How does DLPC350 display multi-bits ?

user4581142

Other Parts Discussed in Thread: DLP4500, DLPC350

Hi there !

I would like to know the pattern sequence when DLP4500 is set to display multi-bits in pattern sequence mode. For example, if the bit depth is set to be 8, from R0 to R7, does it display the 8 bits in turn from R0 to R7? Because when R0~R7 was 127(01111111 in binary) in decimal, I got the following waveform. The rectangle shows a period. It seem that DLP4500 first displayed R0~R5, after some time, it displayed R6 (or in reverse). And it seems that the bits are displayed in different orders under different settings.

over 9 years ago

0 Paul Goedeke over 9 years ago

TI__Mastermind 30600 points

Hello,

Bit depth relates to the exposure time of each bit-plane that the DLP4500 displays. Take a look at section 4 of the Lightcrafter 4500 User's Guide:
http://www.ti.com/lit/dlpu011

I think what you're seeing isn't that the order has changed but that the exposure has changed. Bits 0 through 5 are displayed for relatively short amounts of time.

Let me know if this helps clear up your question.

Thanks,
Paul

0 user4581142 over 9 years ago in reply to Paul Goedeke

Prodigy 70 points

Hi,

Thanks for your reply.

Yes, I understand that the display time is proportional to the weight of the bit in binary representation. So (0111,1111) is displayed as "on" for almost half of the time (sum from bit0 to bit6), as we can see from the waveform that the duty ratio is approximate to 1 in a period. If the bits are display in turn from bit0 to bit7, the first half of the period is "on", corresponding to high level, and the other half is "off". But the high level portion is split into two parts which is almost equal in width, so I guess that bit0~bit5 are displayed continuously while bit6 isn't since the weight of the sum of bit0 to bit5 is almost equal to bit6.

0 Paul Goedeke over 9 years ago in reply to user4581142

TI__Mastermind 30600 points

I misunderstood your initial question I think. Can you provide some more detail on your test set-up? How are you measuring the waveform that you drew above?

Can you attach GUI screenshots or scope screenshots?

Thanks,
Paul

0 Sanjeev over 9 years ago in reply to Paul Goedeke

TI__Mastermind 30875 points

Hi,

What you are seeing is the actual behavior, the DLPC350 controller doesn't display the bits in order, the reason behind is that since the camera is integrating over time it doesn't matter which order the bits are displayed.

Refer to this discussion http://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/f/924/p/386432/1365047

Regards,

Sanjeev

0 user4581142 over 9 years ago in reply to Sanjeev

Prodigy 70 points

Hi,

Thanks for you answer.

So do you mean the displaying sequence is random ? Just to average the intensity in a period ?

Best regards

0 Sanjeev over 9 years ago in reply to user4581142

TI__Mastermind 30875 points

It is not random but follows pre-defined order. For example - You can turn ON each bit of 8-bit data at a time, and you can capture light output on a Photodetector by the DLP system.
Regards,
Sanjeev

DLP®︎ products

DLP products forum

How does DLPC350 display multi-bits ?