Point Grey Research Grasshopper Technical Reference
Camera Operations and Features
Revised 26-Nov-10
Copyright (c) 2010 Point Grey Research Inc.
38
Related Knowledge Base Articles
ID Title URL
166 Extended shutter mode
operation for DCAM 1.31-
compliant PGR Imaging
Products.
www.ptgrey.com/support/kb/index.asp?a=4&q=166
4.5.6. Automatic Inter-Camera Synchronization
Multiple Point Grey FireWire cameras, when they are on the same IEEE-1394 bus and running a
the same frame rate, are automatically synchronized to each other at the hardware level. When
using multiple cameras, the timing of one camera to another camera is as follows:
• If the cameras are on the same bus, the cameras are synchronized to within 125µs
(microseconds) of each other (note: 125µs is the maximum deviation). However, the
1394 bandwidth limits the maximum number of cameras that can be on one bus. See the
section Maximum Number of Cameras on a Single 1394 Bus for more information.
• If the cameras are on separate buses, use PointGrey’s MultiSync
™
software to
synchronize the cameras across buses. This can be used to synchronize cameras on
different buses within the same computer or on different buses across multiple
computers. The software will ensure that the cameras are synchronized to within 125µs.
If Multisync is not running, there is no timing correlation between separate cameras on
separate buses.
It is possible to offset the synchronization of individual cameras relative to other cameras using
the TRIGGER_DELAY register 0x834.
Related Knowledge Base Articles
ID Title URL
112 Synchronizing PGR cameras
across multiple PCs
www.ptgrey.com/support/kb/index.asp?a=4&q=112
4.5.7. Frame Rate Control
The current base frame rate is controlled using the CURRENT_FRAME_RATE register 0x600.
The Grasshopper allows users to further “fine-tune” the frame rates of their cameras using the
FRAME_RATE register 0x83C, which is described in detail in the PGR IEEE-1394 Digital Camera
Register Reference. This is particularly useful for capturing an image stream at a different frame
rate than those outlined in the Supported Data Formats and Modes section, and can be useful for
synchronizing to 50Hz light sources, which can cause image intensity fluctuations due to the light
source oscillations being out of sync with the frame rate.
For example, users may wish to play an image stream back on a PAL-based system that displays
at 25 FPS. To do this, set the CURRENT_FRAME_RATE to 30 FPS, set the A_M_Mode bit [7] of
the FRAME_RATE register 0x83C to zero (manual), then adjust the value using the Value field or
using the ABS_VAL_FRAME_RATE register (recommended).
4.5.8. Pixel Binning and Region of Interest Modes
The Grasshopper implements several DCAM Format_7 customizable video modes (see the
Customizable Formats and Modes section for camera-specific information) that allow for faster
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