Cognex Vision Systems – What Makes Up a Vision System?

1. Lighting

Lighting is an important factor affecting the input of machine vision system, which directly affects the quality and use of input data. Because there is no one-size-fits-all machine vision lighting fixture, it is important to select the appropriate lighting fixture for each specific use case to achieve the best results. Light sources can be divided into visible and invisible light. Several types of visible light sources commonly used are white flags, fluorescent lamps, mercury lamps, and sodium lamps. The defect of visible light is that the light cannot remain stable. How to keep light energy stable to a certain extent is an urgent problem to be dealt with in the process of practical application.

On the other hand, ambient light may affect the quality of the picture, so you can choose to add a protective screen to reduce the impact of ambient light. The lighting system can be divided into back lighting, forward lighting, structured light and frequency lighting according to its illumination method. Among them, back illumination is the place between the light source and the camera, and its advantage is that it can obtain high-contrast pictures. Forward illumination is where the light source and camera are located on the same side of the object to be measured, which is easy to install. Structured illumination is to project a grating or line light source onto the DUT and demodulate the three-dimensional information of the DUT according to the distortion they generate. Frequency lighting is the illumination of high-frequency light pulses onto objects, and the camera shooting is required to be synchronized with the light source.

2. Lens

FOV (FieldOfVision) = Required Resolution * Subpixel * Camera Size / PRTM (Component Measurement Ratio) Lens selection should be noted: (1) Focal length (2) Target height (3) Image height (4) Enlargement factor (5) Distance from the image to the target (6) Center point/node (7) Distortion

3. Camera

According to different standards, it can be divided into: standard resolution digital cameras and imitation cameras. Different cameras and high-resolution cameras should be selected according to different practical use occasions: line scan CCD and area scan CCD; Monochrome cameras and colorful cameras.

4. Drawing capture card

The frame grabber is only one part of a complete machine vision system, but it plays a very important role. The frame grabber directly determines the interface of the camera: black and white, colorful, imitation, digital, etc.

A typical example is a PCI or AGP-compliant capture card that can quickly transfer drawings to computer memory for processing. Some capture cards have built-in multi-way switches. For example, you can connect 8 different cameras and tell the frame grabber which one to capture. Some capture cards have a built-in digital input to trigger the capture card to capture, and the digital output triggers the gate when the capture card captures a picture.

5. a vision processor

The vision processor is a capture card and a processor in one. In the past, when computers were slow, vision processors were used to speed up the vision processing mission. Now because the capture card can quickly transfer drawings to memory, and the computer is much faster, the vision processor is now used less.

Cognex Vision Systems – What Makes Up a Vision System?

Cognex Vision Systems – What Makes Up a Vision System?

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