Part 1 of the OPC Machine Vision Companion Specification defines the VisionSystemType, an instance of which serves as the entry point to the functional view of a machine vision system. This specification introduces the VisionSystemAssetType, an instance of which shall provide an additional entry point into the inner structure of a machine vision system. The VisionSystemAssetType represents the composition of the machine vision system, i.e., it shows which components and other machines together build up the machine vision system. An instance of the VisionSystemType (defined in Part 1) and an instance of VisionSystemAssetType (defined in Part 2), representing the same machine vision system, shall have a RepresentsSameEntityAs reference (OPC 10000-23) connecting them (Figure 6).

The VisionSystemAssetType provides optional folders that can be instantiated individually to organize the different components and other machines that constitute the machine vision systems e.g., ComputingDevices, Lenses, DisplayUnits, etc., as can be seen from Figure 7. The complete set of defined possible common components can be found in section 8.1. With the exception of ImageHandlingAspects all the instances that are organized in the folders of the VisionSystemAssetType can be of any type but need to implement the interface IVisionInfoType (section 7.5) or one of its subtypes. The IVisionInfoType interface contains basic information about identification, maintenance, and health of the machine vision system, as well as all the items (machines or components) that form it.

Figure 6 – Relationship between the ObjectTypes of OPC MV Part 1 and Part 2

Figure 7 – OPC Machine Vision Part 2 Information Model Overview

The idea behind this modelling approach is to enable the implementer to use instances of other ObjectTypes that are already defined in other companion specifications (future or current), when appropriate. The IVisionInfoType interface shall be implemented on the instances organized by the folders in VisionSystemAssetType unless a specific subtype of IVisionInfoType for that particular item type exists (e.g., IComputingDeviceType, IDisplayUnitType, etc.). The implementation of the IVisionInfoType or one of its subtypes can also be done on the ObjectType instead of the instance to be organized in that folder. This specification also defines several convenience ObjectTypes that are not mandatory, that can be directly instantiated, and implement the necessary interfaces for different items.