can measure beam ratios with this one.