VL53L9CX temporal acquisition order and per-zone timing

[amirpatel7625]

Hi,

I am trying to understand the temporal structure of a single VL53L9CX depth-map acquisition for measurements of moving objects.

From UM3683 and the register documentation, I understand that a frame is produced using 6 or 7 ranging steps, with successive channel illuminations within those steps.

I have a few questions:

1. Are all 54 × 42 spatial zones effectively observed over the same sequence of ranging steps, or are different zones/groups of zones acquired at different times within a frame?

2. If there is any spatially varying acquisition timing, is the mapping from zone (row, column) to acquisition step/channel deterministic and documented?

3. Is the timing of each ranging step and Channel 0/1 illumination deterministic relative to an external SYNC_IN trigger? If so, is there documentation giving these offsets or enough information to calculate them from the configured number of shots/blanking periods?

4. Are intermediate 54 × 42 measurements available after individual ranging steps or channel illuminations, before the final depth-map processing? For example, can these be accessed through histogram mode, host-control mode, debug output, or another API?

5. Do Channel 0 and Channel 1 illuminate the same spatial field, or do they illuminate different portions/patterns of the FoV? If the latter, is there a zone-to-channel mapping available?

My aim is to assign the most accurate possible acquisition time to measurements when observing rapidly moving targets, rather than treating the complete output frame as an instantaneous measurement.

 

Many thanks!

[MeganeG]

Hello ​@amirpatel7625,

• The zones use the same sequence of ranging steps at the same time.
• It is not possible to program the ranging steps with an external trigger. Everything is managed by the firmware in the device to make integration easier for customers.
• Only the final measured depth is accessible.
• The zones illuminate different portions of the FoV, but no mapping is available.

For detecting rapidly moving targets, we recommend reducing the exposure time and increasing the frame rate. The ranging sequence cannot be tuned; it is already optimized and designed to be easy to use.

Thanks, Megane