# DMD Chip

Dear sir,

If my dmd has a tilted angle of +/-12 degree, which has a f-number of 2.4. What if I put a lens before the dmd which f-number is 2 (smaller) or 3 (bigger) ??? what would happen??? what would happen to the contrast if I used different f-number of lens?

and what is the specifications of 0.55 xga dc2 dmd?

thanks

### 21 Replies

• Wayne,

A belated Welcome to the DLP section of the TI E2E Community.

I am very sorry that your question appears to have gotten overlooked until now.

2510332 - DiscoveryOptics101.pdf

Dear Sir,

I think it means 0.55 inch in diagonal line. And it is a 4:3 rectangle.

So that makes the size of the dmd, length= 0.55 * 25.4(mm)*(4/5)=11.176 mm       height= 0.55 * 25.4(mm)*(3/5)=8.382 mm

Also I know the gap between the pixels is 1 um, and the pitch between the pixels is 10.8 um

But what's the length of one pixel??  And are these pixels square?

thanks

• In reply to wayne fang:

Wayne,

If you are refering to the 0.55" XGA (1024x768) DMD, here are the dimensions. The DMD is 0.55 inches across diagonally. The mirrors are 10.8um in width and they are squared. The width of the active mirror array is 11.059mm and the height of active mirror array is 8.294mm.

• In reply to wayne fang:

Hello Wayne,

WYA is correct the mirrors are square.  The pixel pitch is 10.8 um and the gap is approximately 1 um.  This makes the actual mirrors approximately 10.8 um minus ~1 um.

I hope that helps.

Fizix.

But I still have a question. When DMD is not activated, are these micro mirror set flat (not tilt +/- 12 degree)??? If this is the case, it should be  convenient to measure the pixel size and the gap.

Besides, as you mentioned, the gap is approximately 1 um. How is  this size measured (measured when set flat or tilt)??

• In reply to wayne fang:

Hello Wayne.

The gap references when the mirrors are nominally flat.

When the mirrors are powered they are actually landed to the surface at + or - 12 degrees.  When no power is applied the mirrors return to their rest position which is approximately flat.  However the flat state cannot be "set".  When the device is powered there are only two states available + and - 12 degrees.

Fizix

Hi, Fizix

One thing that I wanna make sure is that what is the width of one pixel of the DMD?

Is it 10.8 um or 9.8 um (10.8-1)? Because these two is very differnt.

WYA replied by "The mirrors are 10.8um in width. The width of the active mirror array is 11.059mm"

But you replied by "pixel pitch is 10.8"

thanks

• In reply to wayne fang:

Wayne,

The "pixel pitch" refers to the distance from the center of one mirror to the center of an adjacent mirror.  This value is 10.8 um.

The size of the individual mirror is approximately 9.8 microns on each edge.  The gap size can have some variation.   This is why I said the gap is approximately 1 um.

I hope this information helps.

hello  Fizix

I    have   a  question,  is   the    0.7''XGA    DMD    the   same   as    0.55''?   The "pixel pitch" refers to the distance from the center of one mirror to the center of an adjacent mirror,   so  the  "pixel pitch"  is   13.68   um?     Or    it    is   14um?     Because  in   my   experiment   "14um"  is  appropriate.

THANKS

• In reply to xiaofeng ennamelocallanguage=晓峰:

Hello Xiaofeng,

Welcome to the DLP section of the TI E2E community.

These device have the same number of pixels (XGA - 1024 x 768) but the "pixel pitch" is not the same.  The 0.7" XGA DMD is a 13.68 um pixel pitch device and the 0.55" XGA DMD is a 10.8 um pixel pitch device.

I hope this helps.

Fizix