Jump to content


ProfF

Member Since 26 Jun 2009
Offline Last Active May 20 2016 04:15 AM
-----

Topics I've Started

Laser guided snoot - in-line targeting

15 May 2016 - 07:50 PM

Hi,

 

As a photographer and 3D printing enthusiast I created several snots. Usually I find them hard to work with and did not use them much. I recently read article/review about 10bar laser guided snoot. I liked the idea and purchased the laser unit alone for 75$. 

 

The laser unit is nice. It is basically a small box with a laser and a flash detector for autoshut-off. I started playing with the design of my snoot and looked at the 10bar original.

 

10bar-snoot-z240.jpg

Their design has the laser unit "riding" on the snoot, and the user has an adjustable knob to adjust the angle of the laser. This means that the beam intersect the actual snoot output path only on one point. Elsewhere it will be off center (and probably off target in the thin version of the snoot).

 

Attached File  OriginalDesign.png   19.47KB   12 downloads

 

An ideal solution for this would have the laser run through the center of the snoot, this will make it precise at any distance. I knew similar solution from microscopes using beam splitter. The idea is simple. A beam splitter is half-mirror, where  50% of the light pass through it and 50% bounce off. In this design the laser is positioned perpendicular to the strobe. The beam splitter is setup at 45degrees to both beams.

 

Attached File  BeamSplitterDesign.png   12.38KB   11 downloads

 

The price of this solution is reduction in 1/2 of both the laser beam and the strobe light. Since this setup is used for close macro situation, I reasoned that this will not be a big problem.

 

The next question was finding a beam splitter. A professional grade one is expensive (100s of $). However, I found that there is a game "Khet - Eye of Horus" that uses lasers and beam splitter.

 

31eKehAZnqL.jpg

 

For about ~$5 I could buy two beam splitters pieces. A quick test showed that these work fine on the laser beam and on the strobe. Removing the plastic frame, I had a nice beam splitter (and a backup one).

 

I designed a snoot and set out to test it. However, the laser beam was lost somewhere in the snoot. Revisiting my components I discovered that the laser beam was not aligned with its housing. The few degrees of offset were sufficient to cause problems. This required having an adjustable mount for the laser that allowed tuning of the beam.

 

The final design in my CAD visualization:

 

Attached File  Snoot 45deg beam splitter v32 v25.png   151.16KB   11 downloads

 

The yellow object is YS-01 strobe. The blue ring is attached to the strobe and allows quick attachment of the snoot. The red box is the laser. The tip at the end is exchangeable and is held in place by magnets. (I did not take a proper picture of the snoot, but can load one later on)

 

Last month I had a chance to try it on a short visit to the red sea. Using the snoot with a macro lens was harder than I expected. The problem was getting the damn red point into the frame. I practiced on a pair of nudis, and finally managed few shots. 

Attached File  P4070092.jpg   214.35KB   11 downloads

 

Opening the images on my computer, I realized that the laser was visible in the image, the auto-shutoff did not work. I set the sensor on the laser to point into the strobe, and expected the bounced light to reach it. It seems that the black plastic was doing a good job of absorbing the light. Taping a piece of white plastic on the inner lower wall of the strobe solved that problem.

 

The next day I tried the snoot with a fisheye setup. This made it easier to find where the laser is pointing and positioning it. Two attempts:

Attached File  P4080273.jpg   235.57KB   12 downloads

 

Attached File  P4080284.jpg   226.92KB   12 downloads

 

Not perfect, but something to work with. Since my trip was short, I did not have too much time to get more experience with the snoot. Next time hopefully I will get a better sense of it.