The image changes based on the viewing angle. View the lenticular from the correct angle to find out if the gift is yours. The angle is defined by a special dongle attached to your gift under the Christmas tree. Vertical lines block what you are not supposed to see. The gaps between the lines reveal the image you will want to see.
A lenticular is a composite image where multiple pictures are combined onto a single page by interleaving thin vertical strips. There are various types of lenticular images. Many people like to make 3D images using this method. My project, on the other hand, consists of a series of fairly unrelated pictures and words.
[Note: I posted this project on Instructables. The explanation is better there.]
There are programs and services available to help you create extremely precise lenticular images. A professionally done image can use a special plastic prism material to view images. I created a much less precise method. My mask consisted of simple vertical black stripes printed on a sheet of plastic. The mask is placed in front of the interlaced image such that only one picture can be seen at any given time. If this mask is raised to create a separation between the layers, a different image will appear for each of the viewing angles.
Making a Lenticular Plate
Adobe Photoshop to the rescue!
My lenticular has four images on a side. This was a fairly easy number to work with. Since I had eight family members attending Christmas at my house, I created a two sided lenticular. Here are steps for a single-sided lenticular. If you need two sides, simply repeat the following and use two sheets of plexiglass and print pictures on both sides of the sandwiched sheet of paper.
The directions below assume an image resolution of 300 dots per inch and a plexiglass thickness of roughly 1/8 inch. If you have a higher resolution image or a different glass thickness, scale accordingly so the widths of the image slices match the thickness of your plexiglass.
- Start with a blank 8.5×11 inches and 300 pixels per inch. If you use a higher resolution image, you may need to adjust the stripe sizes mentioned below.
- Create four layers for the four images that you are using.
- Create a mask layer for each of the four images. Every layer contains a series of vertical white stripes that are 10 pixels wide with a 30 pixel invisible space between each white stripe. These 1/8 inch stripes worked well with the 1/8 inch thick plexiglass.
- The mask for the first layer starts on the left edge of the picture.
- The mask for the second layer is identical to the first mask but is shifted right by 10 pixels.
- The third mask is shifted 10 more pixels.
- The last mask is again shifted by 10 more pixels.
- Print this 8.5 x 11 inch combined image.
- Next create another image that is simply black vertical stripes.
- The vertical stripes are 10 pixels each with 30 pixels between. Just like the mask layers of the page we printed before except these stripes are black.
- Print the black stripes onto an 8.5 x 11 sheet of plastic.
- Tape the picture face down onto an 11 x 17 sheet of 1/4 inch thick plexiglass. The image will be visible looking through the plexiglass.
- Tape the plastic image of black stripes into the other side of the plexiglass. Be extremely careful to line up the stripes with the image below so the bottom half shows the same view that the top half shows. I had to realign the mask several times before I finally got it right.
- Rotate the lenticular plate back and forth a several times and make sure all four images are intact at certain viewing angles.
Enforced Viewing Angles
Each person who gets a gift will need to know the correct viewing angle to see his or her picture. You will need to provide a method for them to know what this is. I created a series of keyed rings to be placed on gifts under the tree.
- Chop a 2-inch inside-diameter PVC pipe into a number 2-inch tall rings. I used a power chop saw to cut the pieces. If you don’t have one of those, you could do the same with a hack saw.
- Make a keyhole in the Lenticular tag reader — a 3-foot 1×4 piece of wood.
- Take one of these rings and draw a circle onto a 1×4 piece of board — the Lenticular tag reader.
- Along the inside the circle draw a 1/2 inch by 1/2 inch notch. The hole you will next cut in the board will be a full circle with a tab sticking out — like the mouth in the shape of an “O” showing only a single tooth. This tooth that sticks out is very important. Each ring will have a matching notch forcing it to be inserted in only one specific position.
- Cut the single-tooth hole in the wood with a jigsaw or coping saw.
- Cut a notch on one edge on the bottom each ring. This notch will match the tooth sticking out of the hole in the Lenticular reader board.
- Mark each ring by placing it over the hole you cut in the board.
- I made my notches 3/4 inches deep. This allows my rings to sit comfortably on the stable surface of the table on which everything will sit at Christmas.
- Create slots on the top edge of each ring in which the lenticular plate will sit.
- One by one insert each ring one at a time into the keyhole.
- Place the Lenticular plate on top of the ring at the proper viewing angle and mark both edges of the ring on which it sits.
- Cut a 1-inch deep notch on the left edge of the ring.
- Cut a 1/2 inch deep notch on the right edge of the ring. This notch will align with a notch in the lenticular plate.
- Last step. Cut a 1/2 inch deep slot at the bottom of the lenticular plate. Match this with the shallow slot in the pipe rings.
If you don’t want to start from scratch you can download the Adobe Photoshop file that I used for the gifts sent to family in Seattle: Seattle2007.psd.