Adam Kunzman of Keynote Photonics discusses DLP Sequences (Demo)

Apart from highlighting some news or features about our products, I want to help clarify some of the fundamentals of how DLP technology works in a down-to-earth way.

One area that tends to come up frequently in my discussions with users is around what a DLP “sequence” is. To really understand DLP design, basic insight into sequences is useful.  Let’s dive in.

Each DLP chip (also called a DMD) has millions of individual mirrors that tilt in two directions, either “on” or “off” (there is a flat state when power is off, but it’s not available in normal operation). So how are the mirrors controlled?

In video projection systems, a micro-controller in the controller ASIC reads a program from flash-memory that tells the system what data to load into the DMD (a bit-plane) and when to  apply that data to the DMD. This program is often referred to as a “sequence’.  The sequence is designed in such a way by the DLP system designer to maximize the video quality to the human eye. The techniques and methods employed are beyond what we can discuss here, but suffice it to say that it is an art and a science unto itself.

3d-measurement-dlp-technology

Industrial applications of DLP systems are usually targeting something other than the human eye. Often it is a camera sensor, but in practice it can be any photo-senstive material.  Cameras are often used in 3D Metrology, structure lighting and machine vision systems.  When using a camera as the sensor in a DLP industrial application, the sequence designs are quite different than are utilized in typical DLP projection systems. Another factor that must be considered by the system designer is the response (usually quantum efficiency) of the sensor to the spectrum of light that is applied.

Depending on the system where the DLP solution is embedded, another part of the sequence design to consider is whether the application must fully load and reset the data across the entire DMD (all the rows switch together) or if blocks of mirrors can be loaded and operated independently. The former operation is called “Global Reset” and the latter “Phased Reset”. I’ll explain the subtleties of these two different operating modes in our next post.

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