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Introduction

Overview

Optical Table

Environment

Laser

Beamsplitter

Mirrors/Lenses

Table Mounts

Optic Mounts

Plate Holder

Objects/Scenes

Resources

Optic Mounts

Beamsplitters, Mirrors, and Lenses

The homemade optic mount shown in Figure 21 can be used to mount your fixed beam ratio beamsplitter, small directional mirrors, and diverging lenses or microscope objectives (Figures 7, 9, and 10 & 12 respectively). Figure 22 shows the individual parts before painting. If you purchase the circular variable gradient beamsplitter listed on the Resources web page, some have a handle that the aluminum coated glass beamsplitter mounts on to one end and the other end of the handle has a circular 1/2 inch hole for mounting to your table mount. Other circular variable gradient beamsplitters come with their own pole and base mount as shown in Figure 8.

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                                       Figure 21: Optic mount.

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                                     Figure 22: Optic mount parts.
Note: A small band saw with a fine toothed blade is very handy for cutting acrylic plastic and aluminum. A hacksaw with 18 teeth per inch will work also.

To cushion the clamping force of the two pieces of acrylic plastic tightened by the bolts and wing nuts, I have used cut pieces of band aids. The cotton provides the cushion and the adhesive side helps attached them to the plastic . A better cushioning material is the fuzzy portion of Velcro. I've found that the cotton portion of the band aid has a tendency (not always) to produce fibers that stick out and can interfere with the beam. Velcro does not have this problem.

For directional mirrors larger than mentioned previously, the optic mount in Figure 21 will not work. You will have occasions to use one or more 4 inch x 5 inch x 1/4 inch thick directional mirrors. Figures 23 & 24 show a mounting technique you can use for mirrors of this size using 1/2 inch thick acrylic plastic. The mirror shown in both Figures is 4 inches x 5 inches x 1/4 inch thick . The plastic mount is slightly less in size than the mirror itself although the mount could be the same size or a bit larger than the mirror size. Figure 25 shows the plastic mount cut to size and unpainted.

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      Figure 23: Large front surface mirror mount showing front surface facing up.

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          Figure 24: Large front surface mirror mount showing back side of mirror.

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   Figure 25: Large mirror mount cut to size, tapped, and unpainted.

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Figure 26: Important large mirror placement on acrylic plastic mount.

Drill and tap a hole half way along and centered on one 4 inch side and do the same on one 5 inch side to accommodate a short rod with a 1/4-20 bolt as shown in Figure 25. Use a 3/16 inch drill bit and drill the hole 1 inch deep (work from a small bit up to this size). You need this larger bolt size, instead of the 8-32 bolt size, to give better stability for the larger sized mirror and mount. Why two holes for the short rod? If you're setting up your plate holder with the 5 inch side of the holder orientated vertically for recording a vertically orientated figurine, for example, you will want to orientate the 5 inch side of the mirror vertically to get adequate light coverage of the plate. The two tapped holes let you reposition the short rod, and therefore the orientation of the mirror, to accommodate the orientation of your plate holder.

Spray paint the acrylic plastic mount with enamel flat black paint on all sides except the mirror mounting side and allow to dry thoroughly (use masking tape to cover the area where the mirror will be mounted). Attach a painted short rod to the mount tightly. Next, epoxy the mirror to the acrylic mount surface making sure the reflective first surface of the mirror is facing away from the mount as shown in Figures 23 & 24. The mirror, mount, and short rod are then attached to a table mount using a connector.

Caution: When you epoxy the mirror to the mount, make sure the edge of the one 4 inch side of the mirror is a bit inside the 4 inch edge of the mount where the tapped hole is. The same should be done with the 5 inch side of the mirror on the 5 inch edge of the mount where its tapped hole is, as shown in Figure 26. This means that the other two sides of the mirror will be extended further out over the other two sides of the mount, which is fine. The reason for this is that you may not be able to get your holes drilled exactly centered on the 1/2 inch thickness of the acrylic mount which means that when you screw in the short rod in either hole, the edge end of the short rod might stick out above the mounting surface of the mount and not be flush on both sides of the mount even though the diameter of the rod and the thickness of the mount are the same. If the mirror edge stuck out over these mount edges, you would not be able to screw the short rod tightly against the edge of the mount, which is critical for stability.

If you have future plans to make 8 inch x 10 inch holograms or larger, the optic mounts for 8 inch x 10 inch x 1/2 inch thick mirrors and larger require their own special design.

Laser

The laser needs two table mounts as shown in Figure 27. The table mount poles are connected together with a 1/2 inch diameter solid aluminum pole running between them and connected to each table mount pole. The length of the connecting pole will be determined by the width of your laser. The laser sits between the two mounts. At the center of the connecting pole is another connector that has a short rod with a 1/4-20 bolt. This short rod with the bolt screws into a 1/4-20 hole in the bottom of the laser housing. Most small He-Ne lasers are supplied with this 1/4-20 hole. Using this mounting technique allows you to easily adjust the height of the laser on the optical table and allows you to tilt the front of the laser up and down. If you are using a laser with an output power of 20 mW or higher, you can use adjustable table jacks, one on each end of the laser. These lasers are typically 3 feet long.

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                                            Figure 27: Table mounts for the laser.

Spatial Filter

If you plan to use a spatial filter, you will need to mount the base of the spatial filter to a 3 inch x 2 inch x 1/2 inch thick piece of acrylic plastic as shown in Figure 28. Once you've cut your plastic mount, lay the spatial filter's base on top of it. The spatial filter base has three holes drilled in it to accommodate 1/4-20 bolts, but you will just be using the front two holes.

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                                        Figure 28: Mount for the spatial filter.

Before you assemble the plastic mount, spatial filter base, and short rod, paint the plastic mount with enamel flat black paint and allow to dry. Now assemble the parts by bolting the spatial filter base to the plastic mount with 1/4-20 bolts and then screw the short rod into the plastic mount tightly as shown in Figure 29. The completed unit is then attached to a table mount using a connector.

Note: As mentioned previously, when gluing larger mirrors to their acrylic plastic mounts, remember not to let the spatial filter base hang over the 3 inch side of the plastic mount where the short rod hole is drilled so the short rod can be screwed into the plastic mount tightly.

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        Figure 29: Spatial filter assembled with mount and short rod.

Parabolic Mirror

In order to mount the parabolic mirror discussed previously, you should purchase the telescope mirror mount made for this size mirror as shown in Figure 30. Two holes are drilled, opposite one another, in the mirror mount for 1/4-20 bolts using a 1/4 inch bit (no tapping threads here) using drilling methods previously discussed. A short rod with a 1/4-20 bolt is attached to each of the two holes in the mount with 1/4-20 nuts and lock washers. Two table mounts, each with a connector, are attached to the short rods, one on each side of the mount.

I recommend placing and tightening the parabolic mirror in its mount before you attach the telescope mirror mount to the table mounts. You may need someone to help you attach the telescope mirror mount to the table mounts because of its weight. Be very careful not to accidentally scratch the front surface of the mirror. You do not have to paint the telescope mirror mount flat black, but the short rods with lock washers and nuts, connectors, and table mount poles should be painted with enamel flat black paint.

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                                Figure 30: Parabolic mirror telescope mount.