Laser Video & Transparency Projector

Lasers have always intrigued me. I have two Helium-Neon Lasers (gas discharge, not solid state), one red the other green. I also have several laser pointers. I like lasers.

Several years ago I came across an instructable that showed that you could take the narrow beam of a laser and spread it out into a cone of light. Since it is laser light the light stays coherent, and even though it is not parallel and spreading out, it still acts like a laser. If you put a silhouette or a photographic slide in the cone of light it will be projected BY LASER light so no matter where the surface the image falls on it will still be in focus.

I wondered it this would work if the image placed in the cone of laser light was an LCD video display.

This is my proof of concept for such a device.

1 - Star Shower Motion Laser Light by Telebrands. I had this lying around from a post-Christmas sale and I figured it had a fairly powerful laser in it.

1- Holiday Time Video Greeting Card by Gift Card Impressions LLC (2013 vintage Walmart). Another post-Christmas purchase. I had several of these so I figured I could completely destroy this product, especially the LCD panel, and not feel bad about it. The video file lives on a removeable micro SD card. (Unfortunately I discovered too late that the file format is .ani and essentially unusable.)

2 - Wide angle smartphone lenses by e-circuit (Dollar Tree)

1 - Skull Image from Battery powered toy projector (Optional; Halloween at the Dollar Tree). Really any transparency will do.

Hot Glue Gun and glue

Cardboard - (the universal building material)

Razor knife, pen, etc.

Laser safety goggles

CAUTION Laser Radiation. The original Star Shower divides and spreads the laser light so there is no single point of high powered laser light when it is intact. Disassembly makes the laser much more hazardous. Make sure to not view the beam directly and be careful not to direct the beam into your eye off of a reflective surface. I would suggest wearing protective laser goggles.

The laser housing is held together by triangle drive screws so you may have to purchase a special screwdriver to take it apart.

At the front are several gears and revolving holographic sheets that produce the 'star pattern'. They can be removed along with the front cover.

The laser beam needs to be spread into a cone of light. I found that inside the clip-on cell phone wide-angle lens was a double concave lens that worked nicely.

To get the lens apart I unscrewed it from its clip, removed the lens cap and gave the circumference several squeezes as I moved the pliers around. This cracked the glue and allowed the lens to come apart. The double concave is the one behind the front lens. You need two.

Concave graphic reference

I destroyed two clip-on lens to get two concave lenses. I taped the two lens together (no particular orientation) and trimmed the excess tape from one end.

I placed the trimmed end of the double lens assembly onto the laser aperture and tacked it in place over the laser aperture (where the laser light comes out) with hot glue.

At this point it is possible to insert a transparency and see if it is projected. I took a small skull image out of a battery-powered toy projector. The image was clearly projected no matter the distance away the surface was I projected it on.

A photo transparency (aka Slide) would work equally well or better.

It works!

As noted, I had several video greeting cards. So I literally tore one apart. Inside was a single circuit board, a speaker, 2 x AAA battery holder.

The most important aspect of the display was the the LCD panel was easily lifted from off of the circuit board with it being attached on only one side. With the LCD at right angles to the circuit board it provided access to both the front and back of the LCD, since laser light would have to shine through.

LCD panels are a bit of amazing technology. Polarized light is also pretty awesome itself.

LCD panels take advantage of the fact that vertically polarized light will not pass through a horizontally polarized filter. Think of it as light passing through venetian blinds; a vertical set follow by a horizontal set. Not much light gets through.

Liquid Crystals located between the two polarizers (the venetian blinds) twist the vertically polarized light to horizontal to allow it to pass through a horizontal polarizer. You can see in my last photo that taking a piece of polarizing filter will block all light when in a particular orientation.

As it turns out the light of many lasers is polarized. This can be taken advantage of as there is no need for one of the two polarizers. In addition if the liquid crystals alone are relied upon then no polarizing filters are needed at all.

Completely disassemble the LCD panel. Remove the backlight frame diffuser and films. Black out back light LEDs by pulling them away from the panel and light pipe and covering them with black tape.

Remove the polarizing filter. All that should be left is the glass display without backlight or polarizers.

LCD Panel graphic reference

I projected the spread laser light onto a piece of cardboard and sketched out the bright spot. The light looks a bit 'bubbly' and I'm not sure if that is a result of the lenses or inherent to the laser I was using.

I then took the LCD panel and centered it on the spot and traced it.

I cut a window in the cardboard to mount the LCD panel over. I also cut a large slot to allow the circuit board a place to go. I tacked the LCD in place with hot glue.

Since the polarized laser light needs to be oriented 90 degrees in relationship to the liquid crystals the laser must be oriented correctly. This is determined by trial and error.

With the LCD displaying an image (which you can only see in the projected image) rotate the laser until the highest contrast is achieved in the projected image. I hot glued it in place.

I noted that for ease of mounting the image on the LCD was upside down. I would just invert my video to take care of this inconvenience.

As seen in my first image, the LCD greeting card displays "No Video" if a video file is not loaded.

Unfortunately the LCD greeting card uses .ani type files to display the video. The cards were so old (2013) that the video conversion software provided with them would not work. So to my disappointment I did not have a video clip to project. However, the words "No Video" can be seen projected. I would have liked to have projected a video but at this time I cannot.

However, other LCD video displays may be suitable and the concept can be tested with video coming from another source.

And as the skull image shows, static images can also easily be projected.

Have fun and Enjoy!