FPGA Camera Trigger System for Machine Vision Inspection
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Solution Overview
Problem
Existing machine vision defect inspection systems face delays and missed triggers due to limitations in trigger position updating and processing overhead, which hinder accurate and fast inspection demands.
Innovation Solution
A system that includes a memory for storing trigger values corresponding to a moving stage's positions and a controller that generates camera triggers based on current position information, decoupling from servo cycles and processing overhead using a field programmable gate array (FPGA) and static random access memory (SRAM) to provide deterministic and sub-microsecond triggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital signal processor (DSP) with associated software is used to generate camera triggers, then the system can provide trigger generation capability, but trigger delays and missed triggers occur due to servo cycle limitations and processing overhead
Solution Approach 1:
The patent replaces the software-based DSP trigger generation with a hardware-based Field Programmable Gate Array (FPGA) system. This substitution eliminates the processing overhead and servo cycle dependencies of software-based systems, providing deterministic sub-microsecond trigger generation with guaranteed timing accuracy regardless of motion controller workload.
Solution Approach 2:
The patent segments the trigger generation function from the motion control system by implementing it as a separate, dedicated hardware module. The FPGA receives position information directly from encoders and independently generates triggers based on pre-stored trigger position values, separating the critical timing function from the general-purpose motion control processing.
2Speed
If trigger position updating is limited by the motion controller servo cycle, then the system maintains synchronization with motion control, but trigger updating speed and responsiveness are reduced
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing all trigger position values in memory before the inspection process begins. The FPGA simply compares real-time encoder position readings against these pre-computed trigger positions, eliminating the need for real-time trigger position calculations and enabling instantaneous trigger generation when positions are reached.
Solution Approach 2:
The patent introduces an intermediary hardware comparison mechanism within the FPGA that directly compares encoder position readings with stored trigger positions. This intermediary comparison layer operates independently of the motion controller's servo cycle, providing accurate trigger generation based purely on position matching without being constrained by motion control update rates.
Data Source
AI summary
A system for generating a camera trigger that causes a camera to capture image data includes a memory for storing a plurality of trigger values. Each trigger value corresponds to a position of a moving stage. The system includes a controller for receiving position information indicative of a current position of the moving stage, generating a current position value based on the position information, comparing the current position value to at least one of the trigger values, and generating a camera trigger if the current position value matches one of the trigger values.