ALLPCB
Overview
In general, frame drops in industrial cameras are not determined by the transmission interface. Whether USB, IEEE 1394, GigE, or Camera Link, poorly designed drivers or camera hardware are the primary causes, which negatively affect machine vision inspection.
Three sources of image data congestion
Camera-side
The image sensor transfers frames to the camera's interface chip, which then sends them to the PC. If the PC is too busy to process received frames while the sensor continues to deliver new frames, the camera must provide sufficient buffer memory; otherwise frame drops will occur.
Vision software
Vision software needs a buffering mechanism for incoming frames so it can extend the time available for processing. If the overall CPU processing speed is consistently slower than the incoming frame rate, buffers will eventually overflow and frames will be lost.
PC hardware and drivers
This area focuses on PC hardware drivers and system behavior, independent of the vision application. Key factors include driver throughput and how the operating system schedules threads. Poor receive performance combined with insufficient camera buffering will cause frame drops.
Notes on buffers and interfaces
Industrial cameras operate at high frame rates, but camera buffers cannot be enlarged indefinitely; they only need enough capacity to absorb temporary workload spikes. When a USB camera drops frames, the usual cause is that the machine vision software processes images more slowly than they arrive. Over time the software buffer fills and cannot accept new frames; this is system-level data loss, not a camera-internal data loss. Under such conditions, the outcome is the same regardless of whether the camera uses IEEE 1394, USB, or GigE.
