[LASMO] LASER specification, Ethernet and Wi-Fi rate

For the LASER, we need to know which power we have to use, in order to know the LASER’s class. It was a difficult question which I had to think and reflect on. Actually, the class 3B is a higher level of LASER, but more dangerous. On another way, I thought that a 3R LASER couldn’t be powerful enough.  Finally, after some researches, we decided to take a 3R LASER of 5mW, which would be sufficient for projecting animations. Furthermore, the LASER will be in green colour (520 nm) , thus points will be more apparent and distinguishable.

There are 2types of LASER that we can use: The LASER diode, that can be used like a simpleLED or the LASER Diode Pumped Solid Stage. We will use the first one.

With those informations, we can now specified some characteristics like the tension : 2.8 – 6.5V/ DC

We will control our LASER with the TTL modulation and not a analogic one. We can also shade the beam’s brightness with PWM mode.

Now, we also know that in order to show an animation, we need 300KB/s = 2.4 Mbits/s.

Also, 10BASE-T Ethernet can provide us 10Mbits/s which is enough. We can also take another specification of Ethernet that will be widely enough like 100BASE-T .

For the Wi-Fi, norms are differents by the range and the rate. We can use almost every norm, but we prefer to have a considerable range in order to do the LASMO’s configuration everywhere in a site.  So,we will use the 802.11n norm Wi-Fi.

Now, we have to identified the micro-processor we will use

[LASMO] ILDA Format

Informations on this post are taken from ILDA official website.
The ILDA format is intended for frame exchange purposes only. It is not optimized for space or speed, and it is not currently concerned with display issues such as point output rate. Also, the format does not include show information such as timing of frames. Generally, the highest function the ILDA format can provide is a sequence of frames which play back to form an animation.
The ILDA File can provide a 3D or 2D structure, and provide color with Indexed color in a table or True colors on 24 bytes. In order to best estimate the required useful bit-rate, we analyse the most disadvantageous case : format 4 with 3D points and “True Color”. All these numbers are for one frame and N points per frame :

  • a header of 32 bytes
  • N data records of 10 bytes :
    • 2 bytes for X coordinate
    • 2 bytes for Y coordinate
    • 2 bytes for Z coordinate
    • 1 bytes for status code
    • 3 bytes for “True Color” ( 1 bytes red, 1 bytes green, 1 bytes blue )

With frame_rate in fps, N in points per frame and k in pps :

  • N = k / frame_rate
  • bit_rate_per_frame = 32 + 10*N
  • bit_rate = bit_rate_per_frame * frame_rate

For our project, we can assume that the frame rate will not exceed 60fps (and generally 25fps) and the number of points will not exceed 30Kpps (the commercial galvanometers can’t go faster). So, the bit-rate of an ILDA animation will not exceed 300KB/s.