Design Article
Camera design for machine vision
Venkata Raghavan<br>Cypress Semiconductor Corporation
12/19/2008 2:00 AM EST
Machine vision, speaking generally, is an electro optical system (camera) connected to a processing unit such as a computer for image processing and to control a system. It is a system or computer that can "see" a target object. The system under control of machine vision could be production units, product quality control, pick and place machines, etc.
What is required for machine vision?
A machine vision system can be realized with an image sensor and lens system -- a camera -- connected to a computer through an electrical interface such as Firewire, USB, or Ethernet, with the computer connected to the control machinery.
Machine vision applications require a combination of hardware and software to ensure success:
- Camera
- Computer (Host)
- Frame grabber
- Application software
While choosing the right hardware is important, the visual inspection software forms the core of any machine vision system.
Sensors, generally driven by a pixel clock, will have a register set to configure the resolution, speed of operation, gain control, exposure time, and integration time by the user through an SPI or I2C interface. The sensor outputs Frame sync and line sync pulses along with the digital data to be processed.
The electrical interface from the sensor is CMOS for speeds up to 200 MHz. An LVDS interface is required for signal integrity at higher speeds.
Typical system architecture of the machine vision camera:
Figure 1: Elements of a machine vision system
Next: Off-line vs. on-line processing, applications, critical specifications, lenses and sensors
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